Keyword: electron
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MOA01 John Madey: A Short History of My Friend and Colleague ion, FEL, undulator, laser 1
 
  • L.R. Elias
    University of Hawaii at Manoa, Honolulu, USA
 
  I thank the organizing committee for inviting me to share with you some stories of my friend and colleague John Madey, who passed away on July 2016 in Honolulu, Hawaii.  
slides icon Slides MOA01 [0.073 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOA01  
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MOBA02 Coherence Limits of X-ray FEL Radiation ion, FEL, radiation, photon 5
 
  • M.V. Yurkov, E. Schneidmiller
    DESY, Hamburg, Germany
 
  The most simple and robust technique for production of short wavelength radiation is Self Amplified Spontaneous Emission (SASE) FEL. Amplification process in SASE FELs develops from the shot noise in the electron beam, and powerful radiation is produced by single pass of the electron beam through the undulator. Serving as a seed, shot noise effects impose fundamental limits on the coherence properties of the radiation (both, temporal and spatial). FEL theory reached mature status allowing elegant description of the shot noise phenomena, and in this report we present relevant overview.  
slides icon Slides MOBA02 [2.606 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOBA02  
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MOC03 Commissioning and First Lasing of the European XFEL ion, FEL, MMI, linac 9
 
  • H. Weise, W. Decking
    DESY, Hamburg, Germany
 
  Funding: Work supported by the respective funding agencies of the contributing institutes; for details please see http:www.xfel.eu
The European X-ray Free-Electron Laser (XFEL) in Hamburg, Northern Germany, aims at producing X-rays in the range from 260 eV to 24 keV out of three undulators that can be operated simultaneously with up to 27,000 pulses per second. The XFEL is driven by a 17.5 GeV superconducting linac. This linac is the worldwide largest installation based on superconducting radio-frequency acceleration. The design is using the so-called TESLA technology which was developed for the superconducting version of an international electron positron linear collider. After eight years of construction the facility is now brought into operation. First lasing was demonstrated in May 2017. Experience with the super-conducting accelerator as well as beam commissioning results will be presented. The path to the first user experiments will be laid down.
 
slides icon Slides MOC03 [5.418 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOC03  
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MOD02 Status of the FLASH FEL User Facility at DESY ion, operation, experiment, FEL 14
 
  • K. Honkavaara
    DESY, Hamburg, Germany
 
  The FLASH facility at DESY (Hamburg, Germany) provides high brilliance FEL radiation at XUV and soft X-ray wavelengths for user experiments. Since April 2016, the second undulator beamline, FLASH2, is in user operation. We summarize the performance of the FLASH facility during the last two years including our experience to deliver FEL radiation to two user experiments simultaneously.  
slides icon Slides MOD02 [6.543 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOD02  
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MOD04 Status and Perspectives of the FERMI FEL Facility ion, FEL, laser, experiment 19
 
  • L. Giannessi, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, F. Cilento, P. Cinquegrana, M. Coreno, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, M. Di Fraia, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, F. Iazzourene, S. Krecic, M. Lonza, N. Mahne, M. Malvestuto, C. Masciovecchio, M. Milloch, N.S. Mirian, F. Parmigiani, G. Penco, A. Perucchi, L. Pivetta, O. Plekan, M. Predonzani, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, E. Roussel, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, S. Spampinati, C. Spezzani, M. Svandrlik, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
 
  FERMI is the seeded Free Electron Laser (FEL) user facility at the Elettra laboratory in Trieste, operating in the VUV to EUV and soft X-rays spectral range; the radiation produced by the seeded FEL is characterised by a number of desirable properties, such as wavelength stability, low temporal jitter and longitudinal coherence. In this paper, after an overview of the FELs performances, we will present the development plans under consideration for the next 3 to 5 years. These include an upgrade of the LINAC and of the existing FEL lines, the possibility to perform multi-pulse experiments in different configurations and an Echo Enabled Harmonic Generation experiment on FEL-2, the FEL line extending to 4 nm (310 eV).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOD04  
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MOD06 Matter-Radiation Interactions in Extremes (MaRIE) Project Overview ion, photon, FEL, cavity 24
 
  • R.L. Sheffield, C.W. Barnes, J.P. Tapia
    LANL, Los Alamos, New Mexico, USA
 
  The National Nuclear Security Administration (NNSA) requires the ability to understand and test how material structures, defects and interfaces determine performance in extreme environments. The MaRIE Project will provide the science ability for control of materials and their production for vital national security missions. To meet the mission requirements, MaRIE must be an x-ray source that has high brilliance and with very flexible and fast pulses to observe phenomena at shock-relevant time scales, and with high enough energy to study high-Z materials. This talk will cover the rationale for the machine requirements, a pre-conceptual reference design that can meet those requirements, and preliminary research needed to address the critical high risk technologies.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOD06  
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MOP001 Diamond Double-Crystal System for a Forward Bragg Diffraction X-Ray Monochromator of the Self-Seeded PAL XFEL ion, FEL, photon, laser 29
 
  • Yu. Shvyd'ko, J.W.J. Anton, S.P. Kearney, K.-J. Kim, T. Kolodziej, D. Shu
    ANL, Argonne, Illinois, USA
  • V.D. Blank, S. Terentiev
    TISNCM, Troitsk, Russia
  • H.-S. Kang, C.-K. Min, B.G. Oh
    PAL, Pohang, Kyungbuk, Republic of Korea
  • P. Vodnala
    Northern Illinois University, DeKalb, Illinois, USA
 
  An x-ray monochromator for a hard x-ray self-seeding system is planned at PAL XFEL to be used in a 3-keV to 10-keV photon spectral range. The monochromatization in a 5 keV to 7 keV range will be achieved by forward Bragg diffraction (FBD) from a 30-micron-thin diamond crystal in the [110] orientation employing the (220) symmetric Bragg reflection. FBD from the same crystal using the (111) asymmetric Bragg reflection will provide monochromatization in a 3 keV to 5 keV spectral range. In the 7-keV to 10-keV spectral range, a 100-micron crystal in the [100] orientation will be used employing FBD with the (400) symmetric Bragg reflection. Two almost defect-free diamond crystals in the required orientations and thicknesses are mounted in a strain-free mechanically-stable fashion on a common CVD diamond substrate using all-diamond components, ensuring radiation-safe XFEL operations with improved heat transport. We will present results of the optical and engineering designs, manufacturing, and x-ray diffraction topography characterization of the diamond double-crystal system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP001  
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MOP003 Concept for a Seeded FEL at FLASH2 ion, FEL, laser, undulator 34
 
  • C. Lechner, R.W. Aßmann, J. Bödewadt, M. Dohlus, N. Ekanayake, G. Feng, I. Hartl, T. Laarmann, T. Lang, L. Winkelmann, I. Zagorodnov
    DESY, Hamburg, Germany
  • A. Azima, M. Drescher, Th. Maltezopoulos, T. Plath, J. Roßbach, W. Wurth
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • S. Khan, T. Plath
    DELTA, Dortmund, Germany
 
  The free-electron laser (FEL) FLASH is a user facility delivering photon pulses down to 4 nm wavelength. Recently, the second FEL undulator beamline 'FLASH2' was added to the facility. Operating in self-amplified spontaneous emission (SASE) mode, the exponential amplification process is initiated by shot noise of the electron bunch resulting in photon pulses of limited temporal coherence. In seeded FELs, the FEL process is initiated by coherent seed radiation, improving the longitudinal coherence of the generated photon pulses. The conceptual design of a possible seeding option for the FLASH2 beamline envisages the installation of the hardware needed for high-gain harmonic generation (HGHG) seeding upstream of the already existing undulator system. In this contribution, we present the beamline design and numerical simulations of the seeded FEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP003  
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MOP005 FEL Pulse Shortening by Superradiance at FERMI ion, FEL, laser, free-electron-laser 38
 
  • N.S. Mirian, L. Giannessi
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • S. Spampinati
    Private Address, warrigton, United Kingdom
 
  Explorations of saturated superradiant regime is one of the methods that could be used to reduce the duration of the pulses delivered by FERMI. Here we present simulation studies that show the possible application of a superradiant cascade leading to a minimum pulse duration below 8 fs and to a peak power exceeding the GW level in both FEL lines FEL-1 and FEL-2.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP005  
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MOP008 Status of the Hard X-Ray Self-Seeding Project at the European XFEL ion, FEL, laser, free-electron-laser 42
 
  • G. Geloni, S. Karabekyan, L. Samoylova, S. Serkez, H. Sinn
    XFEL. EU, Hamburg, Germany
  • V.D. Blank, S. Terentiev
    TISNCM, Troitsk, Russia
  • W. Decking, C. Engling, N. Golubeva, V. Kocharyan, B. Krause, S. Lederer, S. Liu, A. Petrov, E. Saldin, T. Wohlenberg
    DESY, Hamburg, Germany
  • X. Dong
    European X-Ray Free-Electron Laser Facility GmbH, Schelefeld, Germany
  • D. Shu
    ANL, Argonne, Illinois, USA
 
  A Hard X-ray Self-Seeding setup is currently under realization at the European XFEL, and will be ready for installation in 2018. The setup consists of two single-crystal monochromators that will be installed at the SASE2 undulator line. In this contribution, after a short summary of the physical principles and of the design, we will discuss the present status of the project including both electron beam and X-ray optics hardware. We will also briefly discuss the expected performance of the setup, which is expected to produce nearly Fourier-limited pulses of X-ray radiation with increased brightness compared to the baseline of the European XFEL, as well as possible complementary uses of the two electron chicanes.  
poster icon Poster MOP008 [2.445 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP008  
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MOP010 Constraints on Pulse Duration Produced by Echo-Enabled Harmonic Generation ion, laser, radiation, undulator 46
 
  • G. Penn
    LBNL, Berkeley, California, USA
  • B.W. Garcia, E. Hemsing, G. Marcus
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract Nos. DE-AC02-05CH11231 and DE-AC02-76SF00515.
Echo-enabled harmonic generation (EEHG) is well-suited for producing long, coherent pulses at high harmonics of seeding lasers. There have also been schemes proposed to adapt EEHG to output extremely short, sub-fs pulses by beam manipulations or through extremely short seed lasers, but the photon flux is generally lower than that produced by other schemes. For the standard EEHG layout, it is still interesting to consider different parameter regimes and evaluate how short a pulse can be generated. EEHG at high harmonics uses a large dispersive chicane which can change the relative distance of electrons by substantial distances, even longer than a typical FEL coherence length. We evaluate the ability to produce short pulses (in the femtosecond to 10-fs range) using a combination of theory and simulations.
 
poster icon Poster MOP010 [0.451 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP010  
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MOP011 Strongly Tapered Undulator Design for High Efficiency and High Gain Amplification at 266 nm undulator, ion, quadrupole, simulation 49
 
  • Y. Park, P. Musumeci, N.S. Sudar
    UCLA, Los Angeles, USA
  • D.L. Bruhwiler, C.C. Hall, S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
  • A.Y. Murokh
    RadiaBeam, Santa Monica, California, USA
  • Y. Sun, A. Zholents
    ANL, Argonne, Illinois, USA
 
  Tapering Enhanced Stimulated Superradiant Amplification (TESSA) is a scheme developed at UCLA to increase efficiency of Free Electron Laser (FEL) light from less than 0.1% to above 10% using strongly tapered undulators and prebunched electron beams. Initial results validating this method have already been obtained at 10-um wavelength at Brookhaven National Laboratory. In this paper we will discuss the design of an experiment to demonstrate the TESSA scheme at high gain and shorter wavelength (266 nm) using the Linac Extension Area (LEA) beamline at the Advanced Photon Source of Argonne National Laboratory (ANL) to obtain conversion efficiencies around 10% depending on the length of the tapered undulator (up to 4m).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP011  
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MOP013 Hundred-Gigawatt X-Ray Self-Seeded High-Gain Harmonic Generation ion, FEL, undulator, radiation 53
 
  • L. Zeng, S. Huang, K.X. Liu, W. Qin, G. Zhao
    PKU, Beijing, People's Republic of China
  • Y. Ding, Z. Huang
    SLAC, Menlo Park, California, USA
 
  Self-seeded high-gain harmonic generation is a possible way to extend the wavelength of a soft x-ray free-electron laser (FEL). We have carried out simulation study on harmonic generation within the photon energy range from 2 keV to 4.5 keV, which is difficult to achieve due to a lack of monochromator materials. In this work, we demonstrate the third harmonic FEL with the fundamental wavelength at 1.52 nm. Our results shows that, by using undulator tapering technique, sub-terawatt narrow-bandwidth FEL output can be obtained.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP013  
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MOP016 Comparing FEL Codes for Advanced Configurations ion, FEL, simulation, laser 60
 
  • B.W. Garcia, G. Marcus
    SLAC, Menlo Park, California, USA
  • L.T. Campbell
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  • S. Reiche
    PSI, Villigen PSI, Switzerland
 
  Various FEL codes employ different approximations and strategies to model the FEL radiation generation process. Many codes perform averaging procedures over various length scales in order to simplify the underlying dynamics. As FELs are developed in more advanced configurations beyond simple SASE, the assumptions of some codes may be called into question. We compare the unaveraged code Puffin to averaged FEL codes including a new version of GENESIS in a variety of situations. In particular, we study a harmonic lasing setup, a High-Gain Harmonic Generation (HGHG) configuration modeled after the FERMI setup, and a potential Echo-Enabled Harmonic Generation (EEHG) configuration also at FERMI. We find the codes are in good agreement, although small discrepancies do exist.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP016  
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MOP017 Echo-Enabled Harmonic Generation Results with Energy Chirp ion, laser, bunching, FEL 64
 
  • B.W. Garcia, M.P. Dunning, C. Hast, E. Hemsing, T.O. Raubenheimer, G. Stupakov
    SLAC, Menlo Park, California, USA
  • D. Xiang
    Shanghai Jiao Tong University, Shanghai, People's Republic of China
 
  We report here on several experimental results from the NLCTA at SLAC involving chirped Echo-Enabled Harmonic Generation (EEHG) beams. We directly observe the sensitivity of the different n EEHG modes to a linear beam chirp. This differential sensitivity results in a multi-color EEHG signal which can be fine tuned through the EEHG parameters and beam chirp. We also generate a beam which, due to a timing delay between the two seed lasers, contains both regions of EEHG and High-Gain Harmonic Generation (HGHG) bunching. The two regions are clearly separated on the resulting radiation spectrum due to a linear energy chirp, and one can simultaneously monitor their sensitivities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP017  
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MOP018 Distributed Self-Seeding Scheme for LCLS-II ion, undulator, simulation, FEL 68
 
  • C. Yang, Y. Feng, T.O. Raubenheimer, C.-Y. Tsai, J. Wu, M. Yoon, G. Zhou
    SLAC, Menlo Park, California, USA
  • B. Yang
    University of Texas at Arlington, Arlington, USA
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Self-seeding is a successful approach for generating high-brightness x-ray free electron laser (XFEL). A single-crystal monochromator in-between the undulator sections to generate a coherent seed is adopted in LCLS. However, for a high-repetition rate machine like LCLS-II, the crystal monochromator in current setup cannot sustain the high average power; hence a distributed self-seeding scheme utilizing multi-stages is necessary. Based on the criteria set on the crystal, the maximum allowed x-ray energy deposited in the crystal will determine the machine configuration for such a distributed self-seeding scheme. In this paper, a distributed self-seeding configuration is optimized for LCLS-II type projects in the hard x-ray FEL energy regime. The study is carried out based on numerical simulation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP018  
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MOP019 Transient Thermal Stress Wave Analysis of a Thin Diamond Crystal Under Laser Heat Load ion, laser, FEL, site 72
 
  • J. Wu
    SLAC, Menlo Park, California, USA
  • B. Yang
    University of Texas at Arlington, Arlington, USA
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
When a laser pulse impinges on a thin crystal, energy is deposited resulting in an instantaneous temperature surge in the local volume and emission of stress waves. In the present work, we perform a transient thermal stress wave analysis of a diamond layer 200 μm thick in the low energy deposition per pulse regime. The layer thickness and laser spot size are comparable. The analysis reveals the characteristic non-planar stress wave propagation. The stress wave emission lasts by hundreds of nanoseconds, at a time scale relevant to the high-repetition-rate FELs at the megahertz range. The kinetic energy converted from the thermal strain energy is calculated, which may be important to estimate the vibrational amplitude of the thin crystal when excited under repeated heat loads. The transient heat transfer plays an important role in draining the mechanical energy during the dynamic wave emission process.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP019  
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MOP020 Sideband Instability in a Tapered Free Electron Laser ion, undulator, FEL, laser 76
 
  • C.-Y. Tsai
    Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
  • J. Wu, C. Yang
    SLAC, Menlo Park, California, USA
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • G. Zhou
    IHEP, Beijing, People's Republic of China
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
For a high-gain tapered free electron laser (FEL), it is known that there is a so-called second saturation point where the FEL power growth stops. Sideband instability is one of the major reasons leading to this second-saturation and thus prevents reaching terawatt-level power output in an X-ray FEL. It is believed that a strong taper can effectively suppress the sideband instability and further improve the efficiency and peak power. In this paper, we give quantitative analysis on the necessary taper gradient to minimize the sideband growth. We also discuss the transverse effects of induced electron de-trapping which is yet another major reason for the occurrence of the second-saturation point even with a strong enough taper. The study is carried out analytically together with numerical simulation. The numerical parameters are taken from LCLS-II type electron bunch and undulator system.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP020  
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MOP021 Sideband Suppression in Tapered Free Electron Lasers ion, FEL, undulator, laser 80
 
  • C.-Y. Tsai
    Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
  • J. Wu, C. Yang
    SLAC, Menlo Park, California, USA
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • G. Zhou
    IHEP, Beijing, People's Republic of China
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
It is known that in a high-gain tapered free electron laser, there is the so-called second saturation point where the FEL power ceases to grow. Sideband instability is one of the major reasons causing this second saturation. Electron synchrotron oscillation coupling to the wideband SASE radiation leads to the appearance of sidebands in the FEL spectrum, and is believed to prevent a self-seeding tapered FEL from reaching very high peak power. A strong seed together with a fresh electron bunch or a fresh slice in conjunction with strong tapering of undulators can effectively suppress the sideband instability. In this paper, we give quantitative analysis on the necessary seed power as well as undulator tapering to minimize the sideband effects. The study is carried out semi-analytically together with numerical simulation. The machine and electron bunch parameters are chosen as those of PAL-XFEL and LCLS-II.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP021  
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MOP023 Two-Color Soft X-Ray Generation at the SXFEL User Facility Based on the EEHG Scheme ion, FEL, laser, radiation 84
 
  • Z. Qi, C. Feng, B. Liu, W.Y. Zhang, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
 
  We study the two-color soft x-ray generation at the Shanghai soft X-ray Free Electron Laser (SXFEL) user facility based on the echo-enabled harmonic generation (EEHG) scheme. Using the twin-pulse seed laser with different central wavelengths, an preliminary simulation result indicates that two-color soft x-ray FEL radiation with wavelengths at 8.890 nm and 8.917 nm can be obtained from the ultraviolet seed laser. The radiation power is about 600 MW and the time delay is adjustable.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP023  
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MOP026 Study of an Echo-Enabled Harmonic Generation Scheme for the French FEL Project LUNEX5 ion, FEL, laser, undulator 91
 
  • E. Roussel, M.-E. Couprie, A. Ghaith, A. Loulergue
    SOLEIL, Gif-sur-Yvette, France
  • C. Evain
    PhLAM/CERLA, Villeneuve d'Ascq, France
  • D. Garzella
    CEA, Gif-sur-Yvette, France
 
  In the French LUNEX5 project (Laser à électrons libres Utilisant un Nouvel accélérateur pour l'exploitation du rayonnement X de 5ème génération), a compact advanced free-electron laser (FEL) is driven by either a superconducting linac or a laser-plasma accelerator that can deliver a 400-MeV electron beam. LUNEX5 aims to produce FEL radiation in the ultraviolet and extreme ultraviolet (EUV) range. To improve the longitudinal coherence of the FEL pulses and reduce the gain length, it will operate in Echo-Enabled Harmonic Generation (EEHG) seeding configuration. EEHG is a strongly nonlinear harmonic up-conversion process based on a two-seed laser interaction that enables to reach very high harmonics of the seed laser. Recent experimental demonstration of ECHO-75, starting from an infrared seed laser, was recently achieved at SLAC and is opened the way for EEHG scheme in the EUV and soft x-ray range. Furthermore, FELs are promising candidates for the next generation of lithography technology using EUV light. In this work, we report a preliminary study of EEHG scheme for LUNEX5 in order to reach the target wavelength of 13.5 nm, currently expected for application to lithography.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP026  
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MOP027 Seeding of Electron Bunches in Storage Rings ion, laser, radiation, storage-ring 94
 
  • S. Khan, B. Büsing, N.M. Lockmann, C. Mai, A. Meyer auf der Heide, R. Niemczyk, B. Riemann, B. Sawadski, M. Suski, P. Ungelenk
    DELTA, Dortmund, Germany
 
  Funding: Funded by BMBF (05K16PEA), MERCUR (Pr-2014-0047), DFG (INST 212/236-1 FUGG) and the Land NRW.
Seeding schemes for free-electron lasers (FELs) can be adopted to generate ultrashort radiation pulses in storage rings by creating laser-induced microbunches within a short slice of a long electron bunch giving rise to coherent emission at harmonics of the seed wavelength. In addition, terahertz (THz) radiation is produced over many turns. Even without FEL gain, a storage ring is an excellent testbed to study many aspects of seeding schemes and short-pulse diagnostics, given the high repetition rate and stability of the electron bunches. At DELTA, a storage ring operated by the TU Dortmund University in Germany, coherent harmonic generation (CHG) with single and double 40-fs pulses is performed at seed wavelengths of 800 nm or 400 nm. Seeding with intensity-modulated 10-ps pulses is also studied generating tunable narrowband THz radiation. As a preparation for echo-enabled harmonic generation (EEHG), simultaneous seeding with 800/400-nm pulses in two different undulators is performed and several techniques are employed to ensure optimum timing between the seed pulses. The paper describes these experiments and gives an outlook of future applications of seeding at storage rings.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP027  
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MOP028 Extraction of the Longitudinal Profile of the Transverse Emittance From Single-Shot RF Deflector Measurements at sFLASH ion, FEL, emittance, laser 98
 
  • T. Plath, Ph. Amstutz, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • J. Bödewadt, N. Ekanayake, T. Laarmann, C. Lechner
    DESY, Hamburg, Germany
  • S. Khan
    DELTA, Dortmund, Germany
 
  The gain length of the free-electron laser (FEL) process strongly depends on the slice energy spread, slice emittance, and current of the electron bunch. At an FEL with only moderately compressed electron bunches, the slice energy spread is mainly determined by the compression process. In this regime, single-shot measurements using a transverse deflecting rf cavity enable the extraction of the longitudinal profile of the transverse emittance. At the free-electron laser FLASH at DESY, this technique was used to determine the slice properties of the electron bunch set up for seeded operation in the sFLASH experiment. Thereby, the performance of the seeded FEL process as a function of laser-electron timing can be predicted from these slice properties with the semi-analytical Ming-Xie model where only confined fractions of the electron bunch are stimulated to lase. The prediction is well in line with the FEL peak power observed during an experimental laser-electron timing scan. The power profiles of the FEL pulses were reconstructed from the longitudinal phase-space measurements of the seeded electron bunch that was measured with the rf deflector.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP028  
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MOP031 First Operation of a Harmonic Lasing Self-Seeded FEL ion, FEL, undulator, operation 102
 
  • E. Schneidmiller, B. Faatz, M. Kuhlmann, J. Rönsch-Schulenburg, S. Schreiber, M. Tischer, M.V. Yurkov
    DESY, Hamburg, Germany
 
  Harmonic lasing is a perspective mode of operation of X-ray FEL user facilities that allows it to provide brilliant beams of higher-energy photons for user experiments. Another useful application of harmonic lasing is so called Harmonic Lasing Self-Seeded Free Electron Laser (HLSS FEL), that allows it to improve spectral brightness of these facilities. In the past, harmonic lasing has been demonstrated in the FEL oscillators in infrared and visible wavelength ranges, but not in high-gain FELs and not at short wavelengths. In this paper, we report on the first evidence of the harmonic lasing and the first operation of the HLSS FEL at the soft X-ray FEL user facility FLASH in the wavelength range between 4.5 nm and 15 nm. Spectral brightness was improved in comparison with Self-Amplified Spontaneous emission (SASE) FEL by a factor of six in the exponential gain regime. A better performance of HLSS FEL with respect to SASE FEL in the post-saturation regime with a tapered undulator was observed as well. The first demonstration of harmonic lasing in a high-gain FEL and at a short wavelength paves the way for a variety of applications of this new operation mode in X-ray FELs.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP031  
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MOP033 Baseline Parameters of the European XFEL ion, FEL, undulator, photon 109
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
 
  We present the latest update of the baseline parameters of the European XFEL. It is planned that the electron linac will operate at four fixed electron energies of 8.5, 12, 14, and 17.5 GeV. Tunable gap undulators provide the possibility to change the radiation wavelength in a wide range. Operation with different bunch charges (0.02, 0.1, 0.25, 0.5 and 1 nC) provides the possibility to operate XFEL with different radiation pulse duration. We also discuss potential extension of the parameter space which does not require new hardware and can be realized at a very early stage of the European XFEL operation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP033  
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MOP035 Optimum Undulator Tapering of SASE FEL: Theory and Experimental Results From FLASH2 ion, undulator, FEL, radiation 113
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
 
  Optimization of the amplification process in FEL amplifier with diffraction effects taken into account results in a specific law of the undulator tapering.* It is a smooth function with quadratic behavior in the beginning of the tapering section which transforms to a linear behavior for a long undulator. In practice, an undulator consists of a sequence of modules of fixed length separated with intersections. Two modes of undulator tapering can be implemented: step tapering and smooth tapering. Step tapering uses a step change of the undulator gap from module to module, while smooth tapering assumes additional linear change of the gap along each module. In this report, we simulate the performance of both experimental options and compare with theoretical limit.
* E.A. Schneidmiller and M.V. Yurkov, Optimization of a high efficiency free electron laser amplifier, Phys. Rev. ST Accel. Beams 18-030705 (2015).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP035  
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MOP036 Frequency Doubling Mode of Operation of Free Electron Laser FLASH2 ion, radiation, undulator, operation 117
 
  • M. Kuhlmann, E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
 
  We report on the results of the first operation of a frequency doubler at free electron laser FLASH2. The scheme uses the feature of the variable-gap undulator. The undulator is divided into two parts. The second part of the undulator is tuned to the double frequency of the first part. The amplification process in the first undulator part is stopped at the onset of the nonlinear regime, such that nonlinear higher-harmonic bunching in the electron beam density becomes pronouncing, but the radiation level is still small to disturb the electron beam significantly. The modulated electron beam enters the second part of the undulator and generates radiation at the second harmonic. A frequency doubler allows operation in a two-color mode and operation at shorter wavelengths with respect to standard SASE scheme. Tuning of the electron beam trajectory, phase shifters and compression allows tuning of intensities of the first and the second harmonic. The shortest wavelength of 3.1 nm (photon energy 400 eV) has been achieved with a frequency doubler scheme, which is significantly below the design value for the standard SASE option.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP036  
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MOP037 Opportunities for Two-Color Experiments at the SASE3 Undulator Line of the European XFEL ion, FEL, undulator, photon 121
 
  • S. Serkez, G. Geloni, T. Mazza, M. Meyer
    XFEL. EU, Schenefeld, Germany
  • V. Kocharyan, E. Saldin
    DESY, Hamburg, Germany
 
  As is well known, the installation of a simple magnetic chicane in the baseline undulator of an XFEL allows for producing two-color FEL pulses. In this work we discuss the possibility of applying this simple and cost-effective method at the SASE3 soft X-ray beamline of the European XFEL. We consider upgrades of this method that include the further installation of a mirror chicane. We also discuss the scientific interest of this upgrade for the Small Quantum Systems (SQS) instrument, in connection with the high-repetition rate of the European XFEL, and we provide start-to-end simulations up to the radiation focus on the sample, proving the feasibility of our concept. Our proposed setup has been recently funded by the Finnish Research Infrastructure (FIRI) and will be built at SASE3 in 2020-2021.  
poster icon Poster MOP037 [1.849 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP037  
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MOP038 Overview of the Soft X-Ray Line Athos at SwissFEL ion, undulator, FEL, photon 125
 
  • R. Ganter, S. Bettoni, H.-H. Braun, M. Calvi, P. Craievich, R. Follath, C.H. Gough, F. Löhl, M. Paraliev, L. Patthey, M. Pedrozzi, E. Prat, S. Reiche, T. Schmidt, A.Z. Zandonella
    PSI, Villigen PSI, Switzerland
 
  The Athos line will cover the photon energy range from 250 to 1900 eV and will operate parallel to the hard x-ray line Aramis of SwissFEL. Athos consists of fast kicker magnets, a dog-leg transfer line, a small linac and 16 APPLE undulators. The Athos undulators follow a new design: the so-called APPLE X design where the 4 magnet arrays can be moved radially in a symmetric way. Besides mechanical advantages of such a symmetric distribution of forces, this design allows for easy photon energy scans at a constant polarization or for the generation of transverse magnetic gradients. Another particularity of the Athos FEL line is the inclusion of a short magnetic chicane between every undulator segment. These chicanes will allow the FEL to operate in optical klystron mode, high-brightness SASE mode, or superradiance mode. A larger delay chicane will split the Athos line into two sections such that two colors can be produced with adjustable delay. Finally a post undulator transverse deflecting cavity will be the key tool for the commissioning of the FEL modes. The paper will present the current status of this four years project started in 2017.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP038  
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MOP039 Possible Method for the Control of SASE Fluctuations ion, FEL, undulator, bunching 129
 
  • N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  It is well known that because the SASE FEL starts up from the intrinsic electron beam shot noise, there are corresponding fluctuations in the useful properties of the output pulses which restrict their usability for many applications. In this paper, we discuss possible new methods for controlling the level of fluctuations in the output pulses.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP039  
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MOP041 Commissioning of FEL-Based Coherent Electron Cooling System ion, SRF, gun, FEL 132
 
  • V. Litvinenko, Z. Altinbas, R. Anderson, S.A. Belomestnykh, K.A. Brown, J.C.B. Brutus, A.J. Curcio, A. Di Lieto, C. Folz, D.M. Gassner, T. Hayes, R.L. Hulsart, P. Inacker, J.P. Jamilkowski, Y.C. Jing, D. Kayran, R. Kellermann, R.F. Lambiase, G.J. Mahler, M. Mapes, A. Marusic, W. Meng, K. Mernick, R.J. Michnoff, T.A. Miller, M.G. Minty, G. Narayan, P. Orfin, D. Phillips, I. Pinayev, T. Rao, D. Ravikumar, J. Reich, G. Robert-Demolaize, T. Roser, S.K. Seberg, F. Severino, B. Sheehy, J. Skaritka, L. Smart, K.S. Smith, L. Snydstrup, V. Soria, R. Than, C. Theisen, J.E. Tuozzolo, J. Walsh, E. Wang, G. Wang, D. Weiss, B. P. Xiao, T. Xin, A. Zaltsman, Z. Zhao
    BNL, Upton, Long Island, New York, USA
  • C.H. Boulware, T.L. Grimm
    Niowave, Inc., Lansing, Michigan, USA
  • K. Mihara
    Stony Brook University, Stony Brook, USA
  • I. Petrushina
    SUNY SB, Stony Brook, New York, USA
  • K. Shih
    SBU, Stony Brook, New York, USA
  • W. Xu
    PKU, Beijing, People's Republic of China
 
  Funding: DoE NP office, grant DE-FOA-0000632, NSF grant PHY-1415252
In this talk we are presenting the most recent results from the commissioning of unique Coherent Electron Cooling system, which is using an FEL amplifier to facilitate cooling of hadrons by an electron beam. We present achieved results as well as changes we encountered in the process.
 
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MOP042 Status of Seeding Development at sFLASH ion, laser, FEL, experiment 136
 
  • V. Grattoni, R.W. Aßmann, J. Bödewadt, I. Hartl, T. Laarmann, C. Lechner, M.M. Mohammad Kazemi, A. Przystawik
    DESY, Hamburg, Germany
  • A. Azima, M. Drescher, W. Hillert, L.L. Lazzarino, V. Miltchev, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • S. Khan, N.M. Lockmann, T. Plath
    DELTA, Dortmund, Germany
 
  The experimental seeding setup at FLASH has operated now for two years in high-gain harmonic generation mode. Using a transverse deflecting structure downstream of the seeding section allows a temporal characterization of seeded electron bunches. In addition, temporal characterization of the seeded FEL beam can be performed in a dedicated diagnostic hutch. In this contribution, we give an overview of the latest achievements and present an outlook of the planned studies.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP042  
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MOP043 Plasma Wakefield Accelerated Beams for Demonstration of FEL Gain at FLASHForward ion, plasma, FEL, injection 140
 
  • P. Niknejadi, A. Aschikhin, C. Behrens, S. Bohlen, R.T.P. D'Arcy, J. Dale, L. Di Lucchio, M. Felber, B. Foster, L. Goldberg, J.-N. Gruse, Z. Hu, S. Karstensen, A. Knetsch, O. S. Kononenko, V. Libov, K. Ludwig, A. Martinez de la Ossa, F. Marutzky, T.J. Mehrling, J. Osterhoff, C.A.J. Palmer, K. Poder, P. Pourmoussavi, M. Quast, J.-H. Röckemann, J. Schaffran, L. Schaper, H. Schlarb, B. Schmidt, S. Schreiber, S. Schröder, J.-P. Schwinkendorf, B. Sheeran, M.J.V. Streeter, G.E. Tauscher, V. Wacker, S. Weichert, S. Wesch, P. Winkler, S. Wunderlich, J. Zemella
    DESY, Hamburg, Germany
  • A.R. Maier
    CFEL, Hamburg, Germany
  • A.R. Maier, A. Martinez de la Ossa, M. Meisel, J.-H. Röckemann
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • C.B. Schroeder
    LBNL, Berkeley, California, USA
  • V. Wacker
    University of Hamburg, Hamburg, Germany
 
  Funding: Work supported by Helmholtz ARD program and VH-VI-503
FLASHForward is the Future-ORiented Wakefield Accelerator Research and Development project at the DESY free-electron laser (FEL) facility FLASH. It aims to produce high-quality, GeV-energy electron beams over a plasma cell of a few centimeters. The plasma is created by means of a 25 TW Ti:Sapphire laser system. The plasma wakefield will be driven by high-current-density electron beams extracted from the FLASH accelerator. The project focuses on the advancement of plasma-based particle acceleration technology through the exploration of both external and internal witness-beam injection schemes. Multiple conventional and cutting-edge diagnostic tools, suitable for diagnosis of short electron beams, are under development. The design of the post-plasma beamline sections will be finalized based on the result of these aforementioned diagnostics. In this paper, the status of the project, as well as the progress towards achieving its overarching goal of demonstrating FEL gain via plasma wakefield acceleration, is discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP043  
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MOP046 Progress of Delhi Light Source at IUAC, New Delhi ion, cathode, laser, undulator 149
 
  • S. Ghosh, S. R. Abhilash, R.K. Bhandari, G.K. Chaudhari, V.J. Joshi, D. Kabiraj, D. Kanjilal, B. Karmakar, J. Karmakar, N. Kumar, S. Kumar, A. Pandey, P. Patra, G.O. Rodrigues, B.K. Sahu, A. Sharma, S. Tripathi
    IUAC, New Delhi, India
  • A. Aryshev, M.K. Fukuda, S. Fukuda, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • U. Lehnert, P. Michel
    HZDR, Dresden, Germany
  • V. Naik, A. Roy
    VECC, Kolkata, India
  • T. Rao
    BNL, Upton, Long Island, New York, USA
  • M. Tischer
    DESY, Hamburg, Germany
 
  Funding: This project is jointly supported by Inter University Accelerator Center and Board of Research in Nuclear Science.
The first phase of the pre-bunched FEL based on the Photoinjector RF electron gun, known as Delhi Light Source (DLS),* has been planned at Inter University Accelerator Centre (IUAC), New Delhi. The electron gun made from OFHC copper had already been fabricated and tested with low power RF at KEK, Japan. The beam optics calculation by using ASTRA, GPT codes has been performed and radiation produced from the pre-bunched electron bunches are being calculated.** The high power RF systems will be commissioned at IUAC by the beginning of 2018. The design of the laser system is being finalized and assembly/testing of the complete laser system will be started soon at KEK. The initial design of the photocathode deposition mechanism has also been completed and its procurement/development process will start shortly. The first version of the undulator magnet design has been completed and further improvements are underway.*** The initial arrangements of the DLS beam line have been worked out and various beam diagnostics components are being finalised. The production of the electron beam and THz radiation is expected by 2018 and 2019, respectively.
* S. Ghosh et al., NIM-B, (2017) in press.
** V. Joshi et al., Proc. of this conference.
*** S. Tripathi et al., Proc. of this conference.
 
poster icon Poster MOP046 [1.598 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP046  
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MOP047 Design Calculation on Beam Dynamics and THz Radiation of Delhi Light Source ion, radiation, undulator, simulation 153
 
  • V.J. Joshi, R.K. Bhandari, S. Ghosh, D. Kanjilal, B. Karmakar, J. Karmakar, N. Kumar, S. Tripathi
    IUAC, New Delhi, India
  • A. Aryshev
    KEK, Ibaraki, Japan
  • U. Lehnert
    HZDR, Dresden, Germany
 
  Funding: This project is jointly supported by Inter University Accelerator Center and Board of Research in Nuclear Science.
The development of a compact light source facility, Delhi Light Source (DLS), based on a pre-bunched free electron laser, has been initiated at Inter University Accelerator Centre (IUAC).* A photocathode-based normal conducting RF gun will generate a low-emittance 'comb' electron beam with a maximum energy of ~8 MeV which when injected into ~ 1.5 metre compact undulator magnet (~0.4 < Krms < ~2) will produce intense THz radiation in the frequency range of 0.15 THz to 3.0 THz.** Each microbunch of the electron beam is expected to emit super-radiant radiation, and an enhancement in the overall spectral power can be achieved if the frequency (inverse of the spatial separation) of the electron microbunches coincides with that of the THz radiation being emitted. There will be provisions to vary the spatial separation between the successive microbunches of the 'comb' beam so that by varying the undulator magnetic field and/or electron energy, the THz frequency range can be tuned. The results of the beam optics for the entire range of frequencies mentioned above along with the detailed information of the radiation to be generated from the facility will be presented in the paper.
* S. Ghosh et al., NIMB-2017, in press.
** S.Tripathi et al., Proc. of this conference.
 
poster icon Poster MOP047 [0.959 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP047  
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MOP048 A Compact THz FEL at KAERI: the Project and the Status ion, FEL, undulator, GUI 156
 
  • S.V. Miginsky, S. Bae, B.A. Gudkov, K.H. Jang, Y.U. Jeong, K. Lee, J. Mun, S. Setiniyaz
    KAERI, Daejon, Republic of Korea
  • S. H. Park
    Korea University Sejong Campus, Sejong, Republic of Korea
 
  A new compact THz free electron laser driven by a microtron is being recently developed at KAERI. It uses a hybrid electromagnetic undulator. A novel scheme of injection/extraction/outcoupling is developed. The machine is partially assembled and commissioned. Characteristic features and current state are described in the paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP048  
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MOP049 Development of Compact THz Coherent Undulator Radiation Source at Kyoto University ion, radiation, undulator, detector 158
 
  • S. Krainara, T. Kii, H. Ohgaki, H. Zen
    Kyoto University, Kyoto, Japan
  • S. Suphakul
    Chiang Mai University, Chiang Mai, Thailand
 
  A new THz Coherent Undulator Radiation (THz-CUR) source has been developed to generate intense quasi-monochromatic THz radiation at the Institute of Advanced Energy, Kyoto University. The system consists of a photocathode RF gun, bunch compression chicane, quadrupole magnets, and short planar undulator. The total length of this system is around 5 meters. At present, this compact accelerator has successfully started giving the THz-CUR in the frequency range of 0.16 - 0.65 THz. To investigate the performance of the source, the relationship between the total radiation energy, peak power and power spectrum as a function of bunch charge at the different undulator gaps were measured. The results are reported in the paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP049  
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MOP052 First Observation of Coherent THz Undulator Radiation Driven by NSRRC High Brightness Photo-Injector ion, radiation, undulator, linac 170
 
  • M.C. Chou, K.T. Hsu, S.Y. Hsu, N.Y. Huang, C.-S. Hwang, J.-Y. Hwang, J.C. Jan, C.K. Kuan, W.K. Lau, A.P. Lee, C.C. Liang, G.-H. Luo, I.C. Sheng
    NSRRC, Hsinchu, Taiwan
  • Y.H. Wen
    NTHU, Hsinchu, Taiwan
 
  Generation and characterization of coherent undulator radiation in the THz region using the NSRRC S-band photo-injector linac system is achieved. The system consists of a laser photocathode RF gun and one 5.2-m long S-band accelerating linac. Electron bunches in the linac can be accelerated and compressed simultaneously by velocity bunching. In this work, narrow-band tunable fully-coherent THz radiation can be produced from a U100 planar undulator when it is driven by a 100 pC electron bunch with effective bunch length of 90 fs. The experimental setup and the measurement of the power and the frequency spectrum of the coherent THz undulator radiation are reported.  
poster icon Poster MOP052 [2.116 MB]  
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MOP053 High Spectral Density Compton Back-Scattered Gamma-Ray Sources at Fermilab ion, laser, photon, radiation 174
 
  • D. Mihalcea, A. Khizhanok, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • B.T. Jacobson, A.Y. Murokh
    RadiaBeam, Santa Monica, California, USA
  • P. Piot, J. Ruan
    Fermilab, Batavia, Illinois, USA
 
  A ~1 MeV gamma-ray source is planned to be built at Fermilab following the completion of the ~300 MeV superconducting linac. The high-energy photons are back-scattered from the interactions between electrons and high-intensity IR laser pulses. In this contribution, we discuss some of the experiment design challenges and evaluate the performances of the gamma-ray source. We expect the peak brilliance to be of the order of 1022 photons/s-(mm-mrad)2-0.1\% BW and the spectral density of the radiation in excess of 3x105 photons/s/eV.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP053  
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MOP054 CLARA Facility Layout and FEL Schemes ion, FEL, undulator, laser 178
 
  • D.J. Dunning
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  CLARA is a new FEL test facility being developed at STFC Daresbury Laboratory in the UK. Commissioning has started on the front-end (photo-injector and linac) while the design of the later stages is still being finalised. We present the latest design work, focusing on the layout and specification of components in and around the undulator sections. We give an overview of the design and modelling of the FEL schemes planned to be tested.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP054  
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MOP055 SCLF: An 8-GeV CW SCRF Linac-Based X-Ray FEL Facility in Shanghai ion, FEL, undulator, linac 182
 
  • Z.T. Zhao, D. Wang, L. Yin
    SINAP, Shanghai, People's Republic of China
  • Z.H. Yang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  The Shanghai Coherent Light Facility (SCLF) is a newly proposed high repetition-rate X-ray FEL facility, based on an 8-GeV CW superconducting RF linac. It will be located at Zhangjiang High-tech Park, close to the SSRF campus in Shanghai, at the depth of ~38m underground and with a total length of 3.1 km. Using 3 phase-I undulators, the SCLF aims at generating X-rays between 0.4 and 25 keV at rates up to 1MHz. This paper describes the design concepts of this hard X-ray user facility.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP055  
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MOP059 Synchronized Mid-Infrared Pulses at the Fritz Haber Institute IR-FEL ion, FEL, cavity, laser 188
 
  • R. Kiessling, S. Gewinner, A. Paarmann, W. Schöllkopf, M. Wolf
    FHI, Berlin, Germany
 
  The combined application of FEL radiation and femtosecond table-top lasers for two-color spectroscopy demands an accurate pulse synchronization. In order to employ the Infared FEL at the Fritz Haber Institute for non-linear and time-resolved experiments, an RF-over-fiber-based timing system has been established. Using a balanced optical cross-correlation scheme, we determined an FEL micro-pulse timing jitter of 100-200 fs (rms). The long-term timing drift was found to be well correlated to the energy fluctuations of the accelerated electron bunches. By means of the jitter-corrected cross-correlation signal, we directly measure the FEL pulse shape at different cavity detunings. For large cavity detuning, narrowband IR radiation (~ 0.3 % FWHM) can be generated and utilized for high-resolution non-linear spectroscopy. On the other hand, sub-picosecond pulses are provided at small detuning, which are well-suited for time-resolved measurements. At intermediate detuning values, we observe the build-up and dynamics of multipulses that result in the well-known limit-cycle power oscillations.  
poster icon Poster MOP059 [1.535 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP059  
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MOP061 X-ray Regenerative Amplifier Free-Electron Laser Concepts for LCLS-II ion, FEL, simulation, cavity 192
 
  • G. Marcus, Y. Ding, J.P. Duris, Y. Feng, Z. Huang, J. Krzywinski, T.J. Maxwell, D.F. Ratner, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  • K.-J. Kim, R.R. Lindberg, Yu. Shvyd'ko
    ANL, Argonne, Illinois, USA
  • D.C. Nguyen
    LANL, Los Alamos, New Mexico, USA
 
  High-brightness electron beams that will drive the next generation of high-repetition rate X-ray FELs allow for the possibility of optical cavity-based feedback. One such cavity-based FEL concept is the Regenerative Amplifier Free-Electron Laser (RAFEL). This paper examines the design and performance of possible RAFEL configurations for LCLS-II. The results are primarily based on high-fidelity numerical particle simulations that show the production of high brightness, high average power, fully coherent, and stable X-ray pulses at LCLS-II using both the fundamental and harmonic FEL interactions.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP061  
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MOP062 X-ray FEL Oscillator Seeded Harmonic Amplifier for High Energy Photons ion, FEL, undulator, photon 196
 
  • W. Qin, J. Wu
    SLAC, Menlo Park, California, USA
  • K.-J. Kim, R.R. Lindberg
    ANL, Argonne, Illinois, USA
 
  High-power, high-energy X-ray pulses in the range of several tens of keV have important applications for material sciences.* The unique feature of an X-ray FEL Oscillator (XFELO) makes it possible to seed a harmonic amplifier to produce such high energy photons.** In this contribution, we present simulation studies using 14.4-keV output pulses from an XFELO to generate harmonics around 40 keV (3rd harmonic) and 60 keV (4th harmonic). Techniques such as undulator tapering and fresh bunch lasing are considered to improve the amplifier performance.
* MaRIE project: http://www.lanl.gov/science-innovation/science-facilities/marie/.
** K.-J. Kim, XFELO-Seeded Amplifier, talk on MaRIE workshop, 2016.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP062  
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MOP064 An Experimental Setup for Probing the Thermal Properties of Diamond Regarding Its Use in an XFELO ion, FEL, laser, experiment 200
 
  • C.P. Maag, I. Bahns, J. Roßbach, P. Thiessen
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • H. Sinn
    XFEL. EU, Hamburg, Germany
  • J. Zemella
    DESY, Hamburg, Germany
 
  Funding: Work supported by BMBF (FKZ 05K13GU4 + FKZ 05K16GU4)
This work presents an pump-probe setup for measuring the thermal evolution of diamond crystals at cryogenic temperatures under the heat load conditions of an X-ray free electron laser oscillator (XFELO). As the diamond Bragg reflectors of an XFELO are subjected to intense heat loads during operation, the correct understanding of the thermal evolution in diamond plays a major role in the correct modeling of an XFELO. Stoupin et al.* did a room temperature x-ray diffraction measurement on the nanosecond transient thermal response of diamond to an optical pulse. The measurements presented in this paper for the first time incorporate effects due to the very short penetration depth of only a few μm of an XFELO pulse in combination with the high mean free path in diamond at cryogenic temperatures. While at room temperature the heat equation based on Fourier's law accurately fits the measured results, this vastly changes due to the onset of ballistic processes at cryogenic temperatures. These changes, which are hard to predict theoretically, show the necessity of measurements of the thermal evolution in diamond with special regard to a correct mimicking of the heat load in an XFELO.
*S. Stoupin et al., Phys. Rev. B, vol. 86, p. 054301, 2012.
 
poster icon Poster MOP064 [2.239 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP064  
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MOP066 Free Electron Lasers in 2017 FEL, ion, undulator, laser 204
 
  • P.J. Neyman
    Compass Scientific Engineering, Compass Manufacturing Services, Fremont, USA
  • J. Blau, K. R. Cohn, W.B. Colson
    NPS, Monterey, California, USA
  • S.C. Gottschalk
    STI Optronics, Inc., Redmond, USA
  • A.M.M. Todd
    AES, Medford, New York, USA
 
  Forty-one years after the first operation of the short wavelength free electron laser (FEL) at Stanford University, there continue to be many important experiments, proposed experiments, and user facilities around the world. Properties of FELs in the infrared, visible, UV, and x-ray wavelength regimes are tabulated and briefly discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP066  
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TUA01 Recent FEL Experiments at FLASH ion, undulator, FEL, laser 210
 
  • S. Schreiber, E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
 
  The FLASH free-electron laser user facility at DESY (Hamburg, Germany) provides high brilliance SASE FEL radiation in the XUV and soft X-ray wavelength range. With the recent installation of a second undulator beamline (FLASH2), variable-gap undulators are now available. They now allow various experiments not possible with the FLASH1 fixed gap undulators. We report on experiments on tapering, harmonic lasing, reverse tapering, frequency doubling at FLASH2 and experiments using double pulses for specific SASE and THz experiments at FLASH1.  
slides icon Slides TUA01 [4.124 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUA01  
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TUA04 Suppression of the CSR Effects at a Dogleg Beam Transport Using DBA Lattice ion, optics, operation, FEL 216
 
  • T. Hara, T. Inagaki, C. Kondo, H. Maesaka, Y. Otake, H. Tanaka, K. Togawa
    RIKEN SPring-8 Center, Hyogo, Japan
  • K. Fukami
    JASRI/SPring-8, Hyogo, Japan
  • T. Hasegawa, O. Morimoto, S. Nakazawa, M. Yoshioka
    SES, Hyogo-pref., Japan
 
  Multi-beamline, multi-user operation is an important issue of linac-based XFELs to improve usability and efficiency of facilities. At SACLA, the multi-beamline operation had been tested since 2015 using two beamlines (BL2 and BL3). But the CSR effects at a 3-degree dogleg beam transport of BL2 caused a projected emittance growth and instability of the beam orbit due to a high peak current of 10 kA and a short bunch duration of SACLA. Consequently, stable lasing was obtained only for elongated electron bunches with low peak currents below 3 kA. To mitigate the CSR effects, the beam optics of the dogleg was rearranged. The new beam optics are based on two DBA (double bend achromatic) structures and the transverse effects of CSR are cancelled between four bending magnets. To avoid the bunch length change, the electron beam passes an off-center orbit at the quadrupole magnets of DBA. Under the new beam optics, stable lasing has been successfully obtained with 10 kA electron bunches, and the parallel operation of the two beamlines will be started in September 2017 for user experiments.  
slides icon Slides TUA04 [7.334 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUA04  
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TUB01 Seeding Experiments and Seeding Options for LCLS II ion, FEL, photon, laser 219
 
  • E. Hemsing, R.N. Coffee, W.M. Fawley, Y. Feng, B.W. Garcia, J.B. Hastings, Z. Huang, G. Marcus, D.F. Ratner, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  • G. Penn, R.W. Schoenlein
    LBNL, Berkeley, California, USA
 
  We discuss the present status of FEL seeding experiments toward the soft x-ray regime and on-going studies on possible seeding options for the high repetition soft x-ray line at LCLS-II. The seeding schemes include self-seeding, cascaded HGHG, and EEHG to reach the 1-2 nm regime with the highest possible brightness and minimal spectral pedestal. We describe relevant figures of merit, performance expectations, and potential issues.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUB01  
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TUB03 ASU Compact XFEL ion, FEL, laser, emittance 225
 
  • W.S. Graves, J.P.J. Chen, P. Fromme, M.R. Holl, R. Kirian, L.E. Malin, K.E. Schmidt, J. Spence, M. Underhill, U. Weierstall, N.A. Zatsepin, C. Zhang
    Arizona State University, Tempe, USA
  • K.-H. Hong, D.E. Moncton
    MIT, Cambridge, Massachusetts, USA
  • C. Limborg-Deprey, E.A. Nanni
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by NSF Accelerator Science award 1632780, NSF BioXFEL STC award 1231306 and DOE contract DE-AC02-76SF00515.
ASU is pursuing a concept for a compact x-ray FEL (CXFEL) that uses nanopatterning of the electron beam via electron diffraction and emittance exchange to enable fully coherent x-ray output from electron beams with an energy of a few tens of MeV. This low energy is enabled by nanobunching and use of a short-pulse laser field as an undulator, resulting in an XFEL with 10 m total length and modest cost. The method of electron bunching is deterministic and flexible, rather than dependent on SASE amplification, so that the x-ray output is coherent in time and frequency. The phase of the x-ray pulse can be controlled and manipulated with this method so that new opportunities for ultrafast x-ray science are enabled using e.g. attosecond pulses, very narrow linewidths, or extremely precise timing among multiple pulses with different colors. These properties may be transferred to large XFELs through seeding with the CXFEL beam. Construction of the CXFEL accelerator and laboratory are underway, along with initial experiments to demonstrate nanopatterning via electron diffraction. An overview of the methods, project, and new science enabled are presented.
 
slides icon Slides TUB03 [5.933 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUB03  
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TUB04 Recent On-Line Taper Optimization on LCLS ion, FEL, undulator, experiment 229
 
  • J. Wu, X. Huang, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  • A. Scheinker
    LANL, Los Alamos, New Mexico, USA
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
High-brightness XFELs are demanding for many users, in particular for certain types of imaging applications. Self-seeding XFELs can respond to a heavily tapered undulator more effectively, therefore seeded tapered FELs are considered as a path to high-power FELs in the terawatts level. Due to many effects, including the synchrotron motion, the optimization of the taper profile is intrinsically multi-dimensional and computationally expensive. With an operating XFEL, such as LCLS, the on-line optimization becomes more economical than numerical simulation. Here we report recent on-line taper optimization on LCLS taking full advantages of nonlinear optimizers as well as up-to-date development of artificial intelligence: deep machine learning and neural networks.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUB04  
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TUC04 Enhancement of Radiative Energy Extraction in an FEL Oscillator by Post-Saturation Beam Energy Ramping ion, laser, FEL, wiggler 244
 
  • H. S. Marks, A. Gover
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  • E. Dyunin, Yu. Lurie
    Ariel University, Ariel, Israel
 
  We present experimental results showing a greater than 50% increase in post-saturation radiation power extraction from a Free Electron Laser oscillator based on an electrostatic accelerator. Electrostatic accelerator free electron laser oscillators have the potential for CW operation. Present day operating oscillators rely on long pulses of electrons, tens of microseconds in duration; they generate correspondingly long radiation pulses, at a single longitudinal mode after a mode competition process. The presented post-saturation power extraction enhancement process is based on temporal tapering (up-ramping) of the beam energy, enabling a large synchrotron oscillation swing of the trapped electron bunches in passage along the interaction length. We further discuss the theoretical limits of the temporal tapering efficiency enhancement process.  
slides icon Slides TUC04 [2.647 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUC04  
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TUC05 Start-to-End Simulations for an X-Ray FEL Oscillator at the LCLS-II and LCLS-II-HE ion, FEL, gun, photon 247
 
  • W. Qin, K.L.F. Bane, Y. Ding, Z. Huang, G. Marcus, T.J. Maxwell
    SLAC, Menlo Park, California, USA
  • S. Huang, K.X. Liu
    PKU, Beijing, People's Republic of China
  • K.-J. Kim, R.R. Lindberg
    ANL, Argonne, Illinois, USA
 
  The proposed high repetition-rate electron beam from the LCLS-II and LCLS-II High Energy (LCLS-II-HE) upgrade are promising sources as drivers for an X-ray FEL Oscillator (XFELO) operating at both the harmonic and fundamental frequencies. In this contribution we present start-to-end simulations for an XFELO operating at the fifth harmonic with 4 GeV LCLS-II beam and at the fundamental with 8 GeV LCLS-II-HE beam. The electron beam longitudinal phase space is optimized by shaping the photoinjector laser and adjusting various machine parameters. The XFELO simulations show that high-flux output radiation pulses with 1010 photons and 3 meV (FWHM) spectral bandwidth can be obtained with the 8 GeV configuration.  
slides icon Slides TUC05 [3.802 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUC05  
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TUP002 Numerical Studies on RF-Induced Trajectory Variations at the European XFEL ion, FEL, cavity, alignment 251
 
  • T. Hellert, B. Beutner, W. Decking, N. Walker
    DESY, Hamburg, Germany
 
  At the European X-Ray Free-Electron Laser, superconducting TESLA-type cavities are used for acceleration of the driving electron bunches. Due to the high achievable duty cycle, a long radio frequency (RF) pulse structure can be provided, which allows to operate the machine with long bunch trains. The designated pointing stability of the FEL radiation places stringent restrictions on the acceptable trajectory variations of individual electron bunches. Therefore a transverse intra-bunch-train feedback system (IBFB) is located upstream of the undulator section. However, intra-bunch-train variations of RF parameters and misalignment of RF structures induce significant trajectory variations that may exceed the capability of the IBFB. In this paper we give an estimate of the expected RF-induced intra-bunch-train trajectory variations for different machine realizations and investigate methods for their limitation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP002  
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TUP004 Longitudinal Phase Space Optimization for the Hard X-ray Self-Seeding ion, FEL, simulation, undulator 259
 
  • S. Liu, W. Decking, G. Feng, V. Kocharyan, I. Zagorodnov
    DESY, Hamburg, Germany
  • G. Geloni, S. Serkez
    XFEL. EU, Hamburg, Germany
 
  For the implementation of Hard X-ray Self-Seeding (HXRSS) at European XFEL, short electron-beam bunches (FWHM ≤ 50 fs) are preferred to mitigate spatio-temperal coupling effect and to fit to the seeding bump width. Therefore, operations with low charges (< 250 pC) are preferred. Longitudinal phase-space optimization has been performed for the 100 pC case by flattening the current distribution. Start-to-end simulations show that, with the optimized distribution, for the photon energy of 14.4 keV, the HXRSS output power, pulse energy and spectral intensity can be increased by a factor of approximately 2 as compared to the nominal working point.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP004  
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TUP005 Studies of the Transverse Beam Coupling in the European XFEL Injector ion, FEL, coupling, quadrupole 263
 
  • M. Scholz, B. Beutner
    DESY, Hamburg, Germany
 
  Coupling between the transverse plains leads to an increase of the horizontal and vertical electron beam emittances. The coupling can be measured with dedicated multi quadrupole scans while the correlations of the beam are observed on a screen. In this paper we show the results from first coupling studies in the European XFEL injector.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP005  
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TUP009 The Effect of Transverse Space Charge on Beam Evolution and Photon Coherence ion, emittance, space-charge, focusing 266
 
  • Q.R. Marksteiner
    LANL, Los Alamos, New Mexico, USA
 
  An electron beam experiences a transverse electric field which tends to act like a defocusing force on the electron beam. This defocusing force will act with different strengths at different locations in the electron beam because the current varies along the beam. A simple, quasi-analytic method is presented to calculate the impact of this force on beam projected emittance. In addition, estimates are made regarding the degree to which this could degrade the transverse coherence of x-rays in an XFEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP009  
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TUP010 Double-Bunches for Two-Color Soft X-Ray Free-Electron Laser at the MAX IV Laboratory ion, linac, laser, wakefield 269
 
  • J. Björklund Svensson, O. Lundh
    Lund University, Lund, Sweden
  • J. Andersson, F. Curbis, M. Kotur, F. Lindau, E. Mansten, S. Thorin, S. Werin
    MAX IV Laboratory, Lund University, Lund, Sweden
 
  The ability to generate two-color free-electron laser (FEL) radiation enables a wider range of user experiments than just single-color FEL radiation. There are different schemes for generating the two colors, the original being to use a single bunch and two sets of undulators with different K-parameters. A development of the scheme has recently been shown, where two separate bunches in the same RF bucket are used for lasing at different wavelengths. We here investigate the feasibility of accelerating and compressing a double-bunch time structure generated in the photocathode electron gun for subsequent use in a soft X-ray FEL at the MAX IV Laboratory.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP010  
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TUP013 Experience and Initial Measurements of Magnetic Linearisation in the MAX IV Linac Bunch Compressors ion, linac, sextupole, storage-ring 273
 
  • S. Thorin, J. Andersson, M. Brandin, F. Curbis, L. Isaksson, M. Kotur, F. Lindau, E. Mansten, D. Olsson, R. Svärd, S. Werin
    MAX IV Laboratory, Lund University, Lund, Sweden
  • J. Björklund Svensson
    Lund University, Division of Atomic Physics, Lund, Sweden
 
  The MAX IV Linac is now in routine operation for injection into two storage rings, and as a high-brightness driver for a Short Pulse Facility (SPF). In short-pulse mode the electron bunch is created in a photo cathode gun and compressed in two double achromat bunch compressors that also linearize longitudinal phase space with the second order transfer matrix element T566. T566 in the compressors can be tweaked with weak sextupoles located at high dispersion. In this paper we present the current experience from operating the bunch compressors at MAX IV and results from initial measurements of longitudinal phase space using the zero-crossing method.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP013  
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TUP015 Coherent Transition Radiation from Transversely Modulated Electron Beams ion, radiation, experiment, detector 276
 
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • S.P. Antipov, W. Liu, N.R. Neveu, J.G. Power, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • A.I. Benediktovitch
    BSU, Minsk, Belarus, Belarus
  • S.N. Galyamin, A.V. Tyukhtin
    Saint Petersburg State University, Saint Petersburg, Russia
  • D. Mihalcea, P. Piot
    Fermilab, Batavia, Illinois, USA
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
 
  A transverse laser-shaping optical setup using microlens arrays (MLAs), previously developed and employed at Argonne Wakefield Accelerator (AWA), allows the formation of both highly uniform and modulated (patterned) beams. In the latter case, transverse modulation is imposed in the sub-millimeter scale. In the present study, we report the simulations of backward coherent transition radiation (CTR) emitted from a transversely modulated beam. We compare the case of a uniform round beam against different transverse modulation wavelengths by generating CTR on a steel target and measuring the autocorrelation function of the resulting radiation with an interferometer. We particularly focus on the differences between round and patterned beam distributions and discuss possible future applications of this setup in THz radiation generation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP015  
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TUP022 Modeling and Optimization of the APS Photo-Injector Using OPAL for High Efficiency FEL Experiments ion, linac, gun, simulation 284
 
  • C.C. Hall, D.L. Bruhwiler, S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
  • A.Y. Murokh
    RadiaBeam, Santa Monica, California, USA
  • P. Musumeci, Y. Park
    UCLA, Los Angeles, USA
  • Y. Sun, A. Zholents
    ANL, Argonne, Illinois, USA
 
  Funding: This work was carried out with support for the United State Department of Energy, Office of Scientific Research, under SBIR contract number DE-SC0017161.
The Linac Extension Area (LEA) is a new beamline planned as an extension of Argonne's APS linac. An S-band 1.6-cell copper photo-cathode (PC) RF gun has been installed and commissioned at the APS linac front end. The PC gun will provide a beam to the LEA for accelerator technology development and beam physics experiments, in interleaving with a thermionic RF gun which provides a beam for APS storage ring operations. Recently an experiment was proposed to demonstrate the TESSA high-efficiency concept at LEA. In support of this experiment, we have begun simulating the photo-injector using the code OPAL (Object-oriented Particle Accelerator Library). In this paper, we first benchmark OPAL simulations with the established APS photo-injector optimization using ASTRA and ELEGANT. Key beam parameters required for a successful high-efficiency TESSA demonstration are discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP022  
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TUP024 Stochastic Effects from Classical 3D Synchrotron Radiation ion, simulation, radiation, synchrotron 292
 
  • B.W. Garcia, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  • R.D. Ryne
    LBNL, Berkeley, California, USA
 
  In most cases, the one-dimensional coherent synchrotron radiation wakefield gives an excellent approximation to the total coherent effect due to classical synchrotron radiation in bend magnets. However, full particle Liénard-Wiechert simulations have revealed that there is non-numerical, stochastic noise which generates fluctuations about the approximate 1D solution. We present a model for this stochastic term in which this noise is due to long-range interaction with a discrete number of synchrotron radiation cones. The nature of this noise and how it depends on the 3D dimensions of the beam are explored.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP024  
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TUP027 Cancellation of Coherent Synchrotron Radiation Kicks at LCLS ion, emittance, radiation, linac 296
 
  • D. Khan, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
 
  In this paper, we look at the cancellation of Coherent Synchrotron Radiation (CSR) induced emittance growth using a phase-advance manipulation technique pioneered by R. Hajima, and extended in the Courant-Snyder formalism by S. Di Mitri. Bending systems in a linear accelerator are essential for beam transport and bunch compression. With the ever-growing demands of high-energy, short wavelength free electron laser (FEL) drivers, the CSR effect has emerged to be a detrimental factor in emittance stability. Under linear approximation, it is showed that the CSR driven dispersive kicks in successive bending magnet systems can, with proper balancing of the linac optics, cancel each other to nullify transverse emittance growth. This technique of optics balancing in the constant bunch length regime is the focus of this paper. We will present our findings for the emittance measurements generated in Elegant simulations for the current LCLS-I dogleg system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP027  
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TUP028 Approximated Expressions for the Coherent Synchrotron Radiation Effect in Bending Magnets ion, FEL, radiation, synchrotron 300
 
  • D. Khan, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
 
  In this paper, we describe the development of simplified analytic expressions for the Coherent Synchrotron Radiation's (CSR) root-mean-square induced energy spread, typically found in the bending magnets of short bunch-length charged particle accelerators. The expressions are derived for a Gaussian longitudinal bunch distribution and compared with the full-rigor CSR wakefield integral expressions while entering, traversing and exiting a bending magnet. The validity of the expressions are then tested against ELEGANT with the simulation of an unchirped beam traveling across a bending magnet into a drift section, and the second stage bunch compressor (BC2) of the proposed LCLS-II beamline.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP028  
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TUP030 An Emittance-Preservation Study of a Five-Bend Chicane for the LCLS-II-HE Beamline ion, emittance, FEL, simulation 305
 
  • D. Khan, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
 
  The Linac Coherent Light Source II (LCLS-II) is an upgrade intended to advance the great success of its predecessor, LCLS-I, to maintain its position at the forefront of X-ray science. The introduction of a niobium-metal superconducting linac for LCLS-II not only increases the repetition rate to the MHz level (from 120 Hz), but also boasts an average brightness many orders higher (~10,000) than that of LCLS-I. Though, these improvements do not come without a price: the peak brightness suffers by a factor of 10, owing its degradation to the impact of Coherent Synchrotron Radiation (CSR) diminishing the peak current of the beam in the second bunch compressor (BC2). In this paper, we discuss the impact of implementing a plug-compatible 5-bend chicane for BC2 on the beam's emittance dilution for a high-energy, low-emittance configuration of LCLS-II (LCLS-II-HE). The results are compared with that of a standard 4-bend chicane under various settings in Elegant and CSRTrack.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP030  
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TUP031 Design of a Dogleg Bunch Compressor with Tunable First-Order Longitudinal Dispersion ion, linac, dipole, FEL 309
 
  • W.K. Lau, M.C. Chou, N.Y. Huang, A.P. Lee
    NSRRC, Hsinchu, Taiwan
  • J. Wu
    SLAC, Menlo Park, California, USA
 
  A nonlinear bunch compressor has been designed for the proposed NSRRC VUV FEL facility. It is a double dog-leg configuration that provides a first order longitudinal dispersion function (i.e. R56) with a sign opposite to that of a conventional four-dipole chicane. A large variation in the bunch length or the peak current for various operation conditions can be done by tuning R56. This can be realized by changing the longitudinal positions of the outside dipoles and adjusting the quadrupoles and sextupoles settings for desired bunch compression. Residual energy chirp left after bunch compression as revealed from ELEGANT simulation can be corrected by a capacitive dechirper structure when the bunch is slightly over-compressed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP031  
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TUP034 Novel Aspects of Beam Dynamics in CeC SRF Gun and SRF Accelerator ion, gun, simulation, cavity 313
 
  • I. Petrushina
    SUNY SB, Stony Brook, New York, USA
  • T. Hayes, Y.C. Jing, D. Kayran, V. Litvinenko, G. Narayan, I. Pinayev, F. Severino, K.S. Smith, G. Wang
    BNL, Upton, Long Island, New York, USA
  • K. Mihara
    Stony Brook University, Stony Brook, USA
  • K. Shih
    SBU, Stony Brook, New York, USA
 
  Funding: DoE NP office, grant DE-FOA-0000632, NSF grant PHY-1415252.
A 15 MeV CW SRF accelerator had been commissioned at Brookhaven National Laboratory to test the coherent electron cooling concept. The accelerator consists of an SRF 113-MHz photoemission gun, two 500 MHz bunching cavities and a 704-MHz 5-cell SRF linac. In this paper we describe our experience with this system with focus on unusual phenomena, such as multipacting in the SRF gun. We also discuss issues of wakefields in the CeC accelerator.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP034  
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TUP038 Experiments in Electron Beam Nanopatterning ion, experiment, FEL, simulation 320
 
  • C. Zhang, W.S. Graves, L.E. Malin, J. Spence
    Arizona State University, Tempe, USA
  • D.B. Cesar, J.M. Maxson, P. Musumeci, A. Urbanowicz
    UCLA, Los Angeles, USA
  • R.K. Li, E.A. Nanni, X. Shen, S.P. Weathersby, J. Yang
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by NSF Accelerator Science awards 1632780 and 1415583, NSF BioXFEL STC award 1231306, and DOE contracts DE-AC02-76SF00515 and DE-SC0009914.
We report on experiments in nanopatterning electron beams from a photoinjector as a first step toward a compact XFEL (CXFEL). The nanopatterning is produced by Bragg diffraction of relativistic electron beams through a patterned Si crystal consisting of alternating thick and thin strips to produce nanometer-scale electron density modulations. Multi-slice simulations show that the target can be oriented for a two-beam condition where nearly 80% of the elastically scattered electron beam is diffracted into the 220 Bragg peak. An experiment at the two-beam condition measurement has been carried out at the SLAC UED facility showing this effect with 2.26 MeV electrons. We successfully proved a large portion of the main beam is diffracted into 220 spot by tuning the orientation of the sample. Future plans at UCLA are to observe the nanopatterned beam, and to investigate various grating periods, crystal thicknesses, and sample orientations to maximize the contrast in the pattern and explore tuning the period of the modulation. The SLAC measurement results will be presented along with design of the UCLA experiments.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP038  
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TUP039 Electron Beam Requirements for Coherent Electron Cooling FEL System ion, FEL, undulator, bunching 323
 
  • G. Wang, Y.C. Jing, V. Litvinenko
    BNL, Upton, Long Island, New York, USA
  • J. Ma
    SBU, Stony Brook, New York, USA
 
  Funding: DoE NP office, grant DE-FOA-0000632, NSF grant PHY-1415252.
In this paper, we present results of our studies in amplification of density modulation induced by co-propagating ions in the FEL section of a Coherent Electron Cooling system, as well its interaction with hadrons. We present a set of requirements for electron beam parameters to satisfy for necessary amplification of the density modulation, while preventing loss of the phase information and saturation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP039  
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TUP042 Determination of the Slice Energy Spread of Ultra-Relativistic Electron Beams by Scanning Seeded Coherent Undulator Radiation ion, laser, radiation, undulator 326
 
  • J. Bödewadt, R.W. Aßmann, C. Lechner, M.M. Mohammad Kazemi
    DESY, Hamburg, Germany
  • L.L. Lazzarino, T. Plath, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Modern high-gain free-electron lasers make use of high-brightness ultra-relativistic electron beams. The uncorrelated energy spread of these beams is upon creation of the beam in the sub-permille range and below the resolution of state-of-the-art diagnostics. One method to determine the slice energy spread is to use an external seed laser to imprint a coherent microbunching structure that gives rise to coherent radiation processes, different radiation sources such as transition radiation, synchrotron radiation, or undulator radiation and others. Here, we present a method and show measurements to determine the slice energy spread using an external seed laser with 266 nm wavelength to produce coherent undulator radiation at higher harmonics. The distribution of these harmonics allows retrieval of the electron beam slice energy spread with high precision.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP042  
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TUP045 Interference-Based Ultrafast Polarization Control at Free Electron Lasers ion, polarization, undulator, radiation 329
 
  • S. Serkez, G. Geloni
    XFEL. EU, Schenefeld, Germany
  • E. Saldin
    DESY, Hamburg, Germany
 
  We present a scheme to generate two distinct FEL pulses with different polarization properties and down to 50 fs-order temporal separation. The scheme is based on installation of two consecutive helical undulators, a corrugated structure and emittance spoiler on top of a baseline variable gap undulator, and is exemplified on the SASE3 beamline of the European XFEL. Good temporal coherence by either self or external seeding is preferable. Our schemes can be used for pump-probe experiments and in combination with the "twin-bunch" technique.  
poster icon Poster TUP045 [0.573 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP045  
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TUP050 Beam Driven Acceleration and RF Breakdown in Photonic Band Gap Travelling Wave Accelerator Structure ion, wakefield, experiment, acceleration 333
 
  • J. Upadhyay, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
 
  We report the results of an experiment to demonstrate excitation of wakefields and wakefield acceleration in a photonic band gap (PBG) accelerating structure. The experiment was conducted at the Argonne Wakefield Accelerator (AWA) facility. For modern X-ray free electron lasers (FELs), preservation of the electron beam quality during the beam acceleration is of crucial importance. Therefore, new accelerating structures must be designed with careful attention paid to the suppression of wakefields. PBG structures are widely studied due to their ability to exclude higher order modes. A 16-cell travelling-wave normal conducting PBG structure operating at 11.700 GHz is installed at the AWA beam line. We passed a high-charge single bunch or multiple bunch train through the structure that generated wakefields and evaluated the effect of these wakefields on a low-charge witness beam. We also passed high-charge multiple bunch trains through the structure that generated up to 100 MV/m accelerating gradient and studied the RF breakdown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP050  
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TUP053 The ACHIP Experimental Chambers at PSI ion, experiment, FEL, laser 336
 
  • E. Ferrari, M. Bednarzik, S. Bettoni, S. Borrelli, H.-H. Braun, M. Calvi, Ch. David, M.M. Dehler, F. Frei, T. Garvey, V. Guzenko, N. Hiller, R. Ischebeck, C. Ozkan Loch, E. Prat, J. Raabe, S. Reiche, L. Rivkin, A. Romann, B. Sarafinov, V. Schlott, S. Susmita
    PSI, Villigen PSI, Switzerland
  • E. Ferrari, L. Rivkin
    EPFL, Lausanne, Switzerland
  • P. Hommelhoff
    University of Erlangen-Nuremberg, Erlangen, Germany
  • J.C. McNeur
    Friedrich-Alexander Universität Erlangen-Nuernberg, University Erlangen-Nuernberg LFTE, Erlangen, Germany
 
  Funding: Gordon and Betty Moore Foundation
The Accelerator on a Chip International Program (ACHIP) is an international collaboration, funded by the Gordon and Betty Moore Foundation, whose goal is to demonstrate that a laser-driven accelerator on a chip can be integrated to fully build an accelerator based on dielectric structures. PSI will provide access to the high brightness electron beam of SwissFEL to test structures, approaches and methods towards achieving the final goal of the project. In this contribution, we will describe the two interaction chambers installed on SwissFEL to perform the proof-of-principle experiments. In particular, we will present the positioning system for the samples, the magnets needed to focus the beam to sub-micrometer dimensions and the diagnostics to measure beam properties at the interaction point.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP053  
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TUP057 Measurement of Short-Wavelength High-Gain FEL Temporal Coherence Length by a Phase Shifter ion, FEL, experiment, radiation 344
 
  • G. Zhou
    IHEP, Beijing, People's Republic of China
  • W. Liu
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • W. Qin, T.O. Raubenheimer, J. Wu, C. Yang
    SLAC, Menlo Park, California, USA
  • C.-Y. Tsai
    Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
  • B. Yang
    University of Texas at Arlington, Arlington, USA
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Short-wavelength high-gain free-electron lasers (FELs) are now well established as a source of ultra-fast, ultra-brightness, longitudinally partial coherent light. Since coherence is one of the fundamental properties of light source, so continual effort is devoted to high-gain free-electron laser coherence measurements. In this work, we propose a possible approach, employing a phase shifter to induce electron beam delay to measure the temporal coherence length. Simple analysis, numerical simulation and preliminary experimental results are presented. This approach can be robust and independent of frequency.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP057  
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TUP058 Slippage-Enhanced SASE FEL ion, FEL, undulator, laser 348
 
  • J. Wu, A. Brachmann, K. Fang, A. Marinelli, C. Pellegrini, T.O. Raubenheimer, C.-Y. Tsai, C. Yang, M. Yoon, G. Zhou
    SLAC, Menlo Park, California, USA
  • H.-S. Kang, G. Kim, I.H. Nam
    PAL, Pohang, Kyungbuk, Republic of Korea
  • B. Yang
    University of Texas at Arlington, Arlington, USA
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
High-brightness XFEL is demanding for many users, in particular for certain types of imaging applications. Seeded FELs including self-seeding XFELs were successfully demonstrated. Alternative approaches by enhancing slippage between the x-ray pulse and the electron bunch were also demonstrated. This class of Slippage-enhanced SASE (SeSASE) schemes can be unique for FEL spectral range between 1.5 keV to 4 keV where neither grating-based soft x-ray self-seeding nor crystal-based hard x-ray self-seeding can easily access. SeSASE can provide high-brightness XFEL for high repetition rate machines not suffering from heat load on the crystal monochromator. We report start-to-end simulation results for LCLS-II project and PAL-XFEL project with study on tolerance. Performance comparison between SaSASE FEL and self-seeding FEL in the overlapping frequency range is also presented.
 
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TUP059 Alternative Electron Beam Slicing Methods for CLARA and X-ray FELs ion, FEL, laser, simulation 352
 
  • D.J. Dunning, H.M. Castaneda Cortes, S.P. Jamison, T.A. Mansfield, N. Thompson, D.A. Walsh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • D. Bultrini, S.P. Jamison, N. Thompson
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • D. Bultrini
    University of Glasgow, Glasgow, Scotland, United Kingdom
 
  Methods to generate ultra-short radiation pulses from X-ray FELs commonly slice a relatively long electron bunch to feature one (or more) short regions of higher beam quality which then lase preferentially. The slotted foil approach spoils the emittance of all but a short region, while laser-based alternatives modulate the electron beam energy, improving potential synchronisation to external sources. The CLARA FEL test facility under development in the UK will operate at 100-400 nm, aiming to demonstrate FEL schemes applicable at X-ray wavelengths. We present new laser-based slicing schemes which may better suit the wavelength range of CLARA and provide options for X-ray facilities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP059  
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TUP061 Study of the Electron Transport in the COXINEL FEL Beamline Using a Laser-Plasma Accelerated Electron Beam ion, laser, undulator, plasma 356
 
  • T. André, I.A. Andriyash, F. Blache, F. Bouvet, F. Briquez, M.-E. Couprie, Y. Dietrich, J.P. Duval, M. El Ajjouri, A. Ghaith, C. Herbeaux, N. Hubert, M. Khojoyan, C.A. Kitegi, M. Labat, N. Leclercq, A. Lestrade, A. Loulergue, O. Marcouillé, F. Marteau, P. N'gotta, P. Rommeluère, E. Roussel, M. Sebdaoui, K.T. Tavakoli, M. Valléau
    SOLEIL, Gif-sur-Yvette, France
  • S. Bielawski, C. Evain, C. Szwaj
    PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
  • S. Corde, J. Gautier, G. Lambert, B. Mahieu, V. Malka, K. Ta Phuoc, C. Thaury
    LOA, Palaiseau, France
 
  The ERC Advanced Grant COXINEL aims at demonstrating free electron laser (FEL) at 200 nm, based on a laser-plasma accelerator (LPA). To achieve the FEL amplification a transport line was designed to manipulate the beam properties. The 10 m long COXINEL line comprises a first triplet of permanent-magnet variable-strength quadrupoles (QUAPEVA), which handles the large divergence of LPA electrons, a magnetic chicane, which reduces the slice energy spread, and finally a set of electromagnetic quadrupoles, which provides a chromatic focusing in a 2-m undulator. Electrons were successfully transported through the line from LPA with ionization-assisted self-injection (broad energy spectra up to~250 MeV, few-milliradian divergence).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP061  
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TUP065 Dielectric Laser Acceleration Setup Design, Grating Manufacturing and Investigations Into Laser Induced RF Cavity Breakdowns ion, laser, acceleration, vacuum 365
 
  • M. Hamberg, D.S. Dancila, M. Jacewicz, J. Ögren
    Uppsala University, Uppsala, Sweden
  • M. Karlsson, A. Rydberg, E. Vargas Catalan
    Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
  • M. Kuittinen, I. Vartiainen
    UEF, Joensuu, Finland
 
  Funding: Work supported by Stockholm-Uppsala Centre for Free Electron Research.
Dielectric laser acceleration (DLA) is the technique utilizing strong electric fields in lasers to accelerate electrons in the proximity of nanoscaled dielectric gratings. The concept was recently demonstrated in experimental studies. Here we describe the experimental DLA investigation setup design including laser system and scanning electron microscope (SEM). We also present the grating manufacturing methods as well investigations into vacuum breakdowns occurring at RF accelerating structures.
 
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TUP066 Luminosity Increase in Laser-Compton Scattering by Crab Crossing ion, laser, luminosity, photon 368
 
  • Y. Koshiba
    Waseda University, Tokyo, Japan
  • T. Higashiguchi
    Center for Optical Research and Education, Utsunomiya University, Utsunomiya, Japan
  • S. Ota, T. Takahashi, M. Washio
    RISE, Tokyo, Japan
  • K. Sakaue
    Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
  • J. Urakawa
    KEK, Ibaraki, Japan
 
  Funding: Research Fellow of Japan Society for the Promotion of Science
Laser-Compton Scattering X-ray (LCS-X) sources have been expected as compact and powerful sources, beyond X-ray tubes. They will enable laboratories and companies, opening new X-ray science. It is well known that luminosity depends on the collision angle of a laser and electron beam. Head-on collision is ideal in the point of maximizing the luminosity, though it is difficult to create such a system especially with an optical enhancement cavity for a laser. In collider experiments, however, crab crossing is a promising way to increase the luminosity. We are planning to apply crab crossing to LCS to achieve a higher luminosity leading to a more intense X-ray source. Electron beams will be tilted to half of the collision angle using an RF-deflector. Although crab crossing in Laser-Compton scattering has been already proposed, it has not been demonstrated yet anywhere.* The goal of this study is to experimentally prove the luminosity increase by adopting crab crossing. In this conference, we will report about our compact accelerator system at Waseda University, laser system favorable for crab crossing LCS, and expected results of crab crossing LCS.
* V. Alessandro, et al., "Luminosity optimization schemes in Compton experiments based on Fabry-Perot optical resonators." Physical Review Special Topics-Accelerators and Beams 14.3 (2011): 031001.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP066  
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TUP067 Study on Cherenkov Laser Oscillator Using Tilted Electron Bunches ion, radiation, experiment, laser 371
 
  • K. Sakaue
    Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
  • M. Brameld, Y. Tadenuma, M. Washio, R. Yanagisawa
    Waseda University, Tokyo, Japan
  • R. Kuroda, Y. Taira
    AIST, Tsukuba, Ibaraki, Japan
  • J. Urakawa
    KEK, Ibaraki, Japan
 
  Funding: This work was supported by a research granted from The Murata Science Foundation and JSPS KAKENHI 26286083.
We have been studying a coherent Cherenkov radiation by using tilted electron bunches. Bunch tilting can enhance the radiation power about 10 times due to the wavefront matching of radiations. Recently, we investigated that this technique can produce high peak power THz pulses with sufficient pulse energy. Resulting pulse energy was more than 30 nJ/pulse and peak power was about 10 kW. Introducing the oscillator cavity with two concave mirrors, it would be possible to achieve lasing using tilted electron bunches. In the calculation, 1 uJ/micro-pulse and 100 uJ/macro-pulse broadband THz pulses are expected to be achieved, which are powerful THz sources compared with the existing THz FELs. In this conference, we will report the experimental results of coherent Cherenkov radiation, calculated results toward lasing and future prospectives.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP067  
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TUP069 Simulating Beam Dynamics in Coherent Electron-Cooling Accelerator with WARP ion, cavity, experiment, simulation 374
 
  • K. Shih
    SBU, Stony Brook, New York, USA
  • Y.C. Jing, V. Litvinenko, I. Pinayev, G. Wang
    BNL, Upton, Long Island, New York, USA
  • K. Mihara
    Stony Brook University, Stony Brook, USA
  • I. Petrushina
    SUNY SB, Stony Brook, New York, USA
 
  Funding: DoE NP office, grant DE-FOA-0000632, NSF grant PHY-1415252.
Coherent Electron Cooling (CeC) is a novel cooling technique based on amplification of interaction between hadrons and electron by an FEL. If proven, this CeC could bring a revolution in hadron and electron-hadron colliders. A dedicated CeC proof-of-principle experiment is under way at RHIC collider (BNL) using a sophisticated SRF accelerator for generating and accelerating electron beam. This paper is dedicated to studies of beam dynamics in the CeC accelerator and specifically to emittance preservation in its ballistic compressions section. Two 500-MHz RF cavities are used for generating the necessary energy chirp leading in 1.56-MeV, 0.5-nsec-long electron bunched to compress them to 25-psec duration downstream. During the commissioning of the CeC accelerator we noticed that beam emittance can be strongly degraded when electron beam passes these 500 MHz RF cavities off-axis. We used a full 3D PIC code Wrap to simulate effect of the off-axis beam propagation through these
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP069  
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TUP070 Development of Mid-Infrared Photoacoustic Spectroscopy System for Solid Samples at Kyoto University Free Electron Laser Facility ion, FEL, experiment, laser 378
 
  • J. Okumura, T. Kii, H. Ohgaki, H. Zen
    Kyoto University, Kyoto, Japan
 
  Photoacoustic Spectroscopy (PAS) enables IR absorption spectrum measurements of solid samples without preprocessing of samples. Its sensitivity and resolution depend on the intensity and spectral width of the infrared light, respectively. Mid-infrared free electron laser (MIR-FEL) is an intense, quasi-monochromatic and tunable laser in MIR region, so the method of PAS with FEL (FEL-PAS) was proposed.*,** However, the resolution was not so good since they used the direct FEL beam which has the spectral width of 1%. We considered that the resolution can be significantly increased by inserting a high-resolution grating monochromator before the PAS cell. Based on this consideration, a PAS system using an MIR-FEL with the monochromator is under development. We have already conducted preliminary experiments using a PAS cell which has been used in previous studies and successfully measured quite high PAS signals with this setup.*,** A demonstration of experiments to check the spectral resolution will be conducted soon. In this presentation, the progress of the development including the result of demonstration experiments will be reported.
* M. Yasumoto et al., Proceedings of the 2004 FEL Conference, 703-705 (2004).
** M. Yasumoto et al., Eur. Phys. J. Special Topics, 153, 37-40 (2008).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP070  
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TUP072 Simulation of Phase Shifters Between FEL Amplifiers in Coherent Electron Cooling ion, FEL, wiggler, radiation 386
 
  • Y.C. Jing, V. Litvinenko, I. Pinayev
    BNL, Upton, Long Island, New York, USA
  • V. Litvinenko
    Stony Brook University, Stony Brook, USA
 
  Coherent electron Cooling (CeC) is a proposed advanced beam cooling method that has the potential of reducing the ion beam emittance in significantly shorter amount of time compared to existing cooling methods. A high-gain FEL, composed of three permanent magnet helical wigglers, is acting as an amplifier of the ion's signals picked up by electron beam in CeC. A self-consistent simulation which takes the space and possible phase shifts between wigglers into account is crucial in determining the performance of the FEL. The authors developed an algorithm based on the well-used GENESIS code to properly treat the propagation of particles and radiations in between wigglers and predicted the FEL performance with different beamline layouts. The authors will present their simulation setup and results and provide hardware requirements for future operations and research at CeC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP072  
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WEA02 Model of Photocathode for CW Electron Gun ion, emittance, cathode, scattering 394
 
  • P.W. Huang, W.-H. Huang, C.-X. Tang
    TUB, Beijing, People's Republic of China
 
  Most of the proposed CW guns for free electron lasers use semiconductors as the photocathode due to their high quantum efficiency and potentially low thermal emittance. We manage to establish a model to explain the photoemission of semiconductors with incident photon energy above or below the theoretical threshold and derive the expression for quantum efficiency and thermal emittance. For the incident photon energy near or below the threshold of the cathode, things will be subtle and we should be careful to consider the details we used to neglect. The results of quantum efficiency and thermal emittance agree well with the published work. We also focus on the degradation of the semiconductors and propose a model to examine the development of the thermal emittance. We mainly consider the effect brought by the surface reactions with poisoning gases. The variation of quantum efficiency with time is well-consistent with experiment data. We also present the calculated results of thermal emittance, showing a decline with time. Similar results are presented with typical value of electric field in DC gun and RF gun.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEA02  
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WEA04 Novel Concepts of a High-Brightness Photoinjector RF Gun ion, cathode, gun, brightness 397
 
  • S.V. Kuzikov, O.A. Ivanov, A.A. Vikharev, A.L. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
  • S.P. Antipov
    Euclid Beamlabs LLC, Bolingbrook, USA
  • S.P. Antipov
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  We propose here a program to design and manufacture a high performance, advanced source of electrons having high beam brightness (>1016 A/m2) and high bunch charge (~100 pC). Three innovations are being considered: 1) the use of a high peak cathode field, short-pulse RF gun; 2) the use of multi-layered diamond photocathode at low temperature; and 3) the utilization of THz ultrafast field emission gating. High peak cathode field is necessary to achieve a high brightness (low emittance) beam to be accelerated to relativistic energies before space-charge effects lengthen the bunch. The multilayered diamond photocathode is needed to obtain high QE with long wavelength laser in the first doped layer, beam cooling in the next layer, and negative electron affinity at the emission layer. High field single cycle THz pulses, produced by means of laser light rectification in a nonlinear crystal, allow to avoid a UV laser, provide high field emission charge (up to nC) and ~1 GV/m pre-acceleration of subpicosecond bunches.  
slides icon Slides WEA04 [4.039 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEA04  
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WEA05 Higher Fields and Beam Energies in Continuous-Wave Room-Temperature VHF RF Guns ion, gun, cathode, brightness 401
 
  • F. Sannibale, J.M. Byrd, D. Filippetto, M.J. Johnson, D. Li, T.H. Luo, C.E. Mitchell, J.W. Staples, S.P. Virostek
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231
The development in the last decade of MHz-class repetition rate free electron lasers (FELs), and ultrafast electron diffraction and microscopy (UED/UEM) applications, required new gun schemes capable of generating high-brightness beams at such high rates. The VHF-Gun, a 186 MHz room-temperature continuous-wave RF photogun developed at the Lawrence Berkeley Lab (LBNL) was an answer to that need. The VHF-Gun was constructed and tested in the APEX facility at LBNL successfully demonstrating all design parameters and the generation of FEL-quality electron beams. A close version of the APEX gun is in the final phase of fabrication at LBNL to operate as the electron source for the LCLS-II, the new SLAC X-ray FEL. The recently approved upgrade of the LCLS-II towards higher energies (LCLS-II HE) and the brightness-dependent UED and UEM applications would greatly benefit from an increased brightness of the electron source. Such performance upgrade can be obtained by increasing the electric field at the cathode and the beam energy at the gun exit. In this paper, we present and discuss possible upgrade options that would allow us to extend the VHF-Gun technology towards these new goals.
 
slides icon Slides WEA05 [4.320 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEA05  
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WEC02 Optimization of Superconducting Undulators for Low Repetition Rate FELs ion, FEL, undulator, vacuum 411
 
  • J.A. Clarke, K.B. Marinov, B.J.A. Shepherd, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • V. Bayliss, J. Boehm, T.W. Bradshaw, A.J. Brummitt, S.J. Canfer, M.J.D. Courthold, B. Green, T. Hayler, P. Jeffery, C. Lockett, D.S. Wilsher
    STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
  • S. Milward, E.C.M. Rial
    DLS, Oxfordshire, United Kingdom
 
  Superconducting undulators (SCUs) optimized for storage rings and MHz-level FELs require an intermediate beam screen to intercept the power deposited by the electron beam, due to resistive wall wakefields, to prevent magnet quenching. This beam screen increases the magnet gap by around 2 mm which is a significant increase when compared to the typical electron beam aperture of around 5 mm. However, lower repetition rate FELs only deposit of the order of tens of mW/m and so the beam screen is no longer needed resulting in a significant reduction in undulator magnet gap. We have investigated the impact of this reduced magnet gap and found that the magnetic field level increases greatly. For example, an SCU with a 15 mm period and 5 mm aperture optimized for a low repetition rate FEL instead of a storage ring will generate a field of 2.1 T compared to 1.4 T. Such a major increase in undulator performance could have a significant impact on the optimization of FELs. This paper describes how an SCU optimized for application in a FEL will be able to generate magnetic field levels far beyond those currently foreseen for any other magnet technology.  
slides icon Slides WEC02 [6.234 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEC02  
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WEP004 Calculations for a THz SASE FEL Based on the Measured Electron Beam Parameters at PITZ ion, FEL, simulation, undulator 419
 
  • P. Boonpornprasert, M. Krasilnikov, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
 
  The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops high brightness electron sources for modern linac-based Free Electron Lasers (FELs). The PITZ accelerator can also be considered as a suitable machine for the development of an IR/THz source prototype for pump-probe experiments at the European XFEL. Calculations of THz radiation by means of a SASE FEL based on the simulated and the measured beam profiles at PITZ for the radiation wavelength of 100 microns were performed by using the GENESIS1.3 code. The results of these simulations are presented and discussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP004  
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WEP005 Coaxial Coupler RF Kick in the PITZ RF Gun ion, gun, simulation, cavity 422
 
  • Y. Chen, P. Boonpornprasert, J.D. Good, H. Huck, I.I. Isaev, M. Krasilnikov, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • W. Ackermann, H. De Gersem
    TEMF, TU Darmstadt, Darmstadt, Germany
  • M. Dohlus
    DESY, Hamburg, Germany
  • Q.T. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
 
  We investigate a transverse RF kick induced by the transition between rectangular waveguide and coaxial line of the RF coupler in the 1.6-cell L-band normal conducting (NC) RF gun at the Photo Injector Test Facility at DESY, Zeuthen site (PITZ). A three-dimensional electromagnetic simulation shows the disturbed RF field distributions in the fundamental accelerating mode. Based on the 3D RF field map, an electron beam based characterization and quantification of the coaxial coupler RF kick in the PITZ gun is simulated. Preliminary results of the investigations are presented.  
poster icon Poster WEP005 [1.345 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP005  
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WEP006 Preliminary On-Table and Photoelectron Results from the PITZ Quasi-Ellipsoidal Photocathode Laser System ion, laser, cathode, emittance 426
 
  • J.D. Good, G. Asova, P. Boonpornprasert, Y. Chen, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, D.M. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, T. Rublack, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • A.V. Andrianov, E. Gacheva, E. Khazanov, S. Mironov, A. Poteomkin, V. Zelenogorsky
    IAP/RAS, Nizhny Novgorod, Russia
  • I. Hartl, S. Schreiber
    DESY, Hamburg, Germany
  • E. Syresin
    JINR, Dubna, Moscow Region, Russia
 
  The optimization of photoinjectors is crucial for the successful operation of linac-based free electron lasers, and beam dynamics simulations have shown that ellipsoidal photocathode laser pulses result in significantly lower electron beam emittance than that of conventional cylindrical pulses. Therefore, in collaboration with the Institute of Applied Physics (Nizhny Novgorod, Russia) and the Joint Institute of Nuclear Research (Dubna, Russia), a laser system capable of generating quasi-ellipsoidal laser pulses has been developed and installed at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). The pulse shaping has been realized using the spatial light modulator technique, characterized by cross-correlation and spectrographic measurements, and is demonstrated with electron beam measurements. In this contribution the overall setup, operating principles, and results of first regular electron beam measurements will be presented together with corresponding beam dynamics simulations. Furthermore, the numerous improvements of the simplified re-design currently under construction shall be detailed.  
poster icon Poster WEP006 [1.766 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP006  
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WEP007 Electron Beam Asymmetry Compensation with Gun Quadrupoles at PITZ ion, gun, quadrupole, emittance 429
 
  • M. Krasilnikov, P. Boonpornprasert, Y. Chen, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, X. Li, O. Lishilin, G. Loisch, D.M. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan, Q.T. Zhao
    DESY Zeuthen, Zeuthen, Germany
  • G.A. Amatuni, B. Grigoryan
    CANDLE SRI, Yerevan, Armenia
  • G. Asova
    INRNE, Sofia, Bulgaria
  • Q.T. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
 
  The electron beam asymmetry observed at the Photo Injector Test Facility at DESY in Zeuthen (PITZ) was traced back to multipole kicks in the gun section, namely around the location of the coaxial power coupler and the main solenoid. Several dedicated studies have been performed to quantify the kick location and strength. Based on these studies, two designs of correction quadrupole coils were proposed. The coils were fabricated and tested with an electron beam. The second updated design implies a two quadrupole setup on a frame installed around the gun coaxial coupler close to the main solenoid centre location. Skew and normal quadrupole magnets are powered independently, enabling flexibility in electron beam manipulations. By means of this setup, a more symmetric beam was obtained at several screens. This led also to more equal measured horizontal and vertical phase spaces and to even smaller overall emittance values. Some details of the gun quadrupole designs, magnetic measurements, and results of electron beam measurements including emittance optimization will be reported.  
poster icon Poster WEP007 [1.997 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP007  
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WEP014 Pulse Duration Measurement of Pico-second DUV Photocathode Driving Laser by Autocorrelation Technique Using Two-Photon Absorption in Bulk Material ion, laser, cathode, gun 447
 
  • H. Zen, T. Kii, K. Masuda, T. Nakajima, H. Ohgaki
    Kyoto University, Kyoto, Japan
 
  A multi-bunch, pico-second DUV photocathode drive laser system has been developed for photocathode operation of mid-infrared free electron laser facility, KU-FEL.* By using the laser, KU-FEL has already succeeded in first lasing under the photocathode operation.** The pulse duration of the photocathode driving laser is a quite important parameter because it determines the initial electron pulse duration on the cathode surface. However, the pulse duration of the photocathode driving laser had not been characterized. A very convenient pulse duration measurement method utilizing two-photon absorption in bulk material, which can be used for DUV laser pulses, has been proposed and demonstrated so far.*** In this study, a DUV nonlinear autocorrelator based on the proposed method was developed to measure the pulse duration of the DUV photocathode driving laser. As the result of measurement, the pulse duration was evaluated as 5.8±0.2 ps (FWHM). The principle of this method, experimental setup and measured results will be presented.
* H. Zen et al., Proc. of FEL2014, pp.828-831 (2015).
** H. Zen et al., Proc. of IPAC2016, pp.754-756 (2016).
*** C. Homann et al., Applied Physics B 104, 783 (2011).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP014  
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WEP015 Current Experimental Work with Diamond Field-Emitter Array Cathodes ion, cathode, experiment, site 450
 
  • H.L. Andrews, R.L. Fleming, J.W. Lewellen, K.E. Nichols, D.Y. Shchegolkov, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
  • B.K. Choi
    Vanderbilt University, Nashville, USA
 
  Funding: We gratefully acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program for this work.
Diamond Field-Emitter Array (DFEA) cathodes are arrays of micron-scale diamond pyramids with nanometer-scale tips, thereby providing high emission currents with small emittance and energy spread. To date they have been demonstrated in a close-diode configuration, spaced only a few hundred microns from a solid anode, and have shown very promising results in terms of emittance, energy spread, and per-tip emission currents. We present recent results investigating DFEA performance in a large-gap configuration, such that the cathodes are a few millimeters from a solid anode, and show that performance is the same or better as the close-diode geometry previously studied. However, array performance is still limited by anode damage. We are redesigning our cathode test stand to overcome the inherent limitations of a solid anode, allow for transport of the emitted beam, and further explore real-world DFEA performance.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP015  
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WEP016 Modeling of Diamond Field-Emitter Arrays for High-Brightness Photocathode Applications ion, simulation, scattering, cathode 454
 
  • C. Huang, H.L. Andrews, B.K. Choi, R.L. Fleming, T.J. Kwan, J.W. Lewellen, D.C. Nguyen, K.E. Nichols, V.N. Pavlenko, A. Piryatinski, D.Y. Shchegolkov, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
 
  Funding: Work performed under the auspices of the U.S. DOE by the LANS, LLC, Los Alamos National Laboratory (LANL) under Contract No. DE-AC52-06NA25396. Work supported by the LDRD program at LANL.
Dielectric Laser Accelerator (DLA) is capable of generating high output power for an X-ray free-electron laser (FEL), while having a size 1-2 orders of magnitude smaller than existing Radio-Frequency (RF) accelerators. Single Diamond Field-Emitter (DFE) or array of such emitters (DFEA) can be employed as high-current ultra-low-emittance photocathodes for compact DLAs. We are developing a first principle semi-classical Monte-Carlo (MC) emission model for DFEAs that includes the effects of carriers' photoexcitation, their transport to the emitter surface, and the tunnelling through the surface. The electronic structure size quantization affecting the transport and tunnelling processes within the sharp diamond tips is also accounted for. These aspects of our model and their implementation and validation, as well as macroscopic electromagnetic beam simulation of DFE are discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP016  
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WEP018 Electron Beam Heating with the European XFEL Laser Heater ion, laser, FEL, undulator 458
 
  • M. Hamberg
    Uppsala University, Uppsala, Sweden
  • F. Brinker, I. Hartl, S. Koehler, B. Manschwetus, M. Scholz, L. Winkelmann
    DESY, Hamburg, Germany
 
  Funding: Work supported by Swedish Research council, Sweden, Olle Engkvist foundation and DESY, Hamburg, Germany.
The commissioning of the European XFEL is ongoing. To reduce unwanted longitudinal micro-bunching effects, a laser heater is implemented. Here we present the first heating steps and commissioning of the laser heater at the injector section.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP018  
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WEP019 High Stable Pulse Modulator for PAL-XFEL* ion, FEL, klystron, power-supply 460
 
  • S.S. Park, H.-S. Kang, S.H. Kim, H.-S. Lee
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  Funding: Work supported by Ministry of Science, ICT(Information/Communication Technology) and Future Planning.
The XFEL of Pohang Accelerator Laboratory (PAL) commissioned the 10 GeV PAL-XFEL project in 2015. The PAL-XFEL needs a highly-stable electron beam. The very stable beam voltage of a klystron-modulator is essential to provide the stable acceleration field for an electron beam. Thus, the modulator system for the XFEL requires less than 50 ppm PFN voltage stability. To get this high stability on the modulator system, the HVPS of inverter type is an important component. The modulator also needs lower noise and more smart. In this paper, we will discuss the design and the test results of the high-stability pulse modulator system.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP019  
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WEP021 Preliminary Results of the Dark Current Modelling for the Polfel Superconducting Lead Photocathode ion, cathode, cavity, gun 463
 
  • K. Szymczyk, J.A. Lorkiewicz, R. Nietubyć
    NCBJ, Świerk/Otwock, Poland
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
 
  Preparation for the construction of Polish Free Electron Laser (POLFEL) will begin shortly at National Centre for Nuclear Research (NCBJ) in Warsaw. POLFEL is planned as a fourth-generation light source driven by a superconducting (sc) electron accelerator. The concept includes an all-superconducting injector with a thin-film lead sc photocathode, dedicated to continuous wave or long-pulse linac operation. One of the issues which emerges in connection with operation of high-gradient electron guns furnished with dismountable photocathode plugs is the dark current emitted from the cathode surface inhomogeneities. The dark current usually degrades accelerator performance. The purpose of this paper is to present preliminary investigation results of the dark current generation in the electron gun with a thin lead layer deposited on a niobium plug. Specific features of geometric configuration like rounded plug edges, a gap between the plug and the back gun wall as well as cathode surface roughness have been taken into account for the electron field emission and RF field calculations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP021  
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WEP024 Design and Research of a Micro-Pulse Electron Gun ion, cavity, gun, high-voltage 466
 
  • D.Y. Yang, B.T. Li, X.Y. Lu, W.W. Tan, L. Xiao, Y. Yang, Z.Q. Yang, J. Zhao
    PKU, Beijing, People's Republic of China
  • K. Zhou
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
 
  Micro-pulse electron gun (MPG) is a novel electron source which can produce narrow-pulse, high-repetition rate electron current. Theoretical and experiment work have been done to study physical properties and steady operating conditions of MPG. Proof-of-principle work has been finished and the next work is to research the parameters of the MPG electron beam and master the MPG work property deeply. Thus, a high voltage accelerating platform which can supply 100 kV direct voltage was designed. Furthermore, electromagnetic and mechanism designs were operated to adapt the high voltage platform and measure beam parameters.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP024  
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WEP026 Inducing Microbunching in the CLARA FEL Test Facility ion, laser, FEL, bunching 475
 
  • A.D. Brynes
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  We present simulation studies of the laser heater interaction in the CLARA FEL test facility using a non-uniform laser pulse. The microbunching instability, which manifests itself as correlated energy or density modulations in an electron bunch, can degrade the performance of an FEL. Most x-ray free electron lasers (FELs) utilise a so-called laser heater system to impose a small increase in the uncorrelated energy spread of the bunch at low energy to damp the instability – this technique involves imposing a laser pulse on the bunch while it is propagating through an undulator in a dispersive region. However, if the instability can be controlled, the electron bunch profile can be manipulated, yielding novel applications for the FEL, or for generation of THz radiation. Control of the microbunching instability can be achieved by modulating the intensity profile of the laser heater pulse to impose a non-uniform kick along the electron bunch. We have simulated this interaction for various laser intensity profiles and bunch compression factors.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP026  
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WEP027 Numerical Study of Cherenkov Radiation From Thin Silica Aerogel ion, radiation, experiment, diagnostics 479
 
  • H. Hama, K. Nanbu, H. Saito, Y. Saito
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
 
  Funding: This work was supported by JSPS KAKENHI Grant Numbers JP15K13394 and JP17H01070.
Cherenkov radiation (CR) emitted from low-refractive index material such as silica-aerogel is a useful tool for electron beam diagnostics because the opening angle (Cherenkov angle) is small and the CR can be transported onto a detector located far from the radiator. We have prepared a thin (1-mm thick) hydrophobic silica-aerogel with a refractive index of 1.05 that has been developed at Chiba University.* Since the intensity of CR is much stronger than that of optical transition radiation, the CR is a better light source for low-intensity beam diagnostics. In order to apply the CR to measurements of a bunch length of electron beams, we have investigated sources of finite time resolution by a numerical simulation study using the Liénard-Wiechert potentials. We will report results of simulations such as pulse duration of CR and discuss what deteriorates the time resolution.
* M. Tabata et al., Nucl. Instr. and Meth. A 668 (2012) 64.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP027  
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WEP029 Recent Experimental Results on High-Peak-Current Electron Bunch and Bunch Trains Interacting With a THz Undulator ion, radiation, undulator, laser 482
 
  • X.L. Su, Y. C. Du, W. Gai, W.-H. Huang, Y.F. Liang, C.-X. Tang, D. Wang, L.X. Yan
    TUB, Beijing, People's Republic of China
 
  Funding: supported by the National Natural Science Foundation of China (NSFC Grants No. 11475097) and National Key Scientific Instrument and Equipment Development Project of China (Grants No. 2013YQ12034504).
In this paper, experimental results based on THz undulator with widely tunable gap installed at Tsinghua Thomson scattering X-ray (TTX) beamline are introduced. This is a planar permanent magnetic device with 8 regular periods, each 10 cm long. The undulator parameter varies from 9.24-1.39 by changing the magnetic gap from 23mm to 75mm. The coherent undulator radiation can be used as a narrow-band THz source with central frequency ranging from 0.4 THz to 10 THz. The bunch length was figured out from the radiation intensity at different undulator gap, which agreed well with simulations. Furthermore, slice energy modulation was directly observed when high-peak-current bunch trains based on nonlinear longitudinal space charge oscillation passed through the undulator. The demonstrated experiment in THz regime provides a significant scaled tool for FEL mechanism exploration owing to the simplicity of bunch modulation and diagnostics in this range.
* Corresponding author: yanlx@mail.tsinghua.edu.cn
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP029  
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WEP030 Large-Scale Turnkey Timing Distribution System for New Generation Photon Science Facilities ion, timing, laser, controls 485
 
  • K. Shafak
    CFEL, Hamburg, Germany
  • A. Berg, F.X. Kärtner, A. Kalaydzhyan, J. Meier, D. Schimpf, T. Tilp
    Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany
  • A. Berlin, E. Cano, H.P.H. Cheng, A. Dai, J. Derksen, D. Forouher, W. Nasimzada, M. Neuhaus, P. Schiepel, E. Seibel
    Cycle GmbH, Hamburg, Germany
 
  We report a large-scale turnkey timing distribution system able to satisfy the most stringent synchronization requirements demanded by new generation light sources such as X-ray free-electron lasers and attoscience centers. Based on the pulsed-optical timing synchronization scheme, the system can serve 15 remote optical and microwave sources in parallel via timing stabilized fiber links. Relative timing jitter between two link outputs is less than 1 fs RMS integrated over an extended measurement time from 1 μs to 2.5 days. The current system is also able to generate stabilized microwaves at the link outputs with 25-fs RMS precision over 8 h, which can be easily improved to few-femtosecond regime with higher quality VCOs.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP030  
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WEP034 Diagnostics Upgrades for Investigations of HOM Effects in TESLA-type SCRF Cavities ion, HOM, cavity, detector 492
 
  • A.H. Lumpkin, N. Eddy, D.R. Edstrom, P.S. Prieto, J. Ruan, Y.-M. Shin, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
  • B.E. Carlsten
    LANL, Los Alamos, New Mexico, USA
 
  Funding: Work at FNAL supported by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. DoE. Work at LANL supported by U.S. DoE through the LANL/LDRD Program.
We describe the upgrades to diagnostic capabilities on the Fermilab Accelerator Science and Technology (FAST) electron linear accelerator that will allow investigations of the effects of high-order modes (HOMs) in SCRF cavities on macropulse-average beam quality. We focus here on the dipole modes in the first pass-band generally observed in the 1.6-1.9 GHz regime in TESLA-type SCRF cavities due to uniform transverse beam offsets of the electron beam. Such cavities are the basis of the accelerator for the European XFEL and the proposed MaRIE XFEL facility. Initial HOM data indicate that the mode intensities oscillate for about 10 microseconds after the micropulse enters the cavity, resulting in centroid shifts throughout the train. This results in a blurring of the averaged beam image size. The upgrades will include optimizing the HOM detectors' bandpass filters and adding a 1.3-GHz notch filter, converting the BPM electronics to bunch-by-bunch processing, and using the C5680 streak camera in a framing mode for bunch-by-bunch spatial information at the <20-micron level. The preliminary HOM detector data, prototype BPM test data, and first framing camera OTR data will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP034  
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WEP036 Adaptive Feedback for Automatic Phase-Space Tuning of Electron Beams in Advanced XFELs ion, controls, FEL, feedback 496
 
  • A. Scheinker
    LANL, Los Alamos, New Mexico, USA
  • D.K. Bohler
    SLAC, Menlo Park, California, USA
 
  Particle accelerators are extremely complex having thousands of coupled, nonlinear components which include magnets, laser sources, and radio frequency (RF) accelerating cavities. Many of these components are time-varying. One example is the RF systems which experience unpredictable temperature-based perturbations resulting in frequency and phase shifts. In order to provide users with their desired beam and thereby light properties, LCLS sometimes requires up to 6 hours of manual, experience-based hand tuning of parameters by operators and beam physicists, during a total of 12 hours of beam time provided for the user. Even standard operational changes can require hours to switch between user setups. The main goal of this work is to study model-independent feedback control approaches which can work together with physics-based controls to make overall machine performance more robust, enable faster tuning (seconds to minutes instead of hours), and optimize performance in real time in response to un-modeled time variation and disturbances.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP036  
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WEP044 Beam Loss Monitor for Undulators in PAL-XFEL ion, background, undulator, operation 511
 
  • H. Yang, D.C. Shin
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  Funding: This work is supported by MSIP, Korea.
PAL-XFEL consists of the hard x-ray line with a 4-10 GeV electron beam and the soft x-ray line with a 3-3.5 GeV electron beam. The HX line consists of 20 undulators and the SX line consists of 7 undulators. The permanent magnets in an undulator should be protected from the radiation-induced demagnetization. We develop a beam loss monitor (BLM) for undulators of PAL-XFEL. It consists of a detector part (head) and an ADC part. The BLM head consists of two fused quartz rods, two photo-multiplier tube (PMT) modules, and an LED bulb. It is based on the Cherenkov radiator: two fused quartz rods are used for radiators. 2 sets of the radiator and PMT module are installed up and down the beam tube. An LED bulb is between the radiators for the heartbeat signal. The ADC part digitizes the output signal of the PMT module. It measures and calculates the beam loss, background, and heartbeat. One ADC processes the signal from 6-8 heads. The BLM system generates interlock to the machine interlock system for over-threshold beam loss. The 28 BLM heads are installed downstream of each undulator. Those are calibrated by the heartbeat signal and operated in the electron beam transmission with 150 pC.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP044  
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WEP048 Coherent Undulator Radiation From a Kicked Electron Beam ion, radiation, undulator, simulation 515
 
  • J.P. MacArthur, Z. Huang, J. Krzywinski, A.A. Lutman
    SLAC, Menlo Park, California, USA
 
  The properties of off-axis radiation from an electron beam that has been kicked off axis are relevant to recent Delta undualtor experiments at LCLS. We calculate the coherent emission from a microbunched beam in the far-field, and compare with simulation. We also present a mechanism for microbunches to tilt toward a new direction of propagation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP048  
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WEP051 Helical Undulators for Coherent Electron Cooling System ion, undulator, FEL, hadron 519
 
  • I. Pinayev, Y.C. Jing, R. Kellermann, V. Litvinenko, J. Skaritka, G. Wang
    BNL, Upton, Long Island, New York, USA
  • I.V. Ilyin, Y. Kolokolnikov, P. Vobly
    BINP SB RAS, Novosibirsk, Russia
 
  Funding: DoE NP office, grant DE-FOA-0000632
In this paper we present the description and results of the magnetic measurements and tuning of helical undulators for the Coherent electron Cooling system (CeC). The FEL section of the CeC comprises three 2.5-m long undulators separated by 40-cm drift sections, where BPMs and phase-adjusting 3-pole wigglers are located. We present design, tuning techniques and achieved parameters of this system.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP051  
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WEP054 The Magnetic Field Integral Hysteresis on the European XFEL Gap Movable Undulator Systems ion, undulator, FEL, radiation 522
 
  • F. Wolff-Fabris, Y. Li, J. Pflüger
    XFEL. EU, Schenefeld, Germany
 
  The European XFEL GmbH is a new X-ray FEL facility expected to be lasing to users at the end of 2017. Three gap-movable SASE Undulator Systems are designed to produce FELs with tunable wavelengths from 0.05 to 5.2nm.*,** A total of 91 5m long undulator segments and phase shifters were magnetically tuned respecting tight specifications. Magnetic field hysteresis effects due to the gap shift of the Undulator System while changing the FEL radiation wavelength may impact the machine's operational mode. We report on these effects by either opening or closing the gap while performing field integrals measurements with moving wire technique. The undulator segments show negligible magnetic hysteresis and are expected to be operated with no influence to the FEL and beam trajectories in either feed forward or feed backward mode. The phase shifters show first field integrals hysteretic behavior of few G.cm which is comparable in magnitude to the allowed total field integrals and can be associated to the magnetization of the yoke structure. Phase shifters are magnetically tuned for that the feed forward mode (opening gap) fully satisfies the XFEL. EU magnetic specifications for beam operation.
* M. Altarelli et al., Technical Design Rep. DESY 2006-097, July 2007.
** E. Schneidmiller et al., European XFEL Technical Rep. TR-2011-006, Sep. 2011.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP054  
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WEP055 Tapered Flying Radiofrequency Undulator ion, undulator, FEL, simulation 525
 
  • S.V. Kuzikov, A.V. Savilov, A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
  • S.P. Antipov, A. Liu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • A.V. Savilov
    UNN, Nizhny Novgorod, Russia
 
  Funding: This project is supported by DoE Small Business Innovative Research phase I grant #DE-SC0017145.
We propose an efficient XFEL consisting of sequential RF undulator sections using: 1) tapered flying RF undulators, 2) short pulse, high peak-power RF and 3) driving undulator sections by spent electron beam. In a flying RF undulator, an electron bunch propagates through a high-power, nanosecond, co-propagating RF pulse. Helical waveguide corrugation supports a space harmonic with a negative propagation constant, providing a large Doppler up-shift. The undulator tapering technique improves FEL efficiency by 1-2 orders of magnitude in comparison with other facilities by decreasing the undulator period so that particles are trapped in the combined field of the incident x-ray and undulator field. We develop a so-called non-resonant trapping regime not requiring phase locking for feeding RF sources. Simulations show that by decreasing the corrugation periodicity one can vary an equivalent undulator period by 15%. The spent electron beam can be used to produce wakefields that will drive the RF undulator sections for interaction with the following beam. We have already manufactured and tested the 30 GHz simplified version of the 50 cm long undulator section for cold measurements.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP055  
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WEP056 Effect of Beam Transverse Angle Deflection in TGU on FEL Power ion, FEL, radiation, undulator 529
 
  • G. Zhou, J.Q. Wang
    IHEP, Beijing, People's Republic of China
  • J. Wu
    SLAC, Menlo Park, California, USA
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Recent study shows that electron beams with constant dispersion together with the transverse-gradient undulator (TGU) can reduce the sensitivity to energy spread for free-electron laser (FEL). By inducing dispersion function, electrons with different energy are placed at different positions corresponding to proper magnetic fields. Thus, FEL resonant condition can be kept for electrons with different energy. In this paper, we mainly studied: 1.The effects of electron beam angle deflection at the entrance of the TGU on the radiation power. 2. The utility of a kicker to introduce an angle deflection of electron beam to improve the FEL radiation power.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP056  
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WEP057 Design of a Compact Hybrid Undulator for the THz Radiation Facility of Delhi Light Source (DLS) ion, undulator, radiation, FEL 532
 
  • S. Tripathi, R.K. Bhandari, S. Ghosh, D. Kanjilal
    IUAC, New Delhi, India
  • U. Lehnert
    HZDR, Dresden, Germany
  • M. Tischer
    DESY, Hamburg, Germany
 
  Funding: One author, Sumit Tripathi (PH/16-17/0029), would like to acknowledge University Grant Commission (UGC), New Delhi, India for financial support as D.S.Kothari Postdoctoral fellowship.
A compact Free Electron Laser (FEL) facility to produce coherent THz radiation is in the development stage at Inter-University Accelerator Centre (IUAC), New Delhi, India.*,** The name of this facility is Delhi Light Source (DLS) in which a low-emittance electron beam from a photocathode RF gun with a maximum energy of 8 MeV will be injected into a compact undulator magnet to generate THz radiation. To produce the THz radiation in the range of 0.15 to 3.0 THz, the electron beam energy and the undulator gap need to be varied from 4 to 8 MeV and 20 to 45 mm, respectively. The variable gap undulator of 1.5-m length will consist of NdFeB magnets with vanadium permendur poles. The magnet design and dimensions are optimised by using code 3D RADIA.*** The detailed design of the compact hybrid undulator will be presented in this paper.
* S.Ghosh et al., presented at this conference.
** S.Ghosh et al., NIMB-2017 (in press).
*** RADIA. Available at http://www.esrf.eu/Accelerators/ groups/
Insertion Devices/ Software/ Radia.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP057  
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WEP060 Characterizing Sub-Femtosecond X-ray Pulses from the Linac Coherent Light Source ion, laser, simulation, detector 535
 
  • S. Li, R.N. Coffee, J. Cryan, K.H. Hegazy, Z. Huang, A. Marinelli, A. Natan, T. Osipov, D. Ray
    SLAC, Menlo Park, California, USA
  • G. Guo
    Stanford University, Stanford, California, USA
 
  The development of sub-femtosecond x-ray capabilities at the Linac Coherent Light Source requires the implementation of time-domain diagnostics with attosecond (as) time resolution. Photoelectrons created by attosecond duration x-ray pulses in the presence of a strong-laser field are known to suffer an energy spread which depends on the relative phase of the strong-laser field at the time of ionization. This phenomenon can be exploited to measure the duration of these ultrashort x-ray pulses. We present an implementation which employs a circularly polarized infrared laser pulse and novel velocity map imaging design which maps the phase dependent momentum of the photoelectron onto a 2-D detector. In this paper, we present the novel co-linear VMI design, simulation of the photoelectron momentum distribution, and the reconstruction algorithm.  
poster icon Poster WEP060 [1.260 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP060  
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WEP061 Thermal Stress Analysis of a Thin Diamond Crystal Under Repeated Free Electron Laser Heat Load ion, FEL, laser, free-electron-laser 539
 
  • J. Wu
    SLAC, Menlo Park, California, USA
  • B. Yang
    University of Texas at Arlington, Arlington, USA
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Thin crystals are used in many important optical elements, such as monochromator and spectrometer, in XFELs. To function properly, they must survive the ever-increasing heat load under repeated pulses. Here, we conduct a thermal stress analysis to examine the crystal lattice distortion due to the thermal load under various rep rates from 0.1 to 1 MHz. The thermal field is obtained by solving the transient heat transfer equations. The temperature-dependent material properties are used. It is shown that for pulse adsorption energy around tens of microjoule over a spot size of 10 micrometer, the thermal response of diamond is sensitive to rep rate. The thermal strain components are very different in the in- and out-of-plane directions, due to different constraint conditions. It suggests complicated strain effects in the Bragg and Laue diffraction cases.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP061  
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WEP062 Optical Beam Quality Analysis of the Clara Test Facility Using Second Moment Analysis ion, undulator, brightness, FEL 543
 
  • H.M. Castaneda Cortes, D.J. Dunning, M.D. Roper, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  We studied and characterised the FEL optical radiation in simulations of the CLARA FEL test facility under development at Daresbury Laboratory in the UK. In particular, we determined the optical beam quality coefficient, waist position and other source properties corresponding to different potential FEL operating modes via wavefront propagation in free space using OPC (Optical Propagation Code) and Second Moment Analysis. We were able to find the operation mode and undulator design for which the optical beam has the optimum quality at highest brightness. Furthermore, we studied the way that different properties of the electron bunches (emittance, peak current, bunch length) affect the optical beam. We are now able to understand how the optical beam will propagate from the end of the undulator and through the photon transport system to the experimental stations. This knowledge is necessary for the correct design of the photon transport and diagnostic systems.  
poster icon Poster WEP062 [0.495 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP062  
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WEP063 A Two-in-One Type Undulator undulator, ion, FEL, photon 547
 
  • D. Wang, H.X. Deng, Z. Jiang
    SINAP, Shanghai, People's Republic of China
 
  Funding: This work is supported by the Ministry of Science and Technology of China.
The typical X-ray free electron lasers have long tunnels to accommodate high energy electron linear accelerator and long undulator line to produce intense coherent radiations at very short wavelengths. The number of undulator lines is limited by the available space in the tunnel. This is especially true for those facilities that adopt underground tunnels or utilize the existing tunnels originally built for other purpose. This work explored the possibility to better use the tunnel space for accommodating more FEL undulator lines by designing a new type of undulator structure.
 
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WEP064 Tunable High-Gradient Quadrupoles for a Laser-Plasma Acceleration-Based FEL ion, quadrupole, laser, permanent-magnet 550
 
  • A. Ghaith, F. Blache, M.-E. Couprie, C.A. Kitegi, F. Marteau, P. N'gotta, M. Valléau, J. Vétéran
    SOLEIL, Gif-sur-Yvette, France
  • C. Benabderrahmane
    ESRF, Grenoble, France
  • O. Cosson, F. Forest, P. Jivkov, J.L. Lancelot
    Sigmaphi, Vannes, France
 
  The magnetic design and characterization of tunable high gradient permanent magnet based quadrupole, are presented. To achieve a high gradient field with a compact structure, permanent magnets are chosen rather than usual electro-magnets due to their small aperture. The quadrupole structure consists of two quadrupoles superimposed capable of generating a gradient of 210 T/m. The first quadrupole is composed of permanent magnets following a Halbach configuration shaped as a ring attaining a constant gradient of 160T/m, and the second of four permanent magnet cylinders surrounding the ring and capable of rotating around their axis to achieve a gradient tunability of ±50 T/m. Each tuning magnet is connected to a motor and is controlled independently, enabling the gradient to be tuned with a rather good magnetic center stability (±20 μm) and without any field asymmetry. Seven quadrupoles have been built with different magnetic lengths in order to fulfil the integrated gradient required. A set of QUAPEVA triplet are now in use, to focus a high divergent electron beam with large energy spread generated by a laser plasma acceleration source for a free electron laser application.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP064  
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WEP065 Cryogenic Permanent Magnet Undulator for an FEL Application ion, undulator, radiation, permanent-magnet 554
 
  • A. Ghaith, T. André, I.A. Andriyash, P. Berteaud, F. Briquez, N. Béchu, M.-E. Couprie, C. Herbeaux, M. Labat, O. Marcouillé, F. Marteau, E. Roussel, M. Sebdaoui, K.T. Tavakoli, M. Tilmont, M. Valléau
    SOLEIL, Gif-sur-Yvette, France
 
  A Cryogenic Permanent Magnet Undulator (CMPU) is capable of achieving high brightness radiation at short wavelengths, by taking advantage of the permanent magnets' enhanced performance at low temperature. A CPMU of period 18 mm (U18) that has been built at Synchrotron SOLEIL is used for the COXINEL project to demonstrate Free Electron Laser (FEL) at 200 nm using a laser plasma acceleration source. Another undulator of period 15 mm (U15) is currently being built to replace U18 undulator for FEL demonstration at 40 nm. A new method is also introduced, using SRWE code, to compute the spectra of the large energy spread beam (few percent) taking into account the variation of the Twiss parameters for each energy slice. The construction of U18 undulator and the magnetic measurements needed for optimization, as well as the mechanical design of U15, are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP065  
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WEP073 Lie Map Formalism for FEL Simulation ion, radiation, undulator, coupling 557
 
  • K. Hwang, J. Qiang
    LBNL, Berkeley, California, USA
 
  Funding: U.S. Department of Energy under Contract No. DE-AC02-05CH11231
Undulator averaging and non-averaging are in compromisation between computational speed and reliability. It is hard to catch the advantages of the both methods simultaneously. In this report, we present a method that compromises the between the averaging and non-averaging methods through Lie map formalism.
 
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WEP074 Simulations of the Dependence of Harmonic Radiation on Undulator Parameters ion, undulator, radiation, FEL 560
 
  • G. Penn
    LBNL, Berkeley, California, USA
 
  Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The flux and bandwidth of radiation produced at harmonics of the fundamental are very sensitive to the undulator parameter, and thus the beam energy or undulator period. We look at high-energy XFELs with parameters relevant to the MaRIE FEL design. Both SASE and seeded FELs are considered.
 
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WEP078 Period-Averaged Symplectic Maps for the FEL Hamiltonian ion, FEL, radiation, wiggler 563
 
  • S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
 
  Funding: This work was carried out with support for the United State Department of Energy, Office of Scientific Research, under SBIR contract number DE-SC0017161.
Conventional treatments of synchrotron radiation in electron beams treat the radiation as a non-Hamiltonian aspect to the beam dynamics. However, the radiation can be modeled with an electromagnetic Hamiltonian. We present a period-averaged treatment of the FEL problem which includes the Hamiltonian aspects of the coupled electron-radiation dynamics. This approach is then applied to two problems: a 3D split-operator symplectic integrator, and a 1D single-mode FEL treated using Hamiltonian perturbation theory.
 
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THB02 Non-Standard Use of Laser Heater for FEL Control and THz Generation ion, laser, FEL, controls 566
 
  • E. Allaria, L. Badano, M.B. Danailov, A.A. Demidovich, S. Di Mitri, D. Gauthier, L. Giannessi, G. Penco, E. Roussel, P. Sigalotti, S. Spampinati, M. Trovò, M. Veronese
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • E. Roussel
    SOLEIL, Gif-sur-Yvette, France
 
  The laser heater system is currently used at various FEL facilities for an accurate control of the electron beam energy spread in order to suppress the micro-bunching instabilities that can develop in high brightness electron beams. More recently, studies and experiments have shown that laser-electron interaction developing in the laser heater can open new possibilities for tailoring the electron beam properties to meet special requirements. A suitable time-shaping of the laser heater pulse opened the door to the generation of (tens of) femtosecond-long FEL pulses. Using standard laser techniques it is also possible to imprint onto the electron bunch, energy and density modulations in the THz frequency range that, properly sustained through the accelerator, can be exploited for generation of coherent THz radiation at GeV beam energies. Such recent results at the FERMI FEL are here reported, together with near future plans.  
slides icon Slides THB02 [14.882 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-THB02  
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FRB01 Time-Domain Analysis of Attosecond Pulse Generation in an X-Ray Free-Electron Laser ion, FEL, radiation, undulator 569
 
  • P. Baxevanis, Z. Huang, A. Marinelli
    SLAC, Menlo Park, California, USA
 
  The method of enhanced self-amplified spontaneous emission (eSASE) is one of the strongest candidates for the generation of sub-femtosecond X-ray pulses in a free-electron laser. The optimization of an eSASE experiment involves many independent parameters, which makes the exploration of the parameter space with 3-D simulations computationally intensive. Therefore, a robust theoretical analysis of this problem is extremely desirable. We provide a self-consistent, analytical treatment of such a configuration using a one-dimensional, time-dependent FEL model that includes the key effects of linear e-beam chirp and linear undulator taper. Verified via comparison with numerical simulation, our formalism is also utilized in parameter studies that seek to determine the optimum setup of the FEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB01  
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FRB03 Dynamics of Superradiant Emission by a Prebunched E-Beam and its Spontaneous Emission Self-Interaction ion, radiation, wiggler, undulator 572
 
  • R. Ianconescu, A. Gover
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  • C. Emma, P. Musumeci
    UCLA, Los Angeles, USA
  • A. Friedman
    Ariel University, Ariel, Israel
 
  Funding: Partial support by US-Israel Binational Science Foundation (BSF) and by Deutsche-Israelische Projektkooperation (DIP).
In the context of radiation emission from an electron beam, Dicke's superradiance (SR) is the enhanced coherent spontaneous radiation emission from a prebunched beam, and Stimulated-Superradiance (ST-SR) is the further enhanced emission of the bunched beam in the presence of a phase-matched radiation wave.* These processes are analyzed for undulator radiation in the framework of radiation field mode-excitation theory. In the nonlinear saturation regime the synchronicity of the bunched beam and an injected radiation wave may be sustained by wiggler tapering: Tapering-Enhanced Superradiance (TES) and Tapering-Enhanced Stimulated Superradiance Amplification (TESSA).** Identifying these processes is useful for understanding the enhancement of radiative emission in the tapered wiggler section of seeded FELs.***,**** The nonlinear formulation of the energy transfer dynamics between the radiation wave and the bunched beam fully conserves energy. This includes conservation of energy without radiation reaction terms in the interesting case of spontaneous self-interaction (no input radiation).
* A. Gover, Phys. Rev. ST-AB 8, 030701 (2005).
** J. Duris et al., New J.Phys. 17 063036 (2015).
*** E. A. Schneidmiller et al., PRST-AB 18, 03070 (2015).
**** C. Emma et al., this conference.
 
slides icon Slides FRB03 [1.437 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB03  
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FRB04 Canonical Formulation of 1D FEL Theory Revisited, Quantized and Applied to Electron Evolution ion, FEL, radiation, undulator 576
 
  • P.M. Anisimov
    LANL, Los Alamos, New Mexico, USA
 
  An original FEL theory relied on quantum analysis of photon generation by relativistic electrons in alternating magnetic field.* In most cases, however, the system of pendulum equations for non-canonical variables and the theory of classical electromagnetism proved to be adequate. As XFELs advance to higher energy photons, quantum effects of electron recoil and shot noise has to be considered. This work presents quantization procedure based on the Hamiltonian formulation of an XFEL interaction in 1D case. The procedure relates the conventional variables to canonical coordinates and momenta and does not require the transformation to the Bambini-Renieri frame.** The relation of a field operator to a photon annihilation operator reveals the meaning of the quantum FEL parameter, introduced by Bonifacio, as a number of photons emitted by a single electron before the saturation takes place.*** The quantum description is then applied to study how quantum nature of electrons affects the startup of XFEL and how quantum electrons become indistinguishable from a classical ensemble of electrons due to their interaction with a ponderomotive potential of an XFEL.
* Madey JMJ 1971 J. Appl. Phys. 42 1906 13.
** Bambini A and Renieri A 1978 Lett. Nuovo Cimento 21 399-404.
*** Bonifacio R, Piovella N, Robb G R M and Schiavi A 2006 PRSTAB 9 090701.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB04  
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FRB05 Wide Bandwidth, Frequency Modulated Free Electron Laser ion, FEL, undulator, radiation 581
 
  • L.T. Campbell, B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
 
  The resonant frequency of a free electron laser may be modulated via the undulator or electron beam parameters. This modulation may generate sidebands which can subsequently undergo amplification, analogous to frequency modulation in a conventional cavity laser. However, due to the relative slippage of the light through the relativistic electron beam, the FM-FEL system has a more complex behavior than its conventional laser counterpart. The system may be described in the linear regime by a summation over exponential gain modes, allowing the amplification of multiple light frequencies simultaneously. It is found that, with only small, few percent variations of the FEL parameters, one may generate and amplify multiple modes within a frequency bandwidth which greatly exceeds that of normal FEL operation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-FRB05  
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