Keyword: laser
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MOA01 John Madey: A Short History of My Friend and Colleague ion, FEL, electron, undulator 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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MOD04 Status and Perspectives of the FERMI FEL Facility ion, FEL, electron, 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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MOP001 Diamond Double-Crystal System for a Forward Bragg Diffraction X-Ray Monochromator of the Self-Seeded PAL XFEL ion, FEL, photon, electron 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, electron, 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, electron, 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, electron, 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.  
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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, radiation, electron, 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.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP010  
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MOP016 Comparing FEL Codes for Advanced Configurations ion, FEL, simulation, electron 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, bunching, electron, 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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MOP019 Transient Thermal Stress Wave Analysis of a Thin Diamond Crystal Under Laser Heat Load ion, FEL, site, electron 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, electron, undulator, FEL 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, electron, FEL, undulator 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, radiation, electron 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, electron, 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, electron, 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, electron, FEL, emittance 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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MOP042 Status of Seeding Development at sFLASH ion, electron, 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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MOP046 Progress of Delhi Light Source at IUAC, New Delhi ion, electron, cathode, 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.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP046  
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MOP053 High Spectral Density Compton Back-Scattered Gamma-Ray Sources at Fermilab ion, electron, 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, electron 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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MOP059 Synchronized Mid-Infrared Pulses at the Fritz Haber Institute IR-FEL ion, FEL, cavity, electron 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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MOP064 An Experimental Setup for Probing the Thermal Properties of Diamond Regarding Its Use in an XFELO ion, FEL, electron, 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, electron, undulator 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, electron 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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TUB01 Seeding Experiments and Seeding Options for LCLS II ion, FEL, photon, electron 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, electron, 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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TUC02 Thermal and Mechanical Stability of Bragg Reflectors under Pulsed XFEL Radiation ion, radiation, FEL, photon 240
 
  • I. Bahns, C.P. Maag, J. Roßbach, P. Thiessen
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • H. Sinn, V. Sleziona
    XFEL. EU, Hamburg, Germany
  • J. Zemella
    DESY, Hamburg, Germany
 
  Funding: BMBF FKZ 05K16GU4
Free-electron laser(FEL) x-ray radiation can deliver pulses with a huge amount of energy in short time duration. X-ray optics like Bragg reflectors therefore must be chosen in a way that they can withstand radiation-material interaction without getting damaged so that they can maintain their technical functionality. Therefore thermal and mechanical reactions of Bragg reflectors to the radiation induced thermal strain and force (radiation pressure) have been considered in this study. The theory of thermoelasticity has been used to simulate the strain conditions at saturation of the amplifying process in an X-ray free-electron laser oscillator(XFELO). One aim of this study was to investigate, if the radiation pressure could be an effect that gives a considerable contribution to the strain propagation. The results of the simulations have shown that, if Bragg backscattering of the X-ray pulse by a diamond crystal with 99% reflectivity and 1% absorptivity is assumed, the value of the thermally induced strain is about two magnitudes higher than the radiation pressure induced strain.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUC02  
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TUC04 Enhancement of Radiative Energy Extraction in an FEL Oscillator by Post-Saturation Beam Energy Ramping ion, electron, 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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TUP010 Double-Bunches for Two-Color Soft X-Ray Free-Electron Laser at the MAX IV Laboratory ion, linac, electron, 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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TUP042 Determination of the Slice Energy Spread of Ultra-Relativistic Electron Beams by Scanning Seeded Coherent Undulator Radiation ion, electron, 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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TUP053 The ACHIP Experimental Chambers at PSI ion, electron, experiment, FEL 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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TUP058 Slippage-Enhanced SASE FEL ion, FEL, undulator, electron 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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP058  
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TUP059 Alternative Electron Beam Slicing Methods for CLARA and X-ray FELs ion, FEL, electron, 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, electron, 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, acceleration, electron, 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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP065  
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TUP066 Luminosity Increase in Laser-Compton Scattering by Crab Crossing ion, luminosity, electron, 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, electron, experiment 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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TUP070 Development of Mid-Infrared Photoacoustic Spectroscopy System for Solid Samples at Kyoto University Free Electron Laser Facility ion, FEL, experiment, electron 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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WEB04 Laser-to-RF Synchronization with Femtosecond Precision ion, FEL, LLRF, operation 407
 
  • T. Lamb, L. Butkowski, E.P. Felber, M. Felber, M. Fenner, S. Jabłoński, T. Kozak, J.M. Müller, P. Prędki, H. Schlarb, C. Sydlo, M. Titberidze, F. Zummack
    DESY, Hamburg, Germany
 
  Optical synchronization systems are already in regular operation in many FELs, or they will eventually be implemented in the future. In FLASH and the European XFEL, phase-stable optical reference signals are provided by a pulsed optical synchronization system in order to achieve low timing jitter FEL performance. The generation of phase-stable RF signals from a pulsed optical synchronization system is still a field of active research. The optical reference module (REFM-OPT), designed at DESY for operation in both FELs, employs a laser-to-RF phase detector, based on an integrated Mach-Zehnder interferometer. The phase drift of the 1.3 GHz RF reference signals with respect to the optical pulses is measured and actively corrected within the REFM-OPT at multiple locations in the accelerator. Therefore the REFM-OPT provides phase stable 1.3 GHz RF reference signals at these locations. The short-term and long-term performance in the accelerator tunnel of the European XFEL is presented and carefully reviewed.  
slides icon Slides WEB04 [5.683 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEB04  
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WEP003 Update on the Lifetime of Cs2Te Photocathodes Operated at FLASH ion, cathode, gun, operation 415
 
  • S. Schreiber, S. Lederer
    DESY, Hamburg, Germany
  • P. Michelato, L. Monaco, D. Sertore
    INFN/LASA, Segrate (MI), Italy
 
  The photoinjector of the free-electron laser facility FLASH at DESY (Hamburg, Germany) uses Cs2Te photocathodes. We report on an update of the lifetime and quantum efficiency of cathodes operated at FLASH during the last years.  
poster icon Poster WEP003 [0.286 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP003  
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WEP006 Preliminary On-Table and Photoelectron Results from the PITZ Quasi-Ellipsoidal Photocathode Laser System ion, cathode, electron, 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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WEP008 Beam Brightness Improvement by Ellipsoidal Laser Shaping for CW Photoinjectors ion, emittance, gun, cathode 432
 
  • H.J. Qian, M. Krasilnikov, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
 
  High-brightness photoinjectors operating in a continuous wave (CW) mode are required for many advanced applications, such as CW X-ray FEL, ERL light source, electron coolers for hadron beams and electron-ion colliders and so on. Now, three types of CW electron guns are available: DC gun, SRF gun and normal conducting RF gun, which are under intense development in different institutes based on local expertise and application demands. Compared to pulsed guns, both beam energy and brightness from CW guns are compromised due to a lower acceleration gradient. Flattop laser shaping has been applied in both pulsed and CW guns to improve beam emittance. In this paper, ellipsoidal laser shaping is applied in CW photoinjectors to improve beam brightness, and preliminary ASTRA simulations are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP008  
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WEP012 A 2.45 GHz Photoinjector Gun for an FEL Driven by Laser Wakefield Accelerated Beam ion, klystron, cathode, cavity 444
 
  • S.V. Kuzikov, S.A. Bogdanov, E. Gacheva, E.V. Ilyakov, D.S. Makarov, S. Mironov, A. Poteomkin, A. Shkaev, A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
 
  Funding: This work was supported by the Russian Scientific Foundation (grant #16-19-10448).
The photoinjector of short electron bunches is a key element of investigations aimed on particle acceleration by pulses of the subpetawatt laser PEARL (10 J, 50-70 fs). The projected parameters of the photoinjector are an electron energy level of 5 MeV, a charge > 0.1 nC, a bunch length of about 3 mm, a transversal emittance no worse than 1 mm*mrad, and an energy spread no more than ~0.1%. The photoinjector is based on klystron KIU-111 at frequency 2.45 GHz, produced by company Toriy (output power ~ 5 MW, pulse length ~ 7 mcs, efficiency ~ 44%, power gain ~ 50 dB). It is proposed to use this klystron in order to feed the accelerating resonator of the classical design consisted of 1.5 cells in which the photocathode is inserted. On a base of third harmonics of a Ti:Sa laser, we plan to produce picosecond pulses of no less than 100 mcJ in energy. The photocathode is planned to be made of CVD diamond film which is not critical to vacuum degree and surface contamination, has high QE, a long lifetime, and is capable of being used with cheap, long wavelength optical lasers.
 
poster icon Poster WEP012 [1.194 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP012  
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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, cathode, electron, 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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WEP018 Electron Beam Heating with the European XFEL Laser Heater ion, electron, 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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WEP026 Inducing Microbunching in the CLARA FEL Test Facility ion, electron, 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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WEP029 Recent Experimental Results on High-Peak-Current Electron Bunch and Bunch Trains Interacting With a THz Undulator ion, radiation, undulator, electron 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, controls, electron 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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WEP060 Characterizing Sub-Femtosecond X-ray Pulses from the Linac Coherent Light Source ion, electron, 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, electron, 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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WEP064 Tunable High-Gradient Quadrupoles for a Laser-Plasma Acceleration-Based FEL ion, quadrupole, electron, 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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THB02 Non-Standard Use of Laser Heater for FEL Control and THz Generation ion, electron, 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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