Keyword: undulator
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MOA01 John Madey: A Short History of My Friend and Colleague ion, FEL, electron, 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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MOP003 Concept for a Seeded FEL at FLASH2 ion, FEL, electron, laser 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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MOP010 Constraints on Pulse Duration Produced by Echo-Enabled Harmonic Generation ion, laser, radiation, electron 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 ion, quadrupole, electron, 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, electron, 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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MOP014 Harmonic Lasing Towards Shorter Wavelengths in Soft X-Ray Self-Seeding FELs ion, FEL, radiation, photon 57
 
  • 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
 
  In this paper, we study a simple harmonic lasing scheme to extend the wavelength of X-ray self-seeding FELs. The self-seeding amplifier is comprised of two stages. In the first stage, the fundamental radiation is amplified but well restricted below saturation, and simultaneously harmonic radiation is generated. In the second stage, the fundamental radiation is suppressed while the harmonic radiation is amplified to saturation. We performed a start-to-end simulation to demonstrate third harmonic lasing in a soft x-ray self-seeding FEL at the fundamental wavelength of 1.52 nm. Our simulations show that a stable narrow-band FEL at GW levels can be obtained.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP014  
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MOP018 Distributed Self-Seeding Scheme for LCLS-II ion, simulation, electron, 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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MOP020 Sideband Instability in a Tapered Free Electron Laser ion, electron, 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, electron, FEL, 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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MOP024 Simulation and Optimization for Soft X-Ray Self-Seeding at SXFEL User Facility ion, simulation, FEL, radiation 87
 
  • K.Q. Zhang, C. Feng, D. Wang, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
 
  The simulation and optimization studies for the soft x-ray self-seeding experiment at SXFEL have been presented in this paper. Some critical physical problems have been intensively studied to help us obtain a more stable output and a clearer spectrum. The monochromator is optimized considering various unideal conditions such as the reflection rate, diffraction rate and the roughness of the grating and the mirrors. An integrated self-seeding simulation is also presented. The calculation and simulation results show that the properties of the self-seeding can be significantly improved by using the optimized design of the whole system and the evaluation of grating monochromator shows that the presented design is reliable for soft x-ray self-seeding experiment at SXFEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP024  
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MOP026 Study of an Echo-Enabled Harmonic Generation Scheme for the French FEL Project LUNEX5 ion, FEL, laser, electron 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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MOP031 First Operation of a Harmonic Lasing Self-Seeded FEL ion, FEL, electron, 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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MOP032 Reverse Undulator Tapering for Polarization Control and Background-Free Harmonic Production in XFELs: Results from FLASH ion, FEL, background, radiation 106
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
 
  Baseline design of a typical X-ray FEL undulator assumes a planar configuration which results in a linear polarization of the FEL radiation. However, many experiments at X-ray FEL user facilities would profit from using a circularly polarized radiation. As a cheap upgrade, one can consider an installation of a short helical afterburner, but then one should have an efficient method to suppress powerful linearly polarized background from the main undulator. There is an efficient method for such a suppression: an application of the reverse taper in the main undulator.* In this contribution, we present the results of experiments with reverse taper at FLASH2 where a high contrast between FEL intensities from the afterburner and from the reverse-tapered main undulator was demonstrated. Another important application of the reverse taper is a possibility to produce FEL harmonics in the afterburner (or in the last part of baseline gap-tunable undulator). We present recent results from FLASH2 where the second and the third harmonics were efficiently generated with a low background at the fundamental.
* E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST Accel. Beams 13-080702 (2013).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP032  
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MOP033 Baseline Parameters of the European XFEL ion, FEL, electron, 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, FEL, electron, 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, electron, 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, electron, FEL, 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.  
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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, FEL, photon, electron 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, electron, FEL, 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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MOP044 Commissioning Status of the European XFEL Photon Beam System ion, FEL, photon, MMI 144
 
  • F. Le Pimpec
    XFEL. EU, Hamburg, Germany
 
  The European XFEL located in the Hamburg region in Germany has finished its construction phase and is currently being commissioned. The European XFEL facility aims at producing X-rays in the range from 260~eV up to 24~keV out of three undulators that can be operated simultaneously with up to 27000~pulses/second. The FEL is driven by a 17.5~GeV linear accelerator based on TESLA-type superconducting accelerator modules. The accelerator has finished its first commissioning phase and is currently delivering photon beam to the experimental areas for commissioning in view to the user operation. This paper presents the status of the photon beam system from the undulators to the 3 experimental areas as well as the status of each instruments.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP044  
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MOP046 Progress of Delhi Light Source at IUAC, New Delhi ion, electron, cathode, laser 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, electron, 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.
 
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MOP048 A Compact THz FEL at KAERI: the Project and the Status ion, FEL, electron, 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, electron, 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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MOP050 Present Status of Infrared FEL Facility at Kyoto University ion, FEL, cathode, operation 162
 
  • H. Zen, T. Kii, S. Krainara, K. Masuda, H. Ohgaki, J. Okumura, S. Suphakul, S. Tagiri, K. Torgasin
    Kyoto University, Kyoto, Japan
 
  A mid-infrared free electron laser (FEL) named KU-FEL has been developed for promoting energy-related research at the Institute of Advanced Energy, Kyoto University.* KU-FEL can cover the wavelength range from 3.6 to 23 micrometers and is routinely operated for internal and external user experiments. Recently a THz Coherent Undulator Radiation (CUR) source using a photocathode RF gun has been developed as an extension of the facility.* As the result of commissioning the experiment, it was confirmed that the CUR source can cover the frequency range from 160 to 550 GHz. Present status of these infrared light sources will be presented.
* H. Zen et al., Physics Procedia 84, pp.47-53 (2016).
 
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MOP052 First Observation of Coherent THz Undulator Radiation Driven by NSRRC High Brightness Photo-Injector ion, radiation, electron, 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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MOP054 CLARA Facility Layout and FEL Schemes ion, FEL, laser, 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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MOP055 SCLF: An 8-GeV CW SCRF Linac-Based X-Ray FEL Facility in Shanghai ion, FEL, electron, 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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MOP062 X-ray FEL Oscillator Seeded Harmonic Amplifier for High Energy Photons ion, FEL, electron, 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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MOP066 Free Electron Lasers in 2017 FEL, ion, electron, 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, FEL, laser, 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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TUB04 Recent On-Line Taper Optimization on LCLS ion, FEL, electron, 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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TUC01 Polarization Control of Storage Ring FELs Using Cross Polarized Helical Undulators ion, FEL, polarization, controls 235
 
  • J. Yan, H. Hao, S.F. Mikhailov, V. Popov, Y.K. Wu
    FEL/Duke University, Durham, North Carolina, USA
  • S. Huang
    PKU, Beijing, People's Republic of China
  • J.L. Li
    IHEP, Beijing, People's Republic of China
  • V. Litvinenko
    Stony Brook University, Stony Brook, USA
  • N.A. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
 
  For more than two decades, accelerator researchers have been working to gain control of polarization of synchrotron radiation and FELs using non-optical means. In 2005, the first experimental demonstration of polarization control of an FEL beam was realized with the Duke storage-ring FEL. With the recent upgrade of the undulator system, the Duke FEL can be operated with up to four helical undulators simultaneously. Using two sets of helical undulators with opposite helicities, for the first time, we have demonstrated full polarization control of a storage ring FEL. First, the helicity switch of the FEL beam has been realized with good lasing up to a few Hz. Second, the linearly polarized FEL beam has been generated with a high degree of polarization (Plin>0.95). The FEL polarization direction can be fully controlled using a buncher magnet. Furthermore, the use of non-optical means to control the FEL polarization allows us to extend polarization control to gamma-ray beams generated using Compton scattering. This has been experimentally demonstrated with the production of linearly polarized Compton gamma-ray beams with rotatable polarization direction based upon helical undulators.  
slides icon Slides TUC01 [5.921 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUC01  
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TUP004 Longitudinal Phase Space Optimization for the Hard X-ray Self-Seeding ion, FEL, simulation, electron 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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TUP039 Electron Beam Requirements for Coherent Electron Cooling FEL System ion, electron, FEL, 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.
 
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TUP042 Determination of the Slice Energy Spread of Ultra-Relativistic Electron Beams by Scanning Seeded Coherent Undulator Radiation ion, electron, laser, radiation 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, radiation, electron 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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TUP058 Slippage-Enhanced SASE FEL ion, FEL, electron, 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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TUP061 Study of the Electron Transport in the COXINEL FEL Beamline Using a Laser-Plasma Accelerated Electron Beam ion, laser, electron, 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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TUP062 Electromagnetic and Mechanical Analysis of a 14 mm 10-period NbTi Superconducting Undulator ion, experiment, insertion-device, insertion 360
 
  • F. Trillaud, G.A. Barraza Montiel
    UNAM, Cuernavaca, Morelos, Mexico
  • M. Gehlot, G. Mishra
    Devi Ahilya University, Indore, India
 
  Funding: DGAPA of UNAM, fund PAPIIT TA100617 SERB, India
A 14 mm - 10 period NbTi superconducting undulator for the next generation of Free Electron Laser has been stud- ied. The optimum electromagnetic pre-design was carried out using RADIA, an extension module of the commercial software Mathematica. For this pre-design, a variable gap was considered. Additionally, a thermo-mechanical study of one eighth of the superconducting undulator was conducted. This study utilized a thermal and mechanical contact model between the pancake coils and the carbon steel core. This coupled model allowed estimating the minimum pre-loading of the coil. This pre-loading ensures that the coil would remain stuck to its pole during cooling. Numerical results are presented for both studies.
* M. Gehlot et al., Nucl. Inst. and Meth. in Phys. Res., Sec. A, Vol. 846, p. 13-17, 2017.
** B.J.A. Shepherd et al., Proceedings of IPAC2014, WEPRI095, 2014.
*** J. Grimmer, R. Kmak, PAC 2005.
 
poster icon Poster TUP062 [1.360 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP062  
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WEC02 Optimization of Superconducting Undulators for Low Repetition Rate FELs ion, FEL, electron, 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, electron 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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WEP018 Electron Beam Heating with the European XFEL Laser Heater ion, laser, electron, FEL 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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WEP029 Recent Experimental Results on High-Peak-Current Electron Bunch and Bunch Trains Interacting With a THz Undulator ion, radiation, electron, 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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WEP031 Using A Neural Network Control Policy For Rapid Switching Between Beam Parameters in an FEL ion, FEL, network, controls 488
 
  • A.L. Edelen, S. Biedron, S.V. Milton
    CSU, Fort Collins, Colorado, USA
  • P.J.M. van der Slot
    Mesa+, Enschede, The Netherlands
 
  FEL user facilities often must accommodate requests for a variety of beam parameters. This usually requires skilled operators to tune the machine, reducing the amount of available time for users. In principle, a neural network control policy that is trained on a broad range of operating states could be used to quickly switch between these requests without substantial need for human intervention. We present preliminary results from an ongoing study in which a neural network control policy is investigated for rapid switching between beam parameters in a compact THz FEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP031  
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WEP040 Sub-Femtosecond Time-Resolved Measurements Based on a Variable Polarization X-Band Transverse Deflecting Structures for SwissFEL ion, FEL, diagnostics, polarization 499
 
  • P. Craievich, M. Bopp, H.-H. Braun, R. Ganter, M. Pedrozzi, E. Prat, S. Reiche, R. Zennaro
    PSI, Villigen PSI, Switzerland
  • R.W. Aßmann, F. Christie, R.T.P. D'Arcy, B. Marchetti, D. Marx
    DESY, Hamburg, Germany
  • N. Catalán Lasheras, A. Grudiev, G. McMonagle, W. Wuensch
    CERN, Geneva, Switzerland
 
  The SwissFEL project, under commissioning at the Paul Scherrer Institut (PSI), will produce FEL radiation for soft and hard X-rays with pulse durations ranging from a few to several tens of femtoseconds. A collaboration between DESY, PSI and CERN has been established with the aim of developing and building an advanced X-Band transverse deflector structure (TDS) with the new feature of providing variable polarization of the deflecting force. As this innovative CERN design requires very high manufacturing precision to guarantee highest azimuthal symmetry of the structure to avoid the deterioration of the polarization of the streaking field, the high-precision tuning-free assembly procedures developed at PSI for the SwissFEL C-band accelerating structures will be used for the manufacturing. Such a TDS will be installed downstream of the undulators of the soft X-ray beamline of SwissFEL and thanks to the variable polarization of the TDS, it will be possible to perform a complete characterization of the 6D phase-space. We summarize in this work the status of the project and its main technical parameters.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP040  
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WEP041 HLS to Measure Changes in Real Time in the Ground and Building Floor of PAL-XFEL, Large-Scale Scientific Equipment ion, linac, FEL, real-time 503
 
  • H. J. Choi, J.H. Han, H.-S. Kang, S.H. Kim, H.-G. Lee, S.B. Lee
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  A variety of parts that comprise large-scale scientific equipment should be installed and operated at accurate three-dimensional location coordinates (X, Y, Z) through survey and alignment in order to ensure optimal performance. However, uplift or subsidence of the ground occurs over time, and consequently causes the deformation of building floors. The deformation of the ground and buildings cause changes in the location of installed parts, eventually leading to alignment errors (ΔX, ΔY, ΔZ) of components. As a result, the parameters of the system change and the performance of large-scale scientific equipment is degraded. Alignment errors that result from changes in building floor height can be predicted by real-time measurement of changes in building floors. This produces the advantage of reducing survey and alignment time by selecting the region where great changes in building floor height are shown and re-aligning components in the region in a short time. To do so, HLS (hydrostatic leveling sensor) with a resolution of 0.2 micrometers and a waterpipe of 1 km are installed at the PAL-XFEL building. This paper introduces the installation and operation status of HLS.  
poster icon Poster WEP041 [0.832 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP041  
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WEP044 Beam Loss Monitor for Undulators in PAL-XFEL ion, background, operation, electron 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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WEP048 Coherent Undulator Radiation From a Kicked Electron Beam ion, electron, radiation, 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, electron, 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, FEL, radiation, electron 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, electron, 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, electron, FEL, radiation 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, radiation, electron, 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.
 
poster icon Poster WEP057 [1.117 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP057  
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WEP062 Optical Beam Quality Analysis of the Clara Test Facility Using Second Moment Analysis ion, brightness, FEL, electron 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 ion, FEL, photon, electron 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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP063  
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WEP065 Cryogenic Permanent Magnet Undulator for an FEL Application ion, electron, 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, coupling, electron 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, radiation, electron, 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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FRB01 Time-Domain Analysis of Attosecond Pulse Generation in an X-Ray Free-Electron Laser ion, FEL, radiation, electron 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, electron, wiggler 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, electron, FEL, radiation 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.
 
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FRB05 Wide Bandwidth, Frequency Modulated Free Electron Laser ion, FEL, radiation, electron 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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