TUP —  Tuesday Poster Session   (27-Aug-19   14:15—15:45)
Paper Title Page
TUP001 Extension of the PITZ Facility for a Proof-of-Principle Experiment on THz SASE FEL 38
 
  • P. Boonpornprasert, G.Z. Georgiev, G. Koss, M. Krasilnikov, X. Li, F. Mueller, A. Oppelt, S. Philipp, H. Shaker, F. Stephan, T. Weilbach
    DESY Zeuthen, Zeuthen, Germany
  • Z.G. Amirkhanyan
    CANDLE SRI, Yerevan, Armenia
 
  The Photo Injector Test Facility at DESY in Zeuthen (PITZ) has been proposed as a suitable facility for research and development of an accelerator-based THz source prototype for pump-probe experiments at the European XFEL. A proof-of-principle experiment to generate THz SASE FEL radiation by using an LCLS-I undulator driven by an electron bunch from the PITZ accelerator has been planned and studied. The undulator is foreseen to be installed downstream from the current PITZ accelerator, and an extension of the accelerator tunnel is necessary. Radiation shielding for the extended tunnel was designed, and construction works are finished. Design of the extended beamline is ongoing, not only for this experiment but also for other possible experiments. Components for the extended beamline, including magnets for beam transport, a chicane bunch compressor, electron beam diagnostics devices, and THz radiation diagnostics devices have been studied. An overview of these works will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP001  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP002 Progress in Preparing a Proof-of-Principle Experiment for THz SASE FEL at PITZ 41
 
  • X. Li, P. Boonpornprasert, Y. Chen, G.Z. Georgiev, J.D. Good, M. Groß, P.W. Huang, I.I. Isaev, C. Koschitzki, M. Krasilnikov, S. Lal, O. Lishilin, G. Loisch, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, G. Vashchenko
    DESY Zeuthen, Zeuthen, Germany
 
  A proof-of-princle experiment for a THz SASE FEL is undergoing preparation at the Photo Injector Test facility at DESY in Zeuthen (PITZ), as a prototype THz source for pump-probe experiments at the European XFEL, which could potentially provide up to mJ/pulse THz radiation while maintaining the identical pulse train structure as the XFEL pulses. In the proof-of-principle experiment, LCLS-I undulators will be installed to generate SASE radiation in the THz range of 3-5 THz from electron bunches of 16-22 MeV/c. One key design is to obtain the peak current of nearly 200 A from the heavily charged bunches of a few nC. In this paper, we report our simulation results on the optimization of the space charge dominated beam in the photo injector and the following transport line with two cathode laser setups. Experimental results based on a short Gaussian laser will also be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP002  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP003 Design of a Magnetic Bunch Compressor for the THz SASE FEL Proof-of-Principle Experiment at PITZ 45
 
  • H. Shaker, P. Boonpornprasert, G.Z. Georgiev, G. Koss, M. Krasilnikov, X. Li, A. Lueangaramwong, F. Mueller, A. Oppelt, S. Philipp, F. Stephan, G. Vashchenko, T. Weilbach
    DESY Zeuthen, Zeuthen, Germany
 
  For pump-probe experiments at the European XFEL, a THz source is required to produce intense THz pulses at the same repetition rate as the X-ray pulses from XFEL. Therefore, an accelerator-based THz source with identical electron source as European XFEL was suggested and proof-of-principle experiments utilizing an LCLS I undulator will be performed at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). The main idea is to use a 4nC beam for maximum SASE radiation but to allow different radiation regimes a magnetic bunch compressor can be used. This helps e.g. to reduce the saturation length inside the undulator and also to study super-radiant THz radiation. In this paper a design of a chicane type magnetic bunch compressor using HERA corrector magnets is presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP003  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP004 A Superradiant THz Undulator Source for XFELs 48
 
  • T. Tanikawa, G. Geloni, S. Karabekyan, S. Serkez
    EuXFEL, Schenefeld, Germany
  • V.B. Asgekar
    University of Pune, Pune, India
  • S. Casalbuoni
    KIT, Eggenstein-Leopoldshafen, Germany
  • M. Gensch
    Technische Universität Berlin, Berlin, Germany
  • M. Gensch
    DLR, Berlin, Germany
  • S. Kovalev
    HZDR, Dresden, Germany
 
  The European XFEL has successfully achieved first lasing in 2017 and meanwhile three SASE FEL beamlines are in operation. An increasing number of users has great interest in a specific type of two-color pump-probe experiments in which high-field THz pulses are employed to drive nonlinear processes and dynamics in matter selectively. Here, we propose to use a 10-period superconducting THz undulator to provide intense, narrowband light pulses tunable in wide range between 3 and 100 THz. The exploitation of superconducting technology allows us to meet the challenge of generating such low photon energy radiation despite the very high electron beam energy at the European XFEL. In this presentation, we will present the latest development concerning THz undulator design and present the expected THz pulse properties for the case of the European XFEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP004  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP006 The FHI FEL Upgrade Design 52
 
  • W. Schöllkopf, M. De Pas, D. Dowell, S. Gewinner, H. Junkes, G. Meijer, G. von Helden
    FHI, Berlin, Germany
  • W.B. Colson
    NPS, Monterey, California, USA
  • S.C. Gottschalk
    STI Magnetics LLC, Woodinville, USA
  • J. Rathke, T. Schultheiss
    AES, Medford, New York, USA
  • A.M.M. Todd
    AMMTodd Consulting, Princeton Junction, New Jersey, USA
  • L.M. Young
    LMY Technology, Lincolnton, Georgia, USA
 
  Since coming on-line in November 2013, the Fritz-Haber-Institut (FHI) der Max-Planck-Gesellschaft (MPG) Free-Electron Laser (FEL) has provided intense, tunable infrared radiation to FHI user groups. It has enabled experiments in diverse fields ranging from bio-molecular spectroscopy to studies of clusters and nanoparticles, nonlinear solid-state spectroscopy, and surface science, resulting in 50 peer-reviewed publications so far. A significant upgrade of the FHI FEL is now being prepared. A second short Rayleigh range undulator FEL beamline is being added that will permit lasing from < 5 microns to > 160 microns. Additionally, a 500 MHz kicker cavity will permit simultaneous two-color operation of the FEL from both FEL beamlines over an optical range of 5 to 50 microns by deflecting alternate 1 GHz pulses into each of the two undulators. We will describe the upgraded FHI FEL physics and engineering design and present the plans for two-color FEL operations in November 2020.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP006  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP007 Experience with the Superradiant THz User Facility Driven by a Quasi-CW SRF Accelerator at ELBE 56
 
  • M. Bawatna, B.W. Green
    HZDR, Dresden, Germany
 
  Instabilities in beam and bunch parameters, such as bunch charge, beam energy or changes in the phase or amplitude of the accelerating field in the RF cavities can be the source of noise in the various secondary sources driven by the electron beam. Bunch charge fluctuations lead to intensity instabilities in the super-radiant THz sources. The primary electron beam driving the light sources has a maximum energy of 40 MeV and a maximum current of 1.6 mA. Depending on the mode of operation required, there are two available injectors in use at ELBE. The first is the thermionic injector, which is used for regular operating modes and supports repetition rates up to 13 MHz and bunch charges up to 100 pC. The second is the SRF photo-cathode injector, which is used for experiments that may require lower emittance or higher bunch charges of up to 1 nC. It has a maximum repetition rate of 13 MHz, which can be adjusted to lower rates if desired, also including different macro pulse modes of operation. In this contribution, we will present our work in the pulse-resolved intensity measurement that allows for correction of intensity instabilities.  
poster icon Poster TUP007 [0.658 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP007  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP008 Concept of High-Power CW IR-THz Source for the Radiation Source Elbe Upgrade 59
 
  • P.E. Evtushenko, T.E. Cowan, U. Lehnert, P. Michel
    HZDR, Dresden, Germany
 
  The Radiation Source ELBE at HZDR is a user facility based on a 1 mA, 40 MeV CW SRF LINAC. HZDR is considering upgrade options for the ELBE or its replacement with a new user facility. A part of the user requirements is the capability to generate IR and THz pulse in the frequency range from 0.1 through 30 THz, with pulse energies in the range from 100 uJ through a few mJ, at the repetition rate between 100 kHz and 1 MHz. In this contribution, we outline key aspects of a concept, which would allow achieving such parameters. Such key aspects are: use of a beam with longitudinal density modulation and bunching factor of about 0.5 at the fundamental frequency; achieving the density modulation through the mechanism similar to the one used in optical klystron (OK) and HGHG FEL, generation necessary for the modulation optical beam by an FEL oscillator, using two electron injectors, where one injector provides a beam for the FEL oscillator while second high charge injector provides beam for the high energy per pulse generation for user experiments. All-in-all the concept of the new radiation source is very similar to an OK, but operating with two beams simultaneously.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP008  
About • paper received ※ 29 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP009 Integration of an XFELO at the European XFEL Facility 62
 
  • P. Rauer, I. Bahns, W. Hillert, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • W. Decking
    DESY, Hamburg, Germany
  • H. Sinn
    EuXFEL, Schenefeld, Germany
 
  Funding: Work supported by BMBF (FKZ 05K16GU4)
An X-ray free-electron laser oscillator (XFELO) is a fourth generation X-ray source promising radiation with full three dimensional coherence, nearly constant pulse to pulse stability and more than an order of magnitude higher peak brilliance compared to SASE FELs. Proposed by Kim et al. in 2008 [1] an XFELO follows the concept of circulating the light in an optical cavity - as known from FEL oscillators in longer wavelength regimes - but uses Bragg reflecting crystals instead of classical mirrors. With the new European X-ray Free-Electron Laser (XFEL) facility recently gone into operation, the realization of an XFELO with radiation in the Angstrom regime seems feasible. Though, the high thermal load of the radiation on the cavity crystals, the high sensibility of the Bragg-reflection on reflection angle and crystal temperature as well as the very demanding tolerances of the at least 60 m long optical resonator path pose challenges which need to be considered. In this work these problems shall be summarized and results regarding the possible integration of an XFELO at the European XFEL facility will be presented.
[1] K.-J. Kim, Y. Shvyd’ko and S. Reiche, Phys. Rev. Lett. 100 (2008), 244802.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP009  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP012 Smith-Purcell Radiation Emitted by Pico-second Electron Bunches from a 30 keV Photo-Electron Gun 66
 
  • M.R. Asakawa, S. Yamaguchi
    Kansai University, Osaka, Japan
 
  In this paper, an experiment to generate Smith-Purcell radiation using pico-second electron bunches is reported. The electron bunch was produced by a DC 30 keV photo-electron electron gun driven by a 100 fs Ti:sapphire laser. The charge of the bunch varied from 1 pC to 300 pC by changing the laser power. Smith-Purcell radiation experiment was performed with the central part of the entire electron bunch. Estimation of pulsewidth of the bunch based on the envelope equation showed that the pulsewidth of the bunch at the anode electrode increased from 0.8 ps to 3.2 ps as the bunch charge increase from 0.1 pC to 11 pC. Such electron bunch was traveled along the surface of the metallic grating with a period of 2 mm. The radiation wavelength was estimated to be 4 mm at an obserbation angle of 10 degree. The radiation power was measured by a bolometer and quadraticallly increased with the bunch charge. Numerical simulation of this experiment indicated the enhancement of the harmonic components of the radiation. We are now constructing a THz-TDS system to measure the time-trace of the electric field of the radiation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP012  
About • paper received ※ 14 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP014 Crossed-Undulator Configuration for Variable Polarized THz Source 69
 
  • H. Saito, H. Hamapresenter, S. Kashiwagi, N.M. Morita, T. Muto, K. Nanbu, H. Yamada
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
 
  Funding: This work was supported by JSPS KAKENHI Grant Number JP17H01070 and JP15K13401.
We have developed crossed-undulator configuration to control the polarization of coherent THz radiation at the femto-second electron beam facility, t-ACTS [1], that has been established at Research Center for Electron Photon Science, Tohoku University. The t-ACTS linac equips a thermionic RF gun, a 3 m accelerating structure and a 50 MW klystron modulator. Ultra-short electron bunch (~80 fs) train can be supplied via velocity bunching scheme. The crossed-undulator system is consisted with two identical transverse undulators intersected by a chicane type phase shifter. Deflecting planes of two undulators are at right angles each other, and the phase shifter makes path length difference between the electrons and the radiation. Target radiation frequency is around 2 THz employing a beam energy of 22 MeV. Since electron bunch trails behind the radiation by the slippage-effect and the nonrelativistic-effect that the electron speed is a bit slower than the speed of light, the radiation from 1st undulator has to be much delayed rather than the electrons. The paper will report the characteristics of polarized radiation and designing work of the phase shifter.
[1] H. Hama et al., Int. J. Opt Photonic Eng., 2:004, 2017.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP014  
About • paper received ※ 24 August 2019       paper accepted ※ 17 September 2019       issue date ※ 05 November 2019  
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TUP015 Design of High-Repetition Terahertz Super-Radiation Based on CAEP THz FEL Superconducting Beamline 73
 
  • D. Wu, T.H. He, L.B. Li, M. Li, P. Lipresenter, X. Luo, Q. Pan, L.J. Shan, X. Shen, H. Wang, J. Wang, D.X. Xiao, L.G. Yan, P. Zhang, K. Zhou
    CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
 
  China Academy of Engineering Physics terahertz free electron laser (CAEP THz FEL, CTFEL) is the first THz FEL oscillator in China. CTFEL spectrum covers from 0.7 THz to 4.2 THz. However, there are still many applications requiring lower frequency. The super-radiation of the ultra-short electron beam bunches could generate ultra-fast, carrier-envelope-phase-stable, and high-field terahertz. The coherent diffraction/transition radiation (CDR/CTR) and coherent undulator radiation (CUR) can be also synchronized naturally. In this paper, the dynamic and the design of the super-radiation are introduced. The main parameters of the CDR/CTR and CUR are also discussed. A multi-color pump-probe system based on super-radiation is also proposed.
Work supported by National Natural Science Foundation of China with grant (11575264, 11605190 and 11805192), Innovation Foundation of CAEP with grant (CX2019036, CX2019037)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP015  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP017 Terahertz FEL Simulation in PAL XFEL 77
 
  • J.H. Ko, H.-S. Kang
    PAL, Pohang, Republic of Korea
 
  Terahertz radiation is being used in various fields such as imaging, diagnosis, inspection, etc. For the terahertz research, the Pohang accelerator laboratory (PAL) is planning to make a terahertz free electron laser based on self-amplified spontaneous emission (SASE). Using free electron laser method, we can conduct the THz-pump X-ray probe experiment. For the terahertz free electron laser, we conducted the simulation on accelerators below 40 MeV, using photo-cathode RF gun, S-band accelerator and undulator below 4 meters.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP017  
About • paper received ※ 20 August 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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TUP018 Superradiant Emission of Electron Bunches Based on Cherenkov Excitation of Surface Waves in 1D and 2D Periodical Lattices: Theory and Experiments 80
 
  • A. Malkin, N.S. Ginzburg, A. Sergeev, I.V. Zheleznov, I.V. Zotova
    IAP/RAS, Nizhny Novgorod, Russia
  • M.I. Yalandin
    RAS/IEP, Ekaterinburg, Russia
  • V.Yu. Zaslavsky
    UNN, Nizhny Novgorod, Russia
 
  Funding: The work was supported by RFBR grant no. 17-08-01072
In recent years, significant progress was achieved in generation of high-power ultrashort microwave pulses based on superradiance (SR) of electron bunches extended in the wavelength scale. In this process, coherent emission from the entire volume of the bunch occurs due to the development of microbunching and slippage of the wave with respect to electrons. An obvious method for generation of high-power sub-THz radiation is the implementation of oversized periodical slow-wave structures where evanescent surface waves can be excited. We report of the experiments on Cherenkov generation of 150 ps SR pulses with a central frequency of 0.14 THz, and an extremely high peak power up to 70 MW. In order to generate spatially coherent radiation in shorter wavelength ranges (including THz band) in strongly oversized waveguiding systems, we propose a slow wave structure with double periodic corrugation (2D SWS). Using the quasi-optical theory and PIC simulations, we demonstrate the applicability of such 2D SWS and its advantages against traditional 1D SWS. Proof of principle experiments on observation G-band Cherenkov SR in 2D SWS are currently in progress.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP018  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP019 Regime of Multi-Stage Non-Resonant Trapping in Free Electron Lasers 83
 
  • A.V. Savilov, I.V. Bandurkin, Yu.S. Oparina, N.Yu. Peskov
    IAP/RAS, Nizhny Novgorod, Russia
 
  Funding: This work is supported by the RFBR (grants #18-02-40009, #18-02-00765) and by the IAP RAS Project 0035-2019-0001.
We describe three works united by the idea of the non-resonant regime [1] providing an effective trapping in a beam with a great energy spread. In this regime, the "bucket" corresponding to the resonant electron-wave interaction passes through the electron layer on the energy-phase plane and traps a fraction of electrons. (I) Operability of this regime was demonstrated in the high-efficient 0.8 MeV Ka-band FEM-amplifier [2]. (II) In short-wavelength FELs the multi-stage trapping in several consecutive sections can be organized [3]. In each section a small e-beam fraction is trapped due to a weak electron-wave interaction. However, repetition of this process from section to section involves in the interaction almost the whole e-beam. We describe efficiency enhancement and improving the frequency wave spectrum in multi-stage SASE FELs. (III) The multi-stage amplification of a single-frequency wave signal can provide cooling of the electron bunch. In this regime, tapering of every section is provided such that the "bucket" goes from maximal initial electron energy down to the minimal one and moves down energies of trapped electrons.
[1] A.Savilov et al., Nucl. Instr. Meth. A, vol. 507, p.158, 2003
[2] A.Kaminsky et al., Int. Conf. IRMMW-THz 2018, art. 4057938
[3] S.Kuzikov, A.Savilov, Phys. Plasmas, vol. 25, p.113114, 2018
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP019  
About • paper received ※ 14 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP020 Terahertz Free Electron Maser Based on Excitation of a Talbot-Type Super-Mode in an Oversized Microwave System 87
 
  • A.V. Savilov, Yu.S. Oparina, N.Yu. Peskov
    IAP/RAS, Nizhny Novgorod, Russia
 
  Funding: The work is supported by the Russian Science Foundation, Project # 19-12-00212.
A natural problem arising in the case of realization of a THz FEM with a high-current relativistic e-beam is an inevitable use of an oversized microwave system, which characteristic transverse size significantly exceeds the wavelength of the operating wave. In this situation, it becomes difficult to provide selective excitation of a chosen transverse mode of the operating cavity. Our basic idea is to give up working on a fixed transverse mode. Instead, we propose to work on a supermode, which is a fixed set of several transverse modes of an oversized wavegude. We propose to use the Talbot effect [1,2,3] as a way to create an oversized microwave system of an electron maser that provides a high Q-factor for this supermode. On the basis of a multi-mode set of self-consistent equations of the electron-wave interaction we demonstrate the possibility of the selective self-excitation of the supermode both in the simplest 2-D model and in the detailed modeling of a THz FEM fed by a 10 MeV / 2 kA / 200 e-beam based on excitation of a Talbot-type supermode at a frequency close to 2 THz. The calculated efficiency at the level of 5-10% corresponds to the GW level of the output power.
[1] L. A. Rivlin, Laser Focus, p. 82, 1981
[2] G. G. Denisov, D. A. Lukovnikov, M. Yu. Shmelyov, Digest of 18 Int. Conf. on IR MM Waves, p. 485, 1993
[3] V. L. Bratman et al., Nucl. Instr. Meth. Phys. Res. A, vol. 407, pp. 40-44, 1998
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP020  
About • paper received ※ 14 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP021 Development of Powerful Long-Pulse Terahertz Band FELs Based on Linear Induction Accelerators 91
 
  • V.Yu. Zaslavsky, N.S. Ginzburg, A. Malkin, N.Yu. Peskov, A. Sergeev
    IAP/RAS, Nizhny Novgorod, Russia
  • A.V. Arzhannikov, E.S. Sandalov, S.L. Sinitsky, D.I. Skovorodin, A.A. Starostenko
    BINP SB RAS, Novosibirsk, Russia
 
  Funding: This work was supported by the Russian Scientific Foundation (RSCF), grant No. 19-12-00212.
The paper is devoted to development of high-power long-pulse THz-band FELs based on new generation of linear induction accelerators which have been elaborated recently at Budker Institute (Novosibirsk). These accelerators generate microsecond electron beams with current at kA-level and energy of 2 to 5 MeV (with a possibility to increase electrons energy up to 20 MeV). Based on this beam, we initiated a new project of multi-MW long-pulse FEL operating in the frequency range of 1 to 10 THz using a wiggler period of 3 to 6 cm. For this FEL oscillator, we suggest a hybrid planar two-mirror resonator consisting of an upstream highly selective advanced Bragg reflector and a downstream weakly reflecting conventional Bragg reflector. Simulations demonstrate that the advanced Bragg reflector based on coupling of propagating and quasi-cutoff waves ensures the mode control at the values of the gap between the corrugated plates forming such resonator up to 20 wavelengths. Simulations of the FEL driven by electron beam generated by the LIU’2 in the frame of both averaged approach and 3D PIC code demonstrate that the THz radiation power can reach the level of 10 to 20 MW.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP021  
About • paper received ※ 28 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP023 Analytical and Numerical Comparison of Different Approaches to the Description of SASE in High Gain FELs 94
 
  • O.A. Shevchenko, N.A. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
  • N.A. Vinokurov
    NSU, Novosibirsk, Russia
 
  Correlation function theory which has been developed recently gives rigorous statistical description of the SASE FEL operation. It directly deals with the values averaged over many shots. There are two other approaches which are based either on Vlasov equation or on direct solution of particle motion equations. Both of them use random functions which relate to single shot. To check the validity of these three approaches it might be interesting to compare them with each other. In this paper we present the results of such comparison obtained for the 1-D FEL model. We show that two-particle correlation function approximation is equivalent to the quasilinear approximation of the Vlasov equation approach. These two approximations are in a good agreement with the results of direct solution of particle motion equations at linear and early saturation stages. To obtain this agreement at strong saturation high order harmonics in Vlasov equation have to be taken into account which corresponds to taking into account of three and more particle correlations in the correlation function approach.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP023  
About • paper received ※ 19 August 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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TUP024 Electronic Modulation of the FEL-Oscillator Radiation Power Driven by ERL 98
 
  • O.A. Shevchenko, E.V. Bykov, Ya.V. Getmanov, S.S. Serednyakov, S.V. Tararyshkin
    BINP SB RAS, Novosibirsk, Russia
  • M.V. Fedin, A.R. Melnikov, S.L. Veber
    International Tomography Center, SB RAS, Novosibirsk, Russia
  • Ya.V. Getmanov, S.S. Serednyakov
    NSU, Novosibirsk, Russia
 
  FEL oscillators usually operate in CW mode and produce periodic train of radiation pulses but some user experiments require modulation of radiation power. Conventional way to obtain this modulation is using of mechanical shutters but it cannot provide very short switching time and may lead to decreasing of the radiation beam quality. Another way could be based on the electron beam current modulation but it cannot be used in the ERL. We propose a simple way of fast control of the FEL lasing which is based on periodic phase shift of electron bunches with respect to radiation stored in optical cavity. The phase shift required to suppress lasing is relatively small and it does not change significantly repetition rate. This approach has been realized at NovoFEL facility. It allows to generate radiation macropulses of desirable length down to several microseconds (limited by quality factor of optical cavity and FEL gain) which can be synchronized with external trigger. We present detailed description of electronic power modulation scheme and discuss the results of experiments.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP024  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP025 Current Status of Free Electron Laser @ TARLA 102
 
  • A. Aksoy, Ö. Karslı, Ç. Kaya, İ.B. Koç
    Ankara University, Accelerator Technologies Institute, Golbasi, Turkey
  • Ö.F. Elçim
    Ankara University Institute of Accelerator Technologies, Golbasi, Turkey
 
  Funding: Work supported by Strategy and Budget Department of Turkey with Grand No: 2006K120470
Turkish Accelerator and Radiation Laboratory (TARLA), which is supported by the Presidency Strategy and Budget Directorate of Turkey, aims to be the state of art research instrument for the radiation users from Turkey. Two superconducting accelerating modules of TARLA will drive two different planar undulator magnets with periods of 110 mm (U110) and 35 mm (U35) in order to generate high brightness Continuous Wave (CW) Free Electron Laser (FEL) tunable in between 5-350 µm. In addition, the linac will drive a Bremstrahlung radiation station to generate polarized gamma radiation. Main components of TARLA, such as injector, superconducting accelerating modules and cryoplant are under commissioning currently. In this study, we present current status of the facility in addition to expected FEL performance of the facility.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP025  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP026 Unaveraged Simulation of a Regenerative Amplifier Free Electron Laser 106
 
  • P. Pongchalee, B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  • B.W.J. MᶜNeil
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  A regenerative amplifier free-electron laser (RAFEL) design and simulation requires the modelling of both the electron-light interaction in the FEL undulator and the optical propagation within the cavity. An unaveraged 3D simulation was used to model the FEL interaction within the undulator using the Puffin code. This allows a broadband, high temporal-resolution of the FEL interaction. The Optical Propagation Code (OPC) was used to model the optical beam propagation within the cavity and diagnostics at the cavity mirrors. This paper presents the optical field conversion method between Puffin and the OPC codes and demonstrates the full model via a VUV-RAFEL simulation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP026  
About • paper received ※ 19 August 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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TUP027 Modelling Crystal Misaligments for the X-ray FEL Oscillator 110
 
  • R.R. Lindberg
    ANL, Lemont, Illinois, USA
 
  Funding: Work supported by U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357.
The X-ray FEL oscillator has the potential to be a revolutionary new light source providing unprecedented stability in a narrow bandwidth [1]. However, a detailed understanding of cavity tolerance and stability has only begun, and there are presently no suitable simulation tools. To address this issue, we have developed a fast FEL oscillator code that discretizes the field using a Gauss-Hermite mode expansion of the oscillator cavity. Errors in crystal alignment result in a mixing of the modes that is easily modeled with a loss and coupling matrix. We show first results from our code, including the effects of static and time-varying crystal misalignments.
[1] K.-J. Kim, Y. Shvyd’ko, and S. Reiche, PRL 100 244802 (2008)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP027  
About • paper received ※ 20 August 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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TUP028 Power Variations of an X-ray FEL Oscillator in Saturation 114
 
  • R.R. Lindberg, K. Kim
    ANL, Lemont, Illinois, USA
 
  Funding: Work supported by U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357.
Basic FEL theory predicts that the fractional power fluctuations of an ideal oscillator in steady state should be given by the ratio of the spontaneous power in the oscillator bandwidth to that stored in the cavity at saturation. For the X-ray FEL oscillator with its narrow bandwidth Bragg crystal mirrors, this ratio is typically a few parts per million, but some simulations have shown evidence of power oscillations on the percent level. We show that this is not related to the well-known sideband instability, but rather is purely numerical and can be eliminated by changing the particle loading. We then briefly discuss to what extent variations in electron beam arrival time may degrade the power stability.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP028  
About • paper received ※ 20 August 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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TUP032 Regenerative Amplification for a Hard X-Ray Free-Electron Laser 118
 
  • G. Marcus, Y. Ding, Y. Feng, A. Halavanau, Z. Huang, J. Krzywiński, J.P. MacArthur, R.A. Margraf, T.O. Raubenheimer, D. Zhu
    SLAC, Menlo Park, California, USA
  • V. Fiadonu
    Santa Clara University, Santa Clara, California, USA
 
  Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
An X-ray regenerative amplifier FEL (XRAFEL) utilizes an X-ray crystal cavity to provide optical feedback to the entrance of a high-gain undulator. An XRAFEL system leverages gain-guiding in the undulator to reduce the cavity alignment tolerances and targets the production of longitudinally coherent and high peak power and brightness X-ray pulses that could significantly enhance the performance of a standard single-pass SASE amplifier. The successful implementation of an X-ray cavity in the XRAFEL scheme requires the demonstration of X-ray optical components that can either satisfy large output coupling constraints or passively output a large fraction of the amplified coherent radiation. Here, we present new schemes to either actively Q-switch a diamond Bragg crystal through lattice constant manipulation or passively output couple a large fraction of the stored cavity radiation through controlled FEL microbunch rotation. A beamline design study, cavity stability analysis, and optimization will be presented illustrating the performance of potential XRAFEL configurations at LCLS-II/-HE using high-fidelity simulations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP032  
About • paper received ※ 24 August 2019       paper accepted ※ 26 August 2019       issue date ※ 05 November 2019  
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TUP033 Q-Switching of X-Ray Optical Cavities by Using Boron Doped Buried Layer Under a Surface of a Diamond Crystal 122
 
  • J. Krzywiński, Y. Feng, A. Halavanau, Z. Huang, A.M. Kiss, J.P. MacArthur, G. Marcuspresenter, T. Sato, D. Zhu
    SLAC, Menlo Park, California, USA
 
  Improvement of the longitudinal coherence of X-ray Free Electron Lasers has been the subject of many recent investigations. The XFEL oscillator (XFELO) and Regenerative Amplifier Free-Electron Laser (RAFEL) schemes offer a pathway to fully coherent, high brightness X-ray radiation. The XFELO and RAFEL consist of a high repetition rate electron beam, an undulator and an X-ray crystal cavity to provide optical feedback. The X-ray cavity will be based on diamond crystals in order to manage a high thermal load. We are investigating a ’Q switching’ mechanism that involves the use of a ’Bragg switch’ to dump the X-ray pulse energy built-up inside an X-ray cavity. In particular, one can use an optical laser to manipulate the diamond crystal lattice constant to control the crystal reflectivity and transmission. It has been shown that a 9 MeV focused boron beam can create a buried layer, approximately 5 microns below surface, with a boron concentration up to 1021 atoms/cm3. Here, we present simulations showing that absorbing laser pulses by a buried layer under the crystal surface would allow creating a transient temperature profile which would be well suited for the ’Q switching’ scheme.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP033  
About • paper received ※ 21 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP035 Sensitivity of LCLS Self-Seeded Pedestal Emission to Laser Heater Strength 126
 
  • G. Marcus, D.K. Bohler, Y. Ding, W.M. Fawley, Y. Feng, E. Hemsing, Z. Huang, J. Krzywiński, A.A. Lutman, D.F. Ratner
    SLAC, Menlo Park, California, USA
 
  Measurements of the soft X-ray, self-seeding spectrum at the LCLS free-electron laser generally display a pedestal-like distribution around the central seeded wavelength that degrades the spectral purity. We have investigated the detailed experimental characteristics of this pedestal and found that it is comprised of two separate components: (1) normal SASE whose total strength is nominally insensitive to energy detuning and laser heater (LH) strength; (2) sideband-like emission whose strength positively correlates with that of the amplified seed and negatively with energy detuning and LH strength. We believe this latter, non-SASE component arises from comparatively long wavelength amplitude and phase modulations of the main seeded radiation line. Its shot-to-shot variability and LH sensitivity suggests an origin connected to growth of the longitudinal microbunching instability on the electron beam. Here, we present experimental results taken over a number of shifts that illustrate the above mentioned characteristics.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP035  
About • paper received ※ 28 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP036 A Waveguide-Based High Efficiency Super-Radiant FEL Operating in the THz Regime 127
 
  • P. Musumeci, A.C. Fisher
    UCLA, Los Angeles, California, USA
  • A. Gover
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  • E.A. Nanni, E.J. Snively
    SLAC, Menlo Park, California, USA
  • S.B. van der Geer
    Pulsar Physics, Eindhoven, The Netherlands
 
  Funding: DOE grant No. DE-SC0009914 and NSF grant PHY-1734215
In this paper we describe a novel self-consistent 3D simulation approach for a waveguide FEL operating in the zero-slippage regime to generate high power THz radiation. In this interaction regime, the phase and group velocity of the radiation are matched to the relativistic beam traveling in the undulator achieving long interaction lengths. Our numerical approach is based on expanding the existing 3D particle tracking code GPT (General Particle Tracer) to follow the interaction of the particles in the beam with the electromagnetic field modes of the waveguide. We present two separate studies: one for a case which was benchmarked with experimental results and another one for a test case where, using a longer undulator and larger bunch charge, a sizable fraction of the input beam energy can be extracted and converted to THz radiation. The model presented here is an important step in the development of the zero-slippage FEL scheme as a source for high average and peak power THz radiation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP036  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP037 Optimization of the Transverse Gradient Undulator (TGU) for Application in a Storage Ring Based XFELO 131
 
  • Y.S. Li
    University of Chicago, Chicago, Illinois, USA
  • K. Kim, R.R. Lindberg
    ANL, Lemont, Illinois, USA
 
  Funding: U.S. Dept. of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
The stringent energy spread requirement of the XFELO poses a challenge for its application in storage rings. One way to overcome this is by using a transverse gradient undulator (TGU) [1]. The TGU gain formula was discussed previously [2]. In this paper, we begin by reviewing the analytical 3D gain formula derived from the gain convolution formula. Following that, we apply numerical optimization to investigate the optimal beam and field parameters for maximal TGU gain. We found that a small emittance ratio (i.e. "flat beam" configuration) has a strong positive impact on TGU gain, as well as other patterns in the optimal parameters.
[1] T. I. Smith et al., J. Appl. Phys. 50 (1979) 4580
[2] R. R. Lindberg et al., in Proceedings FEL’13, New York, USA, 2013, pp. 740-748, paper THOBNO02
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP037  
About • paper received ※ 19 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP038 Axial Symmetry in Spontaneous Undulator Radiation for XFELO Two-Bunch Experiment 134
 
  • Y.S. Li
    University of Chicago, Chicago, Illinois, USA
  • K. Kim, R.R. Lindberg
    ANL, Lemont, Illinois, USA
 
  Funding: U.S. DOE, Office of Science, Office of BES, under Contract No. DE-AC02-06CH11357 and National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams.
A well known discrepancy exists between 2D and 3D FEL simulation codes with respect to the radiation field intensity prior to the exponential gain regime [1]. This can be qualitatively explained by the fact that the 3D field representation preserves many more modes than does the axisymmetric field solved for by a 2D code. In this paper, we seek to develop an analytical model that quantifies this difference. We begin by expanding the spontaneous undulator radiation field as a multipole series, whose lowest order mode is axisymmetric. This allows us to calculate the difference in predicted intensity. Next, we confirm these results with numerical calculation and existing FEL codes GINGER and GENESIS. Finally, we discuss the implications of this study with respect to the XFELO two-bunch experiment to be conducted at LCLS-II.
[1] Z. Huang and K.-J. Kim, "Review of X-ray free-electron laser theory", Phys. Rev. ST-AB, vol. 10, p. 034801, 2007.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP038  
About • paper received ※ 19 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP041 X-cos SCILAB Model for Simulation of Intensity and Gain of Planar Undulator Radiation 138
 
  • H. Jeevakhan
    NITTTR, Bhopal, India
  • G. Mishra
    Devi Ahilya University, Indore, India
 
  SCILAB X-cos based model has been designed to simulate the Intensity and Gain of planar undulator radiation. Numerical approach has been used to determine the trajectories of an electron along x and z direction, traversing through a planar undulator. The present paper describes the technical details of the different blocks, parameters and possibility of combined model used for trajectory and intensity simulation Results are compared with the previous conventional syntax based codes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP041  
About • paper received ※ 01 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP042 Analysis of Undulator Radiations With Asymmetric Beam and Non-Periodic Magnetic Field 141
 
  • H. Jeevakhan
    NITTTR, Bhopal, India
  • G. Mishra
    Devi Ahilya University, Indore, India
 
  Harmonic Undulator radiations at third harmonics with non periodic constant magnetic field has been analysed. Symmetric and asymmetric electron beam with homogeneous spread has been used to present viable solution for the resonance shift inherited in undulator with constant magnetic field. The radiation recovers shifts in resonance and regain its intensity with asymmetric electron beam and harmonic field
Harmonic undulator, energy spread
 
poster icon Poster TUP042 [2.886 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP042  
About • paper received ※ 01 August 2019       paper accepted ※ 31 October 2019       issue date ※ 05 November 2019  
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TUP047 An Analysis of Optimal Initial Detuning for Maximum Energy-Extraction Efficiency 145
 
  • Q.K. Jia
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
 
  For low gain free electron laser (FEL), the phase space evolutions of trapped electrons in the phase bucket are analyzed through calculating their synchrotron oscillation periods, which vary with the initial detuning and initial phase. The optimal initial detuning for the maximum energy-extraction efficiency and the corresponding saturation length are given. The analysis demonstrated that for the low gain case the gain of the strong optical field is about a quarter of that of the weak optical field (small signal gain), and the saturation power larger than that of high gain FEL can be achieved in the resonator of oscillator FEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP047  
About • paper received ※ 19 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP049 Simulating Shot-Noise of ’Real’ Electron Bunches 149
 
  • P. Traczykowski, L.T. Campbell, B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  • L.T. Campbell, B.W.J. MᶜNeil, P. Traczykowski
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • L.T. Campbell, P. Traczykowski
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  An algorithm and numerical code for the up-sampling of a system of particles, from a smaller to a larger number, is described. The method introduces a Poissonian ’shot-noise’ to the up-sampled distribution [1], typical of the noise statistics arising in a bunch of particles generated by a particle accelerator. The algorithm is applied on a phase-space distribution of relatively few simulation particles representing an electron beam generated by particle accelerator modelling software, for subsequent injection into an Free Electron Laser (FEL) amplifier which is used here to describe the model. A much larger number of particles is usually required to model the FEL lasing process than is required in the simulation models of the electron beam accelerators that drive it. A numerical code developed from the algorithm was then used to generate electron bunches for injection into to an unaveraged 3D FEL simulation code, Puffin [2]. Results show good qualitative and quantitative agreement with analytical theory. The program and usage manual is available to download from GitHub [3].
[1] B.W.J. McNeil, M.W. Poole and G.R.M. Robb, Physical Review Special Topics - Accelerators and Beams Vol 6, 070701 (2003).
[2] L.T. Campbell and B.W.J. McNeil, Phys. Plasmas 19, 093119 (2012).
[3] https://github.com/UKFELs/JDF
 
poster icon Poster TUP049 [1.419 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP049  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP050 Comparison Between, and Validation Against an Experiment of, a Slowly-varying Envelope Approximation Code and a Particle-in-Cell Simulation Code for Free-Electron Lasers 153
 
  • P. Traczykowski, L.T. Campbell, J. Henderson, B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  • L.T. Campbell, J. Henderson, P. Traczykowski
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • H. Freund
    University of New Mexico, Albuquerque, USA
  • B.W.J. MᶜNeil, P. Traczykowski
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • P.J.M. van der Slot
    Mesa+, Enschede, The Netherlands
 
  Free-electron laser simulation codes employ either the Slowly-Varying Envelope Approximation (SVEA) or a Particle-in-Cell (PiC) formulation. Maxwell’s equations are averaged over the fast time scale in the SVEA so that there is no need to resolve the wave period. In contrast, the fast oscillation is retained in PiC codes. As a result, the SVEA codes are much less computationally intensive and are used more frequently than PiC codes. While the orbit dynamics in PiC codes and some SVEA Codes (MEDUSA and MINERVA) use the full unaveraged Lorentz force equations, some SVEA codes use the Kroll-Morton-Rosenbluth (KMR) approximation (GENESIS, GINGER, FAST, and TDA3D). Steady-state simulation comparisons [1] have appeared in the literature between different codes using the averaged and unaveraged particle dynamics. Recently, a comparison between three KMR SVEA codes (GENESIS, GINGER, and FAST) and the PUFFIN PiC code in the time-dependent regime has been reported [2]. In this paper, we present a comparison between the unaveraged PiC code PUFFIN, the unaveraged SVEA code MINERVA for the time-dependent simulation of SASE free-electron lasers with the experimental measurements from SPARC SASE FEL at ENEA Frascati.
[1] S.G. Biedron et al., NIMA 445, 110 (2000).
[2] B. Garcia et al., paper presented at the 38th International Free Electron Laser Conference, Santa Fe, New Mexico, 20 - 25 August 2017.
 
poster icon Poster TUP050 [0.908 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP050  
About • paper received ※ 02 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP051 Plasma Accelerator Driven Coherent Spontaneous Emission 157
 
  • B.M. Alotaibi, R. Altuijri
    PNU, Riyadh, Kingdom of Saudi Arabia
  • B.M. Alotaibi, R. Altuijri, A.F. Habib, B. Hidding, B.W.J. MᶜNeil, P. Traczykowskipresenter
    USTRAT/SUPA, Glasgow, United Kingdom
  • A.F. Habib, B. Hidding, B.W.J. MᶜNeil, P. Traczykowskipresenter
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  Plasma accelerators [1] are a potentially important source of high energy, low emittance electron beams with high peak currents generated within a relatively short distance. As such, they may have an important application in the driving of coherent light sources such as the Free Electron Laser (FEL) which operate into the X-ray region [2]. While novel plasma photocathodes [3] may offer orders of magnitude improvement to the normalized emittance and brightness of electron beams compared to Radio Frequency-driven accelerators, a substantial challenge is the energy spread and chirp of beams, which can make FEL operation impossible. In this paper it is shown that such an energy-chirped, ultrahigh brightness electron beam, with dynamically evolving current profile due to ballistic bunching at moderate energies, can generate significant coherent radiation output via the process of Coherent Spontaneous Emission (CSE)[4]. While this CSE is seen to cause some FEL-induced electron bunching at the radiation wavelength, the dynamic evolution of the energy chirped pulse dampens out any high-gain FEL interaction.
[1] E. Esary et al., Reviews of Modern Physics p. 1229 (2009).
[2] B. W. J. McNeil and N. R. Thompson, 2010 Nat. Photon.4 814-21
[3] B. Hidding et al., 2012 Phys. Rev. Lett. 108 035001
[4] L. T. Campbell and B. W. J. McNeil, 2012, in Proc. FEL2012
 
poster icon Poster TUP051 [1.401 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP051  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP053 An Investigation of Possible Non-Standard Photon Statistics in a Free-Electron Laser I: Experiment 161
 
  • J.-W. Park
    University of Hawaii, Honolulu,, USA
  • K.-J. Kim, R.R. Lindberg
    ANL, Lemont, Illinois, USA
 
  Funding: Work supported by U.S. DOE, Office of Science, Office of BES, under Award No. DE-SC0018428.
It was reported that the photon statistics of the seventh coherent spontaneous harmonic radiation of the MARK III FEL was sub-Poissonian [1], which concludes that Fano factor F (the ratio of photon number variance to the average photon number) is less than unity. Whether FEL light exhibits such non-standard behavior is an important issue; if it does, our understanding of the FEL needs to be radically modified. In this paper, we re-examine the analyses of experimental data in Ref. [1]. We find that the observed value of F could be explained within the standard FEL theory if one combines the detector dead time effect with photon clustering arising from the FEL gain. We propose an improved experiment for a more definitive measurement of the FEL photon statistics.
[1] T. Chen and J.M. Madey, J. Phys. Rev. Lett. 86, 5906 (2001).
 
poster icon Poster TUP053 [0.929 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP053  
About • paper received ※ 21 August 2019       paper accepted ※ 12 September 2019       issue date ※ 05 November 2019  
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TUP054 An Investigation of Possible Non-Standard Photon Statistics in a Free-Electron Laser II: Theory 165
 
  • J.-W. Park
    University of Hawaii, Honolulu,, USA
  • K.-J. Kim, R.R. Lindberg
    ANL, Lemont, Illinois, USA
  • K.-J. Kim
    University of Chicago, Chicago, Illinois, USA
 
  Funding: Work supported by U.S. DOE, Office of Science, Office of BES, under Award No. DE-SC0018428.
In this paper we explore whether we can at present find a theoretical basis for non-standard, sub-Poissonian photon statistics in the coherent spontaneous harmonic radiation of an FEL as was claimed to have been measured with the Mark III FEL [1]. We develop a one dimensional quantum FEL oscillator model of the harmonic radiation in the linear gain regime to calculate the photon statistics. According to our study, it seems unlikely that the photon statistics for an FEL oscillator starting from the noise could be sub-Poissonian.
[1] T. Chen and J.M. Madey, J. Phys. Rev. Lett. 86, 5906 (2001).
 
poster icon Poster TUP054 [0.386 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP054  
About • paper received ※ 21 August 2019       paper accepted ※ 16 September 2019       issue date ※ 05 November 2019  
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TUP055 Two-Color Operation of FLASH2 Undulator 168
 
  • E. Schneidmiller, M. Braune, B. Faatz, U. Jastrow, M. Kuhlmann, A.A. Sorokin, K.I. Tiedtke, M.V. Yurkov
    DESY, Hamburg, Germany
 
  FLASH is the first soft X-ray FEL user facility, routinely providing brilliant photon beams for users since 2005. The second undulator branch of this facility, FLASH2, is gap-tunable which allows to test and use advanced lasing concepts. In particular, we tested recently a two-color mode of operation based on the alternation of tunes of the undulator segments (every other segment is tuned to the second wavelength). This scheme is advantageous in comparison with a subsequent generation of two colors in two different parts of the undulator. First, source positions of two FEL beams are close to each other which makes it easier to handle them. Second, the amplification is more efficient in this configuration since the segments with respectively "wrong" wavelength act as bunchers. We developed methods for online intensity measurements of the two colors simultaneously that require a combination of two detectors. We present some examples of such measurements in the XUV and soft X-ray regimes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP055  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP056 Feasibility Studies of the 100 keV Undulator Line of the European XFEL 172
 
  • E. Schneidmiller, V. Balandin, W. Decking, M. Dohlus, N. Golubeva, D. Nölle, M.V. Yurkov, I. Zagorodnov
    DESY, Hamburg, Germany
  • G. Geloni, Y. Li, S. Molodtsov, J. Pflüger, S. Serkez, H. Sinn, T. Tanikawa, S. Tomin
    EuXFEL, Schenefeld, Germany
 
  The European XFEL is a multi-user X-ray FEL facility based on superconducting linear accelerator. Presently, three undulators (SASE1, SASE2, SASE3) deliver high-brightness soft- and hard- X-ray beams for users. There are two empty undulator tunnels that were originally designed to operate with spontaneous radiators. We consider instead a possible installation of two FEL undulators. One of them (SASE4) is proposed for the operation in ultrahard X-ray regime, up to the photon energy of 100 keV. In this contribution we present the results of the first feasibility studies of this option.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP056  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP057 Analysis of Parameter Space of Soft X-Ray Free Electron Laser at the European XFEL Driven by High and Low Energy Electron Beam 176
 
  • E. Schneidmiller, M.V. Yurkovpresenter
    DESY, Hamburg, Germany
 
  Three undulator beamlines: SASE1 and SASE2 (hard X-ray), and SASE3 (soft X-ray) are in operation at the European XFEL serving six user instruments. Next stages of the facility development are installation of two undulator beamlines in empty tunnels SASE4 and SASE5 as medium term upgrade, and extension of the facility with the second fan of undulators as long term upgrade. Construction of soft X-ray beamlines is considered in both upgrade scenario. In the case of SASE4/SASE5 electron beam with energies 8.5 GeV - 17.5 GeV will be used in order to provide simultaneous operation of new undulator beamlines with existing SASE1-SASE3. One of the scenarios for a second fan of undulators involves using of low energy (2.5 GeV) electron beam. In this paper we analyze parameter space of soft X-ray SASE FELs driven by high energy and low energy electron beam, compare output characteristics, and discuss potential advantages and disadvantages.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP057  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP058 First Characterization of the Photon Beam at the European XFEL in July, 2017 180
 
  • V. Balandin, B. Beutner, F. Brinker, W. Decking, M. Dohlus, L. Fröhlich, U. Jastrow, R. Kammering, T. Limberg, D. Nölle, M. Scholz, A.A. Sorokin, K.I. Tiedtke, M.V. Yurkovpresenter, I. Zagorodnov
    DESY, Hamburg, Germany
  • U. Boesenberg, W. Freund, J. Grünert, A. Koch, N.G. Kujala, J. Liu, Th. Maltezopoulos, M. Messerschmidt, I. Petrov, L. Samoylova, H. Sinn
    EuXFEL, Schenefeld, Germany
 
  North branch of the European XFEL, SASE1, produced first light on May 3rd, 2017, and XFEL operation has been gradually improved then. First characterization of the photon beam has been performed in July / August 2017, just before an official starting date of user experiments (September 1st, 2017). Energy of the electron beam was 14 GeV, bunch charge was 500 pC, photon energy was 9.3 keV. With photon diagnostics available at that time (X-ray gas monitor (XGM) and FEL imager) we measured the gain curve and traced evolution of the FEL radiation mode along the undulator. An important conclusion is that experimental results demonstrate reasonable agreement with baseline parameters. Developed techniques of the photon beam characterization also provided solid base for identification of the problems and means for improving SASE FEL tuning and operation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP058  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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TUP059 Influence of Energy Chirp in the Electron Beam and Undulator Tapering on Spatial Properties of the Radiation From Seeded and SASE FEL 184
 
  • E. Schneidmiller, M.V. Yurkovpresenter
    DESY, Hamburg, Germany
 
  Energy chirp and undulator tapering change resonance condition along the electron beam and undulator which results in modification of the radiation amplification process. Well known examples are post-saturation undulator tapering for radiation power increase, reverse undulator tapering for effective operation of afterburners, and application of linear undulator tapering for compensation of energy chirp effect. These are essentially one dimensional effects. In addition, energy chirp and undulator tapering also change spatial properties of the radiation which can be important for the users of X-ray FEL facilities. In this report we present detailed analysis of the spatial properties of the radiation from an FEL amplifier with tapered undulator and chirped electron beam. Two configurations, seeded FEL amplifier, and SASE FEL are under consideration. Dependence of the spatial distributions on the electron beam properties is studied, and their evolution along the undulator is traced. It is shown that spatial properties of the radiation may be significantly distorted by the effects of energy chirp in the electron beam and undulator tapering.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP059  
About • paper received ※ 24 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP060 An Advanced Compression Option for the European XFEL 187
 
  • I. Zagorodnov, M. Dohlus, E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
 
  An advanced compression scheme which allows to obtain a high peak current while preserving the low slice emittance is considered. The beam is compressed weakly in the bunch compressors and the current is increased by eSASE setup at the entrance of the undulator line. It is shown by numerical studies that such approach allows to reduce harmful collective effects in the bunch compressors and in the transport line. Simulations of FEL physics confirm the possibility to obtain a high level of SASE radiation at the ultra-hard photon energy level of 100 keV.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP060  
About • paper received ※ 19 August 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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TUP061 Super-X: Simulations for Extremely Hard X-Ray Generation With Short Period Superconducting Undulators for the European XFEL 191
 
  • S. Serkez, G. Geloni, S. Karabekyan, Y. Li, T. Tanikawa, S. Tomin, F. Wolff-Fabris
    EuXFEL, Schenefeld, Germany
  • C. Boffo
    Bilfinger Noell GmbH, Wuerzburg, Germany
  • S. Casalbuoni
    KIT, Eggenstein-Leopoldshafen, Germany
  • M. Dohlus, E. Schneidmiller, M.V. Yurkov, I. Zagorodnov
    DESY, Hamburg, Germany
  • A. Trebushinin
    BINP, Novosibirsk, Russia
 
  The European XFEL is a high-repetition multi-user facility with nominal photon energy range covering almost 3 orders of magnitude: 250 eV - 25 keV. In this work we explore the possibility to extend the photon energy range of the facility up to 100 keV via combination of superconducting undulator technology, period doubling and harmonic lasing, thus allowing for excellent tunability. To this purpose, we propose a dedicated FEL line, discuss its overall concept and provide analytical and numerical estimations of its expected performance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP061  
About • paper received ※ 20 August 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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TUP062 Two Colors at the SASE3 Line of the European XFEL: Project Scope and First Measurements 195
 
  • S. Serkez, G. Geloni, N. Gerasimova, J. Grünert, S. Karabekyan, A. Koch, J. Laksman, Th. Maltezopoulos, T. Mazza, M. Meyer, S. Tomin
    EuXFEL, Schenefeld, Germany
  • W. Decking, L. Fröhlich, V. Kocharyan, Y.A. Kot, E. Saldin, E. Schneidmiller, M. Scholz, M.V. Yurkov, I. Zagorodnov
    DESY, Hamburg, Germany
  • M. Huttula
    University of Oulu, Oulu, Finland
  • E. Kukk
    University of Turku, Turku, Finland
 
  The European XFEL is a high-repetition rate facility that generates high-power SASE radiation pulses in three beamlines. A joint upgrade project, with Finnish universities, to equip the SASE3 beamline with a chicane has been recently approved to generate two SASE pulses with different photon energies and temporal separation. In this work we report the status of the project, its expected performance, and recent experimental results. Additionally, we discuss methods to diagnose the properties of the generated radiation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP062  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP063 Physical Design and FEL Performance Study for FEL-III Beamline of SHINE 199
 
  • N. Huang
    SINAP, Shanghai, People’s Republic of China
  • H.X. Deng, B. Liu, D. Wang
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
 
  The first hard X-ray free electron laser (XFEL) facility in China, the Shanghai High-Repetition-Rate XFEL and Extreme Light Facility (SHINE), is under construction, which allows for generating X-ray pulses in the photon energy range from 3 keV to 25 keV. To produce X-ray pulses with photon energy up to 25 keV, FEL-III undulator line of SHINE employs superconducting undulators. However, the smaller gap of the superconducting undulator poses serious wakefield effect reducing the FEL power, compared to the normal planar undulator. For a setup design optimization, the design and performance of the FEL-III undulator line are presented using start-to-end beam simulations at self-amplified spontaneous emission (SASE) and self-seeding mode. The wakefield impact on FEL performance is then investigated. A linear undulator tapering technique is adopted for recovering the FEL power to the non-wakefield level.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP063  
About • paper received ※ 19 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP064 Effect on FEL Gain Curve Using Phase Shifters 203
 
  • M.H. Cho, H.-S. Kang, G. Kim, C.H. Shim, H. Yang
    PAL, Pohang, Republic of Korea
 
  Phase matching between FEL and electron beam should be precisely controlled for FEL amplification. Phase shifters located between undulators performs the phase matching. An electron beam can be controlled to be in the in- or out-phase by setting the phase shifters from the phase shifter scan. In this article, we show effects of FEL gain curve by setting the in- and out-phase of electron beam. We address reasons of the reduction of FEL intensity in the out-phase condition dividing the linear and saturation FEL amplification regimes. In the linear regime the gain curve is shifted, and in the saturation regime the electron loss occurs during the undulator tapering. Our results show agreements with experiments performed at PAL-XFEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP064  
About • paper received ※ 21 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP065 Optimization of a Coherent Undulator Beamline for New Advanced Synchrotron Light Source in Korea 206
 
  • I.G. Jeong, P. Buaphad, Y.J. Joo, Y. Kim, H.R. Lee
    University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
  • P. Buaphad, Y.J. Joo, Y. Kim, H.R. Lee
    KAERI, Jeongeup-si, Republic of Korea
  • M.Y. Han, I.G. Jeong, J.Y. Lee, S.H. Lee
    Korea Atomic Energy Research Institute (KAERI), Daejeon, Republic of Korea
 
  Recently, the demand for a new advanced synchrotron light source in Korea is rapidly growing. Six local governments in Korea would like to host the new synchrotron light source project in their own provinces. The new advanced synchrotron light source will be the Diffraction-Limited Storage Ring (DLSR), which is based on the Multi-Bend Achromat (MBA) lattice. For the new synchrotron light source, we would like to build a special 60-m long coherent undulator beamline, which can deliver high-intensity coherent radiation at the hard X-ray region. To design the coherent undulator beamline, we have performed numerous beam dynamics simulations with GENESIS and SIMPLEX codes. In this paper, we report design concepts and those simulation results for the coherent undulator beamline.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP065  
About • paper received ※ 26 August 2019       paper accepted ※ 26 August 2019       issue date ※ 05 November 2019  
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TUP066 Start-to-End Simulations for the Soft X-Ray FEL at the MAX IV Laboratory 210
 
  • W. Qin, J. Andersson, F. Curbis, L. Isaksson, M. Kotur, E. Mansten, M.A. Pop, S. Thorin, S. Werin
    MAX IV Laboratory, Lund University, Lund, Sweden
  • F. Curbis, S. Werin
    SLF, Lund, Sweden
 
  Funding: The work is supported by Knut and Alice Wallenberg foundation.
A Soft X-ray FEL (the SXL) using the existing 3 GeV linac at the MAX IV Laboratory is currently in the design phase. In this contribution, start-to-end simulations, including the photo-injector simulations using ASTRA, the linac simulations using ELEGANT and the FEL simulations using GENESIS, are presented for 100 pC and 10 pC operation modes. The features of the electron beam from the MAX IV linac and their impact on the FEL performance are discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP066  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP067 Advanced Concepts in the Design for the Soft X-Ray FEL at MAX IV 214
 
  • W. Qin, F. Curbis, M.A. Pop, S. Werin
    MAX IV Laboratory, Lund University, Lund, Sweden
  • F. Curbis, S. Werin
    SLF, Lund, Sweden
 
  Funding: The work is supported by Knut and Alice Wallenberg foundation.
A Soft X-ray FEL (the SXL) is currently being designed at the MAX IV Laboratory. In the work to adapt the FEL to the scientific cases several advanced options are being studied for coherence enhancement, generation of short pulses and two-color pulses. We will discuss the current status and the schemes studied, especially regarding the FEL performance with the features of the MAX IV linac, including a positive energy chirp.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP067  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP072 Orbital Angular Momentum from SASE 218
 
  • J.F. Morgan, B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  • B.W.J. MᶜNeil, J.F. Morgan, B.D. Muratori, P.H. Williams, A. Wolski
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • B.D. Muratori, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • A. Wolski
    The University of Liverpool, Liverpool, United Kingdom
 
  Radiation with orbital angular momentum, OAM, has many applications such as in imaging systems and microscopic tweezers [1]. The feasibility of generating light with OAM in a free electron laser, FEL, from amplified shot noise in an electron beam is investigated using the FEL simulation code Puffin [2]. This may allow generation of OAM radiation at shorter wavelengths than currently available, as well as the opportunity to incorporate the technique with other SASE manipulation schemes such as mode locking [3].
[1] A. M. Yao and M. J. Padgett, Adv. Opt. Photon. 3, 161(2011)
[2] L. T. Campbell and B. W. J. McNeil, Phys. Plasmas. 19, 093119(2012)
[3] D. J. Dunning, B. W. J. McNeil, and N. R. Thompson, Phys. Rev. Lett. 110, 104801(2013)
 
poster icon Poster TUP072 [1.311 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP072  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP073 High-Repetition-Rate Seeding Schemes Using a Resonator-Amplifier Setup 222
 
  • S. Ackermann, B. Faatz, V. Grattoni, C. Lechner, G. Paraskaki
    DESY, Hamburg, Germany
  • G. Geloni, S. Serkez, T. Tanikawa
    EuXFEL, Schenefeld, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  The spectral and temporal properties of Free-Electron Lasers (FEL) operating on the basis of self-amplified spontaneous emission (SASE) suffer from the stochastic behavior of the start-up process. Several so-called "seeding"-techniques using external radiation fields to overcome this limitation have been proposed and demonstrated. The external seed is usually generated by demanding, high-power laser systems, which are not available with a sufficient laser pulse energy at the high repetition rates of superconducting FEL facilities. In this contribution we discuss several seeding schemes that lower the requirements for the used laser systems, enabling seeded operation at high repetition rates by the means of a resonator-amplifier setup.  
poster icon Poster TUP073 [0.521 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP073  
About • paper received ※ 06 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP074 FLASH Upgrade for Seeding 226
 
  • V. Grattoni, S. Ackermann, B. Faatz, T. Lang, C. Lechner, M.M. Mohammad Kazemi, G. Paraskaki
    DESY, Hamburg, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  An upgrade for FLASH, the SASE FEL in Hamburg, is planned after 2020 aiming at fulfilling user requirements like fully coherent, variable polarization, and multi-colour pulses. In this proceeding, we focus on the FLASH1 beamline that will be operated in seeded mode at a high repetition rate. In particular, we will present and discuss the proposed seeding schemes for delivering FEL radiation with wavelengths from 60 down to 4 nm  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP074  
About • paper received ※ 19 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP076 Seeding R&D at sFLASH 230
 
  • C. Lechner, S. Ackermann, R.W. Aßmann, B. Faatz, V. Grattoni, I. Hartl, S.D. Hartwell, R. Ivanov, T. Laarmann, T. Lang, M.M. Mohammad Kazemi, G. Paraskaki, A. Przystawik, J. Zheng
    DESY, Hamburg, Germany
  • A. Azima, H. Biss, M. Drescher, W. Hillert, V. Miltchev, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • S. Khan
    DELTA, Dortmund, Germany
 
  Funding: Work supported by Federal Ministry of Education and Research of Germany under contract No. 05K13GU4, 05K13PE3, and 05K16PEA.
Free-electron lasers (FELs) based on the self-amplified spontaneous emission (SASE) principle generate photon pulses with typically poor longitudinal coherence. FEL seeding techniques greatly improve longitudinal coherence by initiating FEL amplification in a controlled way using coherent light pulses. The sFLASH experiment installed at the FEL user facility FLASH at DESY in Hamburg is dedicated to the study of external seeding techniques. In this paper, the layout of the sFLASH seeding experiment is presented and an overview of recent developments is given.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP076  
About • paper received ※ 30 September 2019       paper accepted ※ 17 October 2019       issue date ※ 05 November 2019  
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TUP077 Study of a Seeded Oscillator-Amplifier FEL 234
 
  • G. Paraskaki, S. Ackermann, B. Faatz, V. Grattoni, C. Lechner, M. Mehrjoo
    DESY, Hamburg, Germany
  • G. Geloni, S. Serkez, T. Tanikawa
    EuXFEL, Schenefeld, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  In recent years, there is interest of the Free-Electron Laser (FEL) community in external-seeding techniques such as the Echo-Enabled Harmonic Generation (EEHG) and the High-Gain Harmonic Generation (HGHG). With these techniques, pulses of an improved temporal coherence are generated, but at the same time, they are limited by the repetition rates that seed lasers can currently offer with the required pulse energies. A big challenge is to combine the advantages of seeding schemes with high repetition rates. For this purpose, we study a combination of an oscillator-amplifier. The modulator in the oscillator is used at a long wavelength to modulate the electron beam and an amplifier is operated to extract the FEL radiation of the desired harmonic. This way we can use a seed laser of 10 Hz in a burst mode and a resonator to feedback the radiation at repetition rates of superconducting accelerators instead of using an external seed at these high-repetition rates. In this contribution, we present simulation results of a seeded oscillator-amplifier FEL in an HGHG scheme.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP077  
About • paper received ※ 19 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP078 Impact of Electron Beam Energy Chirp on Seeded FELs 238
 
  • G. Paraskaki, S. Ackermann, B. Faatz, V. Grattoni, C. Lechner, J. Zemella
    DESY, Hamburg, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Seeded FELs enable the generation of fully coherent, transform-limited and high brightness FEL pulses, as the start-up process is driven by an external coherent light pulse. During the design process of such FELs, it is important to choose carefully the electron beam parameters to guarantee high performance. One of those parameters is the electron beam energy chirp. In this contribution, we show simulation results and we discuss how the electron beam energy chirp affects the final spectrum.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP078  
About • paper received ※ 16 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP079 Status of the Hard X-Ray Self-Seeding Setup at the European XFEL 242
 
  • G. Geloni, S. Karabekyan, D. La Civita, L. Samoylova, S. Serkez, R. Shayduk, H. Sinn, V. Sleziona, M. Vannoni, M. Yakopov
    EuXFEL, Schenefeld, Germany
  • J.W.J. Anton, S.P. Kearney, D. Shu
    ANL, Lemont, Illinois, USA
  • V.D. Blank, S. Terentiev
    TISNCM, Troitsk, Russia
  • W. Decking, V. Kocharyan, S. Liu, E. Negodin, E. Saldin, T. Wohlenberg
    DESY, Hamburg, Germany
  • X. Dong
    European X-Ray Free-Electron Laser Facility GmbH, Schelefeld, Germany
 
  A Hard X-Ray Self-Seeding (HXRSS) setup will be soon commissioned at the European XFEL. It relies on a two-chicanes scheme to deal, in particular, with the high pulse repetition rate of the facility. In this contribution we review the physics choices made at the design stage and the expected performance of the setup. We will also focus on the description of the hardware installations made at the SASE2 line of the European XFEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP079  
About • paper received ※ 27 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP080 Harmonic Off-Axis Seeding at the DELTA Short-Pulse Source 246
 
  • A. Meyer auf der Heide, B. Büsing, S. Khanpresenter, D. Krieg, C. Mai
    DELTA, Dortmund, Germany
 
  Funding: Work supported by the BMBF (05K16PEA, 05K16PEB), MERCUR (Pr-2014-0047), DFG (INST 212/236-1 FUGG) and the state of NRW
At the 1.5-GeV synchrotron light source DELTA operated by the TU Dortmund University, a short-pulse source employs the coherent harmonic generation (CHG) scheme. Here, a laser pulse interacts with a stored electron bunch forming a microbunching structure to generate ultrashort synchrotron light pulses at harmonics of the laser wavelength. As an upgrade of the short-pulse facility, the echo-enabled harmonic generation (EEHG) scheme will be implemented, which requires a second laser-electron interaction to yield much higher harmonics compared to CHG. In a study towards twofold laser seeding, the possibility of seeding at undulator harmonics with a crossing angle between laser and electron beam was investigated.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP080  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP083 Energy Spread Impact on HGHG and EEHG FEL Pulse Energy 250
 
  • S. Spampinati, E. Allaria, L. Giannessi, P. Rebernik Ribič
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • P. Rebernik Ribič
    University of Nova Gorica, Nova Gorica, Slovenia
 
  VUV and X-ray free electron lasers (FELs) require a very bright electron beam. Seeded FEL harmonic generation is particularly sensible to energy spread and slice energy spread can limit the highest harmonic conversion factor at which coherent radiation can be produced. Different cas-cade schemes can have different sensibility to the slice energy spread. At FERMI we have evaluated the impact of the slice energy spread on the performance of high gain harmonic generation (HGHG) and of echo enable harmonic generation (EEHG) by measuring the FEL pulse energy as function of the electron beam slice energy spread. The measurements were done at different harmon-ics. The slice energy spread was varied trough the laser heater located in the linac that drives FERMI.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP083  
About • paper received ※ 20 August 2019       paper accepted ※ 17 September 2019       issue date ※ 05 November 2019  
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TUP087 Start-to-end Simulations of the Reflection Hard X-Ray Self-Seeding at the SHINE Project 254
 
  • T. Liu, X. Dong, C. Feng
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
 
  The Shanghai high repetition rate XFEL and extreme light Facility (SHINE) project is designed to produce fully coherent X-ray photons covering the photon energy from 3 keV to 25 keV. We have reported our FEL proposal and schemes in the hard X-ray regime which is self-seeding based on the crystal monochromator previously. Comparing to the transmission self-seeding scheme, the reflection one has several advantages and might be the base proposal. Start-to-end (S2E) simulations from the beam generation by Astra, the linac accelerating by Elegant to the FEL simulation by Genesis are performed. In this manuscript, the FEL simulations based on the S2E beam will be presented mainly. The results demonstrate the feasibility of the reflection hard X-ray self-seeding at the SHINE project.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP087  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUP088 Numerical Simulations for Generating Fully Coherent Soft X-Ray Free Electron Lasers With Ultra-Short Wavelength 258
 
  • K.S. Zhou, H.X. Deng, B. Liu, D. Wang
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
 
  For the fully coherent, ultra-short and high power soft X-rays are becoming key instruments in many different research fields, such as biology, chemistry or physics. However, it’s hard to generate this kind of advanced light source by the conventional lasers, especially for the soft X-rays with ultra-short wavelength because of no suitable reflectors. The external seeded free electron laser (FEL) is considered as one feasible method. Here, we give an example to generate highly temporal coherent soft X-rays with the wavelength 1 nm by the two-stage cascaded schemes. EEHG scheme is used as the first-stage while the HGHG scheme is used as the second-stage.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP088  
About • paper received ※ 20 August 2019       paper accepted ※ 22 October 2019       issue date ※ 05 November 2019  
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TUP090 Considerations on Implementing EEHG with a Strong Linear Chirp 262
 
  • M.A. Pop, F. Curbis, W. Qin, S. Werin
    MAX IV Laboratory, Lund University, Lund, Sweden
  • F. Curbis, S. Werin
    SLF, Lund, Sweden
  • W. Qin
    Lund University, Lund, Sweden
 
  Funding: The work is supported by Knut and Alice Wallenberg foundation.
The Soft X-ray Laser (SXL) currently being studied at MAX IV Laboratory is envisioned to produce coherent radiation in the 1-5 nm wavelength range. In this contribution, we present the results of simulations aimed at adding to the SXL an Echo Enabled Harmonic Generation scheme, which has been shown to increase the coherence of FELs in the Soft X-ray regime. Our work puts special emphasis on accommodating the positive energy chirp of the electron bunch coming out of the MAX IV Linac and on generating sufficient bunching at the high harmonics necessary for covering the full wavelength range.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP090  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP091 Start-to-End Simulation of the NSRRC Seeded VUV FEL 266
 
  • S.Y. Teng
    NTHU, Hsinchu, Taiwan
  • C.H. Chen, W.K. Lau, A.P. Leepresenter
    NSRRC, Hsinchu, Taiwan
 
  A free electron laser (FEL) driven by a high brightness electron linac system has been proposed to generate ultrashort intense coherent radiation in the vacuum ultraviolet region. It is a third harmonic high-gain high harmonic generation (HGHG) FEL for generation of VUV radiation with wavelength at 66.7 nm from a 20-mm period length helical undulator. A 200-nm seed laser is used for beam energy modulation in a 10-periods helical undulator of 24-mm period length. A small chicane is placed between the two undulators to optimize power growth in the radiator. In this study, we perform start-to-end simulation to foresee the operational performance of the test facility and preliminary results are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP091  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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TUP092 XFEL Third Harmonic Statistics Measurement at LCLS 269
 
  • A. Halavanau, C. Emma, E. Hemsing, A.A. Lutman, G. Marcus, C. Pellegrini
    SLAC, Menlo Park, California, USA
 
  We investigate the statistical properties of the 6 keV third harmonic XFEL radiation at 2 keV fundamental photon energy at LCLS. We performed third harmonic self-seeding in the hard X-ray self-seeding chicane and characterized the attained non-linear third harmonic spectrum. We compare theoretical predictions with experimental results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP092  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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