FEL Oscillators and Long Wavelengths FEL
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. Hama, 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. Li, 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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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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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. Marcus, 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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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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TUD01
Generating Orbital Angular Momentum Beams in an FEL Oscillator  
 
  • Y.K. Wu, H. Hao, P. Liu, S.F. Mikhailov, V. Popov, J. Yan
    FEL/Duke University, Durham, North Carolina, USA
  • S.V. Benson
    JLab, Newport News, Virginia, USA
 
  Funding: DOE support under grant DE-FG02-97ER41033.
Coherent vortices have been generated with several schemes using a single-pass FEL. This work reports the first experimental demonstration of coherent vortice generation using an oscillator FEL. With the storage ring FEL at Duke University, we have established fundamental harmonic FEL lasing in a variety of coherently mixed orbital angular momentum (OAM) modes, with photons in the |l> and |-l> superposition states (l = 1, 2, 3) and with each eigenstate carrying lh OAM. Spatially organized in Laguerre Gaussian modes, stable FEL lasing of these OAM beams has been achieved with reasonable power. Optical techniques have been developed to characterize these beams. The operation of such an OAM FEL paves the way for the generation of OAM gamma-ray beams via Compton scattering.
 
slides icon Slides TUD01 [23.263 MB]  
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TUD02 Application of Infrared FEL Oscillators for Producing Isolated Attosecond X-Ray Pulses via High-Harmonic Generation in Rare Gases 272
 
  • R. Hajima, K. Kawase, R. Nagai
    QST, Tokai, Japan
  • Y. Hayakawa, T. Sakai, Y. Sumitomo
    LEBRA, Funabashi, Japan
  • T. Miyajima, M. Shimada
    KEK, Ibaraki, Japan
  • H. Ohgaki, H. Zen
    Kyoto University, Kyoto, Japan
 
  Funding: Quantum Leap Flagship Program (MEXT Q-LEAP)
High harmonic generation (HHG) in rare gases is now becoming a common technology to produce attosecond pulses in VUV wavelengths. So far HHG sources have been realized by femtosecond solid-state lasers, not FELs. We propose a FEL-driven HHG source to explore attosecond pulses at photon energies above 1 keV with a MHz-repetition, which is difficult with solid-state lasers [1]. A research program has been launched to establish technologies for the FEL-HHG, which covers generation and characterization of few-cycle IR pulses in a FEL oscillator, stacking of FEL pulses in an external cavity, and a seed laser for stabilization of carrier-envelope phase in a FEL oscillator. In this talk, we present the scheme of FEL-HHG and the status of the research program.
[1] R. Hajima and R. Nagai, Phys. Rev. Lett. 119, 204802 (2017)
 
slides icon Slides TUD02 [8.995 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUD02  
About • paper received ※ 23 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUD03 Fine and Hyperfine Structure of FEL Emission Spectra 276
 
  • V.V. Kubarev, Ya.V. Getmanov, O.A. Shevchenko
    BINP SB RAS, Novosibirsk, Russia
  • S. Bae, Y.U. Jeong
    KAERI, Daejon, Republic of Korea
 
  This paper presents the results of experimental investigations of the fine and hyperfine spectral structures of the Novosibirsk free-electron laser (NovoFEL) and the compact free-electron laser of the Korea Atomic Energy Research Institute (KAERI FEL) by means of the optimal instruments, resonance Fabry-Perot interferometers. The very high coherence of the NovoFEL spectrum was measured in regimes with one pulse circulating inside its optical resonator (the coherence length is 7 km, and the relative width of the hyperfine structure lines is 2E-8) and with total absence of coherence between two circulating pulses, i.e. the fine structure. Sixty pulses circulate simultaneously inside the KAERI FEL optical resonator, and the measured coherence length on average covers ten pulses (the coherence length is 1 m; the relative width of the fine structure lines is 10-4).  
slides icon Slides TUD03 [3.177 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUD03  
About • paper received ※ 16 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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TUD04 Cavity-Based Free-Electron Laser Research and Development: A Joint Argonne National Laboratory and SLAC National Laboratory Collaboration 282
 
  • G. Marcus, F.-J. Decker, G.L. Gassner, A. Halavanau, J.B. Hastings, Z. Huang, Y. Liu, J.P. MacArthur, R.A. Margraf, T.O. Raubenheimer, A. Sakdinawat, T.-F. Tan, D. Zhu
    SLAC, Menlo Park, California, USA
  • J.W.J. Anton, L. Assoufid, K. Goetze, W.G. Jansma, S.P. Kearney, K. Kim, R.R. Lindberg, A. Miceli, X. Shi, D. Shu, Yu. Shvyd’ko, J.P. Sullivan, M. White
    ANL, Lemont, Illinois, USA
  • B. Lantz
    Stanford University, Stanford, California, USA
 
  One solution for producing longitudinally coherent FEL pulses is to store and recirculate the output of an amplifier in an X-ray cavity so that the X-ray pulse can interact with following fresh electron bunches over many passes. The X-ray FEL oscillator (XFELO) and the X-ray regenerative amplifier FEL (XRAFEL) concepts use this technique and rely on the same fundamental ingredients to realize their full capability. Both schemes require a high repetition rate electron beam, an undulator to provide FEL gain, and an X-ray cavity to recirculate and monochromatize the radiation. The shared infrastructure, complementary performance characteristics, and potentially transformative FEL properties of the XFELO and XRAFEL have brought together a joint Argonne National Laboratory (ANL) and SLAC National Laboratory (SLAC) collaboration aimed at enabling these schemes at LCLS-II. We present plans to install a rectangular X-ray cavity in the LCLS-II undulator hall and perform experiments employing 2-bunch copper RF linac accelerated electron beams. This includes performing cavity ring-down measurements and 2-pass gain measurements for both the low-gain XFELO and the high-gain RAFEL schemes.  
slides icon Slides TUD04 [12.425 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUD04  
About • paper received ※ 25 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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