THP —  Thursday Poster Session   (29-Aug-19   14:15—15:45)
Paper Title Page
THP001 Steffen Hard-Edge Model for Quadrupoles with Extended Fringe-Fields at the European XFEL 588
 
  • N. Golubeva, V. Balandin, W. Decking, L. Fröhlich, M. Scholz
    DESY, Hamburg, Germany
 
  For modeling of linear focusing properties of quadrupole magnets the conventional rectangular model is commonly used for the design and calculations of the linear beam optics for accelerators. At the European XFEL the quadrupole magnets are described using a more accurate Steffen hard-edge model. In this paper we discuss the application of the Steffen approach for the European XFEL quadrupoles and present the examination of the model with the orbit response matrix technique.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP001  
About • paper received ※ 20 August 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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THP002 Beam Based Alignment in all Undulator Beamlines at European XFEL 592
 
  • M. Scholz, W. Decking
    DESY, Hamburg, Germany
  • Y. Li
    EuXFEL, Hamburg, Germany
 
  The Free Electron Laser European XFEL aims at delivering X-rays from 0.25 keV up to 25 keV out of three SASE undulators. A good overlap of photon and electron beams is indispensable to obtain good lasing performance, especially for the higher photon energies. Thus the quadrupole magnets in the undulators must be aligned as good as possible on a straight line. This can only be realized with a beam based alignment procedure. In this paper we will report on the method that was performed at the European XFEL. We will also discuss our results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP002  
About • paper received ※ 20 August 2019       paper accepted ※ 12 September 2019       issue date ※ 05 November 2019  
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THP003 Arbitrary Order Perturbation Theory for a Time-Discrete Model of Micro-Bunching Driven by Longitudinal Space Charge 596
 
  • Ph. Amstutz
    LBNL, Berkeley, California, USA
  • M. Vogtpresenter
    DESY, Hamburg, Germany
 
  A well established model for studying the micro-bunching instability driven by longitudinal space charge in ultra-relativistic bunches in FEL-like beamlines can be identified as a time-discrete Vlasov system with general drift maps and Poisson type collective kick maps. Here we present an arbitrary order perturbative approach for the general system and the complete all-orders solution for a special example. For this example we benchmark our theory against our Perron-Frobenius tree-code.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP003  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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THP007 Frequency-Detuning Dependent Transient Coaxial RF Coupler Kick 599
 
  • Y. Chen, J.D. Good, M. Groß, P.W. Huang, I.I. Isaev, C. Koschitzki, M. Krasilnikov, S. Lal, X. Li, 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
  • F. Brinker, W. Decking
    DESY, Hamburg, Germany
 
  We model and characterize a transverse kick which results from the coaxial RF coupler in the L-band RF gun at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). The RF pulse is typically 600 µs long and used to produce a train of up to 2700 electron bunches. The kick is transient and found to be dependent on the detuning of the resonance frequency of the gun cavity. The frequency detuning within the RF macro-pulse results in a variation in the kick strength along the pulse. This leads to a downstream orbit and size change of individual bunches within the train. Using 3D RF field distributions calculated at detuned frequencies of the cavity, particle tracking simulations are performed to simulate the transient kick onto the bunch train. Given a drift distance, the orbit and size change along a train of fixed length is estimated. Systematic measurements of the kick have meanwhile been carried out. The temperature of the cooling water for the gun is tuned allowing detailed characterization of the frequency detuning within the RF pulse, and thereby measurements of the kick under conditions of practical interest. Experimental findings and simulation results will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP007  
About • paper received ※ 13 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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THP008 Design of a Multi-Cell SRF Reduced-Beta Cavity for the Acceleration of Low Energy Electron Beams 603
 
  • D.B. Bazyl, H. De Gersem, W.F.O. Müller
    TEMF, TU Darmstadt, Darmstadt, Germany
  • J. Enders, S. Weih
    TU Darmstadt, Darmstadt, Germany
 
  Funding: Work supported by DFG (GRK 2128)
Recently, the S-DALINAC has successfully passed the first ERL tests. One of the critical requirements for further operation in the ERL regime is minimising the longitudinal energy spread of the electron beam. One of the major sources for the current energy spread at the S-DALINAC is the low energy accelerating section. In order to overcome this problem an SRF reduced-beta cavity has been designed. The new cavity will replace the existing capture section and will allow to accelerate low energy electron beams with a minimised energy spread growth. In this work we discuss the electromagnetic and mechanical design of the SRF 3 GHz 6-cell reduced-beta cavity of elliptic type. In addition, we present the results of beam dynamics simulations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP008  
About • paper received ※ 19 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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THP009 Space Charge Field Beam Dynamics Simulations for the THz SASE FEL at PITZ 606
 
  • S.A. Schmid, H. De Gersem, E. Gjonaj
    TEMF, TU Darmstadt, Darmstadt, Germany
  • M. Dohlus
    DESY, Hamburg, Germany
  • M. Krasilnikov
    DESY Zeuthen, Zeuthen, Germany
 
  Funding: This work is supported by the DFG in the framework of GRK 2128.
A proof-of-principle experiment on a THz SASE FEL is under consideration at the Photo Injector Test facility at DESY in Zeuthen (PITZ). One of its options assumes utilization of 4.0 nC bunches at 16.7 MeV [1]. In this operation mode, space charge interaction strongly influences the dynamics of the electron beam inside the undulator. In this contribution, we investigate the beam dynamics in the THz undulator of PITZ using a particle-particle interaction model based on a Lienard-Wiechert approach. We analyze the influence of retardation and radiation fields on the beam dynamics resulting in the microbunching effect. Furthermore, we compute the radiation field and estimate the radiation power at the exit of the undulator. The validity of the underlying numerical models is discussed.
[1] M. Krasilnikov et al., in Proc. ICAP’18, Key West, USA, paper TUPAF23, 2018
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP009  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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THP010 Simple and Robust Free Electron Laser Doubler 609
 
  • S. Di Mitri, G. De Ninno, R. Fabris, S. Spampinati
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • G. De Ninno
    University of Nova Gorica, Nova Gorica, Slovenia
  • N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • N. Thompson
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  Funding: This work has received funding by the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 777431.
We present the design of a Free-Electron Laser (FEL) doubler suitable for the simultaneous operation of two FEL lines. The doubler relies on the physical selection of two longitudinal portions of an electron bunch at low energy, and on their spatial separation at high energy. Since the two electron beamlets are naturally synchronized, FEL pump-FEL probe experiments are enabled when the two photon pulses are sent to the same experimental station. The proposed solution offers improved flexibility of operation w.r.t. existing two-pulse, two-color FEL schemes, and allows for independent control of the color, timing, intensity and angle of incidence of the radiation pulses at the user end station. Detailed numerical simulations demonstrate its feasibility at the FERMI FEL facility.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP010  
About • paper received ※ 29 July 2019       paper accepted ※ 12 September 2019       issue date ※ 05 November 2019  
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THP011 Experimental Benchmarking of Wakefields at the FERMI FEL Linac and Undulator Line 613
 
  • S. Di Mitri, L. Sturari
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • C. Venier, R. Vescovo
    University of Trieste, Trieste, Italy
 
  Collective effects such as wakefields affect the dynamics of high brightness electron beams in linear accelerators (linacs), and can degrade the performance of short wavelength free-electron lasers (FELs). If a reliable model of wakefields is made available, the accelerator can be designed and configured with parameters that minimize their disrupting effect. In this work, the simulated effect of geometric (diffractive) wakefields and of coherent synchrotron radiation on the electron beam energy distribution at the FERMI FEL is benchmarked with measurements, so quantifying the accuracy of the model. Wakefields modelling is then extended to the undulator line, where particle tracking confirms the limited impact of the resistive wall wakefield on the lasing process. The study reveals an overall good understanding of collective effects in the facility [1].
[1] S. Di Mitri et al., Phys. Rev. Accel. and Beams, 22, 014401 (2019)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP011  
About • paper received ※ 29 July 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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THP012 Compact FEL-Driven Inverse Compton Scattering Gamma-Ray Source 617
 
  • M. Placidi, G. Penn
    LBNL, Berkeley, California, USA
  • S. Di Mitripresenter
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • C. Pellegrini
    UCLA, Los Angeles, California, USA
  • C. Pellegrini
    SLAC, Menlo Park, California, USA
 
  We explore the feasibility of a compact source of quasi-monochromatic, multi-MeV gamma-rays based on Inverse Compton Scattering (ICS) from a high intensity ultra-violet (UV) beam generated in a free-electron laser by the electron beam itself.[1] This scheme introduces a stronger relationship between the energy of the scattered photons and that of the electron beam, resulting in a device much more compact than a classic ICS for a given scattered energy. The same electron beam is used to produce gamma-rays in the 10-20 MeV range and UV radiation in the 10-15 eV range, in a ~4x22 m2 footprint system.
[1] M. Placidi et al., NIM A 855 (2017) 55-60.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP012  
About • paper received ※ 19 August 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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THP013 User Operation of Sub-Picosecond THz Coherent Transition Radiation Parasitic to a VUV FEL 621
 
  • S. Di Mitri, N. Adhlakha, E. Allaria, L. Badano, G. De Ninno, P. Di Pietro, G. Gaio, L. Giannessi, G. Penco, A. Perucchi, P. Rebernik Ribič, E. Roussel, S. Spampinati, C. Spezzani, M. Trovò, M. Veronese
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • G. De Ninno
    University of Nova Gorica, Nova Gorica, Slovenia
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • S. Lupi
    Coherentia, Naples, Italy
  • S. Lupi
    Sapienza University of Rome, Roma, Italy
  • F. Piccirilli
    IOM-CNR, Trieste, Italy
  • E. Roussel
    PhLAM/CERLA, Villeneuve d’Ascq, France
  • E. Roussel
    PhLAM/CERCLA, Villeneuve d’Ascq Cedex, France
 
  Coherent transition radiation is enhanced in intensity and extended in frequency spectral range by the electron beam manipulation in the beam dump beam line of the FERMI FEL, by exploiting the interplay of coherent synchrotron radiation instability and electron beam optics [1]. Experimental observations at the TeraFERMI beamline [2] confirm intensity peaks at around 1 THz and extending up to 8.5 THz, for up to 80 µJ pulse energy integrated over the full bandwidth. By virtue of its implementation in an FEL beam dump line, this work might stimulate the development of user-oriented multi-THz beamlines parasitic and self-synchronized to VUV and X-ray FELs.
[1] S. Di Mitri et al., Scientific Reports, 8, 11661 (2018).
[2] A. Perucchi et al., Synch. Rad. News 4, 30 (2017).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP013  
About • paper received ※ 29 July 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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THP015 The X-Band Linear Compression System in Dalian Coherent Light Source 625
 
  • Y. Yu, Z. Chen, G.K. Cheng, D.X. Dai, H.L. Ding, Z.G. He, L. Huang, Q.M. Li, Z.B. Li, L. Shi, J.T. Sun, K. Tao, Y.H. Tian, G.L. Wang, Z.Q. Wang, G.R. Wu, J.Y. Yang, X.M. Yang, W.Q. Zhang
    DICP, Dalian, People’s Republic of China
 
  Dalian Coherent Light Source (DCLS) is a free-electron laser (FEL) user facility working in the extreme ultraviolet (EUV) wavelength region from 50 to 150 nm. It mainly operates on the High Gain Harmonic Generation (HGHG) mode with the seed laser, although it can also run in the Self Amplified Spontaneous Emission (SASE) mode. The brightness and bandwidth of FEL radiation strongly depends on electron bunch quality, such as normalized transverse emittance, electron bunch energy, energy spread, peak current, etc. The high peak current with uniform longitudinal distribution is especially helpful for high peak power and narrow bandwidth of FEL, although it is not easy to achieve, due to the nonlinearity of sinusoidal accelerating radio frequency (RF) field and the 2nd-order momentum compaction coefficient T566 of bunch compressor. An X-band linearizer will be installed before the bunch compressor in order to correct this nonlinearity properly. In this paper, the beam dynamics design of the X-band linear compression system in DCLS is focused, and the simulation results with Elegant are presented and discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP015  
About • paper received ※ 19 August 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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THP016 Study of Microbunching Instability in SHINE Linac 629
 
  • D. Huang
    SINAP, Shanghai, People’s Republic of China
  • D. Gu
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • M. Zhang
    Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
 
  The SHINE project in China aims at the next generation high repetation rate and high power hard X-ray free electron laser facility. The high quality electron beam is thus requested in the linac to generate such a high quality FEL lasing. As the prerequisite, the microbuncing instability introduced by the nonlinear effects such as the LSC, CSR and wakefields in the bunch compressing process must be taken care of, otherwise the electron beam will not meet the requirements of lasing. In this article, the microbunching effects including the gain of the instability in the linac of SHINE are estimated, and several ways for the control of the instability are proposed.  
poster icon Poster THP016 [0.536 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP016  
About • paper received ※ 24 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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THP018 Transverse Deflecting Structure Dynamics for Time-Resolved Machine Studies of Shine 632
 
  • J.W. Yan, H.X. Deng, B. Liu, D. Wang
    SINAP, Shanghai, People’s Republic of China
  • H.X. Deng, B. Liu, D. Wang
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
 
  Funding: National Natural Science Foundation of China (11775293), the National Key Research and Development Program of China (2016YFA0401900) and Ten Thousand Talent Program.
The transverse deflecting structure (TDS) has been widely used in modern free electron laser facilities for the longitudinal phase space diagnostics of electron beams. As the first hard x-ray free electron laser in China, the SHINE is designed to deliver photons with a repetition rate up to 1 MHz. In this paper, we present the beam dynamics study of the X-band TDS behind the undulator of SHINE. In order to prevent the screen from being damaged by electron bunches with a high repetition rate, the phase of the transverse deflecting cavity is designed to deviate from zero, and only those electron bunches that are kicked by the transverse deflecting cavity are sent to the screen. In addition, the evolutionary algorithm is introduced to optimize the lattice of the TDS line to reach the highest possible resolution.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP018  
About • paper received ※ 19 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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THP020 Microbunching Enhancement by Adiabatic Trapping 635
 
  • X.J. Deng, W.-H. Huang, C.-X. Tang
    TUB, Beijing, People’s Republic of China
  • A. Chao
    SLAC, Menlo Park, California, USA
 
  Storage ring based concept called steady-state microbunching was proposed years ago for high average power narrowband coherent radiation generation. There are now active efforts on-going by the SSMB collaboration established among Tsinghua University and several other institutes. In this paper we study the particle trap and filamentation process of beam in RF or Micro Bucket which is useful for understanding the injection beam dynamics of SSMB. One remarkable result is the steady-state current distribution after full filamentation has little dependence on the bucket height as long as it is several times larger than the energy spread. A discrete increase of bucket height can boost the bunching, with the sacrifice of emittance growth. An adiabatic change of bucket height from a smaller value to the final desired value is then proposed to boost the bunching while preserving the longitudinal emittance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP020  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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THP022 A General Optimization Method for High Harmonic Generation Beamline 638
 
  • Y. Zhang, X.J. Deng, W.-H. Huang, Z. Pan, C.-X. Tang
    TUB, Beijing, People’s Republic of China
 
  Shorter bunches produce a more coherent radiation and contain higher harmonic components. Here, based on transverse and longitudinal phase space coupling, a general method for analyzing the production of very short beam and searching for compression beamline is presented. With this method, several beamlines are found and optimized. The electron beam can be compressed to tens of nanometers, generating coherent high harmonic radiation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP022  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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THP024 Spontaneous Coherent Radiation of Stabilized Dense Electron Bunches 643
 
  • Yu.S. Oparina, V.L. Bratman, A.V. Savilov
    IAP/RAS, Nizhny Novgorod, Russia
  • N. Balal, Yu. Lurie
    Ariel University, Ariel, Israel
 
  Funding: The work is supported by Russian Foundation for Basic Research Project 18-32-00351, 18-02-00765
Modern sources of dense electron beams allow the formation of compact sources of dense electron bunches with energies of 3-6 MeV, ps pulse durations, and charges of up to 1 nC. Such bunches can be used for the realization of relatively simple and compact powerful terahertz sources based on spontaneous coherent radiation. The power and duration of the process of such type of emission are limited due to an increase in the bunch length under the Coulomb repulsion. This complicates the effective implementation of the regime of spontaneous coherent radiation for dense bunches. Therefore, special methods for stabilization of the length of the operating e-bunch during its motion over a long electron-wave interaction region should be used. We propose several methods of the stabilization based on the axial bunch compression by self-radiated wave fields [1] and by quasi-static Coulomb fields inside a bunch [2]. The latter takes place in the case of the motion of electrons through the undulator in the "negative-mass" regime, when the Coulomb field inside the bunch leads not to repulsion of electrons but to their mutual attraction.
[1] I. V. Bandurkin, Yu. S. Oparina and A. V. Savilov, Appl. Phys. Lett. vol 110, p. 263508, 2017
[2] N. Balal, I. V. Bandurkin, V. L. Bratman, E. Magory, and A. V. Savilov, Appl. Phys. Lett. vol. 107, p. 163505, 2015
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP024  
About • paper received ※ 19 August 2019       paper accepted ※ 12 September 2019       issue date ※ 05 November 2019  
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THP027 Simulation and Optimization of the Transport Beamline for the NovoFEL RF Gun 647
 
  • A.S. Matveev, I.V. Davidyuk, O.A. Shevchenko, V.G. Tcheskidov, N.A. Vinokurov, V. Volkov
    BINP SB RAS, Novosibirsk, Russia
  • I.V. Davidyuk, A.S. Matveev, N.A. Vinokurov
    NSU, Novosibirsk, Russia
 
  A new low-frequency CW RF gun was developed and tested at Budker Institute of Nuclear Physics recently. We plan to use it to upgrade the ERL of the Novosibirsk FEL facility. It will allow increasing the average beam current (due to higher beam repetition rate) and thus increasing the average radiation power. The transport beamline for the RF gun uses the ninety-degree achromatic bend. It is designed in a way that keeps an option to operate with the old electrostatic gun as well. Due to the low beam energy (290 keV) the beam dynamics is strongly influenced by space-charge forces. The paper describes results of simulation and optimization of the RF gun transport beamline. Space-charge forces were taken into account with the code ASTRA. Main sources of emittance degradation were considered in order to decrease their influence during the optimization. In addition, the RF gun output beam parameters were measured for various RF gun emission phases. These experiments were simulated and the results were compared. The resulting beam parameters meets requirements of the Novosibirsk FEL facility ERL.  
poster icon Poster THP027 [3.158 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP027  
About • paper received ※ 16 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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THP030 An Updated Design of the NSRRC Seeded VUV Free Electron Laser Test Facility 651
 
  • W.K. Lau, C.K. Chan, C.-H. Chang, C.-C. Chang, L.-H. Chang, C.H. Chen, M.C. Chou, P.J. Chou, F.Z. Hsiao, K.T. Hsu, H.P. Hsueh, K.H. Hu, C.-S. Hwang, J.-Y. Hwang, J.C. Jan, C.K. Kuan, A.P. Leepresenter, M.-C. Lin, G.-H. Luo, K.L. Tsai
    NSRRC, Hsinchu, Taiwan
  • A. Chao, J. Wu
    SLAC, Menlo Park, California, USA
  • S.Y. Teng
    NTHU, Hsinchu, Taiwan
 
  In this report, we present an updated design of the facility which is a 200 nm seeded, HGHG FEL driven by a 250 MeV high brightness electron linac system with dogleg bunch compressor for generation of ultrashort intense coherent radiation in the vacuum ultraviolet region. It employs a 10-periods helical undulator for enhancement of beam energy modulation and a helical undulator of 20 mm period length as the radiator (i.e. THU20) to produce hundreds of megawatts radiation with wavelength as short as 66.7 nm. An optional planar undulator can be added to generate odd harmonics (e.g. 22.2 nm, 13.3 nm etc.) of the fundamental. The facility layout and expected FEL output performance is reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP030  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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THP031 Simulation and Optimization of Injector System for the Pre-bunched THz FEL 654
 
  • N. Chaisueb, S. Rimjaem
    Chiang Mai University, Chiang Mai, Thailand
  • S. Rimjaem
    ThEP Center, Commission on Higher Education, Bangkok, Thailand
 
  A linac-based light source for generation of infrared free-electron laser is under the development at Chiang Mai University, Thailand. The injector system of the facility consists mainly of an S-band thermionic cathode RF electron gun, a pre-bunch compressor in a form of an alpha magnet and a travelling-wave linac structure. Two 180-degree magnetic bunch compressors are installed downstream the injector system. Two separate radiation beamlines for mid-infrared (MIR) and terahertz (THz) free-electron laser (FEL) are located following the bunch compressor systems. In this contribution, we focus only on the coherent and high-power pre-bunch THz FEL that is generated from electron bunches with a femtosecond length. Electron beam dynamic simulations with program ASTRA were performed to obtain optimal electron beam properties. Optimization of the injector system for the THz FEL is thus presented. The simulated results show that the beam at the linac exit has a bunch length of 282 fs with a charge of 200 pC when the linac RF phase is 90° and the alpha gradient is 300 G/cm. This optimal condition will be used as an input for simulation in the 180-degree bunch compressor system and in the THz undulator magnet.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP031  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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THP033 XFEL Isochronous Chicanes: Feasibility Study 658
 
  • N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  FEL schemes such as High-Brightness SASE [1] and Mode-Locking [2] require electron beam delays inserted between undulator sections. These schemes have been shown in simulations to perform most effectively when the electron beam delays are very close to isochronous, i.e. the first order longitudinal dispersion is very small. To minimise the disruption to the FEL process in the inter-undulator gaps, these delays must also be as compact as possible. In this paper we study the maximum longitudinal space that a delay chicane could occupy in an XFEL operating at 6 GeV before the peak power drops below a defined threshold, and we present a limit for the maximum longitudinal dispersion of the delay chicanes. We then present the optical designs of two chicanes that satisfy the requirements of length and isochronicity and show how these designs could be realised practically using small-aperture high-field quadrupoles.
[1] PRL 110, 134802 (2013).
[2] PRL 100, 203901 (2008).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP033  
About • paper received ※ 16 August 2019       paper accepted ※ 09 September 2019       issue date ※ 05 November 2019  
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THP035 Beam Shaping for High-Repetition-Rate X-Ray FELs 661
 
  • Y. Ding, K.L.F. Bane, Y.M. Nosochkov
    SLAC, Menlo Park, California, USA
 
  Beam shaping at normal-conducting, accelerator-based FELs, such as LCLS, plays an important role for improving lasing performance and for supporting special operating modes, such as the self-seeding scheme. Beam shaping methods include horn-collimation and dechirper manipulation. Applying the beam shaping concept to high-repetition-rate FELs driven by a superconducting linac, such as LCLS-II, beam invasive methods are not preferred due to concerns about high power deposition. We have recently studied a few shaping options for LCLS-II, such as manipulating the beam chirp before compression using corrugated devices, and modifying higher order optics terms in a chicane using octupoles. In this report we will discuss the results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP035  
About • paper received ※ 23 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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THP036 Microbunch Rotation for Hard X-Ray Beam Multiplexing 665
 
  • R.A. Margraf, Z. Huang, J.P. MacArthur, G. Marcus
    SLAC, Menlo Park, California, USA
  • X.J. Deng
    TUB, Beijing, People’s Republic of China
  • Z. Huang, J.P. MacArthur, R.A. Margraf
    Stanford University, Stanford, 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.
Electron bunches in an undulator develop periodic density modulations, or microbunches, which enable the exponential gain of X-ray power in a SASE FEL. Many FEL applications could benefit from the ability to preserve microbunching through a dipole kick. For example, X-ray beam multiplexing can be achieved if electron bunches are kicked into separate beamlines and allowed to lase in a final undulator. The microbunches developed in upstream undulators, if properly rotated, will lase off axis, producing radiation at an angle offset from the initial beam axis. Microbunch rotation with soft X-rays was previously published and demonstrated experimentally [1], multiplexing LCLS into three X-ray beams. Additional 2018 data demonstrated multiplexing of hard X-rays. Here we describe efforts to reproduce these hard X-ray experiments using an analytical model and Genesis simulations. Our goal is to apply microbunch rotation to out-coupling from a cavity-based XFEL, (RAFEL/XFELO) [2].
[1] J. P. MacArthur et al., Physical Review X 8, 041036 (2018).
[2] G. Marcus et al. Poster TUD04 presented at FEL2019 (2019).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP036  
About • paper received ※ 24 August 2019       paper accepted ※ 26 August 2019       issue date ※ 05 November 2019  
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THP037 A Novel One-Dimensional Model for CSR Wakefields 669
 
  • G. Stupakov
    SLAC, Menlo Park, California, USA
 
  The existing 1D models of the coherent synchrotron radiation (CSR) wakefield in free space assume that the longitudinal bunch distribution remains constant when the beam propagates through a magnetic lattice. In this paper, we derive a formula for a 1D CSR wake that takes into account variation of the bunch length along the orbit. The formula is valid for arbitrary curvilinear beam trajectory. We analyze the validity of the 1D model in a typical implementation of an FEL bunch compressor.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP037  
About • paper received ※ 12 August 2019       paper accepted ※ 26 August 2019       issue date ※ 05 November 2019  
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THP041 Interaction of Powerful Electro-Magnetic Fields With Bragg Reflectors 673
 
  • I. Bahns, W. Hillert, P. Rauer, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • H. Sinn
    EuXFEL, Schenefeld, Germany
 
  Funding: supported by BMBF FKZ 05K16GU4
The interaction of an X-ray free electron laser (XFEL) with a Bragg Reflector can cause a change of the lattice constant, which has a direct influence on the stability of the reflection conditions [1] and can also excite modes of vibration [2]. The dynamical thermoelastic effects of the photon-matter-interaction are simulated with a finite-element-method (FEM) using the assumptions of continuums mechanics. To compare the simulation results with measured signals, a Michelson interferometer with ultrafast photodiodes (risetime <175ps, bandwith >2GHz) has been built up. To test the experimental setup in an in-house environment a pulsed UV laser is used to introduce a temporal displacement field in a silicon crystal created by about 0.26µJ of absorbed energy. The measured signal is in agreement with the FEM simulation and has shown that if averaging over thousands of pulses is applied a resolution <0.5pm is feasible. This makes this experimental setup useful to investigate the X-ray-matter-interaction of Bragg reflectors at modern X-ray facilities.
[1] S. Stoupin et al., Physical Review B 86.5 (2012): 054301.
[2] B. Yang, S. Wang and J. Wu, J. Synchrotron Rad. (2018) 25, 166-176.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP041  
About • paper received ※ 23 August 2019       paper accepted ※ 31 October 2019       issue date ※ 05 November 2019  
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THP044 The Simulation Study for Single and Multi Turn ERL Based EUV FEL 677
 
  • K.M. Nam, G.S. Yun
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • Y.W. Parc
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  Photolithography technology is the core part of the semiconductor manufacturing process. It has required light having stronger power for higher throughput. ERL based EUV FEL is emerging as a next generation EUV source which can produce the light over 10 kW. In this study, first, EUV-FEL design, which is based on single turn, is represented. It accelerates 40 pC electron beam to 600 MeV and produces EUV, whose wavelength and power are 13.5 nm and 37 kW. Second, multiturn based design is represented. It improved compactness to make it more suitable for industrial use. As a result, the electron beam was able to obtain the kinetic energy and circulate, and the size was reduced to about half without reducing the power greatly. This study is expected to increase the practical industrialization potential of ERL-based photolithography.  
poster icon Poster THP044 [0.584 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP044  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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THP047 Laser-Driven Compact Free Electron Laser Development at ELI-Beamlines 680
 
  • A.Y. Molodozhentsev
    Czech Republic Academy of Sciences, Institute of Physics, Prague, Czech Republic
  • J.T. Green, J. Hawkepresenter, M. Kaur, D. Kocon, G. Korn, K.O. Kruchinin
    ELI-BEAMS, Prague, Czech Republic
  • A.R. Maier
    University of Hamburg, Hamburg, Germany
 
  Funding: Advanced research using high-intensity laser produced photons and particles (CZ.02.1.01/0.0/0.0/16019/0000789) from the European Regional Development Fund.
The ELI-Beamlines Centre, located near Prague (Czech Republic) is an international user facility for fundamental and applied research. Using the optical parametric chirped-pulse amplification (OPCPA) technique, the ELI-Beamlines laser system will provide the laser pulse energy up to 10 Joules with the repetition rate up to 25 Hz. Combination of new laser development with constant improvement of the LWFA electron beam parameters has great potential in future development of the compact high repetition rate Free Electron Laser. The LWFA-driven FEL project, called "LUIS", is currently under preparation at ELI-Beamlines in collaboration with the University of Hamburg. The goal of the project is the improvement of the electron beam parameters in order to demonstrate the amplification and saturation of the SASE-FEL photon power in a single unit of the FEL undulator. A successful realization of the LUIS project will open a way to a next generation of laser-driven X-FELs. An overview of the LUIS project including design features and a description of all instrumentations used to characterize the laser, plasma, electron beam, photon generation will be presented in frame of this report.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP047  
About • paper received ※ 15 August 2019       paper accepted ※ 16 September 2019       issue date ※ 05 November 2019  
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THP048 Progress Towards Laser Plasma Electron Based Free Electron Laser on COXINEL 684
 
  • M.-E. Couprie, T. André, F. Blache, F. Bouvet, F. Briquez, Y. Dietrich, J.P. Duval, M. El Ajjouri, A. Ghaith, C. Herbeaux, N. Hubert, M. Khojoyan, C.A. Kitégi, M. Labat, N. Leclercq, A. Lestrade, A. Loulergue, O. Marcouillé, F. Marteau, D. Oumbarek Espinos, P. Rommeluère, M. Sebdaoui, K.T. Tavakoli, M. Valléau
    SOLEIL, Gif-sur-Yvette, France
  • I.A. Andriyash, V. Malka, S. Smartzev
    Weizmann Institute of Science, Physics, Rehovot, Israel
  • C. Benabderrahmane
    ESRF, Grenoble, France
  • S. Bielawski, C. Evain, E. Roussel, C. Szwaj
    PhLAM/CERLA, Villeneuve d’Ascq, France
  • S. Corde, J. Gautier, J.-P. Goddet, O.S. Kononenko, G. Lambert, K. Ta Phuoc, A. Tafzi, C. Thaury
    LOA, Palaiseau, France
 
  Laser plasma acceleration (LPA) with up to several GeV beam in very short distance appears very promising. The Free Electron Laser (FEL), though very challenging, can be viewed as a qualifying application of these new emerging LPAs. The energy spread and divergence, larger than from conventional accelerators used for FEL, have to be manipulated to fulfil the FEL requirements. On the test experiment COXINEL (ERC340015), the beam is controlled in a manipulation [1,2] line, using permanent magnet quadrupoles of variable strength [3] for emittance handing and a decompression chicane equipped with a slit for the energy selection, enabling FEL amplification for baseline reference parameters [2]. The electron position and dispersion are independently adjusted [4]. The measured spontaneous emission radiated by a 2 m long 18 mm period cryo-ready undulator exhibits the typical undulator spatio-spectral pattern, in agreement with the modelling of the electron beam travelling along the line and of the afferent photon generation. The wavelength is easily tuned with undulator gap variation. A wavelength stability of 2.6% is achieved. The undulator linewidth can be controlled.
[1] A. Loulergue et al., New J. Phys. 17 023028 (2015)
[2] M. E. Couprie et al., PPCF 58, 3 (2016)
[3] F. Marteau et al., APL 111, 253503 (2017)
[4] T. André et al., Nature Comm. 1334 (2018)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP048  
About • paper received ※ 13 August 2019       paper accepted ※ 16 September 2019       issue date ※ 05 November 2019  
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THP049 A Versatile THz Source for High-Repetition Rate XFELs 688
 
  • F. Lemery, M. Dohlus, K. Flöttmann, M. Marx
    DESY, Hamburg, Germany
  • M. Ivanyan, V.M. Tsakanov
    CANDLE, Yerevan, Armenia
 
  Funding: FL was partially funded by the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No. 730871
The development of high-repetition rate XFELs brings an exciting time for novel fundamental science exploration via pump-probe interactions. Laser-based pump sources can provide a wide range of wavelengths (200-10000~nm) via various gain media. These sources can also be extended with optical parametric amplifiers to cover a largely versatile spectral and bandwidth range. However beyond 10~μm, toward the THz regime, there exists no suitable gain media, and optical-to-THz efficiencies are limited below 1\%. In this paper we discuss the use of Cherenkov-based radiators with conventional electron bunches to generate high-power THz radiation over a wide range of parameters for existing and future XFEL facilities.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP049  
About • paper received ※ 25 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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THP051 Generating Trains of Attosecond Pulses with a Free-Electron Laser 692
 
  • S. Serkez, G. Geloni
    EuXFEL, Schenefeld, Germany
  • M.H. Cho, H.-S. Kang, G. Kim, J.H. Ko, C.-K. Min, I.H. Nam, C.H. Shim
    PAL, Pohang, Republic of Korea
  • F.-J. Decker
    SLAC, Menlo Park, California, USA
  • J.H. Ko, C.H. Shim
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • Yu. Shvyd’ko
    ANL, Lemont, Illinois, USA
 
  Recently, a Hard X-ray Self-Seeding setup was commissioned at PAL XFEL. Its main purpose is to increase the temporal coherence of FEL radiation in an active way. We report another application of this setup to generate trains of short sub-femtosecond pulses with linked phases. We discuss preliminary results of both experiment and corresponding simulations as well as indirect diagnostics of the radiation properties.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP051  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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THP054 Nanosecond Pulse Enhancement in Narrow Linewidth Cavity for Steady-State Microbunching 697
 
  • Q.H. Zhou
    Southwest University of Science and Technology, Mianyang, Sichuan, People’s Republic of China
 
  Funding: The National Natural Science Foundation of China under Grant No.11875227.
In steady-state microbunching (SSMB), nanosecond laser pulse with megawatt average power is required. We build up a theoretic model to enhance such pulse in a narrow linewidth (e.g. kHz level) cavity for this demand, which shows that a mode-locked mechanism in frequency domain should be considered. Simulations indicate that such pulse can be enhanced sufficiently under this condition. And we also propose some experimental schematics to realize it.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP054  
About • paper received ※ 25 August 2019       paper accepted ※ 22 October 2019       issue date ※ 05 November 2019  
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THP055 A Storage Ring Design for Steady-State Microbunching to Generate Coherent EUV Light Source 700
 
  • Z. Pan, X.J. Deng, W.-H. Huang, T. Rui, C.-X. Tang, Y. Zhang
    TUB, Beijing, People’s Republic of China
  • A. Chao
    SLAC, Menlo Park, California, USA
  • W. Wan
    ShanghaiTech University, Shanghai, People’s Republic of China
 
  The proposal of Steady State Microbunching (SSMB) makes it available to generate high average power coherent radiation, especially has the potential to generate kW level of EUV source for lithography. In order to achieve and maintain SSMB, we propose several concepts. One is that a very short electron bunch below 100 nm is stored in the ring, inserting a strong focusing part to compress the bunch to ~3 nm, then radiating coherently, which is called longitudinal strong focusing (LSF) scheme. We have optimized the candidate lattice to achieve the very short electron bunch storage and microbunching for electron beam. The tracking results show the equilibrium length of the electron bunch is about 400 nm and no particles lose after 4.3 damping time while only single-particle effect is considered. More optimization and some new design based on the simulation results are still implementing.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP055  
About • paper received ※ 19 August 2019       paper accepted ※ 26 August 2019       issue date ※ 05 November 2019  
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THP060 Development of RF-Undulators and Powering Sources for Compact Efficient Compton FEL-Scattrons 704
 
  • A.V. Savilov, E.D. Abubakirov, N.S. Ginzburg, S.V. Kuzikov, N.Yu. Peskov, A.A. Vikharev, V.Yu. Zaslavsky
    IAP/RAS, Nizhny Novgorod, Russia
 
  Conception of Compton-type FELs operating up to X-ray band is under development currently at IAP RAS (N.Novgorod). This concept is aimed at reducing energy of a driving relativistic electron beam and thereby increasing efficiency of the electron-wave interaction in FEL, as well as achieving relative compactness of the generator. The basis of this concept is RF-undulators of a new type - the so-called ’flying’ undulators. Results of current research of these RF-undulators, their simulations and ’cold’ tests in the Ka-band are presented. For powering RF-undulators spatially-extended narrow-band Cerenkov masers are developed in the specified frequency range. In order to achieve the required sub-gigawatt power level of the pumping wave in a strongly oversized oscillator, we exploit the original idea of using two-dimensional distributed feedback implemented in the 2D doubly-periodical slow-wave structures. The design parameters of Ka-band surface-wave oscillator intended for powering RF-undulators, results of its simulation and initial experimental studies are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP060  
About • paper received ※ 15 August 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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THP061 Bayesian Optimisation for Fast and Safe Parameter Tuning of SwissFEL 707
 
  • J. Kirschner, A. Krause, M. Mutný, M. Nonnenmacher
    ETH, Zurich, Switzerland
  • A. Adelmann, N. Hillerpresenter, R. Ischebeck
    PSI, Villigen PSI, Switzerland
 
  Parameter tuning is a notoriously time-consuming task in accelerator facilities. As tool for global optimization with noisy evaluations, Bayesian optimization was recently shown to outperform alternative methods. By learning a model of the underlying function using all available data, the next evaluation can be chosen carefully to find the optimum with as few steps as possible and without violating any safety constraints. However, the per-step computation time increases significantly with the number of parameters and the generality of the approach can lead to slow convergence on functions that are easier to optimize. To overcome these limitations, we divide the global problem into sequential subproblems that can be solved efficiently using safe Bayesian optimization. This allows us to trade off local and global convergence and to adapt to additional structure in the objective function. Further, we provide slice-plots of the function as user feedback during the optimization. We showcase how we use our algorithm to tune up the FEL output of SwissFEL with up to 40 parameters simultaneously, and reach convergence within reasonable tuning times in the order of 30 minutes (< 2000 steps).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP061  
About • paper received ※ 13 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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THP065 Multi-Objective FEL Design Optimisation Using Genetic Algorithms 711
 
  • D.J. Dunning, H.M. Castañeda Cortés, J.K. Jones, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • J.K. Jones, N. Thompson
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  Simulation studies were carried out to optimise the performance of various FEL designs, with examples including longitudinal current profile shaping for a seeded FEL, and selection of the chicane delays for the High-Brightness SASE technique. In these examples multi-objective genetic algorithms were applied to a single section of the overall facility simulation, i.e. the undulator, as is the common approach. Further studies are also reported in which a full start-to-end simulation chain was optimised, with the aim of delivering a more holistic facility design optimisation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP065  
About • paper received ※ 20 August 2019       paper accepted ※ 25 August 2019       issue date ※ 05 November 2019  
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THP066 XARA: X-Band Accelerator for Research and Applications 715
 
  • D.J. Dunning, L.S. Cowie, J.K. Jones
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • L.S. Cowie, J.K. Jones
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • L.S. Cowie
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
 
  XARA (X-band Accelerator for Research and Applications) is a proposal for a compact ~1 GeV/c accelerator to produce attosecond light pulses in the EUV to soft X-ray region. It is under consideration as a potential future upgrade to the CLARA facility at Daresbury Laboratory, utilising high-performance X-band RF technology to increase the electron beam momentum from 250 MeV/c. Emerging techniques for generating single-cycle undulator light [1] would give access to attosecond timescales, enabling studies of ultra-fast dynamics, while also being very compact. XARA would also enhance the existing capabilities for accelerator science R&D by incorporating X-band development and increasing the electron beam momentum for novel acceleration studies.
[1] Alan Mak et al., Rep. Prog. Phys. 82 025901 (2019)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP066  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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THP068 LCLS-II Extruded Aluminum Undulator Vacuum Chambers — New Approaches to an Improved Aperture Surface Finish 719
 
  • G.E. Wiemerslage, P.K. Den Hartog, J. Qian, M. White
    ANL, Lemont, Illinois, USA
 
  Funding: Work at Argonne National Laboratory is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract # DE-AC02-06CH11357.
The Linac Coherent Light Source, (LCLS) the world’s first x-ray free electron laser (FEL) became operational in 2009. The Advanced Photon Source contributed to the original project by designing and building the undulator line. Two slightly different variations of these chambers were required for LCLS-II: one for a soft X-ray (SXR) undulator line, and one for a hard X-ray (HXR) undulator line. Because of the extremely short electron bunch length, a key physics requirement was to achieve the best possible surface finish within the chamber aperture. Improvements to our earlier fabrication methods allowed us to meet the critical surface roughness finish defined by RF impedance requirements. We were able to improve the surface finish from an average of 812 nm rms to 238 nm rms. The average longitudinal surface roughness slope of all chambers was to be less than 20 mrad. We achieved an average longitudinal surface roughness slope of 8.5 mrad with no chamber exceeding 20 mrad. In the end, sixty-four undulator vacuum chambers and alignment systems were delivered to SLAC for the LCLS-II Upgrade project. Here we will report on the process improvements for the fabrication of these chambers.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP068  
About • paper received ※ 16 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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THP069 Observations on Microbunching of Electrons in Laser-Driven Plasma Accelerators and Free-Electron Lasers 722
 
  • A.H. Lumpkin
    Fermilab, Batavia, Illinois, USA
  • M. Downer, M. LaBerge
    The University of Texas at Austin, Austin, Texas, USA
  • D.W. Rule
    Private Address, Silver Spring, USA
 
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The periodic longitudinal density modulation of relativistic electrons at the resonant wavelength (microbunching) is a fundamental aspect of free-electron lasers (FELs). In one case, microbunching fractions reached 20% at saturation of a self-amplified spontaneous emission (SASE) FEL resulting in gains of 1 million at 530 nm [1]. In that experiment the z-dependent gain of coherent optical transition radiation (COTR) was also measured. In laser-driven plasma accelerators (LPAs), microbunching at visible wavelengths has also been recently reported as evidenced by significant COTR enhancements measured in near-field and far-field images on a single shot for the first time [2]. An analytical model for COTR interferometry (COTRI) addresses both cases. In the FEL, one identified microbunched transverse cores of 25-100 microns while in the LPA the reported transverse sizes at the exit of the LPA were a few microns. In the latter case, signal enhancements of nearly 100, 000 and extensive fringes out to 30 mrad in angle space were recorded. The broadband microbunching observed in the LPA case could act as a seed for a SASE FEL experiment with tunability in principle over the visible regime.
[1] A.H. Lumpkin et al., Phys. Rev. Lett. 88, No.23, 234801 (2002).
[2] A.H. Lumpkin, M. LaBerge, D.W. Rule et al., Proceedings of AAC18, (IEEE), (2019).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP069  
About • paper received ※ 20 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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THP071 Progress in High Power High Brightness Double Bunch Self-Seeding at LCLS-II 726
 
  • A. Halavanau, F.-J. Decker, Y. Ding, C. Emma, Z. Huang, A.K. Krasnykh, J. Krzywiński, A.A. Lutman, G. Marcus, A. Marinelli, A. Ratti, D. Zhu
    SLAC, Menlo Park, California, USA
  • C. Pellegrini
    UCLA, Los Angeles, California, USA
 
  Funding: Work supported by the U.S. Department of Energy Contract No. DE-AC02-76SF00515.
We have previosuly shown that we can generate near TW, 15 fs duration, near transform limited X-ray pulses in the 4 to 8 keV photon energy range using the LCLS-II copper linac, two electron bunches, a 4-crystal monochromator/delay line and a fast transverse bunch kicker. The first bunch generates a strong seeding X-ray signal, and the second bunch, initially propagating off-axis, interacts with the seed in a tapered amplifier undulator, where it propagates on axis. In this paper, we investigate the design of the 4-crystal monochromator, acting also as an X-ray delay system, and of the fast kicker, in preparation of the implementation of the system in LCLS-II.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP071  
About • paper received ※ 20 August 2019       paper accepted ※ 26 August 2019       issue date ※ 05 November 2019  
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THP073 Status Update for the High Gain High Efficiency TESSA-266 Experiment 730
 
  • Y. Park, D.K. Dang, P.E. Denham, P. Musumecipresenter, N.S. Sudar
    UCLA, Los Angeles, USA
  • R.B. Agustsson, T.J. Campese, I.I. Gadjev, A.Y. Murokh
    RadiaBeam, Los Angeles, California, USA
  • C.C. Hall, S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
  • Y. Sun, A. Zholents
    ANL, Lemont, Illinois, USA
 
  Funding: DOE grant No. DE-SC0009914 and DE-SC0018559
Tapering Enhanced Stimulated Superradiant Amplification (TESSA) allows to increase the efficiency of Free Electron Laser (FEL) based radiation generation from ~0.1% to 10% by using intense seed laser pulses, strongly tapered undulators and prebunched electron beams [1]. Initial results validating this method have already been obtained at 10 µm wavelength at Brookhaven National Laboratory [2]. We will present the design of an experiment to demonstrate the TESSA scheme at high gain and shorter wavelength (266 nm) using the APS injector linac at Argonne National Labor-atory (ANL) to obtain conversion efficiency of up to 10%. Undulator and focusing lattice design, as well as beam dynamics and diagnostics for this experiment will be discussed. An extension of the experiment to include the possibility of multi-bunch linac operation and an optical cavity around the undulator to operate in the TESSO regime will also be presented [3].
[1] J. Duris et al., New J. Phys. 17 063036 (2015)
[2] N Sudar et al., Physical review letters, 117, 174801 (2016)
[3] J. Duris et al., Physical Review Accelerators and Beams 21, 080705 (2018)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP073  
About • paper received ※ 20 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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THP074 FLASH: The Pioneering XUV and Soft X-Ray FEL User Facility 734
 
  • K. Honkavaara, S. Schreiber
    DESY, Hamburg, Germany
 
  FLASH, the free-electron laser (FEL) at DESY (Hamburg) started user operation in summer 2005. It delivers high peak and average brilliance XUV and soft X-ray FEL radiation to photon experiments. Nowadays, FLASH has a 1.25 GeV superconducting linac, and two undulator beamlines, which are operated simultaneously. This paper provides an overview of its evolution from a test facility for superconducting accelerator technology to a full-scale FEL user facility.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP074  
About • paper received ※ 20 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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THP078 Status of the CompactLight Design Study 738
 
  • G. D’Auria, S. Di Mitri, R.A. Rochow
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • M. Aicheler
    HIP, University of Helsinki, Finland
  • A. Aksoy
    Ankara University Institute of Accelerator Technologies, Golbasi, Turkey
  • D. Alesini, M. Bellaveglia, B. Buonomo, F. Cardelli, M. Croia, M. Diomede, M. Ferrario, A. Gallo, A. Giribono, L. Piersanti, J. Scifo, B. Spataro, C. Vaccarezza
    INFN/LNF, Frascati, Italy
  • R. Apsimon, G. Burt, A. Castilla
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • J.M. Arnesano, F. Bosco, L. Ficcadenti, A. Mostacci, L. Palumbo
    Sapienza University of Rome, Rome, Italy
  • A. Bernhard, J. Gethmann
    KIT, Karlsruhe, Germany
  • M. Calvi, T. Schmidt, K. Zhang
    PSI, Villigen PSI, Switzerland
  • H.M. Castañeda Cortés, J.A. Clarke, D.J. Dunning, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • A.W. Cross, L. Zhang
    USTRAT/SUPA, Glasgow, United Kingdom
  • G. Dattoli, F. Nguyen, A. Petralia
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • R.T. Dowd, D. Zhu
    AS - ANSTO, Clayton, Australia
  • D. Esperante Pereira, J. Fuster, D. Gonzalez-Iglesias
    IFIC, Valencia, Spain
  • W. Fang
    SINAP, Shanghai, People’s Republic of China
  • A. Faus-Golfe, Y. Han
    LAL, Orsay, France
  • E.N. Gazis, N. Gazis
    National Technical University of Athens, Athens, Greece
  • R. Geometrante, M. Kokole
    KYMA, Trieste, Italy
  • B. Gimeno
    UVEG, Burjasot (Valencia), Spain
  • V.A. Goryashko, M. Jacewicz, R.J.M.Y. Ruber
    Uppsala University, Uppsala, Sweden
  • R. Hoekstra
    ARCNL, Amsterdam, The Netherlands
  • X.J.A. Janssen, J.M.A. Priem
    VDL ETG, Eindhoven, The Netherlands
  • A. Latina, X. Liu, C. Rossi, D. Schulte, S. Stapnes, X.W. Wu, W. Wuensch
    CERN, Geneva, Switzerland
  • O.J. Luiten, P.H.A. Mutsaers, X.F.D. Stragier
    TUE, Eindhoven, The Netherlands
  • J. Marcos, E. Marín, R. Muñoz Horta, F. Pérez
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
  • Z. Nergiz
    Ankara University, Faculty of Sciences, Ankara, Turkey
  • L.J.R. Nix
    University of Strathclyde, Glasgow, United Kingdom
  • E. Tanke, E. Trachnas
    ESS, Lund, Sweden
  • G. Taylor
    The University of Melbourne, Melbourne, Victoria, Australia
 
  Funding: This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No. 777431.
CompactLight (XLS) is an International Collaboration of 24 partners and 5 third parties, funded by the European Union through the Horizon 2020 Research and Innovation Programme. The main goal of the project, which started in January 2018 with a duration of 36 months, is the design of an hard X-ray FEL facility beyond today’s state of the art, using the latest concepts for bright electron photo-injectors, high-gradient accelerating structures, and innovative short-period undulators. The specifications of the facility and the parameters of the future FEL are driven by the demands of potential users and the associated science cases. In this paper we will give an overview on the ongoing activities and the major results achieved until now.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP078  
About • paper received ※ 19 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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THP079 Status and Perspectives of the FERMI FEL Facility (2019) 742
 
  • L. Giannessi, E. Allaria, L. Badano, S. Bassanese, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, F. Cilento, P. Cinquegrana, M. Coreno, I. Cudin, G. D’Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, M. Di Fraia, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, L. Foglia, P. Furlan Radivo, G. Gaio, F. Gelmetti, F. Iazzourene, S. Krecic, G. Kurdi, M. Lonza, N. Mahne, M. Malvestuto, M. Manfredda, C. Masciovecchio, M. Milloch, R. Mincigrucci, N.S. Mirian, I. Nikolov, F.H. O’Shea, G. Penco, A. Perucchi, O. Plekan, M. Predonzani, K.C. Prince, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, L. Rumiz, C. Scafuri, C. Serpico, N. Shafqat, P. Sigalotti, A. Simoncig, S. Spampinati, C. Spezzani, M. Svandrlik, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
 
  FERMI is the seeded Free Electron Laser (FEL) user facility at the Elettra laboratory in Trieste, operating in the VUV to EUV and soft X-rays spectral range; the radiation produced by the seeded FEL is characterized by wavelength stability, low temporal jitter and longitudinal coherence in the range 100-4 nm. During 2018 a dedicated experiment has shown the potential of the Echo Enabled Harmonic Generation (EEHG) scheme [1] to cover most of this spectral range with a single stage cascade [2]. Such a scheme, combined to an increment of the beam energy and of the accelerator performances, could extend the FERMI operating range toward the oxygen k-edge. With this perspective, we present the development plans under consideration for the next 3 to 5 years. These include an upgrade of the linac and of the existing FEL lines, consisting in the conversion of FEL-1 first, and FEL-2 successively, into EEHG seeded FELs.
[1] G. Stupakov, Phys. Rev. Lett. 102, 74801 (2009)
[2] P. Rebernik et al., Nature Photonics https://doi.org/10.1038/s41566-019-0427-1
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP079  
About • paper received ※ 28 August 2019       paper accepted ※ 29 August 2019       issue date ※ 05 November 2019  
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THP081 PolFEL — New Facility in Poland 746
 
  • K. Szamota-Leandersson, P.J. Czuma, P. Krawczyk, J. Krzywiński, R. Nietubyć, M. Staszczak, J. Szewiński
    NCBJ, Świerk/Otwock, Poland
  • W. Bal, J. Poznański
    IBB, Warsaw, Poland
  • A. Bartnik, H. Fiedorowicz, K. Janulewicz, N. Palka
    MUT, Warsaw, Poland
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
 
  Funding: European Regional Development Fund ’ Smart Growth
In 2018 funds for the free electron laser PolFEL project was received. PolFEL will be driven by cw operating superconducting linac with SRF electron source. PolFEL will generate THz, IR and VIS-VUV radiation in two beamlines, respectively. In the first one, with electron beam below 80 MeV, the THz/IR radiation source will be generated in permanent magnet supper-radiant undulator, delivering THz radiation in 0.5 to 6 THz range. In the second beam line with up to 180 MeV electrons, the VIS/VUV radiation will be generated in the SASE undulator delivering coherent radiation down to 55 nm wavelength in the third harmonic, with sub-100 fs pulse duration. At the moment, four end-stations are planned. Experiments will be equipped with dedicated Pump-Probe spectrometer system as well. In the project, also, the Inverse Compton Scattering experiment is planned. In this contribution we will describe PolFEL facility in more details.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP081  
About • paper received ※ 29 August 2019       paper accepted ※ 18 September 2019       issue date ※ 05 November 2019  
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THP084 Status of the Soft X-Ray Laser (SXL) Project at MAX IV Laboratory 749
 
  • F. Curbis, J. Andersson, L. Isaksson, M. Kotur, F. Lindau, E. Mansten, M.A. Pop, H. Tarawneh, P.F. Tavares, S. Thorin, S. Werin
    MAX IV Laboratory, Lund University, Lund, Sweden
  • S. Bonetti, A. Nilsson
    Stockholm University, Stockholm, Sweden
  • V.A. Goryashko
    Uppsala University, Uppsala, Sweden
  • P. Johnsson, W. Qin
    Lund University, Lund, Sweden
  • M. Larsson, P.M. Salén
    FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden
  • J.A. Sellberg
    KTH Physics, Stockholm, Sweden
 
  Funding: The work is supported by Knut and Alice Wallenberg foundation.
A Soft X-ray Laser project (the SXL) aiming to produce FEL radiation in the range of 1 to 5 nm is currently in a conceptual design phase and a report on the design is expected to be delivered by March 2021. The FEL will be driven by the existing 3 GeV linac at MAX IV laboratory, which also serves as injector for the two storage rings. The science case has been pushed by a large group of mainly Swedish users and consists of experiments ranging from AMO physics to condensed matter, chemistry and imaging in life science. In this contribution, we will present the current conceptual design of the accelerator and the FEL operation modes together with a general overview of the beamline and experimental station. In particular design options for the FEL will be discussed in conjunction with the features of the electron beam from the MAX IV linac and the connection with the proposed experiments.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP084  
About • paper received ※ 21 August 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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THP085 Status of Athos, the Soft X-Ray FEL Line of SwissFEL 753
 
  • R. Ganter, G. Aeppli, A. Al Haddad, J. Alex, C. Arrell, V.R. Arsov, S. Bettoni, C. Bostedt, H.-H. Braun, M. Calvi, T. Celcer, P. Craievich, R. Follath, F. Frei, N. Gaiffi, Z.G. Geng, C.H. Gough, M. Huppert, R. Ischebeck, H. Jöhri, P.N. Juranič, B. Keil, F. Löhl, F. Marcellini, G. Marinkovic, G.L. Orlandi, C. Ozkan Loch, M. Paraliev, L. Patthey, M. Pedrozzi, C. Pradervand, E. Prat, S. Reiche, T. Schietinger, T. Schmidt, K. Schnorr, C. Svetina, A. Trisorio, C. Vicario, D. Voulot, U.H. Wagner, A.C. Zandonella
    PSI, Villigen PSI, Switzerland
 
  The Athos line will cover the photon energy range from 250 to 1900 eV and will operate in parallel to the hard X-ray line Aramis of SwissFEL. The paper will describe the current layout of the Athos FEL line starting from the fast kicker magnet followed by the dogleg transfer line, the small linac and the 16 APPLE undulators. From there the photon beam passes through the photonics front end and the beamline optics before reaching the experimental stations AMO and FURKA. The focus of this contribution will be on the two bunch operation commissioning (two bunches in the same RF macropulse), which started in 2018, and the characterization of the major components like the APPLE X undulator UE38, the CHIC chicane and the dechirper. The Athos installation inside the tunnel is alternating with Aramis FEL user operation and the first lasing is planned for winter 2019 / 2020.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP085  
About • paper received ※ 30 July 2019       paper accepted ※ 28 August 2019       issue date ※ 05 November 2019  
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THP086 Operation Modes of the SwissFEL Soft X-Ray Beamline Athos 757
 
  • S. Reiche, E. Ferrari, E. Prat, T. Schietinger
    PSI, Villigen PSI, Switzerland
 
  SwissFEL drives the two FEL beamlines Aramis and Athos, a hard and soft X-ray FEL, respectively. The layout of Athos extends from a simple SASE FEL beamline with the addition of delaying chicanes, external seeding and beam manipulation with wakefield sources (dechirper). It reserves also the space for a possible upgrade to self-seeding. This presentation gives an overview on the detailed layout enabling the unique operation modes of the Athos facility.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP086  
About • paper received ※ 23 August 2019       paper accepted ※ 16 September 2019       issue date ※ 05 November 2019  
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