Keyword: simulation
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MOP011 Strongly Tapered Undulator Design for High Efficiency and High Gain Amplification at 266 nm undulator, ion, quadrupole, electron 49
 
  • Y. Park, P. Musumeci, N.S. Sudar
    UCLA, Los Angeles, USA
  • D.L. Bruhwiler, C.C. Hall, S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
  • A.Y. Murokh
    RadiaBeam, Santa Monica, California, USA
  • Y. Sun, A. Zholents
    ANL, Argonne, Illinois, USA
 
  Tapering Enhanced Stimulated Superradiant Amplification (TESSA) is a scheme developed at UCLA to increase efficiency of Free Electron Laser (FEL) light from less than 0.1% to above 10% using strongly tapered undulators and prebunched electron beams. Initial results validating this method have already been obtained at 10-um wavelength at Brookhaven National Laboratory. In this paper we will discuss the design of an experiment to demonstrate the TESSA scheme at high gain and shorter wavelength (266 nm) using the Linac Extension Area (LEA) beamline at the Advanced Photon Source of Argonne National Laboratory (ANL) to obtain conversion efficiencies around 10% depending on the length of the tapered undulator (up to 4m).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP011  
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MOP016 Comparing FEL Codes for Advanced Configurations ion, FEL, electron, laser 60
 
  • B.W. Garcia, G. Marcus
    SLAC, Menlo Park, California, USA
  • L.T. Campbell
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  • S. Reiche
    PSI, Villigen PSI, Switzerland
 
  Various FEL codes employ different approximations and strategies to model the FEL radiation generation process. Many codes perform averaging procedures over various length scales in order to simplify the underlying dynamics. As FELs are developed in more advanced configurations beyond simple SASE, the assumptions of some codes may be called into question. We compare the unaveraged code Puffin to averaged FEL codes including a new version of GENESIS in a variety of situations. In particular, we study a harmonic lasing setup, a High-Gain Harmonic Generation (HGHG) configuration modeled after the FERMI setup, and a potential Echo-Enabled Harmonic Generation (EEHG) configuration also at FERMI. We find the codes are in good agreement, although small discrepancies do exist.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP016  
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MOP018 Distributed Self-Seeding Scheme for LCLS-II ion, undulator, electron, FEL 68
 
  • C. Yang, Y. Feng, T.O. Raubenheimer, C.-Y. Tsai, J. Wu, M. Yoon, G. Zhou
    SLAC, Menlo Park, California, USA
  • B. Yang
    University of Texas at Arlington, Arlington, USA
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Self-seeding is a successful approach for generating high-brightness x-ray free electron laser (XFEL). A single-crystal monochromator in-between the undulator sections to generate a coherent seed is adopted in LCLS. However, for a high-repetition rate machine like LCLS-II, the crystal monochromator in current setup cannot sustain the high average power; hence a distributed self-seeding scheme utilizing multi-stages is necessary. Based on the criteria set on the crystal, the maximum allowed x-ray energy deposited in the crystal will determine the machine configuration for such a distributed self-seeding scheme. In this paper, a distributed self-seeding configuration is optimized for LCLS-II type projects in the hard x-ray FEL energy regime. The study is carried out based on numerical simulation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP018  
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MOP024 Simulation and Optimization for Soft X-Ray Self-Seeding at SXFEL User Facility ion, FEL, radiation, undulator 87
 
  • K.Q. Zhang, C. Feng, D. Wang, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
 
  The simulation and optimization studies for the soft x-ray self-seeding experiment at SXFEL have been presented in this paper. Some critical physical problems have been intensively studied to help us obtain a more stable output and a clearer spectrum. The monochromator is optimized considering various unideal conditions such as the reflection rate, diffraction rate and the roughness of the grating and the mirrors. An integrated self-seeding simulation is also presented. The calculation and simulation results show that the properties of the self-seeding can be significantly improved by using the optimized design of the whole system and the evaluation of grating monochromator shows that the presented design is reliable for soft x-ray self-seeding experiment at SXFEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP024  
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MOP047 Design Calculation on Beam Dynamics and THz Radiation of Delhi Light Source ion, radiation, undulator, electron 153
 
  • V.J. Joshi, R.K. Bhandari, S. Ghosh, D. Kanjilal, B. Karmakar, J. Karmakar, N. Kumar, S. Tripathi
    IUAC, New Delhi, India
  • A. Aryshev
    KEK, Ibaraki, Japan
  • U. Lehnert
    HZDR, Dresden, Germany
 
  Funding: This project is jointly supported by Inter University Accelerator Center and Board of Research in Nuclear Science.
The development of a compact light source facility, Delhi Light Source (DLS), based on a pre-bunched free electron laser, has been initiated at Inter University Accelerator Centre (IUAC).* A photocathode-based normal conducting RF gun will generate a low-emittance 'comb' electron beam with a maximum energy of ~8 MeV which when injected into ~ 1.5 metre compact undulator magnet (~0.4 < Krms < ~2) will produce intense THz radiation in the frequency range of 0.15 THz to 3.0 THz.** Each microbunch of the electron beam is expected to emit super-radiant radiation, and an enhancement in the overall spectral power can be achieved if the frequency (inverse of the spatial separation) of the electron microbunches coincides with that of the THz radiation being emitted. There will be provisions to vary the spatial separation between the successive microbunches of the 'comb' beam so that by varying the undulator magnetic field and/or electron energy, the THz frequency range can be tuned. The results of the beam optics for the entire range of frequencies mentioned above along with the detailed information of the radiation to be generated from the facility will be presented in the paper.
* S. Ghosh et al., NIMB-2017, in press.
** S.Tripathi et al., Proc. of this conference.
 
poster icon Poster MOP047 [0.959 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP047  
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MOP061 X-ray Regenerative Amplifier Free-Electron Laser Concepts for LCLS-II ion, FEL, electron, cavity 192
 
  • G. Marcus, Y. Ding, J.P. Duris, Y. Feng, Z. Huang, J. Krzywinski, T.J. Maxwell, D.F. Ratner, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  • K.-J. Kim, R.R. Lindberg, Yu. Shvyd'ko
    ANL, Argonne, Illinois, USA
  • D.C. Nguyen
    LANL, Los Alamos, New Mexico, USA
 
  High-brightness electron beams that will drive the next generation of high-repetition rate X-ray FELs allow for the possibility of optical cavity-based feedback. One such cavity-based FEL concept is the Regenerative Amplifier Free-Electron Laser (RAFEL). This paper examines the design and performance of possible RAFEL configurations for LCLS-II. The results are primarily based on high-fidelity numerical particle simulations that show the production of high brightness, high average power, fully coherent, and stable X-ray pulses at LCLS-II using both the fundamental and harmonic FEL interactions.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP061  
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TUP004 Longitudinal Phase Space Optimization for the Hard X-ray Self-Seeding ion, FEL, undulator, electron 259
 
  • S. Liu, W. Decking, G. Feng, V. Kocharyan, I. Zagorodnov
    DESY, Hamburg, Germany
  • G. Geloni, S. Serkez
    XFEL. EU, Hamburg, Germany
 
  For the implementation of Hard X-ray Self-Seeding (HXRSS) at European XFEL, short electron-beam bunches (FWHM ≤ 50 fs) are preferred to mitigate spatio-temperal coupling effect and to fit to the seeding bump width. Therefore, operations with low charges (< 250 pC) are preferred. Longitudinal phase-space optimization has been performed for the 100 pC case by flattening the current distribution. Start-to-end simulations show that, with the optimized distribution, for the photon energy of 14.4 keV, the HXRSS output power, pulse energy and spectral intensity can be increased by a factor of approximately 2 as compared to the nominal working point.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP004  
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TUP016 Beam-Dynamics Analysis of Long-Range Wakefield Effects on the SCRF Cavities at the Fast Facility ion, cavity, wakefield, HOM 280
 
  • Y.-M. Shin
    Northern Illinois University, DeKalb, Illinois, USA
  • K. Bishofberger, B.E. Carlsten, F.L. Krawczyk
    LANL, Los Alamos, New Mexico, USA
  • A.H. Lumpkin, J. Ruan, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
 
  Funding: Work supported by the subcontract (contract No: G2A62653) of LANL-LDRD program and DOE contract No. DEAC02-07CH11359 to the Fermi Research Alliance LLC.
Long-range wakefields in superconducting RF (SCRF) cavities create complicated effects on beam dynamics in SCRF-based FEL beamlines. The driving bunch excites effectively an infinite number of structure modes (including HOMs) which oscillate within the SCRF cavity. Couplers with loads are used to damp the HOMs. However, these HOMs can persist for long periods of time in superconducting structures, which leads to long-range wakefields. Clear understanding of the long-range wakefield effects is a critical element for risk mitigation of future SCRF accelerators such as XFEL at DESY, LCLS-II XFEL, and MaRIE XFEL. We are currently developing numerical tools for simulating long-range wakefields in SCRF accelerators and plan to experimentally verify the tools by measuring these wakefields at the Fermilab Accelerator Science and Technology (FAST) facility. This paper previews the experimental conditions at the FAST 50 MeV beamline based on the simulation results.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP016  
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TUP022 Modeling and Optimization of the APS Photo-Injector Using OPAL for High Efficiency FEL Experiments ion, linac, gun, electron 284
 
  • C.C. Hall, D.L. Bruhwiler, S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
  • A.Y. Murokh
    RadiaBeam, Santa Monica, California, USA
  • P. Musumeci, Y. Park
    UCLA, Los Angeles, USA
  • Y. Sun, A. Zholents
    ANL, Argonne, Illinois, USA
 
  Funding: This work was carried out with support for the United State Department of Energy, Office of Scientific Research, under SBIR contract number DE-SC0017161.
The Linac Extension Area (LEA) is a new beamline planned as an extension of Argonne's APS linac. An S-band 1.6-cell copper photo-cathode (PC) RF gun has been installed and commissioned at the APS linac front end. The PC gun will provide a beam to the LEA for accelerator technology development and beam physics experiments, in interleaving with a thermionic RF gun which provides a beam for APS storage ring operations. Recently an experiment was proposed to demonstrate the TESSA high-efficiency concept at LEA. In support of this experiment, we have begun simulating the photo-injector using the code OPAL (Object-oriented Particle Accelerator Library). In this paper, we first benchmark OPAL simulations with the established APS photo-injector optimization using ASTRA and ELEGANT. Key beam parameters required for a successful high-efficiency TESSA demonstration are discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP022  
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TUP024 Stochastic Effects from Classical 3D Synchrotron Radiation ion, electron, radiation, synchrotron 292
 
  • B.W. Garcia, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  • R.D. Ryne
    LBNL, Berkeley, California, USA
 
  In most cases, the one-dimensional coherent synchrotron radiation wakefield gives an excellent approximation to the total coherent effect due to classical synchrotron radiation in bend magnets. However, full particle Liénard-Wiechert simulations have revealed that there is non-numerical, stochastic noise which generates fluctuations about the approximate 1D solution. We present a model for this stochastic term in which this noise is due to long-range interaction with a discrete number of synchrotron radiation cones. The nature of this noise and how it depends on the 3D dimensions of the beam are explored.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP024  
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TUP030 An Emittance-Preservation Study of a Five-Bend Chicane for the LCLS-II-HE Beamline ion, emittance, electron, FEL 305
 
  • D. Khan, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
 
  The Linac Coherent Light Source II (LCLS-II) is an upgrade intended to advance the great success of its predecessor, LCLS-I, to maintain its position at the forefront of X-ray science. The introduction of a niobium-metal superconducting linac for LCLS-II not only increases the repetition rate to the MHz level (from 120 Hz), but also boasts an average brightness many orders higher (~10,000) than that of LCLS-I. Though, these improvements do not come without a price: the peak brightness suffers by a factor of 10, owing its degradation to the impact of Coherent Synchrotron Radiation (CSR) diminishing the peak current of the beam in the second bunch compressor (BC2). In this paper, we discuss the impact of implementing a plug-compatible 5-bend chicane for BC2 on the beam's emittance dilution for a high-energy, low-emittance configuration of LCLS-II (LCLS-II-HE). The results are compared with that of a standard 4-bend chicane under various settings in Elegant and CSRTrack.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP030  
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TUP034 Novel Aspects of Beam Dynamics in CeC SRF Gun and SRF Accelerator ion, gun, electron, cavity 313
 
  • I. Petrushina
    SUNY SB, Stony Brook, New York, USA
  • T. Hayes, Y.C. Jing, D. Kayran, V. Litvinenko, G. Narayan, I. Pinayev, F. Severino, K.S. Smith, G. Wang
    BNL, Upton, Long Island, New York, USA
  • K. Mihara
    Stony Brook University, Stony Brook, USA
  • K. Shih
    SBU, Stony Brook, New York, USA
 
  Funding: DoE NP office, grant DE-FOA-0000632, NSF grant PHY-1415252.
A 15 MeV CW SRF accelerator had been commissioned at Brookhaven National Laboratory to test the coherent electron cooling concept. The accelerator consists of an SRF 113-MHz photoemission gun, two 500 MHz bunching cavities and a 704-MHz 5-cell SRF linac. In this paper we describe our experience with this system with focus on unusual phenomena, such as multipacting in the SRF gun. We also discuss issues of wakefields in the CeC accelerator.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP034  
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TUP038 Experiments in Electron Beam Nanopatterning ion, electron, experiment, FEL 320
 
  • C. Zhang, W.S. Graves, L.E. Malin, J. Spence
    Arizona State University, Tempe, USA
  • D.B. Cesar, J.M. Maxson, P. Musumeci, A. Urbanowicz
    UCLA, Los Angeles, USA
  • R.K. Li, E.A. Nanni, X. Shen, S.P. Weathersby, J. Yang
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by NSF Accelerator Science awards 1632780 and 1415583, NSF BioXFEL STC award 1231306, and DOE contracts DE-AC02-76SF00515 and DE-SC0009914.
We report on experiments in nanopatterning electron beams from a photoinjector as a first step toward a compact XFEL (CXFEL). The nanopatterning is produced by Bragg diffraction of relativistic electron beams through a patterned Si crystal consisting of alternating thick and thin strips to produce nanometer-scale electron density modulations. Multi-slice simulations show that the target can be oriented for a two-beam condition where nearly 80% of the elastically scattered electron beam is diffracted into the 220 Bragg peak. An experiment at the two-beam condition measurement has been carried out at the SLAC UED facility showing this effect with 2.26 MeV electrons. We successfully proved a large portion of the main beam is diffracted into 220 spot by tuning the orientation of the sample. Future plans at UCLA are to observe the nanopatterned beam, and to investigate various grating periods, crystal thicknesses, and sample orientations to maximize the contrast in the pattern and explore tuning the period of the modulation. The SLAC measurement results will be presented along with design of the UCLA experiments.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP038  
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TUP054 Preparations for Installation of the Double Emittance-Exchange Beamline at the Argonne Wakefield Accelerator Facility ion, emittance, wakefield, experiment 340
 
  • G. Ha
    PAL, Pohang, Republic of Korea
  • M.E. Conde, D.S. Doran, W. Gai, J.G. Power
    ANL, Argonne, Illinois, USA
 
  Funding: This work is supported by Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
Preparations to upgrade the single EEX beamline at the Argonne Wakefield Accelerator (AWA) facility to a double EEX beamline are underway. The single EEX beamline recently demonstrated exchange-based longitudinal bunch shaping (LBS) which has numerous applications including high-energy physics linear colliders, x-ray FELs, and intense radiation sources. The exchange-based method can generate arbitrary LBS in the ideal case but has limitations in the real case. The double EEX beamline was proposed as a means to overcome the limitations of single EEX due to transverse jitter and large horizontal emittance. In this paper, we present the current status of beamline design and installation and simulation results for the planned experiments: collinear wakefield acceleration with tailored beams and tunable bunch compression without the double-horn feature.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP054  
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TUP059 Alternative Electron Beam Slicing Methods for CLARA and X-ray FELs ion, FEL, laser, electron 352
 
  • D.J. Dunning, H.M. Castaneda Cortes, S.P. Jamison, T.A. Mansfield, N. Thompson, D.A. Walsh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • D. Bultrini, S.P. Jamison, N. Thompson
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • D. Bultrini
    University of Glasgow, Glasgow, Scotland, United Kingdom
 
  Methods to generate ultra-short radiation pulses from X-ray FELs commonly slice a relatively long electron bunch to feature one (or more) short regions of higher beam quality which then lase preferentially. The slotted foil approach spoils the emittance of all but a short region, while laser-based alternatives modulate the electron beam energy, improving potential synchronisation to external sources. The CLARA FEL test facility under development in the UK will operate at 100-400 nm, aiming to demonstrate FEL schemes applicable at X-ray wavelengths. We present new laser-based slicing schemes which may better suit the wavelength range of CLARA and provide options for X-ray facilities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP059  
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TUP069 Simulating Beam Dynamics in Coherent Electron-Cooling Accelerator with WARP ion, cavity, electron, experiment 374
 
  • K. Shih
    SBU, Stony Brook, New York, USA
  • Y.C. Jing, V. Litvinenko, I. Pinayev, G. Wang
    BNL, Upton, Long Island, New York, USA
  • K. Mihara
    Stony Brook University, Stony Brook, USA
  • I. Petrushina
    SUNY SB, Stony Brook, New York, USA
 
  Funding: DoE NP office, grant DE-FOA-0000632, NSF grant PHY-1415252.
Coherent Electron Cooling (CeC) is a novel cooling technique based on amplification of interaction between hadrons and electron by an FEL. If proven, this CeC could bring a revolution in hadron and electron-hadron colliders. A dedicated CeC proof-of-principle experiment is under way at RHIC collider (BNL) using a sophisticated SRF accelerator for generating and accelerating electron beam. This paper is dedicated to studies of beam dynamics in the CeC accelerator and specifically to emittance preservation in its ballistic compressions section. Two 500-MHz RF cavities are used for generating the necessary energy chirp leading in 1.56-MeV, 0.5-nsec-long electron bunched to compress them to 25-psec duration downstream. During the commissioning of the CeC accelerator we noticed that beam emittance can be strongly degraded when electron beam passes these 500 MHz RF cavities off-axis. We used a full 3D PIC code Wrap to simulate effect of the off-axis beam propagation through these
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP069  
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WEP004 Calculations for a THz SASE FEL Based on the Measured Electron Beam Parameters at PITZ ion, FEL, electron, undulator 419
 
  • P. Boonpornprasert, M. Krasilnikov, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
 
  The Photo Injector Test facility at DESY, Zeuthen site (PITZ), develops high brightness electron sources for modern linac-based Free Electron Lasers (FELs). The PITZ accelerator can also be considered as a suitable machine for the development of an IR/THz source prototype for pump-probe experiments at the European XFEL. Calculations of THz radiation by means of a SASE FEL based on the simulated and the measured beam profiles at PITZ for the radiation wavelength of 100 microns were performed by using the GENESIS1.3 code. The results of these simulations are presented and discussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP004  
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WEP005 Coaxial Coupler RF Kick in the PITZ RF Gun ion, gun, electron, cavity 422
 
  • Y. Chen, P. Boonpornprasert, J.D. Good, H. Huck, I.I. Isaev, M. Krasilnikov, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • W. Ackermann, H. De Gersem
    TEMF, TU Darmstadt, Darmstadt, Germany
  • M. Dohlus
    DESY, Hamburg, Germany
  • Q.T. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
 
  We investigate a transverse RF kick induced by the transition between rectangular waveguide and coaxial line of the RF coupler in the 1.6-cell L-band normal conducting (NC) RF gun at the Photo Injector Test Facility at DESY, Zeuthen site (PITZ). A three-dimensional electromagnetic simulation shows the disturbed RF field distributions in the fundamental accelerating mode. Based on the 3D RF field map, an electron beam based characterization and quantification of the coaxial coupler RF kick in the PITZ gun is simulated. Preliminary results of the investigations are presented.  
poster icon Poster WEP005 [1.345 MB]  
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WEP016 Modeling of Diamond Field-Emitter Arrays for High-Brightness Photocathode Applications ion, electron, scattering, cathode 454
 
  • C. Huang, H.L. Andrews, B.K. Choi, R.L. Fleming, T.J. Kwan, J.W. Lewellen, D.C. Nguyen, K.E. Nichols, V.N. Pavlenko, A. Piryatinski, D.Y. Shchegolkov, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
 
  Funding: Work performed under the auspices of the U.S. DOE by the LANS, LLC, Los Alamos National Laboratory (LANL) under Contract No. DE-AC52-06NA25396. Work supported by the LDRD program at LANL.
Dielectric Laser Accelerator (DLA) is capable of generating high output power for an X-ray free-electron laser (FEL), while having a size 1-2 orders of magnitude smaller than existing Radio-Frequency (RF) accelerators. Single Diamond Field-Emitter (DFE) or array of such emitters (DFEA) can be employed as high-current ultra-low-emittance photocathodes for compact DLAs. We are developing a first principle semi-classical Monte-Carlo (MC) emission model for DFEAs that includes the effects of carriers' photoexcitation, their transport to the emitter surface, and the tunnelling through the surface. The electronic structure size quantization affecting the transport and tunnelling processes within the sharp diamond tips is also accounted for. These aspects of our model and their implementation and validation, as well as macroscopic electromagnetic beam simulation of DFE are discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP016  
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WEP043 Tune-Up Simulations for LCLS-II ion, quadrupole, emittance, linac 507
 
  • M.W. Guetg, P. Emma
    SLAC, Menlo Park, California, USA
 
  The planned superconducting LCLS-II linac poses new operational constraints with respect to the existing copper linac currently operated for LCLS. We present the results of exhaustive accelerator simulations, including realistic machine errors and exploring beam tune-up strategies. The results are used to pin-point the required beam diagnostics and the key correction elements. Specifically, these simulations concentrate on longitudinal and transverse beam matching as well as orbit and dispersion control through the new linac and up to the hard x-ray FEL. Dispersion control is achieved by a novel method presented within this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP043  
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WEP048 Coherent Undulator Radiation From a Kicked Electron Beam ion, electron, radiation, undulator 515
 
  • J.P. MacArthur, Z. Huang, J. Krzywinski, A.A. Lutman
    SLAC, Menlo Park, California, USA
 
  The properties of off-axis radiation from an electron beam that has been kicked off axis are relevant to recent Delta undualtor experiments at LCLS. We calculate the coherent emission from a microbunched beam in the far-field, and compare with simulation. We also present a mechanism for microbunches to tilt toward a new direction of propagation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP048  
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WEP055 Tapered Flying Radiofrequency Undulator ion, undulator, electron, FEL 525
 
  • S.V. Kuzikov, A.V. Savilov, A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
  • S.P. Antipov, A. Liu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • A.V. Savilov
    UNN, Nizhny Novgorod, Russia
 
  Funding: This project is supported by DoE Small Business Innovative Research phase I grant #DE-SC0017145.
We propose an efficient XFEL consisting of sequential RF undulator sections using: 1) tapered flying RF undulators, 2) short pulse, high peak-power RF and 3) driving undulator sections by spent electron beam. In a flying RF undulator, an electron bunch propagates through a high-power, nanosecond, co-propagating RF pulse. Helical waveguide corrugation supports a space harmonic with a negative propagation constant, providing a large Doppler up-shift. The undulator tapering technique improves FEL efficiency by 1-2 orders of magnitude in comparison with other facilities by decreasing the undulator period so that particles are trapped in the combined field of the incident x-ray and undulator field. We develop a so-called non-resonant trapping regime not requiring phase locking for feeding RF sources. Simulations show that by decreasing the corrugation periodicity one can vary an equivalent undulator period by 15%. The spent electron beam can be used to produce wakefields that will drive the RF undulator sections for interaction with the following beam. We have already manufactured and tested the 30 GHz simplified version of the 50 cm long undulator section for cold measurements.
 
poster icon Poster WEP055 [1.565 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP055  
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WEP060 Characterizing Sub-Femtosecond X-ray Pulses from the Linac Coherent Light Source ion, electron, laser, detector 535
 
  • S. Li, R.N. Coffee, J. Cryan, K.H. Hegazy, Z. Huang, A. Marinelli, A. Natan, T. Osipov, D. Ray
    SLAC, Menlo Park, California, USA
  • G. Guo
    Stanford University, Stanford, California, USA
 
  The development of sub-femtosecond x-ray capabilities at the Linac Coherent Light Source requires the implementation of time-domain diagnostics with attosecond (as) time resolution. Photoelectrons created by attosecond duration x-ray pulses in the presence of a strong-laser field are known to suffer an energy spread which depends on the relative phase of the strong-laser field at the time of ionization. This phenomenon can be exploited to measure the duration of these ultrashort x-ray pulses. We present an implementation which employs a circularly polarized infrared laser pulse and novel velocity map imaging design which maps the phase dependent momentum of the photoelectron onto a 2-D detector. In this paper, we present the novel co-linear VMI design, simulation of the photoelectron momentum distribution, and the reconstruction algorithm.  
poster icon Poster WEP060 [1.260 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP060  
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