Keyword: undulator
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MOYGB2 The LCLS-II: A High Power Upgrade to the LCLS cavity, linac, cryomodule, electron 18
 
  • J.N. Galayda
    SLAC, Menlo Park, California, USA
  
  Funding: The work is supported by DOE under grant No. DE-AC02-76SF00515
The LCLS-II is an upgrade of the LCLS X-ray FEL based on a 4 GeV superconducting RF linac. The LCLS-II is designed to produce 100's of Watts of X-rays from 200 eV up to 5 keV. The linac uses 1.3 GHz 9-cell cavities processed using the N2-doping technique and will be the first large scale CW SCRF linac with a Q of roughly 3x1010 at a gradient of 16 MV/m. The injector which will be commissioned in spring 2018, is based on the normal conducting CW RF APEX gun developed at LBNL. The LCLS-II will have two undulators: the soft X-ray undulator is a 39 mm period hybrid PM with an adjustable vertical gap to cover the range from 200 eV to 1.5 keV and hard X-ray undulator is a novel adjustable horizontal gap hybrid PM undulator with 26 mm period to generate vertically polarized X-rays from 1 to 5 keV. The talk will review the performance goals as well as the hardware fabrication. 		 
slides icon Slides MOYGB2 [11.367 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOYGB2  
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MOZGBD2 FEL Performance Achieved at European XFEL FEL, photon, MMI, electron 29
 
  • M. Scholz
    DESY, Hamburg, Germany
  
  The European XFEL has achieved first lasing by mid-2017 and first user experiments started by the end of that year. This invited talk describes the status of this facility, presenting highlights from the construction and commissioning, outlining experience from early operation, and discussing potential future developments.  
slides icon Slides MOZGBD2 [18.822 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOZGBD2  
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TUZGBD3 Beam Diagnostics for the APS MBA Upgrade feedback, diagnostics, controls, electron 1204
 
  • N. Sereno, N.D. Arnold, R.W. Blake, A.R. Brill, H. Bui, J. Carwardine, G. Decker, L. Emery, T. Fors, P.S. Kallakuri, R.T. Keane, R.M. Lill, D.R. Paskvan, A.F. Pietryla, H. Shang, X. Sun, S. Veseli, J. Wang, S. Xu, B.X. Yang
    ANL, Argonne, Illinois, USA
  
  The Advanced Photon Source (APS) is currently in the preliminary design phase for a multi-bend acromat (MBA) lattice upgrade. Beam stability is critical where the requirements are driven from the beam size which is expected to approach 4 microns vertically at the insertion device (ID) source points. AC rms beam stability requirements are defined as 10 % the minimum source size at the ID in the band 0.01-1000 Hz. The vertical plane stability goal is the most ambitious requiring a stability of 400 nm at the ID source point. In addition, long term drift defined as motion over a seven day timescale can be no more than 1 micron. In order to achieve these demanding beam stability requirements, a suite of beam diagnostics will be required including rf BPMs, X-ray BPMs, a mechanical motion measurement system, beam size monitors and a real time orbit feedback system. In addition, a tune measurement system, transverse multi-bunch feedback system and current monitors are planned for the upgrade. We report on the beam diagnostics design and APS storage ring R&D results used to inform the design.  
slides icon Slides TUZGBD3 [16.748 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBD3  
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TUPMF007 Cryogenic Testing and Initial Performance of a Helical Superconducting Undulator at the APS vacuum, cryogenics, operation, radiation 1260
 
  • J.D. Fuerst, E. Gluskin, Q.B. Hasse, Y. Ivanyushenkov, M. Kasa, I. Kesgin, Y. Shiroyanagi
    ANL, Argonne, Illinois, USA
  
  Funding: Work supported by the U.S. Department of Energy, Office of Science under Contract No. DE-AC02-06CH11357.
A helical superconducting undulator (HSCU) has been installed and is presently operational at the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). We describe the final assembly and cryogenic test program which led to successful operation, representing the culmination of a two-year development effort. Details of the cryostat and cryogenic system design are presented along with as-installed performance data and a comparison with design expectations. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF007  
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TUPMF008 Design, Construction, and Magnetic Field Measurements of a Helical Superconducting Undulator for the Advanced Photon Source photon, storage-ring, electron, experiment 1263
 
  • M. Kasa, S.J. Bettenhausen, J.D. Fuerst, E. Gluskin, Q.B. Hasse, Y. Ivanyushenkov, I. Kesgin, Y. Shiroyanagi, E. Trakhtenberg
    ANL, Argonne, Illinois, USA
  
  Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
A helical superconducting undulator (HSCU) was developed and installed at the Advanced Photon Source (APS). Implementation of a unique design of the helical coil former allowed for a compact turn around scheme of the conductor at the ends of the device during winding. Inherent to the coil winding design was the gradual reduction of the magnitude of the magnetic field at the ends of the device. The coil former design along with the magnetic measurement results will be described. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF008  
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TUPMF018 Simulation Studies of the Helical Superconducting Undulator Installed at APS multipole, simulation, operation, storage-ring 1290
 
  • A. Xiao, V. Sajaev, Y.P. Sun
    ANL, Argonne, Illinois, USA
  
  A multi-year project at APS has resulted in construction of a helical superconducting undulator (HSCU) for installation in the ring. Before installation, simulation studies were done to ensure that APS performance will not be compromised. This paper describes the method used for calculating the HSCU's perturbation effects and the simulation results for both calculated and measured field map.
Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF018  
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TUPMF021 Investigation of Options for Damping Trapped IVU Resonances resonance, impedance, damping, simulation 1296
 
  • R.T. Dowd
    AS - ANSTO, Clayton, Australia
  • W.J. Chi, D. Pelz
    RFS, Kilsyth, Australia
  
  Trapped resonances have been observed within the three In-Vacuum Undulators (IVUs) insertion devices at the Australian Synchrotron. These resonances can create vertical beam instability if not controlled through transverse feedback systems. Similar resonances have been observed at other synchrotron light sources around the world. Under certain conditions of undulator gap, these resonances can couple quite strongly to the beam, requiring high feedback gain. An investigation of the resonances has been carried out using 3D eigenmode and wakefield simulations to understand the resonances and determine the effectiveness of various schemes for modifying the damping the resonances.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF021  
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TUPMF022 Electron Beam Scanning in the Delta-Type Undulators for Sirius electron, radiation, polarization, storage-ring 1300
 
  • A. B. da Cruz, L. Liu
    LNLS, Campinas, Brazil
  
  We report on simulation studies to analyze the possibility of scanning the electron beam, and not scanning the sample, in CDI experiments using a Delta-Type undulator in the 3GeV Sirius electron storage ring presently under construction at LNLS. This would allow much faster scans in diffraction limited storage rings such as Sirius. We study displaced beam trajectories through the undulators and analyze the effects on the emitted radiation. It is possible to show that displacements on the order of ± 500 micrometers around the center will introduce variations in the radiation spectrum that are less that 1 per cent and thus acceptable for Coherent Diffraction Imaging experiments.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF022  
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TUPMF040 Alignment of Current Strips at the Canadian Light Source alignment, closed-orbit, electron, vacuum 1342
 
  • W.A. Wurtz
    CLS, Saskatoon, Saskatchewan, Canada
  • Q.L. Zhang
    SINAP, Shanghai, People's Republic of China
  
  The Quantum Materials Spectroscopy Centre beamline at the Canadian Light Source will employ a 180 mm period elliptically polarizing undulator (EPU180), which will have significant impacts on beam dynamics with large tune shifts and reductions in dynamic aperture. Current strips mounted to the vacuum chamber are intended to mitigate the effects of EPU180 with each strip powered by an independent power supply. It is important to accurately model the current strips in order to calculate the required compensation. We model the current strips as straight wires, parallel to the electron beam, with small horizontal and vertical displacements from their nominal positions. As the real current strips are not completely straight, this is an effective model, but justified as we are mostly interested in the magnetic field integrated along the strips. By activating two strips and measuring the ratio of the two currents needed to minimize closed orbit distortion in the horizontal and vertical planes, we can find the effective horizontal and vertical displacements of the straight wires in the model. Our goal is to create an effective model of the strips from beam-based measurements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF040  
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TUPMF044 First Lasing of the CAEP THz FEL Facility Driven by a Superconducting Accelerator FEL, laser, electron, free-electron-laser 1349
 
  • D. Wu, W. Bai, D.R. Deng, C.L. Lao, M. Li, S.F. Lin, X. Luo, L.J. Shan, X. Shen, H. Wang, J. Wang, Y. Xu, L.G. Yan, X. Yang, K. Zhou
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
  • Y.H. Dou, X.J. Shu
    Institute of Applied Physics and Computational Mathematics, People's Republic of China
  • W.-H. Huang
    TUB, Beijing, People's Republic of China
  • X.Y. Lu
    PKU, Beijing, People's Republic of China
  
  Funding: Work supported by China National Key Scientific Instrument and Equipment Development Project (2011YQ130018), National Natural Science Foundation of China (11475159, 11505173, 11575264 and 11605190)
The stimulated saturation of the terahertz free electron laser at China Academy of Engineering Physics was reached in August, 2017. This THz FEL facility consists of a GaAs photocathode high-voltage DC gun, a superconducting RF linac, a planar undulator and a quasi-concentric optical resonator. The terahertz wave frequency is continuous adjustable from 2 THz to 3 THz. The average power is more than 10 W and the micro-pulse power is more than 0.3 MW. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF044  
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TUPMF045 Performance Optimization of a Prototype Undulator U38 Using Multi-Objective Genetic Algorithm MMI, electron, laser, free-electron-laser 1353
 
  • L.G. Yan, D.R. Deng, P. Li, D. Wu
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
  
  Funding: The project of the national large-scale instrument development: 2011YQ130018; National Natural Science Foundation of China: 11505174, 11505173 and 11605190.
Genetic Algorithm (GA) is one of the most excellent method to search the optimal solution of a problem, which has been applied to solve various problems. It is hard to estimate shim applied on raw undulator precisely. There are many methods have been developed to solve the problem. In this proceeding, we measured the magnetic field distribution of prototype undulator U38 and concluded the shim using multi-objective GA. The code was written with the language of Python and based on the package pyevolve. A multi-objective fitness function was setup to implement the multi-objective optimization. Experimentally，performances satisfied the requirements by shimming U38 three times. The trajectory center deviation, peak-to-peak error and phase error are reduced to 0.15 mm, 0.49% and 1°. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF045  
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TUPMF051 Generating Ultrashort X-Ray Pulse in a Diffraction-Limed Storage Ring by Phase-Merging Enhanced Harmonic Generation with Normal Modulator bunching, radiation, laser, electron 1371
 
  • W. Liu, Y. Jiao
    IHEP, Beijing, People's Republic of China
  
  In recent years, the study of ultrafast processes has increased the demand for ultrashort pulses. The duration of the synchrotron radiation pulse is generally in the range of 10-100 ps, which cannot be used in the experiments of studying the ultrafast process. Thus it is interesting to explore a way of obtaining sub-picosecond radiation pulses in storage ring light sources. The phase-merging enhanced harmonic generation (PEHG) scheme using a transverse gradient undulator as the modulator can be used to generate coherent radiation at high harmonic, which is very suitable for the generating ultrashort pulses in a diffraction-limed storage ring (DLSR). This paper presents a new PEHG modulation scheme, using a normal undulator as the modulator. This scheme is technically easier to be realized in a DLSR. Simulation is performed to demonstrate the effectiveness of this method.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF051  
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TUPMF055 Phase Matching Application in Hard X-Ray Region of HEPS brilliance, radiation, electron, photon 1386
 
  • X.Y. Li, Z. Duan, Y. Jiao, S.K. Tian
    IHEP, Beijing, People's Republic of China
  
  For the 6 meters long straight-section of HEPS, a double collinear double-cryogenic permanent magnet undulator(CPMU) structure is designed for high energy photon users to achieve higher brightness. Angular profiles of radiation produced by the double undulator configuration has been derived analytically. The efficiency of phase shifter on improving the brightness of double-CPMU is therefore evaluated with the beam energy spread is taken into account.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF055  
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TUPMF056 Brightness Dependence Investigation and Optimizaiton for the Heps brightness, lattice, emittance, photon 1390
 
  • Y. Jiao, M. Li, X.Y. Li
    IHEP, Beijing, People's Republic of China
  
  The High Energy Photon Source (HEPS) is an ultralow-emittance, kilometer-scale storage ring light source to be built in China. To maximize the photon spectral brightness, one of the most important performance parameters of the light source, we investigated the dependence of brightness on different parameters, such as the natural emittance, coupling, beta functions of the undulator section, and length of the undulator section. Based on this study, we optimized the HEPS lattice by using brightness as an optimizing objective.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF056  
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TUPMF069 Low Gain FEL Oscillator Option for PETRA IV FEL, emittance, storage-ring, electron 1420
 
  • I.V. Agapov
    DESY, Hamburg, Germany
  • Y.-C. Chae
    ANL, Argonne, Illinois, USA
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  
  Next generation synchrotron storage rings will have electron beam density approaching that necessary for driving an XFEL. It falls short of the quality required for the high-gain x-ray regime above 1 keV, mainly due to the large energy spread and small peak current, bit is sufficient to reach low-gain regime. Here we explore the parameter space of a low gain XFEL oscillator, to establish the feasibility range of such a device for the Petra upgrade project.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF069  
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TUPMF072 Microwave Instability and Energy Spread Measurement via Vertical Dispersion Bump in PETRA III emittance, experiment, quadrupole, wiggler 1427
 
  • Y.-C. Chae, D. Dzhingaev, M. Ebert, G. Falkenberg, J. Keil, G. Kube, G.K. Sahoo, M. Sprung, R. Wanzenberg, F. Westermeier
    DESY, Hamburg, Germany
  • A.I. Novokshonov
    TPU, Tomsk, Russia
  
  The recent measurement of bunch length versus current indicated that the longitudinal impedance (Z/n) is 0.15 Ω in close agreement with the impedance model*. Naive application of Keil-Schnell criteria predicts the threshold of microwave instability at 0.25 mA. Since the single bunch intensity is in the range of 0.2-2.5 mA depending on the fill-pattern of PETRA III, we expect to observe the fill-pattern dependent energy spread according to the theory. However, the 3rd generation light sources comparable to PETRA III often reported the observation which was much greater than the theoretical one. In order to induce the beam size variation we had used skew quadrupoles to generate the dispersion in vertical plane. In particular we made dispersion bump at the undulator sector so that we were able to use the X-ray optics for the precise determination of small vertical beam size. In this paper we report the experimental setup and measurement data with the estimate on the instability threshold. We also report the vertical emittance and energy spread based on the X-ray beam size measurement as well as the RF signal which was excited by the beam at the longitudinal feedback cavity.
* K. Balewski, R. Wanzenberg, "OBSERVATION OF INTENSITY DEPENDENT SINGLE BUNCH EFFECTS AT THE SYNCHROTRON LIGHT SOURCE PETRA III", Proc. of IPAC2011, p. 730. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF072  
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TUPMF073 Impedance Optimization of Small Gap Chambers for the High Single Bunch Current Operation at the Undulator Based Light Sources impedance, lattice, ECR, simulation 1430
 
  • Y.-C. Chae
    DESY, Hamburg, Germany
  
  In the undulator based light sources the intensity limit of single bunch is often determined by the strong vertical instability caused by the wakefield in the ring, where the undulator itself is large impedance source. The optimization of transition from the large aperture to undulator's small-gap chamber is on-going research topic in an effort to reduce the vertical impedance; at the same time, the demand on single-bunch current is high from the timing-mode x-ray user community. In this paper, after showing the results obtained by exploring the parameter space guided by Stupakov's formula, we propose the linearly-segmented transition which can reduce the impedance down to 60% or less of the original linear taper. The reduction can be utilized either to increase the bunch current substantially or to install a smaller gap chamber without impacting the bunch current limit. For the definite result we considered the transition between two ellipses, namely, (a, b) = (42 mm, 21 mm) and (18 mm, 4 mm) over the length 15-30 cm in beam direction.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF073  
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TUPMF079 An Option to Generate Seeded FEL Radiation for FLASH1 FEL, electron, laser, radiation 1448
 
  • V. Grattoni, R.W. Aßmann, J. Bödewadt, I. Hartl, C. Lechner, B. Manschwetus, M.M. Mohammad Kazemi
    DESY, Hamburg, Germany
  • W. Hillert, V. Miltchev, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • S. Khan, T. Plath
    DELTA, Dortmund, Germany
  
  The FLASH free-electron laser (FEL) at DESY is currently operated in self-amplified spontaneous emission (SASE) mode in both beamlines FLASH1 and FLASH2. Seeding offers unique properties for the FEL pulse, such as full coherence, spectral and temporal stability. In this contribution, possible ways to carry the seeded FEL radiation to the user hall are presented with analytical considerations and simulations. For this, components of the sFLASH seeding experiment are used.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF079  
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TUPMF089 Possible Upgrades of FLASH –- A View from the Accelerator-Perspective laser, FEL, optics, electron 1477
 
  • M. Vogt, B. Faatz, K. Honkavaara, J. Rönsch-Schulenburg, S. Schreiber, J. Zemella
    DESY, Hamburg, Germany
  
  Recently FLASH (Free electron LASer in Hamburg) at DESY has been granted funding for a refurbishment project covering among others the replacement of two old SRF modules, an upgrade of the injector lasers and an upgrade of parts of the electron beam diagnostics. In addition we are proposing several possible upgrades and new features for the injector and the drive linac as well as in the undulator beamlines. Here we present options which are in our opinion technically feasible and at the same time operationally manageable.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF089  
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TUPMF090 Status of the Superconducting Soft X-Ray Free-Electron Laser FLASH at DESY FEL, laser, operation, electron 1481
 
  • M. Vogt, K. Honkavaara, M. Kuhlmann, J. Rönsch-Schulenburg, S. Schreiber, R. Treusch
    DESY, Hamburg, Germany
  
  FLASH, the free-electron laser (FEL) user facility at DESY, has delivered high brilliance VUV and soft x-ray FEL radiation for photon experiments since summer 2005. In 2014 and 2015 a second beamline, FLASH2, has been commissioned in parallel to user operation at FLASH1. FLASH's superconducting linac can produce bunch trains of up to 800 bunches within a 0.8 ms RF flat top at a repetition rate of 10 Hz. In standard operation during 2017 FLASH supplied up to 500 bunches in two bunch trains with independent fill patterns and compression schemes. Since mid 2017 initial commissioning of a third experimental beamline, accommodating the FLASHForward plasma wakefield acceleration experiment, has started. We report on the highlights of the FLASH operation in 2017/2018.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF090  
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TUPMK002 First Tests of the Apple II Undulator for the LOREA Insertion Device and Front End vacuum, simulation, optics, insertion-device 1488
 
  • J. Campmany, L.G.O. Garcia-Orta, J. Marcos, Z. Martí, V. Massana, M. Quispe
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
  
  ALBA synchrotron is currently installing the new beamline LOREA (Low-Energy Ultra-High-Resolution Angular Photoemission for Complex Materials at ALBA). It operates in the range of 10 - 1500 eV with polarized light. To produce the light for the beamline, an Apple II undulator with a period of 125 mm has been chosen. It can operate as an undulator at low energies and as a wiggler at high energies, providing a wide energy range. The device was built by KYMA, delivered on February 2017 and installed in August 2017. We present the magnetic measurements made during SAT as well as the simulations of the influence of the ID in the electron beam dynamics and the first measurements with beam. On the other hand, the high demanding characteristics of the beamline lead to a device providing high power and wide beam in some working modes. This situation has been a challenge for the Front End (FE) thermal load. It has been built by the companies RMP and TVP, and the FE modules have been installed in the tunnel along autumn 2017. We present the Site Acceptance Tests results as well as the technical solutions adopted, especially in terms of mechanical design and used materials.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK002  
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TUPMK003 Advances in the Sirius Delta-Type Undulator Project lattice, polarization, storage-ring, MMI 1491
 
  • L.N.P. Vilela, R. Basílio, J.F. Citadini, J.R. Furaer, F. Rodrigues
    LNLS, Campinas, Brazil
  
  The Delta undulator is a compact adjustable-phase insertion device that provides full light polarization control. Five undulators of this type will be installed in the initial operation phase of Sirius, the new 4th generation synchrotron light source that is being built by the Brazilian Synchrotron Light Laboratory (LNLS). In this work we present the recent advances in the development of Sirius Delta-type undulator, the studies of the effects of this device in the storage ring beam dynamics and assembly and measurements strategies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK003  
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TUPML021 A Beamline Design to Transport Laser Wakefield Electrons to a Transverse Gradient Undulator laser, electron, quadrupole, plasma 1577
 
  • K.A. Dewhurst, H.L. Owen
    UMAN, Manchester, United Kingdom
  • E. Brunetti, D.A. Jaroszynski, S.M. Wiggins
    USTRAT/SUPA, Glasgow, United Kingdom
  • B.D. Muratori
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • B.D. Muratori
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  Funding: This work was supported by the UK Science and Technology Facilities Council, Grant No. ST/G008248/1.
The Cockcroft Beamline is to be installed at the Scottish Centre for the Application of Plasma-based Accelerators (SCAPA). The beamline is designed to transport 1 GeV electrons from a laser wakefield acceleration (LWFA) source to a pair of transverse gradient undulators. The project aims to produce X-ray undulator radiation in the first phase and free-electron laser (FEL) radiation in the second phase. The total beamline will be less than 23 m long, thus the Cockcroft Beamline has the potential to be the UK's first compact X-ray FEL. Here we present the main features of the beamline design. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML021  
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TUPML035 FELs Driven by Laser Plasma Accelerators Operated with Transverse Gradient Undulators FEL, electron, radiation, laser 1615
 
  • F. Jafarinia, R.W. Aßmann, F. Burkart, U. Dorda, C. Lechner, B. Marchetti, R. Rossmanith, P.A. Walker
    DESY, Hamburg, Germany
  • A. Bernhard, R. Rossmanith
    KIT, Karlsruhe, Germany
  
  Laser Plasma Accelerators produce beams with a significantly higher energy spread (up to a few percent) compared to conventional electron sources. The high energy spread increases significantly the gain length when used for an FEL. In order to reduce the gain length of the FEL the Transverse Gradient Undulators (TGUs) instead of conventional undulators were proposed. In this paper the limits of this concept are discussed using a modified Version of the GENESIS program*.
*Zhirong Huang et al., Phys. Rev. Lett., 109, 204801 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML035  
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WEXGBD1 Development of Very Short Period Undulators electron, radiation, vacuum, factory 1735
 
  • S. Yamamoto
    KEK, Ibaraki, Japan
  
  Scientists and engineers at KEK have developed undulator magnets having very short period lengths. Magnet plates 100mm and 152mm long with 4-mm period length have been successfully fabricated. They produce an undulator field of approximately 4kG at a gap of 1.6mm. The magnetic field characterization shows that the undulator field is satisfactory in quality for a very short period undulator. KEK has recently installed a short-period undulator at a 50-MeV linac and observed a first light, and will soon start an experiment using a short-period undulator with laser-accelerated electrons for future table-top XFELs. This invited talk summarizes the current status, and experimental activities and results related to short-period undulators and table-top FELs.  
slides icon Slides WEXGBD1 [3.515 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEXGBD1  
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WEXGBD2 Pulse-by-Pulse Multi-XFEL Beamline Operation with Ultra-Short Laser Pulses electron, FEL, optics, operation 1740
 
  • T. Hara, T. Inagaki, H. Maesaka, Y. Otake, H. Tanaka, K. Togawa
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • K. Fukami
    JASRI/SPring-8, Hyogo-ken, Japan
  • T. Hasegawa, O. Morimoto, S. Nakazawa, M. Yoshioka
    SES, Hyogo-pref., Japan
  • H. Kawaguchi, Y. Kawaguchi
    Nichicon (Kusatsu) Corporation, Shiga, Japan
  • C. Kondo
    JASRI, Hyogo, Japan
  
  The parallel operation of multiple beamlines is an important issue to expand the opportunity of user experiments for linac based FELs. At SACLA, the parallel operation of three beamlines, BL1~3, has been open to user experiments since September 2017. BL1 is a soft x-ray beamline driven by a dedicated accelerator, which is a former SCSS linac, and BL2 and 3 are XFEL beamlines, which share the electron beam from the SACLA main linac. In the parallel operation, a kicker magnet with 10 ppm stability (peak-to-peak) switches the two XFEL beamlines at 60 Hz from pulse to pulse. To ensure wide spectral tunability and optimize the laser performance, the energies and lengths of the electron bunches are independently adjusted for the two beamlines according to user experiments. Since the electron bunch of SACLA has typically 10~15 fs (FWHM) in length and its peak current exceeds 10 kA, the CSR effect at a dogleg beam transport to BL2 is quite significant. In order to suppress the CSR effects, an isochronous and achromatic lattice based on two DBA structures was introduced. In this talk, the multiple XFEL beamline operation and achieved laser performance are presented.  
slides icon Slides WEXGBD2 [9.708 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEXGBD2  
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WEYGBD2 Status of the Radiation Damage on the European XFEL Undulator Systems radiation, FEL, operation, electron 1776
 
  • F. Wolff-Fabris, J. Pflüger
    XFEL. EU, Schenefeld, Germany
  • F. Hellberg
    Stockholm University, Stockholm, Sweden
  • F. Schmidt-Föhre
    DESY, Hamburg, Germany
  
  The European XFEL GmbH is a new X-ray FEL user facility and started lasing in 2017. Three gap movable SASE Undulator Systems are designed to produce FELs with tunable wavelengths from 0.05 to 5.2nm [*,**]. A total of 91 5-m long undulator segments based on hybrid NdFeB permanent magnet technology were tuned respecting tight specifications. Radiation damage due to machine operation affects the magnetic properties of the segments and the quality of the SASE process. An array of dosimeters based on Radfets [***] and Gafchromic films monitors the absorbed doses in every undulator segment and each SASE system is equipped with a 12mm gap diagnostic undulator (DU) which is magnetically re-measured during machine maintenance weeks. Doses up to 4 kGy have been observed and magnetic field degradation higher than 3% is measured. These results permit to estimate the effects of radiation damage and life expectancy of the Undulator Systems based on the precise K-parameter determination for beam operation. We will present the results of magnetic re-measurements on the Undulator Systems, the details of the effects of radiation damage and future plans to maximize the beam quality and operation.
* M. Altarelli et al., Tech. Design Rep. DESY 2006-097, July 2007.
** E. Schneidmiller et al., Eur. XFEL Tech. Rep. TR-2011-006, Sep. 2011.
*** F. Schmidt-Föhre et al., IPAC-2018 contribution. 		 
slides icon Slides WEYGBD2 [3.670 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEYGBD2  
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WEPAF047 Status and Commissioning of the Wire Scanner System for the European XFEL detector, FEL, MMI, emittance 1919
 
  • T. Lensch, S. Liu
    DESY, Hamburg, Germany
  
  The European-XFEL (E-XFEL) is an X-ray Free Electron Laser facility located in Hamburg (Germany). The superconducting accelerator for up to 17.5 GeV electrons will provide photons simultaneously to several user stations. Currently 12 Wire Scanner stations are used to image transverse beam profiles in the high energy sections. These scanners provide a slow scan mode which is currently used to measure beam emittance and beam halo distributions. When operating with long bunch trains (>100 bunches) also fast scans are planned to measure beam sizes in an almost nondestructive manner. This paper describes the current installations and the latest developments of the system at European-XFEL. Furthermore, the commissioning status of the system and first results of beam halo studies will be shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF047  
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WEPAF057 Electron Beam Diagnostics Concept for the ELI LUX Project electron, diagnostics, laser, plasma 1954
 
  • K.O. Kruchinin, D. Kocon, A.Y. Molodozhentsev, L. Pribyl
    ELI-BEAMS, Prague, Czech Republic
  • A. Lyapin
    JAI, Egham, Surrey, United Kingdom
  
  Nowadays the popularity of Laser Wakefield Accelerators (LWFA) is increasingly growing. Although the quality of the beams produced by LWFA is still lower than provided by conventional accelerators, they have great potential to be considered as a new basis for future FELs and even colliders. Laser Undulator X-ray (LUX) source is being commissioned at ELI-beamlines in Czech Republic. The goal of this machine is to provide photon beam in so called "water window" wavelength region for user experiments. Possible upgrade of the facility towards the LWFA based FEL is also considered. The electron beam diagnostics is absolutely crucial for achieving the aim of LUX. Specific properties of the beam produced by current LWFA, such as low charge, poor beam stability, big beam divergence and energy spread, require rethinking and adaptation of the conventional diagnostic tools and, in some cases, development of new ones. Ideally, they have to be compact, stable, non-invasive and allow measurements in single-shot mode. In this report we will present an overview and design considerations for the LUX electron beam main diagnostics. We will also discuss the hardware status and future plans.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF057  
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WEPAL058 Beam Loss Studies at the Taiwan Photon Source radiation, injection, vacuum, scattering 2309
 
  • C.H. Huang, J. Chen, Y.-S. Cheng, K.T. Hsu, K.H. Hu, D. Lee, C.Y. Wu
    NSRRC, Hsinchu, Taiwan
  
  PIN-photodiodes and RadFETs are installed in the storage ring of the Taiwan Photon Source (TPS) to study beam loss distributions and mechanisms. In the highest dose area, the radiation comes mainly from hard X-rays produced by synchrotron bending magnets. During beam cleaning and after replacing a vacuum chamber, losses due to inelastic Coulomb scattering occur mostly downstream from bending magnets while elastic scattering causes electrons to get lost mainly after an elliptically polarizing undulator which has a limited vertical aperture. During the injection period, the beam loss pattern can be changed by modifying injection conditions or lattice settings. The beam loss usually happens in the injection section and small-aperture section. The injection efficiency can be improved by minimizing the detected injection loss.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL058  
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WEPML025 Advantages and Challenges of Nb3Sn Superconducting Undulators site, experiment, operation, photon 2734
 
  • A.V. Zlobin, E.Z. Barzi, D. Turrioni
    Fermilab, Batavia, Illinois, USA
  • Y. Ivanyushenkov, I. Kesgin
    ANL, Argonne, Illinois, USA
  
  Funding: This work is supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
Superconducting undulators (SCUs) employ superconducting coils, and due to high critical current density in a superconductor, outperform undulators based on permanent magnets in terms of the level of magnetic field. So far, most of the SCUs, including devices built at Advanced Photon Source (APS), use Nb-Ti superconductor. Utilization of Nb3Sn conductor offers a possibility to increase the undulator field even further but requires to overcome certain challenges that are described in this paper. Based on experience of developing Nb3Sn accelerator magnets at Fermi National Accelerator Laboratory, possible solutions are discussed. The achievable field levels for Nb3Sn version of existing APS and the future APS-Upgrade superconducting undulators are also presented and discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML025  
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THXGBD2 Overview of Undulator Concepts for Attosecond Single-Cycle Light electron, FEL, laser, bunching 2878
 
  • A. Mak, V.A. Goryashko, P.M. Salen, G. K. Shamuilov
    Uppsala University, Uppsala, Sweden
  • D.J. Dunning, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • D.J. Dunning, B.W.J. MᶜNeil, N. Thompson
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • J. Hebling, Z. Tibai, Gy. Tóth
    University of Pecs, Pécs, Hungary
  • Y. Kida, T. Tanaka
    RIKEN SPring-8 Center, Hyogo, Japan
  • B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  
  Funding: Swedish Research Council (VR, 2016-04593); Stockholm-Uppsala Centre for Free-Electron Laser Research; C. F. Liljewalchs stipendiestiftelse.
The production of intense attosecond light pulses is an active area in accelerator research, motivated by the stringent demands of attosecond science: (i) short pulse duration for resolving the fast dynamics of electrons in atoms and molecules; (ii) high photon flux for probing and controlling such dynamics with high precision. While the free-electron laser (FEL) can deliver the highest brilliance amongst laboratory x-ray sources today, the pulse duration is typically 10-100 femtoseconds. A major obstacle to attaining attosecond duration is that the number of optical cycles increases with every undulator period. Hence, an FEL pulse typically contains tens or hundreds of cycles. In recent years, several novel concepts have been proposed to shift this paradigm, providing the basis for single-cycle pulses and paving the way towards high-brilliance attosecond light sources. This article gives an overview of these concepts. 		 
slides icon Slides THXGBD2 [1.758 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THXGBD2  
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THPAF020 Measurement of Transverse Impedance of Specific Components in CESR Using BPM Measurements of Pinged Bunches impedance, cavity, experiment, betatron 2990
 
  • M.P. Ehrlichman, J.P. Shanks, S. Wang
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  A beam-based technique is applied to determine the quadrupole impedance of large-impedance components of the CESR storage ring. Two bunches separated by ~1/3 of the ring circumference are charged to 0.85 and 0.3 mA. Each bunch is given a single kick, either horizontal or vertical. Turn-by-turn, bunch-by-bunch position information is recorded for ~16 k turns. BPM-by-BPM phase is calculated using the All-phase FFT method of spectral analysis. The difference in the BPM-to-BPM phase advance between the two bunches is a measurement of the local transverse impedance. The impedances of the small-aperture in-vacuum undulators, collimators, scrapers, RF cavities, electrostatic separators, and bulk impedance of the remaining ring are determined in this manner.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF020  
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THPAK001 Impedance Evaluation of In-Vacuum Undulator at KEK Photon Factory impedance, simulation, factory, vacuum 3200
 
  • O. Tanaka, M. Adachi, R. Kato, N. Nakamura, T. Obina, S. Sakanaka, R. Takai, K. Tsuchiya, N. Yamamoto
    KEK, Ibaraki, Japan
  
  The estimate of impedance and kick factors of the recently installed at KEK Photon Factory (PF) four In-Vacuum Undulators (IVU) is currently a very important issue, because they could be considerable contributors to the total impedance of PF. Moreover, the coupling impedance of the IVUs could lead to the beam energy loss, changes in the bunch shape, betatron tune shifts and, finally, to the various beam instabilities. Using the simulation tool (CST Particle Studio), longitudinal and transverse impedances of the IVUs were evaluated and compared to analytical formulas and measurement results. The study provides guidelines for mitigation of unwanted impedance, for the accurate estimate of its effects on the beam quality and beam instabilities and also for the impedance budget of a newly designed next-generation machine which has many IVUs and small-aperture beam pipes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK001  
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THPAK057 Simulations of Optical Stochastic Cooling with ELEGANT damping, pick-up, kicker, radiation 3354
 
  • M.B. Andorf, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • V.A. Lebedev, V.A. Lebedev, P. Piot
    Fermilab, Batavia, Illinois, USA
  
  Fermilab is pursuing a proof-of-principle test of the Optical Stochastic Cooling (OSC) of 100 MeV electrons in the Integrable Optics Test Accelerator. In support of this we present simulations of horizontal damping with OSC. We find excellent agreement with theory on the amplitude dependent damping rates. Additionally particle tracking is used to confirm the necessity and effectiveness of sextupoles used to correct non-linear path lengthening in the OSC chicane.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK057  
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THPAK152 Study of GF Symplectic Tracking Method and Compensation for the EPU104 at the HLS-II dynamic-aperture, electron, synchrotron, synchrotron-radiation 3603
 
  • Z.H. Yang, Z.H. Bai, W. Li, G. Liu, L. Wang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  An elliptically polarized undulator (EPU) was applied to obtain high-brightness coherent synchrotron radiation at the upgraded Hefei Light Source, HLS-II. However, the EPU has serious dynamic effects on the beam performances including close orbit, emittance and dynamic aperture etc. when installed at the storage ring. In order to understand the effects, a Taylor expanded generating method was adopted to generate a fast and symplectic map for particle tracking. As for the compensation of the EPU, striplines were equipped above and below the vacuum chamber to reduce the nonlinear effects. With the symplectic tracking routine and the surface fitting method, different parameters such as dynamic aperture and the driving terms, could be set as the objective function to accomplish the optimization of the EPU.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK152  
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THPAL052 Finite Element Analysis on Beam-Induced Heat Load in in-Vacuum Undulators with a Small Magnet Gap simulation, synchrotron, vacuum, synchrotron-radiation 3760
 
  • J.-C. Chang, Y.-H. Liu
    NSRRC, Hsinchu, Taiwan
  
  In-vacuum undulators with a small gap and short period have been applied in synchrotron accelerators for hard X-rays users for years. However, beam-induced heat load resulted from synchrotron radiation or the image current will not only degrade the performance of undulator but damage the magnet foil. It is difficult to quantitatively study heat transfer phenomenon of the magnet foil through physical experiment. In this study, finite element analysis was applied to study the effect of beam-induced heat load on an in-vacuum undulator.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL052  
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THPAL068 Status of the Polarix-TDS Project FEL, electron, status, klystron 3808
 
  • P. Craievich, M. Bopp, H.-H. Braun, R. Ganter, T. Kleeb, M. Pedrozzi, E. Prat, S. Reiche, R. Zennaro
    PSI, Villigen PSI, Switzerland
  • R.W. Aßmann, F. Christie, R.T.P. D'Arcy, U. Dorda, M. Foese, P. González Caminal, M. Hoffmann, M. Hüning, R. Jonas, O. Krebs, S. Lederer, V. Libov, B. Marchetti, D. Marx, J. Osterhoff, F. Poblotzki, M. Reukauff, H. Schlarb, S. Schreiber, G. Tews, M. Vogt, A. Wagner
    DESY, Hamburg, Germany
  • N. Catalán Lasheras, A. Grudiev, G. McMonagle, W. Wuensch
    CERN, Geneva, Switzerland
  
  A collaboration between DESY, PSI and CERN has been established to develop and build an advanced modular X-band transverse deflection structure (TDS) system with the new feature of providing variable polarization of the deflecting force. This innovative CERN design requires very high manufacturing precision to guarantee highest azimuthal symmetry of the structure to avoid the deterioration of the polarization of the streaking field. Therefore, the high-precision tuning-free production process developed at PSI for the C-band and X-band accelerating structures will be used for the manufacturing. We summarize in this paper the status of the production of the prototype and the waveguide networks foreseen in the different facilities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL068  
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THPAL104 The Magnetic Field Measurement Systems for a Cryogenic Undulator and a Superconducting Undulator at SSRF cryogenics, SRF, GUI, vacuum 3878
 
  • H.F. Wang
    SSRF, Shanghai, People's Republic of China
  • M.F. Qian, W. Zhang, Q.G. Zhou
    SINAP, Shanghai, People's Republic of China
  
  Two cryogenic permanent magnet undulators (CPMU) have been developed and assembled into storage ring at SSRF，in order to reach larger magnetic field and to produce higher brilliance in the hard X rays domain. Lowering the temperature of permanent magnets increases the magnetic produced field about by 15%. A set of magnetic measurement system and a suitable magnetic field optimization method have been developed. The design of a magnetic measurement bench based on a Hall probe to perform low temperature measurement has been finished. In addition, a 50-period superconducting undulator prototype with 16mm period length is also being developed for more photons with some specific photon characteristic. And a special hall probe system has been built in order to characterize the magnetic field distribution of the SCU prototype.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL104  
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THPAL106 Heating Unit Controller at NSRC SOLARIS TANGO, vacuum, controls, PLC 3885
 
  • W.T. Kitka, P. Bulira, P. Czernecki, M.K. Fa'owski, K. Kubal, P. Kurdziel, A.M. Marendziak, M.P. Nowak, M. Ostoja-Gajewski, M. Rozwadowski, K. Wawrzyniak, Z. Zbylut
    Solaris National Synchrotron Radiation Centre, Jagiellonian University, Kraków, Poland
  
  Solaris is a third generation light source constructed at the Jagiellonian University in Kraków, Poland. The machine was designed by the MAX IV Laboratory team. Commissioning of the machine was accomplished at 2016 April and now synchrotron operate in decay mode. Two beamlines PEEM/XAS and UARPES were installed and now are being commissioned. Three more PHELIX, XMCD and diagnostic beamline have received funding and it will be installed and commissioned in range of next few years. The SOLARIS Heating Unit Controller (HUC) was designed to perform bake-out process of new installed vacuum systems. It will allow to perform activation process of undulator vacuum chamber inner coated with NEG layer and also activation process of NEG strips installed in dipole vacuum chambers. HUC is able to control independently up to six 2 kW temperature channels and two current channels. System was built based on Allen-Bradley PLC and Tango Controls. Easy access to the device is provided by the GUI design based on Taurus framework.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL106  
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THPMF012 Tapered Flying Radiofrequency Undulator electron, FEL, simulation, ECR 4059
 
  • S.P. Antipov, S.V. Kuzikov, A. Liu
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S.V. Kuzikov, A.V. Savilov, A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
  
  Funding: DOE SBIR DE-SC0017145
The x-ray free electron laser (x-FEL) efficiency, measured as a fraction of the electron beam power converted into light, is typically below 0.1% for most of the x-FEL facilities presently in operation. Undulator tapering techniques can be used to improve the conversion efficiency by 1-2 orders of magnitude. However at present there are no robust tapered undulator x-FEL schemes operating at 10% efficiency. In this paper we report on the development of tapered radiofrequency (RF) undulator. An RF undulator is a microwave waveguide in which strong RF field is excited that interacts with a charged particle beam forcing it to radiate coherent x-rays while undergoing a wiggling motion. RF undulators are attractive for use in x-FELs due to their large beam aperture and a short undulator period. Strongly tapered RF undulators (with tapering of a wavelength) due to non-resonant trapping regime allow keeping high overall XFEL efficiency being driven by laser plasma accelerated beams usually having high enough current but large energy spread (1-10%). 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF012  
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THPMF016 Design of a Terahertz Radiation Source for Pump-Probe Experiments bunching, radiation, electron, FEL 4073
 
  • J. Pfingstner, E. Adli
    University of Oslo, Oslo, Norway
  • E. Marín
    CERN, Geneva, Switzerland
  • S. Reiche
    PSI, Villigen PSI, Switzerland
  
  Narrow-band, tuneable, high-power terahertz radiation is highly demanded for pump-probe experiments at light source facilities. Since the requested radiation properties are not well covered by current terahertz radiation sources, an accelerator-based terahertz source employing the slotted-foil technique in combination with transverse deflecting cavities is proposed in this work. A detailed design has been worked out, and the behaviour of the electron beam and the created terahertz radiation is studied via numerical simulations. The results show that the proposed source produces tuneable terahertz radiation that can meet most of the demanded specifications.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF016  
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THPMF022 Study of Possible Beam Losses After Post-Linac Collimation at European XFEL radiation, FEL, simulation, vacuum 4092
 
  • S. Liu, W. Decking
    DESY, Hamburg, Germany
  • F. Wolff-Fabris
    XFEL. EU, Schenefeld, Germany
  
  The European XFEL has been operating with the undulator beam line SASE1 and SASE3 since April 2017 and February 2018, respectively. Despite of the fact that the post-linac collimation has collimated the beam halo to ~20 σ level*, relative high radiation doses have been measured especially in the diagnostic undulator (DU) section**. In order to find the sources of beam losses after post-linac collimation, BDSIM simulations have been performed. In this paper, we will first present the possible losses generated by the wire scanners upstream of the undulators during a scan. The simulation results will be compared with the measured doses along SASE1 and SASE3 undulators. Based on the simulation results, we will estimate the frequency for wire scanner opera-tions. Besides, the simulations with large extension of beam halo hitting the vacuum chamber aperture transition will also be presented. Finally, other possible radiation dose sources will be discussed.
* S. Liu et al., in Proc. of FEL 2017, Santa-Fe, USA, Aug. 2017, paper TUP003.
** F. Wolff-Fabris et al.,IPAC-2018 contribution. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF022  
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THPMF031 In-Vacuum APPLE II Undulator vacuum, cryogenics, operation, FEL 4114
 
  • J. Bahrdt, W. Frentrup, S. Grimmer, C. Kuhn, C. Rethfeldt, M. Scheer, B. Schulz
    HZB, Berlin, Germany
  
  APPLE II undulators are widely used in many synchrotron radiation facilities for the generation of arbitrarily polarized light, because they provide the highest magnet fields among all planar variably polarizing permanent magnet undulators (PMUs). So far, in-vacuum permanent magnet undulators (IVUs) have a fixed polarization, either planar or elliptical / helical. A variably polarizing in-vacuum undulator was never built due to the engineering challenges. We present the design of a new in-vacuum APPLE II, which will extend the photon energy range to tender X-rays in the 1.7 GeV storage ring BESSY II.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF031  
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THPMF040 Experiences with the SRF Gun II for User Operation at the ELBE Radiation Source gun, radiation, SRF, electron 4145
 
  • J. Teichert, A. Arnold, M. Bawatna, P.E. Evtushenko, M. Gensch, B.W. Green, S. Kovalev, U. Lehnert, P.N. Lu, P. Michel, P. Murcek, H. Vennekate, R. Xiang
    HZDR, Dresden, Germany
  
  Funding: The work is supported by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1.
The second version of the superconducting RF pho-toinjector (SRF Gun II) was successfully commissioned at the ELBE radiation source in 2014. The gun features an improved 3.5-cell niobium cavity combined with a super-conducting solenoid integrated in the cryostat. With a Mg photocathode the SRF Gun II is able to generate bunches with up to 200 pC and with sub-ps length in CW mode with 100 kHz pulse frequency for the THz radiation fa-cility at ELBE. In the ELBE linac, the beam is accelerat-ed, gets a proper correlated energy spread, and is com-pressed in a magnetic chicane. Sub-ps pulses are obtained producing coherent diffraction radiation and superradiant undulator radiation. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF040  
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THPMF050 High-Efficient XFELO Based on Optical Resonator with Self-Modulated Q-Factor FEL, laser, coupling, electron 4172
 
  • S.V. Kuzikov, A.V. Savilov, A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
  • S.P. Antipov, S.V. Kuzikov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  
  In this paper we describe an efficient XFELO having a new non-stationary out-coupling scheme. It consists of two undulator sections placed inside optical cavity. The first section is a conventional uniform undulator and the second one is a tapered undulator. At start time point X-ray radiation is mostly produced by the uniform section. Mirrors of XFELO's optical resonator are designed so that diffraction Q-factor reaches the highest value, i.e losses are near zero. As X-ray power increases the tapered undulator begins to contribute more to radiation power. However a portion of that power misses mirrors of the optical cavity, because those are tuned to confine radiation produced by the first undulator. This process establishes a steady state operation of the XFELO.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF050  
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THPMF051 Research of a Locally-round Beam in HEPS Storage Ring Using Solenoids solenoid, storage-ring, dynamic-aperture, emittance 4175
 
  • C.C. Du, J.Q. Wang
    IHEP, Beijing, People's Republic of China
  
  "Round beam", that is, a beam with equivalent transverse emittance, is expected for a significant fraction of the beamline users in light sources. We investigate the possibility of reaching round beam in a storage ring, by means of a local exchange of the apparent horizontal and vertical emittance, performed with solenoids in a dedicated insertion line in the storage ring. In this paper, we show that a locally-round beam can be achieved by using solenoid in High Energy Photon Source (HEPS) storage ring, particularly to one of the design having natural emittance of 34.2 pm·rad.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF051  
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THPMF066 Performance of a Full Scale Superconducting Undulator with 20 mm Period Length at the KIT Synchrotron synchrotron, storage-ring, operation, electron 4223
 
  • S. Casalbuoni, S. Bauer, E. Blomley, N. Glamann, A.W. Grau, T. Holubek, E. Huttel, D. Saez de Jauregui
    KIT, Eggenstein-Leopoldshafen, Germany
  • C. Boffo, T.A. Gerhard, M. Turenne, W. Walter
    Bilfinger Noell GmbH, Wuerzburg, Germany
  
  Within the collaborative effort between KIT and Bilfinger Noell GmbH the development of a full scale superconducting undulator with 20 mm period length (SCU20) has been completed. This device addresses the reliability and reproducibility aspects of the manufacturing process, allowing for the status of a commercial product. The conduction cooled 1.5 m long coils were characterized in the KIT horizontal test facility CASPER II and later assembled in the final cryostat. The system was extensively tested in the final configuration before installation in the KIT storage ring KARA (Karlsruhe Research Accelerator) to be the source of the NANO beamline in December 2017. Here we present the performance of the device.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF066  
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THPMF067 Design and Tests of Switchable Period Length Superconducting Undulator Coils photon, insertion-device, insertion, synchrotron 4226
 
  • T. Holubek, S. Casalbuoni, S. Gerstl, N. Glamann, A.W. Grau, C.A.J. Meuter, D. Saez de Jauregui
    KIT, Eggenstein-Leopoldshafen, Germany
  
  Several photon beamlines in different synchrotron make use of undulators with switchable period length, which offer a larger tunability of the emitted photons energy. Superconducting technology allows switching the period length by changing the sign of the current in separately powered subset of windings. We present here the design and tests performed in liquid helium of switchable period length superconducting undulator coils performing period doubling from 17 mm to 34 mm.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF067  
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THPMF074 Study of the Saturation of Radiation Energy Caused by the Space Charge Effect in a Compact THz Coherent Radiation Source electron, radiation, simulation, laser 4245
 
  • S. Krainara, Chatani, S. Chatani, T. Kii, H. Ohgaki, H. Zen
    Kyoto University, Kyoto, Japan
  
  Funding: Institute of Advanced Energy, Kyoto University
To generate an intense quasi-monochromatic Terahertz Coherent Undulator Radiation (THz-CUR), a compact linac system, which employs a magnetic electron bunch compressor with a beam energy of 4.6 MeV, has been constructed at Kyoto University. The THz-CUR has suc-cessfully been generated in a frequency range from 0.16 to 0.65 THz with a bunch charge of 60 pC. The maximum micro-pulse energy of THz radiation was observed higher than 1 μJ at 0.16 THz with 160 pC. However, when a bunch charge was higher than 80 pC, the micro-pulse energy of THz radiation gradually went to the saturation and obviously at the bunch charge higher than 110 pC because of the bunch lengthening and degradation of electron beam quality due to the space charge effect. The dependence of a bunch length on a bunch charge has been studied by GPT simulation and compared with CTR and CUR experiments. The trends of the measured results from CUR and CTR are in good agreement with the GPT simulation. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF074  
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THPMK012 Reduction of Dynamic Multipole Content in Insertion Devices Using Flat Wires multipole, electron, MMI, simulation 4313
 
  • T.Y. Chung, S.D. Chen, M.-S. Chiu, S.J. Huang, C.-S. Hwang, J.C. Jan, C.Y. Kuo, Y.T. Li, C.Y. Wu
    NSRRC, Hsinchu, Taiwan
  • C.-S. Hwang
    NCTU, Hsinchu, Taiwan
  
  Multipole errors of an insertion device are generally corrected based on measurements and analysis of the magnetic field integrals. Multipole components in a strong and narrow non-uniform field of an insertion device appear as dynamic multipoles. Flat wires were installed and commissioned to determine if the dynamic multipoles can be eliminated in an APPLE-II type undulator. In this work, we will discuss and compare the reduction of the dynamic multipole content and it's beam dynamics effects with the flat wire through an analysis of field calculations and beam-based measurements in the storage ring.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK012  
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THPMK013 A Wiggler Magnet Design for the TPS emittance, wiggler, photon, electron 4317
 
  • J.C. Jan, Y.L. Chu, C.-S. Hwang, F.H. Tseng
    NSRRC, Hsinchu, Taiwan
  
  The Taiwan Photon Source (TPS) at the National Synchrotron Radiation Research Center (NSRRC) is an advanced photon source facility operating at an electron energy of 3 GeV. Ten insertion devices (IDs) have been installed in phase-I during 2015. Recently, plans and designs for several phase-II IDs including In-vacuum Undulators (IU), Cryogenic Undulators (CU), Elliptical Polarization Undulators (EPU) and Wiggler magnets are pursued at NSRRC. These IDs are expected to be installed before 2020. In particular, a room temperature wiggler magnet with 100 mm period length (W100), will be designed and installed for phase-II. The field strength of the W100 is 1.8 T and the number of main periods is four. It is designed to generate 5-50 keV photons for the microscopy beam line. The magnetic design and photon characteristics of the W100 together with its effects on the stored beam will be discussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK013  
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THPMK014 Quantitative Analysis of Multipole Errors Induced by Mechanical Deformations of an Undulator multipole, operation, dipole, sextupole 4321
 
  • T.Y. Chung, C.H. Chang, C.-S. Hwang
    NSRRC, Hsinchu, Taiwan
  • H.W. Luo
    NTHU, Hsinchu, Taiwan
  
  To minimize unwanted beam dynamics effects in a storage ring, multipole errors in an undulator are normally reduced by sorting and shimming methods. Nonetheless, an investigation of the error source is worth pursuing and interesting. Our work focuses on multipole errors introduced by mechanical deformations of an APPLE-II type undulator, which undergoes complicated forces during operation. Our results give guidelines for mechanical specifications derived from quantitative analyses.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK014  
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THPMK016 Simulation Study of the NSRRC High Brightness Linac System and Free Electron Laser linac, FEL, simulation, electron 4329
 
  • W.K. Lau, C.H. Chen, H.P. Hsueh, N.Y. Huang
    NSRRC, Hsinchu, Taiwan
  • J. Wu
    SLAC, Menlo Park, California, USA
  
  A 263 MeV linac system has been designed to provide a high brightness electron beam for the NSRRC VUV FEL test facility. This system is equipped with a dogleg with linearization optics to compensate the effects of nonlinear energy chirps introduced into the system by the chirper linac voltage during bunch compression. In this study, we performed start-to-end simulation to illustrate the capability of this linac system to generate a beam that can be used to drive a SASE FEL to saturation within reasonable undulator length. It has been demonstrated that, for a 200 pC beam, such FEL has a saturated output power of ~200 MW at 6-m undulator length. Further optimization of bunch current profile and momentum spectrum is required.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK016  
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THPMK017 Experimental Study of Coherent THz Sources Driven by the NSRRC High Brightness Photo-injector radiation, electron, linac, bunching 4332
 
  • M.C. Chou, K.T. Hsu, N.Y. Huang, J.-Y. Hwang, W.K. Lau, A.P. Lee, C.C. Liang, G.-H. Luo
    NSRRC, Hsinchu, Taiwan
  
  Accelerator-based coherent THz radiation sources are being studied with the NSRRC high brightness photoinjector which has been installed in the Accelerator Test Area (ATA) recently. This injector is equipped with a laser-driven photocathode rf gun and a 5.2-m long S-band traveling-wave linac for beam acceleration. A few tens MeV, ultrashort bunches of ~100 fs bunch length can be produced from the injector by velocity bunching technique. Tunable narrow-band THz coherent undulator radiation (CUR) can be generated from a U100 planar undulator when it is driven by such beam. One the other hand, broadband THz coherent transition radiation (CTR) generated by passing this beam through a metallic foil is used for determination of bunch length by autocorrelation technique. The experimental setup and results are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK017  
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THPMK020 Beam-Based Alignment Procedures for Small Gap in-Vacuum Undulators at the Taiwan Photon Source photon, alignment, MMI, electron 4342
 
  • Y.-C. Liu, J.C. Huang, F.H. Tseng
    NSRRC, Hsinchu, Taiwan
  
  We have developed a beam-based alignment procedure for small gap IVUs (In-vacuum undulators) at TPS, which allow us to measure the field center and mechanical canter of IVUs with 0.1 mm accuracy. The measurement method and results are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK020  
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THPMK022 Simulation for THz Coherent Undulator Radiation from Combination of Velocity Bunchings radiation, bunching, electron, simulation 4345
 
  • Y. Sumitomo, K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, Y. Takahashi, T. Tanaka
    LEBRA, Funabashi, Japan
  
  We study the effect of a combination of velocity bunchings and its application to THz coherent undulator radiation at LEBRA, Nihon U. by simulations. The velocity bunching is a technique that is commonly used to make the bunch length shorter at lower energies. However, since one velocity bunching has a correlation between bunch energy and length, we may not have so much room to change energies to obtain different coherent radiation wavelengths. Hence we propose a combination of velocity bunchings, that relaxes the restrictive correlation. We have three 4m traveling-wave accelerator tubes at LEBRA, Nihon U. The undulator is installed after the acceleration tubes and 2 x 45 degree bending magnets. Since the design of current undulator requires less than 25 MeV beam energy to obtain the radiation at THz region, the velocity bunching is reasonable for coherent radiation. We show the simulation results of a combination of velocity bunchings of the three tubes and the magnetic bunching at bending magnets, suitable for the coherent undulator radiation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK022  
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THPMK028 Inverse Free Electron Laser Separatrix Crossing for Energy Gain and Stability FEL, laser, electron, free-electron-laser 4354
 
  • N.S. Sudar, P. Musumeci
    UCLA, Los Angeles, USA
  • D. Garzella
    CEA, Gif-sur-Yvette, France
  
  The laser wakefield accelerator (LWFA) has been proposed as a driver for next generation compact light sources. However, the beams produced by LWFA's typically exhibit correlated energy spread and energy jitter too large to drive the Free Electron Laser instability. We present here a novel scheme whereby using a highly non-linear strongly tapered undulator interaction directly after the LWFA we are able to trap and accelerate a large fraction of charge in the moving Inverse Free Electron Laser ponderomotive bucket. The final correlated energy spread and output energy are determined by the final bucket height and central energy of the ponderomotive bucket which are both determined by the stagnant undulator parameters, resulting in a significant decrease in the normalized energy spread (< 1%) and output energy jitter (< 1%). This interaction is treated both analytically and numerically.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK028  
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THPMK031 Elliptically Polarizing Undulator Design for PAL-XFEL FEL, controls, operation, electron 4362
 
  • S.J. Lee, J.H. Han, D.E. Kim
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  Funding: This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (2017R1C1B1012852).
Elliptically polarizing undulator (EPU) is under consideration as after-burner for the PAL-XFEL soft X-ray beamline to control the FEL polarization. In the soft X-ray line, seven planar undulators with a 35 mm period and 5 m length are in operation. To provide a polarization control of the FEL in the 1 to 3 nm wavelength, we compare the two types of EPUs, APPLE-II, and APPLE-X. The K value ranges for various operation modes are numerically studied for two undulator periods, 35 and 40 mm, of these EPU types. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK031  
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THPMK032 RADFET Installation at PAL-XFEL Undulator radiation, FEL, controls, operation 4366
 
  • J.H. Han, Y.G. Jung, D.E. Kim, S.J. Lee, G. Mun
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  Two undulator beamlines, one hard X-ray and one soft X-ray, are in operation at PAL-XFEL. Radiation produced during the FEL operation may impair the magnetic property of the undulator magnets and affect the FEL performance. Accumulated radiation at the undulator sections is being measured by using optically stimulated luminescent dosimeters (OSLDs) once per few months. Over 10 Gy gamma ray was detected at some locations at both undulator beamlines. However, in the measurement using the OSLDs we do not have information on which accelerator operation modes produce such high level of radiation on the undulators. To measure accumulated radiation in real time, we installed radiation-sensing field-effect transistors (RADFETs). We report the characteristics of the RADFET sensors and the installation at the PAL-XFEL undulator beamlines.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK032  
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THPMK034 Study on Effect of Phase Shifter on FEL Intensity at PAL-XFEL FEL, electron, radiation, simulation 4372
 
  • C.H. Shim
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • J.H. Hong, H. Yang
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  In the PAL-XFEL, the phase shifters are installed be-tween the undulator modules to match the phase of the electron beam and the FEL radiation field at the entrance of next undulator. By varying the phase shifter gap, the FEL intensity measured at the QBPM oscillates and sine curve fitting can be applied to it for optimizing the FEL intensity. However, the optimal gap determined from fitting result is slightly different from the gap at which the maximum intensity is measured because distorted shapes are appeared from some phase shifters. In this presentation, we report and discuss the experimental results of phase shifter gap scanning with simulation results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK034  
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THPMK035 Generation of Isolated Zeptosecond Pulse in Gamma-Ray Free Electron Laser radiation, electron, ISOL, laser 4375
 
  • C.H. Shim, D.E. Kim
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • Y.W. Parc
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  An X-ray pulse with zeptosecond pulse duration is an essential tool to resolve the nuclear dynamics. To make such a short pulse duration, we need to make a very wide frequency range radiation which is known from the uncertainty principle. The spectral range of an isolated zeptosecond pulse has to be of order of few keV which is called as a gamma ray. In this presentation, the generation of an isolated zeptosecond pulses in the gamma-ray free electron laser is studied by the simulation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK035  
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THPMK042 Two and Multiple Bunches at LCLS laser, diagnostics, photon, FEL 4378
 
  • F.-J. Decker, K.L.F. Bane, R.N. Coffee, W.S. Colocho, S. Gilevich, S.H. Glenzer, A.A. Lutman, A. Miahnahri, D.F. Ratner, J.C. Sheppard, S. Vetter
    SLAC, Menlo Park, California, USA
  
  The LCLS X-Ray FEL at SLAC typically delivers one bunch at the time. Different schemes of two pulses have been developed: Two bucket, Twin bunch, split undulator, and fresh slice. Here we discuss a four bunch or even eight bunch setup, where the separation between the individual bunches is two RF buckets: 0.7 ns.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK042  
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THPMK046 Advanced Fresh-Slice Beam Manipulations for FEL X-Ray Applications electron, laser, controls, free-electron-laser 4387
 
  • A.A. Lutman, Y. Ding, M.W. Guetg, Z. Huang, J. Krzywinski, J.P. MacArthur, A. Marinelli, T.J. Maxwell
    SLAC, Menlo Park, California, USA
  • C. Emma
    UCLA, Los Angeles, USA
  
  The recent development of the Fresh-slice technique granted control on which temporal slice lases in each undulator section in an X-ray Free-electron laser. Fresh-slice has been used for several experiments at the Linac Coherent Light Source for the generation of customizable high power two-color beams, and increased the performance of self-seeding schemes. As a novel development of the technique we present the demonstration of multistage self-amplified spontaneous-emission amplification schemes for the production of high-power ultra short pulses and improved control of the temporal duration of each pulse in multi-pulse schemes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK046  
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THPMK051 Theoretical Formulation of Improved SASE FEL Based on Slippage Enhancement Scheme electron, FEL, radiation, laser 4398
 
  • C.-Y. Tsai, J. Wu, C. Yang, G. Zhou
    SLAC, Menlo Park, California, USA
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • G. Zhou
    IHEP, Beijing, People's Republic of China
  
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE- AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
A method to improve the spectral brightness of self-amplified spontaneous emission (SASE) based on slippage enhancement has been proposed*, **. The implementation is to insert a series of magnetic chicanes to introduce a path-length delay of the electron beam to the radiation beam. By correlating the electron slices of neighboring cooperation distances this can lengthen the collective interaction and thus enhance the spectral brightness. In the existing literature most studies rely on numerical simulations and there is limited work on analytical analysis. In this paper we formulate the problem of slippage enhanced SASE (SeSASE) high-gain FEL with inclusion of by-pass magnetic chicanes. The analysis takes the finite energy spread of the electron beam and the nonzero momentum compaction of the chicane into consideration. The evolution of spectral bandwidth of SeSASE is compared with that of usual SASE in theory and numerical simulations. The effects of finite beam energy spread and non-isochronisity are also quantified.
*J. Wu et al., FEL2012
**B. W. J. McNeil et al., PRL 110, 134802 (2013) 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK051  
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THPMK052 Numerical Simulation of Phase-Shift Method for Fel Power Enhancement in PAL-XFEL electron, FEL, radiation, synchrotron 4402
 
  • C.-Y. Tsai, J. Wu, C. Yang, G. Zhou
    SLAC, Menlo Park, California, USA
  • H.-S. Kang
    PAL, Pohang, Kyungbuk, Republic of Korea
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • G. Zhou
    IHEP, Beijing, People's Republic of China
  
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE- AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Recently the phase jump method for efficiency enhancement in free-electron laser (FEL) was proposed*. One of the unique features of PAL-XFEL with phase shifters may be taken for the experimental demonstration of this phase jump scheme. In this paper we numerically investigate the scheme using the three-dimensional numerical simulation code GENESIS**. The physical parameters are based on hard x-ray line of PAL-XFEL***. The preliminary simulation results indicate that this potential phase jump scheme can enhance at least one order of magnitude of FEL power performance. Combination of this scheme with undulator tapering is also discussed in this paper.
*A. Mak, F. Curbis, and S. Werin, PRAB 20, 060703 (2017)
**S. Rieche, NIMA 429(1):243-248 (1999)
***I. S. Ko et al., Appl. Sci. 2017, 7, 479 (2017) 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK052  
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THPMK053 Simulation for LCLS-II Hard X-ray Self Seeding Scheme FEL, photon, simulation, electron 4406
 
  • C. Yang, Y. Feng, J. Krzywinski, T.O. Raubenheimer, C.-Y. Tsai, J. Wu, M. Yoon, G. Zhou
    SLAC, Menlo Park, California, USA
  • H.X. Deng
    SINAP, Shanghai, People's Republic of China
  • D.H. He
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • Y. Hong, B. Yang
    University of Texas at Arlington, Arlington, USA
  • X.F. Wang
    CIAE, Beijing, People's Republic of China
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • G. Zhou
    IHEP, Beijing, People's Republic of China
  
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Typical SASE FELs have poor temporal coherence because of starting from shot noise. Self-seeding scheme is an approach to improve the longitudinal coherence. The single crystal monochromator self-seeding has been in successful operation in LCLS. For the high repetition rate LCLS-II machine, for damage consideration, it was initially proposed to have a two-stage self-seeding scheme, yet we have found the two-stage self-seeding scheme has no advantage over one-stage self-seeding scheme. In this paper, we investigate the optimal self-seeding configuration of LCLS-II for different photon energies, and present a comparison between one-stage and two-stage self-seeding scheme of LCLS-II. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK053  
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THPMK054 Analysis of 1D FEL Sideband Instability with Inclusion of Energy Detune and Space Charge FEL, space-charge, electron, laser 4410
 
  • C.-Y. Tsai, J. Wu, C. Yang, G. Zhou
    SLAC, Menlo Park, California, USA
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE- AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
It has been known that free-electron laser (FEL) is capable of generating a coherent high-power radiation over a broad spectrum. Recently there is a great interest in pursuing higher peak power (for example, at terawatt level) in FEL that can enable coherent diffraction imaging and probe fundamental high-field physics. The FEL radiation power can be increased by virtue of undulator tapering. However the FEL sideband signal begins to exponentially grow in the post-saturation regime. In this paper we extend our sideband analysis* by including both the energy detune due to discrete undulator tapering and longitudinal space charge in an effective 1-D model. A dispersion relation with explicit energy detune and space charge is derived. The study is carried out semi-analytically and compared with simulations. The impact of energy detune and space charge is analyzed.
* C.-Y. Tsai et al., Analysis of the sideband instability based on a one-dimensional high-gain free electron laser model, PRAB (accepted) 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK054  
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THPMK055 Self Seeding Scheme for LCLS-II-HE emittance, electron, FEL, simulation 4414
 
  • C. Yang, Y. Feng, J. Krzywinski, T.O. Raubenheimer, C.-Y. Tsai, J. Wu, M. Yoon, G. Zhou
    SLAC, Menlo Park, California, USA
  • H.X. Deng, X.F. Wang
    SINAP, Shanghai, People's Republic of China
  • D.H. He
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • Y. Hong, B. Yang
    University of Texas at Arlington, Arlington, USA
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • G. Zhou
    IHEP, Beijing, People's Republic of China
  
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Self-seeding is a reliable approach to generate fully coherent FEL pulses. Hard X-ray self-seeding can be realized by using a single crystal in Bragg transmission geometry. However, for a high repetition rate machine, the heat load on the crystal may become an issue. In this paper, we will study the facility performance of LCLS-II-HE by numerical simulations, and discuss the heat load and optimal undulator baseline configuration of LCLS-II-HE self-seeding scheme, and study the emittance tolerance of the LCLS-II-HE. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK055  
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THPMK056 Effect of Transverse Radiation Defocusing in Post-Saturation Regime of High-Gain X-Ray Free-Electron Laser electron, radiation, FEL, laser 4418
 
  • C.-Y. Tsai, J. Wu, C. Yang, G. Zhou
    SLAC, Menlo Park, California, USA
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • G. Zhou
    IHEP, Beijing, People's Republic of China
  
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE- AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
When untapered high-gain free electron laser (FEL) reaches saturation, the exponential growth ceases and the radiation power starts to oscillate about an equilibrium. For a high-gain tapered FEL, although the power is enhanced after the first saturation, it is known that there is a so-called second saturation point where the FEL power growth stops. In addition to the sideband instability, lack of transverse radiation focusing in the post-saturation regime can be another major reason leading to occurrence of the second saturation. In this paper we study the transverse diffraction effect and its impact on tapered FEL in the post-saturation regime. The study is carried out analytically together with three-dimensional numerical simulation. The numerical parameters are taken from LCLS-like electron beam and undulator system. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK056  
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THPMK060 Start-to-End Simulations of the CLARA FEL Test Facility FEL, simulation, electron, laser 4430
 
  • D.J. Dunning, D. Angal-Kalinin, A.D. Brynes, L.T. Campbell, H.M. Castaneda Cortes, J.K. Jones, J.W. McKenzie, N. Thompson, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • D. Angal-Kalinin, A.D. Brynes, D.J. Dunning, J.K. Jones, J.W. McKenzie, B.W.J. MᶜNeil, N. Thompson, P.H. Williams
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • L.T. Campbell, B.W.J. MᶜNeil, P.T. Traczykowski
    USTRAT/SUPA, Glasgow, United Kingdom
  • B.S. Kyle
    University of Manchester, Manchester, United Kingdom
  • B.S. Kyle
    UMAN, Manchester, United Kingdom
  • J.D.A. Smith
    TXUK, Warrington, United Kingdom
  
  CLARA is a new FEL test facility being developed at STFC Daresbury Laboratory in the UK, aiming to deliver advanced FEL capabilities including few-cycle pulse generation and Fourier transform limited output. Commissioning is underway on the front-end (photo-injector and first linac) while the later stages are being procured and assembled. Start-to-end (S2E) simulations of the full facility are presented, including optimisation of the accelerator setup to deliver the required properties of one of the electron beam modes specified for FEL operation. FEL simulations are performed using the Genesis 1.3 and Puffin codes and the results are compared.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK060  
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THPMK066 Cryogenic Permanent Magnet Undulator of SSRF permanent-magnet, SRF, cryogenics, vacuum 4449
 
  • Y.Z. He, M.F. Qian, H.F. Wang, W. Zhang, Q.G. Zhou
    SINAP, Shanghai, People's Republic of China
  
  Funding: Work supported by the State Key Lab of Advanced Metals and Materials (2016-Z03) and the Youth Innovation Promotion Association of CAS (Grant No: 2017305)
The two Cryogenic Permanent Magnet Undulators (CPMU18 with PrFeB magnets P46H and CPMU20 with NdFeB magnets N48H) were designed and developed in SSRF in the past few years (2014-2017).This paper introduces magnetic performance of the permanent magnets, design parameters of the two CPMUs, cryogenic cooling and magnetic field of the two CPMUs and so on. When gap of the two CPMUs is about 6.0 mm, the measurement results showed that the effective magnetic field peak of CPMU18 at 300 K and 77 K was 0.82 T, 0.92T, respectively, and the magnetic field phase error is about 3 degrees and 5 degrees respectively. The effective magnetic field peak of CPMU20 at 300 K and 140 K was 0.94T and 1.03T, respectively, and the magnetic field phase error was 3 degrees and 3.5 degrees respectively. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK066  
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THPMK068 High degree circular polarization at x-ray self-seeding FELs with crossed-planar undulators polarization, FEL, laser, electron 4453
 
  • K. Li, H.X. Deng, Z.F. Gao, B. Liu, D. Wang
    SINAP, Shanghai, People's Republic of China
  
  Funding: Work was supported by the National Natural Science Foundation of China (11775293), the National Key Research and Development Program of China (2016YFA0401900).
The crossed undulator configuration for a high-gain free-electron laser (FEL) is well-known for the ability of versatile polarization control. However, the degree of polarization is very sensitive to power and phase between the two stages of crossed undulators. In this poster, we introduce the generation of high degree circular polarization hard x-ray FEL with crossed-planar undulator seeded by self-seeding. The reverse taper and taper undulator technology are employed for improving its performance. With the combination of high degree (>95%) circular polarization and flexibility of polarization switching, this scheme might be useful for some scientific research in the future. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK068  
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THPMK069 Design of the Beam Switchyard of a Soft X-ray FEL User Facility in Shanghai FEL, linac, dipole, kicker 4456
 
  • S. Chen, H.X. Deng, C. Feng, B. Liu, D. Wang, R. Wang
    SINAP, Shanghai, People's Republic of China
  
  A soft X-ray FEL user facility, which is based on the existing test facility located in the Zhangjiang Campus of SINAP, is under construction. Two undulator lines will be installed parallelly in the undulator hall and their electron beams are served by a 1.5 GeV linac. For simultaneous operation of the two undulator lines, a beam distribution system should be used to connect the linac and the undulator lines. In this paper, the physics design of this beam distribution system will be presented and also the beam dynamic issues will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK069  
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THPMK070 Optimization for the Two-Stage Hard X-Ray Self-Seeding Scheme the SCLF FEL, radiation, electron, simulation 4460
 
  • T. Liu, C. Feng, D. Wang, X. Wang, K.Q. Zhang
    SINAP, Shanghai, People's Republic of China
  
  Funding: Work supported by the National Natural Science Foundation of China 11475250 and 11605277, National Key Research and Development 2016YFA0401901 and Youth Innovation Promotion Association CAS 2015209.
Self-seeding mode has been demonstrated a great advantage for the achievement of a high brightness X-ray with a pure spectrum. Single-bunch self-seeding scheme with wake monochromators is adopted for the realization of the hard X-ray FEL at the Shanghai Coherent Light Facility (SCLF). Limited by the heat-loading of the monochromator, the two or multiple stages self-seeding scheme is required. In this contribution, we present a basic two-stage scheme design and optimization for the generation of the photon energy range of 3 keV to 15 keV at the line FEL-I of the SCLF. Simulation results show the peak power and pulse energy each stage, which illustrates the loaded energy required of the crystal monochromator as a pointcut of its following thermal analysis. The electron beam energy used in the study is 8 GeV and the central photon energy is 12.4 keV. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK070  
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THPMK073 Multi FEL Lines with Compact Undulator Layout FEL, electron, photon, laser 4470
 
  • D. Wang
    SINAP, Shanghai, People's Republic of China
  
  Today the high repetition rate X-ray Free Electron Lasers based on superconducting radiofrequency technologies have come to their age. Such kind of facilities are able to serve many FEL photon beamlines simultaneously with each of which have large flexibilities in selecting wavelength, intensity, polarization, coherence and other properties through independent tuning of the undulator magnets. In reality the space needed to accommodate many undulator lines could be a limiting factor of user capacity, especially for the high rep rate XFELs that tend to utilize the underground tunnel to host long superconducting accelerator machines. In this paper we present a concept of compact undulator layout for more FEL lines in the precious tunnel spaces or similar environment. Shanghai Coherent Light Facility(SCLF) is a high repe-tition rate X-ray Free Electron Lasers installed in under-ground tunnels with an overall length of more than 3 km. The concept described in this paper could be applied to the SCLF or similar FEL facilities. The design and R&D progress will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK073  
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THPMK082 Micro Bunch Rotation and Coherent Undulator Radiation From a Kicked Beam quadrupole, electron, focusing, radiation 4489
 
  • J.P. MacArthur
    Stanford University, Stanford, California, USA
  • Z. Huang, J. Krzywinski, A.A. Lutman
    SLAC, Menlo Park, California, USA
  
  Recent observations of x-rays from a microbunched beam that has been kicked off-axis have shown coherent radiation at surprisingly large angles, in some cases reaching 30-50 uRad. Previous work on the topic has suggested that radiation at such large angles is inconsistent with classical radiation theory because microbunches cannot tilt. Here we show that, when kicked in a quadrupole lattice, microbunches can automatically tilt toward a new direction of propagation. This allows for coherent radiation farther off axis.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK082  
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THPMK092 SOLEIL Status Report operation, storage-ring, synchrotron, controls 4516
 
  • L.S. Nadolski, G. Abeillé, Y.-M. Abiven, P. Alexandre, F. Bouvet, F. Briquez, P. Brunelle, A. Buteau, N. Béchu, M.-E. Couprie, X. Delétoille, T. Didier, J.M. Dubuisson, C. Herbeaux, N. Hubert, C.A. Kitegi, M. Labat, J.-F. Lamarre, P. Lebasque, A. Lestrade, A. Loulergue, P. Marchand, O. Marcouillé, F. Marteau, A. Nadji, R. Nagaoka, P. Prigent, F. Ribeiro, K.T. Tavakoli, M.-A. Tordeux, M. Valléau
    SOLEIL, Gif-sur-Yvette, France
  
  SOLEIL is both a synchrotron light source and a research laboratory at the cutting edge of experimental techniques dedicated to matter analysis down to the atomic scale, as well as a service platform open to all scientific and industrial communities. This French 2.75 GeV third generation synchrotron light source provides today extremely stable photon beams to 29 beamlines (BLs) complementary to ESRF. We report facility performance, ongoing projects and recent major achievements. A significant work was performed in order to secure the operation of the two canted 5.5 mm in-vacuum cryogenic permanent magnet undulators (CPMUs). Major R&D areas will also be discussed, and progress towards a lattice baseline for making SOLEIL a diffraction limited storage ring.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK092  
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THPMK112 An Updated Description of the FEL Simulation Code Puffin electron, FEL, radiation, distributed 4579
 
  • L.T. Campbell, B.W.J. MᶜNeil, P.T. Traczykowski
    USTRAT/SUPA, Glasgow, United Kingdom
  • L.T. Campbell
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • B.W.J. MᶜNeil
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • J.D.A. Smith
    TXUK, Warrington, United Kingdom
  
  Puffin [1] is an unaveraged 3D FEL simulation tool with no Slowly Varying Envelope Approximation (SVEA), no undulator period averaging of the electron motion, and no periodic slicing of the electron beam, enabling simulation of broadband and high resolution FEL phenomena. It is a massively parallel code, written in modern Fortran and MPI, which scales from single core machines to HPC facilities. Its use in a number of projects since its initial description in 2012 has necessitated a number of additions to expand or improve its capability, including new numerical techniques, and the addition of a wide and flexible array of undulator tunings and polarizations along with electron beam optics elements for the undulator line. In the following paper, we provide an updated description of Puffin including an overview of these updates.
[1] L.T. Campbell and B.W.J. McNeil, Phys. Plasmas 19 093119 (2012) 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK112  
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THPMK124 The Radiation Source for a Pre-Bunched THz Free Electron Laser radiation, electron, FEL, laser 4608
 
  • R. Huang, Z.G. He, Q.K. Jia, H.T. Li, W.W. Li, Y. Lu, L. Wang, Z. Zhao
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Funding: Work is supported by National Natural Science Foundation of China (Grant No. 51627901)
Electron beam, generated in a photoinjector and bunched at terahertz (THz) frequency, will excite the coherent THz radiation when entering an undulator. We present a scheme of the radiation source for the pre-bunched THz free electron laser (FEL). The physical design of electron source is described in detail. The radiation frequency is widely tunable by both the pulse train tuning and the undulator gap tuning. It is simulation proved that the radiation power is greatly enhanced in our scheme. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK124  
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THPMK132 Generation of Terahertz Synchrotron Radiation Using Laser-Bunch Slicing at Hefei Light Source laser, radiation, electron, synchrotron 4626
 
  • W. Xu, S.W. Wang, S.C. Zhang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Hefei Light Source is a second-generation low-energy synchrotron light source. The low energy machine is ca- pable of generating intense Terahertz radiation through co- herent synchrotron radiation. To realize this, one method is to shorten the bunch length to the same level of its radi- ation wavelength, e.g. by adopting low-α lattice. Another method is to modulate the electron bunch to produce mi- costructure at picosecond scale and intense Terahertz co- herent synchrotron radiation can be obtained due to the in- crease ofthebunchformfactor. This techniqueis calledthe laser bunch slicing method which introduces a laser beam into an undulator to interact with the electron bunches. In this paper we report our work on the simulation of the laser bunch slicing at Hefei Light Source.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK132  
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THPMK138 Power Enhancement of Free-Electron Lasers Oscillators With the Natural Gradient of a Planar Undulators FEL, simulation, electron, radiation 4632
 
  • Z. Zhao, L.J. Chen, Q.K. Jia, H.T. Li
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Funding: Work supported by National Natural Science Foundation of China (No. 21327901, 11205156)
Transverse Gradient Undulator (TGU) has been proposed with the initial purpose of mitigating the gain degradation in free electron laser (FEL) oscillators driven by beams with a large energy spread. However, a special-designed TGU with a fixed transverse gradient is required to enhance the gain. In this paper, we investigate using the natural field gradient of a normal planar undulator instead of a TGU to enhance the FEL oscillator (FELO) power. In this method, the beam is first vertically dispersed by a dogleg and then the dispersed beam passes through a normal undulator with a vertical off-axis orbit. Theoretical analysis and numerical simulation based on parameters of FELiChEM are presented. It demonstrates that this scheme can enhance the FEL power with careful optimization of dispersion strength and vertical beam orbit offset, especially when the energy spread is relatively large. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK138  
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