Keyword: FEL
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MOOCA01 R&D of a Super-compact SLED System at SLAC cavity, operation, coupling, impedance 39
 
  • J.W. Wang, G.B. Bowden, S. Condamoor, Y. Ding, V.A. Dolgashev, J.P. Eichner, M.A. Franzi, A.A. Haase, P. Krejcik, J.R. Lewandowski, S.G. Tantawi, L. Xiao, C. Xu
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by Department of Energy contract DE-AC03-76SF00515.
We have successfully designed, fabricated, installed and tested a super-compact X-Band SLED system at SLAC. It is composed of an elegant mode converter/polarizer and a single sphere energy store cavity with high Q of 94000 and diameter less than 12 cm. The available RF peak power of 50 MW can be compressed to peak average power of more than 200 MW in order to double the kick for the electron bunches in a RF transverse deflector system and greatly improve the measurement resolution for both the electron bunch and the x-ray FEL pulse. High power operation has demonstrated the excellent performance of this RF compression system without any problems in RF breakdown, pulse heating and radiation. The design physics and fabrication as well as the measurement results will be presented in detail. 		 
slides icon Slides MOOCA01 [20.278 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOOCA01  
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MOPMB040 Design of the Beam Diagnostics System for a New IR-FEL Facility at NSRL diagnostics, laser, cavity, emittance 181
 
  • J.H. Wei, X.Y. Liu, P. Lu, B.G. Sun, L.L. Tang, F.F. Wu, Y.L. Yang, T.Y. Zhou, Z.R. Zhou
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Funding: Work supported by National Natural Science Foundation of China (21327901, 11105141, 11575181)
A new IR-FEL has been commissioned at NSRL. This facility provides a final electron energy from 20 to 70 MeV, beam bunch with a macro-pulse length of 5~10 μs and a general micro-pulse repetition rate of 238 MHz, pulsed radiation with up to 100 mJ at about 0.3%~3% FWHM bandwidth. So a diagnostics system is necessary to monitor the performance of the bunch and the character of the FEL radiation, such as the beam position and profile, emittance, energy spread, laser intensity, etc. The beam diagnostics system mainly consists of Flags, a diagnostics beam line, BPMs, pop-in monitors and a FEL monitor system. This paper introduces the construction of this diagnostics system.
Corresponding author: ylyang@ustc.edu.cn 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB040  
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MOPMB042 Design and Simulation of Button Beam Position Monitor for IR-FEL* vacuum, simulation, electron, electronics 187
 
  • X.Y. Liu, P. Lu, B.G. Sun, L.L. Tang, F.F. Wu, Y.L. Yang, T.Y. Zhou, Z.R. Zhou
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Funding: * Supported by the National Science Foundation of China (11575181, 11175173)
A new button-type beam position monitor(BPM) was designed for the IR-FEL project. Firstly, the longitudinal size of BPM needs to be short enough to save space because the entire machine of IR-FEL is very compact. And in the matter of installation problem, all four electrodes are deviated 30 degrees from the horizontal axis. Then, according to these two limited conditions and beam parameters, we builded up a simple model and did some simulated calculations to ensure a good performance of position resolution, which should be better than 50μm. The simulations include an estimation of induced signals in both time and frequency domains, horizontal and vertical sensitivities, mapping figures and so on. This button BPM will be manufactured in the near future and then we can do some off-line experiments to test it.
# Corresponding author (email: bgsun@ustc.edu.cn) 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB042  
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MOPMB049 Beam Experiment of Low Q CBPM Prototype for SXFEL cavity, simulation, HOM, electron 202
 
  • J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu, R.X. Yuan
    SINAP, Shanghai, People's Republic of China
  
  To meet the high resolution beam position measurement requirement of micron or sub-micron for shanghai soft X-ray free electron laser (SXFEL) under construction, the cavity beam position monitor (CBPM) operating at C-band and the corresponding electronic has been designed by SINAP. In this paper, the design and optimize of the newly low Q cavity BPM is mentioned, the beam test was conducted on the Shanghai Deep ultraviolet free electron laser (SDUV-FEL) facility. CBPM signal processors including broadband oscilloscope and home-made digital BPM processor have been used to evaluate the system performance as well. The beam experimental result, which matched with MAFIA simulation very well, will be presented and discussed in this paper.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB049  
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MOPMR038 Design and Simulation Studies of the Novel Beam Arrival Monitor Pickup at Daresbury Laboratory pick-up, impedance, simulation, laser 334
 
  • A. Kalinin, S.P. Jamison, T.T. Thakker
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R. Apsimon, G. Burt, A.C. Dexter
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  
  We present the novel beam arrival monitor pickup design currently under construction at Daresbury Laboratory, Warrington, UK. The pickup consists of four flat electrodes in a transverse gap. CST Particle Studio simulations have been undertaken for the new pickup design as well as a pickup design from DESY, which is used as a reference for comparison. Simulation results have highlighted two advantages of the new pickup design over the DESY design; the signal bandwidth is 25 GHz, which is half that of the DESY design and the response slope is a factor of 1.6 greater. We discuss optimisation studies of the design parameters in order to maximise the response slope for bandwidths up to 50 GHz and present the final design of the pickup.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR038  
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MOPMW015 Wakefields Studies of High Gradient X-band Accelerating Structure at SINAP wakefield, impedance, simulation, cavity 429
 
  • X.X. Huang, W. Fang, Q. Gu, M. Zhang, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  
  Shanghai compact hard x-ray free electron laser (CHXFEL)* is now proposed accompanied with a high-gradient accelerating structure, which is the trend of large scale and compact facility. This structure operated at X-band (11424 MHz) holds the promise to achieve high gradient up to 80 MV/m. However, due to its particular property, a more serious wakefields** will be generated, leading to worse beam instability effects. In this paper, the computation of this case will be carried out with simulation. Moreover, analysis and optimization will be adopted to suppress beam instability.
* C. Feng, Z. T. Zhao, Chinese Sci Bull, 2010, 55, 221-227.
** K. Bane, SLAC, NLC-Note 9, Feb. 1995.
 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW015  
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MOPMW037 FEL Simulation Using Distributed Computing simulation, electron, GPU, distributed 483
 
  • J. Einstein, S. Biedron, H. Freund, S.V. Milton, P.J.M. van der Slot
    CSU, Fort Collins, Colorado, USA
  • G. Bernabeu Altayo
    Fermi National Accelerator Laboratory, Batavia, Illinois, USA
  • S. Biedron
    University of Ljubljana, Faculty of Electrical Engineering, Ljubljana, Slovenia
  • J. Einstein
    Fermilab, Batavia, Illinois, USA
  • P.J.M. van der Slot
    Twente University, Laser Physics and Non-Linear Optics Group, Enschede, The Netherlands
  
  While simulation tools are available and have been used regularly for simulating light sources, the increasing availability and lower cost of GPU-based processing opens up new opportunities. This poster highlights a method of how accelerating and parallelizing code processing through the use of COTS software interfaces.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW037  
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MOPOR005 Longitudinal Wakefields in the Undulator Section of SXFEL User Facility undulator, wakefield, vacuum, electron 595
 
  • M. Song, H.X. Deng, C. Feng, D. Huang, B. Liu, D. Wang
    SINAP, Shanghai, People's Republic of China
  
  Shanghai soft x-ray free electron laser (SXFEL) user facility based on multi-stage seeded-FEL and self-amplified spontaneous emission (SASE) is recently proposed, which is aiming at generating 4-2nm fully-coherent, high-brightness FEL pulse. In this paper, the wakefields arise from the resistive wall and surface roughness in the vacuum chamber is obtained by theoretical models*. And the computations of geometric wakefields are carried out using ABCI**. According to the tracked beam profile, the overall wakefields in the undulator section of SXFEL user facility are presented.
* K. Bane, G. Stupakov, SLAC-PUB-15951, May 2014.
** ABCI website: http://abci.kek.jp/abci.htm 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR005  
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MOPOW003 RF Phase Jitter Consideration in Bunch Compression klystron, simulation, electron, linac 704
 
  • T.K. Charles, D.M. Paganin
    Monash University, Faculty of Science, Clayton, Victoria, Australia
  • M.J. Boland, R.T. Dowd
    SLSA, Clayton, Australia
  
  Error propagation of RF phase jitter is analysed for various linac layout configurations and the sensitivity of the compression ratio due to RF phase jitter is analysed. Multiple sources of jitter have the opportunity to destructively interfere, and (perhaps counter intuitively) found to not add in quadrature. Results are compared to Elegant simulations.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW003  
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MOPOW004 Electron Trajectory Caustic Formation Resulting in Current Horns present in Bunch Compression electron, linac, wakefield, simulation 708
 
  • T.K. Charles, D.M. Paganin
    Monash University, Faculty of Science, Clayton, Victoria, Australia
  • M.J. Boland, R.T. Dowd
    SLSA, Clayton, Australia
  
  Current horns are ubiquitous in Free Electron Laser (FEL) bunch compression. In this paper, we analyse the formation of these current spikes and identify the cause as caustic formation in the electron trajectories. We also present a possible solution to avoid or mitigate the current horns from developing through using optical linearization.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW004  
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MOPOW008 Reverse Undulator Tapering for Polarization Control at XFELs undulator, resonance, radiation, bunching 722
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  Baseline design of a typical X-ray FEL undulator assumes a planar configuration which results in a linear polarization of the FEL radiation. However, many experiments at X-ray FEL user facilities would profit from using a circularly polarized radiation. As a cheap upgrade one can consider an installation of a short helical afterburner, but then one should have an efficient method to suppress powerful linearly polarized background from the main undulator. We describe a method for such a suppression: an application of the reverse taper in the main undulator*. In a certain range of the taper strength, the density modulation (bunching) at saturation is practically the same as in the case of non-tapered undulator while the power of linearly polarized radiation is suppressed by orders of magnitude. Then strongly modulated electron beam radiates at full power in the afterburner. The scheme was successfully tested at LCLS** and is routinely used in user experiments. In this contribution we present the theoretical description of the method as well as the results of experiments with reverse taper at FLASH2.
* E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST-AB 16, 110702 (2013)
** H.-D. Nuhn et al., "Commissioning of the DELTA polarizing undulator at LCLS", Proc. of FEL2015 Conf., Daejeon, Korea 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW008  
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MOPOW009 Studies of Harmonic Lasing Self-seeded FEL at FLASH2 undulator, simulation, electron, radiation 725
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  A concept of the Harmonic Lasing Self-Seeded (HLSS) FEL was proposed in*,**. A gap-tunable undulator is divided into two parts such that the first part is tuned to a sub-harmonic of the second part. Harmonic lasing occurs in the exponential gain regime in the first part of the undulator, also the fundamental stays well below saturation. In the second part of the undulator the fundamental mode is resonant to the wavelength, previously amplified as the harmonic. The amplification process proceeds in the fundamental mode up to saturation. In this case the bandwidth is reduced by a significant factor depending on harmonic number but the saturation power is still as high as in the reference case of lasing at the fundamental in the whole undulator, i.e. the spectral brightness increases. Application of the post-saturation tapering would allow to generate higher peak power than in SASE mode due to an improved longitudinal coherence. We present feasibility study of the application of the HLSS FEL scheme at FLASH2 and show that it allows to achieve a higher power and a smaller bandwidth than in a standard SASE regime. First experimental tests are eventually discussed.
* E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST-AB 15 (2012) 080702
** E.A. Schneidmiller and M.V. Yurkov, "Harmonic Lasing Self-Seeded FEL", Proc. of FEL2013 Conf., New York, USA 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW009  
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MOPOW010 The Superconducting Soft X-ray Free-Electron Laser User Facility FLASH photon, operation, laser, electron 729
 
  • M. Vogt, J. Feldhaus, K. Honkavaara, J. Rönsch-Schulenburg, S. Schreiber, R. Treusch
    DESY, Hamburg, Germany
  
  FLASH, the superconducting free-electron laser at DESY delivers up to several thousand photon pulses per second with wavelengths ranging from 52 nm down to as low as 4.2 nm and with pulse energies of up to 500 uJ to photon users at the FLASH1 beamline. In 2014 and 2015 a second beamline, FLASH2, has been commissioned in parallel to user operation at FLASH1. FLASH produces bunch trains of up to 800 bunches in 0.8 ms with a train repetition rate of 10 Hz. Each train can be split in sub-trains for FLASH1 and FLASH2, such that both beamlines receive bursts of bunches with full 10 Hz. Operational highlights are the latest SASE energy record of 600 uJ at 15 nm in FLASH2, and the first simultaneous SASE lasing of three undulator systems: FLASH1 (13.7 nm), sFLASH (38 nm), and FLASH2 (20 nm). sFLASH is the seeding experiment in the FLASH1 beamline. Moreover we will report on recent technical and operational improvements. A major success is the improved reliability and stability of the whole facility with shorter SASE tuning times.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW010  
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MOPOW012 Transverse Coherence and Fundamental Limitation on the Pointing Stability of X-ray FELs radiation, electron, photon, emittance 735
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  The radiation from SASE FEL has always limited value of the degree of transverse coherence*. When transverse size of the electron beam significantly exceeds diffraction limit, the mode competition effect does not provide the selection of the ground mode, and spatial coherence degrades due to contribution of the higher azimuthal modes. An important consequence of this effect are fluctuations of the spot size and pointing stability of the photon beam**. These fluctuations are fundamental and originate from the shot noise in the electron beam. The effect of pointing instability becomes more pronouncing for shorter wavelengths. We analyze in detail the case of optimized SASE FEL* and derive universal dependencies applicable to all operating and planned x-ray FELs. We show that the hard x-ray FELs driven by low energy beams may exhibit poor spatial coherence and bad pointing stability.
* E.L. Saldin, E.A. Schneidmiller and M.V. Yurkov, Opt. Commun. 281(2008)1179.
** E.A. Schneidmiller and M.V. Yurkov, Proc. FEL2015 Conference, Daejeon, Korea, 2015, TUP021.
 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW012  
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MOPOW013 Application of Statistical Methods for Measurements of the Coherence Properties of the Radiation from SASE FEL radiation, undulator, electron, photon 738
 
  • E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg, Germany
  
  Radiation of the SASE FEL operating in the linear regime possesses the properties of completely chaotic polarized light which happens due to start up of the amplification properties from the shot noise in the electron beam*. One of the features of this statistical object is that probability distribution of the radiation pulse energy follows gamma distribution. Parameter of this distribution is the number of modes in the radiation pulse which is equal to inverse deviation of the energy fluctuations. Statistical analysis of the radiation energies measured within different spatial apertures allows us to determine the number of longitudinal and transverse modes. In addition, knowledge of the saturation length allows to determine the duration of the lasing part of the electron bunch, photon pulse duration, and coherence time**. Knowledge of the number of transverse modes allows one to determine the degree of transverse coherence. In this report we present theoretical background of the proposed method and experimental results obtained at free electron laser FLASH.
* E.L. Saldin, E.A. Schneidmiller and M.V. Yurkov, Opt. Commun. 148 (1998) 383.
** C. Behrens et al., Phys. Rev. ST Accel. Beams 15 (2012) 030707.
 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW013  
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MOPOW015 Fermi Upgrade Plans laser, operation, electron, linac 744
 
  • A. Fabris, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, F. Cilento, P. Cinquegrana, M. Coreno, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, S. Di Mitri, B. Diviacco, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, L. Giannessi, F. Iazzourene, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, M. Malvestuto, C. Masciovecchio, M. Milloch, F. Parmigiani, G. Penco, A. Perucchi, L. Pivetta, O. Plekan, M. Predonzani, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, E. Roussel, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, M. Svandrlik, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  
  FERMI has reached its nominal performance on both FEL lines, FEL-1 (12 eV to 62 eV) and FEL-2 (62 eV to 310 eV). After a brief overview of the activities with users, we will describe plans for LINAC , FEL and beamline upgrades for 2016-2018 and beyond. This includes EEHG schemes for FEL-2.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW015  
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MOPOW017 Generation of GeV Photons from X-ray Free Electron Laser Oscillators electron, photon, laser, scattering 751
 
  • R. Hajima
    JAEA, Ibaraki-ken, Japan
  • M. Fujiwara
    RCNP, Osaka, Japan
  
  We propose generation of narrow-bandwidth GeV photons, gamma-rays, via Compton scattering of hard X-ray photons in X-ray free-electron laser oscillators. The gamma-rays have a narrow-bandwidth spectrum with a sharp peak, ~0.1% (FWHM), due to the nature of Compton scattering in relativistic regime. Such gamma-rays will be a unique probe for studying hadron physics. We discuss features of the gamma-ray source, flux, spectrum, polarization, tunability and energy resolution.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW017  
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MOPOW018 Feasibility Study of Photocathode Opearation of Thermionic RF Gun at KU-FEL cathode, operation, electron, gun 754
 
  • H. Zen, T. Kii, K. Masuda, K. Morita, T. Murata, T. Nogi, H. Ohgaki, S. Suphakul, K. Torgasin
    Kyoto University, Kyoto, Japan
  • R. Kuroda
    AIST, Tsukuba, Ibaraki, Japan
  
  Kyoto University Free Electron Laser (KU-FEL) is a mid-infrared FEL driven by a compact linac utilizinig a thermionic RF gun as its electron source*. Recently we succeeded in operating KU-FEL with photocathode operation of the RF gun by using the thermionic cathode (LaB6) as a photocathode. The performance of KU-FEL under the thermionic cathode and photocathode operation will be reported. In addition, some recent application experiment results will also be presented in this presentation.
*H. Zen, et al., Infrared Phys. Techn. 51 (2008) 382. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW018  
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MOPOW019 Commissioning Status of the Extreme-Ultraviolet FEL Facility at SACLA electron, undulator, booster, laser 757
 
  • T. Sakurai, T. Asaka, N. Azumi, T. Hara, T. Hasegawa, T. Inagaki, T. Ishikawa, R. Kinjo, C. Kondo, H. Maesaka, T. Ohshima, Y. Otake, H. Tanaka, T. Tanaka, K. Togawa
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • T. Bizen, N. Hosoda, H. Kimura, S. Matsubara, S. Matsui
    JASRI/SPring-8, Hyogo, Japan
  
  To equip SACLA with wide ability to provide a laser beams in EUV and soft X-ray regions to experimental users, we have constructed a new free electron laser facility for SACLA beamline-1. Injector components, such as a thermionic electron gun, two buncher cavities, a S-band standing wave accelerator, S-band travelling wave accelerator and their RF sources, were relocated from the SCSS test accelerator, which was a prototype machine of SACLA. At the downstream of a bunch compressor chicane, three C-band 40 MV/m acceleration units were newly installed to effectively boost a beam energy up to 470 MeV. Two in-vacuum undulators were remodeled by changing the period of magnet array from 15 mm to 18 mm to increase SASE intensity by a larger K-value of 2.1. Beam commissioning was started in autumn 2015. So far SASE radiation at a 33 nm wavelength driven by a 470 MeV electron beam was observed. We will install the third undulator in this winter to obtain SASE saturation and additional C-band accelerator units in the next summer to raise the maximum beam energy to 750 MeV. In this presentation, the overview of the facility and the commissioning status will be reported.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW019  
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MOPOW020 Power Improvement of Free-Electron Laser Using Transverse-Gradient Undulator with External Focusing focusing, radiation, undulator, electron 760
 
  • G. Zhou, Y. Jiao, G. Xu
    IHEP, Beijing, People's Republic of China
  • J. Wu
    SLAC, Menlo Park, California, USA
  • T. Zhang
    SINAP, Shanghai, People's Republic of China
  
  Funding: Supported by National Natural Science Foundation of China (11475202, 11405187) and Youth Innovation Promotion Association of Chinese Academy of Sciences (No. 2015009)
Resent study [Z. Huang et al., Phys. Rev. Lett. 109, 204801 (2012)] shows that the transverse-gradient undu-lator (TGU) together with electron beams with constant dispersion can reduce the sensitivity to energy spread for FEL. In this study, we numerically study FEL using TGU with external focusing. In spite of the dispersion varia-tion, through parameter optimization, FEL using TGU with TGU achieves similar radiation to that without ex-ternal focusing. To achieve a high energy exaction effi-ciency, the initial dispersion should be set with a shift from that corresponding to the resonant condition, and a variation of the transverse gradient in different undulator section is preferred. Other approaches, such as tapering and detuning frequency control, are also discussed to further improve the radiation power and are demonstrated with global parametric optimizations base on simulation. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW020  
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MOPOW023 Proposal of an X-band Linearizer for Dalian Coherent Light Source laser, electron, radiation, undulator 766
 
  • G.L. Wang, X.M. Yang, W.Q. Zhang
    DICP, Dalian, People's Republic of China
  • H.X. Deng, C. Feng
    SINAP, Shanghai, People's Republic of China
  
  Dalian coherent Light Source (DCLS) is a FEL user facility working at 50-150 nm, now under commissioning in Dalian, China. The facility based on HGHG mode, requires high brightness electron beam with small energy spread and low emittance. To linearise the longitudinal phase space before the bunch compression, an X-band linearizer is considered before the bunch compressor. In this paper, we study the performance improvement of DCLS FEL radiation by using such a harmonic cavity, including the jitter of central wavelength induced by arriving time and a larger bunch compression ratio for femtosecond FEL application.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW023  
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MOPOW024 Harmonic Lasing Options for Dalian Coherent Light Source radiation, laser, electron, undulator 770
 
  • G.L. Wang, X.M. Yang, W.Q. Zhang
    DICP, Dalian, People's Republic of China
  • H.X. Deng, C. Feng
    SINAP, Shanghai, People's Republic of China
  
  Harmonic lasing of the Free Electron Laser can be achieved by disrupting the electron interaction with the usually dominant fundamental while allowing the increasing of a harmonic interaction. It's a cheap and relatively efficient way to extend the photon energy range of a particular FEL. In this paper, we discussed the possibility of harmonic lasing concept at Dalian Coherent Light Source by using the combination of tapered undulators and phase shifters. Our calculation shows that it's feasible with the present layout to provide intense, stable, and narrow-band harmonic radiation, the FEL wavelength could be down to 20 nm and the corresponding pulse energy is about 10 μJ.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW024  
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MOPOW026 Status of FELiCHEM, a New IR-FEL in China undulator, radiation, cavity, electron 774
 
  • H.T. Li, Z.G. He, Q.K. Jia, Q. Luo, L. Wang, S.C. Zhang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  FELiChEM is a new experimental facility under construction at University of Science and Technology of China (USTC), whose core device is a FEL oscillator generating middle-infrared and far-infrared laser and covering the spectral range of 2.5-200 μm. It will be a dedicated light source aiming at energy chemistry research, with the photo excitation, photo dissociation and photo detection experimental stations. We present the brief physical and technical design that delivers the required performance for this device and summarize the status of fabrication. Final assembly is scheduled for early in the next year with first light targeted for July 2017.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW026  
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MOPOW027 Generation of Coherent Mode-locked Radiation in a Seeded Free Electron Laser electron, radiation, laser, simulation 777
 
  • Z. Wang, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  • D. Xiang
    Shanghai Jiao Tong University, Shanghai, People's Republic of China
  
  We present the promise of generating mode-locked multichromatic radiations in a seeded free electron laser based on high gain harmonic generation (HGHG). 3D start-to-end simulations have been carried out and analysis & comparisons have been made to have a research on the properties of each system. In these schemes, either the electron beam density or the seed laser intensity is modulated to produce a coherent radiation pulse train that yields multiple spectral lines in FEL output. Stable peak power at gigawatt level can be generated in the undulator finally.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW027  
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MOPOW028 Research on Pulse Energy Fluctuation of a Cascaded High Gain Harmonic Generation Free Electron Laser electron, laser, timing, linac 781
 
  • Z. Wang, C. Feng, Q. Gu, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  
  Shot to shot pulse energy fluctuation is one of the most critical issues for two-stage cascaded high gain harmonic generation (HGHG) free electron lasers (FELs). In this paper, we study the effects of various electron parameters jitters on the output pulse energy fluctuations based on Shanghai Soft X-ray free electron laser facility (SXFEL). The results show that the relative timing jitter between the electron beam and the seed laser is proved to be the most sensitive factor. The energy jitter and charge jitter make some contributions and are non-ignorable as well. Some comparisons between our facility and FERMI have been made and we hope the conclusions draw from this study would be a reference for the optimization of future seeded FEL facilities based on cascading stages of HGHG.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW028  
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MOPOW029 The Soft X-ray Self-seeding System Design for SXFEL User Facility undulator, electron, simulation, photon 785
 
  • K.Q. Zhang, T. Liu, D. Wang
    SINAP, Shanghai, People's Republic of China
  • Y. Feng
    SLAC, Menlo Park, California, USA
  
  X-ray free electron laser driven by SASE probes the evolution of the new generation light source in high brightness, transverse coherence. However, since SASE achieves lasing from random shotnoise, Poor longitudinal coherence and relative wide bandwidth of SASE FEL limit the operation of many type experiments. Self-seeding as a promising scheme produces longitudinal coherence and even narrower bandwidth radiation by a monochromatic seeding instead of external seeding. The self-seeding system design based on the grating monochromator is carried out for SXFEL user facility across the photon energy from 800-1200 eV. The grating monochromator with a resolution power of 〖10〗-4 can provide a monochromatic seeding pulse to the seeding undulator. The layout design and simulations of the scheme are presented. It is showing that the self-seeding system for SXFEL user facility is able to improve SASE FEL longitudinal coherence significantly.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW029  
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MOPOW035 A Compact, Wavelength Tunable MW-THz FEL Amplifier undulator, electron, laser, radiation 789
 
  • C.H. Chen, A.P. Lee
    NSRRC, Hsinchu, Taiwan
  • F.H. Chao, Y.C. Chiu, Y.-C. Huang, M.H. Wu
    NTHU, Hsinchu, Taiwan
  • G. Zhao
    PKU, Beijing, People's Republic of China
  
  We propose a compact scheme of THz free electron laser (FEL) amplifier within a 3.5 m long beam line. The amplification of a tunable THz seed laser in an FEL amplifier is driven by an rf photoinjector*. The THz seed laser is an optical parametric amplifier** pumped by a 1064-nm microchip laser and an external-cavity tunable diode laser. By varying the beam energy and undulator parameter, the radiation frequency of the THz FEL amplifier can be tunable in a broad spectral range between 1.5 and 3.0 THz. Moreover, to extract more radiation power from the electron beam within a short undulator, we employ a linearly tapered undulator in our design. The influence of the seed power on the electron-laser interaction in the undulator is studied in some detail for the FEL amplification. Our simulation results show that the radiation power of the THz FEL amplifier can achieve few MW with a 10-W seed power.
* D.T. Palmer et al., in Proceedings of Particle Acceleration Conference, Vancouver, 1997, p. 2687, (1997).
** S. Hayashi et al., SCIENTIFIC REPORTS, 4, 5045-1-6, (2014).
 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW035  
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MOPOW036 Design Optimization of an X-band based FEL linac, simulation, emittance, gun 793
 
  • A.A. Aksoy
    Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
  • A. Latina, J. Pfingstner, D. Schulte
    CERN, Geneva, Switzerland
  • Z. Nergiz
    Nigde University, Nigde, Turkey
  
  A design effort for a new generation of compact, cost-effective, power-efficient FEL facilities, based on X-band technology, has been launched. High-frequency X-band acceleration implies strong wakefields, tight alignment and mechanical tolerances, and challenging stability issues. In this paper a design is proposed for the injector and the linacs, including the two bunch compressors. RF gun and injector simulations have been performed, successfully meeting the stringent requirements in terms of minimum projected emittance, sliced emittance and minimum bunch length. In the design of the linac and bunch compressors wakefield effects and misalignment have been taken into account. Start-to-end tracking simulations through the optimized lattice are presented and discussed.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW036  
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MOPOW037 Developments in the CLARA FEL Test Facility Accelerator Design and Simulations linac, space-charge, undulator, simulation 797
 
  • P.H. Williams, D. Angal-Kalinin, A.D. Brynes, J.A. Clarke, F. Jackson, J.K. Jones, J.W. McKenzie, B.L. Militsyn, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R.B. Appleby
    UMAN, Manchester, United Kingdom
  • B. Kyle
    University of Manchester, Manchester, United Kingdom
  
  We present recent developments in the accelerator design of CLARA (Compact Linear Accelerator for Research and Applications), the proposed UK FEL test facility at Daresbury Laboratory. In order to prioritise FEL schemes requiring the shortest electron bunches, the layout has changed significantly to enable compression at higher energy. Four proposed modes of operation are defined and tracked from cathode to FEL using ASTRA. Supplementing these baseline mode definitions with CSR-enabled codes (such as CSRTRACK) where appropriate is in progress. The FEL layout is re-optimised to include shorter undulators with delay chicanes between each radiator.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW037  
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MOPOW045 Measurement of Advanced Dispersion-based Beam-tilt Correction lattice, electron, photon, laser 813
 
  • M.W. Guetg, F.-J. Decker, Y. Ding, P. Emma, Z. Huang, T.J. Maxwell
    SLAC, Menlo Park, California, USA
  
  Funding: DOE contract \#DE-AC02-76SF00515
Free electron lasers in the X-ray regime require a good slice alignment along the electron bunch to achieve their best performance. A transverse beam slice shift reduces this alignment and spoils projected emittance and optics matching. Coherent synchrotron radiation, specifically for over-compression going through full compression, and transverse wakefields are major contributors to this. In the case of the large-bandwidth operation, with a strong energy chirp on the bunch, this misalignments furthermore reduce the spectral bandwidth of the FEL pulse. Well-defined manipulation of dispersion allows to compensate for this slice centroid shifts, therefore enhancing lasing power and in case of the large bandwidth mode, spectral bandwidth. This work shows the first application of this correction on an X-ray FEL resulting in increase in beam-power and bandwidth. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW045  
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MOPOW049 Implementation of a Corrugated-Plate Dechirping System for GeV Electron Beam at LCLS electron, controls, laser, experiment 824
 
  • M.A. Harrison, P. Frigola, J.D. McNevin, A.Y. Murokh, M. Ruelas
    RadiaBeam Systems, Santa Monica, California, USA
  • A.M. Babbitt, M. Carrasco, A. Cedillos, R.H. Iverson, P. Krejcik, T.J. Maxwell, '. Oven
    SLAC, Menlo Park, California, USA
  
  Funding: This work is supported by US DOE Grant No. DE-SC0009550.
A new corrugated-plate Dechirper was recently installed in the LCLS and underwent commissioning tests to gauge its efficacy in shaping the longitudinal phase space of bunches entering the FEL. Here, we describe in detail the completed four-meter LCLS Dechirper system along with a narrative of its construction. We detail the various challenges and lessons learned in the manufacturing and assembly of this first-of-its-kind device. An outlook on future designs is presented. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW049  
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MOPOY048 A Novel Approach in the One-Dimensional Phase Retrieval Problem and its Application to the Time Profile Reconstruction electron, optics, laser, operation 955
 
  • F. Bakkali Taheri, J. Cowley, G. Doucas, S.M. Hooker, I.V. Konoplev
    JAI, Oxford, United Kingdom
  • R. Bartolini
    DLS, Oxfordshire, United Kingdom
  
  Funding: This work was supported (in parts) by the UK Science and Technology Facilities Council (STFC UK) grant ST/M003590/1 and The Leverhulme Trust through International Network Grant IN-2015-012
Accurate knowledge of the longitudinal profile of the bunch is important in the context of linear colliders, wake-field accelerators and for the next generation of light sources. As a result the non-destructive, single-shot evaluation of the profile is one of the challenging problems which can be addressed via spectral analysis of coherent radiation generated by a charged particle bunch. To reconstruct the bunch profile from the spectrum the phase retrieval problem has to be solved. Frequently applied methods, e.g. minimal phase retrieval or other iterative algorithms, are reliable if the Blaschke phase contribution is negligible. This is neither known a priori nor can it be assumed to apply to an arbitrary bunch profile. We present a novel approach which gives reproducible, most-probable and stable reconstructions for bunch profiles that would otherwise remain unresolved by the existing techniques. The algorithm proposed uses the output of Kramers-Kronig minimum phase as both initial and boundary conditions, providing a unique solution. To assure a converging solution, new conditions linked to the independently known experimental data such as beam charge were introduced. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOY048  
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TUZA01 Soft X-ray Free Electron Laser at SINAP undulator, laser, electron, radiation 1028
 
  • D. Wang
    SINAP, Shanghai, People's Republic of China
  
  Shanghai X-ray FEL (SXFEL) is a test facility at Shanghai Institute of Applied Physics, Chinese Academy of Sciences originally designed for studying XFEL principle and technologies. It is composed of a warm linac to provide up to 840 MeV electron beam, an undulator line with cascaded EEHG-HGHG setup and a short diagnostic beamline. The project started the construction by the end of 2014. Recently a proposal to upgrade it to an user facility at the soft x-ray regime got approved. The talk will give an overview of the test facility construction and upgrade plan.  
slides icon Slides TUZA01 [9.344 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUZA01  
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TUXB01 High Power Radiation Sources using the Steady-state Microbunching Mechanism laser, radiation, storage-ring, focusing 1048
 
  • A. Chao, E. Granados, X. Huang, D.F. Ratner
    SLAC, Menlo Park, California, USA
  • H.W. Luo
    NTHU, Hsinchu, Taiwan
  
  The mechanism of steady-state microbunching (SSMB) was proposed for providing high power coherent radiation using electron storage rings. The mechanism follows closely the RF bunching in conventional storage rings, except that the energy modulation of by an RF system at a microwave wavelength is replaced by a seeded laser in an undulator at an optical wavelength. No FEL mechanism, and thus no FEL energy heating, is invoked. The basic idea is firstly to make the beam microbunched so that its radiation becomes coherent, and secondly to make the microbunching a steady state so that the coherent radiation is maintained at every turn. The combination of the high repetition rate of a storage ring and the enhanced radiation power by a factor of N (the number of electrons in the microbunches within one coherence length) opens the possibility as well as challenges of very high power SSMB sources. To explore its potential reach, we apply SSMB to the infrared, deep ultraviolet and EUV regions and estimate their respective power levels using SPEAR3 as example. Several variants of the SSMB schemes are discussed. A proof-of-principle configuration without an identified testbed is also suggested.  
slides icon Slides TUXB01 [1.602 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUXB01  
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TUPMB006 The Magnetic Measurement of Conventional Magnets for Free-Electron Laser Project of Chinese Academy of Engineering Physics electron, dipole, collimation, laser 1115
 
  • Z. Zhang, F.S. Chen, Y.F. Yang
    IHEP, Beijing, People's Republic of China
  
  The project of free electron laser is worked together completed by CAEP(Chinese Academy of Engineering Physics）and IHEP(Institute of High Energy Physics, China). Conventional magnet of the project includes a total of three deflecting dipole magnet, an analysis of dipole magnet, and two quadrupole magnets. All of magnets to complete the measurement by IHEP Hall measuring equipment. The measurement trajectory of integral magnetic field for deflection dipole magnet is arc and arc tangent direction, using Labview software written a new measurement procedures, the Hall probe directly read absolute value of the three-axis(X, Y, Z) coordinate point (relative to the Hall probe in terms of absolute zero) measurement functions, Not only achieve the purpose of measuring the trajectory can be freely combined, but also effectively eliminate the accumulated error of Hall mobile devices. All measurement results of conventional magnets have reached the physical design requirements, and each magnet were carried out more than twice the measurement, the reproducibility of the measurement results are better than one-thousandth, fully meet the design claim of CAEP.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMB006  
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TUPMB011 Calculation and Analysis of the Magnetic Field of a Transverse Gradient Undulator undulator, simulation, electron, laser 1130
 
  • J. Li, B. Du, Q.K. Jia, H.T. Li
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Transverse gradient undulator (TGU) is attracting more and more attentions, especially for the rapid progress of laser plasma accelerator techniques. The transverse gradient of TGU is usually given by an empirical formula simply derived from the empirical formula of a uniform-parameter undulator. In this paper, we numerically investigate the transverse magnetic field of TGUs using the RADIA code. Through many simulations for TGUs with different magnet structures, we have given the dependences of transverse gradient parameter on the cant angle, the undulator period and the average gap. Based on these results, when the cant angle is small and the rate of the gap and period is in the range of 0.4-0.6, the simulation results agree with the empirical formula well. But, with the growing of the cant angle, or with the growing of the deviation of the rate of the gap and period from the range of 0.4-0.6, the difference between the simulation results and the empirical formula becomes larger.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMB011  
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TUPMR008 Simulation of Ion Beam under Coherent Electron Cooling ion, simulation, electron, kicker 1243
 
  • G. Wang, M. Blaskiewicz, V. Litvinenko
    BNL, Upton, Long Island, New York, USA
  • V. Litvinenko
    Stony Brook University, Stony Brook, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The proof of coherent electron cooling (CeC) principle experiment is currently under commissioning and it is essential to have the tools to predict the influences of cooling electrons on a circulating ion bunch. Recently, we have developed a simulation code to track the evolution of an ion bunch under the influences of both CeC and Intra-beam scattering (IBS). In this paper, we will first show the results of benchmarking the code with numerical solutions of Fokker-Planck equation and then present the simulation results for the proof of CeC principle experiment. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMR008  
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TUPMY031 Estimation and Suppression of Aberrations in Emittance Exchange based Current Profile Shaping collective-effects, emittance, space-charge, acceleration 1615
 
  • G. Ha, M.-H. Cho, W. Namkung
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • W. Gai, G. Ha, K.-J. Kim, J.G. Power
    ANL, Argonne, Illinois, USA
  
  The longitudinal current profile manipulation has been explored for many applications including THz radiation, FEL and advanced acceleration schemes. Especially, collinear dielectric wakefield accelerations require a microbunch shaping for a high transformer ratio. We have studied aberrations from the emittance exchange based current profile shaping to preserve the high transformer ratio. All second order aberration terms in the double dog-leg emittance exchange beam line are discovered. Aberration patterns from each aberration sources like second order terms, space-charge, and CSR and their effect on the transformer ratio are estimated analytically. These aberration sources and corresponding patterns are confirmed using a particle tracking code GPT. Simple methods to suppress each aberration will be presented too. All calculation in this work is done with a double dog-leg emittance exchange beam line.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY031  
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TUPOR018 Design Optimization of Compensation Chicanes in the LCLS-II Transport Lines simulation, electron, space-charge, undulator 1695
 
  • J. Qiang, C.E. Mitchell, M. Venturini
    LBNL, Berkeley, California, USA
  • Y. Ding, P. Emma, Z. Huang, G. Marcus, Y. Nosochkov, T.O. Raubenheimer, L. Wang, M. Woodley
    SLAC, Menlo Park, California, USA
  
  LCLS-II is a 4th-generation high-repetition rate Free Electron Laser (FEL) based x-ray light source to be built at the SLAC National Accelerator Laboratory. To mitigate the microbunching instability, the transport lines from the exit of the Linac to the undulators will include a number of weak compensation chicanes with the purpose of cancelling the momentum compaction generated by the main bend magnets of the transport lines. In this paper, we will report on our design optimization study of these compensation chicanes in the presence of both longitudinal and transverse space-charge effects.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR018  
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TUPOW006 Six-dimensional Phase-space Rotation and its Applications emittance, cathode, simulation, electron 1754
 
  • M. Kuriki, K. Negishi
    HU/AdSM, Higashi-Hiroshima, Japan
  • H. Hayano, R. Kato, K. Ohmi, M. Satoh, Y. Seimiya, J. Urakawa
    KEK, Ibaraki, Japan
  • S. Kashiwagi
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  
  Funding: This work is partly supported by Grant-in-Aid for Scientific Research by MEXT, Japan (KAKENHI) 25390126.
Recent progress on the accelerator science requires optimized phase space distributions of the beam for each applications. A classical approach to satisfy the requirements is minimizing the beam emittance with a bunch charge as much as possible. This classical approach is not efficient and not compatible to the beam dynamics nature. 6D phase-space rotation, e.g. z-x and x-y, gives a way to optimize the phase space distribution for various applications. In this article, we discus possible applications of the 6D phase space rotation. The x-y rotation generates the high aspect ratio beam for linear colliders directly without DR (Damping Ring). Combination of bunch clipping with a mechanical slit and x-z rotation can generate micro-bunch structure which is applicable for FEL enhancement and drive beam for dielectric acceleration. We present our theoretical and simulation study on these applications. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW006  
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TUPOW030 A CW Normal Conducting RF Cavity for Fast Chirp Control in the LCLS-II linac, cavity, controls, wakefield 1817
 
  • M.H. Nasr, P. Emma, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  
  The LCLS-II is a high repetition-rate Free-Electron Laser (FEL) facility under construction at SLAC. A new 4-GeV continuous wave (CW) superconducting (SC) L-band linac is being built to provide an electron bunch rate of up to 1 MHz, with bunches rapidly switched between two FEL undulators. It is desirable to provide peak current (i.e., pulse length) control in each FEL independently by varying the RF phase (chirp) prior to the first bunch compressor. However, the high-Q, SCRF, with its 1-ms fill-time, cannot be changed within one bunch spacing (1 us). So to provide a small chirp adjustment from bunch to bunch, we propose a short CW copper RF accelerating cavity, located just after the injector, with < 250-ns fill-time designed to adjust the beam chirp at zero-crossing phase. We examined RF cavity designs spanning RF frequencies from L-band to X-band. We considered both SW and TW structures. We found an optimal solution with 2 cm iris diameter, SW RF cavity, operating at C-band with input power of only 10 kW. If one can afford to operate with smaller diameter, from a wakefield point of view, then similar structure at X-band may require only 500 W with 5 mm iris diameter.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW030  
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TUPOW051 Optimization of Electron Beam and Laser Pulse Alignment and Focusing at Interaction Point for a Compact FEL Based Inverse-Compton Scattering X-Ray Source electron, laser, photon, undulator 1881
 
  • P. Niknejadi, J. Madey
    University of Hawaii, Honolulu,, USA
  
  Funding: This work was funded under the Department of Homeland Security Grant No. 2010-DN-077-ARI045.
In July 2015, the first beam of 10 keV X-rays from our FEL based inverse-Compton scattering X-ray source was detected.* In this setup, 3 micron laser pulses at 2.856 GHz repetition rate from a free electron laser are collided head-on with 40 MeV electron bunches driving the laser. To attain our objective the ebeam was required to have 1) a tight focus at the X-ray interaction point, 2) vertical and horizontal envelopes matched to the downstream undulator, 3) minimized transverse dimensions for low ionizing radiation. Optimization of these quantities required information on the evolution of the beam profiles between the beam spot images on the available insertable screens, leading to the need for a simulator to accurately trace the beam profiles through the system. A simulator was developed and used to optimize the system Twiss parameters by comparing the effectiveness of the beam profiles computed by fitting the profiles to the observed beam spot images along the beamline for different cathode positions. This method proved to be considerably more flexible and effective than the more traditional quadrupole scan technique. Summery of the designed system and results are provided.
* John M. J. Madey, ARI final report, December 2015. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW051  
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WEPOW043 Accelerator Based Light Source Projects of Turkey electron, undulator, linac, radiation 2936
 
  • A.A. Aksoy, Ö. Karslı, C. Kaya
    Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
  • B. Ketenoğlu, O. Yavaş
    Ankara University, Faculty of Engineering, Tandogan, Ankara, Turkey
  • Z. Nergiz
    Nigde University, Nigde, Turkey
  
  Three light source project is ongoing in Turkey within the frame of Turkish Accelerator Center (TAC) Project which has been supported by Ministry of Development since 2006. As a first facility of TAC, 3-250 μ mm IR-FEL facility (TARLA) based on superconducting accelerator with an energy of maximum 40 MeV is under construction at Institute of Accelerator Technologies of Ankara University. In addition to TARLA, Conceptual/Technical Design Report of a third generation synchrotron radiation facility based on 3 GeV, and a fourth generation FEL facility based 1-6 GeV is being prepared for the next steps of TAC. Therewithal a proton accelerator facility with up 2 GeV and an electron-positron collider as a super charm factory are proposed within the frame of TAC project. In this presentation, current status of TARLA project and main goals, road map of Turkish Light Sources will be explained.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW043  
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WEPOW055 Bayesian Optimization of FEL Performance at LCLS controls, interface, laser, electron 2972
 
  • M.W. McIntire, T.M. Cope, D.F. Ratner
    SLAC, Menlo Park, California, USA
  • S. Ermon
    Stanford University, Stanford, California, USA
  
  Funding: Research is supported by the U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
The LCLS free-electron laser at SLAC is tuned via a huge number of parameters such as energy and magnet settings. Much of this tuning, including quadrupole magnet settings, is typically done by hand by the LCLS operators. In this paper we introduce an automated tuning system using Bayesian optimization, and describe its application to the optimization of noisy objectives such as FEL performance. We demonstrate with preliminary results from our implementation at LCLS that this system can improve both the speed of tuning procedures as well as the quality of the resulting solution. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW055  
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WEPOY019 Beam Optimization Study for an X-ray FEL Oscillator at the LCLS-II flattop, electron, emittance, linac 3020
 
  • W. Qin, S. Huang, K.X. Liu
    PKU, Beijing, People's Republic of China
  • K.L.F. Bane, Y. Ding, Z. Huang, T.J. Maxwell
    SLAC, Menlo Park, California, USA
  • K.-J. Kim, R.R. Lindberg
    ANL, Argonne, Ilinois, USA
  
  The 4 GeV LCLS-II superconducting linac with high repetition beam rate enables the possibility to drive an X-Ray FEL oscillator at harmonic frequencies *. Compared to the regular LCLS-II machine setup, the oscillator mode requires a much longer bunch length with a relatively lower current. Also a flat longitudinal phase space distribution is critical to maintain the FEL gain since the X-ray cavity has extremely narrow bandwidth. In this paper, we study the longitudinal phase space optimization including shaping the initial beam from the injector and optimizing the bunch compressor and dechirper parameters. We obtain a bunch with a flat energy chirp over 400 fs in the core part with current above 100 A. The optimization was based on LiTrack and Elegant simulations using LCLS-II beam parameters.
* T. J. Maxwell et al., Feasibility study for an X-ray FEL oscillator at the LCLS-II, IPAC15, TUPMA028. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY019  
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WEPOY028 Laser Heater System Test at PAL-XFEL ITF laser, electron, undulator, bunching 3048
 
  • J. H. Lee
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • J.H. Han, J.H. Hong, C.H. Kim, I.S. Ko, S.J. Lee
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  Coherent x-ray photons are generated by a free electron laser (FEL). In PAL-XFEL, a photon beam with a 0.1 nm wavelength is generated from an electron bunch based on self-amplified spontaneous emission (SASE). An electron bunch with an uncorrelated energy spread in a level of 3 keV, which is generated from the photocathode RF gun, may be sensitive to longitudinal micro-bunching instability. The energy spread of an electron bunch can be increased to suppress the instability by Landau damping. In order to control the uncorrelated energy spread, a laser heater system, which has a chicane with four dipoles chicane and a 0.5 m long undulator, was installed in the injector test facility (ITF) of PAL. In this paper, we introduce the parameters of the laser heater and heating effect on the electron bunch.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY028  
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WEPOY035 Free Electron Laser Simulation Tool Based on FDTD/PIC in the Lorentz Boosted Frame simulation, undulator, radiation, electron 3061
 
  • A. Yahaghi, A. Fallahi, F.X. Kärtner
    CFEL, Hamburg, Germany
  • F.X. Kärtner
    MIT, Cambridge, Massachusetts, USA
  
  Funding: Alexander von Humboldt-Foundation European Research Council(ERC)
Free Electron Lasers (FELs) are promising sources capable of generating electromagnetic waves in the whole spectrum. Therefore, it is crucial and additionally very useful to develop sophisticated though complete simulation tools. This goal is mainly motivated by our research focus on the development of compact X-ray sources based on radiation in optical undulators. The currently existing softwares are usually written to tackle special cases with particular approximations, such as 1D FEL theory, steady state, slow wave and forward wave approximation, wiggler-averaged electron motion and slices approximation. Many of the above approximations are hardly valid when sub-femtosecond bunches interact with intense optical lasers. The presented software aims the analysis of the FEL interaction without considering any of the above approximations. The developed tool apparently suffers from long computation times but offers a more accurate picture on the radiation process. In order to overcome the problem of multidimensionality, we exploit Lorentz boosted coordinate system and implement Finite Difference Time Domain (FDTD) method combined with Particle in Cell (PIC) simulation in this frame. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY035  
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WEPOY036 Progress in Automatic Software-based Optimization of Accelerator Performance linac, software, storage-ring, injection 3064
 
  • S.I. Tomin, G. Geloni
    XFEL. EU, Hamburg, Germany
  • I.V. Agapov, I. Zagorodnov
    DESY, Hamburg, Germany
  • W.S. Colocho, T.M. Cope, A.B. Egger, D.F. Ratner
    SLAC, Menlo Park, California, USA
  • Y.A. Fomin, Y.V. Krylov, A.G. Valentinov
    NRC, Moscow, Russia
  
  Funding: partial support from Ioffe Roentgen Institute grant EDYN EMRAD
For modern linac- and storage-ring-based light sources certain amount of empirical tuning is used to reach ultimate performance. The possibility to perform such empirical tuning by automatic methods has now been demonstrated by several authors (e.g. I.Agapov et al. in proc IPAC 2015). In this paper we present the progress in development of our automatic optimisation software based on OCELOT and its applications to SASE FEL optimization at FLASH and LCLS, and its potential for storage ring optimization. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY036  
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THPMB008 Compensation of Steerer Crosstalk between FLASH1 and FLASH2 betatron, electron, laser, free-electron-laser 3237
 
  • F. Christie, B. Schmidt, M. Vogt
    DESY, Hamburg, Germany
  
  The free-electron laser in Hamburg (FLASH) is a user facility delivering soft X-ray radiation. Starting from 2014, a second beam line for user operation, FLASH2, has been commissioned. It uses the same accelerating modules as the initial FLASH beam line (FLASH1) and the beam is deflected into a separate beam line downstream the linac. In the region, where the FLASH2 beam is extracted, both beam lines are close, the angle in between is 6.5 degrees. It has been observed, that steering dipoles in the extraction area, have an influence on both beam lines. Thus steering the orbit in one beam line, perturbs the orbit in the other beam line. This perturbation can significantly degrade the SASE energy in the other beam line. We have found a solution to this problem based the combination of local orbit bumps. The crosstalk from one steerer is corrected using additional steerers in the other beam line. This concept has already been tested at FLASH and has proven to work sufficiently well.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB008  
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THPMB021 Design of the Magnets of the Far-Infrared FEL Project at NSRL dipole, quadrupole, simulation, electron 3269
 
  • T.L. He, H. Xu, W. Xu, S.C. Zhang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Funding: National Natural Science Foundation of China (10875118); National Natural Science Foundation of China (11375176)
This paper describes the magnetic design of the magnets of the far-infrared free electron laser at NSRL, including dipole magnets and quadrupole magnets with limited installing space. The dipoles are of three different effective lengths and strengths. All the magnets are designed and optimized by using POSSION and OPERA-3D. The end shimming and chamfer are modeled and fully determined by 3D simulation to meet the field uniformity requirement. The design consideration and simulation results are presented in detail. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB021  
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THPMB024 Error Analysis for the Lattice of FELiChEM undulator, simulation, lattice, emittance 3278
 
  • S. Huang, Z.G. He, W. Xu, S.C. Zhang, T. Zhang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  FELiChEM is a new experimental facility under construction at University of Science and Technology of China (USTC).The facility consists of the middle-infrared (MID-FEL) beam line for 2.5-50 um and the Far-infrared (FAR-FEL) beam line for 40-200um. To achieve the design FEL performance of IR-FEL, the beam with 30 mm-mrad emittance, 5 ps rms length and 1nC bunch charge is required. We conduct error analysis in order to evaluate the tolerances of machine parameters and alignments. In this paper, we simulate the orbit corrections and emittance growth under exist of misalignments and strength errors of magnets. The simulation results show that the trajectory errors can be corrected to mm levels in the whole lattice and the emittance increase is acceptable. At the entrance of undulator, the position and angular errors can be corrected very well. So the trajectory can be controlled in the undulator to meet the requirement of FEL.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB024  
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THPMB027 Beam Transport Line of the LPA-FEL Facility Based on Transverse Gradient Undulator undulator, radiation, beam-transport, laser 3287
 
  • T. Liu, B. Liu, D. Wang, T. Zhang
    SINAP, Shanghai, People's Republic of China
  • Z. Huang
    SLAC, Menlo Park, California, USA
  • J.S. Liu
    Shanghai Institute of Optics and Fine Mechanics, Shanghai, People's Republic of China
  
  Free electron lasers (FELs) based on Laser Plasma Accelerators (LPAs) present a main research direction for achieving next generation compact advanced light sources. There are several major challenges of the LPA beam to generate high-brilliance FEL radiation including the large initial angular divergence and the large energy spread. Based on the LPA facility in SIOM that has successfully obtained quasi-monochromatic beam with the central energy of hundreds of MeV, a specific design of a beam transport line is proposed to realize FEL gain using Transverse Gradient Undulator to compensate the relatively large beam energy spread. This beamline uses a single dipole, several strong focusing quadrupoles and correcting sextupoles to match proper beta functions and linear dispersion from the LPA beam to FEL radiation. The corresponding experimental facility of LPA-FEL in SIOM has been set up and will perform first tests to generate FEL radiation.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB027  
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THPMW022 The RF Design of a Compact, High Power Pulse Compressor with a Flat Output Pulse cavity, klystron, flattop, linac 3591
 
  • P. Wang, H.B. Chen, J. Shi
    TUB, Beijing, People's Republic of China
  • I. Syratchev, W. Wuensch, H. Zha
    CERN, Geneva, Switzerland
  
  An X-band, high-power pulse compressor, which can produce a flat pulse and a power gain of 4.3, has been designed. The device is compact, with the dimensions of within 1m, and is designed for CLIC first energy stage based on klystrons. We also discuss about a two stage pulse compressor with power gain of 9.18, which may be a candidate of the X-FEL using CLIC X-band linacs and klystrons with low peak power.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW022  
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THPOW007 Cs2Te Photocathode Response Time Measurements and Femtosecond Comb Electron Beam Generation as a Milestone Towards Pre-Bunched Thz Fel Realization electron, radiation, laser, gun 3941
 
  • A. Aryshev, Y. Honda, K. Lekomtsev, M. Shevelev, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  
  Funding: Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan and JSPS KAKENHI: 23226020 and 24654076
Currently there is a rapidly growing demand to increase the brightness of electron beams generated by conventional RF guns as well as to decrease the cost of the injector accelerator system for many research facilities worldwide. To address this demand we investigate one of the most important parameter of the high Q.E. conventional semiconductor Cs2Te photocathode, its response time. It sets the principle limitation for generated bunch length and hence maximum achievable beam brightness of electron diffraction and pre-bunched THz FEL facility's injectors. The experimental investigation was done at KEK: LUCX facility. The Cs2Te photocathode response time better than 250 fs was demonstrated. The generation of 4 micro-bunch comb electron beam with variable time separation as a crucial technology for pre-bunched THz FEL realization was achieved. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW007  
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THPOW008 DC Photoemission Gun Upgrade at the Compact ERL gun, operation, high-voltage, vacuum 3944
 
  • N. Nishimori, R. Hajima, R. Nagai
    JAEA, Ibaraki-ken, Japan
  • Y. Honda, T. Miyajima, T. Uchiyama, M. Yamamoto
    KEK, Ibaraki, Japan
  • M. Mori
    JAEA/Kansai, Kyoto, Japan
  
  Funding: This work is partially supported by a JSPS Grant-in-Aid for Scientific Research in Japan (15H03594).
The DC photoemission gun at the compact ERL (cERL) has stably provided beam for ERL commissioning and laser Compton scattering experiments since April 2013. The operational voltage has however been limited to 390 kV due to failures of two segments out of the ten segmented insulator. In order to recover 500 kV operation, we installed an additional two segmented insulator on the existing ten segmented insulator during summer shutdown in 2015. The details of the gun upgrade and the operational experience of the upgraded cERL gun will be presented. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW008  
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THPOW045 Development of PAL-XFEL Undulator System undulator, laser, electron, radiation 4044
 
  • D.E. Kim, Y.-G. Jung, H.-S. Kang, I.S. Ko, H.-G. Lee, S.B. Lee, W.W. Lee, B.G. Oh, K.-H. Park, H.S. Suh
    PAL, Pohang, Kyungbuk, Republic of Korea
  • J. Pflüger
    XFEL. EU, Hamburg, Germany
  
  Pohang Accelerator Laboratory (PAL) is developing a 0.1 nm SASE based FEL based on 10 GeV S-band linear accelerator named PAL-XFEL. At the first stage, PAL-XFEL needs two undulator lines for photon source. The hard X-ray undulator line requires 20 units of 5 m long hybrid-type conventional planar undulator and soft X-ray line requires 7 units of 5 m long hybrid type planar undulators. PAL is developing undulator magnetic structure based on EU-XFEL concepts. In this report, the results of final pole height tuning results, and magnetic measurement results will be presented.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW045  
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THPOY057 RF Timing Distribution and Laser Synchronization Commissioning of PAL-XFEL timing, laser, linac, LLRF 4234
 
  • C.-K. Min, S.H. Jung, H.-S. Kang, C. Kim, I.S. Ko, S.J. Park
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  PAL-XFEL requires <100 fs synchronization of LLRF systems and optical lasers for stable operation and even lower jitter is favorable in higher performance and pump-probe experiments. The RF timing distribution system is based on a 476 MHz reference line, which is converted to 2.856 GHz at 16 locations over 1.5 km distance using phase-locked DRO. The 2.856 GHz signals are amplified and split to 10 outputs, which is connected to LLRFs, BAMs, and DCMs through low timing drift cables. The jitter between two different PLDRO units is estimated to ~1 fs from 1 Hz to 1 MHz. The synchronization jitter between a Ti:sapphire laser and the 2.856 GHz signal is measured less than 20 fs.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY057  
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