Keyword: FEL
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MOPWA043 FEL Simulations with Ocelot optics, space-charge, simulation, electron 210
 
  • I.V. Agapov, G. Geloni
    XFEL. EU, Hamburg, Germany
  • M. Dohlus, I. Zagorodnov
    DESY, Hamburg, Germany
  • S.I. Tomin
    NRC, Moscow, Russia
  
  Ocelot has been developed as a multiphysics simulation tool for FEL and synchrotron light source studies. In this work we highlight recent code developments focusing on electron tracking in linacs taking into account collective effects and on x-ray optics calculations  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA043  
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MOPJE008 Suppression of Microbunching Instability via a Transverse Gradient Undulator electron, linac, simulation, laser 300
 
  • D. Huang, H.X. Deng, C. Feng, D. Gu, Q. Gu, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  
  Funding: the Major State Basic Research Development Program of China (2011CB808300) and the National Natural Science Foundation of China (11275253, 11475250 and 11322550).
The microbunching instability in the linear accelerator (linac) of a free-electron laser facility has always been a problem that degrades the electron beam quality. In this paper, a quite simple and inexpensive technique is proposed to smooth the electron beam current profile to suppress the instability. By directly adding a short undulator with transverse gradient field right after the injector to couple the transverse spread into the longitudinal direction, additional density mixing in the electron beam is introduced to smooth the current profile, which results in the reduction of the gain of the microbunching instability. The magnitude of the density mixing can be easily controlled by turning the strength of the undulator magnet field. Theoretical analysis and numerical simulations demonstrate the capability of the proposed technique in the accelerator of an X-Ray free-electron laser. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE008  
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MOPJE062 Testing Aspects of Advanced Coherent Electron Cooling Technique electron, hadron, bunching, collider 445
 
  • V. Litvinenko, Y.C. Jing, I. Pinayev, G. Wang
    BNL, Upton, Long Island, New York, USA
  • D.F. Ratner
    SLAC, Menlo Park, California, USA
  • V. Samulyak
    SBU, Stony Brook, USA
  
  An advanced version of the coherent-electron cooling based on the microbunching instability was proposed in *. This approach promised to significantly increase the bandwidth of the system and, therefore, significantly shorter cooling time in high energy hadron colliders. In this paper we present our plans of simulating and testing the key aspects of this proposed technique using the set-up of the coherent-electron-cooling proof-of-principle experiment at BNL.
* D.F. Ratner, Phys. Rev. Lett. 111, 084802 (2013)
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE062  
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MOPMA054 Start-to-end Simulation of Free-electron Lasers simulation, wiggler, linac, electron 675
 
  • C.C. Hall, S. Biedron, H. Freund, S.V. Milton
    CSU, Fort Collins, Colorado, USA
  
  Start-to-end (S2E) modeling of free-electron lasers (FELs) normally requires the use of multiple codes to correctly capture the physics in each region of the machine. Codes such as PARMELA, IMPACT-T or MICHELLE, for instance, may be used to simulate the injector. From there the linac and transport line may be handled by codes such as DIMAD, ELEGANT or IMPACT-Z. Finally, at the FEL a wiggler interaction code such as GENESIS, GINGER, or MINERVA must be used. These codes may be optimized to work with a wide range in magnitude of macro-particle numbers (from 104-108 in different codes) and have different input formats. It is therefore necessary to have translator codes to provide a bridge between each section. It is essential that these translators be able to preserve the statistical properties of the bunch while raising or lowering the number of macro-particles used between codes. In this work we show a suite of such translators designed to facilitate S2E simulations of an FEL with a new wiggler code, MINERVA, and use these codes to provide benchmarking of MINERVA against other common wiggler simulation codes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA054  
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MOPMN009 Cross-platform and Cloud-based Access to Multiple Particle Accelerator Codes via Application Containers Linux, simulation, radiation, software 720
 
  • D.L. Bruhwiler, G. Andonian, M.A. Harrison, S. Seung
    RadiaBeam, Santa Monica, California, USA
  • D.L. Bruhwiler, R. Nagler, S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
  • P. Moeller
    Bivio Software Inc., Boulder, USA
  • T.V. Shaftan
    BNL, Upton, Long Island, New York, USA
  
  Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0006284.
Particle accelerator and radiation modeling codes focus on specific problems, rely on complicated command-line interfaces, are sometimes limited to a small number of computing platforms, and can be difficult to install. There is also a growing need to use two or more codes together for end-to-end design or for complicated sub-systems. RadTrack is a lightweight cross-platform GUI for such codes, based on the Qt framework and PyQt bindings for Python. RadTrack is designed to support multiple codes, placing no burden on the corresponding development teams. Elegant and the Synchrotron Radiation Workshop (SRW) are supported now in a pre-beta stage, and support for GENESIS 1.3 is under development. These codes are being containerized via the open source Docker platform for use in the cloud. The open source Vagrant and Virtual Box are used for MacOS and Windows. We discuss RadTrack and our vision for cloud computing. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN009  
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MOPHA032 All-Optical Synchronization of Pulsed Laser Systems at FLASH and XFEL laser, timing, LLRF, controls 854
 
  • J.M. Müller, M.K. Czwalinna, M. Felber, M. Schäfer, H. Schlarb, B. Schmidt, S. Schulz, C. Sydlo, F. Zummack
    DESY, Hamburg, Germany
  
  The all-optical laser synchronization at FLASH and XFEL provides femtosecond-stable timing of the FEL X-ray photon pulses and associated optical laser pulses (photo-injector laser, seed laser, pump-probe laser, etc.). Based on a two-color balanced optical cross-correlation scheme a high-precision measure of the laser pulse arrival time is delivered, which is used for diagnostic purposes as well as for the active stabilization of the laser systems. In this paper, we present the latest installations of our all-optical synchronization systems at FLASH and the recent developments for the upcoming European XFEL that will ensure a reliable femtosecond-stable timing of FEL and related pulsed laser systems.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPHA032  
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MOPHA035 Beam Optics Measurements at FLASH2 extraction, undulator, linac, optics 863
 
  • M. Scholz, M. Vogt, J. Zemella
    DESY, Hamburg, Germany
  
  FLASH2 is a newly build second beamline at FLASH, a soft X-ray FEL at DESY, Hamburg. Unlike the existing beamline FLASH1, it is equipped with variable gap undulators. This beamline is currently being commissioned. Both undulator beamlines of FLASH are driven by a common linear accelerator. Fast kickers and a septum are installed at the end of the linac to distribute the electron bunches of every train between FLASH1 and FLASH2. A specific beam optics in the extraction arc with horizontal beam waists in the bending magnets is mandatory in order to mitigate effects from coherent synchrotron radiation (CSR). We performed various beam optics measurements to ensure that the conditions for FEL operation at FLASH2 are fulfilled. Here we will show results of measurements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPHA035  
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MOPTY023 Beam Diagnostic of the LINAC for the Compact High-Performance THz-FEL linac, gun, emittance, target 987
 
  • T. Hu, Q.S. Chen, K.F. Liu, B. Qin, P. Tan, Y.Q. Xiong, J. Yang
    HUST, Wuhan, People's Republic of China
  • W. Chen
    Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China
  • J. Liu, Y.J. Pei, Z.X. Tang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • Z.M. Wang
    Chinagray, Hefei, Anhui, People's Republic of China
  
  With the aim to obtain short-pulse bunches with high peak current for a terahertz radiation source, an FEL-based LINAC is employed in HUST THz-FEL, and the LINAC consists of an EC-ITC RF gun, a disk-loaed waveguide structure with a constant gradient and collinear absorbing loads with focusing coils surrounded and so on. To achieve a balance between compactness and high performance, beam diagnostic system should be simple and high-precision. So that a cost-effective measurement scheme for the high-brightness beam extracted by the LINAC is needed. This paper will describe the beam line and beam diagnostic system of the LINAC in the HUST THz-FEL in detail and give corresponding assembly scheme. In addition, online monitor system is introduced.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPTY023  
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MOPWI022 Experimental Study of a Two-Color Storage Ring FEL wiggler, operation, storage-ring, electron 1198
 
  • J. Yan, H. Hao, S.F. Mikhailov, V. Popov, Y.K. Wu
    FEL/Duke University, Durham, North Carolina, USA
  • S. Huang
    PKU, Beijing, People's Republic of China
  • J.Y. Li
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • N. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
  • J. Wu
    SLAC, Menlo Park, California, USA
  
  Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
Multi-color Free-electron Lasers (FELs) have been developed on linac based FELs over the past two decades. On the storage ring, the optical klystron (OK) FEL in its early days was demonstrated to produce lasing at two adjacent wavelengths with their spectral separation limited by the bandwidth of single wiggler radiation. Here, we report a systematic experimental study on the two-color operation at the Duke FEL facility, the first experimental demonstration of a tunable two-color harmonic FEL operation of a storage ring based FEL. We demonstrate a simultaneous generation of two FEL wavelengths, one in infrared (IR) and the other in ultraviolet (UV) with a harmonic relationship. The experimental results show a good performance of the two-color FEL operation in terms of two-color wavelength tunability, power tunability and power stability. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWI022  
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TUBC3 Recent Results from FEL seeding at FLASH electron, laser, operation, radiation 1366
 
  • J. Bödewadt, S. Ackermann, R.W. Aßmann, N. Ekanayake, B. Faatz, G. Feng, I. Hartl, R. Ivanov, T. Laarmann, J.M. Müller, T. Tanikawa
    DESY, Hamburg, Germany
  • S. Ackermann, Ph. Amstutz, A. Azima, M. Drescher, L.L. Lazzarino, C. Lechner, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Roßbach
    Uni HH, Hamburg, Germany
  • K.E. Hacker, S. Khan, R. Molo
    DELTA, Dortmund, Germany
  
  The free-electron laser facility FLASH at DESY operates since several years in SASE mode, delivering high-intensity FEL pulses in the extreme ultra violet and soft x-ray wavelength range for users. In order to get more control of the characteristics of the FEL pulses external FEL seeding has proven to be a reliable method to do so. At FLASH, an experimental setup to test several different external seeding methods has been installed since 2010. After successful demonstration of direct seeding at 38 nm, the setup is now being operated in HGHG and later EEHG mode. Furthermore, other studies on laser induced effects on the electron beam dynamics have been performed. In this contribution, we give an overview of recent experimental results on FEL seeding at FLASH.  
slides icon Slides TUBC3 [6.651 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUBC3  
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TUPWA002 Layout Options for the AXXS Injector and XFEL linac, storage-ring, lattice, dipole 1394
 
  • M.J. Boland, Y.E. Tan, D. Zhu
    SLSA, Clayton, Australia
  
  A new injector is being planned for the Australian Synchrotron that is designed to feed both an upgraded storage ring and an XFEL. The desire to fit the AXXS project on the same site as the existing light source presents several layout difficulties. Several options are studied and simulations are performed to check the impact each choice has on the beam performance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA002  
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TUPWA005 Comparison of Bunch Compression Schemes for the AXXS FEL linac, simulation, electron, synchrotron 1399
 
  • T.K. Charles, D.M. Paganin
    Monash University, Faculty of Science, Clayton, Victoria, Australia
  • A.A. Aksoy
    Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
  • M.J. Boland, R.T. Dowd
    SLSA, Clayton, Australia
  • A. Latina, D. Schulte
    CERN, Geneva, Switzerland
  
  Different types of electron bunch compression schemes are compared for the AXXS FEL design study. The main linac for the proposed machine is based on CLIC x-band structures. This choice leaves several options for the bunch compression schemes which impact the injection system RF band. Both harmonic linearization and phase modulation linearization are considered and their relative strengths and weaknesses compared. Simulations were performed to compare the performance of an s-band injector with a higher harmonic RF linearization and an x-band injector. One motivation for the study is to optimise the length of the AXXS machine, allowing the linac to fit onto the proposed and also act as the injector to the existing storage ring at the Australian Synchrotron.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA005  
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TUPWA008 Mixing and Space-Charge Effects In Free-Electron Lasers laser, electron, radiation, space-charge 1410
 
  • E.A. Peter, A. Endler, F.B. Rizzato
    IF-UFRGS, Porto Alegre, Brazil
  • A.P.B. Serbeto
    UFF, Niterói - RJ, Brazil
  
  Funding: This work was supported by CNPq and FAPERGS, Brazil, and by the Air Force Office of Scientific Research (AFOSR), USA, under the Grant No. FA9550-12-1-0438
Free-electron lasers are devices which efficiently convert the kinetic energy from a relativistic electron beam into electromagnetic radiation, amplifying an initial small sign. The present work revisits the subject of mixing, saturation and space-charge effects in free-electron lasers. Use is made of the compressibility factor, which proves to be a helpful tool in the related systems of charged beams confined by static magnetic fields. The compressibility allows to build a semi-analytical model and to perform analytical estimates of the elapsed time until the onset of mixing, which in turn allows to estimate the saturated amplitude of the radiation field. In addition, the compressibility helps to pinpoint space-charge effects and the corresponding transition from Compton to Raman regimes. The semi-analytical model and the particles simulations are compared, exhibiting a good agreement.*
* E. Peter, A. Endler, F. B. Rizzato, and A. Serbeto, Phys. Plasmas 20,
123104 (2013).
** E. Peter, A. Endler, and F. B. Rizzato, Phys. Plasmas 21, 113104 (2014) 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA008  
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TUPWA011 Progress on the LUNEX5 project laser, undulator, electron, operation 1416
 
  • M.-E. Couprie, C. Benabderrahmane, P. Berteaud, C. Bourassin-Bouchet, F. Bouvet, J.D. Bozek, F. Briquez, L. Cassinari, L. Chapuis, J. Da Silva, J. Daillant, Y. Dietrich, M. Diop, J.P. Duval, M.E. El Ajjouri, T.K. El Ajjouri, C. Herbeaux, N. Hubert, M. Khojoyan, M. Labat, P. Lebasque, N. Leclercq, A. Lestrade, A. Loulergue, P. Marchand, O. Marcouillé, J.L. Marlats, F. Marteau, C. Miron, P. Morin, A. Nadji, R. Nagaoka, F. Polack, F. Ribeiro, J.P. Ricaud, P. Rommeluère, P. Roy, G. Sharma, K.T. Tavakoli, M. Thomasset, M. Tilmont, S. Tripathi, M. Valléau, J. Vétéran, W. Yang, D. Zerbib
    SOLEIL, Gif-sur-Yvette, France
  • S. Bielawski, C. Evain
    PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
  • B. Carré, D. Garzella
    CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette, France
  • X. Davoine
    CEA/DAM/DIF, Arpajon, France
  • N. Delerue
    LAL, Orsay, France
  • G. Devanz, C. Madec, A. Mosnier
    CEA/IRFU, Gif-sur-Yvette, France
  • A. Dubois, J. Lüning
    CCPMR, Paris, France
  • G. Lambert, V. Malka, A. Rousse, C. Thaury
    LOA, Palaiseau, France
  • E. Roussel
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • C. Szwaj
    PhLAM/CERLA, Villeneuve d'Ascq, France
  
  LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, coherent Free Electron Laser (FEL) pulses in the 40-4 nm spectral range. It comprises a 400 MeV superconducting Linear Accelerator for high repetition rate operation (10 kHz), multi-FEL lines and adapted for studies of advanced FEL schemes, a 0.4 - 1 GeV Laser Wake Field Accelerator (LWFA) for its qualification by a FEL application, a single undulator line enabling advanced seeding and pilot user applications. Different studies such as on two color FEL and R&D programs have been launched. A test experiment for the demonstration of 180 MeV LWFA based FEL amplification at 200 nm is under preparation in collaboration with the Laboratoire d’Optique Appliquée, thanks to a proper electron beam manipulation. Specific hardware is also under development such as a cryo-ready 3 m long undulator of 15 mm period.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA011  
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TUPWA026 Simulation of Optical Transport Beamlines for High-quality Optical Beams for Accelerator Applications laser, electron, polarization, simulation 1462
 
  • J. Bödewadt, N. Ekanayake
    DESY, Hamburg, Germany
  
  High-quality optical beams play already an important role in the field of particle accelerators which will most probably become even more prominent in the view of laser-driven particle accelerators. Nowadays, optical transport systems are needed for particle generation in photo injectors, for particle acceleration in laser-driven plasma wakefield accelerators, for particle beam diagnostics such as synchrotron radiation monitoring systems, or for particle manipulation schemes e.g. for external seeding of free-electron lasers. For the latter case, also the photon beam transport to the user end-stations requires dedicated optical transport system. The utilized wavelengths range from the hard x-ray up to the far-infrared spectral range. Parameters like surface quality, polarization effects, damage thresholds in- and out-of-vacuum, mechanical stability, dispersion effect etc. need to be studied for the variaty of applications. Here, we present the simulation results of the optical transport beamline for the seeding setup at FLASH and give a comparision to our measurement results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA026  
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TUPWA033 Status of the Soft X-ray Free Electron Laser FLASH operation, optics, laser, photon 1482
 
  • M. Vogt, B. Faatz, J. Feldhaus, K. Honkavaara, S. Schreiber, R. Treusch
    DESY, Hamburg, Germany
  
  The superconducting free-electron laser FLASH at DESY routinely produces up to several thousand photon pulses per second with wavelengths in the soft X-ray and vacuum UV regime and with energies up to 0.5 mJ per pulse. In 2014 the assembly of a second undulator beamline, FLASH2, was finished. While recommissioning of the FLASH linac and the original FLASH1 beamline was finished already at the end of 2013, the commissioning of FLASH2 could only be started in early February 2014. Only a few weeks have been reserved for dedicated set up of FLASH2, and most of its commissioning has been performed parasitically during the FLASH1 user run. The first beam was extracted through the septum to the FLASH2 beamline on March 4th, 2014, and the first lasing of FLASH2 at a wavelength of about 40 nm was achieved on August 20th, while FLASH1 was lasing simultaneously with 250 bunches at 13.5 nm. We summarize here the status of the FLASH2 commissioning and the FLASH1 operation during its 5th user period.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA033  
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TUPWA035 Progress in Optics Studies at FLASH optics, quadrupole, linac, free-electron-laser 1488
 
  • J. Zemella, T. Hellert, M. Scholz, M. Vogt
    DESY, Hamburg, Germany
  
  FLASH is the superconducting soft X-ray Free Electron Laser in Hamburg at DESY, Germany. Good control over the beam optics is a key aspect of the operation of a SASE FEL. In 2013 a second beam line, FLASH2, was assembled and the modifications necessary to feed the two beam lines were installed downstream of the FLASH linac. As reported before * we started a campaign of optics consolidation. We give an update on the progress of this effort and on results.
* J. Zemella, T. Hellert, M.Scholz, M.Vogt, "Measurements of the Optical Functions at FLASH", Proc. of IPAC'14, TUPRO050. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA035  
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TUPWA036 Possibility of Longitudinal Bunch Compression in Petra III emittance, optics, undulator, storage-ring 1492
 
  • I.V. Agapov
    XFEL. EU, Hamburg, Germany
  • S.I. Tomin
    NRC, Moscow, Russia
  • R. Wanzenberg
    DESY, Hamburg, Germany
  
  A scheme of short bunch production in storage rings using a longitudinally focusing insertion was presented in *. In this work we study the possibility of integrating such insertion into the PetraIII storage ring. In particular, we discuss possible optics solutions to integrate RF stations, chicane-type delay sections, and the undulators into existing ring geometry.
* I. Agapov and G. Geloni, proc. FEL 2014. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA036  
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TUPWA037 Statistical Optimization of FEL Performance quadrupole, controls, simulation, alignment 1496
 
  • I.V. Agapov, G. Geloni
    XFEL. EU, Hamburg, Germany
  • I. Zagorodnov
    DESY, Hamburg, Germany
  
  Modern FEL facilities such as the European XFEL will serve large number of users, thus understanding and optimizing their performance parameters such as the output power is important. In this work we describe the statistical approach to such optimization under assumption that the possibility of modelling is limited by uncertainties. We present results of such statistical optimization of SASE radiation power for FLASH and discuss how the results of such empirical tuning can be fed back into the model used in simulations  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA037  
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TUPWA038 Optics Compensation for Variable-gap Undulator Systems at FLASH undulator, optics, quadrupole, electron 1499
 
  • Ph. Amstutz, C. Lechner, T. Plath
    Uni HH, Hamburg, Germany
  • S. Ackermann, J. Bödewadt, M. Vogt
    DESY, Hamburg, Germany
  
  Variable-gap undulator systems are widely used in storage rings and linear accelerators to generate soft- and hard x-ray radiation for the photon science community. For cases where the effect of undulator focusing significantly changes the electron beam optics, a compensation is needed in order to keep the optics constant in other parts of the accelerator. Since 2010, the free-electron laser (FEL) facility FLASH is equipped with two undulator sections along the same electron beamline. The first undulator is a variable-gap system used for seeding experiments, the second undulator is a fixed-gap system which serves the user facility with FEL radiation. Varying the gap in the first undulator will change the beam optics such that the FEL process in the second undulator is dramatically disturbed. For the correction of the beam optics an analytical model is used to generate feed forward tables which allows to make part of the beamline indiscernible for the subsequent sections. The method makes use of the implicit function theorem and can be used for any perturbation of the beam optics. Here, we present the method and its implementation as well as measurements performed at FLASH.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA038  
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TUPWA039 Transverse Gradient Undulator-Based High-Gain-FELs - a Parameter Study undulator, laser, electron, resonance 1502
 
  • A. Bernhard, V. Afonso Rodríguez, E. Burkard, A.-S. Müller, C. Widmann
    KIT, Karlsruhe, Germany
  
  Transverse gradient undulators (TGU) have recently been discussed as sources for High Gain Free Electron Lasers (FEL) driven by electron beams with an elevated energy spread as for example generated in storage rings or wakefield accelerators. In this contribution we present the results of a parameter study based on the one-dimensional TGU-FEL theory making realistic assumptions on the key parameters achievable for the transverse gradient undulator. We show for which parameter areas LWFA-driven TGU-FELs are virtually technically feasible today and which technical improvements would be required to employ the concept for a laboratory-scale X-Ray FEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA039  
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TUPWA053 Influence of a Non-uniform Longitudinal Heating on High Brightness Electron Beams for FEL electron, laser, undulator, linac 1535
 
  • E. Roussel, E. Allaria, M.B. Danailov, G. De Ninno, S. Di Mitri, E. Ferrari, D. Gauthier, L. Giannessi, G. Penco
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  
  Laser-heater systems are essential tools to control and optimize high-gain free electron lasers (FELs), working in the x-ray wavelength range. Indeed, these systems induce a controllable heating of the energy spread of the electron bunch. The heating allows in turn to suppress longitudinal microbunching instabilities limiting the FEL performance. In this communication, we show that a long-wavelength energy modulation of the electron beam induced by the laser heater can persist until the beam entrance in the undulators, affecting the FEL emission process. This non-uniform longitudinal heating can be exploited to investigate the electron-beam microbunching in the linac, as well as to control the FEL spectral properties. Here, we present experimental, analytical and numerical studies carried out at FERMI.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA053  
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TUPWA054 The FERMI Seeded FEL Facility: Operational Experience and Future Perspectives laser, experiment, electron, operation 1538
 
  • M. Svandrlik, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, 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, A. Fabris, 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, C. Masciovecchio, M. Milloch, F. Parmigiani, G. Penco, 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, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  
  FERMI is the seeded FEL user facility in Trieste, Italy, producing photons from the VUV to the soft X-rays with a high degree of coherence and spectral stability. Both FEL lines, FEL-1 and FEL-2, are now available for users, down to the shortest wavelength of 4 nm. We will report on the completion of the commissioning of the high energy FEL line, FEL-2, and on the operational experience for users, in particular those requiring specific FEL configurations, like two-colour experiments. We will also give a perspective on the improvements and upgrades which have been triggered by our experience and are aiming to maintain as well as to constantly improve the performance of the facility for our user community.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA054  
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TUPWA063 FEL Enhancement by Microbuch Structure Made with Phase-Space Rotation laser, simulation, cavity, bunching 1570
 
  • M. Kuriki, Y. Seimiya
    HU/AdSM, Higashi-Hiroshima, Japan
  • S. Chen, K. Ohmi, J. Urakawa
    KEK, Ibaraki, Japan
  • S. Kashiwagi
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  • R. Kato
    ISIR, Osaka, Japan
  
  Funding: This work is partly supported by MEXT/JSPS KAKENHI (Grant-in-Aid for scientic research) 25390126, Japan.
FEL is one of the ideal radiation source over the wide range of wavelength region with a high brightness and a high coherence. Many methods to improve FEL gain has been proposed by introducing an active modulation on the bunch charge distribution. The transverse-longitudinal phase-space rotation is one of the promising method to realize the density modulation as the micro-bunch structure. Initially, a beam density modulation in the transverse direction made by a mechanical slit, is properly transformed into the density modulation in the longitudinal direction by the phase-space rotation. The micro-bunch structure made with this method has a large tunability by changing the slit geometry, the beam line design, and the beam dynamics tuning. For FEL, enegy chirp made by the emittance exchange and chromaticity made by this chirp should be properly corrected. Simulation results and possible applications are discussed. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA063  
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TUPJE019 Operating Cascaded High-gain Harmonic Generation with Double-pulse Electron Beams electron, radiation, laser, simulation 1661
 
  • Z. Wang, C. Feng, Q. Gu, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  • L. Yu
    BNL, Upton, Long Island, New York, USA
  
  Cascaded high gain harmonic generation (HGHG) is the primary candidate for the generation of high power, full temporal coherent radiation at the wavelength of nanometer. However, the experimental results at the existing facility show large fluctuation of the output energy pulse at the second stage of cascading. In this paper, we study the scheme of double-pulse electron beams, which is helpful to increase the stability of pulse energy against the timing jitter. The method to generate double-pulse electron beams is shown in the paper and comparison between double-pulse scheme and standard cascaded HGHG is present base on three-dimensional start-to-end simulation to give a straightforward image on the obviously improvement of the FEL stability.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE019  
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TUPJE032 Updates of the PAL-XFEL Undulator Program undulator, background, electron, controls 1675
 
  • D.E. Kim, M.-H. Cho, 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
  • S. Karabekyan, 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 18 units of 5 m long hybrid-type conventional planar undulator and soft X-ray line requires 6 units of 5 m long hybrid type planar undulator with additional few EPUs for final polarization control. PAL is developing undulator magnetic structure based on EU-XFEL concepts. The key parameters are min pole gap of 8.3 mm, with period length 26 mm (HXU), 35 mm (SXU), and 5.0 m magnetic length. . In this report, the prototyping, and the development of pole tuning procedure, the impact of the background field error, and the effects of the girder bending on the optical phase error will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE032  
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TUPJE052 Bunch Compression in the Driver Linac for the Proposed NSRRC VUV FEL electron, linac, optics, gun 1738
 
  • N.Y. Huang, W.K. Lau, A.P. Lee
    NSRRC, Hsinchu, Taiwan
  • A. Chao, K. Fang, M.-H. Wang, J. Wu
    SLAC, Menlo Park, California, USA
  
  A bunch compressor is designed for the S-band driver linac system of the proposed NSRRC VUV free electron laser (FEL). Instead of using a more conventional rf harmonic linearizer, one main feature of this compressor is to use electron linearization optics to correct the nonlinearity in the energy-time correlation of the electron bunch longitudinal phase space. The strategy of compressor design will be discussed by an analytical calculation and particle tracking simulation. The beam dynamics which include the collective instabilities such as the space charge effects, the wake fields and the coherent synchrotron radiation (CSR) effects are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE052  
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TUPJE054 Developments in CLARA Accelerator Design and Simulations laser, simulation, undulator, linac 1744
 
  • P.H. Williams, D. Angal-Kalinin, A.D. Brynes, F. Jackson, J.K. Jones, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • S. Spampinati
    Cockcroft Institute, Warrington, Cheshire, 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. The layout changes include a dedicated collimator in CLARA front end to provide some control over the dark current, changes to low energy diagnostics section and modifications to FEL modules. The progress in the design simulations mainly focus on injector simulations incorporating wake fields in ASTRA, comparison of using ELEGANT and CSRTRACK for the Variable Bunch Compressor and first considerations of requirement of laser heater for CLARA.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE054  
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TUPJE073 Results of the Magnetic Tuning of 2.8 m Long Vertically Polarizing Undulator with the Dynamic Compensation of Magnetic Forces undulator, radiation, electron, free-electron-laser 1809
 
  • I. Vasserman
    ANL, Argonne, Ilinois, USA
  
  A novel undulator prototype with a horizontal magnetic field and dynamic compensation of magnetic forces has been recently developed at the APS as a part of the LCLS-II R&D program. This undulator should meet stringent requirements for any LCLS-II insertion device. These requirements include limits on the field integrals and phase errors for all operational gaps, and the reproducibility and accuracy of the gap settings. Extensive mechanical testing has resulted in a performance that meets the requirements on the undulator gap setting. The magnetic tuning has been accomplished by applying a set of magnetic shims. As a result, the satisfactory performance of the undulator prototype has been demonstrated.
The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory. Argonne, Contract No. DE-AC02-06CH11357. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE073  
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TUPJE074 LCLS Injector Laser Modulation to Improve FEL Operation Efficiency and Performance laser, electron, optics, emittance 1813
 
  • S. Li, D.K. Bohler, W.J. Corbett, A.S. Fisher, S. Gilevich, Z. Huang, A. Li, D.F. Ratner, J. Robinson, F. Zhou
    SLAC, Menlo Park, California, USA
  • R.B. Fiorito, E.J. Montgomery
    UMD, College Park, Maryland, USA
  • H.D. Zhang
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • H.D. Zhang
    The University of Liverpool, Liverpool, United Kingdom
  
  In the Linear Coherent Light Source (LCLS) at SLAC, the injector laser plays an important role as the source of the electron beam for the Free Electron Laser (FEL). The injector laser strikes a copper photocathode which emits photo-electrons due to photo-electric effect. The emittance of the electron beam is highly related to the transverse shape of the injector laser. Currently the LCLS injector laser has hot spots that degrade the FEL performance. The goal of this project is to use adaptive optics to modulate the transverse shape of the injector laser, in order to produce a desired shape of electron beam. With a more controllable electron transverse profile, we can achieve lower emittance for the FEL, improve the FEL performance and operation reliability. We first present various options for adaptive optics and damage test results. Then we will discuss the shaping process with an iterative algorithm to achieve the desired shape, characterized by Zernike polynomial deconstruction.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE074  
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TUPMA012 Developing an Improved Pulsed Mode Operation for Duke Storage Ring Based FEL operation, wiggler, storage-ring, damping 1860
 
  • S.F. Mikhailov, H. Hao, V. Popov, Y.K. Wu
    FEL/Duke University, Durham, North Carolina, USA
  
  Funding: This work is supported in part by the US DoE grant # DE-FG02-97ER41033
The Duke FEL and High Intensity Gamma-ray Source (HIGS) facility is operated with an e-beam from 0.24 to 1.2 GeV and a photon beam from 190 to 1060 nm. Currently, the energy range of the gamma-ray beam is from 1 MeV to about 100 MeV, with the maximum total gamma-ray flux about 3·1010 gammas per second around 10 MeV. The FEL is typically operated in quasi-CW mode. Some HIGS user experiments can benefit tremendously from a pulsed mode of FEL operation. For that purpose, a fast steering magnet was developed years ago to modulate the FEL gain. This FEL gain modulator decouples the e-beam from the FEL beam in the interaction region for most of time, but periodically allows a brief overlap of the electron and FEL beams. This allows us to build up a high peak power FEL pulse from a well-damped electron beam. However, the use of this gain modulator at low e-beam energies can dramatically limit e-beam current due to beam instability and poor injection. To overcome these shortcomings, we have successfully tested an RF frequency modulation technique to pulse the FEL beam. In this paper, we will describe this development, and report our preliminary results of this improved pulsed FEL operation. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA012  
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TUPMA014 Extending OK5 Wiggler Operational Limit at Duke FEL/HIGS Facility wiggler, operation, electron, controls 1863
 
  • P.W. Wallace, M. Emamian, H. Hao, J.Y. Li, S.F. Mikhailov, V. Popov, Y.K. Wu
    FEL/Duke University, Durham, North Carolina, USA
  • J.Y. Li
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  
  Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033
Since 2007 the HIGS facility has been operated to produce both linearly and circularly polarized gamma-ray beams using two FELs, the planar OK-4 FEL and helical OK-5 FEL. Presently, with the OK-5 FEL operating at 192 nm, we can produce circularly-polarized gamma-ray beams between 1 and 100 MeV for user applications. Gamma-ray production between 80 and 100 MeV required an extension of the OK-5 wiggler operation beyond the designed current limit of 3.0 kA. In 2009, we upgraded cooling and machine protection systems to successfully extend OK-5 operation to 3.5 kA. To realize HIGS gamma-ray operation beyond 100 MeV and ultimately toward 150 MeV (the pion-threshold energy), with various limitations of the VUV mirror technology, the OK-5 wigglers will need to be operated at an even higher current, between 3.6 and 4.0 kA. In this paper we present our technical solution to further extend the operation range of the OK-5 wigglers, and report our preliminary results with high-current wiggler operation. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA014  
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TUPMA016 Light Source and Accelerator Physics Research Program at Duke University wiggler, storage-ring, operation, electron 1866
 
  • Y.K. Wu
    FEL/Duke University, Durham, North Carolina, USA
  
  Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
The light source and accelerator physics research program at Duke Free-Electron Laser Laboratory (DFELL), TUNL, is focused on the development of the storage ring based free-electron lasers (FELs), and a state-of-the-art Compton gamma-ray source, the High Intensity Gamma-ray Source (HIGS) which is driven by the storage ring FEL. With a maximum total flux about 3·1010 gamma/s and a spectral flux of more than 1,000 gamma/s/eV around 10 MeV, the HIGS is the world's most intense Compton gamma-ray source. Operated in the energy range from 1 to 100 MeV, the HIGS is a premier Compton gamma-ray facility in the world for a variety of nuclear physics research programs, both fundamental and applied. In this paper, we will describe our ongoing light source development to produce gamma-ray beams in the higher energy range of 100 and 158 MeV. We will also provide a summary of our recent accelerator physics and FEL physics research activities. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA016  
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TUPMA017 Pulsed-wire Measurements for Insertion Devices undulator, electron, detector, laser 1869
 
  • A. D'Audney, S. Biedron, S.V. Milton, S.A. Stellingwerff
    CSU, Fort Collins, Colorado, USA
  
  The performance of a Free Electron Laser (FELs) depends in part on the integrity of the magnetic field in the undulator. The magnetic field on the axis of the undulator is transverse and sinusoidally varying due to the periodic sequence of dipoles. The ideal trajectory of a relativistic electron bunch, inserted along the axis, is sinusoidal in the plane of oscillation. Phase errors are produced when the path of the electron is not the ideal sinusoidal trajectory, due to imperfections in the magnetic field. The result of such phase errors is a reduction of laser gain impacting overall FEL performance. A pulsed-wire method can be used to determine the profile of the magnetic field. This is achieved by sending a square current pulse through the wire, which will induce an interaction with the magnetic field. Measurement of the displacement in the wire over time using a motion detector yields the first or second integrals of the magnetic field. Dispersion in the wire can be corrected using algorithms resulting in higher accuracy. Once the fields are known, magnetic shims are placed where any corrections are needed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA017  
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TUPMA021 Optimization of an Improved SASE (iSASE) FEL radiation, lattice, undulator, simulation 1881
 
  • L. Gupta
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • K. Fang, J. Wu
    SLAC, Menlo Park, California, USA
  
  Funding: Supported by US DOE FWP-2013-SLAC-100164 and DOE SULI.
In order to improve free electron laser technology for the future LCLSII at SLAC, a new strategy for creating radiation with increased temporal coherence is under development. The improved Self-Amplified Spontaneous Emission (iSASE) FEL utilizes phase shifters which allow for the spontaneously emitted radiation to interact with and stimulate more electrons to radiate coherently. Five phase shifters were simulated, with 34 normal-conducting undulators and focusing-defocusing quadrupoles as an LCLSII FEL lattice using the FEL software Genesis 1.3. Two general schemes, one providing a total phase shift of arbitrary distribution, the other providing a sequential or distributed phase shift, were simulated and optimized using a simulated annealing algorithm. The results suggest that the phase shifters must provide a total shift comparable to the bunch length, and the shifts must be distributed with one large shift, followed by smaller shifts.
* J. Wu, A. Marinelli, C. Pellegrini, Proc. FEL2012, pp. 237, Japan (2012).
** J. Wu, et al., Proc. IPAC2013, pp. 2068, China (2013). 		 
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TUPMA026 Status of the MaRIE X-FEL Accelerator Design linac, emittance, electron, undulator 1894
 
  • J.W. Lewellen, K. Bishofberger, B.E. Carlsten, L.D. Duffy, F.L. Krawczyk, Q.R. Marksteiner, D.C. Nguyen, S.J. Russell, R.L. Sheffield, N.A. Yampolsky
    LANL, Los Alamos, New Mexico, USA
  
  Funding: Work supported by the MaRIE program at Los Alamos National Laboratory, under contract DE-AC52-06NA25396
The Matter-Radiation Interactions in Extremes (MaRIE) facility is intended to probe and control the time-dependent properties of materials under extreme conditions. At its core, the “MaRIE 1.0” X-FEL is being designed to deliver pulse trains of ~1010 42 keV photons, with a minimum bunch spacing of 2.4 ns, enabling time-dependent studies particularly of mesoscale phenomena. The X-FEL accelerator is also intended to deliver a series of 2 nC electron bunches to enable electron radiography concurrently with the X-ray pulse train, so as to provide multi-probe capability to MaRIE. In 2014, the reference design for the MaRIE X-FEL 12 GeV driver linac was changed from an S-band normal-conducting to an L-band superconducting linac to accommodate pulse trains up to 100 μs in duration. This paper does not present a complete solution for the MaRIE linac design; rather it describes our current reference design, achieved parameters, areas of concern and paths towards mitigation of identified issues. 		 
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TUPMA028 Feasibility Study for an X-ray FEL Oscillator at the LCLS-II electron, cavity, undulator, laser 1897
 
  • T.J. Maxwell, J. Arthur, Y. Ding, W.M. Fawley, J.C. Frisch, J.B. Hastings, Z. Huang, J. Krzywinski, G. Marcus
    SLAC, Menlo Park, California, USA
  • W.M. Fawley
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • K.-J. Kim, R.R. Lindberg, D. Shu, Yu. Shvyd'ko, S. Stoupin
    ANL, Argonne, Ilinois, USA
  
  Funding: This work supported in part under US Department of Energy contract DE-AC02-76SF00515.
We show that a free-electron laser oscillator generating X-ray pulses with hard X-ray wavelengths of order 0.1 nm is feasible using the presently proposed FEL-quality electron beam within the space of existing LCLS-II infrastructure when combined with a low-loss X-ray crystal cavity. In an oscillator configuration driven by the 4 GeV energy electron beam lasing at the fifth harmonic, output x-ray bandwidths as small as a few meV are possible. The delivered average spectral flux is at least two orders of magnitude greater than present synchrotron-based sources with highly stable, coherent pulses of duration 1 ps or less for applications in Mössbauer spectroscopy and inelastic x-ray scattering. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA028  
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TUPMA031 Dispersive Property of the Pulse Front Tilt of a Short Pulse Optical Undulator laser, optics, electron, undulator 1904
 
  • M.-H. Wang, J. Wu, Z. Wu
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by the US DOE No. DE-AC02-76SF00515.
A short pulse laser can be used as an optical undulator to achieve a high-gain and high-brightness X-ray free electron laser (FEL) [1]. To extend the interaction duration of electron and laser field, the electron and the laser will propagate toward each other with an small angle. In addition, to maintain the FEL lasing resonant condition, the laser pulse shape need be flattened and the pulse front will be titled. Due to the short pulse duration, the laser pulse has a broad bandwidth. In this paper, we will first describe the method of generalized Gaussian beam propagation using ray matrix. By applying the Gaussian beam ray matrix, we can study the dispersive property after the pulse front of the short laser is tilted. The results of the optics design for the proposal of SLAC Compton scattering FEL are shown as an example in this paper.
[1] C. Chang, et al.,“High-brightness X-ray free-electron laser with an optical undulator by pulse shaping”. Optics Express, Vol. 21, Issue 26, pp. 32013-32018 (2013). 		 
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TUPMA033 A Bunch Compression Method for Free Electron Lasers that Avoids Parasitic Compressions electron, dipole, laser, acceleration 1907
 
  • S.V. Benson, D. Douglas, C. Tennant, F.G. Wilson
    JLab, Newport News, Virginia, USA
  • D.C. Nguyen
    LANL, Los Alamos, New Mexico, USA
  
  Funding: This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150, the Air Force Office of Scientific Research, DOE Basic Energy Sciences.
Virtually all existing high energy (>few MeV) linac-driven FELs compress the electron bunch length though the use of off-crest acceleration on the rising side of the RF waveform followed by transport through a magnetic chicane. This approach has at least three flaws: 1) it is difficult to correct aberrations- particularly RF curvature, 2) rising side acceleration exacerbates space charge-induced distortion of the longitudinal phase space, and 3) all achromatic "negative compaction" compressors create parasitic compression during the final compression process, increasing the CSR-induced emittance growth. One can avoid these deficiencies by using acceleration on the falling side of the RF waveform and a compressor with M56>0. This approach offers multiple advantages: 1) It is readily achieved in beam lines supporting simple schemes for aberration compensation, 2) Longitudinal space charge (LSC)-induced phase space distortion tends, on the falling side of the RF waveform, to enhance the chirp, and 3) Compressors with M56>0 can be configured to avoid spurious over-compression. We will discuss this bunch compression scheme in detail and give results of a successful beam test in April 2012 using the JLab UV Demo FEL 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA033  
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TUPMA041 On the Characterization of a CCR Source brightness, radiation, impedance, emittance 1926
 
  • A.V. Smirnov
    RadiaBeam, Santa Monica, California, USA
  
  Funding: US Department of Energy, contract # DE- SC-FOA-0000760
Peak and spectral brightness of a resonant long-range wakefield extractor are evaluated. It is shown that the brightness is dominated by beam density within the slow wave structure and antenna gain of the outcoupling. Far field radiation patterns and brightness of circular and high-aspect-ratio planar radiators are compared. A possibility to approach the diffraction limited brightness is demonstrated. Role of group velocity in designing of the Cherenkov source is emphasized. The approach can be applied for design and characterization of various structure-dominated sources (e.g., wakefield extractors with gratings or dielectrics, or FEL-Cherenkov combined sources) radiating into a free space using an antenna (from microwave to far infra-red regions). The high group velocity structures can be also effective as energy dechirpers and for diagnostics of microbunched relativistic electron beams. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA041  
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TUPMA043 Experimental Test of Semiconductor Dechirper electron, wakefield, experiment, emittance 1932
 
  • S.P. Antipov, S.V. Baryshev, C.-J. Jing, A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S. Baturin
    LETI, Saint-Petersburg, Russia
  • M.G. Fedurin, K. Kusche, C. Swinson
    BNL, Upton, Long Island, New York, USA
  • W. Gai, S. Stoupin, A. Zholents
    ANL, Argonne, Illinois, USA
  
  Funding: Work supported by the Department of Energy SBIR program under Contract #DE-SC0006299
We report the observation of de-chirping of a linearly chirped (in energy) electron bunch by its passage through a 4 inch long rectangular waveguide loaded with two silicon bars 0.25 inch thick and 0.5 inch wide. Silicon being a semiconductor has a conductivity that allows it to drain the charge fast in case if some electrons get intercepted by the dechirper. At the same time the conductivity is low enough for the skin depth to be large (on the order of 1 cm) making the silicon loaded waveguide a slow wave structure supporting wakefields that dechirp the beam. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA043  
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TUPWI017 Single-shot Multi-MeV Ultrafast Electron Diffraction on VELA at Daresbury Laboratory electron, gun, scattering, experiment 2278
 
  • L.K. Rudge, D. Angal-Kalinin, J.A. Clarke, F. Jackson, J.K. Jones, A. Kalinin, S.L. Mathisen, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, Y.M. Saveliev, D.J. Scott, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • P. Aden, R.J. Cash, D.M.P. Holland, M.D. Roper
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • P.D. Lane, D.A. Wann
    University of York, York, United Kingdom
  • M. Surman
    STFC/DL/SRD, Warrington, Cheshire, United Kingdom
  • J.G. Underwood
    UCL, London, United Kingdom
  
  Funding: This work was funded by STFC
Accelerator based Ultrafast Electron Diffraction (UED) is a technique for obtaining static structures and for studying sub-100 fs dynamic structural changes on the atomic scale. In this paper we present the first electron diffraction results obtained from the VELA accelerator in 2014. The accelerator was operated to provide typically 4MeV/c electron bunches. Diffraction patterns were observed with <<1 pC transported to the detection screen. Single shot and multi-shot accumulated diffraction data are presented from single crystal and polycrystalline samples, including Au, Al, Pt and C. Contamination of the diffraction pattern with dark current contributions is an issue. A variable size aperture directly in front of the sample offers some mitigation, but at the expense of reduced charge contributing to the diffraction pattern. We discuss future developments for electron diffraction on VELA including further beam optimization, measurement of bunch length with a newly installed Transverse Deflecting Cavity, and the planned developments for pump-probe studies. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWI017  
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WEXB1 Coherent Synchrotron Radiation in Energy Recovery Linacs electron, experiment, linac, dipole 2387
 
  • C.C. Hall, S. Biedron, A.L. Edelen, S.V. Milton
    CSU, Fort Collins, Colorado, USA
  • S.V. Benson, D. Douglas, R. Li, C. Tennant
    JLab, Newport News, Virginia, USA
  • B.E. Carlsten
    LANL, Los Alamos, New Mexico, USA
  
  Collective beam effects, including coherent synchrotron radiation (CSR), have been studied on free-electron lasers (FELs). Here we will discuss a particular case of the CSR effects, that in energy-recovery linacs (ERLs). Special consideration is given to these machines because of their high average beam power and the architecture of the machine for energy recovery forces extreme bends. A recent study conducted on the JLab IR FEL looked at how CSR impacts both average energy and the energy spectrum of the beam. Such studies are important, both broadly, to the understanding of CSR and more specifically for a number of proposed ERL projects. A few proposed examples include the MEIC bunched beam cooler ERL design and ERL FELs for potential lithography purposes that would operate in the EUV range.  
slides icon Slides WEXB1 [16.383 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEXB1  
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WEYC2 Status of the PAL XFEL Construction undulator, klystron, linac, controls 2439
 
  • H.-S. Kang, K.W. Kim, I.S. Ko
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  Funding: This work has been supported by the Ministry of Science, ICT and Future Planning of Korea.
The PAL-XFEL, a 0.1-nm hard X-ray FEL facility consisting of a 10-GeV S-band linac, is being constructed in Pohang, South Korea. Its building construction was completed at the end of 2014. The major procurement contracts were complete for the critical components of S-band linac modules and undulators. The installation of linac, undulator, and beam line will be completed by 2015. The commissioning will get started in January 2016 aiming for the first lasing in 2016. We will report the current status, construction progress, and commissioning plans for the PAL XFEL project, including major subsystem preparations. 		 
slides icon Slides WEYC2 [9.069 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEYC2  
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WEPWA001 Electron Beam Transfer Line for Demonstration of Laser Plasma Based Free Electron Laser Amplification electron, undulator, emittance, quadrupole 2489
 
  • A. Loulergue, M.-E. Couprie, M. Khojoyan, M. Labat, W. Wang
    SOLEIL, Gif-sur-Yvette, France
  • C. Evain
    PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
  
  One direction towards compact Free Electron Lasers is to replace the conventional linac by a laser plasma driven beam, provided proper electron beam manipulation to handle the value of the energy spread and of the divergence is done. Applying seeding techniques enables also to reduce the required undulator length. The rapidly developing LWFA are already able to generate synchrotron radiation. With an electron divergence of typically 1 mrad and an energy spread of the order of 1 %, an adequate beam manipulation through the transport to the undulator is needed for FEL amplification. A test experiment for the demonstration of FEL amplification with a LWFA is under preparation in the frame of the COXINEL ERC contract. A specific design of electron beam transfer line following different steps with strong focusing variable strength permanent magnet quadrupoles, an energy de-mixing chicane with conventional dipoles and second set of quadrupoles for further dedicated focusing in the undulator has been investigated. Beam transfer simulations and expected FEL power in the XUV will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA001  
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WEPMA042 Experience and Developments on the S-band RF Power System of the FERMI Linac klystron, operation, linac, high-voltage 2856
 
  • A. Fabris, P. Delgiusto, F. Pribaz, N. Sodomaco, R. Umer, L. Veljak
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  
  The S-band linac of FERMI, the seeded Free Electron Laser (FEL) located at the Elettra laboratory in Trieste, operates on a 24/7 basis accumulating more than 6000 hours of operation per year. The performance and operability requirements of a users facility pose stringent specifications on reliability and availability on all the systems of the machine and in particular on the RF power plants. This paper provides a review and discusses the operational experience with the S-band power plants, klystrons and modulators, operating at S-band in FERMI. Based on the satisfactorily results and following return of experience, upgrades of the existing power plants are being implemented in the continuous effort of extending the operability and availability of the systems. A description of these activities and an overview of the other developments under consideration on the RF power plants are also provided.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA042  
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WEPMA043 Five Years of Operations for the Magnet Power Supplies of FERMI operation, controls, linac, interface 2859
 
  • R. Visintini
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  
  FERMI, the FEL light source in Trieste, Italy, started its regular operation with external users in 2012. The construction of the facility began in 2008 and the commissioning of the complete system – LINAC, Undulators’ chains (FEL-1 and FEL-2), photon front-end – started in 2010. On December 13, 2010 the first lasing occurred. From the Photo-injector to the electron Main Beam Dump (MBD), there are more than 400 magnets and coils, including those mounted on the accelerating sections of the LINAC and on the Undulators. With few exceptions, each magnet power supply energizes a single magnet/coil: there are about 400 magnet power supplies spanning from few tens of watt up to 42 kW. The power supplies types range from custom-made ones, to COTS (Commercial Off The Shelf), to in-house design (these accounting to 88% of the total). Almost all magnet power supplies are in use since mid-2010. During 5 years of operations, the reliability of the magnet power supplies proved to be extremely high: the downtime of FERMI operations due to magnet power supplies is very low.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA043  
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WEPWI001 An Overview of the MaRIE X-FEL and Electron Radiography Linac RF Systems linac, klystron, cavity, electron 3482
 
  • J.T. Bradley III, D. Rees, A. Scheinker, R.L. Sheffield
    LANL, Los Alamos, New Mexico, USA
  
  The purpose of the Matter-Radiation Interactions in Extremes (MaRIE) facility at Los Alamos National Laboratory is to investigate the performance limits of materials in extreme environments. The MaRIE facility will utilize a 12 GeV linac to drive an X-ray FEL. Most of the same linac will also be used to perform electron radiography. The main linac is driven by two shorter linacs; one short linac optimized for X-FEL pulses and one for electron radiography. The RF systems have historically been the one of the largest single component costs of a linac. We will describe the details of the different types of RF systems required by each part of the linacs. Starting with the High Power RF system, we will present our methodology for the choice of RF system peak power and pulselength with respect to klystrons parameters, modulator parameters, performance requirements and relative costs. We will also present an overview of the low level RF systems that are proposed for MaRIE and briefly describe their use with some proposed control schemes. *
* A. Scheinker, "Adaptive Accelerator Tuning", Proc. of IPAC'15.
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI001  
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THSMS2 50th Anniversary: Accelerator Conferences in the U.S. operation, plasma, linac, site 3668
 
  • S.O. Schriber
    SOS, Eagle, Idaho, USA
  
  50th Anniversary: Accelerator Conferences in the U.S.  
slides icon Slides THSMS2 [1.063 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-THSMS2  
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THPF144 Analysis of FEL-based CeC Amplification at High Gain Limit electron, space-charge, free-electron-laser, laser 4063
 
  • G. Wang, Y.C. Jing, 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.
An analysis of CeC amplifier based on 1D FEL theory was previously performed with exact solution of the dispersion relation, assuming electrons having Lorentzian energy distribution *. At high gain limit, the asymptotic behavior of the FEL amplifier can be better understood by Taylor expanding the exact solution of the dispersion relation with respect to the detuning parameter **. In this work, we make quadratic expansion of the dispersion relation for Lorentzian energy distribution * *** and investigate how longitudinal space charge and electrons’ energy spread affect the FEL amplification process.
* G. Wang, PhD Thesis, SUNY Stony Brook, 2008.
** G. Stupakov, M.S. Zolotorev, Comment on “Coherent Electron Cooling”, PRL 110 (2013) 269503.
*** E.L. Saldin, E.A. Schneidmiller, M.V. Yurkov, The Physics of Free Electron Lasers, 1999. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-THPF144  
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