Keyword: quadrupole
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MOP011 Strongly Tapered Undulator Design for High Efficiency and High Gain Amplification at 266 nm undulator, ion, electron, simulation 49
 
  • Y. Park, P. Musumeci, N.S. Sudar
    UCLA, Los Angeles, USA
  • D.L. Bruhwiler, C.C. Hall, S.D. Webb
    RadiaSoft LLC, Boulder, Colorado, USA
  • A.Y. Murokh
    RadiaBeam, Santa Monica, California, USA
  • Y. Sun, A. Zholents
    ANL, Argonne, Illinois, USA
 
  Tapering Enhanced Stimulated Superradiant Amplification (TESSA) is a scheme developed at UCLA to increase efficiency of Free Electron Laser (FEL) light from less than 0.1% to above 10% using strongly tapered undulators and prebunched electron beams. Initial results validating this method have already been obtained at 10-um wavelength at Brookhaven National Laboratory. In this paper we will discuss the design of an experiment to demonstrate the TESSA scheme at high gain and shorter wavelength (266 nm) using the Linac Extension Area (LEA) beamline at the Advanced Photon Source of Argonne National Laboratory (ANL) to obtain conversion efficiencies around 10% depending on the length of the tapered undulator (up to 4m).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP011  
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TUP005 Studies of the Transverse Beam Coupling in the European XFEL Injector ion, FEL, coupling, electron 263
 
  • M. Scholz, B. Beutner
    DESY, Hamburg, Germany
 
  Coupling between the transverse plains leads to an increase of the horizontal and vertical electron beam emittances. The coupling can be measured with dedicated multi quadrupole scans while the correlations of the beam are observed on a screen. In this paper we show the results from first coupling studies in the European XFEL injector.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP005  
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WEP007 Electron Beam Asymmetry Compensation with Gun Quadrupoles at PITZ ion, gun, electron, emittance 429
 
  • M. Krasilnikov, P. Boonpornprasert, Y. Chen, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, X. Li, O. Lishilin, G. Loisch, D.M. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan, Q.T. Zhao
    DESY Zeuthen, Zeuthen, Germany
  • G.A. Amatuni, B. Grigoryan
    CANDLE SRI, Yerevan, Armenia
  • G. Asova
    INRNE, Sofia, Bulgaria
  • Q.T. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
 
  The electron beam asymmetry observed at the Photo Injector Test Facility at DESY in Zeuthen (PITZ) was traced back to multipole kicks in the gun section, namely around the location of the coaxial power coupler and the main solenoid. Several dedicated studies have been performed to quantify the kick location and strength. Based on these studies, two designs of correction quadrupole coils were proposed. The coils were fabricated and tested with an electron beam. The second updated design implies a two quadrupole setup on a frame installed around the gun coaxial coupler close to the main solenoid centre location. Skew and normal quadrupole magnets are powered independently, enabling flexibility in electron beam manipulations. By means of this setup, a more symmetric beam was obtained at several screens. This led also to more equal measured horizontal and vertical phase spaces and to even smaller overall emittance values. Some details of the gun quadrupole designs, magnetic measurements, and results of electron beam measurements including emittance optimization will be reported.  
poster icon Poster WEP007 [1.997 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP007  
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WEP010 Beam Asymmetry Studies with Quadrupole Field Errors in the PITZ Gun Section ion, solenoid, gun, experiment 440
 
  • Q.T. Zhao, G. Asova, P. Boonpornprasert, Y. Chen, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, D.M. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, T. Rublack, C. Saisa-ard, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • G. Asova
    INRNE, Sofia, Bulgaria
  • C. Saisa-ard
    Chiang Mai University, Chiang Mai, Thailand
  • Q.T. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
 
  The Photo Injector Test Facility at DESY in Zeuthen (PITZ) was built to test and optimize high-brightness electron sources for free electron lasers (FELs) like FLASH and European XFEL. Although the beam emittance has been optimized and experimentally demonstrated to meet the requirements of FLASH and XFEL, transverse beam asymmetries, such as wing structures and beam tilts, were observed during many years of operation with different generations of guns. These cannot be explained by simulations with the rotationally symmetric gun cavities and symmetric solenoid fields. Based on previous RF coupler kick, solenoid field imperfection studies and coupling beam dynamics, the beam asymmetries most probably stem from rotated quadrupole field error in the gun section. A thin-lens static quadrupole model is applied in the RF gun section simulations to fit the position and intensity of quadrupole field errors by comparing the beam asymmetry directions in experiments and ASTRA simulations. Furthermore, by measuring the laser position movement at the photo cathode and the corresponding beam movement at downstream screens, the integrated quadrupole field strength can also be extracted.  
poster icon Poster WEP010 [1.856 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP010  
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WEP043 Tune-Up Simulations for LCLS-II ion, simulation, emittance, linac 507
 
  • M.W. Guetg, P. Emma
    SLAC, Menlo Park, California, USA
 
  The planned superconducting LCLS-II linac poses new operational constraints with respect to the existing copper linac currently operated for LCLS. We present the results of exhaustive accelerator simulations, including realistic machine errors and exploring beam tune-up strategies. The results are used to pin-point the required beam diagnostics and the key correction elements. Specifically, these simulations concentrate on longitudinal and transverse beam matching as well as orbit and dispersion control through the new linac and up to the hard x-ray FEL. Dispersion control is achieved by a novel method presented within this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP043  
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WEP064 Tunable High-Gradient Quadrupoles for a Laser-Plasma Acceleration-Based FEL ion, electron, laser, permanent-magnet 550
 
  • A. Ghaith, F. Blache, M.-E. Couprie, C.A. Kitegi, F. Marteau, P. N'gotta, M. Valléau, J. Vétéran
    SOLEIL, Gif-sur-Yvette, France
  • C. Benabderrahmane
    ESRF, Grenoble, France
  • O. Cosson, F. Forest, P. Jivkov, J.L. Lancelot
    Sigmaphi, Vannes, France
 
  The magnetic design and characterization of tunable high gradient permanent magnet based quadrupole, are presented. To achieve a high gradient field with a compact structure, permanent magnets are chosen rather than usual electro-magnets due to their small aperture. The quadrupole structure consists of two quadrupoles superimposed capable of generating a gradient of 210 T/m. The first quadrupole is composed of permanent magnets following a Halbach configuration shaped as a ring attaining a constant gradient of 160T/m, and the second of four permanent magnet cylinders surrounding the ring and capable of rotating around their axis to achieve a gradient tunability of ±50 T/m. Each tuning magnet is connected to a motor and is controlled independently, enabling the gradient to be tuned with a rather good magnetic center stability (±20 μm) and without any field asymmetry. Seven quadrupoles have been built with different magnetic lengths in order to fulfil the integrated gradient required. A set of QUAPEVA triplet are now in use, to focus a high divergent electron beam with large energy spread generated by a laser plasma acceleration source for a free electron laser application.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP064  
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