Keyword: controls
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TUC01 Polarization Control of Storage Ring FELs Using Cross Polarized Helical Undulators ion, FEL, polarization, undulator 235
 
  • 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.L. Li
    IHEP, Beijing, People's Republic of China
  • V. Litvinenko
    Stony Brook University, Stony Brook, USA
  • N.A. Vinokurov
    BINP SB RAS, Novosibirsk, Russia
 
  For more than two decades, accelerator researchers have been working to gain control of polarization of synchrotron radiation and FELs using non-optical means. In 2005, the first experimental demonstration of polarization control of an FEL beam was realized with the Duke storage-ring FEL. With the recent upgrade of the undulator system, the Duke FEL can be operated with up to four helical undulators simultaneously. Using two sets of helical undulators with opposite helicities, for the first time, we have demonstrated full polarization control of a storage ring FEL. First, the helicity switch of the FEL beam has been realized with good lasing up to a few Hz. Second, the linearly polarized FEL beam has been generated with a high degree of polarization (Plin>0.95). The FEL polarization direction can be fully controlled using a buncher magnet. Furthermore, the use of non-optical means to control the FEL polarization allows us to extend polarization control to gamma-ray beams generated using Compton scattering. This has been experimentally demonstrated with the production of linearly polarized Compton gamma-ray beams with rotatable polarization direction based upon helical undulators.  
slides icon Slides TUC01 [5.921 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUC01  
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WEP030 Large-Scale Turnkey Timing Distribution System for New Generation Photon Science Facilities ion, timing, laser, electron 485
 
  • K. Shafak
    CFEL, Hamburg, Germany
  • A. Berg, F.X. Kärtner, A. Kalaydzhyan, J. Meier, D. Schimpf, T. Tilp
    Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany
  • A. Berlin, E. Cano, H.P.H. Cheng, A. Dai, J. Derksen, D. Forouher, W. Nasimzada, M. Neuhaus, P. Schiepel, E. Seibel
    Cycle GmbH, Hamburg, Germany
 
  We report a large-scale turnkey timing distribution system able to satisfy the most stringent synchronization requirements demanded by new generation light sources such as X-ray free-electron lasers and attoscience centers. Based on the pulsed-optical timing synchronization scheme, the system can serve 15 remote optical and microwave sources in parallel via timing stabilized fiber links. Relative timing jitter between two link outputs is less than 1 fs RMS integrated over an extended measurement time from 1 μs to 2.5 days. The current system is also able to generate stabilized microwaves at the link outputs with 25-fs RMS precision over 8 h, which can be easily improved to few-femtosecond regime with higher quality VCOs.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP030  
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WEP031 Using A Neural Network Control Policy For Rapid Switching Between Beam Parameters in an FEL ion, FEL, network, undulator 488
 
  • A.L. Edelen, S. Biedron, S.V. Milton
    CSU, Fort Collins, Colorado, USA
  • P.J.M. van der Slot
    Mesa+, Enschede, The Netherlands
 
  FEL user facilities often must accommodate requests for a variety of beam parameters. This usually requires skilled operators to tune the machine, reducing the amount of available time for users. In principle, a neural network control policy that is trained on a broad range of operating states could be used to quickly switch between these requests without substantial need for human intervention. We present preliminary results from an ongoing study in which a neural network control policy is investigated for rapid switching between beam parameters in a compact THz FEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP031  
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WEP036 Adaptive Feedback for Automatic Phase-Space Tuning of Electron Beams in Advanced XFELs ion, electron, FEL, feedback 496
 
  • A. Scheinker
    LANL, Los Alamos, New Mexico, USA
  • D.K. Bohler
    SLAC, Menlo Park, California, USA
 
  Particle accelerators are extremely complex having thousands of coupled, nonlinear components which include magnets, laser sources, and radio frequency (RF) accelerating cavities. Many of these components are time-varying. One example is the RF systems which experience unpredictable temperature-based perturbations resulting in frequency and phase shifts. In order to provide users with their desired beam and thereby light properties, LCLS sometimes requires up to 6 hours of manual, experience-based hand tuning of parameters by operators and beam physicists, during a total of 12 hours of beam time provided for the user. Even standard operational changes can require hours to switch between user setups. The main goal of this work is to study model-independent feedback control approaches which can work together with physics-based controls to make overall machine performance more robust, enable faster tuning (seconds to minutes instead of hours), and optimize performance in real time in response to un-modeled time variation and disturbances.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP036  
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THB02 Non-Standard Use of Laser Heater for FEL Control and THz Generation ion, laser, electron, FEL 566
 
  • E. Allaria, L. Badano, M.B. Danailov, A.A. Demidovich, S. Di Mitri, D. Gauthier, L. Giannessi, G. Penco, E. Roussel, P. Sigalotti, S. Spampinati, M. Trovò, M. Veronese
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • E. Roussel
    SOLEIL, Gif-sur-Yvette, France
 
  The laser heater system is currently used at various FEL facilities for an accurate control of the electron beam energy spread in order to suppress the micro-bunching instabilities that can develop in high brightness electron beams. More recently, studies and experiments have shown that laser-electron interaction developing in the laser heater can open new possibilities for tailoring the electron beam properties to meet special requirements. A suitable time-shaping of the laser heater pulse opened the door to the generation of (tens of) femtosecond-long FEL pulses. Using standard laser techniques it is also possible to imprint onto the electron bunch, energy and density modulations in the THz frequency range that, properly sustained through the accelerator, can be exploited for generation of coherent THz radiation at GeV beam energies. Such recent results at the FERMI FEL are here reported, together with near future plans.  
slides icon Slides THB02 [14.882 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-THB02  
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