Author: Doolittle, L.R.
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WEPOR042 LLRF Control of High Loaded-Q Cavities for the LCLS-II 2765
  • C. Serrano, L.R. Doolittle, G. Huang, A. Ratti
    LBNL, Berkeley, California, USA
  • S. Babel, M. Boyes, B. Hong
    SLAC, Menlo Park, California, USA
  • R. Bachimanchi, C. Hovater
    JLab, Newport News, Virginia, USA
  • B.E. Chase, E. Cullerton, J. Einstein
    Fermilab, Batavia, Illinois, USA
  Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515
The SLAC National Accelerator Laboratory is planning an upgrade (LCLS-II) to the Linear Coherent Light Source with a 4 GeV CW Superconducting Radio Frequency (SCRF) linac. The nature of the machine places stringent requirements in the Low-Level RF (LLRF) system, expected to control the cavity fields within 0.01 degrees in phase and 0.01% in amplitude, which is equivalent to a longitudinal motion of the cavity structure in the nanometer range. This stability has been achieved in the past but never for hundreds of superconducting cavities in Continuous-Wave (CW) operation. The difficulty resides in providing the ability to reject disturbances from the cryomodule, which is incompletely known as it depends on the cryomodule structure itself (currently under development at JLab and Fermilab) and the harsh accelerator environment. Previous experience in the field and an extrapolation to the cavity design parameters (relatively high QLc≈ 4×107 , implying a half-bandwidth of around 16 Hz) suggest the use of strong RF feedback to reject the projected noise disturbances, which in turn demands careful engineering of the entire system.
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOR042  
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WEPOR043 End-to-end FEL Beam Stability Simulation Engine 2768
  • C. Serrano, L.R. Doolittle
    LBNL, Berkeley, California, USA
  • D.S. Driver, B. Patel, A.F. Queiruga, Z. Zaky
    UCB, Berkeley, USA
  • Q. Llimona
    UPF, Barcelona, Spain
  Funding: Work supported by U.S. Department of Energy
During the design, commissioning and operation of a linac-driven Free Electron Laser (FEL) it is important to have a good understanding of the implications of accelerator design choices on beam figures of merit. This simulation engine combines a full state-space model of the RF system (High-Power Amplifier, RF cavities, LLRF controllers, etc.), a characterization of beam properties such as energy, bunch length and arrival time as electrons propagate through the Linac and beam-based feedback. The combination of these models with the ability to introduce both correlated and uncorrelated noise sources at any point of the machine, allows for a complete transposition of noise sources to beam performance parameters, including frequency dependence, in order to analyze implications of accelerator design choices in a simulation environment.
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOR043  
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THPOY059 Synchronization System for Tsinghua Thomson Scattering X-ray Source 4237
  • J. Yang, Y.-C. Du, W.-H. Huang, D. Wang, L.X. Yan
    TUB, Beijing, People's Republic of China
  • J.M. Byrd, L.R. Doolittle, Q. Du, G. Huang, R.B. Wilcox, Y.L. Xu
    LBNL, Berkeley, California, USA
  Tsinghua Thomson scattering X-ray Source (TTX) generates X-ray based on inverse thomson scattering method. The synchronization system for TTX includes reference distribution, normal conducting cavity Low Level RF control and Laser-RF synchronization. In collaboration with LBNL, we're working on a prototype synchronization system for TTX. Some test result based on Tsinghua Thomson scattering X-ray Source were obtained. In this paper we will show the synchronization system design and preliminary test result.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY059  
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