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Chao, A.

Paper Title Page
THPCH097 Commissioning of the Digital Transverse Bunch-by-bunch Feedback System for the TLS 3020
 
  • K.H. Hu, J. Chen, P.J. Chou, K.-T. Hsu, S.Y. Hsu, C.H. Kuo, D. Lee, C.-J. Wang
    NSRRC, Hsinchu
  • A. Chao
    SLAC, Menlo Park, California
  • K. Kobayashi, T. Nakamura
    JASRI/SPring-8, Hyogo-ken
  • W.-T. Weng
    BNL, Upton, Long Island, New York
  
  Multi-bunch instabilities degrade the beam quality leading to increased beam emittance, energy spread or even to beam loss. The feedback system is used to suppress multi-bunch instabilities due to resistive wall of the beam ducts, cavity-like structures and trapped ions. A new digital transverse bunch-by-bunch feedback system was commissioned at the Taiwan Light Source recently, and has replaced the previous analog system. The new system has the advantages that it enlarges the tune acceptance compared with the old system, enhances damping for transverse instability at high current, and as a result, top-up operation was achieved. In this new system, a single feedback loop simultaneously suppresses both the horizontal and vertical multi-bunch instabilities. The feedback system employs the latest generation FPGA feedback processor to process bunch signals. Memory installed to capture up to 250 msec bunch oscillation signal has included the considerations for system diagnostic and should be able to support various beam physics study.  
THPLS067 Vertical Beam Size Control in TLS and TPS 3442
 
  • C.-C. Kuo, H.-P. Chang, J.-R. Chen, P.J. Chou, K.-T. Hsu, G.-H. Luo, H.-J. Tsai, D.-J. Wang, M.-H. Wang
    NSRRC, Hsinchu
  • A. Chao
    SLAC, Menlo Park, California
  • W.-T. Weng
    BNL, Upton, Long Island, New York
  
  Vertical beam size control is an important issue in the light source operations. The horizontal-vertical betatron coupling and vertical dispersion were measured and corrected to small values in the TLS 1.5 GeV storage ring. Estimated beam sizes are compared with the measured values. By employing an effective transverse damping system, the vertical beam blow-up due to transverse coherent instabilities such as the fast-ion beam instability was suppressed and as a result, the light source is very stable. In NSRRC we are designing an ultra low emittance 3-GeV storage ring and its designed vertical beam size could be as small as a few microns. The ground and mechanic vibration effects, and coherent instabilities could spoil the expected photon brightness due to blow-up of the vertical beam size if not well taken care of. The contributions of these effects to vertical beam size increase will be evaluated and the counter measures to minimize them will be proposed and reported in this paper.