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Chao, A.

Paper Title Page
WEPLT121 Computer Simulation of Equilibrium Electron Beam Distribution in the Proximity of 4th Order Single Nonlinear Resonance 2134
 
  • T.-S. Ueng, C.-C. Kuo, H.-J. Tsai
    NSRRC, Hsinchu
  • A. Chao
    SLAC, Menlo Park, California
 
  The beam distribution of particles in an electron storage ring is distorted in the presence of nonlinear resonances. A computer simulation is used to study the equilibrium distribution of an electron beam in the presence of 4th order single nonlinear resonance. The results are compared with that obtained using an analytical approach by solving the Fokker-Planck equation to first order in the resonance strength. The effect of resonance on the quantum lifetime of electron beam is also compared and investigated.  
WEPLT122 Investigation of Microwave Instability on Electron Storage Ring TLS 2137
 
  • M.-H. Wang
    NSRRC, Hsinchu
  • A. Chao
    SLAC, Menlo Park, California
 
  With the planned installation of a superconducting rf system, the new operation mode of TLS, the electron storage ring at NSRRC, is expected to double the beam intensity. Several accelerator physics topics need to be examined. One of these topics concerns the beam instability of single-bunch longitudinal microwave instability. We consider different approaches to measure the effective broad band impedance. We compare these measurement results with each other and to the old data [*]. The new measurements of effective broad band impedance are higher than the old measurement since between these two sets of measurements several narrow gap insertion devices were installed into the storage ring. We calculate the threshold current of microwave instability with a mode-mixing analysis code written by Dr. K. Oide of KEK [**]. We also develop a multi-particle tracking code to simulate the instability. The results of simulation and measurement are compared and discussed. We conclude that the doubling of beam current will not onset the microwave instability even without a Landau cavity to lengthen the bunch.

* M.H. Wang, et al.,"Longitudinal Beam Instability Observation with streak Camera at SRRC", proceeding of 1996 European Particle Accelerator Conference, pp. 1120** K. Oide, "Longitudinal Single-Bunch Instability in Electron Storage Rings", KEK Preprint 90-10