Author: Ji, B.
Paper Title Page
TU2PB01 A Study of Multipacting Effects in Large Cyclotron Cavities by Means of Fully 3-Dimensional Simulations 142
  • C. Wang, B. Ji, Y. Lei, P.Z. Li, J.S. Xing, Z.G. Yin, T.J. Zhang
    CIAE, Beijing, People's Republic of China
  • A. Adelmann, A. Gsell, M. Seidel
    PSI, Villigen PSI, Switzerland
  The field emission model and the secondary emission model, as well as 3D boundary geometry handling capabilities, are needed to efficiently and precisely simulate multipacting phenomena. These models have been implemented in OPAL, a parallel framework for charged particle optics in accelerator structures and beam lines. The models and their implementation are carefully benchmarked against a non-stationary multipacting theory. A dedicated multipacting experiment with nanosecond time resolution for the classic parallel plate geometry has also successfully shown the validity of OPAL model. Multipacting phenomena, in the CYCIAE-100 cyclotron, under construction at China Institute of Atomic Energy, are expected to be more severe during the RF conditioning process than in separate-sector cyclotrons. This is because the magnetic fields in the valley are stronger, which may make the impact electrons easier to reach energies that lead to larger multipacting probabilities. We report on simulation results for CYCIAE-100, which gives us an insight view of the multipacting process and help to develop cures to suppress these phenomena.  
slides icon Slides TU2PB01 [7.012 MB]  
TUPPT026 The Design and Testing of an Automatic RF Conditioning System for the Compact Medical Cyclotron 209
  • Y. Lei, B. Ji, P.Z. Li, C. Wang, J.Y. Wei, Z.G. Yin, T.J. Zhang
    CIAE, Beijing, People's Republic of China
  The multipacting phenomenon for a compact medical cyclotron is induced by the fringing magnet field inside the accelerating structure. And it will become more interesting, when the vacuum system is equipped with diffusion pump. A method used for CYCIAE-14 cavity conditioning is reported together with the testing results of an automatic conditioning circuit designed on such basis. Apart from traditional Low Level RF control, in which close-loop regulation plays an important role, the automatic conditioning system emphasizes on the cavity startup process. It takes advantage of the modern digital signal processing technique, combined with the direct digital synthesizer to accurately limit the reflection, will condition the cavity by means of sweeping frequency, using the low RF driven power, in continuous wave mode. The electronics are designed and tested first; it will be used later in the RF system commissioning of other compact medical cyclotrons built by BRIF division of CIAE.