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DeFord, J. F.

Paper Title Page
WEPMN093 Multipactor Simulations in Superconducting Cavities 2248
  • I. G. Gonin, N. Solyak
    Fermilab, Batavia, Illinois
  • J. F. DeFord, B. Held
    STAR, Inc., Mequon
  The multipactor (MP) is a well-known phenomenon. The existence of resonant trajectories can lead to electron avalanche under certain field level and surface conditions. In this paper we describe features of the extension of Analyst software - PT3P code developed for MP simulations in a real 3D RF structures, such as cavities, couplers, RF windows etc. Also we present the results of MP simulations in HOM couplers of TESLA, SNS β=0.61 and β=0.81 and FNAL 3-rd harmonic cavities. We discuss the comparison of simulations with experimental results.  
THPAS047 Adaptive Mesh Refinement for Particle-Tracking Calculation 3600
  • J. F. DeFord
    LLNL, Livermore, California
  • B. Held
    STAR, Inc., Mequon
  • J. J. Petillo
    SAIC, Burlington, Massachusetts
  Funding: U. S. Department of Energy, contract number DE-FG02-05ER84373.

Particle orbit errors in multipacting and dark current computations can arise from inadequate field representation, poor surface modeling, and from the integration algorithm used to advance the particles. Established fields-based adaptive mesh refinement (AMR) methods *,** selectively improve the field and surface representation over several iterations in finite-element codes but they are not optimized for particle tracking. In particular, field emission and secondary emission models require precise surface representations and highly accurate field representations near surfaces, and these requirements are not adequately addressed in standard AMR techniques. In this paper we report on extensions to existing AMR support in the Analyst software package for particle tracking, including adaptive improvement of near-surface and on-surface field representations, and control of element aspect ratios throughout successive iterations. We also discuss the merits of automated identification of important regions of the mesh based on field levels and orbit estimation to guide AMR in multipacting calculations, and multipacting results for a SRF cavity will be presented.

* G. Drago, et al., IEEE Trans. on Mag., 28, 1992, pp. 1743-1746.** D. K. Sun, et al., IEEE Trans. on Mag., 36, July 2000, pp. 1596-1599.