Ecloud Build-Up Simulations for the FNAL MI for a Mixed Fill Pattern: Dependence on Peak SEY and Pulse Intensity During the Ramp

摘要

We present simulation results of the build-up of the electron-cloud density n(sub e) in three regions of the FNAL Main Injector (MI) for a beam fill pattern made up of 5 double booster batches followed by a 6th single batch. We vary the pulse intensity in the range N(sub t) = (2-5) x 10(sup 13), and the beam kinetic energy in the range E(sub k) = 8-120 GeV. We assume a secondary electron emission model qualitatively corresponding to TiN, except that we let the peak value of the secondary electron yield (SEY) (delta)(sub max) vary as a free parameter in a fairly broad range. Our main conclusions are: (1) At fixed N(sub t) there is a clear threshold behavior of n(sub e) as a function of (delta)(sub max) in the range (approx) 1.1-1.3. (2) At fixed (delta)(sub max), there is a threshold behavior of n(sub e) as a function of N(sub t) provided (delta)(sub max) is sufficiently high; the threshold value of N(sub t) is a function of the characteristics of the region being simulated. (3) The dependence on E(sub k) is weak except possibly at transition energy. Most of these results were informally presented to the relevant MI personnel in April 2010.