Spatial distribution of electron cloud footprints from microchannel plates: Measurements and modeling

The measurements of the electron cloud footprints produced by a stack of mi crochannel plates (MCPs) as a function of gain, MCP-to-readout distance and accelerating electric field are presented. To investigate the charge footp rint variation, we introduce a ballistic model of the charge cloud propagat ion based on the energy and angular distribution at the MCP output. We also simulate the Coulomb repulsion in the electron cloud, which is likely to c ause the experimentally observed increase in the cloud size with increasing MCP gain. Calculation results for both models are compared to the charge f ootprint sizes measured both in our experiments with high rear-field values (similar to 200-900 V/mm) and in the experiments of Edgar [Rev. Sci. Instr um. 60, 3673 (1989)] (accelerating electric field similar to 30-130 V/mm). (C) 1999 American Institute of Physics. [S0034-6748(99)04808-X].