The ion detection efficiency of microchannel plates (MCPs)

General expressions are derived for the detection efficiency of microchannel plate ion detectors. The model, based on earlier calculations for electrons and soft X-rays, accounts for the energy, incident angle, mass, electronic charge and nuclear charge of the ion and for the electrical and geometric parameters of the microchannels. The underlying dependence of the ion detection efficiency on ion velocity is derived from first principles. The initial predictions of the model are compared with measurements taken from the literature. Calculated efficiency-versus-angle, efficiency-versus-energy and efficiency-versus-mass curves are presented. The first calculations of the MCP efficiency for high mass ions (up to 100,000 u) are reported. We describe the extension of the model from bare MCPs, in which the active surfaces are the lead silicate glass of the channel walls and the nickel-based electrodes at the channel entrance and exit, to the case of alkali halide-coated plates. (Int J Mass Spectrom 215 (2002) 13-30) (C) 2002 Elsevier Science B.V. All rights reserved.