Transmission line modeling of gain saturation in microchannel plate detectors

We use the transmission line modeling (TLM) technique to model the saturation of the gain in a microchannel plate. To this purpose we represent a generic channel multiplier by a distributed constant, unidimensional electrical network in which the internal structure of the channel wall is neglected. This network is analyzed with the TLM method, i.e. with the techniques developed for transmission lines and a simple system of time-dependent, nonlinear differential equations is derived. Then we consider the system in steady-state conditions and, by introducing a rational approximation of the nonlinear gain equation, we derive an exact analytical solution from which the gain and the voltage along the channel multiplier can be easily computed. Finally the model is used to fit a set of experimental data taken with a MCP photomultiplier, finding that the derived equations describe with satisfactory accuracy the measured data. © 2000 SPIE.