Effect of anode composition on secondary-electron-mediated charge redistribution in charge division anodes

We investigate the role of the mechanical and chemical composition of the anode on the performance of charge division readout systems in microchannel plate (MCP) based detectors. Typically, in these detectors, electrons from the MCP gain stage have sufficient energy to excite secondary electrons from the anode surface. Normally, these are recollected by the anode and can thus modify the effective charge footprint. These secondary electrons can also mediate charge redistribution between the anode electrodes in the presence of differential voltages. We describe an experiment to investigate the error in electrode charge ratio of a charge division anode pattern. The detector used, comprised a microchannel plate intensifier stack with an intermediate grid between MCP and anode for secondary electron control and measurement. The intermediate grid is used to either suppress or collect secondary electrons produced by the anode depending on the configuration of detector voltages. Anode patterns were manufactured on a variety of substrates. One anode pattern design was used for all experiments and consisted of several sets of fixed electrode ratios. The effect of the anode surface finish and electrode composition on the charge ratios was measured for different substrates.