Position sensitive anodes for MCP read-out using induced charge measurement

We investigate the method of an indirect detection of a MCP charge avalanche projected onto a resistive layer (G. Battistoni, et al.. Nucl. Instr. and Meth.. 202 (1982) 459). If the sheet resistance is favourable one can detect the charge cloud by the capacitive coupling to an anode structure a few millimetres behind the layer. The anode structure can be. for example. a wedge-and-strip electrode pattern (M. Unverzagt. Diploniarbeit, Universitat Frankfurt 1992, private communication) as it is used for directly collecting the electron avalanche from a MCP. Detection of the induced charge is beneficial in several respects. Firstly, image distortions produced by secondary electron mediated charge redistribution are eliminated. Secondly. the noise component due to quantized charge collection. commonly referred to as partition noise. is not present. In addition, the dielectric substrate can function both as an element of the vacuum enclosure and HV insulator, making the electrical connections easily accessible and the pattern operable at ground potential. independently of detector operating voltages. This technique can be used to simplify the electronic design requirements where varying high voltages are required at the detector input face such as plasma analysers. etc. It also has application in the manufacture of intensifier tubes (J. Barnstedt, M. Grewing, Nucl. Instr. and Meth.. these proceedings) where the inclusion of a readout pattern inside the intensifier body with associated electrical feed-throughs can prove problematic. We will present data on the performance of such detection geometries using several types of charge division anode, and discuss the advantages compared with the traditional charge collecting method. (C) 2002 Elsevier Science B.V. All rights reserved.