Principle of Opperation

The Charge Detector Array is a discrete anode readout device for microchannel plates (MCPs).The diagram below shows the basic principle of operation:

An electron impinges on the front face of the top MCP and initiates an avalanche of electrons through the pores of the plate. A cloud of approximately 1 million electrons emerges form the rear face of the lower MCP which is in close proximity to the collection anodes on the ASIC. The charge cloud from the MCP gives rise to a voltage pulse on the collection anode, this is picked up by the charge amplifier and discriminator stage which converts the analogue signal to a digital pulse. The digital pulse is counted by means of a counter associated with each pixel. At the end of the integration period, the counters associated with each pixel are read out sequentially to a controller mounted outside the vacuum system.