Gain depression in MCPs utilized in CCD-readout image intensifies

摘要

Micro-channel plate (MCP) based "Generation 2" image intensifiers are used for initial photon detection and amplification in modern photon counting detectors in astronomy. Input photons initially create photo-electrons in a photocathode. Each photo-electron is then amplified by the MCP or an MCP stack producing a cloud of electrons that are proximity focused onto an output anode. During the electron amplification process charge is stripped from the walls of the associated pore (or pores if an MCP stack is employed) and this needs to be replenished before full gain amplification of following events can take place. Charge depletion then provides the ultimate limitation to the brightness of a point source that can be observed. Experimental work has been undertaken to measure the effect of gain depression in intensified CCD detectors using intensifiers with both P20 and P46 phosphors. The results, along with a discussion on their relevance to detector dynamic range, will be presented.