Channel electron multiplier arrays CEMA

A small fraction of the orthopositronium atoms produced pass through the cw-excitation beam, where they are promoted to the 23Si level and then through a multi-pass doubled-YAG beam at 532 nm, where they are photo-ionized. The photo-ionized positron is electro-statically accelerated and magnetically-guided into a channel-electron multiplier array (CEMA) where it is detected. The time-of-Hight between the incident positron pulse and the photo-ionization pulse determines the range of positronium velocities detected. 

One fundamental question which arises in these peeling experiments is from which surface are the particles being emitted Two experiments we have performed helped to answer this question. The first employed a charged particle imaging device called a micro-channel plate or Channel Electron Multiplier Array (CEMA), which produces on a phosphor screen an intensity pattern of the charged particles incident upon the plate. The patterns observed from peeling 3M Magic Tape from a solid surface depended on the orientation of the peel test and substrate relative to the CEMA. 

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