Study of electron avalanche multiplication in gaseous argon detectors at low pressure and operating at cryogenic temperature

We are developing a photodetector sensitive to liquid noble gas scintillation light which is able to operate down to liquid nitrogen temperature (77 K). It has to be a simple, cheap and compact device, with a photocathode surface comparable to that of photomultipliers and it has to be able to produce fast signals for timing and triggering purposes.We studied the possibility of coupling a standard photocathode to a suitable electron multiplication system in gas; this would offer a cheap alternative to the use of photomultipliers. Gas avalanche multiplication at cryogenic temperatures and low pressure was observed in a small prototype chamber. Gains of the order of 103103 were obtained in pure argon, while gains up to 105105 were achieved using argon/methane mixture in cryogenic environment.