On the high gain operation of low-pressure microdot gas avalanche chambers

Microdot avalanche chambers (MDOT) equipped with thin semitransparent Cr photocathodes, were characterized with UV photons at low gas pressure. Gains superior to 104 were reached with gas multiplication at the dots. In a mode where preamplification in the gas volume precedes the additional dot multiplication, gains superior to 106 were measured at 30–60 torr of propane. The fast amplification mechanism results in narrow high amplitude pulses with 2–3 ns rise time, visible with no further electronic amplification means. We present here our preliminary results and briefly discuss potential applications.