V. Peskov et al., FEEDBACK AND BREAKDOWNS IN MICROSTRIP GAS COUNTERS, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 397(2-3), 1997, pp. 243-260
The phenomena of feedback and breakdowns in microstrip gas counters ha
ve been studied. Tests have been performed on a wide variety of micros
trips of different geometries and substrates in various gas mixtures a
nd at several pressures. In addition, for direct comparison, similar m
icrostrip gas counters without substrates were also investigated. In t
he case of ''conventional'' microstrip detectors on substrates, it was
found that as maximum gains were approached, self-quenched streamers
occurred, but that these were present only over a very narrow voltage
range after which they rapidly transited to gliding-discharge-type bre
akdown sparks. For microstrip detectors without substrates, the situat
ion was quite different. At high gains (> similar to 10(4)) they trans
ited from proportional to self-quenched streamer-mode and would operat
e stably in this mode over a very broad voltage range. When breakdown
occurred in these detectors it was through a previously unreported mec
hanism and at gains, without exception, 5-10 times higher than in thei
r counterparts with substrates. The conclusion of these studies is tha
t the substrate represents the weak link in the chain and should ideal
ly be avoided or at least removed from the high-field regions. In case
s where this is not possible, then the multiplication region should be
concentrated to the smallest volume around the anodes and maximally s
uppressed elsewhere. Recipes for achieving this are provided, along wi
th new geometries which permit gas gains in excess of 10(5) to be achi
eved.