S. Ito et al., EFFECT OF SELF-INDUCED SPACE-CHARGE IN A HIGH-PRESSURE POSITION-SENSITIVE PROPORTIONAL COUNTER, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 368(3), 1996, pp. 738-744
The response of a position-sensitive proportional counter filled with
Ar + 30%CH4 counting gas under a pressure of 7 atm has been studied in
detail for 8-keV incident X-rays. The counter was operated in the reg
ion of limited proportionality, where the avalanche growth is greatly
affected by self-induced space charge and hence an unfamiliar distorte
d energy spectrum is often observed. It is confirmed that the avalanch
es caused by the halo effect of Ar K X-rays, emitted in photoelectric
absorption of incident X-rays, have higher gas amplification as compar
ed to other photopeak avalanches due to different origin of primary el
ectrons. The analysis has revealed that the effect of self-induced spa
ce charge hinders the avalanche growth of photopeak events to the exte
nt of 50% of the observed avalanche charge. Comprehensive analysis of
the complicated counter response in the region of limited proportional
ity under high pressure is provided.