Statistical fluctuations in gas amplification factor of a low-pressure proportional counter (CROSBI ID 482383)
Prilog sa skupa u zborniku | sažetak izlaganja sa skupa | međunarodna recenzija
Podaci o odgovornosti
Krajcar Bronić, Ines ; Grosswendt, Bernd
engleski
Statistical fluctuations in gas amplification factor of a low-pressure proportional counter
The electron avalanche formation in low-pressure argon-based gas mixtures at strong non-uniform electric fields was studied by a proportional counter. Concentration of admixtures (propane, DME, isobutane) varied between 1% and 80% and total pressures from 2 kPa to 90 kPa. Gas amplification M and energy resolution R were measured by the 55Fe source as a function of admixture concentration and total gas pressure. The relative variance f of the avalanche size distribution was determined by measuring single-electron (SE) spectra. In pure gases and in mixtures with high content of the admixture, the SE spectra have always a peaked distribution, f<1, although f increases with M. In "thin" mixtures the SE spectra change the shape to the over-exponential distribution, f>1. The f value depends on the partial pressure p of the admixture and on M. Over-exponential increase of gas gain with high voltage above a certain gas gain, M0, was determined in all mixtures. The gas gain where the SE spectra change their shape, f~1, is roughly equal to M0. Both effects in M and f are caused by avalanche chain formation due to insufficient quenching of the admixture. Energy resolution is directly determined by the f value, therefore, in "thin" mixtures above M0 it degrades very quickly. Since this limiting value M0 depends on p, we conclude that partial pressure should be above ~10 kPa to assure good quenching even at the highest gains obtained in the present experiment.
gas amplification; proportional counter; statistical fluctuations
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Podaci o prilogu
219-x.
2001.
objavljeno
Podaci o matičnoj publikaciji
Book of Abstracts
Obelić, B; Ranogajec-Komor, M; Miljanić, S; Krajcar Bronić, I
Zagreb:
Podaci o skupu
IRPA Regional Congress on Radiation Protection in Central Europe: Radiation protection and Health
poster
20.05.2001-25.05.2001
Dubrovnik, Hrvatska