Pregled bibliografske jedinice broj: 256083
Single-electron spectra in a proportional counter filled with argon-based gas mixtures
Single-electron spectra in a proportional counter filled with argon-based gas mixtures // ISRP-10 Book of Abstracts
Coimbra: IRPS, 2006. str. B-16 (poster, nije recenziran, sažetak, znanstveni)
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Naslov
Single-electron spectra in a proportional counter filled with argon-based gas mixtures
Autori
Krajcar Bronić, Ines
Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni
Izvornik
ISRP-10 Book of Abstracts
/ - Coimbra : IRPS, 2006, B-16
Skup
10th International Symposium on Radiation Physics
Mjesto i datum
Coimbra, Portugal, 17.09.2006. - 22.09.2006
Vrsta sudjelovanja
Poster
Vrsta recenzije
Nije recenziran
Ključne riječi
single-electron spectra; proportional counter; argon-based gas mixtures
Sažetak
A pulse height distribution as detected by a proportional counter is determined by two independent ionization processes: 1) the "primary ionization" in which the ionizing particle looses its energy through ionization of the gas, and 2) multiplication of the primary electrons in strong electric field of the counter. The energy resolution of the counter depends on both processes as R2 ≈ W(F+f)T (W mean energy required to form an ion pair, F the Fano factor, T initial energy of the incident particle, they all depend on the incident particle and gas interaction, and f – the relative variance of the electron multiplication - depends on the conditions of the counter). The results of the experimental study of the electron multiplication process in a proportional counter filled with pure propane, isobutane, and DME, and their mixtures (1% – 80%) with argon at low pressures (2 – 90 kPa) is presented here. The gas amplification process has been studied by so-called single-electron spectra (SE). The single electrons, incapable of producing immediate ionizations, were released by the UV light (253.7 nm) from a thin Al film deposited on the quartz rod aligned with the cathode. SE spectra, i.e., the statistical distribution of avalanche sizes triggered by a single primary electron, were recorded for mean gas gain range 700 – 2.5 104. Each SE spectrum was fitted by a Polya distribution [P(n) = a nb exp(-cn), n is the number of electrons in the avalanche], and the relative variance was calculated as f = 1/(1+b). The f value describes the SE spectrum in a unique way. The main results can be summarized as follows: In all gases and gas mixtures f increases with gas gain. In pure molecular gases f is always <1. In gas mixtures at low gas gains f < 1, but it increases with gas gain faster at lower total pressures for the same concentration ratio and at lower concentration ratio for the same total pressure, and eventually reaches f > 1. For a given gas gain, f is a function of the admixture partial pressure. Gas gain at which f = 1 depends on the admixture partial pressure and is caused by insufficient quenching of the molecular admixture (secondary avalanches in strong reduced electric fields form avalanche chains). The experimental results will be compared with the results of recent Monte Carlo simulations of avalanche development in cylindrical proportional counters. The main findings by both methods agree, although the MC simulations are still fragmentary. However, the MC results pointed to some important characteristics of the electron avalanche development and its dependence on gas pressure and gas composition. At the end, a possible further application of MC techniques in analysis of radiation detectors – proportional counters – will be discussed.
Izvorni jezik
Engleski
Znanstvena područja
Fizika
POVEZANOST RADA
