caa a22 4500 397504462 CHVBK 20180308164540.0 cr unu---uuuuu 161202e19950801xx s 000 0 eng 10.1093/oxfordjournals.rpd.a082784 doi 0144-8420 pii (NATIONALLICENCE)oxford-10.1093/oxfordjournals.rpd.a082784 Multi-Level Modelling of the Response of the Ultraminiature Proportional Counter: Gas Gain Phenomena and Pulse Height Spectra [Elektronische Daten] [P. Olko, C. Moutarde, P. Ségur] The ultraminiature proportional counters, UMC, unique radiation detectors for monitoring high intensity therapy fields, designed by Kliauga and operated at Columbia University (USA), have yielded a number of pulse height distributions for photons, neutrons and ions at simulated diameters of 5-50 nm. Monte Carlo calculations of the gas gain in such a counter questioned the possibility of achieving proportionality at such low simulated diameters. The response of the UMC has now been modelled taking into account both fluctuations of energy deposited in the counter volume and its calculated gas gain. Energy deposition was calculated using the MOCA-14, MOCA-8 and TRION codes, whereby distributions of ionisations d(j) after irradiations with 137Cs, 15 MeV neutrons and 7 MeV.amu-1 deuterons were obtained. Monte Carlo calculations of electron avalanches in UMC show that the size of the single-electron avalanche P(n) reaching the anode wire depends strongly on the location of the primary ionisation within the counter volume. Distributions of the size of electron avalanches for higher numbers of primary ionisations, P*j(n), were obtained by successive convolutions of P(n). Finally, the counter response was obtained by weighting P*j(n) over d(j) distributions. On comparing the measured and calculated spectra it was concluded that the previously proposed single-electron peak calibration method might not be valid for the UMC due to the excessive width and overlap of electron avalanche distributions. Better agreement between the measured and calculated spectra is found if broader electron avalanche distributions than those used in the present calculations, are assumed. Radiation Protection Dosimetry Olko P. aut Moutarde C. aut Ségur P. aut Radiation Protection Dosimetry Oxford University Press 61/1-3(1995-08-01), 205-210 0144-8420 61:1-3<205 1995 61 rpd https://doi.org/10.1093/oxfordjournals.rpd.a082784 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1093/oxfordjournals.rpd.a082784 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Olko P. aut NATIONALLICENCE 700 1- Moutarde C. aut NATIONALLICENCE 700 1- Ségur P. aut NATIONALLICENCE 773 0- Radiation Protection Dosimetry Oxford University Press 61/1-3(1995-08-01), 205-210 0144-8420 61:1-3<205 1995 61 rpd Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford