Charge Losses through Recombination while Detecting Fast Neutrons with Gas Proportional Counters

A procedure of calculating the ionization defect in a methane proportional counter is described for the case of heavy charged particles (p, α, 9Ве, and 12C), which are products of the interaction of 14-MeV neutrons with hydrogen and carbon nuclei. A radial structure of a charged-particle track and its decay through diffusion and recombination processes in an electric field are modeled. Certain effects neglected earlier are taken into consideration. Comparing the calculated and counter-measured experimental amplitude distributions has shown that the theory developed for calculating the ionization defect yields qualitatively correct results. Analyzing the compared results has also shown that some important notions concerning the initial data on the differential cross sections of gas ionization by particles with charges Z > 1, electron temperature in the track plasma, and model concepts on the electron escape from the track need refinement.