Experimental gas amplification study in boron-lined proportional counters for neutron detection

Based on theoretical considerations related to the microscopic behaviour of electrons in gases in conjunction with a macroscopic hypothesis, a semi-microscopic gas gain formula for conventional proportional counters has been already developed and was afterwards successfully tested on gas gain data obtained in Ar-CH4- and He-isobutane-filled proportional counters, using an X-ray radiation source. In the present work, it is verified that the semi-microscopic formula works as well in case of the detection of spread energy-spectrum of ionizing charged particles, such as involved within boron lined proportional counters, commonly used for thermal neutron detection. Indeed, we investigate experimentally the validity of the formula for the parameterization of the gas amplification factor data obtained in two boron lined proportional counters, filled with Ar-CH4 (10%) and Ar-CO2 (5%). The obtained results show clearly the ability of the gas gain formula to perfectly describe gas gain characteristics in such counters independently of the filling gas mixture used. Consequently, this provides further evidence of generality of the underlying gas amplification semi-microscopic model.