Experimental study of Xe-Ne proportional counters for X-ray detection

The use of appropriate mixtures of noble gases in proportional counters can take advantage of the Penning effect, a process of energy transfer between the two species which produces extra electrons. The Penning effect can occur in Xe-Ne mixtures and recent Monte Carlo simulation and experimental measurements have shown that a small percentage of Xe (below about 1%) brings to a minimum the fluctuations in the formation of the primary electron cloud and decreases the w-value to a magnitude near the case of pure Xe. In addition, the excitation and ionization thresholds and the fluctuations in charge multiplication become lower and the ionization efficiency becomes higher than in the pure Xe case, indicating that improved gas gain and energy resolution can be achieved at low applied voltages for a Xe-Ne filled proportional counter. In this work, we present an experimental study of the performance of a cylindrical proportional counter filled with several Xe-Ne mixtures at atmospheric pressure, for 5.9 keV X-rays. Results are presented in particular for the energy resolution and gas multiplication factor and a discussion of the experimental results is made.