Absorption of electrons in xenon for energies up to 200 keV: a Monte Carlosimulation study.

Gas proportional scintillation counters are room-temperature, general-purpo se x-ray detectors, which are used in many applications due to their good e nergy resolution, which can be better than standard proportional counters b y a factor of similar to 2. However, for energies higher than similar to 20 keV, the experimentally measured energy resolution is found to deviate fro m the usual 1/root E law. Under these circumstances, it is of great interes t to understand the mechanisms involved in the detection of higher energy x -rays. Since the photoelectrons will then carry most of the absorbed energy , we study in this work the response of xenon detectors to electrons with e nergies up to similar to 200 keV, using a Monte Carlo simulation technique. Distributions of the number of primary (sub-ionization) electrons produced per parent electrons with energy E-e are calculated, and results are prese nted for the Fano factor, the w-value and the intrinsic energy resolution a s a function of E-e in the range 20-200 keV. The influence of an applied re duced electric field on the results is assessed, showing that for 200 keV e lectrons an increase in the field from 0.1 to 0.8 Td causes an increase as high as 35% in the intrinsic energy resolution.