A simulation study of the effect of drift electric fields on the response of radiation detectors using the PENELOPE code

The effect of the presence of a drift electric field on the response of gaseous and semiconductor radiation detectors to energetic X-rays (energies E ph from 20 to 200 keV) is investigated using the PENELOPE code to simulate the photo-absorption and the slow-down of the electrons produced in Si, Ge, and Xe gas at 1 atm. For typical drift fields, the energy E d deposited in the detection media is calculated taking into account the energy exchanged by the electrons with the field. The analysis of the calculated E d distributions shows that the effect of the field on the distributions is negligible in Si and Ge semiconductor detectors, but not in Xe gas detectors, where for E / p = 0.8 V cm - 1 Torr - 1 the fluctuations introduced by the field for E ph ≈ 180 keV approach the intrinsic values for Xe, and the intrinsic discontinuity in linearity when E ph crosses the Xe K -edge (34.56 keV) is further reduced by ≈ 4 % . The simulation data also suggest that this field effect may cause some deviations to the expected Gaussian response of Xe detectors to the absorption of monoenergetic photons.