| |
 |
UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:18 |
 |
|
|
|
Conference: Bucharest University Faculty of Physics 2012 Meeting
Section: Nuclear and Elementary Particles Physics
Title:
Difficulties in Monte Carlo simulation of gamma-ray germanium detectors in the presence of a thick dead layer
Authors:
Elena STANCU, O. SIMA
Affiliation:
Physics Department, Bucharest University
E-mail
elena_robu@hotmail.com
Keywords:
Monte Carlo simulation; GEANT 3; germanium detectors; dead layer; detector efficiency; peak shape
Abstract:
The thickness d of the dead layer of p-type high purity germanium detectors strongly influences the full energy peak efficiency (FEPE) at low photon energies. As the direct measurement of this parameter is difficult, frequently d is evaluated on the basis of measured values of the FEPE at low energy. Of course, using the value of d adjusted in this way, the Monte Carlo simulation of FEPE gives good results. However, in the literature it was shown that using the same value of d for the evaluation of the total efficiency gives underestimated values for low energy photons. Also the values of the coincidence summing corrections due to contributions of low energy photons are not correctly reproduced. In this work GEANT 3 simulations were used to compute the spectra and to evaluate the full energy peak efficiency, the total efficiency as well as the coincidence summing effects, both for the case of single photon sources and for sources with cascade photon emission. The results confirm the strong effect of the thickness of the dead layer on the value of FEPE at low energy and also the difficulties in obtaining simultaneously correct values of the total efficiency and of the coincidence summing corrections. Furthermore, the simulated shape of the peaks affected by coincidence summing effects with low energy photons is not distorted, contrary to the experimental results showing that the shape of such peaks is distorted in the case of p-type detectors, but not in the case of n-type detectors. The results suggest that it is insufficient to evaluate by simulation the energy deposited in the detector; for a correct description of detector response to photons that interact in the dead layer it is necessary to include the charge collection process in the simulation code.
|
|
|
|