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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:21 |
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Conference: Bucharest University Faculty of Physics 2013 Meeting
Section: Nuclear and Elementary Particles Physics
Title:
Monte Carlo simulation of p-type HPGe detectors – the dead layer problem (II)
Authors:
Elena Stancu(1,2), Cristian Costache (1,3), Octavian Sima(1)
Affiliation:
(1) Bucharest University, Physics Department
(2) National Institute for Laser, Plasma and Radiation Physics
(3) Horia Hulubei National Institute of Physics and Nuclear Engineering - IFIN HH
E-mail
elena.stancu@inflpr.ro
Keywords:
Monte Carlo simulation; GEANT 3; PENELOPE; germanium detectors; dead layer; detector efficiency; peak shape
Abstract:
The Monte Carlo method is increasingly applied for simulation of germanium detectors. It can be successfully used for the evaluation of full energy peak efficiency or of the efficiency corrections due to self-attenuation, coincidence summing and geometry effects. Usually the simulation task is to evaluate the energy deposited in the detector, or equivalently, the number of charge carriers produced. Then the spectroscopic information is obtained by assuming complete charge collection in the sensitive volume of the detector, and no contribution to detector signal from charges produced elsewhere, e.g. in the detector dead layer. Thus the experimental spectrum is considered strictly proportional to the spectrum of energy deposition in the detector sensitive volume. In this work it is shown that simulations of the energy deposition in a p-type HPGe detector for low energy photons, carried out with GEANT3 and PENELOPE, do not describe correctly experimental data that depend on the interactions taking place in the dead layer. It is not possible to reproduce experimental data that depend simultaneously on the full energy peak efficiency and total efficiency, such as the magnitude of coincidence summing effects, peak shape (for peaks affected by coincidence summing effects) etc. The reason is that the charge produced in specific regions of the dead layer is partly, but not completely collected, so those interactions contribute to the total efficiency but not to the peak efficiency. It is shown that a simplified procedure to avoid this problem is to define a complex structure of the dead layer. However, the general solution requires the incorporation of the charge collection process into the simulation codes.
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