skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Phenomenological Model for Predicting the Energy Resolution of Neutron-Damaged Coaxial HPGe Detectors

Abstract

The peak energy resolution of germanium detectors deteriorates with increasing neutron fluence. This is due to hole capture at neutron-created defects in the crystal which prevents the full energy of the gamma-ray from being recorded by the detector. A phenomenological model of coaxial HPGe detectors is developed that relies on a single, dimensionless parameter that is related to the probability for immediate trapping of a mobile hole in the damaged crystal. As this trap parameter is independent of detector dimensions and type, the model is useful for predicting energy resolution as a function of neutron fluence.

Authors:
; ; ;
Publication Date:
Research Org.:
Idaho National Laboratory (INL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1061018
Report Number(s):
INL/JOU-11-23339
Journal ID: ISSN 0018--9499
DOE Contract Number:
DE-AC07-05ID14517
Resource Type:
Journal Article
Resource Relation:
Journal Name: IEEE Transactions on Nuclear Science; Journal Volume: 59; Journal Issue: 5, Part 3
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; energy resolution; Germanium detector; neutron damage

Citation Formats

C. DeW. Van Siclen, E. H. Seabury, C. J. Wharton, and A. J. Caffrey. Phenomenological Model for Predicting the Energy Resolution of Neutron-Damaged Coaxial HPGe Detectors. United States: N. p., 2012. Web. doi:10.1109/TNS.2012.2209896.
C. DeW. Van Siclen, E. H. Seabury, C. J. Wharton, & A. J. Caffrey. Phenomenological Model for Predicting the Energy Resolution of Neutron-Damaged Coaxial HPGe Detectors. United States. doi:10.1109/TNS.2012.2209896.
C. DeW. Van Siclen, E. H. Seabury, C. J. Wharton, and A. J. Caffrey. 2012. "Phenomenological Model for Predicting the Energy Resolution of Neutron-Damaged Coaxial HPGe Detectors". United States. doi:10.1109/TNS.2012.2209896.
@article{osti_1061018,
title = {Phenomenological Model for Predicting the Energy Resolution of Neutron-Damaged Coaxial HPGe Detectors},
author = {C. DeW. Van Siclen and E. H. Seabury and C. J. Wharton and A. J. Caffrey},
abstractNote = {The peak energy resolution of germanium detectors deteriorates with increasing neutron fluence. This is due to hole capture at neutron-created defects in the crystal which prevents the full energy of the gamma-ray from being recorded by the detector. A phenomenological model of coaxial HPGe detectors is developed that relies on a single, dimensionless parameter that is related to the probability for immediate trapping of a mobile hole in the damaged crystal. As this trap parameter is independent of detector dimensions and type, the model is useful for predicting energy resolution as a function of neutron fluence.},
doi = {10.1109/TNS.2012.2209896},
journal = {IEEE Transactions on Nuclear Science},
number = 5, Part 3,
volume = 59,
place = {United States},
year = 2012,
month =
}
  • This paper reports on the resolution characteristics of high-purity germanium gamma-ray detectors irradiated with fast neutrons that are studied in detail. The influence of the neutron fluence on the energy resolution, as well as the annealing temperature of irradiated detectors are investigated. Similarities are observed between the annealing behavior of the defects created by fast neutron irradiation in high-purity germanium and the changes in the energy resolution of the detectors when they are annealed. The energy resolution of the detectors measured by the means of a resolution factor which takes into account tailing effects has been investigated. Its behavior hasmore » been illustratively explained by the differences between the respective role of the stable defects at low temperature ({lt}100 K) and those formed by a thermal treatment up to room temperature.« less
  • After being irradiated by high-energy protons, the energy resolution of HPGe detectors degrade extensively. Resulting line shapes depend mostly on detector geometry and doping type. To improve the analysis of measured gamma-ray spectra of HPGe detectors, new algorithms were developed. Since trapping in radiation damaged HPGe detectors is predominantly hole trapping, the full energy peak is the integration of absorption events produced within the detector at various distances from the positive contact. Implementing that information into fit algorithms, peaks produced by detectors irradiated with 6{center_dot}10{sup 8} protons/cm{sup 2} could be analyzed. The tailing structure at the low energy side wasmore » included in the algorithm. Analog algorithms were successfully applied to damaged coaxial detectors of either doping type. Using these algorithms, it was possible to evaluate transients in damaged detectors after having been exposed to room temperature. Also, the development of tail broadening could be examined.« less
  • We have characterized, for the rst time, an n-type segmented Inverted Coaxial Point-Contact detector. This novel detector technology relys on a large variation in drift time of the majority charge carriers, as well as image and net charges observed on the segments, to achieve a potential -ray interaction position resolution of better than 1 mm. However, the intrinsic energy resolution in such a detector is poor (more than 20 keV at 1332 keV) because of charge (electron) trapping e ects. We propose an algorithm that enables restoration of the resolution to a value of 3.44 0.03 keV at 1332 keVmore » for events with a single interaction. The algorithm is based on a measurement of the azimuthal angle and the electron drift time of a given event; the energy of the event is corrected as a function of these two values.« less
  • We describe an improvement of the neutron activation system in operation on the Frascati Tokamak Upgrade (FTU) tokamak for the measurement of the total neutron yield. A HPGe well-type detector (200 cm{sup 3} active volume) is used to detect the photoemission from neutron activated samples ({sup 115m}In336.2 keV {gamma} rays from DD neutrons on indium for FTU). Due to their high geometrical efficiency, HPGe well-type detectors are particularly suited to the FTU low-level activity measurements. A particular effort has been devoted to the calibration of the measuring system. In particular, a multi-{gamma} calibration source (59{endash}1332 keV energy range) with amore » density of 7.31 g/cm{sup 3} consisting of a stack of indium foils has been prepared. This assures that the shape and volume of the calibration source are the same as those of the samples used in the actual measurements. The full-energy-peak efficiency at the {sup 115m}In336.2 keV line is 0.197 with an overall uncertainty of 2{percent} (1{sigma}). For a better characterization of the detector response as a function of the sample density, a further calibration source with the same geometry has been prepared in a gel aqueous solution (density {approximately}1 g/cm{sup 3}). The calibration curves for the well-type detector at the two different density values are compared. {copyright} {ital 1997 American Institute of Physics.}« less
  • This paper presents the progress made by the Neutron Activation Analysis (NAA) laboratory at the Colombian Geological Survey (SGC in its Spanish acronym), towards the characterization of its gamma spectrometric systems for Instrumental Neutron Activation Analysis (INAA), with the aim of introducing corrections to the measurements by variations in sample geometry. Characterization includes the empirical determination of the interaction point of gamma radiation inside the Germanium crystal, through the application of a linear model and the use of a fast Monte Carlo N-Particle (MCNP) software to estimate correction factors for differences in counting efficiency that arise from variations in samplemore » density between samples and standards.« less