Study of a Compton-suppression Gamma-ray Spectrometer Utilizing a Plastic Scintillator Annulus and a Ge(Li) Detector PDF Download

Author: Robert Blair Williams
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ISBN:
Category : Nuclear physics
Languages : en
Pages : 156

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Author: Abdulsalam M. Alhawsawi
Publisher:
ISBN:
Category :
Languages : en
Pages : 118

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A triple layer phoswich detector was designed and assembled in the advanced radiation instrumentation lab at Oregon State University. The detector had three scintillation layers: the first one was a BC-400 for beta and conversion electron detection, the second layer was a CsI(Tl) for x-ray and gamma detection, and the third layer was BGO for shielding the CsI(Tl) crystal from background radiation and identifying scattered photons from the CsI(Tl) layer. Digital pulse processing was utilized to analyze pulses at a 200 MHz sampling rate. Pulses were analyzed according to their light decay time. The detector was able to suppress Compton events in low energy spectrum through pulse shape analysis. Suppression factors were calculated at the 90 keV and 250 keV regions in the 137Cs gamma ray spectrum. Compton suppression capability reduced the Compton continuum at 90 keV region, and at 250 keV region by a factor of 56.5%, and 68.3%, respectively.

Author: Sarah Sarnoski
Publisher:
ISBN:
Category : Gamma rays
Languages : en
Pages :

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Compton suppression is a measurement technique that reduces the intensity of the Compton continuum, which is composed of the partial energy depositions created via Compton scattering of gamma rays in the detector material. The Compton continuum from a high-energy gamma ray can obscure the full-energy gamma ray photopeaks of isotopes with lower energy gamma ray emissions. The reduction from the Compton suppression system enables a more accurate identification of these low-energy gamma rays with energy peaks located within the Compton continuum. The Penn State Compton suppression system (CSS) uses a high purity germanium (HPGe) detector and a cylindrical and plug sodium iodide (NaI(Tl)) guard detector to negate the effect of partially deposited gamma rays on the gamma spectrum produced when measuring a sample. The Penn State CSS negates the effect of partially deposited gamma rays on the overall gamma spectrum, therefore producing a more accurate spectrum with fewer overall counts and reduced background interference. The research performed in this thesis used the Penn State CSS to validate earlier sample measurements obtained prior to the dismantling and reconstruction of the CSS. The Penn State CSS has produced superior results when compared with published literature, and it is important that it continues to perform at this level after reconstruction. 137Cs, 60Co, and irradiated National Institute of Standards and Technology (NIST) standard reference materials were measured in the CSS. A suppression factor (SF) is a comparison of suppressed to unsuppressed peak to Compton ratios, a further explanation and definition is provided in section 6.3 of this thesis. The suppression factor (SF) for the 137Cs calibrated gamma ray spectrum was 9.21, similar to the previous SF measurement of 9.97. These values are approximately 28% larger than most SFs recorded in literature, demonstrating the superior ability of the Penn State CSS. Using the calibrated Penn State CSS, two NIST standard reference materials, SRM 1570 Spinach Leaves and SRM 1571 Orchard Leaves, were measured after irradiation in the Penn State Breazeale Reactor (PSBR). Bare and cadmium covered gold wires were also irradiated in the PSBR to characterize the neutron flux shape of the current core design of the reactor. Peak and average neutron fluxes were determined for each of the irradiation locations, and the axial positions where peak neutron fluxes occurred were determined. The reference materials were irradiated both in the PSBR dry tubes and using the PSBR pneumatic transfer system. The dry tube irradiation of SRM-1570 produced a SF of 3.30 and the pneumatic transfer irradiation of SRM-1570 produced a SF of 3.27±0.21; these values are functionally equivalent. The pneumatic transfer irradiation of SRM-1571 produced a suppression factor of 4.2±0.10, approximately 10% greater than a previous measurement of 3.80. This work irradiated and measured the standard reference materials in triplicate, providing a more accurate evaluation of the CSS capabilities than previous work, which used a single reference material measurement. This thesis further improved upon previous Penn State CSS characterization efforts by clarifying the contributions of two isotopes to a single photopeak: a photopeak that was identified as 56Mn in 2008 was shown to be a combination of two energy peaks with contributions from 56Mn and 27Mg. This distinction was more apparent in the suppressed spectrum. The improved measurements and evaluation of the Penn State CSS validates its performance by producing suppression factors that are consistent to those obtained prior to the dismantling and reconstruction of the CSS. Furthermore, these suppression factor results remain among the highest reported in the literature.

Author: J. A. Cooper
Publisher:
ISBN:
Category : Radiochemical analysis
Languages : en
Pages : 30

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Author: P. R. Howland
Publisher:
ISBN:
Category : Spectrometer
Languages : en
Pages : 90

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Author: Ronald Beetz
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ISBN:
Category :
Languages : en
Pages : 128

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Author: Leslie Edward Beavers
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ISBN:
Category : Fission products
Languages : en
Pages : 104

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Author:
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ISBN:
Category :
Languages : en
Pages : 4

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We have tested a single-crystal bismuth-germanate annulus in conjunction with a high-purity germanium detector as a Compton-suppression spectrometer, and have measured gamma-ray energies of up to 6.13 MeV. 1 ref., 9 figs., 2 tabs.

Author:
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Category :
Languages : en
Pages : 6

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During the last decade the application of arrays of 10--30 Compton Suppressed germanium (CSG) detectors in the field of [gamma]-ray spectroscopy has led to a number of significant advances in studies of nuclear structure. Despite the success of these instruments, most of them are limited to detecting two-fold (and in a few cases three-fold) coincidences from highmultiplicity cascades. To increase the detection sensitivity for weak cascades, proposals have recently emerged for construction of much larger arrays. In the USA, the proposed array, called GAMMASPHERE, is to have 110 large CSG detectors which will subtend a solid angle of almost 2[pi] steradians, sufficient to permit routine acquisition of up to 5-fold coincidences from high-multiplicity cascades. This together with other improvements, will yield a resolving power several orders of magnitude greater than currents arrays. In Europe, an array of similar size and power, called EUROGAM, is currently being constructed. In this paper, we report on measurements of the Compton suppression and overall P/T ratio of two Ge detectors in a BGO shield of the honeycomb pattern. These were the first prototype CSG detector assemblies for GAMMASPHERE.

Author: Gordon L. Nicholson
Publisher:
ISBN:
Category :
Languages : en
Pages : 224

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The following document is a presentation of work undertaken while at The University of Texas at Austin in the Nuclear Engineering program. A literature review of pertaining to Compton suppression and the necessary components associated with it are presented. An overview of the work I have performed at The University of Texas at Austin is presented. The research focused on Compton suppression with emphasis on characterization of the detection system used as well as applications of Compton suppression for real world use. Characterization of the system was performed in such ways as measuring the optimal location for samples to be placed relative to the detector face, determining the ideal location of the detector within the NaI crystal to obtain the best peak to Compton ratio, understanding the relationship between detector dead time and the effectiveness of Compton suppression, and verifying the applicability of Poisson statistics to Compton suppressed detection systems. The applications of Compton suppression for real world use took the form of research carried out with irradiated samples to determine the effectiveness of using such techniques for fission product identification. Finally, an overview of the work performed at Los Alamos National Laboratory is given. The work at LANL focused on setting up electronic components used in nuclear spectroscopy experimentation as well as a complete analysis of the program SYNTH that is used for modeling spectra from radioactive isotopes.