Browsing by Subject "Gamma-gamma coincidence"
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Item Advances in gamma-ray spectroscopy : compton suppression and gamma-gamma coincidence(2011-05) Horne, Steven Michael; Landsberger, Sheldon; Biegalski, StevenThis project aims to improve research in gamma-ray spectroscopy by using advanced detector systems. These systems are designed to reduce interference inherent in gamma-ray spectroscopy by rejecting Compton scattering events from high-energy gamma-rays, as well as look at cascading decays of gamma-rays through gamma-gamma coincidence counting. By combining these methods, one is able to lower detection limits for many elements than would otherwise be possible. This work also takes advantage of neutron activation analysis, which allows stable elements to be analyzed by activating them with neutrons, causing them to become unstable and decay with radioactive signatures. By analyzing these signatures, one is able to detect trace levels of elements with relatively small samples sizes (< 1g) and in a nondestructive manner.Item Angular correlation of gamma-gamma coincidence measurements for neutron activation analysis(2023-04-14) Smith, Kevin George; Landsberger, Sheldon; De Luna, Brandon AThe angular correlation of coincident gamma-rays emitted from Europium-152 (¹⁵²Eu) was determined by measuring coincident gamma-rays at multiple distances and detector orientations. Due to the nature of ¹⁵²Eu, it is possible to look at coincident gamma-rays produced during beta minus (β-) decay and electron capture. By looking at the 344 keV and 778 keV coincident gamma-rays which result from β- decay, and the 121 keV and 244 keV coincident gamma-rays from electron capture, an angular correlation coefficient (W) was calculated. The W for gamma-gamma coincidence produced by electron capture was higher when the detectors were at or close to parallel (180°). The W for gamma-gamma coincidence for β- decay was higher as the angle between detectors approached perpendicular (90°).Item Digital gamma-gamma coincidence measurements for neutron activation analysis(2022-07-01) Martinez, Francis Jude; Landsberger, Sheldon; Bode, Peter; Charlton, William; Haas, DerekThe ability to perform low level counting, specifically gamma spectroscopy, for unknown radionuclides provides some challenges. In many cases, the ability to assess a material requires the use of neutron activation analysis (NAA) to excite the unknown sample to allow for the use of gamma ray measurement techniques to determine the radionuclides that are present. Quite often, the ability to identify unique gamma rays is challenging due to the fact that many radionuclides have gamma rays that have energies that are nearby other gamma rays from other radionuclides. The Compton continuum and high background radiation levels also contribute to the difficulty to make these measurements. This research has explored the use of an advanced digital gamma-gamma coincidence system, XIA Pixie-16, for use in neutron activation analysis. The reason for performing this research is that, although gamma-gamma coincidence in NAA is not a new area of research, there has not been a comprehensive study of the use of gamma-gamma coincidence for all NAA products. This research has the potential to benefit research and experiments that utilize NAA techniques for identifying unknown samples. The new XIA Pixie-16 system was first assembled and characterized. It was then used to perform measurements for all applicable short-lived, medium-lived and long-lived NAA products. The gamma-gamma coincidence system was utilized to identify radionuclides in different samples that have been demonstrated to be difficult to identify using standard gamma spectroscopy techniques. A thorough evaluation of the results of this research should serve as a reference for all future NAA research.Item Identification of the radionuclides in spent nuclear fuel that may be detected by Compton suppression and gamma-gamma coincidence methods(2011-05) Schreiber, Samuel Stuart; Landsberger, Sheldon; Orton, Christopher R.The nuclides present in spent nuclear fuel are categorized according to their capacity for detection by Compton suppression or gamma-gamma coincidence methods. The fifty nuclides with the highest activities in spent fuel are identified, their decay schemes analyzed, and the best detection scheme for each is recommended.Item Multispectral gamma-ray analysis using clover detectors with application to uranium fission product analysis(2013-05) Horne, Steven Michael; Landsberger, Sheldon; Jackman, Kevin RichardA high-efficiency gamma-ray counting system has been built at Los Alamos National Laboratory for use in analyzing nuclear forensics samples. This system consists of two clover high-purity germanium detectors and is surrounded by a thallium-doped sodium iodide annulus. Special precautions have been taken to ensure the system has a low background. The system is connected to XIA Pixie-4 fast digitizers and collects data in list-mode. This work is split into two main parts. The first part describes the proper steps and techniques to initialize the settings of a detector system connected to fast digitizers in order to optimize the system for resolution and throughput. The various counting modes for this particular system are described in detail, including the benefits and drawbacks of each mode. Steps are then shown to characterize the system by obtaining efficiency curves for various counting modes and sample geometries. Because of the close counting geometry involved with this system, true-coincidence summing factors must be calculated, and are done so in part by measuring the peak-to-total ratios of the system in its various counting modes across a wide energy range. The dead-time for the system can be complicated due to the multiple inputs of the system. Techniques for calculating the dead-time of multiple-detector systems are discussed. The second part of this work shows the system's usefulness in analyzing nuclear forensics samples, specifically irradiated enriched uranium. Three fission product parent-daughter pairs of different lifetimes are analyzed over a course of six months. The activities of each nuclide are calculated at each time step. Age dating techniques using the parent-daughter pairs are discussed, as well as the detection limits of each nuclide for a range of sample ages. Finally, avenues for further research are presented, as well as potential sources of error or uncertainty for this work.