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Heimbigner, Tom R

Publications and source records attributed to Heimbigner, Tom R.

2 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

LaCl3:Ce Coincidence Signatures to Calibrate Gamma-ray Detectors

Abstract Calibrating the gamma-ray detection efficiency of radiation detectors in a field environment is difficult under most circumstances. To counter this problem we have developed a technique that uses a Cerium doped Lanthanum-Tri-Chloride (LaCl3:Ce) scintillation detector to provide gated gammas[ , ]. Exploiting the inherent radioactivity of the LaCl3:Ce due to the long-lived radioactive isotope 138La (t1/2 = 1.06 x 1011 yrs) allows the use of the 788 and 1436-keV gammas as a measure of efficiency. In this paper we explore the effectiveness of using the beta-gamma coincidences radiation LaCl3:Ce detector to calibrate the energy and efficiency of a number of gamma-ray detectors.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Interference Terms for Xenon-135

Systems to measure radioxenon concentrations are continually being improved to provide greater sensitivity and precision. As the systems become more capable, additional terms need to be added to the calculations to account for small previously insignificant effects such as minor decay branches. Recently, additional terms present in the {sup 135}Xe decay were added to the calculations to account for the small (5.2%) fraction of decays that produce cesium K-shell x-rays with an average energy of 32 keV and the Compton scatter of the dominant 250-keV gamma ray. These events overlap with the regions of interest of {sup 133}Xe, {sup 131m}Xe, and {sup 133m}Xe. In typical field applications, the amount of expected {sup 135}Xe is low due to the short half-life (9.14 hours) therefore the small fraction that could be mis-categorized as other isotopes is insignificant in most cases. However, for much more active samples, such as those recently measured in calibration and testing samples with high activity, the amount of mis-categorization can be significant. The additions to the calculations use calibration values to estimate the amount of a possible interference of {sup 135}Xe in the other regions of interest, which are then subtracted out. The calibration values, which are ratios of counts in one region of interest to another, are obtained by measuring with single isotope gases during the calibration process.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗