Coincidence-summing in gamma-ray spectrometry by excitation of matrix X-rays

Coincidence summing of X- and gamma rays of 75Se

A study of coincidence summing of X- and gamma rays of (75)Se has been presented in this paper. The computation of the (75)Se spectra was performed by application of the previously published theory by Novković et al. The method enables the treatment of all possible single and sum peaks of (75)Se. The calculation gave the 419 decay path outcomes, resulting in 84 peak count rate equations and also the total count rate equation. By HPGe spectrometers with 15% and 18% relative efficiency, 20 and 30 peaks were recorded, respectively. Some simplification of the decay scheme was introduced and existing metastable level had to be treated separately. Nevertheless, the experimental values of the peak count rates were in good agreement with the theoretical evaluation.

Calculation of coincidence summing corrections for X-ray peaks and for sum peaks with X-ray contributions

In this paper, features of the gamma-ray spectra in the presence of important contributions of X-rays to coincidence summing effects are studied. The experimental results concerning the sum peaks with various X-ray combinations as well as the Ge X-ray escape peaks present in the spectrum of a 133Ba point source measured with an n-type detector are in good agreement with the values computed using the GESPECOR software.

Extension of the efficiency calibration of germanium detectors using the GESPECOR software

To avoid losses due to coincidence summing, the efficiency calibration of gamma-spectrometers is often carried out by means of radionuclides emitting only one photon during a single decay. Calibration with this kind of radionuclides has, however the disadvantage that the energy range of the gamma rays (46 keV<E<1115 keV) is limited. Coincidence-summing corrections can be calculated with the Monte Carlo program Germanium Spectrometry Correction for multi gamma radionuclides which emit photons with energies above this range. The efficiency curve as a function of energy can therefore be extended up to 2.7 MeV with uncertainties below 4%.

Efficiency calibration of high volume samples using the GESPECOR software

In this paper the Monte Carlo simulation program GESPECOR is applied for the computation of the efficiency of an HPGe gamma-spectrometry system used for the measurement of high volume samples. The detector characterization required for Monte Carlo simulation is achieved by a trial and error procedure using the efficiency values measured with point sources placed in several positions. After detector characterization, the efficiency values appropriate for the assessment of 220l waste drums are computed and compared with experimental values.

Application of GESPECOR software for the calculation of coincidence summing effects in special cases

In this work, coincidence summing correction factors have been measured for 133Ba, 152Eu and 88Y point sources with a 50% relative efficiency p-type detector and a 25% relative efficiency n-type detector in two close-to-detector measurement geometries. The experimental data for 133Ba and 152Eu and the results obtained with the GESPECOR software reveal a complex structure of the conventional dead layer of the p-type detector. The high value of the coincidence summing correction factor for the 511 keV peak of 88Y, in agreement with the values computed by GESPECOR, in this case cautions against the application of the semiempirical method for evaluating coincidence summing effects.

Transfer of the efficiency calibration of Germanium gamma-ray detectors using the GESPECOR software

The GESPECOR software was extended to incorporate procedures for the computation of the efficiency transfer factor for cases of practical interest: (a) sources with identical geometry, but different matrices, (b) sources with similar (but not identical) geometry; and (c) transfer from a point source to a volume source. Fast and accurate algorithms. based on correlated sampling, were implemented for solving the first two cases. A procedure to take into account the imperfect charge collection in the detector was implemented.

Accurate computation of coincidence summing corrections in low level gamma-ray spectrometry

The GESPECOR (Germanium Spectrometry Correction factors) software, previously developed for computing the self-attenuation and coincidence summing corrections, was applied to the computation of the coincidence summing correction factors for a well-type and two coaxial HPGe detectors. Cylindrical samples as well as Marinelli beaker samples were considered. The computed values are in good agreement with carefully measured values. A detailed study of the uncertainties assigned to the results was carried out. The analysis shows that the procedures used in GESPECOR are reliable and provide results with a well defined accuracy.