This paper describes a Monte Carlo (MC) simulation method for calculating radioxenon beta-gamma coincidence spectral information.
These spectral components include detector response simulations by Geant4 modeling, detector energy and resolution calibrations
using the histograms of detector response, beta-gamma coincidence efficiency values and spectral interference ratios. The
work presented in this paper demonstrates the feasibility of using the spectral information to create beta-gamma coincidence
spectra at various radioxenon activity concentrations. The analysis of these synthetic spectra by XECON software shows an
excellent correlation between the analysed radioxenon activity concentration and number of MC samplings.
In this work, a Monte Carlo (MC) simulation model is established to accurately characterize a phoswich beta-gamma coincidence
detector system. This model can be easily used to predict the beta-gamma coincidence efficiencies of xenon radioisotopes at
various stable xenon concentrations in the counting cell. The results demonstrate that there is a significant inverse correlation
between beta-gamma coincidence efficiency and stable xenon concentration. The influence of stable xenon concentration on beta-gamma
coincidence counting efficiency has been investigated for each individual xenon radioisotope. The results indicate that the
effect of stable xenon concentration on beta-gamma coincidence efficiency depends on the xenon radioisotope and its decay
modes. The coincidence efficiency of 133Xe with 31.0-keV X-ray decay mode is the most affected one; and then followed by 131mXe, 133Xe with 81.0-keV gamma-ray decay mode, 133mXe and finally 135Xe. The study also indicates that the gamma absorption by xenon gas plays more of a role in the decrease of beta-gamma coincidence
efficiency for 133Xe and 135Xe, and that the conversion electron spectrum shifting and broadening plays more of a role in the reduction of beta-gamma
coincidence efficiency for the metastable radioxenon of 131mXe and 133mXe.
The study demonstrates the advantages of an innovative list-mode multispectral data acquisition system that allows simultaneous
creation of several different single, summed, coincident and anticoincident spectra with a single measurement. One of the
consequences of list-mode data file offline processing is a reconstructed spectrum with Compton continuum suppression and
without any full-energy peak efficiency deduction owing to true coincidence summing. The spectrometer is designed to read
out analogue signal from preamplifier of gamma-ray detectors and to digitalize it using DGF/Pixie-4 software and card package
(XIA LLC). This is realized by converting an Ortec Compton suppression data acquisition system into an all-digital spectrometer.
Instead of using its timing electronic chain to determine the coincidence event, the analog signals from primary and guard
detectors were connected directly into the Pixie-4 card for pulse height and time coincident measurement by individually logging
and time stamping each electronic pulse. The data acquired in list-mode included coincidence and anticoincidence events consisting
of records of energy and timestamp from primary and guard detectors. Every event was stored in a text file for offline processing
and spectral reconstruction. A sophisticated computer simulation was also created with the goals of obtaining a better understanding
of the experimental results and calculating efficiency.
This paper reports on initial efforts for uranium isotopic analysis using gamma-rays and X-ray fluorescence coincidence. In
this study, a gamma–gamma coincidence spectrometry was developed. The spectrometry consists of two NaI(Tl) scintillators and
XIA LLC Digital Gamma Finder (DGF)/Pixie-4 software and card package. The developed spectrometry was optimized according to
the considerations of output count rate and gamma peak energy resolution. It has been demonstrated that the spectrometry provides
an effective method of assessing the content of uranium isotopes for nuclear materials. The main advantages of this approach
over the conventional gamma spectrometry include the fact that 235U enrichment can be graphically characterized by its unique coincidence “fingerprints”. The method could be further developed
for fast uranium isotope verification with an established gamma–gamma coincidence spectral imaging library by various nuclear
In this study, a gamma–gamma coincidence spectrometry was developed and examined for environmental low-level cosmogenic 22Na monitoring purposes. The spectrometry consists of two bismuth germanate scintillators (BGO) and XIA LLC Digital Gamma Finder
(DGF)/Pixie-4 software and card package. The developed spectrometry was optimized according to the considerations of output
count rate and gamma peak energy resolution. This spectrometry provides a more sensitive and effective way to quantify even
trace amounts of 22Na with critical detection limit of 9 mBq. A sophisticated computer simulation was also created with the goal of obtaining
a better understanding of the experimental results and gamma–gamma coincidence efficiencies at different sample geometries.