Estimation of true coincidence corrections for voluminous sources

Kolotov, V. P.; Atrashkevich, V.; Gelsema, S.J.

doi:10.1007/bf02055417

Cited by 23 publications

(6 citation statements)

References 13 publications

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“…The problem remains, however, how to measure accurately this detector characteristic in an easier way. Some recommendations have been given earlier [2], but it is obvious that using the experimental approach it is not possible to eliminate all sources of the scattering of radiation (due to the detector's construction, such as the end cap, contacts, different layers, etc.). This results in an observable decrease of the P/T ratio that may affect the coincidence correction.…”

Section: Resultsmentioning

confidence: 98%

“…To compute the overall TCE correction factor for voluminous samples it is necessary to integrate a volumetric TCE function over the sample volume [2]. The method developed for the computation of this correction factor is based on: (i) a full peak efficiency map generated in advance [1]; (ii) an intrinsic P/T-calibration calculated from previous measurements.…”

Section: Introductionmentioning

confidence: 99%

“…Some authors have suggested to use the experimental P/T-ratios for small subsamples during the integration of the coincidence effect and have demonstrated improvement of the results [1]. We had previously assumed that the intrinsic P/T-calibration is suitable only for small detectors, whereas the scattering must be taken into account for large detectors [2,4]. However, with…”

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confidence: 99%

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Mapping of true coincidence effect value for voluminous sources measured with HPGE

1999

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Based on the methodology of the full peak efficiency mapping of HPGe detectors, a means to model the computation of the true coincidence effect inside a voluminous sample was developed. A summing-in and a summing-out case are used as examples to illustrate the magnitude of the true coincidence effect for a 60% HPGe. The applicability of the intrinsic P/T-calibration in the course of the integration of the coincidence effect is also discussed. IntroductionMeasurement of voluminous samples is a common task in many radioanalytical laboratories. To reach a higher sensitivity of analysis one must use a highly efficient detector and position the sample to the detector as close as possible. Correct determination of the absolute radioactivity of the sample requires the a priori determination of a full peak efficiency curve for the specific source geometry and the appropriate correction for the true coincidence effect (TCE). In fact, the TCE is observed for a great majority of analytical lines in all close geometries. Since the TCE is a geometry effect, placing samples close to the detector results in an increasing need to make the correction. For example, a 60% HPGe detector may exhibit TCE in the range of tens of percents [1].To compute the overall TCE correction factor for voluminous samples it is necessary to integrate a volumetric TCE function over the sample volume [2]. The method developed for the computation of this correction factor is based on: (i) a full peak efficiency map generated in advance [1]; (ii) an intrinsic P/T-calibration calculated from previous measurements. It has been demonstrated that such an approach works quite well for HPGe detectors with the relative efficiency up to 60 % [1]. It is also well known that the magnitude of the effect depends on the distance of the point of emission of the gamma-quanta, the detector peak and total efficiencies and the type of gamma cascade.In our previous papers we have shown that the application of the so called intrinsic P/T-calibration allows to get an estimation of the TCE correction integral that is sufficiently accurate for voluminous samples. At the same time, experiments show that due to the scattering of radiation in the material of a voluminous sample the measured P/T ratio is lower than the intrinsic one. The contribution of the scattered radiation may reach 30 % and more in some cases. Some authors have suggested to use the experimental P/T-ratios for small subsamples during the integration of the coincidence effect and have demonstrated improvement of the results [1]. We had previously assumed that the intrinsic P/T-calibration is suitable only for small detectors, whereas the scattering must be taken into account for large detectors [2,4]. However, with

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Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Mapping of true coincidence effect value for voluminous sources measured with HPGE

1999

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“…The p/t ratio is a directly measurable quantity, at least for a single radionuclide source, and it is a strong function of gamma energy. It has been demonstrated that p/t also depends on the radioactive source position with respect to the Ge detector [48], the feature we explore in the present work.…”

Section: Introductionmentioning

confidence: 89%

Monte Carlo Simulation Study of Hot-Particle Detection in Voluminous Samples by Gamma Spectrometry

Chu¹,

Burn²,

Bradt³

et al. 2021

JAMP

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In this work, we addressed the inhomogeneity problem in gamma spectrometry caused by hot particles, which are dispersed into environment from large nuclear reactor accidents such as at Chernobyl and Fukushima. Using Monte Carlo simulation, we have determined the response of a gamma spectrometer to individual and grouped hot particles randomly distributed in a soil matrix of 1-L and 0.6-L sample containers. By exploring the fact that the peak-to-total ratio of efficiencies in gamma spectrometry is an empirical parameter, we derived and verified a power-law relationship between the peak efficiency and peak-to-total ratio. This enabled creation of a novel calibration model which was demonstrated to reduce the bias range and bias standard deviation, caused by measuring hot particles, by several times, as compared with the homogeneous calibration. The new model is independent of the number, location, and distribution of hot particles in the samples. In this work, we demonstrated successful performance of the model for a single-peak 137 Cs radionuclide. An extension to multi-peak radionuclide was also derived.

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“…As a result of all this, no analytical or semiempirical method proposed today for introducing corrections for true summation has adequate accuracy and universality [1][2][3][4][5]. An alternative method is a calculation using the Monte Carlo method.…”

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Calculations of the corrections for the true summation of cascade γ rays on the basis of statistical simulation using evaluated nuclear data

Berlizov

Даниленко²,

Solov’eva³

et al. 2006

At Energy

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A method of calculating the corrections to the true summation of the γ radiation for arbitrary radionuclides for measuring point and volume sources using scintillation and ultrapure germanium detectors is described. The calculations are based on the Monte Carlo method using ENSDF evaluated data on the structure of atomic nuclei. An experimental check made using IAEA test spectra confirms that the calculations of the correction factors are reliable. The method is integrated into the γ spectrometric packages LSRM-2000 and AkWin, where the corrections for the ture summation are used for developing a library.The increase or decrease in the number of counts recorded in the total-absorption peaks as a result of summing the impulses at the exit of a detector can strongly influence the accuracy of the results of γ spectrometry. Taking account of this effect is now one of the mandatory requirements for modern γ-spectrometric software.The effect appears in measurements of radiation from cascade sources and is due to the summation of impulses while simultaneously detecting two or more γ rays in the sensitive volume of a detector. This distorts the measured γ-ray spectrum, specifically, it changes the areas of the total-absorption peaks, deforms the continuous Compton distribution, and results in the appearance of spurious peaks in the energy, which are absent in the true emission spectrum of the source.In contrast to the random summation, where the probability of detecting impulses simultaneously is proportional to the squared counting rate at the entrance into the spectrometric channel, the intensity of true summation is determined by the measurement geometry, the characteristics of the detector, and the special features of the radionuclide cascade scheme. The difficulty of introducing corrections for the true summation is due, first and foremost, to the fact that it is necessary to know the γ-ray detection efficiency along the total-absorption peak and the total efficiency which depends on the relative arrangement and configuration of the source and detector, as well as of the environment in which scattering and backward reflection of γ rays occur. The problem is exacerbated during measurement of radiation from a volume source, which effectively absorbs and scatters its own radiation.An accurate calculation requires taking into account the possible anisotropy of the angular distribution of the emitted cascade photons. In addition, the coincidence of γ radiation with annihilation (511 keV) photons must be taken into account when measuring a source of β + radiation. A coincidence of the γ radiation from the source and the characteristic and

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Estimation of true coincidence corrections for voluminous sources

Cited by 23 publications

References 13 publications

Mapping of true coincidence effect value for voluminous sources measured with HPGE

Mapping of true coincidence effect value for voluminous sources measured with HPGE

Monte Carlo Simulation Study of Hot-Particle Detection in Voluminous Samples by Gamma Spectrometry

Calculations of the corrections for the true summation of cascade γ rays on the basis of statistical simulation using evaluated nuclear data

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