A. De Wispelaere

Calculation of the absolute peak efficiency of gamma-ray detectors for different counting geometries

Abstract A new technique is outlined for the calculation of the full-energy peak efficiency of cylindrical gamma-detectors, including coaxial Ge(Li) detectors. Different source geometries are considered, i.e. point, disk and cylindrically shaped sources. Full account is taken of gamma attenuation in the source and in any interjacent absorbing layer. No simplifying mathematical model is adopted and no Monte Carlo calculations are required. Although this method is to be qualified as semi-empirical, the experimental work involved in it is simple and of common practice in most nuclear laboratories. For the calculations a FORTRAN IV + computer program is presented on a VAX 11/780 machine.

k0-Measurements and related nuclear data compilation for (n, γ) reactor neutron activation analysis

Recommended k0-factors and related nuclear data for use in (n, γ) activation analysis are given for 72 isotopes. In addition the basic nuclear constants and experimental parameters needed in the k0 standardization method are reviewed. For convenient data reduction, computer programs were developed.

Accuracy and applicability of the k0-standardization method

The present paper deals with the accuracy and applicability of the k0-standardization technique in NAA. Topics included are: user-oriented outline of the method, relevant nuclear data (k0, Q0, ětc.), the non-1/E epithermal flux distribution, small detector separations and/or extended source geometries, (n, γ) reactions with a Westcott-g≠1, primary interferences, subsequent (interrupted) irradiations, the non-constancy of the neutron flux during irradiation, and a final account of the accuracy. Although the paper is written in terms of the k0-methodology, a good deal of the considerations can be transferred to most types of single-comparator standardization.

The accuracy and precision of the experimental α-determination in the 1/E1+α epithermal reactor-neutron spectrum

Some methods for the experimental α-determination in the 1/E1+α epithermal reactorneutron spetrum are critically compared with respect to their accuracy and precision. The analysis is based on the error propagation theory. Besides the general formulae numerical examples are elaborated for specific conditions in the Thetis reactor (Gent) and the WWR-M reactor (Budapest).

Recent advances in the k0-standardization of neutron activation analysis: Extensions, applications, prospects

This paper reports on the contribution made by some cooperating laboratories to the further development of the k0-method. As to the extensions and improvements, emphasis is put on the availability of an Al−0.1% Au reference material for the k0-standardization of NAA, on the counting of large-diameter samples, on the use of a low-energy photon detector, and on the introduction of the Westcott formalism for the handling of “non-1/v” (n, γ) reactions. A survey is given of a large variety of scientific and industrial applications, including the analysis of biological, geological and geochronological samples, various kinds of reference materials, high-purity products and ceramics, and a number of environmental pollution indicators. As shown, the advantage of the k0-standardization will be fully exploited with an increasing level of automation in NAA laboratories. Eventually, new measurements and evaluations of k0-factors and related nuclear data are given in an Appendix.

Comparative study of measured and critically evaluated resonance integral to thermal cross section ratios, III

In the present paper, a tabulation is given of recommended Q0-values [the ratio of the resonance integral (I0) to the 2200 m·s−1 cross-section (δ0)] for 107 (n, γ) reactions of interest in NAA, including a revision and updating of formerly published results for 57 isotopes. The values were either critically evaluated from literature, or-in the majority of cases — experimentally determined according to the Cd-ratio method, with a correction for a non-ideal epithermal neutron flux distribution. These Q0-measurements were performed at INW, Gent, at KFKI, Budapest, and occasionally at Risø. A comparison is made with results obtained by other workers or with values derived from δ0s and I0s quoted in recent compilations.

K0-measurements and related nuclear data compilation for (n,γ) reactor neutron activation analysis. IIIa: Experimental

The determination of k0-factors has been continued covering now the relevant gamma-lines of 112 analytically interesting radionuclides. Experimental details are given, and an extended tabulation is presented of complex activation decay types and the associated expression for the parameters involved in the k0-method.

Instantaneous α-determination without Cd-cover in the 1/E1+α epithermal neutron spectrum

A new method is developed for instantaneous α-determination in the 1/E1+α epithermal neutron spectrum. It is based on coirradiation of three bare resonance detectors, followed by gamma-counting on a calibrated Ge(Li)-detector. The technique is applied in two channels of the Thetis reactor (Gent) and the results are critically compared with those obtained by other methods.

Applicability of the 1/E1+α epithermal spectrum representation and the effective resonance energy\(\bar E_r\) in NAA

AbstractThe practical applicability of the 1/E1+α epithermal spectrum representation and of the effective resonance energy