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Abstract  

The present paper shows that the effective resonance energy
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\overline {E_r }$$ \end{document}
introduced by RYVES, is a useful parameter for the correction of resonance integrals in non-ideal epithermal neutron spectra, which can be approximated by a 1/E1+α-flux distribution. The definition, the characteristics and the calculation of
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are discussed thoroughly. Tabulations are included, giving
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for 96 isotopes.
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Abstract  

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.

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Abstract  

Some methods described in the literature for the determination of α in the 1/E1+α epithermal neutron spectrum are critically reviewed with respect to their accuracy. The multi resonance—detector method with Cd-covered irradiations, as used by SCHUMANN and ALBERT, is generalized by subtracting the epithermal 1/v-tail and by introducing the effective resonance energy, as defined by RYVES. The two-detector method of RYVES is modified by using Cd-ratio measurements, thus eliminating the introduction of systematic errors due to the inaccuracy of absolute nuclear data. The adapted methods are applied in channel 15 of the Thetis reactor (Gent).

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Abstract  

In absolute or comparator standardization methods of (n,
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, introduced to correct for this effect, is reviewed.
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Abstract  

The resonance integrals for 59 isotopes were determined by neutron activation in reactor Thetis. The irradiations were carried out with and without Cd cover. The ratios of the thermal to epithermal fluxes were calculated from the Cd ratio of a Au monitor. From the induced activities in 36 elements, measured by means of γ-spectrometry with Ge(Li) and NaI(Tl) detectors, the values of I0th were obtained.

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Abstract  

In 94 marble samples from 4 quarry districts in Italy (Carrara) and Turkey (Proconnesus, Dokimeion, Usak), minor and trace elements were determined by instrumental neutron activation analysis (INAA) and atomic absorption spectrometry (AAS). The maximum size of the calcite grains (MGS) of the rocks was measured in thin section. For 16 elements considered in this work, the concentration ranges show important inter-district overlaps; this also applies to the maximum grain size. However, the application of cluster analysis, using selected attributes, allows one to discriminate every pair of districts; 90 samples are classified correctly in all classification dendrograms.

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Abstract  

A new method is presented to calculate with improved accuracy the absolute peak efficiency of cylindrical Ge and Ge(Li) detectors for point, disk and cylinder sources, positioned at any source-detector distance. Moreover attention was paid to true-coincidence effects. The method is extensively tested and applied for the analysis of reference materials. The accuracy turned out to be 3% or better.

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