Calculation of the detection limits with the least-squares method in gamma-ray spectrometry: A simple procedure.

A metrologically consistent procedure for assessing the detection limits of activity measurements for gamma-ray emitters with high-resolution spectrometers using the LSQ method is described and tested. As the input to the assessment, besides the measured contents of the spectral channels, the results of the peak analysis, i.e.

Decision threshold as a gauge of the measurement quality in gamma-ray spectrometric measurements.

We show that in gamma-ray spectrometric measurements the decision threshold depends on the observed value of the measurand. Since the decision threshold is intended to describe the sensitivity of the measurement, this dependence restricts its application to measurements where the indication is not expressive. To extend the direct applicability of the decision threshold to expressive indications in gamma-ray spectrometric measurements, where mainly the Region-of-Interest method is used to evaluate the isolated peaks, a recalculation of the decision thresholds to the peak widths corresponding to the inexpressive peaks is proposed.

Influence of the solar activity on the background of a high-resolution gamma-ray spectrometer.

The count rate in the peak of a gamma-ray spectrum at 2223 keV was measured over a period of 25 years. The peak is produced by neutron capture on hydrogen, a constituent of the spectrometer's shield. Since the neutrons are produced by cosmic rays, the count rate in the peak is correlated with the solar activity via the interaction between the solar wind and the cosmic rays.

Comparison of different approaches of soil sampling uncertainty determination.

The ISO/IEC 17025 standard requires that all significant contributions have to be propagated to the measurement uncertainty, including also sampling uncertainties. We evaluated soil sampling uncertainties for gamma-ray spectrometry by using in-house and split-sample methods. By in-house method, the sampling uncertainty was determined by comparing standard deviations of measurement results and average analytical uncertainty.

Calculation of decision thresholds according to the standard ISO 11929-3 in case of presence of the peaked background.

The method of calculation of the decision threshold with the Least Squares Method, described in the standard ISO 11929, is presented for the case when the sources of peaked background contribute to the peak holding the indication. The decision threshold is calculated from spectral data corresponding to the indication zero; therefore, the observed indication must be removed from the spectrum. When the peaked background is present, the indication completely overlaps with the peaked background, so it can't be unfolded directly.