Experimental tests of zero dead time gamma-ray spectrometry of rapidly decaying sources with the DSPEC^{PLUS ®}

Abstract

In the year 2000, at the MARC V conference, the first results obtained at constant count rates with so-called "zero dead time counting" (ZDT) as implemented in ORTEC's DSPEC^{PLUS ®} were presented. In this paper, further experiments are described that were performed to establish how the DSPEC^{PLUS ®} performs at varying count rates. At the same time, the experiments were designed to demonstrate the possible inadequacy of the dual spectrum approach sometimes used to solve the problem of non-Poisson counting statistics encountered in loss-free counting, and to test the "variance spectrum" alternative offered by the DSPEC^{PLUS ®} . It is concluded that the DSPEC^{PLUS ®} performs with good accuracy at dead times lower than 90%, even when count rates vary. It is also concluded that the dual spectrum approach indeed is inadequate. Finally, it is shown that the "variance" spectrum approach provides the correct uncertainties to be used in the treatment of LFC or ZDT data.