A SOFTWARE COUNTING LOSS CORRECTION METHOD FOR NEUTRON-ACTIVATION ANALYSIS WITH SHORT-LIVED RADIONUCLIDES

A method has been developed for the correction of counting losses in N AA for the case of a mixture of short-lived radionuclides. It is appli cable to systems with Ga detectors and Wilkinson or successive approxi mation ADC's and will correct losses from pulse pileup and ADC dead ti me up to 90%. The losses are modeled as a constant plus time-dependent terms expressed as a fourth order polynomial function of the count ra tes of the short-lived radionuclides. The correction factors are calcu lated iteratively using the peak areas of the short-lived radionuclide s in the spectrum and the average losses as given by the difference be tween the live time and true time clocks of the MCA. To calibrate the system a measurement is performed for each short-lived nuclide. In a t est where the dead time varied from 70% at the start of the measuremen t to 13% at the end, the measured activities were corrected with an ac curacy of 1%.