Abstract: Affected by the dead-time, the Digital Multichannel Analyzer (DMCA) which receives gamma spectrum will occur counting rate loss. This effect will bring some errors to γ spectrum analysis. Therefore it is necessary to correct the gamma spectrum with counting rate loss. Based on the dead-time model of Digital Multichannel Analyzer, Lambert W function is used to establish the closed form solution of real counting rate relative to the measured counting rate. Then the definition of counting rate limit of DMCA and the theoretical calculation of the optimal threshold of the dead time of the fast channel are proposed, and the pulse signal detected by fast channel is used as the basis of counting rate correction. Based on this basis, a method for correcting the counting rate of gamma spectrum is proposed. Experimental results show that this method can correct the counting rate loss effectively;Within the range of counting rate less than 1.8 Mcps of DMCA [using LaBr₃(Ce) detector], the relative inherent error of the net counting rate at the corrected characteristic peak is less than 9%, and the linear correlation coefficient between the net counting rate at the characteristic peak and the doserate was above 0.995, which broadens the application range of Digital Multichannel Analyzer.

Key words: Digital Multichannel Analyzer, dead-time, Lambert W function, spectrum correction