Study of dead time estimation method based on pulse interval distribution

Abstract

In nuclear radiation detection, some measured radiation counts are lost due to dead time. Estimation of dead time is necessary to restore the counting information in quantitative analysis. This study aims to propose a method for estimating dead time at high counting rate. First of all, a measurement system of pulse interval distribution was used to estimate the true input counting rate of the detection system and implemented in FPGA. Then, a digital pole-zero cancellation technique was introduced in the measurement system to decrease the decay time constant of pulse. This was aimed at mitigating the impact of pile-up on the pulse interval distribution spectrum, especially at high counting rate. The feasibility of this measurement system at high counting rate was verified by the experimental platform of EDXRF. The dead time was calculated using the measured counting rate and the estimated true input counting rate. The accuracy of the dead time relies on the precision of the estimated true count rate. When the counting rate reaches 600 kCPS, the relative error between the theoretical counting rate and the estimated true input counting rate is less than 5%.