A High Rate 4πβ-γ Coincidence Counting System

A high count rate 4πβ-γ coincidence counting system for the determination of absolute disintegration rates of short half-life radionuclides is described. With this system the dead time per pulse is minimized by not stretching any pulses beyond the width necessary to satisfy overlap coincidence requirements. The pulse widths in the beta-ray (β), gamma-ray (γ), and coincidence channels are extendable and not fixed. Therefore, the dead-time for each channel is measured and recorded along with the gross count data during each counting period. The equations used to correct for the β, , and coincidence channel dead times and for accidental coincidences are presented but not rigorously developed in this paper. Experimental results are presented for a decaying source of ⁵⁶Mn initially at 2 × 10⁶ d/s and a set of ⁶⁰Co sources of accurately known source strengths varying from 10³ to 2 × 10⁶ d/s. A check of the accidental coincidence equation for the case of two independent sources with varying source strengths is presented.