Development of an alpha fast-slow coincidence counter for analysis of ²²³Ra and ²²⁴Ra in seawater

Abstract

An alpha fast-slow coincidence counter has been designed and manufactured for measuring the low alpha activities of ²²³Ra and ²²⁴Ra in the seawater. In this work, Radium from the seawater was absorbed onto a column of MnO₂ coated fiber (Mn fiber). The short-lived Rn daughters of ²²³Ra and ²²⁴Ra which recoil from the Mn fiber are swept into a scintillation detector where alpha decays of Rn and Po occur. Signals from the detector are sent to a delayed coincidence circuit which discriminates decays of the ²²⁴Ra daughters, ²²⁰Rn and ²¹⁶Po, from decays of the ²²³Ra daughters, ²¹⁹Rn and ²¹⁵Po.