Enhanced counting efficiency of Cerenkov radiation from bismuth-210

This paper describes the measurement of Bi-210 by Cerenkov counting in a co mmercial liquid scintillation counter. The counting efficiency in water is 0.17 counts per second per Becquerel (17%). When the enhancers Triton X-100 (15% v/v) and sodium salicylate (1% m/v) are added to the solution the cou nting efficiency for Bi-210 increases from 17% to 75%. The Po-210 daughter of Bi-210 causes interference of 0.85 counts per second per Becquerel in th e presence of the enhancers but not in water. When Bi-210 and Po-210 presen t in secular equilibrium the total counting efficiency is 160%. When Bi-210 and Po-210 not in secular equilibrium the Po-210 can be removed immediatel y before counting by plating onto silver foil. The use of the enhancers giv es a substantial increase in counting efficiency compared to counting in wa ter. Compared with solutions used in liquid scintillation counting the enha ncer solution is inexpensive and can be disposed of without environmental h azard.