Performance of the Packard 2000 CA/LL and 2250 CA/XL Liquid Scintillation Counters for 14C Dating

Abstract

Results are presented on the comparative characteristics of the Packard 2000 CA/LL liquid scintillation counter with and without the low-level option on line. An initial performance assessment using 14C labeled benzene with butyl-PBD as the scintillant revealed that although the background count rate decreased by approximately a factor of 3 using the low-level option, a substantial decrease in efficiency was also observed. However, subsequent investigations have indicated that, by careful manipulation of both scintillant composition and concentration, this loss in efficiency can largely be overcome with little or no concurrent increase in background count rate. The introduction of an active vial sample holder and a new light-guide system proved to be significant advances on the standard 2000 CA/LL.