Quench correction in Čerenkov counting: Channels ratio and external source channels ratio methods

Abstract

Channels ratio and external source ratio methods which may be used for accurate quench correction in Čerenkov counting systems have been developed. In general, the channels ratio method will be more accurate for quench correction in high count rate samples where good ratio statistics are available. For low level samples, the external source channels ratio method will provide more accurate quench correction if efficiencies are greater that 10%. In either method, quench correction curves (efficency vs ratio) will be the same for a given solvent regardless of quencher. However, the solvent must be the same for all standards and samples since quench curves vary somewhat with solvent. Both channels ratio and external source channels ratio calibration methods are volume dependent. In either case, however, the results show that the effect of sample volume is sufficiently small that it will be negligible if volumes are approximately constant (approximately ±10%). An exception to this is present in the high quench region when using external source ratio. In this case, low volume samples are shown to deviate significantly. For this reason, it is recommended that samples be made to a volume of greater than 10 ml when this technique is utilized. The development of simple and accurate quench correction techniques for Čerenkov counting make the technique far more useful for the determination of beta emitters which are sufficiently energetic to generate Čerenkov radiation.