LIQUID SCINTILLATION COUNTING RECENT APPLICATIONS AND DEVELOPMENT VOLUME I. PHYSICAL ASPECTS PULSE SHAPE LIQUID SCINTILLATION COUNTING FOR BETAS GAMMA OR BETA-GAMMA COUNTING

A liquid scintillation counting system has been modified to expand the conventional beta counting capabilities to gamma counting as well as simultaneous beta-gamma counting. The in-creased response of the counter is made possible by utilizing a gamma radiation detector as a sample vial holder and pulse shape electronics. The gamma detector is made up of two NaI(Tl) crystals so designed to be optically coupled to both the sample vial and two 1800 opposed phototubes. In the con-ventional beta pulse height analysis mode of counting the crystal detector serves as a passive light pipe. In the gamma mode of counting the detector functions as a gamma radiation detector. Beta-gamma counting is carried out using pulse shape analysis to sort out the rise time difference of the fast liquid scintillator and the relatively slow NaI(Tl) detector. Experimental data describing the capabilities of the counter will be presented. I