EXTERNAL STANDARD METHOD FOR THE DETERMINATION OF THE EFFICIENCY IN LIQUID SCINTILLATION COUNTING

The use of an external gamma source was investigated to see if the detection of gammas in the C/sup 14/ scintillation counter could be correlated with the efficiency. Cs/sup 137/ Ce/sup 144/, and pitchblende were used as gamma sources, and different quenchers were used to vary the efficiency. The plots of C/sup 14/ efficiency vs gamma count rate show that, for a given source, the degree of quenching is independent of the type of quencher used. It is pointed out, however, that the external source offers only secondary standardization as it relies on the internal standard method for the initial correlation curve. (D.L.C.)