Investigations on the development of a 'proportional' scintillation counter

Theoretical studies on the feasibility of obtaining a scintillation counter whose detecting efficiency is proportional to the energy of the interacting photon have been made. It has been found that it is possible to make the efficiency of the counter proportional to the photon energy by combining a suitable filter with a conventional NaI(Tl) cry NaI(Tl) crystal. Experimental realisation of such a counter presented here has been obtained by combining an aluminium filter of thickness 35 gm/cm2 with a 2'' x 2'' NaI(Tl) crystal. The efficiencies obtained experimentally for five different photon energies (279, 662, 840, 1170 and 1132 keV) show reasonably good agreement with the theoretically predicted values. This type of counter can be used as a sensitive dosimeter or in the measurement of energy albedo of backscattered photons avoiding the tedious response matrix correction of the detector in question. (auth.)