In Figs. 5a and b the variation of b in Eq. (1) as a function of shaping time constant t, are presented for 3He and 4He detectors, respectively. The two data sets in each figure correspond to cases when the detectors were irradiated with a collimated electron beam (90Sr/90Y source) in directions perpendicular and parallel to the anode wire. The same figures show the corresponding dead time of ADC. There is a sharp decrease of b values as the shaping time increases from 2 to 4 ms, indicating that the majority of gamma and beta rays produce pulses with rise times approximately of this value. As expected, the dead time increases proportionally with t, due to the increase in the processing time of the pulses and also because, of the number of pulses with height greater than the lower level discriminator of the ADC (which was set
at 100 mV).