Digital coincidence acquisition applied to portable β liquid scintillation counting device

A digital coincidence acquisition system applied to a portable liquid scintillation counting device is developed. The system which simplifies the device design consists of a digitizer card of Agilent U1066A DC438, a discriminator and a host computer. The anode analog pulses from two photomultiplier tubes are captured by the system, which adopts the sequence acquisition storage mode. By choosing proper threshold for each channel, coincidence time window of +/- 30 ns, and comparing the pulse amplitudes from two channels, the portable scintillation counting device can be used to detect beta particles. For the unquenched standard H-3 sample, the results show that the detection efficiency is (58.5 +/- 0.1)% and the background is (86.7 +/- 0.7) cpm. Meanwhile, H-3 beta spectrum is obtained.