Abstract
In this paper,we have compared the performances of the digital zero-crossing and charge-comparison methods forn/γ discrimination with liquid scintillation detectors at low light outputs. The measurements were performed with a 2″ x 2″ cylindrical liquid scintillation detector of type BC501A whose outputs were sampled by means of a fast wave form digitizer with 10-bit resolution,4G S/s sampling rate and one volt input range. Different light output ranges were measured by operating the photomultiplier tube at different voltages and a new recursive algorithm was developed to implement the digital zero- crossing method.The results of our study demonstrate the superior performance of the digital zero- crossing method at low light outputs when a large dynamic range is measured.However,when the input range of the digitizer is used to measure a narrow range of light outputs, the charge-comparison method slightly outperforms the zero-crossing method. The results are discussed in regard to the effects of the quantization noise and the noise filtration performance of the zero-crossing filter. slightly outperforms the zero-crossing method. The results are discussed in regard to the effects of the quantization noise and the noise filtration performance of the zero-crossing filter.