Digital rise-time discrimination of large-area avalanche photodiode signals in X-ray detection

The response of a large-area avalanche photodiode to X-rays was investigated by applying pulse-shape discrimination techniques based on rise time. The method employed analog preshaping with time constants of 200 ns followed by digital signal processing in a commercial 125-MHz digitizer. Pulse rise-time discrimination was applied to improve detector energy resolution, background level, and peak distortion. Electronic noise pulses can be efficiently removed at the expense of data-acquisition throughput.