High throughput rate digital processor based on real-time current pulse analysis

Abstract

Charge sensitive type preamplifiers are usually used in scintillators, such as NaI (TI) and BGO, to preprocess the current pulse output of detectors. Under high-intensity gamma radioactive field, the wide falling edge of a charge sensitive preamplifier signal will cause a serious pulse pile-up, and the pile-up pulse will be discarded. Consequently, the pulse throughput rate declines significantly. Meanwhile, the charge sensitive amplifier can easily integrate two pulses with an approximate time of arrival into a single pulse to generate an accidental coincidence effect. After using a current-sensitive amplifier on the current pulse output from the detector in the system designed in this work, such output is digitalized by using a waveform digitizer with 125MHz sampling rate. The baseline is estimated statistically via a histogram, a real-time fitting and peeling algorithm is designed for the falling edge pile-up of the current pulse signal to recover the pile-up signal, and the digital charge of the current pulse signal is integrated to obtain particle energy. A 4L NaI(TI) scintillator detector is used in the experiment to measure the 137Cs γ radioactive source. Under a 165kcps counting rate, the pulse throughput rate is up to 99 %, the accidental coincidence probability is 0.387%, and the energy resolution reaches 7.54%, Even under a 3Mcps counting rate, the pulse throughput rate is still 85.43%. Therefore, the overall performance is superior to conventional voltage-type digital spectrometers under high counting rate application.