Preliminary Design of Integrated Digitizer Base for Photomultiplier Tube

Abstract

In many physical experiments and applications with photomultiplier tubes (PMTs), high-speed pulse digitalization is used extensively. The current pulse from a PMT has a rising time of several to a hundred nanoseconds. The current pulse shape can be used to obtain the pulse energy and discriminate between different particles. The conventional readout system with a PMT uses the discrete or integrated pulse-shaping circuits and analogue-to-digital converter boards which are based on the NIM or VME system to implement the data acquisition function. In many applications, such as security instruments, there are only several PMTs used in the whole system, or in some distributed applications, long-distance analogue cable with high-voltage power cable is not applicable due to the tremendous number of channels and enormous distributed space. In this paper, an integrated digitizer base is designed and interfaced with a Cs2LiYCl6 (CLYC) scintillator with a PMT. The CLYC scintillator has the ability to realize the pulse shape discrimination (PSD) between the neutron and gamma-rays. There is only one Gigabit of unscreened twisted-pair cable needed for over 700 Mbps TCP data throughput and more than 10 W power. The boards of high voltage supply, current sensitive preamplifier, 500 MSPS/12-Bit ADC (Analog-to-Digital Converter), readout module based on ZYNQ SoC (System on Chip), power over Ethernet, and user interface circuits are stacked with board-to-board connectors. The system can achieve 4.6% gamma-ray energy resolution at 662 keV with a 20-{\mu}s pulse integral and PSD figure-of-merit of ~3.0 for the whole energy of neutrons and gamma-rays. This integrated digitizer base can also be interfaced with other detectors with a PMT.