Preliminary Design of Integrated Digitizer Base for Photomultiplier Tube

In many physical experiments and applications with photomultiplier tubes (PMTs), high-speed pulse digitization 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 analog-to-digital converter (ADC) boards that are based on the Nuclear Instrument Modules (NIMs) or Versa Module Eurocard (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 analog 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 Cs
₂
LiYCl
₆
(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 Category 5 cable needed for over 700-Mb/s transmission control protocol (TCP) data throughput and more than 10-W power. The boards of high voltage supply, current-sensitive preamplifier, 500-MSPS/12-bit ADC, readout module based on ZYNQ system-on-chip (SoC), power over Ethernet, and user-interface circuits are stacked with board-to-board connectors. The gamma-ray energy resolution is ~4.6% at 662 keV with a 20-μs pulse integral and PSD figure of merit (FOM) is ~3.0 by using the totally recorded events of neutrons and gamma rays. This integrated digitizer base can also be interfaced with other detectors with a PMT.