Design and development of a real-time readout electronics system to retrieve data from a square multi-anode photomultiplier tube for neutron gamma pulse shape discrimination

Abstract

Pulse Shape Discrimination (PSD) algorithms can reliably separate neutrons and gamma-ray photons interacting in a scintillation detector. When implemented in the digital domain, the PSD algorithms allow real-time discrimination between neutron and gamma sources. This paper presents a design of a readout electronics system to retrieve data from a multi-anode photomultiplier tube (MAPMT) for a scintillator based coded-aperture neutron imager. The scintillator is to be coupled with Hamamatsu H9500, a square MAPMT, where each anode of the MAPMT is linked to a resistor network to infer the position of incidence of radiation within the scintillant. Additionally, the resistor network output signals are to be filtered through a novel noise reduction circuit to preserve the data corresponding to each pulse. Localised pulses are digitised using high sampling rate Analogue to Digital Converter (ADC). Sampled signals are temporarily stored in a local ping-pong buffer, before being processed on a field programmable gate array (FPGA). Initial results suggest that 150 MSPS rate provides sufficient information for neutron gamma source discrimination using PSD. Parallel real-time signal processing, implemented on the FPGA, enables multi-channel functioning to generate an array of interactions within the scintillator in terms of gamma rays and neutrons.