Read-Out System for Thermal Neutron Detectors Based on ZnS(Ag)/LiF Scintillator

Abstract

Neutron scintillation detectors based on ZnS(Ag)/LiF, solid-state photomultipliers, and an organic glass light guide developed at the Institute for Nuclear Research, Russian Academy of Sciences (INR RAS) are successfully used in neutron diffractometers facilities at the INR RAS as a replacement for standard counters based on ³He. These detectors use optical light guides with diffuse reflection, which makes it possible to multiply the recorded signal (up to 95 photoelectrons) in comparison with detectors with wavelength shifting fibers. The article describes two types of bias circuit for silicon photomultipliers. A method of dynamic bias has been proposed, which makes it possible to reduce the recovery time of a silicon photomultiplier and to increase the loading capacity of neutron detectors by a factor of 8. Simulation and comparison of two types of preamplifiers showed an increase in the loading capacity. The new electronics makes it possible to increase the loading capacity of the detectors up to 400 kHz. A circuit for digital control of discrimination thresholds has been developed and described. A new data acquisition system for time-of-flight neutron diffractometers for 80 detectors with the possibility of scaling has been developed.