Thermal characterization of high strip current microchannel plate photomultipliers

Abstract

We have investigated the thermal behavior of a set of 40 mm, high strip current, microchannel plate (MCP) photomultipliers developed for a diagnostic system of a fusion plasma by laser scattering. These detectors include a V-stack of very low resistivity (5 X 10<SUP>6</SUP> (Omega) m) microchannel plates and must be operated with a pulsed high voltage power supply under strict control of the temperature. Therefore the resistance of the V-stacks has been studied as a function of the MCP temperature and of the applied voltage by applying short pulses of high voltage to the detectors in a temperature comtrolled environment. At low applied voltage (approximately 1 V) a resistance of 2.05 X 10<SUP>6</SUP> (Omega) was measured for one of the V-stacks, with a resistance coefficient of -1.47 X 10<SUP>4</SUP> (Omega) /degrees C. At high voltage the resistance was found to be lower by about a factor three and showed a linear decrease with both the MCP temperature and the applied high voltage. From these measurements the detector thermal capacitance and thermal conductivity were found to be 0.79 J/degrees C and 1.85 X W/degrees C respectively. The measured parameters are used in a simplified thermal model of the detectors for the construction of the pulsed power supply control system necessary to operate them in safe conditions.