Characterization of fast microchannel plate photomultipliers for the ITER core LIDAR Thomson scattering system

In the new ITER core LIDAR Thomson scattering system under development, detectors with pulse response as low as 330 ps and 10 mm diameter active area, covering with good sensitivity the spectral range 380-1100 nm will be necessary. For the visible region 400-750 nm, fast microchannel plate photomultipliers with a GaAsP photocathode that fulfill the characteristics of speed, sensitivity and active area are already commercially available and have been recently characterized for operation in the JET edge LIDAR Thomson scattering system. In this paper we present a further characterization of these devices to evaluate their usefulness in the more demanding operating conditions of the ITER core LIDAR Thomson scattering system. The characteristics of these detectors with regard to linearity, gain recovery time, pulse repetition rate, quantum efficiency and response time for large F-number illumination, have been measured. Linearity and recovery time data have been interpreted according to a new, time dependent, microchannel plate operational model. The results show that these detectors are suitable also for use in ITER.