New 64-channel area detector for neutrons and gamma rays

The multi-channel photomultiplier (Philips XP1702) can be utilized as a high resolution area detector for thermal neutrons and high energy gamma rays. This detector type is needed for e.g. for special neutron scattering experiments and for the PET method applied to small animals. In various test measurements this will be demonstrated by coupling suitable scintillators (NaI, BGO, and 6LiI single crystals and 6Li-glass) and dispersers to the photocathode and by feeding the 64 output signals of the PM into a resistor network via voltage-to-current converters. The final interpolated position per event is determined by pulse height division of the four amplified signals taken from the corners of the network. Experimental results concerning the achievable spatial resolution, the homogeneity and the linearity of the detector response and of the quantum efficiencies will be presented. Light experiments with well collimated pulsed rays and with beams of different spot sizes at the photocathode are helpful to explain the measured properties of this new neutron and gamma ray detector.