Properties of 100-mm X 100-mm triple stacks of microchannel plates used in a sealed detector for x-ray crystallography

摘要

We report the assembly of an imaging phototube which, together with a thin NaI(Tl) x-ray scintillator, forms a photon counting area detector for x-ray crystallography. The tube contains a bialkali photocathode, a triple (Z) stack of 100 mm $MUL 100 mm MCPs, and a 133 mm $MUL 133 mm two dimensional delay line readout. Some aspects of the processing setup that are unique to the very large tube are described. Design considerations with respect to detective efficiency are discussed. Measured gain characteristics of 100 mm $MUL 100 mm Z stacks are presented, showing fairly narrow pulse height distributions which are improved with UV scrubbing. The MCPs, manufactured from low resistivity glass, are subject to thermal instability, and an account is given of thermal runaway which occurred for a stack of MCPs composed of plates with an average room temperature resistivity of approximately 400 M approximately ega@-cm$+2$/.