A 2-DIMENSIONAL SCINTILLATION DETECTOR FOR SMALL-ANGLE NEUTRON-SCATTERING

A two-dimensional position-sensitive Li-6 glass scintillation detector for neutrons has been constructed and put into operation in a 40 m long small angle neutron scattering instrument. The detector has a detection area of 60 x 60 cm, a neutron capture probability of 96% for subthermal neutrons of 8 angstrom wavelength, a spatial resolution of 8 mm adapted to the scattering experiments, and a counting ability of 100 kHz. The Anger type camera consists of 8 x 8 photomultipliers of 3 in. diameter arranged in a square lattice with 8.4 cm lattice constant. In a coarse fine procedure a neutron capture event is addressed by determining the photomultiplier with maximum anode signal and by a division procedure involving the nine relevant signals of the 3 x 3 photomultiplier matrix centered at the maximum photomultiplier signal. The gain of each photomultiplier is kept constant in time by a gain stabilizing system. Construction, data processing and properties of the detector are described. A few small angle scattering patterns from polymer samples are presented.