Use of 2 pi-PSD systems for quasielastic neutron time-of-flight experiments

Very-large-area detector systems for low-energy-transfer time-of-flight spectrometers are discussed. Four different kinds of linear position-sensitive detector arrays with spherical-or cylindrical-zone geometries are considered. A non-uniform sample-detector distance is involved, varying by up to 40% for cylindrical symmetry using 5m long linear position-sensitive detectors (PSDs). Integration over large solid-angle regions causes practical consequences for data treatment, but no serious problems for spectrometer performance. We demonstrate that energy-resolution function, PWR optimization, and duration of spectral periods are essentially not deteriorated. Consequences for the normalization of measured neutron scattering data and mechanical detector implementation are discussed.