Novel large-area thermal neutron imaging detectors comprising Gd-157/CsI-convertors and micro-strip gas detectors with low-pressure, two-stage amplification and delay line readout

A novel large-area (0.5 x 0.5 m(2)) two-dimensional position-sensitive detector for thermal and sub-thermal neutrons is being developed comprising Gd-157/CsI multilayer convertor foils and two fourfold segmented micro-strip gas detector (MSGC) planes for electron multiplication on either side of the convertor. The MSGC operates in low-pressure, two-stage amplification mode; their novel design is optimized for that mode and for obtaining high signals on both coordinates. Fast signal rise times (5-6 ns) and very high gains (similar to 5 x 10(5)) are expected according to calculations; thus, simple delay line readout, with one interpolating strip between readout nodes, can be used delivering expected position resolutions < 0.5 mm (fwhm) and tolerable count rates of 10(5)-10(6) events/s depending on delay line segmentation.