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

A novel large-area (0.5 × 0.5 m ²) two-dimensional position-sensitive detector for thermal and sub-thermal neutrons is being developed comprising {¹⁵⁷Gd}/{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 (∼ 5 × 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.