Development of a microstrip-based neutron detector

A gas-filled microstrip detector for thermal neutrons has been built and successfully tested in our laboratory. The detector has an active area of 20 mm x 15 mm and consists of alternate anodes and cathodes of widths 12 mum and 300 mum respectively. The anode to cathode gap is 150mum and the pitch is 612 mum. A high resistance, meandering type horizontal strip connects the anodes at one end and aids in position sensing by charge division method. The detector is tested with gas mixtures He-3+Kr (1: 2) and He-3+CF4 (2: 1)at pressure of 3 atmospheres and using a Pu-Be neutron source. The pulse height spectrum shows energy resolution of similar to8% (FWHM) for the 764 keV peak at anode voltage of 525 V for 3 He+Kr and similar to15% at anode voltage of 800 V for He-3+CF4. Gas gains up to 6.3 x 10(3)and 3.6 x 10(3) are obtained respectively with these gas mixtures. The overall efficiency of the detector along the sensitive length is tested by exposing the active area to neutrons and recording the position spectrum. The detector shows fairly uniform efficiency (similar to45%) over the active length