Performance of a prototype large area neutron detector based on 6LiF:ZnS(Ag) with MPPC read-out

Systems based on
⁶
LiF:ZnS(Ag) are good alternatives to
³
He neutron detectors. Whilst the neutron absorption is well characterized in
⁶
LiF:ZnS(Ag) layers, the detector efficiency is more likely to depend upon the light collection efficiency and light attenuation or uniformity across the active area - which can be large. We developed a segmented large area system (2 × 0.3 × 0.12) m comprising 16 neutron sensitive strips (1.6 m long) with embedded wavelength shifting fibers read out by MPPCs. The detector design is flexible and scalable and can be adapted to various applications. The active volume segmentation gives additional position sensitivity not possible with more monolithic designs. It also adds robustness to large fluxes of gamma-rays by triggering on smaller area ensuring a good operation in a mixed field of neutrons and other radiation. We report here the development and test of the prototype with calibrated sources of neutrons and gamma-rays. Measurements made at the Physical National Laboratory (UK) demonstrated a neutron detection rate of 3.05 n/s/ng at 2 m and a GARRn of 1.01. Studies of the uniformity of the efficiency and a drive by test were also conducted.