Results and potential applications of handheld, midsized, and large-area low-cost Li foil MWPCS

Abstract

Three different sizes of Li foil multi-wire proportional counter (MWPC) neutron detectors were constructed with effective areas ranging between 30-1250 cm2. These Li foil MWPC neutron detectors contain five 75 μm thick suspended Li foils. Each foil is less than the summed range (156 μm) of the triton and alpha particle reaction products from the 6Li(n,α)3H reaction. Suspending Li foils offers several advantages over conventional coated gas-filled devices, such as increased detection efficiency and gamma-ray rejection capabilities. Improvements are a direct result of the reaction products simultaneously escaping both sides of suspended Li foils. The three categories of detectors constructed (large-area, mid-sized, handheld) were tested against 3He neutron detectors. Two large-area detectors (1250 cm2 effective area) were position back-to-back in HDPE housing. Various tests were completed with this large-area unit including: 1/R2, transient, field-of-view, and angular response. A mid-sized detector (550 cm2) was delivered to a backpack test campaign where the device outperformed two commercially available 3He tube backpack detectors. Both the large-area and mid-sized Li foil MWPCs had measured intrinsic thermal neutron detection efficiencies of 54% and a gamma-ray rejection ratio (GRR) of 3.0 × 10-9 or better. Lastly, several handheld sized devices were constructed and compared to a 4 atm 3He tube (εth = 81.5%). A smaller version of the five layer devices was constructed (effective area: 30 cm2). This five layer device and another device, referred to as the `5-layer mini' and `Quad', had comparable count rates to the 3He detector.