Inexpensive and practical sealed drift-tube neutron detector

The design, construction, and performance of a type of sealed 3He drift tubes for neutron detection are presented. Because the 3He pressure is in the 25–300 mbar range, the detector costs are not dominated by the 3He gas. Intrinsic neutron detection efficiencies up to 5% have been observed by using high-density polyethylene moderation. Sensitive measurements of the detector lifetime are achieved by monitoring the full-energy peak of the 3He(n, p)3H reaction as a function of time. The neutron peak position shows a 24-h cycle that may be explained by the physical adsorption of gases onto the wall. The estimated lifetimes of the detectors are sufficiently long and therefore, the design and the construction are robust and practical for applications such as fissile material detection.