Electrical Characterization of Crystalline UO2, THO2 and U0.71TH0.29O2

Evaluating the suitability of advanced alloys for use in uranium-based neutron detectors.

Air Force Institute of Technology, Wright-Patterson Air Force Base, Ohio

Tracking and identifying radiation sources in the age of nuclear proliferation and well-resourced non-state actors is a national priority. Current neutron detection methods favor large detector volumes and long data collection times. Additionally, portable neutron detection methods have persistent problems with low signal-to-noise (small pulse height) and require large applied voltages.

Conventional neutron detection usually employs scintillators, gas proportional tubes, or semiconductors with separate conversion layers that convert neutrons to charged reaction products. The challenge in conversion-layer devices is to construct a layer of adequate thickness for neutron capture that is also thin enough to allow the resulting reaction products to interact with the charge-sensitive areas. Standard conversion-layer devices typically employ 30 to 40 μm of enriched ¹⁰B due to the high thermal capture cross section of the isotope ¹⁰B and the ability for the energetic Li (0.84 MeV) and α (1.47 MeV) daughter particles to escape. The conversion layer thickness is thus a compromise between the neutron interaction rate and the ability to capture the charge in an electrically active medium. Some novel solid-state technologies provide a thin-film neutron detector consisting of a (or a stack of) semiconductor diode(s), each surrounded by a thin neutron-absorbing material.