Development of a high-efficiency, glass shell-based, 3He-filled neutron detector

We have developed a new type of neutron sensor based on small, gas-filled, glass shells with external electrodes. The detector functions as a small (<1-cm-diameter) He-3 ion chamber for applied bias voltages from roughly 50 V to 900 V. We have demonstrated that the detectors function with internal gas pressures from 6 to 10 atm. Charge transport times across the detector volume are a few microseconds. The detectors have very low gamma-ray sensitivity due to their small size as compared to the path-length of energetic electrons generated by gamma-ray interactions. Multiple shell detectors are intended to be deployed within a moderator block to form a single detector system. The resulting detector-moderator configuration approaches the efficiency of a homogeneous system. This paper presents device characterizations and performance data.