High-efficiency 3He proportional counter for the detection of delayed neutrons

The characteristics of a high-efficiency 3He proportional counter for the measurement of βi-delayed neutrons have been examined. The detection system required for this experiment needs to meet some stringent requirements such as high-efficiency, low dead time, and gamma-insensitivity. The 3He counter described here meets all these requirements. This detection system consists of an array of 20 3He tubes embedded in polyethylene. The principal operating characteristic of this proportional counter is its high efficiency. The absolute efficiency, determined with an Am/Li source, is 29.04%±0.6%. The system’s dead time is 0.46±0.02 μs. It is also displacement insensitive within a range of 10 cm.