Design of Fast and Compact Detector for a Wide Range of Yield of Pulsed Neutron Source

In this report, we present the development of a 3He-filled neutron detector assembly, which has a possible application for yield measurement of capacitor-driven (single-shot) fusion sources of a wide range of yield. The assembly consists of four helium-3 proportional counters placed in an annular region of a 70 mm diameter cavity where the head of a low-yield neutron-generating device can be placed. The active dimension of the counter is 38 mm (dia) × 230 mm (length). Individual detectors are connected to a fast-electronic module that amplifies and discriminates the pulses and produces a signal of 3–5 V height and 50 ns (ns) pulse width. The output of each detector is also observed so that pile-up can be avoided when used for high-yield sources. The absolute efficiency of the detector when the source is placed at the center and 50 cm in an axial direction is found to be 2.2% and 0.03%, respectively. Monte Carlo simulation for the sensitivity estimation is found in agreement with the experimental results. The functionality of this detector for measuring the neutron yield of capacitor-driven neutron sources with sub-microsecond emission time was demonstrated using a moderate-yield plasma focus device and was observed to be effective within the range from 102 to > 106 neutrons per pulse.