Design of an ultra-sensitive single-moderator directional neutron spectrometer based on 3He detectors

Abstract

The CYlindrical neutron SPectrometer (CYSP) is a polyethylene cylinder with diameter 50 cm and height 65 cm equipped with a collimated aperture and an internal capsule embedding multiple thermal neutron detectors. Analogously to Bonner Spheres, CYSP responds from thermal up to GeV neutrons and the spectrum is obtained via few-channel unfolding methods. Due to the specific design and the use of borated materials, the internal detectors only respond to neutrons coming from the desired direction. By changing the type and sensitivity of the internal detectors, the CYSP was adapted to respond over a variety of fluence rates. This work describes HELIOCYSP, an updated design of CYSP, including Helium-3 proportional counters as internal detectors and a more convenient design of the internal capsule. Due to the increased sensitivity, HELIOCYSP is suited for time-effective measurements in very low fluence rate scenarios, as those encountered in cosmic-ray-induced neutron studies at ground level.