Conceptual design of a heavy-water-moderated “\(^{3}\)He+CF\(_4\)” scintillation neutron detector for nuclear astrophysics measurement

Abstract

Accurate measurement of critical data for astrophysical modeling, such as (\(\alpha \), n) and (\(\gamma \), n) cross-sections and \(\beta \)-delayed neutron emission probabilities, depends heavily on overcoming the low and energy/emission-angle-dependent efficiency of current polyethylene-moderated \(^3\)He neutron detectors. We proposed a novel detector that replaces polyethylene with a large spherical heavy-water-moderator and substitutes \(^3\)He tubes with a layer of “\(^3\)He + CF\(_4\)” scintillation gas coupled to photomultipliers for thermal neutron detection. Simulations performed with MCNPX under varied moderator configurations show that a design employing 7.0 cm boron-11, 0.9 cm beryllium, and 50.0 cm heavy water achieves a neutron capture efficiency of 85.1%, with less sensitivity to neutron energy and emission angle. The newly designed neutron detector demonstrates its potential to replace the conventional polyethylene moderated \(^{3}\)He neutron detector and may enable the researchers to make accurate measurements of (\(\alpha \), n), (\(\gamma \), n) cross-sections and \(\beta \)-delayed neutron emission probabilities.