Concept for a Neutron Spectrometer Based on Optical Detection of 3He(n,p)3H Reactions in a Gas

Abstract

The conceptual framework is described for a new type of neutron spectrometer, based on the recently demonstrated principle of optical detection of charged particle tracks in gas. Whereas the elastic scattering of a neutron gives rise to the single track of a charged recoil particle, the reaction 3He(n,p)3H produces an event in which two tracks (those of the proton and triton) diverge from a common vertex at the capture site. The optical detection method, which allows direct visualisation of tracks, could be used to distinguish between one or two pronged events. The measured total light output from an absorption event would be proportional to Tp + Tt, the sum of the initial kinetic energies of the proton and triton. Independently of its incident direction, the energy of the absorbed neutron would be given by T = Tp + Tt - Q, where Q = 765 keV is the energy released by the reaction.