Plasma Temperature Inference from DT/DD Neutron Discrimination

Abstract

DD and DT reaction rates may be compared to determine plasma temperatures in the 10--200 eV range. Distinguishing neutrons from these two reactions is difficult when yields are low or unpredictable. Time of flight methods fail if the source is extended in time. These neutrons may be distinguished because inelastic scattering of more energetic neutrons by carbon produces a 4.44 Mev gamma-ray, and because hydrogenous material preferentially attenuates lower energy neutrons. We describe a detector system that can discriminate between lower and higher energy neutrons for fluences as low as $\mathcal{O}(10^2)$ neutrons/sterad even when time of flight methods fail, define a figure of merit and calculate its performance over a broad range of parameters.