Plasma Temperature Inference from DT/DD Neutron Discrimination

TL;DR

This paper introduces a neutron discrimination detector system that distinguishes between DD and DT neutrons to infer plasma temperature, effective even at low yields and when traditional time of flight methods are ineffective.

Contribution

The paper presents a novel detector system capable of discriminating neutron energies for plasma temperature inference, especially under challenging low-yield and extended source conditions.

Findings

Effective discrimination at low neutron fluences (~100 neutrons/sterad)

Performance characterized over broad parameter ranges

Applicable when time of flight methods are unsuitable

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.