Modelling the effect of ³He in direct drive capsule implosions

D³He fuels are often used in ICF implosion experiments, either as a surrogate for DT to restrict the output neutron yield, or to produce protons for use in diagnosis of core conditions. Recent experiments have suggested that capsules filled with D³He do not behave as expected, but that both proton and neutron yields are anomalously degraded relative to the pure D₂ case. We have performed direct drive implosion experiments using the Omega laser to examine the effect of ³He on DT-filled glass capsules. The use of DT fuel allows reaction history measurements to be obtained using the Gas Cherenkov diagnostic (GCD). It was hoped that the detailed information provided by GCD measurements would complement existing measurements to constrain modelling. We present recent modelling and analysis of the experiments using radiation-hydrocode simulations, and explore some of the hypotheses proposed to explain the results.