Kinetic Simulations of Plasma-Ion Stratification in Exploding-Pusher Experiments

Recent OMEGA experiments [1] imploded thin spherical glass shells filled with D and ³He mixtures to explore stoichiometric effects on fusion reactivity. As the deuterium atomic fraction in the gas was varied hydro-equivalently, the experiments observed anomalous (w.r.t. single-fluid rad-hydro simulations) reduction of the fusion yield (by up to 50%) and scaling of burn-averaged ion temperatures. Differential heating of D and ³He ions and partial expulsion of deuterium from the capsule center by the shock [2,3], both neglected in rad-hydro simulations, were proposed as the explanations. Semi-analytical theory and reduced-ion-kinetics (RIK) simulations [4] seem to confirm the hypothesis. Herein, we employ Vlasov-Fokker-Planck code iFP [5] to carry out the first kinetic simulations of the experiments to validate, or disprove, the proposed explanations. [1] H. G. Rinderknecht et al., Phys. Rev. Lett. 114, 025001 (2015). [2] W. T. Taitano et al., Phys. Plasmas 25, 056310 (2018). [3] B. D. Keenan et al., Phys. Plasmas 25, 032103 (2018). [4] N. M. Hoffman et al., Phys. Plasmas 22, 052707 (2015). [5] W. T. Taitano et al., J. Comp. Phys. 365, 173 (2018).