Using Shock-Driven Implosions to Probe Kinetic and Multiple-Ion-Species Effects

Hong Sio, Massachusetts Institute of Technology

The ignition effort at the National Ignition Facility is largely guided by hydrodynamic simulations, in which multiple-ion species are treated in an averaged, one-ion fluid approximation, and in which it is implicitly assumed that the ion mean free path is much smaller than the scale length of the system. In actual inertial confinement fusion plasmas, the long ion-ion mean free path suggests that high-energy tail ions are not well-confined, leading to a reduction in fusion reactivity. The pressure and electric field gradients at the shock front may also drive separation of plasma species. Recent experiments and theoretical work have demonstrated that these kinetic and multiple-ion-species effects can have a significant impact on the evolution of these plasmas; such effects are not well modeled in existing codes.

Two recent experimental campaigns at the OMEGA laser facility studied the deviation of observations from hydrodynamic predictions as a function of fuel pressure and ion mixtures in low-density, shock-driven implosions. Preliminary results from this study will be presented, with discussion of some ideas for explaining the observations. Preparations are also underway to study kinetic and multiple-ion-species effects through simultaneous burn-history measurements in shock-driven, D3He implosions.

Abstract Author(s): H. Sio, H. Rinderknecht, M. Rosenberg, A. Zylstra, M. Gatu Johnson, N. Sinenian, J. Frenje, C.K. Li, F. Seguin, R. Petrasso (MIT), C. Stoeckl, F. Marshall, C. Sangster, V. Glebov, W. Seka, and J. Delettrez (LLE)