Deciphering the kinetic structure of multi-ion plasma shocks

Abstract

Strong collisional shocks in multi-ion plasmas are featured in many high-energy-density environments, including Inertial Confinement Fusion (ICF) implosions. However, their basic structure and its dependence on key parameters (e.g., the Mach number and the plasma ion composition) are poorly understood, and controversies in that regard remain in the literature. Using a high-fidelity Vlasov-Fokker-Planck code, iFP, and direct comparisons to multi-ion hydrodynamic simulations and semi-analytic predictions, we critically examine steady-state planar shocks in D-3 He plasmas and put forward a resolution to these controversies.

A drift of Langmuir waves in a magnetized inhomogeneous plasma

“…Implicitly, plasma ensemble substitutions are present in many numerical plasma simulations (see, e.g. Banks et al 2017;Keenan et al 2017;Hill & Kingham 2018).…”

Observation of shock-front separation in multi-ion-species collisional plasma shocks

“…Interspecies ion separation and velocity separation were experimentally observed [19][20][21][22][23]. Additional simulation and theoretical research on multi-ion-species plasmas examined how ion species diffusion causes species separation [24][25][26][27][28][29][30]. The present research reports direct observations of the spatial profile of a multi-ion-species shock, showing shock-front separation and species-dependent shock widths in collisional plasma shocks.…”

“…First-principles theory of interspecies ion diffusion and simulations based on the theory predict that lighter ions diffuse farther ahead within a collisional plasma shock (closer to the pre-shock region) than heavier ions [11][12][13][14][15][16][17][18][24][25][26][27][28][29][30]. The diffusion mechanisms are classical diffusion based on the mass concentration gradient, barodiffusion based on the ion pressure gradient, thermodiffusion based on ion and electron temperature gradients, and electrodiffusion based on the electric field (negative gradient of the electric potential).…”

Probing ion species separation and ion thermal decoupling in shock-driven implosions using multiple nuclear reaction histories

“…9,10 These multi-ion/kinetic effects related to the ion mean free path, 11 ion mass, 12 and ion charge 13 have been modeled using reduced ion-kinetic models, 14 particle-in-cell (PIC) simulations, [15][16][17] and kinetic-ion simulations. [18][19][20][21][22] This work follows the experiments described by Sio et al, 10 and greatly expands on this previous work through the inclusion of (1) two new experiments on DD and D 3 He reaction histories, (2) one new experiment on DD, DT, and D 3 He reaction histories, and (3) kineticion FPION simulations in the interpretation of the data. There are significant experimental challenges in diagnosing the density and temperature differences between different ion species (ion species separation and ion thermal decoupling, respectively).…”

“…Strong shock propagation is inherently a kinetic phenomenon, 20 and can drive differences in ion densities and temperatures (ion species separation and ion temperature decoupling, respectively) in a multi-ion plasma mixture with different masses and charges. FPION simulations for a representative 90%-10% D 3 He (with trace T) shockdriven implosion are used in this section.…”