Comparison of hydrodynamic and kinetic simulations of an ICF hohlraum surrogate*

Recently, Le Pape et. al studied the plasma interpenetration in a surrogate hohlraum environment [1]. Using 3$omega$ (351nm) laser light, they drove counterpropagating carbon and gold plasmas both in vacuum and with a low-density He4 gas fill, and found the presence of the gas fill significantly inhibited interpenetration of the gold and carbon. In this work, we present computational studies of this experimental setup using both 2D (axisymmetric) hydro simulations with xRage [2,3] and 1D kinetic simulations with the Vlasov-Fokker-Planck code iFP [4,5]. We compare both to the experimental measurements of inferred plasma temperature and relative number fraction, as well as directly to the reported experimental Thomson Scattering spectra. Contrary to naïve expectation, we find that iFP reproduces the gas-fill results (which ought to be more “hydro like”) better than xRage, and vice versa for the vacuum results. We hypothesize this is due to significant 3D hydrodynamic effects in the vacuum case (e.g., plasma “fingering”), which are less present in the gas-fill case. Further, the gas-fill case presents kinetic interpenetration and mix of the He4 into the carbon and gold, which is not well represented in a hydro code.

References:

[1] S. Le Pape, et. al, Phys. Rev. Lett. 124, 025003 (2020).

[2] B. M. Haines, et. al, Comput. Fluids 201, 104478 (2020)

[3] B. M. Haines, et. al, Phys. Plasmas 24, 052701 (2017)

[4] S. E. Anderson, et. al, J. Comp. Phys. 419, 109686 (2020).

[5] W. T. Taitano, et. al, Comp. Phys. Comm. 263, 107861 (2021).