Particle-in-cell simulations high-frequency hybrid instability (HFHI) dominated rescattering relevant to inertial fusion energy (IFE)*

In inertial fusion energy (IFE) plasmas, the scattered light from stimulated Raman scattering can undergo re-scatter and generate successively shorter wavelength electron plasma waves (EPWs) which can accelerate electrons to higher and higher energies [1]. However, in some advanced designs where the electron temperature is very high [2] and in direct drive scenarios, the primary laser plasma instabilities (which can be either Raman or the high-frequency hybrid instability (HFHI) [3]) occurs above 0.11 nc.  For these densities, the scattered light cannot rescatter in-place and must propagate down the density gradient to the quarter critical surface of the scattered light where it will undergo HFHI itself due to the high temperature of these plasmas.  Because the primary LPI occurs at higher densities compared to those studied by Winjum et al, the wavelength of the scattered light can increase by a factor of 40% to 100%, making rescatter much more likely even with very modest amounts of reflectivity. 

 

The intricate interplay between the primary laser plasma instability and the secondary absolute instabilities is of fundamental importance, and it has potential implications in current and future experiments.  We will present scenarios where HFHI rescattering is triggered by HFHI scattering near the quarter critical surface and by inflationary stimulated Raman scattering and discuss the relevance of these simulations to future target designs.   We will also present large-scale 2D simulations with different laser polarizations to demonstrate the three-dimensional nature of these interactions, and demonstrate the competition between SRS, TPD, and Raman sidescatter near the quarter critical surface.

 

[1] B. J. Winjum, J. E. Fahlen, F. S. Tsung, and W. B. Mori, Phys. Rev. Lett., 110, 165001 (2013).

[2] W. A. Farmer, M. Tabak, J. H. Hammer, P. A. Amendt, D. E. Hinkel, Phys. Plas., 26, 032701 (2019).

[3] B. B. Afeyan, E. A. Williams, Phys. Plas., 4, 3845 (1997).