Abstract:
A. L. Milder
Many systems of interest to plasma physicists such as inertial confinement
fusion and astrophysical systems contain many coupled physical processes
over multiple scales. A fundamental plasma physics platform has been
developed at the OMEGA laser system to isolate and study individual effects
showing how microscale physics can impact macroscale problems. Angularly
resolved Thomson scattering, a novel form of Thomson scattering, has been
used to measure the electron velocity distribution function showing how
laser heating can lead to a super-Gaussian shape with a Maxwellian tail.
Atomic kinetics such as ionization was shown to further modify the electron
distribution function. Super-Gaussian electron distribution functions have
been shown to alter the dispersion relation for ion-acoustic waves
modifying the gain curve for cross-beam energy transfer, a process known to
cause significant redistribution of energy in inertial confinement fusion
experiments. Growth rates and a threshold for the return current
instability, an electron transport driven instability, have been measured
and are shown to be heavily modified by the non-locality of the electron
transport. Future work will build on the angularly resolved Thomson
scattering technique to measure the 2D electron distribution function in
cases such as heat transport and leverage advanced computational techniques
such as automatic differentiation and deep learning.