Direct measurements of nonlocal heat flux in laser-produced coronal plasmas using Thomson scattering from electron-plasma waves

Thesis (Ph. D.)--University of Rochester. Department of Mechanical Engineering, 2018.Thermal transport is a fundamental process in plasma physics that is not well understood. Historically, local models have been used to describe the heat flux in plasmas but artificially limit the flux at even modest temperature gradients. This Thesis studies electron thermal transport in laser-produced coronal plasmas using a novel Thomson scattering technique. Thomson scattering is sensitive to changes in the electron distribution function caused by heat flux. The experiments show that nonlocal effects must be included in regions where the plasma was not collisional enough for classical theory to be valid. Vlasov-Fokker-Planck simulations self consistently calculated the electron distribution functions used to reproduce the measured Thomson scattering spectra and to determine the heat flux. Measured heat flux values were up to 40% smaller than classical values inferred from the measured plasma conditions in this region. This is the first direct measurement of nonlocal heat flux in plasmas. In the opposite limit, classical theory matched the observed Thomson scattering data. Multigroup nonlocal simulations overestimated the measured heat flux