Measurements of Non-Maxwellian Electron Distribution Functions and Their Effect on Laser Heating

Electron velocity distribution functions driven by inverse bremsstrahlung heating are measured to be non-Maxwellian using a novel angularly resolved Thomson-scattering instrument and the corresponding reduction of electrons at slow velocities results in a similar to 40% measured reduction in inverse bremsstrahlung absorption. The distribution functions are measured to be super-Gaussian in the bulk (v/v(th) < 3) and Maxwellian in the tail (v/v(th) > 3) when the laser heating rate dominates over the electron-electron thermalization rate. Simulations with the particle code QUARTZ show the shape of the tail is dictated by the uniformity of the laser heating.

Automated summary

The electron velocity distribution functions driven by inverse bremsstrahlung heating were measured to be non-Maxwellian using a novel angularly resolved Thomson-scattering instrument. The shape of the tail in the distribution functions is influenced by the uniformity of the laser heating when the laser heating rate dominates over the electron-electron thermalization rate. Simulations with the particle code QUARTZ demonstrate the impact of laser heating uniformity on the distribution functions.