Picosecond Thomson-scattering spectroscopy investigation of thermodynamics in laser-plasma amplifiers

Thesis (Ph. D.)--University of Rochester. Department of Physics and Astronomy, 2019.Ultrafast electron plasma wave dynamics, Thermodynamics, and collisions are fundamental processes in laser-plasma physics that is not well understood. Historically, models have used simple approximations to describe the Thermodynamics in laser-plasma devices or artificially assumed constant plasma conditions. This thesis studies the picosecond ionization and Thermodynamics in laser-produced underdense plasmas using a novel Thomson scattering technique. The unprecedented temporal resolution of the Thomson spectra provided a measurement of collisional electron plasma waves that were modeled to extract the picosecond evolution of the electron temperature and density. This revealed a transition in the plasma-wave dynamics from an initially cold, collisional state to a quasi-stationary, collisionless state. The Thomson-scattering spectra were compared with theoretical calculations of the fluctuation spectrum using either a conventional Bhatnagar Gross Krook (BGK) collision operator or the rigorous Landau collision terms: the BGK model overestimates the electron temperature by 50% in the most-collisional conditions. These picosecond electron temperature and density measurements can be applied to laser-plasma devices that require knowledge of the rapidly evolving plasma conditions, such as a Raman plasma amplifier. These results indicate that the rapidly evolving conditions would result in a strong detuning that would limit the performance of laser-plasma amplifiers