Spectroscopic Characterization of High Temperature, High Density Plasmas with Minimal Gradients

Edward Marley, UC Davis

April 15, 2016, 1:00 - 2:00pm, SERF 383

Abstract:  The presence of gradients in laboratory plasmas increases the uncertainty in measured values of physical quantities and presents a problem when comparing data to theories. The buried layer platform holds a promise in producing HED plasmas with minimal gradients to perform basic plasma physics studies such as opacity measurements. Short pulse laser heated buried layer experiments have been performed with the goal of studying emission characteristics of plasmas with mass densities >= 1 g/cm^3 and electron temperatures >= 500 eV. The buried layer geometry has the advantage of rapid energy deposition before significant hydrodynamic expansion occurs. For brief periods (<50 ps) this provides a low gradient, high density platform for stduing emission characterstics under extreme plasma conditions. Time resolved K-shell spectroscopy was used to determine the range of parameters that may be obtained in this geometry at the Orion laser facility. The time resolved measurements were compared to both Cretin, a radiation transport code with a 1-D hydrodynamics package, and LSP, a particle-in-cell (PIC) code. Because of the ability of collisional PIC codes to model both the absorption and resulting thermalization process, codes such as LSP seem to be a better representation of the physics of short-pulse laser heated buried layers as opposed to standard Rad/Hydro codes. It is shown that this method can be used to generate steller interior like laboratory plasmas with minimal gradients for study and comparison to radtion transport models.

This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Bio:  Edward Marley received his B.S. in physics from Cal Poly San Luis Obispo and is currently finishing his PhD from the Department of Applied Science at UC Davis. After finishing his undergraduate education, he spent four years at Lawrence Livermore National Laboratory as a Laser Electro-Optic Technician working on the National Ignition Facility before enrolling at UC Davis. His graduate research has been done primarily at LLNL, including participation in many experiments at the Jupiter Laser Facility's Titan and Comet lasers, with additional experiments done at the Atomic Weapons Establishment's Orion laser in the United Kingdom. The focus of his graduate work has been time-resolved spectroscopic characterization of high temperature, high density plasmas.