Application of Gaseous Laser Targets and Optical Diagnostics to Study High Mach Number Unstable Plasma Flows

Edwards, J ; MacKinnon, A ; Robey, H

Lawrence Livermore National Laboratory

关键词: Turbulent Flow;    Laser Targets;    Shape;    70 Plasma Physics And Fusion Technology;    Lasers;   

DOI  :  10.2172/15013521
RP-ID  :  UCRL-ID-143428
RP-ID  :  W-7405-ENG-48
RP-ID  :  15013521

美国|英语

来源: UNT Digital Library

【 摘 要 】

The information that can be obtained from current laser driven high Mach number (compressible) hydrodynamics experiments using solid targets and foams is limited by the need to use X-ray diagnostics. These do well at providing the shape of gross 2D structures which we model well, but are a long way from being able to reveal detailed information at the smaller spatial scales, or in 3D turbulent flows, where most of the modeling uncertainties exist. Remedying this is, and will continue to be, an ongoing research effort. An alternative approach that is not being considered is to use gaseous targets coupled with optical diagnostics. The lower density of gases compared to solids or foams means we can use much larger targets for a given laser energy. This should significantly improve spatial resolution, and the dynamic range of scales that are resolvable. In addition, it may be possible to adapt powerful techniques, such as LIF, used by the low Mach number (incompressible) fluid/gas community so that they work in the high Mach number plasma regime. This would provide much more detailed information on turbulent flows than could be achieved with current X-ray diagnostics. We propose a small research effort to use established techniques such as optical interferometry (absolute electron density), and Schlieren photography (electron density gradient), to study compressible hydrodynamic instabilities. We also propose to explore whether techniques such as LIF may be adapted to the plasma regime, thus providing detailed information, particularly about turbulent flows, that is not currently obtainable in plasmas using X-ray diagnostics. The setting will be radiating blast waves, which avoids costly target fabrication, while promising a high physics payoff to the astrophysics community just from using the established diagnostics alone. We propose to conduct the work in collaboration with Dr Todd Ditmire at the University of Texas at Austin, principally on the Janus laser, and Ditmire's short pulse laser, which is expected to be operational towards the beginning of FY02. Dr Stephen Rose at AWE has expressed interest in collaboration and would provide computational support. He would also look into using the Helen laser at AWE, and developing a UK university contact.