Robb Gillespie

Radiative reverse shock laser experiments relevant to accretion processes in cataclysmic variables

We discuss the production of radiative reverse shocks in experiments at the Omega-60 laser facility. The ability of this high-intensity laser to impart large energy densities on micron-thin foils makes it feasible to create supersonic plasma flows. Obtaining a radiative reverse shock in the laboratory requires a sufficiently fast flow (∼100 km/s) of a material whose opacity is large enough to produce energetically significant emission from experimentally achievable shocked layers. The reverse shock forms in the flow once it is impeded. This paper presents the first radiographic data of normal incidence, reverse shockwaves. These experiments are primarily motivated by the contribution of radiative reverse shock waves to the evolving dynamics of the cataclysmic variable (CV) system in which they reside. We show similarity properties to suggest that the experimental production of radiative reserve shocks in the laboratory may be scalable to such astrophysical systems.

Construction of a solenoid used on a magnetized plasma experiment.

Creating magnetized jets in the laboratory is relevant to studying young stellar objects, but generating these types of plasmas within the laboratory setting has proven to be challenging. Here, we present the construction of a solenoid designed to produce an axial magnetic field with strengths in the gap of up to 5 T. This novel design was a compact 75 mm × 63 mm × 88 mm, allowing it to be placed in the Titan target chamber. It was robust, surviving over 50 discharges producing fields ≲ 5 T, reaching a peak magnetic field of 12.5 T.

Novel Target Fabrication Using 3D Printing Developed at University of Michigan

The University of Michigan has been fabricating targets for high-energy-density experiments for the past decade. We utilize the technique of machined acrylic bodies and mating components acting as constraints to build repeatable targets. Combining 3D printing with traditional machining, we are able to take advantage of the very best part of both aspects of manufacturing. Here we present several recent campaigns to act as showcase and introduction of our techniques and our experience with 3D printing, effecting how we utilize 3D printing in our target builds.

Innovations in Target Fabrication Techniques at the University of Michigan

Abstract The University of Michigan has been fabricating targets for OMEGA campaigns since 2003. These experiments explore supernova-relevant high-energy-density physics. The complexity of recent target designs has made it necessary to explore new methods of producing components that satisfy experimental needs. Interest in the dynamics of nonaxisymmetric shocks has led to the development of polyimide tubes with noncircular cross sections. For our latest Thomson scattering target, shielding was a very important component to the target design. We employed techniques to bend gold foils, enabling complex geometries without any of the seams inherent when two separate foils are pieced together. Machined acrylic bases are used to support all the components on our targets, contributing further to their repeatability and providing us with a method that eases our build. Here, we present improvements in our techniques, along with our basic tried-and-true methods of producing repeatable targets.