Dark-Field Study of Rear-Side Density Structure in Laser-Accelerated Foils
NAVAL RESEARCH LAB WASHINGTON DC
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A dark-field, laser-probing diagnostic has produced the first high- resolution photographs of density structure on the rear side of laser- accelerated foils. This diagnostic allows the preferential sampling of the steep-gradient region of an expanding plasma and permits two-dimensional, multiple-time recordings on a single photograph. The studies are aimed at understanding the early-time physics of target implosions for inertial- confinement fusion. Both long 500 psec and short 150 psec probe pulses were used to study the rear-side plasmas of thin foils accelerated by the rocket-like reaction to a hot plasma ablated from the front side by the laser radiation. The longer pulse results, both for angular scatter and the life-time of small, transverse structure, imply a relatively cold 1 eV rear side plasma. The short pulses provide high resolution photographs of the complete structure. One of these was a vortex-like structure, suggestive of the remnants of a hydrodynamic instability. These observations are relevant to two of the basic requirements of inertial-confinement fusion cold fuel isentrope and implosion symmetry.
- Lasers and Masers
- Fusion Devices (Thermonuclear)