ISSN:
1089-7674
Source:
AIP Digital Archive
Topics:
Physics
Notes:
A new method for performing compressible hydrodynamic instability experiments using high-power lasers is presented. A plasma piston is created by supersonically heating a low-density carbon based foam with x-rays from a gold hohlraum heated to ∼200 eV by a ∼1 ns Nova laser pulse [E. M. Campbell et al., Laser Part. Beams 9, 209 (1991)]. The piston causes an almost shockless acceleration of a thin, higher-density payload consisting of a layer of gold, initially 1/2 μm thick, supported on 10 μm of solid plastic, at ∼45 μm/ns2. The payload is also heated by hohlraum x-rays to in excess of 150 eV so that the Au layer expands to ∼20 μm prior to the onset of instability growth. The Atwood number between foam and Au is ∼0.7. Rayleigh–Taylor instability, seeded by the random fibrous structure of the foam, causes a turbulent mixing region with a Reynolds number 〉105 to develop between piston and Au. The macroscopic width of the mixing region was inferred from the change in Au layer width, which was recorded via time resolved x-radiography. The mix width thus inferred is demonstrated to depend on the magnitude of the initial foam seed. For a small initial seed, the bubble front in the turbulent mixing region is estimated indirectly to grow as ∼0.036±0.19 [∫(square root of)(Ag)dt]2 which would imply for a constant acceleration 0.036±0.019 Agt2. More direct measurement techniques must be developed in larger scale experiments to remove potential complicating factors and reduce the error bar to a level that would permit the measurements to discriminate between various theories and models of turbulent mixing. © 2000 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.874177
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