Physics – Plasma Physics
Scientific paper
Oct 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000aps..dppgi3006m&link_type=abstract
American Physical Society, 42nd Annual Meeting of the APS Division of Plasma Physics combined with the 10th International Congre
Physics
Plasma Physics
Scientific paper
The long time development of Rayleigh-Taylor Instability in thin shells remains a central concern in ICF physics. Experiments(S.H. Batha, G.T. Schappert, K.A. Klare, D.E. Hollowell, and R.J. Mason, Bull. Am. Phys. Soc. vol. 44, 57 (1999); R.J. Mason, D.E. Hollowell, G.T. Schappert and S.H. Batha, ibid.) have been performed on NOVA and OMEGA to follow the growth of radiatively driven one-micron amplitude, peak-to-valley, 45 μm wavelength perturbations on thin ( 11 μm thick) plane copper foils into the strongly non-linear regime. Results have been compared to calculations with the Lagrangian code LASNEX, and the Eulerian AMR code RAGE. Buffer layers 5 μm thick of beryllium have been attached to the drive side of these foils to add a hydrodynamic push to the radiative drive. A ``P26"-like pulse was adjusted to rise over 1.6 ns, yielding 160 to 185 eV hohlraum temperatures on OMEGA. Breakup of the foils over 6 ns was observed with front-on observation of a 6.7 keV iron backlighter. Earlier side-on observations of NOVA foil accelerations show a good match of the calculated mean foil trajectories with data. Greater acceleration and higher growth rates are observed with the added buffer pressure. Thermal conduction is found to play an important roll in smoothing micron-size ``filigree" perturbations seen in the Eulerian-AMR simulations. RAGE calculations of the instability growth rates show detailed agreement with the measurements, after careful accounting is made for perturbation viewing at an angle, the modulation transfer function of the backlighter, and, most importantly, saturation of the backlighter illumination upon crossing more than 20 μm of the growing R-T fingers in the foils. A recent extension of these experiments on OMEGA to 10 ns will also be discussed.
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