MODELING OF NOVA INDIRECT DRIVE RAYLEIGH-TAYLOR EXPERIMENTS

The growth due to the Rayleigh-Taylor (RT) instability of single-wavel ength surface perturbations on planar foils of brominated CH [CH(Br)] and fluorosilicone (FS) was measured. The foils were accelerated by x- ray ablation with temporally shaped drive pulses. A range of initial a mplitudes (a0) and wavelengths (lambda) have been used. This paper foc uses upon foils with small a0/lambda, which exhibit substantial growth in the linear regime, and are most sensitive to the calculated growth rate. The CH(Br) foils exhibit slower RT perturbation growth because opacity differences result in a larger ablation velocity and a longer density scale length than for FS. Tabulated opacities from detailed at omic models, OPAL [Astrophys. J. 397, 717 (1992)] and super transition array (STA) [Phys. Rev. A 40, 3183 (1989)] were employed. Unlike prev ious simulations which employed the average atom (XSN) opacity treatme nt, parameter adjustments to fit experimental data no longer appear ne cessary. Nonlocal thermodynamic equilibrium (NLTE) effects do not appe ar to be important. Other variables which may affect the modeling, suc h as changes of the equation of state and radiation drive spectrum, we re also examined. The current calculational model, which incorporates physically justified choices for these calculational ingredients, agre es with the Nova single wavelength RT perturbation growth data.