Structure and scaling laws of laser-driven ablative implosions

Abstract

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Quasi-steady expansion of plasma ablated from laser-irradiated pellets

“…8, is only valid for V unrealistically large; in that case one finds, for the next approximation, 9 ** 9" -(2 Inn)/ (ypjffc/*). It is clear therefore that for \ large, and neglecting terms of order n" 1 lnn e against unity, we may set 0 ff~0s~O .992 , u\ -6 n lnw* -49* lnv e -const ** -3.94 .…”

Self-Similar Hydrodynamics with Heat Conduction

“…4. As mentioned earlier, the spatial profiles thus obtained strikingly contrast with ones for the stationary ablation models (Gitomer et al, 1977;Takabe et al, 1983;Kull, 1989Kull, , 1991.…”

“…Thereby self-similar solutions play a crucial role in the analysis and prediction of the detailed behavior of the shell acceleration. Although some analytical models have been proposed to study the shell acceleration due to mass ablation (Gitomer et al, 1977;Takabe et al, 1983;Kull, 1989Kull, , 1991, most of them have assumed a stationary ablation layer. Pakula and Sigel (1985), for example, reported a self-similar solution for the ablative heat wave.…”

Self-similar motion of laser half-space plasmas. I. Deflagration regime

“…8 The density just behind the deflagration is neither n c ' l,% nor n c x(specific heat ratio) i/2 9 but depends on Z K , (iii) The expansion is isentropic, not isothermal, a point not well established until now [7][8][9] ; thus, temperatures drop to zero in the plasma-vacuum boundary 10 (a look at the numerical results by Mulser 14 and Cooper 15 provides evidence for this point). Isothermal expansions found in numerical simulations of laser fusion, 16 ' 17 correspond to the regimes a «€~i ,s , for which we do find an isothermal expansion 6 (but no deflagration).…”

“…8 Two-dimensional and spherical effects on the deflagration have been considered by Pert, 9 and Gitomer et al , 10 respectively. The expansion of a plasma into a vacuum without energy absorption was considered by Gurevitch et al n and Crow et al} 2 As expected, three different flow regions 7 emerge naturally from our asymptotic analysis for e«l and (ae 4/3 ) 3/2 » 1: a region of shocked material moving isentropically into the undisturbed cold medium, a plasma deflagration layer where radiation is absorbed and heat conduction and ion-electron energy exchange are important, and a region of low density plasma expanding into the vacuum.…”