Irradiation asymmetry effects on the direct drive targets compression for the megajoule laser facility

Abstract

In the previous works (Rozanov et al., 2013; 2015) we have performed one-dimensional (1D) numerical simulations of the target compression and burning at the absorbed energy of ~1.5 MJ. As a result, the target was chosen to have a low initial aspect ratio in order to be less sensitive to the influence of such parameters as laser pulse duration, total laser energy, and equations of state model. The simulation results demonstrated a higher probability of ignition and effective burning of such a system. In the present work we discuss the impact of irradiation asymmetry on this baseline target implosion. The details of the 1D compression and a possible influence of 2D and 3D effects due to the hydrodynamic instability and mixing have been described. In accordance with the 2D calculations the target is still ignited, however, the symmetry analysis of 3D ones gives reasons to further reduce the efficiency of conversion of kinetic energy into potential energy.

Compression and burning of a direct-driven thermonuclear target under the conditions of inhomogeneous heating by a multi-beam megajoule laser

“…Although, the growth of these perturbations is also not a key factor. For the baseline target discussed here the value of parameter γΔt (γ is the growth factor, Δt is the duration of perturbation development) is about 2 [24] that is a rather moderate value.…”

“…Due to these circumstances, the use of a direct-drive scheme becomes justified, even in view of the greater heating inhomogeneity, since a larger available energy can provide the necessary reserve for ignition. In any case, the target should have increased resistance to the development of hydrodynamic instabilities; in particular, it should have a sufficiently low DT-shell aspect ratio [22][23][24].…”

Analysis of the symmetry of the direct-drive target implosion under laser pulse of a megajoule scale

“…In these conditions the possible approach is to look for such targets designs, which would provide maximum compression stability, accompanied by efficient DT-fuel burning. The class of such low aspect targets was proposed in [2][3][4]. In this work the efficiency of these targets for the different variants of inhomogeneity of the absorption of incident laser flux is evaluated.…”

Enhancement of pressure perturbations in ablation due to kinetic magnetized transport effects under direct-drive inertial confinement fusion relevant conditions

“…Kinetic studies, neglecting magnetic fields, have been performed examining the degree of thermal smoothing for both single mode perturbations [28] and optically-smoothed beam like perturbations [29][30][31]. Full-physics hydrodynamic simulations of ICF targets subject to nonuniform irradiation have also been performed in two and three dimensions [32][33][34] and including reduced models of nonlocal effects [2,35]. The solid den-sity target response to pressure perturbations meanwhile is studied in [12,36,37].…”