Effects of non-local electron transport in one-dimensional and two-dimensional simulations of shock-ignited inertial confinement fusion targets

• Published in: Physics of plasmas 2014-01, Vol.21 (1), p.12701
• Main Authors: Marocchino, A., Atzeni, S., Schiavi, A.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Ablation; Computer simulation; Conduction model; Convolution; ELECTRON BEAM TARGETS; Electron energy; ELECTRON TEMPERATURE; Electron transport; ELECTRONS; Flux; GAIN; ICF DEVICES; INERTIAL CONFINEMENT; Inertial confinement fusion; Inertial fusion (reactor); INERTIAL FUSION DRIVERS; ION BEAM TARGETS; Laser beam heating; LASER RADIATION; LASER TARGETS; Lasers; Plasma physics; Plasmas (physics); SIMULATION; Temperature gradients; Temperature profiles; THERMAL CONDUCTION; Two dimensional models
• ISSN: 1070-664X; 1089-7674
• DOI: 10.1063/1.4861389

In some regions of a laser driven inertial fusion target, the electron mean-free path can become comparable to or even longer than the electron temperature gradient scale-length. This can be particularly important in shock-ignited (SI) targets, where the laser-spike heated corona reaches temperatures of several keV. In this case, thermal conduction cannot be described by a simple local conductivity model and a Fick's law. Fluid codes usually employ flux-limited conduction models, which preserve causality, but lose important features of the thermal flow. A more accurate thermal flow modeling requires convolution-like non-local operators. In order to improve the simulation of SI targets, the non-local electron transport operator proposed by Schurtz-Nicolaï-Busquet [G. P. Schurtz et al., Phys. Plasmas 7, 4238 (2000)] has been implemented in the DUED fluid code. Both one-dimensional (1D) and two-dimensional (2D) simulations of SI targets have been performed. 1D simulations of the ablation phase highlight that while the shock profile and timing might be mocked up with a flux-limiter; the electron temperature profiles exhibit a relatively different behavior with no major effects on the final gain. The spike, instead, can only roughly be reproduced with a fixed flux-limiter value. 1D target gain is however unaffected, provided some minor tuning of laser pulses. 2D simulations show that the use of a non-local thermal conduction model does not affect the robustness to mispositioning of targets driven by quasi-uniform laser irradiation. 2D simulations performed with only two final polar intense spikes yield encouraging results and support further studies.