Experiments designed to investigate the transition to non-collisional behavior in D3He-gas ICF target implo- sions display increasingly large discrepancies with respect to simulations by standard hydrodynamics codes as the expected ion mean-free-paths λc increase with respect to the target radius R (i.e. when the Knudsen number NK = λc/R grows). To take properly into account large NK’s, multi-ion-species Vlasov-Fokker- Planck computations of the inner gas in those capsules have been performed, for two different values of NK, one moderate and one large. The results, including nuclear yield, reactivity-weighted ion temperatures, nu- clear emissivities and surface brightness, have been compared with experimental data and with the results of hydrodynamical simulations, some of which include an ad-hoc modeling of kinetic effects. The experimental results are quite accurately rendered by the kinetic calculations in the smaller-NK case, much better than by the hydrodynamical calculations. The kinetic effects at play in that case are thus correctly understood. However, in the higher-NK case, the agreement is much worse. The remaining discrepancies are shown to arise from kinetic phenomena (e.g., inter-species diffusion) occurring at the gas-pusher interface, which should be investigated in future work.
Ion-kinetic simulation of D-3He gas-filled ICF target implosions with moderate to large Knudsen number / Larroche, O.; Rinderknecht, H. G.; Rosenberg, M. J.; Hoffman, N. M.; Atzeni, Stefano; Petrasso, R. D.; Amendt, P. A.; F. H., Seguin. - In: PHYSICS OF PLASMAS. - ISSN 1070-664X. - STAMPA. - 23:(2016). [10.1063/1.4939025]
Ion-kinetic simulation of D-3He gas-filled ICF target implosions with moderate to large Knudsen number
ATZENI, Stefano;
2016
Abstract
Experiments designed to investigate the transition to non-collisional behavior in D3He-gas ICF target implo- sions display increasingly large discrepancies with respect to simulations by standard hydrodynamics codes as the expected ion mean-free-paths λc increase with respect to the target radius R (i.e. when the Knudsen number NK = λc/R grows). To take properly into account large NK’s, multi-ion-species Vlasov-Fokker- Planck computations of the inner gas in those capsules have been performed, for two different values of NK, one moderate and one large. The results, including nuclear yield, reactivity-weighted ion temperatures, nu- clear emissivities and surface brightness, have been compared with experimental data and with the results of hydrodynamical simulations, some of which include an ad-hoc modeling of kinetic effects. The experimental results are quite accurately rendered by the kinetic calculations in the smaller-NK case, much better than by the hydrodynamical calculations. The kinetic effects at play in that case are thus correctly understood. However, in the higher-NK case, the agreement is much worse. The remaining discrepancies are shown to arise from kinetic phenomena (e.g., inter-species diffusion) occurring at the gas-pusher interface, which should be investigated in future work.File | Dimensione | Formato | |
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