Development of Improved Radiation Drive Environment for High Foot Implosions at the National Ignition Facility

Hinkel, D. E.; Hopkins, L. F. Berzak; Ma, T.; Ralph, J. E.; Albert, F.; Benedetti, L. R.; Celliers, P. M.; Döppner, T.; Goyon, C.; Izumi, N.; Jarrott, L. C.; Khan, S. F.; Kline, J. L.; Kritcher, A. L.; Kyrala, G. A.; Nagel, S. R.; Pak, A.; Patel, P. K.; Rosen, M. D.; Rygg, J. R.; Schneider, M. B.; Turnbull, D.; Yeamans, C. B.; Callahan, D. A.; Hurricane, O. A.

doi:10.1103/physrevlett.117.225002

Cited by 70 publications

(14 citation statements)

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“…These simulations correspond to NIF shots N151122 and N151227, 24 respectively (shot numbers are assigned by date as yymmdd). The third simulation is taken from the highadiabat or "high foot" campaign, 25 which uses a CH capsule (roughly 30% the density of HDC). This necessitates a much longer laser pulse, due to the longer shock transit-time.…”

Section: Introductionmentioning

confidence: 99%

Simulation of self-generated magnetic fields in an inertial fusion hohlraum environment

et al. 2017

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We present radiation-hydrodynamic simulations of self-generated magnetic field in a hohlraum, which show an increased temperature in large regions of the underdense fill. Non-parallel gradients in electron density and temperature in a laser-heated plasma give rise to a self-generated field by the “Biermann battery” mechanism. Here, HYDRA simulations of three hohlraum designs on the National Ignition Facility are reported, which use a partial magnetohydrodynamic (MHD) description that includes the self-generated source term, resistive dissipation, and advection of the field due to both the plasma flow and the Nernst term. Anisotropic electron heat conduction parallel and perpendicular to the field is included, but not the Righi-Leduc heat flux. The field strength is too small to compete significantly with plasma pressure, but affects plasma conditions by reducing electron heat conduction perpendicular to the field. Significant reductions in heat flux can occur, especially for high Z plasma, at modest values of the Hall parameter, Ωeτei≲1, where Ωe=eB/mec and τei is the electron-ion collision time. The inclusion of MHD in the simulations leads to 1 keV hotter electron temperatures in the laser entrance hole and high-Z wall blowoff, which reduces inverse-bremsstrahlung absorption of the laser beam. This improves propagation of the inner beams pointed at the hohlraum equator, resulting in a symmetry shift of the resulting capsule implosion towards a more prolate shape. The time of peak x-ray production in the capsule shifts later by only 70 ps (within experimental uncertainty), but a decomposition of the hotspot shape into Legendre moments indicates a shift of P2/P0 by ∼20%. This indicates that MHD cannot explain why simulated x-ray drive exceeds measured levels, but may be partially responsible for failures to correctly model the symmetry.

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Section: Introductionmentioning

confidence: 99%

Simulation of self-generated magnetic fields in an inertial fusion hohlraum environment

et al. 2017

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“…Parallel efforts exploring so-called "exploding pushers" for neutron diagnostic flat-fielding [59,159] and traditional ablative designs [58,160] in near vacuum hohlraums mitigated losses due to LPI leading to a transition away from high gas-fill to low gas-fill hohlraums [161][162][163]. However, without a high gas fill, the ratio of hohlraum to capsule diameter needed to be larger for long pulse CH designs [164] to delay the ingress of hohlraum plasma into the path of the inner laser beams [165], reducing coupling efficiency from hohlraum to capsule.…”

Section: Quantitymentioning

confidence: 99%

Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

Abu-Shawareb¹,

Acree²,

Adams³

et al. 2022

Phys. Rev. Lett.

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257

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“…When the support rod is placed 200-300 lm from the capsule, little to no performance degradation is expected. To observe this improvement in a layered DT implosions, other degradation sources need to be reduced, either by improving the hohlraum 48 or by using a capsule designed to mitigate low-mode asymmetries. 49 The high convergence of low foot and adiabat shaped low foot pulses are more sensitive to the tent and may be candidates to demonstrate a performance improvement.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Improving ICF implosion performance with alternative capsule supports

et al. 2017

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The thin membrane that holds the capsule in-place in the hohlraum is recognized as one of the most significant contributors to reduced performance in indirect drive inertial confinement fusion (ICF) experiments on the National Ignition Facility. This membrane, known as the “tent,” seeds a perturbation that is amplified by Rayleigh-Taylor and can rupture the capsule. A less damaging capsule support mechanism is under development. Possible alternatives include the micron-scale rods spanning the hohlraum width and supporting either the capsule or stiffening the fill-tube, a larger fill-tube to both fill and support the capsule, or a low-density foam layer that protects the capsule from the tent impact. Experiments are testing these support features to measure their imprint on the capsule. These experiments are revealing unexpected aspects about perturbation development in indirect drive ICF, such as the importance of shadows coming from bright spots in the hohlraum. Two dimensional and 3D models are used to explain these features and assess the impact on implosion performance. Experiments and modeling suggest that the fill-tube supported by a perpendicular rod can mount the capsule without any additional perturbation beyond that of the fill tube.

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Development of Improved Radiation Drive Environment for High Foot Implosions at the National Ignition Facility

Cited by 70 publications

References 20 publications

Simulation of self-generated magnetic fields in an inertial fusion hohlraum environment

Simulation of self-generated magnetic fields in an inertial fusion hohlraum environment

Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

Improving ICF implosion performance with alternative capsule supports

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