Inertial confinement fusion implosions with imposed magnetic field compression using the OMEGA Laser

Hohenberger, M.; Chang, Po-Yu; Fiksel, G.; Knauer, J. P.; Betti, R.; Marshall, F. J.; Meyerhofer, D. D.; Séguin, F.H.; Petrasso, R. D.

doi:10.1063/1.3696032

Cited by 137 publications

(131 citation statements)

References 42 publications

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“…16,17 Suppression of the Richtmyer-Meshkov instability, while retaining the effects of shock heating, could be expected to have potentially important consequences for the realization of inertial confinement fusion (ICF). Furthermore, it has been experimentally demonstrated that immersing ICF targets in seed magnetic fields results in an increase in observed ion temperature and neutron yield, 18 which is partially attributed to a reduction in heat losses from the center of the implosion due to electron confinement.…”

Section: Introductionmentioning

confidence: 99%

“…This case is of particular interest as the use of a similar magnetic field in ICF experiments, generated by a seed current through an axial thin wire, has been suggested as a means to further enhance electron confinement. 18 In Sec. II we write the equations of motion for non-resistive ideal inviscid magnetohydrodynamics and develop the appropriate characteristic form.…”

Section: Introductionmentioning

confidence: 99%

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Converging cylindrical shocks in ideal magnetohydrodynamics

et al. 2014

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We consider a cylindrically symmetrical shock converging onto an axis within the framework of ideal, compressible-gas non-dissipative magnetohydrodynamics (MHD). In cylindrical polar co-ordinates we restrict attention to either constant axial magnetic field or to the azimuthal but singular magnetic field produced by a line current on the axis. Under the constraint of zero normal magnetic field and zero tangential fluid speed at the shock, a set of restricted shock-jump conditions are obtained as functions of the shock Mach number, defined as the ratio of the local shock speed to the unique magnetohydrodynamic wave speed ahead of the shock, and also of a parameter measuring the local strength of the magnetic field. For the line current case, two approaches are explored and the results compared in detail. The first is geometrical shock-dynamics where the restricted shock-jump conditions are applied directly to the equation on the characteristic entering the shock from behind. This gives an ordinary-differential equation for the shock Mach number as a function of radius which is integrated numerically to provide profiles of the shock implosion. Also, analytic, asymptotic results are obtained for the shock trajectory at small radius. The second approach is direct numerical solution of the radially symmetric MHD equations using a shock-capturing method. For the axial magnetic field case the shock implosion is of the Guderley power-law type with exponent that is not affected by the presence of a finite magnetic field. For the axial current case, however, the presence of a tangential magnetic field ahead of the shock with strength inversely proportional to radius introduces a length scale \documentclass[12pt]{minimal}\begin{document}$R=\sqrt{\mu _0/p_0}\,I/(2\,\pi )$\end{document}R=μ0/p0I/(2π) where I is the current, μ0 is the permeability, and p0 is the pressure ahead of the shock. For shocks initiated at r ≫ R, shock convergence is first accompanied by shock strengthening as for the strictly gas-dynamic implosion. The diverging magnetic field then slows the shock Mach number growth producing a maximum followed by monotonic reduction towards magnetosonic conditions, even as the shock accelerates toward the axis. A parameter space of initial shock Mach number at a given radius is explored and the implications of the present results for inertial confinement fusion are discussed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Converging cylindrical shocks in ideal magnetohydrodynamics

et al. 2014

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“…There has been recent interest in the role of applied magnetic fields in high-energy-density plasmas [1][2][3] for inertial fusion energy applications [4]. The MagnetoInertial Fusion Electric Discharge System has been developed to provide steady state magnetic fields for long time-scales relative to the experiments.…”

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confidence: 99%

Kinetic modeling of Nernst effect in magnetized hohlraums

et al. 2016

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We present nanosecond timescale Vlasov-Fokker-Planck-Maxwell modeling of magnetized plasma transport and dynamics in a hohlraum with an applied external magnetic field, under conditions similar to recent experiments. Self-consistent modeling of the kinetic electron momentum equation allows for a complete treatment of the heat flow equation and Ohm's Law, including Nernst advection of magnetic fields. In addition to showing the prevalence of non-local behavior, we demonstrate that effects such as anomalous heat flow are induced by inverse bremsstrahlung heating. We show magnetic field amplification up to a factor of 3 from Nernst compression into the hohlraum wall. The magnetic field is also expelled towards the hohlraum axis due to Nernst advection faster than frozen-in-flux would suggest. Non-locality contributes to the heat flow towards the hohlraum axis and results in an augmented Nernst advection mechanism that is included self-consistently through kinetic modeling.There has been recent interest in the role of applied magnetic fields in high-energy-density plasmas [1-3] for inertial fusion energy applications [4]. The MagnetoInertial Fusion Electric Discharge System has been developed to provide steady state magnetic fields for long time-scales relative to the experiments. An experiment on the Omega Laser Facility with a 7.5 T external axial magnetic field imposed on an Omega-scale hohlraum measured a rise in observed temperature along the hohlraum axis [5] and modeling showed that external fields can guide hot electrons from laser-plasma interactions [6] through the hohlraum, rather than the capsule [7]. From Ohm's Law, it has been shown that electron heat transport advects such magnetic fields through the Nernst effect [8][9][10][11][12][13][14] in addition to well-known processes like "frozen-in-flow" and resistive diffusion. Dimensionless numbers comparing the ratio of the magnitudes of the Nernst term to the bulk plasma flow term, R N 1 [10], and the Hall term, H N 1 [13], suggest that Nernst convection should be the dominant mechanism for magnetic field transport in a hohlraum. Such a hot and semi-collisional environment is, however, rich in nonequilibrium effects that may complicate the magnetic field dynamics.Laser heating of the plasma results in steep temperature gradients, typically O(3 keV/50 µm). The collisional * archis@ucla.edu † agrt@umich.edu mean-free-path of a 3 keV electron is O(10 µm), depending on the plasma density. Since λ mfp /L < 100, nonlocality can be expected to be important [15]. The steep temperature gradients caused by intense laser heating in a hohlraum have been shown to result in non-local heat flow [16,17]. Careful consideration of the electron population with 2v th < v < 4v th is required as these carry most of the heat. Additionally, inverse-bremsstrahlung heating of a plasma [18,19] not only leads to deviations from Braginskii transport [20], but also new transport terms [21,22]. Both non-locality and laser heating result in modifications to the distribution function an...

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“…Sano et al [10] performed a numerical simulation and found that due to the fluid motions associated with the RMI, the ambient magnetic field strength was amplified substantially by an order of two magnitude. Hohenberger et al [11] concluded experimentally that compared to the unmagnetized explosion in ICF, the ion temperature was increased by 15% in the presence of magnetic field, which improved the ICF performance.…”

Section: Introductionmentioning

confidence: 99%

Linear Simulations of the Cylindrical Richtmyer-Meshkov Instability in Hydrodynamics and MHD

Gao

Samtaney

2015

29th International Symposium on Shock Waves 2

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Linear Simulations of the Cylindrical Richtmyer-MeshkovInstability in Hydrodynamics and MHD Song GaoThe Richtmyer-Meshkov instability occurs when density-stratified interfaces are impulsively accelerated, typically by a shock wave. We present a numerical method to simulate the Richtmyer-Meshkov instability in cylindrical geometry. The ideal MHD equations are linearized about a time-dependent base state to yield linear partial differential equations governing the perturbed quantities. Convergence tests demonstrate that second order accuracy is achieved for smooth flows, and the order of accuracy is between first and second order for flows with discontinuities.Numerical results are presented for cases of interfaces with positive Atwood number and purely azimuthal perturbations. In hydrodynamics, the Richtmyer-Meshkov instability growth of perturbations is followed by a Rayleigh-Taylor growth phase.In MHD, numerical results indicate that the perturbations can be suppressed for sufficiently large perturbation wavenumbers and magnetic fields. 5 ACKNOWLEDGEMENTSSincere thanks to my supervisor, Prof. Ravi Samtaney, for his profound knowledge, patience and enthusiasm.Thanks to the members of my thesis examination committee, Prof. Sigurdur Thoroddsen and Prof.Georgiy Stenchikov, for their valuable comments and precious time.Thanks to Dr. Manuel Lombardini, for the interesting discussion and invaluable help. Thanks to Mr. Wei Gao, for his great encouragement.Thanks to my parents, for raising me up, and my unmet wife.Last but not least, special thanks to Dr. Fabrizio Bisetti, for the sharp lesson he has taught me. 6

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Inertial confinement fusion implosions with imposed magnetic field compression using the OMEGA Laser

Cited by 137 publications

References 42 publications

Converging cylindrical shocks in ideal magnetohydrodynamics

Converging cylindrical shocks in ideal magnetohydrodynamics

Kinetic modeling of Nernst effect in magnetized hohlraums

Linear Simulations of the Cylindrical Richtmyer-Meshkov Instability in Hydrodynamics and MHD

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