Progress in direct-drive inertial confinement fusion

McCrory, R. L.; Meyerhofer, D. D.; Betti, R.; Craxton, R. S.; Delettrez, J. A.; Edgell, D. H.; Glebov, V. Yu.; Goncharov, V. N.; Harding, D. R.; Jacobs‐Perkins, D.; Knauer, J.P.; Marshall, F. J.; McKenty, P. W.; Radha, P. B.; Regan, S. P.; Sangster, T. C.; Seka, W.; Short, R. W.; Skupsky, S.; Smalyuk, V. A.; Soures, J. M.; Stoeckl, C.; Yaakobi, B.; Shvarts, D.; Frenje, J. A.; Li, C. K.; Petrasso, R. D.; Séguin, F.H.

doi:10.1063/1.2837048

Cited by 114 publications

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“…Because of the moderate laserdrive intensity, the implosion velocity of $2:4 Â 10 7 cm=s was lower than required for ignition on the NIF (3.5 to 4 Â 10 7 cm=s) [4]. Increasing the peak intensity to $1 Â 10 15 W=cm 2 allows the implosion velocity to be raised to levels required for ignition, but hard x-ray signals, associated with TPD hot electrons, increase with laser intensity [6,10,11]. Current hot-electron preheat estimates in plasticablator OMEGA implosions (with the estimated cold-shell preheat energy fraction of $0:1% of the total laser energy) may not preclude achieving ignition-relevant compression (with a shell R of $200 mg=cm 2 ) at high peak intensities of $1 Â 10 15 W=cm 2 and a slightly lower initial shell adiabat of $ 2 [6].…”

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“…Increasing the peak intensity to $1 Â 10 15 W=cm 2 allows the implosion velocity to be raised to levels required for ignition, but hard x-ray signals, associated with TPD hot electrons, increase with laser intensity [6,10,11]. Current hot-electron preheat estimates in plasticablator OMEGA implosions (with the estimated cold-shell preheat energy fraction of $0:1% of the total laser energy) may not preclude achieving ignition-relevant compression (with a shell R of $200 mg=cm 2 ) at high peak intensities of $1 Â 10 15 W=cm 2 and a slightly lower initial shell adiabat of $ 2 [6]. The longer plasma scale lengths in the larger NIF targets make them potentially more susceptible to hot-electron production than OMEGA targets [10].…”

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“…Shell preheat, another source of compression degradation, is caused by hot electrons generated by two-plasmon-decay (TPD) instability [8,9]. This preheat was shown to be virulent in DT and D 2 ablators [6,10] and was reduced by using plastic ablators [6,11]. The highest ignition-relevant areal densities with a shell R of $200 mg=cm 2 were achieved in cryogenic D 2 -ice implosions with plastic ablators, when the hotelectron preheat was suppressed, at a moderate laser-drive peak intensity of $5 Â 10 14 W=cm 2 and a laser energy of $16 kJ on OMEGA [11].…”

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“…Adiabat control is critical to achieving the desired R at peak compression [1,2]. Shock mistiming was an important cause of R degradation in direct-drive, cryogenic implosions on OMEGA and a subject of intensive research [5,6]. Another area of concern to ICF is the unstable growth of target modulations caused by hydrodynamic instabilities [1,2].…”

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Implosion Experiments using Glass Ablators for Direct-Drive Inertial Confinement Fusion

et al. 2010

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Direct-drive implosions with 20-m-thick glass shells were conducted on the Omega Laser Facility to test the performance of high-Z glass ablators for direct-drive, inertial confinement fusion. The x-ray signal caused by hot electrons generated by two-plasmon-decay instability was reduced by more than $40Â and hot-electron temperature by $2Â in the glass compared to plastic ablators at ignition-relevant drive intensities of $1 Â 10 15 W=cm 2 , suggesting reduced target preheat. The measured absorption and compression were close to 1D predictions. The measured soft x-ray production in the spectral range of $2 to 4 keV was $2Â to 3Â lower than 1D predictions, indicating that the shell preheat caused by soft x-rays is less than predicted. A direct-drive-ignition design based on glass ablators is introduced. DOI: 10.1103/PhysRevLett.104.165002 PACS numbers: 52.57.ÀzThe goal of inertial confinement fusion (ICF) [1,2] is to implode a spherical target to achieve high compression of the fuel and high temperature in the hot spot to trigger ignition and maximize the thermonuclear energy gain. To achieve high compression, the shell entropy and temperature must remain low because it is easier to compress the fuel at a low temperature than at a high temperature [2]. The entropy is defined [3] by adiabat ¼ PðMbÞ=½2:2 ðg=ccÞ 5=3 , the ratio of the plasma pressure to the Fermi pressure of a fully degenerate electron gas [3]. In direct-drive spherical implosions, the target is driven by direct illumination with overlapped laser beams. To ignite DT fuel on the National Ignition Facility (NIF) [2] with a laser energy of E L ¼ 1:5 MJ and to achieve a gain of $40 to 50 will require high fuel compression with a total target areal density ( R) of $1500 mg=cm 2 [4]. As shown in Ref.[3], Rðmg=cm 2 Þ % 2600E L ðMJÞ 1=3 À0:6 so high areal densities require low-adiabat, 3 implosions. The fuel adiabat is determined by shocks launched at the beginning of the implosion [2]. The shock waves must be precisely tuned to set the inner portion of the shell on a low adiabat. Adiabat control is critical to achieving the desired R at peak compression [1,2]. Shock mistiming was an important cause of R degradation in direct-drive, cryogenic implosions on OMEGA and a subject of intensive research [5,6]. Another area of concern to ICF is the unstable growth of target modulations caused by hydrodynamic instabilities [1,2]. While the areal densities at peak compression have been shown to be relatively insensitive to hydrodynamic instabilities, the fusion neutron yields are very sensitive [7]. Shell preheat, another source of compression degradation, is caused by hot electrons generated by two-plasmon-decay (TPD) instability [8,9]. This preheat was shown to be virulent in DT and D 2 ablators [6,10] and was reduced by using plastic ablators [6,11]. The highest ignition-relevant areal densities with a shell R of $200 mg=cm 2 were achieved in cryogenic D 2 -ice implosions with plastic ablators, when the hotelectron preheat was suppressed, at a moderate laser-dr...

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Implosion Experiments using Glass Ablators for Direct-Drive Inertial Confinement Fusion

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“…Warm dense matter (WDM) is encountered in systems as diverse as the interiors of giant planets 1,2 and in the pathway to inertial confinement fusion 3,4 . WDM is challenging to theory and simulation because it occurs inconveniently, for theory, between the comparatively wellstudied plasma and condensed matter regimes.…”

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Temperature-dependent behavior of confined many-electron systems in the Hartree-Fock approximation

2012

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Many-electron systems confined at substantial finite temperatures and densities present a major challenge to density functional theory. In particular, there is comparatively little systematic knowledge about the behavior of free-energy density functionals for temperatures and pressures of interest, for example, in the study of warm dense matter. As with ground-state functionals, development of approximate free-energy functionals is faced with significant needs for reliable assessment and calibration data. Here we address, in part, this need for detailed results on well-characterized systems. We present results on a comparatively simple, well-defined, computationally feasible but previously unexplored model, the thermal Hartree-Fock approximation. We discuss the main technical tasks (defining a suitable basis and evaluation of the required matrix elements) and give an illustrative initial application which probes both the content of the model and the solution techniques: a system of eight one-electron atoms with nuclei at fixed, arbitrary positions in a hard-walled box. Even this simple system produces physical behavior different from that produced by simple ground state density functionals used at finite temperature (a common approximation in the study of WDM).

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Perspectives 2012

Dean

2012

Search for the Ultimate Energy Source

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Progress in direct-drive inertial confinement fusion

Cited by 114 publications

References 34 publications

Implosion Experiments using Glass Ablators for Direct-Drive Inertial Confinement Fusion

Implosion Experiments using Glass Ablators for Direct-Drive Inertial Confinement Fusion

Temperature-dependent behavior of confined many-electron systems in the Hartree-Fock approximation

Perspectives 2012

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