Direct-drive, cryogenic target implosions on OMEGA

Marshall, F. J.; Craxton, R. S.; Delettrez, J. A.; Edgell, D. H.; Elasky, L. M.; Epstein, R.; Glebov, V. Yu.; Goncharov, V. N.; Harding, D. R.; Janezic, R.; Keck, R. L.; Kilkenny, J. D.; Knauer, J. P.; Loucks, S. J.; Lund, L. D.; McCrory, R. L.; McKenty, P. W.; Meyerhofer, D. D.; Radha, P. B.; Regan, S. P.; Sangster, T. C.; Seka, W.; Smalyuk, V. A.; Soures, J. M.; Stoeckl, C.; Skupsky, S.; Frenje, J. A.; Li, C. K.; Petrasso, R. D.; Sèguin, F. H.

doi:10.1063/1.1873832

Cited by 28 publications

(16 citation statements)

References 21 publications

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“…Clear evidence of technical problems in correctly positioning the target at shot time is seen in Fig. 8-15 319 for implosions with various values of a. The measured qR reached $100 mg/cm 2 .…”

Section: B Cryogenic Implosionsmentioning

confidence: 80%

Direct-drive inertial confinement fusion: A review

et al. 2015

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The direct-drive, laser-based approach to inertial confinement fusion (ICF) is reviewed from its inception following the demonstration of the first laser to its implementation on the present generation of high-power lasers. The review focuses on the evolution of scientific understanding gained from target-physics experiments in many areas, identifying problems that were demonstrated and the solutions implemented. The review starts with the basic understanding of laser–plasma interactions that was obtained before the declassification of laser-induced compression in the early 1970s and continues with the compression experiments using infrared lasers in the late 1970s that produced thermonuclear neutrons. The problem of suprathermal electrons and the target preheat that they caused, associated with the infrared laser wavelength, led to lasers being built after 1980 to operate at shorter wavelengths, especially 0.35 μm—the third harmonic of the Nd:glass laser—and 0.248 μm (the KrF gas laser). The main physics areas relevant to direct drive are reviewed. The primary absorption mechanism at short wavelengths is classical inverse bremsstrahlung. Nonuniformities imprinted on the target by laser irradiation have been addressed by the development of a number of beam-smoothing techniques and imprint-mitigation strategies. The effects of hydrodynamic instabilities are mitigated by a combination of imprint reduction and target designs that minimize the instability growth rates. Several coronal plasma physics processes are reviewed. The two-plasmon–decay instability, stimulated Brillouin scattering (together with cross-beam energy transfer), and (possibly) stimulated Raman scattering are identified as potential concerns, placing constraints on the laser intensities used in target designs, while other processes (self-focusing and filamentation, the parametric decay instability, and magnetic fields), once considered important, are now of lesser concern for mainline direct-drive target concepts. Filamentation is largely suppressed by beam smoothing. Thermal transport modeling, important to the interpretation of experiments and to target design, has been found to be nonlocal in nature. Advances in shock timing and equation-of-state measurements relevant to direct-drive ICF are reported. Room-temperature implosions have provided an increased understanding of the importance of stability and uniformity. The evolution of cryogenic implosion capabilities, leading to an extensive series carried out on the 60-beam OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)], is reviewed together with major advances in cryogenic target formation. A polar-drive concept has been developed that will enable direct-drive–ignition experiments to be performed on the National Ignition Facility [Haynam et al., Appl. Opt. 46(16), 3276 (2007)]. The advantages offered by the alternative approaches of fast ignition and shock ignition and the issues associated with these concepts are described. The lessons learned from target-physics and implosion experiments are taken into account in ignition and high-gain target designs for laser wavelengths of 1/3 μm and 1/4 μm. Substantial advances in direct-drive inertial fusion reactor concepts are reviewed. Overall, the progress in scientific understanding over the past five decades has been enormous, to the point that inertial fusion energy using direct drive shows significant promise as a future environmentally attractive energy source.

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Section: B Cryogenic Implosionsmentioning

confidence: 80%

Direct-drive inertial confinement fusion: A review

et al. 2015

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“…The pointing of each beam has an uncertainty of ϳ12 m rms. 10 These low-mode laser nonuniformities have been implemented in the 3D ray-tracing laserabsorption package. 19 The effect of each of these nonuniformities and their combined effects on the performance of a uniform target has been examined.…”

Section: Cryogenic D 2 Implosion Experiments On Omegamentioning

confidence: 99%

“…This initial target offset is measured through x-ray pinhole camera image at the beginning of corona plasma formation. 10 The fusion yield is measured with a combination of activation, scintillation, and track recorders. 10 When compared with the predicted symmetric implosion yield, the YOC provides a direct measurement of the target performance.…”

Section: Cryogenic D 2 Implosion Experiments On Omegamentioning

confidence: 99%

“…A variety of perturbations can significantly reduce the fusion yield. 10,11 This paper describes how various perturbation sources affect the neutron yield in low-adiabat cryogenic D 2 implosions conducted on OMEGA. These results will help specify the target nonuniformities required for implosions that are meaningful for studying ICF compression physics on OMEGA.…”

Section: Introductionmentioning

confidence: 99%

“…Cryogenic implosions with ␣ Ն 4 ͑␣ is defined as the ratio of fuel pressure to the Fermi-degenerate pressure͒ were investigated in OMEGA experiments 10 and simulations. 11 To efficiently compress ICF targets to high densities, the fuel must maintain a low adiabat of ␣ Ϸ 2 during a direct-drive implosion.…”

Section: Introductionmentioning

confidence: 99%

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