Experimental Indications of Plasma Instabilities Induced by Laser Heating

Shearer, J. W.; Mead, S.W.; Petruzzi, J.; Rainer, F.; Swain, J.E.; Violet, C.E.

doi:10.1103/physreva.6.764

Cited by 61 publications

(20 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Using a Nd:glass laser, B€ uchl et al 72 observed a twocomponent x-ray spectrum with an $2-keV nonthermal component that disappeared (along with the neutrons) when a background gas was added. Shearer et al 98 irradiated plastic targets with a Nd:glass laser at $2 Â 10 14 W/cm 2 and found 100-keV x rays with a temperature T H $ 50 keV; they suggested the parametric decay instability as the cause. Olsen et al 99 reported 200-to 800-keV x rays, also from a Nd:glass laser.…”

Section: B Suprathermal Electronsmentioning

confidence: 99%

“…10-11(b)], plastic targets were irradiated at LLNL by Shearer et al 98 at a comparable intensity of $2 Â 10 14 W/cm 2 and a wavelength of 1 lm. Bursts of reflected light were seen, with up to 3% of the incident laser power observed in the f/7 lens (4 half-angle).…”

Section: B Stimulated Brillouin Scattering (Sbs) and Crossbeam Energmentioning

confidence: 99%

“…As early as 1972, it was recognized that SBS could be seeded by backscattered light from the target for laser beams with a large bandwidth. 98 (The seed beam must have the correct wavelength to satisfy the frequency-matching conditions.) This was subsequently recognized by Begg and Cairns 468 and Randall et al 469 Using a 1-D model with the laser at normal incidence, Randall et al noted that there is a region with the appropriate Mach number at which the reflected light from the critical surface seeds SBS backscatter and offered this as an alternative to the phase-conjugate explanation of Lehmberg.…”

Section: -70mentioning

confidence: 99%

See 2 more Smart Citations

Direct-drive inertial confinement fusion: A review

et al. 2015

View full text Add to dashboard Cite

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.

show abstract

Section: B Suprathermal Electronsmentioning

confidence: 99%

Section: B Stimulated Brillouin Scattering (Sbs) and Crossbeam Energmentioning

confidence: 99%

Section: -70mentioning

confidence: 99%

See 1 more Smart Citation

Direct-drive inertial confinement fusion: A review

et al. 2015

View full text Add to dashboard Cite

show abstract

“…A record of the nine-pass reflected intensitv is given in Ref. 108. Figure 93 shows the five-pass reflected intensity.…”

Section: Plasma Experimentsmentioning

confidence: 99%

Laser-Fusion Program Semiannual Report: January--June 1972.

Kachen¹,

Clements²,

Genin³

1972

View full text Add to dashboard Cite

“…A small fraction of the laser energy, however, is absorbed into hot -electrons [7,8,9]. These electrons have energies in the range of 20 -40 keV preheating the fusion capsule which in turn results in a reduced capsule compressibility.…”

Section: Introductionmentioning

confidence: 99%

X-ray spectroscopy from fusion plasmas

Glenzer¹

1999

The 14th International Conference on Spectral Line Shapes

View full text Add to dashboard Cite

Our understanding of laser energy coupling into laser-driven inertial confinement fusion targets largely depends on our ability to accurately measure and simulate the plasma conditions in the underdense corona and in high density capsule implosions.X-ray spectroscopy is an important technique which has been applied to measure the total absorption of laser energy into the fusion target, the fraction of laser energy absorbed by hot electrons, and the conditions in the fusion capsule in terms of density and temperature. These parameters provide critical benchmarking data for performance studies of the fusion target and for radiation-hydrodynamic and laser-plasma interaction simulations. Using x-ray spectroscopic techniques for these tasks has required its application to non-standard conditions where kinetics models have not been extensively tested. In particular, for the conditions in high density implosions, where electron temperatures achieve 1 -2 keV and electron densities reach 10 24 cm-3 evolving on time scales of < 1 ns, no independent non-spectroscopic measurements of plasma parameters are available. For these reasons, we have in open-geometry gas bag plasmas at densities of 10 3 frformed experiments cm-3 and which am independently diagnosed with Thomson scattering and stimulated Raman scattering. We find that kinetics modeling is in good agreement with measured intensities of the dielectronic satellites of the He-p line (n= l-3) of Ar XVII. Applying these findings to the experimental results of capsule implosions provides additional evidence of' temperature gradients at peak compression.

show abstract

Experimental Indications of Plasma Instabilities Induced by Laser Heating

Cited by 61 publications

References 17 publications

Direct-drive inertial confinement fusion: A review

Direct-drive inertial confinement fusion: A review

Laser-Fusion Program Semiannual Report: January--June 1972.

X-ray spectroscopy from fusion plasmas

Contact Info

Product

Resources

About