Fine-Scale Structures in Plasmas Stimulated by a C<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Laser

Grek, B.; Martín, F.; Johnston, T. W.; Pépin, H.; Mitchel, G. R.; Rheault, F.

doi:10.1103/physrevlett.41.1811

Cited by 34 publications

(13 citation statements)

References 13 publications

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“…10 Once at the target surface, this return current could also create an x-ray-emitting plasma through Ohmic heating. 11 Interferometry with a short ruby-laser pulse 12 and other observations 5 * 6 indicate that the diameter of the surface plasma is expanding laterally at a velocity above 10 8 cm/sec and reaches a diameter comparable to the 1-keV x-ray emission diameter.…”

Section: Spatial Characteristics Of Continuum X-ray Emission From Latmentioning

confidence: 84%

Spatial Characteristics of Continuum X-Ray Emission from Lateral Energy Transport in CO2-Laser-Produced Plasmas

1981

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A modified layered-target technique is used to provide spatial information about continuum x-ray emission in the plane of an infinite target irradiated by a short-pulse C0 2 laser. Hard x-rays are only observed near or within the laser interaction region. Softer x rays are emitted over a large but shallow area of the target surface. These results are used to discuss lateral energy transport mechanisms.

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Section: Spatial Characteristics Of Continuum X-ray Emission From Latmentioning

confidence: 84%

Spatial Characteristics of Continuum X-Ray Emission from Lateral Energy Transport in CO2-Laser-Produced Plasmas

1981

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“…The spatial scale length of the laser hot spots is about 50 /im in contrast to the scale length of the jets which is up to 10 jLtm for high Z. Grek etal. 9 reported the occurrence of filamentary structures or jets originating in the overdense plasma at up to sixteen times the critical density. In this region heat-flow-driven instabilities could be the origin of the filamentary structure.…”

Section: Employedmentioning

confidence: 97%

Thermal Instability and Magnetic Field Generated by Large Heat Flow in a Plasma, Especially under Laser-Fusion Conditions

Haines

1981

Phys. Rev. Lett.

122

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Representing a large heat flow in a plasma as a flow of hot relatively collisionless electrons balanced by an opposing current of cold collisional electrons, it can be shown that an electrothermal instability can be induced in the cold resistive plasma when the heat flow exceeds about 3% of the free-streaming limit. This is nonconvective if the temperature of the cold plasma is less than 0.2n { l/4 z l/2o K withn in m" 3 . The instability will lead to filamentary magentic structures with a typical growth time of a few picoseconds and wavelength about 10 ^m.PACS numbers: 52.50. Jm, 52.25.Fi, 52.35. In this Letter a new mechanism for an unstability is proposed in laser-produced plasmas. It can generate a filamentary density and temperature structure with associated magnetic fields in the plasma between the critical and ablation surfaces in which a nonlinear heat flux occurs, and could be dangerous for any inertial confinement scheme.A large heat flow can be approximately represented by an inward flow of relatively collisionless hot electrons balanced by a return current of cold electrons driven by an electric field. This is because the mean free path of electrons with a velocity v is proportional to v 4 /Zn 0 , n 0 being the number density of electrons and Z the ionic charge number. Representing the hot and cold equilibrium currents by 3 ft0 and J e0 , respectively, the heat flux q can be written aswhere T h0 and T e0 (

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“…[525][526][527] In the early 1980s, Willi et al 528 and Willi and Rumsby 529 observed clear light and dark streaks in the underdense corona of a spherical target exemplified by the schlieren (dark-field) image of Fig. 10-32, published in Refs.…”

Section: Methodsmentioning

confidence: 98%

“…530 Early evidence of filamentation included various nonlinear electromagnetic emissions that were localized and therefore attributed to filamentation. Localized x-ray emission spots were ascribed to filamentation, 526,531,532 although in some experiments they were re-identified as target contaminants. 533,534 Localized 2x 0 emission 535,536 and 3x 0 =2 emission 537 were also observed.…”

Section: Methodsmentioning

confidence: 99%

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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Fine-Scale Structures in Plasmas Stimulated by a CO2Laser

Cited by 34 publications

References 13 publications

Spatial Characteristics of Continuum X-Ray Emission from Lateral Energy Transport in CO2-Laser-Produced Plasmas

Spatial Characteristics of Continuum X-Ray Emission from Lateral Energy Transport in CO2-Laser-Produced Plasmas

Thermal Instability and Magnetic Field Generated by Large Heat Flow in a Plasma, Especially under Laser-Fusion Conditions

Direct-drive inertial confinement fusion: A review

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