Time-Resolved Study of Nonlocal Electron Heat Transport in High Temperature Plasmas

Ditmire, T.; Gumbrell, E. T.; Smith, R. A.; Djaoui, A.; Hutchinson, M. H. R.

doi:10.1103/physrevlett.80.720

Cited by 65 publications

(38 citation statements)

References 16 publications

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“…The application of linear theory to experimental data, such as [5,6,24,25], and comparison with kinetic simulations and its generalization to include local dependence on plasma parameters, as in Ref. [14], could lead to a nonlocal nonlinear transport theory in magnetized plasmas.…”

Section: Discussionmentioning

confidence: 99%

Linear theory of nonlocal transport in a magnetized plasma

et al. 2003

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A system of nonlocal electron-transport equations for small perturbations in a magnetized plasma is derived using the systematic closure procedure of V. Yu. Bychenkov et al., Phys. Rev. Lett. 75, 4405 (1995). Solution to the linearized kinetic equation with a Landau collision operator is obtained in the diffusive approximation. The Fourier components of the longitudinal, oblique, and transversal electron fluxes are found in an explicit form for quasistatic conditions in terms of the generalized forces: the gradients of density and temperature, and the electric field. The full set of nonlocal transport coefficients is given and discussed. Nonlocality of transport enhances electron fluxes across magnetic field above the values given by strongly collisional local theory. Dispersion and damping of magnetohydrodynamic waves in weakly collisional plasmas is discussed. Nonlocal transport theory is applied to the problem of temperature relaxation across the magnetic field in a laser hot spot.

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Section: Discussionmentioning

confidence: 99%

Linear theory of nonlocal transport in a magnetized plasma

et al. 2003

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“…Sub-picosecond lasers now allow energy deposition to be decoupled from the subsequent 100 ps-100 ns hydrodynamic motion of a plasma, greatly simplifying the understanding of these experiments. As a result, laboratory studies investigating the radial expansion of spherical and cylindrical blast waves in gas media have made significant progress in the last few years (Edens et al, 2004;Ditmire et al, 1998a). In contrast, only a limited number of counter-propagating plasma experiments to investigate shock collisions have been attempted (Elton et al, 1994;Bosch et al, 1992).…”

Section: Creation Of Colliding Blast Wavesmentioning

confidence: 98%

“…A more complete discussion of these processes is given by Moore et al (2006) in this issue. By selecting high Z target species it is also possible to form radiative blast waves (Moore et al, 2006;Ditmire et al, 1998a). This can lead to the pre-heating of un-shocked material, significantly altering the propagation dynamics.…”

Section: Atomic Clusters As a Target Mediummentioning

confidence: 98%

“…The absorption characteristics of a cluster target medium enables high-Mach-number shocks (Ditmire et al, 1998a) to be created efficiently by delta function heating using a small scale, high-repetition-rate laser system. This also enabled us to quickly acquire large (>100 shot) data sets in order to minimize statistical fluctuations arising from shot-to-shot variations in laser energy, and to investigate shock collisions over a broad range of initial particle and energy densities.…”

Section: Creation Of Colliding Blast Wavesmentioning

confidence: 99%

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Colliding Blast Waves Driven by the Interaction of a Short-Pulse Laser with a Gas of Atomic Clusters

Smith

Lazarus

Hohenberger

et al. 2006

Astrophys Space Sci

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Collisions between shocks are commonly found in many astrophysical objects, however robust numerical models or laboratory analogues of these complex systems remain challenging to implement. We report on the development of scaled laboratory experiments which employ new techniques for launching and diagnosing colliding shocks and high Mach number blast waves, scalable to a limited subset of astrophysically-relevant regimes. Use of an extended medium of atomic clusters enables efficient (>80%) coupling of 700 fs, 1 J, 1054 nm laser pulses to a "cluster" gas with an average density of ≈10 19 particles cm −3 , producing an initial energy density >10 5 J cm −3 , equivalent to ≈5 × 10 9 J/g. Multiple laser foci are used to tailor the spatial profile of energy deposition, or to launch pairs of counter-propagating cylindrical shocks which then collide. By probing the collision interferometrically at multiple view angles in 5 • increments and applying an inverse Radon transform to the resulting phase projections we have been able to tomographically reconstruct the full three-dimensional, time-framed electron density profile of the system.

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“…Enhanced absorption of the laser energy by such jet makes it possible to create a plasma with high energy electrons [5]. The expansion of such plasmas have been used to study phenomena ranging from nonlocal heat transport [6] to formation of electrostatic shocks [7] and blast waves [8]. The corresponding time-scale is in the range of tens of ps, because these phenomena either involve ion motion or electron collisions.…”

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confidence: 99%

Observation of Self-Sustaining Relativistic Ionization Wave Launched by a Sheath Field

et al. 2014

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We present experimental evidence supported by simulations of a relativistic ionization wave launched into surrounding gas by the sheath field of a plasma filament with high energy electrons. Such filament is created by irradiating a clustering gas jet with a short pulse laser (∼115 fs) at a peak intensity of 5 × 10 17 W/cm 2 . We observe an ionization wave propagating radially through the gas for about 2 ps at 0.2-0.5 c after the laser has passed, doubling the initial radius of the filament. The gas is ionized by the sheath field, while the longevity of the wave is explained by a moving field structure that traps the high energy electrons near the boundary, maintaining a strong sheath field despite the significant expansion of the plasma.A sheath electric field is a ubiquitous phenomenon caused by electron motion that occurs at the plasma edge. It is employed in applications ranging from plasma discharges [1, 2] to ion acceleration [3,4]. In this paper, we present experimental evidence supported by simulations of a collisionless self-sustaining relativistic ionization wave that is launched into a surrounding un-ionized gas by a plasma sheath field.Suitable experimental conditions are achieved by irradiating a supersonic clustering argon gas jet with a moderate intensity laser pulse (5 × 10 17 W/cm 2 ). Enhanced absorption of the laser energy by such jet makes it possible to create a plasma with high energy electrons [5]. The expansion of such plasmas have been used to study phenomena ranging from nonlocal heat transport [6] to formation of electrostatic shocks [7] and blast waves [8]. The corresponding time-scale is in the range of tens of ps, because these phenomena either involve ion motion or electron collisions. In what follows, we focus on much faster phenomenon. We present direct measurements of a relativistic velocity ionization wave, launched by the radial sheath field of a laser-generated plasma with high energy electrons, that is sustained for up to 2 ps. The measured radial velocity of the wave after the laser pulse is 0.2-0.5 c, causing the plasma radius to double on a ps time scale. Our relatively short laser pulse (115 fs) makes it possible to clearly distinguish energy deposition into the plasma from the propagation of the ionization wave that follows.The measured increase of the plasma radius is clearly too fast to be attributed to hydrodynamic motion, and it is even too fast to be explained by free-streaming electrons ionizing the surrounding gas via impact ionization. Indeed, the velocity of these electrons has to be comparable to the speed of the wave front, v e ≈ 0.5 c, which leads to a collisional time τ e 10 ps at 3 × 10 18 cm −3 gas densities [9]. This is much too long for the observed ionization. In this paper, we also present particle-in-cell (PIC) simulations that reveal a new collisionless mechanism that can launch and maintain the observed fast ionization front. We show that a hot electron minor- ity produced by the laser-cluster interaction generates a strong sheath electric field at...

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Time-Resolved Study of Nonlocal Electron Heat Transport in High Temperature Plasmas

Cited by 65 publications

References 16 publications

Linear theory of nonlocal transport in a magnetized plasma

Linear theory of nonlocal transport in a magnetized plasma

Colliding Blast Waves Driven by the Interaction of a Short-Pulse Laser with a Gas of Atomic Clusters

Observation of Self-Sustaining Relativistic Ionization Wave Launched by a Sheath Field

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