Measurement of Heat Propagation in a Laser Produced Plasma
Measurement of Heat Propagation in a Laser Produced Plasma

Author: J. Edwards

Publisher:

Published: 2003

Total Pages:

ISBN-13:

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We present the observation of a nonlocal heat wave by measuring spatially and temporally resolved electron temperature profiles in a laser produced nitrogen plasma. Absolutely calibrated measurements have been performed by resolving the ion-acoustic wave spectra across the plasma volume with Thomson scattering. We find that the experimental electron temperature profiles disagree with flux-limited models, but are consistent with transport models that account for the nonlocal effects in heat conduction by fast electrons.

Direct Measurements of Nonlocal Heat Flux in Laser-produced Coronal Plasmas Using Thomson Scattering from Electron-plasma Waves
Direct Measurements of Nonlocal Heat Flux in Laser-produced Coronal Plasmas Using Thomson Scattering from Electron-plasma Waves

Author: Robert James Henchen

Publisher:

Published: 2018

Total Pages: 155

ISBN-13:

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"Thermal transport is a fundamental process in plasma physics that is not well understood. Historically, local models have been used to describe the heat flux in plasmas but artificially limit the flux at even modest temperature gradients. This Thesis studies electron thermal transport in laser-produced coronal plasmas using a novel Thomson scattering technique. Thomson scattering is sensitive to changes in the electron distribution function caused by heat flux. The experiments show that nonlocal effects must be included in regions where the plasma was not collisional enough for classical theory to be valid. Vlasov-Fokker-Planck simulations self consistently calculated the electron distribution functions used to reproduce the measured Thomson scattering spectra and to determine the heat flux. Measured heat flux values were up to 40% smaller than classical values inferred from the measured plasma conditions in this region. This is the first direct measurement of nonlocal heat flux in plasmas. In the opposite limit, classical theory matched the observed Thomson scattering data. Multigroup nonlocal simulations overestimated the measured heat flux."--Page xi.

Laser-produced Plasma Measurement of Thermal Diffusivity of Molten Metals
Laser-produced Plasma Measurement of Thermal Diffusivity of Molten Metals

Author:

Publisher:

Published: 1995

Total Pages: 18

ISBN-13:

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We have shown that a laser-produced plasma plume which is representative in composition of the condensed phase target can be reproducibly generated if the movement of the surface due to evaporation is kept in pace with the thermal diffusion front propagating into the bulk. The resulting mass loss is then strongly controlled by the thermal diffusivity of the target matter, and this relationship has been exploited to measure the thermal diffusivity of metallic alloys. We have developed a novel RF levitator-heater as a contamination-free molten metal source to be used as a target for LPP plume generation. In order to determine the mass loss due to LPP excitation, a new high sensitivity transducer has been constructed for measurement of the resulting impulse imparted on the specimen. The impulse transducer is built onto the specimen holder within the levitation-assisted molten metal source. The LPP method has been fully excercised for measurement of the thermal diffusivity of a molten specimen relative to the value for its room temperature solid. The results for SS304 and SS316 are presented together with a critique of the results. A numerical modeling of specimen heating in the molten metal source and the physical basis of the new hod are also presented.

The Physics Of Laser Plasma Interactions
The Physics Of Laser Plasma Interactions

Author: William Kruer

Publisher: CRC Press

Published: 2019-08-20

Total Pages: 176

ISBN-13: 1000754464

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This book focuses on the physics of laser plasma interactions and presents a complementary and very useful numerical model of plasmas. It describes the linear theory of light wave propagation in plasmas, including linear mode conversion into plasma waves and collisional damping.

Frontiers in High Energy Density Physics
Frontiers in High Energy Density Physics

Author: National Research Council

Publisher: National Academies Press

Published: 2003-05-11

Total Pages: 177

ISBN-13: 030908637X

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Recent scientific and technical advances have made it possible to create matter in the laboratory under conditions relevant to astrophysical systems such as supernovae and black holes. These advances will also benefit inertial confinement fusion research and the nation's nuclear weapon's program. The report describes the major research facilities on which such high energy density conditions can be achieved and lists a number of key scientific questions about high energy density physics that can be addressed by this research. Several recommendations are presented that would facilitate the development of a comprehensive strategy for realizing these research opportunities.

Time-resolved Probing of Electron Thermal Conduction in Femtosecond-laser-pulse-produced Plasmas
Time-resolved Probing of Electron Thermal Conduction in Femtosecond-laser-pulse-produced Plasmas

Author:

Publisher:

Published: 1993

Total Pages: 6

ISBN-13:

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We present time-resolved measurements of reflectivity, transmissivity and frequency shifts of probe light interacting with the rear of a disk-like plasma produced by irradiation of a transparent solid target with 0.1ps FWHM laser pulses at peak intensity 5 x 10{sup l4}W/CM2. Experimental results show a large increase in reflection, revealing rapid formation of a steep gradient and overdense surface plasma layer during the first picosecond after irradiation. Frequency shifts due to a moving ionization created by thermal conduction into the solid target are recorded. Calculations using a nonlinear thermal heat wave model show good agreement with the measured frequency shifts, further confining the strong thermal transport effect.