Thomson Scattering Techniques in Laser Produced Plasmas PDF Download
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Author: J. S. Ross
Publisher:
ISBN:
Category :
Languages : en
Pages : 19
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Book Description
Thomson scattering has been shown to be a valuable technique for measuring the plasma conditions in laser produced plasmas. Measurement techniques are discussed that use the ion-acoustic frequency measured from the collective Thomson-scattering spectrum to extract the electron temperature, ion temperature, plasma flow, and electron density in a laser produced plasma. In a recent study, they demonstrated a novel Thomson-scattering technique to measure the dispersion of ion-acoustic fluctuations that employing multiple color Thomson-scattering diagnostics. They obtained frequency-resolved Thomson-scattering spectra of the two separate thermal ion-acoustic fluctuations with significantly different wave vectors. This new technique allows a simultaneous time resolved local measurement of electron density and temperature. The plasma fluctuations are shown to become dispersive with increasing electron temperature. Furthermore, a Thomson-scattering technique to measure the electron temperature profile is presented where recent experiments have measured a large electron temperature gradient (Te = 1.4 keV to Te = 3.2 keV over 1.5-mm) along the axis of a 2-mm long hohlraum when heated asymmetrically.
Author: J. S. Ross
Publisher:
ISBN:
Category :
Languages : en
Pages : 19
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Book Description
Thomson scattering has been shown to be a valuable technique for measuring the plasma conditions in laser produced plasmas. Measurement techniques are discussed that use the ion-acoustic frequency measured from the collective Thomson-scattering spectrum to extract the electron temperature, ion temperature, plasma flow, and electron density in a laser produced plasma. In a recent study, they demonstrated a novel Thomson-scattering technique to measure the dispersion of ion-acoustic fluctuations that employing multiple color Thomson-scattering diagnostics. They obtained frequency-resolved Thomson-scattering spectra of the two separate thermal ion-acoustic fluctuations with significantly different wave vectors. This new technique allows a simultaneous time resolved local measurement of electron density and temperature. The plasma fluctuations are shown to become dispersive with increasing electron temperature. Furthermore, a Thomson-scattering technique to measure the electron temperature profile is presented where recent experiments have measured a large electron temperature gradient (Te = 1.4 keV to Te = 3.2 keV over 1.5-mm) along the axis of a 2-mm long hohlraum when heated asymmetrically.
Author: John Sheffield
Publisher: Academic Press
ISBN: 0080952038
Category : Science
Languages : en
Pages : 512
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Book Description
This work presents one of the most powerful methods of plasma diagnosis in exquisite detail, to guide researchers in the theory and measurement techniques of light scattering in plasmas. Light scattering in plasmas is essential in the research and development of fusion energy, environmental solutions, and electronics.Referred to as the "Bible" by researchers, the work encompasses fusion and industrial applications essential in plasma research. It is the only comprehensive resource specific to the plasma scattering technique. It provides a wide-range of experimental examples and discussion of their principles with worked examples to assist researchers in applying the theory. - Computing techniques for solving basic equations helps researchers compare data to the actual experiment - New material on advances on the experimental side, such as the application of high density plasmas of inertial fusion - Worked out examples of the scattering technique for easier comprehension of theory
Author: Edward Rolfe
Publisher:
ISBN:
Category :
Languages : en
Pages : 178
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Book Description
A plasma diagnostic technique is presented which utilizes the Thomson scattering of a laser beam from free electrons. By this means a measurement may be made of both electron concentration and temperature. An extensive analysis of background radiation (noise) is given, and of the photoionization effects of the laser beam. Details of a plasma source which continuously simulates conditions in a reentry plasma, of a giant pulse laser, and of detection apparatus are described. By taking advantage of the broad Doppler spectrum of the Thomson-scattered light, measurements of the spectral wings to the exclusion of the laser wavelength permits the elimination of background radiation to a substantial degree. The investigation is specialized to conditions encountered in reentry plasmas, but would be applicable to measurements in rocket exhausts and explosion generated plasmas. (Author).
Author: James Alan Hawreliak
Publisher:
ISBN:
Category : Heat equation
Languages : en
Pages : 394
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Book Description
Author: Robert James Henchen
Publisher:
ISBN:
Category :
Languages : en
Pages : 155
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Book Description
"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.
Author:
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Category :
Languages : en
Pages : 9
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Book Description
Thomson scattering has been developed at the Nova laser facility as a direct and accurate diagnostic to characterize inertial confinement fusion plasmas. Measurements from methane-filled, ignition relevant hohlraums apply the theory for two ion species plasmas, which has been tested in separate open geometry experiments, to obtain electron and ion temperatures. The experimental data provide a benchmark for two-dimensional hydrodynamic simulations using LASNEX, which is presently in use to predict he performance of future megajoule laser- driven hohlraums of the National Ignition Facility (NIF). The data are consistent with modeling using significantly inhibited heat transport at the peak of the drive. Furthermore, we find that stagnating plasma regions on the hohlraum axis are well described by the calculations. The result implies that stagnation in gas-filled hohlraums occurs too late to directly affect the capsule implosion in ignition experiments.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 12
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Book Description
Thomson scattering measurements of the electron temperature in laser- produced gold plasmas are presented. We irradiated a flat gold disk target with one laser beam of the Nova laser facility. A second laser beam probed the plasma at a distance of 500[mu]m with temporally resolved Thomson scattering. The electron temperature measurements are compared with hydrodynamic simulations using the code LASNEX for experiments applying smoothed and unsmoothed heater beams. In case of an unsmoothed heater beam the simulations predict temperatures which are about 40% higher than our measured data. Although the agreement is improved for a smoothed heater beam, discrepancies exist in the decay phase of the plasma. We discuss possible explanations for these observations.
Author: Andrew S. Davies
Publisher:
ISBN:
Category :
Languages : en
Pages : 197
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Book Description
"Ultrafast electron plasma wave dynamics, Thermodynamics, and collisions are fundamental processes in laser-plasma physics that is not well understood. Historically, models have used simple approximations to describe the Thermodynamics in laser-plasma devices or artificially assumed constant plasma conditions. This thesis studies the picosecond ionization and Thermodynamics in laser-produced underdense plasmas using a novel Thomson scattering technique. The unprecedented temporal resolution of the Thomson spectra provided a measurement of collisional electron plasma waves that were modeled to extract the picosecond evolution of the electron temperature and density. This revealed a transition in the plasma-wave dynamics from an initially cold, collisional state to a quasi-stationary, collisionless state. The Thomson-scattering spectra were compared with theoretical calculations of the fluctuation spectrum using either a conventional Bhatnagar Gross Krook (BGK) collision operator or the rigorous Landau collision terms: the BGK model overestimates the electron temperature by 50% in the most-collisional conditions. These picosecond electron temperature and density measurements can be applied to laser-plasma devices that require knowledge of the rapidly evolving plasma conditions, such as a Raman plasma amplifier. These results indicate that the rapidly evolving conditions would result in a strong detuning that would limit the performance of laser-plasma amplifiers"--Page xii.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 55
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Book Description
A Comprehensive theory is developed to describe the nonlinear Thomson scattering of intense laser fields from beams and plasmas. This theory is valid for linearly or circularly polarized incident laser fields of arbitrary intensities and for electrons of arbitrary energies. Explicit expressions for the intensity distributions of the scattered radiation are calculated and numerically evaluated. The space-charge electrostatic potential, which is important in high density plasmas and prevents the axial drift of electrons, is included self-consistently. Various properties of the scattered radiation are examined, including the linewidth, angular distribution, and the behavior of the radiation spectra at ultrahigh intensities. Non-ideal effects, such as electron energy spread and beam emittance, are discussed. A laser synchrotron source (LSS), based on nonlinear Thomson scattering, may provide a practical method for generating tunable, near monochromatic, well collimated, short pulse x-rays in a compact, relatively inexpensive source. Two examples of possible LSS configurations are presented: an electron beam LSS generating hard (30 keV, 0.4 A) x-rays and a plasma LSS generating soft (0.3 keV, 40 A) x-rays. These LSS configurations are capable of generating ultrashort (approx. 1 ps) x-ray pulses with high peak flux (> 10(21) photons/s) and brightness (> 10(19) photons/s-mm2- mrad (2) 0.1% BW). Synchrotron radiation, Thomson scattering, Laser-plasma interactions.
Author: National Research Council
Publisher: National Academies Press
ISBN: 030908637X
Category : Science
Languages : en
Pages : 177
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Book Description
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.
