Electron distribution anisotropy in laser-produced plasmas from x-ray line polarization measurements

Kieffer, J. C.; Matte, J. P.; Pépin, H.; Chaker, Mohamed; Beaudoin, Y.; Johnston, T. W.; Chien, C. Y.; Coe, S.; Mourou, G.; Dubau, J.

doi:10.1103/physrevlett.68.480

Cited by 143 publications

(60 citation statements)

References 20 publications

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“…In general, polarized radiation is emitted author's e-mail: yinubusi@ile.osaka-u.ac.jp due to the anisotropy of the electron velocity distribution or the surrounding electromagnetic field [11][12][13]. By utilizing this principle, the anisotropy of a hot electron VDF can be determined by observing the polarization degree P of a specific x ray [14,15]. In the case of a planar target irradiated by a high intensity laser beam of 10 16 -10 17 W/cm 2 , hot electrons are generated predominantly by resonance absorption and/or parametric processes so that hot electrons initially propagate parallel to the direction of the density gradient, that is, perpendicular to the target surface.…”

Section: Introductionmentioning

confidence: 99%

“…Some experiments of x-ray polarization spectroscopy have been performed [14,15,[17][18][19]. Although Heα line emissions from various He-like ions, such as Al [14,15], F [17] and Cl [18,19], have been measured, there are no reports on the relationship between the material emitting polarized x rays and plasma conditions. To use polarization spectroscopy as a diagnostic tool for the anisotropy of hot electron VDF, it is important to investigate this relationship.…”

Section: Introductionmentioning

confidence: 99%

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X-Ray Polarization Spectroscopy of Heα Line Emission for Diagnosis of the Anisotropy of Hot Electrons

Inubushi

Kai

Kawamura

et al. 2007

Plasma and Fusion Research

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X-ray polarization spectroscopy is proposed as an advanced diagnostic tool to measure the anisotropic velocity distribution of hot electrons generated by an ultra-high intensity laser pulse. The relationship between the anisotropy of the hot electron velocity distribution and the polarization degree was investigated for various tracer materials. It is shown that the polarization degrees of Heα lines are a function of electron energy normalized by the excitation threshold. Depolarization is caused by isotropic bulk electrons in high temperature plasma. To diagnose the anisotropy of the hot electron velocity distribution without depolarization, it is essential to select a tracer material whose energy of Heα line is 10 times higher than the bulk electron temperature.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

X-Ray Polarization Spectroscopy of Heα Line Emission for Diagnosis of the Anisotropy of Hot Electrons

Inubushi

Kai

Kawamura

et al. 2007

Plasma and Fusion Research

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“…This plasma polarization spectroscopy has been applied to laser-produced plasmas [3][4][5][6]. Previous studies dealt with high density and high temperature plasmas produced by high power lasers by means of emission lines in the X-ray and soft X-ray region.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the degree of polarization of the spectra from laser-produced Al plasma

Kim

2002

Applied Surface Science

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Using a polarization-resolved UV-visible spectrometer, the degree of polarization of the spectra from laser-produced Al plasma was measured. To generate the Al plasma, Q-switched Nd/glass laser was used. The pulse duration of the laser is 3 ns and the energy per pulse is 6 mJ. The degree of polarization of Al III 4s 2 S 1=2 -4p 2 P 0 3=2 transition was measured at different positions from a target surface using a space and polarization-resolved spectrometer. To resolve the different polarization components of the emission line, a dichroic polarizer was used in front of the entrance slit of the spectrometer. The degree of polarization was observed to be 2:1 AE 0:13% 220 mm from target surface and decreased as the distance from the target increased, vanishing about 1.3 mm from the target surface. To avoid the possible error due to the shot-to-shot variation of the line intensity, a calcite crystal was used to simultaneously observe the two polarization components. Both measurements yielded the same result. The plasma parameters, such as the electron temperature and density, were estimated by spectroscopic methods. The measured electron temperature was about 3 eV and the density was 2 Â 10 17 cm À3 near the target surface and decreased to 4 Â 10 16 cm À3 1.3 mm away from the target surface. #

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“…The polarization of light emitted by these excited atoms can then be used to extract information on the e.d.f. [108][109][110] Applications to laser plasmas 111 and to tokamak plasmas 112 have been limited thus far.…”

Section: Other Measurement Techniquesmentioning

confidence: 99%

Diagnostic techniques for measuring suprathermal electron dynamics in plasmas (invited)

Coda

2008

Review of Scientific Instruments

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Plasmas, both in the laboratory and in space, are often not in thermodynamic equilibrium, and the plasma electron distribution function is accordingly non-Maxwellian. Suprathermal electron tails can be generated by external drives, such as rf waves and electric fields, or internal ones, such as instabilities and magnetic reconnection. The variety and importance of the phenomena in which suprathermal electrons play a significant role explains an enduring interest in diagnostic techniques to investigate their properties and dynamics. X-ray bremsstrahlung emission has been studied in hot magnetized plasmas for well over two decades, flanked progressively by electron-cyclotron emission in geometries favoring the high-energy end of the distribution function ͑high-field-side, vertical, oblique emission͒, by electron-cyclotron absorption, by spectroscopic techniques, and at lower temperatures, by Langmuir probes and electrostatic analyzers. Continuous progress in detector technology and in measurement and analysis techniques, increasingly sophisticated layouts ͑multichannel and tomographic systems, imaging geometries͒, and highly controlled suprathermal generation methods ͑e.g., perturbative rf modulation͒ have all been brought to bear in recent years on an increasingly detailed, although far from complete, understanding of suprathermal electron dynamics.

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Electron distribution anisotropy in laser-produced plasmas from x-ray line polarization measurements

Cited by 143 publications

References 20 publications

X-Ray Polarization Spectroscopy of Heα Line Emission for Diagnosis of the Anisotropy of Hot Electrons

X-Ray Polarization Spectroscopy of Heα Line Emission for Diagnosis of the Anisotropy of Hot Electrons

Measurement of the degree of polarization of the spectra from laser-produced Al plasma

Diagnostic techniques for measuring suprathermal electron dynamics in plasmas (invited)

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