dorsal/arxiv
View SchemaKinetic Enhancement of Raman Backscatter, and Electron Acoustic Thomson Scatter
| Authors | David J. Strozzi, Ed A. Williams, A. Bruce Langdon, Abraham Bers |
|---|---|
| Categories | |
| ArXiv ID | physics/0610029 |
| URL | https://arxiv.org/abs/physics/0610029 |
| DOI | 10.1063/1.2431161 |
| Journal | Phys. Plasmas 14, 013104 (2007) |
Abstract
1-D Eulerian Vlasov-Maxwell simulations are presented which show kinetic enhancement of stimulated Raman backscatter (SRBS) due to electron trapping in regimes of heavy linear Landau damping. The conventional Raman Langmuir wave is transformed into a set of beam acoustic modes [L. Yin et al., Phys. Rev. E 73, 025401 (2006)]. For the first time, a low phase velocity electron acoustic wave (EAW) is seen developing from the self-consistent Raman physics. Backscatter of the pump laser off the EAW fluctuations is reported and referred to as electron acoustic Thomson scatter. This light is similar in wavelength to, although much lower in amplitude than, the reflected light between the pump and SRBS wavelengths observed in single hot spot experiments, and previously interpreted as stimulated electron acoustic scatter [D. S. Montgomery et al., Phys. Rev. Lett. 87, 155001 (2001)]. The EAW is strongest well below the phase-matched frequency for electron acoustic scatter, and therefore the EAW is not produced by it. The beating of different beam acoustic modes is proposed as the EAW excitation mechanism, and is called beam acoustic decay. Supporting evidence for this process, including bispectral analysis, is presented. The linear electrostatic modes, found by projecting the numerical distribution function onto a Gauss-Hermite basis, include beam acoustic modes (some of which are unstable even without parametric coupling to light waves) and a strongly-damped EAW similar to the observed one. This linear EAW results from non-Maxwellian features in the electron distribution, rather than nonlinearity due to electron trapping.
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"abstract": "1-D Eulerian Vlasov-Maxwell simulations are presented which show kinetic\nenhancement of stimulated Raman backscatter (SRBS) due to electron trapping in\nregimes of heavy linear Landau damping. The conventional Raman Langmuir wave is\ntransformed into a set of beam acoustic modes [L. Yin et al., Phys. Rev. E 73,\n025401 (2006)]. For the first time, a low phase velocity electron acoustic wave\n(EAW) is seen developing from the self-consistent Raman physics. Backscatter of\nthe pump laser off the EAW fluctuations is reported and referred to as electron\nacoustic Thomson scatter. This light is similar in wavelength to, although much\nlower in amplitude than, the reflected light between the pump and SRBS\nwavelengths observed in single hot spot experiments, and previously interpreted\nas stimulated electron acoustic scatter [D. S. Montgomery et al., Phys. Rev.\nLett. 87, 155001 (2001)]. The EAW is strongest well below the phase-matched\nfrequency for electron acoustic scatter, and therefore the EAW is not produced\nby it. The beating of different beam acoustic modes is proposed as the EAW\nexcitation mechanism, and is called beam acoustic decay. Supporting evidence\nfor this process, including bispectral analysis, is presented. The linear\nelectrostatic modes, found by projecting the numerical distribution function\nonto a Gauss-Hermite basis, include beam acoustic modes (some of which are\nunstable even without parametric coupling to light waves) and a strongly-damped\nEAW similar to the observed one. This linear EAW results from non-Maxwellian\nfeatures in the electron distribution, rather than nonlinearity due to electron\ntrapping.",
"arxiv_id": "physics/0610029",
"authors": [
"David J. Strozzi",
"Ed A. Williams",
"A. Bruce Langdon",
"Abraham Bers"
],
"categories": [
"physics.plasm-ph"
],
"doi": "10.1063/1.2431161",
"journal_ref": "Phys. Plasmas 14, 013104 (2007)",
"title": "Kinetic Enhancement of Raman Backscatter, and Electron Acoustic Thomson Scatter",
"url": "https://arxiv.org/abs/physics/0610029"
},
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