Effects of Axial Magnetic Fields on Backward Raman Scattering in Inhomogeneous Plasmas

Laham, N. M.; Nasser, A. S. Al; Khateeb, Ahmed M.

doi:10.1088/0031-8949/57/2/018

Cited by 11 publications

(12 citation statements)

References 31 publications

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“…The expression for S 1,−3 can be obtained easily from Eq. (75) using the replacement rule 1 → 2, 2 → 1, 3 → −3, where the minus sign is interpreted using notations (21) and (22). Similarly, to obtain the expression for S 1,−2 , we can replace 1 → 3, 2 → 1, 3 → −2 in Eq.…”

Section: A Action Conservation Of On-shell Equationsmentioning

confidence: 99%

“…where the minus sign in front of the second term comes from notation Eq. (22). Taking time derivative of the displacement operator, ∂ t (Π sÂ ) is the velocity operator for species s, which is proportional to the current operator.…”

Section: Lagrangian Of Three-wave Interactionmentioning

confidence: 99%

“…The nonlinear current can be expressed in terms of a coupling tensor, which is combined with the dielectric tensor to give a nonlinear dispersion relation of the system. Using fluid models, parametric growth rates have been obtained for extraordinary wave pump [18][19][20], lower hybrid wave pump [21], as well as the right-and left-circularly polarized wave pumps [22]. To capture thermal effects, a simple treatment retains only thermal corrections to the dielectric tensor [23].…”

Section: Introductionmentioning

confidence: 99%

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Three-wave scattering in magnetized plasmas: From cold fluid to quantized Lagrangian

2017

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Large amplitude waves in magnetized plasmas, generated either by external pumps or internal instabilities, can scatter via three-wave interactions. While three-wave scattering is well known in collimated geometry, what happens when waves propagate at angles with one another in magnetized plasmas remains largely unknown, mainly due to the analytical difficulty of this problem. In this paper, we overcome this analytical difficulty and find a convenient formula for three-wave coupling coefficient in cold, uniform, magnetized, and collisionless plasmas in the most general geometry. This is achieved by systematically solving the fluid-Maxwell model to second order using a multiscale perturbative expansion. The general formula for the coupling coefficient becomes transparent when we reformulate it as the scattering matrix element of a quantized Lagrangian. Using the quantized Lagrangian, it is possible to bypass the perturbative solution and directly obtain the nonlinear coupling coefficient from the linear response of the plasma. To illustrate how to evaluate the cold coupling coefficient, we give a set of examples where the participating waves are either quasitransverse or quasilongitudinal. In these examples, we determine the angular dependence of three-wave scattering, and demonstrate that backscattering is not necessarily the strongest scattering channel in magnetized plasmas, in contrast to what happens in unmagnetized plasmas. Our approach gives a more complete picture, beyond the simple collimated geometry, of how injected waves can decay in magnetic confinement devices, as well as how lasers can be scattered in magnetized plasma targets.

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Section: A Action Conservation Of On-shell Equationsmentioning

confidence: 99%

Section: Lagrangian Of Three-wave Interactionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Three-wave scattering in magnetized plasmas: From cold fluid to quantized Lagrangian

2017

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“…This is not unexplored territory. For instance, prior work studied how an external axial B field affects Raman backscattering in a hot, inhomogeneous plasma 16 , and the decay of circularly polarised EM waves in cold, homogeneous plasma 17 . Recently, excellent theoretical work on a warm-fluid model for magnetized LPI has been done by Shi 18 .…”

Section: Introductionmentioning

confidence: 99%

Magnetized Laser-Plasma Interactions in High-Energy-Density Systems: Parallel Propagation

Los,

Strozzi

2021

Preprint

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We investigate parametric processes in magnetised plasmas, driven by a large-amplitude pump light wave. Our focus is on laser-plasma interactions relevant to high-energy-density (HED) systems, such as the National Ignition Facility and the Sandia MagLIF concept. We derive dispersion relations for three-wave interactions in a multi-species plasma using Maxwell's equations, the warm-fluid momentum equation and the continuity equation. The application of an external B field causes right and left polarised light waves to propagate with differing phase velocities. This leads to Faraday rotation of the polarisation, which can be significant in HED conditions. Raman and Brilllouin scattering have modified spectra due to the background B field, though this effect is usually small in systems of current practical interest. We identify a scattering process we call stimulated whistler scattering, where a light wave decays to an electromagnetic whistler wave (ω ω ce ) and a Langmuir wave. This only occurs in the presence of an external B field, which is required for the whistler wave to exist. We compute the scattered wavelengths for Raman, Brillouin, and whistler scattering.

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“…They concluded that the focusing nature of the UHW is highly dependent on the initial power of the laser beam, growth rate of the laser spike and the strength of the magnetic field. Laham et al (1998Laham et al ( , 2000 considered the decay of an extraordinary wave into two electrostatic waves at frequencies close to the upper hybrid frequency. They showed that the two plasmon decay growth rate decreases with increasing magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Resonant excitation of the upper hybrid wave by relativistic cross focusing of two laser beams

Purohit¹,

Chauhan

Sharma

2009

Laser Part. Beams

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This article presents the resonant excitation of the upper hybrid wave (UHW) by cross focusing of two high power laser beams in a collisionless hot magnetoplasma; taking into account the relativistic nonlinearity. The electric vectors of the two beams are polarized along uniform static magnetic field and the beams propagate perpendicular to the static magnetic field. The resonant excitation of the UHW occurs when the frequency difference (FD) of the two laser beams and difference of their propagation vector satisfy the dispersion relation corresponding to the UHW. It has been observed that the power associated with the excited UHW, which depends on the background electron concentration, magnetic field and the intensity of the two laser beams, becomes drastically modified with the distance of propagation. The effect of the excited UHW at the FD on the acceleration of electrons has also been discussed. The amplitude of the UHW, excited by two high power laser beams and the electron energy are also calculated. This study is relevant in heating of plasma near the upper hybrid frequency as well as electron acceleration. The results are presented for typical laser plasma parameters.

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Effects of Axial Magnetic Fields on Backward Raman Scattering in Inhomogeneous Plasmas

Cited by 11 publications

References 31 publications

Three-wave scattering in magnetized plasmas: From cold fluid to quantized Lagrangian

Three-wave scattering in magnetized plasmas: From cold fluid to quantized Lagrangian

Magnetized Laser-Plasma Interactions in High-Energy-Density Systems: Parallel Propagation

Resonant excitation of the upper hybrid wave by relativistic cross focusing of two laser beams

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