Stimulated Raman scattering in a non-eigenmode regime

Stimulated Raman scattering (SRS) in plasma in a non-eigenmode regime is studied theoretically and numerically. Different from normal SRS with the eigen electrostatic mode excited, the non-eigenmode SRS is developed at plasma density $n_{e}>0.25n_{c}$ when the laser amplitude is larger than a certain threshold. To satisfy the phase-matching conditions of frequency and wavenumber, the excited electrostatic mode has a constant frequency around half of the incident light frequency $\unicode[STIX]{x1D714}_{0}/2$ , which is no longer the eigenmode of electron plasma wave $\unicode[STIX]{x1D714}_{pe}$ . Both the scattered light and the electrostatic wave are trapped in plasma with their group velocities being zero. Super-hot electrons are produced by the non-eigen electrostatic wave. Our theoretical model is validated by particle-in-cell simulations. The SRS driven in this non-eigenmode regime is an important laser energy loss mechanism in the laser plasma interactions as long as the laser intensity is higher than $10^{15}~\text{W}/\text{cm}^{2}$ .

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Stimulated Brillouin scattering enhanced by stimulated Raman process near the quarter-critical density

Plasma Physics and Controlled Fusion ◽

10.1088/1361-6587/ac3dec ◽

2021 ◽

Author(s):

Zhanjun Liu ◽

Qiang Wang ◽

Bin Li ◽

Jiwei Li ◽

Li-hua Cao ◽

...

Keyword(s):

Raman Scattering ◽

Stimulated Raman Scattering ◽

Brillouin Scattering ◽

Second Harmonic ◽

Scattered Light ◽

Incident Light ◽

Critical Density ◽

Stimulated Brillouin Scattering ◽

Stimulated Brillouin ◽

Stimulated Raman

Abstract Stimulated Raman scattering can occur near the quarter critical density in direct-drive fusions, and the frequency of Raman scattered light is about half of the incident light frequency. The second harmonic of the Raman scattered light can be produced due to the inhomogeneity density profile. It can serve as the seed of stimulated Brillouin scattering (SBS). When the second harmonic of stimulated Raman scattering light propagates against the incident light, some components will match to the frequency of backward SBS and SBS is induced. Thus SBS could be enhanced greatly.

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Raman scattering

Canadian Journal of Physics ◽

10.1139/p86-164 ◽

1986 ◽

Vol 64 (8) ◽

pp. 956-960 ◽

Cited By ~ 1

Author(s):

Albert Simon

Keyword(s):

Raman Scattering ◽

Alternative Explanation ◽

Stimulated Raman Scattering ◽

Scattered Light ◽

Hot Electrons ◽

Critical Surface ◽

Laser Produced Plasma ◽

Stimulated Raman

Observations of Raman scattered light from inhomogeneous laser-produced plasma have shown characteristics quite different from the simple predictions for the stimulated Raman scattering instability. An alternative explanation in terms of enhanced scattering, produced by bursts of hot electrons arising at the quarter-critical or critical surface, is described. Comparison is made between the predictions of this theory and four experiments.

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Investigation of stimulated Raman scattering using a short-pulse diffraction limited laser beam near the instability threshold

Laser and Particle Beams ◽

10.1017/s0263034609000251 ◽

2009 ◽

Vol 27 (1) ◽

pp. 185-190 ◽

Cited By ~ 26

Author(s):

J.L. Kline ◽

D.S. Montgomery ◽

C. Rousseaux ◽

S.D. Baton ◽

V. Tassin ◽

...

Keyword(s):

Raman Scattering ◽

Laser Plasma ◽

Stimulated Raman Scattering ◽

Short Pulse ◽

Electron Plasma ◽

Thomson Scattering ◽

Wave Number ◽

Particle In Cell ◽

Laser Facility ◽

Stimulated Raman

AbstractShort pulse laser plasma interaction experiments using diffraction limited beams provide an excellent platform to investigate the fundamental physics of stimulated Raman scattering. Detailed understanding of these laser plasma instabilities impacts the current inertial confinement fusion ignition designs and could potentially impact fast ignition when higher energy lasers are used with longer pulse durations (>1 kJ and >1 ps). Using short laser pulses, experiments can be modeled over the entire interaction time of the laser using particle-in-cell codes to validate our understanding quantitatively. Experiments have been conducted at the Trident laser facility and the Laboratoire pour l'Utilisation des Lasers Intenses (LULI) to investigate stimulated Raman scattering near the threshold of the instability using 527 nm and 1059 nm laser light, respectively, with 1.5–3.0 ps pulses. In both experiments, the interaction beam was focused into pre-ionized helium gas-jet plasma. Measurements of the reflectivity as a function of intensity and kλD were completed at the Trident laser facility, where k is the electron plasma wave number and λD is the plasma Debye length. At LULI, a 300 fs Thomson scattering probe is used to directly measure the density fluctuations of the driven electron plasma and ion acoustic waves. Work is currently underway comparing the results of the experiments with simulations using the VPIC particle-in-cell code. Details of the experimental results are presented in this manuscript.

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Stimulated Raman scattering in plasmas produced by short intense laser pulses

Laser and Particle Beams ◽

10.1017/s0263034600009666 ◽

1995 ◽

Vol 13 (4) ◽

pp. 525-537 ◽

Cited By ~ 1

Author(s):

H.C. Barr ◽

T.J.M. Boyd ◽

F.I. Gordon ◽

S.J. Berwick

Keyword(s):

Raman Scattering ◽

Growth Rates ◽

Stimulated Raman Scattering ◽

Mode Conversion ◽

Scattered Light ◽

Laser Pulses ◽

Laboratory Frame ◽

Intense Laser ◽

Strongly Coupled ◽

Stimulated Raman

Stimulated Raman scattering driven by intense subpicosecond laser drivers is analyzed, in particular, the effects of the pulse shape and relativity on the instability and its characteristic spectra. The analysis is carried out in the pulse group velocity frame (Lorentz transformed) where growth rates for backscattering are decreased relative to their values when analyzed in the laboratory frame, while forward-scattered growth rates have greatly enhanced values. A range of intensities and densities is considered, appropriate to recent experiments, which ranges from strongly coupled scattering at high densities (even for forwardscattering) to stimulated Compton scattering regimes for backscattering and relativistically trapped forwardscattering at low densities. The inhomogeneities in intensity and density cause mode conversion between waves inside and outside the pulse. This can be at a modest level, as for backscattering, or extreme as in the case of forwardscattering when the Raman scattered light can be trapped within the laser pulse. The consequent feedback between modes within the pulse allows solutions, absolutely growing in the pulse frame, to be found.

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Reducing reflectivity of stimulated Raman scattering by discretely changing phase of incident light in inertial fusion plasmas

Physica Scripta ◽

10.1088/1402-4896/ac3ef7 ◽

2021 ◽

Author(s):

Tian Yang ◽

Shutong Zhang ◽

yuanzhi Zhou ◽

Deji Liu ◽

Xueming Li ◽

...

Keyword(s):

Raman Scattering ◽

Inertial Confinement Fusion ◽

Stimulated Raman Scattering ◽

Brillouin Scattering ◽

Incident Light ◽

Inertial Confinement ◽

Fusion Plasmas ◽

Confinement Fusion ◽

Coupling Equations ◽

Stimulated Raman

Abstract A new method to reduce the stimulated Raman scattering (SRS) in inertial confinement fusion conditions is proposed by changing the incident light phase discretely. The proposal is first examined by three-wave coupling equations and then verified by Vlasov simulations. A remarkable decreasing in SRS reflectivity is observed when the period of phase changing is less than 2π/γ, where γ is the growth rate of SRS. By contrast, some simulations with continuously changing phase of incident light are carried out to compare their influence on SRS. In addition, the proposal may suppress the stimulated Brillouin scattering.

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