Controlling stimulated Raman scattering by two-color light in inertial confinement fusion

Abstract

A method is proposed to control the stimulated Raman scattering in the inertial confinement fusion by using auxiliary 2ω light to suppress the stimulated Raman scattering of the 3ω light. In this scheme, inverse bremsstrahlung absorption and parametric instabilities in the 2ω light increase the electron temperature and the plasma-density fluctuation, thus preventing the development of Raman scattering of the 3ω light. This scheme is successfully demonstrated by both one-dimensional kinetic simulations and two-dimensional radiative hydrodynamic simulations. The one-dimensional Vlasov results show that the time-averaged transmissivity of the 3ω light increases from 0.75 to 0.95 under certain conditions. Results obtained using the particle-in-cell method with Monte Carlo collisions show that the electron temperature is greatly increased with the increasing intensity of the 2ω light. The two-dimensional radiative hydrodynamic simulation results show that the electron temperature increases from 3.2 keV to 3.5 keV, and the time-averaged backscattering level decreases from 0.28 to 0.1 in the presence of the auxiliary 2ω light.

Interaction of parametric instabilities from 3ω and 2ω lasers in large-scale inhomogeneous plasmas

“…The 2ω light can increase the electron temperature by inverse bremsstrahlung absorption or electron-ion collision [65], which will promote the diffusion of plasmas ablated from the target. The increase in electron temperature will suppress the SRS of 3ω light due to the increase in LW Landau damping.…”

“…The ion temperature is T i = 1.3 keV and the slow IAW mode in CH plasmas will be excited and dominate in SBS [52,53]. There are two linearly polarized pump laser beams with the same polarization direction, including a 3ω pump laser with wavelength λ 3ω0 = 0.351 µm and a 2ω pump laser with wavelength λ 2ω0 = 3/2 * 0.351 µm = 0.527 µm [65]. The spatial scale is [0, L x ] discretized with N x = 1 × 10 5 spatial grid points and spatial step dx = 0.0202 µm, and the spatial length is L x = 2020 µm with 2 × 10 µm vacuum layers on the two sides of the plasma boundaries.…”

Suppression of stimulated Brillouin and Raman scatterings using an alternating frequency laser and transverse magnetic fields

“…[26] All these methods or combinations of them have been widely used to control the peak intensities of laser spatial speckles and hence to suppress instabilities in ICF, but they cannot reduce LPIs to a tolerable level. [27,28] Recently, some new theoretical schemes for suppressing LPIs by changing lasers have also been proposed, including various broadband technologies, [29][30][31][32] two-color incident light, [33][34][35] spike trains of uneven duration and delay (STUD), [36][37][38][39] rotating polarization, [40][41][42] alternating polarization, [43,44] the discretely changing phase, [45] etc. It can be seen that in order to reduce the development of LPIs, existing schemes focus on changing the laser frequency, amplitude, polarization direction and phase.…”

Investigation of stimulated Raman scattering in longitudinal magnetized plasma by theory and kinetic simulation

“…Therefore, many concerns have been paid to interpret the SRS mechanism and pursue methods to suppress the instability to a controllable stage [11][12][13]. One kind of feasible method is to construct special laser fields to alleviate the instability, such as a broadband pump [14], a polarization smoothed pump [15] and a rotated polarized pump [16,17], etc.…”