研究目的
Investigating the interaction of parametric instabilities from 3ω and 2ω lasers in large-scale inhomogeneous plasmas and proposing a method to control the total reflectivity of SBS and SRS in inertial confinement fusion by adding 2ω light into 3ω light.
研究成果
The interaction of parametric instabilities from 2ω laser and 3ω laser in inhomogeneous plasmas has been researched. The mechanism of energy transfer from 3ω pump light to SBS of 2ω pump light has been proposed to explain the enhanced SBS of 2ω pump light and decreased SBS of 3ω pump light when 3ω and 2ω pump lights coexist. The total reflectivity will firstly decrease and then increase with increase of the ratio of 2ω pump light intensity to the total light intensity f, and will be controlled in a lower level at f ～ 10% ? 20%. These results give an effective method to control the total reflectivity of parametric instabilities by adding 2ω light into 3ω light.
研究不足
The simulations are one-dimensional in space, the side-scattering of SRS or SBS may be absolutely unstable especially for the 90° side-scattering, which may compete with backward-scattering of SRS or SBS. The study does not account for the effects of side-scattering in real ICF experiments where Gaussian speckle with small FWHM is used.
1：Experimental Design and Method Selection:
The study uses particle-in-cell (PIC) simulations to research the interaction of SBS and SRS from 2ω and 3ω pump lights in inhomogeneous plasmas. The theoretical analyses of key feature parameters such as frequencies, thresholds, growth rates, gains of SBS and SRS from 3ω and 2ω pump lights in inhomogeneous plasmas are given.
2：Sample Selection and Data Sources:
The plasma density is inhomogeneous with a constant electron density gradient, ne(x) = ne0(1 + x/Ln) = 0.04 + 0.03x, where ne is normalized to the critical density of 3ω pump light nc, and x to mm. The initial condition of electron density and ion species is shown in Fig.
3：04 + 03x, where ne is normalized to the critical density of 3ω pump light nc, and x to mm. The initial condition of electron density and ion species is shown in Fig. List of Experimental Equipment and Materials:
1.
3. List of Experimental Equipment and Materials: A one-dimensional (1D) particle-in-cell (PIC) code EPOCH is used. The electron temperature is Te = 3.5keV and electron density is ne[nc] = 0.04 + 0.03x[mm], where nc is the critical density for the 3ω pump light.
4：5keV and electron density is ne[nc] = 04 + 03x[mm], where nc is the critical density for the 3ω pump light.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The spatial scale is [0, Lx] discretized with Nx = 1 × 105 spatial grid points and spatial step dx = 0.0202μm. The total simulation time is tend = 1.5 × 104T0 = 17.55ps discretized with time step dt = 0.0547T0, where T0 = 1.17f s is the period of 3ω pump light.
5：0202μm. The total simulation time is tend = 5 × 104T0 = 55ps discretized with time step dt = 0547T0, where T0 = 17f s is the period of 3ω pump light.
Data Analysis Methods:
5. Data Analysis Methods: The frequency spectra and reflectivities of SBS and SRS from 3ω and 2ω pump lights are analyzed. The gains in Fig. 4 and Fig. 5 demonstrate the Rosenbluth convective gains in the linear stage, which can determine the saturation level of instabilities in the earlier linear stage.
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