Anti-Langmuir decay instability in Langmuir decay instability cascade

Abstract

Backward stimulated Raman scattering (BSRS) with Langmuir decay instability (LDI) and anti-Langmuir decay instability (ALDI or anti-LDI) has been researched by Vlasov simulation. The decay productions of anti-LDI in LDI cascade and their evolution with time are demonstrated for the first time. The BSRS reflectivity will be decreased largely through LDI cascade and ALDI in the small wave-number region. Different mechanisms to saturate BSRS in CH (or H) and C plasmas have been demonstrated. The dominant saturation mechanism of BSRS in CH (or H) plasmas is LDI cascade and ALDI. However, in C plasmas, due to very weak Landau damping of ion acoustic waves, LDI cascade will promote stimulated Brillouin scattering (SBS) excitation, then SBS will compete with BSRS and saturate BSRS in the later stage. The proportion of the hot electrons is decreased largely through LDI cascade and ALDI. These results give an effective mechanism to suppress BSRS and hot electron generation in the small wave-number region, which are of important significance in the inertial confinement fusion.

Investigation of Langdon effect on the nonlinear evolution of SRS from the early-stage inflation to the late-stage development of secondary instabilities

“…3(c-d). In such cases, the reflectivity calculated by the Tang's formula (22) agrees well with the simulation results of the TWC model, as shown in Fig. 3(a-b).…”

“…As time evolves, Langmuir decay instability [20,22], where a primary Langmuir wave (LW) decays into a secondary Langmuir wave and an ion acoustic wave (IAW), begins to become important. LDI satisfies the matching condition…”

“…In the early growth stage of SRS, it is found that apart from the kinetic inflation due to trapped electrons [12][13][14], Langdon effect can broaden the parameter range for absolute SRS modes, and significantly shorten the saturation time for the absolute SRS in certain parameter region. Over a long timescale evolution with the development of secondary instabilities such as the decay of the electron plasma wave to beam acoustic modes (BAM) [15][16][17], rescattering of the primary scattered wave [18,19] and Langmuir decay instability (LDI) [20][21][22], the SRS typically demonstrates a change in dominant saturation mechanism accompanied by a change (usually drop) in the reflectivity. Under many circumstances, Langdon effect is found to be important to these secondary instabilities and thus to the nonlinear saturation mechanism and reflectivity of SRS in the late evolution stage.…”

Burst behavior due to the quasimode excited by stimulated Brillouin scattering in high-intensity laser–plasma interactions

“…We choose the high-temperature and high-density region as an example: the electron temperature and electron density are and , where is the critical density for the incident laser. The electron density is taken to be higher than – thus stimulated Raman scattering [26–28] and two-plasmon decay instability [29, 30] are excluded. We take C, , CH, and H plasmas as typical examples since they are common in ICF [1, 3] .…”

Influences of sinusoidal density modulation on stimulated Raman scattering in inhomogeneous plasmas

“…And we obtain a region of modulational wavelength and amplitude that density modulation can cause the absolute SRS. Secondly, we have carried out the Vlasov simulations [27][28][29] to study the influence of density modulation at linear and nonlinear stage. At linear stage, the Vlasov simu-lations show good agreement with three-wave equations analysis.…”