Competition of stimulated Raman scattering modes in multibeam configuration

In this work, we investigate the competition among collective modes and single-beam side scatter (SSRS) of stimulated Raman scattering (SRS) in multibeam configuration, utilizing theoretical analysis and particle simulations. The shared common electrostatic (SCE) wave is excited, when the crossing angle is smaller than a critical angle. Besides the SCE mode, two electrostatic submodes are developed, which results in a higher growth rate of SCE than the other collective and single-beam SRS modes. The SCE excites an overall intense electrostatic field, which produces a large number of hot electrons compared to SSRS. The SCE mode remains dominant with damping considered. Compared to plane waves, the beams with speckle can enhance the SCE, thus increasing hot-electron generation. In contrast to SSRS, the wavelength of SCE scattered light increases with the exit angle and is concentrated in a small exit angle range. The collective SCE mode is significantly mitigated by two incident beams with a 0.5% frequency difference, and then single-beam SRS dominates, which leads to the suppression of hot-electron generation. When the crossing angle is larger than the critical angle, SSRS is the dominant mode under direct-drive conditions. The shared common scattered light is significantly developed in the kinetic regime of quasi-homogeneous plasmas with density scale length above 1800λ_{0}, where λ_{0} is the wavelength of the incident laser. Additionally, at a high laser intensity or a large crossing angle, SSRS is the dominant mode.