Risks and mitigation of laser plasma instabilities in direct drive inertial confinement fusion

Direct-drive inertial confinement fusion offers high laser-target coupling efficiency and is a promising route toward fusion energy. However, when intense laser beams propagate through coronal plasma and overlap near the target, different types of laser-plasma instabilities can be excited. These processes lead to laser scattering and energy transfer, causing coupling loss, drive asymmetry and hot-electron preheating, thereby degrading target compression and fusion gain. This paper reviews recent experimental, theoretical and simulation studies of laser-plasma instabilities in direct drive. It summarizes the main risks, outlines multiscale numerical methods and experimental diagnostics; and discusses mitigation approaches such as material doping, beam smoothing, dynamic zooming, wavelength detuning, broadband lasers and higher-frequency lasers.