The laser direct-drive inertial confinement fusion (ICF) is one of the most promising routes to realize the high-gain fusion energy. However, laser imprints, arising from beam asymmetries and speckle structures, seed Rayleigh–Taylor instability (RTI) and severely limits its performance. In this work, we propose a novel approach to mitigate RTI by providing a pre-plasma with a hundred-micrometer-scale length prior to the main pulse reach the target surface. This configuration leverages nonlocal electron thermal transport to smooth laser-induced density perturbations. Using the radiation-hydrodynamic code FLASH coupled with the self-consistent Schurtz–Nicolai–Busquet (SNB) nonlocal transport model, we quantitatively investigate the influence of pre-plasma scale length on electron heat transport process and ablative RTI growth. Results show that increasing the pre-plasma scale length significantly extends the longitudinal conduction region and, more importantly, enables nonlocal thermal transport effects to smooth the instability seeds caused by laser imprinst, thereby effectively suppressing RTI growth. We further reveal a scaling relation between pre-plasma scale length and RTI mitigation, demonstrating that optimizing this parameter markedly improves implosion symmetry. This work provides a new design pathway for ICF targets and offers critical guidance for enhancing fusion gain.
 

Laser imprint,Rayleigh-Taylor Instability,Preplasma,Electron thermal transport