Evolution of the rippled inner-interface-initiated ablative Rayleigh–Taylor instability in laser-ablating high-Z doped targets

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Abstract
In the direct drive inertial confinement fusion (ICF) scheme, a rippled interface between the ablator and the deuterium–tritium ice fuel can feed out and form perturbation seeds for the ablative Rayleigh–Taylor instability, with undesirable effects. However, the evolution of this instability remains insufficiently studied, and the effects of high-Z dopant on this instability remain unclear. In this paper, we develop a theoretical model to calculate the feedout seeds and describe this instability. Our theory suggests that the feedout seeds are determined by the ablation pressure and the adiabatic index, while the subsequent growth depends mainly on the ablation velocity. Two-dimensional radiation hydrodynamic simulations confirm our theory. It is shown that targets with high-Z dopant in the outer ablator exhibit more severe feedout seeds, because of their higher ionization compared with undoped targets. The X-ray pre-ablation in high-Z doped targets significantly suppresses subsequent growth, leading to suppression of short-wavelength perturbations. However, for long-wavelength perturbations, this suppression is weakened, resulting in increased instability in high-Z doped targets. The results are helpful for understanding the inner-interface-initiated instability and the influence of high-Z dopant on it, providing valuable insights for target design and instability control in ICF.
Funding Information
  • National Natural Science Foundation of China (12175309, 12475252, 12275356)
  • the Strategic Priority research program of Chinese academy of science (XDA25050200, XDA25010100)
  • the Defense Industrial Technology Development Program (JCKYS2023212807)
  • Natural Science Foundation of Hunan Province (2025JJ20007)
  • Postgraduate Scientific Research Innovation Project of Hunan Province, China (CX20230005)

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