Assessing the Effects of Viscosity and Surface Roughness on the Magneto-Rayleigh-Taylor Instability in FLASH for Cylindrical Implosions

In the past decade, magnetized liner inertial fusion (MagLIF) has risen as a promising method of achieving fusion ignition and gain for power generation. Instabilities that form as the target cylindrical liner compresses – namely, the Magneto-Rayleigh-Taylor instability (MRTI) – can degrade the implosion, decreasing fusion yield. Recent work by Dai et al. [1] developed linear analytical growth rates that discuss the effects of viscosity in MRTI. In this work, we conduct extended analysis of the theoretical growth rates and show that the growth rate can be characterized by two parameters: the perturbation wavelength relative to liner radius kR_out and the ratio of gravitational versus viscous forces, i.e., the Galilei number Ga. We then assess the validity of the derived growth rates via the radiative magnetohydrodynamics code FLASH. MRTI is seeded via single-mode and multi-mode perturbations in the outer liner radii, i.e., surface roughness, at a liner-vacuum interface. We discuss trends that result from varying the viscosity coefficient and the surface roughness wavelength.

[1] J. L. Dai, Y. B. Sun, C. Wang, R. H. Zeng, L. Y. Zou; Linear analytical model for magneto-Rayleigh–Taylor and sausage instabilities in a cylindrical liner. Phys. Plasmas 1 February 2023; 30 (2): 022704. https://doi.org/10.1063/5.0130839