Effect of sheath curvature on Rayleigh-Taylor mitigation in high-velocity uniform-fill, Z-pinch implosions

Recent gas puff experiments on the 7-MA Saturn machine identified a curved surface at the plasma-vacuum interface during the run-in phase of the implosion. Incorporating this topology into a corresponding two-dimensional magnetohydrodynamic calculation revealed that this curvature plays a surprisingly dominant role in mitigating Rayleigh-Taylor (RT) growth prior to stagnation. Calculations with both Saturn and representative PBFA-Z parameters show that sheath curvature contributes to the reduction in RT growth by convecting the instability to the edges of the pinch faster than it can grow.