The effect of load thickness on the performance of high velocity, annular Z-pinch implosions

Abstract

Numerical calculations have been performed to investigate the role that load thickness may play in the performance of fast annular Z-pinch implosions. In particular, the effects of load thickness on the mitigation of the magnetically-driven Rayleigh–Taylor (RT) instability and energy coupling between the plasma load and generator are addressed. Using parameters representative of the Z accelerator [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] at Sandia National Laboratories, two-dimensional magnetohydrodynamic simulations show that increased load thickness results in lower amplitude, slightly longer wavelength RT modes. In addition, there appears to be an optimum in implosion velocity which is directly associated with the thickness of the sheath and subsequent RT growth. Thin, annular loads, which should couple efficiently to the accelerator, show a large reduction in implosion velocity due to extreme RT development and increased load inductance. As a consequence, thicker loads on the order of 5 mm, couple almost as efficiently to the generator since the RT growth is reduced. This suggests that Z-pinch loads can be tailored for different applications, depending on the need for uniformity or high powers.