Influence of density non-uniformity in gas puff Z-pinch behavior

Summary form only given. Non-uniformities in the density profiles of gases such as argon injected into a vacuum chamber have an important influence on the behavior of Z-pinch implosions. In the strongly accelerating fields of a multi-megampere pinch the Rayleigh-Taylor instability may be dominated by the wavelengths associated with the initial mass distribution until late in the pinch. Shorter wavelength excitations do emerge but not until the longer period waves have developed large amplitudes. This occurs because long wavelength non-uniformities at the outer edges of the pinch are reinforced by the variable, but predominantly long wavelength density gradients encountered by the snowplow. We have performed 2D MHD calculations of 300 ns argon gas puff pinches to quantify these assertions and found that the pinching behavior can be modified substantially by axial non-uniformity near the outer edges of the gas puff. If the non-uniformity occurs close to one of the planar electrodes a radial jet forms. We have examined the interaction of two shells to determine how the mass of the inner shell acts to mitigate the large amplitude instability in the outer shell when collision takes place.