The effect of shell thickness on Rayleigh-Taylor mitigation in high velocity, annular z-pinch implosions

Abstract

Summary form only given, as follows. The magnetic implosion of thin annular shells is often accompanied by the Rayleigh-Taylor (RT) instability. At large diameters and high velocities characteristic of PBFA Z, this can lead to deformation of the plasma shell and poor performance. Many techniques have been suggested to decrease the RT growth in such cases. In particular, previous computational and experimental investigations of uniform fill loads have proven to be quite promising in mitigating RT development. However, such loads are known to be less efficient in coupling to the electrical energy of the machine. To capitalize on the stabilizing properties of uniform fill loads while maintaining the efficiencies observed with annular implosions, the transition between these two configurations has been numerically investigated. Using parameters indicative of PBFA Z, two dimensional magnetohydrodynamic simulations have been carried out for a range of shell thicknesses for both aluminum and tungsten loads. Simulations show that RT growth is reduced with increasing shell thickness while the peak implosion velocity appears to be strongly dependent on the severity of the RT instability. These factors combined provide a measure of optimal performance for a given application.