Demonstrated transparent mode in nested wire arrays used for dynamic hohlraum z-pinches

Summary form only given. The mass of the outer and inner wire array used to drive the baseline dynamic hohlraum (DH) with pedestal target [Sanford, et al, Phys. Plasmas 13, 1 (2006)] is reversed in order to determine if the outer array is operating in a hydrodynamic- or transparent-like mode [Chittenden, et al, Phys. Plasmas 8, 675 (2001)] when the outer array impacts the inner. In contrast to the baseline, mass reversal allows the radiation measured to distinguish between the modes. For the reversed mass DH, all parameters such as wire number, array radii and target remained the same, except the diameters of the individual wires were adjusted to reverse the array mass. The measurements show unambiguously that the reversed-mass DH operates in a transparent-like mode, with the baseline consistent with transparency. Numerical simulations in the r-o plane suggest that the underlying physics of the outer array collision with the inner between the two DHs (baseline and reversed-mass) remains similar, implying that the baseline also operates with transparency. Inflection in the rate of change in the current-change is measured 4-7 ns after the radiation signal associated with the outer-inner array collision is detected, indicating that the rear portion of the resulting plasma shell of the outer array carries the current prior to the collision. Detailed analytical modeling of this current (as the outer array passes through the inner) together with numerical simulations describes probable dynamics of the current switching from outer to inner array