Effect of core-corona plasma structure on seeding of instabilities in wire array Z pinches

We present the first measurements by x-ray radiography of the development of instabilities during the implosion phase of wire array Z pinches. The seeding of perturbations on the dense core of each wire is provided by nonuniform sweeping of the low-density coronal plasma from the cores by the global J x B force. The spatial scale of these perturbations (similar to 0.5 mm for Al and similar to 0.25 mm for W) is determined by the size of the wire cares (similar to 0.25 mm for Al and similar to 0.1 mm for W). A qualitative change in implosion dynamics. with transition to OD-like trajectory, was observed in Al arrays when the ratio of interwire pap to wire core size was decreased to similar to 3.