Azimuthal structure and global instability in the implosion phase of wire array Z-pinch experiments

The implosion of aluminum wire array z pinches driven by a 1.4 MA, 240 ns current pulse is studied. Plasma evolution is measured in the r-theta plane for the first time by an end-on laser interferometer. Merging of coronal plasmas with density of 10(17) cm(-3) occurs in 90-65 ns for 16 mm diam arrays with 8-64 wires. Early uncorrelated instabilities (wavelength lambda similar to 0.5 mm) are observed in individual wires with later development of a global m = 0 instability (lambda similar to 2 mm). The number of Rayleigh-Taylor instability e foldings is 5.6-7 when the m = 0 instability reaches an observable level and increases with the number of wires.