Domination of the K-Radiation at a Z-Pinch Stagnation on Z by Numerous Tiny Spots and the Properties of the Spots Inferred by Experimental Determination of the K-Line Opacities

Detailed analysis of both the line-intensity ratios and line shapes of the K-lines of elements of different abundances (Fe, Cr, Ni, and Mn) emitted from the stagnation of a steel wire-array implosion on Z, were used to determine the line opacities. While the opacities at the early time of stagnation appear to be consistent with a nearly uniform hot-plasma cylinder on-axis surrounded by a colder annulus, the opacities during the peak K-emission strongly suggest that the main K-emission is due to small hot regions (spots) spread over the stagnating column. The spots are shown to be at least 4× denser than expected based on a uniform-cylinder emission (namely, n i > 3×10 20 cm -3 ), are of diameters of about 200 μ or less (where the smaller the spots the higher are the densities) , and are thousands in number. The total mass of the spots was determined to be 3–10 % of the load mass, and their total volume 3–15 % of the Ø 1.2-mm stagnation-column volume, both are less than the respective values for the earlier period of lower K power.