RESULTS OF RADIUS SCALING EXPERIMENTS AND ANALYSIS OF NEON K-SHELL RADIATION DATA FROM AN INDUCTIVELY DRIVEN Z-PINCH

The K-shell radiated energy (yield) from neon Z-pinch implosions with annular, gas-puff nozzle radii of 1, 1.75, and 2.5 cm was measured for implosion times from 50 to 300 ns while systematically keeping the im plosion kinetic energy nearly constant. The implosions were driven by the Hawk inductive-storage generator at the 0.65-MA level. Initial neu tral-neon density distributions from the nozzles were determined with laser interferometry. Measured yields are compared with predictions fr om zero-dimensional (0-D) scaling models of ideal, one-dimensional (1- D) pinch behavior to both benchmark the scaling models, and to determi ne their utility for predicting K-shell yields for argon implosions of 200 to >300 ns driven by corresponding currents of 4 to 9 MA, such as envisioned for the DECADE QUAD. For all three nozzles, the 0-D models correctly predict the Z-pinch mass for maximum yield. For the 1- and 1.75-cm radius nozzles, the scaling models accurately match the measur ed yields if the ratio of initial to final radius (compression ratio) is assumed to be 8:1, For the 2.5-cm radius nozzle, the measured yield s are only one-third of the predictions. Analysis of K-shell spectral measurements suggest that as much as 70% (50%) of the imploded mass is radiating in the K-shell for the 1-cm (1.75-cm) radius nozzle, That f raction is only 10% for the 2.5-cm radius nozzle, The 0-D scaling mode ls are useful for predicting 1-D-like K-shell radiation yields (better than a factor-of-two accuracy) when a nominal (approximate to 10:1) c ompression ratio is assumed. However, the compression ratio assumed in the models is only an ''effective'' quantity, so that further interpr etations based on the 0-D analysis require additional justification. T he lower-than-predicted yield for the 2.5-cm radius nozzle is associat ed with larger radius and not with longer implosion time, and is proba bly a result of two-dimensional effects.