Energetics of a long-implosion-time, 12-cm-diameter argon-gas-puff Z pinch at 6.5 MA

We carry out an energy-inventory analysis for a 12-cm-diameter, argon gas-puff shot on the Saturn generator. From the measured pinch inductance time history, we infer the average radius of the pinch current, r ind , and the total work done on the pinch, E coupled , both as functions of time. The kinetic energy as a function of time, E KE , is inferred from r ind and the measured initial mass distribution, assuming all of the mass is accreted as in a snowplow. The results show that early in the implosion, E coupled ≈ E KE . However, when the pinch begins to radiate significantly, E KE begins to decrease while E coupled continues to increase. The increase in coupled energy goes into plasma internal energy, E int , i.e., ionization and thermal energies of the z-pinch plasma, and total radiation, E rad . During the time of K-shell emission, the significant (∼ 150-kJ) increase in E coupled is reflected in approximately the same increase in E rad . There is agreement between E int at the time of peak K-shell emission inferred from E coupled and measurements of E rad , and E int inferred from independent spectroscopic measurements combined with an atomic-physics model.