Energetics of Triple-Nozzle Gas-Puff Z Pinches on the 1-MA COBRA Generator

Gas-puff z-pinches (GPZPs) are efficient sources of intense x-rays or neutrons and are of general interest for magneto-inertial fusion studies. Here we present preliminary results of an energy-inventory analysis for triple-nozzle GPZPs on the 1-MA, 220-ns rise time COBRA generator at Cornell university for both axially magnetized and unmagnetized implosions. The total energy coupled to the plasma is inferred from current and voltage traces while spatially resolved plasma parameters such as flow velocity, temperature, and density are measured at different times across highly repeatable implosions using Thomson scattering and laser interferometry. This enables a calculation of kinetic and internal energies. Directed kinetic energy is also estimated from the radial implosion trajectory and initial mass distribution, assuming the mass is accreted as in a snowplow. Radiated energy is measured using calibrated photoconducting detectors (PCDs) and a bolometer. By including a means of discriminating between thermal and non-thermal broadening of the Thomson scattering spectra, we demonstrate that some energy resides in non-directed turbulence which mediates dissipation in the collisionless shock. Evidence of shock reflected ions in the Thomson scattering signal is also presented.