Development of a Faraday Rotation Diagnostic at 1-MA and Diagnosis of Magnetic Field Distribution in Gas-Puff Z-Pinch Implosions

Gas-puff Z-pinch implosions are magnetically driven implosions of an annular plasma sheath that starts from a cylindrically symmetric gas puff and is compressed onto axis. The distribution of current in this imploding plasma sheath is currently under study. Progress in development of a Faraday Rotation magnetic field diagnostic and measurements of the magnetic field distribution, and thus the current distribution, in the imploding plasma are presented and discussed. The gas-puff Z-pinches are generated on the 1-MA COBRA generator at Cornell University [J. B. Greenly et al., Rev. Sci. Instrum. 79, 073501 (2008)] using a triaxial gas puff nozzle, in which plasmas produced from outer and inner annular nozzles collapse onto a central gas jet, compressing it. The plasmas are generated with current rise times varying from 100-200ns using carbon dioxide and argon gas. The Faraday Rotation measurements are combined with gated visible-UV light self-emission images, XUV (extreme ultraviolet) quadrant camera images, and interferometry measurements to diagnose the implosion dynamics and the electron density. The data presented show the magnetic-field distribution in the plasma with higher spatial resolution and better contrast than previously fielded on the COBRA generator.