Improvements to Passively Switched CTIX Compact Toroid Accelerator

Recent changes in gas injection technique have enabled considerable improvements in plasma density, total mass, and energy conversion efficiency obtained in the CTIX compact-toroid (CT) experiment. A major remaining source of energy loss is magnetic energy stored in residual inductance of an external saturable inductor, used to delay application of CT acceleration voltage. Currently, over 50\% of accelerator capacitor energy is converted to inductive energy in this circuit, versus up to 25\% in plasma kinetic energy. Modifications to CTIX will reduce saturated circuit inductance to less than 40\% of its present value. Results of operation with reduced inductance will be presented, with a goal of increasing CT kinetic energy density, required for penetration of high-magnetic-field target plasmas.Accelerator-region gas puffing will be used to match plasma time of flight to relevant circuit time scales. Diagnostics will include interferometry, deflectometry, magnetic-field, and spectroscopic measurements. Plasma acceleration and mass accumulation will be compared with a one-dimensional plasma/gas/circuit model. Supported by U.S. DOE Grant DE-FG02-03ER54732.