Plasma density measurements in PBFA II opening switch configurations

Summary form only given. Several opening switch configurations have been tested on the PBFA II (Particle Beam Fusion Accelerator II). The plasma density has been measured in a separate vacuum chamber for three opening switch configurations. The measurements were made using a 140-GHz microwave interferometer with quadrature phase detection. Faraday cups were used as a common monitor to correlate the test chamber measurements and the PBFA II experiments. The three opening switch configurations utilize flashboard plasma sources, where plasma is generated by discharging a capacitor through an array of flashover gaps on a carbon-coated insulator. The three configurations differ by the flashboards used, the electrical circuit used to power the flashboard, and the geometrical arrangement. Estimates of plasma displacement by J×B forces, conduction current scaling, and opening mechanisms were obtained