Plasma diagnostics for high power ignitron development

A description is given of plasma diagnostics performed on a demountable ignitron (DIG) which provides optical access to the discharge plasma through four viewports, two of which are on opposite sides on a common optical axis. The latter pair of viewports was used to perform plasma density studies using a Mach-Zehnder interferometer. Time-resolved recordings of the interference patterns, either visual or electronic, during changes in plasma behavior (such as current conduction or plasma heating) yield time-resolved information about the particle density. This technique was applied to the DIG during high-current discharges. The light source was a 2 W CW argon laser which was pulsed using a ferroelectric liquid crystal light valve. The resulting fringe patterns were recorded with a mechanical high-speed camera. All experimental details, results and a theoretical evaluation are given. In addition, high-speed framing photography was used to study the influence on electrode design and placement on the discharge plasma.>