Multiple-gap back-lighted thyratrons for high power applications

Switching of high voltage and high current simultaneously with a fast current rate of rise by an optically triggered back-lighted thyratron is reported at very high pulsed power levels, including 100-kV stand-off voltage and >70-kA switched peak current. This switch is triggered by an unfocused ultraviolet light incident on the back of the cathode and is referred to as a back-of-the-cathode, light-activated thyratron (BLT). It has a simple structure that can be electrically isolated from the trigger circuit. The switch closure is a glow discharge rather than an arc; this dramatically reduces electrode degradation. The holdoff capability of one gap is limited by surface flashover and field emission. Experiments for improved holdoff voltage were conducted by scaling the BLT into multiple-gap switch configurations. The voltage of a multiple-gap chamber is divided among gaps, reducing the voltage across one gap. Hence the holdoff voltage is enhanced by additional stacks of intermediate electrode and insulator. Simultaneous optical triggering of each gap for precision timing, and plasma triggering, are also discussed. The results suggest that fairly simple multiple-gap configurations of the device are useful for applications such as multiple high-power modulator systems for accelerators