Available Technology

Ignitrons are high-current switches that can open and close very quickly by using vaporized-metal plasma arcs to complete a circuit. Mercury is typically used because it does not tend to plate out the internal surfaces of the ignitron structure and cause a short-circuit pathway, permanently closing the switch. Mercury is toxic, making the ignitrons difficult to manufacture, dispose of, and service. Gallium and its alloys have been considered as alternatives to mercury. Not only are they liquid at typical use temperatures like mercury, but they exhibit a lower vapor pressure to withstand even higher voltages. The key obstacle is that using gallium or its alloys in typical ignitron designs results in rapid plating of internal surfaces and premature failure of the switch. The NASA innovation overcomes this obstacle through the use of a novel internal structure of the ignitron that prevents plating of the liquid metal on inner surfaces. Ignitrons are capable of conducting high currents and withstanding high voltages, thus providing high, instantaneous power over a very short time. Such pulsed-power applications as pulsed lasers, pulsed fusion, and power rectification are important to NASA. Other defense, industrial, and commercial applications can benefit from this NASA innovation as well.