High-pressure gas switch for a wideband source

High-power ultrawideband pulses with equivalent center frequencies around 10 GHz require switching in a time scale of about a hundred picoseconds. We are developing a high-pressure gas switch that is designed to store a few joules of energy. Energy is stored in the transmission line upstream of the switch. The switch is a gap in a short transmission line of low impedance. The line is pulse charged to store the desired energy before the electric field across the gap collapses from the avalanche buildup of electrons. To ensure a relatively uniform voltage collapse across the width of the gap, initial electrons are produced by radiation from a bare spark. The switching repeatability is very good when the spark provides the initial electrons. Gap electric fields greater than 1 MV/cm were achieved for a 10-atm switch pressure in air with a voltage collapse less than 150 ps over 6 cm of switch length. The switch was tested with repetitive pulses up to 1 kHz. In a pulse charging mode, the collapse time of the gap will typically be 5 times less than the charging time. For applications where a switching time of tens of picoseconds is desired, a second switch would be required.