Spark-Gap Switches

Gas-filled spark gaps satisfy a range of plasma-closure switching requirements involving capacitive discharge circuits. Series SG switches manufactured by R. E. Beverly III and Associates are designed for use in low-inductance (e.g., strip-line), fast-pulse systems where large peak currents (10~1000 kA) and high voltages (5~200 kV) are commuted. Although nominally designed for single-pulse operation, repetition rates in excess of 100 Hz are possible for decreased charge-transfer rates. Modular construction allows different configurations to be rapidly assembled from off-the-shelf components. Three basic switch types are available: (i) passive, (ii) electrically triggered, and (iii) laser triggered. Passive switches have only two electrodes and operate spontaneously when the applied voltage exceeds the self-breakdown voltage. Electrically triggered switches employ three electrodes and require an external trigger generator to initiate breakdown; three configurations are available: trigatron, field distortion, and railgap (under development). Trigatron switches are the simplest design to install and offer the lowest cost. For those applications that demand a compact design with low jitter, the field-distortion switch is the optimum choice. Railgaps offer the features of a field-distortion switch with the capability for very large charge transfer and exceptionally low inductance. Laser triggered switches consist of two electrodes and a lens that focuses laser radiation onto an on-axis, mid-plane point between these electrodes; the laser-generated spark initiates breakdown. This trigger method offers the fastest turn-on and lowest jitter of all of our switches.

For all switch models, the breakdown characteristics are determined by the gas type, internal pressure, and electrode geometry. The operating voltage is therefore adjustable over a wide range by adjusting the internal pressure and/or by changing the gas mixture. Gas must flow through the switch to purge discharge by-products. An external, pressurized gas supply is therefore required. The nominal operating voltage range given below was obtained with ultra-zero air ("synthetic air"). Other gases/gas mixtures allow substantially lower or higher voltage ranges. We do not manufacture hermetically sealed or vacuum switches. Excelitas (formerly Perkin-Elmer, EG&G) ceased manufacture of this type of switch. Please contact us for possible substitutes.