A new triggered vacuum gap

Abstract

The triggered vacuum gap is a new metal-vapor arc device in which a vacuum gap is broken down by the injection of minute quantities of ionized hydrogen. A glow discharge is first produced which is rapidly transformed into a metal-vapor arc causing the gap to break down in less than one-tenth microsecond. The small quantities of hydrogen released are eventually recovered by a titanium hydride getter. Release of gas from the electrodes during arcing is avoided by the use of zone-refined electrode materials. Properties of the metal-vapor are described which have an effect on the characteristics of the vacuum gap. The ability of a vacuum gap to hold off high voltage and then recover its dielectric strength rapidly after arcing has made it attractive as an overvoltage protection device and as a current switch for crowbar applications. A number of practical sealed-off triggered vacuum gaps are described. These are used to carry capacitor discharge currents of a few microseconds and 60-cycle power line currents for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\frac{1}{2}</tex> cycle. The advantages of vacuum gaps over gas-filled gaps are given and a number of overvoltage protection and switching applications are listed.