Abstract: The switch is usable for switching currents of 40 kiloamperes at 250 kilovolts to produce current pulses a few nanoseconds in duration at kilohertz rates. In a preferred embodiment, the switch includes three independently-triggerable spark gaps which are fired in a desired predetermined sequence; for example, cyclically. The three spark gaps are cooled by parallel streams of fluid, which is supplied to the switch under pressure. Because the firing rate of each individual spark gap is limited by the time required for the fluid to sweep the ions produced by firing out of the spark gap, a threefold increase in firing rate is achieved by the preferred embodiment. In another aspect of the invention, a high-performance low-induction coaxial spark gap switch employs a hollow trigger electrode which has a hole in its wall so that the fluid can flow along both its inner and outer surfaces to cool and clean them.