The installation to study the prebreakdown stage of a gas discharge by laser probing

Abstract

An installation to study a pulsed gas discharge in a diode with a single metal tip by laser probing has been devised. The installation represents a generator comprised of cable sections connected to a five-channel laser-triggered switch. The synchronization of the probing laser beam with the voltage pulse is not worse than ~1 ns. The moment of probing is determined by the optical delay and can be varied independently within the range of 10–20 ns by changing the charging voltage of the cables. The pressure in the discharge chamber can be varied from 10^–5 Torr to atmospheric pressure. Copper or molybdenum wires with a diameter of 10 μm or greater were used as cathode pins. Three independent optical record channels with time delays of 2 and 13 ns relative to the first channel allow one to simultaneously obtain interferograms and shadow and schlieren images of the discharge gap with spatial and time resolutions of 20 μm and 70 ps, respectively, with the exposure time of each frame being equal to a laser pulse duration of 70 ps. Using the devised installation, qualitative and quantitative data on the prebreakdown processes that occur in a tip-type diode have been obtained within a wide range of pressures.