Insulator surface flashover with UV and plasma background and external magnetic field

Abstract

Surface flashover often sets the limit on the maximum voltage of a system in vacuum. UV irradiation and/or plasma will further decrease the flashover potential. This experiment investigates the UV and plasma induced dielectric surface flashover, emphasizes the early phase of breakdown, and uses external magnetic fields to increase the surface flashover potential. In our experimental apparatus, a dc voltage up to 60 kV or a voltage pulse (up to 100 kV with 200 ns duration) is applied to the test gap. The geometry of all interconnecting lines and of the discharge chamber is coaxial and the impedances are closely matched. The current, voltage, and soft X-rays are recorded. The plasma is generated by an electron cyclotron resonance plasma source and the UV radiation originates from a UV enhanced dc Xenon arc lamp. External magnetic fields influence the current in the pre-flashover phase. With a magnetic flux density of only 30 mT, the flashover potential of a UV induced breakdown increases by up to a factor of 4. With a plasma background, the duration of an applied voltage pulse can be increased by a factor of 2 without causing flashover.