Nanosecond pulse surface discharge on insulator of plasma focus device

The performance of a plasma focus device can be influenced by its initial breakdown taking place on the surface of its insulator. A nanosecond square voltage pulse generator was used to study the discharge process on the surface of the insulator. Photos with a time resolution of 5-10 ns have been obtained. The discharge begins and grows on and along the surface of the insulator from the flange of the outer electrode, and its velocity depends on the amplitude, width, and polarity of the applied pulse voltage, as well as the gas pressure. For the pressure range of 5-200 torr, amplitude range of 6-15 kV, and pulse duration of 5-80 ns, the velocity lies in the range of 10⁷-2×20⁹ cm/s. It is observed that the discharge sheath does not turn into a plasma sheath with low resistance after a luminous sheath of initial discharge bridges both electrode