Investigation of vacuum insulator surface dielectric strength with nanosecond pulses

The maximum vacuum insulator surface dielectric strength determines the acceleration electric field gradient possible in a short pulse accelerator. Previous work has indicated that higher electric field strengths along the insulator-vacuum interface might be obtained as the pulse duration is decreased S. Sampayan et al. (1995). In this work, a 250 kV, single ns wide impulse source was applied to small diameter, segmented insulators samples in a vacuum to evaluate the multilayer surface dielectric strength of the sample construction. Resonances in the low inductance test geometry were used to obtain unipolar, pulsed electric fields in excess of 100 MV/m on the insulator surface. The sample construction, experimental arrangement and experimental results are presented for the initial data in this work. Modeling of the multilayer structure is discussed and methods of improving insulator surface dielectric strength in a vacuum are proposed.