Depression of Insulator Charging in Vacuum by Partial Mechanical Processing

Abstract

This paper describes experimental results on surface charging of partially mechanically processed insulators in vacuum. The charging phenomena were observed when insulators were exposed to a ramped dc voltage, by using a capacitive probe embedded in the cathode. First, we examined a partially roughened cylindrical insulator. The height of the roughened surface measured from the cathode, was varied while keeping the total length of the insulator constant. Second, in the same way, we examined a cylindrical insulator having a truncated conical frustum or a chamfer at its cathode-side end. Based on these experiments we have proved that the partial mechanical processing is effective for suppressing insulator charging in vacuum.

Evaluation of a factor for calculating SEEA charge on insulator surface in vacuum

“…The estimated values of k can successfully be adopted for various insulator shapes such as conical frustums [5], hollow cylinders with and without a shield-ring [6] etc. For instance, Figure 8 shows the computation results of SEEA charge distributions, where a cylindrical insulator has smooth and rough surfaces.…”

Charging Characteristics of an Insulating Hollow Cylinder in Vacuum

“…We have been carrying out studies on charging characteristics on the surface of insulators excited by high voltages or high electric fields in vacuum (1) (2) . The charging of insulators in vacuum takes place via a process called Secondary Electron Emission Avalanche (SEEA) and is believed to trigger the flashover in vacuum (3) .…”