Pockels surface potential probe and surface charge density measurement

Abstract

A surface potential probe based on Pockels sensing technique is developed and applied to surface potential distribution measurement on insulating material. The probe consists of a super luminescent diode, a Pockels crystal, a polarized beam splitter, a 1 8 wave plate and optical fibers. As the detecting part of the probe is isolated from a grounded electrode, this probe can be placed closer to the measured object. The resolving power is 2 mm which is equivalent to the twice size of the detecting part. The modulation technique is introduced to this probe and the minimum sensitivity reaches 10 V . This probe is applied to the measurement of the potential distribution on an insulating material just after occurrence of a surface discharge. From this measured potential profile, the distribution of surface charge density is computed through a surface charge method.