In-situ measurement of space-charge distribution in highly stressed samples

The Thermal Step Method (TSM) has been used recently to measure the space charge distribution in stressed insulating samples (i.e. under applied dc field or temperature). After poling the sample in order to establish the space charge, the high voltage (HV) source must be disconnected, and the TSM signal yields the space charge distribution within the sample provided its surface potential remains nearly constant during the measurement. Since it actually varies, the technique used to derive the space charge distribution from the TSM signal may yield inaccurate results. This problem should be solved by using the new improved technique described in this article.