Pockels-Effect Based Diagnostic for Live Surface Charging Studies: Principles, Practice and Challenges

In high tech equipment involving high voltages, such as switchgear, surface charging of solid dielectrics can significantly affect the performance. A Pockels-effect based technique is proposed as a promising diagnostic for its capability to create a 2D surface charge map in real time. However, a characterization and comparison of the performance of the most commonly used Pockels setup configurations is missing in existing literature, which makes it difficult to choose the best configuration for a specific task. To overcome this limitation, current knowledge on the diagnostic is extended by simulations, mimicking the Pockels setup. The transfer function between the measurable quantities and the electric field in a sample is derived by Mueller calculus. Finally, experiments are performed to test its correctness. A homogenous electric field is applied on an electro-optic material (Bismuth Silicon Oxide) using transparent electrodes (Indium Tin Oxide). A pre-compensated transmissive Pockels setup has been found to have a less extensive measurement scheme and larger robustness against errors in the setup than a post-compensated transmissive setup. A reflective setup offers a factor two higher sensitivity and allows a non-transparent surface on the sample. However, it has a higher sensitivity to errors and a smaller measurement range than the transmissive setups. With these results, the Pockels-effect based diagnostic becomes more accessible to future users, as it is faster to implement, and the interpretation of results is improved.