Comparison of electric field and charge density distributions using the Kerr electro-optic method with blade-plane and point-plane electrodes

The Kerr electro-optic field mapping technique has been used to study space charge effects in high voltage pulsed propylene carbonate (C₄H₆O₃) using aluminum blade-plane and point-plane electrode geometries. Measurements presented here were taken using a circular polariscope with aligned polarizers at slightly elevated room temperature (T∼27°C) with calculated space charge free peak electric field strengths of ∼210 kV/cm at the blade electrode tip and ∼240 kV/cm at the point electrode tip and for times ranging from 10 μs to 400 μs. The light intensity was recorded on Polaroid film for the blade- and point-plane electrodes and also with a CCD camera for the point-plane electrodes. A CCD camera was used for the point-plane electrodes to more accurately resolve the gray-scale light intensity distribution because of the short optical path length. These high voltage Kerr electro-optic measurements show significant space charge effects in propylene carbonate as the light intensity maxima and minima significantly differ from the calculated patterns from numerical solutions to Laplace´s equation under space-charge free conditions.