Optical measurements of electric field strength in nonuniform fields

Describes optical measurements of the field-strength map in a liquid dielectric using the Kerr effect. Since electric lines of force are curved in a nonuniform field, the field strength can be measured on a plane which divides the center axis of two sphere electrodes into two equal parts and is perpendicular to the axis. On this plane, all of the field directions are constant and the field direction is perpendicular to that of transmitted light. The sample liquid was nitrobenzene, which has a Kerr constant of 3.62×10^-12 (m/V²). The test cell was rectangular and was made of Teflon with two glass windows. An He-Ne laser was used as the light source. The intensity of the light transmitted through the cell was measured with a photodiode. The two-dimensional field strength was calculated by the ART (algebraic reconstruction technique) method. When a voltage pulse of 50 ms and 8 kV was applied to the electrodes, the maximum field strength was 2.9 kV/cm, while the theoretical value was 3.3 kV/cm