Dielectric breakdown patterns in thin layers of oils

Experimental dielectric breakdown patterns are generated in thin cells of oils. Both mineral oil and olive oil are used. The cell is 6 μm thick and consists of two glass plates with conductive coating on the inner surfaces. A dc voltage across the cell is either increased gradually to above the threshold or applied with a fixed value above the threshold. Different types of patterns due to chemical reactions occurring at the inner surfaces are left behind after the dielectric breakdown process takes place. These patterns consist of filaments with wiggling or winding, depending on the experimental conditions. Time variations of the voltage and current are recorded during and after the discharge process. Some of these patterns are compared with those generated by the active walker model. The physical processes behind these patterns are discussed.