Computation methods for one-dimensional bipolar charge injection

Kerr electrooptic field-mapping measurements have shown strong space charge effects in high-voltage stressed dielectrics, where the magnitude and sign of injected charge depends on electrode material. With appropriate choice of electrode material combinations and voltage polarity is possible to have uncharged, unipolar positively or negatively charged, or bipolar charged dielectrics. The bipolar homocharge case lowers the electric field at both electrodes due to space-charge shielding, and thus allows a higher voltage without breakdown. Using charge-transport analysis the authors consider the general case of charge injection from both electrodes and solve time and space dependences of the electric field and charge distributions and the time dependences of the terminal voltage and current. This analysis extends earlier work by including nonequilibrium charge dissociation and recombination so that the effective ohmic conductivity is not constant but varies with time and position due to local net charge density. Specific cases discussed are the open-circuit voltage decay of an initially charged capacitor, the charging and discharging by a Marx generator, and alternating voltage excitations