Effect of Electrode Geometry on the Positive Impulse Breakdown in Carbon Dioxide

Positive impulse (1.2/50 μs) breakdown voltage measurements were carried out in carbon dioxide (CO2) under different electric field conditions by varying the sphere diameter in sphere-plane geometry. CO2 gas pressures up to 1 MPa were used, with the gap distances varying between 5 and 20 mm. It was observed that there exists a "critical field" (corresponding to the sphere diameter of 20 mm) at which the breakdown voltage is a maximum over the entire range of pressures investigated. This phenomenon is similar to the corona stabilization effect and could be due to presence of negative ion space charge.