Measurement of the corona space charge in a wind tunnel: Influence of the surface charge on the dielectric walls

In a wind tunnel is simulated the effect of the corona space charge on the corona current generated in a needle under thunderstorm-like electric field conditions. The natural cloud-to-ground electric field was simulated under wind conditions. The wind tunnel was built in acrylic. Preliminary measurements have shown that the acrylic walls could affect the corona current measurements. To test the possible influence of surface charge deposits on the chamber walls, different materials were tested: acrylic, wood and glass. Results show that corona current measurements are hardly influence by surface charge deposits on the wind tunnel acrylic walls, in a polarity dependent phenomenon.