A Shack-Hartmann laser wavefront sensor for measuring electron density in low-current arc

A Shack-Hartmann type laser wavefront senor was developed for achieving electron density distributions over an arc channel in an extinguishing phase by only a single measurement with high temporal and spatial resolutions. The sensor was applied to pulsed arcs in 3-mm air gap between rod-to-rod tungsten electrodes with a diameter of 1mm. Electron densities in the arc discharges with currents of several tens of amperes were lower around the gap centre than near the anode and cathode. The behaviour of the electron densities was consistent with the intensity of emission light from arc discharges.