Comparison of point-to-plane corona in different gases

The point-to-plane DC corona discharges at atmosphere pressure have been investigated experimentally in different gases including argon, helium, N-2, O-2 and air in a needle-to-plate configuration. The breakdown voltage (the onset voltage of corona and the inception voltage to spark), current-voltage characteristics and the corona images have been measured in the gases under positive and negative polarity. Generally, the breakdown voltage of the positive corona is higher than the negative in the gases except O-2 in which the results is reversed. The current of the negative corona discharge is much higher than the positive in all gases. There exists a stable negative corona glow in the gases except air or O-2 before the spark occurs, while the pulsed positive corona will transit into the spark directly when the voltage increases, without the stable glow stage.