Laser-induced breakdown characteristics of nonuniform dc corona discharge fields

Abstract

Laser-induced breakdown of nonuniform field gaps in atmospheric air was caused by an XeCl excimer laser. This laser beam was focused on the center of a rod-to-plane, needle-toplane or hemisphere-to-plane gap with dc voltage. The laser energy dependency of breakdown voltage was investigated for positive and negative applied. voltages and gap lengths of 15 to 25 mm. It was found that the positive breakdown voltage was higher than the negative one in the hemisphere-to-plane gaps or the rod-to-plane gaps with low voltages, where there is little or no space charge. However, the effect of polarity is reversed in the rod-to-plane gaps with large spacings and the needle-to-plane gaps. On the basis of the dependence of the discharge mode on this polarity effect, it can be seen that it was caused by the difference in development of positive and negative streamers in the corona discharge.

Simulation of pre-breakdown discharges in high-pressure air. I: The model and its application to corona inception

“…The computed inception voltages of the positive corona in the rod-to-plane configuration in air under the conditions of the experiments [31,35] are shown in figures 11 and 12. (The simulations have been performed for the discharge current I = 1 nA.…”

“…A number of experiments on inception of glow corona in air are reported in the literature; e.g. [26,[31][32][33][34][35]. Typical electrode configurations are concentric cylinders and point-toplane.…”

“…The parameters of the experimental geometry, reported in [31,35], are the rod and plate (cathode) diameters and the rodto-plane distance (length of the discharge gap); the rod length is omitted. The latter is a typical situation: there seems to be no experimental publications where the rod length would be indicated.…”

“…Hemispherically-tipped rod, diameter of 2 cm, plate diameter of 7 cm, p = 1 atm. Triangles: modelling with different values of the rod length L. Squares: experimental data[35].…”

Computational and Experimental Study of Time-Averaged Characteristics of Positive and Negative DC Corona Discharges in Point-Plane Gaps in Atmospheric Air

“…Somewhat surprisingly, it seems that experimental data on corona discharges reported in the literature beyond the simplest one-dimensional wire-cylinder configuration are insufficient for an accurate quantitative comparison: not all relevant geometrical parameters are indicated. For example, the rod length is a parameter omitted in experimental publications on corona discharges in the rod-to-plane configuration; e.g., works [22], [23] and their discussion in [13]. As another example, one can mention wire coronas: they are very sensitive to the environment (see [24]), meaning that the electrostatic boundary conditions are not well defined.…”