Experimental study of argon gas breakdown with symmetric and asymmetric electrode configurations

TL;DR

The study interrogates the breakdown of argon gas under DC discharge for symmetric and asymmetric electrode geometries across a range of inter-electrode gaps. Classical Paschen’s law fails to describe the observed $V_B$ vs $pd$ behavior, prompting a generalized empirical form $V_B=\frac{B^*(pd)^k}{\ln(pd)^m+C^*}$ with geometry- and gap-dependent parameters, which provides consistent fits across configurations. Finite-element analysis reveals nonuniform electric-field distributions as a key mechanism driving shifts in $pd_{min}$ and $V_B$, linking geometry, electrode size, and diffusion to deviations from the classic law. The findings underscore the importance of electrode geometry in gas breakdown predictions and propose a path toward more generalized, geometry-aware Paschen-type models with potential applications in plasma processing and high-voltage design.

Abstract

Paschen law relates the breakdown voltage of a gas to the product of gas pressure and inter-electrode distance, predicting a characteristic minimum voltage at a specific pd value. In this study, the role of electrode configurations (symmetric and asymmetric) and inter-electrode spacing on the gas breakdown processes (or Paschen Law) is examined. Numerous sets of experiments are performed with both symmetric and asymmetric electrode configurations of different sizes to obtain Paschen curves at different inter-electrode distances. The experimentally obtained Paschen's curves for different electrode configurations are fitted using a proposed modified empirical relation for breakdown voltage, incorporating variable power-law dependencies and fitting parameters to better capture the observed deviations. Upon closer inspection, we observed that the breakdown voltage and the corresponding pd value are influenced by both electrode configurations and the inter-electrode discharge gap. The variation in breakdown voltage and pd minima for different electrode configurations is explained by analyzing the electric field distributions between the electrodes (cathode and anode) for an applied voltage.

Figures (13)

• Figure 1: A general Paschen's curve for gas breakdown
• Figure 2: A DC Discharge plasma setup: (1) Borosilicate glass tube, (2) rotary pump, (3) digital ammeter, (4) pressure gauge, (5) needle valve, (6) electrodes, (7) supporting insulating disk, (8) and (9) SS-304 rods, (10) argon gas pipe connected to cylinder, and (11) oscilloscope.
• Figure 3: Schematic diagram of experimental setup
• Figure 4: Fitted Paschen curves for (a) symmetric (80 mm cathode and 80 mm anode diameter) configuration and (b) asymmetric (80 mm cathode and 20 mm anode diameter) configuration at different inter-electrode distances.
• Figure 5: (a) Variation of $V_{B}$, corresponding to minimum value of $pd$ with inter-electrode spacing for symmetric (80 mm cathode and 80 mm anode diameter) and asymmetric electrode (80 mm cathode and 20 mm anode diameter). (b) variation of $pd_{min}$ with inter-electrode spacing for symmetrical and asymmetric electrode configurations.