Modelling and experimental studies of microarcs at low currents

Glow and arc discharges are the most prominent direct current discharges and are found in a wide range of applications – light sources, surface treatment and material processing, nanoparticle synthesis. Arc plasmas of small size are providing alternatives to electron and laser beams. Microarcs, which are less than 1mm in size in at least one direction, are of growing interest in additive manufacturing and microwelding, repair of damaged surfaces of high value components as examples. Furthermore, microarcs are undesirably generated during contact opening in low-voltage switching devices. They can occur as contact discharges in devices used in explosive environment as well.

The studies of direct current microarcs and their characterization are important for the reasons of applications and the gain of fundamental understanding. Experiments on microarcs that can reveal their structure and properties are very scarce and challenging due to the small size. High-speed imaging allows one to reveal their temporal behaviour and measure the arc length. The spatial resolution and the reproducibility can be difficult due to instabilities. Modelling works can significantly contribute to the characterization of the direct current microarcs as the spatial resolution of these small-size objects is enabled in recent years by powerful computers and numerical tools. Such works allow us to explore the microarcs and facilitate their applications.

The present contribution will present recent modelling and experimental studies of microarcs related to microwelding arrangements, test apparatus for explosion protection, and switching devices. The studies include a self-consistent non-equilibrium modelling, electrical and spectroscopic measurements, and a high-speed imaging. The understanding of the underlying physical processes occurring in the microarcs under consideration and the characterization of the microarcs plasma were the main objectives of these studies.