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Laser-triggered electric discharges were diagnosed using fast time-resolved shadowgraphy. A focused laser beam produced a plasma between two parallel plates connected to a high-voltage supply. This plasma, in turn, triggers the main arc between the plates. It was found that arcing occurs at about 400 [micro]s after laser firing. The breakdown mechanism responds to a rarefaction of the air between the electrodes rather than to laser ionization. Index Terms--Laser-induced plasmas (LIPs), laser triggering, shadowgraphy.

Performances of breaking devices are closely linked to the electrical arc dynamics: The arc has to move from the ignition area to an extinction place, and this motion must respect the technical and physical constraints. It is so particularly important to get reliable and precise information on the arc dynamic during a breaking process. In this paper, two complementary means of diagnostics have been implemented to better understand the phenomena implied in breaking arc displacement. A high-speed camera allows the detection of both arc and hot gas surrounding the arc, and magnetic measurements allow one to get more precision on the actual arc shape. Index Terms--Breaking devices, contact materials, electric arc, inverse method, magnetic measurements, optical measurements.