*2.1. Experimental Setup*

Figure 1 presents the experimental setup, comprising a model vacuum interrupter (vacuum chamber 1 with pneumatic drive 2), a high-current generator (visible in the background of Figure 1), as well as electrical and optical diagnostics (3–8).

A vacuum chamber with optical access described in [22] has been used. It contains four optical viewports allowing for simultaneous acquisition of several optical signals. The electrodes are moved by a pneumatic drive with an opening speed of about 1 m/s. The fixed electrode was powered as an anode. The maximum stroke of the drive system was about 10 mm. The electrode distance at which the arc interruption occurs depends on the opening speed and the instant of contact separation start and is typically 3–8 mm.

**Figure 1.** Setup for studies on vacuum arcs: (**1**) vacuum chamber, (**2**) pumping system, (**3**) high-speed camera (general arc dynamics), (**4**) two high-speed cameras equipped with narrow-band optical filters, (**5**) NIR optics, (**6**) NIR spectrometer, (**7**) Xe flash lamp, (**8**) 0.75 m imaging spectrograph.
