Two-Dimensional Spectroscopy for Vacuum Arc in Steady State and Decaying State under Free-Recovery Condition

In this paper, a fundamental experimental system was constructed for observation of vacuum arcs in steady states and transient states. A vacuum arc discharge was formed at currents of DC30 A and DC50 A. The IGBT was used to commutate the arc current to IGBT to make free-recovery state, which is fundamental transient state for decaying arcs. Using this system, high speed imaging for a steady state and transient decaying arcs and two-dimensional spectroscopic observation were carried out. As the result, near the cathode spots, a bright region was present involving copper ion lines as well as copper and chromium atomic lines. From the bright region around cathode, a cone-shaped light emitting area was expanded toward the anode. After current decrease for free-recovery condition, the bright region near the cathode spot decayed gradually, while the cone-shaped light emitting area disappeared rapidly. This result implies that vapor between electrodes was rapidly diffused.