Investigation of plasma evolution in a coaxial small-gap magnetically insulated transmission line

Interferometry and two-frame schlieren imaging were used to study arc discharge evolution in a small-gap, coaxial, magnetically insulated transmission line driven by a 2-TW generator with a current pulse rise time of 70 ns. Two kinds of plasma objects were observed in experiments: plasma of arc discharges and low-density peripheral plasma. Plasma fills most of the magnetically insulated transmission line (MITL) gap in the area of the arc and produces a stripe trace of evaporated metal on the surface of electrodes. Arc discharge typically arises near the cathode. Anode plasma arises in the later stage, after which, the plasma fills the gap. A scenario of plasma evolution of the arc discharge is discussed. Low-density plasma is located in thin layers near the cathode or the anode. It plays a role in the seeding of arc discharges that grow before the closure of the gap and dissipates after the closure.