The experiments were performed in a demountable vacuum chamber under continuous pumping, providing pressure ~10-4 Pa. The block diagram of the experimental setup is shown in the picture on the right. Interelectrode gap was fixed at h=4 mm.
The discharge was ignited on the cathode surface at a distance ≈8 mm from the edge using molybdenum needle. The discharge was powered from a special generator providing rectangular current pulse with adjustable current up to 50 kA and duration up to 10 ms. Prior to measurements, the cathode surface was cleaned with a set of high-current pulses.
Molybdenum needle in an experiment is to provide an auxiliary function, but it is essential, so that the experiment can be performed.