Features of the plasma-channel formation during the voltage generator with the 1-MV/NS-voltage-rise-rate discharge to the vacuum coaxial line containing either closed via microconductor or open-ended gap

In our experiments the high-voltage generator “RADAN-220” was discharged to the 15 cm long and 10 cm internal diameter coaxial line. The gap in the central conductor was open-ended or closed via 5-15 mm long and micron diameter wires of Cu, Ni and W. The voltage amplitude - U₀=220 kV, stored energy - W=1 J; pulse rise duration - 200-500 ps. Sub-nanosecond voltage pulse rise, electric field radial strength at the micro conductors surface high values (E_r ≥ 24 MV/cm for the micro wire with d = 20 μm for the open-ended line) and strong non-uniformity of the line, resulting from the huge difference between the diameters of the central core and conductor in respect to the vacuum chamber diameter - are peculiar properties of our experiments.