parallel-plate configuration; cathode: cylindrical rod (radius: 2 mm, length: 20 mm, material: ceriated Tungsten); anode: copper; Current densities: 2x10^5 A/m^2 to 10^6 A/m^2; gap lengths: 15, 20, 50, 100, and 200 µm; anode and non-plasma-contact cathode end kept at 300 K uri icon