Interelectrode plasma parameters and plasma deposition in a hot refractory anode vacuum arc

The new mode of Vacuum arc-Hot Refractory Anode Vacuum Arc-was studied experimentally using a Langmuir probe, two types of thermal probes, and film collection substrates. The plasma density, electron temperature, plasma energy flux, cathode erosion, mass deposition rate on a substrate, and macroparticle contamination in the deposited films were measured. The arc initially operated as a usual vacuum arc sustained by cathode spots, i.e., and the vapor and plasma source located at the cathode spot. At a later stage the anode heated up and metal vapor originating at the cathode was re-evaporated from the nonconsumable hot graphite anode. Initially, plasma density was about (3-4) · 10²⁰ m^-3 but it increased with time, reaching about 2 · 10²¹m^-3 after 60 s in a 340 A arc. The electron temperature initially was about 1.6 eV and decreased with time to a steady-state value of about 1.1 eV after 20 s. The radial plasma energy flux generated by 175 and 340 A arcs was about 1 and 2 MW/m², respectively, at 1.6 cm from the electrode axis. The deposition rate on substrates placed 110-120 mm from the electrode axis reached about 2 μm/min. The density of macroparticles found on substrates exposed during the first 60 s of arcing was ∼10³ macroparticles per mm², however, this density was reduced to about 1 macroparticle per mm² on substrates exposed to only the second 30 s period.