Independent Control of Electron Temperature and Density in Copper Thermionic Vacuum Arc Plasmas

ABSTRACT The thermionic vacuum arc (TVA) is a plasma source that generates highly ionized metal vapor plasmas via anodic evaporation, with independent control over plasma parameters through operational adjustments. This study investigates copper (Cu) plasmas produced by a TVA system under stable‐state conditions, focusing on the dependencies of electron temperature ( T e ) and electron number density ( N e ) on operating parameters such as arc current ( I arc ) and cathode filament current ( I f ). Optical emission spectroscopy (OES) in the 200–1000 nm range was employed to analyze spectral line intensities of neutral Cu atoms. T e was determined via the Boltzmann plot method, yielding values between 4720 ± 250 K and 5370 ± 300 K as the I arc increased from 300 to 1200 mA (at a fixed I f of 18.5 A), while increasing the I f from 16 to 19 A elevated T e from 4580 ± 250 K to 5180 ± 300 K, demonstrating distinct contributions of both parameters to electron heating. N e was determined using Stark broadening analysis, revealing a weak dependence on operating parameters, with values ranging from (5.0 ± 0.8) × 10 16 cm −3 to (8.9 ± 0.9) × 10 16 cm −3 ). These findings highlight the TVA's unique capability to controllably tailor plasma properties, making it a promising candidate for advanced coating processes requiring precise plasma parameter modulation.