Emission Spectra of Arc Plasmas

Emission spectra of arc plasmas contain valuable information regarding arc sites, plasma parameters and composition, and temporal dynamics of plasma expansion. Emission spectra within the range of 200-800 nm were measured for trigger arcs on triple junctions and sustained arcs between solar array strings. Spectra were recorded from arcs on several different brands of conventionally designed solar array samples immersed in simulated low-Earth-orbit plasma. The arc sites and cathode materials were determined for plasmas generated by primary discharges and sustained arcs. Comparative analysis of temporal dynamics of arc current pulse waveforms with spectral line intensities allowed obtaining estimates for plasma expansion rates. Statistical processing of spectral line intensities resulted in calculations of arc plasma electron temperatures and surface densities of some atomic species. The presence of a flux of energetic electrons (above 100 eV) was confirmed by analysis of the structure of the excited atom and ion energy levels.