Excitation states of titanium and nitrogen gas in an electron beam evaporation sustained arc

The arc discharge studied in this work was sustained by titanium vapor evaporated by an electron beam in nitrogen atmosphere. Optical emission spectroscopy and Langmuir probe diagnostics were carried out to study the excitation of titanium and nitrogen. It was found that with increasing arc current, Ti and nitrogen gas exhibited an opposite tendency of excitation. When arc current increased from 20 to 60 A, Ti was highly excited to Ti+, while the excitation of nitrogen was lowered; this is completely different from that for a conventional cathodic arc, where both Ti and N2 are highly ionized. By Langmuir probe diagnostics, the electron energy distribution followed a two-Maxwellian distribution at an arc current of 60 A; the electron temperatures were 0.98 and 10.1 eV, and the corresponding electron densities were 2.7×1011 and 3.9×109 cm3, respectively. This result provided a theoretical explanation for the difference of excitation between titanium and nitrogen in this arc.