Plasma emission in vacuum arc and rf-discharge plasma sources

Abstract

Optical emission spectra from plasma produced by a copper vacuum arc with argon and nitrogen have been investigated for the case when the plasma was guided by a straight solenoid. The spectra have been compared with those obtained from inductively coupled rf multicusp discharge in the 10−4–10−2 Torr argon and nitrogen pressure range and at an input power of up to 500 W. It has been found that the spectral line intensity distributions of neutral and ion species for arc and rf discharge were different. Also, the intensity evolutions of the lines have shown a different behavior between the arc current and rf power. Electron excitation temperature (Tex) for rf argon plasma at low pressure has been found to be approximately 2.5 eV which was about ten times higher than for Cu-argon arc discharge. Possible mechanisms of ionization-excitation of guest atoms/molecules in the case of metal vacuum arc discharge are discussed.