Optical ion energy measurements in a radio-frequency-induction plasma source

Abstract

In situ, Fabry–Perot interferometry was used to study the translational dynamics of ions in a magnetically confined, radio‐frequency‐induction (RFI) plasma reactor. Radial ion motion was characterized through measurements of the Doppler profile of emission from Ar⁺ ions. Radial ion energies depend on the operating power, pressure, and magnetic‐field configuration. In a magnetically confined RFI plasma at 1000 W, ion energies increase from 0.08 to approximately 0.25 eV as the operating pressure is lowered from 13 to 0.18 mTorr. Complementary Langmuir probe studies of the plasma potential as well as its variation across the radius of the reactor illustrate the influence of electric fields on the radial motion of ions in the RFI system. These measurements illustrate that radially directed ion motion in the RFI reactor is significantly less than that reported previously for a divergent‐field electron cyclotron resonance system.