(Color online) ICP source and vacuum photodiode used for VUV measurements.
(Color online) Combined electrostatic and magnetic model of vacuum photodiode and simulated charged particle trajectories: 20 eV Ar+ ions orange/solid line, 5 eV electrons red/dashed line. Ions are repelled by 60 V biased anode ring. Electrons are deflected inside of the hole by the magnetic field from permanent magnets.
(Color online) Coordinate system for VUV emission model.
Vertical profiles of 1s4 resonance level densities at (a) 2.5 mTorr and (b) 15 mTorr. Points are experimental measurements, long-dashed line is uniform distribution, short-dash is cosine distribution, solid line is average of uniform and cosine distributions [i.e., Eq. (15) ]. z = 0 corresponds to the bottom electrode, z = 8 cm to the midplane where the resonance density is typically measured.
(Color online) VUV transitions are the only dipole-allowed decay channel for the two principal resonance levels (left). Higher resonant levels of the (n ≥ 5) and (n ≥ 3) configurations (right) can radiatively decay to either the ground state (VUV emissions with possibility of radiation trapping) or to other excited levels such as the levels of the configuration.
Results as a function of pressure: (a) Ar(1s4) resonance level density measurements from white-light OAS (solid squares) and from branching-fraction analysis of emissions (OES-BF, open circles); (b) measured VUV photodiode current measured at bottom electrode (points) along with VUV emission model based on measured resonance densities (line); (c) emission model values for photon flux to center of bottom electrode.
(Color online) Results as a function of applied rf power at a pressure of 2.5 mTorr (red/open/dashed) and 15 mTorr (blue/solid): (a) Ar(1s4) resonance level density measurements obtained from white-light OAS; (b) measured VUV photodiode current measured at bottom electrode (points) along with VUV emission model based on measured resonance densities (lines); (c) emission model values for combined 1s2 + 1s4 photon fluxes to the center of bottom electrode.
Lines used in OAS measurements of 1s2 and 1s4 resonance level densities.
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