Inductive discharges with radio-frequency (RF) substrate bias are frequently used for various technological applications. We operate such a hybrid discharge with a phase-locked RF substrate bias at twice the frequency of the inductive coupling with fixed but adjustable phase between both RF sources in neon at low pressures of a few Pa. The ion flux to the substrate is found to be a function of this relative phase in the H-mode at constant RF powers as long as some residual capacitive coupling of the planar coil is present. For distinct choices of the phase, Phase Resolved Optical Emission Spectroscopy measurements show that energetic beam electrons generated by the expanding boundary sheaths (i) are well confined, (ii) are accelerated efficiently, and (iii) propagate vertically through the inductive skin layer at the times of maximum azimuthal induced electric field within the fundamental RF period. This enhances the inductive stochastic electron heating, the power coupling efficiency, and finally the ion flux.
We compare three laser induced fluorescence schemes for measuring velocity distributions of Ar-I 1s 5 metastables in the presence of a magnetic field. In these three-level schemes, the 1s 5 state is optically pumped to 2p 2 , 2p 3 , or 2p 4 by sweeping the frequency of a tuneable CW laser over transitions in the visible range at 696.7352 nm, 706.9167 nm, and 714.9012 nm, respectively. Broadening in the fluorescence spectra is attributed to Zeeman splitting and saturation effects. We present measurements of spectral broadening dependence on injected laser intensity and describe spectral reconstructions that account for Zeeman splitting. For laser injection parallel to a background magnetic field, the separation of the Zeeman-split σ ± clusters is an effective, non-perturbative localized magnetic field diagnostic. We discuss the advantages of the three transition schemes and present the optimal transition for several applications.
Ion temperature anisotropy in an expanding magnetized plasma is investigated using laser induced fluorescence. Parallel and perpendicular ion velocity distribution functions (IVDFs) were measured simultaneously with high spatial resolution in the expanding plasma. Large ion temperature anisotropies (T⊥i/T∥i∼10) are observed in a conical region at the periphery of the expanding plasma plume. A simple 2D Boris stepper model that incorporates the measured electric field structure is able to reproduce the gross features of the measured perpendicular IVDFs. A Nyquist stability analysis of the measured IVDFs suggests that multiple instabilities with k⊥ρi∼1 and k||ρi∼0.2 are likely to be excited in these plasmas.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.