Ion acceleration in plasmas emerging from a helicon-heated magnetic-mirror device

Using laser-induced fluorescence, measurements have been made of metastable argon-ion, Ar{sup +}*(3d{sup 4} f{sub 7/2}), velocity distributions on the major axis of an axisymmetric magnetic-mirror device whose plasma is sustained by helicon wave absorption. Within the mirror, these ions have sub-eV temperature and, at most, a subthermal axial drift. In the region outside the mirror coils, conditions are found where these ions have a field-parallel velocity above the acoustic speed, to an axial energy of {approx}30 eV, while the field-parallel ion temperature remains low. The supersonic Ar{sup +}*(3d{sup 4} f{sub 7/2}) are accelerated to one-third of their final energy within a short region in the plasma column, {le}1 cm, and continue to accelerate over the next 5 cm. Neutral gas density strongly affects the supersonic Ar{sup +}*(3d{sup 4} f{sub 7/2}) density

SPACE-TIME RESOLVED DIAGNOSTICS OF RADIO FREQUENCY GLOW DISCHARGE KINETICS

Three applications of space-time resolved spectroscopy to the study of plasma processes are reviewed briefly. Each application emphasizes a different aspect of plasma chemistry : heterogeneous reactions, homogeneous reactions, and charged-particle transport. Spatially-resolved concentration profiles of reactants near surfaces provides estimates for heterogeneous reaction rates. This is demonstrated using data for CF2 molecules near Si and O atoms near Al, graphite, and kapton. Space-time resolved plasma-induced emission is used to distinguish between dissociative excitation mechanisms in BCl3-Ar discharge mixtures, where superelastic collisions of cold electrons with Ar metastables are shown to be important. Stark-mixed laser-induced fluorescence is used to measure the self-consistent electric fields that are responsible for controlling charged particle transport to and from device surfaces. The low frequency fields breathe periodically as they extract ions from the sheath

3D MAPPING OF ION VELOCITIES IN AN ECR PLASMA REACTOR BY LIF, DOPPLER SHIFT MEASUREMENTS

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