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Full-Text Articles in Physics
Ion Acceleration In A Helicon Source Due To The Self-Bias Effect, Matt Wiebold, Yung-Ta Sung, John E. Scharer
Ion Acceleration In A Helicon Source Due To The Self-Bias Effect, Matt Wiebold, Yung-Ta Sung, John E. Scharer
Physics Faculty Publications
Time-averaged plasma potential differences up to 165 V over several hundred Debye lengths are observed in low pressure (pn < 1 mTorr) expanding argon plasmas in the Madison Helicon eXperiment (MadHeX). The potential gradient leads to ion acceleration greater than that predicted by ambipolar expansion, exceeding Ei≈7 kTe in some cases. RF power up to 500 W at 13.56 MHz is supplied to a half-turn, double-helix antenna in the presence of a nozzle magnetic field, adjustable up to 1 kG. A retarding potential analyzer (RPA) measures the ion energy distribution function (IEDF) and a swept emissive probe measures the plasma potential. Single and double probes measure the electron density and temperature. Two distinct mode hops, the capacitive-inductive (E-H) and inductive-helicon (H-W) transitions, …
Experimental Observation Of Ion Beams In The Madison Helicon Experiment, Matt Wiebold, Yung-Ta Sung, John E. Scharer
Experimental Observation Of Ion Beams In The Madison Helicon Experiment, Matt Wiebold, Yung-Ta Sung, John E. Scharer
Physics Faculty Publications
Argon ion beams up to Eb=165 eV at Prf=500 W are observed in the Madison Helicon eXperiment (MadHeX) helicon source with a magnetic nozzle. A two-grid retarding potential analyzer (RPA) is used to measure the ion energy distribution, and emissive and rf-filtered Langmuir probes measure the plasma potential, electron density, and temperature. The supersonic ion beam (M=vi/cs up to 5) forms over tens of Debye lengths and extends spatially for a few ion-neutral charge-exchange mean free paths. The parametric variation of the ion beam energy is explored, including flow rate, rf power, and …
Observations Of Neutral Depletion And Plasma Acceleration In A Flowing High-Power Argon Helicon Plasma, C. Mark Denning, Matt Wiebold, John E. Scharer
Observations Of Neutral Depletion And Plasma Acceleration In A Flowing High-Power Argon Helicon Plasma, C. Mark Denning, Matt Wiebold, John E. Scharer
Physics Faculty Publications
Neutral depletion effects are observed in a steady-state flowing argon helicon plasma with a magnetic nozzle for high rf input powers (up to 3 kW). Noninvasive diagnostics including 105 GHz microwave interferometry and optical spectroscopy with collisional-radiative modeling are used to measure the electron density (ne), electron temperature (Te), and neutral density (nn). A region of weak neutral depletion is observed upstream of the antenna where increasing rf power leads to increased electron density (up to ne = 1.6×1013 cm-3) while Te remains essentially constant and …