Experimental observation of ion beams in the Madison Helicon eXperiment

Journal Article · Wed Jun 15 00:00:00 EDT 2011 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3596537· OSTI ID:21546973

Wiebold, Matt; Sung, Yung-Ta; Scharer, John E ^[1]

---

1. Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

Argon ion beams up to E{sub b} = 165 eV at P{sub rf} = 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 = v{sub i}/c{sub s} 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 magnetic field dependence. The beam energy is equal to the difference in plasma potentials in the Pyrex chamber and the grounded expansion chamber. The plasma potential in the expansion chamber remains near the predicted eV{sub p} {approx} 5kT{sub e} for argon, but the upstream potential is much higher, likely due to wall charging, resulting in accelerated ion beam energies E{sub b} = e[V{sub beam} - V{sub plasma}] > 10kT{sub e}.

• OSTI ID: 21546973
• Journal Information: Physics of Plasmas, Vol. 18, Issue 6; Other Information: DOI: 10.1063/1.3596537; (c) 2011 American Institute of Physics; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ARGON IONS
CHARGE EXCHANGE
ELECTRON DENSITY
ELECTRON TEMPERATURE
ENERGY SPECTRA
EXPANSION CHAMBERS
FLOW RATE
ION BEAMS
LANGMUIR PROBE
MAGNETIC FIELDS
MEAN FREE PATH
PLASMA POTENTIAL
BEAMS
CHARGED PARTICLES
CLOUD CHAMBERS
ELECTRIC POTENTIAL
ELECTRIC PROBES
GAS TRACK DETECTORS
IONS
MEASURING INSTRUMENTS
PROBES
RADIATION DETECTORS
SPECTRA