Direct measurements of ion dynamics in collisional magnetic presheaths
- Department of Physics, West Virginia University, Morgantown, West Virginia 26506 (United States)
- Department of Engineering Physics, The University of Wisconsin–Madison, Madison, Wisconsin 53706 (United States)
Ion velocities and temperatures are measured in the presheath of a grounded plate downstream from an argon helicon plasma source using laser-induced fluorescence (P{sub rf}≈450→750 W, T{sub e}=2.5→5 eV, T{sub i}=0.1→0.6 eV, n{sub 0}≈1×10{sup 12}cm{sup −3}, p{sub n}=1→6.5 mTorr, λ=0.3→2 cm, ρ{sub i}≈ 0.5 cm). The plate is held 16°→60° relative to the 1 kG background axial magnetic field. The velocity profiles are compared to a 1D fluid model similar to those presented by Riemann [Phys. Plasmas 1, 552 (1994)] and Ahedo [Phys. Plasmas 4, 4419 (1997)] for the 1 mTorr dataset and are shown to agree well. The model is sensitive to parameters such as collision and ionization frequencies and simplified models, such one presented by Chodura [Phys. Fluids 25, 1628 (1982)], are shown to be inaccurate. E{sup →}×B{sup →} flows as large as 40% of c{sub s} at the sheath edge are inferred. Definitions for the term “magnetic presheath” and implications for ion flow to tokamak divertors and Hall thruster walls are discussed.
- OSTI ID:
- 22299646
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 10 Vol. 21; ISSN PHPAEN; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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