Laser-induced-fluorescence characterization of velocity shear in a magnetized plasma column produced by a segmented, Q-machine source

Journal Article · Fri Jul 15 00:00:00 EDT 2005 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.1925616· OSTI ID:20764367

Reynolds, E W; Kaneko, T; Koepke, M E; Hatakeyama, R ^[1]

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1. Physics Department, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

Control over the radial profile of one component of ion drift speed U, either perpendicular or parallel to the magnetic field, is demonstrated in the magnetized plasma column for two configurations of a double-ended Q machine in which one of the hot plates is segmented into a central disk and two concentric annuli. Each hot plate can be heated to {approx}1800 deg. C, and the segmented hot plate is bombarded with barium vapor, resulting in quasineutral, magnetized, barium-ion plasma. Since the electric potential in the plasma magnetically maps to the segments, the radial profile of plasma potential, and hence the ExB flow, can be made inhomogeneous. This configuration is referred to as the perpendicular configuration. A negatively biased, cross-sectional mesh, inserted between the two ends of the plasma column, reflects electrons from each source causing the radial profile of potential on the nonsegmented source side of the mesh to become uniform. In traversing the mesh sheath from the segmented source side, where the radial potential profile is inhomogeneous, to the nonsegmented source side, where the radial potential profile is homogeneous, the ions experience an axial acceleration that has an inhomogeneous radial profile. This configuration with the mesh is referred to as the parallel configuration. Laser-induced-fluorescence is used to measure the ion-velocity-distribution function on the nonsegmented-source side with and without the mesh inserted. Measurements show that the above configurations result in ion temperature anisotropy, 1<(T{sub perpendicular}/T{sub parallel})<5, and radially nonuniform ion flows with a maximum in the shear profile (dU{sub perpendicular}/dx){sub max} as large as 0.6 {omega}{sub i} and (dU{sub parallel}/dx){sub max} as large as 0.17 {omega}{sub i} where {omega}{sub i} is the ion gyrofrequency.

• OSTI ID: 20764367
• Journal Information: Physics of Plasmas, Vol. 12, Issue 7; Other Information: DOI: 10.1063/1.1925616; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANISOTROPY
BARIUM
BARIUM IONS
CONFIGURATION
CONTROL
DISTRIBUTION FUNCTIONS
ELECTROMAGNETIC FIELDS
ELECTRON TEMPERATURE
ELECTRONS
FLUORESCENCE
GYROFREQUENCY
ION DRIFT
ION TEMPERATURE
MAGNETIC FIELDS
PLASMA
PLASMA DIAGNOSTICS
PLASMA DRIFT
PLASMA POTENTIAL
PLASMA SHEATH
PLASMA WAVES
PLATES
SHEAR
VAPORS
VELOCITY