AVS 50th International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS-ThA

Paper PS-ThA8
Ion Collection by a Mach Probe in Flowing Unmagnetized Plasma

Thursday, November 6, 2003, 4:20 pm, Room 315

Session: Plasma Diagnostics: Mechanisms
Presenter: E. Ko, University of Wisconsin, Madison
Authors: E. Ko, University of Wisconsin, Madison
X Wang, University of Wisconsin, Madison
N. Hershkowitz, University of Wisconsin, Madison
Correspondent: Click to Email
The measurement of plasma flow along the presheath in unmagnetized plasma is performed using a spherical Mach probe. Ion flow velocity in unmagnetized plasma is examined experimentally and compared to a recent numerical simulation by Hutchinson.@footnote 1@ The spherical Mach probe, which was inspired by Hutchinson's theoretical model, consists of a conducting sphere that has two conducting probe tips, insulated from the sphere and mounted at @theta@ = 0° and 180° with respect to the flow direction. Although the simulation included T@sub i@ = 0.1T@sub e@ ~ 10T@sub e@ and flow velocity v@sub f@ = 0 ~ 3c@sub s@, where c@sub s@ is the sound speed, the laboratory plasma in the presheath was limited to T@sub i@ < 0.1T@sub e@ and v@sub f@ @<=@ 1.0 c@sub s@. The experiment is performed in a multi-dipole DC plasma with Argon pressure ranging from 0.1 to 3mTorr. The upstream and downstream probe tips and the surface of the sphere were simultaneously biased to minimize the probe edge effects, and to obtain a much closer condition to the simulation. This work also examines a previous experiment@footnote 2@ that used the Hudis and Lidsky formula,@footnote 3@ which though shown to be invalid@footnote 4@ still attained results in good agreement with the simulation. *Work Supported by US DOE grant DE-FG02-97ER 54437. @FootnoteText@ @footnote 1@ I. H. Hutchinson, Plasma Phys. Control. Fusion, 44 1953 (2002)@footnote 2@ L. Oksuz, M. A. Khedr, and N. Hershkowitz, Phys. Plasmas, 8 1729 (2001)@footnote 3@ M. Hudis and L. M. Lidsky, J. Appl. Phys., 41 5011 (1970)@footnote 4@ I. H. Hutchinson, Phys. Plasmas, 9 1832 (2002).