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Charge and Mass Considerations for Plasma Velocity Measurements in Rotating Plasmas

Author: Carlos A. Romero-Talamas
Requested Type: Poster Only
Submitted: 2009-12-04 18:05:48

Co-authors: R.C. Elton, R. F. Ellis, A. B. Hassam, W. C. Young, R. Reid

Contact Info:
University of Maryland
Bldg. #223, Paint Branch Drive
College Park, Maryland   20742
USA

Abstract Text:
Velocity measurements of hydrogen plasmas that are rotating due to imposed E x B fields, where E is the electric field in the radial direction and B the magnetic field in the axial direction of a cylindrical configuration, drifts have traditionally been measured using Doppler shifts of atomic spectra from impurity elements such as carbon or oxygen. These trace elements are normally estimated to conform a small fraction of the total plasma density. Ideally, the gyrocenter of trace particles rotates at the bulk plasma velocity, regardless of the charged state or trace particle mass. However, for sufficiently large applied |E/B| (or equivalently, a sufficiently large ratio of bulk plasma rotation frequency and particle gyrofrequency), charged particles may have gyroradii that depart significantly from quasi-circular orbits drifting about the B field axis. That is, trajectories are sufficiently elongated such that ions experience large accelerations that in turn lead to intermittent velocities that may be much higher than the bulk plasma velocity. This effect is investigated numerically with a single particle code that includes collisions scattering, as well as experimentally at the Maryland Centrifugal Experiment Experiment (MCX) [R.F. Ellis, et al., Phys. Plasmas 12, 055704 (2005)]. Parameters investigated numerically are compared to measured Doppler shifts of different atomic line spectra and different charged states. Work supported by the U.S. Department of Energy.

Characterization: C,E10

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