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Observations of fast anisotropic ion heating, ion cooling, and ion recycling in large-amplitude drift waves

Sanders, S. J. and Bellan, P. M. and Stern, R. A. (1998) Observations of fast anisotropic ion heating, ion cooling, and ion recycling in large-amplitude drift waves. Physics of Plasmas, 5 (3). pp. 716-728. ISSN 1070-664X. http://resolver.caltech.edu/CaltechAUTHORS:SANpop98

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Abstract

Large-amplitude drift wave fluctuations are observed to cause severe ion temperature oscillations in plasmas of the Caltech Encore tokamak [J. M. McChesney, P. M. Bellan, and R. A. Stern, Phys. Fluids B 3, 3370 (1991)]. Experimental investigations of the complete ion dynamical behavior in these waves are presented. The wave electric field excites stochastic ion orbits in the plane normal (perpendicular to) to B, resulting in rapid perpendicular to heating. Ion-ion collisions impart energy along (parallel to) B, relaxing the perpendicular to-parallel to temperature anisotropy. Hot ions with large orbit radii escape confinement, reaching the chamber wall and cooling the distribution. Cold ions from the plasma edge convect back into the plasma (i.e., recycle), causing further cooling and significantly replenishing the density depleted by orbit losses. The ion-ion collision period tau(ii)similar to Tau(3/2)/n fluctuates strongly with the drift wave phase, due to intense (approximate to 50%) fluctuations in n and Tau. Evidence for particle recycling is given by observations of bimodal ion velocity distributions near the plasma edge, indicating the presence of cold ions (0.4 eV) superposed atop the hot (4-8 eV) plasma background. These appear periodically, synchronous with the drift wave phase at which ion fluid flow from the wall toward the plasma center peaks. Evidence is presented that such a periodic heat/loss/recycle/cool process is expected in plasmas with strong stochastic heating.


Item Type:Article
Additional Information:Copyright © 1998 American Institute of Physics. Received 12 August 1997; accepted 26 November 1997. We thank Mr. F. Cosso for invaluable technical assistance. This work was supported by National Science Foundation Grant No. PHY-9413046. Sanders et al., Added discussion of "Observations of fast anisotropic ion heating, ion cooling, and ion recycling in large-amplitude drift waves" Phys. Plasmas, 6(10):4118-4119, October 1999.
Subject Keywords:plasma drift waves; plasma heating; cooling; plasma toroidal confinement; plasma fluctuations; plasma temperature; plasma oscillations; plasma collision processes; plasma boundary layers; Langmuir probes; plasma transport processes; plasma flow
Record Number:CaltechAUTHORS:SANpop98
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:SANpop98
Alternative URL:http://dx.doi.org/10.1063/1.872758
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2191
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:14 Mar 2006
Last Modified:26 Dec 2012 08:47

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