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Experimental results on trapping a gun plasma in a toroidal magnetic cusp experiment

Published online by Cambridge University Press:  13 March 2009

P. A. Pincosy
Affiliation:
Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
B. R. Myers
Affiliation:
Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
M. A. Levine
Affiliation:
Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
B. Feinberg
Affiliation:
Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
R. A. Niland
Affiliation:
Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
L. Soroka
Affiliation:
Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720

Abstract

A start-up method for producing a plasma in the bi-cusp field configuration of a toroidal magnetic cusp (TORMAC) is described. The method uses the radial injection and trapping of a toroidal gun plasma. Measurements of an injected plasma with a velocity of 17 μsec–1 and 4·5 × 1018 particles is presented. The plasma was observed to be stopped and trapped in an equilibrium position. A well-defined outer boundary remained stationary for 20 μsec. Particle flux distribution emanating from the cusp field lines defined a sheath having a width of 1–1·5 ion gyroradii in the poloidial field. This translates to a narrow outer boundary and a broad inner boundary based on the gradient of the poloidial field at the two radial positions. Measurements of Thomson scattering and interferometry give a Te of 15eV, a 15μsec density decay time, and a 5μsec energy decay time. These results show that this injection and trapping method is successful, and thus a higher gun plasma energy combined with a flux conserving barrier may lead to higher temperatures for testing containment in TORMAC.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1984

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