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Plasma Heating and Losses in Toroidal Multipole Fields

Technical Report ·
DOI:https://doi.org/10.2172/1087114· OSTI ID:1087114
 [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Univ. of Wisconsin, Madison, WI (United States)
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The heating and loss of plasmas have been studied in three pulsed, toroidal multipole devices: a large levitated octupole, a small supported octupole and a very .small supported quadrupole. Plasmas are produced by gun injection and heated by electron and ion cyclotron resonance heating and ohmic heating. Electron cyclotron heating rates have been measured over a wide range of parameters, and the results are in quantitative agreement with stochastic heating theory. Electron cyclotron resonance heating produces ions with energies larger than predicted by theory. With the addition of a toroidal field, ohmic heating gives densities as high as 1013cm-3 in the toroidal quadrupole and 1012cm-3 in the small octupole. Plasma losses for n=5 x 109cm-3 plasmas are inferred from Langmuir probe and Fabry-Perot interferometer measurements, and measured with special striped collectors on the wall and rings. The loss to a levitated ring is measured using a modulated light beam telemeter. The confinement is better than Bohm but considerably worse than classical. Low frequency convective cells which are fixed in space are observed. These cells around the ring are diminished when a weak toroidal field is added, and loss collectors show a vastly reduced flux to the rings. Analysis of the spatial density profile shows features of B-independent diffusion. The confinement is sensitive to some kinds of dc field errors, but surprisingly insensitive to perturbations of the ac confining field.
Research Organization:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Organization:
US Atomic Energy Commission (AEC)
OSTI ID:
1087114
Report Number(s):
COO--2387-34
Country of Publication:
United States
Language:
English

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70 PLASMA PHYSICS AND FUSION TECHNOLOGY