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Poloidal divertor experiment with applied E vector x B vector/B/sup 2/ drift

Technical Report ·
DOI:https://doi.org/10.2172/5176100· OSTI ID:5176100
It has been proposed that the E vector x B vector/B/sup 2/ drift arising from an externally applied electric field could be used in a tokamak or other toroidal device to remove plasma and impurities from the region near the wall and to reduce the amount of plasma striking the wall, either assisting or replacing a conventional magnetic field divertor. A poloidal magnetic divertor (without pumping chamber) was added to the Wisconsin Levitated Toroidal Octupole, and the octupole was operated with a tokamak-like magnetic field configuration (q = 0.7). A radial electric field was applied in the scrape-off zone, causing an E vector x B vector/B/sup 2/ drift with a large poloidal component. This reduced plasma flux reaching the wall of the toroid by up to a factor of 5 beyond the effect of the magnetic divertor, for divertor configurations with both high and low magnetic mirror ratios, in good agreement with a simple theoretical model. Plasma density and density scale length were also reduced in the scrape-off zone, in qualitative agreement with the model. This was not accompanied by any new instabilities in the scrape-off zone, nor by any appreciable degradation of confinement of the central plasma.
Research Organization:
Wisconsin Univ., Madison (USA)
Sponsoring Organization:
USDOE Asslstant Secretary for Energy Technology
DOE Contract Number:
AS02-76ET53051
OSTI ID:
5176100
Report Number(s):
DOE/ET/53051-5
Country of Publication:
United States
Language:
English