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Abstract

The highest density discharges are produced by simultaneous neutral beam injection at P-inj <= 1 MW and cold gas feed. Energy balances show electron and ion heat conduction are the most important losses from the discharge centre. Ion conduction is increasingly important as the density is raised and is +- 1-4 times neoclassical expectation. The measured changes in conduction coefficients on injection do not suggest any marked deterioration of confinement. However, global measurements of beta and tau-E over a wide range of discharge parameters show the energy content increases only slowly with P-inj and density and strongly with plasma current. These results can be interpreted as a soft limit on beta-p at beta-p about 1 or an unfavourable scaling of confinement with temperature. Ideal high-n ballooning modes are theoretically stable at the beta values reached. The empirical scaling obtained also fits a range of results from other devices, including those with ohmic heating. The density clamp which occurs with injection in some cases, is overcome by increasing the gas feed rate. Measurements in the scrape-off plasma show that it is associated with an increase in energy and particle fluxes to the limiters, consistent with the decrease in particle containment time.

Additional information

Authors: HUGILL J CULHAM LABORATORY, ABINGDON (UK), CULHAM LABORATORY, ABINGDON (UK)
Bibliographic Reference: WRITE TO HER MAJESTY'S STATIONERY OFFICE, P.O. BOX 276, LONDON SW8 5DT (UK), MENTIONING REPORT CLM-R 239, 1983, PRICE: UKL 3.00
Record Number: 1989122072600 / Last updated on: 1987-01-01
Category: PUBLICATION
Available languages: en