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The performance of high current discharges can be improved by applying central ICRF heating before, or shortly after, the onset of sawtooth activity in the plasma current rise phase. Long sawtooth-free periods are obtained which result in a transiently-enhanced discharge performance. High T(e)(0) with values of 9 - 10.5 keV with peaked profiles T(e)(0)/<T> at values of 3 - 4 are obtained giving values of n(e)(0)T(e)(0) up to 6 x 1.0 E20 (keV/m3). Improvements in T(i)(0) neutron production are observed. Local transport simulation shows that the electron and ion thermal diffusivities do not differ substantially in the two cases of current-rise and flat-top heating, the performance of the central plasma region being enhanced, in case of current-rise, entirely by the elimination of the sawtooth instability. The maximum D-D reaction rate is enhanced by a factor of 2 compared to flat-top value. An appreciable part of the reaction rate is attributed to 2nd harmonic deuterium heating. In all current-rise discharges radiation amounts to 25-50% of total power and Z(eff) remains roughly constant.

Additional information

Authors: BURES M ET AL., JET Joint Undertaking, Abingdon, Oxon. (GB)
Bibliographic Reference: Report: JET-P(89)26 EN (1989)
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199010693 / Last updated on: 1994-12-01
Original language: en
Available languages: en