START-UP OF THE OHMIC PHASE IN JET
Some of the results of this study are of direct interest to the designers of the next generation of reactor-like tokamaks. Discharge initiation with low electric fields 0.5V m**-RU1 has proven to be reliable when the stray poloidal field is small enough. For JET the arrangements for stray field cancellation have proven inadequate for operation at full premagnetisation flux. The technical means for curing this problem have been identified and will be implemented. However, new machines should be designed for breakdown at low electric fields so as to relieve electromechanical stresses and reduce the demands on the power supplies. The current rise is effectively limited to a ramp rate of somewhat less than 1 MA s**-1. Transient ramp rates can be higher. Gas desorption during the current rise limits the lower limit of the density. Therefore it is unlikely that low density RF current drive scenarios are compatible with the use of limiters unless some means of active pumping are available. The volt-seconds consumption of JET discharges have been shown to be consistent with a simple model in which flat top loop voltage represents the resistive drop throughout the current rise.
Bibliographic Reference: WRITE TO THE PUBLICATIONS OFFICER, JET JOINT UNDERTAKING, ABINGDON OXON, OX14 3EA (UK), MENTIONING REPORT JET-P(85)23, 1985
Record Number: 1989125005900 / Last updated on: 1987-01-01
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