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Latest results from the JET tokamak, with beryllium as the first wall material facing the hot plasma, have shown substantial improvements in plasma purity and corresponding reductions in plasma dilution. This has allowed a fusion product of 8 to 9 x 1.0 E20 s.keV/m3 to be reached (within a factor of 8 of that required in a fusion reactor), albeit only transiently. Even so, at high heating powers, an influx of impurities still limits the achievement of better performance and steady state operation. A new phase for JET is planned in which an axi-symmetric pumped divertor configuration will be used to address the problems of impurity control, plasma fuelling and helium ash exhaust in operating conditions close to those of a Next Step tokamak with a stationary plasma of thermonuclear grade. With an efficient axisymmetric pumped divertor, ignition should occur in a tokamak reactor of about 2 to 3 times the size of JET. A Next Step tokamak programme, could comprise several complementary facilities, including a materials test facility. A single Next Step device (such as the ITER Project as currently conceived) would have higher scientific, technical and management risks and does not provide such comprehensive information, particularly in the areas of ignition, reactor performance and blanket testing. Further details of these facilities, expected costs and timescales are discussed.

Additional information

Authors: REBUT P-H, JET Joint Undertaking, Abingdon, Oxon. (GB)
Bibliographic Reference: Report: JET-P(90)66 EN (1990) 21 pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon. OX14 3EA (GB)
Record Number: 199110573 / Last updated on: 1994-12-02
Original language: en
Available languages: en
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