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(EX5/4) Radiating Edge Plasma Experiments on JET

G. P. Maddison1), M. Brix2), R. V. Budny3), M. Charlet1), I. Coffey1), G. Cordey1), P. Dumortier4), S. K. Erents1), N. C. Hawkes1), M. von Hellermann5), D. L. Hillis6), J. Hogan6), L. D. Horton7), L. C. Ingesson5), S. Jachmich2), G. L. Jackson8), A. Kallenbach7), H. R. Koslowski2), K. D. Lawson1), A. Loarte9), G. Matthews1), G. R. McKee8)10), A. Meigs1), A. Messiaen4), F. Milani1), P. Monier-Garbet11), M. Murakami6)8), M. F. F. Nave12), J. Ongena4), M. E. Puiatti13), E. Rachlew14), J. Rapp2), S. Sharapov1), G. M. Staebler8), M. Stamp1), J. D. Strachan3), G. Telesca13), M. Z. Tokar2), B. Unterberg2), M. Valisa13), K.-D. Zastrow1), and EFDA-JET 2000 workprogramme contributors
 
1) EURATOM/UKAEA Fusion Association, Culham, UK
2) IPP, Forschungszentrum Jülich GmbH, EURATOM Association, D-52425 Jülich, Germany
3) Princeton Plasma Physics Laboratory, Princeton University, NJ 08543, USA
4) LPP/ERM-KMS, Association EURATOM-Belgian State, B-1000 Brussels, Belgium
5) FOM-IVP, EURATOM Association, Postbus 1207, NL-3430 BE Nieuwegein, Netherlands
6) ORNL, Oak Ridge, TN 37831-8072, USA
7) Max-Planck IPP, EURATOM Association, D-85748 Garching, Germany
8) DIII-D National Fusion Facility, San Diego, CA 92186-5698, USA
9) EFDA-CSU, D-85748 Garching, Germany
10) University of Wisconsin-Madison, Madison, Wisconsin, USA
11) CEA Cadarache, F-13108 St Paul lez Durance, France
12) CFN, EURATOM-IST Associação,1096 Lisbon, Portugal
13) Consorzio RFX, Corso Stati Uniti 4, 35127 Padova, Italy
14) Association Euratom-NFR, KTH, Stockholm, Sweden

Abstract.  Scaling to larger tokamaks of high confinement plasmas with radiating edges is being studied through internationally collaborative experiments on JET. Three different configurations have been explored. A small number of limiter L-mode discharges have most closely repeated the approach used on TEXTOR-94. Divertor L-modes at intermediate density have pursued transiently improved states found on DIII-D. An original scheme has also examined impurity seeding of higher density ELMy H-modes, formed either in a novel pumped-limiter like arrangement, or again in divertor geometry. While strongly peaked density profiles thought to be important in TEXTOR-94 have not generally been produced, nevertheless beneficial effects have similarly emerged in JET. Confinement up to H-mode quality, together with radiation fractions of $ \approx$ 40%, has briefly been obtained in divertor L-modes. Most notably, ELMy H-mode confinement has been sustained at densities close to the Greenwald level, with little change of central Zeff but up to $ \approx$ 60% radiation, in long, ``afterpuff'' phases following the end of main gas fuelling. Outstanding products of normalized confinement and normalized density H97 . fGwd $ \approx$ 0.9 have consequently been achieved. Marked reductions in the frequency of accompanying ELMs are generally also induced.

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IAEA 2001