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          Institute: MPI für Plasmaphysik     Collection: Articles, Books, Inbooks     Display Documents

ID: 20991.0, MPI für Plasmaphysik / Articles, Books, Inbooks
Impurity-seeded plasma experiments on JET
Authors:Maddison, G. P.; Brix, M.; Budny, R.; Charlet, M.; Coffey, I.; Cordey, J. G.; Dumortier, P.; Erents, S. K.; Hawkes, N. C.; von Hellermann, M.; Hillis, D. L.; Hogan, J.; Horton, L. D.; Ingesson, L. C.; Jachmich, S.; Jackson, G. L.; Kallenbach, A.; Koslowski, H. R.; Lawson, K. D.; Loarte, A.; Matthews, G. F.; McDonald, D.; McKee, G. R.; Meigs, A.; Messiaen, A. M.; Milani, F.; Monier-Garbet, P.; Murakami, M.; Nave, M. F. F.; Ongena, J.; Puiatti, M. E.; Rachlew, E.; Rapp, J.; Sharapov, S.; Staebler, G. M.; Stamp, M.; Strachan, J. D.; Suttrop, W.; Telesca, G.; Tokar, M. Z.; Unterberg, B.; Valisa, M.; Zastrow, K. D.
Date of Publication (YYYY-MM-DD):2003
Title of Journal:Nuclear Fusion
Journal Abbrev.:Nucl. Fusion
Start Page:49
End Page:62
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:Scaling to larger tokamaks of high confinement plasmas with radiating edges, induced by impurities, is being studied through internationally collaborative experiments on JET. In campaigns till the end of 2000, three different regimes have been explored. A small number of limiter L-mode discharges seeded with neon have most closely repeated the approach used on TEXTOR-94, but different collisionality and particle transport in JET impede central peaking of the density associated with improved confinement. Divertor L-modes at intermediate density, again with neon injection, have pursued transiently enhanced states found on DIII-D. Confinement up to H-mode quality, together with radiation fractions of approximate to40%, have briefly been obtained, though central Z(eff) quickly increases. Most effectively, neon and argon seeding of higher density ELMy H-modes formed mainly at low triangularity on the septum of the MkIIGB divertor, resembling a pumped-limiter arrangement, have been examined. Good confinement has been sustained at densities close to the Greenwald level in 'afterpuff' (AP) phases following the end of main gas fuelling, for little change of central Z(eff) but up to approximate to60% radiation. Outstanding normalized properties up to H-97 = 0.99 at f(Gwd) = 0.94 have thus been achieved, above the conventional H-mode density limit for diverted plasmas. Stationarity of states has also been extended to many energy confinement times by including low, extra gas inputs in the 'AP', suggestive of an optimized fuelling scheme. Further development in 2001 is reported separately in [1]. Accompanying ELMs are generally reduced in frequency though not evidently in size, electron pedestal pressure being almost unchanged from unseeded behaviour. There are indications of the most favourable impurity species scaling with plasma parameters, performance, radiation and its concentration within a mantle all increasing with argon compared to neon in JET. These benefits in terms of integrated properties are just as required for long burning pulses in ITER, supporting its use of a radiating mantle to assist not only power exhaust but performance too. Impurity-seeded H-modes can therefore contribute directly to next-step scenario development.
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Plasmaphysik/E1
External Affiliations:UKAEA Euratom Fus Assoc, Culham Sci Ctr, Abingdon OX14 3DB,; Oxon, England; Forschungszentrum Jülich GmbH, IPP, EURATOM Assoc, D-52425 Jülich, Germany; Princeton Univ, Princeton Plasma Phys Lab, Princeton, NJ 08543 USA; EURATOM Assoc Belgian State, LPP, ERM, KMS, B-1000 Brussels, Belgium; EURATOM, FOM IVP, NL-3430 BE Nieuwegein, Netherlands; Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA; DIIID Natl Fus Facil, San Diego, CA 92186 USA; CSU, EFDA, D-85748 Garching, Germany; Univ Wisconsin, Madison, WI USA; CEA Cadarache, F-13108 St Paul Les Durance, France; EURATOM IST Assoc, CFN, P-1096 Lisbon, Portugal; Consorzio RFX, I-35127 Padua, Italy; EURATOM Assoc NFR, KTH, Stockholm, Sweden
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