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Experiments have been performed to disentangle the individual role of upper and lower triangularity on density build-up of lower single null, type-I ELMy H-mode discharges in JET. Comparison with corresponding data from ASDEX Upgrade allowed us to determine a dimensionless representation of the relation between the main chamber recycling and core density and to widen the triangularity variation in the database. To incorporate the recycling flux density Gamma in a dimensionless form, an effective scrape-off layer density n(e,SOL)alpha Gamma {0.5} is introduced allowing us to parametrize and scale the core density by the density rise factor n(e) / n(e,SOL). The scaling uses edge-specific definitions of normalized Larmor radius, collisionality and beta. Rewritten in dimensional form, a behaviour is found which is very similar to energy confinement scaling for the ELM-averaged conditions considered here: the density rise factor exhibits an almost linear dependence on plasma current, a weak negative toroidal field dependence as well as power degradation. While a pronounced positive dependence of density build-up on the upper triangularity is observed, no significant correlation with the lower triangularity is found. In particular the dependences on plasma current and upper triangularity emphasize the importance of transport physics for the density build-up.

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Authors: KALLENBACH A, Max-Planck-Institut für Plasmaphysik, Euratom Association, Garching (DE);SUTTROP W, Max-Planck-Institut für Plasmaphysik, Euratom Association, Garching (DE);BEURSKENS M N A, FOM `Rijnhuizen', EURATOM Association, Trilateral Euregio Cluster, Nieuwegein (NL);KOROTKOV A ET AL, EURATOM/UKAEA Fusion Association, Culham (GB);RAPP J, IPP FZ, EURATOM Association, Trilateral Euregio Cluster, Jülich (DE)
Bibliographic Reference: An article published in: Nuclear Fusion 42 (October 2002) 1184-1192
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Record Number: 200215673 / Last updated on: 2002-12-16
Original language: en
Available languages: en