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          Institute: MPI für Plasmaphysik     Collection: Conference Papers     Display Documents

ID: 60350.0, MPI für Plasmaphysik / Conference Papers
Observations of pre- and postcursor modes of type-I ELMs on JET
Authors:Koslowski, H. R.; Perez, C.; Alper, B.; Eich, T.; Hender, T. C.; Huysmans, G. T. A.; Shaparov, S. E.; Smeulders, P.; Westerhof, E.; JET EFDA Contributors
Publisher:International Atomic Energy Agency
Place of Publication:Vienna
Date of Publication (YYYY-MM-DD):2003
Title of Proceedings:Fusion Energy 2002
Sequence Number:EX/P1-14
Physical Description:CD-ROM
Name of Conference/Meeting:19th Fusion Energy Conference
Place of Conference/Meeting:Lyon (FR)
(Start) Date of Conference/Meeting
End Date of Conference/Meeting 
Review Status:Internal review
Audience:Experts Only
Abstract / Description:Recent observations of MHD activity in type-I ELMy H-mode discharges on JET have revealed two phenomena: (i) the so-called palm tree mode, a new, snake-like MHD mode at the q=3 surface which is excited by type-I ELMs, and (ii) coherent MHD mode activity as a precursor to the ELM collapse. Both modes are detected by magnetic pick up coils and can also be seen on the edge ECE and SXR measurements. They are located a few cm inside the separatrix. Palm tree modes have been identified in a wide range of plasma conditions, which comprise standard ELMy H-modes, ITER-like plasma shapes, pellet fuelling, and even pure helium plasmas. The mode frequency increases in time and starts to saturate until the mode finally decays. A likely explanation of the palm tree mode is, that it is the remnant of an (3,1)-island created due to edge ergodisation by the ELM perturbation. Refined methods of data evaluation allowed to identified low frequency coherent type-I ELM precursor modes with toroidal mode numbers in the range 2 to 14. They seem to have a kink-like structure, and appear normally 0.5-1ms before the ELM, but in many cases even much earlier.
External Publication Status:published
Document Type:Conference-Paper
Communicated by:N. N.
Affiliations:MPI für Plasmaphysik/Tokamak Scenario Development (E1)
External Affiliations:Association EURATOM-FZ Jülich, Institut für Plasmaphysik, Trilateral Euregio Cluster, Jülich, Germany; EURATOM-UKAEA Fusion Ass., Culham Science Centre, Abingdon, Oxfordshire UK; Ass. EURATOM-CEA, Cadarache, St. Paul-lez-Durance, France; Ass. EURATOM-Enea, Centro Ricerche Frascati, Italy; FOM-Rijnhiuzen, Ass. EURATOM-FOM, TEC, Nieuwegein, Netherlands
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