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  Observations of pre- and postcursor modes of type-I ELMs on JET

Koslowski, H. R., Perez, C., Alper, B., Eich, T., Hender, T. C., Huysmans, G. T. A., et al. (2003). Observations of pre- and postcursor modes of type-I ELMs on JET. In Fusion Energy 2002. Vienna: International Atomic Energy Agency.

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 Creators:
Koslowski, H. R.1, Author
Perez, C.1, Author
Alper, B.1, Author
Eich, T.2, Author              
Hender, T. C.1, Author
Huysmans, G. T. A.1, Author
Shaparov, S. E.1, Author
Smeulders, P.3, Author              
Westerhof, E.1, Author
JET EFDA Contributors, Author              
Affiliations:
1Association 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, ou_persistent22              
2Experimental Plasma Physics 1 (E1), Max Planck Institute for Plasma Physics, Max Planck Society, ou_1856295              
3External Organizations, ou_persistent22              

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 Abstract: 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.

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Language(s): eng - English
 Dates: 2003
 Publication Status: Published in print
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 Rev. Type: Internal
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Title: 19th Fusion Energy Conference
Place of Event: Lyon (FR)
Start-/End Date: 2002-10-14 - 2002-10-19

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Title: Fusion Energy 2002
Source Genre: Proceedings
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Publ. Info: Vienna : International Atomic Energy Agency
Pages: CD-ROM Volume / Issue: - Sequence Number: EX/P1-14 Start / End Page: - Identifier: -