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MHD and gyro-kinetic stability of JET pedestals
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.ORCID iD: 0000-0002-9546-4494
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2013 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 53, no 12, 123012- p.Article in journal (Refereed) Published
Abstract [en]

The pedestal profile measurements in high triangularity JET plasmas show that with low fuelling the pedestal width decreases during the ELM cycle and with high fuelling it stays constant. In the low fuelling case the pedestal pressure gradient keeps increasing until the ELM crash and in the high fuelling case it initially increases then saturates during the ELM cycle. Stability analysis reveals that both JET plasmas become unstable to finite-n ideal MHD peeling-ballooning modes at the end of the ELM cycle. During the ELM cycle, n = infinity ideal MHD ballooning modes and kinetic ballooning modes are found to be locally stable in most of the steep pressure gradient region of the pedestal owing to the large bootstrap current, but to be locally unstable in a narrow region of plasma at the extreme edge. Unstable micro-tearing modes are found at the JET pedestal top, but they are sub-dominant to ion temperature gradient modes. They are insensitive to collisionality and stabilized by increasing density gradient.

Place, publisher, year, edition, pages
2013. Vol. 53, no 12, 123012- p.
Keyword [en]
Ballooning modes, Bootstrap current, Collisionality, Density gradients, Ion temperature gradient modes, Pedestal pressure, Profile measurement, Stability analysis
National Category
Fusion, Plasma and Space Physics
URN: urn:nbn:se:kth:diva-140163DOI: 10.1088/0029-5515/53/12/123012ISI: 000327787000014ScopusID: 2-s2.0-84878356304OAI: diva2:689351

QC 20140120

Available from: 2014-01-20 Created: 2014-01-17 Last updated: 2014-01-20Bibliographically approved

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Frassinetti, Lorenzo
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