Multiresonance effect in type-I edge-localized mode control with low n fields on JET.
Multiple resonances in the edge-localized mode (ELM) frequency (f(ELM)) as a function of the edge safety factor q(95) have been observed for the first time with an applied low n (=1,2) field on the JET tokamak. Without an n=1 field applied, f(ELM) increases slightly from 20 to 30 Hz by varying the q(95) from 4 to 5 in a type-I ELMy H-mode plasma. However, with an n=1 field applied, a strong increase in f(ELM) by a factor of 4-5 has been observed with resonant q(95) values, while the f(ELM) increased only by a factor of 2 for nonresonant values. A model, which assumes that the ELM width is determined by a localized relaxation triggered by an unstable ideal external peeling mode, can qualitatively predict the observed resonances when low n fields are applied.
Liang
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Forschungszentrum Jülich GmbH, Association EURATOM-FZ Jülich, Institut für Energieforschung--Plasmaphysik, Trilateral Euregio Cluster, D-52425 Jülich, Germany. y.liang@fz-juelich.de
Gimblett
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Browning
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Devoy
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Koslowski
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Jachmich
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Sun
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Wiegmann
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