title: Multiresonance effect in type-I edge-localized mode control with low n fields on JET.
abstract: 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.
authors.affiliation: Forschungszentrum Jülich GmbH, Association EURATOM-FZ Jülich, Institut für Energieforschung--Plasmaphysik, Trilateral Euregio Cluster, D-52425 Jülich, Germany. y.liang@fz-juelich.de
authors.forename: Y
authors.initials: Y
authors.lastname: Liang
authors.forename: C G
authors.initials: CG
authors.lastname: Gimblett
authors.forename: P K
authors.initials: PK
authors.lastname: Browning
authors.forename: P
authors.initials: P
authors.lastname: Devoy
authors.forename: H R
authors.initials: HR
authors.lastname: Koslowski
authors.forename: S
authors.initials: S
authors.lastname: Jachmich
authors.forename: Y
authors.initials: Y
authors.lastname: Sun
authors.forename: C
authors.initials: C
authors.lastname: Wiegmann