title: Triggered confinement enhancement and pedestal expansion in high-confinement-mode discharges in the national spherical torus experiment.
abstract: We report observation of a new high performance regime in discharges in the National Spherical Torus Experiment, where the H mode edge "pedestal" temperature doubles and the energy confinement increases by 50%. The spontaneous transition is triggered by a large edge-localized mode, either natural or externally triggered by 3D fields. The transport barrier grows inward from the edge, with a doubling of both the pedestal pressure width and the spatial extent of steep radial electric field shear. The dynamics suggest that 3D fields could be applied to reduce edge transport in fusion devices.
authors.affiliation: Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: R
authors.initials: R
authors.lastname: Maingi
authors.forename: R E
authors.initials: RE
authors.lastname: Bell
authors.forename: J M
authors.initials: JM
authors.lastname: Canik
authors.forename: S P
authors.initials: SP
authors.lastname: Gerhardt
authors.forename: S M
authors.initials: SM
authors.lastname: Kaye
authors.forename: B P
authors.initials: BP
authors.lastname: Leblanc
authors.forename: T H
authors.initials: TH
authors.lastname: Osborne
authors.forename: M G
authors.initials: MG
authors.lastname: Bell
authors.forename: E D
authors.initials: ED
authors.lastname: Fredrickson
authors.forename: K C
authors.initials: KC
authors.lastname: Lee
authors.forename: J E
authors.initials: JE
authors.lastname: Menard
authors.forename: J-K
authors.initials: JK
authors.lastname: Park
authors.forename: S A
authors.initials: SA
authors.lastname: Sabbagh