Publication Type
Journal
Journal Name
Physical Review Letters
Publication Date
Page Numbers
1 to 4
Volume
105
Issue
13
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 the 3D fields could be applied to reduce edge transport in fusion devices.