title: High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak.
abstract: Tokamak experiments at near-unity aspect ratio A≲1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A∼3 plasmas, the L-H power threshold P_{LH} is ∼15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. These ultralow-A operations enable heretofore inaccessible J_{edge}(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.
authors.affiliation: Department of Engineering Physics, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA.
authors.forename: K E
authors.initials: KE
authors.lastname: Thome
authors.affiliation: Department of Engineering Physics, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA.
authors.forename: M W
authors.initials: MW
authors.lastname: Bongard
authors.affiliation: Department of Engineering Physics, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Barr
authors.affiliation: Department of Engineering Physics, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA.
authors.forename: G M
authors.initials: GM
authors.lastname: Bodner
authors.affiliation: Department of Engineering Physics, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Burke
authors.affiliation: Department of Engineering Physics, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Fonck
authors.affiliation: Department of Engineering Physics, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Kriete
authors.affiliation: Department of Engineering Physics, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Perry
authors.affiliation: Department of Engineering Physics, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Schlossberg