Characteristics of the First [Formula presented]-Mode Discharges in the National Spherical Torus Experiment

R. Maingi, C. E. Bush, Y. K.M. Peng, M. G. Bell, R. E. Bell, E. D. Fredrickson, D. A. Gates, S. M. Kaye, H. W. Kugel, B. P. LeBlanc, J. E. Menard, D. Mueller, G. Taylor, D. W. Johnson, R. Kaita, M. Ono, S. F. Paul, A. L. Roquemore, C. H. Skinner, V. A. SoukhanovskiiE. J. Synakowski, S. A. Sabbagh, F. Paoletti, D. Stutman, R. J. Maqueda

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3 Scopus citations

Abstract

We report observations of the first low-to-high ([Formula presented]) confinement mode transitions in the National Spherical Torus Experiment. The [Formula presented]-mode energy confinement time increased over reference discharges transiently by [Formula presented], as high as [Formula presented]. This confinement time is [Formula presented] times higher than predicted by a multimachine scaling. Thus the confinement time of spherical tori has been extended to a record high value, leading to an eventual revision of confinement scalings. Finally, the power threshold for [Formula presented]-mode access is [Formula presented] higher than predicted by an international scaling from conventional aspect-ratio tokamaks, which could lead to new understanding of [Formula presented]-mode transition dynamics.

Original languageEnglish
Pages (from-to)4
Number of pages1
JournalPhysical Review Letters
Volume88
Issue number3
DOIs
StatePublished - 2002

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