Description
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This paper describes joint ITPA studies of the I-mode regime, which features an edge thermal barrier but with L-mode-like particle and impurity transport, and without ELMs. The regime has been demonstrated on Alcator C-Mod, ASDEX Upgrade and DIII-D tokamaks, over a wide range of device parameters and pedestal conditions, including low collisionality. Access to I-mode is independent of heating method (neutral beam injection, ICRH and/or ECRH). Normalized energy confinement H98y,2 ≥ 1 has been achieved for a range of 3≤q95≤4.9 and scales favourably with power. Changes in turbulence in the pedestal region accompany the transition from L-mode to I-mode. The L-I threshold increases with plasma density and current, and with device size, but weakly with BT. The upper limit of power for I-modes increases with toroidal field, and is largest on Alcator C-Mod at B > 5 T. Issues for extrapolation to ITER and other future fusion devices are discussed.
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Notes
| PSFC REPORT PSFC/JA-14-43
Work in U.S. supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using User Facilities Alcator C-Mod and DIII-D, under Award Numbers DE-FC02-99ER54512-CMOD, DE-FC02-04ER54698, DE-FG02-94ER54235, DE-AC52-07NA27344, DE-AC02-09CH11466, DE-FG02-89ER53296, DE-FG02- 08ER54999, and DE-FG02-08ER54984. Reproduction, translation, publication, use and disposal, in whole or in part, by or for the United States government is permitted. |