Creation and sustainment of wide pedestal quiescent H-mode with zero net neutral beam torque

Recent experiments on DIII-D have shown it is possible to create and sustain wide pedestal quiescent H-mode (QH-mode) plasmas with zero net torque from neutral beam injection (NBI) for the full discharge duration. Wide pedestal QH-mode has many of the features of the previously investigated QH-mode...

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Bibliographic Details
Published in:Nuclear fusion 2020-08, Vol.60 (8), p.86005
Main Authors: Burrell, K.H., Chen, Xi, Chrystal, C., Ernst, D.R., Grierson, B.A., Haskey, S.R., Osborne, T.H., Paz-Soldan, C., Wilks, T.M.
Format: Article
Language:English
Subjects:
elm-free operation
H-mode
magnetic fusion
zero neutral beam torque
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Summary:Recent experiments on DIII-D have shown it is possible to create and sustain wide pedestal quiescent H-mode (QH-mode) plasmas with zero net torque from neutral beam injection (NBI) for the full discharge duration. Wide pedestal QH-mode has many of the features of the previously investigated QH-mode while having the advantage of increased edge pedestal pressure and excellent energy confinement time. Both QH-mode variants operate without edge localized modes. Accordingly, these new discharges demonstrate that significant input torque is not essential to the exploitation of wide pedestal QH-mode in future devices that are expected to have small or non-existent NBI torque. Developing operating conditions that allowed net zero torque access to wide pedestal QH-mode required implementing several techniques to avoid locked modes including minimizing intrinsic error fields, avoiding large sawteeth, and driving toroidal rotation via neoclassical toroidal viscosity.
ISSN:0029-5515
1741-4326
DOI:10.1088/1741-4326/ab940d