Transport barriers in bootstrap-driven tokamaks

Staebler, G. M.; Garofalo, A. M.; Pan, C.; McClenaghan, J.; Van Zeeland, M. A.; Lao, L. L.

doi:10.1063/1.5019282

Title: Transport barriers in bootstrap-driven tokamaks

Journal Article · Thu May 24 00:00:00 EDT 2018 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.5019282· OSTI ID:1459670

^[1]; Garofalo, A. M. ^[1];

^[2]; McClenaghan, J. ^[1]; Van Zeeland, M. A. ^[1];

^[1]

General Atomics, San Diego, CA (United States)
Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics (IPP)

Experiments have demonstrated improved energy confinement due to the spontaneous formation of an internal transport barrier in high bootstrap fraction discharges. Gyro kinetic analysis, and quasilinear predictive modeling, demonstrates that the observed transport barrier is caused by the suppression of turbulence primarily from the large Shafranov shift. It is shown, that the Shafranov shift can produce a bifurcation to improved confinement in regions of positive magnetic shear or a continuous reduction in transport for weak or negative magnetic shear. Operation at high safety factor lowers the pressure gradient threshold for the Shafranov shift driven barrier formation. Two self-organized states of the internal and edge transport barrier are observed. It is further shown that these two states are controlled by the interaction of the bootstrap current with magnetic shear, and the kinetic ballooning mode instability boundary. Election scale energy transport is shown to be dominant in inner 60% of the profile. Energetic particle driven instabilities could also be playing a role in the thermal energy transport in this region.

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Research Organization:: General Atomics, San Diego, CA (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: FC02-04ER54698; FG02-95ER54309

OSTI ID:: 1459670

Alternate ID(s):: OSTI ID: 1438969

Journal Information:: Physics of Plasmas, Vol. 25, Issue 5; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 27 works

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