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Title: Transport barriers in bootstrap-driven tokamaks

Abstract

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.

Authors:
ORCiD logo [1];  [1]; ORCiD logo [2];  [1];  [1]; ORCiD logo [1]
  1. General Atomics, San Diego, CA (United States)
  2. Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics (IPP)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1459670
Alternate Identifier(s):
OSTI ID: 1438969
Grant/Contract Number:  
FC02-04ER54698; FG02-95ER54309
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; plasma flows; energy transfer; plasma confinement; tokamaks; plasma instabilities; electric currents; self assembly; electrostatics

Citation Formats

Staebler, G. M., Garofalo, A. M., Pan, C., McClenaghan, J., Van Zeeland, M. A., and Lao, L. L. Transport barriers in bootstrap-driven tokamaks. United States: N. p., 2018. Web. doi:10.1063/1.5019282.
Staebler, G. M., Garofalo, A. M., Pan, C., McClenaghan, J., Van Zeeland, M. A., & Lao, L. L. Transport barriers in bootstrap-driven tokamaks. United States. https://doi.org/10.1063/1.5019282
Staebler, G. M., Garofalo, A. M., Pan, C., McClenaghan, J., Van Zeeland, M. A., and Lao, L. L. Thu . "Transport barriers in bootstrap-driven tokamaks". United States. https://doi.org/10.1063/1.5019282. https://www.osti.gov/servlets/purl/1459670.
@article{osti_1459670,
title = {Transport barriers in bootstrap-driven tokamaks},
author = {Staebler, G. M. and Garofalo, A. M. and Pan, C. and McClenaghan, J. and Van Zeeland, M. A. and Lao, L. L.},
abstractNote = {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.},
doi = {10.1063/1.5019282},
url = {https://www.osti.gov/biblio/1459670}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 5,
volume = 25,
place = {United States},
year = {2018},
month = {5}
}

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Cited by: 3 works
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Figures / Tables:

Figure 1 Figure 1: Curve fits to measured profiles of the (a) electron temperature, (b) ion temperature, (c) electron density, (d) toroidal velocity of carbon for the strong ITB (black) and weak ITB (gray) discharges.

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