A self-sustaining mechanism for internal transport barrier formation in HL-2A tokamak plasmas

The formation of Internal Transport Barrier (ITB) is studied in HL-2A plasmas by means of nonlinear gyrokinetic simulations. A new paradigm for the ITB formation is proposed in which different physics mechanisms play a different role depending on the ITB formation stage. In the early stage, fast ion...

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Bibliographic Details
Published in:Nuclear fusion 2023-12, Vol.63 (12), p.126048
Main Authors: Lin, W.H., Garcia, J., Li, J.Q., Mazzi, S., Li, Z.J., He, X.X., Yu, X.
Format: Article
Language:English
Subjects:
gyrokinetic simulation
internal transport barrier
Physics
Plasma Physics
tokamak
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Summary:The formation of Internal Transport Barrier (ITB) is studied in HL-2A plasmas by means of nonlinear gyrokinetic simulations. A new paradigm for the ITB formation is proposed in which different physics mechanisms play a different role depending on the ITB formation stage. In the early stage, fast ions, introduced by Neutral Beam Injection ion system, are found to stabilize the thermal-ion-driven instability by dilution, thus reducing the ion heat fluxes and finally triggering the ITB. Such dilution effects, however, play a minor role after the ITB is triggered as electromagnetic (EM) effects are dominant in the presence of established high pressure gradients. We define the concept of ITB self-sustainment, as the low turbulence levels found within the fully formed ITB are consequences of large scale zonal flows, which in turn are fed by a non-linear interplay with large scale high frequency EM perturbations destabilized by the ITB itself.
ISSN:0029-5515
1741-4326
DOI:10.1088/1741-4326/ad0508