ITB formation in terms of wExB flow shear and magnetic shear s on JET

Tuomas Tala, Jukka Heikkinen, V. Parail

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    A linear empirical threshold condition ωExBITG>0.68s-0.095 has been found for the onset of the ion internal transport barriers in the JET optimised shear database. Here, s is the magnetic shear, ωExB the flow shearing rate and γITG is an approximate of the linear growth rate of the ion temperature gradient instability. The present empirical threshold condition for the ITB formation will provide a first clear indication of the strong correlation of s and ωExB at the ITB transition. The empirical analysis consists of ITB discharges from a wide plasma parameter range; the toroidal magnetic field varies between 1.8-4.0 T, the auxiliary heating power between 10-30 MW and the diamagnetic energy between 3-12 MJ. The predictive simulations of several ITB discharges with the empirical ITB threshold condition reproduce the experiments with time averaged prediction errors of the order of 10-25% in Ti and Te profiles and 10-15% in ne profiles as well as the toroidal flow velocity with errors of the order of 10-20%. The simulated times of the onset of the ITB compared to the experimental ones are typically within 0.4 s and the simulated ITB widths within 0.1 in r/a throughout the whole simulations.
    Original languageEnglish
    Pages (from-to)507-523
    Number of pages17
    JournalPlasma Physics and Controlled Fusion
    Issue number4
    Publication statusPublished - 2001
    MoE publication typeA1 Journal article-refereed


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