Impact of the α parameter on the microstability of internal transport barriers

C. Bourdelle, G.T. Hoang, X. Litaudon, C.M. Roach, Tuomas Tala

    Research output: Contribution to journalArticleScientificpeer-review

    46 Citations (Scopus)

    Abstract

    In plasmas exhibiting an internal transport barrier (ITB), locally very high pressure gradient (∇P) is obtained. It induces high values of the magnetohydrodynamic α parameter (α = −q 2 βRP/P, with R the major radius, q the safety factor, P the pressure, ∇ the radial gradient and β the ratio between kinetic and magnetic pressure). Similarly to low or negative magnetic shear (s), high α reduces the curvature and ∇ B drifts driving curvature-type microinstabilities. Therefore, high values of α can stabilize part of the microturbulence, which leads to higher pressure gradient and to even higher α. This possibility for entering a positive feedback loop is very attractive to sustain ITBs in high performance plasmas. Indeed, α scales favourably with higher pressure and does not require any external momentum input. In this paper, after having discussed the α stabilization mechanism in detail, we report the experimental microstability analyses of ITBs from an international multi-machine database—the International Tokamak Physics Activity database, accessible on the webb. We show that α is indeed a relevant parameter of ITB physics that should be taken into account in interpretative and predictive one-dimensional transport codes.
    Original languageEnglish
    Pages (from-to)110 - 130
    Number of pages21
    JournalNuclear Fusion
    Volume45
    Issue number2
    DOIs
    Publication statusPublished - 2005
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    pressure gradients
    curvature
    safety factors
    positive feedback
    physics
    magnetohydrodynamics
    stabilization
    shear
    momentum
    gradients
    radii
    kinetics

    Keywords

    • JET
    • plasma
    • fusion energy
    • fusion reactors
    • internal transport barriers

    Cite this

    Bourdelle, C. ; Hoang, G.T. ; Litaudon, X. ; Roach, C.M. ; Tala, Tuomas. / Impact of the α parameter on the microstability of internal transport barriers. In: Nuclear Fusion. 2005 ; Vol. 45, No. 2. pp. 110 - 130.
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    title = "Impact of the α parameter on the microstability of internal transport barriers",
    abstract = "In plasmas exhibiting an internal transport barrier (ITB), locally very high pressure gradient (∇P) is obtained. It induces high values of the magnetohydrodynamic α parameter (α = −q 2 βR∇P/P, with R the major radius, q the safety factor, P the pressure, ∇ the radial gradient and β the ratio between kinetic and magnetic pressure). Similarly to low or negative magnetic shear (s), high α reduces the curvature and ∇ B drifts driving curvature-type microinstabilities. Therefore, high values of α can stabilize part of the microturbulence, which leads to higher pressure gradient and to even higher α. This possibility for entering a positive feedback loop is very attractive to sustain ITBs in high performance plasmas. Indeed, α scales favourably with higher pressure and does not require any external momentum input. In this paper, after having discussed the α stabilization mechanism in detail, we report the experimental microstability analyses of ITBs from an international multi-machine database—the International Tokamak Physics Activity database, accessible on the webb. We show that α is indeed a relevant parameter of ITB physics that should be taken into account in interpretative and predictive one-dimensional transport codes.",
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    Impact of the α parameter on the microstability of internal transport barriers. / Bourdelle, C.; Hoang, G.T.; Litaudon, X.; Roach, C.M.; Tala, Tuomas.

    In: Nuclear Fusion, Vol. 45, No. 2, 2005, p. 110 - 130.

    Research output: Contribution to journalArticleScientificpeer-review

    TY - JOUR

    T1 - Impact of the α parameter on the microstability of internal transport barriers

    AU - Bourdelle, C.

    AU - Hoang, G.T.

    AU - Litaudon, X.

    AU - Roach, C.M.

    AU - Tala, Tuomas

    PY - 2005

    Y1 - 2005

    N2 - In plasmas exhibiting an internal transport barrier (ITB), locally very high pressure gradient (∇P) is obtained. It induces high values of the magnetohydrodynamic α parameter (α = −q 2 βR∇P/P, with R the major radius, q the safety factor, P the pressure, ∇ the radial gradient and β the ratio between kinetic and magnetic pressure). Similarly to low or negative magnetic shear (s), high α reduces the curvature and ∇ B drifts driving curvature-type microinstabilities. Therefore, high values of α can stabilize part of the microturbulence, which leads to higher pressure gradient and to even higher α. This possibility for entering a positive feedback loop is very attractive to sustain ITBs in high performance plasmas. Indeed, α scales favourably with higher pressure and does not require any external momentum input. In this paper, after having discussed the α stabilization mechanism in detail, we report the experimental microstability analyses of ITBs from an international multi-machine database—the International Tokamak Physics Activity database, accessible on the webb. We show that α is indeed a relevant parameter of ITB physics that should be taken into account in interpretative and predictive one-dimensional transport codes.

    AB - In plasmas exhibiting an internal transport barrier (ITB), locally very high pressure gradient (∇P) is obtained. It induces high values of the magnetohydrodynamic α parameter (α = −q 2 βR∇P/P, with R the major radius, q the safety factor, P the pressure, ∇ the radial gradient and β the ratio between kinetic and magnetic pressure). Similarly to low or negative magnetic shear (s), high α reduces the curvature and ∇ B drifts driving curvature-type microinstabilities. Therefore, high values of α can stabilize part of the microturbulence, which leads to higher pressure gradient and to even higher α. This possibility for entering a positive feedback loop is very attractive to sustain ITBs in high performance plasmas. Indeed, α scales favourably with higher pressure and does not require any external momentum input. In this paper, after having discussed the α stabilization mechanism in detail, we report the experimental microstability analyses of ITBs from an international multi-machine database—the International Tokamak Physics Activity database, accessible on the webb. We show that α is indeed a relevant parameter of ITB physics that should be taken into account in interpretative and predictive one-dimensional transport codes.

    KW - JET

    KW - plasma

    KW - fusion energy

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