Fast ions and momentum transport in JET tokamak plasmas: Dissertation

    Research output: ThesisDissertationCollection of Articles

    Abstract

    Fast ions are an inseparable part of fusion plasmas. They can be generated using electromagnetic waves or injected into plasmas as neutrals to heat the bulk plasma and to drive toroidal rotation and current. In future power plants fusion born fast ions deliver the main heating into the plasma. Understanding and controlling the fast ions is of crucial importance for the operation of a power plant. Furthermore, fast ions provide ways to probe the properties of the thermal plasma and get insight of its confinement properties. In this thesis, numerical code packages are used and developed to simulate JET experiments for a range of physics issues related to fast ions. Namely, the clamping fast ion distribution at high energies with RF heating, fast ion ripple torque generation and the toroidal momentum transport properties using NBI modulation technique are investi gated. Through a comparison of numerical simulations and the JET experimental data it is shown that the finite Larmor radius effects in ion cyclotron resonance heating are important and that they can prevent fast ion tail formation beyond certain energy. The identified mechanism could be used for tailoring the fast ion distribution in future experiments. Secondly, ASCOT simulations of NBI ions in a ripplefield showed that most of the reduction of the toroidal rotation that has been observed in the JET enhanced ripple experiments could be attributed to fast ion ripple torque. Finally, fast ion torque calculations together with momentum transport analysis have led to the conclusion that momentum transport in not purely diffusive but that a convective component, which increases monotonically in radius, exists in a wide range of JET plasmas. Using parameter scans, the convective transport has been shown to be insensitive to collisionality and q-profile but to increase strongly against density gradient.
    Original languageEnglish
    QualificationDoctor Degree
    Awarding Institution
    • Aalto University
    Award date9 Nov 2012
    Place of PublicationEspoo
    Publisher
    Print ISBNs978-951-38-7467-4
    Electronic ISBNs978-951-38-7468-1
    Publication statusPublished - 2012
    MoE publication typeG5 Doctoral dissertation (article)

    Fingerprint

    momentum
    ions
    ripples
    torque
    ion distribution
    power plants
    heating
    fusion
    Larmor radius
    theses
    thermal plasmas
    cyclotron resonance
    electromagnetic radiation
    simulation
    transport properties
    modulation
    heat
    gradients
    physics
    radii

    Keywords

    • JET
    • tokamak
    • fusion
    • energy
    • plasma
    • toroidal rotation
    • momentum transport
    • fast ions
    • neutral beam injection
    • NBI

    Cite this

    Salmi, A. (2012). Fast ions and momentum transport in JET tokamak plasmas: Dissertation. Espoo: VTT Technical Research Centre of Finland.
    Salmi, Antti. / Fast ions and momentum transport in JET tokamak plasmas : Dissertation. Espoo : VTT Technical Research Centre of Finland, 2012. 156 p.
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    title = "Fast ions and momentum transport in JET tokamak plasmas: Dissertation",
    abstract = "Fast ions are an inseparable part of fusion plasmas. They can be generated using electromagnetic waves or injected into plasmas as neutrals to heat the bulk plasma and to drive toroidal rotation and current. In future power plants fusion born fast ions deliver the main heating into the plasma. Understanding and controlling the fast ions is of crucial importance for the operation of a power plant. Furthermore, fast ions provide ways to probe the properties of the thermal plasma and get insight of its confinement properties. In this thesis, numerical code packages are used and developed to simulate JET experiments for a range of physics issues related to fast ions. Namely, the clamping fast ion distribution at high energies with RF heating, fast ion ripple torque generation and the toroidal momentum transport properties using NBI modulation technique are investi gated. Through a comparison of numerical simulations and the JET experimental data it is shown that the finite Larmor radius effects in ion cyclotron resonance heating are important and that they can prevent fast ion tail formation beyond certain energy. The identified mechanism could be used for tailoring the fast ion distribution in future experiments. Secondly, ASCOT simulations of NBI ions in a ripplefield showed that most of the reduction of the toroidal rotation that has been observed in the JET enhanced ripple experiments could be attributed to fast ion ripple torque. Finally, fast ion torque calculations together with momentum transport analysis have led to the conclusion that momentum transport in not purely diffusive but that a convective component, which increases monotonically in radius, exists in a wide range of JET plasmas. Using parameter scans, the convective transport has been shown to be insensitive to collisionality and q-profile but to increase strongly against density gradient.",
    keywords = "JET, tokamak, fusion, energy, plasma, toroidal rotation, momentum transport, fast ions, neutral beam injection, NBI",
    author = "Antti Salmi",
    year = "2012",
    language = "English",
    isbn = "978-951-38-7467-4",
    series = "VTT Science",
    publisher = "VTT Technical Research Centre of Finland",
    number = "10",
    address = "Finland",
    school = "Aalto University",

    }

    Fast ions and momentum transport in JET tokamak plasmas : Dissertation. / Salmi, Antti.

    Espoo : VTT Technical Research Centre of Finland, 2012. 156 p.

    Research output: ThesisDissertationCollection of Articles

    TY - THES

    T1 - Fast ions and momentum transport in JET tokamak plasmas

    T2 - Dissertation

    AU - Salmi, Antti

    PY - 2012

    Y1 - 2012

    N2 - Fast ions are an inseparable part of fusion plasmas. They can be generated using electromagnetic waves or injected into plasmas as neutrals to heat the bulk plasma and to drive toroidal rotation and current. In future power plants fusion born fast ions deliver the main heating into the plasma. Understanding and controlling the fast ions is of crucial importance for the operation of a power plant. Furthermore, fast ions provide ways to probe the properties of the thermal plasma and get insight of its confinement properties. In this thesis, numerical code packages are used and developed to simulate JET experiments for a range of physics issues related to fast ions. Namely, the clamping fast ion distribution at high energies with RF heating, fast ion ripple torque generation and the toroidal momentum transport properties using NBI modulation technique are investi gated. Through a comparison of numerical simulations and the JET experimental data it is shown that the finite Larmor radius effects in ion cyclotron resonance heating are important and that they can prevent fast ion tail formation beyond certain energy. The identified mechanism could be used for tailoring the fast ion distribution in future experiments. Secondly, ASCOT simulations of NBI ions in a ripplefield showed that most of the reduction of the toroidal rotation that has been observed in the JET enhanced ripple experiments could be attributed to fast ion ripple torque. Finally, fast ion torque calculations together with momentum transport analysis have led to the conclusion that momentum transport in not purely diffusive but that a convective component, which increases monotonically in radius, exists in a wide range of JET plasmas. Using parameter scans, the convective transport has been shown to be insensitive to collisionality and q-profile but to increase strongly against density gradient.

    AB - Fast ions are an inseparable part of fusion plasmas. They can be generated using electromagnetic waves or injected into plasmas as neutrals to heat the bulk plasma and to drive toroidal rotation and current. In future power plants fusion born fast ions deliver the main heating into the plasma. Understanding and controlling the fast ions is of crucial importance for the operation of a power plant. Furthermore, fast ions provide ways to probe the properties of the thermal plasma and get insight of its confinement properties. In this thesis, numerical code packages are used and developed to simulate JET experiments for a range of physics issues related to fast ions. Namely, the clamping fast ion distribution at high energies with RF heating, fast ion ripple torque generation and the toroidal momentum transport properties using NBI modulation technique are investi gated. Through a comparison of numerical simulations and the JET experimental data it is shown that the finite Larmor radius effects in ion cyclotron resonance heating are important and that they can prevent fast ion tail formation beyond certain energy. The identified mechanism could be used for tailoring the fast ion distribution in future experiments. Secondly, ASCOT simulations of NBI ions in a ripplefield showed that most of the reduction of the toroidal rotation that has been observed in the JET enhanced ripple experiments could be attributed to fast ion ripple torque. Finally, fast ion torque calculations together with momentum transport analysis have led to the conclusion that momentum transport in not purely diffusive but that a convective component, which increases monotonically in radius, exists in a wide range of JET plasmas. Using parameter scans, the convective transport has been shown to be insensitive to collisionality and q-profile but to increase strongly against density gradient.

    KW - JET

    KW - tokamak

    KW - fusion

    KW - energy

    KW - plasma

    KW - toroidal rotation

    KW - momentum transport

    KW - fast ions

    KW - neutral beam injection

    KW - NBI

    M3 - Dissertation

    SN - 978-951-38-7467-4

    T3 - VTT Science

    PB - VTT Technical Research Centre of Finland

    CY - Espoo

    ER -

    Salmi A. Fast ions and momentum transport in JET tokamak plasmas: Dissertation. Espoo: VTT Technical Research Centre of Finland, 2012. 156 p.