Abstract
| Original language | English |
|---|---|
| Qualification | Doctor Degree |
| Awarding Institution |
|
| Award date | 9 Nov 2012 |
| Place of Publication | Espoo |
| Publisher | |
| Print ISBNs | 978-951-38-7467-4 |
| Electronic ISBNs | 978-951-38-7468-1 |
| Publication status | Published - 2012 |
| MoE publication type | G5 Doctoral dissertation (article) |
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Keywords
- JET
- tokamak
- fusion
- energy
- plasma
- toroidal rotation
- momentum transport
- fast ions
- neutral beam injection
- NBI
Cite this
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Fast ions and momentum transport in JET tokamak plasmas : Dissertation. / Salmi, Antti.
Espoo : VTT Technical Research Centre of Finland, 2012. 156 p.Research output: Thesis › Dissertation › Collection 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 -