title: Temporal evolution of confined fast-ion velocity distributions measured by collective Thomson scattering in TEXTOR.
abstract: Fast ions created in the fusion processes will provide up to 70% of the heating in ITER. To optimize heating and current drive in magnetically confined plasmas insight into fast-ion dynamics is important. First measurements of such dynamics by collective Thomson scattering (CTS) were recently reported [Bindslev, Phys. Rev. Lett. 97, 205005 2006]. Here we extend the discussion of these results which were obtained at the TEXTOR tokamak. The fast ions are generated by neutral-beam injection and ion-cyclotron resonance heating. The CTS system uses 100-150kW of 110-GHz gyrotron probing radiation which scatters off the collective plasma fluctuations driven by the fast-ion motion. The technique measures the projected one-dimensional velocity distribution of confined fast ions in the scattering volume where the probe and receiver beams cross. By shifting the scattering volume a number of scattering locations and different resolved velocity components can be measured. The temporal resolution is 4ms while the spatial resolution is approximately 10cm depending on the scattering geometry. Fast-ion velocity distributions in a variety of scenarios are measured, including the evolution of the velocity distribution after turnoff of the ion heating. These results are in close agreement with numerical simulations.
authors: Technical University of Denmark, DK-4000 Roskilde, Denmark. stefan.kragh.nielsen@risoe.dk
authors: S K
authors: SK
authors: Nielsen
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authors: Bindslev
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authors: Porte
authors: J A
authors: JA
authors: Hoekzema
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authors: SB
authors: Korsholm
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authors: Leipold
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authors: Meo
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authors: PK
authors: Michelsen
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authors: Michelsen
authors: J W
authors: JW
authors: Oosterbeek
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authors: EL
authors: Tsakadze
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authors: Van Wassenhove
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authors: Westerhof
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authors: Woskov