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Confinement transitions in TJ-II under Li-coated wall conditions

Confinement transitions in TJ-II under Li-coated wall conditions,10.1088/0029-5515/49/10/104018,Nuclear Fusion,J. Sánchez,M. Acedo,A. Alonso,J. Alonso

Confinement transitions in TJ-II under Li-coated wall conditions   (Citations: 5)
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J. Sánchez, M. Acedo, A. Alonso, J. Alonso, P. Alvarez, E. Ascasíbar, A. Baciero, R. Balbín, L. Barrera, E. Blanco, J. Botija, A. de Bustoshttp://academic.research.microsoft.com/io.ashx?type=5&id=10045813&selfId1=0&selfId2=0&maxNumber=12&query=
This paper presents the latest results on confinement studies in the TJ-II stellarator. The inherently strong plasma-wall interaction of TJ-II has been successfully reduced after lithium coating by vacuum evaporation. Besides H retention and low Z, Li was chosen because there exists a reactor-oriented interest in this element, thus giving special relevance to the investigation of its properties. The Li-coating has led to important changes in plasma performance. Particularly, the effective density limit in NBI plasmas has been extended reaching central values of 8 × 1019 m-3 and Te ≈ 250-300 eV, with peaked density, rather flat Te profiles and higher ion temperatures. Due to the achieved density control, a second type of transition has been added to the low density ones previously observed in ECRH plasmas: higher density transitions characterized by the fall in Halpha emission, the onset of steep density gradient and the reduction in the turbulence; which are characteristics of transition to the H mode. Confinement studies in ECH plasmas indicate that lowest order magnetic resonances, even in a low shear environment, locally reduce the effective electron heat diffusivities, while Alfven eigenmodes destabilized in NBI plasmas can influence fast ion confinement.
Journal: Nuclear Fusion - NUCL FUSION , vol. 49, no. 10, 2009
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    • ...TJ-II is an experimental magnetic confinement fusion device [12] constructed in a heliac configuration at the Asociacion EURATOM-Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMA T) in Madrid, Spain...
    • ...At present, each NBI provides up to 450 kW of additional heating (tNBI ::; 100 ms) and, as a result, plasmas with ne(O) ::; 5 x 1019 m-3 have been attained with a lithium coating on the vacuum vessel wall [12]...

    S. K. Combset al. A new four-barrel pellet injection system for the TJ-II stellarator

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