| Autor: |
Fable, E, Angioni, C, Casson, F J, Told, D, Ivanov, A A, Jenko, F, McDermott, R M, Medvedev, S Yu, Pereverzev, G V, Ryter, F, Treutterer, W, Viezzer, E, Team, the ASDEX Upgrade |
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| Zdroj: |
Plasma Physics & Controlled Fusion; Dec2013, Vol. 55 Issue 12, p124028-124036, 9p |
| Abstrakt: |
Tokamak scenario development requires an understanding of the properties that determine the kinetic profiles in non-steady plasma phases and of the self-consistent evolution of the magnetic equilibrium. Current ramps are of particular interest since many transport-relevant parameters explore a large range of values and their impact on transport mechanisms has to be assessed. To this purpose, a novel full-discharge modelling tool has been developed, which couples the transport code ASTRA (Pereverzev et al 1991 IPP Report 5/42) and the free boundary equilibrium code SPIDER (Ivanov et al 2005 32nd EPS Conf. on Plasma Physics vol 29C (ECA) P-5.063 and http://epsppd.epfl.ch/Tarragona/pdf/P5_063.pdf), utilizing a specifically designed coupling scheme. The current ramp-up phase can be accurately and reliably simulated using this scheme, where a plasma shape, position and current controller is applied, which mimics the one of ASDEX Upgrade. Transport of energy is provided by theory-based models (e.g. TGLF (Staebler et al 2007 Phys. Plasmas14 055909)). A recipe based on edge-relevant parameters (Scott 2000 Phys. Plasmas7 1845) is proposed to resolve the low current phase of the current ramps, where the impact of the safety factor on micro-instabilities could make quasi-linear approaches questionable in the plasma outer region. Current ramp scenarios, selected from ASDEX Upgrade discharges, are then simulated to validate both the coupling with the free-boundary evolution and the prediction of profiles. Analysis of the underlying transport mechanisms is presented, to clarify the possible physics origin of the observed L-mode empirical energy confinement scaling. The role of toroidal micro-instabilities (ITG, TEM) and of non-linear effects is discussed. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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