Metal impurity transport control in JET H-mode plasmas with central ion cyclotron radiofrequency power injection

TitleMetal impurity transport control in JET H-mode plasmas with central ion cyclotron radiofrequency power injection
Publication TypeJournal Article
Year of Publication2011
AuthorsM. Valisa, L. Carraro, I. Predebon, M.E Puiatti, C. Angioni, I. Coffey, C. Giroud, L.L Taroni, B. Alper, M. Baruzzo, P.B da Silva, P. Buratti, L. Garzotti, D. Van Eester, E. Lerche, P. Mantica, V. Naulin, T. Tala, M. Tsalas
JournalNuclear Fusion
Volume51
Issue3
Number3
Pagination033002
Date PublishedMar
Type of ArticleArticle
ISBN Number0029-5515
KeywordsASDEX UPGRADE, BARRIER, BEHAVIOR, CONFINEMENT, DISCHARGES, divertor, FUSION DEVICES, NM REGION, TOKAMAK, Tungsten
Abstract

The scan of ion cyclotron resonant heating (ICRH) power has been used to systematically study the pump out effect of central electron heating on impurities such as Ni and Mo in H-mode low collisionality discharges in JET. The transport parameters of Ni and Mo have been measured by introducing a transient perturbation on their densities via the laser blow off technique. Without ICRH Ni and Mo density profiles are typically peaked. The application of ICRH induces on Ni and Mo in the plasma centre (at normalized poloidal flux rho = 0.2) an outward drift approximately proportional to the amount of injected power. Above a threshold of ICRH power of about 3 MW in the specific case the radial flow of Ni and Mo changes from inwards to outwards and the impurity profiles, extrapolated to stationary conditions, become hollow. At mid-radius the impurity profiles become flat or only slightly hollow. In the plasma centre the variation of the convection-to-diffusivity ratio upsilon/D of Ni is particularly well correlated with the change in the ion temperature gradient in qualitative agreement with the neoclassical theory. However, the experimental radial velocity is larger than the neoclassical one by up to one order of magnitude. Gyrokinetic simulations of the radial impurity fluxes induced by electrostatic turbulence do not foresee a flow reversal in the analysed discharges.

DOI10.1088/0029-5515/51/3/033002
Division

FP

Department

PDG

PID

dc8bc3592b534a570ec367324f31bd67

Alternate TitleNucl. Fusion

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