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P: Plasmaphysik

P 3: Magnetischer Einschluß 1

P 3.6: Talk

Monday, March 27, 2006, 16:15–16:30, 1004

A Characterisation of Alfvenic Instabilities at ASDEX Upgrade and its use in the reconstruction of Current density profiles — •K. Sassenberg¹, H. Zohm², S. Guenter², M. Maraschek², P. McCarthy¹, S. Da Graca³, and ASDEX Upgrade Team² — ¹Physics Department, University College Cork, Ireland — ²Max-Planck-Institut fuer Plasmaphysik, EURATOM Assoc., Garching bei Muenchen — ³Centro de Fusao Nuclear, Assoc. cao EURATOM IST, Instituto Superior Tecnico, Av. Rovisco Pais, P-1049-001 Lisboa, Portugal

In a tokamak plasma, knowledge of the toroidal plasma current profile is essential for the calculation of plasma equilibrium and plasma stability against MHD phenomena. Thus the study of the MHD activity of eigenmodes can therefore reveal information about the current profile within the plasma. In a magnetised plasma, Alfvén Eigenmodes with a characteristic velocity dependent on the safety factor q and density, can be excited by fast particles produced by Ion Cyclotron Resonance Heating (ICRH) through Inverse Landau Damping. Under certain plasma conditions various types of Alfven Eigenmodes such as the Toroidicity induced Alfvén Eigenmodes (TAE), Beta induced Alfven Eigenmodes (BAE) and Alfven Cascades (AC) are observed. A temporal variation of relevant plasma parameters allows a scan for these type of resonances. In addition, futher experiments revealed the ability of ICRH-Beatwaves specifically, to drive the very same TAE as with fast particles. This, and the ability to sweep the Beatwave frequency makes it possible to scan the q-profile during stationary plasma conditions. Thus improving current profile reconstruction.