Identification of the beta limit in ASDEX Upgrade
Paper in proceeding, 2013

Tokamak plasma is a subject of various resistive and ideal MHD instabilities which restrict the operation space of the device. For largest fusion outcome, it is preferable to operate the tokamak close to the stability limit with maximal possible pressure characterized by the value of normalized beta, , and thus maximal fusion power . In ASDEX Upgrade, the limit for maximal achievable is typically set by the resistive instabilities (tearing modes). If these instabilities are overcome or prevented, higher values of the normalized beta can be reached limited by the onset of the ideal kink instability. The actual limit depends on several factors, including the stabilizing influence of the conducting components facing the plasma surface. At present, the wall elements are far from the plasma and the stability boundary is expected to be close to the “no wall” limit (no stabilizing wall effect). Investigation of maximum achievable βN values for the different operation scenario in ASDEX Upgrade is presented in this work. Two indicators are used to detect the stability boundary: Increase of the resonant field amplification (RFA) Onset of the ideal kink mode Recently installed internal active coils are used to probe stability of the plasma by the RFA technique. A wide range of different MHD diagnostics are used to identify the behaviour and structure of MHD modes in different discharges with high . Experimentally obtained results are compared with the results of the numerical modelling with linear MHD codes CASTOR-FLOW and MARS-K. Such comparison allows to validate the plasma model used in the codes and therefore to make numerical projection for further experimental studies.

MHD stability

ideal kink modes

Asdex Upgrade

Fusion plasmas


pressure limit


Valentin Igochine

Max Planck Society

L.B. Orte

Max Planck Society

Mikhail Gryaznevich

Culham Science Centre

Jorg Hobirk

Max Planck Society

Mark Maraschek

Max Planck Society

P. McCarthy

University College Cork

Mattias Reich

Max Planck Society

Dimitriy Yadykin

Chalmers, Earth and Space Sciences, Plasma Physics and Fusion Energy

40th EPS Conference on Plasma Physics, EPS 2013, Espoo, Finland, 1-5 July 2013

Vol. 2 1414-1417
978-163266310-8 (ISBN)

Areas of Advance



Basic sciences

Subject Categories

Fusion, Plasma and Space Physics



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