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  • GAE detection for mass measurement for D-T ratio control: Measurment of the effective plasma ion mass in large tokamaks using global Alfvén eigenmodes; and GAE detection for mass measurement for plasma density control

Abstract

One of the simpler measurements put forward in the past for determining the ratio in the centre of a tokamak plasma is the interpretation of the magnetohydrodynamic (MHD) spectrum in the frequency range of the global Alfvén eigenmodes (GAE). This method has been used to assess its likely precision for the JET tokamak. Results show that the low-n GAE modes are sometimes too close to the continuum edge to be detectable and that the interpretation of the GAE spectrum is therefore rendered less direct than had been hoped. However, information on the effective plasma ion mass is still available in the detectable modes and a statistical study is presented on the precision with which this quantity could be estimated from the GAE spectrum on JET.

In view of the interest in obtaining a direct mass measurement in JET D-T plasmas, ultimately for D/T ratio control, numerical simulation work has been performed to verify the underlying method. The work undertaken is described and the conclusions are presented. The use of the GAE in JET is concluded to be less interesting than initially hoped. The reasons are discussed. .

Additional information

Authors: LISTER J B, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne (CH);VILLARD L, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne (CH);DE RIDDER G, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne (CH)
Bibliographic Reference: Article: Plasma Physics and Controlled Fusion (1997)
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