MULTICHANNEL ELECTRON-CYCLOTRON EMISSION RADIOMETRY FOR MAGNETOHYDRODYNAMIC MODE STUDIES IN TEXTOR

Localized magnetohydrodynamic modes occur frequently as precursors to dangerous plasma disruptions in tokamaks. Fast electron cyclotron emis sion (ECE) radiometry permits a space-resolved study of the dynamic be havior of these instabilities. Two types of multichannel, heterodyne E CE systems working on TEXTOR are briefly described. Temperature profil e perturbations caused by tearing modes are shown. Typical T-e fluctua tions generated by rotating magnetic islands are presented. An early d isruption warning system was built and tested on TEXTOR discharges. A real-time cross correlation calculation of two ECE signals is used to identify an m=2 mode. An analog alarm signal is generated then early d uring the instability evolution. An experimental test result is presen ted from a beam-heated tokamak plasma. (C) 1997 American Institute of Physics.