Gyrotron Collective Thomson Scattering Diagnostics of Fast Ions in Textor and Asdex Upgrade

Abstract

Summary form only given. A critical need exists for confined fast ion diagnostics in tokamak fusion experiments, particularly for fusion product alpha particles in ITER and future fusion burning experiments. To develop this diagnostic capability and in support of current fast ion plasma physics research, collective Thomson scattering (CTS) diagnostics have been implemented at TEXTOR and ASDEX Upgrade (AUG) tokamaks using available gyrotron infrastructure with the addition of sensitive scattered signal receiver systems. At TEXTOR a 180 kW, 110 GHz gyrotron and a 42 channel. 6 GHz bandwidth heterodyne receiver has achieved up to 100 CTS scattered spectra per plasma shot with 4 ms time and 10 cm spatial resolution. Large scattering angles (~160deg) with steerable optics enable observation of fast ion spatial and field orientation anisotropies. Studies of fast ion dynamics behavior with neutral beam injection (NBI) and ion cyclotron heating have commenced, resulting in unique observations of fast ions redistributions during sawteeth and slow down after NBI turn off. At AUG a 1 MW, 105 GHz mode of a two-frequency gyrotron with a 50 channel, 10 GHz bandwidth receiver is becoming operational for CTS diagnostics with resolutions similar to TEXTOR. Precise gyrotron frequency measurements, notch filter timing, transmission line alignments, and receiver field of view mappings inside the tokamak have been accomplished using novel beam profile instrumentation. AUG-CTS commissioning progress will be presented. Plasma measurements in AUG are expected to provide new insights into fast ion physics and to further validate gyrotron CTS as a fast ion diagnostic tool for ITER.