Visualization of instabilities in hot magnetized plasmas by ECE Imaging

Summary form only given. Electron cyclotron emission radiometry is a standard technique on most magnetically confined plasmas to measure the electron temperature profile, usually along the plasma mid plane. By combining heterodyne radiometry with optical imaging techniques it is possible to measure the electron temperature and fluctuations in this quantity in a two-dimensional section of the poloidal plasma plane. The first generation of these ECE Imaging devices was employed at the TEXT, RTP [Deng, B.H., et al., 1999 ] and TEXTOR [Wang, J., et al., 2004] tokamaks and typically featured 16 × 8 vertical × radial measuring channels. Later - and more modern - generation ECEI systems featured multiple measuring arrays (at the KSTAR [Yun, G.S., et al., 2010] and DIIID [Tobias, B, et al., 2010] tokamaks), zooming options and detection systems with much higher sensitivity. ECEI systems have been demonstrated to be very powerful instruments to visualize magneto-hydrodynamic instabilities. Detailed measurements have been reported on the sawtooth instability [Park, H.K., et al., 2006] (TEXTOR, DIII-D and KSTAR), neoclassical tearing modes (TEXTOR) [Classen, I.G.J., et al., 2007; Spakman, G.W., et al., 2008], edge localized modes (KSTAR [Yun, G.S., et al., 2011] and ASDEX-Upgrade [Boom, J.E., et al., 2011]), and Alfvénic eigenmodes (DIII-D [Tobias, B., et al., 2011] and ASDEX-Upgrade [Classen, I.G.J., et al., 2011]). This talk will give a brief overview of recent trends in the field of ECE Imaging covering the technological developments as well as examples of recent measurements to illustrate the insight that can be obtained from two dimensional visualization of temperature perturbations in the plasma.