Imaging Techniques for Microwave Diagnostics

Imaging diagnostics, such as Electron Cyclotron Emission Imaging (ECEI) and Microwave Imaging Reflectometry (MIR), exhibit unique characteristics that make them particularly well suited to the validation of theoretical models for plasma instabilities and turbulent fluctuations. A 2-D picture of plasma phenomena is provided unambiguously, from localized, time-resolved measurements. After more than a decade of development and successful demonstrations on RTP [1,2] and TEXTOR [3, 4, 5, 6], ECEI has come into maturity as an electron temperature diagnostic technique, and systems at ASDEX-UG [7] and DIII-D [8] are making regular contributions to plasma physics. The next generation ECEI diagnostic is currently being installed on KSTAR [9, 10]. MIR is a radar reflectometric density fluctuation diagnostic, and hence the perfect complement to ECEI when realized to simultaneously image the same plasma volume. Experiments with MIR at TEXTOR have guided a recent surge in analysis and laboratory experiments aimed at resolving remaining issues [11, 12]. Both techniques are discussed in this tutorial with brief examples of data which illustrate the capabilities of these techniques and motivate future development for application on ITER and burning plasma experiments to come. (c) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim