Dual array ECEI instrument for imaging and visualization of MHD and microturbulence phenomena on the DIII-D tokamak

Summary form only given. An innovative, dual array electron cyclotron emission (ECE) imaging (ECEI) instrument is under construction for use on the DIII-D tokamak. ECEI is a passive radiometric imaging diagnostic technique in which broadband ECE radiation is collected by a 1-D imaging array to generate 2-D localized, time-resolved electron temperature Te images. 1,2 Translatable optics allow each array to independently focus on different portions of the DIII-D plasma, forming 20 (v) I¿¿ 8 (h) = 128 channel images of Te profiles and fluctuations. The two ECEI systems view the DIII-D plasma (see below) through a single midplane port, employing a quasi-optical beamsplitter to separate the high field side (HFS) and low field side (LFS) signals. The HFS system can be focused at any normalized radius from -0.2 < r/a < +0.2, with a vertical coverage that can be extended to >50 cm. The focus of the LFS system can likewise be varied from +0.2 < r/a < +0.95, with a vertical coverage as large as >45 cm. The horizontal channel spacing of both systems can be varied remotely between 600 MHz and 900 MHz for enhanced flexibility.The ECEI instrument will be installed on the DIII-D tokamak in August 2009. ECEI will be employed in a wide range of physics campaigns including the study of neoclassical tearing modes (NTMs) during ECH injection.