Commissioning of electron cyclotron emission imaging instrument on the DIII-D tokamak and first data

Abstract

Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication Citation for published version (APA):Tobias, B. J., Domier, C. W., Liang, T., Kong, X., Yu, L., Yun, G. S., ... Luhmann, N. C. (2010). Commissioning of electron cyclotron emission imaging instrument on the DIII-D tokamak and first data. Review of Scientific Instruments, 81(10), 10D928-1/4. DOI: 10.1063/1.3460456 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Two-dimensional imaging of edge-localized modes in KSTAR plasmas unperturbed and perturbed by n=1 external magnetic fields

“…1(a), providing a simultaneous measurement of two regions in the same poloidal crosssection. The two viewing areas, which correspond to the individual detector arrays as denoted by HFS (high-field side) and LFS (low-field side) in the figure, can be placed anywhere in the poloidal crosssection with a variable vertical coverage from $30 to $90 cm owing to the wide-band (85-145 GHz) microwave heterodyne detection technologies 18 and the optimized zooming and focusing capabilities of the optics. This flexibility has allowed various combinations of HFS and LFS view positions, providing excellent opportunities in studying a variety of plasma instabilities and turbulence phenomena in 2D such as sawteeth, tearing modes, ELMs, and turbulent fluctuations during H-mode transition.…”

Development of KSTAR ECE imaging system for measurement of temperature fluctuations and edge density fluctuations

“…14 Advancements in microwave antenna design, LO coupling, and zoom optics in the DIII-D ECEI system have led to a significant improvement in signal quality compared to its predecessors, TEXTOR and ASDEX-U systems, and the importance of clean signal has been demonstrated in the initial data. 9 The KSTAR ECEI system benefits from the same microwave technology. In addition, the flexible zoom control and accurate focus control will result in wider plasma coverage and further improved signal-to-noise ratio.…”

“…The video bandwidth is selectable up to 400 kHz, corresponding to the temperature resolution ␦T e / T e = ͱ ⌬f IF / ⌬f video Ϸ 3%, where ⌬f indicates bandwidth. Technical details on antenna design and IF/video circuits are discussed in detail by Domier et al 9,12,13 The KSTAR ECEI system has 24 verticalϫ 8 radial channels in each array, which add up to 384 total number of channels. Digitization of this large number channels at least twice as fast as the video bandwidth ͑ϳ400 kHz͒ requires high speed digitizers ͑ϳ1 MHz͒ and results in high data volume ϳ5 Gbyte per typical 5 s operation.…”

“…[5][6][7] The ECE imaging ͑ECEI͒ system is essentially an array of radiometers optically imaged onto the plane of the poloidal cross section of the tokamak plasma. After demonstrating the powerful capabilities as 2D local T e diagnostic, ECEI systems with improved rf electronics and imaging optics have been launched in other major tokamaks including ASDEX-U 8 and DIII-D. 9 These ECEI systems have provided invaluable 2D images of MHD phenomena such as tearing modes, edge localized modes, and Alfvén eigenmodes as well as sawtooth crashes. It should be noted that the ECEI systems have been focused on T e fluctuation measurements rather than absolute T e profile measurements partially due to the difficulty of absolute calibration.…”

Visualization of core and edge MHD instabilities in 2D using ECEI

“…Each detector array box [8,9] has 24 vertically aligned Schottky diode detectors mounted onto wideband strip antennas, which are optimized for the detection of the vertically polarized X2 ECE in the W-and F-band microwave range (i.e., ~75-140 GHz). This corresponds to the 2 nd harmonic ECE frequencies at B 0 = 2 T operation, the magnetic field at the major radius R 0 = 1.8 m. The array box downconverts the ECE microwave and amplifies the intermediate frequency (IF) signals, which are then delivered to the RF electronic modules.…”