Microwave imaging reflectometry studies for turbulence diagnostics on KSTAR

Park, H. K.; Hong, Inho; Kim, M.; Yun, Gunsu; Lee, W.; Kim, J.; Tobias, Benjamin; Domier, C.W.; Luhmann, Neville C.; Kim, K. W.

doi:10.1063/1.3499606

Cited by 7 publications

(8 citation statements)

References 5 publications

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“…In the toroidal geometry of a tokamak, this corresponds to curvature matching between phase fronts of the illumination beam and the virtual plasma cutoff surface, which differs from the actual cutoff surface due to refractive effects [11,30]. Laboratory characterizations of the proof-of-principle TEXTOR MIR system undertaken at POSTECH reveal that this condition could not have been achieved for all operating scenarios [12]. Rather, flaws in both illumination and receive optics which limited the performance of this diagnostic were identified.…”

Section: Recent Advancements In Mirmentioning

confidence: 99%

“…Building upon the successes of LHD MIR with new systems at DIII-D and KSTAR requires a careful design process which makes use of lessons learned over a decade of advancements in quasi-optical antenna coupling in the presence of turbulent fluctuations. A prototype TEXTOR MIR system facilitated the identification of critical areas which have demanded further improvement [12]. Improved modeling of the plasma wave interaction [13], coupled with quasi-optical imaging design techniques refined throughout the development of ECEI systems, result in a synthetic diagnostic capable of addressing these outstanding questions [14,15].…”

Section: Introductionmentioning

confidence: 99%

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Recent Progress on Microwave Imaging Technology and New Physics Results

Tobias

Luhmann

Domier

et al. 2011

Plasma and Fusion Research

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Techniques for visualizing turbulent flow in nature and in the laboratory have evolved over half a millennium from Leonardo da Vinci's sketches of cascading waterfalls to the advanced imaging technologies which are now pervasive in our daily lives. Advancements in millimeter wave imaging have served to usher in a new era in plasma diagnostics, characterized by ever improving 2D, and even 3D, images of complex phenomena in tokamak and stellarator plasmas. Examples at the forefront of this revolution are electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR). ECEI has proved to be a powerful tool as it has provided immediate physics results following successful diagnostic installations on TEXTOR, ASDEX-U, DIII-D, and KSTAR. Recent results from the MIR system on LHD are demonstrating that this technique has the potential for comparable impact in the diagnosis of electron density fluctuations. This has motivated a recent resurgence in MIR research and development, building on a prototype system demonstrated on TEXTOR, toward the realization of combined ECEI/MIR systems on DIII-D and KSTAR for simultaneous imaging of electron temperature and density fluctuations. The systems discussed raise the standard for fusion plasma diagnostics and present a powerful new capability for the validation of theoretical models and numerical simulations.

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Section: Recent Advancements In Mirmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Recent Progress on Microwave Imaging Technology and New Physics Results

Tobias

Luhmann

Domier

et al. 2011

Plasma and Fusion Research

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“…For certain cases, ECEI images of the optically thin plasma edge region can be interpreted as density perturbations, providing valuable information on edge plasma physics. Future upgrades are planned for KSTAR high-field operation ͑Ն3 T͒ and second ECEI system combined with multifrequency imaging reflectometry 16,17 for the 2012 operation.…”

Section: Summary and Upgrade Plansmentioning

confidence: 99%

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

Yun

Lee

Choi

et al. 2010

Review of Scientific Instruments

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111

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The ECE imaging ͑ECEI͒ diagnostic tested on the TEXTOR tokamak revealed the sawtooth reconnection physics in unprecedented detail, including the first observation of high-field-side crash and collective heat transport ͓H. K. Park, N. C. Luhmann, Jr., A. J. H. Donné et al., Phys. Rev. Lett. 96, 195003 ͑2006͔͒. An improved ECEI system capable of visualizing both high-and low-field sides simultaneously with considerably better spatial coverage has been developed for the KSTAR tokamak in order to capture the full picture of core MHD dynamics. Direct 2D imaging of other MHD phenomena such as tearing modes, edge localized modes, and even Alfvén eigenmodes is expected to be feasible. Use of ECE images of the optically thin edge region to recover 2D electron density changes during L/H mode transitions is also envisioned, providing powerful information about the underlying physics. The influence of density fluctuations on optically thin ECE is discussed.

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“…The prototype TEXTOR MIR system [2] based on reflective optics was moved to POSTECH in 2009 and has been tested in the laboratory [3]. The study of the MIR system was focused on designing a new MIR system for the 2012 KSTAR campaign, and the optics was intensively studied.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the imaging properties of Microwave Imaging Reflectometry

Hong¹,

Lee²,

Leem³

et al. 2012

J. Inst.

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Microwave Imaging Reflectometry (MIR) has been developed for unambiguous measurement of electron density fluctuations in fusion plasmas. The loss of phase information limiting the use of conventional reflectometry can be minimized by a large aperture imaging optics and an array of detectors in the MIR embodiment. The evaluation of the optical system is critical for precise reconstruction of the fluctuations. The optical systems of the prototype TEXTOR MIR [2] and newly-designed KSTAR MIR [5] systems have been tested with a corrugated target simulating density fluctuations at the cut-off surface. The reconstructed phase from the MIR system has been compared to the directly measured phase of corrugations taking into account the rotational speed of the target. The effects of optical aberrations and interference between lenses on the phase reconstruction have been investigated by the 2D amplitude measurement of the reflected waves and the diffraction-based optical simulations. (CODE V) A preliminary design of the KSTAR MIR optics has been suggested which can minimize the aberration and interference effects.

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Microwave imaging reflectometry studies for turbulence diagnostics on KSTAR

Cited by 7 publications

References 5 publications

Recent Progress on Microwave Imaging Technology and New Physics Results

Recent Progress on Microwave Imaging Technology and New Physics Results

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

Evaluation of the imaging properties of Microwave Imaging Reflectometry

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