Analysis of edge density fluctuation measured by trial KSTAR beam emission spectroscopy system

Nam, Y. U.; Zoletnik, S.; Lampert, M.; Kovácsik, Á.

doi:10.1063/1.4739078

Cited by 25 publications

(24 citation statements)

References 7 publications

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“…The black markers correspond to measurements of the correlation parameters made in the laboratory frame, whilst the different coloured markers correspond to measurements including the effects of the five PSF cases, which have been introduced in Section 4.3 and are illustrated in Figure 1. The black solid lines correspond to the laboratory-frame relations (B.41), (15), (28), (17)(18), (25), and (27) in each of the panels, respectively. The coloured lines correspond to the Gaussian-model PSF calculations (47), (39), (40), (42)(43), (49), and (48), respectively, which are discussed in Section 6.3.…”

Section: Radial Correlation Lengthmentioning

confidence: 99%

“…However, correlation functions of experimentally measured fluctuating quantities are not directly comparable to the correlation functions of the physical fields that we are interested in. Thus, Beam Emission Spectroscopy (BES) systems [13,14,15,16,17,18] measure the fluctuating intensity, δI i , of the Doppler-shifted D α emission from excited neutral beam atoms, which is nontrivially related to the density field in the plasma via the Point-Spread Functions (PSFs) of the diagnostic [19], see Figure 1,…”

Section: Introductionmentioning

confidence: 99%

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Experimental determination of the correlation properties of plasma turbulence using 2D BES systems

Fox

Field

Wyk

et al. 2017

Plasma Phys. Control. Fusion

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Abstract. A procedure is presented to map from the spatial correlation parameters of a turbulent density field (the radial and binormal correlation lengths and wavenumbers, and the fluctuation amplitude) to correlation parameters that would be measured by a Beam Emission Spectroscopy (BES) diagnostic. The inverse mapping is also derived, which results in resolution criteria for recovering correct correlation parameters, depending on the spatial response of the instrument quantified in terms of Point-Spread Functions (PSFs). Thus, a procedure is presented that allows for a systematic comparison between theoretical predictions and experimental observations. This procedure is illustrated using the MAST BES system and the validity of the underlying assumptions is tested on fluctuating density fields generated by direct numerical simulations using the gyrokinetic code GS2. The measurement of the correlation time, by means of the cross-correlation time-delay (CCTD) method, is also investigated and is shown to be sensitive to the fluctuating radial component of velocity, as well as to small variations in the spatial properties of the PSFs.Keywords: Beam-emission spectroscopy, point-spread functions, synthetic diagnostics, plasma turbulence, plasma diagnostics, tokamaks. Inner Outer Figure 1. Example e −1 amplitude contours of PSFs [1] for five specific cases taken from MAST shots and described in Section 4.3. The dots mark the locations of the focal points of the detector channels. The characterisation of the PSFs is described in Section 4.2.

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Section: Radial Correlation Lengthmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental determination of the correlation properties of plasma turbulence using 2D BES systems

Fox

Field

Wyk

et al. 2017

Plasma Phys. Control. Fusion

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“…This shows the density profiles (measured by BES system in KSTAR [24]) at different times for shot 6352. SMBI was injected at 2.7 s. The time of the closed circles is before SMBI injection, and the blue ones are after SMBI.…”

Section: Density Evolution With and Without Smbimentioning

confidence: 99%

“…However, much further work is required to substantiate the hypothesis above. In KSTAR, the spectrum of edge density fluctuations are measured by beam emission spectroscopy (BES) [24,30] (main vacuum, mid-plane, LFS) in ELM mitigation experiments. increases.…”

Section: Particle Flux and Density Fluctuation Analysis At Mid-plane mentioning

confidence: 99%

ELM mitigation by supersonic molecular beam injection: KSTAR and HL-2A experiments and theory

et al. 2014

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We report recent experimental results from HL-2A and KSTAR on ELM mitigation by supersonic molecular beam injection (SMBI). Cold particle deposition within the pedestal by SMBI is verified in both machines.The signatures of ELM mitigation by SMBI are an ELM frequency increase and ELM amplitude decrease.These persist for an SMBI influence time τI. Here, τI is the time for the SMBI influenced pedestal profile to refill. An increase in f SMBI ELM /f 0 ELM and a decrease in the energy loss per ELM WELM were achieved in both machines. Physical insight was gleaned from studies of density and vφ(toroidal rotation velocity) evolution, particle flux and turbulence spectra, divertor heat load. The characteristic gradients of the pedestal density soften and a change in vφwas observed during a τI time. The spectra of the edge particle flux Г~ < ˜vr˜ne> and density fluctuation with and without SMBI were measured in HL-2A and in KSTAR, respectively. A clear phenomenon observed is the decrease in divertor heat load during the τI time in HL-2A. Similar results are the profiles of saturation current density Jsat with and without SMBI in KSTAR. We note that τI/τp (particle confinement time) is close to ~1, although there is a large difference in individual τI between the two machines. This suggests that τI is strongly related to particle-transport events. Experiments and analysis of a simple phenomenological model support the important conclusion that ELM mitigation by SMBI results from an increase in higher frequency fluctuations and transport events in the pedestal.

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“…Here, we compare the radial density fluctuation profiles with and without RMP using the 4 × 16 beam emission spectroscopy (BES) arrays in KSTAR [20]. The analysis range of the BES measurements in the experiments is from −5.1 to −13.8 cm below the midplane and from the separatrix to a distance 12 cm inside of the plasma.…”

mentioning

confidence: 99%

Propagation Dynamics Associated with Resonant Magnetic Perturbation Fields in High-Confinement Mode Plasmas inside the KSTAR Tokamak

et al. 2017

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Analysis of edge density fluctuation measured by trial KSTAR beam emission spectroscopy system

Cited by 25 publications

References 7 publications

Experimental determination of the correlation properties of plasma turbulence using 2D BES systems

Experimental determination of the correlation properties of plasma turbulence using 2D BES systems

ELM mitigation by supersonic molecular beam injection: KSTAR and HL-2A experiments and theory

Propagation Dynamics Associated with Resonant Magnetic Perturbation Fields in High-Confinement Mode Plasmas inside the KSTAR Tokamak

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