Design of a correlation electron cyclotron emission diagnostic for Alcator C-Mod

Sung, C.; White, Anne; Irby, J.; Leccacorvi, R.; Vieira, R.; Oi, Curran; Peebles, W. A.; Nguyen, X.

doi:10.1063/1.4731750

Cited by 20 publications

(17 citation statements)

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“…In Alcator C-Mod the electron temperature fluctuation and correlation length can be measured using upgraded multichannel CECE [54]. This will be an interesting topic for future experiments.…”

Section: Resultsmentioning

confidence: 99%

Non-local heat transport in Alcator C-Mod ohmic L-mode plasmas

et al. 2014

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Abstract. Non-local heat transport experiments were performed in Alcator C-Mod Ohmic L-mode plasmas by inducing edge cooling with laser blow-off impurity (CaF 2 ) injection. The non-local effect, a cooling of the edge electron temperature with a rapid rise of the central electron temperature, which contradicts the assumption of "local" transport, was observed in low collisionality linear Ohmic confinement (LOC) regime plasmas. Transport analysis shows this phenomenon can be explained either by a fast drop of the core diffusivity, or the sudden appearance of a heat pinch. In high collisionality saturated Ohmic confinement (SOC) regime plasmas, the thermal transport becomes local: the central electron temperature drops on the energy confinement time scale in response to the edge cooling. Measurements from a high resolution imaging x-ray spectrometer show that the ion temperature has a similar behavior as the electron temperature in response to edge cooling, and that the transition density of non-locality correlates with the rotation reversal critical density. This connection may indicate the possible connection between thermal and momentum transport, which is also linked to a transition in turbulence dominance between trapped electron modes (TEMs) and ion temperature gradient (ITG) modes. Experiments with repetitive cold pulses in one discharge were also performed to allow Fourier analysis and to provide details of cold front propagation. These modulation experiments showed in LOC plasmas that the electron thermal transport is not purely diffusive, while in SOC the electron thermal transport is more diffusive like. Linear gyrokinetic simulations suggest the turbulence outside r/a=0.75 changes from TEM dominance in LOC plasmas to ITG mode dominance in SOC plasmas. Non-local Heat Transport in Alcator C-Mod Ohmic L-Mode Plasmas2

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Section: Resultsmentioning

confidence: 99%

Non-local heat transport in Alcator C-Mod ohmic L-mode plasmas

et al. 2014

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“…10 To the past work at C-Mod, we add newly available measurements of long wavelength electron temperature fluctuations from a correlation electron cyclotron emission (CECE) diagnostic. 13,20,21 These new data provide an additional constraint on the simulations. The outer core region, r/a > 0.8, has not been investigated in the past using gyrokinetic simulations in Ohmic L-mode plasmas at C-Mod, so we focus on this region.…”

Section: Introductionmentioning

confidence: 99%

Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges

et al. 2016

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Long wavelength turbulent electron temperature fluctuations (kyρs < 0.3) are measured in the outer core region (r/a > 0.8) of Ohmic L-mode plasmas at Alcator C-Mod [E. S. Marmar et al., Nucl. Fusion 49, 104014 (2009)] with a correlation electron cyclotron emission diagnostic. The relative amplitude and frequency spectrum of the fluctuations are compared quantitatively with nonlinear gyrokinetic simulations using the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] in two different confinement regimes: linear Ohmic confinement (LOC) regime and saturated Ohmic confinement (SOC) regime. When comparing experiment with nonlinear simulations, it is found that local, electrostatic ion-scale simulations (kyρs ≲ 1.7) performed at r/a ∼ 0.85 reproduce the experimental ion heat flux levels, electron temperature fluctuation levels, and frequency spectra within experimental error bars. In contrast, the electron heat flux is robustly under-predicted and cannot be recovered by using scans of the simulation inputs within error bars or by using global simulations. If both the ion heat flux and the measured temperature fluctuations are attributed predominantly to long-wavelength turbulence, then under-prediction of electron heat flux strongly suggests that electron scale turbulence is important for transport in C-Mod Ohmic L-mode discharges. In addition, no evidence is found from linear or nonlinear simulations for a clear transition from trapped electron mode to ion temperature gradient turbulence across the LOC/SOC transition, and also there is no evidence in these Ohmic L-mode plasmas of the “Transport Shortfall” [C. Holland et al., Phys. Plasmas 16, 052301 (2009)].

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“…10 The correlation coefficient was measured in the laboratory with 2-18 GHz noise source as the input of CECE IF section, which is shown in Fig. 1 coefficient of different IF filters is shown in Fig.…”

Section: B Correlation Testmentioning

confidence: 99%

The design of a correlation electron cyclotron emission system on J-TEXT

Yang

Xiao

et al. 2015

Review of Scientific Instruments

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To study the anomalous transport, a correlation electron cyclotron emission (CECE) was planned to be developed on J-TEXT for electron temperature fluctuation measurement. The spectral decorrelation method was employed for the CECE system. It was developed based on the previous 16-channel electron cyclotron emission system. They shared the optical transmission line and mixer. The CECE part consists of 4 channels. Two fixed frequency narrow band filters were used for two channels and two yttrium iron garnet (YIG) filters for the other two channels. To meet the measuring requirement, some tests have been taken for the YIG filters. The results show good performance of the filters. Gaussian optics is used to produce a good poloidal resolution. Wavenumbers resolved by the CECE diagnostic are k(θ) ≤ 1.5 rad/cm and k(r) ≤ 12 rad/cm. Some preliminary experiment results are also presented in this paper.

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Design of a correlation electron cyclotron emission diagnostic for Alcator C-Mod

Cited by 20 publications

References 10 publications

Non-local heat transport in Alcator C-Mod ohmic L-mode plasmas

Non-local heat transport in Alcator C-Mod ohmic L-mode plasmas

Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges

The design of a correlation electron cyclotron emission system on J-TEXT

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