Feasibility study for a correlation electron cyclotron emission turbulence diagnostic based on nonlinear gyrokinetic simulations

White, Anne; Howard, Nathan; Mikkelsen, D. R.; Greenwald, M.; Candy, J.; Waltz, R. E.

doi:10.1088/0741-3335/53/11/115003

Cited by 8 publications

(9 citation statements)

References 43 publications

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“…In the first measurements of long wavelength (k y q s < 0.3) electron temperature fluctuations in Alcator CMod made with a new correlation electron cyclotron emission diagnostic 281 electron temperature fluctuations decrease significantly ($40%) crossing from LOC to SOC, consistent with a change from TEM turbulence domination to ion temperature gradient (ITG) turbulence as the density and collisionality is increased. 221 Linear stability analysis shows that TEMs are dominant for long wavelength turbulence in the LOC regime and the ITG modes are dominant in the SOC regime at the radial location (q $ 0.8) where the changes in electron temperature fluctuations are measured.…”

mentioning

confidence: 97%

20 years of research on the Alcator C-Mod tokamak

et al. 2014

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The object of this review is to summarize the achievements of research on the Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 and Marmar, Fusion Sci. Technol. 51, 261 (2007)] and to place that research in the context of the quest for practical fusion energy. C-Mod is a compact, high-field tokamak, whose unique design and operating parameters have produced a wealth of new and important results since it began operation in 1993, contributing data that extends tests of critical physical models into new parameter ranges and into new regimes. Using only highpower radio frequency (RF) waves for heating and current drive with innovative launching structures, C-Mod operates routinely at reactor level power densities and achieves plasma pressures higher than any other toroidal confinement device. C-Mod spearheaded the development of the vertical-target divertor and has always operated with high-Z metal plasma facing componentsapproaches subsequently adopted for ITER. C-Mod has made ground-breaking discoveries in divertor physics and plasma-material interactions at reactor-like power and particle fluxes and elucidated a) Paper AR1 1, Bull. Am. Phys. Soc. 58, 21 (2013). b) Invited speaker.

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confidence: 97%

20 years of research on the Alcator C-Mod tokamak

et al. 2014

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“…The components in the RF section and the first amplifier for 2-18 GHz signals are installed in front of the diagnostic port as shown in Figure 2(b). The current CECE IF section has 8 channels, two of which are tunable (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). More details about Correlation ECE diagnostic in C-Mod can be found in [5] and upgrades in the IF section will be published in the future [6].…”

Section: Description Of the Correlation Ece Diagnostic In Alcator C-modmentioning

confidence: 99%

“…More details about Correlation ECE diagnostic in C-Mod can be found in [5] and upgrades in the IF section will be published in the future [6]. High poloidal resolution (k θ < 9.8 cm −1 ) with CECE at C-Mod is possible due to a small beam spot size (beam diameter, d < 1 cm), and was one of the important design considerations for the diagnostic [7]. Figure 3 shows the theoretical beam pattern in the poloidal direction based on the optical components such as in-vessel mirror and ex-vessel lens.…”

Section: Description Of the Correlation Ece Diagnostic In Alcator C-modmentioning

confidence: 99%

Correlation ECE diagnostic in Alcator C-Mod

Sung

White

Howard

et al. 2015

EPJ Web of Conferences

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Abstract. Correlation ECE (CECE) is a diagnostic technique that allows measurement of small amplitude electron temperature, T e , fluctuations through standard cross-correlation analysis methods. In Alcator C-Mod, a new CECE diagnostic has been installed [Sung RSI 2012], and interesting phenomena have been observed in various plasma conditions. We find that local T e fluctuations near the edge (ρ ∼ 0.8) decrease across the linearto-saturated ohmic confinement transition, with fluctuations decreasing with increasing plasma density [Sung NF 2013], which occurs simultaneously with rotation reversals [Rice NF 2011]. T e fluctuations are also reduced across core rotation reversals with an increase of plasma density in RF heated L-mode plasmas, which implies that the same physics related to the reduction of T e fluctuations may be applied to both ohmic and RF heated L-mode plasmas. In I-mode plasmas, we observe the reduction of core T e fluctuations, which indicates changes of turbulence occur not only in the pedestal region but also in the core across the L/I transition [White NF 2014]. The present CECE diagnostic system in C-Mod and these experimental results are described in this paper.

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“…Gyrokinetic simulations have provided several constraints on the design of CECE for C-Mod. [8] First, the optical system should provide a small beam diameter (1/e electric field diameter) of 1cm at the measurement position to measure long wavelength (k θ ρ s <0.5) fluctuations in the core. The beam diameter determines poloidal spatial resolution of CECE, and a large beam diameter will result in filtering out of high frequency fluctuations.…”

Section: Design Of Cece Diagnostic In C-modmentioning

confidence: 99%

“…[6] Nonlinear gyrokinetic simulations using the GYRO code [7] were used to reexamine reasons for this, and the results motivate a new CECE diagnostic in C-Mod. [8] In this paper, the system overview and first results from the new CECE diagnostic on C-Mod are presented.…”

Section: Introductionmentioning

confidence: 99%

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

Sung

White

Irby

et al. 2012

Review of Scientific Instruments

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A correlation electron cyclotron emission (CECE) diagnostic has been installed in Alcator C-Mod. In order to measure electron temperature fluctuations, this diagnostic uses a spectral decorrelation technique. Constraints obtained with nonlinear gyrokinetic simulations guided the design of the optical system and receiver. The CECE diagnostic is designed to measure temperature fluctuations which have k(θ) ≤ 4.8 cm(-1) (k(θ)ρ(s) < 0.5) using a well-focused beam pattern. Because the CECE diagnostic is a dedicated turbulence diagnostic, the optical system is also flexible, which allows for various collimating lenses and antenna to be used. The system overview and the demonstration of its operability as designed are presented in this paper.

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Feasibility study for a correlation electron cyclotron emission turbulence diagnostic based on nonlinear gyrokinetic simulations

Cited by 8 publications

References 43 publications

20 years of research on the Alcator C-Mod tokamak

20 years of research on the Alcator C-Mod tokamak

Correlation ECE diagnostic in Alcator C-Mod

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

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