Correlation electron cyclotron emission diagnostic and improved calculation of turbulent temperature fluctuation levels on ASDEX Upgrade

Creely, A. J.; Freethy, S. J.; Burke, W.; Conway, G. D.; Leccacorvi, R.; Parkin, W.; Terry, D.; White, Anne

doi:10.1063/1.5005507

Cited by 25 publications

(20 citation statements)

References 29 publications

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“…New measurements of turbulent electron temperature fluctuation amplitude δT e⊥ /T e , radial correlation length L r (T e⊥ ) and density-temperature phase angle α nT have been made with an upgraded Correlation ECE diagnostic [24] and nT-phase diagnostic on ASDEX Upgrade. The new diagnostic uses a closely spaced channel comb to allow measurement of high radial resolution δT e⊥ /T e and L r (T e⊥ ) profiles.…”

Section: Discussionmentioning

confidence: 99%

“…These measurements were taken during two discharges in the ASDEX Upgrade (AUG) experiment, a reference discharge (#33585) in which only δT e⊥ /T e is available from the pilot CECE diagnostic [23], and a repeat discharge (#34626) where all the aforementioned fluctuation quantities are available from a newly upgraded CECE diagnostic [24].…”

Section: L-mode Plasma Used For Gk Validationmentioning

confidence: 99%

“…Correlation analysis between channel pairs then allows the uncorrelated thermal noise of each channel to be significantly reduced, allowing the measurement of the turbulent fluctuations. The new CECE diagnostic on AUG allows for more detailed measurements of the ion scale electron temperature fluctuations than has been achieved before, due both to the large number of channels (28) and their arrangement in a comb pattern [24]. Rather than relying on individual pairs, as used in the previous AUG CECE diagnostic [23], where the number of radial points is n/2, the comb arrangement allows n − 1 radial points in a δT e⊥ /T e fluctuation profile with a radial resolution of 2 − 4 mm, as shown in Figure 2 a).…”

Section: Turbulence Measurement Techniquesmentioning

confidence: 99%

“…For a more in-depth discussion of the signal analysis techniques, error estimation and sensitivity limits used in this paper, see Ref [24] …”

Section: Turbulence Measurement Techniquesmentioning

confidence: 99%

“…This can only be done by quantitatively comparing the simulation to one or more experimentally measured properties of the turbulence, known in the community as a validation study [21]. At ASDEX Upgrade (AUG), in order to probe the low wavenumber (k) temperature fluctuations contributing to the electron heat flux channel and to compliment the existing turbulence diagnostics used for GK validation [22], a Correlation Electron Cyclotron Emission (CECE) diagnostic has been installed [23,24]. The principles of this diagnostic are briefly outlined in Section III.…”

Section: Introductionmentioning

confidence: 99%

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Validation of gyrokinetic simulations with measurements of electron temperature fluctuations and density-temperature phase angles on ASDEX Upgrade

et al. 2018

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Measurements of turbulent electron temperature fluctuation amplitudes, δT e⊥ /Te, frequency spectra and radial correlation lengths, Lr(T e⊥ ), have been performed at ASDEX Upgrade using a newly upgraded Correlation ECE diagnostic in the range of scales k ⊥ < 1.4cm −1 , kr < 3.5cm(k ⊥ ρs < 0.28 and krρs < 0.7). The phase angle between turbulent temperature and density fluctuations, αnT , has also been measured by using an ECE radiometer coupled to a reflectometer along the same line of sight. These quantities are used simultaneously to constrain a set of ion-scale nonlinear gyrokinetic turbulence simulations of the outer core (ρtor = 0.75) of a low density, electron heated L-mode plasma, performed using the gyrokinetic simulation code, GENE. The ion and electron temperature gradients were scanned within uncertainties. It is found that GK simulations are able to match simultaneously the electron and ion heat flux at this radius within the experimental uncertainties. The simulations were performed based on a reference discharge for which δT e⊥ /Te measurements were available, and Lr(T e⊥ ) and αnT were then predicted using synthetic diagnostics prior to measurements in a repeat discharge. While temperature fluctuation amplitudes are overestimated by > 50% for all simulations within the sensitivity scans performed, good quantitative agreement is found for Lr(T e⊥ ) and αnT . A validation metric is used to quantify the level of agreement of individual simulations with experimental measurements, and the best agreement is found close to the experimental gradient values.

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Section: Discussionmentioning

confidence: 99%

Section: L-mode Plasma Used For Gk Validationmentioning

confidence: 99%

Section: Turbulence Measurement Techniquesmentioning

confidence: 99%

“…For a more in-depth discussion of the signal analysis techniques, error estimation and sensitivity limits used in this paper, see Ref [24] …”

Section: Turbulence Measurement Techniquesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Validation of gyrokinetic simulations with measurements of electron temperature fluctuations and density-temperature phase angles on ASDEX Upgrade

et al. 2018

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A multi-channel correlation ECE system for electron temperature fluctuation measurement on EAST tokamak

Zhao

Zhou

Liu

et al. 2019

Fusion Engineering and Design

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Advances in turbulence measurements using new Correlation ECE and nT-phase diagnostics at ASDEX Upgrade

et al. 2019

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Guided by predictions from nonlinear gyrokinetic simulations, two new turbulence diagnostics were designed and installed at ASDEX Upgrade (AUG) to probe the fundamentals of ion-scale turbulent electron heat transport. The first, a 30-channel correlation ECE (CECE) radiometer (105-128 GHz, 2nd harmonic X-mode), introduces a novel channel comb arrangement. This allows measurements of high radial resolution profiles (0:5 < r/a < 0:8) of low-k (k⍬⍴s < 0:3) temperature fluctuation amplitudes, frequency spectra and radial correlation length profiles in unprecedented detail. The second diagnostic is formed by the addition of two W-band and one V-band X-mode reflectometers on the same line of sight as the CECE to enable measurements of the phase angle between turbulent density and temperature fluctuations. Historically, the radial alignment between reflectometer and radiometer has been a challenge due to the requirement that alignment is achieved within a radial correlation length (< 5 10 mm). This challenge is significantly alleviated by using the CECE channel comb arrangement and the maximal coherence between reflectometer and radiometer can be unambiguously captured. Measurements of these quantities have been made in an AUG L-mode plasma, at the same radial location and have provided simultaneous quantitative constraints on realistic gyrokinetic simulations [Physics of Plasmas 25, 055903 (2018)] using the gyrokinetic code GENE. Here we present diagnostic detail for this study.

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Correlation electron cyclotron emission diagnostic and improved calculation of turbulent temperature fluctuation levels on ASDEX Upgrade

Cited by 25 publications

References 29 publications

Validation of gyrokinetic simulations with measurements of electron temperature fluctuations and density-temperature phase angles on ASDEX Upgrade

Validation of gyrokinetic simulations with measurements of electron temperature fluctuations and density-temperature phase angles on ASDEX Upgrade

A multi-channel correlation ECE system for electron temperature fluctuation measurement on EAST tokamak

Advances in turbulence measurements using new Correlation ECE and nT-phase diagnostics at ASDEX Upgrade

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