Fast sweeping reflectometry upgrade on Tore Supra

Clairet, F.; Heuraux, S.; Bottereau, C.; Molina, Diego Alonso Restrepo; Ducobu, L.; Leroux, F.; Barbuti, A.

doi:10.1063/1.3460624

Cited by 35 publications

(28 citation statements)

References 5 publications

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“…As the density increases, the selected probing frequency of the reflectometer is changed between t 1 (f 1 = 110.9 GHz) and t 2 (f 2 = 122.6 GHz) to ensure a constant measurement location. In figures 2(b,d), an ultra-fast-swept reflectometer [17] is used to provide a radial range of fluctuation spectra (0.65 < r/a < 0.85). These reflectometry spectra are obtained with a Fourier transform of the measured complex signal A(t)e iφ(t) , with A(t) and φ(t) the amplitude and the phase re- spectively.…”

Section: Spectra From Reflectometry Measurementsmentioning

confidence: 99%

Identification of trapped electron modes in frequency fluctuation spectra

Arnichand

Citrin

Hacquin

et al. 2015

Plasma Phys. Control. Fusion

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Abstract.Ion temperature gradient (ITG) and trapped electron modes (TEM) are two important micro-instabilities in the plasma core region of fusion devices (r/a ≤ 0.9). They usually coexist in the same range of spatial scale (around 0.1 < k ⊥ ρ i < 1), which makes their discrimination difficult. To investigate them, one can perform gyrokinetic simulations, transport analysis and phase velocity estimations. In Tore Supra, the identification of trapped electron modes (TEM) is made possible due to measured frequency fluctuation spectra. Indeed, turbulent spectra generally expected to be broad-band can become narrow in case of TEM turbulence, inducing "quasi-coherent" (QC) modes named QC-TEM. Therefore the analysis of frequency fluctuation spectra becomes a possible tool to differentiate TEM from ITG. We have found indications that the TEM can have a QC signature by comparing frequency fluctuation spectra from reflectometry measurements, gyrokinetic simulations and synthetic diagnostic results. Then the scope of the analysis of QC-TEM are discussed and an application is shown, namely transitions between TEM turbulence and MHD fluctuations.

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Section: Spectra From Reflectometry Measurementsmentioning

confidence: 99%

Identification of trapped electron modes in frequency fluctuation spectra

Arnichand

Citrin

Hacquin

et al. 2015

Plasma Phys. Control. Fusion

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“…A V/W-band ultra-fast swept X-mode reflectometer measures up to 100,000 density profiles along a horizontal line of sight across the plasma center with 2 μs resolution [7].…”

Section: Interactionmentioning

confidence: 99%

Experimental turbulence studies for gyro-kinetic code validation using advanced microwave diagnostics

et al. 2015

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Abstract. For a comprehensive comparison with theoretical models and advanced numerical turbulence simulations, a large spectrum of fluctuation parameters were measured on the devices ASDEX Upgrade, TCV, and Tore-Supra. Radial profiles of scale-resolved turbulence levels in H-mode discharges are measured and compared with GENE simulations in the transition range from ion-temperature-gradient to trappedelectron-mode turbulence. Correlation reflectometry is used to study the microscopic structure of turbulence and GAMs in discharges where poloidal flow damping was varied by means of variations of the shape of the poloidal plasma cross-section and collisionality. The aspects of turbulence spreading and non-local transport in response of local changes in density and temperature gradients are studied during phases with ECRH power modulation by means of radial correlation measurements and an ultrafast reflectometer. Full-wave codes and synthetic diagnostics are applied for the interpretation of the data.

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“…Such a technique can be used as far as the turbulence is locally frozen during the sweeping time, which allows us to obtain a valid estimate of the correlation lengths. A comparable study was carried out by Kurzan et al in 2000 [9]; here, the study is performed with a recently improved reflectometer system using faster frequency sweeps (2 µs) and heterodyne detection, where phase and amplitude of the reflected signals can be measured separately [10]. Thanks to the X-mode polarization, the temporal and spatial turbulence correlation properties of the raw fluctuating data have been analysed from the far scrape-off layer (SOL) to the core plasma region in Tore Supra ohmic discharges.…”

Section: Introductionmentioning

confidence: 99%

Turbulence correlation properties measured with ultrafast sweeping reflectometry on Tore Supra

Hornung¹,

Clairet²,

Falchetto³

et al. 2013

Plasma Phys. Control. Fusion

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The ultrafast sweep reflectometry technique is used to investigate plasma turbulence on Tore Supra. Thanks to the X-mode polarization, the plasma density and fluctuations over the whole tokamak radius, from the far scrape-off layer (SOL) to the core can be measured. Cross-correlation analysis is applied to all the signal components to estimate the fluctuation correlation length radial profile. The correlation length decreases from the plasma centre to the last closed flux surface and grows again into the far SOL.

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Fast sweeping reflectometry upgrade on Tore Supra

Cited by 35 publications

References 5 publications

Identification of trapped electron modes in frequency fluctuation spectra

Identification of trapped electron modes in frequency fluctuation spectra

Experimental turbulence studies for gyro-kinetic code validation using advanced microwave diagnostics

Turbulence correlation properties measured with ultrafast sweeping reflectometry on Tore Supra

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