Ordinary-mode reflectometry: modification of the scattering and cut-off responses due to the shape of localized density fluctuations

Fanack, C; Boucher, I; Clairet, F.; Heuraux, S.; Leclert, G.; Zou, X. L.

doi:10.1088/0741-3335/38/11/004

Cited by 59 publications

(72 citation statements)

References 14 publications

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“…32 The phase of the reflectometry signal is inferred directly from the radial structure of the electric field, which is illustrated in Fig. 4 Under the Born approximation valid for low levels of the density fluctuations, it was shown in previous works [33][34][35] that the phase fluctuations could be retrieved directly from the integral of the density fluctuations along the radial line-of-sight…”

Section: B Comparison Between O-mode and X-mode Resultsmentioning

confidence: 98%

Simulation of core turbulence measurement in Tore Supra ohmic regimes

Hacquin¹,

Citrin²,

Arnichand³

et al. 2016

Physics of Plasmas

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This paper reports on a simulation of reflectometry measurement in Tore Supra ohmic discharges, for which the experimental observations as well as gyrokinetic non-linear computations predict a modification of turbulence spectrum between the linear (LOC) and the saturated ohmic confinement (SOC) regimes. Synthetic reflectometry simulations coupling full-wave computations with gyrokinetic data are carried out. This allows a direct comparison between the gyrokinetic non-linear predictions and experimental observations. The synthetic diagnostic results are found in a good agreement with the experimental findings; in particular, they reproduce well the quasi-coherent peak in the fluctuation spectrum of LOC regimes dominated by a trapped electron mode turbulence. It is also shown that such synthetic tools are valuable for (i) an enhanced interpretation of the reflectometry measurement (for instance, through the investigation of the 2D effects) and (ii) a better understanding of the turbulence properties (for instance, via the analysis of its poloidal asymmetry).

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Section: B Comparison Between O-mode and X-mode Resultsmentioning

confidence: 98%

Simulation of core turbulence measurement in Tore Supra ohmic regimes

Hacquin¹,

Citrin²,

Arnichand³

et al. 2016

Physics of Plasmas

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“…10(a) and 10(b)) according the plasma density which modifies the distance between the antenna and the cut-off layer, and modifies as well the influence of the density fluctuations which are less disturbing on the phase signal as the density gradient is getting steeper. 22 Before the first cut-off, the antenna coupling signal is clearly visible at approximately -35 dB below the highest plasma echo. Above 62 GHz, multi-reflections can be distinguished in Fig.…”

Section: Reflectometry and Lhcd Launcher Arrangementmentioning

confidence: 97%

New signal processing technique for density profile reconstruction using reflectometry

Clairet

Ricaud

Briolle

et al. 2011

Review of Scientific Instruments

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Reflectometry profile measurement requires an accurate determination of the plasma reflected signal. Along with a good resolution and a high signal to noise ratio of the phase measurement, adequate data analysis is required. A new data processing based on time-frequency tomographic representation is used. It provides a clearer separation between multiple components and improves isolation of the relevant signals. In this paper, this data processing technique is applied to two sets of signals coming from two different reflectometer devices used on the Tore Supra tokamak. For the standard density profile reflectometry, it improves the initialization process and its reliability, providing a more accurate profile determination in the far scrape-off layer with density measurements as low as 10 16 m −1 . For a second reflectometer, which provides measurements in front of a lower hybrid launcher, this method improves the separation of the relevant plasma signal from multi-reflection processes due to the proximity of the plasma.

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“…EC codes: In the frequency range of electron cyclotron heating, the Helmholtz solvers were used for diagnostics (Fanack et al 1996;Mazzucato 1998) a long time ago. Until recently, the ray tracing method was estimated to be enough to study a beam propagation in ITER plasmas (Prater et al 2008), but it is clear now that the density fluctuations have to be included , and, for these studies, full-wave codes are required for the frequency range of electron cyclotron heating or current drive (Sysoeva et al , 2015.…”

Section: Heating Simulationmentioning

confidence: 99%

“…In the first case, all spatial scales are present, and the scattered is more or less isotropic after averaging. Then, part of the spectrum is truncated and, as a consequence, an anisotropy appears in the scattered field pattern, according to the Bragg rule (see (Fanack et al 1996)). In the last one, only forward scattering is possible, showing a narrow lobe for the scattered wave emission.…”

Section: Conclusion and New Developmentsmentioning

confidence: 99%

Simulation as a tool to improve wave heating in fusion plasmas

et al. 2015

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(Received ?; revised ?; accepted ?. -To be entered by editorial office)Firstly, a brief overview will be given on different models that are able to describe the behaviour of wave propagation as a function of specific frequency ranges. Each range corresponds to different heating systems, namely, 20-100 MHz for the Ion Cyclotron Resonant Heating (ICRH), 2-20 GHz for Lower Hybrid Heating or Current Drive (LHCD), and 100-250 GHz for Electron Cyclotron Resonant Heating (ERCH) or Current Drive (ECCD) systems. Every systems' specifications will be explained in detail, including the typical set of equations and the assumptions needed to describe the properties of these heating or current drive systems, as well as their specific domains of validity. In these descriptions, special attention will be paid to the boundary conditions. A review about specific physical problems associated with the wave heating systems will also be provided. Such review will detail the role of simulation in answering questions coming from experiments on magnetized plasma devices devoted to Fusion. A few examples which will be covered are the impact of edge turbulence on wave propagation and its consequences on the heating system performances, effects of the fast particles, ponderomotive effects, among others. A study that is more focused on Radio Frequency (RF) sheath effects will also be discussed. It shows that such simulations require very sophisticated tools to gain a partial understanding of the observations undertaken in dedicated experiments. To conclude this review, an overview will be given about the requirements and progress necessary to obtain relevant predictive simulation tools able to describe the wave heating systems used in fusion devices.

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Ordinary-mode reflectometry: modification of the scattering and cut-off responses due to the shape of localized density fluctuations

Cited by 59 publications

References 14 publications

Simulation of core turbulence measurement in Tore Supra ohmic regimes

Simulation of core turbulence measurement in Tore Supra ohmic regimes

New signal processing technique for density profile reconstruction using reflectometry

Simulation as a tool to improve wave heating in fusion plasmas

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