Observation of filaments on the globus-M tokamak by Doppler reflectometry

Bulanin, V. V.; Варфоломеев, В. И.; Гусев, В. К.; Иванов, А. Е.; Krikunov, S. V.; Курскиев, Г. С.; Larionov, M. M.; Минаев, В. Б.; Патров, М. И.; Петров, А. В.; Petrov, Yu. V.; Сахаров, Н. В.; Tolstyakov, S. Yu.; Хромов, Н. А.; Yashin, A. Yu.

doi:10.1134/s1063785011040043

Cited by 30 publications

(33 citation statements)

References 3 publications

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“…After normalization BQFs for the both linear and nonlinear look similar as it is shown in figure 2(b) and the relation for the Doppler shift k⊥ = k х = 2k 0 sinα is preserved correspondingly. It is important to note that similarly shaped BQOs were observed in experiments on the Globus-M tokamak (see Figure 2c) [3,4]. The similarity of BQFs in the linear and nonlinear case, on the one hand, explains the fact that similar BQFs were observed The calculations for the case of multiple frequency probing were carried out for the same radial position of the moving filament r = 9cm.…”

Section: Results Of Simulationssupporting

confidence: 61%

“…Various diagnostics are employed for this purpose. A few years ago the authors proposed to use the Doppler backscattering (DBS) method for filaments investigation in the Globus-M spherical tokamak [3,4]. Later this diagnosis was successfully applied to the study of the filaments in the ASDEX Upgrade tokamak [5,6].…”

Section: Introductionmentioning

confidence: 99%

“…Backscattering from filaments manifests itself as a burst of quasi-coherent fluctuations (BQF) of the signals of IQ (In-phase and Quadrature) detectors. Such signals are easy to describe in the Born approximation in a case of linear backscattering [3]. Basing on the concept of linear scattering it is possible to determine the position and velocity of the filament.…”

Section: Introductionmentioning

confidence: 99%

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Full-Wave Modeling of Doppler Backscattering from Filaments

et al. 2020

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It is recognized that the filaments have a significant effect on the anomalous energy and particle transport in the tokamak periphery. They are actively investigated using various diagnostics in this regard. Recently studies of filaments using the Doppler backscattering (DBS) method have been performed in the Globus-M and the ASDEX-Upgrade tokamaks.Backscattering from filaments manifests itself as a burst of quasi-coherent fluctuations (BQF) of the signals of IQ detectors. Such signals are easy to describe in the Born approximation using the diagnostic weighting function. However, the filaments in tokamaks differ noticeably in their size and intensity. With an increase in the amplitude of the filaments, it is necessary to consider the transition from linear scattering to nonlinear one and further up to the transition from backscattering to reflection from a moving over dens filament. This problem can be solved only using a full wave code. Our simulation was carried out using the finite-difference time-domain code IPF-FD3D in slab geometry. We did not resort to using well-known nonlinear MHD codes to determine filament parameters. In the simulation artificial filament-like perturbations were used, the parameters of which varied over a wide range. Modeling DBS signal was focused on the identification of the influence of the amplitude of the filament and its size on the shape and the size of the DBS output signal. The results obtained largely explain the similarity of the IQ detector data registered in different tokamaks.

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Section: Results Of Simulationssupporting

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Full-Wave Modeling of Doppler Backscattering from Filaments

et al. 2020

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“…The first implementation of DBS on a spherical tokamak was carried out on Globus-M [31]. There are specific requirements for DBS application in a spherical tokamak that is characterized by a significant pitch angle (more than 20 • ) at the low magnetic field side.…”

Section: Doppler Backscattering On Globus-m 21 Dbs Systemsmentioning

confidence: 99%

“…Such an implementation is possible when the poloidal size of the filaments is close to π/k ⊥ (1-3 cm in the case of DBS on Globus-M), where k ⊥ is the wave vector of the incident wave in the cutoff region. Such filaments were discovered using DBS inside the separatrix in ELMy H-mode with NBI [31,57] and in Ohmic H-mode with high MHD activity [58,59]. Filaments were observed as a sequence of bursts of quasi-coherent fluctuations (BQFs) in the IQ DBS signals.…”

Section: Filamentsmentioning

confidence: 99%

Review of Advanced Implementation of Doppler Backscattering Method in Globus-M

et al. 2021

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Doppler backscattering (DBS) is a microwave diagnostics method typically used to study the plasma rotation velocity. Apart from conventional techniques, more advanced forms of DBS implementation were suggested on Globus-M. More specifically the study of a variety of oscillating processes was performed using DBS. In this review we present a detailed description of all of the methods and techniques employed in Globus-M alongside results obtained using DBS in all the years up until the shutdown of the tokamak. These include research similar to that done on other devices into the properties of such phenomena like geodesic acoustic modes or limit cycle oscillations, along with innovative works regarding the detection and investigation of Alfven eigenmodes and filaments that were the first of their kind and that provided important and novel results. Apart from that, the specific aspects of DBS application on a spherical tokamak are discussed. An in-depth look into the gradual change and improvement of the DBS diagnostics on Globus-M is also presented in this paper.

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Observation of geodesic acoustic mode in EAST using Doppler backscattering system

et al. 2018

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This paper presents an investigation of the geodesic acoustic mode (GAM) using two poloidally separated Doppler backscattering systems in Experimental Advanced Superconducting Tokamak. Each system allows for the simultaneous measurement of turbulence rotation velocity and density fluctuations with high precision. With the Doppler backscattering systems, the GAM frequency, the symmetric feature of poloidal flow fluctuations, and the interaction between GAM and turbulence are surveyed. The results of bispectral analysis show a clear interaction of GAM with the ambient turbulence. A clear measurement of GAM in the envelope of plasma density fluctuations using Doppler backscatter system is shown, and the modulations of the turbulence perpendicular velocity on the density turbulence are correlated at two different poloidal position.

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Observation of filaments on the globus-M tokamak by Doppler reflectometry

Cited by 30 publications

References 3 publications

Full-Wave Modeling of Doppler Backscattering from Filaments

Full-Wave Modeling of Doppler Backscattering from Filaments

Review of Advanced Implementation of Doppler Backscattering Method in Globus-M

Observation of geodesic acoustic mode in EAST using Doppler backscattering system

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