First Results of the Implementation of the Doppler Backscattering Diagnostic for the Investigation of the Transition to H-Mode in the Spherical Tokamak Globus-M2

Ponomarenko, Anna; Yashin, A. Yu.; Курскиев, Г. С.; Минаев, В. Б.; Петров, А. М.; Petrov, Yu. I.; Сахаров, Н. В.; Zhiltsov, Nikita

doi:10.3390/s23020830

Cited by 9 publications

(2 citation statements)

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“…In this case, the V phase of these instabilities were less than 0.2 km s −1 in a wide range of wave vectors ranging from 1 to 100 cm −1 . The values of the V phase in simulations were significantly smaller than the typical measured perpendicular velocities V ⊥ on Globus-M2, which have a value of about 3 km s −1 in the L-mode and reach values of about 10 km s −1 in the H-mode [12,37]. From this data we conclude that in experiments under consideration, the main contribution to the measured V ⊥ comes from the E × B drift velocity V E×B .…”

Section: Dbs On Globus-m2mentioning

confidence: 56%

“…The DBS method is seen as useful in providing local measurements about the plasma turbulence and allows to follow changes in its behaviour. For example, the suppression of the turbulence due to velocity shear in H-mode was also confirmed on Globus-M2 [12]. An increase in turbulence activity indicating plasma degradation could also be seen during an ELM burst making it a phenomenon worth investigating.…”

Section: Introductionmentioning

confidence: 75%

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The investigation of edge-localized modes on the Globus-M2 tokamak using Doppler backscattering

Ponomarenko,

Gusev,

Kiselev

et al. 2023

Nucl. Fusion

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The first results of investigation of edge localized modes (ELMs) in the Globus-M2 tokamak using the Doppler backscattering method are presented in this paper. Specifically, ELMs that are initiated by sawtooth crashes in the H-mode are discussed. The goal of this paper is study plasma turbulence behaviour during ELMs and to showcase what ELM characteristics can be obtained using Doppler backscattering (DBS). An increase of the poloidal rotation velocity during an ELM burst and a decrease in the inter-ELM periods was observed. The effect of ELMs on the plasma turbulence was investigated and estimated to span around 6 cm inside the separatrix. This is to do with the fact that the sawtooth crashes which are responsible for initiating the ELMs take place in the core plasma. Additional experiments with standard reflectometry indicate that ELMs develop 3 cm inside the separatrix where the pedestal region is believed to be in Globus-M2. The direction of the expansion of the ELMs from the inner plasma region to the edge was determined and the velocity was estimated to be around 8 km s−1. During a single ELM burst a series of filament structures were found in the peripheral DBS channels. In an attempt to understand the processes involved modelling of the reaction of the DBS signals to filaments was done using the BOUT ++ and IPF-FD3D full-wave codes, and the cases for both linear and nonlinear scattering were considered. The results show that the presence of nonlinear scattering during ELMs can lead to an overestimation of the measured velocity values in the region of filament existence near the separatrix.

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Section: Dbs On Globus-m2mentioning

confidence: 56%

Section: Introductionmentioning

confidence: 75%

The investigation of edge-localized modes on the Globus-M2 tokamak using Doppler backscattering

Ponomarenko,

Gusev,

Kiselev

et al. 2023

Nucl. Fusion

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Confinement, heating, and current drive study in Globus-M2 toward a future step of spherical tokamak program in Ioffe Institute

Kurskiev,

Minaev,

Sakharov

et al. 2024

Physics of Plasmas

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This paper highlights the most important results achieved at the spherical tokamak Globus-M2 with a high magnetic field. This paper also covers the most important topics of fusion research: thermal energy confinement in regimes with neutral beam injection, toroidal Alfvén eigenmode and correspondent fast ions confinement issues, L-H transition, turbulence suppression and edge-localized modes' behavior, experimental and theoretical study of regimes with nitrogen seeding that allow to significantly reduce thermal loads on the divertor plates, and experiments and simulations of lower hybrid current drive. The research results provide the basis for the next step toward a fusion neutron source—the development of the Globus-3 spherical tokamak.

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First results of turbulence investigation on Globus-M2 using radial correlation Doppler reflectometry

PONOMARENKO,

YASHIN,

GUSEV

et al. 2024

Plasma Sci. Technol.

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The first results of investigation of the turbulence structure using Doppler backscattering (DBS) on the Globus-M2 tokamak are presented. A one-channel DBS system with a variable probing frequency within the 18-26 GHz range was installed to investigate the edge plasma at normalized minor radii ρ = 0.9 – 1.1. Radial correlation Doppler reflectometry was used to study the changes in turbulence eddies after the LH transition. Correlation analysis was applied to the phase derivative of complex IQ signals of the DBS diagnostic as it contains information about the poloidal plasma rotation velocity. In L-mode the radial correlation length Lr is estimated to be 3 cm and after transition to H-mode reduces to approximately 2 cm. Gyrokinetic modelling in a linear local approximation using code GENE indicates that the instability with positive growth rates at the normalized minor radius ρ = 0.75 in L-mode and H-mode on Globus-M2 was the ion temperature gradient (ITG) mode.

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First Results of the Implementation of the Doppler Backscattering Diagnostic for the Investigation of the Transition to H-Mode in the Spherical Tokamak Globus-M2

Cited by 9 publications

References 31 publications

The investigation of edge-localized modes on the Globus-M2 tokamak using Doppler backscattering

The investigation of edge-localized modes on the Globus-M2 tokamak using Doppler backscattering

Confinement, heating, and current drive study in Globus-M2 toward a future step of spherical tokamak program in Ioffe Institute

First results of turbulence investigation on Globus-M2 using radial correlation Doppler reflectometry

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