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

Yashin, A. Yu.; Bulanin, V. V.; Петров, А. М.; Ponomarenko, Anna

doi:10.3390/app11198975

Cited by 14 publications

(5 citation statements)

References 75 publications

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“…Here, k ⊥ is the wavenumber of turbulent fluctuations perpendicular to the magnetic field, and ρ i is the ion gyroradius. Consequently, it is a widely used diagnostic for both tokamaks and stellarators [8][9][10][11][12][13][14][15][16][17][18][19][20]. Moreover, since DBS is a microwave diagnostic, it is one of the few diagnostics capable of surviving the neutron fluxes generated by burning plasmas of future fusion reactors [21,22].…”

Section: Introductionmentioning

confidence: 99%

Beam model of Doppler backscattering

Hall-Chen

Parra

Hillesheim

2022

Plasma Phys. Control. Fusion

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We use beam tracing --- implemented with a newly-written code, Scotty --- and the reciprocity theorem to derive a model for the linear backscattered power of the Doppler Backscattering (DBS) diagnostic. Our model works for both the O-mode and X-mode in tokamak geometry (and certain regimes of stellarators). We present the analytical derivation of our model and its implications on the DBS signal localisation and the wavenumber resolution. To determine these two quantities, we find that it is the curvature of the field lines and the magnetic shear that are important, rather than the curvature of the cut-off surface. We also provide an explicit formula for the hitherto poorly-understood quantitative effect of the mismatch angle. Consequently, one can use this model to correct for the attenuation due to mismatch, avoiding the need for empirical optimisation. This is especially important in spherical tokamaks, since the magnetic pitch angle is large and varies both spatially and temporally.

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Section: Introductionmentioning

confidence: 99%

Beam model of Doppler backscattering

Hall-Chen

Parra

Hillesheim

2022

Plasma Phys. Control. Fusion

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“…This method has been used on a variety of tokamaks and has garnered results regarding the rotation velocity and radial electric field of the plasma [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. On Globus-M, this diagnostic has also been successfully utilized but only for the study of plasma oscillatory processes, not to investigate the transition to H-mode [ 20 ]. Moreover, a multitude of other phenomena was discovered and fruitfully studied, such as geodesic acoustic modes (GAMs), limit-cycle oscillations (LCOs), Alfven eigenmodes (AEs), filaments, and others [ 21 , 22 , 23 , 24 ].…”

Section: Doppler Backscatteringmentioning

confidence: 99%

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

Yashin

Курскиев

et al. 2023

Sensors

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This paper presents the first results of a study of the LH transition on the new spherical Globus-M2 tokamak using the Doppler backscattering (DBS) diagnostic. New data characterizing the H-mode of discharges with higher values of the plasma parameters, such as magnetic field Bt up to 0.9 T and plasma current Ip up to 450 kA, were collected and analyzed. An upgraded neutral beam injection (NBI) system was used to initiate the LH transition. DBS allows the measurement of the poloidal rotation velocity and the turbulence amplitude of the plasma. The multi-frequency DBS system installed on Globus-M2 can simultaneously collect data in different areas spanning from the separatrix to the plasma core. This allowed for the radial profiles of the rotation velocity and electric field to be calculated before and after the LH transition. In addition, the values and temporal evolution of the velocity shear were obtained. The associated turbulence suppression after the transition to the H-mode was investigated using DBS.

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“…On Globus-M2 the DBS method is used to gather data on the poloidal rotation velocity of the density fluctuations in the tokamak which is used to estimate the radial electric field. Moreover, different oscillatory processes and a multitude of other phenomena were studies using DBS [38]. These include Alfven eigenmodes [39], neoclassical tearing modes [40], quasi-coherent fluctuations (QCFs) [41], limitcycle oscillations [42] and geodesic acoustic modes [43].…”

Section: Dbs On Globus-m2mentioning

confidence: 99%

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

Cited by 14 publications

References 75 publications

Beam model of Doppler backscattering

Beam model of Doppler backscattering

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

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

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