Linear scattering theory of short-pulse reflectometry

Krutkin, O. L.; Brunner, S.; Coda, S.; Aleynikov, P.

doi:10.1088/1361-6587/aca826

Cited by 2 publications

(4 citation statements)

References 31 publications

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“…However, the variation of the turbulence amplitude in the covered radial range has so far been insignificant (around 15%) which is what we are addressing in this computation. The samples for this case were generated according to equation (18) and then multiplied by a factor exp(1 − x L0 ). This resulted in the turbulence amplitude varying by about 40% along the scanned radial range and edge turbulence having the relative amplitude of up to 100%.…”

Section: Spatial Dependenciesmentioning

confidence: 99%

“…The density fluctuations were also adapted to follow the curvature of the background profile, with l cy becoming the correlation length along the circular surface of constant n 0 . This was done by generating δn(x ′ , y ′ ) according to equation (18) and then remapping it to (x, y) following the rule:…”

Section: Geometrical Factorsmentioning

confidence: 99%

“…But similar to the FSR diagnostic, SPR measurements are affected by plasma turbulence and can potentially provide related information. An investigation into the implications of SPR's unique capability to digitally record the reflected pulse for turbulence studies has recently been carried out [18]. Unfortunately, it concludes that, in the current configuration of the SPR diagnostic, the pulse shape is not directly connected to the plasma turbulence parameters.…”

Section: Introductionmentioning

confidence: 99%

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A method for density fluctuation measurements using pulse reflectometry

2023

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An analytical 1D model based on the WKB approximation is used to study the properties of a short pulse reflectometry diagnostic in a magnetic fusion device. Expressions linking the pulse delay with the parameters of the turbulence near the cut-off layer are derived for both ordinary and extraordinary polarizations of the probing beam. These results are used to develop a method for measuring the turbulence amplitude and the radial correlation length. The analytical conclusions and the proposed method are validated using full-wave numerical modelling. The latter is also used to study the limitations of the method and potential experimental effects not included in the reduced model.

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Section: Spatial Dependenciesmentioning

confidence: 99%

Section: Geometrical Factorsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A method for density fluctuation measurements using pulse reflectometry

2023

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“…Frontiers in Physics frontiersin.org 16 fluctuations measured by the SPR [79], and thereby the direct impact of fast ions and TAEs on the electron density fluctuations is not reported in this article.…”

Section: Figure 14mentioning

confidence: 94%

Study of fast-ion-driven toroidal Alfvén eigenmodes impacting on the global confinement in TCV L-mode plasmas

Mazzi,

Vallar,

Kumar

et al. 2023

Front. Phys.

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Following recent observations of unstable Toroidal Alfvén Eigenmodes (TAEs) in a counter-current Neutral Beam Injection (NBI) scenario developed in TCV, an in-depth analysis of the impact of such modes on the global confinement and performance is carried out. The study shows experimental evidence of non-degradation of ion thermal confinement despite the increasing of auxiliary power. During such an improved confinement period, Toroidal Alfvén Eigenmodes (TAEs) driven by fast ions generated through Neutral Beam Injection (NBI) are found unstable. Together with the TAEs, various instabilities associated with the injection of the fast neutrals are observed by multiple diagnostics, and a first characterization is given. Nonlinear wave-wave couplings are also detected through multi-mode analysis, revealing a complex picture of the stability dynamics of the TCV scenario at hand. The measurements provided by a short-pulse reflectometer corroborate the identification and radial localization of the instabilities. A preliminary, but not conclusive, analysis of the impact of TAEs on the amplitude of the electron density fluctuations is carried out. Local flux-tube gyrokinetic simulations show that the dominant underlying instabilities in the absence of fast ions are Trapped Electron Modes (TEM), and that these modes are effectively suppressed by zonal flows. Attempts to simulate the simultaneous presence of fast-ion driven TAEs and TEM turbulence show that elongated streamers develop up to the full radial extent of the flux-tube domain, thereby invalidating the local assumption and indicating that a global approach is mandatory in these TCV plasmas.

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Linear scattering theory of short-pulse reflectometry

Cited by 2 publications

References 31 publications

A method for density fluctuation measurements using pulse reflectometry

A method for density fluctuation measurements using pulse reflectometry

Study of fast-ion-driven toroidal Alfvén eigenmodes impacting on the global confinement in TCV L-mode plasmas

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