Global Analysis of a Reflectometry Database for Systematic Study of Plasma Turbulence in Tokamaks

Abstract : o systematically study the plasma turbulence in tokamaks, a parametrization method of frequency spectra from the Tore Supra reflectometry database has been developed. The database includes 350,000 acquisitions obtained from 6,000 discharges with different heating scenarios. In the parametrization, each spectrum has been decomposed into four component: the direct current component, the low-frequency (LF) fluctuations, the broadband (BB) turbulence and the noise level, and each component has been fitted by a function. Specifically for the BB turbulence component, three different functions have been tested and compared. The generalized Gaussian function and the Taylor function have shown excellent fitting performance. In Ohmic plasmas, EBB in the saturated Ohmic confinement regime is observed to be systematically higher than in the linear Ohmic confinement regime. In L-mode plasmas, EBB in the ion cyclotron resonance heating plasmas is globally much higher than in the lower hybrid heating plasmas. The collisional effects on the modifications of the spectra have also been studied. With the previous kinetic simulation results, a change of the dominating micro-instabilities, i.e., between the trapped electron modes and the ion temperature gradients modes, has been proposed to explain the behaviors of EBB, supported by database analysis of the density peaking and the LF component.
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Yan Sun. Global Analysis of a Reflectometry Database for Systematic Study of Plasma Turbulence in Tokamaks. Accelerator Physics [physics.acc-ph]. Université de Lorraine; Ghent University (Gand, Belgique), 2019. English. ⟨NNT : 2019LORR0051⟩. ⟨tel-02328269⟩

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