Perturbative studies of toroidal momentum transport in KSTAR H-mode and the effect of ion temperature perturbation. (16th April 2018)

• Record Type: Journal Article
• Authors: Yang, S.M.; Na, Yong-Su; Na, D.H.; Park, J.-K.; Shi, Y.J.; Ko, W.H.; Lee, S.G.; Hahm, T.S.
• Is Part Of: Nuclear fusion. Volume 58:Number 6(2018:Jun.)
• Publication Date: 2018-04-16
• Subjects: perturbative analysis -- momentum transport -- KSTAR -- ion temperature perturbation; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/aab90e
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: Perturbative experiments have been carried out using tangential neutral beam injection (NBI) and non-resonant magnetic perturbation (NRMP) to analyze the momentum transport properties in KSTAR H-modes. Diffusive and non-diffusive terms of momentum transport are evaluated from the transient analysis. Although the operating conditions and methodologies applied in the two cases are similar, the momentum transport properties obtained show clear differences. The estimated momentum diffusivity and pinch obtained in the NBI modulation experiments is larger than that in the NRMP modulation experiments. We found that this discrepancy could be a result of uncertainties in the assumption for the analysis. By introducing time varying momentum transport coefficients depending on the temperature gradient, the linearized equation shows that if the temperature perturbation exists, the evolution of toroidal rotation perturbation could be faster than the transport rate of mean quantity, since the evolution of toroidal rotation perturbation is related to, a momentum diffusivity from perturbative analysis. This could explain the estimated higher momentum diffusivity using time independent transport coefficients in NBI experiments with higher ion temperature perturbation compared to that in NRMP modulation experiments. The differences in the momentum transport coefficient with NRMP and NBI are much reduced by considering time varying momentum transport coefficients in the time dependent transport simulation.