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論文

Alfv$'{e}$n acoustic channel for ion energy in high-beta tokamak plasmas revisited with a linear gyrokinetic model (LIGKA)

Bierwage, A.; Lauber, P.*; 相羽 信行; 篠原 孝司; 矢木 雅敏

Proceedings of 14th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems (Internet), 8 Pages, 2015/00

A recently proposed Alfv$'{e}$n acoustic self-heating channel for burning plasmas - where fast-ion-driven shear Alfv$'{e}$n waves transfer energy to sound waves which then heat the bulk ions - is reexamined using a linear gyrokinetic model. A local eigenvalue analysis shows that the ion sound branches required for such a self-heating channel are so strongly damped that they are effectively non-existent when $$T_{rm e} approx 1.7times T_{rm i}$$. However, when $$T_{rm e}$$ is increased by a factor 2.8, low-frequency sound continua in the range of beta-induced Alfv$'{e}$n acoustic eigenmodes (BAAE) are recovered and their excitation becomes feasible. This raises the question whether higher-frequency sound branches in the frequency range of beta-induced Alfv$'{e}$n continuum modes (BACM) and the associated self-heating channels may exist under reactor-relevant conditions. Moreover, it is shown that modifications of the continuous spectra by fast ions may need to be taken into account.

口頭

Long-time simulation of N-NB-driven JT-60U plasmas; Validation and explanation for chirping modes (n=1 EPM) and ALE (multi-n)

Bierwage, A.

no journal, , 

Results of long-time simulations of N-NB-driven JT-60U plasmas are presented. The simulations are performed with an extended version of the MEGA code that includes MHD activity, fast ion sources, collisions and a realistic particle boundary (wall). The plasmas studied exhibit two important phenomena: rapidly chirping modes and Abrupt Large Events (ALE). The long-time MEGA simulations reproduce many of the observed properties both qualitatively and quantitatively. The simulations even predict features that were subsequently confirmed by experimental data mining. This constitutes a successful validation of the code and a demonstration of its predictive capability. An analysis of the simulation results allows us to offer explanations for both phenomena. Chirping modes are interpreted as Energetic Particle Modes (EPM) with single toroidal mode number $$n = 1$$, whereas ALEs occur due to interactions between modes with $$n = 1$$, 2 and 3.

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