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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 Alfvn acoustic self-heating channel for burning plasmas - where fast-ion-driven shear Alfvn 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 
. However, when 
is increased by a factor 2.8, low-frequency sound continua in the range of beta-induced Alfvn 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 Alfvn 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.
Bierwage, A.; Lauber, P.*
no journal, ,
The structure of the continuous spectra of shear Alfven continua and ion sound waves in a high-beta JT-60U tokamak plasma is studied with a linear gyrokinetic code (LIGKA). It is found that increasing the electron temperature relative to that of the ions has a destabilizing effect on ion sound waves at low frequencies (below BAE), but a stabilizing effect at high frequencies (above BAE). Moreover, it is found that the inclusion of (Maxwellian) fast ions gives rise to "hot sound" continua, which have a significant influence on the structure of shear Alfven continua. Implications for a recently proposed Alfven-acoustic self-heating channel for burning tokamak plasmas are discussed. The present linear study lays foundations for nonlinear analyses, that will contribute to a better understanding of energy flows in high-beta fusion experiments (such as JT-60SA) and burning plasmas (DEMO).