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论文类型：期刊论文

发表时间：2014-05-01

发表刊物：PHYSICS OF PLASMAS

收录刊物：SCIE、EI

卷号：21

期号：5

ISSN号：1070-664X

摘要：The coupling of ion temperature gradient (ITG or eta(i)) mode and trapped electron mode (TEM) in the presence of impurity ions is numerically investigated in toroidal collisionless plasmas, using the gyrokinetic integral eigenmode equation. A framework for excitations of the ITG modes and TEMs with respect to their driving sources is formulated first, and then the roles of impurity ions played in are analyzed comprehensively. In particular, the characteristics of the ITG and TEM instabilities in the presence of impurity ions are emphasized for both strong and weak coupling (hybrid and coexistent) cases. It is found that the impurity ions with inwardly (outwardly) peaked density profiles have stabilizing (destabilizing) effects on the hybrid (namely the TE-ITG) modes in consistence with previous works. A new finding of this work is that the impurity ions have stabilizing effects on TEMs in small eta(i) (eta(i) <= 1) regime regardless of peaking directions of their density profiles whereas the impurity ions with density gradient L-ez = L-ne/L-nz > 1 (L-ez < 1) destabilize (stabilize) the TEMs in large eta(i) (eta(i) >= 1) regime. In addition, the dependences of the growth rate, real frequency, eigenmode structure, and wave spectrum on charge concentration, charge number, and mass of impurity ions are analyzed in detail. The necessity for taking impurity ion effects on the features of turbulence into account in future transport experimental data analyses is also discussed. (C) 2014 AIP Publishing LLC.