Publication Date:
2016-04-22
Description:
The collisionless trapped electron modes in the short wavelength region k ⊥ ρ s 〉 1 (SWTEMs) are studied with the gyrokinetic integral eigenmode equation in tokamak plasmas. Here, we present a systematic study of the correlation between the SWTEMs and short wavelength ion temperature gradient (SWITG) modes. The k θ ρ s spectra of TEM have double humps in the short wavelength and long wavelength regions, respectively. The SWITG modes with trapped electron effects taking into account have broader k θ ρ s spectra. Dependences of growth rate and real frequency of SWTEMs on the various parameters, such as ion temperature gradient (η i ), the temperature gradient of trapped electrons (η e ), toroidicity (ε n ), magnetic shear ( s ̂ ), safety factor (q), and the ratio of temperature (T e /T i ), are investigated in detail. It is found that the SWTEMs propagate in the electron diamagnetic drift direction and require temperature gradient of trapped electrons η e exceeding thresholds. Moreover, the ion temperature gradient has a strong stabilizing effect on the SWTEMs. The SWTEMs become stable in both regimes of toroidicity ε n 〉 0.1 and magnetic shear s ̂ 〉 0.5 regardless of the fraction of trapped electrons. In addition, the properties of short wavelength ITG (SWITG) modes are discussed with different ratio of trapped electrons. It is found that trapped electrons of greater fraction have a stronger destabilizing effect on the SWTEM and SWITG modes. These results are significant for the electrons anomalous transport experiments in the future.
Print ISSN:
1070-664X
Electronic ISSN:
1089-7674
Topics:
Physics
