Studies Of TEM And ITG Modes In Tokamak Plasmas

Studies of anomalous transport and micro-instability of plasmas are important topics in the field of magnetically controlled fusion. It is generally believed that micro-drifts wave modes, like trapped electrons mode (TEM) and ion temperature gradient mode (ITG), are responsible for plasmas anomalous transport. Therefore, how to suppress the drift wave mode is significance to enhancing the ability of plasmas confinement. In this dissertation, the TEM and ITG modes are studied and analyzed in-depth based on the gyrokinetic integral equation in tokamak plasmas.Firstly, it is shown that the properties of short wavelength TEM (SWTEM) and short wavelength (SWITG) are discussed. The results are as follows:both the TEM and ITG modes behave double humps in the k?ps spectra. When considering the effect of trapped electrons, these two modes have broader k?ps spectra width. The SWTEM propagates in the electron diamagnetic drift direction and exists a threshold value of trapped electrons temperature. The ion temperature gradient has stabilizing effect on the SWTEM. The SWTEM become stable in both regimes of toroidicity ?n>0.1 and magnetic shear s> 0.5. It is found that trapped electrons of greater fraction have a stronger destabilizing effect on the SWTEM and SWITG modes.Then, the basic properties of the impurity mode are studied alone. It is shown that the greater instability is related to the heavier impurity ion mass and charge higher numbers, but a abnormal fact that heavier impurity ions lead to an bigger destabilizing effect on the mode. In addition, the excitation of impurity mode has to exceed the impurity charge concentration threshold, and the impurity ions with lighter mass and lower charge number produce an smaller threshold. The destabilizing effect of impurity mode is gradually suppressed in the more stronger and more weaker region.Finally, owing to both impurity mode and TEM are mainly located in the edge of plasmas, the coexistence issues of these two mode are studied. In the given parameters, the basic behavior of impurity mode and TEM are discussed. It is found that the impurity modes become more unstable when the parameters are as follows: Lez is more negative, fz is bigger, ?i is lager positive, ?e is smaller ?n is higher, while the TEMs become more dangerous in opposite situations. Moreover, the impurity modes and the TEMs have similar properties with regards to k?ps and s, respectively. A bigger positive magnetic shear s> 3.0 can be used for suppressing these two kinds of modes effectively- These numerical results may provide valuable insights to understanding about the complicated process of plasmas anomalous transport. Specifically, these findings may be used for analysising some transport experimental data more accurately.