Study Of SWITG And SWTEM In The Presence Of Impurities In Tokamak Plasmas

In this paper,the gyrokinetic integral dispersion equation in toroidal geometry is used to study short wavelength ion temperature gradient?SWITG?and trapped electron modes?SWTEM?in presence of impurities.The conclusion is as follow: When the trapped electron is not considered.The numerical results indicate that the growth rate of SWITG is decreased when the impurity ions density profile is peaked inwardly(L_ez>0).Moreover,the modes are more stable and hardly excited with a higher values of L_ez when L_ez>0,and the stabilizing effect is stronger with a higher mass and charge number.For L_ez<0,the impurity ions have destabilizing effect on the SWITG when the fraction of impurity is small,and the modes are more unstable and easily excited with a higher absolute values of L_ez.Furthermore,the destabilizing effect is stronger with a higher mass and charge number.When the fraction of impurity is higher,the impurity ions with L_ez<0 have stabilizing effect on the SWITG.Don't consider the ion temperature gradient.For SWTE,the impurity ions have stabilizing effects on the SWTEM modes regardless the impurity ion density profile is peaked inwardly or outwardly.Moreover,the stabilizing effect is better with a higher value of L_ez and a higher mass and charge number.Consider both ion temperature gradient and trapped electron.SWITG and SWTEM may coexist or form hybrid modes.The SWTEM and SWITG mode have been shown to be strongly coupled when the temperature and the fraction of the trapped electrons are low.The impurity ions always have stabilizing effects on the SWTE-ITG mode with small ?_i??_i<5.0?,which is different from the conventional TE-ITG mode.In the lager ?_i??_i>5.0? regime the impurity ions with the L_ez>0(L_ez<0)stabilize?destabilize?the SWTE-ITG mode.The result for SWTE-ITG mode is similar to the SWITG mode in lager ?_i regime.When the temperature and the fraction of the trapped electrons are moderate or high,the SWITG mode and SWTEM mode are weakly coupled and coexist in tokamak plasma.The impurity ions effect on the coexist modes are similar with the results of consider the trapped electron and the ion temperature gradient respectively.Therefore,we can think that SWTEM mode and SWITG mode in the coexistence state do not affect each other.These results have important significance for suppressing the micro-instabilities of drift wave modes.