Time: Wednesday, Oct. 23, 2:00 pm
Venue: Rm. 413, Bld. 11#, Yuquan Campus
Speaker: Shengming Li
Title: Gyrokinetic Simulations of Isotope Effect on ITG-TEM Driven Turbulent Transport
Abstract:
Isotope effect on the turbulent transport is an important issue in toroidal burning plasmas. The scaling of the confinement with the isotope mass 𝐴𝑖 have been studied experimentally on many devices. Gyro-Bohm scaling predicts that the turbulent diffusivity of ion energy flux increases with √𝐴𝑖 , which is in contrast to experiments.
In this work, simulations using Gyrokinetic Toroidal Code (GTC) are carried out to study isotopic dependence of hydrogen isotope (H, D and T) on typical electrostatic turbulence such as ion temperature gradient (ITG) mode and trapped electron mode (TEM).
Linear simulations show that maximum growth rate γ, real frequency ω, and most unstable poloidal wave vector 𝑘𝜃 have significant isotope dependence for the ITG and TEM instabilities. The linear dispersion of ITG is shrunk toward lower m mode due to the increase of gyroradius from H to T. Linear simulations of mixed ITG and TEM turbulence show that 𝛾𝑚𝑎𝑥 of ITG is close to 𝛾𝑚𝑎𝑥 of TEM in hydrogen plasmas, while they have a big difference in deuterium or tritium plasmas. And 𝛾𝑚𝑎𝑥 of ITG decreases weakly with 𝐴𝑖 , but 𝛾𝑚𝑎𝑥 of TEM increases rapidly as 𝐴𝑖 increases.
Nonlinear simulations show that in linear growth stage, the TEM grows with wavelength shorter than that of ITG. In nonlinear stage, both TEM and ITG saturate at long wavelength and the saturation level has a strong isotope dependence between H, D and T. With the gyroradius increasing from H to T, the ITG-TEM driven turbulent transport is significantly reduced which favors burning plasmas.