889 / 2019-10-08 10:59:19

Synergetic effects of turbulence, MHD and sawtooth crashes on particle transport in low-collisionality L-mode plasmas on HL-2A tokamak

全体主题 > 磁约束核聚变实验

Experiments in low collisionality L-mode plasmas on the HL-2A tokamak show that the background-subtracted SXR reconstructions just after the injection of aluminium trace impurity by laser blow-off the impurity has a stationary hollow profile with large amplitude when ECRH power is deposited inside q=1 surface. By contrast, the impurity profile becomes rather flat when the deposition position moves outside q=1 surface. The transport coefficients evaluated by the integrated use of the 1D impurity transport code STRAHL and the SXR reconstructions indicates that a strong outward convection gives rise to the hollowness of impurity profiles. Concomitantly, inverted sawteeth would be observed after crashes due to the flattening of hollow profiles, which leads to an increase of impurity density inside the inversion radius. It is also found that the synergetic effect of inward impurity convection driven by turbulence and the impurity expulsion by core magneto-hydrodynamic (MHD) activity is responsible for strong hollowness of the impurity density profiles. Gyrokinetic simulations confirm that the local change of affects the relative strength of the trapped electron mode (TEM) and the ion temperature (ITG) mode, eventually determining the electron particle transport in a way consistent with the experimental observations.