Transport analysis based on K-ε anomalous transport model

A K-ε anomalous transport model for resistive interchange turbulence is presented and applied to the transport analysis of ECH plasmas in Heliotron E. In this model, the turbulent kinetic energy K≡1/2 left-angle v2 right-angle and its viscous dissipation rate ε characterize the local turbulence and the anomalous transport coefficient is given by D∼Kw/ε, which has some nonlocal properties not included in the conventional expressions since their temporal and spatial variations are determined by taking into account the transport of the turbulent energy itself. In the case of the homogeneous turbulence where the anomalous transport may be described in terms of the local plasma parameters, the dimensional analysis applied to our model yields the two types of local parameter expressions of the anomalous diffusivity in the high and low collisional cases. We find a familiar diffusivity for the resistive interchange turbulence derived in the high collisional case and we have another one similar to the gyro-reduced Bohm (GRB) diffusivity in the los collisional case. However, it is shown from the transport simulation using our model that, in the region where the turbulence inhomogeneity is significant, the anomalous diffusivity deviates from the local parameter expression due to the transport terms in the K-ε equations. Our model explains the experimental results consistently in that it gives the GRB or LHD scaling for the energy confinement time and reproduces the experimentally obtained profile of the anomalous diffusivity which has large values in the peripheral region in contrast with the GRB model