Impact of Edge Current on ELM Energy Loss Using BOUT++*

Investigation on the edge current effect on Edge-localized-mode (ELM) energy loss is carried out by using BOUT++ 4-field module with zonal ExB flow and zonal magnetic flux perturbation. A set of JET like equilibriums with different edge current are generated self-consistently using CORSICA while keeping the plasma shape, total stored energy fixed. Surprisingly, we found that the linear growth rate of peeling-ballooning mode decreases when edge current increases, which showed that the local magnetic shear stabilize effect should be taken into consideration. Same trend is found in the linear phase of nonlinear simulation, meanwhile the final saturated energy loss fraction does not show a simple linear dependence. Similar phenomenon is found in both low and high collisionality cases. Zonal ExB flow shows an important role in keeping perturbation from spreading inward and results in a following “L-H” transition around peak gradient region. This study tends to shed the light to derive a small ELM energy loss operation scenario for future machines, such as ITER and CFETR, by using edge current control system.