3D simulation of toroidally discontinuous limiter sol configuration of Aditya Tokamak using EMC3-eirene model

The 3D simulations of plasma transport in the SOL of non-axisymmetric limiter configuration in Aditya Tokamak are done for both its original ring limiter (RL) configuration and a block limiter (BL) configuration similar like upcoming Aditya-upgrade. The complexity of connection lengths and variation of long and short connection length is obtained from EMC3 field line mapping for Block limiter but high connection length is seen in the LCFS region and very short in limiter shadow region for Ring Limiter. The enhanced ionization in longer connection lengths in RL case is seen responsible for a radially growing perpendicular flux but a conventional concave radial density profiles in the BL case. This indicates that for equivalent wall conditions, the localized wall recycling can be expected less intense in the BL case. The simplicity of the 3D model keeping uniform perpendicular diffusivity and only limiter wall recycling explains similar like observation in Alcator-C-Mod having radially diverging flux keeping nonuniform diffusivity and wall recycling. A relatively smaller total recycling flux is recovered for the BL configuration over the complete range of diffusivity values and for three different core-SOL density values analyzed in the present study. (author)