Two-dimensional modelling for HT-7U tokamak divertor

The different recycling operations in the HT-7U divertor plasma are studied in the present B2.5 modelling. The modelling results show that in the HT-7U high density operation regime, with a boundary density at the core–SOL interface of Nedge⩾2×1019 m−3, high recycling operation in the divertor plasma can be obtained and plasma with high density and low temperature can be formed in front of the target plate and the plasma heat flux arriving at the target plate is greatly reduced because of the ionization loss in the high recycling processes. For the HT-7U low density operation regime, with Nedge<2×1019 m−3, the high recycling operation cannot be formed and the plasma with low density and higher temperature is formed in front of the target plate, and the plasma heat flux towards the target plate become larger than in the high recycling operation.