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Radiative divertor is an effective method for the divertor heat flux control, but excessive core impurity radiation can deteriorate the confinement in tokamaks. In recent EAST experiments, the compatibility of divertor detachment and impurity control with good core confinement (H98,y2 ∼1) has been achieved simultaneously by combining an upstream deuterium (D2) puff and divertor argon (Ar) seeding. Both experimental and SOLPS-ITER modeling reveal that additional D2 puff can further mitigate the target heat load and facilitate the detachment. The SOLPS-ITER results also show that the D2 puff makes a limited contribution to the Ar line radiation but a significant contribution to the neutral radiation in the SOL and divertor regions. The physical mechanism behind the effect of the D2 puff on the Ar retention is also revealed by the modeling. The increase in the Ar velocity is the major reason for the improved Ar retention in the partial detachment state. The increase in vAr is mainly caused by the strengthening of frictional drag of D+, which is because the additional D2 puff increases the pressure gradient force (FPG) and the electric field force (FE) on D+. Further analysis reveals that in the deep detachment state, some other negative effects play a dominant role in determining the Ar retention, such as the shift of the region of the Ar+ ionization source, the decrease in the strength of the Ar+ ionization source, and the net force on the Ar ions near the target. [ABSTRACT FROM AUTHOR]

A numerical model is developed to study the temporal evolution of helicon discharge. The initiation of helicon discharge is first presented in terms of time-dependent electron density and temperature, electric and magnetic fields, and power deposition; then, their steady-state values are compared with experimental data and previous simulations for benchmark. It is found that the evolutions of electron density and temperature arrive steady state around 100 and $1.5~\mu \text{s}$ , respectively, while electric and magnetic fields become steady prior to 2 $\mu \text{s}$. The spatial distributions of power deposition indicate that RF power is absorbed mostly near the edge, similar to those of electron temperature. Parameter studies show that high background pressure, confining magnetic field strength, and RF power are beneficial to obtaining high-density helicon plasma, while the driving frequency has little effect. These findings are interesting for the design and optimization of helicon plasma source. [ABSTRACT FROM AUTHOR]