27th PSI

4.065 SOLPS-ITER simulations for SPARC advanced divertor configurations

22 May 2026, 09:50

2h 30m

Poster G. Power Exhaust, Plasma Detachment and Heat Load Control Postersession 4

Speaker

Dr Haosheng Wu (NEMO Group, Dipartimento Energia, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy.)

Description

The SOLPS-ITER is employed to model advanced divertor configurations in the SPARC tokamak aiming to explore potential solutions to the power exhaust challenge [1]. The configurations studied include the standard Single Null Divertor (SND), Super-X Divertor (SXD), and X-Point Target Divertor (XPTD).
The outer targets of the SXD and XPTD configurations benefit from their advanced geometries, as the peak heat flux is reduced to approximately 30% of that in the SND case (q_surf~80MWm^-2) without seeding of impurities. Subsequently, simulations were performed with neon and argon impurities injected from the Private Flux Region (PFR). The results indicate that when the impurity seeding rate reaches 5×10¹⁹ neon atom s⁻¹ or 2×10¹⁹ argon atom s⁻¹, the outer targets become detached. However, the inner target faces a severe power exhaust challenge that the peak value of heat load remains ~30 MWm^-2, even as the seeding rate increases to 3×10²⁰ neon atom s^-1.
The simulations indicate that when impurities are puffed from the PFR, even a small seeding rate is sufficient to detach the SXD and XPT outer targets. As a result, a deuterium ion flow develops in the PFR, which direction is from the High-Field-Side (HFS) toward the Low-Field-Side (LFS), driven by the pressure reduction at the outer target. In this situation, most of the injected impurities are ionized within the PFR and are subsequently advected by the strong deuterium flow toward the outer target. Consequently, impurities cannot effectively penetrate the PFR, even puffing at the HFS PFR, and it is hard to enter the HFS SOL region, leading to weak radiation in HFS SOL that the inner target remains attached even if the seeding rate is significantly increased.
In order to explore possible ways for reducing the inner target heat load, a series of numerical simulations are performed, including adjustments to the inner target geometry, modifications to the in–out power sharing, and changes to the impurity puffing locations. A noticeable result is when impurity puffing from the HFS SOL is optimized, both inner and outer target can achieve full detachment. The corresponding seeding rate is ~2×10²⁰ neon atom s^-1 and the resulting q_surf reduced to below 10MWm^-2. In addition, the preliminary results with the activation of E×B drift, which can be expected to drive a flow from LFS to HFS in PFR when B×∇B points towards the lower X-point, are presented.

[1] A.Q. Kuang et al. Journal of Plasma Physics 2020.