Speaker
Description
ITER has switched to full tungsten wall configuration[1].High-Z tungsten dust originated from the Plasma-Surface Interactions(PSIs) may result in the degradation of plasma discharges, the H-L mode back transition or even disruption. Meanwhile, low-Z impurity pellets such as lithium or boron ones are strong candidates for ELM control with impurity injection. The small or grassy ELMs are triggered before the formation of large type-I ELMs. Consequently, the plasma disruptions can be avoided and the high-confinement, long-pulse discharges are achieved.
In this work, the transport of tungsten impurities, originated during the dust ablation process as well as the PSIs, are investigated with STRAHL code. The corresponding core energy dissipation due to radiation during impurity transport is also assessed. Furthermore, the lithium impurity pellet injections are modeled with the NDS-BOUT++ and the BOUT++ transport module. The penetration and the size distribution of the lithium pellet on its trajectory are simulated with the updated ablation module and compared to experiment diagnostics. The fueling pellets are investigated with PAM code to optimize EAST pellet fueling efficiency, considering the ∇B-induced plasmoid drift. In addition, the pellet ablation trail in tokamak plasma provides significant identifier for tokamak safety factor diagnostic. We will also report our recent work on tokamak diagnostics.
Our simulation results[2] show that the sub-micron sized tungsten dust originated from the EAST upper-divertor region is capable of penetrating through the Separatrix. For impurity pellet injections, the lithium pellet is capable of penetrating ~ 20 cm into the HL-3 plasma when injected horizontally from the low-field-side midplane with the initial velocity of 100 m/s. The plasma pressure in the pedestal region increased ~ 25% due to the lithium pellet ablation and ionization[3]. On fueling pellets, we find pellet penetration contribute more to the deep pellet deposition than the ∇B-induced plasmoid drifts in low temperature plasma, while deep pellet fueling in reactor relevant high temperature plasma has to rely on plasmoid drifts[4]. Finally, our developed stereo CCD system for tokamak safety factor diagnostic proves to be robust and accurate with the average difference of 6.8% compared the traditional MSE diagnostic in EAST discharges[5].
[1] C. Angioni, Nuclear Fusion 65, 062001 (2025).
[2] Z. Liu, etc., Physics of Plasmas 28, 122503 (2021);
[3] Z. Liu, etc., Physics of Plasmas, Under Review
[4] J. Zhang, J. L. Hou, Z. Liu, etc., Nuclear Fusion 64, 076012 (2024).
[5] C. Liang, Z. Liu*, etc., Review of Scientific Instruments 95, 043502 (2024)