Advances in the long-pulse steady-state high beta H-mode scenario with active controls of divertor heat and particle fluxes in EAST

Abstract

Since the last IAEA-Fusion Energy Conference, the Experimental Advanced Superconducting Tokamak (EAST) research program has been, in support of ITER and CFETR, focused on development in terms of the long-pulse steady-state (fully noninductive) high beta H-mode scenario with active controls of the stationary and transient divertor heat and particle fluxes. The operational domain of the steady-state H-mode plasma scenario has been significantly extended with ITER-like tungsten mono-block divertor, plasma control and heating schemes. EAST has achieved several important milestones in the development of high β p H-mode scenario and its key physics and technologies. A 60 s-scale long-pulse steady-state high β p H-mode discharge with the major normalized plasma parameters similar to the designed performance of the CFETR 1 GW fusion power operation scenario has been successfully established and sustained by pure RF heating and current drive. Several feedback control schemes have been developed for a sustained detachment with good core confinement. This includes control of the total radiation power, target electron temperature, and particle flux measured using divertor Langmuir probes or a combination of the control of target electron temperature and AXUV radiation near the X point. The detachment feedback control schemes have been integrated with small-ELM regimes and high β p scenario via neon seeding, enabling a core and edge compatible integrated high-beta scenario applicable to long-pulse operations. ELM suppression has been achieved using various methods, including resonant magnetic perturbations and impurity seeding. Full suppression of ELMs by using n = 4 RMPs has been demonstrated for ITER for the first time in low input torque plasmas in EAST. EAST has been operated with helium to support the ITER research requirements for the first time. For a long-pulse, high bootstrap current fraction operation, a new lower tungsten divertor with active water-cooling has been installed, along with improvements in the heating and current drive capability.

Achievements of actively controlled divertor detachment compatible with sustained high confinement core in DIII-D and EAST

“…The strong ITB formation mechanism in DIII-D to be shown in section 4.3 and the EAST results in reference [35], suggesting that neon seeding may offer a more promising tool for favorable core-edge integration in the high β P plasma conditions in EAST, with respect to Ar seeding. In the EAST 2019 winter campaign, the compatible core-edge integration in the high β P scenario has been extended and demonstrated with H 98 > 1.2 at β P ∼ 2.5, β N ∼ 2.0, f bs ∼ 50%, f gw ∼ 0.7 at moderate q 95 ∼ 6.7 (EAST #94437) [33,34], with the peak heat flux on the divertor reduced by ∼30%, using a mixture of 50% neon and 50% D 2 seeding.…”

“…The EAST has demonstrated long-pulse high β P scenario over 1 min with ITER-like tungsten divertor [33,34]. To resolve the critical divertor PWI challenge with even higher heating power injection for future steady-state operation, the active detachment feedback control has also been successfully developed in the high β P scenario since the EAST 2019 spring campaign, showing favorable core-edge-divertor integration.…”

The effect of plasma beta on error-field penetration in radio-frequency wave heated plasmas in EAST

“…EAST is a fully superconducting tokamak equipped with advanced heating schemes [45]. The RMP system has been successfully applied for studies in error-field penetration and ELM control in EAST [9,25,46,47].…”

A neoclassical validation of balanced and unbalanced rotations on EAST H-mode discharges

“…2019YFE03040000). Authors would like to express our sincere appreciation to the EAST team and International/ Domestic Collaborators listed in [47].…”