Speaker
Description
EAST has achieved a pivotal breakthrough by sustaining a steady-state high-confinement plasma for 1066 seconds with an injected energy of 3.05 GJ, setting a world record for both pulse duration and cumulative energy input. This major achievement integrates high-confinement performance with low momentum input, efficient heating and current drive, water-cooled tungsten divertors, active control of heat fluxes, precise recycling and particle balance regulation, magnetic configuration and equilibrium for long-duration operations. With this result, EAST has become the first tokamak that can operate with a pulse length in thousand-second scale, with plasma temperatures in the tens of million degrees Celsius and self-driven current.
Key technical solutions were developed to overcome the challenges of long-pulse H-mode plasma operation over 1066 seconds, which was achieved in a lower single-null configuration with $\beta_p = 2.0$ and $f_{\mathrm{BS}} \sim 50\%$, driven by $P_{\mathrm{LHCD}} = 1.1\,\mathrm{MW}$ and $P_{\mathrm{ECRH}} = 1.9\,\mathrm{MW}$. A no/small ELM regime was realized by positioning the outer strike point on the horizontal target, which not only facilitates efficient radio frequency (RF) power coupling but also mitigates tungsten (W) sputtering and erosion. Fully non-inductive current drive was achieved at an electron density equivalent to 63\% of the Greenwald density, with a confinement enhancement factor $H_{98y2} = 1.3$ enabled by an electron temperature internal transport barrier (e-ITB). The synergistic effects between on-axis ECRH and LHCD are critical for maintaining high-confinement plasmas.
The e-ITB H-mode discharge exhibits nonlinear self-organization characteristics, emerging near the magnetic axis without external momentum injection. This long-term operational stability provides a unique opportunity to investigate the anomalous energy fluxes driven by plasma turbulence. Active control of a high-field side flux loop maintained zero loop voltage for non-inductive operation. Low-Z material wall coating and real-time powder injection techniques were implemented to enhance particle control capability. The evolution of wall materials was systematically studied through plasma-wall integrated modeling, while core-edge integration in high-performance steady-state operation scenarios compatible with metallic walls was experimentally explored.
This paper also presents the detailed physical mechanisms and technological advancements associated with the upgrade of EAST’s operational capabilities, which are tailored to the development of future fusion reactors such as ITER-relevant configurations.