Sustained edge-localized-modes suppression and radiative divertor with an impurity-driven instability in tokamak plasmas

Simultaneous control of the large edge localized modes (ELMs) and divertor heat fluxes in a metal wall environment is a critical issue for steady-state operation of a tokamak fusion reactors. Here we report a sustained ELM suppression scenario achieved in the EAST tokamak compatible with radiative divertor using different seeding impurity species over a wide range of conditions. A low-n mode appears, as manifested by the oscillations of a radiation front near the X-point. This mode appears to drive strong particle transport and tungsten exhaust, which is essential to the maintenance of the ELM-stable state. We have developed a model to explain the mode excitation, by coupling the impurity radiative condensation instability to drift waves, which could explain some characteristics of the low-n mode well. The low-n mode may offer a new ELM-stable scenario compatible with radiative divertor for future fusion reactors.

Automated summary

The study presents a sustained ELM suppression scenario achieved in the EAST tokamak, utilizing a low-n mode to drive strong particle transport and tungsten exhaust for maintaining ELM-stable state. A model has been developed to explain the mode excitation, coupling impurity radiative condensation instability with drift waves, offering a new ELM-stable scenario compatible with radiative divertor for future fusion reactors.