Direct measurement of electron turbulence broadening edge transport barrier for facilitating core-edge integration in tokamak fusion plasmas

Abstract The integration of a high-performance core and a dissipative divertor or the so-called “core-edge integration” has been widely identified as a critical gap for the design of future fusion reactors. In this letter, we report, for the first time, the direct experimental evidence of electron turbulence at DIII-D H-mode pedestal that correlates with the broadening of the pedestal and thus facilitates core-edge integration. In agreement with gyrokinetic simulations, this electron turbulence is enhanced by high ηe (ηe =Ln/LTe, where Ln is the density scale length and LTe is the electron temperature scale length), which is due to a strong shift between density and temperature pedestal profiles associated with a closed divertor. The modeled turbulence drives significant heat transport with lower pressure gradient and that may broaden the pedestal wider than the empirical and theory-predicted pedestal width scaling. Such a wide pedestal, coupled with a closed divertor, enables us to achieve a good core-edge scenario which integrates high-temperature low-collisionality pedestal (pedestal top temperature Te,ped>0.8keV and pedestal top collisionality *ped