The quasi-continuous exhaust regime in ASDEX Upgrade and JET

Abstract

The quasi-continuous exhaust (QCE) regime is a type-I ELM-free high confinement regime obtained at high plasma shaping and high separatrix density. A comparison with various ELM-free regimes in the literature is presented together with potential physics models for accessing the QCE regime. The regime was recently successfully ported from ASDEX Upgrade to JET. We present a first comparison between the achieved plasma conditions in the two tokamaks and an extrapolation towards ITER and EU-DEMO parameters. The step in size from ASDEX Upgrade to JET successfully lowered the pedestal top collisionality, demonstrating that the regime is not limited to high collisionality at the pedestal top but naturally operates at high density. The extrapolation to ITER and EU-DEMO parameters shows that they can reach the conditions in which ASDEX Upgrade and JET are operating in QCE without type-I ELMs applying previously proposed physics models.