Journal article

ITER-relevant H-mode physics at ASDEX upgrade

A variety of techniques are being tested on ASDEX Upgrade for avoiding or reducing the divertor energy load caused by ELMs. Quiescent H-mode operation has been improved by operation with recently boronized vessel walls. Z(eff) values in QH-modes are now similar to2.5, comparable with those found in ELMy H-modes of similar density. Type It ELM operation has been generated in discharges with ICRF additional heating alone, thus demonstrating its compatibility with reactor-relevant low core momentum and particle input. Furthermore, Type II ELM operation at low (< 1) values of edge collisionality has been achieved using strong plasma shaping and high input power. Modification of the ELM frequency and of the ELM energy has been demonstrated using pellet injection, supersonic pulsed gas injection, magnetic triggering via vertical position oscillations and modulated edge electron cyclotron heating and current drive. ELM control using pellet pace making is now being incorporated into integrated scenarios that aim to provide energy and particle exhaust compatible with ITER requirements while maximizing the core confinement.


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