Development of integrated scenarios for ITER and DEMO on ASDEX Upgrade

The ASDEX Upgrade (AUG) programme is directed towards physics input to critical elements of the ITER design and the preparation of ITER operation, as well as addressing physics issues for a future DEMO design. In 2017 AUG will be equipped with 20 MW of NBI, 7 MW of ICRF and 6 MW of ECRH. In 2015 AUG was equipped with a new pair of 3-strap ICRF antennas, which allowed for a significant reduction of tungsten release during ICRF operation [1]. In 2017 two new ECRH units with 2x 1 MW, 10 s, at 140 GHz/105 GHz are taken into operation. There are two main operational scenario lines in AUG. Experiments with low collisionality, which comprise current drive, ELM mitigation / suppression and fast ion physics, are mainly done with freshly boronized walls to reduce the tungsten influx at these high edge temperature conditions. Full ELM suppression [2] and non-inductive operation up to a plasma current of Ip = 0.8 MA could be obtained at low plasma density [3]. Plasma exhaust is studied under conditions of high neutral divertor pressure and separatrix electron density, where a fresh boronization is not required. The integration of all above mentioned operational scenarios will be feasible and naturally obtained in a large device where the edge is more opaque for neutrals and higher plasma temperatures provide a lower collisionality. The combination of exhaust control with pellet fueling has been successfully demonstrated. High divertor enrichment values of nitrogen EN  10 have been obtained during pellet injection, which is a prerequisite for the simultaneous achievement of good core plasma purity and high divertor radiation levels [4]. With respect to the ITER Q=10 scenario at q95=3 low power H-modes at high triangularity were studied which so far only showed H-factors of unity at N2.0, i.e. 10% above the planned value for ITER [5]. These experiments will be complemented in 2017 using pure wave-heating in order to mimic the low torque input in ITER and future reactors. Impurity accumulation observed in the all-metal AUG device caused by the strong neoclassical inward transport of tungsten in the pedestal is expected to be relieved by the higher neoclassical temperature screening in larger devices [6]. So far this is achieved in AUG by sufficient central electron heating.