29th Symposium on Fusion Technology (SOFT 2016)

O5C.3 An optimized upper divertor with divertor-coils to study enhanced divertor configurations in ASDEX Upgrade

8 Sep 2016, 17:20

20m

Meeting Hall V 2nd floor (Prague Congress Centre)

Board: 3

Oral C. Plasma Engineering and Control O5C

Speaker

Albrecht Herrmann (MPI für Plasmaphysik)

Description

ASDEX Upgrade came into operation in 1991. It was designed as a tokamak with reactor relevant shaping. The coil and control system allows to operate in lower single null (LSN), double null (DN) or upper single null (USN) with up to 1.6 MA plasma current and an initially open divertor configuration. Divertor enhancements were concentrated on the lower divertor that was finally transferred to a solid tungsten divertor with vertical target plates and a large flexibility for magnetic configurations. Consequently, the physics program of ASDEX Upgrade is concentrated on LSN magnetic configurations using this optimized lower divertor. The extension of the physics program towards the investigation of advanced divertor configurations requires a new divertor design, the installation of in-vessel coils and of a cryopump. This modification will be done in the upper divertor, keeping the flexibility for physics investigation in the lower divertor as in the past. We will present the conceptual design for the upper divertor structure with embedded divertor coils feeded with up to 50 kAt, the hardening of the upper divertor target structure to cope with the high heating power of ASDEX Upgrade without leading edge effects and finally the cryopump for an effective density control in the upper divertor. Possible coil designs and the forces acting onto the coil support structure and the vacuum vessel will be discussed in detail. The design of the cryopump is based on the existing design for the cryopump in the lower divertor but has to be modified to be fitted behind the upper inner divertor. Hardening of the upper divertor will be done by installing well aligned flat or roof like targets and a minimum gap size between targets. Such a design would keep the option to operate with both directions for the helicity of the magnetic configuration.