H. Kollotzek

Completion of Assembly and Start of Technical Operation of ASDEX Upgrade

The last important steps of the tokamak machine assembly are described. A survey of precision and tolerances is given achieved for the vacuum vessel, the toroidal field (TF) magnet and the poloidal field (PF) coils. The first commissioning tests of vacuum vessel, TF magnet and PF coils are described together with certain features of the control and technical supervisory system. Remarks on improvements of the electric power supply system and the fast plasma control system follow. Finally the programme of the next future is briefly outlined.

Operational behaviour of the ASDEX upgrade in-vessel cryo pump

Abstract The set-up of the Helium (He) supply circuit for the ASDEX Upgrade cryo pump (CP) with 100 m3/s Deuterium pumping speed is described together with the key instrumentation and the method of data interpretation. The main peculiarities of the CP operation are the hydraulic instability of the mass flow below 4 g/s, due to large level differences of the transfer line and the sudden heat input of 130 W to the cryo panel during He discharge cleaning of the vacuum vessel. In both cases, a maintenance free, immersed Helium Circulating Pump (HCP), simplifies operation considerably. It permits quick re-filling and re-cooling after He-glowing and stabilisation of the standby mass flow in an oscillatory way down to 2.5 g/s. The measured He losses show that continuous operation of the CP, including He-glowing, is feasible even with a standard 30/60 l/h He-liquifier.

TECHNICAL FEATURES AND PROGRESS OF ASDEX UPGRADE

The objective of ASDEX Upgrade is to investigage open poloidal divertor configurations as produced by a reactor-compatible, poloidal field coil system. The accessible poloidal and toroidal fields and hence the plasma current provide a sufficiently large plasma parameter regime to ensure the functioning of the open divertor.

THE TECHNICAL CONCEPT OF THE ASDEX UG POLOIDAL FIELD COILS

The ASDEX UG tokamak poloidal field coil system will comprise three ohmic heating coils and three vertical field coils. The ohmic heating coils consist of a highly excited coil in the central bore of the toroidal field magnet and coils outside the toroidal magnet arranged in pairs symmetric to the torus mid-plane. This coil arrangement is expected to generate a magnetic flux swing of about 9.5 Vs for a total discharge time of the plasma of 10s. The vertical field coils can be arranged a) all outside the toroidal magnet system, and b) partially between the toroidal magnet system and the vacuum vessel, likewise in pairs symmetric to the torus midplane.

The ZEPHYR poloidal field coils

The magnetic field of the poloidal coils creates plasma equilibrium conditions, plasma breakdown and heating and may be formed by two separate coil systems (OH; V). All coils without the central OH coil (OH 1) are normally stressed; less than 100 MPa. The extremely stressed OH central coil (350 MPa)must be specially designed for keeping stress and temperature rise low. The start temperature of OH 1 has to be less than 80 K for keeping the temperature rise i=9.1 \frac{KA}{cm^{2}} ; t pulse = 4.5 s. All coils are designed for direct cooling. Cool medium can be Li N2 or supercritical He at high pressure.