W. Woyke

ASDEX-Upgrade Discharge Control and Shot Management

ASDEX Upgrades fully digital control system is described. Discharge control consists of 6 real time computers for discharge and system monitoring, position and shape control and extended plasma control, all synchronized by a supervisor for discharge phase switching. The timing system is integrated giving absolute time for discharge control and diagnostics. Event-dependent operation is supported. Hierarchically organized protection systems are closely coupled with the discharge and machine control systems. All systems run under a software platform for automated experiment operation.

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.

Overview of the ASDEX-Upgrade Experiment Management Software

Abstract A distributed, multi process program is described that consolidates the operation of the ASDEX-Upgrade computer systems by increasing safety, reliability and simplicity. The program integrates the discharge control system and parts of diagnostics and machine control. It allows a single operator to execute a plasma discharge by means of a graphical user interface. Online input checks together with a centralized report of technical malfunctions are realized for best performance.

Position and Shape Control on ASDEX-Upgrade

ASDEX Upgrade utilizes a feedback control system for the plasma current, position and shape, which is novel in its approach to control local and global equilibrium parameters, its algorithm for the determination of the plasma equilibrium (via a function parameterization technique from magnetic measurements), its fully digital implementation, and its combined use of internal (inside the TF coils, for fast position control) and external (outside the TF coils, for slow position and shape control) poloidal field coils. The control scheme has been tested successfully in divertor and limiter discharges with plasma currents up to 800 kA and elongations up to 1.7.

EDDY CURRENT CODES VALIDATION AGAINST ELECTROMAGNETIC TRANSIENTS IN ASDEX-UPGRADE

We present in this paper the experimental validation of 2-D and 3-D eddy current calculation procedures commonly used for the analysis of next step fusion devices (e.g. NET or ITER), performing comparisons with experimental measurements of dry discharges (i.e. without plasma) performed on ASDEX-Upgrade. This choice was motivated by the fact that the validation could be performed on a full scale fusion experiment in controlled benchmark conditions, giving direct indications on the applicability of the eddy current analysis codes in the range of our main interest. A wide spectrum of excitations of different coil systems was available in the data base of ASDEX-Up grade. This gave us the possibility of comparing eddy current simulations to the experiments in different regimes depending on the excitation selected. Here we present briefly the experimental runs chosen, the 2-D and 3-D models developed (which include axisymmetric and non-axisymmetric structures) and we report on the comparison of measurements and simulations both in the time and frequency domain.

ELECTRIC POWER CIRCUIT FOR PLASMA STABILIZATION IN ASDEX UPGRADE

ASDEX Upgrade, a reactor-relevant divertor tokamak now under construction at Garching, requires a sophisticated plasma stabilization system for both the horizontal and vertical position control owing to the strongly elongated plasma. On the basis of nonlinear circuit simulation it is shown that 4-quadrant, phase-controlled thyristor converters operating in circulating-current control mode can meet these requirements. Two pairs of stabilizating coils for active plasma position control are installed. That pair of coils, located between the vacuum vessel and toroidal coils, are inductively coupled to the plasma in a way such that in the event of plasma disruption, a current would be induced in the coil which exceeds the maximum permissible coil current limit. To avoid this, two force-commutated DC thyristor circuit breakers connected in series with these coils are installed. Maximum current and voltage per circuit breaker: 30 kA/1.6 kV. In addition, a pyrobreaker protects the coils in case of malfunctioning of the thyristor switch or the current control system. A short overview of the fast digital controller will also be given, together with the present status of construction.