[en] The basics of the poloidal field system of the ZEPHYR experiment are considered. From the physical data the requirements for the poloidal field are derived. Hence an appropriate coil configuration consisting of coil locations and corresponding currents is obtained. A suitable electrical circuit feeding the coils is described. A preliminary assessment of the dynamic control of the poloidal field system is given. (orig.)

[en] 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 <130 K. The coil characteristics are given. All coils are designed for direct cooling. Cool medium can be Li N2 or supercritical He at high pressure. 2 refs

[en] Incorporation of ¹⁴C-adenine into the metabolic pool of platelet adenine nucleotides is linear over a range of hours and at a rate of 5 nmol/min . 10¹¹ cells. The radioactive equilibrium is reached after 60 minutes incubation. The adenine nucleotides and their catabolites products were separated by a one-dimensional TLC technique. (author)

No abstract available

[en] Scrape-off layer (SOL) currents are measured by means of Langmuir probes and shunts in the divertor of ASDEX Upgrade. They consist of the overlayed contributions of thermoelectric and Pfirsch-Schlueter (PS) currents. The SOL currents exhibit a drastic decrease when the line-averaged density approaches the Greenwald density in the H-mode. An analytical model is presented which reproduces the measured thermoelectric current quantitatively. Matching of the analytical model with the measured current scaling yields information about divertor temperatures and SOL e-folding lengths

[en] ASDEX Upgrade is a tokamak with a reactor-like poloidal divertor configuration now under construction at IPP, and scheduled to go into operation in 1988. In addition to its main object of simulating a reactor-relevant plasma boundary, it is also characterized by reactor-typical features of plasma position and parameter control. Owing to the plasma elongation, the placing of poloidal field coils outside the toroidal field coils and the asymmetry of the poloidal configuration, it involves all the major control problems of present reactor designs, such as vertical instability, high control power required, and mutual dependence of all control variables. The central issue of this paper is to derive a general formulation of model equations for the plasma equilibrium in a tokamak as a basis for positional control considerations. The results are applied to the special case of ASDEX Upgrade for simulating some exemplary control actions

[en] The hydrodynamics of a reduced-scaled model of a radial pump-turbine is investigated under off-design operating conditions, involving runaway and 'S-shape' turbine brake curve at low positive discharge. It is a low specific speed pump-turbine machine of Francis type with 9 impeller blades and 20 stay vanes as well as 20 guide vanes. The computational domain includes the entire water passage from the spiral casing inlet to the draft tube outlet. Completely structured hexahedral meshes generated by the commercial software ANSYS-ICEM are employed. The unsteady incompressible simulations are performed using the commercial code ANSYS-CFX13. For turbulence modeling the standard k-ε model is applied. The numerical results at different operating points are compared to the experimental results. The predicted pressure amplitude is in good agreement with the experimental data and the amplitude of normal force on impeller is in reasonable range. The detailed analysis reveals the onset of the flow instabilities when the machine is brought from a regular operating condition to runaway and turbine break mode. Furthermore, the rotating stall phenomena are well captured at runaway condition as well as low discharge operating condition with one stall cell rotating inside and around the impeller with about 70% of its frequency. Moreover, the rotating stall is found to be the effect of rotating flow separations developed in several consecutive impeller channels which lead to their blockage. The reliable simulation of S-curve characteristics in pump-turbines is a basic requirement for design and optimization at off-design operating conditions.

[en] The appearance of bright spots at several parts in the tokamak vessel during disruptions is a well known phenomenon. In ASDEX-Upgrade an enormous number of bright spots is observed at the lower target plate and at the diaphragm ring of the divertor from a density limit disruption. The investigation of carbon tiles after an operation period of the tokamak shows, that arcs are the reason for the bright spots. In ASDEX-Upgrade, however, bright spots at the divertor plates are observed also during the stationary phases of the tokamak operation. These spots seem to arise from uneven power deposition on the target plates. The energy of the bulk plasma enters the scrape-off layer crossing the separatrix so far it is not radiated from the bulk and the boundary of the plasma. Along the SOL the energy is transferred to the divertor plates. During the stationary state ASDEX-Upgrade is heated with a power up to 10 MW. Power loads of about 10 MW/m² at the target plates are measured by thermography supposing uniform deposition. However due the tile geometry and other irregularities on the surface of the tiles a local power overload will occur unavoidably. Then the sublimation temperature on the carbon tiles may be exceeded. The increased impurity production can produce carbon blooms and following plasma disruptions. Also damage of divertor tiles is possible. (author) 3 refs., 6 figs

[en] ASDEX Upgrade, presently under construction at IPP Garching, is a divertor tokamak allowing experiments with elongated plasmas of Single and Double Null shapes. For this tokamak, we have performed a series of dynamical simulations during the start up, the flat top and the shut down phase, using the Princeton Tokamak Simulation Code (TSC). In the simulations, we have included all coil groups, i.e. the ohmic heating system, the poloidal field coils external to the TF magnets, the inner control coils as well as passive structures such as passive conductors and the vacuum vessel. The feedback control of the plasma position by the inner control coils and the external poloidal field coils, both during regular shot scenarios and for disruption simulations under realistic power supply constraints, is studied. In the following we describe in somewhat more detail two applications, the simulation of a complete discharge including the start up phase and a plasma disruption. Although in both cases of the simulation, model assumptions are required for the thermal energy transport, the emphasis is here on the aspects of plasma position and shape control and the electrodynamics of the poloidal field circuits. (author) 2 refs., 3 figs

No abstract available