1 Forschungszentrum Karlsruhe, Association
FZK-Euratom,
(a) Institute for Materials Research I, (b) Institute for Reactor Safety,
(c) Inst. for Pulsed Power and Microwave Technology, D-76021 Karlsruhe, Germany
2 Pfinzstraße 46, D-76689 Karlsdorf-Neuthard, Germany
3 University Karlsruhe, Institute
of High-Frequency Techniques and Electronics, D- 76128 Karlsruhe, Germany
4 FOM Institute for Plasma
Physics “Rijnhuizen”, Association EURATOM-FOM ,Nieuwegein, The Netherlands
roland.heidinger@imf.fzk.de
Motivation
The upper port positions for the EC wave launching system on ITER are reserved to stabilise the Neoclassical Tearing Modes (NTM) at the q=3/2 and q=2/1 surfaces by inducing off-axis current drive. The design of the upper port plug systems, which is developed by a working group from various EURATOM associations with the overall coordination at FZK, is specified to convey a total of 20 MW mm-wave power at 170 GHz under continuous wave conditions (>1000s). For the mm-wave beam lines, transmission of 1 MW is considered as the basic operation scenario, potential up-grades to 2 MW are accounted for by appropriate layout of the power handling capabilities of the beam line elements. The mm-wave system design under the lead of FOM has defined a reference beam line on the basis of the remote steering concept. The waveguide system has to be integrated into the frame of the plug (‘main structure’) and the blanket shield module which closes the gap in the blanket structure and has to provide effective neutron and thermal shielding. The boundary for in-vessel components in the port plug is set by a closure plate at which CVD diamond ‘torus’ windows form the primary tritium confinement to the mm-wave system. Both structural components as well as the windows form essential parts of the port plug system for which detailed design activities are accompanied by modeling for performance analysis.
The main structure is formed
by a double wall structure to house the coolant for the in-vessel components
which are fed by the blanket cooling water. The wall thickness results from a
trade-off between the space requirements of the square waveguide systems and
the stiffness providing safe margins for launcher displacements under
electromagnetic forces from plasma disruptions. The cooling conditions for the
blanket shield module, consisting of the first wall panel, the outer shells,
the internal shield modules and the blocks for fixed front mirrors, are set-up
following a thermo-hydraulic analysis. The shielding function is qualified by
neutron streaming and activation analysis in order to demonstrate that critical
fluence limits for radiation damage of the torus windows and for hands-on
maintenance of the ex-vessel cooling pipes are satisfied.
Analysis of window concepts
Alternative
options for the cooling arrangement of the torus window are discussed,
especially concepts for edge cooling and for direct and indirect face cooling.
Thermo-mechanical analysis based on finite element modelling and numerical assessment
of effective heat transfer show that edge-cooling is applicable for windows of
95 mm aperture using a CVD diamond disk of 106 mm outer diameter. Indirect
cooling by thermal conduction from the faces of the windows via copper cuffs to
the cooling chambers results in an additional increase of the edge temperature
of the window which can be as high as 70 K for 2 MW power transmission.
[1] A.G.A. Verhoeven, et al., this workshop