Testing a full scale ECRH mm-wave launching system mock-up

 

B.S.Q. Elzendoorn a, M.P.A. van Asselen a, W.A. Bongers a, J.W. Genuit a, M.F. Graswinckel a, R. Heidinger b, B. Piosczyk b, T.C. Plomp a, D.M.S. Ronden a, A.G.A. Verhoeven a

 

a FOM Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, Nieuwegein, The Netherlands,

b FZK, Karlsruhe; ben@rijnh.nl

 

An ECRH (electron-cyclotron resonance heating) launching system for the ITER upper ports is being designed. The aim of the system is to inject Electron Cyclotron Waves (ECW) in the ITER plasma in order to stabilize neoclassical tearing modes (NTM). Each upper-port launcher consists of eight mm-wave lines capable of transmitting high power up to 2 MW at 170 GHz. In order to exploit the capability of ECW for localized heating and current drive over a range of plasma radii in ITER, the ECH&CD upper port launcher must have a beam steering capability. To avoid movable mirrors at the plasma-facing end of the launcher, the concept of remote mm-wave beam steering (RS) is used, having a corrugated square waveguide within the launcher and the steerable optic is then placed outside of the first confinement boundary of the vacuum vessel. FOM will start to test the full-scale mm-wave launching system at the FOM institute in the Netherlands. The tests will be done at low power. In 2005 tests will be done in Karlsruhe. The tests in Karlsruhe are low energy tests (high power short pulses). The mock-up consists of a full-scale mm-wave system placed in a vacuum environment. The mock-up foresees in two separate vacuum systems, which simulates primary or torus vacuum and secondary vacuum. Secondary vacuum is required for the partly quasi-optical mm-wave beam trajectory and to provide a second tritium boundary. A diamond window will provide the first tritium confinement. The mock-up will be shipped again to the Netherlands after the tests in Karlsruhe to prepare for the Lausanne tests.

 

A phased testing plan is made in order to end in Lausanne in 2006 for CW full power tests. CW high power tests require cooling for each mm-wave component. The mock-up requires two separate cooling systems. The cooling system for the square corrugated and the fixed mirror will also be used to simulate ITER baking conditions with a coolant temperature of 240 C and with a pressure of 4.4 MPa. The second cooling system provides cooling for the mm-wave components placed in secondary vacuum. These components, the steerable mirror unit and the diamond window will be integrated in the transmission line cooling system. The operation temperature in the secondary vacuum containment at ITER is 100 C. The mm-wave system will be tested under full power continuous wave operation; these tests will provide information about surface temperatures of mirrors and wall thermal loading of the square corrugated waveguide. The systems efficiency will be checked by calorimetric and antenna-pattern measurements,. The lifecycle tests under influence of temperature variations, realistic coolant pressures and in a vacuum atmosphere will give the final information before the detailed final design of the ECRH launching systems can start.