Development of EC Launcher and Diamond Window for ITER

K. Takahashi¹, K. Sakamoto¹, T. Imai¹, A. Kasugai¹, R. Heidinger² and M. Thumm²

¹JAERI, Naka, Ibaraki, 311-0193 Japan

²FZK, P. O. Box 3640, D-76021 Karlsruhe, Germany

Two types of EC launchers, a front steering (FS) launcher for the equatorial port and a remote steering (RS) one have been studied. In the studies of FS launcher, thermal and mechanical analysis of a mirror (Cu alloy) and a flexible cooling tube (stainless steel) of the mirror were carried out. Maximum temperature of 333°C was estimated at the mirror surface under 1MW/1line in CW operation. Maximum induced stress of 136MPa, which is less than allowable stress (210MPa), was obtained at the mirror surface. The neutron irradiation test of bearings for a mirror was carried out. The neutron fluence was 10²⁴ n/m² equivalent to the ten year fluence at the bearing position in ITER. No degradation of the rotational capability of the bearings was observed. Experiments of a square corrugated waveguide for the RS launcher were carried out to study the properties of RF steering and transmission. It was obtained, in the high power tests, that the inaccurate corrugation depth of the waveguides caused the degradation of transmission performance when the E-field was in the steering plane. The transmission tests of the waveguides with the accurate corrugation depth at 170GHz were carried out. The efficient transmission (h>95%) at –12≤q≤12° was performed for both polarization in the case of the straight waveguide.

RF and pressure tests of the diamond window irradiated by neutron were carried under JA/EU(FZK) collaboration. Neutron fluence of the window was 10²¹ n/m²(En>0.1MeV), whereas the estimated annual fluence at the window position is 10¹⁸~10¹⁹n/m². Transmission of 0.48MW-30sec and 0.2MW-132sec were performed. Loss tangent of 4.8´10^-5 that agrees well with the measurement with a Fabry-Perot resonator was calorimetrically measured. Thermal conductivity of 1.1kW/m/K was also estimated, which agreed with the measurements with a photo acoustic method. It was successfully demonstrated that the irradiated window withstood pressure of 0.4MPa, which was twice higher than the ITER requirement. Small diamond specimens were irradiated at JMTR. Neutron fluence was 10²⁰-10²²n/m²(En>0.1MeV). Loss tangent and permittivity and bending stress did not change up to 10²¹n/m². It was also revealed that thermal conductivity decreased, for instance, to 1100-1400W/m/K at 2´10²⁰n/m². It is, from these test results, concluded that diamond windows are applicable for ITER!