Neutronics analysis of the ECW launching system in the ITER upper port

This paper is devoted to the neutronics analysis of the electron cyclotron wave (ECW) launching system installed in the ITER upper port. The launcher design developed by FOM Rijnhuizen with a twisted arrangement of straight waveguides was selected to facilitate the maintenance of the ECW system by avoiding mitre bends. Two types of ECW launcher designs were considered in this paper: limited and full focusing. Three dimensional MCNP models of the ECW launchers were developed with high accuracy directly from the CAD geometry models by means of an interface programme. A shielding analysis was performed to estimate the length and thickness required for the shield around the waveguides. A two-step method making use of surface sources and point detectors was applied in the neutron streaming calculations in order to estimate the radiation load on the CVD diamond window. The neutron and gamma fluxes, the nuclear heat density, and the helium production were calculated. The results show that the design limits both for the limited and the full focusing ECW models are met.