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In ITER, an Electron Cyclotron Emission (ECE) diagnostic is planned to measure the electron temperature by measuring the cyclotron radiation in the frequency range of 70-1000 GHz. The cyclotron radiation is usually of low power and needs to be transported with low attenuation over a long distance of ~ 43 m, through a suitable transmission system. Pertaining to long distance, the transmission system will consist of straight waveguide sections, miter bends and waveguide joints. Low power, low loss transmission in a broadband frequency range over long distance makes the design of the transmission system challenging. To arrive at a suitable transmission system, attenuation measurements of three types of transmission lines (TLs) have been performed i.e. circular smooth walled, corrugated and dielectric coated waveguide. A polarizing Michelson interferometer based on Martin-Puplett design has been used to measure the spectrum from waveguide set ups and liquid nitrogen has been used as the black body radiation source. The measured spectrum shows atmospheric water vapour absorption lines in all types of TLs. The preliminary measurement shows that the attenuation of smooth walled waveguide is found to be comparable to corrugated waveguide up to ~ 600GHz and better than corrugated waveguide above 600 GHz for the chosen set of experimental conditions. Further, to avoid water absorption lines, a smooth walled TL is evacuated up to rough vacuum (~10-2mbar) and it was observed that the attenuation is decreased and overall transmission is improved.

The ITER Electron Cyclotron Emission (ECE) diagnostic is progressing towards its Preliminary Design Review (PDR). In parallel, the diagnostic integration in the Equatorial Port is ongoing. Port Integration has to address the structural integrity to withstand various loads, maintenance and the safety aspects of ECE diagnostic. The ITER ECE system includes radial and oblique lines-of-sight. Recently, a successful peer-review of the in-port plug Hot Calibration Source has taken place and its performance and integration feasibility has been demonstrated. Four 45-meter long low-loss transmission lines are designed to transmit mm-wave power in the frequency range of 70- 1000 GHz in both X- and O-mode polarization from the port plug to the ECE instrumentation room in the diagnostic building. Prototype transmission lines are being tested [1]. A prototype polarizing Martin-Puplett type Fourier Transform Spectrometer (FTS) operating in the frequency range 70-1000 GHz, has a fast scanning mechanism and a cryo-cooled dual-channel THz detector system. Its performance has been tested as per ITER requirements. Assessment of the instrumentation and control requirements, functional and non-functional requirements, operation procedures, plant automation are ongoing for the PDR. The current status of the diagnostic, together with integration activities, is presented.

ITER ECE diagnostic [1] needs not only to meet measurement requirements, but also to withstand various loads, such as electromagnetic, mechanical, neutronic and thermal, and to be protected from stray ECH radiation at 170 GHz and other millimeter wave emission, like Collective Thomson scattering which is planned to operate at 60 GHz. Same or similar loads will be applied to other millimetre-wave diagnostics [2], located both in-vessel and in-port plugs. These loads must be taken into account throughout the design phases of the ECE and other microwave diagnostics to ensure their structural integrity and maintainability. The integration of microwave diagnostics with other ITER systems is another challenging activity which is currently ongoing through port integration and in-vessel integration work. Port Integration has to address the maintenance and the safety aspects of diagnostics, too. Engineering solutions which are being developed to support and to operate ITER ECE diagnostic, whilst complying with safety and maintenance requirements, are discussed in this paper.