ITER diagnostic shutters

Numerous plasma-near mirrors of optical diagnostics in ITER require protection from erosion and deposition caused by impinging particles. This is achieved by 63 Diagnostic Shutters, which shall operate in vacuum under high thermal and neutron fluxes over 20 years without maintenance, ruling out standard engineering solutions. In fact, these conditions are unprecedented even on fusion devices. Hence,qualification R&D efforts are extensive, because if a shutter fails, so does the respective diagnostic.Shutter design tasks are widespread among Domestic Agencies and their suppliers, because every shutter is part of the diagnostic it shall protect when not in use. However, as these highly resembling systems have obvious synergy potential, a coordination strategy for all ITER shutters was implemented at IO.An extensive shutter experience collection including failure reports from 14 fusion devices was per-formed. These are summarized in the present work. For the first time, the state-of-the-art of shutters is thereby defined and assessed as to its applicability to ITER. Furthermore, design-driving environmental effects due to the specific operating conditions are recalled and evaluated. The findings of both assessments are put into context with the current designs of all ITER shutters. In a next step, these are reviewed with emphasis on synergies between different shutter systems. Finally, recommendations on necessary prototyping and generic components are given

Design of ITER divertor VUV spectrometer and prototype test at KSTAR tokamak

Design and development of the ITER divertor VUV spectrometer have been performed from the year 1998, and it is planned to be installed in the year 2027. Currently, the design of the ITER divertor VUV spectrometer is in the phase of detail design. It is optimized for monitoring of chord-integrated VUV signals from divertor plasmas, chosen to contain representative lines emission from the tungsten as the divertor material, and other impurities. Impurity emission from overall divertor plasmas is collimated through the relay optics onto the entrance slit of a VUV spectrometer with working wavelength range of 14.6–32 nm. To validate the design of the ITER divertor VUV spectrometer, two sets of VUV spectrometers have been developed and tested at KSTAR tokamak. One set of spectrometer without the field mirror employs a survey spectrometer with the wavelength ranging from 14.6 nm to 32 nm, and it provides the same optical specification as the spectrometer part of the ITER divertor VUV spectrometer system. The other spectrometer with the wavelength range of 5–25 nm consists of a commercial spectrometer with a concave grating, and the relay mirrors with the same geometry as the relay mirrors of the ITER divertor VUV spectrometer. From test of these prototypes, alignment method using backward laser illumination could be verified. To validate the feasibility of tungsten emission measurement, furthermore, the tungsten powder was injected in KSTAR plasmas, and the preliminary result could be obtained successfully with regard to the evaluation of photon throughpu

Design of ITER divertor VUV spectrometer and prototype test at KSTAR tokamak

Design and development of the ITER divertor VUV spectrometer have been performed from the year 1998, and it is planned to be installed in the year 2027. Currently, the design of the ITER divertor VUV spectrometer is in the phase of detail design. It is optimized for monitoring of chord-integrated VUV signals from divertor plasmas, chosen to contain representative lines emission from the tungsten as the divertor material, and other impurities. Impurity emission from overall divertor plasmas is collimated through the relay optics onto the entrance slit of a VUV spectrometer with working wavelength range of 14.6–32 nm. To validate the design of the ITER divertor VUV spectrometer, two sets of VUV spectrometers have been developed and tested at KSTAR tokamak. One set of spectrometer without the field mirror employs a survey spectrometer with the wavelength ranging from 14.6 nm to 32 nm, and it provides the same optical specification as the spectrometer part of the ITER divertor VUV spectrometer system. The other spectrometer with the wavelength range of 5–25 nm consists of a commercial spectrometer with a concave grating, and the relay mirrors with the same geometry as the relay mirrors of the ITER divertor VUV spectrometer. From test of these prototypes, alignment method using backward laser illumination could be verified. To validate the feasibility of tungsten emission measurement, furthermore, the tungsten powder was injected in KSTAR plasmas, and the preliminary result could be obtained successfully with regard to the evaluation of photon throughpu