The Mid-Infrared Instrument for the James Webb Space Telescope, III: MIRIM, The MIRI Imager

In this article, we describe the MIRI Imager module (MIRIM), which provides broad-band imaging in the 5 - 27 microns wavelength range for the James Webb Space Telescope. The imager has a 0"11 pixel scale and a total unobstructed view of 74"x113". The remainder of its nominal 113"x113" field is occupied by the coronagraphs and the low resolution spectrometer. We present the instrument optical and mechanical design. We show that the test data, as measured during the test campaigns undertaken at CEA-Saclay, at the Rutherford Appleton Laboratory, and at the NASA Goddard Space Flight Center, indicate that the instrument complies with its design requirements and goals. We also discuss the operational requirements (multiple dithers and exposures) needed for optimal scientific utilization of the MIRIM.Comment: 29 pages, 9 figure

Langmuir probes design for the actively cooled divertor baffle in WEST

The WEST project (W-Environment in Steady-State Tokamak) aims to transform the Tore Supra limiter configuration to an x-point divertor, providing a test bed for ITER-like plasma-facing components (actively cooled W monoblocs) under high heat flux, steady-state plasma irradiation. The lower divertor includes an actively cooled, W-coated CuCrZr baffle to provide neutral compression and improve particle exhaust. As part of the new diagnostic equipment of Tore Supra within WEST project, a set of Langmuir probes will find place on the baffle in order to provide plasma flux and electron temperature measurements for physics studies and real-time machine protection functions during steady-state discharges. On the baffle top surface, irradiation coming from the plasma, energetic ripple-ions losses, photons and energetic neutrals from charge exchange reactions produce power fluxes up to 3 MW/m2, representing a challenge for the Langmuir probes operating conditions. In this paper Copper–Chrome–Zirconium (CuCrZr) cylindrical probe concept design is proposed. Finite element thermo-mechanical analysis (FEA) confirmed the consistency of this solution under the steady-state plasma condition in the worst case (highest thermal load)

ITER CODAC interface for the visible and infra-red wide angle viewing cameras

The amount of data generated by the infra-red and visible cameras at ITER is expected to be considerably larger than most diagnostics. ITER will have 12 infra-red cameras plus 12 visible cameras in four different equatorial port plugs. Each of the ports will have a Plant System Host (PSH) that will provide a standard image of the plant system to the ITER's Control and Data Access and Communication (CODAC) system

Achievements on Engineering and Manufacturing of ITER First-Mirror Mock-ups

Most of ITER optical diagnostics will be equipped with in-vessel metallic mirrors as plasma viewing components. These mirrors will be exposed to severe plasma environment and must withstand these conditions without change of their optical properties. This implies important research and developments on the design and manufacturing of such components. Therefore, investigations on engineering and manufacturing have been carried out on diagnostic mirrors toward the development of full-scale stainless steel and TZM (Mo-based alloy) ITER mirrors. Several-micrometer coatings of rhodium and molybdenum have been deposited on the components to ensure long-lasting of the mirrors exposed to an environment which could be dominated by charge-exchange neutral flux. Three major issues have been addressed and reported in this paper: First, investigations have been performed on the design and manufacturing of the integrated cooling system to limit the mirror optical surface deformation due to radiations from the plasma and nuclear heating. For the thermomechanical design of the mock-ups, a plasma radiation flux of 0.5 MW/m 2 and a neutron head load of 7 MW/m 3 have been considered. Second, the polishing capability of full-scale (109 mm in diameter) metallic mirrors has been demonstrated: The mock-up surface front error is lower than 0.1 μm root mean square, and the mirrors exhibit low roughness ( Ra <; 2 nm) and low surface defects (scratch width lower than 0.02 mm) after polishing. Third, the manufacturing feasibility of thick molybdenum and rhodium coating layers deposited by magnetron sputtering has been evaluated. The objective of depositing layers up to 3-5 μm thick has been achieved on the mock-ups, with spectral reflectance reaching the theoretical values and showing high reflectivity over a large spectral range (from 400 nm to 11 μm). Finally, the test campaign of the manufactured mirrors, which is being prepared in several European facilities to expose the mirrors to deuterium plasma, ELMs, neutrons, erosion, and deposition conditions, is reported

Achievements on Engineering and Manufacturing of ITER First Mirrors Mock-Ups

Most of ITER optical diagnostics will be equipped with in-vessel metallic mirrors as plasma viewing components. These mirrors will be exposed to severe plasma environment which implies important research and developments on their design and manufacturing. Therefore investigations on engineering and manufacturing have been carried out on diagnostic mirrors towards the development of full-scale stainless steel and TZM (Mo-based alloy) ITER mirrors. Several micrometers in thickness of rhodium and molybdenum reflective coating layers have been deposited on the components to insure long-lasting of the mirrors exposed to an environment that could be dominated by neutral flux (charge-exchange). Three major issues have been addressed and reported in this paper: First, investigations have been performed on the design and manufacturing of the mirror integrated cooling system, so that the optical surface deformation due to radiations from the plasma and nuclear heating is limited. For the thermo mechanical design of the mock-ups, plasma radiation flux of 0,5 MW/m2 and neutron head load of 7 MW/m3 have been considered. Secondly, the polishing capability of full-scale (109 mm in diameter) metallic mirrors has been demonstrated: the mock ups Surface Front Error is lower than 0,1 μm Root Mean Square, and the mirrors exhibit low roughness (Ra <; 2 nm) and low surface defects (scratch width lower than 0,02 mm) after polishing. Thirdly, the manufacturing feasibility of molybdenum and rhodium thick coating layers deposited by magnetron sputtering has been evaluated. The objective of depositing layers up to 3 μm to 5 μm thick has been achieved on the mock-ups, with spectral performances reaching the theoretical values and showing high reflectivity over a large spectral range (from 400 nm to 11 μm). Finally the test campaign of the manufactured mirrors, which is being prepared in several European facilities to expose the mirrors to deuterium plasma, ELMs, neutrons, erosion and deposition conditions, is reported

Engineering and manufacturing of ITER first mirror mock-ups

Most of the ITER optical diagnostics aiming at viewing and monitoring plasma facing components will use in-vessel metallic mirrors. These mirrors will be exposed to a severe plasma environment and lead to an important tradeoff on their design and manufacturing. As a consequence, investigations are carried out on diagnostic mirrors toward the development of optimal and reliable solutions. The goals are to assess the manufacturing feasibility of the mirror coatings, evaluate the manufacturing capability and associated performances for the mirrors cooling and polishing, and finally determine the costs and delivery time of the first prototypes with a diameter of 200 and 500 mm. Three kinds of ITER candidate mock-ups are being designed and manufactured: rhodium films on stainless steel substrate, molybdenum on TZM substrate, and silver films on stainless steel substrate. The status of the project is presented in this paper