M. Jouve

Surface temperature measurements on Tokamak target plates with two types of infra red fibres

Abstract Tore Supra has chosen to protect the most heavily solicited and actively cooled target plates by thermography using optical fibres. In consequence to previous experience [J. Nucl. Mater. 290–293 (2001) 701], the prototype periscope for the 2001 experimental campaign was equipped not only with silica fibres but also with a ZrF 4 fibre, transparent up to 4 μm. As then, the measurements in the mid infrared range give lower temperatures than the ones in the near infrared range. The silica fibres are more robust and easier to calibrate, which may justify to use both types side by side using a cross calibration formula. Measurements with an silica fibre embedded in the interior of the target plate exhibited only during discharges with LHCD heating sufficient signal levels to be spectrally analysed. Under these conditions the same kind of additional near infrared radiation as on the silica fibres looking at the exterior of the target plates was observed.

2D surface temperature measurement of plasma facing components with modulated active pyrometry

In nuclear fusion devices, such as Tore Supra, the plasma facing components (PFC) are in carbon. Such components are exposed to very high heat flux and the surface temperature measurement is mandatory for the safety of the device and also for efficient plasma scenario development. Besides this measurement is essential to evaluate these heat fluxes for a better knowledge of the physics of plasma-wall interaction, it is also required to monitor the fatigue of PFCs. Infrared system (IR) is used to manage to measure surface temperature in real time. For carbon PFCs, the emissivity is high and known (ɛ ∼ 0.8), therefore the contribution of the reflected flux from environment and collected by the IR cameras can be neglected. However, the future tokamaks such as WEST and ITER will be equipped with PFCs in metal (W and Be/W, respectively) with low and variable emissivities (ɛ ∼ 0.1-0.4). Consequently, the reflected flux will contribute significantly in the collected flux by IR camera. The modulated active pyrometry, using a bicolor camera, proposed in this paper allows a 2D surface temperature measurement independently of the reflected fluxes and the emissivity. Experimental results with Tungsten sample are reported and compared with simultaneous measurement performed with classical pyrometry (monochromatic and bichromatic) with and without reflective flux demonstrating the efficiency of this method for surface temperature measurement independently of the reflected flux and the emissivity.

Image Analysis of Infrared Quantitative Data Applied to Tokamak Survey and Safety: present and future

During operation of present fusion devices, the plasma facing components (PFCs) are submitted to large heat fluxes within a range of 10-20 MW/m2. Understanding and preventing overheating of these components during long pulse discharges is a crucial issue. The surface temperature of the PFCs in the inner chamber of a tokamak is measured by infrared (IR) cameras interfaced with complex optical systems. Due to the complexity of the observed IR scenes and the large amount of data produced, a computer-aided analysis of infrared images will be a key point for ITER, the next fusion device for both real-time applications and deferred-time analysis. This paper describes the current state of IR image analysis based on region of interest (ROI) approach at Tore Supra with an extrapolation to the future ITER tokamak.

Concept And Development Of Instruments For ITER Thermography

We give here a short overview of the status of the development for ITER thermography as performed by the CEA‐Cadarache and some of its collaboration partners. The topics that have been included in this synthesis are the status of the optical design, the role of multi‐wavelength mesurements, multicolour pyroreflectometry, photothermal methods, and reflection simulations and measurements.

Gamma‐irradiation tests of IR optical fibres for ITER thermography—a case study

In the course of the development of a concept for a spectrally resolving infrared thermography diagnostic for the ITER divertor we have tested 3 types of infrared (IR) fibres in Co60 irradiation facilities under γ irradiation. The fibres were ZrF4 (and HfF4) fibres from different manufacturers, hollow fibres (silica capillaries with internal Ag/AgJ coating) and a sapphire fibre. For the IR range, only the latter fibre type encourages to go further for neutron tests in a reactor. If one restricted the interest onto the near infrared range, high purity core silica fibres could be used. This study might be seen as a typical example of the relation between diagnostic development for a nuclear environment and irradiation experiments.