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

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 ZrF4 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.