In-vessel calibration of the imaging diagnostics for the real-time protection of the JET ITER-like wall

The in situ absolute calibration of the JET real-time protection imaging system has been performed for the first time by means of radiometric light source placed inside the JET vessel and operated by remote handling. High accuracy of the calibration is confirmed by cross-validation of the near infrared (NIR) cameras against each other, with thermal IR cameras, and with the beryllium evaporator, which lead to successful protection of the JET first wall during the last campaign. The operation temperature ranges of NIR protection cameras for the materials used on JET are Be 650-1600 °C, W coating 600-1320 °C, and W 650-1500 °C.