Design, Test, and Validation of Thermometric Chains for ITER Magnets

The accurate measurement of the temperature of ITER magnets is of fundamental importance, to make sure that the magnets operate under well-controlled and reliable conditions, and allows suitable flow distribution in the magnets through the helium piping. Therefore, the temperature measurements shall be reliable and accurate. In this paper, we present the full thermometric chain of ITER magnets, from the sensor and its attachment, to the electronic conditioning of the signals. The thermoblock is based on a CERN design, which has been further optimized due to thermal simulations carried out by CEA. The electronic system is based on a lock-in measurement and amplification of small signals and provides a web interface and a software to monitor and record temperatures. This device allows the reliable, accurate, electromagnetically immune, and fast (100-Hz bandwidth) measurement of resistive temperature sensors between a few ohms to 100 k
$\Omega$
. Measurements are also available through Profinet and Modbus TCP fieldbus for process automation. The cryogenic test bench for validation of the full thermometric chain is described, with a particular attention to the accuracy of the measurement. First results of this qualification are presented, which give good confidence in the reliability and accuracy of the thermometric system for ITER magnets.