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Resilience of Bolometer Sensors

Vibration testing of mechanical resilience of bolometer sensors and sensor holders under ITER-relevant conditions


The ITER bolometer diagnostic will provide the measurement of the total radiation emitted from the plasma, a part of the overall energy balance. Up to 550 sensor channels will be installed in ITER in 71 cameras of various sizes and types. The sensor holder is the component inside those cameras to provide attachment and signal connections to the sensor itself. A design of a sensor holder has been proposed previously based on ceramic front and back plates with wire bonded contacts to the sensor and welded signal cables.

This concept can provide the reliable electrical connections required for ITER at temperatures up to 350 C and had been prototyped and proven to be manufacturable. In order to verify its resilience against mechanical loads as well as that of the sensors, sensor holder assemblies have been subjected to accelerations on a shaking table. The magnitude of the accelerations applied in the frequency range from 5 Hz up to 1 kHz) have been deduced based on load definitions from ITER describing the floor response spectra for typical seismic events as well as the ones expected during disruptions due to electro-magnetically induced forces in bolometer cameras and port structures within which they are mounted.

A particular focus has been placed on testing whether it is beneficial to cover the bond wires with a ceramic paste to protect them against fatigue breaks due to vibrations. The tests demonstrated that the chosen sensor assembly is well capable of withstanding all applied loads without failures and thus demonstrating its structural integrity during the expected operations. Within the limited number of load cycles no need to apply the ceramic paste could be identified.

The ITER bolometer diagnostic shall provide the measurement of the total radiation emitted from the plasma, a part of the overall energy balance. Up to 550 sensor channels will be installed in ITER in up to 71 cameras of various sizes and types. The sensor holder is the component inside all those cameras that provides attachment and signal connections to the sensor itself. It might vary in shape within each camera, but concepts for implementing signal connections and handling of loads in all cameras are very similar, if not identical.

Another important result is that the bolted connections in the sensor holder were neither affected by the acceleration tests nor by the baking afterwards. Despite that bolts were tightened only by hand with a torque of only 0.1 Nm and without specific precautions against loosening under vibrations, all bolts were still tight after each test. Furthermore, no damage was noticed on the sensor holder components after acceleration testing. This demonstrates that the proposed sensor holders can withstand typical mechanical loads as expected for ITER and that they will not lose their structural integrity.
Nonetheless, the assembly process is very demanding and shows significant risks. For final manufacture it is strongly recommended to optimize and practice the assembly procedure thoroughly, involving the provision of a sufficient number of spare sensors and components.

IoT sensors, smart sensors, wireless sensors, optical sensors, biomedical sensors, pressure sensors, temperature sensors, proximity sensors, humidity sensors, chemical sensors, biosensors, motion sensors, infrared sensors, environmental sensors, wearable sensors, industrial sensors, acoustic sensors, microelectromechanical sensors, nanotechnology sensors

#SensorTechnology, #SmartSensors, #IoTSensors, #BiomedicalSensors, #WirelessSensors, #PressureSensors, #TemperatureSensors, #OpticalSensors, #ProximitySensors, #ChemicalSensors, #Biosensors, #InfraredSensors, #HumiditySensors, #EnvironmentalSensors, #MotionSensors, #WearableSensors, #IndustrialSensors, #AcousticSensors, #NanoSensors, #MEMSSensors

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