Performance comparison for the detection of defects in thermal insulating materials using microwave holograms acquired manually and with a robotized scanner

In many cryogenic systems, during useful life, defects or degradation of performance are found. Frequently these malfunctions are due to the presence of alterations in the characteristics of the thermal insulating materials used to coat the metal parts of the system. It is useful to evaluate methods for investigating the quality of insulating coatings by means of instruments, with low cost, that can be easily used during production. Thermal insulating materials are characterized by a relative dielectric constant close to the unit and a low Loss Factor: this work aims to investigate the use of microwave holographic radar for the detection of defects in such materials. The results show good detectability of defects when they are oriented as the antenna axis. Finally, it is shown that the robotic scan can examine large areas with the same detection performances of manual scan but with less set up and scanning time.