Strain monitoring system for cryogenic structure of large helical device

The Large Helical Device has the world's largest class cryogenic structure to support huge electro-magnetic force generated by superconducting coils. The strain monitoring system was designed and installed in the Large Helical Device to evaluate the soundness of the large cryogenic structure and the measurement has been done continuously during the operation. Some experimental results are presented in the paper and the strain behavior is discussed. No significant difference of the strain has been observed up to now. The fact gives a conclusion that the cryogenic structure is working on well without any faults. By piling up the data sets, the understanding for the cryogenic structure will get ahead and the certainty and reliability for the fault or damage will be enhanced. (author)