This paper reviews the recent development of mobile nondestructive evaluation (NDE) systems using high-Tc superconducting quantum interference devices (SQUIDs) for conductive materials and structures. The contents of this paper include a noise cancellation scheme using active shielding, a novel high-Tc SQUID gradiometer with robustness in magnetic fields, mobile SQUID NDE systems and NDE of complex composite-metal structures. Using the novel high-Tc SQUID gradiometer, the superior capability of the mobile SQUID NDE system compared to conventional NDE techniques is demonstrated and discussed.
The development of superconducting rotating machines based on metallic superconductors achieved many excellent results, for example, in the Super-GM project. However, since the end of the 20th century, the focus of development has shifted to developing high-temperature superconducting (HTS) machines. The initial target application was industrial motors for pumps and fans, but this has now changed to low-speed large-torque motors for ship propulsion. Recently large-capacity wind turbine generators have been attracting attention. Furthermore, the development of fundamental technologies for HTS turbine generators in thermal and atomic power stations has started. Excellent features such as smaller size, lighter weight and higher efficiency, and also improvement of functions and characteristics are expected in superconducting rotating machines. However, cost reduction and system reliability verification are still key issues for practical application of the HTS machines. This article describes superconducting rotating machine technologies and technical trends in their development, the fundamental structure and characteristics of the rotating machines, the Super-GM project based on the liquid helium cooling and NbTi metallic superconductor, and the development status of HTS rotating machines.