As the first lecture of the series on high-temperature superconducting materials, this article provides a basic introduction so that non-specialists can catch up with current topics and understand some details about the copper oxides which show high-Tc superconductivity. The crystal structure and the electronic properties of the cuprates are described as a function of carrier doping. Many investigators have recognized that the anisotropic Cooper pairs with d x2-y2-symmetry are formed in the two-dimensional CuO2 planes. Some proposals, which may lead to the basic pairing mechanism for the superconductivity in the cuprates, are discussed. The most likely scenarios have been proposed based on both antiferromagnetic interaction and strong correlation between 3d electrons of Cu. Some trials to improve Tc are reviewed with an optimistic objective achieving room-temperature superconductors.
Through monitoring the temperature inside cryogenic equipment such as superconducting magnets, it is possible to detect indicators of failures and prevent equipment from becoming damaged. An optical fiber sensor is considered a suitable means of measuring the temperature inside cryogenic equipment because of its low heat invasion and high voltage insulating properties. In this study, we used a fiber Bragg grating (FBG) to investigate the reproducibility and multipoint measurement characteristics over a temperature gradient inside the cryogenic equipment. We also investigated the improvement of the wavelength shift change ratio at cryogenic temperature using a coated optical fiber sensor to enhance the thermal expansion coefficient.