The field of spin chemistry includes the magnetic field effects (MFEs) and magnetic isotope effects (MIEs) on chemical and biochemical reactions through radical pairs as well as chemically induced dynamic nuclear polarization (CIDNP) and chemically induced dynamic electron polarization (CIDEP). These phenomena have successfully been explained in terms of the radical pair mechanism (RPM). This paper introduces the fundamentals of spin chemistry, special attention being paid to applications of strong magnetic fields applied with superconducting and pulsed magnets. First, the basic principles of the RPM are described. Here, the conversion rate between the singlet and triplet radical pairs is shown to be appreciably influenced by not only ordinary magnetic fields less than 2 T, but also nuclear spins in the radical pairs. Second, typical results of MFEs on photochemical reactions in solutions that have been obtained by the author's group are reviewed. Using superconducting magnets (B ≤ 10 T) and pulsed magnets (B ≤ 30 T), the author applied strong magnetic fields to find new MFEs in photochemical reactions. Finally, this paper reviews the prospects of spin chemistry, where the effects of environmental electromagnetic fields on human diseases are also discussed.
The flow control of NaCl aqueous solution was examined by applying gas-liquid interface deformation induced by magnetic fields. Detailed studies of the dependence of flow velocity and concentration on the change in flow rate were carried out. In this experiment, with a flow on the order of 100 ml/min, the change in flow rate was measured under magnetic fields up to 10 T. The flow rate decreased due to gas-liquid interface deformation at magnetic fields of about 6 T or more; the decrease in flow rate was approximately 23% at most. The change in flow rate was dependent on the flow velocity and not on the concentration. In addition, the possibility of using gas-liquid interface deformation induced by magnetic fields as a new application for controlling the flow of NaCl solution without contact was discussed.
Buffer layer materials for growing YBa2Cu3O7−δ thin films on MgO substrates are examined from the viewpoint of YBa2Cu3O7−δ thin-film crystallinity. The buffer layers were grown using an excimer laser. Crystallinity of the buffer layers grown on MgO substrates and the YBa2Cu3O7−δ thin films on the buffer layers were evaluated by X-ray diffraction, X-ray rocking curves and X-ray φ-scan methods. One of key points to obtain YBa2Cu3O7−δ thin films of the highest quality on the MgO substrates is the usage of BaZrO3 buffer layers that are lattice matched to the MgO substrates. However, every buffer layer examined here showed the result of high-quality YBa2Cu3O7−δ thin films with a Tc of around 89 K and low surface resistance.
Superconducting power cables are one of the promising ways for handling large volumes of electric power efficiently in the future. The authors have proved that ethylene-propylene rubber (EPR) is suitable for use as the solid electrical insulating material of superconducting cable due to its excellent mechanical and electrical properties at cryogenic temperature. It is therefore imperative to study EPR resistance to treeing in view of long-term reliability as a cable insulator. The objectives of this study were to examine EPR resistance to treeing both at liquid nitrogen and room temperatures and the effect of fillers on resistance to treeing. The results show that EPR has sufficient resistance to AC treeing at liquid nitrogen temperature and the fillers improve resistance to AC treeing slightly.
An internal coil device, Mini-RT, is being constructed for high-beta plasma confinement studies by means of the magnetic field generated using a magnetically levitated high-temperature superconducting (HTS) coil. In the Mini-RT, the coil is directly charged by a DC power supply through removable current feeder terminals, and therefore, the generation of joules at the terminals as the result of contact resistance must be suppressed in order to reduce heat propagation to the HTS coil. Three different terminals with contact springs were trial manufactured and examined under room and liquid nitrogen temperatures. The contact resistances at both temperatures depended on the terminals and the spring materials. We selected the best terminals for Mini-RT, and confirmed that the differences between the design values and the results were less than 20 percent.