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A superconducting bearing fabricated by low temperature superconductors is introduced in which the ball, field-shaping rings all work in the Meissner state. The levitation stability of the ball is related to the values of lower and upper charging currents and the charging method of coils. The distribution of magnetic field and magnetic force are calculated with finite element method during the vibration of the ball. According to the Newton's laws of motion, the vibration characteristics, including the bearing stiffness, tolerable disturbing energy, and vibration amplitude, are analyzed at different charging currents when the coils are charged by constant current source method and closed-loop coil method respectively. The values of charging currents are calculated at which the tolerable disturbing energy reaches the maximum value. The calculated results show that the maximum tolerable disturbing energy with closed-loop coil method is larger than that with constant current source method. Moreover the corresponding vibration amplitude with closed-loop coil method is smaller. With this charging method, the total magnetic flux of the coils is invariable during the vibration of the ball, but their charging currents vary with the displacement. [ABSTRACT FROM AUTHOR]

A superconducting magnet for the superconducting magnetic energy storage system (SMES) fabricated by NbTi monolithic conductor is cooled down and operated at the temperature of liquid helium. The large-scale superconducting magnet with four parallel solenoids was designed, fabricated and tested for the high storage energy density SMES. The superconducting magnet stores 2 MJ of energy with a current of 490 A and a peak magnetic field of 5.4 T. Two GM cryo-coolers cool the whole system to realize zero evaporation of liquid helium. The high temperature superconducting current leads of Bi2223 are used and cooled through one GM cryocooler. The ZnO resistor is used to protect the superconducting magnet. In the paper, the system of superconducting magnet is introduced in detail for the superconducting magnetic energy storage system. [ABSTRACT FROM AUTHOR]

A practical method to measure spin axis position of superconducting sphere rotor in cryogenic instrument using a reflective intensity modulated optical fiber sensor is presented. The deviation amount and direction of the spin axis are obtained by calculating the amplitude and phase of the reflective optical intensity signal. The experiments are carried out for the verification of the theoretical model and the performance evaluation of the sensor system. The experimental results show that the resolution, repeatability and linearity of the sensor system can achieve 10 µm, 2% and 0.9988 respectively. [ABSTRACT FROM AUTHOR]

For the goal of superconducting magnet applications in the advanced testing device for high temperature superconducting (HTS) wire and sample coils, a wide bore conduction-cooled superconducting magnet with available warm bore of Φ186 mm and center field of 5 T for the background magnetic field applications was designed and fabricated and tested. A sample cryostat with two GM cryocoolers is inserted in the background magnet. The system allows measurements to be performed in a repeatable and reliable fashion. The detailed design, fabrication and thermal analysis are presented in the paper. [ABSTRACT FROM AUTHOR]

A spherical superconductor is fixed in a vacuum and surrounded by a harmonic magnetic field. In this paper, we analyze the electromagnetic characteristics and ac loss of the rough sphere by two steps. Firstly, we regard a superconductor as a good conductor and determine the distribution of the magnetic flux density on the surface of a rough sphere. Then, regarding the surface of the sphere as an infinite plane relative to the penetration depth of niobium, we solve the electromagnetic field in a thin layer in which the magnetic field penetrates. By integrating the inner product of electric field and normal current we calculate the ac loss of the rough sphere basing on Maxwell equations and London equations. The results indicate that the superconductor produces ac loss when it is affected by the outside alternating magnetic field, even if it is in the Meissner state. [ABSTRACT FROM AUTHOR]

The reflective intensity modulated (RIM) fiber optic sensor is introduced for the measurement of superconducting sphere rotor spin-axis position in cryogenic instrument. A diffuse reflective rectangle pattern scribed on the circular flat surface at one end of the spin axis was used to modulate the reflective optical intensity on which the deviation value and direction of the spin-axis was determined. The relationship between the deviation of spin axis and the reflective optical intensity modulation is presented and some related factors are analyzed. [ABSTRACT FROM AUTHOR]