S.B. Kim

Characteristics of a 3-D HTS Actuator With Various Shaped Electromagnets

We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulk to develop the transportation device with non-contact and move in free space. Proposed superconducting actuator consists of the stator constructed by two-dimensional arranged electromagnets and HTS bulk superconductor as a mover. The 2-D arranged electromagnets were individually controlled to move the HTS bulk. It is expected that our proposed 3-D superconducting actuator will be useful as a transporter used in clean rooms where silicon wafers are manufactured. Wafers must be protected from contact with dust and other contamination. To realize the superconducting actuator with HTS bulks, the electromagnetic characteristics of HTS bulk, such as trapped field strength and patterns, should be clarified and the optimized controlling system is also required. Therefore, in this study, to construct the optimal 3-D actuator system, the fundamental characteristics of the levitation for HTS bulks with individually controlled four and eight-polarities electromagnets were investigated experimentally. And two kinds of cap cores attached the top of the core to improve the control ability of proposed actuator were fabricated and tested.

Characteristics Measurements of HTS Tape with Parallel HTS Tapes

Many high temperature superconducting (HTS) tape manufactures make an effort to reduce the transport current loss of HTS tapes. The knowledge of critical current and self-field in an HTS tape is very useful to compute the transport current losses. The spatial distribution and magnitude of self-field are variable due to the neighboring materials. In this paper, the critical currents and the transport current losses of BSCCO and YBCO tapes with paralleled magnetic material (Ni tape) and/or diamagnetic material (BSCCO tape) are experimentally investigated to improve the AC loss properties. The critical currents of HTS tapes with paralleled Ni tape are slightly decreased and the transport current losses are markedly increased. However, the critical currents and transport current losses of HTS tapes with paralleled BSCCO tape have not current carrying are more improved than single HTS tape

Magnetic-field properties of high critical current density YBCO films deposited by TFA-MOD

The critical current density, Jc, of metal-organic deposition process using trifluoroacetates (TFA-MOD) based YBCO films was measured between 20 K and 77 K in magnetic fields up to 9.5 T as a function of the field direction. C-axis oriented YBCO films was deposited on LaAlO/sub 3/ single crystalline substrates and also on CeO/sub 2/ buffered IBAD (YSZ/Hastelloy) substrates by TFA-MOD method. The obtained Jc values at 77 K and 0 T were 7 and 1.7 MA/cm/sup 2/ for LaAlO/sub 3/ and IBAD substrates, respectively. High Jc values over 10/sup 5/ A/cm/sup 2/ were maintained up to 4 T (B//c-axis) for the LaAlO/sub 3/ substrate and up to 3 T (B//c-axis) for the CeO/sub 2/ buffered IBAD substrate. These results imply that TFA-MOD with simple fabrication process is very promising for the practical YBCO coated conductor. And the dependences on temperature and angular of the Jc at various external magnetic fields for some different thicknesses YBCO films was reported.

Development of superconducting actuator for the contactless transporter

We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulk to develop the transportation device with non-contact and move in free space. Proposed superconducting actuator consists of the stator constructed by two-dimensional arranged electromagnets and HTS bulk superconductor as a mover. The 2-D arranged electromagnets were individually controlled to move the HTS bulk. It is expected that our proposed 3-D superconducting actuator will be useful as a transporter used in clean room which manufactures the silicon wafer where dislikes mechanical contact and dust. To realize the superconducting actuator with HTS bulks, the electromagnetic characteristics of HTS bulk, such as trapped field strength and patterns, should be clarified and the optimized controlling system is also required. Therefore, in this study, to construct the optimal 3-D actuator system, the fundamental characteristics of the levitation for HTS bulks with individually controlled four electromagnets were investigated experimentally.

Design of Electromagnet for high levitation force in 3D superconducting actuator

We have been developing a new type of 3-D superconducting actuator using the strong pinning force of HTS (high temperature superconducting) bulk. The system includes HTS bulk and two-dimensionally arranged multiple electromagnets. The application of HTS bulk enables stable levitation and suspension, and its performance is determined mainly by the spatial distribution of the generated magnetic field of the electromagnets. To enhance the levitation force in the actuator, it is necessary to design the optimized geometry of the electromagnets. The target of the design is to lead to an intensive concentration and abrupt gradient increase of the perpendicular component in the magnetic field through the HTS bulk over the electromagnets. For the optimized design of the electromagnets, we calculated the spatial distribution of the trapped magnetic field and the levitation force of the HTS bulk using 3-D FEM analysis that is adopted the critical state model.

Fabrication and Application of Two-Axis Hall Sensor Array Using ELO Film Bonding Technology

In this paper, we report a basic study on the development of a two-axis Hall sensor array using epitaxial lift-off (ELO) film bonding technology. We developed a novel Hall sensor array fabricated on a Si substrate that can directly measure axial and radial magnetic field components (Bx and Bz) simultaneously. We investigated conditions of basic fabrication process and fabricated a basic test device. We also estimated basic characteristics of the Hall sensor and measured the DC self-magnetic field profiles of a YBCO strip. The results clarified that the ELO film bonding technology is suitable for fabricating two-axis Hall sensor array.