Teruhiro Takizawa

Generation of magnetic fields over 20 T using a newly developed superconducting magnet system

In February 1992, a newly developed superconducting magnet system at the National Research Institute for Metals accomplished generation of a magnetic field of 20.3 T in its clear bore of 44 mm in diameter. The authors give an outline of the magnet system together with the operation results. The required time to cool down from 4.2 K to 1.8 K was about 4 h. The operations carried out at 1.8 K proved that saturated superfluid helium can be applied as coolant for large scale superconducting magnets because no problems, such as a discharge in the coils, were observed even when quenches occurred. This magnet system may be useful for testing coils of new high-field superconductors.<<ETX>>

Application of 3D eddy current analysis on magnetically levitated vehicles

The eddy currents induced on the superconducting magnet (SCM) vessels of magnetically levitated vehicles (MAGLEV) have been analyzed. A 3D eddy current analysis code, based on a finite-element method (FEM) with thin shell approximation, is developed and verified through a mock-up SCM experiment. Through a coupled electromagnetic and mechanical analysis under SCM vibration, a SCM structure with low-resistivity material coating on the inner vessel of SCM is found to be suitable for the significant reduction of helium evaporation due to eddy current loss. >

Development of a MAGLEV superconducting magnet for the Yamanashi test line in Japan: vibration characteristics and analysis for design

A high-performance and high-reliability magnetically levitated (MAGLEV) superconducting magnet (SCM) was developed. Its heat generation per unit time by the electromagnetic forces due to the spatially fifth ripple magnetic fields from levitation coils is under 2 W at the frequency range in which vehicles are levitated. The vibration mode of inner vessels that makes the largest contribution to heat generation in SCMs is clarified, the torsion mode. A modeling method to analyze SCM vibration, which considers the effect of the bogie frames of a vehicle, is examined, and heat generation in SCMs is calculated from the vibration of the inner vessel. Using the numerical analysis method, new SCMs combined with new bogie frames for the Yamanashi Test Line are designed. Good performance in vibration and heat generation of these SCMs is predicted by numerical analysis.

Electromagnetic force and eddy current loss in dynamic behavior of a superconducting magnetically levitated vehicle

A magnetically levitated vehicle is being designed to travel between Tokyo and Osaka in about 1 h at a 500-km/h speed. When the car runs at a high speed, it moves laterally and vertically from its balanced position at low frequencies. The authors present calculations of electromagnetic forces and eddy currents generated in the onboard cryostat containing the superconducting magnet as a result of these motions. They show that the electromagnetic forces, eddy current losses and damping constants of the motion, especially for the lateral and vertical motions, depend on the materials of the radiation shield and the inner vessel in the magnet and change with the frequencies of car motion. The magnitudes of forces, losses, and damping constants in lateral motion are compared with those in vertical motion. To evaluate these quantities, numerical calculations were performed with a two-dimensional finite-element method.<<ETX>>

Development of a 20 T class superconducting magnet with large bore

A 20 T class superconducting magnet has been constructed at the National Research Institute for Metals in Japan. The two outermost of the four coils have been operated at 4.2 K. Before operating all coils at 1.8 K, in saturated superfluid helium, breakdown voltages within the coils were measured. With an inner coil of preliminary design, the system should generate 20.4 T in a 44 mm free bore. >

Development of a high rigidity superconducting magnet for the Maglev system

A high rigidity type superconducting magnet (SCM) is developed and tested by an electromagnetic vibration simulator which simulates the actual running conditions. To reduce the increase in heat load due to the vibration of the cryostat, several kinds of design concepts are chosen. It is recognized from the experiment result that the most effective design concept is to increase the characteristic frequency in twisting mode of the inner vessel with the high rigidity outer vessel.

Analysis of Electromagnetic-Structural Coupling Behavior using Lumped Parameter Model.

This paper concerns the dynamic behavior of a structure coupled with an electromagnetic field. We study the coupling behavior between vibration and eddy current using the lumped parameter model of a superconducting magnet for magnetically levitated vehicles (MAGLEV). This is a simple model with multidegrees of freedom which consists of mass, spring, resistance, inductance, and differentiation of inductance. We calculate the frequency response of vibration, eddy current, and Joule loss. These results show that the dynamic behavior of a structure in a strong magnetic field is different from the dynamic behavior without the magnetic field. For example, an antiresonance point which does not appear in the structure system appears in the coupling system. We also show the modeling method to understand the vibration behavior under the magnetic field.

Development of 20T Large Bore Superconducting Magnet. (III). Operation Results.

A 20T large bore superconducting magnet has been developed at the National Research Institute for Metals. In this paper, operation results of this magnet are reported. Cooling down to 1.8K was successfully carried out. Magnetic fields of 15T in a 314mmφ chamber, of 18.06T in a 160mmφ bore and of 20.33T in a 44mmφ bore could be generated. Even after the quenches of two inner coils, they could be re-energized immediately. This fact indicates that this magnet provides an ideal environment for high-field coil experiments. Operation results also proved that saturated superfluid helium can be applied as a coolant for large scale superconducting magnets.