１．Introduction

Superconducting(SC) magnets are used in various industries as strong magnetic field generators. Coils wound with superconductors need to be cooled down to about 4K (-269°C) to become a SC state, and the coils are stored in a vacuum vessel for thermal insulation (Fig. 1). Conventional SC magnet basically use a circular shaped coil called solenoid, but it is difficult to generate a complex magnetic field distribution with solenoid coil and it is not efficient to generate magnetic field. Therefore, we have developed a technology for automatically winding three-dimensional SC coils, and the technology has led a significant weight reduction and a high efficiency of heavy-ion radiotherapy systems and silicon single-crystal pullers (Fig. 2).

Fig. 1　Schematic view of a SC magnet

Fig. 2　SC magnet for silicon single-crystal puller

２．Developed Technology

The SC coil is formed by winding conductors with a diameter of about 1 mm for several thousand turns. With the developed technology, it is possible to form a 3D coil by winding while adhering conductors to the surface of the winding frame.

２．１　Coil Design Technology

We developed a calculation code to find the optimized conductor positions that generates a complex magnetic field distribution efficiently. And the code can convert the position into NC data (Fig. 3).

２．２　Automatic Winding Machine

In order to realize the calculated conductor positions with high accuracy, we have developed an automatic winding machine that uses ultrasonic welding for conductor adhering and controls the welding head position with six synchronized axes. By reducing the weight of the welding head and developing control software, we have achieved high-pr  ecision operation of ±0.1㎜ or less.

Fig. 3　The SC coil for heavy-ion radiotherapy

２．３　Resin

Because of a strong electromagnetic force, a resin for impregnation is required high mechanical properties at 4K. Hence we have developed a special epoxy resin filled with nano-filler for the SC coils.
２．４　Applications

The SC rotating gantry for heavy-ion radiotherapy is shown in Fig. 4. By applying this developed technology, we successfully downsized the weight to about 300 tons, which is half of the conventional one. Furthermore, this technology has more than doubled the magnetic field generation efficiency of the silicon single-crystal puller, contributing to cost reduction.

Fig 4　SC rotating gantry for heavy-ion radiotherapy

３．Conclusion

The automatic 3D winding technology for SC coils has make it possible to generate a strong and complex magnetic field distribution efficiently. Therefore, it can be applied in various fields and is expected to contribute to the development of science and technology in the future.

Tomofumi Orikasa,
Member , Toshiba Energy Systems & Solutions Corporation Keihin Product Operations.(2-4 Suehiro-Cho ,Tsurumi-ku,Yokohama 230-0045)

Ikuo Watanabe,
Member , Toshiba Energy Systems & Solutions Corporation Keihin Product Operations.(2-4 Suehiro-Cho ,Tsurumi-ku,Yokohama 230-0045)

Toshiro Fujii,
Member , Toshiba Energy Systems & Solutions Corporation Keihin Product Operations.(2-4 Suehiro-Cho ,Tsurumi-ku,Yokohama 230-0045)

Chiayu Lin,
Member , Toshiba Corporation Manufacturing Engineering Center.(33 Isogo-Cho ,Isogo-ku,Yokohama 235-0071)

Shigeki Takayama,
Member , Toshiba Energy Systems & Solutions Corporation Energy Systems Research and Development Center.(2-4 Suehiro-Cho ,Tsurumi-ku,Yokohama 230-0045)