Basic Research on High Field Superconducting Magnet for High Energy Accelerators

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High field supercondung magnets which can generate field of 10 T have benn developed in a frame work of the collaborative work for the LHC acclerator at CERN.They are dipole and quadrupole magnets.The dipole magnet whose targeted operation field is 8.4 T has been developed as a complementary work to the CERN R & D for the LHC main dipole magnet by taking close mutual communication. In FY1997, an 1 m model magnet fabricated in FY1996 has been tested mainly to obtain the performance by effect of thermal cycle in which it is warmed up to the room temperature. As a result, the developed magnet whowed a good performance with relatively small thermal cycle effect.The target field gradient of the closest focusing superconducting quadrupole magnet to a beam colliding point is the strongest one of 240 T/m ever built. The inner coil diameter is 70 mm and the maximum field in the coil is over 9.6 T.In FY1997, the main purpose is fabrication and test of the first model quadrupole in a base of the design works in FY1995 and 1996. When it was fabricated, we took close communication with CERN staff for mechanical properties of the coil suport structures and items to be tested. The basic data of necessary tolerable size and stresses in the magnet have been obtained prior to the fabrication of the first model. We tested the model and obtained the rated operational field gradient of 205 T/m at the first quench. By training (gradual increasing the quench currents), the magnet was successfully excited over the design value of 240 T/m and finally showed the strongest field gradient of 250 T/m in the world. The fruitful results will be reflected to the fabrication of the practical magnet.In order to put these R & D in practice, the staff exchange has been carried out each other, and five technical meetings have been held. Moreover, the technical meeting was held at CERN in March 1998 in order to discuss and summarize these obtained results of this R & D.