The Japanese government decided to collaborate on the LHC construction project at CERN (European Organization for Nuclear Research) in May, 1995. This proposal was accepted by the CERN Council by a unanimous vote on June 23, 1995. This collaboration is on the construction of the LHC accelerator, especially basic R & D of the main superconducting dipole magnet and production of the low β insertion quadrupole magnet. These magnets, which should generate around 10T, require highly sophisticated technologies. The program should be completed within 10 years, and technologies developed by this program will help raise the technical potential on superconducting magnets and cryogenics. The Japanese collaboration program is described briefly with technical problems of the superconducting magnets to be solved.
Ag-sheathed Bi-2212 multifilamentary tapes were fabricated using the powder-in-tube method. The degassing process of Bi-2212 starting powder not only removed such gases as H2O and CO2, but also improved the core density of the resulting melted tape. The tapes heated and cooled in a low O2 atmosphere had an effect on raising Jc and Tc. The bending strain is estimated to be smaller than 0.3% for excellent Jc and n-value. A small double pancake coil fabricated by the “Wind and React” technique using 6.8m-long tape generated B0 of 1.76T at 664A (at 4.2K, self field).
A Bi-2212 superconducting solenoid coil with a practical size (78mm in diameter) of bore has been fabricated, employing 300m long Ag-sheathed Bi-2212 rectangular wire. A new heat treatment process, controlling an oxygen partial pressure of 2.4atm, has been developed for crystallization of Bi-2212 in the rectangular wire. The coil has been proven to have high homogeneity in critical current density along the longitudinal direction at the outermost layer, however, the critical current density is lower at the innermost layer. In spite of this drawback, the resulting solenoid coil has stably generated maximum magnetic fields up to 0.40T at 4.2K by transporting current densities up to 1.7×104A/cm2.