Since 1998, SACM has been working on a research and development project with the aim of constructing an Nb3Sn quadrupole model. The electromagnetic design of the model is based on the one of the quadrupole magnets used in the LHC, while the manufacturing process has been modified in order to suit the use of a Nb3Sn conductor. This type of superconductor has to be formed at high temperature making it extremely fragile and stress-sensitive. For this reason, the winding is done using a non-reacted conductor insulated by a glass-fiber tape. Once the winding has been shaped, the coils are subjected to a heat treatment at 660°C and then vacuum impregnated with epoxy resin in order to complete conductor insulation and allow coil handling and assembly.
Five certified coils were manufactured and tested in 2006. The electrical tests carried out on the coils revealed shorted turns in two of the coils, and a replacement coil was manufactured during 2007. At the same time, the two coils with short circuits were successfully repaired. The four best coils were assembled in 2007 at the Accel plant in Germany, using the collaring press used for the LHC main quadrupole magnets production. The magnet instrumentation and the cold mass assembly were carried out at Saclay in 2008, and the first campaign of cold tests was carried out in April 2009. Unfortunately, the results of the tests were not as good as had been hoped. The current in the coils was limited to 5000 A rather than the nominal design value of 12000 A. The four coils began to exhibit resistive behavior above 1000 A.
An additional program of tests is planned for 2010 with the aim of identifying the cause of the problem. For future projects using Nb3Sn, it is important to understand whether this was a systematic fault occurring during coil manufacturing, or whether it was due to damage caused during their assembly.
• superconducting magnet physics and technology › Developments for instrumentation
• Accelerators, Cryogenics and Magnetism Division (DACM)
• LCSE
