Niobium-tin quadrupole model

The objective of the project is to design, build and cold test a niobium-tin (Nb₃Sn) quadrupole magnet prototype based on the design of the quadrupole magnets in the LHC, made of niobium-titanium (NbTi). The critical temperature and critical field of the superconducting compound Nb₃Sn are around double that of NbTi. However, it has some disadvantages. A high temperature thermal treatment is needed to produce it (greater than 600°C) and it is very fragile, with critical parameters sensitive to deformation. It was necessary to rethink the design and manufacture of the coils so as to reduce the risk of damaging the conductor.

The coil is made from an unreacted conductor, which contains the precursor of the Nb₃Sn compound, insulated using a fibreglass ribbon. Once the coils are formed, they are subjected to heat treatment at 660°C for 240 hours to allow the formation of the Nb₃Sn compound with the correct stoechiometry. After the heat treatment, the coils are impregnated with epoxy resin in a vacuum to ensure mechanical cohesion and allow them to be handled without risk of the conductor being damaged. It takes approximately two months to make a coil.

The manufacture of the Nb₃Sn conductor was carried out under a collaboration agreement with Alstom/MSA which was concluded in March 2004 with the delivery of 5 lengths of 60 m of Nb₃Sn cable, to make 4 coils for the model magnet and one spare coil. 2004 was devoted to validating the winding components and tools thanks to the manufacture of the first test coil. The reaction and impregnation tools were made in the first half of 2005; the tools were validated firstly on the first test coil, and then on a second coil completed in December 2005.

The manufacture of the first certified coil was started in December 2005. Six certified coils were made in 2006 (one more than the number that was originally planned). The electrical and mechanical tests on the coils were carried out at Accel's factory in Germany, using the equipment used for the LHC quadrupoles. Three assembly and bracing tests were carried out on the 200 mm high models, cut out on the right part of the two test poles and representative of the cross-section of the magnet; these tests validated the mechanical calculation that were the basis for the magnet's design, and the installation procedure of the stress sensors designed to monitor the changes in the coils during the manufacture and the magnet tests.

The assembly of the magnet, the first hot tests and manufacture of the cold mass for the cold tests are planned for the first half of 2007; the cold tests will follow in the second half of 2007

#2427 - Last update : 04/12 2019

Division of accelerators, cryogenics and magnetism

Institute of research into the fundamental laws of the Universe