Design and Manufacture of the Low-Resistance ${\rm Nb}_{3}{\rm Sn}$ Joints for the CHMFL 40 T Hybrid Magnet

DC Resistance Performance of the Low-Resistance <inline-formula> <tex-math notation="TeX">$\hbox{Nb}_{3}\hbox{Sn}$</tex-math></inline-formula> Joints for the CHMFL Hybrid Magnet

“…Therefore, machining of the joints should be avoided after the superconducting coils are heat-treated [6]- [9]. The superconducting outsert of the 40-T hybrid magnet will be operated in the dc state, the joint will be cooled by 4.5-K supercritical helium with 1 g/s, and the temperature rise come from the joint will be controlled to be lower than 0.2 K. Hence, each joint's dc resistance will be crucial to the performance of the outsert and should be lower than 3 nΩ to meet the cryogenic cooling requirements [5]. All the joints will be assembled and fixed outside of the superconducting magnet outsert to reduce the background field below 3 T (see Fig.…”

“…Each terminal is made of a terminal box, a superconducting cable, and a terminal cover, as shown on the right side in Fig. 2 (from [5]), The joint box consists of a copper bottom (sole plate) and a steel side, which are welded together by the vacuum brazing technique. The leak test of the joint box was carried out at room temperature after the brazing.…”

“…The inner two subcoils, A and B, are each layer wound continuously with two different grades of conductor, A and B. Subcoil C is independently layer wound with a whole length of conductor C. Subcoil D is pancake wound with four piece-lengths of conductor D due to the limitations of the conductor piece length. Two kinds of joints with different configurations have been designed [5]. The interlayer joint will be used for connecting between the four piece-lengths of conductor D and for connecting subcoils A and B.…”

Fabrication Technique of the Model Coil for the 40-T Hybrid Magnet Superconducting Outsert

“…After the ground insulation was wrapped, the two superconducting joints were installed following the same process as a tested "terminal joint," which is presented in [11]. After this, the coil and joints were armed with a set of parts [see Fig.…”

“…We did many manufacturing technology experiments and preparations during the model coil R&D process, such as dummy conductor fabrication, dummy coil winding, insulation research, superconducting joint fabrication and test, heat treatment furnace installation and commissioning, etc. Some of the achievements of earlier development stages have been presented in [8]- [11]. In this paper, we will present and summarize the fabrication technique used for the model coil manufacturing process.…”