Joint Design for the EDIPO

Abstract

EFDA is presently responsible for the fabrication of a large bore 12.5 T dipole magnet, for a second Cable-In-Conduit conductor test facility to be installed in CRPP (Switzerland). This dipole magnet is wound from square and rectangular type conductors using Nb 3 Sn strands. Since the magnet is built from multiple, independently cooled double pancakes, a total of twelve joints are required to interconnect them. In order to reduce the footprint of each joint ENEA, in collaboration with EFDA, developed a special joint design that allows the two conductor-ends to interpenetrate, reducing to a minimum value the increase of the magnet cross-section at the joint position. Furthermore, this design maintains the electrical performances of the conductor and gives very low electrical resistance values, on the order of some tenths of n. The properties of first prototypes of this joint were successfully tested at ENEA labs. This paper describes the novel joint design, in the dipole magnet version, and discusses some of the measured results.

Qualification of the Joints for the ITER Central Solenoid

“…We modified the EDIPO joint concept proposed by the ENEA Frascati group [2]. A sintered joint option is shown in Fig.…”

Development of the Joints for ITER Central Solenoid

“…In the case of a negligibly low resistance, the current in the sample will be (2) Thus, at 200 A in the primary winding the current in the sample will be 56 kA.…”

“…A soldered version of a lap joint was dismissed due to doubling of the cooling lines for cooling the joint and significant increase (basically double) of the joint volume. Later, in 2007, a sintered joint was introduced, inspired by the ENEA joint development [2].…”

Application of the ENEA Joint Concept to NbTi CIC Conductors

“…The unsatisfactory results obtained with this technique pushed our team to develop a new chemical method to etch the Ni layer, which allowed not to degrade the strand surface: this point, as it was expected, revealed to be critical in order to obtain a good inter-strand conductivity. Using this new chemical etching method, we prepared a joint sample using a 144 NbTi strands conductor , and 0.81 mm diameter, which has the very same layout as the joint samples already successfully tested by our team [2]. The prototype, manufactured as in the procedure described above, has been U bent, placing the joint in the curved region with an average curvature radius of 11 cm, and tested in self-field up to 11 kA.…”

“…A new joint concept in shaking-hands configuration, developed and patented by ENEA in the framework of the EFDA Dipole (EDIPO) [1] activities has been already presented elsewhere [2]. It is based on the idea of cutting the last-but-one cabling stages of the two conductors to be joined at different complementary lengths, interpenetrating the two ends.…”