Design and fabrication of end spacers for a 13T Nb3Sn dipole magnet

A 13 Tesia R ampersand D dipole magnet is currently being constructed using Nb3Sn superconducting cable. The four-layer ''cosine-theta'' magnet uses a wide cable (∼15 mm) that will undergo a 650 C reaction after each layer is wound. About 75 bronze spacers at the magnet ''ends'' separate the winding blocks in such a way that the stored strain energy in the cable is minimized and the integrated field harmonics are reduced. Wax prototypes of the designed spacers were made on a 5-axis milling machine. This method of rapid prototyping required no tooling and enabled us to produce a large number of different end spacers that can be physically inspected and repeatedly modified before final prototypes are made. Spacers were originally machined from wax billets which were later cast in bronze