Accelerator quality HTS dipole magnet demonstrator design
by Glyn Kirby (CERN)
Figure 1: Aligned block development HTS magnets, (bottom right) Feather-M0 quench detection development coil, (top left) Feather-M2 the EuCARD-2 five Tesla standalone approaching accelerator field quality insert magnet. Image credit: CERN
Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 Future Magnets activity is a collaborative push to take HTS materials into an accelerator quality demonstrator magnet. A new coil layout concept, named aligned block was developed which can result in 2.3 times less conductor that leads to more cost efficiency than with the conventional Cosine Theta design using the same conductor.
The collaboration between CEA-CERN-KIT-TUT-INFN-LNBL aims to develop a High Temperature Superconductor (HTS) accelerator quality magnet demonstrator, capable of producing a 5 T central magnetic field in standalone configuration. Both REBCO and BSCCO conductors are being considered. The BSCCO design is part of the US-BSCCO programme based on Canted Cosine-Theta (CCT) geometry. The European collaboration is focusing on REBCO coated conductors, based on aligned block and cosine-theta.
At CERN scientists are developing the align block concept, named Feather-M0/2 (FeaTHeR - Five Tesla HTS Research, see Figure 1). Feather-M0 is used to develop coil winding and quench detection, while Feather-M2 will produce 5 Tesla standalone and between 17 and 20 Tesla, when inserted into the 100 mm aperture of Fresca-2 high field out-sert magnet. The main objective with the aligned block design is to maintain a close alignment of the magnetic field with the cable throughout the entire coil assembly. This layout makes optimal use of the anisotropy of the REBCO coated conductor (Figure 2). The design, although in its initial phase, addresses most issues related to the use of Roebel cable for a dipole cable. In a second step it is foreseen to approach a 17 T central field when inserted in a 13T high field magnet. Model coils are under construction, cables and magnet designs are progressing. Models will test dynamic field quality and confirm if it is possible to detect and protect the REBCO high current density present in the aligned Roebel cable design.
Figure 2:In the layouts the magnetic field angle is highest at the edges of the cable causing a large variation of the critical current over its width. Image credit: CERN
