In March 7th 2018, our group at LASA-Milan completed with success an important test on a superconducting coil in MgB2 (di-Boride Magnesium based conductor) fully designed, wound, impregnated and instrumented at LASA.
This coil, wound with conductor produced by Columbus Superconductors (Genova), will be part of an innovative concept of superconducting iron based magnets, capable to produce any value of multipole field for accelerators, using simple circular-solenoidal coils to excite iron poles. For this reason we call these magnets RCSM (Round Coil Superferric Magnet).
The superconducting coil, cooled at 4.2 K with boiling helium, yesterday reached without any training quench the specification current (“ultimate current”, 160 A), passing also the stability test of 1 hour at the ultimate current. The coil was then energized to larger currents to investigate the limiting current, which resulted 243 A, which is 73% of the intersection of the load line with the critical current for virgin, not-degraded, conductor. Also this last current limit has been reached without intermediate quench (no training). We consider a success this result because MgB2 virgin conductors are very prone to degradation when are wound and manipulated with even better procedures used for the other common superconductor magnets based on NbTi. With the experience acquired for this first coil and the new possible improvements in procedures, in future we may even hope to obtain better results on limiting current respect to the theoretical current of virgin cable. Our cryogenic test was also complemented with the measurement of the thermal contraction of coil (literature is lacking of this data regarding MgB2 coils), which will allow us to a better design of the mechanical structure for the final magnet.
This activity on RCSM was initiated in 2014 by our late lamented Giovanni Volpini and by some other collaborators at CERN, under the collaboration agreement between CERN and INFN-LASA for the prototyping of the High Order Multipole Corrector Superconducting Magnets of the program High Luminosity LHC (HL-LHC). During the following years, the MgB2 RCSM was considered a bit too innovative as baseline design for the correctors to be installed in HL-LHC, and for this reason the develop of this magnet had to leave the way to the more urgent activities in prototyping the more standard, more mature NbTi superferric magnets for HL-LHC.
In 2017 the activity on RCSM MgB2 magnet was risen again, with new efforts and new developments. The important step of yesterday allow us now to proceed with the mechanical construction of the iron structure for the completion of the magnet.
We want to thank our great team at LASA for this new encouraging result, from the technicians for their competence and devotion, to our 2nd degree level and PhD students for their enthusiastic contribution in this project.
