High Field Superconducting Magnets for Particle Accelerators

Superconducting magnets have been an enabling technology for particle accelerators for more than 40 years. Nb3Sn was considered as an option for LHC; plenary speaker Ezio Todesco recalls the development of Nb3Sn dipole short models in the 10-14 T range in the past 35 years.

An introduction covers the specific challenges of high-field accelerator dipoles with respect to other devices, such as solenoids or detector magnets. This is followed by a brief historical overview of the development of Nb-Ti magnets for particle colliders up to the 8 T dipole fields achieved in the LHC at 1.9 K.

The focus then shifts to the present status of Nb3Sn technology used in the quadrupoles to be installed at CERN in the High Luminosity LHC at the end of this decade, with 11.5 T operational peak field and lengths up to 7.5 m.

To continue, the developments of Nb3Sn dipoles for future colliders aiming at an operational field of the order of 14 T will be discussed. High-temperature superconductors are used as current leads in the LHC and are planned for the HL-LHC: this gives an outlook on the opportunities and challenges of making dipole magnets using HTS to achieve fields of the order of 20 T.

Dr. Ezio Todesco received his PhD in Physics at the University of Bologna, Italy, on the stability of classical mechanical systems and chaotic motion with application to beam dynamics in circular colliders. In the nineties, he participated in the studies of nonlinear motion of protons in the foreseen Large Hadron Collider, and their long-term stability in view of the magnetic field imperfections.

He then joined the CERN magnet group to follow and guarantee the field quality in producing the LHC main magnets. At the end of the LHC production, he oversaw the collider's magnetic model during the commissioning phases and in the following runs. In 2007, he started working on upgrading the LHC luminosity, focusing on magnet design and the optics of the interaction regions.

Since 2011, he has led the worldwide collaboration building the interaction region magnets in the HL-LHC project, with the first Nb3Sn magnets to be installed in a collider in 2026-2028. In 2024, he became the lead for the High Field Magnet program at CERN, in collaboration with numerous institutes and laboratories. He has been teaching superconducting magnets for particle accelerators at the U.S. Particle Accelerator School, CERN Accelerator School, and University of Milano Bicocca. He has been a member of the ASC board since 2020, and he is the author of over 300 publications and a contributor to several books.