How CERN Built the Large Hadron Collider’s Next-Gen Magnets

This article is part of our exclusive IEEE Journal Watch series in partnership with IEEE Xplore. CERN’s Large Hadron Collider (LHC) uses extremely strong magnets to collide particles…

This article is part of our exclusive IEEE Journal Watch series in partnership with IEEE Xplore. CERN’s Large Hadron Collider (LHC) uses extremely strong magnets to collide particles at nearly the speed of light, breaking them up into smaller components for study. The LHC is already capable of slamming about 60 particles together 40 million times per second in a single experiment, which has led to some of the most important particle physics discoveries of the century. But scientists at CERN are not stopping there.

They are currently working on upgrading the LHC for upcoming experiments scheduled to begin after 2030. The new iteration of the particle collider, called the High-Luminosity LHC, will slam more particles together than before. (The phrase “high luminosity” refers to the increased number of particle collisions.) CERN’s goal is to achieve between 140 and 200 particle collisions 40 million times per second in each experiment in order to increase their chances of observing rare particles or phenomena. To succeed, the collider will need extremely compact and high-quality magnets.

In a study published 24 September in IEEE Transactions on Applied Superconductivity, researchers outline their journey to manufacture these next-generation magnets for the LHC, which require new materials and manufacturing techniques. Developing Nb₃Sn Superconducting Magnets The collider’s current magnets contain coils made of niobium and titanium (NbTi) and can achieve strengths of 8.3 tesla. That is about 166,000 times as strong as Earth’s magnetic field. However, this magnetic force is the upper limit of what NbTi coils can achieve.

For the LHC’s new magnets, scientists are creating coils made of niobium and tin (Nb₃Sn), which will yield just under 12 T. Susana Izquierdo Bermúdez, a magnet engineer at CERN who leads a team of about 60 people, has been involved in the development of these magnets since 2012. Over the years, she has contributed to many different aspects of the project, including early winding tests, electromagnetic design, mechanical design, manufacturing and testing.

Izquierdo Bermúdez notes that while NbTi is ductile and can be wound after the superconducting compound has been formed, Nb₃Sn is brittle and cannot tolerate the large strains involved in coil winding. For this reason, the magnets are produced using a process known as wind-and-react: The cable is first wound into its final coil geometry, and the Nb₃Sn superconducting phase is formed only afterwards through a high-temperature heat treatment.