In the round: a new design for high-temperature superconducting magnets

Two new simple, elegant magnets for particle accelerators could lead to significant cost savings.

The science

Superconducting magnets are the workhorses that steer particle beams in most particle accelerators. The problem is that these magnets require costly cryogens to cool. Now, researchers have found a way to create high-temperature superconducting magnets. A group at Fermilab proposed a novel magnet design that works at much higher temperatures. It could substantially simplify magnet fabrication and cooling.

The impact

The team’s design offers cryogen-free magnets. Such magnets are simpler and cheaper to operate. Also, the straightforward, elegant design simplifies magnet fabrication. The new design could improve superconductors and many other devices that produce magnetic fields.

 

Fermilab scientists and engineers developed and tested a novel superconducting magnet configuration where round coils generate the multipole magnetic field. This picture shows the magnet after a recent test. Photo courtesy of Vladimir Kashikhin

Summary

At the heart of a typical electromagnet is a coil that carries electrical current. The current creates the magnetic field. The Fermilab group designed, fabricated, and tested two high-temperature superconducting quadrupole magnets with different coils. Typically, a dipole magnet (one north, one south pole) has two coils. A quadrupole magnet (two north, two south poles) has four coils. Fermilab researchers developed a novel, iron-dominated magnet with a single, circular, high-temperature superconducting coil. The new design creates the same magnetic field as a multicoil magnet would. The magnetic flux is directed from the coil to the magnet poles, which form a quadrupole field configuration, for example. This new magnet configuration substantially simplifies the magnet fabrication and cooling technology, reducing the superconductor volume and the magnet cost. During tests at liquid-nitrogen temperature, researchers observed no incidents of the superconductor becoming normal conducting, as can happen, and the magnets reached specified parameters. The group will continue to upgrade magnets for cryogen-free operation with a cryocooler and for the operation in a mode that when the power source is disconnected from the magnet, the coil-trapped current persists, continuing to generate a magnetic field.

Compared to other configurations, this novel design is more suitable for high-temperature superconductors, which are capable of operating up to a temperature of 77 Kelvin (a temperature that liquid nitrogen can maintain).

The team’s design offers superconducting magnets working at elevated temperatures. Such magnets are simpler and cheaper to operate using liquid nitrogen or cryocoolers. Also, the straightforward, elegant design simplifies magnet fabrication. The new design could drive superconductors improvement and many other devices that produce magnetic fields.

This work is supported through the Fermilab Laboratory Directed Research and Development program.

Learn more in IEEE Transactions on Applied Superconductivity, 2010.

Learn more in IEEE Transactions on Applied Superconductivity, 2012.

Vladimir Kashikhin is a Fermilab engineer.