High-field magnets poised to get an upgrade

A 2-meter-long superconducting coil filled with Matrimid® has been shown to be able to stand up to extreme operating environments. Photo: Sarah Khan

A 2-meter-long superconducting coil filled with Matrimid® has been shown to be able to stand up to extreme operating environments. Photo: Sarah Khan

Recently the Technical Division’s High Field Magnet Group identified and tested a new insulating compound that could help superconducting magnets survive under the harsh conditions of many future accelerator projects.

The new component, called Matrimid® and manufactured by the company Huntsman, can last longer and resist radiation better than the traditional epoxy-based insulation used for magnet coils.

Recently, engineer Steve Krave and lead engineer Rodger Bossert produced 1- and 2-meter long superconducting coils filled with Matrimid. Tests have shown that the new insulation holds up well to extreme fabrication and operating environments.

“These results are very exciting,” said Alexander Zlobin, head of the high-field magnet program. “This technological development will have a great impact on our field.”

Started in 1998, the program aims in part to create niobium-tin magnets that produce very large magnetic fields at very low temperatures. Such magnets have applications in the LHC upgrade and could also be used in a linear collider, a neutrino factory or a muon collider.

“The magnet coils are subjected to high mechanical stresses, extreme temperatures and large amounts of radiation, which, over time, shortens the magnet’s life,” Zlobin said. “Materials and performance often degrade in a few years, too short a time for many accelerator applications.”

The group is specifically concerned about the epoxy used to insulate the turns in niobium-tin superconducting magnets and give the coils a stiff structure.

While operating in high-radiation environments and at very low temperatures, the epoxy is usually the first material to break down.

This shows a cross-section of superconducting wires stacked on top of each other. In between the wires is the insulating component Matrimid. Photo: Marianne Bossert, TD

This shows a cross-section of superconducting wires stacked on top of each other. In between the wires is the insulating component Matrimid. Photo: Marianne Bossert, TD

Degrading magnets lose field strength, and when serving an experiment, that means less data. This poses problems for projects such as the upgraded LHC, which scientists believe will deliver 10 times more data than it did previously, Zlobin said.

The group estimates that Matrimid, an epoxy-like component, can extend magnet life to five or more years.

Matrimid is a dark amber substance normally used in the aerospace industry because it can withstand high temperatures, pressures and radiation. The group realized 10 years ago that the material could also work for superconducting magnet coils.

Since then, they’ve been studying how to get the finicky material into the coils.

“You have to impregnate the coil quickly, but to do that, you have to heat Matrimid to high temperatures, which could damage other parts of the coil,” Krave said. “Additionally, impregnating a coil too quickly could yield bubbles and gaps during curing, which would hamper the magnet’s performance. We looked at all of these different variables and tried to find a process that worked.”

The recent successful tests with the 1- and 2-meter coils means the group can continue refining the production process to work on longer coils of 6 or more meters, Bossert said.

“This is really a breakthrough,” Zlobin said. “We are not just talking about ideas, but real magnet performance.”