Mu2e superconducting cable prototype successful

Vito Lombardo and Giorgio Ambrosio lead the development of the Mu2e transport solenoid. In a recent test, the prototype superconducting cable for the solenoid met every benchmark. Photo: Reidar Hahn

Last month, members of the Technical Division conducted final tests on the first batch of prototype superconducting cable for the proposed Mu2e experiment. The cable met every prescribed benchmark, carrying over 6,800 amps of electrical current — well above its design current — at 4.2 Kelvin in a magnetic field of 5 Tesla.

This aluminum-clad niobium-titanium superconductor is a critical component of one of Mu2e’s three magnets, the transport solenoid. As the name implies, the transport solenoid will help transport a beam of muons from its production source to the detector, where scientists will study the particle interactions.

“This prototype conductor is an important part of our transport solenoid magnet program,” said Giorgio Ambrosio, who is in charge of the transport solenoid design and development. “We know that no superconducting magnet is better than its conductor.”

Having met this milestone ahead of schedule, members of the Superconducting Materials and Magnet Systems departments will march ahead with the other three superconducting cable prototypes for Mu2e: one for the production solenoid and two for the detector solenoid. They plan to complete the cable prototyping stage in a few months’ time.

“Scheduling is quite tight and really adds to the complexity of this project,” said Vito Lombardo, who is leading the Mu2e superconductor effort.

Coordinating its global development adds yet another layer of complexity: Fermilab designed the cable, and a company in Japan manufactured the prototype. The manufacturer shipped niobium-titanium strands to a business in the United States for cabling. It was then sent back to Japan for the aluminum cladding and finally delivered to Fermilab for final testing. Fermilab will eventually send the cable to Italy to be wound into a prototype magnet.

The prototype cable is a considerable three kilometers long. Ultimately, the Mu2e experiment will make use of more than 70 kilometers of superconducting cable for its magnet systems.

“It’s going to be a gigantic effort down the road. We have partners and vendors scattered globally, and Fermilab serves as a hub for the whole process,” Lombardo said.

“We monitored the whole development process from start to finish. Every step of the way, we’ve had samples sent to us and tested,” said Mike Lamm, who leads the Mu2e solenoid development in the Magnet Systems Department. “Vito’s is a big logistical job. It’s absolutely critical to the success of the magnets that these conductors work.”

So far, the Mu2e magnets appear to be on track.


This shows a cross section of the Mu2e transport solenoid superconducting cable prototype. Photo: Reidar Hahn