Niobium-tin magnets could be the key to unlocking the potential of heavy-ion accelerators

Cross-sectional view of the 28 GHz ECRIS superconducting magnet. Credit: Berkeley Lab
Researchers in Berkeley Lab’s Accelerator Technology and Applied Physics (ATAP) department are collaborating with colleagues at Michigan State University’s Rare Isotope Beam Facility (FRIB), the world’s most powerful heavy ion accelerator, to We have developed a new superconducting magnet based on Tin (Nb3Sn) technology.
The first-of-its-kind magnet has the potential to significantly improve the performance of FRIBs, enhance their capabilities, and open up new applications in medicine, industry, and research. The paper will be published in the journal IEEE Transactions on Applied Superconductivity.
In FRIB, a beam of ionized atoms (ions) of elements across the periodic table, including heavy elements like uranium, is accelerated to half the speed of light. When these beams hit a target, they break apart and create short-lived isotopes.
Studying these rare isotopes allows scientists to better understand the structure of matter and the formation of the universe.
“A key component of FRIB is the Electron Cyclotron Resonance Ion Source (ECRIS), which produces high-current, high-charge state ions for injection into the accelerator beamline,” said ATAP’s Superconducting Magnet Program (SMP) staff scientist. Tengming Shen explains. ) is leading the development of new magnets.
“This ECRIS uses sextupole magnets and solenoids to confine electrons and ions within a plasma. The electrons are then heated with high-frequency (28 GHz) microwaves, creating high-energy electrons that A highly charged state ion is created by stripping an electron from a neutral atom.” (This configuration is based on the Versatile ECRIS for Nuclear Science (VENUS) design used in Berkeley Lab’s cyclotron accelerator. (Shen said)
Manufactured at Berkeley Lab, this sextupole magnet is wrapped with superconducting niobium titanium (Nb-Ti) coils. However, the 28 GHz Nb-Ti magnet has a peak magnetic field of 6.7 Tesla (T) at the liquid helium temperature at which ECIRS operates (4.2 Kelvin, -452.1 degrees Fahrenheit).
Professor Shen said that to improve the facility’s performance and expand its range of applications, ECRIS needs to be built with magnets that can generate higher magnetic fields to enable operation at higher microwave frequencies. It states that there is.
“Our goal is to increase the microwave frequency above 45 GHz. At this frequency, the peak magnetic field increases to 10.8 T, but the current-carrying capacity of the Nb-Ti material decreases significantly.”
Towards this end, the researchers chose a magnet design based on superconducting coils made from Nb3Sn. Coils made of Nb3Sn can carry high current densities of over 100 amperes/mm2 at much higher magnetic fields (up to 22 T) than coils made of Nb-Ti at 4.2 K.
However, although the superconducting properties of Nb3Sn exceed those of Nb-Ti, Shen said that the conductive properties of Nb3Sn are very different from those of Nb-Ti.
“For example, unlike Nb-Ti, Nb3Sn is brittle and sensitive to strain. Additionally, coils made from Nb3Sn change dimensions during manufacturing, requiring greater control over the manufacturing process.
“Additionally, the magnet is constructed using small conductors rather than the large Rutherford cables used in current magnet designs, and each coil requires approximately 300 turns.”
These factors make manufacturing the coils and assembling the magnets even more complicated, he says.
“Manufacturing Nb3Sn coils is therefore more difficult, especially for first-of-its-kind magnets for which no blueprints currently exist. Therefore, creating such magnets requires extensive research in superconducting magnet design and manufacturing. Experience is required.”
Fortunately, Berkeley Lab has extensive experience with Nb3Sn-based magnets. Last year, for example, the institute successfully manufactured and assembled the first set of quadrupole magnets made from Nb3Sn superconducting cables.
This research is part of the U.S. Accelerator Upgrade Project for the High-Luminosity Large Hadron Collider, which aims to enhance the capabilities of the Large Hadron Collider and promise new discoveries in high-energy and particle physics. is part of the ongoing contributions of
The development of the ECRIS magnet “is an excellent example of how research and development of high-field accelerator magnets for future collider applications can benefit other scientific applications,” said ATAP Deputy Technical Director and Head of SMP. said Soren Prestemon.
“Furthermore, this provides an exciting opportunity for our talented team of scientists, engineers and technical staff to directly contribute to new and operational facilities like FRIB and the advancement of high-energy physics research. ”
Shen said the team has already performed numerous magnetic and mechanical design calculations to manage Nb3Sn’s dirt-sensitive nature.
“We also evaluated the conductor manufacturing process, conducted winding and manufacturing trials, and developed new designs that addressed coil manufacturing challenges. and the process is nearing completion.”
He added that work has already begun on winding a full-size prototype coil and plans to test a full-size version soon to verify its superconducting performance. If the test is successful, the company plans to develop, build and test a 28 GHz system “with an eye toward future upgrades,” he said.
According to Jie Wei, director of FRIB’s Accelerator Systems Division and the facility’s lead collaborator on this research, the new magnet design, based on Nb3Sn technology, “delivers higher magnetic fields than current Nb-Ti sources and provides excellent performance.” More importantly, it enables new ECR source designs to operate at higher frequencies (up to 45 GHz) and increased plasma power. ”
He said the magnet, once completed, “will ensure that FRIB remains at the forefront of basic science research.”
Further information: Tengming Shen et al, Design and Development of a 28 GHz Nb3Sn ECR Ion Source Superconducting Magnet, IEEE Transactions on Applied Superconductivity (2024). DOI: 10.1109/TASC.2024.3358767
Provided by Lawrence Berkeley National Laboratory
Citation: Niobium-tin magnets could be the key to unlocking the potential of heavy-ion accelerators (October 4, 2024) https://phys.org/news/2024-10-niobium-tin-magnet-key – Retrievable on October 4, 2024 from.html
This document is subject to copyright. No part may be reproduced without written permission, except in fair dealing for personal study or research purposes. Content is provided for informational purposes only.