Manufacturing Bits: April 6

Powerful electromagnets; big superconducting magnets.


Powerful electromagnets
The National High Magnetic Field Laboratory (MagLab) has tested a new and powerful superconducting solenoid or electromagnet that operates at high currents.

MagLab develops several different types of large and powerful magnets, which are used as scientific instruments. MagLab’s solenoid or electromagnet could one day be used to drive particle accelerators and compact fusion machines.

A solenoid is one type of electromagnet. A solenoid is a cylindrical coil of wire, which acts like a magnet as it carries current. Solenoids are used to power a switch. A starter in a car is one example.

MagLab has devised a multi-tesla superconducting insert solenoid. Tesla, or T, is the measurement of magnetic field strength. A refrigerator magnet has a field of 0.01 T. An MRI scanner has a 1.5 tesla magnet.

MagLab’s solenoid is actually a magnet coil. The coil is wound from a cable using a superconductor material called rare earth barium copper oxide (REBCO). The coil is based on a “Conductor on Round Core (CORC)” cable technology using 28 REBCO tapes arranged in 14 layers.

To test the coil, MagLab put the unit inside a large and conventional 14-tesla superconducting magnet. Superconductors are devices that have zero electrical resistance, making them attractive for a range of applications.

Inside the main magnet, the coil was tested at currents exceeding 4 kA. This was done “while operating in a background magnetic field of a low-temperature superconducting outsert magnet,” according to MagLab in IOPscience. “The CORC cable insert solenoid was successfully tested in liquid helium in background magnetic fields of up to 14 T, resulting in a combined central magnetic field of 15.86 T and a peak magnetic field on the conductor of 16.77 T at a critical current of 4,404 A, a winding current density of 169 A/mm2, an engineering current density of 282 A/mm2, and a JBr source stress of 275 MPa.”

Big superconducting magnets
The Department of Energy’s Fermi National Accelerator Laboratory (Fermilab), Brookhaven National Laboratory and Lawrence Berkeley National Laboratory have built an enormous superconducting magnet that will be used in a major particle accelerator project.

Photo: Dan Cheng, Lawrence Berkeley National Laboratory


Weighing eight tons, the superconducting magnet is the size of a semi-truck trailer. The unit is one of 16 magnets they will provide for the High-Luminosity Large Hadron Collider (HL-LHC) particle accelerator project at CERN in Europe.

CERN, the European Organization for Nuclear Research, recently started work on a new and upgraded version of the Large Hadron Collider (LHC). The upgraded version is called the HL-LHC), which will increase the capabilities of the sub-atomic particle collider.

CERN operates a particle physics laboratory that is situated at the Franco-Swiss border near Geneva. The lab consists of the LHC, a giant, 27-kilometer particle accelerator. In 2012, researchers from CERN observed the Higgs boson, an elementary sub-atomic particle.

The HL-LHC project aims to increase the luminosity or brightness in the current LHC by a factor of 10. The HL-LHC, to be operational by 2027, will allow researchers to study sub-atomic particles and other technologies.

Meanwhile, the 16 magnets from U.S.-based labs, along with another eight produced by CERN, will serve as the optics for charged particles in the HL-LHC system.

The magnets are based on a superconducting material called niobium-tin. These will be the first niobium-tin quadrupole magnets ever used in a particle accelerator.

The focusing magnets in the current LHC are based on niobium-titanium. The performance of those magnets reach 8 to 9 T, according to the U.S. Department of Energy (DOE). But the HL-LHC requires 12 T magnets. That equates to 250,000 times stronger than the Earth’s magnetic field at its surface.

In January, the first focusing magnet from U.S. labs achieved an 11.5 T magnetic field. It ran continuously for five straight hours.

“We’ve demonstrated that this first quadrupole magnet behaves successfully and according to design, based on the multi-year development effort made possible by DOE investments in this new technology,” said Fermilab scientist Giorgio Apollinari, head of the U.S. Accelerator Upgrade Project.

“This accomplishment is a major milestone for the High-Luminosity LHC project, which relies heavily on the success of the niobium-tin superconducting magnet technology,” said Lucio Rossi, project leader of the High-Luminosity LHC project.

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