A High-Luminosity LHC coil similar to those incorporated into the successful magnet prototype shows the collaboration between CERN and the LHC Accelerator Research Program, LARP. Credit: Reidar Hahn, Fermilab
Engineers will incorporate more than 20 magnets similar to this model into the next iteration of the LHC, which will take the stage in 2026 and increase LHC’s luminosity by a factor of ten. That translates into a 10X increase in the data rate. “Building this magnet prototype was truly an international effort,” says Lucio Rossi, the head of the High-Luminosity (HighLumi) LHC project at CERN. “Half the magnetic coils inside the prototype were produced at CERN, and half at laboratories in the United States.”
During the original construction of the Large Hadron Collider, US Department of Energy national laboratories foresaw the future need for stronger LHC magnets and created the LHC Accelerator Research Program (LARP): an R&D program committed to developing new accelerator technology for future LHC upgrades.
This 1.5-m-long model, which is a fully functioning accelerator magnet, was developed by scientists and engineers at Fermilab, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, and CERN. The magnet recently underwent an intense testing program at Fermilab, which it passed in March with flying colors. It will now undergo a rigorous series of endurance and stress tests to simulate the arduous conditions inside a particle accelerator.
This new type of magnet will replace about 5% of the LHC’s focusing and steering magnets when the accelerator is converted into the High-Luminosity LHC, a planned upgrade which will increase the number and density of protons packed inside the accelerator. The HL-LHC upgrade will enable scientists to collect data at a much faster rate.
The LHC’s magnets are made by repeatedly winding a superconducting cable into long coils. These coils are then installed on all sides of the beam pipe and encased inside a superfluid helium cryogenic system. When cooled to 1.9 Kelvin, the coils can carry a huge amount of electrical current with zero electrical resistance. By modulating the amount of current running through the coils, engineers can manipulate the strength and quality of the resulting magnetic field and control the particles inside the accelerator.
The magnets currently inside the LHC are made from niobium titanium, a superconductor that can operate inside a magnetic field of up to 10 teslas before losing its superconducting properties. This new magnet is made from niobium-three tin (Nb3Sn), a superconductor capable of carrying current through a magnetic field of up to 20 teslas.
This technology is powerful and versatile – like upgrading from a moped to a motorcycle. But this new super material doesn’t come without its drawbacks. “Niobium-three tin is much more complicated to work with than niobium titanium,” says Peter Wanderer, head of the Superconducting Magnet Division at Brookhaven National Lab. “It doesn’t become a superconductor until it is baked at 650 degrees Celsius. This heat-treatment changes the material’s atomic structure and it becomes almost as brittle as ceramic.” Building a moose-sized magnet from a material more fragile than a teacup is not an easy endeavor. Scientists and engineers at the US national labs spent 10 years designing and perfecting a new and internationally reproducible process to wind, form, bake and stabilize the coils.
http://www.symmetrymagazine.org/article/physicists-build-ultra-powerful-accelerator-magnet
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