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17 May, 2019
In the LHC, 1232 superconducting dipole magnets and 392 quadrupole magnets guide and focus the beams around the accelerator’s 27-kilometre ring, which is divided into eight sectors. These magnets operate at very low temperatures – 1.9 K or −271.3 °C – where even a tiny amount of energy released inside a magnet can warm its windings to above the critical temperature, causing the loss of superconductivity: this is called a quench. When this happens, the energy stored in the affected magnet has to be safely extracted in a short time to avoid damage to the magnet coil.
To do so, two protection elements are activated: at the level of the quenching magnet, a diode diverts the current into a parallel by-pass circuit in less than a second; at the level of the circuit, 13 kA energy extraction systems absorb the energy of the whole magnet circuit in a few minutes. There are equivalent extraction systems installed for about 200 corrector circuits with currents up to 600 A.
Image above: The LS2 team from the NRC Kurchatov-IHEP Institute, Protvino, Russia, with a 13 kA energy extraction system (Image: NRC Kurchatov-IHEP Institute).
“In the framework of a long-lasting and fruitful collaboration between CERN and the Russian Federation, energy extraction systems for quench protection of the LHC superconducting magnets were designed in close partnership with two Russian institutes, the NRC Kurchatov-IHEP Institute in Protvino for the 13 kA systems and the Budker Institute in Novosibirsk for the 600 A systems. Russian industry was involved in the manufacturing of the parts of these systems,” explains Félix Rodríguez Mateos, leader of the Electrical Engineering (EE) section in the Machine Protection and Electrical Integrity (MPE) group of CERN’s Technology department.
With a wealth of expertise and know-how, the Russian teams have continuously provided invaluable support to the MPE group. “Our Russian colleagues come to CERN for every year-end technical stop (YETS) and long shutdown to help us perform preventive maintenance and upgrade activities on the energy extraction systems,” says Rodríguez Mateos.
During LS2, an extensive maintenance campaign is being performed on the 13 kA systems, which already count 10 years of successful operation in the LHC. “We are currently replacing an element, the arcing contact, in each one of the 256 electromechanical switches of the energy extraction systems to ensure their continuous reliable operation throughout the next runs,” adds Rodríguez Mateos. “In February, we fully replaced 32 switches at Point 8 of the accelerator in anticipation of consolidation for the future HL-LHC.”
During LS2, the Electrical Engineering section is involved in many other activities that will be the subject of future articles.
Note:
CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.
The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.
Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 23 Member States.
For more information about European Organization for Nuclear Research (CERN), Visit: https://home.cern/
Image (mentioned), Text, Credits: CERN/Anaïs Schaeffer.
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