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April 3, 2018
Image above: View of the LHC in 2018, before the restart of the accelerato. (Image: Maximilien Brice, Julien Ordan/CERN).
The Large Hadron Collider is back in business! On Friday 30 March, at 12:17 pm, protons circulated in the 27-km ring for the first time in 2018. The world’s most powerful particle accelerator thus entered its seventh year of data taking and its fourth year at 13 TeV collision energy.
Restarting an accelerator involves much more than just flicking a switch, especially as the LHC is the final link in an accelerator chain comprising five separate machines. Following the winter break, which enabled teams to carry out a whole host of maintenance operations, the machine operators gradually have brought the infrastructures and accelerators back on line. At the beginning of March, the first protons were extracted from their hydrogen bottle and injected into the Linac2, and then into the PS Booster. On 8 March, it was the turn of the Proton Synchrotron (PS) to receive beams, and then, a week later, the Super Proton Synchrotron (SPS).
Image above: Applause in the CERN Control Centre after the beam makes a first turn of the LHC loop. Sitting, the operators in charge of restarting the accelerator. Standing behind them, from left to right, Rende Steerenberg, Head of Operation, Frédérick Bordry, Director for Accelerators and Technology, Fabiola Gianotti, CERN Director-General, Rossano Giachino, from the LHC operation team, and Jörg Wenninger, in charge of the LHC operation team. (Image: CERN).
In parallel, the teams have been checking all the LHC hardware, such as the cryogenic cooling systems, the radiofrequency cavities (which accelerate the particles), the power supplies, the magnets, the vacuum system and the safety installations. For example, no fewer than 1 560 electrical circuits had to be powered and about 10 000 tests performed. Only once all these tests had been completed could particles be injected into the LHC.
Even so, commissioning is far from over. The first beams circulating only have one bunch of particles, which contains 20 times fewer protons than in normal operation. And their energy is limited to the injection energy of 450 GeV. Further adjustments and tests will be needed over the coming days before the energy and the number of bunches in each beam can be increased and the bunches squeezed to produce first collisions. Physics operation should start in May.
The operation objective for 2018 is to accumulate more data than in 2017: the target is 60 inverse femtobarns (fb-1) of integrated luminosity (against 50 fb-1 in 2017). Luminosity is a measurement of the number of potential collisions per surface unit in a given period of time.
Image above: "LHC page 1" shows the status of the LHC on 30 March. The blue line on the right of the screen indicates the first beam circulating in the LHC in 2018. (Image: CERN).
While we await collisions in the LHC, data taking is already starting elsewhere. CERN’s accelerators provide particles for a diverse array of experiments. The PS has already started supplying beams to the nuclear physics facility n_TOF and to the experiments in the East Hall. The nuclear physics programme at ISOLDE should start up on 9 April, while the Antiproton decelerator should start again in the second half of April.
2018 is an important year for the collaborations using CERN’s accelerators, as it will be the last year of Run 2. In December, the accelerator complex will be shut down for two years of upgrade work aimed at improving performance further still and preparing for the High-Luminosity LHC.
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 22 Member States.
Read also the story about the restart on Symmetry website: https://www.symmetrymagazine.org/article/the-room-where-it-happens
Related links:
Large Hadron Collider (LHC): https://home.cern/topics/large-hadron-collider
ISOLDE: https://home.cern/about/updates/2017/10/meet-isolde-targeting-new-discoveries
Antiproton decelerator: https://home.cern/about/accelerators/antiproton-decelerator
High-Luminosity LHC: https://home.cern/topics/high-luminosity-lhc
For more information about European Organization for Nuclear Research (CERN), Visit: https://home.cern/
Images (mentioned), Text, Credits: CERN/Corinne Pralavorio.
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