CERN LHC Long Shutdown 2 (LS2)

Run 2 (2015-2018) of CERN LHC operations ended.  There will be no physics experiments for the next 2 years. CERN accelerator complex will be upgraded during the long shutdown between now and spring 2021.

During Run 2 each proton was accelerated to 6.5 Tev. The center-of-mass energy of a proton-proton collision was 13 Tev. The beam itself contained much more energy of course because each counter circulating beam contained more than 2.8 x 10^14 protons. This means that the total energy stored in the beam was high enough to melt 500 kg of copper. That’s why the LHC beams are dumped in a very controlled manner after data taking sessions.

Few parameters of the LHC during Run 2

  • Circumference = 26 659 meters
  • Dipole operating temperature = -271.3 degrees Celcius (colder than outer space)
  • Number of magnets = 9593
  • Number of main dipole magnets (bending the protons into orbit) = 1232
  • Number of main quadrupole magnets (focusing the proton beams) = 392
  • Number of RF cavities (ramping up and maintaining beam energy) = 8 per beam
  • Peak magnetic dipole field strength = 8.33 Tesla
  • Minimum distance between proton bunches = 7 meters (25 ns in units of time)
  • Number of bunches per proton beam = 2556
  • Number of protons per bunch (at start) = 1.1 x 10^11
  • Number of turns per second = 11 245
  • Number of proton-proton collisions per second at the crossing points = 600 million

You can also examine the integrated luminosity delivered during Run 2 (years 2015, 2016, 2017, 2018) from the links provided in my post titled “Updated links: LHC (Large Hadron Collider) Operation“.

Latest CERN press release about the long shutdown:

“Several components of the accelerator chain (injectors) that feed the LHC with protons will be renewed to produce more intense beams. The first link in this chain, the linear accelerator Linac2, will leave the floor to Linac4. The new linear accelerator will accelerate H- ions, which are later stripped to protons, allowing the preparation of brighter beams. The second accelerator in the chain, the Proton Synchrotron Booster, will be equipped with completely new injection and acceleration systems. The Super Proton Synchrotron (SPS), the last injector before the LHC, will have new radio frequency power to accelerate higher beam intensities, and will be connected to upgraded transfer lines.”

“Some improvements of the LHC are also planned during LS2. The bypass diodes – the electrical components that protect the magnets in case of quench – will be shielded, as prerequisite for extending the LHC beam energy to 7 TeV after the LS2, and more than 20 main superconducting magnets will be replaced. Moreover, civil engineering works for the HL-LHC that started in June 2018 will continue, new galleries will be connected to the LHC tunnel, and new powerful magnet and superconducting technologies will be tested for the first time.”

“All the LHC experiments will upgrade important parts of their detectors in the next two years. Almost the entire LHCb experiment will be replaced with faster detector components that will enable the collaboration to record events at full proton-proton rate. Similarly, ALICE will upgrade the technology of its tracking detectors. ATLAS and CMS will undergo improvements and start to prepare for the big experiments’ upgrade for HL-LHC. “

More details of LS2 can be found in this document as well as this one.

About Suresh Emre

I have worked as a physicist at the Fermi National Accelerator Laboratory and the Superconducting Super Collider Laboratory. I am a volunteer for the Renaissance Universal movement. My main goal is to inspire the reader to engage in Self-discovery and expansion of consciousness.
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