Ready for a new season of particle-smashing action? For fans of physics, there is a good reason to get pumped up this month: the LHC (Large Hadron Collider) is back in business after a longer-than-usual winter hiatus.
The LHC's 27-km ring tunnel. Credit: CERN/LHC
The LHC is a colossal piece of machinery that exemplifies the apex of scientific advances. Just like the family wagon parked in your garage (but thousands of times bigger and more complex), the LHC requires intense maintenance on a regular basis. Every winter at the European Organization for Nuclear Research or CERN, technicians and engineers perform numerous repairs and upgrades. The maintenance break this year lasted longer than usual to allow for extensive work, including the replacement of a superconducting magnet. To keep beam particles in a constant orbit inside its 27-km long ring, the LHC demands a massive magnetic field, which only dipole magnets powered by superconducting coils can deliver. As the beam energy gets higher, the magnetic field needs to be stronger.
Many of the upgrades are intended to support CERN’s initiative to crank up the performance of the LHC, known as the High-Luminosity Large Hadron Collider (HL-LHC) project. Luminosity is an important index for particle accelerators. The higher the luminosity, the more data each experiment generates, which can lead to the observation of rare physical phenomena that have not yet been achieved at the current sensitivity level. Last year, the LHC witnessed 6.5 million billion collisions, if not more, due to an integrated luminosity of 40 inverse femtobarns (fb-1). According to Rende Steerenberg, the leader of Operation group at CERN, this record will likely be broken soon: "Our aim for 2017 is to reach an integrated luminosity of 45 fb-1 and preferably go beyond. The big challenge is that, while you can increase luminosity in different ways – you can put more bunches in the machine, you can increase the intensity per bunch and you can also increase the density of the beam – the main factor is actually the amount of time you stay in stable beams."
A proton-proton collision seen in tests by ALICE. Credit: CERN/ALICE
Even after the extensive maintenance, the LHC was still not ready for action – not until a series of tests and adjustments were completed. Like an automobile, while the engine, transmission, and brakes may be functional individually, they must also work in harmony so that the car can be drivable. Far more sophisticated as a machine, the LHC has thousands of subsystems. It requires effort and time (in weeks if not months) for tests and adjustment, so that all subsystems can work in sync. April 29 saw the particles circulating in the LHC for the first time after winter. In early May, the first test collisions were conducted. After two more weeks of equipment adjustment and alignment, during which the operators were working around the clock 24/7, the LHC was finally brought online with the first collision data collected on May 23.
A proton-proton collision captured by LHCb detector. Credit: CERN/LHCb
ATLAS, CMS, LHCb and ALICE are among the experiments scheduled for 2017. Besides seeking out new particles, ATLAS and CMS will continue their investigation of Higgs boson, the so-called God particle discovered in 2012. Measurements of this peculiar particle could lead to discoveries beyond the Standard Model of physics. LHCb will be looking into the imbalance between matter and antimatter through tracking the phenomenon known as “charge-parity violation”. Proton-proton collisions will remain the focus of ALICE. Analyses of the data from 2016 made the ALICE team believe they had observed quark-gluon plasma, a state of matter that can be traced all the way back to the moment of the Big Bang.
Related reading: LHC experiments
With everything prepared and tested, the LHC is ready to spring into action again.
Source information: https://home.cern/about/updates