LHC and ATLAS approaching 2025 take-off

LHC and ATLAS are about to resume the third long measurement campaign with proton-proton collisions. Beams are already circulating in LHC. And first collisions are observed. The LHC crew is steadily rising the number of proton bunches in the accelerator from 75 over 800 to more than 2800 to increase the beam's intensity and thus the luminosity for collisions. In every proton bunch about 100 billion protons are squeezed together into a beam of about 0.7 mm diameter by the alternating gradient magnet beam optics in LHC. Protons are filled into LHC at 450 GeV and once all bunches are filled the beam energy is risen by high frequency resonators (cavities) within 20 minutes to the target beam energy of 6800 GeV. Before the collision the bunches are further squeezed by final focus magnets to about 16 μm diameter so that a collision of a proton of one circulating bunch with a proton of one counter-circulating bunch will be certain. In fact the beam intensity and the tiny focal point will lead to more than 60 collisions between protons in the single crossing of bunches. These bunch crossings happen 40 million times per second when LHC is running at full intensity. The ATLAS detector is able to separate between these many collisions due to the fine granularity and the high spatial resolution of the detecting systems. A very sensitive trigger system will decide in time with the bunch crossings if any of the 60 collisions of the current bunch crossing is due to some a selected physics process, e.g. a weak interaction involving a Z boson. Only for these selected bunch crossings the measured data of the ATLAS detector is recorded for later analysis. On average the trigger will select 1000 collision events per second to be recorded to disk where each collision provides up to gigabytes of data which will be investigated in detail to search for signatures of new particles and to precisely study the properties of particles like the Higgs boson.

But before getting to the results, board now, fasten seat belts, take-off, and enjoy a flight through the LHC tunnel featured by the CERN LHC team.