More than one year has passed since the accident which required an extremely careful repair job and new evaluation of possible risks associated with running at high energy. The machine experts completed their activity and now particles are back in the LHC. Thousands of people belonging to the four LHC experiments (ALICE, ATLAS, CMS, LHCb) keep clicking on the LHC web page to follow the news, meet and discuss at the CERN cafeteria and around the world. Indeed, the machine is following its schedule. All tests carried out so far were successful making collisions possible by the end of year. Here is a bullet summary of what happened in the past months,
- ** The sectors were cooled down during the firs half of October; they reaches the cryogenic temperature of 1.9 K. It marked an important step towards the final commissioning of the machine. At the same time, experts started powering the magnets, so the machine should be fully powered soon after the cool-down is completed.
- ** On Friday 23 October, a first beam of lead ions entered the clockwise beam pipe of the LHC. The beam entered at point 2 where the ALICE detector is sitting and was dumped before point 3. One more step proved to be successful
- ** The following day, the equivalent test was carried out on the anticlockwise beam pipe of the LHC. The first proton beam was injected close to the LHCb experiment and dumped before point 7.
- ** Operators are also progressively increasing the sector current up to 2 *1000 Ampere. This current allows the steering of beams at about 1.2 TeV (this is called “phase 2 of the LHC”)
- ** Bird or Raccoon ? Nature decided to interfere with operations. On Tuesday 3 November, a bird carrying a baguette bread caused a short circuit in an electrical installation supporting two sectors causing an interruption to the cryogenics system. The community is not new to to these “interventions”. Here is an old report from the Tevatron collider (2006/06/19) “Operations reported a raccoon attack in the Linac gallery. It seemed to be a coordinated effort. Fortunately, by 1:53 AM, a joint force of operators and Pbar experts managed to drive the raccoons out of their hastily made fortifications.”
- ** Finally, particles travelled half of the LHC ring. On Saturday evening, November 7th , after passing through the LHCb detector, protons almost reached the CMS experiment. Even if they were dumped in a collimator just upstream CMS, splashes illuminated the detector. Champagne bottles popped in the CMS control room!
The short period of collisions at the injection energy of 450 GeV per beam will occur soon, the four detectors will tune their tools for the new exciting era ahead of us.
