The incident with the controller of the water cooling system of the cryogenic equipment of the accelerator sections of the LHC interrupted the operation of the Large Hadron Collider for a month. The problem has now been solved and in the next few days the proton beams in the main ring of the LHC will start circulating again.
In 2022, a new multi-year operation session of the Large Hadron Collider LHC Run 3 began. Proton collisions with a record energy of 13.6 TeV began on July 5, and within a month, experts brought the collider to almost maximum luminosity. to the expected value. However, on August 23, the explosive pace of data collection was interrupted by a failure in the cooling system of the accelerator sections of the collider. A message on the collider’s online monitor said that the accelerator sections needed to be warmed to room temperature, the malfunction corrected, and cooled again. No additional details were released at the time.
A brief technical report on the current state of the collider was presented at the recent 151st meeting of the LHC Experiments Committee, in which some details were finally given.
The first half of the report briefly listed the main stages of the collider’s launch this year, and also reported on the successful fight against the known problems of previous years (in particular, with the “electron clouds” that prevent the beam from increasing in intensity, and with the so-called UFOs, unidentified incident objects inside the vacuum tube). The main factor limiting the further increase in intensity is now considered to be the release of heat in sector 78, but it is not a significant problem for the operation of the collider.
Towards the end of the report, tell what exactly happened on August 23. The event began with the fact that at about 18.00 hours the programmable controller of the water cooling system of the equipment that served the accelerator sections of the collider failed. As a result, the cryocompressor stopped, cooling these sections to the temperature of liquid helium (4.5 K). The system automatically went into safe mode and began to release evaporating helium in a controlled manner. At 22.00, the problem with the cooling system was solved and the cryogenics returned to normal.
However, during helium bleeding, the protective discs of the valves that regulate the helium pressure managed to break. Apparently, the escaping helium cooled the disks too much, making them more brittle; no such cooling was observed during the development of this safety system. The disks were also replaced quite quickly, overnight. However, due to a malfunction, gas entered the cryomodule and it was impossible to solve this problem even at cryogenic temperatures. The acceleration sections had to be warmed up to room temperature and only then could they return to working conditions.
At present, the accelerator sections have already been safely cooled to the required temperature. According to the online monitor, the proton beams should return to the LHC’s main ring on Tuesday, September 20. Matchups should resume soon, but due to the lost month, this year’s stat collection plan will not be finished. Meanwhile, technicians are already working on improving the entire cooling system of the accelerator sections so that similar incidents do not happen again in the future.