The new cold box transported to the underground tunnel of the HiLumi LHC, near the ATLAS experiment. (Image: CERN)
The vertiginous descent of equipment into the depths of the accelerator tunnels is always a captivating event. The stars of the show over the last few weeks have been the two gleaming cold boxes that have arrived in the new service tunnels of the High-Luminosity LHC (HiLumi LHC), close to the ATLAS and CMS experiments. These two enormous pieces of equipment, manufactured in Germany by the company Linde, are a key component of the future accelerator's two new refrigerators.
The two refrigerators, which will cool the new magnet systems installed on either side of the ATLAS and CMS experiments to -271.3 °C (1.9 kelvins), are complex systems made up of a number of impressive pieces of equipment. The compressors and cold boxes, which were installed on the surface last December, will pre-cool the helium to -268.6 °C (4.5 kelvins). The last few degrees needed to reach -271.3 °C, less than 2 degrees above absolute zero, will be gained by lowering the pressure of the helium circulating in the magnet cryostats and using four cold compressors connected in series and integrated into one of the cold boxes that have just been delivered.
In parallel, the cryogenic lines that will transport the helium are being installed underground. The teams have already completed the first phase of the installation work.
