Twice as cold in the magnet testing hall
A new cold box has just been installed in the SM18 superconducting magnet test hall, but it’s not just a simple box as its name might suggest. CERN’s cold boxes are enormous machines, a bit like giant refrigerators.
This particular cold box is an essential component of the improvements being made to the infrastructure used to test the superconducting magnets and superconducting radiofrequency cavities. In preparation for the High-Luminosity LHC (HL-LHC) project, a major renovation and upgrade campaign has been under way for two years right across the SM18 area.
The High-Luminosity LHC will use new superconducting magnets and crab cavities. The development of these new components requires many tests to be carried out in parallel. “This renovation work will significantly improve our testing capacity,” explains Antonio Perin, who is in charge of the cryogenics upgrade project at SM18.
The main upgrade consists of the installation of a new helium liquefier made up of two components: a two-storey compressor weighing almost 40 tonnes and a cold box weighing almost 30 tonnes. This new assembly will considerably increase the helium production capacity in the hall. “These machines will allow us to more than double the production of liquid helium. The liquefaction capacity will increase from 25 to 60 grams of liquid helium per second,” says Antonio Perin.
The cooling of the helium and its transformation into a liquid take place in two stages. First, the gaseous helium is compressed. The heat produced by the compression is evacuated via water circuits to cooling towers, which have themselves undergone major renovation. The compressed helium is then directed to a cold box. This system consists of turbines and heat exchangers that, after expansion of the helium, deliver it at 1.6 bar and 4.5 kelvins (-268°C).
The new cold box will be able to produce 35 grams of liquid helium per second, which equates to 1100 litres per hour! To generate this torrent of liquid helium, almost 350 g of gaseous helium must be compressed to 18 bar every second, which requires around 1.5 MW of power.
Over the summer, the team and the supplier of the system will connect up multiple pipes and install all the electrical cables. The initial commissioning of the system is scheduled for September, allowing performance tests to take place during the autumn. The system will be connected to the infrastructure of SM18 and brought into service at the end of 2019 or early 2020.
“This new cryogenic installation will allow us to take the performance of our facility to the next level. SM18 houses remarkable and unique infrastructure, which is what makes the test programme for the High-Luminosity LHC possible,” concludes Antonio Perin.