Numerical Analysis of the Final Cooldown of a 3.3 km Sector of the Large Hadron Collider

The final cool-down of a 107-m standard cell of LHC, which consists of the helium filling operation at 4.5 K and the further cool-down from 4.5 K to 1.9 K, has been previously simulated and analyzed numerically. To model and analyze the final cool-down process of a whole 3.3-km sector of the LHC, additional boundary conditions must be introduced. In this paper, the slope of the sector, the efficiency of the sub-cooling heat exchanger, the pressure drops and heat loads in different headers of the cryogenic distribution line as well as the fact that both the filling flow of the cold mass and the vaporized flow in the 1.8 K heat exchanger are concurrently supplied have been taken into account. The simulation results, such as the temperature evolution in the LHC magnet cold mass and the pressure profiles in cryogenic line headers during the filling and cool-down from 4.5 K to 1.9 K of a LHC sector are presented. Taking into account the required distribution of the total flow to each cell, all the cells can be filled up to 67% of the volume and further cooled down to 1.9 K simultaneously in 15 to 20 hours.