Refined Studies of Cooldown and Warmup for the Large Hadron Collider

Compared with the previous study [1], this paper presents and improved mathematical model which takes into account the pressure evolution in the different headers of the cryogenic distribution line and the effect of the pressure drop across the valves during cooldown and warmup modes. The application of the improved model to the LHC sectors shows that the present processes of cooldown and warmup may take a longer time by about 5% than that predicted by using the previous model. Some issues found by using the latest model have also been presented and discussed.