Numerical analysis of cooldown and warmup for the Large Hadron Collider

As the basis of studies, the paper presents the inventory of components and materials for LHC magnets, especially for main dipoles and quadrupoles firstly. Then a mathematical model and analytical method for LHC transient modes, such as cooldown and warmup of a magnet, a standard cell and the eight LHC sectors, has been developed on the basis of the up-to-date layout of the LHC machine, and validated by experimental data. The model and method do not only consider the momentum and continuity equations as well as the energy equations for helium and materials, but also take into account the pressure evolution in the different headers of the cryogenic distribution line and the effect of the pressure drop across the cryogenic valves. Based on the simulation results, the heat transfer in the magnets has been studied and the transient modes optimized.