Numerical Simulations for the Cool-Down of the XFEL and TTF Superconducting Linear Accelerators

The alignment of the superconducting RF-cavities and the magnet packages of the cryomodules of the future XFEL linear accelerator and the existing TTF linear accelerator at DESY can be affected by the mechanical stress caused by thermal gradients during the cool-down and warm-up. Also the design of the XFEL cryogenic system has to include the cool-down and warm-up procedures. An object-oriented software concept is applied to analyze the cool-down procedures for the TTF and the XFEL linear accelerators by numerical simulations. The numerical results are compared to measurements taken during the first cool-down of the TTF linear accelerator. Some results for the XFEL cryogenic system are presented