Abstract. The European X-Ray Free Electron Laser (EuXFEL) at DESY is in operation sincethe beginning of 2017. The free electron laser is based on a superconducting linear acceleratorthat delivers electrons to the undulator section with beam energy up to 17.5 GeV. The linearaccelerator consists of 96 cryomodules; each 12 m long module is an assembly of8 superconducting cavities and one superconducting magnet. This paper focusses on themeasurement of the static and dynamic heat loads of the

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... dules assembled in the linac.Heat loads are an important parameter to evaluate the efficiency of the refrigerator system, thequality of the cryomodule assembly and installation and the accelerating cavity performances,being the dynamic heat loads proportional to the cavity quality factor (Q0, the ratio of the storedenergy to the dissipated energy). The paper describes at first the procedure to measure the staticheat load without beam energy and the dynamic heat loads at different beam energy levels. Themeasurement results are then summarized and compared with the XFEL design values.