A New Type of Waveguide Distribution for the Accelerator Module Test Facility of the European XFEL

Abstract

Abstract:The European XFEL, which has been constructed at DESY in Hamburg, Germany, is an X-ray-Free Electron Laser, which provides X-ray light of unprecedented properties for different experiments in physics, chemistry, biology and technology [1]. The XFEL is based on superconducting cavity technology, which is required to accelerate an electron beam up to 17.5 GeV. The facility is installed about 20 m underground in a 3.4 km long tunnel of 5.2 m diameter. High power RF systems are required to accelerate the beam to the required energy. Each RF station provides RF power to 4 accelerator modules with 8 superconducting cavities by a waveguide RF distribution system [2,3]. Besides electrical and RF properties, mechanical properties are of high importance, since the waveguide distribution system and its components have to be manufactured, assembled and aligned with high precision. In order to test 100 superconducting accelerator modules within two years three test benches have been created in the AMTF (accelerator module test facility) to achieve the rate of one superconducting module per week. Each RF station of the test facility consists of a 5 MW RF station at 1.3 GHz, 1.37 ms pulse width and 10 Hz repetition rate, with a waveguide distribution system. Each waveguide distribution supplies RF power to eight cavities, four times a pair of cavities. The distribution allows for a maximum power of 1 MW per cavity when the distribution is switched to a mode supplying power to only four cavities. A new type of 1 MW isolator and a new compact 5 MW power divider have been developed to achieve that goal. We present the waveguide distribution for this test stand and describe the performance of the different elements.Key words: High power RF, superconducting RF, particle accelerator, kinematic design, precision mechanic adjustment, exact constraint design. Requirements for the AMTF Waveguide Distribution The AMTF (accelerator module test facility) waveguide distribution should meet several specifics sometimes conflicting requirements. On one side the distribution should have a compact size since there is only limited space in the AMTF shielding tunnel. On the other side it should supply high pulse RF power to the individual cryomodule cavities with high flexibility by only one power klystron. In addition the waveguide distribution has to protect the klystron against reflected power from superconducting cavities.The three basic requirements are:Corresponding author: Dr. V. Katalev, senior scientist, research fields: High Power RF,RF distribution, particle accelerators. Power per cavity: 1 MW max pulse power 2.2 kW max average power  One 5 MW klystron as RF power source  The waveguide distribution layout must allow for a free access to the cavity couplers for local clean room installation.In order to satisfy these conditions specific waveguide components, such as a 1 MW isolator and a 5 MW power divider have been developed and integrated in the waveguide distribution. A 3D-view of the AMTF waveguide distribution is shown ...