InternalThe site DESY-Bahrenfeld marks the beginning of the European XFEL. The main tunnel, which will house the electron accelerator, begins here in a depth of around 38 m underground.
Three new buildings will be constructed on the site DESY-Bahrenfeld: the large injector complex in which the electrons will be provided, the modulator hall for the power supply and the entrance building with an access shaft to the tunnel (area: 46 metres times 41 metres). A nearby cryogenics hall that has been used at DESY for several years will be included in the new building complex (area: 72 metres times 32 metres, height: 14 metres).
The site will cover an area of about 2 hectares. About half of it lies in the neighbouring Lise Meitner park, which loses about one fifth of its total area.
The buildings
Before the electron bunches for the European XFEL can be transferred into the main accelerator, they first have to be created and pre-accelerated. This is the task of the injector – a small particle accelerator located seven storeys deep beneath the surface in an approximately 100-metre-long underground building. As the injector technology is to be developed even further during operation of the European XFEL and as potential disruptions in the injector area could disturb the operation of the whole facility, plans call for two independent injectors that could be installed in two tunnel segments lying one on top of the other.
Apart from the entrance halls to the injector complex and the main accelerator, the site will also accommodate the so-called modulator hall in which the radio frequency needed for the acceleration will be generated, and the cryogenics hall in which the liquid helium for the cooling of the superconducting accelerator elements will be produced. Further infrastructure installations on the sites include heat exchangers, buildings for pumps and transformers, and storage tanks for liquid helium.
Operation
During normal operation, the cryogenics facility of the European XFEL will run fully automatically without interruption 24 hours a day. It will be operated by remote control using computerized control systems. There will thus be no permanent workplaces in the cryogenics hall. Only a few people will stay in the hall during normal working hours for controls, servicing and repairs. During the routine maintenance periods of the accelerator (approximately 8 to 12 weeks every two years), maintenance work and necessary repairs will be carried out in the cryogenics hall on the various parts of the facility.
The installations in the modulator hall will also be operated fully automatically and under remote control. There will thus be no permanent crew in this hall either. However, the modulators need to be regularly checked and necessary maintenance work and repairs have to be carried out.
During normal operation, the injector needs to be accessed on a regular basis for adjustment and checks as well as for the transport of smaller components needed for maintenance and repairs. During routine accelerator maintenance periods, bigger remodelling work resulting from further technological developments, e.g. of the electron source, could be carried out.
