Pioneering work by M+W for pioneers of the European XFEL

Unter dem Betriebsgelände Osdorfer Born, im Hamburger Westen, in 20 Metern Tiefe, beginnt die fächerartige Verzweigung des Tunnels. Unter der Verzweigungshalle werden die beschleunigten Elektronen zum ersten Mal auf zwei Tunnel verteilt. Hier werden zudem alle Elektronen gestoppt, für die es keine weitere Verwendung gibt. | © m+w Group

The fan-shaped branch of the tunnel begins under the Osdorfer Born site in western Hamburg at a depth of 20 meters. For the first time, the accelerated electrons are distributed to two tunnels under the switchyard hall. This is also where all redundant electrons are stopped.

The facility is operated by the European company XFEL GmbH, with Hamburg, Schleswig-Holstein, the Federal Government and eleven other states as shareholders together with the internationally leading accelerator center DESY. The investment volume for construction and commissioning amounts to 1.22 billion euros. The objective is to open up valuable new opportunities for research in natural sciences, medicine and industrial production. For example, the atomic structure of biomolecules or materials can be made visible, ultrafast processes such as the formation of molecules can be filmed or forms of matter can be analyzed.

Fascinating research opportunities

The new linear particle accelerator generates ultra-short laser flashes in the X-ray range, 27,000 times per second and with light intensity a billion times higher than the best X-ray radiation sources known to date, whereby the electrons go through a kind of slalom course through a special magnet arrangement, the so-called undulators. For reliable results, they require a stable temperature of 21° C with a maximum deviation of 0.1K to precisely control the strength of the magnetic field.

High-Tech made by M+W

The development of an innovative solution was something only we could realize. However, the greatest challenge was the conflicting requirements in the operation: during the first two to three years, the ground temperature, which is initially too low, must be heated from approx. 17° C to 21° C. From approximately 2022, the task is reversed: the high waste heat from the undulators increases the temperature. Simulations show final values of up to 24° C. The air conditioners must then cool to maintain the required 21° C. We master this balancing act through an automatic control loop. Although this is controlled remotely, we can intervene at any time if necessary.

Sealing the hatches

The internal diameter of the tunnel tube is up to 5.3 m. However, the undulator segments, which require highly accurate conditioning, occupy only about 2/5 of the tunnel cross-section. Climate barriers were therefore installed to seal the precision air conditioning area of the maintenance corridor, in which normal air conditioning is sufficient. An efficient solution which saves power and costs.

Workplace with an “underground” feeling

The underground working conditions are also challenging. Work is performed in tunnels instead of in high factory buildings. A fire alarm with evacuation provided a flash of adrenaline. There are of course extensive fire protection measures in place. Anyone in the tunnel will also carry an oxygen device for self-rescue purposes, for example. Nevertheless, everyone was happy that the whole thing turned out to be a false alarm.