The operating principles of these facilities are very similar. Electrons are first accelerated to high energies and then made to generate high-intensity X-ray laser light using undulators. However, the other facilities rely on conventional accelerator technologies, while the European XFEL operates at -271°C using superconducting accelerator technology. The X-ray FEL in the USA, the LCLS, is undergoing an upgrade called LCLS-II that will also make a portion of its accelerator superconducting within the next few years.
Superconductivity allows the creation of an electron beam of especially high quality composed of many electron bunches aligned one behind the other. This enables the European XFEL to generate many more light flashes per second than the other two facilities. The number of usable light flashes is increased as well. Certain experiments are thus only be possible at the European XFEL, while others can be carried out much faster. The higher number of electron bunches also allows more experiment stations to be operated simultaneously.