European XFEL

The European X-Ray Free-Electron Laser Facility (European XFEL) is an X-ray research laser facility commissioned during 2017. The first laser pulses were produced in May 2017[2][3] and the facility started user operation in September 2017.[4] The international project with twelve participating countries; nine shareholders at the time of commissioning (Denmark, France, Germany, Hungary, Poland, Russia, Slovakia, Sweden and Switzerland), later joined by three other partners (Italy, Spain and the United Kingdom),[5][6] is located in the German federal states of Hamburg and Schleswig-Holstein.[7] A free-electron laser generates high-intensity electromagnetic radiation by accelerating electrons to relativistic speeds and directing them through special magnetic structures. The European XFEL is constructed such that the electrons produce X-ray light in synchronisation, resulting in high-intensity X-ray pulses with the properties of laser light and at intensities much brighter than those produced by conventional synchrotron light sources.

European X-Ray Free-Electron Laser Facility GmbH
TypeFundamental research
Founded23 September 2009 (2009-09-23)[1]
HeadquartersSchenefeld, Germany
Websitewww.xfel.eu
All member nations of the European XFEL project are highlighted in dark purple.

Location

The 3.4-kilometre (2.1 mi) long tunnel for the European XFEL housing the superconducting linear accelerator and photon beamlines runs 6 to 38 m (20 to 125 ft) underground from the site of the DESY research center in Hamburg to the town of Schenefeld in Schleswig-Holstein, where the experimental stations, laboratories and administrative buildings are located.[8]

Accelerator

Electrons are accelerated to an energy of up to 17.5 GeV by a 2.1 km (1.3 mi) long linear accelerator with superconducting RF-cavities.[8] The use of superconducting acceleration elements developed at DESY allows up to 27,000 repetitions per second, significantly more than other X-ray lasers in the U.S. and Japan can achieve.[9] The electrons are then introduced into the magnetic fields of special arrays of magnets called undulators, where they follow curved trajectories resulting in the emission of X-rays whose wavelength is in the range of 0.05 to 4.7 nm.[8]

Laser

The X-rays are generated by self-amplified spontaneous emission (SASE), where electrons interact with the radiation that they or their neighbours emit. Since it is not possible to build mirrors to reflect the X-rays for multiple passes through the electron beam gain medium, as with light lasers, the X-rays are generated in a single pass through the beam. The result is spontaneous emission of X-ray photons which are coherent (in phase) like laser light, unlike X-rays emitted by ordinary sources like X-ray machines, which are incoherent. The peak brilliance of the European XFEL is billions of times higher than that of conventional X-ray light sources, while the average brilliance is 10,000 times higher.[8] The higher electron energy allows the production of shorter wavelengths.[9] The duration of the light pulses can be less than 100 femtoseconds.[8]

Instruments

There are six experiments conducted inside the XFEL by the scientists from all over the world. All of these experiments use the X-rays.

Small Quantum Systems (SQS)

The SQS instrument is developed to investigate fundamental processes of light-matter interaction in the soft X-ray wavelength radiation. Typical objects of investigation are in the range form isolated atoms to large bio-molecules, and typical methods are variety of spectroscopic techniques.[10] The SQS instrument provides three experimental stations:

  • Atomic-like Quantum Systems (AQS) for atoms and small molecules
  • Nano-size Quantum Systems (NQS) for clusters and nano-particles
  • Reaction Microscope (SQS-REMI) enabling the complete characterization of the ionization and fragmentation process by analyzing all products created in the interaction of the target with the FEL pulses

Photon energy range between 260 eV and 3000 ev (4.8 nm to 0.4 nm). The ultrashort FEL pulses of less than 50 fs duration in combination with a synchronized optical laser allow for capturing ultrafast nuclear dynamics with unprecedented resolution.

Control

The experiments in the facility are controlled via the in-house developed control system named Karabo.[11] It is a distributed SCADA system written in C++ and python.

Research

The short laser pulses make it possible to measure chemical reactions that are too rapid to be captured by other methods. The wavelength of the X-ray laser may be varied from 0.05 to 4.7 nm, enabling measurements at the atomic length scale.[8]

Initially, one photon beamline with two experimental stations can be used.[8] Later this will be upgraded to five photon beamlines and a total of ten experimental stations.[12]

The experimental beamlines enable unique scientific experiments using the high intensity, coherence and time structure of the new source to be conducted in a variety of disciplines spanning physics, chemistry, materials science, biology and nanotechnology.[13]

History
Accelerator modules during construction in 2015

The German Federal Ministry of Education and Research granted permission to build the facility on 5 June 2007 at a cost of €850 million, under the provision that it should be financed as a European project.[14] The European XFEL GmbH that built and operates the facility was founded in 2009.[15] Civil construction of the facility began on 8 January 2009. Construction of the tunnels was completed in summer 2012,[16] and all underground construction was completed the following year.[17] The first beams were accelerated in April 2017, and the first X-ray beams were produced in May 2017.[2][3] XFEL was inaugurated in September 2017.[4] The overall cost for the construction and commissioning of the facility is as of 2017 estimated at €1.22 billion (price levels of 2005).[8]

References
  1. "HRB 111165: The European XFEL GmbH has been founded!". 13 October 2009. Retrieved 17 July 2018.
  2. "World's biggest ever X-ray laser shines its first light". 4 May 2017. Retrieved 4 May 2017.
  3. "Größter Röntgenlaser der Welt erzeugt erstes Laserlicht" (in German). 4 May 2017. Retrieved 4 May 2017.
  4. "International X-ray laser European XFEL inaugurated". 1 September 2017. Retrieved 2 September 2017.
  5. "European XFEL - Organization - Company - Shareholders". www.xfel.eu. Retrieved 6 December 2018.
  6. Massimo Altarelli, ed. (2014). Annual Report of 2014 (PDF). European X-ray Free-Electron Laser Facility Gmbh. p. 10.
  7. "DESY's European XFEL project group". Retrieved 20 December 2007.
  8. "European XFEL facts & figures". Retrieved 2 September 2017.
  9. "European XFEL in comparison". Archived from the original on 9 May 2017. Retrieved 4 May 2017.
  10. https://www.xfel.eu/facility/instruments/sqs/index_eng.html
  11. "The Karabo distributed control system". Journal of Synchrotron Radiation. 26 (5): 144–461. 2019. doi:10.1107/S1600577519006696.
  12. "How it works". Retrieved 4 September 2017.
  13. "Science". Retrieved 4 September 2017.
  14. "Launch of the European XFEL".
  15. European XFEL news: "HRB 111165: The European XFEL GmbH has been founded!"
  16. European XFEL news: "Tunnel construction completed"
  17. European XFEL news: "European XFEL underground construction completed"
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