Overview: SwissFEL – the new large research facility at the Paul Scherrer Institute
In 2015, the installation of the X-ray free-electron laser SwissFEL, the new large research facility at the Paul Scherrer Institute, has started. Here an accelerating structure is brought into the beam tunnel. (Photo: Paul Scherrer Institute/Markus Fischer)
As at PSI's other large research facilities, the SwissFEL will be accessible to external researchers, although the requirements of the Swiss Technical Universities and industry have been given special consideration at the planning stage. Until now, there are only two comparable facilities in operation anywhere in the world, with an additional three under construction.
The X-ray laser SwissFEL
Layout of the SwissFEL. Electron pulses will be generated in the injector and then brought to a high energy in the accelerator. The electrons are then forced onto a wavy path by the magnets of the undulators, thereby generating X-rays which will be used for experiments.
The SwissFEL is a free-electron X-ray laser (the
FELin its name stands for
Free Electron Laser), which will deliver extremely short and intense flashes of X-ray radiation of laser quality. The flashes will be only 1 to 60 femtoseconds in duration (1 femtosecond = 0,000 000 000 000 001 second). These properties will enable novel insights to be gained into the structure and dynamics of matter illuminated by the X-ray flashes.
The creation of the X-rays begins at the electron source: Electrons are initially set free when a burst of light strikes a metal plate. They are then brought to the high velocity required by means of an electric field in a linear accelerator. In this process, the electrons acquire as much energy as if they had crossed a voltage of 6 billion volts. They are then fast enough to be fed into a snake-like path along undulators – as the long magnet array used is called by specialists. Along their path, the electrons create X-rays, which amplify like an avalanche, producing the uniquely intense X-ray radiation of the SwissFEL. 12 undulators, each having 1060 magnets, are arranged one behind another over 60 metres at the SwissFEL. The high level of accuracy necessary for guaranteeing good overlap of the electrons and the X-rays along the undulator represents an outstanding achievement in the art of engineering.
The X-ray beam will then be routed to the experimental location, where it will available for researchers' experiments.
New findings for science, technology and medicineIt will be possible at the SwissFEL, for example, to follow step-by-step how the smallest components of a substance separate during a chemical reaction and then recombine to create a new substance. These processes are so fast that it has previously never been possible to observe them. For the first time, the extremely short flashes of the SwissFEL will make it possible to take a snapshot of the individual intermediate steps by means of its extremely
short exposure time. A more precise understanding of this sequence of events could help to make processes in the chemical industry more efficient and therefore more efficient in the use of basic resources.
Ammonia is one of the basic materials used in the manufacture of artificial fertilizers and therefore makes an important contribution to global nutrition. The reaction involved in the production of ammonia proceeds in several stages: initially, the existing nitrogen molecules (blue) and hydrogen molecules (yellow) &ndash each of which comprises two atoms &ndash need to be separated into their component atoms. One nitrogen atom then combines with three hydrogen atoms to form an ammonia molecule. This reaction can only succeed with the help of a catalyst – in this case iron (grey). Although this is a well-understood reaction, it will be used as an example at the SwissFEL, in order to check the scientific potential of the facility.
It will also be possible at the SwissFEL to determine in detail how vital biological molecules are built up. Such molecules are composed of tens of thousands of atoms, and it is crucial for their functioning that the atoms are correctly arranged. Today, researchers can only determine the structure when many copies of such a molecule are arranged in a regular crystal structure. The intense X-rays of the SwissFEL will also make it possible to resolve the structure of molecules which do not form crystals. This knowledge could be the basis for new pharmaceuticals, in that they could show, for example, how important biological processes can be suppressed in pathogenic bacteria.
Workplace for researchers from science and industry
Ideas and experiments are being developed and tried out at the SLS to see how they should be performed at the SwissFEL. A piece of equipment is being developed here with which catalytic reactions can be investigated to find out how they could, for example, be important for new energy technologies. (Photo: Scanderbeg Sauer Photography)
On top of the SwissFEL in spring 2015: The research facility is hidden under the sloping hillside and not visible from the forest path. On the hillside ecologically valuable rough grassland has been planted. (Photo: Paul Scherrer Institute/Markus Fischer)
For industry, the SwissFEL has already offered opportunities for cooperation prior to operation. The SwissFEL is a great technological challenge, which PSI overcomes alongside industry. This also results in a transfer of knowhow to industry, enabling these companies to develop innovative products.
Location, surroundings and costThe SwissFEL is located in the Würenlingen forest, adjoining the existing PSI site in the Swiss Canton of Aargau. After comprehensive analysis, this location proved to be the one most suitable. Here, the temperature variations and ground vibrations are particularly low, which is essential for the successful operation of this high-precision facility. SwissFEL's close proximity to the present PSI site will allow the Institute's existing infrastructure to be used. Most of the building was covered by soil and gravel, creating a natural habitat for threatened plants and animals.
The cost of constructing the SwissFEL will be approximately CHF 275 million, the majority of which will be borne by the Swiss federal government. The Canton of Aargau is also making a financial contribution of CHF 30 million from its Swisslos Fund.