SwissFEL – the new large research facility at the Paul Scherrer Institute

At the beginning of 2019, regular user operations will start at the X-ray laser SwissFEL. The new large research facility at PSI will produce very short pulses of X-ray light, with laser-like properties. Researchers will be able to use these pulses to visualize extremely fast processes, such as how new molecules are created in a chemical reaction; to determine the detailed structure of vital proteins; or to determine the relationship between electronic and atomic structure in materials. From such studies, researchers will gain insights which are not possible to obtain with the methods available today. This new knowledge will expand our understanding of nature and lead to many practical applications; for instance, new pharmaceuticals, more efficient processes in the chemical industry, or new materials for electronics.

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. Worldwide there are only four comparable facilities in operation.

The X-ray laser SwissFEL

The facility is 740 metres long and composed of four sections: Injector with electron source, linear accelerator, an arrangement of undulators, and experimental facilities.

The SwissFEL is a X-ray free-electron laser (the FEL in 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 medicine

It 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.

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

As for the other large research facilities at the Paul Scherrer Institute, the SwissFEL will also be available for use by scientists from research centres and universities – from Switzerland as well as from other countries. Researchers who publish their scientific results will be able to obtain access free of charge upon approval by the scientific selection committee. Individual arrangements will be made for the use of the facility by industrial partners.

For industry, the SwissFEL has already offered opportunities for cooperation prior to operation. The SwissFEL has been a great technological challenge, which PSI overcame alongside industry. This also has resulted in a transfer of knowhow to industry, enabling these companies to develop innovative products.

Location, surroundings and cost

The 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.

Since the end of 2017, the first pilot experiments are being conducted at SwissFEL. Since the beginning of 2017, in parallel with the preparation works at SwissFEL for experimental operations, a second beamline is under construction. Beginning in 2020, it will allow researchers to conduct an even greater variety of experiments. The cost of SwissFEL with the first beamline amounts to around 275 million Swiss francs and is borne in large part by the federal government. The canton of Aargau shares in the financing with 30 million francs from its Swiss lottery endowment fund. The cost of the second beamline is around 44 million francs. Of this, the canton of Aargau is contributing 4 million francs.

Further information