Brilliant prospectsThe Swiss X-Ray Free-Electron Laser

SwissFEL

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The new large research facility at the Paul Scherrer Institute – the Swiss X-ray free-electron-laser SwissFEL – provides new opportunities for cut-ting-edge Swiss research.

The major challenges facing our society are to find a secure, climate-neutral energy supply, to provide long-lasting, affordable health care for an aging population, and to maintain an intact environment that we can pass on to our descendants.Scientists around the world are looking for new industrial processes, new types of substances and materials and new medicines which can help to solve these pressing problems. How-ever, we can only search purposefully for inno-vations if we understand the underlying mech-anisms properly; for example, we need to know the processes associated with a disease in an organism before we can develop drugs that are effective, but free of serious side effects.When scientists investigate such fundamental problems as these, they often come up against questions that are impossible to answer using the currently available research methods. For example, processes occurring in nature, in the human body and in many technical devices are so rapid that although we may be able to see their initial and final states, we cannot follow in any detail what happens in-between. As a result, we are still unable to answer many important questions for the development of better drugs, more efficient energy systems or ultra-fast computers and data storage devices.Sources that work by the X-ray free-electron laser principle (abbreviated to “XFEL”) give us

the ability to follow such fast processes in detail – and, in a certain sense, to film the action. These sources are based on electron accelerators that are able to generate extremely short pulses of coherent X-ray light (X-ray light

Brilliant prospectsfor research into innovative materials and biomolecules

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with the properties of laser light). The new large research facility at the Paul Scherrer Institute, the SwissFEL, will be one such source. These X-ray lasers are research facilities on a huge scale – the machine used to generate the pulses of X-ray light is housed in a tunnel measuring several hundred metres.When the SwissFEL starts with its first pilot experiments in 2017, it will be one of only five such facilities worldwide. With SwissFEL, PSI is responding to the growing demand for ex-perimental facilities, which cannot be covered with the four X-ray free-electron-lasers then available in Europe, Japan, South Corea and

the USA alone. Researchers will be able to carry out investigations at the SwissFEL for up to 5000 hours per year at a number of experimen-tal stations.

PSI – experienced with large research facilities

PSI develops, builds and operates unique large research facilities for investigations in the fields of materials science, physics, chemistry, biology, medicine and energy and environmen-tal technology.

Laser specialist Marta Divall working on a vacuum chamber for the experiments which will be conducted in future at the SwissFEL.

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PSI researchers as well as scientists from uni-versities and industry use these facilities to carry out experiments. External researchers receive competent and comprehensive support from the PSI staff as they put their scientific research plans into action. For this reason, and because of the high technical quality of its facilities, PSI has gained an excellent world-wide reputation as a user laboratory, and its name now stands for cutting-edge research involving demanding, complex interdiscipli-nary projects. The institute has carried out pioneering work in many fields, such as energy technology for environmentally friendly vehicle drives and the development of proton therapy. This treatment method can be used to deal less invasively and more successfully with certain types of cancer than would be achievable by conventional therapeutic techniques. As far back as 2001, PSI had taken on the role of an

international leader in the development of modern X-ray light sources with its Swiss Light Source SLS. The SLS has delivered a large number of major scientific results since that time, including the work of the American re-searcher Venkatraman Ramakrishnan, for which he received the Nobel Prize for Chemis-try in 2009.

Setting international standards

PSI’s specialists have now used the compe-tence they gained from the SLS project to de-velop another technologically unique facility, the SwissFEL. This, like the SLS, will set inter-national standards. For example, researchers at PSI have developed innovative ideas so that the SwissFEL can be built more compactly and less expensively than other X-ray lasers.

Beamline designer Bolko Beutner working on the SwissFEL injector test facility. The electron beam generated in the injector has a diameter of a few micrometres. The transverse beam profile monitors, which render the electron beam visible, therefore have to be adjusted precisely.

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The SwissFEL is also setting new standards with its energy concept: it is the world’s first energy-efficient X-ray free-electron laser, thanks to a drastic reduction in its power consumption compared to other facilities. In addition, the SwissFEL is the only XFEL to have a heat recovery system. The waste heat from the SwissFEL is fed into PSI’s heating network.

SwissFEL – innovative project strengthens the competitiveness of the Swiss economy

The SwissFEL is a national facility that is strongly oriented towards the research inter-ests and expertise of Swiss universities and Swiss industry, and takes account of their re-search interests and requirements. In the long term, the construction of the SwissFEL will In

the long term, the SwissFEL will strengthen Switzerland’s standing as a research location, while making a simultaneous and substantial contribution to the lasting competitiveness of Swiss industry.This competitiveness is largely based on the ability to bring innovative products onto the market before those of competing companies. The availability of a first-class research poten-tial within an industry’s home country allows it to develop new discoveries at an early stage, along with innovative methods and tools, and hence to stay abreast of the global challenge. Swiss industry will also be able to benefit di-rectly from the new research opportunities at the SwissFEL, whether through collaborative ventures with PSI and universities or through investigations undertaken at the SwissFEL as part of industry’s own development activities. This innovative project will thus further strengthen the good relationships built up over the past years between PSI and industry.Even before commissioning, the SwissFEL pro-ject has benefited Swiss industry: the new high-tech equipment was developed and im-plemented in close cooperation with domestic companies. Partners include, for example, mechanical and plant engineering specialists TEL Mechatronics AG (formerly Oerlikon Me-chatronics AG) and MDC Max Daetwyler AG, both of which have been tasked with develop-ing and constructing major SwissFEL compo-nents. Last but not least, the SwissFEL project will also have a positive effect during its con-struction and operation on the training of students, post-graduates and hi-tech special-ists in areas such as power electronics, computer technology, materials processing, vacuum technology, sensor technology and image processing.

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The SwissFEL will generate extremely intense, extremely short flashes of X-ray light for scien-tific experiments. This X-ray light will be emitted within the SwissFEL by fast-moving electrons which are directed by powerful magnets to follow a narrow, slalom-shaped path. This is because when electrons are forced to change their velocity or direction, they emit electro-magnetic radiation – depending on the type of movement of the electron; this could be in the form of radio waves, visible light or the very X-ray light.The SwissFEL facility will stretch over a distance of just under 740 metres and will consist of four

sections: an injector, a linear accelerator, an arrangement of undulators and equipment for experiments. In the injector, electrons are ex-tracted from a metal plate by a flash of light and are then pre-accelerated by an electric field before continuing on to the linear accelerator where they are accelerated to the required energy by means of powerful microwaves. They are then sent on a slalom-shaped path in un-dulators – the technical name for a periodic arrangement of alternately-oriented magnets. In the process, the electrons generate an ava-lanche of increasingly coherent radiation – the uniquely intense X-ray light of the Swiss-FEL.

The SwissFEL facilityConstruction and function

� InjectorThe electrons are generated and pre-accelerated.

� Linear acceleratorThe electrons are accelerated to the required energy.

Quadrupole magnetThis component guides the electron beam along its path. Cavities

The linear accelerator comprises 104 cavities of 113 annular copper discs each. It has an overall length of 335 metres.

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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.

Once the X-ray light has been emitted by the electrons, the electrons are no longer required and are captured in an electron absorber. The beam of X-ray light, however, is sent to the experimental stations, where it will be availa-ble to researchers for use in their experiments.

� UndulatorsThe undulators are composed of ultra-strong neodymium magnets. Magnets with alternating polarity direct the electrons to follow a slalom- shaped path, generating the X-ray light.

� ExperimentsThe extremely short and intense X-ray flashes are transported, by mean of optical elements, to the measuring stations where the most diverse experiments are conducted.

The undulator is located in a vacuum chamber, allowing the magnets to be brought as close as possible to the electron beam.

Neodymium magnets

The illustration is not to scale.

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The SwissFEL was built in the immediate vicin-ity of the Paul Scherrer Institute, in the Würen-lingen forest. The building is a two-storey build-ing. The X-ray light for the experiments is generated on the lower floor where the injector, accelerator and undulators are located. The supply systems required to operate the Swiss-FEL’s accelerator are located on the upper floor above the accelerator tunnel. The experimental area after the accelerator tunnel is a wider, single-storey building.

Respect for the sensitive location

The Würenlingen forest is a habitat for numer-ous species of animals and plants and also provides valuable recreational space for people who live or work in the vicinity. In order to do justice to this sensitive location, an interdisci-plinary team of experts has worked on a project

Hi-tech in harmony with nature

� Injector

� Linear accelerator

The supply systems for the SwissFEL accelerator are located on the first floor.

Wild animals will be able to circulate undisturbed thanks to two wild animal crossings at the SwissFEL facility.

The X-ray light for the experiments will be generated in the basement, where the injector accelerators and undulators are located.

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for two years, developing a concept to achieve the best-possible integration of the SwissFEL within its natural environment. The impacts of the facility on nature and the landscape have been minimized as far as possible by embed-ding it within an ecologically enhanced land-scape, which will, in turn, result in a new abun-dance of species.The facility is mostly covered with earth, so that forest users only see a sloping hillside. Rough grassland, a natural landscape indigenous to Aargau, has been planted on the hillside, creating a habitat for butterflies and wild bees.

Habitat for endangered animal species

Particular attention has also been paid to en-dangered animal species: tthe Grey Long-Eared Bat which has its home nearby is able to find new food in the vicinity of the SwissFEL. Ponds and open areas of land, shrubs and hedges combine to form an appropriate natural habitat for threatened amphibians. Wild animals are able to circulate without im-pediment thanks to two wild animal crossings. Vehicular transport to and from the facility is kept to an absolute minimum on a low-lying road which is barely visible from the nearby forest path and does not affect forest users’ enjoyment. The access lightning is only acti-vated when required.

� Undulators

� Experiments

Laboratories will be made available to researchers at the SwissFEL for the duration of their experiments.

View north: The surroundings of the SwissFEL following completion of the

facility. The SwissFEL buildings are hidden under the sloping hillside on

the left-hand side and are not visible from the forest track. Ecologically valuable

rough grassland has been planted on the hillside.

Production of ammonia from hydrogen and nitrogen: ammonia is one of the basic materials used in the manufacture of artifi-cial 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) – each of which comprises two atoms – 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. In this way, the scientists will learn to observe similar reactions on similarly appropriate catalysts. In a SwissFEL experiment, the catalytic reaction will be initiated by a flash of light at the beginning and then illumi-nated by X-ray pulses at various times to map the current status of the reaction at that time. Like this it will be possible to determine the sequence of the various stages of the reaction or the duration of each.

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The SwissFEL makes it possible to see short-term changes in atomic and molecular struc-tures. Two examples will illustrate the applica-tion of this special X-ray light.

The foundations for a sound environment and a secure, climate-neutral supply of energy

Consider, for example, waste gas scrubbing or the manufacture of raw materials for the chem-ical industry. Countless technical processes involve the conversion of one substance into another by means of a chemical reaction. Special substances – which chemists call cat-alysts – are used to ensure that these reactions proceed as efficiently as possible. The catalysts take part in the reactions but are not consumed by them. Even though catalytic reactions have been used for many decades in countless ap-plications, we often lack a detailed understand-

ing of how they work. Understanding these details will help us to develop catalysts that convert one substance into another in a more environmentally-friendly and energy-saving way. The fact that we don’t yet understand the de-tails of catalysis is due in part to the extremely high speed at which chemical reactions take place; the time required for bonds in an indi-vidual molecule to be broken and for them to reform in a fresh molecule is often just 0.1 millionth of a millionth of a second. In order to properly understand the reaction processes, scientists need to observe the short-lived in-termediate states in a chemical reaction, i.e. to record a kind of a film with an extremely short image exposure time. This is exactly what the SwissFEL will enable them to do: by generating intense X-ray light flashes lasting just 10 fem-toseconds (1 femtosecond = 0.001 millionth of a millionth of a second), individual steps in the reaction can effectively be “frozen”.

Examples of applicationsof the SwissFEL X-ray light

X-ray pulses

NH3N2H2

Flash of light

Reaction time [fs]

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The foundations for long-term health by tailor-made drugs

Proteins form the basic building blocks of living organisms, and are responsible for countless processes vital to life. Many proteins carry out a catalytic function for chemical reactions, while others interact with hormones and signal molecules to control the behaviour of cells and entire organs. A protein molecule has a com-plicated structure made up of many thousands of atoms; these have to be arranged in a unique configuration in order that the molecule can carry out its task. In doing so proteins are not rigid bodies within a living cell; they undergo movements lasting between femtoseconds and a few seconds.Ultra-short X-ray flashes, such as those gener-ated by the SwissFEL, will allow scientists to follow the movements of molecules over time and to observe the processes in which these molecules are involved. For example, future experiments could contribute to our under-standing of the molecular processes that play a role in infectious diseases, or diseases that restrict function of the cells in organs such as the nervous system, the joints and the diges-tive organs or tumour diseases. The results will in future enable the production of tailor-made drugs.The spatial structure of proteins can already be investigated with great success using the method of protein crystallography at the Swiss Light Source (SLS). However, these measure-ments provide only static images of these complex biological “machines”. However, there is a large number of important proteins that

are very difficult to investigate using this pro-cess; these are membrane proteins which are embedded in the outer skin of the cells. This is why we do not know the structure of many membranes proteins. In addition to membrane proteins, the SwissFEL will also provide an efficient way of investigating the structures of entire protein complexes, which occur in many different forms within cells and organs. Such investigations are not possible using conven-tional protein crystallography. The SwissFEL also allows us to observe proteins acting as catalysts, so called enzymes, while “at work”. These enzymes affect important chemical con-versions and facilitate the progress of chemical reactions, and the targeted manufacture of chemical or biological molecules. The Swiss-FEL’s high time-resolution capability will make it possible to directly observe the individual steps in reactions such as the break-up and re-formation of chemical bonds.

The movement of the myoglobin molecule (from position 1 to posi-tion 2), which is responsible for vital processes in breathing. We can predict this movement by computer using suitable calcula-tion methods. The new SwissFEL facility will enable us to experi-mentally check such theoretical models for the very first time.

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If we want to be able to observe ultra-fast processes, we need ultra-short X-ray flashes, such as those that will be produced by the SwissFEL, lasting for about 10 femtoseconds. How can we get a feel for this short time inter-val? Recall the comic hero Lucky Luke, who could draw his gun “quicker than his own shadow”. To perform this feat, how fast does Lucky Luke really have to be? Since light re-quires about 10 nanoseconds to cover a dis-tance of 3 metres, Lucky Luke has this much time to draw his gun before his shadow will

react. This is about a million times faster than the exposure time of a normal camera! By comparison, pictures taken by the SwissFEL will be shot another million times faster than Lucky Luke can draw. In other words: the Swiss-FEL has an exposure time of 10 femtoseconds, which is a thousand billion times faster than a normal camera.

How fast is “ultra-fast”?

Photography with a normal camera

10 milliseconds (0.01 s)

Lucky Luke, quicker than his own shadow

10 nanoseconds (0.00000001 s)

Using the SwissFEL to “photograph” the way molecules form

a new compound

10 femtoseconds (0.00000000000001 s)

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Length: approx. 740 metres

Final energy of electrons: 6 giga electron volts (billion electron volts)

Repetition rate: 100 Hz (pulses per second)

Number of accelerated electrons per pulse: 2 × 1 250 000 000 (two electron bunches)

Wavelength of X-ray light: between 0.1 and 7 nanometres, depending on the beam line

Duration of an X-ray pulse: 1–60 femtoseconds (1–60 × 10–15 s)

Brilliance: almost 10 billion times the peak brilliance of a modern synchrotron radiation source

Availability for experiments: approx. 5000 hours per year

First pilot experiments: 2017

Cost: The cost of constructing 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.

Technical information about the SwissFEL

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SwissFEL

740 m

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Site of the SwissFEL at the Paul Scherrer Institute

� Swiss Light Source SLSThe SLS is a synchrotron light source which has

been used for top-level research since 2001.

� The SwissFEL The SwissFEL will complement the research

opportunities at the SLS.

� Central controlControl room for all PSI‘s accelerator

facilities. In future the SwissFEL will also be controlled from here.

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Bird’s-eye view of the Paul Scherrer Institute.

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The Paul Scherrer Institute PSI is a research institute for natural and engineering sciences, conducting cutting-edge research in the fields of matter and materials, energy and environment and human health. By performing fundamental and applied research, we work on sustainable solutions for major challenges facing society, science and economy. PSI develops, constructs and operates complex large research facilities. Every year more than 2500 guest scientists from Switzerland and around the world come to us. Just like PSI’s own researchers, they use our unique facilities to carry out experiments that are not possible anywhere else. PSI is committed to the training of future generations. Therefore about one quarter of our staff are post-docs, post-graduates or apprentices. Altogether PSI employs 2000 people, thus being the largest research institute in Switzerland.

PSI in brief

More information about the SwissFEL is available from:

SwissFEL Project Manager, AcceleratorDr. Hans BraunTel. + 41 56 310 32 41hans.braun@psi.ch

SwissFEL Project Manager, ExperimentsDr. Luc PattheyTel. +41 56 310 45 62luc.patthey@psi.ch

SwissFEL Science OfficerDr. Mirjam van DaalenTel. + 41 56 310 56 74mirjam.vandaalen@psi.ch

A film about the SwissFEL can be seen at www.psi.ch/en/media/film-swissfel

Imprint

Concept/EditingPaul Scherrer Institute

PhotographyFrank Reiser, PSIMarkus Fischer, PSI

Design and layoutMonika Blétry, PSI

PrintingPaul Scherrer Institute

Available fromPaul Scherrer InstituteEvents and Marketing5232 Villigen PSI, SwitzerlandTelephone +41 56 310 21 11

Villigen PSI, May 2017

Cover picture: The Daetwyler Group developed and built essential components for the undulators of the Swiss X-ray Free Electron Laser SwissFEL: Peter Daetwyler (left) with SwissFEL project leader Hans Braun in the beam tunnel in front of the undula-tors, ready for operation.

SwissFEL_e, 5/2017

Paul Scherrer Institut :: 5232 Villigen PSI :: Switzerland :: Tel. +41 56 310 21 11 :: www.psi.ch