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Brilliant prospects

The Swiss X-Ray Free-Electron Laser

Brilliant prospects for research into innovative materials and biomolecules

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

The major challenges facing our society are to

the ability to follow such fast processes in

find a secure, climate-neutral energy supply,

detail – and, in a certain sense, to film the

to provide long-lasting, affordable health care

action. These sources are based on electron

for an aging population, and to maintain an

accelerators that are able to generate extremely

intact environment that we can pass on to our

short pulses of coherent X-ray light (X-ray light

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. However, we can only search purposefully for innovations if we understand the underlying mechanisms 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 2

with the properties of laser light). The new large

the USA alone. Researchers will be able to carry

research facility at the Paul Scherrer Institute,

out investigations at the SwissFEL for up to

the SwissFEL, will be one such source. These

5000 hours per year at a number of experimen-

X-ray lasers are research facilities on a huge

tal stations.

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

PSI – experienced with large research facilities

such facilities worldwide. With SwissFEL, PSI

PSI develops, builds and operates unique large

is responding to the growing demand for ex-

research facilities for investigations in the

perimental facilities, which cannot be covered

fields of materials science, physics, chemistry,

with the four X-ray free-electron-lasers then

biology, medicine and energy and environmen-

available in Europe, Japan, South Corea and

tal technology.

Laser specialist Marta Divall working on a vacuum chamber for the experiments which will be conducted in future at the SwissFEL. 3

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.

PSI researchers as well as scientists from uni-

international leader in the development of

versities and industry use these facilities to

modern X-ray light sources with its Swiss Light

carry out experiments. External researchers

Source SLS. The SLS has delivered a large

receive competent and comprehensive support

number of major scientific results since that

from the PSI staff as they put their scientific

time, including the work of the American re-

research plans into action. For this reason, and

searcher Venkatraman Ramakrishnan, for

because of the high technical quality of its

which he received the Nobel Prize for Chemis-

facilities, PSI has gained an excellent world-

try in 2009.

wide reputation as a user laboratory, and its name now stands for cutting-edge research involving demanding, complex interdiscipli-

Setting international standards

nary projects. The institute has carried out pioneering work in many fields, such as energy

PSI’s specialists have now used the compe-

technology for environmentally friendly vehicle

tence they gained from the SLS project to de-

drives and the development of proton therapy.

velop another technologically unique facility,

This treatment method can be used to deal less

the SwissFEL. This, like the SLS, will set inter-

invasively and more successfully with certain

national standards. For example, researchers

types of cancer than would be achievable by

at PSI have developed innovative ideas so that

conventional therapeutic techniques. As far

the SwissFEL can be built more compactly and

back as 2001, PSI had taken on the role of an

less expensively than other X-ray lasers.


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 potential 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 directly 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 The SwissFEL is also setting new standards

strengthen the good relationships built up over

with its energy concept: it is the world’s first

the past years between PSI and industry.

energy-efficient X-ray free-electron laser,

Even before commissioning, the SwissFEL pro-

thanks to a drastic reduction in its power

ject has benefited Swiss industry: the new

consumption compared to other facilities. In

high-tech equipment was developed and im-

addition, the SwissFEL is the only XFEL to have

plemented in close cooperation with domestic

a heat recovery system. The waste heat from

companies. Partners include, for example,

the SwissFEL is fed into PSI’s heating network.

mechanical and plant engineering specialists TEL Mechatronics AG (formerly Oerlikon Mechatronics AG) and MDC Max Daetwyler AG,

SwissFEL – innovative project strengthens the competitiveness of the Swiss economy

both of which have been tasked with develop-

The SwissFEL is a national facility that is

struction and operation on the training of

strongly oriented towards the research inter-

students, post-graduates and hi-tech special-

ests and expertise of Swiss universities and

ists in areas such as power electronics,

Swiss industry, and takes account of their re-

computer technology, materials processing,

search interests and requirements. In the long

vacuum technology, sensor technology and

term, the construction of the SwissFEL will In

image processing.

ing and constructing major SwissFEL components. Last but not least, the SwissFEL project will also have a positive effect during its con-


The SwissFEL facility Construction and function

The SwissFEL will generate extremely intense,

sections: an injector, a linear accelerator, an

extremely short flashes of X-ray light for scien-

arrangement of undulators and equipment for

tific experiments. This X-ray light will be emitted

experiments. In the injector, electrons are ex-

within the SwissFEL by fast-moving electrons

tracted from a metal plate by a flash of light

which are directed by powerful magnets to

and are then pre-accelerated by an electric field

follow a narrow, slalom-shaped path. This is

before continuing on to the linear accelerator

because when electrons are forced to change

where they are accelerated to the required

their velocity or direction, they emit electro-

energy by means of powerful microwaves. They

magnetic radiation – depending on the type of

are then sent on a slalom-shaped path in un-

movement of the electron; this could be in the

dulators – the technical name for a periodic

form of radio waves, visible light or the very

arrangement of alternately-oriented magnets.

X-ray light.

In the process, the electrons generate an ava-

The SwissFEL facility will stretch over a distance

lanche of increasingly coherent radiation – the

of just under 740 metres and will consist of four

uniquely intense X-ray light of the Swiss-FEL.

 Linear accelerator The electrons are accelerated to the required energy.

ΠInjector The electrons are generated and pre-accelerated.

Quadrupole magnet This 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.

12 undulators, each having 1060 magnets, are

Once the X-ray light has been emitted by the

arranged one behind another over 60 metres

electrons, the electrons are no longer required

at the SwissFEL. The high level of accuracy

and are captured in an electron absorber. The

necessary for guaranteeing good overlap of the

beam of X-ray light, however, is sent to the

electrons and the X-rays along the undulator

experimental stations, where it will be availa-

represents an outstanding achievement in the

ble to researchers for use in their experiments.

art of engineering.

The illustration is not to scale. The undulator is located in a vacuum chamber, allowing the magnets to be brought as close as possible to the electron beam.

Â? Experiments The 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.

ÂŽ Undulators

Neodymium magnets

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


Hi-tech in harmony with nature The SwissFEL was built in the immediate vicinity of the Paul Scherrer Institute, in the Würen-

Respect for the sensitive location

lingen forest. The building is a two-storey build-

The Würenlingen forest is a habitat for numer-

ing. The X-ray light for the experiments is

ous species of animals and plants and also

generated on the lower floor where the injector,

provides valuable recreational space for people

accelerator and undulators are located. The

who live or work in the vicinity. In order to do

supply systems required to operate the Swiss-

justice to this sensitive location, an interdisci-

FEL’s accelerator are located on the upper floor

plinary team of experts has worked on a project

above the accelerator tunnel. The experimental area after the accelerator tunnel is a wider, single-storey building.

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

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





cele r ac



A Amphibientümpel





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

Habitat for endangered animal species

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

Particular attention has also been paid to en-

been minimized as far as possible by embed-

dangered animal species: tthe Grey Long-Eared

ding it within an ecologically enhanced land-

Bat which has its home nearby is able to find

scape, which will, in turn, result in a new abun-

new food in the vicinity of the SwissFEL. Ponds

dance of species.

and open areas of land, shrubs and hedges

The facility is mostly covered with earth, so that

combine to form an appropriate natural habitat

forest users only see a sloping hillside. Rough

for threatened amphibians.

grassland, a natural landscape indigenous to

Wild animals are able to circulate without im-

Aargau, has been planted on the hillside,

pediment thanks to two wild animal crossings.

creating a habitat for butterflies and wild bees.

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 activated when required.

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







Â? A


er Exp


to ula


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.


Examples of applications of the SwissFEL X-ray light

The SwissFEL makes it possible to see short-

ing of how they work. Understanding these

term changes in atomic and molecular struc-

details will help us to develop catalysts that

tures. Two examples will illustrate the applica-

convert one substance into another in a more

tion of this special X-ray light.

environmentally-friendly and energy-saving way. The fact that we don’t yet understand the de-

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

tails of catalysis is due in part to the extremely

Consider, for example, waste gas scrubbing or

reform in a fresh molecule is often just 0.1

the manufacture of raw materials for the chem-

millionth of a millionth of a second. In order to

ical industry. Countless technical processes

properly understand the reaction processes,

involve the conversion of one substance into

scientists need to observe the short-lived in-

another by means of a chemical reaction.

termediate states in a chemical reaction, i.e.

Special substances – which chemists call cat-

to record a kind of a film with an extremely short

alysts – are used to ensure that these reactions

image exposure time. This is exactly what the

proceed as efficiently as possible. The catalysts

SwissFEL will enable them to do: by generating

take part in the reactions but are not consumed

intense X-ray light flashes lasting just 10 fem-

by them. Even though catalytic reactions have

toseconds (1 femtosecond = 0.001 millionth of

been used for many decades in countless ap-

a millionth of a second), individual steps in the

plications, we often lack a detailed understand-

reaction can effectively be “frozen”.

high speed at which chemical reactions take place; the time required for bonds in an individual molecule to be broken and for them to

X-ray pulses H2



Flash of light

Reaction time [fs]

Production of ammonia from hydrogen and nitrogen: 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) – 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 illuminated 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. 10

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

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 complicated 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.

are very difficult to investigate using this pro-

Ultra-short X-ray flashes, such as those gener-

cess; these are membrane proteins which are

ated by the SwissFEL, will allow scientists to

embedded in the outer skin of the cells. This

follow the movements of molecules over time

is why we do not know the structure of many

and to observe the processes in which these

membranes proteins. In addition to membrane

molecules are involved. For example, future

proteins, the SwissFEL will also provide an

experiments could contribute to our under-

efficient way of investigating the structures of

standing of the molecular processes that play

entire protein complexes, which occur in many

a role in infectious diseases, or diseases that

different forms within cells and organs. Such

restrict function of the cells in organs such as

investigations are not possible using conven-

the nervous system, the joints and the diges-

tional protein crystallography. The SwissFEL

tive organs or tumour diseases. The results will

also allows us to observe proteins acting as

in future enable the production of tailor-made

catalysts, so called enzymes, while “at work”.


These enzymes affect important chemical con-

The spatial structure of proteins can already

versions and facilitate the progress of chemical

be investigated with great success using the

reactions, and the targeted manufacture of

method of protein crystallography at the Swiss

chemical or biological molecules. The Swiss-

Light Source (SLS). However, these measure-

FEL’s high time-resolution capability will make

ments provide only static images of these

it possible to directly observe the individual

complex biological “machines”. However, there

steps in reactions such as the break-up and

is a large number of important proteins that

re-formation of chemical bonds. 11

How fast is “ultra-fast”?

If we want to be able to observe ultra-fast

react. This is about a million times faster than

processes, we need ultra-short X-ray flashes,

the exposure time of a normal camera! By

such as those that will be produced by the

comparison, pictures taken by the SwissFEL

SwissFEL, lasting for about 10 femtoseconds.

will be shot another million times faster than

How can we get a feel for this short time inter-

Lucky Luke can draw. In other words: the Swiss-

val? Recall the comic hero Lucky Luke, who

FEL has an exposure time of 10 femtoseconds,

could draw his gun “quicker than his own

which is a thousand billion times faster than a

shadow”. To perform this feat, how fast does

normal camera.

Lucky Luke really have to be? Since light requires about 10 nanoseconds to cover a distance of 3 metres, Lucky Luke has this much time to draw his gun before his shadow will

Using the SwissFEL to “photograph” the way molecules form a new compound

Lucky Luke, quicker than his own shadow 10 femtoseconds (0.00000000000001 s)

Photography with a normal camera 10 nanoseconds (0.00000001 s)

10 milliseconds (0.01 s)


Technical information about the SwissFEL 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.

Site of the SwissFEL at the Paul Scherrer Institute

Œ Swiss Light Source SLS The 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.

Ž Œ PSI West

Ž Central control Control room for all PSI‘s accelerator facilities. In future the SwissFEL will also be controlled from here.


PSI East




740 m


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


PSI in brief

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.

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 undulators, ready for operation.

Imprint Concept/Editing Paul Scherrer Institute Photography Frank Reiser, PSI Markus Fischer, PSI Design and layout Monika BlĂŠtry, PSI Printing Paul Scherrer Institute Available from Paul Scherrer Institute Events and Marketing 5232 Villigen PSI, Switzerland Telephone +41 56 310 21 11 Villigen PSI, May 2017

More information about the SwissFEL is available from: SwissFEL Project Manager, Accelerator Dr. Hans Braun Tel. + 41 56 310 32 41 SwissFEL Project Manager, Experiments Dr. Luc Patthey Tel. +41 56 310 45 62 SwissFEL Science Officer Dr. Mirjam van Daalen Tel. + 41 56 310 56 74 A film about the SwissFEL can be seen at 15

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

SwissFEL_e, 5/2017

SwissFEL - Brilliant prospects: The Swiss X-Ray Free-Electron Laser (2017)  
SwissFEL - Brilliant prospects: The Swiss X-Ray Free-Electron Laser (2017)  

The Paul Scherrer Institute is planning to construct a new scientific large-scale facility – the SwissFEL X-ray free electron laser. This wi...