Science with neutrons and muons - Science at the Paul Scherrer Institute

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Science with neutrons and muons

Research at the Paul Scherrer Institute

An experiment with muons is being prepared.

Contents 4 Neutrons and muons in 90 seconds 6 Energy and transport

6 Seeing batteries from the inside

6 Refining motorcycle fuel efficiency


Stress-testing turbine blades

8 Earth and environment

8 Cleaning soil with poplar trees

8 Water in clays

9 Watching plants grow

10 Food, health and medicine

10 Secret life of bubbles

10 A recipe for healthy eating

11 Copying nature for medicine

12 Inside the Swiss Spallation Neutron Source SINQ 14 Heritage and culture

14 Making a Bronze Age axe

15 Predicting salt damage to buildings

16 Electronics and technology 16 Spintronics

16 Measuring grains of magnetism

17 Molecular sandwiches

18 Discovering materials 18 Microgels

19 Making smart materials

19 Understanding superconductors

20 Engaging with industry

20 Universities, industry and PSI

21 Solving industry problems

21 Developing new technologies

21 Spin-off company

21 A future neutron source for Europe

22 Inside the Swiss Muon Source SμS 24 Using neutrons and muons

25 What is a neutron?

25 What is a muon?

26 Making neutrons and muons

26 Accelerating protons

26 Making neutrons

26 Making muons

28 We make it work 31 PSI in brief 31 Imprint 31 Contacts

Cover photo Experiments with neutrons and muons allow scientists to measure inside materials and find out where atoms are and what they are doing. 3

Neutrons and muons in 90 seconds The Paul Scherrer Institute PSI, is

Neutrons are abundant particles in

home to three large research facilities:

nature. Along with protons and elec-

the Swiss Spallation Neutron Source

trons, they make up atoms, the basic

SINQ, the Swiss Muon Source SμS, and

building blocks of the natural world.

the Swiss Light Source SLS. PSI is the

Neutrons are tightly bound up with

largest natural and engineering

protons in the nucleus at the centre of

sciences research centre in Switzer-

an atom.

land. Muons are elementary particles that can be embedded in the gaps between atoms inside a material to sense what Using the large research facilities at

is around them. They have an electric

PSI, scientists can get an outstanding

charge and are heavier than an electron

view of the inside world of materials.

but lighter than a proton.

Their measurements connect the microscopic positions and movement of

Over 2500 scientists travel to PSI every

atoms with the properties experienced

year from Switzerland and around the

in the everyday world.

world. Among others they use the beams of neutrons and muons to illu-

The comforts and convenience of mod-

minate their materials and discover

ern life rely on many decades of re-

their microscopic properties.

search and development by scientists and engineers. Through their careful

Every day, discoveries from PSI are

explorations, the potential uses of nat-

being used to advance science and

ural and artificial materials can be re-

solve problems in industry.

alised. You can read more about PSI research Materials are everywhere. Lightweight

using neutrons or muons in the follow-

bikes and fuel-efficient cars, surgical

ing pages.

implants, energy efficient homes, carrying fresh food from supplier to supermarket every day, mobile phones for instant connection to family and friends, and much more. At PSI, beams of neutrons and muons are used for materials research. The beams are made by firing protons from a particle accelerator into targets made of lead or carbon. A fantastic piece of Swiss engineering, the accelerator makes the most powerful beam of protons in the world. 4

The comforts and convenience of modern life would be impossible without many decades of research into new materials. 5

Energy and transport As demand for energy continues to

Using neutron beams, it is possible to

in volume would make it very difficult

increase, ways to reduce fuel consump-

see inside a battery and follow what is

to guarantee the battery would work

tion and improve energy efficiency are

happening in real time to the battery

after it had been charged many times.

a growing concern. Neutron and muon

parts as it is charged and discharged.

beams at PSI are increasingly being

This gives unique insight into the real

used for energy related research.

operating performance of the battery. With muon beams, the movement of chemicals around the battery can be

Refining motorcycle fuel efficiency


Neutron beams can shine right through

Seeing batteries from the inside

For instance, the microscopic changes

metals. This property has been put to

to the volume of a metal hydride can

good use by engineers designing a

be watched as hydrogen is absorbed

clutch lubricated with oil. To their sur-

Rechargable batteries are used every-

during charging. Good commercial ma-

prise, many discs were found to be

where in toys, electronics and electric

terials have a smooth and reversible

running dry. Time to go back to the

vehicles. Common nickel-metal hy-

change in volume. But if a possible new

drawing board.

dride batteries were once just labora-

battery material makes a sudden jump

tory curiosities. Now, materials devel-

in volume rather than a smooth change,

Motorcycle engineers are under con-

oped in the last 20 years allow them

it is not suitable. Such sudden changes

stant pressure to reduce fuel consump-

to be recharged many times. Battery development is a continuous process and neutron and muon beams at PSI are regularly used by manufacturers. A typical AA-type nickel-metal hydride battery (NiMH) is a compact wonder of science you can carry around in your pocket. Inside the battery, two metal strips separated by an insulating foil are rolled up and placed into the metal can. The can is filled with an electrically conducting liquid and sealed with a cap. The positive terminal is made from a nickel compound and the negative terminal is made from a substance known as a metal hydride. As the battery is charged, chemical reactions cause hydrogen to be released from the nickel compound and be soaked up into the metal hydride. When the battery is used, the chemical reactions reverse and an electrical current flows out. 6

Scientists preparing a neutron scattering experiment for research on new materials for batteries.

tion to meet efficiency and emissions

made the surprising discovery that only

gruelling conditions is crucial for im-

targets and increase the driving range

the first three out of eight discs were

proving energy efficiency and guaran-

of their machines. The oil pump is one

being coated with oil. This did not

teeing long-term reliability.

of the biggest consumers of power from

change with engine running speed or

the engine. One of its main tasks is to

how fast oil was pumped in.

Conditions inside gas turbines are ex-

lubricate and cool the bike’s clutch.

Equipped with such precise informa-

treme. Turbine blades can be rotating at

The clutch transfers power and motion

tion, the internal design of oil flow

3600 revolutions per minute, with hot

from the engine to the wheels. The

channels in the clutch can be adapted

gases at 1400°C flowing through and

most common design uses a row of

to achieve good lubrication and cooling

raising blade temperatures to 1000°C.

plates and friction discs that are nor-

using reduced oil flows.

Engineers must have confidence that

mally clamped together, but can be pulled apart to change gear.

the blades can withstand the extreme

conditions found inside the turbines.

Neutron imaging can be used to see

Blade materials are only chosen after

right through the metal casing and map

comprehensive testing of their behav-

out where oil is flowing inside the

iour to determine how they will per-

clutch while it is running at speeds up

form. Ongoing improvements to turbine

to 8000 revolutions per minute.

Stress-testing turbine blades

blade materials and design continue to push up efficiency in fuel use and

In one new clutch design, the aim was to reduce oil flow through the clutch to

Turbines in power stations around the

energy conversion.

reduce the power consumed by the oil

world convert the energy of fast-flow-

By placing turbine blades and other

pump. Oil is supplied through a hole in

ing hot gases into mechanical motion

parts in a beam of neutrons, engineers

the drive shaft that then runs through

to generate electricity. With tempera-

can perform in-situ measurements con-

the clutch and spreads out onto the

tures reaching up to 90% of the melt-

necting material behaviour under ap-

eight spinning discs of the clutch.

ing point of the turbine blades, ongo-

plied loads to the microscopic fine

Taking neutron snapshots lasting just

ing research and development into the

structure of the component. In-built

50 millionths of a second, engineers

performance of materials under such

residual stresses coming from the manufacturing process can also be measured. Residual stresses are a significant problem in a component since they can lead to cracks and unpredictable changes in material properties. PSI is a world leader in in-situ engineering stress measurements using neutron beams, attracting visitors from international engineering companies on a regular basis. In one recent project studying turbine blades, changes in the microstructure of a new design of turbine blade were traced to the casting process used to make the blade. Information from the experiments can be used to optimise the manufacturing procedure and modify the aerofoil design to deliver the best performance and longest operating lifetime.


Earth and environment Many lessons can be learnt from plants

surprisingly, boron can still be ab-

and animals on how to solve common

sorbed by the leaf into the dead

problems and gain a deeper under-

patches. By doing this, the poplar can

standing of our place on Earth.

protect healthy areas of the tree and stop them from being overloaded with boron. In this way, poplar can store 20 times more boron than can be tolerated

Cleaning soil with poplar trees

by other plants.

Boron is one of the lightest chemical

a way to protect food production. Har-

elements found on earth and at low

vesting trees from contaminated sites

levels is an essential nutrient in plants.

stops boron from going back into the

But if soil has too much boron, food

soil. Their timber then can be used for

crops can fail. Experiments with neu-

construction or fuel.

Planting poplar trees alongside crops in areas with poor water and soil offers

trons have found that poplar trees can collect 20 times more boron than other plants and can be an effective way to keep boron at the right levels in agricultural areas.

Water in clays Clay is often used to line rubbish pits and reservoirs as it is very good at

In Turkey, waste water with high levels

stopping water and other liquids from

of boron pumped into rivers from power

passing through into the surrounding

plants has reduced citrus tree crop

soil. New research linking the micro-

yields. In California, the arid environ-

scopic clay structure with how water

ment and weathering of rocks along

travels through the clay is being used

coastal ranges has led to boron accu-

in designs of long term stores for radio­

mulation in the soil and groundwater

active waste.

Living plants are not damaged by neutron beams allowing three-dimensional images of the plant, roots and soil to be made while it is growing.

and interrupted sustainable agriculture. With neutron beams, plants can be

Around the world, there is a growing

easily tested for their boron hardiness.

consensus that deep stores in rock are

For one study, researchers studied the

the most appropriate way to manage

uptake of boron in poplar trees, willow

radioactive waste. In countries such as

Clay has a complex structure with layers

trees, leaf mustard and lupin. Of the

Belgium, France and Switzerland, deep

of small plate-shaped particles sepa-

four, poplar was the most tolerant of

clay formations are being considered.

rated by a network of thin water layers

boron and willow the least. This was a

Sweden and Finland, countries which

and pores of varying sizes.

surprise as poplars and willows belong

do not have deep clay formations, fa-

By combining neutron experiments

to the same family.

vour hard rock formations lined with

with measurements of fluid draining

Within the poplar leaves, boron was

clay-based materials. Precise knowl-

rates through the clay, the “twistiness”

found to build up at the edges and tips.

edge of clay properties is essential for

of the pore network can be measured

At high boron levels, the green colour-

assessing the performance and safety

and the local motion of water as it

ing at the edges and tips fades and

of these various radioactive waste dis-

squeezes through the clay can be fol-

patches of the leaf start dying. But

posal designs.



Watching plants grow

image of the plant roots to be made

It’s normally quite difficult to see what

Around the plant roots, experiments

Clays that might be suitable include

is happening underneath a plant with-

find that the soil is modified and holds

non-swelling clay kaolin (china clay),

out pulling it out of the ground. By

much more water than the soil further

often used for porcelain and pottery,

shining a beam of neutrons through

away. The plants can create an emer-

and a form of bentonite (montmoril-

the roots of plants while they are grow-

gency water supply for short periods of

lonite based clay), which swells in wa-

ing, the location of water in the soil

drought. Measurements like this can

ter. Betonite was found to be most ef-

around the root system can be seen.

also play a part in breeding plants for

while it is growing.

better survival in dry regions.

ficient at slowing water mobility. This new microscopic knowledge can

Because neutron beams are a very del-

be used in computer simulations to

icate measuring tool, living plants

estimate the water flow in potential

aren’t damaged when illuminated by a

disposal sites.

beam of neutrons. This allows a full 3D


Food, health and medicine Good food, good health and good med-

outer surfaces of the bubbles trapping

binding on and breaking the droplet

icine are key ingredients for a happy

a thin watery layer between them and

into smaller ones until they are the right

and healthy life. Neutron scattering

giving firmness to the food.

size for absorbing into the body.

experiments are making unique con-

Studying the stability and structure of

Eating too much fat can lead to obesity

tributions to all three.

the air bubbles over time is a challeng-

and related diet issues. Scientists at

ing task, and is not yet widely attemp­

PSI simulate the acidic conditions

ted. But with the neutron scattering

found in the stomach and use neutrons

techniques at PSI, unique information

to check changes to the structure of fat

within the molecular structure can be

droplets at the molecular level. Fat

easily recorded.

droplets with a celluse-like coating

Secret life of bubbles Dairy products like ice cream, mousse

Manufacturers now have a new way to

and whipped cream must look fabulous

learn how to make the right blend of

and taste delicious days after they are

ingredients before scaling up for their

brought home from the shop. A micro-

production lines.

scopic look with neutrons could be a new way for food manufacturers to quickly find the best mix of ingredients for the most delicious results.

A recipe for healthy eating When it comes to healthy eating, fat

Despite only having a few ingredients,

has always been something to be

dairy foods like ice cream, whipped or

avoided at all costs. But not all fat is

sprayed cream, mousse and yoghurt

bad. Studies at PSI investigate how

have a surprisingly complicated chem-

fats are digested in order to create


low-calorie recipes for greater personal

The basic ingredients are usually water


(or ice crystals), milk fat to add richness and stabilise the base mix, and sugars

In the right amount, fat is a key part of

to add sweetness and improve texture

a healthy balanced diet. It provides

and body.

essential fatty acids which our bodies

The cheapest ingredient in these prod-

can’t make themselves, helps us to

ucts is invisible: air. Tiny air cells whip­

absorb vitamins, and generally plays a

ped into the base mix are largely re-

part in maintaining healthy tissue, skin

sponsible for the general consistency

and immune function.

and greatly affect the texture and vol-

Fat also adds flavour and texture to


food: creamy-smooth cheese and but-

Emulsifiers are added to bind the in-

ter, tender moist cakes, and crispy

gredients together and hold the air

crunchy baked dishes.

bubbles in place. A common emulsifier

Digestion breaks down large food mol-

is egg, although others such as mono-

ecules into smaller ones, releasing

glycerides and diglycerides are also in

energy and making it easier for food to

common use.

be absorbed into the body.

To hold the bubbles in place, the emul-

Acids in the stomach recognise the

sifier molecules coat the inner and

surface structure of fat droplets in food,


Seeing the molecular structure of foams, food ingredients and medicines is straightforward with neutron beams.

from plants have been found to resist

Proteins are large biological molecules

The ball-shaped artificial molecules are

acid breakdown and are not absorbed

that perform a wide range of jobs inside

designed to uncurl in particular condi-

into the body. Disguising fat from the

the body. They help chemical reactions

tions. The goal is to use these molecules

body like this offers a new way to lower

to work, copy DNA, and transport mol-

to hold medicines and then release

the intake of fat and make great-tast-

ecules from one location to another.

them in a particular place.

ing, healthy and nourishing recipes.

Whilst proteins are considered large on

One test successfully completed has

a biological scale, the objects are actu-

looked at the release of vitamin B9

ally very small – thousands of them

(folic acid) over a few hours for a po-

could fit across a piece of dust. The

tential skin treatment for skin damaged

Copying nature for medicine

shape of proteins is important for doing

by sunlight.

Learning from nature, researchers have

particular tasks and for them to be

The artificial molecules could also be

developed tiny artificial particles that

recognised in the body.

attached to the surface of a silicon chip

behave like proteins. They could be

Inspired by natural proteins, a team of

to make a very precise biological sen-

used to release medicines very accu-

researchers have found a simple and

sor for hospital laboratories to test for

rately in the body or make biological

efficient way to make tiny artificial mol-

the presence of particular molecules


ecules. Experiments at PSI confirm that

linked to a medical condition.

they behave in a similar way to proteins.


Inside the Swiss Spallation Neutron Source SINQ



Heritage and culture Valuable objects can be easily exam-

western Switzerland. A deeply curved

ined with neutron beams. They don’t

cutting edge shows that it probably

cause any damage and can see deep

served as a weapon or a status symbol

into the interior. They are the perfect

rather than as a tool for felling timber

tool for looking at rare Bronze Age axes

or for woodworking. The axe has been

or examining corrosion in sculptures

dated to the Early Bronze Age A2a pe-

and carvings.

riod, around 1800 BC, and would probably have been attached to a long wooden haft. Neutron beams are the perfect way to

Making a Bronze Age axe

understand how such a unique object was made, since they cause no damage

Studies of a rare Bronze Age axe found

and can give a clear view into metals.

nearly 200 years ago near Lake Thun

By rotating the axe in the neutron beam

have shown that Bronze Age Central

it can be deduced how the axe was

Europe was heavily influenced by cul-

manufactured. The structure has many

tures in the Balkans and Caucasus.

voids inside suggesting the axe mould was made from clay and residual water

In the Buchholz quarter of Thun in 1829,

turned to bubbles of steam in the

gravel diggers uncovered one of the

molten bronze. Because the voids are

finest hoards of Early Bronze Age treas-

still well-rounded and not elliptical, it

ure in Northern Europe. On the south

is very unlikely that the bronze surface

side of Renzenbühl hill, looking out

saw much forging after the axe was cast.

over Lake Thun, the treasure was found

The golden inlays were cut from a round

in a stone cist burial of an important

rod and hammered into recesses

person. Twelve objects were found

punched into the copper strips, which

along with human remains, and the

were themselves hammered into the

burial is one of several making up a

grooves cast into the axe. In a final

small cemetery in the area.

stage, the resulting uneven surface was

One of the most impressive objects in

smoothed out by grinding and polishing.

the hoard was an axe inlaid with striking

This study has given a new understand-

decoration: 198 diamond-shaped gold

ing of Bronze Age manufacturing tech-

inlays in two parallel rows running along

niques. It shows considerable influ-

the front and back faces. The golden

ence on Bronze Age Central Europe by

inlays are set within two broad, copper

cultures located in the Balkan Penin-

metal strips, which are themselves set

sula and the Caucasus region and

into pre-cut grooves on both faces of

rather less influence from Mediterra-

the axe. The inlays are a rare decorative

nean cultures as was previously

technique for the Early Bronze Age and


are present on only seven bronze artefacts found north of the Alps. The spoon-like “Löffelbeil” design of the axe is typical of those found in 14

single inlay at the flange

Predicting salt damage to buildings Limestone, commonly used for building facades and sculptures, can be damaged by salty water soaking through refilled sample hole

the porous stone. Buildings and sculptures can be easily damaged by salts soaking into porous stone. Salts can come from many sources including road de-icing, flooding, or cattle, bats and pigeons living in the buildings. Salts dissolved in water seep through pores and cracks in the stone and form crystals as the stone dries out. The crystals can cause high stresses inside the stone leading to chipping and cracking. A new computer program now allows civil engineers to test ideas for repairs, conservation techniques or new building materials without having to perform long-term studies over many years.

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Neutron radiography can easily identify the transport of water and salt solutions through the stone as well as the location of salt crystals and cracks.

Left: Bronze axe from the collection of the Bernisches Historisches Museum. Right: Images of the inside of the bronze axe generated with the technique of neutron tomography. Depicted are virtual cuts through the axe. The dark spots are air bubbles and the light spots are gold adorments.

Results from wetting and drying experiments on Savonnières limestone were used to test the program. A key finding was that major damage occurs during rewetting of the stone. The developers of the software anticipate it being widely used across Europe to reduce the life-cycle cost of buildings and extend the lifetime of building materials and structures.

5 cm


Electronics and technology Modern technology completely de-

tic-like materials conduct electricity,

1s and 0s are stored on the disks in

pends on electronics to function and

emit light and can be easily shaped as

small magnetic grains that have their

magnetism for storing data. As elec-

well as having all the properties of

north or south poles pointing out of the

tronic component sizes continue to

traditional semiconductors like silicon.

surface of the disk. A tiny write head

shrink and information volumes rapidly

Muons carefully implanted into a spin-

flies over the surface flipping the poles

expand, new ways of combining elec-

tronic device are able to sense the local

over as it stores information.

tronics and magnetism are being

environment and measure the spin

How the poles of the grains flip direction


direction of electrons passing through.

in a magnetic field can be elegantly and

Using this technique, it has been possible to develop a device that can precisely control the orientation of elec-


tron spins passing in and out of a material.

Spintronics is widely predicted to

The results are particularly exciting as

change the way information is stored

they show that many new devices can

and transmitted in electronics and

be built to have specific functions

computers. Spintronic devices are ex-

such as computer processor elements,

pected to have smaller sizes and con-

sensors, new types of computer mem-

sume less power than existing elec-

ory and intelligent light emitting dis-

tronics. Building components to


control and exploit ‘spin’, a basic physical property of electrons, is in its infancy, but neutron and muon beams at PSI are perfect tools to use in their development.

Measuring grains of magnetism Data storage is big business and con-

For over 100 years, electrons have been

tinues to grow. One hard drive manu-

flowing along wires in all sorts of elec-

facturer recently announced it had

trical circuits and devices. Electrons

shipped 2 billion hard drives, noting

can be pushed around by electric and

that it took 29 years to sell a billion

magnetic fields interacting with their

drives and then only four more years

charge, a natural property they have

to sell another billion. Manufacturers

along with mass. A third natural prop-

are constantly searching for ways to

erty is called ‘spin’ which gives the

increase the amount of information

electron its very own microscopic mag-

that can be stored with their products.

netic field. Controlling the orientation of spin in

Magnetic recording technology is at the

electronic circuits and using it to store

heart of modern computer technology.

and transmit information requires very

Photos, music and video can all be

delicate control of the material design.

broken down and stored as patterns of

New types of material known as organic

1s and 0s on small spinning disks that

semiconductors are well-suited for

can now easily store 1 terabyte (1TB) of

spintronic applications. These plas-



Molecular sandwiches

uniquely studied with neutron scattering.

To pack in so much information, differ-

Magnetic grains are typically made

ent magnetic materials such as

from a cobalt-chromium-platinum alloy

iron-platinum alloys will need to be

Building molecular sandwiches with

separated by a thin shell of silicon

used along with larger magnetic fields

layers just a few atoms thick can create

oxide. The average grain diameter is

to flip the poles of the grains.

structures with entirely new electrical

typically around 8 nanometres, about

Hard disk manufacturers are using re-

and magnetic properties. Experiments

a million times smaller than a grain of

sults from neutron scattering experi-

are the only way to learn about what

sand. The grains are designed to make

ments to develop the materials needed


sure that the magnetic particles can’t

for these future disk designs.

just flip from north to south at any time.

Laying together different compounds

Only when the write head passes over

only a few atoms thick, opens up many

can they change direction.

possibilities for new discoveries. At the

Hard disks will soon be able to store 10

boundaries between the layers, strange

terabytes of data on one disk, and 60

things can happen. Insulators can be-

terabyte hard drives are being forecast.

come conducting or even superconElectronics and data storage rely on the interplay of electricity and magnetism in tiny components. Neutron scattering experiments can watch changes in the components.

ducting, where current flows without generating any heat. Compounds that are usually non-magnetic can become magnetic. Laying down a thin layer of a manganese-containing oxide onto an aluminium-containing oxide causes an external magnetic field to form at the boundary between the two compounds. Neutron beams are able to measure how the atomic structure and magnetism varies through the layers and across the boundary, giving unique information that can’t be obtained in any other way. In this case it was found that for the atomic structures of the two layers to bind together, the manganese-containing layer was stretched and squeezed out of shape compared to its usual form. As a consequence, very large strains built up inside the new structure. Moving away from the boundary between the two layers, the strain in the structures becomes less and the magnetic field is smaller in size, indicating that the strength of the magnetism is tightly connected to the atomic strain in the structure. This is a novel route for controlling magnetism in devices engineered from thin layers and it opens up new ways to develop electronics.


Discovering materials

Studies with neutrons and muons can map out precise information on magnetic structures inside materials that help to optimise them for future applications.

New technology and advances in sci-


ence can only come after thousands

their surroundings by changing size, collapsing to a compact form when

and thousands of experiments testing

Microgels are small soft particles with

squashed, and then expanding back to

out new compounds and learning

a compact core and a fuzzy surface

their original size when released.

about their properties. The tough in-

suspended in a liquid. Extremely soft

When packed very close together, the

tellectual challenges found at the fore-

and flexible, they carry much potential

fuzzy surfaces of microgels can overlap

front of knowledge are a great test of

for various applications.

and merge together producing many

a scientist’s skills.


different and unusual physical properMicrogels are soft particles made from


long polymer molecules loosely linked

Neutron experiments at PSI are explor-

together to form a net. They react to

ing the internal structure and physical

properties of microgels in suspension.

inert and harmless in the human body.

gen or liquid helium, and can carry

One finding is that pressure is a more

They are ideal for transporting medi-

more than 100 times the current of a

precise way to control microgel size


copper cable of the same size. They are

than temperature. Increasing the pres-

Neutron scattering experiments allow

used inside hospital MRI scanners, as

sure squeezes the liquid out of the

developers of new materials to under-

electronic filters in mobile phone base

microgels, and they become more like

stand how the active molecules interact

stations, in the industrial separation

compact individual particles rather

with the host material.

of iron impurities from kaolin clay to

than merging into each other.

In one example, researchers were able

improve its purity and whiteness, and

Microgels are steadily being used in

to identify individual molecules inside

in some power grids to transfer large

more and more applications including

the aerogel and confirm that nearly

amounts of power between nearby in-

water purification, making artificial

80% of the pores were filled. They


muscles, and as tiny switches and

showed that each pore held a single

The simplest superconducting materi-


molecule, and that the molecules had

als are well-understood, but more and

kept their usual shape and response

more superconductors are being dis-

when illuminated with light.

covered with properties that defy ex-

Making smart materials

planation. Neutron scattering experiments at PSI

Understanding superconductors

have recently discovered that a ceri-

light or temperature into a passive

One of the great scientific discoveries

new type of superconductivity coupled

supporting material. One of the first

of the 20th century, the incredible

with well-ordered magnetic field orien-

development stages is to check if the

property of superconductors to let

tations of the ions in the material.

active molecules can still function in-

electricity flow without resistance at

This is surprising, as superconductivity

side their new home.

low temperatures is steadily being

and magnetic fields are normally seen

harnessed. Neutron scattering and

as rivals with very strong magnetic

Embedding active molecules into a

muon spectroscopy experiments at PSI

fields destroying the superconducting

neutral host framework is of interest to

are at the forefront of the worldwide


many areas of science. In medicine,

intellectual effort to explain how they

By constantly pushing at the frontiers

drug molecules could be released

actually work.

of knowledge, PSI scientists are pursu-

Smart materials that react to their natural environment can be designed by embedding molecules activated by

slowly from implants. In optical appli-

um-cobalt-indium material placed in a very strong magnetic field creates a

ing breakthroughs that could lead to

cations, light sensitive materials could

Superconductivity was discovered in

computers working at speeds beyond

be used as switches in electronics or

1911 and occurs in many ordinary met-

the limits of silicon technology, or

laser devices to block or amplify light

als such as lead and aluminium at very

transform the performance of clean

of a particular colour.

low temperatures about 290 degrees

energy generation and distribution.

Aerogels are one of the most popular

below room temperature. Electric cur-

materials to host active molecules.

rent can freely flow in a superconduct-

Discovered in 1931, aerogels are the

ing wire without causing it to heat up.

world’s lightest solid materials with

In contrast, the electrical resistance of

around 99% of the volume made from

a normal copper wire can cause it to

a network of tiny air bubbles. Silica

heat up, glow brightly and even melt.

aerogels made from sand are the most

Superconductors are typically cooled

commonly used as they are chemically

to low temperatures using liquid nitro-


Engaging with industry PSI actively encourages industry to

iour of materials already in use, com-

Varta and Toyota are making use of

make use of its research facilities ei-

panies from Switzerland and across

neutrons and muons to refine their

ther directly or in partnership with

Europe frequently join forces with uni-

understanding of materials found in

university research teams.

versity research teams to combine

commercial NiMH and lithium-ion bat-

their knowledge and expertise with


that of PSI.

Scientists from Hitachi are now able to measure the tiny grains that store data

Universities, industry and PSI

Research projects can range from long

on hard disks and what is taking place

term refinement of procedures for later

physically within each grain.

use in product development, through

Hydrogen storage materials are a popular

When it comes to developing new

to building a systematic understanding

area for researchers. Out of all the ele-

materials or understanding the behav-

of new materials.

ments in the periodic table, hydrogen is


SwissNeutronics is a company founded on expertise developed at PSI. Today it supplies components all over the world. Instruments at SINQ are used by the company for testing and development.

seen best by neutron beams. Nor-

straightforward measurements to solve

way-based SINTEF is the largest inde-

immediate problems.

Spin-off company SwissNeutronics was founded in 1999

pendent research organisation in Scandinavia with an interest in energy

Schaeffler/LuK used neutron imaging

as a PSI spin-off company to commer-

conversion and end use. SINTEF research-

to identify real-time oil distributions in

cialise and exploit knowledge in build-

ers use neutrons to study the uptake of

prototypes for multi-disc clutches and

ing optical components for neutron

hydrogen in materials that could find use

with this knowledge optimise the de-


for bulk storage of hydrogen.

sign to reduce fuel consumption.

The Nestlé Research Centre in Laus-

Alstom make regular use of neutron

The performance of neutron instru-

anne makes regular use of the PSI neu-

scattering to measure the inner stresses

ments depends on the number of neu-

tron facilities for evaluating the poten-

of gas turbine blades made from new

trons arriving at the instrument. This

tial of different innovations that could

alloys or treated in different ways after

can be greatly boosted by installing

be used in manufacturing processes.


special mirrors that efficiently guide

Stihl are working with PSI to reduce

neutrons over long distances from the

emissions from 2-stroke chainsaw en-

source to the instruments.

gines to comply with EU legislation.

Whilst the Swiss Spallation Neutron

Using neutrons, Stihl engineers have

Source SINQ was being built, PSI sci-

Industry users, in many cases, are keen

been able to study the distribution of

entists and engineers built up a deep

to use neutron or muon beams for

fuel and lubricants in an engine run-

understanding of how to make high

ning at 3000 revolutions per minute

quality coatings for neutron supermir-

and understand what changes can be



Today, SwissNeutronics supplies neu-

Solving industry problems

tron optical components to customers

around the world and is considered one of the leading companies in this sector.

Developing new technologies

A future neutron source for Europe

Building new instruments for frontier

Swiss scientists and engineers are

research at a large research centre

using their expertise to help build new

requires careful development and

European science facilities to meet

planning to maximise performance and

future research needs.

meet exacting scientific requirements. The European Spallation Source is a Scientists and engineers at the Swiss

new research centre to be built in Lund

Muon Source SμS have been working

in Sweden. A partnership of 17 coun-

for many years in partnership with com-

tries including Switzerland, it is

panies including Dubna Detectors,

planned to start operating in 2019.

Photonique SA, Hamamatsu Photonics,

Based on technology very similar to the

and Zecotek to develop compact and

Swiss Spallation Neutron Source SINQ,

efficient modern muon detectors. The

staff at PSI are playing a key role in

new detectors can work in very high

developing and testing components for

magnetic fields and be packed closely

the new centre, as well as designing

together. They are now installed on

research instruments together with

several of the muon instruments at PSI,

partner organisations in Denmark.

opening up new areas of research. The technology will be shared with other muon laboratories around the world. 21


Inside the Swiss Muon Source SμS


Using neutrons and muons

Different experimental set-ups are chosen for different experiments because each can give certain types of information. Scientists choose the best instrument for the job. Instruments can be adjusted and adapted to match what is being studied in the experiments.


Everything is made of atoms and atoms

tured by detectors, or cameras, placed

are tiny. A million of them could fit

around the object allowing the loca-

across a piece of dust. At PSI, research-

tions and movements of the atoms to

ers use beams of neutrons and muons

be worked out.

to find out where atoms are and what

Alternatively neutron pictures can be

they are doing.

made. PSI is the world-leader in exploiting this ‘neutron-imaging’ approach to experiments.

What is a neutron?

Neutrons are everywhere. Along with protons and electrons, they make up atoms, the basic building blocks of the natural world. Neutrons are tightly

What is a muon?

bound together with protons in the

They might sound exotic but hundreds

nucleus at the centre of the atom. Set

of muons are raining down on each of

free from the atom, neutrons are a

us every second. Formed by cosmic

valuable tool for materials research.

rays hitting the atmosphere, these elementary particles can also be cre-

At the Swiss Spallation Neutron Source

ated by particle accelerators and used

SINQ, beams of neutrons are made and

for materials research.

used to illuminate samples to discover their microscopic properties.

At the Swiss Muon Source SμS, beams

Neutrons have unique features that

of muons are made and used to illumi-

make them very valuable for research.

nate samples to discover their micro-

They are just the right size to accurately

scopic properties.

measure the distances between atoms

Muons are charged particles that can

in a material, and they can sense how

also behave like a small compass mag-

the atoms are moving and measure the


strength of the forces holding them

When an object is placed in a muon


beam, the muons are implanted at

They also have no electrical charge,

various depths. Electric charges from

allowing them to see deep into the

the atoms inside the material cause

interior of thick objects and not just

muons to stop in the gaps between

look at the surface. Their gentle inter-


action is perfect for examining delicate,

Muons are very sensitive to their local

valuable or rare materials.

environment and can feel weak mag-

They also behave like a tiny compass

netic fields or atomic motion. They spin

magnet, making them ideal for explor-

around at a speed that reflects what

ing magnetism at a microscopic scale.

surrounds them.

In fact, the majority of what is known

By measuring this speed researchers

about microscopic magnetism has

obtain knowledge of the properties of

been learnt through experiments with

surrounding magnetic fields or chemi-

beams of neutrons.

cal environments.

When an object is placed in a neutron beam, the beam passes through and

is scattered by the atoms inside the object. The scattered neutrons are cap25

Making neutrons and muons Making particle beams requires enormous machines blending science with

Making neutrons

engineering. The Swiss Spallation Neu-

Neutrons are released when the proton

tron Source SINQ and Swiss Muon

beam is fired into a target of lead in the

Source SμS are found inside three

neutron target hall. For each proton that

huge buildings on the PSI west site.

strikes, 10 neutrons are released.

A walk inside the huge buildings of the

The proton beam comes up through the

neutron and muon sources is a rare

floor and strikes the lead target which

chance to enter a world that at first

is housed in the middle of the huge

appears chaotic. A maze of walkways

structure in the centre of the hall. The

and walls, cables and cranes, strange

cylinder-shaped target is 50 cm long

and fabulous equipment at every turn,

and 15 cm wide. It is cooled by water to

particle beams traveling along chan-

stop it melting when the proton beam

nels in all directions. But after a little

hits it.

time, the strict logic and order soon

Neutrons are guided to the different

begins to appear.

instruments in the neutron target hall and neutron guide hall inside tubes coated with special mirrors that guide

Accelerating protons

neutrons. There are 18 instruments operating at the

Neutron and muon beams are created

Swiss Spallation Neutron Source SINQ.

at PSI by firing a continuous stream of protons traveling at 80% light-speed

into a sequence of targets made of lead or carbon.

Making muons Protons are sent to the targets by the high intensity proton accelerator. The

Muons are created when the proton

protons are made by splitting apart

beam passes through two carbon tar-

molecules of hydrogen gas.

gets in the experimental hall.

The accelerator, neutron and muon sources work continuously through the

The muons are guided away from the

day and night for more than 220 days

targets by electric and magnetic fields

a year.

and then directed to the different muon

The proton accelerator at PSI delivers


the most powerful proton beam in the

There are 6 instruments operating at


the Swiss Muon Source SμS.


Inside the SINQ neutron target hall. Neutrons are released in the middle of the large blue structure and travel to instruments surrounding it.


Electronics engineer Building hardware to process detector signals

We make it work A large team of people with many different skills keep the PSI facilities working day and night. Meet a few of them:

Crane driver Skillfully moving tonnes of equipment around every day

Radiation protection technician Ensuring a safe working environment for all

Plumber Perfecting pipework carrying cooling water and compressed air

Electrician Installing low voltage cables for control systems, signal and data transfer

Software developer Writing code to squeeze the most out of data

Multi-skilled mechanic Creating precision components for unique scientific equipment Cleaner Cleaning carefully around delicate and expensive equipment 28

Technician Maintaining equipment to keep things colder than outer space

Vacuum engineer Making air-free paths for particle beams

Accelerator physicist Delivering high quality particle beams for experiments

Computer networker Keeping computers and equipment happily communicating

Design engineer Turning instrument ideas into reality Electronics engineer Making cameras and detection systems fast to capture new science

Scientist Designing experiments to make new discoveries


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 the 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 2100 people, thus being the largest research institute in Switzerland.


Imprint Concept/Text Dr. Martyn J. Bull Editing committee Dagmar Baroke, Dr. Martyn J. Bull, Dr. Paul Piwnicki Photography and Graphics All Photos Scanderbeg Sauer Photography except: page 1, 30: Markus Fischer page 6: Frank Reiser page 15: Daniel Berger page 18: graphic by H. M. Rønnow Design and Layout Monika Blétry Printing Paul Scherrer Institut Available from Paul Scherrer Institut Events and Marketing Forschungsstrasse 111 5232 Villigen PSI, Switzerland Tel. +41 56 310 21 11 Villigen PSI, November 2018

Head of Research Division Research with Neutrons and Muons Dr. Alex Amato a.i. Tel. +41 56 310 32 32 Head of the Neutron Scattering and Imaging Laboratory Prof. Dr. Michel Kenzelmann Tel. +41 56 310 53 81 Head of the Muon Spin Spectroscopy Laboratory Dr. Thomas Prokscha a.i. Tel. +41 56 310 42 75 Head of the Neutron and Muon Instrumentation Laboratory Prof. Dr. Marc Janoschek Tel. +41 56 310 49 87 Head of PSI User Office Dr. Stefan Janssen Tel. +41 56 310 28 75 Head Corporate Communications Dr. Mirjam van Daalen Tel. +41 56 310 56 74

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

SINQ/SµS_e, 10/2021