Large Research Facilities
probesthat are needed to examine matter in such a way that the information being sought can be obtained. PSI maintains a number of such facilities, making them available as a service for other institutions, but also using them for its own research. These facilities are unique within Switzerland, and PSI is the only location in the world for some of the facilities
Read more at: Large Research Facilities
The years of careful planning and construction have paid off: At the newest large-scale research facility of the Paul Scherrer Institute PSI – the X-ray free-electron laser SwissFEL – the first experiment has been carried out successfully. With that, two goals have been achieved: First, a new scientific result is already expected. Second, the interaction of the many individual components of the highly complex facility is being optimised.
An X-ray free-electron laser (XFEL) is capable of visualizing extremely fast structural and electronic processes. Pilot experiments will take place at the PSI's Swiss Free-Electron Laser (SwissFEL) from the end of 2017 on. Two current publications in Science and Nature Communications demonstrate the kind of outstanding scientific work that is enabled by such facilities. The work was carried out at the Linac Coherent Light Source (LCLS) in California. Two of the leading authors behind these studies have now relocated to the PSI in order to share their expertise as SwissFEL expands its capabilities.
As fundamental building blocks of matter, protons are part of all the things that surround us. At the Paul Scherrer Institute PSI, though, they step out of their usual role and are deployed to generate other particles, namely neutrons and muons, which are then used to study materials. But for that, the protons first have to be accelerated. An important role in this is played by a three-stage accelerator facility, in the middle of which stands the accelerator known as
The company Daetwyler made the undulators for the X-ray free-electron laser SwissFEL of the Paul Scherrer Institute PSI, to a precision of one-tenth of the width of a hair.
Whether they study materials for the electronics of the future, batteries, or swords from the Bronze Age — for 20 years researchers from a range of disciplines have been using the Swiss Spallation Neutron Source SINQ of the Paul Scherrer Institute PSI for their investigations. At a symposium on 18 April, researchers looked back on the facility's successes and presented plans for modernisation.
This year the first pilot experiments are starting at the X-ray free-electron laser SwissFEL. The X-ray light generated by SwissFEL will enable a broad spectrum of experiments. Beginning in 2020, a second beamline will provide for a still greater variety.
Today, on 5 December 2016, the Paul Scherrer Institute PSI held an inauguration ceremony for its new large-scale research facility SwissFEL, with Johann N. Schneider-Ammann, President of the Swiss Confederation, in attendance.
Physicists at the PSI’s large-scale research facilities are thinking beyond the Nobel Prize theoriesMiscellaneous Large Research Facilities Materials Research Matter and Material
This year’s Nobel Prize for Physics goes to David Thouless, Duncan Haldane, and Michael Kosterlitz. The Academy also cited, in its background report, experiments carried out by Michel Kenzelmann, who today is a laboratory head at the PSI. He and other researchers at the PSI continue to do experiments based on the theories now honoured by the Nobel Prize.
SwissFEL building, 24 August 2016: In the control room above the beam tunnel of the X-ray free-electron laser SwissFEL, the atmosphere is intense and focussed. Marco Pedrozzi’s team has big plans for this late August afternoon. The last adjustments have been made — it’s time to press the big button and start up the electron source. The goal: SwissFEL should generate its first electrons. A report.
Proteins are indispensable building blocks of life. They play a vital role in many biological processes. Researchers have now been able to show how the ultrafast processes by which proteins do their work can be studied with free-electron X-ray lasers such as SwissFEL at the Paul Scherrer Institute PSI. Free-electron X-ray lasers generate extremely short and intense pulses of X-ray light. Currently there are just two such facilities in operation, worldwide. The results were published in the scientific journal Nature Communications.
Interview with Oksana Zaharko
New scientific questions demand ever better experimental equipment. In this interview, PSI researcher Oksana Zaharko reports on the challenges of setting up a new instrument for research with neutrons.
9. March 2016Media Releases Large Research Facilities Research Using Muons Particle Physics
Measuring the rarity of a particle decay
In the so-called MEG experiment at the PSI, researchers are searching for an extremely rare decay signature from a certain kind of elementary particles known as muons. More precisely, they are quantifying its improbability. According to their latest number, this decay occurs less than once in 2.4 trillion events. By means of this result, theoretical physicists can sort out which of their approaches to describing the universe will hold up against reality.
24. February 2016SwissFEL Large Research Facilities
With SwissFEL, a new landscape takes shape
Barely completed, the building housing the X-ray free-electron laser SwissFEL has disappeared again beneath a mound of earth. Since then, planting and landscaping have been under way on and around this major research facility of the Paul Scherrer Institute PSI. Its special location, in a forest, demands that SwissFEL be integrated in an environmentally appropriate way. So the facility is, from the outside, nearly invisible. And rare animals and plants have gained new living space.
21. December 2015Large Research Facilities SwissFEL
Since the autumn of 2015, the SwissFEL beam tunnel has been filling up with the machine components for the new PSI large research facility. Piece by piece, the pre-assembled components are being brought to their final destination.
29. October 2015Matter and Material Research Using Synchrotron Light Large Research Facilities
At first glance, the Swiss Light Source SLS stands out as a striking building. The inside reveals a setting of cutting-edge research. A journey through a world where electrons race a slalom course and X-rays help decode proteins.
26. October 2015Media Releases Large Research Facilities Matter and Material Materials Research SwissFEL
Researchers from the Paul Scherrer Institute PSI have succeeded in using commercially available camera technology to visualise terahertz light. In doing so, they are enabling a low-cost alternative to the procedure available to date, whilst simultaneously increasing the comparative image resolution by a factor of 25. The special properties of terahertz light make it potentially advantageous for many applications. At PSI, it will be used for the experiments on the X-ray free-electron laser SwissFEL.
30. September 2015SwissFEL Large Research Facilities Large Research Facilities
Interview with Luc Patthey
Luc Patthey is in charge of designing and implementing the beamlines for the X-ray free-electron laser SwissFEL. In this Interview, he explains the requirements the beamlines need to meet for the X-ray light pulses generated by SwissFEL to reach the experiments in an optimal form and what role collaborations play in the development of beamlines.
26. May 2015Research Using Synchrotron Light Large Research Facilities SwissFEL Human Health
Decoding biomolecules at SwissFEL and SLS
Proteins are a coveted but stubborn research object. A method developed for x-ray free-electron lasers and PSI’s future SwissFEL should now help researchers to make good headway in this field. It involves x-raying many small, identical protein samples consecutively at short intervals, thereby avoiding the main problem that protein research has faced thus far: producing samples in a sufficient size.
22. May 2015SwissFEL Large Research Facilities
The first undulator frames have arrived at the SwissFEL building. They will take around six months to assemble, after which the finished undulators will be taken to the SwissFEL accelerator tunnel for installation.
21. May 2015Research Using Synchrotron Light Large Research Facilities
Tiny cavities inside eggshells supply the materials that stimulate and control the shell’s growth. Using a novel imaging technique, researchers from the Paul Scherrer Institute (PSI), ETH Zurich and the Dutch FOM Institute AMOLF have succeeded in depicting these voids in 3D for the first time. In doing so, they lift an old limitation of tomographic images and hope that one day medicine will also benefit from their method.
13. May 2015Research Using Synchrotron Light Large Research Facilities Materials Research Micro- and Nanotechnology SwissFEL
Interview with Gabriel Aeppli
Gabriel Aeppli has been head of synchrotron radiation and nanotechnology research at PSI since 2014. Previously, the Swiss-born scientist set up a leading research centre for nanotechnology in London. In this interview, Aeppli explains how the research approaches of the future can be implemented at PSI's large research facilities and talks about his view of Switzerland.
24. March 2015Large Research Facilities SwissFEL Micro- and Nanotechnology
SwissFEL, PSI’s x-ray laser, is to render the individual steps of very rapid processes visible. A new method will facilitate especially precise experiments: the individual x-ray flashes are split into several parts that arrive at the object under examination one by one. The principle of the method harks back to the ideas of the earliest high-speed photography.
17. February 2015SwissFEL Large Research Facilities
For many years, PSI researchers have been testing experimental methods that will provide insights into novel materials for electronic devices. Using a special trick to make the Swiss Light Source (SLS) at PSI generate light with similar properties to that of PSI’s x-ray laser SwissFEL, the researchers were able to demonstrate that the experiments planned for SwissFEL are possible and they are now building an experimental station at SwissFEL.
20. November 2014SwissFEL Large Research Facilities
Researchers from PSI have spent the last four years developing key technologies for the X-ray laser SwissFEL and subjecting them to the acid test in the injector test facility. Now that the development programme has drawn to a close, the installation of the new large research facility is due to get underway in early 2015.
14. October 2014SwissFEL Large Research Facilities
The building of the new PSI large research facility SwissFEL in Würenlingen forest could only enjoy the sunshine for a brief spell: it is now disappearing under a mound of earth. This superstructure is one of the measures taken to integrate the facility as harmoniously as possible into the natural environment.
9. October 2014Large Research Facilities Research Using Neutrons
Today, several hundred members of the European scientific community gathered at the European Spallation Source (ESS) construction site in Lund, Sweden, for the ESS Foundation Stone Ceremony. The event was held to ‘lay the foundation’ both for the new facility, which has recently begun construction, and for a new generation of science in Europe.
25. September 2014Large Research Facilities
Magnets are the unsung heroes in particle accelerators because they keep protons or electrons on track. But such magnets have very little in common with the small ones on the domestic fridge door. Quite a few of the magnets at PSI are heavier and bulkier than the fridge itself, yet despite this they are also masterpieces of precision and control.
23. September 2014Large Research Facilities
The source of the proton beam at PSI is a retro-style Cockcroft-Walton linear accelerator. Since 1984 it has been the first acceleration stage for protons which are taken up to around 80 percent of the speed of light by two further ring accelerators. This has resulted in the generation of a significant proton beam over decades, and which has even held the world record as the highest performing beam since 1994 thanks to ongoing retrofitting.
4. September 2014Media Releases Research Using Synchrotron Light Large Research Facilities Materials Research Matter and Material SwissFEL
PSI researchers garner experience for SwissFEL experiments
Aided by short laser flashes, researchers at the Paul Scherrer Institute have managed to temporarily change a material’s properties to such a degree that they have – to a certain extent –created a new material. This was done using the x-ray laser
LCLSin California. Once the PSI x-ray laser SwissFEL is up and running, experiments of this kind will also be possible at PSI.
25. June 2014SwissFEL Large Research Facilities
Vergangenen Sonntag luden das Paul Scherrer Institut PSI und die Arbeitsgemeinschaft EquiFEL Suisse die Einwohnerinnen und Einwohner der Umgebung zum Tag der offenen SwissFEL-Baustelle ein. Rund 600 Interessierte informierten sich an mehreren Stationen über den aktuellen Bau- und Projektstand.
This news release is only available in German.
26. May 2014Media Releases Biology Research Using Neutrons Large Research Facilities
The way that algae and plants respond to light has been reinterpreted based on results from recent experiments. Under particular lighting conditions during photosynthesis, the well-ordered stacking and alignment of light-sensitive membranes in the algae are disrupted. There is no significant movement of the membrane embedded light harvesting proteins, which rather become largely inactive. These new findings challenge widely accepted views of how algae respond to light where the light harvesting proteins were thought to move around the membranes.
21. May 2014SwissFEL Large Research Facilities
For the electrons to reach the necessary energy level, their path in the linear accelerator needs to be absolutely straight. Even the slightest bend means a loss of energy, which the comparatively short SwissFEL linear accelerator cannot afford. Consequently, even the earth’s curvature needs to be balanced out while constructing the building, which not only requires state-of-the-art measurement technology, but also continuous monitoring.
6. April 2014Media Releases Research Using Neutrons Large Research Facilities
Changes to the aggregate state triggered by quantum effects – in physically correct terms, quantum phase transitions – play a role in many astonishing phenomena in solids, such as high-temperature superconductivity. Researchers from Switzerland, Great Britain, France and China have now specifically altered the magnetic structure of the material TlCuCl3 by exposing it to external pressure and varying this pressure. With the aid of neutrons, they were able to observe what happens during a quantum phase transition, where the magnetic structure melts quantum-physically.
6. March 2014Media Releases Large Research Facilities Research Using Synchrotron Light Materials Research Matter and Material SwissFEL
Researchers from ETH Zurich and the Paul Scherrer Institute PSI demonstrate how the magnetic structure can be altered quickly in novel materials. The effect could be used in efficient hard drives of the future.
24. February 2014Media Releases Large Research Facilities Research Using Muons Research Using Neutrons Particle Physics Matter and Material
Materials research, particle physics, molecular biology, archaeology – for the last forty years, the Paul Scherrer Institute’s large-scale proton accelerator has made top-flight research possible in a number of different fields.
14. February 2014Large Research Facilities SwissFEL
Preventing SwissFEL electrons from going astray
Cost-effective and with a minimal error rate –PSI-engineers from the power electronics section have set ambitious goals for the SwissFEL magnet power supplies.
28. January 2014SwissFEL Large Research Facilities
The construction work in the woods is well underway: the building for SwissFEL, the Paul Scherrer Institute’s new large research facility, is due for completion by the end of 2014. The demands on the building are high: It needs to ensure that the sensitive equipment can run smoothly.
8. November 2013Large Research Facilities SwissFEL
SwissFEL will create X-ray light with laser-like characteristics. The strong amplification of the light needed is produced by a process known as
micro-bunching– electron packets break up in the undulator into thin layers which emit light in phase. At the same time, another process called
seedingis being studied, in which one will be able to establish the properties of the light even more precisely.
15. August 2013Large Research Facilities SwissFEL
X-ray light is produced in SwissFEL when electrons accelerated in its linear accelerator are forced to follow a wavy path. This takes place within the undulators – regular arrangements of magnets that bend the electron beam. The whole undulator section will be 60 metres long.
11. August 2013Media Releases Matter and Material Materials Research Large Research Facilities SwissFEL
A terahertz laser developed at the Paul Scherrer Institute makes it possible to control a material’s magnetisation precisely at a timescale of picoseconds. In their experiment, the researchers shone extremely short light pulses from the laser onto a magnetic material. The light pulse’s magnetic field was able to deflect the magnetic moments from their idle state in such a way that they exactly followed the change of the laser’s magnetic field with only a minor delay. The terahertz laser used in the experiment is one of the strongest of its kind in the world.
31. July 2013Large Research Facilities SwissFEL
In the linear accelerator, the electron beam receives the kinetic energy it needs in order to generate X-ray light. The linear accelerator is, in total, more than 300 metres long and at its heart there are 11,752 specially shaped copper discs in which the accelerating field is created.
26. July 2013Large Research Facilities SwissFEL
The electron beam for SwissFEL will be generated in an electron source. The demands of this component are very high: in order for the SwissFEL to be operated successfully, the electron beam must be of the highest quality from the very beginning.
18. July 2013SwissFEL Large Research Facilities
At the PSI, the first accelerator structure has been completed for the linear accelerator of SwissFEL. A total of 104 of these structures are needed to accelerate the electrons to the required energy to produce the X-ray pulses in SwissFEL. The component manufactured using high-precision technology is currently undergoing high-performance testing.
11. July 2013Energy and Environment Research Using Neutrons Nuclear Power Plant Safety Large Research Facilities
The manipulation and examination of irradiated and therefore radioactive objects, be they from nuclear power stations or research facilities, requires strict safety measures. Tests may only be conducted in so-called “hot cells”, where the radioactivity is hermetically enclosed and shielded behind concrete and lead walls up to 1 metre thick. In the hot cells of the PSI hot lab, the burnt-off fuel rods from the Swiss nuclear power stations are studied from a materials science perspective. The insights gained help nuclear power station operators to optimise the efficiency and safety of their plants. Besides this service, the hot lab is involved in several international research projects.
3. July 2013Media Releases Large Research Facilities SwissFEL
At the ceremony on 3 July 2013, not only did the PSI lay the corner stone for the new large research facility SwissFEL, but it also paved the way for the continuation of twenty-five years of successful research at the institute.
17. May 2013Matter and Material Large Research Facilities Research Using Muons
Muons – unstable elementary particles – provide scientists with important insights into the structure of matter. They provide information about processes in modern materials, about the properties of elementary particles and the nature of our physical world. Many muon experiments are only possible at the Paul Scherrer Institute because of the unique intense muon beams available here.
7. May 2013SwissFEL Large Research Facilities
The X-ray laser SwissFEL will provide researchers with novel experimental opportunities for gaining insights into a large variety of materials and processes. But, how do we identify which scientists will benefit most from the facility and in what way the facility should be configured to best meet their needs? Bruce Patterson, the SwissFEL’s idea-collector, explains how this search is done.
30. April 2013SwissFEL Large Research Facilities
Durch die Bauarbeiten für den SwissFEL kommt es im Würenlinger Wald zu Sperrungen und Umleitungen. Alternativ-Routen für Velofahrer und Fussgänger werden angeboten.
This news release is only available in German.
25. April 2013SwissFEL Large Research Facilities
Construction work for SwissFEL has now started in the Würenlingen forest, and the building for this new Large Research Facility for the Paul Scherrer Institute PSI will be erected during the next year and a half.
24. April 2013Large Research Facilities SwissFEL Materials Research
Materials with special magnetic properties play an important role in modern technologies – for example, in the hard disc drives used to store data on a computer. Research at SwissFEL will help us to develop new magnetic materials, and to observe the fast processes in these materials as they happen. Thus, we will be able to see exactly what happens inside a hard disc when its data content is modified.
8. April 2013Media Releases Large Research Facilities SwissFEL Matter and Material
Prominent among the planned applications of X-ray free electron laser facilities, such as the future SwissFEL at the Paul Scherrer Institute, PSI, are structural studies of complex nano-particles, down to the scale of individual bio-molecules. A major challenge for such investigations is the mathematical reconstruction of the particle form from the measured scattering data. Researchers at PSI have now demonstrated an optimized mathematical procedure for treating such data, which yields a dramatically improved single-particle structural resolution. The procedure was successfully tested at the Swiss Light Source synchrotron at PSI.
28. February 2013SwissFEL Large Research Facilities
The completion of all required approvals gives a green light for the construction of SwissFEL, the new large research facility at the Paul Scherrer Institute PSI.
22. February 2013Large Research Facilities SwissFEL
Experiments at SwissFEL will help us understand important processes in living organisms. They will reveal how vital biomolecules, whose structures cannot be determined using current techniques – are constructed. They will also reveal how the shapes of these molecules change. This knowledge will help us understand disease processes and to develop the drugs needed to treat them.
22. February 2013Media Releases SwissFEL Large Research Facilities
A new Large Research Facility, SwissFEL, is to be built in the Würenlingen forest, very close to the Paul Scherrer Institute (PSI). On Friday, February 22, 2013, the building permit was signed with the Citizens’ Commune of Würenlingen.
29. January 2013Large Research Facilities SwissFEL
Inside the SwissFEL, electrons will be accelerated to almost the speed of light, then forced along a curved pathway by very powerful magnets, emitting X-ray light as they travel. SwissFEL is thus composed of an ‘electron gun’ (which generates the electron beam), an accelerator, and an undulator in which the electrons are guided along a wave-like path. An experimental area lies at the end of this track, where the light produced will be used to perform experiments.
25. January 2013Media Releases Particle Physics Research Using Muons Large Research Facilities Matter and Material
An international team of scientists confirmed the surprisingly small value of the proton radius with laser spectroscopy of exotic hydrogen. The experiments were carried out at PSI which is the only research institute in the world providing the necessary amount of muons for the production of the exotic hydrogen atoms made up of a muon and a proton.
17. January 2013Large Research Facilities SwissFEL
SwissFEL will generate very short pulses of intense X-ray light with laser-like properties, and will therefore provide new insights into a wide variety of materials. The properties of this special "SwissFEL light" will broaden the scope of experiments that can be carried out at this facility.
10. January 2013Large Research Facilities SwissFEL
Experiments at SwissFEL will help us understand in detail how one substance is transformed into another during a chemical reaction. Highest priority will be given to catalytic reactions, as these have numerous industrial applications. This research will point the way towards more energy-efficient industrial processes and environmentally-friendly energy carriers.
11. July 2012Media Releases Large Research Facilities SwissFEL Micro- and Nanotechnology
X-ray lasers are modern light sources from which scientists expect to obtain new knowledge about the structure and function of materials at the atomic level. The scientific value of an X-ray laser stands or falls on the quality of the ultra-short X-ray pulses it produces and which researchers use to illuminate their samples. An international team led by scientists from the Paul Scherer Institute, PSI, has now precisely measured these pulses
23. January 2012Media Releases Large Research Facilities Matter and Material SwissFEL Materials Research
In first-of-their-kind experiments performed at the American X-ray laser LCLS, a collaboration led by researchers from the Paul Scherrer Institute has been able to precisely follow how the magnetic structure of a material changes. The change of structure was initiated by a laser pulse, and investigated with the help of short X-ray pulses. It appears as if the structure begins to change 400 femtoseconds after the laser pulse strikes. Such investigations will be a major focus of research at the planned Swiss X-ray Laser, SwissFEL, at PSI.
7. September 2011Media Releases Large Research Facilities SwissFEL Micro- and Nanotechnology
Einem vom PSI geleiteten Forscherteam ist es gelungen, harte Röntgenlaserstrahlung 100'000-fach zu konzentrieren und so an einem Punkt Röntgenstrahlung zu erzeugen, die so intensiv war wie wohl nirgends zuvor. Als Linsen verwendeten die Forscher winzige Ringstrukturen aus Diamant – dem Material, das am besten dem Röntgenlaserlicht standhält. Diese Entwicklung schafft die Voraussetzung für einen Teil der Experimente am SwissFEL, dem geplanten Röntgenlaser des PSI.
This news release is only available in German.
1. December 2009Research Using Muons Matter and Material Large Research Facilities
Along its path, the beam first strikes one target, then the second, and then moves on to the lead target of the SINQ neutron source. Muons are generated by the collisions of protons with the carbon nuclei in the first two targets. PSI operates two muon targets because a single one could not supply enough muons for all the experiments being performed. The muons are guided with the aid of magnets to the individual measuring stations, of which there are currently six for experiments in solid-state physics using muons.
1. December 2009Matter and Material Research Using Synchrotron Light Large Research Facilities
The synchrotron light in the SLS is emitted from electrons, which move at a velocity of almost the speed of light along a circular path with an overall circumference of 288 metres. The synchrotron light is emitted tangentially to the trajectory of the electrons, i.e. in the same direction as sparks would fly from a grindstone, or a hammer from the hands of a hammer thrower.
The production of synchrotron radiation makes use of the fact that electrically charged particles emit light as they move along a curved path. Bending magnets keep the electrons on their curved track, as a magnetic field deflects fast-moving electrically-charged particles.
1. December 2009Matter and Material Research Using Neutrons Large Research Facilities
In the SINQ spallation source a beam of fast protons (at about 80 % of the speed of light) from the PSI proton accelerator facility strikes a block of lead (the Target). If a fast proton collides with a lead nucleus, the nucleus will be heated up and eject 10 to 20 neutrons. The neutrons set free by this method are extremely fast – much too fast for the experiments. In order to decelerate the neutrons after they have been generated, the whole target is placed in a tank filled with heavy water
1. December 2009Matter and Material Research Using Synchrotron Light Research Using Neutrons Research Using Muons Large Research Facilities Particle Physics
The neutrons and muons used for experiments at PSI are all produced by a beam of fast protons colliding with a target – made of lead in the case of the SINQ neutron source and of carbon in the case of the SμS muon source. For that purpose, the protons are accelerated to 80% of the speed of light at PSI's accelerator facility. The facility has been in operation since 1974. After numerous improvements, it provides the most intense proton beam in the world.
1. December 2009Matter and Material Research Using Synchrotron Light Research Using Muons Research Using Neutrons Large Research Facilities Particle Physics
Neutrons, synchrotron light and muons are very useful for researchers in a variety of disciplines. Using these
probes, we can determine the structure of crystals, they help us understand magnetic processes, or they can reveal the structures of biological materials. However, producing these probes is so difficult that most research groups will not have a neutron, muon or synchrotron light at their own scientific centre.
12. November 2009Media Releases Research Using Synchrotron Light Large Research Facilities Matter and Material Materials Research
Ein neues Mikroskop an der Synchrotron Lichtquelle Schweiz SLS des Paul Scherrer Instituts wird es möglich machen, den Aufbau von Materialien mit bisher unerreichter Auflösung darzustellen. Dazu werden Forschende einzelne Bereiche in einem Material betrachten, die nur wenige Nanometer (millionstel Millimeter) gross sind, und für jeden dieser Bereiche bestimmen, welche chemischen Elemente darin enthalten sind.
This news release is only available in German.
25. September 2007Media Releases Large Research Facilities Medical Science Human Health
A pioneer in proton therapy for the treatment of cancer, PSI has recently introduced one of the most advanced technologies in the field. A new proton accelerator, a superconducting cyclotron, has been put into operation for patient treatment. The accelerator is used in conjunction with a gantry, a device which delivers the protons to the patient from any angle. The desired dose distribution is achieved by scanning a small pencil beam of protons throughout the tumor. The performance of the new accelerator has been excellent since the start of medical operation.