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Paul Scherrer Institute

The Paul Scherrer Institute (PSI) is a multi-disciplinary research institute which belongs to the Swiss ETH-Komplex covering also the ETH Zurich and EPFL. It was established in 1988 by merging in 1960 established EIR (Eidgenössisches Institut für Reaktorforschung = Federal Institure for Reactor Research) and in 1968 established SIN (Schweizerisches Institut für Nuklearphysik = Swiss Institute for Nuclear Physics).

The PSI is a multi-disciplinary research centre for natural sciences and technology. In national and international collaboration with universities, other research institutes and industry, PSI is active in solid state physics, materials sciences, elementary particle physics, life sciences, nuclear and non-nuclear energy research, and energy-related ecology.

It is the largest Swiss national research institute with about 1,250 (year 2006) members of staff, and is the only one of its kind in Switzerland.

PSI is a User Laboratory and runs several Particle accelerators. The 590MeV Cyclotron, with its 72MeV companion pre-accelerator, is one of them. At present (2006), it delivers up to 2mA proton beam, which is the world record for such proton cyclotrons. It drives the Spallation-neutron-source complex. The latest built (in 2001) is the Synchrotron Light Source (SLS), with a 2.4GeV electron Storage-ring. It is one of the world's best in electron beam brilliance and stability.

The proton accelerators are also used for the proton therapy program.


Research fields

Proton accelerators


Type: Cyclotron
Magnet: H-Form
Magnet mass: 500t
Poll-plates Radius: 125cm
Poll=plates Distance: 20cm
Vakuumchamber Volume: 20m³
Energy: Variable

Injector 1 is a variable energy cyclotron built by the Dutch company Philips Gloeilampen-Fabrieken. Its one-piece magnet has an azimuthally varying magnetic field for vertical focusing even at relativistic energies. The beam energy goes up to 72 MeV for protons and 120 MeV Z2/A for ions with charge Z and mass number A. Equipped with several ion sources, Injector 1 offers a wide variety of beams ranging from protons and deuterons to light and heavy ions. Polarized beams of protons and deuterons are also available. In 1994 an ECR ion source was installed to extend its ability to accelerate heavy ions.

At present (2004) it is used mainly for low-energy experiments, OPTIS eye tumor therapy, and for the LiSoR experiment in the scope of the future Megapie project.


Type: Isochronous-Cyclotron
Magnets: 4
Total Magnet mass: 760t
Accelerating elements: 4 Resonators (50 MHz)
Energy: 72MeV

The Injector 2 cyclotron has been built to replace the multiparticle variable energy Injector 1. It provides high intensity, high quality beams of 72 MeV protons to be injected into the 590 MeV Ring cyclotron.

The Injector 2 is itself a ring cyclotron, but with 4 sectormagnets and with an extremely low injection energy of 870 keV. The 870 keV beam comes from the Cockcroft-Walton Pre-Injector.

It was put in operation in 1984.


PSI Ring Cyclotron
Type: Isochronous-Cyclotron
Magnets: 8
Total Magnet mass: 2000t
Accelerating elements: 4 (5) Cavities (50 MHz)
Energy: 590MeV

The Ring Cyclotron is a separated sector cyclotron with a fixed beam energy of 590 MeV, built by PSI and commissioned in 1974. The 72 MeV beam from either one of two injector cyclotron enters from the back of the cyclotron, is injected into an orbit in the center of the Ring, accelerated over about 220 revolutions and extracted at the full energy.

The design is based on criteria that allow operation at very high beam intensities: an open structure of four large and powerful RF-cavities providing a high acceleration voltage, and a flat-top cavity operating at the third harmonic of the accelerating RF-voltage. The resulting strong, phase-independent energy gain per revolution gives good turn separation and hence beam extraction with low beam losses. This is a mandatory condition for high current operation in a cyclotron.

Spallation Neutron Source (SINQ)

Synchrotron Light Source (SLS)

Proton Therapy Program

Since 1984 PSI operates the OPTIS facility for treatment of eye tumours. It was the first such installation in Western Europe, developed by PSI physisists. In close cooperation with the 'Hôpital Opthalmique' of the University of Lausanne by middle of 2007 more than 4700 patients have been treated at PSI with this unique method, in which a proton beam is directed accurately onto the eye tumour.

Since 1996 PSI operates also the first and only compact scanning-Gantry worldwide for proton radiation therapy of deep-seated tumours. The spot-scanning technique developed at PSI enables malignant tumours to be targeted with high precision deep inside in the body, and their growth successfully stopped, without damaging healthy tissue around the target area. By middle of 2007 280 patients have been treated at the Gantry, suffering from brain, head and neck, skull-base, spinal cord or abdominal tumours.

The excellent and promising results of patient treatment have led to the (Project Proscan) with the objectives to install a dedicated and compact superconducting proton accelerator and to develop a new Gantry (Gantry 2) with advanced 2-dimensional and fast parallel scanning features. The new compact superconducting cyclotron is in operation since February 2007. The Gantry 2 is under construction and first beam to the isocenter ist planned for end od 2007. Patient treatment at Gantry 2 will start end of 2008.

The goals of these developments are to increase radiation precision of even moving tumours and to transfer the knowledge and proton therapy technology into hospital-based projects.

With the expansion of the facility, PSI will be able to strengthen the clinical research program and to treat up to 500 patients per year, including those with eye tumours.

See also

Swiss federal institutes of technology and research

Budget 2008 (CHF mil.)

ETH Institutes


Institutes of technology

  • ETH Zurich
  • EPF Lausanne


Research institutes

  • PSI
  • EMPA
  • WSL


Coordinates: 47°32′10″N, 8°13′22″E

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Paul_Scherrer_Institute". A list of authors is available in Wikipedia.
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