Swiss Light Source
Encyclopedia
Synchrotron
A synchrotron is a particular type of cyclic particle accelerator in which the magnetic field and the electric field are carefully synchronised with the travelling particle beam. The proton synchrotron was originally conceived by Sir Marcus Oliphant...
located at the Paul Scherrer Institute
Paul Scherrer Institute
The Paul Scherrer Institute is a multi-disciplinary research institute which belongs to the Swiss ETH-Komplex covering also the ETH Zurich and EPFL...
in Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
for producing electromagnetic radiation
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
of high brightness
Brightness
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target...
. Planning started in 1991, project was approved in 1997, and first light from the storage ring was seen at December 15, 2000.
The experimental program started in June 2001 and it is used for research in materials science, biology and chemistry.
Main component of the SLS is the 2.4 GeV electron storage ring
Storage ring
A storage ring is a type of circular particle accelerator in which a continuous or pulsed particle beam may be kept circulating for a long period of time, up to many hours. Storage of a particular particle depends upon the mass, energy and usually charge of the particle being stored...
of 288 m circumference:
The ring is formed by 36 dipole magnet
Dipole magnet
A dipole magnet, in particle accelerators, is a magnet constructed to create a homogeneous magnetic field over some distance. Particle motion in that field will be circular in a plane perpendicular to the field and collinear to the direction of particle motion and free in the direction orthogonal...
s of 1.4 tesla magnetic field, combined in 12 groups of three (triple bend achromat, TBA) for achromatic deflection of the electron beam. 12 straight sections between the TBAs of different lengths (3×11.5 m, 3×7 m, 6×4 m) accommodate the undulator
Undulator
An undulator is an insertion device from high-energy physics and usually part of a largerinstallation, a synchrotron storage ring. It consists of a periodic structure of dipole magnets . The static magnetic field is alternating along the length of the undulator with a wavelength \lambda_u...
magnets to generate ultraviolet and X-ray light of extreme brightness
Brightness
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target...
. 3 of the dipoles have an increased center field of 3 teslas to produce hard X-rays.
A total of 177 quadrupole magnet
Quadrupole magnet
Quadrupole magnets consist of groups of four magnets laid out so that in the multipole expansion of the field the dipole terms cancel and where the lowest significant terms in the field equations are quadrupole. Quadrupole magnets are useful as they create a magnetic field whose magnitude grows...
s (magnetic lenses) focusses the beam to provide an emittance of 5.5 nm rad.
120 sextupole magnet
Sextupole magnet
Sextupole magnets consist of groups of six magnets set out in an arrangement of alternating north and south magnetic poles arranged around an axis. They are used in particle beam control in particle accelerators....
s correct the chromatic focusing errors of the quadrupoles. 73 horizontal and vertical beam steerers are used to continuously correct the position of the electron beam. Finally 24 skew quadrupole magnets are adjusted to correct any torsion of the beam and to minimize the vertical emittance: a world record low value of 3 pm rad has been
achieved in 2008.
The SLS has achieved a photon beam stability of 1 micrometre: the ring is operated in top-up mode, i.e. the stored current of 400 mA is kept constant to 1 mA by frequent (1–2 minutes) injections. This maintains a constant thermal load from synchrotron radiation. A fast orbit feedback system controlling the 73 beam position monitors and the 73 horizontal and vertical steeres corrects the position of the electron beam 100 times per second to suppress any distortions from ground vibrations etc. Beam distortions from changing the undulator status as done during experiments are minimized by application of a set of feed forward corrections measured once for the undulators, the orbit feedback takes care of the rest. Finally X-ray beam position monitors measuring the location of the synchrotron radiation itself perform the final adjustment in front of the experiment.
SLS has a booster synchrotron
Synchrotron
A synchrotron is a particular type of cyclic particle accelerator in which the magnetic field and the electric field are carefully synchronised with the travelling particle beam. The proton synchrotron was originally conceived by Sir Marcus Oliphant...
optimized for top-up operation: it provides a low emittance of 10 nm rad for efficient beam injection into the storage ring, and it has a low average power consumption of 30 kW. This is achieved by a large circumference of 270 m, a large number (93) of small dipole
Dipole
In physics, there are several kinds of dipoles:*An electric dipole is a separation of positive and negative charges. The simplest example of this is a pair of electric charges of equal magnitude but opposite sign, separated by some distance. A permanent electric dipole is called an electret.*A...
magnets and a low aperture of only 30x20mm. The booster accelerates the beam from 100 MeV to 2.4 GeV (optional 2.7 GeV) at a repetition time of 320 ms. A 100 MeV linear accelerator as pre-injector completes the facility.
In 2006 the SLS-FEMTO facility came into operation: By interaction of a high energy (4 mJ), short pulse (50 fs fwhm) laser pulse with the electron beam in a wiggler
Wiggler (synchrotron)
A wiggler is an insertion device in a synchrotron. It is a series of magnets designed to periodically laterally deflect a beam of charged particles inside a storage ring of a synchrotron...
magnet, a thin slice of the electron beam is modulated in energy. A magnetic chicane bracketing the wiggler
Wiggler (synchrotron)
A wiggler is an insertion device in a synchrotron. It is a series of magnets designed to periodically laterally deflect a beam of charged particles inside a storage ring of a synchrotron...
and creating dispersion translates this energy modulation into a horizontal separation of the slices from the core beam. So radiation from the slices in a subsequent undulator can be separated by a system of apertures. In this way X-ray pulses of 140 fs length (fwhm) and a tunable photon energy of 3-18 keV can be generated.
(This installation caused a major change of the storage ring resulting in the odd numbers of 177 quadrupoles and 73 steeres.)
As of June 2009 SLS has eighteen experimental stations (undulator
Undulator
An undulator is an insertion device from high-energy physics and usually part of a largerinstallation, a synchrotron storage ring. It consists of a periodic structure of dipole magnets . The static magnetic field is alternating along the length of the undulator with a wavelength \lambda_u...
s and bending magnets) and seventeen operational beamlines.
There are three protein crystallography
X-ray crystallography
X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a...
beam-lines, two of which are partially funded by associations of Swiss pharmaceutical companies including Novartis
Novartis
Novartis International AG is a multinational pharmaceutical company based in Basel, Switzerland, ranking number three in sales among the world-wide industry...
, Roche, Actelion
Actelion
Actelion was founded in December 1997 and is headquartered in Allschwil near Basel . Its CEO and co-founder is cardiologist Jean-Paul Clozel. Actelion scientists were among the first to work in the field of endothelian receptor antagonists...
, Boehringer Ingelheim and Proteros.