The ALBA accelerators rely on electromagnets to guide and focus the electrons along the trajectory.

 Under the influence of magnetic fields, electrons follow the Lorentz force:

 At ALBA four different types of magnets are in use: 

  • Dipole magnets - these are typical construction electromagnets with an iron yoke, in a C-form or H-from and two coils wound around the yoke. Dipole magnets are used to deflect the electrons in the transfer lines and also to provide orbit correction.
  • Quadrupole magnets - as the name indicates, these have four magnetic poles and therefore 4 coils. The magnetic field created by a quadrupole increases linearly with the distance from the center. Quadrupoles are used to focus the electrons and enable the transport of an electron beam over long distances, like for example, an electron beam circulating inside the ALBA storage ring.
  • Combined function magnets - are a combination of a dipole magnet and a quadrupole magnet (see the sketch bellow). They are used both in the booster and in the storage ring and fulfil two functions at the same time: on one side, they are responsible for the electrons completing the 360º of circumference around both circular accelerators, and on the other side, they provide additional focusing. By the use of combined magnets, space has been saved inside the accelerators. This space has been used to increase the length available to insertion devices.
  • Sextupole magnets - have six poles as its name indicates and are used to provide additional focusing. The magnetic field increases quadratically with the distance from the center.

  Dipole magnet             Quadrupole magnet              Sextupole magnet              Combined Function Magnet
 Dipole magnet                                              Quadrupole magnet                                     Sextupole magnet                                        Combined function magnet


Main parameters for the magnets used at ALBA. Note the different units on the magnetic field are indicating the different type of field produced.

 Type of magnets Number of magnets   Maximum field  
Dipoles 268 1.40 T
Quadrupoles 188 22 T/m
Combined function 72 1.40 T & 5.5 T/m
Sextupoles 136 650 T/m2


Construction details

The iron yoke of the magnets is made of steel laminations (0.5 to 1 mm thick), which have been stamped with the right pole profile, glued together and then assembled onto the yoke. The precision of the stamping reaches +/- 15 um. For the combined function magnets of the storage ring an additional machining of the poles has been performed.

The coils have been produced from hollow Cu conductor and are refrigerated with demineralised water. Typical current densities are around 5 A/mm2.

The power dissipated by the magnets in the ALBA accelerators during normal operation is around 1 Megawatt.