Magnetic field apparatus for a particle accelerator having a supplemental winding with a hollow groove structure

A magnetic field apparatus for an electrically charged particle accelerator having a particle track, the particle track including at least one curved section having a plurality of magnetic-field-generating windings, and wherein at least one supplemental winding for focusing the electrically charged particles is provided, the supplemental winding comprising means for generating an azimuthal guding field for the particles during acceleration of the particles in a region of the at least one curved section of the particle track, said supplemental winding comprising a curved electrical conductor arrangement which has a curvature adapted to the curvature of the curved section of the particle track and which partly encloses the particle track, said electrical conductor arrangement having a curved hollow groove structure which is slotted on the outside thereby allowing emission of synchrotron radiation laterally outwardly, and further including means for suppressing eddy currents, said conductor arrangement carrying a current transverse to the particle track.