The present invention relates to an undulator for affecting electron beams in for example synchrotrons and free electron lasers. Permanent magnet structures are mounted in individually adjustable pair structures. Such structures are stacked in rotatable discs. This makes it possible to produce a wide range of undulator settings including normal linear with different period length and with a mixture of periods, helical with different helix angle. Furthermore each such magnet pair the distance can be adjusted allowing for individual magnetic flux intensity change in every disc. Also the relative angle of each magnet pair can be adjusted. This facilitate longitudinal as well as transverse tapering including the helical case of the magnetic field in the central passage through the structure.
展开▼
