BINP SB RAS, Novosibirsk
To change the wavelength of undulator radiation people frequently use the variation of undulator magnetic field amplitude. Another option is to change the undulator period. The scheme for such undulator is described. It provides possibility to change both period and number of periods. For the set of undulator sections (like in x-ray FELs) mechanical motion of periods eliminates the necessity of phase shifters between the undulator sections. Magnetic field calculations for some interesting undulator parameters were performed. Numerous advantages of new undulators (fixed gap, strong dependence of undulator radiation wavelength on period, relatively low field amplitude variation and variable number of periods) look very attractive. Prospects for this new type of undulators are discussed.
