Developing an Undulator with a Variable Period for the First Stage of the Novosibirsk Free Electron Laser

The development of a hybrid undulator with a small period-to-gap ratio (0.75) for the Novosibirsk Free Electron Laser (FEL) is described. The design of the undulator allows reconstruction of its period and a change in the number of poles. Since the configuration with permanent magnets can be scaled while preserving the field distribution, this design can be used both in installations operating in the terahertz range and for X-ray lasers. The results are presented from computer simulations and calculating the main parameters of the undulator.