Results of test of prototype of variable period undulator

The development of the permanent-magnet variable-period undulator (VPU) is aimed at improving the parameters of the Novosibirsk free electron laser (FEL). The key features of this design are the possibility of increasing the number of poles for shorter periods with constant undulator length and wider radiation wavelength tuning range as compared with conventional undulators. As the idea of the permanent-magnet VPU has not been properly tested yet, there are several issues to be solved before THE manufacture of the device. Two short prototypes of the VPU were made for the purpose of testing solutions to existing problems. We present here the results of mechanical and magnetic measurements of the undulator prototypes and compare the characteristics of the prototypes with those predicted by simulations.