Self-cancellation of magnetic force by phase-combined undulator

We proposed the new undulator magnetic circuit so-called phase-combined undulator, having nearly zero magnetic force between the upper and lower magnet array is proposed, which significantly simplifies the mechanical structure of undulators. In the undulator, each magnet array is divided into a number of sections, half of which are phase-shifted according to a particular rule without breaking the periodicity in the undulator field. Calculation results show that the magnetic force can be reduced down to less than 1/50 of that in the Halbach undulator, when the gap over period is in practical range, more than or equal to 1/18. (author)