Periodical magnetic field generation device

In a periodical magnetic field generation device, a region is formed, in which the distance between a magnetic gap and opposing magnetic poles is gradually decreased as it is apart from the center of electron beams in the direction of the flow of the electron beams and in the direction perpendicular to NS magnetic pole center line of a permanent magnet. Further, the pitch of disposing permanent magnets is determined to 1/2 of a wiggler period, and opposing permanent magnets are disposed displaced by 1/4. Although the permanent magnets are made of rear earth element-Fe-B type material, the Fe content is preferably within a range of 65 to 85 atom%. Then, it is possible to improve a gap magnetic flux density in the direction of axis y in the vicinity of end face of the permanent magnet in the direction of axis x. Magnetic flux direction components can be formed also in the same direction as the electron beam progressing direction, to prevent scattering of the electron beams. Converging function of the electron beams can also be improved remarkably to finally form synchrotron radiation light efficiently. (N.H.)