Abstract: An undulator comprises at least M permanent magnet periods arranged sequentially in a transmission direction of electron beams, each of the permanent magnet periods comprises four rows of permanent magnet structures, in which each row comprises N rows of permanent magnet groups, and each row of the permanent magnet groups comprises K permanent magnet units, wherein M, N and K are natural numbers greater than or equal to 1; the four rows of the permanent magnet structures are pairwise matched, then relatively disposed on both sides of the transmission direction of electron beams, and are capable of forming at least one composite magnetic fields by relative displacement, such that elliptically polarized light, circularly polarized light, or linearly polarized light with an arbitrary polarization angle of 0°˜360° is generated when electron beams pass through the composite magnetic fields, and such that velocity directions of electrons are deviated from an axis direction of the undulator.

Abstract: An undulator comprises at least M permanent magnet periods arranged sequentially in a transmission direction of electron beams, each of the permanent magnet periods comprises four rows of permanent magnet structures, in which each row comprises N rows of permanent magnet groups, and each row of the permanent magnet groups comprises K permanent magnet units, wherein M, N and K are natural numbers greater than or equal to 1; the four rows of the permanent magnet structures are pairwise matched, then relatively disposed on both sides of the transmission direction of electron beams, and are capable of forming at least one composite magnetic fields by relative displacement, such that elliptically polarized light, circularly polarized light, or linearly polarized light with an arbitrary polarization angle of 0°˜360° is generated when electron beams pass through the composite magnetic fields, and such that velocity directions of electrons are deviated from an axis direction of the undulator.

Abstract: Provided is an image type electron spin polarimeter. It at least comprises a scattering target, a two-dimensional electron detector and an electron bending unit, wherein the electron bending unit is used for bending the orbit of the incident (scattered) electrons to a first (second) angle to arrive the scattering target (two-dimensional electron detector) with an optimal incident angle, and to transfer the image of the electron intensities from the entrance plane (scattering target) to the scattering target (two-dimensional electron detector) with small aberrations, and to separate the orbits of incident and scattered electrons to increase the degree of freedom of the geometric configuration of each component of the spin polarimeter.

Abstract: Provided is an image type electron spin polarimeter. It at least comprises a scattering target, a two-dimensional electron detector and an electron bending unit, wherein the electron bending unit is used for bending the orbit of the incident (scattered) electrons to a first (second) angle to arrive the scattering target (two-dimensional electron detector) with an optimal incident angle, and to transfer the image of the electron intensities from the entrance plane (scattering target) to the scattering target (two-dimensional electron detector) with small aberrations, and to separate the orbits of incident and scattered electrons to increase the degree of freedom of the geometric configuration of each component of the spin polarimeter.