A dual period undulator

Abstract

The application provides a double-period undulator, which comprises upper and lower magnetic carrier structures that can move relative to each other, two magnet array structures fixed on the lower magnetic carrier structure, and two magnet array structures fixed on the upper magnetic carrier structure, wherein the four magnet array structures form a first and a second undulator; the relative positions of the four magnet array structures in the z direction are such that when the two magnet array structures of one of the first and second undulators are aligned and work, the two magnet array structures of the other one are in positions that are staggered with each other in the z direction and can generate repulsive force, and the z direction is the beam propagation direction of the double-period undulator. The double-period undulator of the application generates repulsive force when two of the four magnet array structures are staggered to compensate for the attractive force of the aligned magnet array structures, thereby reducing the magnetic force load of the undulator based on magnetic force compensation, reducing the overall volume of the undulator, and expanding the energy range of the radiated photons under the same undulator volume.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of undulators, and particularly relates to a double-period undulator. BACKGROUND

[0002] An undulator is one of the important components of a free electron laser device, and the magnetic field thereof has periodicity in the direction of the beam. When an electron beam passes through the undulator, radiation light is generated in the tangential direction of the movement.

[0003] Different period lengths of the undulator result in different tuning curves of the photon brightness varying with the photon energy, and when a user has to select a period length, a compromise has to be made between the maximization of the number of photons in the energy range of interest and the guarantee of a wide enough tuning range.

[0004] The double-period undulator can expand the energy range of the radiation light and fully meet the needs of experimental users. The double-period undulator can also be adjusted and operated in different free electron laser modes.

[0005] Currently, the existing double-period undulators are either too bulky or have a small magnetic force. For example, the double-elliptical polarized undulator in the Shanghai Synchrotron Radiation Facility has a structure equivalent to two undulators and occupies a huge area; the double-period undulator in the Spring-8 light source in Japan adopts a roller structure, but the overall length thereof is short and the large beam is not at the Bessel support point, resulting in severe deformation. Two undulator lines will be installed in the tunnel of the SHINE device (hard X-ray free electron laser device) that is being constructed, and the length of the undulator is 4 m and the magnetic field is high, so the magnetic force generated is huge. Due to the limitation of space and cost, it is difficult to place the existing double-period undulators in the tunnel. Therefore, it is necessary to design a double-period undulator. SUMMARY

[0006] The present application aims to provide a double-period undulator to expand the energy range of the radiation light while reducing the overall volume.

[0007] To achieve the above-mentioned purpose, the present application provides a double-period undulator, comprising a lower magnetic carrier structure and an upper magnetic carrier structure that can move relative to each other, a second magnet array structure and a fourth magnet array structure fixed to the lower magnetic carrier structure, and a first magnet array structure and a third magnet array structure fixed to the upper magnetic carrier structure, wherein the first magnet array structure and the second magnet array structure jointly constitute a first undulator when aligned, and the third magnet array structure and the fourth magnet array structure jointly constitute a second undulator when aligned.

[0008] The relative positions of the two magnet array structures on the lower magnetic carrier structure in the z direction and the relative positions of the two magnet array structures on the upper magnetic carrier structure in the z direction are set such that when the two magnet array structures of one of the first and second undulators are aligned and work, the two magnet array structures of the other are in positions staggered with each other in the z direction and can generate repulsive force, and the z direction is the beam propagation direction of the double-period undulator.

[0009] The two magnet array structures of the lower magnetic carrier structure and the two magnet array structures of the upper magnetic carrier structure are staggered in the z direction, and the staggered distances are different, or the staggered distances are the same but the staggered directions are opposite; and the two magnet array structures of the lower magnetic carrier structure and the two magnet array structures of the upper magnetic carrier structure are spaced apart in the x direction, and the x direction is the horizontal direction perpendicular to the beam propagation direction of the double-period undulator.

[0010] The two magnet array structures of one of the lower magnetic carrier structure and the upper magnetic carrier structure are staggered in the z direction.

[0011] The lower magnetic carrier structure and the upper magnetic carrier structure are both arranged on a frame, and the frame is an L-shaped frame composed of a base and a stand.

[0012] A first driving mechanism is arranged between the base and the stand and is arranged to drive the stand to translate in the x direction, and the x direction is the horizontal direction perpendicular to the beam propagation direction of the double-period undulator.

[0013] The lower magnetic carrier structure is connected to the frame through a lower beam, and the upper magnetic carrier structure is connected to the frame through an upper beam.

[0014] A second driving mechanism and a third driving mechanism are arranged between the lower beam and the frame, and a fourth driving mechanism and a fifth driving mechanism are arranged between the upper beam and the stand, and the second driving mechanism, the third driving mechanism, the fourth driving mechanism and the fifth driving mechanism are arranged to drive the upper beam and the lower beam to open and close in the y direction, and the y direction is the vertical direction.

[0015] A sixth driving mechanism and a seventh driving mechanism are arranged between the beam and the magnetic carrier structure, and the sixth driving mechanism and the seventh driving mechanism are arranged to make the lower magnetic carrier structure and the upper magnetic carrier structure relatively translate in the z direction.

[0016] Each magnet array structure includes magnets and magnetic poles arranged periodically and alternately in the beam propagation direction of the double-period undulator, and the arrangement periods of the magnets and the magnetic poles of the first undulator and the second undulator are different.

[0017] The double-period undulator of the present application sets two periodic magnet arrays in each magnetic load structure, and when the two magnet arrays are aligned, the other two magnet arrays are staggered, so as to generate repulsive force to compensate the attractive force of the aligned magnet arrays, thereby reducing the magnetic load of the undulator based on the magnetic force compensation, and due to the reduction of the magnetic force, the undulator can be set more compactly, the overall volume of the undulator is reduced, thereby expanding the energy range of the radiated photons under the same undulator volume, and meeting the needs of more experimental users; and by changing the transverse position of the magnetic load structure, the magnet arrays that are aligned and work can be alternately switched, so as to more conveniently switch the period length of the undulator, meet the experimental needs of more users, and different laser modes can be run. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the overall structure schematic diagram of the double-period undulator according to an embodiment of the present application;

[0019] Figure 2 is the structure schematic diagram of the L-shaped frame and driving mechanism of the double-period undulator according to an embodiment of the present application;

[0020] Figure 3 is the structure schematic diagram of the magnetic load structure of the double-period undulator according to an embodiment of the present application;

[0021] Figure 4 is the structure schematic diagram of a single magnet array structure of the double-period undulator of the present application;

[0022] Figure 5 is the relative position schematic diagram of the magnet array structure when the undulators of different periods are running, the left half shows the case when the first undulator works, and the right half shows the case when the second undulator works.

[0023] Figure 6A is the schematic diagram of the magnetic field of the central axis of the magnet array structure of the undulator with a period length of 55mm in the double-period undulator of the present application;

[0024] Figure 6B is the schematic diagram of the magnetic field of the central axis of the magnet array structure of the undulator with a period length of 75mm in the double-period undulator of the present application. DETAILED DESCRIPTION

[0025] In order to make people in the art better understand the technical solutions of the present application, the technical solutions of the present application will be described clearly and completely below in combination with the drawings of the present application.

[0026] Figure 1 is the overall structure schematic diagram of the double-period undulator according to an embodiment of the present application, Figure 2is a structural schematic diagram of a frame and driving mechanism of a double-period undulator according to an embodiment of the present application. The y direction is the vertical direction, the x direction is the horizontal direction perpendicular to the beam propagation direction of the double-period undulator, and the z direction is the beam propagation direction of the double-period undulator.

[0027] As shown in Figure 1 and Figure 2 , the double-period undulator comprises a frame, two magnetic carrier structures arranged on the frame and movable relative to each other, and each magnetic carrier structure is provided with two magnet array structures fixed to the magnetic carrier structure.

[0028] The frame is an L-shaped frame composed of a base 101 and a column 102.

[0029] The magnetic carrier structure is non-magnetic and made of aluminum material, and the function of the magnetic carrier structure is to fix the magnet array structure. The two magnetic carrier structures movable relative to each other comprise a lower magnetic carrier structure 401 and an upper magnetic carrier structure 402, the magnet array structures fixed to the lower magnetic carrier structure 401 are a second magnet array structure 202 and a fourth magnet array structure 204, and the magnet array structures fixed to the upper magnetic carrier structure 402 are a first magnet array structure 201 and a third magnet array structure 203.

[0030] Among them, the first magnet array structure 201 and the second magnet array structure 202 jointly constitute a first undulator when aligned, the third magnet array structure 203 and the fourth magnet array structure 204 jointly constitute a second undulator when aligned, and the period lengths of the first undulator and the second undulator are different.

[0031] Thus, the relative positions of the second magnet array structure 202 and the fourth magnet array structure 204 are fixed, and the relative positions of the first magnet array structure 201 and the third magnet array structure 203 are fixed. In this embodiment, the upper surfaces of the magnet array structures fixed to the lower magnetic carrier structure 401 are in the same plane, and the lower surfaces of the magnet array structures fixed to the upper magnetic carrier structure 402 are in the same plane.

[0032] In this embodiment, as shown in Figure 3 , the two magnet array structures (i.e. the second magnet array structure 202 and the fourth magnet array structure 204) on the lower magnetic carrier structure 401 are offset by a first fixed distance d1 in the z direction for generating magnetic force compensation, and are also spaced apart in the x direction (with a distance of d2) for reducing the mutual influence between each other; similarly, the two magnet array structures (i.e. the first magnet array structure 201 and the third magnet array structure 203) on the upper magnetic carrier structure 402 are offset by a second fixed distance in the z direction for generating magnetic force compensation, and are also spaced apart in the x direction for reducing the mutual influence between each other.

[0033] Therefore, the relative positions of the two magnet array structures on the lower magnetic carrier structure 401 in the z direction and the relative positions of the two magnet array structures on the upper magnetic carrier structure 402 in the z direction are set so that when the two magnet array structures of one of the first and second undulators are aligned and working, the two magnet array structures of the other are in staggered positions in the z direction that can generate repulsive force, thereby offsetting the suction force generated by the running undulator. Specifically, assuming that the first magnet array structure 201 and the second magnet array structure 202 are aligned up and down, there is an attractive force between the two at this time. At this time, the third magnet array structure 203 and the fourth magnet array structure 204 are offset by a certain distance and show an attractive force, which can reduce the attractive force between the lower magnetic carrier structure 401 and the upper magnetic carrier structure 402; when the third magnet array structure 203 and the fourth magnet array structure 204 need to be operated, the lower magnetic carrier structure 401 and the upper magnetic carrier structure 402 are moved relative to each other along the z direction. After the movement, the third magnet array structure 203 and the fourth magnet array structure 204 are aligned up and down. At this time, there is an attractive force between the two, and the first magnet array structure 201 and the second magnet array structure 202 are in positions offset from each other that can generate repulsive force, which can also reduce the attractive force between the lower magnetic carrier structure 401 and the upper magnetic carrier structure 402.

[0034] Therefore, the dual-period undulator achieves magnetic compensation by translating in the beam direction. When one of the two undulators is in operation, the other one achieves magnetic compensation.

[0035] It should be noted that the z- and x-distance spacing of undulators of different period lengths varies, requiring optimization based on specific circumstances. The z-distance depends on the magnitude of the magnetic field and the length of the undulator, while the x-distance depends on the size of the magnet array structure.

[0036] In this embodiment, if Figure 5 As shown, the two magnet array structures of the upper magnetic carrier structure 402 and the two magnet array structures of the lower magnetic carrier structure 401 are offset by the same distance in the z direction, but in opposite directions. Therefore, when the two magnet array structures of the first undulator are aligned for operation, the two magnet array structures of the second undulator are exactly offset, and when the two magnet array structures of the second undulator are aligned for operation, the two magnet array structures of the first undulator are exactly offset. The two magnet array structures of the upper magnetic carrier structure and the two magnet array structures of the lower magnetic carrier structure are separated by the same distance in the x direction.

[0037] In other embodiments, the two magnet array structures of one of the lower magnetic support structure 401 and the upper magnetic support structure 402 are staggered in the z direction, so as to be able to generate magnetic force compensation. Alternatively, the two magnet array structures of the lower magnetic support structure 401 and the two magnet array structures of the upper magnetic support structure 402 are staggered in the z direction, and the staggering distances are different, or the staggering distances are the same but the staggering directions are opposite.

[0038] Each magnetic support structure is connected to the frame through a girder, and in the embodiment, the girder includes a lower girder 103 and an upper girder 104. The lower magnetic support structure 401 is connected to the frame through the lower girder 103, and the upper magnetic support structure 402 is connected to the frame through the upper girder 104.

[0039] As shown in Figure 4 Each magnet array structure includes magnets 501 with permanent magnetism and poles 502 without permanent magnetism arranged periodically and alternately along the beam propagation direction of the double-period undulator, for generating a periodic magnetic field. The material of the magnet 501 is a neodymium iron boron permanent magnet, a samarium cobalt permanent magnet or a ferrite permanent magnet, wherein the arrow direction of the magnet 501 is the magnetization direction thereof. The pole 502 can also be called soft iron, and is collectively referred to as a pole. The material of the pole 502 is electrical pure iron or cobalt vanadium iron. The magnet 501 functions to provide a stable magnetic field source, and the pole 502 functions to concentrate magnetic field. In the embodiment, the arrangement of the magnet 501 and the pole 502 satisfies the arrangement mode of Halbach. The magnet and the pole are fixed through a fixed groove and a screw on the magnetic support structure.

[0040] The first magnet array structure 201, the second magnet array structure 202, the third magnet array structure 203 and the fourth magnet array structure 204 are core components of the undulator. The arrangement periods of the magnet 501 and the pole 502 in the first magnet array structure 201 and the second magnet array structure 202 are the same, and the first magnet array structure 201 and the second magnet array structure 202 jointly constitute a first undulator. The period length (i.e. the arrangement period of the magnet 501 and the pole 502) of the first undulator is 75 mm, and the magnetic field during operation is as shown in Figure 6B The arrangement periods of the magnet 501 and the pole 502 in the third magnet array structure 203 and the fourth magnet array structure 204 are the same, and the third magnet array structure 203 and the fourth magnet array structure 204 jointly constitute a second undulator. The period length of the second undulator is 55 mm, and the magnetic field during operation is as shown in Figure 6A . Figure 6A and Figure 6B It is illustrated that the arrangement periods of the magnet 501 and the pole 502 of the first undulator and the second undulator are different.

[0041] The double-period undulator further comprises seven driving mechanisms, i.e., a first driving mechanism 301, a second driving mechanism 302, a third driving mechanism 303, a fourth driving mechanism 304, a fifth driving mechanism 305, a sixth driving mechanism 306 and a seventh driving mechanism 307. The first driving mechanism 301 is arranged between the base 101 and the column 102, and is configured to drive the column 102 to translate along the x direction, so as to simultaneously adjust all the magnet array structures along the horizontal direction perpendicular to the beam direction, and then align the beam center with the center of the undulator to be worked; the second driving mechanism 302 and the third driving mechanism 303 are arranged between the lower beam 103 and the frame, and the fourth driving mechanism 304 and the fifth driving mechanism 305 are arranged between the upper beam 104 and the column 102 of the frame, and are configured to drive the beams (i.e., the upper beam 104 and the lower beam 103) to open and close along the y direction, so as to adjust the magnetic gap of the undulator to be worked, wherein the transmission mechanism is connected with the beam through a screw; the sixth driving mechanism 306 and the seventh driving mechanism 307 are arranged between the beams and the magnetic load structures, and are configured to drive the magnetic load structures 401 and 402 to relatively translate along the z direction, so as to adjust the magnet array structures along the beam direction, and then align and work the two magnet array structures of the undulator to be worked along the beam direction.

[0042] Preferably, the driving mechanism is a servo motor.

[0043] The above is only a preferred embodiment of the present application, and is not intended to limit the scope of the present application. The above embodiment of the present application can be variously changed. Any simple, equivalent change and modification made according to the content of the present application shall fall within the scope of the present application. The present application is not described in detail, and all the conventional technical contents are included.

Claims

1. A double-period undulator, characterized in that, The double-period undulator comprises a lower magnetic carrier structure and an upper magnetic carrier structure which are movable relative to each other, a second magnet array structure and a fourth magnet array structure fixed on the lower magnetic carrier structure, and a first magnet array structure and a third magnet array structure fixed on the upper magnetic carrier structure, the first magnet array structure and the second magnet array structure jointly form a first undulator when aligned, and the third magnet array structure and the fourth magnet array structure jointly form a second undulator when aligned. The relative positions of the two magnet array structures on the lower magnetic carrier structure in the z direction and the relative positions of the two magnet array structures on the upper magnetic carrier structure in the z direction are set such that when the two magnet array structures of one of the first and second undulators are aligned and work, the two magnet array structures of the other are in positions staggered with each other in the z direction and can generate repulsive force, and the z direction is the beam propagation direction of the double-period undulator. The two magnet array structures of the lower magnetic carrier structure and the two magnet array structures of the upper magnetic carrier structure are staggered in the z direction, and the staggering distances are different or the staggering distances are the same but the staggering directions are opposite.

2. The dual-period undulator according to claim 1, wherein: The two magnet array structures of the lower magnetic carrier structure and the two magnet array structures of the upper magnetic carrier structure are spaced apart in the x direction, and the x direction is a horizontal direction perpendicular to the beam propagation direction of the double-period undulator.

3. The double-period undulator of claim 1, wherein, The two magnet array structures of one of the lower magnetic carrier structure and the upper magnetic carrier structure are staggered in the z direction.

4. The double-period undulator of claim 1, wherein, The lower magnetic carrier structure and the upper magnetic carrier structure are both arranged on a frame, and the frame is an L-shaped frame composed of a base and a stand.

5. The double-period undulator of claim 4, wherein, A first driving mechanism is arranged between the base and the stand and is configured to drive the stand to translate in the x direction, and the x direction is a horizontal direction perpendicular to the beam propagation direction of the double-period undulator.

6. The double-period undulator of claim 1, wherein, The lower magnetic carrier structure is connected to the frame through a lower beam, and the upper magnetic carrier structure is connected to the frame through an upper beam.

7. The double-period undulator of claim 6, wherein, A second driving mechanism and a third driving mechanism are arranged between the lower beam and the frame, and a fourth driving mechanism and a fifth driving mechanism are arranged between the upper beam and the stand, and the second driving mechanism, the third driving mechanism, the fourth driving mechanism and the fifth driving mechanism are configured to drive the upper beam and the lower beam to perform opening and closing motion in the y direction, and the y direction is a vertical direction.

8. The double-period undulator of claim 6, wherein, A sixth driving mechanism and a seventh driving mechanism are arranged between the beam and the magnetic carrier structure, and the sixth driving mechanism and the seventh driving mechanism are configured to drive the lower magnetic carrier structure and the upper magnetic carrier structure to translate relative to each other in the z direction.

9. The double-period undulator of claim 1, wherein, Each magnet array structure comprises magnets and magnetic poles arranged periodically and alternately in the beam propagation direction of the double-period undulator, and the arrangement periods of the magnets and the magnetic poles of the first undulator and the second undulator are different.

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