CN-122025214-A - Adjustable cone undulator based on beat frequency superposition, device and spectrum broadening method

CN122025214ACN 122025214 ACN122025214 ACN 122025214ACN-122025214-A

Abstract

The disclosure provides an adjustable cone undulator based on beat frequency superposition, a device and a spectrum broadening method, which are applied to the technical field of synchronous radiation and the technical field of free electron laser. The undulator comprises a first magnetic array structure, a second magnetic array structure and a phase shift driving structure, wherein the first magnetic array structure comprises a plurality of groups of first permanent magnet units and is used for generating a first magnetic field, the second magnetic array structure comprises a plurality of groups of second permanent magnet units and is used for generating a second magnetic field, the phase shift driving structure is used for responding to a target superimposed magnetic field obtained by the beat frequency superposition of the first magnetic field and the second magnetic field, determining the beat frequency magnetic cycle length of the target superimposed magnetic field according to the first magnetic cycle length and the second magnetic cycle length, determining target phase shift from a target beat frequency envelope constructed based on the attribute parameters and the beat frequency magnetic cycle length of the adjustable tapering undulator according to the tapering requirement of the undulator, and driving the phase shift driving structure to enable the first magnetic array structure and/or the second magnetic array structure to translate along the advancing direction of an electron beam.

Inventors

ZHAO ZHOUYU
ZHANG BINGHAO
LI HETING
Yang Nanrui

Assignees

中国科学技术大学

Dates

Publication Date: 20260512
Application Date: 20260130

Claims (10)

1. An adjustable cone undulator based on beat frequency superposition, comprising: the first magnetic array structure comprises a plurality of groups of first permanent magnet block units which are arranged along the advancing direction of the electron beam, wherein the plurality of groups of first permanent magnet block units are used for generating a first magnetic field; The second magnetic array structure is arranged opposite to the first magnetic array structure and comprises a plurality of groups of second permanent magnet block units arranged along the advancing direction of the electron beam, and the plurality of groups of second permanent magnet block units are used for generating a second magnetic field; The phase shift driving structure is connected with the first magnetic array structure and the second magnetic array structure, is used for responding to a target superimposed magnetic field obtained after the first magnetic field and the second magnetic field are subjected to beat frequency superposition along the electron beam advancing direction, and determines the beat frequency magnetic cycle length of the target superimposed magnetic field according to the first magnetic cycle length of the first magnetic field and the second magnetic cycle length of the second magnetic field; The first magnetic period length and the second magnetic period length are different, and the target beat frequency envelope represents a corresponding relation between a phase difference between the first magnetic array structure and the second magnetic array structure and envelope translation of the target superimposed magnetic field.
2. The tunable bevel undulator of claim 1 wherein, Determining an initial magnetic field parameter and the beat frequency magnetic cycle length according to the first magnetic cycle length and the second magnetic cycle length in response to the target superimposed magnetic field, wherein the initial magnetic field parameter comprises a first wave number of the first magnetic field, a second wave number of the second magnetic field, a wave number difference between the first wave number and the second wave number, and an average wave number; Determining a target multiple between a phase shift of the adjustable cone undulator and a translation amount of an envelope function of the target superimposed magnetic field translated along the electron beam advancing direction according to the beat magnetic period length and a magnetic period length difference, wherein the magnetic period length difference characterizes a difference between the first magnetic period length and the second magnetic period length; Constructing the target beat frequency envelope according to the physical length of the adjustable cone undulator, the target multiple and the beat frequency magnetic period length based on a first preset relation, wherein the first preset relation represents the change relation between the period magnetic field intensity of the target superimposed magnetic field and the beat frequency magnetic period length; Based on the undulator tapering requirement, determining the target phase shift from the target beat envelope and driving the phase shift driving structure to translate the first magnetic array structure and/or the second magnetic array structure along the electron beam advancing direction.
3. The tunable bevel undulator of claim 2, wherein, Determining a phase shift interval of the adjustable cone undulator according to the target multiple and the beat frequency magnetic period length; Based on the first preset relation, determining the periodic magnetic field strength of the target superimposed magnetic field according to the first magnetic field strength, the second magnetic field strength, the phase shift interval and the initial magnetic field parameter, and constructing an initial beat frequency envelope according to the periodic magnetic field strength and the beat frequency magnetic period length; Determining a phase shift corresponding to a quasi-uniform magnetic field pattern based on a second predetermined relationship, which characterizes a changing relationship between a motion position along the electron beam advancing direction and the phase shift, according to the initial magnetic field parameter and a motion position along the electron beam advancing direction corresponding to a maximum magnetic field intensity of the periodic magnetic field intensities; And dividing the initial beat frequency envelope based on the phase shift corresponding to the quasi-uniform magnetic field mode to obtain the target beat frequency envelope divided with a plurality of working mode intervals.
4. The tunable bevel undulator of claim 3 wherein, The plurality of working mode intervals comprise a quasi-uniform field mode interval, a forward tapering mode interval, a nonlinear tapering mode interval and a reverse tapering mode interval; The quasi-uniform field mode section represents a section in which the change rate of the periodic magnetic field intensity along the electron beam advancing direction is smaller than a preset threshold value, the forward tapering mode section represents a section in which the periodic magnetic field intensity monotonically decreases along the electron beam advancing direction, the reverse tapering mode section represents a section in which the periodic magnetic field intensity monotonically increases along the electron beam advancing direction, and the nonlinear tapering mode section represents a nonlinear section of the target beat envelope along the electron beam advancing direction.
5. The tunable bevel undulator of claim 2, wherein, Determining a target motion position along an electron beam advancing direction from the target beat envelope based on the undulator tapering requirement; converting the target movement position along the electron beam advancing direction by utilizing the target multiple to obtain the target phase shift; Based on the target phase shift, the phase shift driving structure is driven to translate the first magnetic array structure and/or the second magnetic array structure along the electron beam advancing direction.
6. The tunable bevel undulator of claim 1 wherein, The first permanent magnet block unit comprises two first permanent magnet blocks with vertical magnetization directions and two first permanent magnet blocks with horizontal magnetization directions, and the magnetization directions of the first permanent magnet blocks are sequentially and rotatably arranged clockwise or anticlockwise for generating the first magnetic field; The second permanent magnet block unit comprises two second permanent magnet blocks with vertical magnetization directions and two second permanent magnet blocks with horizontal magnetization directions, and the magnetization directions of the second permanent magnet blocks are sequentially and rotatably arranged along anticlockwise or clockwise directions opposite to the first permanent magnet blocks and are used for generating the second magnetic field which is opposite to the horizontal magnetization direction of the first magnetic field and has the same vertical magnetization direction.
7. The adjustable cone undulator of claim 1, wherein the adjustable cone undulator further comprises: the first end magnetic structures are respectively arranged at two ends of the first magnetic array structure and comprise a plurality of first end permanent magnet blocks which are rotationally arranged in the same direction as the magnetization direction of the plurality of first permanent magnet blocks, wherein a preset gap is reserved among the plurality of first end permanent magnet blocks; the second end magnetic structures are respectively arranged at two ends of the second magnetic array structure and comprise a plurality of second end permanent magnet blocks which are rotationally arranged in the same direction as the magnetization direction of the second permanent magnet blocks, wherein the predetermined gaps are reserved among the second end permanent magnet blocks.
8. The adjustable cone undulator of claim 1, wherein the adjustable cone undulator further comprises: the electron beam vacuum chamber is used for transmitting electron beam current so that the electron beam current moves along the advancing direction of the electron beam under the action of the target superimposed magnetic field; a first beam for supporting the first magnetic array structure; a second beam for supporting the second magnetic array structure; And the vertical driving structure is connected with the first magnetic array structure and the second magnetic array structure and is used for driving the first magnetic array structure and/or the second magnetic array structure to translate along the direction vertical to the electron beam advancing direction so as to adjust the working gap between the first magnetic array structure and the second magnetic array structure.
9. A free electron laser device comprising a tunable tapered undulator based on beat frequency superposition as defined in any preceding claim.
10. A method for widening synchronous radiation spectrum of an adjustable cone undulator based on beat frequency superposition, which is applied to the adjustable cone undulator based on beat frequency superposition described in any one of 1-8, and is characterized in that the method comprises the following steps: responding to a target superimposed magnetic field obtained after the first magnetic field and the second magnetic field are subjected to beat frequency superposition along the electron beam advancing direction, and determining the beat frequency magnetic cycle length of the target superimposed magnetic field according to the first magnetic cycle length of the first magnetic field and the second magnetic cycle length of the second magnetic field; Determining a target phase shift from a target beat envelope constructed based on an attribute parameter of an adjustable conical undulator and the beat magnetic period length according to the undulator tapering requirement; based on the target phase shift, the phase shift driving structure is driven to translate the first magnetic array structure and/or the second magnetic array structure along the electron beam advancing direction to change the slope and shape of the magnetic field tapering distribution.

Description

Adjustable cone undulator based on beat frequency superposition, device and spectrum broadening method Technical Field The present disclosure relates to the field of synchrotron radiation technology and free electron laser technology, and more particularly to an adjustable cone undulator based on beat frequency superposition, an apparatus and a method for broadening spectrum. Background As the electron beam in the free electron laser device imparts energy to the light field, its energy gradually decreases. If the magnetic field of the undulator remains constant, problems such as drift of the resonance wavelength, detuning of the electron beam and the optical field, etc. can be caused. Based on the concept of undulator tapering, the prior art compensates for the attenuation of electron energy by adjusting the working gap between the undulator magnetic arrays to gradually decrease the magnetic field strength along the electron beam direction. However, since the electron beam vacuum chamber has a limited size, the tapering effect on the undulator is limited, and it is difficult for the undulator to satisfy the current high demands. In the process of realizing the above inventive concept, the inventor found that in the related art, in the process of tapering the undulator, it is difficult to cover the tapering range of the undulator by adjusting the working gap between the magnetic arrays due to the limited size of the electron beam vacuum chamber, and at the same time, it is difficult for the undulator to obtain a strong magnetic field tapering due to the limited rigidity of the girder for fixing the magnetic arrays, resulting in the technical problems of low flexibility of tapering adjustment of the undulator and general tapering effect. Disclosure of Invention In view of the above, the present disclosure provides an adjustable cone undulator based on beat frequency superposition, an apparatus and a method for broadening spectrum. According to a first aspect of the disclosure, an adjustable cone oscillator based on beat frequency superposition is provided, and the adjustable cone oscillator comprises a first magnetic array structure, a second magnetic array structure, a phase shift driving structure and a target phase shift driving structure, wherein the first magnetic array structure comprises a plurality of groups of first permanent magnet block units which are arranged along the electron beam advancing direction, the plurality of groups of first permanent magnet block units are used for generating a first magnetic field, the second magnetic array structure comprises a plurality of groups of second permanent magnet block units which are arranged along the electron beam advancing direction, the plurality of groups of second permanent magnet block units are arranged along the electron beam advancing direction and are used for generating a second magnetic field, the phase shift driving structure is connected with the first magnetic array structure and the second magnetic array structure and is used for responding to a target superposition magnetic field obtained after beat frequency superposition of the first magnetic field and the second magnetic field along the electron beam advancing direction, the beat frequency cycle length of the first magnetic field and the second magnetic cycle length of the second magnetic field are determined, the beat frequency magnetic cycle length of the target superposition magnetic field is determined according to the first magnetic cycle length of the first magnetic field and the second magnetic cycle length of the first magnetic field, the target is determined from a target frequency envelope constructed based on the attribute parameters of the adjustable cone oscillator and the beat frequency cycle magnetic block units and the beat frequency cycle length, and the target phase shift driving structure is determined according to the cone oscillator cone demand, and the phase shift driving structure is enabled to correspond to the target frequency envelope of the target frequency envelope, and the target frequency envelope is not translated with the target frequency envelope structure, and the beat frequency envelope magnetic structure is represented by the phase shift magnetic structure and the phase shift magnetic array structure and the phase shift magnetic structure. According to an embodiment of the disclosure, an initial magnetic field parameter and a beat magnetic cycle length are determined in response to a target superimposed magnetic field according to a first magnetic cycle length and a second magnetic cycle length, wherein the initial magnetic field parameter comprises a first wave number of the first magnetic field, a second wave number of the second magnetic field, a wave number difference between the first wave number and the second wave number and an average wave number, a target multiple between a phase shift of an adjustable cone undulator and a translation amou