A device for measuring orbital angular momentum of vortex particles based on gradient magnetic field

Abstract

The application discloses a device for measuring orbital angular momentum of vortex particles based on a gradient magnetic field, which is integrated in a beamline system of a particle accelerator or an electron microscope and used for measuring the orbital angular momentum of a vortex particle beam in real time. The device comprises a vortex particle source, a gradient magnetic field device, a detection system and a processing system. The vortex particle source is used for providing a vortex particle beam. The gradient magnetic field device is used for exerting a transverse deflection force related to the orbital angular momentum on the vortex particle beam. The detection system is used for receiving the particle beam after a certain longitudinal movement and obtaining an intensity distribution image of the particle beam. The processing system is used for calculating the orbital angular momentum of the vortex particle beam according to the intensity distribution image and magnetic field gradient parameters. The device for measuring the orbital angular momentum of vortex particles based on the gradient magnetic field has the characteristics of simple structure, fast response and integration in the beamline system, and is suitable for various equipment environments such as particle accelerators, electron microscopes and the like.

Description

Technical Field

[0001] This invention relates to the field of vortex particle beam detection technology, specifically to a device for measuring the orbital angular momentum of vortex particles based on a gradient magnetic field. Background Technology

[0002] Vortex particle beams carrying orbital angular momentum, due to their unique helical wavefront structure and orbital angular momentum degree of freedom, have shown significant application potential in fields such as electron microscopy, quantum information encoding, materials chirality analysis, and high-energy physics collisions. In recent years, significant progress has been made in vortex particle beam generation technology. For example, methods based on helical phase plates, holographic gratings, and mode converters can all achieve orbital angular momentum manipulation of electron beams, while vortex laser-pumped vortex ion generation can achieve orbital angular momentum manipulation of ion beams.

[0003] However, measuring the orbital angular momentum of vortex particle beams still faces significant challenges. Current mainstream methods largely rely on particle interferometry or wavefront reconstruction techniques. These methods are not only complex in their apparatus and extremely sensitive to vibration and beam stability, but also involve cumbersome data processing, making rapid, real-time measurements difficult. Furthermore, traditional methods often require complex phase retrieval algorithms or additional reference beams, making them inconvenient to integrate into existing particle beamline systems (such as transmission electron microscopes and particle accelerators), thus limiting the widespread application of vortex particle beams in practical equipment. Therefore, developing a simple, fast-responding, and easily integrated method and apparatus for measuring the orbital angular momentum of vortex particles is crucial to propelling this technology from the laboratory to practical application. Summary of the Invention

[0004] The purpose of this invention is to provide a device for measuring the orbital angular momentum of vortex particles based on gradient magnetic fields. It features a simple structure, fast response, and easy integration into particle beamline systems. It is suitable for various equipment environments such as particle accelerators and electron microscopes, providing a reliable means for real-time and accurate measurement of the orbital angular momentum of vortex particles.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A device for measuring the orbital angular momentum of vortex particles based on gradient magnetic fields includes a vortex particle source, a gradient magnetic field device, a detection system, and a processing system.

[0006] The vortex particle source is used to provide a vortex particle beam.

[0007] The gradient magnetic field device is used to apply a lateral deflection force related to the orbital angular momentum to the vortex particle beam.

[0008] The detection system is used to receive a particle beam after it has undergone a longitudinal motion and to obtain an image of its intensity distribution.

[0009] The processing system is used to calculate the orbital angular momentum of the vortex particle beam based on the intensity distribution image and the magnetic field gradient parameters.

[0010] The gradient magnetic field device is located at the rear end of the vortex particle source.

[0011] The detection system is positioned behind the gradient magnetic field device.

[0012] The detection system is electrically connected to the processing system.

[0013] In at least one embodiment of the present disclosure, a device for measuring the orbital angular momentum of vortex particles based on a gradient magnetic field is provided, wherein the vortex particle source includes a plane wave electron source and a spiral phase plate.

[0014] The plane wave electron source is used to provide plane electron waves.

[0015] The spiral phase plate is used to induce spiral phase modulation in the passing planar electron wave to form a vortex electron beam carrying orbital angular momentum.

[0016] The plane wave electron source and the spiral phase plate are arranged sequentially along the transmission direction.

[0017] In at least one embodiment of the present disclosure, the device for measuring the orbital angular momentum of vortex particles based on gradient magnetic fields is a quadrupole magnet with an adjustable magnetic field gradient.

[0018] The magnetic field gradient direction of the quadrupole magnet is perpendicular to the transmission direction of the vortex particle beam.

[0019] In at least one embodiment of the present disclosure, the device for measuring the orbital angular momentum of vortex particles based on gradient magnetic fields includes a detector, a fluorescent screen, and a CCD camera.

[0020] The detector is used to receive the particle beam processed by the gradient magnetic field device and generate a position signal.

[0021] The fluorescent screen is used to convert the particle distribution into a visible light image.

[0022] The CCD camera is used to collect the light intensity distribution on the fluorescent screen.

[0023] The detector, fluorescent screen, and CCD camera are sequentially positioned behind the gradient magnetic field device.

[0024] The apparatus for measuring the orbital angular momentum of vortex particles based on gradient magnetic fields, provided in at least one embodiment of this disclosure, further includes a vacuum tube for providing a vacuum environment.

[0025] The vortex particle source, gradient magnetic field device, and detection system are all fixedly installed inside the vacuum tube.

[0026] In at least one embodiment of the present disclosure, the vacuum tube has a vacuum window in the apparatus for measuring the orbital angular momentum of vortex particles based on a gradient magnetic field.

[0027] In at least one embodiment of the present disclosure, the detector in the apparatus for measuring the orbital angular momentum of vortex particles based on gradient magnetic fields is an MCP detector.

[0028] In at least one embodiment of the present disclosure, a device for measuring the orbital angular momentum of vortex particles based on a gradient magnetic field is provided, wherein the vacuum window is fixedly disposed at one end of the vacuum tube and is located behind the vortex particle source.

[0029] The apparatus for measuring the orbital angular momentum of vortex particles based on a gradient magnetic field, provided in at least one embodiment of this disclosure, further includes an aperture correction device for constraining the vortex particle beam so that only the beam in the Z direction remains.

[0030] The aperture correction device is located between the vortex particle source and the gradient magnetic field device.

[0031] In at least one embodiment of the present disclosure, the apparatus for measuring the orbital angular momentum of vortex particles based on a gradient magnetic field is provided, wherein the vortex particle source is either a vortex electron source or a vortex ion source.

[0032] The beneficial effects of this invention are as follows: by applying a gradient magnetic field to a particle beam with orbital angular momentum in a controllable manner, and by detecting the spatial distribution after deflection, the orbital angular momentum can be measured rapidly. It has the advantages of simple structure, fast response, and easy integration into existing beamlines, and is suitable for real-time measurement of the orbital angular momentum of vortex particle beams.

[0033] Based on the physical mechanism of transverse deflection caused by the coupling of orbital angular momentum and magnetic field gradient, this invention realizes non-interference orbital angular momentum measurement without the need for complex wavefront reconstruction, providing an important measurement tool for the practical application of vortex particle beams. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram illustrating the principle and overall structure of the vortex electron source generating vortex electrons in Example 1.

[0036] Figure 2This is a schematic diagram illustrating the intensity distribution principle of vortex electrons under different orbital angular momentum after being deflected by a quadrupole magnet in Example 2.

[0037] Figure 3 This is a schematic diagram of the orbital angular momentum measurement device based on the spiral phase plate generating vortex electrons in Example 3.

[0038] Figure 4 This is a schematic diagram of the orbital angular momentum measurement device of the vortex ion source based on a quadrupole magnet in Example 4.

[0039] In the picture: 10. Vortex electron source; 11. Plane wave electron source; 12. Spiral phase plate; 20. Vortex ion source; 30. Quadrupole magnet; 41. MCP detector; 42. Fluorescent screen; 43. CCD camera; 50. Vacuum tube; 51. Vacuum window; 60. Processing system; 70. Aperture correction device. Detailed Implementation

[0040] The technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments, not all embodiments.

[0041] like Figures 1 to 4 As shown, this embodiment provides a device for measuring the orbital angular momentum of vortex particles based on a gradient magnetic field, including a vortex particle source, a gradient magnetic field device, a detection system, a processing system, a vacuum tube 50, and an aperture correction device 70.

[0042] In this embodiment, a vortex particle source is used to provide a vortex particle beam. The vortex particle source is either a vortex electron source 10 or a vortex ion source 20. Specifically, the vortex electron source 10 includes a plane wave electron source 11 and a spiral phase plate 12.

[0043] The plane wave electron source 11 is used to provide plane electron waves; the spiral phase plate 12 is used to obtain spiral phase modulation of the passing plane electron waves to form a vortex electron beam carrying orbital angular momentum.

[0044] The plane wave electron source 11 and the spiral phase plate 12 are arranged sequentially along the transmission direction.

[0045] In this embodiment, a gradient magnetic field device is used to apply a lateral deflection force related to the orbital angular momentum to the vortex particle beam. The gradient magnetic field device is disposed at the rear end of the vortex particle source.

[0046] Specifically, the gradient magnetic field device uses a quadrupole magnet 30 with an adjustable magnetic field gradient; the magnetic field gradient direction of the quadrupole magnet 30 is perpendicular to the transmission direction of the vortex particle beam.

[0047] Since the magnetic field gradient of the quadrupole magnet 30 is adjustable, it can meet the measurement requirements of different orbital angular momentum.

[0048] In this embodiment, the detection system is used to receive the particle beam after a longitudinal motion and acquire its intensity distribution image; the detection system is configured behind the gradient magnetic field device; the detection system is electrically connected to the processing system.

[0049] Specifically, the detection system includes an MCP detector 41, a fluorescent screen 42, and a CCD camera 43; the MCP detector 41, the fluorescent screen 42, and the CCD camera 43 are arranged sequentially behind the quadrupole magnet 30.

[0050] MCP detector 41 is used to receive the particle beam processed by quadrupole magnet 30 and generate a position signal.

[0051] The fluorescent screen 42 is used to convert the particle distribution into a visible light image.

[0052] CCD camera 43 is used to collect the light intensity distribution on fluorescent screen 42.

[0053] In this embodiment, vacuum tube 50 is used to provide a vacuum environment.

[0054] The vortex particle source, gradient magnetic field device, and detection system are all fixedly installed inside the vacuum tube 50.

[0055] The vacuum tube 50 has a vacuum window 51. The vacuum window 51 is fixedly disposed at one end of the vacuum tube 50 and is located behind the vortex particle source.

[0056] In this embodiment, the aperture correction device 70 is used to confine the vortex particle beam so that only the beam in the Z direction remains. The aperture correction device 70 is located between the vortex particle source and the quadrupole magnet 30.

[0057] In this embodiment, the processing system is used to calculate the orbital angular momentum of the vortex particle beam based on the intensity distribution image and the magnetic field gradient parameters.

[0058] According to the theory of charged particle motion in electromagnetic fields, a particle carrying orbital angular momentum will experience a transverse force when passing through a fourth-order magnetic field: , can be obtained ,in For unit charge, For particle mass, Lorentz factor, The charge number of the particle is given, and the particle transport direction is the positive Z-axis. Let be the orbital angular momentum of the particle. , It is the orbital angular momentum quantum number. To reduce Planck's constant, Let be the magnetic field strength in the Z direction. The average magnetic field gradient of a quadrupole magnet 30. This represents the effective range of the fourth-order magnetic field in the Z direction. Let be the momentum of the particle at the moment of incidence. This represents the Z-direction distance from the particle after it exits the fourth-order magnetic field to the MCP detector 41. for The offset distance in direction. If we use vortex electrons as an example for calculation, then... , can be selected The electron energy is 1 keV. Substituting these parameters into the above parameters, we can obtain... That is, for every increase of 1 in the orbital angular momentum quantum number, the lateral offset increases by approximately ,when Every change hour, This meets the measurement accuracy requirements. Under the influence of the magnetic field, the particle beam generates a magnetic field on the detection surface, similar to... The associated lateral offset or asymmetric distribution can be used to deduce the orbital angular momentum by measuring the offset.

[0059] The specific method for generating vortex electrons and measuring their orbital angular momentum based on the spiral phase plate 12 is as follows: After the plane electron wave passes through the spiral phase plate 12, it obtains a continuous spiral phase delay and carries orbital angular momentum, forming a vortex electron beam. After being constrained by the electron beam aperture correction device 70, only the beam in the Z direction remains, which then enters the region of the quadrupole magnet 30 and undergoes a lateral deflection related to orbital angular momentum under the action of the gradient magnetic field. The detection system receives the electron distribution after deflection, and the processing system calculates the electron orbital angular momentum value and its sign based on the beam offset and distribution characteristics.

[0060] The specific scheme for generating vortex ions and measuring their orbital angular momentum is as follows: A vortex ion source 20 is placed at the inlet of vacuum tube 50, generating a wavefront-helically distributed vortex ion beam carrying orbital angular momentum. After being constrained by the aperture correction device 70, only the beam in the Z direction remains, and then it directly enters the region of the quadrupole magnet 30. Under the action of the gradient magnetic field, ions with different orbital angular momentum separate in the vertical direction. The detection system records its multi-peak distribution image, and the processing system calculates the magnitude and direction of the orbital angular momentum based on the peak spacing and intensity asymmetry.

[0061] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific examples.

[0062] Example 1 like Figure 3 As shown, the vortex electron source 10, which measures the orbital angular momentum of vortex particles based on a gradient magnetic field, includes a plane wave electron source 11 and a spiral phase plate 12.

[0063] The vortex electron source 10 includes a plane wave electron source 11 and a spiral phase plate 12 etched with a spiral phase pattern. This phase plate is mounted on the electron beam path within the vacuum tube 50. When the collimated plane wave electron beam passes through this spiral phase plate 12, its wavefront is modulated, obtaining a defined spiral phase distribution, thereby forming a vortex electron beam carrying a defined orbital angular momentum. This vortex electron beam is constrained by the aperture correction device 70 and then enters the region of the quadrupole magnet 30.

[0064] The magnetic field gradient of the quadrupole magnet 30 is perpendicular to the direction of electron beam transmission, and applies a lateral deflection force to the electrons carrying orbital angular momentum. According to the theory of electron motion in electromagnetic fields, the electrons remain deflected after leaving the magnetic field and maintain their orbital angular momentum value, providing a basis for subsequent orbital angular momentum measurement.

[0065] Example 2 like Figure 4 As shown, the vortex electron beam enters the quadrupole magnet 30 after being constrained. The gradient magnetic field of the quadrupole magnet 30 causes the electron beam to undergo orbital angular momentum-dependent separation in the transverse direction, and the electron components with different orbital angular momentum gradually disperse in space.

[0066] From the formula Therefore, it can be determined by measuring the lateral offset distance. This yields specific values ​​for the orbital angular momentum of vortex electrons. The scheme is simple, reliable, and applicable to integrated orbital angular momentum pre-separation of existing electron beamlines.

[0067] Example 3 like Figure 1 As shown, this embodiment provides a device for measuring the orbital angular momentum of vortex particles based on gradient magnetic field, including a vortex electron source 10, a quadrupole magnet 30, a detection system, a vacuum tube 50, a processing system 60, and an aperture correction device 70.

[0068] The vortex electron source 10 includes a plane wave electron source 11 and a spiral phase plate 12, which is directly mounted at the incident end of the vacuum tube 50. After the plane wave electron beam passes through the phase plate, the wavefront is modulated into a spiral distribution, forming a vortex electron beam carrying orbital angular momentum.

[0069] After being constrained by the aperture correction device 70, the beam enters the quadrupole magnet 30.

[0070] The transverse magnetic field gradient provided by the quadrupole magnet 30 is perpendicular to the electron beam transmission direction, which will exert a transverse deflection force on the electrons related to their orbital angular momentum, providing a basis for subsequent orbital angular momentum measurement.

[0071] The detection system is located behind the quadrupole magnet 30 and includes an MCP detector 41, a fluorescent screen 42, and a CCD camera 43, which are used to receive the deflected electron beam and acquire its spatial intensity distribution image.

[0072] The processing system 60 is electrically connected to the CCD camera 43. After receiving the distribution image, it calculates the magnitude and sign of the orbital angular momentum of the electron beam by analyzing the spot offset or distribution asymmetry and combining the gradient parameters of the quadrupole magnet 30.

[0073] Example 4 like Figure 2 As shown, this embodiment provides a device for measuring the orbital angular momentum of vortex particles based on a gradient magnetic field. The difference between this embodiment and embodiment 3 is that in this embodiment, a vortex ion source 20 is directly installed at the incident end of a vacuum tube 50 to generate a vortex ion beam carrying orbital angular momentum.

[0074] After being generated by the vortex ion source 20, the vortex ion beam is constrained by the aperture correction device 70, leaving only the beam in the z-direction, before entering the quadrupole magnet 30. The gradient magnetic field of the quadrupole magnet 30 causes the ion beam to undergo orbital angular momentum-dependent separation in the transverse direction. Ion components with different orbital angular momentum gradually disperse in space and are received by the detection system. This scheme is simple and reliable, and suitable for integrated orbital angular momentum pre-separation of existing ion beam lines.

[0075] The detection system is located behind the quadrupole magnet 30 and includes an MCP detector 41, a fluorescent screen 42, and a CCD camera 43, which are used to receive the deflected ion beam and acquire its spatial intensity distribution image.

[0076] The processing system 60 is electrically connected to the CCD camera 43. After receiving the distribution image, it calculates the magnitude and sign of the orbital angular momentum of the ion beam by analyzing the spot offset or distribution asymmetry and combining the gradient parameters of the quadrupole magnet 30.

[0077] The magnetic field gradient of the quadrupole magnet 30 can be adjusted according to the electron and ion energies and the expected orbital angular momentum range. The detection system and processing system 60 maintain the same configuration, enabling stable, online measurement of the orbital angular momentum of vortex electrons. This device has the advantages of simple structure, fast response, and easy integration into electron microscopes or accelerator beamline systems, and is suitable for real-time measurement and calibration of the orbital angular momentum of charged vortex particle beams.

[0078] Although embodiments of this application have been shown and described above, the scope of protection of this invention is not limited thereto. Any variations or substitutions that can be conceived without inventive effort should be covered within the scope of protection of this invention. Unless expressly stated otherwise, no element, action or instruction used herein should be construed as critical or necessary.

Claims

1. A device for measuring the orbital angular momentum of a vortex particle based on a gradient magnetic field, characterized in that, include: Vortex particle source, used to provide vortex particle beams; A gradient magnetic field device is used to apply a lateral deflection force related to the orbital angular momentum to the vortex particle beam; A detection system is used to receive a particle beam after it has undergone a longitudinal motion and to acquire an image of its intensity distribution; and A processing system is used to calculate the orbital angular momentum of the vortex particle beam based on the intensity distribution image and magnetic field gradient parameters. The gradient magnetic field device is disposed at the rear end of the vortex particle source; The detection system is positioned behind the gradient magnetic field device; The detection system is electrically connected to the processing system.

2. The device for measuring the orbital angular momentum of a vortex particle based on a gradient magnetic field according to claim 1, characterized in that, The vortex particle source includes: A plane-wave electron source, used to provide plane-wave electron waves; and A spiral phase plate is used to induce spiral phase modulation in the passing planar electron wave to form a vortex electron beam carrying orbital angular momentum; The plane wave electron source and the spiral phase plate are arranged sequentially along the transmission direction.

3. The device for measuring the orbital angular momentum of a vortex particle based on a gradient magnetic field according to claim 1, characterized in that, The gradient magnetic field device is a quadrupole magnet with an adjustable magnetic field gradient; The magnetic field gradient direction of the quadrupole magnet is perpendicular to the transmission direction of the vortex particle beam.

4. The device for measuring the orbital angular momentum of a vortex particle based on a gradient magnetic field according to claim 1, characterized in that, The detection system includes: A detector is used to receive the particle beam processed by the gradient magnetic field device and generate a position signal; A fluorescent screen is used to convert particle distribution into a visible light image; and A CCD camera is used to collect the light intensity distribution on the fluorescent screen; The detector, fluorescent screen, and CCD camera are sequentially positioned behind the gradient magnetic field device.

5. The device for measuring the orbital angular momentum of a vortex particle based on a gradient magnetic field according to claim 1, characterized in that, Also includes: Vacuum tubes are used to provide a vacuum environment; The vortex particle source, gradient magnetic field device, and detection system are all fixedly installed inside the vacuum tube.

6. The device for measuring the orbital angular momentum of a vortex particle based on a gradient magnetic field according to claim 5, characterized in that, The vacuum tube has a vacuum window.

7. The device for measuring the orbital angular momentum of a vortex particle based on a gradient magnetic field according to claim 4, characterized in that, The detector is an MCP detector.

8. The device for measuring the orbital angular momentum of a vortex particle based on a gradient magnetic field according to claim 6, characterized in that, The vacuum window is fixedly disposed at one end of the vacuum tube, and the vacuum window is located behind the vortex particle source.

9. The device for measuring the orbital angular momentum of a vortex particle based on a gradient magnetic field according to claim 1, characterized in that, Also includes: An aperture correction device is used to constrain a vortex particle beam so that only the beam in the Z direction remains. The aperture correction device is located between the vortex particle source and the gradient magnetic field device.

10. The device for measuring the orbital angular momentum of a vortex particle based on a gradient magnetic field according to claim 1, characterized in that, The vortex particle source is either a vortex electron source or a vortex ion source.

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