A device for generating a vortex electron beam based on a magnetic immersion cathode

Abstract

The application relates to the technical field of vortex electron beam preparation, and particularly discloses a device for generating a vortex electron beam based on a magnetic immersion cathode, which comprises an energized solenoid, a laser output device, a photocathode device and an electromagnetic lens. The laser output device is used for outputting laser; the photocathode device is fixedly arranged in the energized solenoid; the electromagnetic lens is fixedly arranged at the rear end of the energized solenoid and is used for amplifying the cross section of the generated vortex beam; the photocathode device is a ring-shaped photocathode structure or a low-temperature-cooled photocathode structure; the device for generating a vortex electron beam based on a magnetic immersion cathode has the characteristics of simple structure, high generation efficiency and strong flexibility and is suitable for various equipment environments such as electron accelerators.

Description

Technical Field

[0001] This invention relates to the field of vortex electron beam preparation technology, and more specifically to a device for generating vortex electron beams based on a magnetically immersed cathode. Background Technology

[0002] Vortex beams carrying orbital angular momentum have found crucial applications in numerous fields, including optics, atomic and molecular physics, nuclear physics, materials science, biomedicine, chemistry, quantum information, and astrophysics. Vortex electrons represent a recent area of ​​research in vortex beams. However, current experimental research on vortex electron beams, both domestically and internationally, primarily relies on electron microscopy, producing beams with energies around 300 keV. Furthermore, methods for generating vortex electrons mainly include helical phase plates, holographic gratings, and magnetic monopole methods. These methods suffer from relatively low flexibility and efficiency, limiting the widespread application of vortex electron beams. Therefore, exploring new principles and methods for generating vortex electrons is an important aspect of experimental research. Based on Bush's theorem, electrons generating Landau states in a magnetic field and then transporting to a region outside the magnetic field can produce vortex electron beams with controllable angular momentum. The orbital angular momentum of the vortex electrons can be freely adjusted simply by changing the strength of the magnetic field. Therefore, magnetic immersion cathodes offer an efficient and flexible method for generating vortex electron beams. By using the magnetic immersion cathode method in accelerators, high-energy vortex electron beams can be generated more efficiently, providing a new approach for studying the properties of high-energy vortex electrons and particle physics. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a device for generating vortex electron beams based on magnetic immersion cathodes. It has the characteristics of simple structure, high generation efficiency and strong flexibility, and is suitable for various equipment environments such as electron accelerators. It can provide a new approach for studying the characteristics of high-energy vortex electrons and particle physics.

[0004] To solve the above problems, the present invention adopts the following technical solution:

[0005] A device for generating a vortex electron beam based on a magnetically immersed cathode includes an energized solenoid, a laser output device, a photocathode device, and an electromagnetic lens.

[0006] The laser output device is used to output laser light.

[0007] The photocathode device is fixedly disposed inside the energized solenoid.

[0008] The electromagnetic lens is fixedly disposed at the rear end of the energized solenoid, which amplifies the cross-section of the generated vortex beam.

[0009] The photocathode device is a ring photocathode structure or a cryogenically cooled photocathode structure.

[0010] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one embodiment of the present disclosure further comprises a vacuum pipe, and the vacuum pipe has a vacuum window.

[0011] The energized solenoid and the electromagnetic lens are arranged in the vacuum pipe.

[0012] The vacuum window is located at the front end of the energized solenoid, and the central axis of the vacuum window coincides with the central axis of the energized solenoid.

[0013] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one embodiment of the present disclosure comprises a light cathode device.

[0014] The light cathode device is fixed in the energized solenoid through the support, and the central axis of the light cathode device is collinear with the central axis of the energized solenoid.

[0015] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one embodiment of the present disclosure comprises an electromagnetic lens, and the central axis of the electromagnetic lens is collinear with the central axis of the energized solenoid.

[0016] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one embodiment of the present disclosure further comprises a detector, a fluorescent screen and a CCD camera.

[0017] The detector, the fluorescent screen and the CCD camera are sequentially arranged behind the electromagnetic lens.

[0018] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one embodiment of the present disclosure comprises a microchannel plate detector.

[0019] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one embodiment of the present disclosure further comprises a collimating lens and a focusing lens.

[0020] The collimating lens, the focusing lens and the vacuum window are sequentially arranged along an optical path.

[0021] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one embodiment of the present disclosure comprises a low-temperature cooled light cathode structure, and the support is provided with a cooling liquid circulation system.

[0022] When the light cathode device is a ring-shaped light cathode structure, a spatial light modulator is further arranged between the focusing lens and the vacuum window.

[0023] The method for generating a magnetic immersion cathode provided by the present application can generate pure-mode vortex electrons, has the characteristics of simple structure, high generation efficiency and strong flexibility, and is suitable for various device environments such as electron accelerators.

[0024] In the present application, there are two schemes for the light cathode device for generating vortex electrons: scheme one is that vortex light acts on a ring-shaped light cathode to ionize and generate vortex electrons; and scheme two is that a Gaussian laser irradiates a low-temperature cooled light cathode to generate vortex electrons; both of the two schemes of the method of the present application are in accordance with the Bohr theorem, and the charged particles generated in a magnetic field still carry angular momentum when being transported to a magnetic field-free region due to the conservation of the regular orbit angular momentum of the particles. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0026] Figure 1 It is a schematic diagram of the principle of the ring-shaped light cathode.

[0027] Figure 2 It is a schematic diagram of the principle of the low-temperature cooled light cathode.

[0028] Figure 3 It is a structural schematic diagram of the device for generating a vortex electron beam based on a magnetic immersion cathode in embodiment 3.

[0029] Figure 4 It is a structural schematic diagram of the device for generating a vortex electron beam based on a magnetic immersion cathode in embodiment 4.

[0030] In the drawings:

[0031] 10, energized solenoid;

[0032] 20, light cathode device; 21, support;

[0033] 30, electromagnetic lens;

[0034] 40, vacuum pipeline; 41, vacuum window;

[0035] 50, laser output device;

[0036] 60, collimating lens;

[0037] 70, focusing lens;

[0038] 80, spatial light modulator;

[0039] 90, microchannel plate detector;

[0040] 100, fluorescent screen;

[0041] 110, CCD camera. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings in the embodiments. Obviously, the described embodiments are only some of the embodiments, but not all of the embodiments.

[0043] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one of the embodiments of the present disclosure comprises a powered solenoid, a laser output device, a photocathode device, and an electromagnetic lens.

[0044] The laser output device is configured to output laser light. The photocathode device is fixedly arranged in the powered solenoid. The electromagnetic lens is fixedly arranged at a rear end of the powered solenoid to magnify a cross section of the generated vortex beam. The photocathode device is in a ring-shaped photocathode structure or a low-temperature cooled photocathode structure.

[0045] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one of the embodiments of the present disclosure further comprises a vacuum pipeline, and the vacuum pipeline has a vacuum window.

[0046] The powered solenoid and the electromagnetic lens are both arranged in the vacuum pipeline.

[0047] The vacuum window is located at a front end of the powered solenoid, and a central axis of the vacuum window coincides with a central axis of the powered solenoid.

[0048] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one of the embodiments of the present disclosure has a support for the photocathode device.

[0049] The photocathode device is fixed in the powered solenoid through the support, and a central axis of the photocathode device is collinear with a central axis of the powered solenoid.

[0050] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one of the embodiments of the present disclosure has a support for the photocathode device.

[0051] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one of the embodiments of the present disclosure further comprises a detector, a fluorescent screen, and a CCD camera.

[0052] The detector, the fluorescent screen, and the CCD camera are sequentially arranged behind the electromagnetic lens.

[0053] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one of the embodiments of the present disclosure has a support for the photocathode device.

[0054] The device for generating a vortex electron beam based on a magnetic immersion cathode provided by at least one of the embodiments of the present disclosure further comprises a collimating lens and a focusing lens.

[0055] The collimating lens, the focusing lens, and the vacuum window are sequentially arranged along an optical path.

[0056] At least one embodiment of the present disclosure provides a device for generating a vortex electron beam based on a magnetic immersion cathode, wherein the photocathode device is a low-temperature cooled photocathode structure, and the bracket is provided with a cooling liquid circulation system.

[0057] When the photocathode device is a ring-shaped photocathode structure, a spatial light modulator is further arranged between the focusing lens and the vacuum window.

[0058] According to the Bohr theory, the initial mechanical angular momentum of the electron generated in the central region of the solenoid is zero, and the angular momentum of the electron when it is transmitted to the space without a magnetic field is , or can be written as . Wherein is the elementary charge, is the charge state of the ion, and ρ is the width of the electron wave packet, is the magnetic field strength. That is, vortex electrons can be generated in a magnetic field, and the vortex electrons remain in a vortex state when they are transmitted until they leave the solenoid.

[0059] The specific scheme for generating vortex electrons by a ring-shaped photocathode is that the laser output by the laser output device is modulated in phase by the spatial light modulator after passing through the collimating lens and the focusing lens to generate vortex light, and then enters the vacuum pipeline from the observation window to act on the ring-shaped photocathode to generate a pure-mode vortex electron beam. The transverse coherence of the electron beam is consistent with that of the vortex light, and has a large transverse coherence length.

[0060] The specific scheme for generating vortex electrons by a low-temperature cooled photocathode is that a cooling channel is processed in the bracket, and the photocathode is cooled to a low temperature by the cooling liquid circulation system in the bracket, so that the generated electrons have a low transverse momentum. The laser output by the laser output device enters the vacuum pipeline from the observation window to act on the low-temperature photocathode to generate vortex electrons.

[0061] In order to more specifically describe the present application, the technical solutions of the present application will be described in detail below in combination with the drawings and specific examples.

[0062] Example 1

[0063] As shown in Figure 1 , the energized solenoid 10, the photocathode device 20, and the electromagnetic lens of the ring-shaped photocathode device for generating a vortex electron beam based on a magnetic immersion cathode are all installed in the vacuum pipeline 40.

[0064] The energized solenoid 10 generates a uniform magnetic field. The laser output device outputs laser light which passes through a collimating lens and a focusing lens, and then passes through a spatial light modulator. The phase distribution of the laser light is changed to obtain vortex light. The vortex light is irradiated to the left face of the annular photocathode device 20 in the energized solenoid 10, and then the vortex electrons of a pure mode are emitted from the right face of the photocathode device 20. In addition to the spatial distribution, the transverse momentum distribution of the electrons also needs to be matched with the phase space of the Laguerre-Gaussian mode. According to the Bohr theory, the regular orbital angular momentum of any charged particle generated in a magnetic field is conserved, so the vortex electron beam generated still has the orbital angular momentum after leaving the energized solenoid 10.

[0065] Embodiment 2

[0066] As shown in FIG. 2, the annular photocathode device for generating a vortex electron beam based on a magnetic immersion cathode includes an energized solenoid 10, a photocathode device 20, an electromagnetic lens 30, a vacuum tube 40, a laser output device 50, a collimating lens 60, a focusing lens 70, a spatial light modulator 80, a microchannel plate detector 90, a phosphor screen 100, and a CCD camera 110. Figure 2 The laser output device 50 outputs laser light which passes through the collimating lens 60 and the focusing lens 70, and then passes through the spatial light modulator 80 to generate vortex light. Subsequently, the vortex light enters the vacuum tube 40 from the vacuum window 41. The energized solenoid 10 is installed in the vacuum tube 40, and generates a uniform magnetic field after being energized.

[0067] According to the formula , the electrons generated in the magnetic field have a certain orbital angular momentum.

[0068] Embodiment 3

[0069] As shown in FIG. 3, the annular photocathode device for generating a vortex electron beam based on a magnetic immersion cathode includes an energized solenoid 10, a photocathode device 20, an electromagnetic lens 30, a vacuum tube 40, a laser output device 50, a collimating lens 60, a focusing lens 70, a spatial light modulator 80, a microchannel plate detector 90, a phosphor screen 100, and a CCD camera 110. Figure 3 The laser output device 50 outputs laser light which passes through the collimating lens 60 and the focusing lens 70, and then passes through the spatial light modulator 80 to generate vortex light. Subsequently, the vortex light enters the vacuum tube 40 from the vacuum window 41. The energized solenoid 10 is installed in the vacuum tube 40, and generates a uniform magnetic field after being energized.

[0070] The photocathode device 20 is fixed in the energized solenoid 10 by the bracket 21, and emits a vortex electron beam of a pure mode from the right face after being irradiated by the focused laser light on the left face. According to the Bohr theory, the electrons excited by the laser light in the magnetic field have a quantum orbital angular momentum, and still maintain the vortex state after leaving the energized solenoid 10 region.

[0071] The laser output device 50 outputs laser light which passes through the collimating lens 60 and the focusing lens 70, and then passes through the spatial light modulator 80 to generate vortex light. Subsequently, the vortex light enters the vacuum tube 40 from the vacuum window 41. The energized solenoid 10 is installed in the vacuum tube 40, and generates a uniform magnetic field after being energized.

[0072] The photocathode device 20 is fixed in the energized solenoid 10 by the bracket 21, and emits a vortex electron beam of a pure mode from the right face after being irradiated by the focused laser light on the left face. According to the Bohr theory, the electrons excited by the laser light in the magnetic field have a quantum orbital angular momentum, and still maintain the vortex state after leaving the energized solenoid 10 region.

[0073] The vortex electron beam derived from the energized solenoid 10 is transmitted through the electromagnetic lens 30 installed downstream of the energized solenoid 10, and the transverse dimension of the beam is enlarged. The "doughnut" pattern of the vortex electron beam is observed by using the microchannel plate detector 90, the phosphor screen 100 and the CCD camera 110 at the downstream end.

[0074] Example 4

[0075] As Figure 4 shown, compared with Example 3, no spatial light modulator is arranged in this example, and the shape of the photocathode device 20 is not annular, and the photocathode device 20 is cooled by the cooling liquid circulation system to be in a low temperature state.

[0076] The laser output device 50 outputs laser, and the output laser enters the vacuum pipe 40 from the vacuum window 41 after passing through the collimating lens 60 and the focusing lens 70 to act on the cooled low-temperature photocathode device 20, and the vortex electron beam is emitted from the right side after the left side is irradiated by the focused laser. In the process of electron emission, the circulating liquid helium or liquid nitrogen in the bracket 21 of the photocathode device 20 cools the photocathode device 20. The generated vortex electron beam is enlarged in transverse dimension after passing through the electromagnetic lens 30 and is detected.

[0077] Although the embodiments of the present application have been shown and described above, the scope of protection of the present application is not limited thereto, and any changes or substitutions not thought of through creative labor should be covered within the scope of protection of the present application; unless explicitly stated, any element, action or instruction used herein should not be interpreted as critical or essential.

Claims

1. A device for generating a vortex electron beam based on a magnetically immersed cathode, characterized in that, include: Energized solenoid; Laser output device, used to output laser light; A photocathode device is fixedly disposed inside the energized solenoid; An electromagnetic lens is fixedly disposed at the rear end of the energized solenoid to amplify the cross-section of the generated vortex beam; Vacuum pipe with a vacuum window; Collimating lens; as well as Focusing lens; The collimating lens, focusing lens, and vacuum window are arranged sequentially along the optical path; Both the energized solenoid and the electromagnetic lens are disposed inside the vacuum pipe; The vacuum window is located at the front end of the energized solenoid; The photocathode device is a ring photocathode structure or a cryogenically cooled photocathode structure; The photocathode device has a support frame; The photocathode device is fixed inside the energized solenoid by the bracket; When the photocathode device is a low-temperature cooled photocathode structure, a coolant circulation system is provided inside the support; When the photocathode device is a ring photocathode structure, a spatial light modulator is also provided between the focusing lens and the vacuum window.

2. The device for generating a vortex electron beam based on a magnetically immersed cathode according to claim 1, characterized in that, The central axis of the vacuum window coincides with the central axis of the energized solenoid.

3. The device for generating a vortex electron beam based on a magnetically immersed cathode according to claim 1, characterized in that, The central axis of the photocathode device is collinear with the central axis of the energized solenoid.

4. The device for generating a vortex electron beam based on a magnetically immersed cathode according to claim 1, characterized in that, The central axis of the electromagnetic lens is collinear with the central axis of the energized solenoid.

5. The apparatus for generating a vortex electron beam based on a magnetically immersed cathode according to claim 1 or 2, characterized in that, Also includes: detector; Fluorescent screen; as well as CCD camera; The detector, fluorescent screen, and CCD camera are sequentially positioned behind the electromagnetic lens.

6. The device for generating a vortex electron beam based on a magnetically immersed cathode according to claim 5, characterized in that, The detector is a microchannel plate detector.

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