CN117766365A - High-energy electron microscope system based on high-repetition frequency microwave acceleration - Google Patents

Abstract

The invention discloses a high-energy electron microscope system based on high repetition frequency microwave acceleration. The corresponding method of the system includes: using an electron gun to generate an initial electron beam; compressing or accelerating the initial electron beam to obtain the first electron beam; The electrons in the first electron beam perform an energy dispersion reduction or acceleration operation to obtain a second electron beam; the lateral size of the electrons in the second electron beam is shaped to obtain a third electron beam; a detector is used to detect the third electron beam after passing through it. The scattered electrons are imaged after being detected by the sample. The invention can solve the problems of low energy of commercial DC electron microscopes, large volume of traditional high-energy DC electron microscopes, low flow intensity and large energy dispersion of microwave accelerated electron microscopy systems.

Description

A high-energy electron microscope system based on high repetition frequency microwave acceleration

Technical field

The invention relates to the technical field of electron microscope systems, and in particular to a high-energy electron microscope system based on high repetition frequency microwave acceleration.

Background technique

An electron microscope is a microscopic detection device capable of achieving sub-nanometer level spatial resolution. Its basic system components include electron source, electron gun, magnetic lens system, sample and detection module. After the electrons are generated, accelerated, and modulated, they are scattered on the sample and the crystal lattice, and are imaged on the detection screen after passing through the intermediate mirror and the projection mirror. Different atomic types, lattice structures, and crystal axis angles correspond to different imaging results. Due to the high sensitivity of electron microscopes to material structures, they play an irreplaceable role in research in fields such as materials science and biology.

The theoretical spatial resolution of electron microscopy is determined by the wavelength of the electron de Broglie wave. For a certain camera, the number of pixels N and the size d of each pixel remain unchanged; for a fixed sample and camera length L, the de Broglie wavelength λ of the radiation source is proportional to the inverse spatial resolution 1/r of the camera. Inverse proportional relationship. As the energy of the radiation emitted by the radiation source (such as an electron beam) increases, the de Broglie wavelength λ will decrease accordingly. Therefore, as the energy of the radiation source increases, the spatial resolution r increases accordingly.

Most of the electron sources used in traditional commercial electron microscopes are field emission electron sources, which are DC electron sources. The advantage of this DC electron source is the high quality of the electron beam. Due to the low energy of DC electron microscopes, the electron emittance can be reduced to the picometer level with the grid cap and collimation system in the electron gun, and the average current intensity can also reach the mA level. In addition, in recent years, in order to further improve the electron To improve the spatial resolution of microscopes, electron microscope systems that reduce astigmatism during the imaging process, such as chromatic aberration corrected electron microscopes and spherical aberration corrected electron microscopes, have gradually been developed. However, the electron beam energy of existing commercial DC electron microscopes does not exceed 300keV. Limited by the electron energy, its resolution improvement is limited. Moreover, due to its low energy, its penetration ability is poor and it cannot detect thicker materials and chips. , biological cells and other samples for imaging.

There are two solutions to the problem of low energy in current commercial electron microscopes. The first solution is to increase the size of the electron gun based on a DC electron microscope with 100 keV energy, and increase the cavity pressure without changing the electric field gradient. However, this kind of solution often has very large equipment size and high construction difficulty. The application is not widespread. The representative of this type of solution is the ultra-high voltage DC electron microscope of Osaka University in Japan. The electron energy of this electron microscope is 2 to 3 MeV, which can achieve high-energy electronic imaging. However, the total height of the equipment is 13 meters, and the construction and maintenance costs are high; another representative It is a 1.2MeV spherical aberration corrected cold field emission DC electron microscope from Japan's Central Research Laboratory, Hitachi, Ltd.. Its spatial resolution can reach below 50pm, but its high-voltage module and electron gun are bulky, and only the electron gun part is large. The size reaches 3 meters.

The second solution is to use a microwave accelerating electron gun to replace the traditional DC electron gun. This solution solves the problem of the large size of the electron source. However, because it works in pulse mode, the average current intensity of the electrons is low, the emissivity and energy are low. Scatters are significantly larger than DC electron guns. A representative of this program is the u-TEM electron microscope built by Shanghai Jiao Tong University. This electron microscope uses a hot cathode as the electron source and a traditional room temperature microwave electron gun. Its repetition frequency is about tens to one hundred Hz. Although in this program, A single long electron pulse is emitted to improve the signal-to-noise ratio, and a high-order harmonic cavity is added to reduce energy dispersion. However, the imaging signal-to-noise ratio is still much lower than that of a DC electron microscope. The main goal of this electron microscope is to achieve the single-electron imaging mode of high-energy electron microscopy. Reduce the damage to beam quality caused by space charge force.

Previous patents have mentioned the use of high-repetition-frequency electron sources to improve the signal-to-noise ratio of the imaging system. However, the imaging system proposed in this plan is relatively simple in beam quality optimization and imaging control, and mainly relies on subsequent iterative algorithms to optimize imaging. quality.

Current solutions for increasing imaging electron energy have some unavoidable shortcomings. In order to retain the DC characteristics, the compactness and cost of the equipment must be sacrificed; in order to maintain the compactness of the equipment, the signal-to-noise ratio and beam quality of the imaging process need to be sacrificed.

Contents of the invention

The present invention aims to solve one of the technical problems in the related art, at least to a certain extent.

To this end, the present invention proposes a high-energy electron microscope system based on high repetition frequency microwave acceleration. The electron emission mode of the present invention is laser-driven photocathode or field emission, and is combined with an accelerating tube and an energy selector in the beam line to solve the problem of low energy of commercial DC electron microscopes, large volume of traditional high-energy DC electron microscopes, and flow of microwave accelerated electron microscopy systems. The problem of low strength and large energy dispersion. At the same time, because the high-energy electron microscope in the invention retains the pulsed electron emission mode in the photocathode emission mode, in addition to the spatial resolution capability, it also has the time resolution capability, and can carry out dynamic pumping on the basis of static imaging- detection process. Moreover, compared with a DC electron microscope, the microblog-accelerated high-energy electron imaging system of the present invention makes the cumulative effect of electron irradiation damage to the sample smaller, thereby reducing the radiation damage during the imaging process and also reducing the damage of the beam cluster to the sample. .

Another object of the present invention is to propose an application method of a high-energy electron microscope system based on high repetition frequency microwave acceleration.

In order to achieve the above objectives, on the one hand, the present invention proposes a high-energy electron microscope system based on high repetition frequency microwave acceleration, including:

Synchronization timing module, used to provide system time synchronization;

Power source module, used to provide the electromagnetic field required for electron acceleration;

An electron gun module, used to generate an initial electron beam using an electron gun under the electromagnetic field;

The electron beam acceleration module is used to compress and accelerate the initial electron beam to obtain the first electron beam;

An energy selection module, used to reduce the energy dispersion of electrons in the first electron beam to obtain a second electron beam;

The magnetic lens module is used to shape the lateral size of the electrons of the second electron beam to obtain the third electron beam;

A detector module is configured to use a detector to image the electrons scattered in the third electron beam after passing through the sample to be detected.

In addition, the high-energy electron microscope system based on high repetition frequency microwave acceleration according to the above embodiments of the present invention can also have the following additional technical features:

Further, in one embodiment of the present invention, it also includes: a laser module. The laser module includes a driving laser module and a pump laser module. The driving laser module and the pump laser module share a laser source. The driving laser module includes frequency doubling system, compression system, broadening system and pulse stacking system;

When the electron gun is a high-repetition-frequency electron gun, the split-beam laser generated by the laser source is transmitted to the driving laser module to generate a driving laser, and the driving laser is irradiated on the high-repetition frequency through an image transmission system composed of a lens. The cathode position of the electron gun generates the initial electron beam and generates electrons based on the principle of photoelectric emission; when the electron gun is a DC electron gun, there is no need to drive a laser module and electrons are generated directly through field emission;

The pump laser module is used to generate a pump laser from the split laser generated by the laser source through the pump laser module and focus it on the sample to be detected. By adjusting the delay line, the pump laser and The initial electron beam is synchronized upon arrival at the sample.

Further, in one embodiment of the present invention, the synchronization timing module includes a signal distribution system, a low-level system and a laser microwave synchronization system;

The reference signal distribution system is used to provide clock signals for high-energy electron microscopy systems based on high repetition frequency microwave acceleration;

The low-level system is used to use the signal acquisition port of the electron gun to use the monitored microwave phase and amplitude of the electron gun as a low-level feedback signal to adjust the phase and amplitude of the low-level output seed microwave;

The laser microwave synchronization system is used to synchronize the phase of the driving laser and pump laser in the laser module with the microwave fed into the electron gun.

Further, in one embodiment of the present invention, when the electron gun is a high repetition frequency electron gun, the power source module includes a microwave system, and the microwave system includes a solid-state amplifier, a high-voltage modulator and a klystron; The low-level system outputs a low-power seed microwave, which is amplified by a solid-state amplifier to generate a first microwave. The first microwave and the high voltage of the modulator are simultaneously fed into the klystron, and a second microwave is output through the klystron. The second microwave is fed into the electron gun or accelerating tube through the waveguide, four-terminal circulator, and waveguide coupler, forming a resonant accelerating electric field to accelerate electrons;

When the electron gun is a DC electron gun, the power source module includes a DC high-voltage power supply, and the DC high-voltage power supply is used to provide a DC high voltage to accelerate the electrons generated by the DC electron gun.

Further, in one embodiment of the present invention, the electron beam acceleration module includes a multi-section accelerating tube; the accelerating tube operates in a high repetition frequency mode;

The first section of the accelerating tube is made to work in the zero-crossing phase, so as to achieve longitudinal compression and partial energy dispersion compensation of the electron beam; the remaining sections are made to work in the acceleration phase, so as to accelerate the initial electron beam, and finally obtain the first Electron beam.

Further, in one embodiment of the present invention, the energy selection module includes a diode combination and a variable collimation hole,

The dipolar iron combination enables electrons with different energies to be separated laterally when passing through the dipolar iron, and the required electrons are selected by changing the aperture and position of the variable collimation hole on the electron path to obtain the third Two electron beams.

Further, in one embodiment of the present invention, the magnetic lens module includes a condenser lens, an objective lens, a projection mirror and a deflection coil, wherein,

The condenser is used to adjust the size and divergence of the second electron beam on the sample within a preset range;

The objective lens is used to image scattered electrons in the second electron beam;

The projection mirror is used to provide magnetic field strength;

The deflection coil is used to provide a transverse magnetic field to deflect the lateral position of the second electron beam.

Further, in one embodiment of the present invention, it also includes a sample support module, which is used to support, move and cool the sample;

The sample support module includes a sample card, a mobile motor and a refrigerator; the sample is installed on the sample card and mechanically connected to the mobile motor, and the refrigerator is connected to the sample card through a conductive belt.

Further, in one embodiment of the present invention, the detector module includes a variety of optional detectors; in diffraction mode, a phosphorescent screen is used in conjunction with an EMCCD camera to record electronic information; in STEM extremely low charge mode, Electronic information is recorded using the EMPAD detector.

Further, in one embodiment of the present invention, the beam measurement module is also used to install a phosphorescent screen and a metal reflector with a preset angle on the lifting device, and use a camera to observe the lateral distribution state of electrons to obtain different Transverse distribution of electron beams; use a Faraday tube and perform signal analysis with an oscilloscope to obtain charge information of different electron beams.

Further, in one embodiment of the present invention, the electron gun module, electron beam acceleration module, sample support module and detector module are in an ultra-high vacuum environment; wherein the ultra-high vacuum environment is controlled by a molecular pump, an ion pump and a suction pump. Air pump build.

In order to achieve the above object, another aspect of the present invention proposes an application method of a high-energy electron microscope system based on high repetition frequency microwave acceleration, including:

Perform time synchronization of the entire system;

Obtain the electromagnetic field required to accelerate electrons;

Use an electron gun to generate an initial electron beam under an electromagnetic field;

Compress and accelerate the initial electron beam to obtain the first electron beam;

Perform a reduction operation on the energy dispersion of electrons in the first electron beam to obtain a second electron beam;

shaping the lateral size of the electrons of the second electron beam to obtain a third electron beam;

Using a detector to image the electrons scattered in the third electron beam after passing through the sample to be detected;

Monitor the states of electrons at different positions after imaging in the third electron beam to obtain electron state information.

The high-energy electron microscope system and its application method based on high repetition frequency microwave acceleration according to the embodiment of the present invention can solve the problem of low energy of commercial DC electron microscope, large volume of traditional high-energy DC electron microscope, low flow intensity and large energy dispersion of microwave accelerated electron microscope system. In addition to spatial resolution, it also has time resolution.

The beneficial effects of the present invention are:

1) The present invention uses an electron source with a high repetition rate to achieve high signal-to-noise ratio imaging of high-energy electrons, and can be used to detect thick samples (on the order of tens of nm) that are difficult to detect with a traditional DC electron microscope; at the same time, its structure is relatively compact, The electron gun part is only 1 meter in size.

2) The present invention adopts a modular structure. In addition to the TEM mode, high-energy electron diffraction, STEM mode or other beam measurement related research can be realized by selectively opening and closing the lens in the magnetic lens module.

3) The present invention uses a monochromator to select electron energy, and by changing the aperture size of the aperture, the energy dispersion of the electron beam can be reduced to one hundred thousandth.

4) The present invention can image ordinary solid material samples and biological samples. Through the cooling system of the sample support module, the sample temperature can be maintained at liquid helium temperature, thereby reducing sample vibration or movement.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

Figure 1 is a schematic structural diagram of a high-energy electron microscope system based on high repetition frequency microwave acceleration according to an embodiment of the present invention;

Figure 2 is a flow chart of an application method of a high-energy electron microscope system based on high repetition frequency microwave acceleration according to an embodiment of the present invention.

Detailed ways

It should be noted that, as long as there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only These are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts should fall within the scope of protection of the present invention.

The following describes a high-energy electron microscope system based on high repetition frequency microwave acceleration and its application method proposed according to embodiments of the present invention with reference to the accompanying drawings.

Figure 1 is a schematic structural diagram of a high-energy electron microscope system based on high repetition frequency microwave acceleration according to an embodiment of the present invention.

As shown in Figure 1, the system includes:

Synchronization timing module 100, used to provide system time synchronization;

The power source module 200 is used to provide the electromagnetic field required for electron acceleration;

The electron gun module 300 is used to generate an initial electron beam using an electron gun under an electromagnetic field;

The electron beam acceleration module 400 is used to compress and accelerate the electron beam to obtain the first electron beam;

The energy selection module 500 is used to reduce the energy dispersion of electrons in the first electron beam to obtain the second electron beam;

The magnetic lens module 600 is used to shape the lateral size of the electrons of the second electron beam to obtain the third electron beam;

The detector module 700 is configured to use a detector to image the electrons scattered in the third electron beam after passing through the sample to be detected.

Specifically, as shown in Figure 1, the high-energy electron microscope system based on high repetition frequency microwave acceleration of the present invention may include the following modules:

In some embodiments of the present invention, the synchronization timing module 100 is composed of a signal distribution system, a low-level (LowLevel Radio Frequency, LLRF for short) system, and a laser microwave synchronization system. The reference signal distribution system provides clock signals for the entire system. The low-level system generates seed microwaves. The signal acquisition port (pick-up) of the electron gun is used to monitor the microwave phase and amplitude of the electron gun as a low-level feedback signal to adjust the low-level The phase and amplitude of the seed microwave are output to make the microwave phase and amplitude of the electron gun more stable. The laser microwave synchronization system synchronizes the phase of the driving laser and pump laser in the laser module with the microwave fed into the electron gun to ensure that the emission phase of electrons remains stable and the electrons and pump laser can reach the sample at the same time.

In some embodiments of the present invention, when the electron gun is a high repetition frequency electron gun, the function of the power source module 200 is to generate high-power microwaves to accelerate electrons. The microwave system consists of a solid state amplifier (SSA), a high-voltage modulator, and a klystron (Klystron). First, the low-level system in the synchronization timing module 100 outputs low-power seed microwaves, which are primary amplified by a solid-state amplifier (Solid-state Amplifier, SSA) to generate microwaves in the order of hundreds of watts. The microwave and the high voltage of the modulator are simultaneously fed into the klystron, and megawatt-level high-power microwaves are output through the klystron. High-power microwaves are fed into the electron gun or accelerating tube through the waveguide, four-terminal circulator, and waveguide coupler, forming a resonant accelerating electric field for accelerating electrons. When the electron gun is a DC electron gun, the power source module 200 functions as a DC high-voltage power supply, and the DC high-voltage power supply is used to provide a DC high voltage to accelerate the electrons generated by the DC electron gun.

In some embodiments of the present invention, the electron gun module 300 may be a room-temperature high repetition frequency very high frequency electron gun (Very-High-Frequency gun, or VHF gun). This electron gun is a laser-driven photocathode electron gun. Compared with the S/L band microwave electron gun commonly used in current accelerator devices or u-TEM, this electron gun works in the very high frequency band (VHF), with a microwave frequency between 30 and 300MHz. It can operate in high repetition frequency mode, and the electron exit energy is ~1MeV. With the subsequent accelerating tube, the electron energy can be increased to a maximum of 30MeV. Previously, this electron gun has been used in X-ray free electron lasers, including LCLS-II and Shanghai Hard X-ray Free Electron Laser Source, and can achieve stable operation at 1MHz in normal temperature mode. The electron gun module 300 ensures that in the pulse acceleration mode, there is still a sufficiently high current intensity of the imaging electron beam, and currently it can achieve an imaging charge of 100 pC for a single shot.

In some embodiments of the present invention, the high-energy electron microscope system based on high repetition frequency microwave acceleration of the present invention also includes a laser module for generating a driving laser to excite photoelectron emission and a pump laser to pump the sample. It can be understood that Yes.

Specifically, the laser module can be subdivided into a driving laser module and a pump laser module. The two modules share a laser source. After the laser source is generated, it is divided into two parts through beam splitting. The driving laser module includes a frequency doubling system, a compression system, a broadening system and a pulse stacking system, which can produce driving lasers of any horizontal and vertical size within a certain range. It is currently the most flexible and easy-to-control method for controlling the generation of cathode electrons; when When the electron gun of the electron gun module 300 is selected as a high-repetition-frequency electron gun, the split-beam laser generated by the laser source is transmitted to the driving laser module to generate a driving laser. The laser generated by the driving laser module is irradiated on the high-repetition-frequency electron gun through an image transmission system composed of a lens. At the cathode position, photoelectrons are generated using the photoelectric effect. When the electron gun of the electron gun module 300 is selected as a DC electron gun, there is no need to drive the laser module and electrons can be generated directly through field emission. The pump laser module is used to transmit the pump light (usually 800nm infrared light) and focus it on the sample to be detected. By adjusting the delay line, the pump laser and the electron beam are synchronized when they reach the sample.

Furthermore, the main function of driving the laser module is to generate electrons through the photoelectric effect at the cathode. This electron generation method is called photoelectric emission. Field emission can also be used to generate electrons. This emission method does not require driving a laser. It only needs to process the cathode into a needle tip shape and use the tip discharge principle under a strong electric field to emit electrons. The needle tip can also be heated during this emission process. , to reduce the emission electric field threshold.

In some embodiments of the present invention, the electron beam acceleration module 400 includes 2 or 3 sections of accelerating tubes. The accelerating tubes all work in high repetition frequency mode. Each section of the accelerating tube can independently compress or accelerate the electron beam longitudinally by changing the phase of the microwave relative to the electron beam. Generally, it is chosen to make the first accelerating tube work in the zero-crossing phase to achieve longitudinal compression and partial energy dispersion compensation of the electron beam; to make the subsequent accelerating tube work in the accelerating phase to achieve the overall acceleration of the electron beam, and finally get the first Electron beam. The accelerating tube is used to further accelerate the lower energy (~1MeV) electrons generated from the electron gun. By changing the feed power of the accelerating tube, the final acceleration energy of the electrons can be continuously adjusted to tens of MeV.

In some embodiments of the invention, an energy selection module 500 is used to further reduce electron energy dispersion. The energy selection module 500 includes a dipolar iron combination and a variable collimation hole. The dipolar iron combination can cause electrons of different energies to be separated laterally when they pass through the diode, and then by changing the variable alignment on the electron path. The aperture and location of the collimated holes are selected as needed for the electrons. The smaller the diameter of the collimation hole, the smaller the energy dispersion of the electron beam obtained; by changing the lateral position of the collimation hole, electron beams with different center energies can be selected. The combination of multiple diodes can make the electrons return to their original direction of motion after energy selection to obtain a second electron beam.

In some embodiments of the present invention, the magnetic lens module 600 is used to shape the lateral (perpendicular to the electron transmission direction) size of electrons. The module includes a set of condenser lenses, an objective lens, a projection lens and a set of deflection coils. The condenser lens and deflection coil are located in front of the sample, and the objective lens and projection lens are located behind the sample. The condenser, objective, and projection lenses provide longitudinal magnetic fields that modulate the lateral dimensions of the electron beam. By adjusting the condenser, the size and divergence angle of the electron beam on the sample can be adjusted within a certain range. The objective lens is used to image scattered electrons. By adjusting the magnetic field strength of the projection mirror, the image plane or back focus of the objective lens can be achieved on the detector. Surface imaging to achieve diffraction or imaging modes. The deflection coil provides a transverse magnetic field to deflect the lateral position of the electron beam, enabling scanning of the electron beam on the sample within a certain range. During actual operation, different magnetic lenses can be selectively switched on and off to achieve different imaging modes: if only the projection mirror and deflection coil are turned on, the STEM mode can be achieved; if the condenser lens, objective lens, and projection mirror are turned on, the TEM mode can be achieved . This plan proposes for the first time the design of implanting a scanning coil into a high-energy imaging system to further improve the functions of the high-energy imaging system.

In some embodiments of the present invention, the high-energy electron microscope system based on high repetition frequency microwave acceleration of the present invention also includes a sample support module, which is used to support, move and cool the sample. The module includes sample cards, moving motors and refrigerators. The sample is mounted on the TEM sample card and mechanically connected to the moving motor. The moving motor includes three-dimensional translational motion and three-dimensional rotational motion. The refrigerator is connected to the sample card through a conductive tape and can cool the sample to liquid helium temperature. At this low temperature, the thermal motion of the sample atoms can be suppressed as much as possible. It can be known that since the current high-energy imaging technology solutions have not considered imaging biological samples, the sample cooling system has not been considered.

In some embodiments of the present invention, the detector module 700 includes a variety of optional detectors. In the diffraction mode, a phosphorescent screen is used with an EMCCD camera to record electronic information; in a very low charge mode such as STEM , using the EMPAD detector to record electronic information.

It is understandable that currently commercial 100 keV energy DC electron microscopes generally use commercial Electronic Magnified Pixel-array Detector (EMPAD). Although this detector has the advantages of fast acquisition speed and large dynamic range, However, it is only suitable for electron imaging of hundreds of keV energy and cannot be used for electron beam imaging of MeV energy. The detector currently commonly used for electron imaging of MeV energy is EMCCD, which records the fluorescence emitted by electrons hitting the phosphorescent screen. For electronic imaging information, the applicable electron energy range is large, but the dynamic range is small, making it difficult to achieve imaging under low charge amounts.

Specifically, the present invention uses an EMPAD detector that has not been used before and is suitable for high-energy electrons. This detector can achieve imaging from a single electron to 1000 electrons, and the acquisition speed can reach more than 100 kHz.

In some embodiments of the present invention, the system further includes a beam measurement module, which is used to monitor the charge amount, lateral distribution and other properties of the electron beam at different positions. Preferably, a combination of a YAG phosphor screen and a 45° metal reflector is suspended on the pulling device, and a CCD camera is used to observe the lateral distribution of electrons; a Faraday tube is used, and the charge information of the electron beam is obtained by analyzing the signal with an oscilloscope.

In some embodiments of the present invention, the electron gun module 300, the electron beam acceleration module 400, the sample support module and the detector module 700 in the above modules are all in an ultra-high vacuum environment. The ultra-high vacuum environment of the system is maintained by molecular pumps, ion pumps and getter pumps.

The high-energy electron microscope system based on high repetition frequency microwave acceleration according to the embodiment of the present invention can solve the problems of low energy of commercial DC electron microscopes, large volume of traditional high-energy DC electron microscopes, low flow intensity and large energy dispersion of microwave accelerated electron microscope systems. At the same time, it can realize high-signal-to-noise ratio imaging of high-energy electrons, realize high-energy electron diffraction, STEM mode, or carry out other beam measurement-related research, can image ordinary solid-state material samples and biological samples, and make pulsed electron beams more damaging to samples. Small.

In order to implement the above embodiment, as shown in Figure 2, this embodiment also provides an application method of a high-energy electron microscope system based on high repetition frequency microwave acceleration. The method includes:

S1, performs time synchronization of the entire system;

S2, obtain the electromagnetic field required for electron acceleration;

S3, use an electron gun to generate an initial electron beam under an electromagnetic field;

S4, compress and accelerate the initial electron beam to obtain the first electron beam;

S5, reduce the energy dispersion of electrons in the first electron beam to obtain the second electron beam;

S6, shaping the lateral size of the electrons of the second electron beam to obtain the third electron beam;

S7, use the detector to image the electrons scattered in the third electron beam after passing through the sample to be detected;

S8, monitor the states of electrons at different positions after imaging in the third electron beam, and obtain electron state information.

According to the application method of high-energy electron microscopy system based on high repetition frequency microwave acceleration according to the embodiment of the present invention, it can solve the problem of low energy of commercial DC electron microscope, large volume of traditional high-energy DC electron microscope, low flow intensity and large energy dispersion of microwave accelerated electron microscopy system. At the same time, it can realize high signal-to-noise ratio imaging of high-energy electrons, realize high-energy electron diffraction, STEM mode or carry out other beam measurement related research, can image ordinary solid-state material samples and biological samples, and enable pulsed electron beams to The damage is smaller.

In the description of this specification, reference to the terms "one embodiment," "some embodiments," "an example," "specific examples," or "some examples" or the like means that specific features are described in connection with the embodiment or example. , structures, materials or features are included in at least one embodiment or example of the invention. In this specification, the schematic expressions of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine different embodiments or examples and features of different embodiments or examples described in this specification unless they are inconsistent with each other.

In addition, the terms “first” and “second” are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Therefore, features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

Claims (12)

1. A high-energy electron microscope system based on high repetition frequency microwave acceleration, which is characterized by including: Synchronization timing module, used to provide time synchronization of the entire system; Power source module, used to provide the electromagnetic field required for electron acceleration; An electron gun module, used to generate an initial electron beam using an electron gun under the electromagnetic field; The electron beam acceleration module is used to compress and accelerate the initial electron beam to obtain the first electron beam; An energy selection module, used to reduce the energy dispersion of electrons in the first electron beam to obtain a second electron beam; The magnetic lens module is used to shape the lateral size of the electrons of the second electron beam to obtain the third electron beam; A detector module is configured to use a detector to image the electrons scattered in the third electron beam after passing through the sample to be detected. 2. The system according to claim 1, further comprising: a laser module, the laser module includes a driving laser module and a pump laser module, the driving laser module and the pump laser module share a laser source , the driving laser module includes a frequency doubling system, a compression system, a broadening system and a pulse accumulation system; When the electron gun is a high-repetition-frequency electron gun, the split-beam laser generated by the laser source is transmitted to the driving laser module to generate a driving laser, and the driving laser is irradiated on the high-repetition frequency through an image transmission system composed of a lens. The cathode position of the electron gun generates the initial electron beam and generates electrons based on the principle of photoelectric emission; when the electron gun is a DC electron gun, there is no need to drive a laser module and electrons are generated directly through field emission; The pump laser module is used to generate a pump laser from the split laser generated by the laser source through the pump laser module and focus it on the sample to be detected. By adjusting the delay line, the pump laser and The initial electron beam is synchronized upon arrival at the sample. 3. The system according to claim 2, characterized in that the synchronization timing module includes a signal distribution system, a low-level system and a laser microwave synchronization system; The reference signal distribution system is used to provide clock signals for high-energy electron microscopy systems; The low-level system is used to use the signal acquisition port of the electron gun to use the monitored microwave phase and amplitude of the electron gun as a low-level feedback signal to adjust the phase and amplitude of the low-level output seed microwave; The laser microwave synchronization system is used to synchronize the phase of the driving laser and pump laser in the laser module with the microwave fed into the electron gun. 4. The system according to claim 3, characterized in that when the electron gun is a high repetition frequency electron gun, the power source module includes a microwave system, and the microwave system includes a solid-state amplifier, a high-voltage modulator and a klystron. ; The low-level system outputs a low-power seed microwave, which is amplified by a solid-state amplifier to generate a first microwave. The first microwave and the high voltage of the modulator are simultaneously fed into the klystron, and a second microwave is output through the klystron. The second microwave is fed into the electron gun or accelerating tube through the waveguide, the four-terminal circulator, and the waveguide coupler to form a resonant accelerating electric field to accelerate the electrons; When the electron gun is a DC electron gun, the power source module includes a DC high-voltage power supply, and the DC high-voltage power supply is used to provide a DC high voltage to accelerate the electrons generated by the DC electron gun. 5. The system according to claim 1, characterized in that the electron beam acceleration module electron beam acceleration module includes a multi-section accelerating tube; the accelerating tube operates in a high repetition frequency mode; The first section of the accelerating tube is made to work in the zero-crossing phase, so as to achieve longitudinal compression and partial energy dispersion compensation of the electron beam; the remaining sections are made to work in the acceleration phase, so as to accelerate the initial electron beam, and finally obtain the first Electron beam. 6. The system according to claim 1, characterized in that the energy selection module includes a diode combination and a variable collimation hole, The dipolar iron combination enables electrons with different energies to be separated laterally when passing through the dipolar iron, and the required electrons are selected by changing the aperture and position of the variable collimation hole on the electron path to obtain the third Two electron beams. 7. The system according to claim 1, wherein the magnetic lens module includes a condenser lens, an objective lens, a projection mirror and a deflection coil, wherein, The condenser is used to adjust the size and divergence of the second electron beam on the sample within a preset range; The objective lens is used to image scattered electrons in the second electron beam; The projection mirror is used to provide magnetic field strength; The deflection coil is used to provide a transverse magnetic field to deflect the lateral position of the second electron beam. 8. The system according to claim 1, further comprising a sample support module, the sample support module is used to support, move and cool the sample; The sample support module includes a sample card, a mobile motor and a refrigerator; the sample is installed on the sample card and mechanically connected to the mobile motor, and the refrigerator is connected to the sample card through a conductive belt. 9. The system according to claim 1, characterized in that the detector module includes a variety of optional detectors; in diffraction mode, a phosphorescent screen is used in conjunction with an EMCCD camera to record electronic information; in STEM extremely low charge mode, the EMPAD detector is used to record electronic information. 10. The system according to claim 1, characterized in that the beam measurement module is also used to install a phosphorescent screen and a preset angle metal reflector on the lifting device, and use a camera to observe the lateral distribution state of electrons , to obtain the lateral distribution of different electron beams; use a Faraday tube and conduct signal analysis through an oscilloscope to obtain the charge information of different electron beams. 11. The system according to any one of claims 1-10, characterized in that the electron gun module, electron beam acceleration module, sample support module and detector module are in an ultra-high vacuum environment; wherein, the ultra-high vacuum The environment is constructed through molecular pumps, ion pumps, and getter pumps. 12. A method applied to the high-energy electron microscopy system based on high repetition frequency microwave acceleration according to claim 1, characterized in that the method includes the following steps: Perform time synchronization of the entire system; Obtain the electromagnetic field required to accelerate electrons; Use an electron gun to generate an initial electron beam under an electromagnetic field; Compress and accelerate the initial electron beam to obtain the first electron beam; Perform a reduction operation on the energy dispersion of electrons in the first electron beam to obtain a second electron beam; shaping the lateral size of the electrons of the second electron beam to obtain a third electron beam; Using a detector to image the electrons scattered in the third electron beam after passing through the sample to be detected; Monitor the states of electrons at different positions after imaging in the third electron beam to obtain electron state information.