A miniaturized, all-electrostatic scanning electron microscope lens suitable for in-situ lunar surface exploration

Abstract

This invention discloses a miniaturized, all-electrostatic scanning electron microscope (SEM) lens suitable for in-situ lunar surface exploration, belonging to the field of lunar exploration technology. It includes: an electron gun, a condenser lens module, a microchannel plate detector, and an objective lens system, all fixed sequentially along the axis. The lens employs an all-electrostatic system, with through-holes in the condenser lens module and objective lens system to introduce the natural vacuum environment of the lunar surface. The condenser lens module features an innovative multi-functional electrode structure, enabling the condenser to also function as an aperture stop. The objective lens system integrates an electrostatic deflector capable of simultaneously performing scanning deflection and astigmatism correction. This invention, through its all-electrostatic design, integrated and compact design for introducing lunar surface vacuum, effectively overcomes the magnetic leakage and heat loss of traditional electromagnetic lenses, reduces reliance on complex vacuum equipment, improves system integration, and meets the requirements for miniaturization and lightweight lunar surface exploration payloads. It also enhances the structural reliability of the system under launch vibration and lunar seismic environments.

Description

Technical Field

[0001] This application belongs to the field of lunar exploration technology, specifically relating to a scanning electron microscope lens, and more specifically, to a fully electrostatic miniaturized scanning electron microscope lens suitable for in-situ exploration on the lunar surface. Background Technology

[0002] Scanning electron microscopy (SEM) has played a crucial role in the analysis of samples returned from lunar sample return missions, and is widely used in experiments to observe the particle size characteristics, morphology, composition, and radiation effects of lunar regolith samples, as well as to acquire raw image data. However, due to its bulky structure and complex peripheral components, traditional SEM equipment can typically only be operated by trained technicians in specialized laboratories. This limitation restricts the analysis of lunar regolith and rock samples to a limited number of high-cost sampling missions carrying returned samples, failing to meet the scientific needs of the International Lunar Research Station (IRR) of the fourth phase of the lunar exploration program for in-situ exploration of the microstructure of lunar dust and regolith.

[0003] Traditional scanning electron microscopes (SEMs) utilize the acceleration and energy regulation properties of electrostatic fields for low-energy electrons, along with the fine focusing and high-energy electron manipulation properties of magnetic fields, to achieve rapid response and excellent aberration control in their electron optical system design and optimization methods. They achieve scanning and focusing functions through a combination of multiple electrostatic and magnetic lenses, along with physical apertures, scanning coils, and other modules. However, the electromagnetic leakage of commonly used semi-immersion objective systems, the electromagnetic interference generated by the strong excitation coils required for the condenser lens module, and the heat dissipation issues in the vacuum environment pose significant challenges for electromagnetic shielding and thermal management in lunar research stations operating numerous scientific instruments simultaneously. These challenges make the electromagnetic hybrid field approach difficult to implement.

[0004] In large scanning electron microscopes used in ground laboratories, the objective lens is usually responsible for the final focusing of the electron beam before it acts on the sample surface, while the scanning deflection function is achieved by a separate scanning coil. Although this fine division of labor has improved focusing accuracy to some extent, enabling the resolution of electron microscopes to break through the nanometer level, it has also made the integration of the electron optical system insufficient, making it difficult to meet the application requirements of miniaturization and integration of satellite payload instruments. Furthermore, the improved nanometer-level resolution is not the basic data acquisition required for low-cost and high-timeliness in-situ lunar surface exploration.

[0005] Furthermore, the precision assembly requirements of ground-based SEMs fundamentally conflict with the launch environment of lunar exploration missions. The vibration acceleration of a launch vehicle during the third-stage separation phase can reach 8-12 times the Earth's gravitational acceleration, and key components such as quartz glass insulators and ceramic magnetic cores used in existing SEMs are susceptible to structural failure during launch.

[0006] Chinese invention patent application CN 120064144 A discloses an in-situ drilling-while-drilling device and method for lunar resource exploration. This device employs real-time scanning and detection of the polarization and spectral characteristics of lunar regolith profiles to explore the depth distribution of lunar resources and measure the physical properties of the lunar regolith in situ, thereby retrieving the resource distribution and content of the profile and acquiring information on the physical properties of the lunar regolith. However, this method cannot provide image information such as the particle size characteristics and morphological structure of the lunar regolith samples. Therefore, this method cannot address the scientific need for in-situ detection of the microstructure of lunar dust and regolith on the lunar surface.

[0007] In addition, Chinese invention patent CN 119044013 B discloses a non-destructive testing method for lunar soil particle size. This method uses computed tomography (CT) technology to detect lunar soil particle size and employs a combination of three-dimensional X-ray microscopy, optical microscopy, and / or scanning electron microscopy to detect the particle size of lunar soil samples. However, while this method improves the accuracy and reliability of force measurement, it is a method used in ground-based laboratories and is difficult to meet the application requirements of miniaturization and integration in satellite payload instrument design. Summary of the Invention

[0008] The purpose of this application is to overcome the technical shortcomings of existing scanning electron microscopes in in-situ lunar surface exploration applications.

[0009] To achieve the above objectives, this application proposes a miniaturized, all-electrostatic scanning electron microscope lens suitable for in-situ lunar surface exploration, the technical solution of which includes the following technical features:

[0010] This application proposes a fully electrostatic miniaturized scanning electron microscope lens suitable for in-situ lunar surface exploration, comprising an electron gun, a condenser lens module, a microchannel plate detector, and an objective lens system that are sequentially fixed along the axis by a support assembly;

[0011] The support component is a frame made of carbon fiber reinforced plastic, honeycomb aluminum or titanium alloy, the surface of the frame is covered with graphene composite thermal interface material, and the connection surface between the support component and each electrode is covered with polyimide film.

[0012] The electron gun consists of an emitter, a suppressor, and an extractor. The emitter typically uses an electron source to emit electrons at a low temperature. A low negative voltage is applied to the suppressor to suppress stray electrons that overflow from the electron source. A high voltage is applied to the extractor to accelerate the emitted electron beam and send it into the downstream condenser module.

[0013] The condenser lens module includes, from top to bottom, a first group of condenser lenses and a second group of condenser lenses. The cavity sidewall of the condenser lens module is provided with an open through-hole array, allowing the lunar surface vacuum environment to enter the cavity through capillary action.

[0014] The first set of condenser lenses includes, from top to bottom, a first set of upstream electrodes, a first set of intermediate electrodes, and a first set of downstream electrodes. The first set of upstream electrodes and the first set of downstream electrodes are both grounded and used to shape and constrain the incident electron beam. The first set of intermediate electrodes consists of a left electrode and a right electrode insulated by an insulating layer. A through hole is provided at the center of the first set of intermediate electrodes, and an integrally formed protruding electrode extends from the through hole on the lower surface of the cylinder. The first set of intermediate electrodes also includes a first high-voltage interface for adjusting the deceleration and focusing of the electron beam. The first high-voltage interface is located at the center of the side of the left electrode.

[0015] The second set of condenser lenses is located downstream of the first set of condenser lenses and includes, from top to bottom, a second set of upstream electrodes, a second set of intermediate electrodes, and a second set of downstream electrodes; both the second set of upstream electrodes and the second set of downstream electrodes are grounded, and the second set of upstream electrodes has a second high-voltage interface;

[0016] The second set of intermediate electrodes is used to maintain the stability of the electron beam focus;

[0017] The lower surface of the second set of downstream electrodes extends a Faraday cup-shaped structure for measuring electron beam current parameters. A through hole is provided at the bottom center of the Faraday cup-shaped structure. The second set of downstream electrodes also includes a third high-voltage interface.

[0018] The microchannel plate detector is located between the condenser lens module and the objective lens system and is used to detect backscattered electrons at high takeoff angles.

[0019] The objective lens system, from top to bottom, includes a first electrode, an insulating support, a second electrode, and a third electrode that are coaxially fixed. The insulating support is assembled below the first electrode via a rotation locking mechanism. The lower end of the insulating support of the objective lens system forms an inward flange, and the upper end of the second electrode forms an outward flange. The insulating support and the second electrode are assembled by engaging with each other through the two flanges.

[0020] The stepped surface of the third electrode and the extension of the third electrode form a cavity for accommodating the electrostatic deflector; the third electrode has a through hole for introducing a high vacuum environment on the lunar surface; the through hole can be covered with a metal mesh for applying electrostatic voltage to remove dust accumulated on the lower surface of the objective lens system.

[0021] The electrostatic deflector is located in the cavity formed by the stepped surface of the third electrode and the extension of the third electrode; the electrostatic deflector includes 4N electrodes, which are fixed in the annular column by embedding; the annular column is coaxially fixed in the central hole of the third electrode to simultaneously realize the scanning deflection and astigmatism correction functions.

[0022] In summary, compared with the prior art, the beneficial effects of this application are as follows:

[0023] 1. A fully electrostatic lens system is adopted to replace the traditional electromagnetic mixed field scheme. Electro-optical control of the condenser lens module and objective lens system is realized through electrostatic electrodes, eliminating the magnetic leakage effect of the magnetic lens and the heat loss of the strong excitation coil.

[0024] 2. By utilizing the natural vacuum environment of the lunar surface, the reliance on complex vacuum equipment can be reduced by setting open through-hole arrays or covering them with porous titanium films in the condenser lens module and objective lens system.

[0025] 3. Through functional integration design, an octet electrostatic deflection module is integrated into the objective lens system to simultaneously realize scanning deflection and astigmatism correction functions; an innovative multi-functional electrode structure is designed in the condenser lens module, enabling the condenser lens to also function as an aperture stop, while improving the structural reliability of the system under emission vibration and lunar seismic environments.

[0026] 4. Through a compact structural design, materials or layouts can be adjusted based on different platform constraints and mission requirements, while further reducing weight and maintaining strength.

[0027] In summary, this application proposes a miniaturized, all-electrostatic scanning electron microscope lens suitable for in-situ lunar surface exploration. Through an all-electrostatic lens electron optics system, a lunar surface vacuum environment-introduced structure, and a compact structural design, it solves the problems of magnetic leakage effect and heat loss of strong excitation coils in existing technologies, as well as the dependence on complex vacuum equipment, insufficient functional integration, and inability to meet the miniaturization and integration requirements of satellite payload instruments. It achieves sub-micron resolution while significantly reducing the thermal power density of the vacuum cavity, reducing treatment to meet lunar payload mass constraints, reducing size to meet the miniaturization requirements of satellite payload instruments, and eliminating reliance on additional vacuum equipment. This also addresses the low-cost, high-timeliness basic data acquisition needs of in-situ lunar surface exploration. Attached Figure Description

[0028] Figure 1 The image shown is a cross-sectional view of a miniaturized scanning electron microscope operating in a fully electrostatic field.

[0029] Figure 2 The image shows the intermediate electrode structure of the first group of condenser lenses in the condenser lens module;

[0030] Figure 3 The diagram shows a common electrode structure used in a condenser lens module.

[0031] Figure 4 The diagram shows the downstream electrode structure of the second condenser lens in the condenser lens module;

[0032] Figure 5 The image shown is an exploded view of the objective lens system.

[0033] Figure 6 The figure shown is a cross-sectional view of the electrostatic deflector in the objective lens system;

[0034] Figure 7 The image shows the overall structure of the condenser lens module.

[0035] Attached image labels:

[0036] 1. Supporting components; 2. Electron gun; 3. First set of focusing lenses.

[0037] 4. Second condenser lens; 5. Microchannel plate detector; 6. Objective lens system

[0038] 7. Electrostatic deflector

[0039] 101. First support; 102. Second support; 103. Third support

[0040] 104. Fourth support; 105. Fifth support; 106. Sixth support

[0041] 107. The seventh support

[0042] 201. Emitter; 202. Suppressor; 203. Extractor

[0043] 301. First group of upstream electrodes; 302. First group of intermediate electrodes; 303. First group of downstream electrodes.

[0044] 302-1, First high-voltage interface; 302-2, Left electrode; 302-3, Protruding electrode

[0045] 302-4, Insulating layer; 302-5, Right electrode

[0046] 401. Second group of upstream electrodes; 402. Second group of intermediate electrodes; 403. Second group of downstream electrodes.

[0047] 401-1, Second high-voltage interface; 403-1, Third high-voltage interface; 403-2, Electron beam through-hole

[0048] 403-3, Faraday cup structure

[0049] 601, First electrode; 602, Insulating support; 603, Second electrode

[0050] 604, Third electrode 601-1, First rotary locking mechanism 602-1, Second rotary locking mechanism

[0051] 604-1, Through Hole Detailed Implementation

[0052] The technical solution of this application will be described in detail below with reference to the accompanying drawings.

[0053] like Figure 1 As shown, a miniaturized scanning electron microscope lens suitable for in-situ lunar surface exploration includes a support assembly 1, an electron gun 2, a first set of condenser lenses 3, a second set of condenser lenses 4, a microchannel plate detector 5, an objective lens system 6, and an electrostatic deflector 7.

[0054] The support component 1 is composed of a first bracket 101, a second bracket 102, a third bracket 103, a fourth bracket 104, a fifth bracket 105, a sixth bracket 106, and a seventh bracket 107. It is generally composed of high-strength aluminum alloy or titanium alloy brackets using 3D printing technology. The surface is coated with graphene-polyimide composite material to take into account both insulation and heat dissipation. For different task requirements or platform limitations, the material selection or structural layout can be adjusted, such as using carbon fiber reinforced plastic instead of honeycomb aluminum to further reduce weight and maintain strength.

[0055] The electron gun 2 consists of an emitter 201, a suppressor 202, and an extractor 203. The emitter 201 typically uses a Schottky electron source to achieve electron emission at a relatively low temperature. A low negative voltage is applied to the suppressor 202 to suppress stray electrons escaping from the electron source. A 5kV high voltage is applied to the extractor 203 to accelerate the emitted electron beam and guide it into the downstream condenser lens module. In the pre-focusing mode with lower electron beam energy, the typical kinetic energy of the emitted electrons is 1keV, at which point the negative voltage of the suppressor 202 is relatively small, ranging from 0 to -100V. In the scanning imaging mode with higher electron beam energy, when the typical kinetic energy of the emitted electrons is 5keV, the suppressor 202 is applied at -300V to further suppress low-energy stray electrons and interference signals.

[0056] The condenser lens module is located downstream of the suppressor 202 and extractor 203 of the electron gun 2 and upstream of the microchannel plate detector 5. It consists of a first set of condenser lenses 3 and a second set of condenser lenses 4. The overall structure of the condenser lens module is as follows: Figure 7 As shown.

[0057] The condenser lens module described in this embodiment is mainly based on the improved design of the electrostatic field focusing principle of a three-electrode single-lens structure for converging charged particle beams, and integrates electron beam on / off control and electromagnetic aperture function. The typical structure of a three-electrode single-lens consists of three coaxial cylindrical electrodes arranged parallel to each other along the axial direction. The electrodes on both sides are grounded while the middle electrode is subjected to a negative voltage, forming a potential difference that focuses the axially passing electron beam.

[0058] In this embodiment, a three-electrode single lens is used as a prototype. Two sets of electrode lenses that conform to the physical arrangement and potential distribution characteristics of a three-electrode single lens are continuously arranged along the axial direction and improved respectively. In the three-electrode single lens immediately downstream of the extraction electrode 203, the middle electrode is first changed to a left electrode and the right electrode are insulated by an insulating layer. A through hole is provided at the center of the hole, and an integrally formed protruding electrode 302-3 extends from the lower surface of the cylinder. The new structure (the first set of condenser lenses 3) can maintain the negative voltage required for focusing the first set of condenser lenses 3 as a whole while forming asymmetrical left and right electrode voltages. The potential difference between the left and right electrodes can be used to deflect the electron beam at a large angle in scenarios where rapid control of the electron beam on / off is required. The protruding electrode 302-3 further extends the length of the deflection region, so that it can also have a good on / off control effect for electron beams with higher initial kinetic energy.

[0059] In this embodiment, the initial kinetic energy of the electron beam is set to E0, which is 5keV, the mass is the electron mass m0, and the speed of light is c. Considering relativistic effects, the initial velocity of the electron beam is calculated as follows: When passing through the first set of intermediate electrodes 302 of the first set of condenser lenses 3, the electric field causes a deceleration effect. In this embodiment, the typical voltage of the first set of intermediate electrodes 302 is -4kV. The length L of the first set of intermediate electrodes 302 and the protruding electrode 302-3 is 5mm. The distance d between the parallel plates generated by the left and right electrodes of the first set of intermediate electrodes 302 is 0.5mm. After entering the deflection electric field, the distance traveled to the end of the downstream electrode is 1cm. The lateral deflection distance generated during this process is... Then, finite element simulation shows that when the voltage difference between the left and right electrodes varies from 0 to 500V, The range is approximately 0-1 cm. Therefore, by setting the electron beam aperture radius of the first set of condenser lenses 3 to be less than 1 cm, the electron beam on / off state can be quickly controlled through the aforementioned innovation.

[0060] The first group of condenser lenses 3 is composed of the first group of upstream electrodes 301, the first group of intermediate electrodes 302, and the first group of downstream electrodes 303. The first group of upstream electrodes 301 and the first group of downstream electrodes 303 are both grounded. The first group of intermediate electrodes 302 applies a negative high voltage to generate a potential difference to decelerate and focus the electron beam in the through hole.

[0061] A detailed diagram of the first set of intermediate electrodes 302 is shown below. Figure 2 As shown, the first high-voltage interface 302-1, the left electrode 302-2, the raised electrode 302-3, the insulating layer 302-4, and the right electrode 302-5 are integrated with the middle electrode 302.

[0062] In pre-focusing mode, the electron kinetic energy is low and the flight speed is slow. At this time, a typical value of -1kV negative high voltage is applied to both electrodes to ensure the electron beam is collimated and emitted onto the sample surface. In scanning imaging mode, the electron kinetic energy is high and the flight speed is fast. At this time, a typical value of -4kV negative high voltage is applied to both electrodes to decelerate and focus the electron beam. When rapid control of the electron beam on / off is required, the voltage is adjusted using -4kV as a reference value, adjusting either the left electrode 302-2 or the right electrode 302-5. The voltage difference between the electrode and the other electrode is 500V, which causes the electron beam to bend its flight trajectory due to the lateral deflection force and eventually hit the side wall of the electrode. When it is necessary to use the Faraday cup structure 403-3 to measure the electron beam current parameters, the voltage of either the left electrode 302-2 or the right electrode 302-5 is adjusted with a negative high voltage of -4kV as the reference value to generate a small deflection voltage of 50V-100V between it and the other electrode, so as to ensure that the electron beam bombards within the range of the Faraday cup structure 403-3.

[0063] The second condenser lens 4 is composed of the second upstream electrode 401, the second intermediate electrode 402, and the second downstream electrode 403. The second upstream electrode 401 and the second downstream electrode 403 are both grounded. In the pre-focusing mode, the second intermediate electrode 402 applies an adjustable positive high voltage of 1kV to 5kV to accelerate and refocus the electron beam, adjusting its focal range. In the scanning imaging mode, the voltage is increased accordingly based on the pre-focusing voltage to maintain the stability of the electron beam focal point.

[0064] The second condenser lens 4 is located downstream of the first condenser lens 3 and upstream of the microchannel plate detector 5. The improvement of the second condenser lens 4 is concentrated on its second downstream electrode 403. By extending a cylindrical electrode on the lower surface of the second downstream electrode 403 and reducing the electron beam through-hole 403-2 on the lower surface of the cylindrical electrode, a Faraday cup structure is formed. In conjunction with the first condenser lens 3 which has a deflection function, the endpoint of the electron beam deflection is controlled within the cavity of the second downstream electrode 403 of the second condenser lens 4, forming a Faraday cup structure. Current is drawn out from the side of the metal electrode to provide the function of monitoring electron beam current parameters.

[0065] An open array of through holes (0.2 mm in diameter, 1 mm spacing) is set on the sidewall of the condenser module cavity. A through hole 604-1 penetrating the third electrode 604 is constructed on the downstream surface of the objective lens system 6. The surface of the through hole 604-1 is covered with a porous titanium film. The natural vacuum environment of the lunar surface (vacuum degree better than 10) is utilized. -12 Torr introduces external vacuum through an open-hole design, eliminating the need for complex vacuum equipment such as molecular pumps or turbopumps, reducing reliance on complex vacuum equipment, and reducing the total mass by more than 80%, thus meeting the lunar payload mass constraint requirements.

[0066] Figure 3 The paper presents the structure of all electrodes in the electron gun 2, the first set of condenser lenses 3, and the second set of condenser lenses 4, excluding the first set of intermediate electrodes 302 and the second set of downstream electrodes 403, as well as the structure of the microchannel plate detector 5. The typical value for the outer cylindrical radius of the second high-voltage interface 401-1 is 1.5 cm, while the radius of the inner cylindrical through-hole is variable according to the requirements of each module. For the suppression electrode 202 and the extraction electrode 203 of the electron gun 2, a typical through-hole radius of 0.6 mm is taken. For the first set of upstream electrodes 301 and the first set of downstream electrodes 303, their shaping effect on the incident electron beam needs to be considered. For the electron beam function, the typical value of the through-hole radius is 0.25 mm. For the second group of upstream electrodes 401 and the second group of intermediate electrodes 402, in order to ensure that the Faraday cup of the second group of downstream electrodes 403 can receive the complete electron beam, the through-hole is enlarged, and the typical value of the radius is 5 mm. For the microchannel plate detector 5, the effective detection area is maximized to detect backscattered electrons with higher takeoff angles. The outer cylinder radius needs to cover the maximum radius of other electrodes, and the value is between 1.5 cm and 2.5 cm. The typical value of the inner cylinder radius is 0.6 cm to reduce the influence of the microchannel plate's own electric field on the electron beam.

[0067] The structure of the second downstream electrode 403 is as follows: Figure 4 As shown, the structure includes a third high-voltage interface 403-1, an electron beam through-hole 403-2, and a Faraday cup structure 403-3. The Faraday cup structure 403-3 is formed by a protruding electrode integrated with the cylindrical electrode. When measuring electron beam current parameters, the electron beam is deflected to the sidewall of the cup structure by the deflection voltage of the first set of intermediate electrodes 302. The electron beam parameters are determined by drawing current from the sidewall. The typical radius of the electron beam through-hole 403-2 is 0.25 mm, and the typical outer radius of the protruding cylinder of the Faraday cup structure 403-3 is 8 mm, while the typical radius of the internal cavity is 5 mm.

[0068] The objective lens system 6, located downstream of the microchannel plate detector 5, is a lens system that controls the final focusing, deflection, and shaping of the electron beam before it interacts with the sample. In this application, the objective lens system 6 not only includes a focusing adjustment system composed of the first electrode 601, the second electrode 603, and the third electrode 604, but also provides extended space for the electrostatic deflector 7 by constructing a stepped surface of the third electrode 604 and extending the third electrode 604 to form a cavity. Figure 5 As shown.

[0069] The electrostatic deflector 7 is an integrated electrostatic deflector composed of 4N electrodes. Preferably, N can be an integer from 1 to 4, meaning the total number of electrodes is generally 4, 8, 12, or 16. In this embodiment, the electrostatic deflector consists of 8 electrodes. The electrodes are fixed in an annular column by embedding. The annular column is coaxially fixed inside the central hole of the third electrode. The focusing effect of the objective lens system 6 originates from a potential distribution similar to a three-electrode single lens. The first electrode 601 and the third electrode 604 are grounded. The second electrode 603 provides an insulating column fixed between the first electrode 601 and the third electrode 604. A high-voltage direct current is applied to create a potential difference for fine focusing of the electron beam.

[0070] The second electrode 603 can select a suitable voltage within the range of -5kV to 5kV according to the sample characteristics. When the sample thickness is large and the required electron beam energy is high, a positive high voltage is selected for accelerated focusing. When the sample has a large charge effect and a low-voltage scanning scenario is required, a negative high voltage is selected for deceleration focusing. The insulating support 602 is assembled with the first rotating locking mechanism 601-1 and the second rotating locking mechanism 602-1. The lower end of the insulating support 602 forms an inward flange, and the upper end of the second electrode 603 forms an outward flange. The insulating support 602 and the second electrode 603 are assembled by interlocking the two flanges. The insulating support 602 can be selected with a suitable length of 1.5cm to 2cm according to the axial focusing range required by the objective lens system 6. The typical value given in this embodiment is 1.8cm, which supports ±0.8cm axial focus modulation on the sample reference surface 5cm away from the end surface of the objective lens system 6 in conjunction with the voltage change of the second electrode 603. The third electrode 604 has a through-hole 604-1 that can be covered with a metal mesh, which introduces a high vacuum environment on the lunar surface into the objective lens system 6. The metal mesh can remove dust accumulated on the lower surface of the objective lens system 6 by applying an electrostatic voltage of -50V to 50V.

[0071] The electrostatic deflector 7 introduced below the stepped surface of the third electrode 604 is powered by a common electrode. The cross-sectional view of the electrostatic deflector 7 is shown below. Figure 6 As shown, that is, with and The two deflection signals are the voltages of the power supply, which simultaneously act on each of the eight electrodes, setting... =1, The relative focus of the electron beam is selected based on the focusing ability of the upstream lens. The value of . The angle between the two electrodes. In the case of smaller values, the potential distribution between the electrodes is approximately considered to be linear, and this applies to any position within the internal space enclosed by the electrodes. It can generate a deflection potential:

[0072] ;

[0073] in, In this embodiment, in order to ensure a good deflection effect and control the speed of the interaction between the electron beam and the sample, In the case of taking and The astigmatism values ​​calculated from the two deflection signals based on deflection requirements and the prefocusing process are in Dynamic adjustment within the range exist Dynamic adjustment within the range, in this embodiment, Take 1, Take typical value This allows for achieving a potential difference of at least [value] across eight electrodes at a distance of 5 cm between the bottom of the objective lens and the sample surface. The scanning function within the area.

[0074] An electrostatic deflector 7 is integrated into the objective lens system 6 to simultaneously achieve scanning deflection and astigmatism correction functions; an innovative multi-functional electrode structure is designed in the condenser lens module to enable the condenser lens to also function as an aperture stop, while improving the structural reliability of the system under emission vibration and lunar seismic environments.

[0075] In scenarios where further reduction of aberrations is desired, multiple short-length electrostatic deflectors 7 can be introduced along the axial direction into the cavity below the third electrode 604 to perform deflection and aberration correction functions respectively.

[0076] In this embodiment, the electron gun 2 (1cm in length and 3cm in diameter), the condenser module (6cm in length and 3cm in diameter), the microchannel plate detector 5 (1cm in length and 5cm in diameter), and the objective lens system 6 (8cm in length and 6cm in diameter) are fixed together as a whole system by a honeycomb aluminum frame and arranged sequentially along the axial direction. The surface of the frame is covered with graphene composite thermal interface material, and the insulating surface is covered with polyimide film, which ensures that the overall length of the payload is less than 20cm, the diameter is less than 10cm, the overall weight is less than 5kg, and the lateral dimensions are compressed to within 8cm×8cm, meeting the miniaturization requirements of satellite payload instruments.

[0077] To meet different mission requirements or platform limitations, material selection or structural layout can be adjusted, such as using carbon fiber reinforced plastic instead of honeycomb aluminum to further reduce weight while maintaining strength.

[0078] The all-electrostatic lens system used in this application realizes the electro-optical control of the condenser lens module and the objective lens system 6 through electrostatic electrodes, eliminating the magnetic leakage effect of the magnetic lens (magnetic field strength <0.01T) and the heat loss of the strong excitation coil (power consumption <50W), so that the electromagnetic interference field strength of the system is controlled below 10μT, which meets the electromagnetic compatibility requirements of the lunar research station for multi-instrument collaborative operation.

[0079] Compared to the magnetic lens module, the thermal power density of the vacuum cavity is significantly reduced, which is in line with the lunar surface's radiation heat dissipation capacity;

[0080] Meanwhile, without relying on additional vacuum equipment, submicron resolution is achieved by optimizing the electric field distribution and design of the electrostatic lens, thus meeting the basic data acquisition needs of in-situ lunar surface exploration for low cost and high timeliness.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application do not depart from the spirit and scope of the technical solutions of this application, and should all be covered within the scope of the claims of this application.

Claims

1. A fully electrostatic miniaturized scanning electron microscope lens suitable for lunar surface in-situ exploration, characterized in that, The electron gun, the condenser module, the micro-channel plate detector and the objective lens system are sequentially fixed along the axis by the support assembly; The condenser module comprises a first group of condensers and a second group of condensers from top to bottom, and the cavity side wall of the condenser module is provided with an open hole array, allowing the vacuum environment on the moon to enter the cavity through capillary action; The first group of condensers comprises a first group of upstream electrodes, a first group of intermediate electrodes and a first group of downstream electrodes from top to bottom, wherein the first group of upstream electrodes and the first group of downstream electrodes are both grounded for shaping and constraining the incident electron beam; the first group of intermediate electrodes comprises a left electrode, an insulating layer and a right electrode, the left electrode and the right electrode are insulated by the insulating layer, and the center of the circle is provided with a through hole, and the through hole extends a protruding electrode integrally formed on the lower surface of the cylinder for decelerating and focusing the electron beam; The second group of condensers is located downstream of the first group of condensers and comprises a second group of upstream electrodes, a second group of intermediate electrodes and a second group of downstream electrodes from top to bottom, the lower surface of the second group of downstream electrodes extends a Faraday cup structure for measuring the electron beam current parameters, and the bottom center of the Faraday cup structure is provided with a through hole; The objective lens system comprises a coaxially fixed first electrode, an insulating support, a second electrode and a third electrode from top to bottom, The first electrode is fixed to the lower end of the support assembly, and the insulating support is assembled below the first electrode through a rotary locking mechanism; The lower end of the insulating support forms a flange inwardly, the upper end of the second electrode forms a flange outwardly, and the insulating support and the second electrode are assembled by the two flanges; The step surface of the third electrode and the extension part of the third electrode form a cavity for accommodating the electrostatic deflector, and the extension part of the third electrode has a through hole for introducing the high vacuum environment on the moon surface; The electrostatic deflector comprises a plurality of electrodes located in the cavity formed by the step surface of the third electrode and the extension part of the third electrode; the electrodes are fixed in the annular cylinder by embedding; the annular cylinder is coaxially fixed in the center hole of the third electrode for synchronous realization of scanning deflection and stigmation function.

2. The all-electrostatic compact scanning electron microscope lens of claim 1, wherein, The support assembly is a frame made of carbon fiber reinforced plastic, honeycomb aluminum or titanium alloy, the surface of the frame is covered with graphene composite thermal interface material, and the contact surface of the support assembly and each electrode is covered with polyimide film.

3. The all-electrostatic miniaturized scanning electron microscope lens according to claim 1, wherein The first group of intermediate electrodes further comprise a first high-voltage interface, and the first high-voltage interface is located at the center of the outer side of the left electrode and the right electrode.

4. The all-electrostatic compact scanning electron microscope lens of claim 1, wherein, The second group of upstream electrodes further comprise a second high-voltage interface; The second group of intermediate electrodes are used to keep the electron beam focus stable; The second group of downstream electrodes further comprise a third high-voltage interface.

5. The all-electrostatic compact scanning electron microscope lens of claim 1, wherein, The micro-channel plate detector is located between the condenser module and the objective lens system, and is used to detect backscattered electrons with high take-off angles.

6. The all-electrostatic compact scanning electron microscope lens of claim 1, wherein, The through hole can be covered with a metal mesh for applying an electrostatic voltage to remove dust accumulated on the lower surface of the objective lens system.

7. The all-electrostatic compact scanning electron microscope lens of claim 1, wherein, The electrostatic deflector is composed of 4N electrodes, N is a natural number, and is used for synchronously realizing scanning deflection and stigmation functions.

8. The all-electrostatic compact scanning electron microscope lens of claim 7, wherein, N is a natural number from 1 to 4.

9. The all-electrostatic compact scanning electron microscope lens of claim 1, wherein, The electron gun is located above the condenser module.

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