A compact volatile ToF mass spectrometer

Abstract

The application provides a small volatile ToF mass spectrometer, comprising: a drift tube structure main body, internally provided with a field-free entrance drift tube and a field-free exit drift tube arranged in an inverted V shape and penetrating through the drift tube structure main body; a multi-stage ion mirror fixed on the upper end surface of the drift tube structure main body; an EI source and a pulse extraction stage assembly fixed on the lower end surface of the drift tube structure main body and covering the opening of the field-free entrance drift tube at the lower end surface of the drift tube structure main body; an MCP assembly component fixed on the lower end surface of the drift tube structure main body and covering the opening of the field-free exit drift tube at the lower end surface of the drift tube structure main body; an MCP shielding body surrounding the MCP assembly component; and a fixed circuit board fixed on the side surface of the drift tube structure main body. The application has the advantages of overall miniaturization and low power consumption, simple assembly, and is suitable for deep space exploration load, portable on-site detection and embedded instrument application.

Description

Technical Field

[0001] This application belongs to the field of mass spectrometry, specifically relating to a small volatile matter ToF mass spectrometer. Background Technology

[0002] ToF mass spectrometers are generally classified into linear mass spectrometers and reflectance mass spectrometers. Linear mass spectrometers, designed to increase flight time and improve mass resolution, are relatively large in length and volume, but their structure and design are relatively simple. Reflectance mass spectrometers introduce an electrostatic reflection field into the mass analyzer, exhibiting energy focusing characteristics. This allows them to compensate for initial ion energy differences within a limited flight path, theoretically enabling high-resolution measurements over a large mass range within a small volume. Reflectance ToF mass spectrometers are characterized by their small size, light weight, high measurement speed, and high resolution, making them particularly suitable for deep space exploration missions. Mass spectrometry is one of the key technological means to explore the origin of matter, planetary evolution, and the existence of life. Currently, small-scale ToF-based mass spectrometers are still relatively cutting-edge analytical instruments, with few publicly available design examples internationally.

[0003] Reflection-type Time-of-Flight (ToF) mass spectrometers are divided into coaxial and off-axis types. In off-axis reflective structures, the spatial angular relationship between the incident and reflected ion beams relative to the multi-stage electrostatic reflection field, as well as the perpendicularity between the reflected ion beam and the detector plane, significantly influences time-of-flight focusing and mass resolution. However, in existing structures, components are often mounted on multiple supports or independent structural parts, and the relative angles and positions between components depend on assembly adjustments. This assembly process is complex, repeatability and stability are difficult to guarantee, and it is challenging to achieve high-resolution performance under miniaturization constraints. Summary of the Invention

[0004] The purpose of this application is to overcome the shortcomings of existing mass spectrometers, such as complex assembly processes, difficulty in ensuring repeatability and stability, and difficulty in achieving high resolution performance under miniaturization constraints.

[0005] To achieve the above objectives, this application proposes a small volatile matter ToF mass spectrometer, comprising: The drift tube structure has an internal structure with fieldless incident drift tubes and fieldless exit drift tubes arranged in an inverted V-shape, which penetrate the drift tube structure. The fieldless incident drift tubes and fieldless exit drift tubes have openings close to each other on the upper end face of the drift tube structure. The fieldless incident drift tubes and fieldless exit drift tubes are used to contain ions during transport. A multi-stage ion reflector is fixed to the upper end face of the main body of the drift tube structure, and is used to reflect ions transmitted from the fieldless incident drift tube into the fieldless exit drift tube. The EI source and pulse extraction stage assembly are fixed to the lower end face of the drift tube structure body, covering the opening of the fieldless incident drift tube on the lower end face of the drift tube structure body, for generating ionized gas to produce ions and accelerating the ions into the fieldless incident drift tube. The MCP assembly is fixed to the lower end face of the drift tube structure body, covering the opening of the fieldless emission drift tube on the lower end face of the drift tube structure body, and is used to detect the ions output by the fieldless emission drift tube. The MCP shield is a U-shaped plate structure surrounding the MCP assembly. The opening is located on the side away from the EI source and the pulse extraction stage assembly to prevent spatial electric fields and stray light from interfering with the MCP assembly. A fixed circuit board is used to provide power, clock and digital communication functions; the main body of the drift tube structure is mounted and fixed on the fixed circuit board.

[0006] As an improvement to the aforementioned mass spectrometer, the inner walls of the fieldless incident drift tube and the fieldless exit drift tube are extinct, conductive, and grounded; the main body of the drift tube structure is equipotential.

[0007] As an improvement to the aforementioned mass spectrometer, the diameters of the fieldless incident drift tube and the fieldless exit drift tube are larger than the envelope diameter of the accelerated ion track.

[0008] As an improvement to the aforementioned mass spectrometer, the axis of the fieldless incident drift tube is perpendicular to the mounting surface of the EI source and pulse extraction stage assembly.

[0009] As an improvement to the aforementioned mass spectrometer, the multi-stage ion reflector includes multiple layers of electrode sheets; wherein the top electrode sheet is a plate-like structure for reflecting ions, and the other electrode sheets are ring-like structures with a hollow center; an insulating gasket ring is provided between adjacent layers of electrode sheets.

[0010] As an improvement to the aforementioned mass spectrometer, the multilayer electrode sheets are respectively connected to different voltages to form a multi-level electrostatic reflection field.

[0011] As an improvement to the aforementioned mass spectrometer, the electrode sheet is made of stainless steel.

[0012] As an improvement to the aforementioned mass spectrometer, it also includes: The connector is a ring-shaped structure with an adjustable included angle between its upper and lower end faces. One end is fixed to the MCP assembly, and the other end is fixed to the lower end face of the drift tube structure body, covering the opening of the fieldless emission drift tube.

[0013] As an improvement to the aforementioned mass spectrometer, the main body of the drift tube structure is made of aluminum alloy; the MCP shield is made of lightweight metal material or low-density non-metallic material with a conductive coating on the surface.

[0014] Compared with existing technologies, the advantages of this application are: 1. The present invention relates to a volatile matter ToF mass spectrometer structure, which uses a drift tube as the main assembly body. The ion source, pulse extraction region, reflector and MCP are assembled around the drift tube. The manufacturing precision ensures the fixed angular relationship between the accelerating ion beam, the incident ion beam and the reflected ion beam relative to the multi-electrode electrostatic reflection field, as well as the parallelism of the multi-stage electrostatic reflection electrodes, thereby achieving high-quality resolution of volatile matter TOF.

[0015] 2. The volatile TOF structure is mounted on a carrier PCB. While ensuring the geometric relationships of all TOF components, the high-voltage divider, gating, and triggering circuits are integrated onto the carrier PCB, reducing interference from flying wires and high-voltage electric fields, resulting in more stable quality resolution. This design, while ensuring simple assembly, robust structure, and convenient disassembly and maintenance, minimizes the system's envelope size. It achieves a compact modular layout and board-level integration, facilitating deployment on lightweight platforms, reducing power consumption and size, making it suitable for deep space exploration payloads, portable field testing, and embedded instrument applications, and demonstrating feasibility for large-scale engineering implementation.

[0016] 3. The MCP's lateral optical and electrical dual shielding effectively reduces background noise. The lateral partitions and matting coating suppress stray light, while the aluminum strip forms an electric field shielding cavity, reducing secondary electron backflow and field edge effects, thus lowering background count, improving signal-to-noise ratio, and extending the MCP's lifetime.

[0017] 4. A dual-guide tube is installed inside the drift tube for both incident and exit directions to limit the effective solid angle and isolate the scattered ion channel. This beam-limiting and decoupling design reduces peak tailing and crosstalk between adjacent peaks, improving peak shape and quantitative stability without altering the original ion optical layout.

[0018] 5. Overall miniaturization and low power consumption. Attached Figure Description

[0019] Figure 1 The figure shown is a schematic diagram of the overall structure of a lightweight, reflective ToF mass spectrometer according to an exemplary embodiment of the present invention; Figure 2 The diagram shows the structure of the drift tube after it is connected to the control PCB board. Figure 3 The diagram shown is a three-dimensional structural diagram of the main body of the drift tube structure. Figure 4 The diagram shown is a cross-sectional view of the main structure of the drift tube. Figure 5 The diagram shown is a three-dimensional structural diagram of a gridless secondary ion reflector. Figure 6 The diagram shown is a structural diagram of the connector.

[0020] Attached image labels: 1. Gridless secondary ion reflector; 2. Drift tube structure main body. 3. Positioning pins 4. Connecting parts 5. MCP shielding body; 6. MCP assembly components 7. EI source and pulse extraction stage assembly; 8. Fixing circuit board 11. Top electrode plate 12. High aperture ratio electrode plate 13. Insulating gasket ring; 21. First assembly hole. 22. Second assembly hole position; 24. First lower end hole 25. Second lower end hole; 26. Fieldless incident drift tube 27. Fieldless Exit Drift Tube Detailed Implementation

[0021] The technical solution of this application will be described in detail below with reference to the accompanying drawings.

[0022] This application provides a small-scale volatile matter ToF mass spectrometer that can strictly define the fixed angular relationship between the incident ion beam and the reflected ion beam relative to the multipolar electrostatic reflection field. It is also simple to assemble, has a robust structure, and is easy to disassemble and maintain.

[0023] This application provides a small-scale volatile matter ToF mass spectrometer comprising: an electron collision ion source (EI source), an ion extraction accelerator, a multi-stage ion reflector, a drift tube structure, a microchannel plate (MCP) assembly, an MCP shield, and a fixed circuit board. The EI ion source generates electrons with energies of approximately 70 eV, ionizing volatile atoms or molecules, typically producing single-charged positive ions. The ion extraction accelerator applies pulsed high voltage and accelerating voltage to extract the EI-ionized ions and accelerate them into the drift tube structure. The drift tube structure serves as the mounting base for the ToF components; the EI source, ion extraction accelerator, multi-stage ion reflector, MCP, and MCP shield are all fixed to the drift tube structure. The drift tube structure is fixed to the fixed circuit board. The fixed circuit board integrates a high-voltage divider network, MCP bias, gating pulse, and acquisition front-end, providing power, clock, and digital communication functions. The drift tube structure is machined from a single metal block and employs a lightweight design. The main structure of the drift tube consists of a through-type field-free incident drift tube and a field-free exit drift tube. To prevent ions from colliding with the tube wall during drift, the diameters of both the field-free incident and exit drift tubes are determined based on the diameter of the simulated ion beam. To ensure the incident angle of the ion beam at the incident end, the axial direction of the field-free incident drift tube is perpendicular to the mounting face of the incident port. The field-free incident drift tube connects the ion extraction accelerator and the multi-stage ion mirror, while the exit drift tube connects the MCP and the multi-stage ion mirror. The mounting surfaces of the MCP and the ion extraction accelerator are both on the main structure of the drift tube. The tilt angle of the mounting surfaces is ensured by the fabrication of the structure, thus greatly simplifying the angle adjustment of the various ToF components. The MCP shielding body shields the MCP to suppress direct irradiation or scattering of EI light onto the MCP. Simultaneously, the MCP shielding body uses conductive materials to prevent spatial electric field interference with the MCP. The multi-stage ion reflector consists of a series of planar electrodes, with insulating pads separating them for mutual insulation. Each planar electrode has a square structure with a hollow center. The spacing and size between the electrodes depend on the Time-of-Flight (ToF) design. To achieve ion reflection, one of the top electrodes of the multi-stage ion reflector uses a non-hollowed-out flat plate electrode. The multi-stage ion reflector is mounted on the upper mounting surface of the drift tube structure. The mounting surface's structural design strictly limits the angle between the drift tube axis and the multi-stage ion reflector axis. Therefore, the design of the drift tube structure in this application strictly limits the angular relationships between the various components of the ToF and simplifies the complex adjustments to the system structure.

[0024] Example 1 The small volatile matter ToF mass spectrometer provided in this application includes: a drift tube structure 2, a gridless secondary ion reflector 1, an EI source and pulse extraction stage assembly 7, an MCP assembly 6, an MCP shield 5, and a fixed circuit board 8 (PCB board).

[0025] The main body 2 of the drift tube structure, as a TOF structure, adopts an integrated assembly with the central shaft: such as Figure 1 As shown, the drift tube structure 2 serves as the assembly reference and mounting base. The upper end is coaxially mounted with a gridless secondary ion reflector 1 (multi-stage ion reflector), and the lower end is connected to the MCP assembly 6, EI source, and pulse extraction stage assembly 7 (including electron collision ion source and ion extraction accelerator). Other TOF components are mounted on the drift tube structure 2 as the base, forming a compact layout.

[0026] The main body 2 of the drift tube structure is directly fixed to the fixed circuit board 8 for power supply and control. Other components of the TOF are mounted on the main body 2 of the drift tube structure. Figure 2 As shown, the drift tube structure body 2 is directly fixed to the fixed circuit board 8 via insulating support positioning posts 3 and non-magnetic screws. The positioning posts 3 achieve positioning of the drift tube structure body 2 and the fixed circuit board 8 by means of the holes on the fixed circuit board 8 and the holes on the drift tube structure body 2. The length of the positioning posts 3 can control the distance between the drift tube structure body 2 and the fixed circuit board 8 and keep them insulated. The fixed circuit board 8 is a PCB board that integrates a high-voltage divider network, MCP bias, gate pulse and acquisition front end, and provides power supply, clock, digital communication and other functions, thereby achieving the integration of TOF with power supply and control without changing the TOF envelope size.

[0027] An MCP shield 5 is installed on the side of the MCP assembly 6 to suppress direct illumination or scattering of EI light onto the MCP, thus avoiding background noise. The MCP shield 5 is a U-shaped plate structure made of conductive material, surrounding the MCP assembly 6. The opening is located on the side away from the EI source and the pulse extraction stage assembly 7 to prevent spatial electric field interference with the MCP. The MCP shield 5 is at the same potential as the drift tube structure body 2, forming a circumferentially closed equipotential surface, blocking lateral stray electric field coupling.

[0028] The MCP shield 5 is used to suppress stray light scattering and secondary interference, and can be fixed to the positioning post 3 with screws. The MCP shield 5 is generally made of lightweight metal material or low-density non-metallic material with a conductive coating on the surface. The MCP shield 5 is at the same potential as the drift tube structure body 2, thus forming an approximately closed equipotential shield structure on the side of the MCP. This not only blocks direct or scattered light from the EI source region from entering the MCP, effectively reducing the background count caused by photoemission, but also suppresses the disturbance of the external non-uniform electric field to the MCP gain region.

[0029] like Figure 4As shown, the drift tube structure 2 is the main body of the TOF structure, internally connecting the fieldless incident drift tube 26 and the fieldless exit drift tube 27. The fieldless incident drift tube 26 and the fieldless exit drift tube 27 form an inverted V-shape and are close to each other on the upper end face of the drift tube structure 2. The diameters of the fieldless incident drift tube 26 and the fieldless exit drift tube 27 are not less than the envelope diameter of the accelerated ion track. The inner walls of the fieldless incident drift tube 26 and the fieldless exit drift tube 27 are extinct and grounded to define the ion solid angle and reduce the interference of thermionic and resputtered particles on the time-of-flight measurement. The inner walls of the fieldless incident drift tube 26 and the fieldless exit drift tube 27 are conductive, and the entire drift tube structure 2 is equipotential. The drift tube structure 2 can reduce the influence of stray ions on time broadening and background along the path, improving peak shape and quality resolution. The axis of the fieldless incident drift tube 26 is perpendicular to the mounting surface of the EI source and pulse extraction stage assembly 7. By directly defining the angle between the aforementioned axis and the axis of the gridless secondary ion reflector 1 during the fabrication stage of the drift tube structure body 2, the designed angular relationship between the incident ion beam and the reflected ion beam relative to the multi-stage electrostatic reflection field can be guaranteed without complex angle adjustments during the overall assembly. This limits the effective solid angle and suppresses the scattered ion channel, reducing peak tailing and crosstalk between adjacent peaks. Furthermore, it improves assembly repeatability and geometric stability, which is beneficial for achieving high and stable quality resolution in a small structure.

[0030] like Figure 3 As shown, the drift tube structure body 2 is made of aluminum alloy, providing sufficient structural support and protection while maintaining a lightweight design. The gridless secondary ion reflector 1 is fixed to the drift tube structure body 2 via a first mounting hole 21. A second mounting hole 22 is provided in the middle of the drift tube structure body 2 for fixing to the fixed circuit board 8. A first lower hole 24 is used to cooperate with the EI source and pulse extraction stage assembly 7, providing a path for ions to enter the drift tube structure body 2; a second lower hole 25 is used to fix to the MCP assembly 6, providing a path for receiving electrons. The two paths are independent and do not interfere with each other. The inner surface of the drift tube structure body 2 is conductive and the entire structure is equipotential, thus forming a near-field-free flight path in the drift region, reducing the distortion of ion flight time.

[0031] like Figure 5As shown, the gridless secondary ion reflector 1 employs a high aperture ratio electrode design 12 to minimize ion loss, thereby shortening measurement time and improving detection sensitivity. The top electrode 11 features a sealed structure, providing a reflective surface for the ions. Stainless steel is used for the electrode 11 to ensure structural rigidity; the specific number of electrode 11 is determined based on design values. Insulating rings 13 are placed between the electrode 11 to provide insulation and determine the height. The insulating rings 13 are typically made of polyimide, offering good insulation and structural stability. A hollow center in the insulating rings 13 is used for fixing screws. Different potentials are sequentially applied to each electrode through an external high-voltage divider network, forming a multi-stage electrostatic reflection field. This allows ions with different initial energies to achieve time-focusing during reflection, improving quality resolution.

[0032] like Figure 6 As shown, the connector 4 is used to achieve precise docking and fastening between the MCP assembly 6 and the drift tube structure body 2. The two surfaces of the connector 4 that contact the drift tube structure body 2 and the MCP assembly 6 are not parallel and have a certain angle. The angle of the MCP assembly 6 can be adjusted by changing the angle between the two surfaces of the connector 4 to make it consistent with the direction of the ion focusing plane, thereby improving the quality resolution and ensuring reliable contact and tight bonding.

[0033] The small-scale volatile matter ToF mass spectrometer structure provided in this application can reduce background, decrease time spread, and improve signal-to-noise ratio and mass resolution without changing the ion optical design. It uses the integrally machined drift tube structure 2 as the central integrated assembly base, combined with the internal fieldless incident drift tube 26 and fieldless exit drift tube 27, gridless secondary ion reflector 1, MCP shield 5 and fixed circuit board 8 for board-level power supply and control integration. At the same time, it has engineering advantages such as small size, low power consumption, simple assembly and calibration, and vibration and thermal robustness. It is suitable for application scenarios such as in-situ analysis in deep space exploration, rapid on-site detection and portable experimental platforms.

[0034] In the existing technology, the sides of microchannel plate detectors (MCPs) are susceptible to interference from stray light and stray electric fields. Thermionic and secondary electrons in the MCP input and output paths can easily introduce trailing and background noise. Furthermore, the entire device is often connected to the printed circuit board (PCB) by cables or pins, resulting in insufficient vibration reliability and maintainability, making it difficult to meet the application requirements of small size, low power consumption, and mass production.

[0035] In planetary exploration missions, landers and rovers need to conduct in-situ composition and isotope measurements under extremely limited size, power consumption, and thermal shock conditions, creating an urgent need for miniaturized, highly reliable, and fast-response mass spectrometry payloads. The miniaturized volatile matter ToF mass spectrometer proposed in this application is a lightweight, reflective ToF mass spectrometer structure featuring an integrated architecture combined with plate-level power supply and control, MCP side-lighting, electrical dual shielding, and dual incident and exit guides. Without altering the optical design, it significantly reduces background and time broadening, improves the mass spectrometry signal-to-noise ratio and mass resolution, while simultaneously achieving structural miniaturization and assembly repeatability. Therefore, the ToF mass spectrometer can be deployed in deep space exploration, portable field testing, and embedded instrument platforms under conditions of lightweight design, low power consumption, and high reliability, providing a scalable engineering solution for high-precision in-situ analysis.

[0036] Furthermore, to ensure the generation of single-charged positive ions from each ionized sample, the pulse extraction stage uses pulsed high voltage to package and accelerate the ions into the drift region, achieving initial synchronization. The drift tube provides a stable and uniform electric field distribution and a high-vacuum flight path, which is crucial for flight time and resolution control. The gridless secondary reflector maintains the uniformity of the high reflectivity field while avoiding signal loss caused by the grid structure, improving ion transmittance and system sensitivity. The MCP detector is responsible for high-speed, wide dynamic range ion signal conversion, ensuring the integrity of isotope peaks and statistical accuracy.

[0037] 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 small volatile matter ToF mass spectrometer, comprising: The drift tube structure has an internal structure containing fieldless incident drift tubes and fieldless exit drift tubes arranged in an inverted V-shape that penetrate the drift tube structure. The fieldless incident drift tube and the fieldless exit drift tube have openings close to each other on the upper end face of the drift tube structure body; the fieldless incident drift tube and the fieldless exit drift tube are used to contain ions in transit; A multi-stage ion reflector is fixed to the upper end face of the main body of the drift tube structure, and is used to reflect ions transmitted from the fieldless incident drift tube into the fieldless exit drift tube. The EI source and pulse extraction stage assembly are fixed to the lower end face of the drift tube structure body, covering the opening of the fieldless incident drift tube on the lower end face of the drift tube structure body, for generating ionized gas to produce ions and accelerating the ions into the fieldless incident drift tube. The MCP assembly is fixed to the lower end face of the drift tube structure body, covering the opening of the fieldless emission drift tube on the lower end face of the drift tube structure body, and is used to detect the ions output by the fieldless emission drift tube. The MCP shield is a U-shaped plate structure surrounding the MCP assembly. The opening is located on the side away from the EI source and the pulse extraction stage assembly to prevent spatial electric fields and stray light from interfering with the MCP assembly. and A fixed circuit board is used to provide power, clock and digital communication functions; the main body of the drift tube structure is mounted and fixed on the fixed circuit board.

2. The small volatile matter ToF mass spectrometer according to claim 1, characterized in that, The inner walls of the fieldless incident drift tube and the fieldless exit drift tube are extinct, conductive, and grounded; the main body of the drift tube structure is equipotential.

3. The small volatile matter ToF mass spectrometer according to claim 1, characterized in that, The diameters of the fieldless incident drift tube and the fieldless exit drift tube are larger than the envelope diameter of the accelerated ion track.

4. The small volatile matter ToF mass spectrometer according to claim 1, characterized in that, The axis of the fieldless incident drift tube is perpendicular to the mounting surface of the EI source and pulse extraction stage assembly.

5. The small volatile matter ToF mass spectrometer according to claim 1, characterized in that, The multi-stage ion reflector includes multiple layers of electrode sheets; the top electrode sheet is a plate-like structure used to reflect ions, while the other electrode sheets are ring-like structures with a hollow center; an insulating gasket ring is provided between adjacent layers of electrode sheets.

6. The small volatile matter ToF mass spectrometer according to claim 5, characterized in that, The multilayer electrode sheets are each externally connected to different voltages to form a multi-level electrostatic reflection field.

7. The small volatile matter ToF mass spectrometer according to claim 1, characterized in that, The electrode sheet is made of stainless steel.

8. The small volatile matter ToF mass spectrometer according to claim 1, characterized in that, Also includes: The connector is a ring-shaped structure with an adjustable included angle between its upper and lower end faces. One end is fixed to the MCP assembly, and the other end is fixed to the lower end face of the drift tube structure body, covering the opening of the fieldless emission drift tube.

9. The small volatile matter ToF mass spectrometer according to claim 1, characterized in that, The main body of the drift tube structure is made of aluminum alloy; the MCP shield is made of lightweight metal material or low-density non-metallic material with a conductive coating on the surface.

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