An ionization device and method based on secondary laser ionization technology

Abstract

The present invention belongs to the technical field of mass spectrometer ionization source, specifically, an ionization device and method based on secondary laser ionization technology. It includes: a first laser, a second laser, a laser timing controller, a first laser optical element, a second laser optical element, a vacuum system, a sample carrier, an ion focusing device, an ion beam deflection device and an imaging system; the first laser beam emitted by the first laser enters the first laser optical element and is reflected onto the sample on the sample carrier to achieve the initial ionization of the sample; at the same time, the second laser beam emitted by the second laser enters above the sample through the second laser optical element to achieve secondary ionization of the sample entering the gas phase, and the imaging system collects sample information on the target plate plane. The present invention successfully introduces two laser beams of any different wavelengths, especially ultraviolet laser and vacuum ultraviolet laser, into the MALDI ion source cavity in a timing sequence, thereby improving the dissociation efficiency of the ion source.

Description

Technical Field

[0001] The present invention belongs to the technical field of ionization sources of mass spectrometers, and specifically relates to an ionization device and method based on secondary laser ionization technology. Background Art

[0002] With the continuous and vigorous development of mass spectrometry analysis technology, mass spectrometers play an increasingly important role in the fields of life science, environmental resources, food and public safety, new material research and development, aerospace, and military. As the core component of a mass spectrometer, the ionization efficiency of the ion source is the key factor determining the analysis sensitivity of the mass spectrometer. In the 1980s, the emergence of matrix-assisted laser desorption / ionization (MALDI) has shown great promise in the detection of organic compounds, analysis of biological macromolecules, and mass spectrometry imaging due to its characteristics of soft ionization, simple sample preparation, and high spatial resolution.

[0003] The principle of MALDI is to disperse the sample in matrix molecules to form crystals. When the crystal is irradiated with a laser, the matrix absorbs energy from the laser and transfers it to the sample molecules. During the ionization process, the matrix transfers protons to the sample molecules or obtains protons from the sample molecules, thereby completing the ionization of the sample. Commercial MALDI ionization sources usually use a single laser beam with a fixed wavelength to desorb and ionize the sample. Most of the particles generated by a single laser irradiation ionization are neutral particles, and the proportion of molecules that can be ionized is only 0.1%. Moreover, the ionization of low-abundance molecules by high-abundance components has a serious inhibitory effect, resulting in severe challenges for the high-sensitivity mass spectrometry detection of difficult-to-ionize components, especially low-abundance components, in the sample. How to improve the ionization efficiency of the MALDI ion source has gradually become an important direction for the development of high-sensitivity mass spectrometry. Currently, methods such as electron gas ionization, electron beam ionization, and laser ionization are often used to perform secondary ionization on the neutral particles generated by primary ionization to improve the ionization efficiency of the ion source. However, the ionization efficiency of both electron gas and electron beam participating in post-ionization is lower than 1%, while the ionization efficiency of laser participating in post-ionization can reach about 10% at a higher level, thus providing the possibility for the efficient utilization of secondary neutral particles. Summary of the Invention

[0004] The object of the present invention is to provide an ionization device and method based on secondary laser ionization technology, which realizes primary ionization of the sample by bombarding the sample surface with a primary laser, and then introduces another ultraviolet or vacuum ultraviolet band laser to perform secondary ionization on the sample molecules entering the gas phase to improve the ionization efficiency of the sample molecules, so as to overcome the defect of the low efficiency of the existing MALDI ion source.

[0005] The technical solution adopted by the present invention to achieve the above object is: an ionization device based on secondary laser ionization technology, comprising: a first laser, a second laser, a laser timing controller, a first laser beam optical element, a second laser beam optical element, a vacuum system, a sample carrier device, an ion focusing device, an ion beam deflection device, and an imaging system;

[0006] Wherein, the sample carrier device, the ion focusing device, and the ion beam deflection device are provided in the vacuum system;

[0007] A sample is placed on the sample carrier device; an ion beam deflection device and an ion focusing device are sequentially provided above the sample carrier device;

[0008] The laser timing controller is respectively connected to the first laser and the second laser, and is used to set the emission interval time of the first laser and the second laser;

[0009] The first laser beam emitted by the first laser enters the first laser beam optical element and is reflected onto the sample on the sample carrier device to achieve primary ionization of the sample and transfer the sample from the solid phase to the gas phase;

[0010] The second laser beam emitted by the second laser enters above the sample through the second laser beam optical element to achieve secondary ionization of the sample entering the gas phase;

[0011] The imaging system captures the reflected light of the sample to collect the sample information on the target plate plane, and magnifies and reflects the target plate sample information on the output device in real time.

[0012] The vacuum system includes: a housing and a sample replacement chamber cover plate provided on the housing; a vacuum chamber is formed inside the housing.

[0013] The sample carrier device includes: a three-axis displacement stage, a target plate mounting plate, and a target plate;

[0014] The target plate mounting plate is mounted on the three-axis displacement stage, and the target plate mounting plate is driven by the movement of the three-axis displacement stage to move in three-axis directions inside the vacuum chamber; the target plate is horizontally provided on the target plate mounting plate;

[0015] The target plate is arranged parallel to the sample replacement chamber cover plate, the target plate is at the z-axis zero position of the three-axis displacement stage, and the height is less than the sample replacement chamber cover plate.

[0016] The ion beam deflection device and the ion focusing device are sequentially arranged above the target plate mounting plate from top to bottom along the center line of the target plate mounting plate.

[0017] The target plate mounting plate is transferred to the three-axis displacement stage through an insulating material, and a DC voltage is applied to the target plate mounting plate.

[0018] The target plate mounting plate is provided with a groove for placing and fixing the target plate, and a sealing rubber ring is provided on the outer circle of the groove. When changing the sample, the z-axis of the three-axis displacement stage is raised to lift the target plate to the cover plate of the sample change chamber. The sealing rubber ring at the groove is squeezed against the inner wall of the shell at the cover plate of the sample change chamber to form a seal, so as to prevent the vacuum environment in the chamber from being damaged during the sample change process.

[0019] The ion focusing device includes: a grounded electrode provided with a grid and three cylindrical electrodes coaxially arranged along the center line of the target plate mounting plate;

[0020] The distance between adjacent cylindrical electrodes is 2 mm - 10 mm; the grounded electrode is arranged above the target plate, and the distance between the grounded electrode and the outer surface of the sample on the target plate is 2 mm - 30 mm;

[0021] An insulating pad is provided on one side of any of the cylindrical electrodes or the grounded electrode; the insulating pad is made of any one of ceramic or PEEK materials;

[0022] The material of the cylindrical electrode or the grounded electrode is any one of stainless steel or aluminum alloy.

[0023] The ion beam deflection device includes: two sets of electrodes arranged oppositely, and the two sets of electrodes are sequentially arranged perpendicular to each other on the upper side of the ion focusing device;

[0024] In any one of the sets of electrodes, the distance between the electrode plates is 4 mm - 20 mm, and an insulating pad is provided between the two sets of electrode plates; the insulating pad is made of any one of ceramic or PEEK materials;

[0025] The material of the electrode plate is any one of stainless steel or aluminum alloy.

[0026] The first laser beam emitted by the first laser is a pulsed laser or a continuous laser;

[0027] The second laser beam emitted by the second laser is: an ultraviolet pulsed laser or a vacuum ultraviolet pulsed laser.

[0028] The first laser beam optical element and the second laser beam optical element both include: any one or more of a convex lens, a concave lens, a reflector, or an optical fiber;

[0029] The included angle between the incident angle of the first laser beam entering the vacuum system and the center line of the target plate mounting plate is θ;

[0030] The second laser beam is parallel to the upper surface of the sample and has a set distance from the sample surface to perform secondary ionization on the sample molecules entering the gas phase.

[0031] An ionization method of an ionization device based on secondary laser ionization technology includes the following steps:

[0032] 1) The laser timing controller sets the emission interval time of the first laser and the second laser;

[0033] When emitting the laser beam, turn on the ion focusing device, set the DC voltage, and apply the DC voltage to the ion focusing device;

[0034] When the laser beam deflects, apply the set DC voltage to the ion beam deflection device to adjust the direction of the laser beam;

[0035] 2) The first laser beam emitted by the first laser enters the first laser optical element and forms an angle θ with the center line of the target plate mounting plate, and is reflected onto the sample on the target plate in the vacuum chamber, bombarding the sample surface to achieve primary ionization;

[0036] 3) The second laser beam emitted by the second laser enters horizontally above the sample in the vacuum chamber at a distance ΔZ higher than the target plate plane through the second laser optical element, achieving secondary ionization of the sample molecules entering the gas phase, thereby increasing the ionization rate of the sample molecules;

[0037] 4) The imaging system collects the sample information on the target plate plane, and the imaging system magnifies the target plate sample information and reflects it on the output device in real time;

[0038] 5) After the three-axis displacement stage moves along the x and y axes to below the sample replacement chamber cover plate, the z-axis of the three-axis displacement stage rises, lifting the target plate to the sample replacement chamber cover plate. The sealing rubber ring at the groove of the target plate is squeezed against the inner wall of the vacuum system housing to form a seal, and the sample replacement chamber cover plate is opened to replace the sample, so as to prevent the vacuum environment in the chamber from being damaged during the sample replacement process.

[0039] The present invention has the following beneficial effects and advantages:

[0040] 1. The present invention successfully introduces two laser beams with arbitrary different wavelengths, especially ultraviolet and vacuum ultraviolet lasers, into the MALDI ion source cavity according to the timing, improving the dissociation efficiency of the ion source.

[0041] 2. The ingenious design among the three-axis displacement stage, the target plate mounting plate and the cavity of the present invention can form a separate sealed space during sample replacement, improving the sample replacement efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is the overall structural schematic diagram of the present invention;

[0043] Figure 2 is the partial enlarged view of the second laser relative to the target plate ΔZ;

[0044] Among them, 1 is the first laser, 2 is the second laser, 3 is the laser timing controller, 4 is the first laser optical element, 5 is the second laser optical element, 6 is the three-axis displacement stage, 7 is the target plate mounting plate, 8 is the ion focusing device, 9 is the ion beam deflection device, 10 is the CCD camera, 11 is the imaging system, 12 is the sample changing chamber cover plate, and 13 is the vacuum chamber. Detailed implementation mode

[0045] The present invention will be further described in detail below in conjunction with the drawings and embodiments.

[0046] As Figure 1 shown, the ion source device based on the secondary laser ionization technology described in the present invention includes a first laser 1, a second laser 2, a laser timing controller 3, a first laser optical element 4, a second laser optical element 5, a three-axis displacement stage 6, a target plate mounting plate 7, an ion focusing device 8, an ion beam deflection device 9, a CCD camera 10, an imaging system 11, a sample changing chamber cover plate 12 and a vacuum chamber 13.

[0047] Among them, a sample carrier device, an ion focusing device 8 and an ion beam deflection device 9 are provided in the vacuum system;

[0048] A sample is placed on the sample carrier device; an ion beam deflection device 9 and an ion focusing device 8 are sequentially provided above the sample carrier device;

[0049] The laser timing controller 3 is respectively connected to the first laser 1 and the second laser 2, and is used to set the emission interval time of the first laser 1 and the second laser 2; the laser timing controller 3 can be, but is not limited to, a pulse time delay generator, and its resolution and accuracy should be higher than the time from ion generation to the position of the second laser beam.

[0050] The first laser beam emitted by the first laser 1 enters the first laser optical element 4 and is reflected onto the sample on the sample carrier device to realize the primary ionization of the sample and transfer the sample from the solid phase to the gas phase;

[0051] The second laser beam emitted by the second laser 2 enters above the sample through the second laser optical element 5 to realize the secondary ionization of the sample entering the gas phase;

[0052] The imaging system 11 captures the reflected light of the sample to collect the sample information on the target plate plane, and magnifies the target plate sample information and reflects it on the output device in real time.

[0053] In this embodiment, the first laser 1 is located in the upper left of the vacuum chamber 13, and this light source is used to ionize the sample for the first time. The light outlet of the second laser 2 is located on the left side at a position ΔZ above the target plate mounting plate 7, and this light source is used to ionize the sample molecules entering the gas phase for the second time. The laser timing controller 3 is used to adjust the emission time of the two laser beams.

[0054] The first laser optical element 4 is located in the upper left of the vacuum chamber 13. This set of optical elements focuses the laser beam emitted by the first laser 1 and changes the direction of the laser optical path, so that the axis of the laser optical path entering the vacuum chamber forms an angle θ with respect to the ion transmission axis and intersects at a point on the target plate.

[0055] The second laser optical element 5 is located on the right side of the second laser 2 and is used for focusing the second laser beam.

[0056] The vacuum chamber 13 provides an ultra-high vacuum experimental environment for the experiment.

[0057] The vacuum experimental environment is formed by a vacuum system, which includes: a housing and a sample-changing chamber cover plate 12 provided on the housing; a vacuum chamber 13 is formed inside the housing.

[0058] Furthermore, the sample carrier device includes: a three-axis displacement stage 6, a target plate mounting plate 7, and a target plate;

[0059] The target plate mounting plate 7 is mounted on the three-axis displacement stage 6, and the movement of the three-axis displacement stage 6 drives the target plate mounting plate 7 to move in three-axis directions inside the vacuum chamber 13; a target plate is horizontally provided on the target plate mounting plate 7;

[0060] The target plate is arranged parallel to the sample-changing chamber cover plate 12, the target plate is at the zero position of the z-axis of the three-axis displacement stage 6, and its height is less than that of the sample-changing chamber cover plate 12.

[0061] The ion beam deflection device 9 and the ion focusing device 8 are sequentially arranged from top to bottom along the center line of the target plate mounting plate 7 above the target plate mounting plate 7.

[0062] The target plate mounting plate 7 is provided with a groove for placing and fixing the target plate, and a sealing rubber ring is provided outside the groove. When changing the sample, the z-axis of the three-axis displacement stage 6 is raised to lift the target plate to the sample-changing chamber cover plate 12 at the top of the housing, and the sealing rubber ring at the groove is squeezed against the inner wall of the top of the housing to form a seal, so as to prevent the vacuum environment in the chamber from being damaged during the sample-changing process.

[0063] The rapid sample-changing process is as follows:

[0064] Before lofting, the three-axis displacement stage 6 moves along the positive X-axis. After the proximity switch detects that it has reached the position, the movement stops. The displacement stage 6 moves along the positive Z-axis to lift the target plate mounting plate 7. After the proximity switch detects that it has reached the position, the Z-axis stops moving. At this time, the rubber rings around the grooves of the target plate mounting plate 7 are compacted against the inner wall of the cavity, forming a sealed cavity separated from the main chamber. Open the sampling chamber cover plate 12, place the target plate with the sample into the groove of the target plate mounting plate 7 and fix it. Close the sampling chamber cover 12. After the vacuum degree is balanced with the vacuum degree in the main chamber, the three-axis displacement stage 6 loads the target plate with the sample into the ionization region.

[0065] The target plate mounting plate 7 is transferred to the three-axis displacement stage 6 through an insulating material, and a DC voltage is applied to the target plate mounting plate 7.

[0066] Further, the first laser beam emitted by the first laser 1 is focused by the first laser optical element 4 and then irradiates the sample surface at an angle θ with respect to the ion transmission axis for primary ionization.

[0067] The first laser 1 can be a pulsed laser or a continuous laser.

[0068] Further, after a time Δt under the control of the laser timing controller 3, the second laser 2 emits a second laser beam, which is focused by the second laser optical element 5 and then irradiates vertically into the vacuum chamber 13 in the ion transmission direction to perform secondary ionization on the ions.

[0069] The second laser 2 can be an ultraviolet pulsed laser or a vacuum ultraviolet pulsed laser.

[0070] To ensure the coordination of the sample ionization process and the systems such as ion transmission and data acquisition in the mass spectrometry, and improve the ionization efficiency, it is necessary to trigger the laser by the laser timing controller 3 at a specified time and introduce the laser into the sample ionization region. The delay time between the primary ionization laser and the secondary ionization laser needs to be optimized according to the experiment.

[0071] Both the first laser optical element 4 and the second laser optical element 5 include any one or more of a convex lens, a concave lens, a reflector, or an optical fiber. When used for laser transmission, focusing, and direction change, an optical fiber adjustment device needs to be added;

[0072] In other embodiments, the first laser optical element 4 and the second laser optical element 5 can use a combination of a lens and an optical fiber to transmit and focus the laser, and add an optical fiber adjustment device to facilitate the control of the direction angle. In this embodiment, a convex lens, a concave lens, and a reflector can be combined with each other or one of them can be selected according to the actual situation. In this application, it is not limited to the combination of a convex lens, a concave lens, a diaphragm, and a reflector, and can also be a combination of a convex lens, a concave lens, a diaphragm, and an optical fiber for laser transmission, focusing, and direction change.

[0073] The included angle between the incident angle of the first laser beam entering the vacuum system and the center line of the target plate mounting plate 7 is θ;

[0074] The second laser beam is parallel to the upper surface of the sample and has a set distance from the sample surface to perform secondary ionization on the sample molecules entering the gas phase.

[0075] Furthermore, the imaging system includes: a CCD camera 10 and imaging optical elements, which can magnify the target plate sample information and reflect it on the output device in real time; the imaging optical elements include: a focusing mirror, a light source, and a light shield arranged along the incident optical path;

[0076] In this embodiment, the CCD camera 10 is located in the upper right outside the vacuum chamber 13 for observing the sample state and the laser spot situation in real time. The imaging optical elements are located on the left side of the CCD camera 10. This group of optical elements is used for imaging focusing and changing the direction of the imaging optical path, so that the axis of the imaging optical path forms an angle θ with the ion transmission axis and intersects at a point on the target plate.

[0077] The CCD camera 10 magnifies and images the target point through the imaging optical elements, and the ionization position on the target point can be selected according to the real-time imaging of the CCD camera 10.

[0078] Furthermore, the ion focusing device 8 includes: a grounded electrode provided with a grid and three cylindrical electrodes coaxially arranged along the center line of the target plate mounting plate 7;

[0079] The distance between adjacent cylindrical electrodes is 2 mm - 10 mm; the grounded electrode is arranged above the target plate, and the distance between the grounded electrode and the outer surface of the sample on the target plate is 2 mm - 30 mm;

[0080] An insulating pad is provided on one side of any of the cylindrical electrodes or the grounded electrode; the insulating pad is made of any one of ceramic or PEEK materials;

[0081] The material of the cylindrical electrode or the grounded electrode is any one of stainless steel or aluminum alloy.

[0082] In this embodiment, the ion focusing device 8 is located directly above the target plate mounting plate to focus and transmit the generated ions. The ion focusing device 8 includes three cylindrical electrodes and a grounded electrode equipped with a grid. The inner diameter of the electrode is 10 - 30 mm, the outer diameter is 12 - 32 mm, the length is 10 - 30 mm, and the electrode spacing is 2 - 10 mm.

[0083] Furthermore, the ion beam deflection device 9 includes: two sets of electrodes arranged on the same longitudinal axis; each set of electrodes includes a pair of oppositely arranged electrode plates, and the two sets of electrodes are perpendicular to each other and not at the same horizontal height;

[0084] In other embodiments, the two sets of electrodes are provided at the same height, and two pairs of electrode plates perpendicular to each other form four surfaces of a cuboid and do not contact each other;

[0085] The distance between the electrode plates in the two sets of electrodes is 4 mm - 20 mm, and an insulating pad is provided on the opposite side between any two adjacent electrode plates; the insulating pad is made of either ceramic or PEEK material;

[0086] The electrode plates are made of either stainless steel or aluminum alloy.

[0087] In this embodiment, the ion beam deflection device 9 is located directly above the ion focusing device 8 to adjust the direction of the focused ion beam, thereby obtaining a more efficient transmission efficiency. The ion beam deflection device 9 is composed of two sets of electrodes, each set of electrodes consists of two parallel metal plates, the two sets of electrodes are arranged perpendicular to each other in sequence on the upper side of the ion focusing device 8, the distance between each set of electrode plates is 15 mm, the electrode plates are rectangular, and the side lengths are 10 mm - 30 mm.

[0088] Furthermore, the materials of the electrodes are all stainless steel or aluminum and its alloy materials.

[0089] The insulating pads used between the electrode plates are all made of insulating materials such as ceramic or PEEK.

[0090] An ionization method for an ionization device based on the secondary laser ionization technology includes the following steps:

[0091] 1) The laser timing controller 3 sets the emission times of the first laser 1 and the second laser 2;

[0092] When emitting the laser beam, turn on the ion focusing device 8, set the DC voltage, and apply the DC voltage to the ion focusing device 8;

[0093] When the laser beam deflects, apply the set DC voltage to the ion beam deflection device 9 to adjust the direction of the laser beam;

[0094] 2) The first laser beam emitted by the first laser 1 enters the first laser optical element 4 and forms an angle θ with the center line of the target plate mounting plate 7, and is reflected onto the sample on the target plate in the vacuum chamber 13 to bombard the sample surface and achieve primary ionization;

[0095] 3) As Figure 2 shown, the second laser beam emitted by the second laser 2 enters horizontally above the sample in the vacuum chamber 13 at a distance ΔZ higher than the target plate plane through the second laser optical element 5, to achieve secondary ionization of the sample molecules entering the gas phase, thereby increasing the ionization rate of the sample molecules;

[0096] 4) The imaging system 11 collects the sample information on the target plate plane, amplifies the target plate sample information and reflects it on the output device in real time;

[0097] 5) After the three-axis displacement stage 6 moves along the x and y axes to the lower part of the sample changing chamber cover plate 12, the z axis of the three-axis displacement stage 6 rises, jacking up the target plate to the sample changing chamber cover plate 12. The sealing rubber ring at the groove of the target plate is squeezed against the inner wall of the vacuum system housing to form a seal, and the sample changing chamber cover plate 12 is opened to replace the sample, so as to prevent the vacuum environment in the chamber from being damaged during the sample changing process.

[0098] The present invention uses a single laser bombardment on the sample surface to achieve the primary ionization of the sample. Most of the ions generated by the above primary laser ionization are neutral ions. The proportion of molecules that can be ionized is only 0.1%, and there is a serious inhibitory effect of high-abundance components on the ionization of low-abundance molecules, which greatly limits the detection accuracy and resolution. The present invention introduces another laser in the ultraviolet or vacuum ultraviolet band to perform secondary ionization on the sample molecules entering the gas phase to improve the ionization efficiency of the sample molecules.

[0099] The above is a further detailed description of the present invention in combination with specific embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can also be made.

Claims

1. An ionization device based on secondary laser ionization technology, characterized in that: include: A first laser (1), a second laser (2), a laser timing controller (3), a first laser optical element (4), a second laser optical element (5), a vacuum system, a sample carrier, an ion focusing device (8), an ion beam deflection device (9), and an imaging system (11); Wherein, the vacuum system is provided with a sample carrying device, an ion focusing device (8) and an ion beam deflecting device (9); A sample is placed on the sample carrier; an ion beam deflection device (9) and an ion focusing device (8) are arranged in order from top to bottom above the sample carrier; The laser timing controller (3) is connected to the first laser (1) and the second laser (2) respectively, and is used to set the emission interval time of the first laser (1) and the second laser (2); The first laser beam emitted by the first laser (1) enters the first laser optical element (4) and is reflected onto the sample on the sample carrier to achieve primary ionization of the sample and transfer the sample from the solid phase to the gas phase; The second laser beam emitted by the second laser (2) enters above the sample through the second laser optical element (5), thereby achieving secondary ionization of the sample entering the gas phase; The imaging system (11) captures the reflected light of the sample to collect sample information on the target plate plane, and amplifies the target plate sample information to be reflected on the output device in real time.

2. The ionization device based on secondary laser ionization technology according to claim 1, characterized in that: The vacuum system comprises: a shell and a sample exchange chamber cover plate (12) arranged on the shell; a vacuum chamber (13) is formed in the shell.

3. The ionization device based on secondary laser ionization technology according to claim 1, characterized in that: The sample carrying device comprises: a three-axis displacement platform (6), a target plate mounting plate (7) and a target plate; The target plate mounting plate (7) is mounted on a three-axis displacement platform (6), and the three-axis displacement platform (6) is moved to drive the target plate mounting plate (7) to move along three-axis directions in the vacuum chamber (13); a target plate is horizontally arranged on the target plate mounting plate (7); The target plate is arranged parallel to the sample changing chamber cover plate (12), the target plate is at the z-axis zero position of the three-axis displacement stage (6), and the height thereof is smaller than the sample changing chamber cover plate (12); The ion beam deflection device (9) and the ion focusing device (8) are arranged above the target plate mounting plate (7) in sequence from top to bottom along the center line of the target plate mounting plate (7).

4. The ionization device based on secondary laser ionization technology according to claim 3, characterized in that: The target plate mounting plate (7) is connected to the three-axis displacement platform (6) via insulating material, and a direct current voltage is applied to the target plate mounting plate (7).

5. The ionization device based on secondary laser ionization technology according to claim 3, characterized in that: The target plate mounting plate (7) is provided with a groove for placing and fixing the target plate, and a sealing rubber ring is provided on the outer ring of the groove, so that when changing samples, the z-axis of the three-axis displacement stage (6) rises, and the target plate is lifted to the sample changing chamber cover plate (12), and the sealing rubber ring at the groove is squeezed on the inner wall of the shell at the sample changing chamber cover plate (12) to form a seal, so as to prevent the vacuum environment in the chamber from being destroyed during the sample changing process.

6. The ionization device based on secondary laser ionization technology according to claim 1, characterized in that: The ion focusing device (8) comprises: a grounding electrode provided with a grid and three cylindrical electrodes coaxially arranged along the center line of the target plate mounting plate (7); The spacing between adjacent cylindrical electrodes is 2mm-10mm; the ground electrode is arranged above the target plate, and the distance between the ground electrode and the outer surface of the sample on the target plate is 2mm-30mm; An insulating pad is provided on the opposite side of any of the cylindrical electrodes or the grounding electrode; the insulating pad is made of ceramic or PEEK material; The material of the cylindrical electrode or the grounding electrode is any one of stainless steel and aluminum alloy.

7. The ionization device based on secondary laser ionization technology according to claim 1, characterized in that: The ion beam deflection device (9) comprises: two groups of electrodes arranged opposite to each other, and the two groups of electrodes are arranged vertically and sequentially on the upper side of the ion focusing device (8); In any one group of electrodes, the spacing between the electrode plates is 4mm-20mm, and an insulating pad is provided between the two groups of electrode plates; the insulating pad is made of any one of ceramic or PEEK materials; The electrode plate is made of stainless steel or aluminum alloy.

8. The ionization device based on secondary laser ionization technology according to claim 1, characterized in that: The first laser beam emitted by the first laser (1) is a pulsed laser or a continuous laser; The second laser beam emitted by the second laser (2) is an ultraviolet pulse laser or a vacuum ultraviolet pulse laser.

9. The ionization device based on secondary laser ionization technology according to claim 1, characterized in that: The first laser optical element (4) and the second laser optical element (5) both include: any one or more of a convex lens, a concave lens, a reflector or an optical fiber; The angle between the incident angle of the first laser beam entering the vacuum system and the center line of the target plate mounting plate (7) is θ; The second laser beam is parallel to the sample surface and has a set distance from the sample surface, so as to perform secondary ionization on the sample molecules entering the gas phase.

10. The ionization method of the ionization device based on secondary laser ionization technology according to claim 1, characterized in that: The following steps are involved: 1) A laser timing controller (3) sets the emission time of the first laser (1) and the second laser (2); When emitting the laser beam, the ion focusing device (8) is turned on. When the laser beam is deflected, a set DC voltage is applied to the ion beam deflection device (9) to adjust the direction of the laser beam; 2) The first laser beam emitted by the first laser (1) enters the first laser optical element (4) and is reflected onto the sample in the vacuum chamber (13) at an angle θ with the center line of the target mounting plate (7), bombarding the sample to achieve primary ionization; 3) The second laser beam emitted by the second laser (2) passes through the second laser optical element (5) at a distance ΔZ higher than the target plate plane and enters horizontally above the sample in the vacuum chamber (13), thereby performing secondary ionization on the sample molecules entering the gas phase, thereby increasing the ionization rate of the sample molecules; 4) The imaging system (11) collects sample information on the target plate plane, amplifies the sample information on the target plate and reflects it on the output device in real time; 5) After the three-axis translation stage (6) moves along the x-axis and the y-axis to the bottom of the sample changing chamber cover plate (12), the z-axis of the three-axis translation stage (6) rises, and the target plate is lifted to the sample changing chamber cover plate (12). The sealing rubber ring on the target plate mounting plate is squeezed on the inner wall of the shell of the vacuum system to form a seal, and the sample changing chamber cover plate (12) is opened to replace the sample, so as to prevent the vacuum environment in the chamber from being destroyed during the sample changing process.

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