CN218101170U

CN218101170U - Variable magnetic induction intensity electron bombardment ionization source

Info

Publication number: CN218101170U
Application number: CN202222207891.0U
Authority: CN
Inventors: 黄泽建; 高佳奇
Original assignee: Shanghai Limu Scientific Instrument Co ltd
Current assignee: Shanghai Limu Scientific Instrument Co ltd
Priority date: 2022-08-22
Filing date: 2022-08-22
Publication date: 2022-12-20
Anticipated expiration: 2032-08-22

Abstract

The utility model provides a variable magnetic induction electron bombardment ionization source, which is suitable for a mass spectrometer and comprises an ionization chamber shell, wherein one end of the ionization chamber shell is provided with an open focusing lens; the other end of the ionization chamber shell is provided with a repulsion electrode; the side of ionization chamber is equipped with the introduction port, the both sides of ionization chamber shell are equipped with the filament slit respectively, the outside correspondence of filament slit is equipped with electron generating device, electron generating device includes the iron core, the winding is equipped with the solenoid on the iron core, be equipped with the filament between the one end of iron core and the filament slit. The utility model provides an electron generating device utilizes the magnetism of its production can adjust the inside magnetic induction intensity of ionization source through current real time control's characteristics, but makes its helical motion orbit of real time control electron and the deflection distance of ion to realized carrying out the method of high-efficient ionization to the sample of different mass ranges.

Description

Variable magnetic induction intensity electron bombardment ionization source

Technical Field

The utility model relates to a structure of ion source in the mass spectrograph belongs to mass spectrum technical field, especially relates to a variable magnetic induction electron bombardment ionization source.

Background

Mass spectrometry is a powerful means of identifying unknown compounds, quantifying known compounds, and exploring the molecular structure of compounds, and is considered to be the most sensitive and specific universal analytical technique with the ability to identify multiple chemical species at low concentrations. As shown in fig. 1, a basic structure of a mass spectrometer of the prior art, the mass spectrometer includes an ion source, a mass analyzer, and a detector. The working principle of the mass spectrometer is as follows: the sample introduction device is used for introducing sample substances to be detected into an ion source and carrying out ionization treatment, so that the sample substances enter a mass analyzer under the action of an electric field, different ions are allowed to enter the mass analyzer at the same time, the ions are separated according to the mass-to-charge ratio (m/z) of the ions, the separated ions are sequentially sent to a detector, the detector converts ion signals into current signals, the current signals are amplified and converted into digital signals through analog-to-digital conversion, and the digital signals are displayed in a mass spectrogram mode and the like by utilizing a computer technology to complete qualitative and quantitative analysis.

The ion source is a core component of the mass spectrometer and is a device for ionizing sample molecules. Many ionization techniques have been developed in recent years, but each ionization method has a specific ionization reaction mechanism, and the applicable environment is different. Electron impact Ionization (EI) is the earliest Ionization technique that emits electrons with energy that collide with and interact with molecules entering the ion chamber to ionize them. At present, the EI technology has developed to a mature level, is convenient to operate, simple in structure, high in ionization efficiency, low in energy loss, good in reproducibility, has a huge standard spectrum library, is very suitable for analyzing high-volatility substances and the like, and is widely applied to the industries of chemistry, chemical engineering, environment, energy, medicine and the like.

Generally, the structure of the EI source mainly includes a filament, an ionization chamber, a repulsion pole, a lens group and a magnet. When current is introduced to the filament to heat the filament in a vacuum state, thermal electrons can be generated, the thermal electrons are promoted to flow into the ionization chamber in a voltage applying mode and act with sample molecules introduced from the sample inlet, the molecules are ionized, the generated ions are accelerated and driven out of the ionization chamber under the influence of the voltage of a repulsion electrode and finally enter the mass analyzer under the action of the lens group. In order to optimize the ionization effect, a pair of magnets is added to apply a magnetic field on the moving path of the electrons, so that the electrons spirally move inside the ionization chamber along the magnetic field line, thereby increasing the collision probability of the electrons and the molecules of the sample and improving the ionization efficiency.

The prior EI source is realized by adopting a permanent magnet with fixed magnetism, so that the magnetic induction intensity at each position in the ion source is invariable.

When the EI source works, an electric field and a magnetic field which are orthogonal to each other are distributed in the ionization chamber, ions move towards a lens group close to the mass analyzer under the action of the electric field after being generated in the ionization chamber, and at the moment, the ions move along the direction of the cutting magnetic induction line and can be subjected to Lorentz force, so that side deviation can be generated. The distance of the offset of the ions is related to the relative mass and the magnetic induction intensity, and the magnetic field inside the ionization chamber is generated by the permanent magnet, so the magnetic induction intensity of the ions is not changed, and therefore, the offset distance of the ions with different relative masses in the process of movement is also different. For a substance with relatively small molecular mass, the offset distance of the generated ions during movement is increased, which may cause the ions to impact on the inner wall of the ionization chamber or not pass through the electric field in the middle of the lens group, and thus not enter the mass analyzer behind, thereby affecting the overall sensitivity of the instrument.

It can be seen that, in the EI source with the permanent magnet, if a magnet with too weak magnetism is used, the moving radius of internal thermal electrons is large, and the probability of collision with molecules is reduced, so that the ionization effect of the EI source on the molecules is reduced, whereas if a magnet with too strong magnetism is used, ions with relatively small mass may be greatly deviated under the action of lorentz force, and the ionization efficiency is also reduced. Therefore, if the mass spectrometer is required to have good sensitivity to substances in different mass ranges, the magnet needs to be replaced, so that the vacuum needs to be broken, the operation process is complicated, and the time is wasted.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a change the novel electron bombardment ionization source that has variable magnetic induction density characteristics of current electron bombardment ionization source structure.

In order to realize the purpose, the utility model adopts the following technical scheme:

a variable magnetic induction intensity electron bombardment ionization source is suitable for a mass spectrometer and comprises an ionization chamber shell, wherein one end of the ionization chamber shell is provided with a focusing lens with an opening; the other end of the ionization chamber shell is provided with a repulsion electrode; the side of ionization chamber is equipped with the introduction port, the both sides of ionization chamber shell are equipped with the filament slit respectively, the outside correspondence of filament slit is equipped with electron generating device, electron generating device includes the iron core, the winding is equipped with the solenoid on the iron core, be equipped with the filament between the one end of iron core and the filament slit.

Preferably, the filament is arranged at one side of the filament slit in a manner of being tightly attached through the filament seat, a filament retaining sheet is arranged at the outer side of the filament, and pins at two ends of the filament are connected with the heating circuit.

Preferably, one end of the ionization chamber shell is sequentially provided with a pull-out lens, a focusing lens and an ejecting lens which are provided with openings from inside to outside, and the pull-out lens (8), the focusing lens (9) and the ejecting lens (10) are coaxially arranged with the mass analyzer.

Preferably, the iron core is of a horseshoe structure, two ends of the iron core are respectively opposite to the filament slit, and the filament is arranged between the filament slit and the iron core.

Preferably, the iron core is made of silicon steel with magnetic permeability.

Preferably, the solenoid is in a wire-wound configuration.

Compared with the prior art, the utility model discloses possess following beneficial effect:

the utility model discloses on integrated electron bombardment ionization source with the electro-magnet, solved the problem that the magnetic induction intensity that the permanent magnet produced the magnetic field can't be adjusted, can carry out real time control to inside magnetic induction intensity according to the difference that detects the material nature to guarantee the production and the transmission of ion, thereby improve ionization efficiency, guarantee the sensitivity of mass spectrometry instrument to different materials, improved the suitability of instrument greatly. The utility model provides an electron generating device utilizes its magnetism can adjust the inside magnetic induction intensity of ionization source through current real time control's characteristics, but makes its helical motion orbit of real time control electron and the deflection distance of ion to realized carrying out the method of high-efficient ionization to the sample of different mass ranges.

Drawings

FIG. 1 is a schematic diagram of a system flow of a variable magnetic induction electron bombardment ionization source according to the present invention;

FIG. 2 is a schematic structural diagram of a first embodiment of an ion source in a variable magnetic induction electron bombardment ionization source according to the present invention;

FIG. 3 is a schematic structural diagram of a second embodiment of an ion source in a variable magnetic induction electron bombardment ionization source according to the present invention;

FIG. 4 is a schematic diagram of the operation of an ion source in a variable magnetic induction electron bombardment ionization source according to the present invention;

1. a solenoid; 2. an iron core; 3. a filament; 4. an ionization chamber housing; 5. a filament slit; 6. a repulsion pole; 7. a sample inlet; 8. pulling out the lens; 9. a focusing lens; 10. ejecting the lens; 11. an electric field; 12. a magnetic field; 13. a positive ion.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments.

Example one

As shown in fig. 1 to fig. 3, for the utility model discloses a variable magnetic induction electron bombardment ionization source, which is suitable for mass spectrometers, including ionization chamber 4, the top of ionization chamber 4 is provided with a pull-out lens 8, a focusing lens 9 and an ejecting lens 10 (wherein pull-out lens 8 is disposed at a position close to ionization chamber 4, and ejecting lens 10 is disposed at a position close to mass analyzer) from inside to outside in sequence, and pull-out lens 8, focusing lens 9, ejecting lens 10 are disposed coaxially with the mass analyzer, and the mass analyzer analyzes ions; the bottom of the center of the ionization chamber 4 is provided with a repulsion electrode 6; the side of the ionization chamber is provided with a sample inlet 7, and the sample inlet 7 is connected with a sample introduction device. The ionization chamber 4 is internally of a cylindrical space structure, two sides of the ionization chamber 4 are respectively provided with a filament slit 5, the two filament slits 5 are arranged oppositely, and the outer sides of the filament slits 5 are correspondingly provided with an electron generating device which comprises an iron core 2, the iron core 2 is made of magnetic silicon steel material, the iron core 2 is wound with a solenoid 1, and the solenoid 1 is of a wire winding structure; be equipped with filament 3 between the one end of iron core 2 and the filament slit 5, setting that filament 3 hugs closely through the filament seat is in one side of filament slit 5, the outside of filament 3 is equipped with the filament separation blade, heating circuit is connected to the pin at 3 both ends of filament.

As shown in fig. 4, the working principle of the present invention is as follows:

as shown in figure 1, a vacuum system (pressure less than 5 x 10) is connected outside the mass spectrometer ^-5 Torr), the ion source is in a vacuum environment, a sample inlet 7 on the ionization chamber 4 is connected with a sample feeding device, a sample in a field environment is introduced into the ionization chamber 4, current is introduced into the filament 3 for heating, so that the filament generates thermal electrons, voltage is applied to the filament blocking piece, so that a potential difference is generated between the blocking piece and the ionization chamber 4, and the generated thermal electrons are promoted to flow into the ionization chamber through the filament slit 5.

When a current flows inside the solenoid 1, a magnetic field is generated around the solenoid 1, and thus the core 2, which is centrally disposed in the solenoid 1, is magnetized, so that the magnetic field around the core is greatly increased. Under the action of the electromagnets at the two sides, a magnetic field is generated inside the ionization chamber 4, so that generated thermal electrons do spiral motion inside the ionization chamber 4 and react with sample molecules introduced from the sample inlet 7 to ionize the molecules.

When the ion source works, positive ions 13 are generated, different voltages are respectively applied to the repulsion electrode 6 and the pull-out lens 8, an electric field 11 is formed inside the ionization chamber 4, and the electromagnets in the electron generating devices on the two sides form a magnetic field 12 which is orthogonal to the electric field 11 inside the ionization chamber 4. The positive ions 13 are accelerated toward the pullout lens 8 by the electric field 11, and are deflected by the lorentz force applied thereto in a direction orthogonal to the magnetic field and the electric field since the movement direction thereof is not parallel to the magnetic field 12.

When the generated ions have a relatively large mass, the deflection distance of the ions generated by the lorentz force is reduced, and the ions do not easily collide with the ionization chamber 4 in the process of moving toward the pull-out lens 8. Therefore, when the environment mainly comprising macromolecular substances is detected, the current in the solenoid 1 can be properly enhanced, the strength of the magnetic field 12 is increased, the spiral motion radius of the thermal electrons is reduced, and the collision probability of the thermal electrons and molecules is increased, so that the ionization efficiency is improved;

when the generated ions have a small relative mass, the deflection distance of the ions due to the lorentz force becomes large, and the ions easily collide with the ionization chamber 4 during the movement toward the pull-out lens 8. Therefore, when detecting an environment mainly containing small molecular substances, the current passing through the solenoid 1 can be properly weakened, the strength of the magnetic field 12 is reduced, the deflection distance of the ions 13 under the action of the Lorentz force is shortened, and more ions enter the pull-out lens 8 through the small hole, so that the ionization efficiency is improved.

Example two

As shown in fig. 3, on the basis of the first embodiment, the iron core 2 provided by the present invention can also adopt a horseshoe-shaped structure, the two ends of the iron core 2 of the horseshoe-shaped structure are respectively opposite to the filament slit 5, and the filament 3 is disposed between the filament slit 5 and the iron core 2. The working principle is the same as that of the first embodiment, and therefore, the description thereof is omitted.

The utility model discloses a replace the electro-magnet with the permanent magnet of traditional electron bombardment ionization source, make full use of the characteristics that the magnetic induction intensity accessible electric current that the electro-magnet produced magnetic field adjusted the size, through electric current real time control's characteristics, adjust the magnetic induction intensity inside the ionization source, but make its helical motion orbit of real time control electron and the deflection distance of ion to realized carrying out the method of high-efficient ionization to the sample of different mass ranges.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and to simplify the description, but do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically limited otherwise.

The above, only be the concrete implementation of the preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art is in the technical scope of the present invention, according to the technical solution of the present invention and the utility model, the concept of which is equivalent to replace or change, should be covered within the protection scope of the present invention.

Claims

1. A variable magnetic induction intensity electron bombardment ionization source is suitable for a mass spectrometer and comprises an ionization chamber shell (4), and is characterized in that one end of the ionization chamber shell (4) is provided with a focusing lens (9); the other end of the ionization chamber shell (4) is provided with a repulsion electrode (6); the side of ionization chamber is equipped with introduction port (7), the both sides of ionization chamber shell (4) are equipped with filament slit (5) respectively, the outside correspondence of filament slit (5) is equipped with electron generating device, electron generating device includes iron core (2), the winding is equipped with solenoid (1) on iron core (2), be equipped with filament (3) between the one end of iron core (2) and filament slit (5).

2. The variable magnetic induction electron bombardment ionization source of claim 1, wherein the filament (3) is closely arranged at one side of the filament slit (5) through a filament seat, a filament baffle is arranged at the outer side of the filament (3), and pins at two ends of the filament (3) are connected with a heating circuit.

3. The variable magnetic induction electron bombardment ionization source according to claim 1, wherein one end of the ionization chamber housing (4) is provided with a pull-out lens (8), a focusing lens (9) and an ejecting lens (10) which are open from inside to outside in sequence, and the pull-out lens (8), the focusing lens (9) and the ejecting lens (10) are coaxially arranged with the mass analyzer.

4. The variable magnetic induction electron bombardment ionization source according to claim 1, wherein the iron core (2) is of a horseshoe-shaped structure, two ends of the iron core (2) are respectively opposite to the filament slit (5), and the filament (3) is arranged between the filament slit (5) and the iron core (2).

5. The variable magnetic induction electron bombardment ionization source of claim 1, wherein the iron core (2) is made of silicon steel material with magnetic permeability.

6. The variable magnetic induction electron bombardment ionization source of claim 1, wherein the solenoid (1) is in a wire wound configuration.