An ion sensor based on FAIMS principle

Abstract

The embodiment of the present invention provides an ion sensor based on the FAIMS principle, which includes: a corona ionization chamber, an ion screening path and an ion detection unit connected in sequence; the corona ionization chamber includes an ionization chamber housing, a corona ionization source and an air inlet, the corona ionization source provides a preset negative high voltage to ionize the sample; the ion screening path includes an outer wall of the screening path, an internal columnar electrode, and a path formed between the outer wall and the electrode, and the path is used for ion screening; the ion detection unit includes a deflection electrode and an ion detection plate, an air outlet is provided between the deflection electrode ring and the ion detection plate, for the outflow of air flowing into the corona ionization chamber, and a deflection electric field is provided between the deflection electrode and the ion detection plate, for making the ions to be measured reach the ion detection plate. The ion source is a non-radioactive ionization source, does not generate radioactive radiation, has the advantage of being able to work normally in an external environment at normal temperature and pressure, and can be applied to various working environments.

Description

Technical Field

[0001] The invention relates to the field of sensors, and in particular to an ion sensor based on the FAIMS principle. Background Art

[0002] With the continuous development of explosive and drug detection equipment based on IMS (Ion mobility spectroscopy) and FAIMS (High-field Asymmetric Waveform Ion Mobility Spectrometry) technology, there are increasingly higher requirements for the size of the equipment, the impact on human health, and the speed of detection. Small size, high efficiency, and no pollution are gradually becoming the goals that new detection equipment needs to focus on.

[0003] At present, most of the explosive detection equipment on the market adopts the method of first using an artificial radioactive ion source to ionize the sample and then conduct the detection. However, this method has a serious disadvantage, that is, the ion source used is an artificial radioactive isotope. First, if the operation process is improper, the artificial radioactive ion source has a certain radioactive hazard to the human body; secondly, due to the possibility of harm to the human body, the procedures for purchasing, storing, selling, and discarding artificial radioactive ion sources are very complicated, and the cost of implementation is also very high. Therefore, the use of a new type of ionization source without radioactive hazards is a very important goal. Summary of the invention

[0004] In order to solve the above problems, an embodiment of the present invention provides an ion sensor based on the FAIMS principle.

[0005] The embodiment of the present invention provides an ion sensor based on the FAIMS principle, comprising: a corona ionization chamber, an ion screening path and an ion detection part connected in sequence; the corona ionization chamber comprises an ionization chamber housing, a corona ionization source and an air inlet, the corona ionization source provides a preset negative high voltage to ionize a sample; the ion screening path comprises an outer wall of the screening path, an internal columnar electrode and a path formed between the outer wall and the electrode, the path being used for ion screening; the ion detection part comprises a deflection electrode and an ion detection plate, an air outlet is provided between the deflection electrode ring and the ion detection plate for outflow of air flowing into the corona ionization chamber, a deflection electric field is provided between the deflection electrode and the ion detection plate for making the ions to be detected reach the ion detection plate.

[0006] Furthermore, a metal absorption net is provided between the corona ionization source and the ion screening passage, and the metal absorption net is provided with a preset negative low pressure.

[0007] Furthermore, any longitudinal cross-section of the outer wall of the passage, the internal columnar electrode, the deflection electrode and the ion detection plate is circular.

[0008] Furthermore, the cross section of the ion detection plate is L-shaped.

[0009] Furthermore, an accelerating electric field is formed between the outer wall and the ionization source, so as to allow the ionized ions to be detected to reach the ion screening passage.

[0010] Furthermore, the corona ionization source is a discharge needle with a diameter of 0.1 mm to 0.3 mm.

[0011] Furthermore, the ionization chamber shell is made of insulating material.

[0012] Furthermore, the central portion of the ion detection plate is hollow, and is used to apply voltage to the internal columnar electrode.

[0013] Compared with the common artificial radioactive ionization sources currently on the market, the ionization source based on the FAIMS principle provided by the embodiment of the present invention is a non-radioactive ionization source, which does not generate radioactive radiation, greatly reducing the possibility of damage to the human body; secondly, compared with the radioactive ionization source, the corona ionization source has the advantages of low cost, convenient purchase, and simple disposal. Finally, compared with other non-radioactive ionization sources, the corona ionization source has the advantages of simple use conditions and normal operation in an external environment at normal temperature and pressure, and can be applied to various working environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 A structural diagram of an ion sensor based on the FAIMS principle provided by an embodiment of the present invention;

[0016] Figure 2 A schematic diagram of the ion movement trajectory inside the ion sensor based on the FAIMS principle provided by an embodiment of the present invention;

[0017] Figure 3 A schematic diagram of the working principle of an ion sensor based on the FAIMS principle provided in an embodiment of the present invention;

[0018] Explanation of reference numerals: 1 corona ionization chamber; 2 ion screening passage; 3 ion detection unit; 11 ionization chamber housing; 12 corona ionization source; 13 air inlet; 14 metal absorption mesh; 21 screening passage outer wall; 22 internal columnar electrode; 31 deflection electrode; 32 ion detection plate; 33 air outlet. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The current non-radioactive ionization sources include PID photoionization, precious metal film photoelectron source, dielectric barrier discharge, electrospray and corona discharge ion sources. Considering the environmental factors of use, the corona ion source has more prominent advantages in this regard: first, the corona ion source has no radioactive harm to the human body; second, the corona ion source can be used in ordinary environments and does not have excessive requirements for detection equipment; finally, because the corona ion source is a pure hardware circuit design, the cost is much lower than other methods.

[0021] The present invention is an ion sensor that can perform ionization detection based on a DC corona ionization source and the FAIMS principle. The sensor ionizes the test sample through the tip discharge of a discharge needle connected to a negative high voltage, and screens and detects the ionized sample. It can detect different types of substances, such as for use in explosive detection equipment.

[0022] Figure 1 The structure diagram of the ion sensor based on the FAIMS principle provided by the embodiment of the present invention is as follows: Figure 1 As shown, an embodiment of the present invention provides an ion sensor based on the FAIMS principle, comprising: a corona ionization chamber 1, an ion screening passage 2 and an ion detection unit 3 connected in sequence; the corona ionization chamber 1 comprises an ionization chamber housing 11, a corona ionization source 12 and an air inlet 13, and the corona ionization source 12 provides a preset negative high voltage; the ion screening passage 2 comprises a screening passage outer wall 21, an internal columnar electrode 22 and a passage formed between the outer wall and the electrode, and the passage is used for ion screening; the ion detection unit 3 comprises a deflection electrode 31 and an ion detection plate 32, an air outlet 33 is provided between the deflection electrode 31 ring and the ion detection plate 32, and is used for the outflow of air flowing into the corona ionization chamber 1, and a deflection electric field is provided between the deflection electrode 31 and the ion detection plate 32, and is used for making the ions to be measured reach the ion detection plate 32.

[0023] The ion sensor provided in the embodiment of the present invention includes three parts. It should be noted that the three parts may not be physically separated. This embodiment is only for the convenience of explanation. For example, the corona ionization chamber 1 and the ion screening passage 2 may be structurally connected together. The current corona discharge technology mainly includes two methods: DC corona discharge and pulse corona discharge. The present invention adopts DC corona discharge technology.

[0024] Corona ionization chamber 1: The sample is pushed into the corona ionization chamber 1 by the air of the air inlet 13. The corona ionization source 12 provides a preset negative high voltage, and the negative high voltage voltage value is set according to specific needs so that the sample is ionized, such as -3000V (can be determined according to the specific sample and the FAIMS principle). The negative ion group generated by the discharge of the corona ionization source 12 ionizes the collected sample. The ionized sample can reach the ion screening path 2 through the air flow of the air inlet 13 (or first pass through the accelerating electric field area of ​​the embodiment of the present invention and then reach the ion screening path 2 through the air flow, see the following embodiment).

[0025] Ion screening passage 2: The sample is pushed into the passage between the outer wall of the ion screening passage 2 and the internal columnar electrode 22 by air. A screening voltage is applied between the outer wall and the internal columnar electrode 22, which can be adjusted according to the specific application scenario. According to the preset screening voltage, specific sample particles can be screened according to the preset screening voltage. Figure 2 The other ions move along the trajectory 4 in the figure, and hit the internal columnar electrode 22, thereby entering the ion detection part 3 through the screening path.

[0026] Ion detection section 3: The deflection electrode 31 of the ion detection section 3 and the ion detection plate 32 form an ion deflection area, and the deflection electrode 31 ring can be fed with an adjustable voltage of -1V to -12V. The air outlet is the last part of the entire sensor passage, and the air flow in the entire sensor is maintained by the connected fan.

[0027] Compared with the common artificial radioactive ionization sources currently on the market, the ionization source based on the FAIMS principle provided by the embodiment of the present invention is a non-radioactive ionization source, which does not generate radioactive radiation, greatly reducing the possibility of damage to the human body; secondly, compared with the radioactive ionization source, the corona ionization source has the advantages of low cost, convenient purchase, and simple disposal. Finally, compared with other non-radioactive ionization sources, the corona ionization source has the advantages of simple use conditions and normal operation in an external environment at normal temperature and pressure, and can be applied to various working environments.

[0028] At present, the corona discharge technology mainly includes two methods: DC corona discharge and pulse corona discharge. Each method has its own advantages and disadvantages. The advantage of DC corona is that the circuit is simple, only a circuit board that can generate negative high voltage is needed, and no circuit that generates current pulse is needed, which has lower cost requirements. However, the disadvantage is that corona discharge will produce nitrogen oxides NOX and O3, which interfere with the ionization of the sample and greatly reduce the detection sensitivity of the sample ionized by negative ions.

[0029] In order to solve this problem, based on the content of the above embodiment, as an optional embodiment, a metal absorption net 14 is provided between the corona ionization source 12 and the ion screening passage 2, and the metal absorption net 14 is provided with a preset negative low voltage. The metal absorption net 14 can be a steel net with an adjustable negative voltage placed between the corona ionization source 12 and the ion screening passage 2, and the preset negative voltage is determined according to the gas concentration and the sample, such as -1V to -12V, for adsorbing positive ions generated in the air ionized by the corona ionization source 12, so as to reduce the influence of nitrogen oxides NOX and O3 generated by the positive ions on the ionization of the sample.

[0030] By placing a negatively charged absorption net between the corona ionization source 12 and the ion deflection path, the low cost advantage of DC corona discharge can be maintained, and the positive ions generated by the discharge needle ionization can be absorbed by the absorption net, thereby reducing the generation of nitrogen oxides NOX and O3, thereby solving the problem of decreased sensitivity of DC corona discharge.

[0031] Based on the content of the above embodiment, as an optional embodiment, any longitudinal section of the passage outer wall, the internal columnar electrode 22, the deflection electrode 31 and the ion detection plate 32 is circular. Figure 1 The cross section is parallel to the viewing angle shown. With this structure, all the space in the ion screening passage 2 can be fully utilized, and the screening voltage between the outer wall and the internal columnar electrode 22 can be used to transport all the ionized ions to the ion detection plate 32 of the ion detection unit 3 for samples with low concentrations, so that it can be applied to low-concentration sample environments.

[0032] The ion sensor based on the FAIMS principle provided by the embodiment of the present invention can allow test samples to pass through in all directions of the entire screening path, which can greatly increase the ventilation volume, thereby improving the sensitivity of the entire sensor.

[0033] Based on the content of the above embodiment, as an optional embodiment, the cross section of the ion detection plate 32 is L-shaped. Figure 1 The cross section of the ion detection plate 32 is L-shaped, and the deflection electrode 31 with negative voltage is used to deflect the ions, so that the ionized sample can be brought closer to the detection electrode, ensuring that the sample can hit the detection electrode, greatly reducing the signal loss.

[0034] Based on the content of the above embodiment, as an optional embodiment, an accelerating electric field is formed between the outer wall and the corona ionization source 12 to enable the ionized ions to be measured to reach the ion screening passage. Figure 2 A schematic diagram of the ion movement trajectory inside the ion sensor based on the FAIMS principle provided by an embodiment of the present invention, specifically as follows Figure 2 As shown in the accelerating electric field area 5, the accelerating electric field area 5 is the part between the ion screening path 2 and the corona ionization source 12, and this part produces a section of accelerating electric field for accelerating negative ions by the corona ionization source 12 and the voltage difference generated between the outer wall 21 of the screening path, and accelerates the sample ionized by the corona, so that the sample enters the subsequent air push area. The air push area is an air passage in the ion screening path 2 where there is no electric field, and the sample ions entering from the electric field acceleration area enter the ion screening area by air flow in the air push area. The sample ionized by the corona is accelerated by the accelerating electric field, and it is ensured that the sample can hit the detection electrode after acceleration through the ion screening area, greatly reducing the loss of the signal.

[0035] Based on the content of the above embodiment, as an optional embodiment, the corona ionization source 12 is a discharge needle with a diameter of 0.1mm to 0.3mm. The corona ion source can be a discharge needle with a diameter of 0.1mm-0.3mm and a length of 5mm connected to a high voltage of about -3000V, and the negative ion group generated by the discharge at the tip of the discharge needle is used to ionize the collected sample.

[0036] Based on the content of the above embodiment, as an optional embodiment, the ionization chamber housing 11 is made of insulating material. The ionization chamber housing 11 is made of insulating material to prevent the corona ionization source 12 with high voltage from injuring the operator.

[0037] Based on the content of the above embodiment, as an optional embodiment, the center of the ion detection plate 32 is empty, which is used to apply voltage to the internal columnar electrodes. Figure 1 As shown, since any longitudinal section of the outer wall of the passage, the internal columnar electrode 22, the deflection electrode 31 and the ion detection plate 32 is circular, in order to be suitable for low-concentration sample environments, the center of the ion detection plate 32 is empty to apply voltage to the internal columnar electrode.

[0038] Based on the above embodiment including the corona discharge needle, the accelerating electric field region 5 and the metal absorption mesh 14, Figure 3 The schematic diagram of the working principle of the ion sensor based on the FAIMS principle provided by the embodiment of the present invention is as follows: Figure 3 As shown:

[0039] When the entire ion sensor is working, airflow can be provided by the terminal fan. There is flowing air as a carrier in the entire sensor to carry the test sample for movement. The sample to be tested is placed at the entrance of the corona ionization chamber at the front end of the entire sensor. The sample to be tested will be brought into the corona discharge needle by the flowing air. Since the discharge needle is connected to a high voltage of about -3000V, the sample to be tested will be ionized and negatively charged. A metal absorption net 14 with a voltage of -1V to -12V is placed next to the discharge needle to absorb the positive ions generated by the discharge needle due to ionization. The voltage is related to the environmental signal detected by the detection electrode 32. When the environmental signal decreases, the negative voltage on the metal absorption net 14 will increase, thereby improving the ability to absorb positive ions and improving the environmental signal. After the sample is ionized, it will be affected by the electric field and enter the accelerating electric field area 5. In the accelerating electric field area 5, because the discharge needle and the metal absorption net 14 are close to the outer wall 21 of the screening passage, about 5 mm, and the outer wall 21 of the screening passage is connected to the ground, a strong electric field pointing to the discharge needle will be generated between the discharge needle / absorption net and the outer wall 21 of the screening passage. Since the ionized sample is negatively charged, the sample will be attracted by this electric field and accelerated into the air promotion area. At the same time, the ionized positive ions will be absorbed by the metal absorption net 14. In the air promotion area, the ionized sample loses the influence of the accelerating electric field of the accelerating electric field area, and will be affected by the air flow in the sensor and transported to the ion screening area. In the ion screening area, because the internal columnar electrode (which can be cylindrical) is passed with a specific screening voltage, specific sample ions can be selected as follows: Figure 2 The ions move along the trajectory shown in the figure, and enter the ion detection part through the screening path. When the ions pass through the ion screening area and enter the ion deflection area, since the deflection electrode 32 (in a ring shape) is connected with a voltage of -1V to -12V, the ions will be deflected toward the detection electrode, and gradually approach the detection electrode until they hit the detection electrode (i.e., the ion detection plate), generating an electrical signal, and then the sample that loses electrons will be discharged from the sensor along with the air flow (discharged at the air outlet 33).

[0040] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, i.e., they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Those of ordinary skill in the art may understand and implement it without creative effort.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ion sensor based on the FAIMS principle, characterized in that: include: A corona ionization chamber, an ion screening passage and an ion detection section connected in sequence; The corona ionization chamber comprises an ionization chamber housing, a corona ionization source and an air inlet, wherein the corona ionization source provides a preset negative high voltage to ionize the sample; The ion screening passage comprises an outer wall of the screening passage, an internal columnar electrode, and a passage formed between the outer wall and the internal columnar electrode, and the passage is used for ion screening; The ion detection part includes a deflection electrode and an ion detection plate, an air outlet is provided between the deflection electrode and the ion detection plate for the outflow of air flowing into the corona ionization chamber, and a deflection electric field is provided between the deflection electrode and the ion detection plate for making the ions to be detected reach the ion detection plate; Through the screening voltage between the outer wall and the inner columnar electrode, all the ions ionized from the low-concentration sample are transported to the ion detection plate; A metal absorption net is provided between the corona ionization source and the ion screening passage, and the metal absorption net is provided with an adjustable preset negative low pressure; the metal absorption net is used to absorb positive ions generated in the air ionized by the corona ionization source; The preset negative low pressure is adjusted based on the low concentration sample.

2. The ion sensor based on the FAIMS principle according to claim 1, characterized in that: Any longitudinal cross-section of the outer wall, the internal columnar electrode, the deflection electrode and the ion detection plate is circular.

3. The ion sensor based on the FAIMS principle according to claim 1, characterized in that: The cross section of the ion detection plate is L-shaped.

4. The ion sensor based on the FAIMS principle according to claim 1, characterized in that: An accelerating electric field is formed between the outer wall and the ionization source, which is used for the ionized ions to be measured to reach the ion screening passage.

5. The ion sensor based on the FAIMS principle according to claim 1, characterized in that: The corona ionization source is a discharge needle with a diameter of 0.1 mm to 0.3 mm.

6. The ion sensor based on the FAIMS principle according to claim 1, characterized in that: The ionization chamber shell is made of insulating material.

7. The ion sensor based on the FAIMS principle according to claim 2, characterized in that: The center of the ion detection plate is hollow and is used to apply voltage to the internal columnar electrode.

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