Quadruple polarity mass analysis device

Abstract

By preventing the formation of a film in the ionization box, the filament can be used for a longer period. [Solution] The ion source 21 of the quadrupole mass spectrometer 100 includes a filament 211 that emits electrons when a voltage is applied, an ionization box 212 into which electrons are incident and which ionizes the sample, and a blocking member 214 provided between the filament 211 and the ionization box 212, which blocks the coating material that forms a coating on the ionization box 212 from moving toward the ionization box 212.

Description

Technical Field

[0001] The present invention relates to a quadrupole mass spectrometer.

Background Art

[0002] Some conventional quadrupole mass spectrometers have an ionization section for ionizing a sample. This ionization section has a filament that is coiled and emits electrons when a voltage is applied, and a grid electrode (hereinafter also referred to as an ionization box) that is irradiated with the electrons emitted from the filament and ionizes the sample by colliding the sample with electrons.

[0003] The ionized sample is emitted from the ionization box to the quadrupole section and separated by the quadrupole section. On the other hand, electrons collide with the ionization box, and the voltage applied to the filament is controlled based on the current generated by the collided electrons at that time.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, when performing mass analysis of a sample in the above mass spectrometer, the material constituting the filament may react to generate molecules that cause a film to be formed in the ionization box. When these molecules enter the ionization box, a film is formed in the ionization box.

[0006] In this case, the coating prevents electrons from directly colliding with the ionization box, which can lead to an excessive voltage being applied to the filament relative to the number of electrons in the ionization box. As a result, the filament may break sooner than expected, making it unusable for extended periods.

[0007] Therefore, the present invention has been made in view of the above problems, and its main objective is to extend the lifespan of the filament by preventing the formation of a coating in the ionization box. [Means for solving the problem]

[0008] In other words, the quadrupole mass spectrometer of the present invention comprises an ion source for ionizing a sample, a filter unit for separating the ions generated by the ion source using a quadrupole, and a detection unit for detecting the ions separated by the filter unit, wherein the ion source comprises a filament that emits electrons when a voltage is applied, an ionization box into which the electrons are incident to ionize the sample, and a blocking member provided between the filament and the ionization box, which blocks the formation of a coating on the ionization box from moving from the filament to the ionization box.

[0009] In the quadrupole mass spectrometer of the present invention, the blocking member is provided between the filament and the ionization box, blocking the formation of a coating from the filament to the ionization box, thereby preventing the formation of a coating on the ionization box. As a result, for example, when controlling the filament voltage based on the current caused by electrons colliding with the ionization box, the filament voltage can be appropriately controlled, and the filament can be used for a longer period than in conventional systems.

[0010] When a coating forms on the ionization box, the number of electrons that directly collide with the ionization box decreases, which can lead to an excessive voltage being applied to the filament relative to the number of electrons in the ionization box. As a result, the lifespan of the filament is shortened. Therefore, a voltage control unit is further provided that controls the voltage applied to the filament based on the current generated by electrons colliding with the ionization box. In this configuration, the blocking member prevents the formation of a film on the ionization box, so that the current generated by electrons colliding with the ionization box accurately reflects the number of electrons in the ionization box. Therefore, the voltage control unit can appropriately control the voltage applied to the filament based on the current generated by electrons colliding with the ionization box.

[0011] The shielding member has an opening facing the ionization box and surrounds the filament, and further comprises a low-potential member with a lower potential than the ionization box, wherein the shielding member covers a portion of the opening of the low-potential member. In this configuration, electrons generated from the filament can travel towards the ionization box through the opening of the low-potential member. Therefore, even if a barrier member is interposed between the filament and the ionization box, electrons can be injected from the filament into the ionization box.

[0012] The aforementioned blocking member is one that is attached to the low-potential member. With this configuration, the blocking member is attached to the low-potential member, which simplifies the assembly of the ion source. Furthermore, since the blocking member will be at the same potential as the low-potential member, it is easy to adjust the potential of the blocking member.

[0013] The ionization box has a potential higher than the filament's potential, and the blocking member has a potential lower than or equal to the filament's potential. In this configuration, electrons generated from the filament are more likely to be directed towards the ionization box.

[0014] The ionization box has a first surface on which an ion emission opening is formed for releasing the generated ions into the filter section, and a second surface other than the portion facing the first surface on which an electron incidence opening is formed for electrons generated from the filament to enter. The filament is provided facing the electron incidence opening, and the shielding member covers a portion of the filament from the side opposite to the ion emission opening. In this configuration, the shielding member covers a portion of the filament from the opposite side of the ion emission opening, so electrons generated from the filament are easily guided to a position close to the ion emission opening within the ionization box. Therefore, even when a shielding member is interposed between the filament and the ionization box, the sample can be ionized at a position close to the ion emission opening within the ionization box, and those ions can be guided to the filter section.

[0015] The blocking member may be such that, as viewed from the ionization box, it covers at least half of the filament. With this configuration, the blocking member can block most of the coating material, further preventing contamination of the ionization box. [Effects of the Invention]

[0016] According to the present invention, the filament can be used for a longer period of time by preventing the formation of a coating in the ionization box. [Brief explanation of the drawing]

[0017] [Figure 1] A schematic diagram showing a quadrupole mass spectrometer according to one embodiment of the present invention mounted in a chamber. [Figure 2] This figure schematically shows the configuration of the quadrupole mass spectrometer of the same embodiment. [Figure 3] This is an enlarged view of the dashed line area in Figure 2. [Figure 4] This figure shows the shielding member and other components in a top view of the same embodiment. [Figure 5] It is an enlarged view of the dashed-line portion in FIG. 2 and shows a film-forming material and the movement of electrons. [Figure 6] It is a diagram comparing the lifespan of the filament of the present invention with that of the filament of the conventional example.

Embodiments for Carrying Out the Invention

[0018] <An Embodiment of the Present Invention> Hereinafter, a quadrupole mass spectrometer according to an embodiment of the present invention will be described with reference to the drawings. Note that, for the sake of clarity, any of the figures shown below may be schematically drawn with appropriate omissions or exaggerations. For the same components, the same reference numerals are used and the description is omitted as appropriate.

[0019] <Device Configuration> The quadrupole mass spectrometer 100 of the present embodiment is, for example, attached to a chamber C or the like and analyzes a sample in the chamber C. Note that a gas such as a fluorine-based corrosive gas is introduced into the chamber C.

[0020] Specifically, as shown in FIGS. 1 and 2, the quadrupole mass spectrometer 100 includes a sensor unit 2 that detects a sample in the chamber C, and an arithmetic control unit 3 that controls the sensor unit 2 and performs analysis processing of the sample based on the output of the sensor unit 2. Hereinafter, first, the sensor unit 2 will be described, and then the arithmetic control unit 3 will be described.

[0021] As particularly shown in FIG. 2, the sensor unit 2 includes an ion source 21 that ionizes a sample, a filter unit 22 that separates the ions generated by the ion source 21 by a quadrupole, a detection unit 23 that detects the ions separated by the filter unit 22, and a casing 24 that houses the ion source 21, the filter unit 22, and the detection unit 23. Since the ion source 21 is characteristic in the present embodiment, first, the filter unit 22, the detection unit 23, and the casing 24 will be described, and then the ion source 21 will be described.

[0022] The filter unit 22 separates the ion beam emitted from the ion source 21 according to the charge-to-mass ratio (m / z) of the ions. Specifically, the filter unit 22 has two sets of cylindrical counter electrodes 22P arranged at 90° intervals. In this embodiment, the filter unit 22 has one set of two counter electrodes 22P, i.e., four counter electrodes 22P, but it may also have multiple sets of two counter electrodes 22P, i.e., five or more counter electrodes 22P.

[0023] These two pairs of opposing electrodes 22P are brought to the same potential by a voltage application unit (not shown), and an incident filter voltage, which is a voltage obtained by superimposing a DC voltage U and a high-frequency voltage V, is applied between each pair that is 90° apart. The incident filter voltage is swept so that it passes through a stable region, which is a set of pairs of DC voltage U and high-frequency voltage V that allow ions to pass through the filter unit 22 and reach the detection unit 23, thereby selectively passing ions incident on the opposing electrodes 22P according to their charge-to-mass ratio (m / z).

[0024] The detection unit 23 is, for example, a Faraday cup, which captures ions separated by the filter unit 22 and detects them as an ion current. Specifically, the detection unit 23 detects ions of specific components separated by the filter unit 22. The current value of the ion current detected by the detection unit 23 is output to the data processing unit 31, which will be described later. The detection unit 23 may also detect all ions of the sample ionized by the ion source 21.

[0025] The casing 24 houses the ion source 21, the filter unit 22, and the detection unit 23 in that order from the tip side. The casing 24 is, for example, cylindrical, but is not particularly limited as long as it has an internal space that can accommodate the ion source 21, the filter unit 22, and the detection unit 23. In the following, as shown in Figures 2 and 3, the side of the casing 24 where the ion source 21 is located is referred to as the tip side, and the side where the detection unit 23 is located is referred to as the base side. The tip wall of the casing 24 is provided with a sample inlet 24h for introducing the sample from the chamber C into the sensor unit 2 when it is attached to the chamber C. The casing 24 is airtightly attached to the mounting hole provided in the chamber C via a sealing member or the like. As a result, the pressure inside the casing 24 becomes the same as the atmospheric pressure inside the chamber C via the sample inlet 24h, and the ion source 21, the filter unit 22, and the detection unit 23 are exposed to the atmospheric pressure inside the chamber C.

[0026] The ion source 21, as shown in particular in Figures 2 and 3, comprises a filament 211 that emits electrons when a voltage is applied, an ionization box 212 into which electrons from the filament 211 are incident to ionize a sample, a low-potential member 213 whose potential is lower than that of the ionization box 212, and a blocking member 214 provided between the filament 211 and the ionization box 212.

[0027] The filament 211 is coiled, and its end is connected to a power source (not shown). When voltage is applied to the filament 211, it heats up and emits electrons. The filament 211 is made of, for example, iridium coated with yttrium oxide (Y2O3).

[0028] The ionization box 212 receives electrons generated from the filament 211, and ionizes the sample by colliding these electrons with the sample inside the box, then releases the ions. Here, the ionization box 212 is a hexagonal prism-shaped cylinder, but it is not limited to this, and may be a cylindrical shape such as a circle or other polygon, or / or a cone. The ionization box 212 is connected to a power supply (not shown) and is controlled to a higher potential than the filament 211 (e.g., 70V).

[0029] Specifically, the ionization box 212 has a first surface S1 on which an ion emission opening h1 is formed for releasing the generated ions into the filter section 22, and a second surface S2 which is a surface other than the opposing surface Sa opposite to the first surface S1, on which an electron incidence opening h2 is formed for electrons generated from the filament 211 to enter. The opposing surface Sa has an opening (not shown) for introducing the sample into the interior of the ionization box 212.

[0030] The first surface S1 is provided facing one axial end of the counter electrode 22P, as shown in particular in Figures 2 and 3. The ion emission opening h1 opens toward the counter electrode 22P and also opens from the first surface S1 toward the inner wall of the casing 24.

[0031] The second surface S2 is the surface adjacent to the first surface S1, as shown in Figures 2 and 3, and constitutes the side surface of the ionization box 212. A slit-shaped electron incidence opening h2 is formed on the second surface S2, and the electron incidence opening h2 opens toward the filament 211. Specifically, the coil-shaped filament 211 is arranged on the outside of the ionization box 212 along the second surface S2, and the filament 211 is provided opposite the electron incidence opening h2. Note that the electron incidence opening h2 is not limited to a slit shape, and the opening edge may be circular or have other polygonal shapes.

[0032] The low-potential member 213 is controlled to a lower potential than the ionization box 212. Here, the low-potential member 213 is controlled to a predetermined potential, such as 0V, via a support member 215, which will be described later, but the low-potential member 213 may also be controlled directly to a predetermined potential.

[0033] In this embodiment, the low-potential member 213 has a cylindrical shape divided in the axial direction and surrounds the filament 211. Specifically, as shown particularly in Figure 3, the low-potential member 213 has a pair of side wall portions 213a that are provided facing each other with the filament 211 in between, and a bottom wall portion 213b that covers the portion of the filament 211 opposite to the second surface S2 and is connected to one end of the side wall portion 213a. With this configuration, the portion of the filament 211 facing the second surface S2 is not covered by the low-potential member 213. Here, of the pair of side wall portions 213a, one side wall portion 213a is provided closer to the tip than the other side wall portion 213a, and the other side wall portion 213a is provided closer to the ion emission opening h1 than the other side wall portion 213a.

[0034] Furthermore, as shown in Figures 2 and 3 in particular, the low-potential member 213 has an opening facing the ionization box 212. Specifically, the low-potential member 213 is arranged along the second surface S2, and a pair of side wall portions 213a define the opening width. The opening of the low-potential member 213 is formed opposite the electron incidence opening h2.

[0035] The blocking member 214 prevents the film-forming material that forms a film on the ionization box 212 from moving toward the ionization box 212. The film-forming material referred to here is a molecule produced by the reaction of the filament 211 and the gas, which forms an insulating film on the ionization box 212. The film-forming product moves from the filament 211 toward the ionization box 212. For example, the film-forming material is yttrium fluoride (YF3) produced by the reaction of yttrium oxide, which constitutes the filament 211, with a fluorine-based corrosive gas.

[0036] As shown in Figures 2 to 4, the blocking member 214 is, for example, a flat plate and covers a part of the opening of the low-potential member 213. Specifically, the blocking member 214 forms a predetermined gap with the side wall portion 213a provided on the ion emission opening h1 side. As a result, the blocking member 214 covers the tip portion of the opening of the low-potential member 213. Note that the shape of the blocking member 214 is not limited to a flat plate; any shape that covers a part of the opening of the low-potential member 213 is acceptable. Furthermore, the blocking member 214 is provided so as to block at least one of the straight lines extending from the filament 211 to the low-potential member 213.

[0037] The blocking member 214 is provided between the filament 211 and the second surface S2, and covers a portion of the filament 211 from the side opposite to the ion emission opening h1. Specifically, by covering the tip portion of the opening of the low-potential member 213, the blocking member 214 covers the portion of the filament 211 opposite to the ion emission opening h1. In Figure 4, the blocking member 214 covers the portion of the filament 211 facing the second surface S2, but it is preferable that it covers at least half of the portion of the filament 211 facing the second surface S2. More specifically, it is sufficient that it covers at least half of the tip portion of the portion of the filament 211 facing the second surface S2.

[0038] Furthermore, the blocking member 214 is attached to the low-potential member 213. In this embodiment, as shown particularly in Figures 2 and 3, a support member 215 that supports the blocking member 214 is attached to the low-potential member 213, and the blocking member 214 is positioned between the low-potential member 213 and the second surface S2 via the support member 215. In this embodiment, the blocking member 214 and the support member 215 are an integrated unit, but they may be separate members.

[0039] Furthermore, the support member 215 is controlled to a predetermined potential, such as 0V, by a control device (not shown). Since the low-potential member 213 is attached to the support member 215, the potential of the support member 215 and the potential of the low-potential member 213 are the same. Since the interrupting member 214 is directly attached to the support member 215, the potential of the interrupting member 214 is also the same as the potential of the low-potential member 213. Note that the potential of the support member 215 only needs to be controlled to be at least below the potential of the filament 211.

[0040] The arithmetic control unit 3 includes an A / D converter, a D / A converter, a CPU, memory, a communication port, and the like. The arithmetic control unit 3 has a data processing unit 31 that performs mass analysis based on the current value of the ion current output from the detection unit 23 of the sensor unit 2, and a voltage control unit 32 that controls the voltage applied to the filament 211 based on the current caused by electrons colliding with the ionization box 212. If necessary, the data processing unit 31 can also transmit its analysis results to a general-purpose computer 200 (see Figure 1) or the like.

[0041] <Operation of the blocking member 214> Next, the operation of the blocking member 214 in this embodiment will be explained with reference to Figure 5.

[0042] Voltage control by the voltage control unit 32 applies voltage to the filament 211, causing it to heat up and emit electrons (white circles in Figure 5).

[0043] Electrons move towards the ionization box 212, which is controlled to a potential higher than that of the low-potential member 213 and the blocking member 214. Specifically, electrons enter the interior of the ionization box 212 by passing through the electron incidence opening h2 from a predetermined gap formed between the side wall portion 213a provided on the ion emission opening h1 side and the blocking member 214.

[0044] Inside the ionization box 212, electrons collide with the sample, causing it to be ionized. The ionized sample is emitted from the ion emission opening h1 to the filter section 22, where it is separated according to its mass-to-charge ratio. Electrons, however, do not move to the filter section 22 but instead collide with the inner wall of the ionization box 212.

[0045] On the other hand, for example, in a corrosive gas environment containing fluorine, the material constituting the filament 211 reacts with the corrosive gas to form a coating (black circle in Figure 5). Since the coating has no charge, it moves linearly from the filament 211 toward the second surface S2. A barrier member 214 is provided between the filament 211 and the second surface S2, so the coating collides with the barrier member 214, preventing the coating from moving into the ionization box 212.

[0046] As a result, the formation of a film on the inner wall of the ionization box 212 is prevented, and the current generated by electrons colliding with the ionization box 212 is appropriately determined according to the number of electrons in the ionization box 212. Consequently, the voltage control unit 32 can appropriately control the voltage applied to the filament 211 based on the current generated by electrons colliding with the ionization box 212.

[0047] <Comparison of this embodiment with a conventional example> Next, referring to Figure 6, a comparison will be made between the lifespan of the filament 211 in this embodiment and the lifespan of a conventional filament.

[0048] As described in this embodiment, when the blocking member 214 is provided above the filament 211, the lifespan of the filament 211 lasted for about 900 hours, as shown in Figure 6. On the other hand, when the blocking member 214 is not provided above the filament 211, as in the conventional method, the filament broke after about 40 hours, as shown in Figure 6.

[0049] <Effects of this embodiment> In the quadrupole mass spectrometer 100 of this embodiment, the blocking member 214 is provided between the filament 211 and the ionization box 212, blocking the coating material from moving toward the ionization box 212, thereby preventing the formation of a coating on the ionization box 212. As a result, for example, when controlling the voltage of the filament 211 based on the current caused by electrons colliding with the ionization box 212, the voltage of the filament 211 can be appropriately controlled, and the filament 211 can be used for a longer period than in conventional systems.

[0050] <Other Embodiments> However, the present invention is not limited to the embodiments described above.

[0051] In the above embodiment, the blocking member 214 formed a predetermined gap with the side wall portion 213a provided on the ion emission opening h1 side, but it may also form a predetermined gap with the side wall portion 213a provided on the inner wall side of the casing 24.

[0052] In the above embodiment, the blocking member 214 was attached to the low-potential member 213 via a support member 215, but is not limited to this. For example, the blocking member 214 may be directly attached to the low-potential member 213, or it may be attached to the inner wall of the casing 24, covering a portion of the opening of the low-potential member 213 from the inner wall of the casing 24.

[0053] In the above embodiment, a plurality of filaments 211 may be provided. In this case, the number of low-potential members 213 and blocking members 214 will be provided according to the number of filaments 211.

[0054] In the above embodiment, if the electron ingress aperture h2 is slit-shaped, the direction in which the slit extends may be along the direction in which the filament 211 extends, or it may be in a direction intersecting the direction in which the filament 211 extends.

[0055] In the above embodiment, the ion source 21 was provided in the quadrupole mass spectrometer 100, but the ion source 21 may also be provided in an analytical instrument that ionizes a sample with electrons, such as an ion trap mass spectrometer, a time-of-flight mass spectrometer, a double-focusing mass spectrometer, or a tandem mass spectrometer.

[0056] Furthermore, the present invention can be modified in various ways, as long as it does not contradict its spirit. [Explanation of symbols]

[0057] 100...quadrupole mass spectrometer 2. Sensor section 21 ···Ion source 211...Filament 212...Ionization box 213... Low-potential components 214... Barrier 22...Filter section 23 ···Detection unit 3. Calculation Control Unit 31 ···Data Processing Unit 32...Voltage Control Unit S1...First side of the ionization box S2...Second side of the ionization box h1 ···Ion emission opening h2...electron incidence aperture

Claims

1. An ion source for ionizing the sample, A filter section that separates ions generated in the ion source using a quadrupole, The system includes a detection unit for detecting ions separated by the filter unit, The aforementioned ion source is A filament that emits electrons when voltage is applied, An ionization box into which the electrons are incident and which ionizes the sample, A quadrupole mass spectrometer comprising a blocking member provided between the filament and the ionization box, which blocks the coating material that forms a coating on the ionization box from moving from the filament toward the ionization box.

2. The quadrupole mass spectrometer according to claim 1, further comprising a voltage control unit that controls the voltage applied to the filament based on the current generated by electrons colliding with the ionization box.

3. The system further comprises a low-potential member that has an opening facing the ionization box, surrounds the filament, and has a potential lower than the potential of the ionization box, The quadrupole mass spectrometer according to claim 1 or 2, wherein the blocking member covers a portion of the opening of the low-potential member.

4. The quadrupole mass spectrometer according to claim 3, wherein the blocking member is attached to the low-potential member.

5. The potential of the ionization box is higher than the potential of the filament. The quadrupole mass spectrometer according to any one of claims 1 to 4, wherein the potential of the blocking member is less than or equal to the potential of the filament.

6. The aforementioned ionization box is A first surface having an ion emission opening formed therein for releasing the generated ions into the filter section, It has a second surface, which is a portion other than the portion facing the first surface, and in which an electron injection opening is formed into which electrons generated from the filament are incident, The filament is provided opposite the electron ingress aperture, The quadrupole mass spectrometer according to any one of claims 1 to 5, wherein the blocking member covers a portion of the filament from the side opposite to the ion emission opening.

7. The quadrupole mass spectrometer according to any one of claims 1 to 6, wherein the blocking member covers at least half of the filament as seen from the ionization box.

Images