Mass spectrometer

Abstract

Four rod electrodes (50a to 50d) for separating ions according to a mass-to-charge ratio are held by a rod holder (51). The rod holder (51) is placed on a metal holder sustaining stand (52) provided on a bottom surface of a vacuum housing (1), and is fixed while being pressed by a fixation band (53) fixed to the holder sustaining stand (52) with screws (56). The fixation band (53) has a coating film layer (532) formed by a black nickel plating process on the entire surface of a main member (531) made from phosphor bronze. The coating film layer (532) has high emissivity, and thus heat transferred from the rod holder (51) to the fixation band (53) is efficiently radiated into the vacuum housing (1). Therefore, heat generated in the rod holder (51) due to dielectric loss is efficiently dissipated, and deformation of the rod holder can be reduced.

Claims

1. A mass spectrometer including an ion optical element including a plurality of rod electrodes arranged around a linear axis, the ion optical element being configured to separate ions derived from a sample component introduced into a space surrounded by the plurality of rod electrodes according to a mass-to-charge ratio using an electric field formed by a voltage including a radio frequency voltage applied to the rod electrodes, the mass spectrometer comprising: a) a boundary member configured to define a region in which the ion optical element is arranged; b) a rod holder made from an insulating material and configured to hold the plurality of rod electrodes; and c) a fixation member configured to fix the rod holder to the boundary member, wherein at least part of a portion of the fixation member, the portion facing the region defined by the boundary member, is subjected to an emissivity improvement processing, the emissivity improvement processing is a surface treatment on a surface of a material from which the fixation member is made.

2. The mass spectrometer according to claim 1, wherein the fixation member includes a holder sustaining stand that is fixed to the boundary member and on which the rod holder is placed and a holder pressing member attached to the fixation member so that the rod holder is sandwiched between the holder pressing member and the holder sustaining stand, and part of at least one of the holder sustaining stand or holder pressing member is subjected to the emissivity improvement processing.

3. A mass spectrometer including an ion optical element including a plurality of rod electrodes arranged around a linear axis and configured to separate ions derived from a sample component introduced into a space surrounded by the plurality of rod electrodes according to a mass-to-charge ratio by an action of an electric field formed by a voltage including a radio frequency voltage to be applied to the rod electrodes, the mass spectrometer comprising: a) a boundary member configured to define a region in which the ion optical element is arranged; b) a rod holder made from an insulating material and configured to hold the plurality of rod electrodes; c) a fixation member configured to fix the rod holder to the boundary member; and d) a connecting member made from a conductive material and disposed to be in contact with, among the plurality of rod electrodes, each of a plurality of rod electrodes to which a same voltage is applied so as to electrically connect the plurality of rod electrodes to which the same voltage is applied, wherein at least part of a portion of the connecting member, the portion facing the region defined by the boundary member, is subjected to an emissivity improvement processing, the emissivity improvement processing is a surface treatment on a surface of a material from which the connecting member is made.

4. The mass spectrometer according to claim 1, wherein the surface treatment is a coating film forming processing of forming a thin coating film on the surface of the material from which the fixation member is made.

5. The mass spectrometer according to claim 1, wherein the surface treatment is a processing of roughening the surface of the material from which the fixation member is made by chemically or physically shaving the surface.

6. The mass spectrometer according to claim 4, wherein the at least part of the fixation member is made from aluminum, and the surface treatment is an anodizing processing.

7. The mass spectrometer according to claim 6, wherein the anodizing processing is a black anodizing processing.

8. The mass spectrometer according to claim 4, wherein the surface treatment is a nickel plating processing.

9. The mass spectrometer according to claim 8, wherein the nickel plating processing is a black nickel plating processing.

10. The mass spectrometer according to claim 4, wherein the surface treatment is a carbon coating film forming processing.

11. The mass spectrometer according to claim 4, wherein the surface treatment is a ceramic spraying processing.

12. The mass spectrometer according to claim 1, wherein the surface treatment is a processing of attaching a thin plate or a thin foil made from another material to a surface.

13. The mass spectrometer according to claim 1, wherein the ion optical element is a quadrupole mass filter.

14. The mass spectrometer according to claim 1, wherein the ion optical element is a linear ion trap.

15. The mass spectrometer according to claim 3, wherein the surface treatment is a processing of attaching a thin plate or a thin foil made from another material to a surface of the connecting member.

16. The mass spectrometer according to claim 3, wherein the ion optical element is a quadrupole mass filter.

17. The mass spectrometer according to claim 3, wherein the ion optical element is a linear ion trap.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 illustrates a configuration of a main part of a quadrupole mass spectrometer according to an embodiment of the present invention.

(2) FIG. 2 is a plan view of a quadrupole mass filter unit in the quadrupole mass spectrometer of this embodiment, which is viewed from an ion entering side.

(3) FIG. 3 is an exploded view of the quadrupole mass filter unit illustrated in FIG. 2.

(4) FIG. 4 is a schematic diagram illustrating short springs that connect rod electrodes in a quadrupole mass filter unit.

(5) FIG. 5 illustrates a configuration of a main part of a quadrupole mass spectrometer according to another embodiment of the present invention.

(6) FIG. 6 is an exploded view of another example of a quadrupole mass filter unit.

(7) FIG. 7 is a plan view illustrating a state in which rod electrodes are held by a rod holder in a general quadrupole mass spectrometer.

(8) FIG. 8 is a cross-sectional view taken along the line A-AA of FIG. 7.

DESCRIPTION OF EMBODIMENTS

(9) An embodiment of a mass spectrometer according to the present invention will be described with reference to the accompanying drawings.

(10) FIG. 1 illustrates a schematic configuration of the mass spectrometer of this embodiment. This mass spectrometer is a single quadrupole mass spectrometer that analyzes components in a sample gas.

(11) As illustrated in FIG. 1, a vacuum housing 1 evacuated by a vacuum pump (not illustrated) is provided with an ion source 2 that performs ionization by an electron ionization method, a chemical ionization method, or the like, and ions derived from a sample component, which are generated in the ion source 2, are introduced into the vacuum housing 1. In the vacuum housing 1, an ion guide 3 that transports ions while converging the ions, a quadrupole mass filter unit 5 including four rod electrodes 50a to 50d (Only two of the four rod electrodes are illustrated in FIG. 1.) arranged around a central axis C that is also an ion optical axis, an ion detector 7 that detects ions, an inlet lens 4 that also serves as a partition separating the ion guide 3 from the quadrupole mass filter unit 5 and has an opening 4a through which ions pass, and an outlet lens 6 that also serves as a partition separating the quadrupole mass filter unit 5 from the ion detector 7 and has an opening 6a through which ions pass are arranged. That is, in this embodiment, part of the vacuum housing 1, the inlet lens 4, and the outlet lens 6 correspond to a boundary member in the present invention, and the quadrupole mass filter unit 5 is arranged in an internal region 20 defined by the boundary member. For convenience of explanation, the ion optical axis is defined as a direction of a Z axis, and X and Y axes orthogonal to the Z axis are defined as illustrated in FIG. 1.

(12) The vacuum housing 1 is made from a conductive material, and aluminum, which is relatively inexpensive, is used herein. The inlet lens 4 and the outlet lens 6 are also made from a conductive material, and aluminum is used herein, as in the case of the vacuum housing 1. However, materials of those members are not limited thereto, and, for example, stainless steel may be used.

(13) FIG. 2 is a plan view of the quadrupole mass filter unit 5 in FIG. 1, which is viewed from an ion entering side (left side in FIG. 1). FIG. 3 is an exploded view of the quadrupole mass filter unit 5 illustrated in FIG. 2. FIG. 4 is a schematic diagram illustrating short springs that connect the rod electrodes 50a to 50d in the quadrupole mass filter unit 5.

(14) Each of the four rod electrodes 50a to 50d having a substantially cylindrical outer shape is fixed to a substantially annular rod holder 51 having a predetermined thickness with screws (not illustrated) while being fitted into a groove inside the rod holder 51. The rod holder 51 is provided on each of the front and rear end sides of the rod electrodes 50a to 50d. With this, a relative positional relationship among the four rod electrodes 50a to 50d is determined. Each of the two rod holders 51 is placed on a substantially semicircular concave portion 52a of a holder sustaining stand 52 attached on a bottom surface of the vacuum housing 1. That is, substantially a lower half of the rod holder 51 is housed in the concave portion 52a of the holder sustaining stand 52. Substantially an upper half of the rod holder 51 is fixed downward, i.e., is fixed to be pressed against the concave portion 52a of the holder sustaining stand 52 by a fixation band 53 fixed to the holder sustaining stand 52 with two screws 56. With this, absolute positions of the four rod electrodes 50a to 50d are determined.

(15) In the quadrupole mass filter, the same voltage is applied to two rod electrodes facing each other across the central axis C, and different voltages are applied to two rod electrodes adjacent to each other around the central axis C. Therefore, in the apparatus of this embodiment, as illustrated in FIG. 4, a pair of the rod electrodes 50a and 50c and a pair of the rod electrodes 50b and 50d facing each other across the central axis C are electrically connected by two respective short springs 54a and 54b corresponding to a connecting member in the present invention. The short springs 54a and 54b adhere to each of the rod electrodes 50a to 50d by elastic force. A voltage U+V cos ωt, which is obtained by superposing a DC voltage U on a radio frequency voltage V cos ωt, is applied to one short spring 54a from a voltage source (not illustrated), and a voltage −(U+V cos ωt), which is obtained by superposing a DC voltage −U having an inverted polarity on a radio frequency voltage −V cos ωt having an inverted phase, is applied to the other short spring 54b.

(16) The four rod electrodes 50a to 50d are made from a conductor, and, for example, stainless steel or molybdenum is used. The rod holder 51 is made from an insulator, and appropriate ceramic is used. The holder sustaining stand 52 is made from the same material as that of the vacuum housing 1, and is made from, for example, aluminum. The other members will be described later.

(17) Basic analysis operation in the mass spectrometer of this embodiment will be briefly described.

(18) The ion source 2 ionizes components in a sample gas introduced from the outside. The generated ions are extracted from the ion source 2, are introduced into the vacuum housing 1, are converged by the ion guide 3, and are introduced into a separated space extending in the Z-axis direction and surrounded by the four rod electrodes 50a to 50d through the opening 4a of the inlet lens 4. A voltage, which is obtained by superposing a DC voltage on a radio frequency voltage according to a mass-to-charge ratio of target ions to be measured, is applied to the four rod electrodes 50a to 50d through the short springs 54a and 54b as described above. A quadrupole electric field formed by the voltage allows only the target ions to pass through the separated space while causing the target ions to stably oscillate. Meanwhile, other ions diverge in the middle. The target ions selected according to the mass-to-charge ratio in this way pass through the separated space and arrive at the ion detector 7 through the opening 6a of the outlet lens 6. The ion detector 7 outputs a detection signal having a signal strength corresponding to an amount of the arrived ions.

(19) During the above analysis, a radio frequency voltage ±V cos ωt having a relatively large amplitude is applied to the four rod electrodes 50a to 50d. With this, a strong radio-frequency electric field is formed in the separated space. Therefore, the rod holder 51 itself generates heat due to dielectric loss of the material of the rod holder 51, and thermal expansion of the rod holder causes a change in a relative positional relationship between the four rod electrodes 50a to 50. Further, in some cases, the heat of the rod holder 51 is transmitted to the rod electrodes 50a to 50d, and the rod electrodes 50a to 50d themselves are deformed due to thermal expansion, and thus distances between the rod electrodes 50a to 50d are changed. If the relative positional relationship or the distances between the rod electrodes 50a to 50 change, characteristics of the quadrupole mass filter, i.e., mass resolution and mass accuracy may be deteriorated. In view of this, various measures are taken in the mass spectrometer of this embodiment in order to reduce a change in the relative positional relationship between the rod electrodes 50a to 50d and deformation of the rod electrodes caused by the heat generation of the rod holder 51. This point will be described in detail.

(20) In order to reduce the heat generation of the rod holder 51, it is only necessary to increase the heat releasing property of the rod holder 51. Herein, there are the following five heat releasing paths:

(21) (1) conduction of the heat from the rod holder 51 to the holder sustaining stand 52, and then to the vacuum housing 1, and release of the heat from the vacuum housing 1 to the outside;

(22) (2) conduction of the heat from the rod holder 51, to the fixation band 53, to the holder sustaining stand 52, and then to the vacuum housing 1, and release of the heat from the vacuum housing 1 to the outside;

(23) (3) conduction of the heat from the rod holder 51 to the fixation band 53, radiation of the heat from the fixation band into the vacuum in the vacuum housing 1, and release of the heat from the vacuum housing 1 to the outside;

(24) (4) conduction of the heat from the rod holder 51 to the rod electrodes 50a to 50d and the short springs 54a and 54b, radiation of the heat from the rod electrodes 50a to 50d and the short springs 54a and 54b into the vacuum in the vacuum housing 1, and release of the heat from the vacuum housing 1 to the outside; and
(5) radiation of the heat from the rod holder 51 into the vacuum in the vacuum housing 1, and release of the heat from the vacuum housing 1 to the outside.

(25) Each of the heat releasing paths (3), (4), and (5) includes radiation of the heat into the vacuum in the vacuum housing 1. Therefore, the heat releasing property in the heat releasing paths (3), (4), and (5) can be increased by increasing efficiency of this heat radiation. One of major factors that deteriorate the efficiency of the heat radiation is that heat is trapped in the internal region 20 in which the quadrupole mass filter unit 5 is arranged. In view of this, in the apparatus of this embodiment, in order to increase the efficiency of this heat radiation, inner wall surfaces of the vacuum housing 1 defining the internal region 20 and surfaces of the inlet lens 4 and the outlet lens 6 facing the quadrupole mass filter unit 5 are subjected to a surface treatment processing to increase emissivity. Herein, the inner wall surfaces of the vacuum housing 1 defining the internal region 20 are a bottom surface, a top surface, and side surfaces (in FIG. 1, a surface behind the quadrupole mass filter unit 5 and a surface in front of the quadrupole mass filter unit 5 (not illustrated)).

(26) In the apparatus of this embodiment, as the surface treatment processing, a coating film layer 10 formed by a black nickel plating process is formed on the inner wall surfaces of the vacuum housing 1 and part of the surfaces of the inlet lens 4 and the outlet lens 6. As is well known, black nickel plating is one of commonly used plating for the purpose of antireflection and decoration, and a processing cost is relatively low. When the coating film layer 10 is formed by black nickel plating, the surfaces become black. This improves the emissivity as compared with a case where the surfaces are aluminum surfaces. High emissivity means high heat absorption. With this, the heat radiated from the rod electrodes 50a to 50d, the fixation band 53, and the like into the vacuum is efficiently absorbed by the inner wall surfaces of the vacuum housing 1, the inlet lens 4, and the outlet lens 6. Thus, the heat is less likely to be trapped in the vicinity of the quadrupole mass filter unit 5. As a result, the heat releasing property in the heat releasing paths (3), (4), and (5) can be increased as compared with conventional ones.

(27) Note that the surface treatment processing for increasing the emissivity is not limited to black nickel plating. For example, in a case where the vacuum housing 1 is made from aluminum as described above, normal nickel plating may be used instead of black nickel plating, or a coating film layer may be formed by an anodizing process (preferably, a black anodizing process). Alternatively, a coating film layer capable of improving the emissivity may be formed on the surfaces by a carbon coating film forming process, a ceramic spraying process, other plating processes, a painting or coating process, a thermal spraying process, or the like. Further, instead of forming a coating film layer made from a material different from the material of the vacuum housing 1, the inlet lens 4, and the outlet lens 6, the surfaces of those members themselves may be chemically or physically shaved to form unevenness. Further, instead of forming a coating film layer by various processes, a thin plate or thin foil made from another material having higher emissivity than that of the vacuum housing 1, the inlet lens 4, and the outlet lens 6 may be attached to the inner wall surfaces of the vacuum housing 1, the inlet lens 4, and the outlet lens 6, or a black body tape may be attached to the inner wall surfaces of the vacuum housing 1, the inlet lens 4, and the outlet lens 6. Those are also surface treatment processings in a broad sense.

(28) As a matter of course, the above surface treatment processings for increasing the emissivity may be performed not on all of the inner wall surfaces of the vacuum housing 1, the inlet lens 4, and the outlet lens 6, but only on part of the inner wall surfaces of the vacuum housing 1, the inlet lens 4, and the outlet lens 6. Further, different kinds of surface treatment processings may be combined. Note that, as a matter of course, both the inlet lens 4 and the outlet lens 6 form an electric field for converging ions. Thus, the surface treatment processing needs to be made so as not to hinder such formation of the electric field.

(29) As can be seen by comparing the above heat releasing paths (1) and (2), the heat is conducted from the rod holder 51 to the holder sustaining stand 52 through the fixation band 53 in (2), and thus heat releasing efficiency is lower in (2) than in (1). Therefore, a temperature of an upper part of the rod holder 51 tends to be higher than that of a lower part of the rod holder. In order to improve the heat releasing efficiency in the heat releasing path (2), it is necessary to improve thermal conductivity of the fixation band 53 itself. Stainless steel is generally used as a material of the fixation band 53, but stainless steel has relatively low thermal conductivity. Therefore, in the apparatus of this embodiment, phosphor bronze, which has higher thermal conductivity than that of stainless steel and is relatively inexpensive, is used as the material of the fixation band 53.

(30) As described above, the fixation band 53 fixes the rod holder 51 so as to press the rod holder 51 against the holder sustaining stand 52, and thus requires an appropriate spring property. If the fixation band 53 has a low spring property, the fixation band 53 is hindered from expanding outward when the rod holder 51 thermally expands. Thus, deformation caused by the heat concentrates on the inside, i.e., on a part holding the rod electrodes 50a to 50d. This increases displacement of the relative positions of the rod electrodes 50a to 50d. Meanwhile, in a case where the fixation band 53 has an appropriate spring property, the fixation band 53 stretches and the rod holder 51 expands outward when the rod holder 51 thermally expands. Thus, the displacement of the relative positions of the rod electrodes 50a to 50d can be small. However, if the fixation band 53 has an extremely high spring property, fixation of the rod holder 51 becomes unstable. Thus, the absolute positions of the rod electrodes 50a to 50d may be displaced due to vibration or the like.

(31) Phosphor bronze has a smaller modulus of longitudinal elasticity than that of stainless steel. Thus, a thickness of the fixation band 53 is increased to obtain the same degree of spring property as that of a stainless fixation band. When the thickness of the fixation band 53 is increased as described above, the thermal conductivity is increased as compared with a case of a thin fixation band. That is, the material itself has high thermal conductivity, and, in addition, a large thickness can further improve the thermal conductivity. This makes it possible to increase the heat radi releasing ation property in the above heat releasing path (2) as compared with conventional ones.

(32) Note that, because phosphor bronze is more likely to rust than stainless steel, a surface of phosphor bronze is subjected to a gold plating processing to prevent rust. As a matter of course, other rustproofing surface treatments may be made.

(33) Further, the short springs 54a and 54b, as well as the fixation band 53, are made from phosphor bronze, and surfaces of the short springs are plated with gold. In a case where the temperature of the upper part of the rod holder 51 is higher than that of the lower part as described above, temperatures of the upper rod electrodes 50a and 50d are higher than those of the lower rod electrodes 50b and 50c due to heat transfer from the rod holder 51. When the short springs 54a and 54b are made from phosphor bronze having higher thermal conductivity than that of stainless steel, the heat of the upper rod electrodes 50a and 50d is easily transmitted to the lower rod electrodes 50b and 50c through the short springs 54a and 54b. Thus, it is possible to reduce a difference in temperature between the upper rod electrodes 50a and 50d and the lower rod electrodes 50b and 50c. This makes it possible to suppress uneven deformation of the rod electrodes 50a to 50d caused by thermal expansion of the rod electrodes themselves.

(34) Further, as described above, the fixation band 53 and the short springs 54a and 54b are made from phosphor bronze that has been subjected to a gold plating surface treatment. In addition, a coating film layer is further formed on a surface of gold-plated phosphor bronze by a surface treatment process for increasing the emissivity which is similar to that of the above coating film layer 10. That is, as illustrated in FIG. 2, the fixation band 53 has a coating film layer 532 formed by a black nickel plating process on the entire surface of a main member 531 made from phosphor bronze that has been subjected to a gold plating surface treatment. Although not illustrated, the same applies to the short springs 54a and 54b.

(35) By providing the coating film layer 532 on the surfaces of the fixation band 53 and the short springs 54a and 54b as described above, the efficiency of the heat radiation from the fixation band 53 and the short springs 54a and 54b into the surrounding space is increased. That is, the heat is not only easily transmitted to the fixation band 53 and the short springs 54a and 54b, but also highly dissipated in the middle of a path of the heat transfer. This makes it possible to further increase the heat releasing property in the heat releasing paths (3) and (4).

(36) The coating film layer 532 formed on the surfaces of the fixation band 53 and the short springs 54a and 54b is not limited to a coating film layer formed by a black nickel plating process, and may be formed by various other methods similar to those of the coating film layer 10.

(37) Further, in the apparatus of this embodiment, when the fixation band 53 is fixed to the holder sustaining stand 52 while the rod holder 51 is being sandwiched between the fixation band 53 and the holder sustaining stand 52, a heat releasing layer 55 is formed between the fixation band 53 and the rod holder 51 and the holder sustaining stand 52. In the apparatus of this embodiment, a coating film layer of an appropriate thickness made from heat dissipation silicone (e.g., a silicone rubber sheet or a silicone tape) is used as the heat releasing layer 55. However, the heat releasing layer is not limited to this, and a coating layer of heat dissipation grease or the like may be used. In a case where the fixation band 53 and the rod holder 51 or the holder sustaining stand 52 are brought into direct contact with each other, a contact surface between the both has a gap at an extremely fine level, and the gap serves as a kind of thermal resistance. Meanwhile, the heat releasing layer 55 provided between the fixation band 53 and the rod holder 51 or the holder sustaining stand 52 fills the gap of such an extremely fine level. This increases the heat transfer property. Further, the heat dissipation silicone and the heat dissipation grease themselves contain components and particles having high thermal conductivity. This makes it possible to increase the heat transfer property from the rod holder 51 to the fixation band 53 and the heat transfer property from the fixation band 53 to the holder sustaining stand 52. Thus, it is possible to further increase the heat releasing property in the above heat releasing paths (2) and (3).

(38) As described above, the apparatus of this embodiment can reduce a rise in temperature of the rod holder 51 and the rod electrodes 50a to 50d by devising structural measures for increasing the heat releasing property in the above heat releasing paths (1) to (5). As a matter of course, even in a case where not all the above structural measures but only some measures are adopted, the rise in temperature of the rod holder 51 and the rod electrodes 50a to 50d can be reduced as compared with conventional apparatuses.

(39) Note that, in the mass spectrometer of the above embodiment, the quadrupole mass filter unit 5 is directly arranged inside the vacuum housing 1. However, as in the apparatus disclosed in Patent Literature 3, the quadrupole mass filter unit 5 may be arranged in the vacuum housing 1 while being attached in a cylindrical container. FIG. 5 illustrates a configuration of a main part of a quadrupole mass spectrometer having such a configuration. In this configuration, the internal region 20 is provided in a container 57 having an inlet opening 57a and an outlet opening 57b, and the quadrupole mass filter unit 5 is arranged in the internal region 20. In this case, the container 57 corresponds to the boundary member in the present invention. In this configuration, the coating film layer 10 may be formed by a black nickel plating process on inner wall surfaces of the container 57 defining the internal region 20, or other surface treatment processes for increasing the emissivity described above may be performed on the inner wall surfaces. This makes it possible to increase the heat releasing efficiency of a heat releasing path to the vacuum housing 1 through the container 57.

(40) In the above embodiment, the rod holder 51 is fixed to the holder sustaining stand 52 by the thin-plate like fixation band 53. However, various fixation members for fixing the rod holder 51 to the holder sustaining stand 52 can be adopted. For example, as illustrated in FIG. 6, a fixation block 58 having a concave portion 58a similar to the concave portion 52a of the holder sustaining stand 52 may be fixed to the holder sustaining stand 52 with screws 59. Also in this case, the fixation block 58 is made from phosphor bronze, and a gold-plated thin film layer is formed on a surface of phosphor bronze as a rustproofing processing. Then, a coating film layer is preferably further formed on the gold-plated thin film layer by a black nickel plating process. As described above, a band-shaped fixation member having an appropriate spring property to fix the rod holder 51 to the holder sustaining stand 52 is preferable to block-shaped one. However, even in a case where the fixation block 58 is adopted, the heat releasing property in the heat releasing paths (3) and (4) can be increased by making a surface treatment processing for increasing the emissivity on a surface of the fixation block 58.

(41) The above embodiment is an example in which the present invention is applied to a single quadrupole mass spectrometer. However, it is apparent that the present invention is applicable to other mass spectrometers including a quadrupole mass filter, specifically, a triple quadrupole mass spectrometer and a quadrupole-time-of-flight mass spectrometer.

(42) Further, the present invention is also applicable to a mass spectrometer including a linear ion trap having a rod electrode structure similar to that of a quadrupole mass filter, instead of a quadrupole mass filter, and having a function of separating ions according to a mass-to-charge ratio. Such a linear ion trap traps ions once in a trapping space surrounded by four rod electrodes, and then applies a radio frequency voltage corresponding to a mass-to-charge ratio of target ions to the four rod electrodes, thereby exciting some of the trapped ions and releasing the ions from the trapping space to the outside. Therefore, if a rod holder that holds the rod electrodes generates heat due to dielectric loss and a relative positional relationship between the rod electrodes changes, the mass-to-charge ratio of the ions released from the trapping space differs, or a range of the mass-to-charge ratio changes. When the present invention is applied to such a mass spectrometer, it is possible to reduce a change in the relative positional relationship among the rod electrodes and increase mass accuracy and mass resolution of the ions released from the trapping space.

(43) Further, the above embodiment and modification examples are merely examples of the present invention, and thus it is apparent that further appropriate modifications, additions, and adjustments within the spirit of the present invention are also included in the scope of the claims of the present application.

REFERENCE SIGNS LIST

(44) 1 . . . Vacuum Housing 2 . . . Ion Source 3 . . . Ion Guide 4 . . . Inlet Lens 4a . . . Opening 5 . . . Quadrupole Mass Filter Unit 50a to 50d . . . Rod Electrode 51 . . . Rod Holder 52 . . . Holder Sustaining Stand 52a . . . Concave Portion 53 . . . Fixation Band 531 . . . Main Member 532 . . . Coating Film Layer 54a, 54b . . . Short Spring 55 . . . Heat Releasing Layer 56, 59 . . . Screw 57 . . . Container 57a . . . Inlet Opening 57b . . . Outlet Opening 58 . . . Fixation Block 58a . . . Concave Portion 6 . . . Outlet Lens 6a . . . Opening 7 . . . Ion Detector 10 . . . Coating Film Layer C . . . Central Axis (Ion Optical Axis)