Multi-pole rod assembly and method for manufacturing rod support therefor

Abstract

A method for manufacturing a multipole assembly of a mass spectrometer, the method comprising: processing a body to form an opening extending through the body along a predetermined axis, where the opening has contours defining a pair of opposing seats, each seat configured to guide a rod of the multipole assembly; cutting the body into a plurality of pieces to form a plurality of identical rod supports; a first pair of rods is disposed in the seats of the first pair of rod supports, and a second pair of rods is disposed in the seats of the second pair of rod supports, where the second pair of rod supports is rotated relative to the first pair of rod supports.

Description

Technical Field

[0001] The present disclosure relates generally to the field of linear multipole rod assemblies for use in mass spectrometers, and more particularly to methods of making rod supports for use in such rod assemblies, and to the multipole rod assemblies themselves. Background Art

[0002] Mass spectrometers including multipole rod assemblies are well known in the art.Multipole rod assemblies are operated to control the motion of ions and include a plurality of round rods (i.e., rod-shaped electrodes), which are arranged in parallel and spaced equidistantly from the central axis.Rods are arranged in relative pairs.For example, four, six or eight rods can be provided.Radio frequency (RF) and direct current (DC) voltages are applied to the rods, wherein the relative rods carry the same voltage.An oscillating electric field is used to selectively stabilize or shake the ions.Each relative rod pair is electrically connected, and an RF alternating voltage is applied between the rods.Then a DC voltage is superimposed on the RF voltage, which causes the ions to adopt an oscillating trajectory when the ions travel between the rods.Ions with only a selected m / z (mass divided by charge) value can achieve a stable trajectory, which allows them to reach the next level of a mass spectrometer, such as a detector.

[0003] It is critical that the distance between opposing pairs of rods is as uniform as possible along the entire axial length of the rods. Errors in the parallelism of the rods along the length of the multipole affect the performance of the device. Rod supports are typically provided for appropriately supporting the rods, with two or more of the support members being axially spaced from each other along the rods.

[0004] The high voltage difference between the poles of opposite phases requires the use of suitable insulators. This limits the potential materials that can be used for the pole supports.

[0005] Many additional features are required to provide connections to each pair of rods, which increases build time and introduces the opportunity for trapped volumes. In addition, shielding rods or the like may need to be provided to prevent charge from accumulating on the rod support assembly.

[0006] The combination of the above problems makes multipole assemblies difficult to manufacture consistently, causing them to be expensive, susceptible to poor yields, and provide large variations in performance between multipole assemblies.

[0007] The present invention is proposed to provide an improved rod support for a multipole rod assembly which is able to ensure high precision while also providing simplified manufacturing. Summary of the invention

[0008] According to a first aspect, a method for manufacturing a multipole assembly of a mass spectrometer is provided, the method comprising: machining a body to form an opening extending through the body along a predetermined axis, wherein the opening has a profile defining two or more seats, each seat being configured to guide a rod of the multipole assembly; and cutting the body into a plurality of pieces to form a plurality of identical rod supports; placing a first plurality of rods in seats of a first pair of rod supports, and placing a second plurality of rods in seats of a second pair of rod supports, wherein the second pair of rod supports are rotated relative to the first pair of rod supports.

[0009] According to a second aspect, a multipole assembly of a mass spectrometer is provided, which includes a plurality of identical rod supports and a plurality of rods supported thereby, wherein each of the rod supports includes an opening extending through the body along a predetermined axis, wherein the opening has a profile defining two or more seats, wherein a first plurality of rods are seated in seats of a first pair of rod supports, the first pair of rod supports being spaced apart from each other in a length direction of the rods, wherein a second plurality of rods are seated in seats of a second pair of rod supports, the second pair of rod supports being spaced apart from each other in a length direction of the rods, and wherein the second pair of rod supports are rotated relative to the first pair of rod supports.

[0010] According to a third aspect, a multipole assembly of a mass spectrometer is provided, the multipole assembly comprising a plurality of rod supports and a plurality of rods supported thereby, wherein each of the rod supports comprises an opening extending through a body along a predetermined axis, the opening having a profile defining two or more seats, wherein each of the rods is seated in some but not all of the seats of the plurality of rod supports, and wherein each of the rods has a field nulling element fixed thereto at each point along its length where the rod passes through an opening in one of the rod supports without being seated in one of its seats.

[0011] The multipole assembly is preferably a quadrupole, wherein each of the supports comprises a pair of opposing seats, and the second pair of rod supports is rotated 90 degrees relative to the first pair of rod supports.

[0012] Features of the above aspects may be combined in any combination.

[0013] The rod supports are preferably metal.

[0014] The field nulling element is preferably metal.

[0015] The field nulling element preferably has substantially the same thickness as the support in the axial direction of the rod and is aligned with the support in the axial direction.

[0016] A constant gap may be provided between the outer surface of each field-nulling element and the inner surface of the opening. The outer surface of each field-nulling element may be configured to match the contour of the opening.

[0017] Furthermore, preferred features are presented in the dependent claims.

[0018] These and other aspects and features of the present disclosure will be more readily understood when read in conjunction with the accompanying drawings.Furthermore, it must be noted that the various features of any of the above statements may be combined without limitation, as will be readily appreciated by those skilled in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a perspective view of a machined body for forming four identical rod supports;

[0020] Figure 2 By cutting Figure 1 A perspective view of a rod support formed by a body of the present invention;

[0021] Figure 3 yes Figure 2 A plan view of a rod support;

[0022] Figure 4 Is included by cutting Figure 1 A perspective view of a quadrupole assembly having four identical rod supports formed by a body of the quadrupole rod assembly;

[0023] Figure 5 Is from Figure 4 a perspective view of a field nulling element of a rod assembly; and

[0024] Figure 6 yes Figure 4 End view of the rod assembly. DETAILED DESCRIPTION

[0025] It should be appreciated that while much of the discussion herein will focus on a quadrupole arrangement, the invention is not limited thereto. For example, different aspects of the invention may be applied, alone or in combination, to a multipole rod assembly comprising six or eight rods, a rod support therefor, and / or its manufacture.

[0026] refer to Figure 4 , a multipole rod assembly 1 for a mass spectrometer is shown. The rod assembly comprises a plurality of rod supports 2 spaced apart from one another along the length of a rod 3 supported thereby. Each of the rod supports 2 comprises an opening 4 through the body of the rod support 2. The opening 4 has a profile defining a pair of opposing seats 5.

[0027] According to one aspect, the rod supports 2 are identical to each other. A first pair of rods 3a, 3b is seated in seats 5 of the first pair of rod supports 2a, 2b. A second pair of rods 3c, 3d is seated in seats of the second pair of rod supports 2c, 2d. The second pair of rod supports 2c, 2d is rotated relative to the first pair of rod supports 2a, 2b.

[0028] In the present quadrupole arrangement, the second pair of rod supports 2c, 2d is rotated 90 degrees relative to the first pair of rod supports 2a, 2b.

[0029] In an alternative arrangement comprising more rods, there may be additional pairs of rod supports arranged at intermediate rotation angles relative to the first and second pairs of rod supports. Furthermore, it is possible that no rod supports are rotated 90 degrees relative to each other.

[0030] In further arrangements involving more rods, each rod support may be provided with an additional seat, regardless of whether four or more rod supports are provided.

[0031] For example, for a hexapolar arrangement, each rod support may be provided with three seats, with two pairs of rod supports provided, and with appropriate angular rotation between pairs of rod supports, which angular rotation will not be 90 degrees. Alternatively, for a hexapolar arrangement, each rod support may have two seats, but with three pairs of rod supports provided, with appropriate angular rotation between each pair of pairs of rod supports.

[0032] Those skilled in the art will readily appreciate various alternatives suitable for any desired number of rods.The invention is not limited to any particular number of rods.

[0033] According to another aspect, each rod 3 is seated in some but not all of the seats 5 of the plurality of rod supports 2, and each of the rods 3 has a field zeroing element 6 fixed to it at each point along its length where the rod 3 passes through an opening 4 in one of the rod supports 2 without being seated in one of its seats 5.

[0034] Obviously, in Figure 4 In an arrangement of, the two aspects described are combined. In alternative arrangements, this need not be the case, for example, the zeroing element 6 may be provided in a rod assembly comprising rod supports 2 that are not identical to one another. A person skilled in the art will readily appreciate many alternative arrangements.

[0035] The rod support 2 is preferably referred to below Figures 1 to 3 The methods discussed are for manufacture, however, it will be appreciated that they may be produced in other ways.

[0036] Figure 1 A machining body 7 for forming a plurality of identical rod supports 2 is shown. Figure 2 and Figure 3 Shown by cutting Figure 1 The rod support 2 is formed by machining a body 7 of a multipole assembly. The method for manufacturing a rod support for a multipole assembly for a mass spectrometer includes machining the body 7 to form an opening 4 extending through the body along a predetermined axis. The opening 4 has a profile defining a pair of opposing seats 5. Each of the seats 5 is configured to guide a rod 3 of the multipole assembly. Once formed, the body 7 is cut into a plurality of pieces (or slices) to form a plurality of identical rod supports 2.

[0037] The body 7 is cut into four identical pieces to form the Figure 4 To form a rod support 2 for a multipole rod assembly comprising more than four rod supports, the body and its openings will be appropriately formed and the body will be cut into an appropriate number of pieces (or slices).

[0038] With identical rod supports formed from a common body, variations between the rod supports 2 and errors in parallelism are minimized.

[0039] The body 7 is preferably formed by machining a unitary body of electrically conductive material. The material is most preferably a metal.

[0040] As shown, the body preferably has a substantially cylindrical outer face 8. However, it is not necessarily so limited. In alternative arrangements, the outer profile may take a variety of different forms, for example, it may have a straight outer face or include a combination of straight and curved faces.

[0041] At least the seat 5 is preferably formed by electrical discharge machining (EDM) of the body 7. The EDM process is a multi-pass process that can be used to produce components with high precision in specific areas. The seat 5 can be made with minimal variation along the length of the component. Other areas that are less critical can be omitted from subsequent passes of the EDM process to save time and cost.

[0042] The form of the seats 5 is not necessarily limited, however, it is preferred that each of the seats has a profile for contacting the respective rod only at two tangent points.

[0043] Each seat 5 preferably comprises a pair of rod contact surfaces 5a, 5b which are straight and arranged at an angle to each other. In the present arrangement, the rod contact surfaces 5a, 5b are arranged at an angle of substantially 90 degrees to each other, such as Figure 3 and Figure 6 It will be appreciated that in alternative arrangements this angle may vary. The rod contact surfaces are preferably spaced apart from each other, such as Figure 3 and Figure 6. In the present arrangement, as is preferred, the spaced apart rod contact surfaces are joined to one another by an intermediate curved surface 5c. With such an arrangement, the seat is substantially V-shaped. The depicted arrangement provides a form that is ideally suited for precision machining. In an alternative arrangement, the rod contact surfaces may be joined directly, wherein for straight rod contact surfaces they would meet at an apex. Regardless of the form, each seat will be arranged to fit a particular rod diameter. Each of the seats 5 is preferably arranged to define a predetermined gap between the rod guided / received thereby and the seat at a center point between two tangent points, as Figure 6 Each seat 5 may be configured to define an opening behind the rod guided thereby, wherein the area of ​​the opening is above a predetermined minimum value to ensure proper pressure equalization in the assembly.

[0044] Return to Figure 4 Preferably, the rod supports 2a, 2b of the first pair of rod supports and the rod supports 2c, 2d of the second pair of rod supports alternate with each other in the length direction of the rod 2, as shown. This need not be the case in alternative arrangements, for example, the first pair of rod supports 2a, 2b may be arranged between the rod supports of the second pair of rod supports 2c, 2d.

[0045] In the present arrangement, two of the rods 3a, 3b are held using a first pair of rod supports 2a, 2b, and two of the rods 3c, 3d are held using a second pair of rod supports 2c, 2d.

[0046] The use of conductive rod supports 2 to hold the rods 3 in place can lead to problems with the fields within the multipole assembly, due to the fields penetrating the gaps between the rods. Even if each of the rod supports is designed to leave a significant gap between itself and the gaps between the rods, performance may be affected. To overcome this, it is possible to add field zeroing elements 6 to each of the opposing rods (i.e., rods in opposite phase to the rod supports that are not seated in the seats of the rod supports) to effectively balance the fields and significantly reduce field penetration.

[0047] Figure 5 An exemplary field nulling element 6 is shown. Figure 4 and Figure 6 The field nulling element 6 is shown in situ.

[0048] The field zeroing element 6 preferably has the same thickness as the support 2 in the axial direction of the rod and is aligned with the support 2 in the axial direction, such as Figure 4 By such arrangement, they are present at the same distance from the rod support 2. In the opening 4 of each rod support a pair of opposing field nulling elements 6 are arranged, such as Figure 4 and Figure 6 As seen in.

[0049] The field zeroing element 6 is preferably formed of a conductive material, most preferably of a metal.

[0050] The field nulling element 6 is preferably attached to the rod 3 using screws or similar fasteners.

[0051] The field nulling elements 6 may be substantially V-shaped, as shown. However, they may take alternative forms.

[0052] Each field nulling element 6 may comprise a pair of rod contact surfaces 6a, 6b which are straight and arranged at an angle to each other. In the present arrangement, the rod contact surfaces are arranged at substantially 90 degrees to each other, such as Figure 3 and Figure 6 By such an arrangement, a substantially square outline is defined by the combination of the rod contact surface of the field nulling element and the rod contact surface of the seat, as shown in FIG. Figure 6 It will be appreciated that in alternative arrangements the angle may be an angle other than 90 degrees. The rod contact surfaces of the field nulling element are preferably spaced apart from each other, as shown in FIG. Figure 3 and Figure 6 6c. In the present arrangement, as is preferred, the spaced apart rod contact surfaces are joined to each other by an intermediate curved surface 6c. With such an arrangement, the rod contact surfaces define a V-shape. In an alternative arrangement, the rod contact surfaces of the field nulling elements may be joined directly, where for straight rod contact surfaces they would meet at an apex.

[0053] A constant gap G may be provided between the outer surface 6d of each field zeroing element 6 and the inner surface of the opening 4, such as Figure 6 The outer surface 6d of each field zeroing element can be configured to match the contour of the opening, such as Figure 6 As seen in.

[0054] Reference again Figure 1 The body 7 preferably also includes a plurality of through holes 10, the axes of which are parallel to the axis of the opening 4 and arranged outside the periphery of the opening. In the present arrangement, four of the holes 10 are provided. In alternative arrangements, more or fewer of the holes 10 may be provided.

[0055] Each of the holes 10 is preferably associated with a respective slot 11 extending between the hole 10 and the outer face 8 of the body 7. The slots 11 extend the length of the body 7, as shown. Each slot 11 is preferably substantially L-shaped, having a first portion extending radially outwardly from the hole 10 and a second portion extending outwardly from the end of the first portion at an angle of 90 degrees relative to the first portion to the outer face 8. The slots define a clamp by such an arrangement in cooperation with a screw (not shown) to be received in an appropriate threaded hole 12.

[0056] The holes 10 are arranged so that once the body 7 is cut to form the rod support 2 and the rod support 2 is installed in the multipole rod assembly 1 to support the rod 3 in its seat 5, as discussed above and in Figure 4 , the holes 10 of adjacent rod supports 2 are aligned with each other. The holes 10 can receive ceramic rods passing through adjacent rod supports. Most preferably, each of the holes 10 of each of the rod supports 2 is aligned with the corresponding holes 10 of each of the other rod supports 2 in the assembly. In such a case, the ceramic rods received by the holes 10 can extend substantially the same length as the rods and are supported in the holes 10 by all the rod supports 2 in the assembly.

[0057] The holes 10 are shown as being circular, however, they may take any alternative shape. They are preferably shaped to match the profile of the ceramic rod received therefrom.

[0058] As discussed above, by providing a clamp, the ceramic rod may be clamped to prevent movement. However, in an alternative arrangement, the slit 11 may be omitted and alternative fixing means provided for the ceramic rod, such as screws, arranged radially to the aperture 10 and penetrating the aperture to clamp the ceramic rod.

[0059] Furthermore, it will be appreciated that the apertures 10 and ceramic rods may be omitted entirely in alternative arrangements.

[0060] One or more of the embodiments as discussed herein may provide one or more or all of the following benefits: ■Alignment -Improve parallelism ■Charging -When the rod supports are metal, they are less likely to become electrically charged than ceramic (and do not require a shielding / grounding rod) - Smaller capture volume due to fewer connections Noise - RF breakdown is less likely due to possible better controlled routing - Lower electron emission from ceramic surface ■ Thermal effect - Matched thermal expansion coefficients to minimize drift with temperature ■Construction - Faster builds due to fewer components - Connection provided by rod supports

[0061] Therefore, the disclosed rod support and the method of manufacture are very suitable for obtaining the objects and advantages mentioned and inherent therein. The specific embodiments disclosed above are illustrative only, because the teachings of the present disclosure can be modified and practiced in different but equivalent ways, which is obvious to those skilled in the art who benefit from the teachings herein. In addition, except as described in the claims below, it is not intended to limit the details of the construction or design shown in this article. Therefore, it is obvious that the specific illustrative embodiments disclosed above can be changed, combined or modified, and all such variations are considered to be within the scope of the present disclosure. In the absence of any element not specifically disclosed herein and / or any optional element disclosed herein, the system and method disclosed illustratively herein can be appropriately practiced. Although the composition and method are described in terms of "including", "containing" or "comprising" various components or steps, the composition and method can also be "essentially composed of various components and steps" or "composed of various components and steps". All numbers and ranges disclosed above can vary by a certain amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range are specifically disclosed. In particular, each value range disclosed herein (having the form "from about a to about b", or equivalently "from about a to b", or equivalently "from about ab") should be understood to set forth each number and range encompassed within the broader value range. In addition, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. In addition, the indefinite articles "a" or "an" used in the claims are defined herein to mean one or more than one of the elements it introduces. If there is any conflict in the usage of a word or term in this specification and one or more patents or other documents that may be incorporated herein by reference, the definition consistent with this specification should be adopted.

[0062] As used herein, the phrase "at least one of" preceding a series of items, any of which is separated by the terms "and" or "or," modifies the list as a whole, rather than each member of the list (i.e., each item). The phrase "at least one of" allows for a meaning that includes at least one of any of the items, and / or at least one of any combination of the items, and / or at least one of each of the items. For example, the phrases "at least one of A, B, and C" or "at least one of A, B, or C" each refer to only A, only B, or only C; any combination of A, B, and C; and / or at least one of each of A, B, and C.

[0063] While various example embodiments have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure.For that reason, the following claims should be studied to determine the scope and content of this disclosure.

Claims

1. A method for manufacturing a multipole assembly for a mass spectrometer, the method comprising: machining the body to form an opening extending through the body along a predetermined axis, wherein the opening has a profile defining two or more seats, each seat being configured to guide a rod of the multipole assembly, cutting the body into a plurality of pieces to form a plurality of identical rod supports, A first plurality of rods are seated in the seats of a first pair of the rod supports, and a second plurality of rods are seated in the seats of a second pair of the rod supports, wherein the second pair of rod supports are rotated relative to the first pair of rod supports.

2. The method according to claim 1, wherein: The body has a substantially cylindrical outer surface.

3. A method according to any one of the preceding claims, wherein: At least the seat portion is formed by electrical discharge machining of the body.

4. A method according to any one of the preceding claims, wherein: Each of the seats has a profile for contacting the rod at two tangent points only.

5. The method according to claim 4, wherein: Each seat comprises a pair of rod contact surfaces which are straight and arranged at an angle to each other.

6. The method according to claim 5, wherein: The rod contact surfaces are arranged at substantially 90 degrees to each other.

7. The method according to claim 5 or 6, wherein: The rod contact surfaces are spaced apart from one another.

8. A rod support according to any one of claims 5 to 7, wherein: The rod contact surfaces are connected by a curved surface.

9. A rod support according to any one of the preceding claims, wherein: The seat is substantially V-shaped.

10. A method according to any one of the preceding claims, wherein: The body is metal.

11. A method according to any one of the preceding claims, wherein: The body is cut into four identical pieces to form four identical rod supports.

12. A method according to any one of the preceding claims, wherein: The multipole assembly comprises a quadrupole assembly wherein each rod support comprises a pair of opposing seats and the second pair of rod supports are rotated 90 degrees relative to the first pair of rod supports.

13. A method according to any one of the preceding claims, wherein: The rod supports of the first pair of rod supports and the rod supports of the second pair of rod supports alternate with each other in a length direction of the rod.

14. A multipole assembly for a mass spectrometer, comprising a plurality of identical rod supports and a plurality of rods supported thereby, in, Each of the rod supports comprises an opening extending through the body along a predetermined axis, wherein the opening has a profile defining two or more seats, wherein a first plurality of said rods are seated in said seats of a first pair of said rod supports, said first pair of said rod supports being spaced apart from each other in a lengthwise direction of said rods, wherein a second plurality of said rods are seated in said seats of a second pair of said rod supports, said second pair of said rod supports being spaced apart from each other in the length direction of said rods, and Wherein, the second pair of rod supports are rotated relative to the first pair of rod supports.

15. The multi-pole assembly according to claim 14, wherein: The rod supports of the first pair of rod supports and the rod supports of the second pair of rod supports alternate with each other in a length direction of the rod.

16. A multi-pole assembly according to claim 14 or 15, wherein: Each of the seats has a profile for contacting the rod at two tangent points only.

17. A multi-pole assembly according to claim 16, wherein: Each seat comprises a pair of rod contact surfaces which are straight and arranged at an angle to each other.

18. A multi-pole assembly according to claim 17, wherein: The rod contact surfaces are arranged at substantially 90 degrees to each other.

19. A multi-pole assembly according to claim 17 or 18, wherein: The rod contact surfaces are spaced apart from one another.

20. A multi-pole assembly according to any one of claims 5 to 7, wherein: The rod contact surfaces are connected by a curved surface.

21. A multi-pole assembly according to any one of claims 14 to 20, wherein: The seat is substantially V-shaped.

22. A multi-pole assembly according to any one of claims 14 to 21, wherein The rod supports are metal.

23. A multi-pole assembly according to any one of claims 14 to 22, wherein: Each of the rods has a field-nulling element secured thereto at each point along its length where the rod passes through an opening in one of the rod supports without seating in one of the seats.

24. A multi-pole assembly according to claim 23, wherein: A constant gap is provided between an outer surface of each field nulling element and an inner surface of the opening.

25. The multi-pole assembly of claim 23, wherein: The field zeroing element has the same thickness as the support member in the axial direction of the rod and is aligned with the support member in the axial direction.

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