WO2024069125A1

WO2024069125A1 - A multipole rod support and a multipole rod assembly comprising the same

Info

Publication number: WO2024069125A1
Application number: PCT/GB2023/052380
Authority: WO
Inventors: Mark Walford; Ian Trivett; David Gordon
Original assignee: Micromass Uk Limited
Priority date: 2022-09-28
Filing date: 2023-09-14
Publication date: 2024-04-04
Also published as: GB202314038D0; GB202214225D0; GB2623188A

Abstract

A rod support for a multipole rod assembly of a mass spectrometer, the rod support comprising a body with an opening extending along a predetermined axis through the body, and two or more rods, which are unitarily formed with the body and extend substantially parallel to the predetermined axis.

Description

A MULTIPOLE ROD SUPPORT AND A MULTIPOLE ROD ASSEMBLY COMPRISING THE SAME

TECHNICAL FIELD

The present disclosure relates generally to the field of linear multipole rod assemblies for use in mass spectrometers, and more particularly to a rod support for use in such a rod assembly, and to a multipole rod assembly itself.

BACKGROUND

Mass spectrometers comprising multipole rod assemblies are well known in the art. The multipole rod assemblies are operated to control the motion of ions and comprise a plurality of rods (i.e. rod-shaped electrodes), which are arranged in parallel and equidistantly spaced from a center axis. The rods are provided in opposed pairs. There may, for example, be four, six or eight rods provided. Radio frequency (RF) and direct current (DC) voltages are applied to the rods, with the opposed rods carrying like voltages. Oscillating electrical fields are used to selectively stabilize or destabilize ions. Each opposing rod pair is connected electrically, and an RF alternating current voltage is applied between the rods. A DC voltage is then superimposed on the RF voltage, which causes the ions to adopt an oscillatory trajectory as they travel between the rods. Only ions with a selected m/z (mass divided by charge) value are able to achieve a stable trajectory, which allows them to reach the next stage of the mass spectrometer, for example, a detector.

It is critical that the distance between the opposed 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 multipole length affects the performance of the device. Rod supports are typically provided for appropriately supporting the rods with two or more of the support members spaced axially from one another along the rods, wherein a typical quadrupole assembly may comprise four (filter) rods, two ceramic rod supports, and eight screws and washers. The parallelism, and consistency of distance between rods is heavily influenced by manufacturing tolerances associated with each part and distortion of the assembly due to tightening screws to bring the parts together.

The combination of the issues above makes multipole assemblies difficult to manufacture consistently, leading to them being expensive, susceptible to poor yield with assembly dimensional outcome not matched by that indicated by the sum of parts, and providing a large variation in performance between multipole assemblies.

The present invention arose in a bid to provide an improved rod support for a multipole rod assembly, capable of ensuring high accuracy whilst also offering simplified manufacture.

SUMMARY

According to a first aspect, there is provided a rod support for a multipole assembly of a mass spectrometer, the rod support comprising a body with an opening extending along a predetermined axis through the body, and at least two rods, which are unitarily formed with the body and extend substantially parallel to the predetermined axis.

By virtue of the unique formation of the body and the rods together from a single piece of material, as a single part, spacing and parallelism accuracy between those rods is a function of a single manufacturing process. A narrower tolerance band becomes possible than in prior art arrangements in which the rods and supports are separately formed and subsequently joined together. Moreover, there is a reduction in the need for component selection processes based on size.

The rod support is preferably electrically conductive. It may be metal. The rod support is preferably formed by electro-discharge machining. It may be formed by wire electro-discharge machining. Such a manufacturing method may, for example, provide a tolerance band of ± 2.5pm. The rod support may comprise an opposed pair of the rods.

According to the present invention in a further aspect, there is provided a multipole rod assembly of a mass spectrometer comprising a pair of the rod supports as defined above.

Preferably, the rod supports are identical to one another.

The rod supports preferably face one another.

The rod supports may be rotated relative to one another (about the predetermined axis). The multipole rod assembly may comprise a quadrupole assembly in which the rod supports are rotated at 90 degrees to one another.

At least one rod of each of the rod supports may be attached to the other of the rod supports, preferably to a body of the other of the rod supports. A spacer is preferably located between the at least one attached rod and the other rod support to which it is attached.

The spacers are preferably electrically insulating. The spacers are preferably non-metallic. They may be ceramic.

The rod supports may be connected to one another by one or more non- conductive rods. The non-conductive rods may be ceramic. They may extend between the bodies of the two rod supports. They may extend parallel to the rods.

Further, preferable, features are presented in the dependent claims.

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

Figure 1 is a perspective view of a rod support according to a first arrangement;

Figure 2 is a plan view of the rod support of Figure 1 ;

Figure 3 is an exploded perspective view of a quadrupole assembly of a mass spectrometer comprising two identical rod supports according to a second arrangement; and

Figure 4 is a perspective view of the assembled quadrupole assembly of Figure 3.

DETAILED DESCRIPTION

It should be appreciated that whilst much of the discussion herein will focus on quadrupole arrangements, the present invention is not to be limited thereto. The different aspects of the present invention may, for example, be applied, in isolation or in combination, to multipole rod assemblies that comprise six or eight rods, to rod supports therefor, and/or to their manufacture.

With reference to Figures 1 and 2, there is shown a rod support 1 for a multipole rod assembly of a mass spectrometer, the rod support 1 comprises a body 2 with an opening 3 extending along a predetermined axis through the body 2, and at least two rods 4, which are unitarily formed with the body and extend substantially parallel to the predetermined axis.

The body 2 and the rods 4 are formed together from a single piece of material. They are preferably formed by electro-discharge machining. Most preferably by wire electro discharge machining.

The rod support 1 is configured for use in a quadrupole assembly. It is provided with a pair of opposed rods 4, as shown. It is configured to be combined with another rod support 1 , which is preferably identical. In such an arrangement, as shown in Figures 3 and 4, and discussed further below, the rod supports will be rotated at 90 degrees to one another for forming the quadrupole rod assembly.

In alternative arrangements, the rod support 1 may be modified to comprise more rods. For example, the rod support 1 could be configured for use in a hexapole or octopole rod assembly and comprise three or four rods respectively. In such arrangements the rods 4 of the support 1 may not oppose one another. Moreover, the angular rotation between the two rod supports 1 forming the hexapole or octapole rod assembly may not be 90 degrees but an alternative appropriate rotation.

Various alternatives to suit any desired number of rods will be readily appreciated by those skilled in the art.

Irrespective of its specific form/configuration, the rod support 1 is preferably metal. It could otherwise be formed from an alternative conductive material.

Whilst it need not be limited as such, the opening 3 may be substantially rectangular, as shown. It may comprise four straight sides at right angles to one another. It could, in other arrangements, have a substantially circular or curved profile, or otherwise.

The rods 4 are preferably formed on an inner surface 5 of the opening 3, as shown. They have a greater length than the thickness of the body 2 (in an axial direction of the rods 4) such that they project from the body 2 by a desired distance. They preferably project from both sides of the body 2, as shown, and project from one side by a greater distance. Of course, they may be otherwise arranged.

The inner surface 5 preferably comprises a recess 6 for receiving a spacer 7, as seen in Figures 3 and 4, for a rod 4 of an adjacent rod support 1 . The recess 6 is preferably provided between two of the rods 6, as shown. There may be a single recess only, as shown, for example, in Figures 1 and 2, or there may be more than one recess provided, as shown, for example, in Figures 3 and 4. There may be a recess between the or each adjacent pair of rods 1 . The inner surface 5 may comprise at least first and second faces 8, 9, which are adjacent to one another, wherein one of the rods 4 is formed on the first inner face 8 and the recess 6 is provided in the second inner face 9. These faces may be substantially perpendicular to one another, as in the depicted arrangements or may be provided at an angle to one another in alternative arrangements, such as arrangements with additional rods 4.

The rods 4 need not be particularly limited in form, as will be appreciated by those skilled in the art. Their profile may be modified in numerous ways to aid in machining or to vary their operational characteristics.

Each of the rods 4 may comprise a joining portion 10 and a main rod portion 11 , wherein the main rod portion 11 is wider than the joining portion 10 and the main rod portion 11 is spaced from the body 2 by the joining portion 10. It should be appreciated that in alternative arrangements, with alternatively formed rods 4, the joining portion 10 may be omitted. Where the rods 4 do comprise joining portions 10, these may be defined by ribs, as shown in the depicted arrangements. The ribs may have a substantially rectangular profile as seen, or may have a different profile.

Irrespective of the form of the rods 4, they may have a constant profile along their entire lengths.

The rods 4 preferably each have a substantially round, hyperbolic or parabolic profile, although need not be limited as such. The profile is applied to at least the portions of the rods 4 that face towards the predetermined axis. Where the rods 4 comprise joining portions 10, then the main rod portion 11 may comprise the profile, be it round, hyperbolic, parabolic or otherwise.

With reference to Figures 3 and 4, there is shown a multipole rod assembly 100 for a mass spectrometer comprising a pair of the rod supports 1 . As noted above, the bodies 2 of the rod supports 1 of the arrangement of Figures 3 and 4 differ slightly from the body 2 of the rod support 1 of Figures 1 and 2. The differences relate to the specific form of the opening 3 of the body 2 of the rod supports 1 . Notably, the form of the opening 3 of the rod support 1 of any arrangement may be varied, and moreover, the rod supports 1 of the arrangement of Figures 3 and 4 could be replaced with rod supports 1 as shown in Figures 1 and 2.

Regardless of the specific form of the bodies 2 or the rods 4, the two rod supports 1 of the multipole rod assembly 100 are preferably identical to one another. The rod supports preferably face one another, as shown. The rod supports 1 are preferably rotated relative to one another, as again shown.

The arrangement of Figures 3 and 4 is a quadrupole rod assembly. Each of the rod supports 1 comprises two rods, which are opposed to one another, i.e. facing one another across the opening. The rod supports 1 are identical to one another and are rotated through 90 degrees relative to one another.

Again, regardless of the specific form of the bodies 2 or the rods 4, it is preferable that at least one rod of each of the rod supports 1 is attached to the other of the rod supports 1 , most preferably attached to the body 2 of the other rod support 1 . A single rod 4, more than one of the rods 4, or even all of the rods 4, may be attached to the other of the rod supports 1 . In the arrangement of Figure 4, a single one of the rods 4 of each of the rod supports 1 is attached to the other of the rod supports 1 . The rod(s) 4 may be attached by any suitable means. Attachment using fasteners 12, such as bolts or screws, is preferable, which fasteners may be received by suitably located holes 13 in the bodies 2, as exemplarily shown. The fasteners are preferably non-metallic. The fasteners may be vented.

Preferably a spacer 7 is located between the or each attached rod and the rod support 1 to which it is attached. The spacers 7 are preferably each sandwiched between a respective rod 4 and the surface 5 of the opening 3. The spacers 7 are preferably electrically insulating. They are preferably non-metallic. They may be ceramic. As will be appreciated by those skilled in the art, the spacer material may be selected to have a thermal expansion that is close to the thermal expansion of the rods. The spacers, as discussed above, may be received within the recesses 6. The spacers 7 are preferably suitably sized and shaped to be received within the recesses and to engage the rods 4. In the depicted arrangements in which the rods 4 are provided with ribs, the spacers may be provided with grooves 14, wherein the profiles of the grooves and ribs are preferably substantially congruent.

It must be appreciated that the interconnection of the rod supports 1 to each other need not be limited to the described attachment of at least one rod of each of the rod supports 1 to the other of the rod supports 1 using fasteners and/or spacers. For example, arrangements are possible where the bodies 2 of the two rod supports 1 are joined to one another by non-conductive rods, such as ceramic rods. Such rods will extend between the two bodies. They will preferably extend parallel to the rods 4. In such case the described spacers and/or fasteners may be omitted.

Various further alternative interconnection arrangements will be readily appreciated by those skilled in the art.

One or more of the arrangements as discussed herein may offer one or more or all of the following benefits:

- Spacing, parallelism accuracy between rods is a function of a single manufacturing process only and is consequently increased.

- Narrower tolerance band than prior art assemblies.

- Each pole pair can be inspected for distance between rods before assembling, giving the possibility of putting two parts together that will most likely function together. This will improve yield.

- The surface finish control can be concentrated on the fixed active faces - this applies to a range of geometry. This will be particularly beneficial in the event post finishing is required.

- Reduction in parts count will result in cost and labor efficiency savings.

- The use of conductive rod supports will aid in connectivity - it is only necessary to connect to one part of the assembly (rather than providing connectivity between opposite rods, for example). - Handling of the rod supports (given any user’s ability to pick up the part without touching “active surfaces”) is easier and the risk of assembly failures due to filter surface scratches or blemishes is likely to be reduced.

Therefore, the disclosed rod supports are well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the teachings of the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope of the present disclosure. The systems and methods illustratively disclosed herein may suitably be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein. While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. All numbers and ranges disclosed above may vary by some 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 is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the elements that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted. As used herein, the phrase “at least one of” preceding a series of items, with the terms “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list (i.e. , each item). The phrase “at least one of” allows a meaning that includes at least one of any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items. By way of 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.

Although 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

CLAIMS:

1 . A rod support for a multipole rod assembly of a mass spectrometer, the rod support comprising a body with an opening extending along a predetermined axis through the body, and at least two rods, which are unitarily formed with the body and extend substantially parallel to the predetermined axis.

2. A rod support as claimed in Claim 1 , which is metal.

3. A rod support as claimed in any preceding claim, wherein the opening is substantially rectangular.

4. A rod support as claimed in any preceding claim, wherein the rods are formed on an inner surface of the opening.

5. A rod support as claimed in Claim 4, wherein the inner surface comprises a recess for receiving a spacer for a rod of an adjacent rod support.

6. A rod support as claimed in Claim 5, wherein the recess is provided between two adjacent rods.

7. A rod support as claimed in Claim 5 or 6, wherein the inner surface comprises at least first and second faces, which are adjacent to one another, wherein one of the rods is formed on the first inner face and the recess is provided in the second inner face.

8. A rod support as claimed in any preceding claim, wherein each rod has a joining portion and a main rod portion, wherein the main rod portion is wider than the joining portion and the main rod portion is spaced from the body by the joining portion.

9. A rod support as claimed in Claim 8, wherein the joining portion is formed by a rib.

10. A rod support as claimed in any preceding claim wherein each rod has a substantially constant profile along its entire length.

11. A rod support as claimed in any preceding claim, wherein each rod has a substantially round, hyperbolic or parabolic profile.

12. A rod support as claimed in any preceding claim, which comprises an opposed pair of the rods.

13. A multipole rod assembly of a mass spectrometer comprising a pair of the rod supports as claimed in any preceding claim.

14. A multipole rod assembly as claimed in Claim 13 wherein the rod supports are identical to one another.

15. A multipole rod assembly as claimed in Claim 13 or 14, wherein the rod supports are rotated relative to one another.

16. A multipole rod assembly as claimed in any of Claims 13 to 15, which comprises a quadrupole assembly, and the rod supports are rotated at 90 degrees to one another.

17. A multipole rod assembly as claimed in any of Claims 13 to 16, wherein at least one rod of each of the rod supports is attached to the other of the rod supports.

18. A multipole rod assembly as claimed in Claim 17, wherein a spacer is located between the at least one attached rod and the other rod support to which it is attached.

19. A multipole rod assembly as claimed in Claim 18, wherein the spacers are non-metallic.

20. A multipole rod assembly as claimed in Claim 18 or 19, wherein the spacers are ceramic.