Quadrupole mass spectrometer design

Abstract

In one aspect, a heat transfer structure for use in a mass spectrometer can include a collar for surrounding a plurality of rods arranged in a multipole configuration, at least one ceramic pad positioned to be in thermal contact with at least one of the rods, and at least one thermally conductive plate positioned to provide a heat transfer path between the at least one ceramic pad and the collar. The heat transfer structure can further include a bracket mounted on a bracket mounting portion of the collar for transferring heat from the collar to a rail.

Description

QUADRUPOLE MASS SPECTROMETER DESIGNRELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 580,778 filed on September 6, 2023, the contents of which are incorporated herein by reference in their entirety.TECHNICAL FIELD

[0002] The present disclosure relates to heat management systems and methods for use in mass spectrometers.BACKGROUND

[0003] The present teachings are generally directed to heat management methods and systems for extracting heat from ion optics employed in mass spectrometric systems.

[0004] Mass spectrometry (MS) is an analytical technique for determining the structure of test chemical substances with both qualitative and quantitative applications. MS can be useful for identifying unknown compounds, determining the composition of atomic elements in a molecule, determining the structure of a compound by observing its fragmentation, and quantifying the amount of a particular chemical compound in a mixed sample. Mass spectrometers detect chemical entities as ions such that a conversion of the analytes to charged ions must occur.

[0005] In many mass spectrometers, a multipole arrangement of rods to which RF and / or DC voltages are applied can be utilized, for example, for providing radial confinement of ions and / or filtering ions based on their mass-to-charge ratios. The application of RF and DC voltages to such rods can cause their heating.

[0006] Thus, methods and systems for dissipating heat generated by components, such as rods, of ion optics utilized in mass spectrometric systems are needed.SUMMARY

[0007] In one aspect, a heat transfer structure for use in a mass spectrometer includes: a collar for surrounding a plurality of rods arranged in a multipole configuration; at least one thermally conductive and electrically insulative pad positioned to be in thermal contact with at least one of the rods; and at least one thermally conductive plate positioned to provide a heat transfer path between the at least one ceramic pad and the collar.

[0008] In some embodiments, the at least one thermally conductive and electrically insulative pad can include a plurality of thermally conductive and electrically insulative pads, each of which is positioned to be in thermal contact with one of said plurality of rods. The at least one thermally conductive plate can include a plurality of thermally conductive plates each positioned to provide a thermal path between one of said plurality of thermally conductive and electrically insulative pads and the collar.

[0009] In some embodiments, the at least one thermally conductive and electrically insulative pad can be further configured to be attached to the at least one of the rods by an adhesive.

[0010] In some embodiments, the adhesive can be an epoxy.

[0011] In some embodiments, the heat transfer structure can further include at least one heat transfer layer configured to be disposed between the collar and the at least one thermally conductive plate.

[0012] In some embodiments, the at least one heat transfer layer can include at least one epoxy layer or at least one thermal pad.

[0013] In some embodiments, a length of the at least one thermally conductive and electrically insulative pad can be in a range of about 4 mm to about 10 mm.

[0014] In some embodiments, the at least one thermally conductive and electrically insulative pad can have a length in a range of about 10 mm to a length that is substantially equal to that of said at least one of the rods.

[0015] In some embodiments, the at least one thermally conductive and electrically insulative pad can have a width in a range of about 4mm to about half of a circumference of said at least one of the rods.

[0016] In some embodiments, the at least one of the rods can have a circular outer surface and the at least one thermally conductive and electrically insulative pad can have a concave bottom surface configured to be mounted on the circular outer surface of said at least one of the rods.

[0017] In some embodiments, at least one of the rods can have a flat outer surface portion and the at least one thermally conductive and electrically insulative pad can have a flat bottom surface configured to be mounted on the flat outer surface portion of said at least one of the rods.

[0018] In some embodiments, the heat transfer structure can further include a bracket configured to be mounted on a bracket-mounting portion of the collar for transferring heat from the collar to a rail.

[0019] In some embodiments, the bracket-mounting portion of the collar can have a surface roughness of 50 microns or less.

[0020] In some embodiments, the thermally conductive and electrically insulative pad can include a ceramic material.

[0021] In some embodiments, the thermally conductive plate can include a metal or a metal alloy.

[0022] In some embodiments, the at least one thermally conductive plate can be mounted on at least one plate-mounting portion of the collar, and either one or both of the at least one thermally conductive plate and the at least one plate-mounting portion can have a surface roughness of 50 microns or less.

[0023] In some embodiments, the at least one thermally conductive and electrically insulative pad can be attached to the at least one of the rods by a brazed joint.

[0024] In some embodiments, the at least one thermally conductive and electrically insulative pad can be fastened to the at least one of the rods with a screw.

[0025] In some embodiments, the at least one thermally conductive and electrically insulative pad can be fixed to said collar by epoxy disposed therebetween.

[0026] In some embodiments, a surface of the at least one thermally conductive and electrically insulative pad mounted on the at least one of the rods can have a surface roughness of 50 microns or less.

[0027] In another aspect, an ion optic for use in a mass spectrometer includes: a plurality of rods arranged in a multipole configuration so as to provide an inlet for receiving ions into a passageway between the rods and an outlet through which ions can exit the passageway; a collar surrounding said rods; a plurality of thermally conductive and electrically insulative pads, wherein each of the thermally conductive and electrically insulative pads is positioned to be in thermal contact with one of said rods; and a plurality of thermally conductive plates, wherein each of the plurality of thermally conductive plates is positioned to provide a thermal path between one of said plurality of thermally conductive and electrically insulative pads and the collar.

[0028] In some embodiments, the ion optic can further include a bracket for coupling said collar to a heat sink so as to provide a thermal path between said collar and the heat sink.

[0029] In some embodiments, the collar can include a recessed surface portion configured to be coupled to the bracket.

[0030] In some embodiments, the recessed surface portion and a surface of the bracket interfacing therewith can have a surface roughness of 50 microns or less.

[0031] In some embodiments, the heat sink can include a metal rail positioned in said ion optic.

[0032] In some embodiments, the ion optic can further include at least one epoxy layer positioned between at least one of the plurality of thermally conductive and electrically insulative pads and the respective one of said rods.

[0033] In some embodiments, the ion optic can further include pins for coupling the rods to an RF voltage source.

[0034] In some embodiments, the plurality of rods can be arranged according to a quadrupole configuration.

[0035] Further understanding of various aspects of the present teachings can be obtained by reference to the following detailed description in conjunction with the associated drawings, which are described briefly below.BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 schematically depicts a conventional quadrupole rod assembly having a heat dissipating structure for removing heat from a plurality of rods arranged in a quadrupole configuration;

[0037] FIG. 2A schematically depicts a quadrupole rod assembly having a heat dissipating structure for removing heat from a plurality of rods arranged in a quadrupole configuration, according to an embodiment of the disclosure;

[0038] FIG.2B schematically depicts some parts of the quadrupole rod assembly, according to an embodiment of the disclosure;

[0039] FIG. 2C schematically depicts a configuration of a rod, electrically conducting pins, and thermally conductive and electrically insulative pads of the quadrupole rod assembly, according to an embodiment of the disclosure;

[0040] FIG. 2D schematically depicts a configuration of a rod and a thermally conductive and electrically insulative pad in a portion of the quadrupole rod assembly, according to an embodiment of the disclosure;

[0041] FIG. 2E schematically depicts a heat transfer layer of the quadrupole rod assembly, according to an embodiment of the disclosure;

[0042] FIG. 3 schematically depicts a portion of a quadrupole rod assembly, according to an embodiment of the disclosure;

[0043] FIG. 4 schematically depicts a mass spectrometer, according to an embodiment of the disclosure.DETAILED DESCRIPTION

[0044] It will be appreciated that for clarity, the following discussion will explicate various aspects of embodiments of the applicant’s teachings, while omitting certain specific details wherever convenient or appropriate to do so. For example, discussion of like or analogous features in alternative embodiments may be somewhat abbreviated. Well-known ideas or concepts may also for brevity not be discussed in any great detail. The skilled person will recognize that some embodiments of the applicant’s teachings may not require certain of the specifically described details in every implementation, which are set forth herein only to provide a thorough understanding of the embodiments. Similarly, it will be apparent that the described embodiments may be susceptible to alteration or variation according to common general knowledge without departing from the scope of the disclosure. The following detailed description of embodiments is not to be regarded as limiting the scope of the applicant’s teachings in any manner.

[0045] As used herein, the terms "about" and "substantially equal" refer to variations in a numerical quantity that can occur, for example, through measuring or handling procedures in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of compositions or reagents; and the like. Typically, the terms "about" and "substantially" as used herein means 10% greater or less than the value or range of values stated or the complete condition or state. For instance, a concentration value of about 30% or substantially equal to 30% can mean a concentration between 27% and 33%. The terms also refer to variations that would be recognized by one skilled in the art as being equivalent so long as such variations do not encompass known values practiced by the prior art.

[0046] As used herein the term "and / or" includes any and all combinations of one or more of the associated listed items and may be abbreviated as " / ".

[0047] The term “surface roughness” refers to a mean square variation of the height of the surface relative to a reference plane.

[0048] In various mass spectrometers, a multipole arrangement of rods to which RF voltages are applied can be used for a variety of purposes. For example, the application of RF voltages to four rods arranged in a quadrupole configuration can generate a quadrupolar electromagnetic field in a space between the rods, which can provide radial confinement of certain ions as they pass through that space. The application of a DC resolving voltage, in addition to the RF voltages, to the rods can configure the quadrupole structure as a mass filter.

[0049] The stability of an electromagnetic field generated within the space between the rods of a multipole rod set, e.g., a quadrupole rod set, is determined, at least in part, by the geometrical stability of the rods. Such stability can in turn help enhance m / z accuracy and peak resolution of the rod set.

[0050] The application of voltages, and in particular RF voltages, to the rods can cause their heating. If the heat is not properly dissipated, it can lead to a change in the geometry of the rods, e.g., it can cause changes in the lengths and / or diameters of the rods. Such changes can in turn lead to degradation of the performance of the rod set.

[0051] A conventional way of removing heat from a rod set utilized in a mass spectrometer is to use a split ceramic holder design. For example, U.S. Published Application 2020 / 0381236 discloses a mass spectrometer including four rod electrodes (“rods”) for separating ions according to a mass-to-charge ratio, wherein the rods are held by a two annular rod holders that are made of an insulating material. The rod holders are disposed on a metal stand provided on a bottom surface of a vacuum housing and are each fixed by a fixation band that is fixed to the metal stand. A heat release layer is inserted between each fixation band and the respective rod holder and between each fixation band and the metal stand, such that heat generated in the rod holder is directly transmitted to the metal stand and is also transmitted to the metal stand throughthe fixation band. However, the manufacturing process of this split ceramic holder design is cumbersome and expensive.

[0052] There are other conventional ways for removing heat from a rod set utilized in a mass spectrometer. For example, FIG. 1, is a schematic depiction of an example of a conventional quadrupole rod assembly 100, which can be employed in a mass spectrometer. The quadrupole rod assembly 100 includes a conventional heat dissipating structure for removing heat from a plurality of rods 120 arranged in a quadrupole configuration. In this embodiment, the heat dissipating structure includes a collar 150 that surrounds the rods 120. The collar 150 includes a plurality of openings 151 for receiving a plurality of electrically conducting pins 128 such that each pin is in electrical contact with a respective one of the plurality of rods 120. The mounting of the electrically conducting pins 128 to the openings 151 in the collar 150 can be achieved via epoxy.

[0053] The heat generated in the rods 120, e.g., due to the application of RF voltage thereto, is transferred via the rods 120 and the epoxy to the collar 150. The heat from the collar 150 is in turn dissipated via a thermal coupling to a rail 110, which is established by support posts 182, a conductive plate 184, a plurality of springs 186, and four positioning pins 112, which hold the quadrupole in place.

[0054] Although the above-described heat dissipating structure is capable of removing heat from the rods 120, it presents certain shortcomings. For example, heat transfer from the rods 120 to the collar 150 occurs mostly through the epoxy used to mount the electrically conducting pins 128 to the openings 51. Therefore, particularly when high RF voltages are applied to the rods 120, the epoxy may be excessively heated, resulting in break-down of the epoxy and loosening or breakage of the connection between the electrically conducting pins 128 and the collar 150. In such circumstances, the rods 120 may deform and move during operation of the mass spectrometer, which can lead to performance degradation or failure of the rods 120.

[0055] Additionally, while the above-described heat dissipation structure transfers heat from the collar to the rail 110 by a first heat transfer path including the plurality of springs 186, the conductive plate 184, and the support posts 182, and second heat transfer paths through the fourpositioning pins 112, these heat transfer paths have relatively small heat transfer areas on the collar 150. Thus, heat transfer from the collar 150 to the rail 110 is limited and inefficient.

[0056] In one aspect, the present disclosure is generally related to heat-dissipating structures that can be utilized to extract heat from various components of a quadrupole rod assembly utilized in a mass spectrometer, such as rods employed in ion guides and mass filters.

[0057] Features and aspects of a quadrupole rod assembly 200 having a heat dissipation structure are described in following paragraphs with reference to FIGS. 2A to 2D. The heat dissipation structures according to various embodiments can be incorporated in a variety of different ion optics utilized in mass spectrometers. By way of illustration, and without limitation, various aspects of the present teachings are described below with reference to the quadrupole rod assembly 200 but it should be understood that the use of such heat dissipation structures is not limited to quadrupole rod assemblies.

[0058] FIG. 2A schematically depicts the quadrupole rod assembly 200, according to an embodiment of the disclosure. FIG.2B schematically depicts some parts of the quadrupole rod assembly 200, according to an embodiment of the disclosure. FIG. 2C schematically depicts a configuration of a rod 220, electrically conducting pins 228, and thermally conductive and electrically insulative pads 230 of the quadrupole rod assembly 200, according to an embodiment of the disclosure. FIG. 2D schematically depicts a configuration of a rod 220 and a thermally conductive and electrically insulative pad 230 in a portion of the quadrupole rod assembly 200, according to an embodiment of the disclosure.

[0059] Referring to FIGS. 2A to 2C, the quadrupole rod assembly 200 includes a plurality of rods 220 arranged in a quadrupole configuration. The heat dissipation structure of the quadrupole rod assembly 200 includes a collar 250 that surrounds the rods 220. The collar 250 includes a plurality of first openings 251 for receiving respective pairs of electrically conducting pins 228 such that each electrically conducting pin 228 is in electrical contact with a respective one of the rods 220. More specifically, two of the electrically conducting pins 228 can be mounted on and in electrical contact with a respective rod 220. Although each first opening 251 in the embodiment illustrated in FIGS. 2A and 2B is depicted as accommodating two electricallyconducting pins 228, the disclosure is not limited to this configuration. For example, in some embodiments, a greater number of first openings of a smaller size may be provided in the collar 250 such that each of the first openings accommodates only one electrically conducting pin 228.

[0060] In some embodiments, RF voltages can be applied to the rods 220 via the electrically conducting pin 228 to generate a quadrupolar electromagnetic field in a space S between the rods 220, which can provide radial confinement of certain ions as they pass through the space S. The application of a DC resolving voltage, in addition to the RF voltages, to the rods 220 can configure the quadrupole structure as a mass filter. As will be described in more detail later, the collar 250 is configured to dissipate heat generated in the rods 220 due to the application of the RF voltages thereto.

[0061] Still referring to FIGS. 2B to 2D, the heat dissipation structure of the quadrupole rod assembly 200 includes a plurality of thermally conductive and electrically insulative pads 230 that are mounted on the plurality of rods 220. As shown in FIG. 2C, in some embodiments, two thermally conductive and electrically insulative pads 230 can be mounted on each of the rods 220. However, in some embodiments only one thermally conductive and electrically insulative pad 230 or more than two thermally conductive and electrically insulative pads 230 can be mounted on each of the rods 220. Thermally conductive and electrically insulative pads 230 that are mounted on the same rod 220 are longitudinally spaced apart on the rod 220. The thermally conductive and electrically insulative pads 230 are mounted on the respective rods 220 such that the thermally conductive and electrically insulative pads 230 are in thermal contact with the respective rods 220, and can be fixed to the respective rods 220. The thermally conductive and electrically insulative pads 230 are made of an electrically insulative material. For example, the thermally conductive and electrically insulative pads 230 can be ceramic pads. However, the thermally conductive and electrically insulative pads 230 are not limited to being made of a ceramic material and may be made of other electrically insulative materials.

[0062] In some embodiments, the thermally conductive and electrically insulative pads 230 can be attached to the respective rods 220 by epoxy. The epoxy can have a high thermal conductivity and a high mechanical stability. Alternatively, in some embodiments, the thermally conductive and electrically insulative pads 230 can be attached to the respective rods 220 byrespective brazed joints. Further, in some embodiments, the electrically insulative pads 230 can be fastened to the respective rods 220 by one or more respective screws.

[0063] The thermally conductive and electrically insulative pads 230 can each include a bottom surface 232 mounted on the respective rod 220 and secured thereto (e.g., by the epoxy, the brazed joint, or the one or more screws), a top surface 234, and side surfaces 236. A protruding ledge or stepped portion 238 can be disposed on the side surfaces 236 to enable the thermally conductive and electrically insulative pad 230 to be securely mounted to the collar 250, as will be described below in more detail. In some embodiments, as illustrated in FIG. 2D, the bottom surfaces 232 of the thermally conductive and electrically insulative pads 230 can be flat or substantially flat, and outer surfaces 222 of the rods 220 can include flat or substantially flat portions 224 on which the bottom surfaces 232 of the thermally conductive and electrically insulative pads 230 are mounted. Providing the flat portions 224 on the rods 220 to match the flat bottom surfaces 232 of the thermally conductive and electrically insulative pads 230 facilitates the establishment of a uniform and substantially continuous contact between the rods 220 and the thermally conductive and electrically insulative pads 230.

[0064] As shown in FIG. 2C, the thermally conductive and electrically insulative pads 230 can have a length LI in a direction parallel to a longitudinal direction of the rods 220 and width W1 in a transverse direction perpendicular to the longitudinal direction of the rods 220. In some embodiments, the length LI can be in a range of about 4 mm to about 10 mm. In some embodiments, the length LI can be in a range of about 10 mm to about a length of the rods 220. For example, only one thermally conductive and electrically insulative pad 230 may be mounted on each rod 220 in embodiments in which the length LI is greater than ’ / 2the length of the rods 220. In some embodiments, the width W1 and a corresponding width of the flat portion 224 of the rod 220 can be in a range of about 4mm to about % of a diameter of the rods 220.

[0065] Referring again to FIG. 2B, the collar 250 includes a plurality of first mounting portions or plate-mounting portions 252 disposed on an outer surface of the collar 250 and corresponding in number to the plurality of thermally conductive and electrically insulative pads 230. That is, each first mounting portion 252 corresponds to a respective thermally conductive and electrically insulative pad 230. Each first mounting portion 252 can have a recessed surface253 and a second opening 254 formed in the recessed surface 253. In some embodiments, recessed surface 253 can be substantially flat and planar. However, in some embodiments, the recessed surface 253 can exhibit a curvature. Thus, the collar 250 includes a plurality of second openings 254 corresponding in number to the plurality of thermally conductive and electrically insulative pads 230. As shown in FIGS. 2B and 2D, each thermally conductive and electrically insulative pad 230 can be received in a respective second opening 254 such that the top surface 234 of the thermally conductive and electrically insulative pad 230 is positioned in or protrudes through the respective second opening 254, and the stepped portion 238 of the thermally conductive and electrically insulative pad 230 interfaces with or engages an inner surface of the collar 250. The thermally conductive and electrically insulative pad 230 can be fixed in the second opening 254 by epoxy disposed between the stepped portion 238 and the inner surface of the collar 250, and in the second opening 254.

[0066] As shown in FIGS. 2A, 2B, and 2D, the heat dissipation structure of the quadrupole rod assembly 200 includes a plurality of thermally conductive plates 240 mounted to the collar 250 in the plurality of first mounting portions 252. Each thermally conductive plate 240 plate can be mounted in a respective first mounting portion 252. Thus, each thermally conductive plate 240 plate can be in thermal contact with the respective thermally conductive and electrically insulative pad 230 and the respective first mounting portion 252 surrounding the thermally conductive and electrically insulative pad 230.

[0067] The thermally conductive plates 240 can be made of a material having a high thermal conductivity. For example, the thermally conductive plates 240 can be metal plates or metal alloy plates, such as stainless steel plates. However, the thermally conductive plates 240 are not limited to being made of a metal or a metal alloy, and other materials having a high thermal conductivity can be used for forming the thermally conductive plates 240. As shown in FIGS. 2A and 2B, each thermally conductive plate 240 has a top surface 241 and a bottom surface 245. In some embodiments, the top surface 241 can have a flat central region 242 and inclined outer regions 244. Thus, the shape of the top surface 241 of the thermally conductive plate 240 can conform closely to the shape of the outer surface of the collar 250. The bottom surface 245 of the thermally conductive plate 240 is disposed on and in thermal contact with the top surface 234 ofthe respective thermally conductive and electrically insulative pad 230 and the recessed surface 253 of the respective first mounting portion 252 of the collar 250. The bottom surface 245 of the thermally conductive plate 240 can have a shape corresponding to (e.g., matching) a shape of the top surface 234 of the respective thermally conductive and electrically insulative pad 230 and a shape of the respective recessed surface 253. For example, the bottom surface 245 of the thermally conductive plate 240, the top surface 234 of the respective thermally conductive and electrically insulative pad 230, and the recessed surface 253 can be substantially flat and planar, or they can be curved. In some embodiments, the bottom surface 245 of the thermally conductive plate 240, the top surface 234 of the respective thermally conductive and electrically insulative pad 230, and the recessed surface 253 can be machined to have a surface roughness of 50 microns or less, to provide excellent heat transfer characteristics.

[0068] The thermally conductive plates 240 can be fixed to the collar 250 by fastening members (e.g., screws or rivets) 247, which can be inserted in mounting holes 246 of the thermally conductive plates 240 and corresponding mounting holes 255 in the first mounting portions 252. In some embodiments, a heat transfer layer can be disposed between the bottom surface 245 of each thermally conductive plate 240 and each of the recessed surface 253 of the respective first mounting portion 252 and the top surface 234 of the respective thermally conductive and electrically insulative pad 230. For example, the heat transfer layer can be an epoxy layer. The epoxy layer can have a high thermal conductivity and a high mechanical stability, for example. However, as shown in FIG. 2E, in some embodiments, the heat transfer layer can be a thermal pad 260. The thermal pad 260 can include mounting holes 262 aligned with the mounting holes 246 and 255 and configured to receive the fastening members 247.

[0069] As shown in FIGS. 2A and 2B, the rods 220 and the plurality of thermally conductive and electrically insulative pads 230 can be arranged such that the thermally conductive and electrically insulative pads 230 are positioned at locations spaced apart along a circumference of the collar 250 and along a length of the collar 250. Thus, the plurality of first mounting portions 252 can be arranged such that the first mounting portions 252 are positioned at locations spaced apart along the circumference of the collar 250 and along the length of the collar 250, the plurality of second openings 254 can be arranged such that the second openings254 are positioned at locations spaced apart along the circumference of the collar 250 and along a length of the collar 250, and the plurality of thermally conductive plates 240 can be arranged such that the thermally conductive plates 240 are positioned at locations spaced apart along the circumference of the collar 250 and along a length of the collar 250.

[0070] In the quadrupole rod assembly 200, each thermally conductive and electrically insulative pad 230 forms a heat transfer path between the respective rod 220 and the respective thermally conductive plate 240. Each thermally conductive plate 240 forms a heat transfer path between the respective thermally conductive and electrically insulative pad 230 and the collar 250. Thus, heat transfer paths are formed between the rods 220 and the collar 250, through respective thermally conductive and electrically insulative pads 230 and thermally conductive plates 240. Due to the thermally conductive plates 240 forming heat transfer paths between the thermally conductive and electrically insulative pads 230 and the collar 250, the epoxy used to fix the thermally conductive and electrically insulative pads 230 and the thermally conductive plates 240 to the collar 250 does not retain an excessive amount of heat when RF voltages are applied to the rods 220. Thus, the configurations of the rods 220, the thermally conductive and electrically insulative pads 230, and the thermally conductive plates 240 resist damage to the epoxy due to heat, and the rods 220 can therefore remain reliably fixed to the collar 250 even during operation of the rods 220 at high voltages. Further, the thermally conductive and electrically insulative pads 230 and the thermally conductive plates 240 efficiently dissipate heat from the rods 220 to the collar 250, thereby ensuring stable operation of the rods 220 at high voltages.

[0071] In some embodiments, the quadrupole rod assembly 200 may not include the thermally conductive plates 240. In such embodiments, the thermally conductive epoxy can be disposed in the second openings 254, on the top surfaces 234 of the thermally conductive and electrically insulative pads 230, and on the recessed surfaces 253.

[0072] As shown in FIG. 2A, the collar 250 is mounted on a rail 210 of the quadrupole rod assembly 200. The rail 210 can be configured as a heat sink and, thus, can form part of the heat dissipation structure. The collar 250 is supported on the rail 210 by mounting pins 212, a pair of mounting brackets 270, and a support frame assembly 280, each of which forms part of the heatdissipation structure. The rail 210, mounting pins 212, the mounting brackets 270, and the support frame assembly 280 can be made of one or more materials having a high thermal conductivity, such as metals or metal alloys, such as stainless steel.

[0073] A lower portion of the collar 250 is supported on the mounting pins 212, which are mounted on the rail 210. In a non-limiting example, four mounting pins 212 can be provided such that two mounting pins 212 are mounted on the rail 210 at one lateral side of the collar 250 at locations that are spaced apart along the length of the collar, and two additional mounting pins 212 (not shown) are mounted on the rail 210 at another lateral side of the collar 250 at locations that are spaced apart along the length of the collar 250. Some of the heat dissipated from the rods 220 to the collar 250 can be dissipated from the collar 250 to the rail 210 through the mounting pins 212.

[0074] The mounting brackets 270 are attached to the rail 210 at the one side of the collar 250 and the other side of the collar 250, respectively. Each of the mounting brackets 270 includes a base 272 attached to the rail 210, an arm member 274 extending from the base 272, and a mounting plate 276 mounted to the collar 250. Referring to FIG. 2B, the collar 250 can include a pair of second mounting portions or bracket-mounting portions 256 disposed on the outer surface of the collar 250 at opposite sides of the collar 250, respectively. Each second mounting portion 256 can have a recessed surface 257 that is substantially flat and planar, and mounting holes 258 disposed in the recessed surface 257. As shown in FIG. 2A, each mounting plate 276 is mounted in a respective second mounting portion 256 to be in thermal contact with the recessed surface 257, and can be fixed to the collar 250 by fastening members 278 inserted in mounting holes 277 of the mounting plate 276 and the mounting holes 258 disposed in the recessed surface 257. Thus, some of the heat dissipated from the rods 220 to the collar 250 can be dissipated from the collar 250 to the rail 210 through the mounting brackets 270.

[0075] Referring again to FIG. 2B, in some embodiments, the recessed surface 257 can be machined to have a surface roughness of approximately 50 microns or less, and thus can optimize the thermal contact with the mounting plate 276 to provide excellent heat transfer properties. In some such embodiments, the mounting plate 276 can be in direct contact with the recessed surface 257. However, in some embodiments in which the recessed surface 257 doesnot have a low surface roughness (e.g., the recessed surface 257 has a surface roughness greater than 50 microns), a thermal pad can be provided between the mounting plate 276 and the recessed surface 257.

[0076] The support frame assembly 280 can include a pair of support arms 282 attached to the rail 210 at the one side of the collar 250 and the other side of the collar 250, respectively, a plate member 284 attached to the support arms 282, and springs 286 attached to the plate member 284 and the collar 250. Some of the heat dissipated from the rods 220 to the collar 250 can be dissipated from the collar 250 to the rail 210 through the springs 286, the plate member 284, and the support arms 282.

[0077] FIG. 3 is a perspective view illustrating a portion of a quadrupole rod assembly 300, according to an embodiment of the disclosure. Referring to FIG. 3, the quadrupole rod assembly 300 is similar to the quadrupole rod assembly 200 of FIGS. 2A to 2E, except that the quadrupole rod assembly 300 includes rods 320 and thermally conductive and electrically insulative pads 330. The rods 320 can be similar to the rods 220 shown in FIGS. 2A to 2D, except that the rods have an outer surface 322 having a completely circular contour. The thermally conductive and electrically insulative pads 330 can be similar to the thermally conductive and electrically insulative pads 230 shown in FIGS. 2B to 2D, except that each thermally conductive and electrically insulative pad 330 has a concave bottom surface 332 shaped to match the circular contour of the outer surface 322 of a respective rod 320. Additionally, the thermally conductive and electrically insulative pad 330 can be dimensionally similar to the thermally conductive and electrically insulative pad 230, except that the thermally conductive and electrically insulative pad 330 can have a width W2 of about 4mm to about half of a circumference of the respective rod 320.

[0078] As compared with the rod 220 of FIGS. 2A to 2D, the rod 320 may be easier to manufacture to be structurally balanced and therefore resist unbalanced vibrations during operation. However, as compared with the thermally conductive and electrically insulative pad 230 shown in FIGS. 2B to 2D, it may be more difficult to manufacture the concave bottom surface 332 of the thermally conductive and electrically insulative pad 330 to precisely match thecircular contour of the outer surface 322 of a respective rod 320. The thermally conductive and electrically insulative pad 230 can be fixed to the rod 320 by a thermally conductive epoxy.

[0079] In some embodiments, various surfaces or surface portions of components along the thermal paths in the quadrupole rod assembly 200 / 300 can be machined to have a surface roughness of 50 microns or less to optimize heat transfer. For example, the following surfaces and surface portions can be machined to have a surface roughness of 50 microns or less: surfaces of the flat or substantially flat portions 224 of the rods 220, the outer surfaces 322 of the rods 320 (or portions thereof that interface with the thermally conductive and electrically insulative pads 330), the bottom surfaces 232 / 332 of the thermally conductive and electrically insulative pads 230 / 330, the bottom surfaces 245 of the thermally conductive plates 240, the recessed surfaces 253, the recessed surfaces 257, the bottom surfaces of the mounting plate 276 that interface with the recessed surfaces 257, the mating surfaces of the support arms 282 and the plate member 284 (e.g., bottom and top surfaces thereof, respectively), surfaces of the springs 286, mating side surfaces of the arm member 274 and the mounting plate 276, mating surfaces of the arm member 274, and the base 272, and mating surface portions of the collar 250 and the mounting pins 212. Additionally or alternatively, an epoxy having a high thermal conductivity can be applied on any of the foregoing surfaces and surface portions (with the exception of the mating surface portions of the collar 250 and the mounting pins 212).

[0080] FIG. 4 schematically depicts a mass spectrometer 10, according to an embodiment of the disclosure. Referring to FIG. 4, the mass spectrometer 10 includes an ion source 20, an ion guide 30, an inlet lens 40, a mass filter unit 50 including the quadrupole rod assembly 200 / 300, an outlet lens 60, and an ion detector 70. The ion guide 30, the inlet lens 40, the mass filter unit 50, the outlet lens 60, and the ion detector 70 can be disposed in a vacuum housing (not shown). The ion source 20 can perform ionization of a sample component, e.g., by an electron ionization method or a chemical ionization method, for example, to generate ions. Ions generated by the ion source 20 can be converged by the ion guide 30 and then introduced to the space S surrounded by the rods 220 / 320. A voltage, which is obtained by superposing a DC voltage on an RF voltage according to a mass-to-charge ratio of target ions to be measured, can be applied to the rods 220 / 320. A quadrupole electric field formed by the voltage applied to the rods 220 / 320allows only target ions to pass through the space S, and other ions diverge in the middle of the space S. The target ions pass through the outlet lens 60 and are received by the ion detector 70. The ion detector 70 can output a detection signal having a signal strength corresponding to an amount of the arrived ions.

[0081] Although FIG. 4 depicts the quadrupole rod assembly 200 / 300 in the mass spectrometer 10 having a single mass filter unit 50, this is only one example of an implementation of the quadrupole rod assembly 200 / 300. For example, the quadrupole rod assembly 200 / 300 can also be implemented in a first (QI) and / or second (Q3) mass filter of a triple-quadrupole mass spectrometer, or as a QI mass filter of a quadrupole-time-of-flight mass spectrometer.

[0082] According to embodiments disclosed herein, a quadrupole rod assembly includes rods arranged in a quadrupole configuration to generate a quadrupolar electromagnetic field in a space between the rods in response to RF voltages applied to the rods. The quadrupole rod assembly further includes a heat dissipation structure including a collar surrounding the rods, thermally conductive and electrically insulative pads mounted on the rods, thermally conductive plates mounted on the thermally conductive and electrically insulative pads and the collar, a rail, and mounting pins, mounting brackets, and a support frame assembly that support the collar on the rail. The quadrupole rod assembly exhibits superior heat management when RF voltages are applied to the rods by dissipating heat generated in the rods to the collar, and dissipating heat from the collar to the rail. More specifically, the quadrupole rod assembly can dissipate heat from the rods to the collar through the thermally conductive and electrically insulative pads mounted on the rods and thermally conductive plates mounted on the thermally conductive and electrically insulative pads and the collar. The quadrupole rod assembly can dissipate heat from the collar to the rail through the mounting pins, the mounting brackets, and the support frame assembly.

[0083] The embodiments disclosed herein mitigate performance problems caused by heat build-up in the rods, particularly when high RF voltages are applied to the rods. For example, by effectively dissipating heat from the rods, the embodiments disclosed herein prevent or reduce change in the rods’ geometry due to excessive heating of the rods, which could lead todegradation of the performance of the rods. Moreover, the embodiments disclosed herein can be easily manufactured at relatively low cost.

[0084] The foregoing description of the embodiments has been presented for purposes of illustration only. It is not exhaustive and does not limit the embodiments to the precise form disclosed. While several exemplary embodiments and features are described, modifications, adaptations, and other implementations may be possible, without departing from the spirit and scope of the embodiments. Accordingly, unless explicitly stated otherwise, the descriptions relate to one or more embodiments and should not be construed to limit the embodiments as a whole. This is true regardless of whether or not the disclosure states that a feature is related to “a,” “the,” “one,” “one or more,” “some,” or “various” embodiments. As used herein, the singular forms “a,” “an,” and “the” may include the plural forms unless the context clearly dictates otherwise. Further, the term “coupled” does not exclude the presence of intermediate elements between the coupled items. Also, stating that a feature may exist indicates that the feature may exist in one or more embodiments.

[0085] In this disclosure, the terms “include,” “comprise,” “contain,” and “have,” when used after a set or a system, mean an open inclusion and do not exclude addition of other, nonenumerated, members to the set or to the system. Further, unless stated otherwise or deducted otherwise from the context, the conjunction “or,” if used, is not exclusive, but is instead inclusive to mean and / or. Moreover, if these terms are used, a subset of a set may include one or more than one, including all, members of the set.

[0086] Further, if used in this disclosure, and unless stated or deducted otherwise, a first variable is an increasing function of a second variable if the first variable does not decrease and instead generally increases when the second variable increases. On the other hand, a first variable is a decreasing function of a second variable if the first variable does not increase and instead generally decreases when the second variable increases. In some embodiment, a first variable may be an increasing or a decreasing function of a second variable if, respectively, the first variable is directly or inversely proportional to the second variable.

[0087] The disclosed systems, methods, and apparatus are not limited to any specific aspect or feature or combinations thereof, nor do the disclosed systems, methods, and apparatus require that any one or more specific advantages be present or problems be solved. Any theories of operation are to facilitate explanation, but the disclosed systems, methods, and apparatus are not limited to such theories of operation.

[0088] Modifications and variations are possible in light of the above teachings or may be acquired from practicing the embodiments. For example, the described steps need not be performed in the same sequence discussed or with the same degree of separation. Likewise various steps may be omitted, repeated, combined, or performed in parallel, as necessary, to achieve the same or similar objectives. Similarly, the systems described need not necessarily include all parts described in the embodiments and may also include other parts not described in the embodiments. Accordingly, the embodiments are not limited to the above-described details, but instead are defined by the appended claims in light of their full scope of equivalents. Further, the present disclosure is directed toward all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another.

[0089] While the present disclosure has been particularly described in conjunction with specific embodiments, many alternatives, modifications, and variations will be apparent in light of the foregoing description. It is therefore contemplated that the appended claims will embrace any such alternatives, modifications, and variations as falling within the true spirit and scope of the present disclosure.

[0090] Those having ordinary skill in the art will appreciate that various changes can be made to the above embodiments without departing from the scope of the present teachings.

Claims

CLAIMSWhat is claimed is:

1. A heat transfer structure for use in a mass spectrometer, comprising: a collar for surrounding a plurality of rods arranged in a multipole configuration; at least one thermally conductive and electrically insulative pad positioned to be in thermal contact with at least one of the rods; and at least one thermally conductive plate positioned to provide a heat transfer path between the at least one thermally conductive and electrically insulative pad and the collar.

2. The heat transfer structure of Claim 1, wherein said at least one thermally conductive and electrically insulative pad comprises a plurality of thermally conductive and electrically insulative pads each of which is positioned to be in thermal contact with one of said plurality of rods, and wherein said at least one thermally conductive plate comprises a plurality of thermally conductive plates each positioned to provide a thermal path between one of said plurality of thermally conductive and electrically insulative pads and a respective one of said plurality of rods.

3. The heat transfer structure of Claim 1, wherein the at least one thermally conductive and electrically insulative pad is further configured to be attached to the at least one of the rods by an adhesive.

4. The heat transfer structure of Claim 3, wherein the adhesive is an epoxy.

5. The heat transfer structure of Claim 1, further comprising at least one heat transfer layer configured to be disposed between the collar and the at least one thermally conductive plate.

6. The heat transfer structure of Claim 5, wherein the at least one heat transfer layer comprises at least one epoxy layer or at least one thermal pad.

7. The heat transfer structure of Claim 1, wherein a length of the at least one thermally conductive and electrically insulative pad is in a range of about 4 mm to about 10 mm.

8. The heat transfer structure of Claim 1, wherein the at least one thermally conductive and electrically insulative pad has a length in a range of about 10 mm to a length that is substantially equal to a length of said at least one of the rods.

9. The heat transfer structure of Claim 1, wherein the at least one thermally conductive and electrically insulative pad has a width in a range of about 4mm to about half of a circumference of said at least one of the rods.

10. The heat transfer structure of Claim 1, wherein said at least one of the rods has a circular outer surface and the at least one thermally conductive and electrically insulative pad has a concave bottom surface configured to be mounted on the circular outer surface of said at least one of the rods.

11. The heat transfer structure of Claim 1, wherein said at least one of the rods has flat outer surface portion and the at least one thermally conductive and electrically insulative pad has a flat bottom surface configured to be mounted on the flat outer surface portion of said at least one of the rods.

12. The heat transfer structure of any one of Claims 1 to 11, further comprising a bracket configured to be mounted on a bracket-mounting portion of the collar for transferring heat from the collar to a rail.

13. The heat transfer structure of Claim 12, wherein the bracket-mounting portion of the collar has a surface roughness of 50 microns or less.

14. The heat transfer structure of Claim 13, wherein a surface of the bracket mounted on the bracket-mounting portion of the collar has a surface roughness of 50 microns or less.

15. The heat transfer structure of Claim 1, wherein said thermally conductive and electrically insulative pad comprises a ceramic material.

16. The heat transfer structure of Claim 1, wherein said thermally conductive plate comprises a metal or a metal alloy.

17. The heat transfer structure of Claim 1, wherein the at least one thermally conductive plate is mounted on at least one plate-mounting portion of the collar, and either one or both of the at least one thermally conductive plate and the at least one plate-mounting portion have a surface roughness of 50 microns or less.

18. The heat transfer structure of Claim 1, wherein said at least one thermally conductive and electrically insulative pad is attached to the at least one of the rods by a brazed joint.

19. The heat transfer structure of Claim 1, wherein said at least one thermally conductive and electrically insulative pad is fastened to the at least one of the rods with a screw.

20. The heat transfer structure of Claim 1, wherein said at least one thermally conductive and electrically insulative pad is fixed to said collar by epoxy disposed therebetween.

21. The heat transfer structure of Claim 1, wherein a surface of the at least one thermally conductive and electrically insulative pad mounted on the at least one of the rods has a surface roughness of 50 microns or less.

22. An ion optic for use in a mass spectrometer, comprising:a plurality of rods arranged in a multipole configuration so as to provide an inlet for receiving ions into a passageway between the rods and an outlet through which ions can exit the passageway; a collar surrounding said rods; a plurality of thermally conductive and electrically insulative pads, wherein each of the thermally conductive and electrically insulative pads is positioned to be in thermal contact with one of said rods; and a plurality of thermally conductive plates, wherein each of the plurality of thermally conductive plates is positioned to provide a thermal path between one of said plurality of thermally conductive and electrically insulative pads and the collar.

23. The ion optic of Claim 22, further comprising a bracket for coupling said collar to a heat sink so as to provide a thermal path between said collar and the heat sink.

24. The ion optic of Claim 23, wherein the collar comprises a recessed surface portion configured to be coupled to the bracket.

25. The ion optic of Claim 24, wherein the recessed surface portion and a surface of the bracket interfacing therewith have a surface roughness of 50 microns or less.

26. The ion optic of Claim 23, wherein said heat sink comprises a metal rail positioned in said ion optic.

27. The ion optic of Claim 22, further comprising at least one epoxy layer positioned between at least one of the plurality of thermally conductive and electrically insulative pads and the one of said rods.

28. The ion optic of any one of Claims 22-27, further comprising pins for coupling the rods to an RF voltage source.

29. The ion optic of Claim 22, wherein said plurality of rods is arranged according to a quadrupole configuration.

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