GB2592619A

GB2592619A - Vacuum system

Info

Publication number: GB2592619A
Application number: GB2003074.8A
Authority: GB
Inventors: Glyn Horler Richard; Cobbett Andrew
Original assignee: Edwards Ltd
Current assignee: Edwards Ltd
Priority date: 2020-03-03
Filing date: 2020-03-03
Publication date: 2021-09-08
Also published as: JP3233364U; DE202021000691U1; CN216922541U; GB202003074D0

Abstract

A vacuum pumping system 1, and method of evacuating a chamber, comprises Siegbahn and regenerative pumps 2, 3 in series. The Siegbahn pump comprises a plurality of stages 6, with a first inlet 4 upstream of the Siegbahn pump, and a second inlet 5 downstream of at least a first Siegbahn stage, and such that fluid entering the second inlet completes at least a single pass of a Siegbahn stage. The Siegbahn and regenerative pumps may be co-axial and positioned on a common drive shaft 9. A pump, such as a turbo-molecular pump, may be provided upstream of the Siegbahn pump. The turbo-molecular pump may comprise at least two pump stacks in series, and a third inlet may be provided between the pump stacks.

Description

Vacuum System

Field

[001] This invention relates to a vacuum system and in particular a vacuum system comprising a Siegbahn pump mechanism and a regenerative pump mechanism.

Background

[2] Fluid flow may be categorised into fluid flow regimes. Such flow regimes may be characterised by the type of gas flow that occurs within a pressure range. A pump mechanism may operate most efficiently when pumping fluid of a specific flow regimes.

[3] For example, a turbomolecular pump typically operates most efficiently with a molecular flow regime. The molecular flow regime is understood to include fluid pressures from about 10-3 mbar to about 10-10 mbar. A turbomolecular pump operates principally by a "momentum transfer" pumping mechanism.

[4] In contrast, a regenerative pump mechanism typically operates most efficiently with a continuum flow regime. The continuum flow regime is understood to include fluid pressures greater than about 10 mbar. A regenerative stage operates by an "aerodynamic" pumping mechanism.

[5] Some vacuum systems may comprise a main pump mechanism operating in a first flow regime, and an auxiliary pump mechanism operating in a second flow regime. Such auxiliary pump mechanisms are commonly known as booster mechanisms. For example, a turbomolecular pump may be the main pump mechanism, and it may have an auxiliary mechanism, such as a regenerative mechanism, fluidly coupled to it.

[006] However, the regenerative pump mechanism operates most efficiently at relatively high pressures of greater than about 10 mbar, whilst the turbomolecular pump operates most efficiently at significantly lower pressures of about 10-3 mbar to about 10-1° mbar. Consequently, when the vacuum system is in use and the pressure within the system is greater than 10 mbar, the regenerative pump mechanism may be pumping fluid effectively, but the turbomolecular pump system may be pumping fluid inefficiently, if at all.

[007] In fact, due to the tight manufacturing tolerances between the components of the turbomolecular pump, the presence of the turbomolecular pump between the chamber being evacuated and the regenerative mechanism acts as a significant impediment to fluid flow through the vacuum system as a whole, reducing the overall efficiency of the pump system. Thus, the time taken to achieve ultimate pressure may be increased significantly.

[8] Furthermore, when the pressure within the system has been reduced to between about 10-3 mbar to about 10-1° mbar, the main fluid flow regime is molecular flow. Thus, the turbomolecular pump may be pumping fluid efficiently, but the pressure is too low for the regenerative mechanism to pump fluid efficiently, if at all.

[9] The flow regime where this type of pump may be particularly inefficient is in the so-called transitional flow regime. This is understood as including pressures ranging from about 10 mbar to about 10-3 mbar, i.e. in the transition between aerodynamic and molecular flow. In this regime, neither the regenerative pump mechanism nor the turbomolecular pump mechanism are pumping fluid efficiently.

[010] An issue with pump systems of this type is that the turbomolecular pump mechanism and regenerative pump mechanism are typically arranged on a common shaft and rotated by a common motor. Thus, the rate of rotation of the rotors of the turbomolecular mechanism is identical to that of the regenerative mechanism. This requires the motor that is powering the motion of the pump to be variable according to the pressure within the pump. This adds complexity to the system, and it is beneficial if the motor is only required to spin at a single operating speed.

[11] It would be beneficial to have a vacuum system that is able to achieve a high levels of pumping performance across a range of pressures (i.e. flow regimes). Particularly, it would be beneficial to have a vacuum system that offers more efficient pumping performance in the transitional flow regime.

[12] The present invention aims to solve, at least in part, these and other problems associated with known vacuum systems.

Summary

[13] Accordingly, in a first aspect, the present invention provides a vacuum system comprising a Siegbahn pump mechanism and a regenerative pump mechanism. The Siegbahn pump mechanism comprises a plurality of Siegbahn pump stages. The Siegbahn pump mechanism and the regenerative pump mechanism are arranged in series. The vacuum system further comprises at least one first pump inlet positioned upstream of the Siegbahn pump mechanism. The vacuum system further comprises at least one second pump inlet positioned downstream of at least a first Siegbahn pump stage, and such that fluid entering via said second pump inlet completes at least a single pass of a Siegbahn pump stage.

[14] Siegbahn pump mechanisms are known in the art. Typically, a Siegbahn pump mechanism may comprise a plurality of Siegbahn pump stages.

A Siegbahn pump stage may comprise a disc rotor (rotor) and an annular stator (stator) arranged in an axially aligned configuration, the disc rotor and annular stator being axially spaced and defining a flow path therebetween. In use, rotation of the disc rotor may urge fluid flow through said flow path.

[15] Typically, each disc rotor may extend radially outwardly from a drive shaft. The one or more disc rotors may be coupled to the drive shaft, and/or one or more disc rotors may be integrally formed therewith so as to form a unitary component. The one or more annular stators may extend substantially radially inwardly from an outer wall of the Siegbahn pump mechanism, such that they substantially surround the drive shaft. Each annular stator may comprise a plurality of walls extending substantially axially from an upper and/or lower surface thereof, the walls defining a plurality of channels therebetween. The channels typically may extend radially inwardly from the outer peripheral edge of the annular stator towards the central axis of the annular stator in at least one spiral arrangement. Typically, each stator may comprise two or more semi-annular components that may be positioned about the drive shaft to form the annular stator.

[16] A Siegbahn pump mechanism may comprise a single Siegbahn pump stage, or preferably, a Siegbahn pump mechanism may comprise a Siegbahn stack. A Siegbahn stack may typically comprise a plurality Siegbahn pump stages. Preferably, the Siegbahn stack may comprise from about one to about eight Siegbahn pump stages, for example four Siegbahn pump stages. More preferably, said Siegbahn pump stages may comprise a coaxial stack of alternating disc rotors and annular stators. Preferably, the disc rotors may be substantially evenly spaced along a portion of the drive shaft.

[17] Typically, a gap may be provided between a radially outermost peripheral edge of each disc rotor and the outer wall of the Siegbahn mechanism pump chamber, to allow fluid to flow from an upstream Siegbahn pump stage to a downstream Siegbahn pump stage. Typically, a gap may be provided between a radially innermost peripheral edge of an annular stator and the drive shaft, to allow fluid to flow from an upstream Siegbahn pump stage to a downstream Siegbahn pump stage.

[018] In use, the one or more disc rotors may be configured to rotate with the rotation of the drive shaft. Fluid molecules may interact with the surface of a rotating disc rotor such that the disc rotor imparts a velocity component to said fluid molecules. As a result, the fluid molecules may take up the same direction of motion as the surface of the disc rotor with which they interact.

[019] Thus, the fluid molecules positioned between a first disc rotor and a first annular stator may be accelerated by the interaction with the disc rotor and directed, for example, substantially radially inwardly by the spiral channels. When the fluid reaches the radially innermost peripheral edge of the annular stator, it may be urged through the gap between the radially innermost peripheral edge of the annular stator and the drive shaft. The fluid may then be urged substantially radially outwardly by the spiral channels on the underside of the annular stator. When the fluid reaches the outermost peripheral edge of the disc rotor, it may be urged through the gap between the radially outermost peripheral edge of the disc rotor and the outer wall of the Siegbahn mechanism pump chamber. This may continue for however many Siegbahn stages make up the Siegbahn pump mechanism, until the fluid exits the Siegbahn mechanism through an outlet port.

[20] Preferably, a disc rotor may be the final component of the Siegbahn mechanism. Preferably, said disc rotor may be integrally formed with the drive shaft as to form a single unitary component.

[21] Typically, a regenerative pump mechanism may comprise a rotor disc (rotor, disc rotor), the rotor disc having at least one regenerative pump stage extending axially therefrom. Each regenerative pump stage may comprise a substantially annular array of axially extending blades mounted on, or integral with, the rotor disc. Typically, the blades may extend substantially axially in a downstream pumping direction. Although, it is appreciated that the blades may extend in a substantially radially outward direction, i.e. away from the rotational axis, preferably such that the blades may extend substantially radially outwardly from an outer periphery of the substantially annular disc.

Alternatively, the blades may extend axially in a substantially upstream pumping direction [22] The regenerative pump mechanism may further comprise a stator defining at least one substantially circular conduit within which, in use, the substantially annular array of axially extending blades may rotate. Each regenerative pump stage of the regenerative pump mechanism may comprise a substantially circular conduit. Each conduit may have a cross-sectional area greater than that of the individual blades about its entire length. A small portion of the conduit, known as the "stripper', may have a reduced cross section providing a relatively closer clearance to the blades in comparison to the remainder of the conduit.

[23] Typically, when in use, fluid may enter the substantially circular conduit through an inlet and may be urged by interaction with the blades on the rotating rotor disc along the substantially circular conduit in the direction of rotation. The circular conduit may further comprise an outlet positioned before the stripper in the direction of rotation of the rotor disc. When the fluid reaches the outlet, the narrowing of the cross-sectional area of the substantially circular conduit at the stripper may lead to compression of the fluid. To minimise pressure increase, fluid may flow through the outlet and exit the substantially circular conduit.

[24] Preferably, the regenerative pump mechanism may comprise a single regenerative stage comprising a single substantially circular conduit, wherein the outlet of the circular conduit is the outlet of the regenerative pump mechanism.

[25] Alternatively, the regenerative pump mechanism may comprise a plurality of regenerative stages, and a plurality of corresponding substantially circular conduits. In such embodiments, the outlet of a first, upstream, substantially circular conduit may be fluidly connected to the inlet of a second, downstream, substantially circular conduit.

[26] The Siegbahn pump mechanism and regenerative pump mechanism are arranged in series. Thus, the outlet of the Siegbahn pump mechanism may be fluidly connected to the inlet of the regenerative pump mechanism.

Preferably, the outlet of the Siegbahn pump mechanism may be directly connected to the inlet of the regenerative pump mechanism. Preferably, the final rotor disc of the Siegbahn pump mechanism and the rotor disc of the regenerative pump mechanism may be integrally formed as a single component.

[27] The at least one first pump inlet positioned upstream of the Siegbahn pump mechanism may preferably be located at a first end of the Siegbahn pump mechanism. More preferably, the first pump inlet may be positioned upstream of the Siegbahn pump mechanism at a first end of the Siegbahn pump mechanism. Typically, the outlet of the Siegbahn pump mechanism may be positioned at an axially distal end of the Siegbahn pump mechanism from the first pump inlet. The plurality of Siegbahn pump stages may be positioned axially between the first pump inlet and the outlet of the Siegbahn pump mechanism.

[28] The at least one second pump inlet is positioned downstream of at least a first Siegbahn pump stage and such that fluid entering the Siegbahn pump mechanism completes at least one pass of a Siegbahn pump stage. Preferably, the second pump inlet may be located in an outer wall of the Siegbahn pump mechanism. Preferably, the second pump inlet may be located upstream of at least the final Siegbahn pump stage of the Siegbahn pump mechanism. In use, the fluid flow through said second pump inlet may be -s -directed substantially radially inwardly by a Siegbahn pump stage of the Siegbahn pump mechanism downstream of the second pump inlet. Following at least one pass of a Siegbahn pump stage, fluid may then flow through further Siegbahn pump stages of the Siegbahn pump mechanism, or may flow into the inlet of the regenerative pump mechanism.

[29] Advantageously, the fluid flow through the second pump inlet and performing at least one pass of a Siegbahn pump stage may increase the fluid flow through the outlet of the Siegbahn pump mechanism and into the regenerative pump mechanism. This may enable the regenerative pump mechanism to pump more efficiently, particularly at lower pressures.

[30] Typically, the vacuum system may, in use, be coupled to an apparatus having at least first and second sub-chambers. Preferably, the first and second sub-chambers may be fluidly connected. For example, the apparatus may comprise a mass spectrometer having first and second sub-chambers. Preferably, the first sub-chamber may be fluidly connected to the second pump inlet. Preferably, the second sub-chamber may be fluidly connected to the first pump inlet. Preferably, in use, the vacuum system may differentially pump the first and second sub-chambers of the apparatus. For example, the vacuum system may pump fluid from the sub-chambers of the apparatus to generate a first pressure of about 1 mbar in the first sub-chamber, and a second pressure lower than the first pressure in the second sub-chamber.

[031] The apparatus may have additional, lower pressure sub-chambers than those described above, which may be pumped by the same vacuum system, or by a separate vacuum system.

[032] Providing a single pass of a Siegbahn pump stage between the second pump inlet and the outlet of the Siegbahn pump mechanism may beneficially require lower power consumption in comparison to passes of multiple Siegbahn pump stages between the second pump inlet and the outlet of the Siegbahn pump mechanism.

[033] Typically, the vacuum system may further comprise a first pump section upstream of the Siegbahn pump mechanism. The first pump section, the Siegbahn pump mechanism, and the regenerative pump mechanism may be arranged in series. Preferably, the fluid outlet of the first pump section may be fluidly connected to a pump inlet of the Siegbahn pump mechanism. In embodiments comprising a first pump section upstream of the Siegbahn pump mechanism, the inlet of the first pump section may comprise the first pump inlet.

Preferably, the outlet of the first pump section may be fluidly connected to an inlet of the Siegbahn pump mechanism, wherein the inlet of the Siegbahn pump mechanism may be upstream of the second pump inlet.

[034] Typically, when the vacuum system is in use, the total flow of fluid exiting the Siegbahn pump mechanism may be up to about 2000 standard cubic centimetres per minute (sccm), preferably up to about 1000 sccm. Typically, when the vacuum system is in use, at least about 20%, preferably at least about 40%, more preferably at least about 50%, more preferably at least about 60%, most preferably at least about 80% of the total flow of fluid exiting the Siegbahn pump mechanism may have passed through the second pump inlet. Preferably, when in use, the majority of total flow of fluid exiting the Siegbahn pump mechanism may have passed through the second pump inlet. For example, when in use, from about 60% to about 80% of the total flow of fluid exiting the Siegbahn pump mechanism may have passed through the second pump inlet.

[035] Typically, the Siegbahn pump mechanism and regenerative pump mechanism may be coaxially aligned. Preferably, the Siegbahn pump mechanism and the regenerative pump mechanism may be positioned on a common drive shaft. Advantageously this may enable both pump mechanisms to be operable by a single drive means coupled to the common drive shaft.

-10 - [036] Typically, the regenerative pump system may comprise at least one generally circular conduit. Preferably, the regenerative pump mechanism may comprise at least two generally circular conduits.

[037] Typically, the first pump section may comprise a turbomolecular pump mechanism comprising at least one turbomolecular stack. Each turbomolecular stack may comprise a plurality of turbomolecular stages. Each turbomolecular stage may comprise a rotor and an axially aligned stator. The rotor may comprise an array of inclined rotor blades extending radially outwardly from a shaft. The stator may comprise an annular array of inclined stator blades extending substantially radially inwardly from an outer wall of the turbomolecular stage.

[38] The skilled person will appreciate that the number of turbomolecular stages in a turbomolecular stack depends on the pump type. As an example, each turbomolecular stack may comprise from about 1 to about 20 turbomolecular stages, preferably from about 6 to about 14 turbomolecular stages. Preferably, the turbomolecular stages may be arranged to form an alternating arrangement of rotors and stators.

[39] Preferably, the turbomolecular pump mechanism may comprise at least one second turbomolecular stack. Preferably the first and second turbomolecular stacks may be arranged in series.

[040] Advantageously, including a Siegbahn pump mechanism and regenerative pump mechanism as described herein in conjunction with a turbomolecular pump mechanism may provide efficient pumping over a range of pressures, particularly at low pressures, for example in the molecular flow regime.

[041] In a further aspect, the present invention provides a method of evacuating a chamber. The method comprises providing a vacuum system having a Siegbahn pump mechanism and a regenerative pump mechanism arranged in series. The Siegbahn pump mechanism comprises a plurality of Siegbahn pump stages. The vacuum system further comprises at least one first pump inlet located upstream of the Siegbahn pump mechanism, and at least one second pump inlet located downstream of at least a first Siegbahn pump stage, and such that fluid entering via said second pump inlet completes at least a single pass of a Siegbahn pump stage. The method further comprises the step of directing fluid through a first pump inlet and a second pump inlet. Substantially all of the fluid that exits the Siegbahn pump mechanism enters and is directed through the regenerative pump mechanism.

[42] In a first embodiment, the first pump inlet may be coupled to a port of the chamber. The second pump inlet may be coupled to an additional system, for example a backup pump.

[43] In an alternate embodiment, the chamber may comprise at least first and second sub-chambers. Preferably, the first and second sub-chambers may be fluidly connected. For example, the vacuum system may be coupled to a chamber of a mass spectrometer, having first and second sub-chambers.

Preferably, the first sub-chamber may be fluidly connected to the second pump inlet. Preferably, the second sub-chamber may be fluidly connected to the first pump inlet. Preferably, in use, the vacuum system may differentially pump the first and second sub-chambers of the apparatus. For example, the vacuum system may pump fluid from the sub-chambers of the apparatus to generate a first pressure about 1 mbar in the first sub-chamber, and a second pressure lower than the first pressure in the second sub-chamber.

[44] The apparatus may have additional, lower pressure sub-chambers than those described above, which may be pumped by the same vacuum system, or by a separate vacuum system.

-12 - [045] Typically, the Siegbahn pump mechanism and regenerative pump mechanism may be those as described in any preceding embodiment or aspect described herein.

[046] Advantageously, the fluid flow through the second pump inlet and across at least one regenerative stage may increase the fluid flow through the outlet of the Siegbahn pump mechanism and into the regenerative pump mechanism. This may enable the regenerative pump mechanism to pump more efficiently, especially at lower pressures, for example, wherein the pressure at the inlet to the regenerative stage is lower than about 0.1 mbar.

[47] Typically, the vacuum system may further comprise a first pump section, positioned upstream of the Siegbahn pump mechanism. Preferably, the first pump section, the Siegbahn pump mechanism, and the regenerative pump mechanism may be arranged in series. Preferably, the fluid outlet of the first pump section may be fluidly connected to the first pump inlet of the Siegbahn pump mechanism.

[48] Typically, the first pump section may comprise a turbomolecular pump mechanism comprising at least one turbomolecular stack. The turbomolecular stack may comprise a plurality of turbomolecular stages. Each turbomolecular stage may comprise a rotor and an axially aligned stator. The rotor may comprise an array of inclined rotor blades extending substantially radially outwardly from a rotor shaft. The stator may comprise an annular array of inclined stator blades extending radially inwardly from an outer wall of the turbomolecular stage. Preferably, the turbomolecular stack may comprise from about 1 to about 20 turbomolecular stages, more preferably, from about 6 to about 14 turbomolecular stages. Preferably, the turbomolecular stages may be arranged to form an alternating arrangement of rotors and stators.

-13 - [049] Preferably, the turbomolecular pump mechanism may comprise at least one second turbomolecular stack. Preferably the first and second turbomolecular stacks may be arranged in series.

[050] Preferably, the first pump section may comprise at least two turbomolecular pump stacks arranged in series, such that, in use, fluid is directed through the first turbomolecular pump stack, and fluid that exits the first turbomolecular pump stack may be directed through the second turbomolecular pump stack, and fluid that exits the second turbomolecular pump stack may enter the first pump inlet.

[51] Preferably, the method may further comprise the step of providing a third pump inlet port between said first turbomolecular pump stack and said second turbomolecular pump stack, such that further fluid may enter the first pump section. Preferably, the third pump inlet port may be fluidly connected to an additional vacuum pump, or alternatively to a further sub-chamber of the apparatus.

[52] In a further aspect, the present invention provides a method of evacuating a chamber, comprising providing a vacuum system according to any preceding embodiments, and/or a method according to any preceding embodiment.

[53] For the avoidance of doubt, all aspects described hereinbefore may be combined mutatis mutandis.

Brief Description of Figures

[054] The invention will now be described according to the following figures, wherein: -14 -Figure 1 illustrates a cutaway view of a portion of a vacuum system according to the present invention.

Figure 2 illustrates a schematic view of a vacuum system according to the present invention.

Detailed Description

[55] Figure 1 shows a cutaway view of a portion of a vacuum system (1) according to the present invention. The vacuum system (1) comprises a Siegbahn pump mechanism (2) and a regenerative pump mechanism (3).

[56] The Siegbahn pump mechanism (2) and the regenerative pump mechanism (3) are arranged in series. The vacuum system (1) comprises a first pump inlet (4) positioned upstream of the Siegbahn pump mechanism (2).

[57] The Siegbahn pump mechanism (2) comprises a plurality of Siegbahn pump stages (6). The Siegbahn pump mechanism (2) may comprise a plurality of disc rotors (7) mounted onto a drive shaft (9). During use, the drive shaft (9) may rotate, driven by a drive means (not shown). The disc rotors (7) may be integrally formed with the drive shaft (9) and configured to rotate therewith. The disc rotors (7) may be mounted onto the drive shaft (9) such that they extend radially outwardly therefrom.

[058] Each disc rotor (7) may be positioned axially adjacent to at least one annular stator (8). The annular stators (8) may be located about the drive shaft (9) and proximate at least one disc rotor (7). The annular stators (8) may extend substantially radially inwardly from the outer wall (15) of the Siegbahn mechanism pump chamber. Each annular stator (8) may comprise a plurality of substantially axially extending walls (16) defining at least one spiral channel therebetween. The plurality of substantially axially extending walls (16) may extend from the surfaces of the annular stators (8) substantially parallel to the -15 -axis of the drive shaft (9) in a substantially upstream direction and/or a substantially downstream direction.

[59] The downstream direction is illustrated by the arrow (A). When the vacuum system (1) is in use, fluid may flow through the vacuum system (1) in a substantially downstream direction (A).

[60] When in use, a "pass" of a Siegbahn pump stage (6) may be defined as fluid flowing through the spiral channel between a single substantially radially extending face of an annular stator (8), and a single substantially radially extending face of a disc rotor (7). The fluid may flow either substantially radially outwardly or substantially radially inwardly, depending on whether the disc rotor (7) is at the downstream side, or upstream side of the stage (6), respectively.

[061] The vacuum system further comprises a second pump inlet (5). The second pump inlet (5) may be a port in the outer wall (15) of the Siegbahn pump mechanism (2) through which fluid may enter the vacuum system (1). The second pump inlet (5) may be positioned downstream of at least the first Siegbahn pump stage. In this embodiment, the second pump inlet (5) is positioned downstream of the first five Siegbahn pump stages. The second pump inlet (5) is positioned such that, in use, fluid entering via the second pump inlet (5) completes at least a single pass of a Siegbahn pump stage (6).

[62] Fluid exiting the Siegbahn pump mechanism (2) may enter the regenerative pump mechanism (3) through the regenerative stage inlet (13).

[63] The regenerative pump mechanism (3) may comprise at least one annular array of axially extending blades (10a, 10b) mounted on, or integral with, a rotor disc (11). The regenerative pump mechanism (3) may further comprise a stator defining at least one annular conduit (12a, 12b) within which the blades (10) can rotate. Each generally circular conduit (12a, 12b) corresponds to an annular array of axially extending blades (10a, 10b).

-16 - [64] The regenerative pump mechanism (3) may further comprise an outlet (14) through which fluid may exit the regenerative pump mechanism (3). The outlet (14) of the regenerative pump mechanism (3) may be fluidly connected to a vacuum system outlet (17).

[65] The embodiment shown in Figure 1 comprises a first conduit (12a) connected to the regenerative stage inlet (13), and a second conduit (12b) connected to the regenerative stage outlet (14). In use, fluid may flow into the first conduit (12a) through the regenerative stage inlet (13). The fluid may then be directed about the first conduit (12a) by the rotation of the blades (10a) mounted on, or integral with, the rotor disc (11). When the fluid reaches the "stripper" (not shown), where the cross-sectional width of the first conduit (12a) narrows to provide a relatively closer clearance with the blades (10a), the fluid may pass from the first conduit (12a), through an outlet (not shown) and into the second conduit (12b). The fluid may then be directed about the second conduit (12b) by rotation of the blades (10b). The fluid may then pass through a regenerative stage outlet (14).

[066] Figure 2 shows a schematic view of a vacuum system (18) according to the present invention.

[67] The vacuum system (18) may comprise a first pump section (19).

Typically, the first pump section (19) may comprise, for example, at least one turbomolecular pump stack, comprising a plurality of turbomolecular pump stages.

[68] The first pump section (19) may have an inlet (20) through which fluid may enter the vacuum system (18), i.e. a first pump inlet. The first pump section (19) may further comprise an outlet (21) through which fluid may exit the first pump section (19).

-17 - [69] The outlet (21) of the first pump section (19) may be fluidly connected to a Siegbahn pump mechanism (22) via a first Siegbahn pump mechanism inlet (23). The Siegbahn pump mechanism (22) may further comprise a first Siegbahn pump stage (24) and a second Siegbahn pump stage (25), wherein the first Siegbahn pump stage (24) is upstream of the second Siegbahn pump stage (25). The Siegbahn pump mechanism (22) may further comprise a second Siegbahn pump mechanism inlet (26), i.e. a second pump inlet, through which fluid may enter the Siegbahn pump mechanism (22). The second Siegbahn pump mechanism inlet (26) may be positioned between the first Siegbahn pump stage (24) and the second Siegbahn pump stage (25).

[70] Fluid may exit the Siegbahn pump mechanism (22) through a Siegbahn pump mechanism outlet (27), which may be positioned downstream of the second Siegbahn pump stage (25).

[71] The Siegbahn pump mechanism outlet (27) may be fluidly connected to an inlet (28) of a regenerative pump mechanism (29). In use, fluid may be pumped through the regenerative pump mechanism (29) and exit through the regenerative pump mechanism outlet (30).

[72] The regenerative pump mechanism outlet (30) may be fluidly coupled to the vacuum system outlet (31).

[73] It will be appreciated that various modifications may be made to the embodiments shown without departing from the spirit and scope of the invention as defined by the accompanying claims as interpreted under patent law.

-18 -Reference Key 1. Vacuum system 2. Siegbahn pump mechanism 3. Regenerative pump mechanism 4. First pump inlet 5. Second pump inlet 6. Siegbahn pump stage 7. Siegbahn disc rotor 8. Siegbahn annular stator 9. Drive shaft 10. Regenerative stage rotor a. Blade array b. Blade array 11. Rotor disc 12. Regenerative stage stator a. Conduit b. Conduit 13. Regenerative stage inlet 14. Regenerative stage outlet 15. Outer wall 16. Axially extending wall 17. Vacuum system outlet 18. Vacuum system 19. First pump section 20. First pump section inlet 21. First pump section outlet 22. Siegbahn pump mechanism 23. First Siegbahn pump mechanism inlet 24. First Siegbahn pump stage 25. Second Siegbahn pump stage 26. Second Siegbahn pump mechanism inlet 27. Siegbahn pump mechanism outlet -19 - 28. Regenerative pump mechanism inlet 29. Regenerative pump mechanism 30. Regenerative pump mechanism outlet 31.Vacuum system outlet

Claims

-20 -Claims 1. A vacuum system comprising a Siegbahn pump mechanism and a regenerative pump mechanism; wherein the Siegbahn pump mechanism comprises a plurality of Siegbahn pump stages; wherein the Siegbahn pump mechanism and the regenerative pump mechanism are arranged in series; wherein the vacuum system further comprises at least one first pump inlet positioned upstream of the Siegbahn pump mechanism, and at least one second pump inlet positioned downstream of at least a first Siegbahn pump stage, and such that fluid entering via said second pump inlet completes at least a single pass of a Siegbahn pump stage.
The vacuum system according to claim 1, wherein the vacuum system further comprises a first pump section upstream of the Siegbahn pump mechanism, such that the first pump section, the Siegbahn pump mechanism, and the regenerative pump mechanism are arranged in series.
3. The vacuum system according to claim 2, wherein a fluid outlet of the first pump section is coupled to the first pump inlet of the Siegbahn pump mechanism.
4. The vacuum system according to any of claims 1 to 3, wherein when the vacuum system is in use, at least about 20%, preferably at least about 40%, more preferably at least about 50%, more preferably at least about 60%, most preferably at least about 80% of the total flow of fluid exiting the Siegbahn pump mechanism has passed through the second pump inlet.
5. The vacuum system according to any preceding claim, wherein the Siegbahn pump mechanism and regenerative pump mechanism are coaxial.
-21 -The vacuum system according to claim 5, wherein the Siegbahn pump mechanism and the regenerative pump mechanism are positioned on a common drive shaft.
The vacuum system according to any preceding claim, wherein each Siegbahn pump stage of the Siegbahn pump mechanism comprises a disk rotor and an opposing stator.
The vacuum system according to any preceding claim, wherein the regenerative pump system comprises at least one conduit.
The vacuum system according to any of claims 2 to 8, wherein the first pump section comprises at least one turbomolecular stack.
10. A method of evacuating a chamber, comprising providing a vacuum system having a Siegbahn pump mechanism and a regenerative pump mechanism arranged in series; wherein the Siegbahn pump mechanism comprises a plurality of Siegbahn pump stages; wherein the vacuum system further comprises at least one first pump inlet positioned upstream of the Siegbahn pump mechanism, and at least one second pump inlet positioned downstream of at least a first Siegbahn pump stage, and such that fluid entering via said second pump inlet completes at least a single pass of a Siegbahn pump stage; further comprising directing fluid through a first pump inlet and a second pump inlet; wherein substantially all of the fluid that exits the Siegbahn pump mechanism enters and is directed through the regenerative pump mechanism.
11. A method according to claim 10, wherein the vacuum system further comprises a first pump section, positioned upstream of the Siegbahn pump mechanism, such that the first pump section, the Siegbahn pump mechanism, and the regenerative pump mechanism are arranged in series.
-22 - 12. A method according to claim 11, wherein the first pump section comprises at least one turbomolecular pump stack.
13. A method according to claims 11 or 12, wherein the first pump section comprises at least two turbomolecular pump stacks arranged in series, such that, in use, fluid is directed through the first turbomolecular pump stack, and fluid that exits the first turbomolecular pump stack is directed through the second turbomolecular pump stack, and fluid that exits the second turbomolecular pump stack enters the first pump inlet.
14. A method according to claim 13, further comprising providing a third pump inlet port between said first turbomolecular pump stack and said second turbomolecular pump stack, such that further fluid may enter the first pump section.
15. A method of evacuating a chamber, comprising providing a vacuum system according to any of claims 1 to 9, and/or a method according to claims 10 to 14.