Deflector gate for ion beam intensity modulation.

Abstract

In one aspect, a mass spectrometer is disclosed comprising an ion path through which an ion beam can propagate, and an ion beam deflector positioned within the ion path and configured to modulate movement of an ion beam received from an upstream section of the ion path to a downstream section, the ion beam deflector comprising at least one conductive electrode positioned relative to one another to provide an aperture through which the ion beam can pass, the two electrodes being electrically isolated from one another to enable each electrode to be maintained at a DC potential independent of the DC potential at which the other electrode is maintained.

Description

[Technical field]

[0001] (Related Applications) This application claims priority to U.S. Provisional Application No. 63 / 249,944, filed September 29, 2021, which is incorporated by reference in its entirety herein.

[0002] (Technical field) FIELD OF THE DISCLOSURE This disclosure relates generally to mass spectrometry, and more particularly to systems and methods for modulating the intensity of an ion beam used in a mass spectrometer. [Background technology]

[0003] The present teachings relate generally to systems and methods for adjusting ion beam intensity in a mass spectrometer.

[0004] Mass spectrometry (MS) is an analytical technique for determining the structure of test chemicals in both qualitative and quantitative applications. MS can be useful in identifying unknown compounds, determining the composition of atomic elements in molecules, determining the structure of compounds by observing the fragmentation of compounds, and quantifying the amount of a particular compound in a mixed sample. Mass spectrometers detect chemicals as ions, and as a result, conversion of the analytes to charged ions must occur during the sampling process.

[0005] In many mass spectrometers, it is necessary to modulate the intensity of the ion beam produced by ionization of a sample as it propagates through the mass spectrometer. Summary of the Invention [Means for solving the problem]

[0006] In one aspect, a mass spectrometer is disclosed comprising an ion path through which an ion beam can propagate, and an ion beam deflector positioned within the ion path and configured to modulate movement of an ion beam received from an upstream section of the ion path to a downstream section, said ion beam deflector comprising at least two conductive electrodes positioned relative to one another to provide an aperture through which the ion beam can pass, the two electrodes being electrically isolated from one another to enable each electrode to be maintained at a DC potential independent of the DC potential at which the other electrode is maintained.

[0007] In some embodiments, the ion deflector may be implemented as a plurality of conductive electrodes positioned relative to each other to allow deflection of an ion beam with a given charge polarity along one of at least two possible directions. The controller may be operatively coupled to at least one voltage source that supplies voltages to the conductive electrodes of the ion deflector to adjust the pattern of voltages applied to those electrodes, e.g., the polarity of the voltages applied to those electrodes, to adjust the direction in which the ion beam is deflected. By way of example, as described in more detail below, in some embodiments, the ion deflector may include four conductive electrodes that are shaped and positioned relative to each other to provide two intersecting slits through which ions can pass. By adjusting the voltages (e.g., the polarity of the voltages) applied to the conductive electrodes, an ion beam of a given charge polarity may be deflected along two directions, one within one of the slits and the other within the other slit.

[0008] At least one DC voltage source is operatively coupled to the two conductive electrodes to apply a DC voltage to the conductive electrodes, and the mass spectrometer further includes a controller in communication with the at least one DC voltage source for modulating the DC voltage applied to the two conductive electrodes to transition a DC potential difference across the two electrodes between a first level at which the ion beam passes through the ion deflector substantially undeflected and a second level at which the ion beam is deflected from the ion path.

[0009] As an example, the two conductive electrodes can be two conductive plates separated by a gap through which the ion beam can pass. Applying a DC voltage difference across the plates can generate an electric field that can cause a deflection of the ion beam passing through the gap. In other embodiments, the conductive electrodes can be in the form of two rods separated from each other to allow the passage of the ion beam between them. The voltage difference applied across the two rods can be modulated to steer the ion beam passing between the rods along a direction of interest. In yet other embodiments, the conductive electrodes can be in the form of two conductive plates separated from each other to provide a passage through which the ion beam can pass. The voltage difference applied across the plates can be adjusted to affect the propagation path of the ion beam, for example, by deflecting the ion beam towards one of the electrodes.

[0010] In some embodiments, at least one beam collection electrode can be positioned downstream of the ion beam deflector to collect the deflected ion beam.

[0011] In some embodiments, the mass spectrometer can include at least one vacuum chamber in which at least a portion of the ion path is disposed. For example, the mass spectrometer can include two vacuum chambers in fluid communication and differentially pumped to be maintained at different pressures. In such embodiments, an ion deflector can be positioned between the two chambers to allow for modulating the intensity of the ion beam traveling between the two chambers.

[0012] The ion beam deflector can be positioned between the two vacuum chambers. In some such embodiments, the ion lens can be positioned upstream of the ion deflector. In such embodiments, the DC voltage source can be configured to apply a voltage difference between the upstream ion lens and the ion deflector to generate an electric field between the upstream ion lens and the ion deflector to deflect the ion beam as it passes through the ion deflector.

[0013] The mass spectrometer may further include a controller configured to control the voltage source to adjust the voltage applied to the conductive electrodes of the ion deflector to modulate the transmission of the ion beam through the ion deflector. As an example, the controller may cause the voltage source to apply substantially similar or different voltages to the two conductive electrodes of the ion deflector to allow the ion beam to pass through the ion beam deflector substantially undeflected or to cause deflection of the ion beam as it passes through the ion deflector. In some embodiments, the conductive electrodes may be formed of a suitable metal, such as stainless steel, copper, copper alloy, gold-plated ceramic, gold-plated PCB, and molybdenum alloy.

[0014] By way of example, the controller can cause the voltage source to apply a voltage difference across two electrodes of the ion deflector to deflect the ion beam by a deflection angle, for example, a deflection angle in the range of about 5 to about 60 degrees, although other deflection angles can be utilized. In some embodiments, the controller can control the voltage source to apply a voltage difference across two electrodes to substantially block passage of the ion beam from one vacuum chamber to another vacuum chamber between which the ion deflector is positioned.

[0015] In some embodiments, the ion beam deflector can be in the form of an ion lens having an aperture through which ions can pass. In some such embodiments, the ion lens can be formed as two conductive electrodes (e.g., two semicircular electrodes) that are insulated from one another and separated to provide at least one aperture for the ion beam to pass through. As an example, the two conductive electrodes can be separated by a slit through which the ion beam can pass.

[0016] In some embodiments, the first chamber can be maintained at a pressure in the range from about 0.1 Torr to about 10 Torr, and the second chamber can be maintained at a pressure in the range from about 0.001 Torr to about 0.1 Torr.

[0017] In some embodiments, a set of rods arranged in a multipole configuration that provides a passageway through which ions can pass can be located anywhere in the vacuum chamber. In some embodiments, DC and / or RF voltages can be applied to the multipole rods, for example via one or more DC and / or RF voltage sources, such that the rod sets function as ion guides and / or mass analyzers.

[0018] In some embodiments, the controller can control DC voltages applied to conductive electrodes of an ion deflector according to the present teachings to steer the ion beam in a direction of interest. For example, the controller switches the polarity of voltages applied to two conductive electrodes separated from each other to provide a slit through which ions pass to change the direction in which the ions are deflected. By way of example, in some embodiments, an ion deflector according to the present teachings can include four conductive electrodes, e.g., four wedge-shaped conductive electrodes, positioned relative to each other to provide a cross slit. By adjusting the voltages applied to the conductive electrodes, the ion beam can be steered along different directions, e.g., right, left, up or down.

[0019] In a related aspect, a mass spectrometer is disclosed that includes an ion path through which an ion beam can propagate, an ion beam deflector positioned within the ion path and configured to modulate movement of an ion beam received from an upstream section of the ion path to a downstream section, the ion beam deflector comprising at least one conductive electrode, at least one DC voltage source operatively coupled to the at least one conductive electrode for applying a DC voltage to the at least one conductive electrode, and a controller in communication with the at least one DC voltage source for modulating the DC voltage applied to the at least one conductive electrode and transitioning the DC voltage applied to the at least one electrode between a first level at which the ion beam passes through the ion deflector substantially undeflected and a second level at which the ion beam is deflected from the ion path. In some embodiments, the at least one conductive electrode includes a single electrode positioned either above or below the ion path. In some embodiments, the second level of DC voltage is configured to cause deflection of the ion beam at an angle ranging from about 5 to about 60 degrees relative to the ion path.

[0020] In some embodiments, an ion lens is positioned upstream of the ion beam deflector, and the controller is configured to cause the at least one DC voltage source to adjust a DC voltage applied to the at least one conductive electrode between a first level, where the at least one conductive electrode and the ion lens are maintained at the same potential, allowing the ion beam to pass through the ion beam deflector without being deflected, and a second level, where the at least one conductive electrode and the ion lens are maintained at a different potential, causing the ion beam to be deflected as it passes through the ion beam deflector.

[0021] In one aspect, a method for modulating the intensity of an ion beam propagating along an ion path is disclosed, the method including passing the ion beam against a conductive electrode to which a DC voltage is applied, and modulating the applied DC voltage between a first level at which the ion beam continues to propagate substantially undeflected along its propagation path, and a second level at which the ion beam is deflected from its propagation path, e.g., with a duty cycle in the range of about 0.001 to about 1.

[0022] In a related aspect, a method for modulating the intensity of an ion beam propagating along an ion path is disclosed, the method including passing the ion beam between two electrodes insulated from one another and allowing a DC potential difference to be maintained between the electrodes, and modulating the DC potential difference across the two electrodes between at least a first level and a second level such that when the DC potential difference is at the first level, the ion beam continues to propagate substantially undeflected along its path, and when the DC potential difference is at the second level, the ion beam is deflected from its propagation path.

[0023] In some embodiments of the above methods, the DC voltage difference applied across the electrodes of the ion deflector may be modulated with a duty cycle, for example in the range of about 0.001 to about 1.

[0024] A further understanding of the various aspects of the present teachings can be obtained by reference to the following detailed description in conjunction with the associated drawings, which are briefly described below. [Brief description of the drawings]

[0025] [Figure 1A] FIG. 1A shows a conventional ion deflection system that can be used in a mass spectrometer, which includes two ion lenses that are axially separated and to which a voltage difference can be applied to cause deflection of the ion beam as it passes through the ion lenses. [Figure 1B]FIG. 1B shows a conventional ion deflection system that can be used in a mass spectrometer, which includes two ion lenses that are axially separated and to which a voltage difference can be applied to cause deflection of the ion beam as it passes through the ion lenses. [Diagram 2] FIG. 2 is a graph showing that ions pass through the ion deflection system shown in FIGS. 1 and 2 when the voltage difference between the two lenses is zero, and that ions are prevented from passing through the ion deflection system when a voltage difference is applied between the two ion lenses. [Diagram 3] 3A and 3B show schematic diagrams of an ion deflector assembly according to one embodiment of the present teachings positioned between two vacuum chambers of a mass spectrometer. [Figure 4A] FIG. 4A illustrates a schematic of an ion deflector according to one embodiment of the present teachings for use in a mass spectrometer, showing the ion deflector assembly in a state in which ions can pass through the deflector substantially undeflected. [Figure 4B] FIG. 4B illustrates a schematic of an ion deflector according to one embodiment of the present teachings for use in a mass spectrometer, showing the ion deflector assembly in a state in which ions are blocked from passing through the ion deflector. [Figure 4C] FIG. 4C is a top schematic view of an ion deflector having two conductive electrodes that are electrically isolated from one another. [Figure 5A] FIG. 5A is a partial view of an ion deflector according to one embodiment (only one conductive electrode is shown in the figure). [Figure 5B] FIG. 5B illustrates a schematic of the voltage difference applied to the ion deflector shown in FIGS. 4A and 4B as a function of time, illustrating the modulation of the ion beam by the ion deflector. [Figure 6A] FIG. 6A illustrates a schematic of a mass spectrometer according to an embodiment of the present teachings incorporating an ion deflector according to an embodiment of the present teachings. [Figure 6B]FIG. 6B shows a schematic of an ion deflector according to an embodiment positioned between two ion guides, each ion guide being positioned within the vacuum chamber of a mass spectrometer. [Figure 6C] FIG. 6C illustrates a schematic of one embodiment of an ion deflector in accordance with the present teachings that includes two plates positioned above and below an ion beam passing on a centerline between the two plates. [Figure 6D] FIG. 6D illustrates a schematic of an ion deflector according to one embodiment of the present teachings for steering the path of an ion beam. [Figure 6E] FIG. 6E illustrates a schematic of an ion deflector according to another embodiment of the present teachings. [Figure 7] FIG. 7 illustrates a schematic diagram of an example of a controller implementation according to an embodiment of the present teachings. [Figure 8] FIG. 8 illustrates generally one example of a controller implementation suitable for use in various embodiments of the present teachings. [Figure 9A] FIG. 9A illustrates a schematic of a single electrode that may be utilized in some embodiments of the present teachings to deflect an ion beam. [Figure 9B] FIG. 9B is a schematic side view of the electrode shown in FIG. 9A further illustrating the deflection of an ion beam through the electrode when an appropriate DC bias voltage is applied to the electrode. [Figure 9C] FIG. 9C illustrates generally a single conductive electrode in the form of a bar that may be used in some embodiments of the present teachings to deflect an ion beam. [Figure 9D] FIG. 9D illustrates generally wires that may be used as conductive electrodes in some embodiments to deflect an ion beam. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] For clarity, the following description will describe various aspects of the embodiments of the present disclosure in detail, but it may be understood that certain specific details may be omitted where convenient or appropriate to do so. For example, descriptions of similar or similar features in alternative embodiments may be somewhat omitted. Well-known concepts or concepts may not be described in detail for the sake of brevity. Those skilled in the art will appreciate that some embodiments of the present disclosure may not require certain specifically described details in all implementations described herein only to provide a complete understanding of the embodiments. Similarly, it will be apparent that the described embodiments are susceptible to change or modification in accordance with common general knowledge without departing from the scope of the present disclosure. The detailed description of the following embodiments should not be considered in any way to limit the scope of the applicant's teachings.

[0027] As used herein, the terms "about" and "substantially equal" refer to variations in numerical quantities that may occur, for example, by real-world measurement or handling procedures, by inadvertent errors in these procedures, and by differences in the manufacture, source, or purity of a composition or reagent. Typically, the terms "about" and "substantially" as used herein mean 10% greater or less than a stated value or range of values, or an intact condition or state. For example, a concentration value of about 30% or substantially equal to 30% may mean a concentration of 27% to 33%. The terms also refer to such variations that would be recognized as equivalent by those of skill in the art, unless the variations encompass known values ​​practiced by the prior art.

[0028] 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 " / ".

[0029] 1A and 1B, in a conventional mass spectrometer, the intensity of an ion beam 1 passing between two differentially pumped chambers 10 and 12 maintained at different pressures and in which two devices 13 and 15 (e.g., two ion guides) are located can be modulated using two ion lenses 14 and 16 that are axially spaced apart from each other and include an aperture through which the ion beam can pass. The ion lens 14 includes an upstream face 14a and a downstream face 14b, and the ion lens 16 has an upstream face 16a and a downstream face 16b.

[0030] 1B, applying the same DC voltage to the ion lenses 14, 16 allows the ion beam to pass through the lenses without a change in its direction of propagation. Typically, the ion lenses are maintained at a DC potential that facilitates the passage of the ion beam from chamber 10 to chamber 12, e.g., via a voltage offset on either the upstream and / or downstream multipole rods.

[0031] To stop the passage of the ion beam from chamber 10 to chamber 12, a differential voltage can be applied across the two ion lenses 14 and 16, as shown in Figure 1, to slow down the ions as they pass between the two lenses and cause them to reverse their direction of propagation so that they impinge on the downstream face 16b of lens 16. Ion impingement on the downstream face 16b of lens 16 can cause contamination of that lens surface, which in turn can cause degradation of the performance of the mass spectrometer in which the two chambers and ion lenses are incorporated.

[0032] By modulating the voltage difference applied between the two ion lenses, the passage of the ion beam between the two chambers 10, 12 can be modulated. By way of example, FIG. 2 shows a hypothetical example, in which the movement of the ion beam between the two chambers is periodically modulated via a periodic change in the voltage difference applied between the two ion lenses. The solid traces show the voltages applied to one conductive electrode of the ion deflector, and the dashed traces show the voltages applied to the other conductive electrode of the ion deflector. In particular, the example shows that the ion beam passes from chamber 10 into chamber 12 when the voltage difference between the two ion lenses is zero, and that its passage between the two chambers can be prevented from passing from chamber 10 into chamber 12 by application of a non-vanishing voltage difference between the two ion lenses.

[0033] As will be described in more detail below, in embodiments, rather than causing the ion beam to flip and impinge on a lens surface, a number of conductive electrodes (also referred to herein as ion deflection electrodes) can be used whereby the ion beam is deflected by applying appropriate voltages to two electrodes as the ion beam passes through a gap provided between them.

[0034] In some embodiments, the deflection angle of the ion beam is such that the ion beam is prevented from entering the second chamber. By modulating the voltage difference applied between the deflection electrodes, the passage of the ion beam from the first chamber to the second chamber can be controlled. As will be further explained below, the ion deflection electrodes can have different shapes and configurations. By way of example, in some embodiments, the ion deflection electrodes can be in the form of two plates separated from each other by a gap through which the ion beam can pass. In other embodiments, the conductive electrodes can be in the form of two parts of an ion lens, the two parts of the ion lens being insulated from each other and including an opening between them through which the ion beam can pass. Other suitable shapes and / or arrangements of the conductive electrodes can also be used.

[0035] 3A and 3B show schematic diagrams of an ion deflector assembly 300 according to one embodiment positioned between two ion guides 1, 2, with ion guide 1 disposed in vacuum zone 1 (e.g., in one vacuum chamber) and ion guide 2 disposed in vacuum zone 2 (e.g., in the other vacuum chamber). Vacuum zones 1 and 2 are differentially pumped to be maintained at different pressures.

[0036] The ion deflector assembly 300 includes an ion lens 302 having an opening 302a through which ions can pass, and an ion deflector 304 according to an embodiment of the present teachings, located downstream of the ion lens 302. In this embodiment, the ion deflector 304 includes two semicircular conductive electrodes 304a / 304b that are separated from each other to form a slit 304c between them through which ions can pass. Furthermore, the semicircular portions are electrically isolated from each other, allowing independent application of voltages to the conductive portions to modulate the electric field in the slit, thereby affecting the propagation path of ions passing through the slit. For example, as shown in FIG. 3A, if the ion lens 302 and the two conductive electrodes 304a / 304b are maintained at the same voltage, ions pass through the ion deflector 304 without being deflected and reach the downstream ion guide 2.

[0037] In contrast, Figure 3B shows an example of voltages that may be applied to the conductive electrodes of the ion lens 302 and the ion deflector 304 to deflect the ion beam received by the ion deflector through ion guide 1 away from the entrance of ion guide 2, thereby preventing the passage of ions from ion guide 1 to ion guide 2. In this example, DC voltages 1 and 2 have the same polarity but different magnitudes, while DC voltages 2 and 3 have the same magnitude but opposite polarity. In this way, ions can be directed into the space between the ion lens 302 and the ion deflector 304 and deflected away from their initial propagation direction, thereby preventing the ions from entering ion guide 2.

[0038] In some embodiments, the ion deflection assembly can include an ion collector electrode for collecting ions deflected via a passage through the ion deflection assembly. For example, Figures 4A and 4B show two differentially pumped chambers 400 and 402 arranged in tandem and in fluid communication with each other. The chambers 400 and 402 are evacuated via one or more pumps such that they are maintained at a differential pressure relative to each other. The differentially pumped chambers 400, 402 can be incorporated into a mass spectrometer. In this embodiment, the chambers 400 and 402 are each: It contains two rod sets 401 and 403, each of which includes four rods arranged in a quadrupole configuration, although other multipole configurations can also be used. The rods of the rod sets are arranged to provide ion propagation paths IPP1 and IPP2 for ions passing through the rod sets.

[0039] One or more DC and / or RF voltage sources (not shown) can apply DC and / or RF voltages to the two rod sets, which can then provide their respective functions, for example as ion guides and / or mass analyzers. In this embodiment, chambers 400 and 402 house the rod sets, although in other embodiments other devices can be located in either of these chambers. In other words, the present teachings are not limited to modulating an ion beam passing through a multipole rod set, but can be applied more generally to deflect an ion beam along its propagation path.

[0040] The chamber 400 extends from an inlet 400a to an outlet 400b, and the chamber 402 extends from an inlet 402a to an outlet 402b. The outlet 400b of the chamber 400 is in fluid communication with the inlet 402a of the chamber 402 to allow passage of ions from the chamber 400 to the chamber 402. In this embodiment, an ion deflector assembly 404 is positioned between the outlet 400b of the chamber 400 and the inlet 402a of the chamber 402. The ion deflector assembly 404 includes an ion lens 405 that can provide focusing of the passing ions, and an ion deflector 407 that can modulate the movement of the ion beam from the chamber 400 to the chamber 402. An ion collector electrode 409 is positioned downstream of the ion deflector 407 to capture ions deflected by the ion deflector 407.

[0041] 4C and 5A, in this embodiment, the ion deflector 407 includes two conductive electrodes 407a and 407b that are electrically isolated from each other and separated to form a slit 407c between them through which ions can pass. As an example, as shown in FIG. 5A, an electrically insulating gasket can help maintain the two conductive electrodes of the ion deflector 407 between the two chambers of the mass spectrometer while providing electrical insulation between the conductive electrodes as well as a vacuum seal between these chambers. A voltage difference applied between the ion lens 405 and the combination of the ion deflector 407 and ion collector electrode 409 can be used to modulate the movement of ions through the ion deflector 407.

[0042] 4A, voltage source 410a can apply DC voltage 1 to the ion lens 405, and DC voltage source 410b can apply DC voltage 2 to the combination of the ion deflector 407 and ion collector electrode 409. Although two separate voltage sources are shown in this embodiment, the application of DC voltages to the ion lens 405 and the combination of the ion deflector 407 and ion collector electrode 409 can be accomplished via a single voltage source, for example a single voltage source having two DC power sources.

[0043] A controller 412 in communication with voltage sources 410a / 410b can control those voltage sources to adjust voltage 1 and voltage 2. For example, the controller can effect adjustment of voltages 1 and 2 to control transmission of ion beam IB from chamber 401 to chamber 402.

[0044] 4A, the controller 410 can cause the voltage sources 410a / 410b to apply the same DC voltage to the ion lens 405 and the combination of the ion deflector 407 and ion collector electrode 409 (i.e., voltage 1 = voltage 2). In this state, the ion beam IB passes undeflected through the ion deflector assembly 404 and into the chamber 402.

[0045] In contrast, as shown in FIG. 4B, the controller 410 can send control signals to voltage sources 410a and 410b to apply different voltages to the ion lens 405 and the combination of the ion deflector 407 and ion collector electrode 409 to cause a deflection of the ion beam sufficient to substantially block its passage into the chamber 402. The deflection angle required to substantially block the passage of the ion beam into the chamber 402 can vary depending on system specific factors such as, among others, geometric factors including, but not limited to, the axial separation between the outlet of the chamber 400 and the inlet of the chamber 402. Generally, in embodiments, the ion deflector assembly can be used to cause a deflection of the ion beam at a deflection angle ranging from about 5 to about 60 degrees, although other deflection angles can be used.

[0046] Furthermore, rather than inhibiting the movement of the ion beam between the two chambers, the voltage difference applied across the ion lens 405 and the combination of the ion deflector 407 and ion collector electrode 409 can be adjusted to inhibit the passage of some of the ions into the chamber 402 while allowing other ions in the ion beam to reach the chamber 402 substantially undeflected, thereby modulating the intensity of the ion beam as it enters the chamber 402 from the chamber 400. As an example, the deflection voltage difference between the combination of the ion lens 405 and the ion deflector 407 can be selected such that the deflection angle is small enough, e.g., less than about 5 degrees, such as 1 degree, such that some of the ions are prevented from entering the chamber 402 while other ions in the beam continue to reach the downstream chamber 402.

[0047] 5B shows an example of using the ion deflector assembly 404 to modulate the transmission of ions between the chambers 400 and 402 by periodically varying the voltage difference between the lens 405 and the combination of the ion deflector 407 and ion collector electrode 409. In some embodiments, the modulation can be performed at a duty cycle, for example in the range of about 0.1 to about 1. In other embodiments, the ion deflector 407 can have other shapes.

[0048] 6A, by way of example, shows diagrammatically such an ion deflector 1000 comprising two plates 1000a / 1000b separated from one another to provide between them a passage 1001 through which ions can pass. Application of a DC voltage across these plates can generate an electric field that can cause deflection of ions as they pass through the passage 1001.

[0049] In some embodiments, the length of the plates 1000a / 1000b and the applied voltages can be selected to allow the deflected ions to exit the passageway and be captured as needed, for example by an ion collector electrode as described above. In other embodiments, the length of the plates and the applied electric field can be selected so that the deflected ions (or at least a portion of them) do not strike one of the plates and therefore exit the ion deflector.

[0050] FIG. 6B is a partial schematic diagram of a mass spectrometer according to an embodiment of the present teachings in which a deflection gate 1002 incorporating the aforementioned deflector 1000 is positioned between an upstream ion guide 1 located in a vacuum zone 1 and a downstream ion guide 2 located in a vacuum zone 2 to allow for regulating the passage of an ion beam 1005 from ion guide 1 to ion guide 2. In this embodiment, an aperture lens 1005 is positioned upstream of the ion deflection plates 1000a / 1000b of the ion deflector 1000. An aperture 1005a provided in the ion lens 1005 can allow ions to pass through the ion lens. As described herein, a voltage source operating under the control of a controller (not shown in this figure) can modulate the DC voltage difference applied across the deflection plates 1000a / 1000b, thereby modulating the passage of the ion beam from ion guide 1 to ion guide 2. For example, a DC voltage difference applied across the ion deflection plates can deflect an ion to block its passage into ion guide 2 for a certain period of time.

[0051] In some implementations, a periodic modulation of the DC voltage difference applied between the plates can provide a periodic modulation of the intensity of the ion beam passing between ion guide 1 and ion guide 2.

[0052] 6C shows a schematic of an ion deflector 2000 according to another embodiment of the present teachings, including two ion deflection plates 2000a and 2000b. This embodiment shows an end view with the deflection plates (2000a and 2000b) positioned adjacent to an aperture / lens (2001). When a potential difference is applied between the deflection plates (2000a and 2000b), ions will not be transferred beyond this device. Having a common potential will cause ions to be transferred to the next stage of the ion path.

[0053] 6D shows a schematic diagram of an ion deflector 2000 according to an embodiment of the present teachings, which is positioned between two vacuum zones 1,2 (each of which may be in the form of a vacuum chamber) to change the propagation direction of an ion beam between two ion guides 1,2 positioned in the vacuum zones 1,2, respectively. The ion deflector 2000 includes four conductive electrodes 2001 / 2002 / 2003 / 2004 separated from each other to provide two orthogonal slits 2000a / 2000b through which ions can pass. Each conductive electrode of the ion deflector is electrically insulated from the other conductive electrodes (e.g., via a dielectric gasket 2005 disposed in a groove surrounding the conductive electrode). In this embodiment, the conductive electrodes have the same size and shape (they are wedge-shaped) and are positioned relative to each other such that their upper surfaces lie in a single plane and the ion deflector is symmetric about a 90 degree rotation about an estimated axis passing through its center and perpendicular to said single plane.

[0054] The DC voltage applied to the conductive electrodes of the ion deflector 2000 can be adjusted under the control of a controller such as that disclosed herein, for example, to deflect the ion beam in a desired direction (e.g., up, down, right or left) as the ions pass through the slits 2000a / 2000b.

[0055] For example, when the voltages 1, 2, 3 and 4 applied to the conductive electrodes 2001 / 2002 / 2003 / 2004 of the ion deflector are equal, the ion beam passes through the ion deflector without deflection. Typically, the ion guide 2 is aligned with respect to the ion deflector such that the ion beam passes through the center of the ion beam deflector (i.e., the intersection of the two slits) when the voltages applied to the conductive electrodes of the ion deflector are equal. As an example, to steer a positive ion beam propagating through ion guide 1 toward the ion guide 2 beam to the right, the magnitudes of the voltages applied to the conductive electrodes of the ion deflector can be equal to voltages V1 and V2 with positive polarity, and voltages V3 and V4 with negative polarity.

[0056] In contrast, to steer the ion beam to the left, the voltages V1, V2, V3, and V4 may have the same magnitude as the voltages V3 and V4 with positive polarity and the voltages V1 and V2 with negative polarity. To steer the ion beam in an upward direction, the magnitudes of the voltages V1, V2, V3, and V4 may be the same as the voltages V2 and V3 with positive polarity and the voltages V1 and V4 with negative polarity, and to steer the ion beam in a downward direction, the magnitudes of the voltages V1, V2, V3, and V4 may be the same as the voltages V1 and V4 with positive polarity and the voltages V2 and V3 with negative polarity.

[0057] The ion deflector 2000 allows the direction of ion deflection to be changed from time to time. More specifically, the ion deflector allows the ion beam to be deflected along each of four directions: left, right, up, and down. In some embodiments, by changing the direction of ion deflection from time to time, potential contamination and their adverse effects caused by the deflected ions can be minimized and preferably eliminated. As an example, a controller operable to the ion deflector 2000 can be programmed to modify the deflection of the ion beam between the above four directions, for example, to change the pattern of voltages applied to the four conductive electrodes of the ion deflector based on a predetermined time schedule.

[0058] As a further illustration, Figure 6E shows a schematic of an ion deflector 3000 positioned between ion guide 1 and ion guide 2. As in the previous embodiment, ion guides 1 and 2 are typically located in vacuum zones 1 and 2 maintained at different pressures. In this embodiment, the ion deflector 3000 includes two rods 3001 / 3002 that are separated and electrically insulated from each other to allow for application of independent voltages. In this embodiment, an ion lens 3003 is positioned upstream of the ion deflector 3000 to facilitate the propagation of the ion beam from ion guide 1 to ion guide 2 via the passage between the two rods 3001 / 3002 of the ion deflector 3000.

[0059] The voltage difference applied between the two rods 3001 / 3002 can be adjusted to modulate the propagation path of the ion beam. As an example, when the voltages V1 and V2 applied to the rods 3001 and 3002, respectively, are equal (i.e., the voltage difference between the two rods is zero), the ion beam passes through the ion deflector without being deflected. To deflect the ion beam upwards so that the ion beam of positive polarity passes through the ion guide 1 and reaches the ion deflector, the voltages V1 and V2 may have the same magnitude with positive and negative polarities, respectively. In contrast, to deflect the ion beam downwards, the voltages V1 and V2 may have the same magnitude with negative and positive polarities, respectively. It should be understood that other configurations of voltages can also be utilized to achieve the desired deflection (steering) of the ion beam. For example, the magnitude of the applied voltages may be different.

[0060] Ion deflectors according to the present teachings can be incorporated into a variety of mass spectrometers. By way of example, and referring to FIG. 7, a mass spectrometer 100 according to an embodiment of the present teachings includes an ion source 104 that receives a sample from a sample source 102 and generates a plurality of ions that are introduced into a chamber 14 that is evacuated via a port 15.

[0061] At least a portion of the ions pass through the orifices 31 in the orifice plate 30 and enter the chamber 121 in which the ion guide 140 (also referred to herein as a QJet® ion guide) is located.

[0062] The chamber 121 can be maintained at a pressure ranging, for example, from about 1 Torr to about 3 Torr. The QJet® ion guide includes four rods (two of which 130 are visible in the figure) arranged according to a quadrupole configuration to provide passages between them through which ions can pass. RF voltage can be applied to the rods of the QJet® ion guide, for example, via capacitive coupling to a downstream ion guide Q0, described further below, or via an independent RF voltage source, to radially confine the ions and to focus the ions for transmission to a downstream chamber 122 in which an ion filter 108 according to an embodiment of the present teachings is located.

[0063] 4A and 4B, is positioned between vacuum chamber 122 and vacuum chamber 121 and serves to regulate the movement of ions between vacuum chamber 121 and vacuum chamber 122. In particular, as previously described, a voltage difference applied between the ion deflector and an upstream lens can be used to allow or prevent the passage of ions from vacuum chamber 121 to vacuum chamber 122.

[0064] Chamber 122 may be maintained at a lower pressure than that at which chamber 121 is maintained. By way of example, chamber 122 may be maintained at a pressure in the range of about 2 mTorr to about 15 mTorr. In this embodiment, ion guide Q0 is positioned within chamber 122. Ion guide Q0 includes a number of rods (not shown) arranged in a multipole configuration. An RF voltage source 197 applies an RF voltage to the rods of the Q0 ion guide to provide radial confinement of passing ions.

[0065] In this embodiment, DC voltage source 193a applies a DC voltage to the ion lens of the ion deflector assembly 107 (see ion lens 405 above) and DC voltage source 193b applies a DC voltage to the combination of the ion deflector and ion collector electrodes of the ion deflector assembly (see ion deflector 407 and ion collector electrodes 409). In some embodiments, a DC voltage source can also be used to apply a DC voltage to the rods of the Q0 ion guide, for example to generate a voltage difference between the QJET ion guide and the Q0 ion guide, to accelerate ions exiting the QJET ion guide towards the Q0 ion guide.

[0066] The controller 3000 controls the operation of the RF voltage source 197, and the DC voltage sources 193a and 193b. In particular, the controller can control the operation of the DC voltage sources 193a and 193b to modulate the transmission of ions between the vacuum chambers 121 and 122, for example, as described herein.

[0067] Mass analyzer Q1 110 receives ions that have passed through ion guide Q0 via ion lens IQ1 and one short, stubby lens ST1. In this embodiment, mass analyzer Q1 110 includes four rods arranged in a quadrupole configuration to which RF and / or DC voltages can be applied to select ions having m / z ratios within a target range. Ions propagating through mass analyzer Q1 110 (referred to herein as precursor ions) pass through stub lens ST2 and ion lens IQ2 to reach collision cell 112 (q2).

[0068] At least some of the precursor ions are fragmented in the collision cell 112, generating multiple product ions. The product ions pass through an ion lens IQ3 and a short, stubby lens ST3 to reach another downstream mass analyzer Q3. In this embodiment, the mass analyzer Q3 includes four rods arranged in a quadrupole configuration and can be applied with RF and / or DC voltages to allow the passage of product ions having an m / z ratio of interest. The product ions that pass through the mass analyzer Q3 pass through an exit lens 115 and are detected by an ion detector 118. In some embodiments, the quadrupole mass analyzer Q3 can be replaced with a time-of-flight (ToF) mass analyzer or any other suitable mass analyzer. The analysis module 119 can receive the detection signals generated by the ion detector 118, process the signals, and generate a mass spectrum of the detected ions.

[0069] A controller 3000 in communication with voltage sources 193a and 193b can control these voltage sources to adjust the voltages applied to the ion lenses and combination ion deflector and ion collector electrodes to modulate the passage of the ion beam between the QJET and Q0 ion guides, as described above. The controller 3000 can also control the operation of the RF voltage sources. Additionally, in embodiments where voltage sources 193a and / or 193b are used to apply DC voltages to the mass analyzer ion guides and / or mass analyzer rods, the controller 3000 can also control the voltage sources to adjust the voltages applied to those devices.

[0070] 9A and 9B, in some embodiments, an ion deflector 900 can be utilized that includes a single conductive electrode 901, e.g., a metal electrode such as those disclosed above, having a notch 902 through which an ion beam 903 can pass. As described in more detail below, the single conductive electrode 901 can be positioned downstream of an ion lens, and a voltage applied to the single conductive electrode 901, e.g., via a DC voltage source operating under the control of a controller, can be adjusted to allow the ion beam to pass undeflected or to cause a deflection of the ion beam. The conductive electrode 901 can be positioned below or above the ion beam and can be biased by applying a DC voltage to it to deflect the ion beam, e.g., upwards or downwards, away from the electrode.

[0071] The conductive electrode 901 can be biased by applying a DC bias voltage to repel the ions in the beam as they pass through, thereby deflecting the ion beam from the electrode, as shown diagrammatically in FIG. 9B. One advantage of such an embodiment is that it reduces, and preferably eliminates, contamination of the ion deflection electrodes by the deflected ions. In other words, in this embodiment, rather than utilizing both "push" and "pull" electrodes to cause the deflection of the ion beam, only the "push" electrode is utilized. This can eliminate potential contamination of the "pull" electrode by ion bombardment.

[0072] As an example, the embodiment shown in FIG. 4A can be modified to replace the ion deflector 407 having conductive electrodes 407a and 407b as shown in FIG. 4C with only one of those conductive electrodes (e.g., conductive electrode 407a or conductive electrode 407b as shown diagrammatically in FIG. 9A and FIG. 9B). In such a modified embodiment, a DC voltage source, e.g., DC voltage source 410a, operating under the control of controller 412 can adjust the bias DC voltage applied to conductive electrode 901. For example, the conductive electrode can be maintained at the same DC voltage as the upstream ion lens 405 to allow the ion beam to pass over or under the conductive electrode without being deflected. The DC bias voltage can be changed to cause a deflection of the ion beam away from the conductive electrode when ion beam deflection is desired.

[0073] 9C and 9D, in some embodiments, the single conductive electrode may be in the form of a conductive bar 910 or conductive wire 912. As described herein, application of a DC bias voltage to the conductive bar 910 or conductive wire 912 may cause deflection of the ion beam 903 passing over or under the conductive bar or wire. By way of example, the conductive bar 910 may have a square cross-sectional profile with a length ranging from about 1 mm to about 50 mm and a width / thickness ranging from about 0.1 mm to about 10 mm. In some embodiments, the conductive wire 912 may have a diameter of about 0.5 mm, by way of example. Other shapes may be utilized, so long as the conductive electrode is capable of causing deflection of the ion beam by application of a DC bias voltage to the electrode.

[0074] The controller 3000 can be implemented in hardware, firmware, and / or software using techniques known in the art as informed by the present teachings.

[0075] By way of example, FIG. 8 illustrates generally one example of an implementation of such a controller 500 including a processor 500a (e.g., a microprocessor), at least one persistent memory module 500b (e.g., a ROM), at least one transient memory module (e.g., a RAM) 500c, and a bus 500d, among other elements commonly known in the art.

[0076] The bus 500d enables communication between the processor and various other components of the controller. In this example, the controller 500 may further include a communication module 500e configured to enable transmission and reception of signals.

[0077] Instructions used by the controller 500, for example to adjust the DC voltage applied to the auxiliary electrodes, can be stored in the persistent memory module 500b and transferred to the transient memory module 500c during run-time for execution. The controller 500 can also be configured to control the operation of other components of the mass spectrometer, such as the ion guide and mass analyzer, among others.

[0078] The present teachings can provide advantages over conventional techniques for adjusting the intensity of an ion beam. For example, modulation of an ion beam using the present teachings can provide a more uniform ion beam than conventional pulsing techniques used to reduce the intensity of an ion beam, for example, as the ion beam passes from one ion chamber to a downstream chamber, while reducing, and preferably eliminating, contamination of ion optics located between the two chambers.

[0079] As will be appreciated by those skilled in the art, various modifications can be made to the above-described embodiments without departing from the scope of the present teachings.

Claims

1. 1. A mass spectrometer, comprising: an ion path through which the ion beam can propagate; an ion beam deflector positioned within the ion path, the ion beam deflector configured to modulate travel of an ion beam received from an upstream section of the ion path to a downstream section thereof, the ion beam deflector comprising at least one conductive electrode; at least one DC voltage source operably coupled to the at least one conductive electrode for application of DC to the at least one conductive electrode; a controller in communication with the at least one DC voltage source; Equipped with the at least one DC voltage source modulates a DC voltage applied to the at least one conductive electrode to transition the DC voltage applied to the at least one conductive electrode between a first level at which the ion beam passes through the ion deflector substantially undeflected and a second level at which the ion beam is deflected from the ion path.

2. 10. The mass spectrometer of claim 1, further comprising at least one beam collection electrode positioned downstream of the ion beam deflector for collecting the deflected ion beam.

3. 10. The mass spectrometer of claim 1, further comprising at least one vacuum chamber within which at least a portion of the ion path is disposed.

4. 4. The mass spectrometer of claim 3, wherein the at least one vacuum chamber comprises a first vacuum chamber and a second vacuum chamber positioned downstream from the first vacuum chamber, the first vacuum chamber and the second vacuum chamber being differentially pumped to be maintained at different pressures.

5. 5. The mass spectrometer of claim 4, wherein the beam deflector is positioned between the two vacuum chambers.

6. 6. A mass spectrometer according to claim 1, further comprising an ion lens arranged upstream of the ion deflector.

7. 7. The mass spectrometer of claim 6, wherein the ion lens comprises an aperture through which the ion beam can pass.

8. 8. The mass spectrometer of claim 7, wherein the controller is configured to cause the at least one DC voltage source to adjust a DC voltage applied to the at least one conductive electrode between a first level in which the at least one conductive electrode and the ion lens are maintained at the same potential, allowing the ion beam to pass undeflected through the ion beam deflector, and a second level in which the at least one conductive electrode and the ion lens are maintained at a different potential, causing the ion beam to be deflected as it passes through the ion beam deflector.

9. 9. The mass spectrometer of claim 8, wherein the DC potential at the second level is selected to cause deflection of the ion beam at an angle in the range of about 5 degrees to about 60 degrees relative to the ion path.

10. 2. The mass spectrometer of claim 1, wherein the at least one conductive electrode comprises at least two conductive electrodes positioned relative to one another to provide an opening through which the ion beam can pass, and optionally the two conductive electrodes comprise two conductive electrodes of an ion lens separated from one another to form a gap, and the ion beam can pass through the gap between the two conductive electrodes.

11. 11. The mass spectrometer of claim 10, wherein the controller is configured to cause the at least one DC voltage source to apply substantially similar DC voltages to the two electrodes to allow the ion beam to pass substantially undeflected through the ion beam deflector.

12. 11. The mass spectrometer of claim 10, wherein the controller is configured to cause the at least one DC voltage source to apply a DC potential difference between the two electrodes to cause deflection of the ion beam at an angle in a range of about 5 degrees to about 60 degrees relative to the ion path.

13. 5. The mass spectrometer of claim 4, wherein the first chamber is maintained at a pressure in the range of 0.1 Torr to about 10 Torr.

14. 14. The mass spectrometer of claim 13, wherein the second chamber is maintained at a pressure in the range of about 0.001 Torr to about 0.1 Torr.

15. 10. The mass spectrometer of claim 1, wherein the controller is configured to modulate the voltage applied to the ion beam deflector to modulate passage of the ion beam through the ion beam deflector with a duty cycle in the range of about 0.1 to about 1.

16. 5. The mass spectrometer of claim 4, wherein the second level of the DC voltage is configured to deflect the ion beam and substantially prevent passage of the ion beam into the second chamber.

17. 10. The mass spectrometer of claim 1, wherein the at least one conductive electrode has a hemispherical shape, and the at least one conductive electrode comprises a conductive plate.

18. 5. A mass spectrometer as claimed in claim 3 or claim 4, further comprising an ion guide disposed within the at least one vacuum chamber.

19. 20. The mass spectrometer of claim 18, wherein the ion guide comprises a plurality of rods disposed within the vacuum chamber, the rods arranged in a multipole configuration to provide a passageway for passage of the ion beam.

20. 20. The mass spectrometer of claim 19, further comprising an RF voltage source for applying an RF voltage to the rods to generate an electromagnetic field, the electromagnetic field configured for radial confinement of ions in the ion beam as the ions pass through the passage.

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