Apparatus for trapping ions

Abstract

To address the problems of space charge effects caused by dense ion packets within analyzers.SOLUTION: A control circuit is configured to: apply a set of oscillatory voltages to an array of electrodes so as to repel ions from the array of electrodes, where each electrode in the array of electrodes has a different phase than each adjacent electrode; apply a trapping voltage to at least one of the one or more further electrodes so as to force the ions towards the array of electrodes, the set of oscillatory voltages and the trapping voltage thereby trapping the ions within the trapping region; cease the application of the set of oscillatory voltages to the array of electrodes during a delay period; apply a focusing voltage to at least one of the one or more further electrodes during the delay period so as to force the ions towards the array of electrodes; and apply an extraction voltage to at least one electrode in the array of electrodes and / or the one or more further electrodes after the delay period so as to extract the ions from the trapping region.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present disclosure relates to an apparatus for trapping ions. [Background technology]

[0002] An extraction trap is a device coupled to a mass analyzer that accumulates and traps ions from an ion source, such as a continuous or pulsed ion source. Extraction traps typically collisionally cool the ions, compress them into packets of favorable spatial and energy characteristics, and then pulse extract the ions into the analyzer. Extraction traps have been paired with many different types of analyzers, including magnetic analyzers (Mather et al., International Journal of Mass Spectrometry and Ion Physics, 1978, 28, 347-364), time-of-flight analyzers (Chien et al., Rapid Communications in Mass Spectrometry, 1993, 7, 837-843), quadrupole analyzers (Bonner et al., International Journal of Mass Spectrometry and Ion Physics, 1972, 10, 197-203) and Fourier transform analyzers (e.g. orbital trap mass analyzers such as the Orbitrap™ (U.S. Pat. No. 7,425,699 B2)).

[0003] Historically, the most common extraction trap was the 3D quadrupole ion trap or Paul trap described in U.S. Patent No. 2,939,952 (A) and shown coupled to a time-of-flight analyzer in U.S. Patent Nos. 5,569,917 (A), 6,803,564 (B2), and 6,380,666 (B1). Figure 1 shows the modern layout of a quadrupole ion trap that serves as the ion source for a reflectron time-of-flight analyzer, whereby high voltages applied to either end of the trap eject ions. Ions travel along the length of the analyzer before being reflected by a reflectron or ion mirror and focused onto an ion detector.

[0004] Paul traps suffer from low trapping efficiency because ions are injected across a high RF field and there is little distance to allow them to be sufficiently cooled and trapped. Paul traps also suffer from strong space charge effects because all ions are focused to a single point. Strong space charge effects are a problem for both analytical traps and time-of-flight analyzers, which rely on very strictly defined ion packet characteristics for optimal focusing and high resolution.

[0005] 3D traps have been largely supplanted by linear ion traps, typically assemblies of elongated RF multipole rods capped by terminal poles DC that use RF pseudopotentials to radially focus ions and trap ions axially via terminal poles DC (Donald J. Douglas et al., Mass Spectrometry Reviews, 2004, 24, 1-29). These advantages are higher trapping efficiency when ions are injected along the longitudinal axis, allowing space for collisional cooling, and a typically 30-50 times improvement in space charge capacity when ion packets are allowed to spread along said axis. Space charge capability can be improved by higher order multipole trapping fields such as the hexapoles shown by Franzen in US Patent 5,763,878(A), but these have the disadvantage of spreading ions along the time-of-flight (ToF) axis, resulting in relatively poor focusing properties upon pulse extraction.

[0006] Additional ion guide / trap structures exist in the form of "RF carpets". In RF carpets, a series or array of closely packed electrodes, each with a different (e.g., opposite) RF amplitude from the adjacent electrodes, form a pseudopotential barrier across the surface over which the electrodes span. Ions may be pinned against this pseudopotential surface by DC electrodes attached opposite the array of electrodes, and the ions diffuse across the area. Ions may also be transported across the RF carpet, for example, by a DC gradient or a traveling wave superimposed on the RF electrodes (G. Bollen, Int. J. Mass. Spectrom, 2011, 299, 131-138). The SLIM (Structures for Lossless Ion Manipulations) family of PCB printed RF surface devices also includes DC barrier electrodes and switches implemented in an integrated manner with the RF electrodes on the same surface (US Patent Application Publication No. 20190103261(A1)).

[0007] The ideal initial ion packet shape for a time-of-flight analyzer is a thin disk, which maximizes the volume for space charge without compromising the small ToF axial spatial distribution required for narrow extracted ion time focus and corresponding high instrument resolution. As the ions spread over the length and width of the RF carpet, they form a wide, flat packet, which is particularly suitable for ToF applications, whose thickness is determined by the strength of the counter DC and the strength of the exponential rise of the RF pseudopotential in close proximity to the RF electrodes. This latter factor can be increased by increasing the density of the electrodes in series to lithographic scale, but this also brings the ions very close to the physical surface, with the resulting risk of charging and mechanical tolerances.

[0008] Whitehouse in US Pat. Nos. 6,683,301 (B2) and 7,365,317 (B2) describes how an RF carpet or surface can be configured to act as an extraction trap. US Pat. No. 8,373,120 shows a similar system. Figure 2 reproduces the proposed layout of the device in US Pat. No. 6,683,301 (B2). In this document, ions are injected onto an RF carpet formed of a 2D array of electrodes and are pinned to the array via opposing DC from a grid-like counter electrode placed above. Ions can then be pulsed through the grid into a time-of-flight analyzer by a high voltage applied to both the grid and the RF surface electrode.

[0009] Figure 1 shows a typical trap-reflectron ToF instrument layout, but multiple reflection time-of-flight analyzers are also relevant, where ions are directed along tightly folded, very elongated flight paths. Such instruments are typically capable of significantly higher resolution than single reflection analyzers, but often suffer from severe space charge problems, as reported by Grinfeld (D. Grinfeld, AE Giannakopulos, I. Kopaev, A. Makarov, M. Monastyrskiy, M. Skoblin, Eur. J. Mass Spectrom. 2014, 20, 131-42). An example of a notable analyzer fed by a linear ion trap is described by Grinfeld in US Pat. No. 9,136,101 (B2), and the complete instrument configuration is shown by Hock in US Pat. No. 10,593,525 (B2). This device extracts ions from a linear ion extraction trap and directs them to oscillate between a pair of elongated ion mirrors. The oscillating ion packets are allowed to drift and expand along the length of the mirrors, which helps reduce space charge effects. The mirrors are tilted relative to one another to create a retarding potential that reflects and redirects the ion packets back to a detector located adjacent to the extraction trap.

[0010] However, even with this space charge limiting feature, the effect of raw space charge on the ion packet remains substantial, and resolution is significantly reduced at around 1500 ions in the packet. Furthermore, if the pseudopotential well depth of the extraction trap is limited and ions are allowed to diffuse into the trap, the tolerance of resolution versus ion number increases substantially. The best of the resolution is substantially compromised, as the expansion of the ion cloud also interferes with the focusing properties. Similarly, the mirror system can be retuned to optimize the level of space charge, but again at the expense of the highest level of resolution performance. It would be desirable to have less of a compromise between space charge and resolution, or to have a much larger accessible space charge range. Figure 3 shows how the MR-ToF resolution and space charge trends change with different linear trap well depths.

[0011] An important feature of extraction traps is that they operate rapidly, processing different injected ion packets into a thermalized cloud and extracting them into the analyzer at competitive acquisition rates significantly greater than 100 Hz for current time-of-flight instruments. This requires the use of relatively high gas pressures in the trap, typically >2 × 10, to rapidly cool the ions injected with kinetic energies of about 7 eV. -3 mbar. However, such pressures cause significant gas leakage into the analyzer, a problem exacerbated by the large open area of ​​the extraction grid in RF carpet traps. A known solution is to rapidly pre-cool the ions in a high pressure region of the trap adjacent to the extraction region, and then move the ions across the gas restriction at relatively low energy, requiring a much lower pressure to adequately thermalize. Giles et al. in US Patent Application Publication No. 20190103263(A1) described a segmented linear quadrupole trap with two such pressure regions and an interface segment with a smaller radius that effectively restricts gas movement without acting as a barrier to ion movement.

[0012] Trap-ToF instruments suffer greatly from space charge effects when many ions of similar m / z are present: as the number of ions in a packet increases, the resolution collapses rapidly and there is often a significant shift in the measured average m / z.

[0013] A further detrimental effect is the overall expansion of the ion cloud when the total number of ions in the trap exceeds the threshold defined by the RF pseudopotential well. When this happens, poorly trapped higher m / z ions are forced outside the trapped ion volume and can suffer substantial resolution degradation, mass shifts, and sensitivity losses caused by trapping and transmission failures.

[0014] There are several ways to increase the trap space charge capacity, essentially by increasing the trap volume. Larger traps, or traps with higher order multipoles, can trap many more ions than Paul traps, but if this increase is accompanied by an increase in ion spatial diffusion in the ToF flight axis, the focusing properties of the extracted ion packets will be compromised and the instrument resolution will be compromised.

[0015] Of particular importance is the shift from a 3D trap to an elongated linear ion trap to allow for the expansion of the ion cloud in one dimension orthogonal to the analyzer axis, i.e., the expansion of the space charge volume without compromising resolution. The next step, which allows ions to expand in both orthogonal dimensions, is achieved via RF surfaces, as described by Whitehouse in US Patents 6,683,301 (B2) and 7,365,317 (B2).

[0016] A drawback of such RF surfaces is that the trapped ion surface is located at the point where the pseudopotential is strong enough to balance the repulsive force from DC, so that ions of different m / z are located at different distances from the RF surface. For time-of-flight analyzers, the pseudopotential strength is mass-dependent and therefore induces a mass-dependence in the position of the time focus (i.e., m / z shift), which can cause problems that have not been addressed or recognized in the art. A further problem is that large planar surfaces require large extraction grids, which inevitably causes much more gas to leak into the analyzer from a gas-filled trap than occurs in a linear or 3D trap.

[0017] One known technique for expanding the ion cloud in an extraction source is "delayed extraction". Originally, this was for laser-based technologies such as MALDI ion sources, where benefits were found for a delay between the laser pulse and the application of the extraction field. These techniques include the reduction of non-ionized material in the MALDI plume, which would otherwise collide with energetic analyte ions and generate fragmentation, and in the ion source, creating a relationship between ion energy and spatial position that can be focused by the extraction field for high resolution, and the expansion of the ion cloud also reduces the effects of space charge. In the case of RF traps, delayed extraction typically means a delay between the quenching of the RF and the application of the extraction field, for example to manipulate the ion phase space as in US Pat. No. 9,595,432 (B2), or to allow time for the RF to be more fully quenched.

[0018] Solutions within the analyzer itself have also been proposed. The MR-ToF analyzer of US Pat. No. 9,136,101 (B2) is specifically designed to allow the ion cloud to expand to limit space charge effects, but in practice it still suffers greatly from space charge effects, making such designs more vulnerable to mechanical errors than analyzers with tightly focused beams. Lenses may be used to expand the extracted ion beam, but this is done somewhere after extraction, where space charge effects already start to have an impact, and the analyzer components can be made larger to accommodate the expanded beam. The analyzer focusing elements may also be tuned to tolerate space charge, but this also typically involves substantial sacrifice of low space charge performance, potentially damaging the instrument.

[0019] One object of the present disclosure is to address the problem of space charge effects caused by high density ion packets in an analyzer (e.g., a time-of-flight analyzer), which can impair resolution and mass accuracy and are related to the initial charge density. Another object of the present disclosure is to address the other problems mentioned above. Summary of the Invention

[0020] Against this background, there is provided an apparatus for trapping ions according to claims 1, 11 and 19. For example, numerous types of ion traps are provided, with embodiments relating to RF carpet extraction traps with one or more of a dual pressure trapping region, a tilted trapping field during ion injection, and / or delayed extraction of ions after the RF field is quenched. Certain embodiments address issues relating to the efficiency of trapping and transport of ions within the trap, as well as the loss of resolution across the m / z range when such traps are coupled to mass analyzers.

[0021] It should be noted that the various aspects of the invention can be combined. For example, the delayed extraction as claimed in any one of claims 1 to 11 may be implemented in combination with a DC trapping voltage whose magnitude increases with time as claimed in any one of claims 12 to 21 and / or a dual pressure apparatus for trapping ions as claimed in any one of claims 22 onwards. Similarly, the DC trapping voltage whose magnitude increases with time as claimed in any one of claims 12 to 21 may be implemented in combination with a dual pressure apparatus for trapping ions as claimed in any one of claims 22 onwards.

[0022] In some embodiments, the extraction of ions from the ion trap may be improved. For example, an embodiment recognizes that a particular problem with RF carpet extraction traps is that the RF pseudopotential strength of the RF carpet may be mass dependent, so that ions of different m / z are trapped in the trap at different distances from the RF surface. This may present a particular problem for extraction traps coupled to a time-of-flight mass (ToF) analyzer, because when ions are extracted from the trap to the ToF, ions with different m / z will have different starting positions in the trap and therefore different path lengths through the analyzer. Thus, a systematic m / z shift may be introduced by the trap. To address this problem, when ions are extracted from the ion trap, the RF on the RF carpet may first be quenched (i.e., turned off), and then an extraction pulse may be applied to the ion trap after an appropriate delay period has expired. During the delay period, ions of different m / z move into a spatial focus under the influence of a DC electric field (e.g., the original trapping electric field), so that when an extraction voltage (e.g., an extraction pulse) is applied to the trap, ions with different m / z will have substantially the same starting height in the trap. Thus, delayed extraction can be used to pre-focus ions of different m / z to align focal planes, which can reduce systematic errors in the m / z values ​​obtained from a ToF analyzer coupled to an ion trap as described herein, thus providing an improved ion trap that emits a planar ion cloud.

[0023] Furthermore, the present disclosure recognizes that another problem with RF carpet extraction traps is that ions entering the trap may be accelerated into the RF electrodes by the DC trapping field. Loss of ions may be undesirable. To address this problem, the DC voltage may be set to a low value while ions are injected into the trap, and then increased or ramped over a period of time as the ions cool in the trap. A gradual or slow increase or ramp of the trapping voltage after ion injection can be used to limit the energy pickup by the ions and gradually compress the ions onto the RF carpet. This can reduce the risk of ion loss due to collisions with the RF carpet.

[0024] In addition, some embodiments of the present disclosure relate to a dual pressure RF carpet extraction trap. That is, some embodiments provide an extraction trap with regions of different pressures. For example, a gas restrictor, which may include an opening (e.g., a slot for allowing ions to pass through), may be suspended from the top plate of the device for trapping ions. This can facilitate a simple construction and allow the RF electrodes to extend unhindered across the opposing bottom substrates of the RF carpet trap. In addition, the top plate in the trapping region (e.g., in the high pressure region of the trapping region) may be formed with a wedge shape, which can enable effective lateral focusing of ions into a small gas limiting aperture. Such a dual pressure extraction trap may be built on a PCB top plate with a gas restrictor suspended therefrom.

[0025] Some embodiments of the present disclosure relate to the provision of one or more barrier electrodes positioned around the trapping region. Such barrier electrodes may be located on or extend from the lower surface of the trapping region (e.g., the surface on which the array is provided, described herein as the first surface). A barrier voltage may be applied to such barrier electrodes to trap ions within the trapping region. Such trapping may be provided by DC electrodes, or RF electrodes, or electrodes supplied with a combination of DC and RF. In addition to or instead of barrier electrodes positioned on the lower surface, it may also be advantageous to trap around the plane of the RF carpet via DC electrodes on the top plate.

[0026] In some aspects of the disclosure, there may be provided an apparatus for trapping ions, the apparatus comprising: an array of electrodes extending along a surface (which may be referred to as a first surface) of the apparatus; one or more further electrodes distinct from the array of electrodes; a trapping region for receiving ions defined by the array of electrodes and the one or more further electrodes; and a control circuit configured to: apply a set of oscillating voltages to the array of electrodes, each electrode in the array of electrodes having a different phase with respect to each adjacent electrode, to repel ions from the array of electrodes, and apply a trapping voltage to at least one of the one or more further electrodes to force ions towards the array of electrodes, the set of oscillating voltages and the trapping voltage thereby trapping ions in the trapping region, the one or more further electrodes including one or more barrier electrodes positioned around the trapping region, the control circuit configured to apply the barrier voltages to the one or more barrier electrodes to trap ions in the trapping region. Such barrier electrodes may comprise DC electrodes positioned on the top plate, for example as electrodes surrounding the extraction region, and / or separate electrodes positioned around the trapping region.

[0027] Furthermore, the above-mentioned wedge-shaped electrodes can be used to provide a funnel effect in any type of device for trapping ions, and are not limited to dual pressure extraction traps.For example, in some aspects of the present disclosure, a device for trapping ions may be provided, comprising: an array of electrodes extending along a surface (which may be referred to as a first surface) of the device; one or more additional electrodes different from the array of electrodes; a trapping region for receiving ions defined by the array of electrodes and the one or more additional electrodes; and a control circuit configured to apply a set of oscillating voltages to the array of electrodes, each electrode in the array of electrodes having a different phase with respect to each adjacent electrode, to repel ions from the array of electrodes, and to apply a trapping voltage to at least one of the one or more additional electrodes to force ions toward the array of electrodes, the set of oscillating voltages and the trapping voltage thereby trapping ions in the trapping region, wherein the one or more additional electrodes comprise a funnel electrode, and the control circuit configured to apply a transport voltage to the funnel electrode. The funnel electrode may have a wedge shape, which can reduce the lateral separation of ions (ie, narrow the ion cloud) and provide improved ion transport.

[0028] Thus, the present disclosure provides various concepts to improve the trapping and transport of ions for RF carpet-based extraction traps. Some embodiments allow a large planar initial ion cloud suitable for extraction into a time-of-flight analyzer. A delayed extraction type process is described between RF quench (i.e., when the oscillating voltage is no longer applied to the RF carpet) and application of the extraction field, during which only a small DC field is applied, which allows the trapped ion planes of different m / z to be better aligned at the extraction point, thus reducing mass-dependent resolution loss. Furthermore, an ion loading mechanism is described that limits the energy uptake when injecting ions into the RF surface trap, and a dual pressure structure with a low pressure extraction region is proposed to limit gas leakage into the analyzer.

[0029] Throughout this disclosure, where a voltage is described as being applied to an electrode, it will be understood that a corresponding electromagnetic field is established. For example, where this disclosure describes, for example, applying an "extraction voltage" (or any other type of voltage) to one or more electrodes, it will be understood that this leads to a corresponding "extraction electric field" being caused by that extraction voltage. Similarly, where this disclosure describes, for example, applying an "RF field" or a "DC field," it will be understood that the control circuitry is configured to apply the appropriate RF or DC voltage to one or more electrodes to establish such field.

[0030] The above advantages and various other advantages will become apparent from the following description and the accompanying drawings. The present disclosure will now be described, by way of example only, with reference to the accompanying figures. [Brief description of the drawings]

[0031] [Figure 1] 1 shows a quadrupole ion trap functioning as a reflectron time-of-flight ion source. [Diagram 2] 1 illustrates a known RF carpet configured to act as an extraction trap. [Diagram 3] MR-ToF resolution and space charge for different linear trap well depths. [Figure 4A] 1 shows different embodiments of an apparatus for trapping ions; [Figure 4B] 1 shows different embodiments of an apparatus for trapping ions; [Figure 4C] 1 shows different embodiments of an apparatus for trapping ions; [Figure 4D] An alternative structure is shown. [Diagram 5] 1 illustrates an embodiment of a dual pressure apparatus for trapping ions. [Figure 6] 1 shows a further embodiment of a dual pressure device for trapping ions; [Figure 7]FIG. 1 shows a top view of an embodiment of a dual pressure apparatus for trapping ions. [Figure 8] 1 illustrates an embodiment of a mass spectrometry system. [Figure 9] 1 shows ion paths through a simulated device for trapping ions. [Figure 10] 1 shows the form of the pseudopotential calculated for a device for trapping ions. [Figure 11] 1 shows ion trajectories as the ions cool into the potential well over time. [Figure 12] 1 shows the simulated ion time diffusion after extraction. [Figure 13] 13 shows the focusing effect on ion position when using an extraction pulse that is delayed after the RF quench. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The present disclosure provides several different RF carpet. Various examples of the core structure of the RF carpet extraction trap 100 are shown in Figures 4A-4C. Such RF carpet extraction trap 100 is also described herein as a device for trapping ions or an ion trap.

[0033] FIG. 4A shows a basic embodiment of a device for trapping ions. The device comprises a series or array of RF electrodes 101+, 101- on a first surface, the lower surface of the device, to provide an RF carpet. The RF electrodes 101+, 101- extend in the x and y directions. A further electrode 102 (which may be a grid electrode) may be attached above the RF carpet on the second surface. A small repulsive DC is applied to the further electrode 102 during trapping, and a strong attractive DC is applied during ion extraction. Thus, the further electrode 102 acts as a trapping electrode 102 to which the control circuit 150 applies a trapping voltage during trapping (i.e. when the trapping voltage and the oscillation voltage are applied simultaneously to trap ions), and the electrode 102 acts as an extraction electrode 102 to which the control circuit 150 applies an extraction voltage to extract ions. The trap / extraction electrode 102 may also be described as a counter electrode 102.

[0034] The control circuit 150 is shown with dashed lines omitted for clarity, with connections to the various electrodes. It will be understood that each embodiment may include such a control circuit 150. The control circuit 150 may apply voltages to any electrodes and receive measurements from any sensors. The control circuit 150 may include logic for applying voltages to the various electrodes of the device of the present disclosure. The control circuit 150 may also perform certain actions (e.g., adjust the voltages on the electrodes) based on measurements received (e.g., charge measurements in the trapping region). The control circuit 150 may be formed using conventional techniques, and therefore will not be described in further detail for clarity and brevity.

[0035] In use, ions are trapped in a trapping region of the device. The trapping region is defined by the array of electrodes and one or more further electrodes. The surface on which the array of electrodes is disposed is preferably a substantially planar surface, but not necessarily completely two-dimensional or completely planar. The array of electrodes may extend in one or two directions. For example, the electrodes of the array may be positioned at various positions in the x and / or y directions. The individual electrodes of the array may be substantially one-dimensional or two-dimensional, in either case having a relatively small spatial extent (thickness or height) in the z direction. The array of electrodes may comprise a series of parallel line electrodes each extending in the y direction and spaced apart in the x direction. That is, the array itself may be one-dimensional, each electrode may be one-dimensional, and the electrodes of the array collectively extend over a two-dimensional surface. In some embodiments, the array may be a two-dimensional array of points at different (x,y) positions, with a small line (one-dimensional) electrode or a small planar (two-dimensional) electrode provided at each (x,y) position of the array. In this case, the electrodes of the array of electrodes again collectively extend across a portion of a two-dimensional surface (ie the lower surface on which the electrodes are disposed).

[0036] The height of the electrodes may be a small fraction (e.g., less than 10%, or less than 1%) of one or both of their widths. In the embodiment shown in Fig. 4A, the RF electrodes 101+, 101- and the counter electrode 102 are substantially planar and substantially parallel. The trapping region is therefore the region between the opposing first surfaces of the RF electrodes 101+, 101- and the second surface of the counter electrode 102. Ions are preferably trapped with a narrow distribution of heights (z values) in a plane parallel to the plane of the RF carpet parallel to the xy plane.

[0037] In PCB design, it is preferred that the electrodes of the array are substantially two-dimensional, although this is not required. For example, the RF surface may be constructed from interlocking teeth of two etched and / or cut metal electrodes. These can be made very deep for stability and can be provided without a heavy substrate. In some embodiments, the thick electrodes can be glued / screwed to the PCB (or attached using any other means) rather than printed, as in Figures 4B and 4C, to keep the ions away from the insulating surface.

[0038] FIG. 4D shows an example of an alternative structure of the array of bottom electrodes 104 that can be used in place of any of the embodiments of FIG. 4A, FIG. 4B, and FIG. 4C, and can also be used in subsequent embodiments. The structure of FIG. 4D can operate similarly to the embodiment of FIG. 4A-FIG. 4C. Each of the electrodes 104 is in the shape of a triangular prism and extends below the surface of the trapping region. Due to their tapered shape, the electrodes 104 appear in plan view as a one-dimensional array of linear electrodes. However, as seen in the perspective view of FIG. 4D, each electrode extends in the y-direction, but also has a substantial non-zero spatial extent in the z-direction. As shown in FIG. 4D, each electrode 104 may be embedded in a matrix 112 that replaces the PCB substrate 103 of FIG. 4A, FIG. 4B, and FIG. 4C.

[0039] Thus, in general terms, the electrodes of the array of the present disclosure may be described as extending along a surface that may be the inner surface of the trapping region. In some embodiments, this means that the electrodes may be disposed on a flat surface, as in Figures 4A, 4B, and 4C, and that the electrodes themselves are positioned on a flat surface and are substantially one-dimensional or two-dimensional. However, the electrodes of the array of electrodes may be a three-dimensional structure that extends along the surface (i.e., the electrodes may extend along the inner surface of the trapping region) and also extends below the surface, as shown in Figure 4D. The surface along which the electrodes extend may be described as the functional surface of the electrode, which may be substantially flat and planar and may be substantially parallel to the electrode(s) provided on the top surface of the device.

[0040] In operation, the RF electrodes 101+, 101- and the counter electrode 102 cooperate to trap ions. The control circuit 150 applies a set of oscillating (e.g., RF) voltages to the RF electrodes 101+, 101- to repel ions from the array, and each electrode in the array of electrodes may have a different phase relative to each adjacent electrode. The array of electrodes may have a spacing (e.g., the shortest distance between any two adjacent electrodes) of less than 5 mm, less than 3 mm, less than 1 mm, less than 0.1 mm, or less than 0.01 mm. Each electrode in the array of electrodes may have an opposite phase relative to each adjacent electrode. For example, each electrode may have the same frequency as each adjacent electrode, but with a 180 degree phase shift. The array of electrodes may be substantially planar.

[0041] The control circuit 150 also applies a trapping voltage to the counter electrode 102 to direct the ions towards the array of electrodes 101+, 101-. The trapping voltage may be activated or applied only after the ions have entered the trapping region. The combined action of the voltages traps the ions in the trapping region of the device. For example, the RF electrodes 101+, 101- and the counter electrode 102 may be operated in a conventional manner, where the closely packed array of electrodes forms a pseudo-potential barrier across a first surface across which the array of electrodes spans, and the ions are pinned against this pseudo-potential surface by DC electrodes attached to the first surface and to a second surface opposite the array of electrodes, spreading the ions across the trapping region. The trapping voltage may be a DC voltage that may have a magnitude smaller than the magnitude (e.g., absolute or RMS magnitude) of the oscillating voltage applied to the array of electrodes.

[0042] When it is desired to remove ions from the device, an extraction voltage is applied to one or more electrodes of the device to establish a potential gradient in the trapping region that results in the extraction of ions. For example, the control circuit 150 may apply an extraction voltage to at least one of the array of electrodes (RF electrodes 101+, 101-) and / or one or more additional electrodes (e.g., counter electrode 102 or some other electrode) to extract ions from the trapping region. For example, an extraction voltage can be applied to two or more electrodes using a push / pull configuration (e.g., push by the RF carpet and pull by the extraction electrode).

[0043] Thus, in general terms, at least one electrode of the device, such as at least one electrode of the array of electrodes and the one or more further electrodes, may be an extraction electrode, and the control circuit may be configured to apply an extraction voltage to the extraction electrode. The extraction electrode may act only on the low pressure region of the device. Application of the extraction voltage to the extraction electrode may eject ions from the trapping region. In a preferred embodiment, the extraction electrode may be opposite the array of electrodes, and the extraction electrode is preferably substantially parallel to the array of electrodes. Both the extraction electrode and the array may be substantially parallel planar structures. The extraction electrode may comprise one or more apertures (e.g. any openings or holes) for allowing ions to pass through. For example, a grid structure may be provided. The extraction electrode may thus be a grid electrode and / or a segmented electrode with a plurality of openings for allowing ions to pass through. Preferably, the extraction voltage has a magnitude greater than the magnitude of the trapping voltage.

[0044] Certain aspects of the present disclosure relate to delayed extraction of ions and gradual ramping of the trapping voltage. For example, ions may be trapped in the trapping region by the combined action of electrodes 101+, 101-, and 102 as described above. To prevent ions entering the trapping region from colliding with electrodes 101+, 101- when the trapping voltage is turned on, the trapping voltage may be gradually increased. For example, the trapping voltage may increase in magnitude over time, which may prevent ions from accelerating towards the bottom electrodes 101+, 101-. That is, ions may be thermally cooled after entering the trapping region before the trapping voltage reaches its maximum value.

[0045] Additionally, a focusing voltage may be applied to the trapping region to reduce the spread of the ions in the z-direction prior to extraction. For example, the RF voltage on electrodes 101+, 101- may be quenched during a delay period during which a focusing voltage (which may simply be the same voltage as the trapping voltage) may be applied to one or more electrodes (e.g., any one or more of electrodes 101+, 101-, 102, and / or 108) to focus the ions. The delay period may have a duration of 0.1 μs to 2 μs or 0.1 μs to 1 μs. However, other durations may be used depending on the sample.

[0046] Then, after the ions are focused, they can be extracted from the trapping region by applying an extraction voltage to the upper electrode 102. For example, application of a set of oscillating voltages (e.g., voltages applied to the RF carpets 101+, 101-) and trapping voltages (e.g., electrode 102) may be such that the ions are located at a certain distance range from the array of electrodes. Application of a focusing voltage may then reduce the distance range from the array of electrodes at which the ions are located. This may improve the properties of the ion cloud, which may be advantageous in reducing the m / z shift when the trap is coupled to a mass analyzer.

[0047] Note that a small attractive force DC may be applied to the electrodes 101+, 101- to provide a focusing voltage. However, this voltage may be defined relative to a counter electrode (e.g., electrode 102), so that the equivalent effect is for the counter electrode to have a repulsive DC voltage (i.e., causing a focusing voltage that repels ions away from the counter electrode and towards the array of electrodes). Thus, a DC voltage may be applied across the set of electrodes to create a focusing field that pushes ions down onto the array of electrodes.

[0048] The RF electrodes 101+, 101- may be printed on the PCB substrate 103 or may comprise solid electrodes glued or otherwise mounted to a support. The electrode structure may also comprise two interlocking combs in the manner of the planar multipole ion trap described by Debatin et al, Physical Review A, 2008, 77, 033422, which is incorporated herein by reference. The material of the substrate 103 may include, for example, PCB, glass, ceramic, or plastic, and need not cover the entire first surface of the electrode structure. The substrate 103 may be of sufficient size to hold the various components attached to it in their intended positions.

[0049] The width and separation of the RF electrodes 101+, 101- can vary widely, from low millimeter and sub-millimeter scale spacings to micron level electrodes that are potentially etched away via lithographic methods. In general, the smaller and more numerous the electrodes 101+, 101-, the stronger the damping of the pseudopotential and the closer the ions are to the electrodes 101+, 101-. This is highly advantageous when ions travel through confined spaces such as gas-confined regions. In the case of an extractive trap, the strongly damping pseudopotential brings ions of similar m / z closer together, better compressing the ion packets and allowing very strong time focusing to be achieved. On the flip side, very high RF (e.g., 10 MHz or higher) is required, rather than the conventional millimeter scale of about 1 MHz levels, and such close proximity to the electrodes risks problems from surface charges, contamination, and loss of unthermalized ions during injection. Thus, the most appropriate electrode spacing for any given application depends on a variety of factors, and aspects of the present disclosure are not limited to any particular scale.

[0050] A potential barrier may be provided by one or more barrier electrodes 104 to prevent ions from escaping beyond the sides of the trap. The devices for trapping ions described herein may have a longitudinal axis extending in a longitudinal direction (i.e., in the x-direction), and multiple barrier electrodes 104 may be spaced longitudinally. Any electrode that provides lateral (i.e., perpendicular to the z-direction perpendicular to the plane of the RF carpet) trapping of ions in the trapping region may be considered a barrier electrode. For example, a DC or RF barrier 104 may be provided that extends at least to a height (i.e., in the z-direction) above the RF electrodes 101+, 101- that the ions occupy during trapping. Figures 4A, 4B, and 4C show examples of barrier electrodes 104 provided via PCB printed DC electrodes, raised RF electrodes (which may, but need not, be segmented), and DC superimposed on RF electrodes. In particular, Figure 4A shows a PCB printed electrode comprising a DC barrier electrode 104 and a gate electrode 105. Figure 4B shows a solid barrier electrode 104 attached to a substrate 103 with raised areas designated RF+, RF- as sideguards. Figure 4C shows a raised barrier electrode 104 with segmented sideguard electrodes with superimposed DC designated DC+RF.

[0051] Various combinations of the barrier electrodes 104 of Figure 4 may be provided. For example, the barrier electrode of Figure 4A may be combined with the barrier electrode of Figure 4B and / or Figure 4C. Similarly, the barrier electrode of Figure 4B may be combined with the barrier electrode of Figure 4A and / or Figure 4C. Various types of electrodes may be disposed around the trapping region to function as barrier electrodes, and any voltage applied to such barrier electrodes may be described as a barrier voltage.

[0052] The raised electrodes of the barrier electrode 104 in Figures 4A-4C should not be unnecessarily raised high as they may interfere with the extraction field, which is otherwise very strong and linear in the preferred embodiment. Also shown among the PCB printed DC electrodes is a small DC electrode 105 that acts as a gate, allowing ions from the upstream ion optics to enter the trap 100 through the ion inlet.

[0053] The barrier electrodes may be described in a general sense as one or more further electrodes (different from the RF carpet or array of electrodes) positioned around the trapping region. For example, the barrier electrodes may be on the same substrate as the array of electrodes, but may be disposed around the edges of the array of electrodes. The control circuitry may be configured to apply a barrier voltage to the one or more barrier electrodes to trap ions within the trapping region. The barrier electrodes may thus provide a lateral trap in the xy plane. It is noted that the one or more barrier electrodes may be provided on a different substrate, such as a top plate, as will be described in more detail in relation to FIG. 7.

[0054] In use, the control circuit preferably applies a set of oscillating voltages to the array of electrodes and a trapping voltage to the trapping electrodes such that ions are positioned at a first distance range from the array of electrodes. This distance range is preferably a narrow range of z values ​​for a substantially planar ion cloud. Preferably, the barrier voltage may define a potential barrier (e.g., for laterally confining ions within the trapping region) that extends to at least the first distance range from the array of electrodes. For example, the potential barrier should preferably extend to at least the highest value (i.e., maximum height in the z direction) of the first distance range to ensure that ions are not lost. However, if some loss of ions is acceptable, it may be acceptable to extend the potential barrier to smaller z values.

[0055] The barrier voltage may take many forms. For example, the control circuitry may be configured to apply one or more of the following: a DC barrier voltage to at least one of the one or more barrier electrodes, a radio frequency (RF) barrier voltage to at least one of the one or more barrier electrodes, and / or a superposition of a DC barrier voltage and an RF barrier voltage to at least one of the one or more barrier electrodes. In some cases, the one or more barrier electrodes may include multiple barrier electrodes. The control circuitry may be configured to apply barrier voltages with opposite phases to adjacent barrier electrodes. This may generate a pseudopotential. One or more of the multiple barrier electrodes may be positioned at the ends of the electrodes of the array of electrodes. Such an arrangement may ensure that ions are trapped within the trapping region and cannot move beyond the edge of the RF carpet.

[0056] Regardless of the nature of the barrier electrodes used, the length and width of the trap 100 can be adapted to the acceptance of the analyzer. For example, a regular ToF analyzer with a large grid-like reflectron can accept a relatively large initial ion packet, perhaps even 10x10 mm, whereas an MR-ToF analyzer may have much tighter limitations, e.g. 10x1 mm. What is important is the overall phase space acceptance, not just the initial spatial distribution. Furthermore, although the RF electrodes 101+, 101- are shown as rectangular, other shapes can be used. For example, a circular (or any other shape) RF carpet may be used instead. The counter electrode 102 may be provided in the same or different shape as the RF carpet, and thus may be rectangular or circular, or any other shape.

[0057] FIG. 5 shows a further embodiment that is an adaptation to an RF carpet trap of the type described by Giles in US Patent Application Publication No. 2019 / 0103263(A1). In the embodiment of FIG. 5, RF carpet electrodes 101+, 101- pass through two separate regions 106A, 106B, which are under different pressures and are separated by a gas restrictor 107. The gas restrictor 107 may be configured to restrict gas flow from the high pressure region to the low pressure region and may have an opening that allows ions to pass through. In general, the array of electrodes may extend, for example, along one or more edges (e.g., the bottom surface) of the relatively low pressure region of the trapping region and along one or more edges (e.g., the bottom surface) of the relatively high pressure region of the trapping region, which may allow ions to be trapped successively as they move along the array of electrodes. For example, the array preferably extends along the bottom surface (i.e., the first surface facing the extraction plate) of the low and high pressure regions. This may mean that the array extends entirely along at least one side of the low pressure and high pressure regions.

[0058] In FIG. 5, it is preferred (but not essential) that the counter electrode 102, functioning as an extraction electrode, should cover only the extraction region 106B, and the remainder of the trapping region (i.e., the high-pressure region 106A) should be provided by a separate transport electrode 108 on the top plate. The transport electrode 108 may also be described as a trapping electrode, since it applies a trapping voltage at a particular time. Such a separate electrode 108 on the top plate may be electrically separated (i.e., electrically insulated) from the extraction electrode 102, allowing ion packets to be processed in parallel in both regions 106A, 106B, thereby improving throughput. Side walls for gas containment are not shown, but may be provided in a conventional manner. Thus, in a general sense, the trapping region may have a region of relatively low pressure and a region of relatively high pressure, and the extraction electrode may extend along the region of relatively low pressure (but need not extend along the region of high pressure). In some cases, the extraction electrodes may extend along the high pressure region if a mechanism is provided for transporting ions along the trap (e.g., a traveling wave, or a DC gradient applied to the RF electrodes). This can provide a low pressure extraction trap with an upstream high pressure region for cooling ions (or to act as a collision or fragmentation cell). Providing a low pressure extraction region can limit gas leakage into the analyzer, thereby improving analysis of the sample.

[0059] Figure 6 shows a cross-sectional view of the trap 100 concept shown in Figure 5, and more particularly how the device can be used as a dual pressure trapping region incorporating an RF carpet, which can be used for high throughput processing of ions. In Figure 6, additional details are shown, such as a gas restrictor 107 and one or more electrodes 109 that can be applied to the entrance aperture 110 (also called the ion entrance).

[0060] Optionally, at the ends of the RF electrode arrays 101+, 101-, end DC repellers or charge collecting surfaces 111 may be provided for optional charge measurement independent of the analyzer, which may be used for control of the ion population in the trapping region. For example, measurement of the charge in the trapping region can be used to control the gating of the ion entrance. Generally, the device may comprise a charge detector, such as a charge collecting surface, that may be used for charge measurement (e.g., independent of the analyzer). Such a charge detector may be provided in the low pressure region or the high pressure region, or one or more detectors may be provided in both regions. The control circuitry described herein may use data from such detectors to measure the ion population and control the entrance of the ions.

[0061] The advantage of this design over existing traps is the simplicity of construction, since a series of RF electrodes 101+, 101- can extend unobstructed across the substrate 103, while the gas restrictor 107 can simply be suspended from the top plate. Because the RF on the electrodes 101+, 101- is relatively low, the restrictor 107 can be positioned close enough to the array of electrodes 101+, 101- (e.g., within a few mm, such as 2 mm, although other distances can be used) to function effectively. Also, one or more of the RF electrodes 101+, 101- can be relatively narrow (e.g., in the y-direction) in the region of the restrictor 107, allowing the restrictor to contact the substrate 103 while still focusing ions through a narrowed slot in the restrictor 107.

[0062] Thus, generally, the present disclosure can provide an apparatus for trapping ions comprising a second surface (e.g., a top plate, which can be the second surface of the apparatus), facing an array of electrodes (provided on the first surface), and a gas restrictor can extend from the second surface towards the array of electrodes, thereby effectively dividing the trapping region between the trapping electrode and the array of electrodes into two separate regions which can be held at different pressures.

[0063] The high pressure region is preferably capable of cooling the ions in a reasonable time, and therefore the preferred pressure in the high pressure region is >1×10 -3 mbar, ideally >2×10 -3 mbar. For fragmenting ions, the high pressure region is >5×10 -3 In some embodiments, the upper pressure limit may be 2×10 -2 mbar, although higher pressures can be used in certain circumstances.

[0064] For the low pressure region, >5×10 -4 mbar is preferred, and 1×10 -3 mbar is preferred. 5×10 -3 Pressures up to mbar can be used, but at higher pressures ion scattering can become an issue and impair performance. For example, the lower pressure regime is 0.5-2×10 -2 mbar and / or the relatively high pressure region may have a pressure of 0.5 to 2×10 -3 The pressure may be in the range of 100 to 2000 mbar. Other pressures may be used depending on the desired application.

[0065] One or more electrodes of the array may be truncated or relatively narrow near the gas restrictor. For example, the one, two, three, or N electrodes (N can be any number) closest to the restrictor may be narrower than the adjacent electrodes. The channel defined by the array of electrodes may narrow near the restrictor (e.g., in the y-direction perpendicular to the longitudinal axis of the device), so that the gas restrictor need not have too wide a hole.

[0066] The two regions 106A and 106B are typically 0.5 to 2×10 -2 mbar and 0.5 to 2×10 -3mbar pressure, although other pressures can be used. Thus, the relatively high pressure region 106A may be at (at least) an order of magnitude higher pressure than the relatively low pressure region 106B. This provides the high pressure region 106A with sufficient pressure to not only cool 7 eV ions, but also to act as a fragmentation cell for isolated ions in a tandem mass spectrometer. Thus, the dual pressure trap can be incorporated into a mass spectrometry system that includes a mass analyzer, such as a tandem mass spectrometer.

[0067] A voltage (e.g., a DC voltage) can be applied to the restrictor 107 to trap ions in the high pressure side 106A, attract ions to the low pressure side 106B, or to match the electric field strength on one or the other side and be set to be effectively invisible to the ions. That is, generally, the control circuitry may be configured to apply a voltage to the gas restrictor (e.g., to an electrode attached to the restrictor or to the restrictor itself) to trap ions in regions of relatively high pressure and / or to transport ions to regions of relatively low pressure and / or to match the electric field strength in the regions of relatively high pressure and / or the regions of relatively low pressure. The gas restrictor can thus act as a transport electrode to transport ions between different regions of the device.

[0068] Ion movement along the trapping region (e.g., to move ions between regions 106A, 106B) can be accomplished in a variety of ways. For example, ions may be moved using a voltage applied to a gas restrictor, as described above. In addition, ions may be transported by applying a transport voltage to one or more other electrodes of the device. For example, a DC gradient can be applied to the RF electrodes 101+, 101-, either as a train of DC pulses (as described in U.S. Pat. No. 6,791,078 (B2) which is incorporated herein by reference) or as RF (as described in U.S. Pat. No. 6,894,286 (B2) which is incorporated herein by reference), by segmentation of the electrodes 108 attached or printed on the top plate, or via application of superimposed traveling waves to the RF electrode series 101+, 101-. Traveling waves may have the advantage of reducing or minimizing energy uptake by ions during transport, potentially allowing extraction of a near-thermalized ion cloud (albeit with some residual axial velocity that the analyzer should be able to handle, for example with deflectors) without requiring time to stop and cool the ions in the low pressure extraction region 106B. In this way, operation up to 1 KHz is possible. Thus, while the RF electrodes 101+, 101- may act as transport electrodes in some cases, various other electrodes, such as electrode 108, may also have a transport voltage applied to them and therefore act as transport electrodes. It should also be noted that combinations of these different approaches may also be combined to achieve ion transport.

[0069] Thus, in general terms, at least one of the array of electrodes and the one or more further electrodes may be a transport electrode. The control circuitry may be configured to apply a transport voltage to the transport electrode to transport (i.e., move) ions along the trapping region. The transport electrode may be any electrode that performs this function, and the transport electrode may perform other functions at other times (e.g., trapping ions or focusing ions). The transport voltage may have a DC gradient configured to transport ions along the DC gradient. The transport voltage may be a DC voltage or an AC voltage with a DC offset. The transport voltage may also be a time-varying voltage with a DC offset, with a time-averaged DC gradient that causes the transport of ions. In some cases, the transport voltage may include a traveling wave (e.g., applied to an RF carpet) configured to transport ions in the direction of the traveling wave. The control circuitry may be configured to superimpose a traveling wave voltage on a set of oscillating voltages. This may maintain trapping while the superimposed traveling wave moves ions along the trapping region without releasing them, and may reduce ion loss. In some embodiments, the control circuitry may be configured to apply the transport voltage to the array of electrodes or any other electrode.

[0070] It will be appreciated that the embodiments of Figures 4A-4C, 5 and 6 show specific examples of advantageous implementations of the invention. However, it will be appreciated that the principles can be applied more generally. For example, the present disclosure advantageously provides an apparatus for trapping ions, comprising: an array of electrodes extending along a (first) surface of the apparatus; one or more further electrodes distinct from the array of electrodes; a trapping region for receiving ions, the trapping region being defined by the array of electrodes and the one or more further electrodes and having regions of relatively low pressure and regions of relatively high pressure; and a control circuit configured to: apply a set of oscillating voltages to the array of electrodes, each electrode in the array of electrodes having a different phase with respect to each adjacent electrode, to repel ions from the array of electrodes, and to apply a trapping voltage to at least one of the one or more further electrodes to force ions towards the array of electrodes, the set of oscillating voltages and the trapping voltage thereby trapping ions in the trapping region. By providing a trapping region having regions of relatively low pressure and regions of relatively high pressure, improved cooling of ions within the RF carpet can be achieved. Furthermore, gas leakage from the extraction region can be reduced if the extraction region is held at a relatively low pressure.

[0071] Since there is no central axis to be injected downwards, ions entering the device may be excited by the electric field from the top plate 108 DC. This creates some risk of ions being accelerated into the RF electrodes 101+, 101-, so it may be advantageous for this repulsive DC to be set low, for example around 1 V, during ion injection and then raised or increased, for example to 10 V over 2 ms, as the ions cool. Thus, in another schematic aspect of the present disclosure, the control circuit may be configured to apply a trapping voltage to at least one of the one or more further electrodes to direct the ions towards the array of electrodes, the set of oscillating voltages and the trapping voltage thereby trapping the ions in the trapping region, the trapping voltage being a time-varying DC voltage that increases in magnitude over time. Such a time-varying trapping voltage may allow the ions to cool before the trapping field is applied. Thus, the trapping voltage may have a relatively low magnitude while the ions are being injected into the trapping region (i.e. the trapping voltage may cause a weak trapping field to be applied) and may increase in magnitude after the ions are injected into the trapping region. This allows the ions to be gradually trapped.

[0072] The magnitude of the trapping voltage while the ions are injected into the trapping region may be less than 5 V, less than 3 V, less than 2 V, or less than 1.5 V. Thus, the voltage can be kept low while the ions enter the trapping region and are cooled. The magnitude of the trapping voltage is at least 1×10 3 Vs -1 , at least 2 × 10 3 Vs -1 , or at least 5 × 10 3 Vs -1 The magnitude of the trapping voltage may increase at a rate of 0.1 to 1.0 times the normalized magnitude of the trapping voltage. The magnitude of the trapping voltage may increase continuously over time, or the magnitude of the trapping voltage may increase linearly over time. A discontinuous (e.g., step-like) increase in magnitude may also be provided.

[0073] The trapping voltage may increase in magnitude over time until a maximum voltage is reached. For example, the magnitude of the trapping voltage may be constant after the maximum voltage is reached. Thus, ions may be gradually trapped and then confined when a certain voltage is reached. The maximum voltage may be at least 5V, at least 10V, or at least 20V. Thus, the trapping voltage may reach the maximum voltage after at least 1 ms, at least 2 ms, or at least 3 ms. The maximum voltage and the time to reach the maximum voltage may depend on the nature and / or number of ions to be trapped. Information about the number of ions in the trapping region may be used to control the trapping voltage. Such information may be provided by a sensor in the trapping region. The upper limit of the delay period may be 20 ms, although any length of delay may be used.

[0074] 7, a specific embodiment of a top plate for a dual pressure trap is shown. Here, the plate is a PCB with extraction electrodes 102 glued into holes in the plate. To protect the sides of the RF carpet 101+, 101- from ion leakage, a barrier electrode 104 is provided in the form of a DC electrode 104 surrounding the gridded extraction electrode 102, which may have a grid voltage applied to it or a separate voltage applied. Locations within the plate are shown to mount a gas restrictor 107 or aperture.

[0075] 7 also shows that the DC electrode 108 above the high pressure region 106A is split laterally into wedge-shaped portions 108A, 108B, and 108C. By applying a slightly higher DC to the outer electrode portions 108A, 108C, ions can be forced towards the center, allowing the gas restrictor 107 to have a narrower slot. In the illustrated embodiment, there is no longitudinal segmentation of these electrodes 108A, 108B, and 108C, and thus in this case the RF electrodes 101+, 101- can have voltages applied to propel ions across the trap 100 (i.e., guide ions in the x-direction). However, instead, any one or more of the portions 108A, 108B, 108C of the electrode 108 may be segmented longitudinally (e.g., in the x-direction) to provide ion movement along the x-direction.

[0076] The electrode 108 can be generally described as a transport electrode, since the wedge portions 108A, 108B, and 108C can be configured to transport ions along the trapping region. Similarly, the wedge portions 108A, 108B, and 108C can be described as transport electrode portions. Furthermore, since the wedge portions 108A, 108B, and 108C of the electrode 108 act to funnel ions, the electrode 108 and the wedge portions 108A, 108B, and 108C are also described herein as funnel electrodes and funnel electrode portions. The funnel electrode 108 can funnel ions as they move along the trapping region. This can mean that the separation of ions in the y-direction is reduced due to the electric field generated by the transport voltage (also described as a funnel voltage). The application of such a voltage reduces the spread of ions in the y-direction (i.e., perpendicular to the general direction of movement of ions and perpendicular to the z-direction of the carpet trap). This improves the handling of ions by confining them more tightly by reducing the lateral separation of the ions as they move along the trapping region. Furthermore, in a dual pressure trapping region, applying a funnel voltage allows a narrower aperture to be used between regions of different pressures due to the reduced lateral extent of the ion cloud. This allows a larger pressure differential to be established.

[0077] As mentioned above, the wedge-shaped portions 108A, 108B, and 108C may be substantially triangular. The shape of the wedge-shaped portions 108A, 108B, and 108C and the voltages applied thereto may provide a funneling or tapering effect on ions. In a general sense, the device may comprise an ion inlet for allowing ions to enter the trapping region, and the funnel electrode may comprise a first portion and a second portion, the first portion of the funnel electrode tapering away from the ion inlet (i.e., widest near the ion inlet). Similarly, the first portion may be described as tapering toward the gas restrictor. The second portion may comprise one or more further tapered (e.g., wedge-shaped) portions tapering toward the inlet (or equivalently, narrowest near the inlet). The second portion preferably comprises two wedge-shaped portions, whereby the funnel electrode comprises a first portion tapered away from the ion inlet, and a second portion and a third portion both tapered toward the ion inlet. The first and second (and optionally third) portions of the funnel electrode are preferably (substantially) coplanar. For example, the portions of the funnel electrode may collectively constitute a rectangular funnel electrode portion. To achieve the funnel effect, the control circuit may be configured to apply a higher voltage to the second portion of the funnel electrode than to the first portion of the funnel electrode. The funnel effect may also be provided using appropriate timing circuitry and segmented funnel electrodes.

[0078] In the general terms used above, the devices described herein may comprise a second surface (e.g., a top plate), which faces an array of electrodes, which may comprise one or more of an extraction electrode, a transport electrode, and / or a funnel electrode. As previously mentioned, the electrodes may perform different functions at different times depending on the voltage applied, and thus the funnel electrode may also act as a transport electrode, or separate funnel and transport electrodes may be provided. In any case, the extraction electrodes described herein preferably serve the relatively low pressure region of the trapping region and may be positioned adjacent to the low pressure region and away from the high pressure region. Although the funnel electrode preferably serves the relatively high pressure region, the funnel electrode may also be used in low pressure regions or single pressure devices. The transport electrodes and RF carpet electrodes preferably serve all regions (e.g., low pressure and high pressure regions) to move ions along the entire device. A preferred embodiment includes an ion inlet for allowing ions to enter the trapping region, and the control circuitry may be configured to apply a voltage to at least one of the one or more further electrodes (i.e. not the RF carpet) to allow ions to enter the trapping region through the ion inlet and / or to prevent ions from entering the trapping region through the ion inlet.

[0079] FIG. 8 shows an exemplary instrument according to one embodiment of the present disclosure. A hybrid mass analyzer of the type described in US Pat. No. 1,069,888 (B2) is shown in combination with a quadrupole mass filter, an orbital trap mass analyzer, and a multi-reflecting time-of-flight mass analyzer as described in detail by Grinfeld in US Pat. No. 9,136,101 (B2). The RF carpet extraction trap replaces the existing extraction trap that feeds the MR-ToF analyzer. In a general sense, the instrument of FIG. 8 can be described as a mass analysis system comprising an apparatus for trapping ions according to any of the embodiments described herein and a mass analyzer configured to receive ions from the apparatus for trapping ions. Preferably, the mass analyzer is a time-of-flight mass analyzer (e.g., an MR-ToF analyzer).

[0080] Simulation results Simulations were constructed in the MASIM3D program for an extraction trap with 0.4 mm wide RF electrodes (2D array) separated by 0.2 mm, guarded at the ends by 1.8 mm wide DC barrier electrodes. The trap was chosen to extend 10 mm from the center, with a distance of 4 mm from the RF array of electrodes to the top grid electrode (trapping electrode). Axisymmetric was used to create a circular trap from the 2D model, generated at the center, with a 1 × 10 -2 An image of this trap with the trajectory of a bunch of m / z 200 ions cooled in mbar background gas is shown in Figure 9. RF of 3 MHz, 50 V was applied with +10 V on the grid (trap) electrode and +5 V on the outer barrier electrode.

[0081] Figure 10 shows a plot of the potential well (for m / z 200 ions) created by the superimposed RF pseudopotential due to the array of electrodes and the repulsive DC from the trapping electrodes. The potential well (DC+RF pseudopotential) between the RF electrode (+2mm) and the top grid (-2mm) is shown and the region where the ions settle is marked. This well structure is characteristic of this style of ion trap or guide and is similar to that shown in US6683301B2.

[0082] Figure 11 shows the ion trajectories of ions of m / z 200 and 2000 as they are cooled into the potential well over time. It can be observed that the spread in ion positions is small, about 0.2 mm, and that m / z 2000 is located at a very different average position than m / z 200 as a result of the difference in the balance between the pseudopotential strength and the counter potential from the grid +10 V. Thus, it can be seen that the cooled ion trajectories for m / z 200 and 2000 result in different average height positions.

[0083] Figure 12 shows the simulated ion time spread at the first time focus of a 0.1 mm (1 sigma) thick plane of m / z 200 ions immediately after extraction with a 500 V / mm field equivalent to -2 KV on the extraction grid. It can be seen that the time spread full width at half maximum is almost exactly 1 ns, which is suitable for time-of-flight applications. Higher fields can be easily applied with stronger extraction voltages or with voltages of opposite polarity applied to the RF electrodes. When the ion starting point is shifted from the m / z 200 plane to the m / z 2000 plane, the FWHM at the same plane position expands by 1.5 ns, which will significantly impair the resolution in most systems.

[0084] FIG. 13 demonstrates an embodiment of the present disclosure in which the extraction pulse is delayed after the RF quench so that it moves only under the low repulsive field provided by the grid electrodes of the present disclosure. This has the effect of focusing the ions and reducing the spread of the average position of the ions in the z-direction. It can be observed that the optimum occurs when the lowest mass coincides with the position of the high mass, which is about 0.5 μs for the 200-2000 mass range under 10 V applied DC, reducing the position deviation from 0.23 to 0.07 mm. It may also be advantageous to vary the DC field during the delay period, or to add additional delays and steps before extraction. Controlling the phase of the RF quench instead of using the simplest zero point electronically may also have applications for manipulation of the ion phase space, as described in US Pat. No. 1,073,4210 (B2).

[0085] The above figures show that delayed extraction of ions can be advantageous. As mentioned above, a drawback of known RF carpets is that the trapped ion surface is located at a point where the pseudopotential is strong enough to balance the repulsive force from DC, so that ions of different m / z settle at different distances from the RF surface. In a time-of-flight analyzer, this becomes problematic because m / z shifts can be introduced. Certain embodiments of the present disclosure address this issue, as demonstrated by these simulation results. Thus, in a general aspect, an apparatus for trapping ions is provided, in which a control circuit is configured to stop applying (i.e., turn off or at least reduce to a negligible fraction of its original value, e.g., less than 10% or less than 1%) a set of oscillating voltages to an array of electrodes during a delay period, apply a focusing voltage to at least one of one or more further electrodes during the delay period to direct ions towards the array of electrodes, and apply an extraction voltage to the array of electrodes and / or at least one of one or more further electrodes after the delay period to extract ions from the trapping region. Applying the extraction voltages after the expiration of the delay period can ensure that the ions are focused within a narrow range of spatial positions, which can provide a more consistent trapping position, thereby reducing the m / z shift introduced by a known RF carpet when coupled to a ToF analyzer. Cessation of the application of the set of oscillating voltages may occur after the ions are trapped within the trapping region.

[0086] Continuing to use the general terms used above, the control circuit of the present disclosure may be configured to apply the focusing voltage and the trapping voltage to the same at least one of the one or more further electrodes (e.g., the top electrodes 102 and / or 108). For example, the focusing voltage may be the trapping voltage. That is, during the delay period, the trapping voltage may continue to be applied, and the continued application of the trapping voltage may have a focusing effect on the ions in the trapping region. Thus, the ions may be focused (i.e., occupy a narrower range of heights (z values)) due to the application of the trapping voltage during the delay period, and thus the trapping voltage may act as a focusing voltage after the set of oscillating voltages is no longer applied to the array of electrodes. The electrodes to which the focusing voltage and / or the trapping voltage are applied may be on the top surface (also described herein as the second surface) of the device for trapping ions, that is, the electrodes may face the array of electrodes (RF carpet).

[0087] In some embodiments, the focusing voltage may have a magnitude less than the magnitude (e.g., peak magnitude or RMS magnitude) of the set of oscillating voltages. For example, the focusing voltage may have a magnitude of at least 5V, at least 10V, or at least 20V. The focusing voltage is preferably a DC voltage. The focusing voltage may increase in magnitude over at least a portion of the delay period, which may allow for a shorter delay period, which may help reduce ion dispersion.

[0088] The focusing voltage does not necessarily have to be the same as the trapping voltage. For example, the trapping voltage may also be stopped when the set of oscillating voltages is no longer applied, and a different focusing voltage may be applied during the delay period. The exact nature of the focusing voltage may vary depending on the particular sample being trapped. In some embodiments, the magnitude of the focusing voltage may be ramped or pulsed during the delay period. The focusing voltage may have a number of different magnitudes during a number of respective time intervals during the delay period (e.g., subintervals of the delay period). The focusing voltage may be constant (e.g., having a constant magnitude) during some time intervals during the delay period (e.g., constant for the entire delay period or constant for certain subintervals of the delay period) and may vary linearly or nonlinearly during other time intervals during the delay period. Thus, the distance (height in the z-direction) range at which the ions are positioned can be fine-tuned before extraction. This can be used to optimize the shape of the ion cloud to ensure that it is suitable for subsequent analysis (e.g., by a mass analyzer).

[0089] It can thus be seen that a number of advantages can be achieved using aspects and embodiments of the present disclosure. For example, delayed extraction can be used to prefocus ions of different m / z to align the focal planes. Furthermore, a gradual slow increase or ramp of the trapping voltage after ion injection can be used to limit the energy pickup by the ions and compress them onto the RF carpet. This can reduce the risk of ion loss due to collisions with the RF carpet. Furthermore, trapping around the plane of the RF carpet via DC electrodes on the top plate can provide improved manipulation of ions. The provision of a dual pressure RF carpet extraction trap, which can be built on a PCB top plate with gas restrictors, also contributes to improved handling of ions. The dual pressure trap is simpler to manufacture and operate than known multipole-based systems and facilitates low energy transfer of ions across pressure regions 106A, 106B with very narrow apertures.

[0090] The trapping concept described above benefits from being very mechanically simple and less electronically complex than existing systems, for example because there is no need to superimpose HV pulses on the RF electrodes (electrodes 101+, 101-, etc.) as in comparable trapping systems. Functionally, the system described herein can provide a more planar ion cloud that is optimal for space charge performance in a time-of-flight mass analyzer. The use of, for example, a PCB board with segmented printed electrodes and resistor chains to provide the voltage gradient provides a simple means for implementing the above aspects and embodiments.

[0091] In this disclosure, RF voltage is broadly described, for example, when referring to an RF carpet (an array of electrodes to which an RF oscillating voltage can be applied), and it will be understood that RF can mean from 20 kHz to 300 GHz.

[0092] Furthermore, although voltages are described in detail herein, it will be understood that all voltages are relative to ground (or some other appropriate reference point), and therefore high voltage should be interpreted as meaning a relatively high potential difference relative to a reference point when compared to the potential difference between other elements and the reference point.

[0093] It will be appreciated that many modifications may be made to the above-described devices, systems, and methods while retaining the advantages set forth above. For example, where particular components have been described, alternative components may be provided which provide the same or similar functionality.

[0094] The embodiments have been described as being provided on one or more substrates. For example, the electrodes described herein (e.g., arrays of electrodes and other electrodes) may be on one or more substrates. Such substrates may be printed circuit boards (PCBs), or other structures for mechanically supporting the electrodes may be used. PCBs provide a particularly cost-effective and easy to manufacture substrate. However, the trapping structures described herein need not be constructed on a substrate 103 as shown, and the electrodes may be supported elsewhere, such as on terminal rods with the electrodes separated via spacers.

[0095] The counter electrode 102 described herein may be provided fully gridded by a metal plate or PCB incorporating a grid, or may even be a gridless aperture for a narrower size. Lateral focusing may be incorporated to help focus the ions through such an aperture during extraction. The RF electrodes 101+, 101- may be printed on a PCB, may be solid machined electrodes, or may be very small electrodes fabricated by MEMS and lithographic methods.

[0096] The extraction trap may be compatible with linear, single and multiple reflection, and sector-based ToF analyzers. Any mass analyzer may be coupled to the device described herein. The trap described herein may also be combined with a Fourier transform analyzer, such as an orbital trap mass analyzer. The trap may be operable combined with a MALDI or desorption-based ion source.

[0097] The dual pressure trap described herein may be completely enclosed or separately pumped, except for the extraction grid 102 and the inlet opening 110. The primary cooling cell may act as an impingement region.

[0098] The delayed extraction methods described herein may include additional stages or voltage pulses.

[0099] The rise time of the extraction pulse may be controlled to compensate for mass-dependent energy variations induced by different ion starting positions (slower rise times cause low m / z ions to appear at lower energies relative to high m / z), which may further help promote mass-independent behavior in conjunction with delayed extraction.

[0100] In some embodiments, a repulsive pulse may be applied to an array of electrodes (at hundreds to thousands of volts) to eject the ions. This may require complex electronics, so the preferred embodiment uses an extraction grid. However, the advantage of using an array to eject the ions is that it is possible to apply extraction voltages of opposite polarity to both the extraction electrodes and the array, thereby doubling the field strength.

[0101] Additionally, in some aspects and embodiments, an oscillating (AC) voltage (possibly with a DC bias towards the carpet) can be applied to the extraction grid (also known as the trapping electrode) to trap ions relative to the array. Thus, an AC counter electrode (or set of counter electrodes) may be provided. Two different AC pseudopotentials may balance ion positions without creating axial well artifacts. In some embodiments, an AC set of voltages may be superimposed on a DC electrode, similar to an RF surface, which may be used to create an additional repulsive force when an ion approaches the DC electrode.

[0102] Each feature disclosed in this specification, unless stated otherwise, may be replaced by alternative features serving the same, equivalent or similar purpose. Thus, unless stated otherwise, each feature disclosed is only an example of a generic series of equivalent or similar features.

[0103] As used herein, including in the claims, unless the context indicates otherwise, the singular form of a term herein is to be construed as including the plural, and vice versa, where the context allows. For example, unless the context indicates otherwise, singular references herein, including in the claims, such as "a" or "an" (e.g., an electrode detector or a voltage) mean "one or more" (e.g., one or more electrodes or one or more voltages). Throughout the description and claims of this disclosure, the words "comprise", "including", "having", and "contain", as well as variations of words such as "comprising" and "comprises" or the like, mean that the described features include additional features that follow and are not intended to (and do not) exclude the presence of other components.

[0104] The use of any and all examples or exemplary language provided herein (such as, for example, and similar language) is intended merely to better illustrate the invention and does not pose a limitation on the scope of the disclosure unless specifically claimed. No language in the specification should be construed as indicating any element not claimed as essential to the practice of the disclosure.

[0105] Any steps described herein may be performed in any order, or simultaneously, unless otherwise stated or otherwise required by context. Furthermore, if a step is described as being performed after another step, this does not exclude intervening steps from being performed.

[0106] All aspects and / or features disclosed herein may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. In particular, preferred features of the present disclosure are applicable to all aspects and embodiments of the present disclosure and may be used in any combination. Similarly, features described in non-essential combinations may be used separately (not in combination).

[0107] Additionally, while aspects and embodiments have been described primarily with reference to physical devices, the present disclosure also provides methods of making and using such devices. For example, methods of making any of the devices described herein are provided, as are methods of using the devices described herein.

[0108] item: 1. An apparatus for trapping ions, comprising: an array of electrodes extending along a surface of the device; one or more further electrodes different from the array of electrodes; a trapping region for receiving ions, the trapping region being defined by the array of electrodes and one or more further electrodes; A control circuit comprising: applying a set of oscillating voltages to the array of electrodes such that each electrode in the array of electrodes has a different phase relative to each adjacent electrode to repel ions from the array of electrodes; applying a trapping voltage to at least one of the one or more further electrodes to force ions towards the array of electrodes, the set of oscillating voltages and the trapping voltage thereby trapping ions within the trapping region; ceasing application of the set of oscillating voltages to the array of electrodes during a delay period; applying a focusing voltage to at least one of the one or more further electrodes during the delay period to force ions towards the array of electrodes; and control circuitry configured to, after a delay period, apply an extraction voltage to at least one of the array of electrodes and / or one or more further electrodes to extract ions from the trapping region. 2. The apparatus of claim 1, wherein the control circuit is configured to apply the focusing voltage and the trapping voltage to the same at least one of the one or more further electrodes. 3. The device according to item 1 or 2, wherein the focusing voltage is a trapping voltage. 4. An apparatus according to any one of the preceding claims, wherein the focusing voltage has a magnitude less than the magnitude of the set of oscillating voltages. 5. An apparatus according to any one of the preceding claims, wherein the focusing voltage has a magnitude of at least 5V, at least 10V, or at least 20V. 6. The apparatus of any one of the preceding claims, wherein the focusing voltage is a direct current (DC) voltage. 7. The delay period is 0.1μs~2μs, or 7. The apparatus of any one of the preceding claims, having a duration of 0.1 μs to 1 μs. 8. The control circuit is applying a set of oscillating voltages and a trapping voltage such that ions are positioned at a first distance range from the array of electrodes; 2. An apparatus according to any one of the preceding claims, configured to apply a focusing voltage to reduce a first distance range from the array of electrodes at which ions are positioned. 9. An apparatus according to any one of the preceding claims, wherein the magnitude of the focusing voltage is ramped or pulsed during the delay period. 10. An apparatus according to any one of the preceding claims, wherein the focusing voltage has a plurality of different magnitudes during a plurality of respective time intervals during the delay period. 11. An apparatus according to any one of the preceding claims, wherein the magnitude of the focusing voltage is constant during the delay period. 12. An apparatus for trapping ions, comprising: an array of electrodes extending along a surface of the device; one or more further electrodes different from the array of electrodes; a trapping region for receiving ions, the trapping region being defined by the array of electrodes and one or more further electrodes; A control circuit comprising: applying a set of oscillating voltages to the array of electrodes such that each electrode in the array of electrodes has a different phase relative to each adjacent electrode to repel ions from the array of electrodes; and a control circuit configured to apply a trapping voltage to at least one of the one or more further electrodes to force ions towards the array of electrodes, the set of oscillating voltages and the trapping voltage thereby trapping ions within the trapping region, the trapping voltage being a time-varying direct current (DC) voltage that increases in magnitude over time. 13. The apparatus of claim 12, wherein the trapping voltage has a relatively low magnitude while ions are being injected into the trapping region and increases in magnitude after ions are injected into the trapping region. 14. The apparatus of claim 12 or 13, wherein the magnitude of the trapping voltage during injection of ions into the trapping region is less than 5V, less than 3V, less than 2V, or less than 1.5V. 15. The device according to any one of items 12 to 14, wherein the trapping voltage increases in magnitude over time until a maximum voltage is reached. 16. The device according to item 15, wherein the magnitude of the trapping voltage is constant after reaching a maximum voltage. 17. The device of any one of paragraphs 12 to 16, wherein the magnitude of the trapping voltage is increased to a maximum voltage of at least 5V, at least 10V, or at least 20V. 18. The device according to any one of paragraphs 12 to 17, wherein the trapping voltage reaches a maximum voltage after at least 1 ms, at least 2 ms, or at least 3 ms. 19. The device according to any one of items 12 to 18, wherein the magnitude of the trapping voltage increases continuously over time. 20. The device according to any one of items 12 to 19, wherein the magnitude of the trapping voltage increases linearly with time. 21. The magnitude of the trapping voltage is at least 1 × 10 3 Vs -1, at least 2 × 10 3 Vs -1 , or at least 5 × 10 3 Vs -1 The device according to any one of items 12 to 20, wherein the amount of the substance increases at a rate of 22. An apparatus for trapping ions, comprising: an array of electrodes extending along a surface of the device; one or more further electrodes different from the array of electrodes; a trapping region for receiving ions, the trapping region being defined by the array of electrodes and one or more further electrodes and having a region of relatively low pressure and a region of relatively high pressure; A control circuit comprising: applying a set of oscillating voltages to the array of electrodes such that each electrode in the array of electrodes has a different phase relative to each adjacent electrode to repel ions from the array of electrodes; and control circuitry configured to apply a trapping voltage to at least one of the one or more further electrodes to force ions towards the array of electrodes, the set of oscillating voltages and the trapping voltage thereby trapping ions within the trapping region. 23. An apparatus as described in paragraph 22, wherein the array of electrodes extends along the region of relatively low pressure of the trapping region and along the region of relatively high pressure of the trapping region. 24. The apparatus of claim 22 or 23, further comprising a gas restrictor between the region of relatively low pressure and the region of relatively high pressure. 25. The control circuit applies a voltage to the gas restrictor to Trapping ions in a region of relatively high pressure; Transporting ions to a region of relatively low pressure, and / or 25. The apparatus of claim 24, configured to match electric field strength in areas of relatively high pressure and / or areas of relatively low pressure. 26. The apparatus of claim 24 or 25, wherein the voltage applied to the gas restrictor is a DC voltage. 27. The apparatus of any one of claims 24 to 26, further comprising a second surface facing the array of electrodes, the gas restrictor extending from the second surface toward the array of electrodes. 28. The apparatus of any one of paragraphs 24 to 27, wherein at least one electrode in the array of electrodes near the gas restrictor is narrower than multiple other electrodes in the array of electrodes. 29. The relatively high pressure region is 0.1 to 2×10 -2 and / or The relatively low pressure region is 0.5 to 5 × 10 -3 29. The apparatus according to any one of items 22 to 28, having a pressure of 1000 psi or less. 30. An apparatus described in any one of the preceding claims, wherein at least one of the array of electrodes and the one or more further electrodes is a transport electrode, and the control circuitry is configured to apply a transport voltage to the transport electrode to transport ions along the trapping region. 31. The apparatus described in paragraph 31, wherein the trapping region has a region of relatively low pressure and a region of relatively high pressure, and the control circuit is configured to apply a transport voltage to transport ions between the relatively high pressure region of the trapping region and the relatively low pressure region of the trapping region. 32. The apparatus of claim 30 or 31, wherein the transport voltage has a DC gradient configured to transport ions along the DC gradient. 33. The device according to any one of claims 30 to 32, wherein the transport voltage is a DC voltage. 34. The apparatus of any one of paragraphs 30 to 32, wherein the transport voltage comprises a traveling wave configured to transport ions in the direction of the traveling wave. 35. The apparatus of claim 34, wherein the control circuit is configured to superimpose a traveling wave voltage onto the set of oscillating voltages applied to the array of electrodes. 36. The device of any one of paragraphs 30 to 35, wherein the control circuit is configured to apply a transport voltage to the array of electrodes. 37. The device of any one of paragraphs 30 to 36, wherein the transport electrode comprises a plurality of transport electrode segments, and the control circuitry is configured to apply a voltage gradient across the plurality of transport electrode segments. 38. The apparatus of any one of clauses 30 to 37, wherein the one or more further electrodes include a transport electrode, the transport electrode being a funnel electrode, and the control circuitry is configured to apply a transport voltage to the funnel electrode. 39. The apparatus of claim 38, wherein the control circuitry is configured to apply a transport voltage to the funnel electrode to funnel ions as they move along the trapping region. 40. The apparatus of claim 39, wherein the control circuitry is configured to apply transport voltages to reduce lateral separation of ions as they move along the trapping region. 41. The apparatus of claim 39 or 40, further comprising an ion inlet for allowing ions to enter the trapping region, the funnel electrode comprising a first portion and a second portion, the first portion of the funnel electrode tapering away from the ion inlet. 42. The apparatus of claim 41, wherein the first and second portions of the funnel electrode are substantially coplanar. 43. The apparatus of claim 41 or 42, wherein the control circuit is configured to apply a higher voltage to the second portion of the funnel electrode than to the first portion of the funnel electrode. 44. An apparatus according to any one of the preceding claims, wherein the control circuitry is configured to apply a trapping voltage to one or more further electrodes after ions have entered the trapping region. 45. An apparatus according to paragraph 44, wherein the trapping voltage has a magnitude smaller than the magnitude of the set of oscillating voltages applied to the array of electrodes. 46. ​​The device according to claim 44 or 45, wherein the trapping voltage is a DC voltage. 47. An apparatus according to any one of the preceding claims, wherein at least one of the array of electrodes and the one or more further electrodes comprises an extraction electrode, and the control circuitry is configured to apply an extraction voltage to the extraction electrode. 48. The device of paragraph 47, wherein the extraction electrode is on the opposite side of the array of electrodes, and preferably the extraction electrode is substantially parallel to the array of electrodes. 49. The device of claim 47 or 48, wherein the extraction electrode comprises one or more apertures to allow ions to pass therethrough. 50. An apparatus according to any one of paragraphs 47 to 49, wherein the extraction electrode is a grid electrode and / or a segmented electrode with a plurality of openings to allow ions to pass therethrough. 51. The apparatus of any one of paragraphs 47 to 50, wherein the extraction voltage has a magnitude greater than the trapping voltage. 52. The control circuit is applying a trapping voltage to the extraction electrode to trap ions within the trapping region; 52. The device according to any one of items 47 to 51, configured to apply an extraction voltage to an extraction electrode to extract ions from the trapping region. 53. An apparatus according to any one of paragraphs 47 to 52, wherein the trapping region has a region of relatively low pressure and a region of relatively high pressure, and the extraction electrode extends along the region of relatively low pressure. 54. A device according to any one of the preceding claims, comprising a second surface, the second surface facing the array of electrodes, the second surface comprising one or more of an extraction electrode, a transport electrode, and / or a funnel electrode. 55. A device according to any one of the preceding claims, wherein the array of electrodes has spacing of less than 5 mm, less than 3 mm, less than 1 mm, less than 0.1 mm, or less than 0.01 mm. 56. A device according to any one of the preceding claims, wherein each electrode in the array of electrodes has an antiphase with respect to each adjacent electrode. 57. A device according to any one of the preceding claims, wherein the array of electrodes is substantially planar. 58. An apparatus as described in any one of the preceding claims, wherein the one or more further electrodes include one or more barrier electrodes positioned around the trapping region, and the control circuitry is configured to apply a barrier voltage to the one or more barrier electrodes to trap ions in the trapping region. 59. the control circuitry is configured to apply the set of oscillating voltages and the trapping voltage such that ions are positioned within a first distance range from the array of electrodes; 59. The apparatus of claim 58, wherein the barrier voltage defines a potential barrier extending to at least a first distance from the array of electrodes. 60. The control circuit comprises: a DC barrier voltage to at least one of the one or more barrier electrodes; a radio frequency (RF) barrier voltage to at least one of the one or more barrier electrodes; and / or 60. The apparatus of claim 58 or 59, configured to apply one or more of a DC barrier voltage and a superposition of an RF barrier voltage to at least one of the one or more barrier electrodes. 61. The device of any one of clauses 58 to 60, wherein the one or more barrier electrodes include a plurality of barrier electrodes. 62. The apparatus of claim 61, wherein the control circuit is configured to apply barrier voltages having opposite phases to adjacent barrier electrodes. 63. The device of claim 61 or 62, wherein one or more of the plurality of barrier electrodes are positioned at the ends of the electrodes of the array of electrodes. 64. A device according to any one of the preceding claims, further comprising one or more substrates, and at least one of the one or more further electrodes and the array of electrodes being on the one or more substrates. 65. The apparatus of claim 64, wherein the one or more substrates are one or more printed circuit boards (PCBs). 66. A mass spectrometry system comprising: An apparatus for trapping ions according to any one of the preceding claims; A mass analysis system comprising: a mass analyzer configured to receive ions from the device for trapping ions, the mass analyzer preferably being a time-of-flight mass analyzer.

Claims

1. 1. An apparatus for trapping ions, comprising: an array of electrodes extending along a surface of the device; one or more further electrodes different from the array of electrodes; a trapping region for receiving the ions, the trapping region being defined by the array of electrodes and the one or more further electrodes; A control circuit, The control circuit includes: applying a set of oscillating voltages to the array of electrodes such that each electrode in the array of electrodes has a different phase relative to each adjacent electrode to repel the ions from the array of electrodes; applying a DC trapping voltage to at least one of the one or more further electrodes to force the ions towards the array of electrodes, the set of oscillating voltages and the DC trapping voltage thereby trapping the ions within the trapping region; ceasing application of the set of oscillating voltages to the array of electrodes during a delay period; applying a DC focusing voltage to at least one of the one or more further electrodes during the delay period to force the ions towards the array of electrodes; configured to apply an extraction voltage to at least one of the array of electrodes and / or the one or more further electrodes after the delay period to extract the ions from the trapping region; The control circuit includes: applying the set of oscillating voltages and the DC trapping voltage such that the ions are positioned at a first distance range from the array of electrodes; 13. An apparatus for trapping ions configured to apply the DC focusing voltage to reduce the first distance range from the array of electrodes at which the ions are positioned.

2. The apparatus of claim 1 , wherein the control circuitry is configured to apply the DC focusing voltage and the DC trapping voltage to the same at least one of the one or more further electrodes.

3. The apparatus of claim 1 , wherein the DC focusing voltage is the DC trapping voltage.

4. The DC focusing voltage is a magnitude less than the magnitude of the set of oscillating voltages; and / or The device of claim 1 having a magnitude of at least 5V, at least 10V, or at least 20V.

5. The delay period is: 0.1 μs to 2 μs, or The device of claim 1 having a duration of 0.1 μs to 1 μs.

6. The apparatus of claim 1 , wherein the magnitude of the DC focusing voltage is ramped or pulsed during the delay period.

7. The apparatus of claim 1 , wherein the DC focusing voltage has a plurality of different magnitudes during a plurality of respective time intervals during the delay period.

8. The apparatus of claim 1 , wherein the magnitude of the DC focusing voltage is constant during the delay period.

9. 2. The apparatus of claim 1 , wherein at least one of the array of electrodes and the one or more further electrodes is a transport electrode, and the control circuitry is configured to apply a transport voltage to the transport electrode to transport ions along the trapping region.

10. 10. The apparatus of claim 9, wherein the trapping region has a region of relatively low pressure and a region of relatively high pressure, and the control circuitry is configured to apply the transport voltage to transport ions between the relatively high pressure region of the trapping region and the relatively low pressure region of the trapping region.

11. The apparatus of claim 1 , wherein the control circuitry is configured to apply the DC trapping voltage to the one or more further electrodes after the ions enter the trapping region.

12. The apparatus of claim 11 , wherein the DC trapping voltage has a magnitude less than a magnitude of the set of oscillating voltages applied to the array of electrodes.

13. 2. The apparatus of claim 1, wherein at least one of the array of electrodes and the one or more further electrodes comprises an extraction electrode, and the control circuitry is configured to apply the extraction voltage to the extraction electrode.

14. The apparatus of claim 13 , wherein the extraction voltage has a magnitude greater than a magnitude of the DC trapping voltage.

15. The control circuit includes: applying the DC trapping voltage to the extraction electrode to trap ions within the trapping region; 14. The apparatus of claim 13 configured to apply the extraction voltage to the extraction electrode to extract the ions from the trapping region.

16. 14. The apparatus of claim 13, wherein the trapping region has a region of relatively low pressure and a region of relatively high pressure, and the extraction electrode extends along the region of relatively low pressure.

17. 2. The apparatus of claim 1 , wherein the one or more further electrodes include one or more barrier electrodes positioned around the trapping region, and the control circuitry is configured to apply a barrier voltage to the one or more barrier electrodes to trap ions in the trapping region.

18. the control circuitry is configured to apply the set of oscillating voltages and the DC trapping voltage such that the ions are positioned within a first distance range from the array of electrodes; 20. The apparatus of claim 17, wherein the barrier voltage defines a potential barrier that extends to at least the first distance from the array of electrodes.

19. 1. A mass spectrometry system comprising: An apparatus for trapping ions as claimed in claim 1; a mass analyzer configured to receive ions from the device for trapping ions.

20. The mass spectrometry system of claim 19, wherein the mass analyzer is a time-of-flight mass analyzer.

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