Electrode for spectrometer
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- SMITHS DETECTION WATFORD LTD
- Filing Date
- 2024-06-27
- Publication Date
- 2026-05-06
Smart Images
Figure GB2024051668_02012025_PF_FP_ABST
Abstract
Description
[0001] ELECTRODE FOR SPECTROMETER
[0002] Field of the invention
[0003] The present disclosure relates to an electrode for a spectrometer, in particular, an electrode for an ion gate and / or ion modifier for a spectrometer, such as an ion mobility spectrometer.
[0004] Background
[0005] Ion mobility spectrometers (IMSs) are used to make determinations of substances in a sample. The sample is vaporised and ionised (e.g. by an ionisation source) and then selectively admitted to a drift chamber by an ion gate. Admitted ions in the drift chamber are moved by drift electrodes against a drift gas of known characteristics until the ions reach a detector at an end of the drift chamber. The time-of-flight (TOF) of the ions (i.e. the time taken for the ions to travel from the ion gate to the detector) is indicative of the mobility of said ion. Ions having different characteristics (e.g. mass and shape) have different mobilities in the drift tube and so a determination of the ions in the sample can be made based on said mobilities.
[0006] Tyndall-Powell ion gates are a specific type of ion gate for use in IMSs which are typically chosen fortheir relative ease of construction. However, typically Tyndall-Powell ion gates often sacrifice ion transmission (i.e. the relative proportion of ions which can pass through the gate) in comparison to other gate designs. Therefore, IMSs with a Tyndall-Powell ion gate often sacrifice sensitivity due to the relatively poor transmission of ions therethrough.
[0007] Bradbury-Neilson ion gates are an alternative to Tyndall-Powell ion gates. Bradbury-Nielson ion gates have two electrodes spaced in a direction of travel of ions passing therethrough (e.g. a spacer may be disposed between the two electrodes). In examples, the two electrodes may have approximately the same position along the direction of travel of ions (e.g. they may be aligned in the direction of travel of ions). Bradbury Nielson ion gate have two main drawbacks which are not present in Tyndall-Powell ion gates.
[0008] A first drawback is that, Bradbury-Nielson ion gates have an open area (e.g. the area of the gate through which ions can pass) which typically provides reduced ion transmission compared to a comparable Tyndall-Powell ion gate which may comparatively reduce the sensitivity of a detector of an IMS.
[0009] A second drawback is that, when a Bradbury-Nielson ion gate is closed, electric field lines around the gate cause a region devoid of ions to form, called the ‘depletion region’. When the Bradbury-Nielson ion gate is then subsequently opened, ions must traverse the depletion region before they can pass through the gate. This effectively extends the ‘cutting width’ of the gate, and reduces the number of ions which can pass through the gate during the short period of time for which it is open.
[0010] Summary
[0011] Aspects of the invention are as set out in the independent claims and optional features are set out in the dependent claims. Aspects of the invention may be provided in conjunction with each other and features of one aspect may be applied to other aspects.
[0012] An aspect provides an electrode for providing a Tyndall-Powell gate structure, the electrode comprising: a conductive structure comprising a hexagonal lattice and a frame around the hexagonal lattice, wherein the hexagonal lattice is planar and the frame is configured to provide additional support to the hexagonal lattice.
[0013] The frame may be configured to provide additional support to the hexagonal lattice, which may advantageously permit a hexagonal lattice with a greater open area (e.g. which may require additional support from a frame) to be provided in comparison to a hexagonal lattice with a comparatively less open area (e.g. which may not require additional support from a frame). Accordingly, a hexagonal lattice with a comparatively greater open area (e.g. a greater ratio of open area to closed area of the lattice) may be provided which may improve ion transmission past the electrode (e.g. through the open areas). For example, a hexagonal lattice with a greater open area may not be self-supporting (e.g. the hexagonal lattice may not be able to retain a planar shape without the additional support provided by a frame).
[0014] The frame may have a thickness perpendicular to the hexagonal lattice which is greater than a thickness of the hexagonal lattice.
[0015] Accordingly the frame may be comparatively more rigid (e.g. than the hexagonal lattice which may advantageously, permit the frame to provide additional support to the hexagonal lattice.
[0016] Tyndall-Powell ion gates may not suffer from the drawbacks of Bradbury-Nielson ion gates. For example, Tyndall-Powell ion gates may not have a significant depletion region, because electric field lines around the electrode may remain substantially parallel which results in ion paths remaining parallel. When a Tyndall-Powell ion gate is opened, there may be ions in very close proximity to the gate electrode (i.e. because there is no or a very small depletion region) which may, for the same open period, permit more ions to pass through a Tyndall-Powell ion gate than a Bradbury-Nielson ion gate. The frame and the hexagonal lattice may be unitary. The frame and hexagonal lattice may be formed as a single element. For example, the frame and the hexagonal lattice may be formed by an additive manufacturing process, for example, by electrodeposition.
[0017] The frame and the conductive structure may substantially consist of a metal suitable for electrodeposition. For example, the metal may be any of the following metals, either singly or provided in combination (e.g. as alloys): aluminium, zinc, silver, palladium, tantalum, zirconium, gadolinium, nickel, cobalt, copper. Particularly preferable metals may be zinc and / or nickel which are readily available, and / or may be comparatively cheaper than at least some of the other listed metals (e.g. compared to silver), and / or may be comparatively less susceptible to corrosion when used as an electrode in a spectrometer (e.g. compared to copper).
[0018] The conductive structure may comprise conductive struts which form the hexagonal lattice wherein the conductive struts may have a width of between 0.080 mm to 0.005 mm in a direction parallel to the hexagonal lattice. More preferably the conductive struts may have a width of between 0.040 mm to 0.010 mm in a direction parallel to the hexagonal lattice. Yet more preferably the conductive struts may have a width of 0.020 mm.
[0019] In examples, reducing the width of conductive struts may reduce the number of ions in a spectrometer which impact the hexagonal lattice which advantageously improves ion throughput through the electrode.
[0020] The conductive structure may comprise conductive struts which form the hexagonal lattice wherein the conductive struts may have a thickness of between 0.080 mm to 0.005 mm in a direction perpendicular to the hexagonal lattice. More preferably the conductive struts may have a thickness of between 0.030 mm to 0.010 mm in a direction perpendicular to the hexagonal lattice. Yet more preferably the conductive struts may have a thickness of 0.018mm.
[0021] In examples, reducing the thickness of conductive struts may reduce the number of ions in a spectrometer which impact the hexagonal lattice which advantageously improve ion throughput through the electrode.
[0022] The frame may comprises a plurality of frame locator features configured to engage a respective plurality of holder locator features on a holder for holding the electrodes.
[0023] The engagement of the frame locator features of each electrode with the holder locator features may arrange the conductive structure of the first electrode parallel to the conductive structure of the second electrode.
[0024] Engagement of the frame locator features of each electrode with the holder locator features may align the hexagonal lattice of the first electrode with the hexagonal lattice of the second electrode in a direction perpendicular to the hexagonal lattice of each electrode.
[0025] In examples, any of: at least one of the frame locator features comprises a hole and at least one of the holder locator features comprises a peg configured to fit the hole; and, at least one of the holder locator features comprise a hole and at least one of the frame locator features comprises a peg configured to fit the holes. The holes may be configured to receive the pegs.
[0026] A given hole and peg may be configured to provide an interference fit therebetween. A given hole and peg may be configured to provide a transition fit therebetween.
[0027] In examples, all of the frame locator features may be pegs and all of the holder locator features may be holes (e.g. a corresponding number of pegs to holes) wherein the holes are configured to receive the pegs. In examples, all of the frame locator features may be holes and all of the holder locator features may be pegs (e.g. a corresponding number of pegs to holes) wherein the pegs configured to receive the holes. In examples, the frame locator features may comprise at least one peg (e.g. X pegs) and at least one hole (e.g. Y holes) and the holder locator features may comprise at least one peg (e.g. Y pegs) and at least one hole (e.g. X holes).
[0028] The frame locator features may be disposed around the frame to provide a plurality of frame locator features wherein the mean horizontal position and / or mean vertical position of the plurality of frame locator features is located less than a predetermined distance from the centre of the hexagonal lattice, wherein the predetermined distance is based on a width of the conductive struts in a direction parallel to the hexagonal lattice.
[0029] Advantageously the above recited feature may permit two electrodes to be provided in an aligned arrangement. For example, providing electrodes with the above arrangement of mean horizontal and / or mean vertical position, The frame locator features may be positioned such that when the frame locator features are located on holder locator features the conductive struts of the respective hexagonal lattice are aligned.
[0030] The first electrode may be aligned with the second electrode. The electrodes may be aligned if the shortest distance between a given conductive strut 116 on the first electrode 110 and a conductive strut on the second electrode 120 is the electrode spacing.
[0031] The first electrode may be antialigned with the second electrode. The first electrode may be antialigned with the second electrode when the shortest distance between the centre of a polygonal opening of a lattice of the first electrode and a conductive strut node of a lattice of the second electrode is the electrode spacing. Antialignment may provide improved ion modification of ions when the first and second electrode are operated as an ion modifier.
[0032] An aspect provides a Tyndall-Powell ion gate comprising: a first electrode and a second electrode, wherein each of the first electrode and the second electrode comprises: a conductive structure comprising a hexagonal lattice wherein the hexagonal lattice is planar, a holder configured to hold the first electrode relative to the second electrode so that the planar hexagonal lattice of the first electrode is: parallel to the planar hexagonal lattice of the second electrode; and, spaced from the second electrode by an electrode spacing.
[0033] The ion gate may comprise two electrodes each comprising a hexagonal lattice which may have a comparatively greater open area (e.g. a greater ratio of open area to closed area of the lattice) in comparison to other electrode lattice geometries (e.g. square lattice geometries) for a given thickness of the conductive stuts of said lattice. For example, all other things being equal (e.g. area of lattice, geometry of lattice) electrodes with a hexagonal lattice have the greatest ratio of open to closed area and, therefore, may advantageously provide improved ion transmission past the electrodes (e.g. through the open areas).
[0034] The Tyndall-Powell ion gate may comprise: a first electrode voltage circuit configured to vary a voltage of the first electrode; and, a second electrode voltage circuit configured to vary a voltage of the second electrode; wherein the first electrode voltage circuit and the second electrode voltage circuit are configured to control a barrier voltage between the first electrode and the second electrode by varying the voltage of the first electrode and the voltage of the second electrode thereby to control passage of ions through the hexagonal holes of the electrodes of the ion gate. The Tyndall-Powell ion gate may comprise: a first electrode voltage circuit configured to control a voltage of the first electrode; and, a second electrode voltage circuit configured to control a voltage of the second electrode; wherein one of the first electrode voltage circuit or the second electrode voltage circuit is configured to control a barrier voltage between the first electrode and the second electrode by varying the voltage of either the first electrode or the second electrode thereby to control passage of ions through the hexagonal holes of the electrodes of the ion gate.
[0035] The gate may advantageously be operated to selectively admit passage of ions with one or more given characteristics.
[0036] The first electrode voltage circuit and the second electrode voltage circuit may be configured to provide a modification voltage between the first electrode and the second electrode by varying the voltage of the first electrode and the voltage of the second electrode thereby to modify ions disposed between the first electrode and the second electrode.
[0037] The ion gate may be operated as an ion modifier. When operated as an ion modifier, the ion gate may break an ion (e.g. a parent ion) in to a plurality of other ions (e.g. daughter ions).
[0038] Each of the first electrode and the second electrode may comprise a frame configured to provide additional support to the hexagonal lattice. The frames may be configured to provide additional support to the hexagonal lattices, which may advantageously permit hexagonal lattices with a greater open area (e.g. which may require additional support from a frame) to be provided in comparison to hexagonal lattices with a comparatively less open area (e.g. which may not require additional support from a frame).
[0039] The frame of each electrode may comprise a plurality of frame locator features which may be configured to engage a respective plurality of holder locator features on a holder for holding the electrodes.
[0040] Engagement of the frame locator features of each electrode with the holder locator features may arrange the conductive structure of the first electrode parallel to the conductive structure of the second electrode.
[0041] Engagement of the frame locator features of each electrode with the holder locator features may align the hexagonal lattice of the first electrode with the hexagonal lattice of the second electrode in a direction perpendicular to the hexagonal lattice of each electrode. In examples, engagement of the frame locator features of each electrode with the holder locator features may align the conductive structure of the first electrode parallel to the conductive structure of the second electrode and may antialign the hexagonal lattice of the first electrode with the hexagonal lattice of the second electrode in a direction perpendicular to the frame area of each electrode. Antialigning electrodes in this way may improve modification of ions when operated as an ion modifier in comparison to similar electrodes being aligned in the direction perpendicular to the hexagonal lattice.
[0042] The first electrode and the second electrode may be aligned so that the difference in alignment between conductive elements of the first electrode and conductive elements of the second electrode is less than the width of the conductive elements in a direction parallel to the conductive structure.
[0043] Advantageously the above recited feature may permit two electrodes to be provided in an aligned arrangement. For example, providing electrodes with the above arrangement of mean horizontal and / or mean vertical position.
[0044] The frame locator features may be positioned such that when the frame locator features are located on holder locator features the conductive struts of the respective hexagonal lattice are aligned.
[0045] The first electrode may be aligned with the second electrode. The electrodes may be aligned if the shortest distance between a given conductive strut 116 on the first electrode 110 and a conductive strut on the second electrode 120 is the electrode spacing.
[0046] The first electrode may be antialigned with the second electrode. The first electrode may be antialigned with the second electrode when the shortest distance between the centre of a polygonal opening of a lattice of the first electrode and a conductive strut node of a lattice of the second electrode is the electrode spacing. Antialignment may provide improved ion modification of ions when the first and second electrode are operated as an ion modifier.
[0047] The holder may comprise a spacer disposed between the first electrode and the second electrode.
[0048] A predetermined spacing between the first electrode and the second electrode may be provided using the spacer without the need for time consuming calibration of the spacing (e.g. distance) between the electrodes. In examples, the electrode spacing (e.g. the distance between the first electrode and the second electrode) may be 0.2 mm.
[0049] The spacer may be formed of any of: a liquid crystal polymer; polytetrafluoroethylene (PTFE); polyether ether ketone (PEEK), or a ceramic. Advantageously these materials have a low susceptibility to electrical creepage.
[0050] The first electrode volage circuit and the second electrode volage circuit may be configured to control a barrier voltage between the first electrode and the second electrode by varying the voltage of the first electrode and the voltage of the second electrode thereby may control passage of ions through the hexagonal holes of the electrodes of the ion gate in a drift direction of the ion mobility spectrometer, wherein the drift direction is perpendicular to the conductive structure of each of the electrodes.
[0051] The gate may advantageously be operated to selectively admit passage of ions with one or more given characteristics.
[0052] An aspect provides an electrode for a Tyndall-Powell ion gate comprising: a frame delimiting a frame area; and, a conductive structure disposed within the frame area, wherein the conductive structure comprises conductive elements arranged in a regular pattern to provide a regular tessellating array of polygonal openings between the conductive elements, wherein the percentage of the frame area comprising open area provided by the polygonal openings is between 75.0% to 95.0%. Preferably the percentage of the frame area comprising open area provided by the polygonal openings may be 88.9%.
[0053] An aspect provides a method of manufacturing a Tyndall-Powell ion gate for an ion mobility spectrometer, the method comprising: mechanically fixing a first electrode and a second electrode relative to each other to provide a spacing therebetween, wherein the first electrode and the second electrode are formed by electrodeposition.
[0054] The method may comprise: forming, by electrodeposition, each of the first electrode and the second electrode.
[0055] Advantageously the electrodes may comprise a frame and lattice which are unitarily formed which may improve strength of the electrodes and / or may reduce manufacturing time and / or cost. Mechanically fixing the first electrode and a second electrode relative to each other to provide a spacing therebetween, may comprise: engaging a first set of holder locator features with corresponding frame locator features of a frame of the first electrode; engaging a second set of holder locator features with corresponding frame locator features a frame of the second electrode.
[0056] Advantageously, an ion gate may be provided comprising two electrodes. The ion gate may be operated as an ion modifier.
[0057] An aspect provides a method of manufacturing an electrode for a Tyndall-Powell ion gate, the electrodes comprising a conductive structure comprising a hexagonal lattice and a frame around the hexagonal lattice, wherein the hexagonal lattice is planar and composed of conductive struts and the frame is configured to provide additional support to the hexagonal lattice, and wherein the frame comprises a plurality of frame locator features configured to engage a respective plurality of holder locator features on a holder for holding the electrodes, wherein the method comprises: disposing the frame locator features around the frame to provide a plurality of frame locator features wherein the mean horizontal position and / or mean vertical position of the plurality of frame locator features is located less than a predetermined distance from the centre of the hexagonal lattice, wherein the predetermined distance is based on a width of the conductive struts in a direction parallel to the hexagonal lattice.
[0058] Advantageously the above recited feature may permit two electrodes to be provided in an aligned arrangement. For example, providing electrodes with the above arrangement of mean horizontal and / or mean vertical position,
[0059] The frame locator features may be positioned such that when the frame locator features are located on holder locator features the conductive struts of the respective hexagonal lattice are aligned.
[0060] The electrodes may be aligned if the shortest distance between a given conductive strut 116 on the first electrode 110 and a conductive strut on the second electrode 120 is the electrode spacing.
[0061] The first electrode may be antialigned with the second electrode. The first electrode may be antialigned with the second electrode when the shortest distance between the centre of a polygonal opening of a lattice of the first electrode and a conductive strut node of a lattice of the second electrode is the electrode spacing. Antialignment may provide improved ion modification of ions when the first and second electrode are operated as an ion modifier.
[0062] An aspect provides a method of manufacturing a Tyndall-Powell ion gate comprising the two electrodes manufactured according any method described herein. In examples, the method may comprise forming the first electrode and second electrode by electrodeposition.
[0063] The first electrode and the second electrode may be aligned so that the difference in alignment between conductive elements of the first electrode and conductive elements of the second electrode is less than the width of the conductive elements in a direction parallel to the frame area.
[0064] Brief description of the drawings
[0065] Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:
[0066] Figure 1 illustrates a perspective view of an ion gate comprising two electrodes;
[0067] Figure 2A illustrates a longitudinal plan view of the ion gate of Figure 1 showing the first electrode;
[0068] Figure 2B illustrates a reverse longitudinal plan view of the ion gate of Figures 1 and 2A showing the second electrode;
[0069] Figure 3A illustrates a side plan view of the first electrode of the ion gate of Figure 1 ;
[0070] Figure 3B illustrates an enlarged side plan view of a portion of the first electrode shown in Figure 3A;
[0071] Figure 3C illustrates a longitudinal plan view of a portion of the lattice of the first electrode 110 shown in Figures 3A & 3B;
[0072] Figure 4 illustrates an enlarged side cross-sectional view of the ion gate of Figure 1 ;
[0073] Figure 5 illustrates a flowchart depicting a method of manufacturing an electrode;
[0074] Figure 6 illustrates a flowchart depicting a method of manufacturing a Tyndall-Powell ion gate. In the drawings, like reference signs indicate like elements.
[0075] Specific description
[0076] Figure 1 illustrates a perspective view of an ion gate 100 comprising a first electrode 110 and a second electrode 120. Figure 2A illustrates a longitudinal plan view of the ion gate 100 of Figure 1 showing the first electrode 110 and Figure 2B illustrates a reverse longitudinal plan view of the ion gate 100 to that shown in Figure 2B thereby showing the second electrode 120.
[0077] The ion gate 100 comprises: a first electrode 110; a second electrode 120; a holder 130; and, a spacer 140. The first electrode 110, second electrode 120, and the spacer 140 (not visible in Figures 1 , 2A, & 2B, but visible in Figure 4) are disposed within the holder 130 i.e. the holder 130 holds the first electrode 110, the second electrode 120, and the spacer 140. The spacer 140 is disposed between the first electrode 110 and the second electrode 120 to thereby provide an electrode spacing Z therebetween (spacing Z is visible in Figure 4).
[0078] The first electrode 110 and the second electrode 120 are identical in the example shown in Figure 1. The first electrode 110 comprises: a frame 111 delimiting a frame area 112; a conductive structure comprising a lattice 113; frame locator features 114. Similarly, the second electrode 120 comprises: a frame 121 delimiting a frame area 122; conductive structure comprising a lattice 123; frame locator features 124.
[0079] Figure 3A illustrates a side plan view of the first electrode 110 of the ion gate of Figure 1 ; Figure 3B illustrates an enlarged side plan view of a portion of the first electrode 110 shown in Figure 3A. Figure 3C illustrates a longitudinal plan view of a portion of the lattice of the first electrode 110 shown in Figures 3A & 3B. It will be appreciated that the first electrode 110 is described here for brevity but that description applies equally to the second electrode 120, because the two electrodes are identical.
[0080] Each electrode has a frame. The frame 111 delimits a frame area 112 which is occupied by the lattice. In Figures 1 and 2 the frame area is circular but any other shape of frame area may be provided (e.g. the hole may be a regular hexagon).
[0081] The lattice 113 is a planar conductive structure disposed within the frame area 112 of frame 111. The lattice 113 comprises a plurality of conductive struts 116. The lattice 113 is connected to the frame 111. The frame 111 has a frame thickness 111 T and the lattice 113 has a lattice thickness 113T. The thicknesses are the spatial extent of each element in the direction perpendicular to the plane defined by the lattice 113. The frame thickness 111 T is greater than the lattice thickness 113T.
[0082] An electrical connection 115 is connected to the frame 111. The electrical connection 115, frame 111 , and lattice 113 are formed of conductive materials. The frame 111 and lattice 113 are unitarily formed (i.e. formed as a single element). In the present example, the electrical connection 115 is unitarily formed with the frame 111 and lattice 113. The lattice 113 is configured to connect to a voltage source via electrical connection 115.
[0083] The conductive struts 116 of the lattice 113 define openings 117 i.e. the openings 117 are spaces provided between conductive struts 116. Figures 1 to 3C illustrate a hexagonal lattice 113. The term hexagonal lattice refers to a lattice wherein the openings 117 have a regular hexagonal shape e.g. the hexagonal lattice has a honeycomb pattern.
[0084] Each conductive strut 116 has a length 116L i.e. they all have the same length. Each conductive strut has a width 116W. In the present example, the width 116W is 0.020mm but a width in the range 0.080 mm to 0.005 mm is acceptable. Each conductive strut has a thickness 116T. In the present example, the thickness 116T is 0.018 mm but a thickness in the range 0.030 mm to 0.010 mm is acceptable.
[0085] Decreasing the width 116W and / or thickness 116T of the lattice 113 improves ion transmission through the electrode 110 but reduces the strength of the lattice 116 and results in an electrode which is comparatively easier to damage. One way to decrease the width and / or thickness of a lattice of an electrode (e.g. first 110 and second electrodes 120) without sacrificing the robustness of the electrode is to provide a frame which provides additional support to the lattice.
[0086] The thickness 111T of the frame 111 is selected so that the frame 111 is self-supporting and to provide additional support to the lattice 113. Unitarily forming the frame 111 and lattice 113 also provides additional support to the lattice 113.
[0087] The frame 111 is self-supporting when the shape of the hole of the frame 111 does not deform under gravity in any orientation (e.g. relative to the gravitational field). In the present example, when the frame is arranged so that the frame area is arranged parallel to a local gravitational field (i.e. the frame is arranged perpendicular to the ground) then the hole remains circular.
[0088] The lattice 113 may not be self-supporting i.e. the lattice thickness 113T and / or the width of the conductive struts 113W may be too thin to permit the lattice to retain its shape under gravity in any orientation. The frame 111 provides additional support to the lattice 113 when the lattice 113 is not self-supporting and the frame 111 resists deformation of the frame 111 and lattice 113 in any orientation relative to a gravitational field.
[0089] The thickness 111T required for the frame to be self-supporting and to provide additional support to the lattice 113 will depend on the material from which the frame is formed. Typically a metal or alloy of metals and the thickness of the frame is approximately 0.05 mm to 0.20 mm. In examples wherein the frame and lattice are unitarily formed of nickel then frame thickness is 0.10 mm. The frame 111 has an electrical connection 115 which extends generally from the lattice. The electrical connection 115 is configured to connect to the first electrode voltage circuit.
[0090] The geometry of the lattice 113 shown in Figure 3C is described in more detail below. However, it is noted that the teaching set out herein is not confined to lattices having a hexagonal geometry. The electrodes for the ion gate can have any lattice geometry (e.g. any polygonal shapes defined by the conductive struts). The electrodes can be characterised in a more general way, without explicitly requiring a description of the lattice geometry. The electrodes comprise a frame delimiting a frame area: the frame delimiting a frame area, and a conductive structure disposed in the frame area. The conductive structure comprises conductive elements arranged in a regular pattern to provide a regular tessellating array of polygonal openings (e.g. triangles, squares, hexagons etc.) between the conductive elements. The percentage of the frame area comprising open area provided by the polygonal openings is between 75.0% to 95.0%. In preferred embodiments wherein the polygonal openings are hexagons, the percentage is 88.9%.
[0091] Increasing the percentage of the frame area comprising open area has a corresponding increase in ion transmission through the electrode which may in turn improve resolution of a spectrometer (e.g. an IMS) in which electrode is disposed. The percentage depends on the chosen regular pattern providing regular the tessellating of polygonal openings and the width of the conductive elements (i.e. the spatial extent of the conductive struts in the frame area).
[0092] The inventors have found that the regular pattern providing a tessellating array of polygonal openings provides strength to a conductive structure, and that reducing the width of conductive struts of the regular pattern improves ion transmission through the electrode. These parameters can be varied to find a trade off between strength and improved ion transmission and the inventors have found that the percentage of the frame area comprising open area provided by the polygonal openings between 75.0% to 95.0% provides a good practical balance between strength and transmission.
[0093] It will be appreciated to one skilled in the art that there are a multitude of possible conductive strut lengths, widths, and thicknesses and also a multitude of possible regular patterns which will provide an electrode with which has a percentage of the frame area comprising an open area provided by the polygonal openings between 75.0% to 95.0%. Therefore those skilled in the art will recognise that this is a fair characterisation of the electrode as it is not so broad that it goes beyond the invention (e.g. balancing strength and ion transmission) but is not so narrow as to deprive the applicant of a just reward for the present disclosure of the invention.
[0094] The hexagonal lattice 113 illustrated in Figure 3C has conductive struts 116. The plurality of the conductive struts 116 are unitarily formed (i.e. formed as a single element) to provide the lattice 113. The conductive stuts 116 are joined at conductive strut nodes 116N. To provide the honeycomb shape, each conductive strut node 116N has three conductive struts 116 radiating therefrom. The three conductive struts 116 are arranged in a plane (i.e. the plane of the conductive structure which is coincident with the frame area 112) and are equidistantly disposed in that plane around the node 116N i.e. there is 60° between a given conductive strut 116 and its two neighbouring conductive struts 116.
[0095] In more detail, each hexagonal opening 117 is delimited by six conductive struts 116. These six conductive struts 116 are arranged end-to-end in a closed arrangement i.e. with a perimeter of 6L. A first conductive strut is connected, at one end to an end of a second conductive strut, and at another end to an end of a sixth conductive strut. The other end of the second conductive strut is connected to an end of a third conductive strut and so on i.e. continuing the pattern for a fourth conductive strut, fifth conductive strut, and sixth conductive strut (the last of which is connected to the fifth and first conductive struts). The angle between neighbouring struts (e.g. between the first and second conductive struts) is 120°. In this way six conductive struts each provide a side of a regular hexagon thereby defining a hexagonal opening (i.e. a hole).
[0096] A hexagonal regular pattern (e.g. honeycomb) provides polygonal openings with a greater area than a square regular pattern or a triangular regular pattern (i.e. when all other factors, such as the conductive strut width are equal). One way of providing an electrode with a percentage of the frame area comprising an open area (i.e. provided by the polygonal openings) between 75.0% to 95.0% is to use a hexagonal regular pattern and an appropriate width of the conductive struts.
[0097] By providing first and second electrodes 110 and 120 comprising hexagonal lattices, electrodes with a comparatively greater open area in comparison to other electrode lattice geometries (e.g. square lattice geometries) for a given thickness of the conductive stuts of said lattice. For example, all other things being equal (e.g. area of lattice, geometry of lattice) electrodes with a hexagonal lattice have the greatest ratio of open to closed area and, therefore, may advantageously provide improved ion transmission past the electrodes (e.g. through the open areas). Figure 4 illustrates an enlarged side cross-sectional view of the ion gate 100 of Figure 1. Figure 4 shows: part of the first electrode 110; a frame locator feature 114 of the first electrode; a corresponding holder locator feature 135-1 for engaging the frame locator feature 114 of the first electrode; part of the second electrode 120; a frame locator feature 124 of the second electrode; a holder 130; a spacer 140; and, an electrode spacing Z between the first electrode 110 and the second electrode 120.
[0098] The spacer 140 is disposed in the holder 130 between the first electrode 110 and the second electrode 120. The first electrode 110 contacts a first side of the spacer 140 and the second electrode 120 contacts a second side of the spacer 140 wherein the first side of the spacer is opposite the second side of the spacer. The spacer 140 has a thickness equal to the electrode spacing Z.
[0099] The spacer 140 is formed from a material with a low susceptibility to electrical creepage. Forming the spacer 140 from a material with a low susceptibility to electrical creepage prevents (or comparatively reduces) damage of the spacer due to the electrical fields generated by the first and second electrodes.
[0100] The frame 111 of the first electrode 110 has four frame locator features 114 (see Figure 2A). The holder 130 has a first set of holder locator features 135-1 disposed on the holder 130. There are four holder locator features 135-1 in the first set.
[0101] The four frame locator features 114 are arranged equidistantly around the centre of the circular hole delimiting the frame area 112 i.e. each frame locator features are disposed on the corners of a square centred on the centre of the circular hole (see e.g. Figure 2A) . The frame locator features 114 are pegs which project perpendicular to the conductive structure of the electrode (i.e. the lattice 113). The first set of holder locator features 135-1 are holes corresponding in size shape and position to the pegs which are the frame locator features 114. Each given hole and peg pair (114 and 135-1) is configured to provide a friction fit therebetween (e.g. an interference or transition fit).
[0102] Each of the four holder locator features 135-1 in the first set are arranged to engage a respective frame locator feature of the first electrode 110 i.e. the holder locator features 114 are positioned around the holder 130 in like manner to the arrangement of the frame locator features 114.
[0103] The frame 121 of the second electrode 120 has four frame locator features 124 (see Figure 2B). The holder 130 has a second set of holder locator features 135-2 disposed on the holder 130. There are four holder locator features 135-2 in the second set.
[0104] Similar to the four frame locator features 114, the four frame locator features 124 are arranged equidistantly around the centre of the circular hole delimiting the frame area 122 i.e. each frame locator features are disposed on the corners of a square centred on the centre of the circular hole (see e.g. Figure 2B) . The frame locator features 124 are pegs which project perpendicular to the conductive structure of the electrode (i.e. the lattice 123). The second set of holder locator features 135-2 are holes corresponding in size shape and position to the pegs which are the frame locator features 124. Each given hole and peg pair (124 and 135-2) is configured to provide a friction fit therebetween (e.g. an interference or transition fit).
[0105] Each of the four holder locator features 135-2 in the second set are arranged to engage a respective frame locator feature of the second electrode 120 i.e. the holder locator features 124 are positioned around the holder 130 in like manner to the arrangement of the frame locator features 124.
[0106] The first set of holder locator features 135-1 and the second set of holder locator features 135- 2 are arranged to locate the first electrode 110 parallel to the second electrode 120 i.e. when the frame locator features 114 of the first electrode 110 engage the first set of holder locator features 135-1 and the frame locator features 124 of the second electrode 120 engage the second set of holder locator features 135-2, the planar conductive structure (i.e. lattice 113) of the first electrode 110 is parallel to the planar conductive structure (i.e. lattice 123) of the second electrode 120.
[0107] The first set of holder locator features 135-1 and the second set of holder locator features 135- 2 are arranged to locate the first electrode 110 in alignment with the second electrode 120 i.e. when the frame locator features of the first electrode engage the first set of holder locator features and the frame locator features of the second electrode engage the second set of holder locator features, the conductive struts in the first electrode are aligned with those of the second electrode 120 in the direction perpendicular to the planar conductive structures of the first electrode 110 and the second electrode 120 (i.e. perpendicular to lattices 113 and 123).
[0108] Alignment of the first electrode 110 and the second electrode 120 are considered aligned if the shortest distance between a given conductive strut 116 on the first electrode 110 and a conductive strut 126 on the second electrode 120 is the electrode spacing Z. In other words, if the first electrode 110 and second electrode 120 are aligned, then a notional ion or molecule moving in a direction perpendicular to the first lattice 113 and second lattice 123, which passes through an opening (e.g. hole) 117 in the lattice 113 of the first electrode 110 will also pass through an opening 127 in the lattice 123 of the second electrode 120.
[0109] In contrast if the first electrode and second electrode are not aligned, then a notional ion or molecule moving in a direction perpendicular to the first lattice and second lattice which passes through a hole in the lattice of the first electrode 110 may hit a conductive strut of the lattice of the second electrode 120.
[0110] Assembly of the ion gate 100 is simplified because the first and second electrodes are held by the holder (i.e. by engagement of the respective locator features) and the locator features provide a parallel arrangement and alignment of the two electrodes. Advantageously, the electrodes do not need to be manually arrangement parallel or aligned.
[0111] Assembly of the ion gate 100 is simplified because the first electrode and second electrode can be arranged with a required electrode spacing Z by disposing the first element and second electrode in abutment with the spacer (i.e. the first electrode abutting the first side of the spacer and the second electrode abutting the second side of the spacer). Advantageously, the electrode spacing Z does not need to be provided manually, for example, by arranging the electrodes and manually checking the spacing and making subsequent adjustments to the spacing and remeasuring until the required spacing is provided.
[0112] Figure 5 illustrates a flowchart depicting a method 500 of manufacturing an electrode such as electrode 110 or electrode 120.
[0113] The method 500 comprises the following steps.
[0114] The method 500 comprises a step of 510 forming the electrode by electrodeposition. This manufacturing process provides a unitary element (i.e. the lattice and frame are integrally formed) which may improve the strength of the electrode.
[0115] The step 510 is optional because the electrode may be formed by another manufacturing process. In examples wherein a unitary electrode is required, any suitable additive or subtractive manufacturing process may be used to provide an electrode.
[0116] Any manufacturing method may be used to obtain a frame 111 and lattice 113 formed as a unitary element, for example, additive manufacture methods such as electrodeposition (described in more detail herein) or subtractive manufacture methods such as computer numerical control (CNC) machining.
[0117] The method 500 comprises a step of 520 disposing the frame locator features around the frame to provide a the plurality of frame locator features wherein the mean horizontal position and / or mean vertical position of the plurality of frame locator features is located less than a predetermined distance from the centre of the hexagonal lattice, wherein the predetermined distance is based on a width of the conductive struts in a direction parallel to the hexagonal lattice.
[0118] It will be appreciated that step 520 and 510 may be carried out together (e.g. in examples wherein the frame locator features are unitarily formed with the frame).
[0119] Repeating step 520 (and optionally step 510, in examples, performing the steps together i.e. simultaneously) to obtain two electrodes provides two electrodes which, when arranged in the holder (i.e. by engaging respective frame locator features with corresponding holder locator features) are aligned within the predetermined distance.
[0120] Preferably the predetermined distance is equal to the width of the conductive struts of the electrodes to thereby provide two electrodes aligned within a tolerance of one width of the conductive struts (described in more detail herein).
[0121] Figure 6 illustrates a flowchart depicting a method 600 of manufacturing a Tyndall-Powell ion gate for an ion mobility spectrometer. The method 600 comprises the following steps.
[0122] The method 600 comprises a step 610 of disposing a spacer element 140 within the holder 130.
[0123] When the ion gate 100 is assembled the spacer element 140 is disposed between the first electrode 110 and second electrode 120 to thereby provide an electrode spacing Z (see Figure 4).
[0124] This step 610 may be optional because either: the electrode spacing may be provided without the use of a spacer element, for example, the holder may hold the first electrode spaced from the second electrode so that the electrode spacing is provided between the two electrodes; or the spacer can be a separate element which is disposable within the holder 130. The method comprises a step of 620 mechanically fixing a first electrode and a second electrode relative to each other to provide a spacing therebetween, wherein the first electrode and the second electrode are formed by electrodeposition.
[0125] The example shown in Figures 1 to 4 wherein the frame locator features 114 of the first electrode 110 are pegs and the first set of holder locator features 135-1 are holes, and the frame locator features 124 of the second electrode 120 are pegs and the second set of holder locator features 135-2 are holes.
[0126] The step 620 may comprise a substep 621 of engaging a first set of holder locator features with corresponding frame locator features of a frame of the first electrode.
[0127] The substep 611 comprises aligning each peg of the first electrode 110 with a respective hole in the holder, then pushing the first electrode 110 and holder 130 together to thereby insert said pegs into said holes until a side of first electrode contacts a first side the spacer 140. The pegs and hole provide an interference fit which holds the first electrode 110 and holder 130 together.
[0128] The substep 612 comprises aligning each peg of the second electrode 120 with a respective hole in the holder, then pushing the second electrode 110 and holder 130 together to thereby insert said pegs into said holes until a side of second electrode contacts a second side the spacer 140. In this way, the first electrode 110 and second electrode 120 are separated by the spacer 140 which spaces the electrodes 110 and 120 by an electrode spacing Z (see Figure 4). Similarly the pegs and hole provide an interference fit which holds the second electrode 120 and holder 130 together.
[0129] More generally step 620 may be performed by engaging frame locator features of the first electrode with holder locator features of the holder and the frame locator features of the second electrode with holder locator features of the holder. In examples:
[0130] • the frame locator features may be pegs (i.e. projections) and all of the corresponding holder locator features may be holes (e.g. with a corresponding number of pegs to holes) wherein the holes are configured to receive and engage the pegs. Therefore, the method comprises inserting the pegs into the holes.
[0131] • the frame locator features may be holes and all of the holder locator features may be pegs (e.g. a corresponding number of pegs to holes) wherein the holes are configured to receive and engage the holes. Therefore, the method comprises inserting the pegs into the holes;
[0132] • the frame locator features may comprise at least one peg (e.g. X pegs) and at least one hole (e.g. Y holes) and the holder locator features may comprise at least one peg (e.g. Y pegs) and at least one hole (e.g. X holes) wherein said holes engage said pegs. Therefore, the method comprises inserting the pegs into the holes..
[0133] It will be appreciated that method 600 may optionally further comprise any of the steps of method 500 for manufacturing electrodes.
[0134] The ion gate 100 is operable as a Tyndall-Powell ion gate. In use, the first electrode 110 is a connected to a first electrode voltage circuit configured to vary a voltage of the first electrode 110, and the second electrode 120 is a connected to a second electrode voltage circuit configured to vary a voltage of the second electrode 120. A controller is provided to control the first electrode voltage circuit and the second electrode voltage circuit.
[0135] The controller controls the voltage between the first electrode 110 and the second electrode 120 to: control a barrier voltage between the first electrode 110 and the second electrode 120 by varying the voltage of the first electrode 110 and the voltage of the second electrode 120 thereby to control passage of ions through the hexagonal holes of the electrodes 110 120 of the ion gate 100; and, provide a modification voltage between the first electrode 110 and the second electrode 120 by varying the voltage of the first electrode 110 and the voltage of the second electrode 120 thereby to modify ions disposed between the first electrode 110 and the second electrode 120.
[0136] Electrodes comprise a frame defining a frame area and a lattice disposed in the frame area. The lattice is a planar structure disposed within the frame area e.g. the lattice defines a plane. The lattice comprises a plurality of conductive struts. The conductive struts define openings.
[0137] It will be appreciated that each lattice described herein may be a mesh-like material and that the frame may be distinct from the lattice (e.g. the frame and lattice may be unitarily formed but the frame and lattice have difference thicknesses).
[0138] Lattices may comprise openings having any polygonal shape or shapes. The lattices described herein may have openings which have convex regular polygons which can tile a space (e.g. a Euclidean tiling). Any regular tiling (e.g. equilateral triangular openings or regular hexagonal openings) or square openings) or semiregular tiling. A hexagonal lattice refers to a plurality of conductive struts arranged to provide regular hexagons which tile the frame area (e.g. in the manner of a honeycomb). The plurality of the conductive struts may be unitarily formed (i.e. formed as a single element). The plurality of conductive struts and the frame may be unitarily formed (i.e. formed as a single element). The frame may be thicker than the lattice e.g. in the direction perpendicular to the plane defined by the lattice the frame has a greater spatial extent than the lattice.
[0139] The lattice may comprise a triangular regular pattern. A triangular regular pattern provides polygonal openings with a lesser area than a hexagonal regular pattern (e.g. the triangular regular pattern may be innately stronger than a hexagonal regular pattern ceteris paribus). One way of providing an electrode with a percentage of the frame area comprising open area provided by the polygonal openings is between 75.0% to 95.0% is to use a triangular regular pattern and an appropriate width of the conductive struts (i.e. conductive struts with less width than a comparable hexagonal regular pattern with the same percentage open area). All other factors being equal, the triangular pattern is innately stronger than a comparable hexagonal pattern (i.e. the conductive struts having the same length, width, and thickness in both cases) but conductive struts of greater width are innately stronger than conductive struts with less width.
[0140] In examples the holder locator features may be disposed on the spacer. In other words, the spacer may comprise: a first set of holder locator features configured to engage frame locator features of a first electrode; and, a second set of holder locator features configured to engage frame locator features of a second electrode. As described herein, engaging a first set of holder locator features (e.g. disposed on the spacer) with frame locator features of a first electrode and, engaging a second set of holder locator features (e.g. disposed on the spacer) with the frame locator features of the second electrode arranges the first electrode parallel to and in alignment with the second electrode.
[0141] Electrodes described herein may have a frame and conductive structure (i.e. lattice which are unitarily formed). This means the frame and lattice are formed integrally of a single continuous piece of conductive material i.e. not from several elements bonded together.
[0142] The first electrode and the second electrode described herein are identical to each other. However, it will be appreciated that the electrodes may have differences, for example, different frame locator features (e.g. a different configuration, number, and / or shape of locator features), different size, and / or different lattice. In examples, engaging the frame locator features of the electrodes with the corresponding holder locator features may align the electrodes within a tolerance. The tolerance may be based on the width of the conductive elements, for example, the width of the conductive elements. For example, the electrodes may be aligned within a tolerance equal to the width of the conductive elements if the shortest distance between a conductive strut of the first electrode and a conductive strut of the second electrode is the electrode spacing Z plus the strut width (i.e. 116W).
[0143] An ion gate may be provided comprising two electrodes described herein. A combined ion gate and modifier may be provided comprising two electrodes described herein (e.g. the same two electrodes may be operated as an ion gate and an ion modifier). In examples, a combined ion gate and modifier may be provided comprising three electrodes described herein (e.g. two of the electrodes may be operated as ion gate, and those two electrodes may also be operated to provide a first half of an ion modifier (e.g. operated as a single electrode connected to the same voltage) and the third electrode may be operated as a second half of an ion modifier).
[0144] Ion gates describes herein may be provided in a spectrometer such as an ion mobility spectrometer. Provided herein is an ion mobility spectrometer comprising an ion gate as described herein and at least one of: a first electrode voltage circuit; a second electrode voltage circuit; a drift tube (e.g. a charge material transportation tube); drift electrodes; and, a detector.
[0145] Ion gates described herein may be provided in kits wherein the kits comprise an ion gate and at least one of: a first electrode voltage circuit; a second electrode voltage circuit; a drift tube (e.g. a charge material transportation tube); drift electrodes; and, a detector.
[0146] It will be appreciated that the ion gates described herein may be provided alone (i.e. not in a kit or in an assembled ion mobility spectrometer), for example, to permit users to replace an ion gate in an existing system such as an ion mobility spectrometer(e.g. to replace ion gates damaged due to wear and tear).
[0147] It will be appreciated that the electrodes for ion gates described herein may be provided alone (i.e. not in a kit or in an assembled ion gate ), for example, to permit users to replace an electrode in an existing ion gate system (e.g. to replace electrodes damaged due to wear and tear).
[0148] In the context of the present disclosure it is clear from inspection of the Figure 3A and Figure 3B drawings that the hexagonal lattice is a planar structure and that the frame has a thickness perpendicular to the plane defined by the hexagonal lattice which is greater than a thickness of the hexagonal lattice perpendicular to the plane defined by the hexagonal lattice.
[0149] It will be appreciated that a Tyndall-Powell gate comprises two electrodes separated in the direction of travel of ions in an ion mobility spectrometer. Each electrode comprises a conductive structure with openings to permit ions to pass therethrough. A barrier voltage is provided between the two electrodes to selectively admit ions past the ion gate. The arrangement of a Tyndall-Powell gate is described in Tyndall and Powell 1930 ‘The mobility of ions in pure gases’. Proc. R. Soc. Lond. A 129: 162-180.
[0150] Certain features of the methods described herein may be implemented in hardware, and one or more functions of the apparatus may be implemented in method steps. It will also be appreciated in the context of the present disclosure that the methods described herein need not be performed in the order in which they are described, nor necessarily in the order in which they are depicted in the drawings. Accordingly, aspects of the disclosure which are described with reference to products or apparatus are also intended to be implemented as methods and vice versa. The methods described herein may be implemented in computer programs, or in hardware or in any combination thereof. Computer programs include software, middleware, firmware, and any combination thereof. Such programs may be provided as signals or network messages and may be recorded on computer readable media such as tangible computer readable media which may store the computer programs in non-transitory form. Hardware includes computers, handheld devices, programmable processors, general purpose processors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), and arrays of logic gates.
[0151] Any processors used in the computer system (and any of the activities and apparatus outlined herein) may be implemented with fixed logic such as assemblies of logic gates or programmable logic such as software and / or computer program instructions executed by a processor. The computer system may comprise a central processing unit (CPU) and associated memory, connected to a graphics processing unit (GPU) and its associated memory. Other kinds of programmable logic include programmable processors, programmable digital logic (e.g., a field programmable gate array (FPGA), a tensor processing unit (TPU), an erasable programmable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM), an application specific integrated circuit (ASIC), or any other kind of digital logic, software, code, electronic instructions, flash memory, optical disks, CD-ROMs, DVD ROMs, magnetic or optical cards, other types of machine-readable mediums suitable for storing electronic instructions, or any suitable combination thereof. Such data storage media may also provide the data store of the computer system (and any of the apparatus outlined herein). It will be appreciated from the discussion above that the embodiments shown in the Figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims. In the context of the present disclosure other examples and variations of the apparatus and methods described herein will be apparent to a person of skill in the art.
Claims
Claims1. An electrode for providing a Tyndall-Powell gate structure, the electrode comprising: a conductive structure comprising a hexagonal lattice and a frame around the hexagonal lattice, wherein the hexagonal lattice is a planar structure defining a plane and the frame is configured to provide additional support to the hexagonal lattice, wherein: the frame has a thickness perpendicular to the plane defined by the hexagonal lattice which is greater than a thickness of the hexagonal lattice perpendicular to the plane defined by the hexagonal lattice.
2. The electrode of claim 1 , wherein: the frame and the hexagonal lattice are unitary.
3. The electrode of claim 2, wherein: the frame and the conductive structure substantially consist of a metal suitable for electrodeposition.
4. The electrode of any of claims 1 to 3, wherein: the conductive structure comprises conductive struts which form the hexagonal lattice wherein the conductive struts have a width of between 0.080 mm to 0.005 mm in a direction parallel to the hexagonal lattice;5. The electrode of any of claims 1 to 4, wherein: the conductive structure comprises conductive struts which form the hexagonal lattice wherein the conductive struts have a thickness of between 0.080 mm to 0.005 mm in a direction perpendicular to the hexagonal lattice.
6. The electrode of any of claims 1 to 5, wherein: the frame comprises a plurality of frame locator features configured to engage a respective plurality of holder locator features on a holder for holding the electrodes.
7. The electrode of claim 6, wherein: engagement of the frame locator features of each electrode with the holder locator features arranges the conductive structure of the first electrode parallel to the conductive structure of the second electrode.
8. The electrode of claim 7, wherein: engagement of the frame locator features of each electrode with the holder locatorfeatures aligns the hexagonal lattice of the first electrode with the hexagonal lattice of the second electrode in a direction perpendicular to the hexagonal lattice of each electrode.
9. The electrode of any of claims 7 to 8, wherein: any of: at least one of the frame locator features comprises a hole and at least one of the holder locator features comprises a peg configured to fit the hole; and, at least one of the holder locator features comprise a hole and at least one of the frame locator features comprises a peg configured to fit the holes.
10. The electrode of any of claims 6 to 9, wherein: the frame locator features are disposed around the frame to provide a plurality of frame locator features wherein the mean horizontal position and / or mean vertical position of the plurality of frame locator features is located less than a predetermined distance from the centre of the hexagonal lattice, wherein the predetermined distance is based on a width of the conductive struts in a direction parallel to the hexagonal lattice.
11. An apparatus comprising at least two electrodes according to any of claims 6 to 9, wherein the frame locator features are positioned such that when the frame locator features are located on holder locator features the conductive struts of the respective hexagonal lattice are aligned.
12. A Tyndall-Powell ion gate comprising: a first electrode and a second electrode, wherein each of the first electrode and the second electrode comprises: a conductive structure comprising a hexagonal lattice wherein the hexagonal lattice is planar; a holder configured to hold the first electrode relative to the second electrode so that the planar hexagonal lattice of the first electrode is: parallel to the planar hexagonal lattice of the second electrode; and, spaced from the second electrode by an electrode spacing.
13. The Tyndall-Powell ion gate of claim 12, comprising: a first electrode voltage circuit configured to vary a voltage of the first electrode; and, a second electrode voltage circuit configured to vary a voltage of the second electrode; wherein the first electrode volage circuit and the second electrode volage circuit are configured to control a barrier voltage between the first electrode and the second electrode by varyingthe voltage of the first electrode and the voltage of the second electrode thereby to control passage of ions through the hexagonal holes of the electrodes of the ion gate.
14. The Tyndall-Powell ion gate of claim 13, wherein: the first electrode volage circuit and the second electrode volage circuit are configured to provide a modification voltage between the first electrode and the second electrode by varying the voltage of the first electrode and the voltage of the second electrode thereby to modify ions disposed between the first electrode and the second electrode.
15. The Tyndall-Powell ion gate of claim 14, wherein: each of the first electrode and the second electrode comprise a frame configured to provide additional support to the hexagonal lattice.
16. The Tyndall-Powell ion gate of any of claims 12 to 15, wherein: the frame of each electrode comprises a plurality of frame locator features configured to engage a respective plurality of holder locator features on a holder for holding the electrodes.
17. The Tyndall-Powell ion gate of claim 16, wherein: engagement of the frame locator features of each electrode with the holder locator features arranges the conductive structure of the first electrode parallel to the conductive structure of the second electrode.
18. The Tyndall-Powell ion gate of claim 17, wherein: engagement of the frame locator features of each electrode with the holder locator features aligns the hexagonal lattice of the first electrode with the hexagonal lattice of the second electrode in a direction perpendicular to the hexagonal lattice of each electrode.
19. The Tyndall-Powell ion gate of any of claims 12 to 18, wherein: the first electrode and the second electrode are aligned so that the difference in alignment between conductive elements of the first electrode and conductive elements of the second electrode is less than the width of the conductive elements in a direction parallel to the hexagonal lattice of each electrode.
20. The Tyndall-Powell ion gate of any of claims 12 to 19, wherein: the holder comprises a spacer disposed between the first electrode and the second electrode.
21. The Tyndall-Powell ion gate of claim 20, wherein: the spacer is formed of any of: a liquid crystal polymer; polytetrafluoroethylene (PTFE); polyether ether ketone (PEEK), or a ceramic.
22. The Tyndall-Powell ion gate of any of claims 12 to 21 , wherein: the electrode spacing is 0.2 mm.
23. An ion mobility spectrometer comprising: the ion gate of any of claims 11 to 22, wherein the first electrode volage circuit and the second electrode volage circuit are configured to control a barrier voltage between the first electrode and the second electrode by varying the voltage of the first electrode and the voltage of the second electrode thereby to control passage of ions through the hexagonal holes of the electrodes of the ion gate in a drift direction of the ion mobility spectrometer, wherein the drift direction is perpendicular to the conductive structure of each of the electrodes.
24. An electrode for a Tyndall-Powell ion gate comprising: a frame delimiting a frame area; and, a conductive structure disposed within the frame area, wherein the conductive structure comprises conductive elements arranged in a regular pattern to provide a regular tessellating array of polygonal openings between the conductive elements, wherein the percentage of the frame area comprising open area provided by the polygonal openings is between 75.0% to 95.0%.
25. A method of manufacturing a Tyndall-Powell ion gate for an ion mobility spectrometer, the method comprising: mechanically fixing a first electrode and a second electrode relative to each other to provide a spacing therebetween, wherein the first electrode and the second electrode are formed by electrodeposition.
26. The method of claim 25, wherein: mechanically fixing the first electrode and a second electrode relative to each other to provide a spacing therebetween, comprises: engaging a first set of holder locator features with corresponding frame locator features of a frame of the first electrode; engaging a second set of holder locator features with corresponding frame locator features a frame of the second electrode.
27. A method of manufacturing an electrode for a Tyndall-Powell ion gate, the electrodes comprising a conductive structure comprising a hexagonal lattice and a frame around the hexagonal lattice, wherein the hexagonal lattice is planar and composed of conductive struts and the frame is configured to provide additional support to the hexagonal lattice, and wherein the frame comprises a plurality of frame locator features configured to engage a respective plurality of holder locator features on a holder for holding the electrodes, wherein the method comprises: disposing frame locator features around the frame to provide a plurality of frame locator features wherein the mean horizontal position and / or mean vertical position of the plurality of frame locator features is located less than a predetermined distance from the centre of the hexagonal lattice, wherein the predetermined distance is based on a width of the conductive struts in a direction parallel to the hexagonal lattice.
28. The method of manufacturing a Tyndall-Powell ion gate of any of claims 25 to 26, wherein the two electrodes are manufactured according to claim 27.
29. The method of any of claims 25 to 28, comprising: forming the first electrode and second electrode by electrodeposition.
30. The method of any of claims 25 to 29, wherein: the first electrode and the second electrode are aligned so that the difference in alignment between conductive elements of the first electrode and conductive elements of the second electrode is less than the width of the conductive elements in a direction parallel to the conductive structures.