Ion guidance

Abstract

Ion guidance (10), comprising: a set of plate electrodes (40, 340), wherein each plate electrode (40, 340) has a plurality of openings formed therein, wherein the set of plate electrodes (40, 340) is spatially arranged such that a relative positioning of each plurality of openings of a respective plate electrode (40, 340) of the set of plate electrodes (40, 340) and of respective adjacent plate electrodes of the set of plate electrodes (40, 340) defines a continuous ion trajectory (50) through the respective plurality of openings of each plate electrode (40, 340) of the set of plate electrodes (40, 340), wherein the continuous ion trajectory (50, 375, 385) has a shape based on a helix and / or spiral, and an RF power supply designed to provide each plate electrode of the set of plate electrodes (40, 340) with a separate RF voltage, so that adjacent plate electrodes (40, 340) receive RF voltages with different phases.

Description

Technical area of ​​disclosure

[0001] The disclosure relates to ion guides, in particular for use in an ion mobility spectrometer or a mass spectrometer. Background of the disclosure

[0002] Ion guides are used in a wide variety of applications, both in mass spectrometry and ion mobility spectrometry (IMS). In IMS, ions are forced into a gas-filled drift tube by an electric field and spatially separated according to their ion mobility. The resolution of an IMS device increases with the length of the drift region, but very long devices are not suitable for commercial instruments due to their size. For this reason, it is advantageous to fold the drift path into a more compact structure, conceptually similar to multi-pass time-of-flight mass spectrometers. The use of IMS in a mass spectrometer is described, for example, in patent publication US 2004 / 031920A1.

[0003] US patent publication US 2011 / 0168882 A1 describes an ion guide or ion mobility spectrometer with a helical, toroidal, partially toroidal, hemitoroidal, semitoroidal, or spiral ion guide region. The ion guide comprises a plurality of stacked electrodes, each having an opening through which ions are transferred. An RF voltage is applied to the electrodes to radially confine ions within the ion guide. A DC voltage or transient DC voltage is applied to at least some of the electrodes to drive ions along the ion guide. The number of electrodes required for such a configuration is proportional to the length of the ion guide.In terms of manufacturing, this is therefore a difficult and costly design, which could also be associated with a high probability of electrical failure due to the large number of electrical connections required.

[0004] US patent publication US 2014 / 0353487A1 describes another IMS technique in which ions are forced multiple times through a closed loop. This saves space but results in a lower duty cycle and limitations in ion mobility range or resolution, as ions with higher ion mobility may catch up with ions with lower ion mobility in the closed loop.

[0005] US patent publication US 2012 / 0018631 A1 also discloses the analysis of ion mobility using an ion mobility analysis device and spectrometer. The ion mobility analysis device comprises a plurality of axially segmented upper and lower electrodes and a plurality of axially segmented intermediate electrodes that together define an ion path. An asymmetric voltage waveform is applied to the upper electrodes, and a compensating DC voltage is applied to the lower electrodes to separate ions in a vertical radial direction according to their rate of change of ion mobility with the electric field strength.

[0006] US patent publication US 2014 / 0042315A1 concerns the measurement of ion mobility in gases at pressures of a few hectopascals. Drift regions are bent into curved shapes that extend into a third dimension. Alternating curvature directions in the curved shapes (i.e., both clockwise and counterclockwise curvatures) compensate for varying trajectory lengths by passing approximately equal drift distances on the outer and inner trajectories. The varying trajectory lengths would otherwise result in a loss of resolution. Ions are kept near the axis of the curved drift region by slice focusing or permanent focusing, so that the average drift trajectory is constant. One possible shape is a double loop in the shape of a figure eight. The shape is perpendicular to its projection plane, so that multiple double loops lie one above the other.While such an arrangement may offer advantages, its fabrication remains complicated. Furthermore, the ions are expected to move back and forth between the inner and outer edges on their way, so the practical effects of this design may be less than originally intended.

[0007] US patent publication US 2013 / 0187044 A1 shows an ion guide device comprising several layers of stretched wire electrodes that intersect in space. These wire electrodes are distributed along a defined ion guide axis within the ion guide device. Each layer of wire electrodes contains at least two wire electrodes spaced a certain distance from the guide axis and rotates at an angle relative to the wire electrodes of the adjacent layer. Several layers of wire electrodes form a cage-like ion guide tunnel. The mounting framework of these wire electrodes is held outside the ion guide tunnel, thereby reducing interference from the gas streams from the ion guide device. A power supply supplies each layer of wire electrodes with voltage and generates an electric field that focuses the ions onto the guide axis.

[0008] EP 2 866 247 A1 shows an ion guiding device and an ion guiding method which serve to realize the ion transfer and focusing in a certain degree of vacuum and the off-axis transfer of the ions.

[0009] DE 11 2005 001 175 T5 and Japanese patent publication JP 2007 / 311111 A describe a time-of-flight (TOF) mass spectrometer. In JP 2007 / 311111 A, the TOF mass spectrometer is constructed using an inner metal plate and an outer metal plate that define a spiral ion trajectory.

[0010] A shunt is provided between the inner and outer metal plates to prevent beam interactions. This arrangement is also described in "A New Spiral Time-of-Flight Mass Spectrometer for High Mass Analysis," Satoh et al., J. Mass Spectrom. Soc. Jpn. Vol. 54, No. 1, 2006.

[0011] For this reason, suitable designs of ion guides for use in IMS are desirable, which are easier to manufacture, more robust and can provide high resolution performance. Brief description of the invention

[0012] Provided are: ion guides according to claims 1 to 28; an ion mobility spectrometer according to claim 29; and a mass spectrometer according to claim 30. Further features of the invention are set forth in the dependent claims and explained in this specification.

[0013] In a first aspect according to the present invention, an ion guide comprises a set of electrodes, each of which is a plate electrode or an electrode structure that functionally mimics a plate electrode (at least one example of which is explained below). For simplicity, the term "plate electrode" is used to cover all such electrode structures. A plurality of openings are formed through each of the plate electrodes. The plate electrodes (each having a plurality of openings) are spatially arranged (or mounted) such that relative positioning of the plurality of openings of each plate electrode and the openings of its adjacent plate electrodes defines a continuous ion trajectory through the plurality of openings of each of the set of plate electrodes.

[0014] This allows a single continuous ion trajectory to be provided through the multiple openings of each of the set of plate electrodes. It is preferred that the plate electrodes are arranged consecutively, i.e., in a stack, such that an nth plate electrode is adjacent to an (n+1)th plate electrode, where n=1 to N-1, where N is the total number of plate electrodes. Preferably, the Nth plate electrode is adjacent to the first (n=1) plate electrode, i.e., such that the last (Nth) electrode meets the first electrode. The plate electrodes are arranged in a curved stack. The number of plate electrodes can be as few as 30 and as many as 180.

[0015] In some embodiments, at least some of the set of plate electrodes are spatially arranged around an axis extending in an axial dimension, for example, in a circle or a circular array around the axis, although other arrays are possible, as described below, such as oval, rectangular with rounded corners, or labyrinthine. In this way, the continuous ion trajectory rotates around the axis extending in the axial dimension. The axis thus becomes an axis of rotation for the ion trajectory. In this way, the continuous ion trajectory has a spiral, coil-like, helical, or helix-like shape (or a combination thereof), as described below.When discussing a spiral, helical, or spiral-based shape, this may refer to a shape that has a fundamental spiral character, such as a curve with a generally increasing (or decreasing) radius from a central point or line. A helical, helix-like, or helix-based shape may refer to a shape that has a fundamental helical character, such as a curve extending along an axis and having a generally repeating shape. These terms are further explained below.

[0016] For radial confinement of the ions, an RF power supply supplies each plate electrode with a respective RF voltage, in particular such that adjacent electrodes receive RF voltages with different phases. Preferably, each plate electrode of the set of plate electrodes has the corresponding plurality of openings spaced along a first dimension. In some embodiments, the first dimension corresponds to the axial dimension (i.e., it is generally parallel to the axis). With such an arrangement, the continuous ion trajectory has a helical character. In other embodiments, the first dimension is perpendicular to the axial dimension. Then, the continuous ion trajectory has a spiral character (although it may also have a helical character, as explained further).The openings are spaced apart from each other along the first dimension by an opening pitch. Preferably, the spacing of the openings of each electrode is the same along the first dimension. Further preferably, a respective plate electrode of the set of plate electrodes has a respective plurality of openings positioned such that they are offset in the first dimension from the respective plurality of openings of a respective adjacent plate electrode. If the first dimension is perpendicular to the axial dimension (so that a spiral continuous ion trajectory is formed), the offset can be present in both the first dimension and the axial dimension. Then, the continuous ion trajectory has both a spiral and a helical character.

[0017] To achieve this, in some embodiments, the respective adjacent plate electrodes of the set of plate electrodes are positioned such that they are offset relative to one another in the first dimension, wherein the plate electrodes are in particular substantially identical. In some other embodiments, which are less preferred from a manufacturing perspective, an offset of the openings can be defined by varying the position of the openings in each plate electrode.

[0018] The offset is preferably less than the aperture pitch. In this way, the continuous ion trajectory extends slightly (i.e., less than the aperture pitch in each electrode) into the first dimension as it travels from a respective plate electrode to a respective adjacent plate electrode. For a complete rotation of the continuous ion trajectory, i.e., after passing each plate electrode, the ion trajectory preferably extends into the first dimension by an amount corresponding to the aperture pitch. This is preferred, for example, in embodiments where the last (Nth) electrode encounters the first electrode. Accordingly, it is preferred that the offset substantially corresponds to y / N, where y is the aperture pitch within each plate electrode and N is the number of plate electrodes.Thus, in some preferred embodiments, after the continuous ion trajectory has passed through each respective first aperture of each plate electrode, the continuous ion trajectory begins to pass through a respective second aperture of each plate electrode, then optionally through a respective third aperture of each plate electrode, and so on. If the plate electrodes each have x apertures (where x is at least 2, preferably 2 to 100, more preferably 3 to 100), the continuous ion trajectory will generally pass through each plate electrode x times, passing through the apertures of each plate electrode sequentially.

[0019] In contrast to previously known ion guide structures, this design can provide high IMS resolution in a relatively compact device, but requires far fewer electrodes (and other components) and electrical connections to achieve a trajectory of the same length, since different parts (apertures) of each electrode provide different portions of a single trajectory. The difference can be an order of magnitude. In embodiments, between 5 and 100 apertures per electrode can be provided. Using fewer electrodes makes the structure more electrically robust, simplifies manufacturing, and reduces costs.

[0020] Accuracy can also be improved. A higher duty cycle can be achieved compared to closed-loop trajectory designs. In closed-loop ion guide structures (see, for example, US 2014 / 0353487 A1), it is possible for some ions to travel more cycles of the closed-loop trajectory than others. This disadvantage is not present in embodiments of the present disclosure, thereby providing a greater range of ion mobility that is maintained at high resolution.

[0021] If the ion trajectory has a helical shape, it is not necessarily helical in the mathematical sense. Thus, helical shape is intended to mean helical, which includes helical, substantially helical, or other shapes that exhibit some aspect of helical character, examples of which are described here. Similarly, a spiral shape is not necessarily spiral in the mathematical sense and may be spiral-like, which includes substantially spiral or other shapes that exhibit some aspect of helical character, examples of which are described here. With this configuration, a variety of spiral and helical shapes for the ion trajectory are possible.The helical shape can define a two-dimensional profile, and typically, the defined ion trajectory extends multiple times along the two-dimensional profile while extending into the first dimension, which is generally perpendicular to the two-dimensional profile. The two-dimensional profile can be, for example, circular, oval, rectangular with rounded corners, labyrinthine, or shaped like a figure eight. An eight-shaped two-dimensional profile (or more generally, one with both clockwise and counterclockwise curvature) can be provided using a first and a second plurality of electrodes, each arranged to define a circular two-dimensional profile.Thus, the first plurality of electrodes may be arranged around a first axis and the second plurality of electrodes may be arranged around a second axis, with both the first and second axes extending in the first dimension along which the plurality of openings of each plate electrode are spaced. Some of the first plurality of electrodes and some of the second plurality of electrodes are arranged to overlap each other such that the two-dimensional profile of the first plurality of electrodes overlies the two-dimensional profile of the second plurality of electrodes. Then, the continuous ion trajectory may be defined by the openings of both the first and second plurality of electrodes.The overlapping electrodes may be provided with alternating portions having an opening and gaps (or cutouts) such that the portion having an opening of one of the first plurality of electrodes fits into the gap portion of a corresponding one of the second plurality of electrodes (and vice versa).

[0022] One or more of the shape; size; and positioning of and / or spacing between the openings may be the same for each plate electrode of the set of plate electrodes. When identical plate electrodes are used, they are typically offset from each other along the axis of the helical shape. The offset between a plate electrode and an adjacent plate electrode is preferably less than the spacing of the openings in a plate electrode. The offset between a plate electrode and an adjacent plate electrode is thus preferably arranged such that after each complete rotation, the p-th opening of the last (N-th) electrode is next to the (p+1)-th opening of the first electrode in the sequence (1 <p<x-1, wobei x die Anzahl der Öffnungen in jeder Elektrode ist).In some embodiments, each of the openings of each plate electrode has a rectangular or ovoid shape. It is not necessary for all of the openings to have the same shape or arrangement, and designs using this approach are explained below with reference to an ion guide according to a second aspect.

[0023] In particular, a first RF voltage can be applied to each second plate electrode according to its spatial arrangement to provide a second RF voltage (with a phase opposite to the first RF voltage) to each second plate electrode of the set of electrodes that does not receive the first RF voltage. A DC voltage supply can supply at least one DC potential to one or more electrodes of the set of electrodes, in particular to form a traveling wave to cause ions to move along the defined ion trajectory.

[0024] Each RF voltage may have an amplitude selected from: (i) <100 V peak-to-peak; (ii) 100-200 V peak-to-peak; (iii) 200-300 V peak-to-peak; (iv) 300-400 V peak-to-peak; (v) 400-500 V peak-to-peak; and (vi) >500 V peak-to-peak. Each RF voltage may have a frequency selected from: (i) <100 kHz; (ii) 100-500 kHz; (iii) 0.5-1.0 MHz; (iv) 1.0-1.5 MHz; (v) 1.5-2.0 MHz; (vi) 2.0-2.5 MHz; (vii) 2.5-3.0 MHz; (viii) 3.0-4.0 MHz; (ix) 4.0-5.0 MHz; (x) 5.0-6.0 MHz; (xi) 6.0-7.0 MHz; (xii) 7.0-8.0 MHz; (xiii) 8.0-9.0 MHz; (xiv) 9.0-10.0 MHz; and (xv) >10.0 MHz. The DC traveling wave voltages or waveforms are preferably translated on the set of electrodes of the ion guide at a velocity selected from: (i) <100 m / s; (ii) 100-500 m / s; (iii) 500-1000 m / s; (iv) 1000-1500 m / s; (v) 1500-2000 m / s; (vi) 2000-2500 m / s; (vii) 2500-3000 m / s; (viii) >3000 m / s.

[0025] A mounting element to which the set of electrodes is attached may be provided to determine the relative positioning of openings between adjacent electrodes of the set of electrodes. The mounting element (e.g., a circuit board) may include one or more electrical connections to the set of electrodes.

[0026] In some embodiments, the attachment element comprises: a first attachment substrate to which a first end of each electrode of the set of electrodes is attached; and a second attachment substrate (opposite the first attachment substrate) to which a second end of each electrode of the set of electrodes is attached. The first and second attachment substrates may be spaced apart from each other along the first dimension, i.e., in the direction in which the openings within each plate electrode are spaced apart, with the plate electrodes therebetween. The first attachment substrate may comprise one or more first electrical connections to each second plate electrode of the set of electrodes according to the spatial arrangement.The second mounting substrate may comprise one or more second electrical connections to each second plate electrode of the set of electrodes between the electrodes connected to the one or more first electrical connections. The second electrical connections may be arranged to provide an electrical power that is different from an electrical power provided by the first electrical connections, for example, the first and second RF voltages and / or the at least one DC potential described above. The first and second mounting substrates may each comprise a printed circuit board (PCB) suitable for providing the electrical connections. Furthermore, the PCB is preferably flexible enough to be bent into a desired shape. In some embodiments, the PCB may comprise a substantially helical shape.In such embodiments, the PCB preferably comprises a ring shape with a cut, in which the two ends of the PCB adjacent to the cut are spaced apart. The ends may be spaced apart by a distance substantially corresponding to the opening pitch within each plate electrode. For this purpose, a spacer may be provided between the cut ends of the PCB.

[0027] The fastening element may comprise a mounting substrate. In certain embodiments, each electrode of the set of electrodes is attached to the mounting substrate, which has a shape such that the relative positioning of openings between adjacent electrodes of the set of electrodes is thereby determined. In other embodiments, the fastening element further comprises a spacer disposed between the mounting substrate and the set of electrodes. The spacer may be configured to determine the relative positioning of openings between adjacent electrodes of the set of electrodes.

[0028] An ion guide according to a second aspect comprises a plurality of electrodes, each electrode having at least one aperture to define an ion trajectory (preferably curved). This second aspect is not claimed independently, but may be combined with the first aspect, in which case each electrode may be a plate electrode (or a structure functionally mimicking a plate electrode) having multiple apertures, and the ion trajectory may have a helical shape. In this second aspect, an aperture of a first electrode is advantageously located adjacent to an aperture of a second electrode along the ion trajectory.The opening of the second electrode has a shape, an electrical potential, and / or a position that differ from those of the opening of the first electrode in order to cause ions migrating along the ion trajectory to shift in a direction perpendicular to the direction of the ion trajectory. Advantageously, the ion trajectory has at least one curvature. In this approach, the ions can be caused to migrate along different parts of the curvature of the same trajectory, which can compensate for the effects of trajectory length differences. Compared to wider openings or smaller helical radii, this should reduce the loss of resolution (or increase any limitations on resolution), thus enabling good resolution in smaller devices or devices with higher space charge capacity. In another sense, the at least one curvature can be assumed to define an average radius of curvature.The ions can then be caused to oscillate between the inner side of the mean radius of curvature and the outer side of the mean radius of curvature. As a result, a difference in trajectory length between ions entering the ion guide at a position on the inner side of the mean radius of curvature and ions entering the ion guide at a position on the outer side of the mean radius of curvature can be corrected.

[0029] Advantageously, the direction perpendicular to the direction of the ion trajectory can be defined by a (further) helix shape, wherein the direction of the ion trajectory is an axis of the (further) helix shape. In the combination of the first and second aspects, the ions can thus migrate along a helical path perpendicular to the helix shape.

[0030] One way to provide this effect is for the opening of the first electrode and the opening of the second electrode to comprise a respective first slot and a respective second slot, each first slot being different and separate from the respective second slot. The first slot of the opening of the second electrode may have a shape and / or position different from those of the first slot of the opening of the first electrode to cause ions migrating along the ion trajectory to displace in a first direction perpendicular to the direction of the ion trajectory.Additionally (and, less preferably, alternatively), the second slit of the opening of the second electrode has a shape and / or position different from that of the second slit of the opening of the first electrode to cause ions traveling along the ion trajectory to shift in a second direction perpendicular to the direction of the ion trajectory. The first and second directions are typically co-rotationally oriented (e.g., both clockwise or both counterclockwise). Each first slit and each second slit may have a shape defined by respective portions of the same rectangle.

[0031] A third aspect of an ion guide (which again is not claimed independently, but may be combined with one or both of the first and second aspects) comprises: a first plurality of electrode assemblies, each electrode assembly comprising respective parallel rod electrodes with a respective gap therebetween; and a second plurality of electrode assemblies, each electrode assembly comprising respective parallel electrode portions with a respective gap therebetween. The parallel electrode portions of the second plurality of electrode assemblies are arranged orthogonally with respect to the parallel rod electrodes of the first plurality of electrode assemblies (the rod electrodes being arranged horizontally and the parallel electrode portions of the second plurality of electrode assemblies being arranged vertically, for example).This can be effected by aligning the respective gaps of the first plurality of electrode assemblies with the respective gaps of the second plurality of electrode assemblies to allow ions to migrate therethrough along a continuous path. The first and second pluralities of electrode assemblies are arranged alternately along the continuous path (i.e., spaced apart from one another, with each first electrode assembly immediately followed by a second electrode assembly, and each second electrode assembly immediately followed by a first electrode assembly, except for the last electrode assembly in the ion guide). Each of the first plurality of electrode assemblies (and optionally each of the second plurality of electrode assemblies) is therefore not exclusively a plate electrode, but rather an electrode structure mimicking a plate electrode with rod electrodes.Successive electrode arrays in the first plurality of electrode arrays (or in the second plurality of electrode arrays) are preferably provided with RF potentials of different (optionally opposite) phase. Such a structure may be a form of plate electrode used in ion guides according to the first aspect.

[0032] In certain embodiments, each of the first plurality of electrode assemblies is provided with (only) an RF potential, and each of the second plurality of electrode assemblies is provided with (only) a DC potential. The potentials can be applied to the first and second plurality of electrode assemblies in a manner similar to embodiments of the aspects described above. For example, a first RF voltage can be applied to every second electrode assembly of the first plurality of electrode assemblies, and a second RF voltage (preferably with a phase opposite to the first RF voltage) can be applied to every second electrode assembly of the first plurality of electrode assemblies that does not receive the first RF voltage.A DC voltage supply may supply the DC potential to each of the second plurality of electrode assemblies to preferably form a traveling wave to cause ions to migrate through the defined ion trajectory.

[0033] Each RF voltage may have an amplitude selected from: (i) <100 V peak-to-peak; (ii) 100-200 V peak-to-peak; (iii) 200-300 V peak-to-peak; (iv) 300-400 V peak-to-peak; (v) 400-500 V peak-to-peak; and (vi) >500 V peak-to-peak. Each RF voltage may have a frequency selected from: (i) <100 kHz; (ii) 100-500 kHz; (iii) 0.5-1.0 MHz; (iv) 1.0-1.5 MHz; (v) 1.5-2.0 MHz; (vi) 2.0-2.5 MHz; (vii) 2.5-3.0 MHz; (viii) 3.0-4.0 MHz; (ix) 4.0-5.0 MHz; (x) 5.0-6.0 MHz; (xi) 6.0-7.0 MHz; (xii) 7.0-8.0 MHz; (xiii) 8.0-9.0 MHz; (xiv) 9.0-10.0 MHz; and (xv) >10.0 MHz. The DC traveling wave voltages or waveforms are preferably converted at the set of electrodes of the ion guide at a velocity selected from: (i) <100 m / s; (ii) 100-500 m / s; (iii) 500-1000 m / s; (iv) 1000-1500 m / s; (v) 1500-2000 m / s; (vi) 2000-2500 m / s; (vii) 2500-3000 m / s; (viii) >3000 m / s.

[0034] Optionally, the second plurality of electrode assemblies could comprise plate electrodes each having an opening to provide the respective gap.

[0035] Other aspects of the disclosure include an ion mobility spectrometer or a mass spectrometer comprising the ion guide of any aspect. In the case of the ion mobility spectrometer, the ion guide is advantageously configured as a drift tube.

[0036] In the case of the mass spectrometer, the ion guide may be configured to receive ions from an upstream ion source or ion-optical device and cause the received ions to migrate along the ion trajectory. The mass spectrometer may further comprise a mass analyzer configured to receive ions that have migrated along the ion trajectory. Optionally, an ion-optical bypass assembly may be provided that is selectively configured to cause ions to migrate from the upstream ion source or ion-optical device to the mass analyzer without passing through the ion guide. Brief description of the drawings

[0037] The invention may be put into practice in various ways and preferred embodiments will now be described by way of example only with reference to the accompanying drawings in which: Fig. 1 is a perspective view of a first embodiment of an ion guide according to the disclosure; Fig. 2 shows a manufacturing step of a mounting substrate according to a first embodiment for the ion guide of Fig. 1 shows; The Fig. 3A, Fig. 3B, Fig. 3C and Fig. 3D manufacturing steps for forming an ion guide according to the design of Fig. 1 show; Fig. 4 an operation of an ion guide according to the design of Fig. 1 schematically depicts; Fig. Figure 5 is a schematic diagram showing connections and contact surfaces with an ion guide according to the embodiment of Fig. 1 shows operation; Fig. 6 schematically shows a mass spectrometer incorporating an ion guide according to the design of Fig. 1 includes; Fig. 7A depicts an exemplary electrode structure and an exemplary mounting substrate according to a second embodiment of an ion guide according to the disclosure; Fig. 7B depicts an exemplary electrode structure and an exemplary mounting substrate according to a third embodiment of an ion guide according to the disclosure; Fig. 8 schematically shows different profiles for ion guides according to the disclosure; Fig. 9 schematically depicts an electrode structure and profile of a fourth embodiment of an ion guide according to the disclosure; Fig. 10A shows a plan view of a fifth embodiment of an ion guide according to the disclosure; Fig. 10B is a plan view of a first part of a variant of the embodiment of Fig. 10A shows; Fig. 10C is a plan view of a second part of the embodiment of Fig. 10B shows; Fig. 10D an ion trajectory for the design of the Fig. 10B and Fig. 10C schematically; Fig. 11A illustrates a first example of electrode opening shapes suitable for ion guides according to the disclosure; Fig. 11B illustrates a second example of electrode opening shapes according to the disclosure that are suitable for ion guides; and Fig. 12 is a perspective view of a sixth embodiment of an ion guide according to the disclosure. Detailed description of preferred embodiments

[0038] Several different designs, structures, and associated manufacturing methods for ion guides are described below. While certain features are described with reference to one or more specific embodiments or configurations, it should be understood that, wherever possible, they may also be applied to other embodiments or configurations disclosed herein. Where like parts are shown in different drawings, like reference numerals have been used for clarity.

[0039] First on Fig. Referring to Figure 1, a perspective view of a first embodiment of an ion guide 10 according to the disclosure is shown. The ion guide 10 includes: a first mounting printed circuit board (PCB) 20; a second mounting PCB 30; and a plurality of plate electrodes 40. Each of the plate electrodes 40 is mounted between the first mounting PCB 20 and the second mounting PCB 30 (in an interlayer structure). The number of electrodes may be limited by a lower limit due to the radius becoming too small to fit into plates (particularly solid plates) or when the curvature between each plate disrupts the field. Complexity and capacity, as well as space, may impose upper limits on the number. Therefore, depending on the radius of curvature and the size of the electrodes, between 30 and 180 plates may be possible.Furthermore, each of the plate electrodes 40 has a plurality of openings; plate electrodes 40 have the same size, shape, and opening arrangement. In principle, the number of openings per plate electrode 40 could be at least two and up to 100 (or possibly more).

[0040] Thus, the resulting ion guide 10 can be considered more generally to comprise a curved stack (in this case, circular) of elongated electrodes 40, each attached to PCB mounting substrates 20, 30, containing a series of apertures, such that the stack defines a series of channels. A small axial displacement from one electrode to the next, due to the shape of the first 20 and second 30 mounting PCBs (or alternatively, the positions of the apertures themselves), causes the channels between the apertures to overlap and merge into a converged, elongated 3D ion trajectory. The ion trajectory has a helical shape.

[0041] In general, therefore, a first aspect of an ion guide can be considered. The ion guide comprises a set of plate electrodes (or electrodes each configured to functionally mimic a plate electrode). Each plate electrode has a plurality of apertures formed therethrough. The set of plate electrodes is spatially arranged (or mounted) such that relative positioning of each plurality of apertures of a respective plate electrode of the set of plate electrodes and of respective adjacent plate electrodes of the set of plate electrodes defines a continuous ion trajectory through the respective plurality of apertures of each plate electrode of the set of plate electrodes. The continuous ion trajectory advantageously has a shape based on a helix and / or spiral (the spiral-based shape is described further below in this disclosure with reference to the Fig. 10A to 10D). The continuous ion trajectory may be considered a single ion trajectory, although in practice the continuous ion trajectory may be divided into multiple ion trajectories (at least one way of achieving this is described below). In another aspect of the disclosure, an ion mobility spectrometer may be contemplated that includes an ion guide as described herein configured as a drift tube.

[0042] The set of plate electrodes can be considered to be arranged in a sequence. Then, a first electrode in the sequence can be arranged to provide an access opening through which ions can enter the continuous ion trajectory. Additionally or alternatively, a last electrode in the sequence can be arranged to provide an exit opening through which ions can exit the continuous ion trajectory. Typically, the number of plate electrodes can be as few as 30 and / or as many as 180. For each plate electrode, the respective plurality of openings comprises at least 3, 5, 10, 20, 30, 50, 70, or 80 openings, and / or preferably no more than 80, 100, or 120 openings.

[0043] Advantageously, for each plate electrode of the set of plate electrodes, the respective plurality of openings are spaced along a first dimension (which, in some embodiments, is the axis of the helical shape). Then, the relative positioning of each plurality of openings can define the continuous ion trajectory such that it extends into the first dimension. The relative positioning of each plurality of openings can define the continuous ion trajectory such that it extends into the first dimension. The set of plate electrodes can be partially or entirely spatially arranged around an axis that extends into the first dimension. Then, the continuous ion trajectory typically has a helical shape. In such cases, the first dimension can define an axis of the ion guide.

[0044] The relative positioning of each plurality of apertures of a respective plate electrode of the set of plate electrodes and of respective adjacent plate electrodes of the set of plate electrodes preferably includes spacing along the first dimension. In other words, respective adjacent plate electrodes of the set of plate electrodes are positioned such that they are offset from one another in the first dimension. This is an implementation of what is sometimes referred to in this disclosure as axial translation. Typically, in such embodiments, each electrode of the set of electrodes has the same spacing between apertures along the first dimension.Then, the offset between the respective plurality of openings of one plate electrode of the set of plate electrodes and the respective plurality of openings of an adjacent plate electrode of the set of plate electrodes is advantageously less than the distance between openings. For example, the offset between respective pluralities of openings of respective adjacent plate electrodes may substantially correspond to y / N, where y is the opening pitch in each plate electrode and N is the number of plate electrodes. Then, an offset between a plate electrode of the set of plate electrodes (which may be referred to as a last of the set of plate electrodes arranged in a sequence) and an adjacent plate electrode of the set of plate electrodes (which may be referred to as a first of the set of plate electrodes in the sequence) advantageously substantially corresponds to the distance between openings (i.e., y).

[0045] Further optional, preferred, and advantageous features of this generalized aspect, which are also applicable to its specific embodiments, are explained below. First, the manufacturing details of the embodiment according to this aspect are set forth in detail.

[0046] To get to Fig. 2, a manufacturing step of a mounting substrate for the ion guide of Fig. 1. For simplicity, the first mounting PCB 20 is shown, but it should be understood that this method is also applicable to the second mounting PCB 30. The PCB 20 is initially a ring that is cut at 21 and then bent or compressed 22 to create a helical shape, with the gap 23 between the cut (terminal) ends of the PCB being bent to a specific size. Provided the PCB 20 is flexible enough, the helical shape can represent a single twist and have a fixed shape by attaching the back of the PCBs to a plate that accommodates this axial displacement, or by placing a spacer between the cut ends of each PCB 20 30.

[0047] The axial displacement during rotation of the PCB 20, 30 (in other words, the helical shape of the PCB, as in Fig. 2) causes the same axial displacement in the stacked ring of electrodes 40 that forms the ion guide 10. If this axial displacement corresponds to the spacing of the openings in each electrode along the first dimension, the openings will ultimately combine to form a single merged helical ion channel with an inlet opening 42 and an outlet opening 44.

[0048] With regard to the generalized aspect of the ion guide discussed above, the ion guide may further comprise a mounting element to which the set of electrodes is attached for determining the relative positioning of openings between adjacent electrodes of the set of electrodes. The mounting element may comprise a plurality of components in a single-piece or separable structure.

[0049] Advantageously, the fastening element comprises one or more electrical connections to the set of electrodes. The fastening element may comprise one or more PCBs.

[0050] In one embodiment, the mounting element comprises: a first mounting substrate to which a first end of each electrode of the set of electrodes is attached; and a second mounting substrate to which a second end of each electrode of the set of electrodes is attached. Each of the first and second mounting substrates may comprise (or be) a respective PCB. Preferably, the first mounting substrate comprises one or more first electrical connections to every second electrode of the set of electrodes according to their spatial arrangement. Then, the second mounting substrate may comprise one or more second electrical connections to electrodes of the set of electrodes that are not connected to every second electrode of the set of electrodes between the electrodes connected to the one or more first electrical connections.The second electrical connections are advantageously arranged to provide an electrical power that differs from an electrical power provided by the first electrical connections, in particular an RF voltage with an opposite phase to that provided for the first electrical connections (as explained below). Alternative embodiments are explained further below.

[0051] With reference to the Fig. 3A, Fig. 3B, Fig. 3C and Fig. 3D shows the manufacturing steps for forming such an ion guide. In Fig. 3A shows a single elongated plate electrode 40 with (for example) 5 openings. Several plate electrodes 40 are formed into a stack, as in Fig. 3B, and by aligning the openings, a plurality of individual channels are formed through which ions can flow, with an exemplary ion path 50 being shown. Referring to Fig. 3C, the plate electrodes 40 are slightly axially displaced relative to each other (less than the opening distance) so that the openings overlap and the ion paths 50 are inclined. In Fig. In Figure 3D, the plate electrodes 40 are arranged along a cylindrical axis of rotation while maintaining axial spacing or function. The axial displacement during one revolution occurs in accordance with the aperture spacing, and as a result, a single helical ion trajectory 50 is formed, as the ion beam switches to the next aperture in the plate electrodes at the end of each revolution. This ion trajectory 50 can form a drift region for ions, particularly in an IMS design.

[0052] At a conceptual level, the approach described above envisions an ion guide (with a corresponding drift region) formed from a stack of fixed electrode plates, each containing a row of apertures, with the last electrode meeting the first. By applying an axial displacement from one plate electrode 40 to the next, the paths are merged through the apertures into a single elongated ion path.

[0053] With reference to Fig. 4 is an operation of an ion guide according to the design of Fig. 1 schematically. Ions enter the ion guide through the inlet 52 and move along the helical ion path 50, exiting the ion guide at the outlet 54. The axial displacement of the plate electrodes 40 (for example, relative to the Fig. 3C and Fig. 3D) provides space for the injection and extraction of ions into and from the helical drift region. Ions can be injected into the ion guide by aligning the outlet of another ion-optical device with the inlet 52, and they can be collected from the ion guide by aligning the inlet of another ion-optical device with the outlet 54. If the spatial offset at the plate electrodes 40 is defined by attaching the electrodes to a molded component or spacer, the shape of this part is desirably designed to allow access to and from the channel.

[0054] Ions are confined inside the channel by applying different RF phases to each adjacent plate electrode 40 (in other words, the phase of the applied RF alternates between adjacent plate electrodes 40). If the plate electrodes 40 are mounted between two PCB substrates (as in the Fig. 1 and Fig. 2), it is advantageous to apply RF voltages with opposite phases to the different PCB substrates to minimize capacitance effects. This is explained with reference to Fig. 5, which is a schematic diagram showing connections and interfaces with such an ion guide 10. The plate electrodes 40 are mounted between the first PCB substrate 20 and the second PCB substrate 30. A metal cover 60 is provided to confine the device, which is then attached to a PEEK or metal holder 70. Confining the ion trajectory (the drift region) makes it possible to maintain it at a relatively elevated pressure compared to a surrounding negative pressure of adjacent parts of the instrument. The pressure of the region surrounding the metal cover 60 could be as low as 1×10 -4 Pa (1×10 -6 mbar) and up to 200 Pa (2 mbar), although 1×10 -3 Pa to 1 Pa (1×10 -5 up to 1×10 -2 mbar) are more typical. Inside the ion guide (metal cover 60) a range of 0.01 to 1000 Pa (1×10 -4up to 10 mbar) is possible, but probably at or around 0.5 Pa (5×10 -3 mbar). Ion mobility itself works over a wide range, but the required voltages can become dangerous if the pressure is too high.

[0055] An ion injection guide 80 is used to provide ions to the ion guide 10, and an extraction guide 90 receives ions from the ion guide 10. The ion injection guide 80 is preceded by an ion source (i.e., the ion source is provided upstream of the ion injection guide 80). The ion source may be of any suitable known type, for example: an atmospheric pressure ion source, an electrospray ion source, a chemical ionization ion source, a MALDI ion source, an electron impact ion source, or a laser ionization ion source. Generally, an ion trap or other ion bunching device is connected downstream of the ion source (which can be integrated into the ion injection guide 80 by applying suitable stopping and extraction DC potentials). This allows compact ion packets (i.e.Pulses are applied, which can then be separated based on their mobility within the drift region. An ion detector is provided behind the extraction guide—or another mass analyzer for more complex analysis.

[0056] A first-phase RF potential 25 is applied to the first PCB substrate 20, which then has electrical connections to other plate electrodes 40. A second, opposite-phase RF potential 35 is applied to the second PCB substrate 30, which then has electrical connections to the other plate electrodes 40 that are not connected to the first PCB substrate 20.

[0057] Ions can be propelled through the trajectory 50 by applying a traveling DC wave to the first PCB substrate 20 and / or the second PCB substrate 30, which has electrical connections to the plate electrodes 40. Specifically, DC potentials are applied to the two confining RF voltages with opposite phases. This may be achieved in the same way using a traveling wave, as explained in US patent publication US 2011 / 0168882 A1, or, less preferably, using transient DC potentials, as explained in US patent publication US 2014 / 0353487 A1.

[0058] In the design of the Fig. 1 to 5, a single plate electrode 40 provides a potential to multiple points along the ion trajectory 50. Consequently, it is difficult and not particularly practical to drive ions with a constant DC voltage gradient, as is common in existing IMS devices. Alternatively, a traveling RF wave can be generated by applying multiple RF phases to adjacent plates in the manner of an ion-propelling device (as explained in U.S. Patent No. 6,894,286 B2 or U.S. Patent No. 9,536,721 B2).

[0059] These features are understood by reference to the general terms used above. In this sense, a power delivery system may additionally be provided, configured to apply one or more voltages to the set of plate electrodes to confine ions to or within the continuous ion trajectory and / or to cause ions to migrate through the continuous ion trajectory.

[0060] An RF power supply is provided which is designed to provide a respective RF voltage to each electrode of the set of electrodes such that adjacent electrodes receive RF voltages with different phases.

[0061] In particular, the RF voltages can cause ions to be confined within the continuous ion trajectory. In some embodiments, the RF power supply can be further configured to provide a respective RF voltage to each electrode of the set of electrodes to cause ions to traverse the defined ion trajectory. The RF power supply is preferably configured to provide a first RF voltage to each second plate electrode of the set of electrodes according to their spatial arrangement and a second RF voltage to each second plate electrode of the set of electrodes that does not receive the first RF voltage. In particular, the first RF voltage generally has a phase opposite to the second RF voltage. Advantageously, the first and second RF voltages have the same amplitude and / or frequency.

[0062] In preferred embodiments, a DC voltage supply is also provided, which is configured to supply at least one DC voltage potential to one or more electrodes of the set of electrodes. The DC voltage supply is preferably configured to supply DC voltages to at least some of the electrodes of the set of electrodes to form a traveling wave to cause ions to migrate along the defined ion trajectory.

[0063] At this point, more specific details are provided regarding the Fig. 1 to 5 is provided. A stacked ring ion guide of the type shown in Fig. 1, typically has plate electrodes 40 spaced every 0.5 mm to 2 mm from each other (the spacing may be uniform or variable), with the plate electrode 40 having a thickness between 0.25 mm and 1 mm (again, uniform or varying thicknesses are possible). Preferably, the plate electrodes 40 would be spaced every millimeter and 0.5 mm thick. The plate electrodes 40 are typically made of metal, preferably steel or aluminum. Additionally or alternatively, the plate electrodes 40 may be partially or fully coated with a metal such as gold, which may be particularly useful when the plate electrodes 40 are to be soldered to a PCB.

[0064] The openings in the plate electrodes 40 can take a variety of shapes, including circular, oval, rectangular, annular, or less regular shapes. It is generally preferred that the openings be letterbox-shaped (rectangular or rectangular with rounded corners) or ovoid-shaped and extend the length of the ion guide. This can maximize the size of the opening for space charge capacity while minimizing diffusion caused by differences in the possible radii of the ion trajectory. In this embodiment, the shapes of the openings are all the same. However, alternatives are discussed below.

[0065] The length and width of rectangular openings can range from 1 mm to more. The opening width is preferably kept small, generally less than (or no more than) 5 mm, to limit the variation in ion path length. Larger widths are possible, especially if the radius of the helix is ​​large (for example, a radius of at least 150 mm or more). The opening length may be limited by the available axial displacement per adjacent opening, which itself must be limited to maintain the integrity of the ion guide. Large axial displacements between openings of adjacent plate electrodes 40 can cause transmission loss and ion diffusion.Generally, an axial displacement between apertures of up to and including about 100 µm is considered safe, as this begins to approach the mechanical accuracy of the assembly, although in the case of rectangular apertures, considerably larger displacements may be tolerated, for example, up to, including, or slightly more than 250 µm. The plate electrodes 40 are advantageously identical to one another; in this case, the spacing between the apertures should be constant across the plate.

[0066] An example of an ion guide according to the design of Fig. 1 would form a helical drift tube comprising 180 plate electrodes 40, each 0.5 mm thick. The plate electrodes 40 are spaced every 1 mm (relative to the center of the apertures). This can result in a compact central helix radius of 57.3 mm, and an axial displacement of 100 µm between adjacent plate electrodes 40 allows a single turn of a helix to be up to 18 mm long. There may be some overhang between the apertures of adjacent plate electrodes 40, particularly for electrode material or to provide space for ion injection or extraction at the terminal ends. As a result, 15 mm long apertures are feasible.

[0067] If such a helix extends over 11 passes to form a device with an axial length of just under 20 cm (19.8 cm), the total drift trajectory (ion trajectory) would be nearly 2 m. In a benchtop device, doubling or tripling this scale in all dimensions is mechanically feasible, yielding trajectory lengths of 16 m or 54 m, respectively. Longer trajectory lengths than this become unnecessary and may be subject to the law of diminishing returns as ions diffuse across the trajectory length (since resolution is proportional to the square root of the trajectory length). One problem is that very long, thin electrode plates can begin to sag, although this effect evens out with each quarter pass across many plates, and an additional central support could be added if necessary.The gas pressure inside the device, which is preferably filled with helium or nitrogen, is normally about 0.1 mbar (10 Pa) to 1 mbar (100 Pa), although considerable variations are possible.

[0068] A peak-to-peak RF voltage of approximately 300 V is suitable. Applying RF voltages with opposite phases to adjacent plate electrodes 40 means that the total number of plates is desirably an even number. When applying a traveling wave with transient DC pulses, for example, if a pulse of approximately 10 V is applied to every fourth electrode and this pulse is designed to "travel down" each row of four electrode plates, the total number of electrodes in a stack is desirably divisible by 4.

[0069] Generally speaking, as explained above, one or more of the shape; size; positioning of the openings; and spacing between the openings may be the same for each plate electrode of the set of plate electrodes. For each plate electrode, all of the plurality of openings optionally have the same shape. The shape of the openings may, in some embodiments, be the same between the plate electrodes. Advantageously, each of the plurality of openings in each plate electrode has a rectangular or ovoid (oval) shape. Circular, rectangular shapes, rings, and other regular (e.g., polygonal) or irregular shapes are also possible. Other opening shapes and differences between opening shapes are explained below.

[0070] With reference to Fig. 6 schematically illustrates a mass spectrometer 100 including an ion guide according to the disclosure. This includes: an ion source 110; an S-objective 120; an input ion guide 130; a 90-degree ion guide 140; the ion guide 10 of the Fig. 1-5 as an ion mobility separator; a quadrupole mass filter 150; an initial ion guide 160; a curved trap (C-trap) 170; a collision chamber 180; and an orbital capture mass analyzer 190. In this example, the ion mobility separator 10 serves to sort out ions upstream of the quadrupole mass filter 150. This can then be used, for example, to: improve the duty cycle of the quadrupole mass filter 150; resolve chemical influences; and / or provide information regarding the mobility of initial ions. In variations of this arrangement, the ion mobility separator 10 can additionally or alternatively be located downstream of the quadrupole mass filter 150 or between the collision chamber 180 and the C-trap 170, which serves to sort out fragmented ions.

[0071] In another design, the collision chamber 180 could be located upstream of the C-trap 170 but downstream of the mass filter 150, and the ion mobility separator 10 could be located behind the collision chamber, serving to sort out fragmented ions according to their mobility. It is understood that other designs of a mass spectrometer with an ion guide according to the disclosure are possible. In general, any suitable existing design of a mass spectrometer including an ion mobility separator can be constructed using the ion guide according to this disclosure as the ion mobility separator.

[0072] It should be noted that while such a system should, in principle, be loss-free, extended drift regions can be associated with significant ion losses. Considering the sensitivity and potentially some fast operating modes of hybrid instruments, an option may be provided to completely bypass the ion mobility separator 10 (with its extended drift region). Branching ion guides (as explained in US patent publication US 2008 / 0061227 A1) or traps (as envisioned in US patent publication US 2014 / 0353487 A1) connected via a short ion guide would be suitable for this purpose.

[0073] Generally speaking, one aspect of the disclosure may be considered a mass spectrometer comprising any ion guide as disclosed herein. Advantageously, the ion guide is configured to receive ions from an upstream ion source or ion-optical device and cause the received ions to migrate along the ion trajectory. The mass spectrometer may further comprise a mass analyzer configured to receive ions that have migrated along the ion trajectory and optionally analyze the received ions. In some embodiments, the mass spectrometer may further comprise an ion-optical bypass assembly selectively configured to cause ions from the upstream ion source or ion-optical device to migrate to the mass analyzer without passing through the ion guide. This may, for example, comprise one or more ion deflectors.

[0074] It should be understood that modifications may be made to the above design, which, however, remain within the scope of the disclosure. For example, the axial displacement of the opening between adjacent plate electrodes 40 need not be created by mounting plates between two helically shaped PCBs. A single helical plate could be used, and the other endpoint could be a block cut from PEEK or ceramic, with slots cut to position the plates and a suitable hole cut to allow access to the endpoint.

[0075] With reference to Fig. 7A depicts an exemplary electrode structure and mounting substrate according to a second embodiment of an ion guide according to the disclosure. In this alternative embodiment, axial displacement is defined entirely on flat PCBs 220 (or, less preferably, additional metal or insulating parts) by providing the plate electrodes 240 with a wedge shape at one or both endpoints. The mounting PCBs 220 carry slots of varying length surrounding the axis of rotation, such that the distance of insertion of the wedge into the slot varies depending on the slot width to control the axial position of the plates. This provides the plate electrodes 240, and thus their respective openings, with increasing axial displacement about the axis of rotation. The slots can be inexpensively laser cut or milled into the PCB 220.The electrode plates are attached (as intermediate layers) between the two flat PCBs 220.

[0076] With reference to Fig. 7B, an electrode structure and mounting substrate are shown according to a third embodiment of an ion guide according to the disclosure. This includes: two opposing PCBs 260; an offset-defining spacer 280; and plate electrodes 40. In this alternative structure, the axial displacement is defined by a feature milled into the spacer piece 280 at an endpoint of the set of plate electrodes 40. As an alternative but similar approach, slots of varying depth may be cut into the spacer. Such approaches allow positions of the plate electrodes 40 to be defined by a part other than the PCB 280. In either embodiment, electrical connections may be made by soldering them to one or more PCBs 260 attached to or near the spacer 280.Advantageously, the PCBs 280 can then be flat, with the connecting part of the plates passing through in different lengths.

[0077] PCBs are not essential, but are useful as a means of power supply. In a further embodiment, electrical connections and, to a certain extent, mechanical definition and support can be achieved using metal rings with etched / cut connection slots or by directly wiring the electrode plates.

[0078] In various designs, the plate electrodes, each provided with a row of electrode openings, can be formed from PCBs or ceramic plates with metallized openings. The advantage of a metallized PCB may be reduced capacitance, but it may be subject to the risk of charging and electrical breakdown from sharp metal edges. Metal plates can be designed to minimize overlapping metal areas with opposing RF. Additional grounded plates can be placed between plate electrodes, to which an RF is applied, to shield opposing RF voltages from each other.

[0079] In the generalized sense explained above, the fastening element may comprise a fastening substrate to which each electrode of the set of electrodes is attached, the fastening substrate having a shape that defines the relative positioning of openings between adjacent electrodes of the set of electrodes. Additionally or alternatively, the fastening element may comprise: a fastening substrate; and a spacer disposed between the fastening substrate and the set of electrodes. The spacer may be configured to define the relative positioning of openings between adjacent electrodes of the set of electrodes.

[0080] In a further alternative embodiment, the plate electrodes can be different from each other, while still achieving the same effect as in the embodiment explained above. One way to achieve this is to create the axial offset between openings in adjacent plate electrodes by adjusting the opening position in each plate electrode accordingly. This can significantly complicate manufacturing but is still feasible. Care is desirably taken to preserve access for ion injection and extraction.

[0081] As mentioned above, resolution can be limited by trajectory length variation caused by ions that are able to sit at the outer or inner radius of the helical trajectory. Space charge effects will exacerbate this problem by forcing ions to the outer edges and trapping them there. While the designs discussed above result in helical ion trajectories with a circular two-dimensional profile (e.g., viewed from directly above or directly below), other two-dimensional profiles are also possible. With reference to Fig. Figure 8 shows schematically other profiles for ion guides, in particular: (a) a rectangular profile with rounded corners (or "square profile"); and (b) a labyrinthine profile. Other closed shapes for the two-dimensional profile could also be considered. Two-dimensional profiles with a lower degree of curvature than a circular profile, such as those shown in Fig. 8 can help minimize the resolution limitation. Labyrinth-like profiles can also compress an ion trajectory more efficiently into the available space. Such structures still define an ion trajectory with a generally helical shape, although the ion trajectory does not necessarily have to describe a helix. This means that the ion trajectories in Fig. 8 still comprise an orbit that also extends in a direction perpendicular to the direction of rotation, as is the case with a helix.

[0082] Another option to address the limited resolution problem is the use of a figure-eight profile, an example of which is explained in the above-mentioned US patent publication US 2014 / 0042315 A1. The approach described there uses equal-length clockwise and counterclockwise curvature regions to equalize the trajectory, allowing, for example, ions to spend equal time in the outer and inner radii of the trajectory, thus compensating for deviations. Space charge effects can be helpful in this approach by preventing ions from migrating between different trajectories.

[0083] A difficulty with the above embodiment of the Fig. 1 to 5 is that it is difficult to implement a figure-eight profile, since ion paths with opposite curvature cannot normally cross. Fig. Referring to Figure 9, an electrode structure and profile of a fourth embodiment of an ion guide designed to address this problem are schematically depicted. The right side shows the two-dimensional profile of the ion guide according to this design, and the left side shows the structure of the electrode plates at three different parts of the two-dimensional profile. Essentially, the two-dimensional figure-eight profile is formed using two helices with overlapping circular profiles to allow ions to move between the helices after each pass. The structure of the electrode plates that enables this is explained below.

[0084] Starting with the upper part of the two-dimensional profile, a first electrode plate structure 300 is shown. This electrode plate structure does not differ from the electrode plate structure shown, for example, in the Fig. 1, 3A to 3D, and 5. In the center of the two-dimensional profile, a first 310 and a second 320 electrode plate structure are shown overlapping each other. These elongated electrode plates have a serrated pattern such that the first 310 and second 320 electrode plates overlap each other. As a result, ions following the curvature of the upper helix are guided to the lower helix to migrate at the end of each pass with an opposite curvature without ion collision. It can be seen that the passing of ions between the trajectories of opposite curvature does not have to occur after each pass, but is preferably induced such that the ions travel the same distance through the trajectories of both opposite curvatures. Such a design can be advantageous but is mechanically complex.

[0085] In the general sense explained above, the helical or helix-based shape can be considered to define a two-dimensional profile. Accordingly, the relative positioning of each plurality of apertures of a respective plate electrode of the set of plate electrodes and of respective adjacent plate electrodes of the set of plate electrodes preferably defines the continuous ion trajectory to extend multiple times along the two-dimensional profile. In other words, the continuous ion trajectory extends over multiple passes around the helix-based shape.

[0086] In one embodiment, the two-dimensional profile has a circular shape. Other closed-loop shapes are also possible, for example oval, rectangular with rounded corners, or labyrinth-like. In certain embodiments, the two-dimensional profile has the shape of a figure eight (lemniscate). One possibility for implementing such a configuration is for the set of plate electrodes to comprise a first and a second plurality of (plate) electrodes. Each of the first and second plurality of electrodes is arranged to define a corresponding circular two-dimensional profile. Some of the first plurality of electrodes and some of the second plurality of electrodes are arranged to overlap one another such that the two-dimensional profile of the first plurality of electrodes covers the two-dimensional profile of the second plurality of electrodes.Then, the continuous ion trajectory is advantageously defined by the plurality of openings of both the first and second plurality of electrodes. For example, the overlapping electrodes may have a serrated shape (typically having a rectangular shape). The serration of the overlapping electrodes of the first plurality of electrodes is advantageously designed to mirror the serration of the overlapping electrodes of the second plurality of electrodes, allowing the electrodes to overlap. The openings of the first plurality of electrodes can thereby receive ions from the openings of the second plurality of electrodes, and the openings of the second plurality of electrodes can correspondingly receive ions from the openings of the first plurality of electrodes.

[0087] Other alternative structures may be considered. With reference to Fig. Figure 10A is a plan view of a fifth embodiment of an ion guide according to the disclosure. It depicts another structure that can be efficiently constructed with multi-aperture electrodes as a "flat spiral." In this embodiment, adjacent plates along the rotation axis along which the plate electrodes are arranged do not need to be translated relative to each other. Instead, the distance of the plate electrodes from the rotation axis is shifted between successive plate electrodes. When the plates are arranged facing away from the rotation axis, this creates a single spiral path for the ions instead of a helical path.

[0088] In Fig. In Figure 10A, the electrodes 340 with multiple openings (shown here with five openings 341 each) are each displaced perpendicular to the rotation axis (marked by point 342 and extending into and out of the plane of the drawing). As shown in this drawing, ions would enter the structure at the inlet opening 350 and exit the structure at the outlet opening 360. Therefore, they would migrate along the spiral ion trajectory 365. This approach can be combined with others disclosed herein; for example, the other described methods for balancing the trajectory for ions on the inner and outer radius can also be applied, as explained below.

[0089] The axial offset can be implemented in the same way as in the case of the helical structures, i.e., by bending the PCB (which would be located at the outer edge of the plate electrodes 340 and extend into the plane of the drawing), the slots defining the penetration of the electrodes into the support, or a spacer piece or other suitable structure.

[0090] As generally considered above, some or all of the set of plate electrodes may be spatially arranged about an axis that is perpendicular to the first dimension (the dimension along which the plurality of openings of each plate electrode are spaced apart). Then, the first dimension is typically radial to the axis, and the continuous ion trajectory has a spiral-based shape. A spiral-based shape may refer to a shape that has a fundamental spiral character, for example, a curve with a generally increasing (or decreasing) radius from the axis. In particular, this may be achieved by positioning each of the respective adjacent plate electrodes of the set of plate electrodes such that they are offset from one another in the first dimension (the radial dimension).Variants of a spiral shape (where the spiral character is modified by another shape, for example with a slight variation in a dimension perpendicular to the direction of spiral movement, forming a “zigzag shape”) can also be considered.

[0091] Some helical character can be incorporated by adding an axial shift in addition to the radial one to allow for: space for adjacent ion-optical components; or space to switch the ion trajectory from helical to counter-helical designs (by reversing the trend of the radial shift). Thus, the trajectory length can be greatly increased within a small space by stacking alternating helical and counter-helical structures. A structure according to this latter proposal is described with reference to the Fig. 10B, Fig. 10C and Fig. 10D explained.

[0092] With reference to Fig. Figure 10B is a plan view of a first part of a variant of the embodiment of Fig. 10A, and with reference to Fig. Figure 10C shows a plan view of a second part of this alternative embodiment. The two parts are stacked (in two levels), with the Fig. 10B shown below (level 1) and the part in Fig. 10C is at the top (level 2). Ions enter the structure through the ion inlet 370 and pass the first plate electrodes 374 to travel along the first spiral ion trajectory 375 (an outward spiral) and exit through the intermediate ion outlet 378. These ions are then guided (possibly by further deflection electrodes, not shown) to the intermediate ion outlet 380 on the second level ( Fig. 10C). From here, the ions pass through the second plate electrodes 384 to migrate along the second spiral ion trajectory 385 (an inward spiral) and exit through the ion outlet 388.

[0093] Electrode plates can be constructed (e.g., etched) with two dimensions of the aperture stack, allowing multiple levels to be integrated into a single ring of electrode plates. With reference to Fig. 10D is the ion trajectory for the design of the Fig. 10B and Fig. 10C, using the same reference numerals as in those drawings to show the path of the ions from the ion inlet 370 through the spiral ion flight region 375 and opposite spiral ion flight region 385 to the ion outlet 388 through which they exit.

[0094] Generally speaking, each adjacent plate electrode of the set of plate electrodes can be positioned such that they are axially offset from each other. This can cause the continuous ion trajectory to have a shape based on both a spiral and a helix.

[0095] In embodiments, it is contemplated that the set of plate electrodes comprises a first and a second plurality of electrodes. The first plurality of electrodes are typically spatially arranged such that a relative positioning of each plurality of openings of a respective plate electrode of the first plurality of electrodes and of respective adjacent plate electrodes of the first plurality of electrodes defines a first continuous ion trajectory through the respective plurality of openings of each plate electrode of the first plurality of electrodes.The second plurality of electrodes are spatially arranged generally such that relative positioning of each plurality of apertures of a respective plate electrode of the second plurality of electrodes and of respective adjacent plate electrodes of the second plurality of electrodes defines a second continuous ion trajectory through the respective plurality of apertures of each plate electrode of the second plurality of electrodes.The second plurality of electrodes may be stacked on top of the first plurality of electrodes (e.g., the first plurality of electrodes being generally arranged in a first plane and the second plurality of electrodes being generally arranged in a second plane parallel to the first plane but spaced from the first plane in a direction perpendicular to it) such that ions exiting the first continuous ion trajectory are directed to the second continuous ion trajectory. This is particularly advantageous when the first and / or second continuous ion trajectories have a shape based on a spiral and a helix.

[0096] For example, an entrance to the first continuous ion trajectory may be provided at a first end of one of the first plurality of electrodes, and an exit from the first continuous ion trajectory may be provided at a second end of one of the first plurality of electrodes opposite the first end (where the first and second ends are defined in the first dimension). Then, an entrance to the second continuous ion trajectory may be provided at the second end of one of the second plurality of electrodes (aligned with the second end of the first plurality of electrodes), and an exit from the first continuous ion trajectory may be provided at the first end of one of the second plurality of electrodes (aligned with the first end of the first plurality of electrodes).

[0097] Optionally, the first plurality of electrodes are spatially arranged around a first axis (the first continuous ion trajectory extending along a direction of the first axis), and the second plurality of electrodes are spatially arranged around a second axis (the second continuous ion trajectory extending along a direction of the second axis). Then, the first and second axes can be (substantially) parallel or (substantially) coaxial.

[0098] As previously mentioned, while it may be advantageous for each of the plate electrodes to be identical, this is not necessary. A further advantage of minimizing the reduction in resolution may arise from changing the aperture shape between apertures of adjacent electrodes along the ion trajectory. This will be discussed with reference to Fig. This is explained in Figure 11A, which shows initial examples of electrode aperture shapes 400, 410, 420, 430, 440, 450, 460, 470. By sequentially changing the shape of the apertures along the ion trajectory (represented by increasing reference numerals), ions can be induced to follow a tight path around the outer and inner radii at least once per pass through the main helix. This can be equivalent to swirling the trapped ion packets so that they follow a more uniform path length. This approach could potentially be applied to any ion mobility device with curvature and need not be used only with the previously described ion guides (which, for example, have a helically shaped ion trajectory). The force that creates this effect can be exerted by varying the shape of the apertures as ions advance around each bend or curve of the ion trajectory.At a conceptual level, it is understood that the variation in the structure of the apertures is such that entrained ions undergo similar drift trajectories to each other, even if the inner and outer radii of the aperture stack vary considerably.

[0099] The Fig. The procedure shown in Figure 11A has two connected slots 405, 415 as openings (although more such slots could be used if desired). For example, each of the openings in the plate electrode embodiments shown in Figures Fig. 1, 3A-D, and 5, may be configured to encompass the two slits. Tethers or sliders 406, 407 separating the slits appear to move and / or change shape with increasing distance along the ion trajectory, that is, with progressive movement through openings from plate to plate, causing ions to move back and forth in the region of the opening. It is not necessary for the tethers or sliders 406, 407 to completely separate the openings, although this is shown for simplicity. While the slits 405, 415 and the tethers or sliders 406, 407 are shown only for a first electrode 400, the corresponding portions in the other electrodes are readily apparent. Thus, ions traveling along the ion trajectory are caused to shift in a direction perpendicular to the direction of the ion trajectory.By displacing the ions in a perpendicular direction, particularly in the one or more curved portions of the ion trajectory, the ions can be caused to migrate along different segments of the ion trajectory cross-section, for example, to rotate around the apertures and thereby define a helical shape, wherein the direction of the ion trajectory is the axis of the helical shape.

[0100] Fig. Figure 11A illustrates this approach with an opening formed from two interconnected slots in a generally rectangular shape. To continue, with reference to Fig. 11B shows further examples of electrode aperture shapes according to the disclosure that are suitable for ion guides. As shown in this drawing, the aperture could also be: a ring shape 480 (shown in this drawing with a single slider 481, although more than one such slider or attachment point could be used) that rotates circumferentially between successive electrodes as shown by the arrow, about only a wide slot 482, with force applied by rotation of the slot between electrodes arranged in series as shown by the arrows, or a ring slot 484 with one or more attachment points 485 projecting from the aperture side that translate according to the direction (this is less preferred because ions could naturally move back and forth in the region of the slot, resulting in diffusion).

[0101] Although this effect is shown to be created by changing the shape of apertures along the ion trajectory length, it can alternatively be achieved by applying a voltage to additional electrodes attached between the RF apertures, to give one example.

[0102] In a second aspect, in a generalized sense (which can be combined with other aspects described herein), an ion guide comprising a plurality of electrodes can be considered. Each electrode comprises at least one opening to define an ion trajectory (through the openings) having at least one curvature, which can define a mean radius of curvature. An opening of a first electrode of the plurality of electrodes is adjacent to an opening of a second electrode of the plurality of electrodes along the ion trajectory. Then, the opening of the second electrode has a shape, an electrical potential, and / or a position that differ from those of the opening of the first electrode, so as to cause ions migrating along the ion trajectory to displace in a direction perpendicular to the direction of the ion trajectory.By shifting the ions in a perpendicular direction, particularly at the one or more curved sections of the ion trajectory, the ions can be caused to migrate along different segments of the ion trajectory cross-section. In particular, the ions do not necessarily have to be forced toward an inner or outer part of the curved section. In a preferred embodiment, the ions can be caused to oscillate between the inside of the mean radius of curvature and the outside of the mean radius of curvature. Such approaches can minimize limitations in resolution due to variations in trajectory length. For example, a difference in trajectory length between ions entering the ion guide at a position on the inside of the mean radius of curvature and ions entering the ion guide at a position on the outside of the mean radius of curvature can be corrected.

[0103] To combine this with the first aspect, it can be assumed (for example) that the ion trajectory has a shape based on a spiral and / or a helix. Furthermore, each electrode can have a plurality of openings. The electrodes can be a plate electrode or an electrode structure that functionally mimics a plate electrode.

[0104] In this second aspect, the direction perpendicular to the direction of the continuous ion trajectory is preferably defined by a helical (or helix-based) shape, wherein the direction of the ion trajectory is an axis of the helical shape. By causing ions to "spiral" (which in this context means migrating in a helical shape), the ions are effectively swirled. It should be noted that the ion trajectory (particularly in combination with the first aspect) may in itself have a spiral and / or helical shape, such that the ions may migrate along an ion trajectory having a spiral and / or helix-based shape in a helical motion (which may be referred to as a further helical shape) perpendicular to that trajectory.

[0105] In some embodiments, the opening of the first electrode and the opening of the second electrode each comprise a respective first slot and a respective second slot. Advantageously, each first slot is different from and / or separate from the respective second slot. Then, the first slot of the opening of the second electrode advantageously has a shape and / or position that differs from those of the first slot of the opening of the first electrode, so as to cause ions migrating along the ion trajectory to displace in a first direction that is perpendicular to the direction of the ion trajectory.Additionally or alternatively, the second slit of the opening of the second electrode has a shape and / or position that differs from those of the second slit of the opening of the first electrode, thereby causing ions migrating along the ion trajectory to shift in a second direction that is perpendicular to the direction of the ion trajectory.

[0106] In one embodiment, each first slot and each second slot have a shape defined by respective portions of one and the same rectangle (where each of the first and second slots optionally includes at least one corner of the rectangle). In embodiments, the opening of the first electrode and / or the opening of the second electrode each comprise a ring shape (which may be circular, oval, rectangular, or another ring-shaped shape).

[0107] In some embodiments, the opening of the first electrode and / or the opening of the second electrode further each comprise one or more sliders or attachment points that protrude from one side of the respective opening and move circumferentially between the first and second electrodes. In other embodiments, the opening of the first electrode and the opening of the second electrode each comprise a wide or straight slit. The slit can then move circumferentially between the first and second electrodes. The rotational displacement of the sliders, attachment points, and / or the slit can cause the ions to shift perpendicular to the trajectory direction.

[0108] Preferably, the first and second directions are the same direction. In other words, the relative positioning of both the first and second slits causes ions to be propelled in the same manner. This typically occurs in a helical motion, as explained above, such that the first direction is defined by a first further helical shape and the second direction is defined by a second further helical shape. Then, the direction of the ion trajectory is preferably an axis of both the first and second further helical shapes. The first and second further helical shapes may be the same. Optionally, the second direction may differ from the first direction, for example, if one of the first and second further helical shapes is right-handed and the other left-handed (different chirality).

[0109] As explained above, electrode arrangements or structures can be used that are not necessarily plate electrodes, but have the same functional effect. Such a structure is described with reference to Fig. 12, which shows a perspective view of a sixth embodiment of an ion guide. Stacked rod electrodes 510, 520 are used instead of plate electrode openings. The stacked rod electrodes 510, 520 can be viewed as a stack of electrode assemblies, each assembly comprising two parallel rod electrodes with a respective gap between them (where the gap is a dimension orthogonal to a direction of longitudinal extension of the rod electrodes). An RF voltage with a first phase is applied to the first rod electrodes 510, and an RF voltage with a second, opposite phase is applied to the second rod electrodes 520. Preferably, no DC voltages are applied to the first rod electrodes 510 and the second rod electrodes 520. Additional electrodes 500 with an applied DC voltage are provided between the RF rod electrodes 510 and the RF rod electrodes 520.Preferably, no RF voltages are applied to the additional electrodes 500. Therefore, the DC voltage electrodes 500 overlap between successive RF rod electrodes 510, 520.

[0110] These DC electrodes 500 provide lateral focusing. In this embodiment, they are depicted as plate electrodes, but they can equivalently be provided by rod electrodes or wires fixed from above or below. It can be seen that the DC electrodes 500 provide parallel electrode portions (vertical portions in the figure) with a respective gap between them (where the plane of the gap is generally parallel to and spatially separated from the plane of the gap between the rod electrodes 510 and / or the plane of the gap between the rod electrodes 520), which are arranged orthogonally (at right angles) with respect to the parallel RF rod electrodes 510, 520. The electrode portions of the DC electrodes 500 can be portions of the plate on the sides of the plate opening or parallel DC rods or wires.In this way, the ion trajectory or ion trajectory channel is defined in one dimension by the stacked arrays of parallel rod electrodes carrying alternating RF potentials, and in another (orthogonal) dimension by DC electrode portions (which may be rod electrodes or aperture sides in an elongated plate). The rod electrodes 510, 520 therefore traverse the circumference of the ion trajectory cross-section (the effective "aperture" defined by the parallel

[0111] HF rod electrodes 510, 520 together with the DC voltage electrodes 500).

[0112] A disadvantage of this design is that the DC electrodes 500 are placed between the RF rod electrodes 510, 520, which increases the separation in the RF stack. However, it does offer some advantages in that the DC sections 500 can shield opposing RF potentials from each other, reducing capacitance. The channel height in this arrangement can be greatly varied using the DC sections 500 and is not limited by the physical constraints imposed by the RF electrodes 510, 520. This can be useful when narrow channels are desirable (since tall channels can cause resolution losses). Furthermore, the traveling-wave DC voltage could be applied using the DC sections 500 alone and would not need to be mixed with RF voltages. Alternatively, the RF electrodes 510, 520 and the DC components 500 can be interchanged. A particular advantage of a like in 。 Fig. The structure shown in Figure 12 can be realized when such a structure is used in the construction of a spiral ion guide, for example of the type described with reference to Fig.1 to 5. In such an implementation, two relatively long parallel rod electrodes with RF (optional only; i.e., supplied only with one or more RF potentials) can be used to create an elongated channel in a first plane. Then, a layer of orthogonal DC wires, rods, or apertures is provided (attached) in a second plane that is separate from the first plane (and preferably substantially parallel to the first plane, at least in one dimension). The layer of DC electrodes (only; i.e., supplied only with one or more DC potentials) divides the channel and defines the ion trajectory and / or the number of turns in the spiral. Alternatively (and in accordance with the reversed arrangement explained above), the relatively long parallel rod electrodes with DC voltage (only; i.e.only one or more DC potentials), and the layer of orthogonal wires, rods, or openings can be provided with RF (only; ie, only one or more RF potentials).

[0113] In a generalized sense, an ion guide according to a third aspect can be considered. This ion guide comprises: a first plurality of electrode assemblies, each electrode assembly comprising respective parallel rod electrodes with a respective gap therebetween; and a second plurality of electrode assemblies, each electrode assembly comprising respective parallel electrode parts with a respective gap therebetween. The parallel electrode parts of the second plurality of electrode assemblies are preferably arranged orthogonally (at right angles) with respect to the parallel rod electrodes of the first plurality of electrode assemblies. The respective gaps of the first plurality of electrode assemblies are aligned with the respective gaps of the second plurality of electrode assemblies to allow ions to migrate therethrough along a continuous path (orto effectively provide openings that enable this). The first and second pluralities of electrode assemblies are advantageously arranged alternately along the continuous path. The parallel rod electrodes of the first plurality of electrode assemblies and the parallel electrode portions of the second plurality of electrode assemblies can effectively mimic plate electrodes in a functional sense.

[0114] Preferably, each of the first plurality of electrode assemblies is provided with an RF potential, and in some embodiments, only an RF potential (i.e., each potential or potentials applied to each electrode have no DC component). Additionally or alternatively, each of the second plurality of electrode assemblies is provided with a DC potential, and more preferably, only a DC potential (i.e., each potential or potentials applied to each electrode have no RF component). This can be reversed, such that each of the first plurality of electrode assemblies is provided with a DC potential, and more preferably, only a DC potential (i.e., each potential or potentials applied to each electrode have no RF component).Additionally or alternatively, in this case, each of the second plurality of electrode assemblies is provided with an RF potential, and in some embodiments, only with an RF potential (i.e., each potential or potentials supplied to each electrode have no DC component). Optionally, successive electrode assemblies in the first plurality of electrode assemblies (or, in the case of the reversed arrangement, in the second plurality of electrode assemblies) are provided with RF potentials of different (optionally opposite) phase. The use of DC voltage electrodes alone can partially shield the RF electrodes (particularly when successive electrodes are supplied with RF potentials of different phases), as explained above.In some embodiments, each electrode assembly of the second plurality of electrode assemblies comprises a respective electrode (optionally plate electrode; in this sense, a plate is meant and not a structure simulating a plate) having an opening to provide the respective gap.

Claims

[1] Ion guide (10), comprising: a set of plate electrodes (40, 340), each plate electrode (40, 340) having a plurality of openings formed therethrough, the set of plate electrodes (40, 340) being spatially arranged such that a relative positioning of each plurality of openings of a respective plate electrode (40, 340) of the set of plate electrodes (40, 340) and of respective adjacent plate electrodes of the set of plate electrodes (40, 340) defines a continuous ion trajectory (50) through the respective plurality of openings of each plate electrode (40, 340) of the set of plate electrodes (40, 340), the continuous ion trajectory (50, 375, 385) having a shape based on a helix and / or spiral, and an RF power supply configured to provide a respective RF voltage to each plate electrode of the set of plate electrodes (40, 340) such that adjacent plate electrodes (40, 340) receive RF voltages having different phases. [2] The ion guide of claim 1, wherein in each plate electrode (40, 340) of the set of plate electrodes (40, 340), one or more of the shape; size; and spacing between openings are the same. [3] The ion guide of claim 2, wherein each plate electrode (40, 340) of the set of plate electrodes has its respective plurality of apertures spaced along a first dimension, and the respective plurality of apertures of respective adjacent plate electrodes (40, 340) of the set of plate electrodes are positioned to be offset from one another in the first dimension. [4] The ion guide of claim 3, wherein respective adjacent plate electrodes (40, 340) of the set of plate electrodes (40, 340) are positioned such that they are offset from one another in the first dimension. [5] The ion guide of claim 3 or claim 4, wherein each plate electrode (40, 340) of the set of plate electrodes (40, 340) has the same spacing between apertures along the first dimension, and the offset between the respective plurality of apertures of one plate electrode (40, 340) and the respective plurality of apertures of an adjacent plate electrode (40, 340) is less than the spacing between apertures. [6] The ion guide of claim 5, wherein the offset between respective pluralities of apertures of respective adjacent plate electrodes (40, 340) is substantially equal to y / N, where y is the aperture pitch in each plate electrode (40, 340) and N is the number of plate electrodes (40, 340). [7] An ion guide according to any preceding claim, wherein each plate electrode (40, 340) of the set of plate electrodes has its respective plurality of apertures spaced along a first dimension, the relative positioning of each plurality of apertures defining the continuous ion trajectory (50, 375, 385) such that the ion trajectory (50, 375, 385) extends along the first dimension. [8] The ion guide of claim 7, wherein at least some of the set of plate electrodes (40) are spatially arranged about an axis extending in the first dimension, the continuous ion trajectory (50) having a helical shape. [9] The ion guide of claim 7, wherein at least some of the set of plate electrodes (40, 340) are spatially arranged about an axis perpendicular to the first dimension such that the first dimension is radial to the axis and the continuous ion trajectory (385) has a shape based on a spiral. [10] An ion guide according to any preceding claim, wherein the plurality of openings of each plate electrode (40, 340) have the same shape. [11] The ion guide of claim 10, wherein each of the plurality of openings of each plate electrode (40, 340) has a rectangular or ovoid shape. [12] An ion guide according to any preceding claim, wherein for each plate electrode (40, 340), the respective plurality of openings comprises at least 3 openings. [13] An ion guide according to any preceding claim, wherein the continuous ion trajectory (50) has a helical shape defining a two-dimensional profile, the relative positioning of each plurality of apertures of a respective plate electrode (40, 340) of the set of plate electrodes and of respective adjacent plate electrodes (40, 340) of the set of plate electrodes defining the continuous ion trajectory (50) to extend a plurality of times along the two-dimensional profile. [14] The ion guide of claim 13, wherein the two-dimensional profile is circular, oval, rectangular with rounded corners, labyrinthine or figure-eight-shaped. [15] The ion guide of claim 14, wherein the two-dimensional profile is figure-eight shaped, and wherein the set of plate electrodes (40, 340) comprises a first and a second plurality of plate electrodes, each of which is arranged to define a circular two-dimensional profile, some of the first plurality of plate electrodes (40, 340) and some of the second plurality of plate electrodes (40, 340) being arranged to overlap each other such that the two-dimensional profile of the first plurality of plate electrodes (40, 340) overlies the two-dimensional profile of the second plurality of plate electrodes (40, 340), the continuous ion trajectory being defined by the plurality of openings of both the first and second plurality of plate electrodes (40, 340). [16] An ion guide according to any preceding claim, wherein the set of plate electrodes comprises a first and a second plurality of plate electrodes (40, 340); wherein the first plurality of plate electrodes (40, 340) are spatially arranged such that a relative positioning of each plurality of openings of a respective plate electrode of the first plurality of plate electrodes (40, 340) and of respective adjacent plate electrodes of the first plurality of plate electrodes (40, 340) defines a first continuous ion trajectory through the respective plurality of openings of each plate electrode of the first plurality of plate electrodes (40, 340); wherein the second plurality of plate electrodes (40, 340) are spatially arranged such that a relative positioning of each plurality of openings of a respective plate electrode of the second plurality of plate electrodes (40, 340) and of respective adjacent plate electrodes of the second plurality of plate electrodes (40, 340) defines a second continuous ion trajectory through the respective plurality of openings of each plate electrode of the second plurality of plate electrodes (40, 340); and wherein the second plurality of plate electrodes (40, 340) are stacked on the first plurality of plate electrodes (40, 340) such that ions exiting the first continuous ion trajectory are guided to the second continuous ion trajectory. [17] The ion guide of claim 16, wherein the first plurality of plate electrodes (40, 340) are spatially arranged about a first axis and the second plurality of plate electrodes (40, 340) are spatially arranged about a second axis, the first and second axes being parallel. [18] Ion guide according to any preceding claim, wherein: an opening of a first plate electrode (40, 340) of the set of plate electrodes is adjacent to an opening of a second plate electrode (40, 340) of the set of plate electrodes along the continuous ion trajectory path, and the opening of the second plate electrode (40, 340) has a shape, an electrical potential and / or a position that differ from those of the opening of the first plate electrode (40, 340) to cause ions migrating along the continuous ion trajectory path to displace in a direction that is perpendicular to the direction of the continuous ion trajectory path. [19] An ion guide according to claim 18, wherein each of the openings of the first plate electrode (40, 340) and the opening of the second plate electrode (40, 340) comprise a respective first slot and a respective second slot, each first slot being different from and separate from the respective second slot; wherein the first slit of the opening of the second plate electrode (40, 340) has a shape and / or position different from that of the first slit of the opening of the first plate electrode (40, 340) so as to cause ions migrating along the continuous ion trajectory to displace in a first direction perpendicular to the direction of the continuous ion trajectory; and wherein the second slit of the opening of the second plate electrode has a shape and / or position different from those of the second slit of the opening of the first plate electrode (40, 340) to cause ions migrating along the continuous ion trajectory to displace in a second direction perpendicular to the direction of the continuous ion trajectory. [20] The ion guide of claim 19, wherein each first slot and each second slot have a shape defined by respective portions of one and the same rectangle. [21] Ion guide according to one of the preceding claims, wherein the RF power supply is designed to provide a first RF voltage to each second plate electrode of the set of plate electrodes (40, 340) according to their spatial arrangement and to provide a second RF voltage to each second plate electrode of the set of plate electrodes (40, 340) that does not receive the first RF voltage, wherein the first RF voltage has a phase opposite to the second RF voltage. [22] Ion guide according to any preceding claim, further comprising: a DC voltage supply configured to supply at least one DC voltage potential to one or more plate electrodes (40, 340) of the set of plate electrodes (40, 340); wherein the DC voltage supply is configured to supply DC voltages to at least some plate electrodes (40, 340) of the set of plate electrodes (40, 340) to form a traveling wave to cause ions to traverse the defined ion trajectory. [23] An ion guide according to any preceding claim, further comprising: a fastening element to which the set of plate electrodes (40, 340) is fastened in order to determine the relative positioning of openings between adjacent plate electrodes (40, 340) of the set of plate electrodes (40, 340). [24] The ion guide of claim 23, wherein the attachment member comprises one or more electrical connections to the set of plate electrodes (40, 340). [25] An ion guide according to claim 23 or claim 24, wherein the fastening element comprises: a first mounting substrate to which a first end of each electrode of the set of plate electrodes (40, 340) is attached; and a second mounting substrate to which a second end of each electrode of the set of plate electrodes (40, 340) is attached. [26] The ion guide of claim 25, wherein the first mounting substrate comprises one or more first electrical connections to each second electrode of the set of plate electrodes (40, 340) according to their spatial arrangement, and wherein the second mounting substrate comprises one or more second electrical connections to plate electrodes (40, 340) of the set of plate electrodes (40, 340) that are not connected to each second electrode of the set of plate electrodes (40, 340) between the one or more first electrical connections connected to the plate electrodes (40, 340), wherein the second electrical connections are arranged to provide an electrical power that is different from an electrical power provided by the first electrical connections. [27] The ion guide of any one of claims 23 to 26, wherein the mounting member comprises a mounting substrate to which each electrode of the set of plate electrodes (40, 340) is mounted, the mounting substrate having a shape that defines the relative positioning of openings between adjacent plate electrodes (40, 340) of the set of plate electrodes (40, 340). [28] The ion guide of any one of claims 23 to 26, wherein the mounting member comprises: a mounting substrate; and a spacer disposed between the mounting substrate and the set of plate electrodes (40, 340), the spacer being configured to determine the relative positioning of openings between adjacent plate electrodes (40, 340) of the set of plate electrodes (40, 340). [29] An ion mobility spectrometer comprising the ion guide according to any preceding claim, which is designed as a drift tube. [30] Mass spectrometer comprising: the ion guide according to any one of claims 1 to 28, which is designed to receive ions from an upstream ion source or ion optical device and to cause the received ions to migrate along the ion trajectory; and a mass analyzer designed to detect ions that have migrated along the ion trajectory. [31] A mass spectrometer according to claim 30, further comprising: an ion optical bypass assembly selectively configured to cause ions to migrate from the upstream ion source or ion optical device to the mass analyzer without passing through the ion guide.

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