GB2601811A

GB2601811A - Apparatus and method

Info

Publication number: GB2601811A
Application number: GB2019596.2A
Authority: GB
Inventors: Pantalei Simone; Allison John; Kalinina Diana; Gwen-Ham Ho Alex; Pursehouse James
Original assignee: Ascend Diagnostics Ltd
Current assignee: Ascend Diagnostics Ltd
Priority date: 2020-12-11
Filing date: 2020-12-11
Publication date: 2022-06-15
Also published as: WO2022123251A1; EP4085477A1; GB202019596D0

Abstract

An ion optical element 10, which may form an ion acceleration region for a Time of Flight mass spectrometer, comprises a set of stacked electrodes 110 having apertures 111 therethrough (e.g. a ring stack), and a set of shield electrodes 120. A first shield electrode 120A surrounds, shrouds or encircles a first electrode 110A of the stacked electrodes at least partially, and spans or bridges between the first electrode and a second electrode 110B of the stacked electrodes at least partially. The first electrode and the first shield electrode are coupled electrically, e.g. at the same electrical potential. The shield electrodes may be arranged on a flexible insulating substrate (e.g. a flexible printed circuit board). A mass spectrometer and method of shielding ions is also claimed. The invention may reduce susceptibility to ion deflection and perturbation of the ion optical axis due to radial field penetration or an asymmetric electrical element of the mass spectrometer.

Description

APPARATUS AND METHOD

Field

The present invention relates to ion optical elements comprising sets of stacked electrodes.

Background to the invention

Ion optical devices, for example mass spectrometers, include ion optical elements. A parallel plate ion optical element comprises a set of stacked electrodes (i.e. a series of parallel plates), defining, at least in part, an ion optical axis therethrough, and the electrical potentials applied to which form ion acceleration regions. Ideally, the fields between the electrodes are free from distortions that cause ion trajectory aberrations, thereby compromising sensitivity and/or resolving power of a mass spectrometer.

Typically, the stacked electrodes have respective apertures for the ions to pass through and the respective electrodes are of finite sizes (for example, diameter). The edges of the apertures and the outer edges of the electrodes give rise to axial and radial field penetration, respectively, resulting in field distortion and ion trajectory aberrations, in turn.

Axial field penetration may be reduced by using relatively smaller apertures and/or by establishing field free regions between the acceleration regions.

Radial field penetration may be reduced by reducing the distance d+, between adjacent electrodes n, n + 1 with respect to electrode size, for example electrode radius i,. Empirically, radial field penetration can be controlled by ensuring that the electrode radius r", is at least 3.5x greater than the electrode spacing distance d""+,. That is, a ratio R" of the radius c to the distance cln."+, is at least 3.5. This should not only prevent field distortions from the edge of the electrodes from adversely affecting the ion beam, but also screen the ions from charged or ground structures close to the ion optics, such as those associated with electrical connections to the electrodes and/or other ion optical elements.

Hence, the condition to minimise radial field penetration may, broadly, be met by for a parallel plate ion optical element of a given length by using a relatively smaller number of relatively large radius electrodes (i.e. large radius r,.) or a relatively larger number (i.e. small distance c/nm+.1) of relatively small radius electrodes, such that ratio R, of the radius r,. to the distance cl,"" is at least 3.5.

Using electrodes such that ratio R7, of the radius r, to the distance d, is less than 3.5, for example significantly less than 3.5, may result in field distortion to such an extent that the resolving power is compromised and, more crucially, deflection of the ion beam away from the ion optical axis. The latter is important for two main reasons: Firstly, any ion beam deflection could cause the ion beam to fully or partially miss the ion detector, causing total or significant loss of signal; and Secondly, any ion beam deflection causing the ions to pass through other ion optical elements off axis, such as an Einzel lens, could significantly degrade performance of those other ion optical elements. For example, in the case of the Einzel lens, varying the potential applied to the Einzel lens would, by design, radially focus a beam passing along its axis. However, an ion beam passing through the Einzel lens off-axis would also be laterally deflected, causing the ion beam to scan across the plane of the detector as the potential on the Einzel lens is varied to achieve the required radial focussing. In extreme cases, the ion beam may fully or partially miss the ion detector.

For relatively larger ion optical devices such as floor-standing mass spectrometers, it may be relatively easy to meet the condition to minimise radial field penetration: using relatively larger electrodes and/or a relatively larger number of relatively closely spaced electrodes.

However, for relatively smaller ion optical devices such as benchtop mass spectrometers, meeting the condition to minimise radial field penetration may not be so readily achievable. For example, due to other design constraints, there may not be enough space in the vacuum chamber for relatively larger electrodes while it may not be possible to incorporate a larger number of electrodes to reduce the distance between them, for example due to the increased number of electrical connections. The latter may be particularly problematic in relatively more complex ion optical elements where each additional electrode requires a high voltage (HV) electrical vacuum feedthrough, for which there again might not be enough space, particularly where HV coupling components, such as resistors and capacitors, are required inside and/or outside of the vacuum chamber.

Hence, there is a need to improve ion optical elements comprising sets of stacked electrodes.

Summary of the Invention

It is one aim of the present invention, amongst others, to provide an ion optical element which at least partially obviates or mitigates at least some of the disadvantages of the prior art, whether identified herein or elsewhere. For instance, it is an aim of embodiments of the invention to provide an ion optical element comprising a set of stacked electrodes that mitigates effects of radial field penetration, for example due to outer edges thereof and/or asymmetrical electrical element(s), while having a relatively smaller form factor and/or reduced number of electrodes. For instance, it is an aim of embodiments of the invention to provide an ion optical element comprising a set of stacked electrodes having relatively reduced suscepfibility to ion deflection due to radial field penetration and/or asymmetrical electrical element(s), such as charged or ground structures. For instance, it is an aim of embodiments of the invention to provide a method of shielding ions, thereby improving sensitivity and/or resolving power.

A first aspect provides an ion optical element comprising: a set of stacked electrodes, including a first electrode and a second electrode, having respective apertures therethrough, wherein an ion optical axis is defined through the respective apertures and wherein the first electrode and the second electrode are mutually spaced apart by a distance dr,2: a set of shield electrodes, including a first shield electrode, wherein the first shield electrode surrounds, at least in part, the first electrode and spans, at least in part, between the first electrode and the second electrode; and wherein the first electrode and the first shield electrode are mutually electrically coupled.

A second aspect provides a shield electrode assembly according to the first aspect or a printed circuit board, PCB, according to the first aspect.

A third aspect provides a mass spectrometer, MS, comprising an ion optical element according to the first aspect.

A fourth aspect provides a method of shielding ions moving through respective apertures of a set of stacked electrodes, including a first electrode and a second electrode, from an asymmetrical electrical element, wherein an ion optical axis is defined through the respective apertures and wherein the first electrode and the second electrode are mutually spaced apart by a distance d1,2, the method comprising: disposing, between the asymmetrical electrical element and the set of stacked electrodes, a set of shield electrodes, including a first shield electrode, comprising surrounding, at least in part, by the first shield electrode, the first electrode and spanning, at least in part, by the first shield electrode, between the first electrode and the second electrode; and mutually electrically coupling the first electrode and the first shield electrode.

A fifth aspect provides a method of manufacturing a shield electrode assembly according to the first aspect.

Detailed Description of the Invention

According to the present invention there is provided an ion optical element, as set forth in the appended claims. Also provided is a shield electrode assembly, a PCB, a mass spectrometer, a method of shielding ions and a method of manufacturing a shield electrode assembly. Other features of the invention will be apparent from the dependent claims, and the description that follows.

Ion optical element The first aspect provides an ion optical element comprising: a set of stacked electrodes, including a first electrode and a second electrode, having respective apertures therethrough, wherein an ion optical axis is defined through the respective apertures and wherein the first electrode and the second electrode are mutually spaced apart by a distance d1.2; a set of shield electrodes, including a first shield electrode, wherein the first shield electrode surrounds, at least in part, the first electrode and spans, at least in part, between the first electrode and the second electrode; and wherein the first electrode and the first shield electrode are mutually electrically coupled.

The set of shield electrodes mitigates effects of radial field penetration, for example due to outer edges of the respective electrodes of the set there of and/or asymmetrical electrical element(s). It should be understood that the asymmetrical electrical element(s) are external to the ion optical element (though maybe electrically coupled thereto) and conventionally, in the absence of the set of shield electrodes, adversely affect the electric field due to the set of stacked electrodes.

That is, the asymmetrical element(s) would, in the absence of the set of shield electrodes, perturb (for example displace or shift) the ion optical axis, for example by asymmetrically affecting the radial distribution of the electric field due to the set of stacked electrodes such that the optical axis is displaced radially, at least in a region local to the asymmetrical electrical element(s), such as axially corresponding therewith. In other words, in use, the asymmetrical electrical element(s) shift the ion optical axis away from the intended ion optical axis. For example, asymmetrical electrical element(s) may include an electrically-grounded vacuum chamber housing the set of stacked electrodes wherein the chamber is asymmetrical and/or wearing the set of stacked electrodes is disposed asymmetrically thereto, an electrical element such as an HV feedthrough, a circuit board neighbouring the set of stacked electrodes and/or an unshielded electrical coupling. The asymmetrical electrical element(s) may be electrically-grounded or a static electrical potential or a time-varying electrical potential applied thereto. While electrically-grounded and static electrical potentials applied to such asymmetrical electrical element(s) may be result in constant (i.e. non-time varying) asymmetrical radial field penetration and hence constant ion trajectory aberrations, time-varying electrical potentials may result in time-varying asymmetrical radial field penetration that may be quasi-independent of ion flux and thus relatively unpredictable and hence relatively more problematic.

In this way, the set of stacked electrodes may have a relatively smaller form factor, for example having a relatively smaller radius rn and/or include a relatively larger distance d+1, such that ratio 12,, of the radius Tit to the distance 41,2.7,+, is lower than 3.5 while susceptibility to ion deflection is reduced. That is, such ion optical elements according to the first aspect comprising parallel plate electrodes, having relatively smaller diameters and/or relatively larger spacings, may provide equivalent performance to conventional parallel plate electrodes, having relatively larger diameters and/or relatively smaller spacings.

As described in more detail below, the respective shield electrodes surround and span, at least partially, between respectively adjacent stacked electrodes, thereby shrouding or encircling edges of the stacked electrodes while also bridging across the spacings or gaps between the adjacent stacked electrodes. Furthermore, respective shield electrodes are electrically coupled to respective stacked electrodes such that these mutually electrically-coupled electrodes are at the same electrical potential. In this way, the electric field in the spacing between the adjacent stacked electrodes is determined substantially by these mutually electrically-coupled electrodes, thereby mitigating effects of radial field penetration, for example due to outer edges of the respective electrodes of the set there of and/or asymmetrical electrical element(s).

The ion optical element comprises the set of stacked electrodes, including the first electrode and the second electrode, having respective apertures therethrough, wherein the ion optical axis is defined through the respective apertures and wherein the first electrode and the second electrode are mutually spaced apart by the distance cl1,2.

The set of stacked electrodes may also be known as a parallel plate electrode or a ring stack. A function of the set of stacked electrodes depends, at least in part, on electrical potentials applied thereto. For example, by applying static electrical potentials to the electrodes of the set thereof, static electric fields are defined thereby and constant ion acceleration regions are formed therebetween. For example, by applying ramped electrical potentials to the electrodes of the set thereof, ramped electric fields are defined thereby and ramped ion acceleration regions are formed therebetween. For example, by applying opposed phases of an RF electrical potential to alternate electrodes of the set thereof, time-varying electric fields are defined thereby, confining ions radially -such ion optical elements are also known as ion guides or ion tunnels. Other electrical potentials may be applied to the set of stacked electrodes.

It should be understood that the electrodes comprise electrical conductors, for example typically metals for example provided by a solid metal and/or a metal coating such as deposited on an electrically insulating substrate, for example on one side or both sides of a PCB.

In one example, the set of stacked electrodes includes N electrodes, including the first electrode and the second electrode, wherein N is a natural number greater than or equal to 2. In one example, N is a range from 2 to 100, preferably in a range from 3 to 50, more preferably in a range from 4 to 25. That is, the set of stacked electrodes may include multiple electrodes, such that the set there of extends along the ion optical axis. In one example, the second electrode is as described with respect to the first electrode, mutatis mutandis. In one example, the N electrodes are as described with respect to the first electrode, mutatis mutandis.

The set of stacked electrodes have respective apertures (also known as passageways) therethrough for conveying of ions therethrough. Typically, apertures have a circular cross-section, so as to define radially symmetric electric fields. In one example, the respective apertures are cylindrical, thereby having constant diameters therethrough. In one example, the respective apertures are frustoconical, thereby having tapering diameters therethrough. In one example, the respective apertures have the same diameter. In one example, the respective apertures have different diameters, for example in which the respective diameters increase or decrease, for example linearly, through the set of stacked electrodes. In one example, the respective apertures are aligned, for example coaxially.

In one example, the first electrode comprises and/or is a plate (or a sheet), having a respective aperture therethrough, transverse, preferably orthogonal, to opposed surfaces of the plate. In one example, the first electrode comprises and/or is a circular plate, having a radius r and a circular peripheral edge. In one example, the first electrode has a thickness t in a range from 100 nm (for example, a coating deposited on an electrically insulating substrate, such as by Physical Vapour Deposition) to 10 mm (for example, provided by a solid metal), preferably in a range from 1 pm to 2.5 mm, more preferably in a range from 10 pm to 0.25 mm, most preferably in a range from 20 pm to 50 pm.

The ion optical axis is defined through the respective apertures. It should be understood that the ion optical axis is the ion path for a hypothetical perfect ion. It should be understood that the optical axis is ideally defined through the respective apertures by the set of stacked electrodes and is not defined by radial and/or axial field penetration, for example. However, in practice as described above, aberrations to the ion optical axis may arise from radial and/or axial field penetration, such as due to edges and/or other electrical elements. In one example, the ion optical axis through the respective apertures is defined, at least in part, by the set of stacked electrodes (i.e. in use, when electrical potentials are applied thereto). In one example, the ion optical axis through the respective apertures is defined, at least in part, by the set of stacked electrodes and by the set of shield electrodes. In one example, the ion optical axis through the respective apertures is substantially defined by the set of stacked electrodes and by the set of shield electrodes. By substantially, it should be understood that the ion optical axis through the respective apertures is within 5°, preferably within 2.5°, more preferably within 1°, most preferably within 0.5°, at the exit of the set of stacked electrodes compared with the ideal ion optical axis. That is, the ion optical axis through the respective apertures approximates closely the ideal ion optical axis, for example even in the presence of edges and/or other electrical elements.

The first electrode and the second electrode are mutually spaced apart by the distance (11,2. It should be understood that the first electrode and the second electrode are mutually spaced apart axially (i.e. along and/or parallel to the ion optical axis) by the distance c/12. It should be understood that the subscripts 1,2 refer to the first electrode and the second electrode, respectively. It should be understood that the first electrode is downstream or upstream of the second electrode, with respect to the ion optical axis. It should be understood that the first electrode and the second electrode are adjacent, without any other electrodes therebetween. In one example, the first electrode and the second electrode are mutually parallel. In one example, the respective electrodes of the set of stacked electrodes are equispaced, for example by the distance cf1,2. In this way, equal electrical potential differences between adjacent electrodes provides a linear accelerating field along the ion optical axis. In one example, the respective electrodes of the set of stacked electrodes are not equispaced, for example wherein the spacing increases or decreases downstream or upstream, for example linearly or non-linearly. In this way, the accelerating field along the ion optical axis may be customised.

In one example, the first electrode comprises and/or is an annular electrode (also known as a ring electrode) having a radius 7-1 (i.e. an outer radius) and wherein a ratio R1 of the radius 4 to the distance d1.2 is at most 3.5, for example at most 3.4, preferably at most 3.0, more preferably at most 2.75, most preferably at most 2.5. That is, the ratio R, maybe significantly less than the empirical ratio conventionally required to control radial field penetration, thereby enabling the set of stacked electrodes to have a relatively smaller diameter and thus smaller form factor, compared with a conventional set of stacked electrodes. In contrast, radial field penetration is controlled by the set of shield electrodes. In one example, the ratio R1 of the radius r1 to the distance d1t2 is in a range from 1 to 3.5, preferably in a range from 1.5 to 3.4, more preferably in a range from 2.0 to 3.25, even more preferably in a range from 2.25 to 3.0, most preferably in a range from 2.6 to 2.9. More generally, in one example, a ratio R of the radius rt, to the distance "" between adjacent electrodes n, n + 1 is at most 3.5, preferably at most 3.0, more preferably at most 2.75, most preferably at most 2.5. That is, the ratio RT, applies for equispaced electrodes having the same radius, variably spaced electrodes having the same radius and variably spaced electrodes having different radii. More generally, in one example, a ratio Rn of the radius rn to the distance cln," between adjacent electrodes n, n + 1 is in a range from 1 to 3.5, preferably in a range from 1.5 to 3.4, more preferably in a range from 2.0 to 3.25, even more preferably in a range from 2.25 to 3.0, most preferably in a range from 2.6 to 2.9.

S

The ion optical element comprises the set of shield electrodes, including the first shield electrode, wherein the first shield electrode surrounds, at least in part, the first electrode and spans, at least in part, between the first electrode and the second electrode.

As described previously, the respective shield electrodes shroud edges of the stacked electrodes while bridging across the spacings between adjacent stacked electrodes, thereby controlling radial field penetration. It should be understood that the first shield electrode surrounds, at least in part, a periphery of the first electrode i.e. an edge or a peripheral edge of the first electrode.

In one example, the first shield electrode fully surrounds the first electrode. In one example, the first shield electrode surrounds a portion of a periphery of the first electrode, wherein the portion is in a range from 50% to 100% of the periphery thereof. In one example, the portion comprises and/or is a continuous portion, for example a single continuous portion extending fully around the periphery of the first electrode, thereby enveloping completely the first electrode. In one example, the first shield electrode comprises and/or is and unperforated electrode, having no perforations therethrough. In this way, radial field penetration mitigation is improved. In one example, the first shield electrode comprises and/or is a perforated electrode, having one or more perforations therethrough, for example a mesh or a punched strip. In this way, pumping of the ion optical element may be improved while radial field penetration mitigated.

In one example, the set of shield electrodes includes M shield electrodes, including the first shield electrode, wherein M is a natural number greater than or equal to 1. In one example, M is a range from 2 to 100, preferably in a range from 3 to 50, more preferably in a range from 4 to 25. In one example, the M shield electrodes are as described with respect to the first shield electrode, mutabs mutandis.

In one example, the set of stacked electrodes includes N electrodes, including the first electrode and the second electrode, wherein N is a natural number greater than or equal to 2, and wherein the set of shield electrodes includes M electrodes, including the first shield electrode, wherein M is a natural number greater than or equal to 1.

In one example, (N -1) < M < (N +1). That is, in one example, the number of shield electrodes is equal to or one fewer than or one greater than the number of electrodes. If the number of shield electrodes is one fewer than the number of electrodes, the shield electrodes are disposed only between adjacent electrodes. If the number of shield electrodes is equal to the number of electrodes, the first shield electrode may be disposed upstream of the first electrode or the last shield electrode may be disposed downstream of the last electrode. If the number of shield electrodes is one greater than the number of electrodes, shield electrodes are disposed upstream and downstream of the first and last electrode, respectively.

In one example, respective shield electrodes of the set thereof are disposed surrounding and spanning between predetermined electrodes, for example selectively, according to the relative positions of asymmetrical electrical element(s). That is, the shield electrodes may be arranged selectively, so as to mitigate anticipated radial field penetration.

In one example, the first shield electrode has a shape corresponding with a periphery, for example a peripheral edge, of the first electrode. That is, the shape of the first shield electrode may contour or follow that of the first electrode. In one example, the first shield electrode comprises and/or is a cylinder or a cone electrode. In one example, the first electrode comprises and/or is an annular electrode and the first shield electrode comprises and/or is a cylinder or a cone, for example a frustoconical, electrode. In this way, the shape of the first field electrode corresponds with a periphery of the first electrode. Similarly, in one example, the first electrode comprises and/or is a polygonal electrode, for example a regular polygon such as an equilateral triangle, a square, a hexagon, and the first shield electrode comprises and/or is a similarly polygonal tube.

In one example, the first shield electrode has a length /, in a range from 0.4c/12 to 0.99c/12, preferably in a range from 0.6d1,2 to 0.95c/1,2, more preferably in a range from 0.8(4,2 to 0.9(4,2.

That is, the first shield electrode has a length (i.e. parallel to the ion optical axis) that is in a range between 40% and 99% of the distance between the first electrode and the second electrode. In this way, radial field penetration is reduced and by increasing the length /1 of the first shield electrode, radial field penetration may be further reduced. It should be understood that a gap between the first shield electrode and the second electrode has a length /, = 0/1,2 /1 and is sufficient to avoid electrical discharge therebetween.

In one example, the first shield electrode is disposed symmetrically with respect to the first electrode. For example, the first shield electrode may span equally towards the second electrode and towards, for example, a zeroth electrode preceding the first electrode. In one example, the first shield electrode is disposed asymmetrically with respect to the first electrode. For example, the first shield electrode may span unequally towards the second electrode and towards, for example, a zeroth electrode preceding the first electrode. For example, the first shield electrode may span only towards the second electrode and not towards, for example, a zeroth electrode preceding the first electrode, or vice versa. Since the first shield electrode and the first electrode are at the same electrical potential, the symmetrical or asymmetrical disposition of the first shield electrode with respect to the first electrode defines, at least in part, the electric field between the first electrode and the second electrode.

In one example, the distance a1,2 is at least a diameter Di of the aperture in the first electrode. That is, the spacing between the first electrode and the second electrode is greater than or equal to the aperture diameter. In this way, the radius r, of the first electrode may be relatively small compared with the distance (11,2 while the distance (11,2 is relatively large compared with the diameter D1 of the aperture. In other words, the set of stacked electrodes may include relatively fewer electrodes, of smaller radius, than a conventional set of stacked electrodes. In one example, the distance (/1.2 is in a range from 1D1 to 20D1, preferably in a range from 2D1 to 15D1, more preferably in a range from 3D1 to 10D1, wherein D, is the diameter of the aperture in the first electrode. In one example, the first electrode comprises and/or is an annular electrode having a radius r, and wherein a ratio R, of the radius r, to the distance c11,2 is at most 3.5, preferably at most 3.0, more preferably at most 2.75 and the distance d12 is at least a diameter D, of the aperture in the first electrode. More generally, in one example, the distance d,, is at least a diameter Dr, of the aperture in the 71 electrode and a ratio Rn of the radius r, to the distance d" ,n÷:, between adjacent electrodes n, it + 1 is at most 3.5, preferably at most 3.0, more preferably at most 2.75, most preferably at most 2.5.

In one example, the first electrode and the first shield electrode are mutually spaced apart transversely, for example radially, to the ion optical axis by a distance pl. In one example, the first electrode comprises and/or is an annular electrode having a radius rl and the first electrode and the first shield electrode are mutually spaced apart radially to the ion optical axis by a distance pr, wherein pr is in a range from 0.0057-1 to 0.2n, preferably in a range from 0.01r1 to 0.1r1, more preferably in a range from 0.02r1 to 0.05/1. In this way, radial field penetration may be mitigated whilst pumping improved. By reducing /31 relative to r, , the diameter of the ion optical element is reduced, thereby improving the form factor thereof.

In one example, the first electrode and the first shield electrode are mutually spaced apart axially by a distance SI, for example wherein SI is in a range from 0.005(42 to 0.2d1,2, preferably in a range from 0.01(11.2 to 01(112, more preferably in a range from 0.02(11.2 to 0.05(112. That is, the first shield electrode does not necessarily have to overlap the first electrode but may be positioned before or after the first electrode. In this way, radial field penetration may be mitigated, since the first shield electrode still effectively shrouds the edge of the first electrode, whilst pumping improved. By reducing 62. relative to d2, radial field penetration is reduced.

The first electrode and the first shield electrode are mutually electrically coupled. That is, in use, the first electrode and the first shield electrode are at the same electrical potential and thus define an equipotential. It should be understood that the first electrode and the first shield electrode may be mutually electrically coupled by being electrically coupled to the same power supply or via an electrical interconnect, for example. It should be understood that equivalently, the first electrode and the first shield electrode maybe be respectively electrically coupled to different power supplies which are configured to apply, in use, the same electrical potential thereto. Alternatively, the different power supplies may be configured to apply, in use, similar electrical potentials thereto. It should be understood that the second electrode and the first shield electrode are mutually electrically isolated.

In one example, the first electrode and the first shield electrode mutually contact. For example, the peripheral edge of the first electrode may contact directly an inner surface of the first shield electrode, for example via a corresponding set of resiliently-biased contacts such as spring contacts (also known as spring loaded connectors or spring-loaded pogo pins), for example available from Mill-Max Mfg. Corp. (NY, USA) and Harwin PLC (Portsmouth, UK). In this way, assembly and disassembly are facilitated, since the electrical contact is made by directly contacting the first electrode and the first shield electrode via the resiliently-biased contacts while accommodating tolerances in assembly. In one example, the first electrode and the first shield electrode are integrally formed i.e. unitary. Conversely, in one example, the first electrode and the first shield electrode are separately formed, and subsequently assembled so as to mutually contact and/or to mutually electrically couple via an electrical interconnect.

In one example, the ion optical element comprises a shield electrode assembly comprising the set of shield electrodes arranged on and/or in an insulating substrate, for example a PCB. In this way, the set of shield electrodes may be provided on/and or in the insulating substrate, for example integrally formed such that all the shield electrodes are physically mutually coupled while electrically mutually isolated. In one example, the set of shield electrodes is provided as a set of tracks on the insulating substrate. In this way, manufacturing of the set of shield electrodes is facilitated. In one example, the substrate comprises a corresponding set of resiliently-biased contacts such as spring contacts, as described above, electrically coupled to the set of shield electrodes, for example provided in and/or through the set of tracks, for directly contacting against the set of stacked electrodes.

In one example, the substrate comprises and/or is a flexible substrate, for example a flexible PCB. In this way, the shield electrode assembly may be manufactured on a sheet and subsequently, formed into a shape corresponding with a shape of the set of stacked electrodes. In this way, manufacture and/or assembly of the ion optical element is improved. Since the substrate comprises and/or is a flexible substrate, a thickness of the shield electrode assembly may be reduced, thereby reducing a cross-sectional dimension of the ion optical element.

Generally, the flexible substrate should be thick enough to provide mechanical support for the shield electrodes. The flexible substrate should also be thick enough to support a local electric field without dielectric failure. The flexible substrate should be suitably thin such that the thickness of the flexible substrate is no more than half that of the shield electrodes. The dielectric and shield electrode thickness should be thin enough to provide flexibility needed to be shaped in to a tubular configuration, for example. That is to say, the maximum flexible substrate and shield electrode thicknesses should be a compromise between flexibility and rigidity for a given tube size, for example diameter.

In one example, a thickness of the flexible substrate is in a range from 5 pm to 500 pm, preferably in a range from 10 pm to 250 pm, more preferably in a range from 20 pm to 150 pm, for example, 7.5 pm (0.3 mil), 12.5 pm (0.5 mil), 25 pm (1 mil), 50 pm (2 mil), 75 pm (3 mil), 125 pm (5 mil) or 250 pm (5 mil). In this way, a flexibility of the shield electrode assembly may be further improved since the thickness of the flexible substrate is relatively small.

In one example, the flexible substrate comprises and/or is a single sheet. In one example, the flexible substrate comprises a laminate (i.e. a plurality of layers). In one example, the flexible substrate comprises a single layer (i.e. a homogeneous sheet). In this way, a risk of delamination of the shield electrode assembly may be further reduced.

It should be understood that the flexible substrate provides a substrate for the set shield electrodes, including the first shield electrode and thus an electrical conductivity of the flexible substrate is relatively low (i.e. an insulator). In one example, the flexible substrate comprises or consists of a material having an electrical conductivity of at most 1 x 10-5 Sm-1, preferably at most 1 x 10-10 Sm-1, more preferably at most 1 x 10-15 Sm-1, most preferably at most 1 x 10-20 Sm-1, measured at 20 °C.

In one example, the flexible substrate comprises or consists of a material having a dielectric strength of at least 100 kVmm-1, preferably at least 200 kVmm-1, more preferably at least 300 kVmm-1. In this way, a risk of electrical breakdown of the ion optical element may be reduced and/or the ion optical element may be operated at higher electric fields.

In one example, the flexible substrate comprises or consists of a material having a thermal conductivity of at least 0.01 Wm-1K-1, preferably at least 0.05 Wm-1K-1, more preferably at least 0.1 Wm-1K-1. In this way, thermal equilibration of the shield electrode assembly may be accelerated, allowing shorter start up times.

In one example, the flexible substrate comprises or consists of a material having a relative permittivity of at least 2, preferably at least 3, more preferably at least 4. In this way, a capacitance of the ion optical element may be increased, thereby further improving the homogeneity and/or the linearity of the electric field provided by the ion optical element.

In one example, the flexible substrate comprises or consists of a polymeric composition comprising a polymer, for example a polyester, a polyimide, a polyamide, polyetherimide, polyaryletherketone and/or fluropolymer. In one example, the polymer is a polyimide for example a thermosetting polyimide such as Kapton® i.e. poly (4,4'-oxydiphenylene-pyromellitimide), Apical®, UPILEX®, VTEC PIO, Norton THO or Kaptrex®. In one example, the polymer is Teflon® (polytetrafluoroethylene), PEEK (poly ether ether ketone), PEN (polyethylene napthalate) or Ultem® (polyetherimide). Preferably, the polymer is Kapton, for example Kapton HN, FN, HPP-ST. Kapton is flexible, has good dielectric properties, thermal stability, chemical resistance, mechanical properties and is available as a film. Kapton is suitable for flexible electronics. In one example, the polymeric composition comprises an additive, for example a reinforcement such as graphite or glass fibres.

It should be understood that the set of shield electrodes, including the first shield electrode, are solid electrical conductors and thus an electrical conductivity of the tracks is relatively high. In one example, the tracks comprise or consist of a material having an electrical conductivity of at least 1 x 105 Sm-1, preferably at least 1 x 106 Sm-1, more preferably at least 1 x 107 Sm-1, measured at 20°C. In one example, the tracks comprise a material such as one or more metals, for example Cu, Al, Ag, Au, Ni, Cr, Ti, Pt, Pd and/or an alloy thereof and/or a conductive oxide, for example Indium Tin Oxide (ITO). For Physical Vapour Deposition (PVD), for example on polymeric compositions, Cr and/or Ti may be used in particular as adhesion promoters for Au and Pt) while Pt, Ti and/or Pd may be used for the electrode layer (i.e. multilayers). Other examples of mulfilayers for PVD include Cu or Al / Ni or Cr or Ti / Au or Pt, wherein the Cu or Al is provided on the substrate.

In one example, the tracks are provided on the flexible substrate, at least in part, by deposition of a material, for example electrodeposition, sputtering, physical vapour deposition, evaporation, spraying, printing and/or adhesion. In one example, the tracks are provided on the first surface, at least in part, by patterning the deposited track material, for example using photolithography.

In this way, tracks having relatively complex shapes and/or relatively high tolerances may be readily provided on the flexible substrate.

In one example, the patterning defines a reticulated, for example a mesh or a grid such as a cross-hatch, pattern and/or a linear pattern i.e. an open structure c.f. a continuous structure. For example, the metallisafion could be made with a cross-hatched pattern, instead of a fully coated region. This has the effect of increasing the flexibility of the shield electrode assembly, because of the reduced adhesion surface between the metal and the flexible substrate. Additionally and/or alternatively, this technique has the benefit of reducing the surface stress between the metal and the flexible substrate (depending on the direction of the cross-hatch pattern compared to the bending direction) thus increasing the mechanical reliability of the shield electrode assembly in the long term -in particular for reduced bending radius compared to the overall thickness of the structure. Additionally and/or alternatively, since the flexible substrate may absorb moisture, using an open metal structure reduces the time needed to bake the part when it is necessary to remove such humidity from the part.

It should be understood that a track has a length, a width and a thickness.

In one example, a width of a track is as described with respect to a length of the first shield electrode.

In one example, a thickness of a track (i.e. the first shield electrode) is in a range from 5 pm to 500 pm, preferably in a range from 10 pm to 250 pm, more preferably in a range from 20 pm to 150 pm, for example, 7.5 pm, 12.5 pm, 25 pm, 35pm, 50 pm, 75 pm, 125 pm or 250 pm, wherein the thickness of the track (i.e. the first shield electrode) is measured orthogonally to a surface thereof. In this way, a flexibility of the shield electrode assembly may be further improved since the thickness of the track (i.e. the first shield electrode) is relatively small.

In one example, the shield electrode assembly is configurable, for example repeatedly, in: a first configuration, wherein the first configuration comprises and/or is a planar configuration; and a second configuration, wherein the second configuration comprises and/or is a tubular, for example a cylindrical, configuration.

In this way, manufacture, assembly, maintenance and/or reassembly of the ion optical element is improved, as described previously. It should be understood that in the planar configuration, the shield electrode assembly is substantially flat. It should be understood that in the tubular configuration, the shield electrode assembly has an open-ended hollow shape, thereby defining or forming a passageway to receive the set of stacked electrodes therein.

In one example, the shield electrode assembly is arranged to move from the first configuration to the second configuration by rolling (also known as reeling, winding, spooling or wrapping), for example around the set of stacked electrodes. In this way, a shape of the shield electrode assembly may conform with a shape of the set of stacked electrodes.

In one example, the ion optical element comprises a coupling member arrangeable to couple, for example releasably, the shield electrode assembly in the second configuration. In this way, the coupling member may secure the shield electrode assembly in the second configuration but may be released so as to move the shield electrode assembly to the first configuration.

In one example, the shield electrode assembly comprises and/or is a flexible printed circuit board, PCB (i.e. a first PCB). In this way, the shield electrode assembly may be readily manufactured and/or assembled.

In one example, the ion optical element comprises a printed circuit board, PCB, for example a rigid PCB (i.e. a second PCB), having a set of electrical contacts, including a first electrical contact and a second electrical contact, electrically coupleable to the respective electrodes of the set thereof, for example via the respective shield electrodes of the set thereof. In this way, the electrical potentials applied to the respective electrodes of the set thereof may be applied via the respective electrical contacts of the set thereof and hence via the PCB, which may include one or more electrical components, as described below.

In one example, the PCB comprises the shield electrode assembly. That is, the shield electrode assembly may be part of the PCB, for example mechanically coupled thereto or integrally formed therewith.

In one example, the PCB comprises a lift-off region, for example disposed between the PCB and the shield electrode assembly. In this way, the shield electrode assembly may be moved from the first configuration to the second configuration while remaining mechanically coupled or entered reformed with the PCB, with movement enabled by the lift-off region.

In one example, the PCB comprises one or more electrical components and/or networks thereof, for example passive electrical components including resistors, capacitors, inductors, transducers, sensors and/or detectors and/or active electrical components including diodes, transistors, and/or integrated circuits, and/or networks thereof.

In one example, the ion optical element comprises a set of power supplies, including a first power supply, coupled to the set of stacked electrodes and to the set of shield electrodes.

Shield electrode assembly and PCB The second aspect provides a shield electrode assembly according to the first aspect or a printed circuit board, PCB, according to the first aspect.

Mass spectrometer The third aspect provides a mass spectrometer, MS, comprising an ion optical element according to the first aspect.

In one example, the MS comprises an asymmetrical electrical element, wherein the set of shield electrodes is disposed between the asymmetrical electrical element and the set of stacked electrodes. In this way, radial field penetration due to the asymmetrical electrical element is reduced.

Method of shielding The fourth aspect provides a method of shielding ions moving through respective apertures of a set of stacked electrodes, including a first electrode and a second electrode, from an asymmetrical electrical element, wherein an ion optical axis is defined through the respective apertures and wherein the first electrode and the second electrode are mutually spaced apart by a distance c/1,2, the method comprising: disposing, between the asymmetrical electrical element and the set of stacked electrodes, a set of shield electrodes, including a first shield electrode, comprising surrounding, at least in part, by the first shield electrode, the first electrode and spanning, at least in part, by the first shield electrode, between the first electrode and the second electrode; and mutually electrically coupling the first electrode and the first shield electrode.

The apertures, the set of stacked electrodes, the first electrode, the second electrode, the asymmetrical electrical element, the ion optical axis, the distance c11,2, the set of shield electrodes and/or the first shield electrode may be as described with respect to the first aspect Method of manufacturing The fifth aspect provides a method of manufacturing a shield electrode assembly according to the first aspect.

Definitions Throughout this specification, the term "comprising" or "comprises" means including the component(s) specified but not to the exclusion of the presence of other components. The term "consisting essentially or or "consists essentially of' means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention, such as colourants, and the like.

The term "consisting of' or "consists of' means including the components specified but excluding other components.

Whenever appropriate, depending upon the context, the use of the term "comprises" or "comprising" may also be taken to include the meaning "consists essentially or or "consisting essentially of', and also may also be taken to include the meaning "consists or or "consisting of'.

The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each aspect or exemplary embodiment of the invention, as set out herein are also applicable to all other aspects or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each aspect or exemplary embodiment of the invention as interchangeable and combinable between different aspects and exemplary embodiments.

Brief description of the drawings

For a better understanding of the invention, and to show how exemplary embodiments of the same may be brought into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which: Figure 1A schematically depicts a mass spectrometer comprising an ion optical element according to an exemplary embodiment; Figure 1B is a cutaway perspective CAD drawing of the ion optical element of Figure 1A, in more detail; and Figure 1C is a perspective CAD drawing of the set of shield electrodes of the ion optical element of Figure 1A, in more detail; Figure 2 schematically depicts an axial cross-section of a conventional ion optical element, in the presence of an asymmetrical electrical element; Figure 3A schematically depicts a simulation of the conventional ion optical element of Figure 2, in which a ratio R" of the radius rn to the distance d+i is 3.5; and Figure 3B schematically depicts a simulation of the conventional ion optical element of Figure 2, in which a ratio R of the radius rn to the distance cl".,+, is 1.3; Figure 4 schematically depicts a simulation of an ion optical element according to an exemplary embodiment, in the presence of an asymmetrical electrical element, in which a ratio Fen of the radius rn to the distance cln," is 1.3; Figure 5 is a graph of ion beam deflection as a function of a ratio R" of the radius rn to the distance d+1, comparing conventional ion optical elements and ion optical elements according to exemplary embodiments; Figure 6 schematically depicts manufacturing of a shield electrode assembly for an ion optical element according to an exemplary embodiment; Figures 7A to 7H schematically depict manufacturing of a shield electrode assembly for an ion optical element according to an exemplary embodiment; Figure 7A is a perspective CAD drawing of a PCB; Figure 7B is a plan view of the PCB of Figure 7A; Figure 7C is a perspective CAD drawing of the PCB and a shield electrode assembly, mounted thereon, configured in a first configuration; Figure 7D is a plan view of the PCB and shield electrode assembly of Figure 7C; Figure 7C is a perspective CAD drawing of the PCB and the shield electrode assembly of Figure 7C, in more detail; Figure 7F is a plan view of the PCB and shield electrode assembly of Figure 7C, in more detail; Figure 7G is a perspective CAD drawing of the PCB and the shield electrode assembly of Figure 7C, configured in a second configuration; Figure 7H is a plan view of the PCB and shield electrode assembly of Figure 7G; Figure SA schematically depicts a cross-section of part of an ion optical element according to an exemplary embodiment, configured in a first configuration; and Figure 8B schematically depicts a cross-section of part of the ion optical element of Figure 8A, configured in a second configuration; Figure 9A schematically depicts a shield electrode assembly for an ion optical element according to an exemplary embodiment; and Figure 9B shows the shield electrode assembly, in more detail; and Figure 10 schematically depicts a method according to an exemplary embodiment.

Detailed Description of the Drawings

Figure 1A schematically depicts a mass spectrometer 1 comprising an ion optical element 10 according to an exemplary embodiment; Figure 1B is a cutaway perspective CAD drawing of the ion optical element 10 of Figure 1A, in more detail; and Figure 1C is a perspective CAD drawing of the set of shield electrodes of the ion optical element 10 of Figure 1A, in more detail.

In this example, the mass spectrometer 1 is a MALDI linear TOF, comprising a sample plate S, the ion optical element 10, an Einzel lens E, a linear flight tube F and a detector D, arranged in series.

The invention described here is an enabling technology that allows complex ion optics to be utilised in a relatively small envelope that would otherwise be susceptible to radial field penetration, thus allowing it to be implemented in a small instrument configuration, such as a benchtop design.

The ion optical element 10 is housed within a housing H under vacuum. In this example, the ion optical element 10 is a parallel plate ion optical element comprising a set of stacked electrodes 110 (i.e. a series of parallel plates), defining, at least in part, an ion optical axis therethrough, and the electrical potentials applied to which form ion acceleration region for accelerating ions from the sample plate S into the linear flight tube F. HV electrical connections are made to each electrode of the set of stacked electrodes 100 through HV vacuum feedthrough pins. An 'in-vacuum' interface PCB connects the HV vacuum feedthough pins to their respective electrodes. In this example, the ratio R1 of the radius 7-1 to the distance c/1,2 is 2.7 and thus conventionally, the set of stacked electrodes 100 would be susceptible to radial field penetration. In this example, it would not have been practical to increase the radius of the electrodes, due to size constraint. It would have also been very difficult to introduce further electrodes, to reduce the separation between the plates, since further feedthrough pins would be required that would have increased size and complexity of HV electronics on the air side of the feedthroughs.

To minimise radial field penetration, metal rings encircle each electrode and a portion of the gap between the electrode and an adjacent electrode. Each metal ring is mounted on a flexible PCB that is itself mechanical attached to the rigid PCB. Each metal ring is electrically connected to the same potential as the electrode that it encircles. When in position, the in-vacuum PCB and flexible PCB locate within the inner bore of the vacuum housing in such a way that the ion optics can be removed (say for cleaning) and replaced without disturbing the shield assembly. The ion optics electrodes are electrically connected to the PCB via spring connections attached to PCB.

In more detail, the ion optical element 10 comprises: a set of stacked electrodes 110, including a first electrode 110A and a second electrode 110B, having respective apertures 111 therethrough, wherein an ion optical axis A is defined through the respective apertures 111 (111A, 111B) and wherein the first electrode 110A and the second electrode 110B are mutually spaced apart by a distance d1,2; a set of shield electrodes 120, including a first shield electrode 120A, wherein the first shield electrode 120A surrounds, at least in part, the first electrode 110A and spans, at least in part, between the first electrode 110A and the second electrode 110B; and wherein the first electrode 110A and the first shield electrode 120A are mutually electrically coupled.

In this example, the set of stacked electrodes 110 includes N electrodes, 110A to 110F, including the first electrode 110A and the second electrode 110B, wherein N is 6. In this example, the N electrodes are as described with respect to the first electrode 110A, mutafis mutand is.

In this example, the respective apertures 111 are cylindrical, thereby having constant diameters therethrough. In this example, the respective apertures 111 are aligned coaxially.

In this example, the first electrode 110A comprises and/or is a circular plate, having a radius n and a circular peripheral edge. In this example, the first electrode 110A has a thickness t of 1 mm.

In this example, the ion optical axis A through the respective apertures 111 is substantially defined by the set of stacked electrodes 110 and by the set of shield electrodes 120. By substantially, it should be understood that the ion optical axis A through the respective apertures 111 is within 2.5°, at the exit of the set of stacked electrodes 110 compared with the ideal ion optical axis A. In this example, the first electrode 110A and the second electrode 110B are mutually parallel. In this example, the respective electrodes of the set of stacked electrodes 110 are generally equispaced, by the distance d1,2. Particularly, the electrodes 110A to 110E are equispaced, by the distance d1.2. However, a spacing between mutually-adjacent electrodes 110A and 110F, wherein the electrode 110F is upstream of the electrode 110A, is about 25% of the distance 0'1,2.

In this example, the first electrode 110A is an annular electrode (also known as a ring electrode) having a radius I-, (i.e. an outer radius) and wherein a ratio R1 of the radius r, to the distance d1,2 is 2.7. More generally, in this example, a ratio Rn of the radius r" to the distance d".",, between adjacent electrodes rt,rt + 1 is 2.7, for the electrodes 110A to 110E.

In this example, the first shield electrode 120A fully surrounds the first electrode 110A. In this example, the first shield electrode 120A comprises and/or is and unperforated electrode, having no perforations therethrough In this example, the set of shield electrodes 120 includes M shield electrodes 120, including the first shield electrode 120A, wherein M is a 6. In this example, the M shield electrodes 120 are generally as described with respect to the first shield electrode 120A, mutatis mutandis.

In this example, M = N. That is, in this example, the number of shield electrodes 120 is the same as the number of electrodes 110.

In this example, the first shield electrode 120A has a shape corresponding with a periphery, for example a peripheral edge, of the first electrode 110A. In this example, the first electrode 110A is an annular electrode and the first shield electrode 120A is a cylinder.

In this example, the first shield electrode 120A has a length /, of about 10 mm and hence in a range from 0.8d12 to 0.9d1,2. Hence, the first shield electrode 120A and the second shield electrode 120B are thus mutually spaced apart by a gap in a range from 0.1d2 to 0.2d1,2.

In this example, the first shield electrode 120A is disposed asymmetrically with respect to the first electrode 110A. In this example, the first shield electrode 120A spans only towards the second electrode 110B (i.e. upstream). In this example, the shield electrodes 120B to 120E similarly span only upstream. In contrast, in this example, the shield electrode 120F spans only downstream In this example, the distance d1,2 is about 5D1, wherein D, is the diameter of the aperture in the first electrode 110A.

In this example, the first electrode 110A and the first shield electrode 120A are mutually spaced apart radially to the ion optical axis A by a distance p, of about 1 mm. In this example, the first electrode 110A is an annular electrode having a radius 7-1 = 20 mm and the first electrode 110A and the first shield electrode 120A are mutually spaced apart radially to the ion optical axis A by a distance p,, wherein pi is in a range from 0.02r1 to 0.05r.

In this example, the first electrode 110A and the first shield electrode 120A are mutually spaced apart axially by a distance 6, of about 1 mm, wherein SI is in a range from 0.01d1,2 to 0.1d1,2.

In this example, the first electrode 110A and the first shield electrode 120A mutually contact. In this example, the first electrode 110A and the first shield electrode 120A are separately formed, and subsequently assembled so as to mutually contact and/or to mutually electrically couple via an electrical interconnect.

In this example, the ion optical element 10 comprises a shield electrode assembly 12 comprising the set of shield electrodes 120 arranged on and/or in an insulating substrate 121, particularly a PCB. In this example, the set of shield electrodes 120 is provided as a set of tracks 122 on the insulating substrate 121.

In this example, the substrate 121 comprises and/or is a flexible substrate 121, for example a flexible PCB.

In this example, a thickness of the flexible substrate 121 is about 50 pm.

In this example, the flexible substrate 121 comprises and/or is a single sheet.

In this example, the flexible substrate 121 comprises or consists of a polymeric composition comprising a polymer. In this example, the polymer is a polyimide for example a thermosetting polyimide such as Kapton.

In this example, the tracks 122 are provided on the flexible substrate 121, at least in part, by adhesion.

In this example, a thickness of a track (i.e. the first shield electrode 120A) is about 35 pm, wherein the thickness of the track (i.e. the first shield electrode 120A) is measured orthogonally to a surface thereof.

In this example, the track is deposited by PVD and is a multilayer of Cu / Ni / Au.

In this example, the shield electrode assembly 12 is configurable, for example repeatedly, in: a first configuration, wherein the first configuration comprises and/or is a planar configuration; and a second configuration, wherein the second configuration comprises and/or is a tubular, for example a cylindrical, configuration.

In this example, the shield electrode assembly 12 is arranged to move from the first configuration to the second configuration by rolling, around the set of stacked electrodes 110.

In this example, the ion optical element 10 comprises a coupling member arrangeable to couple, for example releasably, the shield electrode assembly 12 in the second configuration.

In this example, the shield electrode assembly 12 comprises and/or is a flexible printed circuit board, PCB (i.e. a first PCB).

In this example, the ion optical element 10 comprises a rigid PCB 13 (i.e. a second PCB), having a set of electrical contacts 130, including a first electrical contact 130A and a second electrical contact 130B, electrically coupleable to the respective electrodes 110A, 110B of the set 110 thereof via the respective shield electrodes 120A, 1208 of the set 120 thereof In this example, the PCB comprises a lift-off region, for example disposed between the PCB and the shield electrode assembly 12. In this way, the shield electrode assembly 12 may be moved from the first configuration to the second configuration while remaining mechanically coupled or entered reformed with the PCB, with movement enabled by the lift-off region.

Figure 2 schematically depicts an axial cross-section of a conventional ion optical element, in the presence of an asymmetrical electrical element.

Simulations using ion optics simulation program SIMION (RIM) demonstrate the principles of this invention. The geometry comprised an ion source, a field free region and ion detector, generally as described with respect to Figure 1.

The ion optical source (Figure 2) comprising a sample plate S and series of apertured annular electrodes 110, to which electrical potentials can be applied to accelerate ions formed at the surface of the sample plate through a field free region to the ion detector. The electrodes are of radius r and have maximum spacing of d.

An asymmetric electrical element X is shown that could be grounded or at a potential relating to the ion source, such as an electrical connection to one or more of the electrodes.

Figure 3A schematically depicts a simulation of the conventional ion optical element of Figure 2 in the presence of an asymmetrical electrical element X, in which a ratio R" of the radius r" to the distance d"r"+, is 3.5; and Figure 38 schematically depicts a simulation of the conventional ion optical element of Figure 2 in the presence of an asymmetrical electrical element X, in which a ratio R" of the radius r" to the distance d"+, is 1.3.

In the simulations shown, 1000 Da ions are accelerated with an energy of 10 key and pass through a 500 mm field free region from the ion source to the detector. The asymmetric electrical element X, for example a part of a housing, in these simulations is grounded.

In more detail, Figure 3A schematically depicts a simulation in which the ratio R" of the radius rn to the distance cln,n+1 is 3.5 and hence sufficiently large to prevent significant radial field penetration and the ion beam is not deflected.

In contrast, Figure 3B schematically depicts a simulation in which the ratio R" of the radius rn to the distance d., is 1.3 and hence not sufficiently large to prevent significant radial field penetration, such that the ion beam is deflected transversely by 9 mm at the detector plane D. Figure 4 schematically depicts a simulation of an ion optical element according to an exemplary embodiment, in the presence of an asymmetrical electrical element, in which a ratio R," of the radius r" to the distance d"."+, is 1.3.

In more detail, Figure 4 schematically depicts a simulation in which the ratio 12 of the radius rri to the distance d","+1 is 1.3, for an optical element according to an exemplary embodiment. In this case, the ion optical shield, formed by a series of metal ring encircles each electrode and a portion of the gap between the electrode and an adjacent electrode (i.e. the set shield electrodes), is introduced. Each ring is held at the same potential as the electrode it encircles.

The radial field penetration along the ion optical axis has now been significantly reduced to the extent that the beam deflection has been reduced from 9 mm (Figure 3B) at the detector plane to just 1 mm (Figure 4).

Figure 5 is a graph of ion beam deflection as a function of a ratio R. of the radius rn to the distance comparing conventional ion optical elements and ion optical elements according to exemplary embodiments.

In more detail, Figure 5 shows results of simulations showing deflection as a function of the ratio Rt,, with and without the ion shield (i.e. set of shield electrodes) fitted. The results demonstrate: 1. without the ion shield, the radial field penetration is not sufficient to deflect the ion beam for a ratio R of the radius into the distance d of at least 3.5; and 2. the ion shield reduces the radial field penetration for a ratio R" of the radius r" to the distance of less than3.5 to such an extent that the ion beam deflection is reduced by an order of magnitude.

Shield electrode assembly Shield electrode assemblies based on PCBs may be broadly divided in two main categories: 1. A hybrid assembly made of a standard PCB and a flexible PCB 2. An integrated Rigid-Flex PCB Figure 6 schematically depicts manufacturing of a shield electrode assembly for an ion optical element according to an exemplary embodiment.

In the case of a hybrid assembly, two separate structures are initially produced, of which the first is a standard rigid PCB, while the second is a flexible PCB. The two structures are manufactured separately and then mechanically bonded together. The bonding provides the necessary mechanical adhesion and strength, and also ensures adequate electrical conductivity between the two structures, while leaving intact the required flexibility of the original flexible PCB.

Figure 6 depicts a method of realisation of such a hybrid structure. In the Top-Left inset, a simple stack-up for a flexible PCB is shown. In this case, a simple single layer flexible PCB has been represented, that includes a Polyimide substrate with a top metal layer. Any other more complicated flexible PCB could be used, including but not limited to multilayer structures, adhesiveless metal layers, other flexible substrates and external coverlay. In the Bottom-Left inset, a representative stack-up for a rigid PCB has been depicted. In this case, a simple two-layers board has been shown but any other rigid stack-up could be used. By means of a mechanical bonding between the two structures, a rigid-flexible hybrid assembly can be achieved.

Figures 7A to 7H schematically depict manufacturing of a shield electrode assembly for an ion optical element according to an exemplary embodiment; Figure 7A is a perspective CAD drawing of a PCB; Figure 7B is a plan view of the PCB of Figure 7A; Figure 7C is a perspective CAD drawing of the PCB and a shield electrode assembly, mounted thereon, configured in a first configuration; Figure 7D is a plan view of the PCB and shield electrode assembly of Figure 7C; Figure 7C is a perspective CAD drawing of the PCB and the shield electrode assembly of Figure 7C, in more detail; Figure 7F is a plan view of the PCB and shield electrode assembly of Figure 7C, in more detail; Figure 7G is a perspective CAD drawing of the PCB and the shield electrode assembly of Figure 7C, configured in a second configuration; Figure 7H is a plan view of the PCB and shield electrode assembly of Figure 7G.

Figure 7A to 7H show an embodiment of the hybrid assembly implementation, for the proposed ion optics geometry of Figures 1A and 1B. Figures 7A and 7B show the first part of the assembly, this being the rigid PCB interface granting the electrical connection between the high voltage feedthroughs and the ion optics electrodes. The separate flexible PCB -which includes the metal stripes that will form the ion optics electrodes shielding -is then placed on top of the rigid PCB, as shown in Figures 7C and 7D. A set of spring contacts is then slid in the through holes of both the rigid and flexible PCBs, as depicted in Figures 7E Onset showing an enlarged portion as indicated by the dashed bounding box) and 7F. In this case, a solder joint ensures the electrical continuity and the mechanical stability between the rigid and flexible PCBs. As the solder joint guarantees the flexible PCB to be constraint only in proximity of the joint, it is still possible to shape the shield so to be accommodated in the inner bore of the ion optics chamber, as shown in Figures 7G and 7H.

Figure 8A schematically depicts a cross-section of part of an ion optical element according to an exemplary embodiment, configured in a first configuration; and Figure 8B schematically depicts a cross-section of part of the ion optical element of Figure 8A, configured in a second configuration.

The second possible implementation does not require two separate PCBs to be bonded together, but the Rigid-Flex assembly is created within the same manufacturing process. In this case, the flexible layer is manufactured as the top and final layer of a Rigid-Flex PCB, whereas the bonding region between the rigid and the flex layers includes a "lift-off" area (see Figure 8A). This lift-off area ensures that -after the manufacturing process -the flexible layer is able to partially detach from the underlying layer (see Figure 8B), so that the flexible layer can be freely shaped to conform the inner surface of the ion optics chamber.

The lift-off area can be realised mechanically, through cut-outs in the layer between the flexible and rigid structures, or by means of photolithography when photosensitive adhesive layers are used.

Figure 9A schematically depicts a shield electrode assembly 22 for an ion optical element according to an exemplary embodiment; and Figure 9B shows the shield electrode assembly 22, in more detail, particularly an enlarged portion as indicated by the dashed bounding box.

The shield electrode assembly 22 is generally as described with respect to the shield electrode assembly 12. Like reference signs denote like features.

In this example, the set of shield electrodes 220 is provided as a set of tracks 222 on the insulating substrate 221. In this example, the substrate 221 comprises and/or is a flexible substrate 221, for example a flexible PCB.

In contrast to the set of tracks 122 of the shield electrode assembly 12, in this example, the set of tracks is reticulated, particularly a cross-hatch pattern.

Figure 10 schematically depicts a method according to an exemplary embodiment.

The method is of shielding ions moving through respective apertures of a set of stacked electrodes, including a first electrode and a second electrode, from an asymmetrical electrical element, wherein an ion optical axis is defined through the respective apertures and wherein the first electrode and the second electrode are mutually spaced apart by a distance d"2.

At S1001, the method comprises disposing, between the asymmetrical electrical element and the set of stacked electrodes, a set of shield electrodes, including a first shield electrode, comprising surrounding, at least in part, by the first shield electrode, the first electrode and spanning, at least in part, by the first shield electrode, between the first electrode and the second electrode.

At S1002, the method comprises mutually electrically coupling the first electrode and the first shield electrode.

Although a preferred embodiment has been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims and as described above.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at most some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1. An ion optical element comprising: a set of stacked electrodes, including a first electrode and a second electrode, having respective apertures therethrough, wherein an ion optical axis is defined through the respective apertures and wherein the first electrode and the second electrode are mutually spaced apart by a distance a set of shield electrodes, including a first shield electrode, wherein the first shield electrode surrounds, at least in part, the first electrode and spans, at least in part, between the first electrode and the second electrode; and wherein the first electrode and the first shield electrode are mutually electrically coupled.
2. The ion optical element according to claim 1, wherein the first electrode comprises and/or is an annular electrode having a radius ri and wherein a ratio R, of the radius r to the distance c11,2 is at most 3.5, preferably at most 3.0, more preferably at most 2.75.
3. The ion optical element according to claim 2, wherein the first shield electrode comprises and/or is a cylinder electrode.
4. The ion optical element according to any previous claim, wherein the first shield electrode has a length in a range from 0.4c/12 to 0.99c/12, preferably in a range from 0.6d1,2 to 0.95d1,2, more preferably in a range from 0.8d1,2 to 0.9(4,2.
5. The ion optical element according to any previous claim, wherein the set of stacked electrodes includes N electrodes, including the first electrode and the second electrode, wherein N is a natural number greater than or equal to 2, and wherein the set of shield electrodes includes M electrodes, including the first shield electrode, wherein M is a natural number greater than or equal to 1.
6. The ion optical element according to claims, wherein (N -1) < M < (N + 1).
7. The ion optical element according to any of claims 5 or 6, wherein N is a range from 2 to 100, preferably in a range from 3 to 50, more preferably in a range from 4 to 25.
8. The ion optical element according to any previous claim, wherein distance c11,2 is at least a diameterD1 of the aperture in the first electrode.
9. The ion optical element according to any previous claim, wherein the first electrode and the first shield electrode mutually contact.
10. The ion optical element according to any of claims 1 to 8, wherein the first electrode and the first shield electrode are mutually spaced apart transversely to the ion optical axis by a distance Pi and/or wherein the first electrode and the first shield electrode are mutually spaced apart axially by a distance 5,.
11. The ion optical element according to any previous claim, wherein the first shield electrode is disposed asymmetrically with respect to the first electrode.
12. The ion optical element according to any previous claim, comprising a shield electrode assembly comprising the set of shield electrodes arranged on and/or in an insulating substrate.
13. The ion optical element according to claim 12, wherein the substrate comprises and/or is a flexible substrate. 15
14. The ion optical element according to any of claims 12 to 13, wherein the shield electrode assembly is configurable, for example repeatedly, in: a first configuration, wherein the first configuration comprises and/or is a planar configuration; and a second configuration, wherein the second configuration comprises and/or is a cylindrical configuration.
15. The ion optical element according to claim 14, wherein the shield electrode assembly is arranged to move from the first configuration to the second configuration by rolling, for example around the set of stacked electrodes.
16. The ion optical element according to any of claims 14 to 15, comprising a coupling member arrangeable to couple, for example releasably, the shield electrode assembly in the second configuration.
17. The ion optical element according to any of claims 12 to 16, wherein the shield electrode assembly comprises and/or is a flexible printed circuit board, PCB.
18. The ion optical element according to any previous claim, comprising a printed circuit board, PCB, having a set of electrical contacts, including a first electrical contact and a second electrical contact, electrically coupleable to the respective electrodes of the set thereof
19. The ion optical element according to claim 18 when dependent on any of claims 12 to 17, wherein the PCB comprises the shield electrode assembly.
20. The ion optical element according to claim 18, wherein the PCB comprises a lift-off region.
21. A shield electrode assembly according to any of claims 12 to 17 or a printed circuit board, PCB, according to any of claims 19 to 20.
22. A mass spectrometer, MS, comprising an ion optical element according to any of claims 1 to 20.
23. The MS according to claim 22, comprising an asymmetrical electrical element, wherein the set of shield electrodes is disposed between the asymmetrical electrical element and the set of stacked electrodes.
24. A method of shielding ions moving through respective apertures of a set of stacked electrodes, including a first electrode and a second electrode, from an asymmetrical electrical element, wherein an ion optical axis is defined through the respective apertures and wherein the first electrode and the second electrode are mutually spaced apart by a distance d12, the method comprising: disposing, between the asymmetrical electrical element and the set of stacked electrodes, a set of shield electrodes, including a first shield electrode, comprising surrounding, at least in part, by the first shield electrode, the first electrode and spanning, at least in part, by the first shield electrode, between the first electrode and the second electrode; and mutually electrically coupling the first electrode and the first shield electrode.
25. A method of manufacturing a shield electrode assembly according to any of claims 12 to 17.