This application claims priority to UK Patent Application 1907139.8, filed on May 21, 2019, and titled “Improved Electrode Arrangement” by Alexander A. Makarov et al., which is hereby incorporated herein by reference in its entirety.
This invention relates to an improved electrode arrangement for an ion guide, ion filter, ion trap, ion storage device, ion reaction cell, in particular an ion collision cell, or an ion analyser, in particular a mass analyser.
Mass spectrometry is an important technique for analysis of chemical and biological samples. In general, a mass spectrometer comprises an ion source for generating ions from a sample, various lenses, ion guides, mass filters, ion traps/storage devices, and/or reaction cell(s), and one or more mass analysers.
A reaction cell may be a collision and/or fragmentation cell. The reaction in the reaction cell may be an electron capture dissociation, a higher energy collisional dissociation (HCD), an electron-transfer dissociation, oxidation, hybridisation, clustering or complex reaction. The reaction cell may comprise a quadrupole or a hexapole, a octopole or a higher order multipole device.
Known electrode arrangements for ion guides, ion traps/storage devices and reaction cells typically comprise RF electrodes for radial confinement of ions and DC electrodes for driving ions along an axis of the ion guide/ion trap/storage device/reaction cell. Such an electrode arrangement may comprise RF electrodes in the form of rods having a circular or hyperbolic cross-section arranged to form a multipole or a mass filter. These electrodes could be mounted on dielectric spacers as presented in GB2554626, U.S. Pat. Nos. 5,616,919, 7,348,552. The electrode arrangement may also comprise DC electrodes arranged to provide a DC field along the axis of the ion guide, ion trap, storage device or reaction cell.
In order to simplify the manufacture of electrode arrangements for ion guides, planar configurations, such as those discussed in U.S. Pat. No. 9,536,722B2, have been designed. The planar configurations also provide greater flexibility for the design of the DC field. Such planar configurations could be implemented with printed circuit boards (PCBs) to which planar RF and DC electrodes are connected. The PCBs are formed of non-conductive material, normally a dielectric material that may be reinforced, such as fiberglass. Typically, the planar RF electrodes extend axially along the length of the ion guide in an arrangement to form an RF multipole. The DC electrodes also extend axially along the length of the ion guide thereby providing a DC field along its axis. The planar RF electrodes may be secured to the surface of a PCB by glue or soldering. A spacer made from the dielectric material of the PCB may be provided along the length of the planar RF electrode between the PCB and the RF electrode. The DC electrodes may be etched onto the PCB surface. Typically, the DC electrodes are provided on portions of the PCB surface that are adjacent to the RF electrodes such that the DC electrodes are separated from the RF electrodes by the dielectric (PCB) material.
However, as a result of such a planar design, the RF field created by the RF electrodes penetrates the dielectric material of the PCB in areas that are not shielded by the DC electrodes. This penetration causes heating of the PCB by dielectric loss. More specifically, the RF field penetrating the material of the PCB causes energy to be dissipated as the molecules of the dielectric (PCB) material attempt to line up with the continuously changing RF field. This dielectric loss is described by the dissipation factor, Df, which will be discussed in further detail in the detailed description. The heating of the PCB causes material of the PCB to evaporate (outgassing). The glue used to secure the RF electrode(s) to the PCB may also evaporate. The evaporated material (and glue) may contaminate the ions contained within the ion guide. Those contaminants may be carried through the spectrometer to the detector and so peaks corresponding to the contaminants may be generated in the resulting mass spectra. The contaminants may also cause undesirable changes to the analyte contained within the ion guide. For example, the contaminants may combine with the analyte molecules thereby forming adducts and/or react with the analyte molecules and remove part of their charge (charge reduction). Both of these undesirable changes to the analyte will generate erroneous peaks in the resulting mass spectra. The ion guide/ion trap/storage device/collision cell may also have a buffer gas therein. The heat generated in the dielectric (PCB) material may provide sufficient energy to buffer gas molecules thereby causing reactions of the analyte with the buffer gas molecules. For example, the buffer gas molecules may react with and combine with the analyte molecules forming adducts. The reaction of buffer gas molecules with analyte molecules may also reduce the charge on analyte molecules. Accordingly, these reactions cause undesirable changes to the analyte molecules. In collision cells, the ions are stored for longer periods of time (for example a number of milliseconds) and are exposed to stronger RF fields compared to ion guides. Indeed, collision cells typically operate at RF voltages of 1200-1500 V, which is much greater than that of ion guides, which typically operate at less than 1000V. Accordingly, the heating of PCBs and consequent undesirable effects are particularly prominent for collision cells.
The results of an experiment, referred to herein as experiment 1, involving one isolated charge state (+11) of multiply charged ubiquitin ions which is trapped for 500 ms in a HCD (Higher-energy collisional dissociation) cell having the known electrode assembly 1 depicted in
Two temperature sensors (e.g. platinum resistors with 100 Ohm resistance at room temperature, here and below PT100) were used in this experiment. The first temperature sensor (PT100) was located on the dielectric material 4 of the PCB of the HCD cell, to which the planar RF electrodes 3 were attached. The first temperature sensor and the RF electrode were arranged at the same position within the plane of the dielectric material 4 except that the temperature sensor was attached to the opposite surface of the dielectric material 4 to the RF electrodes 3.
Accordingly the RF electrode 3 and the first temperature sensor were only separated by the thickness of the dielectric material 4. By locating the first temperature sensor close to the RF electrodes 3, the temperature measured by the first temperature sensor provided accurate results regarding the heating of the dielectric material 4 due to penetration of the RF field generated by the RF electrodes 3.
The second temperature sensor (OT block PT100) was not arranged in the HCD cell. Instead, the second temperature sensor was positioned in the housing of the Orbitrap mass analyser close to the HCD cell. Accordingly, the second temperature sensor provided further results regarding the increase in temperature of the Orbitrap mass analyser caused by the RF field of the HCD cell.
It would be desirable to provide an electrode arrangement comprising a PCB with RF electrodes attached thereto that may operate without significant generation of heat thereby minimising outgassing and undesirable changes to analyte molecules, particularly when RF voltages of high amplitude are applied to the RF electrodes 3. Indeed, by providing such an electrode arrangement, for the first time, it would be possible to provide a reliable collision cell, such as a HCD cell, having an electrode arrangement that comprises a PCB with RF electrodes attached thereto.
Another problem with known electrode arrangements having PCBs is ensuring precise manufacturing. Therefore, it would also be desirable to provide a method for manufacturing electrode arrangements comprising PCBs having RF electrodes attached thereto at a greater level of precision than enabled by standard PCB production processes.
In accordance with a first aspect of the present invention, there is provided an electrode arrangement for an ion trap, ion filter, an ion guide, a reaction cell or an ion analyser, the electrode arrangement comprising an RF electrode mechanically coupled to a dielectric material, wherein the RF electrode is mechanically coupled to the dielectric material by a plurality of separators that are spaced apart and configured to define a gap between the RF electrode and the dielectric material and wherein each of the plurality of separators comprises a projecting portion and the dielectric material comprises corresponding receiving portions such that on coupling of the RF electrode to the dielectric material, the projecting portion of each separator is received within the corresponding receiving portion of the dielectric material. The plurality of separators may be any one of or a combination of the pin separator, receptacled separator or projecting separator described below.
In accordance with a first aspect of the present invention, there is provided an electrode arrangement as set out in claim 1.
The electrode arrangement of claim 1 comprises an RF electrode mechanically coupled to a dielectric material. The RF electrode is coupled to the dielectric material by a plurality of separators that are spaced apart and configured to define a gap between the RF electrode and the dielectric material. By providing the gap between the RF electrode and the dielectric material, penetration of the dielectric material close to the RF electrodes by the strong RF field in this region is avoided.
Each of the plurality of separators comprises a projecting portion and the dielectric material comprises corresponding receiving portion(s). The projecting portion of each separator is received within the corresponding receiving portion of the dielectric material. The coupling of the dielectric material is nearly limited to this connection. Each corresponding receiving portion(s) may have a shape that is complementary to the projecting portion of the separator(s) so as to receive the projecting portion.
Furthermore, a DC electrode located between the dielectric material and the RF electrode shields the dielectric material from the RF field generated by the RF electrode. This shielding prevents the RF field from penetrating the dielectric material and so prevents generation of heat within the dielectric material by dielectric loss. The only penetration of the RF field into the dielectric material occurs at the contact points between each separator and the dielectric material.
The use of a plurality of separators to generate the gap is advantageous, since a gap of a constant height may be achieved with minimal areas of contact between the RF electrode and the dielectric material. Indeed, by using a plurality of spaced apart separators, a DC electrode, and so DC field, may cover and shield the majority of the surface of the dielectric material that is directly above or underneath the RF electrode.
This is in contrast to known electrode arrangements whereby it is not possible for a DC electrode to extend along the majority of the dielectric surface that is directly above or underneath the RF electrode. Indeed, in known prior art, the majority of the dielectric surface that is directly above or underneath the RF electrode is covered with glue or solder or a spacer.
Furthermore, in known arrangements, such as in U.S. Pat. No. 7,348,552, typically a spacer made of the dielectric material is located between the surface of the PCB and the RF electrode to provide a gap between the PCB and the RF electrode and accordingly between the DC electrodes arranged on the surface of the PCB and the RF electrode. However, the dielectric material of the spacer, which is very close to the RF electrodes, is heated by the RF field of the RF electrodes. This heating causes the problems of contamination and charge reduction in an ion guide, ion filter, ion analyser, ion trap or reaction cell comprising the electrode arrangement.
Accordingly, operation of the electrode arrangement of the claimed invention results in significantly reduced generation of heat, and consequently reduced outgassing (evaporation of the dielectric (PCB) material). Therefore, fewer contaminants are produced and fewer undesirable changes to the analyte occur. Consequently, fewer erroneous peaks in the resulting mass spectra are generated.
Preferably, the electrode arrangement comprises at least one DC electrode located between the dielectric material and the RF electrode. As discussed above, the DC electrode and so DC field, may cover and shield the majority of the surface of the dielectric material that is directly above or underneath the RF electrode. This shielding prevents the RF field from penetrating the dielectric material and so prevents generation of heat within the dielectric material by dielectric loss. The only penetration of the RF field into the dielectric material occurs at the contact points between each separator and the dielectric material.
Preferably, the RF electrode has a face opposing the dielectric material and the DC electrode extends across the dielectric material such that at least a part of the DC electrode lies directly between the face of the RF electrode and the dielectric material. The proportion of the surface area of the face of the RF electrode which is shielded from the dielectric material by the DC electrode is at least 50%, preferably 80% and most preferably 95%. The term “shielding” refers to a significant reduction of electric field flux (at least an order of magnitude) generated by a charged electrode at a given point due to introduction of a shield. In the present invention, the RF field generated by the RF electrode is shielded by using a DC electrode as a shield. By providing a part of the DC electrode directly between the face of the RF electrode and the dielectric material, the shield is provided in the region of the dielectric material that would otherwise experience the strongest RF field. Accordingly, penetration of the RF field and generation of heat within the dielectric material is minimised.
Preferably, in the claimed invention, the plurality of separators are electrically conductive, and more preferably, metallic. Then the RF field of the RF electrodes penetrates only the dielectric material around the separators. But this is a very limited area of the RF electrodes. Due to the separators in general there is a gap between the RF electrodes and the dielectric material, which is preferably shielded by a DC electrode. This is in contrast to the known spacers, discussed above, which are formed of a dielectric material having dielectric losses. These spacers are located over the whole area of the RF electrodes close to the RF electrodes and are therefore penetrated (and heated) by their RF field.
In accordance with a second aspect of the present invention, there is provided an ion guide comprising the electrode arrangement of any preceding claim.
In accordance with a third aspect of the present invention, there is provided an ion filter comprising the electrode arrangement of any one of claims 1 to 30.
In accordance with a fourth aspect of the present invention, there is provided an ion analyser comprising the electrode arrangement of any one of claims 1 to 30.
In accordance with a fifth aspect of the present invention, there is provided an ion trap comprising the electrode arrangement of any one of claims 1 to 30.
In accordance with a sixth aspect of the present invention, there is provided a reaction cell comprising the electrode arrangement of any one of claims 1 to 30.
In accordance with a seventh aspect of the present invention, there is provided a method of manufacturing the electrode arrangement of claims 1 to 30, as set out in claim 36.
The invention may be put into practice in a number of ways and some specific embodiments will now be described by way of example only and with reference to the accompanying drawings in which:
In this specification, the term RF electrode refers to an electrode to which an RF voltage supply is connected. The term DC electrode herein refers to an electrode to which a DC voltage supply is connected. The term “inner” in relation to a surface herein refers to the surface that is facing towards the centre of the electrode assembly 100. The term “outer” in relation to a surface herein refers to the surface that is facing away from the centre of the electrode assembly 100.
The electrode assembly 100 has first and second electrode arrangements 10, 10′ that extend in the longitudinal direction from the first end 100a to the second end 100b. Indeed, the term “electrode assembly” refers to an electrode arrangement, such as that of claim 20, having both first and second electrode arrangements 10, 10′. The first and second electrode arrangements 10, 10′ are spaced apart from each other and parallel thereto such that the first and second electrode arrangements are substantially mirror images of each other with the axis of symmetry corresponding with the central longitudinal axis of the electrode assembly 100. The first and second electrode arrangements 10, 10′ are spaced apart by first and second minor side walls 101, 102. Indeed, as shown in
As shown in
As best shown
In the embodiment shown in
Each pin separator 13 is attached to a major (planar) surface of the RF electrode 12a, 12b, 12a′, 12b′. Preferably, the pin separator 13 is permanently attached to the surface of the RF electrode 12a, 12b, 12a′, 12b′. Typically, the pin separator 13 is attached to the surface of the RF electrode by welding. Each pin separator 13 comprises a head portion 13a and a projecting portion 13b.
The head portion 13a is attached to the outer major surface of the RF electrode 12a, 12b, 12a′, 12b′ (the planar surface of the RF electrode 12a, 12b, 12a′, 12b′ that is proximal to and opposing the respective dielectric material 11) such that a projecting portion 13b extends from the head portion 13a in a direction orthogonal to the plane of the RF electrode 12a, 12b, 12a′, 12b′ and orthogonal to the plane of the dielectric material 11. The head portion 13a has at least electrical contact with the RF electrode 12a, 12b, 12a′, 12b′.
The dielectric material 11 has a corresponding receiving portion 11a configured to receive the projecting portion on coupling of the RF electrode 12a, 12b, 12a′, 12b′ to the dielectric material 11. In the embodiment shown in
In the embodiment of
Each projecting portion 13b of each pin separator 13 is electrically connected to an RF voltage supply to supply an RF voltage to the respective RF electrode 12a, 12b, 12a′, 21b′. This connection may be provided by connectors configured to provide electrical connection to the RF voltage supply. Each connector may have an opening/recess configured to receive the respective projecting portion 13b. By directly connecting the pin separator 13 to the RF voltage supply instead of using tracks on the dielectric material 11, dielectric losses and heating of the dielectric material 11 may be reduced.
The connectors configured to provide electrical connection between the projecting portion 13b and the RF voltage supply may be, for example, wires. The wires may have spring loaded contacts on their ends to ensure reliable electrical contact. For example, the wires may have spring loaded gold-coated tubes soldered or crimped on their ends. The inner diameter of the tubes is slightly larger than the outer diameter of the ends of the wires. A small circular spring is provided within a groove inside each tube to ensure reliable cold-welded electrical contact to the wire end.
Optionally, the ends of the projecting portions 13b distal from the respective head portions 13a may also be soldered to the outer major surface of the dielectric material so that any force on the connectors does not cause bending of RF electrodes 12a, 12b, 12a′, 12b′.
In each electrode arrangement 10, 10′, at least one DC electrode 14 is provided on the majority of the inner major surface of the dielectric material 11. In the embodiment shown in
The exposed portions prevent electrical contact between the RF electrodes 12a, 12b, 12a′, 12b′ and the DC electrodes 14. As best shown in
Accordingly, the DC electrodes 14 extend over the entirety of the inner major surface of the dielectric material 11 extending between the first and second minor side walls 101, 102 except for the contact area 11b and the groove 11c. Indeed, the DC electrodes 14 are arranged directly between the outer planar surface of the RF electrode 12a, 12b, 12a′, 12b′ and the inner major surface of the dielectric material 11 (except for the exposed portions where the pin separators 13 are located). Indeed, the DC electrode 14 of the first electrode arrangement 10 extends directly underneath the RF electrodes 12a, 12b of the first electrode arrangement 10. The DC electrode 14 of the second electrode arrangement 10′ extends directly above the RF electrodes 12a′, 12b′ of the second electrode arrangement 10′.
As discussed above, the pin separators 13 are configured to define a gap between the RF electrodes 12a, 12b, 12a′, 12b′ and the dielectric material 11. The gap is provided in the direction orthogonal to the plane of the dielectric material 11. Accordingly, a gap also extends between the outer surface of the RF electrodes 12a, 12b, 12a′, 12b′ and the DC electrodes 14 formed on the inner major surface of the dielectric material 11. The gap is typically defined by the height of the head portion 13a of the pin separators 13 and reduced by the thickness of the DC electrodes 14 arranged on the inner surface of the dielectric material 11.
Preferably in the inventive electrode arrangement the RF electrodes 12a, 12b, 12a′, 12b′ overhang the pin separator 13. In a particularly preferred embodiment, there is a line of sight in the direction orthogonal to the plane of the dielectric material 11 between the area of the RF electrodes 12a, 12b, 12a′, 12b′ overhanging the pin separator 13 and the DC electrode 14.
Manufacture and Assembly
As best shown in
The through-holes 11a are formed through the thickness of the dielectric material 11 by a standard PCB manufacturing process. The through-holes 11a are formed at spaced apart positions that correspond to the locations of the pin separators 13 on the RF electrodes 12a, 12b, 12a′, 12b′. Preferably, the through-holes 11a are equally spaced along the length of the dielectric material 11.
The DC electrodes 14 are etched onto the surface of the dielectric material 11 except for the exposed portions, which are discussed above. Voltage can be provided to the DC electrodes 14 via supply lines on the PCB formed by the dielectric material 11 and a connector 20, for example a Molex connector.
The annular groove 11c of each exposed portion is formed in the dielectric material 11 by laser- or mechanical cutting. The DC electrodes 14 are segmented in the transverse direction, as discussed above, by grooves formed in the dielectric material 11 by etching.
A specific DC voltage is applied to each segment of the DC electrodes 14 to control the movement of the ions through the electrode assembly, in particular in the longitudinal direction of the electrode assembly.
The head portions 13a of the plurality of pin separators 13 are welded to each RF electrode 12a, 12b, 12a′, 12b′ when the RF electrode 12a, 12b, 12a′, 12b′ has a first length. The pin separators 13 are positioned along the length of the RF electrodes 12a, 12b, 12a′, 12b′ such that they correspond to the positions of the through-holes in the dielectric material 11. Preferably, the pin separators 13 are equally spaced along the length of the RF electrodes 12a, 12b, 12a′, 12b′.
Each RF electrode 12a, 12b, 12a′,12b′ having a first length is coupled to the respective dielectric material 11 by the plurality of pin separators 13. As discussed above, for mechanically coupling together of each RF electrode 12a, 12b, 12a′, 12b′ and the respective dielectric material 11, the projecting portion 13b of each pin separator 13 is inserted into and retained within the corresponding through-hole 11a extending through the thickness of the dielectric material 11. This is best shown in
Once all of the RF electrodes 12a, 12b, 12a′, 12b′ have been mechanically coupled to the respective dielectric material 11 using the plurality of pin separators 13, and preferably once the first electrode arrangement 10 is coupled to the second electrode arrangement 10′, the RF electrodes 12a, 12b, 12a′, 12b′ are cut to remove excess material. The RF electrodes 12a, 12b, 12a′, 12b′ may be re-shaped by the cutting process. In particular, the RF electrodes 12a, 12b, 12a′, 12b′ are cut to reduce the length of the RF electrodes 12a, 12b, 12a′, 12b′ from the first length to the second length. The second length of the RF electrodes 12a, 12b, 12a′, 12b′ is the same as the length of the dielectric material 11. All four of the RF electrodes 12a, 12b, 12a′, 12b′ are cut from the first length to the second length at the same time. The cutting the RF electrodes 12a, 12b, 12a′, 12b′ is performed by a wire-erosion process with a wire extending orthogonal to the longitudinal direction of the RF electrodes 12a, 12b, 12a′, 12b′. Optionally, the wire-erosion process may be used with a wire extending parallel to the longitudinal direction to accurately reduce the width and/or re-shape the RF electrodes 12a, 12b, 12a′, 12b′. By cutting the RF electrodes 12a, 12b, 12a′, 12b′ at the same time, once coupled to the dielectric material 11, the precision of manufacturing and assembly is increased. Indeed, this process enables manufacturing and assembly of the RF electrodes 12a, 12b, 12a′, 12b′ with a relative error of less than 10 μm to each other while tolerances of manufacturing PCBs are typically within the range of 50-200 μm. Therefore, this process of manufacturing and assembling the RF electrodes 12a, 12b, 12a′, 12b′ leads to superior mechanical precision and reduces variability between systems in which the electrode arrangements 10, 10′ are employed. Furthermore, the precision of ion transmission and focussing of ions achieved using the RF electrodes 12a, 12b, 12a′, 12b′ is improved.
The improved cutting process for the RF electrodes 12a, 12b, 12a′, 12b′ is possible due to, in particular, the new arrangement by which the RF electrodes are coupled to the dielectric material. They are only positioned by the pin separators 13 and therefore the outline of the RF electrodes 12a, 12b, 12a′, 12b′ can be precisely reshaped, in particular when hanging over the pin separators 13.
At least one of the pin separators 13 coupled to each RF electrode 12a, 12b, 12a′, 12b′ is then electrically connected to an RF voltage supply such that RF voltage is supplied to the RF electrodes 12a, 12b, 12a′, 12b′ by the pin separators 13. Preferably, the distal end of projecting portion 13b of each pin separator 13 is electrically connected to the RF voltage supply. This may be achieved by soldering the distal ends of the pin separators 13 to wires configured to supply the RF voltage.
In Use
In use, an RF voltage is applied to the RF electrodes 12a, 12b, 12a′, 12b′ from a RF voltage supply. The RF electrodes 12a, 12b, 12a′, 12b′ form a multipole (in this case a quadrupole). Indeed, the RF voltage is applied such that adjacent RF electrodes 12a, 12b, 12a′, 12b′ of the multipole have opposite phase. Therefore, electrodes 12a and 12b′ are connected as one set so that they have the same phase as each other whilst electrodes 12b and 12a′ are connected as another set so that they have the same phase as each other but opposite to that of 12a and 12b′. Accordingly, the RF electrodes 12a, 12b, 12a′, 12b′ produce a pseudopotential well defining an ion flow path in the form of ion optical axis extending parallel to the longitudinal direction of the electrode assembly 100.
In use, a DC voltage may be applied to the DC electrodes 14. The DC voltage is applied to the DC electrode segments such that the DC electrode segments provide a DC potential that increases preferably monotonously from the first end 100a to the second end 100b of the electrode assembly. Preferably, the increasing DC potential is provided by using a resistive divider located on an outer surface of dielectric material 11, which is connected to each DC electrode segment by a connector 22 and has equal resistors. Preferably, a linear voltage distribution is defined, though more complicated and time-dependent distributions could be also employed to enable ion manipulation within the ion electrode assembly. For example, ions could be driven to either the first end 100a or the second end 100b of the electrode assembly 100 in synchronization with further stages of mass analysis. Also, ion mobility separation in gas-filled guide could be enabled. This can be accomplished when the drift velocity is provided by a DC gradient on the electrode assembly. Preferably the RF electrodes 12a, 12b, 12a′, 12b′ may be split into multiple segments, each having its own DC voltage applied thereto. The DC voltage may be supplied by, for example, the same resistive divider as that used to supply the DC electrode segments). By splitting the RF electrodes 12a, 12b, 12a′, 12b′ into multiple segments, each having its own DC voltage applied thereto, in addition to the DC electrode segments, enables generation of stronger axial gradients in the electrode assembly.
The gap between the RF electrode 12a, 12b, 12a′, 12b′ and the dielectric material 11 enables the DC electrode 14 provided directly therebetween to shield the dielectric material 11 from the RF field generated by the RF electrode 12a, 12b, 12a′, 12b′. This shielding prevents the RF field from penetrating the dielectric material 11, as shown by the equipotential lines 27, 28 in
This is significantly different from the known electrode assembly 1 shown in
The electrode arrangements 10, 10′ of the present invention, as shown in
The electrode arrangements 10, 10′ of the present invention, as shown in
In a preferred embodiment, the electrode assembly 100 having the electrode arrangements 10, 10′, as depicted in
When the electrode assembly 100 having the first and second electrode arrangements 10, 10′, as depicted in
The difference between the receptacled separators 13′ and the pin separators 13 is that for receptacled separators 13′, each head portion 13a comprises a receptacle 13d for receiving a protruding portion 12c extending from the main body of the RF electrodes 12a, 12b, 12a′, 12b′. The description of the other components of
The receptacled separators 13′ are mechanically coupled to the RF electrodes 12a, 12b, 12a′, 12b′. The RF electrodes 12a, 12b, 12a′, 12b′ each have a main body, which is elongate and extends in the longitudinal direction of the electrode assembly 10. The main body of the RF electrodes 12a, 12b, 12a′, 12b′ comprises the major and minor surfaces described above. As described above, the major surfaces of the RF electrodes 12a, 12b, 12a′, 12b′ are parallel to the plane of the dielectric surface 11. The minor surfaces of the RF electrodes 12a, 12b, 12a′, 12b′ are orthogonal to the planar dielectric surface 11. In the second embodiment, the RF electrodes 12a, 12b, 12a′, 12b′ comprise the main body and a plurality of protruding portions 12c extending from the main body. Each protruding portion 12c is received by the respective receptacle 13d. Each protruding portion 12c of each RF electrode 12a, 12b, 12a′, 12b′ is inserted into and retained within the corresponding receptacle 13d of the receptacled separator 13′.
Each receptacle 13d comprises an opening 13e for receiving the protruding portion 12c. The opening 13e may have a complementary shape to the corresponding protruding portion 12c. The opening 13e may be a through-hole or may instead be a recess that only extends partially through the receptacle 13d. The receptacle 13d and its opening 13e have a longitudinal axis extending in the direction orthogonal to the plane of the dielectric material 11. The opening 13e extends in the direction orthogonal to the plane of the RF electrodes 12a, 12b, 12a′, 12b′. The diameter of the opening 13e formed in the receptacle 13d may be the same or greater than the diameter of the protruding portion 12c of the RF electrode 12a, 12b, 12a′, 12b′. Preferably, the receptacle comprises a circular spring (not shown) that exerts a retaining force on the protruding portion 12c to retain the protruding portion 12c in the opening 13e of the receptacle 13d. The receptacle 13d may provide mechanical support and alignment for the RF electrodes 12a, 12b, 12a′, 12b′.
As discussed above in respect of the pin separators 13, the receptacled separators 13′ are configured to define a gap between the RF electrodes 12a, 12b, 12a′, 12b′ and the dielectric material 11. The gap is provided in the direction orthogonal to the plane of the dielectric material 11. Accordingly, a gap also extends between the outer (major) surface of the RF electrodes 12a, 12b, 12a′, 12b′ and the DC electrodes 14 formed on the inner (major) surface of the dielectric material 11. This is discussed in further detail above in respect of the pin separators 13 in the embodiment shown in
Each protruding portion 12c preferably only partially extends into the opening 13e such that a gap is formed between the bottom wall 13f of the receptacle 13d and the end of the protruding portion 12c distal from the main body of the respective RF electrode 12a, 12b, 12a′, 12b′. This gap is provided along the longitudinal axis of the receptacle (i.e. orthogonal to the plane of the RF electrodes 12a, 12b, 12a′, 12b′). By inserting the protruding portion 12c into the opening 13e in the receptacle 13d, vibrations or bending of electrodes is avoided.
The protruding portions 12c are preferably integrally formed with and are part of the RF electrodes 12a, 12b, 12a′, 12b′. Each protruding portion 12c extends from the minor surface of the main body of the respective RF electrode 12a, 12b, 12a′, 12b′. Each protruding portion 12c connects the minor surface of the RF electrode 12a, 12b, 12a′, 12b′ to the separator 13. Each protruding portion 12c has a first section in a first plane and a second section in a second plane. The first plane is the plane of the main body of the RF electrodes 12a, 12b, 12a′, 12b′ i.e. the first section extends in the plane of the RF electrodes 12a, 12b, 12a′, 12b′. The first section extends in a direction away from the main body of the respective RF electrode 12a, 12b, 12a′, 12b′ (i.e. in a direction at a non-zero angle to the longitudinal axis of the RF electrode 12a, 12b, 12a′, 12b′). Most preferably, the first section extends in the plane of the RF electrode 12a, 12b, 12a′, 12b′ in a direction perpendicular to the longitudinal axis of the RF electrode 12a, 12b, 12a′, 12b′. At least a part of the second section is received within the receptacle 13d. The second section extends at an angle to the plane of the RF electrode 12a, 12b, 12a′, 12b′ (i.e. the second section extends out of the plane of the RF electrode 12a, 12b, 12a′, 12b′) such that it enters the receptacle 13d. The second plane is at an angle relative to the first plane. In a preferred embodiment, the second plane is orthogonal to the first plane. Preferably, each protruding portion has a curved section connecting the first and second sections and so transitioning the protruding portion from the first plane to the second plane. However, in an alternative arrangement, the protruding portion 12c may not have a curved section and instead, the first section may be directly connected to the second section such that the first section intersects the second section at a non-zero angle.
The description of the projecting portions 13b of the pin separators 13 above in respect of the embodiment shown in
Each protruding portion 12c of the RF electrode 12a, 12b, 12a′, 12b′ is formed integrally with the RF electrode 12a, 12b, 12a′, 12b′ and so has been described as a part of the RF electrode 12a, 12b, 12a′, 12b′. Preferably, RF electrodes 12 are made as flat plates e.g. by laser cutting or pressing and then protruding portion 12c is bent downwards from the flat plate on a special jig. In this case, cross-section of the protruding portion 12c is typically square Alternatively and less preferably, the protruding portion 12c may be attached to the RF electrode 12a, 12b, 12a′, 12b′ by laser- or electron-beam welding rather than being formed integrally with the RF electrode 12a, 12b, 12a′, 12b′.
The receptacle 13d is illustrated as having a square cross section and its opening 13e has a circular cross section. Of course it will be appreciated that other shapes may be employed. For example, the receptacle 13d may have a cylindrical cross section and its opening 13e may have a square cross section. Of course, the cross-section of the protruding portion 12c may also have a different shape from the square shape shown in
As discussed above, the receptacled separators 13′ are offset from the RF electrodes 12a, 12b, 12a′, 12b′ so that there is no overlap between the major surfaces of the RF electrodes 12a, 12b, 12a′, 12b′ and the receptacled separators 13′. The receptacled separators 13′ may instead be offset such that there is some overlap between the major surface of the RF electrodes 12a, 12b, 12a′, 12b′ and the receptacled separators 13′.
The receptacled separators 13′ are shown to be arranged on the same side of the respective RF electrode 12a, 12b, 12a′, 12b′. Instead, the receptacled separators 13′ may be arranged on either side of the RF electrodes 12a, 12b, 12a′, 12b′.
The protruding portions 12c are shown as having first and second sections and are preferably manufactured from flat sheet. Instead, each protruding portions 12c may extend from the RF electrode 12a, 12b, 12a′, 12b′ in the plane of the RF electrode at an angle to the longitudinal axis of the RF electrode. The protruding portions 12c may be linear. In one arrangement, each receptacle 13d may extend in the plane of the RF electrode 12a, 12b, 12a′, 12b′ at an angle to the longitudinal axis of the RF electrode such that the protruding portion 12c, which is linear, is received within the receptacle 13d. The projecting portion 13b may have a first part that extends in the plane of the RF electrode and is connected to the receptacle 13d and a second part that extends at an angle to the plane of the RF electrode and is received within the receiving portion 11a of the dielectric material 11. The first and second parts may be connected by a curved part. The second part may extend in the direction out of the plane of the RF electrode 12a, 12b, 12a′, 12b′ preferably orthogonal to the plane of the RF electrode 12a, 12b, 12a′, 12b′. Alternatively, each protruding portion 12c may extend from the major surface of the RF electrode 12a, 12b, 12a′, 12b′ in the direction out of the plane of the RF electrodes 12a, 12b, 12a′, 12b′ and into the receptacle 13d. In this arrangement, the receptacle separators 13′ may be positioned in-line with or proximal to the central longitudinal axis of the RF electrodes 12a, 12b, 12a′, 12b′.
In this second embodiment, optionally a plurality of projecting separators 13″ are also provided in addition to the receptacled separators 13′. The plurality of projecting separators 13″ are spaced apart from each other. The plurality of projecting separators 13″ may be positioned at a plurality of points along the RF electrode 12a, 12b, 12a′, 12b′ preferably two or three points, as shown in
Similarly to pin separators 13 and receptacled separators 13′, projecting separators 13″ may define the gap between the RF electrode(s) 12a, 12b, 12a′, 12b′ and the dielectric material 11. Each projecting separators 13″ connect the major planar surface of the RF electrode 12a, 12b, 12a′, 12b′ to the dielectric material 11. Projecting Separators 13″ differ from the pin separators 13 of the embodiment shown in
Each receiving portion 11a in the dielectric material 11 and each opening 12d in the RF electrode 12a, 12b, 12a′, 12b′ may have complementary shapes to the first end 13g and second end 13h of the projecting portion 13b. Each receiving portion 11a and/or each opening 12d may be a through-hole or may instead be a recess. Preferably, the receiving portion 11a is a through-hole and the first end 13g of the projecting portion 13b extends through the receiving portion 11a such that the first end 13g extends beyond the outer surface of the dielectric material 11. Preferably, the opening 12d in the RF electrode 12a, 12b, 12a′, 12b′ is a through-hole and the second end 13h of the projecting portion 13b extends through the opening 12d in the RF electrode such that the second end 13h extends beyond the inner surface of the RF electrode 12a, 12b, 12a′, 12b′.
Each receiving portion 11a in the dielectric material and each opening 12d in the RF electrode 12a, 12b, 12a′, 12b′ may be machined, punched or laser-cut. The first end 13g and second end 13h of the projecting separators 13″ may be fastened to the dielectric material 11 and RF electrodes 12a, 12b, 12a′, 12b′ respectively, for example, by nuts and screws, circular clips, soldering, adhesive or welding. As discussed, above, each projecting portion 13b may be soldered to the outer major surface of dielectric material 11. Typically, each projecting portion 13b is soldered to a conductive pad provided on the outer major surface of the dielectric material 11. Each projecting portion 13b of the projecting separators 13″ may also be soldered to the inner major surface of the RF electrode 12a, 12b, 12a′, 12b′.
As shown in
In the embodiment shown in
As discussed above in respect of the projecting portion 13b of the pin separators, the first end 13g of the projecting portion 13b of the projecting separators 13″ may be electrically connected to an RF voltage supply to supply an RF voltage to the respective RF electrode 12a, 12b, 12a′, 21b′. This connection may be provided by connectors configured to provide electrical connection to the RF voltage supply. The connectors have been discussed above.
As discussed above, the inclusion of the projecting separators 13″ in addition to the receptacled separators 13′ is optional. Similarly, the inclusion of the receptacled separators 13′ in addition to the projecting separators 13″ is optional. In
Although not shown in
In the embodiment shown in
As discussed above in respect of pin separators 13, the receptacled separators 13′ and projecting separators 13″ may also be electrically conductive and preferably metallic. The receptacled separators 13′ and projecting separators 13″ are spaced apart along a surface of the dielectric material 11 and are preferably equally spaced apart. The receptacled separators 13′ and projecting separators 13″ may typically be formed of copper or the same material as RF electrodes 12a, 12b, 12a′, 12b′. The receptacled separators 13′ and projecting separators 13″ may not be permanently attached to the surface of the RF electrode 12a, 12b, 12a′, 12b′. For example, for the receptacled separator 13′, the protruding portion of the RF electrode 12a, 12b, 12a′, 12b′ may be removably received in the receptacle 13d. For the projecting separator 13″, the projecting portion 13b may be removably received within the opening 12d.
The description of use of the electrode assembly 1 comprising the electrode arrangement 10 of the first embodiment shown in
The manufacturing and assembly of the electrode assembly 1, which involves mechanically coupling the RF electrode to the dielectric material using the plurality of separators that are spaced apart such that a gap is defined between the RF electrode and the dielectric material and then cutting the RF electrode while the RF electrode is coupled to the dielectric material so as to reshape the RF electrode applies to both the embodiments shown in
Experimental Results
The results of an experiment, referred to herein as experiment 2, involving the same isolated charge state (+11) of multiply charged ubiquitin ions as in experiment 1 in a HCD (Higher-energy collisional dissociation) cell having the electrode assembly 100 of the claimed invention shown in
The data was of
In addition to the advantageous electrode arrangements 10, 10′ of the claimed invention, a further improvement may be provided by using Megtron6 as the dielectric material 11 forming the PCB instead of Panasonic 1755M. In known electrode arrangements, the dielectric material forming the PCB typically comprises Panasonic 1755M. In the claimed invention, the dielectric material 11 is preferably Megtron6. The use of Megtron6 results in further reduced dielectric losses. Indeed, the dissipation factor, Df, for Megtron6 is 0.0015-0.0020 whereas the dissipation factor, Df, for Panasonic 1755M is 0.014.
Whilst
It will be understood that the embodiments described above in relation to
Further embodiments of the invention might combine several features of different embodiments described in this specification. E.g. different embodiments may use any one or a combination of pin separators 13, receptacled separators 13′ or projecting separators 13″ in one electrode arrangement.
Whilst the RF electrodes 12a, 12b, 12a′, 12b′ of
The first and second minor side walls 101, 102 may be bent or curved.
The size of the space between the first and second electrode arrangements 10, 10′ may be varied. For example, by changing the distance between the dielectric materials 11 or by varying the thickness of the head portion 13a of each pin separator 13, or by varying the thickness of the bottom wall 13f of each receptacled separator 13′ or by varying the height of each projecting separator 13″.
The DC electrodes 14 are described as being etched on the surface of the dielectric material 11 but may instead be formed by other methods. For example, the DC electrodes 14 may be formed by stamping, extrusion, laser cutting or other suitable fabrication methods.
The RF electrodes 12a, 12b, 12a′, 12b′ may be formed by machining, stamping, laser cutting, extrusion, etching etc.
Whilst
Whilst the embodiment shown in
Whilst the separators 13, 13′, 13″ (pin separators 13, receptacled separators 13′ or projecting separators 13″) of
The separators 13, 13′, 13″ (pin separators 13, receptacled separators 13′ or projecting separators 13″) are at least electrically connected to the RF electrodes 12a, 12b, 12a′, 12b′. The separators 13, 13′, 13″ (pin separators 13, receptacled separators 13′ or projecting separators 13″) are described as being permanently connected to the RF electrodes 12a, 12b, 12a′, 12b′ received within the receiving portion 11a of the dielectric material 11 and soldered to a conductive pad on the dielectric material 11. Alternatively, the separators 13, 13′, 13″ could be removable received within the receiving portion 11a of the dielectric material 11. In an alternative embodiment, the separators 13, 13′, 13″ could be permanently connected to the dielectric material 11, received within a receiving portion of the RF electrode 12a, 12b, 12a′, 12b′ and soldered to the RF electrode 12a, 12b, 12a′, 12b′. Alternatively, the separators 13, 13′. 13″ could be removable received within a receiving portion of the RF electrode 12a, 12b, 12a′, 12b′. In an alternative embodiment, the separators 13, 13′, 13″ could be removably connected to both the dielectric material 11 and the RF electrode 12a, 12b, 12a′, 12b′.
In
In
The pin separators 13 of
As shown in
For the embodiment shown in
For the embodiment shown in
For both the embodiment shown in
The separators 13, 13′, 13″ (pin separators 13, receptacled separators 13′ or projecting separators 13″) may be spacers/stand-offs.
For the embodiments shown in
Number | Date | Country | Kind |
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1907139 | May 2019 | GB | national |
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Number | Date | Country | |
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20200373138 A1 | Nov 2020 | US |