Device for reacting analyte IONS with electrons

Abstract

A method of manufacturing a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device, the method comprising using a relationship that represents the magnetic field along the axis of the device due to the two magnets as a function of position along the axis.

Description

[0001] 173982 / 02v1

[0002] DEVICE FOR REACTING ANALYTE IONS WITH ELECTRONS

[0003] CROSS-REFERENCE TO RELATED APPLICATION

[0004] This application claims priority from and the benefit of United Kingdom patent application No. 2417408.8 filed on 27 November 2024. The entire contents of this application are incorporated herein by reference.

[0005] FIELD OF THE INVENTION

[0006] The present invention relates generally to a method of mass and / or ion mobility spectrometry in which analyte ions are reacted with electrons so as to produce charge- reduced analyte ions, fragment ions or other product ions. The present invention also provides a reaction cell and mass and / or mobility spectrometer configured to perform the method.

[0007] BACKGROUND

[0008] It is well known to conduct ion-electron reactions, in the field of mass spectrometry, during the analysis of analyte ions. Examples of such reactions include electron capture dissociation (ECD) and electron induced dissociation (EID). In order to perform ECD, multiply protonated analyte molecules, i.e. analyte ions, may be confined along with low energy electrons such that the analyte molecules and electrons react with each other so as to cause the analyte molecules to fragment into fragment ions.

[0009] Mass spectrometry techniques that use electron-based fragmentation techniques such those described above are beneficial in that they may be more informative than using other fragmentation techniques, such as collisional induced dissociation (CID), since the product ions produced by the electron-based reactions retain labile post-translational modifications. Also, during the above-mentioned ion-electron interactions, some of the analyte molecules may not dissociate into fragment ions but may become charge-reduced instead. Such charge reduction may be useful for separating ions that would otherwise have overlapping mass to charge ratios due to their charge states. Also, electron-based fragmentation techniques can generate higher-quality, more complete or complementary fragment information for polymers such as peptides.

[0010] Although ion-electron reaction devices are known, their design is typically complex and their operation can be challenging, e.g. due to the difficulty in confining the analyte ions and the low energy electrons in the same region for a sufficient time and with sufficient density for the reactions to be performed. For example, ECD devices are known that employ an RF electric field to confine the analyte ions, but this RF field increases the energy of the reactant electrons and so the probability of the analyte ions capturing the electrons is relatively low, and hence so is the probability of a reaction taking place. Furthermore, for devices where electrons are trapped, the additional energy they receive from the RF field causes them to be lost from the electron trapping fields.

[0011] Other known reaction devices use strong magnetic fields in order to confine the electrons at low energy, but these also present difficulties in confining both the analyte ions and reactant electrons in the same region such that the reactions take place at the required rate. For example, difficulties may arise if the magnetic fields are too weak or are inhomogeneous.

[0012] SUMMARY

[0013] A first aspect of the present invention provides A method of manufacturing a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device, the method comprising: i) obtaining a relationship that represents the magnetic field along the axis of the device due to the two magnets as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other, wherein the relationship is a polynomial having a second and / or higher order term of z, and wherein the value of the coefficient of the second and / or higher order term of z is dependent on said dimensions of the magnets and their spacing from each other; ii) determining a combination of values of said variables that provide said coefficient with a value that is less than or equal to a pre-selected value; and iii) manufacturing said device comprising two magnets such that the dimensions of the magnets and their spacing from each other correspond to values that are represented by said combination of values determined in step ii).

[0014] Step ii) may comprise determining the combination of values of said variables that provide said coefficient with a value of zero.

[0015] Each of the two magnets in the device may be a cylindrical magnet having an axis therethrough, wherein the axes through the magnets are colinear with said axis of the device.

[0016] The axis through the cylindrical magnet is the axis of rotational symmetry of the magnet.

[0017] Said dimensions of each magnet that are represented by said variables may include an inner radius of the magnet, an outer radius of the magnet and a length of the magnet in a direction along said axis of the device.

[0018] The two magnets preferably have the same dimensions, although it contemplated that they may have different dimensions.

[0019] It will be appreciated that the method comprises selecting a magnetic material for each magnet, which defines the remanence field for the magnet. The two magnets preferably have the same remanence field, although it is contemplated that they may have different remanence fields.

[0020] The two magnets may be substantially identical to each other.

[0021] Obtaining said relationship may comprise determining an expression for the magnetic field due to the two magnets at the axis of the device as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other, and expanding said expression in terms of z so as to obtain said relationship that is a polynomial.

[0022] The two magnets may be cylindrical magnets having the same dimensions and the same remanence field, and the expression for the magnetic field due to the two magnets at the axis of the device may be given by: where Ro is the outer radius of each magnet, in mm; Ri is the inner radius of each magnet, in mm; D is the length of each magnet along the axis, in mm; pitch is the distance along the axis from the centre of one magnet to the centre of the other magnet, in mm; Br is the remanence field of each magnet, in Tesla; and z is the position along the axis (in mm), where z=0 is the centre point between the two magnets.

[0023] The coefficient of the second order term of z, F1, may be given by:

[0024] Step ii) may comprise selecting fixed values for all of the variables except for one of the variables, and using these fixed values to numerically determine the value for said one of the variables that provides said coefficient with a value that is less than or equal to said pre-selected value.

[0025] The step of numerically determining the value for said one of the variables may comprise choosing an initial value for said one of the variables and determining the value of the coefficient based on that chosen value, and based on the fixed values for the other variables. This process may be repeated a plurality of times, using a plurality of different respective values for said one of the variables, until the coefficient has a value that is less than or equal to said pre-selected value. The value for said one of the variables may be incremented each time the process is repeated so as to determine, in an iterative manner, the value of said one of the variables that gives the coefficient a value that is less than or equal to said pre-selected value.

[0026] The two magnets may be cylindrical magnets having the same dimensions, and step ii) may comprise: a) selecting fixed values for the outer radius of each magnet, the length of each magnet along the axis, and the spacing between the magnets; and then using these fixed values to numerically determine the value for the inner radius of each magnet that provides said coefficient with said value that is less than or equal to said preselected value; and / or b) selecting fixed values for the outer radius of each magnet, the length of each magnet along the axis, and the inner radius of each magnet; and then using these fixed values to numerically determine the value for the spacing between the magnets that provides said coefficient with said value that is less than or equal to said pre-selected value.

[0027] Alternatively, or additionally, step ii) may comprise: selecting fixed values for the outer radius of each magnet, the inner radius of each magnet, and the spacing between the magnets; and then using these fixed values to numerically determine the value for the length of each magnet along the axis that provides said coefficient with said value that is less than or equal to said pre-selected value.

[0028] Alternatively, or additionally, step ii) may comprise: selecting fixed values for the length of each magnet along the axis, the inner radius of each magnet, and the spacing between the magnets; and then using these fixed values to numerically determine the value for the outer radius of each magnet that provides said coefficient with said value that is less than or equal to said pre-selected value.

[0029] The device may be an ion-electron reaction device and the step of manufacturing said device may comprise providing the device with an electron source for supplying electrons to the axis of the device such that they become radially confined about the axis of the device by the magnetic field along the axis due to the two magnets.

[0030] The electron source may comprise a filament and a voltage supply connected to the filament such that when the voltage supply is activated electrons are released from the filament; optionally wherein the filament extends to a location that is between the magnets so as to release electrons onto a central axis of the device.

[0031] As described above, the magnets may be cylindrical magnets having axes therethrough that are colinear. These colinear axes may also be colinear with the central axis of the device.

[0032] The filament may extend through a first electrode or electrode portion to a location that is between the magnets for releasing electrons onto a central axis of the device; and one or more second electrodes or electrode portions may be arranged radially inward of the first electrode or electrode portion and around the filament so as to block the electric field generated by the filament. The filament may comprise a loop that extends around the central axis, optionally such that ions and / or electrons are able to pass along the central axis and through the loop.

[0033] Alternatively, an electron emitting heated disk may be provided for supplying electrons. The disk may have an aperture, e.g. on the central axis, so as to allow electrons and ions to pass therethrough.

[0034] The step of manufacturing said device may comprise: providing the device with electrically conductive magnets or with magnets having electrically conducting surfaces thereon; and providing one or more voltage sources for applying voltages to the electrically conductive magnets or to the electrically conducting surfaces thereon for confining the electrons between the magnets; optionally where the voltages are DC voltages.

[0035] The step of manufacturing said device may comprise: providing the device with one or more ion-guiding electrode between the magnets; and providing one or more voltage sources for applying one or more voltages to the ion-guiding electrodes for focusing ions passing through the device onto the axis; optionally wherein the one or more voltages are DC voltages.

[0036] Electrically insulating spacers may be provided between the magnets and the one or more ion-guiding electrodes. Alternatively, or additionally, where multiple ion-guiding electrodes are provided, electrically insulating spacers may be provided between the ionguiding electrodes.

[0037] Preferably, RF voltages are not applied to the magnets and / or one or more ionguiding electrode. Preferably, RF voltages are not applied to any components within the device.

[0038] The first aspect of the present invention also provides a method of designing the device described above.

[0039] Accordingly, the present invention provides a method of designing a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device, the method comprising: i) obtaining a relationship that represents the magnetic field along the axis of the device due to the two magnets as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other, wherein the relationship is a polynomial having a second and / or higher order term of z, and wherein the value of the coefficient of the second and / or higher order term of z is dependent on said dimensions of the magnets and their spacing from each other; ii) determining a combination of values of said variables that provide said coefficient with a value that is less than or equal to a pre-selected value; and iii) designing said device comprising two magnets so that the dimensions of the magnets and their spacing from each other correspond to values that are represented by said combination of values determined in step ii).

[0040] The first aspect of the present invention also provides a device for reacting ions with other charged particles that has been manufactured according to the methods described above.

[0041] The present invention also provides a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device; wherein the magnets have dimensions and are arranged relative to each other such that the magnetic field along the axis of the device due to the two magnets is represented by a relationship that represents the magnetic field as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other, wherein the relationship is a polynomial having a second and / or higher order term of z, wherein the value of the coefficient of the second and / or higher order term of z is dependent on said dimensions of the magnets and their spacing from each other; and wherein the combination of values of said variables provide said coefficient with a value that is substantially zero.

[0042] Each magnet may be a cylindrical magnet having an outer radius of about 12.5 mm, an inner radius of about 4 mm, a length along the axis of about 6 mm, and a distance from the centre of one of the magnets to the centre of the other of the magnets of about 30 mm.

[0043] The present invention also provides a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device; wherein each magnet is a cylindrical magnet having an outer radius of about 12.5 mm, an inner radius of about 4 mm, a length along the axis of about 6 mm, and a distance from the centre of one of the magnets to the centre of the other of the magnets of about 30 mm.

[0044] The device may have any of the device features described above in relation to the method of manufacturing the device.

[0045] The first aspect of the present invention also provides a method of reacting ions with other charged particles comprising: providing a device as described above; confining said other charged particles in said device using the magnetic field due to the magnets; and providing ions in the device so as to react with the charged particles.

[0046] The device may comprise a plurality of electrodes located between the two magnets. The plurality of electrodes may be arranged so that the magnetic field along the axis of the device is not affected.

[0047] The method may comprise applying one or more RF and / or DC voltages to the plurality of electrodes in order to trap ions within the device such that the other charged particles react with the ions.

[0048] The present invention also provides a method of mass spectrometry comprising the method described above. The product ions that are produced by reacting the ions with the charged particles, or ions derived therefrom, are subjected to mass analysis and / or ion mobility analysis.

[0049] The minimum magnetic field between the two magnets, at any point along the axis, may be greater than 0.01 T, 0.05 T, 0.1 T or 0.2 T.

[0050] Although a method has been described in which a polynomial expansion series of the magnetic field along the axis is obtained, it is contemplated that an alternative expansion series, such as a Fourier series may be used.

[0051] Accordingly, the present invention also provides a method of manufacturing a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device, the method comprising: i) obtaining a relationship that represents the magnetic field along the axis of the device due to the two magnets as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other, wherein the relationship is an expansion series of an equation representing the magnetic field along the axis, and wherein the value of a coefficient in the expansion series is dependent on said dimensions of the magnets and their spacing from each other; ii) determining a combination of values of said variables that provide said coefficient with a value that is less than or equal to a pre-selected value; and iii) manufacturing said device comprising two magnets such that the dimensions of the magnets and their spacing from each other correspond to values that are represented by said combination of values determined in step ii).

[0052] The expansion series may be a Fourier series or another type of expansion series.

[0053] The method may have any of the optional features described above in relation to the first aspect of the invention (except for the specific formula for F1).

[0054] The present invention also provides a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device; wherein the magnets have dimensions and are arranged relative to each other such that the magnetic field along the axis of the device due to the two magnets is represented by a relationship that represents the magnetic field as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other, wherein the relationship is an expansion series of an equation for the magnetic field along the axis, and wherein the value of a coefficient in the expansion series is dependent on said dimensions of the magnets and their spacing from each other; and wherein the combination of values of said variables provide said coefficient with a value that is substantially zero.

[0055] A second aspect of the present invention provides a method of manufacturing a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device, the method comprising: i) obtaining a relationship that represents the homogeneity of the magnetic field along the axis due to the two magnets, over at least a portion of the distance between the magnets, as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other; wherein the homogeneity of the magnetic field is the sum of the absolute deviation of the magnetic field from the mean value of the magnetic field over said at least a portion of the distance between the magnets, and where said deviation of the magnetic field at any given position along the axis is given by the magnetic field at that position minus said mean value of the magnetic field; ii) determining a combination of values of said variables that provide said homogeneity with a value that is less than or equal to a pre-selected value; and iii) manufacturing said device comprising two magnets such that the dimensions of the magnets and their spacing from each other correspond to values that are represented by said combination of values determined in step ii).

[0056] The pre-selected value may be < 0.20, < 0.15, or < 0.10.

[0057] Each of the two magnets in the device may be a cylindrical magnet having an axis therethrough, wherein the axes through the magnets are colinear with said axis of the device. Optionally, said dimensions of each magnet that are represented by said variables may include an inner radius of the magnet, an outer radius of the magnet and a length of the magnet in a direction along said axis of the device.

[0058] The axis through the cylindrical magnet is the axis of rotational symmetry of the magnet.

[0059] The two magnets preferably have the same dimensions, although it contemplated that they may have different dimensions.

[0060] It will be appreciated that the method comprises selecting a magnetic material for each magnet, which defines the remanence field for the magnet. The two magnets preferably have the same remanence field, although it is contemplated that they may have different remanence fields.

[0061] The two magnets may be substantially identical to each other.

[0062] In the second aspect of the invention, step ii) may comprise selecting fixed values for all of the variables except for one of the variables, and using these fixed values to numerically determine the value for said one of the variables that provides said homogeneity with a value that is less than or equal to said pre-selected value.

[0063] The step of numerically determining the value for said one of the variables may comprise choosing an initial value for said one of the variables and determining the value of the homogeneity based on that chosen value, and based on the fixed values for the other variables. This process may be repeated a plurality of times, using a plurality of different respective values for said one of the variables, until the homogeneity has a value that is less than or equal to said pre-selected value. The value for said one of the variables may be incremented each time the process is repeated so as to determine, in an iterative manner, the value of said one of the variables that gives the homogeneity a value that is less than or equal to said pre-selected value.

[0064] The two magnets may be cylindrical magnets having the same dimensions, and step ii) may comprise: a) selecting fixed values for the outer radius of each magnet, the length of each magnet along the axis, and the spacing between the magnets; and then using these fixed values to numerically determine the value for the inner radius of each magnet that provides said homogeneity with said value that is less than or equal to said pre-selected value; and / or b) selecting fixed values for the outer radius of each magnet, the length of each magnet along the axis, and the inner radius of each magnet; and then using these fixed values to numerically determine the value for the spacing between the magnets that provides said homogeneity with said value that is less than or equal to said preselected value.

[0065] Alternatively, or additionally, step ii) may comprise: selecting fixed values for the outer radius of each magnet, the inner radius of each magnet, and the spacing between the magnets; and then using these fixed values to numerically determine the value for the length of each magnet along the axis that provides said homogeneity with said value that is less than or equal to said pre-selected value.

[0066] Alternatively, or additionally, step ii) may comprise: selecting fixed values for the length of each magnet along the axis, the inner radius of each magnet, and the spacing between the magnets; and then using these fixed values to numerically determine the value for the outer radius of each magnet that provides said homogeneity with said value that is less than or equal to said pre-selected value. The device may be an ion-electron reaction device and the step of manufacturing said device may comprise providing the device with an electron source for supplying electrons to the axis of the device such that they become radially confined about the axis of the device by the magnetic field along the axis due to the two magnets.

[0067] The electron source may comprise a filament and a voltage supply connected to the filament such that when the voltage supply is activated electrons are released from the filament; optionally wherein the filament extends to a location that is between the magnets so as to release electrons onto a central axis of the device.

[0068] As described above, the magnets may be cylindrical magnets having axes therethrough that are colinear. These colinear axes may also be colinear with the central axis of the device.

[0069] The filament may extend through a first electrode or electrode portion to a location that is between the magnets for releasing electrons onto a central axis of the device; and one or more second electrodes or electrode portions may be arranged radially inward of the first electrode or electrode portion and around the filament so as to block the electric field generated by the filament.

[0070] The filament may comprise a loop that extends around the central axis, optionally such that ions and / or electrons are able to pass along the central axis and through the loop.

[0071] Alternatively, an electron emitting heated disk may be provided for supplying electrons. The disk may have an aperture, e.g. on the axis, so as to allow electrons and ions to pass therethrough.

[0072] The step of manufacturing said device may comprise: providing the device with electrically conductive magnets or with magnets having electrically conducting surfaces thereon; and providing one or more voltage sources for applying voltages to the electrically conductive magnets or to the electrically conducting surfaces thereon for confining the electrons between the magnets; optionally where the voltages are DC voltages.

[0073] The step of manufacturing said device may comprise: providing the device with one or more ion-guiding electrode between the magnets; and providing one or more voltage sources for applying one or more voltages to the ion-guiding electrodes for focusing ions passing through the device onto the axis; optionally wherein the one or more voltages are DC voltages.

[0074] Electrically insulating spacers may be provided between the magnets and the one or more ion-guiding electrodes. Alternatively, or additionally, where multiple ion-guiding electrodes are provided, electrically insulating spacers may be provided between the ionguiding electrodes.

[0075] Preferably, RF voltages are not applied to the magnets and / or one or more ionguiding electrode. Preferably, RF voltages are not applied to any components within the device.

[0076] The first second of the present invention also provides a method of designing the device described above. Accordingly, the present invention provides a method of designing a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device, the method comprising: i) obtaining a relationship that represents the homogeneity of the magnetic field along the axis due to the two magnets, over at least a portion of the distance between the magnets, as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other; wherein the homogeneity of the magnetic field is the sum of the absolute deviation of the magnetic field from the mean value of the magnetic field over said at least a portion of the distance between the magnets, and where said deviation of the magnetic field at any given position along the axis is given by the magnetic field at that position minus said mean value of the magnetic field; ii) determining a combination of values of said variables that provide said homogeneity with a value that is less than or equal to a pre-selected value; and iii) designing said device comprising two magnets so that the dimensions of the magnets and their spacing from each other correspond to values that are represented by said combination of values determined in step ii).

[0077] The second aspect of the present invention also provides a device for reacting ions with other charged particles that has been manufactured according to the method described above in relation to the second aspect of the invention.

[0078] Accordingly, the present invention provides a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device; wherein the magnets have dimensions and are arranged relative to each other such that the homogeneity of the magnetic field along the axis due to the two magnets, over at least a portion of the distance between the magnets, is represented by a relationship that represents the homogeneity of the magnetic field as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other; wherein the homogeneity of the magnetic field is the sum of the absolute deviation of the magnetic field from the mean value of the magnetic field over said at least a portion of the distance between the magnets, and where said deviation of the magnetic field at any given position along the axis is given by the magnetic field at that position minus said mean value of the magnetic field; and wherein the combination of values of said variables provide said homogeneity with a value that is < 0.20, < 0.15, or < 0.10.

[0079] Each magnet may be a cylindrical magnet having an outer radius of about 12.5 mm, an inner radius of about 4 mm, a length along the axis of about 6 mm, and a distance from the centre of one of the magnets to the centre of the other of the magnets of about 30 mm.

[0080] The device may have any of the device features described above in relation to the method of manufacturing the device according to the second aspect of the invention.

[0081] The second aspect of the present invention also provides a method of reacting ions with other charged particles comprising: providing a device according to the second aspect of the invention; confining said other charged particles in said device using the magnetic field due to the magnets; and providing ions in the device so as to react with the charged particles.

[0082] The device may comprise a plurality of electrodes located between the two magnets. The plurality of electrodes may be arranged so that the magnetic field along the axis of the device is not affected.

[0083] The method may comprise applying one or more RF and / or DC voltages to the plurality of electrodes in order to trap ions within the device such that the other charged particles react with the ions. The present invention also provides a method of mass spectrometry comprising the method described above. The product ions that are produced by reacting the ions with the charged particles, or ions derived therefrom, are subjected to mass analysis and / or ion mobility analysis.

[0084] In the method or device described above, the minimum magnetic field at the axis, over said at least a portion of the distance between the magnets, may be greater than 0.01 T, 0.05 T, 0.1 T or 0.2 T.

[0085] The magnitude of the magnetic field being relatively high is important, as well as the field uniformity, as charged particles such as electrons are better confined by higher magnetic fields.

[0086] A third aspect of the present invention provides an ion-electron reaction device for reacting ions with electrons, comprising: two magnets having apertures therethrough that are spaced apart such that an axis passes through the apertures, wherein the magnets are electrically conductive or have an electrically conductive surface thereon; an electron source for supplying electrons to the axis of the device such that they become radially confined about the axis by a magnetic field due to the two magnets; and one or more voltage sources for applying voltages to the electrically conductive magnets or to the electrically conducting surfaces thereon; wherein the magnets, or the electrically conducting surfaces thereon, are arranged within the device such that when the voltages are applied thereto, electric fields are generated within the apertures of the magnets for focusing ions passing therethrough onto the axis.

[0087] The voltages are preferably DC voltages. As such, the magnets are able to electrostatically focus the ions onto the axis.

[0088] The device may comprise one or more ion-guiding electrodes between the magnets. The device may comprise at least one voltage supply for applying voltages, e.g. DC voltages, to these ion-guiding electrodes so that the electrodes focus the ions onto the axis. The electrodes are preferably non-magnetic, material such as stainless steel.

[0089] Electrically insulating spacers may be provided between the magnets and the one or more ion-guiding electrodes. Alternatively, or additionally, where multiple ion-guiding electrodes are provided, electrically insulating spacers may be provided between the ionguiding electrodes.

[0090] Preferably, RF voltages are not applied to the magnets and / or one or more ionguiding electrode. Preferably, RF voltages are not applied to any components within the device.

[0091] The diameter of the aperture in each magnet may be constant along the length of the magnet, i.e. along the axis. Alternatively, the diameter may decrease as a function of distance from one axial end of the magnet towards the other axial end of the magnet, and optionally then increase towards said other end of the magnet. For example, the radially inner surface of each magnet may have a shape corresponding to the radially inner surface of a ring torus.

[0092] The electron source may comprise a filament and a voltage supply connected to the filament such that when the voltage supply is activated electrons are released from the filament; optionally wherein the filament extends to a location that is between the magnets so as to release electrons onto the axis.

[0093] The magnets may be cylindrical magnets having central axes therethrough that are colinear.

[0094] The magnets preferably have the same dimensions, although it contemplated that they may have different dimensions.

[0095] The two magnets preferably have the same remanence field, although it is contemplated that they may have different remanence fields.

[0096] The two magnets may be substantially identical to each other.

[0097] The filament may extend through a first electrode or electrode portion to a location that is between the magnets for releasing electrons onto the axis; and one or more second electrodes or electrode portions may be arranged radially inward of the first electrode or electrode portion and around the filament so as to block the electric field generated by the filament.

[0098] The filament may comprise a loop that extends around the central axis, optionally such that ions and / or electrons are able to pass along the central axis and through the loop.

[0099] Alternatively, an electron emitting heated disk may be provided for supplying electrons. The disk may have an aperture, e.g. on the axis, so as to allow electrons and ions to pass therethrough.

[0100] The device may have any of the optional features that have been described above in relation to the first or second aspects of the invention.

[0101] The third aspect of the present invention also provides a method of reacting ions with electrons comprising: providing a device according to the third aspect of the invention; confining said electrons in said device using the magnetic field due to the magnets; and providing ions in the device so as to react with the charged particles.

[0102] The device may comprise a plurality of electrodes located between the two magnets. The plurality of electrodes may be arranged so that the magnetic field along the axis of the device is not affected.

[0103] The method may comprise applying one or more RF and / or DC voltages to the plurality of electrodes in order to trap ions within the device such that the other charged particles react with the ions.

[0104] The present invention also provides a method of mass spectrometry comprising the method described above. The product ions that are produced by reacting the ions with the electrons, or ions derived therefrom, are subjected to mass analysis and / or ion mobility analysis.

[0105] The present invention also provides a mass spectrometer having any one of the devices described herein. The spectrometer may also have an ion source, for supplying ions into the device.

[0106] BRIEF DESCRIPTION OF THE DRAWINGS

[0107] Various embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which: Figs. 1A-1B illustrate an ion-electron reaction device according to an embodiment of the present invention;

[0108] Figs. 2A-2B show simulations illustrating the magnetic field lines and electric field lines within the device;

[0109] Fig. 3 shows an example of a ring magnet and illustrates the variables that define the magnetic field along an axis that extends through the centre of the bore through the magnet;

[0110] Figs. 4A-4C show the magnetic fields along the axis of the device due to magnets having a particular spacing and dimensions;

[0111] Fig. 5 shows a plot that represents the numerical solution for the magnet inner radius Ri for various different magnet outer radii Ro;

[0112] Fig. 6 shows four plots of the total magnetic field due to the magnets as a function of position, where the four different plots have been calculated using four different respective values of inner radius of each magnet;

[0113] Fig. 7A illustrates the total magnetic field due to the magnets as a function of position z, and also illustrates the mean magnetic field over this region, whereas Fig. 7B illustrates the deviation of the total magnetic field relative to the mean magnetic field 30;

[0114] Figs. 8A-8B shows plots indicating how different values of the inner and outer radii of the magnets affects the homogeneity of the magnetic field; and

[0115] Fig. 9A shows an example of the geometric configuration of two ring magnets in an ion-electron reaction device not according to the invention, and Fig. 9B shows a plot of the magnetic fields due to the magnets.

[0116] DETAILED DESCRIPTION

[0117] An ion-electron reaction device is known that comprises a Penning trap having a quadrupolar electric field for confining electrons axially along a central axis. The device also comprises magnets for maintaining a magnetic field along the axis in order to retain the electrons radially relative to the axis. Electrons may then be introduced onto the axis within the device and they become confined within the device in the axial and radial directions. Analyte ions are then introduced into the region where the electrons are confined such that ion-electron reactions take place that cause the ions to fragment. However, such devices present difficulties in confining both the analyte ions and reactant electrons in the same region such that the reactions take place at the required rate. For example, difficulties arise because the magnetic fields are too weak and / or too inhomogeneous.

[0118] Embodiments of the present invention provide an ion-electron reaction device comprising magnets that are configured and arranged in a geometry that provides a relatively high magnetic field homogeneity along an axis of the device. Figs. 1A-1B illustrate an ion-electron reaction device according to an embodiment of the present invention. More specifically, Fig. 1 A shows a schematic of a cross-section through a portion of the device, whereas Fig. 1B shows a perspective view of a crosssection through the device. The device comprises two permanent magnets 2 that are ring magnets, i.e. that each has a cylindrical shape. The ring magnets are arranged such that the axes through them are co-linear so as to define a central axis through the device. The device also comprises a filament insert electrode 4 arranged between the ring magnets, through which a wire filament 6 extends. The filament insert electrode may be arranged equidistant from the two ring magnets. The filament may extend through the filament insert electrode to the central axis, for generating electrons at the axis. The device also comprises a further cylindrical ion-guiding electrode 8 between each ring magnet and the filament insert electrode. The axes through these ion-guiding electrodes are co-linear with the axes through the magnets. The device also has apertured end-plate lenses 10 arranged on the axially outer sides of the magnet as shown in Fig. 1B, but not Fig. 1A. The device also has electrically insulating spacers 12 between adjacent electrodes, and between each magnet and the adjacent electrode and end-plate lens, such that these components may be maintained at different electrical potentials, as will be described below. The spacers may be, for example, ceramic spacers. These spacers are shown in Fig. 1 B, but not Fig. 1A.

[0119] The magnets are configured to generate magnetic fields that are substantially homogenous along the central axis for radially confining the electrons, as will be described in more detail further below. For example, each magnet may be axially magnetised such that its north pole points in one direction parallel to the central axis and its south pole points in the other direction parallel to the central axis. The two faces of the magnets that face each other have the opposite poles, i.e. one of these faces is the north pole and the other of these faces, i.e. of the other magnet, is the south pole.

[0120] The magnets may be electrically conductive, or may have electrically conductive surfaces thereon, such that they can be maintained at electrical potentials for trapping electrons axially between the magnets. For example, the magnets may be made from Samarium Cobalt, which is electrically conductive. In such embodiments, the device includes DC voltage supplies connected to the magnets or said surfaces for applying DC voltages that confine the electrons axially between the magnets.

[0121] In use, the voltage supplies that are connected to magnets and electrodes are activated. A voltage supply that is connected to the filament is also activated such that the filament emits free electrons, in the known manner, from its end that is located proximate the central axis. The filament electrode may have a radially outer portion 8a having a relatively large inner diameter, through which the filament extends radially relative to the central axis, and it may also have shield portions 8b at the axial ends of the filament electrode that extend radially inwards from outer portion towards the central axis so as to shield the rest of the device from the high electric field generated by the filament. The shield portions may extend from the radially outer portion at least to an inner diameter that is substantially the same as the inner diameter of the adjacent ion-guiding electrodes. Alternatively, the shield portions may extend continuously between diametrically opposing sides of the radially outer portion and may define windows therethrough so as to allow electrons and ions to pass along the central axis. The filament electrodes may be formed from an electrically conductive, and preferably non-magnetic, material such as stainless steel. The filament may be formed from rhenium, tungsten or rhenium doped with yttria (e.g. SISAIloy).

[0122] The combined magnetic field due to the two magnets has field lines extending along the central axis in the region between the two magnets. As such, the electrons that are generated by the filament are radially confined about the central axis by the magnetic field. Also, the magnets may be maintained at electrical potentials that trap the electrons between the magnets.

[0123] Fig. 2A shows a simulation illustrating the magnetic field lines within the device due to the two magnets 2. Fig. 2B shows a simulation illustrating the electric field lines within the device due to the voltages applied to the magnets 2 and electrodes 4,8. The electrons 14 that are trapped in the device are also illustrated. The end of the filament may comprise a loop that surrounds the central axis so as to allow electrons and ions to pass along the axis and through the loop, rather than striking the filament. Alternatively, an electron emitting heated disk may be provided for supplying electrons. The disk may have an aperture, e.g. on the central axis, so as to allow electrons and ions to pass therethrough.

[0124] Analyte ions are introduced into the device so as to react with the electrons confined therein and produce fragment ions via electron induced dissociation (EID), such as electron capture dissociation (ECD), or to produce other product ions, such as charge- reduced ions. The ion-guiding electrodes 8, magnets 2 and end-plate lenses 10 are connected to DC voltage supplies that maintain these components at DC electrical potentials so as to electrostatically focus the ions onto the central axis. As such, the ionguiding electrodes and the end-plate lenses are formed from an electrically conductive, and preferably non-magnetic, material such as stainless steel. The analyte ions may be transmitted into the device through the aperture in one of the end-plate lenses and are guided along the central axis by the electrodes and hence through the electrons that are trapped in the device. The analyte ions are therefore caused to react with the electrons so as to produce product ions, such as fragment ions. The product ions may then be caused to exit the device, e.g. by applying different DC potentials along the device so as to provide a DC potential difference along the device that urges the ions to exit the device. The potentials applied to the device may be controlled such that analyte ions enter the device through one of the end-plate lenses and the product ions exit the device through the other of the end-plate lenses. Alternatively, the potentials applied to the device may be controlled such that analyte ions enter the device through one of the end-plate lenses and the product ions exit the device through the same end-plate lens. Alternatively, ions may be urged through the device by other means, such as by a gas flow or by entering the device with sufficient energy that the product ions continue in the same direction and exit the device. Ions that exit the device may be analysed in an ion mobility analyser and / or a mass analyser, such as a Time of Flight mass analyser.. In known ion-electron reaction devices the magnets are not used to focus the ions passing therethrough. Rather, in known devices the magnets are mounted on stainless steel electrodes, which substantially shield the axis along which ions travel from any electric field from the magnets. Therefore, unlike the preferred embodiments of the present invention, in known devices the magnets themselves are not directly used as focussing electrodes. The inner diameter of each magnet may be constant along the length of the magnet. Alternatively, the inner diameter may decrease as a function of distance from one axial end of the magnet towards the other axial end of the magnet, and optionally then increase towards said other end of the magnet. For example, the radially inner surface of each magnet may have a shape corresponding to the radially inner surface of a ring torus.

[0125] The dimensions and spacing of the magnets may be specially configured, as will be described in more detail below. The magnets may have the same inner diameter, and optionally the same outer diameter, as the ion-guiding electrodes. The inner diameters of the magnets and ion-guiding electrodes are preferably relatively small, as this allows more effective tuning of the device.

[0126] The inventors have developed techniques that may be used to determine the dimensions and spacing of the magnets that provide a magnetic field along the central axis, which is the superposition of the magnetic fields from both magnets, that is highly homogenous. This is particularly beneficial in electron-reaction devices and such techniques are described below.

[0127] Fig. 3 shows an example of a ring magnet and illustrates the variables that define the magnetic field along an axis that extends through the centre of the bore through the magnet. More specifically, the illustrated magnet is a permanent magnet having its north pole (N) and south pole (S) arranged at opposite ends, in a direction along the axis. The illustrated distance D represents the length of the magnet along the axis. The distance Ri represents the inner radius of the magnet and the distance Ro represents the outer radius of the magnet. The illustrated parameter z represents the distance along the axis from an axial end of the magnet.

[0128] The following equation provides an analytical simplification of the magnetic field B on the axis of the magnet in Fig. 3, where the magnet has a remanence field Br:

[0129] For a pair of spaced apart ring magnets having central axes that are co-linear, such as shown in Fig. 1, the magnetic field along the central axis is a superposition of the magnetic fields from both magnets. The magnetic field for each magnet, as a function of position along the axis z, inner radius Ri and outer radius Ro, can be determined from the equation above. Accordingly, the magnetic field of a first of the magnets, B1(z,Ri,Ro), is given by: where Ro is the outer radius of the magnet, in mm; Ri is the inner radius of the magnet, in mm; D is the length of the magnet along the axis, in mm; pitch is the distance along the axis from the centre of one magnet to the centre of the other magnet, in mm; Br is the remanence field of the magnet, which is independent of the magnet geometry, in Tesla; and z is the position along the axis (in mm), where z=0 is the centre point between the two magnets.

[0130] Similarly, the magnetic field of the other magnet, B2(z,Ri,Ro), is given by:

[0131] Figs. 4A-4C show the magnetic fields due to the magnets when the parameters have the following values: Ro for each magnet is 12.5 mm; Ri for each magnet is 4 mm; D is 6 mm; the pitch is 30 mm; and Bris 2 T. More specifically, Fig. 4A shows a plot 16 of the magnetic field due to the first magnet as a function of position z along the axis, Fig. 4B shows a plot 18 of the magnetic field due to the other magnet as a function of position z along the axis, and Fig. 4C shows both of these plots along with a plot 20 of the total magnetic field (in Tesla) due to the two magnets as a function of position z along the axis.

[0132] The equation for the total magnetic field as a function of position z along the axis is given by summing the equation above for the magnetic field of the first magnet, B1(z,Ri,Ro), with the equation above for the magnetic field of the other magnet, B2(z,Ri,Ro). The total magnetic field is therefore given by:

[0133] If the above equation for the total magnetic field is expanded to a series in z, and terms above the second order of z (i.e. above z2) are ignored, then the equation for the total magnetic field is provided as follows: where F1 is the coefficient of the z2term and is given by:

[0134] In order to obtain a substantially homogenous magnetic field along the axis between the magnets, it is required for the second order z2term in the above equation for the total magnetic field to be zero. This requires the coefficient of the z2term, F1 , to be zero.

[0135] The numerical solution for any given one of the variables in F1 can be found that provides the coefficient F1 with a value of zero, when the other variables are allocated fixed values. For example, it is possible to numerically solve the equation for F1 so as to determine the value of Ri that gives a value of F1 =0, when the variables D, pitch and Ro have fixed, selected values.

[0136] Fig. 5 shows a plot that represents the numerical solution for the magnet inner radius Ri for various different magnet outer radii Ro that together provide the coefficient F1 with a value of zero, when the pitch is fixed at 30 mm and the magnet length D is fixed at 6 mm. In this example the initial estimate for the value of Ri was 4 mm. The numerical solution for Ri that gives F1=0 was then determined for incremental values of Ro between 7 and 15 mm, e.g. by incrementing the value of Ro by 0.1 mm each time from 7.0 mm, 7.1 mm, 7.2 mm etc. up to 15 mm. The plot in Fig. 5 correlates the values of Ro and Ri that provide the coefficient F1 with a value of zero, for the fixed values of pitch and D mentioned above. For example, it can be seen from Fig. 5 that when Ro is 12.5 mm, the value of Ri that provides the coefficient F1 with a value of zero is 5.25 mm.

[0137] Fig. 6 shows four plots of the total magnetic field due to the two magnets as a function of position z, where the total magnetic field has been calculated based on the equation above. All of the plots have been calculated using values of Ro = 12.5 mm, D = 6 mm and pitch = 30 mm, but the four different plots have been calculated using four different respective values of Ri. More specifically, plot 22 was calculated using Ri = 2 mm, plot 24 was calculated using Ri = 4 mm, plot 26 was calculated using Ri = 5.25 mm, and plot 28 was calculated using Ri = 7 mm. The plots are only illustrated over a range of z from -5 mm to +5 mm, as in the embodiments described above this is the region in which the ion-electron reactions primarily take place and in which the magnetic field is desired to be highly homogenous.

[0138] As can be seen from Fig. 6, plot 26 has the most uniform magnetic field at the central region between the magnets, i.e. the region around z=0. This is somewhat expected, as plot 26 was calculated using a value of Ri = 5.25 mm and a value of Ro=12.5 mm, which provide the coefficient F1 with a value of 0, as is shown in Fig. 5.

[0139] As mentioned above, the numerical solution for any given one of the variables in F1 can be found that provides the coefficient F1 with a value of zero, when the other variables are allocated fixed values. Accordingly, it is also, or alternatively, possible to numerically solve the equation for F1 so as to determine the value of D that gives a value of F1 =0, when the variables Ri, pitch and Ro have fixed selected value. Similarly, it is possible to numerically solve the equation for F1 so as to determine the value of pitch that gives a value of F1 =0, when the parameters D, Ri and Ro are fixed. Similarly, it is possible to numerically solve the equation for F1 so as to determine the value of Ro that gives a value of F1 =0, when the parameters D, pitch and Ri are fixed.

[0140] As described above, the equation for F1 may be numerically solved so as to determine the values of Ri that gives a value of F1 =0, for a plurality of different respective values of Ro, when pitch and D have fixed selected values. Additionally, or alternatively, the equation for F1 may be numerically solved so as to determine the values of Ri that gives a value of F1 =0, for a plurality of different respective values of D, when pitch and Ro have fixed selected values. Additionally, or alternatively, the technique may numerically solve the equation for F1 so as to determine the values of Ri that gives a value of F1 =0, for a plurality of different respective values of pitch, when D and Ro have fixed selected values. Additionally, or alternatively, the technique may numerically solve the equation for F1 so as to determine the values of Ri that gives a value of F1 =0, for a plurality of different respective values of Ro, when D and pitch have fixed selected values. This provides a plurality of different combinations of values for the four variables, where each combination provides a value of F1=0. One of these combinations may then be selected based on one or more criteria, such as by selecting the combination that allows the ion-electron interaction device to be fitted into a spectrometer in an optimal manner. For example, the values of pitch and / or Ro for the ion-electron interaction device may be restricted by the dimensions of the spectrometer that it is to be arranged within. The ion-electron interaction device may then be manufactured such that the magnets therein have the geometry and spacing defined by the selected combination of values for the variables.

[0141] It can be seen from plot 26 in Fig. 6 that the magnetic field appears relatively homogenous when Ri is 5.25 mm and Ro is 12.5 mm. The level of homogeneity can be quantified by defining it as the sum of the absolute deviations of the magnetic field from the mean magnetic field, for positions of z between -Zmax and Zmax, where these positions are the z positions at which it is desired for the ion-electron reactions to take place. As described above, in the above example -Zmax is -5 mm and Zmax is 5 mm.

[0142] In the above embodiments the total magnetic field for the two magnets is symmetrical about z=0 and so in order to determine the level of homogeneity of the total magnetic field it is only necessary to consider the magnetic field between z = 0 and z = Zmax. Accordingly, it is only necessary to determine the mean magnetic field, mean B(z,Ri,Ro), over this region, which is given by:

[0143] Fig. 7A illustrates the total magnetic field 20 due to the two magnets as a function of position z between -Zmax and Zmax, and also illustrates the mean magnetic field 30 over this region, for the example of plot 26 in Fig. 6. It will be appreciated that the magnetic field only appears more variable in Fig. 7A than Fig. 6 because the scales on the y-axes are different in these Figures.

[0144] The deviation of the total magnetic field from the mean magnetic field, as a function of z, may be defined as the total magnetic field minus the mean magnetic field, i.e. by:

[0145] Fig. 7B illustrates a plot of the deviation of the total magnetic field 32 relative to the mean magnetic field 30, as a function of position z for the example of Fig. 7A.

[0146] As explained above, the level of homogeneity can be quantified by defining it as the sum of the absolute deviations of the magnetic field from the mean magnetic field, for positions of z between 0 and Zmax. The percentage inhomogeneity may be defined as the level of homogeneity divided by the mean magnetic field, multiplied by 100. Accordingly, the percentage inhomogeneity, F2, may be defined as: Fig. 8A shows a plot in which the y-axis represents Ro, the x-axis represents Ri and the intensity of the shading represents the value of the percentage inhomogeneity F2 for the values of Ro and Ri. The plot also includes contour lines, where each contour line indicates the combinations of Ro and Ri that provide the percentage inhomogeneity that the contour line is labelled with. For example, it can be seen that the region of the plot that extends diagonally between the top left and bottom right corners represents percentage inhomogeneity of < 10%. Fig. 8B shows a plot of the same data as in Fig. 8A, except that contours representing a greater number of percentage inhomogeneity values are shown. It was determined from this plot that the central region provides a percentage inhomogeneity of < 2%.

[0147] The values of Ro and Ri for the ion-electron interaction device may be selected so that the percentage inhomogeneity is below a preselected value, such as < 10%.

[0148] The value of Ri that provides the minimum value of percentage inhomogeneity F2 may be determined, for a given value of Ro, from the above equation for F2. The minimum percentage inhomogeneity F2 may be determined numerically. For instance, in the example described above, where Ro is 12.5 mm, D = 6 mm and pitch = 30 mm, the lowest percentage inhomogeneity F2 may be determined numerically starting with an initial estimate for Ri of 3 mm and incrementing the value of Ri until the minimum percentage inhomogeneity F2 is found. In this example the minimum percentage inhomogeneity F2 was determined to be 1.9% when Ri = 4.47mm.

[0149] In contrast, as described above, when the value of Ri is determined as the value when the coefficient of the z2term of the magnetic field, F1, is zero (for Ro = 12.5 mm, D = 6 mm and pitch = 30 mm), the value of Ri was determined to be 5.25 mm and the corresponding percentage inhomogeneity F2 was 7.1%.

[0150] The technique for determining Ri based on minimising the percentage inhomogeneity F2 therefore obtains a value for Ri that slightly smaller and an improved percentage inhomogeneity than when Ri is determined based on the coefficient F1 being zero. This is thought to be because higher order terms of the magnetic field, such as 4thorder and above terms were not considered in the technique where Ri is determined based on the coefficient F1 being zero.

[0151] In the above examples the magnetic field between -Zmax and + Zmax is strong enough to provide very effective radial trapping of electrons with <10% variation in field.

[0152] Although ion-electron reaction devices are known that have two ring magnets for providing radial confinement of electrons, such devices are relatively poor at confining electrons, e.g. as will be described in relation to Figs. 9A and 9B.

[0153] Fig. 9A shows an example of the geometric configuration of two ring magnets in an ion-electron reaction device not according to the invention. The magnets each have a length of 7 mm, an inner diameter of 18 mm, an outer diameter of 25 mm, and a pitch of 13 mm. Fig. 9B a plot of the magnetic field 34 along the central axis due to a first of the magnets as a function of position z along the axis, a plot of the magnetic field along the central axis due to the other of the magnets 36 as a function of position z along the axis, and a plot of the total magnetic field 38 due to the two magnets as a function of position z along the axis. It can be seen that the superposition of the near fields, rather than far fields, of the magnets results in a relatively weak field in the central region. This low field strength originates from the magnets having a relatively large inner diameter, with less magnetic material. The magnitude of the field along the axis is also significantly less homogenous than the embodiments of the present invention, and this is detrimental to the electron trapping as electrons in the weaker fields rotate about the axis with larger diameters. It can be seen that the magnetic field is inhomogeneous and varies between 0.026T and 0.05T, due to the mismatched field functions when summing the two ring magnet fields.

[0154] Although the present invention has been described with reference to various embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as set forth in the accompanying claims.

[0155] Embodiments have been described in which the equation for the total magnetic field is expanded and the geometric variables of the magnet are determined at which the coefficient of the second order term, F1, is zero. However, instead the geometric variables of the magnet may be determined at which the coefficient of a higher order term, such as the fourth order term z4, is minimised or zero.

[0156] Although an example has been described, in relation to coefficient F1 , in which a polynomial expansion series of the equation for the magnetic field along the axis is obtained, it is contemplated that an alternative expansion series, such as a Fourier series may be used.

[0157] When determining solutions for F1 and F2, various variables have been described as being maintained fixed. It will be appreciated that the magnet material is also maintained constant in these calculations.

[0158] Although embodiments of the ion-electron reaction device has been described in which no RF voltages are applied to the electrodes and magnets of the device, embodiments are contemplated in which one or more RF voltage may be applied to one or more of the electrodes and / or magnets in the device, e.g. in order to radially confine ions to the central axis through the device.

[0159] Embodiments have been described in which the magnets are permanent magnets. However, it is contemplated that one or more of the magnets may instead be an electromagnet. Alternatively, a pair of electromagnets may be provided in addition to the two permanent magnets, e.g. for correcting higher order inhomogeneities of the permanent magnets. The geometries and locations of these electromagnets may be selected based on the techniques described above.

[0160] Although certain magnet configurations have been described herein, it will be appreciated that any magnet shape configuration may be used and the equations altered accordingly. For example, less preferably, the two magnets may have different lengths and / or outer radii, and / or inner radii.

[0161] The device described herein may comprise a plurality of electrodes located between the two magnets. One or more RF and / or DC voltages may be applied to the electrodes in order to trap the ions within the device. After a desired period of time, the one or more RF and / or DC voltages may be adjusted to cause the ions to exit the device. The plurality of electrodes may be arranged so that the magnetic field lines along the axis of the device are not affected when the one or more RF and / or DC voltages are applied to the plurality of electrodes or otherwise.

[0162] Although the devices described above have been described as confining electrons for reaction with ions, it is contemplated that they may instead confine other particles that are able to be confined by magnetic fields, such as other charged particles.

Claims

173982 / 02v1Claims:

1. A method of manufacturing a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device, the method comprising: i) obtaining a relationship that represents the magnetic field along the axis of the device due to the two magnets as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other, wherein the relationship is a polynomial having a second and / or higher order term of z, and wherein the value of the coefficient of the second and / or higher order term of z is dependent on said dimensions of the magnets and their spacing from each other; ii) determining a combination of values of said variables that provide said coefficient with a value that is less than or equal to a pre-selected value; and iii) manufacturing said device comprising two magnets such that the dimensions of the magnets and their spacing from each other correspond to values that are represented by said combination of values determined in step ii).

2. The method of claim 1, wherein step ii) comprises determining the combination of values of said variables that provide said coefficient with a value of zero.

3. The method of claim 1 or 2, wherein each of the two magnets in the device is a cylindrical magnet having an axis therethrough, and wherein the axes through the magnets are colinear with said axis of the device.

4. The method of claim 3, wherein said dimensions of each magnet that are represented by said variables include an inner radius of the magnet, an outer radius of the magnet and a length of the magnet in a direction along said axis of the device.

5. The method of any preceding claim, wherein obtaining said relationship comprises determining an expression for the magnetic field due to the two magnets at the axis of the device as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other, and expanding said expression in terms of z so as to obtain said relationship that is a polynomial.

6. The method of claim 5, wherein the two magnets are cylindrical magnets having the same dimensions and the same remanence field, and wherein the expression for the magnetic field due to the two magnets at the axis of the device is given by:where Ro is the outer radius of each magnet, in mm; Ri is the inner radius of each magnet, in mm; D is the length of each magnet along the axis, in mm; pitch is the distance along the axis from the centre of one magnet to the centre of the other magnet, in mm; Br is the remanence field of each magnet, in Tesla; and z is the position along the axis (in mm), where z=0 is the centre point between the two magnets.

7. The method of claim 6, wherein the coefficient of the second order term of z, F1 is given8. The method of any preceding claim, wherein step ii) comprises selecting fixed values for all of the variables except for one of the variables, and using these fixed values to numerically determine the value for said one of the variables that provides said coefficient with a value that is less than or equal to said pre-selected value.

9. The method of any preceding claim, wherein the two magnets are cylindrical magnets having the same dimensions, and wherein step ii) comprises: a) selecting fixed values for the outer radius of each magnet, the length of each magnet along the axis, and the spacing between the magnets; and then using these fixed values to numerically determine the value for the inner radius of each magnet that provides said coefficient with said value that is less than or equal to said pre-selected value; and / or b) selecting fixed values for the outer radius of each magnet, the length of each magnet along the axis, and the inner radius of each magnet; and then using these fixed values to numerically determine the value for the spacing between the magnets thatprovides said coefficient with said value that is less than or equal to said pre-selected value.

10. The method of any preceding claim, wherein the device is an ion-electron reaction device and the step of manufacturing said device comprising providing the device with an electron source for supplying electrons to the axis of the device such that they become radially confined about the axis of the device by the magnetic field along the axis due to the two magnets.

11. The method of claim 10, wherein the electron source comprises a filament and a voltage supply connected to the filament such that when the voltage supply is activated electrons are released from the filament; optionally wherein the filament extends to a location that is between the magnets so as to release electrons onto a central axis of the device.

12. The method of claim 11, wherein the filament extends through a first electrode or electrode portion to a location that is between the magnets for releasing electrons onto a central axis of the device; and wherein one or more second electrodes or electrode portions are arranged radially inward of the first electrode or electrode portion and around the filament so as to block the electric field generated by the filament.

13. The method of claim 11 or 12, wherein the filament comprises a loop that extends around the central axis, optionally such that ions and / or electrons are able to pass along the central axis and through the loop.

14. The method of any one of claims 10-13, wherein the step of manufacturing said device comprises: providing the device with electrically conductive magnets or with magnets having electrically conducting surfaces thereon; and providing one or more voltage sources for applying voltages to the electrically conductive magnets or to the electrically conducting surfaces thereon for confining the electrons between the magnets; optionally where the voltages are DC voltages.

15. The method of any preceding claim, wherein the step of manufacturing said device comprises: providing the device with one or more ion-guiding electrode between the magnets; and providing one or more voltage sources for applying one or more voltages to the ion-guiding electrodes for focusing ions passing through the device onto the axis; optionally wherein the one or more voltages are DC voltages.

16. A method of designing a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device, the method comprising: i) obtaining a relationship that represents the magnetic field along the axis of the device due to the two magnets as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from eachother, wherein the relationship is a polynomial having a second and / or higher order term of z, and wherein the value of the coefficient of the second and / or higher order term of z is dependent on said dimensions of the magnets and their spacing from each other; ii) determining a combination of values of said variables that provide said coefficient with a value that is less than or equal to a pre-selected value; and iii) designing said device comprising two magnets so that the dimensions of the magnets and their spacing from each other correspond to values that are represented by said combination of values determined in step ii).

17. A device for reacting ions with other charged particles that has been manufactured according to the method of any one of claims 1-15.

18. A device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device; wherein the magnets have dimensions and are arranged relative to each other such that the magnetic field along the axis of the device due to the two magnets is represented by a relationship that represents the magnetic field as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other, wherein the relationship is a polynomial having a second and / or higher order term of z, wherein the value of the coefficient of the second and / or higher order term of z is dependent on said dimensions of the magnets and their spacing from each other; and wherein the combination of values of said variables provide said coefficient with a value that is substantially zero.

19. The device of claim 18, wherein each magnet is a cylindrical magnet having an outer radius of about 12.5 mm, an inner radius of about 4 mm, a length along the axis of about 6 mm, and a distance from the centre of one of the magnets to the centre of the other of the magnets of about 30 mm.

20. A device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device; wherein each magnet is a cylindrical magnet having an outer radius of about 12.5 mm, an inner radius of about 4 mm, a length along the axis of about 6 mm, and a distance from the centre of one of the magnets to the centre of the other of the magnets of about 30 mm.

21. A method of reacting ions with other charged particles comprising: providing a device as claimed in claim 18, 19 or 20; confining said other charged particles in said device using the magnetic field due to the magnets; and providing ions in the device so as to react with the charged particles.

22. The method of claim 21 , wherein the device comprises a plurality of electrodes located between the two magnets and the method comprises applying one or more RFand / or DC voltages to the plurality of electrodes in order to trap ions within the device such that the other charged particles react with the ions.

23. A method of manufacturing a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device, the method comprising: i) obtaining a relationship that represents the magnetic field along the axis of the device due to the two magnets as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other, wherein the relationship is an expansion series of an equation representing the magnetic field along the axis, and wherein the value of a coefficient in the expansion series is dependent on said dimensions of the magnets and their spacing from each other; ii) determining a combination of values of said variables that provide said coefficient with a value that is less than or equal to a pre-selected value; and iii) manufacturing said device comprising two magnets such that the dimensions of the magnets and their spacing from each other correspond to values that are represented by said combination of values determined in step ii).

24. A method of manufacturing a device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device, the method comprising: i) obtaining a relationship that represents the homogeneity of the magnetic field along the axis due to the two magnets, over at least a portion of the distance between the magnets, as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other; wherein the homogeneity of the magnetic field is the sum of the absolute deviation of the magnetic field from the mean value of the magnetic field over said at least a portion of the distance between the magnets, and where said deviation of the magnetic field at any given position along the axis is given by the magnetic field at that position minus said mean value of the magnetic field; ii) determining a combination of values of said variables that provide said homogeneity with a value that is less than or equal to a pre-selected value; and iii) manufacturing said device comprising two magnets such that the dimensions of the magnets and their spacing from each other correspond to values that are represented by said combination of values determined in step ii).

25. The method of claim 24, wherein the pre-selected value is < 0.20, < 0.15, or < 0.10.

26. The method of claim 24 or 25, wherein each of the two magnets in the device is a cylindrical magnet having an axis therethrough, and wherein the axes through the magnets are colinear with said axis of the device; optionally wherein said dimensions of each magnet that are represented by said variables include an inner radius of the magnet, an outer radius of the magnet and a length of the magnet in a direction along said axis of the device.

27. A device for reacting ions with other charged particles, wherein the device comprises two magnets that are spaced apart along an axis of the device; wherein the magnets have dimensions and are arranged relative to each other such that the homogeneity of the magnetic field along the axis due to the two magnets, over at least a portion of the distance between the magnets, is represented by a relationship that represents the homogeneity of the magnetic field as a function of position z along the axis and as a function of variables that represent the dimensions of the magnets and their spacing from each other; wherein the homogeneity of the magnetic field is the sum of the absolute deviation of the magnetic field from the mean value of the magnetic field over said at least a portion of the distance between the magnets, and where said deviation of the magnetic field at any given position along the axis is given by the magnetic field at that position minus said mean value of the magnetic field; and wherein the combination of values of said variables provide said homogeneity with a value that is < 0.20, < 0.15, or < 0.10.

28. The method or device of any one of claims 24-27, wherein the minimum magnetic field at the axis, over said at least a portion of the distance between the magnets, is greater than 0.01 T, 0.05 T, 0.1 T or 0.2 T.

29. An ion-electron reaction device for reacting ions with electrons, comprising: two magnets having apertures therethrough that are spaced apart such that an axis passes through the apertures, wherein the magnets are electrically conductive or have an electrically conductive surface thereon; an electron source for supplying electrons to the axis of the device such that they become radially confined about the axis by a magnetic field due to the two magnets; and one or more voltage sources for applying voltages to the electrically conductive magnets or to the electrically conducting surfaces thereon; wherein the magnets, or the electrically conducting surfaces thereon, are arranged within the device such that when the voltages are applied thereto, electric fields are generated within the apertures of the magnets for focusing ions passing therethrough onto the axis.

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