High voltage RF generator for ion optics

Abstract

To improve analytical instruments such as a mass spectrometer.SOLUTION: An analytical instrument comprise an RF generator configured to generate an RF voltage having a first frequency, a first transformer having a primary winding and a secondary winding, a first ion optical device, a second transformer having a primary winding and a secondary winding, an amplifier having an input and an output, a second ion optical device, and a phase difference detector unit having a first input and a second input. The analytical instrument is configured such that at least part of a secondary LC circuit has a variable inductance, and the inductance of the at least part of the secondary LC circuit varies in dependence on a magnitude of the output DC current or voltage of the phase difference detector unit. Thereby, the second resonant frequency varies in dependence on the magnitude of the output DC current or voltage of the phase difference detector unit.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to analytical instruments such as mass spectrometers, and in particular to analytical instruments comprising ion optical devices such as multipole ion optical devices. [Background technology]

[0002] For the ion optics of an analytical instrument it is sometimes necessary to have several RF powered ion optical devices, such as multipoles, that are mechanically and electrically separated but operate at the same RF frequency with a fixed (preferably zero) phase between them. In this case the amplitudes of the RF voltages applied to the different ion optical devices may be different and may be set independently.

[0003] To reduce the power consumption supplied to the RF generator, such configurations are typically designed based on the LC resonance principle, utilizing the inductance of the RF transformer in the generator and the parasitic capacitance of the ion optical device fed from this generator.

[0004] For two different ion optical devices, the self-resonant frequencies may differ significantly, which means that it is not possible to power them at the same frequency and a given phase between them without adjusting the parameters of the resonant tank in one of the generators.

[0005] Existing technical solutions to this problem have been developed for small RF voltage amplitudes, but the voltages required for the ion optics can be several kilovolts, and the only really known way to tune the resonant circuit is to use a variable HV capacitor with an air dielectric.

[0006] However, this solution has several drawbacks: (i) high-voltage capacitors have significant mass and size; (ii) even after tuning to resonance with the master generator, the phase between the two generators varies uncontrollably; and (iii) a bulky electromechanical device such as a stepper motor is required to implement automatic frequency control using a Phase Locked Loop (PLL) circuit.

[0007] It is believed that there is still room for improvement in analytical instruments such as mass spectrometers. Summary of the Invention

[0008] A first aspect provides an analytical instrument according to claim 1.

[0009] Analytical equipment: an RF generator configured to generate an RF voltage having a first frequency; a first transformer having a primary winding and a secondary winding, the RF generator being coupled to the primary winding of the first transformer; a first ion optical device coupled to a secondary winding of the first transformer; and a second transformer having a primary winding and a secondary winding; an amplifier having an input and an output, wherein a first signal from an RF generator or from a first transformer is provided to the input of the amplifier (7), and the output of the amplifier is coupled to a primary winding of a second transformer; a second ion optical device coupled to a secondary winding of the second transformer; and a phase difference detector unit having a first input and a second input, the phase difference detector unit configured to output a DC current or a voltage proportional to a phase difference between signals received at the first input and the second input, the first signal being provided to the first input of the phase difference detector and a second signal from a second transformer being provided to the second input of the phase difference detector unit; a secondary winding of the first transformer and the first ion optical device form a primary LC circuit having a first resonant frequency, and a first frequency of an RF voltage generated by the RF generator is configured to correspond to the first resonant frequency; The secondary winding of the second transformer and the second ion optical device form a secondary LC circuit having a second resonant frequency, and the analytical instrument is configured such that at least a portion of the secondary LC circuit has a variable inductance, and the analytical instrument is configured such that the inductance of at least a portion of the secondary LC circuit varies depending on the magnitude of the DC current or voltage output from the phase difference detector unit, thereby causing the second resonant frequency to vary depending on the magnitude of the DC current or voltage output from the phase difference detector unit.

[0010] Thus, embodiments provide purely electrical control of the inductance in the secondary LC circuit, preferably by controlling the inductance of the coil.

[0011] The analytical instrument may be configured such that the first ion optical device receives a first operating RF voltage having a first frequency and the second ion optical device receives a second operating RF voltage having the first frequency. The analytical instrument may be configured such that a variation in the second resonant frequency in response to a magnitude of an output DC current or voltage of the phase difference detector unit creates a negative feedback loop, thereby reducing or eliminating any phase difference between the first operating RF voltage and the second operating RF voltage.

[0012] The secondary winding of the first transformer may have a first inductance, the first ion optical device may have a first self-capacitance, and the first inductance and the first self-capacitance together may form a primary LC circuit having a first resonant frequency.

[0013] The secondary winding of the second transformer may have a variable inductance, and the device may be configured such that the inductance of the secondary winding of the second transformer varies depending on the magnitude of the DC current or voltage output by the phase difference detector unit.

[0014] The second transformer may comprise one or more transformers, and the apparatus may be configured such that the inductance of a secondary winding of the second transformer comprising the one or more transformers varies depending on the magnitude of the DC current or voltage output by the phase difference detector unit.

[0015] The second ion optical device may have a second self-capacitance, and the variable inductance and the second self-capacitance together may form a secondary LC circuit having a second resonant frequency.

[0016] The analytical instrument may further comprise an inductor having a variable inductance, the DC current or voltage outputted from the phase difference detector unit is provided to the inductor, the inductor being configured such that its inductance varies depending on the magnitude of the DC current or voltage outputted from the phase difference detector unit, and the inductor is coupled to a secondary winding of a second transformer. Thus, the secondary winding of the second transformer may have a second inductance, the second ion optical device may have a second self-capacitance, and the second inductance, the variable inductance and the second self-capacitance may together form a secondary LC circuit having a second resonant frequency.

[0017] The inductor may be formed from a converter having a primary winding and a secondary winding, and the output DC current or voltage of the phase difference detector unit is provided to the primary winding of the converter, and the secondary winding of the converter is coupled to the secondary winding of the second transformer.

[0018] The secondary winding of the converter may be connected in series with the secondary winding of the second transformer, or the secondary winding of the converter may be connected in parallel with the secondary winding of the second transformer.

[0019] The second transformer (e.g., one or more of the one or more transformers) or inductor (i.e., the converter) may include a magnetic core, and the output DC current or voltage of the phase difference detector unit may be configured to magnetize the magnetic core (e.g., by providing an output DC current to a primary winding of the converter), such that the inductance of the secondary winding of the second transformer or the inductance of the inductor varies depending on the magnitude of the output DC current of the phase difference detector unit.

[0020] The analytical instrument may be configured such that the first ion optical device receives a first operating RF voltage having a first frequency, and the first signal corresponds to the first operating RF voltage. The first signal may be generated by a first feedback module coupled to an RF generator, a primary winding of a first transformer, or a secondary winding of the first transformer.

[0021] The first signal may be provided to an input of the amplifier via a phase shifter.

[0022] The analytical instrument may be configured such that the second ion optical device receives a second operating RF voltage having a first frequency, and the second signal corresponds to the second operating RF voltage. The second signal may be generated by a second feedback module coupled to a primary winding of the second transformer or a secondary winding of the second transformer.

[0023] The phase difference detector unit may comprise a phase detector configured to output a voltage proportional to a phase difference between signals received at the first and second inputs, and a voltage-to-current converter configured to convert the output voltage into an output DC current.

[0024] The phase difference detector unit may be configured such that the magnitude range of the output DC current is controllable.

[0025] The second transformer may include a magnetic core or may be air core.

[0026] The first ion optical device may be a first multipole and / or the second ion optical device may be a second multipole, the first ion optical device may be a first quadrupole ion trap and / or the second ion optical device may be a second quadrupole ion trap.

[0027] The first ion optical device may be configured such that a first operating RF voltage generates a first RF field that confines ions in a trapping region of the first ion optical device. The second ion optical device may be configured such that a second operating RF voltage generates a second RF field that confines ions in a trapping region of the second ion optical device. The apparatus may be configured such that the first operating RF voltage and the second operating RF voltage have substantially the same frequency and matched phase.

[0028] The first ion optical device may be disposed in a region of relatively low gas pressure and the second ion optical device may be arranged in a region of relatively high gas pressure. The apparatus may include a gas conductance restriction configured to restrict flow of gas from the region of relatively high gas pressure to the region of relatively low gas pressure, the gas conductance restriction having an opening that allows ions to pass from the second ion optical device to the first ion optical device (and / or vice versa).

[0029] The instrument may be configured such that (i) ions may be stored and / or processed (e.g., cooled and / or fragmented) in the second ion optical device, (ii) stored and / or processed ions may pass from the second ion optical device to the first ion optical device, and (iii) ions may be ejected from the first ion optical device. The first ion optical device and / or the second ion optical device may form part of a mass analyzer, and the instrument may be configured such that ions may be ejected from the first ion optical device into the mass analyzer for mass analysis. The mass analyzer may be a time-of-flight (ToF) mass analyzer, such as a multi-reflection time-of-flight (MR-ToF) mass analyzer, and the instrument may be configured such that ions may be ejected from the first ion optical device into the flight path of the time-of-flight (ToF) mass analyzer.

[0030] The analytical instrument may be or may comprise a mass spectrometer.

[0031] Various embodiments will now be described in more detail with reference to the accompanying drawings. [Brief description of the drawings]

[0032] [Figure 1] 1 illustrates a schematic diagram of an analytical instrument according to an embodiment; [Diagram 2] 2 shows a schematic diagram of details of an analytical instrument according to an embodiment; [Diagram 3] 1 illustrates schematic details of a synchronized high voltage resonant RF generator for ion optics of an analytical instrument according to an embodiment; [Figure 4] 1 illustrates schematic details of a synchronized high voltage resonant RF generator for ion optics of an analytical instrument according to an embodiment; [Diagram 5] 1 illustrates schematic details of a synchronized high voltage resonant RF generator for ion optics of an analytical instrument according to an embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] 1 illustrates a schematic diagram of an analytical instrument, such as a mass spectrometer, that may be constructed and operated in accordance with an embodiment. As shown in FIG. 1, the analytical instrument includes an ion source 15, one or more ion transmission stages 20, and an analyzer 30.

[0034] The ion source 15 is configured to generate ions from the sample. The ion source 15 may be any suitable continuous or pulsed ion source, such as an Electrospray Ionisation (ESI) ion source, a MALDI ion source, an Atmospheric Pressure Ionisation (API) ion source, a plasma ion source, an electron ionisation source, a chemical ionisation source, etc. In some embodiments, two or more ion sources may be provided and used. The ions may be any suitable type of ion to be analysed, for example small and large organic molecules, biomolecules, DNA, RNA, proteins, peptides, fragments thereof, etc.

[0035] The ion source 15 may optionally be coupled to a separation device, such as a liquid chromatography separation device, a gas chromatography separation device, or a capillary electrophoresis separation device (not shown), whereby the sample that is ionized in the ion source 15 comes from the separation device.

[0036] The ion transport stage 20 is disposed downstream of the ion source 15 and may include an atmospheric pressure interface, as well as one or more ion guides, lenses, traps and / or other ion optical devices configured to enable some or all of the ions generated by the ion source 15 to be transported from the ion source 15 to the analyzer 30. The ion transport stage 20 may include any suitable number and configuration of ion optical devices, for example, optionally including any one or more of one or more RF and / or multipole ion guides, one or more ion guides for cooling ions, one or more mass-selective ion guides, etc.

[0037] The mass analyzer 30 is positioned downstream of the ion transmission stage 20 and is configured to receive ions from the ion transmission stage 20. The mass analyzer is configured to analyze the ions to determine their mass to charge ratio (m / z). The analyzer 30 may be any suitable mass analyzer, such as a time-of-flight (ToF) mass analyzer, an ion trap mass analyzer, a quadrupole mass analyzer, etc.

[0038] 1 is merely schematic, and the analytical instrument can, and in embodiments does, include any number of one or more additional components. For example, in some embodiments the analytical instrument includes a collision or reaction cell for fragmenting or reacting ions, and the ions analyzed by mass analyzer 30 can be fragment or product ions produced by fragmenting or reacting parent ions generated by ion source 15.

[0039] 1, the instrument is under the control of a control unit 50, such as a suitably programmed computer, which controls the operation of the various components of the instrument, including the ion transmission stage 20 and the analyzer 30. The control unit 50 may also receive and process data from the various components, including the analyzer 30.

[0040] Figure 2 illustrates in schematic detail one exemplary mass spectrometer including an MR-ToF mass analyzer that may be constructed and operated in accordance with embodiments, it being understood that the apparatus shown in Figure 2 is a non-limiting example and that many variations are possible.

[0041] In the embodiment shown in Figure 2, the ion source 15 of the instrument is an electrospray ionisation (ESI) ion source. The instrument includes a transfer tube 21, an ion funnel 22, a quadrupole pre-filter ion guide 23 and a vacuum interface including a "bent flat pole" ion guide 24. The bent flat pole ion guide 24 may be of the design described in US Patent No. 9,536,722.

[0042] The instrument also includes a mass filter in the form of a quadrupole mass filter 26, an ion trap 28 in the form of a curved linear ion trap ("C-trap"), and a collision cell 29 in the form of an ion routing multipole ("IRM") collision cell. Ions from the ion source 15 may be accumulated in the C-trap 28 and / or the collision cell 29 by opening and closing gate electrodes located in a charge detector assembly 27 that is disposed between the C-trap 28 and the mass filter 26.

[0043] The instrument also includes a first mass analyzer 60 in the form of an orbital ion trap mass analyzer. Once accumulated in the ion trap 28 and / or collision cell 29, the ions may be ejected into the mass analyzer 60. To do this, the ions may be ejected from the trap 28 in a direction orthogonal to the axis of the trap (orthogonal ejection), for example, by applying one or more suitable DC voltages to the ion trap 28.

[0044] A collision or reaction cell 29 is positioned downstream of the ion trap 28. Ions collected in the ion trap 28 may be ejected orthogonally to the mass analyzer 60 without entering the collision or reaction cell 29, or the ions may be transmitted axially to the collision or reaction cell 29 for processing and then the processed ions may be returned to the ion trap 28 for subsequent orthogonal ejection to the mass analyzer 60. This processing may include, for example, fragmenting the ions by collision with a collision gas and / or reagents in the collision cell 29, or further cooling the ions by collision with a gas at a lower energy that fragments the ions.

[0045] The instrument also includes a second mass analyzer 30 in the form of a multi-reflecting time-of-flight (ToF) mass analyzer added to the rear of the instrument. This hybrid instrument is described in more detail in U.S. Pat. No. 10,699,888.

[0046] 2, the instrument includes a multipole ion guide 61 that allows ions to be transported from the collision cell 29 to a time-of-flight mass analyzer 30. Ions are sent from the collision cell 29 through the multipole ion guide 61 to the extraction trap 31 of the mass analyzer 30. The ions are accumulated in the extraction trap 31 and cooled.

[0047] The extraction trap 31 may incorporate two trapping regions, one at relatively high pressure for rapid ion cooling and a second low pressure region for ion extraction. Ions are cooled in the high pressure region and then transported to the low pressure region where they are pulsed into the ToF analyzer via a pair of deflectors 36, 38. Ions oscillate between a pair of mirrors 34, 35, which are tilted relative to each other such that the ion path is slowly deflected and redirected to the detector 33. A compensation stripe electrode 40 counters loss of ion focusing otherwise caused by mirror non-parallelism.

[0048] The mass analyzer depicted in FIG. 2 is particularly preferred, but it will be understood that many alternative mass analyzer configurations are possible. For example, the mass analyzer depicted in FIG. 2 has two mass analyzers 30, 60, but the mass analyzer may have only a single mass analyzer (or may have more than two mass analyzers). In the instrument depicted in FIG. 2, the ToF analyzer 30 is of the tilted mirror type described in U.S. Pat. No. 9,136,101, but it will be understood that any type of ToF analyzer may be used. For example, the analyzer may be a single lens type multi-reflection time-of-flight mass analyzer, such as described in British Patent No. 2,580,089, a linear ToF mass analyzer, an orthogonal acceleration ToF mass analyzer, a reflectron ToF mass analyzer, a closed loop multi-reflection mass analyzer, another type of multi-reflection time-of-flight (MR-ToF) analyzer, etc.

[0049] For the ion optics of a mass spectrometer, it is sometimes necessary to have several RF powered ion optical devices, such as multipoles, that are mechanically and electrically separated but operate at the same RF frequency with a fixed (preferably 0) phase between them. In this case, the amplitudes of the RF voltages applied to the different ion optical devices may be different and may be set independently.

[0050] For example, in one embodiment the extraction trap 31 of the instrument depicted in Figure 2 may be of the design described in co-pending UK patent application No. 2613439 (the contents of which are incorporated herein by reference) having a first multipole ion optical device and a second multipole ion optical device, and it may be desirable to operate the first and second multipole ion optical devices at the same RF frequency with a fixed (preferably zero) phase between them. It will be appreciated that there are many other possible embodiments of analytical instruments having two or more ion optical devices and where it is desirable to operate the ion optical devices at the same RF frequency with a fixed (preferably zero) phase between them.

[0051] It has been recognised that existing solutions that allow the same RF frequency with a fixed (preferably zero) phase difference to be applied to two or more ion optical devices are inadequate for the reasons mentioned above.

[0052] FIG. 3 illustrates a synchronized high voltage resonant RF generator for ion optics of an analytical instrument according to an embodiment.

[0053] As shown in Figure 3, the ion optical system comprises at least two ion optical devices, a first ion optical device 3 and a second ion optical device 13, both of which are powered with RF voltage. In the embodiment depicted in Figure 3, the ion optical devices 3, 13 are both quadrupoles, but in general the ion optical devices 3, 13 can be any suitable type or types of ion optical devices. There can be more than two ion optical devices. In Figure 3, capacitors 4 and 14 are shown as representing the self-capacitance of the quadrupoles 3, 13.

[0054] 3, the master RF generator 1 is tuned to resonate with a resonant tank circuit (also known as an LC circuit) formed by the output inductance and capacitance 4 of the first transformer 2. From the secondary winding of the first transformer 2, a signal corresponding to the operating frequency of the first ion optical device 3 is generated by a feedback module 5, which is sent to a reference input of a phase shifter 6 and a phase detector 8. Alternatively, the feedback module 5 could generate its signal from the master RF generator 1 or from the primary winding of the first transformer 2.

[0055] The phase shifter 6 is used for coarse compensation of the phase difference between the RF voltages applied to the two quadrupoles 3 and 13. Although in Figure 3 the phase shifter 6 is shown as not affecting the signal from the feedback module 5 that is applied to the reference input of the phase detector 8, it is also possible to instead use the phase shifter 6 (or a second phase shifter) to apply coarse phase compensation to the signal sent to the reference input of the phase detector 8.

[0056] The control signal after the phase shifter 6 is amplified by an amplifier 7 and sent to a primary winding of a second transformer 11. The output voltage of the second transformer 11 is fed to a second drive quadrupole 13.

[0057] A secondary winding of a current controlled transformer 10 is connected in series with a secondary winding of a second transformer 11. The sum of the inductance and capacitance 14 of these windings determines the resonant frequency of this second resonant tank circuit (secondary LC circuit).

[0058] Device 10 is a tunable inductor that does not have a conventional primary winding. It contains two identical sections connected only by a control winding. These windings are connected in anti-series so that at the input of the entire winding (the output of converter 9), the RF voltages are subtracted, resulting in a value of zero. Device 10 therefore does not transform the input voltage.

[0059] From the secondary winding of the second transformer 11, the feedback module 12 generates a signal corresponding to the operating frequency of the voltage supplied to the second ion optical device 13, which is sent to a feedback input of the phase detector 8. Alternatively, it is also possible for the feedback module 12 to generate its signal from the primary winding of the second transformer 11.

[0060] A voltage proportional to the phase difference between the RF voltages applied to the quadrupoles from the output of phase detector 8 is converted into a controlled bias current that magnetizes the core of current controlled transformer 10, thereby causing a change in its inductance.

[0061] This in turn leads to a change in the resonant frequency of the secondary LC circuit. Because of the negative feedback in the frequency and phase control loops, this has the effect of reducing the phase difference between the RF voltages, preferably to zero.

[0062] By applying a bias voltage to any converter 9, this phase shift can be varied within a certain range, if desired.

[0063] It will thus be appreciated that in an embodiment, electrical control of the output inductance of the RF transformer in the slave generator (or generators) is provided by magnetizing its magnetic material core with DC, which enables this generator (or generators) to be synchronized with the master generator.

[0064] Various alternatives are possible to the configuration depicted in Figure 3. For example, although Figure 3 depicts a master generator circuit (primary LC circuit) and a single slave generator circuit (secondary LC circuit), it is possible to have multiple slave generator circuits, each driving a respective ion optical device.

[0065] FIG. 3 illustrates one possible configuration of an RF transformer with an electrically adjustable output inductance, although various other embodiments are possible.

[0066] For example, in FIG. 3, the secondary windings of the converter 10 and the second transformer 11 are connected in series, but it is also possible to connect the secondary winding of the inductor 10 in parallel with a portion of the secondary winding of the second transformer 11, which also makes it possible to control the total inductance of these devices 10, 11.

[0067] FIG. 4 shows one such embodiment, where the variable inductance is provided by a parallel connection of a variable inductor 10 to a portion of the secondary winding of a second RF transformer 11.

[0068] It is also possible for the second LC circuit to comprise only a transformer 10 constructed from a larger but even number of coils connected in series with an additional primary winding for connection to the amplifier 7. Figure 5 shows one such embodiment in which a controlled high voltage RF inductor is constructed from several identical elements with variable inductance including a magnetic core, primary and secondary windings, and a control winding. However, comparing Figures 3 and 5, it will be appreciated that the transformer 11 depicted in Figure 3 reduces the number of coils relative to Figure 5, simplifying the drive from the RF generator.

[0069] It will therefore be appreciated that in general the embodiments provide purely electrical control of the inductance in the second high voltage resonant tank circuit (secondary LC circuit), preferably by controlling the inductance of a coil.

[0070] The configuration depicted in Figure 3 has been implemented and fully verified in the development of the mass spectrometer depicted in Figure 2. The phase difference between the RF voltages in the quadrupoles did not exceed 1 degree over the entire applicable range of amplitudes and ambient temperatures. The operating frequency of the generator was about 4 MHz and the output voltage was up to 1800 Vpp.

[0071] Although the invention has been described with reference to various embodiments, it will be understood that various modifications can be made without departing from the scope of the invention as set forth in the appended claims.

Claims

1. An analytical instrument comprising: an RF generator (1) configured to generate an RF voltage having a first frequency; a first transformer (2) having a primary winding and a secondary winding, the RF generator (1) being coupled to the primary winding of the first transformer (2); a first ion optical device (3) coupled to the secondary winding of the first transformer (2); a second transformer (11) having a primary winding and a secondary winding; an amplifier (7) having an input and an output, wherein a first signal from the RF generator (1) or from the first transformer (2) is provided to the input of the amplifier (7) and the output of the amplifier (7) is coupled to the primary winding of the second transformer (11); a second ion optical device (13) coupled to the secondary winding of the second transformer (11); a phase difference detector unit (8, 9) having a first input and a second input, the phase difference detector unit (8, 9) configured to output a DC current or a voltage proportional to a phase difference between signals received at the first input and the second input, the first signal being provided to the first input of the phase difference detector unit and a second signal from the second transformer (11) being provided to the second input of the phase difference detector unit, the secondary winding of the first transformer (2) and the first ion optical device (3) form a primary LC circuit having a first resonant frequency, and the first frequency of the RF voltage generated by the RF generator (1) is configured to correspond to the first resonant frequency; the secondary winding of the second transformer (11) and the second ion optical device (13) form a secondary LC circuit having a second resonant frequency, the analytical instrument being configured such that at least a portion of the secondary LC circuit has a variable inductance, and the analytical instrument being configured such that the inductance of the at least a portion of the secondary LC circuit varies in response to the magnitude of the output DC current or voltage of the phase difference detector unit (8, 9), such that the second resonant frequency varies in response to the magnitude of the output DC current or voltage of the phase difference detector unit (8, 9).

2. the analytical instrument is configured such that the first ion optical device (3) receives a first operating RF voltage having the first frequency; the analytical instrument is configured such that the second ion optical device (13) receives a second operating RF voltage having the first frequency; 2. The analytical instrument of claim 1, wherein the variation of the second resonant frequency in response to the magnitude of the output DC current or voltage of the phase difference detector unit (8, 9) creates a negative feedback loop such that any phase difference between the first operating RF voltage and the second operating RF voltage is reduced or eliminated.

3. the secondary winding of the first transformer (2) has a first inductance; the first ion optical device (3) has a first self-capacitance (4); 3. The analytical instrument of claim 1, wherein the first inductance and the first self-capacitance together form the primary LC circuit having the first resonant frequency.

4. 3. The analytical instrument of claim 1 or 2, wherein the secondary winding of the second transformer (11) has a variable inductance, and the instrument is configured such that the inductance of the secondary winding of the second transformer (11) varies depending on the magnitude of the output DC current or voltage of the phase difference detector unit (8, 9).

5. 5. The analytical instrument of claim 4, wherein the second transformer (11) comprises one or more transformers (10), and the instrument is configured such that the inductance of the secondary winding of the second transformer (11) comprising one or more transformers (10) varies depending on the magnitude of the output DC current or voltage of the phase difference detector unit (8, 9).

6. the second ion optical device (13) has a second self-capacitance (14); The analytical instrument of claim 4 , wherein the variable inductance and the second self-capacitance together form the secondary LC circuit having the second resonant frequency.

7. 3. The analytical instrument of claim 1, further comprising an inductor having a variable inductance, the output DC current or voltage of the phase difference detector unit (8, 9) being provided to the inductor, the inductor being configured such that its inductance varies depending on the magnitude of the output DC current or voltage of the phase difference detector unit (8, 9), and the inductor being coupled to the secondary winding of the second transformer (11).

8. The secondary winding of the second transformer (11) has a second inductance; the second ion optical device (13) has a second self-capacitance (14); The analytical instrument of claim 7 , wherein the second inductance, the variable inductance, and the second self-capacitance together form the secondary LC circuit having the second resonant frequency.

9. 8. The analytical instrument of claim 7, wherein the inductor is formed from a converter having a primary winding and a secondary winding, the output DC current or voltage of the phase difference detector unit (8, 9) is provided to the primary winding of the converter, and the secondary winding of the converter is coupled to the secondary winding of the second transformer.

10. 10. The analytical instrument of claim 9, wherein the secondary winding of the converter is connected in series with the secondary winding of the second transformer (11).

11. 10. The analytical instrument of claim 9, wherein the secondary winding of the converter is connected in parallel with the secondary winding of the second transformer (11).

12. 5. The analytical instrument of claim 4, wherein the second transformer (11) comprises a magnetic core, and the output DC current or voltage of the phase difference detector unit (8, 9) is configured to magnetize the magnetic core, whereby the inductance of the secondary winding of the second transformer (11) varies according to the magnitude of the output DC current of the phase difference detector unit (8, 9).

13. the analytical instrument is configured such that the first ion optical device (3) receives a first operating RF voltage having the first frequency; the first signal is generated by a first feedback module (5) coupled to the RF generator (1), to the primary winding of the first transformer (2), or to the secondary winding of the first transformer (2); 3. The analytical instrument of claim 1, wherein the first signal corresponds to the first operating RF voltage.

14. 3. Analytical instrument according to claim 1 or 2, wherein the first signal is provided to the input of the amplifier (7) via a phase shifter (6).

15. the analytical instrument is configured such that the second ion optical device (13) receives a second operating RF voltage having the first frequency; the second signal is generated by a second feedback module (12) coupled to the primary winding of the second transformer (11) or to the secondary winding of the second transformer (11); 3. The analytical instrument of claim 1, wherein the second signal corresponds to the second operating RF voltage.

16. 3. The analytical instrument of claim 1 or 2, wherein the phase difference detector unit (8, 9) comprises a phase detector (8) configured to output a voltage proportional to a phase difference between the signals received at the first input and the second input, and a voltage-to-current converter (9) configured to convert the output voltage into the output DC current.

17. 3. Analytical instrument according to claim 1 or 2, wherein the phase difference detector unit (8, 9) is configured such that the magnitude range of the output DC current is controllable.

18. 3. Analytical instrument according to claim 1 or 2, wherein the second transformer (11) comprises a magnetic core or is air-core.

19. 3. Analytical instrument according to claim 1 or 2, wherein the first ion optical device (3) is a first multipole and / or the second ion optical device (13) is a second multipole.

20. 3. Analytical instrument according to claim 1 or 2, wherein the first ion optical device (3) is a first quadrupole ion trap and / or the second ion optical device (13) is a second quadrupole ion trap.

21. 3. The analytical instrument of claim 1 or 2, wherein the analytical instrument is or comprises a mass spectrometer.

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