Mass spectrometer and RF choke for use within an RF choke

Abstract

A radio frequency (RF) choke for use within a mass spectrometer comprises a bobbin having a hollow channel, a plurality of wire windings wound around the bobbin, each of the wire windings presenting a lattice winding pattern having a number of crossovers per turn of from about 1 to about 4, and a magnetic core disposed within the hollow channel of the bobbin. The RF choke exhibits an impedance in the range of from about 15 M ohms to about 150 M ohms with respect to an RF frequency generated by an RF voltage source within the range of from about 500 KHz to about 3 MHz, and a power dissipation equal to, or less than, about 3 W with respect to a peak-to-peak RF voltage of an RF voltage source of at least about 1 kV.

Description

Technical Field

[0001] (Related Application) This application claims priority to U.S. Provisional Application No. 63 / 350,697, filed on June 9, 2022, entitled "RF Choke for use in a Mass Spectrometer and RF Choke", which is incorporated herein by reference in its entirety.

[0002] (Technical Field) The present teachings generally relate to systems and methods for mass spectrometry, and more specifically, to such systems and methods that can be employed within a mass spectrometer, for example, to reduce MRM mass spectrometry time.

Background Art

[0003] (Background) Mass spectrometry (MS) is an analytical technique for determining the elemental composition of a test substance, involving both qualitative and quantitative applications. MS can be useful for identifying unknown compounds, determining the isotopic composition of elements in a molecule, determining the structure of a particular compound by observing its fragmentation, and quantifying the amount of a particular compound in a sample. A mass spectrometer detects chemical substances as ions such that the conversion of the analyte to charged ions must occur during the sampling process.

[0004] In some mass spectrometers, RF and / or DC voltages are applied to the rods of an ion guide or mass filter, implemented as a plurality of rods arranged within various components of the mass spectrometer, such as a multipole configuration (e.g., quadrupole configuration), to confine ions and / or generate an electromagnetic field for selecting ions having a targeted m / z ratio. Typically, an RF blocking filter or RF choke is employed within such a mass spectrometer to completely block or suppress a high-frequency alternating current signal (typically at an RF frequency) and allow the passage of low-frequency and DC signals to the desired components. However, these filters generally exhibit high power dissipation and can be bulky. Further, these filters can have a low cut-off frequency and a high settling time, which can result in an overshoot and undershoot time of the DC bias voltage element. This can affect the ability to achieve rapid DC voltage changes. Summary of the Invention Means for Solving the Problems

[0005] (Abstract) According to at least one embodiment of the present disclosure, a mass spectrometer is provided, the mass spectrometer including a vacuum chamber, at least one ion optical element disposed within the vacuum chamber, a DC voltage source positioned outside the vacuum chamber and electrically coupled to the ion optical element for applying a DC voltage thereto, an RF voltage source positioned outside the vacuum chamber and electrically coupled to the ion optical system for applying an RF voltage thereto, and an RF choke positioned within the vacuum chamber and electrically connected between the DC voltage source and the RF voltage source. The RF choke includes a bobbin having a hollow channel, a plurality of windings wound around the bobbin, each of the windings presenting a lattice winding pattern, and a magnetic core disposed within the hollow channel of the bobbin. The RF choke exhibits an impedance within a range of about 15 MΩ to about 150 MΩ with respect to an RF frequency generated by the RF voltage source within a range of about 500 kHz to about 3 MHz, and a power dissipation equal to or less than about 3 W with respect to a peak-to-peak RF voltage of the RF voltage source of at least about 1 kV.

[0006] According to another embodiment of the mass spectrometer of the present disclosure, the peak-to-peak RF voltage is within a range of about 1 kV to about 10 kV.

[0007] Another embodiment of the mass spectrometer of the present disclosure further includes a resin dispersed within the hollow channel of the bobbin to prevent the formation of air pockets between the magnetic core and the bobbin.

[0008] According to another embodiment of the mass spectrometer of the present disclosure, the resin further coats at least a portion of the outer surface of the plurality of windings.

[0009] According to another embodiment of the mass spectrometer of the present disclosure, each of the windings has a lattice winding pattern presenting a number of crossings per turn within a range of about 1 to about 4.

[0010] According to another embodiment of the mass spectrometer of the present disclosure, the number of crossings per turn is within a range of about 1.7 to about 2.5.

[0011] According to another embodiment of the mass spectrometer of the present disclosure, the number of intersections per turn is selected based on the frequency generated by the RF voltage source and the impedance of the RF choke.

[0012] According to another embodiment of the mass spectrometer of the present disclosure, the magnetic core exhibits a power dissipation of less than about 3 W with respect to the RF frequency within the range of about 500 kHz to about 3 MHz with respect to the peak-to-peak RF voltage of at least about 1 kV.

[0013] According to another embodiment of the mass spectrometer of the present disclosure, the magnetic core comprises either a ferromagnetic or a ferrimagnetic material.

[0014] According to another embodiment of the mass spectrometer of the present disclosure, the magnetic core comprises ferrite.

[0015] According to another embodiment of the mass spectrometer of the present disclosure, the RF choke has a maximum size of less than about 3 cm in any of the X, Y, and Z Cartesian coordinates.

[0016] According to another embodiment of the mass spectrometer of the present disclosure, the RF choke has a length of less than about 5 cm and a diameter of less than about 3 cm.

[0017] According to another embodiment of the mass spectrometer of the present disclosure, the mass ion optical element comprises a set of rods arranged within a multipole configuration.

[0018] According to another embodiment of the mass spectrometer of the present disclosure, the multipole configuration is a quadrupole configuration.

[0019] According to another embodiment of the mass spectrometer of the present disclosure, the ion optical element comprises an ion lens.

[0020] According to another embodiment of the mass spectrometer of the present disclosure, the ion optical element comprises an ion mass filter.

[0021] According to another embodiment of the mass spectrometer of the present disclosure, the ion optical element includes an ion guide.

[0022] According to another embodiment of the mass spectrometer of the present disclosure, the vacuum chamber is maintained at a pressure in the range of about 1×10 -8 torr to about 50 millitorr.

[0023] According to another embodiment of the mass spectrometer of the present disclosure, the mass spectrometer is configured to perform MRM (multiple reaction monitoring) mass spectrometry.

[0024] Another embodiment of the mass spectrometer of the present disclosure further includes a plurality of ion optical elements, a plurality of RF chokes, and a plurality of vacuum chambers, and each ion optical element is connected to a corresponding RF choke within an individual vacuum chamber.

[0025] According to at least one embodiment of the present disclosure, a radio frequency (RF) choke for use within a mass spectrometer is provided, the RF choke comprising a bobbin having a hollow channel, and a plurality of wire windings wound around the bobbin, each of the wire windings presenting a lattice winding pattern having a number of crossovers per turn of about 1 to about 4, and a magnetic core disposed within the hollow channel of the bobbin, the RF choke presenting an impedance in the range of about 15 MΩ to about 150 MΩ with respect to an RF frequency generated by an RF voltage source in the range of about 500 KHz to about 3 MHz, and a power dissipation equal to or less than about 3 W with respect to a peak-to-peak RF voltage of the RF voltage source of at least about 1 kV.

[0026] According to another embodiment of the RF choke of the present disclosure, the peak-to-peak RF voltage is in the range of about 1 kV to about 10 kV.

[0027] Another embodiment of the RF choke of the present disclosure further includes a resin dispersed within the hollow channel of the bobbin to prevent the formation of air pockets between the magnetic core and the bobbin.

[0028] According to another embodiment of the RF choke of the present disclosure, the resin further coats at least a part of the outer surface of the plurality of windings.

[0029] According to another embodiment of the RF choke of the present disclosure, each of the windings has a lattice winding pattern exhibiting a number of crossovers per turn within the range of about 1 to about 4.

[0030] According to another embodiment of the RF choke of the present disclosure, the number of crossovers per turn is within the range of about 1.7 to about 2.5.

[0031] According to another embodiment of the RF choke of the present disclosure, the number of crossovers per turn is selected based on the frequency generated by the RF voltage source and the impedance of the RF choke.

[0032] According to another embodiment of the RF choke of the present disclosure, the magnetic core exhibits a power dissipation of less than about 3 W with respect to RF frequencies within the range of about 500 kHz to about 3 MHz with respect to the peak-to-peak RF voltage of at least about 1 kV.

[0033] According to another embodiment of the RF choke of the present disclosure, the magnetic core comprises either a ferromagnetic or a ferrimagnetic material.

[0034] According to another embodiment of the RF choke of the present disclosure, the magnetic core comprises ferrite.

[0035] According to another embodiment of the RF choke of the present disclosure, the RF choke has a maximum size of less than about 3 cm in any of the X, Y, and Z Cartesian coordinates.

[0036] According to another embodiment of the RF choke of the present disclosure, the RF choke has a length of less than about 5 cm and a diameter of less than about 3 cm.

Brief Description of the Drawings

[0037]

Figure 1

[0038]

Figure 2A

Figure 2B

[0039]

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 3E

Figure 3F

Best Mode for Carrying Out the Invention

[0040] (Detailed Description) For clarity, it should be understood that while the following discussion details various aspects of embodiments of the present disclosure, certain specific details will often be omitted when it is convenient or appropriate to do so. For example, the discussion of similar or analogous features in alternative embodiments may be somewhat abbreviated. Well-known concepts or ideas may also not be discussed in any detail for the sake of brevity. Those skilled in the art will recognize that some embodiments of the present disclosure may not require some of the details specifically described herein in order to provide a thorough understanding of the embodiments. Similarly, it will become apparent that the embodiments described may be subject to modifications or variations without departing from the scope of the present disclosure, in accordance with common general knowledge. The following detailed description of the embodiments should not be construed as in any way limiting the scope of the applicant's teachings.

[0041] As used herein, the terms “about,” “substantially,” and “substantially equal” refer to variations in numerical quantities and / or in the complete state or condition that can occur, for example, through measurements or handling procedures in the real world, through inadvertent errors in these procedures, through differences in the manufacture, source, or purity of a composition or reagent, and through equivalents. Typically, the terms “about” and “substantially” as used herein mean 10% above or below the recited value or range of values, or the complete condition or state. For example, a value of about 10 or substantially equal to 10 can mean a concentration of 9 - 11. These terms also refer to variations that will be recognized by those skilled in the art as being equivalent, provided such variations do not include known values practiced by the prior art.

[0042] As used herein, the term “and / or” includes any combination of one or more of the associated listed items and may be abbreviated as “ / ”.

[0043] The term "crossover per turn" is known in the art as being applicable to wire winding and refers to the number of wire crossovers from one side of a winding segment to the opposite side of the winding segment in one complete revolution of a bobbin. Figure 2 of "Universal Coil Winding" from Radio and Electrical Review (March 1961; pages 13 - 20, 38), which is incorporated herein by reference in its entirety, illustrates an exemplary winding pattern having a crossover per turn of 2.

[0044] The term "vacuum" as used herein refers to a pressure scale of less than about 10 Torr, for example, in the range of about 10 Torr to about 10 -8 Torr.

[0045] The term "ion optic element" as used herein refers to any component of a mass spectrometer to which RF and DC voltages are applied and which affects the trajectory of ions by generating an electromagnetic field.

[0046] Typically, an RF blocking filter or RF choke is designed as a fixed inductor and is employed in a mass spectrometer for the purpose of completely blocking or suppressing a high - frequency alternating current (AC) signal and allowing the passage of low - frequency and DC signals to one or more components of the mass spectrometer, such as its ion guide. For example, an RF choke inductor can be used in a mass spectrometer to facilitate the application of a DC voltage to an ion optic element, which is also connected to a high - frequency RF voltage source. The RF choke inductor can be coupled to the electrical connection of a mass spectrometer element contained within a vacuum device, such as a quadrupole assembly.

[0047] The present disclosure relates to RF blocking filters, RF chokes, and resonant inductive filters for use within a mass spectrometer. The RF choke of the present disclosure can be designed as a fixed inductor that can completely block or suppress high-frequency alternating current (AC) signals and allow the passage of low-frequency and DC signals. The RF choke can be constructed to exhibit a high impedance at RF frequencies associated with RF signals applied to components of the mass spectrometer, such as, in particular, RF signals that can be applied to the rods of a multipole (e.g., quadrupole) ion guide at high RF voltages. The RF choke according to the present teachings can also exhibit a rapid settling time when a rapid switching of high DC voltages applied to components of the mass spectrometer, such as a mass filter, is required. Increasing the speed of DC switching can enable rapid ion transfer and ion trapping between different regions of the ion path within the mass spectrometer. For example, such rapid switching of high DC voltages can be employed within multiple reaction monitoring (MRM), and in some embodiments, the use of the RF choke according to the present teachings, when employed in the MRM mass spectrometry of a sample, can increase the switching speed of the voltage, thereby enabling an improvement in the MRM throughput.

[0048] The RF choke according to the present teachings can also exhibit a sufficiently low power dissipation such that it can be realized to employ it within the vacuum chamber of the mass spectrometer in a state without cooling via convection when a high RF voltage is applied thereto. The RF choke can also be constructed to exhibit a low impedance within the DC domain, which facilitates rapid changes at the DC levels applied to the ion optical elements.

[0049] Due to its low power dissipation, the RF choke inductor of the present disclosure can be used in combination with the electrical connection of mass spectrometer elements (e.g., ion optical elements) contained within a vacuum chamber, such as multiple pole assemblies (e.g., quadrupole assemblies) and rods of ion lenses, installed within a vacuum apparatus. In such a vacuum environment, cooling via convection is not possible, and thus the power dissipation of elements installed within the vacuum environment becomes a limiting factor that can determine whether the element can be employed within that environment. As described above, the RF choke inductor of the present disclosure can exhibit low power dissipation and thus can be used within a vacuum environment. For example, the power dissipation of an RF choke according to the present teachings, for frequencies in the range of about 500 kHz to about 3 MHz and peak-to-peak voltage amplitudes in the range of about 1 kV to about 10 kV, can be equal to or less than about 5 watts (W), for example, can be in the range of about 0 W to about 5 W, such as in the range of about 1 W to about 3 W.

[0050] Furthermore, the RF choke can have a small footprint that allows for the simultaneous incorporation of multiple RF chokes into multiple segments of an ion path within a mass spectrometer. In fact, in some embodiments, the combination of the small size of the RF choke and its low power dissipation at the RF frequencies of interest allows for connecting the RF choke to all of the ion optical elements of interest, including those that can be subject to rapid changes in the DC voltage applied thereto.

[0051] Various aspects of the present teachings are described in connection with a quadrupole / time-of-flight mass spectrometer. However, it should be understood that the present teachings can be used in combination with other types of mass spectrometry systems, such as triple quadrupole mass spectrometers, linear ion trap mass spectrometers, or 3D ion trap mass spectrometers.

[0052] FIG. 1 schematically depicts an exemplary mass spectrometer 100 in which one or more RF chokes according to the present teachings may be incorporated. The mass spectrometer 100 includes an ion source 102 for generating a plurality of ions. Various ion sources can be employed in the practice of the present teachings. Some examples of suitable ion sources include, but are not limited to, electrospray ionization devices, aerosol-assisted electrospray devices, chemical ionization devices, aerosol-assisted atomization devices, chemical ionization devices, matrix-assisted laser desorption / ionization (MALDI) ion sources, photoionization devices, laser ionization devices, thermospray ionization devices, inductively coupled plasma (ICP) ion sources, sonic spray ionization devices, glow discharge ion sources, and electron impact ion sources.

[0053] The generated ions pass through the orifice 104a of the curtain plate 104 and the orifice 106a of the orifice plate 106, which is positioned downstream of the curtain plate and separated from the curtain plate, such that a gas curtain chamber is formed between the orifice and the curtain plate. A curtain gas supply (not shown) provides a curtain gas flow (e.g., of N2) between the curtain plate 104 and the orifice plate 106, which can help keep the downstream section of the mass spectrometer clean by deagglomerating and deflecting large neutral particles. The curtain chamber can be maintained at a high pressure (e.g., a pressure above atmospheric pressure), while the downstream section of the mass spectrometer can be maintained at one or more selected pressures via evacuation through one or more vacuum pumps (not shown).

[0054] In this embodiment, the ions pass through the orifice 106a of the orifice plate 106 and are received by an ion optical system QJet, which includes four rods (two of which are shown in the figure) arranged in a quadrupole configuration that can have an RF voltage applied thereto to generate a quadrupole electric field within the space between the rods. The Qjet optical system can use a combination of gas dynamics and radio frequency fields to trap and focus the ions.

[0055] The ions are then transmitted into an ion guide Q0 comprising four rods 108 (two of which are visible in this figure), which are arranged within a quadrupole configuration to form an ion beam for transmission to a downstream component of the mass spectrometer via an ion lens IQ0.

[0056] The ion beam exits the Q0 ion guide and is focused into a subsequent ion mass filter Q1 via an ion lens IQ1 and a quadrupole pre-filter lens ST1, which comprises four rods 110 (two of which are visible in this figure) that are arranged within a quadrupole configuration and to which an RF voltage as well as a DC resolving voltage can be applied to radially focus the ions as they pass through the Q1 mass analyzer and select ions having a target m / z ratio (referred to herein as precursor ions). In other embodiments, other multipole configurations such as a hexapole or octapole configuration can also be utilized.

[0057] More specifically, in the present embodiment, the quadrupole rod set Q1 can be operated as a conventional transmission RF / DC quadrupole mass filter for selecting ions having an m / z value of interest or an m / z value within the range of interest. As an example, the quadrupole rod set Q1 can be provided with an RF / DC voltage suitable for operation in a mass resolution mode. For example, the parameters of the applied RF and DC voltages can be selected such that Q1 establishes a transmission window for the selected m / z ratio so that these ions can traverse Q1 in a state that is hardly perturbed. However, ions having an m / z ratio corresponding outside the window can be prevented from forming a stable orbit within the quadrupole and traversing the quadrupole rod set Q1. It should be understood that this operating mode is only one possible operating mode for Q1. In the present embodiment, the Q0 ion guide and the Q1 mass filter are respectively disposed in vacuum chambers 151 and 152 that are differentially pumped. As an example, the vacuum chamber 151 can be maintained at a pressure within the range of about 3 to about 12 millitorr, and the vacuum chamber 152 can be maintained at a pressure within the range of about 1 to about 50 μtorr.

[0058] Ions passing through the Q1 mass analyzer are focused into the collision cell Q2 through the quadrupole pre-filter lens ST2 and the ion lens IQ2A. The collision cell Q2 is arranged within a quadrupole configuration and includes four rods 112 (two of which are visible in this figure) to which an RF voltage can be applied to provide radial confinement of the ions. The rods 112 are disposed within an enclosure 113 such that the pressure within the collision cell can be increased relative to other stages, for example, through the introduction of gas (e.g., nitrogen) into the enclosure. In some embodiments, the collision cell Q2 is employed to cause fragmentation of the ions received by the collision cell, while in other embodiments, the collision cell Q2 is utilized rather for causing, for example, collision cooling of the ions than for ion fragmentation.

[0059] Fragment ions emitted from the collision cell are received by the downstream Q3 quadrupole mass analyzer 116 and separated based on their m / z ratios to be detected via the ion detector 118. The Q3 quadrupole mass analyzer is arranged within a quadrupole configuration and includes four rods to which RF and DC voltages can be applied.

[0060] Analysis module 119 communicates with ion detector 118, receives ion detection signals (e.g., electrical pulses) generated by ion detector 118, processes those signals, and generates a mass spectrum of the detected ions.

[0061] The RF voltage source 115a and the DC voltage source 115b, operating under the control of the controller 117, can apply the required RF and DC voltages to various components of the mass spectrometer 100. As an example, the RF voltage source 115a can apply an RF voltage to the quadrupole rods of the Q0 ion guide. The Q1 mass filter, Q2 collision cell, and Q3 mass analyzer are capacitively coupled to the rods of the Q0 ion guide and receive the RF voltage via such capacitive coupling. The RF voltages applied to the rods of the Q0 ion guide, Q1 mass filter, and Q2 collision cell cause radial confinement of the ions and / or provide an electromagnetic field for selecting ions with a desired m / z ratio to pass through the quadrupole rods. The DC voltage source 115b can apply a DC discrimination voltage to the quadrupole rods of the Q1 mass filter to select ions having the m / z ratio of interest.

[0062] The RF choke according to the present teachings can be used within any mass spectrometer, including within a mass spectrometer such as the mass spectrometer 100 of FIG. 1, or within a vacuum chamber, and includes ion optical elements to which RF and DC voltages are to be applied. The ion optical elements can be any component that is powered by a DC voltage source and / or an RF voltage source, such as an ion lens, an ion mass filter, an ion guide, or rods arranged within a multipole configuration.

[0063] As an illustration, FIGS. 2A and 2B depict the incorporation of an RF choke according to certain embodiments of the present teachings into a mass spectrometer having a plurality of ion optical elements that receive RF voltage via capacitive coupling to the quadrupole rods of a main quadrupole Q0 ion guide that is directly coupled to an RF voltage source to receive its RF voltage (i.e., these ion optical elements slave their RF from the main quadrupole Q0). More specifically, as shown in FIGS. 2A and 2B, the mass spectrometer can include a main quadrupole ion guide Q0, a quadrupole prefilter ST1, a quadrupole mass filter Q1, and another quadrupole prefilter ST2. Quadrupole Q1, which is electrically coupled to RF source RFA and DC source DCA, can be capacitively coupled to quadrupole prefilters ST1 and ST2 and main quadrupole Q0.

[0064] As shown in FIG. 2A, in a conventional mass spectrometry system, very large chokes (shown schematically as inductors L1 and L2) are coupled to the main quadrupole Q0 to reduce the settling time when the applied voltage (e.g., a DC voltage) is switched. Due to their large size, these chokes may not be coupled to quadrupole prefilters ST1 and ST2. Instead, resistors (R3 - R6) having long settling times are typically used. As will be described in detail below, in many embodiments, the RF choke according to the present disclosure can have a small size and thus, as shown in FIG. 2B, can be used in place of resistors R3 - R6 such that all of the critical optical elements can exhibit a more rapid settling time, which can be advantageous, for example, in rapid MRM analysis of a sample. Also, replacing the resistors with RF chokes can allow for higher RF coupling since there is lower power dissipation. This can, in turn, eliminate ion trapping in the combination of rapid rise and fall times of the DC voltage. Also, replacing the resistors with RF chokes can eliminate crosstalk across the RF coupling optical elements.

[0065] The use of the RF choke according to the present teachings within a mass spectrometer is not limited to the circuitry employed for applying RF and DC voltages to the quadrupole rods of a mass filter or ion guide. Rather, the RF choke according to the present teachings can be used within a mass spectrometer as part of the circuitry used for applying DC and RF voltages to any ion optical element.

[0066] In some embodiments, one or more RF chokes according to the present teachings can be employed within the Q0 region of a mass spectrometer.

[0067] Preferably, an RF choke according to the present teachings, such as the RF choke 200 described below, is disposed within a vacuum chamber where the ion optical element of interest (e.g., an ion guide rod such as a pre-filter quadrupole rod) is positioned. Generally, the RF choke according to the present teachings can be used anywhere, including in a vacuum environment where convective cooling of the RF choke is not feasible. In one embodiment, individual RF chokes can be positioned within each of a plurality of vacuum chambers, each containing at least one ion optical element to which RF and / or DC voltages are applied, and each ion optical element is connected to the corresponding RF choke within the individual vacuum chamber.

[0068] As presented below, an RF choke according to an embodiment of the present teachings can be constructed to exhibit high impedance at the frequency of the RF signal to which it is applied. This can reduce power dissipation, which makes the use of the RF choke within a vacuum environment practical. The RF choke can also be constructed to exhibit low impedance within the DC domain, which facilitates rapid changes in the DC voltage applied to the ion optical element. Also, the choke can be constructed to have a small footprint that allows for the simultaneous use of multiple RF chokes within multiple segments of the ion path within a mass spectrometer.

[0069] As shown in FIGS. 3A - 3E, at least one embodiment of the RF choke 200 according to the present teachings includes a bobbin 202 on which a wire can be wound as described below to provide three wire winding segments, although other numbers of wire winding segments can also be used. The bobbin 202 can be formed from a material that exhibits low dielectric loss at RF frequencies in the range of about 500 kHz to about 3 MHz, such as a low dissipation rate plastic or glass or mineral filled plastic material like polyetherimide (e.g., ULTEM, polyethylene, polypropylene), resin (polyphthalamide), or machinable ceramic (e.g., Macore, aluminum nitride, etc.). The bobbin 202 includes two flanges 204 into which pins 206 are inserted, as shown in FIG. 3A. The pins 206 can be press - fit into the flanges 204. As shown in FIG. 3B, a wire 208 can be wound around the base of the pins 206 and then soldered to the pins 206. The wire 208 is then wound onto the bobbin as shown in FIG. 3C, forming a plurality of circular segments 210 on the central portion 209 of the bobbin 202. The number of wire circular segments can be in the range of about 2 to 6.

[0070] As an example, the wire 208 can be wound about 400 turns in each of the plurality of circular segments 210, although other numbers of turns in the range of about 300 to about 1,500 turns can also be employed. In at least one embodiment, the wire 208 can be wound around the bobbin such that the winding exhibits a cross - pattern of wire layers, as shown in FIG. 3F, where each wire in a layer intersects an individual wire in a lower layer at an angle. Such a cross - pattern is known in the art as a "general - purpose winding", "honeycomb winding", or "lattice winding".

[0071] More specifically, each section can be constructed using a number of crossings per turn in the range of about 1 to 4, preferably in the range of 1.7 to 2.5. The number of crossings per turn can be selected, at least in part, based on the RF frequency (or RF frequency range) for which the RF choke is designed and the desired impedance of the RF choke at those frequencies. For example, for RF frequencies in the range of about 500 kHz to about 3 MHz and individual impedances in the range of about 15 M ohms to about 150 M ohms, the number of crossings per turn of the wire winding of the RF choke according to the present teachings can be in the range of about 1 to about 4, such as, for example, in the range of about 1.7 to about 2.5, or in the range of about 1.8 to about 2.2.

[0072] As shown in FIG. 3D, in the present embodiment, the bobbin 202 includes a central cavity 202a that extends along the length of the bobbin 202 between its flanges 204, and a magnetic core 212 is inserted into the central cavity. A ferrimagnetic or ferromagnetic material can be used for the magnetic core 212. The magnetic core 212 can be made of a material such that the desired low loss of the choke at the frequency of the applied RF signal can be achieved. Some examples of suitable ferrimagnetic or ferromagnetic materials include, but are not limited to, ferrites (e.g., 4B1 NiZn), powdered molypermalloy, sendust, iron powder, or powdered silicon iron alloy. An epoxy seal 214 can be added to the ends of the bobbin 202, as shown in FIG. 3E, to seal the magnetic core 212 within the cavity 202a of the bobbin 202.

[0073] As an example, in at least one embodiment, the length of the bobbin 202 can be in the range of about 3 cm to about 5 cm. The flange 204 of the bobbin 202 can have a diameter in the range of about 2 cm to about 3 cm. Further, the inner diameter of the cavity 202a is about 6 mm, and the wall thickness of the cavity 202a can be about 2 mm. The circular wire section 210 of the bobbin 202 can have a diameter in the range of about 12 mm to about 20 mm and a thickness in the range of about 3 mm to about 3.5 mm. In at least one embodiment, the maximum size of the bobbin 202 in any of the three dimensions (e.g., X, Y, and Z Cartesian dimensions) is equal to or less than about 3 cm, and can be, for example, in the range of about 1 cm to about 2 cm.

[0074] A low gas emission type resin (also referred to herein as varnish) can be introduced into the central cavity so that, when applicable, it fills the gap between the magnetic core 212 and the bobbin 202 to prevent, preferably, the occurrence of arcing (corona discharge) when a high RF voltage is applied to the wire winding. Such varnish or a different varnish can also be applied to the outer surface of the wire winding.

[0075] In at least one embodiment, the inductance of the RF choke (e.g., the inductance measured between pins 206) can be about 42.5 mH, or within the range of about 40 - 45 mH, with respect to RF frequencies in the range of about 500 kHz to about 3 MHz. Further, in some such embodiments, the DC resistance of the RF choke (such as measured between pins 206) can be about 108 Ω or within the range of about 100 - 115 Ω. The configuration described above with respect to the RF choke can result in an equivalent impedance of about 15 MΩ to 150 MΩ within the frequency range of about 500 KHz to 3 MHz, which enables the operation of the RF choke at a sufficiently low power level such that the positioning of the RF choke can operate within a vacuum environment, particularly within a evacuated chamber in a mass spectrometer. For example, in some embodiments, the power dissipation presented by the RF choke according to the present teachings with respect to an applied peak - to - peak RF voltage of at least about 1 kV can be less than about 3 W.

[0076] In at least one embodiment, the RF choke can comprise a resin layer coating on at least a portion of at least one outer surface of the wire winding(s).

[0077] Those skilled in the art will understand that various changes can be made to the above - described embodiments without departing from the scope of the invention.

[0078] The above detailed description refers to the accompanying drawings. Identical or similar reference numerals may be used in the drawings or description to refer to the same or similar parts. Also, elements with the same name can perform similar functions and can be designed similarly, unless otherwise specified. The details are described to provide an understanding of the exemplary embodiments. Embodiments, such as alternative embodiments, can be practiced without some of these details. In other cases, well - known techniques, procedures, and components are described in detail to avoid obscuring the described embodiments.

[0079] The foregoing description of the present embodiment is presented for illustrative purposes only. It is not comprehensive and does not limit the embodiment to the precise form disclosed. Although some exemplary embodiments and features are described, modifications, adaptations, and other implementations may be contemplated without departing from the spirit and scope of the present embodiment. Therefore, unless explicitly stated otherwise, this description should not be construed as relating to one or more embodiments and limiting the embodiments as a whole. This applies whether the present disclosure describes a feature as relating to "a", "the", "one", "one or more", "some", or "various" embodiments. As used herein, the singular forms "a", "an", and "the" may include the plural unless the context clearly indicates otherwise. Further, the term "coupled" does not exclude the presence of intermediate elements between the items being coupled. Also, describing that a feature may be present indicates that the feature may be present within one or more embodiments.

[0080] In the present disclosure, the terms "include", "comprise", "contain", and "have", when used after a set or system, mean non-limiting inclusion and do not exclude the addition of other unenumerated components to that set or system. Further, unless otherwise described or inferred from the context, the conjunction "or", when used, is not exclusive and instead is inclusive so as to mean "and / or". Also, when these terms are used, a subset of a set may include one or more that include all of the components of the set.

[0081] Further, as used in the present disclosure and unless otherwise described or inferred, the first variable is an increasing function of the second variable if the first variable does not decrease and, instead, generally increases when the second variable increases. On the other hand, the first variable is a decreasing function of the second if the first variable does not increase and, instead, generally decreases when the second variable increases. In certain embodiments, the first variable can be an increasing or decreasing function of the second variable if the first variable is directly or inversely proportional to the second variable, respectively.

[0082] The disclosed systems, methods, and devices are not limited to any specific aspect or feature or combination thereof, and the disclosed systems, methods, and devices do not require the presence of any one or more specific advantages or the solution of any problems. Any theory of operation is for the purpose of facilitating explanation, but the disclosed systems, methods, and devices are not limited to such theories of operation.

[0083] Modifications and variations are possible in light of the above teachings and can be obtained from practicing the embodiments. For example, the steps described need not be performed in the same sequence or with the same degree of separation as discussed. Similarly, various steps may be omitted, repeated, combined, or performed in parallel as necessary to achieve the same or similar objectives. Similarly, the systems described need not necessarily include all of the parts described in this embodiment and may also include other parts not described in this embodiment. Thus, the embodiments are not limited to the details described above, but instead are defined by the appended claims in light of the full scope of their equivalents. Further, the present disclosure is directed to all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with each other.

[0084] Although the present disclosure has been described in conjunction with specific embodiments, many alternatives, modifications, and variations will be apparent to those of ordinary skill in the art in light of the foregoing description. Accordingly, it is intended that the appended claims embrace any such alternatives, modifications, and variations as fall within the true spirit and scope of the present disclosure.

Claims

1. A mass spectrometer, Vacuum chamber and At least one ion optical element disposed within the vacuum chamber, A DC voltage source is located outside the vacuum chamber and electrically coupled to the ion optical element for applying a DC voltage thereto, An RF voltage source located outside the vacuum chamber and electrically coupled to the ion optical system for applying an RF voltage thereto, An RF choke is located within the vacuum chamber and electrically connected between the DC voltage source and the RF voltage source. Equipped with, The RF choke is A bobbin having a hollow channel, A plurality of windings wound around the bobbin, each of which exhibits a grid winding pattern, A magnetic core disposed within the hollow channel of the bobbin and Equipped with, The RF choke exhibits an impedance in the range of approximately 15 M ohms to approximately 150 M ohms with respect to the RF frequency generated by the RF voltage source in the range of approximately 500 kHz to approximately 3 MHz, and a power dissipation of approximately 3 W or less with respect to the peak-to-peak RF voltage of the RF voltage source of at least approximately 1 kV, in a mass spectrometer.

2. The mass spectrometer according to claim 1, wherein the peak-to-peak RF voltage is in the range of approximately 1 kV to approximately 10 kV.

3. The mass spectrometer according to any one of claims 1 and 2, further comprising a resin dispersed within the hollow channel of the bobbin, which prevents the formation of an air pocket between the magnetic core and the bobbin.

4. The mass spectrometer according to claim 3, wherein the resin further covers at least a portion of the outer surface of the plurality of windings.

5. The mass spectrometer according to any one of claims 1 and 2, wherein each of the windings has a grid winding pattern exhibiting a number of crosses per winding in the range of about 1 to about 4.

6. The mass spectrometer according to claim 5, wherein the number of crossovers per turn is in the range of approximately 1.7 to approximately 2.

5.

7. The mass spectrometer according to claim 5, wherein the number of crossovers per turn is selected based on the frequency generated by the RF voltage source and the impedance of the RF choke.

8. The mass spectrometer according to claim 4, wherein the magnetic core exhibits a power dissipation of less than 3 W with respect to the RF frequency in the range of about 500 kHz to about 3 MHz with respect to the peak-to-peak RF voltage of at least about 1 kV.

9. The mass spectrometer according to claim 8, wherein the magnetic core comprises either a ferromagnetic material or a ferrimagnetic material.

10. The mass spectrometer according to claim 8, wherein the magnetic core comprises ferrite.

11. The mass spectrometer according to any one of claims 1 and 2, wherein the RF choke has a maximum size of less than about 3 cm in any of the X, Y, and Z Cartesian coordinates.

12. The mass spectrometer according to claim 11, wherein the RF choke has a length of less than approximately 5 cm and a diameter of less than approximately 3 cm.

13. The mass ion optical element comprises a set of rods arranged within a multipole configuration, as described in claim 1.

14. The mass spectrometer according to claim 13, wherein the multipole configuration is a quadrupole configuration.

15. The mass spectrometer according to claim 1, wherein the ion optical element comprises an ion lens.

16. The mass spectrometer according to claim 1, wherein the ion optical element comprises an ion mass filter.

17. The mass spectrometer according to claim 1, wherein the ion optical element comprises an ion guide.

18. The vacuum chamber is approximately 1 × 10 －８ The mass spectrometer according to claim 1, which maintains a pressure in the range of Torr to approximately 50 milliliters.

19. The mass spectrometer according to claim 1, wherein the mass spectrometer is configured to perform MRM (multiple reaction monitoring) mass spectrometry.

20. The mass spectrometer according to claim 1, further comprising a plurality of ion optical elements, a plurality of RF chokes, and a plurality of vacuum chambers, wherein each ion optical element is connected to a corresponding RF choke in a separate vacuum chamber.

21. A radio frequency (RF) choke for use in a mass spectrometer, A bobbin having a hollow channel, A plurality of wire windings wound around the bobbin, each of the wire windings exhibiting a grid winding pattern with approximately 1 to approximately 4 crossings per turn, A magnetic core disposed within the hollow channel of the bobbin and Equipped with, The RF choke exhibits an impedance in the range of approximately 15 M ohms to approximately 150 M ohms with respect to an RF frequency generated by an RF voltage source in the range of approximately 500 kHz to approximately 3 MHz, and a power dissipation of approximately 3 W or less with respect to the peak-to-peak RF voltage of the RF voltage source of at least approximately 1 kV.

22. The RF choke according to claim 21, wherein the peak-to-peak RF voltage is in the range of approximately 1 kV to approximately 10 kV.

23. The RF choke according to any one of claims 21 and 22, further comprising a resin dispersed within the hollow channel of the bobbin, which prevents the formation of an air pocket between the magnetic core and the bobbin.

24. The RF choke according to claim 23, wherein the resin further covers at least a portion of the outer surface of the plurality of windings.

25. The RF choke according to any one of claims 21 and 22, wherein each of the windings has a grid winding pattern exhibiting a number of crosses per turn in the range of about 1 to about 4.

26. The RF choke according to claim 25, wherein the number of crosses per turn is in the range of approximately 1.7 to approximately 2.

5.

27. The RF choke according to claim 25, wherein the number of crossovers per turn is selected based on the frequency generated by the RF voltage source and the impedance of the RF choke.

28. The RF choke according to claim 24, wherein the magnetic core exhibits a power dissipation of less than 3 W with respect to the RF frequency in the range of about 500 kHz to about 3 MHz with respect to the peak-to-peak RF voltage of at least about 1 kV.

29. The RF choke according to claim 26, wherein the magnetic core comprises either a ferromagnetic material or a ferrimagnetic material.

30. The RF choke according to claim 28, wherein the magnetic core comprises ferrite.

31. The RF choke according to any one of claims 21 and 22, wherein the RF choke has a maximum size of less than about 3 cm in any of the X, Y, and Z Cartesian coordinates.

32. The RF choke according to claim 31, wherein the RF choke has a length of less than approximately 5 cm and a diameter of less than approximately 3 cm.

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