RF Choke and RF Choke for use in mass spectrometer

Abstract

A radio frequency (RF) choke for use in a mass spectrometer, comprising: a bobbin having a hollow channel; a plurality of wire windings wound around the bobbin, each of the wire windings exhibiting a lattice winding pattern having a span per turn of from about 1 to about 4; and a magnetic core disposed in the hollow channel of the bobbin.

Description

[0001] Related Applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 350,697, filed on June 9, 2022, entitled “RF Choke and RF Choke for Use in a Mass Spectrometer,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present teachings relate generally to systems and methods for mass spectrometry, and more particularly to such systems and methods that can be employed in a mass spectrometer, for example, to reduce MRM mass analysis time. Background Art

[0004] Mass spectrometry (MS) is an analytical technique used to determine the elemental composition of a test substance, with 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 specific compound by observing its fragmentation, and quantifying the amount of a specific compound in a sample. A mass spectrometer detects chemical entities as ions, so the analyte must be converted into charged ions during the sampling process.

[0005] In some mass spectrometers, RF and / or DC voltages may be applied to various components of the mass spectrometer, for example, rods of an ion guide or mass filter, which are implemented as multiple rods arranged in a multipole configuration (e.g., a quadrupole configuration) to generate an electromagnetic field for limiting ions and / or selecting ions with an m / z ratio of interest. Typically, RF blocking filters or RF chokes are used in such mass spectrometers to block or suppress high-frequency AC signals (usually at RF frequencies) and allow low-frequency and DC signals to pass through to reach the desired (one or more) components. However, these filters typically exhibit high power dissipation and may be bulky. In addition, these filters may have low cut-off frequencies and high settling times, which may result in long rise and fall times for DC bias voltage elements. This can affect the ability to achieve rapid DC voltage changes. Summary of the invention

[0006] According to at least one embodiment of the present disclosure, a mass spectrometer is provided, comprising: a vacuum chamber; at least one ion optical element disposed in the vacuum chamber; a DC voltage source located outside the vacuum chamber and electrically coupled to the ion optical element to apply a DC voltage thereto; an RF voltage source located outside the vacuum chamber and electrically coupled to the ion optical element to apply an RF voltage thereto; an RF choke located in the vacuum chamber and electrically connected between the DC voltage source and the RF voltage source, the RF choke comprising a bobbin having a hollow channel, a plurality of windings wound around the bobbin, and a magnetic core disposed in the hollow channel of the bobbin, each of the windings exhibiting a lattice winding pattern, wherein, for an RF frequency in the range of about 500 KHz to about 3 MHz generated by the RF voltage source, the RF choke exhibits an impedance in the range of about 15 Mohm to about 150 Mohm, and for a peak-to-peak RF voltage of at least about 1 kV of the RF voltage source, the RF choke exhibits a power dissipation equal to or less than about 3 W.

[0007] According to another embodiment of the mass spectrometer of the present disclosure, the peak-to-peak RF voltage is in the range of about 1 kV to about 10 kV.

[0008] Another embodiment of the mass spectrometer of the present disclosure further includes a resin dispersed in the hollow channel of the bobbin to prevent air pockets from forming between the magnetic core and the bobbin.

[0009] According to another embodiment of the mass spectrometer of the present disclosure, the resin further covers at least a portion of the outer surface of the plurality of windings.

[0010] According to another embodiment of the mass spectrometer of the present disclosure, each winding has a lattice winding pattern exhibiting a number of spans per turn in a range of about 1 to about 4.

[0011] According to another embodiment of the mass spectrometer of the present disclosure, the number of spans per turn is in a range from about 1.7 to about 2.5.

[0012] According to another embodiment of the mass spectrometer of the present disclosure, the number of spans per turn is selected based on a frequency generated by the RF voltage source and an impedance of the RF choke.

[0013] 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 for RF frequencies in the range of about 500 kHz to about 3 MHz for the peak-to-peak RF voltage of at least about 1 kV.

[0014] According to another embodiment of the mass spectrometer of the present disclosure, the magnetic core includes any one of a ferromagnetic material and a ferrimagnetic material.

[0015] According to another embodiment of the mass spectrometer of the present disclosure, the magnetic core includes ferrite.

[0016] According to another embodiment of the mass spectrometer of the present disclosure, the RF choke has a maximum dimension in any of the X, Y, and Z Cartesian coordinates that is less than about 3 cm.

[0017] According to another embodiment of the mass spectrometer of the present disclosure, the RF choke has a length less than about 5 cm and a diameter less than about 3 cm.

[0018] According to another embodiment of the mass spectrometer of the present disclosure, the mass ion optical element includes a rod set arranged in a multipole configuration.

[0019] According to another embodiment of the mass spectrometer of the present disclosure, the multipole configuration is a quadrupole configuration.

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

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

[0022] According to another embodiment of the mass spectrometer of the present disclosure, the ion optical element comprises an ion guide.

[0023] According to another embodiment of the mass spectrometer of the present disclosure, the vacuum chamber is maintained at about 1×10 -8 Torr to a pressure in the range of about 50 mTorr.

[0024] According to another embodiment of the mass spectrometer of the present disclosure, the mass spectrometer is configured to perform MRM (Multiple Reaction Monitoring) mass analysis.

[0025] 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, each ion optical element being connected to a corresponding RF choke in a corresponding vacuum chamber.

[0026] According to at least one embodiment of the present disclosure, there is provided a radio frequency (RF) choke for use in a mass spectrometer, comprising: a bobbin having a hollow channel; a plurality of wire windings wound around the bobbin, each of the wire windings exhibiting a lattice winding pattern having a span number of about 1 to about 4 per turn; and a magnetic core disposed in the hollow channel of the bobbin, wherein for an RF frequency in the range of about 500 KHz to about 3 MHz generated by an RF voltage source, the RF choke exhibits an impedance in the range of about 15 Mohm to about 150 Mohm, and for a peak-to-peak RF voltage of at least about 1 kV of the RF voltage source, the RF choke exhibits a power dissipation equal to or less than about 3 W.

[0027] According to another embodiment of the RF choke of the present disclosure, the peak-to-peak RF voltage is in a range of about 1 kV to about 10 kV.

[0028] Another embodiment of the RF choke of the present disclosure further includes a resin dispersed in the hollow passage of the bobbin to prevent air pockets from forming between the magnetic core and the bobbin.

[0029] According to another embodiment of the RF choke of the present disclosure, the resin further covers at least a portion of an outer surface of the plurality of windings.

[0030] According to another embodiment of the RF choke of the present disclosure, each winding has a lattice winding pattern exhibiting a number of spans per turn in a range of about 1 to about 4.

[0031] According to another embodiment of the RF choke of the present disclosure, the number of spans per turn is in a range from about 1.7 to about 2.5.

[0032] According to another embodiment of the RF choke of the present disclosure, the number of spans per turn is selected based on a frequency generated by the RF voltage source and an impedance of the RF choke.

[0033] 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 for RF frequencies in the range of about 500 kHz to about 3 MHz for the peak-to-peak RF voltage of at least about 1 kV.

[0034] According to another embodiment of the RF choke of the present disclosure, the magnetic core includes any one of a ferromagnetic material and a ferrimagnetic material.

[0035] According to another embodiment of the RF choke of the present disclosure, the magnetic core includes ferrite.

[0036] According to another embodiment of the RF choke of the present disclosure, the RF choke has a maximum dimension in any of the X, Y, and Z Cartesian coordinates that is less than about 3 cm.

[0037] According to another embodiment of the RF choke of the present disclosure, the RF choke has a length less than about 5 cm and a diameter less than about 3 cm. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a schematic diagram of a mass spectrometer according to an embodiment of the present teachings,

[0039] Figure 2A-2B Depicted is an RF choke incorporating an embodiment of the present teachings in a mass spectrometer having multiple ion optical elements, and

[0040] Figure 3A-Figure 3FVarious schematic diagrams of RF chokes according to embodiments of the present teachings are shown. DETAILED DESCRIPTION

[0041] It will be understood that, for the sake of clarity, the following discussion will illustrate various aspects of the embodiments of the present disclosure, while omitting certain specific details where it is convenient or appropriate to omit them. For example, the discussion of similar or similar features in alternative embodiments may be slightly simplified. Well-known ideas or concepts may also not be discussed in any detail for the sake of brevity. Those of ordinary skill will recognize that some embodiments of the present disclosure may not require certain details of the details specifically described in each embodiment, and these details are set forth herein only to provide a thorough understanding of the embodiments. Similarly, it will be understood that the described embodiments can be easily changed or varied according to common common sense without departing from the scope of the present disclosure. The following detailed description of the embodiments should not be construed as limiting the scope of the applicant's teaching in any way.

[0042] As used herein, the terms "about", "substantially" and "substantially equal" refer to changes in numerical quantities and / or complete states or conditions, which may occur, for example, through the following situations: measurement or processing procedures in the real world; unintentional errors in these procedures; differences in the manufacture, source or purity of compositions or reagents; etc. In general, the terms "about" and "substantially" as used herein mean 10% larger or 10% smaller than the stated value or range of values ​​or complete conditions or states. For example, a value of about 10 or substantially equal to 10 can mean a concentration between 9 and 11. These terms also refer to changes that will be considered equivalent by those skilled in the art, as long as such changes do not include known values ​​practiced by the prior art.

[0043] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items and may be abbreviated as " / ".

[0044] The term "crossover per turn" is known in the art as applied to wire windings and refers to the number of times the wire crosses from one side of a winding section to the opposite side of the winding section in one complete rotation of the bobbin. FIG. 2 of "Universal Coil Windings" in Radio and Electrical Review, March 1961, pp. 13-20, 38, which is incorporated herein by reference in its entirety, shows an example winding pattern with a crossover per turn of two (2).

[0045] As used herein, the term "vacuum" refers to a pressure state of less than about 10 Torr, for example, between about 10 Torr and about 10 -8 within the scope of support.

[0046] As used herein, the term "ion optical element" 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 electromagnetic fields.

[0047] Typically, RF blocking filters or RF chokes are designed as fixed inductors and are used in mass spectrometers for the purpose of blocking or suppressing high frequency alternating current (AC) signals and allowing low frequency and DC signals to pass through to reach one or more components of the mass spectrometer, such as its ion guide. For example, an RF choke inductor may be used in a mass spectrometer to cause a DC voltage to be applied to an ion optical element that is also connected to a high frequency RF voltage source. The RF choke inductor may be coupled to an electrical connection of a mass spectrometer element (such as a quadrupole assembly) contained in a vacuum.

[0048] The present disclosure relates to RF blocking filters, RF chokes and resonant inductor filters for use in mass spectrometers. The RF choke of the present disclosure can be designed as a fixed inductor that can block or suppress high-frequency alternating current (AC) signals and allow low-frequency and DC signals to pass through. The RF choke can be configured so that it exhibits high impedance at RF frequencies associated with RF signals applied to components of a mass spectrometer (e.g., RF signals that can be applied to rods of a multipole (e.g., quadrupole) ion guide), especially at high RF voltages. When it is necessary to quickly switch (one or more) high DC voltages applied to components of a mass spectrometer (e.g., a mass filter), the RF choke according to the present teachings can also exhibit fast settling times. Increasing the speed of DC switching can achieve fast ion transfer and ion capture between different regions of the ion path in a mass spectrometer. For example, such fast switching of (one or more) high DC voltages can be used for multiple reaction monitoring (MRM), and in some embodiments, the use of the RF choke according to the present teachings can allow the switching speed of (one or more) voltages to be increased when used for MRM mass analysis of samples, thereby increasing MRM flux.

[0049] RF chokes according to the present teachings can exhibit sufficiently low power dissipation even when high RF voltages are applied so that they can be used in vacuum chambers of mass spectrometers without convection cooling. RF chokes can also be constructed to exhibit low impedance in the DC domain, which facilitates rapid changes in the DC level applied to ion optical elements.

[0050] Due to its low power dissipation, the RF choke inductor of the present disclosure can be used with electrical connections of mass spectrometer elements (e.g., ion optical elements) contained in a vacuum chamber, such as ion lenses and rods of multipole assemblies (e.g., quadrupole assemblies) placed in a vacuum. In such a vacuum environment, cooling via convection is not possible, and therefore the power dissipation of the element placed in the vacuum environment becomes a limiting factor that can determine whether the element can be used in the environment. As described above, the RF choke inductor of the present disclosure can exhibit low power dissipation and can therefore be used in a vacuum environment. For example, 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, the power dissipation of the RF choke according to the present teachings can be equal to or less than about 5 watts (W), for example in the range of about 0 W to about 5 W, such as in the range of about 1 W to about 3 W.

[0051] In addition, the RF choke can have a small footprint, thereby allowing multiple RF chokes to be simultaneously incorporated into multiple sections of the ion path within a mass spectrometer. In fact, in some embodiments, the small size of the RF choke combined with its low power dissipation at the RF frequencies of interest makes it possible to connect the RF choke to each ion optical element of interest, including those ion optical elements that experience rapid changes in applied DC voltage.

[0052] Various aspects of the present teachings are described with respect to a quadrupole / time-of-flight mass spectrometer. However, it should be understood that the present teachings can be used with other types of mass spectrometry systems, such as a triple quadrupole mass spectrometer, a linear ion trap mass spectrometer, or a 3-D ion trap mass spectrometer.

[0053] Figure 1 Schematically depicted is an example 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 may be employed in the practice of the present teachings. Some examples of suitable ion sources may include, but are not limited to, electrospray ionization devices, nebulizer-assisted electrospray devices, chemical ionization devices, nebulizer-assisted atomization devices, chemical ionization devices, matrix-assisted laser desorption / ionization (MALDI) ion sources, photoionization devices, laser ionization devices, thermal spray ionization devices, inductively coupled plasma (ICP) ion sources, sonic spray ionization devices, glow discharge ion sources, and electron impact ion sources, etc.

[0054] The generated ions pass through the orifice 104a of the curtain plate 104 and the orifice 106a of the orifice plate 106, which is located downstream of the curtain plate and spaced apart from the curtain plate, thereby forming a gas curtain chamber between the orifice and the curtain plate. A curtain gas supply (not shown) can provide a curtain gas flow (e.g., N2) between the curtain plate 104 and the orifice plate 106 to help keep the downstream section of the mass spectrometer clean by de-clustering and rejecting large neutral particles. The curtain chamber can be maintained at an elevated pressure (e.g., a pressure greater than atmospheric pressure), and the downstream section of the mass spectrometer can be maintained at one or more selected pressures by evacuating one or more vacuum pumps (not shown).

[0055] In this embodiment, ions are received by ion optics QJet through aperture 106a of aperture plate 106, which includes four rods (two of which are shown in the figure) arranged in a quadrupole configuration to which RF voltages can be applied to generate a quadrupole electric field in the space between the rods. Qjet optics can use a combination of gas dynamics and radio frequency fields to trap and focus ions.

[0056] The ions are then transmitted via ion lens IQ0 into an ion guide Q0 which comprises four rods 108 (two of which are visible in the figure) arranged in a quadrupole configuration to form an ion beam for transmission to downstream components of a mass spectrometer.

[0057] The ion beam leaves the Q0 ion guide and is focused via an ion lens IQ1 and a quadrupole pre-filter lens ST1 into a subsequent ion mass filter Q1, which includes four rods 110 (two of which are visible in the figure) arranged in a quadrupole configuration and to which RF voltages as well as DC resolving voltages can be applied to radially focus the ions as they pass through the Q1 mass analyzer and select ions with a target m / z ratio (referred to herein as precursor ions). In other embodiments, other multipole configurations may be utilized, such as a hexapole configuration or an octopole configuration.

[0058] More specifically, in this embodiment, the quadrupole group Q1 can be operated as a conventional transmission RF / DC quadrupole mass filter to select ions with m / z values ​​of interest or m / z values ​​within a range of interest. For example, the quadrupole group Q1 can be provided with an RF / DC voltage suitable for operation in mass resolution mode. For example, the parameters of the applied RF voltage and DC voltage can be selected so that Q1 establishes a transmission window of the selected m / z ratio, whereby these ions can pass through Q1 largely undisturbed. However, ions with m / z ratios that fall outside the window will not obtain stable ion trajectories within the quadrupole and will be prevented from passing through the quadrupole group Q1. It should be understood that this operating mode is only one possible operating mode of Q1. In this embodiment, the Q0 ion guide and the Q1 mass filter are respectively disposed in differentially pumped vacuum chambers 151 and 152. For example, the vacuum chamber 151 can be maintained at a pressure in the range of about 3 to about 12 mTorr, and the vacuum chamber 152 can be maintained at a pressure in the range of about 1 to about 50 microTorr.

[0059] Ions passing through the Q1 mass analyzer are focused into the collision cell Q2 via a quadrupole pre-filter lens ST2 and an ion lens IQ2A. The collision cell Q2 includes four rods 112 (two of which are visible in the figure) that are arranged in a quadrupole configuration and to which an RF voltage can be applied to provide radial confinement of the ions. The rods 112 are arranged in a housing 113 so that the pressure in the collision cell can be increased relative to other stages, for example, by introducing a gas (e.g., nitrogen) into the housing. Although in some embodiments, the collision cell Q2 is used to cause fragmentation of ions received by the collision cell, in other embodiments, the collision cell Q2 is not used for ion fragmentation, but is used to cause, for example, collision cooling of ions.

[0060] Fragment ions exiting the collision cell are received by the downstream Q3 quadrupole mass analyzer 116 and separated based on their m / z ratios for detection via ion detector 118. The Q3 quadrupole mass analyzer includes four rods arranged in a quadrupole configuration and to which RF and DC voltages may be applied.

[0061] The analysis module 119 communicates with the ion detector 118 to receive ion detection signals (eg, electrical pulses) generated by the ion detector 118 and processes those signals to generate a mass spectrum of the detected ions.

[0062] The RF voltage source 115a and the DC voltage source 115b operated under the control of the controller 117 can apply the required RF voltage and DC voltage to the various components of the mass spectrometer 100. For example, the RF voltage source 115a can apply the RF voltage to the quadrupole of the Q0 ion guide. The Q1 mass filter, the Q2 collision cell, and the Q3 mass analyzer are capacitively coupled to the rods of the Q0 ion guide to receive the RF voltage via this capacitive coupling. The RF voltage applied to the rods of the Q0 ion guide, the Q1 mass filter, and the Q2 collision cell provides an electromagnetic field for causing radial confinement of ions and / or selecting ions with a desired m / z ratio to pass through the quadrupole. The DC voltage source 115b can apply a DC resolution voltage to the quadrupole of the Q1 mass filter to select ions with an m / z ratio of interest.

[0063] RF chokes according to the present teachings may be used in mass spectrometers, such as Figure 1 The mass spectrometer 100 of the present invention, or any mass spectrometer including an ion optical element located in a vacuum chamber to which an RF voltage and a DC voltage should be applied. The ion optical element can be any component 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 in a multipole configuration.

[0064] For example, Figure 2A and Figure 2B Depicted is an RF choke incorporating an embodiment of the present teachings in a mass spectrometer having a plurality of ion optical elements that receive RF voltage by capacitively coupling to the quadrupoles of a main quadrupole Q0 ion guide that are directly coupled to an RF voltage source to receive their RF voltage (i.e., the ion optical elements obtain their RF from the main quadrupole Q0). More specifically, as Figure 2A and Figure 2B As shown, the mass spectrometer may include a main quadrupole ion guide Q0, a quadrupole prefilter ST1, a quadrupole mass filter Q1 and another quadrupole prefilter ST2. The quadrupole Q1 electrically coupled to the RF source RFA and the DC source DCA may be capacitively coupled to the quadrupole prefilters ST1 and ST2 and the main quadrupole Q0.

[0065] like Figure 2A As shown, in conventional mass spectrometry systems, very large chokes (schematically shown as inductors L1 and L2) are coupled to the main quadrupole Q0 in order to reduce the settling time when switching an applied voltage (e.g., a DC voltage). Due to the large size of these chokes, they cannot be coupled to the quadrupole pre-filters ST1 and ST2. Instead, resistors (R3-R6) with larger settling times are typically used. As described in detail below, in many embodiments, the RF chokes according to the present disclosure can have a compact size and can therefore replace resistors R3-R6 (e.g., Figure 2BBy using a DC voltage (as shown) all key optical components can exhibit faster settling times, which is advantageous, for example, when performing fast MRM analysis of analytes. In addition, replacing resistors with RF chokes can allow for higher RF coupling due to lower power dissipation. This, in turn, combined with the fast rise and fall times of the DC voltage can eliminate ion trapping. Furthermore, replacing resistors with RF chokes can eliminate crosstalk between RF coupled optical components.

[0066] The use of (one or more) RF chokes according to the present teachings in a mass spectrometer is not limited to circuits for applying RF voltages and DC voltages to the quadrupoles of a mass filter or ion guide. Instead, RF chokes according to the present teachings can be used in a mass spectrometer as part of a circuit for applying DC voltages and RF voltages to any ion optical element.

[0067] In some embodiments, one or more RF chokes according to the present teachings may be employed in the Q0 region of a mass spectrometer.

[0068] Preferably, an RF choke according to the present teachings (such as the RF choke 200 described below) is arranged in a vacuum chamber where the (one or more) ion optical elements of interest (e.g., ion guide rods, such as a pre-filter quadrupole) are located. In general, an RF choke according to the present teachings can be used in any location, including in a vacuum environment where convective cooling of the RF choke is not feasible. In one embodiment, a corresponding RF choke may be located in each of a plurality of vacuum chambers, each vacuum chamber containing at least one ion optical element to which an RF voltage and / or a DC voltage is applied, wherein each ion optical element is connected to a corresponding RF choke in the corresponding vacuum chamber.

[0069] As described below, an RF choke according to an embodiment of the present teachings can be constructed so that it exhibits a high impedance at the frequency of the applied RF signal. This can reduce power dissipation, thereby making the use of the RF choke in a vacuum environment feasible. The RF choke can also be constructed so that it exhibits a low impedance in the DC domain, which helps to quickly change the DC voltage applied to the ion optical element. In addition, the choke can be constructed so that it has a small footprint, thereby allowing multiple RF chokes to be used in multiple sections of the ion path of the mass spectrometer at the same time.

[0070] like Figure 3A-3EAs shown, at least one embodiment of an RF choke 200 according to the present teachings includes a bobbin 202 about which wire may be wound as described below, thereby providing three wire winding sections, although other numbers of wire winding sections may be used. The bobbin 202 may be formed of a material that exhibits low dielectric losses at RF frequencies in the range of about 500 kHz to about 3 MHz, such as a low dissipation factor plastic or glass or a mineral-filled plastic material - such as a polyetherimide (e.g., ULTEM, polyethylene, polypropylene), a resin (polyphthalamide), or a machinable ceramic (e.g., Macore, aluminum nitride, etc.). The bobbin 202 includes two flanges 204 into which a pin 206 is inserted, such as Figure 3A As shown. The pin 206 can be press-fitted into the flange 204. Figure 3B As shown, the wire 208 may be wrapped around the base of the pin 206 and then welded to the pin 206. The wire 208 may then be wound onto a bobbin to form a plurality of circular segments 210 on a central portion 209 of the bobbin 202, such as Figure 3C The number of line circular segments may be in the range of about 2-6.

[0071] By way of example, wire 208 may be wound about 400 turns on each of plurality of circular segments 210, although other numbers of turns may be used, for example, in the range of about 300 to about 1500 turns. In at least one embodiment, wire 208 may be wound around the bobbin such that the winding exhibits a crisscross pattern of wire layers, such that each wire in one layer crosses a corresponding wire in the next layer at an angle, such as Figure 3F This cross-shaped pattern is known in the art as a "universal winding", "honeycomb winding" or "lattice winding".

[0072] More specifically, each section can be constructed using a span number per turn between about 1 and 4, and preferably in the range of 1.7 and 2.5. The span number per turn can be selected based at least in part on the RF frequency (or RF frequency range) for which the RF choke is designed and the desired impedance of the RF choke at these frequencies. For example, for RF frequencies in the range of about 500 kHz to about 3 MHz and corresponding impedances in the range of about 15 Mohm to about 150 Mohm, the span number 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 in the range of about 1.7 to about 2.5, or in the range of about 1.8 to about 2.2.

[0073] like Figure 3DAs shown, in this 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 that enables the desired low losses of the choke to be achieved at the frequency of the applied RF signal. Some examples of suitable ferrimagnetic or ferromagnetic materials include, but are not limited to, ferrites (e.g., 4B1NiZn), powdered molypermalloy, sendust, iron powder, or powdered ferrosilicon. An epoxy seal 214 can be added to the end of the bobbin 202, such as Figure 3E As shown, the magnetic core 212 is sealed in the cavity 202 a of the bobbin 202 .

[0074] For example, in at least one embodiment, the length of the bobbin 202 may be in the range of about 3 cm to about 5 cm. The diameter of the flange 204 of the bobbin 202 may be in the range of about 2 cm to about 3 cm. In addition, the inner diameter of the cavity 202a may be about 6 mm, and the wall thickness of the cavity 202a may be about 2 mm. The diameter of the circular wire segment 210 of the bobbin 202 may be in the range of about 12 mm to about 20 mm and the thickness may be in the range of about 3 mm to about 3.5 mm. In at least one embodiment, the largest dimension of the bobbin 202 in any one of the three dimensions (e.g., X, Y, and Z Cartesian dimensions) may be equal to or less than about 3 cm, such as in the range of about 1 cm to about 2 cm.

[0075] A low outgassing type resin (also referred to herein as a varnish) may be introduced into the central cavity to fill the gap (if any) between the magnetic core 212 and the bobbin 202 to inhibit and preferably prevent arcing (corona discharge) when high RF voltages are applied to the wire windings. This varnish or a different varnish may also be applied to the outer surface of the wire windings.

[0076] In at least one embodiment, the inductance of the RF choke (e.g., as measured between pins 206) can be approximately 42.5 mH, or in the range of approximately 40-45 mH for RF frequencies in the range of approximately 500 kHz to approximately 3 MHz. Additionally, in some such embodiments, the DC resistance of the RF choke (e.g., as measured between pins 206) can be approximately 108 Ω, or in the range of approximately 100-115 Ω. The above configuration of the RF choke can produce an equivalent impedance of approximately 15 Mohm-150 Mohm in the frequency range between approximately 500 KHz and 3 MHz, which can allow the RF choke to operate at sufficiently low power levels to allow the RF choke to be positioned for operation in a vacuum environment, particularly within an evacuated chamber of a mass spectrometer. For example, in some embodiments, the power dissipation exhibited by an RF choke according to the present teachings for an applied peak-to-peak RF voltage of at least approximately 1 kV can be less than approximately 3 W.

[0077] In at least one embodiment, the RF choke may include a resin layer coated on at least a portion of an outer surface of at least one wire winding.

[0078] Those skilled in the art will appreciate that various changes may be made to the above-described embodiments without departing from the scope of the present invention.

[0079] The above detailed description refers to the accompanying drawings. The same or similar reference numerals may be used in the accompanying drawings or descriptions to refer to the same or similar parts. In addition, unless otherwise specified, similarly named elements can perform similar functions and can be similarly designed. The details are set forth to provide an understanding of the exemplary embodiments. Embodiments (e.g., alternative embodiments) can be practiced without some of these details. In other cases, well-known techniques, procedures, and components are not described in detail to avoid blurring the described embodiments.

[0080] The description of the above-mentioned embodiments is for illustrative purposes only. It is not exhaustive and does not limit the embodiments to the precise form disclosed. Although several exemplary embodiments and features are described, modifications, adjustments and other implementations can be made without departing from the spirit and scope of the embodiments. Therefore, unless otherwise explicitly stated, these descriptions relate to one or more embodiments and should not be interpreted as limiting the embodiments to a whole. Whether or not the present disclosure states that a feature is related to "one", "the", "one", "one or more", "some" or "various" embodiments, this is correct. As used herein, the singular forms "one", "an" and "the" may include plural forms unless the context clearly specifies otherwise. In addition, the term "coupling" does not exclude the presence of intermediate elements between coupling items. In addition, when a feature may be present in a statement, it is indicated that the feature may be present in one or more embodiments.

[0081] In the present disclosure, the terms "includes," "comprising," "including," and "having" when used after a group or system represent open inclusion and do not exclude the addition of other unlisted members to the group or system. Furthermore, unless otherwise stated or inferred from the context, if the conjunction "or" is used, it is not exclusive but inclusive, meaning and / or

[0082] Or. Also, if these terms are used, a subset of a set may include one or more than one member of the set (including all members).

[0083] Furthermore, if used in the present disclosure, and unless otherwise specified or inferred, if the first variable does not decrease when the second variable increases but generally increases, the first variable is an increasing function of the second variable. On the other hand, if the first variable does not increase when the second variable increases but generally decreases, the first variable is a decreasing function of the second variable. In some embodiments, if the first variable is directly proportional or inversely proportional to the second variable, the first variable can be an increasing function or a decreasing function of the second variable, respectively.

[0084] The disclosed systems, methods and devices are not limited to any specific aspect or feature or combination thereof, nor do the disclosed systems, methods and devices require the existence of any one or more specific advantages or solutions to problems. Any operating theory is for ease of explanation, but the disclosed systems, methods and devices are not limited to such operating theories.

[0085] In view of the above teachings, modifications and changes can be made, or modifications and changes can be obtained by practicing the embodiments. For example, the steps described need not be performed in the same order or the same degree of separation as discussed. Similarly, various steps can be omitted, repeated, combined or performed in parallel as needed to achieve the same or similar purposes. Similarly, the above-mentioned system does not necessarily need to include all the parts described in the embodiments, and may also include other parts not described in the embodiments. Therefore, the embodiments are not limited to the above details, but are defined by the attached claims according to the full scope of their equivalents. In addition, the present disclosure is directed to all novel and non-obvious features and aspects of the various disclosed embodiments (individually and in various combinations and sub-combinations with each other).

[0086] While the present disclosure has been described in detail in conjunction with specific embodiments, many alternatives, modifications and variations will be apparent from the foregoing description. Therefore, it is contemplated that the appended claims will cover any such alternatives, modifications and variations that fall within the true spirit and scope of the present disclosure.

Claims

1. A mass spectrometer comprising: Vacuum chamber, at least one ion optical element disposed in the vacuum chamber, A DC voltage source located outside the vacuum chamber and electrically coupled to the ion optical element to apply a DC voltage to the ion optical element, an RF voltage source located outside the vacuum chamber and electrically coupled to the ion optical element to apply an RF voltage to the ion optical element, an RF choke located in the vacuum chamber and electrically connected between the DC voltage source and the RF voltage source, The RF choke comprises: A bobbin having a hollow passage, a plurality of windings wound around a bobbin, each of said windings exhibiting a lattice-like winding pattern, a magnetic core disposed in the hollow passage of the bobbin, Wherein, for the frequency generated by the RF voltage source at about 500 KHz to about 3 MHz range, the RF choke exhibits approximately 15Mohm The RF choke has an impedance in the range of about 150 Mohm, and exhibits a power dissipation equal to or less than about 3 W for a peak-to-peak RF voltage of at least about 1 kV of the RF voltage source.

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

3. The mass spectrometer according to any one of claims 1 and 2, further comprising a resin dispersed in the hollow channel of the bobbin to prevent air pockets from being formed between the magnetic core and the bobbin.

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

5. A mass spectrometer according to any one of the preceding claims, wherein Each of the windings has a lattice winding pattern exhibiting a number of spans per turn in a range of about 1 to about 4.

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

5.

7. The mass spectrometer according to any one of claims 5 and 6, wherein: The number of spans 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: For the peak-to-peak RF voltage of at least about 1 kV, the magnetic core exhibits a power dissipation of less than about 3 W for RF frequencies in the range of about 500 kHz to about 3 MHz.

9. The mass spectrometer according to claim 8, wherein: The magnetic core includes any one of a ferromagnetic material and a ferrimagnetic material.

10. The mass spectrometer according to claim 8, wherein: The magnetic core includes ferrite.

11. A mass spectrometer according to any one of the preceding claims, wherein The RF choke has a maximum dimension in any of the X, Y, and Z Cartesian coordinates that is less than about 3 cm.

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

13. The mass spectrometer according to claim 1, wherein: The mass ion optical element includes a set of rods arranged in a multipole configuration.

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 includes an ion lens.

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

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

18. The mass spectrometer according to claim 1, wherein: The vacuum chamber is maintained at approximately 1x10 -8 Torr to a pressure in the range of about 50 mTorr.

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

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

21. A radio frequency (RF) choke for use in a mass spectrometer, comprising: A bobbin having a hollow passage, a plurality of wire windings wound around the bobbin, each of the wire windings exhibiting a lattice winding pattern having a number of spans per turn of from about 1 to about 4, and A magnetic core is disposed in the hollow passage of the bobbin, wherein the RF choke exhibits an impedance in the range of about 15 Mohm to about 150 Mohm for an RF frequency in the range of about 500 KHz to about 3 MHz generated by an RF voltage source, and the RF choke exhibits a power dissipation equal to or less than about 3 W for a peak-to-peak RF voltage of at least about 1 kV of the RF voltage source.

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

23. The RF choke of any one of claims 21 and 22, further comprising a resin dispersed in the hollow passage of the bobbin to inhibit the formation of air pockets between the magnetic core and the bobbin.

24. The RF choke of claim 23, wherein: The resin also covers at least a portion of an outer surface of the plurality of windings.

25. An RF choke according to any one of claims 21 to 24, wherein Each of the windings has a lattice winding pattern exhibiting a number of spans per turn in a range of about 1 to about 4.

26. The RF choke of claim 25, wherein: The number of spans per turn is in the range of about 1.7 to about 2.

5.

27. An RF choke according to any one of claims 25 and 26, wherein The number of spans 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 of claim 24, wherein: For the peak-to-peak RF voltage of at least about 1 kV, the magnetic core exhibits a power dissipation of less than about 3 W for RF frequencies in the range of about 500 kHz to about 3 MHz.

29. The RF choke of claim 26, wherein: The magnetic core includes any one of a ferromagnetic material and a ferrimagnetic material.

30. The RF choke of claim 28, wherein: The magnetic core includes ferrite.

31. An RF choke according to any one of claims 21 to 30, wherein The RF choke has a maximum dimension in any of the X, Y, and Z Cartesian coordinates that is less than about 3 cm.

32. The RF choke of claim 31 , wherein: The RF choke has a length less than about 5 cm and a diameter less than about 3 cm.

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