Device geometry for controlling mass spectrometer pressure

Abstract

A geometry for a device used to control pressure in a mass spectrometer. A mass spectrometer collision cell system comprising: a gas containment chamber including an inner chamber having an ion inlet and an ion outlet, and a cross-sectional area A. 室 Gas inlet pore; first and second gas outlet pores, respectively disposed at or near the ion inlet and outlet ends, and having corresponding outlet pore cross-sectional areas A. 孔隙1 and A 孔隙2 The longitudinal axis of the chamber extends from the ion inlet end to the ion outlet end and has a length L, and the average outlet pore cross-sectional area. 室 ; and a set of multipole electrodes, at least a portion of each multipole electrode being in the room, wherein A 室 L 室 The values ​​of and ensure that the combined gas conductivity of the chamber and the gas outlet orifice is not greater than 95% of the gas conductivity of the gas outlet orifice alone.

Description

Technical Field

[0001] This disclosure relates to mass spectrometry. More specifically, this disclosure relates to the geometry that affects pressure within components of a mass spectrometer. Background Technology

[0002] Mass spectrometry (MS) analysis is generally performed under high vacuum conditions. For example, some components of a mass spectrometer (such as the mass analyzer) require high vacuum conditions to function properly, where the gas pressure is maintained at 10... -6 The pressure difference is typically lower than 1000 rpm. Meanwhile, the ions to be analyzed are often generated at atmospheric pressure. Due to the large pressure difference between the ion source and the mass analyzer, mass spectrometry systems often include multiple vacuum chambers. These chambers are connected via a small-aperture pump to restrict fluid flow and are gradually maintained at a lower pressure (i.e., a higher vacuum) along the general ion channel between the ion source and the mass analyzer. Furthermore, for tandem mass spectrometry measurements, a collision-induced dissociation cell is required, in which precursor ions are generated from a high vacuum environment (1000 rpm or lower). -5 Up to 10 -6 The torpedo is transported to an intermediate vacuum environment (approximately 10). -3 In the process, fragment ions are transported from an intermediate vacuum environment to another high vacuum environment.

[0003] Correspondingly, many mass spectrometry systems employ ion-cooled cells, in which high-kinetic-energy ions collide with bath gas molecules within the cooling cell, preferably without fragmentation. Ion / molecule collisions within the ion-cooled cell cause most of the initial kinetic energy of the ions to be absorbed by the gas and conducted away, thereby promoting ion focusing and guidance within downstream mass spectrometer components. The structure of the ion-cooled cell is similar to that of the collision cell, except that the cooling cell lacks any measures to provide additional kinetic energy to the ions before or within the cell. Therefore, fragmentation is minimized or eliminated. Consequently, the effective management of gas pressure and flow rate within the mass spectrometry system remains a challenging problem.

[0004] As an example of a mass spectrometer system that can use a collision cell Figure 1A This is a schematic diagram of a portion of an exemplary liquid chromatography-mass spectrometry (LCMS) analysis system, generally shown as 10, which includes a conventional triple quadrupole mass spectrometer. Reference Figure 1AThe ion source 12, located in the ionization chamber 14, is configured to receive liquid or gas samples from an associated device, such as a liquid chromatograph or a syringe pump, via a capillary 37. An atmospheric pressure electrospray ionization source is illustrated only as an example. However, any ion source can be used, such as a heated electrospray ionization (H-ESI) source, an atmospheric pressure chemical ionization (APCI) source, an atmospheric pressure matrix-assisted laser desorption / resorption (MALDI) source, a photoionization source, or a source employing any other suitable ionization technique. The ion source 12 forms charged particles 39 (ions or charged droplets that can be desolvated to release ions) representing the sample. These charged particles are then transported from the ion source 12 to a mass analyzer 36 in a high vacuum chamber 26 through one or more intermediate vacuum chambers 18 and 25 whose pressure is continuously reduced in the direction of ion travel. Specifically, droplets or ions are entrained in a background gas and transported from the ion source 12 through an ion migration tube 16 into an intermediate vacuum chamber 18, which passes through a first separating element or wall 15a. This intermediate vacuum chamber is maintained at a pressure lower than that of the ionization chamber 14 but higher than that of the high vacuum chamber 26. The ion migration tube 16 may be physically coupled to a heating element or block 23 that provides heat to the gas and entrained particles in the ion migration tube to assist in the desolvation of the charged droplets, thereby releasing free ions.

[0005] A second plate, partition element, or wall 15b can separate the intermediate vacuum chamber 18 from the second intermediate pressure region 25. Similarly, another plate, partition element, or wall 15c separates the intermediate pressure region, i.e., region 25, from the high vacuum chamber 26. An ion optics assembly 20a provides an electric field that guides and focuses the ion flow leaving the ion migration tube 16 through an aperture 22 in the second partition element or wall 15b, which may be an aperture of the skimmer 21. A second ion optics assembly 20b may be provided to transfer or guide ions into an aperture 27 in the plate, partition element, or wall 15c. Both ion optics 20a and ion optics 20b can serve as ion cooling pools, where the initial kinetic energy of the ions is attenuated by interaction with gas molecules that absorb energy as heat. Ion cooling helps to focus the ion path into a narrow, directional beam. Another ion optics assembly 20c may be disposed in the high vacuum chamber 26 containing the mass analyzer 36. Ion optics components or lenses 20a-20c may include migration elements, such as multipole ion guides, to guide ions through aperture 22 and into mass analyzer 36. Mass analyzer 36 includes detector 40, the output of which can be displayed as a mass spectrum. Vacuum ports, such as vacuum ports 13, 17, and 19 shown, can be used to evacuate various vacuum chambers.

[0006] Figure 1B This is a schematic diagram of a portion of an exemplary gas chromatography-mass spectrometry (GCMS) analysis system 200, which employs a conventional triple quadrupole mass spectrometer that may include a collision cell. GCMS system 200 ( Figure 1B The mass spectrometer components inside the high vacuum chamber 26 can be integrated with the LCMS system 10. Figure 1A The components within are similar or identical. However, the GCMS system 200 does not use an electrospray ionization source, but instead can use an electron ionization (EI) ionization source, such as... Figure 1B 203 is generally shown in the figure.

[0007] The ion source 203 of the GCMS system 200 includes an ionization volume 210, into which sample molecules, including analyte molecules, are introduced via the outlet portion of a gas chromatography (GC) column 235. The GC column 235 may be a fused silica capillary of a type known in the art. The ionization volume 210 is located within a vacuum chamber 210, which is evacuated to a suitable pressure via a pumping system (not shown) through a vacuum port 17. An electron flow is generated by passing a current supplied by a filament current source 265 through a thermionic filament 240. The filament current source 265 is located outside the vacuum chamber and is electrically connected to the filament 240 via a vacuum feedthrough (not shown). The filament 240 is typically made of a refractory metal such as rhenium or tungsten (or alloys thereof). The refractory metal may include a low work function coating, such as thorium oxide or yttrium oxide. Electrons emitted by filament 240 travel through aperture 245 into the ionization volume 210 under the influence of an electric field established by applying a suitable potential to filament 240 and electrode 250. The electron beam can also be guided by a magnetic field established by a magnet (not shown) located behind the ionization volume 210 and opposite the filament 240. Electrons interact with sample molecules within the ionization volume 210 to form sample ions. The sample ions are extracted from the ionization volume 210 through lens 260 via ion outlet aperture 255 and transported to chamber 26 containing a triple quadrupole assembly, where they are prepared for mass analysis and subsequent mass analysis.

[0008] Other suitable ion sources can be used, such as chemical ionization, inductively coupled plasma (ICP) ionization, secondary ion mass spectrometry, metastable atom bombardment, or photoionization. ICP-MS instruments may include cells that can be used as collision cells or reaction cells.

[0009] LCMS system 10 ( Figure 1A ) and GCMS system 200 ( Figure 1BThe triple quadrupole mass spectrometer components shown in the diagram include a first quadrupole device 32, a second quadrupole device 34, and a third quadrupole device 36, as well as an ion detector 40. In variant systems, one or more quadrupoles may be replaced by non-quadrupole devices. For example, the second quadrupole device 34 may be replaced by a general-purpose multipole device, such as an octupole device, a stacked ring ion guide, a non-RF device, etc. However, for illustrative purposes, this device will continue to be referred to herein as the "second quadrupole device". In many operating modes, the first quadrupole device acts as a mass filter, capable of transmitting only selected ions with a specific mass-to-charge ratio m / z while discarding other unselected ions. The selected ions are then delivered to the second quadrupole device 34. In many operating modes, the second quadrupole device acts as a fragmentation device, inducing collisional fragmentation of the selected precursor ions through interaction with inert collisional gas molecules introduced through tube 35. When collision-induced fragmentation is not desired or required, the second quadrupole device 34 can operate as an RF-only device, transmitting ions covering a range of m / z values. Ions, either received from an ion source or fragmented ions generated within the second quadrupole device 34, are transmitted from the second quadrupole device 34 to the mass analyzer 36 for mass analysis.

[0010] For use as a device for fragmenting ions via collision-induced dissociation, the second quadrupole device 34 includes a gas containment 38 that encloses an internal chamber, retaining the collision gas during operation. The chamber also contains a set of quadrupoles or other multipoles 4. Precursor ions are introduced from the first quadrupole device 32 into the chamber of the containment 38 through a first gas flow restricting orifice 6. An oscillating radio frequency (RF) voltage waveform applied to the poles 4 by one or more power sources (not shown) generates a pseudopotential trap centered on the longitudinal axis of the collision cell. This pseudopotential trap confines the introduced ion precursor near the longitudinal axis.

[0011] When the second quadrupole device 34 is used as a collision cell, precursor ions introduced into the device 34 collide with neutral molecules of the collision gas in the inner chamber of the containment 38. Fragment ions generated by the ion-molecule collisions are confined in a pseudopotential trap centered on the longitudinal axis. After their generation, the fragment ions and any remaining precursor ions exit the second quadrupole device 34 through a second gas flow confinement aperture 6 facing the mass analyzer 36. Note that, as used herein, the term "aperture" generally refers to a hole or opening, including holes or channels through ion lenses, and openings in multipole device sections that confine gas flow but allow the majority of ions to flow. Generally, one or more electrostatic lenses are positioned at both ends (inlet and outlet) of the second quadrupole device 34 to control ion entry and exit from the device. These electrostatic end lenses can also be used to generate an electric field within the containment chamber parallel to the longitudinal axis and facilitating ion passage through the chamber from the inlet to the outlet. Therefore, aperture 6 is generally not defined by holes or gaps in the containment 38, but rather is defined as corresponding to the aperture of the electrostatic end lens. Often, the aperture diameter of electrostatic end lenses is limited to certain predetermined values ​​based on ion guidance principles that are independent of the ion fragmentation process.

[0012] Figure 2 This is a schematic cross-sectional view of a known collision cell device 34a, which is used at the position of quadrupole 34 to generate fragment ions by collision-induced fragmentation. Figure 2 The cross-section shown is taken transversely to the longitudinal axis of the device. During operation of the collision cell device 34a, precursor ions are introduced into the inner chamber 53, which contains an inert gas, alternatively, a reactive gas or a reactive gas, with a typical internal pressure of approximately 1-20 mTorr. Figure 2 The chamber 53 depicted has a straight cylindrical geometry. Inside the chamber, precursor ions collide with neutral gas molecules, resulting in fragmentation or other reactions with the gas to form product ions. A set of quadrupoles 54 are disposed within the chamber 53 and extend parallel to the longitudinal axis of the collision cell 34a, which is perpendicular to the drawing. The four quadrupoles 54 are separated from the housing 58 of the collision cell device 34a by insulating spacers 55 and receive an RF-only voltage waveform from a power source (not shown). The applied RF-only voltage waveform is maintained within a pseudopotential well centered at the free ends of the four poles 54, with precursor ions and fragment ions (or other product ions) having a range of m / z values. Inert gas is supplied through a gas inlet pipe 35 (see...). Figure 1A , 1B And 7) is supplied to chamber 53, the gas inlet pipe is in Figure 2 Not described in the text but different from Figure 2 The transverse cross-section shown passes through the housing 58 and the insulating spacer 55.

[0013] A set of drag vanes 51 are also disposed within chamber 55 and attached to the insulating spacer layer via mounting structure 57. Each drag vane is in the form of an elongated plate, the length of which is parallel to the longitudinal axis of the collision cell 34a, i.e., perpendicular to the plane of chamber 53. As described in U.S. Patent No. 7,675,031, each drag vane includes a substrate, such as a printed circuit board material, on which an array of finger electrodes (not shown) are disposed, spaced apart along the longitudinal axis. A voltage ranging from a gradually increasing range can be applied along the length of the auxiliary electrodes by implementing a voltage divider utilizing electrostatic resistors of the individual finger electrodes of the interconnected array. The voltage applied to the finger electrodes generates an axial electric field within chamber 53, which is parallel to the longitudinal axis and helps to draw fragment ions through the gas within the chamber toward the outlet orifice 6 disposed at the ion outlet end of collision cell 34a. Figure 2 In the figure, the projections of the airflow-restricting inlet and outlet orifices 6 with the same diameter on the cross section are shown as dashed lines.

[0014] The collision pool requires sufficiently high internal pressure of the collision gas to break up and ultimately dampen the kinetic energy of the impact-damped ions. This process becomes increasingly difficult as the m / z value of the parent ions increases, because these ions lose less energy in each collision and are often introduced into the collision pool with a deliberately higher kinetic energy than that used for ionic materials with lower m / z values. Figure 7 As schematically depicted, collision gas from inlet pipe 35 is introduced into chamber 53 through gas inlet orifice 9 located approximately in the middle between the two ends of the collision cell. The gas escapes through front and rear orifices 6, which respectively receive precursor ions from the upstream component into the collision cell and deliver product ions to the mass analyzer.

[0015] The collision cell pressure is typically maintained in the range of 1–20 mTorr, which is a thousand times higher than the optimal operating pressure of other mass spectrometer components upstream and downstream of the collision cell (such as mass filters and mass analyzers). Therefore, the diameters of the front and rear pores 6 of the collision cell must be very small, as any gas that can escape through the pores and subsequently enter other mass spectrometer components (e.g., mass analyzers, ion traps, etc.) has a very detrimental effect on ion transport. However, there is a practical lower limit to the size of these pores. Therefore, mass spectrometry requires collision cell designs that achieve the highest possible internal pressure while reducing the flow rate of the collision gas into the collision cell, thereby reducing the burden on the vacuum pump and minimizing the amount of collision gas that can escape into other mass spectrometer components. Summary of the Invention

[0016] The inventors of this paper present a strategy for selecting the geometry of collision-induced fragmentation cells (“collision cells”), ion-cooled cells, and other ion / gas reaction cells that, for a given gas flow rate, advantageously generate internal gas pressures greater than those produced in conventional collision and ion-cooled cells. During tandem mass spectrometry measurements, achievable higher pressures can be used to enhance and / or better control ion fragmentation. The novel strategy disclosed herein is based on the non-intuitive properties of how molecules move within a structure under molecular flow.

[0017] According to a first aspect of this teaching, a mass spectrometer collision cell system is provided, the system comprising:

[0018] A gas containment structure includes an internal chamber having an ion inlet and an ion outlet, the chamber having a cross-sectional area A. 室 It is transverse to the longitudinal axis;

[0019] Gas inlet orifice, used to supply gas to the internal chamber;

[0020] First and second gas outlet orifices are respectively located at or near the ion inlet and ion outlet ends of the inner chamber, and the first and second gas outlet orifices have corresponding outlet orifice cross-sectional areas A. 孔隙1 and A 孔隙2 and average outlet pore cross-sectional area

[0021] The longitudinal axis of the chamber extends from the ion inlet end to the ion outlet end and has a length L. 室 ;and

[0022] A set of multipole electrodes, wherein at least a portion of each multipole electrode is disposed indoors.

[0023] Where A 室 L 室 and The value makes the combined gas conductivity of the chamber and the gas outlet orifice less than or equal to 95% of the gas conductivity of the individual gas outlet orifice.

[0024] Preferably, A 室 L 室 and The value makes the combined gas conductivity of the chamber and gas outlet orifice less than or equal to 90%, 80%, or 70% of the gas conductivity of the individual gas outlet orifice.

[0025] According to a second aspect of this teaching, a method for quality analysis of a sample is provided, the method comprising:

[0026] The first plurality of ions originating from the sample are generated and the plurality of ions are transported into a chamber with an internal pressure P1;

[0027] The first plurality of ions are transported through a first gas-confined pore to a second chamber having an internal pressure P2, where P2 > P1;

[0028] Alternatively, the first or more ions in the cooling chamber may be cooled, or the first or more ions may react with the gas in the chamber to generate multiple product ions.

[0029] The cooled first plurality of ions or plurality of product ions are transported through a second gas-confined pore into a third chamber having an internal pressure P3, where P2 > P3; and

[0030] The first multiple ions or multiple product ions cooled by the mass analyzer in the third chamber were analyzed.

[0031] The combined gas conductivity of the second chamber and the gas-confined pore is less than or equal to 95% of the gas conductivity of the gas-confined pore alone.

[0032] Preferably, A 室 L 室 and The value makes the combined gas conductivity of the chamber and gas outlet orifice less than or equal to 90%, 80%, or 70% of the gas conductivity of the individual gas outlet orifice. Attached Figure Description

[0033] The above and other aspects of the invention will become apparent from the following description, which is given by way of example only and with reference to the accompanying drawings, which are not necessarily drawn to scale. In the drawings:

[0034] Figure 1A This is a schematic diagram of a liquid chromatography-mass spectrometry (LCMS) analysis system using a conventional triple quadrupole mass spectrometer system;

[0035] Figure 1B This is a schematic diagram of a gas chromatography-mass spectrometry (GCMS) analysis system using a conventional triple quadrupole mass spectrometer system;

[0036] Figure 2 This is a schematic cross-sectional view of a known collision pool device.

[0037] Figure 3A It is a graph showing the change of the clausing factor, which is the change of the probability of transporting gas or ion particles through a tube of length L and diameter d as a function of the rate of change L / d.

[0038] Figure 3B It is a graph of the cumulative probability density of a particle's reflection or scattering from the surface, calculated based on Lambert reflection, as a function of the angle of emission from the surface;

[0039] Figure 4AIt is a graph with a set of graphical curves, each curve representing a different collision cell tube length, which has the average pressure in the collision cell calculated at different tube diameter to pore diameter ratios, and the value of each curve is calculated for a steady-state argon flow rate of 0.248 ml / min at 300 K.

[0040] Figure 4B yes Figure 4A The graphs depict the same pressure information inside the collision pool, but the vertical axis shows the ratio of the calculated pressure to the asymptotic minimum possible pressure.

[0041] Figure 5A This is a schematic transverse cross-sectional view of the first collision pool device according to this teaching;

[0042] Figure 5B This is a schematic transverse cross-sectional view of the second collision pool device according to this teaching;

[0043] Figure 6 This is a graph with a set of curves, each representing the length of the collision cell tube, with calculated gas conductivity through the collision cell at different ratios of tube diameter to pore diameter. The values ​​for each curve are calculated for a steady-state argon flow rate of 0.248 mL / min at 300 K. The graph also shows the gas conductivity values ​​for six known conventional collision cells. Figure 5A and 5B The gas conductivity values ​​of the novel collision cell are described in the figure;

[0044] Figure 7 This is a schematic longitudinal cross-sectional view of the third collision pool device according to this teaching;

[0045] Figure 8A This is a schematic longitudinal cross-sectional view of the fourth collision pool apparatus according to this teaching; and

[0046] Figure 8B Is it through Figure 8A A schematic cross-sectional view of a portion of the collision pool equipment. Detailed Implementation

[0047] The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the described embodiments will be apparent to those skilled in the art, and the general principles herein can be applied to other embodiments. Therefore, the invention is not intended to be limited to the embodiments and examples shown, but should be accorded the widest possible scope based on the features and principles shown and described. For a more detailed and complete understanding of the features of the invention, please refer to Figures 1-7, 8A, and 8B in conjunction with the following description.

[0048] In this description of the invention, it should be understood that, unless otherwise implicitly or explicitly understood or stated, words appearing in the singular form encompass their plural counterparts, and words appearing in the plural form encompass their singular counterparts. Furthermore, it should be understood that, unless otherwise implicitly or explicitly understood or stated, for any given component or embodiment described herein, any possible candidates or alternatives listed for said component may generally be used individually or in combination with each other. Furthermore, it should be understood that the drawings shown herein are not necessarily drawn to scale, wherein only some elements may be drawn for clarity of the invention. And, reference numerals may be repeated in the various drawings to indicate corresponding or similar elements. Furthermore, it should be understood that, unless otherwise implicitly or explicitly understood or stated, any list of candidates or alternatives is merely illustrative and not restrictive.

[0049] The cladding factor κ is often used in static molecular flow calculations (clausing, Pieter). dasKosinusgesetz der Zurückwerfung als Folge des zweiten Hauptsatzes der Thermodynamik." Annals of Physik 396, no. 5 (1930): 533-566.). The clausing factor is a transport probability correction factor ranging from zero to one, and it must be applied to correct gas flux calculations through theoretical pores in an infinitely thin plane to actual pores of non-zero thickness (e.g., tubes of length L). This factor accounts for the phenomenon that, when the tube has a non-zero length L, certain molecular trajectories are excluded from passing through the pores from the tube due to angular constraints. The initial calculations of κ were based on early Monte Carlo simulations of molecular flow through tubes with different L / d ratios. Subsequently, the results of these calculations were fitted with empirical formulas and tabulated. Clausing tables can also be used for gas conductivity values ​​and internal pressures for various types of tubes and chambers.

[0050] Figure 3A Figure 101 shows the Clausing factor κ as a function of the rate of change L / d for a simple tube of length L and diameter d. It can be observed that the transport probability decreases with increasing L / d ratio; molecules are less likely to pass through tubes with large aspect ratios. A key phenomenon affecting the Clausing factor value is that the bounce of gas molecules from the internal surface follows the so-called Lambert reflection, also known as the cosine law.

[0051] The Lambert reflection discussed in this article is similar to Lambert's cosine law in optics, which states that the intensity of radiation or luminescence observed from an ideal diffuse reflective surface or ideal diffuse radiator is proportional to the cosine of the angle θ between the incident light direction and the surface normal. When molecules interact with a surface (metal, ceramic, plastic, etc.), the molecular structure is rough relative to the size of the molecules. Molecules interact with this roughness and eventually lose the "memory" of the original incident angle. This phenomenon results in a desorption angle centered on the surface normal and the cosine law. Regarding this phenomenon, Rozanov (Rozanov, LN, “Vacuum Technology” (2002), edited by Hablanian, MH) points out that a particularly relevant idea from Clausing's paper is that "molecules leaving the surface in equilibrium consist of molecules that generally interact with the surface in various ways: elastic scattering (specular reflection, diffraction in various channels), inelastic scattering (annihilation or generation of one or more phonons), or desorption (after adsorption). If more than one of these processes is effective, then as a result of one of these processes, the distribution of molecules leaving the surface is, in principle, arbitrary, even in equilibrium. The only constraint imposed by the existence of equilibrium is that the sum of all distributions must be cosine." Figure 3B Figure 111 shows the cumulative probability density of a particle's reflection or scattering from the surface as a function of the angle of emission from the surface, calculated based on Lambert reflection.

[0052] Based on the above considerations, the inventors have recognized that the general reason for preventing molecules from escaping from tubes with a large L / d ratio is that even when using the largest diameter opening at the tube end (i.e., a pore with the same diameter as the tube), the average trajectory of molecules bouncing off the inner surface of the tube is transverse to the longitudinal axis of the tube. Therefore, the number of internal paths through which molecules can bounce off the inner surface and immediately pass through the pore after bouncing is relatively small. As a result of the Lambert reflection phenomenon, for a given constant diameter d... 孔隙 It has airflow-restricting pores at the end of a tube with a length L and a tube diameter d. As the ratio L / d increases, the probability of gas molecules passing through the pores decreases (e.g., Figure 3A In this case, an increase in L / d at a constant gas flow rate will lead to an increase in the internal pool pressure.

[0053] To utilize the Lambertian reflection phenomenon, the inventors investigated how changing the geometry of the collision cell affected its internal gas pressure. As shown in Table 1 below, three simple empty tubes with different inner diameters were fabricated using 3D printing. At an argon flow rate of 300 K, the internal gas pressure of each tube was determined to be the inlet pressure required to generate a steady-state flow rate of 0.248 mL / min through the corresponding tube. Furthermore, the expected tube pressure was calculated using direct Monte Carlo simulation (DSMC) [e.g., see GABird, “Direct Simulation of Molecular Gas Dynamics and Gas Flow” (Oxford University Press, Oxford, 1994)] and by using a clausing factor. The experimental and computational results are shown in Table 1 below.

[0054]

[0055] Table 1. Experimental data from 3D printed tubes. 2.5mm pore size, 125mm total internal chamber length, L 室 (See Figure 7 ).

[0056] Further discussion in subsequent paragraphs Figure 7 This illustrates how the length L for calculating and measuring pressure in a simple tube relates to the dimensions of a mass spectrometer collision cell, ion / gas reaction cell, or cooling cell. Each simple tube includes an inlet orifice and an outlet orifice located at opposite ends of the tube. Therefore, the inlet and outlet orifices of the simple tube are spaced apart by a distance L, where L is exactly the length of the tube in question. However, in a mass spectrometer collision cell, ion / gas reaction cell, or cooling cell, gas does not enter the cell interior at one end. Instead, gas is introduced into the cell interior chamber 53 through an ion inlet orifice 9, which is positioned approximately midway between the two end orifices 6. Each of the two end orifices 6 is a gas outlet end, even if one end orifice is an ion inlet end and the other is an ion outlet end. Therefore, the effective cell length L that must be used for comparison with theoretical pressure calculations and simulations, as well as with pressure measurements in a simple tube, is the length L of the cell interior chamber 53. 室 Half of it, as shown in the figure.

[0057] As described in the background section of this document, the inventors have identified a need in the field of mass spectrometry for collision cell designs that achieve the highest possible internal pressure while minimizing the flow rate of the collision gas into the cell. The ratio of gas flow rate to pressure is called conductivity, and it can be expressed in liters per second (L / s) as follows:

[0058]

[0059] Therefore, the aforementioned need in this field can be met by minimizing the cell conductivity. Due to the close correspondence between the observed measured pressure and the pressure calculated using the clausing factor (Table 1), the internal pressure generated in tubular collision cells of other sizes under steady-state gas flow can be predicted, and the conductivity can then be calculated. More generally, the conductivity of any experimental collision cell design can be measured. A quantity referred to herein as “relative conductivity” can then be calculated as the ratio of the conductivity of the complete collision cell system (including the internal chambers and their gas inlet and outlet pores) to the theoretical conductivity of the pores themselves. This document refers to the theoretical gas conductivity C of the pores (or “theoretical pore conductivity”). 孔隙 Defined as the limiting conductivity of a circular tube with an inner diameter of d when the tube length L approaches zero. Generally, for any tube of finite length...

[0060] C 管 =vk 管 A 管 / 4, where v is the average molecular velocity, κ 管 It is the Clausing factor of the tube and A 管 It is the cross-sectional area of ​​the pipe. Similarly,

[0061] C 孔隙 =vκ 孔隙 A 孔隙 / 4 of which κ 孔隙 and A 孔隙 These are the clausing factor and the cross-sectional area of ​​the pores, respectively. The above procedure gives the ratio by which the conductivity of the complete collision cell geometry is lower compared to the conductivity of individual pores. This procedure also normalizes the molecular velocity and temperature of the gas.

[0062] For example, Figure 4A This is a graph showing the calculated pressure inside simple tubes with different lengths, inner diameters, and inlet and outlet orifices. The values ​​for each curve in Figure 4A1 are calculated for a steady-state argon flow rate of 0.248 mL / min at 300 K. Figure 4A Curve 121 represents a series of tubes with an inner diameter ranging from 39.5 mm to 2.5 mm, all with a length of 250 mm and located near an outlet orifice with a diameter of 2.5 mm. Curve 122 represents a series of tubes with an inner diameter ranging from 39.5 mm to 2.5 mm, all with a length of 125 mm and located near an outlet orifice with a diameter of 2.5 mm. Curve 123 represents a series of tubes with an inner diameter ranging from 79.0 mm to 5.0 mm, all with a length of 125 mm and located near an outlet orifice with a diameter of 5.0 mm.

[0063] exist Figure 4AThe asymptotic value of the pressure approaching the right side of the curve (i.e., the baseline value) represents the pressure formed in the collision pool, where the conductivity is determined solely by the diameters of the inlet and outlet pores. Figure 4B middle, Figure 4A The data was migrated to a common baseline. Therefore, curves 131, 132, and 133 represent the same data plotted in curves 121, 122, and 123, respectively, and represent the ratio of the calculated pressure in each tube pool to the corresponding baseline value. In many cases, due to external constraints, the length L and diameter d of the collision pool... 孔隙 It cannot change freely. Figure 4B The curves show that, under the condition of constrained pore diameter, a favorable pressure gain can be achieved at a constant gas flow rate by reducing the pipe diameter and thus the electrical conductivity of the device.

[0064] To leverage these insights, the inventors developed a novel collision pool design that achieves higher internal pressures than achievable in conventional collision pools without increasing airflow relative to conventional designs. Therefore, Figure 5A and Figure 5B Each of these is a schematic cross-sectional view of a collision pool, cooling pool, or reaction pool apparatus 34b, 34c according to this teaching. Figures 5A-5B The cross-section shown is taken transversely to the longitudinal axis of the corresponding device. Similar to... Figure 2 The collision pool 34a depicted, and each of the devices 34b and 34c, includes a set of four quadrupoles 4 extending parallel to the longitudinal axis of the respective device 34b or 34c. Within each device, the quadrupoles are disposed within the central chamber 7 of the housing structure 5. Gas is introduced through a gas inlet pipe 35 (see...). Figure 1A , 1B The gas is supplied to chamber 7, and the gas inlet pipe is in Figures 5A-5B Not described in the text but different from Figures 5A-5B The cross-section shown penetrates the shell 5 within its transverse section. Figures 5A-5B In each of the cells, the outlet aperture 6 is shown as a projection on the plane of the diagram. An axial field can be generated within the cells 34b, 34c by multiple electrodes printed on each of the circuit boards 1. Figures 5A-5B Each of the collision, cooling, or reaction tank devices 34b and 34c depicted employs an improved design, wherein the ratio between the cross-sectional area of ​​the central chamber 7 and the cross-sectional area of ​​the pores 6 is relative to that of the conventional tank 34a. Figure 2 The ratio of similar calculations is significantly reduced. Specifically, the ratio of the chamber cross-sectional area to the pore cross-sectional area of ​​the conventional pool 34a is approximately 103, but the similar calculation ratios for the novel pools 34b and 34c are approximately 22 and 9, respectively.

[0065] Figure 6 This involves comparing the measured relative gas conductivity values ​​of several commercially available collision-induced dissociation cells with... Figure 5A The graph shows a comparison of the measured conductivity of the novel collision-induced dissociation cell. Figure 6 All data shown were obtained at 300 K using an argon flow rate of 0.248 mL / min. The relative conductivity values ​​are relative to the average inner diameter d of the internal chamber identified as the collision cell. 平均 The diameter d of the boundary gas contraction pore 孔隙 The ratio is plotted on the ordinate. To compare two different physical collision pool structures, the number d... 平均 The calculations should be consistent. In simple cases, the cross-section of the inner chamber can be circular, similar to... Figure 2 The depicted cross-section has a diameter of d. 管 In such cases,

[0066] d 平均 =d 管 .

[0067] Otherwise, if the cross-section is a rectangle with height h and width w, then d can be... 平均 Approximately

[0068]

[0069] If the tube or chamber in question is long and narrow, then instead of estimating the relative conductivity value by comparing diameters or cross-sectional areas (as above), it is better to directly calculate the conductivity using the rectangular pipe clausing factor or DSMC calculation.

[0070] The clausing factor of the rectangular tube can be calculated using Santerer, DJ; Boeckmann, MD, “Molecular Flow Transport Probability in Rectangular Tubes,” *Journal of Vacuum Science Technology*, A, 1991, 9(4), 2378-2383. Then, the conductivity of the rectangular chamber is calculated as follows:

[0071] C 室 =(vκ) 室 A 室 ) / 4

[0072] Where A 室 =hw is the cross-sectional area of ​​the rectangular chamber and k 室 It is the clausing factor of the rectangular chamber.

[0073] For tubes or chambers with more complex cross-sectional shapes, different chamber designs can be compared, or the estimated chamber conductivity can be compared to the pore conductivity by comparing cross-sectional areas rather than average diameters. For example, the cross-sectional area A of the chamber can be determined through graphical integration. 室 Then A室 With A 孔隙 Comparison (where generally speaking, Or, consider A′ of the cross-sectional area of ​​the first collision pool structure. 室 With regard to A″ of the cross-sectional area of ​​the second collision pool structure 室 The first collision pool structure is compared with the second collision pool structure.

[0074] Figure 6 The point 144c drawn above belongs to Figure 2 The example of a pool design is shown. Point 145a is plotted. Figure 5A The novel pool design is shown. Point 145b belongs to... Figure 5B The novel cell design is shown. Points 144a, 144b, 144d, 144e, and 144f are plotted for other known cell designs. For comparison, curves 141, 142, and 143 depict the calculated relative conductivity values ​​for various tube and pore combinations. Figure 6 The x-coordinate value of each plotted point—whether on one of curves 141-143 or plotted individually—represents the ratio between the conductivity of the elongated internal volume and the theoretical pore conductivity of the boundary pores adjacent only to the ends of the elongated internal volume. As mentioned above, the theoretical conductivity of the pores (or "theoretical pore conductivity") is defined in this paper as the limiting conductivity of a circular tube with an inner diameter of d when the tube length L approaches zero. Curve 141 pertains to a length L of 250 mm and a variable inner diameter d. 管 A circular tube with a 2.5mm diameter boundary pore. Curve 142 belongs to a length L of 125mm and a variable inner diameter d. 管 A circular tube with a 5.0 mm diameter boundary pore. Curve 143 belongs to a length L of 125 mm and a variable inner diameter d. 管 The circular tube, along with the boundary pores with a diameter of 2.5 mm.

[0075] Figure 6 The data depicted in the text highlights a somewhat anomaly: the diameter of the collision pool gas chamber—either d for a chamber with a circular cross-section—is... 管 Or in other cases it is d 平均 — Greater than the pore diameter d 孔隙 In all cases, the gas conductivity of the collision cell decreases as the diameter of the collision cell chamber decreases. When the diameter of the collision cell is much larger than the diameter of the surrounding gas confining pores (i.e., 7 times or more larger) (see...), the conductivity decreases further. Figure 6In a collision pool system (i.e., collision pool and pores), the gas conductivity is primarily controlled by the pore diameter. However, as the collision pool diameter decreases, the influence of the clausing factor of the chamber on the system conductivity value increases significantly because the collision pool has a nontrivial length L. Therefore, the conductivity of the collision pool system decreases—and correspondingly, the pressure at constant flow rate increases—as the collision pool diameter decreases to the pore diameter. Consequently, for a given flow rate, the internal pressure increases as the collision pool diameter decreases to the size of the boundary pores.

[0076] As a concrete example of how reducing the diameter of the collision gas chamber increases internal pressure, the inventors have already... Figure 2 The known collision pool 34a (by Figure 6 Point 144c in the middle represents) and Figure 5B A novel collision, cooling, or reaction tank 34c (made of Figure 6 Point 145b in the diagram was compared. Using the same pool length, pore diameter, and gas flow rate, device 34c was found to be superior. Figure 5B The average pressure inside chamber 7 of the collision pool is 6.7 millitor, while that in collision pool 34a is... Figure 2 The pressure in the internal chamber 53 of pool 34c is 4.2 millitor. This 60 percent pressure increase is at least partly attributable to the pressure in the corresponding internal chamber (i.e., in pool 34c compared to pool 34a). Figure 5B The room shown is 7 and Figure 2 The cross-sectional area A of chamber 53 shown is compared to that of chamber 53. 室 The area a of the corresponding gas outlet orifice 6 孔隙 The smaller ratio between them. For example, for device 34a ( Figure 2 The ratio of the cross-sectional area of ​​chamber 53 to the cross-sectional area of ​​outlet orifice 6 is approximately 103, while for device 34c... Figure 5B The ratio of the cross-sectional area of ​​chamber 7 to the cross-sectional area of ​​outlet orifice 6 is approximately 8.9. It should also be noted that a comparison of curves 142 (length L equals 125 mm) and 141 (length L equals 250 mm) shows that, for the same pool and orifice diameter, increasing (e.g., doubling) the length of the collision pool can significantly further increase the pressure within it. Increasing the length reduces the clausing factor of the chamber, thereby decreasing conductivity and increasing pressure.

[0077] As another concrete example of how reducing the diameter of the collision gas chamber increases internal pressure, the inventors have already... Figure 2 The known collision pool 34a (by Figure 6 Point 144c in the middle represents) and Figure 5A A novel collision, cooling, or reaction tank 34b (made of Figure 6Point 145a in the diagram was compared. Using the same pool length, pore diameter, and gas flow rate, device 34b was found to be superior. Figure 5A The average pressure inside chamber 7 of the collision pool is 4.8 millitor, while that in collision pool 34a is... Figure 2 The pressure in the internal chamber 53 of pool 34b is 4.2 millitor. This 14 percent pressure increase is at least partly attributable to the pressure in the corresponding internal chamber (i.e., in pool 34b compared to pool 34a). Figure 5A The room shown is 7 and Figure 2 The cross-sectional area A of chamber 53 shown is compared to that of chamber 53. 室 The area A of the corresponding gas outlet orifice 6 孔隙 The smaller ratio between them. For example, for device 34a ( Figure 2 The ratio of the cross-sectional area of ​​chamber 53 to the cross-sectional area of ​​outlet orifice 6 is approximately 103, while for device 34b... Figure 5A The ratio of the cross-sectional area of ​​chamber 7 to the cross-sectional area of ​​outlet orifice 6 is approximately 22. It should also be noted that a comparison of curves 142 (length L equals 125 mm) and 141 (length L equals 250 mm) shows that, for the same pool and orifice diameter, increasing (e.g., doubling) the length of the collision pool can significantly further increase the pressure within it. Increasing the length reduces the clausing factor of the chamber, thereby decreasing conductivity and increasing pressure.

[0078] Figure 6 Line 147 indicates that the electrical conductivity of the collision pool system is reduced by 5 percent relative to the conductivity of the gas-confined pores of the system. At a constant gas flow rate, this reduction in conductivity would correspond to an increase of approximately 5 percent in the internal collision pool pressure. However, based on existing data, no known collision pool design achieves this level of conductivity reduction relative to the pores. Figure 5B The novel collision cell design of device 34c shown achieves a relative conductivity reduction of approximately 35-37%, which corresponds to an increase in collision cell pressure of approximately 56-58% at a constant flow rate. In other words, the gas conductivity of device 34c is approximately 63-65% of that of device 34a, thereby generating a constant flow rate pressure in device 34c, which is approximately 1.55-1.59 times the pressure generated in device 34a at the same gas flow rate. Figure 6 The results indicate that, in order to achieve a 5 percent reduction in relative conductivity, the known collision pool system requires modification, either by reducing the diameter d of the circular cross-section. 室 A certain amount makes the ratio d 室 / d 孔隙 ≤7, either by increasing (e.g., doubling) the length L of the collision pool, or by decreasing d. 室 And add a certain combination of L.

[0079] The total conductivity of the gas flowing out of the collision cell includes the gas flowing from the central gas inlets 9 and 35 (Figures 1 and 7) through a "half-tube" of length L, i.e., the total length L of the cell. 室 Half of (for example, see Figure 7 The current flows through orifice 6. The conductivity of this half-tube must be multiplied by 2 because there are two parallel paths leaving the chamber, one towards the inlet orifice and the other towards the outlet orifice. Therefore, the conductivity C of the cell... 池 It can be approximated as:

[0080]

[0081] Where C 孔隙 It is the conductivity of each pore and C 半管 This is the electrical conductivity from the center of the tube at the gas inlet to the pore. The formula in Haefer, RA; *Vacuum*, 1980, 30, 217, pp. 217 and 221 can be used to sum for more complex structures. For tubes with large cross-sections, C... 半管 With C 孔隙 Compared to becoming very large, the above formula simply simplifies to C. 池 =2C 孔隙 However, as the cross-sectional area of ​​the tube decreases and / or the chamber length increases, the resulting conductivity C... 半管 Smaller cross-sections reduce area, while longer distances decrease the clausing factor. These trends lead to the inequality C. 池 <2C 孔隙 This results in the higher pressure required for a given airflow.

[0082] As an example, if we have pores with a diameter of 2.5 mm in a 0.75 mm thick plate, the conductivity of each such pore would be 0.377 L / s for argon gas at 300 K. For a large-diameter tube, there is no significant obstruction to gas flow. Therefore, in this case, the conductivity of the cell is approximately equal to 2C. 孔隙 = 0.76 L / s. For a total pool length of 125 mm, the conductivity of the half-tube decreases as the inner diameter decreases. Once the inner diameter decreases to approximately 40 mm, the conductivity of the tube itself becomes a limitation on gas reaching the pores. At an inner diameter of approximately 20 mm, the pool conductivity has decreased to approximately 0.96 of the two pores themselves. At an inner diameter of approximately 10 mm, the pool conductivity has decreased to approximately 0.77 of the two pores themselves. The conductivity of the half-pool is 1.26 L / s. This results in a total pool conductivity of 0.58 L / s, which is 0.77 times the conductivity of the pores themselves, or 0.76 L / s. This leads to lower conductivity outside the pool. This, in turn, generates higher pressure within the pool at a given flow rate.

[0083] These formulas can be used for asymmetric cells, in other words, cells where the gas inlet is not at the center of the device. These formulas can also be used for cells where there are no identical pores at either end. Calculate the conductivity from the gas inlet to each of the two pores, C. 半管1 and C 半管2 Then calculate the conductivity C of the two pores. 孔隙1 and C 孔隙2 The total cell conductivity is

[0084]

[0085] For more complex geometries, DSMC can be used to calculate the total conductivity of the cell. This can then be compared to the conductivity of the pores themselves. This may include curved cells (e.g., 90°, 180°, or any other). The conductivity of cell geometries with other internal shapes (not simply circles or rectangles) can be calculated through simulation. This also includes cell geometries with internal parts that cause the actual conductivity to differ from that of a simple circular or rectangular tube.

[0086] Figure 7 This is a schematic longitudinal cross-sectional view of a third collision cell, cooling cell, or reaction cell apparatus 34d according to this teaching. The collision, cooling, or reaction cell 34d includes a set of multipole electrodes 74, which are used in operation to contain ions within an ion channel 73. An inlet lens 71a and an outlet lens 71b are used to control the introduction of ions into the cell 34d and to control the flow of ions through the cell along the ion channel 73. The collision cell 34d differs from conventional collision cell apparatus in that the conventional inlet end lens is replaced by a special single-crystal lens, wherein the aperture of the plate electrodes constituting each lens gradually decreases in the direction toward the interior of the cell. Thus, the incident lens 71a includes three plate electrodes 78a, 78b, and 78c, with the outermost plate electrode 78a having the largest diameter aperture and the innermost electrode 78c having the smallest diameter aperture. At the ion outlet of the device, the exit lens 71b includes three plate electrodes 79a, 79b, and 79c. The outermost plate electrode 79a has the largest diameter aperture, while the innermost electrode 79c has the smallest diameter aperture. The apertures in plates 78c and 79c are the gas flow restriction inlet and outlet apertures, respectively. These apertures have smaller diameters than those in a conventional single lens, or more generally, smaller cross-sectional areas. Therefore, for Lambertian reflection, assuming a constant gas flow rate, the probability of gas molecules passing through the apertures in plates 78c and 79c is lower than the probability of gas molecules passing through the apertures in a conventional single lens, resulting in a higher internal cell pressure.

[0087] Figure 8A This is a schematic longitudinal cross-sectional view of the fourth collision pool, cooling pool, or reaction pool device 34e according to this teaching. Figure 8BThis is a schematic transverse cross-sectional view of the device along cross section CC'. (and) Figure 7 In contrast to device 34d shown, device 34e ( Figures 8A-8B No end lens is used. Instead, in device 34e, the ion focusing properties provided by the end lens are provided by an extension of a multipole electrode outside the gas containment housing 38. One such extension, with a length ΔL, is... Figure 8A As shown in the image. Figure 8B The cross-section shown illustrates one or more insulators 72 forming a gas flow barrier between the paired rod electrodes, such that the gas flow out of each end of the gas containment housing 38 is confined within a short channel 6, which acts as a gas confinement orifice and is located at the center between the rod electrode extensions. The one or more insulators 72 may include, but are not limited to: spacers supporting the rod electrodes, gaskets fitted between the electrodes, or vacuum “feedthrough” components fixed to the ion containment housing wall.

[0088] In an alternative embodiment, the extension of the internal rod electrode passes through the gas containment housing 38. Figure 8A The wall portion of the enclosure 34e can be replaced by a separate set of short "short column" electrodes (not shown), which are partially disposed outside the enclosure 38 and separated from the internal rod electrodes 74 by gaps. In this type of embodiment, each aperture 6 is a short channel centered between the short column electrodes. Each set of short electrodes—one set at the inlet end of the device 34e and / or a separate set at the ion outlet end of the device—comprises a separate quadrupole or multipole device. Therefore, a power supply (not shown) is configured to provide an RF voltage to the short electrodes. The power supply can also be configured to provide a DC voltage difference between the internal rod electrodes and each set of short column electrodes to induce ions to enter and exit the device 34e.

[0089] The discussions included in this application are intended to serve as a basic description. The scope of the invention is not limited to the specific embodiments described herein, which are intended as individual illustrations of separate aspects of the invention. Functionally equivalent methods and components are within the scope of the invention. By way of example only, the collision cell and ion cooling cell used in the examples herein have been described above as having a linear longitudinal axis. However, the principles described herein can also be applied more broadly to non-straight collision cells and ion cooling cells. Thus, collision cells, ion cooling cells, and reaction cells having rod electrodes that are curved along their length and have a curved longitudinal axis are also considered. Such curved multipole devices are described, for example, in U.S. Patent Nos. 8,461,524, 9,543,136, and 6,576,897. The curvature facilitates the separation of uncharged molecules (traveling along a straight trajectory without collisions) from ions whose trajectories are largely constrained by a pseudopotential well around the curved longitudinal axis. In such cases, the chamber length L 室(Equal to 2L) should be taken as the total length of the curved longitudinal axis from the inlet orifice to the outlet orifice. Various other modifications of the invention, in addition to those shown and described herein, will become apparent to those skilled in the art from the foregoing description and figures.

Claims

1. A mass spectrometer collision cell, cooling cell, or reaction cell system comprising: A gas containment vessel comprising an interior chamber having an ion inlet end and an ion outlet end, said chamber having a cross-sectional area A 室 , transverse to a longitudinal axis of said chamber, said longitudinal axis of said chamber extending from said ion inlet end to said ion outlet end and having a length L 室 ; a gas inlet aperture for providing a gas to the interior chamber; a first and second gas outlet aperture disposed at or near the ion inlet and ion outlet ends of the internal chamber, respectively, the first and second gas outlet apertures having respective outlet aperture cross-sectional areas A 孔隙1 and A 孔隙2 , and respective gas conductivity values C 孔隙1 and C 孔隙2 ; and a set of multipole rod electrodes, wherein at least a portion of each multipole rod electrode is disposed within the chamber, wherein A 室 , L 室 , A 孔隙1 and A 孔隙2 have values such that the combined gas conductance of the chamber and the first and second gas outlet apertures is less than or equal to 95% of the gas conductance C 孔隙 of the individual gas outlet aperture, wherein gas conductance is determined based on the ratio of gas flow rate to pressure, and the C 孔隙 is given by the following equation: C 孔隙 = C 孔隙1 + C 孔隙2 .

2. The mass spectrometer collision cell, cooling cell, or reaction cell system of claim 1, wherein the values of A 室 , L 室 , A 孔隙1 , and A 孔隙2 are such that the combined gas conductance of the chamber and the first and second gas outlet apertures is less than or equal to 90% of the C 孔隙 .

3. The mass spectrometer collision cell, cooling cell, or reaction cell system of claim 1, wherein the values of A 室 , L 室 , A 孔隙1 , and A 孔隙2 are such that the combined gas conductance of the chamber and the first and second gas outlet apertures is less than or equal to 80% of the C 孔隙 .

4. The mass spectrometer collision cell, cooling cell, or reaction cell system of claim 1, wherein the values of A 室 , L 室 , A 孔隙1 , and A 孔隙2 are such that the combined gas conductance of the chamber and the first and second gas outlet apertures is less than or equal to 70% of the C 孔隙 .

5. The mass spectrometer collision cell, cooling cell, or reaction cell system of claim 1, wherein each of the first and second gas outlet apertures comprises an opening in or a passage through an electrostatic lens.

6. The mass spectrometer collision cell, cooling cell, or reaction cell system of claim 1, wherein each of the first and second gas outlet apertures is defined by a respective passage between portions of the multipole rod electrodes that extend outside of the chamber.

7. The mass spectrometer collision cell, cooling cell, or reaction cell system of claim 1, wherein each of the first and second gas outlet apertures is defined by a respective passage between rod electrodes of a respective multipole rod device disposed outside of the chamber.

8. The mass spectrometer collision cell, cooling cell, or reaction cell system of claim 1, wherein the longitudinal axis and the multipole rod are curved.

9. The mass spectrometer collision cell, cooling cell, or reaction cell system of claim 1, wherein a diameter d of each of the first and second gas outlet apertures is less than or equal to 5 millimeters. 孔隙 less than or equal to 5 millimeters.

10. A method of mass analyzing a sample comprising: generating a first plurality of ions from the sample and transmitting the plurality of ions into a chamber having an internal pressure P1; transmitting the first plurality of ions through a first gas limiting aperture into a second chamber having an internal pressure P2, where P2 > P1; cooling the first plurality of ions within the chamber, reacting the first plurality of ions with a gas in the chamber, or colliding the first plurality of ions with a gas in the chamber to generate a plurality of product ions; transmitting the cooled first plurality of ions or the plurality of product ions through a second gas limiting aperture into a third chamber having an internal pressure P3, where P2 > P3; and mass analyzing the cooled first plurality of ions or the plurality of product ions using a mass analyzer within the third chamber, wherein the combined gas conductance of the second chamber and the first and second gas restrictive apertures is less than or equal to the gas conductance C of the individual gas restrictive apertures 孔隙 of 95%, wherein the gas conductance is determined based on the ratio of gas flow rate to pressure, and the C 孔隙 is given by the following equation: C 孔隙 = C 孔隙1 + C 孔隙2 wherein C 孔隙1 is the gas conductivity of the first gas limiting aperture, C 孔隙2 is the gas conductivity of the second gas limiting aperture.

11. The method of mass analyzing a sample of claim 10, wherein the combined gas conductance of the second chamber and the first and second gas restrictive apertures is less than or equal to 90% of the C 孔隙 of claim 10.

12. The method of mass analyzing a sample of claim 10, wherein the combined gas conductance of the second chamber and the first and second gas limiting orifices is less than or equal to 70% of the C 孔隙 of claim 10.

13. The method of mass analyzing a sample of claim 10, wherein each gas limiting aperture comprises a diameter d 孔隙 that is less than or equal to 5 millimeters.

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