Detector with improved structure

Abstract

To provide an electron multiplier tube with an improved structure.SOLUTION: The invention may be implemented in the form of a detector containing 11 or more electron emitting surfaces. A detector includes one or more detector components configured to define an environment inside the detector on one side and an environment outside the detector on the other side, and the one or more detector components are configured to restrict or prevent gas flow from an environment external to the detector to an environment internal to the detector. Such a detector can be used in a mass spectrometer.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention generally relates to components of scientific analysis apparatuses. More specifically, the present invention relates to electron multiplier tubes and modifications to electron multiplier tubes to extend the operating life or improve the performance with an improved configuration.

Background Art

[0002] In a mass spectrometer, a sample is ionized to form a series of charged particles (ions). The resulting ions are generally separated according to their mass-to-charge ratio by acceleration and exposure to an electric or magnetic field. The separated signal ions collide with an ion detector surface to generate one or more secondary electrons. The result is displayed as a spectrum of the relative abundance of the detected ions as a function of the mass-to-charge ratio.

[0003] In other applications, the detected particles may not be ions and can be neutral atoms, neutral molecules, or electrons. In any case, a detector surface where the particles collide is still provided.

[0004] Secondary electrons generated from the collision of input particles with the collision surface of the detector are typically amplified by an electron multiplier tube. Electron multiplier tubes generally operate by secondary electron emission, whereby the collision of one or more particles with the collision surface of the multiplier tube causes one or (preferably) more electrons associated with the atoms of the collision surface to be emitted.

[0005] As one type of electron multiplier tube, discrete dynode electron multiplier tubes are known. Such multiplier tubes include a series of surfaces called dynodes, each dynode being set to a more positive voltage. Each dynode can emit one or more electrons by collision with secondary electrons emitted from the previous dynode, thereby amplifying the input signal.

[0006] Another type of electron multiplier tube operates using a single continuous dynode. In these versions, the resistive material of the continuous dynode itself is used as a voltage divider to distribute voltage along the length of the emission surface.

[0007] A simple example of a continuous dynode type multiplier is the channel electron multiplier (CEM). This type of multiplier consists of a single tube of resistive material with a treated surface. The tube is usually curved along its long axis to reduce ion feedback. In the art, the term "bullet detector" is sometimes used.

[0008] CEMs can have multiple tubes combined to form a configuration often called a multi-channel CEM. The tubes are often twisted together rather than simply curved as in the case of the single tube described above.

[0009] Yet another type of electron multiplier tube is the magneTOF detector, which is both a cross-field detector and a continuous dynode detector.

[0010] An additional type of electron multiplier tube is the cross-field detector. A combination of electric and magnetic fields perpendicular to the motion of ions and electrons is used to control the motion of charged particles. This type of detector is typically implemented as a discrete or continuous dynode detector.

[0011] The detector can include a microchannel plate detector, which is a planar component used for detecting single particles (electrons, ions, and neutrons). The detector is closely related to the electron multiplier tube because both multiply single particles through the multiplication of electrons via secondary electron emission. However, the microchannel plate detector can provide additional spatial resolution because it has many separate channels. Summary of the Invention Problems to be Solved by the Invention

[0012] The degradation of the performance of an electron-emitting base detector over time is a problem in the art. It is thought that the secondary electron emission decreases over time, resulting in a decrease in the gain of the electron multiplier tube. In order to compensate for this process, the operating voltage applied to the multiplier tube must be periodically increased to maintain the required gain of the multiplier tube. However, ultimately, the replacement of the multiplier tube becomes necessary. The gain of the detector can be negatively affected both acutely and chronically.

[0013] Conventional artisans have addressed the problem of the aging degradation of dynodes by increasing the surface area of the dynodes. The increase in surface area acts to spread the workload of the electron multiplication process over a wider area, effectively delaying the aging process and improving the operating life and gain stability. This approach only slightly extends the life and is, of course, limited by the size constraints of the detector unit in a mass spectrometer.

[0014] A further problem in the art is the problem of internal ion feedback, which is particularly a problem in the case of microchannel plate detectors. As the number of electrons increases exponentially through the amplification means of the detector, the adsorbed atoms can be ionized. And these ions are accelerated towards the detector input by the detector bias. Unless specific countermeasures are taken, these ions can have sufficient energy to eject electrons when they collide with the channel walls. This collision initiates a second exponential increase in electrons. These "false" afterpulses not only interfere with ion measurements but can also lead to permanent discharge and substantial destruction of the detector over time.

[0015] One aspect of the present invention overcomes or ameliorates the problems of the prior art by providing a detector with an extended service life and / or improved performance. A further aspect provides a useful alternative to the prior art.

[0016] Discussions of documents, acts, materials, devices, articles, etc. are included in this specification only for the purpose of providing a context for the present invention. It is not intended to suggest or represent that any or all of these matters form part of the prior art standards or are common general knowledge in the art related to the present invention that existed prior to the priority date of each claim of the present application.

Means for Solving the Problems

[0017] Although not necessarily in the broadest aspect, in a first aspect, the present invention provides a detector including one or more electron-emitting surfaces, the detector including one or more detector elements configured such that one side defines an environment inside the detector and the other side defines an environment outside the detector, the one or more detector elements being configured to suppress or prevent a gas flow from flowing from the environment outside the detector to the environment inside the detector.

[0018] In one embodiment of the first aspect, the flow is a non-conventional flow.

[0019] In one embodiment of the first aspect, the detector includes one or more electron-emitting surfaces, the detector including (i) a first detector element and a second detector element associated to form an interface or (ii) a single detector element having a discontinuity, the associated first detector element and second detector element or the single detector element having a discontinuity defining an environment inside the detector on one side and an environment outside the detector on the other side, the interface or discontinuity being configured to suppress or prevent a non-conventional gas flow from flowing from the environment outside the detector to the environment inside the detector.

[0020] In one embodiment of the first aspect, the non-conventional flow is a molecular flow or a transitional-conventional / molecular flow.

[0021] In one embodiment of the first aspect, a sealant is disposed within or around the contact surface or discontinuity to suppress or prevent a non-conventional flow of gas from the environment external to the detector to the environment internal to the detector.

[0022] In one embodiment of the first aspect, the sealant can form a substantially airtight seal with the detector components.

[0023] In one embodiment of the first aspect, the sealant is also an adhesive.

[0024] In one embodiment of the first aspect, the first detector component and / or the second detector component are configured such that a non-linear or tortuous path between the environment external to the detector and the environment internal to the detector is provided at the contact surface between the first detector component and the second detector component.

[0025] In one embodiment of the first aspect, the first detector component and the second detector component are arranged or angled relative to each other such that a non-linear or tortuous path between the environment external to the detector and the environment internal to the detector is provided at the contact surface between the first detector component and the second detector component.

[0026] In one embodiment of the first aspect, the first detector component and / or the second detector component have a shape such that a non-linear or tortuous path between the environment external to the detector and the environment internal to the detector is provided at the contact surface of the first detector component and / or the second detector component.

[0027] In one embodiment of the first aspect, the non-linear or tortuous path is at a macroscopic level.

[0028] In one embodiment of the first aspect, the non-linear or tortuous path includes two linear sub-paths, and an angle is formed at the intersection of the two linear sub-paths.

[0029] In one embodiment of the first aspect, the angle formed is greater than about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 or 85°.

[0030] In one embodiment of the first aspect, the angle formed is greater than about 45°.

[0031] In one embodiment of the first aspect, the angle formed is about 90°.

[0032] In one embodiment of the first aspect, the non-linear or tortuous path includes more than 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 linear sub-paths, and an angle is formed at each intersection of the two linear sub-paths.

[0033] In one embodiment of the first aspect, one, most or each of the angles formed is greater than about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 or 85°.

[0034] In one embodiment of the first aspect, one, most or each of the angles formed is greater than about 45°.

[0035] In one embodiment of the first aspect, one, most or each of the angles formed is about 90°.

[0036] In one embodiment of the first aspect, the non-linear or tortuous path is curved, includes a curve or includes a series of curves.

[0037] In one embodiment of the first aspect, the first detector component includes a first formation or recess, and the second detector component includes a second formation or recess, and the first formation or recess fits precisely into the second formation or recess to provide the contact surface between the first detector component and the second detector component.

[0038] In one embodiment of the first aspect, the first detector component includes a plurality of formations and / or recesses, and the second detector component includes a plurality of formations and / or recesses, and the formations and / or recesses of the first detector component fit precisely into the formations and / or recesses of the second detector component to provide the contact surface or a part of the contact surface between the first detector component and the second detector component.

[0039] In one embodiment of the first aspect, one or more of the detector components are a detector housing element, a detector enclosure element, or a detector support element.

[0040] In one embodiment of the first aspect, the detector includes at least about 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, or 50 contact surfaces between the detector components, and the contact surfaces between the detector components are configured to suppress or prevent a non-conventional flow of gas from the external environment of the detector to the internal environment of the detector.

[0041] In one embodiment of the first aspect, the detector is a first detector component and a second detector component, and a space is defined between the first detector component and the second detector component, and includes the first detector component, the second detector component, and a deformable member or mass occupying the space, and the first detector component, the second detector component, and the deformable member or mass are configured such that one side defines the internal environment of the detector and the other side defines the external environment of the detector.

[0042] In one embodiment of the first aspect, the deformable member or mass is configured to suppress or prevent gas outside the detector from entering the detector.

[0043] In one embodiment of the first aspect, one or more of the detector components are components configured to suppress or prevent gas outside the detector from entering the detector.

[0044] In one embodiment of the first aspect, the gas is a residual gas that can be used as a sample carrier gas in a mass spectrometer.

[0045] In one embodiment of the first aspect, the detector includes at least about 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, or 50 contact surfaces between detector components, and the contact surfaces between the detector components are configured to suppress or prevent conventional flow and / or molecular flow of gas from the external environment of the detector to the internal environment of the detector.

[0046] In one embodiment of the first aspect, the particles are configured as an original or replacement part of a mass spectrometer.

[0047] In one embodiment of the first aspect, when the detector is operating within a vacuum chamber of a mass spectrometer, suppressing or preventing non-conventional flow of gas from the external environment of the detector to the internal environment of the detector means that the environment around the electron emission surface or anode / collector surface of the detector and the environment immediately outside the detector differ in terms of the presence, absence, or partial pressure of gas species and / or the presence, absence, or concentration of contaminant species in their respective environments.

[0048] In one embodiment of the first aspect, the first detector component and / or the second detector component and / or the contact surface between the first detector component and the second detector component are configured to reduce the vacuum conductance of the detector.

[0049] In one embodiment of the first aspect, the contact surface between the first detector component and the second detector component is configured to reduce the vacuum conductance of the detector.

[0050] In one embodiment of the first aspect, the first detector component and / or the second detector component is a gas flow barrier capable of reducing the vacuum conductance of the detector.

[0051] In one embodiment of the first aspect, the detector includes a series of electron emission surfaces arranged to form an electron multiplier tube.

[0052] In the second aspect, the present invention provides a mass spectrometer including a detector according to any embodiment of the first aspect.

Brief Description of the Drawings

[0053]

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DETAILED DESCRIPTION OF THE INVENTION

[0054] After considering this description, those skilled in the art will understand how the present invention may be implemented in various alternative embodiments and alternative uses. However, while various embodiments of the present invention are described herein, it will be understood that these embodiments are merely illustrative and not limiting. Accordingly, the description of various alternative embodiments should not be construed as limiting the scope or breadth of the present invention. Further, the description of advantages or other aspects is applicable to specific exemplary embodiments and does not necessarily apply to all embodiments covered by the claims.

[0055] Throughout the description and claims of this specification, the terms "comprising" and variations thereof such as "comprised of" and "comprising" are not intended to exclude other additional elements, components, integers or steps.

[0056] As used herein, the term "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, although they may be.

[0057] It will be understood that all embodiments of the invention described herein do not necessarily have all of the advantages disclosed herein. Some embodiments may have one advantage, while other embodiments may have no advantage at all and are merely useful alternatives to the prior art.

[0058] It will be understood that not all embodiments of the invention described herein have all of the advantages disclosed herein. Some embodiments may have a single advantage, while other embodiments may have no advantage at all and are merely useful alternatives to the prior art.

[0059] The present invention is based at least in part on the discovery that the performance and / or service life of a detector is affected by the environment in which it operates. In particular, it has been found that gases and other substances (some of which can act as contaminants of the dynode) can change the ability of these substances to enter the detector under the vacuum established around them through any contact surface or discontinuity of the detector, which affects the service life and / or performance. When designing detectors for use in mass spectrometry and other applications, those skilled in the art heretofore have not considered the need to prevent or inhibit the entry and exit of gases or other substances into and out of the detector due to contact surfaces and discontinuities.

[0060] The applicant proposes a series of features for incorporation into existing detector designs or alternatively as a basis for a new detector design. These features have the common function of forming a barrier, partial barrier or other means for retarding the entry of atoms, molecules or larger species into the detector. In the absence of the present invention, such atoms, molecules or larger species could enter the detector by taking advantage of the discontinuities within the detector components or the contact surfaces between two detector components, potentially contaminating the electron emission surface or anode / collector of the detector or causing other malfunctions.

[0061] The detector of the present invention can function to reduce the vacuum conductance of gases or other substances entering and leaving the detector. As such, the detector of the present invention can have the further effect of isolating the internal environment of the detector from the external environment. The desired end result is to reduce the chance that potential contaminants will enter the detector and contaminate the electron emission surface (e.g., dynode surface) or collector / anode surface of the detector.

[0062] As will be understood by those skilled in the art, detectors operate in various pressure regimes. At sufficiently low pressures, the gas inside and outside the detector no longer flows like a conventional fluid and instead operates either in a transitional flow or a molecular flow regime. Without wishing to be theoretically limiting in any way, Applicants propose that when the internal and external detector environments are operating in a transitional flow and / or molecular flow regime (i.e., a non-conventional flow regime), the contact surfaces between elements or discontinuities within an element can provide a path by which contaminants can enter the internal detector environment.

[0063] In light of this discovery, solutions are proposed that prevent or at least impede the molecular or transitional flow of gas into the detector by various means. Such means include the use of seals composed of materials that are substantially gas-impermeable and capable of forming a substantially airtight seal with the detection elements. Other means include the implementation of various strategies for joining detector elements to provide a non-linear or tortuous path for restricting or preventing the ability of gas to enter the detector.

[0064] As will be understood, any contact surface is actually three-dimensional, and thus, even if a linear line of sight through the contact surface is drawn, many paths are available to molecules passing through the contact surface. In the context of the present invention, the term "non-linear or tortuous" is intended to include any configuration where a linear line of sight through the contact surface from one side to the other cannot be drawn when a two-dimensional cross-section is considered.

[0065] Means for preventing or at least suppressing the molecular or transitional flow of gas to the detector can function to absolutely prevent the external passage of gas molecules (or actually other contaminants) into the detector. In some forms of the present invention, the means acts to delay or retard the passage of gas molecules such that the number of molecules entering the detector over a given unit of time is less than it would be if such means were not provided. The unit of time can be considered with reference to the length of time required for mass spectrometry. When the mass spectrometer is connected to a separation device (e.g., a gas chromatography device), it is desirable to block or prevent the sample carrier gas from entering the spectrometer's detector for at least about one hour, such a period being necessary for the sample to pass through the chromatography medium and continuously detect the species emerging therefrom. When the sample is directly injected into the mass spectrometer, the unit of time can be about 10 minutes or less.

[0066] To reduce the connection between the external detector environment and the internal detector environment, the features described below are considered useful. For example, when the detector is incorporated into a mass spectrometer, disconnection allows the detector itself to function as a pump. By sealing / shielding the detector, this internal pump mechanism creates a beneficial environment. Without the seal / shield, the internal pump is weak and thus there is little or no internal pump generated. This internal pump acts additively to the mass spectrometer's vacuum pump to create an excellent operating environment in which the electron emission surface or anode / collector surface can operate. The main advantage of a better operating environment is that the operating life of the detector is extended. Secondary advantages include a reduction in noise, a reduction in ion feedback, an increase in sensitivity, and an increase in dynamic range.

[0067] In some embodiments, the means for preventing or at least suppressing the molecular or transitional flow of gas to the detector is intended to be effective against the carrier gas (e.g., hydrogen, helium, or nitrogen) used to direct the sample to the ionization means of the mass spectrometer in which the detector is installed. Once the sample is ionized, the passage of the resulting ions is under the control of the mass analyzer, but the residual carrier gas continues to move beyond the mass analyzer towards the ion detector. In the prior art, the effect of the residual carrier gas on the lifetime and / or performance of the detector has not been considered. The Applicant has found that the residual carrier gas usually contains contaminants that contaminate the dynode (which is the amplified electron emission surface) of the detector or the collector / anode of the detector, or that interfere with its operation. In some situations, the carrier gas itself can have a harmful effect on the dynode or the collector / anode.

[0068] The detector may comprise a single element having a discontinuity therein. The element may be dedicated or may carry an incidental responsibility for maintaining the separation between the internal detector environment (i.e., the environment around the electron emission surface or the collector / anode surface) and the external detector environment (i.e., the environment within the vacuum chamber in which the detector is operable). The separation of the environment provided by the single element does not necessarily provide a complete separation and in many cases may only reduce the possibility of gas molecules entering the internal environment of the detector.

[0069] The discontinuity within the single detector component may be, for example, an individual aperture that allows the molecular or transitional flow of gas to enter the detector. Alternatively, the discontinuity may arise from the porosity of the material from which the detector component is manufactured, and the molecular or transitional flow of gas can enter the detector through the material. In either case, a sealant may be applied to the discontinuity to provide a barrier or partial barrier to the passage of the gas or any other contaminant mixed with the gas.

[0070] To facilitate adhesion to the surface of the discontinuity and the surrounding material and prevent peeling during the daily formation and breaking of the vacuum within the vacuum chamber of the mass spectrometer, the sealant may have adhesive properties.

[0071] Suitable sealants / adhesives can include polymers such as solder, polyimide (optionally in the form of tapes such as Kapton TM tape). Once cured, the sealant / adhesive preferably contributes minimally to "virtual leaks" in that it does not substantially desorb liquid, vapor, or gas within the chamber under vacuum. Such materials are often referred to as "vacuum safe". Desorbed substances can have a detrimental effect on the vacuum pump system of the device.

[0072] In some situations, the detector configuration requires the joining of two or more elements to provide a composite structure. The composite structure can be dedicated or incidental to maintaining the separation between the internal detector environment (i.e., the environment around the electron emission surface or the collector / anode surface) and the external detector environment (i.e., the environment within the vacuum chamber in which the detector is operable).

[0073] The composite structure can provide means for preventing or at least suppressing the entry of molecular or transitional gas flow into the detector. In that case, the contact surface of the two detector components provides a potential means for gas to enter the detector by molecular or transitional flow.

[0074] Any one or both of the detector components contributing to the composite structure can be configured to be dedicated or incidental to achieving the purpose of preventing or at least suppressing the molecular or transitional gas flow of gas into the detector. These features can be incorporated into the detector either alone or in combination with one or more of any other features disclosed herein.

[0075] In other embodiments, a third component may be added to the composite structure to further prevent or at least suppress the molecular or transitional flow of gas into the detector. For example, if the first component and the second component are in contact to form a contact surface, the third component may be applied over the first and second components so as to straddle the contact surface. The third component may be secured in place by any means, preferably by an adhesive, more preferably an adhesive having sealant properties. One or more of these features may be incorporated into the detector alone or in combination with one or more of any other features disclosed herein.

[0076] Referring to FIG. 2 showing the first detector component "A" and the second detector component "B", the detector component "B" has a recess into which the component "A" can fit precisely. Components "A" and "B" are shown separated to more clearly show their respective contours and the "U"-shaped contact surface between the two components. In reality, components "A" and "B" are in contact with each other to form a contact surface that provides a barrier or partial barrier to the gas.

[0077] Even when components "A" and "B" are in contact with each other, gas can pass through the contact surface by molecular or transitional flow in order to move from the external environment of the detector to the internal environment of the detector. However, the non-linear or tortuous path provided by the two 90-degree corners of the contact surface inhibits the transitional or molecular flow of gas through the path. One or more of these features may be incorporated into the detector alone or in combination with one or more of any other features disclosed herein.

[0078] The configuration of FIG. 2 is in contrast to a situation where component "B" does not have a recess and component "A" is simply placed on the plane of component "B". In such a situation, since the contact surface is strictly linear, gas is more likely to move from the outside to the inside of the detector by molecular or transitional flow as compared to the configuration of FIG. 2 where the contact surface defines a non-linear or tortuous path. One or more of these features may be incorporated into the detector alone or in combination with one or more of any other features disclosed herein.

[0079] Figure 3 shows a configuration similar to that of Figure 2, but differs in that the component "B" is provided with a relatively deep longitudinal slot into which the component "A" fits precisely. The contact surface formed between the components "A" and "B" in Figure 3 is longer than that shown in Figure 2 because the depth of the slot in component "B" is greater. By increasing the length, the ability of gas molecules to move along the length of the contact surface per unit time is minimized. One or more of these features may be incorporated into the detector either alone or in combination with one or more of any other features disclosed herein.

[0080] Figure 4 shows a contact surface formed by components "A" and "B" similar to those of the embodiment of Figure 1, but component "A" has a downwardly extending protrusion configured to fit precisely into a recess formed in component "B". This configuration provides an improved barrier or partial barrier to gas movement by molecular flow or transitional flow compared to the embodiment of Figure 1. This improvement is due to the longer path defined by the contact surface, which is a non-linear or tortuous path having four 90° corners. One or more of these features may be incorporated into the detector either alone or in combination with one or more of any other features disclosed herein.

[0081] Figure 5 shows a contact surface formed by components "A" and "B" similar to those of the embodiment of Figure 4, but component "A" has a series of downwardly extending protrusions configured to fit precisely into complementary recesses in component "B". This configuration provides an improved barrier or partial barrier to gas movement by molecular flow or transitional flow compared to the embodiment of Figure 4. This improvement is due to the longer path defined by the contact surface (each protrusion extending the length of the path), which is a non-linear or tortuous path having ten 90° corners and three 45° corners. One or more of these features may be incorporated into the detector either alone or in combination with one or more of any other features disclosed herein.

[0082] Figure 6 shows an embodiment in which component "B" includes a lip and the side surface of component "A" abuts against the lip. The end surface of component "A" facing downward contacts the surface of component "B" facing upward. In this configuration, the contact surface provides a non-linear or tortuous path having one 90° angle. As understood, the depth of the lip adds length to the path and a deeper lip enhances the suppression or prevention of molecular or transitional flow of gas along the contact surface. One or more of these features can be incorporated into the detector either alone or in combination with one or more of any other features disclosed herein.

[0083] Figure 7 shows a more complex configuration that includes the use of a protrusion on component "A" and complementary recesses and lips in component "B". The thickness of component "A" (in the y-direction) provides an increase in the length of the path that more effectively blocks the passage of gas across the contact surface.

[0084] The non-linear or tortuous path may at least partially include a curved section or multiple curved sections. For example, referring to FIG. 1, the surface of component "A" facing downward may be curved or formed in a wavy shape, and the recess in component "B" is complementary such that the two components fit together precisely. In general, the use of a shallow curve is less effective than a 90° angle in preventing or suppressing the passage of gas across the contact surface based on molecular or transitional flow.

[0085] In some embodiments, the non-linear or tortuous path is provided by a combination of a curved section and a linear section.

[0086] In any of the above-described embodiments and any further embodiments conceivable by those skilled in the art, in order to further restrict the gas flow through the contact surface, a sealant (which may also function as an adhesive) may be applied to the mutual contact area of component "A" and / or component "B" prior to assembly. In addition or alternatively, the sealant / adhesive may be disposed outside the contact surface to cover any area where component "A" and component "B" abut (e.g., along a line formed by the side surface of component "A" and the surface facing upward of component "B"). One or more of these features may be incorporated into the detector alone or in combination with one or more of any other features disclosed herein.

[0087] The sealant may be used within or around the contact surface of the two components that provide a straight or non-tortuous path for the gas from the external environment of the detector to the internal environment of the detector. Even if a straight or non-tortuous path is provided, in some situations the presence of the seal may be sufficient to appropriately suppress or prevent gas molecules from entering the detector.

[0088] In some embodiments of the detector, the two detector components do not form a contact surface. Instead, a space is defined between them. This space may allow for an unconventional fluid flow of gas (e.g., transitional flow and / or molecular flow) from the outside to the inside of the detector. In order to suppress or prevent the gas flow through this space, a deformable member or a deformable mass may be disposed within the space. The member or mass is configured to occupy the space by deformation (e.g., by bending, stretching, compressing, expanding, or exuding). The deformation (i.e., occlusion or partial occlusion) may be caused by one component moving relative to the other. Otherwise, the two components remain in a fixed spatial relationship, but a deformable member or mass that occupies the space between them is caused or allowed to occur.

[0089] The deformable member or mass may be composed of a substance or composition that inhibits the passage of gas to maintain a difference between the internal environment of the detector and the external environment of the detector. The substance or composition has a low tendency to emit atoms or molecules into the significant vacuum formed within the vacuum chamber of the mass spectrometer.

[0090] FIG. 8A shows a configuration having a space in which a deformable member (10) is disposed between two detector components (``A'' and ``B''). FIG. 8B shows the configuration of FIG. 8A after moving component ``A'' downward so that the deformable member (10) closes or partially closes the space between component ``A'' and component ``B''. The deformable member in this embodiment is a rigid, substantially U-shaped member. The pre-formed shape of the member is interrupted by moving component ``A'' relative to component ``B''. The rigidity of the member generates a force on the components by attempting to return the member to its original U-shape. Stated another way, the member is biased to assume a predetermined shape when deformed, and the shape is configured to close or partially close the space. Members having other shapes, including triangular, curved, and irregular shapes, are of course contemplated.

[0091] FIG. 9A shows three detector components ("A", "B", "C"), with a first space formed between component "A" and component "B", a second space formed between component "A" and component "C", and a deformable member (10) disposed within the first and second spaces. FIG. 9B shows the configuration of FIG. 9A after a downward pressure is applied in the direction indicated by the arrow such that the deformable member (10) closes or partially closes the first and second spaces. In this embodiment, a rigid U-shaped member is disposed across the central component ("A"), and the flanges of the member flare out like a trumpet under pressure to seal the gap between the central component and the two adjacent components. The configuration of the member transmits a force applied to one region of the member to another region of the member via tension, and those regions flare in and / or out. And these flared regions can be disposed within the space where the two components contact. By careful placement, these flared regions form a pressure contact with one or both of the components forming the joint gap.

[0092] FIG. 10A shows a configuration in which a space is formed between two detector components ("A" and "B"), and a deformable mass (20) is disposed within the space. FIG. 10B shows the configuration of FIG. 10A after component "A" is moved downward such that the deformable mass closes or partially closes the space between component "A" and component "B". A flexible mass is placed between the two components. This mass needs to be held in place or is thicker than the nominal gap between the two components and is held in place by pressure contact with the two components.

[0093] The detector may include any combination of approaches using the deformable members or masses disclosed herein.

[0094] In some situations, two detector components may form a contact surface and define a space therebetween. In such cases, the approaches disclosed herein for suppressing or preventing the flow of gas through both the contact surface and the space may be utilized in the detector.

[0095] The detector of the present invention can be used in any application that those skilled in the art consider appropriate. A typical application is as an ion detector in a mass spectrometer. Refer to FIG. 1 showing a typical configuration of a gas chromatography apparatus connected to a mass spectrometer. A sample is injected and mixed with a carrier gas that propels the sample to pass through a separation medium in an oven. The separated components of the sample exit from the end of the transfer line and enter the mass spectrometer. These components are ionized and accelerated through an ion trap mass analyzer. The ions exiting the mass analyzer enter the detector, and the signal for each ion is amplified by a discrete dynode electron multiplier tube (not shown) within the detector. The amplified signal is processed by a connected computer.

[0096] The applicant first recognized that the carrier gas and other substances exiting from the end of the transfer line together with the components of the sample can enter the interior of the detector and cause contamination. This has an acute negative effect (temporarily changing the performance of the detector), but also leads to more chronic negative effects, resulting in long-term performance degradation and a reduction in the life of the detector. After discovering the true nature of the problem, the applicant provides a detector having one or more features that suppress or prevent contaminants from entering through discontinuities within the detector components or through the contact surfaces between two detector components.

[0097] Considering that the applicant has discovered the advantage of isolating the internal detector environment from the external detector environment, it is proposed that the development of the detector structure includes providing a more complete enclosure and housing to protect the electron emission surface or the collector / anode surface from contaminants inherent in the vacuum chamber. Therefore, various housing or enclosure elements are added to the prior art detector, and contact surfaces between components can be formed in that context.

[0098] In addition to the configuration of the contact surfaces of the detector components described above, further structural features can be incorporated into the detector. As a first feature, the outer surface of the detector enclosure can be composed of as few continuous parts (components) as possible. The housing can be made from a single material to provide a continuous outer surface, in which case any discontinuities can be sealed with a sealant. This feature can be incorporated into the detector either alone or in combination with one or more of any other features disclosed herein.

[0099] The size of any engineered discontinuities within the detector enclosure can be dimensioned to be as small as possible (from the perspective of area). As used in this context, the term "engineered discontinuities" is intended to include any means such as any opening, grid, grill, vent, aperture or slot, etc. intentionally machined into the detector through which gas can move from the outside to the inside of the detector. Usually, such discontinuities have a function (e.g., to allow an ion current to enter the detector) and can be formed in a size sufficient to perform the necessary function, but preferably not more than that. In some embodiments, the engineered discontinuities are larger than the minimum required to function properly, but do not exceed 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20% of the minimum value. This feature can be incorporated into the detector either alone or in combination with one or more of any other features disclosed herein.

[0100] The engineered discontinuities within the detector enclosure can be oriented (face away from), arranged, or otherwise spatially disposed so as to face away from the gas flowing in the external environment of the detector, such as the flow of residual carrier gas present within the mass spectrometer. This feature can be incorporated into the detector either alone or in combination with one or more of any other features disclosed herein.

[0101] The outer surface of the detector enclosure may utilize rounded features to generate laminar flow and / or vortices from any gas flowing around the outer environment of the detector. These laminar flows and / or vortices may provide high gas pressure regions that effectively seal discontinuities (otherwise, the discontinuities would allow other residual carrier gas to enter). This feature may be incorporated into the detector alone or in combination with one or more of any of the other features disclosed herein.

[0102] Discontinuities in the surface of the detector enclosure may have associated gas flow barriers to suppress the ingress of residual carrier gas. In some embodiments, the gas flow barrier is part of a detector component that forms a contact surface with another detector component. While the gas flow barrier may provide advantages, it can be seen that such a barrier may also provide additional portals for gas to enter the detector at the portion where the barrier forms a contact surface with another component of the detector. In view of the benefits of this specification, one of ordinary skill in the art can conceive of a series of mechanisms suitable for such a function.

[0103] In some embodiments, the barrier has first and second openings, one of which is in gas communication with the discontinuity of the detector enclosure (and thus the internal environment of the detector), and the second opening is in gas communication with the environment outside the detector. The second opening may be distal to the detector to substantially eliminate gas flow (e.g., residual carrier gas). One or more of these features may be incorporated into the detector alone or in combination with one or more of any of the other features disclosed herein.

[0104] In some embodiments, although the second opening is still exposed to the gas flow, the barrier is configured to prevent or suppress the entry of the gas flow into the internal environment of the detector. This objective can be achieved by suppressing or preventing the gas flow entering the barrier so that the entering gas flows into the internal environment of the detector less or not at all. For example, the gas flow barrier may be as long as possible and / or as narrow as possible and / or may include one or more bends or corners and / or may include one or more 90-degree bends and / or may include internal baffles to minimize the internal line of sight. One or more of these features can be incorporated into the detector alone or in combination with one or more of any other features disclosed herein.

[0105] The gas flow barrier can be configured, arranged, or oriented to face outward from the gas flowing in the external environment of the detector, such as the flow of the residual carrier gas used by the mass spectrometer. This feature can be incorporated into the detector alone or in combination with one or more of any other features disclosed herein.

[0106] The gas flow barrier can include a rounded outer surface so as to prevent or suppress any discharge. In addition or alternatively, such a rounded surface can generate a laminar gas flow and / or vortices from the gas flowing within the external environment of the detector. These laminar flows and / or vortices can provide a high-pressure region that essentially seals the opening of the shield. This feature can be incorporated into the detector alone or in combination with one or more of any other features disclosed herein.

[0107] To prevent or suppress the entry of the gas flowing outside the detector into the internal environment of the detector, two or more gas flow barriers can be configured, arranged, or oriented to cooperate additively or multiplicatively. This feature can be incorporated into the detector alone or in combination with one or more of any other features disclosed herein.

[0108] As a further feature, the detector may include internal baffles to limit or completely remove any or all internal lines of sight across the detector. This feature is generally applicable as long as it does not negatively impact the optics of the particles (e.g., ions and electrons). This feature can be incorporated into the detector either alone or in combination with one or more of any of the other features disclosed herein.

[0109] The detector typically includes an input aperture for receiving the particle beam. Applicants have found that such an aperture typically accepts a large amount of residual carrier gas and associated substances and effectively connects the internal and external environments of the detector. As described in other parts of this specification, since such a connection is undesirable in many situations, the size of the input aperture should be minimized as much as possible. This feature can be incorporated into the detector either alone or in combination with one or more of any of the other features disclosed herein.

[0110] When the detector includes two apertures, the apertures are preferably arranged such that there is no complete or partial direct line of sight between the apertures. Such an arrangement acts to impede the free flow of gas through the detector and thus prevent or suppress the ingress of residual carrier gas into the detector. This feature can be incorporated into the detector either alone or in combination with one or more of any of the other features disclosed herein.

[0111] When the detector is associated with off-axis input optics, such an apparatus may include discontinuities (e.g., vents, grills, apertures or holes) to facilitate the flow of gas through the apparatus rather than allowing the gas to accumulate in the apparatus. This approach prevents or suppresses the local accumulation of gas around the input optics and outside the detector since such gas tends to enter the internal environment of the detector. This feature can be incorporated into the detector either alone or in combination with any one or more of any of the other features disclosed herein. This feature can be incorporated into the detector either alone or in combination with one or more of any of the other features disclosed herein.

[0112] Many embodiments of the present invention realize advantages by controlling the vacuum conductance of a detector and thus controlling the coupling between the internal detector environment and the external detector environment.

[0113] When the conductance is decreased according to the present invention, the level of decrease can be expressed as a percentage of the conductance measured in the absence of the conductance modulation function of the present invention. The decrease in conductance may be greater than about 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 100%, 200%, 300%, 400%, 500%, 600%, 700%, 800%, 900% or 1000%.

[0114] One skilled in the art can understand the concept of vacuum conductance and measure the conductance of a detector or at least the relative conductance of two detectors (i.e., the conductance of one detector compared to another detector). As an approximation, the detector can be considered a straight cylindrical pipe or tube, and its conductance can be calculated with reference to the (overall) length (M) and radius (cm) of the pipe. Dividing the length by the radius gives an L / a ratio, and the conductance (e.g., L / second) is read from a reference table. Since the geometric shape of the detector may vary somewhat from a straight cylindrical pipe or tube, the calculated absolute conductance may not be exact. However, such an approximation will be useful for the purpose of evaluating the effectiveness of the detector's conductance modulation function.

[0115] General improvements can be obtained in the internal environment of a detector by reducing the detector's vacuum conductance to minimize the connection between the internal and external environments. Without wishing to be bound by any theory, this approach enables the electron beam of the detector's electron multiplier to act as a pump, thereby creating a cleaner environment for the operation of the detector. This clean internal environment mainly extends the service life of the multiplier. Depending on the way the detector operates, there are also secondary benefits including a reduction in noise, an improvement in sensitivity, an increase in dynamic range, and a reduction in ion feedback. The reduction of the detector's vacuum conductance limits the impact of the harmful external environment on the detector's performance and lifespan. This includes both continuous and acute effects.

[0116] A further advantage is to minimize the negative impact of the detector's operation on the detector's performance and lifespan. The applicant has found that the duty cycle, ion input current, and mode selected by the user affect the detector's performance and have a significant impact on the detector's lifespan. Such effects arise due to the vacuum relaxation time, which is the time required to form a substantially complete vacuum inside the detector so as to equal the external environment. The relaxation time generally coincides with the "off time" in the duty cycle.

[0117] Similarly, the discrete nature of the charge has been demonstrated to result in pseudo-off times in typical ion input currents. These pseudo-off times are on the order of the detector's vacuum relaxation time at sufficiently low currents, especially when the detector operates in the time-of-flight (TOF) mode. In the TOF mode, the analyte ions are collected together within a time. Therefore, the number of different analytes and their mass distributions also determine the pseudo-off times in the TOF mode. By minimizing the detector's vacuum conductance, the detector's vacuum relaxation time is extended. Thereby, the detector can achieve its intended performance and lifespan over a wider range of duty cycles and ion input currents. The extension of the vacuum-related time also limits the influence of the detector's operation mode and the mixture of analyte ions on the detector's performance and lifespan.

[0118] A further effect of reducing the vacuum conductance is to minimize changes in the calibration of the detector due to changes in the external environment of the detector. This includes both a sudden loss of gain due to the acute arrival of contaminants and a temporary recovery of gain due to the arrival of water molecules at the surface of the detector.

[0119] The present invention is implemented in many forms and has one or a combination of features that cause or assist in reducing the vacuum conductance of the detector. The present invention relates to a sealed detector, a partially sealed detector, a detector having one or more gas flow barriers, a detector associated with an off-axis input optical system appropriately designed to push a gas flow away from the detector, a detector including one or more gas flow barriers associated with an off-axis input optical system appropriately designed to push a gas flow away from the detector, a detector having a sight line input aperture and including machined discontinuities such as vents, grills, apertures, and / or holes to prevent a local increase in gas, and a detector including a gas flow barrier further including machined discontinuities such as vents, grills, apertures, and / or holes to prevent a local increase in gas in a detector having a sight line input aperture, and can be implemented in the form of a detector using an adjustable (preferably movable) gas flow barrier to minimize the conductance during operation.

[0120] In one embodiment, the detector is a discrete dynode electron multiplier tube of a type known to those skilled in the art. Such a multiplier tube may or may not include a conversion dynode in addition to a series of amplification dynodes.

[0121] A further embodiment is a microchannel plate (MCP) detector configured by stacking four or more separate elements to minimize the vacuum conductance. Currently, a maximum of three elements are required to achieve the required detector gain, and at least four elements are used to further minimize the MCP vacuum conductance, with each additional element adding another bend in the path.

[0122] The MCP detector may use a collector sealed to minimize vacuum conductance and a stacked MCP detector rotating element to minimize vacuum conductance. The MCP may include a multi-channel pinch point (MPP) element to minimize vacuum conductance. The MPP is a thin element located between two conventional amplification elements of the MCP stack and constitutes many local narrowings. There may be two or more narrowings for each channel in the amplification element surrounding the MPP. In this case, the pinch points in the MPP are clustered together to align with the channels of the amplification element.

[0123] The MCP detector includes four or more distinct components with a rotating element, including a multi-channel pinch point, and includes a closed collector.

[0124] Another embodiment is in the form of a continuous electron multiplier (CEM) including one or more "pinch points" to minimize vacuum conductance. The pinch points are defined as local narrowings of the CEM structure. When multiple pinch points are used, they can be arranged continuously / continuously, in parallel, or in a combination of both.

[0125] Another embodiment is a CEM including one or more bends to minimize vacuum conductance, a CEM including a closed collector to minimize vacuum conductance, a CEM having one or more twists around the detector axis to minimize vacuum conductance, or a CEM including a combination of pinch points, bends, twists, and closed collectors.

[0126] Although the present invention has been mainly described with reference to detectors of the type used in mass spectrometers, it should be understood that the present invention is not limited to such configurations. In other applications, the particles to be detected may not be ions, but may be neutral atoms, neutral molecules, or electrons. In any case, a detector surface where the particles collide is still provided.

[0127] In the description of the exemplary embodiments of the present invention, for the purpose of simplifying the disclosure and assisting the understanding of one or more aspects of the various inventions, it may be found that the various features of the present invention are grouped together in a single embodiment, drawing, or description thereof. However, this method of disclosure should not be construed as reflecting an intention that the present invention requires more features than are explicitly recited in each claim. Rather, as represented by the following claims, aspects of the present invention are present in no fewer features than all of the features of a single previously disclosed embodiment.

[0128] Furthermore, some of the embodiments described herein include some features and not others that are included in other embodiments. As will be appreciated by those skilled in the art, combinations of features of different embodiments are within the scope of the present invention and form different embodiments. For example, in the following claims, the embodiments recited in the claims can be used in any combination.

[0129] In the description provided herein, numerous specific details are set forth. However, it will be understood that embodiments of the present invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description.

[0130] Accordingly, while what are considered to be preferred embodiments of the present invention have been described, those skilled in the art will recognize that additional changes can be made without departing from the spirit of the present invention, and it is intended that all such changes and modifications be included within the scope of the present invention. Functionality can be added or removed with respect to the figures, and operations can be exchanged between functional blocks. Steps can be added to or removed from the methods described within the scope of the present invention.

[0131] Although the present invention has been described with reference to specific examples, those skilled in the art will understand that the present invention can be practiced in many other forms.

Claims

[Claim 1] A detector including one or more electron emissive surfaces, the detector having a vacuum established therearound, the detector including first and second housing elements configured to define an internal environment of the detector on one side and an external environment of the detector on the other side, the first and second housing elements forming a non-linear or tortuous path between an external environment of the detector and an internal environment of the detector to inhibit or prevent non-conventional gas flow from the external environment of the detector into the internal environment of the detector; Detector.

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