Electrode chamber, electrode assembly, and ion detecting device

Abstract

The invention refers to an electrode chamber for an ion detecting device, comprising a gas-tight chamber configured to maintain a negative pressure therein, and a first electrode unit for generating an electric field inside the gas-tight chamber when the first electrode unit is connected to a voltage source. A first wall of the gas-tight chamber is formed at least in part by the first electrode unit. The first electrode unit includes a first surface and a second surface. The first surface of the first electrode unit is configured to be exposed to the negative pressure in the gas-tight chamber. The second surface of the first electrode unit is exposed on an outer surface of the gas-tight chamber for being subjected to the atmospheric pressure.

Description

[0001] ELECTRODE CHAMBER, ELECTRODE ASSEMBLY, and ION DETECTING DEVICE

[0002] Field of the Invention

[0003] The present invention relates to an electrode chamber for an ion detecting device. The electrode chamber includes a gas-tight chamber configured to maintain a negative pressure therein and a first electrode unit for generating an electric field inside the gas-tight chamber when the first electrode unit is connected to a voltage source.

[0004] The present invention further refers to an electrode assembly for an ion detecting device which comprises the electrode chamber as well as to an ion detecting device which comprises the electrode chamber or the electrode assembly.

[0005] Background

[0006] The term ion mobility spectrometry (IMS) refers to the methods and apparatus used to characterise ions from sample substances in terms of the speed at which ensembles of those ions progress through a supporting gas atmosphere when urged through it by an applied electric field. Ion mobility measurements involve injecting an ion ensemble into a “drift region”. An ion detector, or simply an ion outlet, may be provided at the output end of the drift region. While within the drift region, the ion ensemble moves longitudinally towards an output end of the drift region e.g., within a flow of purified neutral support gas (e.g., molecular Nitrogen), also known as a “buffer gas”, in which it is entrained. Simultaneously, in one IMS technique for example, the ion ensemble moves transversely to the buffer gas flow direction under the urging force of an applied electric field, E, generated by an appropriate voltage gradient applied transversely to the buffer gas flow direction.

[0007] Notably, ion mobility measurements pertain only to ion ensembles and not to individual ions for which the speeds can be comparatively large. For example, the median speed between collisions for molecular Nitrogen ions at ambient pressure and at a temperature of 25 degrees Celsius is about 450 metres per second. By comparison, as an example, an ion ensemble may typically be urged by the applied electric field, E, to move transversely to the buffer gas flow direction with a velocity of, say, v = 4 m / s.

[0008] It is established practice to normalise such an ion ensemble velocity value, v, by dividing it with the value of the electric field strength, E, applied transversely to the buffer gas flow direction. This normalisation produces an ion mobility coefficient, K = v / E, which is the measure of the ion ensemble velocity per unit field strength. The relationship between ion ensemble velocity, v, and electric field strength, E, is valid for an ion ensemble at thermal energies measured in a buffer gas atmosphere of constant composition, pressure, and temperature. The value of an ion mobility coefficient is dependent upon buffer gas temperature, T, and pressure, P, inside the drift region. Importantly, the value of an ion mobility coefficient is dependent upon the collision cross-section of the ion under study and an ion mobility coefficient, K, for a given ion is sensitive to fluctuations in this quantity. Mewburn Ref: 008628448

[0009] 2

[0010] A distinction of IMS in contrast to mass spectrometry (MS) is that ions are characterised in a supporting buffer gas atmosphere, also called a drift gas, which is refreshed continuously. A main practical purpose of this gas is to maintain a purified and constant atmosphere for collision-based movement of the ion ensemble.

[0011] Field asymmetric IMS, differential mobility spectrometry, or ion drift spectrometry are different names given to the same process, which is a type of IMS. An ion mobility measurement begins when ions formed from components in a sample, called product ions, are injected into the drift region. These methods are based on ions undergoing changes in ion mobility coefficients, K, as a result of changes in the applied transverse electric field, E, at constant buffer gas particle number density, N, i.e., the number of buffer gas particles per unit volume. An approach in IMS technology has enabled studies of field dependence using a Field Asymmetric Ion Mobility Spectrometer (FAIMS) or DMS. The method of high field asymmetric IMS for ion separations is based on a non-linear, high-field dependence of ion mobility coefficients. In particular:

[0012] Here, a(E / N) = <z2x (E / / V)2+ a4x (E / N)4+ - + a2nx (E / / V)2n

[0013] This function describes the non-linear electric field dependence of ion mobility of an ion. The terms a2n(n = 1,2, ...) are constant coefficients the values of which are particular to a given combination of ion and buffer gas set-up. The function a(E / N) is a function describing the dependence of ion mobility on the ratio, E / N, of the electric field strength to neutral gas density. The units of E / N are Townsends (Td) where 1 Td = 10-17Vcm2.

[0014] In this method, termed variously field-asymmetric IMS (FAIMS), or differential mobility spectrometry (DMS), ions are contained in a gas, e.g., entrained by a gas flow, extending along a drift space between conducting surfaces (e.g., electrodes). The space between the electrodes defines an “analytical gap”. The drift space can be defined between parallel curved or flat electrodes (e.g., plates). A transverse electric field, E, is applied across this analytical gap using an asymmetric voltage waveform known as a “dispersion voltage” (FD), which generates a corresponding dispersion electric field, EDe.g., of ED= +20,000 V I cm or greater in the positive amplitude part of the asymmetric wave cycle and ED= -1,000 V I cm in the negative amplitude part of the asymmetric wave cycle. Ion ensembles move with a speed v within the electric field E according to equations: v = K x ED

[0015] K = K(ED / N) = K0(l + a(ED / N~)~)

[0016] Of course, the value of EDchanges in magnitude and polarity as the wave cycle switches between its positive and negative amplitude parts. As a result, the value of K(ED / N) is different during these two different parts of a wave cycle for ions for which a(ED / N) + 0. The asymmetric voltage waveform of the dispersion voltage (FD) is designed so that the time integrals of these two parts of the wave cycle are Mewburn Ref: 008628448

[0017] 3 equal. Notably, ions with mobility coefficients, K(ED / l\r), that are independent of ED, (i.e., such that a(ED / Nj' « 0 even at high field values) are able to pass through the drift region and emerge from it to be detected. In contrast, ions with a dependence of K on ED(i.e., a(ED / Nj' 0) undergo a net displacement towards a surface of an electrode with repeated exposure of the ion ensemble to the periodic changes in direction and strength of the electric field, ED. The magnitude of displacement depends on the differences in mobility, K(ED / l\r) = K0(l + a(ED / N ), at electric field extremes i.e., the “high-field” amplitude, ED!Hi, and “low-field” amplitude, E^Lparts of the asymmetric wave cycle. In other words:

[0018] The “high-field” amplitude, EDHi, and “low-field” amplitude parts of the waveform have opposite polarity with the “high-field” amplitude, EDHi, conventionally being denoted as having positive polarity. The immediate effects of dispersion electric field, ED, in DMS or FAIMS are revealed in the dependence of the mobilities, K(ED / Nj', of ions on dispersion electric field strength, ED, at the two extremes of the asymmetric waveform. The waveform is designed in field strength, ED, and duty cycle (as between durations of positive polarity and negative polarity parts) so that an ion with little or no dependence of mobility on dispersion electric field strength, ED, will pass through the centre of the analyser by being carried by a flow of buffer gas. Ions that do have a dependence of mobility on dispersion electric field strength, ED, will undergo with each complete cycle of the dispersion voltage waveform, successive net displacements from the central ion axis of ion flow. Eventually, the ion ensemble will collide with an electrode defining the analytical gap and will be discharged and removed from the measurement process. When a direct current (DC) “compensation voltage” (Fc) is applied to the electrodes of the analyser, the effects of the dispersion electric field may be compensated, and ion motion can be restored to the centre of the analyser.

[0019] A comparatively low direct current (DC) “compensation voltage” (Fc) may be added to the electrodes or plates defining the analytical gap so as to superimpose that DC electric field (compensation field, Ec) upon the dispersion electric field, ED, to enable control or “compensation” of ion motion towards an electrode. Ions restored to the centre of the analytical gap will be made able to pass through the drift region. A sweep of this compensation voltage, often 10V to 40V in size (producing compensation electric fields of typically 100V / cm to 500V / cm), provides a means to measure mobility of all ions in the analyser for a given dispersion voltage wave form. This method provides ion mobility filtering, and ion separations are based on differences in ion mobility, leading to the name “Differential Mobility Spectrometry”, also known as FAIMS.

[0020] To achieve high quality (e.g., sensitivity) measurements, the ions under study should preferably undergo a sufficiently large number of complete cycles of the dispersion voltage waveform such that ions with even a relatively small dependence of K on EDmay undergo a sufficiently large number of successive net displacements, per cycle of the dispersion waveform, from the central ion axis of ion flow, that they too collide with an electrode defining the analytical gap. Consequently, only those ions with mobility Mewburn Ref: 008628448

[0021] 4 coefficients, K(ED / l\r), that are closer to being truly independent of ED, (i.e., such that a(ED / l\r) « 0) are able to pass through the drift region and emerge from it to be detected.

[0022] The present invention has been devised in light of the above considerations.

[0023] Summary of the Invention

[0024] At its most general, the invention relates to cooling an electrode for an ion detecting device by thermally coupling the electrode to a gas environment having a pressure that is higher than inside a chamber in which the electrode is arranged. For example, the electrode is thermally coupled to the atmosphere. This may increase the cooling of the electrode compared to an arrangement in which the electrode is completely inside the chamber and, therefore, only exposed to the pressure inside the chamber.

[0025] In a first aspect, an electrode chamber for an ion detecting device is provided. The electrode chamber comprises a gas-tight chamber configured to maintain a negative pressure therein and / or a first electrode unit for generating an electric field inside the gas-tight chamber when the first electrode unit is connected to a voltage source. A first wall of the gas-tight chamber is formed at least in part by the first electrode unit. The first electrode unit includes a first surface and a second surface. The first surface of the first electrode unit is configured to be exposed to the negative pressure in the gas-tight chamber. The second surface of the first electrode unit is exposed on an outer surface of the gas-tight chamber for being subjected to the atmospheric pressure or a pressure outside the gas-tight chamber.

[0026] In a second aspect, an electrode assembly for an ion detecting device is provided. The electrode assembly comprises the electrode chamber as described herein and a housing surrounding the electrode chamber. The housing includes a door for accessing the electrode chamber. The door is movable between an open position in which the electrode chamber is accessible and a closed position in which access to the electrode chamber is prevented.

[0027] In a third aspect, an ion detecting device is provided. The ion detecting device comprises the electrode chamber as described herein or the electrode assembly as described herein. Optionally, the ion detecting device further comprises a low-pressure chamber and / or a closure means configured to be movable between an open position and a closed position. In the closed position, the closure means blocks a gas flow between the electrode chamber and the low-pressure chamber. In the open position, the closure means unblocks the gas flow between the electrode chamber and the low-pressure chamber.

[0028] In this way, the first electrode unit can be cooled by the gas or air that surrounds the electrode chamber. This is different to commonly known arrangements of electrodes inside a chamber of low pressure or vacuum. There, only little thermal energy can only be transferred to the gas inside chamber because only little gas is available to the low-pressure or vacuum. Consequently, with prior art electrodes, the electrodes are essentially thermally insulated which may lead in the electrode warming up inside the chamber. In contrast thereto, the first electrode unit as described herein is exposed to the atmospheric pressure (in general the pressure surrounding the gas-tight chamber) which can drastically increase the Mewburn Ref: 008628448

[0029] 5 heat exchange between the first electrode unit and the gas, optionally air, surrounding the electrode chamber. This is due to the increased amount of gas molecules compared the amount of gas molecules inside a low-pressure or vacuum chamber. In this way, the first electrode unit can be reliably cooled without providing any additional cooling means, such as channels for supplying a cooling gas or cooling fluid to the electrodes. Rather, the first electrode unit can be passively cooled by surrounding air.

[0030] In this way, thermal heating of the first electrode unit can be avoided or reduced. In other words, thermal stability of the first electrode unit can be provided. This may also lead to the effect that the first electrode unit does not warm up a gas flow (e.g. including the ions to be analysed) which flow along the first electrode unit. Thus, the first electrode unit may also contribute to the thermal stability of the ions to be analysed by the ion detecting device.

[0031] The ion detecting device can be any means and / or device with which ions can be detected, measured, and / or analysed. For example, the ion detecting device can include a mass spectrometer. The electrode chamber may be any chamber of the ion detecting device and / or the mass spectrometer which operates under negative pressure (e.g. a vacuum) and which includes at least one electrode for generating an electrical field, e.g. for interaction with the ions.

[0032] For example, the electrode chamber may be used for field-asymmetric IMS (FAIMS), or differential mobility spectrometry (DMS), applications, wherein the first electrode unit provides a conducting surface forming a portion of a drift space along which the ions move in or relative to a gas flow. Further, the first electrode unit may form part of a system of quadrupole electrodes, direct current (DC) electrodes, and / or ion mobility spectrometry (IMS) systems.

[0033] The gas-tight chamber may be any chamber in which a negative pressure and / or vacuum can be generated. The gas-tight chamber may include one or more inlets for inserting a gas (e.g. for generating a gas flow for ion mobility spectrometry), molecules, atoms, and / or ions (e.g. the ions to be analysed). The gas-tight chamber may further include one or more outlets for removing the gas, the molecules, the atoms and / or the ions. For example, a gas flow and / or ions are inserted by the one or more inlets and the one or more outlets are in fluid communication with a further low-pressure or vacuum chamber or a pump for removing the gas flow inserted via the one or more inlets. The gas-tight chamber may include a drift region for ion mobility spectrometry as outlined in the background section above. The gas-tight chamber may also be connected to a gas pump (e.g. a rotary pump) for generating negative pressure inside the gas-tight chamber.

[0034] The gas-tight chamber may include one or more walls which delimit the cavity in which the negative pressure is maintained. The first wall may be a wall of the one or more walls that constitute the gas-tight chamber. The gas-tight chamber may have the shape of a cuboid or a cylinder. The first electrode unit may therefore form a part or portion of the gas-tight chamber.

[0035] The first electrode unit may be configured to be electrically connected to a voltage source. Further, the first electrode unit may be provided with the gas-tight chamber for generating electrical field inside the gas-tight chamber. The electrical field generated by the first electrode unit may be provided for generating Mewburn Ref: 008628448

[0036] 6 an electrical force that interacts with ions, for example for changing the speed, orientation, and / or acceleration of the ions as commonly known with ion detecting devices such as mass spectrometers.

[0037] The first electrode unit may provide an entire wall of the gas-tight chamber. Alternatively, only an area or region of the first wall is provided by the first electrode unit. For example, the first electrode unit provides the entire sidewall of a cuboid-shaped gas-tight chamber or a section of a side wall of the cuboid-shaped gas-tight chamber.

[0038] The first surface of the first electrode unit may be considered the surface that is exposed inside the gastight chamber. Further, the first surface may be electrically conductive for generating the electrical field inside the gas-tight chamber. The first surface may be arranged such that ions and / or a gas inside the gas-tight chamber may contact or collide with the first surface.

[0039] The second surface of the first electrode unit may be considered the surface that is not exposed inside the gas-tight chamber. Rather, the second surface of the first electrode unit may be arranged on an outer surface of the gas-tight chamber. Thus, the second surface may be in contact with air or any other gas having a pressure higher than the pressure inside the gas-tight chamber. The second surface may be arranged such that ions and / or a gas inside the gas-tight chamber may not contact or collide with the second surface. The first surface and the second surface may form inner and outer surfaces of the first wall of the gas-tight chamber.

[0040] The first surface may extend parallel to the second surface. However is also possible that a distance between the first surface and the second surface may vary along the extension of the first surface or the second surface.

[0041] The first surface is thermally coupled to the second surface. For example, the first electrode unit may be configured and / or designed such that thermal energy can flow from the first surface to the second surface (and vice versa) via thermal conduction. The first electrode unit may be free from cavities, channels, etc, between the first surface and the second surface. In other words, the first electrode unit may not include a portion between the first surface and the second surface that prevents heat transfer by thermal conduction. Thermal conduction is the diffusion of thermal energy (heat) within one material or between materials in contact. Thus, the first electrode unit is configured to provide thermal conduction between the first surface and the second surface. As thermal conduction provides the highest rate of heat transfer at room temperatures (compared to heat radiation and diffusion), the first surface can be maintained and / or is self-controlled to be on a temperature of the second surface. In other words, the first electrode unit may be configured in such a way that temperature differences between the first surface and the second surface are balanced or cancelled out, whereby the second surface can be considered the cooling surface and the first surface can be considered the surface that is heated.

[0042] The first surface may be the surface that is heated by ions and / or gas inside the gas-tight chamber and the second surface may be the surface at which the thermal energy received by the first surface is emitted into the gas surrounding electrode chamber. Mewburn Ref: 008628448

[0043] 1

[0044] The second surface may be subjected to any gas and / or environment that surrounds the gas-tight chamber. For example, this may be air or any gas / fluid that surrounds the electrode chamber. The pressure of the gas surrounding the electrode chamber may be higher than the pressure inside the gastight chamber. Alternatively or additionally, the second surface may be actively cooled, for example by a pumping a cooling liquid or cooling gas to the second surface.

[0045] The housing of the electrode assembly may completely surround the electrode chamber. For example, the housing is provided for preventing access to the electrode chamber, for shielding the electrode chamber from external influences, and / or for integrating the electrode chamber into a housing structure of the ion detecting device.

[0046] The electrode assembly may further comprise a support structure that supports and / or holds the electrode chamber within the housing or vice versa. The housing may not be in contact with the electrode chamber. For example, there may be a gap between the electrode chamber and the housing which may be filled with a gas, for example air. Thus, the second surface of the first electrode unit may not be in contact with the housing. For example, the second surface may be offset to the housing. In general, the second surface of the first electrode unit may not be in contact with any other component.

[0047] The gap between the housing and electrode chamber may provide that the second surface is exposed to gas, for example air, for facilitating the heat exchange between the second surface and the gas inside the gap between the electrode chamber and the housing. Commonly known housings for ion detecting devices can be used.

[0048] The housing may include one or more doors which may have to configuration of a gate, flap, or the like. The one or more doors can be moved between the open position and the closed position, for example manually and / or using an actuator. In the closed position, the door prevents access of a user to the electrode chamber. In particular, the door prevents that a user can touch or contact the second surface of the electrode chamber.

[0049] In the open position, a user may access the electrode chamber, optionally the first electrode unit. For example, parts of the electrode chamber, such as the first electrode unit, may be accessible in the open position, for example for maintenance work and / or for exchanging parts of the electrode chamber, such as the first electrode unit. The door may be used for replacing the first electrode unit with another first electrode unit.

[0050] The door may be attached to the housing using one or more hinges. The housing may include an aperture or opening that can be closed by the door in the closed position.

[0051] The electrode assembly may also include the voltage source which may be a generator for supplying electrical energy to the first electrode unit (e.g. a DC voltage and / or an AC voltage). In the open position, the voltage source is prevented from supplying electrical energy to the first electrode unit to avoid the risk that a user is subjected to the electrical energy provided by the voltage source. This may reduce the risk Mewburn Ref: 008628448

[0052] 8 of electronic shocks to a user. In closed position of the door, a user has no access to the electrode chamber such that it can be safe to supply electric energy to the first electrode unit.

[0053] The electrode assembly may include a sensor for sensing whether the door is in the open or the closed position. Mechanical sensors and / or Hall sensors may be used to this end. Further, the electrode assembly may include a controller in data-communication with the sensor and the voltage source. The controller may receive a signal from the sensor that the door is in the closed position. In this case, the controller may control the voltage source to supply electric energy to the first electrode unit. If the controller receives a signal from the sensor that the door is in the open position, the controller may control the voltage source not to supply any electric energy to the first electrode unit or the electrode chamber.

[0054] The low-pressure chamber of the ion detecting device may include any chamber that contains a negative pressure or vacuum and / or that can be used with the ion detecting device such as a mass spectrometer. The pressure in the low-pressure chamber may be lower than the pressure in the electrode chamber. For example, it requires more time to generate the desired low pressure in the low-pressure chamber compared to the pressure in the electrode chamber. Thus, the provision of the closure means is helpful for maintaining the pressure in the low-pressure chamber while changing the pressure in the electrode chamber. In this way, components with the electrode chamber, such as the first electrode unit, may be replaced while maintaining the pressure in the low-pressure chamber.

[0055] In the closed position of the closure means, gas communication between the electrode chamber and the low-pressure chamber is blocked. In the open position of the closure means, gas communication between the low-pressure chamber and the electrode chamber is possible. For example, a pipe and / or gas line provides a gas communication between the low-pressure chamber and the electrode chamber.

[0056] In an optional embodiment, the closure means includes one or more valves.

[0057] The one or more valves may be provided in the pipe and / or gas line that connects the low-pressure chamber to the electrode chamber. Thus, by closing the valve, the electrode chamber may be sealed off from the low-pressure chamber such that the pressure in the electrode chamber can be changed without changing the pressure in the low-pressure chamber.

[0058] In an optional embodiment, the low-pressure chamber includes an inlet in gas-connection with the electrode chamber. Optionally, the closure means includes a sealing element, optionally made from an elastic material. Further optionally, the sealing element is configured to be placed on the inlet for closing the inlet.

[0059] The inlet of the low-pressure chamber may allow gas communication between the inside of the low- pressure chamber and the outside of the low-pressure chamber. The inlet of the low-pressure chamber may include one or more through-holes and / or one or more pipes that provide the gas communication. For example, the inlet of the low-pressure chamber may be provided for supplying a gas flow, for example containing ions to be analysed, into the low-pressure chamber. Mewburn Ref: 008628448

[0060] 9

[0061] The closure device may be configured to block the inlet of the low-pressure chamber. For example, the sealing element closes the inlet in the closed position, e.g. by closing the one or more through-holes and / or the one or more pipes. The sealing element may be made from elastic material such as rubber. The elastic properties of the sealing element may ensure that gas tight sealing can be provided between the sealing element and the inlet. Commonly known materials and / or shapes for sealing a through-hole or a pipe may be used.

[0062] The sealing element may be provided on a handle for moving the sealing element from the open position to the closed position. The sealing element may be manually handled or by an actuator which places the sealing element on the inlet in the closed position. Due to the low-pressure inside the low-pressure chamber, the sealing element may be sucked into the inlet which may increase the sealing effect of the sealing element. This effect may be increased if the pressure outside the low-pressure chamber is higher than the pressure inside the low-pressure chamber.

[0063] The handle of the closure means may include a rod onto which the sealing element can be attached. In closed position, the sealing element may be placed between the electrode chamber and the low-pressure chamber for closing the inlet of the low-pressure chamber.

[0064] In an optional embodiment, the electrode chamber further comprises a second electrode unit. Optionally, a second wall of the gas-tight chamber is formed at least in part by a second electrode unit. Further optionally, the second electrode unit includes a first surface and a second surface. In some examples, the first surface of the second electrode unit is configured to be exposed to the negative pressure in the gastight chamber. Optionally, the second surface of the second electrode unit is exposed on an outer surface of the gas-tight chamber for being subjected to the atmospheric pressure.

[0065] The optional features, characteristics, and / or technical effects of the first electrode unit and of the first wall may equally apply to the second electrode unit and the second wall, respectively.

[0066] The first surface of the first electrode unit may be inclined with respect to the first surface of the second electrode unit. The size and / or the shape of the first electrode unit and the second electrode unit, for example the first surfaces and / or the second surfaces, may differ. Alternatively, the first electrode unit may be identical to the second electrode unit (except for their positions in the electrode chamber). Further is possible that only the first surfaces of the first and second electrode units and / or the second surfaces of the first and second electrode unit are identical to each other.

[0067] The shape, size, and / or location of the first surfaces of the first electrode unit and the second electrode unit may be selected depending on the electric field that is generated by the first electrode unit and the second electrode unit. In other words, the shape, size, and / or the location of the first surfaces can be used to shape the electric generated inside the gas-tight chamber. The first surfaces of the first electrode unit and / or the second electrode unit may be made from an electrically conductive material, such as metal. Mewburn Ref: 008628448

[0068] 10

[0069] The first surface of the first electrode unit may be electrically connected to a first pole of the voltage source and the first surface of the second electrode unit may be electrically connected to a second pole of the voltage source. In other words, the electric field generated inside the gas-tight chamber may extend between the first surfaces of the first electrode unit and the second electrode unit.

[0070] The first surfaces of the first electrode unit and the second electrode unit may be spatially offset to each other (e.g. for forming an analytical gap) and / or do not contact each other. Further, the first surfaces of the first electrode unit and the second electrode unit may be electrically isolated from each other.

[0071] The first surfaces of the first electrode unit and the second electrode unit may form the analytical gap to form a drift region for receiving ions input into the electrode chamber. For example, the first surfaces of the first electrode unit and the second electrode unit may form a drift region for ion mobility spectrometry.

[0072] In an optional embodiment, the first wall and second wall are opposing walls of the gas-tight chamber and are configured such that the first surfaces of the first electrode unit and the second electrode unit face each other for providing an electrical field therebetween.

[0073] For example the first wall and the second wall are opposing walls in cuboid-shaped gas-tight chamber. In this case, the electric field may extend across the gas-tight chamber. Further, a gas flow and / or ions may move between the first surfaces of the first electrode unit and the second electrode unit.

[0074] The first surfaces of the first electrode unit and the second electrode unit may be electrodes for Field asymmetric IMS, differential mobility spectrometry, or ion drift spectrometry. The first surfaces of the first electrode unit and the second electrode unit may have a length direction and a width direction perpendicular to the length direction. The dimension in the length direction of the first surfaces may be greater than the dimension in the width direction of the first surfaces. The gas flow and / or the ions may move along the length direction of the first surfaces. The first surfaces of the first electrode unit and the second electrode unit may be spaced from each other in a direction perpendicular to the length direction and the width direction.

[0075] In an optional environment, the gas-tight chamber includes one or more walls that are made from an electrically non-conductive material for electrically isolating the first electrode unit and / or the second electrode unit.

[0076] The one or more walls that are made from the electrically non-conductive material may be those walls of the gas-tight chamber that are in direct contact with the first electrode unit and / or the second electrode unit. Optionally, the first electrode unit and / or the second electrode unit may only be in contact with the electrically non-conductive walls of the gas-tight chamber. Thus, the first electrode unit / or the second electrode unit can be electrically isolated from each other by the electrically non-conductive walls of the gas-tight chamber.

[0077] It is also possible that the one or more electrically non-conductive walls may only be electrically non- conductive in areas that are in direct contact with the first electrode unit and / or the second electrode unit. This provides the same technical effect as outlined above. Mewburn Ref: 008628448

[0078] 11

[0079] Alternatively or additionally, the one or more electrically non-conductive walls may include the first wall and / or the second wall. In this case, the first electrode unit and / or the second electrode unit may be attached to and / or supported by only the first wall and the second wall, respectively. Again, this provides that the first electrode unit is electrically isolated from the second electrode unit by the first wall and / or the second wall. The other walls of the gas-tight chamber may be made from electrically conductive material.

[0080] Optionally, the first wall includes a first aperture that is configured to receive the first electrode unit and / or the second wall includes a second aperture that is configured to receive the second electrode unit. The first aperture and / or the second aperture may be through-holes in the gas-tight chamber which would allow gas communication between the inside of the gas-tight chamber and the outside of the gas-tight chamber if the first electrode unit and / or the second electrode unit would not be placed in the first aperture and / or the second aperture, respectively.

[0081] The first electrode unit may be supported by the first aperture in the first wall. For example, the first electrode unit may be solely supported by and / or in the first aperture. In other words, the first electrode unit may be solely in contact with the circumference of the first aperture. The first electrode unit may be arranged in the first aperture in a gas tight manner. Further, first fastening means may be provided for (removably) fixing the first electrode unit to the first aperture. The first fastening means may include mechanical fastening means, such as a lock, bar, screw, and the like. In case of a low pressure in the gas-tight chamber, the first electrode unit may be held in the first aperture by the negative pressure inside the gas-tight chamber. Thus, the first fastening means may fix the first electrode unit to the gas-tight chamber in case no low pressure is provided in the gas-tight chamber.

[0082] The second electrode unit may be supported by the second aperture in the second wall. For example, the second electrode unit may be solely supported by and / or in the second aperture. In other words, the second electrode unit may be solely in contact with the circumference of the second aperture. The second electrode unit may be arranged in the second aperture in a gas-tight manner. Further, second fastening means may be provided for (removably) fixing the second electrode unit to the second aperture. The second fastening means may include mechanical fastening means, such as a lock, bar, screw and the like. In case of a low pressure in the gas-tight chamber, the second electrode unit may be held in the second aperture by the negative pressure inside the gas-tight chamber. Thus, the second fastening means may fix the second electrode unit to the gas-tight chamber in case no low pressure is provided in the gas-tight chamber.

[0083] The areas surrounding the first aperture and / or the second aperture may be made from an electrically non-conductive material. Alternatively, the entire first wall including the first aperture and / or the entire second wall including the second aperture may be made from an electrically non-conductive material. In both cases, the first electrode unit and the second electrode unit are electrically isolated from the first wall and the second wall, respectively.

[0084] In an optional embodiment, the gas-tight chamber includes one or more walls that are made from an electrically conductive material. Optionally, the gas-tight chamber further includes an electrical isolator for Mewburn Ref: 008628448

[0085] 12 electrically isolating the first electrode unit and / or the second electrode unit from the electrically conductive walls.

[0086] The one or more walls that are made from the electrically conductive material may be those walls of the gas-tight chamber that are in direct contact with the first electrode unit and / or the second electrode unit. Optionally, the first electrode unit and / or the second electrode unit may only be in contact with the electrically conductive walls of the gas-tight chamber. Thus, the first electrode unit / or the second electrode unit are not isolated from each other without the electrical isolator.

[0087] The electrical isolator may extend around the (entire) circumference of the first electrode unit and / or the second electrode unit. The electrical isolator may be made from a plastic and / or ceramic material. The electric isolator may also be elastic and / or may provide a gas-tight seal between the first electrode unit and the walls of the gas-tight chamber and / or between the second electrode unit and the walls of the gastight chamber.

[0088] The electrical isolator may be arranged between the first electrode unit and the walls of the gas-tight chamber and / or between the second electrode unit and the walls of the gas-tight chamber. The electrically isolator may be in contact with the first electrode unit and the walls of the gas-tight chamber and / or the second electrode unit and the walls of the gas-tight chamber.

[0089] It is also possible that the one or more electrically conductive walls may only be electrically conductive in areas that are in direct contact with the first electrode unit and / or the second electrode unit. This provides the same technical effect as outlined above when the electrical isolator is provided.

[0090] Alternatively or additionally, the one or more electrically conductive walls may include the first wall and / or the second wall. In this case, the first electrode unit and / or the second electrode unit may be attached to and / or supported only by the first wall and the second wall, respectively, via the electrical isolator. Again, this provides that the first electrode unit is electrically isolated from the second electrode unit by the first wall and / or the second wall. The other walls of the gas-tight chamber may be made from electrically non- conductive material.

[0091] Further, the electrical isolator may be arranged between the first electrode unit and the first aperture and / or between the second electrode unit and the second aperture. Again, the electrical isolator may also be used for providing a gas-tight seal.

[0092] In an optional embodiment, the first electrode unit and / or the second electrode unit are removably attached to the remainder of the gas-tight chamber.

[0093] In this way, the first electrode unit and / or the second electrode unit can be easily replaced and / or removed for maintenance work of the electrode units themselves and / or other parts of the gas-tight chamber. Thus, the first electrode unit and / or the second electrode unit may not only provide a cooling of the respective first surfaces but can also be used as apertures or access points for accessing the gastight chamber. Further, the first electrode unit and / or the second electrode unit can be easily replaced or cleaned by simply removing the first electrode unit and / or the second electrode unit from the gas-tight Mewburn Ref: 008628448

[0094] 13 chamber. This is not as easily possible with commonly known chambers for ion detecting devices in which the electrodes are completely arranged inside the chamber.

[0095] The first electrode unit and / or the second electrode unit may be removably attached to the remainder of the gas-tight chamber by the first fastening means and the second fastening means, respectively, as described above. Further, the first electrode unit and / or the second electrode unit may be removably attached to the first aperture and / or the second aperture, respectively, which simplifies the attachment and the removal of the electrode units.

[0096] The electrode chamber optionally includes a kit of first electrode units and / or second electrode units. A distance between the first surface and the second surface may be different between each first electrode unit and / or second electrode unit of the kit.

[0097] In this way, the distance between the first surfaces can be varied by selecting an appropriate pair of first electrode units and second electrode units. Each one of the first electrode units of the kit may fit into the first aperture, for example in such a way that the second surface of each one of the first electrode units of the kit may be located at the same position. Thus, as the distance between first surface and the second surface varies between the first electrode units of the kit, the position of the first surface inside the gastight chamber varies between each one of the first electrode units of the kit. Similar considerations may apply for each one of the second electrode units of the kit. For example, the first electrode units and / or the second electrode units of the kids vary in their thickness.

[0098] In an optional embodiment, the first electrode unit and / or the second electrode unit each include a first portion providing the first surface and a second portion providing the second surface. Optionally, the first portion and the second portion are made from an electrically conductive material. Further optionally, the first portion is coupled to the second portion for providing thermal conduction between the first portion and the second portion.

[0099] The first portion may be considered the “actual” electrode, for example the electrode that generates the electrical field inside the gas-tight chamber. The first portion may be entirely made from an electrically conductive material such as metal. The first portion and / or the second portion each may have a plate-like shape. The first portion may extend parallel to the second portion. A thickness of the first portion may be less than, equal to, or more than a thickness of the second portion. A length and / or a width of the first portion may be less then, equal to, or more than a length and / or a width, respectively, of the second portion.

[0100] The first portion may be directly attached to the second portion, for example using welding and / or an adhesive. The first portion and / or the second portion may each be unitary components, such as plates. Optionally, no cavity is provided between the first portion and to second portion. This configuration may help to maximise the thermal conduction between the first portion and the second portion. For example, the first portion is directly connected to the second portion, optionally over the entire area of contact between the first portion and the second portion. For example, a side surface of a plate-like first portion is Mewburn Ref: 008628448

[0101] 14 directly connected to a side surface of a plate-like second portion. A thickness of the first electrode unit may be the sum of a thickness of the first portion and a thickness of the second portion.

[0102] The first portion may have a first side surface and a second side surface and / or the second portion may have a first side surface and a second side surface. The first side surface of the first portion may form the first surface. The second side surface of the first portion may be attached to the first side surface of the second portion. The second side surface of the second portion may form the second surface. Circumferential surfaces connecting the first side surface to the second side surface of the first and / or second portions may be in contact with the circumference or perimeter of the first aperture or the second aperture.

[0103] In an optional embodiment, the first portion and the second portion are made from electrically conductive material, such as metal. Thus, when the first electrode unit is connected to voltage source, an electrical potential that is applied to the first electrode unit equally applies to the first portion and the second portion. Similarly considerations apply for the first portion and second portion of the second electrode. In other words, the entire first electrode unit and / or the second electrode unit are subjected to the same electrical potential.

[0104] Further, manufacturing the first portion and the second portion from an electrically conductive material such as metal, provides a high thermal conductivity throughout the first electrode unit and / or the second electrode unit. Thus, the first electrode unit and / or the second electrode unit provides a good thermal conduction of heat from the first surface to the second surface.

[0105] In an optional embodiment, the first portion and the second portion form a unitary component.

[0106] With this example, the first electrode unit and / or the second electrode unit may form a unitary component that can be made from a single piece of metal or another electrically conductive material. For example, a block of an electrically conductive material may provide the first electrode unit and / or second electrode unit. In this case, the first portion and the second portion may be two virtual parts of the single piece block of electrically conductive material. Alternatively, the single piece of electrically conductive material may be processed in that a circumferential edge is applied. The region over which the circumferential edge is present, may be considered a first portion and the remainder of the block may be considered the second portion.

[0107] In an optional embodiment, the first electrode unit and / or the second electrode unit each include a first portion providing the first surface and a second portion providing the second surface. Optionally, the first portion is made from an electrically conductive material. Further optionally, the second portion is made from an electrically non-conductive material. In some examples, the first portion is coupled to the second portion for providing thermal conduction between the first portion and the second portion.

[0108] The above-described optional features, embodiments, and / or technical effect may equally be present with this embodiment except that the second portion is made from an electrically non-conductive material. As the second portion provides the second surface, an outer surface of the gas-tight chamber is not Mewburn Ref: 008628448

[0109] 15 electrically conductive and, therefore, not subjected to the electrical potential of the voltage source. In other words, unlike the previous embodiment, there is no risk with this embodiment that the person touching the electrode chamber is at risk of receiving electrical shock because the outer surface provided by the first electrode unit and / or the second electrode unit is electrically non-conductive.

[0110] The second portion may be made from a plastic material and / or from ceramics. These materials may not have high thermal conduction coefficient as high as a metal material. Thus, the thermal transfer of heat from the first surface to the second surface may not be as high as with the embodiment in which the first portion and the second portion of both made from electrically conductive material. However, as explained above, this embodiment may be considered more secure because no outer surface of the gas-tight chamber is electrically conductive and coupled to the voltage source.

[0111] The thickness of the second portion may be smaller than the thickness of the first portion. In some examples, the second portion may be a layer covering the first portion. In this case, the first portion of first electrode unit and / or the second electrode unit may have a sufficiently high volume for receiving an amount of heat which is then transferred to the second portion and emitted into the air or gas surrounding the electrode chamber. In other words, the first portion made of an electrically conductive material may include sufficient thermal capacity for receiving heat without significantly warming up the first portion. In this case, the comparatively low heat transfer through the second portion may be acceptable due to the high thermal capacity of the first portion.

[0112] In case the first portion and the second portion of both made of an electrically conductive material, the thermal capacity for storing heat is even greater and the emission of heat into the surrounding air or gas can be higher compared to the embodiments described above.

[0113] In an optional embodiment, the first portion of the first electrode unit is sized to fit into the first aperture in the first wall and / or the second portion of the first electrode unit is configured to abut against an outer perimeter of the first aperture when it is fitted in the first aperture. Alternatively or additionally, the first portion of the second electrode unit is sized to fit into a second aperture in the second wall and the second portion of the second electrode unit is configured to abut against an outer perimeter of the second aperture when it is fitted in the second aperture.

[0114] The first portion may be sized to tightly fit into the first aperture. For example, the first portion may be sized to fit into the first aperture in a gas-tight manner. Optionally, the electrical isolator is arranged between the first / second aperture and the first portion.

[0115] As discussed above, the second portion may have a larger size compared to the first portion. Thus, the second portion may not fit into the first aperture. The second portion may act as an abutment or stopper which prevents the first electrode unit and / or the second electrode unit to be further move into the first aperture. The second portion may abut against the outer surface of the gas-tight chamber. Again, the electrical isolator may also be arranged between walls of the gas-tight chamber and the second portion. In this case, when the first electrode unit and / or the second electrode unit are fully inserted into the first aperture and / or the second aperture, respectively, the first electrode unit and / or the second electrode unit Mewburn Ref: 008628448

[0116] 16 may protrude from the outer surface or walls of the gas-tight chamber. For example, the first portion, optionally the second side surface of the first portion, may be flush with the outer surface of the walls of the gas-tight chamber and the second portion protrudes from the outer surface of the walls of the gastight chamber.

[0117] The first / second aperture may include an edge which may extend along the entire perimeter or circumference of the first / second aperture. The first / second aperture may include a step or a recessed portion forming the edge. The edge may have a side surface and a top surface. A side surface of the first portion may abut against the side surface of the edge. In other words, the first portion may be sized to fit into the opening that is provided by the side surface of the edge. The second portion may abut against the top surface. Optionally, the first side surface of the second portion may abut against the top surface of the first / second aperture. The top surface of the edge may be offset from the outer surface of the gastight chamber. The distance between the outer surface of the gas-tight chamber and the top surface of the edge may correspond to the thickness of the second portion. In this case, the second side surface of the second portion may be flush with the outer surface of the gas-tight chamber.

[0118] Of course, different shapes of the circumferential surface of the first aperture and / or the second aperture are possible. For example, one or more edges and / or curved surfaces can be provided on the circumferential surface of the first aperture and / or the second aperture. This may be done to increase the area of contact between the first aperture and the first electrode unit. This may be helpful for increasing a gas tight seal and / or for minimising movement of the first electrode unit within the first aperture.

[0119] The above optional features, characteristics and / or technical effect of the first electrode unit arranged in the first aperture may equally apply to the second electrode unit arranged in the second aperture.

[0120] In an optional embodiment, in a top view onto the first surface, the second portion provides an edge circumferentially extending around the first portion.

[0121] The edge circumferentially extending around the first portion may be shaped and / or sized to fit to the edge of the first aperture and / or the second aperture as described above. For example, the first surface of the electrode unit may be flush with the inner surface of the gas-tight chamber. Thus, the first electrode unit and / or the second electrode unit may be arranged such that the first surface is flush with the inner surface of the gas-tight chamber and / or the second surface is flush with the outer surface of the gas-tight chamber.

[0122] In an optional embodiment, in a cross-sectional view, the first electrode unit and / or the second electrode unit have a T-shape.

[0123] The T-shaped may be provided by the circumferentially extending edge provided between the first portion and the second portion.

[0124] In an optional embodiment, the second surfaces of the first second electrode unit and / or second electrode unit include one or more radiating fins. Mewburn Ref: 008628448

[0125] 17

[0126] More generally, the second surface of the first electrode unit and / or the second electrode unit may not be flush and / or may include structures for increasing the area of the second surface for increasing heat exchange between the second surface and the surrounding gas or air. Radiating fins are an example of structures for increasing the area of the second surface. Commonly known radiating fins can be used. Further, the size and / or the number of the radiating fins may be adapted with regard to the desired increase in heat exchange and / or the available space within the housing of the electrode assembly.

[0127] Further, the electrode assembly may include ventilation means for providing a flow of gas or air along the second surface of the first electrode unit and / or the second electrode unit. The ventilation means may include one or more fans and are provided for increasing the heat exchange between the second surface and the surrounding gas or air.

[0128] Thus, the radiating fins may be provided for increasing heat exchange between the first electrode unit and / or the second electrode unit and the surrounding gas and air. This may increase the cooling effect provided by the first electrode unit and / or the second electrode unit.

[0129] An example of the invention may also be summarised as follows:

[0130] The solution described herein can achieve thermal stability of (DMS) electrodes units by making them not entirely part of the vacuum chamber. Natural air circulation in a working room (e.g. as provided by the housing of the electrode assembly) will remove or reduce the effect of electrodes heating from low density gas coming from the dissolvation line. Additional means to stabilise temperature could be provided through radiators mounted on electrodes units or being part of electrodes units.

[0131] Optional advantages of the solution are: the system can be easily maintained, for example with regard to cleaning electrodes units; the electrode units can be easily changed, for example with electrodes having different analytical gap; it can be easier and cheaper to manufacture electrodes that are part of the gastight chamber compared to electrodes inside vacuum chamber (because electrodes inside the gas-tight chamber needs support, the chamber needs to be larger, feedthroughs and wires inside the vacuum needs to be provided); and simple system is provided for allowing to vent gas-tight chamber without venting the mass spectrometer which further simplifies DMS maintenance.

[0132] The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

[0133] Summary of the Figures

[0134] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0135] Figure 1 shows a schematical perspective view of an ion detecting device of the prior art. Mewburn Ref: 008628448

[0136] 18

[0137] Figure 2 shows a schematical perspective view of an embodiment of an ion detecting device and, separately, schematic perspective views from a front and back sides as well as an exploded view of an electrode chamber of the ion detecting device.

[0138] Figure 3 shows various views of a first electrode unit and a second electrode unit of the electrode chamber of Figure 2.

[0139] Figure 4 shows a schematical perspective view of a further embodiment of the ion detecting device including a closure means in an open position (top view) and a closed position (bottom view).

[0140] Detailed Description of the Invention

[0141] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0142] Figure 1 shows an example of an ion detecting device 100 of the prior art which is a vacuum differential mobility spectrometry (DMS) system combined with triple-quadrupole mass spectrometer (MS). Ions are generated by electrospray ionisation (ESI) source 102 in atmospheric pressure. The generated ions are sucked inside MS vacuum trough a heated capillary 104, where heating is helping to dissolve remaining sample droplets from ESI, also referred as dissolvation line DL. The vacuum DMS comprises two planar electrodes 106 that are filtering ions according to their differential mobility. From there, the ions move to the quadrupole 108 also referred as Q-array, which operates in higher vacuum and its main purpose is to gather and focus ions. The ions then pass an ion focusing optic 110, first quadrupole 112 for filtering ions according to their ratio between mass and charge, a collision-induced dissociation cell CID 114, a second quadrupole 116, and an ion detector 118.

[0143] Figure 2 shows an ion detecting device 200 which includes an electrospray ionisation chamber 202, and electrode assembly 203, and a mass spectrometer 204. The electrospray ionisation chamber 202 may include the electrospray ionisation source 102 as described in connection with Figure 1 . Similarly, the mass spectrometer 204 may include the features and / or components of the mass spectrometer as discussed in connection with Figure 1 . The mass spectrometer 204 can include a low-pressure chamber 264 as further discussed in connection with Figure 4.

[0144] The electrode assembly 203 includes a housing 206 and an electrode chamber 220 which is arranged inside the housing 206. As apparent from Figure 2, the housing 206 has the shape of tube which connects the electrospray ionisation chamber 202 to the mass spectrometer 204. The housing 206 further includes an opening 208 through which the electrode chamber 220 is accessible. The opening 208 can be closed by a door (not shown in the figures) such that the electrode chamber 220 is no longer accessible. In other words, the door in the closed position and the housing 206 prevent access of a user to the electrode chamber 220. Mewburn Ref: 008628448

[0145] 19

[0146] The housing 206 may be provided with one or more sensors (not shown in figures) which detect whether the door is in an open position (as shown in Figure 2) or in a closed position. The one or more sensors may be in data-communication with a controller (not shown in figures) which controls a voltage source (not shown in figures). The voltage source may be configured to supply electrical energy to the electrode chamber 220. The controller may be configured to stop the supply of electrical energy to the electrode chamber 220 if it is detected that the door is not in the closed position. In other words, if the door is moved from the closed position towards the open position, the controller prevents the voltage source from supplying electric energy to the electrode chamber 220.

[0147] The electrode chamber 220 may have the function of the vacuum differential mobility spectrometry (DMS) system discussed in connection with Figure 1 . The electrode chamber 220 may be configured to receive ions from the electrospray ionisation chamber 202 and forward these ions or a selection of the ions to the mass spectrometer 204.

[0148] The electrode chamber 220 includes a gas-tight chamber 210, a first electrode unit 212a, and / or a second electrode unit 212b. The first electrode unit 212a and / or the second electrode unit 212b are removably attached to the gas-tight chamber 210.

[0149] The gas-tight chamber 210 includes a first aperture 214 and a second aperture (not visible in the figures). The first electrode unit 212a is inserted into the first aperture 214 for closing the first aperture 214, optionally in a gas-tight manner. As apparent from Figure 2, the first electrode unit 212a protrudes from the walls of the gas-tight chamber 210. The second electrode unit 212b is inserted into the second aperture for closing the second aperture, optionally in a gas-tight manner. As apparent from Figure 2, the second electrode unit 212b protrudes from the walls of the gas-tight chamber 210.

[0150] In the embodiment of Figure 2, the first electrode unit 212a and the second electrode unit 212b are used as replicable top and bottom walls of the gas-tight chamber 210 which are examples of a first wall and a second wall, respectively. As apparent from Figures 2 and 3, the first electrode unit 212a and the second electrode unit 212b each include a first portion 222 and a second portion 224 which is larger than the first portion 222. In a cross-sectional view of the first electrode unit 212a and the second electrode unit 212b, the first portion 222 and the second portion 224 from a T-shape. The first portion 222 is sized and shaped to tightly fit into the first aperture 214 and the second portion 224 is larger than the first aperture 214 such that the second portion 224 provides an abutment surface or stopper abutting against the outer surface of the gas-tight chamber 210.

[0151] When inserted into the first aperture 214 and the second aperture, the first portions 222 of the first electrode unit 212a and the second electrode unit 212b are spaced apart from each other by a gap 226 between which the ions move.

[0152] The first portion 222 of the first electrode unit 212a has a first surface 222a which faces the first surface 222a of the first portion 222 of the second electrode unit 212b. The first surfaces 222a are the electrode surfaces between which an electric field is generated when the first electrode unit 212a and the second electrode unit 212b are connected to the voltage source. Mewburn Ref: 008628448

[0153] 20

[0154] The second portion 224 of the first electrode unit 212a and the second portion 224 of the second electrode unit 212b each have a second surface 224a that forms a part of the outer surface of the gastight chamber 210. Thus, the second surfaces 224a are exposed to the gas or air in which the gas-tight chamber 210 is arranged. Radiating fins 228 are provided on the second surface 224a.

[0155] The first electrode unit 212a and the second electrode unit 212b are single-piece component made from metal (e.g. the radiating fins 228 can also be integrally made with the second portions 224). In general, the first electrode unit 212a and the second electrode unit 212b are configured to conduct thermal energy from the first surface 222a to the second surface 224a such that the heat is emitted from the second surface 224a, for example into the surrounding gas or air. Thus, the configuration and the positioning of the first electrode unit 212a and the second electrode unit 212b cool the first surface 222a.

[0156] As the first electrode unit 212a and the second electrode unit 212b are bulky single-piece components, the first electrode unit 212a and the second electrode unit 212b have a high thermal capacity for absorbing heat. Thus, heating of the first surface 222a due impacting ions may not result in rapid increase in the temperature of the first surface 222a as observed with thin plate-shaped electrodes because the thermal energy is absorbed by the bulky first electrode unit 212a and the second electrode unit 212b (and later emitted via the second surface 224a). The emission of the heat via the second surface 224a is improved by the radiating fins 228.

[0157] The size of the gap 226 can be varied by replacing the first electrode unit 212a and / or the second electrode unit 212b by respective electrodes units that have a different thickness. In this way, the size of the gap 226 can be changed in a simple manner because the first electrode unit 212a and the second electrode unit 212b are removably. This also simplifies cleaning and maintenance work for the first electrode unit 212a and the second electrode unit 212b.

[0158] The ion detecting device 200 may further include a closure means 274 as shown in Figure 4. The ion detecting device 200 is shown in Figure 4 without the gas-tight chamber 210 for better visibility of the closure means 274. Further, the first electrode unit 212a and the second electrode unit 212b are only schematically shown (e.g. without the configuration as shown in Figures 2 and 3). The ion detecting device 200 includes an inlet 270 to the Q-array chamber 264 (an example of a low-pressure chamber) which is a first stage of the mass spectrometer 204.

[0159] The ion detecting device 200 includes a valve 282 connected between a rotary pump (not shown in Figure 4) and the gas-tight chamber 210. The rotary pump may be provided for generating a low pressure in the gas-tight chamber 210.

[0160] For replacing and / or cleaning the first electrode unit 212a and / or the second electrode unit 212b, the valve 282 may be closed and the closure means 274 is moved to close the inlet 270 which may provide a gas connection between the gas-tight chamber 210 and the Q-array chamber 264. The closure means 270 includes a handle (e.g. a rod in Figure 4) and sealing element such as rubber ball. The sealing element is attached to the handle such that the sealing element can be moved using the handle. The closure means 274 blocks or seals the inlet 270 such that the Q-array chamber 264 is sealed from the Mewburn Ref: 008628448

[0161] 21 gas-tight chamber 210. Further, the negative pressure inside the Q-array chamber 264 sucks the sealing element into the inlet 270 which increases the sealing effect of the sealing member.

[0162] Thereafter, the gas-tight chamber 210 can be vented via the heated capillary 104. As a next step, the first electrode unit 212a and / or the second electrode unit 212b can be removed from the gas-tight chamber 210, e.g. for cleaning the first surfaces 222a or for replacing the first electrode unit 212a and / or the second electrode unit 212b.

[0163] After placing the first electrode unit 212a and / or the second electrode unit 212b into the apertures of the gas-tight chamber 210, the valve 282 can be opened again for lowering the pressure inside the gas-tight chamber 210 to the desired pressure. Once the desired pressure is reached, the closure means 270 can be removed from the inlet 270.

[0164] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0165] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0166] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0167] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0168] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0169] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example + / - 10%.

Claims

1. Mewburn Ref: 00862844822Claims:1 . An electrode chamber for an ion detecting device, comprising a gas-tight chamber configured to maintain a negative pressure therein, and a first electrode unit for generating an electric field inside the gas-tight chamber when the first electrode unit is connected to a voltage source, wherein a first wall of the gas-tight chamber is formed at least in part by the first electrode unit, wherein the first electrode unit includes a first surface and a second surface, wherein the first surface of the first electrode unit is configured to be exposed to the negative pressure in the gas-tight chamber, and wherein the second surface of the first electrode unit is exposed on an outer surface of the gastight chamber for being subjected to the atmospheric pressure.

2. The electrode chamber of claim 1 , further comprising a second electrode unit, wherein a second wall of the gas-tight chamber is formed at least in part by a second electrode unit, wherein the second electrode unit includes a first surface and a second surface, wherein the first surface of the second electrode unit is configured to be exposed to the negative pressure in the gas-tight chamber, and wherein the second surface of the second electrode unit is exposed on an outer surface of the gas-tight chamber for being subjected to the atmospheric pressure.

3. The electrode chamber of claim 2, wherein the first wall and second wall are opposing walls of the gas-tight chamber and are configured such that the first surfaces of the first electrode unit and the second electrode unit face each other for providing an electrical field therebetween.

4. The electrode chamber of any preceding claim, wherein the gas-tight chamber includes one or more walls that are made from an electrically non-conductive material for electrically isolating the first electrode unit and / or the second electrode unit.

5. The electrode chamber of any one of the claims 1 to 3, wherein the gas-tight chamber includes one or more walls that are made from an electrically conductive material,Mewburn Ref: 00862844823 wherein the gas-tight chamber further includes an electrical isolator for electrically isolating the first electrode unit and / or the second electrode unit from the electrically conductive walls.

6. The electrode chamber of any preceding claim, wherein the first electrode unit and / or the second electrode unit are removably attached to the remainder of the gas-tight chamber.

7. The electrode chamber of any preceding claim, wherein the first electrode unit and / or the second electrode unit each include a first portion providing the first surface and a second portion providing the second surface, wherein the first portion and the second portion are made from an electrically conductive material, and wherein the first portion is coupled to the second portion for providing thermal conduction between the first portion and the second portion.

8. The electrode chamber of claim 7, wherein the first portion and the second portion form a unitary component.

9. The electrode chamber of any one of the claims 1 to 6, wherein the first electrode unit and / or the second electrode unit each include a first portion providing the first surface and a second portion providing the second surface, wherein the first portion is made from an electrically conductive material, wherein the second portion is made from an electrically non-conductive material, and wherein the first portion is coupled to the second portion for providing thermal conduction between the first portion and the second portion.

10. The electrode chamber of any one of the claims 7 to 9, wherein the first portion of the first electrode unit is sized to fit into a first aperture in the first wall and the second portion of the first electrode unit is configured to abut against an outer perimeter of the first aperture when it is fitted in the first aperture, and / or wherein the first portion of the second electrode unit is sized to fit into a second aperture in the second wall and the second portion of the second electrode unit is configured to abut against an outer perimeter of the second aperture when it is fitted in the second aperture.Mewburn Ref: 0086284482411. The electrode chamber of claim 10, wherein, in a top view onto the first surface, the second portion provides an edge circumferentially extending around the first portion.

12. The electrode chamber of claim 10 or 11 , wherein, in a cross-sectional view, the first electrode unit and / or the second electrode unit have a T-shape.

13. The electrode chamber of any preceding claim, wherein the second surfaces of the first and / or second electrode units include one or more radiating fins.

14. An electrode assembly for an ion detecting device, comprising the electrode chamber of any preceding claim, and a housing surrounding the electrode chamber, wherein the housing includes a door for accessing the electrode chamber, wherein the door is movable between an open position in which the electrode chamber is accessible and a closed position in which access to the electrode chamber is prevented.

15. The electrode assembly of claim 14, further comprising the voltage source, wherein the voltage source is configured to only supply electromagnetic energy to the first electrode unit and / or the second electrode unit when the door is in the closed position.

16. An ion detecting device, comprising the electrode chamber of any one of the claims 1 to 13 or the electrode assembly of claim 14 or 15, a low-pressure chamber, and a closure means configured to be movable between an open position and a closed position, wherein, in the closed position, the closure means blocks a gas flow between the electrode chamber and the low-pressure chamber, and wherein, in the open position, the closure means unblocks the gas flow between the electrode chamber and the low-pressure chamber.

17. The ion detecting device of claim 16, wherein the closure means includes a valve.Mewburn Ref: 0086284482518. The ion detecting device of claim 16, wherein the low-pressure chamber includes an inlet in gasconnection with the electrode chamber, wherein the closure means includes a sealing element, optionally made from an elastic material, the sealing element being configured to be placed on the inlet for closing the inlet.

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