Plasma source chamber for spectrometer

Abstract

A plasma source chamber (10) for a spectrometer comprises an inner housing (11) for accommodating a plasma source (31) and an outer housing (12) accommodating the inner housing. The outer housing (12) comprises at least one outer inlet opening (21) in a first wall and at least one outer exhaust opening (22) in a second wall. The walls of the inner housing and the outer housing define a gap (25) to allow a first air flow (1) to pass through the gap (25) between the inner housing and the outer housing from the at least one outer inlet opening (21) to the at least one outer exhaust opening (22). The inner housing (11) comprises at least one inner inlet opening (23) in a first wall and at least one inner exhaust opening (24) in a second wall to allow a second air flow (2) to pass through the inner housing from the at least one inner inlet opening to the at least one inner exhaust opening. Thus, improved cooling of the outer surface of the plasma source chamber is achieved.

Description

Technical Field

[0001] The present invention relates to a plasma source chamber for a spectrometer. More particularly, the present invention relates to a plasma source chamber for a spectrometer capable of housing a plasma source without requiring active cooling elements within the chamber. Background Art

[0002] As is well known, plasma sources are used in spectrometers such as emission spectrometers and mass spectrometers. Plasma sources, such as inductively coupled plasma (ICP) sources, produce plasmas in which atoms and molecules can be ionized. In such plasmas, extremely high temperatures, such as temperatures of 8,000 K or even 10,000 K, may occur. In conventional spectrometers, the plasma source is housed in a large chamber, thereby allowing a relatively large distance between the plasma and the walls and other parts of the chamber. As users of spectrometers increasingly demand more compact instruments, the size of the plasma source chamber has been reduced, resulting in a smaller distance between the plasma source and other components. It should be understood that this has caused problems related to temperature and temperature gradients.

[0003] It is known to use air flow for cooling in a plasma chamber. For example, the ) produced by Thermo Scientific TM iCAP TM The 7000 ICP-OES analyzer system has a plasma chamber in which a plasma torch is housed and in which air flow is used for cooling. An exhaust port opening is provided in the top wall of the plasma chamber, above the plasma torch, while an air inlet opening is provided in the bottom wall, near the side wall, allowing air flow from the bottom to the top of the plasma chamber, past the plasma torch. Although this arrangement works well for radially viewing a vertical torch, it is less suitable for axial viewing of a vertical torch. For this reason, the iCAP TM The 7000 system's torch is arranged horizontally while maintaining the top exhaust port and allowing axial viewing from the side in a dual view arrangement.

[0004] To maintain the freedom to mount the plasma torch horizontally or vertically in single view and dual view arrangements, top exhaust ports may be provided on the sides of the plasma chamber to free up clearance above the plasma torches, as required. However, exhaust ports away from the center of the plasma chamber will cause cross-flow of air, which may disturb the plasma and cause instability of the plasma source. However, the air flow should be large enough to cool the plasma chamber so that its outer surface does not constitute a safety hazard even when the size of the plasma chamber is limited.

[0005] Japanese patent application JP2005-205296 discloses an ICP spectrometer with an exhaust cooling device. The plasma chamber of JP2005-205296 has a curved precooling pipe fixed to a precooler. A gas cooler arranged downstream of the precooling pipe contains a water-cooled heat exchange coil. An exhaust fan is also provided. The elbow shape of the cooling pipe prevents a line of sight between the inlet and the outlet, which is undesirable in some applications. In addition, the plasma chamber of JP2005-205296 requires a precooler, a gas cooler and a fan, making the arrangement complicated and relatively expensive. Summary of the invention

[0006] The present invention seeks to overcome the shortcomings of the prior art and to provide a plasma source chamber for a spectrometer that can be compact, that allows the use of a vertical plasma source, and that does not require an active cooling mechanism. In particular, the present invention seeks to provide a plasma source chamber that provides sufficient cooling of its outer surfaces without requiring strong air flows that disturb the plasma.

[0007] Therefore, the present invention provides a plasma source chamber for a spectrometer, the plasma source chamber comprising an inner shell for accommodating a plasma source and an outer shell accommodating the inner shell, wherein the outer shell comprises at least one outer air inlet opening in a first wall and at least one outer exhaust opening in a second wall, wherein the wall of the inner shell and the wall of the outer shell define a gap to allow a first air flow to pass through the gap between the inner shell and the outer shell from the at least one outer air inlet opening to the at least one outer exhaust opening, and wherein the inner shell comprises at least one inner air inlet opening in the first wall and at least one inner exhaust opening in the second wall to allow a second air flow to pass through the inner shell from the at least one inner air inlet opening to the at least one inner exhaust opening.

[0008] By providing an inner shell and an outer shell, a double-layer thermal protection structure is obtained. By providing a gap between the inner shell and the outer shell, direct heat transfer between the inner shell and the outer shell is avoided, thereby significantly improving thermal insulation. In addition, the gap allows air flow to pass between the inner shell and the outer shell, so that the air that does not pass through the inner shell cools the outer shell. As a result, the volume and speed of the air flow through the inner shell can be limited, while the temperature of the outer shell can be limited to a value that complies with safety regulations, even when the internal volume of the plasma source chamber is small. In particular, the present invention allows the use of less than 250m 3 When a vertical plasma torch is used, the plasma source chamber of the present invention can be suitable for radial and axial observation of the plasma.

[0009] In an advantageous embodiment of the invention, the walls, inlet and outlet are arranged so that in use the first air flow is greater than the second air flow. That is, in such embodiments, the air flow through the outer shell is greater in volume and / or air velocity than the air flow through the inner shell. Conversely, the air flow through the inner shell is less than the air flow through the outer shell, thereby preventing the plasma from being disturbed by the air flow. This can be achieved by the relative sizes of the inlet opening and the exhaust opening and their relative orientation.

[0010] The invention is based on the recognition that the air flow in the plasma source chamber should be directed in such a way that the outer surface of the plasma source chamber is sufficiently cooled. The invention benefits from the further recognition that the air flow at and around the plasma torch should be limited in volume and velocity to avoid that the plasma is disturbed by the air flow.

[0011] The present invention also benefits from the further recognition that inner and outer housings providing a gap allows air to flow through the gap, thereby allowing the outer surface to be cooled while directing air away from the plasma in the inner housing.

[0012] In order to avoid that the plasma is disturbed by the air flow, preferably, the air flow through the inner housing is smaller than the air flow through the gap between the inner housing and the outer housing. In other words, the main air flow is guided rather than passing through the inner housing.

[0013] The inner shell and the outer shell both have at least one air inlet opening in the first wall and at least one exhaust opening in the second wall, the first wall and the second wall are preferably different walls, such as opposing side walls. In either of the inner shell and the outer shell, or in both, at least one air inlet opening can be located below at least one outlet opening in use. That is, when a plasma chamber is used, the inlet opening can be located at and / or in the bottom wall, and the outlet opening can be located at and / or in the top wall of the inner shell and the outer shell. In this way, natural air flow is promoted because the air will significantly heat up when it passes through the plasma chamber. As the air expands when it heats up, the exhaust port can be advantageously larger than the air inlet port, that is, for example, the exhaust port can have a larger cross-section.

[0014] At least one outer air inlet opening, i.e., the air inlet opening of the outer shell, may extend substantially over the width of the wall of the outer shell. Similarly, at least one outer air outlet opening, i.e., the air outlet opening of the outer shell, may extend substantially over the width of the wall of the outer shell. Additionally or alternatively, at least one air inlet opening of the inner shell and / or at least one air inlet opening of the outer shell may extend substantially over the width of the wall of the inner shell.

[0015] In the plasma source chamber according to the present invention, at least one inner air inlet opening may be in direct communication with the gap between the inner shell and the outer shell. As a result, the air flow passing through the inner shell (which may be referred to as the second air flow) may be derived from the air flow passing through the gap between the inner shell and the outer shell (which may be referred to as the first air flow). That is, part of the (first) air flow passing through the gap branches off to constitute the (second) air flow passing through the inner shell.

[0016] Alternatively, at least one inner air inlet opening may be connected to a duct extending through the gap and through the wall of the outer shell, thereby allowing air flow from outside the outer shell. In such embodiments, the (first) air flow through the gap and the (second) air flow through the inner shell are separate air flows.

[0017] Similarly, at least one inner exhaust port opening may be in direct communication with the gap between the inner shell and the outer shell. That is, the (second) air flow through the inner shell may join the (first) air flow in the gap, preferably at or near the exhaust port opening of the outer shell. Alternatively or additionally, at least one inner exhaust port opening may be connected to a duct extending through the gap and through the wall of the outer shell, thereby allowing the air flow to reach the exterior of the outer shell.

[0018] In a particularly advantageous embodiment, the inner housing is removable. That is, the inner housing can be removed from the plasma chamber and can therefore be removably attached to the outer housing. By providing a removable inner housing, it is easier to clean the interior of the plasma chamber, which may be necessary due to the accumulation of deposits in the inner housing. Furthermore, by providing a removable inner housing, the inner housing can be replaced when necessary.

[0019] In an embodiment, the plasma source chamber may further comprise a shielding element located outside the outer shell, which is used to cover at least one wall of the outer shell, the shielding element and the wall defining an additional gap, thereby allowing a third air flow between the shielding element and the outer shell. The additional gap and the associated air flow provide cooling outside the outer shell, while providing additional thermal insulation due to the additional layer formed by the shielding element. The shielding element may be arranged to cover two substantially vertical walls of the outer shell, the additional gap extending between the shielding element and the wall, one of the walls being preferably a top wall in use. The shielding element may face the (usually temperature-sensitive) optical part of the spectrometer.

[0020] As mentioned above, both the inner and outer shells may have more than one inlet opening and / or more than one exhaust opening. Specifically, the inner shell may have at least one additional inlet opening in a wall which is the bottom wall in use. Additional openings may be provided in the walls of the inner and outer shells to accommodate a plasma source and at least one viewing piece, such as a periscope, for observing the plasma. Since an exhaust opening directly above the plasma torch is not required in such an arrangement, an axial viewing piece may be located substantially above the plasma torch. The axial viewing piece may be purged by supplying argon gas to provide a purified optical path.

[0021] The plasma source chamber according to the present invention may include an inner door for the inner housing and an outer door for the outer housing, which doors may be coupled to provide a combined movement of the doors. At least one of the inner door and the outer door may be a sliding door. In an embodiment, both the inner door and the outer door are sliding doors.

[0022] The plasma source chamber according to the present invention can advantageously be arranged to accommodate a vertical plasma source. However, embodiments accommodating a horizontal plasma source are also possible. In either orientation, the plasma source can be an inductively coupled plasma (ICP) source. Other sources, such as flame sources, MIP (microwave induced plasma) sources or ETA (electrothermal ionization) sources, can also be arranged horizontally or vertically in the source chamber of the present invention.

[0023] The present invention additionally provides a spectrometer comprising a plasma source chamber as described above, such as an emission spectrometer, more specifically, an optical emission spectrometer or a mass spectrometer. The emission spectrometer according to the present invention may further comprise a sample introduction system for introducing the sample to be analyzed into the plasma and a detection unit for detecting the plasma emission. The mass spectrometer according to the present invention may further comprise a separator cone, a sampling cone, at least one mass filter, such as a quadrupole mass filter, an ion optical device and a detection unit for detecting ions. The spectrometer provided by the present invention may also alternatively be an atomic fluorescence spectrometer or an atomic absorption spectrometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 An exemplary embodiment of a plasma source chamber according to the prior art is schematically illustrated.

[0025] Figure 2 A first exemplary embodiment of a plasma source chamber according to the present invention is schematically illustrated.

[0026] Figure 3 A second exemplary embodiment of a plasma source chamber according to the present invention is schematically illustrated.

[0027] Figure 4An embodiment of an inner housing of a plasma source chamber according to the present invention is schematically illustrated.

[0028] Figure 5 An embodiment of an outer housing of a plasma source chamber according to the present invention is schematically illustrated.

[0029] Figure 6 An embodiment of a plasma source chamber according to the invention is schematically illustrated.

[0030] Figure 7 An exemplary embodiment of an optical emission spectrometer comprising a plasma source chamber according to the invention is schematically illustrated. DETAILED DESCRIPTION

[0031] exist Figure 1 A plasma chamber according to the prior art is schematically illustrated in the cross-sectional view in FIG. Such a plasma chamber (or plasma source chamber) is used, for example, by Thermo Fisher Scientific Inc. iCAP 7000 manufactured by TM The plasma chamber 10' shown comprises a housing 15 in which a plasma torch 31 is housed. The plasma torch 31 is provided with an RF induction coil 38 which is arranged around a portion of the length of the plasma torch 31. The RF induction coil 38 is used as a heating element for generating plasma. A viewing piece 39 protrudes from the side wall of the plasma chamber to observe the plasma in use from the side. An exhaust pipe 18 is arranged on the top wall of the plasma chamber 10' and is directly connected to an exhaust port opening 29 located above the plasma torch 31. An inlet opening 21 is arranged in the bottom wall of the plasma chamber, adjacent to the side wall.

[0032] The location of the exhaust pipe 18 prevents the viewing member from being located in the top wall of the plasma chamber, which is not convenient in some applications. In addition, the air flow 5 through the plasma chamber is from the air inlet opening 21 through the plasma above the plasma torch 31 to the exhaust opening 29. It should be understood that the air flow cannot be too strong, otherwise the plasma will be disturbed.

[0033] exist Figure 2An exemplary embodiment of a plasma source chamber 10 according to the present invention is schematically shown in a cross-sectional view in FIG. 1 , comprising an inner housing (or inner chamber) 11 housed in an outer housing (or outer chamber) 12. In the inner housing 11, a plasma torch 31 is arranged, which can generate a plasma 30 in use. Above the plasma torch 31, a viewing piece 32 is arranged for axially observing the plasma. In the illustrated embodiment, the viewing piece 32 is composed of a tube through which a gas is supplied to provide a clean optical path. The gas is preferably a dry gas that does not contain oxygen, such as argon (Ar), to allow deep ultraviolet (UV) light to pass through the viewing piece 32. It should be noted that in the illustrated embodiment, the plasma torch is arranged vertically in the inner housing 11 in use, and the viewing piece 32 is arranged substantially axially above the plasma torch 31.

[0034] The inner housing 11 is provided with an inlet opening 23 and an exhaust opening 24, which are arranged in the opposite walls of the inner housing 11 in the illustrated embodiment, thereby allowing the air flow 2 to pass through the inner housing 11. Additional inlet openings may be present in the walls of the inner housing, such as an inlet opening 23A arranged in the bottom wall adjacent to the plasma torch 31, which allows additional air flow 2A to pass through the inner housing. Similarly, additional exhaust openings may be provided. In the illustrated embodiment, in use, the exhaust opening 24 is located higher than the inlet openings 23 and 23A to help the natural flow of air heated by the plasma. However, in some embodiments, the inlet openings may be located at substantially the same height, or even higher than the exhaust openings.

[0035] In the illustrated embodiment, the outer shell 12 is provided with an air inlet opening 21, an air outlet opening 22 and an additional air outlet opening 22A. In the illustrated embodiment, the air inlet opening and the air outlet openings 21 and 22 are arranged at opposite walls of the outer shell 12, and the air outlet openings 22 and 22A are arranged to be higher than the air inlet opening 21 in use to assist the natural flow of heated air through the outer shell. However, in some embodiments, the air inlet openings may be located at substantially the same height, or even higher than the air outlet openings.

[0036] According to the invention, there is a gap 25 between the inner housing 11 and the outer housing 12, which allows the air flow 1 to pass through the outer housing 12, but substantially surrounds the inner housing 11. Figure 2 In the embodiment shown in FIG. 1 , it can be seen that the air flow 1 exists in Figure 2 Around all four walls of the inner housing 11 shown in FIG.

[0037] It should be understood that such air flow can also be between the respective front walls of the inner shell and the outer shell, and / or in the gap between the respective rear walls of the inner shell and the outer shell (in the gap between the respective rear walls of the inner shell and the outer shell). Figure 2In some embodiments, there is no gap in front of and / or behind the plasma source chamber for air flow, and the gap is only between at least one pair of side walls (i.e., between the corresponding side walls of the inner shell and the outer shell) and between at least one pair of upper walls (i.e., between the corresponding upper walls or covers of the inner shell and the outer shell).

[0038] By providing a gap between the inner shell and the outer shell, air can flow between the inner shell and the outer shell.In addition, the double wall so arranged above the plasma torch provides double shielding of the heat of the plasma torch for any object above the plasma chamber.

[0039] According to another aspect of the invention, the inner housing 11 and the outer housing 12 are arranged so that the air flow 1 passing through the gap between the inner housing and the outer housing is greater than the air flow 2 passing through the inner housing 11. That is, the (second) air flow 2 passing through the inner housing 11 has, for example, a smaller volume velocity than the (first) air flow 1 passing through the gap 25. By passing a smaller portion of the total air flow through the inner housing 11 and a larger portion through the gap 25, strong air flows passing through the plasma and thus disturbance of the plasma are avoided, while providing an excellent cooling effect of both the inner housing and the outer housing.

[0040] By appropriately selecting the (relative) dimensions, a smaller air flow through the inner housing can be obtained. Specifically, the diameter and / or surface area of ​​the inlet opening 23 and the exhaust opening 24 of the inner housing 11 and the diameter and / or surface area of ​​the inlet opening 21 and the exhaust openings 22 and 22A of the outer housing 12 are selected so that the first air flow 1 passing through the gap is greater than the second air flow 2 passing through the inner housing. In addition, the relative orientation of the various openings helps to provide the required airflow. For example, the orientation of the inlet opening 23 is substantially perpendicular to the longitudinal direction of the gap 25 at the position of the inlet opening 23. As a result, the air flow passing through the gap 25 is not directed but along the inlet opening 23. This helps to reduce the air flow 2 passing through the inner housing relative to the air flow passing through the gap.

[0041] In the exemplary embodiment shown, the gap between the inner shell 11 and the outer shell 12 has a width of about 3 cm at both the side walls and the top wall where the opening 23 is located. In the embodiment shown, the air inlet opening 21 and the exhaust opening 22 have a width of about 48 cm. 2 The air inlet opening 23 has an area of ​​about 24 cm 2 The exhaust port opening 24 has an area of ​​about 52 cm 2Thus, it can be seen that the area of ​​the air inlet opening 23 of the inner shell is about half the area of ​​the air inlet opening 21 of the outer shell, while the area of ​​the air outlet opening 24 of the inner shell is twice the area of ​​the air inlet opening 23 of the inner shell, in this example, about 2.2 times the area of ​​the air inlet opening 23 of the inner shell. The additional air outlet opening 22A may have a diameter of about 11 cm 2 , that is, approximately one quarter of the area of ​​the exhaust port opening 22 .

[0042] It should be understood that the dimensions given above are merely examples, and the actual dimensions of the plasma source chamber according to the present invention may also vary depending on their relative orientation. For example, in the illustrated example, the inlet opening 23 of the inner housing is arranged at right angles to the inlet opening 21 of the outer housing. If this angle is greater or less than 90°, the area of ​​the inlet opening 23 of the inner housing may be adapted to achieve the same air flow 2. Similarly, in the illustrated example, the additional inlet opening 23A of the inner housing is arranged at right angles to the air flow 1 passing through the gap, and may have other dimensions when arranged at different angles.

[0043] The ratio of the area of ​​the air inlet opening 23 of the inner shell to the area of ​​the air inlet opening 21 of the outer shell does not need to be equal to about 0.5, but may be, for example, in the range of from 0.1 to 2.0, or in the range of from 0.25 to 1.0. Similarly, the ratio of the area of ​​the exhaust port opening 24 of the inner shell to the area of ​​the air inlet opening 23 of the inner shell does not need to be equal to about 2, but may be, for example, in the range of from 1 to 4, or in the range of from 1.5 to 3.

[0044] As in Figure 3 As shown in , by providing a shielding component, the shielding effect and air cooling effect can be further improved. Figure 3 The exemplary embodiment further comprises an inner shell 11 and an outer shell 12, such as Figure 2 In addition, Figure 3 The embodiment of the present invention includes a shielding member 13, which in the embodiment shown extends over the side walls and the top wall to provide an additional layer of shielding between the plasma source 31 and any objects located above the plasma chamber 10. In addition, the shielding member 13 can be spaced apart from the outer shell 13 to provide an additional gap 26 through which an additional air flow 3 can flow. The additional air flow 3 provides additional cooling for the outer surface of the plasma chamber, resulting in a lower temperature.

[0045] Note that in some embodiments, shielding member 13 may extend beyond Figure 3, and can for example also extend beyond the rear wall. Thus, the shielding element can be used as an additional outer shell. Optionally, the shielding element can extend only on a single wall portion, for example only on the top wall, or possibly only on the side walls.

[0046] As in Figure 3 As shown in , the shielding element 13 extends substantially parallel to the wall of the outer housing 12 at a distance from the wall of the outer housing 12 (e.g. a few centimeters or millimeters), leaving a gap 26 between the outer housing 12 and the shielding element 13. According to the invention, this additional gap 26 can advantageously be used to allow an additional gas flow through the plasma chamber 10. An additional air inlet opening 27 is provided to allow an additional or third air flow 3 to pass through the gap 26 between the outer housing 12 and the shielding element 13. In the embodiment shown, an opening 28 located near the (external) exhaust opening 22 constitutes the exhaust opening of the additional gap 26. In Figure 3 In the embodiment of the invention, a common exhaust opening or exhaust opening 29 is provided, through which the first air flow 1 , the second air flow 2 and the third air flow 3 leave the plasma chamber.

[0047] In the exemplary embodiment shown, the exhaust port opening 29 has a width of approximately 130 cm. 2 The air inlet opening 27 has an area of ​​about 8 cm 2 , resulting in a ratio of about 16. Of course, other ratios are possible, such as ratios in the range of from about 4 to about 64, or from about 8 to about 32.

[0048] exist Figure 4 1 shows an embodiment of the inner housing 11 in a perspective view. The inner housing 11 is shown as having an air inlet opening 23 in a side wall and an exhaust opening 24 in another side wall opposite to the first side wall. It can be seen that in the embodiment shown, the exhaust opening 24 is located higher than the air inlet opening 23.

[0049] Figure 4 The inner housing 11 also includes a viewing opening 34 in the top wall to accommodate an axial plasma viewing member (in Figure 1 and 2 The axial plasma viewing member may constitute a clean optical path. The viewing opening 34 is preferably as small as possible. The inner housing 11 also includes a plasma torch (in Figure 2 and 3 The inner shell may include additional openings, such as additional gas inlet openings 23A surrounding the plasma torch opening 35 (see also FIG. Figure 2 and 3The rear wall of the illustrated embodiment is provided with a radial plasma viewing member (in Figure 6 39). It should be understood that the opening 36 for accommodating the radial plasma viewing member can be provided in any side wall. In the illustrated embodiment, the side wall is provided with a camera opening 48 that allows a plasma camera to observe the plasma. In the illustrated embodiment, the opening 48 is arranged below the exhaust port opening 24. In some embodiments, such a camera opening can be omitted.

[0050] The embodiment of the outer shell 12 according to the present invention is Figure 5 The outer shell is shown as having an air inlet opening 21 in both the side wall and the bottom wall at the bottom corner, and an exhaust port opening 22 located in the upper portion of the side wall, the side wall being opposite to the side wall adjacent to the air inlet opening 21. Figure 4 ) corresponding opening 35A to accommodate the plasma torch 31 (see Figure 1 and 2 Two adjacent openings 37A and 37B are provided in the top wall of the outer shell 12 to accommodate a radial plasma viewing member and an axial plasma viewing member (in the Figure 1 and 2 32 in the outer shell 12). The opening 37A in the outer shell 12 corresponds to the opening 34 in the inner shell 11 (see Figure 4 ). The opening 42 in the side wall is used to accommodate an RF electric heating element or an RF induction coil (in Figure 2 and 3 38 in the inner shell 11) and corresponds to the opening 23 in the inner shell 11 (see Figure 4 ). The radial viewing member can be accommodated by the opening 37B in the outer shell 12 and the opening 36 in the inner shell 11. The side wall is provided with a camera opening 49 that allows a plasma camera to observe the plasma. The opening 49 in the outer shell is aligned with the corresponding camera opening 48 in the inner shell in use (see Figure 4 In the illustrated embodiment, the opening 49 is arranged below the exhaust port opening 22. In some embodiments, such a camera opening 49 may be omitted. Ridges 41 at the top of the rear and front walls of the outer shell 12 define the outer shell and the shielding element (at Figure 3 13) between the gaps (in Figure 3 26).

[0051] The inner housing and the outer housing are preferably made of metal, such as stainless steel or aluminum. The inner housing and / or the outer housing can be produced by milling, casting or a combination of sheet metal cutting, bending and welding.

[0052] The inner housing may be removable, allowing cleaning and / or replacement. This is advantageous because sample atomization in a plasma torch will inevitably result in material being deposited in the plasma chamber, i.e. in the inner housing 11. A removable inner housing is easier to clean and can be replaced when cleaning is not or no longer possible.

[0053] Figure 6 An exemplary embodiment of a plasma source chamber according to the present invention is schematically illustrated in a cross-sectional view of FIG. Figure 6 The plasma source chamber 10 is shown to include an inner housing 11 and an outer housing 12 with a gap 25 therebetween. A plasma torch 31 provided with an RF coil 38 protrudes through an opening in the bottom wall of the inner housing 11 (at Figure 4 35 in the inner shell), and the viewing member 32 protrudes through the opening in the top wall of the inner shell 11 (in Figure 4 34 in the middle). Viewing piece 32 passes through another opening (in Figure 5 The periscope viewing member 39 protrudes through the opening in the top wall of the outer shell 12 (at Figure 5 37B in the inner shell 11) and through the opening in the rear wall of the inner shell 11 (in Figure 4 36 in). The periscope viewing piece 39 allows radial observation of the plasma generated by the plasma torch 31. In this embodiment, the plasma can be observed axially by observing through the viewing piece 32. It can be seen that the viewing piece 39 is arranged in the gap between the inner shell 11 and the outer shell 12.

[0054] In the illustrated embodiment, the inner housing 11 is closed by a door 45. Similarly, the outer housing 12 is closed by a door 46. The inner door 45 and the outer door 46 can be, for example, hinged and / or removable. They can be connected by a mechanism that allows the doors 45 and 46 to move together, for example, so that when an operator opens or closes the outer door 46, the inner door is opened or closed by the mechanism connecting the inner door and the outer door, respectively. At least one of the doors 45 and 46 can be a sliding door. In an embodiment, both the inner door 45 and the outer door 46 are sliding doors.

[0055] The plasma source chamber of the present invention is particularly suitable for emission spectrometers, but can also be applied to other spectrometers, such as mass spectrometers and atomic absorption spectrometers. Emission spectrometers that can use the present invention are, for example, optical emission spectrometers and atomic fluorescence spectrometers. Although the source chamber is described here with reference to a plasma source (i.e., an ICP torch), the present invention is not limited thereto and can also be used with a flame source, a MIP (microwave induced plasma) source, or an ETA (electrothermal ionization) source.

[0056] The emission spectrometer comprising a plasma source chamber according to the present invention may further comprise a plasma torch, a gas (e.g. argon) source, a sample introduction system for introducing a sample to be analyzed into the plasma, and a detector arrangement for detecting the emitted light. Figure 7 An exemplary embodiment of an emission spectrometer is schematically illustrated in FIG. 1 , wherein the spectrometer 100 shown comprises a plasma chamber 10 and an analyzer and detector unit 60, which are coupled via an optical conduit 50. For example, the plasma chamber 10 according to the present invention may be a Figure 2 or the plasma chamber shown in 3. The analyzer and detector unit 60 may comprise a detector unit for detecting emitted light according to the prior art, such as an optical analyzer and / or an optical detection system.

[0057] Light duct 50 may be comprised of axial and radial viewing members as described above, such as viewing member 32 and periscope 39 protruding into inner housing 11 through openings 34 and 36, respectively (see FIG. Figure 4 and 6 ).

[0058] It will be appreciated by those skilled in the art that the invention is not limited to the embodiments shown and that numerous modifications and additions are possible without departing from the invention as defined in the accompanying claims.

Claims

1. A plasma source chamber for use in a spectrometer, the plasma source chamber comprising: - an inner housing for housing the plasma source, and - an outer casing accommodating said inner casing; wherein the outer shell comprises at least one external air inlet opening in the first wall and at least one external air outlet opening in the second wall, wherein a wall of the inner shell and a wall of the outer shell define a gap, thereby allowing a first air flow to pass through the gap between the inner shell and the outer shell from the at least one outer air inlet opening to the at least one outer air outlet opening, thereby cooling the outer shell with air that does not pass through the inner shell, wherein the inner housing comprises at least one inner air inlet opening in the first wall and at least one inner air outlet opening in the second wall to allow a second air flow through the inner housing from the at least one inner air inlet opening to the at least one inner air outlet opening, wherein the wall, the outer air inlet opening, the outer air outlet opening, the inner air inlet opening and the inner air outlet opening are arranged such that in use the first air flow is greater than the second air flow, wherein at least one of the inner air inlet openings is in direct communication with the gap between the inner shell and the outer shell, and Further openings are provided in the walls of the inner shell and the outer shell to accommodate a plasma source and at least one periscope viewing member. 2 . The plasma source chamber of claim 1 , wherein the at least one outer gas inlet opening and the at least one outer exhaust opening are disposed in opposing walls of the outer housing.

3. The plasma source chamber of claim 1, wherein the at least one outer gas inlet opening is located, in use, below the at least one outer outlet opening.

4. The plasma source chamber of claim 1, wherein the at least one outer exhaust port opening is larger than the at least one outer inlet port opening.

5. The plasma source chamber of claim 1, wherein the at least one outer gas inlet opening extends substantially across a width of a wall of the outer housing.

6. The plasma source chamber of claim 1, wherein the at least one outer exhaust opening extends substantially across a width of a wall of the outer housing.

7. The plasma source chamber of claim 1, wherein the at least one inner gas inlet opening and the at least one inner gas exhaust opening are disposed in opposing walls of the inner housing.

8. The plasma source chamber of claim 1, wherein the at least one inner gas inlet opening is located, in use, below the at least one inner gas exhaust opening.

9. The plasma source chamber of claim 1, wherein the at least one inner exhaust port opening is larger than the at least one inner inlet port opening.

10. The plasma source chamber of claim 1, wherein the at least one inner gas inlet opening extends substantially across a width of a wall of the inner housing.

11. The plasma source chamber of claim 1 , wherein the at least one inner exhaust opening extends substantially across a width of a wall of the inner housing.

12. The plasma source chamber of claim 1, wherein the at least one inner exhaust opening is in direct communication with the gap between the inner housing and the outer housing.

13. The plasma source chamber of claim 1, wherein the at least one inner exhaust opening is connected to a duct extending through the gap and through a wall of the outer shell to allow air flow to an exterior of the outer shell.

14. The plasma source chamber of claim 1, wherein the inner housing is removable.

15. The plasma source chamber of claim 1, further comprising a shielding element for covering at least one wall of the outer shell, the shielding element and the wall defining an additional gap to allow a third air flow between the shielding element and the outer shell.

16. The plasma source chamber of claim 15, wherein the shielding element is arranged to cover two substantially vertical walls of the outer housing, the further gap extending between the shielding element and the walls.

17. A plasma source chamber as claimed in claim 16, wherein one of the walls is, in use, a top wall.

18. The plasma source chamber of claim 1, wherein the inner housing has at least one further gas inlet opening in a wall, which in use is a bottom wall.

19. The plasma source chamber of claim 1, arranged to house a vertical plasma source.

20. The plasma source chamber of claim 1 arranged to house a horizontal plasma source.

21. The plasma source chamber of claim 1, wherein the plasma source is an inductively coupled plasma source, a flame source, a microwave induced plasma source, or an electrothermal ionization source.

22. The plasma source chamber of claim 1, further comprising an inner door for the inner housing and an outer door for the outer housing.

23. The plasma source chamber of claim 22, wherein at least one of the inner door and the outer door is a sliding door.

24. The plasma source chamber of claim 22 or 23, wherein the inner door and the outer door are connected such that opening or closing the outer door also opens or closes the inner door.

25. A spectrometer comprising a plasma source chamber according to any one of the preceding claims.

26. The spectrometer according to claim 25, wherein the spectrometer is: - Emission spectrometer, or - Atomic absorption spectrometer, or - Mass spectrometer.

27. The spectrometer of claim 26, wherein the emission spectrometer is an optical emission spectrometer or an atomic fluorescence spectrometer.

28. The spectrometer of claim 26, being a plasma optical emission spectrometer.

Images