DE202020107491U1 - Plasma source for a spectrometer - Google Patents

Abstract

Plasma source (1) for use in a spectrometer, comprising a plasma torch (2) with at least one tube (10)
- A feed area (11) into which a first gas stream (15) is fed into the tube (10) and
- An ionization area (12) in which inductive energy is fed into the first gas flow (15) through a coil (40) arranged around the tube (10), the energy at least partially ionizing the first gas flow (15) and a plasma ( 50) is ignited and
- An exit region (13) from which the first gas flow (15) with the plasma (50) emerges, characterized in that the plasma source (1) has a cooling gas duct (60) for a cooling gas flow (61), the cooling gas duct (60) on the outside of the tube (10) has a cooling gas inlet (62) and a cooling section (14) is provided in which the cooling gas flows in the direction of the first gas flow (15) on the outside of the tube (10) to a cooling gas outlet (63), wherein the cooling section (14) extends annularly around the outlet region (13) of the tube.

Description

The invention relates to a plasma source for a spectrometer, in particular a source for generating an inductively coupled plasma (ICP) for use in mass spectrometry (ICP-MS) or in optical emission spectroscopy (ICP-OES).

In spectrometry devices in which an inductively coupled plasma is used (for example ICP-MS or ICP-OES), a plasma is generated by means of a high-frequency electromagnetic field. The plasma is fed from a flow of noble gas, for which argon is usually used. For this purpose, a tubular plasma torch is provided in the prior art, in which the noble gas is conducted to a high-frequency coil. Due to the interaction of the electromagnetic field generated by the high-frequency coil with the noble gas, the noble gas is heated to temperatures of 5000 K or higher and the noble gas changes into the state of a plasma. The plasma is ignited by a high voltage discharge, creating charged particles. Inside the plasma torch there is a feed line for a sample, which can be in the form of an aerosol or also in gaseous form. The sample components are vaporized within the plasma, broken down into their atomic components, ionized and then fed to the spectrometer for further analysis.

Although temperature-resistant materials must be used for the plasma torch, the high temperatures cause increased wear on the plasma torch. Increased wear is particularly evident in the areas of the plasma torch that are in the immediate vicinity of the plasma. Accordingly, cooling concepts for cooling the plasma torch are provided in the prior art, which is intended to extend the service life of the plasma torch.

One possibility according to US 2018/0332697 A1 consists in using part of the noble gas flow within the plasma torch not for generating the plasma, but for cooling the plasma torch. This portion of the noble gas flow flows inside the plasma torch and absorbs its heat. The noble gas flow that is used for cooling does not predominantly change into a plasma, but flows around the plasma and escapes from the plasma torch, appropriately enriched with heat from the plasma torch.

This eliminates the possibility that within the plasma, in addition to the noble gas and the sample components, another substance, for example from the surface of the plasma torch, is ionized and would dilute the subsequent analysis. This also increases the consumption of noble gas. This can be disadvantageous in particular when using argon as the noble gas, since a high argon flow is required for cooling due to the low heat capacity of argon. The argon, which must also be kept available for cooling for an analysis, also gives rise to further problems, in particular with regard to the often provided supply by means of gas cylinders and their replacement and with regard to the cost of argon as a cooling gas.

U.S. 5,066,125 shows a device for removing precipitates or condensate from tubes of a plasma torch after it has been used. For this purpose, a gas flow is directed past the tube of the plasma torch via a distributor pipe. This gas flow can supply heat to the tube to remove condensate, or it can also extract heat.

The object on which the invention is based is therefore to improve the efficiency of the cooling of a plasma torch, in particular with regard to the consumption of the gas (cooling gas) necessary for cooling the plasma torch.

This object is achieved by the solution according to the invention according to claims 1 and 35. Advantageous configurations emerge from the dependent claims 2 to 34 and 36 to 37.

For a plasma source for use in a spectrometer, comprising a plasma torch with at least one tube with a feed area into which a first gas flow is fed into the tube and an ionization area in which energy is inductively fed into the gas flow through a coil arranged around the tube, wherein the energy at least partially ionizes the gas flow and a plasma is ignited and an exit area from which the gas flow with the plasma exits, according to the invention it is provided that the plasma source has a cooling gas duct for a cooling gas flow, the cooling gas duct having a cooling gas inlet on the outside of the tube and a Cooling section is provided in which the cooling gas flows in the direction of the first gas flow on the outside of the tube to a cooling gas outlet, the cooling section extending annularly around the outlet area of the tube.

By providing a corresponding cooling gas duct, the cooling gas can either be guided parallel to the first gas flow or transversely to the first gas flow. In the case of a parallel flow of the cooling gas to the first gas flow, it is conceivable that the cooling gas flow is guided or flows in cocurrent or in countercurrent to the first gas flow in the cooling gas duct. It is also conceivable that the cooling gas flow over a distance flows parallel to the tube in countercurrent, while the cooling gas flow flows in cocurrent at the outlet area. The routing of the cooling gas in the cooling gas duct has the advantage that the plasma torch is cooled or heat is absorbed by a second, separate gas flow. Because this cooling gas flow absorbs the heat at least partially and preferably for the most part, the first gas flow can be reduced within the tube, since the heat is transported away by the cooling gas. This results in a reduced consumption of the first gas, which is at the same time also the gas from which the plasma is formed. In this way the invention contributes to the solution of the problem. The volume consumption of the first gas is reduced. The cooling function of the first gas should preferably not be completely replaced. The volume flow of the first gas should be reduced by partially taking over the heat transport in a range from 30 to 70%, preferably in a range from 40 to 60% and particularly preferably by 50%. This results in longer change intervals in the event that the gas provided for the first gas flow is stored in containers. This contributes to a more efficient use of the plasma source. It goes without saying that the cooling gas in embodiments of the invention does not completely take over the cooling of the tube and part of the heat dissipation from the plasma torch also takes place in the gas of the first gas flow. This has the advantage that the tube does not get dirty too quickly and the plasma torch does not lose its routine capabilities. It is also clear that some of the heat that passes from the plasma to the plasma torch is conductively propagated within the plasma torch and in particular within the tube. In this way, the heat from the cooling gas which flows around the tube in the cooling section of the cooling gas guide can be absorbed and transported away from the tube. In particular, it can therefore be provided that the wall thickness of the tube is 0.5 to 2 mm, preferably 1 mm. Alternatively, it can be specified that a wall thickness-to-diameter ratio is on the order of 1:20. The fact that the cooling section extends around the exit area of the tube results in the further advantage that this area in particular is cooled directly by the cooling gas. The plasma also emerges from the tube in the exit area, which is why an intensive thermal load on the tube from the radiant heat of the plasma is to be expected, and cooling by the cooling gas and possibly also by the first gas flow is indicated.

According to one embodiment of the invention, it is provided that the first gas flow comprises a noble gas. In a further embodiment of the invention it is provided that the noble gas is argon. The plasma can be generated by means of an electromagnetic field, preferably from a noble gas and in particular from argon. This embodiment is also advantageous since the analysis methods of spectrometers are tailored to the use of argon as the gas for the plasma.

According to one embodiment of the invention it is provided that the tube extends downstream beyond the cooling gas duct. This has the advantage that an outflow of the first gas is not impaired by the cooling gas flow. This advantageously contributes to the stability of the plasma.

According to a further development of the invention, it is provided that the tube has a satin finish at its exit area. By satinizing the exit area of the tube, its surface area is enlarged, as a result of which the heat exchange with the first gas and / or the cooling gas is improved. The satin finish can be carried out in relation to the tube in the inner circumference and / or in the outer circumference. Furthermore, it is advantageous that the exit area is satinized, since this is where the highest heat input into the tube is to be expected.

In one embodiment of the invention it can be provided that the tube has a black coating on its exit area. A black coating advantageously accelerates the heat dissipation from the tube for efficient cooling.

A further development of the invention shows that the tube has cooling structures. The heat dissipation to the cooling gas and / or the first gas can be further improved by cooling structures on the tube. The cooling structures can be in different shapes, for example as cooling fins, cooling coils, etc. or from a combination of different shapes.

In a refinement, it can be provided that a second tube is arranged inside the tube and the gas of the first gas stream flows within the second tube and the first tube. It can be provided that the plasma is fed essentially from the portion of the first gas flow that flows in the second tube and the portion of the first gas flow that flows between the outside of the second tube and the inside of the first tube is essentially fed to Cooling of the first and second tubes and to stabilize the plasma is used.

In a further development, it can be provided that a third tube is arranged within the second tube, through which a gaseous analyte or an aerosol composed of a nebulized analyte and a Carrier gas flows. The provision of a third tube for supplying the analyte or the sample has the advantage that a plasma set in a stable manner via the flow of the first gas remains stable even while the analyte is being supplied. In addition, a concentric arrangement of the first, second and third tubes can advantageously ensure that the analyte is supplied to the hottest part of the plasma, as a result of which the ionization of the analyte is improved.

According to one embodiment of the invention it is provided that the gas of the first gas flow forms the carrier gas for the nebulized analyte. This has the advantage that the flow of the first gas with added or not added analyte can be kept essentially constant or constant. This contributes advantageously to the stability of the plasma.

In a further development of the invention it is provided that the first gas flow is spatially separated from the cooling gas flow in the area of the plasma torch by the tube. This advantageously ensures that the first gas, which is at least partially ionized and finds its way into further analysis when used in a spectrometer, is not contaminated by the cooling gas, which may have a different composition. In this way, only the ionized analyte and the ionized gas of the first gas flow are fed to the analysis.

It can be provided that the respective tube is a quartz tube. The provision of a quartz tube is advantageous because it is largely electromagnetically inert and so there is no interaction with the electromagnetic field of the coil. Furthermore, quartz is heat-resistant over a wide range, which reduces the heat-related wear on the tube. Alternatively, a ceramic tube can be used.

According to a further embodiment, it can be provided that the coil is let into the cooling gas duct. Because the coil is embedded in the cooling gas duct, the coil is positioned in relation to the plasma torch. This results in the advantage that after replacing the plasma torch or the tube (s), constant excitation of the first gas flow and constant formation of the plasma can be expected. In addition, letting in the coil reduces the risk that the coil will be damaged or spatially displaced during maintenance of the plasma source. It can be provided that the coil is cast into the cooling gas duct.

According to a further development of the invention it is provided that the coil lies in front of the ionization area in the direction of flow of the first gas stream. This has the advantage that the size of the plasma source can be reduced. In addition, this has a structurally favorable effect on the arrangement of the cooling gas duct.

According to one embodiment of the invention it is provided that the coil lies in the direction of flow of the first gas stream in the region of the ionization region. Thus, the coil and the electromagnetic field generated by the coil can advantageously be applied directly to the ionization region. In this way, the efficiency of the plasma generation is increased.

In a further development, it can be provided that the ionization region of the tube at least partially surrounds the plasma. The fact that the plasma is at least partially surrounded by the tube and its ionization region results in the advantage that the flow of the first gas flow in the region of the plasma is guided in a defined manner in the tube, which increases the stability of the plasma.

According to one embodiment of the invention, it is provided that the plasma extends out of the exit area of the tube, in particular when the plasma source is in use. In this way, the advantage is achieved that part of the heat generated by the plasma is not given off directly to the tube. This reduces the need for cooling the tube and also the need for cooling the tube from the inside, for example by means of the first gas flow.

According to a further development of the invention it is provided that the cooling gas flow comprises air. Providing air as a cooling gas or as a component of the cooling gas flow has the advantage that air is readily available on the one hand and, on the other hand, has a higher thermal capacity than, for example, noble gases and in particular argon. In this way, the consumption of cooling gas can be reduced.

Accordingly, it can be provided in a design that the cooling gas flow consists of air. For a cooling gas flow that consists of air, there is the further advantage that the cooling gas, provided it has not otherwise been contaminated, can be released into the environment without any problems and thus the heat can be removed from the system very quickly. In an alternative embodiment it can be provided that the cooling gas contains nitrogen or consists of nitrogen.

Furthermore, it can be provided that the cooling gas flow is fed from a cooling air flow of the plasma torch. This turns out to be particularly advantageous because an existing system with supply and discharge lines for cooling air also for the cooling gas flow can be used. This results in a deep integration of the cooling gas flow in the plasma torch while utilizing synergies from other air cooling devices of the plasma torch.

In an optional development, it is provided that the cooling gas duct surrounds the tube in a ring shape and the cooling gas flow flows through a space formed between the tube and the cooling gas duct. In this way, an optimal heat exchange between the tube heated by the plasma and the cooling gas can be achieved. Part of the cooling of the tube is effectively taken over by the cooling gas, so that the first gas flow can be dimensioned correspondingly smaller with regard to cooling the tube.

According to one embodiment of the invention, the result is accordingly that the space formed between the tube and the cooling gas duct extends in the flow direction of the first gas stream at least from the ionization area to the exit area. This ensures that the area of the tube that is most likely to be exposed to the heat of the plasma is cooled from the outside by the cooling gas flow, as a result of which the need for cooling inside the tube by the first gas flow is reduced.

According to a further development, the cooling gas duct, in particular during the use of the plasma source, directs the cooling gas flow beyond the outlet area of the tube. In this way, the cooling gas flow is directed over the end most exposed to the heat at the outlet area of the tube, so that effective cooling is made possible there.

In a further embodiment of the invention it is provided that the cooling gas duct has windows for observation or sampling of the plasma. As a result, the design freedom for the cooling gas guide is increased by advantageously ensuring that sampling or observation of the plasma is still possible.

According to a further development, the cooling gas guide has cooling structures. Because the cooling gas can in turn give off the heat absorbed by the tube to the cooling gas duct, it is advantageous if this heat can be transported away efficiently by the cooling gas duct. In this way, a build-up of heat in the area of the plasma torch is avoided and the volume flow of cooling gas and / or from the first gas can be reduced with regard to the cooling effect.

It can also be provided that the cooling gas guide consists of a non-metallic, temperature-resistant material or has a coating made of such a material. This is advantageous because an interaction with the electromagnetic field that is generated by the coil is largely avoided.

Accordingly, it can be provided in a further development that the material of the cooling gas guide or its coating is a ceramic or PFA or Teflon. In a further embodiment it can be provided that the material of the cooling gas guide is a material made of perfluorocarbon (PFC). Plastics, in particular, are well suited for guiding the cooling gas, since they can be easily shaped and, if necessary, can be molded onto the coil to accommodate the coil, or the coil can be cast into such a cooling gas duct.

In an optional embodiment it is provided that the cooling gas flow flows around the tube parallel to the direction of the first gas flow. In this way, an optimal heat exchange between the tube heated by the plasma and the cooling gas can be achieved. So part of the cooling of the tube is effectively taken over by the cooling gas, so that the first gas flow can be dimensioned correspondingly smaller with regard to the cooling of the tube.

According to an optional development, it is provided that the cooling gas flow flows into the cooling gas inlet of the cooling gas duct in the base area of the plasma torch. Such a construction allows the external cooling of the tube to be implemented in a particularly space-saving manner, especially when plasma torches with a corresponding base area are used, in which, for example, the gas of the first gas flow and / or the analyte is also passed into the tube (s) / become.

In addition, it can be provided that the cooling gas flow in the area of the cooling section flows transversely to the direction of the first gas flow. In addition to structurally favorable effects, the cross flow can have the advantage that the cooling gas cannot heat up at the plasma torch by way of the supply line, so that the heat absorption in the area of the cooling section is ideal. In this way, the first gas flow for cooling the tube can be further reduced from the inside.

The invention can be further developed in that the cooling gas duct for the cooling gas forms a flow channel around the tube which runs parallel to the first gas flow. This is particularly advantageous for the above-described plasma torches with a base area or similar constructions with regard to the installation space required.

According to a further development of the invention it is provided that the flow channel extends in the flow direction of the first gas stream from the ionization area of the tube to the exit area of the tube. In this way, the cooling gas also flows around the downstream end of the tube, even if the cooling gas guide is not arranged directly around the outlet region of the tube.

After all of this, it can be provided that the cooling gas flow flows into the cooling gas inlet of the cooling gas duct at a housing of the plasma torch and flows out of the cooling gas outlet of the cooling gas duct at the housing of the plasma torch. In this way, the cooling gas is efficiently conducted to the cooling section and the heat is equally quickly transported away from the area of the plasma torch, which has a positive effect on the cooling and, in particular, on the cooling requirement of the tube by means of the first gas flow.

Finally, the invention can be embodied in that part of the cooling gas flow is guided along an outer wall of the housing in order to cool the outer wall of the housing. In this way, a synergy can be created with a cooling gas flow that is already available for cooling the housing.

The invention also relates to a spectrometer with a plasma source as described above.

The spectrometer can be developed in that the spectrometer is a mass spectrometer and the plasma source is a plasma source for generating an inductively coupled plasma.

An alternative embodiment results in the spectrometer being a spectrometer for optical emission spectroscopy and the plasma source being a plasma source for generating an inductively coupled plasma.

Further features, details and advantages of the invention emerge from the wording of the claims and from the following description of exemplary embodiments based on the drawings.

• 1: eine schematische Darstellung einer Plasmaquelle nach dem Stand der Technik;
• 2: eine schematische Darstellung einer ersten Ausführungsform der erfindungsgemäßen Plasmaquelle;
• 3: eine schematische Darstellung einer Variante der ersten Ausführungsform der erfindungsgemäßen Plasmaquelle;
• 4: eine schematische Darstellung einer weiteren Ausführungsform der erfindungsgemäßen Plasmaquelle;
• 5: eine schematische Darstellung des Austrittsbereichs gemäß der weiteren Ausführungsform der Plasmaquelle; und
• 6: eine schematische Schnittansicht einer Variante der weiteren Ausführungsform der Plasmaquelle.

In the figures show:

• 1 : a schematic representation of a plasma source according to the prior art;
• 2 : a schematic representation of a first embodiment of the plasma source according to the invention;
• 3 : a schematic representation of a variant of the first embodiment of the plasma source according to the invention;
• 4th : a schematic representation of a further embodiment of the plasma source according to the invention;
• 5 : a schematic representation of the exit area according to the further embodiment of the plasma source; and
• 6th : a schematic sectional view of a variant of the further embodiment of the plasma source.

In the following description of the figures, the same reference symbols are used for the elements shown in the respective figures that are similar, regardless of whether they are one and the same embodiment or a variant of an embodiment.

1 shows a schematic representation of a plasma source 1 According to the state of the art. The plasma source 1 has a plasma torch 2 with a tube 10 within which a second tube is concentric 20th and a third tube 30th are arranged. Inside the tube 10 and within the second tube 20th a first gas stream flows 15th . The second tube 20th and third tube 30th extend in the direction of flow of the first gas flow 15th less far than the tube 10 . In an ionization area 12, energy is inductively introduced into the gas flow 15th through one around the tube 10 arranged coil 40 fed. The energy ionizes the gas flow 15th at least partially and a plasma 50 can be ignited in this area. In this variant according to the prior art, the tube protrudes 10 the ignited plasma at least partially, which in an exit area 13th emerges from the tube.

The first gas stream 15th serves on the one hand to supply the plasma 50 with the gas to be ionized and, on the other hand, has a volume fraction that is not ionized and for cooling the tube and the second tube 20th and third tube 30th as well as to stabilize the plasma 50 is provided.

Inside the third tube 30th can be a gaseous or a nebulized analyte 31 be supplied as an aerosol. The analyte 31 can from a carrier gas, which is the gas of the first gas stream 15th can be within the third tube 30th be transported. This analyte 31 gets into the plasma 50 injected and ionized there.

2 shows a schematic representation of a first embodiment of the plasma source according to the invention 1 . The plasma source 1 can be used in a spectrometer, for example in a mass spectrometer or in a spectrometer for optical emission spectroscopy. The plasma source 1 creates an inductively coupled plasma.

The plasma source 1 has a plasma torch 2 with a tube 10 within which a second tube is concentric 20th and a third tube 30th are arranged. Inside the tube 10 and within the second tube 20th a first gas stream flows 15th . The second tube 20th and third tube 30th extend in the direction of flow of the first gas flow 15th less far than the tube 10 . In an ionization area 12, energy is inductively introduced into the gas flow 15th through one around the tube 10 arranged coil 40 fed. The energy ionizes the gas flow 15th at least partially and a plasma 50 can be ignited in this area. The tube 10 surrounds the ignited plasma 50 at least partially, which in an exit area 13th emerges from the tube.

In this embodiment it is around the plasma torch 2 a cooling gas duct 60 arranged in which the coil 40 is let in. The cooling gas flow 60 encloses a cooling section 14th the tube 10 . Embodiments are also conceivable in which the coil 40 is not admitted. Between the tube 10 and the cooling gas flow 60 a cooling gas flows. Air, which is present in the spectrometer as process air, can be used as cooling gas. Equally, the air can also be supplied from the environment and, if necessary, appropriately conditioned. The cooling gas flows in the exit area 13th the tube 10 from the cooling gas duct 60 and flows over the end of the tube 10 .

The plasma torch 2 has a base area 6th on, in which in this embodiment also the tube 10 , the second tube 20th and the third tube 30th are arranged. In the base area 6th there are entrances for the first gas stream 15th and for the nebulized or gaseous analyte 31 .

There is also a cooling gas inlet in the base area 62 arranged. In this exemplary embodiment, the cooling gas is routed 60 designed chimney-shaped and has one in the direction of the exit area 3 the tube 10 tapering inner diameter.

The cooling gas occurs next to the exit area 13th in an annulus. The cooling gas guide can move in the direction of flow 60 either wider than the tube 10 extend with the tube 10 end at the same height or in the direction of flow before the end of the tube 10 end up.

The tube 10 , the second tube 20th and / or the third tube 30th can improve the heat exchange in the outlet area 13th or be satined in the ionization area 12 or have a black coating. In addition, one or more cooling structures (not shown in greater detail in the figures) can be attached to the respective tube in order to further improve the cooling effect. The cooling gas flow 60 can also have one or more cooling structures.

Above the plasma torch 2 can be connected to the spectrometer, as shown here schematically, via a conical interface 70 , be arranged.

3 shows a schematic representation of a variant of the first embodiment of the plasma source according to the invention 1 . Here's essentially a too 2 comparable structure shown, which is why for elements that have already been introduced 2 Is referred to.

The cooling gas flow 60 differs from the cooling gas routing 60 according to 2 in that the cooling gas guide 60 at least partially, in particular laterally to the plasma torch 2 , up to an enclosure 5 the plasma source 1 approaches. In this way, a flow of cooling gas 61 , which is used to cool the housing 5 in the enclosure 5 can be passed, also into the cooling gas duct 61 via the cooling gas inlet 62 in the base area 6th the plasma torch 2 be initiated. In particular, it can be provided for this that the cooling gas inlets 62 through the enclosure 5 protrude through and in the housing 5 Vents (also not shown) for discharging the cooling gas and / or the first gas are present.

4th shows a schematic representation of a further embodiment of the plasma source according to the invention 1 . In contrast to the embodiment according to FIG 1 to 3 is the plasma torch 2 arranged here rotated by 90 degrees. It goes without saying that the embodiments according to. 1 to 3 or 4th each can be arranged horizontally or vertically. The first gas stream 15th flows analogously to the first embodiment within the tube 10 and the second tube 20th . The analyte 31 flows inside the third tube 30th .

Around the plasma torch 2 is a cooling gas guide 60 arranged, which also has the coil 40 with one house. The sink 40 can in this case within the cooling gas duct 60 be embedded. The cooling gas flows here essentially perpendicular to the flow direction of the first gas flow 15th . The cooling gas flow 60 encloses a cooling section 14th the tube 10 and the cooling gas is in the cooling gas duct 61 at least directed so that it is at the exit area 13th the tube 10 at least partially via that, based on the first gas stream 15th , downstream end of the tube 10 flows.

5 shows a schematic representation of the exit area 13th according to this further embodiment of the plasma source 1 . It can be seen here that part of the cooling gas flow 61 in one in the Cooling gas supply 60 trained flow channel 4th in the direction of, based on the first gas flow 15th , downstream end of the tube 10 and this end of the tube 10 overflows.

6th shows a schematic sectional view of a variant of the further embodiment of the plasma source 1 . Here's essentially a too 4th comparable structure shown, which is why for elements that have already been introduced 4th Is referred to.

The cooling gas flow 60 differs from the cooling gas routing 60 according to 4th in that the cooling gas guide 60 through the enclosure 5 the plasma source 1 protrudes. It is also conceivable that the cooling gas guide 60 up to the enclosure 5 the plasma source 1 approaches and establishes a flow connection for the cooling gas outside the housing. In this way, a flow of cooling gas 61 , which is used to cool the housing 5 in the enclosure 5 or around the enclosure 5 can be passed, also into the cooling gas duct 60 via the cooling gas inlet 62 be initiated. The cooling gas flows within the cooling gas duct 60 over the cooling section 14th . Here is through the flow channel 4th a partial volume flow parallel to the tube 10 distracted (see also the remarks on 5 ). The main flow of the cooling gas is within the cooling gas duct 60 from the cooling section 14th further to the cooling gas outlet 63 the cooling gas flow 60 which in turn to the housing 5 the plasma torch 2 connected.

The invention is not restricted to the above-mentioned embodiments. It can be modified in a number of ways.

All features and advantages that emerge from the claims, the description and the drawing, including structural details, spatial arrangements and method steps, can be essential for the invention both alone and in various combinations.

List of reference symbols

1

Plasma source

2

Plasma torch

3

room

4th

Flow channel

5

Enclosure

6th

Base area

10

tube

11

Supply area

12th

ionization area

13th

Exit area

14th

Cooling section

15th

first gas stream

20th

second tube

30th

third tube

31

Analyte

40

Kitchen sink

50

plasma

60

Cooling gas supply

61

Cooling gas flow

62

Cooling gas inlet

63

Cooling gas outlet

70

conical interface

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 2018/0332697 A1 [0004]
• US 5066125 [0006]

Claims (37)

Plasma source (1) for use in a spectrometer, having a plasma torch (2) with at least one tube (10) with - a feed area (11) into which a first gas stream (15) is fed into the tube (10) and - an ionization area (12), in which energy is inductively fed into the first gas flow (15) through a coil (40) arranged around the tube (10), the energy at least partially ionizing the first gas flow (15) and igniting a plasma (50) and - an outlet area (13) from which the first gas flow (15) with the plasma (50) emerges, characterized in that the plasma source (1) has a cooling gas duct (60) for a cooling gas flow (61), the cooling gas duct ( 60) has a cooling gas inlet (62) on the outside of the tube (10) and a cooling section (14) is provided in which the cooling gas flows in the direction of the first gas flow (15) on the outside of the tube (10) to a cooling gas outlet (63) , wherein the cooling section (14) rin G-shaped around the outlet area (13) of the tube. Plasma source (1) Claim 1 , characterized in that the first gas stream (15) comprises a noble gas. Plasma source (1) Claim 2 , characterized in that the noble gas is argon. Plasma source (1) according to one of the preceding claims, characterized in that the tube (10) extends downstream beyond the cooling gas duct (60). Plasma source (1) according to one of the preceding claims, characterized in that the tube (10) has a satin finish at its exit area (13). Plasma source (1) according to one of the preceding claims, characterized in that the tube (10) has a black coating on its exit area (13). Plasma source (1) according to one of the preceding claims, characterized in that the tube (10) has cooling structures. Plasma source (1) according to one of the preceding claims, characterized in that a second tube (20) is arranged inside the tube (10) and the gas of the first gas flow (15) within the second tube (20) and the first tube (10) ) flows. Plasma source (1) Claim 8 , characterized in that a third tube (30) is arranged inside the second tube (20) through which a gaseous analyte (31) or an aerosol consisting of a nebulized analyte (31) and a carrier gas flows. Plasma source (1) Claim 9 , characterized in that the gas of the first gas stream (15) forms the carrier gas for the nebulized analyte (31). Plasma source (1) according to one of the preceding claims, characterized in that the first gas flow (15) in the region of the plasma torch (2) is spatially separated from the cooling gas flow (61) by the tube (10). Plasma source (1) according to one of the preceding claims, characterized in that the respective tube (10, 20, 30) is a quartz tube Plasma source (1) according to one of the preceding claims, characterized in that the coil (40) is let into the cooling gas duct (60). Plasma source (1) according to one of the preceding claims, characterized in that the coil (40) lies in front of the ionization region (12) in the direction of flow of the first gas stream (15). Plasma source (1) according to one of the Claims 1 to 13th , characterized in that the coil (40) lies in the flow direction of the first gas stream (15) in the region of the ionization region (12). Plasma source (1) according to one of the preceding claims, characterized in that the ionization region (12) of the tube (10) at least partially surrounds the plasma (50). Plasma source (1) according to one of the preceding claims, characterized in that the plasma (50) extends out of the exit region (13) of the tube (10). Plasma source (1) according to one of the preceding claims, characterized in that the cooling gas flow (61) comprises air. Plasma source (1) according to one of the preceding claims, characterized in that the cooling gas flow (61) consists of air. Plasma source (1) according to one of the preceding claims, characterized in that the cooling gas flow (61) is fed from a cooling air flow of the plasma torch (2). Plasma source (1) according to one of the preceding claims, characterized in that the cooling gas duct (60) forms the tube (10) in an annular manner and the cooling gas stream (61) flows through a space (3) formed between the tube and the cooling gas duct (60). Plasma source (1) according to one of the preceding claims, characterized in that the space (3) formed between the tube (10) and the cooling gas duct (60) extends in the flow direction of the first gas stream at least from the ionization area (12) to the exit area ( 13) extends. Plasma source (1) according to one of the preceding claims, characterized in that the cooling gas duct (60) guides the cooling gas flow (61) beyond the outlet region (13) of the tube (10). Plasma source (1) according to one of the preceding claims, characterized in that the cooling gas duct (60) has windows for observing or sampling the plasma (50). Plasma source (1) according to one of the preceding claims, characterized in that the cooling gas duct (60) has cooling structures. Plasma source (1) according to one of the preceding claims, characterized in that the cooling gas duct (60) consists of a non-metallic, temperature-resistant material or has a coating made of such a material. Plasma source (1) according to one of the preceding claims, characterized in that the material of the cooling gas duct (60) or its coating is a ceramic or PFA or Teflon. Plasma source (1) according to one of the preceding claims, characterized in that the cooling gas flow (61) flows around the tube (10) parallel to the direction of the first gas flow (15). Plasma source (1) according to one of the preceding claims, characterized in that the cooling gas flow (61) in the base area (6) of the plasma torch (2) flows into the cooling gas inlet (62) of the cooling gas duct (60). Plasma source (1) according to one of the Claims 1 to 27 , characterized in that the cooling gas flow (61) flows in the region of the cooling section (14) transversely to the direction of the first gas flow (15). Plasma source (1) Claim 30 , characterized in that the cooling gas duct (60) for the cooling gas forms a flow channel (4) around the tube (10) which runs parallel to the first gas flow (15). Plasma source (1) Claim 31 , characterized in that the flow channel (4) extends in the flow direction of the first gas stream (15) from the ionization area (12) of the tube (10) to the outlet area (13) of the tube (10). Plasma source (1) according to one of the Claims 30 to 32 , characterized in that the cooling gas stream (61) flows at a housing (5) of the plasma torch (2) into the cooling gas inlet (62) of the cooling gas duct (60) and at the housing (5) of the plasma torch (2) from the cooling gas outlet (63 ) the cooling gas duct (60) flows. Plasma source (1) Claim 33 , characterized in that part of the cooling gas flow (61) is passed along an outer wall of the housing (5) in order to cool the outer wall of the housing (5). Spectrometer with a plasma source (1) according to one of the preceding claims. Spectrometer according to Claim 35 , characterized in that the spectrometer is a mass spectrometer and the plasma source (1) is a plasma source (1) for generating an inductively coupled plasma (50). Spectrometer according to Claim 35 , characterized in that the spectrometer is a spectrometer for optical emission spectroscopy and the plasma source (1) is a plasma source (1) for generating an inductively coupled plasma (50).

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