Microwave driven plasma ion source

Abstract

The present invention relates to a microwave-driven plasma ion source (1) for ionizing a sample into sample ions, the microwave-driven plasma ion source (1) comprising a sample inlet (6) for feeding a sample from the outside of the microwave-driven plasma ion source (1) into the interior (3) of the microwave-driven plasma ion source (1); a microwave generator (10) for generating microwaves to generate plasma (101) from plasma gas (100); a plasma torch (20) providing an orientation (29) of the plasma torch having an interior (21) for accommodating (2) the process of generating plasma (101) from plasma gas (100) and the process of ionizing the sample into sample ions by exposing the sample to the plasma (101), wherein the plasma torch (20) includes a torch outlet (22) for discharging plasma (101) and sample ions substantially along the orientation (29) of the plasma torch from the interior (21) of the plasma torch (20) to the outside, the torch outlet (22) having a torch aperture. Furthermore, the microwave-driven plasma ion source (1, 201) includes a shielding layer (4) for shielding microwaves transmitted from the interior (3) of the microwave-driven plasma ion source (1) to the exterior of the microwave-driven plasma ion source (1). The shielding layer (4) includes a shielding outlet (5) for discharging plasma (101) and sample ions substantially along the orientation direction (29) of the plasma torch from the interior (3) of the microwave-driven plasma ion source (1) to the exterior of the microwave-driven plasma ion source (1). The shielding outlet (5) has a shielding aperture. Thus, the shielding outlet (5) is fluidly coupled to the torch outlet (22) to discharge plasma (101) and sample ions substantially along the orientation direction (29) of the plasma torch from the interior (21) of the plasma torch (20) to the exterior of the microwave-driven plasma ion source (1). The size of the shielding aperture is less than 150% of the size of the torch aperture, preferably less than 125% of the size of the torch aperture, and particularly preferably less than 110% of the size of the torch aperture. Both the size of the shield aperture and the size of the torch aperture are measured in area.

Description

Technical Field

[0001] This invention relates to a microwave-driven plasma ionization source for ionizing a sample into sample ions. The microwave-driven plasma ionization source includes a sample inlet, a microwave generator, and a plasma torch. The sample inlet is used to introduce a sample from outside the microwave-driven plasma ionization source into its interior. The microwave generator generates microwaves to generate plasma from a plasma gas. The plasma torch provides a plasma torch orientation, and the interior of the plasma torch accommodates the processes of generating plasma from the plasma gas and ionizing the sample into sample ions by exposing the sample to the plasma. The plasma torch includes a torch outlet for discharging plasma and sample ions substantially along the orientation of the plasma torch from its interior to the exterior of the plasma torch. The torch outlet has a torch aperture. Background Technology

[0002] Microwave-driven plasma ionization sources for ionizing samples into sample ions are known in relation to the initially mentioned technical field. For example, Radom Corporation describes such a microwave-driven plasma ionization source in US 2016 / 0025656 A1, which includes a microwave generator and a plasma torch. This microwave-driven plasma ionization source also includes a microwave resonator supported within a cylindrical radio frequency shielding layer. The microwave resonator has an annular shape and provides a gap. The plasma torch is partially disposed within this gap. During operation, microwaves are generated by the microwave generator and guided to the microwave resonator in the shielding layer via waveguides. Furthermore, a plasma gas is introduced into the interior of the plasma torch to generate plasma by inductively coupling the plasma gas with an electromagnetic field generated by the microwave resonator exposed to the microwaves generated by the microwave generator. Simultaneously, a sample is introduced into the interior of the plasma torch and exposed to the plasma to be ionized into sample ions.

[0003] Sample ionization can be maximized by optimizing the operating parameters of such known microwave-driven plasma ion sources to obtain the most sample ions for a given sample. However, the optimal operating parameters vary depending on the microwave-driven plasma ion source used. In particular, if the instrument using the sample ions generated by such a microwave-driven plasma ion source changes, the optimal operating parameters of each microwave-driven plasma ion source may also change. Therefore, a disadvantage of such microwave-driven plasma ion sources is that optimizing them to maximize sample ion generation is both difficult and complex. This is especially true when individual microwave-driven plasma ion sources are used to generate sample ions, which are then used by other instruments, such as ion mobility spectrometers and mass spectrometers. For the same reason, it is difficult to optimize the generation of sample ions to the maximum extent whenever such a microwave-driven plasma ion source is used as part of an ion mobility spectrometer and / or mass spectrometer.

[0004] In this paper, the expression "and / or" is sometimes used to connect two features. This expression should be understood as referring to one or both of the two features. Therefore, "A and / or B" should be understood as three equivalent options, one of which is A, another is B, and yet another is both A and B. Summary of the Invention

[0005] The purpose of this invention is to create a microwave-driven plasma ion source belonging to the technical field initially mentioned, which can be easily and stably optimized in terms of its operating parameters to maximize the generation of sample ions.

[0006] According to the present invention, a microwave-driven plasma ion source includes a shielding layer for shielding microwaves transmitted from the interior to the exterior of the microwave-driven plasma ion source. The shielding layer includes a shielding outlet for discharging plasma and sample ions substantially along the orientation direction of the plasma torch from the interior to the exterior of the microwave-driven plasma ion source. The shielding outlet has a shielding aperture, wherein the shielding outlet is fluidly coupled to the torch outlet to discharge plasma and sample ions substantially along the orientation direction of the plasma torch from the interior to the exterior of the microwave-driven plasma ion source. The size of the shielding aperture is less than 150% of the torch aperture size, preferably less than 125% of the torch aperture size, and particularly preferably less than 110% of the torch aperture size. Both the size of the shielding aperture and the size of the torch aperture are measured in area.

[0007] According to the present invention, a microwave-driven plasma ionization source includes a sample inlet for introducing a sample from the outside of the microwave-driven plasma ionization source into the interior of the microwave-driven plasma ionization source. In one example, the sample inlet is an entrance for introducing a sample from the surrounding environment of the microwave-driven plasma ionization source into the interior of the microwave-driven plasma ionization source. In another example, the sample inlet is a connector for connecting a sample source so that a sample can be introduced from the sample source through the sample inlet into the microwave-driven plasma ionization source, thereby ionizing the sample.

[0008] Advantageously, the sample is a gas, an aerosol composed of aerosol particles dispersed in the gas, or more broadly, discrete particles entrained in the gas. When the sample is an aerosol composed of aerosol particles dispersed in the gas, the aerosol particles can be solid or liquid particles. The size of aerosol particles is typically in the range of 10 nm to 10 µm. Aerosol particles smaller than 10 nm can rapidly grow into larger aerosol particles due to their large surface area ratio. On the other hand, aerosol particles larger than 10 µm are too heavy to remain suspended for long periods and eventually fall to the ground. Therefore, the typical size range of aerosol particles in aerosol samples is 50 nm to 2000 nm (or 2 µm). Discrete particle samples entrained in a gas should be understood more broadly than aerosols. Such discrete particles entrained in a gas can be generated, for example, by laser ablation of some sample material directly in front of the sample inlet of a microwave-driven plasma ion source. In this case, the size of discrete particles can exceed the upper limit of 10 µm for aerosol particles, or it can be below the lower limit of 10 nm for aerosol particles. Of course, discrete particles can also have the same size as aerosol particles.

[0009] According to the solution of the present invention, the microwave-driven plasma ionization source includes a microwave generator for generating microwaves to generate plasma from plasma gas. Therefore, microwaves are electromagnetic waves of radio frequency electromagnetic radiation in the microwave range. The microwave range is preferably an electromagnetic radiation range with frequencies in the range of 1 MHz to 10 GHz, particularly preferably in the range of 30 MHz to 3 GHz, and most preferably in the range of 30 MHz to 300 MHz or 300 MHz to 3 GHz.

[0010] Microwaves generated by a microwave generator can be used directly and / or indirectly to generate plasma from plasma gas. Therefore, in the first example, plasma gas is exposed to microwaves generated by a microwave generator to generate plasma from the plasma gas. In the second example, the microwave-driven plasma ion source includes a microwave resonator, which is exposed to microwaves generated by a microwave generator such that the microwave resonator generates an electromagnetic field due to its resonant behavior when exposed to microwaves, wherein the plasma gas is inducedly coupled to the electromagnetic field generated by the microwave resonator to generate plasma from the plasma gas. In the third example, the first and second examples are combined, i.e., plasma gas is exposed to microwaves generated by a microwave generator and inducedly coupled to the electromagnetic field generated by the microwave resonator to generate plasma from the plasma gas.

[0011] In all three examples, the plasma is generated directly or indirectly by the plasma gas and is therefore ultimately driven by microwaves generated by a microwave generator. Thus, in all three examples, the microwave generator is a device used to generate microwaves to produce plasma from the plasma gas.

[0012] According to the present invention, a microwave-driven plasma ionization source includes a plasma torch that provides orientation for the plasma torch, the plasma torch having an interior where the processes of generating plasma from the plasma gas and ionizing the sample into sample ions by exposing the sample to the plasma occur. Therefore, the process of generating plasma from the plasma gas takes place in a first region inside the plasma torch, while the process of ionizing the sample into sample ions by exposing the sample to the plasma takes place in a second region inside the plasma torch. Thus, the first and second regions can be completely separate regions, partially overlapping regions, or completely overlapping regions. When the first and second regions completely overlap, in one example, one of the first and second regions is larger than the other and completely covers the other. In another example where the first and second regions are completely overlapping regions, the two regions are identical. Regardless of the shape of the first and second regions, and whether they are separate, partially overlapping, or completely overlapping, the common feature of the first and second regions is that they are both located inside the plasma torch and thus contained within the plasma torch. Therefore, both the process of generating plasma from the plasma gas and the process of ionizing the sample into sample ions by exposing the sample to the plasma occur inside the plasma torch.

[0013] According to the present invention, the microwave-driven plasma ion source includes a shielding layer for shielding microwaves transmitted from the interior of the microwave-driven plasma ion source to the exterior. Therefore, preferably, "shielding" means that less than 5%, particularly less than 1%, of the total intensity, i.e., power (energy per unit time) of the electromagnetic radiation generated inside the microwave-driven plasma ion source reaches the exterior. Therefore, preferably, the intensity of the electromagnetic radiation (i.e., the microwaves reaching the exterior of the microwave-driven plasma ion source) is the sum of locally measured intensities at all locations on the surface of a sphere surrounding the microwave-driven plasma ion source.

[0014] According to the present invention, a plasma torch includes a torch outlet for discharging plasma and sample ions substantially along the orientation direction of the plasma torch from the interior of the plasma torch to the exterior of the plasma torch, the torch outlet having a torch aperture. Furthermore, according to the present invention, a shielding layer includes a shielding outlet for discharging plasma and sample ions substantially along the orientation direction of the plasma torch from the interior of a wave-driven plasma ion source to the exterior of a microwave-driven plasma ion source, the shielding outlet having a shielding aperture. The shielding outlet is fluidly coupled to the torch outlet to discharge plasma and sample ions substantially along the orientation direction of the plasma torch from the interior of the plasma torch to the exterior of the microwave-driven plasma ion source. Therefore, the plasma torch can be partially or completely disposed within the microwave-driven plasma ion source.

[0015] In one example, the plasma torch includes a tube surrounding the interior of the plasma torch, with one end of the tube open to form a torch outlet. In this example, the orientation of the plasma torch is parallel to the longitudinal axis of the tube and points from the inside of the tube outward, thus pointing towards the open end of the tube forming the torch outlet. Therefore, the plasma and sample ions, which have a certain divergent motion along the tube, move substantially along the orientation of the plasma torch as they exit the plasma torch through the torch outlet.

[0016] In this example, if the tube extends from the interior of the microwave-driven plasma ion source through a shielded outlet, with the torch outlet located outside the interior of the microwave-driven plasma ion source, then the plasma torch is partially positioned inside the microwave-driven plasma ion source. However, if the tube terminates at the torch outlet inside the microwave-driven plasma ion source, and the remainder of the plasma torch is also positioned inside the microwave-driven plasma ion source, then the plasma torch is completely positioned inside the microwave-driven plasma ion source. In both cases, the shielded outlet is fluidly coupled to the torch outlet to discharge plasma and sample ions substantially along the orientation of the plasma torch from the interior of the plasma torch to the exterior of the microwave-driven plasma ion source.

[0017] Independent of this example, preferably, the shielded outlet is located near the torch outlet to ensure that plasma and sample ions are discharged substantially along the orientation of the plasma torch from the interior of the plasma torch to the exterior of the microwave-driven plasma ion source. Preferably, the distance between the shielded outlet and the torch outlet is less than 5 mm, particularly preferably less than 2.5 mm. In a variation, the shielded outlet is flush with the torch outlet.

[0018] According to the present invention, the size of the shielding aperture is less than 150% of the size of the torch aperture, preferably less than 125% of the size of the torch aperture, and particularly preferably less than 110% of the size of the torch aperture, wherein both the size of the shielding aperture and the size of the torch aperture are measured in units of area. This means that the size of the shielding aperture is limited. Due to the limited size, microwaves are better shielded within the shielding exit region, preventing them from being transmitted from the interior to the exterior of the microwave-driven plasma ion source. Therefore, less electromagnetic radiation (i.e., microwaves generated inside the microwave-driven plasma ion source) can reach the exterior of the microwave-driven plasma ion source within the shielding exit region. Thus, if a conductive element is placed near the shielding exit, the conductive element is exposed to less microwaves, resulting in less microwave generation due to induction. Simultaneously, the limited size of the shielding exit has the effect that microwaves generated by induction by the conductive element are better shielded within the shielding exit region, preventing them from being transmitted from the exterior to the interior of the microwave-driven plasma ion source. As a result, the microwave field inside the microwave-driven plasma ion source changes less due to feedback effects when the conductive element moves near the shielded exit. Therefore, the microwave field inside the microwave-driven plasma ion source is more stable and less affected by the movement of the conductive element near the shielded exit. Consequently, the operating parameters of the microwave-driven plasma ion source can be optimized to maximize sample ion generation, and the changes in operating parameters are minimal when another instrument (such as an ion mobility analyzer and / or mass analyzer) moves relative to the microwave-driven plasma ion source, or when the settings of such another instrument change. Therefore, the operating parameters of the microwave-driven plasma ion source can be optimized simply and more stably to maximize sample ion generation. This advantage increases as the shielded aperture decreases. Therefore, the advantage increases when the shielded aperture is less than 125% of the torch aperture, compared to a shielded aperture size less than 150% of the torch aperture size. Furthermore, the advantage increases when the shielded aperture is less than 110% of the torch aperture size, compared to a shielded aperture size less than 125% of the torch aperture size.

[0019] Regardless of whether the size of the shielding aperture is less than 150%, 125%, or 110% of the torch aperture size, advantageously, the size of the shielding aperture is at least 100% of the torch aperture size, wherein both the size of the shielding aperture and the torch aperture size are measured in units of area. The advantage of this is that the shielding aperture is large enough to allow plasma and a maximum number of sample ions to be discharged from the interior of the plasma torch to the exterior of the microwave-driven plasma ion source.

[0020] Alternatively, the size of the shield aperture is less than 100% of the size of the torch aperture.

[0021] Preferably, the plasma torch includes a plasma gas inlet for introducing plasma gas from a plasma gas source into the interior of the plasma torch. Therefore, the plasma gas source can be part of a microwave-driven plasma ion source, or it can be separate from the microwave-driven plasma ion source. In the latter case, advantageously, the microwave-driven plasma ion source includes a plasma gas source connector fluidly coupled to the plasma gas inlet, which can be fluidly connected to a separate plasma gas source to supply plasma gas from the separate plasma gas source into the interior of the plasma torch via the plasma gas source connector and the plasma gas inlet.

[0022] Advantageously, the microwave-driven plasma ion source includes a plasma gas source that can be fluidly coupled to the plasma gas inlet.

[0023] Alternatively, the plasma torch may not have such a plasma gas inlet.

[0024] Preferably, the plasma torch includes a sample inlet fluidly coupled to a sample inlet for feeding a sample from the sample inlet into the interior of the plasma torch. In a variation, the sample inlet and the sample entrance can be merged and thus identical. In this variation, the sample inlet of the plasma torch also serves as the sample entrance of a microwave-driven plasma ion source.

[0025] Alternatively, the plasma torch may not require such sample imports.

[0026] Advantageously, the plasma torch is positioned internally, particularly entirely within the microwave-driven plasma ion source. This has the advantage of allowing for more stable operation at given operating parameters, as the plasma torch is optimally shielded from external influences. Therefore, when operating the microwave-driven plasma ion source to maximize sample ion generation, the optimal operating parameters can be maintained more stably.

[0027] Alternatively, the plasma torch is not located inside the microwave-driven plasma ion source.

[0028] Preferably, the torch aperture size, measured in units of area, is 70 mm. 2 Up to 900mm 2 Within the range, especially preferred at 110mm 2 Up to 600mm 2 Within this range. The advantage of doing so is that the generation of sample ions by the microwave-driven plasma ion source can be optimized by balancing the maximization of the absolute number of sample ions generated per unit time with the maximization of the density of sample ions generated by the microwave-driven plasma ion source in the regions of the torch aperture and the shield aperture, where the term "density" refers to the number of sample ions per spatial unit.

[0029] Alternatively, the torch aperture size is a maximum of 70 mm. 2 Or minimum 900mm 2 .

[0030] Preferably, the interior of the microwave-driven plasma ion source has an outer boundary serving as a closed surface, wherein the shielding layer defines the closed surface and covers at least 98%, preferably at least 99%, and particularly preferably at least 99.5% of the closed surface. Advantageously, at any opening in the shielding layer, the outer boundary of the interior of the microwave-driven plasma ion source is a surface that connects the edges of each opening to the closed surface having the smallest possible surface area. Advantageously, openings in the shielding layer with a maximum diameter less than 20% of the shortest microwave wavelength that the microwave generator can produce, particularly openings with a maximum diameter less than 6 mm, are considered to be completely covered by the shielding layer. Therefore, advantageously, the maximum diameter refers to the longest possible straight line measured across each opening from any position at the edge of each opening to any other position at the edge of each opening. However, it is considered that the shielding layer does not cover larger openings in the shielding layer.

[0031] Alternatively, however, the shielding layer covers less than 98% of the enclosed surface, i.e., the outer boundary inside the microwave-driven plasma ion source.

[0032] Preferably, the shielding layer is made of metal. In this case, the shielding layer is a metallic shielding layer. Therefore, it is irrelevant whether the shielding layer is a metallic coating on a shielding support structure, or whether the shielding layer is made of a metal plate, mesh, or grid, and thus supported by a shielding support structure or self-stabilized by an integrated support structure or by forming its own support structure. Regardless of how the metallic shielding layer is formed, its advantage is that it can provide an effective shielding layer to prevent microwaves from being transmitted from the interior of the microwave-driven plasma ion source to the exterior of the microwave-driven plasma ion source.

[0033] Particularly preferably, in the region of the shielded exit, the shielding layer is made of tungsten. Because tungsten has the highest melting point, this allows the shielding layer to withstand high temperatures when subjected to impacts from partial plasma and sample ions transported from the inside of the plasma torch to the outside of the microwave-driven plasma ion source. In a variant, in the region of the shielded exit, the shielding layer is made of a metal other than tungsten.

[0034] In one preferred variation, the entire shielding layer is made of tungsten. However, in another preferred variation, the main portion of the shielding layer is made of a metal other than tungsten, while the shielding layer is made of tungsten in the area of ​​the shielded outlet. The advantage of the latter variation is that the shielding layer has a lower construction cost.

[0035] Alternatively, the shielding layer is made of materials other than metal.

[0036] Preferably, the microwave-driven plasma ion source includes a coolant circuit containing a coolant for cooling a shielding layer, wherein the shielding layer, particularly in the region of the shielding outlet, can be cooled by the coolant. Advantageously, the coolant is part of the microwave-driven plasma ion source and is included in the coolant circuit. However, the microwave-driven plasma ion source may exist without a coolant, and the coolant may not be included in the coolant circuit. For example, the latter variant is advantageous for transporting the microwave-driven plasma ion source.

[0037] Preferably, the coolant circuit is a closed-loop circuit.

[0038] Advantageously, the coolant is water or liquid nitrogen. However, other liquids may also be used.

[0039] Alternatively, microwave-driven plasma ion sources may not have such a coolant circuit, which contains coolant for cooling the shielding layer.

[0040] Advantageously, the microwave-driven plasma ionization source includes a microwave resonator that generates an electromagnetic field to inductively couple a plasma gas to the electromagnetic field, thereby generating plasma from the plasma gas. The microwave resonator exhibits resonant behavior and generates an electromagnetic field when exposed to microwaves generated by a microwave generator. In this case, plasma is generated by inductively coupling the plasma gas with the electromagnetic field generated by the microwave resonator. In one variant, the microwaves generated by the microwave generator participate only indirectly, as they are used to drive the microwave resonator. However, in another variant, the plasma gas is exposed to microwaves generated by the microwave generator and inductively coupled with the electromagnetic field generated by the microwave resonator, thereby generating plasma from the plasma gas. In the latter variant, the microwaves generated by the microwave generator participate both indirectly and directly in the process of generating plasma from the plasma gas.

[0041] When the microwave resonator is part of a microwave-driven plasma ion source, preferably, the shielding layer used to shield microwaves from being transmitted from inside the microwave-driven plasma ion source to the outside of the microwave-driven plasma ion source is used to shield the microwaves generated by the microwave generator and the electromagnetic field generated by the microwave resonator.

[0042] Preferably, the microwave resonator provides a gap in which the majority of the electromagnetic field generated by the microwave resonator is located when the microwave-driven plasma ionization source is operating. Therefore, preferably, the fact that the majority of the electromagnetic field generated by the microwave resonator is located in the gap of the microwave resonator means that more than half of the total intensity of the electromagnetic field generated by the microwave resonator occurs within the gap. Advantageously, the plasma torch is at least partially disposed within the gap of the microwave resonator. Preferably, a first region inside the plasma torch, i.e., the region where the plasma gas generates plasma, is located, is disposed within the gap of the microwave resonator. In a preferred variation, a second region inside the plasma torch, i.e., the region where the sample is ionized into sample ions by exposing it to plasma, is also disposed within the gap of the microwave resonator. However, in another variation, the second region inside the plasma torch, i.e., the region where the sample is ionized into sample ions by exposing it to plasma, is at least partially or completely disposed outside the gap of the microwave resonator. In alternatives to these variations, the first region inside the plasma torch, i.e., the region where the plasma gas generates plasma, is at least partially or completely disposed outside the gap of the microwave resonator.

[0043] Alternatively, microwave resonators do not provide such a gap, which is intended to house the main portion of the electromagnetic field generated by the microwave resonator when the microwave-driven plasma ion source is operating.

[0044] In an alternative, the microwave-driven plasma ion source does not have a microwave resonator that generates an electromagnetic field to inductively couple the plasma gas to the electromagnetic field so as to generate plasma from the plasma gas, and wherein the microwave resonator exhibits resonant behavior and generates an electromagnetic field when exposed to microwaves generated by a microwave generator.

[0045] In a preferred variant, the microwave-driven plasma ionization source includes a plasma gas source, wherein the plasma torch includes a plasma gas inlet for introducing plasma gas from the plasma gas source into the interior of the plasma torch, wherein the plasma gas contains a nitrogen content of 80 to 100% by volume. This approach offers the advantage that the plasma gas is cost-effective and readily available.

[0046] Advantageously, the plasma gas is nitrogen. Therefore, nitrogen may include trace amounts of other gases. However, preferably, when the plasma gas is nitrogen, at least 98% by volume of the plasma gas is nitrogen, thus including 2% by volume or less of other gases.

[0047] In another preferred variant, the microwave-driven plasma ionization source includes a plasma gas source, and the plasma torch includes a plasma gas inlet for introducing plasma gas from the plasma gas source into the interior of the plasma torch, wherein the plasma gas contains argon at a content of 0.9 to 100 volume percent, particularly 95 to 100 volume percent. Therefore, argon may include trace amounts of other gases. However, preferably, when the plasma gas is argon, at least 98 volume percent of the plasma gas is argon, thus including 2 volume percent or less of other gases. Regardless of the content of other trace gases, the advantage of argon as the plasma gas is that the plasma gas does not chemically react with the sample during the ionization of the sample into sample ions.

[0048] Besides nitrogen and argon, other gases or mixtures of gases can be used as plasma gases. Furthermore, microwave-driven plasma ionization sources may or may not have a plasma gas source. If a microwave-driven plasma ionization source does not have a plasma gas source, it can advantageously be connected to a separate plasma gas source.

[0049] Advantageously, a mass spectrometer for mass analysis of a sample includes a microwave-driven plasma ion source according to the invention for ionizing the sample into sample ions, and a mass analyzer for mass analysis of the sample ions. The mass analyzer has an ion inlet for introducing sample ions from outside the mass analyzer into its interior, thereby performing mass analysis on the sample ions. The ion inlet has an aperture.

[0050] In this document, preferably, "mass analysis of a sample" refers to determining the mass spectrum of the sample. To determine the mass spectrum of a sample, the sample is ionized into sample ions, and then the mass spectrum of the obtained sample ions is determined. Therefore, the expression "mass analysis of a sample" refers to ionizing the sample into sample ions and then performing mass analysis on the sample ions. Thus, the expressions "mass spectrum of the sample" and "mass spectrum of the sample ions" refer to the same mass spectrum because the mass spectrum ultimately provides information on the distribution of the mass-charge ratio of the sample ions relative to the sample ions. However, when obtaining the "mass spectrum of the sample," the sample is first ionized into sample ions, and then the mass spectrum is determined from the sample ions.

[0051] Advantageously, the mass analyzer is fluidly coupled to a microwave-driven plasma ion source to receive sample ions discharged substantially along the orientation direction of the plasma torch from the shielded outlet of the shielded layer of the microwave-driven plasma ion source, and thus to receive sample ions through an ion inlet for mass analysis. The ion inlet is at least partially, advantageously, entirely located within a volume extending from the torch outlet and pointing towards the orientation direction of the plasma torch. The cross-section of this volume is perpendicular to the orientation direction of the plasma torch and corresponds to the projection of the torch aperture onto a plane perpendicular to the orientation direction of the plasma torch. Therefore, the cross-section of the volume perpendicular to the orientation direction of the plasma torch and the position of the volume are defined by the torch outlet, while the extension of the volume away from the torch outlet is defined by the orientation direction of the plasma torch.

[0052] Regardless of the orientation of the ion inlet relative to the plasma torch orientation direction, the ion inlet is at least partially or completely located within a volume extending from the torch exit and pointing towards the plasma torch orientation direction. The cross-section of this volume is perpendicular to the cross-section of the plasma torch orientation direction and corresponds to the projection of the torch aperture onto a plane perpendicular to the plasma torch orientation direction. This has the advantage that more sample ions exiting from the torch exit and the shielded exit are subsequently received by the mass spectrometer through the ion inlet for mass analysis. Therefore, the efficiency of the mass spectrometer is improved.

[0053] Advantageously, the mass analyzer and the microwave-driven plasma ion source can move relative to each other within a plane whose normal is tilted by a maximum of 20° relative to the orientation direction of the plasma torch. Therefore, the normal of this plane can be parallel to the orientation direction of the plasma torch, or it can be tilted at an angle of 20° or less relative to the orientation direction of the plasma torch. Thus, the position of the ion inlet of the mass analyzer relative to the shielded outlet of the microwave-driven plasma ion source can be changed. The advantage of doing so is that by moving the mass analyzer relative to the microwave-driven plasma ion source, the number of sample ions exiting from the torch outlet and the shielded outlet and subsequently undergoing mass analysis through the ion inlet can be easily maximized. This maximization improves the efficiency of the mass spectrometer even under different operating parameters of the microwave-driven plasma ion source because, inside the plasma torch, the position and shape of the second region where sample ions are generated by exposing the sample to plasma, and the location of the highest sample ion density within the second region, vary depending on the operating parameters of the microwave-driven plasma ion source. Therefore, the mass spectrometer can optimize not only the efficiency of sample ion generation from the sample, but also the efficiency of ion transfer from the microwave-driven plasma ion source to the mass analyzer used for mass analysis of the sample ions.

[0054] Preferably, the movement of the mass analyzer relative to the microwave-driven plasma ion source is actuated by at least one actuator, particularly at least one motor. Therefore, preferably, the mass spectrometer includes at least one actuator, particularly at least one motor, for driving the movement of the mass analyzer relative to the microwave-driven plasma ion source. However, alternatively, the mass spectrometer may not have such an actuator. In this case, the mass analyzer can be moved manually relative to the microwave-driven plasma ion source.

[0055] In a first preferred variant, the mass analyzer and the microwave-driven plasma ion source can move relative to each other only in a plane whose normal is tilted by a maximum of 20° relative to the orientation direction of the plasma torch. However, in a second preferred variant, the mass analyzer and the microwave-driven plasma ion source can move relative to each other in directions other than the aforementioned plane whose normal is tilted by a maximum of 20° relative to the orientation direction of the plasma torch.

[0056] Preferably, the mass analyzer and the microwave-driven plasma ion source are capable of moving relative to each other along two mutually perpendicular axes.

[0057] If the mass analyzer and the microwave-driven plasma ion source can move relative to each other simultaneously within a plane whose normal is tilted by a maximum of 20° relative to the orientation direction of the plasma torch, then the two axes are preferably positioned within this plane. This has the advantage that the mass analyzer and the microwave-driven plasma ion source can be easily and controllably moved relative to each other within a plane whose normal is tilted by a maximum of 20° relative to the orientation direction of the plasma torch. Therefore, the efficiency optimization of the mass spectrometer can be well controlled.

[0058] However, in one variation, only one of the two axes is set in the plane, or neither axis is set in the plane.

[0059] Preferably, the mass analyzer and the microwave-driven plasma ion source are movable relative to each other along three mutually perpendicular axes. This allows the mass analyzer and the microwave-driven plasma ion source to be easily and controllably moved relative to each other in all directions to maximize the efficiency of the mass spectrometer.

[0060] However, in a preferred variant, the mass analyzer and the microwave-driven plasma ion source can only move relative to each other along two mutually perpendicular axes. Advantageously, these two axes are arranged in a plane whose normal is tilted at a maximum of 20° relative to the orientation direction of the plasma torch.

[0061] In another variant, the mass analyzer and the microwave-driven plasma ion source can only move relative to each other along one axis.

[0062] Regardless of whether the mass analyzer and the microwave-driven plasma ion source can move relative to each other in a plane whose normal is tilted by a maximum of 20° relative to the orientation direction of the plasma torch, both the mass analyzer and the microwave-driven plasma ion source can pivot relative to each other about a pivot axis oriented substantially perpendicular to the orientation direction of the plasma torch. Therefore, the tilt angle of this pivot axis relative to the orientation direction of the plasma torch is preferably in the range of 45° to 135°, particularly preferably in the range of 70° to 110°. Most advantageously, the tilt angle of the pivot axis relative to the orientation direction of the plasma torch is 90°. The advantage of allowing the mass analyzer and the microwave-driven plasma ion source to pivot relative to each other about this pivot axis is that the orientation of the mass analyzer relative to the microwave-driven plasma ion source can be optimized in a plane perpendicular to the pivot axis orientation to maximize the number of sample ions leaving the torch exit and shield exit and subsequently undergoing mass analysis through the ion inlet. Therefore, the mass spectrometer can optimize the efficiency of ion transfer from the microwave-driven plasma ion source to the mass analyzer for further mass analysis of the sample ions.

[0063] In a preferred variant, the mass analyzer and the microwave-driven plasma ion source are pivotable relative to each other about two pivot axes oriented substantially perpendicular to the orientation direction of the plasma torch. Therefore, the tilt angle of this pivot axis relative to the orientation direction of the plasma torch is preferably in the range of 45° to 135°, particularly preferably in the range of 70° to 110°. Most advantageously, the tilt angle of the pivot axis relative to the orientation direction of the plasma torch is 90°. Regardless of the precise angle, the advantage of this is that the orientation of the mass analyzer relative to the microwave-driven plasma ion source can be optimized in a plane perpendicular to the pivot axis orientation to maximize the number of sample ions leaving the torch exit and shield exit and subsequently undergoing mass analysis through the ion inlet. Thus, the mass spectrometer can optimize the efficiency of sample ion transfer from the microwave-driven plasma ion source to the mass analyzer for further mass analysis of the sample ions.

[0064] Of particular advantage, the two pivot axes are oriented perpendicularly to each other. This allows for the systematic optimization of the efficiency of ion transfer from the microwave-driven plasma ion source to the mass analyzer for sample ion mass analysis.

[0065] As an alternative to these variants with one or two pivot axes, the mass analyzer and microwave-driven plasma ion source may not pivot relative to each other about any axis, or they may pivot relative to each other about two or more pivot axes.

[0066] Other advantageous embodiments and combinations of features can be derived from the detailed description below. Attached Figure Description

[0067] In the accompanying drawings used to explain the embodiments:

[0068] Figure 1 A simplified schematic diagram of a microwave-driven plasma ion source for ionizing a sample into sample ions according to the present invention is shown.

[0069] Figure 2 A simplified schematic diagram of another microwave-driven plasma ion source according to the present invention for ionizing a sample to be ionized into sample ions is shown.

[0070] Figure 3 A simplified schematic diagram of a mass spectrometer for mass analysis of a sample and a mass analyzer for mass analysis of sample ions is shown, wherein the mass spectrometer includes a microwave-driven plasma ion source according to the invention for ionizing the sample into sample ions.

[0071] Figure 4 It shows a kind of Figure 3 The diagram shows a simplified illustration of a mass spectrometer similar to the one used for mass analysis of samples; and

[0072] Figure 5 A simplified schematic diagram of another similar mass spectrometer used for mass analysis of samples is shown.

[0073] In the accompanying drawings, the same reference numerals denote the same parts. Detailed Implementation

[0074] exist Figure 1 The diagram shows a simplified schematic of a microwave-driven plasma ionization source 1 according to the present invention for ionizing a sample into sample ions. Here, the sample is an aerosol comprising aerosol particles dispersed in a gas. Of these aerosol particles, some are solid particles, while others are liquid particles. However, in one variation, all aerosol particles are solid particles. In another variation, the aerosol particles are liquid particles. In yet another variation, the sample is a gas. Regardless of the sample type, the microwave-driven plasma ionization source 1 includes a sample inlet 6 for introducing the sample to be ionized from the outside of the microwave-driven plasma ionization source 1 into its interior 3.

[0075] Figure 1The microwave-driven plasma ion source 1 shown includes a microwave generator 10 and a microwave resonator 11 for generating microwaves, both arranged inside the microwave-driven plasma ion source 1. The microwave generator 10 is an antenna connected to an AC voltage power supply 30 of the microwave-driven plasma ion source 1. The AC voltage power supply 30 generates an alternating AC voltage at a frequency of 1 MHz to 10 MHz and supplies this AC voltage to the microwave generator 10. In one variant, the frequency is in the range of 30 MHz to 3 GHz. In another variant, the frequency is in the range of 30 MHz to 300 MHz. In yet another variant, the frequency is in the range of 300 MHz to 3 GHz. In one specific example, the frequency is 250 MHz. In another specific example, the frequency is 350 MHz.

[0076] The microwave resonator 11 is circular and exhibits resonant behavior. When the microwave resonator 11 is exposed to microwaves generated by the microwave generator 10, it generates an electromagnetic field to generate plasma 101 from the plasma gas 100. Therefore, the microwave generator 10 is used to generate microwaves to generate plasma 101 from the plasma gas 100, which indirectly generates an electromagnetic field inducedly coupled to the plasma gas 100 by the microwave generator 10 generating microwaves that excite the microwave resonator 11, so as to generate plasma 101 from the plasma gas 100.

[0077] The microwave-driven plasma ion source 1 also includes a plasma torch 20 extending through the opening of the annular microwave resonator 11. The plasma torch 20 includes a sample inlet 26, which is fluidly coupled to a sample inlet 6 of the microwave-driven plasma ion source 1 to deliver a sample from the sample inlet 6 into the interior 21 of the plasma torch 20. Furthermore, the plasma torch 20 includes a plasma gas inlet 23 to deliver plasma gas 100 from a plasma gas source 8 of the microwave-driven plasma ion source 1 into the interior 21 of the plasma torch 20. Here, the nitrogen content of the plasma gas 100 is 80% to 100% by volume. In one variation, the plasma gas 100 is nitrogen. In another variation, the plasma gas 100 is argon. In yet another variation, the plasma gas source 8 is not part of the microwave-driven plasma ion source 1. In this configuration, the microwave-driven plasma ion source includes a plasma gas source connector fluidly coupled to the plasma gas inlet 23, which is fluidly connected to a separate plasma gas source to supply plasma gas to the interior 21 of the plasma torch 20 via the plasma gas source connector and the plasma gas inlet 23.

[0078] The interior 21 of the plasma torch 20 is used to accommodate the process of generating plasma 101 from plasma gas 100 and the process of ionizing the sample into sample ions by exposing the sample to plasma 101. Here, the process of generating plasma 101 from plasma gas 100 takes place in a first region 24 of the interior 21 of the plasma torch 20, within the opening region of the annular microwave resonator 11. During operation of the microwave-driven plasma ion source 1, microwaves generated by the microwave generator 10 excite the microwave resonator to generate an electromagnetic field in the first region 24. Plasma gas 100 is induced to couple with the electromagnetic field in the first region 24 to generate plasma 101 from plasma gas 100. The sample is exposed to a second region 25 inside the plasma torch 20 to ionize the sample into sample ions within the second region 25 inside the plasma torch 20. Here, the first region 24 and the second region 25 coincide. In another variation, the first region 24 and the second region 25 are identical.

[0079] The plasma torch 20 also includes a torch outlet 22 for discharging plasma 101 and sample ions from the interior 21 of the plasma torch 20 to the exterior of the plasma torch 20. The torch outlet 22 has a torch aperture. This torch aperture is measured in area and is 70 mm². 2 In one variant, the torch aperture is 100 mm. 2 In another variant, the torch aperture is 111 mm. 2 In another variation, the torch aperture is 300 mm. 2 In another variation, the torch aperture is 500 mm. 2 In another variation, the torch aperture is 600 mm. 2 In another variant, the torch aperture is 900mm. 2 .

[0080] The plasma torch 20 has an elongated shape. This shape can be considered as that of a tube. In the accompanying drawings, the open end of the tube forms a torch outlet 22. Inside the tube, a plasma gas inlet 23 is arranged concentrically with the tube, such that plasma gas 100, which is fed into the interior 21 of the plasma torch 20 through the plasma gas inlet 23, flows along the longitudinal axis of the tube. Inside the plasma torch 20, the plasma gas 100 is induced to couple with an electromagnetic field in the first region 24 to generate plasma 101. The plasma 101 is then discharged from the plasma torch 20 through the torch outlet 22 formed by the open end of the tube.

[0081] Similar to plasma gas inlet 23, sample inlet 26 is arranged inside plasma torch 20 21, concentrically with the tube forming plasma torch 20, such that the sample fed into the interior 21 of plasma torch 20 through sample inlet 26 flows along the longitudinal axis of the tube. More precisely, sample inlet 26 is concentrically arranged in plasma gas inlet 23, such that the sample fed into the interior 21 of plasma torch 20 flows through plasma 101 generated by plasma gas 100 to be ionized into sample ions. Since plasma gas 100, plasma 101, and sample fed into the interior 21 of plasma torch 20 flow along the longitudinal axis of the tube forming plasma torch 20, plasma 101 and sample ions are discharged from plasma torch 20 through torch outlet 22, which is the open end of the tube forming plasma torch 20. Therefore, the flow direction of plasma gas 100, plasma 101, and sample ions is... Figure 1 The orientation direction 29 of the plasma torch is indicated by the middle arrow. This orientation direction 29 is parallel to the longitudinal axis of the tube forming the plasma torch 20 and extends from the interior 21 of the plasma torch 20 to the exterior through the torch outlet 22. Since the plasma 101 and sample ions are discharged from the plasma torch 20 in a beam with a certain divergence along the orientation direction 29, the statement that the plasma 101 and sample ions are discharged substantially along the orientation direction 29 from the torch outlet 22 is applicable.

[0082] The microwave-driven plasma ion source 1 also includes a housing 2 surrounding the interior 3 of the microwave-driven plasma ion source 1. The housing 2 is made of tungsten and forms a shielding layer 4, which shields microwaves transmitted from the interior 3 of the microwave-driven plasma ion source 1 to the exterior of the microwave-driven plasma ion source 1. Here, the interior 3 of the microwave-driven plasma ion source 1 has an outer boundary, which is a closed surface defined by the shielding layer 4. However, the shielding layer 4 includes a shielding outlet 5 for discharging plasma 101 and ions from the interior 3 of the microwave-driven plasma ion source 1 to the exterior of the microwave-driven plasma ion source 1, wherein the shielding outlet 5 has a shielding aperture.

[0083] The shielded outlet 5 is fluidly coupled to the torch outlet 22 to discharge plasma 101 and sample ions substantially along the orientation direction 29 of the plasma torch from the interior 21 of the plasma torch 20 to the exterior of the microwave-driven plasma ion source 1. Here, the size of the shielded aperture is 149% of the size of the torch aperture, where both the size of the shielded aperture and the size of the torch aperture are measured in area. In one variant, the size of the shielded aperture is 124% of the size of the torch aperture. In another variant, the size of the shielded aperture is 109% of the size of the torch aperture.

[0084] Therefore, the shielding aperture is slightly larger than the torch aperture. Figure 1 In the illustrated embodiment, the shielding aperture is even larger than the outer diameter of the plasma torch 20. Here, the largest portion of the plasma torch 20 is arranged inside the microwave-driven plasma ion source 1, 3. Only the area of ​​the torch outlet 22 of the plasma torch 20 extends from the inside 3 of the microwave-driven plasma ion source 1 to the outside of the microwave-driven plasma ion source 1 through the shielding outlet 5. Here, the torch outlet 22 of the plasma torch 20 extends 3 mm from the shielding outlet 5.

[0085] Although the shielded outlet 5 is within the shielding layer 4 of the microwave-driven plasma ion source 1, the shielding layer 4 still covers 98.5% of the enclosed surface, which defines the outer boundary of the interior 3 of the microwave-driven plasma ion source 1.

[0086] The microwave-driven plasma ion source 1 also includes a coolant circuit 7, which is a closed-loop circuit containing coolant for cooling the shielding layer 4. The coolant circuit 7 includes a coolant reservoir 9 and passes particularly around the shielding outlet 5 to cool the shielding layer 4 in the region of the shielding outlet 5. Therefore, the shielding layer 4 can be effectively cooled in the region of the shielding outlet 5 where ions from the plasma 101 are most likely to strike and heat it.

[0087] exist Figure 1 In the illustrated embodiment, the coolant is water. However, in a variation, a coolant other than water is used. In one example, the coolant is liquid nitrogen. Therefore, in either case, the respective coolant can be used to cool the shielding layer 4, particularly the area of ​​the shielding layer 4 where the shielding outlet 5 is located.

[0088] exist Figure 2 The diagram shows a simplified schematic of another microwave-driven plasma ion source 201 according to the present invention for ionizing a sample into sample ions. Most of this microwave-driven plasma ion source 201 is similar to... Figure 1 The microwave-driven plasma ion source 1 shown is the same. However, it is similar to... Figure 1 Compared to the microwave-driven plasma ion source 1 shown, Figure 2The microwave-driven plasma ion source 201 shown includes a plasma torch 202 disposed within the interior 203 of the microwave-driven plasma ion source 201. However, a shielded outlet 205 is also fluidly coupled to the torch outlet 222 to discharge plasma 101 and sample ions substantially along the plasma torch orientation direction 229 from the interior 221 of the plasma torch 220 to the exterior of the microwave-driven plasma ion source 201. Here, a 4.5 mm gap exists between the torch outlet 222 and the shielded outlet 205. In a variant, this gap is only 2 mm. In either case, the shielded outlet 205 is disposed near the torch outlet 222.

[0089] exist Figure 2 In the illustrated embodiment, the size of the shielding aperture is 105% of the size of the torch aperture, and the shielding layer 204 covers 99.1% of the closed surface defined by the shielding layer 204. In a variation, the size of the shielding aperture is 100% of the size of the torch aperture, and the shielding layer 204 covers 99.5% of the closed surface defined by the shielding layer 204. In another variation, the torch outlet 222 and the shielding outlet 205 are flush and there is no gap between them. In the latter variation, the size of the shielding aperture is also 100% of the size of the torch aperture.

[0090] exist Figure 3 A simplified schematic diagram of a mass spectrometer 50 for mass analysis of samples according to the present invention is shown. The mass spectrometer 50 includes a microwave-driven plasma ionization source according to the present invention for ionizing samples into sample ions. Figure 3 In the example shown Figure 1 The microwave-driven plasma ion source in the mass spectrometer 50. Alternatively, the microwave-driven plasma ion source included in the mass spectrometer 50 can also be... Figure 2 The microwave-driven plasma ion source 201 or any other microwave-driven plasma ion source according to the present invention.

[0091] In addition to the microwave-driven plasma ion source according to the invention, the mass spectrometer 50 also includes a mass analyzer 70 for mass analysis of sample ions. The mass analyzer 70 has an ion inlet 71 for introducing sample ions from the outside of the mass analyzer 70 into its interior 72 for mass analysis. Here, compared to the ion inlet 71, a second opening 73 is arranged further inside the mass analyzer 70, such that sample ions with trajectories oriented within a certain orientation range can first pass through the ion inlet 71 of the mass analyzer 70, and then through the second opening 73, thereby entering the interior 72 of the mass analyzer 70 for mass analysis.

[0092] The mass analyzer 70 is fluidly coupled to a microwave-driven plasma ion source 1 to receive sample ions through an ion inlet 71. The sample ions are discharged substantially along the orientation direction 29 of the plasma torch from the shielded outlet 5 of the shielding layer 4 of the microwave-driven plasma ion source 1. Here, the ion inlet 71 is entirely arranged within a volume extending from the torch outlet 22 and pointing towards the orientation direction 29 of the plasma torch. This volume has a cross-section perpendicular to the orientation direction 29 of the plasma torch and corresponds to the projection of the torch aperture onto a plane perpendicular to the orientation direction 29. Therefore, the cross-section of the volume perpendicular to the orientation direction 29 of the plasma torch and the position of the volume are defined by the torch outlet 22, while the extension of the volume away from the torch outlet 22 is defined by the orientation direction 29 of the plasma torch.

[0093] Inside the plasma torch 20 21, the position and shape of the second region 25 containing sample ions generated by exposing the sample to plasma 101 depends on the operating parameters of the microwave-driven plasma ion source 1. Furthermore, the location of the highest density of sample ions generated within the second region 25 also depends on the operating parameters of the microwave-driven plasma ion source 1. Therefore, when the operating parameters of the microwave-driven plasma ion source 1 change, the location with the highest number of sample ions generated inside the plasma torch 20 21 also changes. As a result, the position where most sample ions emerge from inside the plasma torch 20 21 through the torch exit 22, substantially along the orientation direction 29 of the plasma torch, within the aperture of the torch exit 22, varies depending on the operating parameters of the microwave-driven plasma ion source 1.

[0094] The operating parameters of the microwave-driven plasma ion source 1 can be optimized to generate the maximum number of sample ions. Here, the optimal operating parameters depend on the type of sample to be ionized. To further optimize a portion of the total number of sample ions generated, which emerge from the interior 21 of the plasma torch 20 and enter the interior 72 of the mass analyzer 70 through the aperture of the ion inlet 71 for mass analysis, the mass analyzer 70 and the microwave-driven plasma ion source 1 should be able to move relative to each other in a plane having a normal to the orientation direction 29 of the plasma torch. Figure 3In the embodiment of the mass spectrometer 50 shown, the mass spectrometer 50 includes a motor 28 for driving a microwave-driven plasma ion source 1 to move within the mass spectrometer 50 along two linear tracks 27.1 and 27.2. These two linear tracks 27.1 and 27.2 are oriented perpendicularly to each other and perpendicular to the orientation direction 29 of the plasma torch. Therefore, the linear tracks 27.1 and 27.2 are arranged parallel to a plane having a normal to the orientation direction 29 of the plasma torch. This allows the position of the ion inlet 71 of the mass analyzer 70 to be changed relative to the shielded outlet 5 of the shielding layer 4 of the microwave-driven plasma ion source 1. Therefore, by moving the mass analyzer 70 to the correct position relative to the microwave-driven plasma ion source 1, the number of sample ions discharged from the shielded outlet 5 and subsequently passing through the ion inlet 71 for mass analysis can be easily maximized. This maximization can improve and thus optimize the efficiency of the mass spectrometer 50 under different operating parameters of the microwave-driven plasma ion source 1.

[0095] In one variant, the two linear orbits are not oriented perpendicularly, but at an angle to each other, allowing the microwave-driven plasma ion source 1 to move in two different directions that are oriented perpendicularly to each other on a plane with the orientation direction 29 of the plasma torch as the normal.

[0096] In another variation, the microwave-driven plasma ion source 1 can move within the mass spectrometer 50 along a first linear track, while the mass analyzer 70 can move along a second linear track. The first and second tracks are arranged at an angle to each other and parallel to a plane with the orientation direction 29 of the plasma torch as the normal, such that the microwave-driven plasma ion source 1 and the mass analyzer 70 can move in two different directions that are perpendicular to each other on a plane with the orientation direction 29 of the plasma torch as the normal.

[0097] In another variation that achieves the same optimization, the mass analyzer 70 can move within the mass spectrometer 50 along two linear tracks, which are oriented perpendicular to each other or at another angle to each other, and are arranged on a plane with the orientation direction 29 of the plasma torch as the normal. Here, the mass analyzer 70 can move within the mass spectrometer 50, or both the mass analyzer 70 and the microwave-driven plasma ion source 1 can move within the mass spectrometer 50.

[0098] In one variation of the aforementioned variant, the plane parallel to the arranged linear track has a normal inclined at a 44° angle to the orientation direction 29 of the plasma torch. In another variation, the plane parallel to the arranged linear track has a normal inclined at a 19° angle to the orientation direction 29 of the plasma torch.

[0099] What these variations and modifications have in common is that the mass analyzer 70 and the microwave-driven plasma ion source 1 can move relative to each other along two axes that are oriented perpendicularly to each other.

[0100] In either of these two variations, the mass spectrometer 50 may include one motor for driving the microwave-driven plasma ion source 1 or the mass analyzer 70 to move along one track, and another motor for driving the microwave-driven plasma ion source 1 or the mass analyzer 70 to move along the other track. If both the microwave-driven plasma ion source 1 and the mass analyzer 70 can move along two tracks, then the mass spectrometer 50 may of course include four motors for driving this movement.

[0101] In either of these variations, the mass analyzer 70 and the microwave-driven plasma ion source 1 can also pivot relative to each other about two pivot axes oriented perpendicular to the plasma torch orientation direction 29. These two pivot axes are structurally incorporated into two linear tracks 27.1 and 27.2. Therefore, these two linear tracks 27.1 and 27.2, and the aforementioned drive, allow the mass analyzer 70 and the microwave-driven plasma ion source 1 to move relative to each other along their respective linear tracks 27.1 and 27.2, and allow the mass analyzer 70 and the microwave-driven plasma ion source 1 to pivot relative to each other about their respective linear tracks 27.1 and 27.2, and thus about their respective axes. Therefore, the orientation of the mass analyzer 70 relative to the microwave-driven plasma ion source 1 can be optimized in a plane perpendicular to the pivot axis orientation to maximize the number of sample ions discharged substantially along the plasma torch orientation direction 29 from the torch outlet 22 and the shield outlet 5, and subsequently through the ion inlet 71 for mass analysis. Therefore, the mass spectrometer 50 can further optimize the efficiency of transferring sample ions from the microwave-driven plasma ion source 1 to the mass analyzer 70 for mass analysis.

[0102] exist Figure 4 In the middle, a kind of similar Figure 3 The mass spectrometer 50 shown is a simplified schematic diagram of a mass spectrometer 60 used for mass analysis of samples. Figure 4 The mass spectrometer 60 shown also includes a microwave-driven plasma ionization source according to the invention for ionizing a sample into sample ions. Figure 3 Compared to the mass spectrometer 50 shown, Figure 4The mass spectrometer 60 shown also provides a third linear track 27.3 along which the microwave-driven plasma ion source 1 can move. Therefore, the microwave-driven plasma ion source 1 can move within the mass spectrometer 50 along three linear tracks 27.1, 27.2, and 27.3. These three linear tracks 27.1, 27.2, and 27.3 are oriented perpendicularly to each other. Two of these linear tracks, 27.1 and 27.2, are oriented perpendicular to the orientation direction 29 of the plasma torch, while the third linear track 27.3 is oriented parallel to the orientation direction 29 of the plasma torch. Therefore, the mass analyzer 70 and the microwave-driven plasma ion source 1 can be easily moved relative to each other in a controlled manner in all directions to maximize the efficiency of the mass spectrometer 60.

[0103] exist Figure 5 The diagram shows a simplified schematic of another similar mass spectrometer 65 used for mass analysis of samples. In this embodiment, the mass spectrometer 65 includes... Figure 2 The microwave-driven plasma ion source 201 is shown. In various variations, the mass spectrometer 65 includes any other microwave-driven plasma ion source according to the invention, such as... Figure 1 The microwave-driven plasma ion source is shown.

[0104] Figure 5 The mass spectrometer 65 shown also includes a mass analyzer 170, which is a sector-shaped mass analyzer that uses an electromagnetic field 175 to spatially separate sample ions by mass, such that the sample ions reach the position-sensitive detector 176 of the mass analyzer 170 at a position that depends on the mass-to-charge ratio of each sample ion and thus indicates the mass-to-charge ratio of each sample ion. Therefore, the resolution of the mass analyzer 170 depends on the divergence of the beam of sample ions reaching the interior 172 of the mass analyzer 170 for mass analysis. In particular, the resolution of the mass analyzer 170 depends on the divergence of the beam of sample ions in the ion separation direction in which they are spatially separated by the electromagnetic field 175.

[0105] The mass analyzer 170 includes an ion inlet 171 and a second opening 173. The mass analyzer 170 and the microwave-driven plasma ion source 201 are movable relative to each other along an axis perpendicular to the orientation direction 229 of the plasma torch. Here, this axis is a linear track 27.1 along which the microwave-driven plasma ion source 201 can be moved to move the mass analyzer 170 relative to the microwave-driven plasma ion source 201. By moving the mass analyzer 170 relative to the microwave-driven plasma ion source 201, the number of sample ions discharged from the torch outlet and reaching the interior of the mass analyzer 170 for mass analysis can be maximized.

[0106] This invention is not limited to the embodiments and variations described above. Other variations can be readily obtained by those skilled in the art.

[0107] In summary, it should be noted that by creating a microwave-driven plasma ion source belonging to the technical field initially mentioned, the optimization of the operating parameters of the microwave-driven plasma ion source is simple and stable, thereby generating the largest number of sample ions.

Claims

1. A microwave-driven plasma ion source (1, 201) for ionizing a sample into sample ions, comprising: a) Sample inlet (6), used to send the sample from the outside of the microwave-driven plasma ion source (1, 201) into the interior (3) of the microwave-driven plasma ion source (1, 201); b) A microwave generator (10) for generating microwaves to generate plasma (101) from plasma gas (100), wherein the microwaves are electromagnetic waves of radio frequency electromagnetic radiation in the microwave range, wherein the microwave range is electromagnetic radiation in the range of frequencies from 00MHz to 3GHz. as well as c) A plasma torch (20) having an orientation (29, 229) for accommodating (2) the process of generating the plasma (101) from the plasma gas (100) and the process of ionizing the sample into sample ions by exposing the sample to the plasma (101), wherein the plasma torch (20) includes a torch outlet (22) for discharging the plasma (101) and the sample ions substantially along the orientation (29, 229) from the interior (21) of the plasma torch (20) to the exterior of the plasma torch (20), the torch outlet (22) having a torch aperture; The microwave-driven plasma ion source (1, 201) is characterized in that it includes a shielding layer (4) for shielding microwaves transmitted from the interior (3) of the microwave-driven plasma ion source (1, 201) to the exterior of the microwave-driven plasma ion source (1, 201), wherein the shielding layer (4) includes a shielding outlet (5) for discharging the plasma (101) and the sample ions substantially along the plasma torch orientation direction (29, 229) from the interior (3) of the microwave-driven plasma ion source (1, 201) to the exterior of the microwave-driven plasma ion source (1, 201), and the shielding outlet (5) has a shielding aperture; The shielding outlet (5) is fluidly coupled to the torch outlet (22) to discharge the plasma (101) and the sample ions substantially along the orientation direction (29, 229) of the plasma torch from the interior (21) of the plasma torch (20) to the exterior of the microwave-driven plasma ion source (1, 201), wherein the size of the shielding aperture is less than 150% of the size of the torch aperture, and wherein both the size of the shielding aperture and the size of the torch aperture are measured in area.

2. The microwave-driven plasma ion source (1, 201) according to claim 1, characterized in that, The size of the shielding aperture is less than 125% of the size of the torch aperture.

3. The microwave-driven plasma ion source (1, 201) according to claim 1, characterized in that, The size of the shielding aperture is less than 110% of the size of the torch aperture.

4. The microwave-driven plasma ion source (201) according to claim 1, characterized in that, The plasma torch (20) is disposed inside (3) of the microwave-driven plasma ion source (201).

5. The microwave-driven plasma ion source (1, 201) according to claim 1, characterized in that, The size of the torch aperture, measured in units of area, is 70 mm. 2 Up to 900mm 2 Within the range.

6. The microwave-driven plasma ion source (1, 201) according to claim 1, characterized in that, The interior (3) of the microwave-driven plasma ion source (1, 201) has an outer boundary as a closed surface, wherein the shielding layer (4) defines the closed surface and covers at least 98% of the closed surface.

7. The microwave-driven plasma ion source (1, 201) according to claim 1, characterized in that, The shielding layer (4) is made of metal.

8. The microwave-driven plasma ion source (1, 201) according to claim 1, characterized in that, The microwave-driven plasma ion source (1, 201) includes a coolant circuit (7) containing a coolant for cooling the shielding layer (4), wherein the shielding layer (4) is coolable by the coolant.

9. The microwave-driven plasma ion source (1, 201) according to claim 1, characterized in that, The microwave-driven plasma ion source (1, 201) includes a microwave resonator (11) for generating an electromagnetic field to inductively couple the plasma gas to the electromagnetic field so as to generate the plasma (101) from the plasma gas (100), wherein the microwave resonator (11) exhibits resonant behavior and generates the electromagnetic field when exposed to the microwaves generated by the microwave generator (10).

10. The microwave-driven plasma ion source (1, 201) according to claim 1, characterized in that, The microwave-driven plasma ion source (1, 201) includes a plasma gas source (8), wherein the plasma torch (20) includes a plasma gas inlet (23) for introducing the plasma gas (100) from the plasma gas source (8) into the interior (21) of the plasma torch (20), wherein the plasma gas (100) contains nitrogen at a content of 80 to 100 volume percentages.

11. The microwave-driven plasma ion source (1, 201) according to claim 1, characterized in that, The microwave-driven plasma ion source (1, 201) includes a plasma gas source (8), wherein the plasma torch (20) includes a plasma gas inlet (23) for introducing the plasma gas (100) from the plasma gas source (8) into the interior (21) of the plasma torch (20), wherein the plasma gas (100) contains argon at a content of 0.9 to 100 volume percentages.

12. The microwave-driven plasma ion source (1, 201) according to claim 11, characterized in that, The plasma gas (100) contains argon at a content of 0.95 to 100 volume percent.

13. A mass spectrometer (50, 60, 65) for mass analysis of samples, comprising: The microwave-driven plasma ion source (1, 201) according to claim 1 is used to ionize the sample into sample ions; as well as A mass analyzer (70, 170) for mass analysis of the sample ions, the mass analyzer (70, 170) having an ion inlet (71, 171) for introducing the sample ions from outside the mass analyzer (70, 170) into the interior (72, 172) of the mass analyzer (70, 170) for mass analysis of the sample ions; and the ion inlet (71, 171) having an aperture.

14. The mass spectrometer (50, 60, 65) according to claim 13, characterized in that, The mass analyzer (70, 170) is fluidly coupled to the microwave-driven plasma ion source (1, 201) to receive sample ions discharged substantially along the orientation direction (29, 229) of the microwave-driven plasma ion source (1, 201) from the shielding outlet (5) of the shielding layer (4), and thus receives the sample ions through the ion inlet (71, 171) for mass analysis, wherein the ion inlet (71, 171) is at least partially disposed within a volume extending from the torch outlet (22, 222) and pointing toward the orientation direction (29, 229) of the plasma torch, the cross-section of which is perpendicular to the orientation direction (29, 229) of the plasma torch and corresponds to the projection of the torch aperture onto a plane perpendicular to the orientation direction (29, 229) of the plasma torch.

15. The mass spectrometer (50, 60, 65) according to claim 14, characterized in that, The ion inlets (71, 171) are completely disposed within a volume extending from the torch outlet (22, 222) and pointing toward the orientation direction (29, 229) of the plasma torch, the cross-section of which is perpendicular to the orientation direction (29, 229) of the plasma torch and corresponds to the projection of the torch aperture onto a plane perpendicular to the orientation direction (29, 229) of the plasma torch.

16. The mass spectrometer (50, 60, 65) according to claim 13, characterized in that, The mass analyzers (70, 170) and the microwave-driven plasma ion sources (1, 201) are capable of moving relative to each other in a plane whose normal is tilted by a maximum of 20° relative to the orientation direction (29, 229) of the plasma torch.

17. The mass spectrometer (50, 60) according to claim 13, characterized in that, The mass analyzer (70) and the microwave-driven plasma ion source (1, 201) are capable of moving relative to each other along two mutually perpendicular axes.

18. The mass spectrometer (60) according to claim 16, characterized in that, The mass analyzers (70, 170) and the microwave-driven plasma ion sources (1, 201) are capable of moving relative to each other along three mutually perpendicular axes.

19. The mass spectrometer (50, 60) according to any one of claims 13 to 18, characterized in that, The mass analyzers (70, 170) and the microwave-driven plasma ion sources (1, 201) are capable of pivoting relative to each other about a pivot axis that is substantially perpendicular to the orientation direction (29, 229) of the plasma torch.

20. The mass spectrometer (60) according to claim 13, characterized in that, The mass analyzer (70) and the microwave-driven plasma ion source (1, 201) are capable of pivoting relative to each other about two pivot axes oriented substantially perpendicular to the orientation direction (29, 229) of the plasma torch.

Images