Method and device for detecting electrically charged particles of a particle stream and system for analyzing ionized components of an analyte

Description

[0001] The present invention relates to a method and a device for detecting electrically charged particles of a particle stream extracted from a particle source and to a system for analyzing ionized components of an analyte using such a device.

[0002] Various state-of-the-art analysis methods utilize a stream of electrically charged particles extracted from a particle source. For example, inductively coupled plasma mass spectrometry (ICP-MS) is used to perform trace analysis. In this method, a plasma medium is generated in a plasma source by applying a high-frequency alternating field, into which a carrier medium is introduced. During measurement, the carrier medium carries an analyte, for example, particles of a solid generated by laser ablation. The components of the analyte, particularly individual atoms and / or their isotopes, are ionizable in the plasma and can be extracted from the plasma as an ion beam via pinhole diaphragms, so-called samplers or skimmer cones, and subsequently analyzed in a mass spectrometer.

[0003] The results of such a mass spectrometric analysis and / or their reliability depend on the plasma conditions in the plasma source. For example, it is known that the ratio of the number of detection signals of different trace elements to each other is temperature-independent at high plasma temperatures, whereas a temperature dependence of the relative ratios of the elements has been observed at low plasma temperatures.

[0004] US 2015 / 0235827 A1 discloses methods and systems for automatically tuning inductively coupled multimode plasma mass spectrometers (ICP-MS). A user enters data relating to a system optimization to be performed and including an identification of one or more selected operating modes in which the system is to be operated.

[0005] US 6,674,068 B1 discloses a time-of-flight mass spectrometer comprising an ion source, a time-of-flight mass spectrometer region through which the ion pulses emitted by the ion source move, an ion detector for detecting ion pulses that have traveled a certain distance through the region and have been dispersed into several ion pulses according to the flight speed, a time-of-flight measuring section for measuring the times required for the dispersed ion pulses to travel from the ion source to the ion detector, an intermediate ion detector mounted in the time-of-flight mass spectrometer region that detects the current values ​​of the dispersed ion pulses before reaching the ion detector, a measuring means for measuring the elapsed times of the dispersed ion pulses reaching the intermediate ion detector since leaving the ion source, means for predicting the time of flight,at which the dispersed ion pulses will reach the ion detector, based on the measurement of elapsed times since leaving the ion source, and a saturation prevention means for controlling the gain of the ion detector according to the current values ​​of the dispersed ion pulses detected by the intermediate ion detector and according to the predicted arrival times of the dispersed ion pulses at the ion detector in step with the arrival of the dispersed ion pulses, in order to prevent the dispersed ion pulses from saturating the ion detector.

[0006] US 2007 / 0045247 A1 discloses an inductively coupled plasma alignment device comprising a coil for generating an inductively coupled plasma in a gas, the coil having a first axis, a torch extending at least partially through the coil, the torch having a second axis, and an adjustment mechanism for adjusting the position of the torch with respect to the coil to change the relative configuration of the first and second axes. The position of the torch can be automatically adjusted based on an analyte signal detected by an associated spectrometer.

[0007] US 2006 / 097195 A1 discloses a method and apparatus for measuring a profile of an ion beam. The apparatus includes an array of beam current sensors, each generating a sensor signal in response to incident ions of the ion beam, a translation mechanism configured to translate the array of beam current sensors along a translation path relative to the ion beam, and a controller configured to acquire the sensor signals generated by the beam current sensors at a plurality of positions along the translation path, the acquired sensor signals being representative of a two-dimensional profile of the ion beam.

[0008] WO 87 / 07076 A1 discloses an apparatus for determining the ion dose and ion dose uniformity of an ion beam scanned across a target plane in response to scanning signals. The apparatus comprises a mask assembly for detecting the beam current at several different locations and providing a single beam current signal. The mask assembly includes a mask plate with measurement apertures and an annular Faraday cup aligned with the apertures for measuring the beam current. The beam current signal is integrated over time to determine the ion dose. A demultiplexer separates the beam current signal into separate signal components in response to x- and y-scanning signals. Ion dose uniformity is determined by comparing the separate, time-integrated signal components with an average value of the signal component.

[0009] It is an object of the invention to improve the detection of electrically charged particles of a particle stream extracted from a particle source, in particular to facilitate a targeted analysis of properties of the particle source and / or the particle stream.

[0010] This object is achieved by a method and a device for detecting electrically charged particles of a particle stream extracted from a particle source and a system for analyzing ionized components of an analyte with such a device according to the independent claims.

[0011] A method according to the invention relates to the detection of electrically charged particles of a particle stream extracted from a particle source, in particular an ion stream extracted from a plasma of a plasma source or an electron beam extracted from an electron source, comprising the steps of: detecting at least one measurement signal generated by a measuring probe, wherein the measuring probe is arranged and / or designed in the particle stream extracted from the particle source such that at least some of the particles of the particle stream strike the measuring probe and / or pass the measuring probe and the measurement signal generated in this way is characterized by the number of particles striking or passing, and storing the at least one detected measurement signal.

[0012] A device according to the invention for detecting electrically charged particles of a particle stream extracted from a particle source, in particular an electron beam extracted from a plasma of a plasma source or an electron beam extracted from an electron source, comprises a measuring probe which is arranged in or on the particle stream extracted from the particle source and / or is designed such that at least a portion of particles of the particle stream strike the measuring probe and / or pass through the measuring probe. The measuring probe is preferably configured to generate at least one measurement signal characterized by the number of particles striking or passing through. The device further comprises a storage device configured to store the measurement signal generated by the measuring probe.

[0013] A system according to the invention for analyzing ionized components of an analyte comprises a plasma source for generating an inductively coupled plasma from which an ion stream can be extracted. The system also comprises a device according to the invention and an analysis device, in particular a mass spectrometer, which is arranged in the ion stream such that ions of the ion stream can be analyzed.

[0014] One aspect of the invention is based on the finding that the particle stream exiting the particle source contains information about the properties of the particle source and / or the particle stream. An analysis of the particle stream, in particular the detection of a particle density, can provide a measure of various physical properties of the particle source, in particular a plasma temperature, a charge carrier density, a particle density, a degree of ionization and / or the spatial distribution of the particles in the particle stream. This applies in particular during stable operation of the particle source, in which, for example, a plasma of a plasma source is transitioning or has transitioned to a stationary state and the physical properties have a spatial distribution characteristic of this stationary state.This can, for example, be essentially determined by a power supplied by means of a high-frequency alternating field, a plasma, a carrier medium and / or their inflow rates.

[0015] The particle stream emerging from the particle source, in particular its profile and / or progression, can be characterized by suitable measured variables, such as an electrical potential, an electrical current, an electrical capacitance, and / or the like. This allows properties of the particle stream and / or the particle source to be reliably determined, in particular calculated or at least estimated. This enables, among other things, targeted control of the particle source and / or a change or adjustment of operating parameters of the particle source. In particular, the power fed into a plasma source, a plasma and / or carrier medium used, and / or their inflow rates by means of the high-frequency alternating field can be adapted to desired plasma conditions.

[0016] Alternatively or additionally, the determined properties of the particle stream and / or the particle source enable a definition of a state of the particle stream and / or the particle source, so that, for example, measurements of an analyte using the particle stream in this defined state become comparable and / or reproducible. In addition, this also enables testing or calibration of the particle source or a system comprising a particle source and / or an analysis device.

[0017] Overall, the invention enables a reliable detection of electrically charged particles of a particle stream extracted from a particle source, in particular a precise analysis of the properties of the particle stream and / or the particle source.

[0018] The detected electrically charged particles of the particle stream preferably correspond to the ions of a plasma medium generated in a plasma of a plasma source, for example argon ions.

[0019] In a preferred embodiment, at least one property of the particle source is determined based on the at least one stored measurement signal. Preferably, the intensity of the particle stream and / or the spatial distribution of the particles in the particle stream is determined based on the measurement signal, in particular a voltage signal. This allows properties of the particle stream and / or the particle source, for example, the temperature, charge carrier density, particle density, and / or the degree of ionization of a plasma source or a plasma generated by the plasma source, to be reliably and precisely determined.

[0020] In a further preferred embodiment, the at least one property of the particle source is determined based on a comparison of the stored measurement signal with at least one stored reference signal. The reference signal preferably characterizes a defined state of the particle source with known properties. If the measurement signal deviates from the reference signal, an actual state or corresponding properties of the particle stream and / or the particle source are preferably inferred, for example estimated, based on an extrapolation, based on a difference between the measurement signal and the reference signal on the basis of the defined state of the particle source with known properties. The reference signal can be present in a storage device, for example a database, for comparison with the stored measurement signal.

[0021] By taking the reference signal into account, at least one property of the particle source and / or the particle stream can be determined particularly reliably and precisely.

[0022] In a further preferred embodiment, the method further comprises the following steps: determining the at least one reference signal by detecting at least one measurement signal in a defined state of the particle source with known properties or by calculating a parameterized model of the particle source and / or the extracted particle stream; and storing the at least one determined reference signal. The parameters of the model can relate to the type of particles provided by the particle source and / or their properties, for example their charge, mass, and the like. These steps are preferably carried out before detecting the at least one measurement signal. This allows the measurement signal or the measuring probe to be calibrated easily and reliably.

[0023] In a further preferred embodiment, at least one of the following signals is generated based on the at least one determined property of the particle source: a control signal for controlling the particle source; a maintenance signal relating to a recommendation or a need for maintenance of the particle source; and / or an indication signal relating to the determined property of the particle source.

[0024] Using a control signal, the particle source or particle stream can be specifically transferred to a predetermined state, i.e., predetermined properties of the particle source or particle stream can be adjusted. This makes it possible, in particular, to adjust the particle source or particle stream, for example, by positioning extraction devices (samplers or skimmer cones) designed to extract electrically charged particles from the particle source, controlling ion-optical lenses of an analysis device, and / or regulating inflow rates of a gas flow of a plasma and / or carrier medium, and / or regulating a power supply to the particle source, for example, a high-frequency alternating field for generating a plasma.In particular, the control signal can be used to adjust the plasma conditions in a plasma source, for example the plasma temperature, the charge carrier density, the particle density and / or the degree of ionization.

[0025] The particle source or particle stream can be controlled automatically based on the control signal, for example, by a control device, in particular a control unit. Alternatively, the control signal can be output to a user of the particle source or particle stream, so that the user can control the particle source or particle stream based on the control signal, in particular manually.

[0026] A maintenance signal can be used to signal to a user of the particle source or particle stream that maintenance, such as adjustment and / or repair or replacement of one or more components of the particle source, is necessary to ensure reliable use of the particle source or particle stream. Alternatively or additionally, the maintenance signal can also be transmitted to a manufacturer or distributor of the particle source or a system for analyzing components of an analyte, for example, via an internet service. This ensures the reliable operation of the particle source over the long term.

[0027] Using an indication signal, a user of the particle source or particle stream can be informed about the properties of the particle source or particle stream. If necessary, the user can use the indication signal to adapt their use of the particle source or particle stream to the state of the particle source or particle stream, i.e., its properties, or take these into account during use. In particular, the indication signal enables reproducible use of the particle source or particle stream. Preferably, the user can use the indication signal to generate a control signal or initiate its generation.

[0028] In a further preferred embodiment, the particle source is controlled using the control signal in such a way that the difference between at least one newly acquired measurement signal and at least one stored reference signal is reduced, in particular compared to the difference between the stored measurement signal and the at least one stored reference signal. The reference signal preferably corresponds to a target value, and the measurement signal or the renewed measurement signal preferably corresponds to an actual value, wherein the actual value can be regulated to the target value within the framework of a control loop. This enables simple and reliable adaptation of the actual or current state of the particle source or the particle stream with corresponding properties to a defined and / or predetermined state in which the particle source and / or the particle stream has defined and / or predetermined properties.

[0029] In a further preferred embodiment, the method is repeated iteratively until the at least one newly acquired measurement signal substantially corresponds to the at least one stored reference signal. Preferably, in each iteration step of the method, an evaluation is performed to determine how much the newly acquired measurement signal has changed compared to the stored reference signal by controlling the particle source using the control signal in the current iteration step, and the control signal for the next iteration step is generated based on the evaluation. This enables a reliable transition of the current state of the particle source or the particle stream to the defined and / or predetermined state.

[0030] In a further preferred embodiment, the control signal is used to adjust a position of the particle source and / or the position of at least one extraction device extracting the particles provided by the particle source relative to the measuring probe. Alternatively or additionally, the control signal is used to adjust the number of particles provided by the particle source and / or extracted from the particle source per unit of time and / or to adjust a spatial distribution of the particles extracted from the particle source within the particle stream.

[0031] Preferably, one or more positioning devices, for example actuators, which are operatively connected to the particle source and / or one or more extraction devices, can be actuated based on the control signal, so that the particle source and / or the extraction devices can be moved relative to the measuring probe. This allows, in particular, the propagation direction and / or the profile of the particle stream to be changed, in particular adjusted.

[0032] Alternatively or additionally, the control signal can be used to control the inflow rate of the gas flow of the plasma and / or carrier medium or the phase of an alternating field for generating a plasma in a plasma source and / or an inflow rate of a plasma medium, for example, argon. This allows properties of the plasma or the plasma source and / or an ion current extracted from the plasma source, in particular the spatial distribution of particles in the plasma of the plasma source, the degree of ionization in the plasma source, and / or the temperature in the plasma source, to be reliably and precisely adjusted.

[0033] The adjustment of the particle source or particle stream described above can advantageously be carried out without the use and consumption of an analyte or a carrier medium. Ions of a plasma medium, such as argon ions, generated in the plasma of the particle source configured as a plasma source, preferably serve as electrically charged particles of the particle stream.

[0034] In a further preferred embodiment, the analysis device, in particular the mass spectrometer, and / or the particle source, in particular the plasma source, has an ion-optical lens designed as a measuring probe of the device. This makes it possible to use one or more components of an existing system with a particle source and / or an analysis device for detecting electrically charged particles in the particle stream extracted from the particle source. In particular, such a system can be easily expanded to include a device for detecting electrically charged particles in the particle stream extracted from the particle source.

[0035] Further features, advantages, and possible applications of the invention will become apparent from the following description taken in conjunction with the figures, in which the same reference numerals are used throughout for the same or corresponding elements of the invention. They show, at least partially schematically: Fig. 1 shows an example of a system for analyzing components of an analyte; Fig. 2 shows an example of a measuring probe; Fig. 3 shows a first example of a measurement signal curve; and Fig. 4 shows a second example of measurement signal curves.

[0036] In Figure 1An example of a system 100 for analyzing components of an analyte is shown. The system 100 comprises a particle source 1, an extraction device 2, an analysis device 5, and a device 3 for detecting electrically charged particles with a measuring probe 4 and a control device 7. For a better understanding of directional information, a coordinate system is shown next to the particle source 1, which has an x-axis, a y-axis, and a z-axis.

[0037] The particle source 1 is configured to provide electrically charged particles. The particle source 1 can, for example, be designed as a plasma source which is configured to inductively generate a plasma by means of a high-frequency alternating field. The electrically charged particles can be extracted from the particle source 1 in the form of a particle stream 6 by the extraction device 2, for example a sampler and / or skimmer cone. The particle stream 6 contains, for example, ions of a plasma medium supplied to the plasma source 1 to generate the plasma, such as argon ions. Properties of the particle stream 6, for example the strength or intensity of the particle stream 6, i.e. the number of electrically charged particles extracted per unit of time, depend on the conditions, in particular plasma conditions, at the location of the particle extraction, i.e. the state of the particle source 1.In addition, the properties of the particle stream 6 may also depend on the extraction device 2, in particular its position relative to the particle source 1.

[0038] The electrically charged particles of the particle stream 6 move in a propagation direction along the z-axis toward the analysis device 5, which can, for example, analyze ions of an analyte supplied to the plasma source using mass spectrometry. The particle stream 6 passes through the measuring probe 4, which in the present figure is designed, for example, as a pinhole. A central portion of the particle stream 6 passes through a central opening 11 of the pinhole. However, since the particle stream 6 is divergent, a portion of the electrically charged particles, in particular an edge stream of the particle stream 6, strikes the pinhole. The electrical charge collected by the measuring probe 4 can, for example, be detected as an electrical voltage by the control device 7 or can be conducted to the control device 7 and measured as an electrical current.

[0039] The control device 7 has a storage device 8, which is configured to store the measurement signals M generated by the measuring probe 4, i.e., information corresponding to the electrical voltages or electrical currents. One or more stored measurement signals M can then be (further) processed, in particular analyzed, by the control device 7, in particular as a series of measurements.

[0040] Based on the one or more stored measurement signals M, the control device 7 can determine properties of the particle stream 6 and / or the particle source 1 and preferably also of the extraction device 2. The properties of the particle source 1 relate, for example, to the state of the particle source 1 or the plasma in the particle source 1, such as a temperature, an ion density, and / or a spatial position, in particular relative to the extraction device 2, the measuring probe 4, and / or the analysis device 5.

[0041] The properties of the particle stream 6 relate, for example, to the spatial distribution of the electrically charged particles in the particle stream, ie the current profile, in particular along the x-axis and / or the y-axis, and / or the intensity of the particle stream 6, ie the number of electrically charged particles passing through a surface perpendicular to the propagation direction per unit time.

[0042] The properties of the extraction device 2 relate, for example, to the diameter of a passage opening of a pinhole, in particular a so-called sampler or so-called skimmer cone, on which particles of the particle stream 6 can settle, so that the diameter of the passage opening is reduced and fewer particles can be extracted from the particle source 1.

[0043] In order to determine a spatial distribution of the electrically charged particles in the particle stream 6 in a plane perpendicular to the propagation direction of the particle stream 6, i.e. in the xy-plane, the pinhole can be moved into various measuring positions in the xy-plane, for example along the x-axis. For this purpose, the measuring probe 4 is coupled to a positioning device 9a, for example one or more actuators, which can be controlled by the control device 7. In each of the measuring positions, a measuring signal M generated by the pinhole can then be recorded and stored in the storage device 8, wherein the stored measuring signals M allow conclusions to be drawn about the spatial distribution of the particles in the particle stream 6. The course of the measuring signals M along the x-axis or the y-axis is described in detail below in connection with Figure 2 explained.

[0044] Based on the determined properties of particle source 1, extraction device 2 and / or particle stream 6, the control device 7 can control the particle source 1, the extraction device 2 and / or the analysis device 5.

[0045] The control device 7 can, for example, generate a control signal S for controlling the particle source 1, by means of which a power supplied to the particle source 1, an inflow rate of plasma medium and / or an inflow rate of carrier medium of the analyte can be regulated.

[0046] Alternatively or additionally, the control device 7 can control a positioning device 9b coupled to the particle source 1 such that the particle source 1 can be aligned relative to the extraction device 2, the measuring probe 4 and / or the analysis device 5, in particular along the x-axis and / or the y-axis.

[0047] If, for example, it is determined on the basis of the one or more stored measurement signals M that the particle stream 6 does not hit the analysis device 5, in particular an inlet opening of the analysis device 5, or only hits it with insufficient accuracy, the particle source 1 can be positioned by means of the positioning device 9b controlled by the control device 7, in particular along the x-axis and / or the y-axis, in such a way that the particle stream 6 extracted from the particle source 1 hits the analysis device 5, in particular its inlet opening, in a centered manner.

[0048] Alternatively or additionally, the extraction device 2, which is coupled to a positioning device 9c controllable by the control device 7, can also be moved along the x-axis and / or along the y-axis, taking into account the stored measurement signals M, in order, for example, to extract particles from the particle source 1 in such a way that the particle stream 6 strikes the analysis device 5, in particular its inlet opening, in a centered manner.

[0049] Preferably, the particle source 1 is moved relative to the measuring probe 4, wherein the measuring probe 4 and the extraction device 2, for example a respective extraction aperture, are rigidly connected to one another, whereby an optimal positioning of the particle source 1, for example in relation to the analysis device 5, and thus of the entire measuring arrangement can be achieved based on the evaluation of the measuring signal M.

[0050] Alternatively, the particle source 1 and the extraction device 2, for example, a respective extraction aperture, can be rigidly connected to each other. Here, too, optimal positioning of the particle source 1, for example, relative to the analysis device 5, and thus of the entire measurement arrangement, can be achieved by evaluating the measurement signal M and a corresponding movement of the particle source 1.

[0051] Likewise, the analysis device 5, in particular one or more magnetic fields of the analysis device 5 for guiding the particle stream 6 within the analysis device 5, can be controlled taking into account the stored measurement signals M using the control signal S generated by the control device 7, so that components of an analyte contained in the particle stream 6 can be reliably analyzed.

[0052] Preferably, the storage device 8 is also configured to store one or more reference signals with which the measurement signals M generated by the measuring probe 4 can be compared. Such reference signals relate, for example, to a predetermined, in particular optimized, positioning of the particle source 1 and / or the extraction device 2 relative to the analysis device 5. If the measurement signal(s) M generated do not match the reference signal(s) or do not match them sufficiently accurately, the control device 7 can generate a corresponding control signal S for controlling the particle source 1, the analysis device 5 and / or the positioning device 9b, 9c coupled to the particle source 1 or the extraction device 2, such that one or more measurement signals M generated again by the measuring probe 4 do not deviate from the reference signal(s) or deviate only to a lesser extent.

[0053] For this purpose, the control device 7 can have a control unit 10 which can establish a predetermined state of the particle source 1 or the system 100, for example a certain strength or intensity of the particle stream 6 and / or its orientation or propagation direction relative to the analysis device 5, based on the comparison of the (re)acquired measurement signals with the stored reference signals.

[0054] Alternatively or additionally, the control device 7 can also be configured to generate a maintenance signal and / or an indication signal and to transmit it to a service center or to output it to a user of the system 100.

[0055] Such a maintenance signal can, for example, be output or transmitted to a service center if it is determined from the stored measurement signals, in particular from a comparison of the stored measurement signals with the stored reference signals, that the particle source needs maintenance, for example, readjustment, and / or components of the particle source or the extraction device 2 need to be replaced or repaired. This case can arise, for example, if the number of particles made available in the particle source 1 per unit of time or the strength of the particle stream 6 is (permanently) selected to be too high, so that a skimmer cone of the extraction device 2 is damaged, or if an opening of the skimmer cone becomes clogged over time at low strengths of the particle stream 6.

[0056] The indication signal preferably provides the user with information about the state of the particle source 1, the particle stream 6, or the system 100. For example, the indication signal may relate to the orientation of the particle source 1, the extraction device 2, and / or the analysis device 5 relative to one another. Based on the indication signal, the user can then change the relative orientation of these components of the system 100, for example, to enable a reliable analysis of components of an analyte contained in the particle stream 6 in the analysis device 5.

[0057] Figure 2 shows an example of a measuring probe 4, which is designed as a sector electrode with three sectors 4a, 4b, 4c forming a central opening 11. The measuring probe 4 is preferably made of a material that has good electrical conductivity and is resistant to impinging, electrically charged particles, in particular ions.

[0058] Electrically charged particles of a particle stream 6 passing through the sector electrode have a direction in the plane of the sector electrode, in particular along the Figure 1 x- and y-axis, a substantially Gaussian distribution. In Figure 2 the distribution along the x-axis is shown as an example, with the maximum of the distribution, ie the location of the highest particle density within the particle stream 6 in the x- and y-direction, on the z-axis, along which the particle stream 6 spreads (see Figure 1), lies. Since a spatial extent σ, for example the half-width of the distribution, of the particle stream 6 is preferably larger than the central opening 11 of the sector electrode, a small part of particles from the edge region of the particle stream 6 strikes the three sectors 4a, 4b, 4c even when the z-axis, ie the propagation direction of the particle stream 6, is aligned with a center point of the central opening 11 (or vice versa).

[0059] The electrical charge deposited by the impact of the electrically charged particles of the particle stream 6 on the sectors 4a, 4b, 4c can flow away via the resistors Ra, Rb, Rc assigned to the sectors 4a, 4b, 4c and can be detected as a voltage signal by one of the voltage measuring units Ua, Ub, Uc.

[0060] If the propagation direction of the particle stream 6 or the z-axis shifts relative to the center of the central opening 11, an increased number of particles from the particle stream 6 impinge on one of the sectors 4a, 4b, 4c, so that the corresponding voltage measuring unit Ua, Ub, Uc detects an increased voltage signal. This allows the direction of the shift of the z-axis or the propagation direction of the particle stream 6, particularly along the x- and / or y-axis, relative to the center of the central opening 11 to be determined.

[0061] Alternatively, the sector electrode may also have fewer or more than three, in particular two or four, sectors.

[0062] In a preferred embodiment, the measuring probe 4 can also be designed as a so-called iris electrode (not shown), which has a central opening 11 with an adjustable diameter. This allows the sensitivity of the measuring probe 4, in particular the number of particles of the particle beam 6 impinging on the iris electrode, to be regulated.

[0063] In another preferred embodiment, the measuring electrode 4 can also be designed as a so-called corona electrode (not shown), in which several sectors are formed from metal tips arranged radially around the central opening 11. The charge deposited on the metal tips can be discharged individually or in groups, and corresponding voltage signals can be determined.

[0064] Figure 3shows a first example of a curve V of a measurement signal M along an x-axis. The measurement signal M was generated at various measurement positions along the x-axis by a measuring probe designed as a ring-shaped electrode through which a particle stream of electrically charged particles flows. The x-axis extends perpendicular to the direction of flight of the particles, i.e., the propagation direction of the particle stream along the z-axis (see Figure 1 ).

[0065] The course V of the measurement signal M, for example a voltage signal, allows conclusions to be drawn both about the distribution of the particles within the particle stream and about the position of the center of the particle beam relative to a given position x = 0 of the measuring probe.

[0066] To record the curve V of the measurement signal M, the measuring probe is moved along the x-axis into different measuring positions so that in each measuring position a different proportion of particles from the particle stream strikes the measuring probe. The minimum M min of the curve V corresponds to the center of the particle stream. This measuring signal M = M min is recorded when the particle stream essentially passes through the center of the ring-shaped electrode and only particles from an edge area of ​​the particle stream strike the measuring probe (see Figure 2 ), ie the measuring probe has been moved along the x-axis so far that the center of the particle stream lies in the center of a central opening of the ring-shaped electrode.

[0067] The minimum M min lies along the x-axis between two maximums M max , where the measurement signal M = M max is recorded when particles from the center of the particle stream hit the ring-shaped electrode.

[0068] Based on the determination of the minimum M min lying between the maxima M max and the position of the minimum M min relative to the predetermined position x = 0 of the annular electrode, a control signal can be generated, for example, by means of which a particle source and / or an extraction device is controlled, in particular moved along the x-axis, in such a way that the particle stream passes centrally through the annular electrode, ie the minimum M min is at x = 0. Alternatively, the annular electrode can also be aligned in such a way that the particle stream passes centrally through the annular electrode, ie the minimum M min is at x = 0.

[0069] Preferably, the alignment of the particle stream can also be based on a comparison of one or more measurement signals M with one or more stored reference signals (not shown). For this purpose, the reference signal(s) is / are recorded when it is ensured that the particle stream passes centrally through the annular electrode.

[0070] The spatial distance between the measurement positions along the x-axis is preferably between 0.1 mm and 1 mm. In a preferred embodiment, the curve V for aligning the particle source or the extraction device relative to the measuring probe, in particular to a predetermined position of the measuring probe, is determined more than once. In particular, during a second or subsequent determination of the curve V, the spatial distance between the measurement positions along the x-axis is selected to be smaller, in particular between 0.05 mm and 0.1 mm.

[0071] Analogous to the Figure 3The curve V of the measuring signal M along an x-axis shown can also be the curve of the measuring signal M along a y-axis perpendicular to the x-axis (see Figure 1 ) and the orientation of the particle source or particle stream along the y-axis can be controlled accordingly. When determining the profile V of the measurement signal M along the x- or y-axis, the position of the measuring probe on the y- or x-axis is kept constant. Preferably, the position of the measuring probe on the y- or x-axis is selected as the position of the respective minimum M min on the y- or x-axis.

[0072] Figure 4shows a second example of curves U of a measurement signal M along an x-axis as a function of second measurement positions along a z-axis. For each curve, the measurement signal M was generated at various first measurement positions along the x-axis by a measuring probe designed as a ring-shaped electrode through which a particle stream of electrically charged particles flows. The x-axis extends perpendicular to the direction of flight of the particles, i.e. the propagation direction of the particle stream along the z-axis (see Figure 1 ).

[0073] In the example, the ring-shaped electrode is aligned with the minimum M min of the curves U, so that the minimum M min is at x = 0.

[0074] The curves U of the measurement signal M shown, in particular the shape of the curves U and the relative depth of the minima M min , i.e. the differences between the values ​​of the measurement signal M at the location of the minima M min and a different value of the measurement signal M that is characteristic of the curves U, for example a mean value, are characteristic of a state of a particle source from which the particle stream was extracted. The curves U of the measurement signal M shown are, for example, characteristic of a thermal state of a plasma of a particle source designed as a plasma source, in particular of the charge carrier density distribution within the plasma.

[0075] The state of the particle source can be determined by comparing the curves U of the measurement signal M with a reference signal, in particular one or more curves of the reference signal. For this purpose, the reference signal, in particular the one or more curves of the reference signal, is determined in a predetermined, i.e., known or defined, state of the particle source, in which the particle source is operated, for example, at a predetermined power and / or a plasma or carrier medium of an analyte is introduced into the particle source at a predetermined inflow rate.

[0076] By changing the operating parameters of the particle source, for example the aforementioned power supply and / or the inflow rates, the state of the particle source can be changed in such a way that the difference between the measurement signal M or the curves U of the measurement signal M and the reference signal or the curves of the reference signal is reduced and the current state of the particle source is thereby adapted to the predetermined state.

[0077] The determination of Figure 4 The curves U of the measurement signal M shown, the comparison of the measurement signal M or the curves U of the measurement signal M with the reference signal or the curves of the reference signal and the change of the operating parameters can be repeated iteratively until the particle source has been transferred to the specified state, in particular to a state optimal for the use of the particle source.

[0078] If the particle source is operated for a longer period of time, particles contained in the particle stream, in particular ions of an analyte contained in the particle stream, may precipitate at openings of the extraction device, for example a sampler or a skimmer cone, i.e., an aperture, so that the transmissivity of the extraction device decreases. In a further embodiment, the measurement signal M can therefore preferably also be recorded as a function of time and compared with a reference value, which preferably corresponds to the measurement signal M recorded at the beginning, in order to identify changes in the intensity of the particle stream, i.e., the number of electrically charged particles extracted from the particle source per unit time.Preferably, when a predetermined measurement signal threshold value is reached or undershot, which corresponds, for example, to a transmission loss of 20% or more, a maintenance signal and / or an indication signal can be generated, which indicates the need for maintenance, in particular cleaning, of the particle source or the extraction device. Alternatively or additionally, based on a rate of change of the detected measurement signal M, in particular with respect to the reference signal, a period of time after which the measurement signal threshold value is expected to be reached or undershot can be estimated and, if necessary, output to a user. This allows measurements to be ended in a timely manner or their end or interruptions can be planned, so that low transmissions and the associated loss of data quality can be avoided during subsequent measurement operations.

[0079] The devices and methods described above can preferably be operated or applied in the context of any type of particle stream containing electrically charged particles. Such particle streams occur, for example, in particle accelerators, ion sources, extraterrestrial measurements, and / or ion propulsion systems, which can be monitored and / or controlled by the devices and / or methods described above. List of reference symbols

[0080] 1 Particle source 2 Extraction device 3 Device for detecting electrically charged particles 4 Measuring probe 4a, 4b, 4c Sectors 5 Analysis device 6 Particle stream 7 Control device 8 Storage device 9a, 9b, 9c Positioning devices 10 Control unit 11 Central opening Ra, Rb, Rc Resistors Ua, Ub, Uc Voltage measuring units V Measurement signal curve UV Measurement signal curve MMeasurement signal M min Minimum M max Maximum S Control signal

Claims

1. A method of detecting electrically charged particles of a particle stream (6) extracted from a particle source (1) by means of an extraction device (2), in particular an ion stream extracted from a plasma of a plasma source by means of an extraction device (2), wherein the electrically charged particles of the particle stream (6) move, in a direction of propagation (z), towards an analysing device (5) which can analyse ions of an analyte by mass spectroscopy, which analyte is supplied to the plasma source, wherein the particle stream (6) passes a measuring probe (4) which is constructed as an ion optical lens of the analysing device (5) and / or of the particle source (1), as a sector electrode which has two or more sectors (4a, 4b, 4c) which form a central opening (11), as an iris electrode which has a central opening (11) with an adjustable diameter, or as a corona electrode in which a plurality of sectors are formed from metal tips which are arranged radially around a central opening (11), wherein the method comprises the following steps: - detecting measurement signals (M) generated by the measuring probe (4), wherein the measuring probe (4) is arranged in the particle stream (6) extracted from the particle source (1) and / or constructed in such a way that a portion of particles of the particle stream (6) impinges on the measuring probe (4) and the measurement signal (M) generated thereby is characterised by the number of impinging particles, wherein the measuring probe (4) is moved to different measurement positions in an x-y plane perpendicular to the direction of propagation (z) of the particle stream (6); - storing the measurement signal (M) generated and detected by the measuring probe (4) in each of the measuring positions; - determining properties of the particle stream (6) on the basis of the stored measurement signals (M), wherein the properties of the particle stream (6) relate to a spatial distribution of the electrically charged particles in the particle stream (6) along an x-axis and / or a y-axis extending perpendicularly to the direction of propagation (z) of the particle stream (6); and - controlling the particle source (1), the extraction device (2) and / or the analysing device (5) on the basis of the properties of the particle stream (6) that have been determined.

2. The method according to claim 1, wherein at least one property of the particle source (1) is determined on the basis of the stored measurement signals (M).

3. The method according to claim 2, wherein the at least one property of the particle source (M) is determined on the basis of a comparison of the stored measurement signals (M) with at least one stored reference signal.

4. The method according to claim 3, further comprising the following steps: - determining the at least one reference signal by detecting at least one measurement signal (M) in a defined state of the particle source (1) with known properties or by calculating a parameterised model of the particle source (1) and / or of the extracted particle stream (6); and - storing the at least one reference signal that has been determined.

5. The method according to any one of claims 2 to 4, wherein at least one of the following signals is generated on the basis of the at least one property of the particle source (1) that has been determined: - a control signal for controlling the particle source (1); - a maintenance signal which relates to a recommendation or a need for maintenance of the particle source (1); and / or - a notification signal which relates to the property of the particle source (1) that has been determined.

6. The method according to claim 5, wherein the particle source (1) is controlled on the basis of the control signal in such a way that the difference between at least one newly detected measurement signal (M) and at least one stored reference signal is reduced.

7. The method according to claim 6, wherein the method is repeated iteratively until the at least one newly detected measurement signal (M) substantially corresponds to the at least one stored reference signal.

8. The method according to any one of claims 5 to 7, wherein, on the basis of the control signal, - a position of the particle source (1) and / or the position of at least one extraction device (2) that extracts the particles that are provided by the particle source (1) is adjusted relative to the measuring probe (4); and / or - the number of particles that are provided by the particle source (1) per unit of time and / or that are extracted from the particle source (1) per unit of time is adjusted; and / or - a spatial distribution of the particles that are being extracted from the particle source (1) is adjusted within the particle stream (6).

9. A system for the analysis of ionised components of an analyte, wherein the system comprises: - a particle source (1) which is set up to provide electrically charged particles, - a device (3) for detecting electrically charged particles of a particle stream (6) which have been extracted from the particle source (1) by means of an extraction device (2), in particular an ion stream which has been extracted from a plasma of a plasma source by means of an extraction device (2), and - an analysing device (5), in particular a mass spectrometer, which is arranged in the ion stream and which is set up to analyse ions of the ion stream of an analyte supplied to the particle source (1), in particular the plasma source, by mass spectroscopy, wherein the electrically charged particles of the particle stream (6) move towards the analysing device (5) in a direction of propagation (z), wherein the analysing device (5) comprises: - a measuring probe (4) which the particle stream (6) extracted from the particle source (1) can pass, and which is arranged in or on the particle stream (6) extracted from the particle source (1) and / or is constructed in such a way that a portion of the particles of the particle stream (6) impinge on the measuring probe (4), and which is set up to generate measurement signals (M) that are characterised by the number of impinging particles, wherein the measuring probe (4) is constructed as an ion-optical lens of the analysing device (5) and / or of the particle source (1), as a sector electrode which has two or more sectors (4a, 4b, 4c) which form a central opening (11), as an iris electrode which has a central opening (11) with an adjustable diameter, or as a corona electrode in which a plurality of sectors are formed from metal tips which are arranged radially around a central opening (11); - a storage device (8) which is set up to store the measurement signals (M) which have been generated by the measuring probe (4); - a positioning device (9a) to which the measuring probe (4) is coupled; - a control device (7) for the control of the positioning device (9a) in such a way that the measuring probe (4) is moved to different measuring positions in an x-y plane perpendicular to the direction of propagation (z) of the particle stream (6), wherein the measurement signal (M) generated by the measuring probe (4) in each of the measuring positions is detected and stored in the storage device (8), the determination of properties of the particle stream (6) on the basis of the stored measurement signals (M), wherein the properties of the particle stream (6) relate to a spatial distribution of the electrically charged particles in the particle stream (6) along an x-axis and / or y-axis which extends perpendicular to the direction of propagation (z) of the particle stream (6), and the control of the particle source (1), the extraction device (2) and / or the analysing device (5) on the basis of the properties of the particle stream (6) that have been determined.

10. The system according to claim 9, wherein the particle source (1) is constructed as a plasma source for generating an inductively coupled plasma from which the ion stream can be extracted.