Transverse energy compensator for a spectrometer

Abstract

The invention relates to a transverse energy compensator (1) for a spectrometer (2), in particular of the MAC-E filter type, for pre-processing charged particles (A), wherein the transverse energy compensator (1) has a particle input (3) and a particle output (4), the transverse energy compensator (1) has a coil (5) for generating a magnetic field (6), the transverse energy compensator (1) has a drift tube (7) arranged in the magnetic field (6), wherein the drift tube (7) is arranged such that the charged particles (A) are moved from the particle input (2) through the drift tube (7) to the particle output (3), and a predefined and changeable potential (8) can be applied at the drift tube (7). The invention makes it possible to improve the energy resolution when measuring charged particles (A) without it being necessary to increase the dimensions or further reduce the magnetic field at the analysis level.

Description

[0001] Transverse energy compensator for a spectrometer

[0002] The present invention relates generally to the field of charged particle spectrometry, and in particular to techniques for the energy-resolved analysis of such particles using MAC-E filter spectrometers. Such spectrometers are used to analyze the kinetic energy of charged particles, with applications in electron and ion spectroscopy being of particular interest. MAC-E filter spectrometers are characterized by a combination of magnetic adiabatic collimation and electrostatic energy analysis, enabling high energy resolution with a large solid angle acceptance.

[0003] Spectrometers for measuring charged particles, particularly those of the MAC-E type, are known from the prior art. Such devices combine an inhomogeneous magnetic field with an electrostatic counterpotential to precisely analyze the kinetic energy of charged particles. First, the direction of the particle momentum is aligned along the magnetic field lines by adiabatic reduction of the magnetic field strength. The particles then pass through a region of minimal magnetic field strength, where they encounter an electrostatic potential that acts as an energy barrier. Only particles with sufficient longitudinal energy overcome this barrier and reach the detector. The region of the electrostatic barrier and the minimal magnetic field is also called the "analysis plane." The energy of the detected particles can thus be determined indirectly, thereby capturing an integral energy distribution.

[0004] A key advantage of these spectrometer types is their high solid angle acceptance. Since MAC-E filters typically exhibit an acceptance of nearly 2K, they can capture a large portion of the particle spectrum. This makes them particularly suitable for applications requiring high particle yield. Furthermore, they can achieve high energy resolution by selecting appropriate magnetic field profiles. The resulting relative resolution depends primarily on the ratio of the maximum to the minimum magnetic field along the particle trajectory. High resolution requires a small minimum magnetic field combined with a high entrance field, which in practice is achieved through a large spatial extent of the system. However, a disadvantage of conventional MAC-E filters is that high energy resolution necessitates a significant reduction of the magnetic field in the electrostatic potential range.Due to the conservation of magnetic flux, this typically entails a significant increase in the cross-sectional area in the region of minimum field strength. This leads to a considerable increase in the overall size of the apparatus, which not only increases the complexity of the equipment but also imposes limitations on its integration into existing experimental setups. Furthermore, a transverse energy, which cannot be completely suppressed, always remains in the analysis plane. Its magnitude depends on the particle's emission angle, its primary energy, and the ratio of the maximum to the minimum magnetic field along the particle's trajectory. This transverse energy is "missing" from the particle's ability to overcome the electrostatic potential, thus resulting in the finite energy resolution of the MAC-E filter.

[0005] Starting from this, the object of the present invention is to provide a way to improve the energy resolution when measuring charged particles without requiring an increase in dimensions or a further reduction of the magnetic field in the analysis plane.

[0006] This task is solved by the subject matter of the independent claims. Further details are found in the dependent claims.

[0007] According to the invention, a transverse energy compensator for a spectrometer, in particular of the type of a MAC-E filter, is provided for preprocessing charged particles (A), wherein the transverse energy compensator has a particle inlet and a particle outlet, the transverse energy compensator has a coil for generating a magnetic field, the transverse energy compensator comprises a drift tube arranged in the magnetic field, the drift tube being arranged such that the charged particles are moved from the particle inlet through the drift tube to the particle outlet, and a predetermined and variable potential can be applied to the drift tube. One aspect of the present invention relates to a transverse energy compensator for a spectrometer, in particular of the type of a MAC-E filter, for preprocessing charged particles.A transverse energy compensator can be understood, in particular, as a device positioned upstream of a spectrometer that serves to influence the initial energy conditions of charged particles in such a way that their transverse energy components are specifically modified to enable angle-independent analysis. A spectrometer of the MAC-E filter type is an energy-analyzing system in which charged particles are selected according to their energy by combining an inhomogeneous magnetic field with an electrostatic counter-potential. Preprocessing of charged particles describes measures taken before the actual energy analysis to compensate for systematic influences such as the dependence on emission angles and thus improve the energy resolution.

[0008] The transverse energy compensator is designed to have a particle inlet and a particle outlet. A particle inlet is the area where the charged particles enter the compensator unit, while the particle outlet is the area where the particles, after passing through the compensator, are transferred to the downstream spectrometer. This creates a defined transport path within the compensator, along which the particles can be selectively manipulated.

[0009] The transverse energy compensator is designed to include a coil for generating a magnetic field. A coil is an electrically conductive wire, such as a cylindrical winding, through which a magnetic field is generated when current flows. In this context, the magnetic field is the controllable field that influences the trajectory of the charged particles within the compensator. This allows the particles to be guided along defined field lines and enables controlled changes to their transverse energy components. One advantage is that the particles' motion remains adiabatic and their trajectory is stabilized by the magnetic field, allowing for undisturbed interaction with the time-controlled electrical potential within the drift tube.The transverse energy compensator comprises a drift tube positioned within the magnetic field. The drift tube is arranged such that the charged particles are moved from the particle inlet through the drift tube to the particle outlet. A drift tube is an elongated, electrically conductive structure, preferably cylindrical, through which the particles are guided in the axial direction. This creates a clearly defined potential space in which the particles can be accelerated or decelerated. An advantage is that the drift tube's orientation within the magnetic field allows the energy gain of the particles to be influenced as a function of their transit time through the tube, thereby achieving longitudinally energy-dependent changes in longitudinal energy. This compensates for any angle-dependent residual transverse energy that is "missing" from the longitudinal energy.

[0010] The drift tube is designed to allow for the application of both a predetermined and a variable potential. A predetermined potential is a fixed electrical voltage level, while a variable potential is one that changes over time, for example, in the form of a rising ramp. This allows the energy of the passing particles to be influenced depending on the specific time of their passage. One advantage is that particles with different starting angles and thus different flight times will receive different energy contributions from the electrical potential.This allows the resulting longitudinal energy at the entrance to the spectrometer to be modified so that the particles can overcome the electric potential of the downstream MAC-E filter largely independently of the starting angle, thereby achieving a significant improvement in energy resolution without having to change its size or magnetic field ratio.

[0011] A key aspect of the invention is that a voltage ramp is created by the variable potential, particularly by a uniform increase or decrease over time. A voltage ramp is a potential profile in which the voltage rises or falls linearly or approximately linearly from an initial value to a target value over a defined period of time. As charged particles traverse the drift tube, they encounter different voltage values ​​of the ramp, depending on their respective emission time and flight time. Particles with a shallower entry angle cross the drift tube faster than those with a large entry angle and therefore experience a lower energy gain.

[0012] One advantage of the voltage ramp is that it enables angle-dependent energy compensation, allowing particles with higher transverse energy to receive a correspondingly higher energy gain. This results in the longitudinal energy at the point of entry into a region of the spectrometer where the electric potential is at its maximum and the magnetic field at its minimum—the so-called analysis plane—exhibiting a nearly uniform level for all particles. The analysis plane serves as an energy selection threshold, determining whether a particle with its longitudinal energy can overcome the potential barrier and reach the detector. This significantly reduces the influence of the remaining transverse energy in the analysis plane and leads to an improvement in energy resolution without requiring further reduction of the magnetic field in the spectrometer region or an increase in the instrument's cross-sectional area.

[0013] According to a further embodiment of the invention, the coil comprises a cylindrical coil and the magnetic field is a solenoidal magnetic field. A cylindrical coil can be understood as a coil arrangement with a rotationally symmetrical coil geometry around a longitudinal axis, thereby generating a homogeneous magnetic field inside. A solenoidal magnetic field is a magnetic field with an approximately constant field distribution along the longitudinal axis within the coil. An advantage of this geometry is that the charged particles in the drift tube are guided within a stable, rectilinear field, thus ensuring uniform trajectory guidance. The solenoidal field enables adiabatic guidance of the particles along cyclotron paths within the magnetic field, which makes the change in the longitudinal energy of the particles controllable and is essential for the effectiveness of potential modulation for energy compensation.

[0014] A further embodiment of the invention provides that the first magnetic field has a magnetic field strength of, in particular, 50 mT to 5 T and is adaptable to the magnetic field strength of the second magnetic field of the MAC-E filter, which, depending on the mass and energy of the particles under investigation, also lies in the range of many mT to several Tesla. An advantage of this embodiment is that a sufficiently high magnetic field ensures that the adiabatic condition is met, even with small diameters of the drift tube. This allows for a compact design of the transverse energy compensator while maintaining stability of the particle trajectories, which in turn enables precise control of the energy absorption by the first potential.

[0015] According to the invention, a spectrometer system is further provided with a spectrometer, in particular of the type of a MAC-E filter, for measuring charged particles and a transverse energy compensator for preprocessing the charged particles, wherein the transverse energy compensator has a first particle input and a first particle output, the transverse energy compensator has a first coil for generating a first magnetic field, the transverse energy compensator comprises a drift tube arranged in the first magnetic field, wherein the drift tube is arranged such that the charged particles are moved from the first particle input through the drift tube to the first particle output, and a predetermined and variable first potential can be applied to the drift tube;and a second particle input and a second particle output, at least a second coil at the second particle input and a third coil at the second particle output for generating an inhomogeneous second magnetic field between the second particle input and the second particle output, an electrode structure configured to apply a second potential between the coils, a detector arranged at the second particle output for detecting the charged particles passing through the magnetic field, wherein the first particle output of the transverse energy compensator is arranged at the second particle input of the spectrometer.

[0016] One aspect of the present invention relates to a spectrometer, in particular of the type of a MAC-E filter, for measuring charged particles. A spectrometer can be understood as a device for measuring or analyzing the properties of particles or radiation, typically with respect to their energy, mass, or charge. A MAC-E filter is a specific type of spectrometer in which an inhomogeneous magnetic field and an electrostatic counter-potential are combined to determine the energy distribution of charged particles. Charged particles are electrically charged particles such as electrons or ions that can move under the influence of electromagnetic fields and whose kinetic energy is evaluated in spectrometry.

[0017] The spectrometer is designed to have a second particle inlet and a second particle outlet. A particle inlet can be understood as the region where charged particles enter the spectrometer, while the particle outlet refers to the region where they exit the spectrometer after passing through the analysis unit. This provides a defined trajectory for the particles, enabling reproducible analysis of their kinetic energy. An advantage is that the passage through the spectrometer is controlled, allowing for a clear mapping of the particle dynamics along the measurement path, which contributes to improved measurement accuracy.

[0018] It is further provided that at least a second coil is located at the second particle input and a third coil is located at the second particle output to generate an inhomogeneous second magnetic field between the second particle input and the second particle output. A coil, as defined in the present invention, is an electrical conductor loop or a coil system through which an electric current flows, thereby generating a magnetic field. An inhomogeneous magnetic field is a magnetic field with a location-dependent field strength. This results in magnetic guidance of the charged particles in the region between the input and output, whereby their transverse energy is largely converted into longitudinal energy up to the analysis plane of the spectrometer and then back into transverse energy.One advantage is that the particles move adiabatically along the magnetic field lines, homogenizing their momentum direction. This allows for high-resolution analysis of the total energy at the analysis level using the downstream electrostatic potential. This contributes to achieving very good energy resolution. Furthermore, an electrode structure is designed to apply a second potential between the coils. An electrode structure can be understood as an arrangement of conductive elements that generate a defined potential field when an electrical voltage is applied. A second potential, in this context, refers to an electrostatic counter-potential that acts as an energy barrier for the charged particles at the analysis level. This enables selective energy analysis, as only particles with sufficient longitudinal energy can overcome the potential barrier and be detected.One advantage is that the combination of an inhomogeneous magnetic field and a potential barrier makes precise spectrometry focused on the total energy possible, which directly contributes to improving energy resolution.

[0019] Furthermore, a detector is provided at the particle outlet to detect the particles passing through the electric potential. A detector is a device for registering and measuring the arriving particles, particularly with regard to their number, arrival time, or energy. This allows for the detection of the particles after they have passed through the spectrometer. One advantage is that the spatial arrangement of the detector at the particle outlet establishes a clear correlation between the arrival at the detector and the potential overcome, which improves the accuracy of the energy determination and thus increases the spectral resolution.

[0020] According to the invention, a transverse energy compensator is arranged upstream of the particle inlet for pre-processing the charged particles. The transverse energy compensator has a first particle inlet and a first particle outlet, with the first particle outlet of the transverse energy compensator being located at the second particle inlet of the spectrometer. A transverse energy compensator can be understood as a device for selectively influencing the kinetic parameters of the charged particles before they enter the actual spectrometer. This allows for adjustment of the energy distribution of the particles before they are subjected to energy analysis. Furthermore, the transverse energy compensator includes a first coil for generating a first magnetic field. The first coil is a coil element that generates a magnetic field within the transverse energy compensator.A first magnetic field refers to the magnetic field provided by the first coil, independent of the spectrometer's second magnetic field. This guides the charged particles within the transverse energy compensator in a defined magnetic field. The transverse energy compensator comprises a drift tube positioned within the first magnetic field. The drift tube is oriented such that the charged particles are moved from the first particle inlet through the drift tube to the first particle outlet. A drift tube is a conductive component, typically cylindrical, through which charged particles can be transported along a nearly electric field-free zone. This stabilizes the particles' trajectory within the transverse energy compensator and simultaneously allows for the controlled modification of the drift tube's electric potential.One advantage is that the particles can be guided through the drift tube in a precisely time-defined potential profile, which leads in particular to targeted accelerations or decelerations upon entering or exiting the drift tube. This allows for an angle-dependent adjustment of the particles' longitudinal energy without altering their transverse momentum components.

[0021] Finally, it is provided that a predetermined first potential can be applied to the drift tube. The first potential is a time-varying electrical potential that is generated at the drift tube.

[0022] A key aspect of the invention is that it allows the longitudinal energy of charged particles to be influenced during their transport through the transverse energy compensator. One advantage is that by selectively varying the first potential, the angle-dependent transverse energy can be compensated, so that the particles in the spectrometer's analysis plane exhibit a largely uniform longitudinal energy, regardless of the emission angle. This results in the electrostatic counterpotential in the MAC-E filter acting under comparable conditions for all particles, which directly contributes to improved energy resolution of the overall system without requiring an increase in the size of the spectrometer.

[0023] According to the invention, a method for operating a spectrometer is further provided, comprising the following process steps: a) supplying charged particles to the transverse energy compensator (i); b) setting the second potential; c) uniformly increasing or decreasing the first potential from an initial value to a target value; d) simultaneously measuring the charged particles passing through the second potential with the spectrometer; e) resetting the first potential to the initial value; f) repeating steps c) to e) multiple times for the set potential.

[0024] According to the invention, the predetermined first potential is variable. A predetermined potential can be understood as an electrical voltage applied to a drift tube in the transverse energy compensator region, the temporal profile of which can be specifically adjusted. A variable potential is a potential whose value is dynamically adjusted during operation. One advantage is that, by selectively varying the potential, the energy of the charged particles can be controlled as a function of their entry time into the drift tube.This allows for an almost angle-dependent compensation of the transverse energy largely independent of the entry time into the drift tube within the period in which the drift tube voltage is periodically changed and returned to the starting value, and leads to a more uniform longitudinal energy distribution at the entry into the MAC-E filter, which improves the energy resolution.

[0025] "Uniform increase or decrease" refers specifically to a uniform increase or decrease over time. This means, in particular, that the rise or fall is linear.

[0026] The uniform increase or decrease of the first potential preferably occurs over a period in the picosecond range, while the entire measurement, including repetition of the increase or decrease of the first potential, preferably takes place over a period of seconds to minutes. It is preferably provided that the first potential can be varied uniformly over time such that, for non-pulsed sources of charged particles, a time-squared component of the potential ramp is added to compensate for the different arrival times into the potential tube, since the charged particles already change their longitudinal energy and thus their velocity upon entering the potential tube. Preferably, the most suitable time-dependent potential profile depends on the various magnetic fields as well as the initial energy and mass of the charged particles under investigation.

[0027] Preferably, the variable potential lies in the range of -1000 V to +1000 V. Specifying a voltage range allows for the technical definition of an operating point for the system. One advantage is that, with a suitable voltage range, the energy difference for compensating the angle-dependent components of the transverse energy can be specifically selected, so that even at high starting angles an effective reduction of the remaining transverse energy is achieved.

[0028] A further preferred configuration is a variable first potential that is periodically almost linearly increasing when positive particles are to be analyzed, or decreasing when negative particles are to be analyzed. A periodically almost linearly increasing potential is a time-dependent voltage ramp with an approximately constant rate of increase that is repeated regularly. An advantage of this configuration is that different emission angles, due to their different transit times, interact with different potential height differences between the entry and exit points of the drift tube, thereby achieving angle-dependent energy compensation. This contributes to increasing the energy resolution without requiring modifications to the spectrometer's magnetic design.

[0029] According to a preferred embodiment of the invention, the method comprises the following further steps: g) changing the second potential; h) repeating steps c) to f) for the changed second potential. In this way, the measurement described above can be performed for a second potential that differs from the first, so that, in particular, larger energy intervals can also be spectroscopically measured.

[0030] In a further development of the invention, it is provided that the level of the first potential depends on the level of the second potential. The level of a potential denotes the absolute voltage value relative to a reference level. The dependency between the first and second potentials means that the electrical voltage at the drift tube is related to the counter-potential in the MAC-E filter. An advantage of this dependency is that, by precisely adjusting the potentials, optimal compensation of the transverse energy in the drift tube can be achieved, with the compensation level being precisely adapted to the threshold of the subsequent energy filter.

[0031] The plan is to first supply charged particles to the transverse energy compensator. Charged particles are electrically charged particles such as electrons or ions that can be influenced by electromagnetic fields. The transverse energy compensator is a device located upstream of the actual spectrometer, in which the charged particles are guided through a drift tube in a first magnetic field. Supplying charged particles to the transverse energy compensator can mean either a continuous feed into the drift tube or a targeted and synchronous feed into the drift tube.One advantage of this measure is that the particles enter the drift tube in a defined temporal relationship with the subsequent voltage ramp, which allows precise control of their energy absorption and thus targeted control of the longitudinal energy to improve the energy resolution in the spectrometer.

[0032] Furthermore, the procedure includes setting the spectrometer's second potential. This step can be performed before the first. The second potential is the electrostatic counter-potential in the analysis plane of the MAC-E filter, which acts as an energy barrier and defines which particles are detected. Setting this potential ensures that the energy analysis is referenced to a specific energy range. An advantage of this step is that the selectivity of the energy analysis can be precisely defined, enabling high spectral resolution and allowing for targeted calibration of the overall system.

[0033] Furthermore, the system is designed to increase or decrease the initial potential uniformly from a starting value to a target value. This initial potential is applied to the drift tube within the transverse energy compensator and is varied along the particle's path. The uniform increase or decrease of this potential results in a continuous, nearly linear voltage ramp that runs synchronously with the particles' passage through the drift tube. An advantage of this is that the energy gain experienced by the particles depends on their starting angle, as differently emitted particles encounter the rising potential ramp at different times.This allows the angle-dependent transverse energy to be compensated, so that all particles have a comparable longitudinal energy when entering the analysis plane, leading to a reduction in energy uncertainty and thus to an improvement in energy resolution.

[0034] In a parallel step, the charged particles passing through the second magnetic field are detected. Detection refers to the identification of the particles after they have overcome the electrostatic second potential. The second magnetic field is the inhomogeneous magnetic field between the particle input and output of the spectrometer. Parallel detection means that the number of detected particles is continuously recorded throughout the entire voltage ramp. One advantage is that continuous detection allows for a complete recording of the energy-dependent particle distribution without missing any individual time windows or energy intervals. Parallel detection ensures that the energy changes of the particles caused by the ramp are fully captured, enabling high-resolution spectral reconstruction.

[0035] After the linear increase or decrease of the first potential, the first potential is reset to its initial value. This reset refers to the return of the drift tube voltage to its initial state after the ramp has finished. An advantage of this is that the transverse energy compensator is returned to a defined initial state, thus ensuring a reproducible process for cyclic repetition. This reset minimizes unwanted effects caused by undesired gains or losses of longitudinal energies and ensures comparable initial conditions in each cycle.

[0036] The steps of increasing or decreasing the first potential, detecting the particles, and resetting the potential are repeated. The spectrometer's analysis potential, i.e., the second potential, remains constant, particularly for seconds or minutes, while the rapid voltage ramp at the transverse energy compensator, i.e., the first potential, is preferably traversed many tens of thousands of times per second. Repeating these steps allows for continuous spectral measurement with a constant system configuration. An advantage of this cyclical approach is that even low intensities can be detected with high accuracy through statistical averaging, while the system size remains compact because the angle-dependent compensation in each cycle provides improved energy resolution.Furthermore, repeated execution allows synchronization with periodic sources such as pulsed lasers, making the method compatible with existing experimental systems.

[0037] Preferably, after the first measurement cycle of a predetermined and set second potential, the second potential is changed so that the measurement via the voltage ramps is repeated for a modified second potential. In this way, different second potentials can be measured, with a plurality of voltage ramps being measured for each second potential.

[0038] According to a further development of the invention, the initial value and / or the target value of the first potential is dependent on the second potential. An initial value denotes the electrical voltage at which the ramp of the first potential begins, and a target value the voltage at which it ends. The second potential is the electrostatic counter-potential used in the spectrometer for energy analysis of the charged particles. The dependence between these potential values ​​means that the first potential is not chosen independently of the analysis potential, but rather is adapted to its level or gradient. An advantage of this approach is that the energy gain of the particles due to the voltage ramp of the drift tube can be related to the energy barrier potential that must subsequently be overcome.This allows for fine-tuning of the energy compensation depending on the spectrometer's filter properties, ensuring that particles with different emission angles pass through the spectrometer with comparable longitudinal energy. The energy resolution is improved without requiring more complex equipment or larger magnetic field gradients.

[0039] According to the invention, a spectrometer system as described above is used for electron and / or ion spectroscopy. "Use" refers to the targeted application of a technical object for a specific application. Electron spectroscopy is an analytical technique for determining the energy distributions of free or bound electrons, while ion spectroscopy is used to investigate charged ions. An advantage of the claimed use is that the configuration described in the preceding claims enables precise energy-resolved detection, even with large solid angle acceptance. Since many spectroscopic applications, particularly in the fields of surface analysis or plasma physics, rely on high energy resolution combined with high signal efficiency, the claimed use enables improved measurement accuracy without compromising acceptance or size.The angular dependence of the residual energy can be selectively suppressed, thereby improving the spectral sharpness and enabling a more accurate analysis of emission processes.

[0040] The invention will now be explained in more detail with reference to the drawings and a preferred embodiment.

[0041] The drawings show

[0042] Fig. 1 shows a spectrometer system with a transverse energy compensator according to a preferred embodiment of the invention in a schematic view; Fig. 2 shows a method according to a preferred embodiment of the invention in a schematic view.

[0043] Fig. 3a, b shows the resolution of an energy spectrum in comparison.

[0044] Fig. 4a, b compares the flight time of particles depending on their "excess energy".

[0045] Fig. 1 schematically shows a spectrometer system according to a preferred embodiment of the invention. The spectrometer system comprises, in particular, a spectrometer 2 of the type of a MAC-E filter and a transverse energy compensator 1 arranged upstream of it.

[0046] The transverse energy compensator 1 comprises a drift tube 7, which is arranged in a first magnetic field 6 of a first coil 5. A first potential 8 is applied to the drift tube 7. The charged particles A thus pass through the drift tube 7, acquire a velocity-dependent, additional longitudinal energy component, and are then presented to the MAC-E filter. Energy selection then takes place via the potential barrier of the second potential 15 of the spectrometer 2.

[0047] The spectrometer 2, of the MAC-E type, consists of a second coil 11 and a third coil 12. A second inhomogeneous magnetic field 13 is thus generated between the coils. A second electrical potential 15 is applied to the electrode structure 14, generating the electrostatic analysis potential in the analysis plane in the center of the MAC-E filter. The spectrometer 2 is configured such that the particle input 9 is located at the second coil 11 and the particle output 10 at the third coil 12. A transverse energy compensator 1 is arranged upstream of the spectrometer 2. The transverse energy compensator 1 comprises a first particle input 3 and a first particle output 4.The first particle output 4 is arranged at the second particle input 9, so that the charged particles A are moved from the first particle input 3 through the transverse energy compensator 1 to the first particle output 4, then through the MAC-E filter to the second particle output 10. Fig. 2 schematically shows a method according to a preferred embodiment of the invention, particularly with a continuous supply of particles.

[0048] Initially, the charged particles A are supplied to the transverse energy compensator 1, and the second potential 15, which determines the energy selection in the spectrometer 2, is set. These two steps can be performed in any order. During the measurement, for positively charged particles A, the first potential 8 at the drift tube 7 is increased uniformly, and in particular almost linearly, until a target value is reached. During the measurement of negatively charged particles A, the second potential 15 at the drift tube 7 is decreased correspondingly uniformly, and in particular almost linearly, until a target value is reached. The measurement is carried out continuously during this process. Once the target value is reached, the first potential 8 is reset to an initial value.Subsequently, the steps of the rising or falling first potential 8 are repeated with simultaneous measurement, so that a periodic almost linearly rising or falling electric potential 8 is applied to change the longitudinal energy of the charged particle A flying through the drift tube 7 so that it has an almost constant longitudinal energy in the analysis plane of the spectrometer, in particular the MAC-E filter, regardless of the starting angle of the charged particle A.

[0049] The second potential 15 remains constant, particularly for seconds or minutes, while the first potential is increased or decreased, and the voltage ramp is preferably traversed many tens of thousands of times per second. Repeating these steps allows for continuous spectral measurement with a constant system configuration. Only then is the second potential 15 changed, and the measurement or the aforementioned steps repeated.

[0050] Figures 3a and 3b show the energy resolution of the transmitted particles in direct comparison for a continuous particle source in integral mode. Figure 3a shows the energy spectrum of a MAC-E filter without a preceding transverse energy compensator. The energy resolution of the step-like transmission function of the width is obtained from

[0051] In the example shown, AE = 0.9 eV for electrons with an energy of E = 18600 eV. These have an isotopic angular distribution up to 50°. The magnetic field has minimum and maximum values ​​of = 0.0003 T and = 6.0 T. It is evident that in this example the area AE is wide.

[0052] Figure 3b shows the energy spectrum of a MAC-E filter with a preceding transverse energy compensator. A better possible energy resolution of the step-shaped transmission function is evident. This results from

[0053] In the example shown, E is TEC “0.15 eV for the same electron example from Fig. 3a. The energy resolution can thus be reduced many times over, leading to increased accuracy.”

[0054] Figures 4a and 4b refer to the application example of determining the flight time T of charged particles passing through the second potential as the difference between the start time and the arrival time at the detector. The flight time T depends on the "excess energy" E. surp ab. The measurement of the flight time T at a fixed energy threshold U ret allowed from E surp = E — qU retto directly determine the energy of the particles. Figure 4a shows the measurement of the flight time without a transverse energy compensator. The poor energy resolution is due to low excess energies resulting from the different angles (multiple graphs) of the particle source. If a transverse energy compensator is placed upstream of the MAC-E filter, the energy resolution is significantly improved, allowing for more accurate time-of-flight determination. The start time can be known, for example, by pulsed particle delivery, while the arrival time is typically measured by the particle detector downstream of the second particle output 10 of the MAC-E filter. Reference numeral list

[0055] Transverse energy compensator

[0056] Spectrometer first particle input first particle output first coil first magnetic field

[0057] Drift tube, first potential, second particle input, second particle output, second coil, third coil, second magnetic field

[0058] Electrode structure second potential charged particles

Claims

Patent claims 1. Transverse energy compensator (1) for a spectrometer (2), in particular of the type of a MAC-E filter, for preprocessing charged particles (A), wherein the transverse energy compensator (1) has a particle inlet (3) and a particle outlet (4), the transverse energy compensator (1) has a coil (5) for generating a magnetic field (6), the transverse energy compensator (1) comprises a drift tube (7) arranged in the magnetic field (6), wherein the drift tube (7) is arranged such that the charged particles (A) are moved from the particle inlet (2) through the drift tube (7) to the particle outlet (3), and a predetermined and variable potential (8) can be applied to the drift tube (7).

2. Transverse energy compensator (1) according to claim 1, wherein the coil (5) comprises a cylindrical coil and the magnetic field (6) is a solenoidal magnetic field.

3. Transverse energy compensator (1) according to claim 1 or 2, wherein the magnetic field (6) has a magnetic field strength of in particular 50 mT to 5 T.

4. Spectrometer system comprising a spectrometer (2), in particular of the type of a MAC-E filter, for measuring charged particles (A) and a transverse energy compensator (1) for preprocessing the charged particles (A), wherein the transverse energy compensator (1) has a first particle inlet (3) and a first particle outlet (4), the transverse energy compensator (1) has a first coil (5) for generating a first magnetic field (6), the transverse energy compensator (1) comprises a drift tube (7) arranged in the first magnetic field (6), wherein the drift tube (7) is arranged such that the charged particles (A) are moved from the first particle inlet (3) through the drift tube (7) to the first particle outlet (4), and a predetermined and variable first potential (8) can be applied to the drift tube (7); and a second particle input (9) and a second particle output (10), at least a second coil (11) at the second particle input (10) and a third coil (12) at the second particle output (10) for generating an inhomogeneous second magnetic field (13) between the second particle input (9) and the second particle output (10), an electrode structure (14) configured to apply a second potential (15) between the coils (11, 12), a detector arranged at the second particle output (10) for detecting the charged particles (A) passing through the magnetic field (13), wherein the first particle output (4) of the transverse energy compensator (1) is arranged at the second particle input (9) of the spectrometer (2).

5. Spectrometer system according to claim 4, wherein the first coil (5) comprises a cylindrical coil and the first magnetic field (6) is a solenoidal magnetic field.

6. Spectrometer system according to claim 4 or 5, wherein the level of the first potential (8) depends on the level of the second potential (15).

7. Method for operating a spectrometer system according to any one of claims 4 to 6, comprising the following method steps: a) supplying charged particles (A) to the transverse energy compensator (1); b) setting the second potential (15); c) increasing or decreasing the first potential (8) uniformly over time from an initial value to a target value; d) measuring the charged particles (A) passing through the second magnetic field (13) in parallel with the spectrometer (2); e) resetting the first potential (8) to the initial value; f) repeating steps c) to e) multiple times for the set second potential (15).

8. The method according to claim 7, comprising the following further method step: g) Changing the second potential (15); h) Repeating steps c) to f) for the changed second potential (15).

9. Method according to claim 7 or 8, wherein the initial value and / or the target value of the first potential (8) depends on the second potential (15).

10. Use of a transverse energy compensator (1) according to one of the claims 1 to 2 for a spectrometer system according to one of claims 3 to 6 for electron and / or ion spectroscopy.

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