Method for generating and / or detecting magnetization, magnetometer and spectrometer

Abstract

This invention provides a spectroscopic apparatus capable of achieving particularly high measurement accuracy using pulse excitation signals generated by a voltage-controlled oscillator. [Solution] The present invention provides a method for supplying a second magnetic field to a sample position by exciting an induction assembly with an excitation signal, wherein the excitation signal is periodically switched between an excitation period in which the operating frequency has a sample-specific resonant frequency and an idle period in which the operating frequency has an idle frequency different from the resonant frequency, and the operating phase of the excitation signal is matched to the excitation reference phase of an excitation reference signal separately from the excitation signal when the operating frequency is switched from the idle frequency to the resonant frequency, the excitation signal is generated by a primary voltage-controlled oscillator, the excitation reference signal is generated by a first secondary voltage-controlled oscillator, and the matching of the operating phase to the excitation reference phase is performed by injection-synchronizing the primary voltage-controlled oscillator with the first secondary voltage-controlled oscillator.

Description

[Technical Field]

[0001] The present invention, according to the preamble of claim 1, relates in particular to a method for generating and / or detecting the magnetization of a sample at a sample location for the purpose of inspecting the sample by electron spin resonance spectroscopy or measuring a first magnetic field acting on the sample at the sample location.

[0002] Furthermore, according to the preamble of claim 13, the present invention relates to a magnetometer that measures a first magnetic field by generating and / or detecting the magnetization of a sample at a sample position, comprising an induction assembly and a control device, more particularly to a magnetometer based on nuclear magnetic resonance or a magnetometer based on electron spin resonance.

[0003] In addition, according to the preamble of claim 15, the present invention relates to a spectroscopic apparatus for inspecting a sample at a sample location, particularly an electron spin resonance spectrometer or a nuclear magnetic resonance spectrometer, comprising a device for generating a first magnetic field at the sample location, an induction assembly, and a control device. [Background technology]

[0004] Magnetic field sensors, or magnetometers, are used in many technical applications. They detect and measure magnetic fields, making it possible to obtain information about the magnetic environment.

[0005] Magnetic field sensors play a crucial role in medical technology. In particular, in magnetic resonance imaging (MRI), for example, they are used to generate detailed images of the inside of the body by measuring the magnetic field used for imaging with extremely high precision, determining and correcting for non-uniformity in this magnetic field.

[0006] Magnetic field sensors are also applied to electron spin resonance (ESR) spectroscopy. Also known as EPR (electron paramagnetic resonance spectroscopy), it is particularly used for radical measurement in food and medical samples (e.g., blood samples, pharmaceuticals). In electron spin resonance spectroscopy, a sample in a statically homogeneous, statically heterogeneous, or dynamic (pulsed heterogeneous) magnetic field (hereinafter referred to as the "first magnetic field"), usually called B0, is typically exposed to an additional high-frequency alternating electromagnetic field (hereinafter referred to as the "second magnetic field"), usually called B1. The coupling of these additional alternating fields induces transitions between energy levels of discrete spin states of the sample's atomic nuclei (NMR) and / or electrons (ESR, DNP, ENDOR). This results in a detectable absorption process within the alternating field. From the detected absorption process, various aspects of material analysis information about the sample can be determined. Therefore, electron spin resonance spectroscopy is a powerful technique that utilizes the spins of unpaired electrons within molecules as nanoscale probes to obtain information about the chemical structure and composition of a sample through slight changes in resonance frequency. The sample may be a liquid, solid, or gas. In particular, when investigating reaction kinetics or the sequence / changes of biological or chemical processes, even fluctuations at short time intervals can directly affect the quality of the measurement results, thus requiring extremely fast and highly accurate magnetic field measurement and control.

[0007] A similar technique is nuclear magnetic resonance (NMR) spectroscopy. This method can be applied to samples that have a "net nuclear spin" because the atomic nucleus has an odd number of nucleons.

[0008] For further technical background information regarding ESR and NMR, please refer to, for example, Patent Document 1.

[0009] In recent years, various concepts have been disclosed regarding oscillator-based CMOS integrated ESR detectors ("EPR / ESR-on-a-chip") that support various fundamental frequencies up to 146 GHz. For example, in a publication cited in Non-Patent Document 1 in 2016, a voltage-controlled oscillator (VCO) in the form of an electron spin resonance (ESR) sensor was proposed.

[0010] A more compact, cost-effective, and high-performance system overall can be provided, in particular, by using a voltage-controlled LC oscillator to generate the second magnetic field B1. While the corresponding VCO-based B1 source has many advantages, including the possibility of inductively detecting spin magnetization during excitation pulses, it suffers from the disadvantage of a low threshold for the minimum oscillation current in the inductor due to the finite quality factor of the built-in LC resonator. Because the VCO's tank inductor is directly coupled to the spin assembly, there is no means to switch the B1 field on / off as needed, and VCO-based pulse excitation signals require switching the VCO operating frequency to the sample-specific resonant frequency.

[0011] However, switching the operating frequency leads to a loss of phase information between consecutive excitation pulses or excitation periods. This loss of coherence makes it more difficult to evaluate the sample's response signal and significantly reduces measurement accuracy.

[0012] To address the aforementioned coherence problem, a control loop for correcting the phase of the excitation signal is proposed in a publication cited in Non-Patent Document 2. However, the proposed technique is relatively complex, and further improvements in measurement accuracy are needed. This is because phase stabilization is desirable to be performed in picoseconds, and the bandwidth required for a phase-locked loop (PLL) is not easily achievable from a technical standpoint. Consequently, the delay during phase matching can still cause significant coherence loss, which negatively impacts the accuracy and sensitivity of the measurement. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] DE 10 2016 102 025 A1 [Non-patent literature]

[0014] [Non-Patent Document 1] Handwerker, J. et al. "A 14 GHz battery-operated point-of-care ESR spectrometer based on a 0.13 μm CMOS ASIC", IEEE International Solid-State Circuits Conference (ISSCC), pp. 476-477 [Non-Patent Document 2] M. Hassan et. al., "Towards single-cell pulsed EPR using VCO-based EPR-on-a-chip detectors", Frequenz, vol. 76, no. 11-12, pp. 699-717, Sept. 2022 [Summary of the Invention] [Problems to be Solved by the Invention]

[0015] Based on known prior art, an object of the present invention is to provide a method for generating and / or detecting magnetization of a sample, which can achieve particularly high measurement accuracy, preferably using a pulse excitation signal generated by a voltage-controlled oscillator.

[0016] Another object of the present invention is to provide a magnetometer that can achieve particularly high measurement accuracy, preferably using a pulse excitation signal generated by a voltage-controlled oscillator.

[0017] Finally, an object of the present invention is also to provide a spectroscopic apparatus that can achieve particularly high measurement accuracy, preferably using a pulse excitation signal generated by a voltage-controlled oscillator. [Means for Solving the Problems]

[0018] The object is achieved by a method having the features described in claim 1. For the magnetometer, the object is achieved by the features of claim 13, and for the spectroscopic apparatus, the object is achieved by the features of claim 15.

[0019] The dependent claims and the features described below relate to advantageous embodiments and modifications of the present invention.

[0020] A method is provided for generating and / or detecting the magnetization of a sample at a sample location, by exciting an induction assembly with an excitation signal, and supplying a second magnetic field to the sample location.

[0021] The method according to the present invention is particularly advantageous for spectroscopic examination of a sample (for example, by electron spin resonance spectroscopy or nuclear magnetic resonance spectroscopy) and for measuring an external magnetic field acting on a sample at the sample location (hereinafter referred to as the "first magnetic field").

[0022] According to the present invention, the excitation signal is periodically switched between an excitation period in which the operating frequency of the excitation signal is the sample-specific resonant frequency, and an idle period in which the operating frequency of the excitation signal is an idle frequency different from the resonant frequency.

[0023] Therefore, during the excitation period of the excitation signal, it is possible to generate an "excitation pulse" that is time-separated from the subsequent excitation pulse by the subsequent idle period of the excitation signal. In the present invention, "excitation pulse" means an electrical signal supplied to the induction assembly that is functionally suitable for generating a second magnetic field. In particular, the excitation pulse can have a sufficiently large amplitude and an appropriate frequency to appropriately deflect the magnetization of the sample from its initial or equilibrium state.

[0024] It is possible to set the time interval between all directly consecutive excitation pulses to be the same. However, in principle, it is also possible to set different time intervals between at least two consecutive excitation pulses.

[0025] Preferably (but not necessarily), the induction assembly is positioned and oriented such that the second magnetic field at the sample position is at least substantially orthogonal to the first magnetic field. This is because, in conventional ESR, only the orthogonal component of the second magnetic field provides the deflection corresponding to the magnetization of the sample. Thus, the second magnetic field can have at least one component that is orthogonal to the first magnetic field.

[0026] The inductive assembly can be of any design advantageously suited to supplying a second magnetic field in the above applications. In particular, the inductive assembly may include one or more inductive elements (e.g., “plate” or planar inductive elements formed from a metallic material, or inductive elements formed from coiled wires).

[0027] Preferably, the sample location is positioned in the near field of the induction assembly. However, if appropriate, the sample location may also be positioned in the far field of the induction assembly.

[0028] The first magnetic field can preferably be a static or quasi-static magnetic field.

[0029] Solids, gases, and / or liquids can be considered as samples. Liquid samples can be fixed, for example, in a glass capillary on or inside a circuit component (using CMOS technology, for example). When the frequency of the first magnetic field is low, up to the so-called X-band (approximately 10 GHz), the coil of the induction assembly can also be implemented as a volume coil into which a capillary containing the liquid sample can be introduced. This method (or corresponding apparatus) can also be optionally implemented inside the liquid, gas, or solid being measured, for example, to detect phase transitions or transitions in the state of matter.

[0030] It should be noted that, in principle, any number of excitation pulses or excitation periods can be set in this invention, but at least two consecutive excitation pulses or excitation periods can be set. Generally, measurement accuracy improves by increasing the number of excitation pulses / excitation periods, or the corresponding number of measurements. Therefore, it may be necessary to weigh measurement duration and accuracy depending on the application.

[0031] The excitation pulse or excitation signal during the excitation period (and optionally, the excitation signal during the idle period) can preferably be a periodic signal, such as a sinusoidal signal. In particular, a square wave signal can be supplied as the envelope or envelope curve of the excitation signal, but other waveforms, such as a Gaussian curve, can also be suitable as the envelope. The periodic signal of the excitation signal can, in principle, be any desired signal and does not necessarily have to be a sinusoidal wave. However, the configuration of using a square wave signal as the envelope and combining it with a sinusoidal signal is the simplest implementation method in terms of technology and is generally sufficient, and has been demonstrated to be particularly suitable for the intended application.

[0032] In the present invention, the pulse duration of each excitation pulse is arbitrary. However, it is desirable that the excitation pulse includes at least one period of the periodic signal described above, preferably at least two, three, for example, four, five or more periods (although in principle, the excitation pulse may include only a portion of the period of the periodic signal).

[0033] It is desirable that the pulse durations of consecutive excitation pulses be the same. However, in principle (depending on the experiment and application), it is also possible to have different pulse durations between at least two consecutive excitation pulses. The use of phase-coherent excitation pulses with displacement spacing is advantageous, for example, in the measurement of intramolecular distances (so-called PELDOR or DEER spectroscopy).

[0034] The present invention matches the operating phase of the excitation signal to the excitation reference phase of an excitation reference signal separate from the excitation signal, at least when switching the operating frequency from the idle frequency to the resonant frequency (however, as described later, this matching may also occur at other points in time, such as when switching from excitation to measurement).

[0035] Preferably, the excitation reference signal is generated continuously during the process.

[0036] In other words, individual excitation pulses (and / or readout pulses, as described later) can be configured to be generated from individual time intervals of a common continuous reference signal. Therefore, the periodic signal of the reference signal is preferably generated continuously and used solely to match the operating phase of the excitation signals. As a result, phase coherence of all excitation and / or readout pulses, and even phase matching if necessary or desired, can be guaranteed using technically simple means.

[0037] Accordingly, the proposed invention solves the problem of phase information loss when switching the excitation signal for the B1 magnetic field between two consecutive excitation pulses by, at least during the excitation pulse, matching the operating phase of the excitation signal to the phase of the excitation reference signal which is continuously progressing or operating.

[0038] As an advantageous method, in the context of the present invention, the excitation pulse (and optionally, the readout pulse described below) can be made phase-coherent or in-phase. In the context of the present invention, “in-phase progression” means that each subsequent excitation or readout pulse begins at the phase position that the preceding excitation or readout pulse would have been at at the same time if it had not been interrupted. In the context of the present invention, “phase-coherent progression” means, in particular, that each subsequent excitation or readout pulse is in-phase coherent with the preceding pulse, regardless of whether the phase of the excitation pulse is changed (e.g., intentionally switched).

[0039] The proposed method allows for arbitrary selection of the time interval between individual excitation or readout pulses. This increases the flexibility of the method and can be used, for example, to significantly increase the measurement speed. Because the excitation and / or readout pulses proceed in phase coherently, the evaluation of the sample response signal is simplified, and measurement accuracy can be improved.

[0040] The excitation signal can, in principle, be supplied in any desired manner. However, in a particularly advantageous development of the present invention, the excitation signal can be configured to be generated by a primary voltage-controlled oscillator (VCO).

[0041] Preferably, the primary voltage-controlled oscillator is a voltage-controlled oscillator based on an LC resonant circuit. However, in principle, the resonant circuit can be realized in any way and is particularly suitable for applications where an LC VCO is generally expected.

[0042] According to one advanced form of the present invention, the operating phase of the excitation signal can be matched to the readout reference phase of a continuously generated readout reference signal, separately from the excitation signal, when switching the operating frequency from the resonant frequency to the idle frequency.

[0043] Preferably, the readout reference signal is different from the excitation reference signal.

[0044] Therefore, in the context of the present invention, if the excitation signal is switched between two consecutive idle periods as needed, it is also possible to prevent phase loss by preferably matching the operating phase of the excitation signal during the idle period to the phase of a reference signal that is further progressing or operating continuously.

[0045] It is also possible to set the time interval between directly consecutive excitation pulses (i.e., the readout duration) to be the same in each case. However, in principle (although not very desirable), it is also possible to set the readout duration to be variable.

[0046] According to one advanced version of the present invention, the excitation reference signal can be generated by a first secondary voltage-controlled oscillator, and / or the readout reference signal can be generated by a second secondary voltage-controlled oscillator.

[0047] Preferably, but not necessarily, the secondary voltage-controlled oscillator can again be an LC-based VCO.

[0048] Therefore, the primary voltage-controlled oscillator can be connected to the first and / or second secondary voltage-controlled oscillators by "injection synchronization" in a particularly advantageous manner for the purpose of matching the operating phase to their respective references. The "injection synchronization" process for voltage-controlled oscillators is known in the literature and makes it possible to match the phase in an extremely short time (only a few picoseconds).

[0049] It should be emphasized that the phases of the excitation reference signal and / or the readout reference signal can be adjusted or switched as needed.

[0050] In order to enable excitation and / or readout pulses of different phases as desired, in one advanced form of the present invention, the first secondary voltage-controlled oscillator and / or the second secondary voltage-controlled oscillator can be realized as a voltage-controlled polyphase oscillator.

[0051] Preferably, a multiplexer can be used to select from different output signals of a multiphase oscillator that are out of phase with respect to each other, as needed.

[0052] In particular, a multiphase oscillator can supply two, three, four, five, or six or more different output signals that are out of phase with each other (for example, if there are four output signals, they are out of phase by 90° with each other), and can be selected from them as needed to match the operating phase of the excitation signal.

[0053] In one advanced form of the present invention, the operating phase can be matched to the excitation reference phase and / or the readout reference phase by injection synchronization between the primary voltage-controlled oscillator and the first secondary voltage-controlled oscillator and / or the second secondary voltage-controlled oscillator, respectively.

[0054] However, the agreement between the operating phase and the reference phase (i.e., preferably, but not necessarily, an approximation to a perfect correspondence) does not necessarily have to be achieved by injection synchronization and can also be achieved by alternative technical implementations in the context of the present invention.

[0055] In one advantageous evolution of the present invention, a primary voltage-controlled oscillator can be configured to receive a first input signal for generating a resonant frequency during the excitation period and a second input signal for generating an idle frequency during the idle period.

[0056] In one advanced form of the present invention, at least two, preferably all, of the directly consecutive excitation periods can be configured to proceed in phase coherently with respect to each other. A similar configuration can be applied to any idle or readout period as needed.

[0057] In one advantageous evolution of the present invention, the resonant frequency can be configured to increase by at least twice, preferably at least 1.5 times, and particularly preferably at least 1.05 times, the idle frequency. For example, a bandwidth of at least 100 MHz may be sufficient to cover the ESR spectrum.

[0058] In one advantageous evolution of the present invention, the induction assembly can be excited without interruption by the excitation signal.

[0059] Therefore, preferably, the excitation signal is not switched on or off. For this reason, it is preferable to switch only the operating frequency in order to supply time-interval excitation pulses. This advantageously avoids the long stabilization process of the associated oscillator.

[0060] Preferably, during the idle period of the excitation signal, the induction assembly is used as a sensor element for detecting the electromagnetic response signal of the sample. Various methods for this are already known, and further background should be consulted in the relevant technical literature. Thus, the idle period of the excitation signal is also called the "readout period." The excitation signal can optionally supply "readout pulses" during the idle period that are suitable for reading out the response signal of the sample.

[0061] Accordingly, in one advantageous evolution of the present invention, the system can be configured to detect the sample's response signal by an induction assembly during the idle period of the excitation signal and to evaluate it by a control device.

[0062] The control device can be implemented as a microprocessor. Alternatively, any other device for implementing the control device can be provided, such as one or more discrete electrical components arranged on a printed circuit board, a programmable logic controller (PLC), an application-specific integrated circuit (ASIC), or other programmable circuits, such as a field-programmable gate array (FPGA), a programmable logic array (PLA), and / or a commercially available computer.

[0063] Preferably, the control device is a circuit component of an integrated circuit.

[0064] In one advanced form of the present invention, the operating amplitude of the excitation signal can be reduced to preferably at least 50%, particularly preferably at least 20%, and more preferably at least 10% during the idle period relative to the excitation period.

[0065] As an advantageous method, the proposed principle can be extended by switching the amplitude of the oscillation or excitation signal between pulse excitation (i.e., the VCO operating frequency at resonance) and subsequent detection (i.e., the VCO operating frequency outside of resonance) in order to increase excitation efficiency or optimize detection sensitivity.

[0066] The present invention also relates to a magnetometer that measures a first magnetic field by generating and / or detecting the magnetization of a sample at a sample location, the magnetometer comprising an induction assembly and a control device configured to excite the induction assembly with an excitation signal to supply a second magnetic field at the sample location.

[0067] This magnetometer can be, in particular, a nuclear magnetic resonance magnetometer (NMR magnetometer) or an electron spin resonance magnetometer (ESR magnetometer).

[0068] It should be noted here that the sample and / or sample position do not necessarily have to be part of the magnetometer. The sample and / or sample position can be independent of the magnetometer. However, preferably, the sample and / or sample position can be a component of the magnetometer. A similar configuration applies to the spectrometer described later.

[0069] The sample location preferably includes means for fixing and storing the sample.

[0070] According to the present invention, in a magnetometer, the excitation signal is configured to periodically switch between an excitation period in which the operating frequency of the excitation signal is the sample-specific resonant frequency and an idle period in which the operating frequency of the excitation signal is an idle frequency different from the resonant frequency. At least when switching the operating frequency of the excitation signal from the idle frequency to the resonant frequency, the operating phase of the excitation signal is matched to, or at least approximated to, the excitation reference phase of an excitation reference signal that is generated separately from the excitation signal, preferably continuously.

[0071] The proposed excitation technique enables not only highly accurate magnetic field measurements but also significantly faster magnetic field measurements compared to known magnetometers.

[0072] According to one advanced form of the present invention, it is possible to arrange the induction assembly and the control device on a common integrated circuit.

[0073] Preferably, the sample position and / or the sample can also be placed on a common integrated circuit. As a result, a magnetometer that is entirely based on an integrated circuit can preferably be provided.

[0074] Therefore, chip-based ESR or NMR magnetometers can be advantageously provided.

[0075] Preferably, by integrating the entire electronic circuit, optionally the sample position, and the sample onto or on a single miniature chip, it becomes possible to integrate the sensor directly into the magnetic field of an MRI system, for example. This makes it possible for the first time to perform substantially continuous magnetic field measurements while the MRI system is in operation. Measuring the magnetic field of the MRI system in real time minimizes motion artifacts and generates much higher-resolution MRI images, improving the overall medical image. Furthermore, faster image formation improves not only patient convenience but also diagnostic efficiency.

[0076] Accordingly, the present invention also relates to an MRI system equipped with a magnetometer according to the embodiments described above and below. The magnetometer can be used in an MRI system to improve image formation as described above.

[0077] The present invention also relates to a spectroscopic apparatus for inspecting a sample at a sample location, the spectroscopic apparatus comprising a device for generating a first magnetic field at the sample location, an induction assembly, and a control device configured to excite the induction assembly with an excitation signal to supply a second magnetic field at the sample location.

[0078] This spectroscopic device is preferably an ESR spectrometer or an NMR spectrometer.

[0079] The device that generates the first magnetic field can be designed, in particular, to supply a static (or quasi-static) first magnetic field having a predetermined direction and intensity at the sample location. The device that generates the first magnetic field can be realized, for example, by a superconducting magnet or electromagnet or a permanent magnet of any desired embodiment.

[0080] The first magnetic field is preferably static and corresponds to the aforementioned magnetic field B0, and is used to magnetize a sample suitable for magnetization. The strength of the first magnetic field is, in principle, arbitrary, as long as the frequency of the excitation B1 magnetic field ("second magnetic field") is selected based on the resonance conditions of the sample or the so-called Larmor frequency.

[0081] According to the present invention, the excitation signal periodically switches between an excitation period in which the operating frequency of the excitation signal is the sample-specific resonant frequency and an idle period in which the operating frequency of the excitation signal is an idle frequency different from the resonant frequency. At least when switching the operating frequency of the excitation signal from the idle frequency to the resonant frequency, the operating phase of the excitation signal is matched to, or at least approximated to, the excitation reference phase of a continuously generated excitation reference signal, separately from the excitation signal.

[0082] The spectroscopic apparatus may be equipped with an evaluation circuit that processes the output voltage of the induction assembly. This evaluation circuit preferably comprises demodulation means, analog-to-digital conversion, and / or digital data processing means. Corresponding evaluation circuit switches suitable for evaluating the output signal of a sample are known in principle.

[0083] The evaluation circuit may be configured to determine the magnetization of the sample and the spin concentrations of the individual spectral components to be identified therefrom.

[0084] The present invention enables particularly fast and highly accurate magnetic field measurements in ESR applications, for example. As mentioned above, further advantageous applications of the method according to the present invention include medical technologies (e.g., MRI systems).

[0085] Features described in relation to one of the subjects of the present invention, specifically the method, magnetometer, MRI system, and spectrometer according to the present invention, are also advantageously implementable for other subjects of the present invention. Similarly, advantages identified in relation to one of the subjects of the present invention can be understood in relation to other subjects of the present invention.

[0086] It should be noted here that the terms “connected” or “connected” as used herein and in the patent claims may refer to either a direct electrical connection of the described component or an indirect electrical connection of the described component (i.e., a connection via further electrical wiring or electronic components such as resistors, inductors, and / or capacitors). On the other hand, the terms “attached” or “contacted” usually refer to a direct connection of the described component.

[0087] It should be further emphasized that the method steps do not necessarily have to be performed in the order they are first described or mentioned in the specification or claims. For example, individual method steps or groups of method steps are interchangeable unless technically excluded. Method steps can also be combined with each other, divided into separate intermediate steps, or intermediate steps can be added. Furthermore, the methods according to the present invention are not necessarily exhaustively described by the method steps and can be extended with further method steps that are not mentioned.

[0088] Furthermore, it should be noted that terms such as "include," "possess," and "equip" do not exclude other features or steps. Similarly, terms like "one" and "it," which indicate steps or features in the singular form, do not exclude multiple features or steps. The reverse is also true.

[0089] However, in pure embodiments, it is also possible to define the features introduced in the present invention by terms such as “includes,” “has,” and “equipped with,” so as to constitute an exhaustive enumeration. Thus, in the context of the present invention, an enumeration of one or more features can be considered to stand on its own, for example, for each claim. For example, the present invention may consist only of the features defined in claim 1.

[0090] Labels such as "first" and "second" are primarily used to distinguish the characteristics of each apparatus or method, and are not necessarily intended to indicate that the characteristics are interdependent or related to one another.

[0091] It should be further emphasized that the values ​​and parameters described herein include deviations and variations of ±10%, preferably ±5%, more preferably ±1%, and most preferably ±0.1% or less of the respective stated values ​​and parameters, provided that these deviations are not actually excluded in the implementation of the invention. The designation of a range by start and end values ​​includes all values ​​and some thereof included in the respective range, particularly the start value, the end value, and their respective mean values.

[0092] Exemplary embodiments of the present invention will be described in detail below with reference to the drawings.

[0093] Each drawing shows a preferred exemplary embodiment illustrating individual features of the present invention in combination with one another. Features of one exemplary embodiment can be implemented independently of other features of the same exemplary embodiment, and thus, those skilled in the art can easily combine them with features of other exemplary embodiments to form further useful combinations or partial combinations.

[0094] In the drawings, functionally identical elements are given the same reference symbol. [Brief explanation of the drawing]

[0095] [Figure 1] This shows a magnetometer and spectrometer according to one exemplary embodiment of the present invention. [Figure 2] Figure 1 shows an example of excitation signals for a magnetometer or spectrometer. [Figure 3] An exemplary embodiment of the method according to the present invention is shown below. [Figure 4] Further illustrative examples of the method according to the present invention are shown. [Figure 5] Further illustrative examples of the method according to the present invention are shown. [Figure 6] This paper presents simulation results of a proposed method for elucidating the principle of matching the operating phase of the excitation signal to the excitation reference signal through injection synchronization. [Figure 7] The simulation results of the proposed method for representing the detected ESR signal after the excitation pulse are shown. [Figure 8] Further illustrative examples of the method according to the present invention are shown. [Modes for carrying out the invention]

[0096] Figure 1 shows an example of a spectrometer 1 for examining sample 2 at sample position 3. This apparatus is of a type usable in the context of electron spin resonance spectroscopy or nuclear magnetic resonance spectroscopy according to the present invention. Since the basic principles of ESR or NMR spectrometers are well known, only a basic explanation of these principles will be given below. For further details, please refer to the relevant literature.

[0097] The spectrometer 1 includes a device 4 that generates or supplies a first magnetic field B0 (preferably static) at the sample position 3. The device 4 can be implemented as, for example, a magnet, such as a superconducting magnet (e.g., a 9.4T magnet), an electromagnet of any desired embodiment, a permanent magnet, or an internal sample-specific magnet (e.g., a dipole field). At sample 2, the first magnetic field B0 induces magnetization according to the magnetic susceptibility of sample 2.

[0098] The spectrometer 1 further comprises an induction assembly 5 and a control device 6 for exciting the induction assembly 5 with an excitation signal S and supplying an additional second magnetic field B1 to the sample position 3. The control device 6 is configured to generate the second magnetic field B1 using the induction assembly 5 so that the magnetization of the sample 2 is deflected from the equilibrium position. In particular, in the case of conventional transverse magnetization ESR, the second magnetic field B1 has a direction perpendicular to the first magnetic field B0, or at least a component perpendicular to the first magnetic field B0 (however, it should be noted that the longitudinal magnetization ESR method can also be employed in the context of the present invention). In Figure 1, the induction assembly 5 and the control device 6 are schematically shown simply as black boxes.

[0099] Subsequently, the response signal detected from sample 2 can be transferred to the evaluation circuit 7 via the induction assembly 5 in order to also detect the magnetization of sample 2. The evaluation circuit 7 preferably includes demodulation means, analog-to-digital conversion, and / or digital data processing means, which are shown only illustratively in Figure 1. The evaluation circuit 7 can be configured to determine the magnetization of sample 2 and the spin concentrations of the individual spectral components observed therefrom. It is also possible to configure the evaluation circuit 7 to be part of the control device 6, or vice versa.

[0100] However, the present invention is also advantageously applicable to a magnetometer 8, or to a magnetometer 8 used to measure a first magnetic field B0. That is, when investigating an external first magnetic field B0 by measurement, the magnetometer 8 according to the present invention can generate a second magnetic field B1 via an induction assembly 5 excited by an excitation signal S, and determine the first magnetic field B0 in combination with the known material properties of the sample 2.

[0101] Preferably, all electronic components and / or sample positions 3 and / or sample 2 can be placed on a common integrated circuit 9. The corresponding magnetometer 8 is advantageously suited, for example, to image correction in an MRI system (not shown).

[0102] Thus, in particular, a method for generating and / or detecting the magnetization of sample 2 at sample position 3 is proposed for the examination of sample 2 by means of ESR spectroscopy or NMR spectroscopy, or for the measurement of the first magnetic field B0 acting on sample 2 at sample position 3.

[0103] In the context of the present invention, the excitation signal S has an operating frequency f of the excitation signal S ESR which is the resonance frequency f specific to the sample res for an excitation period TX and an operating frequency f of the excitation signal S ESR which is different from the resonance frequency f res for an idle frequency f idle and is set to be periodically switched between the idle period RX.

[0104] FIG. 2 shows an example of the excitation signal S for the proposed magnetometer 8 or the proposed spectroscopic apparatus 1. The induction assembly 5 can be configured to be excited by the excitation signal S without interruption (or at least substantially without interruption). However, during the idle period RX, the operating frequency f of the excitation signal S ESR can be 、 reduced preferably to at least one half with respect to the resonance frequency f res Furthermore, the amplitude of the excitation signal S ("operating amplitude") can also be optionally reduced during the idle period RX, preferably (not necessarily) to at least one half, which is also schematically shown in FIG. 2. 。 In the context of the present invention, furthermore, the operating phase of the excitation signal S is preferably generated separately from, preferably continuously with respect to, the excitation reference signal S

[0105] at least when switching the operating frequency f of the excitation signal S from the idle frequency f ESR to the resonance frequency f idle res ref ​​This provides matching the excitation reference phase. This ensures that at least two directly consecutive excitation periods TX, preferably all excitation periods TX, proceed in phase matching with each other. For illustrative purposes, Figure 2 shows the excitation reference signal S ref The dashed lines show the continuous progression of the line.

[0106] In the context of the present invention, the evaluation of the response signal of sample 2 can be simplified and measurement accuracy can be improved by avoiding the loss of phase information when switching the excitation signal S between two consecutive excitation pulses (in fact, some measurements become possible only as a result). Excitation reference signal S ref By using this method, the operating phase of the excitation signal S can be matched particularly easily and quickly immediately after the switching time. As a result, the time interval between individual excitation pulses or readout pulses can be shortened, and the measurement speed can be significantly increased compared to conventional techniques.

[0107] Figure 3 schematically shows one possible embodiment of the proposed method, and Figure 4 shows an illustrative embodiment with more specific details.

[0108] The excitation signal S for generating the second magnetic field B1 can preferably be generated by a primary voltage-controlled oscillator 10, in particular a voltage-controlled oscillator 10 based on an LC resonant circuit. ref This can be generated by a first secondary voltage-controlled oscillator 11, which is implemented as a polyphase oscillator in the exemplary embodiment. A multiplexer 13 can be used to select as needed from four different output signals of the first secondary voltage-controlled polyphase oscillator 11, which are 90° out of phase with respect to each other. Matching the operating phase to the excitation reference phase is preferably done by injection synchronization of the primary voltage-controlled oscillator 10 by the first secondary voltage-controlled oscillator 11.

[0109] Operating frequency f ESRFor switching between these modes, a first input signal for generating the resonant frequency and a second input signal for generating the idle frequency during the idle period can be selectively applied to the primary voltage-controlled oscillator 10. Each input signal to the primary voltage-controlled oscillator 10 can be applied to the input varactor diode of the oscillator in a well-known manner, and the output or target frequency can be selected so that it matches at least the respective reference frequencies of the reference oscillators 11 or 12, with a frequency difference small enough to allow injection synchronization. Final synchronization, in particular phase matching and optionally fine-tuning of the output frequency of the primary voltage-controlled oscillator 10, can then be performed by injection synchronization.

[0110] As shown in the exemplary embodiment, the operating frequency f ESR The reference frequency f res From idle frequency f idle When switching, additional settings can be made to match the operating phase of the excitation signal S to the reference phase. For this purpose, the excitation signal S and the excitation reference signal S ref A separate, preferably continuously generated, read-reference phase can be set for the read-reference signal. The read-reference signal can be generated by a second secondary voltage-controlled oscillator 12. For this purpose, injection synchronization can be set between the primary voltage-controlled oscillator 10 and the secondary voltage-controlled oscillator 12 to match the operating phases. It is also optionally possible to set the read-reference phase to be derived sequentially from the excitation reference phase.

[0111] As described above, in the context of the present invention, in the excitation period TX 、 It is also possible to increase the amplitude of the second magnetic field B1 compared to the readout or idle period RX. An example of this is shown in Figure 5. In this case, the bias current of the primary voltage-controlled oscillator 10 is changed during excitation. This allows for improved spin excitation and efficiency, as well as optimal detection sensitivity using a small bias current during the idle or readout period.

[0112] Figures 6 and 7 show an example of the simulation results of the proposed method. Referring to Figure 6, the operating frequency f of the primary voltage-controlled oscillator 10 is ESR However, it can be easily determined that the excitation reference phase of the auxiliary oscillator or the first secondary voltage-controlled oscillator 11 is matched within a few nanoseconds. Figure 7 shows an example of the ESR response signal of the sample after the excitation pulse.

[0113] Finally, Figure 8 shows another exemplary embodiment in which the output signal of the ESR oscillator or primary voltage-controlled oscillator 10 is down-converted using a reference oscillator for phase-coherent detection.

Claims

1. A method for generating and / or detecting the magnetization of a sample at a sample location, inspecting the sample by electron spin resonance spectroscopy or nuclear magnetic resonance spectroscopy, or measuring a first magnetic field acting on the sample at the sample location, wherein an induction assembly is excited by an excitation signal to supply a second magnetic field at the sample location, and the excitation signal is periodically switched between an excitation period in which the operating frequency of the excitation signal has a sample-specific resonant frequency and an idle period in which the operating frequency of the excitation signal has an idle frequency different from the resonant frequency. A method characterized in that the operating phase of the excitation signal is matched to the excitation reference phase of an excitation reference signal, separately from the excitation signal, at least when switching the operating frequency from the idle frequency to the resonant frequency, the excitation signal is generated by a primary voltage-controlled oscillator, the excitation reference signal is generated by a first secondary voltage-controlled oscillator, and the matching of the operating phase to the excitation reference phase is performed by injection-synchronizing the primary voltage-controlled oscillator with the first secondary voltage-controlled oscillator.

2. The method according to claim 1, characterized in that the voltage-controlled oscillator is based on an LC resonant circuit.

3. The method according to claim 1, characterized in that the operating phase of the excitation signal S is matched to the read reference phase of a read reference signal, which is separate from the excitation signal and the excitation reference signal and preferably continuously generated, when the operating frequency is switched from the reference frequency to the idle frequency.

4. The method according to claim 3, characterized in that the readout reference signal is generated by a second secondary voltage-controlled oscillator.

5. The method according to claim 4, characterized in that the first secondary voltage-controlled oscillator and / or the second secondary voltage-controlled oscillator are implemented as voltage-controlled polyphase oscillators, and preferably a multiplexer is used to select as needed from four different output signals of the polyphase oscillators, each being 90° out of phase with respect to the other.

6. The method according to claim 4 or 5, characterized in that the operation phase is matched to the readout reference phase by injection-synchronizing the primary voltage-controlled oscillator with the second secondary voltage-controlled oscillator.

7. The method according to claim 1, characterized in that a first input signal for generating the resonant frequency during the excitation period and a second input signal for generating the idle frequency during the idle period are applied to the primary voltage-controlled oscillator.

8. The method according to claim 1, characterized in that at least two directly consecutive excitation periods, preferably all of the excitation periods, proceed in a phase-coherent manner with respect to each other.

9. The method according to claim 1, characterized in that the resonant frequency is increased to at least twice, preferably at least 1.5 times, and particularly preferably at least 1.05 times, the idle frequency.

10. The method according to claim 1, characterized in that the induction assembly is excited without interruption by the excitation signal.

11. The method according to claim 1, characterized in that the response signal of the sample is detected by the induction assembly during the idle period of the excitation signal and evaluated by the control device.

12. The method according to claim 1, characterized in that the operating amplitude of the excitation signal is reduced, preferably to at least 50%, particularly preferably to at least 20%, and more preferably to at least 10%, during the idle period with respect to the excitation period.

13. A magnetometer for measuring a first magnetic field by generating and / or detecting the magnetization of a sample at a sample position, comprising an induction assembly and a control device for exciting the induction assembly with an excitation signal to supply a second magnetic field to the sample position, wherein the excitation signal is periodically switched between an excitation period in which the operating frequency of the excitation signal has a sample-specific resonant frequency and an idle period in which the operating frequency of the excitation signal has an idle frequency different from the resonant frequency. A magnetometer characterized in that, at least when switching the operating frequency of the excitation signal from the idle frequency to the resonant frequency, the operating phase of the excitation signal is matched to the excitation reference phase of an excitation reference signal, separately from the excitation signal, and the magnetometer further includes a primary voltage-controlled oscillator for generating the excitation signal and a first secondary voltage-controlled oscillator for generating the excitation reference signal, and the primary voltage-controlled oscillator is injection-synchronized with the first secondary voltage-controlled oscillator in order to match the operating phase to the excitation reference phase.

14. The magnetometer according to claim 13, characterized in that the induction assembly and the control device are arranged on a common integrated circuit.

15. A spectroscopic apparatus for inspecting a sample at a sample location, comprising: a device for generating a first magnetic field at the sample location; an induction assembly; and a control device for exciting the induction assembly with an excitation signal to supply a second magnetic field at the sample location, wherein the excitation signal is periodically switched between an excitation period in which the operating frequency of the excitation signal has a sample-specific resonant frequency and an idle period in which the operating frequency of the excitation signal has an idle frequency different from the resonant frequency. At a minimum, when switching the operating frequency of the excitation signal from the idle frequency to the resonant frequency, the operating phase of the excitation signal is matched to the excitation reference phase of an excitation reference signal, separately from the excitation signal, and the spectrometer further includes a primary voltage-controlled oscillator for generating the excitation signal and a first secondary voltage-controlled oscillator for generating the excitation reference signal, and the primary voltage-controlled oscillator is injection-synchronized with the first secondary voltage-controlled oscillator in order to match the operating phase to the excitation reference phase, characterized in that.

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