Inductive array, oscillator assembly, device, and method for generating and / or detecting a magnetization of a sample

Abstract

The invention relates to an inductive array (1), in particular for use in an oscillator assembly (2) for generating and / or detecting a magnetization of a sample (3), having a plurality of interconnected inductive segments (5), wherein each of the inductive segments (5) has an inductive element (6) and a connection circuit (7), which is electrically connected to the inductive element (6), for electrically connecting to an adjacent inductive segment (5).

Description

[0001] Inductive assembly, oscillator arrangement, device and method for generating and / or

[0002] Detection of magnetization of a sample

[0003] The present patent application claims the priority of German patent application No. 10 2023 103 994.6 of February 17, 2023, the disclosure content of which is fully integrated into the present description by this reference.

[0004] The invention relates to an inductive assembly, in particular for use in an oscillator arrangement for generating and / or detecting a magnetization of a sample.

[0005] The invention further relates to an oscillator arrangement, in particular for use in a device for generating and / or detecting a magnetization of a sample.

[0006] The invention also relates to a device and a method for generating and / or detecting a magnetization of a sample, in particular for electron spin resonance spectroscopy or nuclear magnetic resonance spectroscopy.

[0007] The invention relates in particular to the generation and / or detection of a magnetic resonance of a sample, as used, for example, in electron spin resonance spectroscopy and nuclear magnetic resonance spectroscopy, which are used, among other things, in experimental physics, chemistry, medical technology or geosciences.

[0008] In electron spin resonance spectroscopy (ESR, sometimes also called EPR, electron paramagnetic resonance) and nuclear magnetic resonance spectroscopy (NMR, nuclear magnetic resonance spectroscopy), samples in a statically homogeneous, statically inhomogeneous or dynamic (pulsed inhomogeneous) magnetic field, usually referred to as Bo, are exposed to additional high-frequency, alternating electromagnetic fields (in ESR mostly in the microwave range between 1 and 263 GHz), usually referred to as Bi.

[0009] By coupling alternating fields (Bi) of suitable frequency and polarization, transitions between the energy levels of discrete spin states of the atomic nucleus and / or electron configuration of a sample are induced, which in turn lead to absorption processes in the alternating field, which can be detected. Various analytical information about the sample can be determined from the detected absorption processes. The Bi field is usually oriented perpendicular to Bo.

[0010] Samples amenable to characterization by ESR or NMR experiments are therefore all linearly magnetizable samples, i.e., paramagnetic samples with unpaired electrons (ESR) or diamagnetic samples with atomic nuclei with a "net nuclear spin" due to an odd number of nucleons (NMR). The samples can be liquid, solid, or gaseous. In the following, the term "sample" generally refers to a magnetizable sample, as introduced above.

[0011] For further technological background, reference is made to DE 10 2016 102 025 A1 or WO 2017 / 088852 A1, the respective disclosure content of which is fully integrated into the present patent application by this reference.

[0012] Electron spin resonance spectroscopy is a powerful technique that uses the spin of an unpaired electron as a nanoscopic probe inside a molecule to obtain information about the chemical structure and composition through small changes in the resonance frequency.

[0013] Electron spin resonance spectroscopy is used to investigate and monitor a wide range of materials, from defects in semiconductors to free radicals in blood to metal catalysts in the production of hydrogen as a fuel. Measurements are typically performed in moderate static magnetic fields around 0.3 T, corresponding to ESR frequencies around 9 GHz. This combination of magnetic flux density and ESR frequency is frequently used because it is usually technically feasible to generate 0.3 T magnetic fields with sufficient homogeneity and the required 9 GHz frequency signal.

[0014] However, access to higher frequencies and magnetic fields would be desirable due to the possibility of higher spin polarization (with correspondingly larger signal amplitude), higher spectral resolution (e.g., for determining the electronic and geometric structures of active centers in enzymes), and access to higher-energy transitions (such as those found in metal complexes or materials of interest for antiferromagnetic spintronics). High-frequency ESR (HFEPR or HFESR) with operating frequencies above 90 GHz are therefore desirable.

[0015] Another important driving force for HFESR is dynamic nuclear polarization (DNP), a method that can improve the relatively low sensitivity of nuclear magnetic resonance spectroscopy by transferring the inherently higher electron polarization to the nuclear spins. Currently, the main commercially available spectrometer is HFESR-based DNP, with an ESR operating frequency of 263 GHz (9.4 T), corresponding to a proton NMR frequency of 400 MHz. This spectrometer uses a gyrotron as the source of the millimeter-wave magnetic field (Bi-field) and is extremely expensive to purchase.

[0016] Current HFESR spectrometers use one of four methods to generate bi-fields for HFESR / DNP: vacuum tubes (gyrotrons and backward-wave oscillators), active frequency multiplier chains, synchrotron radiation, and, more recently, THz photomixers. However, all of these methods have significant drawbacks in terms of complexity and cost. The first three methods require large, complex quasi-optical arrays (on the order of > 1 m). 2 ) to efficiently manipulate the millimeter wave and also use cryogenically cooled radiation detectors (bolometers) for sufficiently sensitive detection. THz photomixers require only a few THz lenses, but require complex fiber optic equipment to achieve sufficient spectral resolution and are less sensitive than the other three methods.

[0017] To overcome the limitations of conventional ESR setups, several oscillator-based CMOS integrated ESR detectors (“EPR / ESR-on-a-chip”) for various fundamental frequencies up to 146 GHz have been introduced in recent years. For example, voltage-controlled oscillators (VCOs) were proposed as electron spin resonance (ESR) sensors in the 2016 publication by Handwerker, J. et al., “A 14 GHz battery-operated point-of-care ESR spectrometer based on a 0.13 pm CMOS ASIC,” IEEE International Solid-State Circuits Conference (ISSCC), pp. 476-477. This technique enables a frequency sweep of the VCO frequency with nearly constant sensitivity across all resonance frequencies of the sample. Since then, this technique has gained increasing attention in the research community because it can lead to extreme miniaturization of the entire ESR spectrometer at very low cost.

[0018] In the meantime, improvements to this basic concept have already been proposed to extend the oscillation frequency into the millimeter-wave range for better spin sensitivity. Furthermore, approaches are known to simplify the modulation and demodulation electronics (see Benedikt Schlecker et al., "Towards Low-Cost, High-Sensitivity Point-of-Care Diagnostics Using VCO-Based ESR-on-a-Chip Detectors," IEEE Sensors Journal, vol. 19, no. 20, pp. 8995–9003, 2019), and to excite and detect the transient behavior of electron spin ensembles (Silvio Künstner et al., "Rapid Scan Electron Paramagnetic Resonance using an EPR-on-a-Chip Sensor," Magnetic Resonance, May 2021).

[0019] For example, in the publication by Matheoud, AV et al., "Single-chip electron spin resonance detectors operating at 50 GHz, 92 GHz, and 146 GHz", Journal of Magnetic Resonance, 278, 113 - 121 , 2017, a single HFESR oscillator operating at 90 GHz was used to measure ESR at 360 GHz using its fourth harmonic—albeit with comparatively lower excitation power and sensitivity. Furthermore, due to the small coil diameter of only 45 pm for the 146 GHz oscillator, caused by the wavelength of the fundamental frequency, and the resulting very small active volume, the method cannot be effectively used for ESR and DNP experiments at very high operating frequencies.

[0020] Although VCOs have demonstrated their great potential as extremely robust and user-friendly ESR sensors for solid samples with limited mass, their use for the spectroscopic measurement of liquid samples is still limited due to the relatively low concentration sensitivity (i.e., the minimum detectable spin density in a liquid sample that fills the entire volume) in view of the relatively small measurement volumes of planar chip-integrated (“on-chip”) detectors.

[0021] One approach to achieving a larger detectable volume would be the use of larger-diameter, on-chip coils. However, compromises are necessary when choosing the coil size. First and foremost, the maximum coil diameter is limited by the wavelength associated with the VCO operating frequency. To avoid radiation losses and large electric fields within the sample, the total length of the coil path should not exceed a certain fraction a of the wavelength, where a is typically between 5 and 10. Second, the large inductances associated with large-diameter coils prevent wide VCO tuning ranges and lead to comparatively high phase noise.

[0022] An approach to increasing the detectable volume of VCO-based ESR detectors was presented by Anh Chu et al. in their paper "An 8-channel 13GHz ESR-on-a-Chip injection-locked VCO array achieving 200pM concentration sensitivity," IEEE International Solid-State Circuits Conference (ISSCC), pp. 354-355, in 2018. Injection locking between a large number of planar VCOs was used to synchronize all participating VCOs to a single, common frequency and phase. The use of injection-locked VCO arrays can be beneficial for increasing the laterally detectable volume while simultaneously reducing phase noise.

[0023] However, this technique does not allow for the enlargement of a single array element and thus also does not allow for the enlargement of the detectable volume perpendicular to the planar array. Furthermore, due to injection locking, the signals from the individual VCOs are not added, so the improvement in concentration sensitivity is only due to improved phase noise. Therefore, there is still a need for a method that enlarges the active volume both laterally and perpendicular to the coil surface. When enlarging the active volume perpendicular to the coil surface, it should be noted that, according to the prior art, the sensitivity along this spatial direction decreases very rapidly depending on the coil diameter.

[0024] In view of the known state of the art, the object of the present invention is, inter alia, to provide an inductive assembly with which a large active volume during excitation and detection and a high concentration sensitivity can be achieved, preferably with low energy consumption.

[0025] The present invention is also based, inter alia, on the object of providing an oscillator arrangement with which a large active volume during excitation and detection and high concentration sensitivity can be achieved, preferably with low energy consumption. Furthermore, it is, inter alia, an object of the invention to provide a device and a method for generating and / or detecting a magnetization of a sample, with which a large active volume during excitation and detection and high concentration sensitivity can be achieved, preferably with low energy consumption.

[0026] The problem is solved for the inductive assembly with the features listed in claim 1. With regard to the oscillator arrangement, the problem is solved by the features of claim 17. With regard to the device, the problem is solved by claim 20 and with regard to the method by claim 27.

[0027] The dependent claims and the features described below relate to advantageous embodiments, variants and subordinately claimable aspects of the invention.

[0028] The invention relates to an inductive assembly, particularly (but not exclusively) for use in an oscillator arrangement for generating and / or detecting a magnetization of a sample.

[0029] The inductive assembly includes a plurality of interconnected inductive segments, each of the inductive segments including an inductive element and a connecting circuit electrically connected to the inductive element for electrical connection to an adjacent inductive segment.

[0030] Solid, gaseous, and / or liquid samples can be considered. Liquid samples can, for example, be placed in glass capillaries on planar designs (e.g., using CMOS technology). At lower frequencies from Bi down to the so-called X-band (approx. 10 GHz), the coils of the LC oscillators can also be implemented as volume coils, into which the capillaries containing liquid samples can be inserted, or they can be combined with (micro-)fluidic systems for transporting samples into the detector. Alternatively, the device can be immersed in or inserted into the liquid, gas, or solid to be measured, or linked to it in another way, such as by spraying. Phase transitions and changes (transitions) of aggregate states can be recorded in this way. Alternatively, a hole can be drilled into the planar coils, for example, using a laser, to introduce a liquid sample.

[0031] Advantageously, the size of the "tank inductance" can be greatly increased according to the invention, e.g., beyond the limit of A / a (where a can be any number between 1 and 50, e.g., 5 to 10). The enlarged composite coil (referred to above and below as the "inductive assembly") can then be divided into shorter sub-sections (referred to above and below as "inductive elements"). Each sub-segment or inductive element can be controlled by suitable electronics (referred to above and below as the "connecting circuit"), e.g., in the form of individual VCO cores. By embedding phase-locking circuits between the electronic control blocks, their phases can be synchronized such that a circulating current flows within the large composite coil or inductive assembly as a whole, simulating the behavior of a hypothetical coil with a larger diameter.At the same time, radiation losses and parasitic electric fields remain low.

[0032] When using the proposed split-coil technique (hereinafter also referred to as "split-coil" technology), each inductive segment exhibits a significantly reduced inductance, enabling low phase noise and wide tuning ranges. This is especially true when the individual electronic driver blocks or connecting circuits between the inductive elements are designed as VCO cores or have VCO cores, and the overall system, i.e., the entire inductive assembly, thus also functions as a VCO.

[0033] It should be noted that the possibility of dividing a coil into multiple segments with VCO cores arranged between them was already proposed by R. Aparicio and A. Hajimiri in the publication "Circular-geometry oscillators" (ISSCC, pp. 378-533) in 2004 to increase the coil's Q factor. In contrast, the segmented coil technique is used in the present invention to provide enlarged inductors or inductive assemblies as sensors for HFESR and bi-field sources for high-field ESR / DNP measurements and imaging at low frequencies, with a significantly larger active measurement volume compared to conventional coils.

[0034] According to a further development of the invention, it can be provided that the inductive elements are formed in the form of a plate made of a metal material (“slab metal inductor”) or of a coil wire (“single turn spiral inductor”).

[0035] The above variants are merely examples and should not be understood as limiting. The inductive elements can, in principle, be implemented in any way.

[0036] In a further development of the invention, it can be provided, in particular, that the inductive elements are each one-piece, monolithic components. For example, they can be respective contiguous, metallized sections in an integrated circuit, such as conductor tracks.

[0037] If necessary, the inductive elements can also be constructed in several parts (less preferred).

[0038] In a further development of the invention, it can be provided that the inductive elements are elongated components, in particular with a straight line. It can be provided that the longitudinal extent of the inductive elements does not exceed 20 millimeters each (although applications with greater longitudinal extents are of course not excluded), preferably does not exceed 10 millimeters, more preferably does not exceed 5 millimeters, and even more preferably does not exceed 2 millimeters. A preferred application of the invention can, however, relate to significantly smaller dimensions, wherein the longitudinal extent of the inductive elements does not exceed 1,000 micrometers, preferably does not exceed 500 micrometers, more preferably does not exceed 200 micrometers, and even more preferably does not exceed 100 micrometers.In particular, the individual inductive elements can be designed to be sufficiently small with regard to the wavelengths used in order to avoid parasitic radiation or at least to reduce it sufficiently depending on the application.

[0039] In an advantageous development of the invention, it can be provided that the inductive segments are connected to one another in a series arrangement, preferably in an at least substantially annular, self-contained arrangement.

[0040] Two to 100 (or more) inductive segments can be provided, in particular up to 20 inductive segments, preferably four to eight inductive segments, for example exactly four inductive segments.

[0041] In particular, an even number of inductive segments can be provided.

[0042] In an advantageous development of the invention, it can be provided that the inductive elements are directly electrically connected to the corresponding connecting circuits or that the inductive elements directly electrically contact corresponding terminals of the corresponding connecting circuits.

[0043] However, an indirect electrical connection between the inductive elements and the connecting circuits via further components or structures may also be provided if necessary.

[0044] In particular, it can be provided that the connecting circuits each have a first connection interface which is electrically connectable or connected to the inductive element of the same inductive segment and / or each have a second connection interface which is electrically connectable or connected to an inductive element of an adjacent inductive segment.

[0045] According to a further development of the invention, the connecting circuits can each comprise a capacitive component, preferably a controllable capacitive component, in particular a variable-capacitance diode ("varactor"). The capacitive component can preferably be arranged between two directly adjacent inductive elements in the assembly of the inductive segments. The capacitive component can therefore be connected, for example, between the connection interfaces of the connecting circuit.

[0046] In an advantageous development of the invention, it can be provided that the connecting circuits each have two cross-coupled transistors, preferably MOSFETs, bipolar transistors or GaN-based transistors.

[0047] The circuit arrangement of a single LC-VCO can, for example, be designed such that a differential capacitance diode and a differential inductance together form an LC resonant circuit.

[0048] The two cross-coupled transistors can ensure stable oscillation in the differential output (i.e., the output voltage) through negative resistance and nonlinearity between two nodes. The tuning characteristics can be ensured by the differential capacitance diode.

[0049] A time-dependent variation of the oscillation amplitude is achieved, for example, by manipulating the voltage supply of the LC-VCO. This simple design of an LC-VCO ensures low power consumption, small space requirements, and also operates at low (down to cryogenic) temperatures.

[0050] Overall, within the scope of the present invention, higher power consumption can be exchanged for a larger measurement volume with greatly reduced unwanted electric fields.

[0051] The proposed technique is extendable to generate homogeneous bi-fields (in this context, bi-fields are the microwave magnetic fields that resonate with the spin ensemble) in three dimensions by combining two large-coil VCOs in a Helmholtz configuration or multiple large-coil VCOs into a single cylindrical coil. If the individual coils are monolithic, the latter can be achieved, for example, by drilling a hole through each large-coil VCO.

[0052] According to a further development of the invention, it can be provided in particular that some or preferably all of the inductive elements are electrically connected to a common (central) star point, preferably arranged in a symmetrical arrangement around the common star point. The star point can then therefore preferably form the center of the arrangement. The electrical connection can be established in particular via respective high-impedance line sections. In this context, a "high-impedance line section" can be understood in particular as a line section whose electrical resistance is greater than an electrical resistance of the inductive elements, preferably much greater, for example by one, two, three, four, five or even more orders of magnitude.

[0053] In an advantageous further development, it can be provided in particular that the common star point is connected to an electrical reference potential, preferably to a ground potential.

[0054] Preferably, the connecting circuits are designed as voltage-controlled oscillators. However, in a further development of the invention, the connecting circuits can also be designed as driver circuits or other suitable circuits.

[0055] The proposed arrangement of LC oscillators can be implemented using integrated circuit technology, i.e., entirely with active and / or passive elements. This reduces the number of discrete components, and may eliminate the need for additional external components. This enables the realization of cost-effective, low-power, and potentially portable devices. Advantages of the device according to the invention are the symmetrical implementation and high reproducibility of the individual circuit elements, as is possible, for example, with MEMS technology. This allows for the reduction of interference signals (especially during amplitude detection).

[0056] According to a further development of the invention, it can be provided that the inductive element and the connecting circuit of a common inductive segment are formed in a common integrated circuit.

[0057] Preferably, all inductive segments of the inductive assembly are formed in a common integrated circuit.

[0058] However, it can also be provided that individual components or all components are not formed on an integrated circuit, but for example as discrete electrical components, for example on an electrical circuit board.

[0059] The invention also relates to an oscillator arrangement, in particular for use in a device for generating and / or detecting a magnetization of a sample, comprising at least one inductive assembly according to the above and following embodiments.

[0060] Preferably, the entire oscillator arrangement, in particular all inductive components of the oscillator arrangement, are formed in a common integrated circuit.

[0061] In an advantageous development of the invention, it can be provided that a plurality of the inductive assemblies are connected to one another in a frequency-synchronized manner, preferably at least two inductive assemblies, more preferably at least four inductive assemblies, even more preferably at least eight inductive assemblies, even more preferably at least 16 inductive assemblies, for example at least 32 inductive assemblies or even more inductive assemblies.

[0062] Frequency synchronization (frequency locking) can be understood here as meaning that the inductive components are forced to have the same free oscillation frequency by means of circuitry.

[0063] Advantageously, comparatively large inductors, i.e. inductors whose circumference represents a significant fraction of the wavelength, can be used as "tank inductors" in arrays of injection-locked VCO-based ESR detectors in order to enlarge the measurement volume in the direction perpendicular to the chip surface compared to conventional loop inductors.

[0064] In one embodiment, the frequency synchronization of the inductive components can be realized by interconnecting them as a coupling network. "Interconnected by a coupling network" can mean that the oscillation signal of one oscillator is fed into one or more other oscillators in the array through passive or active circuit elements. The effect of this is that the output signals of all oscillators oscillate at the same frequency. The phase of the oscillation signals depends on the coupling network. This has the advantage that the oscillators are synchronized in frequency and, by selecting the appropriate coupling network, a desired fixed phase shift between the oscillation signals of the oscillators can be set. Depending on the type of coupling network, the phase noise is reduced compared to the phase noise of a single oscillator.In passive coupling networks, the power consumption is lower than in active networks.

[0065] In another embodiment, the frequency synchronization of the inductive components can be realized by a network connection, where each LC oscillator has an additional input and an output voltage of at least one further LC oscillator is fed into the additional input, with the LC oscillators each being interconnected at least on two sides. The effect of this is also that the output signals of all oscillators oscillate at the same frequency. The phase is also dependent on the coupling network. This also has the advantage that the oscillators are synchronized in their frequency and, by appropriately selecting the network connection, a desired fixed phase shift between the oscillation signals of the oscillators can be set.

[0066] In a further development of the invention, it can be provided that a plurality of the inductive modules are arranged in a row and / or column arrangement, in particular in an array, wherein preferably at least two columns and / or at least two rows are provided. Therefore, the oscillator arrangement is sometimes also referred to below as a "VCO array". The spatial design of the arrangement of the inductive modules is implemented, if there are more than two inductive modules, as a planar interconnected system of individual inductive modules, preferably in rows and columns (also referred to as an "array" in English). This allows any desired arrangement of the inductive modules relative to one another. The special case of a single row or chain is included here. The characterization as "planar" includes not only a flat design but also arbitrarily curved surfaces with and without edges (e.g.cylinder surface, cone surface, sphere).

[0067] The invention also relates to a device for generating and / or detecting a magnetization of a sample, comprising an oscillator arrangement according to the above and following embodiments and a sample location for the sample.

[0068] The sample location can be a location in the device where the sample is placed (optionally the sample can be attached or fixed to the sample location) and where both the magnetic field (Bo) and, if applicable, the additional (e.g. transient) magnetic field (Bi) are applied.

[0069] Means for securing and storing the sample may be provided.

[0070] The embodiment in which the transmitting device and the receiving device are both implemented by a common arrangement is particularly advantageous, since it enables a particularly simplified, cost- and space-saving construction.

[0071] In a further development, it can be provided that the device has a device for providing a magnetic field, in particular for providing a static (or quasi-static) magnetic field, in a predetermined direction and strength at the sample location, wherein by means of the oscillator arrangement an additional magnetic field can be provided at the sample location and / or the magnetization of the sample can be detected at the sample location.

[0072] The device for generating said magnetic field of predetermined direction in the proposed device can be realized, for example, by superconducting magnets or electromagnets of any design or permanent magnets.

[0073] The generated magnetic field is preferably static and corresponds to the magnetic field Bo used to magnetize a suitable sample, as mentioned above. The magnetic field can be of any strength, as long as the frequency of the exciting Bi magnetic field is chosen according to the resonance conditions.

[0074] In a further development of the invention, it can also be provided that the device has a control device for controlling the oscillator arrangement, which is set up and connected to the oscillator arrangement so that a magnetic field is generated by means of the oscillator arrangement, which is able to deflect a magnetization of the sample at the sample location from an equilibrium position.

[0075] The control device can be embodied as a microprocessor. Instead of a microprocessor, any other device can also be provided for implementing the control device, for example, one or more arrangements of discrete electrical components on a circuit board, a programmable logic controller (PLC), an application-specific integrated circuit (ASIC), or another programmable circuit, for example, a field-programmable gate array (FPGA), a programmable logic array (PLA), and / or a commercially available computer.

[0076] In an advantageous development of the invention, it can be provided that the sample location is in the near field of the oscillator arrangement.

[0077] The near field for the device can be understood as the field of the LC oscillator, in which, for magnetically linear sample materials, the rotation of the Bi field is largely determined by the current density J in the inductive element due to / » ö£) / öt and, due to div B = 0, the entire Bi field is also largely determined by the current density J in the inductive element. In contrast, in the far field, wave propagation occurs due to / « ö£) / öt. For the near field, therefore, the Bi field can be generated largely independently of the Ei field, since no wave is present in the near field. Due to this circumstance, the Ei field can be optimized much more freely and can be kept low. Low Ei fields minimize electrical losses in the sample as well as the loss caused by heating the sample, which can be an advantage of the device.

[0078] In a further development, it can be provided that the device has an evaluation circuit for processing an output voltage of the oscillator arrangement, wherein the evaluation circuit preferably has means for demodulation, analog-digital converters and / or means for digital data processing.

[0079] The changes in the oscillation frequency of the LC oscillator array can be detected by a demodulator connected downstream of the LC oscillator array. Demodulation can be performed using a frequency demodulator. Depending on the selected converter or demodulator, the analog signals are converted to digital signals using appropriate means before or after conversion or demodulation.

[0080] Changes in the oscillation amplitude can be detected using devices connected downstream of the array of LC oscillators. The amplitude of the individual LC oscillators in the array is not synchronized by coupling. Therefore, a signal can be tapped from each individual LC oscillator that corresponds to the magnetization of the sample in the sensitive volume of this LC oscillator. This provides additional signals that allow spatial resolution. It should be noted that the amplitudes of the LC oscillators may be subject to coupling within the LC oscillator, for which the signals may need to be corrected. The amplitude-modulated signal can be tapped from the individual LC oscillators using simple means.This only requires an amplifier for each LC oscillator for the signal (usually in the kHz range for continuous-wave experiments). This signal is obtained through intrinsic demodulation, which is available directly in the baseband when using a current source to power the LC oscillator and is tapped at nodes in the LC oscillators. The signal does not need to be downconverted from the Larmor frequency. This not only reduces circuit complexity but also optimizes power consumption.

[0081] In a further development of the invention, it can be provided that the evaluation circuit is set up to determine the magnetization of the sample and the spin concentration of individual spectral components to be determined therefrom.

[0082] According to a further development of the invention, it can also be provided that the individual inductive elements of the inductive assemblies have a longitudinal extent which does not exceed the wavelength of the operating frequency of the oscillator arrangement, preferably does not exceed half the wavelength of the operating frequency, particularly preferably does not exceed a quarter of the wavelength of the operating frequency, further preferably does not exceed a fifth of the wavelength of the operating frequency, for example does not exceed a tenth of the operating frequency.

[0083] At this point, it should be noted that the term "connected" or "connection" used in this description and in the patent claims can describe a direct electrical connection between the components mentioned, but also an indirect electrical connection between the components mentioned (e.g., via additional electrical lines or electronic components such as resistors, inductors, and / or capacitors, etc.). The terms "connected" or "contacted," on the other hand, generally indicate a direct connection between the components mentioned.

[0084] The invention also relates to a method for generating and / or detecting a magnetization of a sample at a sample location, in particular for electron spin resonance spectroscopy or nuclear magnetic resonance spectroscopy, comprising at least the following step:

[0085] Providing at least one inductive assembly having a plurality of interconnected inductive segments, each of the inductive segments having an inductive element and a connecting circuit electrically connected to the inductive element for electrical connection to an adjacent inductive segment.

[0086] Optionally, the following additional method steps may be provided, among others: providing a magnetic field, in particular a static magnetic field, in a predetermined direction and strength at the sample location; operating the at least one inductive assembly to provide an additional magnetic field at the sample location, preferably a transient magnetic field, and / or to detect the magnetization of the sample at the sample location.

[0087] It should be emphasized here that process steps do not necessarily have to be performed in the order in which they are first described or mentioned in the description or patent claims. Therefore, individual process steps or groups of process steps may, for example, be interchangeable, provided this is not technically impossible. Process steps may also be combined, divided into separate intermediate steps, or supplemented with intermediate steps. The process is not necessarily described exhaustively with the process steps described below and may be supplemented with further process steps, even those not mentioned.

[0088] In an advantageous development of the invention, it can be provided that a plurality of the inductive assemblies are operated with frequency synchronization with one another, preferably within a common oscillator arrangement.

[0089] In summary, a method for synthesizing electrically large coils for improved 3D detection volumes in spin detection experiments such as ESR, NMR or FMR (ferromagnetic resonance) is proposed.

[0090] Several oscillator cores can be advantageously combined to increase the sensitive volume for electron spin resonance detection.

[0091] In the case of VCO-based detection, the proposed method preferably combines multiple VCOs to form a composite VCO with an electrically large coil. However, the method can also be applied in conventional transmit-receive spin detection setups.

[0092] The proposed method eliminates or suppresses the radiation effect associated with a large coil (preferably at least to a level negligible in practice or for the intended application), which is highly undesirable especially for liquid samples, while enabling widely tunable VCO detectors with low phase noise.

[0093] The invention also relates to a computer program comprising control commands which, when the program is executed by a control device, cause the control device to carry out the method according to the above and following details (or other work steps within the scope of the overall inventive concept). Features described in connection with one of the subject matters of the invention, namely the inductive assembly, the oscillator arrangement, the device, the method, and the computer program, can also be advantageously implemented for the other subject matters of the invention. Likewise, advantages mentioned in connection with one of the subject matters of the invention can also be understood to relate to the other subject matters of the invention.

[0094] It should also be noted that terms such as "comprising," "having," or "with" do not exclude other features or steps. Furthermore, terms such as "a" or "the," which indicate a singular number of steps or features, do not exclude a plurality of features or steps—and vice versa.

[0095] In a purist embodiment of the invention, however, it may also be provided that the features introduced in the invention with the terms "comprising," "having," or "with" are listed exhaustively. Accordingly, one or more lists of features may be considered complete within the scope of the invention, for example, for each claim. The invention may, for example, consist exclusively of the features mentioned in claim 1.

[0096] It should be noted that terms such as "first" or "second" etc. are used primarily for reasons of distinguishing between respective device or process features and are not necessarily intended to indicate that features are mutually dependent or related to one another.

[0097] Furthermore, it should be emphasized that the values ​​and parameters described herein include deviations or fluctuations of ±10% or less, preferably ±5% or less, more preferably ±1% or less, and most preferably ±0.1% or less of the respective specified value or parameter, provided that these deviations are not excluded in the practical implementation of the invention. The specification of ranges by initial and final values ​​also includes all those values ​​and fractions enclosed by the respective specified range, in particular the initial and final values ​​and a respective mean value.

[0098] It should also be emphasized that the figures each show preferred embodiments in which individual features of the present invention are illustrated in combination with one another. However, features of one embodiment can also be implemented independently of the other features of the same embodiment and can therefore be readily combined by a person skilled in the art to form further useful combinations and subcombinations with features of other embodiments.

[0099] The invention will be explained in more detail with reference to the following figures.

[0100] The further figures each show schematically: Figure 1 An inductive assembly according to the invention for use in an oscillator arrangement, with a plurality of interconnected inductive segments;

[0101] Figure 2 An inductive assembly according to the invention with further details;

[0102] Figure 3 An exemplary chip-integrated realization of an inductive assembly according to the invention;

[0103] Figure 4 An exemplary circuit arrangement of an inductive assembly according to the invention;

[0104] Figure 5 A device according to the invention for generating and / or detecting a magnetization of a sample at a sample location, with an oscillator arrangement which has a plurality of inductive components in a row and column arrangement;

[0105] Figure 6 A circuit diagram of a device according to the invention;

[0106] Figure 7 Measured electrical characteristics of a device according to the invention;

[0107] Figure 8 A further schematic circuit diagram of a device according to the invention with further details;

[0108] Figure 9 Example measurement data of an ESR measurement; and

[0109] Figure 10 A schematic circuit diagram of a device for generating and detecting magnetic resonance.

[0110] Figure 1 shows an inductive assembly 1 in a highly schematic representation according to an embodiment of the present invention. Figure 2 illustrates some further details and optional developments of the inductive assembly 1. Exemplary implementations are shown in Figures 3 and 4.

[0111] The proposed inductive assembly 1 is particularly suitable for use in an oscillator arrangement 2 (see, for example, Figure 5) for generating and / or detecting a magnetization of a sample 3 at a sample location 4.

[0112] The inductive assembly 1 has a plurality of interconnected inductive segments 5. Each of these inductive segments 5 comprises an inductive element 6 and a connecting circuit 7 electrically connected to the inductive element 6 for electrical connection to an adjacent inductive segment 5. The inductive segments 5 are interconnected in a series arrangement and, in the exemplary embodiments, form an annular, self-contained arrangement.

[0113] Figures 1 and 2 illustrate the proposed concept using an example split coil with eight coil segments or inductive elements 6 and eight electronic blocks / driver circuits or connecting circuits 7. However, the representation with exactly eight inductive segments 5 is only intended as an example. In principle, two to 20 inductive segments 5 can be provided, preferably four to eight inductive segments 5, for example, exactly four inductive segments 5 (see also the implementations in Figures 3 and 4). Preferably, an even number of inductive segments 5 is provided.

[0114] As shown in the figures, a functionally comparatively large induction coil can be divided into several inductive (coil) segments 6, which are then electrically connected to one another by said connecting circuits 7, e.g., driver circuits. The connecting circuits 7 can ensure (preferably at least approximately) a phase relationship between the currents in the individual inductive elements 6 that corresponds to the current distribution in a low-frequency loop coil. With appropriate phase synchronization of the individual inductive elements 6 or inductive segments 5, a continuous alternating current I can flow (indicated in Figure 1 by an arrow in the center of the inductive assembly 1), which mimics the behavior of the low-frequency alternating current in a simple loop coil.

[0115] In principle, an N-fold segmentation allows an N-fold increase in the outer circumference of the coil for a given radiation loss.

[0116] The inductive elements 6 can, in particular, be electrically connected directly to the corresponding connecting circuits 7 or can directly electrically contact corresponding terminals of the connecting circuits 7. The connecting circuits 7 can, in particular, each have a first connection interface 8, which is electrically connected to the inductive element 6 of the same inductive segment 5, and each have a second connection interface 9, which is electrically connected to an inductive element 6 of an adjacent inductive segment 5 (see, in particular, Figure 2).

[0117] It can optionally be provided to electrically and symmetrically connect all inductive elements 6 to a common star point 10, as indicated by way of example in Figures 2 and 3. This can preferably be done via respective high-impedance line sections 11. The common star point 10 can be connected to an electrical reference potential Vdd, preferably to a ground potential. This ensures correct phase synchronization between the VCO cores and avoids possible DC latching and other parasitic oscillation modes. The high-impedance line sections 11 can be implemented by thin conductor tracks for bridging the central points of the inductive elements 6 connected to Vdd.

[0118] Optionally, auxiliary circuits (e.g. diodes) can be used instead of the high-impedance line sections 1 1 in order to suppress the unwanted parasitic oscillation modes and at the same time to keep the central region of the large composite coil free, among other things to enable the introduction of bores.

[0119] The connecting circuits 7 for connecting the adjacent inductive elements 6 to each other can, in particular, be VCO cores. The VCO cores can, in particular, each comprise a variable-capacitance diode Cvar and two cross-coupled transistors (in particular MOSFETs, bipolar transistors, or GaN-based transistors), as indicated, for example, in Figures 2 and 4.

[0120] Controllable switches can be provided to turn each individual VCO core or connecting circuit 7 on and off as needed, allowing the total inductance of the coil to be flexibly adjusted. This allows for a highly configurable, composite voltage-controlled oscillator with a very wide tuning range for ESR measurement in different frequency bands. According to the prior art, the only way to achieve this is to use multiple ESR modules, each for different frequency bands, which entails very high implementation costs.

[0121] As an alternative to the VCO case illustrated in Figure 2, the connecting circuits 7 can also be implemented as driver circuits or current sources, respectively, which allows large volumes to be excited with a homogeneous bi-field for conventional ESR experiments based on transmit / receive. To capture the ESR signal, the induced electromotive forces (EMFs) of each inductive segment 5 can be detected and combined.

[0122] The connecting circuits 7 can be implemented as cross-coupled VCO cores, which can lead, for example, to an implementation according to Figure 3. Figure 3 shows an exemplary layout of a 263 GHz segment coil VCO cell (210 pm x 210 pm) with four inductive segments, with VCO cores as connecting circuits 7.

[0123] The inductive element 6 and the connecting circuit 7 of a common inductive segment 5 can therefore preferably be formed in a common integrated circuit (preferably all inductive segments 5 of the inductive assembly 1 are formed in a common integrated circuit).

[0124] The inductive elements 6 can be plate-shaped and made of a metal material or of a coil wire. The inductive elements 6 are generally designed as elongated components and, in particular, have a straight line, wherein the longitudinal extent of the inductive elements 6 preferably does not exceed 1,000 micrometers, more preferably does not exceed 500 micrometers, even more preferably does not exceed 200 micrometers, and most preferably does not exceed 100 micrometers. At this point, it should be emphasized again that larger dimensions can also be used, wherein the longitudinal extent of the inductive elements 6 then, for example, does not exceed 20 millimeters, preferably does not exceed 10 millimeters, more preferably does not exceed 5 millimeters, and even more preferably does not exceed 2 millimeters.

[0125] Figure 3 shows only an advantageous example implementation, including exemplary connection interfaces to the adjacent inductive assemblies 1. In Figure 3, the segmented coil forms the central square with a side length of 100 pm. Four VCO cores connect the individual inductive elements 6.

[0126] Thanks to the significantly increased diameter of the overall coil, the alternating current I generates the desired bi-field in a much larger volume than with a conventional, non-segmented loop coil, while the radiation losses still remain low.

[0127] It has been shown that in the proposed segmented VCO, the oscillating VCO voltage is accessible at multiple outputs, enabling the implementation of 2D injection-locked VCO arrays (see Figure 3). In contrast, state-of-the-art on-chip injection-locked ESR detectors can only be coupled to the two nearest VCO neighbors, resulting in a largely linear injection scheme.

[0128] Figure 4 shows an exemplary circuit model (e.g. for the implementation shown in Figure 3) with exemplary size specifications for the individual electronic components of the VCO cell.

[0129] In order to provide a sufficient negative differential conductance through the cross-coupled pairs at the desired frequency (e.g. 263 GHz), a capacitive circuit (“capacitive degeneration circuit”) can be used, which can act as an open element in combination with tail inductors (Ltaii) and tail capacitors (Ctaii) arranged in parallel with the MOS varactors Cvar.

[0130] The base point inductances Ltaii can be realized, for example, as transmission lines or slab inductances (see Figure 3).

[0131] An exemplary oscillator arrangement 2, particularly for use in a device 12 for generating and / or detecting a magnetization of a sample, is shown in Figure 5. The oscillator arrangement 2 comprises several inductive assemblies 1 according to the invention and a suitable sample location 4 for the sample 3. A possible device 12 according to the invention for generating and / or detecting a magnetization of the sample 3, with a corresponding oscillator arrangement 2, is also shown in the circuit diagram of Figure 6.

[0132] The overall architecture of the VCO array chip shown in Figures 5 and 6 consists, for example, of 8x4 segmented VCOs or inductive modules 1, each of which is injection locked with the four neighboring inductive modules 1 via coupling capacitors 13 (e.g. 10 fF coupling capacitors).

[0133] The specific number of inductive modules 1 connected to one another in a frequency-synchronized manner is not necessarily important within the scope of the invention - however, a plurality of inductive modules 1 are preferably arranged in a row and column arrangement ("array"), as indicated in Figure 5 and Figure 6, wherein preferably at least two columns and / or at least two rows are provided.

[0134] The common frequency of the oscillator array 2 can be taken over by one of the VCOs, buffered, and further processed by a divide-by-3 injection-locked frequency divider (ILFD). The input-related tuning range of the ILFD in the free-running state can be designed to be larger than that of the VCO array (e.g., 1 to 5 times larger, in particular 3 times larger) to ensure overlap between the two ranges under all so-called PVT conditions ("process, supply voltage, and temperature").

[0135] The tuning voltage of the ILFD can be generated on-chip or off-chip (e.g., to provide an additional degree of freedom for the joint tuning of the ILFD and the VCO array or oscillator array 2). The output frequency of the ILFD can be fed into a regenerative divide-by-2 circuit (Db2), the output of which feeds a chain of CML dividers.

[0136] In the exemplary implementation, the oscillator arrangement 2 has two frequency outputs with division factors of 192 and 384, which correspond to output frequencies of 1.37 GHz and 685 MHz, respectively.

[0137] An exemplary chip was manufactured in 130 nm BiCMOS technology (fmax=450 GHz), with a chip area of ​​4.2 mm 2and a power consumption of 4.3 W. The chip's potential tuning characteristics were measured (see left graph in Figure 7); this is 2 GHz, which is sufficient for detecting most ESR spectra and covers the range of most DNP active ingredients. The phase and frequency noise were then measured. The corresponding results, relative to the VCO frequency, are also shown in Figure 7 (the two right-hand graphs). The measured results are in good agreement with the worst-case corner simulations.

[0138] Figure 8 shows an exemplary measurement setup for a device 12 according to the invention. Figure

[0139] Figure 10 shows a further schematic circuit arrangement of a device 12 according to the invention. Since the basic principle of the measuring method is known, it will be described only in a basic manner below. For further details, reference is made, for example, to DE 10 2016 102 025 A1 or WO 2017 / 088852 A1.

[0140] The device 12 comprises a device 14 for providing a static magnetic field Bo in a predetermined direction and strength at the sample location 4 (see in particular Figure 10). A magnet, which can be, for example, a superconducting magnet (e.g., a 9.4 T magnet), an electromagnet of any design, a permanent magnet, or an internal sample-intrinsic magnet (e.g., dipole fields), provides the static magnetic field Bo at the sample location 4 where a sample 3 is arranged. The magnetic field Bo induces a magnetization in the sample 3 corresponding to the susceptibility of the sample 3.

[0141] By means of the oscillator arrangement 2, an additional magnetic field Bi is provided at the sample location 4. For this purpose, the sample location 4 is preferably located in the near field of the oscillator arrangement 2. The oscillator arrangement 2 is controlled by a time-dependent waveform, which serves as a control voltage by which the frequency of the oscillators in the oscillator arrangement 2 is determined, and a second time-dependent waveform, which serves to manipulate the amplitude of the oscillation of the inductive components 1 in the oscillator arrangement 2. The device 12 can comprise a control device 15 for controlling the oscillator arrangement 2, which is configured to generate the magnetic field Bi by means of the oscillator arrangement 2, which is capable of deflecting the magnetization of the sample 3 at the sample location 4 from the equilibrium position. The time-dependent waveforms can therefore be controlled by the control device 15 (e.g., a personal computer or other digital data processing device, cf.Figure 8) and converted by digital-to-analog converters (not shown).

[0142] To also detect the magnetization of sample 3 at sample location 4, the output voltage 16 of the oscillator arrangement 2 is transferred to an evaluation circuit 17. The evaluation circuit 17 can preferably comprise demodulation means, analog-to-digital converters, and / or digital data processing means. This evaluation circuit 17 can be configured to determine the magnetization of sample 3 and the spin concentration of individual spectral components to be determined therefrom.

[0143] Information about the sample 3 contained in the frequency of the output voltage 16 of the array of LC oscillators (e.g. resonance energies) can be prepared for further processing, e.g. in imaging or process control.

[0144] The magnetic field generated by the current-carrying inductive elements 6 inside the inductive assemblies 1 of the oscillator arrangement 2 is used to manipulate the magnetization of a sample 3. The resulting change in the sample magnetization, in turn, causes a change in the inductance of the inductive elements 6 or in the coils. This change in the individual coils or elements or inductive assemblies 1 then causes a change in the frequency of the arrangement of frequency-synchronized inductive assemblies 1 of the oscillator arrangement 2. The oscillator arrangement 2 thus represents a transmitting device with an extended active area.In addition, it simultaneously also represents a receiving device for the changes in magnetization caused in the sample 3, which can be determined via the oscillation frequency of the oscillator arrangement 2, which is a common oscillation frequency of the coupled, frequency-synchronized inductive assemblies 1.

[0145] Preferably, the individual inductive elements 6 of the inductive assemblies 1 have a longitudinal extension which does not exceed the wavelength of the operating frequency of the oscillator arrangement 2, preferably does not exceed half the wavelength of the operating frequency, particularly preferably does not exceed a quarter of the wavelength of the operating frequency, further preferably does not exceed a fifth of the wavelength of the operating frequency, for example does not exceed a tenth of the operating frequency.

[0146] The resulting spectrum of an exemplary sample of BDPA, a common ESR standard (i.e., a preliminary ESR spectrum measured on a 720+ / -30 nm film of α,γ-bisdiphenylene-β-phenylallyl (BDPA):benzene complex diluted in polymethyl methacrylate (PMMA), 1.5 wt%), is shown in Figure 9. The spectrum was recorded through the fabricated chip in a real measurement setup according to Figure 8. For this purpose, the chip was embedded in a PLL at the PCB level. The ESR experiment was performed with continuous wave frequency scanning (i.e., in the so-called continuous wave mode) in a preclinical 9.4 T MRI scanner.

[0147] Overall, the proposed device 12 based on the oscillator arrangement 2 according to the invention represents a promising alternative to the bulky and costly conventional HFESR and high-frequency DNP devices due to the increased detectable measurement volume at high frequencies due to the large number of channels and the measurement range perpendicular to the chip surface extended by the segmented coil design.

[0148] Compared to a conventional gyrotron, the exemplary chip according to the invention generates similar Bi intensities in the relevant range with a 109-fold reduction in size and a 1000-fold reduction in power consumption. The chip offers the frequency flexibility required by all modern DNP sequences and requires no additional detection electronics. This could pave the way for the next generation of affordable yet powerful HFESR and DNP spectrometers.

[0149] For example, the invention can be used at field strengths in the range between 0.01 and 50 T, preferably in the range between 0.5 and 20 T, particularly preferably in the range between 5 T and 10 T, e.g. 9.4 T.

[0150] The invention can be used, for example, at operating frequencies between 1 and 500 GHz, preferably in the range between 10 and 400 GHz, particularly preferably in the range between 200 and 300 GHz, e.g., in the range between 261.3 and 263.6 GHz. The invention can also be advantageously used for particularly low-frequency applications (in particular for imaging), e.g., at frequencies below 100 MHz, for example, below 50 MHz, below 20 MHz, below 10 MHz, or below 5 MHz. Even at such low frequencies, it is advantageous to implement comparatively large coils in order to increase the concentration sensitivity, for example, to measure small animals using ESR imaging.

[0151] The sensitive volume can be, for example, 10 nl and more, for example, 30 nl and more, for example, 32 nl.

Claims

Patent claims 1. Inductive assembly (1) for use in an oscillator arrangement (2) for generating and / or detecting a magnetization of a sample (3), comprising a plurality of interconnected inductive segments (5), each of the inductive segments (5) comprising an inductive element (6) and a connecting circuit (7) electrically connected to the inductive element (6) for electrical connection to an adjacent inductive segment (5).

2. Inductive assembly (1) according to claim 1, characterized in that the inductive element (6) and the connecting circuit (7) of a common inductive segment (5) are formed in a common integrated circuit, wherein preferably all inductive segments (5) of the inductive assembly (1) are formed in a common integrated circuit.

3. Inductive assembly (1) according to claim 1 or 2, characterized in that the inductive elements (6) are plate-shaped and made of a metal material (“slab metal inductor”) or of a coil wire (“single turn spiral inductor”).

4. Inductive assembly (1) according to one of claims 1 to 3, characterized in that the inductive elements (6) are each one-piece, monolithic components.

5. Inductive assembly (1) according to one of claims 1 to 4, characterized in that the inductive elements (6) are elongated components, in particular with a straight line, wherein the longitudinal extent of the inductive elements in each case preferably does not exceed 10 millimeters, more preferably does not exceed 5 millimeters, even more preferably does not exceed 1,000 micrometers, most preferably does not exceed 500 micrometers.

6. Inductive assembly (1) according to one of claims 1 to 5, characterized in that the inductive segments (5) are connected to one another in a series arrangement, preferably in an at least substantially annular, self-contained arrangement.

7. Inductive assembly (1) according to one of claims 1 to 6, characterized in that two to 20 inductive segments (5) are provided, preferably four to eight inductive segments (5), for example exactly four inductive segments (5).

8. Inductive assembly (1) according to one of claims 1 to 7, characterized in that an even number of inductive segments (5) is provided.

9. Inductive assembly (1) according to one of claims 1 to 8, characterized in that the inductive elements (6) are directly electrically connected to the corresponding connecting circuits (7) or that the inductive elements (6) directly electrically contact corresponding terminals of the corresponding connecting circuits (7).

10. Inductive assembly (1) according to one of claims 1 to 9, characterized in that the connecting circuits (7) each have a first connection interface (8) which is electrically connected to the inductive element (6) of the same inductive segment (5), and each have a second connection interface (9) which is electrically connected to an inductive element (6) of an adjacent inductive segment (5).

11. Inductive assembly (1) according to one of claims 1 to 10, characterized in that the connecting circuits (7) are each designed as a driver circuit and / or as a voltage-controlled oscillator (“Voltage-Controlled Oscillator”, VCO).

12. Inductive assembly (1) according to one of claims 1 to 11, characterized in that the connecting circuits (7) each have a capacitive component, preferably a controllable capacitive component (Ovar), in particular a capacitance diode.

13. Inductive assembly (1) according to claim 12, characterized in that the capacitive component (Ovar) in the assembly of the inductive segments (5) is connected between two immediately adjacent inductive elements (6).

14. Inductive assembly (1) according to one of claims 1 to 13, characterized in that the connecting circuits (7) each have two cross-coupled transistors.

15. Inductive assembly (1) according to one of claims 1 to 14, characterized in that all inductive elements (6) are electrically connected to a common star point (10), preferably arranged in a symmetrical arrangement around the common star point (10), in particular via respective high-impedance line sections (11).

16. Inductive assembly (1) according to claim 15, characterized in that the common star point (10) is connected to an electrical reference potential (Vdd), preferably to a ground potential.

17. Oscillator arrangement (2), in particular for use in a device (12) for generating and / or detecting a magnetization of a sample (3), comprising at least one inductive assembly (1) according to one of claims 1 to 16.

18. Oscillator arrangement (2) according to claim 17, characterized in that a plurality of the inductive assemblies (1) are connected to one another in a frequency-synchronized manner, preferably at least two inductive assemblies (1), more preferably at least four inductive assemblies (1), even more preferably at least eight inductive assemblies (1), even more preferably at least 16 inductive assemblies (1), for example at least 32 inductive assemblies (1).

19. Oscillator arrangement (2) according to claim 17 or 18, characterized in that a plurality of the inductive assemblies (1) are arranged in a row and column arrangement ("array"), wherein preferably at least two columns and / or at least two rows are provided.

20. Device (12) for generating and / or detecting a magnetization of a sample (3), comprising an oscillator arrangement (2) according to one of claims 17 to 19 and a sample location (4) for the sample (3).

21. Device (12) according to claim 20, characterized by a device (14) for providing a magnetic field, in particular a static magnetic field (Bo), in a predetermined direction and strength at the sample location (4), wherein by means of the oscillator arrangement (2) an additional magnetic field (Bi) can be provided at the sample location (4) and / or the magnetization of the sample (3) can be detected at the sample location.

22. Device (12) according to claim 20 or 21, characterized by a control device (15) for controlling the oscillator arrangement (2) in such a way that a magnetic field (Bi) is generated by means of the oscillator arrangement (2) which is capable of deflecting a magnetization of the sample (3) at the sample location (4) from an equilibrium position.

23. Device (12) according to one of claims 20 to 22, characterized in that the sample location (4) is located in the near field of the oscillator arrangement (2).

24. Device (12) according to one of claims 20 to 23, characterized by an evaluation circuit (17) for processing an output voltage (16) of the oscillator arrangement (2), wherein the evaluation circuit (17) preferably has means for demodulation, analog-digital converters and / or means for digital data processing.

25. Device (12) according to one of claims 20 to 24, characterized in that the evaluation circuit (17) is arranged to determine the magnetization of the sample (3) and the spin concentration of individual spectral components to be determined therefrom.

26. Device (12) according to one of claims 20 to 25, characterized in that the individual inductive elements (6) of the inductive assemblies (1) have a longitudinal extent which does not exceed the wavelength of the operating frequency of the oscillator arrangement (2), preferably does not exceed half the wavelength of the operating frequency, particularly preferably does not exceed a quarter of the wavelength of the operating frequency, further preferably does not exceed a fifth of the wavelength of the operating frequency, for example does not exceed a tenth of the operating frequency.

27. Method for generating and / or detecting a magnetization of a sample (3) at a sample location (4), in particular for electron spin resonance spectroscopy or nuclear magnetic resonance spectroscopy, comprising at least the following steps: Providing at least one inductive assembly (1) having a plurality of interconnected inductive segments (5), each of the inductive segments (5) having an inductive element (6) and a connecting circuit (7) electrically connected to the inductive element (6) for electrical connection to an adjacent inductive segment (5); Providing a magnetic field (Bo), in particular a static magnetic field, in a predetermined direction and strength at the sample location (4); and Operating the at least one inductive assembly (1) to provide an additional magnetic field (Bi) at the sample location (4), preferably a transient magnetic field, and / or to detect the magnetization of the sample (3) at the sample location (4).

28. Method according to claim 27, characterized in that a plurality of the inductive assemblies (1) are operated with their frequencies synchronized with one another, preferably within a common oscillator arrangement (2).

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