Inductive arrays, oscillator assemblies, devices, and methods for generating and / or detecting magnetization in a sample

Abstract

An inductive assembly is provided that can be used to achieve a large effective volume for excitation and detection and high concentration sensitivity, preferably with low power consumption. [Solution] The present invention relates to an inductive array particularly for use in an oscillator arrangement for generating and / or detecting magnetization of a sample, having a plurality of inductive segments, each of which has an inductive element and a connection circuit electrically connected to the inductive element for electrically connecting to adjacent inductive segments.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims priority from German Patent Application No. 10 2023 103 994.6, filed February 17, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present invention particularly relates to an inductive assembly for use in an oscillator configuration for generating and / or detecting the magnetization of a sample.

[0003] Furthermore, the invention relates in particular to an oscillator configuration for use in an apparatus for generating and / or detecting the magnetization of a sample.

[0004] The invention also relates to an apparatus and method for generating and / or detecting the magnetization of a sample, in particular in electron spin resonance or nuclear magnetic resonance spectroscopy.

[0005] The invention particularly relates to generating and / or detecting magnetic resonance of a sample, such as is used in electron spin resonance spectroscopy or nuclear magnetic resonance spectroscopy, which are used, inter alia, in experimental physics, chemistry, medical technology or geosciences. [Background technology]

[0006] In electron spin resonance spectroscopy (abbreviated ESR, sometimes also called EPR (electron paramagnetic resonance)) and nuclear magnetic resonance spectroscopy (abbreviated NMR), a sample in a static uniform, static non-uniform, or dynamic (pulsed non-uniform) magnetic field, commonly referred to as B0, is exposed to an additional high-frequency alternating electromagnetic field (most commonly in the microwave range of 1-263 GHz for ESR), commonly referred to as B1.

[0007] Coupling an alternating magnetic field (B1) of appropriate frequency and polarization induces transitions between the energy levels of the discrete spin states of the sample's nuclei and / or between the sample's electronic configurations, which then cause detectable absorption processes in the alternating magnetic field. From the detected absorption processes, various material analysis information about the sample can be determined. In this case, the B1 field is typically oriented perpendicular to B0.

[0008] Therefore, all samples that can be characterized by ESR or NMR experiments are linearly magnetizable samples, i.e., paramagnetic samples with unpaired electrons (ESR) or diamagnetic samples with nuclei having a "net nuclear spin" with an odd number of nucleons (NMR). Samples can be liquid, solid, or gaseous. Hereinafter, the term "sample" will generally always refer to the magnetizable sample mentioned above.

[0009] For further technical background, see US Pat. No. 6,299,629 or US Pat. No. 6,299,629, the disclosures of which are hereby incorporated by reference in their entirety into this patent application.

[0010] Electron spin resonance spectroscopy is a powerful method that uses the spin of unpaired electrons as a nanoscale probe into the interior of molecules to obtain information about chemical structure and composition through minute changes in their resonant frequency.

[0011] Electron spin resonance spectroscopy is used to examine and monitor a wide spectrum of materials, ranging from defects in semiconductors to free radicals in blood to metal catalysts in hydrogen production as a fuel. Measurements are typically performed in a moderate static magnetic field of about 0.3 T, which corresponds to an ESR frequency of about 9 GHz. This combination of magnetic flux density and ESR frequency is widely used because it is generally technically easy to generate a 0.3 T magnetic field with sufficient homogeneity to obtain the required 9 GHz frequency signal.

[0012] However, access to higher frequencies and magnetic fields is desirable due to the possibility of higher spin polarization (and correspondingly larger signal amplitudes), higher spectral resolution (e.g., determination of the electronic and geometric structure of active centers in enzymes), and access to higher energy transitions (e.g., those occurring in metal complexes and materials of interest in antiferromagnetic spintronics). High frequency ESR (HFESR or HFESR) with operating frequencies above 90 GHz is therefore desirable.

[0013] Another important driving force for HFESR is dynamic nuclear polarization (DNP). This method can be used to improve the relatively low sensitivity of nuclear magnetic resonance spectroscopy by transferring higher electron polarization itself to nuclear spins. Currently, the market is mainly dominated by commercial HFESR-based DNP spectrometers with an ESR operating frequency of 263 GHz (9.4 T), which corresponds to a proton NMR frequency of 400 MHz. These known spectrometers use gyrotrons as the source of the millimeter-wave magnetic field (B1 field), which makes them extremely expensive to purchase.

[0014] Current HFESR spectrometers use one of four methods to generate the B1 field for HFESR / DNP: vacuum tubes (gyrotrons and inverse wave oscillators), active frequency multiplier chains, synchrotron radiation, and more recently, THz photomixers.

[0015] However, all these methods have significant drawbacks in terms of their complexity and cost. The first three methods require the use of large, complex quasi-optical systems (size >1 m2) to efficiently manipulate the millimeter waves, and furthermore, cryogenically cooled radiation detectors (bolometers) to detect them with sufficient sensitivity. THz photomixers require only a few THz lenses, but for this purpose require complex fiber optic equipment to achieve sufficient spectral resolution, and are less sensitive than the other three methods.

[0016] To overcome the limitations of conventional ESR designs, many oscillator-based CMOS-integrated ESR detectors ("EPR / ESR-on-a-chip") for different fundamental frequencies up to 146 GHz have been proposed in recent years. For example, in Non-Patent Document 1, a voltage-controlled oscillator (VCO) was proposed as an electron spin resonance (ESR) sensor. This technology allows the VCO frequency to be swept with nearly constant sensitivity over the entire resonant frequency range of the sample. This technology continues to attract attention in the research community because it allows for extremely miniaturized entire ESR spectrometers at very low cost.

[0017] On the other hand, improvements to the basic concept have already been proposed to extend the oscillation frequency up to the millimeter wave band to improve spin sensitivity. Furthermore, methods to simplify the modulation / demodulation electronics (Non-Patent Document 2) and to excite and detect the transient response of electron spin ensembles (Non-Patent Document 3) are also known.

[0018] In Non-Patent Document 4, for example, a single HFESR oscillator operating at 90 GHz was used for ESR measurements at 360 GHz using its fourth harmonic, but the excitation power and sensitivity were relatively low. However, because the coil diameter of the 146 GHz oscillator, which is due to the wavelength of the fundamental frequency, is only 45 μm, and the associated effective volume is extremely small, this technique cannot be effectively used for ESR and DNP experiments at even higher operating frequencies.

[0019] Although VCOs have shown great potential as extremely robust and user-friendly ESR sensors for mass-limited solid samples, their application to spectroscopic measurements of liquid samples is still limited due to the relatively low concentration sensitivity (i.e., the minimum detectable spin density that fills the entire volume of a liquid sample) due to the relatively small measurement volume of planar chip-integrated ("on-chip") detectors.

[0020] One approach to expanding the detectable volume is to use larger diameter chip-integrated coils. However, compromises must be made when selecting the coil size. First, 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 must not exceed a certain fraction α of the wavelength, which is typically between 5 and 10. Second, the large inductance associated with large diameter coils hinders the wide tuning range of the VCO and results in relatively high phase noise.

[0021] One approach to enlarging the detectable volume of a VCO-based ESR detector was presented by [5]. In this case, injection locking between multiple planar VCOs was used to lock all involved VCOs to a single common frequency and phase. The use of an "injection-locked" VCO array has the advantage of simultaneously enlarging the lateral detectable volume and reducing phase noise.

[0022] However, this technique does not allow for the expansion of a single array element, and therefore does not allow for the expansion of the detectable volume perpendicular to the planar array. Furthermore, because the signals of a single VCO are not summed due to injection locking, the improvement in focusing sensitivity is limited to improvements in phase noise. Therefore, a method for increasing the effective volume both transversely and perpendicularly to the coil surface is still needed. It should be noted that when increasing the effective volume perpendicular to the coil surface, known prior art techniques result in a very rapid decrease in sensitivity in this spatial direction, depending on the coil diameter. [Prior art documents] [Patent documents]

[0023] [Patent Document 1] DE 10 2016 102 025 A1 [Patent Document 2] International Publication No. WO 2017 / 088852 A1 [Non-patent literature]

[0024] [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 in 2016 [Non-patent document 2] 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 [Non-patent document 3] Silvio Kunstner et al., "Rapid Scan Electron Paramagnetic Resonance using an EPR-on-a-chip Sensor", Magnetic Resonance, May 2021 [Non-patent document 4] 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 [Non-Patent Document 5] Anh Chu et al. in the publication "An 8-Channel 13GHz ESR-on-a-chip injection-locked VCO-array achieving 200μm-concentration sensitivity", IEEE International Solid-State Circuits Conference (ISSCC), pp. 354-355, in 2018 [Non-patent document 6] R. Aparicio and A. Hajimiri in the publication "Circular-geometry oscillators" ISSCC, p. 378-533 in 2004 Summary of the Invention [Problem to be solved by the invention]

[0025] In light of the known prior art, it is an object of the present invention to provide an induction assembly that can be used to achieve, inter alia, a large effective volume for excitation and detection and high concentration sensitivity, preferably with low power consumption.

[0026] The present invention also aims, inter alia, to provide an oscillator arrangement that can be used to achieve a large effective volume for excitation and detection and high concentration sensitivity, preferably with low energy consumption.

[0027] Furthermore, it is an object of the present invention to provide, inter alia, an apparatus and method for generating and / or detecting the magnetization of a sample, with which a large effective volume for excitation and detection and high concentration sensitivity can be achieved, preferably with low energy consumption. [Means for solving the problem]

[0028] For the induction assembly, the object is achieved by the features of claim 1. For the oscillator arrangement, the object is achieved by the features of claim 17. For the device, the object is achieved by claim 20 and for the method, the object is achieved by claim 27.

[0029] The dependent claims and the features described below relate to advantageous embodiments, modifications and alternatively claimable aspects of the invention.

[0030] The present invention relates particularly (but not exclusively) to an inductive assembly for use in an oscillator arrangement for generating and / or detecting magnetization of a sample.

[0031] The inductive assembly has a plurality of interconnected inductive segments, each of which has an inductive element and a connection circuit electrically connected to the inductive element for electrically connecting with adjacent inductive segments.

[0032] Solid, gaseous and / or liquid samples can be used as samples. Liquid samples can be placed, for example, in glass capillaries on planar designs (e.g., CMOS technology). At low frequencies, from B1 to the so-called X-band (approximately 10 GHz), the coil of the LC oscillator can be realized as a volume coil, into which a capillary containing the liquid sample can be inserted, or in combination with a (micro)fluidic system to transport the sample to the detector. Alternatively, these can be combined with other methods, such as immersing or introducing the device into the liquid, gas or solid to be measured, or by spraying. This allows the detection of phase transitions or changes in the aggregation state (transitions). Alternatively, holes can be drilled in the planar coil, e.g., using a laser, and the liquid sample can be introduced.

[0033] Advantageously, the present invention allows for a significant increase in the size of the "tank inductance," e.g., beyond the λ / α limit (where α is any number between 1 and 50, e.g., 5 to 10). The expanded composite coil (also referred to herein as an "inductive assembly") can ultimately be divided into short subsections (also referred to herein as "inductive elements"). Each subsegment or inductive element can be controlled by appropriate electronics (also referred to hereinafter as "connection circuitry"), e.g., in the form of an individual VCO core.

[0034] By incorporating a phase coupling circuit between the electronic control blocks, it is possible to synchronize their phases, which allows circulating currents to flow within the large composite coil or the entire inductive assembly, replicating the response characteristics of a virtual large diameter coil, while keeping radiation losses and parasitic fields at low levels.

[0035] When using the proposed splitting technique (hereinafter also referred to as "split coil" technique), the inductance of each inductive segment is significantly reduced, resulting in low phase noise and a wide tuning range. This is especially true when the individual electronic driving blocks or the connection circuits between the inductive elements are designed as or comprise VCO cores, and the whole system, i.e., the whole inductive assembly, functions as a VCO as well.

[0036] Incidentally, a technique of dividing a coil into multiple segments and arranging a VCO core between the segments has already been proposed in Non-Patent Document 6 for the purpose of improving the Q value of the coil. In contrast, the segmented coil technology of the present invention can be used to provide a large inductor or inductive assembly with a significantly increased effective measurement volume compared to conventional coils as a sensor for HFESR and B1 field sources for high-field ESR / DNP measurements and low-frequency imaging.

[0037] According to one development of the invention, the inductive element can be formed from a metal material in the form of a plate ("slab metal inductor") or from a coil of wire ("single-turn spiral inductor").

[0038] The above variants are merely examples and are not limiting: in principle, the inductive element can be realized in any way.

[0039] In one development of the invention, it can be provided in particular that the inductive elements are each single-piece monolithic components, for example they are adjacent metallization sections, such as tracks, in an integrated circuit.

[0040] However, if desired, each inductive element can also be made from several parts (although this is less preferred).

[0041] In one development of the invention, the inductive element can be configured as an elongated part, in particular with a straight profile.

[0042] In each case, the longitudinal extent of the inductive elements can be configured to preferably not exceed 20 millimeters (although applications with longer longitudinal extents are of course not excluded), more preferably not exceed 10 millimeters, even more preferably not exceed 5 millimeters, and even more preferably not exceed 2 millimeters. However, one preferred application of the invention can relate to even smaller dimensions, i.e., the longitudinal extent of the inductive elements can be no more than 1000 micrometers, preferably no more than 500 micrometers, more preferably no more than 200 micrometers, and even more preferably no more than 100 micrometers. In particular, depending on the specific application, the individual inductive elements can be made sufficiently small relative to the wavelength used to avoid or at least sufficiently reduce parasitic radiation.

[0043] In one advantageous development of the invention, the guide segments can be connected to one another in a series arrangement, preferably in an at least substantially annular self-contained arrangement.

[0044] In this case, between 2 and 100 (or more) guide segments can be provided, in particular up to 20 guide segments, preferably between 4 and 8 guide segments, for example exactly 4 guide segments.

[0045] In particular, the number of induction segments may be an even number.

[0046] In an advantageous development of the invention, the inductive element can be configured to be directly electrically connected to the corresponding connection circuit or to be in direct electrical contact with the corresponding terminal of the corresponding connection circuit.

[0047] However, if desired, an indirect electrical connection between the inductive element and the connecting circuitry can be made via further components or structures.

[0048] In particular, the connection circuits may be configured to each have a first connection interface electrically connected to or connectable to an inductive element of the same inductive segment, and / or each have a second connection interface electrically connected to or connectable to an inductive element of an adjacent inductive segment.

[0049] According to one development of the invention, the connection circuits can each be configured to comprise a capacitive component, preferably a controllable capacitive component, in particular a varactor diode ("varactor").

[0050] The capacitive component is preferably arranged in each case between two directly adjacent inductive elements in the combination of inductive segments, and thus can be joined, for example, between the connection interfaces of the connecting circuit.

[0051] In an advantageous development of the invention, the connection circuits can each comprise two cross-coupled transistors, preferably MOSFETs, bipolar transistors or GaN-based transistors.

[0052] A circuit arrangement for a single LC VCO can be designed, for example, with a differential varactor diode and a differential inductor together forming an LC oscillator circuit.

[0053] Two cross-coupled transistors can ensure stable oscillation at the differential output (i.e., output voltage) through negative resistance and nonlinearity between the two nodes. Tuning characteristics can be ensured by differential varactor diodes.

[0054] The time-dependent variation of the oscillation amplitude can be achieved, for example, by manipulating the power supply of the LC VCO. This simple LC VCO design achieves low power consumption, small size, and can operate in low temperature (down to cryogenic) environments.

[0055] Overall, within the scope of the present invention, a larger measurement volume and a significant reduction in unwanted electric fields can be achieved at the expense of higher power consumption.

[0056] The proposed technique can be extended to generate a uniform B1 field in three dimensions (in this context, the B1 field is the microwave magnetic field that resonates with the spin ensemble) by combining two large coil VCOs in a Helmholtz configuration or multiple large coil VCOs to form a cylindrical coil, which can be achieved, for example, by drilling through holes in each large coil VCO if the individual coils are monolithic.

[0057] According to one development of the invention, it is possible in particular to electrically connect some, preferably all, of the inductive elements to a common (central) star point and preferably to arrange them in a symmetrical arrangement around the common star point, which in this case preferably forms the central point of the arrangement, and the electrical connection can in particular be established via the respective high-resistance cable sections.

[0058] A "high resistance cable section" in this context means in particular a cable section whose electrical resistance is greater than the electrical resistance of the inductive element, preferably much greater, for example by 1, 2, 3, 4, 5 or more orders of magnitude.

[0059] In one advantageous development, it can be provided, in particular, that the common star point is connected to an electrical reference potential, preferably to ground potential.

[0060] Preferably, the connection circuits are designed as voltage-controlled oscillators. However, in one development of the invention, it is also possible to design the connection circuits respectively as driver circuits or any other circuit which seems appropriate.

[0061] The proposed configuration of the LC oscillator can be implemented entirely using integrated circuit technology, i.e., using only active and / or passive elements. This reduces the number of discrete components and, where appropriate, eliminates the need for external components. This allows for cost-effective, low-power, and potentially portable devices. The symmetrical design and high reproducibility of the individual circuit elements, as is possible with MEMS technology, are advantageous for the device according to the invention. This allows for the reduction of interfering signals (especially in amplitude detection).

[0062] According to one development of the invention, the inductive elements and the connection circuit of the common inductive segment can be formed in a common integrated circuit.

[0063] Preferably, all of the inductive segments of the inductive assembly are formed within a common integrated circuit.

[0064] However, it is also possible that individual components or all of the components are formed as individual electrical components on an electrical circuit board, for example, rather than on an integrated circuit.

[0065] The present invention also relates to an oscillator arrangement comprising at least one inductive assembly according to embodiments herein, in particular an oscillator arrangement for use in an apparatus for generating and / or detecting the magnetization of a sample.

[0066] Preferably, the entire oscillator arrangement, and in particular all the inductive assemblies of the oscillator arrangement, are formed in a common integrated circuit.

[0067] In one advantageous development of the invention, it is possible to connect a plurality of induction assemblies to one another in a frequency-synchronized manner, preferably at least two induction assemblies, more preferably at least four induction assemblies, even more preferably at least eight induction assemblies, even more preferably at least 16 induction assemblies, for example at least 32 induction assemblies or even more induction assemblies.

[0068] Here, frequency synchronization (frequency locking) is understood to mean that the same free oscillation frequency is forced on the inductive assemblies by circuit means.

[0069] Advantageously, a relatively large inductor, i.e., one whose perimeter is a significant fraction of the wavelength, can be used as the "tank inductor" in an injection-locked VCO-based ESR detector array, which allows for an increased measurement volume perpendicular to the chip surface compared to conventional loop inductors.

[0070] In one embodiment, frequency synchronization of the inductive assemblies can be achieved by interconnection as a coupling network. "Interconnection by a coupling network" means that the oscillating signal of an oscillator is fed to one or more other oscillators in the array by passive or active circuit elements. This has the effect of causing the output signals of all oscillators to oscillate at the same frequency. In this case, the phase of the oscillating signal depends on the coupling network. This has the advantage that the oscillators are frequency synchronized, and by appropriately selecting the coupling network, it is also possible to set a predetermined phase difference between the oscillating signals of the oscillators. Depending on the type of coupling network, phase noise can be reduced compared to the phase noise of a single oscillator. Passive coupling networks consume less power than active networks.

[0071] In another embodiment, the frequency synchronization of the inductive assemblies can be achieved by a network interconnection. In this case, each LC oscillator has an additional input and an output voltage, and at least one additional LC oscillator is fed to the additional input, with the LC oscillators interconnected on at least two sides. This likewise ensures that the output signals of all oscillators oscillate at the same frequency. The phase also depends on the coupling network. Here, too, it is advantageous that the oscillators are synchronized in frequency, and by appropriately selecting the network interconnection, it is even possible to set a defined phase difference, if any, between the oscillating signals of the oscillators.

[0072] In one development of the invention, it is possible to arrange a plurality of inductive assemblies in an arrangement of rows and / or columns, in particular in an array, preferably with at least two columns and / or at least two rows, and therefore the oscillator arrangement may also be referred to below as a "VCO array".

[0073] The spatial design of the arrangement of individual guide assemblies, preferably as a planar composite system of rows and columns (also called an "array"), when the number is greater than two, allows for any arrangement of the guide assemblies relative to one another, including the special cases of a single row or a single chain. In this case, the characterization "planar" encompasses not only flat designs but also any curved surface (e.g., cylindrical, conical, spherical), with or without edges.

[0074] The invention also relates to an apparatus for generating and / or detecting the magnetization of a sample, comprising an oscillator arrangement according to the embodiments described herein and a sample position relative to the sample.

[0075] The sample position is the position within the device where the sample is placed (optionally the sample can be fastened or fixed to the sample position) and where both the magnetic field (B0) and, if appropriate, an additional (e.g., transient) magnetic field (B1) are present.

[0076] Means for fastening and storing the sample can be provided.

[0077] Designs that implement both transmitter and receiver in a common location are particularly advantageous, as this allows for a particularly simplified, cost- and space-saving construction.

[0078] In one development, the apparatus can be configured to include a device for providing a magnetic field, in particular a static (or quasi-static) magnetic field at the sample position in a predetermined direction and strength, in which case the oscillator arrangement can be used to provide an additional magnetic field at the sample position and / or to detect the magnetization of the sample at the sample position.

[0079] The device generating the directional magnetic field in the proposed arrangement can be realized, for example, by a superconducting magnet, an electromagnet of any design, or a permanent magnet.

[0080] The generated magnetic field is preferably static and corresponds to the aforementioned magnetic field B0 used to magnetize a sample suitable for magnetization, and in this case the strength of the magnetic field can be arbitrary, provided that the frequency of the excitation magnetic field B1 is selected according to the resonance condition.

[0081] In one development of the invention, the apparatus can further be configured to comprise a control device for controlling the oscillator arrangement, which control device is set up and connected to the oscillator arrangement in such a way that the oscillator arrangement is used to generate a magnetic field capable of deflecting the magnetization of the sample at the sample location from its equilibrium position.

[0082] The control device can be designed as a microprocessor. Instead of a microprocessor, any other device implementing the control device can be provided, such as one or more arrangements of discrete electrical components on a printed circuit board, a programmable logic controller (PLC), an application specific integrated circuit (ASIC), or other programmable circuitry, such as a field programmable gate array (FPGA), a programmable logic array (PLA), and / or a commercially available computer.

[0083] In an advantageous development of the invention, it can be provided that the sample position is arranged in the near field of the oscillator arrangement.

[0084] The near-field in the device can be understood here as the field of the LC oscillator. In the case of a magnetically linear sample material, the B1 field rotates due to J≫∂D / ∂t, and the entire B1 field is primarily determined by the current density J in the inductive element due to div B = 0. In contrast, in the far-field, wave propagation occurs due to J≪∂D / ∂t. In the near-field, the B1 field can therefore be generated almost independently of the E1 field, since no waves exist in the near-field region yet. This fact allows for greater freedom to optimize the E1 field or keep it low. A low E1 field minimizes electrical losses in the sample and losses due to sample heating, which can be one of the advantages of this device.

[0085] In one development, the device can be provided with an evaluation circuit for processing the output voltage of the oscillator arrangement, which evaluation circuit preferably comprises demodulation means, an analog-to-digital converter and / or digital data processing means.

[0086] By performing demodulation downstream of the LC oscillator arrangement, the oscillation frequency change of the LC oscillator arrangement can be detected. Demodulation can be performed by a frequency demodulator. Depending on the converter or demodulator selected, before or after conversion or demodulation, the analog signal is converted to a digital signal by appropriate means.

[0087] Changes in the oscillation amplitude can be detected by means downstream of the LC oscillator array. The amplitudes of the individual LC oscillators in the array are not synchronized by coupling. Therefore, a signal corresponding to the magnetization of the sample in the sensitive volume of this LC oscillator can be extracted from each individual LC oscillator. This provides additional signals that allow local resolution. It should be noted that in this case, the amplitude of the LC oscillators is subject to coupling within the LC oscillators, which may require signal correction. The amplitude-modulated signal can be extracted by simple means at the individual LC oscillators. Therefore, each LC oscillator only requires one amplifier for the signal (usually in the kHz range in continuous wave experiments), which, when using the power supply that powers the LC oscillators, is directly available at baseband by inherent demodulation and is extracted at the LC oscillator node. In this case, there is no need to downmix the signal from the Larmor frequency. In addition to optimizing the circuit complexity, this also optimizes power consumption.

[0088] In one development of the invention, the evaluation circuit can be configured to determine the magnetization of the sample and the spin concentrations of the individual spectral components identified therefrom.

[0089] According to one development of the invention, it can further be provided that the individual inductive elements of the inductive assembly do not exceed the wavelength of the operating frequency of the oscillator arrangement, preferably do not exceed half the wavelength of the operating frequency, particularly preferably do not exceed a quarter wavelength of the operating frequency, more preferably do not exceed a fifth wavelength of the operating frequency, for example do not exceed one tenth of the operating frequency.

[0090] It should be noted here that the term "connected" or "connection" used in this specification and claims can describe not only a direct electrical connection of the described components, but also an indirect electrical connection of the described components (i.e., a connection via, for example, a further electrical cable or electronic components such as a resistor, inductor, and / or capacitor), whereas the terms "joined" or "contacting" typically indicate a direct connection of the described components.

[0091] The present invention also relates to a method for generating and / or detecting the magnetization of a sample at a sample location, in particular in electron spin resonance spectroscopy or nuclear magnetic resonance spectroscopy, comprising at least the steps of: providing at least one induction assembly having a plurality of interconnected induction segments, each induction segment having an induction element and a connection circuit electrically connected to the induction element for electrically connecting adjacent induction segments.

[0092] Optionally, among other things, the method further comprises: - providing a magnetic field, in particular a static magnetic field, with a predetermined direction and strength at the sample location; - operating at least one induction assembly to provide an additional magnetic field, preferably a transient magnetic field, at the sample location and / or to detect the magnetization of the sample at the sample location; can also be provided.

[0093] It should be emphasized that the method steps do not necessarily have to be performed in the order originally described or mentioned in the description or claims. For example, individual method steps or groups of method steps are interchangeable unless technically precluded. Method steps may also be combined with one another, divided into separate intermediate steps, or additional intermediate steps may be added. Also, the method is not necessarily described in complete detail by the method steps described below, and additional method steps not described may be added.

[0094] In an advantageous development of the invention, a number of inductive assemblies can be arranged to operate frequency-synchronously with one another, preferably within a common oscillator arrangement.

[0095] In summary, a method is proposed to synthesize electrically large coils for improved 3D detection volumes in spin-detection experiments such as ESR, NMR, or FMR (ferromagnetic resonance).

[0096] To increase the sensitivity volume of electron spin resonance detection, multiple oscillator cores can be advantageously combined.

[0097] For VCO-based detection, the proposed method preferably combines multiple VCOs to form a composite VCO with an electrically large coil, however, the method is also applicable to conventional transmit-receive spin detection setups.

[0098] The proposed method eliminates or suppresses radiation effects associated with large coils, which are highly undesirable especially in the case of liquid samples, preferably to a level that is negligible in practice or for each intended application, while at the same time realizing a low phase noise and widely tunable VCO detector.

[0099] The invention also relates to a computer program comprising control commands which cause the method according to the present invention (or any other work step in the general inventive concept) to be carried out when the program is executed by a control device.

[0100] Features described in relation to one of the inventive objects, i.e., the induction assembly, the oscillator arrangement, the device, the method and the computer program, can also be advantageously applied to the other inventive objects, and likewise, advantages identified in relation to one of the inventive objects can also be understood in relation to the other inventive objects.

[0101] Furthermore, it should be noted that the words "comprising", "having" or "comprising" do not exclude other features or steps, and the words "a", "an" or "the" referring to a step or feature in the singular do not exclude a plurality of features or steps (and vice versa).

[0102] However, in a pure embodiment of the invention, it may be provided that the features introduced into the invention by the expressions "comprises", "has" or "comprises" constitute an exhaustive list. Thus, in the context of the invention, for example, one or more lists of features can be considered self-contained for each claim. For example, the invention may consist only of the features specified in claim 1.

[0103] It should be noted that terms such as "first" and "second" are primarily used to distinguish features of each device or method, and are not necessarily intended to indicate that the features are interdependent or related to each other.

[0104] It should further be noted that the values ​​and parameters described herein also include deviations or variations of up to ±10%, preferably up to ±5%, more preferably up to ±1%, and particularly preferably up to ±0.1% of the respective stated value or parameter, unless such deviations are practically excluded in the practice of the invention. The specification of ranges by starting and ending values ​​also encompasses all values ​​and subvalues ​​thereof, in particular the starting value, the ending value and the respective average value, respectively, included in the stated range.

[0105] It should also be noted that each of the drawings depicts a preferred exemplary embodiment showing individual features of the invention in combination with one another, however, features of one exemplary embodiment may also be practiced separately from other features of the same exemplary embodiment and, therefore, may be readily combined with features of other exemplary embodiments by one skilled in the art to form further useful combinations and sub-combinations.

[0106] The invention will be explained in more detail below on the basis of the drawings, in which: [Brief explanation of the drawings]

[0107] [Figure 1] An inductive assembly according to the present invention having a plurality of interconnected inductive segments for use in an oscillator arrangement. [Figure 2] 1 shows a guide assembly according to the present invention in further detail. [Figure 3] 1 shows an example of chip integration of an inductive assembly according to the present invention. [Figure 4] 1 shows an example of a circuit layout for an inductive assembly according to the present invention. [Figure 5] An apparatus according to the invention for generating and / or detecting the magnetization of a sample at a sample location, the apparatus comprising an oscillator arrangement in which a plurality of induction assemblies are arranged in a matrix. [Figure 6] 1 is a circuit diagram of a device according to the invention; [Figure 7] Measured electrical properties of a device according to the invention. [Figure 8] 3 is a circuit schematic diagram showing further details of the device according to the invention; [Figure 9] Example measurement data of ESR measurement. [Figure 10] 1 is a schematic circuit diagram of an apparatus for generating and detecting magnetic resonance. DETAILED DESCRIPTION OF THE INVENTION

[0108] Figure 1 shows very schematically a guide assembly 1 according to an exemplary embodiment of the present invention. Figure 2 shows further details and optional developments of exemplary guide assembly 1. Exemplary implementations are shown in Figures 3 and 4.

[0109] The proposed induction assembly 1 is particularly suitable for use in an oscillator arrangement 2 (see for example FIG. 5) for generating and / or detecting the magnetization of a sample 3 at a sample position 4 .

[0110] The inductive assembly 1 includes a plurality of interconnected inductive segments 5. Each inductive segment 5 includes an inductive element 6 and a connection circuit 7 electrically connected to the inductive element 6 for electrically connecting adjacent inductive segments 5. The inductive segments 5 are connected to one another in a series arrangement, forming a self-contained circular arrangement in the illustrated embodiment.

[0111] 1 and 2 illustrate the proposed concept using an exemplary split coil with eight coil segments or inductive elements 6 and eight electronic blocks / drive circuits or connection circuits 7. However, the illustration with exactly eight inductive segments 5 should be understood as an example only. In principle, it is possible to provide 2 to 20 inductive segments 5, preferably 4 to 8 inductive segments 5, for example exactly four inductive segments 5 (see also the implementations of FIGS. 3 and 4). Preferably, the number of inductive segments 5 is an even number.

[0112] As shown, functionally, a relatively large induction coil can be divided into multiple induction (coil) segments 6, which can be electrically connected by a connection circuit 7, e.g., a driver circuit. The connection circuit 7 can ensure (preferably, at least approximately) a phase relationship between the currents in the individual induction elements 6 that corresponds to the current distribution in a low-frequency loop coil. Corresponding to the phase synchronization of the individual induction elements 6 or induction segments 5, a continuous AC current I (indicated by the arrow in the center of the induction assembly 1 in FIG. 1) can flow, which mimics the response of a low-frequency AC current in a simple loop coil.

[0113] In principle, N-fold segmentation allows the perimeter of the coil to be increased by a factor of N for a given radiation loss.

[0114] The inductive elements 6 are in particular directly electrically connected to or in direct electrical contact with the terminals of the corresponding connection circuits 7. The connection circuits 7 in particular each have a first connection interface 8 electrically connected to the inductive elements 6 of the same inductive segment 5 and may also have a second connection interface 9 electrically connected to the inductive elements 6 of the adjacent inductive segment 5 (see in particular FIG. 2 ).

[0115] 2 and 3, an optional configuration can be adopted in which all inductive elements 6 are electrically and symmetrically connected to a common star point 10. This is preferably realized via respective high-resistance cable sections 11. The common star point 10 can be connected to an electrical reference potential Vdd, preferably ground potential, thereby ensuring correct phase synchronization between the VCO cores and avoiding the possibility of DC latching or other parasitic oscillation modes. The high-resistance cable sections 11 can be realized by thin conductor tracks bridging the midpoints of the inductive elements 6 connected to Vdd.

[0116] Optionally, auxiliary circuitry (e.g., diodes) can be used in place of the high resistance cable section 11 to suppress undesirable parasitic oscillation modes while keeping the central region of the large composite coil free, particularly for drilling.

[0117] In order to connect adjacent inductive elements 6 to each other in each case, the connection circuits 7 can in particular be VCO cores, each of which is connected to a varactor diode C, as shown in particular in FIGS. var and two cross-coupled transistors (especially MOSFETs, bipolar transistors or GaN-based transistors).

[0118] Controllable switches can be provided to enable each individual VCO core or each connecting circuit 7 to be switched on or off as required, allowing the overall inductance of the coil to be flexibly adjusted. In this way, a highly configurable composite voltage-controlled oscillator can be provided with a very wide tuning range for ESR measurements in different frequency bands. In the prior art, the only way to achieve this was to use multiple ESR assemblies, in each case for different frequency bands, which resulted in very high implementation costs.

[0119] As an alternative to the VCO illustrated in Figure 2, the connection circuit 7 can also be implemented as a driver circuit or power supply, allowing for large-capacity excitation by a uniform B1 field on a transmit-receive basis in conventional ESR experiments. To detect the ESR signal, the electromotive forces (EMFs) induced in each inductive segment 5 can be detected and combined with each other.

[0120] The connection circuit 7 can be realized as a mutually coupled VCO core, for example, as shown in Figure 3. Figure 3 shows an example layout of a 263 GHz segment coil VCO cell (210 μm × 210 μm) with four inductive segments, using a VCO core as the connection circuit 7.

[0121] Therefore, the inductive elements 6 and the connection circuitry 7 of the common inductive segment 5 are preferably formed in a common integrated circuit (in particular, it is preferred that all inductive segments 5 of the inductive assembly 1 are formed in a common integrated circuit).

[0122] The inductive element 6 can be formed in the shape of a plate from a metal material or a coiled wire. The inductive element 6 is usually designed as an elongated part, in particular having a linear profile. Here, the longitudinal extent of the inductive element 6 in each case preferably does not exceed 1000 micrometers, more preferably does not exceed 500 micrometers, even more preferably does not exceed 200 micrometers, and particularly preferably does not exceed 100 micrometers. It should be noted here again that larger dimensions are also possible, in which case the longitudinal extent of the inductive element 6 would, for example, 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.

[0123] Figure 3 shows just one example of an advantageous implementation, including an exemplary connection interface to an adjacent inductive assembly 1. In Figure 3, the segmented coil forms a central square with sides of 100 μm length. Four VCO cores connect the individual inductive elements 6.

[0124] Thanks to this significantly increased diameter of the entire coil, the alternating current I generates the desired B1 field in a much larger volume than a conventional unsplit loop coil, while still maintaining low radiation losses.

[0125] It has been shown that the proposed segmented VCO allows oscillating VCO voltages to be available at multiple outputs, enabling the realization of a two-dimensional "injection-locked" VCO array (see Figure 3). In contrast, prior art chip-integrated "injection-locked" ESR detectors can only couple to the two nearest neighboring VCOs, resulting in a nearly linear injection scheme.

[0126] FIG. 4 shows an example circuit model (eg, the implementation shown in FIG. 3) along with example size specifications for the individual electronic components of the VCO cell.

[0127] To obtain sufficient negative differential conductivity through the cross-coupled pair at the desired frequency (e.g., 263 GHz), a capacitive degeneration circuit can be used. This circuit uses a MOS varactor C var The base point inductor or tail inductor (L tail ) and "tail capacitor" (C tail ) can function as an opening element.

[0128] Base point inductor L tail can be realized, for example, as a transmission line or a slab inductor (see FIG. 3).

[0129] 5 shows, in particular, an exemplary oscillator arrangement 2 for use in an apparatus 12 for generating and / or detecting the magnetization of a sample. The oscillator arrangement 2 comprises a plurality of inductive assemblies 1 according to the invention and suitable sample positions 4 for the sample 3.

[0130] A possible device 12 according to the invention for generating and / or detecting the magnetization of a sample 3 with a corresponding oscillator arrangement 2 is also illustrated with reference to the circuit diagram of FIG.

[0131] The overall configuration of the VCO array chip shown in Figures 5 and 6 is, for example, composed of 8 x 4 segmented VCO or inductive assemblies 1, each assembly being injection locked to four adjacent inductive assemblies 1 via coupling capacitors 13 (e.g., 10 fF coupling capacitors).

[0132] The specific number of inductive assemblies 1 connected to each other in a frequency synchronized manner is not necessarily a requirement in the context of the present invention, but it is preferred to arrange a plurality of inductive assemblies 1 in an arrangement of rows and columns ("array"), preferably with at least two columns and / or at least two rows, as shown in Figures 5 and 6.

[0133] The common frequency of oscillator arrangement 2 can be taken from one of the VCOs and buffered and further processed by an "injection-locked divider by 3 (ILFD)". The input-related tuning range of the ILFD in free-running state can be designed to be larger than that of the VCO array (e.g., 1-5 times, especially 3 times) to ensure overlap of the two ranges under so-called PVT (process P, voltage V, temperature T) conditions.

[0134] The tuning voltage for the ILFD can be generated on-chip or off-chip (e.g., to provide an additional degree of freedom for common tuning of the ILFD and the VCO array, or oscillator configuration 2). The output frequency of the ILFD is fed to a regenerative divide-by-2 circuit (Db2), whose output feeds a chain of CML dividers.

[0135] In the exemplary implementation, 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.

[0136] Chip area 4.2mm 2 The example chip, which consumes 4.3W of power, is manufactured using 130nm BiCMOS technology (f max The chip was fabricated at a frequency of 450 GHz. The tuning capability of the chip (see the left graph in Figure 7) is 2 GHz, which is sufficient for most ESR spectrum detection and covers the range of most DNP-active materials. Phase and frequency noise were then measured. The measurement results related to VCO frequency are also shown in Figure 7 (the two right graphs). The measurement results showed good correlation with worst-case corner simulations.

[0137] Figure 8 shows an exemplary measurement setup of the device 12 according to the invention. Figure 10 shows yet another schematic circuit arrangement of the device 12 according to the invention. The basic principles of the measurement method are known, so only a basic description will be given below. For further details, see, for example, US Pat. No. 5,629,997 or US Pat. No. 5,629,997.

[0138] The apparatus 12 comprises a device 14 for providing a static magnetic field B of a predetermined direction and strength at the sample position 4 (see in particular FIG. 10 ). A magnet, which may be, for example, a superconducting magnet (e.g., a 9.4 T magnet), an electromagnet of any design, a permanent magnet, or an internal magnet specific to the sample (e.g., a dipole field), provides the static magnetic field B at the sample position 4 where the sample 3 is placed. The magnetic field B induces a magnetization in the sample 3 according to the magnetic susceptibility of the sample 3.

[0139] The oscillator arrangement 2 is used to supply an additional magnetic field B1 to the sample position 4. For this purpose, the sample position 4 is preferably within the magnetic field proximity of the oscillator arrangement 2. The oscillator arrangement 2 is controlled by a time-dependent waveform that serves as a control voltage used to determine the frequency of an oscillator in the oscillator arrangement 2, and a second time-dependent waveform that serves to manipulate the oscillation amplitude of the induction assembly 1 in the oscillator arrangement 2. The apparatus 12 can comprise a control device 15 for controlling the oscillator arrangement 2, which is set up to use the oscillator arrangement 2 to generate a magnetic field B1 that can deflect the magnetization of the sample 3 at the sample position 4 from its equilibrium position. Thus, the time-dependent waveform is provided by the control device 15 (e.g., a personal computer or other digital data processing device, see FIG. 8) and converted by a digital-to-analog converter (not shown).

[0140] In order to detect the magnetization of the sample 3 at the sample position 4, the output voltage 16 of the oscillator arrangement 2 is transferred to an evaluation circuit 17, which may preferably comprise demodulation means, an analog-to-digital converter and / or digital data processing means. This evaluation circuit 17 may be set up to determine the magnetization of the sample 3 and the spin concentrations of individual spectral components identified therefrom.

[0141] Information about the sample 3 (eg, resonance energy) contained in the frequency of the output voltage 16 of the LC oscillator arrangement can be prepared for further processing, such as imaging or process control.

[0142] The magnetic field generated by the current-carrying inductive element 6 inside the inductive assembly 1 in the oscillator arrangement 2 is used to manipulate the magnetization of the sample 3. The resulting change in the sample magnetization causes an inductance change in the inductive element 6 or coil. This change in the individual coil, element, or inductive assembly 1 results in a frequency change in the frequency-locked inductive assembly 1 arrangement of the oscillator arrangement. The oscillator arrangement 2 therefore constitutes a transmitter with an extended effective range. Furthermore, it simultaneously functions as a receiver of the magnetization change induced in the sample 3. This magnetization can also be determined by the oscillation frequency of the oscillator arrangement 2, which is the common oscillation frequency of the coupled frequency-locked inductive assembly 1.

[0143] Preferably, the individual inductive elements 6 of the inductive assembly 1 have a longitudinal extent that 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 wavelength of the operating frequency, more preferably does not exceed a fifth wavelength of the operating frequency, for example does not exceed one tenth of the operating frequency.

[0144] Figure 9 shows the spectrum obtained for an exemplary sample of α,γ-bisdiphenylene-β-phenylallyl (BDPA) according to a standard ESR standard (i.e., a preliminary ESR spectrum measured on a 720±30 nm film of BDPA:benzene complex diluted at 1.5 wt. % in polymethyl methacrylate (PMMA)). This spectrum was recorded with a fabricated chip in the actual measurement setup according to Figure 8. For this purpose, the chip was embedded in a PLL at PCB level. The ESR experiments were performed in a preclinical 9.4 T MRI scanner with continuous wave frequency scanning (i.e., in the so-called continuous wave mode).

[0145] Overall, the proposed apparatus 12 based on the oscillator arrangement 2 according to the present invention is a promising alternative to bulky and expensive 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 extended measurement range perpendicular to the chip surface due to the segmented coil design.

[0146] Compared to conventional gyrotrons, the exemplary chip of the present invention reduces size by a factor of 109 and power consumption by a factor of 1000 while producing similar B1 intensities in the relevant range. In this case, the chip provides the frequency flexibility required for all modern DNP sequences and does not require additional detection electronics. This could pave the way for affordable yet powerful next-generation HFESR and DNP spectrometers.

[0147] For example, the present invention can be used at a field strength in the range of 0.01 to 50T, preferably in the range of 0.5 to 20T, particularly preferably in the range of 5T to 10T, for example, 9.4T.

[0148] The present invention can be used at operating frequencies in the range of, for example, 1 to 500 GHz, preferably 10 to 400 GHz, particularly preferably 200 to 300 GHz, for example, 261.3 to 263.6 GHz.

[0149] The present invention may be particularly advantageously used in low frequency applications (especially imaging), for example at frequencies below 100 MHz, e.g., below 50 MHz, below 20 MHz, below 10 MHz, or below 5 MHz. Even at such low frequencies, it may be advantageous to implement relatively large coils to increase concentration sensitivity, for example for measuring small animals using ESR imaging.

[0150] The sensitive volume may be, for example, 10 nl or more, for example, 30 nl or more, for example, 32 nl.

Claims

1. 1. An oscillator arrangement for use in an apparatus for generating and / or detecting magnetization of a sample, comprising a plurality of inductive assemblies, each comprising a plurality of interconnected inductive segments, each of said inductive segments having an inductive element and a connection circuit electrically connected to said inductive element for electrically connecting to an adjacent inductive segment, said plurality of inductive assemblies being connected to each other in a frequency synchronized manner, said inductive element and said connection circuit of a common inductive segment being formed in a common integrated circuit, and said inductive segments being connected to each other in an at least substantially circular self-contained series arrangement.

2. 2. The oscillator arrangement of claim 1, wherein all of the inductive segments of the inductive assembly are formed in a common integrated circuit.

3. 2. The oscillator arrangement according to claim 1, characterized in that the inductive element is formed in the form of a plate from a metallic material ("slab metal inductor") or a coiled wire ("single turn spiral inductor").

4. 2. An oscillator arrangement according to claim 1, characterized in that said inductive elements are each single-piece monolithic components.

5. 2. The oscillator arrangement according to claim 1, characterized in that the inductive element is an elongated part, in particular having a linear profile, the longitudinal extent of which in each case preferably does not exceed 10 millimeters, more preferably does not exceed 5 millimeters, even more preferably does not exceed 1000 micrometers, particularly preferably does not exceed 500 micrometers.

6. 2. The oscillator arrangement according to claim 1, characterized in that the inductive elements are directly electrically connected to the corresponding connection circuits, or the inductive elements are in direct electrical contact with the corresponding terminals of the corresponding connection circuits.

7. 2. The oscillator arrangement according to claim 1, characterized in that the connection circuits each have a first connection interface electrically connected to the inductive elements of the same inductive segment and a second connection interface electrically connected to the inductive elements of an adjacent inductive segment.

8. 2. The oscillator arrangement according to claim 1, characterized in that the connection circuits are configured as driver circuits and / or voltage controlled oscillators (VCO), respectively.

9. The connection circuits each include a capacitive component, preferably a controllable capacitive component (C ｖａｒ 2. The oscillator arrangement according to claim 1, characterized in that it comprises a rectifier, in particular a varactor diode.

10. 2. The oscillator arrangement of claim 1, wherein said connection circuits each comprise two cross-coupled transistors.

11. 2. The oscillator arrangement according to claim 1, characterized in that all said inductive elements are electrically connected to a common star point, preferably arranged in a symmetrical arrangement around said common star point, in particular via respective high resistance line sections.

12. 12. An oscillator arrangement according to claim 11, characterized in that the common star point is connected to an electrical reference potential (Vdd), preferably ground potential.

13. 2. The oscillator arrangement according to claim 1, characterized in that the inductive assemblies are arranged in a column and row arrangement ("array"), preferably with at least two columns and / or at least two rows.

14. 10. An apparatus for generating and / or detecting the magnetization of a sample, comprising an oscillator arrangement according to claim 1 and a sample position relative to the sample.

15. A magnetic field, in particular a static magnetic field (B ０ ) at the sample position, the oscillator arrangement comprising a device for providing an additional magnetic field (B １ 15. The device of claim 14, wherein the device is operable to provide a magnetization of the sample at the sample location.

16. The oscillator arrangement is used to generate a magnetic field (B) capable of deflecting the magnetization of the sample at the sample location from its equilibrium position. １ 15. The apparatus of claim 14, further comprising a control device for controlling the oscillator arrangement to generate a

17. 15. The apparatus of claim 14, wherein the sample location is within the near field of the transmitter arrangement.

18. 15. The device according to claim 14, further comprising an evaluation circuit for processing the output voltage of the oscillator arrangement, said evaluation circuit preferably comprising demodulation means, an analog-to-digital converter and / or digital data processing means.

19. 15. The apparatus of claim 14, wherein the evaluation circuitry is set up to determine the magnetization of the sample and the spin concentrations of individual spectral components ascertained therefrom.

20. A method for generating and / or detecting the magnetization of a sample at a sample location, in particular in electron spin resonance spectroscopy or nuclear magnetic resonance spectroscopy, comprising at least - providing at least one inductive assembly having a plurality of interconnected inductive segments connected together in an at least substantially annular self-contained series arrangement, each of said inductive segments having an inductive element and a connection circuit electrically connected to said inductive element for electrically connecting to adjacent inductive segments, said inductive element and said connection circuit of a common inductive segment being formed in a common integrated circuit; - At the sample position, a magnetic field (B ０ ), in particular providing a static magnetic field; - operating at least one induction assembly to generate an additional magnetic field (B １ ), preferably providing a transient magnetic field and / or detecting the magnetization of the sample at the sample location.

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