Magnetic field spike detection device, detection method, and power equipment equipped with same

Abstract

To detect magnetic field spikes generated by partial discharge with no-contact and high sensitivity.SOLUTION: A magnetic field spike detection device 10 includes: an electromagnetic wave irradiation unit 2 that repeatedly irradiates a quantum sensor element 1 with an electromagnetic wave for manipulating an electron spin state of the quantum sensor element 1 that changes due to interaction with a magnetic field including a magnetic field spike to be detected in a pulse sequence in which a time τ between π / 2 pulses is determined according to magnitude of the magnetic field spike; and a magnetic field spike detection unit 3 that acquires a plurality of electron spin states after the interaction with the magnetic field including the magnetic field spike, and detects the magnetic field spike based on the acquired electron spin states.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to technology using quantum sensors, and more particularly to a magnetic field spike detection apparatus and method using quantum sensors, and to electric power equipment equipped with the magnetic field spike detection apparatus. [Background technology]

[0002] Electricity is indispensable in modern society, and power facilities have become an essential part of the infrastructure. Once power facilities, including power transmission and transformation equipment such as transformers and switches, are in operation, there are few opportunities to stop them, and if a failure occurs in such power facilities, it can have a major impact on society.

[0003] When power equipment begins to fail in the early stages, partial discharges cause tiny, extremely short pulse-like magnetic fields (hereafter referred to as magnetic field spikes) to be generated in the power equipment. It is known that partial discharges occur when tiny void-like defects exist in the insulators that make up the power equipment, and an electric field concentrates at the defective portion. When partial discharges occur in power equipment, the insulators of the power equipment gradually deteriorate. After a long period of time, this leads to insulation breakdown, causing malfunctions in the operation of the power equipment. For this reason, partial discharges that occur in power equipment are detected in order to quickly detect failures in the power equipment.

[0004] Conventional methods for detecting partial discharge include, for example, electrical detection methods such as the electromagnetic effect method, the outer electrode method, and the electrostatic coupling method. In addition to electrical detection methods, for example, acoustic, chemical, and optical detection methods are known. In the acoustic method, an ultrasonic sensor detects sound pressure waves generated by partial discharge. In the chemical detection method, for example, a color reaction with a trace amount of decomposition gas generated by partial discharge is used to detect partial discharge. In the optical detection method, a light sensor detects discharge light generated by partial discharge.

[0005] In recent years, diamond has been attracting attention as a material for sensor elements that measure magnetic fields. In the crystal structure of diamond, a complex defect called a nitrogen-vacancy center can be seen. This nitrogen-vacancy center is a pair of a nitrogen atom that replaces the carbon atom in the crystal lattice and a vacancy (where a carbon atom is missing) that exists in the adjacent position of the nitrogen atom, and is also called an NV center (Nitrogen Vacancy center). In addition to the NV center, complex defects called silicon-vacancy centers and germanium-vacancy centers can be seen in the crystal structure of diamond, and these complex defects including the NV center are called color centers.

[0006] The NV center is a state in which an electron is captured by a vacancy (negative charge state, hereafter referred to as "NV - In the NV - is the state where no electrons are captured (neutral state, hereafter referred to as "NV 0 ) has a long transverse relaxation time (decoherence time, hereafter referred to as T 2 "). In other words, NV - In the electron spin state of NV, after the magnetization of the electron spins aligned in the vertical direction of the external magnetic field (hereafter referred to as the "quantization axis") is tilted to the transverse direction, the individual spins are precessed to cause the individual directions to shift, and it takes a long time for the overall transverse magnetization to disappear. - Even at room temperature (approximately 300 K), 2 Indicates the value.

[0007] N.V. - The electron spin state of diamond changes in response to an external magnetic field, and this electron spin state can be measured even at room temperature; therefore, diamond containing NV centers can be used as a material for magnetic field sensor elements.

[0008] For example, Patent Document 1 discloses a method for measuring an AC magnetic field by magnetic resonance caused by electron spins in diamond, in which a pulse sequence based on the spin echo method is applied to the spins.

[0009] For example, Patent Document 2 discloses a method for measuring an AC magnetic field by the Optically Detected Magnetic Resonance (ODMR) method for electron spins in diamond. The NV center is excited by laser light, and a magnetic resonance signal (phase information) related to the spin state is detected by measuring the change in the intensity of the fluorescence emitted from the NV center.

[0010] In addition to the sensor using the color center of diamond, there are various types of sensors used as magnetic field sensor elements, such as sensors using color centers in silicon carbide (SiC), optically pumped atomic magnetometers (OPM), superconducting quantum interference devices (SQUID), etc. These diamond color centers, silicon carbide color centers, optically pumped magnetometers, and superconducting quantum interference devices are called quantum sensors because they use quantum effects to measure physical quantities. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2012-103171 A [Patent Document 2] JP 2017-75964 A Summary of the Invention [Problem to be solved by the invention]

[0012] Magnetic field spikes occurring in power facilities have minute amplitudes of about tens of nT to hundreds of nT, and in order to detect magnetic field spikes, it is necessary to detect the magnetic field with high sensitivity.

[0013] Up to now, electrical detection methods such as electrostatic coupling and electromagnetic coupling have been used to detect partial discharges with high sensitivity. However, in these conventional electrical detection methods, the device for detecting partial discharges is electrically connected to the power equipment, and there is a risk that the detection device itself may break down if a surge occurs in the power equipment, causing an abnormal overvoltage or overcurrent to flow in a short period of time due to the influence of lightning or the like. On the other hand, in methods other than these conventional electrical detection methods, the measurement accuracy of the magnetic field is low, making it difficult to detect the magnetic field with high sensitivity.

[0014] Therefore, there is a demand for a method to detect minute, extremely short pulse-like magnetic field spikes generated by partial discharges with high sensitivity without directly connecting electrically to power equipment.

[0015] An object of the present invention is to detect magnetic field spikes generated by partial discharges in a non-contact manner with high sensitivity. [Means for solving the problem]

[0016] The present invention for solving the above problems includes, for example, the following aspects. (Section 1) an electromagnetic wave irradiation unit that repeatedly irradiates the quantum sensor element with electromagnetic waves for manipulating the electronic spin state of the quantum sensor element, which changes due to interaction with a magnetic field including a magnetic field spike to be detected, in a pulse sequence in which the time τ between π / 2 pulses is determined according to the magnitude of the magnetic field spike; a magnetic field spike detector that acquires a plurality of electron spin states after interacting with the magnetic field including the magnetic field spike, and detects the magnetic field spike based on the acquired plurality of electron spin states; A magnetic field spike detection device comprising: (Section 2) Item 2. The magnetic field spike detection device of item 1, wherein the time τ between the π / 2 pulses is determined according to the pulse height of the magnetic field spike and the duration of the magnetic field spike. (Section 3) 3. The magnetic field spike detection device according to item 1 or 2, wherein the magnetic field spike detection unit detects the magnetic field spikes based on a statistical analysis of a plurality of the electron spin states. (Section 4) The magnetic field spike detection unit includes: a histogram creation unit that creates a histogram of the intensity of the magnetic field by calculating the intensity of the magnetic field based on each of the plurality of electron spin states after the interaction; a magnetic spike extractor for extracting the magnetic spikes by subtracting measurement noise from the histogram; 4. A magnetic field spike detection device according to any one of claims 1 to 3, comprising: (Section 5) Item 5. The magnetic field spike detection device according to item 4, wherein the noise from the measurement is shot noise. (Section 6) 5. The magnetic field spike detection device according to item 4, wherein the magnetic field spike extraction unit extracts the magnetic field spikes by fitting two Gaussian functions having different distributions to the histogram. (Section 7) The magnetic field spike detection unit includes: a light irradiation unit that irradiates the quantum sensor element with light for reading information on the phase of the electron spin state after interacting with the magnetic field including the magnetic field spike; a detection unit that detects a change that occurs in the quantum sensor element due to the irradiation of the light; Further comprising: The histogram creation unit 7. A magnetic field spike detection device according to any one of items 4 to 6, which reads out information about the phase from the detected change, and calculates the strength of the magnetic field based on the read-out information about the phase. (Section 8) 8. The magnetic field spike detection device according to any one of claims 1 to 7, wherein the magnetic field spike detection unit further includes an alarm unit that outputs an alarm signal when the magnetic field spike is detected. (Section 9) A step of repeatedly irradiating the quantum sensor element with electromagnetic waves for manipulating the electronic spin state of the quantum sensor element, which changes due to interaction with a magnetic field including a magnetic field spike to be detected, in a pulse sequence in which the time τ between π / 2 pulses is determined according to the magnitude of the magnetic field spike; acquiring a plurality of electron spin states after interacting with the magnetic field including the magnetic field spike, and detecting the magnetic field spike based on the acquired plurality of electron spin states; 23. A method for detecting magnetic field spikes comprising: (Section 10) The step of detecting magnetic field spikes comprises: creating a histogram of the intensity of the magnetic field by calculating the intensity of the magnetic field based on each of the plurality of electron spin states after the interaction; extracting the magnetic field spikes by subtracting measurement noise from the histogram; Item 10. A method for detecting magnetic field spikes according to item 9, comprising: (Section 11) The step of detecting magnetic field spikes comprises: irradiating the quantum sensor element with light for reading out information of the phase of the electron spin state after interaction with the magnetic field including the magnetic field spike; detecting a change in the quantum sensor element caused by the irradiation of the light; Further comprising: The step of creating a histogram of the magnetic field strength comprises: Item 11. A magnetic field spike detection method according to item 10, further comprising the steps of: reading out phase information from the detected change; and calculating the strength of the magnetic field based on the read out phase information. (Section 12) Item 9. An electric power facility equipped with a magnetic field spike detection device according to any one of items 1 to 8. Effect of the Invention

[0017] According to the present invention, magnetic field spikes generated by partial discharges can be detected in a non-contact manner with high sensitivity. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram showing a schematic configuration of a magnetic field spike detection device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram illustrating an example of a specific configuration of the magnetic field spike detection device shown in FIG. [Diagram 3] 1 is a schematic diagram of an electric power utility including a magnetic field spike detection apparatus according to an embodiment of the present invention; [Figure 4] 1 is a schematic diagram of an electric power utility including a magnetic field spike detection apparatus according to an embodiment of the present invention; [Diagram 5] FIG. 1 is a diagram showing a schematic diagram of the energy levels of electrons in the NV-center of diamond. [Figure 6] 1 is an exemplary pulse sequence for sensing an AC magnetic field by an optically detected magnetic resonance (ODMR) method. [Figure 7] FIG. 2 illustrates an example waveform of a magnetic field spike. [Figure 8] FIG. 2 is a diagram for explaining the magnetic field spike detection concept of the present invention. [Figure 9] FIG. 2 is a diagram for explaining the magnetic field spike detection concept of the present invention. [Figure 10] 3 is a flowchart showing steps of a method for detecting magnetic field spikes according to an embodiment of the present invention. [Figure 11] 4 is an exemplary histogram of magnetic field strength measured in accordance with the present invention, the histogram after subtraction of shot noise. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description and drawings, the same reference numerals denote the same or similar components, and therefore, redundant description of the same or similar components will be omitted.

[0020] In this specification, a physical quantity means a quantity whose dimension is determined under a certain system in physics and which can be expressed as a multiple of a defined physical unit. Examples of physical quantities include a magnetic field, an electric field, temperature, and a mechanical quantity (mechanical stress, pressure, etc.). The magnetic field, the electric field, and the mechanical quantity include a physical quantity that does not change with time, and a physical quantity whose direction repeatedly changes with time. That is, the magnetic field includes a static magnetic field and an alternating magnetic field, the electric field includes a static electric field and an alternating electric field, and the mechanical quantity includes a static mechanical quantity and an alternating mechanical quantity.

[0021] [Device configuration] Fig. 1 is a diagram showing a schematic configuration of a magnetic field spike detector 10 according to an embodiment of the present invention. Fig. 2 is a diagram showing a schematic example of a specific configuration of the magnetic field spike detector 10 shown in Fig. 1.

[0022] A magnetic field spike detection device 10 (hereinafter simply referred to as detection device 10) includes a sensor element 1, an electromagnetic wave irradiation unit 2, and a magnetic field spike detection unit 3. In this embodiment, the sensor element 1 is attached to the tip of a probe 11 of the detection device 10.

[0023] The sensor element 1 is a quantum sensor element. In this embodiment, the sensor element 1 is a diamond crystal having a color center, and an NV center is used as the color center. The NV center is a complex (complex defect) of nitrogen (N) substituting a carbon atom and a vacancy (V) adjacent to the nitrogen. In this embodiment, the sensor element 1 is generated in advance by a known method in a predetermined region on the diamond crystal 12. Illustratively, there are approximately several thousand particles (concentration: 1×10 12 / cm -3) A plurality of sensor elements 1 are generated. In this embodiment, the sensor elements 1 are ensemble NV centers.

[0024] The electronic spin state of the sensor element 1 is changed by an interaction 8 with an object 9. In this embodiment, the object 9 is an electric power facility, and the interaction 8 is an interaction due to a magnetic field. When the interaction 8 is due to a magnetic field, the electronic spin state of the color center of the sensor element 1 becomes a state according to the strength of the magnetic field generated around the object 9, which is the electric power facility.

[0025] The electromagnetic wave application unit 2 applies electromagnetic waves to the sensor element 1 for manipulating the electronic spin state of the sensor element 1 by magnetic resonance. As an example, in this embodiment, the electromagnetic wave application unit 2 includes a known microwave (MW) oscillator 21, a switch 22 for applying electromagnetic waves in a pulsed form, and an amplifier 23. The switch 22 and the amplifier 23 may have any configuration. In this embodiment, the electromagnetic wave application unit 2 applies electromagnetic waves to the sensor element 1 in a pulsed form for manipulating the electronic spin state of the sensor element 1.

[0026] Various pulse sequences for generating magnetic resonance can be used as the pulse sequence of the electromagnetic waves irradiated by the electromagnetic wave irradiating unit 2 to the sensor element 1. For example, when sensing an AC magnetic field, the electromagnetic wave irradiating unit 2 irradiates the sensor element 1 with the electromagnetic waves using a pulse sequence based on the Hahn echo method of the spin echo method.

[0027] The electromagnetic wave irradiation unit 2 irradiates the sensor element 1 with electromagnetic waves for manipulating the electronic spin state of the sensor element 1 in a pulse sequence in which the time τ between π / 2 pulses is determined according to the magnitude of the magnetic field spike. In this embodiment, the time τ between π / 2 pulses is determined according to the magnitude of the magnetic field spike B S The pulse sequence is determined according to the pulse height h and the duration d of the magnetic field spike. The improvements made to the pulse sequence will be described later with reference to FIG.

[0028] The electromagnetic wave irradiating unit 2 irradiates the sensor element 1 with electromagnetic waves through an antenna 14 for irradiating electromagnetic waves that is arranged in the vicinity of the sensor element 1. The antenna 14 is formed on the diamond crystal 12 using a conductive metal, for example, by lithography technology.

[0029] The magnetic field spike detection unit 3 detects magnetic field spikes based on a change in the electronic spin state of the sensor element 1 after the change is caused by an interaction 8 with the object 9. In this embodiment, the magnetic field spike detection unit 3 detects magnetic field spikes based on a statistical analysis of a plurality of electronic spin states. Statistically analyzing the plurality of electronic spin states includes creating a histogram of magnetic field strength by calculating the magnetic field strength for each of the plurality of electronic spin states based on the respective electronic spin states. In this embodiment, the magnetic field spike detection unit 3 calculates the strength of the magnetic field generated around the electric power equipment, which is the object 9, and detects magnetic field spikes based on the calculated magnetic field strength. The magnetic field spike detection unit 3 includes a light irradiation unit 31, a detection unit 32, and a data processing unit 33.

[0030] The light irradiating unit 31 irradiates the sensor element 1 with light for reading out phase information of the electron spin state of the sensor element 1 after interacting with the object 9. The light irradiating unit 31 also irradiates the sensor element 1 with light for initializing the electron spin state of the sensor element 1. As an example, in this embodiment, the light irradiating unit 31 includes a light source 311, an acousto-optical modulator (AOM) 312, and an objective lens 313. The acousto-optical modulator 312 and the objective lens 313 can have any configuration.

[0031] The light source 311 emits light for reading out phase information of the electronic spin state of the sensor element 1 after interaction with the object 9. The light source 311 also emits light for exciting and initializing the electronic spin state of the sensor element 1. The wavelength of the light emitted by the light source 311 is determined according to the type of the sensor element 1. In this embodiment, the light source 311 emits laser light with a wavelength of 532 nm (green). For example, various known laser generating devices can be used as the light source 311. In this embodiment, the light source 311 is a semiconductor laser that emits green laser light.

[0032] The objective lens 313 focuses the light emitted from the light source 311 and irradiates it onto the area on the diamond crystal 12 where the sensor element 1 is generated. Illustratively, the spot size of the laser light focused on the diamond crystal 12 has a diameter of about 2 μm. As the spot size of the laser light decreases, the intensity of the laser light per unit area increases, and the efficiency of the photocurrent generated in the conductive band of the diamond also increases.

[0033] 2, the spot of the laser light is positioned so as to cover the area where the sensor element 1 is generated on the diamond crystal 12. Preferably, the spot of the laser light can be positioned at a position offset from approximately the center of the area where the sensor element 1 is generated.

[0034] The detection unit 32 detects a change occurring in the sensor element 1. In this embodiment, the detection unit 32 detects the light emitted from the sensor element 1, and detects a magnetic resonance signal as a change in light emission intensity by a known optically detected magnetic resonance (ODMR) method. In this case, the detection unit 32 may be, for example, a known photodiode. The photodiode may be, for example, an avalanche photodiode.

[0035] In this embodiment, the electromagnetic wave for operation is irradiated in a pulsed form in the electromagnetic wave irradiation unit 2. Therefore, in this embodiment, specifically, detection is performed by a Pulsed Optically Detected Magnetic Resonance (pODMR) method.

[0036] The data processing unit 33 is connected to the detection unit 32, reads out phase information of the electron spin state of the sensor element 1 after interaction with the object 9 from the change detected by the detection unit 32, and detects magnetic field spikes based on the read out phase information. The data processing unit 33 includes a histogram creation unit 331, a magnetic field spike extraction unit 332, and an alarm unit 333.

[0037] For example, a known general-purpose computer or various information terminal devices such as a smartphone can be used for the data processing unit 33. The data processing unit 33 may be configured to be integrated with the detection device 10, or may be provided outside the detection device 10 and connected to the detection device 10 via a wired or wireless network 99 as shown in the figure.

[0038] The histogram creation unit 331 creates a histogram of the magnetic field strength by calculating the magnetic field strength based on each of the multiple electron spin states after the interaction.

[0039] The magnetic field spike extraction unit 332 extracts magnetic field spikes from the histogram of magnetic field strength. In this embodiment, the magnetic field spike extraction unit 332 extracts magnetic field spikes by subtracting measurement noise from the histogram of magnetic field strength. In this embodiment, the measurement noise is shot noise. In another embodiment, the magnetic field spike extraction unit 332 extracts magnetic field spikes by fitting two Gaussian functions with different distributions to the histogram of magnetic field strength.

[0040] When a magnetic field spike is detected, the alarm unit 333 issues an alarm by, for example, outputting an alarm signal. The alarm signal is transmitted, for example, via a network 99 to a computer device (not shown) that centrally manages the operation status of other power facilities. Alternatively, the alarm signal may be a signal that activates an alarm device (not shown), such as a buzzer.

[0041] 3 and 4 are schematic diagrams of an electric power facility 9 including a magnetic field spike detection device 10 according to an embodiment of the present invention. As the electric power facility 9, a current transformer 9a is illustrated in FIG. 3, and a voltage transformer 9b is illustrated in FIG. The locations of the detection device 10 illustrated in these figures are merely examples.

[0042] The detection device 10 is disposed at a position where it can sense the magnetic field generated around the electric power equipment 9 (9a, 9b). Preferably, the detection device 10 is disposed so that the axial direction along which the sensor element 1 senses the magnetic field is aligned with the direction of the magnetic field generated around the electric power equipment 9.

[0043] [Detection principle] In the present invention, the quantum sensor 1 is used to measure the strength of the magnetic field generated around the target electric power equipment 9. This allows for highly sensitive detection of magnetic field spikes. The magnetic resonance signal used to calculate the magnetic field strength is detected by the optically detected magnetic resonance (ODMR) method. This allows for contactless detection of magnetic field spikes without direct electrical connection to the target electric power equipment 9.

[0044] In the present invention, we devise a pulse sequence of electromagnetic waves to manipulate the electron spin state when measuring magnetic resonance signals, which improves the measurement sensitivity of the magnetic field strength and enables highly sensitive detection of minute, extremely short pulse-like magnetic field spikes generated by partial discharges.

[0045] In the following, the principle and procedure of detecting magnetic resonance signals by the optically detected magnetic resonance (ODMR) method will be described first, and the method of calculating the magnetic field strength from the detected magnetic resonance signals will be described. Next, the invention of the pulse sequence in the present invention will be described. Finally, the concept of detecting magnetic field spikes randomly occurring in an AC magnetic field will be described based on the above-described principle of detecting magnetic resonance signals and the method of calculating the magnetic field strength.

[0046] <Detection of magnetic resonance signals by optically detected magnetic resonance (ODMR) method> Figure 5 shows the NV structure of diamond. - FIG. 2 is a diagram showing a schematic diagram of the energy level of an electron at the center.

[0047] In this embodiment, the NV center of diamond is used as the sensor element 1. The ground state of the NV center has a magnetic quantum number m s =-1,0,+1 spin triplet states, and in the steady state at room temperature, all levels are equally distributed in the ground state.

[0048] The magnetic quantum number m in the ground state s When an electron with a magnetic quantum number m = 0 is irradiated with a laser beam with a wavelength of 532 nm (green), it transitions to an excited state, emits red fluorescence, and has a magnetic quantum number m s =0 ground state.

[0049] On the other hand, the magnetic quantum number m in the ground state s When an electron with a magnetic quantum number m = 0 is irradiated with microwaves with a resonant frequency of 2.87 GHz, electron spin resonance (ESR) occurs, and the magnetic quantum number m s = ±1. The magnetic quantum number m s When an electron with a magnetic quantum number m = ±1 is irradiated with a laser beam with a wavelength of 532 nm (green), it transitions to an excited state, and then, with a certain probability, the magnetic quantum number m s = 0. This series of processes is a non-radiative transition that does not emit fluorescence.

[0050] In this way, the process of emitting red fluorescence occurs when magnetic resonance occurs and the electron changes its magnetic quantum number m s This is unlikely to occur when the magnetic quantum number m s The doubly degenerate ground states of =±1 are split by Zeeman splitting in proportion to the strength of the external magnetic field, so the fluorescence intensity also changes with the magnetic quantum number m s = ±1. Therefore, the magnetic resonance signal can be detected as the point where the red fluorescence intensity decreases when the microwave frequency is swept around 2.87 GHz.

[0051] Fig. 6 shows an exemplary pulse sequence for sensing an AC magnetic field by a method using an optically detected magnetic resonance (ODMR) method. The pulse sequence of an electromagnetic wave for operation shown in Fig. 6 is a pulse sequence based on the Hahn echo method of the spin echo method.

[0052] State I represents the state in which the electron spins are initialized by irradiation with laser light. In the Bloch sphere, which is a notation for expressing a quantum state on a unit sphere, the electron spins are aligned along the z-axis, which is the quantization axis.

[0053] Next, in state II, a π / 2 pulse is applied to tilt the electron spin along the quantization axis to a plane perpendicular to the quantization axis. The electron spin is tilted to the xy plane of the Bloch sphere. After that, the electron spin tilted to the xy plane is in state III for a predetermined time τ 0 During this time, the electron spins undergo dephasing due to interactions with the alternating magnetic field and the static magnetic field. The strength of the interaction corresponds to the strength of the magnetic field felt by the electron spins.

[0054] In state III, a predetermined time τ 0After a time has elapsed, a π pulse is applied in state IV to invert the electron spins, which have been dephased by interaction with the object being measured, in the plane. From state III to state IV, the electron spins dephase while rotating in the xy plane of the Bloch sphere. At this time, in state V after the inversion, the electron spins refocus, canceling out the static magnetic field components, but the AC magnetic field components are not canceled out because their strength is reversed compared to state III.

[0055] While dephasing in state V for a given time τ 0 After a further lapse of time, a π / 2 pulse is applied in state VI to project the dephasing electron spins onto the quantization axis. The electron spins, which were located within the xy plane of the Bloch sphere, are projected onto the z-axis, which is the quantization axis, and aligned along the z-axis.

[0056] Then, in state VII, the sensor element is irradiated with laser light and the light emitted from the sensor element is detected to read out the phase information of the electron spin state after the interaction. The measurement of the magnetic resonance signal (phase information) related to the spin state using such a pulse sequence is repeatedly performed to integrate the signal intensity and improve the S / N ratio.

[0057] In the pulse sequence of the Hahn echo method shown in Fig. 6, the electron spin undergoes phase relaxation while rotating in the xy plane of the Bloch sphere from state III to state V, and in the magnetic resonance method, the signal generated when the electron spin undergoes phase relaxation in this way is detected as a magnetic resonance signal. The time τ between the π / 2 pulses corresponds to the period from state III to state V in which the electron spin undergoes phase relaxation, and this time τ determines the sensitivity of the measurement. This is because the degree to which the electron spin undergoes phase relaxation due to interaction with a magnetic field corresponds to the strength of the magnetic field felt by the electron spin.

[0058] <Method of calculating magnetic field strength based on magnetic resonance signals> In the optically detected magnetic resonance (ODMR) method, phase information (magnetic resonance signal) of the electron spin state of the sensor element 1 after interaction with the object 9 is detected as a change in emission intensity. The detected phase information corresponds to the physical quantity of the object. Therefore, by appropriately processing the detected phase information of the electron spin state after interaction, the physical quantity of the object can be calculated. The physical quantity of the object can be calculated based on the Hamiltonian of the electron spin.

[0059] Electron spin Hamiltonian H gs is expressed by the following formula:

number

[0060] First term

number

[0061] The second and third terms are due to dipole interactions (i.e., spin-spin interactions). The second term

number

number

[0062] Thus, the strength of the magnetic field can be calculated based on the first term, the strength of the temperature and mechanical quantities can be calculated based on the second term, and the strength of the electric field can be calculated based on the third term.

[0063] <Ingenuity applied to pulse sequence> Referring again to FIG. 6, in the pulse sequence for sensing the AC magnetic field B(t) using the method shown in FIG. 6, the time τ between π / 2 pulses is a fixed value corresponding to the wavelength 2π of the AC magnetic field to be measured, and the time τ in state III 0 and time τ for state V 0 is also a fixed value. As described with reference to Fig. 6, the electron spin undergoes phase relaxation while rotating in the xy plane of the Bloch sphere from state III to state V. Here, if the strength of the AC magnetic field is large, the rotation angle of the electron spin in the xy plane exceeds 2π, and conversely, if the strength of the AC magnetic field is small, the rotation angle of the electron spin in the xy plane becomes insufficient, and there is a risk that the strength of the AC magnetic field cannot be measured.

[0064] For these reasons, the strength of the AC magnetic field to be measured is limited by the rotation angle of the electron spin in the xy plane of the Bloch sphere, and the range of the strength of the AC magnetic field that can be measured is also limited by the time τ. When the time τ is fixed, the range of the AC magnetic field that can be measured is also fixed.

[0065] In the present invention, the time τ between π / 2 pulses is determined according to the magnitude of the magnetic field spike to be detected. The time τ is the coherence time T 2 (Transverse relaxation time T 2 ) for a time shorter than the

[0066] 7 shows an example waveform of a magnetic field spike, the actual waveform of which is unknown and is used only to illustrate the concept of magnetic field spike magnitude.

[0067] Magnetic field spike B S The magnitude of the magnetic field spike B S The pulse height h and the magnetic field spike B S Using the duration d of the pulse, it can be expressed as the integral of the pulse height h and duration d. This integral value is the magnetic field spike B S In the magnetic resonance method, a quantity equivalent to this integral value is detected as a magnetic resonance signal. In this embodiment, the magnetic field spike B S The product of the pulse height h and duration d is used as an approximation of the magnitude of the magnetic field spike B. Illustratively, the pulse height h is about 100 nT (nanotesla) and the duration d is about 1 ns (nanosecond). S The magnitude of the pulse height h and the magnetic field spike B S and the full width at half maximum (FWHM) can be used.

[0068] In the present invention, the time τ between π / 2 pulses is determined according to the magnitude of the magnetic field spike, and in this embodiment, the time τ is determined to ensure a sufficient magnitude of the magnetic field spike represented by the product of the pulse height h and the duration d. As described below, the time τ is related to the probability that the magnetic field spike can be measured. In order to achieve efficient measurement, if one tries to achieve both measurement sensitivity and the range of measurable magnetic field strength (dynamic range), there is a trade-off between the time τ and the pulse height h of the detectable magnetic field spike.

[0069] For example, shortening the time τ between π / 2 pulses increases the pulse height h of the detectable magnetic field spike. However, the probability of measuring a magnetic field spike decreases because the time τ between π / 2 pulses is shortened. This is because only magnetic field spikes that occur within the time τ can be detected among the multiple magnetic field spikes that occur randomly and repeatedly in the AC magnetic field.

[0070] Conversely, increasing the time τ between π / 2 pulses increases the probability of being able to measure a magnetic field spike, but at the expense of decreasing the pulse height h of the detectable magnetic field spike, since the range of measurable AC magnetic field strengths is limited by the time τ, as discussed above.

[0071] <Magnetic field spike detection concept> 8 and 9 are diagrams for explaining the magnetic field spike detection concept of the present invention. FIG. 8 shows a magnetic field spike B(t) generated around an AC magnetic field B(t) of a target 9, which is a power facility. S1 ,B S2 This shows how this is occurring.

[0072] FIG. 9A shows the magnetic field spike B shown in FIG. S1 (B) is an enlarged view of the magnetic field spike B shown in FIG. S2 8 and 9, the magnetic field spike B S1 ,B S2 The intensity of the signal is scaled and displayed. For the sake of explanation, the scaling ratio is 10 3 The magnetic field strength on the vertical axis is 10 4 It is.

[0073] Please refer to Figure 8. AC current flows through power equipment that transmits AC power. When a partial discharge begins to occur due to a failure in the power equipment, a magnetic field spike B(t) appears in the AC magnetic field B(t) around the power equipment. S1 ,B S2 occurs randomly.

[0074] Illustratively, the amplitude of the alternating magnetic field B(t) is about 5 mT (millitesla) and the frequency is about 60 Hz. Illustratively, the magnetic field spike B S1 ,B S2 The amplitude (pulse height) of is about 100 nT and the duration is about 1 ns.

[0075] Magnetic field spike B S1 ,B S2 When the AC magnetic field B(t) is generated, the measured value of the AC magnetic field B(t) contains the magnetic field spike B shown in Figure 8 in addition to the so-called shot noise component, which is a noise component contained in the measurement signal itself. S1 ,B S2 Therefore, by subtracting the shot noise component from the measured value of the strength of the alternating magnetic field B(t), the magnetic field spike B S1 ,B S2 It is possible to detect changes in magnetic field strength due to the generation of

[0076] However, as described with reference to FIG. 6, when the time τ between π / 2 pulses is determined in order to measure the alternating magnetic field B(t), the magnetic field strength is limited to 10 3 Small magnetic field spike B S1 ,B S2 It may not be possible to measure the

[0077] In the present invention, the time τ between π / 2 pulses is determined according to the magnitude of the magnetic field spike to be detected, not the magnitude of the alternating magnetic field B(t). Here, as described with reference to FIG. 6, the magnetic field to be detected is not the alternating magnetic field B(t), but a magnetic field spike having a magnetic field strength of 10 3 Small magnetic field spike B S1 ,B S2 In this case, the magnetic field spike B S1 ,B S2 The magnetic resonance signal is detected as an integral of the pulse height and duration of the magnetic field spike B S1 ,B S2This corresponds to the amount of change in magnetic field strength caused by the occurrence of a magnetic field spike B. However, this amount, which corresponds to the integral value, is extremely small, and it is difficult to detect this amount by measuring the magnetic resonance signal only once. S1 ,B S2 The magnetic field strength of is 10 times that of the alternating magnetic field B(t). 3 This is because the magnitude of the spikes is small. In addition, it is difficult to detect all of the multiple randomly occurring magnetic spikes in an AC magnetic field. Of the multiple randomly occurring magnetic spikes, only those that occur within the time τ between π / 2 pulses can be detected.

[0078] In the present invention, magnetic field spikes are detected by statistically analyzing multiple magnetic resonance signals. Specifically, the magnetic resonance signal measurements are repeated many times to increase the number of samples and create a histogram of magnetic field strength. Next, in this embodiment, the components due to shot noise are subtracted from the created histogram to extract the components due to magnetic field spikes. In another embodiment, the components due to magnetic field spikes are extracted by fitting two Gaussian functions with different distributions to the created histogram.

[0079] Please refer to Fig. 9. Symbols I to VII in Fig. 9 correspond to states I to VII of the pulse sequence shown in Fig. 6. In the figure, the solid line indicates the irradiation timing of the laser light, and the dashed line indicates the irradiation timing of the electromagnetic wave for manipulating electron spins.

[0080] In state I, laser light is applied at the timing shown by the solid line. This aligns the electron spin with the z-axis, which is the quantization axis, and initializes the state of the electron spin. In state II, a π / 2 pulse is applied at the timing shown by the dashed line, which tilts the electron spin to the xy plane of the Bloch sphere. In state III, the electron spin undergoes phase relaxation. In state IV, a π pulse is applied at the timing shown by the dashed line, which inverts the electron spin in the xy plane of the Bloch sphere. Note that the electron spin remains phase relaxed even during this inversion. In state V, the electron spin undergoes phase relaxation. In state VI, a π / 2 pulse is applied at the timing shown by the dashed line, which projects the electron spin onto the z-axis, which is the quantization axis. In state VII, laser light is applied at the timing shown by the solid line. This reads out the phase information of the electron spin state after the interaction.

[0081] From state III to state V, the electron spins undergo phase relaxation while rotating in the xy plane of the Bloch sphere. In the detection concept of the present invention, of the multiple magnetic field spikes that occur repeatedly and randomly in the alternating magnetic field B(t), magnetic field spikes that occur between states III and V are detected. In the example shown in FIG. 9, S1 ,B S2 Both occur during state III or state V, and the magnetic field spike B S1 ,B S2 Both of these occur at timings within the time width of a detection window in which a magnetic field spike can be detected. The time width of this detection window in which a magnetic field spike can be detected is the time τ between π / 2 pulses, and as described with reference to FIG. 6, this time τ is determined according to the magnitude of the magnetic field spike to be detected.

[0082] [Detection procedure] FIG. 10 is a flow chart showing steps of a magnetic field spike detection method according to one embodiment of the present invention.

[0083] In step S1, the sensor element 1 is irradiated with laser light to initialize the electron spin of the color center (NV center) of the sensor element 1. Then, the initialized electron spin of the NV center is caused to interact with the AC magnetic field of the object 9. When the interaction is allowed to occur for a sufficient period of time, the electron spin state of the NV center becomes a state corresponding to the intensity of the AC magnetic field. The state of step S1 corresponds to state I of the pulse sequence shown in FIG. 6. When a magnetic field spike is generated in the AC magnetic field, the electron spin of the initialized NV center interacts with the AC magnetic field including the magnetic field spike and becomes a state corresponding to the intensity of the AC magnetic field including the magnetic field spike.

[0084] In step S2, magnetic field sensing is performed by irradiating the sensor element 1 with electromagnetic waves for spin manipulation. In this embodiment, AC magnetic field sensing is performed by irradiating a π / 2 pulse and a π pulse according to the pulse sequence shown in Fig. 6. That is, in this embodiment, the electron spin state of the NV center is manipulated so as to correspond to states II to VI of the pulse sequence shown in Fig. 6. When a magnetic field spike occurs in the AC magnetic field, sensing of the AC magnetic field including the magnetic field spike is performed.

[0085] In step S3, the sensor element 1 is irradiated with laser light, and a change occurring in the sensor element 1 is detected, thereby reading out phase information of the electron spin state after the interaction. In this embodiment, the phase information of the electron spin state after the interaction is read out by detecting light emitted from the sensor element 1. The phase information of the electron spin state after the interaction is detected by the detection unit 32 as a change in emission intensity by an optically detected magnetic resonance (ODMR) method. The state in step S3 corresponds to state VII of the pulse sequence shown in FIG. 6.

[0086] In step S4, it is determined whether the series of measurement processes from steps S1 to S3 has been repeatedly executed a predetermined number of times. If the series of measurement processes has been repeatedly executed a predetermined number of times (Yes in step S4), the process of step S5 is performed, and if it has not been repeatedly executed the predetermined number of times (No in step S4), the process is performed again from step S1. Note that the number of times such a series of measurement processes is repeatedly executed can be changed depending on the frequency or magnitude of the magnetic field spike to be detected.

[0087] It should be noted that when a series of measurement processes are repeatedly performed, the signal strength is accumulated, and therefore the more times the measurement processes are repeatedly performed, the more the S / N ratio of the signal improves.

[0088] In step S5, a histogram of the magnetic field strength is created from the phase information of the electron spin state after the interaction.

[0089] The strength of the magnetic field is calculated from the phase information of the electron spin state after the interaction read out in step S3. The phase information of the electron spin state after the interaction detected by the detection unit 32 corresponds to the AC magnetic field of the object 9. Therefore, the strength of the AC magnetic field can be calculated by appropriately processing the phase information of the detected electron spin state after the interaction. For example, the strength of the AC magnetic field of the object 9 can be calculated by determining the probability that the electron spin state after the interaction will be the ground state. The strength is calculated using the electron spin Hamiltonian H gs When a magnetic field spike occurs in the alternating magnetic field, the phase information of the electron spin state after the interaction corresponds to the alternating magnetic field including the magnetic field spike, and the strength of the alternating magnetic field including the magnetic field spike is calculated.

[0090] The histogram of magnetic field strength is created by calculating the magnetic field strength for each of a plurality of electron spin states after the interaction, based on each electron spin state.

[0091] In step S6, magnetic field spikes are extracted from the magnetic field strength histogram. In this embodiment, the magnetic field spikes are extracted by subtracting measurement noise from the magnetic field strength histogram. In this embodiment, the measurement noise is shot noise.

[0092] 11 shows an exemplary histogram of magnetic field strength measured by the present invention after subtraction of shot noise: (A) shows the entire histogram, and (B) shows a scaled portion of the vertical axis of the histogram shown in (A).

[0093] As shown in (A), there is a large peak near the magnetic field strength of 0 pT (picotesla), and as shown in the enlarged view in (B), there is a fairly small side peak near the magnetic field strength of 3.333 pT. The large peak near 0 pT has width due to shot noise. The fairly small side peak near 3.333 pT is the magnetic field spike B in FIG. 8 that is to be detected in the present invention. S1 ,B S2 This is the peak corresponding to the intensity of

[0094] In step S7, it is determined whether a magnetic field spike has been extracted. For example, it is determined whether the strength of the extracted magnetic field spike is equal to or greater than a predetermined magnitude. Alternatively, referring to FIG. 11, the ratio of the magnetic field strength of the extracted side peak to the magnetic field strength of a large peak near 0 pT is calculated, and the magnetic field strength of the side peak is determined to be approximately 10 times that of the large peak. -3 If so, the extracted side peak is determined to be a magnetic field spike.

[0095] If a magnetic field spike is extracted (Yes in step S7), an alarm is issued in step S8. For example, an alarm signal is output, for example via network 99, to a computer device that centrally manages the operating status of other power equipment. Upon receiving the alarm signal, the computer device for centralized management displays, for example, a message urging maintenance of the power equipment on a monitor of the computer device for centralized management. Alternatively, an alarm such as an alarm that operates upon receiving an alarm signal may be connected to magnetic field spike detection device 10. If a magnetic field spike is not detected (No in step S7), the process is repeated from step S1 to repeatedly detect magnetic field spikes.

[0096] [effect] As described above, according to the present invention, magnetic field spikes caused by partial discharges can be detected in a non-contact manner with high sensitivity, which makes it possible to quickly detect faults in power equipment.

[0097] In the present invention, the strength of the magnetic field generated around the target electric power equipment is measured using a quantum sensor. This makes it possible to detect magnetic field spikes with high sensitivity. The magnetic resonance signal used to calculate the magnetic field strength is detected by the optically detected magnetic resonance (ODMR) method. This makes it possible to detect magnetic field spikes in a non-contact manner without directly connecting electrically to the target electric power equipment.

[0098] In the present invention, we devise a pulse sequence of electromagnetic waves to manipulate the electron spin state when measuring magnetic resonance signals, which improves the measurement sensitivity of the magnetic field strength and enables highly sensitive detection of minute, extremely short pulse-like magnetic field spikes generated by partial discharges.

[0099] [Other formats] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the above-described embodiments.

[0100] In the above embodiment, the sensor element 1 is irradiated with an electromagnetic wave for manipulating the electron spin state in a pulse sequence based on the Hahn echo method of the spin echo method, but the pulse sequence of the electromagnetic wave for manipulating the electron spin state is not limited to the Hahn echo method. For example, when sensing an AC magnetic field, the sensor element 1 can be irradiated with an electromagnetic wave for manipulating the electron spin state in a pulse sequence based on the double echo method of the spin echo method. Alternatively, the π pulse may be omitted in the Hahn echo method exemplified in the above embodiment, and a magnetic resonance signal may be detected by a pulse sequence including two π / 2 pulses. That is, a free induction decay (FID) signal may be used instead of the echo method to detect the magnetic resonance signal.

[0101] The double echo method is explained. In the double echo method, electromagnetic waves for manipulating the electron spin state are irradiated in the order of a first π / 2 pulse, a first π pulse, a second π pulse, and a second π / 2 pulse. Expressed using the time τ between π / 2 pulses, the first π pulse is irradiated at a time τ / 4 after the first π / 2 pulse is irradiated. The second π pulse is irradiated at a time τ / 2 after the first π pulse is irradiated. The second π / 2 pulse is irradiated at a time τ / 4 after the second π pulse is irradiated.

[0102] In the present invention, even when a pulse sequence other than the Hahn echo method is used, the time τ between π / 2 pulses is determined according to the magnitude of the magnetic field spike to be detected, as explained in the above embodiment. Of course, the time τ is determined based on the coherence time T 2 (Transverse relaxation time T 2 ) for a time shorter than the

[0103] In the above embodiment, the magnetic field spikes are extracted by subtracting the shot noise, which is a noise caused by the measurement, from the histogram of the magnetic field strength, but the method of extracting the magnetic field spikes is not limited to this. For example, the magnetic field spikes can be extracted by fitting two Gaussian functions with different distributions to the histogram of the magnetic field strength.

[0104] A method for extracting a magnetic field spike using two Gaussian functions will be described by way of example. For example, as the two Gaussian functions, a first Gaussian function representing a large peak and a second Gaussian function representing a small side peak are defined as shown in FIG. 11. Next, these two Gaussian functions are data-fitted to a histogram of the magnetic field strength. After the data fitting, the accuracy of the fitting is confirmed. If it is determined that the data fitting has been performed with appropriate accuracy, the second Gaussian function representing the small side peak represents the magnetic field spike. Therefore, the second Gaussian function obtained by the data fitting corresponds to the magnetic field spike to be extracted.

[0105] In the above-described embodiment, the magnetic field spike detection device 10 detects magnetic field spikes in the magnetic field occurring around the power equipment 9, and although a current transformer 9a and a voltage transformer 9b are exemplified as examples of the power equipment 9, the power equipment 9 is not limited to these. The power equipment 9 can include, for example, power transmission and transformation equipment such as a transformer and a switchgear.

[0106] [Example] The following examples of the present invention will make the features of the present invention clearer. EXAMPLES

[0107] In the first embodiment, a numerical simulation was performed for each of a case where a magnetic field spike occurs in the power equipment and a case where a magnetic field spike does not occur.

[0108] Numerical simulation conditions The amplitude of the AC magnetic field used as the basis for the numerical simulation was set to 5 mT and the frequency to 60 Hz. It was also assumed that one magnetic field spike would occur on average for every 60 Hz period of the AC magnetic field. In other words, the rate of the magnetic field spikes was also set to 60 Hz.

[0109] The assumed conditions (a) to (e) for the sensor element samples and pulse sequences are as follows:

[0110] (a) Coherence time T 2 is 60μs (b) The diameter of the laser spot is 40 μm, and the NV center density “NV” is 1×10 19 cm -3 Therefore, the number of NV centers in a spherical volume is approximately 3.3 × 10 11 (c) The contrast between spin states is about 2%. (d) On average, 0.1 photons per readout per NV center. (e) The laser pulse length is 30 μs, the waiting time is 1 μs, the π / 2 pulse length is 40 ns, and the delay between these pulses is about 30 μs.

[0111] The assumed measurement models (i) to (vi) are as follows: (i) The probability that a randomly occurring magnetic field spike will be present between π / 2 pulses is the delay between the π / 2 pulses divided by the length of the entire pulse sequence: in this example, 30 μs / 62.08 μs ≈ 0.48325, or about 48%.

[0112] (ii) The probability of a magnetic field spike occurring during a pulse sequence is given by its rate. In this example, it is 60 Hz x 62.08 μs x 10 -6 =0.0037248.

[0113] (iii) The total probability that the pulse sequence measures a magnetic field spike is 0.48325 × 0.0037248 = 0.0018... or 0.18%. Here, the same result was obtained if we calculated the probability of a single magnetic field spike in any 30 μs interval, assuming a Poisson distribution.

[0114] (iv) The probability of multiple magnetic field spikes occurring during a single pulse sequence is low and negligible, and is therefore ignored in this embodiment.

[0115] (v) The background is completely subtracted. In this embodiment, the background is a magnetic field that oscillates periodically at 60 Hz. Note that it is not essential to subtract the background. As long as the background is within the range of the selected pulse sequence, a non-zero average background also works.

[0116] (vi) Only the largest noise source, shot noise, is considered.

[0117] Comparison of cases with and without magnetic field spikes The comparison by numerical simulation was performed assuming multiple cases with different combinations of the occurrence rate of magnetic field spikes, the amplitude of the magnetic field spikes, the duration of the magnetic field spikes, and the measurement time.

[0118] The generation rate of the magnetic field spike was set to three patterns: 0Hz, 60Hz, and 600Hz. The amplitude of the magnetic field spike was set to three patterns: N / A (not available), 100nT, and 300nT. The duration of the magnetic field spike was set to three patterns: N / A (not available), 1ns, and 3ns. The measurement time was set to three patterns: 200 hours, 2 hours, and 72 seconds.

[0119] From the results of the numerical simulation, the expected magnetic field strength, average magnetic field strength, and measurement uncertainty of the magnetic field spike were considered. The results of the numerical simulation are shown in Table 1. In Table 1, the average magnetic field strength and uncertainty are obtained from the statistics of the measurement simulation data proposed in this embodiment. [Table 1] Based on the specification conditions of the NV center and the measurement sequence, the measurement sensitivity is about 1pTHz. -0.5 Therefore, the theoretical uncertainty in a 200-hour measurement is 1×10 13 / √(200×3600)=1.1785 fT (femtotesla). The expected magnetic field strength was about 6 fT.

[0120] The results of the numerical simulations shown in Table 1 indicate that if the magnetic field spike to be detected has the rate, amplitude, and duration shown in Simulation No. 3 or No. 4, for example, it is possible to detect the magnetic field spike through approximately two hours of measurement. [Explanation of symbols]

[0121] 1. Sensor element (Nano-Voltage center in diamond) 2 Electromagnetic wave irradiation section 3 Magnetic field spike detector 8 Interaction 9 (9a, 9b) Electric power equipment (current transformers, voltage transformers) 10 Magnetic field spike detector 11 Probe 12 Diamond Crystal 14 Antenna 21 Microwave (MW) Oscillator 22 Switch 23 Amplifier 31 Light irradiation unit 311 Light source 312 Acousto-optic Modulator (AOM) 313 Objective Lens 32 Detection unit 33 Data Processing Section 331 Histogram Creation Section 332 Magnetic field spike extractor 333 Alarm section 99 Network

Claims

1. an electromagnetic wave irradiation unit that repeatedly irradiates the quantum sensor element with electromagnetic waves for manipulating the electronic spin state of the quantum sensor element, which changes due to interaction with a magnetic field including a magnetic field spike to be detected, in a pulse sequence in which the time τ between π / 2 pulses is determined according to the magnitude of the magnetic field spike; a magnetic field spike detector that acquires a plurality of electron spin states after interacting with the magnetic field including the magnetic field spike, and detects the magnetic field spike based on the acquired plurality of electron spin states; Equipped with The magnetic field spike detection unit includes: a histogram creation unit that creates a histogram of the intensity of the magnetic field by calculating the intensity of the magnetic field based on each of the plurality of electron spin states after the interaction; a magnetic spike extractor for extracting the magnetic spikes by subtracting measurement noise from the histogram; 1. A magnetic field spike detection apparatus comprising:

2. 2. The magnetic field spike detection apparatus of claim 1, wherein the time τ between said π / 2 pulses is determined as a function of the pulse height of said magnetic field spike and the duration of said magnetic field spike.

3. 3. The magnetic field spike detection apparatus according to claim 1, wherein the magnetic field spike detector detects the magnetic field spikes based on a statistical analysis of a plurality of the electron spin states.

4. 2. The magnetic field spike detection apparatus of claim 1, wherein said measurement noise is shot noise.

5. 2. The magnetic spike detection device according to claim 1, wherein the magnetic spike extraction section extracts the magnetic spikes by fitting two Gaussian functions having different distributions to the histogram.

6. The magnetic field spike detection unit includes: a light irradiation unit that irradiates the quantum sensor element with light for reading out information on the phase of the electron spin state after interacting with the magnetic field including the magnetic field spike; a detection unit that detects a change that occurs in the quantum sensor element due to the irradiation of the light; Further comprising: The histogram creation unit 6. The magnetic field spike detection device according to claim 1, further comprising: a detector for detecting a change in phase of the detected change; and a detector for detecting a change in phase of the detected change;

7. 7. The magnetic field spike detection device according to claim 1, wherein the magnetic field spike detection section further comprises an alarm section that outputs an alarm signal when the magnetic field spike is detected.

8. A step of repeatedly irradiating the quantum sensor element with electromagnetic waves for manipulating the electronic spin state of the quantum sensor element, which changes due to interaction with a magnetic field including a magnetic field spike to be detected, in a pulse sequence in which the time τ between π / 2 pulses is determined according to the magnitude of the magnetic field spike; acquiring a plurality of electron spin states after interacting with the magnetic field including the magnetic field spike, and detecting the magnetic field spike based on the acquired plurality of electron spin states; Including, The step of detecting magnetic field spikes comprises: creating a histogram of the intensity of the magnetic field by calculating the intensity of the magnetic field based on each of the plurality of electron spin states after the interaction; extracting the magnetic field spikes by subtracting measurement noise from the histogram; 23. A method for detecting magnetic field spikes comprising:

9. The step of detecting magnetic field spikes comprises: irradiating the quantum sensor element with light for reading out information of the phase of the electron spin state after interaction with the magnetic field including the magnetic field spike; detecting a change in the quantum sensor element caused by the irradiation of the light; Further comprising: The step of creating a histogram of the magnetic field strength comprises: The method for detecting magnetic spikes according to claim 8 , further comprising the steps of: reading out information about the phase from the detected change; and calculating a strength of the magnetic field based on the read-out information about the phase.

10. An electric power facility comprising a magnetic field spike detection device according to any one of claims 1 to 7.

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