JP7675969B2 - Magnetic field spike detection device, detection method, and power equipment equipped with same - Google Patents

Description

The present invention relates to technology using quantum sensors, and more specifically to a magnetic field spike detection device and method using quantum sensors, and to electric power equipment equipped with a magnetic field spike detection device.

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 shut them down, and if a breakdown were to occur in such power facilities, it would have a major impact on society.

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, causing an electric field to concentrate at the defective area. When partial discharges occur in power equipment, the insulation of the power equipment gradually deteriorates. 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 can be detected to quickly detect failures in the power equipment.

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

In recent years, diamond has also 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 a carbon atom in the crystal lattice and a vacancy (where a carbon atom is missing) that exists in the position adjacent to the nitrogen atom, and is also called an NV center (Nitrogen Vacancy center). In addition to NV centers, complex defects called silicon-vacancy centers and germanium-vacancy centers can also be seen in the crystal structure of diamond, and these complex defects, including NV centers, are called color centers.

The NV center exhibits a magnetic property called electron spin in a state where an electron is captured by a vacancy (negative charge state, hereafter referred to as "NV ^- "). This NV ^- exhibits a long transverse relaxation time (decoherence time, hereafter referred to as "T ₂ ") compared to a state where an electron is not captured (neutral state, hereafter referred to as "NV ⁰ "). In other words, in the electron spin state of NV ^- , after the magnetization of the electron spin aligned in the vertical direction of the external magnetic field (hereafter referred to as the "quantization axis") is tilted in the transverse direction, the individual spins are displaced due to the precession of the individual spins, and it takes a long time for the transverse magnetization as a whole to disappear. In addition, NV ^- exhibits a long T ₂ value even at room temperature (approximately 300 K).

The electron spin state of NV ⁻ 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.

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

For example, Patent Document 2 discloses a method for measuring an AC magnetic field using 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.

In addition to sensors using diamond color centers, there are various other types of sensors used as magnetic field sensor elements, such as sensors using color centers in silicon carbide (SiC), optically pumped atomic magnetometers (OPMs), and superconducting quantum interference devices (SQUIDs). 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.

JP 2012-103171 A JP 2017-75964 A

The magnetic field spikes that occur in power equipment are very small, with amplitudes ranging from a few tens to a few hundreds of nT, and in order to detect them, it is necessary to detect the magnetic field with high sensitivity.

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

Therefore, there is a need for a highly sensitive method to detect the extremely short pulse-like magnetic field spikes generated by partial discharges without directly connecting electrically to power equipment.

The objective of the present invention is to detect magnetic field spikes generated by partial discharges non-contact and with high sensitivity.

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)
2. The magnetic field spike detection device of claim 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 claim 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;
Item 4. A magnetic field spike detection device according to any one of items 1 to 3, comprising:
(Section 5)
5. The magnetic field spike detection device according to claim 4, wherein the noise from the measurement is shot noise.
(Section 6)
5. The magnetic spike detection device according to claim 4, wherein the magnetic spike extraction unit extracts the magnetic 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 claims 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)
Item 8. The magnetic field spike detection device according to any one of items 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;
10. The method for detecting magnetic field spikes according to claim 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:
11. The magnetic field spike detection method according to claim 10, further comprising 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 comprising the magnetic field spike detection device according to any one of items 1 to 8.

The present invention makes it possible to detect magnetic field spikes caused by partial discharges non-contact and with high sensitivity.

1 is a diagram showing a schematic configuration of a magnetic field spike detection device according to an embodiment of the present invention; FIG. 2 is a diagram showing a schematic diagram of an example of a specific configuration of the magnetic field spike detection device shown in FIG. 1 . 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; 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; FIG. 2 is a schematic diagram showing the energy levels of electrons in the NV ⁻ center of diamond. 1 is an exemplary pulse sequence for sensing an AC magnetic field using an optically detected magnetic resonance (ODMR) technique. FIG. 2 illustrates an example waveform of a magnetic field spike. FIG. 2 is a diagram for explaining the magnetic field spike detection concept of the present invention. FIG. 2 is a diagram for explaining the magnetic field spike detection concept of the present invention. 3 is a flowchart showing steps of a method for detecting magnetic field spikes according to an embodiment of the present invention. 4 is an exemplary histogram of magnetic field strength measured in accordance with the present invention, the histogram after subtraction of shot noise.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description and drawings, the same reference numerals indicate the same or similar components, and therefore, redundant descriptions of the same or similar components will be omitted.

In this specification, a physical quantity means a quantity whose dimensions are 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 magnetic fields, electric fields, temperature, and mechanical quantities (mechanical stress, pressure, etc.). Magnetic fields, electric fields, and mechanical quantities include physical quantities that do not change over time, and physical quantities whose direction repeatedly changes over time. In other words, magnetic fields include static magnetic fields and alternating magnetic fields, electric fields include electrostatic fields and alternating electric fields, and mechanical quantities include static mechanical quantities and alternating mechanical quantities.

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

The magnetic field spike detection device 10 (hereinafter simply referred to as the detection device 10) comprises 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 the probe 11 of the detection device 10.

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, a plurality of sensor elements 1 on the order of several thousand (concentration: 1×10 ¹² /cm ⁻³ ) are generated in the region. In this embodiment, the sensor element 1 is an ensemble NV center.

The electronic spin state of the sensor element 1 is changed by an interaction 8 with the object 9. In this embodiment, the object 9 is an electric power equipment, 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 equipment.

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 by magnetic resonance. As an example, in this embodiment, the electromagnetic wave irradiation unit 2 includes a known microwave (MW) oscillator 21, a switch 22 for irradiating the electromagnetic wave in a pulsed form, and an amplifier 23. The switch 22 and the amplifier 23 can be of any configuration. In this embodiment, the electromagnetic wave irradiation unit 2 irradiates the sensor element 1 with electromagnetic waves in a pulsed form for manipulating the electronic spin state of the sensor element 1.

The electromagnetic wave pulse sequence that the electromagnetic wave irradiating unit 2 irradiates to the sensor element 1 can use various pulse sequences for generating magnetic resonance. For example, when sensing an AC magnetic field, the electromagnetic wave irradiating unit 2 irradiates the sensor element 1 with electromagnetic waves using a pulse sequence based on the Hahn echo method of the spin echo method.

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 pulse height h of the magnetic field spike B _S and the duration d of the magnetic field spike. The innovations applied to the pulse sequence will be described later with reference to FIG. 6.

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

The magnetic field spike detection unit 3 detects magnetic field spikes based on changes in the electronic spin state of the sensor element 1 after the change is caused by the 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 multiple electronic spin states. Statistically analyzing multiple electronic spin states includes creating a histogram of magnetic field strength by calculating the magnetic field strength for each of the multiple 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 object 9, which is the power equipment, 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.

The light irradiation unit 31 irradiates the sensor element 1 with light for reading out phase information of the electronic spin state of the sensor element 1 after interaction with the object 9. The light irradiation unit 31 also irradiates the sensor element 1 with light for initializing the electronic spin state of the sensor element 1. As an example, in this embodiment, the light irradiation unit 31 includes a light source 311, an acoustic optical modulator (AOM) 312, and an objective lens 313. The acoustic optical modulator 312 and the objective lens 313 can be configured in any manner.

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.

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.

In the configuration illustrated in FIG. 2, the spot of the laser light is positioned so as to cover the area on the diamond crystal 12 where the sensor element 1 is generated. 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.

The detection unit 32 detects changes occurring in the sensor element 1. In this embodiment, the detection unit 32 detects the light emitted from the sensor element 1, and detects the 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 can be, for example, a known photodiode. The photodiode can be, for example, an avalanche photodiode.

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 the Pulsed Optically Detected Magnetic Resonance (pODMR) method.

The data processing unit 33 is connected to the detection unit 32, reads out phase information of the electronic spin state of the sensor element 1 after interaction with the object 9 from the changes 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.

The data processing unit 33 may be, for example, a known general-purpose computer or various information terminal devices such as a smartphone. The data processing unit 33 may be configured as an integral part of the detection device 10, or, as shown in the figure, may be provided outside the detection device 10 and connected to the detection device 10 via a wired or wireless network 99.

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

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 other embodiments, 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.

When a magnetic field spike is detected, the alarm unit 333 issues an alarm, for example by 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 operating status of other power facilities. Alternatively, the alarm signal may be a signal that activates an alarm device (not shown), such as a buzzer.

Figures 3 and 4 are schematic diagrams of an electric power facility 9 equipped with a magnetic field spike detection device 10 according to one embodiment of the present invention. As the electric power facility 9, Figure 3 illustrates a current transformer 9a, and Figure 4 illustrates a voltage transformer 9b. The locations of the detection device 10 illustrated in these figures are merely examples.

The detection device 10 is disposed in a position where it can sense the magnetic field generated around the 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 power equipment 9.

[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.

In this invention, we have devised a pulse sequence of electromagnetic waves to manipulate the electron spin state when measuring magnetic resonance signals. This 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.

Below, we first explain the principle and procedure for detecting magnetic resonance signals using the optically detected magnetic resonance (ODMR) method, and then explain the method for calculating the magnetic field strength from the detected magnetic resonance signals. Next, we explain the innovations applied to the pulse sequence in the present invention. Finally, we explain the concept of detecting magnetic field spikes that occur randomly in an AC magnetic field, based on the above-described principle of detecting magnetic resonance signals and the method for calculating the magnetic field strength.

<Detection of magnetic resonance signals using optically detected magnetic resonance (ODMR) method>
FIG. 5 is a schematic diagram showing the energy levels of electrons in the NV ⁻ center of diamond.

In this embodiment, an NV center of diamond is used as the sensor element 1. The ground state of the NV center is a spin triplet state with magnetic quantum number m _s =−1, 0, +1, and in a stationary state at room temperature, all levels are equally distributed in the ground state.

When an electron in the ground state with magnetic quantum number m _s =0 is irradiated with laser light having a wavelength of 532 nm (green), it transitions to an excited state, emits red fluorescent light, and relaxes to the ground state with magnetic quantum number m _s =0.

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

In this way, the process of emitting red fluorescence is less likely to occur when magnetic resonance occurs and the electrons are in the ground state with magnetic quantum number m _s = ±1. In addition, the doubly degenerate ground state with magnetic quantum number m _s = ±1 is split in proportion to the strength of the external magnetic field by Zeeman splitting, so the fluorescence intensity also changes depending on whether the electrons are in the state with 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.

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

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

Next, by irradiating a π/2 pulse in state II, the electron spin along the quantization axis is tilted 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 dephased in state III by interaction with the AC magnetic field and the static magnetic field for a predetermined time τ _0. The strength of the interaction corresponds to the strength of the magnetic field felt by the electron spin.

After a predetermined time τ ₀ has elapsed in state III, a π pulse is applied in state IV to invert the electron spins, which have been dephased by interaction with the object to be 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 inversion, the electron spins refocus, and the static magnetic field components are cancelled out, but the AC magnetic field components are not cancelled out because their strength is reversed compared to that in state III.

After a predetermined time τ ₀ has elapsed while the phase is relaxed in state V, a π/2 pulse is applied in state VI to project the phase-relaxed electron spin onto the quantization axis. The electron spin located within the xy plane of the Bloch sphere is projected onto the z-axis, which is the quantization axis, and aligned in the direction along the z-axis.

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. Measurement of the magnetic resonance signal (phase information) related to the spin state using such a pulse sequence is repeatedly performed to accumulate the signal intensity and improve the S/N ratio.

In the Hahn echo pulse sequence shown in Figure 6, the electron spins are dephasing 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 spins are dephasing 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 during which the electron spins are dephasing, and this time τ determines the sensitivity of the measurement. This is because the degree to which the electron spins are dephasing due to interaction with a magnetic field corresponds to the strength of the magnetic field felt by the electron spins.

<Method of calculating magnetic field strength based on magnetic resonance signal>
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.

ここで、μ_Ｂはボーア磁子であり、ｇ_ｅは電子のｇ因子であり、ｈはプランク定数である。ベクトルＳは電子スピンである。ベクトルＢは印加磁場である。Ｄ_ｇｓは零磁場分裂定数である。Ｓ_ｘ，Ｓ_ｙ，Ｓ_ｚはそれぞれ、電子スピンＳのｘ，ｙ，ｚ方向成分である。ｄ_ｇｓ ^⊥は、電気双極子モーメントである。Ｅ_ｘ，Ｅ_ｙはそれぞれ、電場のｘ，ｙ方向成分である。 The Hamiltonian H _gs of electron spin is expressed by the following equation.

Here, _μB is the Bohr magneton, g _e is the electron g-factor, and h is the Planck constant. Vector S is the electron spin. Vector B is the applied magnetic field. _{D gs} is the zero magnetic field splitting constant. S _x , S _y , and S _z are the x-, y-, and z-components of the electron spin S, respectively. _{d gs} ^⊥ is the electric dipole moment. _{E x} and E _y are the x-, y-components of the electric field, respectively.

は、ゼーマン効果による項であり、電子スピンが磁場センサとして機能することを意味している。 First term

is a term due to the Zeeman effect, and means that the electron spin functions as a magnetic field sensor.

は、電子スピンが温度センサおよび力学量（圧力）センサとして機能することを意味している。３番目の項

は、電子スピンが電場センサとして機能することを意味している。 The second and third terms are due to dipole interactions (i.e., spin-spin interactions).

means that electron spin functions as a temperature sensor and a mechanical quantity (pressure) sensor. The third term

means that the electron spin functions as an electric field sensor.

The strength of the magnetic field can thus be calculated based on the first term. The strength of the temperature and mechanical quantities can be calculated based on the second term. The strength of the electric field can be calculated based on the third term.

<Ingenuity applied to pulse sequence>
Referring again to FIG. 6, in the pulse sequence when sensing the AC magnetic field B(t) by 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 ₀ of state III and the time τ ₀ of state V are also fixed values. 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 intensity of the AC magnetic field is large, the rotation angle of the electron spin in the xy plane exceeds 2π, and conversely, if the intensity of the AC magnetic field is small, the rotation angle of the electron spin in the xy plane is insufficient, and there is a risk that the intensity of the AC magnetic field cannot be measured.

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. Accordingly, the range of measurable AC magnetic field strengths is also limited according to the time τ, and when the time τ is fixed, the range of measurable AC magnetic fields is also fixed.

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, and is set to be shorter than the coherence time T ₂ (transverse relaxation time T ₂ ).

Figure 7 shows an example waveform of a magnetic field spike. Note that the actual waveform of the magnetic field spike is unknown, and Figure 7 is used only to illustrate the concept of magnetic field spike magnitude.

The magnitude of the magnetic field spike B _S can be expressed by the integral value of the pulse height h and duration d of the magnetic field spike B _S , using the pulse height h and duration d of the magnetic field spike B _S. This integral value represents the area of the magnetic field spike B _S shown in the figure, and in the magnetic resonance method, a quantity equivalent to this integral value is detected as a magnetic resonance signal. In this embodiment, the product of the pulse height h and duration d is used as an approximation value of the magnitude of the magnetic field spike B _S. Exemplarily, the pulse height h is about 100 nT (nanotesla), and the duration d is about 1 ns (nanosecond). In another embodiment, the product of the pulse height h and the full width at half maximum (FWHM) of the magnetic field spike B _S can be used as an approximation value of the magnitude of the magnetic field spike B _S.

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 so as to ensure sufficient magnitude of the magnetic field spike, which is expressed as the product of the pulse height h and the duration d. As will be explained below, the time τ is related to the probability that the magnetic field spike can be measured. In order to achieve efficient measurement, in order 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.

For example, shortening the time τ between π/2 pulses increases the pulse height h of the detectable magnetic field spike. However, as the time τ between π/2 pulses becomes shorter, the probability of being able to measure a magnetic field spike decreases. This is because, of the multiple magnetic field spikes that occur repeatedly and randomly in an AC magnetic field, only magnetic field spikes that occur within the time τ range can be detected.

Conversely, increasing the time τ between π/2 pulses increases the probability of being able to measure a magnetic field spike. In exchange, the pulse height h of the detectable magnetic field spike decreases. This is because, as mentioned above, there is a limit to the range of measurable AC magnetic field strengths depending on the time τ.

<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 magnetic field spikes B _S1 and B _S2 occurring in an AC magnetic field B(t) occurring around an electric power facility, which is an object 9.

Fig. 9A is an enlarged view of the vicinity of the magnetic spike B _S1 shown in Fig. 8, and Fig. 9B is an enlarged view of the vicinity of the magnetic spike B _S2 shown in Fig. 8. Note that in Fig. 8 and Fig. 9, the intensities of the magnetic spikes B _S1 and B _S2 are scaled for illustration purposes. The scaling ratio for illustration purposes is 10 ³ for the time axis on the horizontal axis and 10 ⁴ for the magnetic field intensity on the vertical axis.

Referring to Fig. 8, an AC current flows through a power facility that transmits AC power. When a partial discharge begins to occur due to a failure in the power facility, magnetic field spikes B _S1 and B _S2 randomly occur in the AC magnetic field B(t) generated around the power facility.

Illustratively, the amplitude of the alternating magnetic field B(t) is about 5 mT (millitesla) and the frequency is about 60 Hz. Illustratively, the amplitude (pulse height) of the magnetic field spikes B _S1 and B _S2 is about 100 nT and the duration is about 1 ns.

When magnetic field spikes B _S1 and B _S2 are occurring, the measured value of the AC magnetic field B(t) contains not only a noise component contained in the measurement signal itself, i.e., a so-called shot noise component, but also random components due to the magnetic field spikes B _S1 and B _S2 shown in Fig. 8. Therefore, by subtracting the shot noise component from the measured value of the strength of the AC magnetic field B(t), it is possible to detect the change in magnetic field strength due to the occurrence of the magnetic field spikes B _S1 and B _S2 .

However, as explained with reference to FIG. 6, when the time τ between π/2 pulses is determined in order to measure the AC magnetic field B(t), there is a risk that the time τ determined in this manner will not be able to measure the magnetic field spikes B _S1 and B _S2 , which have a magnetic field strength that is approximately 10 ³ smaller, due to limitations imposed on the rotation angle of the electron spin.

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 AC magnetic field B(t). As described with reference to FIG. 6, when the magnetic field to be detected is not the AC magnetic field B(t) but the magnetic field spikes B _S1 and B _S2 whose magnetic field strength is about 10 ³ smaller, the magnetic resonance method detects an amount equivalent to the integral value of the pulse height and duration of the magnetic field spikes B _S1 and B _S2 as a magnetic resonance signal. This amount equivalent to the integral value corresponds to the amount of change in the magnetic field strength caused by the occurrence of the magnetic field spikes B _S1 and B _S2 . However, this amount equivalent to the integral value is extremely small, and it is difficult to detect the amount by measuring the magnetic resonance signal only once. This is because the magnetic field strength of the magnetic field spikes B _S1 and B _S2 is about 10 ³ smaller than the magnetic field strength of the AC magnetic field B(t). In addition, it is difficult to detect all of the multiple magnetic field spikes that are repeatedly and randomly generated in the AC magnetic field. Of the multiple randomly occurring magnetic field spikes, only those that occur within the time τ between π/2 pulses can be detected.

In the present invention, magnetic field spikes are detected by statistically analyzing multiple magnetic resonance signals. Specifically, the magnetic resonance signal measurements are repeated multiple 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.

Refer to Figure 9. Symbols I to VII in Figure 9 correspond to states I to VII of the pulse sequence shown in Figure 6. In the figure, the solid lines indicate the timing of irradiation of the laser light, and the dashed lines indicate the timing of irradiation of the electromagnetic wave for electron spin manipulation.

In state I, the laser light is irradiated 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, the electron spin is tilted to the xy plane of the Bloch sphere by irradiating a π/2 pulse at the timing shown by the dashed line. In state III, the electron spin is dephased. In state IV, the electron spin is inverted in the xy plane of the Bloch sphere by irradiating a π pulse at the timing shown by the dashed line. Note that the electron spin is dephased even during this inversion. In state V, the electron spin is dephased. In state VI, the electron spin is projected onto the z-axis, which is the quantization axis, by irradiating a π/2 pulse at the timing shown by the dashed line. In state VII, the laser light is irradiated at the timing shown by the solid line. This reads out the phase information of the electron spin state after the interaction.

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, among a plurality of magnetic field spikes that occur repeatedly and randomly in the AC magnetic field B(t), magnetic field spikes occurring between state III and state V are detected. In the example shown in FIG. 9, both magnetic field spikes B _S1 and B _S2 occur between state III or state V, and both magnetic field spikes B _S1 and B _S2 occur at timings within the time width of the detection window in which the magnetic field spikes can be detected. The time width of this detection window in which the magnetic field spikes 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.

[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.

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. The initialized electron spin of the NV center is then allowed to interact with the AC magnetic field of the object 9. When the interaction is allowed to continue for a sufficient period of time, the state of the electron spin of the NV center becomes a state corresponding to the strength 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 initialized electron spin of the NV center interacts with the AC magnetic field including the magnetic field spike and becomes a state corresponding to the strength of the AC magnetic field including the magnetic field spike.

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 π/2 pulses and π pulses according to the pulse sequence shown in FIG. 6. That is, in this embodiment, the electron spin state of the NV center is manipulated 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.

In step S3, the sensor element 1 is irradiated with laser light, and the change occurring in the sensor element 1 is detected to read out the 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 the 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 the optically detected magnetic resonance (ODMR) method. The state of step S3 corresponds to state VII of the pulse sequence shown in FIG. 6.

In step S4, it is determined whether the series of measurement processes from steps S1 to S3 has been repeated a predetermined number of times. If the series of measurement processes has been repeated a predetermined number of times (Yes in step S4), step S5 is performed. If the series of measurement processes has not been repeated a 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 repeated can be changed depending on the frequency or magnitude of the magnetic field spikes to be detected.

Note that the signal strength is accumulated when the series of measurement processes are repeatedly performed, so the more times the measurement processes are repeatedly performed, the more the signal-to-noise ratio of the signal improves.

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

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 becomes the ground state. The strength can be calculated based on the term due to the Zeeman effect of the Hamiltonian _Hgs of the electron spin. When a magnetic field spike occurs in the AC magnetic field, the phase information of the electron spin state after the interaction corresponds to the AC magnetic field including the magnetic field spike, and the strength of the AC magnetic field including the magnetic field spike is calculated.

The histogram of magnetic field strength is created by calculating the magnetic field strength for each of the multiple electron spin states after the interaction based on each electron spin state.

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

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

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 peak that corresponds to the strength of the magnetic field spikes B _S1 and B _S2 in FIG. 8 that are to be detected in the present invention.

In step S7, it is determined whether a magnetic spike is extracted. For example, it is determined whether the strength of the extracted magnetic spike is equal to or greater than a predetermined value. 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 if the magnetic field strength of the side peak is approximately 10 ⁻³ of the magnetic field strength of the large peak, the extracted side peak is determined to be a magnetic field spike.

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. When the centralized management computer device receives the alarm signal, it displays, for example, a message encouraging maintenance of the power equipment on the monitor of the centralized management computer device. Alternatively, an alarm such as an alarm that operates when an alarm signal is received may be connected to the 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.

[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, thereby enabling early detection of failures in power equipment.

In the present invention, the strength of the magnetic field generated around the target object, the 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 contactlessly, without directly connecting electrically to the target object, the power equipment.

In this invention, we have devised a pulse sequence of electromagnetic waves to manipulate the electron spin state when measuring magnetic resonance signals. This improves the measurement sensitivity of the magnetic field strength, making it possible to detect minute, extremely short pulse-like magnetic field spikes generated by partial discharges with high sensitivity.

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

In the above embodiment, the electromagnetic waves for manipulating the electron spin state are irradiated to the sensor element 1 in a pulse sequence based on the Hahn echo method of the spin echo method, but the pulse sequence of the electromagnetic waves for manipulating the electron spin state is not limited to the Hahn echo method. For example, when sensing an AC magnetic field, the electromagnetic waves for manipulating the electron spin state can be irradiated to the sensor element 1 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 the magnetic resonance signal may be detected by a pulse sequence including two π/2 pulses. In other words, the magnetic resonance signal may be detected using a free induction decay (FID) signal instead of the echo method.

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 the π/2 pulses, the first π pulse is irradiated a time τ/4 after the first π/2 pulse is irradiated. The second π pulse is irradiated a time τ/2 after the first π pulse is irradiated. The second π/2 pulse is irradiated a time τ/4 after the second π pulse is irradiated.

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, and the time τ is, of course, shorter than the coherence time _T2 (transverse relaxation time _T2 ).

In the above embodiment, the magnetic field spikes are extracted by subtracting shot noise, which is 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.

An exemplary method for extracting magnetic field spikes using two Gaussian functions is described below. 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 magnetic field strength. After 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 data fitting corresponds to the magnetic field spike to be extracted.

In the above-described embodiment, the magnetic field spike detection device 10 detects magnetic field spikes in the magnetic field generated around the power equipment 9. Although a current transformer 9a and a voltage transformer 9b are given 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 transformers and switches.

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

In Example 1, numerical simulations were performed for both a case where a magnetic field spike occurs in the power equipment and a case where a magnetic field spike does not occur.

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

The assumed conditions (a) to (e) for the sensor element sample and pulse sequence are as follows:

(a) Coherence time _T2 is 60 μs
(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 the 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) Laser pulse length is 30 μs, with a waiting time of 1 μs, π/2 pulse length of 40 ns, and a delay between these pulses of approximately 30 μs.

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%.

(ii) The probability of a magnetic field spike occurring during a pulse sequence is given by its rate: in this example 60 Hz x 62.08 μs x 10 ⁻⁶ = 0.0037248.

(iii) The total probability that the pulse sequence measures a magnetic field spike is 0.48325 x 0.0037248 = 0.0018... or 0.18%. The same result was obtained if we calculated the probability of a single magnetic field spike at 30 μs intervals, assuming a Poisson distribution.

(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.

(v) The background is completely subtracted. In this example, the background is a magnetic field oscillating periodically at 60 Hz. Note that subtracting the background is not essential. A non-zero average background also works as long as the background is within the range of the selected pulse sequence.

(vi) Only consider shot noise, which is the largest noise source.

Comparison between cases where magnetic field spikes occur and cases where they do not occur. The comparison using numerical simulation was performed assuming multiple cases with different combinations of magnetic field spike occurrence rate, magnetic field spike amplitude, magnetic field spike duration, and measurement time.

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

ＮＶ中心の仕様条件および測定シーケンスから、測定感度は約１ｐＴＨｚ^－０．５と計算された。よって、２００時間の測定における不確かさの理論値は、１×１０^１３／√（２００×３６００）＝１．１７８５ｆＴ（フェムトテスラ）と計算された。予想される磁場強度は約６ｆＴであった。 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.

From the specification conditions of the NV center and the measurement sequence, the measurement sensitivity was calculated to be about 1 pTHz ^-0.5 . Therefore, the theoretical uncertainty in the 200-hour measurement was calculated to be 1 x 10 ¹³ /√(200 x 3600) = 1.1785 fT (femtotesla). The expected magnetic field strength was about 6 fT.

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.

1. Sensor element (Diamond NV center)
2 Electromagnetic wave irradiation unit 3 Magnetic field spike detection unit 8 Interaction 9 (9a, 9b) Power equipment (current transformer, voltage transformer)
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-optical modulator (AOM)
313 Objective lens 32 Detector 33 Data processor 331 Histogram creator 332 Magnetic field spike extractor 333 Alarm unit 99 Network

Claims (10)

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 : The magnetic field spike detection device of claim 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. The magnetic field spike detection device according to claim 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. 2. The magnetic field spike detection apparatus of claim 1 , wherein said measurement noise is shot noise. 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. 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
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. 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. 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;
A method for detecting magnetic field spikes comprising : 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. An electric power facility comprising a magnetic field spike detection device according to any one of claims 1 to 7 .

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