Diamond spin sensor and diamond spin sensor system

Abstract

This diamond spin sensor includes: a diamond that includes a color center having electron spin; and a heat transfer part that contacts the diamond. The heat transfer part is fixed to an object, and at

Description

TITLE OF INVENTION: Diamond Spin Sensor and Diamond Spin Sensor System TECHNICAL FIELD

[0001] The present disclosure relates to a diamond spin sensor and a diamond spin sensor system. The present application claims priority to Japanese Patent Application No. 2023-100678 filed on June 20, 2023, the entire contents of which are herein incorporated by reference. BACKGROUND ART

[0002] In a power cable arranged at a high altitude such as an electric power pylon as an electric power transmission and distribution facility, for maintenance and management, abnormality detection, and the like thereof, equipment provided with a temperature detector, a current detector, and the like is provided at the power cable. For example, PTL 1 below discloses a configuration in which an optical sensor (using a Faraday effect or a Pockeles effect) is arranged at a high voltage portion side for detection of a location of failure that has occurred in an electric power transmission and distribution line or the like and a detected optical signal is transmitted to a monitoring and control system on a ground side through an optical fiber of an optical-fibercontaining insulator.

[0003] A diamond spin sensor system using an NV center (that is, an NV center) of diamond has been known as a sensor for detecting magnetic field, a current, a temperature, and the like. As the NV center formed by nitrogen located at a substitution position of carbon in diamond and a vacancy adjacent to nitrogen is negatively charged (this state being denoted as an W center), a ground state thereof becomes a triplet state (that is, spin S being S = 1). As the NV center is excited at a wavelength of 532 nm (that is, by green light), fluorescence having a wavelength of 637 nm (that is, red light) is emitted. Since emission intensity of fluorescence is varied by a spin state and the spin state is varied by magnetic resonance between magnetic field applied to the NV center and microwaves or radio waves, diamond including an NV center can serve as a magnetic sensor.

[0004] For example, a diamond spin sensor system includes a diamond substrate that includes an NV center, an optical system through which excitation light from a light source is transmitted and the NV center is irradiated therewith, an optical system through which fluorescence from the NV center is collected and transmitted to a photodetector, and a waveguide through which microwaves from a power supply are transmitted and the NV center is irradiated therewith. For example, NPL 1 below discloses a configuration in which a diamond sensor is carried on a coplanar waveguide and microwaves are emitted. The diamond substrate is in a rectangular parallelepiped shape, excitation light is emitted from a lateral side of the diamond substrate, and fluorescence is collected from above the diamond substrate. CITATION LIST PATENT LITERATURE

[0005] PTL 1: Japanese Patent Laying-Open No. 2003-35852 NON PATENT LITERATURE

[0006] NPL 1: Yuta Masuyama, Yuji Hatano, Takayuki Iwasaki, and Mutsuko Hatano, "Highly sensitive macro-scale diamond magnetometer operated with coplanar waveguide resonator," The 79th JSAP Autumn Meeting Extended Abstracts (issued: September 5, 2018) NPL 2: Takaaki Shimo-Oka, Ippei Nakamura, Hiroki Morishita, Masanori Fujiwara, Shiro Saito, and Norikazu Mizuochi, "Temperature sensing with an ensemble of nitrogen vacancy centers," The 78th JSAP Autumn Meeting Extended Abstracts (issued: August 25, 2017) SUMMARY OF INVENTION

[0007] A diamond spin sensor according to one aspect of the present disclosure includes diamond having a color center having electron spin and a heat conduction portion in contact with the diamond. The heat conduction portion is fixed to a target. At least one of magnetic field, a current, and a temperature of the target is detected by measuring fluorescence radiated from the color center after the color center is irradiated with excitation light. BRIEF DESCRIPTION OF DRAWINGS

[0008] [Fig. 1] Fig. lisa block diagram showing a configuration of a diamond spin sensor system according to a first embodiment. [Fig. 2] Fig. 2 is a perspective view showing a configuration of a sensor portion (that is, a diamond spin sensor) shown in Fig. 1. [Fig. 3] Fig. 3 is a perspective view showing a method of arranging a heat conduction portion shown in Fig. 2 at an electric power transmission line. [Fig. 4] Fig. 4 is a three-view drawing showing a shape of diamond at the sensor portion and arrangement relation between diamond and an optical waveguide. [Fig. 5] Fig. 5 is a cross-sectional view showing a state in which the sensor portion is fixed to the electric power transmission line according to a first modification. [Fig. 6] Fig. 6 is a three-view drawing showing a shape of diamond included in the sensor portion and arrangement relation between diamond and an optical waveguide according to a second modification. [Fig. 7] Fig. 7 is a block diagram showing a configuration of a diamond spin sensor system according to a second embodiment. [Fig. 8] Fig. 8 is a perspective view showing a configuration of a sensor portion (that is, a diamond spin sensor) shown in Fig. 7. [Fig. 9] Fig. 9 is a two-view drawing (a plan view and a front view) showing positional relation between diamond and an optical waveguide used in an experiment. [Fig. 10] Fig. 10 is a diagram showing in a table format, information on a sample and a result of the experiment. [Fig. 11] Fig. 11 is a cross-sectional view showing a state in which a heat conduction portion used in the experiment has been attached to an electric power transmission line which is a target of measurement. [Fig. 12] Fig. 12 is a cross-sectional view showing a state in which a heat conduction portion that is used in the experiment and is different from that in Fig. 11 has been attached to the electric power transmission line which is the target of measurement. [Fig. 13] Fig. 13 is a cross-sectional view showing a state in which a heat conduction portion that is used in the experiment and is different from those in Figs. 11 and 12 has been attached to the electric power transmission line which is the target of measurement. [Fig. 14] Fig. 14 is a diagram showing in a table format, information on a sample and a result of the experiment. DETAILED DESCRIPTION

[0009] [Problem to be Solved by the Present Disclosure] A power cable is a columnar solid wire or a twisted wire obtained by twisting a plurality of solid wires, and is uncoated. In order to measure a temperature of the power cable with a sensor (for example, a thermocouple), the sensor should be fixed to the power cable in a stable manner. For example, the sensor is attached to the power cable by being tied, and the temperature is measured therewith. With such an attachment method, however, it is not easy to bring the sensor in intimate contact with the power cable which is a target of measurement, and to fix the sensor for a long period in a stable manner. A similar problem arises also when diamond including an NV center is used as a sensor.

[0010] Therefore, an object of the present disclosure is to provide a diamond spin sensor and a diamond spin sensor system that can be fixed to a measurement target in a stable manner

[0011] [Advantageous Effect of the Present Disclosure] According to the present disclosure, a diamond spin sensor and a diamond spin sensor system that can be fixed to a measurement target in a stable manner can be provided.

[0012] [Description of Embodiments of the Present Disclosure] Contents of an embodiment of the present disclosure will be listed and described. At least a part of the embodiment described below may freely be combined.

[0013] (1) A diamond spin sensor according to a first aspect of the present disclosure includes diamond having a color center having electron spin and a heat conduction portion in contact with the diamond. The heat conduction portion is fixed to a target. At least one of magnetic field, a current, and a temperature of the target is detected by measuring fluorescence radiated from the color center after the color center is irradiated with excitation light. The diamond spin sensor can thus be fixed to the target of measurement in a stable manner. Therefore, a physical state (a voltage, a current, a temperature, and the like) can be detected in a stable manner. Since a sensor element contains diamond that can withstand a harsh environment, it can detect the physical state in the harsh environment.

[0014] (2) In (1) above, the target can be a linear member, a columnar member, or a twisted-wire-like member. With a power cable at an electric power transmission facility being defined as the target of measurement, the physical state (the voltage, the current, the temperature, and the like) thereof can thus be detected.

[0015] (3) In (2) above, the diamond may include a flat main surface, the target may be the columnar member or the twisted-wire-like member, the heat conduction portion may have a curved surface, the main surface may be in contact with a surface of the heat conduction portion other than the curved surface, and the curved surface may be in contact with a side surface of the columnar member or the twisted-wire-like member. The diamond spin sensor can thus be fixed to the measurement target as being in intimate contact therewith.

[0016] (4) In (3) above, the diamond may further include a side surface perpendicular to the main surface. The excitation light may be incident on the side surface of the diamond and the fluorescence may be radiated from the side surface of the diamond. Diamond and an optical fiber which is an optical waveguide through which excitation light and fluorescence propagate can thus be fixed to the measurement target in a stable manner. Excitation light and fluorescence can thus be transmitted through a single optical waveguide.

[0017] (5) In (3) above, the diamond may further include a side surface perpendicular to the main surface and a rear surface in parallel to the main surface. The excitation light may be incident on the side surface of the diamond. The fluorescence may be radiated from the rear surface. Efficiency in collecting fluorescence radiated from the color center of diamond can be thus enhanced.

[0018] (6) In (3) above, the diamond may be in a form of a plate. The main surface may be in a shape of a right isosceles triangle. Diamond can thus be fixed to the heat conduction portion in a stable manner.

[0019] (7) In any one of (1) to (6) above, the target may be an uncoated electric power transmission line. The heat conduction portion may be formed of metal that is not electrolytically corroded by contact with the electric power transmission line. Thus, in an example where metals different in type are joined, occurrence of corrosion caused by a potential difference therebetween, that is, electrolytic corrosion, can be suppressed.

[0020] (8) In (7) above, the heat conduction portion may be formed of aluminum or copper. The diamond spin sensor can thus be fixed to the power cable formed of aluminum or copper in a stable manner, and occurrence of electrolytic corrosion can further be suppressed.

[0021] (9) In any one of (1) to (8) above, a microwave circuit may further be included. The diamond may include a flat main surface and a rear surface in parallel to the main surface. The microwave circuit may be arranged at the main surface. Metal may be arranged at the rear surface. Magnetic field can thus be calculated from an interval between two valleys in a frequency spectrum observed by irradiation with microwaves. A mechanism for irradiation with microwave does not have to separately be provided, and a compact diamond spin sensor can be realized.

[0022] (10) In (1) or (2) above, an optical waveguide through which the excitation light is transmitted may further be included. The optical waveguide may be an optical guide or an optical fiber. The diamond may have a thickness not smaller than half a diameter of the optical waveguide and not larger than 2.5 times as large as the diameter. The physical state of the measurement target can thus be detected.

[0023] (11) In (10) above, the diamond may include a flat main surface. The main surface may be in a shape of a right triangle. In a portion where an end surface of the optical waveguide is in contact with the diamond, a central axis of the optical waveguide may be arranged in parallel to a straight line that bisects an interior angle of the main surface, the interior angle being a right angle. The physical state of the measurement target can thus efficiently be detected.

[0024] (12) In (11) above, the main surface may be in a shape of a right isosceles triangle. A height to a vertex of the right isosceles triangle may be at least two times as large as the thickness of the diamond. The physical state of the measurement target can thus efficiently be detected.

[0025] (13) In (11) or (12) above, the diamond may further include a side surface perpendicular to the main surface and a rear surface in parallel to the main surface. The excitation light may be incident on the diamond from the side surface. A detection unit that detects fluorescence radiated from the rear surface may further be included. The physical state of the measurement target can thus efficiently be detected.

[0026] (14) In (13) above, the detection unit may include a photodiode on which the fluorescence radiated from the rear surface is directly incident. The physical state of the measurement target can thus efficiently be detected.

[0027] (15) In (13) above, an optical fiber through which the fluorescence is transmitted to the detection unit may further be included, and at an end surface of the optical fiber, an optical system that collects the fluorescence radiated from the rear surface may further be included. The physical state of the measurement target can thus efficiently be detected.

[0028] (16) In (11) or (12) above, the diamond may further include a side surface perpendicular to the main surface. The excitation light may be incident on the diamond from the side surface. A detection unit that detects fluorescence radiated from the side surface may further be included. The physical state of the measurement target can thus efficiently be detected.

[0029] (17) In any one of (13) to (16) above, an angle formed between a normal to the side surface and a central axis of the optical waveguide may be a Brewster's angle. Excitation light can thus efficiently enter the inside of diamond without being reflected by the side surface, and efficiency in generation of fluorescence can be improved.

[0030] (18) A diamond spin sensor system according to a second aspect of the present disclosure includes the diamond spin sensor according to any one of (1) to (17) above and a control power supply portion that generates the excitation light and detects the fluorescence. The diamond spin sensor can thus be fixed to the measurement target in a stable manner. Therefore, a physical state (a voltage, a current, a temperature, and the like) can be detected in a stable manner. Since a sensor element contains diamond that can withstand a harsh environment, it can detect the physical state in the harsh environment.

[0031] [Details of Embodiments in the Present Disclosure] In embodiments below, the same elements have the same reference characters allotted. Their labels and functions are also the same. Therefore, detailed description thereof will not be repeated.

[0032] (First Embodiment) Referring to Fig. 1, a diamond spin sensor system 100 according to a first embodiment of the present disclosure includes a sensor portion 102, an optical waveguide 104, and a control power supply portion 106. Sensor portion 102 includes diamond 110 including an NV“ center (which will be denoted as an NV center below) and a heat conduction portion 112. Sensor portion 102 is also referred to as a diamond spin sensor. Optical waveguide 104 contains a medium through which light is transmitted and it is coated with resin or the like. Optical waveguide 104 is, for example, an optical fiber. Optical waveguide 104 may be an optical guide, for example, in such a structure that optical fibers are bundled. Optical waveguide 104 allows bidirectional transmission of light therethrough.

[0033] Referring to Fig. 2, heat conduction portion 112 of sensor portion 102 includes a first member 150 and a second member 152. An electric power transmission line 900 is a linear or columnar solid wire formed, for example, of aluminum or copper or a twisted wire formed by twisting solid wires, and it is not coated. Heat conduction portion 112 is fixed around electric power transmission line 900. Diamond 110 is arranged at heat conduction portion 112. As will be described later, diamond 110 is formed like a plate of a triangular prism. In other words, a height of the triangular prism corresponds to a thickness of the plate. Of two triangular planes of diamond 110, a first plane (which is referred to as a main surface below) is in contact (that is, surface contact) with heat conduction portion 112. Diamond 110 is fixed to heat conduction portion 112 by a fixing member 154 arranged as being opposed to heat conduction portion 112 (specifically, first member 150) with diamond 110 being interposed. In other words, of the two triangular planes of diamond 110, a second plane (which is referred to as a rear surface below) is in contact (that is, surface contact) with fixing member 154. For example, by fixing fixing member 154 to heat conduction portion 112 with a screw, diamond 110 may be fixed to heat conduction portion 112. Fixing member 154 may be formed, for example, of ceramic or resin. Resin is preferably high in resistance to discharging, and for example, poly ether ether ketone (PEEK) can be employed as resin.

[0034] Referring to Fig. 3, each of first member 150 and second member 152 has a curved surface that may be arranged in intimate contact with a cylindrical side surface of electric power transmission line 900 which is a solid wire or a twisted wire. First member 150 and second member 152 may each be provided with a plurality of holes (for example, through holes) and fixed around electric power transmission line 900 by an inserted screw. For example, in an example in which a male screw is to be inserted in a direction shown with an arrow for fixing, a through hole may be provided in first member 150 and a female screw to which the male screw can be fastened may be provided at a hole of second member 152. For example, the curved surface of each of first member 150 and second member 152 is semicylindrical, and a radius thereof is equal to a radius of the cylindrical side surface of electric power transmission line 900. Heat conduction portion 112 can thus be in intimate contact with electric power transmission line 900 and can be fixed thereto in a stable manner. In other words, sensor portion 102 can be fixed to electric power transmission line 900 in a stable manner.

[0035] First member 150 and second member 152 may be formed of any of metal, ceramic, or resin. In measurement of a temperature of electric power transmission line 900 with diamond 110, first member 150 and second member 152 are preferably formed of metal high in thermal conductivity. A temperature of diamond 110 can thus quickly become equal to the temperature of electric power transmission line 900 and the temperature of electric power transmission line 900 can accurately be detected. In an example in which first member 150 and second member 152 are formed of metal, first member 150 and second member 152 may be formed of a material the same as that for electric power transmission line 900. For example, in an example in which electric power transmission line 900 is formed of aluminum, first member 150 and second member 152 are formed of aluminum, and in an example in which electric power transmission line 900 is formed of copper, first member 150 and second member 152 are formed of copper. Occurrence of electrolytic corrosion (that is, corrosion caused by a potential difference in an example where metals different in type are joined) can thus be prevented.

[0036] In an example where magnetic field or a current is to be detected, first member 150 and second member 152 may be formed of ceramic or resin. Resin is preferably high in resistance to discharging, and for example, PEEK can be employed.

[0037] Referring to Fig. 4, diamond 110 is formed like a plate provided with two parallel planes (that is, a main surface and a rear surface) as set forth above. The two parallel planes are each, for example, in a shape of a right isosceles triangle. Diamond 110 includes three side surfaces orthogonal to the main surface and the rear surface. Of the three side surfaces, an end surface of optical waveguide 104 is arranged at a side surface 110C. Thus, as will be described later, excitation light 304 enters the inside of diamond 110 from side surface 110C. Fluorescence 306 radiated from the NV center within diamond 110 is outputted from side surface 110C to the outside of diamond 110 and propagates through optical waveguide 104.

[0038] Sensor portion 102 thus includes diamond 110 including the NV center and heat conduction portion 112 in contact with diamond 110. Heat conduction portion 112 includes first member 150 and second member 152 as a mechanism that brings sensor portion 102 in intimate contact with electric power transmission line 900 which is a measurement target. At least one of magnetic field, the current, and the temperature of the measurement target (that is, magnetic field generated by the measurement target, the current that flows through the measurement target, and the temperature of the measurement target) is detected by measurement of fluorescence radiated from the NV center after it is irradiated with excitation light. Sensor portion 102 which is the diamond spin sensor can thus be fixed to the measurement target in a stable manner. Therefore, the physical state (the voltage, the current, the temperature, and the like) can be detected in a stable manner. Since the sensor element contains diamond 110 that can withstand a harsh environment, it can detect the physical state in the harsh environment.

[0039] As set forth above, with electric power transmission line 900 located at an electric power transmission facility, which is the linear member, the columnar member, or the twisted-wire-like member, being defined as the target of measurement, the physical state thereof (the voltage, the current, the temperature, and the like) can be detected.

[0040] As set forth above, each of first member 150 and second member 152 included in heat conduction portion 112 includes the curved surface, the main surface of diamond 110 is in contact with a surface of heat conduction portion 112 different from the curved surface, and the curved surface is fixed as abutting on the side surface of electric power transmission line 900 which is the columnar member or the twisted-wire-like member. Sensor portion 102 can thus be fixed to electric power transmission line 900 which is the measurement target, as being in intimate contact therewith.

[0041] As set forth above, diamond 110 includes side surface 110C perpendicular to a first surface 110A (main surface), excitation light is incident on side surface 1 IOC, and fluorescence is radiated from that side surface. Excitation light and fluorescence can thus be transmitted through a single optical waveguide 104 (for example, the optical fiber).

[0042] Though an example in which excitation light is incident on side surface 110C and fluorescence is radiated from side surface 110C is described above, limitation thereto is not intended. For example, excitation light may be incident on side surface HOC and fluorescence may be radiated from a second surface 110B (rear surface). In this case, fixing member 154 shown in Fig. 2 may be formed of a member (for example, resin) that allows transmission of fluorescence therethrough and structured such that a fluorescence detection unit such as a photodiode is embedded therein. Efficiency in collecting fluorescence radiated from the NV center of diamond 110 can thus be enhanced. In addition, an optical waveguide (for example, an optical fiber) through which fluorescence radiated from second surface 110B (rear surface) is transmitted to the detection unit may be provided, and an optical system (for example, a lens) that collects fluorescence radiated from second surface HOB may be provided at an end surface of the optical waveguide.

[0043] As set forth above, diamond 110 is in the form of the plate, and first surface 110A is in the shape of the right isosceles triangle. Diamond 110 can thus be fixed to heat conduction portion 112 in a stable manner.

[0044] Referring back to Fig. 1, control power supply portion 106 irradiates diamond 110 with excitation light and detects fluorescence radiated from diamond 110. Control power supply portion 106 includes an excitation light generator 120, a filter 122, a light collecting element 124, a long pass filter (LPF) 126, a photodetector 128, and a controller 130. Controller 130 includes a central processing unit (CPU), a storage, and a wireless communication unit (none of which is shown). Later-described processing to be performed by controller 130 is realized by reading and execution by the CPU, of a program stored in advance in the storage. As will be described later, controller 130 obtains a signal (that is, intensity of fluorescence) detected by photodetector 128 and transmits the signal to an external apparatus by means of the wireless communication unit. The external apparatus calculates a physical state (for example, magnetic field and a temperature) based on a detection signal of photodetector 128 received from controller 130.

[0045] Excitation light generator 120 generates excitation light 304 for excitation of the NV center of diamond 110 under the control by controller 130. For example, controller 130 causes a voltage for light emission by excitation light generator 120 to be supplied to excitation light generator 120 at prescribed timing. Excitation light 304 is green light (that is, having a wavelength from 490 nm to 560 nm). Excitation light 304 is preferably laser beams and excitation light generator 120 is preferably semiconductor laser (for example, radiated light therefrom having a wavelength of 532 nm).

[0046] Filter 122 is an element for separation between excitation light 304 incident from excitation light generator 120 and light (that is, fluorescence 306) radiated from diamond. For example, filter 122 is a filter that cuts off (that is, reflects) light having a wavelength not longer than a prescribed wavelength and allows passage therethrough of light having a wavelength longer than the prescribed wavelength, or a band-pass filter that allows passage therethrough of light having a wavelength within a prescribed wavelength range and cuts off (that is, reflects) light having a wavelength out of the prescribed wavelength range. In general, excitation light is shorter in wavelength than fluorescence, and hence such a configuration is preferred. Filter 122 is preferably a dichroic mirror that performs such a function.

[0047] Light collecting element 124 collects excitation light 304 inputted from filter 122. Light collecting element 124 is, for example, a sphere lens. Light collecting element 124 provides excitation light 304 outputted as being diffused from excitation light generator 120 to the end of optical waveguide 104, as much as possible. Optical waveguide 104 is provided with a first end and a second end, and it allows transmission therethrough of excitation light 304 incident on the first end from light collecting element 124 to the second end. In addition, optical waveguide 104 allows transmission therethrough of radiated light (that is, fluorescence 306) from diamond that is incident on the second end to the first end and outputs the same.

[0048] LPF 126 refers to a long pass filter, and it allows passage therethrough of light having a wavelength equal to or longer than a prescribed wavelength and cuts off (for example, reflects) light having a wavelength shorter than the prescribed wavelength. Radiated light from diamond is red light and passes through LPF 126, whereas excitation light 304 outputted from excitation light generator 120 is shorter in wavelength than that and hence it does not pass through LPF 126. Thus, excitation light 304 radiated from excitation light generator 120 being detected by photodetector 128 and becoming noise, which leads to lowering in sensitivity in detection of radiated light (that is, fluorescence 306) from diamond, can be suppressed. Photodetector 128 generates and outputs an electrical signal in accordance with incident light. Photodetector 128 is, for example, a photodiode. An output signal from photodetector 128 is obtained by controller 130. The signal obtained by controller 130 is transmitted to an external apparatus by means of the wireless communication unit of controller 130 as set forth above. The external apparatus can thus calculate the physical state (for example, magnetic field and the temperature) at a location where diamond 110 is arranged, based on the received output signal from photodetector 128.

[0049] Diamond spin sensor system 100 is arranged at an electric power transmission facility (for example, an overhead electric power transmission facility) and used for maintenance and management, abnormality detection, and the like of a power cable. Specifically, sensor portion 102 is arranged at electric power transmission line 900 and control power supply portion 106 is arranged at a steel mast of an electric power pylon. Optical waveguide 104 through which sensor portion 102 and control power supply portion 106 are connected to each other is fixed to an arm or the like of the electric power pylon.

[0050] The NV center can be used to calculate magnetic field from variation in electron spin resonance (ESR) spectrum. A resonance frequency of the NV center has been known to have temperature dependency within a range from 120 K to 700 K. For example, as disclosed in NPL 2, a temperature can be measured based on variation in intensity of an optically detected magnetic resonance (ODMR) signal around a resonance frequency.

[0051] Fluorescence in accordance with magnetic field generated by a current that flows through electric power transmission line 900 or a temperature of electric power transmission line 900 can be detected by diamond 110 in sensor portion 102, and a resultant detection signal can be transmitted to control power supply portion 106 through optical waveguide 104. Control power supply portion 106 can transmit the detection signal to a terrestrial apparatus. Magnetic field or the temperature at a position where diamond 110 is arranged can thus be detected. In an area in the vicinity of electric power transmission line 900 where a high voltage not lower than several thousand kilovolts (for example, 6600 kV) is transmitted, that is, a harsh environment at a high voltage, sensor portion 102 and a part of optical waveguide 104 are arranged, and control power supply portion 106 is arranged in an ordinary environment distant from electric power transmission line 900. Diamond 110 and optical waveguide 104 included in sensor portion 102 are not affected by the high-voltage environment even when they are arranged in such an environment. Control power supply portion 106 is arranged in the ordinary environment. Therefore, the diamond spin sensor system that is long in lifetime and easily maintained can be realized. The "harsh environment" means an environment difficult for a person to enter, and in Fig. 3, it is, for example, the high-voltage environment around electric power transmission line 900. The "ordinary environment" means an environment other than the "harsh environment." In the harsh environment, at least one of intensity of electric field, intensity of magnetic field, the temperature, and the pressure is higher (by at least one order of magnitude) than in the ordinary environment.

[0052] (First Modification) Though an example in which sensor portion 102 is fixed to electric power transmission line 900 such that electric power transmission line 900 lies between first member 150 and second member 152 is described above, limitation thereto is not intended. In an example in which a diameter of electric power transmission line 900 is larger than a size of sensor portion 102, a band-like member may be used to fix sensor portion 102 to electric power transmission line 900. Referring to Fig. 5, a sensor portion 140 includes diamond 110, a heat conduction portion 160, and a fixing member 162, and it is fixed to electric power transmission line 900 by a band-like fixing member 164. Heat conduction portion 160 corresponds to heat conduction portion 112 shown in Fig. 2. Heat conduction portion 160 includes a curved surface in a shape to be in intimate contact with the side surface of electric power transmission line 900. Heat conduction portion 160 is formed of a material similar to that for heat conduction portion 112. Fixing member 162 corresponds to fixing member 154 shown in Fig. 2. Band-like fixing member 164 is formed into the band shape having a prescribed width from flexible resin or the like. Sensor portion 140 may thus be fixed to the side surface of electric power transmission line 900 larger than sensor portion 140, as being in intimate contact therewith. Therefore, magnetic field, the current, the temperature, and the like can be detected with diamond 110 in a stable manner.

[0053] (Second Modification) Though an example in which the main surface and the rear surface of diamond 110 in the form of the plate are in a triangular shape and excitation light is incident perpendicularly to the side surface is described above, limitation thereto is not intended. The main surface and the rear surface of diamond 110 may be in a shape of a polygon including at least four sides. Excitation light may obliquely be incident on a side surface of diamond 110. Referring to Fig. 6, diamond 114 includes a first surface 114A (main surface), a second surface 114B (rear surface), and a side surface 114C. First surface 114A and second surface 114B are in a quadrangular shape. Side surface 114C is irradiated with excitation light 304 that propagates through optical waveguide 104, and excitation light enters the inside of diamond 114 from side surface 114C. An end surface of optical waveguide 104 is inclined with respect to a central axis thereof and in intimate contact with side surface 114C. Fluorescence 306 generated in diamond 114 is radiated from side surface 114C to the outside of diamond 114 and incident on the end surface of optical waveguide 104, and propagates through optical waveguide 104.

[0054] In arrangement shown in Fig. 6, an angle (|) formed by the end surface of optical waveguide 104 with respect to the central axis is a complement of 0, where 0 represents an angle of incidence of excitation light 304 on side surface 114C (an angle formed between a normal to side surface 114C and excitation light 304), and it is expressed as <|) = 7t / 2-0 (rad). Angle of incidence 0 i s preferably a Brewster's angle. The Brewster's angle means an angle of incidence at which intensity of reflected light of p polarization is 0. In other words, when diamond 114 (that is, side surface 114C) and optical waveguide 104 are arranged such that angle of incidence 0 is set to the Brewster's angle, excitation light 304 that propagates through optical waveguide 104 and is emitted to side surface 114C can efficiently enter the inside of diamond 114 without being reflected by side surface 114C. Therefore, efficiency in generation of fluorescence by the NV center can be improved.

[0055] (Second Embodiment) The diamond spin sensor system that does not use microwaves is described in the first embodiment. In contrast, a diamond spin sensor system according to a second embodiment uses microwaves.

[0056] Referring to Fig. 7, a diamond spin sensor system 200 according to the second embodiment of the present disclosure includes a sensor portion 202, optical waveguide 104, control power supply portion 106, a modulated signal generator 204, a light modulator 206, and an optical waveguide 208. Diamond spin sensor system 200 is a diamond spin sensor system obtained by replacing sensor portion 102 with sensor portion 202 in diamond spin sensor system 100 shown in Fig. I and adding modulated signal generator 204, light modulator 206, and optical waveguide 208 therein. Sensor portion 202 includes diamond 110, heat conduction portion 112, and a photoelectric converter 210. Sensor portion 202 is a sensor portion obtained by adding photoelectric converter 210 to sensor portion 102 shown in Fig. 1. An element in Fig. 7 labeled with a reference numeral the same as in Fig. 1 performs a function the same as in Fig. 1. Therefore, redundant description will not be repeated. Controller 130 performs a function to control modulated signal generator 204 in addition to the function above. Specifically, a program for controlling modulated signal generator 204 is stored in the storage included in controller 130, and executed by the CPU included in controller 130.

[0057] Referring to Fig. 8, heat conduction portion 112 of sensor portion 202 includes first member 150 and second member 152. Diamond 110 is arranged at heat conduction portion 112. Diamond 110 is formed like the plate of the triangular prism. Of two triangular planes of diamond 110, first surface 110A (main surface) is in contact (that is, surface contact) with heat conduction portion 112. Photoelectric converter 210 is arranged at diamond 110. Specifically, of the two triangular planes of diamond 110, second surface HOB (rear surface) is in contact (that is, surface contact) with photoelectric converter 210. Diamond 110 and photoelectric converter 210 are fixed to heat conduction portion 112 by fixing member 154 arranged as being opposed to heat conduction portion 112 (specifically, first member 150) with diamond 110 and photoelectric converter 210 being interposed.

[0058] Referring back to Fig. 7, modulated signal generator 204 generates a signal having a prescribed frequency (that is, a microwave frequency band) and provides the signal to light modulator 206 under the control by controller 130. Light modulator 206 modulates an amplitude of light having the prescribed frequency with the signal supplied from modulated signal generator 204 to generate modulated light and outputs modulated light. In other words, the signal outputted from modulated signal generator 204 is a modulated signal to be used for generation of modulated light. The frequency of the signal outputted from modulated signal generator 204 is a modulation frequency. Light having the prescribed frequency and being to be modulated is carrier waves. Modulated light generated by light modulator 206 is transmitted through optical waveguide 208 to photoelectric converter 210 of sensor portion 202. Optical waveguide 208 is, for example, an optical fiber.

[0059] Photoelectric converter 210 converts (that is, photoelectrically converts) modulated light transmitted through optical waveguide 208 into an electrical signal and outputs the electrical signal. The electrical signal having a frequency (that is, the microwave frequency) of carrier waves thereof is thus generated from modulated light and diamond 110 is irradiated with the electrical signal as electromagnetic waves. Electromagnetic waves emitted to diamond 110 are used for magnetic resonance of the NV center.

[0060] Controller 130 controls excitation light generator 120 to output excitation light 304 at prescribed timing for a prescribed time period (for example, a period tl). Controller 130 controls modulated signal generator 204 such that electromagnetic waves are outputted from photoelectric converter 210 at prescribed timing for a prescribed time period (for example, a period t2). An appropriate pulse sequence should only be used as appropriate as a pulse sequence during period t2. Diamond 110 is thus irradiated with electromagnetic waves, as being temporally and spatially combined with excitation light. Controller 130 takes in an output signal from photodetector 128 at prescribed timing (for example, within a period t3) and has the output signal stored in the storage.

[0061] For example, diamond 110 (that is, the NV center) is irradiated with microwaves at 2.87 GHz, and thereafter excited by irradiation with green excitation light. Since transition at the time when spin of the NV center returns to the ground state includes transition in which light (that is, fluorescence) is not radiated, observed intensity of radiated light lowers. Therefore, two valleys (that is, drop of a signal) are observed in an ESR spectrum. An interval Af (that is, a frequency difference) between the two observed valleys is dependent on intensity of magnetic field at a position of diamond 110. As controller 130 transmits the output signal from photodetector 128 to an external apparatus by means of the wireless communication unit, the external apparatus calculates Af and magnetic field can be calculated from Af.

[0062] Though an example in which microwaves are optically transmitted and photoelectric converter 210 converts them into electromagnetic waves (microwaves) is described above, limitation thereto is not intended. Microwaves may be generated by an electromagnetic wave generator. Generated microwaves are transmitted through a microwave transmission channel (for example, a coaxial cable) to diamond 110 and diamond 110 is irradiated therewith by means of a microwave circuit. The microwave circuit may be a circuit such as a coplanar line or a microstrip line. For example, the microwave circuit is directly formed by patterning metal on first surface 110A (main surface) of diamond 110 shown in Fig. 4. Metal is arranged by vapor deposition on the entire surface of second surface 110B (rear surface) of diamond 110 and used as a ground. Microwaves thus penetrate into diamond 110. The power cable may be arranged on a main surface side or a rear surface side. For metal to form the microwave circuit, metal which is a non-magnetic element and low in resistance value such as gold (Au), silver (Ag), copper (Cu), and aluminum (Al) is employed. In arrangement in which patterned first surface 110A (main surface) is opposed to electric power transmission line 900 (see, for example, Fig. 2), fluorescence cannot be detected from second surface HOB (rear surface) where metal is arranged. In that case, of the side surfaces, fluorescence is detected from a surface the same as a surface where excitation light is incident. Since metal is arranged at the rear surface, fluorescence radiated from the NV center of diamond 110 can efficiently be emitted from the side surface. By thus forming the microwave circuit at the surface of diamond 110, a mechanism for irradiation with microwaves does not have to separately be provided, and a compact diamond spin sensor can be realized.

[0063] Though an example in which a diamond element having the NV center is employed for the diamond spin sensor is described above, limitation thereto is not intended. Any diamond element having the color center having electron spin should only be provided. The color center having electron spin is a center that forms a spin triplet state and emits light by being excited, and the NV center is a representative example. In addition, it has been known that there is a color center having electron spin also at a silicon-vacancy center (that is, an Si-V center), a germanium-vacancy center (that is, a Ge-V center), or a tin-vacancy center (that is, an Sn-V center). Therefore, the diamond element including such a center may be employed in place of the diamond element including the NV center to form the diamond spin sensor.

[0064] (Example) A result of an experiment is shown below. The diamond spin sensor system including the heat conduction portion as set forth above was used to measure magnetic field originating from a measurement target and the temperature. Diamond to be used for the experiment was made as below. Specifically, diamond containing 30 ppm of substitution nitrogen was synthesized by a high pressure and high temperature process and formed to a 2 mm x 2 mm square and a thickness from 0.1 mm to 2 mm. Obtained diamond was irradiated with electron beams having energy of 3 MeV at a dose of lx 1018 cm-2, and thereafter annealed for one hour at 950°C. It was confirmed based on an optically detected magnetic resonance spectrum (ODMR spectrum) that an NW color center was formed in formed diamond, and magnetic field and a temperature could be sensed based on spin thereof.

[0065] Made diamond was machined into the shape of the triangular prism and employed as diamond 110 in the arrangement shown in Fig. 2, and magnetic field and the temperature were measured with two types of measurement methods (measurement A and measurement B which will be described later). For measurement A, a phenomenon in which, when magnetic field was sensed by irradiating diamond with intensity of an excitation light source being set constant and observing fluorescence, intensity of fluorescence lowered (magnetic field sensing only by using the excitation light source) was used. Magnetic field is sensed based on variation in intensity of fluorescence. Therefore, when variation in intensity of fluorescence becomes less and buried in noise or the like, it is determined that it is unable to sense magnetic field. For measurement B, a feature that emitted microwaves to diamond was added to the configuration shown in Fig. 1, and a method of converting to magnetic field, an interval (frequency difference) between two peaks in an ODMR spectrum obtained by sensing fluorescence intensity with a frequency of emitted microwaves being varied was employed (magnetic field sensing based on the ODMR spectrum). In measurement B as well, when variation in intensity of fluorescence becomes less and buried in noise or the like, a spectrum cannot be obtained and it is determined that it is unable to sense magnetic field. The temperature was measured based on the ODMR spectrum as in measurement B.

[0066] Diamond was set at the measurement target in the shape of the column or the twisted wire with the heat conduction portion being interposed (see Fig. 2). The main surface and the side surface of diamond machined into the shape of the triangular prism were both mirror polished (specifically, arithmetic mean roughness Ra after polishing being Ra <5 nm). The side surface was at a right angle with respect to the main surface. By polishing to achieve Ra <5 nm, efficiency in collection of fluorescence could be improved.

[0067] Various types of diamond different in dimension although they were in the shape of the triangular prism were made and subjected to the experiment. The main surface of diamond in the triangular shape was arranged as being in contact with the flat surface of the heat conduction portion, and an optical waveguide (specifically, an optical fiber having a core diameter (diameter) of 200 pm)) for transmission of excitation light and fluorescence was arranged. The shape of diamond 400 used in the experiment and arrangement relation between diamond 400 and an optical fiber 410 which is the optical waveguide will be described with reference to Fig. 9. Diamond 400 had a shape of a triangle ABC (main surface) having vertices at a point A, a point B, and a point C in a plan view. Optical fiber 410 was arranged such that excitation light was incident on diamond 400 from a side surface 402 including one base BC of triangle ABC. A point of intersection 406 between the normal from vertex A to base BC and base BC in triangle ABC was designed to be located near a middle point 404 of base BC. An angle (interior angle) D of vertex A was designed to approximately 90°. With angle D of vertex A being defined as the right angle, a length from point of intersection 406 to vertex A is defined as a height to the vertex of the right isosceles triangle.

[0068] Fig. 10 shows a result of measurement where diamond 400 of various dimensions was used. The table in Fig. 10 shows measured intensity of fluorescence, whether or not magnetism could be sensed, and whether or not the temperature of the measurement target could precisely be measured. Fluorescence intensity represents a ratio (%) to intensity of excitation light which is incident light. In the table in Fig. 10, El (%) represents a ratio of a distance b between middle point 404 and point of intersection 406 to a half length a of base BC. E2 (%) represents a ratio of a distance (perpendicular distance) c between a central axis of optical fiber 410 and middle point 404 to half length a of base BC. F (mm) represents the height (that is, the thickness) of diamond 400 in the shape of the triangular prism. In fields of the result of measurement A and the result of measurement B, "GOOD" represents that measurement was successful and "NG" represents that measurement failed.

[0069] It can be seen in Fig. 10 that, when angle D of vertex A was within a range of 90°±10°, measurement could be conducted. It can be seen that, when E1-E2 was equal to or less than 10%, that is, deviation between the normal from vertex A to base BC and the central axis of optical fiber 410 was equal to or less than 10%, measurement could be conducted. This means that the central axis of optical fiber 410 should be substantially in parallel to a straight line that bisects angle D of vertex A (the straight line that connects point A and middle point 404 to each other). It can be seen that, when thickness F of diamond 400 was equal to or more than 50% of the core diameter (200 pm) of the optical fiber, measurement could be conducted. That is, thickness F of diamond should be not smaller than half a diameter (|) of the optical waveguide and not larger than 2.5 times as large as diameter 0 of the optical waveguide. Under the condition the same as that for sample No. 1 shown in Fig. 10, fluorescence intensity was checked with materials different in height to the vertex of the right isosceles triangle being prepared, the materials having the height 0.8 time, 1 time, 2 times (sample No. 1), and 4 times as large as thickness F of diamond. Consequently, a sample in which the height to the vertex of the right isosceles triangle was at least two times as large as thickness F of diamond achieved the result GOOD in measurement A and measurement B. The sample in which the height to the vertex of the right isosceles triangle was at least two times as large as thickness F of diamond achieved fluorescence intensity of 80% or higher. In contrast, a sample in which the height to the vertex of the right isosceles triangle was at most one time as large as thickness F of diamond was extremely low in fluorescence intensity, that is, 10% or lower.

[0070] Influence on measurement by the shape of the heat conduction portion was evaluated. Specifically, heat conduction portions different in shape of a portion of contact with a columnar measurement target (electric power transmission line) were made. Referring to Fig. 11, a heat conduction portion 420 including a first member 422 and a second member 424 was made. First member 422 and second member 424 were attached to a columnar measurement target 910 having a radius R by inserting a screw or the like in a through hole 426. Furthermore, diamond including the NV-center made as above was arranged on first member 422 as shown in Fig. 2 and the temperature was measured. The portion of contact of first member 422 and second member 424 with measurement target 910 was flat (radius co).

[0071] Referring to Fig. 12, a heat conduction portion 430 including a first member 432 and a second member 434 was made. First member 432 and second member 434 each had a cross-section in a shape of an arc 438, the cross-section being perpendicular to an axis of measurement target 910, and arc 438 had a radius r (r >R). First member 432 and second member 434 were attached to measurement target 910 by inserting a screw or the like in a through hole 436. Furthermore, diamond including the NV-center made as above was arranged on first member 432 as shown in Fig. 2 and the temperature was measured. Referring to Fig. 13, a heat conduction portion 440 including a first member 442 and a second member 444 was made. First member 442 and second member 444 each had a cross-section in a shape of an arc, the cross-section being perpendicular to the axis of measurement target 910, and the arc had a radius equal to radius R of measurement target 910. First member 442 and second member 444 were attached to measurement target 910 by inserting a screw or the like in a through hole 446. Furthermore, diamond including the NV- center made as above was arranged on first member 442 as shown in Fig. 2 and the temperature was measured.

[0072] In an environment at a room temperature of 25°C, the temperature of measurement target 910 was maintained at 150°C and diamond arranged on the first member was used to measure the temperature in measurement B (measurement based on an ODMR spectrum). Fig. 14 shows a result. Measured fluorescence intensity represents a ratio (%) to intensity of excitation light which is incident light. A field "determination" represents reliability of the result of measurement, a indicates high accuracy in measurement, and reliability lowers in the order of a, 0, and y. It can be seen in Fig. 14 that, when a difference (r-R) between radius r of the arc formed at the heat conduction portion and radius R of measurement target 910 is equal to or less than 20% of radius R (see sample No. 21 to sample No. 23), an error of the measured temperature was within 10°C.

[0073] Though the present disclosure is described by describing embodiments above, the embodiments above are illustrative and the present disclosure is not restricted only to the above embodiments. The scope of the present disclosure is defined by the claims in scope of claims with reference to the description in detailed description of the invention, and includes any modifications within the scope and meaning equivalent to the language therein. REFERENCE SIGNS LIST

[0074] 100, 200 diamond spin sensor system 102, 140,202 sensor portion 104, 208 optical waveguide 106 control power supply portion 110, 114,400 diamond 110A, 114A first surface HOB, 114B second surface 110C, 114C, 402 side surface 112, 160, 420, 430, 440 heat conduction portion 120 excitation light generator 122 filter 124 light collecting element 126 LPF 128 photodetector 5 130 controller 150, 422, 432, 442 first member 152,424,434,444 second member 154,162 fixing member 164 band-like fixing member 10 204 modulated signal generator 206 light modulator 210 photoelectric converter 304 excitation light 306 fluorescence 15 404 middle point 406 point of intersection 410 optical fiber 426, 436, 446 through hole 438 arc 20 900 electric power transmission line 910 measurement target A, B, C point a length b, c distance 25 D angle R, r radius 0 angle of incidence

Claims

1. A diamond spin sensor comprising:diamond having a color center having electron spin; anda heat conduction portion in contact with the diamond, whereinthe heat conduction portion is fixed to a target, andat least one of magnetic field, a current, and a temperature of the target is detected by measuring fluorescence radiated from the color center after the color center is irradiated with excitation light.

2. The diamond spin sensor according to claim 1, whereinthe target is a linear member, a columnar member, or a twisted-wire-like member.

3. The diamond spin sensor according to claim 2, whereinthe diamond includes a flat main surface,the target is the columnar member or the twisted-wire-1 ike member,the heat conduction portion has a curved surface,the main surface is in contact with a surface of the heat conduction portion other than the curved surface, andthe curved surface is in contact with a side surface of the columnar member or the twisted-wire-like member.

4. The diamond spin sensor according to claim 3, whereinthe diamond further includes a side surface perpendicular to the main surface, andthe excitation light is incident on the side surface of the diamond and the fluorescence is radiated from the side surface of the diamond.

5. The diamond spin sensor according to claim 3, whereinthe diamond further includes a side surface perpendicular to the main surface and a rear surface in parallel to the main surface,the excitation light is incident on the side surface of the diamond, and the fluorescence is radiated from the rear surface.

6. The diamond spin sensor according to claim 3, wherein the diamond is in a form of a plate, andthe main surface is in a shape of a right isosceles triangle.

7. The diamond spin sensor according to any one of claims 1 to 6, whereinthe target is an uncoated electric power transmission line, andthe heat conduction portion is formed of metal that is not electrolytically corroded by contact with the electric power transmission line.

8. The diamond spin sensor according to claim 7, wherein the heat conduction portion is formed of aluminum or copper.

9. The diamond spin sensor according to any one of claims 1 to 8, further comprising a microwave circuit, whereinthe diamond includes a flat main surface and a rear surface in parallel to the main surface,the microwave circuit is arranged at the main surface, andmetal is arranged at the rear surface.

10. The diamond spin sensor according to claim 1 or 2, further comprising an optical waveguide through which the excitation light is transmitted, whereinthe optical waveguide is an optical guide or an optical fiber, andthe diamond has a thickness not smaller than half a diameter of the optical waveguide and not larger than 2.5 times as large as the diameter.

11. The diamond spin sensor according to claim 10, whereinthe diamond includes a flat main surface,the main surface is in a shape of a right triangle, andin a portion where an end surface of the optical waveguide is in contact with the diamond, a central axis of the optical waveguide is arranged in parallel to a straight line that bisects an interior angle of the main surface, the interior angle being a right angle.

12. The diamond spin sensor according to claim 11, wherein the main surface is in a shape of a right isosceles triangle, anda height to a vertex of the right isosceles triangle is at least two times as large as the thickness of the diamond.

13. The diamond spin sensor according to claim 11 or 12, whereinthe diamond further includes a side surface perpendicular to the main surface and a rear surface in parallel to the main surface,the excitation light is incident on the diamond from the side surface, andthe diamond spin sensor further comprises a detection unit that detects fluorescence radiated from the rear surface.

14. The diamond spin sensor according to claim 13, whereinthe detection unit includes a photodiode on which the fluorescence radiated from the rear surface is directly incident.

15. The diamond spin sensor according to claim 13, further comprising an optical fiber through which the fluorescence is transmitted to thedetection unit and further comprising, at an end surface of the optical fiber, an optical system that collects the fluorescence radiated from the rear surface.

16. The diamond spin sensor according to claim 11 or 12, wherein5 the diamond further includes a side surface perpendicular to the main surface,the excitation light is incident on the diamond from the side surface, and the diamond spin sensor further comprises a detection unit that detects fluorescence radiated from the side surface.10

17. The diamond spin sensor according to any one of claims 13 to 16,whereinan angle formed between a normal to the side surface and a central axis of the optical waveguide is a Brewster's angle.15

18. A diamond spin sensor system comprising:the diamond spin sensor according to any one of claims 1 to 17; and a control power supply portion that generates the excitation light and detects the fluorescence.INTERNATIONAL SEARCH REPORT International application No. PCT / JP2024 / 022I91A. CLASSIFICATION OF SUBJECT MATTER G01R 33 / 20(2006.01)1; G01K 11 / 3213(2021.01)i; G01R 15 / 24(2006.01)1 FI: G01R33 / 20; G01R15 / 24 D; G01K11 / 3213 According to International Patent Classification (IPC) or to both national classification and IPC B. FIELDS SEARCHED Minimum documentation searched (classification system followed by classification symbols) G01R33 / 20: G01K11 / 3213; G01R15 / 24; G01R33 / 032; G01N24 / 00; G01N21 / 64; G02B6 / 00 Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched Published examined utility model applications of Japan 1922-1996 Published unexamined utility model applications of Japan 1971-2024 Registered utility model specifications of Japan 1996-2024 Published registered utility model applications of Japan 1994-2024 Electronic data base consulted during the international search (name of data base and, where practicable, search terms used) C. DOCUMENTS CONSIDERED TO BE RELEVANT Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. X Y A Y JP 2018-136316 A (NISSIN ELECTRIC CO., LTD.) 30 August 2018 (2018-08-30) paragraphs [0001], [0058]-[0077], [0113]-[0115], fig. 2, 9 JP 2014-517322 A (PRESIDENT AND FELLOWS OF HARVARD COLLEGE) 17 July 2014 (2014-07-17) paragraphs [0012]-[0033], fig. 1-3A 1-2, 18 9-10 3-8, 11-17 9-10 A WO 2022 / 210695 Al (SUMITOMO ELECTRIC INDUSTRIES, LTD.) 06 October 2022 (2022-10-06) entire text, all drawings 1-18 A WO 2022 / 163677 Al (SUMITOMO ELECTRIC INDUSTRIES, LTD.) 04 August 2022 (2022-08-04) entire text, all drawings 1-18 | J | Further documents are listed in the continuation of Box C. | Z | See patent family annex. * Special categories of cited documents: “A” document defining the general state of the art which is not considered to be of particular relevance “D” document cited by the applicant in the international application ‘4E” earlier application or patent but published on or after the international filing date *4L” document which may throw doubts on priority claim(s) or which is cited to establish the publication date of another citation or other special reason (as specified) “O” document referring to an oral disclosure, use, exhibition or other means “P” document published prior to the international filing date but later than the priority date claimed “T” later document published after the international filing date or priority date and not in conflict with the application but cited to understand the principle or theory underlying the invention “X” document of particular relevance; the claimed invention cannot be considered novel or cannot be considered to involve an inventive step when the document is taken alone “Y” document of particular relevance; the claimed invention cannot be considered to involve an inventive step when the document is combined with one or more other such documents, such combination being obvious to a person skilled in the art document member of the same patent family Date of the actual completion of the international search 16 July 2024 Date of mailing of the international search report 30 July 2024 Name and mailing address of the ISA / JP Japan Patent Office (ISA / JP) 3-4-3 Kasumigaseki, Chiyoda-ku, Tokyo 100-8915 Japan Authorized officer Telephone No.

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