Diamond spin sensor system

Abstract

This diamond spin sensor system includes: a sensor part that includes diamond having a color center with an electron spin; a control power supply part that generates excitation light for irradiating t

Description

TITLE OF INVENTION: Diamond Spin Sensor System TECHNICAL FIELD

[0001] The present disclosure relates to a diamond spin sensor system. The present application claims priority to Japanese Patent Application No. 2023-100677 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] In order to eliminate a wire (an optical fiber or the like) for connection between detection equipment provided at the power cable and equipment provided on the ground, the detection equipment is also provided with a wireless communication function. Specifically, information such as a temperature, a current value, and the like detected by the detection equipment provided at the power cable is transmitted to the equipment provided on the ground through a wireless communication unit within the detection equipment.

[0004] 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 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 NV^ 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 the NV center can serve as a magnetic sensor.

[0005] 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

[0006] PTL 1: Japanese Patent Laying-Open No. 2003-35852 NON PATENT LITERATURE

[0007] 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

[0008] A diamond spin sensor system according to one aspect of the present disclosure includes a sensor portion that includes diamond including a color center having electron spin, a control power supply portion that generates excitation light to be emitted to the sensor portion, and a joint portion that connects the sensor portion and the control power supply portion to each other, and the joint portion allows transmission therethrough of the excitation light to the sensor portion for irradiation of the diamond and allows transmission therethrough of fluorescence radiated from the diamond to the control power supply portion. BRIEF DESCRIPTION OF DRAWINGS

[0009] [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 cross-sectional view showing a configuration of a joint portion shown in Fig. 1. [Fig. 3] Fig. 3 is a schematic diagram showing exemplary provision of the diamond spin sensor system shown in Fig. 1. [Fig. 4] Fig. 4 is a schematic diagram showing a configuration of a joint portion according to a first modification. [Fig. 5] Fig. 5 is a schematic diagram showing a configuration of a joint portion according to a second modification. [Fig. 6] Fig. 6 is a cross-sectional view showing a configuration of a joint portion according to a third modification. [Fig. 7] Fig. 7 is a schematic diagram showing a configuration of a joint portion according to a fourth modification. [Fig. 8] Fig. 8 is a block diagram showing a configuration of a diamond spin sensor system according to a second embodiment. [Fig. 9] Fig. 9 is a cross-sectional view showing a configuration of a microwave joint portion shown in Fig. 8. [Fig. 10] Fig. 10 is a schematic diagram showing a configuration of a diamond spin sensor system according to a first example. [Fig. 11] Fig. 11 is a diagram showing in a table format, a result of measurement according to the configuration shown in Fig. 10. [Fig. 12] Fig. 12 is a schematic diagram showing a configuration of a measurement system according to a first comparative example. [Fig. 13] Fig. 13 is a diagram showing in a table format, a result of measurement according to the configuration shown in Fig. 12. [Fig. 14] Fig. 14 is a schematic diagram showing a configuration of a diamond spin sensor system according to a second example. [Fig. 15] Fig. 15 is a diagram showing in a table format, a result of measurement according to the configuration shown in Fig. 14. [Fig. 16] Fig. 16 is a schematic diagram showing a configuration of a diamond spin sensor system according to a third example. [Fig. 17] Fig. 17 is a diagram showing in a table format, a result of measurement according to the configuration shown in Fig. 16. [Fig. 18] Fig. 18 is a schematic diagram showing a configuration of a diamond spin sensor system according to a fourth example. [Fig. 19] Fig. 19 is a diagram showing in a table format, a result of measurement according to the configuration shown in Fig. 18. DETAILED DESCRIPTION

[0010] [Problem to be Solved by the Present Disclosure] A conventional system for maintenance and management of a power cable includes a mechanism that replenishes detection equipment with electric power through an electric cable separate from the power cable, a mechanism that detects a temperature and a current at different portions, and a mechanism that transmits detected information to equipment arranged on the ground through a wire or wirelessly. Therefore, a large number and a wide variety of electronic components such as an electronic component that converts electric power to electric power for control, an electronic component that converts the temperature and the current to digital information, and an electronic component that transmits the information to the ground are used. In addition, for use in an environment where variation is great such as a temperature cycle, hermeticity of equipment should be high, which disadvantageously leads to such a problem as confinement of heat in the equipment, a shorter lifetime of the electronic component, and likeliness of failure of the electronic component. When the electronic component fails, supply of electric power through the power cable should be stopped for repair. This is also applicable to high-voltage equipment, without being limited to the electric cable. In order to do maintenance before failure of the electronic component in the conventional system including a large number and a wide variety of electronic components, intervals of maintenance of each electronic component should be set in consideration of the lifetime of each electronic component, which is troublesome.

[0011] A similar problem also arises in real-time sensing of a physical state (a voltage, a current, a temperature, and the like) in a harsh environment such as a high pressure, a high temperature, an extremely low temperature, strong acid, and strong alkali, without being limited to a high-voltage environment such as an electric power transmission and distribution facility.

[0012] Therefore, an object of the present disclosure is to provide a diamond spin sensor system that is capable of detecting a physical state in a harsh environment, has a long lifetime, and is easy to be maintained.

[0013] [Effect of the Present Disclosure] According to the present disclosure, a diamond spin sensor system that is capable of detecting a physical state in a harsh environment, has a long lifetime, and is easy to be maintained can be provided.

[0014] [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.

[0015] (1) A diamond spin sensor system according to a first aspect of the present disclosure includes a sensor portion that includes diamond including a color center having electron spin, a control power supply portion that generates excitation light to be emitted to the sensor portion, and a joint portion that connects the sensor portion and the control power supply portion to each other, and the joint portion allows transmission therethrough of the excitation light to the sensor portion for irradiation of the diamond and allows transmission therethrough of fluorescence radiated from the diamond to the control power supply portion. Since the sensor portion thus includes diamond that can withstand a harsh environment as a sensor element, the diamond spin sensor system that is capable of detecting a physical state (a voltage, a current, a temperature, or the like) in a harsh environment, has a long lifetime, and is easy to be maintained can be realized.

[0016] (2) In (1) above, the sensor portion can be arranged in a first environment, the control power supply portion can be arranged in a second environment different from the first environment, and the first environment can be higher than the second environment in at least one of a voltage and a temperature by at least one order of magnitude. The diamond spin sensor system in which the control power supply portion can be arranged in an ordinary environment, the diamond spin sensor system being long in lifetime and easy to be maintained, can thus be realized.

[0017] (3) In (1) or (2) above, the sensor portion may further include an optical waveguide through which the excitation light is transmitted to the diamond, the optical waveguide may be formed of translucent resin, translucent nitride, or translucent oxide, and the diamond and a portion of connection between the diamond and the optical waveguide may be shielded against outside air. The sensor portion can thus be arranged in a harsher environment.

[0018] (4) In (3) above, the joint portion may include an insulator and the insulator may contain therein, a structure through which the excitation light passes. Excitation light can thus efficiently be transmitted and damage to a mechanism arranged inside the joint portion can be prevented.

[0019] (5) In (4) above, in the diamond spin sensor system, inside the joint portion, an uncoated optical transmission member through which the excitation light passes may be arranged, or a space through which the excitation light passes may be provided. The number of man-hours in manufacturing can thus be reduced and cost for manufacturing can be reduced.

[0020] (6) In (5) above, in the diamond spin sensor system, inside the joint portion, the space may be provided and a lens through which the excitation light passes may be provided. Efficiency in transmission of excitation light in the space within the joint portion can thus be improved.

[0021] (7) In (6) above, the diamond spin sensor system may include a plurality of optical fibers through which the fluorescence radiated from the diamond is transmitted and is incident on the lens, and the plurality of optical fibers may be bundled. Efficiency in collection of fluorescence radiated from diamond can thus be improved.

[0022] (8) In (1) or (2) above, the joint portion may include an insulator, and the insulator may contain therein, a structure through which the excitation light passes. Excitation light can thus efficiently be transmitted and damage to a mechanism arranged inside the joint portion can be prevented.

[0023] (9) In any one of (1) to (3) and (8) above, in the diamond spin sensor system, inside the joint portion, an uncoated optical transmission member through which the excitation light passes may be arranged. The number of man-hours in manufacturing can thus be reduced and cost for manufacturing can be reduced.

[0024] (10) In any one of (1) to (3) and (8) above, in the diamond spin sensor system, inside the joint portion, a space through which the excitation light passes may be provided. The number of man-hours in manufacturing can thus be reduced and cost for manufacturing can be reduced.

[0025] (11) In any one of (1) to (10) above, the diamond spin sensor system may further include an electromagnetic wave generator that outputs microwaves and a microwave joint portion, the sensor portion may include a microwave circuit or a microwave waveguide, the microwave joint portion may include a transmitter that radiates microwaves inputted from the electromagnetic wave generator and a receiver that receives the microwaves radiated from the transmitter, the microwaves received by the receiver may be outputted to the microwave circuit or the microwave waveguide included in the sensor portion, and in the microwave joint portion, a space where microwaves radiated from the transmitter propagate may be provided. Magnetic field can thus be calculated from an interval between two valleys of an observed frequency spectrum.

[0026] (12) In (11) above, the transmitter may include a first concave surface from which the microwaves are radiated, the receiver may include a second concave surface at which the microwaves converge, and a shape of each of the first concave surface and the second concave surface may be a part of a paraboloid or a spherical surface. Efficiency in transmission of microwaves in the space within the microwave joint portion can thus be improved.

[0027] [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.

[0028] (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, a joint portion 104, a control power supply portion 106, and an optical waveguide 108. Sensor portion 102 includes diamond 110 including an NV“ center (which will be denoted as an NV center below) and an optical waveguide 112. Optical waveguide 112 contains a medium through which light is transmitted and it is coated with resin or the like. Optical waveguide 112 is, for example, an optical fiber. Sensor portion 102 (specifically, optical waveguide 112) is connected to joint portion 104 by a connection portion 140. As will be described later, joint portion 104 contains a medium through which light is transmitted, and is connected to optical waveguide 108 by a connection portion 142. Optical waveguide 108 contains a medium through which light is transmitted. Optical waveguide 108 is, for example, an optical fiber. Each of optical waveguide 112, joint portion 104, and optical waveguide 108 allows bidirectional transmission of light therethrough.

[0029] Referring to Fig. 2, joint portion 104 includes a first accommodation portion 200, a second accommodation portion 202, and a third accommodation portion 204. First accommodation portion 200 is, for example, an insulator and formed of ceramic, resin, or the like. Joint portion 104 further includes an optical transmission member 206, a weight-like member 208, and a weight-like member 210 accommodated inside first accommodation portion 200 (that is, a space surrounded by a cylindrical inner wall). Optical transmission member 206 is, for example, quartz in a form of a rod. Optical transmission member 206 may have a side surface coated or uncoated. Weight-like member 208 is arranged at a first end of optical transmission member 206 and weight-like member 210 is arranged at a second end of optical transmission member 206.

[0030] Second accommodation portion 202 and third accommodation portion 204 are formed, for example, of resin. Joint portion 104 further includes an optical fiber 212 accommodated inside second accommodation portion 202 and an optical connector 216 arranged at a wall surface of second accommodation portion 202. Optical fiber 212 has a first end connected to weight-like member 208 and has a second end connected to optical connector 216. Optical connector 216 is connected to optical waveguide 108 (see Fig. 1). Optical connector 216 corresponds to connection portion 142 shown in Fig. 1. Joint portion 104 further includes an optical fiber 214 accommodated in third accommodation portion 204 and an optical connector 218 arranged at a wall surface of third accommodation portion 204. Optical fiber 214 has a first end connected to weight-like member 210 and has a second end connected to optical connector 218. Optical connector 218 is connected to optical waveguide 112 (see Fig. 1). Optical connector 218 corresponds to connection portion 140 shown in Fig. 1.

[0031] A bonded portion between first accommodation portion 200 and second accommodation portion 202 and a bonded portion between first accommodation portion 200 and third accommodation portion 204 are preferably securely bonded by a sealing member such as resin, as measures against moisture inside first accommodation portion 200, second accommodation portion 202, and third accommodation portion 204. A bonded portion between second accommodation portion 202 and optical connector 216 and a bonded portion between third accommodation portion 204 and optical connector 218 are preferably also similarly securely bonded by a sealing member.

[0032] Weight-like member 208 is a member for connection between optical fiber 212 and optical transmission member 206. Specifically, as will be described later, weightlike member 208 allows excitation light inputted from optical connector 216 to optical fiber 212, transmitted through optical fiber 212, and radiated from the first end of optical fiber 212 to be incident on the first end of optical transmission member 206. Weight-like member 210 is a member for connection between optical transmission member 206 and optical fiber 214. Specifically, weight-like member 210 collects excitation light that propagates through optical transmission member 206 and is outputted from the second end of optical transmission member 206 and allows excitation light to be incident on the first end of optical fiber 214. Weight-like member 208 and weight-like member 210 are formed, for example, of glass (quartz glass or the like).

[0033] 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 gathering element 124, an 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.

[0034] Excitation light generator 120 generates excitation light 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 is green light (that is, having a wavelength from 490 nm to 560 nm). Excitation light is preferably laser beams and excitation light generator 120 is preferably semiconductor laser (for example, radiated light therefrom having a wavelength of 532 nm).

[0035] Filter 122 is an element for separation between excitation light incident from excitation light generator 120 and light (that is, fluorescence) 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.

[0036] Light collecting element 124 collects excitation light inputted from filter 122. Light collecting element 124 is, for example, a sphere lens. Light collecting element 124 provides excitation light outputted as being diffused from excitation light generator 120 to the end of optical waveguide 108, as much as possible. Optical waveguide 108 is provided with a first end and a second end, and it allows transmission therethrough of excitation light incident on the first end from light collecting element 124 to the second end. In addition, optical waveguide 108 allows transmission therethrough of radiated light (that is, fluorescence) from diamond that is incident on the second end to the first end and outputs the same.

[0037] 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 outputted from excitation light generator 120 is shorter in wavelength than that and hence it does not pass through LPF 126. Thus, excitation light 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) 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.

[0038] Referring to Fig. 3, 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 (diamond 110 and optical waveguide 112) is arranged at an electric power transmission line 900 and control power supply portion 106 is arranged at a steel mast of an electric power pylon 902. Joint portion 104 is arranged, for example, inside an insulator 904. Optical waveguide 108 through which joint portion 104 and control power supply portion 106 are connected to each other is fixed to an arm or the like of electric power pylon 902.

[0039] 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.

[0040] 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 joint portion 104 and optical waveguide 108. 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, only sensor portion 102 is arranged, and optical waveguide 108 and control power supply portion 106 are arranged in an ordinary environment distant from electric power transmission line 900. Diamond 110 and optical waveguide 112 included in sensor portion 102 are not affected by the high-voltage environment even when they are arranged in such an environment. Optical waveguide 108 and control power supply portion 106 are arranged in the ordinary environment. Therefore, the diamond spin sensor system that is long in lifetime and easily maintained can be realized.

[0041] As joint portion 104 is configured as shown in Fig. 2, joint portion 104 may be arranged astride two different environments. For example, third accommodation portion 204 can be arranged in the harsh environment and second accommodation portion 202 can be arranged in the ordinary environment. In Fig. 3, joint portion 104 is arranged between the high-voltage environment and the ordinary environment. Each component included in joint portion 104 is formed from a member less likely to be affected by the high voltage. The diamond spin sensor system in which control power supply portion 106 and optical waveguide 108 can be arranged in the ordinary environment, the diamond spin sensor system being long in lifetime and easily maintained, can thus 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.

[0042] Optical waveguide 112 and optical waveguide 108 may be formed of translucent resin, translucent nitride, or translucent oxide. Diamond 110 is preferably covered with resin or ceramic so as to be shielded against outside air. A portion of connection between diamond 110 and optical waveguide 112 is also preferably sealed with resin or ceramic so as to be shielded against outside air. Sensor portion 102 can thus be arranged in a harsher environment.

[0043] As set forth above, the insulator is employed for first accommodation portion 200 of joint portion 104 and the feature (that is, optical transmission member 206) for transmission of excitation light can be provided in first accommodation portion 200 (that is, the insulator). Excitation light can thus efficiently be transmitted and damage by the harsh environment such as the high voltage to a mechanism arranged inside joint portion 104 can be prevented.

[0044] As set forth above, a side surface of optical transmission member 206 may optionally be coated. In an example where the side surface of optical transmission member 206 is not coated, the number of man-hours in manufacturing can be reduced and cost for manufacturing can be reduced.

[0045] (First Modification) Though the example where joint portion 104 includes optical transmission member 206 in the form of the rod and optical fiber 212 and optical fiber 214 (see Fig. 2) is described above, limitation thereto is not intended. Referring to Fig. 4, joint portion 104 may include an optical fiber 230 instead of optical transmission member 206 and optical fiber 212 and optical fiber 214. Optical fiber 230 is helically formed and arranged inside first accommodation portion 200. A coated portion 232 and a coated portion 234 are arranged at respective opposing ends of optical fiber 230, and other portions of optical fiber 230 are not coated. Coated portion 232 and coated portion 234 are formed, for example, of a resin coating. The opposing ends of optical fiber 230 where coated portion 232 and coated portion 234 are arranged are connected to optical connector 216 and optical connector 218, respectively (see Fig. 2).

[0046] Optical fiber 230 is fixed to an inner wall 240 of first accommodation portion 200 by a plurality of support members 236. Support member 236 is formed of fluoroplastic such as Teflon™. Contact of uncoated portions of optical fiber 230 with each other can thus be avoided. Therefore, light (that is, excitation light) inputted from optical connector 216 to optical fiber 230 can be transmitted to optical connector 218 in a stable manner, and light (that is, fluorescence) inputted from optical connector 218 to optical fiber 230 can be transmitted to optical connector 216 in a stable manner.

[0047] (Second Modification) In an example where optical transmission member 206 is arranged inside first accommodation portion 200 as shown in Fig. 2, a mechanism that holds optical transmission member 206 is preferably provided. For example, with reference to Fig. 5, optical transmission member 206 is held inside first accommodation portion 200 by a plurality of support members 250. Support member 250 is formed, for example, of Teflon™ in a ring (doughnut) shape around optical transmission member 206, and support member 250 has an outer periphery in contact with inner wall 240 of first accommodation portion 200. Optical transmission member 206 can thus be arranged inside first accommodation portion 200 in a stable manner. Even when mechanical vibration is applied in an environment (for example, the power cable) where joint portion 104 is arranged, the configuration inside joint portion 104 can be maintained and damage to the inside of joint portion 104 can be prevented.

[0048] (Third Modification) Though the example in which optical transmission member 206 is arranged inside joint portion 104 (see Fig. 2) is described above, limitation thereto is not intended. A function of the space itself for propagation of light may be used. Referring to Fig. 6, a joint portion 114 according to a third modification includes first accommodation portion 200, second accommodation portion 202, and third accommodation portion 204 and optical fiber 212, optical fiber 214, optical connector 216, and optical connector 218. Joint portion 114 is a joint portion that is obtained by removing optical transmission member 206 from joint portion 104 (see Fig. 2) and replacing weight-like member 208 and weight-like member 210 with a lens 300 and a lens 302. A space 220 surrounded by the cylindrical inner wall of first accommodation portion 200 is provided. An element in Fig. 6 labeled with a reference numeral the same as in Fig. 2 performs a function the same as in Fig. 2. Therefore, redundant description will not be repeated.

[0049] Lens 300 and lens 302 are each a convex lens. In joint portion 114, optical fiber 212 has the first end arranged at a position of a focus F of lens 300 and optical fiber 214 has the first end arranged at a position of a focus F of lens 302. Light inputted to optical connector 216 and radiated from the first end of optical fiber 212, that is, excitation light 304, is thus incident on lens 300 and thereafter outputted as parallel light from lens 300. Excitation light 304 outputted from lens 300 and outputted as parallel light is incident on lens 302, thereafter collected from lens 302 toward focus F of lens 302, and incident on the first end of optical fiber 214.

[0050] Light inputted to optical connector 218 and radiated from the first end of optical fiber 214, that is, fluorescence, is incident on lens 302 and thereafter outputted as parallel light from lens 302. Fluorescence outputted as parallel light from lens 302 is incident on lens 300, thereafter outputted from lens 300, collected toward focus F of lens 300, and incident on the first end of optical fiber 212. Thereafter, fluorescence 306 propagates through optical fiber 212 and is outputted from optical connector 216.

[0051] As joint portion 114 is configured as shown in Fig. 6, joint portion 114 may be arranged astride two different environments, similarly to joint portion 104 (see Fig. 2). For example, third accommodation portion 204 can be arranged in the harsh environment and second accommodation portion 202 can be arranged in the ordinary environment. The diamond spin sensor system in which control power supply portion 106 and optical waveguide 108 can be arranged in the ordinary environment, the diamond spin sensor system being long in lifetime and easily maintained, can thus be realized.

[0052] As set forth above, space 220 through which excitation light 304 passes is provided inside joint portion 114. Thus, as compared with joint portion 104 shown in Fig. 2 or the like, the number of man-hours in manufacturing can be reduced and cost for manufacturing can be reduced.

[0053] As set forth above, lens 300 and lens 302 through which excitation light 304 passes are arranged inside joint portion 114. Efficiency in transmission of excitation light 304 through space 220 within joint portion 114 can thus be improved.

[0054] (Fourth Modification) Though the example where one optical fiber 212 and one optical fiber 214 are arranged in second accommodation portion 202 and third accommodation portion 204 of joint portion 114 (see Fig. 6), respectively, is described above, limitation thereto is not intended. A plurality of fibers may be arranged in each of second accommodation portion 202 and third accommodation portion 204. As shown in Fig. 7, in joint portion 114 (see Fig. 6), optical fiber 212 and optical fiber 214 may be replaced with a plurality of optical fibers 310 and a plurality of optical fibers 312, respectively, and optical connector 216 and optical connector 218 may be replaced with an optical connector 314 and an optical connector 316, respectively. A multi-core optical fiber cable 318 and a multi-core optical fiber cable 320 replace optical waveguide 108 and optical waveguide 112 (see Fig. 1), respectively. Fig. 7 does not show first accommodation portion 200, second accommodation portion 202, and third accommodation portion 204.

[0055] The plurality of optical fibers 310 are connected to optical connector 314 and the plurality of optical fibers 312 are connected to optical connector 316. A plurality of optical fibers included in the plurality of optical fibers 310 are joined to optical fibers included in multi-core optical fiber cable 318 through optical connector 314 on a one-to-one basis. A plurality of optical fibers included in the plurality of optical fibers 312 are joined to optical fibers included in multi-core optical fiber cable 320 through optical connector 316 on a one-to-one basis. The plurality of optical fibers 310 are bundled and the plurality of optical fibers 312 are bundled. One optical fiber (which will be referred to as a first excitation light optical fiber below) among the plurality of optical fibers 310 has a first end arranged at the position of the focus of lens 300, similarly to optical fiber 212 (see Fig. 6). One optical fiber (which will be referred to as a second excitation light optical fiber below) among the plurality of optical fibers 312 has a first end arranged at the position of the focus of lens 302, similarly to optical fiber 214 (see Fig. 6).

[0056] Excitation light 304 is inputted to one optical fiber (an optical fiber joined to the first excitation light optical fiber) of multi-core optical fiber cable 318. Thus, similarly to joint portion 114 (see Fig. 6), excitation light 304 propagates through the first excitation light optical fiber among the plurality of optical fibers 310, is radiated from the first end of the first excitation light optical fiber, is incident on lens 300, and thereafter is outputted from lens 300 as parallel light. Excitation light 304 outputted as parallel light from lens 300 is incident on lens 302, thereafter outputted from lens 302, collected toward focus F of lens 302, and incident on the first end of the second excitation light optical fiber among the plurality of optical fibers 312. Excitation light 304 thereafter propagates through one optical fiber of multi-core optical fiber cable 320 joined to the second excitation light optical fiber, and thereafter diamond 110 is irradiated therewith.

[0057] Fluorescence radiated from diamond 110 is inputted to a plurality of optical fibers except for one optical fiber (an optical fiber joined to the second excitation light optical fiber) of multi-core optical fiber cable 320. Fluorescence 306 thus propagates through the optical fibers except for the second excitation light optical fiber among the plurality of optical fibers 312, is radiated from the first end (located in the vicinity of the focus of lens 302) of each optical fiber, is incident on lens 302, and thereafter is outputted as substantially parallel light from lens 302. Fluorescence outputted as substantially parallel light from lens 302 is incident on lens 300, thereafter outputted from lens 300, collected toward the vicinity of the focus of lens 300, and incident on first ends of optical fibers except for the first excitation light optical fiber among the plurality of optical fibers 310. Fluorescence 306 thereafter propagates through a plurality of optical fibers not joined to the first excitation light optical fiber, of multicore optical fiber cable 318. More of fluorescence radiated from diamond 110 can thus be incident on the optical fibers of multi-core optical fiber cable 320 and efficiently be transmitted to multi-core optical fiber cable 318.

[0058] As set forth above, the plurality of optical fibers 312 through which fluorescence radiated from diamond 110 is transmitted and is incident on lens 302 are provided and the plurality of optical fibers are bundled. Efficiency in collection of fluorescence radiated from diamond 110 can thus be improved.

[0059] (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.

[0060] A diamond spin sensor system 150 according to the second embodiment of the present disclosure includes sensor portion 102, joint portion 104, control power supply portion 106, optical waveguide 108, an electromagnetic wave generator 152, a micro wave joint portion 154, a microwave transmission channel 156, a microwave transmission channel 158, and a microwave circuit 160. Diamond spin sensor system 150 is a diamond spin sensor system obtained by adding electromagnetic wave generator 152, microwave joint portion 154, microwave transmission channel 156, microwave transmission channel 158, and microwave circuit 160 to diamond spin sensor system 100 shown in Fig. 1. An element in Fig. 8 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 electromagnetic wave generator 152 in addition to the function described above. Specifically, a program for controlling electromagnetic wave generator 152 is stored in the storage included in controller 130, and executed by the CPU included in controller 130.

[0061] Electromagnetic wave generator 152 generates electromagnetic waves (for example, microwaves) under the control by controller 130. Generated electromagnetic waves are transmitted through microwave transmission channel 156 and inputted to microwave joint portion 154. Microwave transmission channel 156 is, for example, a coaxial cable. Microwave joint portion 154 allows inputted electromagnetic waves to propagate therethrough and to be inputted to microwave transmission channel 158. Microwave transmission channel 158 allows transmission therethrough of inputted electromagnetic waves to microwave circuit 160, and diamond 110 is irradiated with electromagnetic waves by means of microwave circuit 160. Microwave transmission channel 158 is, for example, a coaxial cable. Microwave circuit 160 is, for example, a coil containing an electrical conductor. Microwave circuit 160 may be a circuit such as a coplanar line or a microstrip line.

[0062] 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 electromagnetic wave generator 152 to output electromagnetic waves 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 excitation light, as being temporally and spatially combined with electromagnetic waves. 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.

[0063] For example, diamond 110 (that is, the NV center) is irradiated with microwaves at 2.87 GHz, and thereafter excited by irradiation with green 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.

[0064] Referring to Fig. 9, microwave joint portion 154 includes a first accommodation portion 400, a second accommodation portion 402, and a third accommodation portion 404. First accommodation portion 400 is, for example, an insulator and formed of ceramic, resin, or the like. A space 406 surrounded by a cylindrical inner wall is provided inside first accommodation portion 400.

[0065] Second accommodation portion 402 and third accommodation portion 404 are formed, for example, of resin. Microwave joint portion 154 further includes a transmitter 410 accommodated inside second accommodation portion 402 and a receiver 412, a high-frequency cut filter 414, and a microwave transmission channel 416 accommodated inside third accommodation portion 404. Each of transmitter 410 and receiver 412 is, for example, an antenna, and provided with a concave surface (for example, a paraboloid (for example, a circular paraboloid or an elliptic paraboloid)) formed from a member that reflects electromagnetic waves. Transmitter 410 and receiver 412 are arranged such that openings thereof are opposed to each other. The concave surface of each of transmitter 410 and receiver 412 may be a part of a spherical surface. In that case, when a solid angle of the concave surface is small, electromagnetic waves incident in parallel to a central axis of the concave surface can converge to one point (that is, the focus).

[0066] Microwave transmission channel 156 has an end arranged at a position of a focus of transmitter 410. Electromagnetic waves that propagate through microwave transmission channel 156 and are radiated from the end of microwave transmission channel 156 are reflected by transmitter 410 and radiated in parallel. Microwave transmission channel 416 has an end arranged at a position of a focus of receiver 412. Electromagnetic waves radiated in parallel by transmitter 410 are reflected by receiver 412, converge to the focus of receiver 412, and are received at the end of microwave transmission channel 416. Electromagnetic waves received by microwave transmission channel 416 are outputted to high-frequency cut filter 414. High- frequency cut filter 414 removes a high frequency equal to or higher than a prescribed frequency from inputted electromagnetic waves and outputs resultant electromagnetic waves to microwave transmission channel 158. Thus, as set forth above, electromagnetic waves outputted from electromagnetic wave generator 152 are transmitted to microwave circuit 160 through microwave transmission channel 156, microwave joint portion 154, and microwave transmission channel 158, and diamond 110 is irradiated therewith by means of microwave circuit 160.

[0067] Thus, as set forth above, magnetic field can be calculated from interval Af between the two valleys in the observed frequency spectrum.

[0068] As set forth above, transmitter 410 includes a first concave surface from which microwaves are radiated, receiver 412 includes a second concave surface at which microwaves converge, and a shape of each of the first concave surface and the second concave surface is a part of a paraboloid or a spherical surface. Efficiency in transmission of microwaves in space 406 within microwave joint portion 154 can thus be improved.

[0069] In an example where electromagnetic waves are microwaves and a wavelength thereof is too long, microwaves may be carried on millimeter waves, that is, electromagnetic waves may be transmitted as being modulated by microwaves with millimeter waves serving as carrier waves. If microwaves having a wavelength around 10 cm are used as they are in irradiation of diamond therewith, the wavelength is too long and a property of travel in straight lines and a light collecting property would be unfavorable. Millimeter waves have a such a short wavelength as several millimeters, and they are better than microwaves in property of travel in straight lines and light collecting property. Therefore, millimeter waves propagate as being used as carrier waves and they are collected to collect energy and then split, so that microwaves are taken out and diamond is irradiated with microwaves. A system enhanced in energy efficiency can thus be realized.

[0070] Though an example where microwaves are transmitted to microwave circuit 160 through microwave transmission channel 158 and diamond 110 is irradiated therewith is described above, limitation thereto is not intended. Microwaves outputted from microwave joint portion 154 may be transmitted through a microwave waveguide to diamond 110 and diamond 110 may be irradiated therewith. The microwave waveguide means a circuit containing a cavity in a cylindrical shape or a square shape, and microwaves propagate through the cavity. The microwave waveguide may be a coaxial cable through which microwaves can pass or it may be a hollow (cavitary) element having a square cross-section. For the microwave waveguide in a hollow square shape, a microwave waveguide having a size adapted to the wavelength of microwaves is employed.

[0071] An experimental result is shown below. Magnetic field generated by a current that flowed through an electric wire was measured with the use of the diamond spin sensor system including the joint portion as set forth above. (First Example) Referring to Fig. 10, a diamond spin sensor system according to a first example includes diamond 500, an optical waveguide 502, an optical waveguide 504, an optical waveguide 510, a measurement unit 520, and a power supply portion 522. Optical waveguide 502, optical waveguide 504, and optical waveguide 510 are connected by an optical connector 506 and an optical connector 508.

[0072] Diamond 500 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 size of 2 mm x 2 mm square and a thickness of 2 mm. Obtained diamond was irradiated with electron beams having energy of 3 MeV at a dose of lx 1018 cm2. and thereafter annealed for one hour at 950°C. It was confirmed based on an optically detected magnetic resonance spectrum (ODMR spectrum) that an NV“ color center was formed in formed diamond, and magnetism and a temperature could be sensed based on spin thereof.

[0073] Optical waveguide 502 was connected to a first end of optical waveguide 504 by optical connector 506 and optical waveguide 510 was connected to a second end of optical waveguide 504 by optical connector 508. Optical waveguide 504 had a length of approximately 2 m, and was helically arranged inside an insulator 906 having a hole inner diameter of approximately 0.2 m and a hole length of approximately 0.6 m (see Fig. 4 in connection with the joint portion). For optical waveguide 502 and optical waveguide 510, a linear optical guide (uncoated) having a diameter of 0.8 mm and made of quartz glass or an optical fiber (uncoated) having a core diameter of 200 pm was employed. A linear optical guide having a diameter of 0.8 mm and made of quartz glass or an optical fiber having a core diameter of 200 gm was employed also for optical waveguide 504. As will be described later, however, a coated optical guide or optical fiber and an uncoated optical guide or optical fiber were employed to evaluate a difference in insulation durability.

[0074] Diamond 500 was attached to a tip end of optical waveguide 502 with a general translucent adhesive. By using an adhesive material, intensity of fluorescence from diamond 500 can be measured in a stable manner. Diamond 500, together with a part of optical waveguide 502, was wrapped by a heat shrinkable tube 530, and heat shrinkable tube 530 was heated to shrink to shield diamond 500 against outside air. Without coating of diamond 500 by heat shrinkable tube 530, a droplet may attach to diamond 500 or diamond 500 may be flawed, which may affect detection of magnetic characteristics. With coating of diamond 500 with heat shrinkable tube 530, such a problem can be prevented from occurring.

[0075] A lead 614 was arranged on a first plate 610 and an insulating layer 612 that were layered, and further thereon, diamond 500 coated with heat shrinkable tube 530 was arranged. An environment where diamond 500 wad arranged is called a first environment. First plate 610 was formed of conductive metal. Lead 614 was connected between a direct-current (DC) power supply 622 and a variable resistor 620 having one end grounded. DC power supply 622 can output up to 20 kV at the maximum.

[0076] Measurement unit 520 generates excitation light (laser) to be emitted to diamond 500, and detects fluorescence radiated from diamond 500 and transmitted through optical waveguide 502, optical waveguide 504, and optical waveguide 510. Power supply portion 522 supplies electric power for allowing measurement unit 520 to function. Measurement unit 520 and power supply portion 522 are arranged on a second plate 624 formed of conductive metal. An environment where measurement unit 520 and power supply portion 522 are arranged is called a second environment below. A prescribed DC voltage lower than a voltage applied to first plate 610 was supplied to second plate 624 by a DC power supply 626.

[0077] With the diamond spin sensor system shown in Fig. 10, intensity of fluorescence from diamond 500 was measured, and magnetic field generated by a current that flowed through lead 614 arranged near diamond 500 was measured with two types of measurement methods (measurement A and measurement B which will be described later). Difference originating from whether or not there was a coating (that is, heat shrinkable tube 530) at a portion of connection between diamond 500 and optical waveguide 502 and a voltage applied to first plate 610 where diamond 500 was provided was evaluated. The current that flowed through lead 614 was adjustable with variable resistor 620, and adjusted such that a steady current of 1 A flowed for the applied voltage. Fig. 11 shows an experimental result. A field "coating" represents whether or not optical waveguide 504 was coated. A field "outside air cut-off at connection portion" represents whether or not heat shrinkable tube 530 was provided.

[0078] For measurement A, a phenomenon in which, when magnetic field was sensed by irradiating diamond 500 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 500 was added to the configuration in Fig. 10, and a method of converting to magnetic field, an interval (frequency difference) between 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). 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.

[0079] A dielectric withstand voltage of an uncoated optical guide and an uncoated optical fiber was checked in advance. By checking the dielectric withstand voltage with the optical guide or the optical fiber as it was, the dielectric withstand voltage of 20 kV in a longitudinal direction thereof could be confirmed. The dielectric withstand voltage of 20 kV could be confirmed also in a state in which the optical guide or the optical fiber was helically arranged in the hollow insulator (having the hole inner diameter of approximately 0.2 m and the hole length of approximately 0.6 m). When metal was wound around opposing ends of the optical guide or the optical fiber to obtain measurement terminals, a voltage was then applied across the measurement terminals, and a current not lower than 0.1 mA did not flow, the dielectric withstand voltage was determined as being present. In actual, a low-voltage side plate may be set to ground (0 V), however, owing to presence of a drive power supply or the like, the low-voltage side plate may not strictly be set to 0 V, and in the experiment, 10 V was always applied. Fig. 11 shows as a voltage ratio, a ratio of a voltage (specifically, 10 V) in the first environment (first plate 610) to a voltage in the second environment (second plate 624). The current that flowed through lead 614 was adjusted with variable resistor 620. Specifically, for each applied voltage applied to first plate 610, adjustment was made such that steady current of 1 A flowed in measurement A and steady current of 100 mA flowed in measurement B.

[0080] As can be seen in Fig. 11, in each of measurement A and measurement B, magnetic field generated by the current that flowed through lead 614 could be sensed by detecting intensity of fluorescence from diamond 500. The fluorescence intensity exhibited such a tendency as lowering as intensity of magnetic field was higher (that is, as the voltage supplied from DC power supply 622 was higher). In an example where the coated optical guide or optical fiber was employed for the waveguide of light (see experiment No. 9 and experiment No. 11), when the applied voltage became high, a leakage current was generated, which affected the excitation light source and the microwave power supply, and stable measurement could not be conducted.

[0081] Based on comparison between the uncoated optical guide or the uncoated optical fiber (see experiment No. 1 to experiment No. 8) and the coated optical guide or the coated fiber (see experiment No. 9 to experiment No. 12), in both of measurement method A and measurement B, difference in insulation durability was observed when the voltage ratio was equal to or higher than three orders of magnitude. Specifically, the uncoated optical waveguide was better in insulation durability than the coated optical waveguide. Furthermore, based on comparison between an example where the portion of connection between diamond 500 and optical waveguide 502 was coated with heat shrinkable tube 530 (see experiment No. 1 to experiment No. 12) and an example where heat shrinkable tube 530 was not provided (see experiment No. 13 and experiment No. 14), difference was observed when the portion of connection was contaminated with oil or oil and sand. In other words, by coating with heat shrinkable tube 530, magnetic field could be detected in a stable manner without contamination and damage.

[0082] (First Comparative Example) As a first comparative example, a Hall element was used to conduct magnetic field measurement in a voltage environment similar to that in Fig. 10. Referring to Fig. 12, a Hall element 630 was arranged in the first environment (first plate 610) and a drive unit 632 was arranged in the second environment (second plate 624). As in the first example, with the voltage of second plate 624 being set to be constant (10 V) and with the voltage of first plate 610 being varied, magnetic field generated by the current that flowed through lead 614 was measured with Hall element 630. Fig. 13 shows a result. When the voltage ratio was equal to or higher than one order of magnitude (see experiment No. 21 to experiment No. 23), drive unit 632 was affected, which led to increase in noise and failure, and magnetic field could not be measured.

[0083] (Second Example) An experiment was conducted with a joint portion different from that in the first example. Referring to Fig. 14, a diamond spin sensor system according to a second example includes diamond 500, optical waveguide 502, an optical waveguide 544, a mirror 542, a lens 552, optical waveguide 510, measurement unit 520, and power supply portion 522. A configuration shown in Fig. 14 is a configuration obtained by replacing optical waveguide 504 with optical waveguide 544, mirror 542, and lens 552 in the configuration shown in Fig. 10 and removing optical connector 508 therefrom (see Fig. 6 in connection with the joint portion). Since the configuration is otherwise the same as in Fig. 10, redundant description will not be repeated. Fig. 15 shows an experimental result according to the configuration shown in Fig. 14.

[0084] An optical guide having a diameter of 1.5 mm was employed as optical waveguide 544. An open first end surface 546 of optical waveguide 544 was arranged at a central portion of a first opening 908 of insulator 906 so as to face a second opening of insulator 906. Excitation light 540 (laser) outputted from measurement unit 520 propagates through air and is reflected by mirror 542. An angle of a reflection surface of mirror 542 is adjustable. The angle of mirror 542 was adjusted to cause excitation light 540 to be incident on first end surface 546 of optical waveguide 544 arranged at the central portion of first opening 908 of insulator 906. Excitation light 540 could thus propagate to optical waveguide 544 and optical waveguide 502, and diamond 500 could be irradiated therewith.

[0085] Fluorescence 550 radiated from diamond 500 propagated through optical waveguide 502 and optical waveguide 544 and was radiated from first end surface 546 of optical waveguide 544, collected by lens 552 arranged near the second opening of insulator 906, and incident on optical waveguide 510. Thus, as shown in Fig. 15, in each of measurement A and measurement B, fluorescence radiated from diamond 500 could be detected with measurement unit 520.

[0086] (Third Example) An experiment was conducted with a joint portion different from those in the first example and the second example. Referring to Fig. 16, a diamond spin sensor system according to a third example includes diamond 500, optical waveguide 502, optical waveguide 544, a lens 560, mirror 542, lens 552, optical waveguide 510, measurement unit 520, and power supply portion 522. A configuration shown in Fig. 16 is a configuration obtained by adding lens 560 to the configuration shown in Fig. 14 (see Fig. 6 in connection with the joint portion). Lens 560 is arranged near first opening 908 within insulator 906. Since the configuration is otherwise the same as in Fig. 14, redundant description will not be repeated. Fig. 17 shows an experimental result according to the configuration shown in Fig. 16. A field "lens within insulator" means whether or not there is lens 560.

[0087] Excitation light 540 (laser) outputted from measurement unit 520 propagated through air and was reflected by mirror 542. The angle of mirror 542 was adjusted such that excitation light 540 was incident through lens 560 on first end surface 546 of optical waveguide 544 arranged at the central portion of first opening 908 of insulator 906. Excitation light 540 could thus propagate through optical waveguide 544 and optical waveguide 502, and diamond 500 could be irradiated therewith.

[0088] Fluorescence 550 radiated from diamond 500 propagated through optical waveguide 502 and optical waveguide 544 and was radiated from first end surface 546 of optical waveguide 544, collected by lens 560 arranged near first opening 908 of insulator 906 and lens 552 arranged near the second opening of insulator 906, and incident on optical waveguide 510. Thus, as shown in Fig. 17, in each of measurement A and measurement B, fluorescence radiated from diamond 500 could be detected with measurement unit 520.

[0089] (Fourth Example) An experiment was conducted with the joint portion the same as in the first example, with a temperature in the environment where diamond was arranged being varied. Referring to Fig. 18, a diamond spin sensor system according to a fourth example includes diamond 500, optical waveguide 502, optical waveguide 504, optical waveguide 510, measurement unit 520, and power supply portion 522. The diamond spin sensor system shown in Fig. 18 is the same as the diamond spin sensor system shown in Fig. 10. Therefore, redundant description will not be repeated. An environment where diamond 500 was arranged and an environment where measurement unit 520 was arranged, however, were different. Specifically, DC power supply 626 was removed from the configuration shown in Fig. 10 and a heater controller 642 was added thereto.

[0090] Lead 614 was arranged on first plate 610 and a first plate 640 that were layered, and further thereon, diamond 500 coated with heat shrinkable tube 530 was arranged (first environment). First plate 640 includes a flat plate made of conductive metal and a heater (not shown) that generates heat by being supplied with electric power from heater controller 642. First plate 640 may be increased in temperature to 600°C by heater controller 642. By arranging a portion of first plate 640 (including a member arranged on first plate 640) in vacuum and conducting an experiment, the temperature could be increased to 1000°C. Unlike first plate 610 (see Fig. 10), a voltage from DC power supply 622 is not applied to first plate 640. In addition, unlike Fig. 10, a voltage is not applied either to second plate 624 where measurement unit 520 and power supply portion 522 are arranged.

[0091] Insulated heat resistance of the uncoated optical guide or the uncoated optical fiber that was employed as optical waveguide 504 was checked in advance. Insulated heat resistance to 1000°C could be confirmed also in a state where optical waveguide 504 was helically arranged in hollow insulator 906 having a size of 0.5 m. Insulated heat resistance means such isolation that, while a temperature on a side of a diamond sensor is high, a temperature of a drive power supply portion does not become high in coordination. Specifically, unless the temperature of second plate 624 in the second environment increases by 10°C or more under the influence by first plate 640 in the first environment, insulated heat resistance was determined as being achieved. A low-temperature side plate (second plate 624) is actually at a room temperature (from 10°C to 20°C). In the fourth example, the low-temperature side plate (second plate 624) was always set to 10°C by using a Peltier element.

[0092] With a configuration shown in Fig. 18, magnetic field was measured in measurement A and measurement B as in the first example. As in the first example, the current to be fed to lead 614 was adjusted with variable resistor 620. Specifically, for each applied voltage, adjustment was made such that steady current of 1 A flowed in measurement A and steady current of 100 mA flowed in measurement B. Fig. 19 shows a result. In Fig. 19, a plate temperature in the first environment represents the temperature of first plate 640 and a plate temperature in the second environment represents the temperature of second plate 624. As shown in experiment No. 51 to experiment No. 54, at any temperature ratio, magnetic field could be measured. By coating the portion of connection between diamond 500 and optical waveguide 502 with heat shrinkable tube 530, magnetic field could be detected in a stable manner without contamination and damage to diamond 500.

[0093] (Second Comparative Example) An experiment was conducted with the use of a thermocouple, as a comparative example. In the configuration shown in Fig. 18, a temperature was measured with a thermocouple being arranged in the first environment (first plate 640 and insulating layer 612) and with a drive power supply for the thermocouple being arranged in the second environment (second plate 624). Consequently, the temperature in the second environment affected the temperature in the first environment, and an accurate temperature in the first environment could not be measured.

[0094] 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

[0095] 100,150 diamond spin sensor system 102 sensor portion 104,114 joint portion 106 control power supply portion 108, 112, 502, 504, 510, 544 optical waveguide 110,500 diamond 120 excitation light generator 122 filter 124 light collecting element 126 LPF 128 photodetector 130 controller 140, 142 connection portion 152 electromagnetic wave generator 154 mi crowave j oint portion 156, 158,416 microwave transmission channel 160 microwave circuit 200, 400 first accommodation portion 202, 402 second accommodation portion 204, 404 third accommodation portion 206 optical transmission member 208, 210 weightdike member 212, 214, 230 optical fiber 216, 218, 314, 316, 506, 508 optical connector 220,406 space 232, 234 coated portion 236, 250 support member 240 inner wall 300, 302, 552, 560 lens 304, 540 excitation light 306,550 fluorescence 310, 312 a plurality of optical fibers 318, 320 multi-core optical fiber cable 410 transmitter 412 receiver 414 high-frequency cut filter 520 measurement unit 5 522 power supply portion 530 heat shrinkable tube 542 mirror 546 first end surface 610,640 first plate 10 612 insulating layer 614 lead 620 variable resistor 622, 626 DC power supply 624 second plate 15 630 Hall element 632 drive unit 642 heater controller 900 electric power transmission line 902 electric power pylon 20 904,906 insulator 908 first opening F focus

Claims

1. A diamond spin sensor system comprising:a sensor portion that includes diamond including a color center having electron spin;a control power supply portion that generates excitation light to be emitted to the sensor portion; anda joint portion that connects the sensor portion and the control power supply portion to each other, whereinthe joint portionallows transmission of the excitation light to the sensor portion for irradiation of the diamond, andallows transmission of fluorescence radiated from the diamond to the control power supply portion.

2. The diamond spin sensor system according to claim 1, whereinthe sensor portion is arranged in a first environment,the control power supply portion is arranged in a second environment different from the first environment, andthe first environment is higher than the second environment in at least one of a voltage and a temperature by at least one order of magnitude.

3. The diamond spin sensor system according to claim 1 or 2, wherein the sensor portion further includes an optical waveguide through which the excitation light is transmitted to the diamond,the optical waveguide is formed of translucent resin, translucent nitride, or translucent oxide, andthe diamond and a portion of connection between the diamond and the optical waveguide are shielded against outside air.

4. The diamond spin sensor system according to claim 3, wherein the joint portion includes an insulator, andthe insulator contains a structure through which the excitation light passes.

5. The diamond spin sensor system according to claim 4, wherein inside the joint portion,an uncoated optical transmission member through which the excitation light passes is arranged, ora space through which the excitation light passes is provided.

6. The diamond spin sensor system according to claim 5, wherein inside the joint portion,the space is provided, anda lens through which the excitation light passes is provided.

7. The diamond spin sensor system according to claim 6, comprising a plurality of optical fibers through which the fluorescence radiated from the diamond is transmitted and is incident on the lens, whereinthe plurality of optical fibers are bundled.

8. The diamond spin sensor system according to claim 1 or 2, wherein the joint portion includes an insulator, andthe insulator contains a structure through which the excitation light passes.

9. The diamond spin sensor system according to any one of claims 1 to 3 and 8, whereininside the joint portion, an uncoated optical transmission member through which the excitation light passes is arranged.

10. The diamond spin sensor system according to any one of claim 1to 3 and 8, whereininside the joint portion, a space through which the excitation light passes is provided.

11. The diamond spin sensor system according to any one of claims 1 to 10, further comprising:an electromagnetic wave generator that outputs microwaves; anda microwave joint portion, whereinthe sensor portion includes a microwave circuit or a microwave waveguide,the microwave joint portion includesa transmitter that radiates microwaves inputted from the electromagnetic wave generator, anda receiver that receives the microwaves radiated from the transmitter, the microwaves received by the receiver are outputted to the microwave circuit or the microwave waveguide included in the sensor portion, andin the microwave joint portion, a space where microwaves radiated from the transmitter propagate is provided.

12. The diamond spin sensor system according to claim 11, wherein the transmitter includes a first concave surface from which the microwaves are radiated,the receiver includes a second concave surface at which the microwaves converge, anda shape of each of the first concave surface and the second concave surface is a part of a paraboloid or a spherical surface.INTERNATIONAL SEARCH REPORT International application No. PCT / JP2024 / 022I90A. CLASSIFICATION OF SUBJECT MATTER G01R 33 / 20(2006.01)1; GOIN23 / 64(2006.01)i; GOIN24 / 00(2006.01)i; G01R 33 / 032(2OO6.Ol)i; G02B 0 / 42(2006.01)1 FI: G01R33 / 20; G01N24 / 00 E; G01N21 / 64 Z; G01R33 / 032; G02B6 / 42 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: G01N21 / 64; G01N24 / 00; G01R33 / 032; G02B6 / 00; G01R15 / 24; G01K11 / 3213 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 WO 2022 / 163677 Al (SUMITOMO ELECTRIC INDUSTRIES, LTD.) 04 August 2022 (2022-08-04) paragraphs [0001]-[0002], [0034]-[0052], fig. 2 JP 2018-136316 A (NISSIN ELECTRIC CO LTD) 30 August 2018 (2018-08-30) paragraphs [0001], [0119], fig. 13 1-3,9 4-5, 8, 11 6-7, 10, 12 4-5, 8, 11 A WO 2022 / 210695 Al (SUMITOMO ELECTRIC INDUSTRIES, LTD.) 06 October 2022 (2022-10-06) entire text, all drawings 1-12 A WO 2022 / 210696 Al (SUMITOMO ELECTRIC INDUSTRIES, LTD.) 06 October 2022 (2022-10-06) entire text, all drawings 1-12 | | Further documents are listed in the continuation of Box C. | Z | See patent family annex. * Special categories of cited documents: “T” later document published after the international filing date or priority “A” document defining the general state of the art which is not considered date and not in conflict with the application but cited to understand the to be of particular relevance principle or theory underlying the invention “D” document cited by the applicant in die international application “X” document of particular relevance; the claimed invention cannot be “E" earlier application orpatent but published on or after the international considered novel or cannot be considered to involve an inventive step filing date when the document is taken alone •SL” document which may throw doubts on priority claim(s) or which is “Y” document of particular relevance; the claimed invention cannot be cited to establish the publication date of another citation or other considered to involve an inventive step when the document is special reason (as specified) combined with one or more other such documents, such combination “O” document referring to an oral disclosure, use, exhibition or other being obvious to a person skilled in the art means document member of the same patent family “P” document published prior to the international filing date but later than the priority date claimed 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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