Tilt angle detection mechanism

Abstract

The steering mirror tilt angle detection mechanism using an optical lever is designed to reduce the risk of radiation exposure to workers during maintenance. [Solution] A tilt angle detection mechanism for detecting the tilt angle of a steering mirror that adjusts the direction of travel by reflecting laser light irradiated onto fuel in an arbitrary direction in a laser fusion reactor, comprising: a light emission unit that emits detection light which is low coherence light; an optical fiber that transmits the detection light emitted from the light emission unit and emits it toward a detection surface set on the steering mirror; a light receiving element that receives the detection light reflected from the detection surface and measures its position or intensity; and a tilt angle calculation unit that calculates the tilt angle of the steering mirror or a related value based on the measurement result of the light receiving element.

Description

Technical Field

[0001] The present invention relates to an inclination angle detection mechanism for detecting the inclination angle of a steering mirror.

Background Art

[0002] In recent years, research has been actively conducted towards the practical application of a laser fusion reactor that generates energy by irradiating a fuel pellet composed of deuterium and tritium with high-power laser light to cause implosion and produce a fusion reaction.

[0003] As a laser fusion reactor, a fuel injection mechanism is used to inject fuel pellets at high speed into the reactor body for energy extraction, and high-power pulsed laser light is uniformly irradiated on the fuel pellets that have reached a predetermined position (for example, the central position) in the reactor body from all directions to cause a fusion reaction. There is a fuel injection type. In such a fuel injection type, energy is continuously generated by repeating the injection of fuel pellets and the irradiation of laser light at a rate of several times per second, and it is considered that power generation of several million kilowatts can be performed by guiding this to the outside.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in the fuel projection method described above, the position of the fuel pellets projected onto the reactor body is not always constant. Due to slight changes in friction between the fuel projection mechanism and the fuel pellets, the position shifts slightly (a few millimeters) each time a pellet is projected. Therefore, it is being considered to place a steering mirror equipped with a gimbal mechanism having multiple rotation axes in the optical path of the laser beam, and to drive an actuator each time a fuel pellet is projected to finely adjust the reflection angle, thereby irradiating the center of the shifted fuel pellet with the laser beam.

[0006] Furthermore, the inventors are attempting to utilize optical lever technology in the mechanism for controlling the tilt angle of the steering mirror. Specifically, they are attempting to detect the tilt angle of the steering mirror by irradiating a detection light from a light source onto a detection surface set on the back of the steering mirror, and sensing the reflected light with a photodetector.

[0007] The problem here is the radiation exposure of workers during maintenance. Specifically, in a laser fusion reactor that handles tritium, the environment in which steering mirrors are installed is designated as a controlled area where the radiation level exceeds a certain amount. When optical levers are used in the control mechanism, workers need to periodically enter the controlled area to maintain the light source that emits detection light and the photodetector. In particular, since the light source generally has a lifespan of about 1 to 10 years, periodic replacement work is essential. As mentioned above, in a laser fusion reactor that irradiates the fuel with pulsed laser light from all directions, the number of laser irradiation mechanisms can be, for example, 10 to 200, and if steering mirrors are installed in each laser irradiation mechanism, the radiation dose received by workers for maintenance of the light sources for the optical levers used in each control mechanism will be considerable.

[0008] The present invention has been made in view of these problems, and its main objective is to reduce the risk of radiation exposure to workers during maintenance in a steering mirror tilt angle detection mechanism using an optical lever. [Means for solving the problem]

[0009] In other words, the tilt angle detection mechanism according to the present invention detects the tilt angle of a steering mirror that adjusts the direction of travel by reflecting laser light irradiated onto fuel in an arbitrary direction in a laser fusion reactor, and is characterized by comprising: a light emission unit that emits detection light which is low coherence light; an optical fiber that transmits the detection light emitted from the light emission unit and emits it toward a detection surface set on the steering mirror; a light receiving element that receives the detection light reflected from the detection surface and measures its position or intensity; and a tilt angle calculation unit that calculates the tilt angle of the steering mirror or a related value based on the measurement result of the light receiving element.

[0010] With this configuration, the detection light emitted from the light emitter is transmitted via optical fiber and guided to the detection surface. Therefore, even if the steering mirror is placed in a controlled area with high radiation levels, the light emitter can be installed outside the controlled area. This eliminates the need to enter the controlled area with high radiation levels when maintaining the light emitter, thus reducing the risk of radiation exposure for workers.

[0011] In a configuration where detection light is transmitted using an optical fiber, if a light source that emits highly coherent light, such as a laser diode, is used in the light emission unit, vibrations transmitted to the optical fiber (e.g., vibrations from a vacuum pump or acoustic noise associated with laser light emission) due to light interference are mixed in as beam spot fluctuations (cladding noise) on the surface to be detected, reducing the accuracy of tilt angle detection. Therefore, the present invention uses a light emission unit that emits low-coherence light as detection light, which is less prone to light interference. This makes it possible to reduce beam spot fluctuations on the surface to be detected even when the detection light is transmitted over long distances using an optical fiber, and to detect the tilt angle with high accuracy.

[0012] A specific configuration of the tilt angle detection mechanism is one in which the light emitting section is equipped with an LED (light-emitting diode) or an SLD (superluminescent diode) as a light source. By using LEDs or SLDs as light sources, it is possible to emit detection light with low coherence that is less prone to beam spot fluctuations on the detection surface.

[0013] In the tilt angle detection mechanism, it is preferable that a collimator lens is provided between the optical output end face of the optical fiber and the surface to be detected. In this way, the broadly spreading detection light emitted from the light-emitting end face can be made into nearly parallel light and irradiated onto the surface to be detected, thereby improving the sensing accuracy of the light-receiving element.

[0014] Furthermore, it is preferable that the tilt angle detection mechanism has an optical fiber that emits detection light from one of the optical emission units toward the detection surfaces of multiple steering mirrors. In this configuration, it is not necessary to provide a light-emitting unit for each of the multiple steering mirrors, thus reducing the burden of maintenance and management of the light-emitting units. Furthermore, in this configuration with multiple steering mirrors, the effect of the present invention in reducing the risk of radiation exposure to workers during maintenance and management becomes even more pronounced.

[0015] Furthermore, it is preferable that the tilt angle detection mechanism is configured using polarization-maintaining fibers for the optical fibers. The surface of a steering mirror is sometimes coated with a dielectric multilayer film to give it high reflectivity for specific wavelengths. However, the reflectivity of a dielectric multilayer film depends on the polarization state of the detected light. When using a general optical fiber, the polarization of the transmitted detected light may change due to externally applied tension, potentially reducing the reflectivity on the detected surface. However, by using a polarization-maintaining fiber, the polarization state of the transmitted detected light can be maintained, keeping the reflectivity on the detected surface constant. This stabilizes the reflectivity, allowing the amount of detected light entering the photodetector to remain constant, thus improving sensing accuracy. This effect is particularly pronounced when the detected surface is coated with a dielectric multilayer film.

[0016] Furthermore, the tilt angle detection mechanism is configured such that the optical fiber is made up of multiple optical fiber cables connected together, and adjacent optical fiber cables are connected by ferrules provided at their respective ends using optical adapters, and it is preferable that the end faces of the ferrules are polished into an oblique spherical shape. When using an SLD as the light source for the light emission section, there is a risk of damage to the SLD's active layer due to excessive light intensity from reflected light. Therefore, by making the end face of the ferrule provided at the end of the optical fiber cable obliquely spherical, reflected light can be radiated outwards at the connection point of the optical fiber cable, thereby reducing the risk of SLD failure.

[0017] One embodiment in which the tilt angle detection mechanism of the present invention is particularly effective is when the light emitting unit is installed in a space with a lower radiation dose than the space in which the light receiving element is installed.

[0018] Furthermore, in an embodiment in which the effect of the tilt angle detection mechanism of the present invention becomes even more pronounced, the tilt angle detection mechanism is configured such that the steering mirror and the light receiving element are installed within a controlled area where the radiation dose is above a certain amount, the light emitting unit is installed outside the controlled area, and the optical fiber is laid across the inside and outside of the controlled area.

[0019] Furthermore, the tilt angle detection mechanism becomes even more pronounced when the steering mirror adjusts its direction of travel by reflecting laser light used to irradiate fuel in a laser fusion reactor. [Effects of the Invention]

[0020] According to the present invention configured in this way, the risk of radiation exposure to workers during maintenance can be reduced in a steering mirror tilt angle detection mechanism using an optical lever. [Brief explanation of the drawing]

[0021] [Figure 1]A diagram schematically showing a laser fusion reactor according to an embodiment of the present invention. [Figure 2] A front-side perspective view schematically showing the configuration of the steering mirror of the embodiment. [Figure 3] A rear-side perspective view schematically showing the configuration of the steering mirror of the embodiment. [Figure 4] A diagram schematically showing the configuration of the control mechanism of the steering mirror of the embodiment. [Figure 5] A diagram schematically showing the configuration of the tilt angle detection mechanism of the steering mirror of the embodiment. [Figure 6] A diagram schematically showing the configuration of the tilt angle detection mechanism of the steering mirror of another embodiment.

Mode for Carrying Out the Invention

[0022] Hereinafter, a steering mirror 100 and a laser fusion reactor 200 including a tilt angle detection mechanism 42 according to an embodiment of the present invention will be described based on the drawings.

[0023] The steering mirror 100 of the present embodiment is used in a laser fusion reactor 200 that generates energy by irradiating a fuel pellet P (for example, a small spherical fuel composed of deuterium and tritium. Note that the constituent elements and shape are not limited to this) with high-power laser light to cause implosion and generate a nuclear fusion reaction. Specifically, as shown in FIG. 1, this laser fusion reactor 200 includes a reactor main body V, a fuel injection mechanism F that injects fuel pellets P into the reactor main body V at high speed (for example, about 100 m / s), and a laser irradiation mechanism L that irradiates the fuel that has reached a predetermined irradiation position R set in the reactor main body V with laser light (laser light for implosion) at the right timing. In this laser fusion reactor 200, fuel pellets P are injected into the reactor main body V by the fuel injection mechanism F at a constant cycle (for example, about 10 Hz), and laser light is sequentially irradiated from the laser irradiation mechanism L to the fuel pellets P that are injected one after another.

[0024] The laser irradiation mechanism L comprises a laser light source L1 that emits laser light and an optical system L2 that guides the laser light emitted from the laser light source L1 to the fuel pellets P projected into the reactor body V. The laser fusion reactor 200 is equipped with multiple (e.g., 100 or more) laser irradiation mechanisms L, and can simultaneously irradiate the fuel pellets P projected into the reactor body V with laser light from multiple directions (all around).

[0025] The laser light source L1 is capable of outputting high-energy pulsed laser light at a high repetition frequency (e.g., about 10 Hz) sufficient to implode the fuel pellet P, and is installed outside the reactor body V.

[0026] The optical system L2 is equipped with multiple mirrors that reflect laser light. This optical system L2 is equipped with a steering mirror 100 (also called a movable mirror) that reflects the laser light in any direction to adjust its direction of travel. The laser irradiation mechanism L drives the steering mirror 100 to adjust the direction of travel of the laser light, so that the laser light can be irradiated onto the fuel pellet P, which is slightly (a few millimeters) off the center of the irradiation position R each time it is projected onto the reactor body V.

[0027] The following provides a detailed explanation of the steering mirror 100.

[0028] As shown in Figures 2 and 3, the steering mirror 100 comprises a mirror body 1 that reflects high-energy laser light (implosion laser light), a support part 2 that supports the mirror body 1, a gimbal mechanism 3 interposed between the mirror body 1 and the support part 2 to tilt the mirror body 1 at an arbitrary angle relative to the support part 2, and a control mechanism 4 that drives the gimbal mechanism 3 to control the tilt angle of the mirror body 1.

[0029] The mirror body 1 has a disc shape with a circular reflective surface 1s. This reflective surface 1s is coated with a dielectric multilayer film coating, such as titanium oxide, barium oxide, or zirconium oxide, to provide high laser damage resistance to high-energy implosion laser light. The surface shape of the reflective surface 1s of the mirror may be planar or concave. Furthermore, the back surface of the mirror body 1, which is the back surface of the reflective surface 1s, may also be coated with a dielectric multilayer film coating, for example, to improve reflectivity.

[0030] The support portion 2 of this embodiment comprises a plate-shaped base 21 and a pair of support plates 22 that are mounted upright on the surface of the base 21 (also called the base surface 21s). The pair of support plates 22 are positioned so that their face plates face each other. The mirror body 1 is installed so that its outer circumferential surface is sandwiched between the face plates of the pair of support plates 22, and the mirror body 1 is supported by this pair of support plates 22 so that its reflective surface 1s stands approximately perpendicular to the base surface 21s.

[0031] The gimbal mechanism 3 has multiple rotation axes extending in directions that intersect each other. Specifically, this gimbal mechanism 3 includes a first rotation axis 3a, which is a pitch axis that rotates the reflective surface 1s of the mirror body 1 in the vertical direction within a predetermined range, and a second rotation axis 3b, which is a yaw axis that rotates the reflective surface 1s of the mirror body 1 in the horizontal direction within a predetermined range. Here, the first rotation axis 3a is parallel to the base surface 21s, and the second rotation axis 3b is set to be perpendicular to the first rotation axis 3a. In the following, the optical axis direction of the mirror body 1 at the reference position (initial position) where the rotation angle of each rotation axis of the gimbal mechanism 3 is 0° (i.e., the direction perpendicular to the reflective surface 1s and perpendicular to the first rotation axis 3a and the second rotation axis 3b) will be defined as the reference axis direction.

[0032] More specifically, the gimbal mechanism 3 comprises a first rotating frame 31 connected to the support plate 22 of the support section 2 and rotatable about a first rotation axis 3a, and a second rotating frame 32 that supports the mirror body 1 and is connected to the first rotating frame 31 and rotatable about a second rotation axis 3b. The first rotating frame 31 is an annular plate shape, and its outer circumferential surface is connected to the pair of support plates 22 via the first rotation axis 3a. The second rotating frame 32 is also an annular plate shape, and its outer diameter is smaller than the inner diameter of the first rotating frame 31. This second rotating frame 32 is mounted inside the first rotating frame 31. Specifically, the outer circumferential surface of the second rotating frame 32 is connected to the inner circumferential surface of the first rotating frame 31 via the second rotation axis 3b. The mirror body 1 is then fitted inside the second rotating frame 32.

[0033] In the steering mirror 100 of this embodiment, at least one (specifically both) of the first rotation axis 3a and the second rotation axis 3b is made up of an elastically deformable shaft with both ends fixed, and the mirror body 1 rotates around the rotation axis as this shaft twists, but it is not limited to this configuration. For example, at least one or both of the first rotation axis 3a and the second rotation axis 3b may be configured as a highly flexible rotation mechanism using bearings or the like, with neither end of the shaft fixed.

[0034] Next, the control mechanism 4, which drives the gimbal mechanism 3 to control the tilt angle of the mirror body 1, will be described. The tilt angle of the mirror body 1 referred to here is the tilt angle of the optical axis of the reflective surface 1s of the mirror body 1 with respect to the reference axis direction.

[0035] As shown in Figure 4, the control mechanism 4 includes an actuator 41 that drives the gimbal mechanism 3, a tilt angle detection mechanism 42 that detects the tilt angle of the mirror body 1, a fuel position detection sensor 43 that detects the passage position and passage time of fuel pellets P projected into the furnace body V, and a control unit 44 that controls the actuator 41.

[0036] This actuator 41 is configured to expand and contract in the direction of the reference axis in accordance with the voltage output from the control unit 44, and uses, for example, a voice coil motor. The control mechanism 4 of this embodiment includes, as actuators 41, a pair of first actuators 41a for driving the gimbal mechanism 3 around the first rotation axis 3a, and a pair of second actuators 41b for driving the gimbal mechanism 3 around the second rotation axis 3b.

[0037] The first actuator 41a and the second actuator 41b are installed in contact with the back surface of the first rotating frame 31 and the second rotating frame 32, respectively, so that their extension and retraction directions coincide with the reference axis direction. The first actuator 41a is installed in a pair, vertically arranged on the back side of the first rotating frame 31, when viewed from the reference axis direction. The second actuator 41b is installed in a pair, horizontally arranged on the back side of the second rotating frame 32, when viewed from the reference axis direction.

[0038] The tilt angle detection mechanism 42 utilizes the principle of optical levers and detects the tilt angle of the mirror body 1 by irradiating detection light onto the detection surface 1d (the back surface in this embodiment) set on the mirror body 1 and sensing the reflected light.

[0039] Specifically, the tilt angle detection mechanism 42 includes a light emission unit 42a that emits detection light to irradiate the detection surface 1d of the mirror body 1, a light receiving element 42b (e.g., a PSD [Position Sensitive Detector] or a QPD [Quadrant Photo Detector]) that receives the detection light reflected from the detection surface 1d and measures the position of the light spot and the intensity of the detection light, and a tilt angle calculation unit 42c that calculates the tilt angle of the mirror body 1 or a related value (e.g., the amount of displacement of the tilt angle) based on a predetermined algorithm using the measurement results of the light receiving element 42b. Specifically, the tilt angle calculation unit 42c receives an electrical signal from the light receiving element 42b that changes depending on the intensity of the detection light and the position of the light spot, calculates the tilt angle of the mirror body 1 or a related value based on the change in the electrical signal, and outputs an angle information signal indicating this calculated value to the control unit 44.

[0040] The fuel position detection sensor 43 detects the time it takes for fuel pellets P projected into the reactor body V by the fuel projection mechanism F to pass through the irradiation position R, and the amount of displacement (passage position) of the fuel pellets P from the center of the irradiation position R. This fuel position detection sensor 43 may be configured using, for example, a plurality of reflective or transmissive photointerrupters (not shown) arranged in the projection direction of the fuel pellets P. The fuel position detection sensor 43 generates a signal (fuel position information signal) indicating the detected passage position and passage time of the fuel pellets P, and outputs this to the control unit 44.

[0041] The control unit 44 outputs control signals to the first actuator 41a and the second actuator 41b based on the angle information signal output from the tilt angle detection mechanism 42 and the fuel position information signal output from the fuel position detection sensor 43. Specifically, the control unit 44 calculates the target tilt angle of the mirror body 1 (target tilt angle) based on a predetermined algorithm, using the position of the fuel pellet P indicated by the fuel position information signal. The control unit 44 then compares the calculated target tilt angle with the current tilt angle of the mirror body 1 (measured tilt angle) indicated by the angle information signal, and based on the difference in angles, generates control signals to control the displacement of the first actuator 41a and the second actuator 41b using a predetermined control algorithm, and outputs them to each actuator 41. Specifically, the control unit 44 generates control signals to match the measured tilt angle to the target tilt angle. The control unit 44 generates control signals each time a fuel pellet P is projected from the fuel projection mechanism F and outputs them to each actuator 41.

[0042] Furthermore, in the control mechanism 4 of this embodiment, the tilt angle detection mechanism 42 has the following features. Specifically, the tilt angle detection mechanism 42 of this embodiment is configured such that the light emission unit 42a emits detection light which is low coherence light, and as shown in Figure 5, it further includes an optical fiber 42d that transmits the detection light emitted from the light emission unit 42a and emits it toward the reflective surface of the mirror body 1.

[0043] Specifically, the light-emitting section 42a is equipped with an LED (light-emitting diode) or an SLD (superluminescent diode) as a light source.

[0044] The optical fiber 42d is laid such that one end face (light incident end face S1) faces the light-emitting surface of the light-emitting section 42a, and the other end face (light-emitting end face S2) faces the detection surface 1d of the mirror body 1.

[0045] The optical fiber 42d in this embodiment is constructed by connecting multiple optical fiber cables in the axial direction. Each optical fiber cable is constructed using polarization-maintaining fibers to maintain the polarization state of the detected light within its optical waveguide (transmission path). Adjacent optical fiber cables are connected by so-called FC connectors, in which ferrules provided at their opposite ends are fixed and connected using an optical adapter in a screw-tightening manner. In this embodiment, the ferrules provided at the ends of each optical fiber cable are formed by polishing their end faces into an oblique spherical shape (so-called APC polishing process).

[0046] As shown in Figure 5, in the laser fusion reactor 200 of this embodiment, a controlled area where the radiation dose is above a certain level and there is a risk of radiation exposure is set up within the housing building. The steering mirror 100 and the photodetector 42b are installed within the controlled area, while the light emission unit 42a is installed outside the controlled area (also called the general area). The optical fiber 42d is laid across the inside and outside of the radiation controlled area, that is, its light incidence end face S1 is located within the general area and its light emission end face S2 is located within the controlled area.

[0047] Here, a controlled area is defined, for example, by the "Regulations for the Prevention of Ionizing Radiation Hazards (Article 3)," and is an area where the sum of the effective dose from external radiation and the effective dose from radioactive materials in the air may exceed 1.3 mSv over a three-month period, but is not limited to this. This controlled area and the general area are spatially separated from each other by, for example, concrete walls.

[0048] Furthermore, a collimator lens 42e is provided between the optical output end face S2 of the optical fiber 42d and the detection surface 1d to focus the detection light emitted from the optical output end face S2 into approximately parallel light.

[0049] Furthermore, in this embodiment, the optical fiber 42d is equipped with an optical splitter that branches the transmitted light, and is configured to branch the detection light emitted from one optical emission unit 42a and emit it toward the detection surfaces 1d of multiple (for example, 10 or more) mirror bodies 1. In other words, in this embodiment, the optical emission unit 42a is common to multiple tilt angle detection mechanisms 42, and the detection light emitted from one optical emission unit 42a is reflected by the detection surfaces 1d of multiple mirror bodies 1, and each of these detection lights is sensed by the corresponding light receiving element 42b.

[0050] With the steering mirror 100 and laser fusion reactor 200 using the tilt angle detection mechanism 42 of this embodiment configured in this way, the detection light emitted from the light emitter is transmitted via an optical fiber and guided to the detection surface 1d. Therefore, even if the steering mirror is placed in a controlled area with high radiation levels, the light emitter can be installed outside the controlled area. As a result, there is no need to enter the controlled area with high radiation levels when maintaining the light emitter, thus reducing the risk of radiation exposure to workers. In a configuration where detection light is transmitted using an optical fiber, if a light source that emits highly coherent light, such as a laser diode, is used in the light emission unit, vibrations transmitted to the optical fiber (e.g., vibrations from a vacuum pump or acoustic noise associated with laser light emission) due to light interference are mixed in as beam spot fluctuations (cladding noise) on the detection surface 1d, reducing the accuracy of tilt angle detection. Therefore, the present invention uses a light emission unit that emits low-coherence light as detection light, which is less prone to light interference. This makes it possible to reduce beam spot fluctuations on the detection surface 1d even when the detection light is transmitted over long distances using an optical fiber, and to detect the tilt angle with high accuracy.

[0051] However, the present invention is not limited to the embodiments described above. For example, the steering mirror 100 of the above embodiment was used to reflect implosion laser light in a laser fusion reactor 200, but is not limited to this. The steering mirror 100 of other embodiments may be used for other purposes, for example, in a fast-ignition type laser fusion reactor 200 to reflect laser light for heating fuel pellets P, or in other types of laser fusion reactors. The steering mirror 100 of the present invention only needs to reflect laser light for irradiating fuel pellets P projected into the reactor body V in a laser fusion reactor.

[0052] Furthermore, while the optical fiber in the above embodiment was laid across both the inside and outside of the controlled area, it is not limited to this. In other embodiments, the light emitting unit is installed in a space within the controlled area where the radiation dose is lower than the space where the steering mirror 100 and the photodetector are installed, and the entire optical fiber may be laid within the controlled area.

[0053] In another embodiment, as shown in Figure 6, the optical fiber may not be branched, and the detection light emitted from one optical emitter may be guided to the detection surface 1d of one mirror body 1.

[0054] Furthermore, while the optical fibers in the above embodiment are connected by FC connectors and the end faces of each ferrule are APC polished, the embodiment is not limited to this. In other embodiments, the multiple optical fiber cables may be connected by other types of optical connectors, such as SC connectors and ST connectors, and the end faces of each ferrule may be subjected to other polishing processes, such as PC polishing, SPC polishing, and UPC polishing.

[0055] Furthermore, in the above embodiment, the detection light was irradiated onto the back surface 1d of the mirror body 1, which was the surface to be detected, but this is not limited to this. In other embodiments, the surface to be detected 1d irradiated with detection light may not be the back surface of the mirror body 1, but may be any other surface such as the front surface, and may be set at any location as long as the tilt changes due to the driving of the mirror body 1.

[0056] Furthermore, although the optical fiber cable in the above embodiment was constructed using polarization-maintaining fibers, this is not limited to other embodiments.

[0057] Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. [Explanation of symbols]

[0058] 200... Laser fusion reactor P...Meat pellets V...furnace body F...Fuel injection mechanism L... Laser irradiation mechanism L1... Laser light source L2...Optical system 100... Steering mirror 1 ···Mirror body 1s...reflective surface 1d ···Detected surface, back 2...Support part 21 ···Base 21s... Base surface 22...Support plate 3. Gimbal mechanism 3a ···First axis of rotation 3b...Second rotation axis 31 ···First Rotating Frame 32 ···Second Rotating Frame 5 ···Shaft 4. Control mechanism 41... Actuator 41a...First Actuator 41b...Second Actuator 42. Tilt angle detection mechanism 42a...Light output section 42b... Light-receiving element 42c...Inclination angle calculation section 42d... Fiber optic S1...Light incidence end face S2...Light emission end face 42e...Collimator lens 43 ···Fuel position detection sensor 44... Control Unit R...Irradiation position

Claims

1. This system detects the tilt angle of a steering mirror that adjusts the direction of travel by reflecting the laser beam irradiated onto the fuel in a laser fusion reactor in any direction. A light emission unit that emits detection light, which is low-coherence light, An optical fiber that transmits the detection light emitted from the light emission unit and emits it toward the detection surface set on the steering mirror, A light-receiving element that receives the detection light reflected from the surface to be detected and measures its position or intensity, An inclination angle detection mechanism comprising an inclination angle calculation unit that calculates the inclination angle of the steering mirror or a related value based on the measurement result of the light receiving element.

2. The tilt angle detection mechanism according to claim 1, wherein the light emitting unit comprises an LED or an SLD as a light source.

3. The tilt angle detection mechanism according to claim 1, wherein a collimator lens is provided between the optical output end face of the optical fiber and the surface to be detected.

4. The tilt angle detection mechanism according to claim 1, wherein the optical fiber emits detection light emitted from one of the optical emission units toward the detection surfaces of a plurality of steering mirrors.

5. The tilt angle detection mechanism according to claim 1, wherein the optical fiber is configured using a polarization-maintaining fiber.

6. The optical fiber is constructed by connecting multiple optical fiber cables. The adjacent optical fiber cables are connected by ferrules provided at each end using optical adapters. The tilt angle detection mechanism according to claim 1, wherein the end face of the ferrule is polished into an oblique spherical shape.

7. The tilt angle detection mechanism according to claim 1, wherein the light emitting unit is installed in a space with a lower radiation dose than the space in which the light receiving element is installed.

8. The steering mirror and the light-receiving element are installed in a controlled area where the radiation level is above a certain amount. The light emission unit is installed outside the controlled area, The tilt angle detection mechanism according to claim 7, wherein the optical fiber is laid across the inside and outside of the controlled area.

9. The tilt angle detection mechanism according to claim 1, wherein the steering mirror adjusts its direction of travel by reflecting laser light used to irradiate fuel in a laser fusion reactor.

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