Mitigation of attenuation effects due to ionizing radiation in silica optical fibers by photobleaching.

Abstract

Systems and methods are provided for optically annealing an optical fiber disposed in a cryogenic environment subjected to ionizing radiation, such as a fusion energy source. The technique includes optically annealing the optical fiber with a first light having a first peak wavelength and a second light having a second peak wavelength different from the first peak wavelength. The first and second peak wavelengths can be selected to optically anneal defects associated with temporary radiation induced attenuation (RIA) and permanent RIA.

Description

Related Applications

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 282,503, entitled "Mitigating the Attenuation Effects of Ionizing Radiation in Silica Optical Fiber by Photobleaching," filed November 23, 2021, which is incorporated by reference in its entirety. [Background technology]

[0002] An optical fiber is a flexible, transparent fiber used as a means of transmitting light between two ends of the fiber. Optical fibers typically contain a core surrounded by a cladding material that has a lower refractive index than the core. Due to the phenomenon of total internal reflection, light remains in the core of the optical fiber and is transmitted along the length of the optical fiber. Optical fibers are commonly used in applications such as fiber optic communications, lighting and imaging, and fiber optic sensing. Summary of the Invention

[0003] Some embodiments relate to a system arranged to perform optical annealing of an optical fiber disposed in an environment receiving ionizing radiation, the system including a first light source configured to illuminate and optically anneal the optical fiber by generating a first light having a first peak wavelength, a second light source configured to illuminate and optically anneal the optical fiber by generating a second light having a second peak wavelength, and an optical multiplexer coupled between the first light source and the optical fiber and between the second light source and the optical fiber.

[0004] In some embodiments, the first light source is configured to generate the first light having a first peak wavelength in the range of 770 nm to 1170 nm, hi some embodiments, the first light source is configured to generate the first light having a first peak wavelength of about 970 nm.

[0005] In some embodiments, the second light source is configured to generate the second light having a second peak wavelength in the range of 1350 nm to 1750 nm, in some embodiments, the second light source is configured to generate the second light having a second peak wavelength of about 1550 nm.

[0006] In some embodiments, the first light source is configured to generate the first light having an optical power in the range of 5 mW to 500 mW.

[0007] In some embodiments, the optical multiplexer is configured to perform wavelength division multiplexing (WDM) of the first light and the second light.

[0008] In some embodiments, the optical multiplexer is configured to perform time division multiplexing (TDM) of the first light and the second light.

[0009] In some embodiments, the optical multiplexer is configured to simultaneously illuminate the optical fiber with the first light and the second light.

[0010] In some embodiments, the optical multiplexer is configured to alternately illuminate the optical fiber with the first light and the second light.

[0011] In some embodiments, the system is arranged to irradiate the optical fiber with the first light source and / or the second light source while the optical fiber is exposed to the ionizing radiation.

[0012] In some embodiments, the optical fiber is disposed in a cryogenic environment while illuminated by the first light source and / or the second light source, hi some embodiments, the optical fiber is at a temperature between 0 K and 120 K while illuminated by the first light source and / or the second light source.

[0013] In some embodiments, the optical fiber extends along the length of a high temperature superconducting (HTS) cable, the HTS cable including at least one HTS tape stack.

[0014] In some embodiments, the system is used in a fusion energy system.

[0015] In some embodiments, the ionizing radiation is artificial ionizing radiation. In some embodiments, the dose rate of the environmental ionizing radiation is greater than the dose rate of the background ionizing radiation. In some embodiments, the dose rate of the ionizing radiation is greater than 0.2 nGy / s.

[0016] Some embodiments relate to a method for optically annealing an optical fiber disposed in an environment experiencing ionizing radiation, the method including optically annealing the optical fiber with a first light having a first peak wavelength and optically annealing the optical fiber with a second light having a second peak wavelength.

[0017] In some embodiments, optically annealing the optical fiber with the first light and the second light comprises optically annealing the optical fiber with the first light and the second light simultaneously.

[0018] In some embodiments, optically annealing the optical fiber with the first light and the second light comprises alternatingly annealing the optical fiber with the first light and the second light.

[0019] In some embodiments, optically annealing the optical fiber with the first light and the second light includes multiplexing the first light and the second light into the optical fiber.

[0020] In some embodiments, multiplexing the first light and the second light into the optical fiber includes using wavelength division multiplexing (WDM).

[0021] In some embodiments, multiplexing the first light and the second light onto the optical fiber includes using time division multiplexing (TDM).

[0022] In some embodiments, optically annealing the optical fiber with the first and / or second light comprises optically annealing the optical fiber with the first and / or second light while the optical fiber is exposed to ionizing radiation.

[0023] In some embodiments, optically annealing the optical fiber with the first light comprises irradiating the optical fiber with a first light having a peak wavelength in the range of 770 nm to 1170 nm. In some embodiments, optically annealing the optical fiber with the first light comprises optically annealing the optical fiber with a first light having a peak wavelength of about 970 nm.

[0024] In some embodiments, optically annealing the optical fiber with the second light comprises optically annealing the optical fiber with a second light having a peak wavelength in the range of 1350 nm to 1750 nm. In some embodiments, optically annealing the optical fiber with the second light comprises optically annealing the optical fiber with a second light having a peak wavelength of about 1550 nm.

[0025] In some embodiments, optically annealing the optical fiber with the first light and / or the second light includes optically annealing the optical fiber with the first light and / or the second light while the optical fiber is disposed in the cryogenic environment.

[0026] In some embodiments, optically annealing the optical fiber with the first light and / or the second light comprises optically annealing the optical fiber with the first light and / or the second light while the optical fiber is at a temperature between 0 K and 120 K.

[0027] In some embodiments, optically annealing the optical fiber with the first light and / or the second light includes optically annealing the optical fiber with the first light and / or the second light while the optical fiber is disposed along a length of a high temperature superconducting (HTS) cable, the HTS cable including at least one HTS tape stack.

[0028] In some embodiments, optically annealing the optical fiber with the first light and / or the second light comprises optically annealing the optical fiber with the first light and / or the second light while the optical fiber is in use in a fusion energy system.

[0029] Some embodiments relate to a system arranged to optically anneal an optical fiber, the system including a first light source configured to optically anneal the optical fiber by generating a first light having a first peak wavelength, a second light source configured to optically anneal the optical fiber by generating a second light having a second peak wavelength, and an optical multiplexer coupled between the first light source and the optical fiber and between the second light source and the optical fiber, the optical fiber being disposed in a fusion energy source, the optical fiber being subjected to ionizing radiation generated by the fusion energy source while the first light source and / or the second light source optically anneal the optical fiber, and the optical fiber being at a cryogenic temperature.

[0030] In some embodiments, the first light source is configured to generate the first light having a first peak wavelength in the range of 770 nm to 1170 nm, in some embodiments, the first light source is configured to generate the first light having a first peak wavelength of about 970 nm.

[0031] In some embodiments, the second light source is configured to generate the second light having a second peak wavelength in the range of 1350 nm to 1750 nm, in some embodiments, the second light source is configured to generate the second light having a second peak wavelength of about 1550 nm.

[0032] In some embodiments, the first light source is configured to generate the first light having an optical power in the range of 5 mW to 500 mW.

[0033] In some embodiments, the optical multiplexer is configured to perform wavelength division multiplexing (WDM) of the first light and the second light.

[0034] In some embodiments, the optical multiplexer is configured to perform time division multiplexing (TDM) of the first light and the second light.

[0035] In some embodiments, the optical multiplexer is configured to simultaneously illuminate the optical fiber with the first light and the second light.

[0036] In some embodiments, the optical multiplexer is configured to alternately illuminate the optical fiber with the first light and the second light.

[0037] In some embodiments, the optical fiber is at a temperature between 0K and 120K while illuminated by the first light source and / or the second light source.

[0038] In some embodiments, the optical fiber extends along the length of a high temperature superconductor (HTS) cable, the HTS cable including at least one HTS tape stack. [Brief description of the drawings]

[0039] Various aspects and embodiments are described with reference to the following figures. It should be understood that the figures are not necessarily drawn to scale. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For clarity, not every component is labeled in every figure.

[0040] [Figure 1] 1 is a schematic diagram of a system for optically annealing an optical fiber, according to certain embodiments described herein. [Figure 2A] 1 is a plot showing the optical annealing effect of two peak wavelengths of light on a first optical fiber according to certain embodiments described herein. [Figure 2B] 11 is a plot showing the optical annealing effect of two peak wavelengths of light on a second optical fiber according to certain embodiments described herein. [Diagram 3] 1 is a plot illustrating the optical annealing effect of light applied to an optical fiber at different values ​​of optical power, in accordance with certain embodiments described herein. [Figure 4] 1 is a flowchart of a process for optically annealing an optical fiber disposed in an environment subjected to ionizing radiation, according to certain embodiments described herein. [Diagram 5] FIG. 1 is a schematic diagram of a system for detecting a quench event in a superconducting material and a system for optically annealing an optical fiber used to detect the quench event, according to some embodiments described herein. [Figure 6A] FIG. 1 is a diagram of a high temperature superconductor (HTS) cable according to some embodiments described herein. [Figure 6B] FIG. 1 is a diagram of a high temperature superconductor (HTS) cable according to some embodiments described herein. [Figure 7] FIG. 1 is a perspective view of an HTS tape stack according to certain embodiments described herein. [Figure 8A]FIG. 1 is a cross-sectional view of an HTS cable including an optical fiber for quench detection according to some embodiments described herein. [Figure 8B] FIG. 8B is a close-up view of the optical fiber of FIG. 8A according to certain embodiments described herein. [Figure 8C] FIG. 2 is a cross-sectional view of another HTS cable including an optical fiber for quench detection according to certain embodiments described herein. [Figure 8D] FIG. 8D is a close-up view of the optical fiber of FIG. 8C according to certain embodiments described herein. [Figure 9] FIG. 1 is a schematic diagram of an exemplary computing device in accordance with certain embodiments described herein. [Figure 10] FIG. 1 illustrates a cross-sectional view of an example tokamak in accordance with certain embodiments described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Fusion energy is a possible solution to the global need for clean energy. It is safe, energy dense, and does not emit greenhouse gases. In a fusion reaction, light atomic nuclei (e.g. hydrogen) combine to form heavier atomic nuclei (e.g. helium) to produce energy. Magnetic confinement is an approach to fusion power that uses a magnetic field to confine plasma and create the conditions for the plasma to undergo nuclear fusion. To produce a fusion reaction, a very high plasma temperature of 150 million degrees Celsius is required, and the plasma is heated by a magnetic field and an external heating means.

[0042] The nuclear reactor design known as a tokamak is an approach to magnetic confinement that attempts to address the problem of instabilities that arise in plasmas when they heat up or undergo fusion reactions. In a tokamak, the plasma is confined within a toroid, and the plasma instabilities are controlled by arranging the magnetic field so that the plasma particles pass between the inside and outside of the toroid multiple times per orbit. This "twisting" of the magnetic field dramatically increases the stability of the plasma. To control the plasma in a tokamak, magnets are used to create toroidal and poloidal magnetic fields that shape and position the plasma within the toroid and drive the movement of the plasma around the toroid.

[0043] An overview of some aspects of an exemplary tokamak is shown in FIG. 10, which shows a cross-sectional view of a tokamak 1000 according to some embodiments. As shown in FIG. 10, in the tokamak 1000, a core plasma 1010 circulates within a vacuum vessel 1020 that is toroidally shaped. The tokamak 1000 also includes a number of toroidal field (TF) electromagnets 1040, a number of poloidal field (PF) electromagnets 1050, and one or more central solenoid (CS) electromagnets 1060. The TF magnets 1040 are D-shaped (or approximately D-shaped) magnets configured to confine the plasma 1010 to a desired region of the vacuum vessel 1020 and generate a magnetic flux within the plasma. The PF magnets 1050 are approximately ring-shaped magnets configured to shape and position the plasma 1010. The CS magnets 1060 are located at the center of the tokamak and are configured to inductively drive the plasma current.

[0044] During operation of the tokamak 1000, an axisymmetric toroidal plasma 1010 is generated within the vacuum vessel 1020. This plasma carries a toroidal current, which creates a poloidal magnetic field and provides confinement of the plasma. The TF magnets 1040 provide stability to the plasma current, while the PF magnets 1050 and CS magnets 1060 shape and control the position of the plasma. The plasma is heated by the CS magnets 1060, radio frequency (RF) signals, and / or high energy neutral particle beams, initiating nuclear fusion, and the energy from the resulting neutrons is captured in a blanket, a structure containing low atomic number atoms such as lithium that readily collide with neutrons to capture energy.

[0045] The TF magnet 1040, PF magnet 1050, and / or CS magnet 1060 include one or more conductor windings within the illustrated housing. These magnets generally utilize superconducting materials that are cryogenically cooled to generate high magnetic fields. According to some embodiments, these conductors may include high temperature superconductors (HTS) (e.g., rare earth barium copper oxides (ReBCOs)). As used herein, the phrase "HTS material" or "HTS superconductor" refers to a superconducting material that has a critical temperature above 30 K at zero self-magnetic field.

[0046] Superconducting magnets consist of multiple electrically insulated cable turns, often grouped in a multi-layer arrangement. When the superconducting material is cold enough to be below its critical temperature (the temperature at which the material's electrical resistivity drops to near zero), driving the magnet allows electrical current to pass through the superconducting path without loss. However, for various reasons, some or all of the superconducting material may heat up above its critical temperature and lose its superconducting properties. If such heating is not controlled, the superconductor will lose its superconducting ability, often referred to as a "quench." Furthermore, if a quench is not properly addressed by the system (e.g., by shutting down), components may be damaged by the heating. Thus, to mitigate the effects of a quench, there is a need to monitor the temperature of the superconducting material during operation to detect a quench.

[0047] Some superconducting magnet systems handle quench events through a system of active alarms and detection mechanisms, such as detecting voltages at different points in the superconductor. However, the sensing wires for such electrically-based quench detection techniques are highly susceptible to electromagnetic interference generated by the varying magnetic fields present during Tokamak reactor operation. Alternatively, optical sensing techniques (e.g., using optical fibers) can be used to perform quench detection in a fusion reactor environment, as optical signals are not susceptible to such interference.

[0048] The present inventors recognize and understand that optical fibers exposed to ionizing radiation, such as that present in a tokamak, can exhibit significant radiation-induced attenuation (RIA). RIA is caused by material defects introduced into the atomic structure of the optical fiber. These defects cause scattering of the transmitted light, resulting in attenuation of the transmitted optical signal and a less sensitive optical sensing system. At temperatures above cryogenic temperatures (e.g., room temperature, above room temperature), at least a portion of these induced defects can "self-heal" using environmental thermal energy.

[0049] However, in cryogenic environments (e.g., environments with temperatures ranging from 0 K to 120 K), optical fibers may increase their RIA over time and become less functional because there is not enough environmental thermal energy for the optical fiber to self-repair these induced defects. In cryogenic environments, optical energy can augment or substitute for thermal energy to heal the defects induced by ionizing radiation in the optical fiber. Thus, optical annealing can be utilized to reduce the RIA of optical fibers, allowing the optical fiber to be used as a sensor or signal transmission line in cryogenic environments subjected to ionizing radiation.

[0050] RIAs are caused by two different types of RIAs: permanent RIAs and transient RIAs. Permanent RIAs include defects with larger trapping energies that persist even with thermal annealing at room temperature. Transient RIAs, on the other hand, include defects with lower trapping energies that do not persist with thermal annealing at room temperature. The impact of permanent RIAs is approximately proportional to the total dose of ionizing radiation, whereas the impact of transient RIAs is approximately proportional to the dose rate. The inventors recognize and understand that the unique operating conditions of tokamak increase the prevalence and impact of transient RIAs, in addition to the impact of permanent RIAs. During tokamak operation, optical fibers for quench detection of tokamak magnets may experience dose rates of about 0.1 to 20 Gy / s for a short period of operation (e.g., in some embodiments, about 10 seconds). During this period of operation, optical fibers are used to monitor the temperature of the tokamak magnets for quench detection. However, the optical fiber is also held at such cryogenic temperatures that the material defects that cause the transient RIA cannot be thermally annealed, thereby affecting the function of the optical fiber-based quench detection system.

[0051] Thus, for optical sensing in a cryogenic environment exposed to high dose rates of ionizing radiation, mitigating the effects of both temporary and permanent RIAs is important to maintain the functionality of the optical sensing system. The inventors have recognized and appreciated that optical annealing of an optical fiber using light with at least two peak wavelengths can provide optical annealing that counteracts the effects of both temporary and permanent RIAs. Accordingly, the inventors have developed a system for optical annealing of an optical fiber disposed in a cryogenic environment subjected to ionizing radiation. In some embodiments, the system includes a first light source, a second light source, and an optical multiplexer. The first light source is configured to illuminate and optically anneal the optical fiber by generating light having a first peak wavelength, and the second light source is configured to illuminate and optically anneal the optical fiber by generating light having a second peak wavelength different from the first peak wavelength. In some embodiments, the system is configured to irradiate the optical fiber with the first light source and / or the second light source while the optical fiber is exposed to ionizing radiation. In some embodiments, the optical fiber is placed in a cryogenic environment (eg, having a temperature in the range of 0 K to 120 K) while being illuminated by the first light source and / or the second light source.

[0052] In some embodiments, an optical multiplexer is coupled between the first light source and the optical fiber and between the second light source and the optical fiber. The optical multiplexer may be configured to perform, for example, wavelength division multiplexing (WDM) and / or time division multiplexing (TDM) of the first light and the second light. As an example, the optical multiplexer may be configured to simultaneously irradiate the optical fiber with the first light and the second light. As another example, the optical multiplexer may be configured to alternately irradiate the optical fiber with the first light and the second light (e.g., irradiate the optical fiber with the first light and then with the second light, or vice versa).

[0053] In some embodiments, the first light source and the second light source are configured to generate light having different distinct peak wavelengths. The first light source may be configured to generate a first light having a first peak wavelength, for example, in the range of 770 nm to 1170 nm, in the range of 700 nm to 1170 nm, in the range of 600 nm to 1100 nm, in the range of 500 nm to 1100 nm, or in the range of 850 nm to 1050 nm. Any suitable combination of the above ranges is also possible (e.g., a first peak wavelength in the range of 600 nm to 1170 nm). For example, the first light source may be configured to generate a first light having a first peak wavelength of about 970 nm. As a further example, the first light source may be configured to generate a first light having a first peak wavelength of about 650 nm, 800 nm, or 1060 nm.

[0054] In some embodiments, the second light source may be configured to generate a second light having a second peak wavelength in the range of 1350 nm to 1750 nm, in the range of 1400 nm to 1700 nm, in the range of 1450 nm to 1650 nm, or in any suitable range within these ranges. For example, the second light source may be configured to generate a second light having a second peak wavelength of about 1550 nm. As another example, the second light source may be configured to generate a second light having a second peak wavelength of 1600 nm.

[0055] In some embodiments, the first light source and / or the second light source are configured to generate light having an optical power in the range of 5 mW to 1 W, in the range of 5 mW to 500 mW, in the range of 10 mW to 600 mW, in the range of 15 mW to 500 mW, or any suitable range therebetween. For example, the first light source and / or the second light source may be configured to generate light having an optical power of about 10 mW, 20 mW, 50 mW, 100 mW, 200 mW, 250 mW, and / or 500 mW.

[0056] In some embodiments, the optical fiber is disposed within a fusion energy source. For example, the optical fiber may be disposed to operate as a temperature sensor and / or strain sensor configured to detect a quench event in a high temperature superconductor (HTS) of the fusion energy source. The HTS may be, for example, an HTS cable including at least one HTS tape stack. The optical fiber may also be disposed in a cryogenic environment at a temperature below the critical temperature of the HTS.

[0057] In some embodiments, the optical fiber may be placed in an environment that is subject to ionizing radiation. For example, the ionizing radiation may be generated by an artificial or man-made source (e.g., a fusion energy source). The ionizing radiation incident on the optical fiber may have a dose rate that is greater than the dose rate of background ionizing radiation (e.g., ionizing radiation from cosmic rays and other background ionizing radiation sources). For example, the ionizing radiation incident on the optical fiber may have a dose rate that is greater than the average background dose rate (e.g., about 0.2 nGy / s in the United States). As another example, the ionizing radiation incident on the optical fiber may have a dose rate in the range of about 5 Gy / s to 30 Gy / s.

[0058] The following is a more detailed description of various concepts related to the technology for quench detection and its embodiments. It should be understood that the various aspects described herein can be implemented in any of a number of ways. Specific examples are provided herein for illustrative purposes only. In addition, the various aspects described in the following embodiments can be used alone or in any combination, and are not limited to the combinations expressly described herein.

[0059] 1 is a schematic diagram of a system 100 for optically annealing an optical fiber according to some embodiments described herein. The system 100 includes an optical system 110 optically coupled to an optical fiber 120 and a controller 130 communicatively coupled to the optical system 110. The optical system 110 includes a first light source 112, a second light source 114, and an optical multiplexer 116. Although only two light sources are depicted in the example of FIG. 1, it should be understood that in some embodiments, the system 100 may include a different number of light sources, such as three or more light sources, as aspects of the technology described herein are not limited in this respect.

[0060] In some embodiments, the system 100 is arranged to illuminate the optical fiber 120 with the first light source 112 and / or the second light source 114 while the optical fiber 120 is exposed to the ionizing radiation. The optical fiber 120 may be exposed to the ionizing radiation having a dose rate greater than the dose rate of background ionizing radiation (e.g., from cosmic rays and / or other natural ionizing radiation sources). For example, the dose rate of the ionizing radiation may be greater than 0.2 nGy / s. In some embodiments, the ionizing radiation may be man-made or artificial ionizing radiation. For example, the system 100 may be implemented in a nuclear fusion energy system.

[0061] In some embodiments, the optical fiber 120 may be disposed in a cryogenic environment while being illuminated by the first light source 112 and / or the second light source 114. For example, the optical fiber 120 may be in an environment that is at a temperature ranging between 0 K and 120 K while being illuminated by the first light source 112 and / or the second light source 114.

[0062] In some embodiments, the optical fiber 120 may be an optical fiber suitable for supporting wavelengths of light for telecommunications. For example, the optical fiber 120 may be a pure silica core fiber (e.g., a radiation hardened optical fiber). As another example, the optical fiber 120 may be a standard germanium doped optical fiber. In some embodiments, the optical fiber 120 may be an optical fiber suitable for sensing applications (e.g., temperature and / or strain sensing).

[0063] In some embodiments, the first light source 112 and the second light source 114 are configured to irradiate the optical fiber 120 to perform optical annealing of the optical fiber 120. The first light source 112 may be configured to generate light having a first peak wavelength, and the second light source 114 may be configured to generate light having a second peak wavelength different from the first peak wavelength.

[0064] In some embodiments, the first light source 112 may be configured to generate light having a first peak wavelength in the range of 770 nm to 1170 nm, in the range of 700 nm to 1170 nm, in the range of 600 nm to 1100 nm, in the range of 500 nm to 1100 nm, in the range of 850 nm to 1050 nm. Any suitable combination of the above ranges is also possible (e.g., a first peak wavelength in the range of 600 nm to 1170 nm). For example, the first light source may be configured to generate a first light having a first peak wavelength of about 970 nm. As a further example, the first light source may be configured to generate a first light having a first peak wavelength of about 650 nm, 800 nm, or 1060 nm.

[0065] In some embodiments, the second light source 114 may be configured to generate light having a first peak wavelength in the range of 1350 nm to 1750 nm, in the range of 1400 nm to 1700 nm, in the range of 1450 nm to 1650 nm, or any suitable range within these ranges. For example, the second light source may be configured to generate a second light having a second peak wavelength of about 1550 nm. As another example, the second light source may be configured to generate a second light having a second peak wavelength of 1600 nm.

[0066] In some embodiments, the first light source 112 and the second light source 114 may be configured to generate light having a first peak wavelength and a second peak wavelength, respectively, the first peak wavelength and the second peak wavelength having values ​​that are at least a threshold difference value apart. For example, the difference in peak wavelength value between the first peak wavelength and the second peak wavelength may be at least 500 nm. In some embodiments, the difference in peak wavelength value between the first peak wavelength and the second peak wavelength may be in a range of 250 nm to 750 nm.

[0067] In some embodiments, the first light source 112 and / or the second light source 114 may include one or more laser light sources, superluminescent diode (SLD) light sources, laser diode light sources, light emitting diode (LED) light sources, solid-state laser light sources, quantum well or quantum dot laser light sources, and / or any other suitable light sources. The first light source 112 and the second light source 114 may both be the same type of light source or may be different types of light sources, as aspects of the technology described herein are not limited in this respect.

[0068] In some embodiments, the first light source 112 and / or the second light source 114 may be configured to generate the first light and / or the second light with sufficient optical power to anneal the optical fiber 120. For example, the first light source 112 and / or the second light source 114 may be configured to generate the first light and / or the second light having an optical power in a range of 5 mW to 1 W, in a range of 5 mW to 500 mW, in a range of 10 mW to 600 mW, in a range of 15 mW to 500 mW, or any suitable range within these ranges. For example, the first light source and / or the second light source may be configured to generate light having an optical power of about 10 mW, 20 mW, 50 mW, 100 mW, 200 mW, 250 mW, and / or 500 mW.

[0069] In some embodiments, the optical multiplexer 116 is arranged to multiplex the first light and / or the second light into the optical fiber 120. In some embodiments, the optical multiplexer 116 may be arranged to multiplex the first light and the second light simultaneously into the optical fiber 120 such that the optical fiber 120 is illuminated by both the first light and the second light. For example, the optical multiplexer 116 may be arranged to perform wavelength division multiplexing (WDM). In some embodiments, the optical multiplexer 116 may be arranged to multiplex the first light and the second light into the optical fiber 120 in an alternating order such that the optical fiber 120 is alternately illuminated by the first light and the second light. For example, the optical multiplexer 116 may be arranged to perform time division multiplexing (TDM). In some embodiments, the first light and the second light may be time division multiplexed into the optical fiber 120 at a frequency of 50 Hz or greater.

[0070] In some embodiments, the controller 130 may be used to control one or more components of the optical system 110. For example, the controller 130 may be configured to turn each of the first light source 112 and the second light source 114 on and / or off during operation of the system 100. The controller 130 may alternatively or additionally be configured to control the optical multiplexer 116 to multiplex the first and / or second light into the optical fiber 120.

[0071] In some embodiments, controller 130 may include one or more processors and a non-transitory computer-readable medium (e.g., a computer memory, one or more floppy disks, compact disks, optical disks, magnetic tapes, flash memories, circuitry in field programmable gate arrays or other semiconductor devices, or other non-transitory tangible computer storage media) encoded with one or more programs that, when executed on the one or more processors, perform methods for implementing various embodiments of the present disclosure described above. The computer-readable medium may be located adjacent to optical system 110 (e.g., in the same room or facility) or, in some embodiments, may be located remotely from optical system 110 (e.g., communicatively coupled via a network or cloud).

[0072] The effect of optical annealing with light having two different peak wavelengths on two different optical fibers is shown in Figures 2A and 2B. Figure 2A shows the effect of optical annealing on an IXF-SRAD fiber manufactured by iXblue in accordance with some embodiments of the techniques described herein. Curve 202 shows the measured RIA as a function of radiation dose without optical annealing. Curve 204 shows the measured RIA as a function of radiation dose when the fiber was optically annealed with light having a wavelength of 970 nm and an optical power of 20 mW. Curve 206 shows the measured RIA as a function of radiation dose when the fiber was optically annealed with light having a wavelength of 1550 nm and an optical power of 20 mW. As shown in Figure 2A, both curves 206 and 208 have an order of magnitude reduction in RIA compared to curve 202, with curve 206 showing a very low RIA at a low radiation dose.

[0073] FIG. 2B illustrates the effect of optical annealing on a low bend loss (LBL) fiber manufactured by FBGS, Inc., in accordance with some embodiments described herein. Curve 208 illustrates the measured RIA as a function of radiation dose without optical annealing. Curve 210 illustrates the measured RIA as a function of radiation dose when the fiber is optically annealed with light having a wavelength of 970 nm and an optical power of 20 mW. Curve 212 illustrates the measured RIA as a function of radiation dose when the fiber is optically annealed with light having a wavelength of 1550 nm and an optical power of 20 mW. As shown in FIG. 2B, both curves 210 and 212 have an order of magnitude reduction in RIA compared to curve 208, with curve 212 showing a very low RIA at a low radiation dose.

[0074] 3 is a plot showing the optical annealing effect of light applied to an optical fiber over a four day period at different values ​​of optical power, in accordance with certain embodiments described herein. The upper plot 300a and the lower plot 300b include data from two separate annealing tests performed on the same optical fiber using light having peak wavelengths of approximately 1550 nm and 970 nm, respectively. The applied optical power is shown along the upper axis of each plot 300a, 300b and includes optical powers having values ​​of approximately 0 μW, 24 μW, 143 μW, and 214-218 μW.

[0075] Curves 302a, 302b show the RIA as a function of dose over the course of the experiment. Curves 304a and 304b are extrapolated RIA over time for photoannealing performed at an optical power of about 24 μW, curves 306a and 306b are extrapolated RIA over time for photoannealing performed at an optical power of about 143 μW, and curves 308a and 308b are extrapolated RIA over time for photoannealing performed at an optical power of about 214-218 μW. Using lower optical power for photoannealing results in a larger RIA for both curves 302a and 302b, and a larger extrapolated RIA as shown by curves 304a and 304b compared to curves 306a and 308a, or curves 306b and 308b, respectively.

[0076] 4 is a flow chart of a process 400 for optically annealing an optical fiber disposed in an environment receiving ionizing radiation, according to some embodiments described herein. The process 400 may be controlled using any suitable computing device. For example, in some embodiments, the process 400 may be performed by a computing device that is co-located (e.g., in the same room or facility) with an optical system configured to perform the optical annealing (e.g., optical system 110 as described in connection with FIG. 1 ). As another example, in some embodiments, the process 400 may be performed by one or more processors located remotely from the optical system that performs the optical annealing.

[0077] Process 400 may optionally begin with act 402, where two or more optical signals (e.g., light) having different peak wavelengths are multiplexed onto an optical fiber disposed within an environment that is subject to ionizing radiation. In some embodiments, the multiplexing of the two or more optical signals may be performed using WDM and / or TDM. For example, the first light and the second light may be multiplexed onto the optical fiber using WDM and / or TDM.

[0078] Process 400 may alternatively begin with act 404, or after act 402, process 400 may proceed to act 404 where the fiber is optically annealed with a first light. In some embodiments, optically annealing the optical fiber with the first light may include irradiating the optical fiber with a first light having a peak wavelength in a range of 770 nm to 1170 nm. For example, in some embodiments, optically annealing the optical fiber with the first light may include irradiating the optical fiber with a first light having a peak wavelength of about 970 nm.

[0079] After act 404, process 400 may proceed to act 406 of optically annealing the optical fiber with a second light. In some embodiments, optically annealing the optical fiber with the second light may include irradiating the optical fiber with a second light having a peak wavelength in a range of 1350 nm to 1750 nm. For example, in some embodiments, optically annealing the optical fiber with the second light may include irradiating the optical fiber with a second light having a peak wavelength of about 1550 nm.

[0080] In some embodiments, acts 404 and 406 can be performed simultaneously such that optically annealing the optical fiber with the first light and the second light includes optically annealing the optical fiber with the first light and the second light simultaneously. In some embodiments, the first light and the second light may be wavelength multiplexed onto the optical fiber to optically anneal the optical fiber with the first light and the second light simultaneously.

[0081] In some embodiments, acts 404 and 406 may be performed sequentially such that optically annealing the optical fiber with the first light and the second light includes optically annealing the optical fiber with the first light and the second light in alternating order. In some embodiments, the first light and the second light may be time division multiplexed onto the optical fiber to optically anneal the optical fiber by alternately irradiating it with the first light and the second light.

[0082] In some embodiments, acts 404 and / or 406 may include optically annealing the optical fiber with the first and / or second light while the optical fiber is exposed to ionizing radiation. For example, the ionizing radiation may be generated by an artificial or man-made source (e.g., a nuclear fusion energy source). The ionizing radiation incident on the optical fiber may have a dose rate that is greater than the dose rate of background ionizing radiation (e.g., ionizing radiation from cosmic rays or other background ionizing radiation sources). For example, the ionizing radiation incident on the optical fiber has a dose rate that is greater than 0.2 nGy / s.

[0083] In some embodiments, acts 404 and / or 406 may include optically annealing the optical fiber with the first light and / or the second light while the optical fiber is disposed in a cryogenic environment. For example, the optical fiber may be disposed in an environment with a temperature ranging from 0 K to 120 K.

[0084] In some embodiments, acts 404 and / or 406 may include annealing the optical fiber with the first light and / or the second light while the optical fiber is disposed adjacent to the superconducting material, for example, the optical fiber is disposed along a length of at least one high temperature superconductor (HTS) tape stack.

[0085] FIG. 5 is a schematic diagram of an exemplary system 500 for use of the optical system 110 to detect quench events in a superconductor 530. A superconductor is a material that has near zero electrical resistance to electrical current (is "superconducting") below a critical temperature. Superconductors have applications in nuclear fusion energy, high-efficiency motors, high-efficiency power transmission, magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR), high-field particle accelerators, and more. To maintain a superconducting state, a superconducting material must remain at a temperature below its critical temperature. However, localized energy dissipation (e.g., due to current flow within the superconductor) can cause localized heating that, if not controlled or detected, can cause a thermal runaway event in which the entire superconductor transitions ("quenches") from the superconducting region to a normally resistive region. Quench events can result in downtime of superconducting devices as well as damage to the superconducting device.

[0086] The inventors recognize and appreciate that optical systems are less susceptible to electromagnetic interference and can be used to develop more robust and accurate optical-based quench detection systems. Such optical-based quench detection systems can detect quench events by embedding a fiber optic cable in or adjacent to a superconductor using a fiber optic thermometer that measures the temperature and strain response of the optical fiber. The optical fiber used in such optical-based quench detection systems includes a number of Bragg gratings (e.g., fiber Bragg gratings (FBGs), ultra-long fiber Bragg gratings (ULFBGs)) and is configured to reflect a portion of the light incident on the Bragg gratings. The spectrum of the reflected light can be indicative of the change in temperature and / or strain experienced by the Bragg gratings such that a quench event can be detected by analyzing the spectrum of the reflected light.

[0087] The inventors recognize and understand that optical systems may be used to develop more robust and accurate optical-based quench detection systems. Such optical-based quench detection systems may detect quench events by embedding a fiber optic cable in or adjacent to a superconductor using a fiber optic thermometer that measures the temperature and strain response of the optical fiber. The optical fiber used in such optical-based quench detection systems includes a number of Bragg gratings (e.g., fiber Bragg gratings (FBGs), ultra-long fiber Bragg gratings (ULFBGs)) and is configured to reflect a portion of the light incident on the Bragg gratings. The spectrum of the reflected light is indicative of the changes in temperature and / or strain experienced by the Bragg gratings, and a quench event may be detected by analyzing the spectrum of the reflected light.

[0088] In the illustrative example of FIG. 5, system 500 includes optical system 110 (e.g., optical system 110 described in connection with FIG. 1), superconductor 530, optical fiber 520, photodetector 540, circuitry 550, optionally network 560, and computing system 570. It should be understood that system 500 is illustrative and that the quench detection system can have one or more other components of any suitable type in addition to or in place of the components illustrated in FIG. 5. For example, there may be additional computing systems (e.g., two or more) in the quench detection system. As another example, in some embodiments, optical system 110, photodetector 540, and / or circuitry 550 may be combined into a single device (e.g., disposed within a single housing).

[0089] In some embodiments, the superconductor 530 may be any suitable superconducting material. For example, the superconductor 530 may include LTS and / or HTS materials. In some embodiments, the superconductor 530 may be arranged to form a superconducting electromagnet and / or power transmission line, such as for use in motors, power transmission, MRI, NMR, particle accelerators, and / or fusion energy systems. In some embodiments, the superconductor 530 may include one or more HTS tape stacks, as described in more detail in connection with Figures 6A and 6B.

[0090] In some embodiments, the optical fiber 520 may be in thermal contact with the superconductor 510. For example, the optical fiber 520 may be disposed proximate to the superconductor 510 and / or embedded in the superconductor 510. While the example of FIG. 5 shows a single optical fiber 520, it should be understood that aspects of the technology described herein are not limited in this respect. In some embodiments, there may be multiple optical fibers. For example, there may be a number of optical fibers between 2 and 50, between 2 and 25, between 2 and 10, or between 2 and 7, or any range within these ranges.

[0091] In some embodiments, the optical fiber 520 may include multiple gratings 522 arranged along the length of the optical fiber 520. The gratings may be configured to reflect certain wavelengths of light and transmit other wavelengths of light. For example, the gratings 522 may be fiber Bragg gratings (FBGs) or ultra-long fiber Bragg gratings (ULFBGs). While the illustration of FIG. 5 shows four equally spaced gratings 522, it should be understood that there may be more than four gratings 522, which may be equally or non-equally spaced, as aspects of the technology described herein are not limited with respect to the number of gratings 522 or their spacing. In some embodiments, the gratings 522 may be spaced apart by one or more distances suitable for detecting a quench event within a sufficiently short period of time such that stored energy in the superconductor 510 may be removed before damaging the superconductor 530 or other components of the device housing the superconductor 530.

[0092] As shown in FIG. 5, the system 500 includes an optical system 110 optically coupled to an optical fiber 520 and an optical detector 540 optically coupled to the optical system 110. As described in connection with FIG. 1, the optical system 110 may include a first light source 112, a second light source 114, and an optical multiplexer 116. The first light source 112 and the second light source 114 may be configured to generate first and second light provided to the optical fiber 520 to perform both optical annealing and optical quench detection of the optical fiber 520. The light generated by one of the first light source 112 or the second light source 114 may have a peak wavelength centered near or near the Bragg wavelength of the grating 522 of the optical fiber 520 at the operating temperature of the superconductor 530.

[0093] In some embodiments, during operation of the system 500, the optical system 110 may provide light from the first light source 112 and the second light source 114 to the optical fiber 520 (e.g., simultaneously, sequentially, etc.). The provided light may illuminate and optically anneal the optical fiber 520. Additionally, light having a peak wavelength centered about the Bragg wavelength of the grating 522 may be reflected back to the optical system 110. The optical multiplexer 116 may demultiplex or otherwise separate this returned light for analysis and quench detection. It should be understood that in some embodiments, rather than analyzing the reflected light, light having a peak wavelength centered at or near the Bragg wavelength may be analyzed after transmission through the optical fiber 520, as aspects of the technology are not limited in this respect.

[0094] In some embodiments, the photodetector 540 may be configured to detect light reflected or transmitted by the grating 522 of the optical fiber 520. For example, the photodetector 540 may be configured to detect the spectrum, intensity, and / or peak wavelength of the received light 542. In some embodiments, the photodetector 540 may be an optical spectrum analyzer (OSA), an integrating sphere detector, a wavemeter, or any other suitable photodetector. In some embodiments, the photodetector 540 may be an interrogator configured to transmit and receive light separate from the light generated by the first light source 112 and the second light source 114.

[0095] In some embodiments, the photodetector 540 may be coupled to a circuit 550. The circuit 550 may be configured to determine a temperature of the superconductor 530 based on an output of the photodetector 540. For example, the circuit 550 may be configured to receive an optical spectrum from the photodetector 540, determine a peak wavelength of the received optical spectrum, and determine a temperature corresponding to the peak wavelength. The circuit 550 may be implemented using any suitable electronic circuitry, including, but not limited to, an FPGA, an ASIC, a microcontroller, and / or other microprocessing technology. In some embodiments, the circuit 550 may include a controller 130 as described in connection with FIG. 1 herein.

[0096] In some embodiments, system 500 includes a computing system 570 communicatively coupled to circuitry 550. Computing system 570 may be any suitable electronic device configured to receive information from and / or process information received from circuitry 550. In some embodiments, computing system 570 may be a fixed electronic device, such as a desktop computer, a rack-mounted computer, or any other suitable fixed electronic device. Alternatively, computing system 570 may be a portable device, such as a laptop computer, a smartphone, a tablet computer, or any other portable device that may be configured to receive information from and / or process information received from circuitry 550.

[0097] In some embodiments, the circuitry 550 and the computing system 570 may be communicatively connected by any network 560. The network 560 may be or may include one or more local and / or wide area, wired and / or wireless networks, including local or wide area enterprise networks and / or the Internet. Thus, the network 560 may be, for example, a hardwired network (e.g., a local area network within a facility), a wireless network (e.g., connected via Wi-Fi and / or cellular networks), a cloud-based computing network, or any combination thereof. For example, in some embodiments, the superconductor 530, the optical fiber 520, the optical system 110, the photodetector 540, and the circuitry 550 may be located in the same facility and connected to each other directly or via the network 560, while the computing system 570 may be located in a remote facility and connected to the circuitry 550 via the network 560. It should be understood, however, that in some embodiments, computing system 570 may be connected directly to circuitry 550 rather than being connected by network 560, as aspects of the technology described herein are not limited in this respect.

[0098] In some embodiments, computing system 570 may include quench detection facility 572. Quench detection facility 572 may be configured to analyze data obtained by photodetector 540 and processed by circuit 550. Quench detection facility 572 may be configured, for example, to analyze temperature data output by circuit 550 to determine whether a quench event is imminent and / or currently occurring in superconductor 530. For example, quench detection facility 572 may be configured to determine whether the temperature data output by circuit 550 is greater than a threshold temperature value and / or may be configured to fit a function to the temperature data over time to determine whether a thermal runaway event is imminent and / or currently occurring.

[0099] In some embodiments, computing system 570 may further include a quench mitigation facility 574. The quench mitigation facility 574 may be configured to generate instructions that cause the removal of energy from superconductor 530 in response to a determination of a quench event by quench detection facility 572. For example, quench mitigation facility 574 may be configured to generate instructions that cause the removal of current flowing through superconductor 530 (e.g., by shunting or otherwise shorting superconductor 530) to remove energy stored in superconductor 530.

[0100] The quench detection facility 572 and / or the quench mitigation facility 574 may be implemented as hardware, software, or any suitable combination of hardware and software, such that aspects of the technology described herein are not limited in this respect. As illustrated in FIG. 5, the quench detection facility 572 and the quench mitigation facility 574 may be implemented by the computing system 570, such as by being implemented in software (e.g., executable instructions) executed by one or more processors of the computing system 570. However, in other embodiments, the quench detection function 572 and / or the quench mitigation facility 574 may additionally or alternatively be implemented in one or more other elements of the system 500. For example, the quench detection function 572 and / or the quench mitigation facility 574 may be implemented in the circuit 550. In other embodiments, the quench detection function 572 and / or the quench mitigation facility 574 may be implemented in or with another device, such as a computing device that is located remotely from the system 500 and receives data via the network 560.

[0101] In the example of FIG. 5, the superconductor 530 corresponds to a high temperature superconducting (HTS) cable. As seen in FIGS. 6A and 6B, the HTS cable 600 includes a former 616 having an HTS tape stack 618 disposed within a channel extending along the length of the former 616 on an outer surface of the former 616. The HTS tape stack 618 is held in its respective channel via solder 619. An inner jacket 620 (e.g., a copper jacket) may be disposed around the former 616 and the HTS tape stack 618, and a plating 622 (e.g., a silver plating) may be disposed on the inner jacket 620. The entire surface of the inner jacket 620 may be plated, but in some embodiments, only a portion of the inner jacket 620 may be plated. Thus, as shown in FIG. 6A, only about one-half of the surface of the inner jacket 620 has the plating 622 disposed thereon. An outer jacket 624 (e.g., a steel or stainless steel jacket) is disposed around the inner jacket 620.

[0102] In this exemplary embodiment, cable 600 has multiple channels in a conductive (e.g., copper) former surrounded by one or more jackets. Each channel has an HTS tape stack and is filled with a metal (e.g., solder). Cable 600 also includes optional cooling channels 629.

[0103] 6B, an exemplary channel width is W1, the diameter of the former 616 is D1, the diameter of the inner jacket 620 is D2, and the diameter of the outer jacket 624 is D3. In some embodiments, the inner jacket 620 may be constructed from copper and the outer jacket 624 may be constructed from stainless steel. However, this is merely exemplary as other suitable materials for the jacket and former may be used.

[0104] 7, an exemplary HTS tape stack 700 includes a first layer 702 corresponding to a first stabilizer layer (here, stabilizer layer 702 is comprised of copper). Disposed on layer 702 is an overlayer 704 (here, overlayer 702 is comprised of silver). Disposed on layer 704 is a substrate 706. In this example, substrate 706 may be provided from any suitable material and is provided to have an electropolished surface. Disposed on substrate 706 is a buffer stack 708. In this example, buffer stack 708 is comprised of one or more materials disposed using magnetron sputtering techniques. Disposed on buffer stack 708 is an HTS material 710. In this exemplary embodiment, the HTS material may be comprised of a rare earth barium copper oxide superconductor (REBCO), such as yttrium barium copper oxide (YBCO). Disposed on HTS material layer 710 is an overlayer 712, and disposed on overlayer 712 is a second stabilizer layer 714. Overlayer 712 and stabilizer layer 714 can be constructed of the same materials as overlayer 704 and stabilizer layer 702, respectively, as described above.

[0105] 8A and 8B, an HTS cable 800 can include one or more grooves 810 configured to receive an optical fiber 812. As shown in Figures 8A and 8B, the grooves 810 can be disposed on an outer surface of the inner jacket 620 of the HTS cable 800. In some embodiments, the grooves 810 can be disposed on other surfaces of the HTS cable 800 (e.g., an inner surface of the inner jacket 620, an inner surface of the cooling channel 629).

[0106] The grooves 810, in some embodiments, may extend along the length of the HTS cable 800. The grooves may be disposed on one side of the HTS cable 800, as shown in the example of Figure 8A. In some embodiments, the grooves 810 and optical fibers 812 may be disposed around a smaller or larger portion, including the entire circumference, of the cable 800.

[0107] In some embodiments, the optical fiber 812 may be secured in the groove 810 using an adhesive. For example, the optical fiber 812 may be secured in the groove 810 using a thermally conductive adhesive (e.g., a silver adhesive) to ensure thermal coupling between the optical fiber 812 and the former 616 and the HTS tape stack 618. As another example, the optical fiber 812 may be secured in the groove 810 using solder.

[0108] The optical fiber 812 may be disposed anywhere within or proximate to the HTS cable 800. In some embodiments, the optical fiber 812 may be disposed on a surface of the HTS cable 800 rather than being disposed within a groove (e.g., groove 810). For example, the optical fiber 812 may be adhered to any suitable surface of the HTS cable 800 (e.g., the outer or inner surface of the inner jacket 620, the inner surface of the cooling channel 629) using an adhesive (e.g., a thermally conductive adhesive).

[0109] 8C and 8D show an alternative HTS cable 820 that includes a groove 830 formed in an inner surface of the former 616 such that an optical fiber 832 is disposed between the HTS tape stack 618 and the former 616. In some embodiments, the groove 830 may be filled with solder (e.g., to bond the HTS tape stack 618 to the former 616). The optical fiber 832 may be embedded in the solder such that the solder bonds the optical fiber 832 within the groove 830.

[0110] In some embodiments, the techniques described herein may be embodied in computer-executable instructions implemented as software, including application software, system software, firmware, middleware, embedded code, or any other suitable type of computer code. Such computer-executable instructions may be written using any of a number of suitable programming languages ​​and / or programming or scripting tools, and may be compiled as executable machine code or intermediate code that runs on a framework or virtual machine.

[0111] When the techniques described herein are embodied as computer-executable instructions, these computer-executable instructions can be implemented in any suitable manner, such as as a number of functional facilities, each providing one or more operations to complete the execution of an algorithm operating according to these techniques. A "functional facility" is a structural component of a computer system, however generated, that, when integrated with one or more computers and executed by the one or more computers, causes the one or more computers to perform a particular operational role. A functional facility may be part or the whole of a software element. For example, a functional facility is implemented as a process function, or as a discrete process, or as other suitable processing units. When the techniques described herein are implemented as multiple functional facilities, each functional facility may be implemented in a unique manner, and need not all be implemented in the same manner. Furthermore, these functional facilities may be executed in parallel and / or serially as needed, and may pass information between each other using shared memory on the computer on which they are executing, using a message passing protocol, or in any other suitable manner.

[0112] Generally, functional facilities include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In general, the functionality of the functional facilities may be combined or distributed as desired in the systems in which they operate. In some implementations, one or more functional facilities that perform the techniques herein may together form a complete software package. These functional facilities may, in alternative embodiments, be adapted to interact with other, unrelated functional facilities and / or processes to implement software program applications, such as, for example, quench detection facilities.

[0113] Several exemplary functional facilities have been described herein for performing one or more tasks. However, it should be understood that the described functional facilities and division of tasks are merely illustrative of the types of functional facilities that may implement the exemplary techniques described herein, and that the embodiments are not limited to being implemented with any particular number, division, or type of functional facilities. In some embodiments, all functions may be implemented in a single functional facility. It should also be understood that in some implementations, some of the functional facilities described herein may be implemented together with or separately from other functional facilities (i.e., as a single unit or separate units), or some of these functional facilities may not be implemented.

[0114] Computer-executable instructions implementing the techniques described herein may be encoded on one or more computer-readable media to provide functionality to the media in some embodiments (whether implemented as one or more functional facilities or in any other manner). Computer-readable media include magnetic media such as hard disk drives, optical media such as compact disks (CDs) or digital versatile disks (DVDs), persistent or non-persistent solid-state memory (e.g., flash memory, magnetic RAM, etc.), or any other suitable storage media. Such computer-readable media may be implemented in any suitable manner, such as as computer-readable storage medium 906 of FIG. 9 described below (i.e., as part of computing device 900) or as a standalone separate storage medium. As used herein, a "computer-readable medium" (also referred to as a "computer-readable storage medium") refers to a tangible storage medium. A tangible storage medium is non-transitory and has at least one physical, structural component. As used herein, in a "computer-readable medium," at least one physical, structural component has at least one physical characteristic that can be altered in some way during the process of creating the medium with embedded information, recording information thereon, or other process of encoding the medium with information. For example, the magnetization state of a portion of the physical structure of the computer-readable medium can be altered during the recording process.

[0115] In some, but not all, embodiments in which the techniques may be embodied as computer-executable instructions, these instructions may be executed on one or more suitable computing devices operating in any suitable computer system, including the exemplary computer system of FIG. 9, or one or more computing devices (or one or more processors of one or more computing devices) may be programmed to execute the computer-executable instructions. A computing device or processor may be programmed to execute the instructions if the instructions are stored in a manner accessible by the computing device or processor, such as a data store (e.g., an on-chip cache or instruction register, a computer-readable storage medium accessible via a bus, a computer-readable storage medium accessible via one or more networks and accessible by the device / processor, etc.). The functional facilities that make up these computer-executable instructions may be integrated with and direct the operation of a single general-purpose programmable digital computing device, a cooperative system of two or more general-purpose computing devices that share processing power and jointly perform the techniques described herein, a single computing device or a cooperative system of computing devices (co-located or geographically distributed) dedicated to performing the techniques described herein, one or more field programmable gate arrays (FPGAs) for performing the techniques described herein, or any other suitable system.

[0116] 9 illustrates one exemplary implementation of a computing device in the form of a computing device 900 that may be used in a system implementing the techniques described herein, although other implementations are possible. It should be understood that FIG. 9 is not intended to be a depiction or comprehensive depiction of the components necessary for a computing device to operate as a quench detection system and / or quench mitigation system in accordance with the principles described herein.

[0117] The computing device 900 may include at least one processor 902, a network adapter 904, and a computer-readable storage medium 906. The computing device 900 may be, for example, a desktop or laptop personal computer, a personal digital assistant (PDA), a smart mobile phone, or any other suitable computing device. The network adapter 904 may be any suitable hardware and / or software for enabling the computing device 900 to communicate wired and / or wirelessly with any other suitable computing devices over any suitable computing network. The computing network may include wireless access points, switches, routers, gateways, and / or other network equipment, as well as any suitable wired and / or wireless communication medium or media for exchanging data between two or more computers, including the Internet. The computer-readable medium 906 may be adapted to store data processed and / or instructions executed by the processor 902. The processor 902 enables the processing of data and the execution of instructions. The data and instructions may be stored in the computer-readable storage medium 906.

[0118] The data and instructions stored on the computer-readable storage medium 906 may be comprised of computer-executable instructions that implement techniques that operate according to the principles described herein. In the example of FIG. 9, the computer-readable storage medium 906 stores computer-executable instructions that implement various facilities and store various information as described above. The computer-readable storage medium 906 may store a quench detection facility 908 configured to derive information indicative of a quench event from the optical fiber temperature measurement data and / or a quench mitigation facility 910 configured to cause stored energy to be removed from the superconducting material if a quench event is detected.

[0119] Although not shown in FIG. 9, the computing device may further have one or more components and peripherals, including input devices and output devices. These devices may be used, among other things, to present a user interface. Examples of output devices that may be used to provide a user interface include a printer or display screen for visually presenting output, and a speaker or other sound generating device for audibly presenting output. Examples of input devices that may be used for a user interface include a keyboard and a pointing device, such as a mouse, a touchpad, or a digitizing tablet. As another example, the computing device may receive input information through voice recognition or in other audible formats.

[0120] Having thus described several aspects of at least one embodiment of the technology, it will be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art.

[0121] Various aspects of the technology described herein may be used alone, in combination, or in various arrangements not specifically described in the embodiments above, and thus are not limited in application to the details and arrangements of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

[0122] In the claims, the use of ordinal terms such as "first," "second," "third," etc. to modify a claim element does not, per se, imply a priority, precedence, or order of a claim element relative to other claim elements, or the temporal order in which acts of a method are performed, but is merely used as a label to distinguish a claim element having a certain name from other claim elements having the same name (but which use ordinal terms).

[0123] Additionally, the techniques described herein may be embodied as methods, examples of which are provided herein, including with reference to Figure 4. The acts performed as part of a method may be ordered in any suitable manner. Thus, while shown in the exemplary embodiments as sequential acts, embodiments may be constructed in which acts are performed in an order different from that shown, including performing some acts simultaneously.

[0124] Also, the phraseology and terminology used herein is for purposes of description and should not be regarded as limiting. The use of "including," "comprising," "having," "containing," "involving," and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

[0125] The terms "approximately" and "about" may be used to mean, in some embodiments, within ±20% of a target value, in some embodiments, within ±10% of a target value, in some embodiments, within ±5% of a target value, and in some embodiments, within ±2% of a target value. The terms "approximately" and "about" may include the target value.

Claims

1. 1. A system arranged to perform optical annealing of an optical fiber disposed in an environment subjected to ionizing radiation, comprising: a first light source configured to illuminate and optically anneal the optical fiber by generating first light having a first peak wavelength; a second light source configured to illuminate and optically anneal the optical fiber by generating second light having a second peak wavelength; and An optical multiplexer coupled between the first light source and the optical fiber and between the second light source and the optical fiber.

2. The system of claim 1 , wherein the first light source is configured to generate the first light having a first peak wavelength in the range of 770 nm to 1170 nm.

3. 3. The system of claim 1 or 2, wherein the first light source is configured to generate the first light having a first peak wavelength of about 970 nm.

4. 3. The system of claim 1, wherein the second light source is configured to generate the second light having a second peak wavelength in the range of 1350 nm to 1750 nm.

5. 3. The system of claim 1, wherein the second light source is configured to generate second light having a second peak wavelength of about 1550 nm.

6. 3. The system of claim 1, wherein the first light source is configured to generate the first light having an optical power in the range of 5 mW to 500 mW.

7. 3. The system of claim 1, wherein the optical multiplexer is configured to perform wavelength division multiplexing (WDM) of the first light and the second light.

8. 3. The system of claim 1, wherein the optical multiplexer is configured to perform time division multiplexing (TDM) of the first light and the second light.

9. 3. The system of claim 1 or 2, wherein the optical multiplexer is configured to simultaneously illuminate the optical fiber with the first light and the second light.

10. 3. The system of claim 1, wherein the optical multiplexer is configured to alternately irradiate the first light and the second light.

11. 3. A system according to claim 1 or 2, wherein the system is arranged to irradiate the optical fiber with the first light source and / or the second light source while the optical fiber is exposed to ionising radiation.

12. 3. The system of claim 1 or 2, wherein the optical fiber is placed in a cryogenic environment while being illuminated by the first light source and / or the second light source.

13. 3. The system of claim 1 or 2, wherein the optical fiber is at a temperature between 0K and 120K while illuminated by the first light source and / or the second light source.

14. 3. The system of claim 1 or 2, wherein the optical fiber extends along the length of a high temperature superconducting (HTS) cable, the HTS cable including at least one HTS tape stack.

15. 3. The system of claim 1 or 2, wherein the system is used in a nuclear fusion energy system.

16. 3. The system according to claim 1, wherein the ionizing radiation is artificial ionizing radiation.

17. 3. The system of claim 1, wherein the dose rate of ionizing radiation to the environment is greater than the dose rate of background ionizing radiation.

18. 3. The system of claim 1 or 2, wherein the dose rate of the ionizing radiation is greater than 0.2 nGy / s.

19. 1. A method for optically annealing an optical fiber disposed in an environment exposed to ionizing radiation, comprising: optically annealing the optical fiber with a first light having a first peak wavelength; and optically annealing the optical fiber with a second light having a second peak wavelength.

20. 20. The method of claim 19, wherein optically annealing the optical fiber with the first light and the second light comprises optically annealing the optical fiber with the first light and the second light simultaneously.

21. 21. The method of claim 19 or 20, wherein optically annealing the optical fiber with the first light and the second light comprises alternately optically annealing the optical fiber with the first light and the second light.

22. 21. The method of claim 19 or 20, wherein optically annealing the optical fiber with the first light and the second light comprises multiplexing the first light and the second light into the optical fiber.

23. 23. The method of claim 22, wherein multiplexing the first light and the second light into an optical fiber comprises using wavelength division multiplexing (WDM).

24. 23. The method of claim 22, wherein multiplexing the first light and the second light onto an optical fiber comprises using time division multiplexing (TDM).

25. 21. The method of claim 19 or 20, wherein optically annealing the optical fiber with the first and / or second light comprises optically annealing the optical fiber with the first and / or second light while the optical fiber is exposed to ionizing radiation.

26. 21. The method of claim 19 or 20, wherein optically annealing the optical fiber with the first light comprises irradiating the optical fiber with the first light having a peak wavelength in the range of 770 nm to 1170 nm.

27. 21. The method of claim 19 or 20, wherein optically annealing the optical fiber with a first light comprises optically annealing the optical fiber with a first light having a peak wavelength of about 970 nm.

28. 21. The method of claim 19 or 20, wherein optically annealing the optical fiber with the second light comprises optically annealing the optical fiber with the second light having a peak wavelength in the range of 1350 nm to 1750 nm.

29. 21. The method of claim 19 or 20, wherein optically annealing the optical fiber with the second light comprises optically annealing the optical fiber with the second light having a peak wavelength of about 1550 nm.

30. 21. The method of claim 19 or 20, wherein optically annealing the optical fiber with the first light and / or the second light comprises optically annealing the optical fiber with the first light and / or the second light while the optical fiber is disposed in a cryogenic environment.

31. 21. The method of claim 19 or 20, wherein optically annealing the optical fiber with the first light and / or the second light comprises optically annealing the optical fiber with the first light and / or the second light while the optical fiber is at a temperature between 0 K and 120 K.

32. 21. The method of claim 19 or 20, wherein optically annealing the optical fiber with the first light and / or the second light comprises optically annealing the optical fiber with the first light and / or the second light while the optical fiber is disposed along a length of a high temperature superconductor (HTS) cable, the HTS cable including at least one HTS tape stack.

33. 21. The method of claim 19 or 20, wherein optically annealing the optical fiber with the first light and / or the second light comprises optically annealing the optical fiber with the first light and / or the second light while the optical fiber is in use in a fusion energy system.

34. 1. A system arranged to perform optical annealing of an optical fiber, comprising: a first light source configured to optically anneal the optical fiber by generating first light having a first peak wavelength; a second light source configured to optically anneal the optical fiber by generating second light having a second peak wavelength; and an optical multiplexer coupled between the first light source and the optical fiber and between the second light source and the optical fiber; the optical fiber is disposed in a fusion energy source; the optical fiber is exposed to ionizing radiation produced by a fusion energy source while the first light source and / or the second light source optically anneal the optical fiber; and The optical fiber is in a cryogenic temperature system.

35. 35. The system of claim 34, wherein the first light source is configured to generate the first light having a first peak wavelength in a range of 770 nm to 1170 nm.

36. 36. The system of claim 34 or 35, wherein the first light source is configured to generate the first light having a first peak wavelength of about 970 nm.

37. 36. The system of claim 34 or 35, wherein the second light source is configured to generate second light having a second peak wavelength in the range of 1350 nm to 1750 nm.

38. 36. The system of claim 34 or 35, wherein the second light source is configured to generate second light having a second peak wavelength of about 1550 nm.

39. 36. The system of claim 34 or 35, wherein the first light source is configured to generate the first light having an optical power in the range of 5 mW to 500 mW.

40. 36. The system of claim 34 or 35, wherein the optical multiplexer is configured to wavelength division multiplex (WDM) the first light and the second light.

41. 36. The system of claim 34 or 35, wherein the optical multiplexer is configured to time division multiplex (TDM) the first light and the second light.

42. 36. The system of claim 34 or 35, wherein the optical multiplexer is configured to simultaneously illuminate the optical fiber with the first light and the second light.

43. 36. The system of claim 34 or 35, wherein the optical multiplexer is configured to alternately illuminate the first light and the second light.

44. 36. The system of claim 34 or 35, wherein the optical fiber is at a temperature between 0K and 120K while illuminated by the first light source and / or the second light source.

45. 36. The system of claim 34 or 35, wherein the optical fiber extends along the length of a high temperature superconducting (HTS) cable, the HTS cable including at least one HTS tape stack.

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