Study On Strain Measurement Of Strong Pulsed Magnet Based On Embedded Fiber Bragg Gratings

With the development of strong pulsed magnetic field technology, scientific researchers take the improving of the strength of pulsed magnetic field as the research target. However, the huge strain generated in the excitation process is still one of the main obstacles which limit the improving of the strength of pulsed magnetic field. Therefore, solving the measurement of magnetic stress can help researchers to study the internal mechanism of pulsed strong magnet. What’s more, it promotes the further development of strong pulsed magnetic field technology. But because the pulsed strong magnet works in the liquid nitrogen (77K), strong electromagnetic field environment, the interior space is narrow, conventional electric sensors can’t be embedded inside the magnet coil. And the wire connection of electric sensors is complex and they are sensitive to electromagnetic interference. In the study of pulsed strong magnetic field technology, researchers urgently need to find a measuring tool that can be use to measurement of the internal strain magnet accurately. Fiber Bragg Grating (FBG) sensors are new kinds of sensors, which exhibit many advantages such as small size, high sensitivity, intrinsic electrical isolation, and immune to electromagnetic interference, etc. Therefore, Fiber Bragg Grating sensors satisfy the application requirements of the strain measurement inside pulsed strong magnets.At present, the territory of using FBG sensor to measure the internal strain of pulsed strong magnets is blank both at home and abroad. In view of this research situation, this paper takes FBG strain sensors as the research object. First, research the sensing characteristics and strain measurement of optical fiber Bragg grating in liquid nitrogen temperature. Then, study the technology and craft of embedding optical fiber Bragg grating into strong pulsed magnet through simulative coiling experiments and the fabrication of two small magnet models of low intensity and a pulsed strong magnet of60Tesla. And test the dynamic strains internal the pulsed strong magnet of60Tesla for normal temperature and liquid nitrogen temperature, respectively. Finally, test the strain of the cryogenic shrunken store box by using FBG strain gauges. The main content of this article is arranged as following: (1) Introduce the development and application situation of fiber Bragg grating sensor technology, and research status of strain measurement theory of the optical fiber Bragg grating sensor in low temperature.(2) Introduce the basic theory of optical fiber Bragg gratings.(3) Study the temperature and strain sensing characteristics of optical fiber Bragg gratings in liquid nitrogen temperature. Research the strain measurement with optical fiber Bragg gratings. Analyze and discuss the feasibility of using FBG sensors for distributed strain measurement in cryogenic applications.(4) Study the technology and craft of embedding optical fiber Bragg grating into strong pulsed magnet through simulative coiling experiments and the fabrication of pulsed strong magnets.(5) Test the dynamic strains internal the pulsed strong magnet for room temperature and liquid nitrogen temperature, respectively.The experimental results show that the packaged fibers Bragg grating strain sensors have a good adaptability in low temperature. And the optical coefficient in liquid nitrogen temperature is obtained. It is about0.086. Realize the distributed strain measurement of shrinkage fuel storage box. The internal strain of pulsed strong magnets are measured successfully by20FBGs, and the success rate of the FBG embedding has reached over90%, which indicates that taking fiber Bragg grating sensors as a measurement tool for strong pulsed magnets is effective and feasible.