## 1 Introduction  
Livelihood research, like bio-sciences and power technologies, has been developing rapidly in recent years [1, 2, 3]. Among them, superconducting magnets have been widely applied in particle accelerators, nuclear fusion devices, nuclear magnetic resonance imagers (MRI) and external magnetic fields (MCZ) for monocrystalline silicon growth furnaces. Compared with traditional copper coil magnets, superconducting magnets have the advantages of high field strength, low energy consumption, small size, long life and stable performance [4]. In recent years, researchers contributed plenty of references for the development of superconducting magnets. [PERSON] et al. [5] discussed the optimization, development and experiments of superconducting Cryogenic Probe Stations (CPS) with conduction cooling cryostat in which a Gifford-McMahon (G-M) cryocooler is applied to keep the temperature of a magnet with a power value about 1.2 W. [PERSON] et al. [6] reported a novel Superconducting Magnetic Energy Storage (SMES) for power system storage, and presented the state-space relationship by first-order differential equations. [PERSON] et al. [7] developed a thermal and mechanical fields model for the Superconducting Magnet and Dewar (SCMD) system through finite element analysis. It is said that the structure's reinforcement for mechanical and thermal properties is assessed generally. The coils of superconducting magnets are wound by superconducting strips, which can only exhibit superconducting properties at specific low temperatures. It is now common practice to use a tie rod device to suspend the coil module (cold mass) in a vacuum dewar to isolate external heat transfer while using a refrigerator to cool it to superconducting temperatures. It is reported that the traditional low-temperature magnet cooling experiments need to apply coolants, such as liquid nitrogen and liquid neon, and then the temperature could be controlled between 4.2 K and 300 K [8]. The suspension rod not only needs to withstand the gravity of the cold mass, but also needs to ensure the relative geometric position accuracy of the cold mass inside the magnet under different working conditions, so the rod must have a high tensile strength. One end of the tie rod is connected to the vacuum dewar of 300 K, and the other end is connected to the cold mass of the 4 K temperature zone, which becomes the main path of heat conduction and heat leakage. In view of the limited power of the chiller, it is necessary to minimize the thermal conductivity of the tie rod. At present, high-strength materials such as titanium alloy [9], glass fiber resin composite material (GFRP) [10] and carbon fiber resin reinforced composite material (CFRP) [11] are used to make slender rods, and the structural forms include cylinder shape, runway shape and sheet shape. In particular, titanium alloys have shown low heat conduction properties [12; 13; 14]. For example, CFRP materials are often used in MRI magnets to make a strip bar [15] or a cylindrical bar [16] with a cross-section of runway shape to fix the support main coil and shield coil. Compact muon solenoid (CMS) uses a titanium alloy cylinder to fix 225 tons of cold mass in a superconducting magnet [17]. The 8300 tons of cold mass was fixed with a titanium alloy cylinder in a superconducting ring cyclotron [18]. Muon ionization cooling experiment (MICE) magnets use CFRP material to make a two-stage, racetrack-shaped strip rod body to hold the superconducting coil [19]. In high-temperature superconducting motors, GFRP is used to make a strip tie rod with a runway cross-section to support the fixed rotor [20]. Generally, after the completion of the design of the cold mass of the magnet and the vacuum dewar, it is necessary to design the suspension rod according to the force of the cold mass of the magnet and the position accuracy requirements. After determining the basic parameters such as the load, length and geometric shape of the rod, the corresponding parts are processed according to the design drawings.