Due to the excellent current carrying performance of Bi2Sr2CaCu2O8+x (Bi-2212) and the development of its industrial manufacturing technology, Bi-2212 is a promising material to be developed as superconductor for application in fusion reactor magnets. The cable-in-conduit conductor (CICC) concept is often chosen for the development of large-scale magnets because of their high stability. Bi-2212 is presently the only kind of copper oxide superconducting material which can be made into solid round wire, which provides a good basis for developing CICCs. The over pressure (OP) heat treatment can significantly improve the superconducting performance of Bi-2212 wires but it also reduces the wire diameter by ∼5%. This leads to an increase of the void fraction of CICCs, typically from 30% to 40% for a CICC with ITER scale dimensions. A pre-OP heat treatment before OP is proposed in this study. The reduction of the wire diameter can be completed before the formation of the continuous superconducting phase, which would dramatically decrease the CICC void fraction. One Bi-2212 cable consisting of 84 wires, was first pre-OP heat treated successfully and after completing the OP heat treatment, the cable’s transport performance was tested. The results showed good performance with a critical current (I c) of 35.7 kA at 5.8 T background field in 4.2 K, which is consistent with the predication.
The CFETR, "China Fusion Engineering Test Reactor," is a new tokamak device. Its magnet system includes the toroidal field (TF), central solenoid (CS), and poloidal field coils. The main goal of this study is to build a fusion engineering tokamak reactor with fusion power of 50-200 MW and self-sufficiency by blanket. The maximum field of CS and TF will get around 15 T, which is much higher than that of other reactors. New materials could be used to develop the magnet technology for the next generation of fusion reactors. Bi2Sr2CaCu2Ox is considered as a potential material for the superconducting magnets. An R&D activity is running at ASIPP for the feasibility demonstration of cable-in-conduit conductor based on the Bi2212 wire. One subsize conductor cabled with 42 wires was designed and manufactured. In this paper, the manufacturing procedures and first test results of Bi-2212 conductor samples are described in details, including wire specifications, cabling and compaction process, conductor heat treatment, as well as test results on ac loss and critical current.
CFETR, "China Fusion Engineering Test Reactor," is a new tokamak device. Its magnet system includes the toroidal field (TF), central solenoid (CS), and poloidal field coils. The main goal of this project is to build a fusion engineering tokamak reactor with fusion power of 50-200 MW and self-sufficiency by blanket. The maximum field of CS and TF will get around 16 T, which is much higher than that of other reactors. New materials could be used to develop the technology of magnet for the next generation of fusion reactors. Bi 2 Sr 2 CaCu 2 O x as a potential material is considered. However, the Bi-2212 phase is brittle, and the sheath of the round wire (RW) is Ag/Ag-Mg alloy with high plasticity and low strength. During cabling or conductor manufacturing, the compression on wire is inevitable, which could cause severe indentation on wire. With the aim of investigating the impact of indentations on the critical current of Bi-2212, the artificially indented wires were made, and I c was measured. The results show that I c of a Bi-2212 RW, unlike Nb 3 Sn and NbTi wires, linearly decreased by the increased depth of indentation. The results are foreseen to be useful for Bi-2212 conductor design and manufacturing.
Laser-based three-dimensional (3D) printing of polymers is a promising technology in fabricating complicated structures for applications in bioengineering, optics and molding. Infrared (IR) laser-assisted thermal curing printing technique offers high controllability by heating up the sample locally. Compared with other techniques like ultraviolet (UV) curing, IR laser-assisted thermal curing avoids yellowing issue, which is a common problem in UV curing. Accurate thermal simulations of the polymer curing processes under the laser heat is crucial to the design and improvement of the printing apparatus. In this work, a multi-physics simulation is carried out to predict the temperature rise and the curing extent profile of polydimethylsiloxane (PDMS) heated by a periodic, pulsed laser. The simulation incorporates the coupling between the local heating and the curing extent change. The cured spot sizes are provided for the given duty cycle and laser pulse period. The exothermic enthalpy of PDMS during the curing process is also measured to improve the simulation accuracy. The simulation results are validated with experiments using a pulsed 2 µm IR laser. This technique can control the polymer curing to achieve a minimum feature size of ~20 µm. Various patterns are fabricated to demonstrate the flexibility of this technique.
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