Qiuliang Wang

Stress-Strain Distribution Analysis in Bi2212 Subcable Based on Numerical Modeling and Experiment

There has been sustained interest in the development of the Bi2212/Ag round wire (RW) because of its unique potential for applications in high-field magnets (25 T or higher). The Bi2212 conductor is a round strand, which is a very favorable shape to produce multistage twisted cable-in-conduit conductors (CICCs) for the next fusion machine (DEMO). One drawback of Bi2212 is its fragile mechanical properties. The stress and strain accumulated during cabling, the thermal contraction during cooldown, and the electromagnetic load can have a severe impact on the transport properties of the Bi2212 RW. In order to investigate the strain distribution of Bi2212 in CICC, some research and development work was made at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). A simple cable wound with three Bi2212 RWs was manufactured and subjected to mechanical tests. A numerical model was proposed to analyze the stress-strain distribution of a wire inside a cable at cryogenic temperature. Comparisons were made between the model and experimental results. Based on the results and improved understanding of the mechanical behavior, an optimization could be implemented to reduce the Bi2212 cable degradation, in terms of conductor design, manufacture, and operation.

Impact of Indentation on the Critical Current of Bi2212 Round Wire

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. Bi2Sr2CaCu2Ox 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 Ic was measured. The results show that Ic of a Bi-2212 RW, unlike Nb3Sn 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.

Analysis of Temperature Rise of TF Magnet During Plasma Discharges on EAST

For the safe operation of Experimental Advanced Superconducting Tokamak (EAST) with higher plasma performance discharge in future, it is important to estimate the operation state of Toroidal Field (TF) magnet. The outlet temperature rise of TF coils and TF cases measured in experiment is analyzed. It is found that the outlet temperature rise of TF coils and TF cases increases with plasma current. The outlet temperature rise of TF coils and TF cases induced by plasma disruption is a small value, about 0.01 K. In addition, the outlet temperature rise of TF coils is not related to the plasma duration, but the outlet temperature rise of TF cases seems to increase with plasma duration.

High Field Superconducting Magnet Technologies for Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) has become one of the most powerful tools in modern medical diagnosis and interventional therapy. It can achieve very fast scanning due to the synchronization in time and space under the high field with high homogeneity. High field with high stability in time can improve the ratio of signal to noise and the imaging resolution. It has become an important diagnostic tool in the early stages of cancer, and the evaluation of the efficacy of treatment and high-risk surgery, neuroscience, and molecular imaging. On the other hand, in recent years, the development of openness in high field magnets can combine the MRI with positron emission tomography and/or accelerator, which contributes to form more excellent medical diagnosis tools. The high-field superconducting has been widely used in medical imaging. The superconducting magnet technology depends on the development of material and cryogenic technology. In this paper, the superconducting MRI systems applied in the medical diagnosis and interventional therapy in China were reviewed.