多芯MgB2超导线材的稳定化机理研究

项目名称： 多芯MgB2超导线材的稳定化机理研究

项目编号： No.50877067

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 张平祥

作者单位： 西北有色金属研究院

项目金额： 36万元

中文摘要： 二硼化镁（MgB2）超导体生产工艺简单、生产周期短、临界电流密度高、成本低、可工作于制冷机环境下等优点使之成为应用于核磁共振超导磁体中较有前景的超导材料。与低温超导体相同，MgB2能否成功应用于磁体、电源等大电流设备取决于超导体的稳定性和绕组失超保护措施。深入了解超导线材的失超发生和传播过程对改善超导线材乃至磁体的稳定性起着重要的作用。 着重研究MgB2的失超传播特性，包括最小触发能（MQE）及失超传播速度。通过实验测量和数值计算分析MgB2超导线材的失超传播过程。实验上，在制冷机环境（20 K）中，测量了超导线材在自场条件下，加载不同电流强度时的失超行为。通过电阻加热器给超导体加载脉冲热，测量超导线材上各个引线的电压值随时间的演化关系来研究超导线材的失超行为。同时，通过有限元方法（FEM）计算系统的一维热传导方程来研究超导线材的失超行为。由数值计算得到的超导线材失超传播规律与实验测得值相吻合。

中文关键词： MgB2超导线材；稳定性；最小触发能；失超传播速度；有限元方法

英文摘要： MgB2 superconductor with advantages of simple fabrication techniques, short product period, high critical current density, low cost and suitability to work in cryogenic refrigerator emerges to be a promising candidate superconductive material in large-scale applications such as magnetic resonance imaging (MRI). Just as for low temperature superconductors (LTS), the success of MgB2 in high current applications, such as magnets and power electrical devices, relies on the development of practical conductors with sufficient stability and appropriate cryogenic design of the winding structure for quench protection. Understanding the quench process from initiation to propagation is a key element in this development-design cycle. The quench parameters including minimum quench energy (MQE) and quench propagation velocity of MgB2 superconducting wires are studied.quench process of superconducting MgB2 wires are studied experimentally and numerically, focusing on the estimation of the quench propagation velocity and minimum quench energy. The measurements are taken at self-field in cryogenic refrigerator condition at 20 K with variable transport currents. Experimentally, energy pulses are deposited into the wire by loading current to the resistive heater. The electric field profiles and their time evolution are measured from multiple voltage taps along the wire. Finite element method (FEM) is used to solve the one-dimensional heat balance equation of the system to study the quench process numerically. The simulation results are in qualitative agreement with experimental ones.

英文关键词： MgB2 wires; stability; minimum quench energy; quench propagation velocity; finite element method