Thermal-Engineering Stucy on Early Detection of Quench and Hyper Stabilization Method of Superconducting Coil

本课题的主要目的是阐明超导线圈失超的热机理，建立超导线圈的热稳定性理论，提出失超的早期检测方法。下文概述了这一为期三年的研究项目所取得的成果。对强制冷却和浸没冷却超导线圈的失超机理和热稳定性进行了数值分析。定量地阐明了各种控制因素对它们的影响，建立了淬火早期预报的基本概念.由于失超现象是极其迅速的瞬态和不确定的，而且它发生在非常强的磁场中，因此几乎不可能预测其发生的时间和地点。为此，我们提出了两种新的检测方法：一种是薄膜热传感器，另一种是可视化技术，并对薄膜热传感器的实用性进行了检验 ...更多信息 d在液氦中脉冲加热板条的快速瞬态沸腾传热实验。实验中获得的数据也是精确分析热稳定性所必需的。测试片是20 μ m厚的不锈钢带，其两个表面都涂覆有PVF膜和碳糊膜。这种条形结构是为了模拟实际应用中的绝缘超导体，而碳糊膜则充当了电阻温度计的一部分。考虑到涂层的热容和瞬态温度分布，通过数值计算对实验数据进行了简化，所得结果具有满意的精度，可用于薄膜传感器失超起始的早期检测。结果表明，可视化技术将是一种很有前途的失超早期检测工具，但要将这一迷人的技术应用于实际超导线圈，还需要进一步的研究。少

The aim of this research project is to clarify thermal mechanism of quench in forced-and immersion-cooled superconducting coils, and to establish theory of thermal stability of superconducting coil, and to propose methods for early detection of the quench. The outline of the results obtained in this 3-year research project is given below.1. Numerical analyzes of quench mechanism and thermal stability of forced-and immersion-cooled superconducting coils were carried out. Various influences of governing factors on them were clarified quantitatively and the basic concept of early prediction of quench was established.2. Since the quench phenomenon is extremely rapid transient and indeterminate, and it occurs in a very strong magnetic field, it is almost impossible to predict the time and place of its occurrence. hence we propose two novel detecting methods : one is a film thermal sensor, and another is a visualization technique.Practical applicability of the film thermal sensor was examine … More d in an experiment on rapid transient boiling heat transfer of a pulse-heated strip in liquid helium. The data obtained in the experiment are also necessary for the precise analysis of the thermal stability. The test piece was a 20-mum-thick stainless steel strip, both surface of which were coated with PVF film and a carbon-paste film. This strip structure was to simulate an insulated superconductor in practical use and the carbon-paste film performed the part of an electric resistance thermometer. The heat-transfer data were reduced from the experimental raw values by numerical calculation considering the heat capacity and transient temperature distribution of the coating layrs : the obtained results had satisfactory accuracy to apply the film sensor to the early detection of quench initiation.As for a visualization technique of quench and its rapid propagation was investigated using a pancake-type superconducting coil immesed in liquid helium. It was found that the visualization technique will be a promising tool of the early detectin of quench ; however, we need further research to make applicatin of this charming technique to practical superconducting coils. Less