【作者】 郭兴龙；

【导师】 王莉；

【作者基本信息】 哈尔滨工业大学 ， 制冷及低温工程， 2010， 博士

【摘要】 国际离子化冷却μ介子实验(Muon Ionization Cooling Experiment,简称MICE)是验证中微子工厂和μ介子对撞机可行性的关键技术预研性工作之一。作为MICE实验装置中的重要组件之一的超导耦合螺线管磁体将提供约2.6T的中心磁场,以控制位于其内部的射频腔内的μ介子束流。超导磁体的失超会导致磁体线圈内部的过热和过电压,从而可能对磁体造成永久性损害,失超过程的研究及失超保护系统的设计是超导磁体设计的关键内容之一。以商用铜基铌钛超导线绕制、环氧树脂浸渍的耦合磁体拟采用线圈分段并结合骨架诱发失超效应(quench-back)的被动失超保护方式。本文以MICE超导耦合螺线管磁体为研究对象,建立了失超过程的数值模拟模型,深入地研究了失超过程中主要参数的变化规律,设计了合理可行的失超保护系统。本文的研究结果对耦合磁体及类似螺线管磁体的失超保护系统设计具有重要的理论指导意义和实际应用价值。主要研究内容包括:为了设计合理的耦合磁体失超保护电路,对耦合磁体的失超过程进行了半经验数值模拟研究。在经典的基于失超传播速度的失超模拟方法中考虑了骨架的诱发失超效应,为耦合磁体失超过程的模拟建立了一个半经验数值模型。采用已成功运行的一个实验超导磁体的失超过程实验结果,经与模型计算结果比较,验证了模型的正确性。用该模型研究了磁体分段数目、保护电阻值和绑扎带材料对于耦合磁体失超过程的影响,为耦合磁体设计了合理的失超保护电路。为了深入理解耦合磁体的失超过程和骨架内的涡流及其引起的诱发失超效应,对耦合磁体的失超过程进行了进一步的有限元模拟研究。基于ANSYS耦合场分析功能,考虑了骨架的诱发失超效应,建立了失超过程瞬态耦合热电磁有限元模型。应用该模型计算了耦合磁体失超过程,比较了有限元模型与半经验模型的计算结果,验证了该有限元模型的正确性。利用该模型进一步分析了失超过程中骨架的诱发失超效应,并指出了有限元模型与半经验模型的优缺点。已公开的失超模拟方法对于磁体内部的过热计算比较准确,对于过电压计算非常保守,为此本文提出了分段螺线管磁体失超过程过电压的一个较准确计算方法。准确的过电压计算需要分析磁体内部的电压分布。将磁体看做是以匝为单元组成的电路,每匝同时具备电阻与电感属性。失超过程中各匝的电感不变,电阻随匝温度而变。根据每匝的瞬态温度和电流,可计算出磁体内部沿导线方向的电阻电压、电感电压以及合电压分布。提出了分段螺线管线圈失超过程中最大内电压、层间电压及匝间电压的较准确的计算方法。用该方法研究了分段螺线管线圈内部失超过程过电压以及分段数目对磁体内电压的影响。冷二极管组件是MICE超导耦合磁体失超保护系统的关键组件,工作在温度4.2~4.8K,磁场1.5~2.5T环境下。耦合磁体的励磁、卸载以及失超保护电路的模拟、分析与设计均需要了解冷二极管组件的低温工作特性。搭建了一套二极管组件低温性能测试系统,测试了室温和液氮温度下二极管的正反向通电特性和二极管组件在大电流下的工作特性。利用耦合磁体的试样线圈的测控系统,测试了~10K温度下二极管的工作特性。更多还原

【Abstract】 International Muon Ionization Cooling Experiment– MICE is one of the advanced research tasks on key technology to verify the feasibility of neutrino factory and muon collider. The superconducting coupling solenoid magnet, as one of the key components in the MICE equipment, is to produce a magnetic field about 2.6T along the beam center line to control the muon beam in the RF cavity located inside them. Quench of superconducting magnet will induce over heating and over voltage in the coil of the magnet and result in permanent damage to the magnet, so the study on quench process and design of the quench protection system are both key aspects for the superconducting magnet design. The coupling magnet wound with commercial copper matrix NbTi conductor and impregnated with epoxy resin is designed to be passivly quench protected by coil subdivision combined with quench-back effect of the mandrel. This dissertation takes the MICE superconducting coupling solenoid magnet as the research object, built its quench process numerical simulation model, studied the variation of its main parameters during quench process in detail and designed its reasonable and feasible quench protection system. The research results of this dissertation will provide theoretical and practical application guidance for the quench protection system design of the coupling magnet and similar solenoid magnets. The main research contents in this dissertation are as follows:In order to design reasonable quench protection circuit for the coupling magnet, the quench process of the coupling magnet was studied by semi-empirical numerical simulation. Considering the quench-back effect from mandrel in the classical quench simulation method based on quench propagation method, a semi-empirical numerical model for simulation of the quench process of the coupling magnet was built. According to the experimental results of the quench process of a successfully operated experimental superconducting magnet, compared with the calculated results of the model, the model was verified. The model was applied to study the effect of subdivision number, protection resistance, material of banding on the quench process of the coupling magnet, and a reasonable quench protection circuit was designed for the coupling magnet. In order to throughly understand the quench process of the coupling magnet, the eddy current in the mandrel and the quench-back effect induced, the quench process of the coupling magnet was further studied by finite element simulation. Based on the coupled field analysis function of ANSYS, considering quench-back effect of the mandrel, a transient coupled thermal and electromagnetic finite element model for the quench process was build. The model was applied to calculate the quench process of the coupling magnet, the calculated results by the finite element model were compared with the calculated results by the semi-empirical model and the finite element model was verified. The quench-back effect of mandrel was further studied by this model, and the advantage and disadvantage of the finite element model and the semi-empirical model were pointed out.The calculation results of the over heating in the magnet is roughly accurate by the open quench simulation methods, but that of the over voltage is very conservative,and a more accurate calculation method for the over voltage in the sub-divided solenoid during quench process is presented in this dissertation. The accurate calculation of the over voltage needs to analyze the voltage distribution in the magnet. The magnet is treated as a circuit comprised of turn unit, and each turn has property of resistance and inductance simultaneously. During quench process the inductance of each turn does not vary and the resistance of each turn varies with the temperature of the turn. According to the transient temperature and current of each turn, the distribution of the resistive voltage, inductive voltage and resultant voltage along the conductor in the magnet were calculated. The more accurate calculation method for the maximum internal voltage, layer-to-layer voltage and turn-to-turn voltage in the sub-divided solenoid during quench process was presented. This method was applied to study the over voltage in the sub-divided solenoid during quench process and the effect of the subdivision number on the over voltage.Cold diode assembly is a key component of the quench protection system for the coupling magnet, and it works in the temperature range of 4.2~4.8K and at the magnetic field of 1.5~2.5T. All the simulation, analysis and design of the charging, discharging and quench protection circuit of the coupling magnet must be based on the cryogenic performance of the cold diode assembly. A set of cryogenic test system for the diode assembly was built. The forward and the reverse electrifying characteristic of the diode at room temperature and liquid nitrogen temperature, as well as the cryogenic performance of the cold diode assembly under larger forward current condition were measured. Utilizing the measurement and control system of the prototype coil for the coupling magnet, the cryogenic performance of the cold diode at ~10K was tested as well.更多还原