低温永磁波荡器冷却关键技术的研究

发布时间：2018-03-16 21:25

本文选题：低温永磁波荡器　切入点：磁体冷却技术　出处：《中国科学院研究生院(上海应用物理研究所)》2017年博士论文　论文类型：学位论文

【摘要】：低温永磁波荡器(Cryogenic Permanent Magnet Undulator,简称CPMU)利用稀土永磁材料钕铁硼或镨铁棚在低温下的剩磁及内禀矫顽力大幅增大的特性,通过使磁体工作在50K~150K的低温环境,获得相比于常规真空内波荡器(In-vacuum Undulator,简称IVU)高约30%~50%的磁场性能。低温永磁波荡器是近几年同步辐射光源插入件技术发展方向的一大热点,它依赖高性能永磁铁在低温下的特殊性能大幅提高了波荡器的峰值磁场,因而对光源束流品质的提高有着重要的作用。当前,CPMU仍处于试制阶段,低温冷却是其研制的关键技术之一。本论文对CPMU及其冷却技术的国内外研究工作进行了较全面的调研,对低温永磁波荡器冷却的总体方案、热负载特性、磁体冷却回路和传热特性、冷却结构和调温方案,磁体冷缩变形等开展了细致且深入的理论分析和实验研究工作,验证了仿真模型和分析结果的可靠性和适用性。具体研究内容如下:1)CPMU磁体冷却的总体方案设计。根据CPMU样机的物理和冷却设计要求,结合所采用的钕铁硼磁化块的磁物性特点以及磁结构特点,分析CPMU研制过程(如先磁场测试与垫补再上线运行)各阶段的低温测试及运行的特点和要求,确定上海光源的钕铁硼CPMU样机采用过冷液氮冷却方式并采用导冷隔热组件结构对CPMU的内大梁及其上固定的磁体进行传导冷却的总体方案。2)CPMU热负载研究。首先对CPMU在线运行和离线磁测两种工况下对磁体冷却的要求进行分析,对各工况下的热负载来源进行综合分析,对热负载的各组成部分的关键影响因素构建理论模型进行研究,合理确定其设计工况。其次,利用理论分析模型对CPMU试验件进行热负载的分析,以减小漏热量为目标,对相关结构进行优化设计;然后,对其进行实验测试,修正相关理论分析模型,探索热负载的实验测量方法,实验论证了采用导冷组件传热法进行热负载分析相比于液氮换热法的合理和准确性。最后,根据经验证并改进了的CPMU热负载理论分析方法和实验测试方法,对CPMU样机进行了静态热负载的理论分析和离线磁测工况下的实验测试。CPMU样机的离线测试的工作温区120K~170K,冷量消耗为200W~418W,满足离线磁场测试的温区调节要求。此外,CPMU样机成功安装与上海光源在线测试,测到了220W的最大动态热负载,基本符合动态热负载估算值200W。3)CPMU磁体的冷却回路研究。首先对CPMU磁体冷却回路的布局方案进行定性分析,利用有限元分析方法对不同方案进行模拟分析,结合CPMU磁体温度均匀性的要求以及过冷液氮的流动阻力和液氮均等分配问题,对CPMU上下大梁采用两条并联冷却回路分别进行冷却的方案。其次,对CPMU磁体冷却回路建立了对流换热理论分析模型,从过冷液氮的流态、流动阻力、冷却工质过冷度等方面进行优化,确定了冷却管内径为8mm。再次,结合CPMU热负载分析结果,对冷却回路中过冷液氮的流动换热参数进行分析,研究其流动阻力、对流换热系数、对流换热热阻等参数的变化规律,分析得出CPMU磁体冷却结构中对流换热热阻仅占总热阻的1.3%,可以被忽略。最后,利用CPMU试验件对CPMU磁体的冷却回路进行了试验研究,实验证明CPMU试验件所采用的冷却回路布局方案具有大梁温度均匀性受冷却回路过冷液氮进出口温差影响小的优点,该方案已应用于CPMU样机的研制中。4)CPMU磁体冷却结构和调温方案研究。首先,结合CPMU的热负载理论分析结果与热源分布特点,提出了对CPMU样机磁体及其内大梁的端部和吊杆附近采用不同的导冷隔热组件的冷却结构方案。之后,以降低CPMU磁体内大梁温度不均匀性为目标,利用有限元分析软件对导冷隔热组件的设计方案建立仿真模型并进行了优化和模拟验证。最后,对CPMU样机变工况过程中的温度分布变化与热负载变化进行了试验研究。CPMU样机在离线磁测过程中大梁最大温差始终低于2K,为CPMU样机磁场相位误差达到设计要求提供了有力保证。5)CPMU磁体冷缩变形的研究。首先,建立了CPMU磁体冷缩变形的理论分析数值模拟仿真模型。然后,利用CPMU磁测平台上集成的磁间隙测量装置对CPMU低温下的磁间隙进行测量实验,验证了磁间隙冷缩变形的仿真模型和分析结果的准确性。此外,针对CPMU样机磁场相位误差随温度发生变化的现象,利用有限元分析软件对CPMU样机低温下的冷缩变形分布进行仿真模拟研究,分析CPMU磁间隙冷缩变形对峰值磁场分布的影响。结合CPMU样机的低温磁测结果,得出了CPMU磁体内大梁冷缩变形引起的磁间隙变化一致性是CPMU低温下磁场相位误差的关键影响因素之一,指出了CPMU样机的改进方向。通过对CPMU样机局部磁场进行室温下的预垫补,补偿磁间隙低温下的不一致冷缩变形,使CPMU样机的相位误差在室温与低温下均小于3度,达到国际水平。
[Abstract]:Low temperature permanent magnet undulator (Cryogenic Permanent Magnet Undulator, referred to as CPMU) based on the characteristics of rare earth permanent magnet materials or praseodymium neodymium iron boron iron shed at low temperature, remanence and intrinsic coercivity increases sharply, the magnet in the low temperature environment of 50K~150K, was compared with the conventional vacuum undulator (In-vacuum Undulator referred to as IVU) high performance magnetic field of about 30%~50%. Low temperature permanent magnet undulator is a hot topic in recent years, the synchrotron radiation source insert technology development direction, it depends on the high performance permanent magnet properties at low temperature, a substantial increase in the peak magnetic undulator, plays an important role in the quality of light beam flow improved. At present, CPMU is still in the trial stage, low temperature cooling is one of the key technologies to develop a more comprehensive research. This paper on the CPMU and its cooling technology at home and abroad research work on low temperature permanent magnet The overall scheme of undulator cooling, heat load, cooling circuit and heat transfer characteristics of magnet, cooling structure and temperature shrinkage deformation magnet program, carried out theoretical analysis and experimental research work detailed and thorough, verify the reliability of the simulation model and analysis results and applicability. The specific contents are as follows: 1) the overall design scheme of CPMU magnet cooling. According to the requirement of the CPMU prototype and physical cooling design, combined with the magnetic properties of NdFeB magnetic blocks and magnetic structure characteristics, analysis of the CPMU development process (such as the first field test and re shimming on-line operation characteristics and requirements of low temperature test) and the operation of each stage, Shanghai the source of Nd-Fe-B CPMU prototype using supercooled liquid nitrogen cooling and the overall scheme used in beam guide cold insulation structure of CPMU and the fixed magnet.2 CPMU heat conduction cooling) Study on load. The requirements of the magnet cooling CPMU online and offline magnetic operation under two conditions were analyzed under the condition of the heat load on the source of comprehensive analysis, the key factors of each part of the construction of the theoretical model of thermal load were studied, to determine a reasonable design conditions. Secondly, analyze the heat the load on the CPMU test by using the model of theory analysis, by Jian Xiaolou heat as the goal, to optimize the design of the relevant structure; then, the experimental test is carried out for the analysis, model updating theory, explore the experimental method to measure the thermal load. The experiment demonstrated that using conductance method heat transfer component thermal load analysis compared to the liquid nitrogen heat exchanger the method is reasonable and accurate. Finally, according to the CPMU verified and improved the thermal load of theoretical analysis and experimental method, the CPMU prototype of the static heat load theory The off-line test test.CPMU prototype analysis and off-line magnetic conditions of the working temperature range of 120K~170K, the consumption of cooling capacity is 200W~418W, meet the temperature regulation requirements off-line magnetic field test. In addition, the CPMU prototype successfully installed with Shanghai light source online testing, measuring up to 220W maximum dynamic thermal load, accord with dynamic thermal load estimated 200W.3) cooling circuit of CPMU magnet. The qualitative analysis of the first CPMU magnet cooling circuit layout scheme, simulation analysis of different schemes by using the finite element analysis method, combined with the requirements of CPMU magnet temperature uniformity and subcooled liquid nitrogen flow and distribution of liquid nitrogen. All the problems on the CPMU under the beam by two a parallel cooling circuit for respectively cooling scheme. Secondly, the CPMU magnet cooling circuit has established the theory of convection heat transfer analysis model, the flow state of the subcooled liquid nitrogen, flow resistance, Cooling subcooling degree has been optimized, the cooling pipe diameter is 8mm. again, with CPMU thermal load analysis, thermal parameters of the supercooled liquid nitrogen cooling circuit of the flow analysis on the flow resistance, heat transfer coefficient, convective heat transfer and thermal resistance variation parameters, analysis the CPMU magnet cooling structure in convective thermal resistance accounted for only 1.3% of the total thermal resistance, can be ignored. Finally, experiments were carried out using CPMU CPMU magnet cooling circuit of test pieces, and prove that the CPMU test of the cooling circuit layout case with beam temperature uniformity by the import and export of subcooled liquid nitrogen cooling circuit the advantages of small temperature difference, the development scheme has been applied in the prototype of CPMU.4 CPMU) study cooling structure and temperature regulation scheme with CPMU magnets. Firstly, the thermal load of the results of theoretical analysis and heat distribution characteristics, put forward Cooling structure of CPMU prototype magnet and its inner girder end and the boom near the cold conducting different insulation components. After that, in order to reduce the uneven temperature of CPMU magnet beam as target, using finite element analysis software design scheme to guide cold insulation of the simulation model is established and optimized and simulated. Finally, the prototype of CPMU variable temperature distribution and thermal conditions in the process of load change test has been carried out on the.CPMU prototype in the process of off-line magnetic beam maximum temperature is lower than 2K, the CPMU prototype field phase error to meet the design requirements to provide a strong guarantee and.5) CPMU magnet deformation research. Firstly, established the CPMU magnet and contraction the deformation of the theoretical analysis numerical simulation model. Then, the CPMU magnetic platform integrated magnetic gap measuring device using magnetic gap of CPMU low temperature measurement experiment, To verify the accuracy of the magnetic gap and simulation model and analysis results of deformation. In addition, the prototype of CPMU magnetic phase error changes with temperature and contraction of the phenomenon, the prototype of CPMU low temperature deformation simulation of distribution using finite element analysis software, CPMU analysis of the magnetic gap and contraction deformation effect on peak magnetic field combined with low temperature. The magnetic CPMU prototype, the CPMU magnet in the magnetic gap and beam deformation caused by the change of consistency is one of the key factors influencing the magnetic phase error CPMU under low temperature, pointed out the improvement direction of CPMU prototype. Through pre shimming at room temperature on CPMU prototype of the local magnetic field, the magnetic gap compensation under low temperature and inconsistent the phase error of deformation, the prototype of CPMU at room temperature and low temperature are less than 3 degrees, reached the international level.

【学位授予单位】：中国科学院研究生院(上海应用物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TL503

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