【作者】 贺守波；

【导师】 赵红卫； 张小奇； 何源；

【作者基本信息】 中国科学院研究生院（近代物理研究所） ， 核技术与应用， 2014， 博士

【摘要】 超导半波长谐振腔（half-wave resonator, HWR）在二十世纪九十年代由美国阿贡国家实验室首次研制成功。超导HWR腔具有结构紧凑，无横向束流偏转效应等优点，已经逐渐发展成为中低能直线加速器的主要加速结构之一。它是基于TEM电磁场模式的二分之一波长的同轴型加速结构。中国科学院先导科技专项ADS嬗变系统计划研制流强达到10mA，能量达到50MeV的超导直线质子加速器，其直线注入器II中2.1~10MeV加速器采用两种不同β的超导HWR腔。对于超导腔而言，Q值一般较高，论文研究的超导HWR腔工作在162.5MHz，有载品质因数较高，工作带宽窄，通常仅有几十赫兹，因此超导腔工作的稳定性是国际上的难点课题。本论文研究了用于直线注入器II中频率为162.5MHz，最优β为0.10的Squeezed型HWR腔的结构稳定性。基于有限元法的多物理场耦合分析计算了HWR腔的各失谐因素，包括氦压敏感度系数计算，洛仑兹失谐效应分析，颤噪效应分析，以及腔体降温频漂等。论文引入弹性边界作为超导腔约束条件，提高了仿真计算与超导腔垂直测试、水平测试的结果的符合程度。此外，根据失谐分析结果，对Squeezed型HWR腔体进行了结构上的优化设计，提出了有效提高腔体结构稳定性的设计方案，确保超导HWR腔运行的稳定。直线注入器II5~10MeV超导段拟采用频率162.5MHz，最优β为0.151的Taper型HWR腔。论文分析腔体的电场和磁场分别对氦压敏感度系数K P的贡献量。鉴于HWR腔体的电磁场模式和Taper型腔结构的特殊性，提出一种氦压敏感度系数为零的设计方法。通过对提高腔体磁场区的结构稳定性和降低腔体电场区的结构稳定性两方面的深入探讨，最终确定了腔体氦压敏感度系数为零的设计方案。论文研究了低β超导HWR腔频率调谐方法。首先从理论上分析HWR腔体的调谐参数，包括腔体的调谐敏感度、调谐范围、调谐精度、幅值相位稳定度要求等。根据超导HWR腔对频率调谐的要求，结合HWR超导腔的结构特点，设计并研制了一套由步进电机驱动的慢调谐装置，通过超导HWR腔常温测试和水平测试结果表明调谐器能够稳定运行。此外，论文提出常温运行下和低温运行下的piezo快调谐器两种设计方案，提高了调谐器的调谐性能，抑制回程滞后等现象，实现对氦压波动、洛仑兹失谐等因素引起超导HWR腔频漂漂移的快速响应与调整。更多还原

【Abstract】 The superconducting (SC) half-wave resonator (HWR) was firstly proposed andfabricated at Argonne National Laboratory in1990s. It has a compact structure. Themain advantage of HWR cavity is that there is no vertical beam steering effect becauseof the geometry symmetry in vertical direction. Considering the advantage, it has beendeveloped as one of the primary choice of accelerating structures in low and medialbeta sections. The SC HWR is a coaxial type element based on the TEM mode. Thesuperconducting linac of China ADS (Accelerator Driven sub-critical System) is about10mA of current and50MeV of energy. Two different types of superconductingHWR are employed by injector-II in ADS project, which is in the charge of Institute ofModern Physics. However, because the load quality factor of SC cavity usually isextremely higher than that of room temperature cavity, its bandwidth is quite narrow(generally scores of Hz). Furthermore, the resonant frequency of the SC HWR ishighly sensitive to mechanical deformations. Therefore, the study on mechanicalstability of a superconducting cavity is an important and difficult issue around theworld.Mechanical stability of the HWR (optimum beta=0.10and the frequency162.5MHz) is studied in the thesis. Mainly, the multi-physics coupled analysis basedon the finite element method is used to calculate the detuning effects of the HWR. Generally, it includes the helium pressure coefficient, the Lorentz force detuningcoefficient, microphonics and the cooling down. A novel analysis method of the elasticboundary condition effect is adopted during the cavity detuning study, which makes asuperposition between the simulation and the measurement. According to thesimulation results, the structure optimization for a squeezed HWR cavity has beenfinished and a new design for higher mechanical stability is obtained. In addition, theinitial test results show that the improvement of the cavity is highly effective.Based on the design of a162.5MHz and beta=0.15taper HWR, the contributionof electric field and magnet field to the helium pressure coefficient are analyzedrespectively. Then a new conceptual design, which the helium pressure coefficientequals zero, is introduced in the thesis.The frequency tuning for the low beta HWR is also focused by the thesis. Firstly,the parameters of the tuning are all introduced such as frequency sensitivity, range,resolution and the stability of amplitude and phase and so on. A slow tuner driven bystep motor is designed based on the studies above. The results of the measurementduring room temperature and horizontal test prove the tuner can operate stably. Animprovement plan for the mechanical tuner is proposed after many tests. Finally, theHWR can operate at the correct frequency and suitable accelerating voltage range withthe slow tuner and fast tuner, which are controlled by low level RF. Also two kinds ofpiezo tuner design, operating at room temperature and low temperature, are achieved.The fast tuning systems, which meet the requirement of fast response, improve theperformance of the tuner and reduce the backlash effect.更多还原