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题名	高梯度射频超导腔及其功率耦合器材料的研究; 高梯度射频超导腔及其功率耦合器材料的研究
作者	1温华明,电工研究所
学位类别	博士
答辩日期	2005
授予单位	中国科学院电工研究所
导师	1严陆光,电工研究所
关键词	射频超导电性 超导腔 高纯铌 直线加速器 TESLA（ILC） 热失超 电子束焊接 低温热导 RRR Superconducting Cavity High Purity Niobium Copper Plated Steel Linear Collider TESLA(ILC) High Gradient Superconducting Cavity
其他题名	高梯度射频超导腔及其功率耦合器材料的研究
学位专业	电工理论与新技术
中文摘要	国际高能物理界一致认为下一个大型高能加速器将是500GeV-ITeV正负电子直线对撞机并已确定采用超导技术。TESLA（TevEnergysuperconductingLilleorAccelerator）计划始于1992年，研究目的是将超导腔的加速场梯度从当时的lOMV／m左右的平均水平提高到25MV／m以上。本论文介绍了射频超导腔的墓本知识及其最新研究成果，重点介绍高梯度场射频超导腔用高纯妮材料及功率琦祝合器用不锈钢铜镀层方面的研究成果。首先，研制了一套基于液氦贮槽的低温测量系统，测量温区为2．5K至10K，深入地研究了高纯妮的热导性能。大量的测星表明热导与RRR之间在3-1OK之间的一致关系。其次，建立了一系列RRR测量系统。在国际上首次对不同RRR值高纯度妮的磁阻进行了大量试验，发现在O-3T的磁场区，磁阻特性为线性关系，并得到高钝妮的磁阻系数约为2．93x10~(-12)ΩmT。这些数据为在'磁场外延法，测量超导铌的RRR建立国际标准提供了重要的数据。对涡流无损探测RRR的方法进行了深入的研究，独创了一套有效的测量及校准的方法。研制了一套用于超导腔RRR在线测试的27探头的测量系统，实际应用于TTF超导腔在加工和热处理过程中腔体材料性能的监测。对近100个超导腔与RRR的关系进行的统计分析表明BCP（bufferedcllemicalpolislling）化学抛光的超导腔加速场梯度呈现E_accOC（RRR）~（1/2）的关系，而对于EP（Eleetro-Polishing）电化学抛光的超导腔，当RRR大于2OO时，E_acc基本上与RRR无关。第三，实验研究了一些污染高纯度妮的一些因素，如机加工、电子束焊接、机械抛光、化学抛光、电化学抛光等以及彤响纯妮RRR均匀性的各种因素。在国际上率先开展了超高真空（10~(-6)mbar-10~(-8)mbar）下的电子束焊接对高纯妮性能的影响研究并探讨了其机理。研究表明，在气压低于5xl0~(-6)mbar时，可以适当提高焊接区的性能，但在热影响区仍存在着一定程度的退化，表明在高真空下，热影响区的性能对腔体性能影响更为值得关注。真空高于10~(-7)mbar时，焊接区性能不再提高，表明更高的真空度已没有必要。气体分析表明，在电子束焊接的搭接区发现氢和氧的过度集中现象，氧和氢的含量远远高于其他地方。由于氢与超导腔品质因素的退化有直接关系，这一发现对进一步改进电子束焊接工艺有着重要的意义。第四，实验研究了热处理对高纯度妮机械性能的影响。研究表明高温800一1400℃热处理对高纯铌的弹性形变基本没有影响，但对塑性形变影响较大。为优化无焊缝超导铌腔液压成形技术，研究了高纯铌管的脉冲应力应变性能。第五，参与了涡流无损检测技术应用于铌板的缺陷和杂质的扫描研究，试验表明这种方法可以检测出O．2mm大小的缺陷。目前正在参与sQUID扫描系统在铌板缺陷和杂质的扫描研究，初步试验表明可以检测出O，lmm大小的缺陷。最后，研究了热处理对功率耦合器用不锈钢表面铜镀层的影响，为优化工艺提供了理论和实验的依据。 TESLA international collaboration R&D program has been dramatically successful at pushing the gradient of bulk niobium superconducting cavities from the non competitive level around lOMV/m to the level required for linear collider application. The best 9-cell cavity AC71 has reached the highest accelerating gradient over 40MV/m. To the progress of the cavity performance, many technical aspects have made contributions, among which strict material and welding quality control plays a very important role. This thesis is devoted to the investigations of the high purity niobium for high gradient superconducting cavity and copper plated steel for the power coupler.For material investigation, a series of test systems were developed, including a computer controlled ciyogenic thermal conductivity measurement apparatus based on a transportable storage dewar, two kinds of RRR measurement methods for samples and an eddy current RRR measurement system for cavity in-situ material property control, eddy current scanning system and SQUID scanning system, tensile test device and gases analysis instalments.Based on the above-mentioned test systems, basic properties of high purity niobium such as thermal conductivity, RRR, microstructures, mechanical properties, foreign inclusions and heat treatments influence on the properties of copper plated steel were investigated. Eddy current RRR measurement system made it available to record the RRR data for over 100 TTF cavities. The investigation shows that for BCPpolished cavities the relationship Eacc x -JRRR was statistically observed, while for EP polished cavities Eacc seems to be independent on RRR when RRR>200. Itsuggests that E-polishing probably produces defect-free surface. High RRR and E-polishing has played the main role on pushing the limit of RF superconductivity. The quench driven by local defects, impurity contents and geometrical consideration can be greatly improved or avoided by post purification or e-polishing. The unique DESY electron beam welding facility with the chamber of ultra-high vacuum ( 10" smbar -10"8mbar), made it available to investigate the behaviour of high purity niobium electron beam welded at ultra high vacuum. The RRR degradation and gases concentration at heat affected area were observed, even at the pressure of 10'8mbar. At welding seam, RRR improvement at the pressure < 5*10"6 mbar was seen, but the vacuum higher than 10"7mbar makes no more contribution. The heat affected area near the overlapped place shows more dangerous due to the high gas concentration. These risks may finally be avoided by the fabrication technology of seamless cavity. Some contamination cases of high purity niobium such as machining, CBP polishing, BCP and EP and homogeneity of high purity niobium were also studied.
语种	中文
公开日期	2010-10-18
页码	167
内容类型	学位论文
源URL	[http://ir.iee.ac.cn/handle/311042/6870]
专题	电工研究所_其他部门_其他部门_博士学位论文
推荐引用方式 GB/T 7714	1温华明,电工研究所. 高梯度射频超导腔及其功率耦合器材料的研究, 高梯度射频超导腔及其功率耦合器材料的研究[D]. 中国科学院电工研究所. 2005.

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