超导波荡器磁体关键技术研究

A superconducting undulator has many advantages, such as a short cycle length, a high magnetic field strength, and a flexible adjustability of both magnetic field strengths and polarization modes. When applied in a synchrotron radiation light source, a superconducting undulator can produce x-rays with a high strength and a high brightness, which could be used in many applications, such as biological molecules structure determinations, early stage cancer diagnosis and treatments, which will greatly upgrade the research capacity of a synchrotron radiation light source. At present, superconducting prototype undulators are under development in many foreign synchrotron radiation facilities. A superconducting magnet for a superconducting undulator is required not only to withstand the long time high energy x-ray radiation, and the heat arising from x-rays beam imaging currents, but also to meet the demanding requirement of producing an ultra short period magnetic field with amplitudes and phases of a high degree of consistency based on axial arrayed coils. This project is planned to research niobium titanium superconducting racetrack magnets for superconducting undulators through the magnet design, the coil winding, the epoxy impregnation, and the analysis of magnet stability by shimming between layers edges, using winding clamps to make the superconducting wires align compactly, expecting to master key technologies of developing superconducting undulator magnets, to lay a foundation for the independent development of superconducting undulators for both the third phase of Shanghai Synchrotron Radiation Facility project and Shanghai Free Electron Laser project.

超导波荡器具有周期长度小、磁场强度高、磁场强度和极化方式调节方便等优点。将超导波荡器应用在同步辐射光源上，可提高x射线的强度和亮度，开展生物分子结构测定、癌症早期诊断及治疗等，极大地提升同步辐射光源的综合研究能力。目前国外很多同步辐射机构正在开展超导波荡器的样机研制工作。用于超导波荡器的超导磁体不但要长期承受高能x射线辐射和束流镜像电流产生的热量，并且要满足多对线圈轴向排列产生的超短周期磁场的幅值和相位高度一致等苛刻要求。本课题拟以铌钛超导线材绕制的跑道磁体为研究对象，开展磁体设计、绕线工艺研究、环氧浸渍工艺研究、磁体稳定性分析，采用爬层垫补工艺、利用绕线夹具，使超导线紧密排列，掌握超导波荡器线圈磁体研制的关键技术，为上海同步辐射光源三期工程和上海自由电子激光项目所需超导波荡器的自主研制奠定基础。

波荡器是一种同步辐射光源插入件。相比于已有的永磁波荡器，超导波荡器在给定的磁间隙和周期长度能产生更高的磁场，或者维持较高磁场强度的同时缩短周期长度，因此能够提高同步辐射光源的能量与亮度。超导波荡器是第三代和第四代光源插入件未来的发展趋势，目前国外多个同步辐射机构正在开展超导波荡器的研制工作或已经实现稳定运行。超导波荡器磁体是产生所需磁场的核心部件。本课题的研究内容为超导波荡器磁体所涉及的关键技术，包括磁体的磁场与机械设计、磁体绕线技术研究、磁体的环氧浸渍技术研究，以及低温测试、磁场测量与失超保护技术。本课题研究取得的重要结果包括：研制成功多个超导螺线管线圈，研制成功2台5周期超导波荡器磁体，进行了低温励磁实验，实现了5周期磁体的长时间稳定运行，并完成了5周期磁体的磁场测量实验，测量结果与设计结果相符合。磁体临界电流达到433.2 A，接近超导线材短样的临界电流，并且能稳定运行在400 A，沿束流轴线产生正弦波形磁场，峰值达到0.93 T（磁间隙为8 mm时）。研究结果验证了超导波荡器磁体工艺技术的可行性与可靠性，表明课题组已经掌握了NbTi超导波荡器磁体研制的关键技术，对于我国同步辐射光源插入件的自主研发具有重要意义。