同步辐射加速器小孔径真空系统关键技术研究

The thin-wall small aperture vacuum system was originally developed for Shanghai Synchrotron Radiation Facility (SSRF). It is also designed to be compatible with next generation low-emission synchrotron radiation facility vacuum system. In order to get high quality of synchrotron radiation, insertion device is introduced to synchrotron radiation accelerator. In SSRF, the small size of the magnetic gap (~16 mm) at elliptical polarization undulators sets an upper limit on the aperture of the vacuum system. The next-generation low-emission synchrotron radiation facilities will be compact systems. These raise many challenges in vacuum system design, such as vacuum chamber fabrication, vacuum pump arrangement and synchrotron radiation power adaption. We propose to study several key technologies of small aperture vacuum system, including the effect of small aperture to electron beam, antisymmetric hole aperture and the Non-Evaporable Getter (NEG) coating technique on the inner wall of the bend section of the vacuum chamber. We propose to build a prototype to be installed and tested on the SSRF storage ring. This study is of great significance not only to SSRF insertion device vacuum system, but aslo to free electron laser facility and low-emission synchrontron radiation facility vacuum system.

随着同步辐射和自由电子激光技术的发展，先进的束流物理设计要求磁聚焦强度越来越高，磁铁孔径或间隙越来越小，同时元件布局也非常紧凑。这些发展趋势给真空系统设计、建造和运行维护带来诸多挑战，包括真空室结构对束流的影响、真空室制造、真空获得与保持、同步辐射功率处理等等。本课题将以同步辐射光源小孔径真空系统为对象，对电子束流及同步辐射光子与小孔径真空室相互作用进行分析，确定对插入件真空系统的技术要求；对薄壁非对称小孔径真空室制造中的关键技术进行研究，包括真空室成型、加工及表面处理，内表面抽气膜蒸镀工艺等；完成一台用于椭圆极化波荡器的铝合金真空室研制，并安装在上海光源直线节上进行带束流运行与测试。本项目研究对于上海光源插入件高性能真空系统建设、自由电子激光装置真空系统设计，以及未来更低发射度光源设计与建设具有重要意义。

经过四年研发，完成了小孔径真空室的研制，包含椭圆孔径铝拉伸真空室和圆孔径无氧铜真空室；并对研制成功的小孔径真空进行了NEG镀膜研究，特别是低激活温度的小孔径铝拉伸真空室NEG镀膜后极限真空达到5E-9Torr水平，；建立了小孔径真空度NEG镀膜装置系统；在上海光源储存环上测试了小孔径椭圆未NEG镀膜真空室带束流运行情况。为上海光源未来的低发射度储存环研究计划提供真空技术储备。