Study on electron beam dynamics in a merger section of energy recovery linac light sources

能量回收直线加速器是未来X射线和γ射线光源的一种很有前途的候选光源。由于ERL光源的性能受到电子束参数的限制，高亮度电子束的产生是实现未来ERL光源的关键问题之一。研究了ERL并合中的电子束动力学。合并器是将注入和再循环两个光束合并到同一轨迹中的部件。在并合过程中，由于横向空间电荷力、纵向空间电荷力和相干同步辐射的作用，发射度会发生增长。我们已经开发出一种策略性的方法来设计一个ERL合并，以尽量减少发射度的增长，其中发射度的增长是通过匹配空间电荷诱导的色散，以电子感应加速器包络补偿。还开发了粒子跟踪模拟程序，用于计算ERL合并中发射度的增长。我们已经应用我们的发射度补偿技术的紧凑型ERL和伽玛射线源的设计。紧凑型EEL是未来X射线光源的测试设施。基于我们设计的ERL注入器的典型性能如下：平均电流100 mA（77 pC，1.3GHz）时的归一化隆起为0. 3 mm-mrad，10 mA（7.7pC，L3 GHz）时的归一化隆起为0. 1 mm-mrad。

Energy-recovery linac is a promising candidate fir future X-ray and gamma-ray light sources. Since performance of the ERL light source is restricted by electron beam parameters, generation of high-brightness electron beam is one of the critical issues to realize future ERL light sources. We studied on electron beam dynamics in a merger of ERL. The merger is a component to merger two beams, injection and recirculation, into the same trajectory. In the merger, emittance growth may occur due to transverse space charge force, longitudinal space charge force, and coherent synchrotron radiation. We have developed a strategic method to design an ERL merger to minimize the emittance growth, in which emittance growth is compensated by matching space-charge-induced dispersion to betatron envelope. A simulation code for particle tracking has also been developed for calculation of emittance growth in an ERL merger. We have applied our emittance compensation technique to design of the Compact ERL and gamma-ray sources. The Compact EEL is a test facility for future X-ray light sources. Typical performance of ERL injectors based on our design is as follows: normalized eminence 0.3 mm-mrad for average current 100mA (77pC, 1.3GHz), 0.1 mm-mrad for 10 mA (7.7pC, L3GHz).