基于（准）衍射极限环的同步辐射光源因其优异的性能成为当前同步辐射光源领域研究的热点。然而，（准）衍射极限环通常动力学孔径较小，这一特点极大地影响了其注入方案的选择。横向在轴注入成为解决（准）衍射极限环注入问题的重要研究方向。在轴置换注入方式是其中唯一已被在设计的（准）衍射极限环光源选用的横向在轴注入方式。而在轴置换注入最关键要解决的问题是增强器能否俘获、加速大电荷量束团。本项目拟结合（准）衍射极限环光源增强器的特点，进行（准）衍射极限环光源增强器中的束流集体不稳定性研究。通过系统地研究增强器物理参数对增强器中的束流集体不稳定性的影响，及系统地研究朗道阻尼等阻尼机制对增强器中的束流集体不稳定性的影响，给出增强器中提高流强限的方法，为增强器设计提供参考。本项目的研究成果将对（准）衍射极限环光源的发展做出原创性贡献，对未来（准）衍射极限环光源的发展具有深远影响和重要的现实意义。

The (quasi-) diffraction limited storage ring based synchrotron light sources have attracted great amount of interests of the synchrotron light sources community, mainly because of the excellent expected performance. However, the very small dynamic aperture of the (quasi-) diffraction limited storage rings limits tremendously the choice of the injection schemes. The transverse on-axis injection becomes the very promising direction to go. The on-axis Swap-out injection scheme has become the only transverse on-axis injection scheme chosen by the specific (quasi-) diffraction limited storage rings under design. However, the essential problem of the on-axis swap-out injection scheme is whether the booster can capture and accelerate the bunches with very high single-bunch charges. In this project, we would like to study the collective beam instabilities in the booster synchrotrons of the (quasi-) diffraction limited storage rings. By carrying out the systematic study of the influences of the booster physical parameters on both single-bunch and coupled-bunch instabilities, we would like to find out the ways of increasing the threshold currents. We would also like to study effects of Landau damping on the beam instabilities. After the studies of this project, we foresee that we could get the strategies of increasing the thresholds of beam instabilities in optimizing the booster design. Therefore, the design of boosters of the future (quasi-) diffraction limited storage rings can follow the strategies. The foreseen results generated from this project will be creative and are important for the future development of the (quasi-) diffraction limited storage ring based light sources.