磁压缩对高频稳定性的要求

Impact on the magnetic compression due to RF instability

曲柄式磁压缩系统是北京大学SASE自由电子激光装置中非常重要的部分,通过其对电子束团的压缩为扭摆器提供高流强、短脉冲的电子束,使电子束在扭摆器内较短的距离实现饱和出光。曲柄式磁压缩需要利用偏离高频峰位的加速相位使得电子束产生能量-位置关联,主要讨论高频相位抖动与能量-位置关联的相互关系,高频相位抖动使得束团的能量-位置关联不同,即束团内电子能量随位置分布不同。进而研究其对磁压缩性能的影响,即能量-位置关联不一样会导致磁压缩得到的束团长度出现涨落。

Magnetic compressor is a very important part for SASE FEL facility at Peking University （PKU SASE FEL）, which is used to produce short electron bunches in order to satisfy fast lasing saturation of SASE in undulator. In this paper, the fundamental principle of magnetic compression is analyzed, which shows that the effect of bunch compression is closely related with the RF instability. By using the design parameters of magnetic Chicane of PKU SASE FEL, the impact of RF instability on the magnetic compression is given. The final bunch length will change due to RF instability. So, a goal for RF instability control is proposed according to the requirement of PKU FEL.