基于非线性空间电荷振荡效应的电子束序列产生与优化

Generation and optimization of electron bunch trains from nonlinear longitudinal space charge oscillation

基于非线性空间电荷振荡效应可以进行超短电子束纵向整形,本文在清华大学汤姆逊散射X射线源平台上,利用此效应对ps间隔超短电子束序列的产生进行了优化研究.实验分别产生了总电荷量约为1 nC的7个和15个微束团,通过控制束流参数优化其聚束因子,并通过改变微波电子枪的发射相位实现了电子束微脉冲间隔从0.5到1.4 ps的调节.电子束序列形成后,由S波段加速管进一步将能量提高到~45 MeV以冻结纵向分布.本文还测量了该电子束相干渡越辐射产生的窄带太赫兹辐射,结果与电子束序列纵向结构预测一致.

We report the generation and optimization of electron bunch trains consisting of femtosecond microbunches with picosecond spacing using nonlinear longitudinal space charge oscillations at the Tsinghua Thomson scattering X-ray source platform.The electron source parameters were optimized to enhance the final bunching of the electron bunch trains with different numbers of microbunches and modulation periods.Seven or 15 microbunches with a total beam charge of up to~1 nC were produced in the experiment,and the spacing was tuned from 0.5 to 1.4 ps by changing the launching phase of the radiofrequency gun.After the formation of microbunches,the beam was accelerated to~45 MeV with an S-band linac to freeze the longitudinal phase space.Narrow-band coherent transition radiation from the bunch trains that passed through a thin Al film was measured.