FEL振荡器的短脉冲和三维效应

SHORT PULSE AND THREE-DIMENsIONAL EFFECTS OF FEL OSCILLATOR

利用自编的ＦＥＬＯＳ程序，考察了自由电子激光振荡器的短脉冲效应和三维效应，看到了光束团的亮斑化过程。除了初始阶段的Ｌｅｔｈａｒｇｙ效应外，亮斑的移动速度大于光速。而三维效应则部分减弱了电子束的群聚，模糊了超辐射所带来的亮斑束周期结构，形成了几乎单一的亚皮秒主亮斑。应当指出，这为ＦＥＬ的应用提供了新的可能。

sing FELOS code developed by us,effects of short pulse and three dimension are investi-gated for FEL oscillator.It show that the short pulse effects result in three aspects:(a)The sat-uration phenomenon of fundamental mode is washed out.(b)The sidebands instability is en-hanced,(c)Optical pulse width is contracted and phenomenon of optical spike appears Thoughthere is so called “lethargy” effect during the early stage of FEL oscillation,the speed of spikes isalways larger than speed of lihgt in vacuum,after the length of synchrotron oscillation periodequals to the one of wiggler.Comparing with one dimensional calculation,we point out that,the3D effects destroy the bunching of electron beam,it causes the degression of optical power and re-sults in washing out the periodic structure of optical spikes appearing in l-D simulation andmakes the optical beam being nearly single spike of sub-picosecond length.It is stressed thatsub-picosecond-scaled pulse will open new possibility of application of FEL.