I must say that after reading about this concept over the last few days it is one of the most fascinating things. Specificaly the concept of self amplification of spontaneous emission.(SASE) I am wondering is it possible to use a coventional synchronotron as an EFL? Apart from the undulator what else would need to be changed.Because in both cases the electrons need to acquire a relativistic speed. Or does the EFL need to be built from scratch. Also is it a pre condition that in an EFL the path of the elctrons is curved,i mean because the radiation is emmited as they pass over the undulator, so i am thinking it should not make a difference. If anyone understands an EFL a lot, i think its pretty cool and would like some feedback.