ENEA C.R. Frascati, Frascati (Roma), Italy
A significant progress has been made in controlling the properties of the radiation emitted by a FEL amplifier. Experiments have demonstrated the possibility both to increase the temporal coherence and to reduce the amplifier length to reach saturation, by seeding it with an external source. This may be a solid state, short pulse, laser (Ti:Sa,OPA..), doubled or tripled in a crystal, or a high order harmonic pulse generated in gas. The coherence improvement and the increased compactness of the source are only the first beneficial offspring of this marriage between the optical laser world and that of FELs. Non-linear effects in the seeded FEL dynamics may be exploited to shorten the pulse length beyond that allowed by the FEL natural gain bandwidth. Multiple seed pulses can be used to generate pulses whose temporal distance and properties are also controlled. Similarly, the FEL gain can be adapted to match the seed properties by tailoring the electrons phase space to generate ultra-short output pulses at unparalleled intensities. I had the honor (and luck) to participate in many relevant experiments at the SPARC and FERMI FELs and I will give my personal overview.
KAERI, Daejon, Republic of Korea
Shanghai Jiao Tong University, Shanghai, People's Republic of China
Beam manipulation is a process to rearrange beam's distribution in 6-D phase space. In many cases, a simple phase space manipulation may lead to significant enhancement in the performance of accelerator based facilities. In this paper, I will discuss various beam manipulation techniques for tailoring beam distribution in modern accelerators to meet the requirements of various applications. These techniques become a new focus of accelerator physics R&D and hold great promise in opening up new opportunities in accelerator based scientific facilities.