Test of HHG chambers for seeding at SPARC

We propose to use High Order Harmonic Generation (HHG) in gases to seed the SPARC FEL (Frascati, Italy) in the high gain harmonic generation configuration. HHG produces a coherent XUV source by focussing an intense laser pulse into a gas medium. This output radiation is composed of fundamental and odd harmonics of the laser. Dedicated chambers have been realized and tested at the CEA (Saclay, France). They allow generation and shaping of the harmonic beam for further focussing at variable position. A final periscope will allow the injection of the selected harmonics inside the first section of the undulator. The SPARC facility will deliver an electron beam at 200 MeV, passing through a six sections long undulator. Injection of the third and fifth harmonics (266 and 114 nm) is foreseen. Nonlinear harmonics could enable to reach 32 nm. In this paper, we present the tests performed on the seeding chambers, as well as simulations of the expected performances of the HHG seeded FEL