Seeding the FEL of the SCSS prototype accelerator with harmonics of a TI: SA laser produced in gas

A particular seeded configuration will be tested in 2006 on the SCSS prototype accelerator (SPring-8 Compact Sase Source, Japan). This facility is based on a thermionic cathode electron gun (1 nC), a C-band LINAC (5712 MHz, 35 MV/m) and an in-vacuum undulator (15 mm of period. 2 sections of 4.5 m length). The maximum electron beam energy is 250 MeV and the SASE emission from visible to 60 nm can be obtained. The external source, coming from the High order Harmonic Generation (HHG) process, can be tuned from the 3^rd (266 nm) to the 13^th harmonic (60 nm) of a Ti: Sa laser generated in a gas cell. The experiment contains a first chamber, dedicated to harmonic generation and a second one for harmonic beam diagnostics and adaptation of the harmonic waist in the first undulator section. The tests have been performed in Saclay (15 mJ, 10 Hz, 50 fs). An energy of 2 μJ with a high stability for the 3 ^rd harmonic and a good transversal shape with an optimized energy level and a high stability for the 13^th harmonic have been obtained at the first undulator center place. The performances using analytical formulas, GENESIS and SRW have been updated. The chambers will be installed on the SCSS prototype accelerator in the beginning of October for the seeding tests.