Technical Design of the XUV Seeding Experiment at FLASH

The Free electron laser at Hamburg FLASH operates in the Self Amplified Spontaneous Emission SASE mode, delivering to users photons in the XUV wavelength range. The FEL seeding schemes promise to improve the properties of the generated radiation in terms of stability in intensity and time. Such an experiment using higher harmonics of an optical laser as a seed is currently under construction at FLASH. The installation of the XUV seeding experiment sFLASH is going to take place in fall 2009. This includes mounting of new variable gap undulators upstream of the existing SASE undulators, building the XUV seed source as well as installation of additional photon diagnostics and electron beam instrumentation. In this contribution the layout of sFLASH will be discussed together with the technical design of its major component