FLASH II:A SEEDED FUTURE AT FLASH

FLASH has been a user facility since 2005, delivering radiation in the wavelength range between 7 and 47 nm using the SASE principle. After the present upgrade, the wavelength range will be extended to wavelengths below 5 nm and with the 3rd harmonic accelerating module in place to linearize the longitudinal phase space, the stability and reproducibility of the machine will be improved. So far the user requests for beam time by far exceeds the time available. In order to increase user beam time and improve the radiation properties delivered to users, a mayor extension of the user facility called FLASH II has been proposed by DESY in collaboration with the HZB, which is a seeded FEL over the parameter range of FLASH. As logical continuation, the HHG development program started with sFLASH will result in direct seeding. Because in the foreseeable future there will probably not be HHG seed lasers available at high repetition rates down to wavelengths of 4 nm, a cascaded HGHG scheme is proposed to produce short wavelengths. After a first design report, the project now enters its preparation phase until the decision for funding will be taken. During this time, the FLASH beam parameters after the present upgrade 2009/2010 will be characterized and the present design will be re-evaluated and adjusted. In addition, complete start-to-end simulations will complete the simulations which have been performed so far, including a complete design of the extraction area.