• A. Willner, S. Düsterer, B. Faatz, J. Feldhaus, H. Schlarb, S. Schreiber, F. Tavella
  DESY, Hamburg
• S. Hädrich, J. Limpert, J. Rothhardt, E. Seise, A. Tünnermann
  Friedrich Schiller Universität, Jena
• J. Roßbach
  Uni HH, Hamburg

The performance of fourth generation light sources is of interest in many fields in nature science. Different seeding schemes for FELs are under investigation to improve timing stability, pulse shape and spectrum of the amplified XUV or X-ray pulses. One of the most promising schemes is direct seeding by high-harmonic generation (HHG) in gas. A seeded free electron laser with a tuneable wavelength range from 10 to 40nm and a bunch frequency of up to 100 kHz (1 MHz upgraded), as proposed for FLASH II (collaboration HZB/DESY), makes high demands on the HHG seed source concerning conversion efficiency and stability. However, the most challenging task is the conception of a laser system with a repetition rate of 100 kHz (1 MHz upgraded). The key parameters for this laser amplifier system are pulse energies of 1-2mJ and sub-10fs pulse duration. We report on the development status of the required laser system for the seed source and give an overview of first concepts for the HHG target setup which can comply with the requirements of a new seeded FEL at DESY.