• F. Curbis, A. Azima, J. Bödewadt, H. Delsim-Hashemi, M. Drescher, U. Hipp, Th. Maltezopoulos, V. Miltchev, M. Mittenzwey, M. Rehders, J. Roßbach, J. Rönsch-Schulenburg, R. Tarkeshian, M. Wieland
  Uni HH, Hamburg
• S. Bajt, S. Düsterer, T. Laarmann, H. Schlarb
  DESY, Hamburg

Since 2004, the free-electron laser FLASH at DESY has operated in the Self-Amplified Stimulated Emission mode (SASE), delivering gigawatt pulses with wavelengths between 6.5 nm and 40 nm in the femtosecond domain. In 2009, DESY installed an additional radiofrequency module for controlling the phase space of the electron bunches that gives the possibility to generate bunches with high peak currents (~kA), but ten times larger pulse durations (~250 fs) compared to the previous configuration. The relaxed timing requirements of the new configuration make it possible to externally seed FLASH with high-order harmonics of an optical laser below 40nm generated in a gas target (sFLASH). Because in this case amplification is triggered within the seed pulse length instead of starting from shot-noise as in the SASE process, spikes in the temporal/spectral pulse profiles should be absent and the temporal jitter should be eliminated. In this contribution the present status of the sFLASH photon diagnostics including first commissioning will be discussed.

• J. Bödewadt, A. Azima, F. Curbis, H. Delsim-Hashemi, M. Drescher, E. Hass, U. Hipp, Th. Maltezopoulos, V. Miltchev, M. Mittenzwey, M. Rehders, J. Roßbach, J. Rönsch-Schulenburg, R. Tarkeshian, M. Wieland
  Uni HH, Hamburg
• S. Bajt, S. Düsterer, J. Feldhaus, K. Honkavaara, T. Laarmann, H. Schlarb
  DESY, Hamburg
• R. Ischebeck
  PSI, Villigen
• S. Khan
  DELTA, Dortmund

The free-electron laser facility FLASH at DESY (Hamburg) was upgraded during a five month shutdown in winter 2009. Part of this upgrade was the installation of a direct seeding experiment in the XUV spectral range. Beside all components for transport and diagnostics of the photon beam in and out of the accelerator environment, a new 10m long variable gap undulator was installed upstream of the existing FLASH undulator system. The seed pulses are generated within a noble gas jet by focusing 40 fs long Ti:Sa laser pulses into it resulting a comb of higher harmonics. In the first phase of the experiment the 21st harmonic of the 800nm drive laser will be used to seed the FEL process. The commissioning of the experiment has started in April and the first results are expected after the FLASH commissioning period mid of summer 2010. The experimental setup and the commissioning procedures as well as first result will be presented.

Slides