• H. Delsim-Hashemi, A. Azima, J. Bödewadt, F. Curbis, M. Drescher, Th. Maltezopoulos, V. Miltchev, M. Mittenzwey, J. Roßbach, J. Rönsch-Schulenburg, R. Tarkeshian, M. Wieland
  Uni HH, Hamburg
• S. Bajt, K. Honkavaara, T. Laarmann, H. Schlarb
  DESY, Hamburg
• R. Ischebeck
  PSI, Villigen
• S. Khan
  DELTA, Dortmund
• A. Meseck
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin

Recently, the free-electron laser in Hamburg (FLASH) at DESY has been upgraded considerably. Besides increasing the maximum energy to about 1.2 GeV and installation of a third harmonic rf cavity linearizing the longitudinal phase space distribution of the electron bunch, an FEL seeding experiment at wavelengths of about 35 nm has been installed. The goal is to establish direct FEL seeding employing coherent VUV pulses produced from a powerful drive laser by high-harmonic generation (HHG) in a gas cell. The project, called sFLASH, includes generation of the required HHG pulses, transporting it to the undulator entrance of a newly installed FEL-amplifier, controlling spatial, temporal and energy overlap with the electron bunches and setting up a pump-probe pilot experiment. Sophisticated diagnostics is installed to characterize both HHG and seeded FEL pulses, both in time and frequency domain. Compared to SASE-FEL pulses, almost perfect longitudinal coherence and improved synchronization possibilities for the user experiments are expected. In this paper the status of the experiment is presented.

• P. Hartmann, S. Khan, D. Schirmer, G. Schünemann, P. Towalski, T. Weis
  DELTA, Dortmund

A stable beam orbit is essential for safe operation of particle accelerators. This applies to electron machines and even more to hadron machines running high beam currents. Based on developments at DELTA, basic designs of fast orbit feedbacks systems for the FAIR rings SIS18 and HESR (planned) and COSY at the Forschungszentrum Jülich are presented.

• S. Khan, J. Fürsch, P. Hartmann, T. Weis
  DELTA, Dortmund
• D. Teytelman
  Dimtel, San Jose

DELTA is a 1.5-GeV synchrotron radiation source at the TU Dortmund University with 2 ns bunch spacing. At nominal operating currents, the beam exhibits significant longitudinal centroid motion due to coupled-bunch instabilities. Two techniques were successfully used at DELTA to damp such instabilities: RF phase modulation, which also improves the beam lifetime, and bunch-by-bunch feedback. Using diagnostic data from the bunch-by-bunch feedback system, modal spectra and growth rates of the longitudinal instabilities were characterized. We also present a preliminary characterization of transverse coupled-bunch oscillations observed at the highest beam currents.