• B. Keil, A. Citterio, M.M. Dehler, R. Ditter, V. Schlott, L. Schulz, D.M. Treyer
  PSI, Villigen

This paper introduces the architecture and first beam commissioning results of the standard BPM system for the SwissFEL test injector, a 250MeV linac that is progressively being commissioned in order to perform R&D for the "SwissFEL" 5.8GeV hard-X-ray FEL facility proposed at PSI. Since the SwissFEL has a nominal bunch charge range of 10-200pC, the test injector is equipped with 500MHz resonant stripline BPMs that are optimized for high dynamic range and sensitivity, to support machine operation well below 10pC. Beam tests with a 5 GSa/s direct sampling electronics designed at PSI showed a single-bunch resolution of <20um RMS at 2pC and typically 7um RMS for charges >10pC. The BPMs also measure bunch charge, insensitively to dark current, with <30fC RMS resolution at 2pC.

• P. Craievich, S. Biedron, M. Ferianis, D. La Civita
  ELETTRA, Basovizza
• D. Alesini, L. Palumbo
  INFN/LNF, Frascati (Roma)
• L. Ficcadenti
  Rome University La Sapienza, Roma
• M. Petronio, R. Vescovo
  DEEI, Trieste

A RF deflector is a useful tool to completely characterize the beam phase space by means of measurements of the bunch length and the transverse slice emittance. At FERMI@Elettra, a soft X-ray next-generation light source under development at the Sincrotrone Trieste laboratory in Trieste, Italy, we are installing low-energy and high-energy deflectors. In particular, two deflecting cavities will be positioned at two points in the linac. One will be placed at 1.2 GeV (high energy), just before the FEL process starts; the other at 250 MeV (low energy), after the first bunch compressor (BC1). This paper concerns only the low-energy deflector. The latter was built over the past year in collaboration with the SPARC project team at INFN-LNF-Frascati, Italy and the University of Rome. In this paper we will describe the RF measurements performed to characterize the standing wave cavity before the installation in the FERMI@Elettra linac, and we will compare them with the simulations done using the electromagnetic code HFSS.

• P. Gessler, M.K. Bock, M. Felber, K.E. Hacker, W. Koprek, F. Ludwig, H. Schlarb, B. Schmidt, S. Schulz
  DESY, Hamburg

Electron bunches at the free electron laser FLASH at DESY have a duration of 10 fs to 150 fs and an arrival-time jitter of about 150 fs (rms). It is anticipated that the newly installed optical synchronisation system will stabilize the seed and pump-probe lasers to within ~10 fs. In order to perform reliable and stable seeding, the electron bunch timing jitter needs to be reduced. Bunch arrival-time monitors measure the arrival-time fluctuations at different locations and are used in a beam-based feedback loop to correct the amplitude of the accelerator RF. In order to provide reliable operation and high availability of the bunch arrival-time feedback, intensive efforts have been undertaken in system automation and exception handling. This will be discussed along with the latest results and limitations on the stability of the arrival-times at FLASH.