• J.A. Clarke, D.J. Dunning, S. Leonard, A.D. Smith, N. Thompson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• M. Surman
  STFC/DL/SRD, Daresbury, Warrington, Cheshire

An infra-red oscillator FEL was installed into the accelerator test facility, ALICE, at Daresbury Laboratory at the end of 2009. The FEL will be used to study energy recovery performance with a disrupted, large energy spread, beam and also to test novel FEL concepts. This paper will describe the installed hardware, the pre-alignment techniques that have been employed, the diagnostics that are being used to detect the infra-red output, and the progress with commissioning of the FEL itself.

• J. Breunlin, L.-G. Wißmann
  Uni HH, Hamburg
• B. Schmidt, B. Steffen
  DESY, Hamburg

The free electron laser in Hamburg (FLASH) underwent major modifications during a 6 months shutdown like the installation of a 3rd harmonic module, a seeding experiment (sFLASH) and a 7th accelerating module. Also instrumentation has been improved. A new compact electro-optic (EO) bunch length monitor has been installed downstream the first bunch compressor. At this position, the bunches are expected to have a length of about 1 ps, well suited for the resolution of an EO bunch length monitor with spectral decoding of the time (EO-SD). The setup uses a commercial ytterbium fiber laser, a compact optics inside the beam pipe designed at PSI (Switzerland) and a spectrometer with fast InGaAs line scan camera. These components, together with RF synchronisation unit and readout electronics, will be installed in the accelerator tunnel. Reliability, robustness and high uptime are key features as the EO monitor is meant to serve as permanent beam diagnostics. Here we report on the commissioning of the components and first experiments with the complete system.

• T. Tanikawa
  Sokendai - Okazaki, Okazaki, Aichi
• M. Adachi, M. Katoh, J. Yamazaki, H. Zen
  UVSOR, Okazaki
• M. Hosaka, Y. Taira, N. Yamamoto
  Nagoya University, Nagoya

Light source technologies based on laser seeding are under development at the UVSOR-II electron storage ring. In the last FEL conference (FEL2009), we reported spectral measurements of coherent harmonic generation (CHG) seeded by the fundamental of Ti: Sapphire laser, in the region of vacuum-ultra violet (VUV). In this conference, we will report some systematic measurements such as the undulator gap dependence and seed laser power dependence. In the laser power dependence, we have observed a saturation of CHG intensity. The result will be compared with simulations. A seeding light source based on high harmonic generation (HHG) in rare gas is under development. The status will be reported.

• S. Zhang, S.V. Benson, J.G. Gubeli, G. Neil, F.G. Wilson
  JLAB, Newport News, Virginia

A sophisticated research device such as an advanced photo-cathode injector for a high energy accelerator-based X-ray light source requires drive lasers with a flat-top shape both in time and space in order to generate high-quality short electron beam bunches. There are a number of different ways to spatially shape laser beams, but the practical methods for temporal shaping, in particular in the picosecond or femtosecond regime, are quite limited. One simple way to shape laser pulses is pulse stacking by birefringent crystals. This method has been adopted for several applications. While the method itself has the great advantage of simplicity, the overall performance depends on many factors. In this paper, we will present both analysis and a recent experimental study about important pulse shaping characteristics that, to our knowledge, have not been adequately explored before. Evaluation on the pros and cons of the method and how to improve the overall performance will be discussed.

• P. Gessler, M.K. Bock, M. Felber, K.E. Hacker, F. Ludwig, H. Schlarb, B. Schmidt, S. Schulz
  DESY, Hamburg
• J. Szewinski
  Warsaw University of Technology, Institute of Electronic Systems, Warsaw

Bunch arrival-time monitors measure the arrival-time of each bunch in the electron bunch train at several locations at FLASH. The temporal reference for the monitors is provided by the optical synchronization system which distributes laser pulses with a repetition rate of 216 MHz and a length of around 200 fs FWHM. The pulses are delivered to the monitors with an arrival-time stability of about 10 fs. The bunch arrival-time is encoded as an amplitude modulation of a laser pulse from the optical synchronization system. These laser pulse amplitudes need to be sampled and processed together with additional input parameters. Because the arrival-time information is used in a feedback loop to adjust the accelerator fields, the signal processing, calibration and transmission of the bunch arrival-time information via a low-latency, high-speed link to an accelerator RF control station is needed. The most challenging problems of the signal processing are the synchronisation of several clock domains, regeneration and conversion of optical laser pulses, on-line calibration, and exception handling.

• M. Aiba, H.-H. Braun, M. Böge, C. Calvi, T. Garvey, B. Keil, S. Reiche, V. Schlott, T. Schmidt
  PSI, Villigen

Transverse beam trajectory control is of great importance for SwissFEL as the lasing strategy is based on a relatively low energy and low emittance beam compared with other X-FEL facilities, thus aiming at a reasonable construction cost and size of the facility. A study of beam based alignment and orbit feedback has been performed, and a trajectory correction scenario, which would fulfill the beam requirements as well as the hardware constraints, has been set up. The beam based alignment will be discussed for the linac and the undulator section separately because of the much tighter tolerance in the latter. Several correction algorithms are examined using numerical simulations. BPM requirements and orbit feedback concept will be discussed, with reference to some available data on dynamic disturbances such as ground motion at the PSI site, e.g. at the SwissFEL injector test facility currently under commissioning.

• A. Hedqvist, H. Danared, F. Hellberg
  MSL, Stockholm
• W. Decking, B. Krause
  DESY, Hamburg
• S. Karabekyan, J. Pflüger
  European XFEL GmbH, Hamburg

The Manne Siegbahn Laboratory at Stockholm University is currently involved in two separate projects at the European XFEL. The first concerns the fiducialization and characterization of the quadrupole magnets in the undulator sections. A recently upgraded rotating coil system measures the magnetic centre stability during magnet excitation, magnet gradient and field error components. In connection, a coordinate measuring machine is used to fiducialize the quadrupole magnetic centre to better than 0.050 mm. The second project concerns high precision measurements of the undulator temperature. The SASE radiation intensity depends strongly on the undulator period and the magnetic field strength, which are both sensitive to temperature. Instead of keeping the temperature within 0.1 degrees along the undulator tunnel, a temperature compensation scheme can be applied. Here, a change in temperature initiates adjustment of the undulator gap to compensate for changes in magnetic field. A system for undulator segment temperature measurement, with resolution of 0.03 degrees, necessary for the compensation scheme, is presented together with a brief overview of the upgraded rotating coil system.