• T. Kii, M. A. Bakr, Y.W. Choi, K. Ishida, N. Kimura, R. Kinjo, K. Masuda, H. Ohgaki, T. Sonobe, M. Takasaki, S. Ueda, K. Yoshida
  Kyoto IAE, Kyoto

The bulk high temperature superconductor staggered array undulator (Bulk HTSC SAU) has potential to generate strong periodic magnetic field in short period and to control K value without a mechanical gap control structure.* However, availability of the bulk HTSC magnets having matched performance of critical current density is a problem to be solved. In this study, we have numerically and experimentally estimated influence of variation of critical density upon field error. It was numerically found that the field error was naturally compressed, because the difference in critical current density was compensated by natural variation of the region where the supercurrent flows. In the conference, the experimental results of the field error compression and principle of the compression will be discussed.

* R. Kinjo, et al., “BULK HIGH-TC SUPERCONDUCTOR STAGGERED ARRAY UNDULATOR”, Proceedings of FEL 2008, 473 (2009).

• Y. Li, J. Pflüger
  European XFEL GmbH, Hamburg

In the European XFEL permanent magnet phase shifters are routinely between two undulator segments. Its main purpose is to control the phase of the electrons with respect to the emitted radiation. In addition the path length is dependent on the electron energy, which corresponds to a small R56 . In this paper we investigate the R56 of a permanent magnet phase shifter and propose to use it to fine tune R56 by adjusting the phase shifter gap.

• U. Lehnert, M. Helm, P. Michel, H. Schneider, W. Seidel, S. Winnerl
  FZD, Dresden
• A. Aksoy
  Ankara University, Faculty of Engineering, Tandogan, Ankara

To extend the wavelength range of possible experiments from the FIR into the THz region a dedicated beamline is planned at the ELBE Radiation Source. The beamline will deliver coherent transition radiation and coherent synchrotron radiation as broad-band (essentially single-cycle) radiation. Superradiant undulator radiation will be produced for a tunable narrow-band radiation source in the 100GHz to 3THz range. This requires a compression of the ELBE electron beam down to 150fs bunchlength. The beam transport and bunch compression scheme as well as the properties of the produced radiation are presented in detail.

• C. Boffo, W. Walter
  BNG, Würzburg
• T. Baumbach, S. Casalbuoni, S. Gerstl, A.W. Grau, M. Hagelstein, D. Saez de Jauregui
  Karlsruhe Institute of Technology (KIT), Karlsruhe

Superconducting undulators show, with respect to permanent magnet undulators, a larger magnetic field strength for the same gap and period length, being able to generate a harder X-ray spectrum and higher brilliance X-ray beams. The worldwide first short period length superconducting undulator is in operation since 2005 at the synchrotron light source ANKA in Karlsruhe. To further drive the development in this field a research and development program has been defined. A 1.5 m long superconducting undulator with a period length of 15 mm is planned to be installed in ANKA at the end of 2010 to be the light source of the new beamline NANO for high resolution X-ray diffraction. The key specifications of the system are an undulator parameter K higher than 2 and a phase error smaller than 3.5 degrees. The coils will be cooled using cryocoolers and should have a capability of withstanding a 4 W beam heat load at 4 K. Here we describe the main features of the 1.5 m long superconducting undulator, the test results of the coils in liquid helium and the test results of a prototype switchable period length device.

• M. Kokole, T. Milharcic, M. Zambelli
  KYMA, Trieste
• B. Diviacco
  ELETTRA, Basovizza
• G. Soregaroli, M. Tedeschi
  Euromisure srl, Pieve S. Giacomo (CREMONA)

During 2009 and the first months of 2010, Kyma Srl, the spin-off company set-up by Sincrotrone Trieste, designed and realized all the insertion devices for the undulator chain at the FERMI@Elettra free-electron laser. The insertion devices manufactured and characterized so far are the following: The Laser Heater Undulator, a short, linearly polarized device, already installed in the FERMI linac. The Modulator, a 3.2 m long, linearly polarized undulator. The Radiator, comprising of six APPLE-II variable polarization undulators, each 2.4 m long. All the above devices have been characterized, both from the mechanical and the magnetic point of view. The measured parameters are in good agreement with the design values. This paper presents the most relevant results of the magnetic measurements carried out on all the above undulators, and describes the characteristics and the performance of the dedicated equipment set-up and used for this measurements.

• L. Froehlich, G. Cautero, D. Giuressi, R.H. Menk
  ELETTRA, Basovizza
• D. Di Giovenale
  INFN-Roma II, Roma

FERMI@Elettra is a linac-driven free-electron laser currently under construction at the synchrotron radiation facility Elettra in Trieste, Italy. In order to prevent damage to accelerator components, an active machine protection system (MPS) monitors beam losses along the linac and, if necessary, inhibits the beam production in the injector. Special attention is paid to the protection of permanent undulator magnets from demagnetization by the excessive absorption of radiation. This paper discusses the system architecture and gives an overview of the major diagnostic subsystems: A beam loss position monitor based on the detection of Cherenkov light induced in quartz fibers, an array of discrete ionization chambers, and a system for differential charge loss measurements. The dose deposition in the undulator magnets will be monitored with electronic RadFET dosimeters; first details of the readout system are presented.

• P. Craievich
  ELETTRA, Basovizza
• M. Dal Forno
  DEEI, Trieste

The cavity Beam Position Monitor (BPM) is a fundamental beam diagnostic instrument for a seeded FEL, like FERMI@Elettra. It allows the measurements of the electron beam trajectory in a non-destructive way and with sub-micron resolution. The high resolution cavity BPM relies on the excitation of the dipole mode that is originated when the bunch passes off axis in the cavity. In this paper we present the prototype of cavity BPM developed for the FERMI@Elettra facility. The RF parameters of the cavities have been determined by means of Ansoft HFSS; while using the CST Particle Studio the level of the output signals from the cavities have been also estimated. Furthermore, the design of the RF frontend for the acquisition and conditioning of the signals from the BPM cavities is presented as well. The prototype has been succesfully installed in the FERMI Linac during the last commissioning phase and preliminary results with the electron beam are also presented.

• 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.

• R. Kinjo, M. A. Bakr, Y.W. Choi, K. Ishida, T. Kii, N. Kimura, K. Masuda, K. Nagasaki, H. Ohgaki, T. Sonobe, M. Takasaki, S. Ueda, K. Yoshida
  Kyoto IAE, Kyoto

The bulk high temperature superconductor staggered array undulator (Bulk HTSC SAU) has several advantages: such as strong magnetic field, potential of short period undulator, K value variability without gap control. In addition to these advantages, the Bulk HTSC SAU can be used near the electron beam because the undulator is expected to show good performance at 20 – 30 K. In the conference, we will report the expected performance of the undulator at low temperature through magnetic measurement by using a superconducting quantum interference device (SQUID) magnetometer. Also we will report the results of the first operation at 4 – 77 K of new prototype undulator consisting of a helium cooling system and a 2 T superconducting solenoid.