• D. Saez de Jauregui, S. Casalbuoni, A.W. Grau, M. Hagelstein, E.M. Mashkina
  FZK, Eggenstein
• R. Cimino, M. Commisso
  INFN/LNF, Frascati (Roma)
• R. Weigel
  Max-Planck Institute for Metal Research, Stuttgart

Recent investigations with the cold bore superconducting undulator installed at ANKA indicate that the main contribution to the beam heat load is caused by electron bombardment. For a quantitative understanding of the problem a cold vacuum chamber for diagnostics has been designed. Among other important parameters (heat load, pressure, etc) this device shall monitor the spectrum of the low energy electrons bombarding the wall. In this contribution we report on the measurements of the spectrum of the low energy electrons bombarding the wall of the cold vacuum chamber in a room temperature region of the ANKA storage ring performed using a in house developed retarding field analyzer (RFA). The calibration of the RFA performed at the national laboratories of Frascati is also described.

• E.M. Mashkina, A.J. Magerl
  University Erlangen-Nurnberg, Institute of Condensed Matter Physics, Erlangen
• C. Boffo, M. Borlein, W. Walter
  BNG, Würzburg
• S. Casalbuoni, A.W. Grau, M. Hagelstein, D. Saez de Jauregui
  FZK, Karlsruhe
• N. Vassiljev
  University Erlangen-Nuernberg, Institute of Condensed Matter Physics, Erlangen

A new 15 mm period, 1.5 m long planar undulator is being fabricated by Babcock Noell GmbH (BNG) for the ANKA synchrotron light source. In order to qualify the production process and to optimize both the quench protection scheme and the magnetic field correction system, a short prototype has been fabricated. The prototype has been tested in vertical configuration and liquid helium at 4.2K in the CASPER facility at ANKA. The magnetic field has been measured along the beam axis direction by Hall probes with a positioning precision of 3 μm. We report here on the field shimming scheme and the resulting performance of the coils.

• A. Plech, S. Casalbuoni, B. Gasharova, E. Huttel, Y.-L. Mathis, A.-S. Müller, K.G. Sonnad
  FZK, Karlsruhe
• A. Bartels
  CAP Konstanz, Konstanz
• R. Weigel
  Max-Planck Institute for Metal Research, Stuttgart

In a synchrotron radiation source coherent synchrotron radiation is emitted when the bunch length is comparable to the wavelength of the emitted radiation. To generate coherent THz (far IR) radiation, the ANKA storage ring is operated regularly with a dedicated low-alpha optics. Typical effective pulse lengths are of the order of 1 ps and below. In order to characterize the THz emission and beam oscillations in this mode a femtosecond laser system has been set up. This allows resolving the Terahertz electrical field by electro-optical sampling in a ZnTe crystal. The laser system consists of a 500 MHz repetition rate oscillator that can be phase locked to the repetition rate of the synchrotron. First results are presented. In contrast to previous approaches the high repetition rate is used in conjunction with a high frequency detection scheme in order to significantly increase the sensitivity of the detection. The discussion will concentrate on the limits in synchronization by locking the laser to either the bunch clock, a stripline signal in the ring or the visible light emission co-propagating with the THz radiation. The observations are compared to calculated pulse shapes.

• A.-S. Müller, T. Baumbach, S. Casalbuoni, B. Gasharova, M. Hagelstein, E. Huttel, Y.-L. Mathis, D.A. Moss, A. Plech, R. Rossmanith
  FZK, Karlsruhe
• E. Bründermann, M. Havenith
  Ruhr-Universität Bochum, Bochum
• S. Hillenbrand, K.G. Sonnad
  KIT, Karlsruhe

A linac based coherent radiation source in the THz to mid-IR range is proposed. The TBONE machine will deliver pulses of radiation as short as a few fs in the frequency range from 0.1 to 150 THz with up to MW peak power. This combination of parameters will open up unprecedented opportunities in THz and infrared applications, such as e.g. microscopy or spectroscopy. This paper presents the main parameters and design considerations. Special emphasis is put on the study of suitable bunch compression and beam transport schemes.

• C. Boffo, M. Borlein, W. Walter
  BNG, Würzburg
• T. Baumbach, A. Bernhard
  KIT, Karlsruhe
• S. Casalbuoni, A.W. Grau, M. Hagelstein, R. Rossmanith
  FZK, Karlsruhe
• E.M. Mashkina
  University Erlangen-Nuernberg, Erlangen

Superconducting insertion devices (IDs) are very attractive for synchrotron light sources since they allow increasing the flux and/or the photon energy with respect to permanent magnet IDs. Babcock Noell GmbH (BNG) is completing the fabrication of a 1.5 m long unit for ANKA at FZK. The period length of the device is 15 mm for a total of 100.5 full periods plus an additional matching period at each end. The key specifications of the system are: a K value higher than 2 and the capability of withstanding a 4 W beam heat load and a phase error of 3.5 degrees. In addition, during the injection phase of the machine, the nominal gap of 5 mm can be increased up to 25 mm. The magnets have been tested with liquid helium in a vertical dewar and are now being installed in the cryostat. This paper describes the technical design concepts of the device and the status of the assembly process.

• M. Hagelstein, T. Baumbach, S. Casalbuoni, A.W. Grau, B. Kostka, R. Rossmanith, D. Saez de Jauregui
  FZK, Karlsruhe
• A. Bernhard, D. Wollmann
  KIT, Karlsruhe
• J. Chavanne, P. Elleaume
  ESRF, Grenoble
• B. Diviacco
  ELETTRA, Basovizza
• E.M. Mashkina
  University Erlangen-Nurnberg, Institute of Condensed Matter Physics, Erlangen
• E.J. Wallén
  MAX-lab, Lund

Within the framework of a joint research activity of the European project IA-SFS (RII3-CT2004-506008) four synchrotron facilities have jointly developed diagnostic systems for superconducting undulators. Four work packages have been successfully completed: Design and construction of a test cryostat for field measurements; design and construction of a mock-up coil; field measurement and field error compensation; diagnostics and measurement of the spectrum of low energy electrons responsible for beam heat load in a superconducting undulator. The development advanced the knowledge of magnetic field error compensation considerably and might be of help in understanding the different beam heat load sources. Based on the development a second generation planar superconducting undulator with 15 mm period length for the synchrotron light source ANKA has been specified and procured.

• S. Casalbuoni, M. Hagelstein, D. Saez de Jauregui, S. Schleede
  FZK, Eggenstein-Leopoldshafen

Preliminary studies performed with the cold bore superconducting undulator installed in the ANKA storage ring suggest that the beam heat load is mainly due to the electron wall bombardment. Electron bombardment can both heat the cold vacuum chamber and induce an increase in the pressure because of gas desorption. In this contribution we compare the measurements of the pressure in a cold bore performed in the electron storage ring ANKA with the prediction obtained using the equations of gas dynamic balance in a cold vacuum chamber exposed to synchrotron radiation and electron bombardment. The balance results from two competitive effects: the photon and electron desorption of the gas contained in the oxide layer of the chamber wall and of the gas cryosorbed, and the cryopumping of the cold surface. We show that photodesorption alone cannot explain the pressure rise observed and that electron multipacting is needed.

• U. Iriso
  CELLS-ALBA Synchrotron, Cerdanyola del Vallès
• S. Casalbuoni
  FZK, Karlsruhe
• G. Rumolo, F. Zimmermann
  CERN, Geneva

One of the key issues for the developments of superconducting insertion devices is the understanding of the beam heat load in the vacuum chamber. The beam heat load observed in the superconducting cold bore undulator installed in the ANKA storage ring is higher than the one predicted by the synchrotron radiation and resistive wall heating. A non linear increase of the dynamic pressure with the beam current is also observed in the cold bore. In order to investigate whether the nature of these effects is due to an electron cloud formation, we have performed several simulations using the ECLOUD code.

• K.G. Sonnad, I. Birkel, S. Casalbuoni, E. Huttel, D. Saez de Jauregui, N.J. Smale
  FZK, Eggenstein
• F. Caspers
  CERN, Geneva
• A.-S. Müller, K.G. Sonnad
  KIT, Karlsruhe
• R. Weigel
  Max-Planck Institute for Metal Research, Stuttgart

Funding: This work has partly been supported by the Initiative and Networking Fund of the Helmholtz Association under contract number VH-NG-320.

A superconducting undulator is installed in the ANKA electron storage ring. Electron clouds could potentially contribute to the heat load of this device. A microwave transmission type electron cloud diagnostic has been installed for the undulator section of the ANKA machine. We present the system layout with particular emphasis on the electron machine aspects. Hardware transfer function results and e-cloud data for different machine settings are discussed. Special care has been taken for front end filter design both on the microwave injection and pick-up side.

• K.G. Sonnad, I. Birkel, S. Casalbuoni, E. Huttel, N.J. Smale
  FZK, Eggenstein
• F. Caspers
  CERN, Geneva
• N. Hiller, A.-S. Müller, K.G. Sonnad
  KIT, Karlsruhe
• R. Weigel
  Max-Planck Institute for Metal Research, Stuttgart

Funding: This work has partly been supported by the Initiative and Networking Fund of the Helmholtz Association under contract number VH-NG-320

The status of longitudinal and transverse Schottky observation systems for the synchrotron light source ANKA is presented. ANKA regularly operates in a dedicated low alpha mode with short bunches for the generation of coherent THz radiation. The Schottky measurement results are shown and compared with theoretical predictions for the regular as well as the different stages of the low alpha mode of operation. Special care had to be taken to control and mitigate the impact from strong coherent lines of the short bunches on the signal processing chain. The system setup is shown, expected and unexpected observations as well as applications are discussed.