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Harms, E.R.

Paper Title Page
TUP034 Status of the 3rd Harmonic Systems for FLASH and XFEL in Summer 2008 471
  • E. Vogel, W. Decking, M. Dohlus, M.G. Hoffmann, M. Hüning, J. Iversen, K. Jensch, G. Kreps, T. Limberg, A. Matheisen, W.-D. Möller, K. Rehlich, A. Schmidt, J.K. Sekutowicz, W. Singer
    DESY, Hamburg
  • A. Bosotti, P. Pierini, D. Sertore
    INFN/LASA, Segrate (MI)
  • H.T. Edwards, E.R. Harms, T.N. Khabiboulline
    Fermilab, Batavia

Ultra short bunches with high peak current are required for the creation of high brilliance coherent light in the VUV and X-ray range in undulators. At the Free Electron Laser in Hamburg (FLASH) and the European X-ray free electron laser (XFEL) they are obtained by a two stage bunch compression scheme based on acceleration off the rf field crest and transverse magnetic chicanes. The deviation of the rf field's sine shape from a straight line leads to long bunch tails and reduces the peak current. This effect can be eliminated by adding a third harmonic rf system. The paper gives an overview on the actual status of the beam dynamical examinations and as well on the development of the third harmonic sub-systems like modules, cavities and radio frequency systems for FLASH and the XFEL.

THP019 Third Harmonic Superconducting Cavity Prototypes for the XFEL 821
  • P. Pierini, A. Bosotti, N. Panzeri, D. Sertore
    INFN/LASA, Segrate (MI)
  • H.T. Edwards, M.H. Foley, E.R. Harms, D.V. Mitchell
    Fermilab, Batavia
  • J. Iversen, W. Singer, E. Vogel
    DESY, Hamburg

The third harmonic cavities that will be used at the injector stage in the XFEL to linearize the rf curvature distortions and minimize beam tails in the bunch compressor are based on the rf structures developed at FNAL for the DESY FLASH linac. The design and fabrication procedures have been modified in order to match the slightly different interfaces of XFEL linac modules and the procedures followed by the industrial production of the main (1.3 GHz) XFEL cavities. A revision of the helium vessel design has been required to match the layout of the cryomodule strings, and a lighter version of the tuner has been designed (derived from the 1.3 GHz ILC blade tuner activities). The main changes introduced in the design of the XFEL cavities and the preliminary experience of the fabrication of three industrially produced and processed third harmonic rf structures are described here.

THP027 Welding Helium Vessels to the 3.9 GHz Superconducting Third Harmonic Cavities 842
  • M.H. Foley, T.T. Arkan, H. Carter, H.T. Edwards, J. Grimm, E.R. Harms, T.N. Khabiboulline, D.V. Mitchell, D.R. Olis, T.J. Peterson, P.A. Pfund, N. Solyak, D.J. Watkins, M. Wong
    Fermilab, Batavia
  • G. Galasso
    University of Udine, Udine

Funding: This work was supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
The 3.9 GHz 3rd harmonic cavities are designed to serve as compensation devices for improving the longitudinal emittance of the free-electron laser FLASH at DESY. These cavities operate in the TM010 mode, and will be located between the injector and the accelerating cavities. Fermilab is obligated to provide DESY with a cryomodule containing four 3rd harmonic cavities. In this paper we discuss the process of welding helium vessels to these cavities. Included will be a description of the joint designs and weld preparations, development of the weld parameters, and the procedure for monitoring the frequency spectrum during TIG welding to prevent the cavity from undergoing plastic deformation. Also discussed will be issues related to qualifying the dressed cavities as exceptional vessels (relative to the ASME Boiler and Pressure Vessel Code) for horizontal testing and eventual installation at DESY, due to the necessary use of non-ASME code materials and non-full penetration electron beam welds.

THP028 Status of 3.9 GHz Superconducting RF Cavity Technology at Fermilab 845
  • E.R. Harms, T.T. Arkan, V.T. Bocean, H. Carter, H.T. Edwards, M.H. Foley, T.N. Khabiboulline, M.W. McGee, D.V. Mitchell, D.R. Olis, A.M. Rowe, N. Solyak
    Fermilab, Batavia

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Fermilab is involved in an effort to design, build, test and deliver four 3.9 GHz superconducting rf cavities within a single cryomodule to be delivered to DESY as a 'third harmonic' structure for the FLASH facility to improve the longitudinal emittance. In addition to an overall status update we will present recent results from single 'dressed' cavity horizontal tests and shipping and alignment measurements.


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THP029 Performance of 3.9-GHZ Superconducting Cavities 848
  • E.R. Harms, H.T. Edwards, A. Hocker, T.N. Khabiboulline, N. Solyak
    Fermilab, Batavia

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
3.9 GHz SRF cavities have been built and tested at Fermilab for use in the DESY FLASH facility. Six cavities have undergone testing in various scenarios. Comparisons of performance in these different conditions, from bare cavities in a vertical dewar to 'dressed' in the horizontal test stand and intermediate test configurations are presented. We also report on analysis of expected maximum performance and an estimate of same.