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Wendt, M.

Paper Title Page
CT04 The Beam Inhibit System for TTF II 62
 
  • D. Nölle, P. Göttlicher, R. Neumann, D. Pugachov, K. Wittenburg, M. Wendt, M. Werner, H. Schlarb, M. Staack
    DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
  • M. Desmons, A. Hamdi, M. Jablonka, M. Loung
    CEA, Commissariat à l'Energie Atomique, Saclay, France
 
  The new generation of light sources based on SASE Free-Electron-Lasers driven by LINACs operate with electron beams with high beam currents and duty cycles. This is especially true for the superconducting machines like TTF II and the X-RAY FEL, under construction or planning at DESY. Elaborate fast protections systems are required not only to protect the machine from electron beams hitting and destroying the vacuum chamber, but also to prevent the machine from running at high loss levels, dangerous for components like the FEL undulator. This paper will give an overview over the different protection systems currently under construction for TTF II. The very fast systems, based on transmission measurements and distributed loss detection monitors, will be described in detail. This description will include the fast electronics to collect and to transmit the different interlock signals.  
CT11 Beam Based HOM Analysis of Acceleating Structures at the TESLA Test Facility LINAC 83
 
  • M. Wendt, S. Schreiber, A. Gössel
    DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
  • M. Hüning
    FNAL, Fermi National Accelerator Laboratory, Batavia, IL, USA
  • G. Devanz, M. Jablonka, C. Magne, O. Napoly
    CEA, Commissariat à l'Energie Atomique, Saclay, France
  • N. Baboi* (on leave from NTLPRP)
    SLAC, Stanford Linear Accelerator, Stanford, CA, USA
 
  The beam emittance in future linear accelerators for high energy physics and SASE-FEL applications depends highly on the field performance in the accelerating structures, i.e. the damping of higher order modes (HOM). Besides theoretical and laboratory analysis (network analyzer), a beam based analysis technique was established [S. Fartoukh, et.al., Proceedings of the PAC99 Conference] at the TESLA Test Facility (TTF) linac. It uses a charge modulated beam of variable modulation frequency to excite dipole modes. This causes a modulation of the transverse beam displacement, which is observed at a downstream BPM and associated with a direct analysis of the modes at the HOM couplers. Emphasis of this presentation is put on beam instrumentation and signal analysis aspects. A brief introduction of eigenmodes in resonant structures, as well as some interesting measurement results are further presented.  
PT26 Cryogenic Current Comparator for Absolute Measurement of the Dark Current of the Superconducting Cavities for Tesla 234
 
  • K. Knaack, M. Wendt, K. Wittenburg
    DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
  • R. Neubert, S. Nietzsche, W. Vodel
    FSU Jena, Friedrich-Schiller Universität, Jena, Germany
  • A. Peters
    GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
 
  A newly high performance SQUID based measurement system for detecting dark currents, generated by superconducting cavities for TESLA is proposed. It makes use of the Cryogenic Current Comparator principle and senses dark currents in the nA range with a small signal bandwidth of 70 kHz. To reach the maximum possible energy in the TESLA project is a strong motivation to push the gradients of the superconducting cavities closer to the physical limit of 50 MV/m. The field emission of electrons (the so called dark current) of the superconducting cavities at strong fields may limit the maximum gradient. The absolute measurement of the dark current in correlation with the gradient will give a proper value to compare and classify the cavities. This contribution describes a Cryogenic Current Comparator (CCC) as an excellent and useful tool for this purpose. The most important component of the CCC is a high performance DC SQUID system which is able to measure extremely low magnetic fields, e.g. caused by the extracted dark current. For this reason the SQUID input coil is connected across a special designed pick-up coil for the electron beam. Both the SQUID input coil and the pick-up coil form a closed superconducting loop so that the CCC is able to detect dc currents down to 2 pA/√Hz. Design issues and the application for the CHECHIA cavity test stand at DESY as well as preliminary experimental results are discussed.