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Peters, A.

Paper Title Page
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.  
DW03 Beam Synchronous Timing Systems
Session 3: Wednesday (11:15--13:00 Hrs) 		261
 
  • A. Peters
    GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
  • M. Ferianis
    ELETTRA, Sincrotrone Trieste, Trieste, Italy
  
  For many beam diagnostics purposes beam synchronous timing systems are needed in addition to the timing systems supplied by the control systems of the different accelerators. The demands and techniques of different accelerator facilities will be discussed along the following aspects:
  • Bunch and macro pulse synchronous timing systems
  • Solutions for different time scales from ps to ms
  • Coupling to the RF and control systems of the different accelerators
  • Electronics for the beam synchronous timing systems: parameters, techniques, controlling
  • Use of industrial products for bunch synchronous timing systems, e.g. function generators
  • Distribution of the timing signals: electronically via cables, optically via fibres or wireless
  • Coupling to and use of timing standards: IRIG-B, GPS, …
The participants should present and describe solutions from their facilities with some transparencies as a starting point for the discussion.