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- 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
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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.
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