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- N. Baboi, M. Dohlus, A. Jöstingmeier, N. Holtkamp, M. Wendt, M. Nagl, J. Boster, H. Hartwig
DESY, Deutsches Elektronen Synchrotron, Hamburg, Germany
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High order modes (HOM) are generated by the interaction
of a bunched beam with an accelerator environment. They
may act destructively on following particle bunches, leading
to an increase of the transverse oscillation amplitude
and finally to the deterioration of the emittance. Dipole
modes have been studied at the S-Band Test Facility at
DESY. One accelerating structure, specially designed for
this test linac, is equipped with waveguide pick-ups for
measuring the HOMs. For one part of the experiments, a
modulation of the transverse offset of the bunches at the
structure entrance has been induced using a fast broadband
kicker and the effect was measured with a precise stripline
BPM. No high impedance modes were clearly found in the
structure, which has been detuned and damped by both the
tapered geometry of the structure and an absorbing stainless
steel coating applied on the iris tips.
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