Résumé du preprint DAPNIA-05-492

Optimization of beam injection into the first accelerating module at TTF with cavity dipole mode signals.
N. Baboi, H. Schlarb, M. Wendt† , G. Kreps, O. Napoly, R.G. Paparella , J. Frisch, M. Ross, T. Smith, D. McCormick
The TESLA Test Facility (TTF) is a user facility for intense VUV-FEL light. The facility is densely equipped with diagnostics, essential in obtaining the necessary beam parameters, in particular the low emittance. However there is no dedicated component for alignment of the beam in the accelerating modules, each containing eight superconducting cavities. Large beam offsets can lead to an increase of the beam emittance. The centering of the beam in these modules is therefore important, mostly at the low energy end. A misalignment of the rst TTF module with respect to the gun axis has already been observed using cavity dipole modes. This paper presents the experimental results of the optimization of the beam injection into the rst module, based on the monitoring of dipole modes through the couplers installed for wakeeld damping. For this we use a spectrum analyzer together with a multiplexer. By scanning the beam position and tilt with two pairs of steerers, we can nd the trajectory which minimizes the dipole modes amplitude. The impact of the beam steering in the module on the beam is discussed. A time domain setup is also being presented.
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