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Baboi, N.

Paper Title Page
TPPP033 Cavity Alignment Using Beam Induced Higher Order Modes Signals in the TTF Linac 2284
 
  • M.C. Ross, J.C. Frisch, K.E. Hacker, R.M. Jones, D.J. McCormick, C.L. O'Connell, T.J. Smith
    SLAC, Menlo Park, California
  • N. Baboi, M.W. Wendt
    DESY, Hamburg
  • O. Napoly, R. Paparella
    CEA/DSM/DAPNIA, Gif-sur-Yvette
 
  Funding: DE-AC02-76SF00515.

Each nine cell superconducting accelerator cavity in the TESLA Test Facility (TTF) at DESY* has two higher order mode (HOM) couplers that efficiently remove the HOM power.** They can also provide useful diagnostic signals. The most interesting modes are in the first 2 cavity dipole passbands. They are easy to identify and their amplitude depends linearly on the beam offset from the cavity axis making them excellent beam position monitors (BPM). By steering the beam through an eight-cavity cryomodule, we can use the HOM signals to estimate internal residual alignment errors and minimize wakefield related beam emittance growth. We built and commissioned a four channel heterodyne receiver and time-domain based waveform recorder system that captures information from each mode in these two bands on each beam pulse. In this paper we present an experimental study of the single-bunch generated HOM signals at the TTF linac including estimates of cavity alignment precision and HOM BPM resolution.

*P. Piot, DESY-TESLA-FEL-2002-08. **R. Brinkmann et al. (eds.), DESY-2001-011.

 
RPPP043 Emittance Dilution Due to Many-Band Long-Range Dipole Wakefields in the International Linear Collider Main Linacs 2792
 
  • R.M. Jones
    SLAC, Menlo Park, California
  • N. Baboi
    DESY, Hamburg
 
  Funding: This work is supported by Department of Energy grant number DE-AC02-76SF00515.

We investigate the emittance dilution that occurs due to long range wakefields in the ILC L-band linacs. The largest kick factors (proportional to the transverse fields which transversely kick the beam off axis) from the first six bands are included in our simulations. These higher order dipole modes are damped by carefully orientating higher order mode couplers at both ends of each cavity. We investigate the dilution in the emittance of a beam with a random misalignment of cavities down the complete linac. In particular, the impact of a poorly damped dipole mode, on the overall emittance dilution down the complete linac is focused upon. The transverse alignment tolerances imposed on the cavities due to these wakefields are also discussed.