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Summary Notes of the SSWG meeting on the 03/12/2002

Present: G. Arduini, Ph. Baudrenghien, T. Bohl, R. Cappi, P. Collier, 
H. Burkhardt (secretary), K. Cornelis (chairman), B. Dehning, J. 
Gareyte, D. Manglunki, E. Shaposhnikova J. Tuckmantel, J. Wenninger.

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Agenda :

1) Review of HRF long MDs in 2002    E. Shaposhnikova

2)  TWC 200 MHz Hardware and Rephasing,
  results from last MD                Ph. Baudrenghien

3)  TWC 800 MHz                      T. Bohl

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1) E.S. reviewed the rf-related machine developments performed this 
year. There has been a substantial progress allowing to get close to 
the nominal longitudinal parameters for the LHC beam at injection 
energy: (4 sigma) bunch length of 1.6 ns and a (2 sigma) longitudinal 
emittance of 0.6 eV s were obtained at 450 GeV for 4 batches in the SPS.
Besides improvements on the main 200 MHz rf control, feedback and bunch 
to bunch damping systems, the use of the 800 MHz rf as Landau cavity 
has been essential. A controlled blow-up on the flat bottom was 
achieved by a mismatch in the rf-voltage (capture in the SPS at 2 MV 
rather than 0.7 MV).
See also the summary transparencies.

2) P.B. reported about the status of the 200 MHz travelling wave 
cavities, rephasing and synchronization for LHC injection. Feedback and 
longitudinal damping was improved. Longitudinal injection oscillations 
can be damped quickly. Transparent rephasing and automatic adjustments 
using training cycles were studied. See the transparencies.

  3) T.B. reported about the 800 MHz travelling wave rf. The system is 
needed for stabilization of coupled bunch instabilities with 
frequencies outside the bandwidth of the longitudinal damper. For this 
purpose the cavities are used in bunch shortening mode. Although the 
requirements for control of rf amplitude and phase are less demanding 
in this mode than in bunch lengthening mode, the amplitude should be 
controlled to better than +/-10% and the 800 MHz phase to better than 
about +/-25 degrees. Beam loading is significant and can vary a lot 
along the batch, especially at flat bottom. There is a hardware 
improvement program.