Minutes December 19th, 2007
Present: Gianluigi Arduini, Fritz Caspers, Elias Métral, Giovanni Rumolo, Benoit Salvant, Bruno Zotter.
Agenda
- Elias Métral (slides)
"SPS impedance budget"
- Bruno Spataro (slides)
"Simulations of the impedance of SPS elements with MAFIA"
- Rama Calaga (slides)
"Follow up of the localization of SPS transverse impedance)"
Minutes
- review of where we stands on the SPS impedance budget.
- Longitudinal plane:
- Reasonably well understood => Contribution from the 200 MHz cavities can explain ~ 3-4 W (according to Spataro’s simulations). Elena said that in the past Dome computed this and it was more like 2-3 W, because the TW cavity is difficult to simulate as the waves are traveling and one needs to take into account the slip factor (difference between the wave and the beam) because this is what is important for the impedance.
- Next step: simulate the other RF system which is the 800 MHz, as Elena said that it should contribute to ~ 1 W. - One still to understand the spike at 1.4 GHz. - May be one should devote more time to understand the HOMs responsible for the longitudinal coupled-bunch instability, whose threshold is quite low.
- Transverse plane:
- ~ ˝ missing vertical impedance, i.e. 13 MW/m
- Simulate BWS, look at the (missing) shielding of the kickers and septa.
- Schottky monitor has a spike near 1.7 GHz according to Fritz…
- Rama should have a look also at the horizontal plane to may be learn more on the transverse impedance. However, it might be very difficult as the tune shift is really very small…
Author: Benoit Salvant
CERN AB/ABP-LIS