| Paper |
Title |
Page |
| MOPLT037 |
Simulation of Transient Beam-feedback Interaction with Application to the Extraction of the CNGS Beam from the SPS
|
626 |
| |
- E. Vogel, W. Höfle
CERN, Geneva
|
|
| |
For actual and future high energy proton accelerators, such as the LHC, transverse feedback systems play an essential role in supplying the physics experiments with high intensity beams at low emittances. We developed a simulation model to study the interaction between beam and transverse feedback system in detail, bunch-by-bunch and turn-by-turn, considering the real technical implementation of the latter. A numerical model is used as the nonlinear behavior (saturation) and limited bandwidth of the feedback system, as well as the transient nature at injection and extraction, complicates the analysis. The model is applied to the practical case of the CNGS beam in the SPS accelerator. This beam will be ejected from the SPS in two batches causing residual oscillations by kicker ripples on the second batch. This second batch continues to circulate for some 1000 turns after the first batch has been extracted and oscillations are planned to be damped by the feedback system. It is shown how the model can be extended to the case of transients at injection (LHC), and to include coupled bunch instability effects.
|
|
| WEPLT041 |
RF Amplitude Modulation to Suppress Longitudinal Coupled Bunch Instabilities in the SPS
|
1921 |
| |
- E. Vogel, T. Bohl, U. Wehrle
CERN, Geneva
|
|
| |
In the SPS, even after a considerable impedance reduction including the removal of all RF cavities used for lepton acceleration in the past, longitudinal coupled bunch instabilities develop with an LHC beam of about one fifth of the nominal bunch intensity. The nominal LHC beam is stabilised using both, the 800 MHz Landau damping cavities, in bunch shortening mode, and pre-emptive emittance blow-up. An alternative method to increase the synchrotron frequency spread and thus stabilise the beam is amplitude modulation of the accelerating RF voltage. This method might be especially suitable in accelerators without a higher harmonic RF system, as will be the case in LHC. The main results of recent studies using this method in the SPS and considerations about its use in LHC are presented.
|
|