Paper 
Title 
Page 
WEPPR073 
Effects of an Asymmetric Chamber on the Beam Coupling Impedance 
3099 

 C. Zannini, K.S.B. Li, G. Rumolo
CERN, Geneva, Switzerland
 C. Zannini
EPFL, Lausanne, Switzerland



The wake function of an accelerator device appears to have a constant term if the geometry of the device is asymmetric or when the beam passes off axis in a symmetric geometry. Its contribution can be significant and has to be taken into account. In this paper a generalized definition of the impedance/wake is presented to take into account also this constant term. An example of a device where the constant term appears is analyzed. Moreover, the impact of a constant wake on the beam dynamics is discussed and illustrated by a HEADTAIL simulation.



WEPPR074 
Effect of the TEM Mode on the Kicker Impedance 
3102 

 C. Zannini, G. Rumolo, V.G. Vaccaro
CERN, Geneva, Switzerland
 C. Zannini
EPFL, Lausanne, Switzerland



The kickers are major contributors to the CERN SPS beam coupling impedance. As such, they may represent a limitation to increasing the SPS bunch current in the frame of a luminosity upgrade of the LHC. The CMagnet supports a transverse electromagnetic (TEM) mode due to the presence of two conductors. Due to the finite length of the structure this TEM mode affects the impedance below a certain frequency (when the penetration depth in the ferrite becomes comparable to the magnetic circuit length). A theoretical model was developed to take into account also the impedance contribution due to the TEM mode. The model is found to be in good agreement with CST 3D electromagnetic (EM) simulations. It allows for generic terminations in the longitudinal direction. An example of kicker is analyzed taking into account also the external cables.



WEPPR074 
Effect of the TEM Mode on the Kicker Impedance 
3102 

 C. Zannini, G. Rumolo, V.G. Vaccaro
CERN, Geneva, Switzerland
 C. Zannini
EPFL, Lausanne, Switzerland



The kickers are major contributors to the CERN SPS beam coupling impedance. As such, they may represent a limitation to increasing the SPS bunch current in the frame of a luminosity upgrade of the LHC. The CMagnet supports a transverse electromagnetic (TEM) mode due to the presence of two conductors. Due to the finite length of the structure this TEM mode affects the impedance below a certain frequency (when the penetration depth in the ferrite becomes comparable to the magnetic circuit length). A theoretical model was developed to take into account also the impedance contribution due to the TEM mode. The model is found to be in good agreement with CST 3D electromagnetic (EM) simulations. It allows for generic terminations in the longitudinal direction. An example of kicker is analyzed taking into account also the external cables.


