CERN Accelerating science

Article
Title	Steering and Focusing Effects in TESLA Cavity Due to High Order Mode and Input Couplers
Author(s)	Piot, Philippe ; Dohlus, Martin ; Flöttmann, Klaus ; Marx, Michaela ; Wipf, Susan
Affiliation	(DESY, Hamburg) ; (Fermilab, Batavia, Illinois)
Publication	2005
In:	21st IEEE Particle Accelerator Conference, Knoxville, TN, USA, 16 - 20 May 2005, pp.4135
Subject category	Accelerators and Storage Rings
Abstract	Many state-of-art electron accelerator proposals incorporate TESLA-type superconducting standing wave cavities. These cavities include input coupler (to feed the RF power into the cavity) and a pairs of high order mode couplers (HOM) to absorb the energy associated to HOM field excited as the bunch passes through the cavity. In the present paper we investigate, using numerical simulations, the impact of the input and HOM couplers on the beam dynamics. We show the overall effects are: a dipole kick (zeroth order) and normal and skew quadrupole-type focusing (first order). We present parametric studies of the strength of these effect for various operating gradients and incoming beam energies. We finally study the impact of this non-asymmetric field on the beam dynamics, taking as an example the low energy section of the European X-FEL injector.