Abstract
In this paper we study the impact of the rf deflectors beam loading on the transverse beam dynamics of the CTF3 combiner ring. A general expression for the single-passage wake field is obtained. Different approximated formulas are derived applying linearization of the rf deflector dispersion curve either on a limited or an unlimited frequency range. A dedicated tracking code has been written to study the multibunch multiturn effects on the transverse beam dynamics. The numerical simulations reveal that the beam emittance growth due to the wake field in the rf deflectors is a small fraction of the design emittance if the trains are injected perfectly on axis. Nevertheless in case of injection errors the final emittance growth strongly depends on the betatron phase advance between the rf deflectors. If the finite bunch length is included in the tracking code, the scenario for the central part of the bunches does not change. However, for some particular injection errors, the tails of the bunches can increase the total transverse bunch emittances.
Highlights
The CTF3 (CLIC test facility 3) [1] is the third test facility of the CLIC (Compact Linear Collider) project [2 – 4]
In the first stage the pulse is compressed by a factor of 2 by using a transverse rf deflector at 1.499 GHz and a 42 m circumference delay loop
An 84 m circumference combiner ring (CR) is used in the second stage to further compress the pulse by a PACS numbers: 29.27.Bd, 42.79.Fm, 29.27.Ac factor of 5 [5]
Summary
The CTF3 (CLIC test facility 3) [1] is the third test facility of the CLIC (Compact Linear Collider) project [2 – 4]. An 84 m circumference combiner ring (CR) is used in the second stage to further compress the pulse by a PACS numbers: 29.27.Bd, 42.79.Fm, 29.27.Ac factor of 5 [5] This will be achieved by means of two rf deflectors working at 2.998 GHz already constructed [6,7] and successfully tested in the CTF3 preliminary phase [8]. In this paper we investigate the beam loading effects in the rf deflectors of the CR which may result in transverse bunch emittance growth, particle loss, and degradation of the drive beam quality reducing effectiveness of power conversion at 30 GHz. In Sec. II we analyze the single- and multipassage wake field models that we have introduced to study the multibunch effects.
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