The resistive wall impedance and the effects of the non-evaporable getter thickness in an ultra-low emittance ring

Abstract

In modern particle accelerators with ultra-low emittance, the vacuum chambers are designed based on Non-Evaporable Getter (NEG)-coated vacuum chambers. The thickness of the NEG coating plays a critical role in the dynamic beam effects. So, in this paper, the longitudinal and transverse impedance of a copper chamber coated with a NEG are investigated, and the effects of the NEG thickness over a wide range of frequencies have been studied. A good selection of NEG layer thickness could minimize the coating effects on the longitudinal and transverse beam impedance. The numerical results in this work show that the beam dynamic effects could be minimal with selecting a NEG coating thickness of about 1 μm.