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Description
Vacuum vessels of the Diamond-II storage ring feature metallic coatings which cause a resonator-like peak in the longitudinal impedance. This work demonstrates how different parameters of non-evaporable getter (NEG) coatings can increase momentum-spread growth. The first key insight of this study: The spread of the coating-layer thickness amongst vacuum vessels results in significantly reduced momentum-spread growth. Therefore, we recommend varying the coating thickness when designing vacuum components and modelling the impedance for a synchrotron light source. The second key insight of this study: Insertion devices featuring rectangular geometry and NEG coating might cause a multi-peak structure of the longitudinal impedance which can drive additional momentum-spread growth.
