PHYSICAL AND ELECTROMAGNETIC PROPERTIES OF CUSTOMIZED COATINGS FOR SNS INJECTION CERAMIC CHAMBERS AND EXTRACTION FERRITE KICKERS

In the SNS accumulator ring, ceramic vacuum chambers are used for the 8 injection. kickers to avoid shielding of a fast-changing kicker field and to minimize eddy current heating. The inner surface of the ceramic chambers was coated with Cu to reduce the beam coupling impedance and provide passage for beam image current, and a TiN over layer to reduce secondary electron yield. The ferrite surfaces of the 14 extraction kicker modules were also coated with TiN. Customized masks were used to produce longitudinal coating strips of 1 cm x 5 cm with ∼ 1 mm separation among the strips. The coating methods, the physical and electromagnetic properties of the coatings and the effect to the beam and to the electron cloud build-up are summarized