CERN Accelerating science

Article
Title	Physical and Electromagnetic Properties of Customized Coatings for SNS Injection Ceramic Chambers and Extraction Ferrite Kickers
Author(s)	Hseuh Hsiao Chaun ; Blaskiewicz, Michael ; He, Ping ; Henderson, Stuart ; Pai, Chien ; Raparia, Deepak ; Todd, Robert J ; Wang, Lanfa ; Wei, Jie ; Weiss, Daniel ; Yung Lee, Yong
Affiliation	(BNL, Upton, Long Island, New York) ; (ORNL/SNS, Oak Ridge, Tennessee)
Publication	2005
In:	21st IEEE Particle Accelerator Conference, Knoxville, TN, USA, 16 - 20 May 2005, pp.3028
Subject category	Accelerators and Storage Rings
Abstract	The inner surfaces of the 248 m SNS accumulator ring vacuum chambers are coated with  100 nm of titanium nitride (TiN) to reduce the secondary electron yield (SEY) of the chamber walls. All the ring inner surfaces are made of stainless or inconel, except those of the injection and extraction kickers. Ceramic vacuum chambers are used for the 8 injection kickers to avoid shielding of a fast-changing kicker field and to reduce eddy current heating. The internal diameter was coated with Cu to reduce the beam coupling impedance and provide passage for beam image current, and a TiN overlayer to reduce SEY. The ferrite surfaces of the 14 extraction kicker modules were coated with TiN to reduce SEY. Customized masks were used to produce coating strips of 1 cm x 5 cm with 1 to 1.5 mm separation among the strips. The masks maximized the coated area to more than 80%, while minimizing the eddy current effect to the kicker rise time. The coating method, as well as the physical and electromagnetic properties of the coatings for both types of kickers will be summarized, with emphasis on the effect to the beam and the electron cloud buildup.