Titanium Coating of Ceramics for Accelerator Applications

Titanium thin films can be deposited on ceramics, in particular alumina, without adherence problems. Even after air exposure their secondary electron yield is low compared to alumina and can be further reduced by conditioning or beam scrubbing. In addition, depending on the film thickness, titanium provides different surface resistances that fulfil requirements of ceramics in particle accelerators. Titanium thin films (MOhm square range) are used to suppress electron multipacting and evacuate charges from ceramic surfaces. Thicker films (5-25 Ω square range) are applied to lower the surface resistance so that the beam impedance is reduced. In this contribution, we present the results of a development aimed at coating 2-meter long alumina vacuum chambers with a uniform surface resistivity by a dedicated DC magnetron sputtering configuration.