SURFACE RESISTIVITY TAILORING OF CERAMICS BY METAL-ION IMPLANTATION

An important technique used for the suppression of high-voltage surfac e flashover on ceramic insulators as well as for RF windows is to prov ide some surface conduction to bleed off the accumulated surface charg e. We have used metal ion implantation to modify the surface of high-v oltage ceramic vacuum insulators so as to provide a uniform surface re sistivity of the order of 10(10) Omega square(-1). A broad-beam vacuum are ion source-based implanter was used to implant Pt at about 130 ke V to doses of up to similar to 6 x 10(16) ions cm(-2) into both small ceramic test coupons and also into the inside surface of several ceram ic accelerator columns 25 cm I.D. by 28 cm long. For implantation of t he large columns, an appendage to the implanter was made that allowed the column to be continuously rotated while being implanted. A rotatin g cradle held the column at an appropriate angle to the incident energ etic large-area ion beam while continuously slowly rotating it about i ts axis so that the entire inside surface was uniformly implanted. The mechanism was insulated, and the high-voltage resistance could be mea sured in-situ (with implantation switched off) at selected times durin g the processing. By appropriate choice of dose, the surface resistivi ty could be tailored over a range from its pre-implantation value of > 10(15) Omega square(-1) down to similar to 10(9) Omega square(-1). Th e results indicate that even lower resistivity values can be achieved if desired. Here, we describe the experimental set-up used to do the i on implantation and summarize the results of our work on implantation into test coupons and ceramic columns. (C) 1998 Elsevier Science S.A.