Patent ID: 8747631

Claim:
A method for coating of substrates within an evacuable chamber comprising: providing a cylindrical target surface on a magnetron, a hollow substrate to be coated where an inside surface of the substrate includes surface oxides, and an electrically conductive shield tube between the cylindrical target surface and said hollow substrate; applying a relatively high negative voltage to said hollow substrate and a relatively low negative voltage to said shield tube, evacuating the evacuable chamber to a specified pressure, introducing a gas flow of inert gas at a specified flow, and cleaning said inside surface of said hollow substrate, wherein said surface oxides are sputtered from said inside surface of said hollow substrate and deposited on an outer surface of said shield tube and not on said magnetron; grounding said shield tube and turning on said magnetron, cleaning said cylindrical target surface, removing surface oxides from said cylindrical target surface and depositing said surface oxides from said cylindrical target surface onto an inner surface of said shield tube; and removing said shield tube and sputtering a coating from the cylindrical target surface onto said inside surface of the hollow substrate.