The coating of internal surfaces of a workpiece is achieved by connecting abias voltage (20 and 47) such that the workpiece functions as a cathode and byconnecting an anode (22 and 24) at each opening of the workpiece. A source gas(16 and 18) is introduced at an entrance opening, while a vacuum source (32)is connected at an exit opening. Pressure within the workpiece is monitored(34) and the resulting pressure information is used for maintaining acondition that exhibits the hollow cathode effect. Optionally, a pre-cleaning(52) may be provided by introducing a hydrocarbon mixture and applying anegative bias to the workpiece, so as to sputter contaminants from theworkpiece using argon gas (16). Argon gas may also be introduced during thecoating processing to re-sputter the coating, thereby improving uniformityalong the length of the workpiece. The coating may be a diamond-like carbonmaterial having properties which are determined by controlling ion bombardmentenergy.
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