Abstract: Disclosed herein is a X-ray lithography system in which X-rays are generated by a laser beam focused upon a target within an evacuated chamber to create a soft X-ray emitting plasma which also emits debris particles. A thin sheet of X-ray transparent gas is provided between the target and a mask used in the lithographic process to displace the particles away from the mask. The sheet of gas may also be used to maintain a pressure differential across an opening in the evacuated chamber through which the X-rays pass towards the target. In addition, the gas sheet may be used to cool the X-ray mask by placing the mask close to the sheet but at a sufficient distance so that the sheet does not interfere with the mask.