Abstract: In a vacuum system for processing workpieces, a vacuum chamber has a workpiece-entrance opening. Load lock means for said entrance opening include a door for sealing the outside of said opening, a movable closure member within the chamber to seal the entrance opening from the interior of the vacuum chamber, and forming a load lock chamber when the door and closure member are both in closed positions. The load lock chamber is connected to a roughing pump and is separately connected to a high vacuum pump through a pumping opening in one or the other of said internal closure member or said door. A large aperture valve is provided in said pumping opening. In one embodiment said pumping opening is connected via suitable conduits and valves to a roughing pump and also to a high vacuum pump.