Gate valve with improved seal arrangement

An ion implanter comprising:

• a first chamber housing defining a first chamber, the first chamber housing having a chamber wall defining an aperture;
• a second chamber housing defining a second chamber, the second chamber coupled to the first chamber, wherein the chamber wall separates the first chamber from the second chamber;
• a vacuum pumping system configured to maintain the first chamber and the second chamber at a vacuum condition;
• a gate positioned in the second chamber, the gate having a gate opening with a first seal fixed to the gate and positioned along a periphery of the gate opening, the gate also having a blocking portion with a second seal fixed to the gate and positioned along a periphery of the blocking portion;
• and
• an actuator configured to move the gate between an open position and a closed position, wherein the gate opening is aligned to the aperture and the first seal engages a sealing surface of the chamber wall in the open position and wherein the blocking portion is aligned to the aperture in the chamber wall and the second seal engages the sealing surface of the chamber wall in the closed position.