| 摘要 |
<p>An inner lid (16) is attached to a vacuum chamber (11), covering an inner region (10) of the vacuum chamber. An outer lid (12), also attached to the vacuum chamber, covers the inner lid (16), leaving a region (20) between the inner lid (16) and the outer lid (12). A gas conduit (22) allows gas to flow between the inner region of the vacuum chamber (10) and the region (20) between the inner lid (16) and the outer lid (12). A filter (21) is placed in or immediately outside the gas conduit (22) to prevent particles from entering the inner region (10) of the vacuum chamber from the region (20) between the inner lid and the outer lid. Since the pressure is the same on the top and bottom of the inner lid (16), the inner lid does not flex and thus does not rub against the vacuum chamber (11) when the vacuum chamber (11) is pumped down or vented up. <IMAGE></p> |
