| 摘要 |
<p>PURPOSE:To outwardly discharge a generated heat and prevent the entrance of dust into a vacuum by sealing electromagnetic actuators in a space in which a refrigerant is circulated. CONSTITUTION:Air is fed under pressure from a tube 9A and returned from a tube 9B, to circulate air in a sealed container 2. A current is allowed to flow in the coil of each electromagnetic actuator 3 in the container 2 through lead wires in the tubes 9A, 9B, exciting the coils to act electromagnetic force, thereby, attracting the movable piece 4 of a magnetic material installed on a holding member 5 made of a flexible material to close a holding portion 6. A wafer 50 is held by this holding portion 6.</p> |
