Specimen elevator for an ion milling machine

Abstract

An ion milling machine specimen elevator comprising a vertically oriented piston which supports a specimen holder at its top and is movable between a lowered operating position and a raised viewing position. When the piston is in the lowered operating position, it is slowly rotated about its vertical axis by a suitable drive. The elongated piston passes through an O-ring seal into an evacuated ion milling or work chamber. At the bottom of the work chamber is disposed a pneumatic control cylinder into which the piston extends. The piston can be moved up or down by altering the pressure in the pneumatic cylinder. During ion milling the piston is at its lowest position in the evacuated work chamber and is held there by pressurized gas in the pneumatic control cylinder. A second small chamber is provided above the work chamber for specimen viewing and specimen exchange. The disclosed specimen elevator can move the specimen into the second chamber and at the same time provide a seal so the work chamber does not lose vacuum during specimen viewing or exchange. If it is desired to remove the specimen from the work chamber without disturbing its vacuum, the pressure in the pneumatic control cylinder is released and the elongated piston is automatically forced to its highest position by the exerted atmospheric pressure. As the elongated piston rises to its upper position the top of the piston passes through a second O-ring seal, at the top of the work chamber, then into the small second chamber. As the piston moves into the small second chamber, it seals the work chamber from the small second chamber so air admitted to the second chamber does not enter the work chamber. The small chamber can be lifted from the larger work chamber after the internal pressure of the small chamber is raised to atmospheric. Removing the small chamber exposes the specimen holder, allowing the specimen to be removed or closely examined to study the progress of the ion milling operation. The specimen is reinserted into the work chamber by replacing and then evacuating the small chamber and then by repressurizing the pneumatic control cylinder. This forces the piston to move through the seal between the work chamber and the small chamber to its lowest position. The piston has a beveled gear attached thereto which engages a driven bevel gear when the piston is in the lowered operating position to slowly rotate the specimen in the work chamber.