Specimen transfer device for an ultra-high vacuum field ion microscope

A device is described that enables the specimen in a field ion microscope to be replaced without disturbing the ultra-high vacuum conditions, thus improving the utilization of the microscope. Specimen transfer is accomplished in three stages: atmosphere to low vacuum, low vacuum to high vacuum and high vacuum to ultra-high vacuum. The path travelled by the specimen between the ultra-high vacuum and the intermediate high vacuum chambers is of very low conductance, while the area of unbaked surface exposed to the ultra-high vacuum is negligible. The device is of all-metal construction and all parts exposed to ultra-high vacuum are bakeable; since the intermediate high vacuum chamber can be partly outgassed by heat conducted from the microscope itself during baking, specimen holders parked in that chamber can also receive a preliminary outgassing. Construction of the transfer tools to very precise limits enables the specimen to be positioned in the microscope to within a few thousands of an inch.