Specimen Devices for in Situ Experiments

Abstract

The space available in the specimen region of the electron microscope has been the major limitation controlling the development of specimen devices. There has always been a tendency for microscope designers to minimize this available space in order to achieve the best electron optical resolution and this has made it very difficult to construct workable specimen devices for double tilting, heating, cooling, straining, etc. This problem has been recognized, however, and some microscopes have been equipped with a second interchangeable objective pole piece which although having a lower resolution has a large upper bore capable of accepting relatively complex top entry cartridges. This design feature has contributed greatly to the development of specimen devices capable of performing in situ experiments. Further impetus to the development of specimen devices has come from the availability of higher voltage microscopes which for equivalent resolutions have a larger working volume in the specimen region than conventional 100KV instruments. A particularly versatile pole piece design used in the AEI EM7 high voltage microscope is shown in figure 1. This design permits rapid exchange between a high resolution top entry pole piece, a wide gap (20mm) pole piece for side entry specimen rods and a wide bore (30mm) pole piece for large top entry specimen cartridges.