an improved electron microscope anticontaminator having a conduction rod enclosed within an independent vacuum system and micropositioning capability is described . the micropositioning facility allows the use of unusually small apertures in the cold anticontaminator block with a consequent improvement in efficiency of function . a self - contained contact sensor provides immediate audible warning of contact between a specimen holder and the cold anticontaminator block , permitting the removal of the usual mechanical end - stops for the specimen tilt mechanism and allowing the maximum specimen movement possible at any time . the independent vacuum system in combination with a heater positioned close to the anitcontaminator block allows the microscopist to vent the microscope column without removing the anticontaminator from the microscope . special anticontaminator blocks incorporating multiple apertures or an x - ray collimator eliminate the need for separate microscope objective aperture or x - ray collimator mechanisms and also ease design constraints imposed by the very limited space around specimens in high resolution microscopes .