Integrated electron optical/differential pumping/imaging signal

Abstract

This invention provides for an integrated electron optical/differential pumping/imaging signal detection system for an environmental scanning electron microscope (ESEM). The ESEM includes a substantially cylindrical objective lens magnetic housing containing an axially disposed vacuum liner tube and containing means for magnetically focusing a beam of electrons passing through said liner tube. An annular ring comprised of magnetic materials abuts said magnetic housing at the lower end thereof and contains at least two pumping ports therein located axially with respect to one another. At least two annular nonmagnetic diaphragms and a final magnetic annular diaphragm are attached to the annular ring at different axial locations and extending inwardly therefrom. The diaphragms define at least two interior passages which each communicate with one of the pumping ports formed in the annular ring. A combination aperture holder and electron detector is releasably received and sealed with in the central openings of the annular diaphragms. The aperture holder has apertures therein for the passage of the electron beam and gas into and out of the specimen chamber of the ESEM and the interior passages and has electron detector means associated with the lower portion thereof.