A Liquid Helium Cooled Stage for an Electron Microscope

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Abstract
A liquid helium cooled stage for an electron microscope has been constructed. Liquid helium flows through a thin copper pipe around the specimen holder. The flexible pipe allows the specimen movement for observation. The holder and pipe are enclosed in a shield case which is kept nearly at liquid nitrogen temperature. The specimen temperature is controlled by the flow of helium, and is measured with an Au+Co-chromel thermo-element attached to the stage. The specimen can be exchanged by means of a usual mechanism without breaking the column vacuum. Observation of magnetic effect in a superconducting film is described. In a defocused image of Nb3Sn film we observed the beam deflection due to the magnetic field pushed out of the film below the transition temperature. The inhomogeneity of the mixed state of a niobium film appeared as a zig-zag edge in the defocused image. The relaxation of the magnetic flux frozen in Nb3Sn film was recorded on a 16 mm cine-film.