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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 Nb 3 Sn 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 Nb 3 Sn film was recorded on a 16 mm cine-film.
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Watanabe et al. (1967) studied this question.
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