An electron microscopy imaging system comprises an electronic microscope including an electron column and a vacuum chamber and having an optical axis; a helium supply assembly for selectively supplying helium to a helium-rich volume region near the optical axis outside the vacuum chamber; a sample support base outside the vacuum chamber, the sample support base being disposed for supporting a sample, outside the vacuum chamber, to be imaged in an electron microscope and further including a translation assembly which is operable for relative translation of the sample into and out of the helium-rich volume region.