Low-pressure chamber for scanning electron microscopy in a wet environment

A specimen enclosure assembly for use in an electron microscope and including a rigid specimen enclosure dish having an aperture and defining an enclosed specimen placement volume, an electron beam permeable, fluid impermeable, cover sealing the specimen placement volume at the aperture from a volume outside the enclosure and a pressure controller communicating with the enclosed specimen placement volume and being operative to maintain the enclosed specimen placement volume at a pressure, which exceeds a vapor pressure of a liquid sample in the specimen placement volume and is greater than a pressure of a volume outside the enclosure, whereby a pressure differential across the cover does not exceed a threshold level at which rupture of the cover would occur.