Development of Versatile Environmental Cell for Electron Microscope

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The closed type environmental cell (EC) has been put into practical use for observing the hydrated specimens with the standard electron microscopes. Based on this design of the closed type cell, the film-sealed type EC for versatile use has been developed.(1)Improvement of the closed type EC and confirmation of the estimation of the gas pressure in the ECThe closed type EC was newly designed to control the gas layer thickness from 0 to 0.2mm for observation with high resolution and for holding very thin liquid layer. For the closed type EC, the sealing film is the most important component of the cell because it must withstand the pressure higher than the atmospheric pressure when the EC is closed in the atmospheric condition. We developed the method for the best sealing film with high withstanding pressure and high electron transmittance. We also made the device for testing the withstanding pressure of the sealing films for improving the efficiency of the EC experiment.For high resolut … More ion observations, a pre-evacuation unit was made to set the gas pressure lower than the atmospheric pressure before sealing up the cell. The thickness of the gas layer in the cell can be estimated from the transmittance value plotted as the function of the mass thickness of the electron path, involving two sealing films and the gas layer. This method may be applied to estimate the thickness of the liquid layer in the cell for observing the biological specimens in the nearly natural environment.(2)Development of the film-sealed type environmental cell for versatile use and the gas control unitFor the practical use, the configuration of the film sealed type EC and the gas pressure control system were improved. By reducing the components of the EC, it became easy to assemble and handle the EC. In addition to this, the sealing film of high withstanding pressure could make the procedure of controlling the gas pressure in the EC simple, so we made a new gas control device to make the operation easy.For versatile use of the EC, small electrode unit was made and fitted into the EC. The pipes for gas circulation can be used as the passages for the conducting wires and some electric field can be made in the EC. With the use of the electrode unit, it was confirmed that the ions, produced by the electron irradiation to the gas molecules in the EC, can be collected efficiently.This technique can set not only the gas environment, but also some liquid environment in the EC and the thickness of the liquid layer can be controlled by balancing the speed between supplying and evacuating the gas in the EC. This technique must be useful tool for in-situ observation of hydrated specimens. Less