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Detekce signálu použitím segmantového ionizačního detektoru
Jirák, Josef ; Černoch, P. ; Autrata, Rudolf
For signal electrons detection at environmental conditions, it is often used a detector that utilizes impact ionization in the gaseous environment of a specimen chamber for a signal amplification. An electrostatic field created in a space between a grounded specimen and a detector electrode provides the energy needed for efficient ionization of secondary electrons. A voltage of several hundred volts is attached to the detector electrode. It was proposed an electrode system of a ionization detector, with several concentric electrodes divided into two halves - right and left. It was shown that the higher diameter of the electrodes brings an increased contribution of backscattered electrons to the detected signal. Different contrast mechanisms were studied
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Měření a nastavování vlhkosti v Environmnetálním rastrovacím elektronovém mikroskopu
Autrata, Rudolf ; Jirák, Josef ; Neděla, Vilém ; Špinka, J.
When we are detecting signal electrons with an ionization detector in ESEM, the most advantageous is to use, with respect to the effectiveness of ionization, environment of water vapours in the specimen chamber. The most suitable are saturated water vapours (relative humidity of 100%). This environment is also advantageous for observation of specimens containing water. At pumping of the specimen chamber to the working pressure (typically around 1000 Pa), in the case of wet specimens, evaporation of specimen can occur, or on the contrary, condensation of water on them. It means, that in some cases the specimen will not remain in the original state. That is why we try to adjust and optimize the pumping procedure and pumping of water vapors to minimize deformation of the observed specimens
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