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Optická část mnohakanálového energiového analyzátoru elektronů
Čižmár, Petr
Our version of the multichannel energy analyzer consists of two main parts. At first it is an electron optical part, which separates the entering electrons by their energy. Then the electrons land onto a scintillating screen. Secondly there is the optical part, which should project the light signal on the scintillator onto a detecting CCD. There are several ways how to do this
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Optimalizace podmínek hydratace v ESEM
Autrata, Rudolf ; Neděla, Vilém
Study of biological specimens of soft tissues with fine and very fine hydrated structure still remains a big problem because this structure can be easily damaged by dehydration during the initiating phase of vacuum pumping of a microscope. The attention is thus focused on setting up the conditions for complete dehydration of samples, ensuring the nature state of a sample during the critical phase of pumping of a microscope
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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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Využití opticky zachycené sondy pro studium velmi slabých interakcí na molekulární úrovni - přehled
Zemánek, Pavel ; Jonáš, Alexandr
A micron-sized dielectric particle confined in a laser trap can be employed as a probe for the measurement of forces in the range from piconewtons to hundreds of piconewtons. Thus, if a biological system of interest (e.g. DNA molecule, single myosin or kinesin molecule, cell membrane) is attached to such a probe, its mechanical and dynamical properties (elasticity, viscosity, forces associated with movement) can be studied during its interaction with the environment with unprecedented resolution. This article introduces the basic principles of the laser trapping and force measurement and illustrates on several examples the great potential of the light-based force transducer for exploiting non-invasively the dynamics of molecular systems
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Emisivita a absorptivita tepelného záření povrchů konstrukčních kovů za velmi nízkých teplot
Musilová, Věra ; Hanzelka, Pavel ; Králík, Tomáš ; Srnka, Aleš
Comparison of thermal radiation properties of surfaces of several metals commonly used in cryogenics is presented. We have measured heat absorbed by a surface of Cu, Al and stainless steel kept at a temperature of about 5 K - 10 K. The source of heat was a parallel black surface placed in a small distance from a tested sample. As a result of our measurement, the dependences of absorptivity on the temperature of the heat radiation source are plotted between 30 K and 140 K. The influence of different types of metal treatment, e.g. chemical and mechanical surface finish and annealing, on radiation heat transfer is presented
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Zařízení pro měření tepelné emisivity při nízkých teplotách
Králík, Tomáš ; Hanzelka, Pavel ; Musilová, Věra ; Srnka, Aleš
In the described device, the thermal emissivity or absorptivity of the sample is measured by substitution of the radiative heat flow between two parallel surfaces by thermal output of a heater. Fast measurements of the mutual emissivity for the range of the temperature of the radiating surface 25 K - 150 K are possible. The absorbing surface has a temperature between 5 K and 10 K when LHe is used as cryoliquid. The desired measurement sensitivity is 1 mK for temperature and 0.1 mikroW for heat power, respectively. The diameter of the whole device is 50 mm and so it is possible to use a commercial Dewar can for the cooling. The form of the sample is a circular plate 40 mm in diameter and 1 mm in thickness with one tested side. The emissivity and its temperature dependence for various surface treatments can be checked immediately before application in a cryogenic system
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