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Influence Boundary Layer In The Differentially Pumped Chamber
Bílek, Michal ; Hlavatá, Pavla
The goal of this thesis is the analysis of a gas flowing through the drain channels within the apertures of differentially pumped chamber of the Environmental Scanning Electron Microscope (ESEM). This thesis contains a verification of current simulation results of gas flow within the differentially pumped chamber published by D. Danilatos using Monte Carlo method in comparison with simulation results achieved by using simulation program ANSYS Fluent, which uses the mechanism of continuum for its calculations and where it was effect of the boundary layer taken into account.
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The Impact Of Critical Flow In Differentially Pumped Chamber
Hlavatá, Pavla
Environmentální rastrovací elektronový mikroskop (EREM), který je konstruován pro vysoký tlak plynů v komoře vzorku namísto vakua, umožňuje studovat vzorky obsahující vodu nebo živé biologické vzorky bez nutnosti jejich speciální úpravy. To z důvodu, že mezi komoru vzorku a tubus je vložena diferenciálně čerpaná komora. Vzhledem k velkým tlakovým spádům u této konstrukce dochází při čerpání plynu k nadzvukovému proudění za clonou oddělující komoru vzorku od diferenciálně čerpané komory. To se projevuje specifickým jevem kritického proudění ve cloně a poklesem tlaku v proudu v nadzvukové oblasti. Vhodnou konstrukční úpravou je možné využít daný jev a docílit snížení průměrného tlaku plynu ve dráze primárního svazku. To má za následek snížení rozptylu primárního svazku a zvýšení ostrosti výsledného obrazu.
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Supersonic Flow Measurement Within A Lowpressure
Area
Bayer, Robert ; Hlavatá, Pavla ; Bílek, Michal
The goal of this paper is to describe the idea of measuring a supersonic gas flow within low-pressure areas in order to describe its behavior and to compare the measurement data with the generally described supersonic gas flow behavior derived from its behavior within high-pressure areas. This data should help to make low-pressure supersonic flow simulations more accurate.
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Analysis of the gas glow
Hladká, K. ; Maxa, J. ; Neděla, Vilém ; Vyroubal, P. ; Vaculík, S. ; Hlavatá, P.
In order to optimize the shape of the Differentially pumped chamber in the area of the Primary Electron Beam passage for the current concept of the location of the foci of the Primary Electron Beam, it was necessary to adapt to the size and shape of the limitations of the existing structure. On fig. 1a is the total cross sectional view of the Differentially pumped chamber. Three variants were examined: Current concept with an easily machined shape of the passage of the primary beam, semi-closed concept with a conical shape, cone concept with a wider cone.
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Use systems for the analysis of gas flow
Maxa, J. ; Neděla, Vilém ; Hladká, K. ; Vyroubal, P. ; Vaculík, S. ; Hlavatá, P.
Environmental scanning electron microscope is explaining withdrawing of two differentially pumped chambers in a drawing area. To solve this problem is used finite volume method. This method includes several steps: - With using of mesh the area is dividing into discrete volume. - Discretization and balancing of the unknown quantities in each finite volume - Numerical solution of discretized equations.
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