Analysis of Impact of Conic Aperture in Differentially Pumped Chamber

Abstract

The paper focuses on the simulation of medium dynamics in the environmental scanning electron microscope. In particular, the paper examines the conical aperture location effect in the differentially pumped chamber and the width of the pumping channel in this chamber. The solution is based on the Taylor-Maccoll theory about the impact of the shock wave and was obtained by the use of continuum and finite volume methods in the ANSYS Fluent system.

Electrohydrodynamic Model Of Electron Microscope

“…For better clarity, the displayed velocity is scaled to 100 m•s -1 (the maximum velocity was 460 m•s -1 ). Due to the low pressure as well as the significant pressure difference between these chambers a supersonic choked flow can be observed [3]. As the gas moves through the aperture to the area with lower pressure, the velocity increases and the gas expands in all directions, which would not be visible for a subsonic flow in which only a narrow stream would be created.…”

“…On the other hand, numerical simulations are often able to study these processes, as they only require knowledge of the geometry and general operating and boundary conditions. Currently, the numerical simulations in electron microscopy are often focused only on one area of physics (electromagnetics, particle-matter interactions, or hydrodynamics) [1,2,3]. Usually, the individual investigation of one specific area will not bring any inconsistencies in the results, however in some cases the multiphysics nature of these processes might be very important.…”

“…A huge amount of research is focused on the area of gas-particle interactions as it is a very complex phenomenon. However, the transport of electrons from the electron gun and the gas flow in the differentially pumped chamber is usually ignored [2,3]. This paper presents a custom numerical model implemented into a CFD software ANSYS Fluent, which was shown to be able to successfully model the rarefied gas flow in an ESEM [3].…”

“…However, the transport of electrons from the electron gun and the gas flow in the differentially pumped chamber is usually ignored [2,3]. This paper presents a custom numerical model implemented into a CFD software ANSYS Fluent, which was shown to be able to successfully model the rarefied gas flow in an ESEM [3]. The custom model consists of a description of an electromagnetic field and a description of a relativistic electron transport.…”

Analysis of gas thermal conductivity at low pressures using a mathematical-physical model

“…The results are used in the design of vacuum chambers of the Environmental Electron Microscope [13,14]. In planned future research, the shape and distribution of shock waves during the formation of a supersonic flow behind a small aperture separating two chambers with different pressures will be investigated [15,16].…”