Influence of the Electric Field Enhanced Thermal Electron Emission on Temperature of the Cathode with a Thin Insulating Film in the Arc Gas Discharge
A model of the electric field enhanced thermal (thermo-field) emission of electrons from the metal
cathode substrate into a thin insulating film on its surface is developed. A system of equations for the cathode
surface temperature in the arc discharge and the electric field strength in the film, providing the required discharge
current density, is formulated. It is shown that existence of the insulating film can result in a considerable
reduction of the cathode temperature in the discharge due to lower potential barrier height at the
metal-insulator boundary than at the metal-discharge boundary in case of the cathode without the film. It is
found that due to an enhancement of the thermal emission of electrons into the film by the electric field generated
in it, an additional decrease in the cathode temperature by about 100 K takes place.
The heat transfer process is simulated in a nano-sized cone-shaped cathode. A model of heat transfer is constructed using the phase field system and the Nottingham effect. We consider influence of the free boundary curvature and the Nottingham effect on the heat balance in the cathode.
This book is the proceedings of the IX International Conference for Professionals & Young Scientists “LOW TEMPERATURE PHYSICS” ICPYS LTP 2018 dedicated to the 100th anniversary of the National Academy of Sciences of Ukraine, and contains 150 peer-reviewed abstracts. These materials present and discuss the studies of modern aspects of experimental and theoretical physics at low and ultralow temperatures, including electronic properties of conducting and superconducting systems, magnetism and magnetic materials, optics, photonics and optical spectroscopy, quantum liquids and quantum crystals, cryocrystals, nanophysics and nanotechnologies, biophysics and physics of macromolecules, materials science, theory of condensed matter physics, technological peculiarities of the instrumentation for physical experiments, and other related fields.
The factors affecting the thermal degradation of a single silicon field-emission pointed cathode during the take-off of the emission current are described experimentally. The results of the numerical modeling of the temperature dynamics of the field-emission cathode in conditions of the presence of a free interface between the liquid and solid phases allowing for the surface tension are described.
A model of field electron emission from the metal cathode with a thin insulating film under the strong electric field, generated in the film by ions bombarding its surface in gas discharge, is developed. It takes into account tunneling of electrons from the electrode metal substrate into the insulating film, their motion in the film and going out of it into the discharge volume. An analytical solution of the onedimensional kinetic equation for the energy distribution function of emitted electrons in the film conduction band is found and an expression for the film emission efficiency equal to the fraction of emitted electrons, which escapes from the film and increases the cathode effective secondary electron emission yield, is obtained. It is demonstrated that calculated dependence of the emission efficiency on the electric field strength in the aluminum oxide film is in an agreement with experimental data for metal-insulatormetal tunneling cathodes. The proposed model can be used for investigation of an influence of the field electron emission from the cathode with a thin insulating film on its emission characteristics in gas discharge devices.
In this work, a model describing the field emission of electrons from the electrode metal substrate into the insulating film, their motion in the film and going out of it into the dischargevolume is formulated. An analytical expression for the film emission efficiency is obtained and its dependence on the film parameters is studied.
Mechanical performances of titanium biomedical implants manufactured by superplastic forming are strongly related to the process parameters: the thickness distribution along the formed sheet has a key role in the evaluation of post-forming characteristics of the prosthesis. In this work, a finite element model able to reliably predict the thickness distribution after the superplastic forming operation was developed and validated in a case study. The material model was built for the investigated titanium alloy (Ti6Al4V-ELI) upon results achieved through free inflation tests in different pressure regimes. Thus, a strain and strain rate dependent material behaviour was implemented in the numerical model. It was found that, especially for relatively low strain rates, the strain rate sensitivity index of the investigated titanium alloy significantly decreases during the deformation process. Results on the case study highlighted that the strain rate has a strong influence on the thickness profile, both on its minimum value and on the position in which such a minimum is found.
The ХХV International scientific – technical conference “Foundry 2018” was held of the 18-20 April 2018 at “Rostov” hotel in the city of Pleven, Bulgaria. Its aim is to provide a meeting place for scholars from different countries to present their scientific achievements and to discuss the problems of casting production.
The structural and spectroscopic features of the EuAl3(BO3)4 individual skeletal microcrystals synthesized by a melt solution method have been studied. Their infrared spectra taken from the as-grown microcrystal surfaces mainly contain the lines of the rhombohedral modification of EuAl3(BO3)4 and additional peaks of its monoclinic modification. TEM and X-ray diffraction studies confirm that these additional peaks in the IR spectra belong to the monoclinic C2/c polytype of the EuAl3(BO3)4 compound. We are the first to demonstrate the presence of coherent monoclinic domains in rhombohedral EuAl3(BO3)4 crystals by TEM. Cathodoluminance spectroscopy shows that the microcrystals generate strong emission lines in the range 580–630 nm, and their intensities are strongly influenced by the crystal orientation.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.