Персона: Кулагин, Владимир Владимирович
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FESTIM: An open-source code for hydrogen transport simulations
FESTIM (Finite Element Simulation of Tritium In Materials), is a versatile open-source finite element code developed in Python for simulating hydrogen transport in materials. FESTIM addresses limitations observed in existing codes by enabling multi-dimensional, multi-material simulations, leveraging the flexible finite element method and the open-source FEniCS library. Use cases illustrating FESTIMs applicability and efficacy are presented: reproduction of thermo-desorption experiments, modelling plasma-facing components (divertor monoblocks), and modelling breeding blankets. A comparative analysis with two other numerical tools (TMAP8 and COMSOL‚?) is then performed. FESTIM is in very good agreement with these codes and shows similar (or better) computing performances. Finally, the thorough validation and verification (using the method of manufactured solutions) of the code is described, highlighting the codes reliability.
Nano-tendril bundles behavior under plasma-relevant electric fields
© 2020 Elsevier LtdThe appearance of unipolar arcs is a negative phenomenon that occurs among plasma-wall interaction processes in thermonuclear devices. Nano-tendril bundles (NTBs) can be formed on a plasma-facing surface of tungsten after irradiation by helium plasma that contains impurities of neon or nitrogen. These structures can increase the probability of unipolar arcing because of significant electron emission under a relatively small applied electric field of several kV/mm. The electron emission can appear due to sufficient field enhancement factor that can be up to several thousand. Furthermore, NTBs can be easily overheated, which leads to initiation of the thermofield emission, consequently triggering explosive emission because of intensive heating by Joule source, even without any additional external power load. This paper shows the results of the field enhancement factor estimations, as well as the critical field strength for NTBs when they can collapse because of explosive electron emission caused by Joule heating. The results were obtained by numerical simulations in COMSOL Multiphysics© and experimentally in a vacuum diode.
Analytical Estimation of the Atomic and Molecular Flux Ratio from the Tungsten Surface
Overheating of Nanostructured Tendril Bundles due to Thermo-Field Emission
© 2021 IEEEField emission current accompanied by visualization of emission sites distribution was measured for nanostructured tendril bundles (NTB) on a tungsten surface. These structures are formed in linear simulators of plasma-surface interaction under helium plasma irradiation with Ne or N2 mixture, and unipolar arcing is often observed for such surfaces. It was shown that field emission current from NTB could be stable for a long period under constant electric field making these structures promising to use as flat cold cathodes. A numerical model was developed for calculating the thermo-field emission current and for checking the possibility of self-heating of the structures depending on their shape. Critical electric field values that lead to self-heating were estimated for different NTB shapes and compared with experimental results.
Impact of helium nanobubbles on tungsten fuzz nanostructure conductivity
Автоэмиссионные свойства вольфрамовых образцов с NTB структурами на поверхности
Working area of the mephist tokamak: Preliminar estimation ОБЛАСТЬ РАБОЧИХ ПАРАМЕТРОВ ТОКАМАКА МИФИСТ: ПРЕДВАРИТЕЛЬНАЯ ОЦЕНКА
© 2020 National Research Center Kurchatov Institute. All rights reserved.Small spherical tokamak MEPHIST is under construction at the NRNU MEPhI. This paper is devoted to the analysis of the working area of the MEPHIST tokamak and modeling of ohmic discharges in the different plasma configurations, which can be obtained in it.