MATHEMATICAL MODELLING OF RF PLASMA AT LOW PRESSURES FOR CYLINDRIC VACUUM CHAMBER WITH CHARGED SPECIMAN

Для моделирования процессов в ВЧ-плазме пониженного давления с продувом газа разработана гибридная математическая модель при числах Кнудсена - для несущего газа. Модель включает начально-краевую задачу для кинетического уравнения Больцмана, описывающего функцию распределения несущего нейтрального газа, краевые задачи для уравнения неразрывности электронной, ионной и метастабильной компонент, уравнения сохранения энергии электронов, для ВЧ-уравнений Максвелла в форме телеграфных уравнений и уравнения Пуассона для потенциальной составляющей поля. Приводятся результаты расчета электрической напряженности, концентрации электронов, ионов и метастабилей, потенциальной составляющей электромагнитного поля в цилиндрической вакуумной камере. A hybrid mathematical model for the Knudsen numbers - for the carrier gas has been developed to simulate processes in a low pressure RF plasma with gas flow. The model includes an initial boundary value problem for the kinetic Boltzmann equation describing the distribution function of the carrier neutral gas, boundary value problems for the continuity equation of the electronic, ionic and metastable components, the electron energy conservation equations, for Maxwell’s RF equations in the form of telegraphic equations and the Poisson equation for the potential part of field. The results of the calculation of the electric intensity, the concentration of electrons, iones and metastables, the potential component of the electromagnetic field in a cylindrical vacuum chamber are presented.

Spatial profile of Al-ZnO thin film on polycarbonate deposited by ring-shaped magnetized rf plasma sputtering with two facing cylindrical Al2O3 - ZnO targets

Radial profiles of the ion saturation current are measured in a ring-shaped magnetized radio-frequency plasma sputtering process with two facing cylindrical ZnO targets including Al2O3 (2% wt.). The profile has a non-uniform shape with a peak whose position corresponds to the target near the electrode due to the effect of the magnetic field distribution. It becomes uniform at large distances between the substrate and a target (d st ≥ 50 mm). The radial profile of the resistivity of the Al-ZnO (AZO) films deposited on a polycarbonate plate at Ar gas pressure of 0.27 Pa is uniform at about 10-3 Ω·cm for d st ≥ 50 mm. The films deposited at various positions and room-substrate-temperature also show a good crystallinity based on an X-ray diffraction peak of about 33.95 - 34.44°. The grains exhibit a preferential orientation along the [002] axis with its size ranging from 18.15 to 28.17 nm. A higher transmittance of 95.6 % in the visible region is also obtained.

Coupling bimetallic Ni-La/MCM-41 catalyst enhanced by Radio frequency (RF) plasma for dry reforming

Controlling nickel particle size and inhibiting coke deposition on the supported catalyst was an enormous challenge. To solve this problem, La-doped nickel-based catalysts using MCM-41 as the support were prepared...

RF and microwave diagnostics for compact plasma traps and possible perspectives for fusion devices

Plasma diagnostics is a topic having a great impact on R&D in compact ion sources as well as in large fusion reactors. Towards this aim, non-invasive microwave diagnostics approaches, such as interferometric, polarimetric and microwave imaging profilometric techniques can allow obtaining volumetric, line-integrated or even space-resolved information about plasma electron density. Special probes can be also designed and implemented in order to characterize external and/or self-generated radio-waves in the plasmas. In particular, the design, construction and operation of a K-band microwave interferometry/polarimetry setup based on the Frequency-Modulated Continuous-Wave (FMCW) method at INFN-LNS will be described: this tool provides reliable measurements of the plasma density even in the extreme unfavorable wavelength-to-plasma scale ratio in plasma-based ion sources. A “frequency sweep” and a post-processing filtering method (for interferometry and polarimetry, respectively) were used to filter out the multipath contributions or cavity induced depolarizations in the detected signals. Besides this, the use of the aforementioned RF plasma-immersed probes will also be discussed, which allow measuring local E-fields and fast temporal response in order to characterize turbulent (through kinetic instabilities, cyclotron maser emission, etc.) vs. stable plasma regimes. An analysis based on wavelet transform applied to measurements of plasma radio self-emission in B-minimum and simple mirror traps will be presented. These tools and methods have the potential to be applied to plasma machines both in compact traps and large-size reactors with a proper scaling.

Deflections of dynamic momentum flux and electron diamagnetic thrust in a magnetically steered rf plasma thruster

Two-dimensional characterization of the plasma plume is experimentally performed downstream of a magnetically steered radiofrequency plasma thruster, where the ion beam current, the ion saturation current, and the horizontal dynamic momentum flux, are measured by using the retarding field energy analyzer, the Langmuir probe, and the momentum vector measurement instrument, respectively, in addition to the previously measured horizontal thrust. The measurements show the deflections of the dynamic momentum flux including both the ions and the neutrals; the change in the direction of the dynamic momentum flux is consistent with the previously measured horizontal thrust. Furthermore, the ion saturation current profile implies that the deflected electron-diamagnetic-induced Lorentz force exerted to the magnetic nozzle contributes to the change in the thrust vector. Therefore, it is demonstrated that the deflections of both the dynamic momentum flux and the electron-diamagnetic-induced Lorentz force play an important role in the thrust vector control by the magnetic steering.

Plasma enhanced chemical vapor deposition of gallium phosphide at low temperature

This article is devoted to the formation and study of the properties of amorphous gallium phosphide layers obtained by plasma-chemical deposition at a temperature of 250 °C. The optical and structural properties of the obtained layers on fused silica and silicon substrates were investigated. The possibility of the formation of a homogeneous amorphous gallium phosphide with a smooth surface at a low temperature and low power of RF plasma was shown.