Calculation Of Plasma Parameters Research Articles

Laser–plasma driven green synthesis of size controlled silver nanoparticles in ambient liquid

This article explores the expansion behavior of laser produced silver plasma in stationary and stirring liquid media using space resolved optical emission spectroscopy and plasma instigated size controlled synthesis of silver nanoparticles via laser ablation. Second harmonics (532 nm) of an Nd:YAG laser was employed for the ablation of a silver target in ambient liquid for plasma formation. Calculation of plasma parameters — electron temperature and electron number density were done for different laser fluences and in various liquid media at room temperature. The Electron temperature (Te) was measured by exploiting the Boltzmann plot method and the electron number density (ne) was estimated from Stark broadened profiles of isolated lines from optical emission spectra. UV–Vis spectroscopy, fluorescence spectroscopy and high-resolution transmission electron microscopy further substantiated the optical and morphological characteristics of silver nanoparticles. Obtained novel versatile results pave way for a far-reaching understanding in creation and characterization of silver plasma, in ambient liquid; and provides a methodical green approach towards the synthesis of metallic nanoparticles that can be fine tuned for size and morphology, by varying laser parameters.

ЗОНДОВІ ТА СПЕКТРАЛЬНІ ДОСЛІДЖЕННЯ МАЛОПОТУЖНОГО ЕЛЕКТРОРЕАКТИВНОГО ХОЛЛОВСЬКОГО ДВИГУНА

The work is devoted to the study of a low-power Hall Effect Thruster. The currency of developing and increasing of integral characteristics of Hall Effect Thruster with power consumption less 0,3 kW is substantiated. The main directions of low-power Hall Effect Thruster investigation are considered. The analysis of latest investigations and studies of low-power Hall Effect Thruster showed the existence of three main directions - development of fundamentally new schemes, improvement of existing models, as well as works on study of physical processes features in Hall Effect Thruster with power consumption up to 0,3 kW.Using developed Hall Effect Thruster ITM-31, distribution of plasma parameters in the discharge channel has been studied by probe diagnostic, and the wear of the discharge chamber walls has been studied by optical spectroscopy. Thruster characteristics are given. Investigations were carried out in a vacuum chamber 0,5 m in diameter and 0,8 m in length. The pumping was carried out by a diffusion pumps. At a maximum xenon consumption rate 1,5 mg/s, the working pressure in the vacuum chamber did not exceed 2∙10-3 Torr. Probe measurements were performed using a single probe; probe was inserted into the discharge channel from the anode side. Calculation of plasma parameters was carried out graphically. The temperature and concentration of charged particles are calculated, and the electric potential distribution is obtained. Conclusions are made about the properties of the accelerating layer.It is shown that one of the non-intrusive methods of diagnostics is the method of optical emission spectroscopy (OES). With the help of this method it is possible to provide plasma parameters investigation and characteristics of the construction wear during the thruster testing at different regimes of operation and on each stage of thruster lifetime. For the spectroscopic investigation of the Hall Effect Thruster discharge chamber walls wear the scheme of the experiment and the equipment description is presented. For the estimation of the discharge chamber insulators erosion rate the spectral lines criteria and method of wavelengths selection is presented. Mathematical model of the thruster plasma plume experimental emission spectral data processing is described that was developed on the basis of actinometry hypothesis and corona model. Results of the spectroscopic investigation of the discharge chamber erosion rate at different thruster operational regimes are presented. From experimental and theoretical model the dependence of the discharge chamber insulators erosion rate from the discharge voltage was processed.

Modelling of plasma behaviour in the vicinity of intensive impurity sources

Plasma behaviour in the vicinity of strong sources of impurities is considered by taking into account quasi-neutrality, Coulomb collisions of background particles with impurity ions, radiation losses and sinks of charged particles to bounding material surfaces. If several ion species are present in the plasma the generalized Bohm criterion requires that a certain function of the main ion velocity changes its sign when moving along the magnetic field from the distant plasma through the impurity source to the surface. This allows us to formulate the ‘regularity’ conditions for the motion equation of the main ions and a numerical approach to find the only physical solution without singularities is elaborated. Calculations of plasma parameters in the shadow of a limiter, through which impurities are injected, have been done for the conditions of impurity seeding experiments in the tokamak TEXTOR.

Dust crystals in plasma created by a proton beam

In this work we present the first observations of dust crystal generated in plasma by the slowing-down proton beam. The crystal observed has a simple cubical lattice with the mean distances between particles for different gases (He, Ne, Ar, Kr, Xe) from 90 µm to 140 µm. For calculation of plasma parameters the model of kinetic processes was developed. Results of our simulation showed that anisotropic dust particles interaction can be the main physical reason for the appearance of the crystal-like structure.

Langmuir probe measurements in commercial plasma plants

We developed and tested a Langmuir double-probe system suitable for measurement in industrial environments, where quick and easy-to-handle methods are required. Data acquisition and calculation of plasma parameters are controlled by a personal computer. An evaluation algorithm is presented and its properties are briefly discussed. Successful operation of the system can be proved in a variety of different plasma configurations, namely in radiofrequency driven, pulsed direct current and microwave plasmas. Typical measurements and the conclusions that have been drawn are presented. Plasma densities were in the range 108-1013 cm-3. From the end user's point of view the main application areas are trouble-shooting, on-line process control and plasma source characterization during the development stages of a plasma plant.