The Effect of Cross-sectional Area of The Microwave Argon Discharge Tube on Some Plasma Parameters using COMSOL Multiphysics

<p>Electron precipitation and ion frictional heating events cause rapid variations in electron temperature, ion temperature and F1 region ion composition of the high-latitude ionosphere. Four plasma parameters: electron density, electron temperature, ion temperature, and plasma bulk velocity, are typically fitted to incoherent scatter radar (ISR) data.</p><p>Many ISR data analysis tools extract the plasma parameters using an ion composition profile from an empirical model. The modeled ion composition profile may cause bias in the estimated ion and electron temperature profiles in the F1 region, where both atomic and molecular ions exist with a temporally varying proportion.</p><p>In addition, plasma parameter estimation from ISR measurements requires integrating the scattered signal typically for tens of seconds. As a result, the standard ISR observations have not been able to follow the rapid variations in plasma parameters caused by small scale auroral activity.</p><p>In this project, we implemented Bayesian filtering technique to the EISCAT’s standard ISR data analysis package, GUISDAP. The technique allows us to control plasma parameter gradients in altitude and time.</p><p>The Bayesian filtering implementation enabled us to fit electron density, ion and electron temperatures, ion velocity and ion composition to ISR data with high time resolution. The fitted ion composition removes observed artifacts in ion and electron temperature estimates and the plasma parameters are calculated with 5 s time resolution which was previously unattainable.</p><p>Energy spectra of precipitating electrons can be calculated from electron density and electron temperature profiles observed with ISR. We used the unbiased high time-resolved electron density and temperature estimates to improve the accuracy of the estimated energy spectra. The result shows a significant difference compared to previously published results, which were based on the raw electron density (backscattered power) and electron temperature estimates calculated with coarser time resolution.</p><p> </p>

Comparison of the measured and modeled electron densities and temperatures in the ionosphere and plasmasphere during 14–16 May 1991

Optical emission spectroscopy (OES) combined with the models of plasma light emission becomes non- intrusive and versatile method of plasma parameters determination. In this paper we have studied the densities of charge carriers and electron temperature in Ar plasma of pulsed DC magnetron in different experimental conditions. Electron density and temperature were determined by fitting of relative emis- sion line intensities calculated from collisional-radiative model (CRM) to experimental ones. The model describes the kinetics of the first 40 excited states of neutral argon Ar and takes into account the fol- lowing processes: electron impact excitation/deexcitation, spontaneous light emission, radiation trapping, electron impact ionization, and metastable quenching due to diffusion to walls. Then, ions density was determined from relative intensity of 488 nm Ar + emission line and simple CRM accounting excitation from ground states of neutral Ar and ion Ar + . The values of electron and ion density agree very well. To test the stability of results, we performed Monte-Carlo calculations with random variation of exper- imental spectrum as well as of excitation cross-sections and estimated confidence intervals and errors for plasma parameters. Also, we validated OES study by comparison with Langmuir probe measurements. The agreement between optical and probe techniques is satisfactory.

Optical emission spectroscopy (OES) combined with the models of plasma light emission becomes non-intrusive and versatile method of plasma parameters determination. In this paper we have studied the densities of charge carriers and electron temperature in Ar plasma of pulsed DC magnetron in different experimental conditions. Electron density and temperature were determined by fitting of relative emission line intensities calculated from collisional-radiative model (CRM) to experimental ones. The model describes the kinetics of the first 40 excited states of neutral argon Ar and takes into account the following processes: electron impact excitation/deexcitation, spontaneous light emission, radiation trapping, electron impact ionization, and metastable quenching due to diffusion to walls. Then, ions density was determined from relative intensity of 488 nm Ar + emission line and simple CRM accounting excitation from ground states of neutral Ar and ion Ar + . The values of electron and ion density agree very well. To test the stability of results, we performed Monte-Carlo calculations with random variation of experimental spectrum as well as of excitation cross-sections and estimated confidence intervals and errors for plasma parameters. Also, we validated OES study by comparison with Langmuir probe measurements. The agreement between optical and probe techniques is satisfactory.

Helicobacter felis infection in mouse alters the amount of peripheral blood phagocytic leukocytes

The effect of neutral Ar injection on the plasma parameters is investigated numerically by using a multi-fluid code in this research. Reduction of electron and ion temperature has been observed according to the increment in injected neutral Ar density. The heat flux on the target plate has been also reduced with the increasing of injected neutral Ar density. For Ar: 2.0 × 1018 m−3 injection, electron temperature on the target plate reduced to about 1.5 eV. Increase in electron and ion density has been observed at lower injected Ar density. However, at higher Ar injection, electron density and ion density goes to be saturated. These outcomes indicate that the plasma in the end region approaches towards the plasma detachment state.

A time‐dependent three‐dimensional computer simulation of equatorial F region ionosphere has been carried out to understand the electron temperature structure observed by Hinotori satellite in the low and middle ionosphere. This model provides three‐dimensional distributions of ion densities, electron temperature, and ion temperatures. The simulations showed the electron temperature enhancements around the equator in the morning, in the midlatitude in the afternoon, and around the equatorial anomaly region from afternoon to midnight. The enhancements in the morning are due to photoelectron heating. The afternoon enhancements in the midlatitude come from the balance of heating and cooling. When no meridional neutral wind is included in the simulation, the electron temperature did not show remarkable enhancements in the midlatitude in the afternoon because of strong cooling by the dense electron density. Around the equatorial anomaly region the electron temperature increased at high altitude in the evening because of the competing effects of plasma cooling and the plasma movements. Since the ionospheric plasma zonal E×B drift is eastward near the sunset (where E is ionospheric electric field and B is magnetic field) and the vertical drift is downward, the high‐altitude dayside hot plasma can enter into the topside F region in the premidnight. The computer simulations were directly compared with the Hinotori satellite data. The simulation results were consistent with the equatorial electron density and temperature observed by the Hinotori satellite.

The influence of electric fields and neutral particles on the plasma sheath at ITER divertor conditions

Simulation of argon-excited microwave plasma reactor for green energy and CO2 conversion application

A superorbital reentry flow was realized in the X2 expansion tunnel of the Centre for Hypersonics of the University of Queensland, resulting in measurements of electronic excitation temperature, electron density, and particle densities of neutral and ionized atomic nitrogen and oxygen. A rectangular cold wall model was exposed to a flow corresponding to a flight equivalent velocity. Vacuum ultraviolet optical emission spectroscopy in the wavelength range between 116 and 185 nm was conducted through a window at the stagnation point. Spatially resolved optical emission spectroscopy of the stagnation streamline in the near-infrared wavelength range from 695 to 880 nm was conducted, analyzing the flow from the side. Population densities of excited atomic states, electronic excitation temperatures, and electron and ion densities were determined by analyzing the radiative transport in the flowfield. Additionally, the flowfield was numerically simulated using the code URANUS. Agreement in electron density () and electron temperature () in the equilibrium region is observed between the numerical simulations and the measurement. Significant differences between measurement and simulation in the distribution of the electron temperature at the shock are attributed to the modeling of the URANUS electron temperature.

Abstract. A new theoretical model of the Earth’s low- and mid-latitude ionosphere and plasmasphere has been developed. The new model uses a new method in ionospheric and plasmaspheric simulations which is a combination of the Eulerian and Lagrangian approaches in model simulations. The electron and ion continuity and energy equations are solved in a Lagrangian frame of reference which moves with an individual parcel of plasma with the local plasma drift velocity perpendicular to the magnetic and electric fields. As a result, only the time-dependent, one-dimension electron and ion continuity and energy equations are solved in this Lagrangian frame of reference. The new method makes use of an Eulerian computational grid which is fixed in space co-ordinates and chooses the set of the plasma parcels at every time step, so that all the plasma parcels arrive at points which are located between grid lines of the regularly spaced Eulerian computational grid at the next time step. The solution values of electron and ion densities Ne and Ni and temperatures Te and Ti at the Eulerian computational grid are obtained by interpolation. Equations which determine the trajectory of the ionospheric plasma perpendicular to magnetic field lines and take into account that magnetic field lines are "frozen" in the ionospheric plasma are derived and included in the new model. We have presented a comparison between the modeled NmF2 and hmF2 and NmF2 and hmF2 which were observed at the anomaly crest and close to the geomagnetic equator simultaneously by the Huancayo, Chiclayo, Talara, Bogota, Panama, and Puerto Rico ionospheric sounders during the 7 October 1957 geomagnetically quiet time period at solar maximum. The model calculations show that there is a need to revise the model local time dependence of the equatorial upward E × B drift velocity given by Scherliess and Fejer (1999) at solar maximum during quiet daytime equinox conditions. Uncertainties in the calculated Ni , Ne , Te , and Ti resulting from the difference between the NRLMSISE-00 and MSIS-86 neutral temperatures and densities and from the difference between the EUV97 and EUVAC solar fluxes are evaluated. The decrease in the NRLMSISE-00 model [O]/[N2] ratio by a factor of 1.7–2.1 from 16:12 UT to 23:12 UT on 7 October brings the modeled and measured NmF2 and hmF2 into satisfactory agreement. It is shown that the daytime peak values in Te , and Ti above the ionosonde stations result from the daytime peak in the neutral temperature. Our calculations show that the value of Te at F2-region altitudes becomes almost independent of the electron heat flow along the magnetic field line above the Huancayo, Chiclayo, and Talara ionosonde stations, because the near-horizontal magnetic field inhibits the heat flow of electrons. The increase in geomagnetic latitude leads to the increase in the effects of the electron heat flow along the magnetic field line on Te . It is found that at sunrise, there is a rapid heating of the ambient electrons by photoelectrons and the difference between the electron and neutral temperatures could be increased because nighttime electron densities are less than those by day, and the electron cooling during morning conditions is less than that by day. This expands the altitude region at which the ion temperature is less than the electron temperature near the equator and leads to the sunrise electron temperature peaks at hmF2 altitudes above the ionosonde stations. After the abrupt increase at sunrise, the value of Te decreases, owing to the increasing electron density due to the increase in the cooling rate of thermal electrons and due to the decrease in the relative role of the electron heat flow along the magnetic field line in comparison with cooling of thermal electrons. These physical processes lead to the creation of sunrise electron temperature peaks which are calculated above the ionosonde stations at hmF2 altitudes. We found that the main cooling rates of thermal electrons are electron-ion Coulomb collisions, vibrational excitation of N2 and O2, and rotational excitation of N2. It is shown that the increase in the loss rate of O+(4S) ions due to the vibrational excited N2 and O2 leads to the decrease in the calculated NmF2 by a factor of 1.06–1.44 and to the increase in the calculated hmF2, up to the maximum value of 32 km in the low-latitude ionosphere between –30 and +30° of the geomagnetic latitude. Inclusion of vibrationally excited N2 and O2 brings the model and data into better agreement.Key words. Ionosphere (equatorial ionosphere; electric fields and currents, plasma temperature and density; ion chemistry and composition; ionosphere-atmosphere interactions; modeling and forecasting)

The plasma environment in low-pressure systems allows coating different materials such as glasses, textiles, metals, etc. at the atomic level. Although vacuum coating is one of the best methods for thin film coating, the coating quality is closely affected by the spatial and temporal non-uniformities inside the reactor. Therefore it is quite important to determine the plasma properties within the chamber. The determination of plasma parameters such as electron temperature, electron excitation temperature, electron and ion densities can be realized using Langmuir probe systems, and by Optical Emission Spectroscopy (OES) by using Boltzmann plot method. Knowing such parameters can provide important information about specific reaction mechanisms, as well as it provides invaluable information that can increase reproducibility in various discharge process control in thin film coating. In this study, a homemade single Langmuir probe (s-LP) and a multiple Langmuir probe system (m-LP) were used to calculate electron temperature, electron density, saturation current, and plasma potential of the plasma at different pressures and at different voltages. One of the objectives of this work was to evaluate the electron temperature and ion density inside the plasma during a coating process. The second objective was to find the spatial change of electron temperature in the axial direction between cathode and anode by m-LP system including 8 independent tips. The last objective was to measure the axial plasma electron temperature distribution inside the vacuum chamber by using OES.

In the calculation of atomic structures within the plasma environment, the plasma screening effect on nuclei - electron interactions is generally considered, but the plasma screening effect on electron - electron interactions is less considered. In this work, the MCDHF method combined with the screening potential is used to study plasma screening effect on the atomic structure parameters versus the electron density, electron temperature, nuclear charge and the number of bound electrons. For the ground states and the first excited states of helium-like ions, the energy shifts, transition energy shifts and transition probability shifts caused by the plasma screening effect on electron-electron interactions increase with the increase of electron densities and decrease with increasing the electron temperatures, respectively. With the increase of nuclear charge, the energy shifts increase gradually and tends to a stable value, while the transition energy shifts and transition probability shifts decrease gradually and tend to 0. The energy shifts increase with the increase of the number of bound electrons. The electron density, electron temperature, nuclear charge and number of bound electrons corresponding to the percentages of transition energy shifts and transition probability shifts caused by plasma screening on electron-electron interactions greater than or equal to 10%, are called as the critical electron density, critical electron temperature, critical nuclear charge and critical number of bound electrons, respectively. When one of the following four conditions is satisfied, the percentages of transition energy shifts and transition probability shifts caused by plasma screening on electron-electron interactions will be greater than or equal to 10%, and the plasma screening effect on electron - electron interactions can not be ignored. 1) The electron density is greater than or equal to the critical electron density, when the electron temperature is a fixed value. 2) The electron temperature is less than or equal to the critical electron temperature, when the electron density is a fixed value. 3) The nuclear charge is less than or equal to the critical nuclear charge, when the electron density and temperature are both fixed. 4) The number of bound electrons is greater than or equal to the critical number of bound electrons, when the electron density and temperature are both fixed.

The decomposition characteristics of CF4 with Argon or oxygen in 2.45GHz microwave has been investigated by using a Langmuir probe with variation of the microwave power and chamber pressure. For CF4/Ar and CF4/O2/Ar discharges, the ion density and the electron density decrease with increasing microwave power. The electron temperature was decreased by reducing the mean free path of electrons with increasing microwave power. Also with increasing pressure, the electron temperature increase, and ion and electron density decrease by increase of inelastic collision frequency and of collision with the walls in the chamber. The electron temperature is 13.6 ~ 5.9 [eV], the electron density is 4.4×1010 ~ 2.2×1010 [cm-3] and ion density is 5.2×1011 ~ 4×1010 [cm-3]. According as add oxygen, ion and electron density increased relatively comparing to CF4/Ar discharge. The electron temperature is 8.5 ~ 6.2 [eV], the electron and ion density is 5.1×1010 ~ 2.1×1010 [cm-3] and 3.7×1011 ~ 7.3×1010 [cm-3], respectively.

Electron temperature and density in pure He, Ar, and Xe plasmas are estimated by zero-dimensional particle and power balance equations and measured by a Langmuir probe. Both of the modeling and experimental results show that the He (Xe) plasma has the highest (lowest) electron temperature and lowest (highest) electron density for a given fill pressure and source power. We find that the electron temperature is weakly dependent on the rf power, and thus the electron density can be controlled using the rf power. The electron temperature and density are also modeled and measured in mixtures of two noble gas species. We find that the electron temperature can be controlled by altering the composition of the noble gas mixture. Thus modulation of noble gas admixture ratios and rf power allows the electron density and temperature to be controlled independently. This independent control is shown to maintained with the addition of up to 20% partial pressure of oxygen, suggesting binary noble gas admixtures may provide additional control of dissociation kinetics.