Plasma Parameters From Reentry Signal Attenuation

The research is focused on determining the plasma parameters such as electron temperature and density, and plasma and collision frequencies, that can be applied on plasma antenna simulation. From the characteristics of plasma parameters obtained, the antenna parameters are then investigated. The Ar-Hg discharge tube is used, and energized by using a high voltage power supply. The plasma parameters are obtained by using numerical programming namely Glomac based on the different voltage, current, pressure and size diameter of the discharge tube. Plasma antenna parameters are characterized by using Computer Simulation Technology (CST) software with different plasma frequency, gas pressure, tube size and material used to analyze the antenna performance. The plasma and collision frequencies are calculated based on the plasma parameter obtained from Glomac programming. It shows that the electron temperature decrease while electron density increase when the current is increased. The gas pressure and diameter of tubes are also influences the plasma parameters. From CST simulation, the antenna's performance can be analyzed in terms of return loss, resonant frequency, bandwidth, gain, and radiation pattern. The plasma frequency increase when the electron density increases. By changing the plasma frequency, gas pressure and tube diameter, the antenna performance can be improved in particular at their return loss, gain, directivity and conductivity. In addition, the efficiency of the plasma column as a radiating element is related to the conductivity of the plasma. From this study, the characteristics of the monopole plasma antenna is investigated and evaluated.

The theoretical analysis of hybrid surface wave propagation at chiral-plasma planar interface is presented in this manuscript. The dispersion relation is obtained for the proposed structure by applying boundary conditions at the chiral-plasma interface. The characteristic of hybrid surface wave can be tuned by changing the plasma frequency, plasma collisional frequency, and chirality parameter. It is shown that phase constant , attenuation or propagation loss and propagation length are dependent on plasma and chiral parameters. The effect of plasma frequency, plasma collisional frequency, and chirality parameter on the normalized phase constant , attenuation constant, and propagation length are presented computationally. Moreover, to verify the surface wave's condition normalized filed distribution is also presented. The present work may have potential applications in chiral and plasma-sensing based waveguide and enantiomeric sensing devices.

As is well known, the mask in projection printing is a thin (about 1,am thick) object, composed of numerous variable domains. The various domains contain different complex refractive indices. These refractive indices form a discontinuous "mask function" ,appearing as a coefficient in the Maxwell-Material (MM) equation1 that describes the transmission of the electric field through the 3D mask domain. The right-hand side of this equation involves the gradient of the dot-product of the electric field with the gradient of the log of the refractive index. Within each feature, the refractive index is a constant. Therefore its gradient vanishes, and the resulting local MM equation is the wave equation. However, at a feature boundary (chrome-quartz, phase-i— phase-2, etc.) the complex refractive index is discontinuous, resulting in a highly singular delta-function-like coefficient. The trailing components of the field display the standard Maxwell discontinuity conditions, resulting in two very singular terms, i.e. a derivative of a delta function and a product of two delta functions. Such a source term, with such a remarkable oscillation, will be the origin of extreme instability in the numerical solution of the equations, no matter which direct solution algorithm is employed. Accordingly, the derivation of a preconditioner, namely a function which contains most of the unpleasantness of the equation times a function to be found, is absolutely essential to obtain accurate solutions in a reasonable time. Through an elaborate uniformly asymptotic scheme and scale analysis, we have derived such a preconditioner. The solution of the direct MM equation was compared with the solution using the preconditioner, and it gave us the confidence that we were on the right track. It actually means that one wishes to find the mask's Green function which, when convolved with the electric field incident on the mask, yields the exiting field which then enters the imaging optical system. It is the purpose of this paper to demonstrate the results obtained thus far, as well as to illustrate its implications on defocus linewidth control.

Abstract. Modeling the interaction of dust with long-wave (LW) radiation is still a challenge because of the scarcity of information on the complex refractive index of dust from different source regions. In particular, little is known about the variability of the refractive index as a function of the dust mineralogical composition, which depends on the specific emission source, and its size distribution, which is modified during transport. As a consequence, to date, climate models and remote sensing retrievals generally use a spatially invariant and time-constant value for the dust LW refractive index. In this paper, the variability of the mineral dust LW refractive index as a function of its mineralogical composition and size distribution is explored by in situ measurements in a large smog chamber. Mineral dust aerosols were generated from 19 natural soils from 8 regions: northern Africa, the Sahel, eastern Africa and the Middle East, eastern Asia, North and South America, southern Africa, and Australia. Soil samples were selected from a total of 137 available samples in order to represent the diversity of sources from arid and semi-arid areas worldwide and to account for the heterogeneity of the soil composition at the global scale. Aerosol samples generated from soils were re-suspended in the chamber, where their LW extinction spectra (3–15 µm), size distribution, and mineralogical composition were measured. The generated aerosol exhibits a realistic size distribution and mineralogy, including both the sub- and super-micron fractions, and represents in typical atmospheric proportions the main LW-active minerals, such as clays, quartz, and calcite. The complex refractive index of the aerosol is obtained by an optical inversion based upon the measured extinction spectrum and size distribution. Results from the present study show that the imaginary LW refractive index (k) of dust varies greatly both in magnitude and spectral shape from sample to sample, reflecting the differences in particle composition. In the 3–15 µm spectral range, k is between ∼ 0.001 and 0.92. The strength of the dust absorption at ∼ 7 and 11.4 µm depends on the amount of calcite within the samples, while the absorption between 8 and 14 µm is determined by the relative abundance of quartz and clays. The imaginary part (k) is observed to vary both from region to region and for varying sources within the same region. Conversely, for the real part (n), which is in the range 0.84–1.94, values are observed to agree for all dust samples across most of the spectrum within the error bars. This implies that while a constant n can be probably assumed for dust from different sources, a varying k should be used both at the global and the regional scale. A linear relationship between the magnitude of the imaginary refractive index at 7.0, 9.2, and 11.4 µm and the mass concentration of calcite and quartz absorbing at these wavelengths was found. We suggest that this may lead to predictive rules to estimate the LW refractive index of dust in specific bands based on an assumed or predicted mineralogical composition, or conversely, to estimate the dust composition from measurements of the LW extinction at specific wavebands. Based on the results of the present study, we recommend that climate models and remote sensing instruments operating at infrared wavelengths, such as IASI (infrared atmospheric sounder interferometer), use regionally dependent refractive indices rather than generic values. Our observations also suggest that the refractive index of dust in the LW does not change as a result of the loss of coarse particles by gravitational settling, so that constant values of n and k could be assumed close to sources and following transport. The whole dataset of the dust complex refractive indices presented in this paper is made available to the scientific community in the Supplement.

During physical simulation of light transport, we separate materials between conductors and dielectrics. The for-mer have a complex refractive index and are treated as opaque, the latter a real one and are treated as transparent.However, thin layers with a complex refractive index can become transparent if their thickness is small compared to the extinction coefficient. This happens with thin metallic layers, but also with many pigments that are semi-conductors: their extinction coefficient (the imaginary part of their refractive index) is close to zero for part of the visible spectrum. Spectral effects inside these thin layers (attenuation and interference) result in dramatic color changes.

The scope of the present work was to evaluate the role of the complex refractive index in optical diffusion studies for imaging purposes. In particular, phosphor materials and their corresponding optical transmission characteristics play significant role in x-ray detectors, cathode ray tubes, microscopy techniques, white LED applications and have an impact on other scientific fields including chemical, energy, optoelectronic and space industries. The complex refractive index is associated with the optical attenuation capabilities of phosphor materials, either scattering or absorption, which in turn influences their imaging characteristics. In order to examine the complex refractive index effects, a simulation model was developed by taking into account the following: (i) phosphors of different layer thickness, 100 μm (thin layer) and 200 μm (thick layer), (ii) packing density 50%, (iii) three values of light wavelengths 400, 550, and 700 nm, and (iv) particle diameter in the range 10–10 mm. The complex refractive index was considered to vary: (a) from 1.5 up to 2.0 the real part and (b) from 10−6 up to 10−4 the imaginary part. The role of the complex refractive index on the optical parameters was examined within the framework of Mie scattering theory. Optical diffusion was assessed through Monte Carlo simulation techniques and the most important conclusion of the results was the achievement of improved phosphor spatial resolution by increasing the real part of the refractive index and not the imaginary one.

In this research, the effect of laser beam energy on the properties and behavior of plasma produced from aluminum and nickel alloy was studied using the Optical Stimulated Emission Spectroscopy method. The properties of the plasma were characterized by exposing the target material (the alloy) to high-energy laser pulses ranging from 500 to 900 mJ using a pulsed Nd:YAG laser with a pulse rate of up to 50 Hz. This ensures a balanced energy distribution and allows monitoring of the increasing effects in the plasma without strong thermal effects. This method allows for a detailed study of the physical properties of the plasma, including the spectral radiation intensity and associated emission peak as well as the study of various plasma properties such as temperature and electron density and other plasma parameters, including the plasma frequency, Debye length, and Debye number. The results obtained show that both temperature and density increase with increasing laser power, with both effects peaking at a laser power of 900 mJ. Calculations of the plasma frequency and Debye number also show a concomitant increase in these two effects with increasing laser power. This work demonstrates how laser power can increase plasma stability and significantly improve physical processes within plasma. It also demonstrates how diagnostic techniques can be useful in plasma analysis and have numerous medical, industrial, and technological applications.

In the present work, the effect of the cylindrical configurations of the sputtering device electrodes on the plasma parameters (Debye length, electron temperature, electron density, plasma frequency) is studied. Also, the effect of the argon gas pressure on the discharge properties is examined with gas pressures of (0.08, 0.2, 0.4 and 0.6) Torr. The properties of the plasma are diagnosed by optical emission spectrometry. The spectroscopic method is adopted for examining the atomic spectra of argon emission. The electron temperature is determined by the Boltzmann method. While, the Stark-widening method was employed for calculating the electron number density. The voltage against current curves of the cylindrical sprayer discharges shows the voltage to be nearly constant with slight increase in current. An increase in pressure causes the cathode cascades to compress and the negative glow to become thinner and more luminous. Plasma properties such as electron temperature and Debye length decrease with increasing pressure, while electron number density and plasma frequency increase.

Hypersonic boost-glide systems: Flight mechanics and plasma parameters evaluation through aero-thermo-chemical computational fluid dynamics

This paper presents an effective medium approach to calculate the attenuation and phase constants of modes in a 3D connected wire medium both below and above the plasma frequency. Physical and nonphysical modes in the structure are identified for all the important lattice directions. According to this, the medium behaves as an isotropic material in the vicinity of the plasma frequency. These results were compared with the numerical simulation and it was observed that the wave spreads below the plasma frequency along all the important lattice directions with the same attenuation constant. This implies isotropic behavior of the 3D wire lattice below the plasma frequency, and thus this medium can be considered as an isotropic negative permittivity medium.

Vacuum birefringence in strong magnetic fields: (II) Complex refractive index from the lowest Landau level

Numerous workers have studied rf resonance probe under the condition ν m ≪ω ep , i.e. under collisionless condition, where ν m is angular collision frequency and ω ep is angular plasma frequency. In the present paper, the interaction of rf signal with a back diffusion type plasma has been studied without neglecting collision frequency. The problem has been discussed theoretically under this condition, and the derivation yields two expressions for which impedance is minimum. To verify the result experimentally, a rectangular plasma chamber is designed and fabricated, where electron density can be changed without changing the discharging potential and vacuum conditions. From the experiment two resonance peaks are obtained in the I – f 2 curve ( I : current and f : applied frequency) corresponding to the two minimum impedance conditions, from which plasma parameters like electron density, collision frequency and electron temperature have been estimated.

In this article, the electromagnetic wave scattering from plasma columns with inhomogeneous electron density distribution is studied by the Green's function volume integral equation method. Due to the ready production of such plasmas in the laboratories and their practical application in various technological fields, this study tries to find the effects of plasma parameters such as the electron density, radius, and pressure on the scattering cross-section of a plasma column. Moreover, the incident wave frequency influence of the scattering pattern is demonstrated. Furthermore, the scattering cross-section of a plasma column with an inhomogeneous collision frequency profile is calculated and the effect of this inhomogeneity is discussed first in this article. These results are especially used to determine the appropriate conditions for radar cross-section reduction purposes. It is shown that the radar cross-section of a plasma column reduces more for a larger collision frequency, for a relatively lower plasma frequency, and also for a smaller radius. Furthermore, it is found that the effect of the electron density on the scattering cross-section is more obvious in comparison with the effect of other plasma parameters. Also, the plasma column with homogenous collision frequency can be used as a better shielding in contrast to its inhomogeneous counterpart.

In this paper, propagation constant estimation techniques in the frequency domain for monitoring the insulation status of the cable have been proposed. The attenuation constant and phase constant are calculated by comparing the energy and location of the incident signal applied to the cable and the reflected signal from the endpoint. The performance of the technique is verified by comparing the estimated propagation constant based on the reflectometry with the measured propagation constant.

This study used spectroscopy to investigate how the properties of calcium plasma generated by a Q-switched Nd:YAG laser at its fundamental wavelength were influenced by laser energy.Electron temperature and electron density were determined using the Boltzmann plot and Stark broadening techniques,The electron temperature ranged from 0.101 eV to 0.67 eV across samples 1 to 6The electron density ranged from 0.639 10 to 0.722 10 cm as the laser energy increased from 400 to 700 mJ, Fundamental plasma parameters such as the Debye length, the number of particles in the Debye sphere, and the plasma frequency were also analyzed The results indicate that laser energy significantly affects the physical properties of the generated plasma.