Influence of the Distance between Focusing Lens and Target Surface on the Characteristics of Laser-excited Lead Plasma

The present work investigated the effect of distance from target surface on the parameters of lead plasma excited by 1064nm Q-switched Nd:YAG laser. The excitation was conducted in air, at atmospheric pressure, with pulse length of 5 ns, and at different pulse laser energies. Electron temperature was calculated by Boltzmann plot method based on the PbI emission spectral lines (369.03 nm, 416.98 nm, 523.48, and 561.94 nm). The PbI lines were recorded at different distances from the target surface at laser pulse energies of 260 and 280 mJ. The emission intensity of plasma increased with increasing the lens-to-target distance. The results also detected an increase in electron temperature with increasing the distance between the focal lens and the surface of the target in all laser energies under study. In addition, the electron number density was determined by using the Stark broadening method. The data illustrated that the electron number density was increased with increasing the distance from target surface, reaching the maximum at a distance of 11 cm for all pulse laser energy levels under study.

The effect of gamma quanta absorption due to interaction with thermal bremsstrahlung photons of hot gas in galaxy clusters

The interaction of gamma quantum from distant sources with thermal bremsstrahlung photons of hot intracluster gas with producing electron-positron pair in case of 10 galaxy clusters is considered. It is supposed that intracluster gas in considered clusters is isothermal and electron number density may be described by β distribution with β = 2/3. It is presented that the optical depth due to considered interaction is about 10−8 — 10−.

Measurements of electron number density and temperature in a supersonic plasma jet by optical emission spectroscopy

The results of experimental studies of the shock-wave region of the supersonic plasma jet flow formed by a pulsed capillary discharge with a polymeric wall are presented. Using optical emission spectroscopy of high spatial resolution, a detailed picture of the evolution of the radial profiles of the electron number density and temperature along the initial section of an underexpanded plasma jet, starting from the capillary outlet and ending with the flow stagnation zone, has been obtained. It was found that the profiles of the electron number density and temperature reflect all the features of the shock-wave flow region, tracing the influence of intercepting, central and reflected shock waves.

Spectroscopic Characterization of Laser Ablated Germanium Plasma

In the present study, the germanium (Ge) sample has been studied by laser induced breakdown spectroscopy which leads to the formation of plasma plume in the air. This research work comprises on pure Ge sample, and it has been studied using laser irradiance 1.831011 watt.cm-2 and Q-Switched Nd:YAG laser pulse (λ ~ 1064 nm wavelength and  ~ 5 ns pulse width). The spatially resolved plasma plume parameters are investigated, such as variation of electron temperature Te and electron number density ne as a function of detector position. These parameters show variation in the plasma plume and yield electron temperature Te from 12340 to 7640 ± 1200 K. Whereas electron number density ne varies from 3.61017 to 1.601017 cm-3 with the change in detector position is moving away from plasma plume from 0 to 3 mm. The results show that electron temperature Te and electron number density ne are estimated from the Boltzmann plot method and by using Lorentzian function at spectral line using FWHM full width at half maximum at 265.11 nm (4p5s 3 p2 → 4p 2 3 p2) wavelength of Ge (I) line, respectively.

Controlling the plasma electron number density of copper metal using NIR picosecond laser-induced plasma spectroscopy

In this paper, we investigate a new method to control the plasma electron number density of copper metal using a near-infrared (NIR) picosecond Nd:YAG laser-induced plasma spectroscopy (LIPS) technique. The applied laser parameters are as follows; laser pulse energy and intensity varied from 29.2 to 59.4 mJ ± 3% and from 6.01×1010 to 12.35×1010 W/cm2 ± 5%, respectively, for a single pulse at 170 ps pulse duration, and beam diameter about 0.5 ± 0.1 mm. By considering the Stark broadening of a specific spectral line, electron density can be calculated using a neutral copper line at 521.8 nm, assuming the local thermodynamic equilibrium (LTE) condition. The observed electron density values were 1.09×1016, 2.24×1016, 3.60×1016, and 4.75×1016 cm–3 for the laser pulse energies 29.2, 41, 52.4, and 59.4 mJ, respectively. The plasma electron density values are increased with the increase in laser pulse energy. Such findings were interpreted due to an increase in the mass ablation rates with laser pulse energy. The obtained results explore the ability to control the plasma electron density by controlling the picosecond pulse energy. These results can contribute to the development of plasma technologies and their applications in many fields.

Simulation of Ion Current in Oxyfuel Flame Subject to an Electric Field

This paper presents a computational model to study ion and electron transportation and current-voltage characteristics inside a methane-oxygen flame. A commercial software is used to develop the model by splitting the simulation into the combustion and electrochemical transportation parts. A laboratory experiment is used to compare the results from the model. The initial and boundary conditions represented in the model are similar to the experimental conditions in the laboratory experiment. In the combustion part, the general GRI3.0 mechanism plus three additional ionization reactions are applied and results are then used as input into the electrochemical transportation part. A particular inspection line is created to analyze the results of the electrochemical transportation part. Ion, electron number density, and current density are studied along the interval from −40V to 40V electric potential. The ions are heavier and more difficult to move than electrons. The results show that at both torch and work surfaces charged sheaths are formed and cause three different regions of current-voltage relations.

Background for gravitational wave signal at LISA from refractive index of solar wind plasma

ABSTRACT A strong indication is presented that the space-based gravitational antennas, in particular the Laser Interferometer Space Antenna (LISA) concept introduced in 2017 in response to the ESA call for L3 mission concepts, are going to be sensitive to a strong background signal interfering with the prospected signal of gravitational waves. The false signal is due to variations in the electron number density of the solar wind, causing variations in the refractive index of plasma flowing through interplanetary space. As countermeasures, two solutions are proposed. The first solution is to deploy enough solar wind detectors to the LISA mission to allow for reliable knowledge of the solar wind background. The second solution is to equip the LISA interferometer with a second laser beam with a distinct wavelength to allow cancelling of the background solar wind signal from the interferometric data.