Showing 12 results for Plasma
H. Ghomi, M. Yousefi, Sh. Rostami, Y. Hayashi, E. Hotta,
Volume 4, Issue 2 (6-2010)
Abstract
A capillary plasma z-pinch as an alternative active medium of soft X-Ray lasers was studied experimentally and theoretically. The theoretical analysis was based on the self consistent solution of the so called “snow plow” model. The dynamics of pinched plasma is determined by the capillary parameters and by the time dependence of electrical current passing through it. The current time dependence is strongly influenced by the electrical circuit connected to the capillary. In order to optimize the pinch dynamics from the point of view of laser pumping, the effects of the electrical circuit parameters on plasma evolution are studied in this paper
Ms. Fateme Salehi-Marzijani, Dr. Seyede Zahra Shoursheini, Dr. Hamidreza Shirvani-Mahdavi, Ms. Somayye Pashaei,
Volume 8, Issue 1 (1-2014)
Abstract
The identification and concentration of heavy metals, which may be so harmful for the body, is determined by the method of calibration-free laser-induced breakdown spectroscopy using a special strategy. First, the plasma temperature is obtained using the Boltzmann plot. Then, a line with an inappreciable self-absorption is considered for each element as the reference. The modified intensities of other lines of the element are calculated through their self-absorbed intensities in terms of the reference intensity. The plasma temperature is again computed by line pair ratio method. This procedure is carried out by an iterative algorithm until the self-absorption coefficient of selected lines converges on one. In the last step, the corrected temperature is evaluated by the Boltzmann plot drawn using true (non self-absorbed) line intensities of each element. The concentration of the elements is finally determined by the corrected temperature and intensities. The results indicate that the accuracy of this method in determining the concentrations is significantly better than the normal way.
Dr. Hossein Zahed, Ms. Elham Emadi,
Volume 10, Issue 2 (11-2016)
Abstract
The behavior of linear and nonlinear dust acoustic waves (DAWs) in an unmagnetized plasma including inertialess electrons and positrons, ions, and mobile positive/negative dust grains are studied. Reductive perturbation method is employed for small and finite amplitude DAWs. To investigate the solitary waves, the Korteweg–de Vries (KdV) equation is derived and the solution is presented. By numerical analysis, it is found that the soliton structure of the dust acoustic wave depends upon plasma parameters like electron to ion Fermi temperature ratio, s, dust to ion temperature ratio d and quantum diffraction parameter H.
Hossein Mozaffari, Marzieh Akbari Jafarabadi, Mohammad Hossein Mahdieh,
Volume 11, Issue 2 (8-2017)
Abstract
In this paper, the dynamic behavior of laser induced optical breakdown in impure water was studied by using a pump- probe technique. The plasma was induced by a 1064 nm Nd:YAG laser pulse (with pulse duration ~10 ns) in distilled water with two types of impurities: (I) a solution (highly diluted salt water as a conductor) and (II) a colloidal (TiO2 in colloidal nanoparticle form as a dielectric); and finally the results were compared. The results show that, for both liquids, the probe beam transmission is reduced with pump laser intensity. Our results also show that, impurity size and type of conductivity can influence on plasma time evolution and transmissivity.
Mohammad Sadegh Soltani Gishini, Alireza Ganjovi, Majid Taraz, Masoud Saeed,
Volume 12, Issue 1 (1-2018)
Abstract
In this work, applicability of Particle in Cell-Monte Carlo Collisions (PIC-MCC) simulation method for better understanding of the plasma physical mechanisms and real important aspects of a plasma column driven by surface wave plasma discharges that is used in plasma antennas is examined. Via the implementation of geometry and physical parameters of the plasma column to an Object Oriented PIC-MCC code, the plasma density, electrical conductivity, plasma kinetic energy and electric field inside the plasma column as its essential properties are obtained. The gas within the plasma column is taken to be argon which is kept at the low operational background pressures. The radial increasing and axial decreasing of the electric field in the plasma column is observed. Moreover, the plasma density reduces radially, while it is maximized along the axial positions. It is seen that, the density of charged particles and their corresponding current densities are maximized at the positions closer to the surface wave launcher.
Hossein Zahed, Mohammad Reza Sayyar, Sayyed Jalal Pestehe, Samad Sobhanian,
Volume 12, Issue 2 (12-2018)
Abstract
The propagation of arbitrary amplitude dust ion acoustic waves (DIAWs) in a magnetized collisional dusty plasma including hot electrons, with kappa velocity distribution for electrons, warm ions and dust particles has been studied. In the presence of immobile massive dust particulates, DIAWs have been investigated through the Sagdeev pseudo-potential method. It is demonstrated that the amplitude and width of the pseudo-potential are increased with the ion density and also with Directional cosines. It is shown that the behaviors of the amplitude and the width of the wave in terms of all of plasma parameters is similar to the our recently work, and the spectral index has a little effect on the wave.
Amir Rahimian, Hossein Zahed,
Volume 13, Issue 2 (12-2019)
Abstract
In this paper, we have simulated the excitation of wake fields in the interaction of an intensive laser pulses having Half-Sine and Gaussian time envelopes with a fully ionized cold plasma using particle in cell (PIC) method. We investigated the dependency of wake filed amplitude to different laser and plasma parameters such as laser wavelength, pulse duration and electron number density. In addition, the effect of employing a longitudinal magnetic field on the intensity of wake field is studied. It has been seen that the wake field intensity is enhanced in the presence of a magnetic field for both Half-Sine and Gaussian shape pulses. Our aim has been finding optimum values of different parameters for which higher accelerating wake electric fields can be obtained.
Elham Emadi, Hossein Zahed,
Volume 14, Issue 1 (1-2020)
Abstract
In this article, linear and nonlinear dust ion acoustic (DIA) waves are studied in a magnetized quantum dusty plasma which consists of inertialess electrons and positrons, cold ions and negatively charged dust grains. For this purpose, quantum Hydrodynamic model (QHD) and reductive perturbation method are employed. To investigate linear and nonlinear waves, dispersion relation and a quantum Zakharov-Kuznetsov (ZK) equation are derived respectively. A stationary solution of the ZK equation is obtained to investigate the effects of plasma parameters on the amplitude of the solitons.
Vahid Eskandari, Nafiseh Sharifi,
Volume 14, Issue 1 (1-2020)
Abstract
In this study, silver nanoparticles were chemically synthesized and deposited on glass substrates using a reducing agent of sucrose, at 50°C. Different characterizations including atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and Raman spectroscopy were obtained to study silvery substrates. Then, the silvery substrates were used as the SERS substrates to detect vibrational modes of phenylalanine amino acid up to the concentration of 10-7 M. The importance of phenylalanine amino acid detection is due to the early diagnosis of phenylketonuria in neonates. Therefore, the blood plasma of a healthy neonate and a neonate with phenylketonuria disease were adsorbed on the SERS substrates. They enhance the intensity of molecular vibration peaks of phenylalanine amino acid of two kinds of blood plasmas. The intensities of molecular vibrations of unhealthy plasma are stronger than healthy plasma due to the higher concentrations of phenylalanine amino acid, which is the sign of Phenylketonuria disease.
Farshad Sohbatzadeh, Mojgan Barzegar, Colagar Abasalt Hosseinzadeh Colagar,
Volume 15, Issue 2 (7-2021)
Abstract
Pulsed UV sterilizer lamps and cold atmospheric pressure plasma are the newest technologies that have been proposed as feasible alternatives in the traditional sterilization method. The main objective of this project was to compare the sterilization effect of these two technologies (Pulsed UV lamps and cold atmospheric pressure plasma) with continuous UV lamps on Escherichia coli bacteria. Although Continuous UV lamps are widely used in different organizations such as hospitals for sterilization, they take hours to sterilize the medium. There are methods that can effectively decay the bacteria surface in a few minutes; it is called cold atmospheric plasma jet. Since sterilization has gained lots of attention, many researches are performing by other methods. This project releases how atmospheric plasma can strongly influence better on decaying Escherichia coli bacteria compared to two other techniques; Xenon arc lamp, continuous UV lamp. The results suggested that the xenon pulsed flash lamps with Pyrex envelope have the ability to sterilize the surface of the bacterium with at least 80 pulses. The results of atmospheric plasma flow on the bacterial surface have been proved that the reactive species (OH radicals, charged particles, NO, ozone, O3, in the plasma jet caused a significant decline in the colony numbers; after 6 minutes treatment by plasma jet, there was a great reduction in the number of colonies up to zero. Also, the effect of the commercial continuous UV sterilizer lamp was used and its sterilization results were compared to pulsed flash lamps and cold atmospheric plasma. These results demonstrate that pulsed light treatment can be effective on destroying Escherichia coli bacteria due to its high energy and short operating time.
Shadi Davoudi, Somayeh Mehrabian,
Volume 16, Issue 1 (1-2022)
Abstract
In this study, the self-guiding of an ultrashort laser pulse through air is investigated. Therefore, the terms of self-focusing, plasma defocusing and the pulse energy depletion due to the ionization, are considered in the wave equation. Then the laser pulse spot size equation is obtained using the source-dependent expansion method. Our results show that the laser pulse self-guiding occurs for the first twenty Rayleigh lengths. However, the laser pulse undergoes diffraction as it propagates further along the z axis. Moreover, it is seen that the back of the laser pulse is diffracted the most owing to the fact that the plasma is formed as the laser pulse propagates through air. It is also shown that the spot size variations affect the temporal and spatial profiles of the laser intensity, the laser pulse power and the ionization process.
Masume Moshkelgosha, Fatemeh Asem_abadi, Hajar Tavakoli,
Volume 17, Issue 1 (1-2023)
Abstract
The creation of single zeptosecond pulses is important in various scientific fields, particularly for studying time-resolved nuclear processes. In this study, a clean single sub-attosecond (270 zeptosecond) pulse is obtained in the simulation of a femtosecond laser with over dense plasma. First, the desired laser and plasma parameters are utilized to achieve the nano-bunches in the plasma surface and the desired spectrum up to 2000th harmonics is obtained. Then, different filters such as filtering the harmonics and different intensity filters are applied where, the special exponential function is due to a very clean single zeptosecond pulse.
