Channel Of Plasma Research Articles

Nonlinear excitation of wakefields in quantum plasma channel

A detailed analytical study for wakefields excitation in a channel of quantum plasma is presented. The recently developed quantum hydrodynamic (QHD) model has been used to develop the interaction picture. Applying the perturbations in the laser fields orders, the magnetic and electric wakefields have been obtained for a Gaussian laser pulse. The electrons trapped by the wakefields are accelerated to extremely high energies. The quantum effects of Fermi statistical pressure and the quantum Bohm potential have been found to make significant changes in the nature of wakefields generated. The plasma channel helps in self-focusing and also contributes to acceleration. Both the longitudinal and transverse forces acting on the accelerating electron have been calculated.

Effect of pressure on discharge mode transition in radio-frequency capacitively coupled micro-beam plasmas

Micro-beam radio-frequency (RF) capacitive discharges have been widely used in the plasma enhanced chemical vapor deposition of nanocrystalline particles such as nano silicon crystal. However, the plasma column shrinks radially at a sufficiently high gas pressures as manifested by their glow not entirely filling the radial cross-section of the discharge tube. This greatly limits the dissociation rate of gas in plasma. In order to obtain the information about the plasma column varying with gas pressure, the formation of different gas discharge mode under different pressure is discussed. In this paper the spatial characteristics of micro-beam RF capacitive discharges are investigated by using an intensified charged-coupled device (ICCD) and a single lens reflex camera (SLR camera). Furthermore, high voltage probe and current probe are used to record the electrical characteristics of the high voltage electrode. The results indicate that in a pure argon discharge, the discharge mode evolves from a glow discharge into a filament discharge with the increase of pressure. As the pressure continues to increase, the filament is split: a single channel of plasma is split into two or more filaments at a certain gas pressure. However, the glow discharge in a mixture of 99% argon and 1% hydrogen at a low pressure is observed: the plasma spreads throughout the tube. As the pressure increases, the filament disappears, and the plasma column still can be observed in the center of quartz tube. The glow shrinks in the radial center at a moderate pressure. At a high pressure, the "annulus" glow discharge is achieved as manifested by a glow ring on the surface of the discharge tube. In addition, in pure hydrogen discharges, the discharge mode evolves from the full-space glow discharge into an "annulus" glow discharge with pressure increasing. Finally, through the interaction between the electron heating by the radio frequency electric field and heat conduction of gas, the filament discharge in a low thermal conduction gas is explained. In addition, special attention is paid to the pure argon filamentation, which is the splitting of a single channel of plasma into two or more smaller filaments as a result of the skin effect.

Current pulses caused by streamers in sphere-sphere electrode system

Streamer is a channel of a low temperature plasma growing due to ionization in the area of the strong electric field at the tip of the channel. Streamer investigation presents a technically highly complicated task due to fleetingness of the process: growing velocity is 106-107 m/s and characteristic duration is 10-8-10-7 s. The electric current pulse registration is a moderate method for investigating so fast process. However, the major part of streamer current investigations refers to low voltage range (about 103-104 V) and short streamers length range 10-2-10-1 cm. Also positive streamers are usually considered and there is a lack of information about current pulses caused by negative streamers. Both positive and negative streamers and their interaction are considered in the present paper. A multibranch streamer corona emerging at voltages above 250 kV and in long gaps (above 40 cm) was investigated.

Development and Comparison of Mathematical Model for EN19 Material Using Statistical Analysis Software on WEDM

Wire cut EDM (WEDM) is a thermo electric nontraditional manufacturing process in which material is removed by localized heating and melting. It is discrete spark generation method applicable for hard and difficult to machine materials. In this paper mathematical model developed for EN19 material with Stastical analysis software. Experiments are carried out using L27 Orthogonal array by varying Material Thickness, pulse on time, Pulse Off time, Flushing Pressure, Wire Tension and Servo voltage. Analysis found that varying parameters are affected for consumable wire with constant wire feed in different way for different response. Attempt to compare different order mathematical model for accurate modeling done in this research. Higher order mathematical model developed with R 2 value 0.9863 for MRR and 0.9918 for Surface roughness obtained which gives more accurate output for given input parameters. Keywords-WEDM, PULSE ON TIME, PULSE OFF TIME , MRR, REGRESSION I. INTRODUCTION WEDM is a non conventional thermo electric material removal method for conductive materials to cut intricate shapes and profiles with a thin wire electrode. The electrode is a thin wire of a diameter 0.05 to 0.25 mm copper or brass coated with mo lybdenum. As wire feeds fro m reel to reel, material is eroded fro m work material by a series of discrete sparks occurring between the work p iece and the wire under the presence of dielectric fluid which is continuously fed to the mach ining zone (1). The WEDM process makes use of electrical energy generating a channel of plasma between the cathode and anode (2) and turns it into thermal energy at a temperature in the range of 8000-12,000 oC (3). When the pulsating direct current power supply occurring between 20,000 and 30,000 Hz is turned off, the plasma channel breaks down. This causes a sudden reduction in temperature allowing circulat ing dielectric fluid to implore plas ma channel and flush mo lten particles fro m the pole surfaces in fo rm of microscopic debris (4).Erosion of metals by spark was first reported by Joseph Priesily in 1978, however controlled machining by sparks was first introduced by Lazarenko in Russia in 1944. The first Britis h patent was granted to Rudorff in 1950 (5). In 1974 D.H. Dulebohn applied optical-line follower system to auto matically control shape of component to be machined by W EDM proc ess. By 1975, its popularity was rapidly increasing, as the process and its capabilities were better understood by the industry. II. MATHEMATICAL MODELING Regression analysis is used to investigate and model the relat ionship between a response variable and one or more predictors. The term mu ltip le regression literally means stepping back toward the average. It was used by British mathematician Sir Francis Galton. Regression analysis is a mathematical measure of the average relationship between two or more variables in terms of the orig inal units of the data. In regression analysis there are two types of variables. The value whose value is influenced or is to be predicted is called dependent variable and the variable which influences the values or is to be used for prediction is called independent variable. Regression analysis can be done in two ways; A. Bivariate regression B. Multi ple regression a) Bivariate regression Two variables X and Y may be related to each other or inexactly. In physical sciences, variab les frequently have an exact relationship to each other. The simp lest relationship can be expressed by Y=a+Bx Where the values of the coefficient, a and b, determine respectively the p recise height and steepness of the line. Thus coefficient a represent to as the intercept or constant, and coefficient b referred to as the slope. In contrast, relationship between variables in social sciences is almost always inexact. The equation for a linear relationship between two social science variables would be written as: Y=a+bX+e , Where e represents the presence of error. b) Multiple regression analysis Multiple regression analysis is use when more than two parameters are used. In this research work, six control parameters were used. For mu ltip le reg ression analysis various types of modeling tool used as shown in fig

Advantages and effects of nitrogen doping into the central channel of plasma in axially viewed-inductively coupled plasma optical emission spectrometry

The effects and benefits of N2 addition to the central channel of the ICP through the nebulizer gas used in ICP OES with axial view configuration were investigated in the present study. The N2 flow rate, nebulizer gas flow rate, RF power and sample uptake rate were evaluated and compared for two sample introduction systems (pneumatic nebulization/aerosol desolvation and conventional pneumatic nebulization). It was observed that N2 did not affect solution nebulization and aerosol transport but affects the ICP characteristics. The higher thermal conductivity of N2 (in comparison with Ar) changes energy distribution in the ICP, observed by monitoring the signals of Ar emission lines and sodium emission. The ratio Mg(II)-280.270nm/Mg(I)-285.213nm was utilized as a diagnostic tool for plasma robustness. The addition of N2 (20mLmin−1) increased plasma robustness significantly and mitigated effects caused by Na, K and Ca. For 40 spectral lines evaluated, it was observed that the emission signals of ionic spectral lines were in general more affected by N2 than those of atomic spectral lines. Detection limits, precision, sensitivity and linearity of calibration curves obtained using N2-Ar-ICP were almost similar to those obtained using Ar-ICP. The analysis of 5 different reference materials revealed that accuracy was not degraded by adding N2 to the Ar-ICP.

Effect of laser pulse on recovery delay of arc plasma based on ion migration behavior in the pulsed laser–arc hybrid welding process

This paper presents the investigation on effect of laser pulse on the recovery delay of arc plasma during pulsed laser–arc hybrid welding of Mg alloy based on the dynamic behavior of Mg atoms. High-speed camera and spectrograph are employed to monitor the behaviors of Mg atom in the arc plasma and to characterize the effect of laser pulse on the arc plasma, respectively. It is found that the arc plasma cannot recover to its original state immediately after laser pulse action and it takes 0–5ms for the excessive Mg atoms to escape from the arc plasma depending on the given parameters. According to the calculation, time for Mg ions to travel from the anode to the cathode in the conduction channel of the arc plasma is less than 0.1ms. The high temperature of the laser keyhole region on the base material surface still exists when the laser pulse is removed and sustaining supply of the Mg ions from this region is the essential factor influencing recovery delay of the arc plasma.

One‐way coupled OpenGGCM/RCM simulation of the 23 March 2007 substorm event

We present results of a simulation of a substorm on 23 March 2007 using the one‐way coupled Open Geospace General Circulation Model–Rice Convection Model (OpenGGCM/RCM). In the standalone RCM, inputs are typically taken from empirical models or inferred from satellite data; however, in this simulation, the OpenGGCM magnetic field and plasma information are used to supply inputs and boundary conditions for the RCM. The OpenGGCM ionospheric potential is used to drive a RCM run. That simulation is used to investigate the short time scale dynamics that occurred around substorm onset and assumes the OpenGGCM has a realistic representation of the inner magnetospheric magnetic field during this event. In these runs, a channel of low total entropy plasma opened up on the RCM tailward boundary around substorm onset, and plasma bubbles were injected into the inner magnetosphere. These bubbles were produced by nonadiabatic processes in the OpenGGCM such as magnetic reconnection. We compare the RCM energetic particle flux with measurements from two Los Alamos National Laboratory (LANL) satellites. A dispersionless electron injection is reproduced at the LANL‐89 location and a dispersed flux increase at the LANL‐97A location. The results indicate the low‐PV5/3 plasma accompanying magnetic field dipolarization produced earthward plasma motion as the result of these low‐entropy flux tubes interchanging their way into the inner magnetosphere; this process may play an important role in substorm particle injection. A comparison simulation in which the electric field is solved by the RCM is also presented, suggesting the need to use RCM's electric field for more accurate inner magnetosphere modeling.

Improved Cd determination in glasses by laser ablation inductively coupled plasma mass spectrometry using nitrogen as a matrix modifier

The addition of 5–10 mL min −1 nitrogen to the central channel of plasma in Laser ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) increases the sensitivities of Cd by a factor of 3 and decreases oxide interferences by one order of magnitude, which allows the direct analysis of trace levels of Cd in glass samples. This simple method shows a great potential for the direct determination of Cd in various kinds of samples.

An auroral westward flow channel (AWFC) and its relationship to field-aligned current, ring current, and plasmapause location determined using multiple spacecraft observations

Abstract. An auroral westward flow channel (AWFC) is a latitudinally narrow channel of unstable F-region plasma with intense westward drift in the dusk-to-midnight sector ionosphere. AWFCs tend to overlap the equatorward edge of the auroral oval, and their life cycle is often synchronised to that of substorms: they commence close to substorm expansion phase onset, intensify during the expansion phase, and then decay during the recovery phase. Here we define for the first time the relationship between an AWFC, large-scale field-aligned current (FAC), the ring current, and plasmapause location. The Tasman International Geospace Environment Radar (TIGER), a Southern Hemisphere HF SuperDARN radar, observed a jet-like AWFC during ~08:35 to 13:28 UT on 7 April 2001. The initiation of the AWFC was preceded by a band of equatorward expanding ionospheric scatter (BEES) which conveyed an intense poleward electric field through the inner plasma sheet. Unlike previous AWFCs, this event was not associated with a distinct substorm surge; rather it occurred during an interval of persistent, moderate magnetic activity characterised by AL~−200 nT. The four Cluster spacecraft had perigees within the dusk sector plasmasphere, and their trajectories were magnetically conjugate to the radar observations. The Waves of High frequency and Sounder for Probing Electron density by Relaxation (WHISPER) instruments on board Cluster were used to identify the plasmapause location. The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) EUV experiment also provided global-scale observations of the plasmapause. The Cluster fluxgate magnetometers (FGM) provided successive measurements specifying the relative location of the ring current and filamentary plasma sheet current. An analysis of Iridium spacecraft magnetometer measurements provided estimates of large-scale ionospheric FAC in relation to the AWFC evolution. Peak flows in the AWFC were located close to the peak of a Region 2 downward FAC, located just poleward of the plasmapause. DMSP satellite observations confirmed the AWFC was located equatorward of the nightside plasmasheet, sometimes associated with ~10 keV ion precipitation.

Study of QGP signatures with the ϕ → K + K – signal in Pb-Pb ALICE events

The phi->K+K- decay channel in Pb-Pb collisions at LHC is studied through a full simulation of the ALICE detector. The study focuses on possible signatures in this channel of quark-gluon plasma (QGP) formation. On a basis of 10^6 collisions at high centrality some proposed QGP signatures are clearly visible both in K+K- invariant mass and transverse mass distributions. The high significance of this observation appears to reside heavily on the use of the TOF (Time Of Flight) system of ALICE in addition to its central tracking detectors.

Improved laser triggering and guiding of meqavolt discharges with dual fs-ns pulses

We demonstrate that the capacity of ultrashort high-power laser pulses to trigger and guide high-voltage discharges can be significantly enhanced by a subsequent visible nanosecond laser pulse. The femtosecond pulse induces a bundle of filaments, which creates a conducting channel of low density and cold plasma connecting the electrodes. The subsequent laser pulse photodetaches electrons from O2− ions in the electrode leader. The resulting electrons allow efficient heating by Joule effect in a retroaction loop, resulting in a 5% reduction of the breakdown voltage.

Study of QGP signatures with the ϕ → K + K – signal in Pb-Pb ALICE events

The ϕ → K+K– decay channel in Pb-Pb collisions at LHC is studied through a full simulation of the ALICE detector. The study focuses on possible signatures in this channel of quark-gluon plasma (QGP) formation. On a basis of 106 collisions at high centrality some proposed QGP signatures are clearly visible both in K + K– invariant mass and transverse mass distributions. The high significance of this observation appears to reside heavily on the use of the TOF (Time Of Flight) system of ALICE in addition to its central tracking detectors.

The effects of sound stimulation on the permeability of K + channel of Chrysanthemum Callus plasma

The patch-clamp technology is used to analyze the sound stimulation effects on the K + channel of plasma membrane. The results indicate that there are K + channels on the plasma membrane that are sensitive to the sound stimulation. The single channel current is 42 ps, and the current is obviously voltage-dependent. The opening frequency of the K + channels increases under the sound stimulation.

Radial contraction of microwave-sustained plasma columns at atmospheric pressure

Plasma columns sustained at high enough gas pressures undergo radial contraction as manifested by their glow not entirely filling the radial cross-section of the discharge tube. This phenomenon has been reported with direct current, radio frequency, and microwave discharges. However, its modeling is still incomplete, in particular for rf and microwave discharges, a situation attributed to a lack of experimental data. To fill this gap, we took advantage of the extreme flexibility in terms of field frequency, tube diameter and gas nature of surface-wave sustained discharges to achieve a parametric study of this phenomenon. Special attention was paid to filamentation, specific to rf and microwave discharges, which is the breaking of a single channel of plasma into two or more smaller filaments as a result of the skin effect. We used emission spectroscopy as the main diagnostic means. Electron density was obtained from Stark broadening of the Hβ line, while molecular-band spectra emitted by the OH radical and the N2+ molecule were employed to determine the discharge gas temperature, leading to its radial distribution upon performing Abel inversion. For a given tube radius, contraction is shown to increase with decreasing thermal conductivity of the discharge. As a result, He and N2 discharges are the least contracted, while contraction increases with increasing atomic mass of noble gases. Of all these discharges, the N2 discharge appears to be the closest to local thermodynamic equilibrium.

Plasma parameters in the channel of a long leader in air

The time evolution of the electric field in the leader channel and other characteristics of the leader plasma in long air gaps are simulated. Calculations are performed in the one-dimensional time-dependent model with allowance for the time-varying energy deposition in the channel, the channel expansion, and the nonequilibrium ionization kinetics in the leader plasma. The calculations show that, at a gas temperature of 4500–6000 K, associative ionization becomes a dominant ionization mechanism in the leader channel; as a result, the electric field decreases to 100–200 V/cm in 10−4–10−3 s under the conditions typical of the leader discharge. The calculated electric field agrees well with the data from the experimental modeling of long leaders by a spark discharge in short gaps.

A ubiquitous 64-kDa protein is a component of a chloride channel of plasma and intracellular membranes.

Chloride channels are present in the plasma and intracellular membranes of most cells. Previously, using the ligand indanyloxyacetic acid (IAA), we purified four major proteins from bovine kidney cortex membrane vesicles. These proteins gave rise to chloride channel activity when reconstituted into phospholipid vesicles. Two of these proteins (97 and 27 kDa) were found to be drug-binding proteins by N-terminal sequence analysis. Antibodies raised to the 64-kDa protein stained only this protein on immunoblots, and only this protein was present after purification on an immunoaffinity column. In addition, these same antibodies were able to deplete IAA-94 inhibitable chloride channel activity from solubilized kidney membranes. Of fractions obtained from the gel filtration of solubilized kidney membranes, only those containing this 64-kDa protein exhibited measurable chloride channel activity. Immunoblots of a variety of species and cell types, both epithelial and nonepithelial, revealed that this protein is ubiquitous and highly conserved. Immunocytochemistry in CFPAC-1 cells revealed staining for this protein on the apical plasma membrane and in the membranes of intracellular organelles. These results demonstrate that the integral membrane protein p64 is a component of chloride channels present in both epithelial plasma membrane and the membranes of intracellular organelles.

A STUDY ON REACTION KINETICS OF THE RADICALS PRODUCED IN THE LASER-INDUCED SILANE PLASMA

The reaction kinetic processes of species produced in a pulsed TEA CO2 laser induced si-lane plasma were studied with the time-resolved OES. It is showed that the time position of main peaks for different fragments' charactristic lines are appreciably different. The reaction kinetic processes are discussed based on the results. By comparing the time evolution of the lines of the fragments and considering the other results of OES, We infer that the final reaction channel of the laser-induced silane plasma is a Si producing channel.

Simultaneous determination of wear metals in lubricating oils by inductively-coupled plasma atomic emission spectrometry

The simultaneous determination of 15 different wear metals in lubricating oil by inductively-coupled plasma-atomic emission spectrometry is described. An aerosol formed from a solution of the lubricating oil in 4-methyl-2-pentanone is injected into the axial channel of an inductively-coupled plasma where the atomic spectra are excited. Detection limits range 0.0004 to 0.3 ppM for the elements studied. Low and high viscosity oils (nominally 1.9 x 10/sup -5/ to 2.45 x 10/sup -4/ m/sup 2//s, respectively) can be accommodated without biasing the analytical results. Approximately 1.5 min are required for completing the analytical cycle for one sample. Relevant data on precision and accuracy are included. (auth)