Variation Of Plasma Parameters Research Articles

Obliquely propagating solitary wave structures in nonextensive magneto-rotating plasmas

The propagation of the nonlinear electrostatic ion acoustic solitary wave structures in two component, non relativistic, homogenous, magneto rotating plasma are studied. The inertialess electrons are assumed to follow nonextensive q velocity distribution. Small amplitude reductive perturbation technique is applied to derive Korteweg de Vries (KdV) equation and its analytical solution is presented. The effects of variation of different plasma parameters on propagation characteristics of solitary wave structure in the presence of the Coriolis force are discussed. It is observed that nonextensive parameter q modifies the structure of solitary wave structures in rotating plasmas.

Nonlinear electrostatic coherent structures: solitary and shock waves in a dissipative, nonplanar multi-component quantum plasma

The nonlinear propagation of ion-acoustic solitary and shock waves in a dissipative, nonplanar quantum plasma comprised of electrons, positrons, and ions are studied. A modified Korteweg-de Vries Burgers equation is derived in the limit of low frequency and long wavelength by taking into account the kinematic viscosity among the plasma constituents. It is shown that this plasma system supports the propagation of both compressive and rarefactive nonlinear waves. The effects of variation of various plasma parameters on the time evolution of nonplanar solitary waves, the profile of shock waves, and the nonlinear structure induced by the collision of solitary waves are discussed. It is found that these parameters have significant effects on the properties of nonlinear waves in cylindrical and spherical geometries, and these effects for compressive and rarefactive nonlinear waves are obviously different.

Study on the effect of target on plasma parameters of magnetron sputtering discharge plasma

In this study, the effect of magnetron target on different plasma parameters of Argon/Hydrogen (Ar - H2) direct current (DC) magnetron discharge is examined. Here, Copper (Cu) and Chromium (Cr) are used as magnetron targets. The value of plasma parameters such as electron temperature (kTe), electron density (Ne), ion density (Ni), degree of ionization of Ar, and degree of dissociation of H2 for both the target are studied as a function of input power and hydrogen content in the discharge. The plasma parameters are determined by using Langmuir probe and Optical emission spectroscopy. On the basis of the different reactions in the gas phase, the variation of plasma parameters and sputtering rate are explained. The obtained results show that electron and ion density decline with gradual addition of Hydrogen in the discharge and increase with rising input power. It brings significant changes on the degree of ionization of Ar and dissociation of H2. The enhanced value of electron density (Ne), ion density (Ni), degree of Ionization of Ar, and degree of dissociation of H2 for Cr compared to Cu target is explained on the basis of it's higher Ion Induced Secondary Electron Emission Coefficient (ISEE) value.

The solar cycle variation of plasma parameters in equatorial and mid latitudinal areas during 2005–2010

Based on the ISL data detected by DEMETER satellite, the solar cycle variation in electron density (Ne) and electron temperature (Te) were studied separately in local daytime 10:30 and nighttime 22:30 during 2005–2010 in the 23rd/24th solar cycles. The semi-annual, annual periods and decreasing trend with the descending solar activity were clearly revealed in Ne. At middle and high latitudes, there exhibited phase shift and even reversed annual variation over Southern and Northern hemisphere, and the annual variation amplitudes were asymmetrical at both hemispheres in local daytime. In local nighttime, the annual variations of Ne at south and north hemispheres were symmetrical at same latitudes, but the annual variation amplitudes at different latitudes differed largely, showing obviously zonal features. As for Te, the phase shift in annual variations was not as apparent as Ne with the increase of latitudes at Southern and Northern hemisphere in local daytime. While in local nighttime the reversed annual variations of Te were shown at low latitudinal areas, not at high latitudes as those in Ne. The correlation study on Ne and Te illustrated that, in local daytime, Ne and Te showed strong negative correlation at equator and low latitudes, but during the solar minimum years the correlation between Ne and Te changed to be positive at 25–30° latitudes in March 2009. The correlation coefficient R between Ne and Te also showed semi-annual periodical variations during 2005–2010. While in local nighttime, Ne and Te exhibited relatively weak positive correlation with R being about 0.6 at low latitudes, however no correlation beyond latitudes of 25° was obtained.

Effect of process parameters on properties of argon–nitrogen plasma for titanium nitride film deposition

In this study, the effect of working pressure and input power on the physical properties and sputtering efficiencies of argon–nitrogen (Ar/N2) plasma in direct current magnetron discharge is investigated. The discharge in Ar/N2 is used to deposit TiN films on high speed steel substrate. The physical plasma parameters are determined by using Langmuir probe and optical emission spectroscopy. On the basis of the different reactions in the gas phase, the variation of plasma parameters and sputtering rate are explained. A prominent change of electron temperature, electron density, ion density, and degree of ionization of Ar is found as a function of working pressure and input power. The results also show that increasing working pressure exerts a negative effect on film deposition rate while increasing input power has a positive impact on the same. To confirm the observed physical properties and evaluate the texture growth as a function of deposition parameters, x-ray diffraction study of deposited TiN films is also done.

Characteristics of Cold Argon Arc-Jet Plasma Flowing Along Open-Field-Line and the Effects of Collisions on Deceleration

We report basic characteristics of a cold supersonic argon arc-jet plasma accelerated along open-field-line. The arc jet is generated by arc discharge, and ejected through an anode-nozzle into a rarefied gas wind tunnel with a uniform longitudinal magnetic field. The plasma further expands at the end of magnets, which we refer to as a magnetic-nozzle, where we examine variation in plasma parameters using a para–perp type Mach probe and a four-tip type Mach probe. Our experiments show that plasma potential drops at the magnetic-nozzle area and that the ion flow velocity increases up to about Mach 3, followed by deceleration into subsonic transition. To discuss the mechanism of acceleration and deceleration, we assume a 1-D quasi-neutral flow, and constructed a model to describe the deceleration because of friction between ions and neutral particles at the end of electromagnets, where charged particles are accelerated but neutrals are not. We find reasonable agreement of the experimental results with our modeling of the acceleration and deceleration, although a few issues are left for us to improve.

Langmuir probe diagnostics of plasma in high current electron cyclotron resonance proton ion source

A high current Electron Cyclotron Resonance (ECR) proton ion source has been developed for low energy high intensity proton accelerator at Bhabha Atomic Research Centre. Langmuir probe diagnostics of the plasma generated in this proton ion source is performed using Langmuir probe. The diagnostics of plasma in the ion source is important as it determines beam parameters of the ion source, i.e., beam current, emittance, and available species. The plasma parameter measurement in the ion source is performed in continuously working and pulsed mode using hydrogen as plasma generation gas. The measurement is performed in the ECR zone for operating pressure and microwave power range of 10(-4)-10(-3) mbar and 400-1000 W. An automated Langmuir probe diagnostics unit with data acquisition system is developed to measure these parameters. The diagnostics studies indicate that the plasma density and plasma electron temperature measured are in the range 5.6 × 10(10) cm(-3) to 3.8 × 10(11) cm(-3) and 4-14 eV, respectively. Using this plasma, ion beam current of tens of mA is extracted. The variations of plasma parameters with microwave power, gas pressure, and radial location of the probe have been studied.

Two-dimensional cylindrical ion-acoustic solitary and rogue waves in ultrarelativistic plasmas

The propagation of ion-acoustic (IA) solitary and rogue waves is investigated in a two-dimensional ultrarelativistic degenerate warm dense plasma. By using the reductive perturbation technique, the cylindrical Kadomtsev–Petviashvili (KP) equation is derived, which can be further transformed into a Korteweg–de Vries (KdV) equation. The latter admits a solitary wave solution. However, when the frequency of the carrier wave is much smaller than the ion plasma frequency, the KdV equation can be transferred to a nonlinear Schrödinger equation to study the nonlinear evolution of modulationally unstable modified IA wavepackets. The propagation characteristics of the IA solitary and rogue waves are strongly influenced by the variation of different plasma parameters in an ultrarelativistic degenerate dense plasma. The present results might be helpful to understand the nonlinear electrostatic excitations in astrophysical degenerate dense plasmas.

Temporal variations in solar magnetic bright points intensity and plasma parameters

Magnetic bright points are one of the finest magnetic structures observed in the solar atmosphere. They possibly represent single flux tubes in quiet Sun regions. Their formation is described by the convective collapse model, while the decay phase of these structures is not well characterized yet. We attempt to follow the evolution of a few selected examples of MBPs and to study their changes in brightness and also the variations of plasma parameters during their lifetime. We use data from the Hinode satellite and the Sunrise mission. The G-band observations taken with a cadence of 30 seconds by the Hinode Solar Optical Telescope (SOT) show very fast changes of the maximum intensity of these structures. The complementary spectropolarimetric data, which are used to estimate the plasma parameters, were taken with a cadence of approximately two minutes. The variations of plasma parameters cannot be matched one to one to the changes in intensity due to the different temporal resolution. However, the slow changes of intensity with large amplitude are matched with variations of magnetic field strength and line-of-sight (LOS) velocity. The Sunrise/IMaX data have a temporal resolution of 32 seconds and show fast variations in the line wing intensity. These variations are associated with changes in the magnetic field strength and LOS velocity.

SOLAR ENERGETIC PARTICLE MODULATIONS ASSOCIATED WITH COHERENT MAGNETIC STRUCTURES

In situ observations of solar energetic particles (SEPs) often show rapid variations of their intensity profile, affecting all energies simultaneously, without time dispersion. A previously proposed interpretation suggests that these modulations are directly related to the presence of magnetic structures with a different magnetic topology. However, no compelling evidence of local changes in magnetic field or in plasma parameters during SEP modulations has been reported. In this paper, we performed a detailed analysis of SEP events and we found several signatures in the local magnetic field and/or plasma parameters associated with SEP modulations. The study of magnetic helicity allowed us to identify magnetic boundaries, associated with variations of plasma parameters, which are thought to represent the borders between adjacent magnetic flux tubes. It is found that SEP dispersionless modulations are generally associated with such magnetic boundaries. Consequently, we support the idea that SEP modulations are observed when the spacecraft passes through magnetic flux tubes, filled or devoid of SEPs, which are alternatively connected and not connected with the flare site. In other cases, we found SEP dropouts associated with large-scale magnetic holes. A possible generation mechanism suggests that these holes are formed in the high solar corona as a consequence of magnetic reconnection. This reconnection process modifies the magnetic field topology, and therefore, these holes can be magnetically isolated from the surrounding plasma and could also explain their association with SEP dropouts.

Simulation of spectroscopic patterns obtained in W/C test-limiter sputtering experiment at TEXTOR

On the TEXTOR tokamak various experiments aimed at investigation of tungsten erosion and transport are performed. In one experiment a spherical W/C twin limiter positioned close to the last-closed flux surface in the near scrape-off layer was exposed to a number of comparable plasma discharges with stepwise variations of edge plasma parameters. Spatial distribution of tungsten and carbon light emission was recorded with two dimensional CCD cameras and spectrometer systems with high spectral and spatial resolution. Penetration depths, tungsten sputtering fluxes and erosion yields were measured. Comparison between experimental data and the results of modelling with the 3D Monte-Carlo code ERO is performed. The main objective of this study was to test the adequacy of the existing atomic data for neutral tungsten. The modelled penetration depths of the light emission of tungsten are a factor of 2–3 smaller than in experiment, which may indicate the overestimation of ionization rates.

Robust sawtooth period control based on adaptive online optimization

The systematic design of a robust adaptive control strategy for the sawtooth period using electron cyclotron current drive (ECCD) is presented. Recent developments in extremum seeking control (ESC) are employed to derive an optimized controller structure and offer practical tuning guidelines for its parameters. In this technique a cost function in terms of the desired sawtooth period is optimized online by changing the ECCD deposition location based on online estimations of the gradient of the cost function. The controller design does not require a detailed model of the sawtooth instability. Therefore, the proposed ESC is widely applicable to any sawtoothing plasma or plasma simulation and is inherently robust against uncertainties or plasma variations. Moreover, it can handle a broad class of disturbances. This is demonstrated by time-domain simulations, which show successful tracking of time-varying sawtooth period references throughout the whole operating space, even in the presence of variations in plasma parameters, disturbances and slow launcher mirror dynamics. Due to its simplicity and robustness the proposed ESC is a valuable sawtooth control candidate for any experimental tokamak plasma, and may even be applicable to other fusion-related control problems.

Effects of applied power on hydrogenated amorphous carbon (a-C:H) film deposition by low frequency (60 Hz) plasma-enhanced chemical vapor deposition (PECVD)

Hydrogenated amorphous carbon (a-C:H) films were deposited onto glass substrates using low frequency (60Hz) plasma-enhanced chemical vapor deposition and the effects of the applied power on a-C:H films deposition were investigated. During deposition, the electron temperature and the density of CH4–H2 plasma were 2.4–3.1eV and about 108cm−3, respectively. The main optical emission peak of the carbon species observed in the CH4–H2 plasma is shown to be excited carbon CH* at 431nm. The sp3/sp2 ratio, band gap, hydrogen content, and refractive index of a-C:H films gradually increased up to a power of 25W and then saturated at higher power. This tendency is similar to the variation of plasma parameters with varying applied power, thereby indicating that a strong relationship exists between the properties of the films and the plasma discharge.

PROTECTIVE EFFECT OF SOME MEDICINAL PLANTS ON BLOOD PARAMETERS, KIDNEY AND LIVER FUNCTIONS AND HISTOPATHOGICAL FEATURES OF KIDNEY IN RATS

The study was undertaken in the animal house belonging to the Animal Production Department, Faculty of Agriculture, Al-Azhar University. Twenty four adult male albino rats with an average live body weight of 130 gm were allocated to 4 equal groups (6 rats each): group 1 (G1) served as the control group and was orally given 1 ml of distilled water, group 2 (G2) was orally given 1 ml Cymbopogon proximus (CP, halfa barr) suspension, group 3 (G3) was orally given 1 ml Ammi visnaga (AV, Khella) suspension and group 4 (G4) was orally given administrated 1 ml Ambrosia maritime (AM, deamsissa) suspension. Feeding and drinking water were offered ad-libitum during the experimental period. Two experiments were carried out during hot season in summer (August and September, 2009). The first experiment was designed to investigate the effect of medicinal plants (CP, AV and AM) after 60 days from the start of the treatments on kidney function and histological structure. The second experiment was designed to test the effect of medicinal plants on diurnal variations of blood plasma parameters within each treatment at the end of the experiment. In the first experiment, blood samples were collected and kidney were studied,whereos in the second experiment, blood samples were collected in heparinized tubes three times daily from all animals within each group at 8 am, 4 pm and 12 pm.. The aim of the study was to investigate the effect of using Cymbopogon proximus (Halfa barr, CP), Ammi visnaga (Khella, AV) and Ambrosia maritime (Deamsissa, AM) on kidney structure and function of albino rats. Results indicate that the kidney histopathological sections of the control and CP groups showed normal renal glomeruli and tubules. On the other renal section showed minimal degenerative changes in renal glomeruli in AV group with normal tubules and mild degenerative changes of renal glomeruli in the form of proeifuation of glomerular epithelium and mild atrophy in some glomeruli in AM group.Oral administration of medicinal plants had no significant effect on plasma creatinine, urea nitrogen, total protein, albumin, globulin, albumin /globulin, ALT, AST. Meanwhile, AV significantly increased plasma glucose to be higher than that in other groups. It could be concluded that CP is safe to be used as an effective remedy for renal spasms and diabetes treatment without any side effects on kidney function. Also, it could be recommended that AV could be used for treatment of kidney stone but the duration of treatment have to be no longer than two weeks. Meanwhile, kidney function must be considered during any treatment with AM which is mainly used for its hypoglycemic effect.

Variation of the electron energy distribution with He dilution in an inductively coupled argon discharge

We present experimental evidence of different behaviors of plasma parameters depending on changes in the electron energy distribution (EED), caused by an electron heating mechanism and electron-neutral collision processes in an Ar/He mixture inductively coupled plasma. At a low gas pressure of 3 mTorr, where the electron neutral collision frequency νm is much smaller than the driving frequency ωRF, the EEDs evolved from a bi-Maxwellian distribution to a Maxwellian distribution, due to the efficient heating of low energy electrons when the He flow rate increased at a fixed total gas pressure. The plasma density slowly decreased with the He flow rate portion ([He]/[Ar] + [He]) in a range of 0%–70%, while the plasma density largely decreased in the He flow rate portion of 70%–100%. On the other hand, at a high gas pressure of 350 mTorr where νm ≫ ωRF, the EEDs evolved from a Druyvesteyn-like distribution to a Maxwellian distribution, due to a cooling of low energy electrons and an increase in the population of high energy electrons, when the mixing ratio of the He gas is increased. In this case, plasma density abruptly decreased for a He flow rate ratio of 0%–30%. This result directly shows that the EEDs significantly affect the different variations of plasma parameters, even in the case of the same mixing ratio of the gases.

Ionospheric anomalies associated with the Haiti earthquake of 12 January 2010 observed by DEMETER satellite

Abstract. This paper examines the ionospheric anomalies around the time of a strong earthquake (M = 7.0) which occurred in Haiti region (18.457° N, 72.533° W) on 12 January 2010. DEMETER satellite data have been used to study the plasma parameters variation during the Haiti earthquake. One day (11 January 2010) before the earthquake there is a significant enhancement of electron density and electron temperature near the epicenter. Decrease of electron temperature is observed few days after the earthquake. Anomalous plasma parameter variations are detected both in day and nighttimes before the quake. Statistical processing of the DEMETER data demonstrates that satellite data can play an important role for the study of precursory phenomena associated with earthquakes.

Simulation of convection-stabilized modulated discharges in atmospheric-pressure air

A model describing modulated regimes of convection-stabilized discharges in atmospheric-pressure air is developed that accounts for deviation of the plasma state from the local thermodynamic equilibrium. The model is based on an approximate approach relating the variation of plasma parameters with time and their variation along the discharge axis. The validity of this approach is supported by agreement, for steady-state regimes, of calculated plasma parameters with those obtained on the basis of a more rigorous model. Results of calculation of modulated discharge parameters over a wide current range are presented for various current modulation frequencies and depths.

Dynamics of a Nanosecond High-Voltage Microdischarge

Microdischarges have drawn much attention in plasma research in recent years. Extreme operating conditions, such as high pressure, high current density, and rapid variation of plasma parameters lead to challenging problems in plasma diagnostics. Here, we demonstrate that imaging in microplasma research opens a direct way to gain knowledge about discharge dynamics.

Caesium influence on plasma parameters and source performance during conditioning of the prototype ITER neutral beam injector negative ion source

Systematic Langmuir probe measurements were performed during the caesium (Cs) conditioning of the IPP prototype negative hydrogen ion source. Conditioning consists of slowly injecting caesium into the source in order to increase the extracted negative ion current and minimize the co-extracted electrons. This process usually takes several days. Measurements were taken near the plasma grid (PG) where the majority of the extracted negative ions are created. A clear transition between a poorly conditioned (volume dominated H− production) and a well conditioned (surface dominated H− production) source was seen. By following the plasma parameter variations, an overall decrease in the plasma potential, the floating potential and also the electron saturation current was observed. However, the ion saturation current remained constant. Consequently, near the PG where negative ions are generated and extracted, a transition occurred in the space charge balance (quasineutrality): the space charge is balanced by electrons when the source is poorly conditioned and by negative ions when the source is well conditioned.

A THEMIS multicase study of dipolarization fronts in the magnetotail plasma sheet

[1] We discuss results of a superposed epoch analysis of dipolarization fronts, rapid (δt 10 nT) increases in the northward magnetic field component, observed during six Time History of Events and Macroscale Interactions during Substorms (THEMIS) conjunction events. All six fronts propagated earthward; time delays at multiple probes were used to determine their propagation velocity. We define typical magnetic and electric field and plasma parameter variations during dipolarization front crossings and estimate their characteristic gradient scales. The study reveals (1) a rapid 50% decrease in plasma density and ion pressure, (2) a factor of 2–3 increase in high-energy (30–200 keV) electron flux and electron temperature, and (3) transient enhancements of ∼5 mV/m in duskward and earthward electric field components. Gradient scales of magnetic field, plasma density, and particle flux were found to be comparable to the ion thermal gyroradius. Current densities associated with the Bz increase are, on average, 20 nA/m2, 5–7 times larger than the current density in the cross-tail current sheet. Because j · E > 0, the dipolarization fronts are kinetic-scale dissipative regions with Joule heating rates of 10% of the total bursty bulk flow energy.