Plasma In Thermal Equilibrium Research Articles

Kinetics of wet sodium vapor complex plasma

In this paper, we have investigated the kinetics of wet (partially condensed) Sodium vapor, which comprises of electrons, ions, neutral atoms, and Sodium droplets (i) in thermal equilibrium and (ii) when irradiated by light. The formulation includes the balance of charge over the droplets, number balance of the plasma constituents, and energy balance of the electrons. In order to evaluate the droplet charge, a phenomenon for de-charging of the droplets, viz., evaporation of positive Sodium ions from the surface has been considered in addition to electron emission and electron/ion accretion. The analysis has been utilized to evaluate the steady state parameters of such complex plasmas (i) in thermal equilibrium and (ii) when irradiated; the results have been graphically illustrated. As a significant outcome irradiated, Sodium droplets are seen to acquire large positive potential, with consequent enhancement in the electron density.

Alternating current-driven non-thermal arc plasma torch working with air medium at atmospheric pressure

This work is devoted to the investigation of the discharge characteristics of high-frequency alternating current (ac) plasma torch working with air medium using electrical and spectroscopic techniques. A simple structure and compact ac plasma torch associated with a resonance power supply allows the generation of low power discharges (lower than 1 kW) with high voltage and low current. The discharge shows a negative resistance characteristic, and its curve shifts up with gas flow increased. The effects of power on the emission intensity of NO (A 2Σ+ → X 2Π), OH (A 2Σ → X 2Π, 0–0), N2(C 3Πu → B 3Πg), Hα and O and their spatial distributions in plasma jet axial direction were investigated. It has been found that the emission intensities of NO, OH, N2, Hα and O rise with an increase in power dissipation. With increasing axial distances of plasma jet from nozzle exit, the emission intensity of OH increases and then decreases, while the emission intensities of other species decrease sharply. The vibrational temperature is much higher than the gas temperature, which demonstrates the ac-driven arc discharge deviation from thermal equilibrium plasma.

On the determination of plasma electron number density from Stark broadened hydrogen Balmer series lines in Laser-Induced Breakdown Spectroscopy experiments

In this work, different theories for the determination of the electron density in Laser-Induced Breakdown Spectroscopy (LIBS) utilizing the emission lines belonging to the hydrogen Balmer series have been investigated. The plasmas were generated by a Nd:Yag laser (1064nm) pulsed irradiation of pure hydrogen gas at a pressure of 2·104Pa. Hα, Ηβ, Ηγ, Ηδ, and Hε Balmer lines were recorded at different delay times after the laser pulse. The plasma electron density was evaluated through the measurement of the Stark broadenings and the experimental results were compared with the predictions of three theories (the Standard Theory as developed by Kepple and Griem, the Advanced Generalized Theory by Oks et al., and the method discussed by Gigosos et al.) that are commonly employed for plasma diagnostics and that describe LIBS plasmas at different levels of approximations. A simple formula for pure hydrogen plasma in thermal equilibrium was also proposed to infer plasma electron density using the Hα line. The results obtained showed that at high hydrogen concentration, the Hα line is affected by considerable self-absorption. In this case, it is preferable to use the Hβ line for a reliable calculation of the electron density.

Langmuir probe diagnostics of an atmospheric pressure, vortex–stabilized nitrogen plasma jet

Langmuir probe measurements in an atmospheric pressure direct current (dc) plasma jet are reported. Sweeping probes were used. The experiment was carried out using a dc non–transferred arc torch with a rod–type cathode and an anode of 5 mm diameter. The torch was operated at a nominal power level of 15 kW with a nitrogen flow rate of 25 Nl min−1. A flat ion saturation region was found in the current–voltage curve of the probe. The ion saturation current to a cylindrical probe in a high–pressure non local thermal equilibrium (LTE) plasma was modeled. Thermal effects and ionization/recombination processes inside the probe perturbed region were taken into account. Averaged radial profiles of the electron and heavy particle temperatures as well as the electron density were obtained. An electron temperature around 11 000 K, a heavy particle temperature around 9500 K and an electron density of about 4 × 1022 m−3, were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found throughout the plasma jet. The electron and heavy particle temperature profiles showed good agreement with those reported in the literature by using spectroscopic techniques. It was also found that the temperature radial profile based on LTE was very close to that of the electrons. The calculations have shown that this method is particularly useful for studying spraying–type plasma jets characterized by electron temperatures in the range 9000–14 000 K.

The Isentropic Exponent of Single-Ionized Mono-Atomic Plasmas

The isentropic exponent of single-ionized mono-atomic plasmas in thermal equilibrium is studied. Its behavior as a function of the ionization degree and temperature is examined for argon and zinc plasmas at two pressures (1 bar and 1 mbar, 1 mPa and 1 Pa), respectively. The results show that for the two sorts of plasma the isentropic exponent equals typically about 1.1∼1.2 within a considerably wide range of the ionization degree (5%∼80%).

Electron-ion energy partition when a charged particle slows in a plasma: Theory

The preceding paper [Brown, Preston, and Singleton Jr., Phys. Rev. E 86, 016406 (2012)] presented precise results for the partition of the initial energy E(0) of a fast particle into the ions and electrons--E(I)/E(0) and E(e)/E(0)--when the fast particle slows in a plasma whose ion and electron temperatures may differ. As emphasized in that paper, this is an important problem because nuclear fusion reactions, such as those that occur in an inertial confinement fusion capsule, involve ion temperatures that run away from the electron temperatures. As also noted in the preceding paper, a precise evaluation entails the use of a well-defined Fokker-Planck equation for the phase-space evolution of initially fast projectile particles. When the plasma has differing ion and electron temperatures, the projectiles must slow into a "schizophrenic" final ensemble of particles that has neither the electron nor the ion temperature. This is not a simple Maxwell-Boltzmann distribution since the electrons are not in thermal equilibrium with the ions. Thus, detailed calculations are required for the solution of the problem. These we provide here for a weakly to moderately coupled plasma. The Fokker-Planck equation holds to first subleading order in the dimensionless plasma coupling constant, which translates to computing to order n ln n (leading) and n (subleading) in the plasma density n. The energy partitions for a background plasma in thermal equilibrium have been previously computed, but the order n terms have not been calculated, only estimated. The "schizophrenic" final ensemble of slowed particles gives a new mechanism to bring the electron and ion temperatures together. The rate at which this new mechanism brings the electrons and ions in the plasma into thermal equilibrium will be computed.

The quantum equations of state of plasma under the influence of a weak magnetic field

The aim of this paper is to calculate the magnetic quantum equations of state of plasma, the calculation is based on the magnetic binary Slater sum in the case of low density. We consider only the thermal equilibrium plasma in the case of nλab3≪1, where λab2=ℏ2mabKT is the thermal De Broglie wave length between two particles. The formulas contain the contributions of the magnetic field effects. Using these results we compute the magnetization and the magnetic susceptibility. Our equation of state is compared with others.

Analysis of indium zinc oxide thin films by laser-induced breakdown spectroscopy

We have performed spectroscopic analysis of the plasma generated by Nd:YAG (λ = 266 nm) laser irradiation of thin indium zinc oxide films with variable In content deposited by combinatorial pulsed laser deposition on glass substrates. The samples were irradiated in 5 × 104 Pa argon using laser pulses of 5 ns duration and 10 mJ energy. The plasma emission spectra were recorded with an Echelle spectrometer coupled to a gated detector with different delays with respect to the laser pulse. The relative concentrations of indium and zinc were evaluated by comparing the measured spectra to the spectral radiance computed for a plasma in local thermal equilibrium. Plasma temperature and electron density were deduced from the relative intensities and Stark broadening of spectral lines of atomic zinc. Analyses at different locations on the deposited thin films revealed that the In/(In + Zn) concentration ratio significantly varies over the sample surface, from 0.4 at the borders to about 0.5 in the center of the film. The results demonstrate that laser-induced breakdown spectroscopy allows for precise and fast characterization of thin films with variable composition.

The Calculation of the Optical Depths of Homogeneous Plasmas: Analytical, Experimental, and Numerical Considerations

Starting from the general expressions describing the line emission by a homogeneous plasma in local thermal equilibrium (LTE), in the approximation of Lorentzian shape of the line profile, a universal expression can be obtained relating the optical depth of the line to measurable quantities such as integrated line intensity, peak value, and full width at half-maximum (FWHM). This universal curve could be used for calculating the optical depth from experimental spectra without knowledge of the spectroscopic parameters of the emission line. Examples are given using experimental and computer-generated synthetic spectra.

Analyses of Plasmas Produced by Laser Ablation of Fresh Aliments

Detection and analysis of trace mineral elements in vegetables, and more generally in food by laser-induced breakdown spectroscopy (LIBS) promises applications with expected outcomes in nutrition quality. LIBS ensures contactless, real-time measurements of multielemental samples without any preparation of the samples surface. However, its application to analyses of aliments such as vegetables has one main drawback. Organic materials are strongly inhomogeneous and the physical properties that govern the processes of laser energy absorption, material ablation and plasma formation depend on a large number of parameters making calibration with standard samples impossible. This technique requires therefore a calibration-free approach that allows one to deduce the relative elemental concentrations from the intensities of spectral lines emitted from the laser-produced plasma. The main difficulty of such an approach is related to the temporal and spatial variation of the plasma properties. Therefore we have performed spectroscopic analysis of the plasma produced by Nd:Yag laser ablation of potato flesh and skin. The emission spectra recorded with an Echelle spectrometer with ICCD detector were compared to the spectral radiance computed for a plasma in local thermal equilibrium to deduce the mass fractions of the mineral elements.

Investigation of plasmas produced by laser ablation using single and double pulses for food analysis demonstrated by probing potato skins

We report on investigations of plasmas produced by laser ablation of fresh potatoes using infrared nanosecond laser radiation. A twin laser system consisting of two Nd:YAG oscillators was used to generate single or double pulses of adjustable interpulse delay. The potatoes were irradiated under ambient air with moderate pulse energies of about 10 mJ. The expansion dynamics of the ablation plume was characterized using fast imaging with a gated camera. In addition, time-resolved optical emission spectroscopy was applied to study the spectral line emission of the various plasma species. The electron density was deduced from Stark broadening, and the plasma temperature was inferred from the relative emission intensities of spectral lines. The relative concentrations of metals were estimated from the comparison of the measured emission spectra to the spectral radiance computed for a plasma in local thermal equilibrium. It is shown that the plasma produced by double pulses has a larger volume and a lower density. These properties lead to an increase of the signal-to-noise ratio by a factor of 2 and thus to an improved measurement sensitivity.

Validity of Saha’s equation of thermal ionization for negatively charged spherical particles in complex plasmas in thermal equilibrium

The authors have discussed the validity of Saha’s equation for the charging of negatively charged spherical particles in a complex plasma in thermal equilibrium, even when the tunneling of the electrons, through the potential energy barrier surrounding the particle is considered. It is seen that the validity requires the probability of tunneling of an electron through the potential energy barrier surrounding the particle to be independent of the direction (inside to outside and vice versa) or in other words the Born’s approximation should be valid.

Kinetics of Complex Plasmas Having Dust of Different Materials With Corresponding Size Distribution

In this paper, the authors have presented a formulation of the kinetics of complex plasmas, having dust of different materials (different work functions) and size distributions, which is based on the number and energy balance of constituents; this is in deference to the present emphasis on considering complex plasma as an open system. The formulation is based on a size-independent dust surface potential; this simplifies the problem to a form, similar to that for the case of uniform size dust grains, characterized by the mean <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(a_{m})$</tex></formula> and the root mean square <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$(a_{rms})$</tex></formula> radius of the dust particles. Two cases, viz., complex plasma in thermal equilibrium and complex plasma irradiated by monochromatic radiation, have been considered in detail, and corresponding computations have been made for a mixture of two varieties of dust grains having high <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(\varphi_{2} &gt; h\nu)$</tex></formula> and low <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$(h\nu &gt; \varphi_{1})$</tex></formula> work functions. The relevance of the first case to flames and rocket exhausts has been pointed out. The fluctuation of charge corresponding to individual dust grains has also been evaluated. A discussion based on numerical results and conclusion have been also given.

The classical equation of state of fully ionized plasmas

The aim of this paper is to calculate the analytical form of the equation of state until the third virial coefficient of a classical system interacting via an effective potential of fully Ionized Plasmas. The excess osmotic pressure is represented in the forms of a convergent series expansions in terms of the plasma Parameter $\mu _{ab} = {{{e_a e_b \chi } \over {DKT}}}$μab=eaebχDKT, where χ2 is the square of the inverse Debye radius. We consider only the thermal equilibrium plasma.

The Quantum Equation of State of Fully Ionized Plasmas

AbstractThe quantum equation of state of the electron‐ion‐plasmas in thermal equilibrium is derived; the pressure until the third virial coefficient is calculated. We consider only the thermal equilibrium plasma in the case of nλ3ab ≪ 1 where λ2ab = ((ħ2)/(mabKT)) is the thermal De Broglie wavelength. The formulas contain the contributions of the exchange effects. Our equation of state is compared with result of Ebeling et al. who calculated the pressure until the second virial coefficient only and in the case of χλee ≪ 1 where χ is the Debye length. Upon comparison with Ebeling et al. one observes that the considerable contribution of the third virial coefficient in the region of high temperatures (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

The Quantum Excess Free Energy for Two Component Plasma

AbstractThe aim of this paper is to calculate the quantum excess free energy until the third virial coefficient for the two component plasma (TCP). We consider only the thermal equilibrium plasma in the case of nλ3ab ≪ 1 where λ2ab = (ħ2/(mabKT)) is the thermal De Broglie wave‐length. The second and third virial coefficients are represented in forms of a convergent series expansion in terms of the interaction Parameter ξ2ab = ((eaeb)/(λabKT)). We obtained the excess free energy until the third virial coefficient to the order ξ6ab. The effects of symmetry are taken into account, also the exchange effects were taken in account. We compared our results with others. Upon comparison with Ebeling et al. one observes that the considerable contribution of the third virial coefficient in the region of high temperatures (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Statistical mechanics of the distribution of charge on particles in complex plasmas

This paper presents an analytical study of the distribution of charge on the particles in a complex plasma; the study is based on statistical mechanics and ensures that the charge on the particles is an integral multiple of the electronic charge. The formulation incorporates both the number and energy balance of electrons/ions. Three specific cases of charging of particles have been considered, namely (i) in a plasma in the absence of electron emission from the particles, (ii) in a complex plasma in thermal equilibrium and (iii) in a complex plasma irradiated by monochromatic radiation, causing photoelectric emission of electrons from the particles. The effect of various parameters on the charge distribution has also been investigated. This paper is in reasonably good agreement with the fluctuation theory for large values of Z (Ze is the charge on a particle). It is seen that under certain conditions, a significant number of oppositely charged particles occur in the complex plasma.

Shear viscosity in a perturbative quark–gluon plasma

Among the key features of hot and dense QCD matter produced in ultra-relativistic heavy-ion collisions at RHIC is its very low shear viscosity, indicative of the properties of a near-ideal fluid, and a large opacity demonstrated by jet energy loss measurements. In this work, we utilize a microscopic transport model based on the Boltzmann equation with quark and gluon degrees of freedom and cross sections calculated from perturbative quantum chromodynamics to simulate an ideal quark–gluon plasma in full thermal and chemical equilibrium. We then use the Kubo formalism to calculate the shear viscosity to entropy-density ratio of the medium as a function of temperature and system composition. One of our key results is that the shear viscosity over entropy-density ratio η/s becomes invariant to the chemical composition of the system when plotted as a function of energy-density instead of temperature.

Transient growth in stable linearized Vlasov–Maxwell plasmas

Large amplitude transient growth of kinetic scale perturbations in stable collisionless magnetized plasmas has recently been demonstrated using a linearized Landau fluid model. Initial perturbations with lengthscales of the order of the ion gyroradius were shown to have transient timescales that in some cases were long compared to the ion gyroperiod, Ωit⪢1. Moreover, it was suggested that such perturbations are not rare but instead form a large class within the set of all possible initial conditions. For collisionless plasmas, the Vlasov–Maxwell equations provide a more complete description of kinetic physics and the existence of transient growth of solutions for the linearized Vlasov–Maxwell system is an interesting question. The existence of transient growth of solutions is demonstrated here for a special case of the Vlasov–Maxwell equations, namely, the one dimensional Vlasov–Poisson system. The analysis is different from the standard approach of nonmodal analysis since the initial value problem is described by a Volterra integral equation of the second kind, reflecting the fact that the time evolution of the system depends on the memory of the state from time zero through time t. For the case of a thermal equilibrium plasma, it is shown how initial conditions may be constructed to obtain solutions that grow linearly in time; the duration of this growth is the time required for a thermal electron to traverse the wavelength of the initial perturbation, a timescale that can last for many plasma periods 2π/ωpe, thus demonstrating the existence of transient growth of solutions for the linearized Vlasov–Poisson system. The results suggest that the phenomenon of transient growth may be a common feature of the linearized Vlasov–Maxwell system as well as for Landau fluid models.

Dynamical plasma study during CaCu3Ti4O12 and Ba0.6Sr0.4TiO3 pulsed laser deposition by local thermodynamic equilibrium modelling

We performed space- and time-resolved plasma diagnostics during pulsed laser deposition of CaCu3Ti4O12 (CCTO) and Ba0.6Sr0.4TiO3 (BSTO) thin films. A KrF excimer laser irradiation at 248 nm with 25 ns pulse duration irradiates targets with a fluence varying from 1 to 2 J cm−2 under an oxygen pressure varying from 5 to 30 Pa. The plasma is shown to be optically thick and strongly non-uniform during the early expansion stage and the resonance lines Ca II 393 and 396 nm are strongly self-reversed during this time. Plasma temperature, electron density and relative elemental concentrations were obtained by comparing the experimental emission spectra with the spectral radiance computed for a non-uniform plasma in local thermal equilibrium. In this way, it was possible to evaluate very low concentrations of pollutants present in irradiated samples.