Plasma In Thermal Equilibrium Research Articles

Elevated Electron Temperature Coincident with Observed Fusion Reactions in a Sheared-Flow-Stabilized Z Pinch.

The sheared-flow-stabilized Z pinch concept has been studied extensively and is able to produce fusion-relevant plasma parameters along with neutron production over several microseconds. We present here elevated electron temperature results spatially and temporally coincident with the plasma neutron source. An optical Thomson scattering apparatus designed for the FuZE device measures temperatures in the range of 1-3keV on the axis of the device, 20cm downstream of the nose cone. The 17-fiber system measures the radial profiles of the electron temperature. Scanning the laser time with respect to the neutron pulse time over a series of discharges allows the reconstruction of the T_{e} temporal response, confirming that the electron temperature peaks simultaneously with the neutron output, as well as the pinch current and inductive voltage generated within the plasma. Comparison to spectroscopic ion temperature measurements suggests a plasma in thermal equilibrium. The elevated T_{e} confirms the presence of a plasma assembled on axis, and indicates limited radiative losses, demonstrating a basis for scaling this device toward net gain fusion conditions.

Synthesis of NbC@C(Nx) nanoparticles using DC arc discharge plasma for highly efficient oxygen reduction reaction

Development of the low-cost, high-efficiency, and durable non-precious metal electrocatalysts for cathodic oxygen reduction reaction (ORR) is of vital importance for fuel cells and metal-air batteries. Herein, the carbon-coated NbC nanoparticles (NbC@C NPs) were prepared using DC arc discharge plasma under a methane atmosphere. Then, the nitrogen-doping was conducted by heat treatment, resulting in nitrogen-doped carbon-coated NbC nanoparticles (NbC@C(Nx) NPs). Benefiting from the merit of unique core-shell structure and best synergy between the nitrogen-doped carbon shell and the NbC core, the obtained highest nitrogen-doped NbC@C(N1.36) NPs showed an onset potential (Eonset) of 0.89 V (vs. RHE) and a half-wave potential (E1/2) of 0.79 V, which are comparable to those of commercial Pt/C (20 wt%) (Eonset = 0.90 V, E1/2 = 0.80 V), and its diffusion-limited current density (JL) of 5.99 mA·cm−2 is even higher than that of commercial Pt/C (5.43 mA·cm−2). Moreover, it exhibited a remarkable long-term durability and impressive methanol resistance than Pt/C catalyst. In addition, the real-time optical emission spectrum (OES) analysis of arc plasma shows that the electron temperature (Te) is 7562.9 K in local thermal equilibrium (LTE) plasma. Therefore, the use of the DC arc discharge plasma method opens a fast and simple way to develop cost-effective and highly efficient non-precious metal catalysts for ORR.

Temperature dependence of the static quark diffusion coefficient

The propagation of a low momentum heavy quark in a deconfined quark-gluon plasma can be understood in terms of a Langevin description. The momentum exchange with the plasma in thermal equilibrium can then be parametrized in terms of a single heavy quark momentum diffusion coefficient κ, which needs to be determined nonperturbatively. In this work, we study the temperature dependence of κ for a static quark in a gluonic plasma, with a particular emphasis on the temperature range of interest for heavy ion collision experiments.

Experimental Investigation on Gliding Arc Plasma Ignition and Assisted Combustion Actuator

In a scramjet engine, the viscosity of kerosene increases, the oxygen content decreases, the atomization evaporation rate and chemical reaction rate of kerosene decrease significantly, and the flame propagation speed decreases significantly under the condition of low total temperature, leading to the difficulty of ignition. Therefore, it is urgent to innovate the repeatable ignition method suitable for ramjet from the source. Gliding arc plasma has the advantages of both thermal equilibrium and nonequilibrium plasma. It can be used as a stable high-temperature heat source and chemical reaction source to strengthen the whole process from ignition to flame combustion, which has a critical application prospect in broadening the ignition boundary of scramjet engines at low total temperature and improving flame stability. In this article, a gliding arc plasma igniter is designed and developed. The research of gliding arc plasma ignition technology in scramjet combustor is carried out from two aspects of the discharge characteristics of gliding arc plasma igniter and kerosene cracking characteristics experiment. The results show that the average power of the gliding arc igniter in the air environment is higher than that in the nitrogen environment. With the increase of flow rate, the average power of the igniter increases first and then decreases. The maximum average power of the igniter with nitrogen is 193.56 W, and the maximum average power in the air environment is 323.49 W. The cracking products of kerosene are mainly hydrogen, methane, ethylene, acetylene, and other hydrocarbons below C3. The concentration of the product was positively correlated with the excitation voltage and channel length, and the concentration of hydrogen was the largest. The concentration of cracking products is higher in air, where hydrogen is three times higher than that in nitrogen. The main flow ignition of scramjet was successfully achieved under the condition of 2-Ma inlet velocity and 1000 K inlet temperature.

X-Ray Spectroscopic Evidence of Charge Exchange Emission in the Disk of M51

In the disks of spiral galaxies, diffuse soft X-ray emission is known to be strongly correlated with star-forming regions. However, this emission is not simply from a thermal-equilibrium plasma and its origin remains greatly unclear. In this work, we present an X-ray spectroscopic analysis of the emission from the northern hot spot; a region with enhanced star formation off the nucleus of M51. Based on the high spectral resolution data from XMM-Newton/Reflection Grating Spectrometer (RGS) observations, we unambiguously detect a high G ratio () of the O vii Heα triplet. This high G ratio is also spatially confirmed by oxygen emission-line maps from the same data. A physical model consisting of a thermal plasma and its charge exchange (CX) with neutral cool gas gives a good explanation for the G ratio and the entire RGS spectra. This model also gives a satisfactory characterization of the complementary Chandra ACIS-S data, which enables a direct imaging of the diffuse emission, tracing the hot plasma across the galaxy. The hot plasma has a similar characteristic temperature of ∼0.34 keV and an approximately solar metallicity. The CX contributes ∼50% to the diffuse emission in the 0.4–1.8 keV band, suggesting an effective hot/cool gas interface area about five times the geometric area of the M51 disk. Therefore, the CX appears to play a major role in the soft X-ray production and may be used as a powerful tool to probe the interface astrophysics, important for studying galactic ecosystems.

Numerical investigation of the spark discharge process in a crossflow

The present study numerically investigates the spark discharge process under crossflow conditions using a thermal equilibrium plasma solver that fully couples the electromagnetic physics and fluid dynamics in a computational framework. Numerical results are validated by the comparison with experimental data. The spark discharge experiment is performed in a constant volume vessel using an inductive coil ignition system for automotive applications, and the evolution of the spark channel is measured using high-speed imaging. The crossflow in the gap between the spark-plug electrodes is generated by a rotating fan with two different fan speeds, and the flow velocity across the gap is characterized by particle image velocimetry (PIV) measurement. A computational fluid dynamics (CFD) solver is employed to simulate the crossflow and provide the flow field variables (velocity, pressure, temperature) to the plasma solver. The crossflow velocity predicted in the flow simulation agrees well with the PIV data in that the non-uniform velocity profiles at monitoring points are reproduced by the CFD code. With the crossflow initialization in the plasma solver, the simulated spark discharge process from the breakdown to spark discharge matches the experimental data, including the voltage and circuit waveforms and the high-speed images of the spark channel evolution. The stretch of spark channel captured by plasma simulations agrees with the measured data. The plasma simulation reveals that the mean temperature of the spark channel is maintained at 5000 K during the discharge phase, and the temperature varies along the spark channel so that the highest value is obtained at the spark root on the center electrode. Overall, the results presented in this paper are meant to provide valuable information about the properties of the plasma generated by the spark discharge.

The shear viscosity of parton matter under anisotropic scatterings

The shear viscosity eta of a quark–gluon plasma in equilibrium can be calculated analytically using multiple methods or numerically using the Green–Kubo relation. It has been realized, which we confirm here, that the Chapman–Enskog method agrees well with the Green–Kubo result for both isotropic and anisotropic two-body scatterings. We then apply the Chapman–Enskog method to study the shear viscosity of the parton matter from a multi-phase transport model. In particular, we study the parton matter in the center cell of central and midcentral Au + Au collisions at 200A GeV and Pb + Pb collisions at 2760A GeV, which is assumed to be a plasma in thermal equilibrium but partial chemical equilibrium. As a result of using a constant Debye mass or cross section sigma for parton scatterings, the eta /s ratio increases with time (as the effective temperature decreases), contrary to the trend preferred by Bayesian analysis of the experimental data or pQCD results that use temperature-dependent Debye masses. At sigma =3 mb that enables the transport model to approximately reproduce the elliptic flow data of the bulk matter, the average eta /s of the parton matter in partial equilibrium is found to be very small, between one to two times 1/(4pi ).

Numerical simulation for wire X-pinch plasma on 2D/3D geometry

This paper investigates wire X-pinch (WXP) evolutions by the Eulerian resistive magneto-hydrodynamic code, STHENO, on 2D/3D geometry. A single-fluid two-temperature model is applied to pinch plasmas in local thermal equilibrium. The equation of state based on the Thomas–Fermi model is used to determine the ionization degree of the plasma. Electron internal energy is determined by the local density, temperature, and ionization potential with the average ion charge state. Lee–More–Desjarlais transport models are employed to obtain the thermal conductivities and resistivity for a non-ideal plasma. The radiation loss rate is calculated by the Bremsstrahlung and recombination emissivity within the ionization balance. The crossing point, which is the central part of the X-pinch, is assumed to be an axisymmetric configuration on a small computational domain in the RZ plane. The 2D simulation demonstrates that the micrometer size plasma column is elongated axially with the onset of the neck cascading structure. The radiation power is calculated and compared with the measured x-ray power from a modular X-pinch device (120-kA in 650-ns) at Seoul National University. The time evolution of the radiation power reproduces the trend of the measured x ray. 3D analyses are performed for the aluminum WXP configurations by varying wire numbers and cross-angles. The relation between the radiation performance and the numbers of wires reveals that the current density, rather than the line density, determines the central pinching condition. In addition, the multiple plasma instabilities (m = 0) near the central regions are found to degrade the radiation performance on the small cross-angle WXP.

Fast magnetosonic solitonic structures in a quasi-neutral collision-free finite-beta plasma

The equations of the model of two fluids of a two component collision-free, isotropic and fully ionized plasma in thermal equilibrium consisting of singly-ionized ions and electrons in a uniform magnetic field with heated ions and electrons are treated. We focus our attention on determining the global hydromagnetic fast magnetosonic traveling solitonic waves for plane wave equations. Ordinary solitary waves, bifurcating from the zero wave number, exist for the angles of inclination θ of the magnetic field vector to the direction x of the wave propagation, located in some left neighborhood of π/2. A global family of solitary waves containing solitary waves of all possible amplitudes is numerically determined. The dynamic stability of these solitary waves is investigated by numerical methods: the problem of the evolution of solitary waves via the time dependent field equations of the quasi-neutral collision-free finite beta-plasma is analyzed. We also concern the domains in parameter space where traveling generalized and envelope solitary waves exist and compute the possible forms of these waves and of so-called multi-soliton waves with several humps. The evolution of a localized perturbation is also treated numerically.

Gap probability and full counting statistics in the one-dimensional one-component plasma

We consider the 1d one-component plasma in thermal equilibrium, consisting of N equally charged particles on a line, with pairwise Coulomb repulsion and confined by an external harmonic potential. We study two observables: (i) the distribution of the gap between two consecutive particles in the bulk and (ii) the distribution of the number of particles N I in a fixed interval I = [−L, +L] inside the bulk, the so-called full-counting-statistics (FCS). For both observables, we compute, for large N, the distribution of the typical as well as atypical large fluctuations. We show that the distribution of the typical fluctuations of the gap g is described by the scaling form , where α is the interaction coupling and the scaling function H α (z) is computed explicitly. It has a faster than Gaussian tail for large z: as z → ∞. Similarly, for the FCS, we show that the distribution of the typical fluctuations of N I is described by the scaling form , where is the average value of N I and the scaling function U α (z) is obtained explicitly. For both observables, we show that the probability of large fluctuations is described by large deviations forms with respective rate functions that we compute explicitly. Our numerical Monte-Carlo simulations are in good agreement with our analytical predictions.

Applications of Plasma Produced with Electrical Discharges in Gases for Agriculture and Biomedicine

The use of thermal and non-thermal atmospheric pressure plasma to solve problems related to agriculture and biomedicine is the focus of this paper. Plasma in thermal equilibrium is used where heat is required. In agriculture, it is used to treat soil and land contaminated by the products of biomass, plastics, post-hospital and pharmaceutical waste combustion, and also by ecological phenomena that have recently been observed, such as droughts, floods and storms, leading to environmental pollution. In biomedical applications, thermal plasma is used in so-called indirect living tissue treatment. The sources of thermal plasma are arcs, plasma torches and microwave plasma reactors. In turn, atmospheric pressure cold (non-thermal) plasma is applied in agriculture and biomedicine where heat adversely affects technological processes. The thermodynamic imbalance of cold plasma makes it suitable for organic syntheses due its low power requirements and the possibility of conducting chemical reactions in gas at relatively low and close to ambient temperatures. It is also suitable in the treatment of living tissues and sterilisation of medical instruments made of materials that are non-resistant to high temperatures. Non-thermal and non-equilibrium discharges at atmospheric pressure that include dielectric barrier discharges (DBDs) and atmospheric pressure plasma jets (APPJs), as well as gliding arc (GAD), can be the source of cold plasma. This paper presents an overview of agriculture and soil protection problems and biomedical and health protection problems that can be solved with the aid of plasma produced with electrical discharges. In particular, agricultural processes related to water, sewage purification with ozone and with advanced oxidation processes, as well as those related to contaminated soil treatment and pest control, are presented. Among the biomedical applications of cold plasma, its antibacterial activity, wound healing, cancer treatment and dental problems are briefly discussed.

Second order equilibrium transport in strongly coupled mathcal{N} = 4 supersymmetric SU(Nc) Yang-Mills plasma via holography

A relativistic fluid in 3+1 dimensions with a global U(1) symmetry admits nine independent static susceptibilities at the second order in the hydrodynamic derivative expansion, which capture the response of the fluid in thermal equilibrium to the presence of external time-independent sources. Of these, seven are time-reversal mathbbm{T} invariant and can be obtained from Kubo formulas involving equilibrium two-point functions of the energy-momentum tensor and the U(1) current. Making use of the gauge/gravity duality along with the aforementioned Kubo formulas, we compute all seven mathbbm{T} invariant second order susceptibilities for the mathcal{N} = 4 supersymmetric SU(Nc) Yang-Mills plasma in the limit of large Nc and at strong ’t-Hooft coupling λ. In particular, we consider the plasma to be charged under a U(1) subgroup of the global SU(4) R-symmetry of the theory. We present analytic expressions for three of the seven mathbbm{T} invariant susceptibilities, while the remaining four are computed numerically. The dual gravitational description for the charged plasma in thermal equilibrium in the absence of background electric and magnetic fields is provided by the asymptotically AdS5 Reissner-Nordström black brane geometry. The susceptibilities are extracted by studying perturbations to the bulk geometry as well as to the bulk gauge field. We also present an estimate of the second order transport coefficient κ, which determines the response of the fluid to the presence of background curvature, for QCD, and compare it with previous determinations made using different techniques.

Optical clearing of laser-induced tissue plasma

We studied the effect of optical clearing (OC) by glycerol on laser-induced tissue plasma using the immersion method. The results demonstrated the apparently enhanced effect of glycerol on the molecular spectra of the laser induced plasma. The OC is more sensitive to the molecular bands than atomic lines. After tissue immersion in the glycerol, the electron density of tissue plasma is decreased. The laser plasma temperature of the glycerol treated tissue is higher than for virgin fresh tissue. The tissue plasma after the glycerol application is still in the local thermal equilibrium plasma state. This work presents a new perspective for OC application that can extend from tissue better imaging quality to improvement of laser plasma generation.

Enhanced thermionic emission of mayenite electride composites in an Ar glow discharge plasma

Mayenite electride has attracted increasing research interests because of its unique electronic properties. The thermionic emission behavior of the mayenite electride is relatively unknown. Previous studies revealed that mayenite electride exhibited a bare work function ranged from 2.1–2.6 eV when the thermionic emission was tested in vacuum, and enhanced emission currents could be achieved by applying a super-high external electric field. In this paper, the thermionic emission behavior and the corresponding effective work function of two types of mayenite electride based composites, mayenite electride-titanium and mayenite electride-carbon, were investigated in an Ar glow discharge plasma at elevated temperatures (400–1000 K) without applying a high external electric field, which is critical for the application in electric propulsion and other aerospace apparatus, yet never had been done before. During the testing, the thermal equilibrium process and plasma sheath expansion were observed. The effective work function of the two mayenite electride composites were determined as a function of temperature. The Rasor-Warner model was applied to determine the bare work function and adsorption-site density of the mayenite electride based composites. Results suggested that the adsorption of Ar ions led to the enhanced thermionic emission (~30 A/m2 at 985 K) and low effective work functions (0.9–2.2 eV) of mayenite electride based composites, without the need of applying high electric fields. Our findings will pave the ways for the application of mayenite electride and its composites as the thrust cathode materials for electric propulsion where plasma is present.

Transverse momentum broadening of a jet in quark-gluon plasma: an open quantum system EFT

We utilize the technology of open quantum systems in conjunction with the recently developed effective field theory for forward scattering to address the question of massless jet propagation through a weakly-coupled quark-gluon plasma in thermal equilibrium. We discuss various possible hierarchies of scales that may appear in this problem, by comparing thermal scales of the plasma with relevant scales in the effective field theory. Starting from the Lindblad equation, we derive and solve a master equation for the trans- verse momentum distribution of a massless quark jet, at leading orders both in the strong coupling and in the power counting of the effective field theory. Markovian approximation is justified in the weak coupling limit. Using the solution to the master equation, we study the transverse momentum broadening of a jet as a function of the plasma temperature and the time of propagation. We discuss the physical origin of infrared sensitivity that arises in the solution and a way to handle it in the effective field theory formulation. We suspect that the final measurement constraint can only cut-off leading infrared singularities and the solution to the Markovian master equation resums a logarithmic series. This work is a stepping stone towards understanding jet quenching and jet substructure observables on both light and heavy quark jets as probes of the quark-gluon plasma.

Gravitational wave background from Standard Model physics: complete leading order

We compute the production rate of the energy density carried by gravitational waves emitted by a Standard Model plasma in thermal equilibrium, consistently to leading order in coupling constants for momenta k ∼ πT. Summing up the contributions from the full history of the universe, the highest temperature of the radiation epoch can be constrained by the so-called Neff parameter. The current theoretical uncertainty ∆Neff≤ 10−3 corresponds to Tmax≤ 2 × 1017 GeV. In the course of the computation, we show how a subpart of the production rate can be determined with the help of standard packages, even if subsequently an IR subtraction and thermal resummation need to be implemented.

On the Magnetic Field Spectrum and Its Fluctuations in a Primeval Cold Plasma in Thermal Equilibrium

This work reassesses previous results and generalizes the expression for the low-frequency spectrum of magnetic fields fluctuations in a thermal plasma, that was previously obtained within the framework of the fluctuation-dissipation theorem. The new approach presented here is able to avoid any approximation yielding a unique expression that covers both the low- and high-frequency spectrum, without the need of procedures to smooth the junction between the two limit frequency regions formerly used. Also, the simultaneous dependence of this intensity on the plasma and on the collisional frequencies is discussed. Finally, the total emitted plasma energy is compared to the Stefan-Boltzmann law of a pure black-body.

Screening properties of quark-gluon plasma obtained from distribution and correlation functions of the constituent quasiparticle model

Based on the constituent quasiparticle model of quark-gluon plasma (QGP), the matrix elements of the density operator and the Wigner function in the color phase space are presented in form of color path integrals over Wiener and SU(3) group Haar measures. Monte Carlo calculations of quark and gluon momentum distributions and spatial pair distribution functions have been carried out for the strongly coupled QGP plasma in thermal equilibrium at zero baryon chemical potential. The Debye screening mass and the running coupling constant have been obtained from the spatial pair distribution function and are in agreement with the available lattice QCD data. At densities related to the average interparticle distance more than 0.4 fm the gluon bound states in the form of glueballs have been found. Comparison with the Maxwell Boltzmann distribution shows significant influence of interparticle interaction on high energy asymptotics of the momentum distribution functions, resulting in appearance of quantum tails. The new color pair correlation function has been introduced, and related new color screening mass has been discussed.

Effective coupling constant of plasmons

We study an ultrarelativistic QED plasma in thermal equilibrium. Plasmons - photon collective excitations - are postulated to correspond not to poles of the retarded photon propagator but to poles of the propagator multiplied by the fine structure constant. This product is an invariant of the renormalization group that is independent of an arbitrarily chosen renormalization scale. In addition, our proposal is physically motivated since one needs to scatter a charged particle off a plasma system to probe its spectrum of collective excitations. We present a detailed calculation of the QED running coupling constant at finite temperature using the Keldysh-Schwinger representation of the real-time formalism. We discuss the issue of how to choose the renormalization scale and show that the temperature is a natural choice which prevents the breakdown of perturbation theory through the generation of potentially large logarithmic terms. Our method could be applied to anisotropic systems where the choice of the renormalization scale is less clear, and could have important consequences for the study of collective modes.

Quarkonium in-medium transport equation derived from first principles

We use the open quantum system formalism to study the dynamical in-medium evolution of quarkonium. The system of quarkonium is described by potential non-relativistic QCD while the environment is a weakly coupled quark-gluon plasma in local thermal equilibrium below the melting temperature of the quarkonium. Under the Markovian approximation, it is shown that the Lindblad equation leads to a Boltzmann transport equation if a Wigner transform is applied to the system density matrix. Our derivation illuminates how the microscopic time-reversibility of QCD is consistent with the time-irreversible in-medium evolution of quarkonium states. Static screening, dissociation and recombination of quarkonium are treated in the same theoretical framework. In addition, quarkonium annihilation is included in a similar way, although the effect is negligible for the phenomenology of the current heavy ion collision experiments. The methods used here can be extended to study quarkonium dynamical evolution inside a strongly coupled QGP, a hot medium out of equilibrium or cold nuclear matter, which is important to studying quarkonium production in heavy ion, proton-ion, and electron-ion collisions.