Kind Of Plasma Research Articles

Target Density Effects on Charge Transfer of Laser-Accelerated Carbon Ions in Dense Plasma.

We report on charge state measurements of laser-accelerated carbon ions in the energy range of several MeV penetrating a dense partially ionized plasma. The plasma was generated by irradiation of a foam target with laser-induced hohlraum radiation in the soft x-ray regime. We use the tricellulose acetate (C_{9}H_{16}O_{8}) foam of 2 mg/cm^{3} density and 1mm interaction length as target material. This kind of plasma is advantageous for high-precision measurements, due to good uniformity and long lifetime compared to the ion pulse length and the interaction duration. We diagnose the plasma parameters to be T_{e}=17 eV and n_{e}=4×10^{20} cm^{-3}. We observe the average charge states passing through the plasma to be higher than those predicted by the commonly used semiempirical formula. Through solving the rate equations, we attribute the enhancement to the target density effects, which will increase the ionization rates on one hand and reduce the electron capture rates on the other hand. The underlying physics is actually the balancing of the lifetime of excited states versus the collisional frequency. In previous measurement with partially ionized plasma from gas discharge and z pinch to laser direct irradiation, no target density effects were ever demonstrated. For the first time, we are able to experimentally prove that target density effects start to play a significant role in plasma near the critical density of Nd-glass laser radiation. The finding is important for heavy ion beam driven high-energy-density physics and fast ignitions. The method provides a new approach to precisely address the beam-plasma interaction issues with high-intensity short-pulse lasers in dense plasma regimes.

Penetration of plasma jet into porous dielectric layer: confirmed by surface charge dissipation of silicone rubber

The penetration of plasma in the porous structure is important for its application in plasma catalysis, plasma medicine, etc. In this paper, the penetration of plasma species in the porous kaolin layer was investigated. The silicone rubber was chosen as a probe and the inorganic porous dielectric layer was constructed with granular kaolin coated on the surface of silicone rubber. AC and pulsed plasma jets were applied to the silicone rubber, and the surface charge dissipation of bulk silicone rubber was measured to characterize the changes of surface property caused by the plasma penetration. The results showed that plasma could penetrate the porous dielectric layer on the silicone rubber and interact with the surface of silicone rubber, thus accelerating the surface charge dissipation of the bulk silicone rubber. The increase of shallow traps and surface conductivity after plasma treatment was the main reason for the acceleration of surface charge dissipation. The surface charge dissipation is enhanced with the increase of treatment time and the generating voltage of plasma. The surface charge dissipation declined for silicone rubber with a thicker kaolin layer due to the blocking of the kaolin layer on the interaction of plasma and the silicone rubber. For the same kind of plasma, the charge dissipation rate was linearly related to plasma dose which was represented by the energy density of plasma applied on the coated silicone rubber. At the same energy density, the surface charge dissipation of silicone rubber after pulsed plasma treatment was faster than that of AC plasma.

Numerical characterization of the breakdown process of dc-driven micro-discharges sustained by thermionic emission

Because of the larger surface-area-to-volume ratio, micro-discharges can be sustained by surface emission processes. If the cathode is heated, a micro-discharge can be sustained mainly by thermionic emission. However, we still know little about how this kind of plasma is ignited and sustained. In order to explore the breakdown process of dc-driven micro-discharge sustained by thermionic emission, a one-dimensional implicit particle-in-cell/Monte Carlo collision method is adopted, coupled with the external circuit and thermionic emission model. The breakdown process of micro-discharge lasts about 8 , and this process can be roughly divided into two phases, i.e. pre-breakdown and breakdown phase. The dynamic plasma parameters during the evolution process are analyzed, such as particle density, electron energy distribution function, electric potential, average particle temperature, and particle current density. The plasma electrical characteristics as well as the article and power balance, are also presented to show the evolutionary features of the whole gas breakdown process.

Cold Plasma as a Practical Approach to Cancer Treatment

The application of cold plasma therapy for the treatment of cancer is one promising field of study. This therapy can target and kill cancer cells while sparing healthy cells. The reactive oxygen species (ROS) and reactive nitrogen species (RNS), produced during plasma treatment is responsible for the cancer cells death. The research on cold plasma therapy is underway and has the potential to enhance current cancer treatments. Breast, lung, and skin cancer have all been treated with excellent success with cold plasma treatment. Cold plasma therapy has been shown to have anti-inflammatory, anti-angiogenic, and immunomodulatory properties in addition to its capacity to target cancer cells specifically, which may further increase its therapeutic potential. Additionally, it has been demonstrated that the efficiency of cold plasma therapy combined with other cancer therapies like chemotherapy, radiation therapy, and immunotherapy enhance the overall success of cancer treatment. Despite the positive outcomes of cold plasma treatment, additional studies are required to completely comprehend its mechanisms of action and improving its application in clinical settings. We entail further research on the ideal therapy variables, such as the kind of plasma used, the amount of energy given, the length of the procedure, and the creation of new, more effective plasma devices. In general, cold plasma therapy promises to revolutionize cancer treatment and prolong the lives of many cancer patients. The mechanisms of cold plasma treatment are examined in this review, along with its uses in oncology, including <i>in vitro</i> and<i> in vivo</i> investigations.

Effect of dielectric barrier discharge plasma on film cooling performance

To improve film cooling effectiveness of a gas turbine blade, a kind of plasma actuator is introduced on the blade surface. The effect of three arrangements of plasma actuators on flow characteristics and film cooling performance is numerically investigated by a verified turbulence model. Results show that the coolant air under plasma is pulled down to the wall, and the near-wall air is sped up to promote the film cooling effectiveness downstream the wall. It is discovered that the plasma actuators near the film hole show weaker aerodynamic actuation than that downstream the wall. Compared with the plasma actuators off case, the maximum improvement in the wall-averaged film cooling effectiveness of the case with up plasma actuators is 11.7% under low blowing ratios. The wall-averaged film cooling effectivenesses of the cases with down plasma actuators and up-down plasma actuators increase by 138.3% and 122.9% under the blowing ratio of 1.5.. Vortex structures are broken up, and vortex is separated by two jets induced by aerodynamic actuation. The maximum wall pressure difference reaches 1.89% when plasma actuator is arranged downstream the wall.

Argon low-pressure plasma treatment to stainless steel particles to augment the wear resistance of Cu-free brake-pads

Nowadays, the usage of Copper in brake friction materials (FMs)/pads is a major concern in the brake industry. Despite some of the earlier attempts for the Cu substitution, an issue with high wear of FMs due to their low adhesion of metal particles with the matrix (i.e., phenolic resin) is still largely unresolved. In the current study, the surface energy (SE) of stainless steels (SS316, SS410) and Cu particles was augmented using the right kind of plasma in optimized dose to improve the wettability/adhesion of metal particles with the matrix. The SE of treated particles increased significantly due to the reduction of oxides from the surfaces. A series of seven types of brake-pads was developed containing 3 vol% of SS and Cu (untreated and treated) particles as the theme ingredients keeping parent composition fixed. A reference pad without metal particles was also developed for benchmarking. The developed pads were characterized for physical properties and then evaluated for the tribological and noise-vibration (NV) performance on a brake-dynamometer following global test standards. The results revealed that the pads with treated SS and Cu particles showed a higher fade resistance (~ 2–3%) and reduced wear by ~ 10% compared to the pads with untreated particles. Overall, based on optimized technique, treated SS316 particles proved the best. The underlying mechanisms were studied through worn surface analysis using a field emission scanning electron microscope attached (FESEM) with an energy dispersive X-ray spectroscopy (EDAX).

Cavitation Bubble Plasma Technology and Its Applications

A cavitation bubble plasma, which is a kind of plasma in solution, is a low-temperature plasma generated in a large number of microbubbles of a solvent component generated by a cavitation phenomenon. In this paper, the cavitation bubble plasma technology is explained by introducing the originally developed apparatus, the discharge phenomenon, and the effect of cavitation bubbles. As application examples of cavitation bubble plasma, the results of water dispersion of carbon nanotubes, synthesis of silver nanoparticles, sterilization of Escherichia coli, and decomposition of methylene blue are introduced.

Reforming of CH4 and CO2 by Combination of Alternating Current-Driven Nonthermal Arc Plasma and Catalyst

An experimental plasma reforming reactor for conversion of CH4–CO2 to synthesis gas (syngas) has been developed, in which the plasma is generated by a nonthermal arc plasma torch with simple and compact structure. The effects of total flux of feed gases and the molar ratio of CH4/CO2 on syngas production, selectivities of H2 and CO, and energy conversion efficiency were investigated. It is proven that this kind of plasma is an effective way to reforming of CO2–CH4 with energy conversion efficiency of 5.25 mmol/kJ and energy efficiency of 81%. Moreover, the heat generated by the plasma can be fully utilized to activate catalyst.

Expectation values of general observables in the Vlasov formalism

Collisionless plasmas in an arbitrary dynamical state are described by the Vlasov equation, which gives the time evolution of the probability density ρ(x, v). In this work we introduce a new analytical procedure to generate particular partial differential equations (PDEs) for an arbitrary macroscopic observable w(x, v) that can be expressed as a function of positions and velocities, without solving the time evolution of the probability itself. This technique, which we will call the “Ehrenfest procedure” (as it produces relations that are analogous to Ehrenfest’s theorem in Quantum Mechanics), is based on the iterative application of the fluctuation-dissipation theorem and the recently proposed conjugate variables theorem (CVT) in order to eliminate the explicit dependence on ρ. In particular, we show how this formalism is applied to the Vlasov equation for collisionless plasmas, and derive a general evolution equation for the fluctuations of any macroscopic property w in this kind of plasma.

Higher order corrections to dust-acoustic shock waves in a strongly coupled cryogenic dusty plasma

To investigate the contribution of higher-order nonlinearity and dissipation to nonlinear ultra-low-frequency dust-acoustic shock waves (DASWs), a reductive perturbation technique is employed in a strongly coupled cryogenic dusty plasma. The model consists of Boltzmann distributed electrons and ions, as well as equations for strongly coupled charged dust grains. A nonlinear Burger equation and a linear inhomogeneous Burger-type equation are derived. The present model admits both compressive and rarefactive dust-acoustic (DA) shocks. Including these higher-order corrections results in creating new shock wave structures called “humped DASWs.” It is shown that the effects of kinematic viscosity, the number of electrons residing on the dust grain surface, Zd, and the dust number density via β have important roles in the basic features of the produced DA shocks and the associated electric fields. It has been shown that it is more important to be included. These findings are devoted to explaining the observed waves propagating in the laboratory plasma experiments at cryogenic temperature. This kind of plasma is used for etching nano-patterns without defects, used in nonideal systems, and physics of nucleation to deposit nanosize Si compounds.

Study of Condensed Phases, of Vaporization Temperatures of Aluminum Oxide and Aluminum, of Sublimation Temperature of Aluminum Nitride and Composition in an Air Aluminum Plasma

With the Gibbs free energy method, we determine the molar fraction in a plasma at and out of thermal equilibrium consisting of air and aluminum for several percentages in the temperature range of 500–6000 K. We take three temperatures into account (Trot = Th; Tvib; Tex = Te). We indicate the formulae and the numerical method used to perform the calculation taking three condensed phases AlN, Al, Al2O3 into account. We show that the air percentage plays a major role to create these phases. We clarify the role plays on the vaporization temperatures and on the sublimation temperature by the non-thermal equilibrium of the plasma. This kind of plasma is found in arc roots, near a wall, in plasmas with a high value of electrical field,… The influence of the pressures until 30 9 105 Pa. is shown on molar fraction of the chemical species, on the vaporization temperatures and on the sublimation temperature. The vaporization temperatures are given versus the thermal non equilibrium versus various mixtures (air, aluminum) and versus the pressures (10^5 Pa–30 10^5 Pa).

Nanosecond laser pulse interactions with breakdown plasma in gas medium confined in a microhole

The previous investigations on nanosecond laser pulse interactions with breakdown plasma in a gas medium confined in a microhole have been limited. This kind of plasma has been studied in this paper. Due to the significant measurement difficulty resulted from the very small spatial and temporal scales involved, a physics-based computational model has been employed as the investigation tool. The model is developed by solving gas dynamic equations numerically using the finite difference method based on an essentially non-oscillatory scheme. The gas dynamic equations are coupled with suitable equation of state, where the electron number density for plasma region is calculated through the Saha equation. Using the model, the spatial confinement effects of the microhole sidewall on the plasma evolution under laser radiation have been investigated. It has been found that under the studied conditions the hole sidewall confinement can greatly enhance the plasma temperature, pressure, and thrust (over the same surface area). The enhancement should be due to the sidewall’s restriction on the plasma lateral expansion and the sidewall’s reflection of the pressure wave induced by plasma. This study implies potential advantages of the breakdown plasma confined in a microhole in many relevant applications, such as laser propulsion and laser-induced breakdown spectroscopy. The developed model also provides a useful guiding tool for future fundamental research and practical applications in many areas related to laser interactions with gas breakdown plasma.

Accelerated Mice Skin Acute Wound Healing In Vivo by Combined Treatment of Argon and Helium Plasma Needle

The efficacy of a direct application of plasma needle to invivo wound healing was experimentally studied in mice. This kind of plasma has achieved considerable success in blood coagulation and tissue restoration in mice. In the development of the present study, an argon plasma needle was chosen for coagulation purposes, whereas for healing purposes, a helium plasma needle was used. Treatment was applied with a plasma needle produced by argon and helium to a wound induced in laboratory mice. Tissue regeneration was carried out by three argon plasma treatments with 0.5 SLPM flow for 1 min and three treatments of helium with 1.5SLPM flow. Intervals between each treatment were 5 min and 60 min for argon and helium plasmas, respectively, thus completing a total treatment time of 180 min. Histological sections were performed to corroborate the internal bleeding and tissue regeneration. After three treatments with argon plasma, the blood produced in the wound was coagulated and protein material appeared. By means of treatment with helium plasma, an approach of the wound edges was produced until the conclusion thereof. These results were corroborated histologically. This type of acceleration during the skin wound healing process can be attributed to the formation of reactive species such as NO, which were increased in the helium plasma needle with respect to the argon plasma needle.

Radiative improved mode in the HT-7 tokamak

The neon puffing for inducement of a Radiative Improved (RI) mode has been investigated on HT-7 tokamak. The results show that the central electron temperature is increased 1.4times and electron density is strongly peaked with ne0/nGR about 0.7. It has an improved energy confinement (17–25ms) and improved particle confinement (7.5–23ms) at the same time. The confinement factor H (H=τe/τeITER93ELMy-free) of 0.96 is obtained. There is a large fraction of radiation power losses. In our cases it is up to 80% of total input power. This kind of plasma has a high Z-effective, but there is not detrimental concentration of the seeded impurity at the core plasma, which induce a reduction in the growth rate of Ion Temperature Gradient (ITG) driven modes. Fluctuation experimental measurement obtained by CO2 scattering with kθρs of 1.4 also shows a reduction of turbulence in the core plasma after neon seeding.

Interaction between oppositely directed compression plasma flows

The dynamics of the interaction of two oppositely directed plasma flows generated by miniature gas-discharge magnetoplasma compressors is studied. The maximum plasma electron temperature and density in the region where the plasmas interact are found to be 4.5 eV and 1.4⋅1017 cm–3. Exposure of samples to this kind of plasma near the interaction region leads to an energy flux at the surface of 2–8 J/cm2, which is sufficient for modification of the surface properties of various materials.

Korteveg-de Vries solitons in a cold quark-gluon plasma

The relativistic heavy ion program developed at RHIC and now at LHC motivated a deeper study of the properties of the quark gluon plasma (QGP) and, in particular, the study of perturbations in this kind of plasma. We are interested on the time evolution of perturbations in the baryon and energy densities. If a localized pulse in baryon density could propagate throughout the QGP for long distances preserving its shape and without loosing localization, this could have interesting consequences for relativistic heavy ion physics and for astrophysics. A mathematical way to proove that this can happen is to derive (under certain conditions) from the hydrodynamical equations of the QGP a Korteveg-de Vries (KdV) equation. The solution of this equation describes the propagation of a KdV soliton. The derivation of the KdV equation depends crucially on the equation of state (EOS) of the QGP. The use of the simple MIT bag model EOS does not lead to KdV solitons. Recently we have developed an EOS for the QGP which includes both perturbative and non-perturbative corrections to the MIT one and is still simple enough to allow for analitycal manipulations. With this EOS we were able to derive a KdV equation for the cold QGP.

New views on the emission and structure of the solar transition region

The Sun is the only star that we can spatially resolve and it can be regarded as a fundamental plasma laboratory of astrophysics. The solar transition region (TR), the layer between the solar chromosphere and corona, plays an important role in solar wind origin and coronal heating. Recent high-resolution observations made by SOHO, TRACE, and Hinode indicate that the TR is highly nonuniform and magnetically structured. Through a combination of spectroscopic observations and magnetic field extrapolations, the TR magnetic structures and plasma properties have been found to be different in coronal holes and in the quiet Sun. In active regions, the TR density and temperature structures also differ in sunspots and the surrounding plage regions. Although the TR is believed to be a dynamic layer, quasi-steady flows lasting from several hours to several days are often present in the quiet Sun, coronal holes, and active regions, indicating some kind of plasma circulation/convection in the TR and corona. The emission of hydrogen Lyman lines, which originates from the lower TR, has also been intensively investigated in the recent past. Observations show clearly that the flows and dynamics in the middle and upper TR can greatly modify the Lyman line profiles.

On the Purity of Atmospheric Glow-Discharge Plasma

Purity of the glow-discharge plasma at atmospheric pressure for surface modification applications is always debatable, since it works at ambient atmosphere. We have demonstrated on the use of optical emission spectroscopy to test the purity of this kind of plasma. The effect of gas flow pattern, nature of gas, and its flow rate on the plasma chemistry was studied. The importance of proper system design in maintaining a uniform flow of heavy and inert gases as carrier gas in atmospheric glow-discharge plasma was confirmed. The surface of a plasma-treated PET sample was analyzed using X-ray photoelectron spectroscopy to verify the studies on plasma purity done using emission spectrum.

Beam-plasma dielectric tensor with Mathematica

We present a Mathematica notebook allowing for the symbolic calculation of the 3 × 3 dielectric tensor of an electron-beam plasma system in the fluid approximation. Calculation is detailed for a cold relativistic electron beam entering a cold magnetized plasma, and for arbitrarily oriented wave vectors. We show how one can elaborate on this example to account for temperatures, arbitrarily oriented magnetic field or a different kind of plasma. Program summary Title of program: Tensor Catalog identifier: ADYT_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADYT_v1_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: Computers: Any computer running Mathematica 4.1. Tested on DELL Dimension 5100 and IBM ThinkPad T42. Installations: ETSI Industriales, Universidad Castilla la Mancha, Ciudad Real, Spain Operating system under which the program has been tested: Windows XP Pro Programming language used: Mathematica 4.1 Memory required to execute with typical data: 7.17 Mbytes No. of bytes in distributed program, including test data, etc.: 33 439 No. of lines in distributed program, including test data, etc.: 3169 Distribution format: tar.gz Nature of the physical problem: The dielectric tensor of a relativistic beam plasma system may be quite involved to calculate symbolically when considering a magnetized plasma, kinetic pressure, collisions between species, and so on. The present Mathematica notebook performs the symbolic computation in terms of some usual dimensionless variables. Method of solution: The linearized relativistic fluid equations are directly entered and solved by Mathematica to express the first-order expression of the current. This expression is then introduced into a combination of Faraday and Ampère–Maxwell's equations to give the dielectric tensor. Some additional manipulations are needed to express the result in terms of the dimensionless variables. Restrictions on the complexity of the problem: Temperature effects are limited to small, i.e. non-relativistic, temperatures. The kinetic counterpart of the present Mathematica will usually not compute the required integrals. Typical running time: About 1 minute on a Intel Centrino 1.5 GHz Laptop with 512 MB of RAM. Unusual features of the program: None.

The Interaction of the Collisional Plasma with Microwave

The generation of plasma which can absorb microwaves is currently a research topic of interest. This kind of plasma is often produced by the discharge or electron-beam impact of noble gases. In this paper an alternatice approach, combustion plasma, is studied. The plasma is produced by combusting solid grains prepared specially. Six groups of powders were made and used to generate the plasma. The transmissivity of the wave in plasma was measured by employing a microwave scalar network analyser system. In addition, the electron density and the collision frequency of the plasma were examined by microwave double-frequency diagnosis. The measurement results showed that the plasma could absorb microwaves remarkably with an average transmission attenuation being more than 18 dB in a frequency range of 2 GHz to 15 GHz. The diagnosis indicated that the electron density of the plasma varied from 1017 m−3 to 1019 m−3 and the collision frequency was about 5×1010 s−1.