High-velocity Plasma Jet Research Articles

Numerical Simulation of the Interaction of High-Velocity Plasma Jets Injected in the Earth’s Ionosphere

The paper presents a numerical simulation of the dynamics of high-velocity aluminum plasma jets with multiple injection in the Earth’s ionosphere. Scenarios of single injection, counter injection, and collimation of plasma jets at a given convergence angle are considered. The gas-dynamic parameters of plasma formations and their optical characteristics are determined.

Numerical Simulation of the Interaction of High-Velocity Plasma Jets Injected in the Earth’s Ionosphere

Numerical Simulation of the Interaction of High-Velocity Plasma Jets Injected in the Earth’s Ionosphere

Synthesis of Hf6Ta2O17 superstructure via spark plasma sintering for improved oxidation resistance of multi-component ultra-high temperature ceramics

Ultra-high temperature ceramics (UHTCs) have shown aspiration to overcome challenges in the thermal protection system (TPS) by designing new materials referred to as multi-component UHTCs (MC-UHTCs) in the compositional space. MC-UHTCs have shown remarkable improvement in oxidation resistance due to the formation of the Hf 6 Ta 2 O 17 superstructure during plasma exposure. Herein, the Hf 6 Ta 2 O 17 superstructure is synthesized via a solid-state reaction between HfO 2 and Ta 2 O 5 powder mixtures during spark plasma sintering (SPS). The compositions chosen are 50 vol% of HfO 2 -50 vol% of Ta 2 O 5 (50HO-50TO) and 70 vol% of HfO 2 -30 vol% of Ta 2 O 5 (70HO-30TO). The phase quantification via Rietveld analysis showed Hf 6 Ta 2 O 17 as a principal phase with some residual Ta 2 O 5 phase in both the samples. The high-temperature thermal stability of the samples was evaluated using high-velocity plasma jet exposure for up to 3 min. 50HO-50TO was able to withstand the intense plasma condition, which is attributed to the higher content of the Hf 6 Ta 2 O 17 phase (∼84%) and lower strain in the Ta 2 O 5 phase. The augmentation in the Hf 6 Ta 2 O 17 phase to 94.7% (in 50HO-50TO) post plasma exposure has been attributed to the invariant transformation from a liquid state to Hf 6 Ta 2 O 17 at temperatures >2500 °C during testing. The mechanical integrity is elucidated from the insignificant change in the hardness ∼13.3 GPa before and 11.2 GPa after plasma exposure of the 50HO-50TO sample. As a result, the Hf 6 Ta 2 O 17 superstructure's thermo-mechanical stability suggests developing novel oxidation-resistant MC-UHTCs in compositional space for reusable space vehicle applications.

Reconfiguration of an Electrothermal-Arc Plasma Source for In Situ PMI Studies

An electrothermal-arc plasma source (ET-Arc) has been developed to produce transient plasma heat and particle fluxes similar to those produced by edge localized modes onto divertor plasma-facing components in tokamaks. The ET-Arc utilizes a capacitive discharge to send current through a 4-mm-diameter, 9-cm-long capillary source liner. The liner material is ablated to form a high-velocity plasma jet that impacts the target downstream. With the current discharge circuit configuration, pulse lengths are 1 to 2 ms in duration and deliver heat fluxes of 0.25 to 2.1 GW m−2. The plasma was previously characterized with optical emission spectroscopy (OES) on helium emission lines. The He I line ratios were interpreted with collisional radiative analysis to calculate ne and Te. The electron temperature and electron density ranged from Te = 1 to 5 eV and ne = 1022 to 1028 electrons/m3, respectively. Recently, the vacuum configuration and target of the ET-Arc device were modified to allow greater diagnostic access for plasma-material interaction (PMI) studies and diagnostic development. The diagnostic suite included two Tektronix high-voltage probes to measure the capacitor and discharge potentials, a discharge current monitor, Edgertronic SC1 high-speed cameras to image the discharge, and a FLIR SC4000 infrared camera to estimate heat flux on the target. The system used OES for plasma characterization, but a new Thomson scattering (TS) diagnostic has been implemented. This system is an Advanced Research Projects Agency - Energy (ARPA-E)-funded, portable diagnostic package for spectroscopic measurements of ne, Te, ni, Ti,, and vi, which includes both TS and OES. Additionally, a novel digital holography (DH) surface-imaging diagnostic was implemented to measure erosion rates in situ. Results from ex situ DH characterization of stainless steel targets exposed to the ET-Arc source indicated that surface erosion of ~150 nm per shot occurred and an in situ DH characterization of similar targets was planned. The arc-triggering system will be revised and optimized to better synchronize with the laser diagnostics. Details of the reconfigured ET-Arc source are reported here.

Supersonic plasma turbulence in the laboratory

The properties of supersonic, compressible plasma turbulence determine the behavior of many terrestrial and astrophysical systems. In the interstellar medium and molecular clouds, compressible turbulence plays a vital role in star formation and the evolution of our galaxy. Observations of the density and velocity power spectra in the Orion B and Perseus molecular clouds show large deviations from those predicted for incompressible turbulence. Hydrodynamic simulations attribute this to the high Mach number in the interstellar medium (ISM), although the exact details of this dependence are not well understood. Here we investigate experimentally the statistical behavior of boundary-free supersonic turbulence created by the collision of two laser-driven high-velocity turbulent plasma jets. The Mach number dependence of the slopes of the density and velocity power spectra agree with astrophysical observations, and supports the notion that the turbulence transitions from being Kolmogorov-like at low Mach number to being more Burgers-like at higher Mach numbers.

The Possibility of Boron Carbide Coating Formation by Using a Coaxial Magnetoplasma Accelerator

A coaxial magnetoplasma accelerator can generate a dense and high velocity plasma jet by applying a pulsed high-current arc-discharge. The results of the experiment investigations of plasmadynamic synthesis in the B-C system have been shown while hyper speed jet boron carbide electric–discharged plasma steams onto copper substrate. The boron carbide coatings were formed on the copper substrate without a binder material. The formation of the crystalline boron carbide coating on the copper substrate was analysed through X-ray diffraction, transmission electron microscopy and scanning electron microscopy.

The possibility of boron carbide coating formation by using a coaxial magnetoplasma accelerator

A coaxial magnetoplasma accelerator can generate a dense and high velocity plasma jet by applying a pulsed high-current arc-discharge. The results of the experiment investigations of plasmodynamic synthesis in the B-C system have been shown while hyper speed jet boron carbide electric-discharged plasma steams onto copper substrate. The boron carbide coatings were formed on the copper substrate without a binder material. The formation of the crystalline boron carbide coating on the copper substrate was analyzed through X-ray diffractometry, transmission electron microscopy and scanning electron microscopy.

High-Velocity Neutral Plasma Jet Formed by Dense Plasma Deflagration

High-velocity high-energy-density plasma jets are an invaluable tool for studying plasma-material interactions under extreme thermal, physical, chemical, and electrostatic stresses. Such a jet has been generated in an experimental facility utilizing a pulsed plasma deflagration accelerator. Time-averaged and fast-frame-rate intensified charge-coupled device images of the plasma jet are presented, showing a concentrated high-density plasma near the exit that is characterized with laser interferometry.

Influence of plasma characteristics on nitrogen mixing into shielding gas in helium gas tungsten arc welding

The influence of welding condition on the mixing of atmospheric nitrogen into the arc plasma in helium gas tungsten arc welding was analysed by numerical simulations. In order to evaluate the effects of the convection flow and the diffusion on the nitrogen mixing phenomenon, the distributions of the Peclet number were used. Elongation of the electrode length has low impact on the decrease of shielding gas concentration because the convection flow becomes dominant in this area, which indicates higher Peclet numbers. Meanwhile, nitrogen diffusion increases in the plasma area with a temperature of about 10,000 K, so that elongation of the arc length leads to a remarkable decrease of shielding gas concentration. Additionally, the impact of convection flow increases in the arc centre area where high-velocity plasma jet exists, and the shielding gas concentration tends to rise owing to higher welding current in the condition of sufficient shielding gas flow rate.

The employment of a high density plasma jet for the investigation of thermal protection materials

This paper describes the results of tests of thermal protection materials (TPM) at conditions that simulate the atmospheric re-entry of space vehicles, tested by means of a high velocity and enthalpy air plasma jet generated with a dc plasma torch. Such a high velocity and enthalpy air plasma jet allows us to investigate TPM by simulating heat flux values varying with time in accordance with real re-entry altitudes and trajectories. The main research interests include the measurements of plasma flow temperature and heat flux for the testing of materials used for thermal protection systems of space vehicles. The test results of investigations of light composite thermal protective system material and graphite are presented.

Using arc voltage to locate the anode attachment in plasma arc cutting

Plasma arc cutting is a widely used industrial process in which an electric arc in the form of a high velocity plasma jet is used to melt and blow away metal. The arc attaches inside the resulting cut slot, or kerf, where it both provides a large heat flux and determines the flow dynamics of the plasma. Knowledge of the position of the arc attachment is essential for understanding the phenomena present at the work piece. This work presents a new method of measuring the location of the arc attachment in which the arc voltage is measured during the cutting of a range of work piece thicknesses. The attachment location is then interpreted from the voltages. To support the validity of this method, the kerf shape, dross particle size and dross adhesion to the work piece are also observed. While these do not conclusively give an attachment location, they show patterns which are consistent with the attachment location found from the voltage measurements. The method is demonstrated on the cutting of mild steel, where the arc attachment is found to be stationary in the upper portion of the cut slot and in reasonable agreement with existing published findings. For a process optimized for the cutting of 12.7 mm mild steel, the attachment is found at a depth of 1.5–3.4 mm. For a slower process optimized for the cutting of 25.4 mm mild steel, the attachment is found at a depth of 3.4–4.8 mm, which enhances heat transfer further down in the kerf, allowing cutting of the thicker work piece. The use of arc voltage to locate the position of the arc attachment is unique when compared with existing methods because it is entirely independent of the heat distribution and visualization techniques.

Experimental results to study astrophysical plasma jets using Intense Lasers

We present experimental results of plasma jet, interacted with an ambient medium, using intense lasers to investigate the complex features of astrophysical jets. This experiment was performed in France at the LULI facility, Ecole Polytechnique, using one long pulse laser to generate the jet and a short pulse laser to probe it by proton radiography. A foam filled cone target was used to generate high velocity plasma jet, and a gas jet nozzle produced the well known ambient medium. Using visible pyrometry and interferometry, we were able to measure the jet velocity and electronic density. We get a panel of measurements at various gas density and time delay. From these measurements, we could underline the growth of a perturbed shape of the jet interaction with the ambient medium. The reason of this last observation is still in debate and will be presented in the article.

Luminescence of the disturbed upper atmosphere in the visible and infrared spectral ranges in the conditions of injection of a high-velocity plasma jet: II. Theoretical interpretation of the luminescence in the visible spectral range

A theoretical interpretation is given to the experimental data on the luminescence in the visible spectral region of the disturbed upper atmosphere in the conditions of injection of a high-velocity aluminum plasma jet (the “Fluxus” experiment). Mathematical models of optical effects are presented. It is demonstrated that the results of the calculations and the experimental data agree satisfactorily. The principal physical and chemical processes responsible for the observed luminescence are determined.

Effects of Nozzle Length and Process Parameters on Highly Constricted Oxygen Plasma Cutting Arc

The influence of nozzle length and two process parameters (arc current, mass flow rate) on the plasma cutting arc is investigated. Modeling results show that nozzle length and these two process parameters have essential effects on plasma arc characteristics. Long nozzle torch can provide high velocity plasma jet with high heat flux. Both arc voltage and chamber pressure increase with the nozzle length. High arc current increases plasma velocity and temperature, enhances heat flux and augments chamber pressure and thus, the shock wave. Strong mass flow has pinch effect on plasma arc inside the torch, enhances the arc voltage and power, therefore increases plasma velocity, temperature and heat flux.

A Theoretical Analysis of Vacuum Arc Thruster and Vacuum Arc Ion Thruster Performance

Thrusters that exploit vacuum arc discharges to produce high-velocity plasma jets directly or as sources of plasma that is subsequently accelerated electrostatically have been proposed or are currently under development. Vacuum arc discharges exhibit certain regularities in their behavior that allow the performance of these thrusters to be described by simple semiempirical models. Empirical data on the current density distribution, charge state and velocity of ions created in vacuum arc discharges, and the total cathode mass loss rate are used to develop expressions for the expected thrust and specific impulse as a function of thruster geometry. Thruster electrical efficiency and thrust-to-power ratio are calculated based on measurements of the burning voltage for given thruster operating parameters. Estimates of achievable thruster performance for a wide range of cathode materials are presented. This analysis suggests that thrusters using vacuum arc sources can be operated efficiently with a range of propellant options that gives great flexibility in specific impulse. In addition, the efficiency of plasma production in these devices appears to be largely independent of scale because the metal vapor is ionized within tens of micrometers of the cathode electron emission sites, so this approach is well suited for micropropulsion.

Effect of pulsed plasma and high-current electron beam treatments on the structure and properties of nickel-based coatings

Using plasma-detonation technology (PDT), nickel-based powder (PGAN-33, PG-10N-01 and PG-19N-01) coatings 80–300 μm thick were deposited on a low-carbon St-3 steel substrate. Coatings were then subjected to additional treatment either by a high-current electron beam (HCEB) or by a high-velocity pulsed plasma jet until melting. The structure was analyzed using x-ray diffraction and conversion Mossbauer spectroscopy in the transmission and scattering modes. The morphology and elemental composition were studied using scanning electron microscopy and microanalysis. The micro-and nanohardness, volumetric wear, and corrosion resistance of the grown coatings were measured. It was found that, as the HCEB and PDT energy density increase, the phase composition changes, phase redistribution occurs, and new phases are formed. The last process is caused by mass transfer from the erosion plasmatron electrode and from a gas plasma jet, and interdiffusion of coating and substrate elements. After the exposure to concentrated energy fluxes, the coating surface roughness decreased. It is shown that physicochemical and mechanical characteristics of modified coatings improve in the case of optimum treatment conditions.

Plasma jet experiments in vacuum and in ambient medium using high energy lasers

We present promising experimental results for laboratory astrophysics. These experiments were performed in France at the LULI2000 facility to study jet propagation in vacuum and in Japan at ILE using Gekko XII HIPER Laser for jet evolution in an ambient medium. A foam filled cone target was used to generate high velocity plasma jet, and a gas jet nozzle was used to produce the ambient medium. Using visible and X-ray diagnostics, we measured the jet parameters such as: density, temperature and velocity. We were able to determine experimentally the jet dimensionless quantities to compare with astrophysical objects.

Numerical simulation of temperature and velocity fields in plasma spray

Based on the turbulence jet model, with respect to Ar-He mixture plasma gas injecting to ambient atmosphere, the temperature filed and velocity field under typical working conditions were investigated. Given the conditions of I=900 A, F Ar = 1.98 m3/h, F He = 0.85 m3/h, it is found that both the temperature and the velocity undergo a plateau region near the nozzle exit (0–10 mm) at the very first stage, then decrease abruptly from initial 13 543 K and 778.2 m/s to 4 000 K and 260.0 m/s, and finally decrease slowly again. Meanwhile, the radial temperature and radial velocity change relatively slow. The inner mechanism for such phenomena is due to the complex violent interaction between the high-temperature and high-velocity turbulent plasma jet and the ambient atmosphere. Compared with traditional methods, the initial working conditions can be directly related to the temperature and velocity fields of the plasma jet by deriving basic boundary conditions.

Hyper-Velocity Fullerene-Dusty Plasma Jets for Disruption Mitigation

High-velocity hydrogen plasma jets demonstrated deep penetration into magnetically confined tokamak plasma during fueling experiments. Disruption mitigation with plasma jets requires much larger mass (∼0.3 g for DIII-D and ∼30 g for ITER) to be delivered into the plasma core. We present a concept of using hyper-velocity C60 fullerene-dusty plasma jets for disruption mitigation of magnetically confined plasmas. The C60-fullerenes can form a compact plasma slug which can be accelerated to hyper-velocity (∼50 km/s) allowing for deep penetration into the tokamak target plasma. We evaluate the principle advantages, means to create it using a pulsed source, the atomic processes during acceleration to hyper-velocity and subsequent transport, and the interaction with the ambient target tokamak plasma during penetration.

The effect of electron beam fusion on the structure and properties of plasma jet sprayed nickel alloy coatings

Nickel-based alloy coatings were obtained on carbon steel (steel 3) samples by means of high-velocity pulsed plasma jet spraying of PG-10N-01 and PGAN-33 commercial powders, followed by electron beam fusion of the coating and substrate. The coated samples were studied by methods of X-ray diffraction, scanning electron microscopy, and electron-beam microprobe (energy-dispersive X-ray spectroscopy) and tested for hardness, friction wear, corrosion resistance, and adhesion. It was found that the electron beam processing leads to an almost tenfold increase in the friction wear resistance, a threefold growth in microhardness (relative to that of the substrate), and a significant increase in the resistance to corrosion in acid media. The observed increase in the working characteristics is related to changes in the phase composition, grain structure refinement, and redistribution of alloy components in the substrate and film and a decrease in porosity of the coating material.