Pulsed Plasma Gun Research Articles

Thrust of a pulsed plasma jet measured from deviations of a ballistic pendulum

We measured the peak force of the plasma jet produced by a pulsed coaxial plasma gun operated at voltages up to 2 kV, using a home-made ballistic pendulum positioned in two locations, one in the proximity of the gun nozzle at 0.75 cm and the second at a distance of 9 cm from the gun nozzle. The force of the plasma wind is inferred and ranges from 11 to 60 N, which is almost an order of magnitude higher than that of typical ion-based thrusters. The results of various models of self-field magneto-plasmadynamic thrusters indicate that the magnetic component thrust tends to dominate over the thermal expansion, particularly at higher discharge voltages of 1.5 kV and 2 kV. The highest thrust of 60 N is obtained for a 2 kV discharging voltage. The plasma was ignited in CO2 at pressures between 1 and 5 Torr. The displacement of the pendulum pushed by the plasma wind force was measured using a high-speed camera.

MK-200 Plasma Gun Facility

Plasma flows with high velocity, density, and energy are widely used in research on the interaction of plasma with materials, modeling of astrophysical processes, development of plasma thrusters and plasma radiation sources, and plasma injection into fusion devices. Electrodynamic plasma guns can be used to generate such flows. This paper describes the design features of a powerful pulsed plasma gun and diagnostic tools for measuring the parameters of the plasma flow generated by it.

Preliminary study for the evaluation of a pulsed coaxial plasma gun for removal of iron rust stain from bone artifacts

• Iron stain is one of the most crucial aspects of archaeological bone deterioration. • Chemical reaction between bones and the iron stain was explained. • The coaxial plasma cleaning was used for the first time for removal of iron stain. • The efficiency of plasma cleaning depended on power, numbers of pulses, and etc. • Analytical methods were utilized for the evaluation of the coaxial plasma cleaning. The pulsed coaxial plasma gun is an effective and fast way to remove stains found on the surface of cultural heritage materials. Invisible oil films, dust deposition, corrosion products, or other contaminants can be cleaned by plasma. Iron stain can be found on bone when it is in direct contact with the corroded iron object or in proximity to the corrosion products in the soil. This study aims to evaluate the removal of iron stain from the surface of bone by using Pulsed coaxial plasma. Different parameters of pulsed plasma have been evaluated to reach the best condition of the treatment. Pulsed coaxial plasma was applied to modern bone samples artificially stained with ferric hydroxides. Analytical techniques used to evaluate the iron stain removal were digital microscope, SEM-EDX, FTIR, color measurement by UV spectrophotometer, AFM, pH value, and contact angle measurement. The results indicated that the coaxial plasma is highly effective for iron stain removal and does not affect treated bones. The best cleaning was performed by pulsed argon plasma at 50 pulses, pressure of 0.2 mbar, 0.5 cm distance, and 3kV plasma power.

Dual mode operation of a hydromagnetic plasma thruster to achieve tunable thrust and specific impulse

We report here on initial studies of a pulsed hydromagnetic plasma gun that can operate in either a pre-filled or a gas-puff mode on demand. These modes enable agile and responsive performance through tunable thrust and specific impulse. Operation with a molecular nitrogen propellant is demonstrated to show that the hydromagnetic thruster is a candidate technology for air-harvesting and drag compensation in the very low Earth orbit. A dual mode operation is achieved by leveraging propellant gasdynamics to change the fill fraction and flow collisionality within the thruster. This results in the formation of distinct modes that are characterized by the current-driven hydromagnetic waves that they allow, namely, magneto-deflagration and magneto-detonation, respectively. These modes form the basis of using gasdynamics to enable responsive thruster performance. Using time-of-flight emission diagnostics to characterize near-field flow velocities, we find that a relatively dramatic transition occurs between modes as gas is allowed to expand in the thruster, with exhaust velocities ranging from 10 to 55 km/s in the deflagration and detonation regimes, respectively. Simulations of the processed mass bit offer the first glimpse into possible thruster performance and trade-offs between specific impulse and thrust. An impulse bit tunability of ∼22% is predicted, with differing propellant fill fractions when operating in a burst mode.

Two-colour interferometry and Thomson scattering measurements of a plasma gun

We present experimental measurements of a pulsed plasma gun, using two-colour imaging laser interferometry and spatially resolved Thomson scattering. Interferometry measurements give an electron density cm−3 at the centre of the plasma plume, at 5 mm from the plasma gun nozzle. The Thomson scattered light is collected from two probing angles allowed us to simultaneously measure the collective and non-collective spectrum of the electron feature from the same spatial locations. The inferred electron densities from the location of the electron plasma waves is in agreement with interferometry. The electron temperatures inferred from the two spectra are not consistent, with Te ≈ 10 eV for non-collective scattering and Te ≈ 30 eV for collective scattering. We discuss various broadening mechanisms such as finite aperture effects, density gradients within the collective volume and collisional broadening to account for some of this discrepancy. We also note the significant red/blue asymmetry of the electron plasma waves in the collective scattering spectra, which could relate to kinetic effects distorting the distribution function of the electrons.

Effect of Surface Damage on Thermal Response of Tungsten Monoblocks

In this study, surface damaged W monoblocks (melting and cracking) by a pulsed plasma gun and an e-beam devices were exposed to cyclic heat loads (simulating normal heat loads and slow transients) and pulsed heat loads (simulating ELMs) to observe the effects of surface damage on surface erosion and heat removal capability. Heat load tests simulating the normal heat load (10 MW/m2, 10 sec, 300 cycles) and the slow transient (~20 MW/m2, 10 sec, 300 cycles) were performed by the e-beam. The surface morphology changes after the heat load tests were observed using laser scanning microscopy and FE-SEM. After e-beam irradiation of ~20 MW/m2, the longitudinal cracks crossing over entire monoblocks appeared on the surfaces of all monoblocks. Recrystallization and additional crack formation were also observed on the surface. However, there was no significant change of heat removal capability. In the additional pulsed heat load test, the energy fluence of 0.042-0.30MJ/m2 was applied with pulse numbers of 103 and 104.The surface morphology changes after laser irradiation were observed using laser scanning microscope. After laser irradiation, the grain ejection occurred above a certain energy fluence (~25 % of melting threshold).

Plasma exposure of different tungsten grades with plasma accelerators under ITER-relevant conditions

This paper presents the results of tungsten irradiation experiments performed with three plasma facilities: the QSPA Kh-50 quasi-steady-state plasma accelerator, the PPA pulsed plasma gun and the magneto-plasma compressor. Targets made of different kinds of tungsten (sintered, rolled and deformed) were irradiated with powerful plasma streams at heat fluxes relevant to edge-localized modes in ITER. The irradiated targets were analyzed and two different meshes of cracks were identified. It has been shown that the major cracks do not depend on the tungsten grade. This has been attributed to ductile-to-brittle transition effects. Meshes of inter-granular micro-cracks were detected for energy loads above the melting threshold and these were probably caused by the re-solidification process. The blister-like and cellular-like structures were observed on sample surfaces exposed to helium and hydrogen plasmas.

Simulation of ITER edge-localized modes' impacts on the divertor surfaces within plasma accelerators

Experimental simulations of ITER transient events with relevant surface heat load parameters (energy density and pulse duration) as well as particle loads were performed with a quasi-steady-state plasma accelerator Kh-50 and pulsed plasma guns. Additional shielding was observed during irradiation of the combined carbon–tungsten (C–W) surface. An evaporated C cloud protects W from evaporation even at an energy density of 2.4 MJ m−2 in impacting plasma. The spectrum of tungsten and parameters of shielding layers were found under powerful exposure of the tungsten surface. An influence of material modification through plasma exposures on cracking thresholds of tungsten is emphasized. It was found that increasing the number of exposures to more than 20 plasma pulses of 0.25 ms in duration shifts the energy threshold for crack development from 0.3 down to 0.2 MJ m−2. Differences in the evolution of tungsten substructure after exposure to helium and hydrogen plasma streams of different duration are also analyzed.

The latest results from ELM-simulation experiments in plasma accelerators

Recent results of ELM-simulation experiments with quasi-stationary plasma accelerators (QSPAs) Kh-50 (Kharkov, Ukraine) and QSPA-T (Troitsk, Russia) as well as experiments in the pulsed plasma gun MK-200UG (Troitsk, Russia) are discussed. Primary attention in Troitsk experiments has been focused on investigating the carbon-fibre composite (CFC) and tungsten erosion mechanisms, their onset conditions and the contribution of various erosion mechanisms (including droplet splashing) to the resultant surface damage at varying plasma heat flux. The obtained results are used for validating the numerical codes PEGASUS and MEMOS developed in FZK. Crack patterns and residual stresses in tungsten targets under repetitive edge localized mode (ELM)-like plasma pulses are studied in simulation experiments with QSPA Kh-50. Statistical processing of the experimental results on crack patterns after different numbers of QSPA Kh-50 exposures as well as those on the dependence of cracking on the heat load and surface temperature is performed.

Features of materials alloying under exposures to pulsed plasma streams

Surface modifications and features of materials alloying under pulsed plasma exposures are investigated in this paper. The experiments were carried out with a pulsed plasma gun, which generates plasma streams with ion energies of up to 2 keV, a plasma density of (2– $20)\times 10^{14}~{\rm cm}^{-3}$ , an average specific power of 10 MW/cm2 and plasma energy densities in the range of (5– $40)~{\rm J/cm}^{2}$ . Nitrogen, helium, hydrogen, oxygen and different mixtures can be used as working gases. Modification of thin (1–2 μm) PVD coatings of molybdenum coating mixed with substrate in liquid phase under the pulsed plasma processing are analyzed. After alloying of ferritic/martensitic steel EP-823 with Mo the concentration of molybdenum in the modified layer of 15–20 μm achieved 20% for single treatment cycle and 30% after two cycles. Decrease of grain sizes (from tens of μm to hundreds of nm), roughness and porosity were obtained by plasma irradiation of thick (~0.1–0.3 mm) plasma sprayed coatings of Co-32Ni-21Cr-8Al-0.5Y and Ti64. A modified layer with homogeneous structure and thickness up to 50 μm is formed as a result of plasma treatment. Mechanisms of surface modification of WC-Co under irradiation with pulsed plasma streams of different ions are discussed.

Application of piezodetectors for diagnostics of pulsed and quasi-steady-state plasma streams

The paper reports on studies of the plasma streams generated by two experimental devices: the quasi-steady-state plasma accelerator (QSPA) Kh-50 and the pulsed plasma gun PROSVET. The radial distributions of the plasma pressure for different times and varied distances from the accelerator output have been used for investigation of the plasma stream dynamics and study the plasma compression in the focus region for different operational regimes of plasma accelerators. In experiments for the application of pulsed plasma streams for surface modification of different industrial steels, optimal regimes of surface processing have been chosen on the basis of the plasma pressure measurements. Examples of application of the piezodetectors in simulation experiments on plasma surface interaction under high heat loads are presented.

Characterization of Superhard Ternary (Ti,Al)N Coatings Prepared by Pulsed High Energy Density Plasma

Traditional TiN coatings cannot meet the requirements in many applications under extreme conditions because of their relatively low hardness (similar to2000Hv), high friction coefficient (>0.4), inade- quate thermal stability and insufficient corrosion. (Ti,Al)N coatings are a promising alternative to TiN coatings, which have recently been obtained by some groups. However, The deposition of coatings on ceramic substrates prepared by traditional physical vapor deposition was puzzled by low adhesions. In this work, (Ti,Al)N deposition was realized by a new technique namely pulsed high energy density plasma. The ratio of Ti and Al atoms was kept constant at 1:1, since this was known to be the best ratio for (Ti,Al)N synthesis. However, the process allows many other deposition parameters to be varied. In this study, the influences of the discharge voltage between the inner and outer electrode, the distance between the sample and the pulsed plasma gun, and the shot number of the pulsed plasma on coating formation and properties were investigated. Under the optimum deposition conditions, the adhesive strength of (Ti,Al)N coating to Si3N4 ceramic substrate was satisfactory with the critical load up to more than 80 mN. In addition, the coatings were investigated with respect to mechanical and wear behavior, including nanohardness, Young's modulus and cutting performances. The (Ti,Al)N coatings possess resulted very high values of nanohardness and Young's modulus, which are near to 40 GPa and 680 GPa, respectively. Because of the deposition of (Ti,Al)N coatings the wear resistance and edge life of the coated tools were improved dramatically evaluated by the cutting perforinances of the coated tools in turning HT250 (HB230) steel under industrial conditions. These improvements were attributed to a combination of four effects of deposition, ion implantation, quench and solid solution strengthening in terms of the structural analyses.

2D numerical modeling of pulsed plasma acceleration by a magnetic field

Pulsed plasma guns are used to obtain high-velocity (107–108 cm/s) plasma flows. Their performance is restricted by an instability of the plasma acceleration by a magnetic field. This paper presents results of a 2D numerical study of plasma dynamics in the plasma gun. The ZENIT-2D code solving the magnetohydrodynamic (MHD) equations on a fixed Eulerian mesh is used. The plasma parameters and geometry are chosen to be close to the parameters of the MK-200 installation (Sidnev et al., 1983). The influence of the initial distribution of a neutral gas on accelerator performance is investigated. A brief description of the code and details of the simulations are presented. It is shown that the instability of acceleration leads to turbulent mixing of the plasma and magnetic field and, correspondingly, to a broader current channel than that predicted by the classical diffusion with the Spitzer conductivity. Numerical results are compared with experimental data (Bakhtin & Zhitlukhin, 1998) displaying a good qualitative agreement.

Investigation of titanium coating on Si 3N 4 by using a pulsed high energy density plasma (PHEDP) gun

Titanium films were deposited on Si 3N 4 ceramic surface by using a pulsed high energy density plasma (PHEDP) gun. The films have been investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The investigation results show that the pulsed plasma energy plays an important role in determining the surface morphology of the film, the deposition rate and the Ti–Si 3N 4 reactions. XRD results show the formation of TiN, Ti 5Si 3 and free Si in the reaction products. The treated Si 3N 4 surface became conductive and the sheet resistance of the film was measured.

Erosion and microstructure change of materials during disruption-simulation experiments in plasma accelerator

The behaviour of G-4, MPG-6, MPG-8, MIG, MIG-1, SG-T, PG-MS, USB-15 graphites, boron surface-modified MPG-8 and USB-15 graphites, Ni, Fe, Ti, V, Nb, Mo, austenitic and ferritic steels, austenitic steels with Al and Be coatings have been tested by using a high temperature pulsed plasma gun to simulate plasma disruption. The heat flux of the hydrogen and deuterium plasma has been 10 to 100 J/cm 2 and pulse durations 25 μs. Material weight loss has been estimated. Structure changes in the surface layer of the metal materials, the influence of microstructure changes on sputtering, blistering and hydrogen permeability have been investigated.

Two-dimensional magnetic field evolution measurements and plasma flow speed estimates from the coaxial thruster experiment

Local, time-dependent magnetic field measurements have been made in the Los Alamos coaxial thruster experiment (CTX) [C. W. Barnes et al., Phys. Fluids B 2, 1871 (1990); J. C. Fernández et al., Nucl. Fusion 28, 1555 (1988)] using a 24 coil magnetic probe array (eight spatial positions, three axis probes). The CTX is a magnetized, coaxial plasma gun presently being used to investigate the viability of high pulsed power plasma thrusters for advanced electric propulsion. Previous efforts on this device have indicated that high pulsed power plasma guns are attractive candidates for advanced propulsion that employ ideal magnetohydrodynamic (MHD) plasma stream flow through self-formed magnetic nozzles. Indirect evidence of magnetic nozzle formation was obtained from plasma gun performance and measurements of directed axial velocities up to vz∼107 cm/s. The purpose of this work is to make direct measurement of the time evolving magnetic field topology. The intent is to both identify that applied magnetic field distortion by the highly conductive plasma is occurring, and to provide insight into the details of discharge evolution. Data from a magnetic fluctuation probe array have been used to investigate the details of applied magnetic field deformation through the reconstruction of time-dependent flux profiles. Experimentally observed magnetic field line distortion has been compared to that predicted by a simple one-dimensional (1-D) model of the discharge channel. Such a comparison is utilized to estimate the axial plasma velocity in the thruster. Velocities determined in this manner are in approximate agreement with the predicted self-field magnetosonic speed and those measured by a time-of-flight spectrometer.

Development of a dc, broad beam, Mevva ion source

We are developing an embodiment of metal vapor vacuum arc (Mevva) ion source which will operate dc and have a very large area beam. In preliminary testing, a dc titanium ion beam was formed with a current of approximately 0.6 A at an extraction voltage of 9 kV (about 18 keV ion energy, by virtue of the ion-charge state distribution) using an 18-cm-diameter set of multiaperture extraction grids. Separately, we have tested and formed a beam from a 50-cm-diameter (2000 cm2) set of grids using a pulsed plasma gun. This configuration appears to be very efficient in terms of plasma utilization, and we have formed beams with a diameter of 33 cm (FWHM) and ion current up to 7 A at an extraction voltage of 50 kV (about 100 keV mean ion energy) and up to 20 A peak at the current overshoot part of the beam pulse. Here we describe this part of our Mevva development program and summarize the results obtained to date.

Research on pulsed and steady-state plasma guns and their applications in the Troitsk branch of Kurchatov Institute of Atomic Energy

The parameters of plasma guns developed and plasma streams generated are presented. The streams were used for the studies of plasma dynamics in a magnetic field, for high-temperature plasma production, for plasma injection into open magnetic traps, as well as for industrial applications. The main results in these areas of studies are presented.

Pulsed plasma guns for intense ion beam injectors

Plasma guns designed to provide high-pulsed fluxes of ions for intense ion beam injectors are described. The guns use pulsed radial magnetic fields to accelerate ions longitudinally into magnetically insulated extraction gaps. Plasma was supplied using both spark sources and pulsed gas injection. In typical operation, a 1-Ω pulse of nitrogen ions with an ion flux equivalent to 50 A/cm2 was produced. A variety of ions ranging in mass from protons to argon was investigated.

Conical Z-Pinch Gun

A pulsed plasma gun is described which has several advantages over other commonly used guns. Among these are simplicity of operation, construction and analysis, and stability of operation. The output has a sharply peaked velocity distribution. The initial model, described herein, emits a burst of 5×1018 Ar ions moving at 9 cm/μsec. A snowplow analysis predicts operating characteristics generally in agreement with observations.