On the structure of pulsed plasma jets

NASA Astrophysics Data System (ADS)

Cavolowsky, John Arthur

A pulsed plasma jet is a turbulent, inhomogeneous fluid mechanical discharge capable of initiating and inhancing combustion. Having shown the ability to ignite lean fuel mixtures, is now offers the potential for real-time control of combustion processes. The fluid mechanical and chemical properties of such jets are explored. The fluid mechanical structure of the jet was examined using two optical diagnostic techniques. Self-light streak photography provided information on the motion of luminous gas particles in its core. The turbulent, thermal evolution of the jet was explored using high speed laser schlieren cinematography. By examine plasma jet generators with both opaque and transparent plasma cavities, detailed information on plasma formation and jet structure, beginning with the electric arc discharge in the cavity, was obtained. Molecular beam mass spectroscopy was used to determine temperature and species concentration in the jet. Both noncombustible and combustible jets were studied. Species measurements in combustible jets revealed significant concentrations of radicals and products of complete as well as incomplete combustion.

Laboratory simulations of astrophysical jets: results from experiments at the PF-3, PF-1000U, and KPF-4 facilities

NASA Astrophysics Data System (ADS)

Krauz, V. I.; Myalton, V. V.; Vinogradov, V. P.; Velikhov, E. P.; Ananyev, S. S.; Dan'ko, S. A.; Kalinin, Yu G.; Kharrasov, A. M.; Vinogradova, Yu V.; Mitrofanov, K. N.; Paduch, M.; Miklaszewski, R.; Zielinska, E.; Skladnik-Sadowska, E.; Sadowski, M. J.; Kwiatkowski, R.; Tomaszewski, K.; Vojtenko, D. A.

2017-10-01

Results are presented from laboratory simulations of plasma jets emitted by young stellar objects carried out at the plasma focus facilities. The experiments were performed at three facilities: the PF-3, PF-1000U and KPF-4. The operation modes were realized enabling the formation of narrow plasma jets which can propagate over long distances. The main parameters of plasma jets and background plasma were determined. In order to control the ratio of a jet density to that of background plasma, some special operation modes with pulsed injection of the working gas were used.

Multiple Plasma Ejections and Intermittent Nature of Magnetic Reconnection in Solar Chromospheric Anemone Jets

NASA Astrophysics Data System (ADS)

Singh, K. A. P.; Isobe, H.; Nishizuka, N.; Nishida, K.; Shibata, K.

2012-11-01

The recent discovery of chromospheric anemone jets with the Solar Optical Telescope (SOT) on board Hinode has shown an indirect evidence of magnetic reconnection in the solar chromosphere. However, the basic nature of magnetic reconnection in chromosphere is still unclear. We studied nine chromospheric anemone jets from SOT/Hinode using Ca II H filtergrams, and we found multiple bright, plasma ejections along the jets. In most cases, the major intensity enhancements (larger than 30% relative to the background intensity) of the loop correspond to the timing of the plasma ejections. The typical lifetime and size of the plasma ejecta are about 20-60 s and 0.3-1.5 Mm, respectively. The height-time plot of jet shows many sub-structures (or individual jets) and the typical lifetime of the individual jet is about one to five minutes. Before the onset of the jet activity, a loop appears in Ca II H and gradually increases in size, and after few minutes several jets are launched from the loop. Once the jet activity starts and several individual jets are launched, the loop starts shrinking with a speed of ~4 km s-1. In some events, a downward moving blob with a speed of ~35 km s-1 was observed, associated with the upward moving plasma along one of the legs of the loop hosting the jets. The upward moving plasma gradually developed into jets. Multiple plasma ejections in chromospheric anemone jet show the strongly time-dependent as well as intermittent nature of magnetic reconnection in the solar chromosphere.

Eulerian and Lagrangian Plasma Jet Modeling for the Plasma Liner Experiment

NASA Astrophysics Data System (ADS)

Hatcher, Richard; Cassibry, Jason; Stanic, Milos; Loverich, John; Hakim, Ammar

2011-10-01

The Plasma Liner Experiment (PLX) aims to demonstrate the feasibility of using spherically-convergent plasma jets to from an imploding plasma liner. Our group has modified two hydrodynamic simulation codes to include radiative loss, tabular equations of state (EOS), and thermal transport. Nautilus, created by TechX Corporation, is a finite-difference Eulerian code which solves the MHD equations formulated as systems of hyperbolic conservation laws. The other is SPHC, a smoothed particle hydrodynamics code produced by Stellingwerf Consulting. Use of the Lagrangian fluid particle approach of SPH is motivated by the ability to accurately track jet interfaces, the plasma vacuum boundary, and mixing of various layers, but Eulerian codes have been in development for much longer and have better shock capturing. We validate these codes against experimental measurements of jet propagation, expansion, and merging of two jets. Precursor jets are observed to form at the jet interface. Conditions that govern evolution of two and more merging jets are explored.

Experimental studies of collisional plasma shocks and plasma interpenetration via merging supersonic plasma jets

NASA Astrophysics Data System (ADS)

Hsu, S. C.; Moser, A. L.; Merritt, E. C.; Adams, C. S.

2015-11-01

Over the past 4 years on the Plasma Liner Experiment (PLX) at LANL, we have studied obliquely and head-on-merging supersonic plasma jets of an argon/impurity or hydrogen/impurity mixture. The jets are formed/launched by pulsed-power-driven railguns. In successive experimental campaigns, we characterized the (a) evolution of plasma parameters of a single plasma jet as it propagated up to ~ 1 m away from the railgun nozzle, (b) density profiles and 2D morphology of the stagnation layer and oblique shocks that formed between obliquely merging jets, and (c) collisionless interpenetration transitioning to collisional stagnation between head-on-merging jets. Key plasma diagnostics included a fast-framing CCD camera, an 8-chord visible interferometer, a survey spectrometer, and a photodiode array. This talk summarizes the primary results mentioned above, and highlights analyses of inferred post-shock temperatures based on observations of density gradients that we attribute to shock-layer thickness. We also briefly describe more recent PLX experiments on Rayleigh-Taylor-instability evolution with magnetic and viscous effects, and potential future collisionless shock experiments enabled by low-impurity, higher-velocity plasma jets formed by contoured-gap coaxial guns. Supported by DOE Fusion Energy Sciences and LANL LDRD.

Interaction of argon and helium plasma jets and jets arrays with account for gravity

NASA Astrophysics Data System (ADS)

Babaeva, Natalia Yu.; Naidis, George V.; Panov, Vladislav A.; Wang, Ruixue; Zhao, Yong; Shao, Tao

2018-06-01

In this paper, we discuss results from an experimental and computational study of the properties of a single jet and two-tube jet arrays operating in argon and helium. The jets are positioned horizontally. It was shown in experiments that the helium plasma plume bends upward and the plumes in the two-tubes jet array tend to divert due to the jet-jet interaction. To investigate these potential interactions, a computational study was performed of one- and two-tube argon and helium jet arrays having variable spacing. The effects of buoyancy forces on the jet-to-jet interaction of the plasma plumes are also investigated. Velocities of ionization waves inside and outside the tubes are estimated and compared for the argon and helium ionization waves. We show that in helium jet-jet interactions primarily depend on the spacing between the tubes and on the buoyancy forces. The helium plumes tend to merge into one single stream before dissipating, while the argon plasma plumes are less sensitive to the spacing of the jet tubes.

How plasma induced oxidation, oxygenation, and de-oxygenation influences viability of skin cells

NASA Astrophysics Data System (ADS)

Oh, Jun-Seok; Strudwick, Xanthe; Short, Robert D.; Ogawa, Kotaro; Hatta, Akimitsu; Furuta, Hiroshi; Gaur, Nishtha; Hong, Sung-Ha; Cowin, Allison J.; Fukuhara, Hideo; Inoue, Keiji; Ito, Masafumi; Charles, Christine; Boswell, Roderick W.; Bradley, James W.; Graves, David B.; Szili, Endre J.

2016-11-01

The effect of oxidation, oxygenation, and de-oxygenation arising from He gas jet and He plasma jet treatments on the viability of skin cells cultured in vitro has been investigated. He gas jet treatment de-oxygenated cell culture medium in a process referred to as "sparging." He plasma jet treatments oxidized, as well as oxygenated or de-oxygenated cell culture medium depending on the dissolved oxygen concentration at the time of treatment. He gas and plasma jets were shown to have beneficial or deleterious effects on skin cells depending on the concentration of dissolved oxygen and other oxidative molecules at the time of treatment. Different combinations of treatments with He gas and plasma jets can be used to modulate the concentrations of dissolved oxygen and other oxidative molecules to influence cell viability. This study highlights the importance of a priori knowledge of the concentration of dissolved oxygen at the time of plasma jet treatment, given the potential for significant impact on the biological or medical outcome. Monitoring and controlling the dynamic changes in dissolved oxygen is essential in order to develop effective strategies for the use of cold atmospheric plasma jets in biology and medicine.

Diagnostics of an AC driven atmospheric pressure non-thermal plasma jet and its use for radially directed jet array

NASA Astrophysics Data System (ADS)

Zhu, W.; Wang, R.

2017-08-01

An alternating current atmospheric pressure plasma jet is generated with noble gas or noble gas/oxygen admixture as working gas. A "core plasma filament" is observed at the center of the dielectric tube and extends to the plasma jet at higher peak-to-peak voltages. This type of plasma jet is believed to be of the same nature with the reported plasma bullet driven by pulsed DC power sources. Double current probes are used to assess the speed of the plasma bullet and show that the speed is around 104-105 m/s. The time dependence of the downstream bullet speed is attributed to the gas heating and in turn the increase of the reduced electric field E/N. Optical emission spectra show the dependence of helium and oxygen emission intensities on the concentration of oxygen additive in the carrier gas, with peak values found at 0.5% O2. Multiple radial jets are realized on dielectric tubes of different sizes. As a case study, one of these multi-jet devices is used to treat B. aureus on the inner surface of a plastic beaker and is shown to be more effective than a single jet.

The magnetically driven plasma jet produces a pressure of 33 GPa on PTS

NASA Astrophysics Data System (ADS)

Xu, Qiang; Dan, Jiakun; Wang, Guilin; Guo, Shuai; Zhang, Siqun; Cai, Hongchun; Ren, Xiao; Wang, Kunlun; Zhou, Shaotong; Zhang, Zhaohui; Huang, Xianbin

2017-01-01

We report on experiments in which a magnetically driven plasma jet was used to hit a 500 μm thick planar aluminum target. The plasma jet was produced by using a 50 μm thick aluminum radial foil, which was subjected to 4 MA, 90 ns rising time current on the primary test stand pulsed power facility. The subsequent magnetic bubbles propagate with radial velocity reaching 200 km/s and an axial velocity of 230 km/s. After the plasma knocks onto the target, a shock forms in the target. When the shock gets to the backside of the target, we measure the velocity of the moving surface using dual laser heterodyne velocimetry. By using the Hugoniot relations, we know that the plasma jet produced a pressure of 33 GPa. According to the measured pressure and the velocity of the plasma jet, the density of the jet can be also roughly estimated.

Magnetic field generation in core-sheath jets via the kinetic Kelvin-Helmholtz instability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nishikawa, K.-I.; Hardee, P. E.; Duţan, I.

2014-09-20

We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas, we find generation of strong large-scale DC currents and magnetic fields that extend over the entire shear surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas, we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shearmore » surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates a transverse structure similar to that produced by the Weibel instability.« less

Ram-pressure scaling and non-uniformity characterization of a spherically imploding liner formed by hypervelocity plasma jets

NASA Astrophysics Data System (ADS)

Cassibry, Jason; Dougherty, Jesse; Thompson, Seth; Hsu, Scott; Witherspoon, F. D.; University of AL in Huntsville Team; Los Alamos National Laboratory Team; HyperV Technologies Corp. Team

2014-10-01

Three-dimensional modeling of plasma liner formation and implosion is performed using the Smoothed Particle Hydrodynamics Code (SPHC) with radiation, thermal transport, and tabular equations of state (EOS), accounting for ionization, in support of a proposed 60-gun plasma liner formation experiment for plasma-jet driven magneto-inertial fusion (PJMIF). Previous SPHC modeling showed that ideal gas law scaling of peak stagnation pressure increased linearly with density and number of jets, quadratically with jet radius and velocity, and inversely with the initial jet length, while results with tabular EOS, thermal transport, and radiation have greater sensitivity to the initial jet distribution. A series of simulations are conducted to study the effects of initial jet conditions on peak ram pressure and liner non-uniformity during plasma liner implosion. The growth rate of large-amplitude density perturbations introduced by the discrete jets are computed and compared with predictions by the Bell-Plesset equation.

Control of radial propagation and polarity in a plasma jet in surrounding Ar

NASA Astrophysics Data System (ADS)

Gong, W.; Yue, Y.; Ma, F.; Yu, F.; Wan, J.; Nie, L.; Bazaka, K.; Xian, Y.; Lu, X.; Ostrikov, K.

2018-01-01

In recent years, the use of shielding gas to prevent the diffusion of the ambient air, particularly oxygen and nitrogen species, into the effluent of the atmospheric pressure plasma jet, and thus control the nature of chemical species used in the plasma treatment has increased. In this paper, the radial propagation of a plasma jet in ambient Ar is examined to find the key determinants of the polarity of plasma jets. The dynamics of the discharge reveal that the radial diffusion discharge is a special phenomenon observed only at the falling edge of the pulses. The radial transport of electrons, which is driven by the radial component of the applied electric field at the falling edge of the pulse, is shown to play an important role in increasing the seed electron density in the surrounding Ar. This result suggests a method to provide seed electrons at atmospheric pressure with a negative discharge. The polarity of the plasma jet is found to be determined by the pulse width rather than the polarity of the applied voltage, as it dictates the relative difference in the intensity of the two discharges in a single pulse, where the stronger discharge in a pulse dominates the behavior of the plasma jet. Accordingly, a method to control the polarity of a plasma jet through varying the pulse width is developed. Since plasma jets of different polarities differ remarkably in terms of their characteristics, the method to control the polarity reported in this paper will be of use for such applications as plasma-enhanced processing of materials and plasma biomedicine.

Two-dimensional numerical study of two counter-propagating helium plasma jets in air at atmospheric pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Wen; Sang, Chaofeng; Wang, Dezhen, E-mail: wangdez@dlut.edu.cn

In this paper, a computational study of two counter-propagating helium plasma jets in ambient air is presented. A two-dimensional fluid model is applied to investigate the physical processes of the two plasma jets interaction (PJI) driven by equal and unequal voltages, respectively. In all studied cases, the PJI results in a decrease of both plasma bullets propagation velocity. When the two plasma jets are driven by equal voltages, they never merge but rather approach each other around the middle of the gas gap at a minimum approach distance, and the minimal distance decreases with the increase of both the appliedmore » voltages and initial electron density, but increases with the increase of the relative permittivity. When the two plasma jets are driven by unequal voltages, we observe the two plasma jets will merge at the position away from the middle of the gas gap. The effect of applied voltage difference on the PJI is also studied.« less

Cellular membrane collapse by atmospheric-pressure plasma jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Kangil; Sik Yang, Sang, E-mail: jsjlee@ajou.ac.kr, E-mail: ssyang@ajou.ac.kr; Jun Ahn, Hak

2014-01-06

Cellular membrane dysfunction caused by air plasma in cancer cells has been studied to exploit atmospheric-pressure plasma jets for cancer therapy. Here, we report that plasma jet treatment of cervical cancer HeLa cells increased electrical conductivity across the cellular lipid membrane and caused simultaneous lipid oxidation and cellular membrane collapse. We made this finding by employing a self-manufactured microelectrode chip. Furthermore, increased roughness of the cellular lipid membrane and sequential collapse of the membrane were observed by atomic force microscopy following plasma jet treatment. These results suggest that the cellular membrane catastrophe occurs via coincident altered electrical conductivity, lipid oxidation,more » and membrane roughening caused by an atmospheric-pressure plasma jet, possibly resulting in cellular vulnerability to reactive species generated from the plasma as well as cytotoxicity to cancer cells.« less

Plasma Jet Simulations Using a Generalized Ohm's Law

NASA Technical Reports Server (NTRS)

Ebersohn, Frans; Shebalin, John V.; Girimaji, Sharath S.

2012-01-01

Plasma jets are important physical phenomena in astrophysics and plasma propulsion devices. A currently proposed dual jet plasma propulsion device to be used for ISS experiments strongly resembles a coronal loop and further draws a parallel between these physical systems [1]. To study plasma jets we use numerical methods that solve the compressible MHD equations using the generalized Ohm s law [2]. Here, we will discuss the crucial underlying physics of these systems along with the numerical procedures we utilize to study them. Recent results from our numerical experiments will be presented and discussed.

Laminar and turbulent flow modes of cold atmospheric pressure argon plasma jet

NASA Astrophysics Data System (ADS)

Basher, Abdulrahman H.; Mohamed, Abdel-Aleam H.

2018-05-01

Laminar and turbulent flow modes of a cold atmospheric pressure argon plasma jet are investigated in this work. The effects of the gas flow rate, applied voltage, and frequency on each plasma mode and on intermodal transitions are characterized using photographic, electrical, and spectroscopic techniques. Increasing the gas flow rate increases the plasma jet length in the laminar mode. Upon transition to the turbulent mode, increasing the gas flow rate leads to a decrease in the plasma jet length. The flow rate at which the jet transitions from laminar to turbulent increases with the applied voltage. The presence of nitric oxide (NO) radicals is indicated by the emission spectra of the turbulent plasmas only, while excited Ar, N2, OH, and O excited species are produced in both laminar and turbulent modes. With no distinctive behavior observed upon transition between the two operating modes, the power consumption was found to be insensitive to gas flow rate variation, while the energy density was found to decrease exponentially with the gas flow rate. Rotational and vibrational temperature measurements of the two plasma modes indicated that they are of the non-thermal equilibrium plasma type. Since they offer NO radicals while maintaining the benefits of the laminar plasma jet, the turbulent plasma jet is more useful than its laminar counterpart in biomedical applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, K. A. P.; Nishida, K.; Shibata, K.

The recent discovery of chromospheric anemone jets with the Solar Optical Telescope (SOT) on board Hinode has shown an indirect evidence of magnetic reconnection in the solar chromosphere. However, the basic nature of magnetic reconnection in chromosphere is still unclear. We studied nine chromospheric anemone jets from SOT/Hinode using Ca II H filtergrams, and we found multiple bright, plasma ejections along the jets. In most cases, the major intensity enhancements (larger than 30% relative to the background intensity) of the loop correspond to the timing of the plasma ejections. The typical lifetime and size of the plasma ejecta are aboutmore » 20-60 s and 0.3-1.5 Mm, respectively. The height-time plot of jet shows many sub-structures (or individual jets) and the typical lifetime of the individual jet is about one to five minutes. Before the onset of the jet activity, a loop appears in Ca II H and gradually increases in size, and after few minutes several jets are launched from the loop. Once the jet activity starts and several individual jets are launched, the loop starts shrinking with a speed of {approx}4 km s{sup -1}. In some events, a downward moving blob with a speed of {approx}35 km s{sup -1} was observed, associated with the upward moving plasma along one of the legs of the loop hosting the jets. The upward moving plasma gradually developed into jets. Multiple plasma ejections in chromospheric anemone jet show the strongly time-dependent as well as intermittent nature of magnetic reconnection in the solar chromosphere.« less

Control of ROS and RNS productions in liquid in atmospheric pressure plasma-jet system

NASA Astrophysics Data System (ADS)

Uchida, Giichiro; Ito, Taiki; Takenaka, Kosuke; Ikeda, Junichiro; Setsuhara, Yuichi

2016-09-01

Non-thermal plasma jets are of current interest in biomedical applications such as wound disinfection and even treatment of cancer tumors. Beneficial therapeutic effects in medical applications are attributed to excited species of oxygen and nitrogen from air. However, to control the production of these species in the plasma jet is difficult because their production is strongly dependent on concentration of nitrogen and oxygen from ambient air into the plasma jet. In this study, we analyze the discharge characteristics and the ROS and RNS productions in liquid in low- and high-frequency plasma-jet systems. Our experiments demonstrated the marked effects of surrounding gas near the plasma jet on ROS and RNS productions in liquid. By controlling the surround gas, the O2 and N2 main plasma jets are selectively produced even in open air. We also show that the concentration ratio of NO2- to H2O2 in liquid is precisely tuned from 0 to 0.18 in deionized water by changing N2 gas ratio (N2 / (N2 +O2)) in the main discharge gas, where high NO2- ratio is obtained at N2 gas ratio at N2 / (N2 +O2) = 0 . 8 . The low-frequency plasma jet with controlled surrounding gas is an effective plasma source for ROS and RNS productions in liquid, and can be a useful tool for biomedical applications. This study was partly supported by a Grant-in-Aid for Scientific Research on Innovative Areas ``Plasma Medical Innovation'' (24108003) from the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT).

Plasma-surface interaction in the Be/W environment: Conclusions drawn from the JET-ILW for ITER

NASA Astrophysics Data System (ADS)

Brezinsek, S.; JET-EFDA contributors

2015-08-01

The JET ITER-Like Wall experiment (JET-ILW) provides an ideal test bed to investigate plasma-surface interaction (PSI) and plasma operation with the ITER plasma-facing material selection employing beryllium in the main chamber and tungsten in the divertor. The main PSI processes: material erosion and migration, (b) fuel recycling and retention, (c) impurity concentration and radiation have be1en studied and compared between JET-C and JET-ILW. The current physics understanding of these key processes in the JET-ILW revealed that both interpretation of previously obtained carbon results (JET-C) and predictions to ITER need to be revisited. The impact of the first-wall material on the plasma was underestimated. Main observations are: (a) low primary erosion source in H-mode plasmas and reduction of the material migration from the main chamber to the divertor (factor 7) as well as within the divertor from plasma-facing to remote areas (factor 30 - 50). The energetic threshold for beryllium sputtering minimises the primary erosion source and inhibits multi-step re-erosion in the divertor. The physical sputtering yield of tungsten is low as 10-5 and determined by beryllium ions. (b) Reduction of the long-term fuel retention (factor 10 - 20) in JET-ILW with respect to JET-C. The remaining retention is caused by implantation and co-deposition with beryllium and residual impurities. Outgassing has gained importance and impacts on the recycling properties of beryllium and tungsten. (c) The low effective plasma charge (Zeff = 1.2) and low radiation capability of beryllium reveal the bare deuterium plasma physics. Moderate nitrogen seeding, reaching Zeff = 1.6 , restores in particular the confinement and the L-H threshold behaviour. ITER-compatible divertor conditions with stable semi-detachment were obtained owing to a higher density limit with ILW. Overall JET demonstrated successful plasma operation in the Be/W material combination and confirms its advantageous PSI behaviour and gives strong support to the ITER material selection.

On the evolution of jet energy and opening angle in strongly coupled plasma

NASA Astrophysics Data System (ADS)

Chesler, Paul M.; Rajagopal, Krishna

2016-05-01

We calculate how the energy and the opening angle of jets in {N} = 4 SYM theory evolve as they propagate through the strongly coupled plasma of that theory. We define the rate of energy loss dE jet /dx and the jet opening angle in a straightforward fashion directly in the gauge theory before calculating both holographically, in the dual gravitational description. In this way, we rederive the previously known result for dE jet /dx without the need to introduce a finite slab of plasma. We obtain a striking relationship between the initial opening angle of the jet, which is to say the opening angle that it would have had if it had found itself in vacuum instead of in plasma, and the thermalization distance of the jet. Via this relationship, we show that {N} = 4 SYM jets with any initial energy that have the same initial opening angle and the same trajectory through the plasma experience the same fractional energy loss. We also provide an expansion that describes how the opening angle of the {N} = 4 SYM jets increases slowly as they lose energy, over the fraction of their lifetime when their fractional energy loss is not yet large. We close by looking ahead toward potential qualitative lessons from our results for QCD jets produced in heavy collisions and propagating through quark-gluon plasma.

On the evolution of jet energy and opening angle in strongly coupled plasma

DOE PAGES

Chesler, Paul M.; Rajagopal, Krishna

2016-05-17

We calculate how the energy and the opening angle of jets in N = 4SYM theory evolve as they propagate through the strongly coupled plasma of that theory. We define the rate of energy loss dE jet/dx and the jet opening angle in a straightforward fashion directly in the gauge theory before calculating both holographically, in the dual gravitational description. In this way, we rederive the previously known result for dE jet/dx without the need to introduce a finite slab of plasma. We obtain a striking relationship between the initial opening angle of the jet, which is to say themore » opening angle that it would have had if it had found itself in vacuum instead of in plasma, and the thermalization distance of the jet. Via this relationship, we show that N = 4SYM jets with any initial energy that have the same initial opening angle and the same trajectory through the plasma experience the same fractional energy loss. We also provide an expansion that describes how the opening angle of the N = 4SYM jets increases slowly as they lose energy, over the fraction of their lifetime when their fractional energy loss is not yet large. In conclusion, we close by looking ahead toward potential qualitative lessons from our results for QCD jets produced in heavy collisions and propagating through quark-gluon plasma.« less

Results from the Mochi.Labjet Experiment

NASA Astrophysics Data System (ADS)

Lavine, Eric Sander; You, Setthivoine

2017-10-01

Magnetized plasma jets are generally modeled as magnetic flux tubes filled with flowing plasma governed by magnetohydrodynamics (MHD). Recent theoretical work has outlined a more fundamental approach based on flux tubes of canonical vorticity, where canonical vorticity is defined as the circulation of a species' canonical momentum. This approach extends the concept of magnetic flux tube evolution to include the effects of finite particle momentum and enables visualization of the topology of plasma jets in regimes beyond MHD. Under the appropriate conditions this framework suggests how to form and drive stable, collimated plasma jets with very long aspect-ratios. To explore this possibility, a triple electrode planar plasma gun (Mochi.LabJet) has been designed to produce helical shear flows inside a driven magnetized plasma jet. High speed video confirms the experiment can produce long ( 1m), collimated, stable jets with core plasma currents of 60 - 80 kA, skin currents of 100 - 120 kA and axial velocities on the order of 40 - 80 km/s (for hydrogen). Presented here are magnetic and ion flow velocity measurements as well as stability space analysis that suggests the jets are stable to kink instabilities over many Alfvén times.

Discharge characteristics and hydrodynamics behaviors of atmospheric plasma jets produced in various gas flow patterns

NASA Astrophysics Data System (ADS)

Setsuhara, Yuichi; Uchida, Giichiro; Nakajima, Atsushi; Takenaka, Kosuke; Koga, Kazunori; Shiratani, Masaharu

2015-09-01

Atmospheric nonequilibrium plasma jets have been widely employed in biomedical applications. For biomedical applications, it is an important issue to understand the complicated mechanism of interaction of the plasma jet with liquid. In this study, we present analysis of the discharge characteristics of a plasma jet impinging onto the liquid surface under various gas flow patterns such as laminar and turbulence flows. For this purpose, we analyzed gas flow patters by using a Schlieren gas-flow imaging system in detail The plasma jet impinging into the liquid surface expands along the liquid surface. The diameter of the expanded plasma increases with gas flow rate, which is well explained by an increase in the diameter of the laminar gas-flow channel. When the gas flow rate is further increased, the gas flow mode transits from laminar to turbulence in the gas flow channel, which leads to the shortening of the plasm-jet length. Our experiment demonstrated that the gas flow patterns strongly affect the discharge characteristics in the plasma-jet system. This study was partly supported by a Grant-in-Aid for Scientific Research on Innovative Areas ``Plasma Medical Innovation'' (24108003) from the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT).

[Temperature measurement of DC argon plasma jet].

PubMed

Yan, Jian-Hua; Pan, Xin-Chao; Ma, Zeng-Yi; Tu, Xin; Cen, Ke-Fa

2008-01-01

The electron temperature of DC arc plasma jet is an important parameter, which determines the characteristics of plasma jet. The measurement of emission spectrum was performed to obtain the spectral intensities of some Ar lines and the method of diagrammatic view of Boltzmann was adopted to calculate the electron temperature. The results indicated that the electron temperature dropped at different speed along with the axes of the plasma jet and rose rapidly when the current was increased, and it also rose when the flowrate of argon was increased.

Cosmic jets

NASA Technical Reports Server (NTRS)

Rees, M. J.

1986-01-01

The evidence that active galactic nuclei produce collimated plasma jets is summarised. The strongest radio galaxies are probably energised by relativistic plasma jets generated by spinning black holes interacting with magnetic fields attached to infalling matter. Such objects can produce e(+)-e(-) plasma, and may be relevant to the acceleration of the highest-energy cosmic ray primaries. Small-scale counterparts of the jet phenomenon within our own galaxy are briefly reviewed.

Ion Beam And Plasma Jet Generated By A 3 kJ Plasma Focus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, L. K.; Ngoi, S. K.; Yap, S. L.

The plasma focus device is well known as a copious source of X-ray, neutrons, ion and electron beams. In this work, the characteristics of energetic ion beam emission in a 3 kJ Mather-type plasma focus is studied. The plasma focus system is operated at low pressure with argon as the working gas. The objective of the project is to obtain the argon ion beam and the plasma jet. The ion beam and plasma jet are used for material processing. In order to investigate the effect of the ion beam and plasma jet, crystalline silicon substrates are placed above the anode.more » Samples obtained after irradiation with the plasma focus discharge are analyzed by using the Scanning electron microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX).« less

Modeling the Compression of Merged Compact Toroids by Multiple Plasma Jets

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Knapp, Charles E.; Kirkpatrick, Ron; Rodgers, Stephen L. (Technical Monitor)

2000-01-01

A fusion propulsion scheme has been proposed that makes use of the merging of a spherical distribution of plasma jets to dynamically form a gaseous liner. The gaseous liner is used to implode a magnetized target to produce the fusion reaction in a standoff manner. In this paper, the merging of the plasma jets to form the gaseous liner is investigated numerically. The Los Alamos SPHINX code, based on the smoothed particle hydrodynamics method is used to model the interaction of the jets. 2-D and 3-D simulations have been performed to study the characteristics of the resulting flow when these jets collide. The results show that the jets merge to form a plasma liner that converge radially which may be used to compress the central plasma to fusion conditions. Details of the computational model and the SPH numerical methods will be presented together with the numerical results.

Influence of O2 or H2O in a plasma jet and its environment on plasma electrical and biochemical performances

NASA Astrophysics Data System (ADS)

Adhikari, Ek R.; Samara, Vladimir; Ptasinska, Sylwia

2018-05-01

Because environmental conditions, such as room temperature and humidity, fluctuate arbitrarily, effects of atmospheric pressure plasma jets (APPJs) used in medical applications operating at various places and time might vary. Therefore, understanding the possible effects of air components in and outside APPJs is essential for clinical use, which requires reproducibility of plasma performance. These air components can influence the formation of reactive species in the APPJ, and the type and amount of these species formed depend on the feed gas inside the APPJ and the plasma jet environment. In this study, we monitored changes in plasma current and power, as well as in the level of DNA damage attributable to plasma irradiation, by adjusting the fraction of oxygen and water vapor in the plasma jet environment and feed gas. Here, DNA was used as a molecular probe to identify chemical changes that occurred in the plasma jet under these various environmental conditions. The damaged and undamaged fractions of DNA were quantified using agarose gel electrophoresis. We obtained an optimal amount of oxygen or water vapor in the plasma jet environment, as well as in the feed gas, which increased the level of DNA damage significantly. This increase can be attributed primarily to the formation of reactive species caused by water and oxygen decomposition in the APPJ detected with mass spectrometry. Moreover, we observed that the plasma power remained the same or decreased when gas was added to the jet environment or the feed gas, respectively, but in both cases, DNA damage increased. This indicates the superiority of plasma chemistry over the electrical power applied for APPJ ignition of the plasma sources used in medical applications.

Atmospheric Pressure Plasma Jet as a Dry Alternative to Inkjet Printing in Flexible Electronics

NASA Technical Reports Server (NTRS)

Gandhiraman, Ram Prasad; Lopez, Arlene; Koehne, Jessica; Meyyappan, M.

2016-01-01

We have developed an atmospheric pressure plasma jet printing system that works at room temperature to 50 deg C unlike conventional aerosol assisted techniques which require a high temperature sintering step to obtain desired thin films. Multiple jets can be configured to increase throughput or to deposit multiple materials, and the jet(s) can be moved across large areas using a x-y stage. The plasma jet has been used to deposit carbon nanotubes, graphene, silver nanowires, copper nanoparticles and other materials on substrates such as paper, cotton, plastic and thin metal foils.

Mechanisms of Plasma Acceleration in Coronal Jets

NASA Astrophysics Data System (ADS)

Soto, N.; Reeves, K.; Savcheva, A. S.

2016-12-01

Jets are small explosions that occur frequently in the Sun possibly driven by the local reconfiguration of the magnetic field, or reconnection. There are two types of coronal jets: standard jets and blowout jets. The purpose of this project is to determine which mechanisms accelerate plasma in two different jets, one that occurred in January 17, 2015 at the disk of the sun and another in October 24, 2015 at the limb. Two possible acceleration mechanisms are chromospheric evaporation and magnetic acceleration. Using SDO/AIA, Hinode/XRT and IRIS data, we create height-time plots, and calculate the velocities of each wavelength for both jets. We calculate the potential magnetic field of the jet and the general region around it to gain a more detailed understanding of its structure, and determine if the jet is likely to be either a standard or blowout jet. Finally, we calculate the magnetic field strength for different heights along the jet spire, and use differential emission measures to calculate the plasma density. Once we have these two values, we calculate the Alfven speed. When analyzing our results we are looking for certain patterns in our velocities. If the plasma in a jet is accelerated by chromospheric evaporation, we expect the velocities to increase as function of temperature, which is what we observed in the October 24th jet. The magnetic models for this jet also show the Eiffel Tower shaped structure characteristic of standard jets, which tend to have plasma accelerated by this mechanism. On the other hand, if the acceleration mechanism were magnetic acceleration, we would expect the velocities to be similar regardless of temperature. For the January 17th jet, we saw that along the spire, the velocities where approximately 200 km/s in all wavelengths, but the velocities of hot plasma detected at the base were closer to the Alfven speed, which was estimated to be about 2,000 km/s. These observations suggest that the plasma in the January 17th jet is magnetically accelerated. The magnetic model for this jet needs to be studied further by using a NLFFF magnetic field model and not just the potential magnetic field. This work supported by the NSF-REU solar physics program at SAO, grant number AGS-1560313 and NASA Grant NNX15AF43G

A model for straight and helical solar jets: II. Parametric study of the plasma beta.

PubMed

Pariat, E; Dalmasse, K; DeVore, C R; Antiochos, S K; Karpen, J T

2016-12-01

Jets are dynamic, impulsive, well-collimated plasma events that develop at many different scales and in different layers of the solar atmosphere. Jets are believed to be induced by magnetic reconnection, a process central to many astrophysical phenomena. Within the solar atmosphere, jet-like events develop in many different environments, e.g., in the vicinity of active regions as well as in coronal holes, and at various scales, from small photospheric spicules to large coronal jets. In all these events, signatures of helical structure and/or twisting/rotating motions are regularly observed. The present study aims to establish that a single model can generally reproduce the observed properties of these jet-like events. In this study, using our state-of-the-art numerical solver ARMS, we present a parametric study of a numerical tridimensional magnetohydrodynamic (MHD) model of solar jet-like events. Within the MHD paradigm, we study the impact of varying the atmospheric plasma β on the generation and properties of solar-like jets. The parametric study validates our model of jets for plasma β ranging from 10 -3 to 1, typical of the different layers and magnetic environments of the solar atmosphere. Our model of jets can robustly explain the generation of helical solar jet-like events at various β ≤ 1. This study introduces the new original result that the plasma β modifies the morphology of the helical jet, explaining the different observed shapes of jets at different scales and in different layers of the solar atmosphere. Our results allow us to understand the energisation, triggering, and driving processes of jet-like events. Our model allows us to make predictions of the impulsiveness and energetics of jets as determined by the surrounding environment, as well as the morphological properties of the resulting jets.

Arc Plasma Gun With Coaxial Powder Feed

NASA Technical Reports Server (NTRS)

Zaplatynsky, Isidor

1988-01-01

Redesigned plasma gun provides improved metallic and ceramic coatings. Particles injected directly through coaxial bore in cathode into central region of plasma jet. Introduced into hotter and faster region of plasma jet.

Laser-optical measurements of the velocities of the plasma jets formed from different gases in a kilojoule-range plasma focus facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polukhin, S. N., E-mail: snpol@lebedev.ru; Dzhamankulov, A. M.; Gurei, A. E.

The velocities of the plasma jets formed from Ne, N{sub 2}, Ar, and Xe gases in plasma focus facilities were determined by means of laser-optical shadowgraphy of the shock waves generated at the jet leading edge. In spite of the almost tenfold ratio between the atomic weights of these gases, the outflow velocities of the plasma jets formed in experiments with these gases differ by less than twice, in the range of (0.7–1.1) × 10{sup 7} cm/s under similar discharge conditions. The energies of the jet ions were found to vary from 0.7 keV for nitrogen to 4 keV formore » xenon.« less

Direct current plasma jet at atmospheric pressure operating in nitrogen and air

NASA Astrophysics Data System (ADS)

Deng, X. L.; Nikiforov, A. Yu.; Vanraes, P.; Leys, Ch.

2013-01-01

An atmospheric pressure direct current (DC) plasma jet is investigated in N2 and dry air in terms of plasma properties and generation of active species in the active zone and the afterglow. The influence of working gases and the discharge current on plasma parameters and afterglow properties are studied. The electrical diagnostics show that discharge can be sustained in two different operating modes, depending on the current range: a self-pulsing regime at low current and a glow regime at high current. The gas temperature and the N2 vibrational temperature in the active zone of the jet and in the afterglow are determined by means of emission spectroscopy, based on fitting spectra of N2 second positive system (C3Π-B3Π) and the Boltzmann plot method, respectively. The spectra and temperature differences between the N2 and the air plasma jet are presented and analyzed. Space-resolved ozone and nitric oxide density measurements are carried out in the afterglow of the jet. The density of ozone, which is formed in the afterglow of nitrogen plasma jet, is quantitatively detected by an ozone monitor. The density of nitric oxide, which is generated only in the air plasma jet, is determined by means of mass-spectroscopy techniques.

Plasma Jet Interaction with Thomson Scattering Probe Laser

NASA Astrophysics Data System (ADS)

Byvank, Tom; Banasek, Jacob; Potter, William; Kusse, Bruce

2016-10-01

Thomson scattering systems can diagnose plasma temperatures and velocities. When probing a plasma jet with the Thomson scattering laser, we observe a laser-plasma interaction that inputs energy into the plasma jet. The absorbed energy causes a bubble of low density ( 5*1017 cm-2) in the jet (unperturbed 1018 cm-2). A pulsed power machine (1 MA peak current, 100 ns rise time) with a radial foil (15 μm thick Al) configuration generates the plasma jet. We compare the effects of using 10 J and 1 J laser energies, for which the 10 J laser is a larger perturbation. We discuss how the interaction affects the Thomson scattering temperature and velocity measurements. Work supported by National Nuclear Security Administration (NNSA) Stewardship Sciences Academic Programs under Department of Energy (DOE) Cooperative Agreement DE-NA0001836 and National Science Foundation (NSF) Grant PHY-1102471.

Characterization of a low pressure supersonic plasma jet

NASA Astrophysics Data System (ADS)

Caldirola, S.; Barni, R.; Riccardi, C.

2014-11-01

Plasma assisted supersonic jet deposition (PA-SJD) is a technique which combines a inductively coupled plasma (ICP) with a supersonic jet for the fabrication of thin films having a desired morphology. A reactive argon-oxygen plasma is employed to dissociate an organic precursor (titanium tetra-isopropoxide for TiO2 thin films) in a first vacuum chamber which is connected through a nozzle to a lower pressure chamber. The pressure difference produces a supersonic jet, seeded with nanoparticles. Along the jet the nucleation and aggregation of nanoparticles can be controlled to obtain nanostructured depositions. We report here the results of an analysis performed with a quadrupole mass spectrometer (QMS) which was used to sample neutrals and ions from the jet at different positions along the centerline of the supersonic expansion.

Double-Layered Atmospheric Pressure Plasma Jet

NASA Astrophysics Data System (ADS)

Choi, Jaegu; Matsuo, Keita; Yoshida, Hidekazu; Namihira, Takao; Katsuki, Sunao; Akiyama, Hidenori

2009-08-01

In this paper, we present a double-layered atmospheric pressure plasma jet (DLAPPJ) that is expected to improve conventional single-layered atmospheric pressure plasma jets. With the additional introduction of nitrogen gas into the outer nozzle between the inner and outer tubes, the plasma plume is boosted, resulting in a brighter and longer plasma torch, which may have more radicals and which may broaden the application range of atmospheric pressure plasma jets. The characteristics of the proposed device were investigated with the measurement of the visible torch length, wettability tests and optical emission spectroscopy. The results obtained imply that the DLAPPJ can be used for target-based plasma treatments, that is, (a) oxidation-related applications, such as surface treatment, biological decontamination and apoptosis induction, and (b) nitrification-related applications such as NO generation for wound healing and surface modification, by controlling radicals in plasmas.

On non-equilibrium atmospheric pressure plasma jets and plasma bullet

NASA Astrophysics Data System (ADS)

Lu, Xinpei

2012-10-01

Because of the enhanced plasma chemistry, atmospheric pressure nonequilibrium plasmas (APNPs) have been widely studied for several emerging applications such as biomedical applications. For the biomedical applications, plasma jet devices, which generate plasma in open space (surrounding air) rather than in confined discharge gaps only, have lots of advantages over the traditional dielectric barrier discharge (DBD) devices. For example, it can be used for root canal disinfection, which can't be realized by the traditional plasma device. On the other hand, currently, the working gases of most of the plasma jet devices are noble gases or the mixtures of the noble gases with small amount of O2, or air. If ambient air is used as the working gas, several serious difficulties are encountered in the plasma generation process. Amongst these are high gas temperatures and disrupting instabilities. In this presentation, firstly, a brief review of the different cold plasma jets developed to date is presented. Secondly, several different plasma jet devices developed in our lab are reported. The effects of various parameters on the plasma jets are discussed. Finally, one of the most interesting phenomena of APNP-Js, the plasma bullet is discussed and its behavior is described. References: [1] X. Lu, M. Laroussi, V. Puech, Plasma Sources Sci. Technol. 21, 034005 (2012); [2] Y. Xian, X. Lu, S. Wu, P. Chu, and Y. Pan, Appl. Phys. Lett. 100, 123702 (2012); [3] X. Pei, X. Lu, J. Liu, D. Liu, Y. Yang, K. Ostrikov, P. Chu, and Y. Pan, J. Phys. D 45, 165205 (2012).

Optimal Design of Nozzle for Supersonic Atmosphere Plasma Spraying

NASA Astrophysics Data System (ADS)

Wei, Pei; Wei, Zhengying; Zhao, Guangxi; Bai, Y.; Tan, Chao

2016-08-01

Through numerical simulation, key issues concerning the plasma jet features as well as the sizes of nozzle for supersonic atmosphere plasma spraying (SAPS) were analyzed in this paper. Numerical results were compared with the experimental measurements and a good agreement has been achieved. Due to the effect of mechanical compression, the increasing sizes of r1, r2, r3 and r4 (r1, r2, r3 and r4 are the sizes of nozzle) lead to a decrease in temperature and velocity of plasma jet. But large size of r5 can increase the external temperature and velocity of plasma jet, which benefit particles accelerating at the far downstream region. A new nozzle was designed based on the simulation results. Compared to the temperature and velocity of plasma jet in the original nozzle, the maximum temperature and velocity of plasma jet in new structure are increased by about 9.8% and 44.5%, which is a benefit to the particles to reach a higher speed and surface temperature.

Influence of Plasma Jet Temperature Profiles in Arc Discharge Methods of Carbon Nanotubes Synthesis

PubMed Central

Raniszewski, Grzegorz; Wiak, Slawomir; Pietrzak, Lukasz; Szymanski, Lukasz; Kolacinski, Zbigniew

2017-01-01

One of the most common methods of carbon nanotubes (CNTs) synthesis is application of an electric-arc plasma. However, the final product in the form of cathode deposit is composed of carbon nanotubes and a variety of carbon impurities. An assay of carbon nanotubes produced in arc discharge systems available on the market shows that commercial cathode deposits contain about 10% CNTs. Given that the quality of the final product depends on carbon–plasma jet parameters, it is possible to increase the yield of the synthesis by plasma jet control. Most of the carbon nanotubes are multiwall carbon nanotubes (MWCNTs). It was observed that the addition of catalysts significantly changes the plasma composition, effective ionization potential, the arc channel conductance, and in effect temperature of the arc and carbon elements flux. This paper focuses on the influence of metal components on plasma-jet forming containing carbon nanotubes cathode deposit. The plasma jet temperature control system is presented. PMID:28336884

Influence of Plasma Jet Temperature Profiles in Arc Discharge Methods of Carbon Nanotubes Synthesis.

PubMed

Raniszewski, Grzegorz; Wiak, Slawomir; Pietrzak, Lukasz; Szymanski, Lukasz; Kolacinski, Zbigniew

2017-02-23

One of the most common methods of carbon nanotubes (CNTs) synthesis is application of an electric-arc plasma. However, the final product in the form of cathode deposit is composed of carbon nanotubes and a variety of carbon impurities. An assay of carbon nanotubes produced in arc discharge systems available on the market shows that commercial cathode deposits contain about 10% CNTs. Given that the quality of the final product depends on carbon-plasma jet parameters, it is possible to increase the yield of the synthesis by plasma jet control. Most of the carbon nanotubes are multiwall carbon nanotubes (MWCNTs). It was observed that the addition of catalysts significantly changes the plasma composition, effective ionization potential, the arc channel conductance, and in effect temperature of the arc and carbon elements flux. This paper focuses on the influence of metal components on plasma-jet forming containing carbon nanotubes cathode deposit. The plasma jet temperature control system is presented.

Pulsed plasma thruster by applied a high current hollow cathode discharge

NASA Astrophysics Data System (ADS)

Watanabe, Masayuki; N. Nogera Team; T. Kamada Team

2013-09-01

The pulsed plasma thruster applied by a high current hollow cathode discharge has been investigated. In this research, the pseudo-spark discharge (PSD), which is a one of a pulsed high current hollow cathode discharge, is applied to the plasma thruster. In PSD, the opposite surfaces of the anode and cathode have a small circular hole and the cathode has a cylindrical cavity behind the circular hole. To generate the high speed plasma flow, the diameter of the anode hole is enlarged as compared with that of the cathode hole. As a result, the plasma is accelerated by a combination of an electro-magnetic force and a thermo-dynamic force inside a cathode cavity. For the improvement of the plasma jet characteristic, the magnetic field is also applied to the plasma jet. To magnetize the plasma jet, the external magnetic field is directly induced nearby the electrode holes. Consequently, the plasma jet is accelerated with the self-azimuthal magnetic field. With the magnetic field, the temperature and the density of the plasma jet were around 5 eV and in the order of 10 19 m-3. The density increased several times as compared with that without the magnetic field.

Atmospheric-Pressure Plasma Interaction with Soft Materials as Fundamental Processes in Plasma Medicine.

PubMed

Takenaka, Kosuke; Miyazaki, Atsushi; Uchida, Giichiro; Setsuhara, Yuichi

2015-03-01

Molecular-structure variation of organic materials irradiated with atmospheric pressure He plasma jet have been investigated. Optical emission spectrum in the atmospheric-pressure He plasma jet has been measured. The spectrum shows considerable emissions of He lines, and the emission of O and N radicals attributed to air. Variation in molecular structure of Polyethylene terephthalate (PET) film surface irradiated with the atmospheric-pressure He plasma jet has been observed via X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). These results via XPS and FT-IR indicate that the PET surface irradiated with the atmospheric-pressure He plasma jet was oxidized by chemical and/or physical effect due to irradiation of active species.

Comparison of characteristics and downstream uniformity of linear-field and cross-field atmospheric pressure plasma jet array in He

NASA Astrophysics Data System (ADS)

Zhang, Bo; Fang, Zhi; Liu, Feng; Zhou, Renwu; Zhou, Ruoyu

2018-06-01

Using an atmospheric pressure plasma jet array is an effective way for expanding the treatment area of a single jet, and generating arrays with well downstream uniformity is of great interest for its applications. In this paper, a plasma jet array in helium is generated in a linear-field jet array with a ring-ring electrode structure excited by alternating current. The characteristics and downstream uniformity of the array and their dependence on the applied voltage and gas flow rate are investigated through optical, electrical, and Schlieren diagnostics. The results are compared with those of our reported work of a cross-field jet array with a needle-ring electrode structure. The results show that the linear-field jet array can generate relatively large-scale plasma with better uniformity and longer plumes than the cross-field case. The divergences observed in gas channels and the plasma plume trajectories are much less than those of the cross-field one. The deflection angle of lateral plumes is less than 6°, which is independent of the gas flow rate and applied voltage. The maximum downstream plumes of 23 mm can be obtained at 7 kV peak applied voltage and 4 l/min gas flow rate. The better uniformity of linear-field jet arrays is due to the effective suppression of hydrodynamic and electrical interactions among the jets in the arrays with a more uniform electric field distribution. The hydrodynamic interaction induced by the gas heating in the linear-field jet array is less than that of the cross-field one. The more uniform electric field distribution in the linear-field jet arrays can reduce the divergence of the propagation trajectories of the plasma plumes. It will generate less residual charge between the adjacent discharges and thus can reduce the accumulation effect of Coulomb force between the plasma plumes. The reported results can help design controllable and scalable plasma jet arrays with well uniformity for material surface and biomedical treatments.

Numerical study of the influence of dielectric tube on propagation of atmospheric pressure plasma jet based on coplanar dielectric barrier discharge

NASA Astrophysics Data System (ADS)

Haixin, HU; Feng, HE; Ping, ZHU; Jiting, OUYANG

2018-05-01

A 2D fluid model was employed to simulate the influence of dielectric on the propagation of atmospheric pressure helium plasma jet based on coplanar dielectric barrier discharge (DBD). The spatio-temporal distributions of electron density, ionization rate, electrical field, spatial charge and the spatial structure were obtained for different dielectric tubes that limit the helium flow. The results show that the change of the relative permittivity of the dielectric tube where the plasma jet travels inside has no influence on the formation of DBD itself, but has great impact on the jet propagation. The velocity of the plasma jet changes drastically when the jet passes from a tube of higher permittivity to one of lower permittivity, resulting in an increase in jet length, ionization rate and electric field, as well as a change in the distribution of space charges and discharge states. The radius of the dielectric tube has a great influence on the ring-shaped or solid bullet structure. These results can well explain the behavior of the plasma jet from the dielectric tube into the ambient air and the hollow bullet in experiments.

Laboratory plasma physics experiments using merging supersonic plasma jets

DOE PAGES

Hsu, S. C.; Moser, A. L.; Merritt, E. C.; ...

2015-04-01

We describe a laboratory plasma physics experiment at Los Alamos National Laboratory that uses two merging supersonic plasma jets formed and launched by pulsed-power-driven railguns. The jets can be formed using any atomic species or mixture available in a compressed-gas bottle and have the following nominal initial parameters at the railgun nozzle exit: n e ≈ n i ~ 10¹⁶ cm⁻³, T e ≈ T i ≈ 1.4 eV, V jet ≈ 30–100 km/s, mean chargemore » $$\\bar{Z}$$ ≈ 1, sonic Mach number M s ≡ V jet/C s > 10, jet diameter = 5 cm, and jet length ≈ 20 cm. Experiments to date have focused on the study of merging-jet dynamics and the shocks that form as a result of the interaction, in both collisional and collisionless regimes with respect to the inter-jet classical ion mean free path, and with and without an applied magnetic field. However, many other studies are also possible, as discussed in this paper.« less

Laboratory plasma physics experiments using merging supersonic plasma jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsu, S. C.; Moser, A. L.; Merritt, E. C.

We describe a laboratory plasma physics experiment at Los Alamos National Laboratory that uses two merging supersonic plasma jets formed and launched by pulsed-power-driven railguns. The jets can be formed using any atomic species or mixture available in a compressed-gas bottle and have the following nominal initial parameters at the railgun nozzle exit: n e ≈ n i ~ 10¹⁶ cm⁻³, T e ≈ T i ≈ 1.4 eV, V jet ≈ 30–100 km/s, mean chargemore » $$\\bar{Z}$$ ≈ 1, sonic Mach number M s ≡ V jet/C s > 10, jet diameter = 5 cm, and jet length ≈ 20 cm. Experiments to date have focused on the study of merging-jet dynamics and the shocks that form as a result of the interaction, in both collisional and collisionless regimes with respect to the inter-jet classical ion mean free path, and with and without an applied magnetic field. However, many other studies are also possible, as discussed in this paper.« less

Prospects for Alpha Particle Heating in JET in the Hot Ion Regime

NASA Astrophysics Data System (ADS)

Cordey, J. G.; Keilhacker, M.; Watkins, M. L.

1987-01-01

The prospects for alpha particle heating in JET are discussed. A computational model is developed to represent adequately the neutron yield from JET plasmas heated by neutral beam injection. This neutral beam model, augmented by a simple plasma model, is then used to determine the neutron yields and fusion Q-values anticipated for different heating schemes in future operation of JET with tritium. The relative importance of beam-thermal and thermal-thermal reactions is pointed out and the dependence of the results on, for example, plasma density, temperature, energy confinement and purity is shown. Full 1½-D transport code calculations, based on models developed for ohmic, ICRF and NBI heated JET discharges, are used also to provide a power scan for JET operation in tritium in the low density, high ion temperature regime. The results are shown to be in good agreement with the estimates made using the simple plasma model and indicate that, based on present knowledge, a fusion Q-value in the plasma centre above unity should be achieved in JET.

Structure and Dynamics of Colliding Plasma Jets

DOE PAGES

Li, C.; Ryutov, D.; Hu, S.; ...

2013-12-01

Monoenergetic-proton radiographs of laser-generated, high-Mach-number plasma jets colliding at various angles shed light on the structures and dynamics of these collisions. The observations compare favorably with results from 2D hydrodynamic simulations of multistream plasma jets, and also with results from an analytic treatment of electron flow and magnetic field advection. In collisions of two noncollinear jets, the observed flow structure is similar to the analytic model’s prediction of a characteristic feature with a narrow structure pointing in one direction and a much thicker one pointing in the opposite direction. Spontaneous magnetic fields, largely azimuthal around the colliding jets and generatedmore » by the well-known ∇T e ×∇n e Biermann battery effect near the periphery of the laser spots, are demonstrated to be “frozen in” the plasma (due to high magnetic Reynolds number R M ~5×10⁴) and advected along the jet streamlines of the electron flow. These studies provide novel insight into the interactions and dynamics of colliding plasma jets.« less

Self-consistent fluid modeling and simulation on a pulsed microwave atmospheric-pressure argon plasma jet

NASA Astrophysics Data System (ADS)

Chen, Zhaoquan; Yin, Zhixiang; Chen, Minggong; Hong, Lingli; Xia, Guangqing; Hu, Yelin; Huang, Yourui; Liu, Minghai; Kudryavtsev, A. A.

2014-10-01

In present study, a pulsed lower-power microwave-driven atmospheric-pressure argon plasma jet has been introduced with the type of coaxial transmission line resonator. The plasma jet plume is with room air temperature, even can be directly touched by human body without any hot harm. In order to study ionization process of the proposed plasma jet, a self-consistent hybrid fluid model is constructed in which Maxwell's equations are solved numerically by finite-difference time-domain method and a fluid model is used to study the characteristics of argon plasma evolution. With a Guass type input power function, the spatio-temporal distributions of the electron density, the electron temperature, the electric field, and the absorbed power density have been simulated, respectively. The simulation results suggest that the peak values of the electron temperature and the electric field are synchronous with the input pulsed microwave power but the maximum quantities of the electron density and the absorbed power density are lagged to the microwave power excitation. In addition, the pulsed plasma jet excited by the local enhanced electric field of surface plasmon polaritons should be the discharge mechanism of the proposed plasma jet.

Dynamics of apokamp-type atmospheric pressure plasma jets

NASA Astrophysics Data System (ADS)

Sosnin, Eduard A.; Panarin, Victor A.; Skakun, Victor S.; Baksht, Evgeny Kh.; Tarasenko, Victor F.

2017-02-01

The paper describes a new discharge source of atmospheric pressure plasma jets (APPJs) in air with no gas supply through the discharge region. In this discharge mode, plasma jets develop from the bending point of a bright current channel between two electrodes and are therefore termed an apokamp (from Greek `off' and `bend'). The apokamp can represent single plasma jets of length up 6 cm or several jets, and the temperature of such jets can range from more than 1000 °C at their base to 100-250 °C at their tip. Apokamps are formed at maximum applied voltage of positive polarity, provided that the second electrode is capacitively decoupled with ground. According to high-speed photography with time resolution from several nanoseconds to several tens of nanoseconds, the apokamp consists of a set of plasma bullets moving with a velocity of 100-220 km/s, which excludes the convective mechanism of plasma decay. Estimates on a 100-ns scale show that the near-electrode zones and the zones from which apokamps develop are close in temperature.

Investigation of MHD Instabilities in Jets and Bubbles Using a Compact Coaxial Plasma Gun in a Background Magnetized Plasma

NASA Astrophysics Data System (ADS)

Zhang, Y.; Fisher, D. M.; Wallace, B.; Gilmore, M.; Hsu, S. C.

2016-10-01

A compact coaxial plasma gun is employed for experimental investigation of launching plasma into a lower density background magnetized plasma. Experiments are being conducted in the linear device HelCat at UNM. Four distinct operational regimes with qualitatively different dynamics are identified by fast CCD camera images. For regime I plasma jet formation, a global helical magnetic configuration is determined by a B-dot probe array data. Also the m =1 kink instability is observed and verified. Furthermore, when the jet is propagating into background magnetic field, a longer length and lifetime jet is formed. Axial shear flow caused by the background magnetic tension force contributes to the increased stability of the jet body. In regime II, a spheromak-like plasma bubble formation is identified when the gun plasma is injected into vacuum. In contrast, when the bubble propagates into a background magnetic field, the closed magnetic field configuration does not hold anymore and a lateral side, Reilgh-Taylor instability develops. Detailed experimental data and analysis will be presented for these cases.

EDITORIAL: Plasma jets and plasma bullets Plasma jets and plasma bullets

NASA Astrophysics Data System (ADS)

Kong, M. G.; Ganguly, B. N.; Hicks, R. F.

2012-06-01

Plasma plumes, or plasma jets, belong to a large family of gas discharges whereby the discharge plasma is extended beyond the plasma generation region into the surrounding ambience, either by a field (e.g. electromagnetic, convective gas flow, or shock wave) or a gradient of a directionless physical quantity (e.g. particle density, pressure, or temperature). This physical extension of a plasma plume gives rise to a strong interaction with its surrounding environment, and the interaction alters the properties of both the plasma and the environment, often in a nonlinear and dynamic fashion. The plasma is therefore not confined by defined physical walls, thus extending opportunities for material treatment applications as well as bringing in new challenges in science and technology associated with complex open-boundary problems. Some of the most common examples may be found in dense plasmas with very high dissipation of externally supplied energy (e.g. in electrical, optical or thermal forms) and often in or close to thermal equilibrium. For these dense plasmas, their characteristics are determined predominantly by strong physical forces of different fields, such as electrical, magnetic, thermal, shock wave, and their nonlinear interactions [1]. Common to these dense plasma plumes are significant macroscopic plasma movement and considerable decomposition of solid materials (e.g. vaporization). Their applications are numerous and include detection of elemental traces, synthesis of high-temperature materials and welding, laser--plasma interactions, and relativistic jets in particle accelerators and in space [2]-[4]. Scientific challenges in the understanding of plasma jets are exciting and multidisciplinary, involving interweaving transitions of all four states of matter, and their technological applications are wide-ranging and growing rapidly. Using the Web of Science database, a search for journal papers on non-fusion plasma jets reveals that a long initial phase up to 1990 with only 31 papers per year on average, and a total of some 1300 papers, precedes a considerable growth of some 35-50% in research activity every five years, over the last 20 years or so. As shown in the table, the annual dissemination of the field is more than 1600 papers and the total number of papers is in excess of 20000. This upwards trajectory is typical of a strong and growing subject area in physical science, with considerable capacity in both fundamental science and applications. PeriodNumber of papersPapers per annum 1948-1990130031 1991-19952279456 1996-20003447689 2001-20054571914 2006-201066401328 2011 1658 In many of the dense plasma jets discussed above, strong physical forces generated by the plasma are often desired and this favours plasma generation at elevated gas pressure, including atmospheric pressure, which favours a high level of gas ionization. Historically it has been challenging to reduce and control the strong physical forces in high-pressure plasmas for applications where these are unwanted, for example, surface modification of polymeric sheets [5]. Indeed, there is a real need for a vast range of material processing applications at temperatures below 100oC (or below 400 K) and this favours atmospheric-pressure plasma jets sustained far from thermal equilibrium with the dissipated electrical energy largely used not in heat generation but in unleashing non-equilibrium chemical reactions. The long-standing difficulty of effectively controlling the level of gas ionization at atmospheric pressure was overcome by the technological breakthrough of achieving atmospheric-pressure glow discharges in the late 1980s [6]. A related challenge stemming from high collisionality of atmospheric-pressure plasmas (v >> ω0) means that large-area plasmas sustained between parallel-plate electrodes are very susceptible to strong plasma instabilities when molecular gases are introduced for processing applications. This led to an effective technological solution in the early to late 1990s of confining atmospheric plasmas in a small volume of plasma generation (i.e. with a small volume-to-surface ratio) and then extending it towards a downstream sample [7]-[9]. These are among the first low-temperature atmospheric plasmas aimed particularly at the exploitation of their ability to invoke the active and rich reactive chemistry close to ambient temperature. The main applications of these early devices are precision surface modification of low-temperature dielectric materials, for example thin film deposition and etching [7]-[9]. Variations of the early plasma jets include atmospheric plasma sheet jets [10] for the treatment of largely planar objects (e.g. polymeric sheets) as well as large arrays of many plasma jets for the treatment of complex-structured objects (e.g. surgical tools and open human wounds) [11]. As a material processing technology, the sub-100oC atmospheric-pressure plasma jet has benefited over the years from many innovations. Whilst a detailed account and analysis of these is clearly outside the scope of this Editorial, it is worth stating that there are different avenues with which to maintain a moderate electron density at the plasma core so as to keep the gas temperature at the sample point below a ceiling level. Most of the early studies employed excitation at radio frequencies above 10 MHz, at which electrons are largely confined in the plasma generation region, and this limits the current flow to and gas heating in the plume region of the plasma jet. Other techniques of current limitation have since been shown to be effective, including the use of dielectric barriers across a very large frequency range of 1 kHz--50 MHz, sub-microsecond pulses sustained at kHz frequencies, pulse-modulated radio frequencies and dual-frequency excitation [12]-[15]. These and other techniques have considerably advanced the atmospheric-pressure plasma jet technology. The period of some 15 years since the above-mentioned early studies has witnessed a considerable and exciting growth in terms of new phenomena observed, new physics and chemistry uncovered, new plasma jet sources conceived, and new applications developed. Examples include the observations of plasma bullets on a nanosecond scale [16], the similarity of plasma bullets to streamers [17], arrays of plasma jets as metamaterials [18], and a rapid increase of applications in biomedicine [19]. However the considerable growth in the research of plasma jets has not been adequately supported, so far, by a sound fundamental underpinning, partly resulting from a somewhat underdevelopment of effective diagnostics and modelling tools. Recognizing the critical importance of basic science for future growth of low-temperature plasma jet technology, this special issue on plasma jets and bullets aims to address some of the most important fundamental questions. Many of the special issue papers continue the established line of investigation to characterize the formation of plasma bullets, using typically ultrafast imaging, electrical detection including electric field and plasma conductivity measurement, and optical emission spectrometry [20]-[26]. These offer strong experimental evidence for the well-known hypothesis that a plasma jet is a form of streamer, and that the ionization wave plays a critical role in their formation. The interaction of two parallel plasma jets [27] and manipulation of plasma jet characteristics [28, 29] are also reported using a similar combination of experimental techniques. Some of the common characteristics of plasma jets are summarized in a review paper in this special issue [30]. A somewhat different line of investigation is employed in a detailed experimental characterization of deterministic chaos in atmospheric plasma jets [31], one of the few non-bullet modes of plasma jets. Although chaos in ionized gases have been observed in other types of discharge plasmas, their applications have not so far been linked to material processing applications, possibly because chaotic patterns of reaction chemistry could be undesirable for sample-sample reproducibility of application efficacy. Nevertheless, the lack of reproducibility in the presence of chaos may actually offer an advantage in tackling drug resistance in the new field of plasma medicine. As a material processing tool, it is important to characterize the reaction chemistry of plasma jets at a downstream point. Four special issue papers report measurement of argon and helium metastable atoms, ozone, oxygen atoms and UV irradiation using a variety of diagnostic tools including laser absorption spectroscopy, molecular beam mass spectrometry, optical emission and UV absorption spectrometry [32]-[35]. There is, however, a gap in these measurements of key reactive plasma species and characterization of plasma bullet formation [20]-[26], both in this special issue and elsewhere in the literature. Whilst atmospheric plasma modes are known to operate in bullet and non-bullet modes, it is unclear whether electron excitation of helium and/or argon metastables is different in the bullet mode from the non-bullet mode. Similarly, it remains little known whether the bullet mode facilitates a particularly efficient production of reactive plasma species [36]. An encouraging sign of our ability to address this and other knowledge gaps is evident from three excellent modelling investigations, looking into the behaviours of ionization waves [37], interaction of two counter-propagating streamers [38], and the two-dimensional structure of streamers [39]. Considerable detail unravelled from these and similar simulation studies is likely to not only uncover the physics of plasma bullet formation, but also link it to the design and manipulation of downstream reaction chemistry. In fact, very recent studies have combined experimental characterization of plasma jets with their numerical modelling [40].

Effect of discharge polarity on the propagation of atmospheric-pressure helium plasma jets and the densities of OH, NO, and O radicals.

PubMed

Yonemori, Seiya; Ono, Ryo

2015-06-01

The atmospheric-pressure helium plasma jet is an emerging technology for plasma biomedical applications. In this paper, the authors focus on the effect of discharge polarity on propagation of the discharge and the densities of OH, NO, and O radicals. The plasma jet is applied to a glass surface placed on a grounded metal plate. Positive or negative voltage pulses with 25 μs duration, 8 kV amplitude, and 10 kpps repetition rate are used for the plasma jet. The plasma propagation is measured using a short-gated ICCD camera. The light emission intensity of the discharge generated at the rising phase of the voltage pulse is approximately equivalent for both polarities, while that generated during the falling phase is much higher for the negative discharge than the positive one. The shape of the discharge changes with the discharge polarity. The OH, NO, and O densities in the plasma jet are also measured for both polarities. It is found that the OH density is almost the same regardless the discharge polarity. Conversely, the negative discharge produces more O atoms and the positive discharge produces more NO molecules. These results indicate that the polarity of the discharge affects the densities of some reactive species produced in the plasma jet.

Use of Atmospheric-Pressure Plasma Jet for Polymer Surface Modification: An Overview

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuettner, Lindsey A.

Atmospheric-pressure plasma jets (APPJs) are playing an increasingly important role in materials processing procedures. Plasma treatment is a useful tool to modify surface properties of materials, especially polymers. Plasma reacts with polymer surfaces in numerous ways thus the type of process gas and plasma conditions must be explored for chosen substrates and materials to maximize desired properties. This report discusses plasma treatments and looks further into atmospheric-pressure plasma jets and the effects of gases and plasma conditions. Following the short literature review, a general overview of the future work and research at Los Alamos National Laboratory (LANL) is discussed.

Experimental investigation of coaxial-gun-formed plasmas injected into a background transverse magnetic field or plasma

NASA Astrophysics Data System (ADS)

Zhang, Yue; Fisher, Dustin M.; Gilmore, Mark; Hsu, Scott C.; Lynn, Alan G.

2018-05-01

Injection of coaxial-gun-formed magnetized plasmas into a background transverse vacuum magnetic field or into a background magnetized plasma has been studied in the helicon-cathode (HelCat) linear plasma device at the University of New Mexico [M. Gilmore et al., J. Plasma Phys. 81, 345810104 (2015)]. A magnetized plasma jet launched into a background transverse magnetic field shows emergent kink stabilization of the jet due to the formation of a sheared flow in the jet above the kink stabilization threshold 0.1kVA [Y. Zhang et al., Phys. Plasmas 24, 110702 (2017)]. Injection of a spheromak-like plasma into a transverse background magnetic field led to the observation of finger-like structures on the side with a stronger magnetic field null between the spheromak and the background field. The finger-like structures are consistent with magneto-Rayleigh-Taylor instability. Jets or spheromaks launched into a background, low-β magnetized plasma show similar behavior as above, respectively, in both cases.

Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

NASA Astrophysics Data System (ADS)

Jablonowski, H.; Bussiahn, R.; Hammer, M. U.; Weltmann, K.-D.; von Woedtke, Th.; Reuter, S.

2015-12-01

Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100-400 nm) and, in particular, vacuum ultraviolet (VUV, 10-200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH2O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H2O2) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O2•-) and hydroxyl radicals (•OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.

Effects of the electrical parameters and gas flow rate on the generation of reactive species in liquids exposed to atmospheric pressure plasma jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baek, Eun Jeong; Joh, Hea Min; Kim, Sun Ja

2016-07-15

In this work, an atmospheric pressure plasma jet was fabricated and studied for plasma–liquid interactions. The plasma jet consists of a quartz-covered pin electrode and outer quartz tube with a tapered nozzle. Using the current–voltage (I-V) and optical emission characteristics of the plasma jet, the plasma density and the speed of the plume were investigated. The optical emission spectra clearly indicated the excited NO, O, OH, N{sub 2}, and N{sub 2}{sup +} in the plasma plumes. Then the plasma jets were applied to the deionized water. We investigated the effects of the operating parameters such as applied voltage, pulse frequency,more » and gas flow rate on the generation of reactive species in the gas and liquid phases. The densities of reactive species including OH radicals were obtained at the plasma–liquid surface and inside the plasma-treated liquids using ultraviolet absorption spectroscopy and chemical probe method. The nitrite concentration was detected by Griess assay. The data are very suggestive that there is a strong correlation among the production of reactive oxygen and nitrogen species (RONS) in the plasmas and liquids.« less

Collisional-radiative simulations of a supersonic and radiatively cooled aluminum plasma jet

NASA Astrophysics Data System (ADS)

Espinosa, G.; Gil, J. M.; Rodriguez, R.; Rubiano, J. G.; Mendoza, M. A.; Martel, P.; Minguez, E.; Suzuki-Vidal, F.; Lebedev, S. V.; Swadling, G. F.; Burdiak, G.; Pickworth, L. A.; Skidmore, J.

2015-12-01

A computational investigation based on collisional-radiative simulations of a supersonic and radiatively cooled aluminum plasma jet is presented. The jet, both in vacuum and in argon ambient gas, was produced on the MAGPIE (Mega Ampere Generator for Plasma Implosion Experiments) generator and is formed by ablation of an aluminum foil driven by a 1.4 MA, 250 ns current pulse in a radial foil Z-pinch configuration. In this work, population kinetics and radiative properties simulations of the jet in different theoretical approximations were performed. In particular, local thermodynamic equilibrium (LTE), non-LTE steady state (SS) and non-LTE time dependent (TD) models have been considered. This study allows us to make a convenient microscopic characterization of the aluminum plasma jet.

Cold atmospheric pressure air plasma jet for medical applications

NASA Astrophysics Data System (ADS)

Kolb, J. F.; Mohamed, A.-A. H.; Price, R. O.; Swanson, R. J.; Bowman, A.; Chiavarini, R. L.; Stacey, M.; Schoenbach, K. H.

2008-06-01

By flowing atmospheric pressure air through a direct current powered microhollow cathode discharge, we were able to generate a 2cm long plasma jet. With increasing flow rate, the flow becomes turbulent and temperatures of the jet are reduced to values close to room temperature. Utilizing the jet, yeast grown on agar can be eradicated with a treatment of only a few seconds. Conversely, animal studies show no skin damage even with exposures ten times longer than needed for pathogen extermination. This cold plasma jet provides an effective mode of treatment for yeast infections of the skin.

Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL Karles Fellowship

DTIC Science & Technology

2015-11-30

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6750--15-9650 Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL... Plasma Physics Division i REPORT DOCUMENTATION PAGE Form ApprovedOMB No. 0704-0188 3. DATES COVERED (From - To) Standard Form 298 (Rev. 8-98...ABSTRACT Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL Karle’s Fellowship Sandra (Hernandez) Hangarter Naval Research Laboratory 4555

New insights on the propagation of pulsed atmospheric plasma streams: From single jet to multi jet arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robert, E.; Darny, T.; Dozias, S.

2015-12-15

Atmospheric pressure plasma propagation inside long dielectric tubes is analyzed for the first time through nonintrusive and nonperturbative time resolved bi-directional electric field (EF) measurements. This study unveils that plasma propagation occurs in a region where longitudinal EF exists ahead the ionization front position usually revealed from plasma emission with ICCD measurement. The ionization front propagation induces the sudden rise of a radial EF component. Both of these EF components have an amplitude of several kV/cm for helium or neon plasmas and are preserved almost constant along a few tens of cm inside a capillary. All these experimental measurements aremore » in excellent agreement with previous model calculations. The key roles of the voltage pulse polarity and of the target nature on the helium flow patterns when plasma jet is emerging in ambient air are documented from Schlieren visualization. The second part of this work is then dedicated to the development of multi jet systems, using two different setups, based on a single plasma source. Plasma splitting in dielectric tubes drilled with sub millimetric orifices, but also plasma transfer across metallic tubes equipped with such orifices are reported and analyzed from ICCD imaging and time resolved EF measurements. This allows for the design and the feasibility validation of plasma jet arrays but also emphasizes the necessity to account for voltage pulse polarity, target potential status, consecutive helium flow modulation, and electrostatic influence between the produced secondary jets.« less

MMS Observations of Protons and Heavy Ions Acceleration at Plasma Jet Fronts

NASA Astrophysics Data System (ADS)

Catapano, F.; Retino, A.; Zimbardo, G.; Cozzani, G.; Breuillard, H.; Le Contel, O.; Alexandrova, A.; Mirioni, L.; Cohen, I. J.; Turner, D. L.; Perri, S.; Greco, A.; Mauk, B.; Torbert, R. B.; Russell, C. T.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Ergun, R.; Giles, B. L.; Fuselier, S. A.; Moore, T. E.; Burch, J.

2017-12-01

Plasma jet fronts in the Earth's magnetotail are kinetic-scale boundaries separating hot fast plasma jets, generally attributed to reconnection outflows, from colder ambient plasma. Jet fronts are typically associated with a sharp increase of the vertical component of the magnetic field Bz, an increase of the plasma temperature and a drop of plasma density. Spacecraft observations and numerical simulations indicate that jet fronts are sites of major ion acceleration. The exact acceleration mechanisms as well as the dependence of such mechanisms on ion composition are not fully understood, yet. Recent high-resolution measurements of ion distribution functions in the magnetotail allow for the first time to study the acceleration mechanisms in detail. Here, we show several examples of jet fronts and discuss ion acceleration therein. We show fronts that propagate in the mid-tail magnetotail both as isolated laminar boundaries and as multiple boundaries embedded in strong magnetic fluctuations and turbulence. We also show fronts in the near-Earth jet braking region, where they interact with the dipolar magnetic field and are significantly decelerated/diverted. Finally, we study the acceleration of different ion species (H+, He++, O+) at different types of fronts and we discuss possible different acceleration mechanisms and how they depend on the ion species.

A Model for Straight and Helical Solar Jets: II. Parametric Study of the Plasma Beta

NASA Technical Reports Server (NTRS)

Pariat, E.; Dalmasse, K.; DeVore, C. R.; Antiochos, S. K.; Karpen, J. T.

2016-01-01

Context. Jets are dynamic, impulsive, well-collimated plasma events that develop at many different scales and in different layers of the solar atmosphere. Aims. Jets are believed to be induced by magnetic reconnection, a process central to many astrophysical phenomena. Within the solar atmosphere, jet-like events develop in many different environments, e.g. in the vicinity of active regions as well as in coronal holes, and at various scales, from small photospheric spicules to large coronal jets. In all these events, signatures of helical structure and/or twisting/rotating motions are regularly observed. The present study aims to establish that a single model can generally reproduce the observed properties of these jet-like events. Methods. In this study, using our state-of-the-art numerical solver ARMS, we present a parametric study of a numerical tridimensional magnetohydrodynamic (MHD) model of solar jet-like events. Within the MHD paradigm, we study the impact of varying the atmospheric plasma beta on the generation and properties of solar-like jets. Results. The parametric study validates our model of jets for plasma beta ranging from 10(sup 3) to 1, typical of the different layers and magnetic environments of the solar atmosphere. Our model of jets can robustly explain the generation of helical solar jet-like events at various beta less than or equal to 1. We show that the plasma beta modifies the morphology of the helical jet, explaining the different observed shapes of jets at different scales and in different layers of the solar atmosphere. Conclusions. Our results allow us to understand the energisation, triggering, and driving processes of jet-like events. Our model allows us to make predictions of the impulsiveness and energetics of jets as determined by the surrounding environment, as well as the morphological properties of the resulting jets.

Propagation of atmospheric pressure helium plasma jet into ambient air at laminar gas flow

NASA Astrophysics Data System (ADS)

Pinchuk, M.; Stepanova, O.; Kurakina, N.; Spodobin, V.

2017-05-01

The formation of an atmospheric pressure plasma jet (APPJ) in a gas flow passing through the discharge gap depends on both gas-dynamic properties and electrophysical parameters of the plasma jet generator. The paper presents the results of experimental and numerical study of the propagation of the APPJ in a laminar flow of helium. A dielectric-barrier discharge (DBD) generated inside a quartz tube equipped with a coaxial electrode system, which provided gas passing through it, served as a plasma source. The transition of the laminar regime of gas flow into turbulent one was controlled by the photography of a formed plasma jet. The corresponding gas outlet velocity and Reynolds numbers were revealed experimentally and were used to simulate gas dynamics with OpenFOAM software. The data of the numerical simulation suggest that the length of plasma jet at the unvarying electrophysical parameters of DBD strongly depends on the mole fraction of ambient air in a helium flow, which is established along the direction of gas flow.

Note: Design and investigation of a multichannel plasma-jet triggered gas switch.

PubMed

Tie, Weihao; Liu, Xuandong; Zhang, Qiaogen; Liu, Shanhong

2014-07-01

We described the fabrication and testing of a multichannel plasma-jet triggered gas switch (MPJTGS). A novel six-channel annular micro-plasma-gun was embedded in the trigger electrode to generate multichannel plasma jets as a nanosecond trigger pulse arrived. The gas breakdown in multiple sites of the spark gap was induced and fixed around jet orifices by the plasma jets. We tested the multichannel discharge characteristics of the MPJTGS in two working modes with charge voltage of 50 kV, trigger voltage of +40 kV (25 ns rise time), and trigger energy of 240 J, 32 J, and 2 J, respectively, at different working coefficients. Results show that the average number of discharge channels increased as the trigger energy increased, and decreased as the working coefficient decreased. At a working coefficient of 87.1% and trigger energy of 240 J, the average number of discharge channels in Mode II could reach 4.1.

A plasma deflagration accelerator as a platform for laboratory astrophysics

NASA Astrophysics Data System (ADS)

Underwood, Thomas C.; Loebner, Keith T. K.; Cappelli, Mark A.

2017-06-01

The replication of astrophysical flows in the laboratory is critical for isolating particular phenomena and dynamics that appear in complex, highly-coupled natural systems. In particular, plasma jets are observed in astrophysical contexts at a variety of scales, typically at high magnetic Reynolds number and driven by internal currents. In this paper, we present detailed measurements of the plasma parameters within deflagration-produced plasma jets, the scaling of these parameters against both machine operating conditions and the corresponding astrophysical phenomena. Using optical and spectroscopic diagnostics, including Schlieren cinematography, we demonstrate the production of current-driven plasma jets of ∼100 km/s and magnetic Reynolds numbers of ∼100, and discuss the dynamics of their acceleration into vacuum. The results of this study will contribute to the reproduction of various types of astrophysical jets in the laboratory and indicate the ability to further probe active research areas such as jet collimation, stability, and interaction.

The effect of working gas impurities on plasma jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, X. Y.; He, M. B., E-mail: pulhmb@mail.hust.edu.cn; IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240

Air intrusion reduced the purity of working gas inside the tube for plasma jet, and thereby, affected the discharge dynamics. In this paper, the effect of using working gas with different purity level (helium purity 99.99999%, 99.99%, 99.9%, and 99%) on photoionization and the chemical reactivity of plasma jet were studied using a 2 dimensional plasma jet model. Photoionization of air species acted as a source of pre-ionization in front of the ionization region, which facilitated the transition from localized discharge to streamers inside the tube. The density of reactive species inside the tube was found to increase with themore » concentration of working gas impurities. For the highest purity helium (99.99999%), despite a low photoionization rate and the distance between the photoionization region and ionization region inside the tube, by increasing the applied voltage and decreasing the distance between the electrode and nozzle, plasma jets were formed.« less

Sterilization of bacterial endospores by an atmospheric-pressure argon plasma jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uhm, Han S.; Lim, Jin P.; Li, Shou Z.

2007-06-25

Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological warfare agents. However, the spore-killing efficiency of the atmospheric-pressure argon-oxygen jet depends very sensitively on the oxygen concentration in the argon gas.

Air plasma effect on dental disinfection

NASA Astrophysics Data System (ADS)

Duarte, S.; Kuo, S. P.; Murata, R. M.; Chen, C. Y.; Saxena, D.; Huang, K. J.; Popovic, S.

2011-07-01

A nonthermal low temperature air plasma jet is characterized and applied to study the plasma effects on oral pathogens and biofilms. Experiments were performed on samples of six defined microorganisms' cultures, including those of gram-positive bacteria and fungi, and on a cultivating biofilm sample of Streptococcus mutans UA159. The results show that the plasma jet creates a zone of microbial growth inhibition in each treated sample; the zone increases with the plasma treatment time and expands beyond the entire region directly exposed to the plasma jet. With 30s plasma treatment twice daily during 5 days of biofilm cultivation, its formation was inhibited. The viability of S. mutans cells in the treated biofilms dropped to below the measurable level and the killed bacterial cells concentrated to local regions as manifested by the fluorescence microscopy via the environmental scanning electron microscope. The emission spectroscopy of the jet indicates that its plasma effluent carries an abundance of reactive atomic oxygen, providing catalyst for the observed plasma effect.

A Concept for Directly Coupled Pulsed Electromagnetic Acceleration of Plasmas

NASA Technical Reports Server (NTRS)

Thio, Y.C. Francis; Cassibry, Jason T.; Eskridge, Richard; Smith, James; Wu, S. T.; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

Plasma jets with high momentum flux density are required for a variety of applications in propulsion research. Methods of producing these plasma jets are being investigated at NASA Marshall Space Flight Center. The experimental goal in the immediate future is to develop plasma accelerators which are capable of producing plasma jets with momentum flux density represented by velocities up to 200 km/s and ion density up to 10(exp 24) per cu m, with sufficient precision and reproducibility in their properties, and with sufficiently high efficiency. The jets must be sufficiently focused to allow them to be transported over several meters. A plasma accelerator concept is presented that might be able to meet these requirements. It is a self-switching, shaped coaxial pulsed plasma thruster, with focusing of the plasma flow by shaping muzzle current distribution as in plasma focus devices, and by mechanical tapering of the gun walls. Some 2-D MHD modeling in support of the conceptual design will be presented.

Air plasma effect on dental disinfection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duarte, S.; Murata, R. M.; Saxena, D.

2011-07-15

A nonthermal low temperature air plasma jet is characterized and applied to study the plasma effects on oral pathogens and biofilms. Experiments were performed on samples of six defined microorganisms' cultures, including those of gram-positive bacteria and fungi, and on a cultivating biofilm sample of Streptococcus mutans UA159. The results show that the plasma jet creates a zone of microbial growth inhibition in each treated sample; the zone increases with the plasma treatment time and expands beyond the entire region directly exposed to the plasma jet. With 30s plasma treatment twice daily during 5 days of biofilm cultivation, its formationmore » was inhibited. The viability of S. mutans cells in the treated biofilms dropped to below the measurable level and the killed bacterial cells concentrated to local regions as manifested by the fluorescence microscopy via the environmental scanning electron microscope. The emission spectroscopy of the jet indicates that its plasma effluent carries an abundance of reactive atomic oxygen, providing catalyst for the observed plasma effect.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chesler, Paul M.; Rajagopal, Krishna

We calculate how the energy and the opening angle of jets in N = 4SYM theory evolve as they propagate through the strongly coupled plasma of that theory. We define the rate of energy loss dE jet/dx and the jet opening angle in a straightforward fashion directly in the gauge theory before calculating both holographically, in the dual gravitational description. In this way, we rederive the previously known result for dE jet/dx without the need to introduce a finite slab of plasma. We obtain a striking relationship between the initial opening angle of the jet, which is to say themore » opening angle that it would have had if it had found itself in vacuum instead of in plasma, and the thermalization distance of the jet. Via this relationship, we show that N = 4SYM jets with any initial energy that have the same initial opening angle and the same trajectory through the plasma experience the same fractional energy loss. We also provide an expansion that describes how the opening angle of the N = 4SYM jets increases slowly as they lose energy, over the fraction of their lifetime when their fractional energy loss is not yet large. In conclusion, we close by looking ahead toward potential qualitative lessons from our results for QCD jets produced in heavy collisions and propagating through quark-gluon plasma.« less

The Reel Deal In 3D: The Spatio-Temporal Evolution of YSO Jets

NASA Astrophysics Data System (ADS)

Frank, Adam

2014-10-01

Jets are a ubiquitous phenomena in astrophysics, though in most cases their central engines are unresolvable. Thus the structure of the jets often acts as a proxy for understanding the objects creating them. Jets are also of interest in their own right, serving as critical examples of rapidly evolving astrophysical magnetized plasma systems. And while millions of CPU hours {at least} have been spent simulating the kinds of astrophysical plasma dynamics that occur routinely in jets, we rarely have had the chance to study their real-time evolution. In this proposal we seek to use a unique multi-epoch HST dataset of protostellar jets to carry forward an innovative theoretical, numerical and laboratory-based study of magnetized outflows and the plasma processes which determine their evolution. Our work will make direct and detailed contact with these HST data sets and will articulate newly-observed features of jet dynamics that have not been possible to explore before. Using numerical simulations and laboratory plasma studies we seek to articulate the full 3-D nature of new behaviors seen in the HST data. Our collaboration includes the use of scaled laboratory plasma experiments with hypersonic magnetized radiative jets. The MHD experiments have explored how jets break up into clumps via kink-mode instabilities. Therefore such experiments are directly relevant to the initial conditions in our models.

Contrasting characteristics of aqueous reactive species induced by cross-field and linear-field plasma jets

NASA Astrophysics Data System (ADS)

Xu, Han; Chen, Chen; Liu, Dingxin; Xu, Dehui; Liu, Zhijie; Wang, Xiaohua; Kong, Michael G.

2017-06-01

A comparative study on aqueous reactive species in deionized water treated by two types of plasma jets is presented. Classified by the direction of the electric field in the jet device, a linear-field jet and cross-field jet have been set up. Concentrations of several aqueous reactive species are measured quantitatively by chemical fluorescent assays and electron spin resonance spectrometer. Results show that these two-type plasma jets would generate approximately the same gaseous reactive species under the same discharge power, but the linear-field plasma jet is much more efficient at delivering those species to the remote deionized water. This leads to a much more aqueous short-lived species including OH and \\text{O}2- produced in water, which are mainly correlated to the solvation of gaseous short-lived species such as ions and electrons. Regarding the long-lived species of aqueous H2O2, the concentration grows faster when treated by the linear-field plasma jet in the initial stage, but after 10 min it is similar to that treated by the cross-field counterpart due to the vapor-liquid equilibrium. The aqueous peroxynitrite is also predicted to be produced as a result of the air inclusion in the feeding gas.

Intra-jet shocks in two counter-streaming, weakly collisional plasma jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryutov, D. D.; Kugland, N. L.; Park, H.-S.

2012-07-15

Counterstreaming laser-generated plasma jets can serve as a test-bed for the studies of a variety of astrophysical phenomena, including collisionless shock waves. In the latter problem, the jet's parameters have to be chosen in such a way as to make the collisions between the particles of one jet with the particles of the other jet very rare. This can be achieved by making the jet velocities high and the Coulomb cross-sections correspondingly low. On the other hand, the intra-jet collisions for high-Mach-number jets can still be very frequent, as they are determined by the much lower thermal velocities of themore » particles of each jet. This paper describes some peculiar properties of intra-jet hydrodynamics in such a setting: the steepening of smooth perturbations and shock formation affected by the presence of the 'stiff' opposite flow; the role of a rapid electron heating in shock formation; ion heating by the intrajet shock. The latter effect can cause rapid ion heating which is consistent with recent counterstreaming jet experiments by Ross et al.[Phys. Plasmas 19, 056501 (2012)].« less

Experimental investigation of supersonic low pressure air plasma flows obtained with different arc-jet operating conditions

NASA Astrophysics Data System (ADS)

Lago, Viviana; Ndiaye, Abdoul-Aziz

2012-11-01

A stationary arc-jet plasma flow at low pressure is used to simulate some properties of the gas flow surrounding a vehicle during its entry into celestial body's atmospheres. This paper presents an experimental study concerning plasmas simulating a re-entry into our planet. Optical measurements have been carried out for several operating plasma conditions in the free stream, and in the shock layer formed in front of a flat cylindrical plate, placed in the plasma jet. The analysis of the spectral radiation enabled the identification of the emitting species, the determination of the rotational and vibrational temperatures in the free-stream and in the shock layer and the determination of the distance of the shock to the flat plate face. Some plasma fluid parameters like, stagnation pressure, specific enthalpy and heat flux have been determined experimentally along the plasma-jet axis.

Effects of Anode Arc Root Fluctuation on Coating Quality During Plasma Spraying

NASA Astrophysics Data System (ADS)

An, Lian-Tong; Gao, Yang; Sun, Chengqi

2011-06-01

To obtain a coating of high quality, a new type of plasma torch was designed and constructed to increase the stability of the plasma arc and reduce the air entrainment into the plasma jet. The torch, called bi-anode torch, generates an elongated arc with comparatively high arc voltage and low arc fluctuation. Spraying experiments were carried out to compare the quality of coatings deposited by a conventional torch and a bi-anode torch. Alumina coatings and tungsten carbide coatings were prepared to appraise the heating of the sprayed particles in the plasma jets and the entrainment of the surrounding air into the plasma jets, respectively. The results show that anode arc root fluctuation has only a small effect on the melting rate of alumina particles. On the other hand, reduced air entrainment into the plasma jet of the bi-anode torch will drastically reduce the decarbonization of tungsten carbide coatings.

Influence of gas flow and applied voltage on interaction of jets in a cross-field helium plasma jet array

NASA Astrophysics Data System (ADS)

Wan, Meng; Liu, Feng; Fang, Zhi; Zhang, Bo; Wan, Hui

2017-09-01

Atmospheric Pressure Plasma Jet arrays can greatly enhance the treatment area to fulfill the need for large-scale surface processing, while the spatial uniformity of the plasma jet array is closely related to the interactions of the adjacent jets. In this paper, a three-tube one-dimensional (1D) He plasma jet array with a cross-field needle-ring electrode structure is used to investigate the influences of the gas flow rate and applied voltage on the interactions of the adjacent jets through electrical, optical, and fluid measurements. The repulsion of the adjacent plume channels is observed using an intensified charge-coupled device (ICCD) and the influence of the gas flow rate and applied voltage on the electrostatic repulsion force, Coulomb force, is discussed. It is found that electrical coupling, mainly electrostatic repulsion force, exists among the jets in the array, which causes both the divergence of the lateral plumes and the nonlinear changes of the discharge power and the transport charge. The deflection angle of the lateral plumes with respect to the central plume in the optical images increases with the increase of applied voltage and decreases with the increase of gas flow rate. The deflection angle of the lateral plumes in the optical images is obviously larger than that of the lateral gas streams in the Schlieren images under the same experimental conditions, and the unconformity of the deflection angles is mainly attributed to the electrostatic repulsion force in adjacent plasma plume channels. The experimental results can help understand the interaction mechanisms of jets in the array and design controllable and scalable plasma jet arrays.

Novel laboratory simulations of astrophysical jets

NASA Astrophysics Data System (ADS)

Brady, Parrish Clawson

This thesis was motivated by the promise that some physical aspects of astrophysical jets and collimation processes can be scaled to laboratory parameters through hydrodynamic scaling laws. The simulation of astrophysical jet phenomena with laser-produced plasmas was attractive because the laser- target interaction can inject energetic, repeatable plasma into an external environment. Novel laboratory simulations of astrophysical jets involved constructing and using the YOGA laser, giving a 1064 nm, 8 ns pulse laser with energies up to 3.7 + 0.2 J . Laser-produced plasmas were characterized using Schlieren, interferometry and ICCD photography for their use in simulating jet and magnetosphere physics. The evolution of the laser-produced plasma in various conditions was compared with self-similar solutions and HYADES computer simulations. Millimeter-scale magnetized collimated outflows were produced by a centimeter scale cylindrically symmetric electrode configuration triggered by a laser-produced plasma. A cavity with a flared nozzle surrounded the center electrode and the electrode ablation created supersonic uncollimated flows. This flow became collimated when the center electrode changed from an anodeto a cathode. The plasma jets were in axially directed permanent magnetic fields with strengths up to 5000 Gauss. The collimated magnetized jets were 0.1-0. 3 cm wide, up to 2.0 cm long, and had velocities of ~4.0 × 10 6 cm/s. The dynamics of the evolution of the jet were compared qualitatively and quantitatively with fluxtube simulations from Bellan's formulation [6] giving a calculated estimate of ~2.6 × 10 6 cm/s for jet evolution velocity and evidence for jet rotation. The density measured with interferometry was 1.9 ± 0.2 × 10 17 cm -3 compared with 2.1 × 10 16 cm -3 calculated with Bellan's pressure balance formulation. Kinks in the jet column were produced consistent with the Kruskal-Shafranov condition which allowed stable and symmetric jets to form with the background magnetic fields. The Euler number for the laboratory jet was 9 compared with an estimate of 40 for young stellar object jets [135] which demonstrated adequate scaling between the two frames. A second experiment was performed concerning laboratory simulations of magnetospheres with plasma winds impinging on permanent magnetic dipoles. The ratio of the magnetopause measured with ICCD photography to the calculated magnetopause standoff distance was ~2.

Battery-Powered RF Pre-Ionization System for the Caltech Magnetohydrodynamically-Driven Jet Experiment: RF Discharge Properties and MHD-Driven Jet Dynamics

NASA Astrophysics Data System (ADS)

Chaplin, Vernon H.

This thesis describes investigations of two classes of laboratory plasmas with rather different properties: partially ionized low pressure radiofrequency (RF) discharges, and fully ionized high density magnetohydrodynamically (MHD)-driven jets. An RF pre-ionization system was developed to enable neutral gas breakdown at lower pressures and create hotter, faster jets in the Caltech MHD-Driven Jet Experiment. The RF plasma source used a custom pulsed 3 kW 13.56 MHz RF power amplifier that was powered by AA batteries, allowing it to safely float at 4-6 kV with the cathode of the jet experiment. The argon RF discharge equilibrium and transport properties were analyzed, and novel jet dynamics were observed. Although the RF plasma source was conceived as a wave-heated helicon source, scaling measurements and numerical modeling showed that inductive coupling was the dominant energy input mechanism. A one-dimensional time-dependent fluid model was developed to quantitatively explain the expansion of the pre-ionized plasma into the jet experiment chamber. The plasma transitioned from an ionizing phase with depressed neutral emission to a recombining phase with enhanced emission during the course of the experiment, causing fast camera images to be a poor indicator of the density distribution. Under certain conditions, the total visible and infrared brightness and the downstream ion density both increased after the RF power was turned off. The time-dependent emission patterns were used for an indirect measurement of the neutral gas pressure. The low-mass jets formed with the aid of the pre-ionization system were extremely narrow and collimated near the electrodes, with peak density exceeding that of jets created without pre-ionization. The initial neutral gas distribution prior to plasma breakdown was found to be critical in determining the ultimate jet structure. The visible radius of the dense central jet column was several times narrower than the axial current channel radius, suggesting that the outer portion of the jet must have been force free, with the current parallel to the magnetic field. The studies of non-equilibrium flows and plasma self-organization being carried out at Caltech are relevant to astrophysical jets and fusion energy research.

Cell Internal Treatable Microplasma Jets in Cancer Therapies

NASA Astrophysics Data System (ADS)

Kim, Jae Young; Wei, Yanzhang; Li, Jinhua; Kim, Sung-O.

2011-10-01

We developed a 15- μm-sized, single-cellular-level, and cell-manipulatable microplasma jet device with a microcapillary glass tip and described its potential in physical cancer therapies. The microcapillary tip is a funnel shaped glass tube and its nozzle has an inner diameter of 15 μm and an outer diameter of 20 μm with 20 capillary angle. The electrical and optical properties of this plasma jet and apoptosis results of cultured murine B16F0 melanoma tumor cells and CL.7 fibroblast cells treated with the plasma jets were described. In spite of the small inner diameter and the low gas flow rate of the microplasma jet device, the generated plasma jets are stable enough to treat tumor cells. The microplasma jet was observed inducing apoptosis in cultured murine melanoma tumor cells in a dose-dependent manner. Furthermore, the percentage of apoptotic cells of murine melanoma tumor cells induced by this plasma device was approximately 2.5 times bigger than that of murine fibroblast cells as indicated by an Annex V-FITC method. This highly precise plasma medicine, which enables new directed cancer therapies, can be combined with current cell manipulation and cell culturing technologies without much difficulty.

Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL Karle’s Fellowship

DTIC Science & Technology

2015-11-30

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6750--15-9650 Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL... Plasma Physics Division i REPORT DOCUMENTATION PAGE Form ApprovedOMB No. 0704-0188 3. DATES COVERED (From - To) Standard Form 298 (Rev. 8-98...ABSTRACT Plasma Jet Interactions with Liquids in Partial Fulfillment of an NRL Karle’s Fellowship Sandra (Hernandez) Hangarter Naval Research Laboratory 4555

A New Way to Generate Collimated Plasma Jets?

NASA Astrophysics Data System (ADS)

Young, Rachel; Kuranz, C. C.; Sweeney, R. M.; Drake, R. P.

2012-05-01

We may have a new way to generate collimated, high-Mach-number plasma jets for laboratory astrophysics experiments. Analytic calculations show that irradiating the rear side of a cone-shaped foil can produce a collimated plasma jet with a Mach number of more than 2. Preliminary numeric simulations confirm this. We intend to test this method with a day of experiments at OMEGA (Laboratory for Laser Energetics, Rochester, New York) in April 2012; results may be available in time for this meeting. If successful, this will be the first step in an experimental campaign to investigate the affects of magnetic fields on mixing plasma jets. We hope to create a swirling disk of magnetized plasma_and possibly witness the turbulent dynamo_by firing roughly half a dozen such jets towards each other. However, for such an experiment to succeed, the disk must rotate more quickly than it expands, requiring the contributing jets to have M > 2. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-FG52-09NA29548, and by the National Laser User Facility Program, grant number DE-NA0000850.

Formation of Imploding Plasma Liners for HEDP and MIF Applications - Diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilmore, Mark; Hsu, Scott; Witherspoon, F. Douglas

The goal of the plasma liner experiment (PLX) was to explore and demonstrate the feasibility of forming imploding spherical plasma liners that can reach High Energy Density (HED)-relevant (~ 0.1 Mbar) pressures upon stagnation. The plasma liners were to be formed by a spherical array of 30 – 36 railgun-driven hypervelocity plasma jets (Mach 10 – 50). Due to funding and project scope reductions in year two of the project, this initial goal was revised to focus on studies of individual jet propagation, and on two jet merging physics. PLX was a collaboration between a number of partners including Losmore » Alamos National Laboratory, HyperV Technologies, University of New Mexico (UNM), University of Alabama, Huntsville, and University of Nevada, Reno. UNM’s part in the collaboration was primary responsibility for plasma diagnostics. Though full plasma liner experiments could not be performed, the results of single and two jet experiments nevertheless laid important groundwork for future plasma liner investigations. Though challenges were encountered, the results obtained with one and two jets were overwhelmingly positive from a liner formation point of view, and were largely in agreement with predictions of hydrodynamic models.« less

Studying the non-thermal plasma jet characteristics and application on bacterial decontamination

NASA Astrophysics Data System (ADS)

Al-rawaf, Ali F.; Fuliful, Fadhil Khaddam; Khalaf, Mohammed K.; Oudah, Husham. K.

2018-04-01

Non-thermal atmospheric-pressure plasma jet represents an excellent approach for the decontamination of bacteria. In this paper, we want to improve and characterize a non-thermal plasma jet to employ it in processes of sterilization. The electrical characteristics was studied to describe the discharge of the plasma jet and the development of plasma plume has been characterized as a function of helium flow rate. Optical emission spectroscopy was employed to detect the active species inside the plasma plume. The inactivation efficiency of non-thermal plasma jet was evaluated against Staphylococcus aureus bacteria by measuring the diameter of inhibition zone and the number of surviving cells. The results presented that the plasma plume temperature was lower than 34° C at a flow rate of 4 slm, which will not cause damage to living tissues. The diameter of inhibition zone is directly extended with increased exposure time. We confirmed that the inactivation mechanism was unaffected by UV irradiation. In addition, we concluded that the major reasons for the inactivation process of bacteria is because of the action of the reactive oxygen and nitrogen species which formed from ambient air, while the charged particles played a minor role in the inactivation process.

Development and Benchmarking of a Hybrid PIC Code For Dense Plasmas and Fast Ignition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Witherspoon, F. Douglas; Welch, Dale R.; Thompson, John R.

Radiation processes play an important role in the study of both fast ignition and other inertial confinement schemes, such as plasma jet driven magneto-inertial fusion, both in their effect on energy balance, and in generating diagnostic signals. In the latter case, warm and hot dense matter may be produced by the convergence of a plasma shell formed by the merging of an assembly of high Mach number plasma jets. This innovative approach has the potential advantage of creating matter of high energy densities in voluminous amount compared with high power lasers or particle beams. An important application of this technologymore » is as a plasma liner for the flux compression of magnetized plasma to create ultra-high magnetic fields and burning plasmas. HyperV Technologies Corp. has been developing plasma jet accelerator technology in both coaxial and linear railgun geometries to produce plasma jets of sufficient mass, density, and velocity to create such imploding plasma liners. An enabling tool for the development of this technology is the ability to model the plasma dynamics, not only in the accelerators themselves, but also in the resulting magnetized target plasma and within the merging/interacting plasma jets during transport to the target. Welch pioneered numerical modeling of such plasmas (including for fast ignition) using the LSP simulation code. Lsp is an electromagnetic, parallelized, plasma simulation code under development since 1995. It has a number of innovative features making it uniquely suitable for modeling high energy density plasmas including a hybrid fluid model for electrons that allows electrons in dense plasmas to be modeled with a kinetic or fluid treatment as appropriate. In addition to in-house use at Voss Scientific, several groups carrying out research in Fast Ignition (LLNL, SNL, UCSD, AWE (UK), and Imperial College (UK)) also use LSP. A collaborative team consisting of HyperV Technologies Corp., Voss Scientific LLC, FAR-TECH, Inc., Prism Computational Sciences, Inc. and Advanced Energy Systems Inc. joined efforts to develop new physics and numerical models for LSP in several key areas to enhance the ability of LSP to model high energy density plasmas (HEDP). This final report details those efforts. Areas addressed in this research effort include: adding radiation transport to LSP, first in 2D and then fully 3D, extending the EMHD model to 3D, implementing more advanced radiation and electrode plasma boundary conditions, and installing more efficient implicit numerical algorithms to speed complex 2-D and 3-D computations. The new capabilities allow modeling of the dominant processes in high energy density plasmas, and further assist the development and optimization of plasma jet accelerators, with particular attention to MHD instabilities and plasma/wall interaction (based on physical models for ion drag friction and ablation/erosion of the electrodes). In the first funding cycle we implemented a solver for the radiation diffusion equation. To solve this equation in 2-D, we used finite-differencing and applied the parallelized sparse-matrix solvers in the PETSc library (Argonne National Laboratory) to the resulting system of equations. A database of the necessary coefficients for materials of interest was assembled using the PROPACEOS and ATBASE codes from Prism. The model was benchmarked against Prism's 1-D radiation hydrodynamics code HELIOS, and against experimental data obtained from HyperV's separately funded plasma jet accelerator development program. Work in the second funding cycle focused on extending the radiation diffusion model to full 3-D, continued development of the EMHD model, optimizing the direct-implicit model to speed up calculations, add in multiply ionized atoms, and improved the way boundary conditions are handled in LSP. These new LSP capabilities were then used, along with analytic calculations and Mach2 runs, to investigate plasma jet merging, plasma detachment and transport, restrike and advanced jet accelerator design. In addition, a strong linkage to diagnostic measurements was made by modeling plasma jet experiments on PLX to support benchmarking of the code. A large number of upgrades and improvements advancing hybrid PIC algorithms were implemented in LSP during the second funding cycle. These include development of fully 3D radiation transport algorithms, new boundary conditions for plasma-electrode interactions, and a charge conserving equation of state that permits multiply ionized high-Z ions. The final funding cycle focused on 1) mitigating the effects of a slow-growing grid instability which is most pronounced in plasma jet frame expansion problems using the two-fluid Eulerian remap algorithm, 2) extension of the Eulerian Smoothing Algorithm to allow EOS/Radiation modeling, 3) simulations of collisionless shocks formed by jet merging, 4) simulations of merging jets using high-Z gases, 5) generation of PROPACEOS EOS/Opacity databases, 6) simulations of plasma jet transport experiments, 7) simulations of plasma jet penetration through transverse magnetic fields, and 8) GPU PIC code development The tools developed during this project are applicable not only to the study of plasma jets, but also to a wide variety of HEDP plasmas of interest to DOE, including plasmas created in short-pulse laser experiments performed to study fast ignition concepts for inertial confinement fusion.« less

Modelling the helium plasma jet delivery of reactive species into a 3D cancer tumour

NASA Astrophysics Data System (ADS)

Szili, Endre J.; Oh, Jun-Seok; Fukuhara, Hideo; Bhatia, Rishabh; Gaur, Nishtha; Nguyen, Cuong K.; Hong, Sung-Ha; Ito, Satsuki; Ogawa, Kotaro; Kawada, Chiaki; Shuin, Taro; Tsuda, Masayuki; Furihata, Mutsuo; Kurabayashi, Atsushi; Furuta, Hiroshi; Ito, Masafumi; Inoue, Keiji; Hatta, Akimitsu; Short, Robert D.

2018-01-01

Cold atmospheric plasmas have attracted significant worldwide attention for their potential beneficial effects in cancer therapy. In order to further improve the effectiveness of plasma in cancer therapy, it is important to understand the generation and transport of plasma reactive species into tissue fluids, tissues and cells, and moreover the rates and depths of delivery, particularly across physical barriers such as skin. In this study, helium (He) plasma jet treatment of a 3D cancer tumour, grown on the back of a live mouse, induced apoptosis within the tumour to a depth of 2.8 mm. The He plasma jet was shown to deliver reactive oxygen species through the unbroken skin barrier before penetrating through the entire depth of the tumour. The depth and rate of transport of He plasma jet generated H2O2, NO3 - and NO2 -, as well as aqueous oxygen [O2(aq)], was then tracked in an agarose tissue model. This provided an approximation of the H2O2, NO3 -, NO2 - and O2(aq) concentrations that might have been generated during the He plasma jet treatment of the 3D tumour. It is proposed that the He plasma jet can induce apoptosis within a tumour by the ‘deep’ delivery of H2O2, NO3 - and NO2 - coupled with O2(aq); the latter raising oxygen tension in hypoxic tissue.

Investigation of Plasmas Having Complex, Dynamic Evolving Morphology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bellan, Paul M.

2017-01-03

Three different types of plasmas have been investigated using both experimental and theoretical methods. The first type of plasma is dense, highly ionized, governed by magnetohydrodynamics, and highly dynamic. This plasma is relevant to solar coronal loops, astrophysical jets, and other situations where strong magnetic forces act on the plasma. A well-diagnosed laboratory experiment creates a magnetohydrodynamically driven highly collimated plasma jet. This jet undergoes a kink instability such that it rapidly develops a corkscrew shape. The kink causes lateral acceleration of the jet, and this lateral acceleration drives a Rayleigh-Taylor instability that in turn chokes the current flowing inmore » the jet and causes a magnetic reconnection. The magnetic reconnection causes electron and ion heating as well as emission of whistler waves. This entire sequence of events has been observed, measured in detail, and related to theoretical models. The second type of plasma is a transient rf-produced plasma used as a seed plasma for the magnetohydrodynamic experiments described above. Detailed atomic physics ionization processes have been investigated and modeled. The third type of plasma that has been studied is a dusty plasma where the dust particles are spontaneously growing ice grains. The rapid growth of the ice grains to large size and their highly ordered alignment has been investigated as well as collective motion of the ice grains, including well-defined flows on the surface of nested toroids. In addition to the experimental work described above, several related theoretical models have been developed, most notably a model showing how a complex interaction between gravity and magnetic fields on extremely weakly ionized plasma in an accretion disk provides an electric power source that can drive astrophysical jets associated with the accretion disk. Eighteen papers reporting this work have been published in a wide variety of journals.« less

LIF and fast imaging plasma jet characterization relevant for NTP biomedical applications

NASA Astrophysics Data System (ADS)

Riès, D.; Dilecce, G.; Robert, E.; Ambrico, P. F.; Dozias, S.; Pouvesle, J.-M.

2014-07-01

In the field of biomedical application, many publications report on non-thermal plasma jet potentialities for cell behaviour modifications in cancer treatment, wound healing or sterilization. However most previous plasma jet characterizations were performed when jets expend freely in air. Only recently has the influence of the targeted surface been properly considered. In this work, modifications induced by various types of targets, mimicking the biological samples, in the plasma propagation and production of hydroxyl radicals are evidenced through time-resolved intensified charge-coupled device imaging and laser-induced fluorescence (LIF) measurements. A LIF model, also specifically dedicated to estimate air and water penetration inside the jet, is used and proves to be well adapted to characterize the plasma jet under biomedical application conditions. It is shown that the plasma produced by the plasma gun counter-propagates after impinging the surface which, for the same operating parameters, leads to an increase of almost one order of magnitude in the maximum OH density (from ˜2 × 1013 cm-3 for open-air propagation to ˜1 × 1014 cm-3 for a grounded metal target). The nature of the target, especially its electrical conductivity, as well as gas flow rate and voltage amplitude are playing a key role in the production of hydroxyl radicals. The strong interplay between gas flow dynamics and plasma propagation is here confirmed by air and water distribution measurements. The need for a multi-diagnostic approach, as well as great care in setting up the in situ characterization of plasma jets, is here emphasized. Special attention must not only be paid to voltage amplitude and gas flow rate but also to the nature, humidity and conductivity of the target.

Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jablonowski, H.; Hammer, M. U.; Reuter, S.

Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100–400 nm) and, in particular, vacuum ultraviolet (VUV, 10–200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH{sub 2}O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stablemore » reactive oxygen species, hydrogen peroxide (H{sub 2}O{sub 2}) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O{sub 2}{sup •−}) and hydroxyl radicals ({sup •}OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.« less

Development of atmospheric pressure large area plasma jet for sterilisation and investigation of molecule and plasma interaction

NASA Astrophysics Data System (ADS)

Zerbe, Kristina; Iberler, Marcus; Jacoby, Joachim; Wagner, Christopher

2016-09-01

The intention of the project is the development and improvement of an atmospheric plasma jet based on various discharge forms (e.g. DBD, RF, micro-array) for sterilisation of biomedical equipment and investigation of biomolecules under the influence of plasma stress. The major objective is to design a plasma jet with a large area and an extended length. Due to the success on small scale plasma sterilisation the request of large area plasma has increased. Many applications of chemical disinfection in environmental and medical cleaning could thereby be complemented. Subsequently, the interaction between plasma and biomolecules should be investigated to improve plasma strerilisation. Special interest will be on non equilibrium plasma electrons affecting the chemical bindings of organic molecules.

Dynamics of Plasma Jets and Bubbles Launched into a Transverse Background Magnetic Field

NASA Astrophysics Data System (ADS)

Zhang, Yue

2017-10-01

A coaxial magnetized plasma gun has been utilized to launch both plasma jets (open B-field) and plasma bubbles (closed B-field) into a transverse background magnetic field in the HelCat (Helicon-Cathode) linear device at the University of New Mexico. These situations may have bearing on fusion plasmas (e.g. plasma injection for tokamak fueling, ELM pacing, or disruption mitigation) and astrophysical settings (e.g. astrophysical jet stability, coronal mass ejections, etc.). The magnetic Reynolds number of the gun plasma is 100 , so that magnetic advection dominates over magnetic diffusion. The gun plasma ram pressure, ρjetVjet2 >B02 / 2μ0 , the background magnetic pressure, so that the jet or bubble can easily penetrate the background B-field, B0. When the gun axial B-field is weak compared to the gun azimuthal field, a current-driven jet is formed with a global helical magnetic configuration. Applying the transverse background magnetic field, it is observed that the n = 1 kink mode is stabilized, while magnetic probe measurements show contrarily that the safety factor q(a) drops below unity. At the same time, a sheared axial jet velocity is measured. We conclude that the tension force arising from increasing curvature of the background magnetic field induces the measured sheared flow gradient above the theoretical kink-stabilization threshold, resulting in the emergent kink stabilization of the injected plasma jet. In the case of injected bubbles, spheromak-like plasma formation is verified. However, when the spheromak plasma propagates into the transverse background magnetic field, the typical self-closed global symmetry magnetic configuration does not hold any more. In the region where the bubble toroidal field opposed the background B-field, the magneto-Rayleigh-Taylor (MRT) instability has been observed. Details of the experiment setup, diagnostics, experimental results and theoretical analysis will be presented. Supported by the National Science Foundation under Grant No. AST-0613577 and the Army Research Office under Award No. W911NF1510480. This work performed in collaboration with D. Fisher, A. G. Lynn, M Gilmore, and S. C. Hsu.

Influence of Xe and Kr impurities on x-ray yield from debris-free plasma x-ray sources with an Ar supersonic gas jet irradiated by femtosecond near-infrared-wavelength laser pulses

NASA Astrophysics Data System (ADS)

Kantsyrev, V. L.; Schultz, K. A.; Shlyaptseva, V. V.; Petrov, G. M.; Safronova, A. S.; Petkov, E. E.; Moschella, J. J.; Shrestha, I.; Cline, W.; Wiewior, P.; Chalyy, O.

2016-11-01

Many aspects of physical phenomena occurring when an intense laser pulse with subpicosecond duration and an intensity of 1018-1019W /cm2 heats an underdense plasma in a supersonic clustered gas jet are studied to determine the relative contribution of thermal and nonthermal processes to soft- and hard-x-ray emission from debris-free plasmas. Experiments were performed at the University of Nevada, Reno (UNR) Leopard laser operated with a 15-J, 350-fs pulse and different pulse contrasts (107 or 105). The supersonic linear (elongated) nozzle generated Xe cluster-monomer gas jets as well as jets with Kr-Ar or Xe-Kr-Ar mixtures with densities of 1018-1019cm-3 . Prior to laser heating experiments, all jets were probed with optical interferometry and Rayleigh scattering to measure jet density and cluster distribution parameters. The supersonic linear jet provides the capability to study the anisotropy of x-ray yield from laser plasma and also laser beam self-focusing in plasma, which leads to efficient x-ray generation. Plasma diagnostics included x-ray diodes, pinhole cameras, and spectrometers. Jet signatures of x-ray emission from pure Xe gas, as well as from a mixture with Ar and Kr, was found to be very different. The most intense x-ray emission in the 1-9 KeV spectral region was observed from gas mixtures rather than pure Xe. Also, this x-ray emission was strongly anisotropic with respect to the direction of laser beam polarization. Non-local thermodynamic equilibrium (Non-LTE) models have been implemented to analyze the x-ray spectra to determine the plasma temperature and election density. Evidence of electron beam generation in the supersonic jet plasma was found. The influence of the subpicosecond laser pulse contrast (a ratio between the laser peak intensity and pedestal pulse intensity) on the jets' x-ray emission characteristics is discussed. Surprisingly, it was found that the x-ray yield was not sensitive to the prepulse contrast ratio.

Evolution of Photon and Particle Spectra in Compact, Luminous Objects

NASA Technical Reports Server (NTRS)

Eilek, Jean A.; Caroff, Lawrence J.

1995-01-01

Physical conditions in the radiating plasma in the cores of radio-strong quasars and active galactic nuclei cannot be derived from observations until the effects of relativistic aberration are understood. This requires determining both the bulk flow speeds and any wave or signal speed in the parsec-scale nuclear jets. In this project we studied several aspects of such waves. We considered constraints on jet deceleration by mass pickup, and found that bolometric luminosities of the active nuclei cannot constrain core jet speeds usefully. We also simulated observations of ballistic, helical trajectories and helical waves moving directly outwards along the jet. We found that ballistic trajectories are not allowed by the data; the helical features seen are very likely to be helical waves. We believe these are waves propagating in the jet plasma. To this end, we studied waves propagating in relativistic pair plasma jets. In particular, we undertook a program whose goal was to determine the nature of waves which can propagate in relativistic pair plasmas, and how such waves propagating in streaming jet plasma would be observed by an external observer. We developed the possibility of using pulsars as test cases for our models; this takes advantage of new technology in pulsar observations, and the similarity of the physical conditions in the pulsar magnetosphere to the dense, relativistic pair plasmas which exist in radio-strong quasars.

Capillary plasma jet: A low volume plasma source for life science applications

NASA Astrophysics Data System (ADS)

Topala, I.; Nagatsu, M.

2015-02-01

In this letter, we present results from multispectroscopic analysis of protein films, after exposure to a peculiar plasma source, i.e., the capillary plasma jet. This plasma source is able to generate very small pulsed plasma volumes, in kilohertz range, with characteristic dimensions smaller than 1 mm. This leads to specific microscale generation and transport of all plasma species. Plasma diagnosis was realized using general electrical and optical methods. Depending on power level and exposure duration, this miniature plasma jet can induce controllable modifications to soft matter targets. Detailed discussions on protein film oxidation and chemical etching are supported by results from absorption, X-ray photoelectron spectroscopy, and microscopy techniques. Further exploitation of principles presented here may consolidate research interests involving plasmas in biotechnologies and plasma medicine, especially in patterning technologies, modified biomolecule arrays, and local chemical functionalization.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Formation of a plasma jet of multiply charged ions in the interaction of a laser plasma with an external pulsed magnetic field

NASA Astrophysics Data System (ADS)

Dyakin, V. M.; Pikuz, T. A.; Skobelev, I. Yu; Faenov, A. Ya; Wolowski, J.; Karpinski, L.; Kasperczuk, A.; Pisarczyk, T.

1994-12-01

A dense jet of a plasma consisting of multiply charged ions was generated in the interaction of a laser plasma with a strong external axial magnetic field. Images were formed by spectral lines and the soft x-ray spectrum range of the plasma jet was obtained with a large-aperture spectrograph containing a mica crystal bent to form a spherical surface with a radius of R = 10 cm. A tenfold increase in the density of the He-like Mg XI plasma, compared with a freely expanding plasma, was observed at a distance of 5 mm from the target.

Experimental results from magnetized-jet experiments executed at the Jupiter Laser Facility

NASA Astrophysics Data System (ADS)

Manuel, M. J.-E.; Kuranz, C. C.; Rasmus, A. M.; Klein, S. R.; MacDonald, M. J.; Trantham, M. R.; Fein, J. R.; Belancourt, P. X.; Young, R. P.; Keiter, P. A.; Drake, R. P.; Pollock, B. B.; Park, J.; Hazi, A. U.; Williams, G. J.; Chen, H.

2015-12-01

Recent experiments at the Jupiter Laser Facility investigated magnetization effects on collimated plasma jets. Laser-irradiated plastic-cone-targets produced collimated, millimeter-scale plasma flows as indicated by optical interferometry. Proton radiography of these jets showed no indication of strong, self-generated magnetic fields, suggesting a dominantly hydrodynamic collimating mechanism. Targets were placed in a custom-designed solenoid capable of generating field strengths up to 5 T. Proton radiographs of the well-characterized B-field, without a plasma jet, suggested an external source of trapped electrons that affects proton trajectories. The background magnetic field was aligned with the jet propagation direction, as is the case in many astrophysical systems. Optical interferometry showed that magnetization of the plasma results in disruption of the collimated flow and instead produces a hollow cavity. This result is a topic of ongoing investigation.

Patterned graphene functionalization via mask-free scanning of micro-plasma jet under ambient condition

NASA Astrophysics Data System (ADS)

Ye, Dong; Wu, Shu-Qun; Yu, Yao; Liu, Lin; Lu, Xin-Pei; Wu, Yue

2014-03-01

In this work, a mask-free method is introduced for patterned nitrogen doping of graphene using a micro-plasma jet under ambient condition. Raman and X-ray photoelectron spectroscopy spectra indicate that nitrogen atoms are incorporated into the graphene lattice with the two-dimensional spatial distribution precisely controlled in the range of mm down to 10 μm. Since the chemistry of the micro-plasma jet can be controlled by the choice of the gas mixture, this direct writing process with micro-plasma jet can be a versatile approach for patterned functionalization of graphene with high spatial resolution. This could have promising applications in graphene-based electronics.

Non-thermal plasma jet without electrical shock for biomedical applications

NASA Astrophysics Data System (ADS)

Baik, Ku Youn; Kang, Han Lim; Kim, Junseong; Park, Shin Young; Bang, Ji Yun; Uhm, Han S.; Choi, Eun Ha; Cho, Guangsup

2013-10-01

A plasma jet without an electrical shock was generated through a Y-shaped tube in which voltages with opposite phases were applied to a pair of tubes. The plasma plume generated at the intersection had a plasma potential of a 60-90 V and high concentrations of reactive species sufficient to induce a high level of lethality on gram-negative bacteria on a tissue mimic. The selective lethality of bacteria on an epithelial-cell-containing tissue mimic could be modulated using oxidant and antioxidant chemicals, thereby leading to the possibility of a shock-reduced plasma jet for biomedical applications.

Effects of irradiation distance on supply of reactive oxygen species to the bottom of a Petri dish filled with liquid by an atmospheric O{sub 2}/He plasma jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawasaki, Toshiyuki, E-mail: kawasaki@nbu.ac.jp; Kusumegi, Shota; Kudo, Akihiro

The impact of irradiation distances on plasma jet-induced specific effects on the supply of reactive oxygen species (ROS) to the bottom of a Petri dish filled with liquid was investigated using a KI-starch gel reagent that can be employed as a ROS indicator even in water. O{sub 3} exposure experiments without plasma irradiation were also performed to elucidate the specific effects of the plasma jet. Relative concentrations of ROS transported to the bottom were evaluated using absorbance measurements. The results indicated that ROS supply to the bottom is markedly enhanced by the plasma jet irradiation at shorter irradiation distances, whereasmore » similar results could not be obtained for the O{sub 3} exposure. In these cases, the liquid mixing in the depth direction was also enhanced by the plasma jet irradiation only, and the supply of reactive atomic oxygen to the liquid surface was markedly increased as well.« less

Complex astrophysical experiments relating to jets, solar loops, and water ice dusty plasma

NASA Astrophysics Data System (ADS)

Bellan, P. M.; Zhai, X.; Chai, K. B.; Ha, B. N.

2015-10-01

> Recent results of three astrophysically relevant experiments at Caltech are summarized. In the first experiment magnetohydrodynamically driven plasma jets simulate astrophysical jets that undergo a kink instability. Lateral acceleration of the kinking jet spawns a Rayleigh-Taylor instability, which in turn spawns a magnetic reconnection. Particle heating and a burst of waves are observed in association with the reconnection. The second experiment uses a slightly different setup to produce an expanding arched plasma loop which is similar to a solar corona loop. It is shown that the plasma in this loop results from jets originating from the electrodes. The possibility of a transition from slow to fast expansion as a result of the expanding loop breaking free of an externally imposed strapping magnetic field is investigated. The third and completely different experiment creates a weakly ionized plasma with liquid nitrogen cooled electrodes. Water vapour injected into this plasma forms water ice grains that in general are ellipsoidal and not spheroidal. The water ice grains can become quite long (up to several hundred microns) and self-organize so that they are evenly spaced and vertically aligned.

Radial magnetic compression in the expelled jet of a plasma deflagration accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loebner, Keith T. K., E-mail: kloebner@stanford.edu; Underwood, Thomas C.; Mouratidis, Theodore

2016-02-29

A spectroscopic study of a pulsed plasma deflagration accelerator is carried out that confirms the existence of a strong compression in the emerging jet at the exit plane of the device. An imaging spectrometer is used to collect broadened Hα emission from a transaxial slice of the emerging jet at high spatial resolution, and the radial plasma density profile is computed from Voigt fits of the Abel inverted emissivity profiles. The plasma temperature, determined via Doppler broadening of impurity line emission, is compared against the temperature predictions of a radial magnetohydrodynamic equilibrium model applied to the measured density profiles. Empiricalmore » scaling laws developed for the plasma density, combined with the measured and predicted temperatures, indicate that a radially equilibrated Z-pinch is formed within the expelled plasma jet at the exit plane during the deflagration process.« less

Optical Emission Spectroscopy of an Atmospheric Pressure Plasma Jet During Tooth Bleaching Gel Treatment.

PubMed

Šantak, Vedran; Zaplotnik, Rok; Tarle, Zrinka; Milošević, Slobodan

2015-11-01

Optical emission spectroscopy was performed during atmospheric pressure plasma needle helium jet treatment of various tooth-bleaching gels. When the gel sample was inserted under the plasma plume, the intensity of all the spectral features increased approximately two times near the plasma needle tip and up to two orders of magnitude near the sample surface. The color change of the hydroxylapatite pastille treated with bleaching gels in conjunction with the atmospheric pressure plasma jet was found to be in correlation with the intensity of OH emission band (309 nm). Using argon as an additive to helium flow (2 L/min), a linear increase (up to four times) of OH intensity and, consequently, whitening (up to 10%) of the pastilles was achieved. An atmospheric pressure plasma jet activates bleaching gel, accelerates OH production, and accelerates tooth bleaching (up to six times faster).

Numerical and experimental study on a pulsed-dc plasma jet

NASA Astrophysics Data System (ADS)

Liu, X. Y.; Pei, X. K.; Lu, X. P.; Liu, D. W.

2014-06-01

A numerical and experimental study of plasma jet propagation in a low-temperature, atmospheric-pressure, helium jet in ambient air is presented. A self-consistent, multi-species, two-dimensional axially symmetric plasma model with detailed finite-rate chemistry of helium-air mixture composition is used to provide insights into the propagation of the plasma jet. The obtained simulation results suggest that the sheath forms near the dielectric tube inner surface and shields the plasma channel from the tube surface. The strong electric field at the edge of the dielectric field enhances the ionization in the air mixing layer; therefore, the streamer head becomes ring-shaped when the streamer runs out of the tube. The avalanche-to-streamer transition is the main mechanism of streamer advancement. Penning ionization dominates the ionization reactions and increases the electrical conductivity of the plasma channel. The simulation results are supported by experimental observations under similar discharge conditions.

Effect of nitrogen seeding on the energy losses and on the time scales of the electron temperature and density collapse of type-I ELMs in JET with the ITER-like wall

NASA Astrophysics Data System (ADS)

Frassinetti, L.; Dodt, D.; Beurskens, M. N. A.; Sirinelli, A.; Boom, J. E.; Eich, T.; Flanagan, J.; Giroud, C.; Jachmich, M. S.; Kempenaars, M.; Lomas, P.; Maddison, G.; Maggi, C.; Neu, R.; Nunes, I.; Perez von Thun, C.; Sieglin, B.; Stamp, M.; Contributors, JET-EFDA

2015-02-01

The baseline type-I ELMy H-mode scenario has been re-established in JET with the new tungsten MKII-HD divertor and beryllium on the main wall (hereafter called the ITER-like wall, JET-ILW). The first JET-ILW results show that the confinement is degraded by 20-30% in the baseline scenarios compared to the previous carbon wall JET (JET-C) plasmas. The degradation is mainly driven by the reduction in the pedestal temperature. Stored energies and pedestal temperature comparable to the JET-C have been obtained to date in JET-ILW baseline plasmas only in the high triangularity shape using N2 seeding. This work compares the energy losses during ELMs and the corresponding time scales of the temperature and density collapse in JET-ILW baseline plasmas with and without N2 seeding with similar JET-C baseline plasmas. ELMs in the JET-ILW differ from those with the carbon wall both in terms of time scales and energy losses. The ELM time scale, defined as the time to reach the minimum pedestal temperature soon after the ELM collapse, is ˜2 ms in the JET-ILW and lower than 1 ms in the JET-C. The energy losses are in the range ΔWELM/Wped ≈ 7-12% in the JET-ILW and ΔWELM/Wped ≈ 10-20% in JET-C, and fit relatively well with earlier multi-machine empirical scalings of ΔWELM/Wped with collisionality. The time scale of the ELM collapse seems to be related to the pedestal collisionality. Most of the non-seeded JET-ILW ELMs are followed by a further energy drop characterized by a slower time scale ˜8-10 ms (hereafter called slow transport events), that can lead to losses in the range ΔWslow/Wped ≈ 15-22%, slightly larger than the losses in JET-C. The N2 seeding in JET-ILW significantly affects the ELMs. The JET-ILW plasmas with N2 seeding are characterized by ELM energy losses and time scales similar to the JET-C and by the absence of the slow transport events.

Contoured-gap coaxial guns for imploding plasma liner experiments

NASA Astrophysics Data System (ADS)

Witherspoon, F. D.; Case, A.; Brockington, S.; Cassibry, J. T.; Hsu, S. C.

2014-10-01

Arrays of supersonic, high momentum flux plasma jets can be used as standoff compression drivers for generating spherically imploding plasma liners for driving magneto-inertial fusion, hence the name plasma-jet-driven MIF (PJMIF). HyperV developed linear plasma jets for the Plasma Liner Experiment (PLX) at LANL where two guns were successfully tested. Further development at HyperV resulted in achieving the PLX goal of 8000 μg at 50 km/s. Prior work on contoured-gap coaxial guns demonstrated an approach to control the blowby instability and achieved substantial performance improvements. For future plasma liner experiments we propose to use contoured-gap coaxial guns with small Minirailgun injectors. We will describe such a gun for a 60-gun plasma liner experiment. Discussion topics will include impurity control, plasma jet symmetry and topology (esp. related to uniformity and compactness), velocity capability, and techniques planned for achieving gun efficiency of >50% using tailored impedance matched pulse forming networks. Mach2 and UAH SPH code simulations will be included. Work supported by US DOE DE-FG02-05ER54810.

Spectroscopic studies of non-thermal plasma jet at atmospheric pressure formed in low-current nonsteady-state plasmatron for biomedical applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demkin, V. P.; Melnichuk, S. V.; Demkin, O. V.

The optical and electrophysical characteristics of the nonequilibrium low-temperature plasma formed by a low-current nonsteady-state plasmatron are experimentally investigated in the present work. It is demonstrated that experimental data on the optical diagnostics of the plasma jet can provide a basis for the construction of a self-consistent physical and mathematical plasma model and for the creation of plasma sources with controllable electrophysical parameters intended for the generation of the required concentration of active particles. Results of spectroscopic diagnostics of plasma of the low-current nonsteady-state plasmatron confirm that the given source is efficient for the generation of charged particles and short-wavelengthmore » radiation—important plasma components for biomedical problems of an increase in the efficiency of treatment of biological tissues by charged particles. Measurement of the spatial distribution of the plasma jet potential by the probe method has demonstrated that a negative space charge is formed in the plasma jet possibly due to the formation of electronegative oxygen ions.« less

Radiographic research of the Bi plasma jet formed by the vacuum arc discharge

NASA Astrophysics Data System (ADS)

Artyomov, A. P.; Rousskikh, A. G.; Fedunin, A. V.; Chaikovsky, S. A.; Zhigalin, A. S.; Oreshkin, V. I.

2017-05-01

The results of experiments on a soft x-ray radiography (≈ 1-2 keV) of a bismuth plasma formed by the high-current vacuum arc discharge are represented. The plasma gun with the arc current ≈ 60 kA and the current rise time ≈ 7 μs was used to produce the Bi plasma jet. The compact pulsed radiograph XPG-1 (250 kA, 220 ns) with an X-pinch load consisting of four Mo wires with a diameter 25 μm was used as a source of the soft X-ray radiation. The X-ray backlighting images of the researched plasma jet and the Bi step-wedge with a step thickness of ≈ 100 nm were recorded simultaneously in the course of the experiment. A comparison of the plasma jet x-ray image with the current trace has enabled to estimate dependencies of the linear mass on the arc current. The experiments have shown that when the arc current density reaches ≈ 3·105 A/cm2, the evaporation rate of the electrode material reaches ≈ 100 μg/μs, that under the plasma velocity ≈ 0.5 cm/μs, provides a plasma jet linear mass ≈ 200 μg/cm. At a distance of ≈ 1-2 mm from the arc cathode surface, the sharp increase of the jet linear mass (up to ≈ 500 μg/cm) occurred.

Production of simplex RNS and ROS by nanosecond pulse N2/O2 plasma jets with homogeneous shielding gas for inducing myeloma cell apoptosis

NASA Astrophysics Data System (ADS)

Liu, Zhijie; Xu, Dehui; Liu, Dingxin; Cui, Qingjie; Cai, Haifeng; Li, Qiaosong; Chen, Hailan; Kong, Michael G.

2017-05-01

In this paper, atmospheric pressure N2/O2 plasma jets with homogeneous shielding gas excited by nanosecond pulse are obtained to generate simplex reactive nitrogen species (RNS) and reactive oxygen species (ROS), respectively, for the purpose of studying the simplex RNS and ROS to induce the myeloma cell apoptosis with the same discharge power. The results reveal that the cell death rate by the N2 plasma jet with N2 shielding gas is about two times that of the O2 plasma jet with O2 shielding gas for the equivalent treatment time. By diagnosing the reactive species of ONOO-, H2O2, OH and \\text{O}2- in medium, our findings suggest the cell death rate after plasma jets treatment has a positive correlation with the concentration of ONOO-. Therefore, the ONOO- in medium is thought to play an important role in the process of inducing myeloma cell apoptosis.

Nanosecond pulsed humid Ar plasma jet in air: shielding, discharge characteristics and atomic hydrogen production

NASA Astrophysics Data System (ADS)

Yatom, Shurik; Luo, Yuchen; Xiong, Qing; Bruggeman, Peter J.

2017-10-01

Gas phase non-equilibrium plasmas jets containing water vapor are of growing interest for many applications. In this manuscript, we report a detailed study of an atmospheric pressure nanosecond pulsed Ar  +  0.26% H2O plasma jet. The plasma jet operates in an atmospheric pressure air surrounding but is shielded with a coaxial argon flow to limit the air diffusion into the jet effluent core. The jet impinges on a metal plate electrode and produces a stable plasma filament (transient spark) between the needle electrode in the jet and the metal plate. The stable plasma filament is characterized by spatially and time resolved electrical and optical diagnostics. This includes Rayleigh scattering, Stark broadening of the hydrogen Balmer lines and two-photon absorption laser induced fluorescence (TaLIF) to obtain the gas temperature, the electron density and the atomic hydrogen density respectively. Electron densities and atomic hydrogen densities up to 5 × 1022 m-3 and 2 × 1022 m-3 have been measured. This shows that atomic hydrogen is one of the main species in high density Ar-H2O plasmas. The gas temperature does not exceed 550 K in the core of the plasma. To enable in situ calibration of the H TaLIF at atmospheric pressure a previously published O density calibration scheme is extended to include a correction for the line profiles by including overlap integrals as required by H TaLIF. The line width of H TaLIF, due to collision broadening has the same trend as the neutral density obtained by Rayleigh scattering. This suggests the possibility to use this technique to in situ probe neutral gas densities.

Magnetic Black Hole Waves

NASA Image and Video Library

2015-07-09

This cartoon shows how magnetic waves, called Alfvén S-waves, propagate outward from the base of black hole jets. The jet is a flow of charged particles, called a plasma, which is launched by a black hole. The jet has a helical magnetic field (yellow coil) permeating the plasma. The waves then travel along the jet, in the direction of the plasma flow, but at a velocity determined by both the jet's magnetic properties and the plasma flow speed. The BL Lac jet examined in a new study is several light-years long, and the wave speed is about 98 percent the speed of light. Fast-moving magnetic waves emanating from a distant supermassive black hole undulate like a whip whose handle is being shaken by a giant hand, according to a study using data from the National Radio Astronomy Observatory's Very Long Baseline Array. Scientists used this instrument to explore the galaxy/black hole system known as BL Lacertae (BL Lac) in high resolution. http://photojournal.jpl.nasa.gov/catalog/PIA19822

Applied axial magnetic field effects on laboratory plasma jets: Density hollowing, field compression, and azimuthal rotation

DOE PAGES

Byvank, T.; Banasek, J. T.; Potter, W. M.; ...

2017-12-07

We experimentally measure the effects of an applied axial magnetic field (B z) on laboratory plasma jets and compare experimental results with numerical simulations using an extended magnetohydrodynamics code. A 1 MA peak current, 100 ns rise time pulse power machine is used to generate the plasma jet. On application of the axial field, we observe on-axis density hollowing and a conical formation of the jet using interferometry, compression of the applied B z using magnetic B-dot probes, and azimuthal rotation of the jet using Thomson scattering. Experimentally, we find densities ≤ 5×10 17 cm -3 on-axis relative to jetmore » densities of ≥ 3×10 18 cm -3. For aluminum jets, 6.5 ± 0.5 mm above the foil, we find on-axis compression of the applied 1.0 ± 0.1 T B z to a total 2.4 ± 0.3 T, while simulations predict a peak compression to a total 3.4 T at the same location. On the aluminum jet boundary, we find ion azimuthal rotation velocities of 15-20 km/s, while simulations predict 14 km/s at the density peak. We discuss possible sources of discrepancy between the experiments and simulations, including: surface plasma on B-dot probes, optical fiber spatial resolution, simulation density floors, and 2D vs. 3D simulation effects. Lastly, this quantitative comparison between experiments and numerical simulations helps elucidate the underlying physics that determine the plasma dynamics of magnetized plasma jets.« less

Applied axial magnetic field effects on laboratory plasma jets: Density hollowing, field compression, and azimuthal rotation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byvank, T.; Banasek, J. T.; Potter, W. M.

We experimentally measure the effects of an applied axial magnetic field (B z) on laboratory plasma jets and compare experimental results with numerical simulations using an extended magnetohydrodynamics code. A 1 MA peak current, 100 ns rise time pulse power machine is used to generate the plasma jet. On application of the axial field, we observe on-axis density hollowing and a conical formation of the jet using interferometry, compression of the applied B z using magnetic B-dot probes, and azimuthal rotation of the jet using Thomson scattering. Experimentally, we find densities ≤ 5×10 17 cm -3 on-axis relative to jetmore » densities of ≥ 3×10 18 cm -3. For aluminum jets, 6.5 ± 0.5 mm above the foil, we find on-axis compression of the applied 1.0 ± 0.1 T B z to a total 2.4 ± 0.3 T, while simulations predict a peak compression to a total 3.4 T at the same location. On the aluminum jet boundary, we find ion azimuthal rotation velocities of 15-20 km/s, while simulations predict 14 km/s at the density peak. We discuss possible sources of discrepancy between the experiments and simulations, including: surface plasma on B-dot probes, optical fiber spatial resolution, simulation density floors, and 2D vs. 3D simulation effects. Lastly, this quantitative comparison between experiments and numerical simulations helps elucidate the underlying physics that determine the plasma dynamics of magnetized plasma jets.« less

Shielding methods of quasilaminar jets outflowing from plasma torch with interelectrode insert

NASA Astrophysics Data System (ADS)

Solonenko, O. P.; Smirnov, A. V.

2017-05-01

Investigations of two methods of protection against mixing of surrounding air atmosphere with the free lengthy jets outflowing at low Reynolds numbers from plasma torches with interelectrode insertion (IEI) were carried out. The offered methods allow to significantly reduce the mixing of oxygen with plasma jets that gives a possibility of synthesis, treatment and spraying of powder materials, as well as melting of coatings critical to oxidation.

Dynamics of Magnetized Plasma Jets and Bubbles Launched into a Background Magnetized Plasma

NASA Astrophysics Data System (ADS)

Wallace, B.; Zhang, Y.; Fisher, D. M.; Gilmore, M.

2016-10-01

The propagation of dense magnetized plasma, either collimated with mainly azimuthal B-field (jet) or toroidal with closed B-field (bubble), in a background plasma occurs in a number of solar and astrophysical cases. Such cases include coronal mass ejections moving in the background solar wind and extragalactic radio lobes expanding into the extragalactic medium. Understanding the detailed MHD behavior is crucial for correctly modeling these events. In order to further the understanding of such systems, we are investigating the injection of dense magnetized jets and bubbles into a lower density background magnetized plasma using a coaxial plasma gun and a background helicon or cathode plasma. In both jet and bubble cases, the MHD dynamics are found to be very different when launched into background plasma or magnetic field, as compared to vacuum. In the jet case, it is found that the inherent kink instability is stabilized by velocity shear developed due to added magnetic tension from the background field. In the bubble case, rather than directly relaxing to a minimum energy Taylor state (spheromak) as in vacuum, there is an expansion asymmetry and the bubble becomes Rayleigh-Taylor unstable on one side. Recent results will be presented. Work supported by the Army Research Office Award No. W911NF1510480.

FAR-TECH's Nanoparticle Plasma Jet System and its Application to Disruptions, Deep Fueling, and Diagnostics

NASA Astrophysics Data System (ADS)

Thompson, J. R.; Bogatu, I. N.; Galkin, S. A.; Kim, J. S.

2012-10-01

Hyper-velocity plasma jets have potential applications in tokamaks for disruption mitigation, deep fueling and diagnostics. Pulsed power based solid-state sources and plasma accelerators offer advantages of rapid response and mass delivery at high velocities. Fast response is critical for some disruption mitigation scenario needs, while high velocity is especially important for penetration into tokamak plasma and its confining magnetic field, as in the case of deep fueling. FAR-TECH is developing the capability of producing large-mass hyper-velocity plasma jets. The prototype solid-state source has produced: 1) >8.4 mg of H2 gas only, and 2) >25 mg of H2 and >180 mg of C60 in a H2/C60 gas mixture. Using a coaxial plasma gun coupled to the source, we have successfully demonstrated the acceleration of composite H/C60 plasma jets, with momentum as high as 0.6 g.km/s, and containing an estimated C60 mass of ˜75 mg. We present the status of FAR-TECH's nanoparticle plasma jet system and discuss its application to disruptions, deep fueling, and diagnostics. A new TiH2/C60 solid-state source capable of generating significantly higher quantities of H2 and C60 in <0.5 ms will be discussed.

Atmospheric pressure plasma jet with high-voltage power supply based on piezoelectric transformer.

PubMed

Babij, Michał; Kowalski, Zbigniew W; Nitsch, Karol; Silberring, Jerzy; Gotszalk, Teodor

2014-05-01

The dielectric barrier discharge plasma jet, an example of the nonthermal atmospheric pressure plasma jet (APPJ), generates low-temperature plasmas that are suitable for the atomization of volatile species and can also be served as an ionization source for ambient mass and ion mobility spectrometry. A new design of APPJ for mass spectrometry has been built in our group. In these plasma sources magnetic transformers (MTs) and inductors are typically used in power supplies but they present several drawbacks that are even more evident when dealing with high-voltage normally used in APPJs. To overcome these disadvantages, high frequency generators with the absence of MT are proposed in the literature. However, in the case of miniaturized APPJs these conventional power converters, built of ferromagnetic cores and inductors or by means of LC resonant tank circuits, are not so useful as piezoelectric transformer (PT) based power converters due to bulky components and small efficiency. We made and examined a novel atmospheric pressure plasma jet with PT supplier served as ionization source for ambient mass spectrometry, and especially mobile spectrometry where miniaturization, integration of components, and clean plasma are required. The objective of this paper is to describe the concept, design, and implementation of this miniaturized piezoelectric transformer-based atmospheric pressure plasma jet.

Atmospheric pressure plasma jet with high-voltage power supply based on piezoelectric transformer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babij, Michał; Kowalski, Zbigniew W., E-mail: zbigniew.w.kowalski@pwr.wroc.pl; Nitsch, Karol

The dielectric barrier discharge plasma jet, an example of the nonthermal atmospheric pressure plasma jet (APPJ), generates low-temperature plasmas that are suitable for the atomization of volatile species and can also be served as an ionization source for ambient mass and ion mobility spectrometry. A new design of APPJ for mass spectrometry has been built in our group. In these plasma sources magnetic transformers (MTs) and inductors are typically used in power supplies but they present several drawbacks that are even more evident when dealing with high-voltage normally used in APPJs. To overcome these disadvantages, high frequency generators with themore » absence of MT are proposed in the literature. However, in the case of miniaturized APPJs these conventional power converters, built of ferromagnetic cores and inductors or by means of LC resonant tank circuits, are not so useful as piezoelectric transformer (PT) based power converters due to bulky components and small efficiency. We made and examined a novel atmospheric pressure plasma jet with PT supplier served as ionization source for ambient mass spectrometry, and especially mobile spectrometry where miniaturization, integration of components, and clean plasma are required. The objective of this paper is to describe the concept, design, and implementation of this miniaturized piezoelectric transformer-based atmospheric pressure plasma jet.« less

Z-pinch Plasma Temperature and Implosion Velocity from Laboratory Plasma Jets using Thomson Scattering

NASA Astrophysics Data System (ADS)

Banasek, Jacob; Byvank, Tom; Kusse, Bruce; Hammer, David

2016-10-01

We discuss the use of collective Thomson scattering to determine the implosion velocity and other properties of laboratory plasma jets. The plasma jet is created using a 1 MA pulsed power machine with a 15 μm Al radial foil load. The Thomson scattering laser has a maximum energy of 10 J at 526.5 nm with a pulse duration of 3 ns. Using a time gated ICCD camera and spectrometer system we are able to record the scattered spectrum from 9 or 18 regions along the laser path with sub-mm spatial resolution. Collecting scattered radiation from the same area at two different angles simultaneously enables determination of both the radial and azimuthal velocities. The scattered spectrum for non-magnetized jets indicates a radial implosion velocity of 27 km/s into the jets. A determination of ion and electron temperatures from the scattered spectrum is in progress. Comparing results using a laser energy of 10 J and 1 J shows noticeable effects on plasma jet properties when using 10 J. Therefore the lower laser energy must be used to determine the plasma properties. This research is supported by the NNSA Stewardship Sciences Academic Programs under DOE Cooperative Agreement DE-NA0001836.

Exploring lower-cost pathways to economical fusion power

DOE PAGES

Hsu, Scott C.

2017-08-04

This project, the Plasma Liner Experiment–ALPHA (PLX-α)5,is one of nine projects supported by the ALPHA Program6 of the Advanced Research Projects Agency–Energy (ARPA-E) of the U.S. Department of Energy (DOE). We use innovative, low-cost coaxial plasma guns (Fig. 1), developed and built by partner HyperV Technologies Corp.7, to launch a spherically converging array of supersonic plasma jets toward the middle of a large, spherical vacuum chamber (Fig. 2). A key near-term goal of PLX-α is to merge up to 60 plasma jets to form a spherically imploding plasma liner, as a low-cost, high-shot-rate driver for compressing magnetised target plasmas tomore » fusion conditions. Our approach is known as plasma-jet-driven MIF (or PJMIF)8. A new startup company HyperJet Fusion Corporation (which recently received seed funding from Strong Atomics, LLC, a new fusion venture fund) aims to develop PJMIF under continued public and private sponsorship.« less

Exploring lower-cost pathways to economical fusion power

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsu, Scott C.

This project, the Plasma Liner Experiment–ALPHA (PLX-α)5,is one of nine projects supported by the ALPHA Program6 of the Advanced Research Projects Agency–Energy (ARPA-E) of the U.S. Department of Energy (DOE). We use innovative, low-cost coaxial plasma guns (Fig. 1), developed and built by partner HyperV Technologies Corp.7, to launch a spherically converging array of supersonic plasma jets toward the middle of a large, spherical vacuum chamber (Fig. 2). A key near-term goal of PLX-α is to merge up to 60 plasma jets to form a spherically imploding plasma liner, as a low-cost, high-shot-rate driver for compressing magnetised target plasmas tomore » fusion conditions. Our approach is known as plasma-jet-driven MIF (or PJMIF)8. A new startup company HyperJet Fusion Corporation (which recently received seed funding from Strong Atomics, LLC, a new fusion venture fund) aims to develop PJMIF under continued public and private sponsorship.« less

The kINPen—a review on physics and chemistry of the atmospheric pressure plasma jet and its applications

NASA Astrophysics Data System (ADS)

Reuter, Stephan; von Woedtke, Thomas; Weltmann, Klaus-Dieter

2018-06-01

The kINPen® plasma jet was developed from laboratory prototype to commercially available non-equilibrium cold plasma jet for various applications in materials research, surface treatment and medicine. It has proven to be a valuable plasma source for industry as well as research and commercial use in plasma medicine, leading to very successful therapeutic results and its certification as a medical device. This topical review presents the different kINPen plasma sources available. Diagnostic techniques applied to the kINPen are introduced. The review summarizes the extensive studies of the physics and plasma chemistry of the kINPen performed by research groups across the world, and closes with a brief overview of the main application fields.

LARGE—A Plasma Torch for Surface Chemistry Applications and CVD Processes—A Status Report

NASA Astrophysics Data System (ADS)

Zimmermann, Stephan; Theophile, Eckart; Landes, Klaus; Schein, Jochen

2008-12-01

The LARGE ( LONG ARG GENERATOR) is a new generation DC-plasma torch featuring an extended arc which is operated with a perpendicular gas flow to create a wide (up to 45 cm) plasma jet well suited for large area plasma processing. Using plasma diagnostic systems like high speed imaging, enthalpy probe, emission spectroscopy, and tomography, the LARGE produced plasma jet characteristics have been measured and sources of instability have been identified. With a simple model/simulation of the system LARGE III-150 and numerous experimental results, a new nozzle configuration and geometry (LARGE IV-150) has been designed, which produces a more homogenous plasma jet. These improvements enable the standard applications of the LARGE plasma torch (CVD coating process and surface activation process) to operate with higher efficiency.

Schlieren flow visualization of helium atmospheric plasma jet and influence of the gas flow rate and applied voltage frequency

NASA Astrophysics Data System (ADS)

Borghei, S. M.; Vaziri, N.; Alibabaei, S.

2018-03-01

We used schlieren photography to visualize the influence of gas flow rates of 1, 2.5, 5, 10 L/min and of the applied voltage frequency on a helium atmospheric plasma jet induced at the nozzle of a capillary tube. The expansion of the gas in the surrounding medium (air) was analyzed in the two different modes – plasma on/plasma off. Changes in the above parameters affect the gas flow regime and the hydrodynamics of the jet.

Experimental results from magnetized-jet experiments executed at the Jupiter Laser Facility

DOE PAGES

Manuel, M. J. -E.; Kuranz, C. C.; Rasmus, A. M.; ...

2014-08-20

Recent experiments at the Jupiter Laser Facility investigated magnetization effects on collimated plasma jets. Laser-irradiated plastic-cone-targets produced collimated, millimeter-scale plasma flows as indicated by optical interferometry. Proton radiography of these jets showed no indication of strong, self-generated magnetic fields, suggesting a dominantly hydrodynamic collimating mechanism. Targets were placed in a custom-designed solenoid capable of generating field strengths up to 5 T. Proton radiographs of the well-characterized B-field, without a plasma jet, suggested an external source of trapped electrons that affects proton trajectories. The background magnetic field was aligned with the jet propagation direction, as is the case in many astrophysicalmore » systems. Optical interferometry showed that magnetization of the plasma results in disruption of the collimated flow and instead produces a hollow cavity. Furthermore, this result is a topic of ongoing investigation.« less

Experimental results from magnetized-jet experiments executed at the Jupiter Laser Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manuel, M. J. -E.; Kuranz, C. C.; Rasmus, A. M.

Recent experiments at the Jupiter Laser Facility investigated magnetization effects on collimated plasma jets. Laser-irradiated plastic-cone-targets produced collimated, millimeter-scale plasma flows as indicated by optical interferometry. Proton radiography of these jets showed no indication of strong, self-generated magnetic fields, suggesting a dominantly hydrodynamic collimating mechanism. Targets were placed in a custom-designed solenoid capable of generating field strengths up to 5 T. Proton radiographs of the well-characterized B-field, without a plasma jet, suggested an external source of trapped electrons that affects proton trajectories. The background magnetic field was aligned with the jet propagation direction, as is the case in many astrophysicalmore » systems. Optical interferometry showed that magnetization of the plasma results in disruption of the collimated flow and instead produces a hollow cavity. Furthermore, this result is a topic of ongoing investigation.« less

Spatial-temporal diagnostics of the system of a plasma stream interacting with a surface of heat resistant material

NASA Astrophysics Data System (ADS)

Chinnov, V. F.; Sargsyan, M. A.; Gadzhiev, M. Kh; Khromov, M. A.; Kavyrshin, D. I.; Chistolinov, A. V.

2018-01-01

In an automated measuring complex using optical and spectral methods the spatial and temporal changes in the parameters and composition of nitrogen plasma jet were investigated. The plasma jet was flowing out of the nozzle of the plasma torch with 10-12 kK temperature and acting on the sample of MPG-6 graphite. Due to the heating of the sample to the temperatures of 2.5-3 kK the influence of the sublimating material of the sample on the plasma composition and temperature in the near-surface region of the sample was investigated. An original method based on the analysis of movement of optical inhomogeneities in the plasma flow was used to estimate the plasma jet velocity in the region where it interacts with the sample. The combined analysis of the results of two-positioning video recordings opens up the possibility of determining spatial-temporal distributions of the plasma jet velocities, in medium and high pressure environments, in the ranges from few to thousands of m/s and 3-15 kK temperatures.

Slowing of magnetic reconnection concurrent with weakening plasma inflows and increasing collisionality in strongly-driven laser-plasma experiments

DOE PAGES

Rosenberg, M.  J.; Li, C.  K.; Fox, W.; ...

2015-05-20

An evolution of magnetic reconnection behavior, from fast jets to the slowing of reconnection and the establishment of a stable current sheet, has been observed in strongly-driven, β ≲ 20 laser-produced plasma experiments. This process has been inferred to occur alongside a slowing of plasma inflows carrying the oppositely-directed magnetic fields as well as the evolution of plasma conditions from collisionless to collisional. High-resolution proton radiography has revealed unprecedented detail of the forced interaction of magnetic fields and super-Alfvénic electron jets (V jet~ 20V A) ejected from the reconnection region, indicating that two-fluid or collisionless magnetic reconnection occurs early inmore » time. The absence of jets and the persistence of strong, stable magnetic fields at late times indicates that the reconnection process slows down, while plasma flows stagnate and plasma conditions evolve to a cooler, denser, more collisional state. These results demonstrate that powerful initial plasma flows are not sufficient to force a complete reconnection of magnetic fields, even in the strongly-driven regime.« less

The Mochi LabJet Experiment for Measurements of Canonical Helicity Injection in a Laboratory Astrophysical Jet

NASA Astrophysics Data System (ADS)

You, Setthivoine; von der Linden, Jens; Sander Lavine, Eric; Carroll, Evan Grant; Card, Alexander; Quinley, Morgan; Azuara-Rosales, Manuel

2018-06-01

The Mochi device is a new pulsed power plasma experiment designed to produce long, collimated, stable, magnetized plasma jets when set up in the LabJet configuration. The LabJet configuration aims to simulate an astrophysical jet in the laboratory by mimicking an accretion disk threaded by a poloidal magnetic field with concentric planar electrodes in front of a solenoidal coil. The unique setup consists of three electrodes, each with azimuthally symmetric gas slits. Two of the electrodes are biased independently with respect to the third electrode to control the radial electric field profile across the poloidal bias magnetic field. This design approximates a shear azimuthal rotation profile in an accretion disk. The azimuthally symmetric gas slits provide a continuously symmetric mass source at the footpoint of the plasma jet, so any azimuthal rotation of the plasma jet is not hindered by a discrete number of gas holes. The initial set of diagnostics consists of current Rogowski coils, voltage probes, magnetic field probe arrays, an interferometer and ion Doppler spectroscopy, supplemented by a fast ion gauge and a retarding grid energy analyzer. The measured parameters of the first plasmas are ∼1022 m‑3, ∼0.4 T, and 5–25 eV, with velocities of ∼20–80 km s‑1. The combination of a controllable electric field profile, a flared poloidal magnetic field, and azimuthally symmetric mass sources in the experiment successfully produces short-lived (∼10 μs, ≳5 Alfvén times) collimated magnetic jets with a ∼10:1 aspect ratio and long-lived (∼100 μs, ≳40 Alfvén times) flow-stabilized, collimated, magnetic jets with a ∼30:1 aspect ratio.

Comparison of Magnetospheric Multiscale Ion Jet Signatures with Predicted Reconnection Site Locations at the Magnetopause

NASA Technical Reports Server (NTRS)

Petrinec, S. M.; Burch, J. L.; Fuselier, S. A.; Gomez, R. G.; Lewis, W.; Trattner, K. J.; Ergun, R.; Mauk, B.; Pollock, C. J.; Schiff, C.;

Degradation of bromophenol blue molecule during argon plasma jet irradiation

NASA Astrophysics Data System (ADS)

Matinzadeh, Ziba; Shahgoli, Farhad; Abbasi, Hamed; Ghoranneviss, Mahmood; Salem, Mohammad Kazem

2017-06-01

The aim of this paper is to study degradation of a bromophenol blue molecule (C19H10Br4O5S) using direct irradiation of cold atmospheric argon plasma jet. The pH of the bromophenol blue solution has been measured as well as its absorbance spectra and conductivity before and after the irradiation of non-thermal plasma jet in various time durations. The results indicated that the lengths of conjugated systems in the molecular structure of bromophenol blue decreased, and that the bromophenol blue solution was decolorized as a result of the decomposition of bromophenol blue. This result shows that non-thermal plasma jet irradiation is capable of decomposing, and can also be used for water purification.

Comparison of pulsating DC and DC power air-water plasma jet: A method to decrease plume temperature and increase ROS

NASA Astrophysics Data System (ADS)

Liu, K.; Hu, H.; Lei, J.; Hu, Y.; Zheng, Z.

2016-12-01

Most air-water plasma jets are rich in hydroxyl radicals (•OH), but the plasma has higher temperatures, compared to that of pure gas, especially when using air as working gas. In this paper, pulsating direct current (PDC) power was used to excite the air-water plasma jet to reduce plume temperature. In addition to the temperature, other differences between PDC and DC plasma jets are not yet clear. Thus, comparative studies of those plasmas are performed to evaluate characteristics, such as breakdown voltage, temperature, and reactive oxygen species. The results show that the plume temperature of PDC plasma is roughly 5-10 °C lower than that of DC plasma in the same conditions. The •OH content of PDC is lower than that of DC plasma, whereas the O content of PDC plasma is higher. The addition of water leads in an increase in the plume temperature and in the production of •OH with two types of power supplies. The production of O inversely shows a declining tendency with higher water ratio. The most important finding is that the PDC plasma with 100% water ratio achieves lower temperature and more abundant production of •OH and O, compared with DC plasma with 0% water ratio.

The collective emission of electromagnetic waves from astrophysical jets - Luminosity gaps, BL Lacertae objects, and efficient energy transport

NASA Technical Reports Server (NTRS)

Baker, D. N.; Borovsky, Joseph E.; Benford, Gregory; Eilek, Jean A.

1988-01-01

A model of the inner portions of astrophysical jets is constructed in which a relativistic electron beam is injected from the central engine into the jet plasma. This beam drives electrostatic plasma wave turbulence, which leads to the collective emission of electromagnetic waves. The emitted waves are beamed in the direction of the jet axis, so that end-on viewing of the jet yields an extremely bright source (BL Lacertae object). The relativistic electron beam may also drive long-wavelength electromagnetic plasma instabilities (firehose and Kelvin-Helmholtz) that jumble the jet magnetic field lines. After a sufficient distance from the core source, these instabilities will cause the beamed emission to point in random directions and the jet emission can then be observed from any direction relative to the jet axis. This combination of effects may lead to the gap turn-on of astrophysical jets. The collective emission model leads to different estimates for energy transport and the interpretation of radio spectra than the conventional incoherent synchrotron theory.

Atmospheric pressure resistive barrier air plasma jet induced bacterial inactivation in aqueous environment

NASA Astrophysics Data System (ADS)

Thiyagarajan, Magesh; Sarani, Abdollah; Gonzales, Xavier

2013-03-01

An atmospheric pressure resistive barrier air plasma jet is designed to inactivate bacteria in aqueous media in direct and indirect exposure modes of treatment. The resistive barrier plasma jet is designed to operate at both dc and standard 50-60 Hz low frequency ac power input and the ambient air at 50% humidity level was used as the operating gas. The voltage-current characteristics of the plasma jet were analyzed and the operating frequency of the discharge was measured to be 20 kHz and the plasma power was measured to be 26 W. The plasma jet rotational temperatures (Trot) are obtained from the optical emission spectra, from the N2C-B(2+) transitions by matching the experimental spectrum results with the Spectra Air (SPECAIR) simulation spectra. The reactive oxygen and nitrogen species were measured using optical emission spectroscopy and gas analyzers, for direct and indirect treatment modes. The nitric oxides (NO) were observed to be the predominant long lived reactive nitrogen species produced by the plasma. Three different bacteria including Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative), and Neisseria meningitidis (Gram-negative) were suspended in an aqueous media and treated by the resistive barrier air plasma jet in direct and indirect exposure modes. The results show that a near complete bacterial inactivation was achieved within 120 s for both direct and indirect plasma treatment of S. aureus and E. coli bacteria. Conversely, a partial inactivation of N. meningitidis was observed by 120 s direct plasma exposure and insignificant inactivation was observed for the indirect plasma exposure treatment. Plasma induced shifts in N. meningitidis gene expression was analyzed using pilC gene expression as a representative gene and the results showed a reduction in the expression of the pilC gene compared to untreated samples suggesting that the observed protection against NO may be regulated by other genes.

Astrophysics of magnetically collimated jets generated from laser-produced plasmas.

PubMed

Ciardi, A; Vinci, T; Fuchs, J; Albertazzi, B; Riconda, C; Pépin, H; Portugall, O

2013-01-11

The generation of astrophysically relevant jets, from magnetically collimated, laser-produced plasmas, is investigated through three-dimensional, magnetohydrodynamic simulations. We show that for laser intensities I∼10(12)-10(14) W cm(-2), a magnetic field in excess of ∼0.1  MG, can collimate the plasma plume into a prolate cavity bounded by a shock envelope with a standing conical shock at its tip, which recollimates the flow into a supermagnetosonic jet beam. This mechanism is equivalent to astrophysical models of hydrodynamic inertial collimation, where an isotropic wind is focused into a jet by a confining circumstellar toruslike envelope. The results suggest an alternative mechanism for a large-scale magnetic field to produce jets from wide-angle winds.

Atmospheric pressure plasma jet for bacterial decontamination and property improvement of fruit and vegetable processing wastewater

NASA Astrophysics Data System (ADS)

Mohamed, Abdel-Aleam H.; Shariff, Samir M. Al; Ouf, Salama A.; Benghanem, Mohamed

2016-05-01

An atmospheric pressure plasma jet was tested for decontaminating and improving the characteristics of wastewater derived from blackberry, date palm, tomato and beetroot processing industries. The jet was generated by blowing argon gas through a cylindrical alumina tube while a high voltage was applied between two electrodes surrounding the tube. Oxygen gas was mixed with argon at the rate of 0.2% and the argon mass flow was fixed at 4.5 slm. Images show that the generated plasma jet penetrated the treated wastewater samples. Plasma emission spectra show the presence of O and OH radicals as well as excited molecular nitrogen and argon. Complete decontamination of wastewater derived from date palm and tomato processing was achieved after 120 and 150 s exposure to the plasma jet, respectively. The bacterial count of wastewater from blackberry and beetroot was reduced by 0.41 and 2.24 log10 colony-forming units (CFU) per ml, respectively, after 180 s. Escherichia coli was the most susceptible bacterial species to the cold plasma while Shigella boydii had the minimum susceptibility, recording 1.30 and 3.34 log10 CFU ml-1, respectively, as compared to the 7.00 log10 initial count. The chemical oxygen demands of wastewater were improved by 57.5-93.3% after 180 s exposure to the plasma jet being tested. The endotoxins in the wastewater were reduced by up to 90.22%. The variation in plasma effectiveness is probably related to the antioxidant concentration of the different investigated wastewaters.

Characteristics of Plasma Synthetic Jet Actuators in Crossflow

NASA Astrophysics Data System (ADS)

Santhanakrishnan, Arvind; Jacob, Jamey

2006-11-01

The plasma synthetic jet actuator (PSJA) consists of two annular electrodes separated by dielectric material that results in a circular region of dielectric barrier discharge plasma. In quiescent conditions, this plasma ring produces a synthetic jet which can be used for active flow control applications. Unsteady pulsing of the actuator results in the formation of multiple primary and secondary vortex rings, the latter remaining fixed or trapped in space. The jet is observed to be formed by the advection and interaction of the primary vortices, resembling a conventional synthetic jet. This presentation examines the operation of the PSJA in a crossflow at three different jet to freestream velocity ratios. PIV measurements in the streamwise and cross-stream planes are used to illustrate the three dimensionality of the jet and associated vortical structures. The strength of the vortex ring is found to vary along its circumference due to interaction with the freestream. The boundary layer characteristics obtained from these experiments suggest that the mechanism of the PSJA in crossflow is similar to an active boundary layer trip. Both the penetration of the jet and effectiveness of the trip action are found to decrease with increase in freestream velocity. The effects of unsteady pulsing and increasing input power on actuator created crossflow vortices will also be presented.

High-energy-density plasma jet generated by laser-cone interaction

NASA Astrophysics Data System (ADS)

Ke, Y. Z.; Yang, X. H.; Ma, Y. Y.; Xu, B. B.; Ge, Z. Y.; Gan, L. F.; Meng, L.; Wang, S. W.; Kawata, S.

2018-04-01

The generation of high-energy-density (HED) plasma jet from a laser ablating thin cone target is studied theoretically and by numerical simulations. Theoretical analysis and 1D simulations show that a maximum kinetic energy conversion efficiency (CE) of 26% can be achieved when nearly 80% of the foil is ablated by laser. A HED plasma jet is generated when an intense laser (˜1015 W/cm2) irradiates the cone target, inducing a great enhancement of energy density compared to that of the planar target, which is attributed to the cumulative effect of the cone shape and the new generation mechanism of jet, i.e., laser directly accelerating the cone wall onto the axis. The characteristic of jet is influenced by the cone geometry, i.e., thickness and cone angle. It is found that a cone with a half opening angle around 70 ° and the optimized thickness (˜5 μm) can induce a jet with a high CE and long duration, whose peak energy density can reach 3.5 × 1015 erg/cm3. The results can be beneficial for laser-driven novel neutron sources and other fusion related experiments, where HED plasma jet can be applied.

Nonequilibrium atmospheric pressure plasma jet using a combination of 50 kHz/2 MHz dual-frequency power sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yong-Jie; Yuan, Qiang-Hua; Li, Fei

2013-11-15

An atmospheric pressure plasma jet is generated by dual sinusoidal wave (50 kHz and 2 MHz). The dual-frequency plasma jet exhibits the advantages of both low frequency and radio frequency plasmas, namely, the long plasma plume and the high electron density. The radio frequency ignition voltage can be reduced significantly by using dual-frequency excitation compared to the conventional radio frequency without the aid of the low frequency excitation source. A larger operating range of α mode discharge can be obtained using dual-frequency excitation which is important to obtain homogeneous and low-temperature plasma. A larger controllable range of the gas temperaturemore » of atmospheric pressure plasma could also be obtained using dual-frequency excitation.« less

Experimental investigation on the effect of plasma jet in the triggered discharge process of a gas switch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tie, W., E-mail: twh.110.666@163.com, E-mail: 84470220@qq.com; Xi'an Jiaotong University, Xi'an 710049; Liu, S.

The temporal and spatial evolution of a plasma jet generated by a spark discharge was observed. The electron temperature and density were obtained under different time and gas pressures by optical emission spectroscopy. Moreover, the discharge process of the plasma-jet triggered gas switch was recorded and analyzed at the lowest working coefficient. The results showed that the plasma jet moved forward in a bullet mode, and the advancing velocity increased with the decrease of pressure, and decreased with time growing. At initial time, the maximum velocity of a plasma jet could reach 3.68 × 10{sup 6 }cm/s. The electron temperature decreased from 2.0 eVmore » to 1.3 eV, and the electron density increased from 3.1 × 10{sup 15}/cm{sup 3} to 6.3 × 10{sup 15}/cm{sup 3} at the initial moment as the gas pressure increases from 0.1 MPa to 0.32 MPa. For a two-gap gas switch, the discharge performances were more depended on the second discharge spark gap (gap 2). Because plasma jet promoted the discharge in Gap 2, the gas switch operating in mode II had better triggered discharge characteristics. In the discharge process, the plasma-jet triggering had the effect of non-penetrating inducing, which not only provided initial electrons for reducing statistical lag but also enhanced the local electric field. The discharge was initiated and accelerated from electron avalanche to streamer. Therefore, a fast discharge was occurred in the gas switch.« less

Strong-coupling jet energy loss from AdS/CFT

NASA Astrophysics Data System (ADS)

Morad, R.; Horowitz, W. A.

2014-11-01

We propose a novel definition of a holographic light hadron jet and consider the phenomenological consequences, including the very first fully self-consistent, completely strong-coupling calculation of the jet nuclear modification factor R AA, which we find compares surprisingly well with recent preliminary data from LHC. We show that the thermalization distance for light parton jets is an extremely sensitive function of the a priori unspecified string initial conditions and that worldsheets corresponding to non-asymptotic energy jets are not well approximated by a collection of null geodesics. Our new string jet prescription, which is defined by a separation of scales from plasma to jet, leads to the re-emergence of the late-time Bragg peak in the instantaneous jet energy loss rate; unlike heavy quarks, the energy loss rate is unusually sensitive to the very definition of the string theory object itself. A straightforward application of the new jet definition leads to significant jet quenching, even in the absence of plasma. By renormalizing the in-medium suppression by that in the vacuum we find qualitative agreement with preliminary CMS RAAjet >( p T) data in our simple plasma brick model. We close with comments on our results and an outlook on future work.

Implementation of an Unequal Path Length, Heterodyne Interferometer on the MOCHI LabJet Experiment

NASA Astrophysics Data System (ADS)

Card, Alexander Harrison

The MOCHI LabJet experiment aims to explore the stability of magnetic flux tubes through the medium of laboratory astrophysical plasmas. The boundary conditions of large gravitational bodies, namely accretion disks, are replicated and allowed to influence a plasma over short timescales. Observation of the plasma is enabled through use of a variety of fast diagnostics, including an unequal path length, heterodyne, quadrature phase differential interferometer, the development and implementation of which is described in detail. The LabJet gun, a triple-electrode planar plasma gun featuring azimuthally symmetric gas injection achieves a new, long-duration, highly-stabilized, jet plasma formation. The line-integrated density in this new LabJet formation is found to be ne = (6 +/- 3)x1020 [m-2]. By observing the axial expansion rate of the jet over multiple chord locations (all perpendicular to the propagation axis), the interferometer provides an Alfvén velocity measurement of vA = 41.3 +/- 5.4 [km/s], which at the jet density observed indicates an axial magnetic field strength of Bz = 0.15 +/- 0.04 [T]. Various other laboratory components are also detailed, such as a shot-based MDSplus data storage architecture implemented into the LabVIEW experiment control code, and the production and performance of ten fast neutral gas injection valves which when fired in unison provide a total particle inventory of (7.8 +/- 0.6)x1023 [HI particles].

Experimental Characterization of Magnetogasdynamic Phenomena in Ultra-High Velocity Pulsed Plasma Jets

NASA Astrophysics Data System (ADS)

Loebner, Keith; Wang, Benjamin; Cappelli, Mark

2014-10-01

The formation and propagation of high velocity plasma jets in a pulsed, coaxial, deflagration-type discharge is examined experimentally. A sensitive, miniaturized, immersed probe array is used to map out magnetic flux density and associated radial current density as a function of time and axial position. This array is also used to probe the magnetic field gradient across the exit of the accelerator and in the jet formation region. Sensitive interferometry via a continuous-wave helium-neon laser source is used to probe the structure of the plasma jet over multiple chords and axial locations. A two dimensional plasma density gradient profile at an instant in time during jet formation is compiled via Shack-Hartmann wavefront sensor analysis. The qualitative characteristics of rarefaction and/or shock wave formation as a function of chamber back-pressure is examined via fast-framing ICCD imaging. These measurements are compared to existing resistive MHD simulations of the coaxial deflagration accelerator and the ensuing rarefaction jet that is expelled from the electrode assembly. The physical mechanisms governing the behavior of the discharge and the formation of these high energy density plasma jets are proposed and validated against both theoretical models and numerically simulated behavior. This research was conducted with Government support under and awarded by DoD, Air Force Office of Scientific Research, National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a.

Heat sink effects in variable polarity plasma arc welding

NASA Technical Reports Server (NTRS)

Abdelmessih, Amanie N.

1991-01-01

The Space Shuttle External Tank is fabricated by the variable polarity plasma arc (VPPA) welding process. In VPPA welding, a noble gas, usually argon, is directed through an arc to emerge from the torch as a hot plasma jet. This jet is surrounded by a shielding gas, usually helium, to protect the weld from contamination with air. The high velocity, hot plasma jet completely penetrates the workpiece (resembling a line heat source) when operated in the 'keyhole' mode. The metal melts on touching the side of the jet, as the torch travels in the perpendicular direction to the direction of the jet, and melted metal moves around the plasma jet in the keyhole forming a puddle which solidifies behind the jet. Heat sink effects are observed when there are irregularities in the workpiece configuration, especially, if these irregularities are close to the weld bead. These heat sinks affect the geometry of the weld bead, i.e., in extreme cases they could cause defects such as incomplete fusion. Also, different fixtures seem to have varying heat sink effects. The objective of this research is to study the effect of irregularities in workpiece configuration and fixture differences (heat sink effects) on the weld bead geometry with the ultimate objective to compensate for the heat sink effects and achieve a perfect weld. Experiments were performed on different workpiece geometries and compared to approximate models.

The effect of liquid target on a nonthermal plasma jet—imaging, electric fields, visualization of gas flow and optical emission spectroscopy

NASA Astrophysics Data System (ADS)

Kovačević, Vesna V.; Sretenović, Goran B.; Slikboer, Elmar; Guaitella, Olivier; Sobota, Ana; Kuraica, Milorad M.

2018-02-01

The article describes the complex study of the interaction of a helium plasma jet with distilled water and saline. The discharge development, spatial distribution of the excited species, electric field measurement results and the results of the Schlieren imaging are presented. The results of the experiments showed that the plasma-liquid interaction could be prolonged with the proper choice of the gas composition between the jet nozzle and the target. This depends on the gas flow and the target distance. Increased conductivity of the liquid does not affect the discharge properties significantly. An increase of the gas flow enables an extension of the plasma duration on the liquid surface up to 10 µs, but with a moderate electric field strength in the ionization wave. In contrast, there is a significant enhancement of the electric field on the liquid surface, up to 30 kV cm-1 for low flows, but with a shorter time of the overall plasma liquid interaction. Ignition of the plasma jet induces a gas flow modification and may cause turbulences in the gas flow. A significant influence of the plasma jet causing a mixing in the liquid is also recorded and it is found that the plasma jet ignition changes the direction of the liquid circulation.

Synthesis of Silane and Silicon in a Non-equilibrium Plasma Jet

NASA Technical Reports Server (NTRS)

Calcote, H. F.

1978-01-01

The original objective of this program was to determine the feasibility of high volume, low-cost production of high purity silane or solar cell grade silicon using a non equilibrium plasma jet. The emphasis was changed near the end of the program to determine the feasibility of preparing photovoltaic amorphous silicon films directly using this method. The non equilibrium plasma jet should be further evaluated as a technique for producing high efficiency photovoltaic amorphous silicon films.

Removal of floating dust in glow discharge using plasma jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ticos, C. M.; Jepu, I.; Lungu, C. P.

2010-07-05

Dust can be an inconvenient source of impurities in plasma processing reactors and in many cases it can cause damage to the plasma-treated surfaces. A technique for dust expulsion out of the trapping region in plasma is presented here, based on the wind force exerted on dust particles by a pulsed plasma jet. Its applicability is demonstrated by removing floating dust in the sheath of parallel-plate capacitive radio-frequency plasma.

Mixing and unmixedness in plasma jets 1: Near-field analysis

NASA Technical Reports Server (NTRS)

Ilegbusi, Olusegun J.

1993-01-01

The flow characteristics in the near-field of a plasma jet are simulated with a two-fluid model. This model accounts for both gradient-diffusion mixing and uni-directional sifting motion resulting from pressure-gradient-body-force imbalance. This latter mechanism is believed to be responsible for the umixedness observed in plasma jets. The unmixedness is considered to be essentially a Rayleigh-Taylor kind instability. Transport equations are solved for the individual plasma and ambient gas velocities, temperatures and volume fractions. Empirical relations are employed for the interface transfers of mass, momentum and heat. The empirical coefficients are first established by comparison of predictions with available experimental data for shear flows. The model is then applied to an Argon plasma jet ejecting into stagnant air. The predicted results show the significant build-up of unmixed air within the plasma gas, even relatively far downstream of the torch. By adjusting the inlet condition, the model adequately reproduces the experimental data.

Model analysis and electrical characterization of atmospheric pressure cold plasma jet in pin electrode configuration

NASA Astrophysics Data System (ADS)

Deepak, G. Divya; Joshi, N. K.; Prakash, Ram

2018-05-01

In this study, both model analysis and electrical characterization of a dielectric barrier discharge based argon plasma jet have been carried at atmospheric pressure in a pin electrode configuration. The plasma and fluid dynamics modules of COMSOL multi-physics code have been used for the modeling of the plasma jet. The plasma parameters, such as, electron density, electron temperature and electrical potential have been analyzed with respect to the electrical parameters, i.e., supply voltage and supply frequency with and without the flow of gas. In all the experiments, gas flow rate has been kept constant at 1 liter per minute. This electrode configuration is subjected to a range of supply frequencies (10-25 kHz) and supply voltages (3.5-6.5 kV). The power consumed by the device has been estimated at different applied combinations (supply voltage & frequency) for optimum power consumption at maximum jet length. The maximum power consumed by the device in this configuration for maximum jet length of ˜26 mm is just ˜1 W.

Filament Eruptions, Jets, and Space Weather

NASA Technical Reports Server (NTRS)

Moore, Ronald; Sterling, Alphonse; Robe, Nick; Falconer, David; Cirtain, Jonathan

2013-01-01

Previously, from chromospheric H alpha and coronal X-ray movies of the Sun's polar coronal holes, it was found that nearly all coronal jets (greater than 90%) are one or the other of two roughly equally common different kinds, different in how they erupt: standard jets and blowout jets (Yamauchi et al 2004, Apl, 605, 5ll: Moore et all 2010, Apj, 720, 757). Here, from inspection of SDO/AIA He II 304 A movies of 54 polar x-ray jets observed in Hinode/XRT movies, we report, as Moore et al (2010) anticipated, that (1) most standard x-ray jets (greater than 80%) show no ejected plasma that is cool enough (T is less than or approximately 10(exp 5K) to be seen in the He II 304 A movies; (2) nearly all blownout X-ray jets (greater than 90%) show obvious ejection of such cool plasma; (3) whereas when cool plasma is ejected in standard X-ray jets, it shows no lateral expansion, the cool plasma ejected in blowout X-ray jets shows strong lateral expansion; and (4) in many blowout X-ray jets, the cool plasma ejection displays the erupting-magnetic-rope form of clasic filament eruptions and is thereby seen to be a miniature filament eruption. The XRT movies also showed most blowout X-ray jets to be larger and brighter, and hence to apparently have more energy, than most standard X-ray jets. These observations (1) confirm the dichotomy of coronal jets, (2) agree with the Shibata model for standard jets, and (3) support the conclusion of Moore et al (2010) that in blowout jets the magnetic-arch base of the jet erupts in the manner of the much larger magnetic arcades in which the core field, the field rooted along the arcade's polarity inversion line, is sheared and twisted (sigmoid), often carries a cool-plasma filament, and erupts to blowout the arcade, producing a CME. From Hinode/SOT Ca II movies of the polar limb, Sterling et al (2010, ApJ, 714, L1) found that chromospheric Type-II spicules show a dichotomy of eruption dynamics similar to that found here for the cool-plasma component of coronal X-ray jets. This favors the idea that Type-II spicules are miniature counterparts of coronal X-ray jets. In Moore et al (2011, ApJ, 731, L18), we pointed out that if Type-II spicules are magnetic eruptions that work like coronal X-ray jets, they carry an area-averaged mechanical energy flux of approximately 7x10)(exp 5) erg cm(exp -2) s(exp-1) into the corona in the form of MHD waves and jet outflow, enough to power the heating of the global corona and solar wind. On this basis, from our observations of mini-filament eruptions in blowout X-ray jets, we infer that magnetic explosions of the type that have erupting filaments in them are the main engines of both (1) the steady solar wind and (2) the CMEs that produce the most severe space weather by blasting out through the corona and solar wind, making solar energetic particle storms, and bashing the Earth's magnetosphere. We conclude that in focusing on prominences and filament eruptions, Einar had his eye on the main bet for understanding what powers all space weather, both the extreme and the normal.

Dichotomy of X-Ray Jets in Solar Coronal Holes

NASA Astrophysics Data System (ADS)

Robe, D. M.; Moore, R. L.; Falconer, D. A.

2012-12-01

It has been found that there are two different types of X-ray jets observed in the Sun's polar coronal holes: standard jets and blowout jets. A proposed model of this dichotomy is that a standard jet is produced by a burst of reconnection of the ambient magnetic field with the opposite-polarity leg of the base arcade. In contrast, it appears that a blowout jet is produced when the interior of the arcade has so much pent-up free magnetic energy in the form of shear and twist in the interior field that the external reconnection unleashes the interior field to erupt open. In this project, X-ray movies of the polar coronal holes taken by Hinode were searched for X-ray jets. Co-temporal movies taken by the Solar Dynamics Observatory in 304 Å emission from He II, showing solar plasma at temperatures around 80,000 K, were examined for whether the identified blowout jets carry much more He II plasma than the identified standard jets. It was found that though some jets identified as standard from the X-ray movies could be seen in the He II 304 Å movies, the blowout jets carried much more 80,000 K plasma than did most standard jets. This finding supports the proposed model for the morphology and development of the two types of jets.

Inductive Measurement of Plasma Jet Electrical Conductivity

NASA Technical Reports Server (NTRS)

Turner, Matthew W.; Hawk, Clark W.; Litchford, Ron J.

2005-01-01

An inductive probing scheme, originally developed for shock tube studies, has been adapted to measure explosive plasma jet conductivities. In this method, the perturbation of an applied magnetic field by a plasma jet induces a voltage in a search coil, which, in turn, can be used to infer electrical conductivity through the inversion of a Fredholm integral equation of the first kind. A 1-inch diameter probe was designed and constructed, and calibration was accomplished by firing an aluminum slug through the probe using a light-gas gun. Exploratory laboratory experiments were carried out using plasma jets expelled from 15-gram high explosive shaped charges. Measured conductivities were in the range of 3 kS/m for unseeded octol charges and 20 kS/m for seeded octol charges containing 2% potassium carbonate by mass.

Comparative analysis of core heat transport of JET high density H-mode plasmas in carbon wall and ITER-like wall

NASA Astrophysics Data System (ADS)

Kim, Hyun-Tae; Romanelli, M.; Voitsekhovitch, I.; Koskela, T.; Conboy, J.; Giroud, C.; Maddison, G.; Joffrin, E.; contributors, JET

2015-06-01

A consistent deterioration of global confinement in H-mode experiments has been observed in JET [1] following the replacement of all carbon plasma facing components (PFCs) with an all metal (‘ITER-like’) wall (ILW). This has been correlated to the observed degradation of the pedestal confinement, as lower electron temperature (Te) values are routinely measured at the top of the edge barrier region. A comparative investigation of core heat transport in JET-ILW and JET-CW (carbon wall) discharges has been performed, to assess whether core confinement has also been affected by the wall change. The results presented here have been obtained by analysing a set of discharges consisting of high density JET-ILW H-mode plasmas and comparing them against their counterpart discharges in JET-CW having similar global operational parameters. The set contains 10 baseline ({βN}=1.5∼ 2 ) discharge-pairs with 2.7 T toroidal magnetic field, 2.5 MA plasma current, and 14 to 17 MW of neutral beam injection (NBI) heating. Based on a Te profile analysis using high resolution Thomson scattering (HRTS) data, the Te profile peaking (i.e. core Te (ρ = 0.3) / edge Te (ρ = 0.7)) is found to be similar, and weakly dependent on edge Te, for both JET-ILW and JET-CW discharges. When ILW discharges are seeded with N2, core and edge Te both increase to maintain a similar peaking factor. The change in core confinement is addressed with interpretative TRANSP simulations. It is found that JET-ILW H-mode plasmas have higher NBI power deposition to electrons and lower NBI power deposition to ions as compared to the JET-CW counterparts. This is an effect of the lower electron temperature at the top of the pedestal. As a result, the core electron energy confinement time is reduced in JET-ILW discharges, but the core ion energy confinement time is not decreased. Overall, the core energy confinement is found to be the same in the JET-ILW discharges compared to the JET-CW counterparts.

Studies on cryogenic Xe capillary jet target for laser-produced plasma EUV-light source

NASA Astrophysics Data System (ADS)

Inoue, T.; Nica, P. E.; Kaku, K.; Shimoura, A.; Amano, S.; Miyamoto, S.; Mochizuki, T.

2006-03-01

In this paper, characterizations of a cryogenic Xe capillary jet target for a laser-produced plasma extreme ultraviolet (EUV) light source are reported. The capillary jet target is a candidate of fast-supplying targets for mitigating debris generation and target consumption in a vacuum chamber without reducing the EUV conversion efficiency. Xe capillary jets (jet velocity ~ 0.4 m/s) were generated in vacuum by using annular nozzles chilled to ~ 170 K at a Xe backing pressure of ~ 0.7 MPa. Forming mechanisms of the capillary jet targets were studied by using numerical calculations. Furthermore, laser-produced plasma EUV generation was performed by irradiating a Nd:YAG laser (1064 nm, ~ 0.5 J, 10 ns, 120 μmφ, ~ 4×10 11 W/cm2) on a Xe capillary jet target (outer / inner diameter = 100 / 70 μmφ). The angular distribution of EUV generation was approximately uniform around the Xe capillary jet target, and the peak kinetic energy of the fast-ions was evaluated to be ~ 2 keV.

Interfacial Stability of Spherically Converging Plasma Jets for Magnetized Target Fusion

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Cassibry, Jason; Wu, S. T.; Eskridge, Richard; Smith, James; Lee, Michael; Rodgers, Stephen L. (Technical Monitor)

2000-01-01

A fusion propulsion scheme has been proposed that makes use of the merging of a spherical distribution of plasma jets to dynamically form a gaseous liner to implode a magnetized target to produce the fusion reaction. In this paper, a study is made of the interfacial stability of the interaction of these jets. Specifically, the Orr-Sommerfeld equation is integrated to obtain the growth rate of a perturbation to the primary flow at the interface between the colliding jets. The results lead to an estimate on the tolerances on the relative flow velocities of the merging plasma jets to form a stable, imploding liner. The results show that the maximum temporal growth rate of the perturbed flow at the jet interface is very small in comparison with the time to full compression of the liner. These data suggest that, as far as the stability of the interface between the merging jets is concerned, the formation of the gaseous liner can withstand velocity variation of the order of 10% between the neighboring jets over the density and temperature ranges investigated.

A new flexible DBD device for treating infected wounds: in vitro and ex vivo evaluation and comparison with a RF argon plasma jet

NASA Astrophysics Data System (ADS)

Boekema, B. K. H. L.; Vlig, M.; Guijt, D.; Hijnen, K.; Hofmann, S.; Smits, P.; Sobota, A.; van Veldhuizen, E. M.; Bruggeman, P.; Middelkoop, E.

2016-02-01

Cold plasma has been shown to provide a promising alternative antimicrobial treatment for wound healing. We developed and tested a flexible surface dielectric barrier discharge (DBD) and compared it to an argon gas based plasma jet operated remotely with a distance between plasma plume and sample of 8 mm. Tests were conducted using different models: on cultured cells, on ex vivo human skin and on bacteria (Pseudomonas aeruginosa) (on agar, in suspension, in collagen/elastin matrix or on ex vivo human skin), allowing us to directly compare bactericidal with safety aspects under identical conditions. Both plasma devices were highly efficient when used on bacteria in non-buffered solutions, but DBD was faster in reaching the maximum bacterial reduction. Treatment of bacteria on intact skin with DBD resulted in up to 6 log reductions in 3 min. The jet was far less efficient on intact skin. Even after 8 min treatment no more than 2 log reductions were obtained with the jet. Treatment of bacteria in burn wound models with DBD for 6 min resulted in a 4.5 log reduction. Even when using DBD for 6 min on infected burn wound models with colonizing or biofilm phase bacteria, the log reductions were 3.8 or 3.2 respectively. DBD plasma treatment for 6 min did not affect fibroblast viability, whereas a treatment for 8 min was detrimental. Similarly, treatment with DBD or plasma jet for 6 min did also not affect the metabolic activity of skin biopsies. After treatment for 8 min with DBD or plasma jet, 78% or 60% of activity in skin biopsies remained, respectively. Multiple treatments of in vitro burn wound models with surface DBD for 6 min or with plasma jet for 8 min did not affect re-epithelialization. With the flexible surface DBD plasma strip we were able to quickly inactivate large numbers of bacteria on and in skin. Under the same conditions, viability of skin cells or re-epithelialization was not affected. The DBD source has potential for treating larger wound areas.

Plasma confinement at JET

NASA Astrophysics Data System (ADS)

Nunes, I.; JET Contributors

2016-01-01

Operation with a Be/W wall at JET (JET-ILW) has an impact on scenario development and energy confinement with respect to the carbon wall (JET-C). The main differences observed were (1) strong accumulation of W in the plasma core and (2) the need to mitigate the divertor target temperature to avoid W sputtering by Be and other low Z impurities and (3) a decrease of plasma energy confinement. A major difference is observed on the pedestal pressure, namely a reduction of the pedestal temperature which, due to profile stiffness the plasma core temperature is also reduced leading to a degradation of the global confinement. This effect is more pronounced in low β N scenarios. At high β N, the impact of the wall on the plasma energy confinement is mitigated by the weaker plasma energy degradation with power relative to the IPB98(y, 2) scaling calculated empirically for a CFC first wall. The smaller tolerable impurity concentration for tungsten (<10-5) compared to that of carbon requires the use of electron heating methods to prevent W accumulation in the plasma core region as well as gas puffing to avoid W entering the plasma core by ELM flushing and reduction of the W source by decreasing the target temperature. W source and the target temperature can also be controlled by impurity seeding. Nitrogen and Neon have been used and with both gases the reduction of the W source and the target temperature is observed. Whilst more experiments with Neon are necessary to assess its impact on energy confinement, a partial increase of plasma energy confinement is observed with Nitrogen, through the increase of edge temperature. The challenge for scenario development at JET is to extend the pulse length curtailed by its transient behavior (W accumulation or MHD), but more importantly by the divertor target temperature limits. Re-optimisation of the scenarios to mitigate the effect of the change of wall materials maintaining high global energy confinement similar to JET-C is underway and JET has successfully achieved H 98(y,2)  =  1 for plasma currents up to 2.5 MA at moderate β N.

Historical Overview of Directed-Energy Work at Dahlgren

DTIC Science & Technology

2012-01-01

discharge of electrical energy at the gun breech to generate a plasma jet. This plasma jet heated a low- molecular-weight working fluid, such as water, to...cept augmented the electrical energy generating the plasma jet with a chemical reaction. A 127mm ETC gun was investigated, and a 60mm ETC gun was...ANSI Std Z39-18 13 Historical Overview of Directed-Energy Work at Dahlgren coaxial pipe, which was switched at one end, to create the oscillating

FAST TRACK COMMUNICATION: Effects of Penning ionization on the discharge patterns of atmospheric pressure plasma jets

NASA Astrophysics Data System (ADS)

Li, Qing; Zhu, Wen-Chao; Zhu, Xi-Ming; Pu, Yi-Kang

2010-09-01

Atmospheric pressure plasma jets, generated in a coaxial dielectric barrier discharge configuration, have been investigated with different flowing gases. Discharge patterns in different tube regions were compared in the flowing gases of helium, neon and krypton. To explain the difference of these discharge patterns, a theoretical analysis is presented to reveal the possible basic processes. A comparison of experimental and theoretical results identifies that Penning ionization is mainly responsible for the discharge patterns of helium and neon plasma jets.

Dielectric barrier discharge and jet type plasma surface modifications of hybrid polymeric poly (ε-caprolactone)/chitosan scaffolds.

PubMed

Ozkan, Ozan; Turkoglu Sasmazel, Hilal

2018-04-01

In this study, dry air plasma jet and dielectric barrier discharge Ar + O 2 or Ar + N 2 plasma modifications and their effects on wettability, topography, functionality and biological efficiency of the hybrid polymeric poly (ε-caprolactone)/chitosan scaffolds were reported. The samples treated with Ar + O 2 dielectric barrier discharge plasma (80 sccm O 2 flow rate, 3-min treatment) or with dry air plasma jet (15-cm nozzle-sample distance, 13-min treatment) had the closest wettability (49.11 ± 1.83 and 53.60 ± 0.95, respectively) to the commercial tissue culture polystyrene used for cell cultivation. Scanning electron microscopy images and X-ray photoelectron spectrometry analysis showed increase in topographical roughness and OH/NH 2 functionality, respectively. Increased fluid uptake capacity for the scaffolds treated with Ar + O 2 dielectric barrier discharge plasma (73.60% ± 1.78) and dry air plasma jet (72.48% ± 0.75) were also noted. Finally, initial cell attachment as well as seven-day cell viability, growth and proliferation performances were found to be significantly better for both plasma treated scaffolds than for untreated scaffolds.

The study of the plasma jets of lead and silver simulating spent nuclear fuel components

NASA Astrophysics Data System (ADS)

Antonov, N. N.; Gavrikov, A. V.; Smirnov, V. P.; Liziakin, G. D.; Usmanov, R. A.; Vorona, N. A.; Timirkhanov, R. A.

2018-01-01

One of the tasks that must be solved to develop a spent nuclear fuel (SNF) plasma separation method is a creation of plasma source of substances simulating SNF components. Plasma of the diffuse arc discharge in a magnetic field with an incandescent cathode was considered in this paper, as such source. The discharge was initiated in a model substances vapor (lead and silver). Evaporation was carried out by crucible induction heating. Current- voltage characteristics of the discharge were obtained. Spectral analysis of the plasma jets radiation and double probe characteristics measurements in the area behind the anode were carried out. The minimum potential difference between the anode and cathode reached a value of about 7 V at current of about 1 A. When the potential difference in the discharge gap was close to 30 V (4.5 A) and 10 V (5.2 A) electron temperature in the plasma jet was 5-7 eV and 1-3 eV, respectively. Plasma density in jets took the value from 1011 cm-3 to 1012 cm-3. The obtained results indicate the possibility of using this type of discharge for the SNF plasma separation method approbation.

Confluence or independence of microwave plasma bullets in atmospheric argon plasma jet plumes

NASA Astrophysics Data System (ADS)

Li, Ping; Chen, Zhaoquan; Mu, Haibao; Xu, Guimin; Yao, Congwei; Sun, Anbang; Zhou, Yuming; Zhang, Guanjun

2018-03-01

Plasma bullet is the formation and propagation of a guided ionization wave (streamer), normally generated in atmospheric pressure plasma jet (APPJ). In most cases, only an ionization front produces in a dielectric tube. The present study shows that two or three ionization fronts can be generated in a single quartz tube by using a microwave coaxial resonator. The argon APPJ plumes with a maximum length of 170 mm can be driven by continuous microwaves or microwave pulses. When the input power is higher than 90 W, two or three ionization fronts propagate independently at first; thereafter, they confluence to form a central plasma jet plume. On the other hand, the plasma bullets move independently as the lower input power is applied. For pulsed microwave discharges, the discharge images captured by a fast camera show the ionization process in detail. Another interesting finding is that the strongest lightening plasma jet plumes always appear at the shrinking phase. Both the discharge images and electromagnetic simulations suggest that the confluence or independent propagation of plasma bullets is resonantly excited by the local enhanced electric fields, in terms of wave modes of traveling surface plasmon polaritons.

Atmospheric nonequilibrium mini-plasma jet created by a 3D printer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takamatsu, Toshihiro, E-mail: toshihiro@plasma.es.titech.ac.jp; Tokyo Institute of Technology, Department of Energy Sciences, J2-32, 4259 Nagatsuta, Midori-ku, Yokohama, 226-8502; Kawano, Hiroaki

2015-07-15

In this study, a small-sized plasma jet source with a 3.7 mm head diameter was created via a 3D printer. The jet’s emission properties and OH radical concentrations (generated by argon, helium, and nitrogen plasmas) were investigated using optical emission spectrometry (OES) and electron spin resonance (ESR). As such, for OES, each individual gas plasma propagates emission lines that derive from gases and ambient air inserted into the measurement system. For the case of ESR, a spin adduct of the OH radical is typically observed for all gas plasma treatment scenarios with a 10 s treatment by helium plasma generatingmore » the largest amount of OH radicals at 110 μM. Therefore, it was confirmed that a plasma jet source made by a 3D printer can generate stable plasmas using each of the aforementioned three gases.« less

Inactivation of myeloma cancer cells by helium and argon plasma jets: The effect comparison and the key reactive species

NASA Astrophysics Data System (ADS)

Chen, Zeyu; Cui, Qingjie; Chen, Chen; Xu, Dehui; Liu, Dingxin; Chen, H. L.; Kong, Michael G.

2018-02-01

In plasma cancer therapy, the inactivation of cancer cells under plasma treatment is closely related to the reactive oxygen and nitrogen species (RONS) induced by plasmas. Quantitative study on the plasma-induced RONS that related to cancer cells apoptosis is critical for advancing the research of plasma cancer therapy. In this paper, the effects of several reactive species on the inactivation of LP-1 myeloma cancer cells are comparatively studied with variable working gas composition, surrounding gas composition, and discharge power. The results show that helium plasma jet has a higher cell inactivation efficiency than argon plasma jet under the same discharge power. By comparing the concentration of aqueous phase reactive species and the cell inactivation efficiency under different working gases and discharge powers, it is demonstrated that the inactivation efficiency of LP-1 myeloma cancer cells is strongly correlated with the concentration of peroxynitrite (ONOOH/ONOO-).

Cold atmospheric plasma jet in an axial DC electric field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Li, E-mail: lilin@gwu.edu, E-mail: keidar@gwu.edu; Keidar, Michael, E-mail: lilin@gwu.edu, E-mail: keidar@gwu.edu

2016-08-15

Cold atmospheric plasma (CAP) jet is currently intensively investigated as a tool for new and potentially transformative cancer treatment modality. However, there are still many unknowns about the jet behavior that requires attention. In this paper, a helium CAP jet is tested in an electrostatic field generated by a copper ring. Using Rayleigh microwave scattering method, some delays of the electron density peaks for different ring potentials are observed. Meanwhile, a similar phenomenon associated with the bullet velocity is found. Chemical species distribution along the jet is analyzed based on the jet optical emission spectra. The spectra indicate that amore » lower ring potential, i.e., lower DC background electric field, can increase the amount of excited N{sub 2}, N{sub 2}{sup +}, He, and O in the region before the ring, but can decrease the amount of excited NO and HO almost along the entire jet. Combining all the results above, we discovered that an extra DC potential mainly affects the temporal plasma jet properties. Also, it is possible to manipulate the chemical compositions of the jet using a ring with certain electric potentials.« less

Using radiative energy losses to constrain the magnetization and magnetic reconnection rate at the base of black hole jets

NASA Astrophysics Data System (ADS)

Potter, William J.

2017-02-01

We calculate the severe radiative energy losses which occur at the base of black hole jets using a relativistic fluid jet model, including in situ acceleration of non-thermal leptons by magnetic reconnection. Our results demonstrate that including a self-consistent treatment of radiative energy losses is necessary to perform accurate magnetohydrodynamic simulations of powerful jets and that jet spectra calculated via post-processing are liable to vastly overestimate the amount of non-thermal emission. If no more than 95 per cent of the initial total jet power is radiated away by the plasma travels as it travels along the length of the jet, we can place a lower bound on the magnetization of the jet plasma at the base of the jet. For typical powerful jets, we find that the plasma at the jet base is required to be highly magnetized, with at least 10 000 times more energy contained in magnetic fields than in non-thermal leptons. Using a simple power-law model of magnetic reconnection, motivated by simulations of collisionless reconnection, we determine the allowed range of the large-scale average reconnection rate along the jet, by restricting the total radiative energy losses incurred and the distance at which the jet first comes into equipartition. We calculate analytic expressions for the cumulative radiative energy losses due to synchrotron and inverse-Compton emission along jets, and derive analytic formulae for the constraint on the initial magnetization.

A CONNECTION BETWEEN PLASMA CONDITIONS NEAR BLACK HOLE EVENT HORIZONS AND OUTFLOW PROPERTIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koljonen, K. I. I.; Russell, D. M.; Bernardini, F.

Accreting black holes are responsible for producing the fastest, most powerful outflows of matter in the universe. The formation process of powerful jets close to black holes is poorly understood, and the conditions leading to jet formation are currently hotly debated. In this paper, we report an unambiguous empirical correlation between the properties of the plasma close to the black hole and the particle acceleration properties within jets launched from the central regions of accreting stellar-mass and supermassive black holes. In these sources the emission of the plasma near the black hole is characterized by a power law at X-raymore » energies during times when the jets are produced. We find that the photon index of this power law, which gives information on the underlying particle distribution, correlates with the characteristic break frequency in the jet spectrum, which is dependent on magnetohydrodynamical processes in the outflow. The observed range in break frequencies varies by five orders of magnitude in sources that span nine orders of magnitude in black hole mass, revealing a similarity of jet properties over a large range of black hole masses powering these jets. This correlation demonstrates that the internal properties of the jet rely most critically on the conditions of the plasma close to the black hole, rather than other parameters such as the black hole mass or spin, and will provide a benchmark that should be reproduced by the jet formation models.« less

On a non-thermal atmospheric pressure plasma jet used for the deposition of silicon-organic films

NASA Astrophysics Data System (ADS)

Schäfer, Jan; Sigeneger, Florian; Foest, Rüdiger; Loffhagen, Detlef; Weltmann, Klaus-Dieter

2018-05-01

This work represents a concise overview on the results achieved by the authors over the last years on the plasma of a non-thermal reactive plasma jet at atmospheric pressure and of related thin film formation by plasma enhanced chemical vapour deposition (PECVD). The source was developed considering the application of the plasma self-organization for PECVD. The experimental methods comprise spectroscopic measurements of plasma parameters in the active zone, temperature measurements in the active zone and the effluent as well as the analysis of deposited films at the substrate surface. The theoretical investigations are devoted to a single filament in the active zone using a phase-resolved model and to an overall description of the jet including the substrate using a period-averaged model.

Schlieren Cinematography of Current Driven Plasma Jet Dynamics

NASA Astrophysics Data System (ADS)

Loebner, Keith; Underwood, Thomas; Cappelli, Mark

2016-10-01

Schlieren cinematography of a pulsed plasma deflagration jet is presented and analyzed. An ultra-high frame rate CMOS camera coupled to a Z-type laser Schlieren apparatus is used to obtain flow-field refractometry data for the continuous flow Z-pinch formed within the plasma deflagration jet. The 10 MHz frame rate for 256 consecutive frames provides high temporal resolution, enabling turbulent fluctuations and plasma instabilities to be visualized over the course of a single pulse (20 μs). The Schlieren signal is radiometrically calibrated to obtain a two dimensional mapping of the refraction angle of the axisymmetric pinch plasma, and this mapping is then Abel inverted to derive the plasma density distribution as a function radius, axial coordinate, and time. Analyses of previously unknown discharge characteristics and comparisons with prior work are discussed.

Particle-in-cell simulations of collisionless shock formation via head-on merging of two laboratory supersonic plasma jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thoma, C.; Welch, D. R.; Hsu, S. C.

2013-08-15

We describe numerical simulations, using the particle-in-cell (PIC) and hybrid-PIC code lsp[T. P. Hughes et al., Phys. Rev. ST Accel. Beams 2, 110401 (1999)], of the head-on merging of two laboratory supersonic plasma jets. The goals of these experiments are to form and study astrophysically relevant collisionless shocks in the laboratory. Using the plasma jet initial conditions (density ∼10{sup 14}–10{sup 16} cm{sup −3}, temperature ∼ few eV, and propagation speed ∼20–150 km/s), large-scale simulations of jet propagation demonstrate that interactions between the two jets are essentially collisionless at the merge region. In highly resolved one- and two-dimensional simulations, we showmore » that collisionless shocks are generated by the merging jets when immersed in applied magnetic fields (B∼0.1–1 T). At expected plasma jet speeds of up to 150 km/s, our simulations do not give rise to unmagnetized collisionless shocks, which require much higher velocities. The orientation of the magnetic field and the axial and transverse density gradients of the jets have a strong effect on the nature of the interaction. We compare some of our simulation results with those of previously published PIC simulation studies of collisionless shock formation.« less

PALS laser-driven radiative jets for astrophysical and ICF applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pisarczyk, T.; Kasperczuk, A.; Stenz, Ch.

2008-03-19

High speed, well-collimated plasma jets were generated in the interaction of defocused single laser beam with planar, massive Cu target. The experiment was carried out at the iodine laser facility (Prague Asterix Laser System--PALS) using the third harmonic beam (0.438 {mu}m) with a pulse duration of 250 ps (FWHM) and an energy of 100 J. The information about geometry of plasma expansion, plasma dynamics and electron density were obtained by means of a 3-frame interferometric system. The plasma jet parameters reach the following values: the velocity up to 7x10{sup 7} cm/s, the internal Mach number greater than 10 and themore » electron density above 10{sup 19} cm{sup -3}. The jet characteristics are appropriate for the astrophysical and ICF applications. To ensure the interaction of this jet with gas or plasma as an ambient medium, a high-pressure supersonic gas nozzle was used, which created a cylindrical column of Ar or He. The results of first experiments dedicated to studies of collision of such a jet with a gas cloud are also presented. They clearly show the effect of shocks formation in ambient gases (He and Ar) due to the jet action. In the case of He the shock waves have usually a conical shape with a thickness of 1-1.5 mm, whereas in the case of Ar, the shock wave configuration is more complex and its thickness is less than 1 mm.« less

Multiprobe characterization of plasma flows for space propulsion

NASA Astrophysics Data System (ADS)

Damba, Julius; Argente, P.; Maldonado, P. E.; Cervone, A.; Domenech-Garret, J. L.; Conde, L.

2018-02-01

Plasma engines for space propulsion generate plasma jets (also denominated plasma plumes) having supersonic ion groups with typical speeds in the order of tens of kilometers per second, which lies between electron and ion thermal speeds. Studies of the stationary plasma expansion process using a four-grid retarding field energy analyzer (RFEA), an emissive probe (EP) and a Langmuir probe (LP), all mounted on a three dimensionally (3D) displaced multiprobe structure are discussed. Specifically, the determination of plasma beam properties from the RFEA current-voltage (IV) characteristic curves is presented. The experimental results show the ion energy spectra to be essentially unchanged over 300 mm along the plasma-jet expansion axis of symmetry. The measured ion velocity distribution function (IVDF) results from the superposition of different ion groups and has two dominant populations: A low-energy group constituted of ions from the background plasma is produced by the interaction of the plasma jet with the walls of the vacuum chamber. The fast-ion population is composed of ions from the plasma beam moving at supersonic speeds with respect to the low-energy ions. The decreasing spatial profiles of the plasma-jet current density are compared with those of the low-energy ion group, which are not uniform along the axis of symmetry because of the small contributions from other ion populations with intermediate speeds.

Progress in Development of C60 Nanoparticle Plasma Jet for Diagnostic of Runaway Electron Beam-Plasma Interaction and Disruption Mitigation Study for ITER

NASA Astrophysics Data System (ADS)

Bogatu, I. N.; Thompson, J. R.; Galkin, S. A.; Kim, J. S.

2013-10-01

We produced a C60 nanoparticle plasma jet (NPPJ) with uniquely fast response-to-delivery time (~ 1 - 2 ms) and unprecedentedly high momentum (~ 0 . 6 g .km/s). The C60 NPPJ was obtained by using a solid state TiH2/C60 pulsed power cartridge producing ~180 mg of C60 molecular gas by sublimation and by electromagnetic acceleration of the C60 plasma in a coaxial gun (~35 cm length, 96 kJ energy) with the output of a high-density (>1023 m-3) hyper-velocity (>4 km/s) plasma jet. The ~ 75 mg C60/C plasma jet has the potential to rapidly and deeply deliver enough mass to significantly increase electron density (to ne ~ 2 . 4 ×1021 m-3, i.e. ~ 60 times larger than typical DIII-D pre-disruption value, ne 0 ~ 4 ×1019 m-3), and to modify the 'critical electric field' and the runaway electrons (REs) collisional drag during different phases of REs dynamics. The C60 NPPJ, as a novel injection technique, allows RE beam-plasma interaction diagnostic by quantitative spectroscopy of C ions visible/UV line intensity. The system is scalable to ~ 1 - 2 g C60/C plasma jet output and technology is adaptable to ITER acceptable materials (BN and Be) for disruption mitigation. Work supported by US DOE DE-FG02-08ER85196 grant.

Dust generation at interaction of plasma jet with surfaces

NASA Astrophysics Data System (ADS)

Ticos, Catalin; Toader, Dorina; Banu, Nicoleta; Scurtu, Adrian; Oane, Mihai

2013-10-01

Coatings of W and C with widths of a few microns will be exposed to plasma jet for studying the erosion of the surface and detachment of micron size dust particles. A coaxial plasma gun has been built inside a vacuum chamber for producing supersonic plasma jets. Its design is based on a 50 kJ coaxial plasma gun which has been successfully used for accelerating hypervelocity dust. Initial shots were carried out for a capacitor bank with C = 12 μF and charged up to 2 kV. Currents of tens of amps were measured with a Rogowsky coil and plasma flow speeds of 4 km/s were inferred from high-speed images of jet propagation. An upgrade consisting in adding capacitors in parallel will be performed in order to increase the energy up to 2 kJ. A coil will be installed at the gun muzzle to compress the plasma flow and increase the energy density of the jet on the sample surface. A CCD camera with a maximum recording speed of 100 k fps and a maximum resolution of 1024 × 1024 pixels was set for image acquisition of the plasma and dust. A laser system used to illuminate the ejected dust from the surface includes a laser diode emitting at 650 nm with a beam power of 25 mW. The authors acknowledge support from EURATOM WP13-IPH-A03-P2-02-BS22.

Experimental evidence of multimaterial jet formation with lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nicolaie, Ph.; Stenz, C.; Tikhonchuk, V.

2010-11-15

Laser-produced multimaterial jets have been investigated at the Prague Asterix Laser System laser [K. Jungwirth et al., Phys. Plasmas 8, 2495 (2001)]. The method of jet production is based on the laser-plasma ablation process and proved to be easy to set up and robust. The possibility of multimaterial laboratory jet production is demonstrated and complex hydrodynamic flows in the jet body are obtained. Two complementary diagnostics in the optical ray and x-ray ranges provide detailed information about jet characteristics. The latter are in agreement with estimates and two-dimensional radiation hydrodynamic simulation results. The experiment provides a proof of principle thatmore » a velocity field could be produced and controlled in the jet body. It opens a possibility of astrophysical jet structure modeling in laboratory.« less

Detailed characterization of laser-produced astrophysically-relevant jets formed via a poloidal magnetic nozzle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Higginson, D. P.; Revet, G.; Khiar, B.

We report that the collimation of astrophysically-relevant plasma ejecta in the form of narrow jets via a poloidal magnetic field is studied experimentally by irradiating a target situated in a 20 T axial magnetic field with a 40 J, 0.6 ns, 0.7 mm diameter, high-power laser. The dynamics of the plasma shaping by the magnetic field are studied over 70 ns and up to 20 mm from the source by diagnosing the electron density, temperature and optical self-emission. These show that the initial expansion of the plasma is highly magnetized, which leads to the formation of a cavity structure whenmore » the kinetic plasma pressure compresses the magnetic field, resulting in an oblique shock [A. Ciardi et al., Phys. Rev. Lett. 110, 025002 (2013)]. The resulting poloidal magnetic nozzle collimates the plasma into a narrow jet [B. Albertazzi et al., Science 346, 325 (2014)]. At distances far from the target, the jet is only marginally magnetized and maintains a high aspect ratio due to its high Mach-number (M~20) and not due to external magnetic pressure. The formation of the jet is evaluated over a range of laser intensities (10 12–10 13 W/cm 2), target materials and orientations of the magnetic field. Lastly, plasma cavity formation is observed in all cases and the viability of long-range jet formation is found to be dependent on the orientation of the magnetic field.« less

Detailed characterization of laser-produced astrophysically-relevant jets formed via a poloidal magnetic nozzle

DOE PAGES

Higginson, D. P.; Revet, G.; Khiar, B.; ...

2017-02-24

We report that the collimation of astrophysically-relevant plasma ejecta in the form of narrow jets via a poloidal magnetic field is studied experimentally by irradiating a target situated in a 20 T axial magnetic field with a 40 J, 0.6 ns, 0.7 mm diameter, high-power laser. The dynamics of the plasma shaping by the magnetic field are studied over 70 ns and up to 20 mm from the source by diagnosing the electron density, temperature and optical self-emission. These show that the initial expansion of the plasma is highly magnetized, which leads to the formation of a cavity structure whenmore » the kinetic plasma pressure compresses the magnetic field, resulting in an oblique shock [A. Ciardi et al., Phys. Rev. Lett. 110, 025002 (2013)]. The resulting poloidal magnetic nozzle collimates the plasma into a narrow jet [B. Albertazzi et al., Science 346, 325 (2014)]. At distances far from the target, the jet is only marginally magnetized and maintains a high aspect ratio due to its high Mach-number (M~20) and not due to external magnetic pressure. The formation of the jet is evaluated over a range of laser intensities (10 12–10 13 W/cm 2), target materials and orientations of the magnetic field. Lastly, plasma cavity formation is observed in all cases and the viability of long-range jet formation is found to be dependent on the orientation of the magnetic field.« less

Development of non-thermal plasma jet and its potential application for color degradation of organic pollutant in wastewater treatment

NASA Astrophysics Data System (ADS)

Pirdo Kasih, Tota; Kharisma, Angel; Perdana, Muhammad Kevin; Murphiyanto, Richard Dimas Julian

2017-12-01

This paper presents the development of non-thermal plasma-based AOPs for color degradation in wastewater treatment. The plasma itself was generated by an in-house high voltage power supply (HVPS). Instead of gas-phase plasma system, we applied plasma jet system underwater during wastewater treatment without additional any chemicals (chemical-free processing). The method is thought to maximize the energy transfer and increase the efficient interaction between plasma and solution during the process. Our plasma jet system could proceed either by using helium (He), argon (Ar) and air as the medium in an open air atmosphere. Exploring the developed plasma to be applied in organic wastewater treatment, we demonstrated that the plasma jet could be generated underwater and yields in color degradation of methylene blue (MB) wastewater model. When using Ar gas as a medium, the color degradation of MB could be achieved within 90 minutes. Whereas, by using Ar with an admixing of oxygen (O2) gas, the similar result could be accomplished within 60 minutes. Additional O2 gas in the latter might produce more hydroxyl radicals and oxygen-based species which speed up the oxidative reaction with organic pollutants, and hence accelerate the process of color degradation.

Method of and apparatus for accelerating a projectile

DOEpatents

Goldstein, Yeshayahu S. A.; Tidman, Derek A.

1986-01-01

A projectile is accelerated along a confined path by supplying a pulsed high pressure, high velocity plasma jet to the rear of the projectile as the projectile traverses the path. The jet enters the confined path at a non-zero angle relative to the projectile path. The pulse is derived from a dielectric capillary tube having an interior wall from which plasma forming material is ablated in response to a discharge voltage. The projectile can be accelerated in response to the kinetic energy in the plasma jet or in response to a pressure increase of gases in the confined path resulting from the heat added to the gases by the plasma.

High velocity pulsed wire-arc spray

NASA Technical Reports Server (NTRS)

Kincaid, Russell W. (Inventor); Witherspoon, F. Douglas (Inventor); Massey, Dennis W. (Inventor)

1999-01-01

Wire arc spraying using repetitively pulsed, high temperature gas jets, usually referred to as plasma jets, and generated by capillary discharges, substantially increases the velocity of atomized and entrained molten droplets. The quality of coatings produced is improved by increasing the velocity with which coating particles impact the coated surface. The effectiveness of wire-arc spraying is improved by replacing the usual atomizing air stream with a rapidly pulsed high velocity plasma jet. Pulsed power provides higher coating particle velocities leading to improved coatings. 50 micron aluminum droplets with velocities of 1500 m/s are produced. Pulsed plasma jet spraying provides the means to coat the insides of pipes, tubes, and engine block cylinders with very high velocity droplet impact.

Fundamental Studies of Transient, Atmospheric-Pressure, Small-Scale Plasmas

DTIC Science & Technology

2017-01-23

e.g. plasma brush) were explored for surface decontamination against pathogenic bacteria and biofilms , as well as for treatment of cervical cancer , in...pressure plasma jets and jet arrays (e.g. plasma brush) were explored for surface decontamination against pathogenic bacteria and biofilms , as well as...for treatment of cervical cancer , in vitro. 4) Other studies involving portable nanosecond pulsed power generation based gas switches or

Inductive and electrostatic acceleration in relativistic jet-plasma interactions.

PubMed

Ng, Johnny S T; Noble, Robert J

2006-03-24

We report on the observation of rapid particle acceleration in numerical simulations of relativistic jet-plasma interactions and discuss the underlying mechanisms. The dynamics of a charge-neutral, narrow, electron-positron jet propagating through an unmagnetized electron-ion plasma was investigated using a three-dimensional, electromagnetic, particle-in-cell computer code. The interaction excited magnetic filamentation as well as electrostatic plasma instabilities. In some cases, the longitudinal electric fields generated inductively and electrostatically reached the cold plasma-wave-breaking limit, and the longitudinal momentum of about half the positrons increased by 50% with a maximum gain exceeding a factor of 2 during the simulation period. Particle acceleration via these mechanisms occurred when the criteria for Weibel instability were satisfied.

Plasma injector for a three-phase plasma torch with rail electrodes and some results of its investigation

NASA Astrophysics Data System (ADS)

Dudnik, Yu D.; Borovskoy, A. M.; Shiryaev, V. N.; Safronov, A. A.; Kuznetsov, V. E.; Vasilieva, O. B.; Pavlov, A. V.; Ivanov, D. V.

2018-01-01

Plasma injector made on the basis of the alternating-current plasma torch designed for the three-phase ac plasma torch with 100-500 kWrail electrodes is studied. The construction of the plasma injector is examined. Different materials for manufacture of injector electrodes are investigated. Current-voltage characteristics of the injector are obtained. Investigations of the plasma jet are carried out, and the jet temperature dependence versus the gas flow rate and electric power of the injector is measured.

Interaction of the jet from the neutron star with the interstellar medium

NASA Astrophysics Data System (ADS)

Kiikov, S. O.

2017-12-01

The interaction between the hypersonic plasma jet from the accreting neutron star and the ambient interstellar medium is studied. It is assumed that the jet is launched from the accretion disk via the open magnetic field anchored in the disk. The analytical investigation for the structure of the working surface of the jet is carried out. The estimates of the volume stream functions in the region of the interaction between the jet and the interstellar medium are derived. The obtained results allow to examine the distribution of the plasma velocity fields in the interaction region.

FAST TRACK COMMUNICATION: Modelling of streamer propagation in atmospheric-pressure helium plasma jets

NASA Astrophysics Data System (ADS)

Naidis, G. V.

2010-10-01

The results of a two-dimensional numerical simulation of positive streamer propagation in atmospheric-pressure helium jets injected into ambient air are presented. It is shown that depending on the jet width and the initial radial distribution of electron number density streamer structures of two types can be formed: one with maxima of electric field and electron density at the jet axis and another with maxima of these parameters near the boundary between the jet and surrounding air. The latter structure is similar to the observed ring-shaped structures of plasma bullets.

Cold plasma decontamination using flexible jet arrays

NASA Astrophysics Data System (ADS)

Konesky, Gregory

2010-04-01

Arrays of atmospheric discharge cold plasma jets have been used to decontaminate surfaces of a wide range of microorganisms quickly, yet not damage that surface. Its effectiveness in decomposing simulated chemical warfare agents has also been demonstrated, and may also find use in assisting in the cleanup of radiological weapons. Large area jet arrays, with short dwell times, are necessary for practical applications. Realistic situations will also require jet arrays that are flexible to adapt to contoured or irregular surfaces. Various large area jet array prototypes, both planar and flexible, are described, as is the application to atmospheric decontamination.

Modeling the Transport Phenomena in the Solution Precursor Plasma Spraying

NASA Astrophysics Data System (ADS)

Shan, Yanguang

2008-10-01

Solution precursor plasma spraying has been used to produce finely structured ceramic coatings with nano- and sub-micrometric features. This process involves the injection of a solution spray of ceramic salts into a DC plasma jet under atmospheric condition. During the process, the solvent vaporizes as the droplet travel downstream. Solid particles are finally formed due to the precipitation of the solute, and the particle are heated up and accelerated to the substrate to generate the coating. This work describes a 3D model to simulate the transport phenomena and the trajectory and heating of the solution spray in the process. The jet-spray two-way interactions are considered. A simplified model is employed to simulate the evolution process and the formation of the solid particle from the solution droplet in the plasma jet. O'Rourke's droplet collision model is used to take into account of the influence of droplet collision. The influence of droplet breakup is also considered by implementing TAB droplet breakup models into the plasma jet model. The temperature and velocity fields of the jet are obtained and validated. The particle size, velocity, temperature and position distribution on the substrate are predicted.

Reduction and degradation of amyloid aggregates by a pulsed radio-frequency cold atmospheric plasma jet

NASA Astrophysics Data System (ADS)

Bayliss, D. L.; Walsh, J. L.; Shama, G.; Iza, F.; Kong, M. G.

2009-11-01

Surface-borne amyloid aggregates with mature fibrils are used as a non-infectious prion model to evaluate cold atmospheric plasmas (CAPs) as a prion inactivation strategy. Using a helium-oxygen CAP jet with pulsed radio-frequency (RF) excitation, amyloid aggregates deposited on freshly cleaved mica discs are reduced substantially leaving only a few spherical fragments of sub-micrometer sizes in areas directly treated by the CAP jet. Outside the light-emitting part of the CAP jet, plasma treatment results in a 'skeleton' of much reduced amyloid stacks with clear evidence of fibril fragmentation. Analysis of possible plasma species and the physical configuration of the jet-sample interaction suggests that the skeleton structures observed are unlikely to have arisen as a result of physical forces of detachment, but instead by progressive diffusion of oxidizing plasma species into porous amyloid aggregates. Composition of chemical bonds of this reduced amyloid sample is very different from that of intact amyloid aggregates. These suggest the possibility of on-site degradation by CAP treatment with little possibility of spreading contamination elsewhere , thus offering a new reaction chemistry route to protein infectivity control with desirable implications for the practical implementation of CAP-based sterilization systems.

Influence of oxygen in atmospheric-pressure argon plasma jet on sterilization of Bacillus atrophaeous spores

NASA Astrophysics Data System (ADS)

Lim, Jin-Pyo; Uhm, Han S.; Li, Shou-Zhe

2007-09-01

A nonequilibrium Ar /O2 plasma discharge at atmospheric pressure was carried out in a coaxial cylindrical reactor with a stepped electrode configuration powered by a 13.56MHz rf power supplier. The argon glow discharge with high electron density produces oxygen reactive species in large quantities. Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological warfare agents. The decimal reduction time (D values) of the Ar /O2 plasma jet at an exposure distance of 0.5-1.5cm ranges from 5 to 57s. An actinometric comparison of the sterilization data shows that atomic oxygen radicals play a significant role in plasma sterilization. When observed under a scanning electron microscope, the average size of the spores appears to be greatly reduced due to chemical reactions with the oxygen radicals.

Pulsed high energy synthesis of fine metal powders

NASA Technical Reports Server (NTRS)

Witherspoon, F. Douglas (Inventor); Massey, Dennis W. (Inventor)

1999-01-01

Repetitively pulsed plasma jets generated by a capillary arc discharge at high stagnation pressure (>15,000 psi) and high temperature (>10,000 K) are utilized to produce 0.1-10 .mu.m sized metal powders and decrease cost of production. The plasma jets impact and atomize melt materials to form the fine powders. The melt can originate from a conventional melt stream or from a pulsed arc between two electrodes. Gas streams used in conventional gas atomization are replaced with much higher momentum flux plasma jets. Delivering strong incident shocks aids in primary disintegration of the molten material. A series of short duration, high pressure plasma pulses fragment the molten material. The pulses introduce sharp velocity gradients in the molten material which disintegrates into fine particles. The plasma pulses have peak pressures of approximately one kilobar. The high pressures improve the efficiency of disintegration. High gas flow velocities and pressures are achieved without reduction in gas density. Repetitively pulsed plasma jets will produce powders with lower mean size and narrower size distribution than conventional atomization techniques.

Characterization of Wet Air Plasma Jet Powered by Sinusoidal High Voltage and Nanosecond Pulses for Plasma Agricultural Application

NASA Astrophysics Data System (ADS)

Takashima, Keisuke; Shimada, Keisuke; Konishi, Hideaki; Kaneko, Toshiro

2015-09-01

Not only for the plasma sterilization but also for many of plasma life-science applications, atmospheric pressure plasma devices that allowed us to control its state and reactive species production are deserved to resolve the roles of the chemical species. Influence of the hydroxyl radical and ozone on germination of conidia of a strawberry pathogen is presented. Water addition to air plasma jet significantly improves germination suppression performance, while measured reactive oxygen species (ROS) are reduced. Although the results show a negative correlation between ROS and the germination suppression, this infers the importance of chemical composition generated by plasma. For further control of the plasma product, a plasma jet powered by sinusoidal high voltage and nanosecond pulses is developed and characterized with the voltage-charge Lissajous. Control of breakdown phase and discharge power by pulse-imposed phase is presented. This work is supported by JSPS KAKENHI Grant-in-Aid for Young Scientists (B) Grant Number 15K17480 and Exploratory Research Grant Number 23644199.

Cold atmospheric plasma jet-generated RONS and their selective effects on normal and carcinoma cells

PubMed Central

Kim, Sun Ja; Chung, T. H.

2016-01-01

Cold atmospheric helium plasma jets were fabricated and utilized for plasma–cell interactions. The effect of operating parameters and jet design on the generation of specific reactive oxygen and nitrogen species (RONS) within cells and cellular response were investigated. It was found that plasma treatment induced the overproduction of RONS in various cancer cell lines selectively. The plasma under a relatively low applied voltage induced the detachment of cells, a reduction in cell viability, and apoptosis, while the plasma under higher applied voltage led to cellular necrosis in our case. To determine whether plasma-induced reactive oxygen species (ROS) generation occurs through interfering with mitochondria-related cellular response, we examined the plasma effects on ROS generation in both parental A549 cells and A549 ρ0 cells. It was observed that cancer cells were more susceptible to plasma-induced RONS (especially nitric oxide (NO) and nitrogen dioxide (NO2−) radicals) than normal cells, and consequently, plasma induced apoptotic cell responses mainly in cancer cells. PMID:26838306

Simulation of Plasma Jet Merger and Liner Formation within the PLX- α Project

NASA Astrophysics Data System (ADS)

Samulyak, Roman; Chen, Hsin-Chiang; Shih, Wen; Hsu, Scott

2015-11-01

Detailed numerical studies of the propagation and merger of high Mach number argon plasma jets and the formation of plasma liners have been performed using the newly developed method of Lagrangian particles (LP). The LP method significantly improves accuracy and mathematical rigor of common particle-based numerical methods such as smooth particle hydrodynamics while preserving their main advantages compared to grid-based methods. A brief overview of the LP method will be presented. The Lagrangian particle code implements main relevant physics models such as an equation of state for argon undergoing atomic physics transformation, radiation losses in thin optical limit, and heat conduction. Simulations of the merger of two plasma jets are compared with experimental data from past PLX experiments. Simulations quantify the effect of oblique shock waves, ionization, and radiation processes on the jet merger process. Results of preliminary simulations of future PLX- alpha experiments involving the ~ π / 2 -solid-angle plasma-liner configuration with 9 guns will also be presented. Partially supported by ARPA-E's ALPHA program.

Artificial plasma jet in the ionosphere

NASA Astrophysics Data System (ADS)

Haerendel, G.; Sagdeev, R. Z.

The dynamics of an artificially injected plasma beam in the near-earth space are analyzed in terms of the beam structure, its propagation across the magnetic field, and the resulting wave phenomena (Porcupine Project, flight 4, March 31, 1979). Out of the four ejectable canisters attached to the main payload, two were instrumented by the U.S., one by the USSR (the Xenon plasma beam experiment), and one by West Germany (carrying a barium ion jet experiment). The propagation of the plasma seems to occur in three stages, with high-frequency broad-band oscillations mainly localized in the 'core' of the jet, while low-frequency oscillations were spatially separated from it. The generation region of LF oscillations was found to be much wider than the jet core. As a result of the interaction between the plasma beam and the ambient medium a heating of electrons, up to energies of about 20 eV, associated with LF noise was observed. The behavior of high-energy ions and the observed HF wave phenomena need further analysis.

Inactivation of Gram-positive biofilms by low-temperature plasma jet at atmospheric pressure

NASA Astrophysics Data System (ADS)

Marchal, F.; Robert, H.; Merbahi, N.; Fontagné-Faucher, C.; Yousfi, M.; Romain, C. E.; Eichwald, O.; Rondel, C.; Gabriel, B.

2012-08-01

This work is devoted to the evaluation of the efficiency of a new low-temperature plasma jet driven in ambient air by a dc-corona discharge to inactivate adherent cells and biofilms of Gram-positive bacteria. The selected microorganisms were lactic acid bacteria, a Weissella confusa strain which has the particularity to excrete a polysaccharide polymer (dextran) when sucrose is present. Both adherent cells and biofilms were treated with the low-temperature plasma jet for different exposure times. The antimicrobial efficiency of the plasma was tested against adherent cells and 48 h-old biofilms grown with or without sucrose. Bacterial survival was estimated using both colony-forming unit counts and fluorescence-based assays for bacterial cell viability. The experiments show the ability of the low-temperature plasma jet at atmospheric pressure to inactivate the bacteria. An increased resistance of bacteria embedded within biofilms is clearly observed. The resistance is also significantly higher with biofilm in the presence of sucrose, which indicates that dextran could play a protective role.

Magnetohydrodynamic simulation study of plasma jets and plasma-surface contact in coaxial plasma accelerators

DOE PAGES

Subramaniam, Vivek; Raja, Laxminarayan L.

2017-06-13

Recent experiments by Loebner et al. [IEEE Trans. Plasma Sci. 44, 1534 (2016)] studied the effect of a hypervelocity jet emanating from a coaxial plasma accelerator incident on target surfaces in an effort to mimic the transient loading created during edge localized mode disruption events in fusion plasmas. In this study, we present a magnetohydrodynamic (MHD) numerical model to simulate plasma jet formation and plasma-surface contact in this coaxial plasma accelerator experiment. The MHD system of equations is spatially discretized using a cell-centered finite volume formulation. The temporal discretization is performed using a fully implicit backward Euler scheme and themore » resultant stiff system of nonlinear equations is solved using the Newton method. The numerical model is employed to obtain some key insights into the physical processes responsible for the generation of extreme stagnation conditions on the target surfaces. Simulations of the plume (without the target plate) are performed to isolate and study phenomena such as the magnetic pinch effect that is responsible for launching pressure pulses into the jet free stream. The simulations also yield insights into the incipient conditions responsible for producing the pinch, such as the formation of conductive channels. The jet-target impact studies indicate the existence of two distinct stages involved in the plasma-surface interaction. A fast transient stage characterized by a thin normal shock transitions into a pseudo-steady stage that exhibits an extended oblique shock structure. A quadratic scaling of the pinch and stagnation conditions with the total current discharged between the electrodes is in qualitative agreement with the results obtained in the experiments. Finally, this also illustrates the dominant contribution of the magnetic pressure term in determining the magnitude of the quantities of interest.« less

Magnetohydrodynamic simulation study of plasma jets and plasma-surface contact in coaxial plasma accelerators

NASA Astrophysics Data System (ADS)

Subramaniam, Vivek; Raja, Laxminarayan L.

2017-06-01

Recent experiments by Loebner et al. [IEEE Trans. Plasma Sci. 44, 1534 (2016)] studied the effect of a hypervelocity jet emanating from a coaxial plasma accelerator incident on target surfaces in an effort to mimic the transient loading created during edge localized mode disruption events in fusion plasmas. In this paper, we present a magnetohydrodynamic (MHD) numerical model to simulate plasma jet formation and plasma-surface contact in this coaxial plasma accelerator experiment. The MHD system of equations is spatially discretized using a cell-centered finite volume formulation. The temporal discretization is performed using a fully implicit backward Euler scheme and the resultant stiff system of nonlinear equations is solved using the Newton method. The numerical model is employed to obtain some key insights into the physical processes responsible for the generation of extreme stagnation conditions on the target surfaces. Simulations of the plume (without the target plate) are performed to isolate and study phenomena such as the magnetic pinch effect that is responsible for launching pressure pulses into the jet free stream. The simulations also yield insights into the incipient conditions responsible for producing the pinch, such as the formation of conductive channels. The jet-target impact studies indicate the existence of two distinct stages involved in the plasma-surface interaction. A fast transient stage characterized by a thin normal shock transitions into a pseudo-steady stage that exhibits an extended oblique shock structure. A quadratic scaling of the pinch and stagnation conditions with the total current discharged between the electrodes is in qualitative agreement with the results obtained in the experiments. This also illustrates the dominant contribution of the magnetic pressure term in determining the magnitude of the quantities of interest.

Magnetohydrodynamic simulation study of plasma jets and plasma-surface contact in coaxial plasma accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Subramaniam, Vivek; Raja, Laxminarayan L.

Recent experiments by Loebner et al. [IEEE Trans. Plasma Sci. 44, 1534 (2016)] studied the effect of a hypervelocity jet emanating from a coaxial plasma accelerator incident on target surfaces in an effort to mimic the transient loading created during edge localized mode disruption events in fusion plasmas. In this study, we present a magnetohydrodynamic (MHD) numerical model to simulate plasma jet formation and plasma-surface contact in this coaxial plasma accelerator experiment. The MHD system of equations is spatially discretized using a cell-centered finite volume formulation. The temporal discretization is performed using a fully implicit backward Euler scheme and themore » resultant stiff system of nonlinear equations is solved using the Newton method. The numerical model is employed to obtain some key insights into the physical processes responsible for the generation of extreme stagnation conditions on the target surfaces. Simulations of the plume (without the target plate) are performed to isolate and study phenomena such as the magnetic pinch effect that is responsible for launching pressure pulses into the jet free stream. The simulations also yield insights into the incipient conditions responsible for producing the pinch, such as the formation of conductive channels. The jet-target impact studies indicate the existence of two distinct stages involved in the plasma-surface interaction. A fast transient stage characterized by a thin normal shock transitions into a pseudo-steady stage that exhibits an extended oblique shock structure. A quadratic scaling of the pinch and stagnation conditions with the total current discharged between the electrodes is in qualitative agreement with the results obtained in the experiments. Finally, this also illustrates the dominant contribution of the magnetic pressure term in determining the magnitude of the quantities of interest.« less

A pulsed plasma jet with the various Ar/N2 mixtures

NASA Astrophysics Data System (ADS)

Barkhordari, A.; Ganjovi, A.; Mirzaei, I.; Falahat, A.; Rostami Ravari, M. N.

2017-12-01

In this paper, using the Optical Emission Spectroscopy technique, the physical properties of a fabricated pulsed DBD plasma jet are studied. Ar/N2 gaseous mixture is taken as operational gas, and Ar contribution in Ar/N2 mixture is varied from 75 to 95%. Through the optical emission spectra analysis of the pulsed DBD plasma jet, the rotational, vibrational and excitation temperatures and density of electrons in plasma medium of the pulsed plasma jet are obtained. It is seen that, at the wavelength of 750.38 nm, the radiation intensity from the Ar 4p → 4 s transition increases at the higher Ar contributions in Ar/N2 mixture. It is found that, for 95% of Ar presence in the mixture, the emission intensities from argon and molecular nitrogen are higher, and the emission line intensities will increase nonlinearly. In addition, it is observed that the quenching of Ar* by N2 results in the higher intensities of N2 excited molecules. Moreover, at the higher percentages of Ar in Ar/N2 mixture, while all the plasma temperatures are increased, the plasma electron density is reduced.

Effect of the relative shift between the electron density and temperature pedestal position on the pedestal stability in JET-ILW and comparison with JET-C

NASA Astrophysics Data System (ADS)

Stefanikova, E.; Frassinetti, L.; Saarelma, S.; Loarte, A.; Nunes, I.; Garzotti, L.; Lomas, P.; Rimini, F.; Drewelow, P.; Kruezi, U.; Lomanowski, B.; de la Luna, E.; Meneses, L.; Peterka, M.; Viola, B.; Giroud, C.; Maggi, C.; contributors, JET

2018-05-01

The electron temperature and density pedestals tend to vary in their relative radial positions, as observed in DIII-D (Beurskens et al 2011 Phys. Plasmas 18 056120) and ASDEX Upgrade (Dunne et al 2017 Plasma Phys. Control. Fusion 59 14017). This so-called relative shift has an impact on the pedestal magnetohydrodynamic (MHD) stability and hence on the pedestal height (Osborne et al 2015 Nucl. Fusion 55 063018). The present work studies the effect of the relative shift on pedestal stability of JET ITER-like wall (JET-ILW) baseline low triangularity (δ) unseeded plasmas, and similar JET-C discharges. As shown in this paper, the increase of the pedestal relative shift is correlated with the reduction of the normalized pressure gradient, therefore playing a strong role in pedestal stability. Furthermore, JET-ILW tends to have a larger relative shift compared to JET carbon wall (JET-C), suggesting a possible role of the plasma facing materials in affecting the density profile location. Experimental results are then compared with stability analysis performed in terms of the peeling-ballooning model and with pedestal predictive model EUROPED (Saarelma et al 2017 Plasma Phys. Control. Fusion). Stability analysis is consistent with the experimental findings, showing an improvement of the pedestal stability, when the relative shift is reduced. This has been ascribed mainly to the increase of the edge bootstrap current, and to minor effects related to the increase of the pedestal pressure gradient and narrowing of the pedestal pressure width. Pedestal predictive model EUROPED shows a qualitative agreement with experiment, especially for low values of the relative shift.

Analysis of Ar plasma jets induced by single and double dielectric barrier discharges at atmospheric pressure

NASA Astrophysics Data System (ADS)

Judée, F.; Merbahi, N.; Wattieaux, G.; Yousfi, M.

2016-09-01

The aim is the comparison of different plasma parameters of single and double dielectric barrier discharge plasma jet configurations (S-DBD and D-DBD) which are potentially usable in biomedical applications. Both configurations are studied in terms of electric field distribution, electrical discharge characteristics, plasma parameters (estimated by optical emission spectroscopy analysis), and hydrodynamics of the plasma jet for electrical parameters of power supplies corresponding to an applied voltage of 10 kV, pulse duration of 1 μs, frequency of 9.69 kHz, and Ar flow of 2 l/min. We observed that the D-DBD configuration requires half the electrical power one needs to provide in the S-DBD case to generate a plasma jet with similar characteristics: excitation temperature around 4700 K, electron density around 2.5 × 1014 cm-3, gas temperature of about 320 K, a relatively high atomic oxygen concentration reaching up to 1000 ppm, the presence of reactive oxygen and nitrogen species (nitric oxide, hydroxyl radical, and atomic oxygen), and an irradiance in the UV-C range of about 20 μW cm-2. Moreover, it has been observed that D-DBD plasma jet is more sensitive to short pulse durations, probably due to the charge accumulation over the dielectric barrier around the internal electrode. This results in a significantly longer plasma length in the D-DBD configuration than in the S-DBD one up to a critical flow rate (2.25 l/min) before the occurrence of turbulence in the D-DBD case. Conversely, ionization wave velocities are significantly higher in the S-DBD setup (3.35 × 105 m/s against 1.02 × 105 m/s for D-DBD), probably due to the higher electrostatic field close to the high voltage electrode in the S-DBD plasma jet.

Particle Acceleration, Magnetic Field Generation, and Emission in Relativistic Pair Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Ramirez-Ruiz, E.; Hardee, P.; Hededal, C.; Mizuno, Y.

2005-01-01

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created by relativistic pair jets are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet propagating through an ambient plasma with and without initial magnetic fields. The growth rates of the Weibel instability depends on the distribution of pair jets. Simulations show that the Weibel instability created in the collisionless shock accelerates particles perpendicular and parallel to the jet propagation direction. The simulation results show that this instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Particle Acceleration, Magnetic Field Generation, and Emission in Relativistic Pair Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K. I.; Hardee, P.; Hededal, C. B.; Richardson, G.; Sol, H.; Preece, R.; Fishman, G. J.

2004-01-01

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., Buneman, Weibel and other two-stream instabilities) created in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating into an ambient plasma. We find that the growth times depend on the Lorenz factors of jets. The jets with larger Lorenz factors grow slower. Simulations show that the Weibel instability created in the collisionless shock front accelerates jet and ambient particles both perpendicular and parallel to the jet propagation direction. The small scale magnetic field structure generated by the Weibel instability is appropriate to the generation of "jitter" radiation from deflected electrons (positrons) as opposed to synchrotron radiation. The jitter radiation resulting from small scale magnetic field structures may be important for understanding the complex time structure and spectral evolution observed in gamma-ray bursts or other astrophysical sources containing relativistic jets and relativistic collisionless shocks.

Magnetized Target Fusion Driven by Plasma Liners

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Eskridge, Richard; Smith, James; Lee, Michael; Richeson, Jeff; Schmidt, George; Knapp, Charles E.; Kirkpatrick, Ronald C.; Turchi, Peter J.; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

Magnetized target fusion (MTF) attempts to combine the favorable attributes of magnetic confinement fusion (MCF) for energy confinement with the attributes of inertial confinement fusion (ICF) for efficient compression heating and wall-free containment of the fusing plasma. It uses a material liner to compress and contain a magnetized plasma. For practical applications, standoff drivers to deliver the imploding momentum flux to the target plasma remotely are required. Spherically converging plasma jets have been proposed as standoff drivers for this purpose. The concept involves the dynamic formation of a spherical plasma liner by the merging of plasma jets, and the use of the liner so formed to compress a spheromak or a field reversed configuration (FRC). For the successful implementation of the scheme, plasma jets of the requisite momentum flux density need to be produced. Their transport over sufficiently large distances (a few meters) needs to be assured. When they collide and merge into a liner, relative differences in velocity, density and temperature of the jets could give rise to instabilities in the development of the liner. Variation in the jet properties must be controlled to ensure that the growth rate of the instabilities are not significant over the time scale of the liner formation before engaging with the target plasma. On impact with the target plasma, some plasma interpenetration might occur between the liner and the target. The operating parameter space needs to be identified to ensure that a reasonably robust and conducting contact surface is formed between the liner and the target. A mismatch in the "impedance" between the liner and the target plasma could give rise to undesirable shock heating of the liner leading to increased entropy (thermal losses) in the liner. Any irregularities in the liner will accentuate the Rayleigh-Taylor instabilities during the compression of the target plasma by the liner.

Lab experiments investigating astrophysical jet physics

NASA Astrophysics Data System (ADS)

Bellan, Paul

2014-10-01

Dynamics relevant to astrophysical plasmas is being investigated in lab experiments having similar physics and topology, but much smaller time and space scales. High speed movies and numerical simulations both show that highly collimated MHD-driven plasma flows are a critical feature; these collimated flows can be considered to be a lab version of an astrophysical jet. Having both axial and azimuthal magnetic fields, the jet is effectively an axially lengthening plasma-confining flux tube with embedded helical magnetic field (flux rope). The jet velocity is in good agreement with an MHD acceleration model. Axial stagnation of the jet compresses embedded azimuthal magnetic flux and so results in jet self-collimation. Jets kink when they breach the Kruskal-Shafranov stability limit. The lateral acceleration of a sufficiently strong kink can provide an effective gravity which provides the environment for a spontaneously-developing, fine-scale, extremely fast Rayleigh-Taylor instability that erodes the current channel to be smaller than the ion skin depth. This cascade from the ideal MHD scale of the kink to the non-MHD ion skin depth scale can result in a fast magnetic reconnection whereby the jet breaks off from its source electrode. Supported by USDOE and NSF.

Thruster Plume Plasma Diagnostics: A Ground Chamber Experiment for a 2-Kilowatt Arcjet

NASA Technical Reports Server (NTRS)

Galofaro, Joel T.; Vayner, Boris V.; Hillard, G. Barry; Chornak, Michael T.

2005-01-01

Although detailed near field (0 to 3 cm) information regarding the exhaust plume of a two kilowatt arc jet is available (refs. 1 to 6), there is virtually little or no information (outside of theoretical extrapolations) available concerning the far field (2.6 to 6.1 m). Furthermore real information about the plasma at distances between (3 to 6 m) is of critical importance to high technology satellite companies in understanding the effect of arc jet plume exhausts on space based power systems. It is therefore of utmost importance that one understands the exact nature of the interaction between the arc jet plume, the spacecraft power system and the surrounding electrical plasma environment. A good first step in understanding the nature of the interactions lies in making the needed plume parameter measurements in the far field. All diagnostic measurements are performed inside a large vacuum system (12 m diameter by 18 m high) with a full scale arc jet and solar array panel in the required flight configuration geometry. Thus, necessary information regarding the plume plasma parameters in the far field is obtained. Measurements of the floating potential, the plasma potential, the electron temperature, number density, density distribution, debye length, and plasma frequency are obtained at various locations about the array (at vertical distances from the arc jet nozzle: 2.6, 2.7, 2.8, 3.2, 3.6, 4.0, 4.9, 5.0, 5.4, 5.75, and 6.14 m). Plasma diagnostic parameters are measured for both the floating and grounded configurations of the arc jet anode and array. Spectroscopic optical measurements are then acquired in close proximity to the nozzle, and contamination measurements are made in the vicinity of the array utilizing a mass spectrometer and two Quartz Crystal Microbalances (QCM's).

Scaled laboratory experiments explain the kink behaviour of the Crab Nebula jet.

PubMed

Li, C K; Tzeferacos, P; Lamb, D; Gregori, G; Norreys, P A; Rosenberg, M J; Follett, R K; Froula, D H; Koenig, M; Seguin, F H; Frenje, J A; Rinderknecht, H G; Sio, H; Zylstra, A B; Petrasso, R D; Amendt, P A; Park, H S; Remington, B A; Ryutov, D D; Wilks, S C; Betti, R; Frank, A; Hu, S X; Sangster, T C; Hartigan, P; Drake, R P; Kuranz, C C; Lebedev, S V; Woolsey, N C

2016-10-07

The remarkable discovery by the Chandra X-ray observatory that the Crab nebula's jet periodically changes direction provides a challenge to our understanding of astrophysical jet dynamics. It has been suggested that this phenomenon may be the consequence of magnetic fields and magnetohydrodynamic instabilities, but experimental demonstration in a controlled laboratory environment has remained elusive. Here we report experiments that use high-power lasers to create a plasma jet that can be directly compared with the Crab jet through well-defined physical scaling laws. The jet generates its own embedded toroidal magnetic fields; as it moves, plasma instabilities result in multiple deflections of the propagation direction, mimicking the kink behaviour of the Crab jet. The experiment is modelled with three-dimensional numerical simulations that show exactly how the instability develops and results in changes of direction of the jet.

The influence of the Hall term on the development of magnetized laser-produced plasma jets

NASA Astrophysics Data System (ADS)

Hamlin, N. D.; Seyler, C. E.; Khiar, B.

2018-04-01

We present 2D axisymmetric simulation results describing the influence of the Hall term on laser-produced plasma jets and their interaction with an applied magnetic field parallel to the laser axis. Bending of the poloidal B-field lines produces an MHD shock structure surrounding a conical cavity, and a jet is produced from the convergence of the shock envelope. Both the jet and the conical cavity underneath it are bound by fast MHD shocks. We compare the MHD results generated using the extended-MHD code Physics as an Extended-MHD Relaxation System with an Efficient Upwind Scheme (PERSEUS) with MHD results generated using GORGON and find reasonable agreement. We then present extended-MHD results generated using PERSEUS, which show that the Hall term has several effects on the plasma jet evolution. A hot low-density current-carrying layer of plasma develops just outside the plume, which results in a helical rather than a purely poloidal B-field, and reduces magnetic stresses, resulting in delayed flow convergence and jet formation. The flow is partially frozen into the helical field, resulting in azimuthal rotation of the jet. The Hall term also produces field-aligned current in strongly magnetized regions. In particular, we find the influence of Hall physics on this problem to be scale-dependent. This points to the importance of mitigating the Hall effect in a laboratory setup, by increasing the jet density and system dimensions, in order to avoid inaccurate extrapolation to astrophysical scales.

[Study on the fluctuation phenomena of arc plasma spraying jet].

PubMed

Zhao, Wen-hua; Liu, Di; Tian, Kuo

2002-08-01

The turbulence phenomenon is one of the most attractive characteristics of a DC arc plasma spraying jet. Most of the previous investigations believe that there is a laminar flow region in core of the jet. A spectrum diagnostic system has been built up in this paper to investigate these effects with the aid of high-speed digital camera. The FFT method has been applied to the analysis on the arc voltage and light signals. The influence of the arc behavior and the power supply on the jet is full-scale. It seems that there is not a laminar flow region in core of the jet. Moreover, from the light dynamic variation graph, the jet fluctuation due to the arc voltage behavior maybe is the dominant characteristic of the jet behavior.

Flux of OH and O radicals onto a surface by an atmospheric-pressure helium plasma jet measured by laser-induced fluorescence

NASA Astrophysics Data System (ADS)

Yonemori, Seiya; Ono, Ryo

2014-03-01

The atmospheric-pressure helium plasma jet is of emerging interest as a cutting-edge biomedical device for cancer treatment, wound healing and sterilization. Reactive oxygen species such as OH and O radicals are considered to be major factors in the application of biological plasma. In this study, density distribution, temporal behaviour and flux of OH and O radicals on a surface are measured using laser-induced fluorescence. A helium plasma jet is generated by applying pulsed high voltage of 8 kV with 10 kHz using a quartz tube with an inner diameter of 4 mm. To evaluate the relation between the surface condition and active species production, three surfaces are used: dry, wet and rat skin. When the helium flow rate is 1.5 l min-1, radial distribution of OH density on the rat skin surface shows a maximum density of 1.2 × 1013 cm-3 at the centre of the plasma-mediated area, while O atom density shows a maximum of 1.0 × 1015 cm-3 at 2.0 mm radius from the centre of the plasma-mediated area. Their densities in the effluent of the plasma jet are almost constant during the intervals of the discharge pulses because their lifetimes are longer than the pulse interval. Their density distribution depends on the helium flow rate and the surface humidity. With these results, OH and O production mechanisms in the plasma jet and their flux onto the surface are discussed.

Cracks and nanodroplets produced on tungsten surface samples by dense plasma jets

NASA Astrophysics Data System (ADS)

Ticoş, C. M.; Galaţanu, M.; Galaţanu, A.; Luculescu, C.; Scurtu, A.; Udrea, N.; Ticoş, D.; Dumitru, M.

2018-03-01

Small samples of 12.5 mm in diameter made from pure tungsten were exposed to a dense plasma jet produced by a coaxial plasma gun operated at 2 kJ. The surface of the samples was analyzed using a scanning electron microscope (SEM) before and after applying consecutive plasma shots. Cracks and craters were produced in the surface due to surface tensions during plasma heating. Nanodroplets and micron size droplets could be observed on the samples surface. An energy-dispersive spectroscopy (EDS) analysis revealed that the composition of these droplets coincided with that of the gun electrode material. Four types of samples were prepared by spark plasma sintering from powders with the average particle size ranging from 70 nanometers up to 80 μm. The plasma power load to the sample surface was estimated to be ≈4.7 MJ m-2 s-1/2 per shot. The electron temperature and density in the plasma jet had peak values 17 eV and 1.6 × 1022 m-3, respectively.

Simulation Study of Structure and Properties of Plasma Liners for the PLX- α Project

NASA Astrophysics Data System (ADS)

Samulyak, Roman; Shih, Wen; Hsu, Scott; PLX-Alpha Team

2017-10-01

Detailed numerical studies of the propagation and merger of high-Mach-number plasma jets and the formation and implosion of plasma liners have been performed using the FronTier code in support of the Plasma Liner Experiment-ALPHA (PLX- α) project. Physics models include radiation, physical diffusion, plasma-EOS models, and an anisotropic diffusion model that mimics deviations from fully collisional hydrodynamics in outer layers of plasma jets. Detailed structure and non-uniformity of plasma liners of due to primary and secondary shock waves have been studies as well as averaged quantities of ram pressure and Mach number. Synthetic data from simulations have been compared with available experimental data from a multi-chord interferometer and survey and high-resolution spectrometers. Numerical studies of the sensitivity of liner properties to experimental errors in the initial masses of jets and the synchronization of plasma gun valves have also been performed. Supported by the ARPA-E ALPHA program.

Comparative study between chemical and atmospheric pressure plasma jet cleaning on glass substrate

NASA Astrophysics Data System (ADS)

Elfa, Rizan Rizon; Ahmad, Mohd Khairul; Fhong, Soon Chin; Sahdan, Mohd Zainizan; Nayan, Nafarizal

2017-01-01

The atmospheric pressure plasma jet with low frequency and argon as working gas is presented in this paper to demonstrate its application for glass substrate clean and modification. The glass substrate clean by atmospheric pressure plasma jet is an efficient method to replace other substrate clean method. A comparative analysis is done in this paper between substrate cleaned by chemical and plasma treatment methods. Water contact angle reading is taken for a different method of substrate clean and period of treatment. Under the plasma treatment, the sample shows low surface adhesion due to having the surface property of super hydrophilic surface 7.26°. This comparative analysis is necessary in the industrial application for cost production due to sufficient time and method of substrate clean.

Effect of cold atmospheric pressure He-plasma jet on DNA change and mutation

NASA Astrophysics Data System (ADS)

Yaopromsiri, C.; Yu, L. D.; Sarapirom, S.; Thopan, P.; Boonyawan, D.

2015-12-01

Cold atmospheric pressure plasma jet (CAPPJ) effect on DNA change was studied for assessment of its safety. The experiment utilized a home-developed CAPPJ using 100% helium to directly treat naked DNA plasmid pGFP (plasmid green fluorescent protein). A traversal electric field was applied to separate the plasma components and both dry and wet sample conditions were adopted to investigate various factor roles in changing DNA. Plasma species were measured by using optical emission spectroscopy. DNA topological form change was analyzed by gel electrophoresis. The plasma jet treated DNA was transferred into bacterial Escherichia coli cells for observing mutation. The results show that the He-CAPPJ could break DNA strands due to actions from charge, radicals and neutrals and potentially cause genetic modification of living cells.

Destruction of {alpha}-synuclein based amyloid fibrils by a low temperature plasma jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karakas, Erdinc; Laroussi, Mounir; Munyanyi, Agatha

2010-10-04

Amyloid fibrils are ordered beta-sheet aggregates that are associated with a number of neurodegenerative diseases such as Alzheimer and Parkinson. At present, there is no cure for these progressive and debilitating diseases. Here we report initial studies that indicate that low temperature atmospheric pressure plasma can break amyloid fibrils into smaller units in vitro. The plasma was generated by the 'plasma pencil', a device capable of emitting a long, low temperature plasma plume/jet. This avenue of research may facilitate the development of a plasma-based medical treatment.

Coronal Jets Simulated with the Global Alfvén Wave Solar Model

NASA Astrophysics Data System (ADS)

Szente, J.; Toth, G.; Manchester, W. B., IV; van der Holst, B.; Landi, E.; Gombosi, T. I.; DeVore, C. R.; Antiochos, S. K.

2017-01-01

This paper describes a numerical modeling study of coronal jets to understand their effects on the global corona and their contribution to the solar wind. We implement jets into a well-established three-dimensional, two-temperature magnetohydrodynamic (MHD) solar corona model employing Alfvén-wave dissipation to produce a realistic solar-wind background. The jets are produced by positioning a compact magnetic dipole under the solar surface and rotating the boundary plasma around the dipole's magnetic axis. The moving plasma drags the magnetic field lines along with it, ultimately leading to a reconnection-driven jet similar to that described by Pariat et al. We compare line-of-sight synthetic images to multiple jet observations at EUV and X-ray bands, and find very close matches in terms of physical structure, dynamics, and emission. Key contributors to this agreement are the greatly enhanced plasma density and temperature in our jets compared to previous models. These enhancements arise from the comprehensive thermodynamic model that we use and, also, our inclusion of a dense chromosphere at the base of our jet-generating regions. We further find that the large-scale corona is affected significantly by the outwardly propagating torsional Alfvén waves generated by our polar jet, across 40° in latitude and out to 24 R⊙. We estimate that polar jets contribute only a few percent to the steady-state solar-wind energy outflow.

Transfer of a cold atmospheric pressure plasma jet through a long flexible plastic tube

NASA Astrophysics Data System (ADS)

Kostov, Konstantin G.; Machida, Munemasa; Prysiazhnyi, Vadym; Honda, Roberto Y.

2015-04-01

This work proposes an experimental configuration for the generation of a cold atmospheric pressure plasma jet at the downstream end of a long flexible plastic tube. The device consists of a cylindrical dielectric chamber where an insulated metal rod that serves as high-voltage electrode is inserted. The chamber is connected to a long (up to 4 m) commercial flexible plastic tube, equipped with a thin floating Cu wire. The wire penetrates a few mm inside the discharge chamber, passes freely (with no special support) along the plastic tube and terminates a few millimeters before the tube end. The system is flushed with Ar and the dielectric barrier discharge (DBD) is ignited inside the dielectric chamber by a low frequency ac power supply. The gas flow is guided by the plastic tube while the metal wire, when in contact with the plasma inside the DBD reactor, acquires plasma potential. There is no discharge inside the plastic tube, however an Ar plasma jet can be extracted from the downstream tube end. The jet obtained by this method is cold enough to be put in direct contact with human skin without an electric shock. Therefore, by using this approach an Ar plasma jet can be generated at the tip of a long plastic tube far from the high-voltage discharge region, which provides the safe operation conditions and device flexibility required for medical treatment.

Plasma diagnostics of non-equilibrium atmospheric plasma jets

NASA Astrophysics Data System (ADS)

Shashurin, Alexey; Scott, David; Keidar, Michael; Shneider, Mikhail

2014-10-01

Intensive development and biomedical application of non-equilibrium atmospheric plasma jet (NEAPJ) facilitates rapid growth of the plasma medicine field. The NEAPJ facility utilized at the George Washington University (GWU) demonstrated efficacy for treatment of various cancer types (lung, bladder, breast, head, neck, brain and skin). In this work we review recent advances of the research conducted at GWU concerned with the development of NEAPJ diagnostics including Rayleigh Microwave Scattering setup, method of streamer scattering on DC potential, Rogowski coils, ICCD camera and optical emission spectroscopy. These tools allow conducting temporally-resolved measurements of plasma density, electrical potential, charge and size of the streamer head, electrical currents flowing though the jet, ionization front propagation speed etc. Transient dynamics of plasma and discharge parameters will be considered and physical processes involved in the discharge will be analyzed including streamer breakdown, electrical coupling of the streamer tip with discharge electrodes, factors determining NEAPJ length, cross-sectional shape and propagation path etc.

Three-dimensional particle-in-cell simulations of a plasma jet/cloud streaming across a transverse magnetic field

NASA Astrophysics Data System (ADS)

Voitcu, Gabriel; Echim, Marius

2014-05-01

The dynamics of collisionless plasma jets/clouds in magnetic field configurations typical for the terrestrial magnetotail and frontside magnetosheath is a topic of interest for understanding the physics of the magnetosphere and its interaction with the solar wind. The presence of high-speed jets in the frontside magnetosheath has been recently proved experimentally by Cluster and THEMIS spacecrafts. There is increasing evidence that the bursty bulk flows in the magnetotail have jet-like features. In the present paper we use fully electromagnetic 3D explicit particle-in-cell (PIC) simulations to investigate the interaction of a localized three-dimensional plasma element/jet/cloud with a transverse magnetic field. We consider a plasma jet/cloud that moves in vacuum and perpendicular to an ambient magnetic field. Ampère and Faraday's laws are used to compute the self-consistent electric and magnetic fields on a three-dimensional spatial grid having a step-size of the order of the Debye length and using a time-step that resolves the plasma frequency. The initial magnetic field inside the simulation domain is uniform and the plasma bulk velocity at the beginning of the simulation is normal to the magnetic field direction. The total time scale of the simulation is of the order of few ion Larmor periods. Space and time variations of the plasma parameters and of the electromagnetic field are analyzed and discussed. We emphasize non-MHD effects like the energy-dispersion signatures at the edges of the plasma element, similar to results previously reported by Voitcu and Echim (2012) using test-kinetic simulations. Acknowledgments: Research supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 313038/STORM, and a grant of the Romanian Ministry of National Education, CNCS - UEFISCDI, project number PN-II-ID-PCE-2012-4-0418.

Scaled laboratory experiments explain the kink behaviour of the Crab Nebula jet

PubMed Central

Li, C. K.; Tzeferacos, P.; Lamb, D.; Gregori, G.; Norreys, P. A.; Rosenberg, M. J.; Follett, R. K.; Froula, D. H.; Koenig, M.; Seguin, F. H.; Frenje, J. A.; Rinderknecht, H. G.; Sio, H.; Zylstra, A. B.; Petrasso, R. D.; Amendt, P. A.; Park, H. S.; Remington, B. A.; Ryutov, D. D.; Wilks, S. C.; Betti, R.; Frank, A.; Hu, S. X.; Sangster, T. C.; Hartigan, P.; Drake, R. P.; Kuranz, C. C.; Lebedev, S. V.; Woolsey, N. C.

2016-01-01

The remarkable discovery by the Chandra X-ray observatory that the Crab nebula's jet periodically changes direction provides a challenge to our understanding of astrophysical jet dynamics. It has been suggested that this phenomenon may be the consequence of magnetic fields and magnetohydrodynamic instabilities, but experimental demonstration in a controlled laboratory environment has remained elusive. Here we report experiments that use high-power lasers to create a plasma jet that can be directly compared with the Crab jet through well-defined physical scaling laws. The jet generates its own embedded toroidal magnetic fields; as it moves, plasma instabilities result in multiple deflections of the propagation direction, mimicking the kink behaviour of the Crab jet. The experiment is modelled with three-dimensional numerical simulations that show exactly how the instability develops and results in changes of direction of the jet. PMID:27713403

Integrated modelling of H-mode pedestal and confinement in JET-ILW

NASA Astrophysics Data System (ADS)

Saarelma, S.; Challis, C. D.; Garzotti, L.; Frassinetti, L.; Maggi, C. F.; Romanelli, M.; Stokes, C.; Contributors, JET

2018-01-01

A pedestal prediction model Europed is built on the existing EPED1 model by coupling it with core transport simulation using a Bohm-gyroBohm transport model to self-consistently predict JET-ILW power scan for hybrid plasmas that display weaker power degradation than the IPB98(y, 2) scaling of the energy confinement time. The weak power degradation is reproduced in the coupled core-pedestal simulation. The coupled core-pedestal model is further tested for a 3.0 MA plasma with the highest stored energy achieved in JET-ILW so far, giving a prediction of the stored plasma energy within the error margins of the measured experimental value. A pedestal density prediction model based on the neutral penetration is tested on a JET-ILW database giving a prediction with an average error of 17% from the experimental data when a parameter taking into account the fuelling rate is added into the model. However the model fails to reproduce the power dependence of the pedestal density implying missing transport physics in the model. The future JET-ILW deuterium campaign with increased heating power is predicted to reach plasma energy of 11 MJ, which would correspond to 11-13 MW of fusion power in equivalent deuterium-tritium plasma but with isotope effects on pedestal stability and core transport ignored.

Effect of Pulsed Plasma Jets on the Recovering Boundary Layer Downstream of a Reflected Shock Interaction

NASA Astrophysics Data System (ADS)

Greene, Benton; Clemens, Noel; Magari, Patrick; Micka, Daniel; Ueckermann, Mattheus

2015-11-01

Shock-induced turbulent boundary layer separation can have many detrimental effects in supersonic inlets including flow distortion and instability, structural fatigue, poor pressure recovery, and unstart. The current study investigates the effect of pulsed plasma jets on the recovering boundary layer downstream of a reflected shock wave-boundary layer interaction. The effects of pitch and skew angle of the jet as well as the heating parameter and discharge time scale are tested using several pulsing frequencies. In addition, the effect of the plasma jets on the undisturbed boundary layer at 6 mm and 11 mm downstream of the jets is measured. A pitot-static pressure probe is used to measure the velocity profile of the boundary layer 35 mm downstream of the plasma jets, and the degree of boundary layer distortion is compared between the different models and run conditions. Additionally, the effect of each actuator configuration on the shape of the mean separated region is investigated using surface oil flow visualization. Previous studies with lower energy showed a weak effect on the downstream boundary layer. The current investigation will attempt to increase this effect using a higher-energy discharge. Funded by AFRL through and SBIR in collaboration with Creare, LLC.

The PLX- α Project: Progress and Plans

NASA Astrophysics Data System (ADS)

Hsu, S.; Witherspoon, F. D.; Cassibry, J.; Gilmore, M.; Samulyak, R.; Stoltz, P.; PLX-α Team

2016-10-01

The Plasma Liner Experiment-ALPHA (PLX- α) project aims to demonstrate the viability of spherically imploding plasma liners as a standoff driver for plasma-jet-driven magneto-inertial fusion (PJMIF). In the past year, progress has been made in designing and testing new contoured-gap coaxial guns, 3D model development and simulations (via Eulerian and Lagrangian hydrocodes) of PLX- α-relevant plasma-liner formation/implosion via up to 60 plasma jets ( 100 kJ of liner kinetic energy), 1D semi-analytic and numerical modeling of reactor-scale PJMIF (10s of MJ of liner kinetic energy), and preparation/upgrade of the PLX facility/diagnostics. The design goal for the coaxial guns is to form plasma jets of up to initial n 2 ×1016 cm-3, mass 5 mg, Vjet 50 km/s, rjet = 4 cm, and length 10 cm. The modeling research is assessing ram-pressure amplification and Mach-number degradation during liner convergence, evolution of liner non-uniformity amplitude and mode number, and exploration of PJMIF configurations with promising 1D and 2D fusion gains. Conical multi-jet-merging and full-4 π experiments will commence in Fall, 2016 and late 2017, respectively. Supported by the ARPA-E ALPHA Program.

First Production of C60 Nanoparticle Plasma Jet for Study of Disruption Mitigation for ITER

NASA Astrophysics Data System (ADS)

Bogatu, I. N.; Thompson, J. R.; Galkin, S. A.; Kim, J. S.; Brockington, S.; Case, A.; Messer, S. J.; Witherspoon, F. D.

2012-10-01

Unique fast response and large mass-velocity delivery of nanoparticle plasma jets (NPPJs) provide a novel application for ITER disruption mitigation, runaway electrons diagnostics and deep fueling. NPPJs carry a much larger mass than usual gases. An electromagnetic plasma gun provides a very high injection velocity (many km/s). NPPJ has much higher ram pressure than any standard gas injection method and penetrates the tokamak confining magnetic field. Assimilation is enhanced due to the NP large surface-to-volume ratio. Radially expanding NPPJs help achieving toroidal uniformity of radiation power. FAR-TECH's NPPJ system was successfully tested: a coaxial plasma gun prototype (˜35 cm length, 96 kJ energy) using a solid state TiH2/C60 pulsed power cartridge injector produced a hyper-velocity (>4 km/s), high-density (>10^23 m-3), C60 plasma jet in ˜0.5 ms, with ˜1-2 ms overall response-delivery time. We present the TiH2/C60 cartridge injector output characterization (˜180 mg of sublimated C60 gas) and first production results of a high momentum C60 plasma jet (˜0.6 g.km/s).

Measurement of hydroxyl radical density generated from the atmospheric pressure bioplasma jet

NASA Astrophysics Data System (ADS)

Hong, Y. J.; Nam, C. J.; Song, K. B.; Cho, G. S.; Uhm, H. S.; Choi, D. I.; Choi, E. H.

2012-03-01

Atmospheric pressure bioplasmas are being used in a variety of bio-medical and material processing applications, surface modifications of polymers. This plasma can generate the various kinds of radicals when it contacs with the water. Especially, hydroxyl radical species have very important role in the biological and chemical decontamination of media in this situation. It is very important to investigate the hydroxyl radical density in needle-typed plasma jet since it plays a crucial role in interaction between the living body and plasma. We have generated the needle-typed plasma jet bombarding the water surface by using an Ar gas flow and investigated the emission lines by OES (optical emission spectroscopy). It is noted that the electron temperature and plasma density are measured to be about 1.7 eV and 3.4 × 1012 cm-3, respectively, under Ar gas flow ranged from 80 to 300 sccm (standard cubic centimeter per minute) in this experiment. The hydroxyl radical density has also been investigated and measured to be maximum value of 2.6 × 1015 cm-3 for the gas flow rate of 150 sccm in the needle-typed plasma jet by the ultraviolet optical absorption spectroscopy.

Influence of oxygen in atmospheric-pressure argon plasma jet on sterilization of Bacillus atrophaeous spores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Jin-Pyo; Uhm, Han S.; Li, Shou-Zhe

2007-09-15

A nonequilibrium Ar/O{sub 2} plasma discharge at atmospheric pressure was carried out in a coaxial cylindrical reactor with a stepped electrode configuration powered by a 13.56 MHz rf power supplier. The argon glow discharge with high electron density produces oxygen reactive species in large quantities. Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as freemore » from toxic biological warfare agents. The decimal reduction time (D values) of the Ar/O{sub 2} plasma jet at an exposure distance of 0.5-1.5 cm ranges from 5 to 57 s. An actinometric comparison of the sterilization data shows that atomic oxygen radicals play a significant role in plasma sterilization. When observed under a scanning electron microscope, the average size of the spores appears to be greatly reduced due to chemical reactions with the oxygen radicals.« less

Risk assessment of the application of a plasma jet in dermatology

NASA Astrophysics Data System (ADS)

Lademann, Juergen; Richter, Heike; Alborova, Alena; Humme, Daniel; Patzelt, Alexa; Kramer, Axel; Weltmann, Klaus-Dieter; Hartmann, Bernd; Ottomann, Christian; Fluhr, Joachim W.; Hinz, Peter; Hübner, Georg; Lademann, Olaf

2009-09-01

Regardless of the fact that several highly efficient antiseptics are commercially available, the antiseptic treatment of chronic wounds remains a problem. In the past, electrical plasma discharges have been frequently used in biometrical science for disinfection and sterilization of material surfaces. Plasma systems usually have a temperature of several hundred degrees. Recently, it was reported that ``cold'' plasma can be applied onto living tissue. In in vitro studies on cell culture, it could be demonstrated that this new plasma possesses excellent antiseptic properties. We perform a risk assessment concerning the in vivo application of a ``cold'' plasma jet on patients and volunteers. Two potential risk factors, UV radiation and temperature, are evaluated. We show that the UV radiation of the plasma in the used system is an order of magnitude lower than the minimal erythema dose, necessary to produce sunburn on the skin in vivo. Additionally, thermal damage of the tissue by the plasma can be excluded. The results of the risk assessment stimulate the in vivo application of the investigated plasma jet in the treatment of chronic wounds.

Modelling of plasma generation and thin film deposition by a non-thermal plasma jet at atmospheric pressure

NASA Astrophysics Data System (ADS)

Sigeneger, F.; Becker, M. M.; Foest, R.; Loffhagen, D.

2016-09-01

The gas flow and plasma in a miniaturized non-thermal atmospheric pressure plasma jet for plasma enhanced chemical vapour deposition has been investigated by means of hydrodynamic modelling. The investigation focuses on the interplay between the plasma generation in the active zone where the power is supplied by an rf voltage to the filaments, the transport of active plasma particles due to the gas flow into the effluent, their reactions with the thin film precursor molecules and the transport of precursor fragments towards the substrate. The main features of the spatially two-dimensional model used are given. The results of the numerical modelling show that most active particles of the argon plasma are mainly confined within the active volume in the outer capillary of the plasma jet, with the exception of molecular argon ions which are transported remarkably into the effluent together with slow electrons. A simplified model of the precursor kinetics yields radial profiles of precursor fragment fluxes onto the substrate, which agree qualitatively with the measured profiles of thin films obtained by static film deposition experiments.

Characteristics of polar coronal hole jets

NASA Astrophysics Data System (ADS)

Chandrashekhar, K.; Bemporad, A.; Banerjee, D.; Gupta, G. R.; Teriaca, L.

2014-01-01

Context. High spatial- and temporal-resolution images of coronal hole regions show a dynamical environment where mass flows and jets are frequently observed. These jets are believed to be important for the coronal heating and the acceleration of the fast solar wind. Aims: We studied the dynamics of two jets seen in a polar coronal hole with a combination of imaging from EIS and XRT onboard Hinode. We observed drift motions related to the evolution and formation of these small-scale jets, which we tried to model as well. Methods: Stack plots were used to find the drift and flow speeds of the jets. A toymodel was developed by assuming that the observed jet is generated by a sequence of single reconnection events where single unresolved blobs of plasma are ejected along open field lines, then expand and fall back along the same path, following a simple ballistic motion. Results: We found observational evidence that supports the idea that polar jets are very likely produced by multiple small-scale reconnections occurring at different times in different locations. These eject plasma blobs that flow up and down with a motion very similar to a simple ballistic motion. The associated drift speed of the first jet is estimated to be ≈27 km s-1. The average outward speed of the first jet is ≈171 km s-1, well below the escape speed, hence if simple ballistic motion is considered, the plasma will not escape the Sun. The second jet was observed in the south polar coronal hole with three XRT filters, namely, C-poly, Al-poly, and Al-mesh filters. Many small-scale (≈3″-5″) fast (≈200-300 km s-1) ejections of plasma were observed on the same day; they propagated outwards. We observed that the stronger jet drifted at all altitudes along the jet with the same drift speed of ≃7 km s-1. We also observed that the bright point associated with the first jet is a part of sigmoid structure. The time of appearance of the sigmoid and that of the ejection of plasma from the bright point suggest that the sigmoid is the progenitor of the jet. Conclusions: The enhancement in the light curves of low-temperature EIS lines in the later phase of the jet lifetime and the shape of the jet's stack plots suggests that the jet material falls back, and most likely cools down. To further support this conclusion, the observed drifts were interpreted within a scenario where reconnection progressively shifts along a magnetic structure, leading to the sequential appearance of jets of about the same size and physical characteristics. On this basis, we also propose a simple qualitative model that mimics the observations. Movies 1-3 are available in electronic form at http://www.aanda.org Warning, no authors found for 2014A&A...561A..97.

Generating Long Scale-Length Plasma Jets Embedded in a Uniform, Multi-Tesla Magnetic-Field

NASA Astrophysics Data System (ADS)

Manuel, Mario; Kuranz, Carolyn; Rasmus, Alex; Klein, Sallee; Fein, Jeff; Belancourt, Patrick; Drake, R. P.; Pollock, Brad; Hazi, Andrew; Park, Jaebum; Williams, Jackson; Chen, Hui

2013-10-01

Collimated plasma jets emerge in many classes of astrophysical objects and are of great interest to explore in the laboratory. In many cases, these astrophysical jets exist within a background magnetic field where the magnetic pressure approaches the plasma pressure. Recent experiments performed at the Jupiter Laser Facility utilized a custom-designed solenoid to generate the multi-tesla fields necessary to achieve proper magnetization of the plasma. Time-gated interferometry, Schlieren imaging, and proton radiography were used to characterize jet evolution and collimation under varying degrees of magnetization. Experimental results will be presented and discussed. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-NA0001840, by the National Laser User Facility Program, grant number DE-NA0000850, by the Predictive Sciences Academic Alliances Program in NNSA-ASC, grant number DEFC52-08NA28616, and by NASA through Einstein Postdoctoral Fellowship grant number PF3-140111 awarded by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060.

Formulation and Characterization of a Plasma Sterilized, Pharmaceutical Grade Chitosan Powder

PubMed Central

Crofton, Andrew R; Hudson, Samuel M; Howard, Kristy; Pender, Tyler; Abdelgawad, Abdelrahman; Wolski, Daniel; Kirsch, Wolff M

2016-01-01

Chitosan has great potential as a pharmaceutical excipient. In this study, chitosan flake was micronized using cryo-ball and cryo-jet milling and subsequently sterilized with nitrogen plasma. Micronized chitosan was characterized by laser diffraction, scanning electron microscopy (SEM), conductometric titration, viscometry, loss on drying, FTIR, and limulus amebocyte lysate (LAL) assays. Cryo-jet milling produced mean particle size of 16.05 μm, 44% smaller than cryo-ball milling. Cryomilled chitosan demonstrated increased hygroscopicity, but reduced molecular weight and degree of deacetylation (DD). SEM imaging showed highly irregular shapes. FTIR showed changes consistent with reduced DD and an unexplained shift at 1100 cm−1. Plasma treated chitosan was sterile with <2.5 EU/g after low-pressure plasma and <1.3 EU/g after atmospheric pressure plasma treatment. Plasma treatment decreased the reduced viscosity of chitosan flake and powder, with a greater effect on powder. In conclusion, pharmaceutical grade, sterile chitosan powder was produced with cryo-jet milling and plasma sterilization. PMID:27112892

Thermalization of mini-jets in a quark-gluon plasma

NASA Astrophysics Data System (ADS)

Iancu, Edmond; Wu, Bin

2015-10-01

We complete the physical picture for the evolution of a high-energy jet propagating through a weakly-coupled quark-gluon plasma by investigating the thermalization of the soft components of the jet. We argue that the following scenario should hold: the leading particle emits a significant number of mini-jets which promptly evolve via quasi-democratic branchings and thus degrade into a myriad of soft gluons, with energies of the order of the medium temperature T. Via elastic collisions with the medium constituents, these soft gluons relax to local thermal equilibrium with the plasma over a time scale which is considerably shorter than the typical lifetime of the mini-jet. The thermalized gluons form a tail which lags behind the hard components of the jet. We support this scenario, first, via parametric arguments and, next, by studying a simplified kinetic equation, which describes the jet dynamics in longitudinal phase-space. We solve the kinetic equation using both (semi-)analytical and numerical methods. In particular, we obtain the first exact, analytic, solutions to the ultrarelativistic Fokker-Planck equation in one-dimensional phase-space. Our results confirm the physical picture aforementioned and demonstrate the quenching of the jet via multiple branching followed by the thermalization of the soft gluons in the cascades.

Revealing plasma oscillation in THz spectrum from laser plasma of molecular jet.

PubMed

Li, Na; Bai, Ya; Miao, Tianshi; Liu, Peng; Li, Ruxin; Xu, Zhizhan

2016-10-03

Contribution of plasma oscillation to the broadband terahertz (THz) emission is revealed by interacting two-color (ω/2ω) laser pulses with a supersonic jet of nitrogen molecules. Temporal and spectral shifts of THz waves are observed as the plasma density varies. The former owes to the changing refractive index of the THz waves, and the latter correlates to the varying plasma frequency. Simulation of considering photocurrents, plasma oscillation and decaying plasma density explains the broadband THz spectrum and the varying THz spectrum. Plasma oscillation only contributes to THz waves at low plasma density owing to negligible plasma absorption. At the longer medium or higher density, the combining effects of plasma oscillation and absorption results in the observed low-frequency broadband THz spectra.

The Influence of the Hall Term on the Development of Magnetized Laser-Produced Plasma Jets

DOE PAGES

Hamlin, N.D.; Seyler, C. E.; Khiar, B.

2018-04-29

We present 2D axisymmetric simulation results describing the influence of the Hall term on laser-produced plasma jets and their interaction with an applied magnetic field parallel to the laser axis. Bending of the poloidal B-field lines produces an MHD shock structure surrounding a conical cavity, and a jet is produced from the convergence of the shock envelope. Both the jet and the conical cavity underneath it are bound by fast MHD shocks. We compare the MHD results generated using the extended-MHD code Physics as an Extended-MHD Relaxation System with an Efficient Upwind Scheme (PERSEUS) with MHD results generated using GORGONmore » and find reasonable agreement. We then present extended-MHD results generated using PERSEUS, which show that the Hall term has several effects on the plasma jet evolution. A hot low-density current-carrying layer of plasma develops just outside the plume, which results in a helical rather than a purely poloidal B-field, and reduces magnetic stresses, resulting in delayed flow convergence and jet formation. The flow is partially frozen into the helical field, resulting in azimuthal rotation of the jet. The Hall term also produces field-aligned current in strongly magnetized regions. In particular, we find the influence of Hall physics on this problem to be scale-dependent. In conclusion, this points to the importance of mitigating the Hall effect in a laboratory setup, by increasing the jet density and system dimensions, in order to avoid inaccurate extrapolation to astrophysical scales.« less

The Influence of the Hall Term on the Development of Magnetized Laser-Produced Plasma Jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamlin, N.D.; Seyler, C. E.; Khiar, B.

We present 2D axisymmetric simulation results describing the influence of the Hall term on laser-produced plasma jets and their interaction with an applied magnetic field parallel to the laser axis. Bending of the poloidal B-field lines produces an MHD shock structure surrounding a conical cavity, and a jet is produced from the convergence of the shock envelope. Both the jet and the conical cavity underneath it are bound by fast MHD shocks. We compare the MHD results generated using the extended-MHD code Physics as an Extended-MHD Relaxation System with an Efficient Upwind Scheme (PERSEUS) with MHD results generated using GORGONmore » and find reasonable agreement. We then present extended-MHD results generated using PERSEUS, which show that the Hall term has several effects on the plasma jet evolution. A hot low-density current-carrying layer of plasma develops just outside the plume, which results in a helical rather than a purely poloidal B-field, and reduces magnetic stresses, resulting in delayed flow convergence and jet formation. The flow is partially frozen into the helical field, resulting in azimuthal rotation of the jet. The Hall term also produces field-aligned current in strongly magnetized regions. In particular, we find the influence of Hall physics on this problem to be scale-dependent. In conclusion, this points to the importance of mitigating the Hall effect in a laboratory setup, by increasing the jet density and system dimensions, in order to avoid inaccurate extrapolation to astrophysical scales.« less

3-D MHD modeling and stability analysis of jet and spheromak plasmas launched into a magnetized plasma

NASA Astrophysics Data System (ADS)

Fisher, Dustin; Zhang, Yue; Wallace, Ben; Gilmore, Mark; Manchester, Ward; Arge, C. Nick

2016-10-01

The Plasma Bubble Expansion Experiment (PBEX) at the University of New Mexico uses a coaxial plasma gun to launch jet and spheromak magnetic plasma configurations into the Helicon-Cathode (HelCat) plasma device. Plasma structures launched from the gun drag frozen-in magnetic flux into the background magnetic field of the chamber providing a rich set of dynamics to study magnetic turbulence, force-free magnetic spheromaks, and shocks. Preliminary modeling is presented using the highly-developed 3-D, MHD, BATS-R-US code developed at the University of Michigan. BATS-R-US employs an adaptive mesh refinement grid that enables the capture and resolution of shock structures and current sheets, and is particularly suited to model the parameter regime under investigation. CCD images and magnetic field data from the experiment suggest the stabilization of an m =1 kink mode trailing a plasma jet launched into a background magnetic field. Results from a linear stability code investigating the effect of shear-flow as a cause of this stabilization from magnetic tension forces on the jet will be presented. Initial analyses of a possible magnetic Rayleigh Taylor instability seen at the interface between launched spheromaks and their entraining background magnetic field will also be presented. Work supported by the Army Research Office Award No. W911NF1510480.

Streaked Thomson Scattering on Laboratory Plasma Jets

NASA Astrophysics Data System (ADS)

Banasek, Jacob; Byvank, Tom; Rocco, Sophia; Kusse, Bruce; Hammer, David

2017-10-01

Streaked Thomson scattering measurements have been performed on plasma jets created from a 15 μm thick radial Al or Ti foil load on COBRA, a 1 MA pulsed power machine. The goal was to measure the electron temperatures inside the center of the plasma jet created by the radial foil. The laser used for these measurements had a maximum energy of 10 J at 526.5 nm in a 3 ns duration pulse. Early experiments showed using the full energy significantly heats the 5 ×1018 cm-3 jet by inverse bremsstrahlung radiation. Here we used a streak camera to record the scattered spectrum and measure the evolving electron temperature of this laser heated jet. Analysis of the streak camera image showed that the electron temperature of the Al jet was increased from about 25 eV to 80-100 eV within about 2 ns. The Ti jets showed even stronger interaction with the laser, being heated to over 150 eV, and showed some heating even when only 1 J of laser energy was used. Also, the ion-acoustic peaks in the scattered spectrum from the Ti jets were significantly narrower than those from Al jets. Initial results will also be presented with scattered spectra taken at two different times within a single experiment by splitting the probe beam. This research is supported by the NNSA Stewardship Sciences Academic Programs under DOE Cooperative Agreement DE-NA0001836.

Supersonic plasma jets in experiments for radiophysical testing of bodies flow

NASA Astrophysics Data System (ADS)

Balakirev, B. A.; Bityurin, V. A.; Bocharov, A. N.; Brovkin, V. G.; Vedenin, P. V.; Lashkov, V. A.; Mashek, I. Ch; Pashchina, A. S.; Petrovskiy, V. P.; Khoronzhuk, R. S.; Dobrovolskaya, A. S.

2018-01-01

The action of differently oriented magnetic fields on the parameters of bow shock created in the vicinity of aerodynamic bodies placed into the supersonic gas-plasma flows is studied. For these experiments two types of the high speed plasma jet sources are used—magneto-plasma compressor (MPC) and powerful pulse capillary type discharge. MPC allows to create the plasma jets with gas flow velocity of 10 ± 2 km/s, lifetime 30-50 μs, temperature Te ≈ 3 ± 0.5 eV, electron density about ne ˜ 1016cm-3 and temperature Te ≈ 3 ± 0.5 eV. The jet source based on powerful capillary discharge creates the flows with lifetime 1-20 ms, Mach numbers 3-8, plasma flow velocity 3-10 km/s, vibration and rotation temperatures 9000-14000 and 3800-6000 K respectively. The results of our first experiments show the possibility of using gas-plasma sources based on MPC and powerful capillary discharge for aerodynamic and radiophysical experiments. Comparatively small magnetic field B = 0.23-0.5 T, applied to the obtained bow shocks, essentially modify them. This can lead to a change in shape and an increase in the distance between the detached shock wave and the streamlined body surface if B is parallel to the jet velocity or to decrease this parameter if B is orthogonal to the oncoming flow. Probably, the first case can be useful for reducing the thermal load and aerodynamic drug of streamlined body and the second case can be used to control the radio-transparency of the plasma layer and solving the blackout problem.

Particle Acceleration, Magnetic Field Generation in Relativistic Shocks

NASA Technical Reports Server (NTRS)

Nishikawa, Ken-Ichi; Hardee, P.; Hededal, C. B.; Richardson, G.; Sol, H.; Preece, R.; Fishman, G. J.

2005-01-01

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. We find only small differences in the results between no ambient and weak ambient parallel magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. New simulations with an ambient perpendicular magnetic field show the strong interaction between the relativistic jet and the magnetic fields. The magnetic fields are piled up by the jet and the jet electrons are bent, which creates currents and displacement currents. At the nonlinear stage, the magnetic fields are reversed by the current and the reconnection may take place. Due to these dynamics the jet and ambient electron are strongly accelerated in both parallel and perpendicular directions.

Particle Acceleration, Magnetic Field Generation, and Emission in Relativistic Shocks

NASA Technical Reports Server (NTRS)

Nishikawa, Ken-IchiI.; Hededal, C.; Hardee, P.; Richardson, G.; Preece, R.; Sol, H.; Fishman, G.

2004-01-01

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (m) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. We find only small differences in the results between no ambient and weak ambient parallel magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. New simulations with an ambient perpendicular magnetic field show the strong interaction between the relativistic jet and the magnetic fields. The magnetic fields are piled up by the jet and the jet electrons are bent, which creates currents and displacement currents. At the nonlinear stage, the magnetic fields are reversed by the current and the reconnection may take place. Due to these dynamics the jet and ambient electron are strongly accelerated in both parallel and perpendicular directions.

Titanium nitride plasma-chemical synthesis with titanium tetrachloride raw material in the DC plasma-arc reactor

NASA Astrophysics Data System (ADS)

Kirpichev, D. E.; Sinaiskiy, M. A.; Samokhin, A. V.; Alexeev, N. V.

2017-04-01

The possibility of plasmochemical synthesis of titanium nitride is demonstrated in the paper. Results of the thermodynamic analysis of TiCl4 - H2 - N2 system are presented; key parameters of TiN synthesis process are calculated. The influence of parameters of plasma-chemical titanium nitride synthesis process in the reactor with an arc plasmatron on characteristics on the produced powders is experimentally investigated. Structure, chemical composition and morphology dependencies on plasma jet enthalpy, stoichiometric excess of hydrogen and nitrogen in a plasma jet are determined.

CORONAL JETS SIMULATED WITH THE GLOBAL ALFVÉN WAVE SOLAR MODEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szente, J.; Toth, G.; Manchester IV, W. B.

This paper describes a numerical modeling study of coronal jets to understand their effects on the global corona and their contribution to the solar wind. We implement jets into a well-established three-dimensional, two-temperature magnetohydrodynamic (MHD) solar corona model employing Alfvén-wave dissipation to produce a realistic solar-wind background. The jets are produced by positioning a compact magnetic dipole under the solar surface and rotating the boundary plasma around the dipole's magnetic axis. The moving plasma drags the magnetic field lines along with it, ultimately leading to a reconnection-driven jet similar to that described by Pariat et al. We compare line-of-sight syntheticmore » images to multiple jet observations at EUV and X-ray bands, and find very close matches in terms of physical structure, dynamics, and emission. Key contributors to this agreement are the greatly enhanced plasma density and temperature in our jets compared to previous models. These enhancements arise from the comprehensive thermodynamic model that we use and, also, our inclusion of a dense chromosphere at the base of our jet-generating regions. We further find that the large-scale corona is affected significantly by the outwardly propagating torsional Alfvén waves generated by our polar jet, across 40° in latitude and out to 24 R {sub ⊙}. We estimate that polar jets contribute only a few percent to the steady-state solar-wind energy outflow.« less

Inductive Measurement of Plasma Jet Electrical Conductivity (MSFC Center Director's discretionary Fund). Part 2

NASA Technical Reports Server (NTRS)

Turner, M. W.; Hawk, C. W.; Litchford, R. J.

2001-01-01

Measurement of plasma jet electrical conductivity has utility in the development of explosively driven magnetohydrodynamic (MHD) energy converters as well as magnetic flux compression reaction chambers for nuclear/chemical pulse propulsion and power. Within these types of reactors, the physical parameter of critical importance to underlying MHD processes is the magnetic Reynolds number, the value of which depends upon the product of plasma electrical conductivity and velocity. Therefore, a thorough understanding of MHD phenomena at high magnetic Reynolds number is essential, and methods are needed for the accurate and reliable measurement of electrical conductivity in high-speed plasma jets. It is well known that direct measurements using electrodes suffer from large surface resistance, and an electrodeless technique is desired. To address this need, an inductive probing scheme, originally developed for shock tube studies, has been adapted. In this method, the perturbation of an applied magnetic field by a plasma jet induces a voltage in a search coil, which, in turn, can be used to infer electrical conductivity through the inversion of a Fredholm integral equation of the first kind. A 1-in.-diameter probe using a light-gas gun. Exploratory laboratory experiments were carried out using plasma jets expelled from 15-g shaped charges. Measured conductivities were in the range of 4 kS/m for unseeded octol charges and 26 kS/m for seeded octol charges containing 2-percent potassium carbonate by mass.

Evaluation of the sensitivity of bacterial and yeast cells to cold atmospheric plasma jet treatments.

PubMed

Sharkey, Michael A; Chebbi, Ahmed; McDonnell, Kevin A; Staunton, Claire; Dowling, Denis P

2015-06-07

The focus of this research was first to determine the influence of the atmospheric plasma drive frequency on the generation of atomic oxygen species and its correlation with the reduction of bacterial load after treatment in vitro. The treatments were carried out using a helium-plasma jet source called PlasmaStream™. The susceptibility of multiple microbial cell lines was investigated in order to compare the response of gram-positive and gram-negative bacteria, as well as a yeast cell line to the atmospheric plasma treatment. It was observed for the source evaluated that at a frequency of 160 kHz, increased levels of oxygen-laden active species (i.e., OH, NO) were generated. At this frequency, the maximum level of bacterial inactivation in vitro was also achieved. Ex vivo studies (using freshly excised porcine skin as a human analog) were also carried out to verify the antibacterial effect of the plasma jet treatment at this optimal operational frequency and to investigate the effect of treatment duration on the reduction of bacterial load. The plasma jet treatment was found to yield a 4 log reduction in bacterial load after 6 min of treatment, with no observable adverse effects on the treatment surface. The gram-negative bacterial cell lines were found to be far more susceptible to the atmospheric plasma treatments than the gram-positive bacteria. Flow cytometric analysis of plasma treated bacterial cells (Escherichia coli) was conducted in order to attain a fundamental understanding of the mode of action of the treatment on bacteria at a cellular level. This study showed that after treatment with the plasma jet, E. coli cells progressed through the following steps of cell death; the inactivation of transport systems, followed by depolarization of the cytoplasmic membrane, and finally permeabilization of the cell wall.

Development of a fluid model for DC arc plasma torches and its integration with downstream models of atmospheric plasma spray particle plumes

NASA Astrophysics Data System (ADS)

Cannamela, Michael J., III

The plasma spray process uses plasma flames to melt micron sized particles of e.g. ceramic and propel the droplets to impinge upon and freeze to the target workpiece, forming a functional coating. Variations in the process arise from many sources, and because sensing of the process is imperfect one is motivated to pursue a modeling approach. This dissertation models the major elements of the process; the torch that produces the plasma flame, the jet of hot plasma issuing from the torch, and the plume of particles conveyed and heated by the jet. The plasma in the torch is modeled by a one-fluid magnetohydrodynamic (MHD) approach and it is found that the MHD equations can accurately predict the power dissipated in the bulk of the plasma, while special treatment is required in regions near the electrodes. Treatment of the cathode region is eased since it can be de-coupled from the bulk flow. Treatment of the anode region aims to extract the correct amount of power from the plasma. With MHD in the bulk and these special conditions at the electrode boundaries, the net power into the plasma can be matched with experiment. For one simulation of an SG-100 torch operating at 500A, the measured net power was 7.0kW while the computed net power was 7.1kW. Using outlet information from the torch, the impact of plasma arc oscillations on the free jet and on the in-flight particle states is predicted. The model of the plasma jet is validated against the existing LAVA code, and is able to predict the fraction of entrained air in the jet to within 20% of the experimental value. The variations in particle states due to the arc fluctuations are found to be similar in size to variations due to changes in particle injection velocity, and so cannot be neglected when considering particle state distributions. The end result of this work is to make available a complete chain of models for the plasma spray process, from torch input conditions to in-flight particle state.

Nanowelding and patterning of silver nanowires via mask-free atmospheric cold plasma-jet scanning

NASA Astrophysics Data System (ADS)

Liu, Lang; Li, Han-Yu; Ye, Dong; Yu, Yao; Liu, Lin; Wu, Yue

2017-06-01

Silver nanowire (AgNW) thin film is a promising candidate to replace traditional indium tin oxide in optoelectronics applications. To date however, the widespread application of AgNW thin film is limited by the weak point contacts between individual AgNWs and the lack of facile patterning techniques. Here, we demonstrate a novel and facile method to not only nanoweld AgNW junctions but also pattern AgNW thin films via mask-free cold plasma-jet scanning in ambient conditions. After the plasma-jet nanowelding treatment, the morphology of AgNWs change substantially and the junctions are welded together. The nanowelded AgNWs-based thin film shows enhanced electrical and mechanical properties. On the other hand, after the plasma-jet patterning treatment, the AgNWs are etched and transformed into separated large particles. Different kinds of patterns are produced via this patterning technique. At last, a simple light emitting diode circuit is fabricated to demonstrate the suitability of the nanowelded and patterned AgNW electrodes for flexible electronic devices.

Surface processing and ageing behavior of silk fabrics treated with atmospheric-pressure plasma for pigment-based ink-jet printing

NASA Astrophysics Data System (ADS)

Zhang, Chunming; Wang, Libing; Yu, Miao; Qu, Lijun; Men, Yajing; Zhang, Xiangwu

2018-03-01

Pigment inkjet printing has highlighted the advantages of cost-effective, short production cycle and environment-friendly. However, patterns directly printed with pigment inks usually have low color yields and blurry images which are caused by bleeding phenomenon. This work presents an atmospheric-pressure plasma method for improving the pigment-based ink-jet printing performance of silk fabrics. The effects of surface changes induced are discussed, with data derived from morphological study by atomic force microscopy (AFM), chemical analysis using X-ray photoelectron spectroscopy (XPS) and contact angle measurement. Ink-jet printing experiments were conducted to study the influence of measured changes on anti-bleeding property and color strength of treated and original samples. The ageing experiment indicates that the modified silk fabrics should be printed within 24 h after plasma processing for maximum color yields. This study explores an effective approach for the atmospheric-pressure plasma, which can provide its significant use in improving the surface properties and ink-jet printing performance of fabrics.

3D Modeling of Transport Phenomena and the Injection of the Solution Droplets in the Solution Precursor Plasma Spraying

NASA Astrophysics Data System (ADS)

Shan, Yanguang; Coyle, Thomas W.; Mostaghimi, Javad

2007-12-01

Solution precursor plasma spraying has been used to produce finely structured ceramic coatings with nano- and sub-micrometric features. This process involves the injection of a solution spray of ceramic salts into a DC plasma jet under atmospheric condition. During the process, the solvent vaporizes as the droplet travel downstream. Solid particles are finally formed due to the precipitation of the solute, and the particle are heated up and accelerated to the substrate to generate the coating. This article describes a 3D model to simulate the transport phenomena and the trajectory and heating of the solution spray in the process. The jet-spray two-way interactions are considered. A simplified model is employed to simulate the evolution process and the formation of the solid particle from the solution droplet in the plasma jet. The temperature and velocity fields of the jet are obtained and validated. The particle size, velocity, temperature, and position distribution on the substrate are predicted.

Gas and plasma dynamics of RF discharge jet of low pressure in a vacuum chamber with flat electrodes and inside tube, influence of RF discharge on the steel surface parameters

NASA Astrophysics Data System (ADS)

Khristoliubova, V. I.; Kashapov, N. F.; Shaekhov, M. F.

2016-06-01

Researches results of the characteristics of the RF discharge jet of low pressure and the discharge influence on the surface modification of high speed and structural steels are introduced in the article. Gas dynamics, power and energy parameters of the RF low pressure discharge flow in the discharge chamber and the electrode gap are studied in the presence of the materials. Plasma flow rate, discharge power, the concentration of electrons, the density of RF power, the ion current density, and the energy of the ions bombarding the surface materials are considered for the definition of basic properties crucial for the process of surface modification of materials as they were put in the plasma jet. The influence of the workpiece and effect of products complex configuration on the RF discharge jet of low pressure is defined. The correlation of the input parameters of the plasma unit on the characteristics of the discharge is established.

Real-time sensing and gas jet mitigation of VDEs on Alcator C-Mod

NASA Astrophysics Data System (ADS)

Granetz, R. S.; Wolfe, S. M.; Izzo, V. A.; Reinke, M. L.; Terry, J. L.; Hughes, J. W.; Zhurovich, K.; Whyte, D. G.; Bakhtiari, M.; Wurden, G.

2006-10-01

Experiments have been carried out in Alcator C-Mod to test the effectiveness of gas jet disruption mitigation of VDEs with real-time detection and triggering by the C-Mod digital plasma control system (DPCS). The DPCS continuously computes the error in the plasma vertical position from the magnetics diagnostics. When this error exceeds an adjustable preset value, the DPCS triggers the gas jet valve (with a negligible latency time). The high-pressure gas (argon) only takes a few milliseconds to enter the vacuum chamber and begin affecting the plasma, but this is comparable to the VDE timescale on C-Mod. Nevertheless, gas jet injection reduced the halo current, increased the radiated power fraction, and reduced the heating of the divertor compared to unmitigated disruptions, but not quite as well as in earlier mitigation experiments with vertically stable plasmas. Presumably a faster overall response time would be beneficial, and several ways to achieve this will also be discussed.

Enhancement of Quasistationary Shocks and Heating via Temporal Staging in a Magnetized Laser-Plasma Jet

DOE PAGES

Higginson, D. P.; Khiar, B.; Revet, G.; ...

2017-12-22

Here, we investigate the formation of a laser-produced magnetized jet under conditions of a varying mass ejection rate and a varying divergence of the ejected plasma flow. This is done by irradiating a solid target placed in a 20 T magnetic field with, first, a collinear precursor laser pulse (10 12 W/cm 2) and, then, a main pulse (10 13 W/cm 2) arriving 9–19 ns later. Varying the time delay between the two pulses is found to control the divergence of the expanding plasma, which is shown to increase the strength of and heating in the conical shock that ismore » responsible for jet collimation. These results show that plasma collimation due to shocks against a strong magnetic field can lead to stable, astrophysically relevant jets that are sustained over time scales 100 times the laser pulse duration (i.e., >70 ns), even in the case of strong variability at the source.« less

MTF Driven by Plasma Liner Dynamically Formed by the Merging of Plasma Jets: An Overview

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Eskridge, Richard; Martin, Adam; Smith, James; Lee, Michael; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

One approach for standoff delivery of the momentum flux for compressing the target in MTF consists of using a spherical array of plasma jets to form a spherical plasma shell imploding towards the center of a magnetized plasma, a compact toroid (Figure 1). A 3-year experiment (PLX-1) to explore the physics of forming a 2-D plasma liner (shell) by merging plasma jets is described. An overview showing how this 3-year project (PLX-1) fits into the program plan at the national and international level for realizing MTF for energy and propulsion is discussed. Assuming that there will be a parallel program in demonstrating and establishing the underlying physics principles of MTF using whatever liner is appropriate (e.g. a solid liner) with a goal of demonstrating breakeven by 2010, the current research effort at NASA MSFC attempts to complement such a program by addressing the issues of practical embodiment of MTF for propulsion. Successful conclusion of PLX-1 will be followed by a Physics Feasibility Experiment (PLX-2) for the Plasma Liner Driven MTF.

Cold atmospheric pressure plasma jets: Interaction with plasmid DNA and tailored electron heating using dual-frequency excitation

NASA Astrophysics Data System (ADS)

Niemi, K.; O'Neill, C.; Cox, L. J.; Waskoenig, J.; Hyland, W. B.; McMahon, S. J.; Reuter, S.; Currell, F. J.; Graham, W. G.; O'Connell, D.; Gans, T.

2012-05-01

Recent progress in plasma science and technology has enabled the development of a new generation of stable cold non-equilibrium plasmas operating at ambient atmospheric pressure. This opens horizons for new plasma technologies, in particular in the emerging field of plasma medicine. These non-equilibrium plasmas are very efficient sources for energy transport through reactive neutral particles (radicals and metastables), charged particles (ions and electrons), UV radiation, and electro-magnetic fields. The effect of a cold radio frequency-driven atmospheric pressure plasma jet on plasmid DNA has been investigated. The formation of double strand breaks correlates well with the atomic oxygen density. Taken with other measurements, this indicates that neutral components in the jet are effective in inducing double strand breaks. Plasma manipulation techniques for controlled energy delivery are highly desirable. Numerical simulations are employed for detailed investigations of the electron dynamics, which determines the generation of reactive species. New concepts based on nonlinear power dissipation promise superior strategies to control energy transport for tailored technological exploitations.

Large area atmospheric-pressure plasma jet

DOEpatents

Selwyn, Gary S.; Henins, Ivars; Babayan, Steve E.; Hicks, Robert F.

2001-01-01

Large area atmospheric-pressure plasma jet. A plasma discharge that can be operated at atmospheric pressure and near room temperature using 13.56 MHz rf power is described. Unlike plasma torches, the discharge produces a gas-phase effluent no hotter than 250.degree. C. at an applied power of about 300 W, and shows distinct non-thermal characteristics. In the simplest design, two planar, parallel electrodes are employed to generate a plasma in the volume therebetween. A "jet" of long-lived metastable and reactive species that are capable of rapidly cleaning or etching metals and other materials is generated which extends up to 8 in. beyond the open end of the electrodes. Films and coatings may also be removed by these species. Arcing is prevented in the apparatus by using gas mixtures containing He, which limits ionization, by using high flow velocities, and by properly spacing the rf-powered electrode. Because of the atmospheric pressure operation, there is a negligible density of ions surviving for a sufficiently long distance beyond the active plasma discharge to bombard a workpiece, unlike the situation for low-pressure plasma sources and conventional plasma processing methods.

Atmospheric-pressure plasma jet

DOEpatents

Selwyn, Gary S.

1999-01-01

Atmospheric-pressure plasma jet. A .gamma.-mode, resonant-cavity plasma discharge that can be operated at atmospheric pressure and near room temperature using 13.56 MHz rf power is described. Unlike plasma torches, the discharge produces a gas-phase effluent no hotter than 250.degree. C. at an applied power of about 300 W, and shows distinct non-thermal characteristics. In the simplest design, two concentric cylindrical electrodes are employed to generate a plasma in the annular region therebetween. A "jet" of long-lived metastable and reactive species that are capable of rapidly cleaning or etching metals and other materials is generated which extends up to 8 in. beyond the open end of the electrodes. Films and coatings may also be removed by these species. Arcing is prevented in the apparatus by using gas mixtures containing He, which limits ionization, by using high flow velocities, and by properly shaping the rf-powered electrode. Because of the atmospheric pressure operation, no ions survive for a sufficiently long distance beyond the active plasma discharge to bombard a workpiece, unlike low-pressure plasma sources and conventional plasma processing methods.

An Experimental Investigation Into The Effect Of Plasma On The Flow Features Of An Axisymmetric Jet

DTIC Science & Technology

2007-10-01

document contains color images. 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18 . NUMBER OF PAGES 386...Prescribed by ANSI Std Z39- 18 AN EXPERIMENTAL INVESTIGATION INTO THE EFFECT OF PLASMA ON THE FLOW FEATURES OF AN AXISYMMETRIC JET BY RICHARD E. HUFFMAN...A. 18 Comparison of Plasma Effects on Skewness and Kurtosis: Case 611LINE3051 . . . . . . . . . 223 A.19 Comparison of Plasma Effects on Mean Velocity

Optimizing Dense Plasma Focus Neutron Yields with Fast Gas Jets

NASA Astrophysics Data System (ADS)

McMahon, Matthew; Kueny, Christopher; Stein, Elizabeth; Link, Anthony; Schmidt, Andrea

2016-10-01

We report a study using the particle-in-cell code LSP to perform fully kinetic simulations modeling dense plasma focus (DPF) devices with high density gas jets on axis. The high density jet models fast gas puffs which allow for more mass on axis while maintaining the optimal pressure for the DPF. As the density of the jet compared to the background fill increases we find the neutron yield increases, as does the variability in the neutron yield. Introducing perturbations in the jet density allow for consistent seeding of the m =0 instability leading to more consistent ion acceleration and higher neutron yields with less variability. Jets with higher on axis density are found to have the greatest yield. The optimal jet configuration is explored. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Nanocapillary Atmospheric Pressure Plasma Jet: A Tool for Ultrafine Maskless Surface Modification at Atmospheric Pressure.

PubMed

Motrescu, Iuliana; Nagatsu, Masaaki

2016-05-18

With respect to microsized surface functionalization techniques we proposed the use of a maskless, versatile, simple tool, represented by a nano- or microcapillary atmospheric pressure plasma jet for producing microsized controlled etching, chemical vapor deposition, and chemical modification patterns on polymeric surfaces. In this work we show the possibility of size-controlled surface amination, and we discuss it as a function of different processing parameters. Moreover, we prove the successful connection of labeled sugar chains on the functionalized microscale patterns, indicating the possibility to use ultrafine capillary atmospheric pressure plasma jets as versatile tools for biosensing, tissue engineering, and related biomedical applications.

Surface Catalysis and Oxidation on Stagnation Point Heat Flux Measurements in High Enthalpy Arc Jets

NASA Technical Reports Server (NTRS)

Nawaz, Anuscheh; Driver, David M.; Terrazas-Salinas

2013-01-01

Heat flux sensors are routinely used in arc jet facilities to determine heat transfer rates from plasma plume. The goal of this study is to assess the impact of surface composition changes on these heat flux sensors. Surface compositions can change due to oxidation and material deposition from the arc jet. Systematic surface analyses of the sensors were conducted before and after exposure to plasma. Currently copper is commonly used as surface material. Other surface materials were studied including nickel, constantan gold, platinum and silicon dioxide. The surfaces were exposed to plasma between 0.3 seconds and 3 seconds. Surface changes due to oxidation as well as copper deposition from the arc jets were observed. Results from changes in measured heat flux as a function of surface catalycity is given, along with a first assessment of enthalpy for these measurements. The use of cupric oxide is recommended for future heat flux measurements, due to its consistent surface composition arc jets.

Effect of external electric and magnetic field on propagation of atmospheric pressure plasma jet

NASA Astrophysics Data System (ADS)

Zhu, Ping; Meng, Zhaozhong; Hu, Haixin; Ouyang, Jiting

2017-10-01

The behaviors of atmospheric pressure plasma jet produced by a coplanar dielectric barrier discharge (CDBD) in helium in external electrostatic and magnetic field are investigated experimentally. Time-resolved ICCD images of jet in electric field, magnetic field, and floating metal ring are recorded, respectively. The results show that the jet dynamics is affected significantly by a metal ring, an electric, and/or a magnetic field. In a transverse electric field, the jet shows behavior of deflection, broadening, and shortening according to the structure of electric field. In a transverse magnetic field, the jet deflects to up or down depending on the magnetic direction. The jet can be slowed down or obstructed by a floating metal ring on the jet path, but will still pass through the tube at higher applied voltages of DBD, without significant change in jet length or shape out of the tube compared with that without metal ring. A positive DC voltage on the metal ring helps to improve the jet length, but a negative voltage will reduce the length or completely stop the jet. The electric field to sustain the jet in helium is estimated to be about 24 ± 15 kV/cm from this experiment.

Keyhole and weld shapes for plasma arc welding under normal and zero gravity

NASA Technical Reports Server (NTRS)

Keanini, R. G.; Rubinsky, B.

1990-01-01

A first order study of the interfacial (keyhole) shape between a penetrating argon plasma arc jet and a stationary liquid metal weld pool is presented. The interface is determined using the Young-Laplace equation by assuming that the plasma jet behaves as a one-dimensional ideal gas flow and by neglecting flow within the weld pool. The solution for the keyhole shape allows an approximate determination of the liquid-solid metal phase boundary location based on the assumption that the liquid melt is a stagnant thermal boundary layer. Parametric studies examine the effect of plasma mass flow rate, initial plasma enthalpy, liquid metal surface tension, and jet shear on weldment shape under both normal and zero gravity. Among the more important findings of this study is that keyhole and weld geometries are minimally affected by gravity, suggesting that data gathered under gravity can be used in planning in-space welding.

The Role of Helium Metastable States in Radio-Frequency Helium-Oxygen Atmospheric Pressure Plasma Jets: Measurement and Numerical Simulation

NASA Astrophysics Data System (ADS)

Niemi, Kari; Waskoenig, Jochen; Sadeghi, Nader; Gans, Timo; O'Connell, Deborah

2011-10-01

Absolute densities of metastable He atoms were measured line-of sight integrated along the plasma channel of a capacitively-coupled radio-frequency driven atmospheric pressure plasma jet operated in helium oxygen mixtures by tunable diode-laser absorption spectroscopy. Dependencies of the He metastable density with oxygen admixtures up to 1 percent were investigated. Results are compared to a 1-d numerical simulation, which includes a semi-kinetical treatment of the electron dynamics and the complex plasma chemistry (20 species, 184 reactions), and very good agreement is found. The main formation mechanisms for the helium metastables are identified and analyzed, including their pronounced spatio-temporal dynamics. Penning ionization through helium metastables is found to be significant for plasma sustainment, while it is revealed that helium metastables are not an important energy carrying species into the jet effluent and therefore will not play a direct role in remote surface treatments.

Hybrid model for simulation of plasma jet injection in tokamak

NASA Astrophysics Data System (ADS)

Galkin, Sergei A.; Bogatu, I. N.

2016-10-01

Hybrid kinetic model of plasma treats the ions as kinetic particles and the electrons as charge neutralizing massless fluid. The model is essentially applicable when most of the energy is concentrated in the ions rather than in the electrons, i.e. it is well suited for the high-density hyper-velocity C60 plasma jet. The hybrid model separates the slower ion time scale from the faster electron time scale, which becomes disregardable. That is why hybrid codes consistently outperform the traditional PIC codes in computational efficiency, still resolving kinetic ions effects. We discuss 2D hybrid model and code with exact energy conservation numerical algorithm and present some results of its application to simulation of C60 plasma jet penetration through tokamak-like magnetic barrier. We also examine the 3D model/code extension and its possible applications to tokamak and ionospheric plasmas. The work is supported in part by US DOE DE-SC0015776 Grant.

Searching for order in atmospheric pressure plasma jets

NASA Astrophysics Data System (ADS)

Schäfer, Jan; Sigeneger, Florian; Šperka, Jiří; Rodenburg, Cornelia; Foest, Rüdiger

2018-01-01

The self-organized discharge behaviour occurring in a non-thermal radio-frequency plasma jet in rare gases at atmospheric pressure was investigated. The frequency of the azimuthal rotation of filaments in the active plasma volume and their inclination were measured along with the gas temperature under varying discharge conditions. The gas flow and heating were described theoretically by a three-dimensional hydrodynamic model. The rotation frequencies obtained by both methods qualitatively agree. The results demonstrate that the plasma filaments forming an inclination angle α with the axial gas velocity u z are forced to a transversal movement with the velocity {u}φ =\\tan (α )\\cdot {u}z, which is oriented in the inclination direction. Variations of {u}φ in the model reveal that the observed dynamics minimizes the energy loss due to convective heat transfer by the gas flow. The control of the self-organization regime motivates the application of the plasma jet for precise and reproducible material processing.

Absolute atomic oxygen density measurements for nanosecond-pulsed atmospheric-pressure plasma jets using two-photon absorption laser-induced fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Jiang, C.; Carter, C.

2014-12-01

Nanosecond-pulsed plasma jets that are generated under ambient air conditions and free from confinement of electrodes have become of great interest in recent years due to their promising applications in medicine and dentistry. Reactive oxygen species that are generated by nanosecond-pulsed, room-temperature non-equilibrium He-O2 plasma jets among others are believed to play an important role during the bactericidal or sterilization processes. We report here absolute measurements of atomic oxygen density in a 1 mm-diameter He/(1%)O2 plasma jet at atmospheric pressure using two-photon absorption laser-induced fluorescence spectroscopy. Oxygen number density on the order of 1013 cm-3 was obtained in a 150 ns, 6 kV single-pulsed plasma jet for an axial distance up to 5 mm above the device nozzle. Temporally resolved O density measurements showed that there are two maxima, separated in time by 60-70 µs, and a total pulse duration of 260-300 µs. Electrostatic modeling indicated that there are high-electric-field regions near the nozzle exit that may be responsible for the observed temporal behavior of the O production. Both the field-distribution-based estimation of the time interval for the O number density profile and a pulse-energy-dependence study confirmed that electric-field-dependent, direct and indirect electron-induced processes play important roles for O production.

Enhancement of EUV emission from a liquid microjet target by use of dual laser pulses

NASA Astrophysics Data System (ADS)

Higashiguchi, Takeshi; Rajyaguru, Chirag; Koga, Masato; Kawasaki, Keita; Sasaki, Wataru; Kubodera, Shoichi; Kikuchi, Takashi; Yugami, Noboru; Kawata, Shigeo; Andreev, Alexander A.

2005-03-01

Extreme ultraviolet (EUV) radiation at the wavelength of around 13nm waws observed from a laser-produced plasma using continuous water-jet. Strong dependence of the conversion efficiency (CE) on the laser focal spot size and jet diameter was observed. The EUV CE at a given laser spot size and jet diameter was further enhanced using double laser pulses, where a pre-pulse was used for initial heating of the plasma.

Plasma-Jet-Driven Magneto-Inertial Fusion (PJMIF): Physics and Design for a Plasma Liner Formation Experiment

NASA Astrophysics Data System (ADS)

Hsu, Scott; Cassibry, Jason; Witherspoon, F. Douglas

2014-10-01

Spherically imploding plasma liners are a potential standoff compression driver for magneto-inertial fusion, which is a hybrid of and operates in an intermediate density between those of magnetic and inertial fusion. We propose to use an array of merging supersonic plasma jets to form a spherically imploding plasma liner. The jets are to be formed by pulsed coaxial guns with contoured electrodes that are placed sufficiently far from the location of target compression such that no hardware is repetitively destroyed. As such, the repetition rate can be higher (e.g., 1 Hz) and ultimately the power-plant economics can be more attractive than most other MIF approaches. During the R&D phase, a high experimental shot rate at reasonably low cost (e.g., < 1 k/shot) may be achieved with excellent diagnostic access, thus enabling a rapid learning rate. After some background on PJMIF and its prospects for reactor-relevant energy gain, this poster describes the physics objectives and design of a proposed 60-gun plasma-liner-formation experiment, which will provide experimental data on: (i) scaling of peak liner ram pressure versus initial jet parameters, (ii) liner non-uniformity characterization and control, and (iii) control of liner profiles for eventual gain optimization.

Influences of the cold atmospheric plasma jet treatment on the properties of the demineralized dentin surfaces

NASA Astrophysics Data System (ADS)

Xiaoming, ZHU; Heng, GUO; Jianfeng, ZHOU; Xiaofei, ZHANG; Jian, CHEN; Jing, LI; Heping, LI; Jianguo, TAN

2018-04-01

Improvement of the bonding strength and durability between the dentin surface and the composite resin is a challenging job in dentistry. In this paper, a radio-frequency atmospheric-pressure glow discharge (RF-APGD) plasma jet is employed for the treatment of the acid-etched dentin surfaces used for the composite restoration. The properties of the plasma treated dentin surfaces and the resin-dentin interfaces are analyzed using the x-ray photoemission spectroscopy, contact angle goniometer, scanning electron microscope and microtensile tester. The experimental results show that, due to the abundant chemically reactive species existing in the RF-APGD plasma jet under a stable and low energy input operating mode, the contact angle of the plasma-treated dentin surfaces decreases to a stable level with the increase of the atomic percentage of oxygen in the specimens; the formation of the long resin tags in the scattered clusters and the hybrid layers at the resin-dentin interfaces significantly improve the bonding strength and durability. These results indicate that the RF-APGD plasma jet is an effective tool for modifying the chemical properties of the dentin surfaces, and for improving the immediate bonding strength and the durability of the resin-dentin bonding in dentistry.

A dc non-thermal atmospheric-pressure plasma microjet

NASA Astrophysics Data System (ADS)

Zhu, WeiDong; Lopez, Jose L.

2012-06-01

A direct current (dc), non-thermal, atmospheric-pressure plasma microjet is generated with helium/oxygen gas mixture as working gas. The electrical property is characterized as a function of the oxygen concentration and show distinctive regions of operation. Side-on images of the jet were taken to analyze the mode of operation as well as the jet length. A self-pulsed mode is observed before the transition of the discharge to normal glow mode. Optical emission spectroscopy is employed from both end-on and side-on along the jet to analyze the reactive species generated in the plasma. Line emissions from atomic oxygen (at 777.4 nm) and helium (at 706.5 nm) were studied with respect to the oxygen volume percentage in the working gas, flow rate and discharge current. Optical emission intensities of Cu and OH are found to depend heavily on the oxygen concentration in the working gas. Ozone concentration measured in a semi-confined zone in front of the plasma jet is found to be from tens to ˜120 ppm. The results presented here demonstrate potential pathways for the adjustment and tuning of various plasma parameters such as reactive species selectivity and quantities or even ultraviolet emission intensities manipulation in an atmospheric-pressure non-thermal plasma source. The possibilities of fine tuning these plasma species allows for enhanced applications in health and medical related areas.

Measurement of electron temperature and density of the edge plasma of JET by ECE and microwave reflectometry

NASA Astrophysics Data System (ADS)

Bartlett, D. V.; Costley, A. E.; Porte, L.; Prentice, R.; Salmon, N. A.; Sips, G.

1990-12-01

The potential of electron cyclotron emission and microwave reflectometry as techniques for measuring the electron temperature and density in the edge region of tokamak plasmas is investigated. Experiments to realize this potential on JET are described and some illustrative results presented.

An Alternative to Annealing TiO2 Nanotubes for Morphology Preservation: Atmospheric Pressure Plasma Jet Treatment.

PubMed

Seo, Sang-Hee; Uhm, Soo-Hyuk; Kwon, Jae-Sung; Choi, Eun Ha; Kim, Kwang-Mahn; Kim, Kyoung-Nam

2015-03-01

Titanium oxide nanotube layer formed by plasma electrolytic oxidation (PEO) is known to be excellent in biomaterial applications. However, the annealing process which is commonly performed on the TiO2 nanotubes cause defects in the nanotubular structure. The purpose of this work was to apply a non-thermal atmospheric pressure plasma jet on diameter-controlled TiO2 nanotubes to mimic the effects of annealing while maintaining the tubular structure for use as biomaterial. Diameter-controlled nanotube samples fabricated by plasma electrolytic oxidation were dried and prepared under three different conditions: untreated, annealed at 450 °C for 1 h in air with a heating rate of 10 °C/min, and treated with an air-based non-thermal atmospheric pressure plasma jet for 5 minutes. The contact angle measurement was investigated to confirm the enhanced hydrophilicity of the TiO2 nanotubes. The chemical composition of the surface was studied using X-ray photoelectron spectroscopy, and the morphology of TiO2 nanotubes was examined by field emission scanning electron microscopy. For the viability of the cell, the attachment of the osteoblastic cell line MC3T3-E1 was determined using the water-soluble tetrazolium salt assay. We found that there are no morphological changes in the TiO2 nanotubular structure after the plasma treatment. Also, we investigated a change in the chemical composition and enhanced hydrophilicity which result in improved cell behavior. The results of this study indicated that the non-thermal atmospheric pressure plasma jet results in osteoblast functionality that is comparable to annealed samples while maintaining the tubular structure of the TiO2 nanotubes. Therefore, this study concluded that the use of a non-thermal atmospheric pressure plasma jet on nanotube surfaces may replace the annealing process following plasma electrolytic oxidation.

Magnetic Field Effects on Plasma Plumes

NASA Technical Reports Server (NTRS)

Ebersohn, F.; Shebalin, J.; Girimaji, S.; Staack, D.

2012-01-01

Here, we will discuss our numerical studies of plasma jets and loops, of basic interest for plasma propulsion and plasma astrophysics. Space plasma propulsion systems require strong guiding magnetic fields known as magnetic nozzles to control plasma flow and produce thrust. Propulsion methods currently being developed that require magnetic nozzles include the VAriable Specific Impulse Magnetoplasma Rocket (VASIMR) [1] and magnetoplasmadynamic thrusters. Magnetic nozzles are functionally similar to de Laval nozzles, but are inherently more complex due to electromagnetic field interactions. The two crucial physical phenomenon are thrust production and plasma detachment. Thrust production encompasses the energy conversion within the nozzle and momentum transfer to a spacecraft. Plasma detachment through magnetic reconnection addresses the problem of the fluid separating efficiently from the magnetic field lines to produce maximum thrust. Plasma jets similar to those of VASIMR will be studied with particular interest in dual jet configurations, which begin as a plasma loops between two nozzles. This research strives to fulfill a need for computational study of these systems and should culminate with a greater understanding of the crucial physics of magnetic nozzles with dual jet plasma thrusters, as well as astrophysics problems such as magnetic reconnection and dynamics of coronal loops.[2] To study this problem a novel, hybrid kinetic theory and single fluid magnetohydrodynamic (MHD) solver known as the Magneto-Gas Kinetic Method is used.[3] The solver is comprised of a "hydrodynamic" portion based on the Gas Kinetic Method and a "magnetic" portion that accounts for the electromagnetic behaviour of the fluid through source terms based on the resistive MHD equations. This method is being further developed to include additional physics such as the Hall effect. Here, we will discuss the current level of code development, as well as numerical simulation results

Innovative diagnostics for ITER physics addressed in JET

NASA Astrophysics Data System (ADS)

Murari, A.; Edlington, T.; Alfier, A.; Alonso, A.; Andrew, Y.; Arnoux, G.; Beurskens, M.; Coad, P.; Crombe, C.; Gauthier, E.; Giroud, C.; Hidalgo, C.; Hong, S.; Kempenaars, M.; Kiptily, V.; Loarer, T.; Meigs, A.; Pasqualotto, R.; Tala, T.; Contributors, JET-EFDA

2008-12-01

In recent years, JET diagnostic capability has been significantly improved to widen the range of physical phenomena that can be studied and thus contribute to the understanding of some ITER relevant issues. The most significant results reported in this paper refer to the plasma wall interactions, the interplay between core and edge physics and fast particles. A synergy between new infrared cameras, visible cameras and spectroscopy diagnostics has allowed investigating a series of new aspects of the plasma wall interactions. The power loads on the plasma facing components of JET main chambers have been assessed at steady state and during transient events like ELMs and disruptions. Evidence of filaments in the edge region of the plasma has been collected with a new fast visible camera and high resolution Thomson scattering. The physics of detached plasmas and some new aspects of dust formation have also been devoted particular attention. The influence of the edge plasma on the core has been investigated with upgraded active spectroscopy, providing new information on momentum transport and the effects of impurity injection on ELMs and ITBs and their interdependence. Given the fact that JET is the only machine with a plasma volume big enough to confine the alphas, a coherent programme of diagnostic developments for the energetic particles has been undertaken. With upgraded γ-ray spectroscopy and a new scintillator probe, it is now possible to study both the redistribution and the losses of the fast particles in various plasma conditions.

The effect of a metal wall on confinement in JET and ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Beurskens, M. N. A.; Schweinzer, J.; Angioni, C.; Burckhart, A.; Challis, C. D.; Chapman, I.; Fischer, R.; Flanagan, J.; Frassinetti, L.; Giroud, C.; Hobirk, J.; Joffrin, E.; Kallenbach, A.; Kempenaars, M.; Leyland, M.; Lomas, P.; Maddison, G.; Maslov, M.; McDermott, R.; Neu, R.; Nunes, I.; Osborne, T.; Ryter, F.; Saarelma, S.; Schneider, P. A.; Snyder, P.; Tardini, G.; Viezzer, E.; Wolfrum, E.; the ASDEX Upgrade Team; Contributors, JET-EFDA

2013-12-01

In both JET and ASDEX Upgrade (AUG) the plasma energy confinement has been affected by the presence of a metal wall by the requirement of increased gas fuelling to avoid tungsten pollution of the plasma. In JET with a beryllium/tungsten wall the high triangularity baseline H-mode scenario (i.e. similar to the ITER reference scenario) has been the strongest affected and the benefit of high shaping to give good normalized confinement of H98 ˜ 1 at high Greenwald density fraction of fGW ˜ 0.8 has not been recovered to date. In AUG with a full tungsten wall, a good normalized confinement H98 ˜ 1 could be achieved in the high triangularity baseline plasmas, albeit at elevated normalized pressure βN > 2. The confinement lost with respect to the carbon devices can be largely recovered by the seeding of nitrogen in both JET and AUG. This suggests that the absence of carbon in JET and AUG with a metal wall may have affected the achievable confinement. Three mechanisms have been tested that could explain the effect of carbon or nitrogen (and the absence thereof) on the plasma confinement. First it has been seen in experiments and by means of nonlinear gyrokinetic simulations (with the GENE code), that nitrogen seeding does not significantly change the core temperature profile peaking and does not affect the critical ion temperature gradient. Secondly, the dilution of the edge ion density by the injection of nitrogen is not sufficient to explain the plasma temperature and pressure rise. For this latter mechanism to explain the confinement improvement with nitrogen seeding, strongly hollow Zeff profiles would be required which is not supported by experimental observations. The confinement improvement with nitrogen seeding cannot be explained with these two mechanisms. Thirdly, detailed pedestal structure analysis in JET high triangularity baseline plasmas have shown that the fuelling of either deuterium or nitrogen widens the pressure pedestal. However, in JET-ILW this only leads to a confinement benefit in the case of nitrogen seeding where, as the pedestal widens, the obtained pedestal pressure gradient is conserved. In the case of deuterium fuelling in JET-ILW the pressure gradient is strongly degraded in the fuelling scan leading to no net confinement gain due to the pedestal widening. The pedestal code EPED correctly predicts the pedestal pressure of the unseeded plasmas in JET-ILW within ±5%, however it does not capture the complex variation of pedestal width and gradient with fuelling and impurity seeding. Also it does not predict the observed increase of pedestal pressure by nitrogen seeding in JET-ILW. Ideal peeling ballooning MHD stability analysis shows that the widening of the pedestal leads to a down shift of the marginal stability boundary by only 10-20%. However, the variations in the pressure gradient observed in the JET-ILW fuelling experiment is much larger and spans a factor of more than two. As a result the experimental points move from deeply unstable to deeply stable on the stability diagram in a deuterium fuelling scan. In AUG-W nitrogen seeded plasmas, a widening of the pedestal has also been observed, consistent with the JET observations. The absence of carbon can thus affect the pedestal structure, and mainly the achieved pedestal gradient, which can be recovered by seeding nitrogen. The underlying physics mechanism is still under investigation and requires further understanding of the role of impurities on the pedestal stability and pedestal structure formation.

Progress In Magnetized Target Fusion Driven by Plasma Liners

NASA Technical Reports Server (NTRS)

Thio, Francis Y. C.; Kirkpatrick, Ronald C.; Knapp, Charles E.; Cassibry, Jason; Eskridge, Richard; Lee, Michael; Smith, James; Martin, Adam; Wu, S. T.; Schmidt, George;

Influences of the shielding cylinder on the length of radio-frequency cold atmospheric plasma jets

NASA Astrophysics Data System (ADS)

Li, He-Ping; Li, Jing; Zhang, Xiao-Fei; Guo, Heng; Chen, Jian; Department of Engineering Physics Team

2017-10-01

Cold atmospheric plasma jets driven by a radio frequency power supply contain abundant species and complex chemical reactions, which have wide applications in the fields of materials processing and modifications, food engineering, bio-medical science, etc. Our previous experiments have shown that the total length of a radio-frequency cold atmospheric plasma (RF-CAP) jet can exceed 1 meter with the shielding of a quartz tube. However, the shielding mechanisms of the solid cylinder has not been studied systematically. In this study, a two-dimensional, quasi-steady fluid model is used to investigate the influences of the shielding tube on the length of the RF-CAP jets under different conditions. The simulation results show that the total jet length grows monotonously; while simultaneously, the jet length out of the tube shows a non-monotonic variation trend, with the increase of the tube length, which is in good agreement with the experimental observations. The shielding mechanisms of the solid cylinder on the RF-CAP jet is also discussed in detail based on the modeling results. This work was supported by the National Natural Science Foundation of China (11475103, 21627812), the National Key Research and Development Program of China (2016YFD0102106) and Tsinghua University Initiative Scientific Program (20161080108).

Calibration of neutron detectors on the Joint European Torus.

PubMed

Batistoni, Paola; Popovichev, S; Conroy, S; Lengar, I; Čufar, A; Abhangi, M; Snoj, L; Horton, L

2017-10-01

The present paper describes the findings of the calibration of the neutron yield monitors on the Joint European Torus (JET) performed in 2013 using a 252 Cf source deployed inside the torus by the remote handling system, with particular regard to the calibration of fission chambers which provide the time resolved neutron yield from JET plasmas. The experimental data obtained in toroidal, radial, and vertical scans are presented. These data are first analysed following an analytical approach adopted in the previous neutron calibrations at JET. In this way, a calibration function for the volumetric plasma source is derived which allows us to understand the importance of the different plasma regions and of different spatial profiles of neutron emissivity on fission chamber response. Neutronics analyses have also been performed to calculate the correction factors needed to derive the plasma calibration factors taking into account the different energy spectrum and angular emission distribution of the calibrating (point) 252 Cf source, the discrete positions compared to the plasma volumetric source, and the calibration circumstances. All correction factors are presented and discussed. We discuss also the lessons learnt which are the basis for the on-going 14 MeV neutron calibration at JET and for ITER.

Optical characteristics of a RF DBD plasma jet in various {Ar}/ {O}_{2}Ar/O2 mixtures

NASA Astrophysics Data System (ADS)

Falahat, A.; Ganjovi, A.; Taraz, M.; Ravari, M. N. Rostami; Shahedi, A.

2018-02-01

In this paper, using the optical emission spectroscopy (OES) technique, the optical characteristics of a radiofrequency (RF) plasma jet are examined. The Ar/O2 mixture is taken as the operational gas and, the Ar percentage in the Ar/O2 mixture is varied from 70% to 95%. Using the optical emission spectrum analysis of the RF plasma jet, the excitation temperature is determined based on the Boltzmann plot method. The electron density in the plasma medium of the RF plasma jet is obtained by the Stark broadening of the hydrogen Balmer H_{β }. It is mostly seen that, the radiation intensity of Ar 4p→ 4s transitions at higher argon contributions in Ar/O2 mixture is higher. It is found that, at higher Ar percentages, the emission intensities from atomic oxygen (O) are higher and, the line intensities from the argon atoms and ions including O atoms linearly increase. It is observed that the quenching of Ar^{*} with O2 results in higher O species with respect to O2 molecules. In addition, at higher percentages of Ar in the Ar/O2 mixture, while the excitation temperature is decreased, the electron density is increased.

Controlling the nitric and nitrous oxide production of an atmospheric pressure plasma jet

NASA Astrophysics Data System (ADS)

Douat, Claire; Hubner, Simon; Engeln, Richard; Benedikt, Jan

2016-09-01

Atmospheric pressure plasma jets are non-thermal plasmas and have the ability to create reactive species. These features make it a very attractive tool for biomedical applications. In this work, we studied NO and N2O production, which are two species having biomedical properties. NO plays a role in the vascularization and in ulcer treatment, while N2O is used as anesthetic and analgesic gas. In this study, the plasma source is similar to the COST Reference Microplasma Jet (µ-APPJ). Helium is used as feed gas with small admixtures of molecular nitrogen and oxygen of below 1%. The absolute densities of NO and N2O were measured in the effluent of an atmospheric pressure RF plasma jet by means of ex-situ quantum-cascade laser absorption spectroscopy via a multi-pass cell in Herriot configuration. We will show that the species' production is dependent on several parameters such as power, flow and oxygen and nitrogen admixture. The NO and N2O densities are strongly dependent on the N2-O2 ratio. Changing this ratio allows for choosing between a NO-rich or a N2O-rich regime.

Temporally resolved ozone distribution of a time modulated RF atmospheric pressure argon plasma jet: flow, chemical reaction, and transient vortex

NASA Astrophysics Data System (ADS)

Zhang, S.; Sobota, A.; van Veldhuizen, E. M.; Bruggeman, P. J.

2015-08-01

The ozone density distribution in the effluent of a time modulated RF atmospheric pressure plasma jet (APPJ) is investigated by time and spatially resolved by UV absorption spectroscopy. The plasma jet is operated with an averaged dissipated power of 6.5 W and gas flow rate 2 slm argon  +2% O2. The modulation frequency of the RF power is 50 Hz with a duty cycle of 50%. To investigate the production and destruction mechanism of ozone in the plasma effluent, the atomic oxygen and gas temperature is also obtained by TALIF and Rayleigh scattering, respectively. A temporal increase in ozone density is observed close to the quartz tube exit when the plasma is switched off due to the decrease in O density and gas temperature. Ozone absorption at different axial positions indicates that the ozone distribution is dominated by the convection induced by the gas flow and allows estimating the on-axis local gas velocity in the jet effluent. Transient vortex structures occurring during the switch on and off of the RF power also significantly affect the ozone density in the far effluent.

A contoured gap coaxial plasma gun with injected plasma armature.

PubMed

Witherspoon, F Douglas; Case, Andrew; Messer, Sarah J; Bomgardner, Richard; Phillips, Michael W; Brockington, Samuel; Elton, Raymond

2009-08-01

A new coaxial plasma gun is described. The long term objective is to accelerate 100-200 microg of plasma with density above 10(17) cm(-3) to greater than 200 km/s with a Mach number above 10. Such high velocity dense plasma jets have a number of potential fusion applications, including plasma refueling, magnetized target fusion, injection of angular momentum into centrifugally confined mirrors, high energy density plasmas, and others. The approach uses symmetric injection of high density plasma into a coaxial electromagnetic accelerator having an annular gap geometry tailored to prevent formation of the blow-by instability. The injected plasma is generated by numerous (currently 32) radially oriented capillary discharges arranged uniformly around the circumference of the angled annular injection region of the accelerator. Magnetohydrodynamic modeling identified electrode profiles that can achieve the desired plasma jet parameters. The experimental hardware is described along with initial experimental results in which approximately 200 microg has been accelerated to 100 km/s in a half-scale prototype gun. Initial observations of 64 merging injector jets in a planar cylindrical testing array are presented. Density and velocity are presently limited by available peak current and injection sources. Steps to increase both the drive current and the injected plasma mass are described for next generation experiments.

Liquid injection plasma deposition method and apparatus

DOEpatents

Kong, Peter C.; Watkins, Arthur D.

1999-01-01

A liquid injection plasma torch deposition apparatus for depositing material onto a surface of a substrate may comprise a plasma torch for producing a jet of plasma from an outlet nozzle. A plasma confinement tube having an inlet end and an outlet end and a central bore therethrough is aligned with the outlet nozzle of the plasma torch so that the plasma jet is directed into the inlet end of the plasma confinement tube and emerges from the outlet end of the plasma confinement tube. The plasma confinement tube also includes an injection port transverse to the central bore. A liquid injection device connected to the injection port of the plasma confinement tube injects a liquid reactant mixture containing the material to be deposited onto the surface of the substrate through the injection port and into the central bore of the plasma confinement tube.

MMS observations of guide field reconnection at the interface between colliding reconnection jets inside flux rope-like structures at the magnetopause

NASA Astrophysics Data System (ADS)

Oieroset, M.; Phan, T.; Haggerty, C. C.; Shay, M.; Eastwood, J. P.; Gershman, D. J.; Drake, J. F.; Fujimoto, M.; Ergun, R.; Mozer, F.; Oka, M.; Torbert, R. B.; Burch, J. L.; Wang, S.; Chen, L. J.; Swisdak, M.; Pollock, C. J.; Dorelli, J.; Fuselier, S. A.; Lavraud, B.; Kacem, I.; Giles, B. L.; Moore, T. E.; Saito, Y.; Avanov, L. A.; Paterson, W. R.; Strangeway, R. J.; Schwartz, S. J.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Malakit, K.

2017-12-01

The formation and evolution of magnetic flux ropes is of critical importance for a number of collisionless plasma phenomena. At the dayside magnetopause flux rope-like structures can form between two X-lines. The two X-lines produce converging plasma jets. At the interface between the colliding jets a compressed current sheet can form, which in turn can undergo reconnection. We present MMS observations of the exhaust and diffusion region of such reconnection.

Temporal and spatial profiles of emission intensities in atmospheric pressure helium plasma jet driven by microsecond pulse: Experiment and simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Ruixue; Zhang, Cheng; Yan, Ping

2015-09-28

A needle-circular electrode structure helium plasma jet driven by microsecond pulsed power is studied. Spatially resolved emission results show that the emission intensity of He(3{sup 3}S{sub 1}) line decreases monotonically along the axial direction, while those of N{sub 2}(C{sup 3}Π{sub u}), N{sub 2}{sup +}(B{sup 2}∑{sup +}{sub u}), and O(3p{sup 5}P) reach their maxima at 3 cm, 2.6 cm, and 1.4 cm, respectively. The plasma plume of the four species shows different characteristics: The N{sub 2} emission plume travels at a fast speed along the entire plasma jet; the N{sub 2}{sup +} emission plume is composed of a bright head and relatively weak tailmore » and travels a shorter distance than the N{sub 2} emission plume; the He emission plume travels at a slower speed for only a very short distance; propagation of the O emission plume is not observed. Results of calculation of radiation fluxes emitted by positive streamers propagating along helium plasma jets are presented. It is shown, in agreement with the results of the present experiment and with other available experimental data, that the intensities of radiation of N{sub 2}(C{sup 3}Π{sub u}) molecules and He(3{sup 3}S{sub 1}) atoms vary with time (along the plasma jet) quite differently. The factors resulting in this difference are discussed.« less

Experimental evidence for collisional shock formation via two obliquely merging supersonic plasma jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Merritt, Elizabeth C., E-mail: emerritt@lanl.gov; Adams, Colin S.; University of New Mexico, Albuquerque, New Mexico 87131

We report spatially resolved measurements of the oblique merging of two supersonic laboratory plasma jets. The jets are formed and launched by pulsed-power-driven railguns using injected argon, and have electron density ∼10{sup 14} cm{sup −3}, electron temperature ≈1.4 eV, ionization fraction near unity, and velocity ≈40 km/s just prior to merging. The jet merging produces a few-cm-thick stagnation layer, as observed in both fast-framing camera images and multi-chord interferometer data, consistent with collisional shock formation [E. C. Merritt et al., Phys. Rev. Lett. 111, 085003 (2013)].

Statistical validation of predictive TRANSP simulations of baseline discharges in preparation for extrapolation to JET D-T

NASA Astrophysics Data System (ADS)

Kim, Hyun-Tae; Romanelli, M.; Yuan, X.; Kaye, S.; Sips, A. C. C.; Frassinetti, L.; Buchanan, J.; Contributors, JET

2017-06-01

This paper presents for the first time a statistical validation of predictive TRANSP simulations of plasma temperature using two transport models, GLF23 and TGLF, over a database of 80 baseline H-mode discharges in JET-ILW. While the accuracy of the predicted T e with TRANSP-GLF23 is affected by plasma collisionality, the dependency of predictions on collisionality is less significant when using TRANSP-TGLF, indicating that the latter model has a broader applicability across plasma regimes. TRANSP-TGLF also shows a good matching of predicted T i with experimental measurements allowing for a more accurate prediction of the neutron yields. The impact of input data and assumptions prescribed in the simulations are also investigated in this paper. The statistical validation and the assessment of uncertainty level in predictive TRANSP simulations for JET-ILW-DD will constitute the basis for the extrapolation to JET-ILW-DT experiments.

3D Mapping of plasma effective areas via detection of cancer cell damage induced by atmospheric pressure plasma jets

NASA Astrophysics Data System (ADS)

Han, Xu; Liu, Yueing; Stack, M. Sharon; Ptasinska, Sylwia

2014-12-01

In the present study, a nitrogen atmospheric pressure plasma jet (APPJ) was used for irradiation of oral cancer cells. Since cancer cells are very susceptible to plasma treatment, they can be used as a tool for detection of APPJ-effective areas, which extended much further than the visible part of the APPJ. An immunofluorescence assay was used for DNA damage identification, visualization and quantification. Thus, the effective damage area and damage level were determined and plotted as 3D images.

The distribution of radio plasma in time and space.

PubMed

Blundell, Katherine M

2005-03-15

The influence of jet-ejected plasma has been an important theme of this meeting; I draw attention to the prevalence of jet-ejected plasma, in particular that which has not been properly accounted for in the past. There are three strands to this paper: important emission which is prominent only at the lowest radio frequencies; relic radio plasma which must exist if even the most basic aspects of radio source evolutionary models are correct; and evidence that some 'radio-quiet' quasars could be FR-I radio sources.

Experimental demonstration of Martian soil simulant removal from a surface using a pulsed plasma jet.

PubMed

Ticoş, C M; Scurtu, A; Toader, D; Banu, N

2015-03-01

A plasma jet produced in a small coaxial plasma gun operated at voltages up to 2 kV and working in pure carbon dioxide (CO2) at a few Torr is used to remove Martian soil simulant from a surface. A capacitor with 0.5 mF is charged up from a high voltage source and supplies the power to the coaxial electrodes. The muzzle of the coaxial plasma gun is placed at a few millimeters near the dusty surface and the jet is fired parallel with the surface. Removal of dust is imaged in real time with a high speed camera. Mars regolith simulant JSC-Mars-1A with particle sizes up to 5 mm is used on different types of surfaces made of aluminium, cotton fabric, polyethylene, cardboard, and phenolic.

Experimental demonstration of Martian soil simulant removal from a surface using a pulsed plasma jet

NASA Astrophysics Data System (ADS)

Ticoş, C. M.; Scurtu, A.; Toader, D.; Banu, N.

2015-03-01

A plasma jet produced in a small coaxial plasma gun operated at voltages up to 2 kV and working in pure carbon dioxide (CO2) at a few Torr is used to remove Martian soil simulant from a surface. A capacitor with 0.5 mF is charged up from a high voltage source and supplies the power to the coaxial electrodes. The muzzle of the coaxial plasma gun is placed at a few millimeters near the dusty surface and the jet is fired parallel with the surface. Removal of dust is imaged in real time with a high speed camera. Mars regolith simulant JSC-Mars-1A with particle sizes up to 5 mm is used on different types of surfaces made of aluminium, cotton fabric, polyethylene, cardboard, and phenolic.

Expansion of a multicomponent current-carrying plasma jet into vacuum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krasov, V. I.; Paperny, V. L., E-mail: paperny@math.isu.runnet.ru

An expression for the ion−ion coupling in a multicomponent plasma jet is derived for an arbitrary ratio between the thermal and relative velocities of the components. The obtained expression is used to solve the problem on the expansion of a current-carrying plasma microjet emitted from the cathode surface into vacuum. Two types of plasmas with two ion components are analyzed: (i) plasma in which the ion components of equal masses are in the charge states Z{sub 1}= +1 and Z{sub 2}= +2 and (ii) plasma with ions in equal charge states but with the mass ratio m{sub 1}/m{sub 2} =more » 2. It is shown that, for such plasmas, the difference between the velocities of the plasma components remains substantial (about 10% of the average jet velocity in case (i) and 15% in case (ii)) at distances of several centimeters from the emission center, where it can be measured experimentally, provided that its initial value at the emitting cathode surface exceeds a certain threshold. This effect is investigated as a function of the mass ratio and charge states of the ion components.« less

Maskless localized patterning of biomolecules on carbon nanotube microarray functionalized by ultrafine atmospheric pressure plasma jet using biotin-avidin system

NASA Astrophysics Data System (ADS)

Abuzairi, Tomy; Okada, Mitsuru; Purnamaningsih, Retno Wigajatri; Poespawati, Nji Raden; Iwata, Futoshi; Nagatsu, Masaaki

2016-07-01

Ultrafine plasma jet is a promising technology with great potential for nano- or micro-scale surface modification. In this letter, we demonstrated the use of ultrafine atmospheric pressure plasma jet (APPJ) for patterning bio-immobilization on vertically aligned carbon nanotube (CNT) microarray platform without a physical mask. The biotin-avidin system was utilized to demonstrate localized biomolecule patterning on the biosensor devices. Using ±7.5 kV square-wave pulses, the optimum condition of plasma jet with He/NH3 gas mixture and 2.5 s treatment period has been obtained to functionalize CNTs. The functionalized CNTs were covalently linked to biotin, bovine serum albumin (BSA), and avidin-(fluorescein isothiocyanate) FITC, sequentially. BSA was necessary as a blocking agent to protect the untreated CNTs from avidin adsorption. The localized patterning results have been evaluated from avidin-FITC fluorescence signals analyzed using a fluorescence microscope. The patterning of biomolecules on the CNT microarray platform using ultrafine APPJ provides a means for potential application of microarray biosensors based on CNTs.

Optical emission spectroscopic diagnostics of a non-thermal atmospheric pressure helium-oxygen plasma jet for biomedical applications

NASA Astrophysics Data System (ADS)

Thiyagarajan, Magesh; Sarani, Abdollah; Nicula, Cosmina

2013-06-01

In this work, we have applied optical emission spectroscopy diagnostics to investigate the characteristics of a non-thermal atmospheric pressure helium plasma jet. The discharge characteristics in the active and afterglow region of the plasma jet, that are critical for biomedical applications, have been investigated. The voltage-current characteristics of the plasma discharge were analyzed and the average plasma power was measured to be around 18 W. The effect of addition of small fractions of oxygen at 0.1%-0.5% on the plasma jet characteristics was studied. The addition of oxygen resulted in a decrease in plasma plume length due to the electronegativity property of oxygen. Atomic and molecular lines of selected reactive plasma species that are considered to be useful to induce biochemical reactions such as OH transitions A2Σ+(ν=0,1)→X2Π(Δν =0) at 308 nm and A2Σ+(ν=0,1)→X2Π(Δν =1) at 287 nm, O I transitions 3p5P→3s5S0 at 777.41 nm, and 3p3P→3s3S0 at 844.6 nm, N2(C-B) second positive system with electronic transition C3Πu→B3Πg in the range of 300-450 nm and N2+(B-X) first negative system with electronic transition B2Σu+→X2Σg+(Δν =0) at 391.4 nm have been studied. The atomic emission lines of helium were identified, including the He I transitions 3p3P0→2s3S at 388.8 nm, 3p1P0→ 2s1S at 501.6 nm, 3d3D→2p3P0 at 587.6 nm, 3d1D→2p1P0 at 667.8 nm, 3s3S1→2p3P0 at 706.5 nm, 3s1S0→2p1P0 at 728.1 nm, and Hα transition 2p-3d at 656.3 nm. Using a spectral fitting method, the OH radicals at 306-312 nm, the rotational and vibrational temperatures equivalent to gas temperatures of the discharge was measured and the effective non-equilibrium nature of the plasma jet was demonstrated. Our results show that, in the entire active plasma region, the gas temperature remains at 310 ± 25 K and 340 ± 25 K and it increases to 320 ± 25 K and 360 ± 25 K in the afterglow region of the plasma jet for pure helium and helium/oxygen (0.1%) mixture, respectively. Additionally, the vibrational temperatures range from 2200 ± 100 K and 2500 ± 100 K for pure helium and helium/oxygen (0.1%) mixture, respectively. The plasma jet was tested on heat sensitive polymer films used in biomedical applications such as polyethylene terephthalate and poly-L-lactide samples continuously for several minutes without causing any physical or thermal damage to the films. The plasma jet produces significant reactive species of interest while the gas temperatures remain very low demonstrating its potential for a range of biomedical applications.

LES of a Jet Excited by the Localized Arc Filament Plasma Actuators

NASA Technical Reports Server (NTRS)

Brown, Clifford A.

2011-01-01

The fluid dynamics of a high-speed jet are governed by the instability waves that form in the free-shear boundary layer of the jet. Jet excitation manipulates the growth and saturation of particular instability waves to control the unsteady flow structures that characterize the energy cascade in the jet.The results may include jet noise mitigation or a reduction in the infrared signature of the jet. The Localized Arc Filament Plasma Actuators (LAFPA) have demonstrated the ability to excite a high-speed jets in laboratory experiments. Extending and optimizing this excitation technology, however, is a complex process that will require many tests and trials. Computational simulations can play an important role in understanding and optimizing this actuator technology for real-world applications. Previous research has focused on developing a suitable actuator model and coupling it with the appropriate computational fluid dynamics (CFD) methods using two-dimensional spatial flow approximations. This work is now extended to three-dimensions (3-D) in space. The actuator model is adapted to a series of discrete actuators and a 3-D LES simulation of an excited jet is run. The results are used to study the fluid dynamics near the actuator and in the jet plume.

Resonant ion acceleration by plasma jets: Effects of jet breaking and the magnetic-field curvature.

PubMed

Artemyev, A V; Vasiliev, A A

2015-05-01

In this paper we consider resonant ion acceleration by a plasma jet originating from the magnetic reconnection region. Such jets propagate in the background magnetic field with significantly curved magnetic-field lines. Decoupling of ion and electron motions at the leading edge of the jet results in generation of strong electrostatic fields. Ions can be trapped by this field and get accelerated along the jet front. This mechanism of resonant acceleration resembles surfing acceleration of charged particles at a shock wave. To describe resonant acceleration of ions, we use adiabatic theory of resonant phenomena. We show that particle motion along the curved field lines significantly influences the acceleration rate. The maximum gain of energy is determined by the particle's escape from the system due to this motion. Applications of the proposed mechanism to charged-particle acceleration in the planetary magnetospheres and the solar corona are discussed.

Effects of low temperature plasmas and plasma activated waters on Arabidopsis thaliana germination and growth

PubMed Central

Martinez, Yves; Merbahi, Nofel; Eichwald, Olivier; Dunand, Christophe

2018-01-01

Two plasma devices at atmospheric pressure (air dielectric barrier discharge and helium plasma jet) have been used to study the early germination of Arabidopsis thaliana seeds during the first days. Then, plasma activated waters are used during the later stage of plant development and growth until 42 days. The effects on both testa and endospserm ruptures during the germination stage are significant in the case of air plasma due to its higher energy and efficiency of producing reactive oxygen species than the case of helium plasma. The latter has shown distinct effects only for testa rupture. Analysis of germination stimulations are based on specific stainings for reactive oxygen species production, peroxidase activity and also membrane permeability tests. Furthermore, scanning electron microscopy (SEM) has shown a smoother seed surface for air plasma treated seeds that can explain the plasma induced-germination. During the growth stage, plants were watered using 4 kinds of water (tap and deionized waters activated or not by the low temperature plasma jet). With regards to other water kinds, the characterization of the tap water has shown a larger conductivity, acidity and concentration of reactive nitrogen and oxygen species. Only the tap water activated by the plasma jet has shown a significant effect on the plant growth. This effect could be correlated to reactive nitrogen species such as nitrite/nitrate species present in plasma activated tap water. PMID:29630641

Synthetic NPA diagnostic for energetic particles in JET plasmas

NASA Astrophysics Data System (ADS)

Varje, J.; Sirén, P.; Weisen, H.; Kurki-Suonio, T.; Äkäslompolo, S.; contributors, JET

2017-11-01

Neutral particle analysis (NPA) is one of the few methods for diagnosing fast ions inside a plasma by measuring neutral atom fluxes emitted due to charge exchange reactions. The JET tokamak features an NPA diagnostic which measures neutral atom fluxes and energy spectra simultaneously for hydrogen, deuterium and tritium species. A synthetic NPA diagnostic has been developed and used to interpret these measurements to diagnose energetic particles in JET plasmas with neutral beam injection (NBI) heating. The synthetic NPA diagnostic performs a Monte Carlo calculation of the neutral atom fluxes in a realistic geometry. The 4D fast ion distributions, representing NBI ions, were simulated using the Monte Carlo orbit-following code ASCOT. Neutral atom density profiles were calculated using the FRANTIC neutral code in the JINTRAC modelling suite. Additionally, for rapid analysis, a scan of neutral profiles was precalculated with FRANTIC for a range of typical plasma parameters. These were taken from the JETPEAK database, which includes a comprehensive set of data from the flat-top phases of nearly all discharges in recent JET campaigns. The synthetic diagnostic was applied to various JET plasmas in the recent hydrogen campaign where different hydrogen/deuterium mixtures and NBI configurations were used. The simulated neutral fluxes from the fast ion distributions were found to agree with the measured fluxes, reproducing the slowing-down profiles for different beam isotopes and energies and quantitatively estimating the fraction of hydrogen and deuterium fast ions.

Research on Plasma Synthetic Jet Actuator

NASA Astrophysics Data System (ADS)

Che, X. K.; Nie, W. S.; Hou, Z. Y.

2011-09-01

Circular dielectric barrier surface discharge (DBDs) actuator is a new concept of zero mass synthetic jet actuator. The characteristic of discharge and flow control effect of annular-circular plasma synthetic jet actuator has been studied by means of of numerical simulation and experiment. The discharge current density, electron density, electrostatic body force density and flowfield have been obtained. The results show annular-circular actuator can produce normal jet whose velocity will be greater than 2.0 m/s. The jet will excite circumfluence. In order to insure the discharge is generated in the exposed electrode annular and produce centripetal and normal electrostatic body force, the width and annular diameter of exposed electrode must be big enough, or an opposite phase drove voltage potential should be applied between the two electrodes.

Liquid injection plasma deposition method and apparatus

DOEpatents

Kong, P.C.; Watkins, A.D.

1999-05-25

A liquid injection plasma torch deposition apparatus for depositing material onto a surface of a substrate may comprise a plasma torch for producing a jet of plasma from an outlet nozzle. A plasma confinement tube having an inlet end and an outlet end and a central bore therethrough is aligned with the outlet nozzle of the plasma torch so that the plasma jet is directed into the inlet end of the plasma confinement tube and emerges from the outlet end of the plasma confinement tube. The plasma confinement tube also includes an injection port transverse to the central bore. A liquid injection device connected to the injection port of the plasma confinement tube injects a liquid reactant mixture containing the material to be deposited onto the surface of the substrate through the injection port and into the central bore of the plasma confinement tube. 8 figs.

Interferometric analysis of laboratory photoionized plasmas utilizing supersonic gas jet targets.

NASA Astrophysics Data System (ADS)

Swanson, Kyle James; Ivanov, Vladimir; Mancini, Roberto; Mayes, Daniel C.

2018-06-01

Photoionized plasmas are an important component of active galactic nuclei, x-ray binary systems and other astrophysical objects. Laboratory produced photoionized plasmas have mainly been studied at large scale facilities, due to the need for high intensity broadband x-ray flux. Using supersonic gas jets as targets has allowed university scale pulsed power generators to begin similar research. The two main advantages of this approach with supersonic gas jets include: possibility of a closer location to the x-ray source and no attenuation related to material used for containment and or tamping. Due to these factors, this experimental platform creates a laboratory environment that more closely resembles astrophysical environments. This system was developed at the Nevada Terawatt Facility using the 1 MA pulsed power generator Zebra. Neon, argon, and nitrogen supersonic gas jets are produced approximately 7-8mm from the z-pinch axis. The high intensity broadband x-ray flux produced by the collapse of the z-pinch wire array implosion irradiates the gas jet. Cylindrical wire arrays are made with 4 and 8 gold 10µm thick wire. The z-pinch radiates approximately 12-16kj of x-ray energy, with x-ray photons under 1Kev in energy. The photoionized plasma is measured via x-ray absorption spectroscopy and interferometry. A Mach-Zehnder interferometer is used to the measure neutral density of the jet prior to the zebra shot at a wavelength of 266 nm. A dual channel air-wedge shearing interferometer is used to measure electron density of the ionized gas jet during the shot, at wavelengths of 532nm and 266nm. Using a newly developed interferometric analysis tool, average ionization state maps of the plasma can be calculated. Interferometry for nitrogen and argon show an average ionization state in the range of 3-8. Preliminary x-ray absorption spectroscopy collected show neon absorption lines. This work was sponsored in part by DOE Office of Science Grant DE-SC0014451.

Control of unsteadiness of a shock wave/turbulent boundary layer interaction by using a pulsed-plasma-jet actuator

NASA Astrophysics Data System (ADS)

Narayanaswamy, Venkateswaran; Raja, Laxminarayan L.; Clemens, Noel T.

2012-07-01

A pulsed-plasma jet actuator is used to control the unsteady motion of the separation shock of a shock wave/boundary layer interaction formed by a compression ramp in a Mach 3 flow. The actuator is based on a plasma-generated synthetic jet and is configured as an array of three jets that can be injected normal to the cross-flow, pitched, or pitched and skewed. The typical peak jet exit velocity of the actuators is about 300 m/s and the pulsing frequencies are a few kilohertz. A study of the interaction between the pulsed-plasma jets and the shock/boundary layer interaction was performed in a time-resolved manner using 10 kHz schlieren imaging. When the actuator, pulsed at StL ≈ 0.04 (f = 2 kHz), was injected into the upstream boundary layer, the separation shock responded to the plasma jet by executing a rapid upstream motion followed by a gradual downstream recovery motion. Schlieren movies of the interaction showed that the separation shock unsteadiness was locked to the pulsing frequency of the actuator, with amplitude of about one boundary layer thickness. Wall-pressure measurements made under the intermittent region showed about a 30% decrease in the overall magnitude of the pressure fluctuations in the low-frequency band associated with unsteady large-scale motion of the separated flow. Furthermore, by increasing the pulsing frequency to 3.3 kHz, the amplitude of the separation shock oscillation was reduced to less than half the boundary layer thickness. Investigation into the effect of the actuator location on the shock wave/boundary layer interaction (SWBLI) showed qualitatively and quantitatively that the actuator placed upstream of the separation shock caused significant modification to the SWBLI unsteadiness, whereas injection from inside the separation bubble did not cause a noticeable effect.

Resolution effects in the hybrid strong/weak coupling model

NASA Astrophysics Data System (ADS)

Hulcher, Zachary; Pablos, Daniel; Rajagopal, Krishna

2018-03-01

Within the context of a hybrid strong/weak coupling model of jet quenching, we study the consequences of the fact that the plasma produced in a heavy ion collision cannot resolve the substructure of a collimated parton shower propagating through it with arbitrarily fine spatial resolution. We introduce a screening length parameter, L res, proportional to the inverse of the local temperature in the plasma, estimating a range for the value of the proportionality constant via comparing weakly coupled QCD calculations and holographic calculations appropriate in strongly coupled plasma. We then modify the hybrid model so that when a parton in a jet shower splits, its two offspring are initially treated as unresolved, and are only treated as two separate partons losing energy independently after they are separated by a distance L res. This modification delays the quenching of partons with intermediate energy, resulting in the survival of more hadrons in the final state with p T in the several GeV range. We analyze the consequences of different choices for the value of the resolution length, L res, and demonstrate that introducing a nonzero L res results in modifications to the jet shapes and jet fragmentations functions, as it makes it more probable for particles carrying a small fraction of the jet energy at larger angles from the jet axis to survive their passage through the quark-gluon plasma. These effects are, however, small in magnitude, something that we confirm via checking for effects on missing- p T observables.

Laboratory Plasma Source as an MHD Model for Astrophysical Jets

NASA Technical Reports Server (NTRS)

Mayo, Robert M.

1997-01-01

The significance of the work described herein lies in the demonstration of Magnetized Coaxial Plasma Gun (MCG) devices like CPS-1 to produce energetic laboratory magneto-flows with embedded magnetic fields that can be used as a simulation tool to study flow interaction dynamic of jet flows, to demonstrate the magnetic acceleration and collimation of flows with primarily toroidal fields, and study cross field transport in turbulent accreting flows. Since plasma produced in MCG devices have magnetic topology and MHD flow regime similarity to stellar and extragalactic jets, we expect that careful investigation of these flows in the laboratory will reveal fundamental physical mechanisms influencing astrophysical flows. Discussion in the next section (sec.2) focuses on recent results describing collimation, leading flow surface interaction layers, and turbulent accretion. The primary objectives for a new three year effort would involve the development and deployment of novel electrostatic, magnetic, and visible plasma diagnostic techniques to measure plasma and flow parameters of the CPS-1 device in the flow chamber downstream of the plasma source to study, (1) mass ejection, morphology, and collimation and stability of energetic outflows, (2) the effects of external magnetization on collimation and stability, (3) the interaction of such flows with background neutral gas, the generation of visible emission in such interaction, and effect of neutral clouds on jet flow dynamics, and (4) the cross magnetic field transport of turbulent accreting flows. The applicability of existing laboratory plasma facilities to the study of stellar and extragalactic plasma should be exploited to elucidate underlying physical mechanisms that cannot be ascertained though astrophysical observation, and provide baseline to a wide variety of proposed models, MHD and otherwise. The work proposed herin represents a continued effort on a novel approach in relating laboratory experiments to astrophysical jet observation. There exists overwhelming similarity among these flows that has already produced some fascinating results and is expected to continue a high pay off in future flow similarity studies.

Atmospheric-Pressure Plasma Jet Surface Treatment for Use in Improving Adhesion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuettner, Lindsey Ann

Atmospheric-pressure plasma jets (APPJs) are a method of plasma treatment that plays an important role in material processing and modifying surface properties of materials, especially polymers. Gas plasmas react with polymer surfaces in numerous ways such as oxidation, radical formation, degradation, and promotion of cross-linking. Because of this, gas and plasma conditions can be explored for chosen processes to maximize desired properties. The purpose of this study is to investigate plasma parameters in order to modify surface properties for improved adhesion between aluminum and epoxy substrates using two types of adhesives. The background, results to date, and future work willmore » be discussed.« less

Gamma-jet physics with the electro-magnetic calorimeter in the ALICE experiment at LHC

NASA Astrophysics Data System (ADS)

Bourdaud, G.

2008-05-01

The Electro-Magnetic Calorimeter (EMCal) will be fully installed for the first LHC heavy ion beam in order to improve the ALICE experiment performances in detection of high transverse momentum particles and in particular in reconstruction of γ-jet events. These events appear to be very interesting to probe the strongly interacting matter created in ultra-relativistic heavy ion collisions and the eventual Quark Gluon Plasma (QGP) state. Indeed, they may give information on the degree of medium opacity which induces the jet-quenching phenomenon: measuring the energy of the γ and comparing it to that of the associated jet may provide a unique way to quantify the jet energy loss in the dense matter. The interest of γ-jet studies in the framework of the quark gluon plasma physics will be discussed. A particular highlight will be stressed on the EMCal calorimeter. The detection of the γ-jet events will be then presented using this new ALICE detector.

Laboratory Investigation of Astrophysical Collimated Jets with Intense Lasers

NASA Astrophysics Data System (ADS)

Yuan, Dawei; Li, Yutong; Tao, Tao; Wei, Huigang; Zhong, Jiayong; Zhu, Baojun; Li, Yanfei; Zhao, Jiarui; Li, Fang; Han, Bo; Zhang, Zhe; Liang, Guiyun; Wang, Feilu; Hu, Guangyue; Zheng, Jian; Jiang, Shaoen; Du, Kai; Ding, Yongkun; Zhou, Shenlei; Zhu, Baoqiang; Zhu, Jianqiang; Zhao, Gang; Zhang, Jie

2018-06-01

One of the remarkable dynamic features of the Herbig–Haro (HH) object is its highly collimated propagation far away from the accretion disk. Different factors are proposed to give us a clearly physical explanation behind these fascinating phenomena, including magnetic field, radiation cooling, surrounding medium, and so on. Laboratory astrophysics, as a new complementary method of studying astrophysical issues, can provide an insight into these behaviors in a similar and controllable laboratory environment. Here we report the scaled laboratory experiments that a well-collimated radiative jet with high Mach number is successfully created to mimic the evolution of HH objects. According to our results, we find that the radiation cooling effect within the jet and the outer rare surrounding plasmas from the X-ray (>keV) photoionized target contribute to the jet collimation. The local nonuniform density structures along the collimated radiative jet axis are caused by the pressure competition between the inner jet and the outer plasmas. The corresponding simulations performed with radiation-hydrodynamic codes FLASH reveal how the radiative jet evolves.

Particle acceleration, magnetic field generation, and emission in relativistic pair jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Ramirez-Ruiz, E.; Hardee, P.; Hededal, C.; Kouveliotou, C.; Fishman, G. J.; Mizuno, Y.

2005-01-01

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Recent simulations show that the Weibel instability created by relativistic pair jets is responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet propagating through an ambient plasma with and without initial magnetic fields. The growth rates of the Weibel instability depends on the distribution of pair jets. The Weibel instability created in the collisionless shock accelerates particles perpendicular and parallel to the jet propagation direction. This instability is also responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron s transverse deflection behind the jet head. The jitter radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Gas flow rate dependence of the discharge characteristics of a helium atmospheric pressure plasma jet interacting with a substrate

NASA Astrophysics Data System (ADS)

Yan, Wen; Economou, Demetre J.

2017-10-01

A 2D (axisymmetric) computational study of the discharge characteristics of an atmospheric pressure plasma jet as a function of gas flow rate was performed. The helium jet emerged from a dielectric tube, with an average gas flow velocity in the range 2.5-20 m s-1 (1 atm, 300 K) in a nitrogen ambient, and impinged on a substrate a short distance dowstream. The effect of the substrate conductivity (conductror versus insulator) was also studied. Whenever possible, simulation predictions were compared with published experimental observations. Discharge ignition and propagation in the dielectric tube were hardly affected by the He gas flow velocity. Most properties of the plasma jet, however, depended sensitively on the He gas flow velocity, which determined the concentration distributions of helium and nitrogen in the mixing layer forming in the gap between the tube exit and the substrate. At low gas flow velocity, the plasma jet evolved from a hollow (donut-shaped) feature to one where the maximum of electron density was on axis. When the gas flow velocity was high, the plasma jet maintained its hollow structure until it struck the substrate. For a conductive substrate, the radial ion fluxes to the surface were relatively uniform over a radius of ~0.4-0.8 mm, and the dominant ion flux was that of He+. For a dielectric substrate, the radial ion fluxes to the surface peaked on the symmetry axis at low He gas flow velocity, but a hollow ion flux distribution was observed at high gas flow velocity. At the same time, the main ion flux switched from N2+ to He2+ as the He gas flow velocity increased from a low to a high value. The diameter of the plasma ‘footprint’ on the substrate first increased with increasing He gas flow velocity, and eventually saturated with further increases in velocity.

Vorticity generation and jetting caused by a laser-induced optical breakdown

NASA Astrophysics Data System (ADS)

Wang, Jonathan; Buchta, David; Freund, Jonathan

2017-11-01

A focused laser can cause optical breakdown of a gas that absorbs energy and can seed ignition. The local hydrodynamics are complex. The breakdown is observed to produce vorticity that subsequently collects into a jetting flow towards the laser source. The strength and the very direction of the jet is observed to be sensitive to the plasma kernel geometry. We use detailed numerical simulations to examine the short-time (< 1 μ s) dynamics leading to this vorticity and jetting. The simulation employs a two-temperature model, free-electron generation by multi-photon ionization, absorption of laser energy by inverse Bremsstrahlung, and 11 charged and neutral species for air. We quantify the early-time contributions of different thermodynamic and gas-dynamic effects to the baroclinic torque. It is found that the breakdown produces compression waves within the plasma kernel, and that the mismatch in their strengths precipitates the involution of the plasma remnants and yields the net vorticity that ultimately develops into the jet. We also quantify the temperature distribution and local strain rates and demonstrate their importance in seeding ignition in non-homogeneous hydrogen/air mixtures.

Investigation of plasma-induced erosion of multilayer condenser optics

NASA Astrophysics Data System (ADS)

Anderson, Richard J.; Buchenauer, Dean A.; Williams, K. A.; Clift, W. M.; Klebanoff, L. E.; Edwards, N. V.; Wood, O. R., II; Wurm, S.

2005-05-01

Experiments are presented that investigate the mechanistic cause of multilayer erosion observed from condenser optics exposed to EUV laser-produced plasma (LPP) sources. Using a Xe filament jet source excited with Nd-YAG laser radiation (300 mJ/pulse), measurements were made of material erosion from Au, Mo, Si and C using coated quartz microbalances located 127 mm from the plasma. The observed erosion rates were as follows: Au=99nm/106 shots, Mo= 26nm/106 shots, Si=19nm/106 shots, and C=6nm/106 shots. The relative ratio Au:Mo:Si:C of erosion rates observed experimentally, 16:4:3:1 compares favorably with that predicted from an atomic sputtering model assuming 20 kV Xe ions, 16:6:4:1. The relative agreement indicates that Xe-substrate sputtering is largely responsible for the erosion of Mo/Si multilayers on condenser optics that directly face the plasma. Time-of-flight Faraday cup measurements reveal the emission of high energy Xe ions from the Xe-filament jet plasma. The erosion rate does not depend on the repetition rate of the laser, suggesting a thermal mechanism is not operative. The Xe-filament jet erosion is ~20x that observed from a Xe spray jet. Since the long-lived (millisecond time scale) plasma emanating from these two sources are the same to within ~30%, sputtering from this long-lived plasma can be ruled out as an erosion agent.

Characteristics of a Direct Current-driven plasma jet operated in open air

NASA Astrophysics Data System (ADS)

Li, Xuechen; Di, Cong; Jia, Pengying; Bao, Wenting

2013-09-01

A DC-driven plasma jet has been developed to generate a diffuse plasma plume by blowing argon into the ambient air. The plasma plume, showing a cup shape with a diameter of several centimeters at a higher voltage, is a pulsed discharge despite a DC voltage is applied. The pulse frequency is investigated as a function of the voltage under different gap widths and gas flow rates. Results show that plasma bullets propagate from the hollow needle to the plate electrode by spatially resolved measurement. A supposition about non-electroneutral trail of the streamer is proposed to interpret these experimental phenomena.

Effects of atmospheric pressure plasma jet with floating electrode on murine melanoma and fibroblast cells

NASA Astrophysics Data System (ADS)

Xu, G.; Liu, J.; Yao, C.; Chen, S.; Lin, F.; Li, P.; Shi, X.; Zhang, Guan-Jun

2017-08-01

Atmospheric pressure cold plasma jets have been recently shown as a highly promising tool in certain cancer therapies. In this paper, an atmospheric pressure plasma jet (APPJ) with a one inner floating and two outer electrode configuration using helium gas for medical applications is developed. Subjected to a range of applied voltages with a frequency of 19.8 kHz at a fixed rate of gas flow (i.e., 3 l/min), electrical and optical characteristics of the APPJ are investigated. Compared with the device only with two outer electrodes, higher discharge current, longer jet, and more active species in the plasma plume at the same applied voltage together with the lower gas breakdown voltage can be achieved through embedding a floating inner electrode. Employing the APPJ with a floating electrode, the effects of identical plasma treatment time durations on murine melanoma cancer and normal fibroblast cells cultured in vitro are evaluated. The results of cell viability, cell apoptosis, and DNA damage detection show that the plasma can inactivate melanoma cells in a time-dependent manner from 10 s to 60 s compared with the control group (p < 0.05). However, for fibroblast cells compared with their control group, the plasma with treatment time from 30 s to 60 s can induce significant changes (p < 0.05), showing a less cytotoxic effect than that on melanoma cells at the same treatment time. The different basal reactive oxygen species level and antioxidant superoxide dismutase level of two kinds of cells may account for their different responses towards the identical plasma exposure.

Thermometry of the system “heat-resistant sample - incident plasma stream”

NASA Astrophysics Data System (ADS)

Sargsyan, M. A.; Chinnov, V. F.; Kavyrshin, D. I.; Gadzhiev, M. Kh; Khromov, M. A.; Chistolinov, A. V.; Senchenko, V. N.

2017-11-01

To study the interacting system “heat-resistant sample - an incident plasma stream” a setup of synchronized measurement equipment was developed and tested that recorded the main parameters of such interaction. Heat resistance tests were carried out on the samples of MPG-6 grade isotropic graphite, and samples of pyrolytic graphite that were subjected to a long (60 … 100 s) exposure to nitrogen, argon and air plasma streams at atmospheric pressure. As plasma generators a series of plasma torches with a vortex stabilization of the stream and an expanding anode channels was used. The temperature and composition of the plasma in the jet and near the sample were determined using two AvaSpec2048 and AvaSpec3648 scanning optical spectrometers and the MS5402i spectrograph with the Andor matrix at its outlet. The surface temperature of the sample was determined in real time using three independent ways: two pyrometric systems - a high-speed micro-pyrometer FMP1001 and a two-position visualization of the heated sample by high-speed Motion Pro X3 and VS-FAST cameras, and the spectral analysis of the wide-range thermal radiation of the samples. The main method for determining the rate of material loss during the action of a plasma jet on it was to analyze a two-position synchronous visualization of the “jet-sample” system. When a crater was formed on the surface of the sample under the “dagger” effect of a plasma jet, a video recording system of the crater zone was used, backlit using the “laser knife” method.

EDITORIAL: Special section on recent progress on radio frequency heating and current drive studies in the JET tokamak Special section on recent progress on radio frequency heating and current drive studies in the JET tokamak

NASA Astrophysics Data System (ADS)

Ongena, Jef; Mailloux, Joelle; Mayoral, Marie-Line

2009-04-01

This special cluster of papers summarizes the work accomplished during the last three years in the framework of the Task Force Heating at JET, whose mission it is to study the optimisation of heating systems for plasma heating and current drive, launching and deposition questions and the physics of plasma rotation. Good progress and new physics insights have been obtained with the three heating systems available at JET: lower hybrid (LH), ion cyclotron resonance heating (ICRH) and neutral beam injection (NBI). Topics covered in the present issue are the use of edge gas puffing to improve the coupling of LH waves at large distances between the plasma separatrix and the LH launcher. Closely linked with this topic are detailed studies of the changes in LH coupling due to modifications in the scrape-off layer during gas puffing and simultaneous application of ICRH. We revisit the fundamental ICRH heating of D plasmas, include new physics results made possible by recently installed new diagnostic capabilities on JET and point out caveats for ITER when NBI is simultaneously applied. Other topics are the study of the anomalous behaviour of fast ions from NBI, and a study of toroidal rotation induced by ICRH, both again with possible implications for ITER. In finalizing this cluster of articles, thanks are due to all colleagues involved in preparing and executing the JET programme under EFDA in recent years. We want to thank the EFDA leadership for the special privilege of appointing us as Leaders or Deputies of Task Force Heating, a wonderful and hardworking group of colleagues. Thanks also to all other European and non-European scientists who contributed to the JET scientific programme, the Operations team of JET and the colleagues of the Close Support Unit (CSU). Thanks are also due to the Editors, Editorial Board and referees of Plasma Physics and Controlled Fusion together with the publishing staff of IOP Publishing who have supported and contributed substantially to this initiative.

Atomic oxygen behavior at downstream of AC excited atmospheric pressure He plasma jet

NASA Astrophysics Data System (ADS)

Takeda, Keigo; Ishikawa, Kenji; Tanaka, Hiromasa; Sekine, Makoto; Hori, Masaru

2016-09-01

Applications of atmospheric pressure plasma jets (APPJ) have been investigated in the plasma medical fields such as cancer therapy, blood coagulation, etc. Reactive species generated by the plasma jet interacts with the biological surface. Therefore, the issue attracts much attentions to investigate the plasma effects on targets. In our group, a spot-size AC excited He APPJ have been used for the plasma medicine. From diagnostics of the APPJ using optical emission spectroscopy, the gas temperature and the electron density was estimated to be 299 K and 3.4 ×1015 cm-3. The AC excited He APPJ which affords high density plasma at room temperature is considered to be a powerful tool for the medical applications. In this study, by using vacuum ultraviolet absorption spectroscopy, the density of atomic oxygen on a floating copper as a target irradiated by the He APPJ was measured as a function of the distance between the plasma source and the copper wire. The measured density became a maximum value around 8 ×1013 cm-3 at 12 mm distance, and then decreased over the distance. It is considered that the behavior was due to the changes in the plasma density on the copper wire and influence of ambient air.

Spatial Dependence of DNA Damage in Bacteria due to Low-Temperature Plasma Application as Assessed at the Single Cell Level

NASA Astrophysics Data System (ADS)

Privat-Maldonado, Angela; O'Connell, Deborah; Welch, Emma; Vann, Roddy; van der Woude, Marjan W.

2016-10-01

Low temperature plasmas (LTPs) generate a cocktail of reactive nitrogen and oxygen species (RNOS) with bactericidal activity. The RNOS however are spatially unevenly distributed in the plasma. Here we test the hypothesis that this distribution will affect the mechanisms underpinning plasma bactericidal activity focussing on the level of DNA damage in situ. For the first time, a quantitative, single cell approach was applied to assess the level of DNA damage in bacteria as a function of the radial distance from the centre of the plasma jet. Salmonella enterica on a solid, dry surface was treated with two types of LTP: an atmospheric-pressure dielectric barrier discharge plasma jet (charged and neutral species) and a radio-frequency atmospheric-pressure plasma jet (neutral species). In both cases, there was an inverse correlation between the degree of DNA damage and the radial distance from the centre of the plasma, with the highest DNA damage occurring directly under the plasma. This trend was also observed with Staphylococcus aureus. LTP-generated UV radiation was eliminated as a contributing factor. Thus valuable mechanistic information can be obtained from assays on biological material, which can inform the development of LTP as a complementary or alternative therapy for (topical) bacterial infections.

First Breakthrough for Future Air-Breathing Magneto-Plasma Propulsion Systems

NASA Astrophysics Data System (ADS)

Göksel, B.; Mashek, I. Ch

2017-04-01

A new breakthrough in jet propulsion technology since the invention of the jet engine is achieved. The first critical tests for future air-breathing magneto-plasma propulsion systems have been successfully completed. In this regard, it is also the first time that a pinching dense plasma focus discharge could be ignited at one atmosphere and driven in pulse mode using very fast, nanosecond electrostatic excitations to induce self-organized plasma channels for ignition of the propulsive main discharge. Depending on the capacitor voltage (200-600 V) the energy input at one atmosphere varies from 52-320 J/pulse corresponding to impulse bits from 1.2-8.0 mNs. Such a new pulsed plasma propulsion system driven with one thousand pulses per second would already have thrust-to-area ratios (50-150 kN/m²) of modern jet engines. An array of thrusters could enable future aircrafts and airships to start from ground and reach altitudes up to 50km and beyond. The needed high power could be provided by future compact plasma fusion reactors already in development by aerospace companies. The magneto-plasma compressor itself was originally developed by Russian scientists as plasma fusion device and was later miniaturized for supersonic flow control applications. So the first breakthrough is based on a spin-off plasma fusion technology.

Model polymer etching and surface modification by a time modulated RF plasma jet: role of atomic oxygen and water vapor

NASA Astrophysics Data System (ADS)

Luan, P.; Knoll, A. J.; Wang, H.; Kondeti, V. S. S. K.; Bruggeman, P. J.; Oehrlein, G. S.

2017-01-01

The surface interaction of a well-characterized time modulated radio frequency (RF) plasma jet with polystyrene, poly(methyl methacrylate) and poly(vinyl alcohol) as model polymers is investigated. The RF plasma jet shows fast polymer etching but mild chemical modification with a characteristic carbonate ester and NO formation on the etched surface. By varying the plasma treatment conditions including feed gas composition, environment gaseous composition, and treatment distance, we find that short lived species, especially atomic O for Ar/1% O2 and 1% air plasma and OH for Ar/1% H2O plasma, play an essential role for polymer etching. For O2 containing plasma, we find that atomic O initiates polymer etching and the etching depth mirrors the measured decay of O atoms in the gas phase as the nozzle-surface distance increases. The etching reaction probability of an O atom ranging from 10-4 to 10-3 is consistent with low pressure plasma research. We also find that adding O2 and H2O simultaneously into Ar feed gas quenches polymer etching compared to adding them separately which suggests the reduction of O and OH density in Ar/O2/H2O plasma.

Spatial Dependence of DNA Damage in Bacteria due to Low-Temperature Plasma Application as Assessed at the Single Cell Level

PubMed Central

Privat-Maldonado, Angela; O’Connell, Deborah; Welch, Emma; Vann, Roddy; van der Woude, Marjan W.

2016-01-01

Low temperature plasmas (LTPs) generate a cocktail of reactive nitrogen and oxygen species (RNOS) with bactericidal activity. The RNOS however are spatially unevenly distributed in the plasma. Here we test the hypothesis that this distribution will affect the mechanisms underpinning plasma bactericidal activity focussing on the level of DNA damage in situ. For the first time, a quantitative, single cell approach was applied to assess the level of DNA damage in bacteria as a function of the radial distance from the centre of the plasma jet. Salmonella enterica on a solid, dry surface was treated with two types of LTP: an atmospheric-pressure dielectric barrier discharge plasma jet (charged and neutral species) and a radio-frequency atmospheric-pressure plasma jet (neutral species). In both cases, there was an inverse correlation between the degree of DNA damage and the radial distance from the centre of the plasma, with the highest DNA damage occurring directly under the plasma. This trend was also observed with Staphylococcus aureus. LTP-generated UV radiation was eliminated as a contributing factor. Thus valuable mechanistic information can be obtained from assays on biological material, which can inform the development of LTP as a complementary or alternative therapy for (topical) bacterial infections. PMID:27759098

Surface modification of polyester fabrics by atmospheric-pressure air/He plasma for color strength and adhesion enhancement

NASA Astrophysics Data System (ADS)

Zhang, Chunming; Zhao, Meihua; Wang, Libing; Qu, Lijun; Men, Yajing

2017-04-01

Surface properties of water-based pigmented inks for ink-jet printed polyester fabrics were modified with atmospheric-pressure air/He plasma to improve the color strength and pigment adhesion of the treated surfaces. The influence of various parameters, including the surface morphology, chemical compositions, surface energy and dynamic contact angles of the control and plasma treated samples was studied. Color strength and edge definition were used to evaluate the ink-jet printing performance of fabrics. The change in pigment adhesion to polyester fibers was analyzed by SEM (scanning electron microscopy). AFM (Atomic force microscope) and XPS (X-ray photoelectron spectroscopy) analyses indicated the increase in surface roughness and the oxygen-containing polar groups(Cdbnd O, Csbnd OH and COOH) reinforced the fixation of pigments on the fiber surface. The result from this study suggested that the improved pigment color yield was clearly affected by alteration of pigment adhesion enhanced by plasma surface modification. Polyester fabrics exhibited better surface property and ink-jet printing performance after the air/He mixture plasma treatment comparing with those after air plasma treatment.

Clearing of ventilating emissions in low temperature environment of plasma

NASA Astrophysics Data System (ADS)

Mansurov, R. Sh; Rafalskaya, T. A.

2017-11-01

The method of high-temperature processing of streams of the ventilating air which is a subject clearing from organic pollutions is developed. Data about its efficiency, including on a number of economic parameters are obtained. Results of work are recommended for use, first of all, by development clearing plasma-thermal reactors (CPTR) for clearing air, especially from toxic substances, and also for large technological clearing installations, containing organic ventilating emissions (OVE). It is created experimental CPTR. Laws of the expiration of a plasma jet in stream of OVE limited by cylindrical walls, water-cooled channel are experimentally investigated. Dependences of a trajectory and long-range the plasma jet blown radially in stream of OVE are received. Heat exchange of stream of OVE with walls of CPTR after blowing a plasma jet is experimentally investigated; dependences of distribution of temperatures on length of a reactor and a thermal stream in a wall of channel of CPTR are received. Are investigated chemical compound of OVE after plasma-thermal clearing, some experimental data by formation of oxides of nitrogen and mono-oxide of carbon during clearing are received.

Formation and dynamics of plasma bullets in a non-thermal plasma jet: influence of the high-voltage parameters on the plume characteristics

NASA Astrophysics Data System (ADS)

Jarrige, Julien; Laroussi, Mounir; Karakas, Erdinc

2010-12-01

Non-thermal plasma jets in open air are composed of ionization waves commonly known as 'plasma bullets' propagating at high velocities. We present in this paper an experimental study of plasma bullets produced in a dielectric barrier discharge linear-field reactor fed with helium and driven by microsecond high-voltage pulses. Two discharges were produced between electrodes for every pulse (at the rising and falling edge), but only one bullet was generated. Fast intensified charge coupled device camera imaging showed that bullet velocity and diameter increase with applied voltage. Spatially resolved optical emission spectroscopy measurements provided evidence of the hollow structure of the jet and its contraction. It was shown that the pulse amplitude significantly enhances electron energy and production of active species. The plasma bullet appeared to behave like a surface discharge in the tube, and like a positive streamer in air. A kinetics mechanism based on electron impact, Penning effect and charge transfer reactions is proposed to explain the propagation of the ionization front and temporal behavior of the radiative species.

Impact of electric field from a plasma jet on biological targets

NASA Astrophysics Data System (ADS)

Douat, Claire; Darny, Thibault; Iseni, Sylvain; Damany, Xavier; Dozias, Sebastien; Pouvesle, Jean-Michel; Robert, Eric; Vijayarangan, Vinodini; Delalande, Anthony; Pichon, Chantal

2016-09-01

Atmospheric pressure plasma jets have demonstrated their ability in biomedical applications thanks to their low gas temperature and their capacity to produce radicals, ions, electrons, UV radiation and electric fields. However the understanding of the interactions between the plasma and living cells and tissues is still far from being completely understood. Recently, Robert et al characterized two components of the electric field from a plasma jet and showed that the latter can propagate deeply in tissues on several mm. In this work, we focus on the study of the electric field induced by the plasma and its influence on the cell membrane. Propidium iodide, dextran sulfate and plasmid DNA are used to measure the permeability of the membrane, while an electro-optic probe is used to measure the longitudinal and the radial components of the electric field. The two components are both spatially and temporally resolved. To investigate the contribution of the electric field on the cell membrane, a dielectric barrier is used between the plasma and the biological target. A comparison with and without the barrier will be presented for both biological and agriculture applications.

Formation of X-ray emitting stationary shocks in magnetized protostellar jets

NASA Astrophysics Data System (ADS)

Ustamujic, S.; Orlando, S.; Bonito, R.; Miceli, M.; Gómez de Castro, A. I.; López-Santiago, J.

2016-12-01

Context. X-ray observations of protostellar jets show evidence of strong shocks heating the plasma up to temperatures of a few million degrees. In some cases, the shocked features appear to be stationary. They are interpreted as shock diamonds. Aims: We investigate the physics that guides the formation of X-ray emitting stationary shocks in protostellar jets; the role of the magnetic field in determining the location, stability, and detectability in X-rays of these shocks; and the physical properties of the shocked plasma. Methods: We performed a set of 2.5-dimensional magnetohydrodynamic numerical simulations that modelled supersonic jets ramming into a magnetized medium and explored different configurations of the magnetic field. The model takes into account the most relevant physical effects, namely thermal conduction and radiative losses. We compared the model results with observations, via the emission measure and the X-ray luminosity synthesized from the simulations. Results: Our model explains the formation of X-ray emitting stationary shocks in a natural way. The magnetic field collimates the plasma at the base of the jet and forms a magnetic nozzle there. After an initial transient, the nozzle leads to the formation of a shock diamond at its exit which is stationary over the time covered by the simulations ( 40-60 yr; comparable with timescales of the observations). The shock generates a point-like X-ray source located close to the base of the jet with luminosity comparable with that inferred from X-ray observations of protostellar jets. For the range of parameters explored, the evolution of the post-shock plasma is dominated by the radiative cooling, whereas the thermal conduction slightly affects the structure of the shock. A movie is available at http://www.aanda.org

Production and correlation of reactive oxygen and nitrogen species in gas- and liquid-phase generated by helium plasma jets under different pulse widths

NASA Astrophysics Data System (ADS)

Liu, Zhijie; Zhou, Chunxi; Liu, Dingxin; Xu, Dehui; Xia, Wenjie; Cui, Qingjie; Wang, Bingchuan; Kong, Michael G.

2018-01-01

In this paper, we present the effects of the pulse width (PW) on the plasma jet's discharge characteristics, particularly focusing on the production and correlation of the reactive oxygen and nitrogen species (RONS) in gas- and liquid-phase. It is found that the length of plasma jet plume first increases before the PW of 10 μs, then gradually decreases and finally almost remains unchanged beyond 150 μs. The plasma bullet disappears after the falling edge of the voltage pulse at low PW, while it terminates far ahead of the falling edge of voltage pulse at high PW. This is mainly attributed to accumulation of space charges that lead to weakening of the reduced electric field with an increase of PW from low to high. More important, it is found that the excited reactive species, the positive and negative ions from plasma jet, and the concentrations of NO2- and NO3- in deionized water exposed to plasma jet also display the first increasing and then decreasing change trend with increase of PW, while the concentration of H2O2 in water almost displays the linearly increasing trend. This mainly results from the formation of the H3O+ and HO2-, as well as their ion water clusters that can produce more OH radicals to be converted into H2O2, while the NO2- and NO3- in gas phase can transport into water and exist most stably in water. The water cluster formation at gas-liquid interface is an important key process that can affect the chemical nature and dose of aqueous RONS in water; this is beneficial for understanding how the RONS are formed in liquid-phase.

Mitigation of divertor heat loads by strike point sweeping in high power JET discharges

NASA Astrophysics Data System (ADS)

Silburn, S. A.; Matthews, G. F.; Challis, C. D.; Frigione, D.; Graves, J. P.; Mantsinen, M. J.; Belonohy, E.; Hobirk, J.; Iglesias, D.; Keeling, D. L.; King, D.; Kirov, K.; Lennholm, M.; Lomas, P. J.; Moradi, S.; Sips, A. C. C.; Tsalas, M.; Contributors, JET

2017-12-01

Deliberate periodic movement (sweeping) of the high heat flux divertor strike lines in tokamak plasmas can be used to manage the heat fluxes experienced by exhaust handling plasma facing components, by spreading the heat loads over a larger surface area. Sweeping has recently been adopted as a routine part of the main high performance plasma configurations used on JET, and has enabled pulses with 30 MW plasma heating power and 10 MW radiation to run for 5 s without overheating the divertor tiles. We present analysis of the effectiveness of sweeping for divertor temperature control on JET, using infrared camera data and comparison with a simple 2D heat diffusion model. Around 50% reduction in tile temperature rise is obtained with 5.4 cm sweeping compared to the un-swept case, and the temperature reduction is found to scale slower than linearly with sweeping amplitude in both experiments and modelling. Compatibility of sweeping with high fusion performance is demonstrated, and effects of sweeping on the edge-localised mode behaviour of the plasma are reported and discussed. The prospects of using sweeping in future JET experiments with up to 40 MW heating power are investigated using a model validated against existing experimental data.

AN INSTRUMENT TO MEASURE THE ELECTRICAL CONDUCTIVITY OF ARC PLASMA JETS

DTIC Science & Technology

The instrument was calibrated by moving aluminum or graphite rods through the transducer. By using thin-wall, stainless steel tubing, the influence ... function for the transducer was also obtained. Tests were run on two different arc plasma jet facilities. Values of s, u ranged from 0.02 to 9 megamhos per second. (Author)

Plasma jet takes off.

PubMed Central

Frazer, L

1999-01-01

Thanks to a series of joint research projects by Los Alamos National Laboratory, Beta Squared of Allen, Texas, and the University of California at Los Angeles, there is now a more environmentally sound method for cleaning semiconductor chips that may also be effective in cleaning up chemical, bacterial, and nuclear contaminants. The Atmospheric Pressure Plasma Jet uses a type of ionized gas called plasma to clean up contaminants by binding to them and lifting them away. In contrast to the corrosive acids and chemical solvents traditionally used to clean semiconductor chips, the jet oxidizes contaminants, producing only benign gaseous by-products such as oxygen and carbon dioxide. The new technology is also easy to transport, cleans thoroughly and quickly, and presents no hazards to its operators. PMID:10417375

X-ray crystal spectrometer upgrade for ITER-like wall experiments at JET.

PubMed

Shumack, A E; Rzadkiewicz, J; Chernyshova, M; Jakubowska, K; Scholz, M; Byszuk, A; Cieszewski, R; Czarski, T; Dominik, W; Karpinski, L; Kasprowicz, G; Pozniak, K; Wojenski, A; Zabolotny, W; Conway, N J; Dalley, S; Figueiredo, J; Nakano, T; Tyrrell, S; Zastrow, K-D; Zoita, V

2014-11-01

The high resolution X-Ray crystal spectrometer at the JET tokamak has been upgraded with the main goal of measuring the tungsten impurity concentration. This is important for understanding impurity accumulation in the plasma after installation of the JET ITER-like wall (main chamber: Be, divertor: W). This contribution provides details of the upgraded spectrometer with a focus on the aspects important for spectral analysis and plasma parameter calculation. In particular, we describe the determination of the spectrometer sensitivity: important for impurity concentration determination.

Electrical and optical properties of Ar/NH{sub 3} atmospheric pressure plasma jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Zheng-Shi, E-mail: changzhsh1984@163.com, E-mail: gjzhang@xjtu.edu.cn; Yao, Cong-Wei; Chen, Si-Le

Inspired by the Penning effect, we obtain a glow-like plasma jet by mixing ammonia (NH{sub 3}) into argon (Ar) gas under atmospheric pressure. The basic electrical and optical properties of an atmospheric pressure plasma jet (APPJ) are investigated. It can be seen that the discharge mode transforms from filamentary to glow-like when a little ammonia is added into the pure argon. The electrical and optical analyses contribute to the explanation of this phenomenon. The discharge mode, power, and current density are analyzed to understand the electrical behavior of the APPJ. Meanwhile, the discharge images, APPJ's length, and the components ofmore » plasma are also obtained to express its optical characteristics. Finally, we diagnose several parameters, such as gas temperature, electron temperature, and density, as well as the density number of metastable argon atoms of Ar/NH{sub 3} APPJ to help judge the usability in its applications.« less

Evolution of the mean jet shape and dijet asymmetry distribution of an ensemble of holographic jets in strongly coupled plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brewer, Jasmine; Rajagopal, Krishna; Sadofyev, Andrey

Some of the most important experimentally accessible probes of the quark- gluon plasma (QGP) produced in heavy ion collisions come from the analysis of how the shape and energy of sprays of energetic particles produced within a cone with a specified opening angle (jets) in a hard scattering are modified by their passage through the strongly coupled, liquid, QGP. We model an ensemble of back-to-back dijets for the purpose of gaining a qualitative understanding of how the shapes of the individual jets and the asymmetry in the energy of the pairs of jets in the ensemble are modified by theirmore » passage through an expanding cooling droplet of strongly coupled plasma, in the model in a holographic gauge theory that is dual to a 4+1-dimensional black-hole spacetime that is asymptotically anti-de Sitter (AdS). We build our model by constructing an ensemble of strings in the dual gravitational description of the gauge theory. We model QCD jets in vacuum using strings whose endpoints are moving “downward” into the gravitational bulk spacetime with some fixed small angle, an angle that represents the opening angle (ratio of jet mass to jet energy) that the QCD jet would have in vacuum. Such strings must be moving through the gravitational bulk at (close to) the speed of light; they must be (close to) null. This condition does not specify the energy distribution along the string, meaning that it does not specify the shape of the jet being modeled. We study the dynamics of strings that are initially not null and show that strings with a wide range of initial conditions rapidly accelerate and become null and, as they do, develop a similar distribution of their energy density. We use this distribution of the energy density along the string, choose an ensemble of strings whose opening angles and energies are distributed as in perturbative QCD, and show that we can then fix one of the two model parameters such that the mean jet shape for the jets in the ensemble that we have built matches that measured in proton-proton collisions reasonably well. This is a novel way for hybridizing relevant inputs from perturbative QCD and a strongly coupled holographic gauge theory in the service of modeling jets in QGP. We send our ensemble of strings through an expanding cooling droplet of strongly coupled plasma, choosing the second model parameter so as to get a reasonable value for R AA jet , the suppression in the number of jets, and study how the mean jet shape and the dijet asymmetry are modified, comparing both to measurements from heavy ion collisions at the LHC.« less

Evolution of the mean jet shape and dijet asymmetry distribution of an ensemble of holographic jets in strongly coupled plasma

DOE PAGES

Brewer, Jasmine; Rajagopal, Krishna; Sadofyev, Andrey; ...

2018-02-02

Some of the most important experimentally accessible probes of the quark- gluon plasma (QGP) produced in heavy ion collisions come from the analysis of how the shape and energy of sprays of energetic particles produced within a cone with a specified opening angle (jets) in a hard scattering are modified by their passage through the strongly coupled, liquid, QGP. We model an ensemble of back-to-back dijets for the purpose of gaining a qualitative understanding of how the shapes of the individual jets and the asymmetry in the energy of the pairs of jets in the ensemble are modified by theirmore » passage through an expanding cooling droplet of strongly coupled plasma, in the model in a holographic gauge theory that is dual to a 4+1-dimensional black-hole spacetime that is asymptotically anti-de Sitter (AdS). We build our model by constructing an ensemble of strings in the dual gravitational description of the gauge theory. We model QCD jets in vacuum using strings whose endpoints are moving “downward” into the gravitational bulk spacetime with some fixed small angle, an angle that represents the opening angle (ratio of jet mass to jet energy) that the QCD jet would have in vacuum. Such strings must be moving through the gravitational bulk at (close to) the speed of light; they must be (close to) null. This condition does not specify the energy distribution along the string, meaning that it does not specify the shape of the jet being modeled. We study the dynamics of strings that are initially not null and show that strings with a wide range of initial conditions rapidly accelerate and become null and, as they do, develop a similar distribution of their energy density. We use this distribution of the energy density along the string, choose an ensemble of strings whose opening angles and energies are distributed as in perturbative QCD, and show that we can then fix one of the two model parameters such that the mean jet shape for the jets in the ensemble that we have built matches that measured in proton-proton collisions reasonably well. This is a novel way for hybridizing relevant inputs from perturbative QCD and a strongly coupled holographic gauge theory in the service of modeling jets in QGP. We send our ensemble of strings through an expanding cooling droplet of strongly coupled plasma, choosing the second model parameter so as to get a reasonable value for R AA jet , the suppression in the number of jets, and study how the mean jet shape and the dijet asymmetry are modified, comparing both to measurements from heavy ion collisions at the LHC.« less

Evolution of the mean jet shape and dijet asymmetry distribution of an ensemble of holographic jets in strongly coupled plasma

NASA Astrophysics Data System (ADS)

Brewer, Jasmine; Rajagopal, Krishna; Sadofyev, Andrey; van der Schee, Wilke

2018-02-01

Some of the most important experimentally accessible probes of the quark- gluon plasma (QGP) produced in heavy ion collisions come from the analysis of how the shape and energy of sprays of energetic particles produced within a cone with a specified opening angle (jets) in a hard scattering are modified by their passage through the strongly coupled, liquid, QGP. We model an ensemble of back-to-back dijets for the purpose of gaining a qualitative understanding of how the shapes of the individual jets and the asymmetry in the energy of the pairs of jets in the ensemble are modified by their passage through an expanding cooling droplet of strongly coupled plasma, in the model in a holographic gauge theory that is dual to a 4+1-dimensional black-hole spacetime that is asymptotically anti-de Sitter (AdS). We build our model by constructing an ensemble of strings in the dual gravitational description of the gauge theory. We model QCD jets in vacuum using strings whose endpoints are moving "downward" into the gravitational bulk spacetime with some fixed small angle, an angle that represents the opening angle (ratio of jet mass to jet energy) that the QCD jet would have in vacuum. Such strings must be moving through the gravitational bulk at (close to) the speed of light; they must be (close to) null. This condition does not specify the energy distribution along the string, meaning that it does not specify the shape of the jet being modeled. We study the dynamics of strings that are initially not null and show that strings with a wide range of initial conditions rapidly accelerate and become null and, as they do, develop a similar distribution of their energy density. We use this distribution of the energy density along the string, choose an ensemble of strings whose opening angles and energies are distributed as in perturbative QCD, and show that we can then fix one of the two model parameters such that the mean jet shape for the jets in the ensemble that we have built matches that measured in proton-proton collisions reasonably well. This is a novel way for hybridizing relevant inputs from perturbative QCD and a strongly coupled holographic gauge theory in the service of modeling jets in QGP. We send our ensemble of strings through an expanding cooling droplet of strongly coupled plasma, choosing the second model parameter so as to get a reasonable value for R AA jet , the suppression in the number of jets, and study how the mean jet shape and the dijet asymmetry are modified, comparing both to measurements from heavy ion collisions at the LHC.

Determination of temperature maps of EUV coronal hole jets

NASA Astrophysics Data System (ADS)

Nisticò, Giuseppe; Patsourakos, Spiros; Bothmer, Volker; Zimbardo, Gaetano

2011-11-01

Coronal hole jets are fast ejections of plasma occurring within coronal holes, observed at Extreme-UltraViolet (EUV) and X-ray wavelengths. Recent observations of jets by the STEREO and Hinode missions show that they are transient phenomena which occur at much higher rates than large-scale impulsive phenomena like flares and Coronal Mass Ejections (CMEs). In this paper we describe some typical characteristics of coronal jets observed by the SECCHI instruments of STEREO spacecraft. We show an example of 3D reconstruction of the helical structure for a south pole jet, and present how the angular distribution of the jet position angles changes from the Extreme-UltraViolet-Imager (EUVI) field of view to the CORonagraph1 (COR1) (height ∼2.0 R⊙ heliocentric distance) field of view. Then we discuss a preliminary temperature determination for the jet plasma by using the filter ratio method at 171 and 195 Å and applying a technique for subtracting the EUV background radiation. The results show that jets are characterized by electron temperatures ranging between 0.8 and 1.3 MK. We present the thermal structure of the jet as temperature maps and we describe its thermal evolution.

Application of mid-infrared pulses for quasi-phase-matching of high-order harmonics in silver plasma.

PubMed

Ganeev, Rashid A; Husakou, Anton; Suzuki, Masayuki; Kuroda, Hiroto

2016-02-22

We demonstrate the quasi-phase-matching of a group of harmonics generated in Ag multi-jet plasma using tunable pulses in the region of 1160 - 1540 nm and their second harmonic emission. The numerical treatment of this effect includes microscopic description of the harmonic generation, propagation of the pump pulse, and the propagation of the generated harmonics. We obtained more than 30-fold growth of harmonics at the conditions of quasi-phase-matching in the region of 35 nm using eight-jet plasma compared with the case of imperforated plasma.

Degeneration of amyloid-ß fibrils caused by exposure to low-temperature atmospheric-pressure plasma in aqueous solution

NASA Astrophysics Data System (ADS)

Takai, Eisuke; Ohashi, Gai; Yoshida, Tomonori; Margareta Sörgjerd, Karin; Zako, Tamotsu; Maeda, Mizuo; Kitano, Katsuhisa; Shiraki, Kentaro

2014-01-01

Low-temperature atmospheric-pressure plasma was applied to degenerate amyloid-ß (Aß) fibrils, which are a major component of neuritic plaque associated with Alzheimer's disease (AD). We showed that an Aß fibril exposed to a low-frequency (LF) plasma jet in aqueous solution retained its morphology, molecular weight, and cytotoxicity, but, intriguingly, decreased in protease resistance and ß-sheet content. These results suggested that an LF plasma jet could be utilized for the treatment of AD to eliminate neuritic plaque by accelerating the proteolysis of Aß fibrils.

Jet outflow and open field line measurements on the C-2U advanced beam-driven field-reversed configuration plasma experiment.

PubMed

Sheftman, D; Gupta, D; Roche, T; Thompson, M C; Giammanco, F; Conti, F; Marsili, P; Moreno, C D

2016-11-01

Knowledge and control of the axial outflow of plasma particles and energy along open-magnetic-field lines are of crucial importance to the stability and longevity of the advanced beam-driven field-reversed configuration plasma. An overview of the diagnostic methods used to perform measurements on the open field line plasma on C-2U is presented, including passive Doppler impurity spectroscopy, microwave interferometry, and triple Langmuir probe measurements. Results of these measurements provide the jet ion temperature and axial velocity, electron density, and high frequency density fluctuations.

Jet outflow and open field line measurements on the C-2U advanced beam-driven field-reversed configuration plasma experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheftman, D., E-mail: dsheftman@trialphaenergy.com; Gupta, D.; Roche, T.

Knowledge and control of the axial outflow of plasma particles and energy along open-magnetic-field lines are of crucial importance to the stability and longevity of the advanced beam-driven field-reversed configuration plasma. An overview of the diagnostic methods used to perform measurements on the open field line plasma on C-2U is presented, including passive Doppler impurity spectroscopy, microwave interferometry, and triple Langmuir probe measurements. Results of these measurements provide the jet ion temperature and axial velocity, electron density, and high frequency density fluctuations.

Experimental investigation of adiabatic compression and heating using collision of an MHD-driven jet with a gas target cloud for magnetized target fusion

NASA Astrophysics Data System (ADS)

Seo, Byonghoon; Li, Hui; Bellan, Paul

2017-10-01

We are studying magnetized target fusion using an experimental method where an imploding liner compressing a plasma is simulated by a high-speed MHD-driven plasma jet colliding with a gas target cloud. This has the advantage of being non-destructive so orders of magnitude more shots are possible. Since the actual density and temperature are much more modest than fusion-relevant values, the goal is to determine the scaling of the increase in density and temperature when an actual experimental plasma is adiabatically compressed. Two new-developed diagnostics are operating and providing data. The first new diagnostic is a fiber-coupled interferometer which measures line-integrated electron density not only as a function of time, but also as a function of position along the jet. The second new diagnostic is laser Thomson scattering which measures electron density and temperature at the location where the jet collides with the cloud. These diagnostics show that when the jet collides with a target cloud the jet slows down substantially and both the electron density and temperature increase. The experimental measurements are being compared with 3D MHD and hybrid kinetic numerical simulations that model the actual experimental geometry.

Experimental investigation of multi-scale non-equilibrium plasma dynamics

NASA Astrophysics Data System (ADS)

Bellan, Paul

2013-10-01

Lab experiments at Caltech resolve complex, detailed MHD dynamics spatially and temporally. Unbalanced forces drive fast plasma flows which tend to self-collimate via self-pinching. Collimation results from flow stagnation compressing embedded magnetic flux and so amplifying the magnetic field responsible for pinching. Measurements show that the collimated flow is essentially a dense plasma jet with embedded axial and azimuthal magnetic fields, i.e., a magnetic flux tube (flux rope). The measured jet velocity is in good agreement with an MHD acceleration model. Depending on how flux tube radius varies with axial position, jets flow into a flux tube from both ends or from just one end. Jets kink when the flux tube in which they are embedded breaches the Kruskal-Shafranov stability limit. The lateral acceleration of a sufficiently strong kink can produce an enormous effective gravity which provides the environment for an observed fine-scale, extremely fast Rayleigh-Taylor (RT) instability. The RT can erode the jet current channel to be smaller than the ion skin depth so there is a cascade from the ideal MHD scale of the kink to the non-MHD ion skin depth scale. This process can result in a magnetic reconnection whereby the jet and its embedded flux tube break. Supported by USDOE.

Particle Acceleration and Radiation associated with Magnetic Field Generation from Relativistic Collisionless Shocks

NASA Technical Reports Server (NTRS)

Nishikawa, K.; Hardee, P. E.; Richardson, G. A.; Preece, R. D.; Sol, H.; Fishman, G. J.

2003-01-01

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. We find only small differences in the results between no ambient and weak ambient magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. While some Fermi acceleration may occur at the jet front, the majority of electron acceleration takes place behind the jet front and cannot be characterized as Fermi acceleration. The simulation results show that this instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron s transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Axial plasma jet characterization on a microsecond x-pinch

NASA Astrophysics Data System (ADS)

Jaar, G. S.; Appartaim, R. K.

2018-06-01

The jets produced on a microsecond x-pinch (quarter period T1/4 ˜ 1 μs, dI/dt ˜ 0.35 kA/ns) have been studied through light-field schlieren imaging and optical framing photographs across 4 different materials: Al, Ti, Mo, and W. The axial velocity of the jets was measured and exhibited no dependence on atomic number (Z) of the wire material. There may be a dependence on another factor(s), namely, the current rise rate. The average axial jet velocity across all four materials was measured to be 2.9 ± 0.5 × 106 cm/s. The average jet diameter and the average radial jet expansion rate displayed inverse relationships with Z, which may be attributed to radiative cooling and inertia. Asymmetry between the anode and cathode jet behavior was observed and is thought to be caused by electron beam activity. The mean divergence angle of the jet was found to vary with wire material and correlated inversely with the thermal conductivity of the cold wire. Optical images indicated a two-layer structure in Al jets which may be caused by standing shocks and resemble phenomena observed in astrophysical jet formation and collimation. Kinks in the jets have also been observed which may be caused by m = 1 MHD instability modes or by the interaction of the jet with the electrode plasma.

Advanced properties of extended plasmas for efficient high-order harmonic generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganeev, R. A.; Physics Department, Voronezh State University, Voronezh 394006; Suzuki, M.

We demonstrate the advanced properties of extended plasma plumes (5 mm) for efficient harmonic generation of laser radiation compared with the short lengths of plasmas (∼0.3–0.5 mm) used in previous studies. The harmonic conversion efficiency quadratically increased with the growth of plasma length. The studies of this process along the whole extreme ultraviolet range using the long plasma jets produced on various metal surfaces, particularly including the resonance-enhanced laser frequency conversion and two-color pump, are presented. Such plasmas could be used for the quasi-phase matching experiments by proper modulation of the spatial characteristics of extended ablating area and formation of separated plasmamore » jets.« less

Plasma Liner Development for MTF Applications: A Status Report

NASA Technical Reports Server (NTRS)

Eskridge, R. E.; Thio, Y. F.; Lee, M.; Martin, A.; Smith, J. W.; Griffin, S. T.; Schafer, Charles (Technical Monitor)

2001-01-01

An experimental plasma gun for Magnetic Target Fusion (MTF) applications under development at the NASA Marshall Space Flight Center is described. This gun has been tested experimentally and plasma jet velocities of approximately 50 km/sec have been obtained. The plasma jet structure has been photographed with 10 ns exposure times to reveal a stable and repeatable plasma structure. Data for velocity profile information has been obtained using light pipes embedded in the gun walls to record the plasma transit at various barrel locations. A high speed triggering system has been developed and tested as a means of reducing the gun "jitter". This jitter has been characterized and future work for second generation "ultra-low jitter" gun development is identified.

Localization of the magnetic field in a plasma flow in laboratory simulations of astrophysical jets at the KPF-4-PHOENIX installation

NASA Astrophysics Data System (ADS)

Mitrofanov, K. N.; Anan'ev, S. S.; Voitenko, D. A.; Krauz, V. I.; Astapenko, G. I.; Markoliya, A. I.; Myalton, V. V.

2017-09-01

The results of experiments aimed at investigating axial plasma flows forming during the compression of a current-plasma sheath are presented. These experiments were carried out at the KPF-4-PHOENIX plasma-focus installation, as part of a program of laboratory simulations of astrophysical jets. The plasma flows were generated in a discharge when the chamber was filled with the working gas (argon) at initial pressures of 0.5-2 Torr. Experimental data obtained using a magnetic probe and optical diagnostics are compared. The data obtained can be used to determine the location of trapped magnetic field relative to regions of intense optical glow in the plasma flow.

Characterizations of atmospheric pressure low temperature plasma jets and their applications

NASA Astrophysics Data System (ADS)

Karakas, Erdinc

2011-12-01

Atmospheric pressure low temperature plasma jets (APLTPJs) driven by short pulses have recently received great attention because of their potential in biomedical and environmental applications. This potential is due to their user-friendly features, such as low temperature, low risk of arcing, operation at atmospheric pressure, easy handheld operation, and low concentration of ozone generation. Recent experimental observations indicate that an ionization wave exists and propagates along the plasma jet. The plasma jet created by this ionization wave is not a continuous medium but rather consists of a bullet-like-structure known as "Plasma Bullet". More interestingly, these plasma bullets actually have a donut-shaped makeup. The nature of the plasma bullet is especially interesting because it propagates in the ambient air at supersonic velocities without any externally applied electric field. In this dissertation, experimental insights are reported regarding the physical and chemical characteristics of the APLTPJs. The dynamics of the plasma bullet are investigated by means of a high-speed ICCD camera. A plasma bullet propagation model based on the streamer theory is confirmed with adequate explanations. It is also found that a secondary discharge, ignited by the charge accumulation on the dielectric electrode surfaces at the end of the applied voltage, interrupts the plasma bullet propagation due to an opposing current along the ionization channel. The reason for this interesting phenomenon is explained in detail. The plasma bullet comes to an end when the helium mole fraction along the ionization channel, or applied voltage, or both, are less than some critical values. The presence of an inert gas channel in the surrounding air, such as helium or argon, has a critical role in plasma bullet formation and propagation. For this reason, a fluid dynamics study is employed by a commercially available simulation software, COMSOL, based on finite element method. Spatio-temporally resolved optical emission spectroscopy (OES) gives the evolution of excited species along the trajectory of the plasma bullets. The APLTPJs' chemical composition includes short-lived species, such as He, N2, N+2 , and long-lived species, such as Hem (helium metastable), O3, NO, NO2. It is worth noting that metastable level excited atoms play an important role in promoting an enhanced chemistry along the plasma jet. Some of the APLTPJs' biomedical applications, such as dental hygiene applications and destruction of amyloid fibrils underlying Parkinson's disease, are explored along with an important discussion showing that the APLTPJs do not have a cytotoxic effect on living cells.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prevosto, L.; Mancinelli, B. R.; Kelly, H.

Langmuir probe measurements in an atmospheric pressure direct current (dc) plasma jet are reported. Sweeping probes were used. The experiment was carried out using a dc non-transferred arc torch with a rod-type cathode and an anode of 5 mm diameter. The torch was operated at a nominal power level of 15 kW with a nitrogen flow rate of 25 Nl min{sup -1}. A flat ion saturation region was found in the current-voltage curve of the probe. The ion saturation current to a cylindrical probe in a high-pressure non local thermal equilibrium (LTE) plasma was modeled. Thermal effects and ionization/recombination processesmore » inside the probe perturbed region were taken into account. Averaged radial profiles of the electron and heavy particle temperatures as well as the electron density were obtained. An electron temperature around 11 000 K, a heavy particle temperature around 9500 K and an electron density of about 4 Multiplication-Sign 10{sup 22} m{sup -3}, were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found throughout the plasma jet. The electron and heavy particle temperature profiles showed good agreement with those reported in the literature by using spectroscopic techniques. It was also found that the temperature radial profile based on LTE was very close to that of the electrons. The calculations have shown that this method is particularly useful for studying spraying-type plasma jets characterized by electron temperatures in the range 9000-14 000 K.« less

Phillips-Tikhonov regularization with a priori information for neutron emission tomographic reconstruction on Joint European Torus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bielecki, J.; Scholz, M.; Drozdowicz, K.

A method of tomographic reconstruction of the neutron emissivity in the poloidal cross section of the Joint European Torus (JET, Culham, UK) tokamak was developed. Due to very limited data set (two projection angles, 19 lines of sight only) provided by the neutron emission profile monitor (KN3 neutron camera), the reconstruction is an ill-posed inverse problem. The aim of this work consists in making a contribution to the development of reliable plasma tomography reconstruction methods that could be routinely used at JET tokamak. The proposed method is based on Phillips-Tikhonov regularization and incorporates a priori knowledge of the shape ofmore » normalized neutron emissivity profile. For the purpose of the optimal selection of the regularization parameters, the shape of normalized neutron emissivity profile is approximated by the shape of normalized electron density profile measured by LIDAR or high resolution Thomson scattering JET diagnostics. In contrast with some previously developed methods of ill-posed plasma tomography reconstruction problem, the developed algorithms do not include any post-processing of the obtained solution and the physical constrains on the solution are imposed during the regularization process. The accuracy of the method is at first evaluated by several tests with synthetic data based on various plasma neutron emissivity models (phantoms). Then, the method is applied to the neutron emissivity reconstruction for JET D plasma discharge #85100. It is demonstrated that this method shows good performance and reliability and it can be routinely used for plasma neutron emissivity reconstruction on JET.« less

A linear-field plasma jet for generating a brush-shaped laminar plume at atmospheric pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xuechen; Jia, Pengying, E-mail: plasmalab@126.com; Key Laboratory of Photo-Electronics Information Materials of Hebei Province, Baoding 071002

2016-06-15

A linear-field plasma jet composed of line-to-plate electrodes is used to generate a large-scale brush-shaped plasma plume with flowing argon used as working gas. Through electrical measurement and fast photography, it is found that the plasma plume bridges the two electrodes for the discharge in the positive voltage half-cycle, which behaves like fast moving plasma bullets directed from the anode to the cathode. Compared with the positive discharge, the negative discharge only develops inside the nozzle and propagates much slower. Results also indicate that the gas temperature of the plume is close to room temperature, which is promising for biomedicalmore » application.« less

Holographic Jet Shapes and their Evolution in Strongly Coupled Plasma

NASA Astrophysics Data System (ADS)

Brewer, Jasmine; Rajagopal, Krishna; Sadofyev, Andrey; van der Schee, Wilke

2017-11-01

Recently our group analyzed how the probability distribution for the jet opening angle is modified in an ensemble of jets that has propagated through an expanding cooling droplet of plasma [K. Rajagopal, A. V. Sadofyev, W. van der Schee, Phys. Rev. Lett. 116 (2016) 211603]. Each jet in the ensemble is represented holographically by a string in the dual 4+1- dimensional gravitational theory with the distribution of initial energies and opening angles in the ensemble given by perturbative QCD. In [K. Rajagopal, A. V. Sadofyev, W. van der Schee, Phys. Rev. Lett. 116 (2016) 211603], the full string dynamics were approximated by assuming that the string moves at the speed of light. We are now able to analyze the full string dynamics for a range of possible initial conditions, giving us access to the dynamics of holographic jets just after their creation. The nullification timescale and the features of the string when it has nullified are all results of the string evolution. This emboldens us to analyze the full jet shape modification, rather than just the opening angle modification of each jet in the ensemble as in [K. Rajagopal, A. V. Sadofyev, W. van der Schee, Phys. Rev. Lett. 116 (2016) 211603]. We find the result that the jet shape scales with the opening angle at any particular energy. We construct an ensemble of dijets with energies and energy asymmetry distributions taken from events in proton-proton collisions, opening angle distribution as in [K. Rajagopal, A. V. Sadofyev, W. van der Schee, Phys. Rev. Lett. 116 (2016) 211603], and jet shape taken from proton-proton collisions and scaled according to our result. We study how these observables are modified after we send the ensemble of dijets through the strongly-coupled plasma.

Blob Formation and Ejection in Coronal Jets due to the Plasmoid and Kelvin–Helmholtz Instabilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ni, Lei; Lin, Jun; Zhang, Qing-Min

2017-05-20

We perform 2D resistive magnetohydrodynamic simulations of coronal jets driven by flux emergence along the lower boundary. The reconnection layers are susceptible to the formation of blobs that are ejected in the jet. Our simulation with low plasma β (Case I) shows that magnetic islands form easily and propagate upward in the jet. These islands are multithermal and thus are predicted to show up in hot channels (335 Å and 211 Å) and the cool channel (304 Å) in observations by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory . The islands have maximum temperatures of 8 MK,more » lifetimes of 120 s, diameters of 6 Mm, and velocities of 200 km s{sup −1}. These parameters are similar to the properties of blobs observed in extreme-ultraviolet (EUV) jets by AIA. The Kelvin–Helmholtz instability develops in our simulation with moderately high plasma β (Case II) and leads to the formation of bright vortex-like blobs above the multiple high magnetosonic Mach number regions that appear along the jet. These vortex-like blobs can also be identified in the AIA channels. However, they eventually move downward and disappear after the high magnetosonic Mach number regions disappear. In the lower plasma β case, the lifetime for the jet is shorter, the jet and magnetic islands are formed with higher velocities and temperatures, the current-sheet fragments are more chaotic, and more magnetic islands are generated. Our results show that the plasmoid instability and Kelvin–Helmholtz instability along the jet are both possible causes of the formation of blobs observed at EUV wavelengths.« less

Highly porous micro-roughened structures developed on aluminum surface using the jet of rotating arc discharges at atmospheric pressure

NASA Astrophysics Data System (ADS)

Asadollahi, Siavash; Farzaneh, Masoud; Stafford, Luc

2018-02-01

Aluminum 6061 samples were exposed to the jet of an atmospheric pressure rotating arc discharge operated in either nitrogen or air. After multiple passes of treatment with an air-based plasma jet at very short source-to-substrate distances, scanning electron microscopy combined with x-ray photoelectron spectroscopy revealed a highly porous micro-roughened alumina-based structure on the surface of aluminum. Based on optical emission spectroscopy and high-speed optical imaging of the jet interacting with aluminum samples, it was found that the process is mainly driven by the energy transfer from the plasma source to the surface through transient plasma-transferred arcs. The occurrence of multiple arc discharges over very short time scales can induce rapid phase transformations of aluminum with characteristics similar to the ones usually observed during laser ablation of materials with femto- to nanosecond laser pulses or during the formation of cathode spots on the surface of metals.

On the use of the double floating probe method to infer the difference between the electron and the heavy particles temperatures in an atmospheric pressure, vortex-stabilized nitrogen plasma jet

NASA Astrophysics Data System (ADS)

Prevosto, L.; Kelly, H.; Mancinelli, B. R.

2014-05-01

Sweeping double probe measurements in an atmospheric pressure direct current vortex-stabilized plasma jet are reported (plasma conditions: 100 A discharge current, N2 gas flow rate of 25 Nl/min, thoriated tungsten rod-type cathode, copper anode with 5 mm inner diameter). The interpretation of the double probe characteristic was based on a generalization of the standard double floating probe formulae for non-uniform plasmas coupled to a non-equilibrium plasma composition model. Perturbations caused by the current to the probe together with collisional and thermal processes inside the probe perturbed region were taken into account. Radial values of the average electron and heavy particle temperatures as well as the electron density were obtained. The calculation of the temperature values did not require any specific assumption about a temperature relationship between different particle species. An electron temperature of 10 900 ± 900 K, a heavy particle temperature of 9300 ± 900 K, and an electron density of about 3.5 × 1022 m-3 were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found toward the outer border of the plasma jet. These results showed good agreement with those previously reported by the authors by using a single probe technique. The calculations have shown that this method is particularly useful for studying spraying-type plasma torches operated at power levels of about 15 kW.

On the use of the double floating probe method to infer the difference between the electron and the heavy particles temperatures in an atmospheric pressure, vortex-stabilized nitrogen plasma jet.

PubMed

Prevosto, L; Kelly, H; Mancinelli, B R

2014-05-01

Sweeping double probe measurements in an atmospheric pressure direct current vortex-stabilized plasma jet are reported (plasma conditions: 100 A discharge current, N2 gas flow rate of 25 Nl/min, thoriated tungsten rod-type cathode, copper anode with 5 mm inner diameter). The interpretation of the double probe characteristic was based on a generalization of the standard double floating probe formulae for non-uniform plasmas coupled to a non-equilibrium plasma composition model. Perturbations caused by the current to the probe together with collisional and thermal processes inside the probe perturbed region were taken into account. Radial values of the average electron and heavy particle temperatures as well as the electron density were obtained. The calculation of the temperature values did not require any specific assumption about a temperature relationship between different particle species. An electron temperature of 10,900 ± 900 K, a heavy particle temperature of 9300 ± 900 K, and an electron density of about 3.5 × 10(22) m(-3) were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found toward the outer border of the plasma jet. These results showed good agreement with those previously reported by the authors by using a single probe technique. The calculations have shown that this method is particularly useful for studying spraying-type plasma torches operated at power levels of about 15 kW.

Damage-free polymer surface modification employing inward-type plasma

NASA Astrophysics Data System (ADS)

Kanou, Ryo; Suga, Hiroshi; Utsumi, Hideyuki; Takahashi, Satoshi; Shirayama, Yuya; Watanabe, Norimichi; Petit, Stèphane; Shimizu, Tetsuo

2017-08-01

Inward-type plasmas, which spread upstream against the gas flow in the capillary tube where the gas is discharged, can react with samples placed near the entrance of such a capillary tube. In this study, surface modification of polymer surfaces is conducted using inward plasma. The modification is also done by conventional microplasma jet, and the modified surfaces with two plasma techniques are characterized by contact angle measurement, X-ray photoemission spectroscopy (XPS), and atomic force microscopy (AFM). Although inward-plasma-treated surfaces are less hydrophilic than conventional plasma-treated ones, they are still sufficiently hydrophilic for surface coatings. In addition, it turns out that the polymer surfaces irradiated with the inward plasma yield much smoother surfaces than those treated with the conventional plasma jet. Thus, the inward plasma treatment is a viable technique when the surface flatness is crucial, such as for the surface coating of plastic lenses.

A handheld low temperature atmospheric pressure air plasma gun for nanomaterial synthesis in liquid phase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Shuang; Wang, Kaile; Zuo, Shasha

A handheld low temperature atmospheric pressure air plasma gun based on a dielectric barrier structure with hollow electrodes was proposed. The portable plasma gun with an embedded mini air pump was driven by a 12 V direct voltage battery. The air plasma jet generated from the gun could be touched without a common shock hazard. Besides working in air, the plasma gun can also work in water. The diagnostic result of optical emission spectroscopy showed the difference in reactive species of air plasma jet between in air and in water. The plasma gun was excited in 20 ml chloroauric acid aqueous solutionmore » with a concentration of 1.214 mM. A significant amount of gold nanoparticles were synthesized after 2 min continuous discharge. The plasma gun with these unique features is applicable in plasma medicine, etching, and s-nthesis of nanomaterials.« less

Plasma core power exhaust in ELMy H-Mode in JET with ITER-Like Wall

NASA Astrophysics Data System (ADS)

Guillemaut, C.; Metzger, C.; Appel, L.; Drewelow, P.; Horvath, L.; Matthews, G. F.; Szepesi, G.; Solano, E. R.; contributors, JET

2018-07-01

The mitigation of target heat load in future steady state fusion devices will require dissipation of a significant amount of power through radiation. Plasma operations relying on ELMy H-modes could be problematic since ELMs may transport substantial amounts of power to the target without significant dissipation. Therefore, estimation of the average ELM power exhaust from the plasma core is crucial to evaluate the potential limitation on the power dissipation in ELMy H-mode regime. A series of more than 50 Type-I ELMy H-mode discharges in JET with ITER-Like Wall (JET-ILW) with a wide range of conditions has been used here to compare the average ELM power to the average input power. The effect of input power, ELM frequency, plasma current, confinement and radiation on ELM power exhaust has been studied and reported in this paper. Good agreement has been found here with previous studies made in carbon machines. This work suggests that it should not be possible to dissipate more than 70%–80% of the input power in Type-I ELMy H-modes in JET-ILW which is consistent with the maximum radiative fraction found experimentally.

Experimental investigation on frequency characteristics of plasma synthetic jets

NASA Astrophysics Data System (ADS)

Zong, Haohua; Kotsonis, Marios

2017-11-01

The performance of a two-electrode plasma synthetic jet actuator (PSJA) is investigated for a wide range of dimensionless actuation frequencies ( f*) using high-speed phase-locked particle imaging velocimetry measurements. The jet-induced velocity fields in the axisymmetric plane are measured during both transient and steady working stages of the PSJA. When f* increases, the jet duration time (Tjet) is reduced, while the peak suction velocity (Us) increases consistently. Three integral parameters including the total expelled gas mass, impulse, and issued mechanical energy also decline considerably with increasing frequency, which is shown to relate to both the reduced cavity density and the decreasing jet duration. Theoretical analysis reveals that the mean cavity density decreases monotonically with the square root of the discharge frequency. The decreasing rate is inversely proportional to a thermal cut-off frequency ( fc, 210 Hz for the current study), which scales with the convective heat transfer coefficient between the actuator cavity walls and the cavity gas, as well as the area of the cavity internal surface. In the time-averaged velocity fields, the jet centreline velocity (U¯ c) exhibits a local maximum in the axial coordinate. The nondimensional maximum centreline velocity reduces with increasing frequency of operation. The jet spreading rate of the plasma synthetic jets (PSJs) decreases from 0.14 to 0.09 with increasing frequency. During the transient working stage of a PSJ, the exit velocity trace elapses 20 successive actuation cycles to stabilize. In contrast to the exit velocity, approximately 130 cycles are needed for the mean cavity density/temperature to reach steady values.

The Role of Combined ICRF and NBI Heating in JET Hybrid Plasmas in Quest for High D-T Fusion Yield

NASA Astrophysics Data System (ADS)

Mantsinen, Mervi; Challis, Clive; Frigione, Domenico; Graves, Jonathan; Hobirk, Joerg; Belonohy, Eva; Czarnecka, Agata; Eriksson, Jacob; Gallart, Dani; Goniche, Marc; Hellesen, Carl; Jacquet, Philippe; Joffrin, Emmanuel; King, Damian; Krawczyk, Natalia; Lennholm, Morten; Lerche, Ernesto; Pawelec, Ewa; Sips, George; Solano, Emilia R.; Tsalas, Maximos; Valisa, Marco

2017-10-01

Combined ICRF and NBI heating played a key role in achieving the world-record fusion yield in the first deuterium-tritium campaign at the JET tokamak in 1997. The current plans for JET include new experiments with deuterium-tritium (D-T) plasmas with more ITER-like conditions given the recently installed ITER-like wall (ILW). In the 2015-2016 campaigns, significant efforts have been devoted to the development of high-performance plasma scenarios compatible with ILW in preparation of the forthcoming D-T campaign. Good progress was made in both the inductive (baseline) and the hybrid scenario: a new record JET ILW fusion yield with a significantly extended duration of the high-performance phase was achieved. This paper reports on the progress with the hybrid scenario which is a candidate for ITER longpulse operation (˜1000 s) thanks to its improved normalized confinement, reduced plasma current and higher plasma beta with respect to the ITER reference baseline scenario. The combined NBI+ICRF power in the hybrid scenario was increased to 33 MW and the record fusion yield, averaged over 100 ms, to 2.9x1016 neutrons/s from the 2014 ILW fusion record of 2.3x1016 neutrons/s. Impurity control with ICRF waves was one of the key means for extending the duration of the high-performance phase. The main results are reviewed covering both key core and edge plasma issues.

The effect of ethanol gas impurity on the discharge mode and discharge products of argon plasma jet at atmospheric pressure

NASA Astrophysics Data System (ADS)

Xia, Wenjie; Liu, Dingxin; Xu, Han; Wang, Xiaohua; Liu, Zhijie; Rong, Mingzhe; Kong, Michael G.

2018-05-01

Argon is a widely used working gas of plasmas, which is much cheaper than helium but on the other hand much more difficult to generate diffuse discharge at atmospheric pressure. In order to meet the application requirements, plenty of researches have been reported to facilitate the diffuse discharge happening for argon plasmas, and in this paper an approach of using ethanol gas (EtOH) impurity is investigated. The discharge characteristics of Ar + EtOH plasma jet are studied as a function of the applied voltage and the concentration of EtOH, from which the concentration of EtOH between ∼200 and ∼3300 parts per million (ppm) is determined necessary for the generation of diffuse discharge. Compared with the helium plasma jet in literature, it is deduced that the diffuse discharge is probably caused by the Penning ionization happening between the metastable argon and EtOH. The discharge products of Ar + EtOH (672 ppm) plasma jet are measured and the corresponding chemistry pathways are analyzed. About 20% of EtOH is decomposed via complex chemical reactions to form more than a dozen of neutral species, such as CH3CHO, CH3COOH, CO, H2O, and C n H2n+2 (n ≥ 3), and various kinds of ionic species, including C+, CH+, ArH+, {{{{O}}}2}-, CH3CH2O‑, etc.

Investigation of metastable production in a closed-cell dielectric capillary variable pressure He plasma jet with Ar admixture

NASA Astrophysics Data System (ADS)

Sands, Brian; Ganguly, Biswa

2011-10-01

For plasma processing applications of streamer-like atmospheric pressure plasma jets generated in a dielectric capillary, we have demonstrated that an admixture of Ar to the He gas flow greatly increases the lifetime of energetic species in the core flow through enhanced afterglow production of Ar 1s5 metastable species. To study this effect in more detail, we have used a closed-cell plasma jet that allows control over the background gas pressure and composition. We used a 20 ns risetime positive unipolar voltage pulse for excitation. A He flow with a 0-30% Ar admixture was studied using time-resolved emission and tunable diode laser absorption spectroscopy of the Ar 1s5 and He 23S metastable states. Nitrogen was used as the background gas. In pure He and pure Ar gases the He and Ar metastables respectively are produced in the first ~100 ns only in the active discharge. With Ar added to the He gas flow, He metastables produced in the active discharge are quickly quenched via Penning ionization of Ar while Ar 1s5 is enhanced over 1-2 μs in the afterglow, increasing the number density as high as 1013/cc and extending the effective lifetime up to 10 μs. This implies that He heavy particle kinetics are a key driver of enhanced afterglow plasma chemistry in plasma jets with rare gas mixtures.

Characterization of gas targets for laser produced extreme ultraviolet plasmas with a Hartmann-Shack sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peth, Christian; Kranzusch, Sebastian; Mann, Klaus

2004-10-01

A table top extreme ultraviolet (EUV)-source was developed at Laser-Laboratorium Goettingen for the characterization of optical components and sensoric devices in the wavelength region from 11 to 13 nm. EUV radiation is generated by focusing the beam of a Q-switched Nd:YAG laser into a pulsed xenon gas jet. Since a directed gas jet with a high number density is needed for an optimal performance of the source, conical nozzles with different cone angles were drilled with an excimer laser to produce a supersonic gas jet. The influence of the nozzle geometry on the gas jet was characterized with a Hartmann-Shackmore » wave front sensor. The deformation of a planar wave front after passing the gas jet was analyzed with this sensor, allowing a reconstruction of the gas density distribution. Thus, the gas jet was optimized resulting in an increase of EUV emission by a factor of two and a decrease of the plasma size at the same time.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang Ronglin; Fang Cheng; Shibata, Kazunari

Magnetic reconnection is a fundamental process in space and astrophysical plasmas in which the oppositely directed magnetic field changes its connectivity and eventually converts its energy into kinetic and thermal energy of the plasma. Recently, ubiquitous jets (for example, chromospheric anemone jets, penumbral microjets, umbral light bridge jets) have been observed by the Solar Optical Telescope on board the satellite Hinode. These tiny and frequently occurring jets are considered to be a possible evidence of small-scale ubiquitous reconnection in the solar atmosphere. However, the details of three-dimensional (3D) magnetic configuration are still not very clear. Here, we propose a newmore » model based on 3D simulations of magnetic reconnection using a typical current sheet magnetic configuration with a strong guide field. The most interesting feature is that the jets produced by the reconnection eventually move along the guide field lines. This model provides a fresh understanding of newly discovered ubiquitous jets and moreover a new observational basis for the theory of astrophysical magnetic reconnection.« less

Studies of supersonic, radiative plasma jet interaction with gases at the Prague Asterix Laser System facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nicolaie, Ph.; Stenz, C.; Tikhonchuk, V.

2008-08-15

The interaction of laser driven jets with gas puffs at various pressures is investigated experimentally and is analyzed by means of numerical tools. In the experiment, a combination of two complementary diagnostics allowed to characterize the main structures in the interaction zone. By changing the gas composition and its density, the plasma cooling time can be controlled and one can pass from a quasiadiabatic outflow to a strongly radiation cooling jet. This tuning yields hydrodynamic structures very similar to those seen in astrophysical objects; the bow shock propagating through the gas, the shocked materials, the contact discontinuity, and the Machmore » disk. From a dimensional analysis, a scaling is made between both systems and shows the study relevance for the jet velocity, the Mach number, the jet-gas density ratio, and the dissipative processes. The use of a two-dimensional radiation hydrodynamic code, confirms the previous analysis and provides detailed structure of the interaction zone and energy repartition between jet and surrounding gases.« less

Particle Acceleration, Magnetic Field Generation, and Associated Emission in Collisionless Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.

2007-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electro-positron)jets show that acceleration occurs within the downstream jet. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Particle Acceleration, Magnetic Field Generation and Associated Emission in Collisionless Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K. I.; Ramirez-Ruiz, E.; Hardee, P.; Mizuno, Y.; Fishman. G. J.

2007-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Formation of a rotating jet during the filament eruption on 2013 April 10-11

NASA Astrophysics Data System (ADS)

Filippov, B.; Srivastava, A. K.; Dwivedi, B. N.; Masson, S.; Aulanier, G.; Joshi, N. C.; Uddin, W.

2015-07-01

We analyse multiwavelength and multiviewpoint observations of a helically twisted plasma jet formed during a confined filament eruption on 2013 April 10-11. Given a rather large-scale event with its high spatial and temporal resolution observations, it allows us to clearly understand some new physical details about the formation and triggering mechanism of twisting jet. We identify a pre-existing flux rope associated with a sinistral filament, which was observed several days before the event. The confined eruption of the filament within a null-point topology, also known as an Eiffel tower (or inverted-Y) magnetic field configuration results in the formation of a twisted jet after the magnetic reconnection near a null point. The sign of helicity in the jet is found to be the same as that of the sign of helicity in the filament. Untwisting motion of the reconnected magnetic field lines gives rise to the accelerating plasma along the jet axis. The event clearly shows the twist injection from the pre-eruptive magnetic field to the jet.

Impurity re-distribution in the corner regions of the JET divertor

NASA Astrophysics Data System (ADS)

Widdowson, A.; Coad, J. P.; Alves, E.; Baron-Wiechec, A.; Barradas, N. P.; Catarino, N.; Corregidor, V.; Heinola, K.; Krat, S.; Likonen, J.; Matthews, G. F.; Mayer, M.; Petersson, P.; Rubel, M.; Contributors, JET

2017-12-01

The International Thermonuclear Experimental Reactor (ITER) will use a mixture of deuterium (D) and tritium (T) as the fuel to generate power. Since T is both radioactive and expensive the Joint European Torus (JET) has been at the forefront of research to discover how much T is used and where it may be retained within the main reaction chamber. Until the year 2010 the JET plasma facing components were constructed of carbon fibre composites. During the JET carbon (C) phases impurities accumulated at the corners of the divertor located towards the bottom of the chamber in regions shadowed from the plasma where they are very difficult to reach and remove. This build-up of C and the associated H-isotope (including T) retention were of particular concern for future fusion reactors therefore, in 2010 JET changed the wall protection to (mainly) Be and the divertor to tungsten (W)—the JET ITER-like wall (ILW)—the choice of materials for ITER. This paper reveals that with the JET ILW impurities are still accumulating in the shadowed regions, with Be being the majority element, though the overall quantities are very much reduced from those in the C phases. Material will be transported into the shadowed regions principally when the plasma strike points are on the corner tiles, but particles typically have about a 75% probability of reflection from line-of sight surfaces, and multiple reflection/scattering results in deposition over all surfaces.

A Sub-microsecond Pulsed Plasma Jet for Endodontic Biofilm Disinfection

NASA Astrophysics Data System (ADS)

Jiang, Chunqi; Schaudinn, Christoph; Jaramillo, David E.; Gundersen, Martin A.; Costerton, J. William

A pulsed, tapered cylindrical plasma jet, several centimeter long and <2 mm in diameter, has been generated by a concentric tubular device for root canal disinfection. This plasma dental probe is typically powered with ˜100 ns, 1 kHz, multi-kilovolt electric pulses and filled with 5 SLPM (standard liter per minute) He/(1%)O2 flow. We report here an in vitro study of the antimicrobial effect of the room temperature plasma jet against monolayer Enterococcus faecalis biofilms on bovine dentins. Resultant colony-forming unit counts were associated with changes in bacterial cell morphology observed using scanning electron microscopy (SEM) following the treatment and control. Treatment of dentin discs cultivated with E. faecalis monolayer biofilms with the plasma (average power ≈ 1 W) for 5 min resulted in 92.4% kill (P < 0.0001). Severe disruption of the cell membranes was observed for the plasma treatment group, while the morphology of the cells remained intact for the negative control group. In addition, a pilot ex vivo test was conducted to examine the bactericidal effect of the plasma against saliva-derived biofilms cultivated in human root canals. Conspicuous biofilm disruption and cleared dentinal surfaces were observed in the canal after the plasma treatment for 5 min. We ­conclude that this non-thermal pulsed plasma-based technology is a potential ­alternative or supplement to existing protocols for root canal disinfection.

Plasma Jet (V)UV-Radiation Impact on Biologically Relevant Liquids and Cell Suspension

NASA Astrophysics Data System (ADS)

Tresp, H.; Bussiahn, R.; Bundscherer, L.; Monden, A.; Hammer, M. U.; Masur, K.; Weltmann, K.-D.; Woedtke, Th. V.; Reuter, S.

2014-10-01

In this study the generation of radicals in plasma treated liquids has been investigated. To quantify the contribution of plasma vacuum ultraviolet (VUV) and ultraviolet (UV) radiation on the species investigated, three cases have been studied: UV of plasma jet only, UV and VUV of plasma jet combined, and the plasma effluent including all reactive components. The emitted VUV has been observed by optical emission spectroscopy and its effect on radical formation in liquids has been analyzed by electron spin resonance spectroscopy. Radicals have been determined in ultrapure water (dH2O), as well as in more complex, biorelevant solutions like phosphate buffered saline (PBS) solution, and two different cell culture media. Various compositions lead to different reactive species formation, e.g. in PBS superoxide anion and hydroxyl radicals have been detected, in cell suspension also glutathione thiyl radicals have been found. This study highlights that UV has no impact on radical generation, whereas VUV is relevant for producing radicals. VUV treatment of dH2O generates one third of the radical concentration produced by plasma-effluent treatment. It is relevant for plasma medicine because although plasma sources are operated in open air atmosphere, still VUV can lead to formation of biorelevant radicals. This work is funded by German Federal Ministry of Education a Research (BMBF) (Grant # 03Z2DN12+11).

DNA damage in oral cancer cells induced by nitrogen atmospheric pressure plasma jets

NASA Astrophysics Data System (ADS)

Han, Xu; Klas, Matej; Liu, Yueying; Stack, M. Sharon; Ptasinska, Sylwia

2013-09-01

The nitrogen atmospheric pressure plasma jet (APPJ) has been shown to effectively induce DNA double strand breaks in SCC-25 oral cancer cells. The APPJ source constructed in our laboratory consists of two external electrodes wrapping around a quartz tube and nitrogen as a feed gas and operates based on dielectric barrier gas discharge. Generally, it is more challenging to ignite plasma in N2 atmosphere than in noble gases. However, this design provides additional advantages such as lower costs compared to the noble gases for future clinical operation. Different parameters of the APPJ configuration were tested in order to determine radiation dosage. To explore the effects of delayed damage and cell self-repairing, various incubation times of cells after plasma treatment were also performed. Reactive species generated in plasma jet and in liquid environment are essential to be identified and quantified, with the aim of unfolding the mystery of detailed mechanisms for plasma-induced cell apoptosis. Moreover, from the comparison of plasma treatment effect on normal oral cells OKF6T, an insight to the selectivity for cancer treatment by APPJ can be explored. All of these studies are critical to better understand the damage responses of normal and abnormal cellular systems to plasma radiation, which are useful for the development of advanced plasma therapy for cancer treatment at a later stage.

Letter: Transient interaction between plasma jet and supersonic compression ramp flow

NASA Astrophysics Data System (ADS)

Huang, He-Xia; Tan, Hui-Jun; Sun, Shu; Zhang, Yu-Chao; Cheng, Lin

2018-04-01

The rapid flow evolution between a plasma jet and a 20° compression ramp flow is captured by a high-speed schlieren system at Mach 2.0. Several interesting flow phenomena are observed for the first time. The pulsed jet, which generates strong perturbations, forces the crossflow boundary layer to separate and forms a forward moving shock. A typical shock-on-shock interaction occurs when the precursor shock intersects with the original shock. The interaction is initially regular, and then it transforms into an irregular one with a Mach stem connecting the precursor shock and original ramp shock.

ICRH system performance during ITER-Like Wall operations at JET and the outlook for DT campaign

NASA Astrophysics Data System (ADS)

Monakhov, Igor; Blackman, Trevor; Dumortier, Pierre; Durodié, Frederic; Jacquet, Philippe; Lerche, Ernesto; Noble, Craig

2017-10-01

Performance of JET ICRH system since installation of the metal ITER-Like Wall (ILW) has been assessed statistically. The data demonstrate steady increase of the RF power coupled to plasmas over recent years with the maximum pulse-average and peak values exceeding respectively 6MW and 8MW in 2016. Analysis and extrapolation of power capabilities of conventional JET ICRH antennas is provided and key performance-limiting factors are discussed. The RF plant operational frequency options are presented highlighting the issues of efficient ICRH application within a foreseeable range of DT plasma scenarios.

Jet-conversion photons from an anisotropic quark-gluon plasma

NASA Astrophysics Data System (ADS)

Bhattacharya, Lusaka; Roy, Pradip

2010-10-01

We calculate the pT distributions of jet-conversion photons from a quark-gluon plasma with pre-equilibrium momentum-space anisotropy. A phenomenological model has been used for the time evolution of the hard momentum scale phard(τ) and anisotropy parameter ξ(τ). As a result of pre-equilibrium momentum-space anisotropy, we find significant modification of the jet-conversion photon pT distribution. For example, with fixed initial condition pre-equilibrium anisotropy, we predict a significant enhancement of the jet-photon pT distribution in the entire region, whereas for pre-equilibrium anisotropy with fixed final multiplicity (FFM), suppression of the jet-conversion photon pT distribution is observed. The results with FFM (as it is the most realistic situation) have been compared with high pT PHENIX photon data. It is found that the data are reproduced well if the isotropization time lies within 1.5 fm/c.

Test of electical resistivity and current diffusion modelling on MAST and JET

NASA Astrophysics Data System (ADS)

Keeling, D. L.; Challis, C. D.; Jenkins, I.; Hawkes, N. C.; Lupelli, I.; Michael, C.; de Bock, M. F. M.; the MAST Team; contributors, JET

2018-01-01

Experiments have been carried out on the MAST and JET tokamaks intended to compare the electrical resistivity of the plasma with theoretical formulations. The tests consist of obtaining motional stark effect (MSE) measurements in MHD-free plasmas during plasma current ramp-up (JET and MAST), ramp-down (MAST) and in stationary state (JET and MAST). Simulations of these plasmas are then performed in which the current profile evolution is calculated according to the poloidal field diffusion equation (PFDE) with classical or neoclassical resistivity. Synthetic MSE data are produced in the simulations for direct comparison with the experimental data. It is found that the toroidal current profile evolution modelled using neoclassical resistivity did not match the experimental observations on either device during current ramp-up or ramp-down as concluded from comparison of experimental and synthetic MSE profiles. In these phases, use of neoclassical resistivity in the modelling systematically overestimates the rate of current profile evolution. During the stationary state however, the modelled toroidal current profile matched experimental observations to a high degree of accuracy on both devices using neoclassical resistivity. Whilst no solution to the mismatch in the dynamic phases of the plasma is proposed, it is suggested that some physical process other than MHD which is not captured by the simple diffusive model of current profile evolution is responsible.

An Experimental Study of a Low-Jitter Pulsed Electromagnetic Plasma Accelerator

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Lee, Michael; Eskridge, Richard; Smith, James; Martin, Adam; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

An experimental plasma accelerator for a variety of applications under development at the NASA Marshall Space Flight Center is described. The accelerator is a pulsed plasma thruster and has been tested experimentally and plasma jet velocities of approximately 50 kilometers per second have been obtained. The plasma jet structure has been photographed with 10 ns exposure times to reveal a stable and repeatable plasma structure. Data for velocity profile information has been obtained using light pipes embedded in the gun walls to record the plasma transit at various barrel locations. Preliminary spatially resolved spectral data and magnetic field probe data are also presented. A high speed triggering system has been developed and tested as a means of reducing the gun "jitter". This jitter has been characterized and future work for second generation "ultra-low jitter" gun development is identified.

Atmospheric cold plasma jet for plant disease treatment

NASA Astrophysics Data System (ADS)

Zhang, Xianhui; Liu, Dongping; Zhou, Renwu; Song, Ying; Sun, Yue; Zhang, Qi; Niu, Jinhai; Fan, Hongyu; Yang, Si-ze

2014-01-01

This study shows that the atmospheric cold plasma jet is capable of curing the fungus-infected plant leaves and controlling the spread of infection as an attractive tool for plant disease management. The healing effect was significantly dependent on the size of the black spots infected with fungal cells and the leaf age. The leaves with the diameter of black spots of <2 mm can completely recover from the fungus-infected state. The plasma-generated species passing through the microns-sized stomas in a leaf can weaken the function of the oil vacuoles and cell membrane of fungal cells, resulting in plasma-induced inactivation.

DNA damage in oral cancer cells induced by nitrogen atmospheric pressure plasma jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Xu; Ptasinska, Sylwia; Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556

2013-06-10

The nitrogen atmospheric pressure plasma jet (APPJ) was applied to induce DNA damage of SCC-25 oral cancer cells. Optical emission spectra were taken to characterize the reactive species produced in APPJ. In order to explore the spatial distribution of plasma effects, cells were placed onto photo-etched grid slides and the antibody H2A.X was used to locate double strand breaks of DNA inside nuclei using an immunofluorescence assay. The number of cells with double strand breaks in DNA was observed to be varied due to the distance from the irradiation center and duration of plasma treatment.

DNA damage in oral cancer cells induced by nitrogen atmospheric pressure plasma jets

NASA Astrophysics Data System (ADS)

Han, Xu; Klas, Matej; Liu, Yueying; Sharon Stack, M.; Ptasinska, Sylwia

2013-06-01

The nitrogen atmospheric pressure plasma jet (APPJ) was applied to induce DNA damage of SCC-25 oral cancer cells. Optical emission spectra were taken to characterize the reactive species produced in APPJ. In order to explore the spatial distribution of plasma effects, cells were placed onto photo-etched grid slides and the antibody H2A.X was used to locate double strand breaks of DNA inside nuclei using an immunofluorescence assay. The number of cells with double strand breaks in DNA was observed to be varied due to the distance from the irradiation center and duration of plasma treatment.

Emission spectroscopy of an atmospheric pressure plasma jet operated with air at low frequency

NASA Astrophysics Data System (ADS)

Giuliani, L.; Gallego, J. L.; Minotti, F.; Kelly, H.; Grondona, D.

2015-03-01

Low-temperature, high-pressure plasma jets have an extensive use in plasma biology and plasma medicine, such as pathogen deactivation, wound disinfection, stopping of bleeding without damage of healthy tissue, acceleration of wound healing, control of bio-film proliferation, etc. In this work, a spectroscopic characterization of a typical plasma jet, operated in air at atmospheric pressure, is reported. Within the spectrum of wavelengths from 200 to 450 nm all remarkable emissions of N2 were monitored. Spectra of the N2 2nd positive system (C3Πu-B3Πg) emitted in air are the most convenient for plasma diagnostics, since they enable to determine electronic Te, rotational Tr and vibrational Tv temperatures by fitting the experimental spectra with the simulated ones. We used SPECAIR software for spectral simulation and obtained the best fit with all these temperatures about 3500K. The conclusion that all temperatures are equal, and its relatively high value, is consistent with the results of a previous work, where it was found that the experimentally determined electrical characteristic was consistent with the model of a thermal arc discharge, together with a highly collisional cathode sheet.

Variable polarity plasma arc welding on the Space Shuttle external tank

NASA Technical Reports Server (NTRS)

Nunes, A. C., Jr.; Bayless, E. O., Jr.; Jones, C. S., III; Munafo, P. M.; Biddle, A. P.; Wilson, W. A.

1984-01-01

Variable polarity plasma arc (VPPA) techniques used at NASA's Marshall Space Flight Center for the fabrication of the Space Shuttle External Tank are presentedd. The high plasma arc jet velocities of 300-2000 m/s are produced by heating the plasma gas as it passes through a constraining orifice, with the plasma arc torch becoming a miniature jet engine. As compared to the GTA jet, the VPPA has the following advantages: (1) less sensitive to contamination, (2) a more symmetrical fusion zone, and (3) greater joint penetration. The VPPA welding system is computerized, operating with a microprocessor, to set welding variables in accordance with set points inputs, including the manipulator and wire feeder, as well as torch control and power supply. Some other VPPA welding technique advantages are: reduction in weld repair costs by elimination of porosity; reduction of joint preparation costs through elimination of the need to scrape or file faying surfaces; reduction in depeaking costs; eventual reduction of the 100 percent-X-ray inspection requirements. The paper includes a series of schematic and block diagrams.

The role of helium metastable states in radio-frequency driven helium-oxygen atmospheric pressure plasma jets: measurement and numerical simulation

NASA Astrophysics Data System (ADS)

Niemi, K.; Waskoenig, J.; Sadeghi, N.; Gans, T.; O'Connell, D.

2011-10-01

Absolute densities of metastable He(23S1) atoms were measured line-of-sight integrated along the discharge channel of a capacitively coupled radio-frequency driven atmospheric pressure plasma jet operated in technologically relevant helium-oxygen mixtures by tunable diode-laser absorption spectroscopy. The dependences of the He(23S1) density in the homogeneous-glow-like α-mode plasma with oxygen admixtures up to 1% were investigated. The results are compared with a one-dimensional numerical simulation, which includes a semi-kinetical treatment of the pronounced electron dynamics and the complex plasma chemistry (in total 20 species and 184 reactions). Very good agreement between measurement and simulation is found. The main formation mechanisms for metastable helium atoms are identified and analyzed, including their pronounced spatio-temporal dynamics. Penning ionization through helium metastables is found to be significant for plasma sustainment, while it is revealed that helium metastables are not an important energy carrying species into the jet effluent and therefore will not play a direct role in remote surface treatments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brady, P.; Ditmire, T.; Horton, W.

Magnetosphere-solar wind interactions are simulated in a laboratory setting with a small permanent magnet driven by two types of supersonic plasma wind sources. The first higher speed, shorter duration plasma wind is from a laser blow-off plasma while the second longer duration, lower speed plasma wind is produced with a capacitor discharge driven coaxial electrode creating plasma jets. The stand off distance of the solar wind from the magnetosphere was measured to be 1.7{+-}0.3 cm for the laser-produced plasma experiment and 0.87{+-}0.03 cm for the coaxial electrode plasma experiment. The stand off distance of the plasma was calculated using datamore » from HYADES[J. T. Larsen and S. M. Lane, J. Quant. Spectrosc. Radiat. Transf. 51, 179 (1994)] as 1.46{+-}0.02 cm for the laser-produced plasma, and estimated for the coaxial plasma jet as r{sub mp}=0.72{+-}0.07 cm. Plasma build up on the poles of the magnets, consistent with magnetosphere systems, was also observed.« less

Kelvin-Helmholtz instability in an active region jet observed with Hinode

NASA Astrophysics Data System (ADS)

Zhelyazkov, I.; Chandra, R.; Srivastava, A. K.

2016-02-01

Over past ten years a variety of jet-like phenomena were detected in the solar atmosphere, including plasma ejections over a range of coronal temperatures being observed as extreme ultraviolet (EUV) and X-ray jets. We study the possibility for the development of Kelvin-Helmholtz (KH) instability of transverse magnetohydrodynamic (MHD) waves traveling along an EUV jet situated on the west side of NOAA AR 10938 and observed by three instruments on board Hinode on 2007 January 15/16 (Chifor et al. in Astron. Astrophys. 481:L57, 2008b). The jet was observed around log Te = 6.2 with up-flow velocities exceeded 150 km s^{-1}. Using Fe xii λ186 and λ195 line ratios, the measured densities were found to be above log Ne = 11. We have modeled that EUV jet as a vertically moving magnetic flux tube (untwisted and weakly twisted) and have studied the propagation characteristics of the kink (m = 1) mode and the higher m modes with azimuthal mode numbers m = 2, 3, 4. It turns out that all these MHD waves can become unstable at flow velocities in the range of 112-114.8 km s^{-1}. The lowest critical jet velocity of 112 km s^{-1} is obtained when modeling the jet as compressible plasma contained in an untwisted magnetic flux tube. When the jet and its environments are treated as incompressible media, the critical jet velocity becomes higher, namely 114.8 km s^{-1}. A weak twist of the equilibrium magnetic field in the same approximation of incompressible plasmas slightly decreases the threshold Alfvén Mach number, MA^{cr}, and consequently the corresponding critical velocities, notably to 114.4 km s^{-1} for the kink mode and to 112.4 km s^{-1} for the higher m modes. We have also compared two analytically found criteria for predicting the threshold Alfvén Mach number for the onset of KH instability and have concluded that one of them yields reliable values for MA^{cr}. Our study of the nature of stable and unstable MHD modes propagating on the jet shows that in a stable regime all the modes are pure surface waves, while the unstable kink (m = 1) mode in untwisted compressible plasma flux tube becomes a leaky wave. In the limit of incompressible media (for the jet and its environment) all unstable modes are non-leaky surface waves.

Progress In Plasma Accelerator Development for Dynamic Formation of Plasma Liners

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Eskridge, Richard; Martin, Adam; Smith, James; Lee, Michael; Cassibry, Jason T.; Griffin, Steven; Rodgers, Stephen L. (Technical Monitor)

2002-01-01

An experimental plasma accelerator for magnetic target fusion (MTF) applications under development at the NASA Marshall Space Flight Center is described. The accelerator is a coaxial pulsed plasma thruster (Figure 1). It has been tested experimentally and plasma jet velocities of approx.50 km/sec have been obtained. The plasma jet has been photographed with 10-ns exposure times to reveal a stable and repeatable plasma structure (Figure 2). Data for velocity profile information has been obtained using light pipes and magnetic probes embedded in the gun walls to record the plasma and current transit respectively at various barrel locations. Preliminary spatially resolved spectral data and magnetic field probe data are also presented. A high speed triggering system has been developed and tested as a means of reducing the gun "jitter". This jitter is being characterized and future work for second generation "ultra-low jitter" gun development is being identified.

Plasma Accelerator Development for Dynamic Formation of Plasma Liners: A Status Report

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Eskridge, Richard; Martin, Adam; Smith, James; Lee, Michael; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

An experimental plasma accelerator for magnetic target fusion (MTF) applications under development at the NASA Marshall Space Flight Center is described. The accelerator is a pulsed plasma thruster and has been tested experimentally and plasma jet velocities of approximately 50 km/sec have been obtained. The plasma jet structure has been photographed with 10 ns exposure times to reveal a stable and repeatable plasma structure. Data for velocity profile information has been obtained using light pipes embedded in the gun walls to record the plasma transit at various barrel locations. Preliminary spatially resolved spectral data and magnetic field probe data are also presented. A high speed triggering system has been developed and tested as a means of reducing the gun "jitter". This jitter is being characterized and future work for second generation "ultra-low jitter" gun development is being identified.

Laser interferometry of radiation driven gas jets

NASA Astrophysics Data System (ADS)

Swanson, Kyle James; Ivanov, Vladimir; Mancini, Roberto; Mayes, Daniel C.

2017-06-01

In a series of experiments performed at the 1MA Zebra pulsed power accelerator of the Nevada Terawatt Facility nitrogen gas jets were driven with the broadband x-ray flux produced during the collapse of a wire-array z-pinch implosion. The wire arrays were comprised of 4 and 8, 10μm-thick gold wires and 17μm-thick nickel wires, 2cm and 3cm tall, and 0.3cm in diameter. They radiated 12kJ to 16kJ of x-ray energy, most of it in soft x-ray photons of less than 1keV of energy, in a time interval of 30ns. This x-ray flux was used to drive a nitrogen gas jet located at 0.8cm from the axis of the z-pinch radiation source and produced with a supersonic nozzle. The x-ray flux ionizes the nitrogen gas thus turning it into a photoionized plasma. We used laser interferometry to probe the ionization of the plasma. To this end, a Mach-Zehnder interferometer at the wavelength of 266 nm was set up to extract the atom number density profile of the gas jet just before the Zebra shot, and air-wedge interferometers at 266 and 532 nm were used to determine the electron number density of the plasma right during the Zebra shot. The ratio of electron to atom number densities gives the distribution of average ionization state of the plasma. A python code was developed to perform the image data processing, extract phase shift spatial maps, and obtain the atom and electron number densities via Abel inversion. Preliminary results from the experiment are promising and do show that a plasma has been created in the gas jet driven by the x-ray flux, thus demonstrating the feasibility of a new experimental platform to study photoionized plasmas in the laboratory. These plasmas are found in astrophysical scenarios including x-ray binaries, active galactic nuclei, and the accretion disks surrounding black holes1. This work was sponsored in part by DOE Office of Science Grant DE-SC0014451.1R. C. Mancini et al, Phys. Plasmas 16, 041001 (2009)

Experimental Characterization of a Plasma Deflagration Accelerator for Simulating Fusion Wall Response to Disruption Events

NASA Astrophysics Data System (ADS)

Underwood, Thomas; Loebner, Keith; Cappelli, Mark

2016-10-01

In this work, the suitability of a pulsed deflagration accelerator to simulate the interaction of edge-localized modes with plasma first wall materials is investigated. Experimental measurements derived from a suite of diagnostics are presented that focus on the both the properties of the plasma jet and the manner in which such jets couple with material interfaces. Detailed measurements of the thermodynamic plasma state variables within the jet are presented using a quadruple Langmuir probe operating in current-saturation mode. This data in conjunction with spectroscopic measurements of H α Stark broadening via a fast-framing, intensified CCD camera provide spatial and temporal measurements of how the plasma density and temperature scale as a function of input energy. Using these measurements, estimates for the energy flux associated with the deflagration accelerator are found to be completely tunable over a range spanning 150 MW m-2 - 30 GW m-2. The plasma-material interface is investigated using tungsten tokens exposed to the plasma plume under variable conditions. Visualizations of resulting shock structures are achieved through Schlieren cinematography and energy transfer dynamics are discussed by presenting temperature measurements of exposed materials. This work is supported by the U.S. Department of Energy Stewardship Science Academic Program in addition to the National Defense Science Engineering Graduate Fellowship.

A Laboratory Astrophysical Jet to Study Canonical Flux Tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

You, Setthivoine

Understanding the interaction between plasma flows and magnetic fields remains a fundamental problem in plasma physics, with important applications to astrophysics, fusion energy, and advanced space propulsion. For example, flows are of primary importance in astrophysical jets even if it is not fully understood how jets become so long without becoming unstable. Theories for the origin of magnetic fields in the cosmos rely on flowing charged fluids that should generate magnetic fields, yet this remains to be demonstrated experimentally. Fusion energy reactors can be made smaller with flows that improve stability and confinement. Advanced space propulsion could be more efficientmore » with collimated and stable plasma flows through magnetic nozzles but must eventually detach from the nozzle. In all these cases, there appears to be a spontaneous emergence of flowing and/or magnetic structures, suggesting a form of self-organization in plasmas. Beyond satisfying simple intellectual curiosity, understanding plasma self-organization could enable the development of methods to control plasma structures for fusion energy, space propulsion, and other applications. The research project has therefore built a theory and an experiment to investigate the interaction between magnetic fields and plasma flows. The theory is called canonical field theory for short, and the experiment is called Mochi after a rice cake filled with surprising, yet delicious fillings.« less

Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet

PubMed Central

Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T. H.; Kang, Tae-Hong

2014-01-01

The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment. PMID:25319447

Measurement of activated species generated by AC power excited non-equilibrium atmospheric pressure Ar plasma jet with air engulfment

NASA Astrophysics Data System (ADS)

Takeda, Keigo; Ishikawa, Kenji; Tanaka, Hiromasa; Kano, Hiroyuki; Sekine, Makoto; Hori, Masaru

2013-09-01

Non-equilibrium atmospheric pressure plasma jet (NEAPPJ) is very attractive tool for bio and medical applications. In the plasma treatments, samples are typically located at a far region from main discharge, and treated in open air without purge gases. Influence of air engulfment on generation of activated species in the NEAPPJ in open air is a large issue for the application. In this study, the AC excited argon NEAPPJ with the gas flow rate of 2 slm was generated under the open air condition. The densities of the grand state nitrogen monoxide (NO) and the ground state O atom generated by the NEAPPJ were measured by laser induced fluorescence spectroscopy and vacuum ultraviolet absorption spectroscopy. The length of the plasma jet was around 10 mm. Up to 10 mm, the NO density increased with increasing the distance from plasma head, and then saturated in remote region of plasma. On the other hand, the O atom density decreased from 1014 to 1013 cm-3 with increasing the distance. Especially, the amount of decrease in O atom density became the largest at the plasma edge. We will discuss the generation and loss processes of activated species generated in the NEAPPJ with the measurement results using spectroscopic methods.

Resolving the Inner Arcsecond of the RY Tau Jet with HST

NASA Astrophysics Data System (ADS)

Skinner, Stephen L.; Schneider, P. Christian; Audard, Marc; Güdel, Manuel

2018-03-01

Faint X-ray emission from hot plasma (T x > 106 K) has been detected extending outward a few arcseconds along the optically delineated jets of some classical T Tauri stars including RY Tau. The mechanism and location where the jets are heated to X-ray temperatures are unknown. We present high spatial resolution Hubble Space Telescope (HST) far-ultraviolet long-slit observations of RY Tau with the slit aligned along the jet. The primary objective was to search for C IV emission from warm plasma at T C IV ∼ 105 K within the inner jet (<1″) that cannot be fully resolved by X-ray telescopes. Spatially resolved C IV emission is detected in the blueshifted jet extending outward from the star to 1″ and in the redshifted jet out to 0.″5. C IV line centroid shifts give a radial velocity in the blueshifted jet of ‑136 ± 10 km s‑1 at an offset of 0.″29 (39 au) and deceleration outward is detected. The deprojected jet speed is subject to uncertainties in the jet inclination, but values ≳200 km s‑1 are likely. The mass-loss rate in the blueshifted jet is at least {\\dot{M}}jet,{blue}}=2.3× {10}-9 M ⊙ yr‑1, consistent with optical determinations. We use the HST data along with optically determined jet morphology to place meaningful constraints on candidate jet-heating models including a hot-launch model in which the jet is heated near the base to X-ray temperatures by an unspecified (but probably magnetic) process, and downstream heating from shocks or a putative jet magnetic field.

A MODEL OF THE HELIOSPHERE WITH JETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drake, J. F.; Swisdak, M.; Opher, M., E-mail: drake@umd.edu, E-mail: swisdak@umd.edu, E-mail: mopher@bu.edu

2015-08-01

An analytic model of the heliosheath (HS) between the termination shock (TS) and the heliopause (HP) is developed in the limit in which the interstellar flow and magnetic field are neglected. The heliosphere in this limit is axisymmetric and the overall structure of the HS and HP is controlled by the solar magnetic field even in the limit in which the ratio of the plasma to magnetic field pressure, β = 8πP/B{sup 2}, in the HS is large. The tension of the solar magnetic field produces a drop in the total pressure between the TS and the HP. This samemore » pressure drop accelerates the plasma flow downstream of the TS into the north and south directions to form two collimated jets. The radii of these jets are controlled by the flow through the TS and the acceleration of this flow by the magnetic field—a stronger solar magnetic field boosts the velocity of the jets and reduces the radii of the jets and the HP. MHD simulations of the global heliosphere embedded in a stationary interstellar medium match well with the analytic model. The results suggest that mechanisms that reduce the HS plasma pressure downstream of the TS can enhance the jet outflow velocity and reduce the HP radius to values more consistent with the Voyager 1 observations than in current global models.« less

Magnetic Flux Compression Experiments Using Plasma Armatures

NASA Technical Reports Server (NTRS)

Turner, M. W.; Hawk, C. W.; Litchford, R. J.

2003-01-01

Magnetic flux compression reaction chambers offer considerable promise for controlling the plasma flow associated with various micronuclear/chemical pulse propulsion and power schemes, primarily because they avoid thermalization with wall structures and permit multicycle operation modes. The major physical effects of concern are the diffusion of magnetic flux into the rapidly expanding plasma cloud and the development of Rayleigh-Taylor instabilities at the plasma surface, both of which can severely degrade reactor efficiency and lead to plasma-wall impact. A physical parameter of critical importance to these underlying magnetohydrodynamic (MHD) processes is the magnetic Reynolds number (R(sub m), the value of which depends upon the product of plasma electrical conductivity and velocity. Efficient flux compression requires R(sub m) less than 1, and a thorough understanding of MHD phenomena at high magnetic Reynolds numbers is essential to the reliable design and operation of practical reactors. As a means of improving this understanding, a simplified laboratory experiment has been constructed in which the plasma jet ejected from an ablative pulse plasma gun is used to investigate plasma armature interaction with magnetic fields. As a prelude to intensive study, exploratory experiments were carried out to quantify the magnetic Reynolds number characteristics of the plasma jet source. Jet velocity was deduced from time-of-flight measurements using optical probes, and electrical conductivity was measured using an inductive probing technique. Using air at 27-inHg vacuum, measured velocities approached 4.5 km/s and measured conductivities were in the range of 30 to 40 kS/m.

Optical emission spectroscopic diagnostics of a non-thermal atmospheric pressure helium-oxygen plasma jet for biomedical applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thiyagarajan, Magesh; Sarani, Abdollah; Nicula, Cosmina

In this work, we have applied optical emission spectroscopy diagnostics to investigate the characteristics of a non-thermal atmospheric pressure helium plasma jet. The discharge characteristics in the active and afterglow region of the plasma jet, that are critical for biomedical applications, have been investigated. The voltage-current characteristics of the plasma discharge were analyzed and the average plasma power was measured to be around 18 W. The effect of addition of small fractions of oxygen at 0.1%-0.5% on the plasma jet characteristics was studied. The addition of oxygen resulted in a decrease in plasma plume length due to the electronegativity propertymore » of oxygen. Atomic and molecular lines of selected reactive plasma species that are considered to be useful to induce biochemical reactions such as OH transitions A{sup 2}{Sigma}{sup +}({nu}=0,1){yields}X{sup 2}{Pi}({Delta}{nu}=0) at 308 nm and A{sup 2}{Sigma}{sup +}({nu}=0,1){yields}X{sup 2}{Pi}({Delta}{nu}=1) at 287 nm, O I transitions 3p{sup 5}P{yields}3s{sup 5}S{sup 0} at 777.41 nm, and 3p{sup 3}P{yields}3s{sup 3}S{sup 0} at 844.6 nm, N{sub 2}(C-B) second positive system with electronic transition C{sup 3}{Pi}{sub u}{sup {yields}}B{sup 3}{Pi}{sub g}'' in the range of 300-450 nm and N{sub 2}{sup +}(B-X) first negative system with electronic transition B{sup 2}{Sigma}{sub u}{sup +}{yields}X{sup 2}{Sigma}{sub g}{sup +}({Delta}{nu}=0) at 391.4 nm have been studied. The atomic emission lines of helium were identified, including the He I transitions 3p{sup 3}P{sup 0}{yields}2s{sup 3}S at 388.8 nm, 3p{sup 1}P{sup 0}{yields} 2s{sup 1}S at 501.6 nm, 3d{sup 3}D{yields}2p{sup 3}P{sup 0} at 587.6 nm, 3d{sup 1}D{yields}2p{sup 1}P{sup 0} at 667.8 nm, 3s{sup 3}S{sup 1}{yields}2p{sup 3}P{sup 0} at 706.5 nm, 3s{sup 1}S{sup 0}{yields}2p{sup 1}P{sup 0} at 728.1 nm, and H{sub {alpha}} transition 2p-3d at 656.3 nm. Using a spectral fitting method, the OH radicals at 306-312 nm, the rotational and vibrational temperatures equivalent to gas temperatures of the discharge was measured and the effective non-equilibrium nature of the plasma jet was demonstrated. Our results show that, in the entire active plasma region, the gas temperature remains at 310 {+-} 25 K and 340 {+-} 25 K and it increases to 320 {+-} 25 K and 360 {+-} 25 K in the afterglow region of the plasma jet for pure helium and helium/oxygen (0.1%) mixture, respectively. Additionally, the vibrational temperatures range from 2200 {+-} 100 K and 2500 {+-} 100 K for pure helium and helium/oxygen (0.1%) mixture, respectively. The plasma jet was tested on heat sensitive polymer films used in biomedical applications such as polyethylene terephthalate and poly-L-lactide samples continuously for several minutes without causing any physical or thermal damage to the films. The plasma jet produces significant reactive species of interest while the gas temperatures remain very low demonstrating its potential for a range of biomedical applications.« less

Simulated In Situ Measurements and Structural Analysis of Reconnection-Driven Solar Polar Jets

NASA Astrophysics Data System (ADS)

Roberts, Merrill A.; Uritsky, Vadim M.; Karpen, Judith T.; DeVore, C. R.

2015-04-01

Solar polar jets are observed to originate in regions within the open field of solar coronal holes. These so called “anemone” regions are associated with an embedded dipole topology, consisting of a fan-separatrix and a spine line emanating from a null point occurring at the top of the dome shaped fan surface (Antiochos 1998). In this study, we analyze simulations using the Adaptively Refined MHD Solver (ARMS) that take into account gravity, solar wind, and spherical geometry to generate polar jets by reconnection between a twisted embedded bipole and the surrounding open field (Karpen et al. 2015). These new simulations confirm and extend previous Cartesian studies of polar jets based on this mechanism (Pariat et al. 2009, 2010, 2015). Focusing on the plasma density, velocity, and magnetic field, we interpolate the adaptively gridded simulation data onto a regular grid, and analyze the signatures that the jet produces as it propagates outward from the solar surface. The trans-Alfvénic nature of the jet front is confirmed by temporally differencing the plasma mass density and comparing the result with the local Alfvén speed. We perform a preliminary analysis of the magnetized plasma turbulence, and examine how the turbulence affects the overall structure of the jet. We also conduct simulated spacecraft fly-throughs of the jet, illustrating the signatures that spacecraft such as Solar Probe Plus may encounter in situ as the jet propagates into the heliosphere. These fly-throughs are performed in several different velocity regimes to better model the changing velocity of Solar Probe Plus relative to the Sun and its jets over the course of the mission.This research was supported by NASA grant NNG11PL10A 670.036 to CUA/IACS (M.A.R. and V.M.U.) and the Living With a Star Targeted Research and Technology (J.T.K. and C.R.D.) program.

Application of atmospheric-pressure argon plasma jet for bread mold decontamination

NASA Astrophysics Data System (ADS)

Thonglor, P.; Amnuaycheewa, P.

2017-09-01

Atmospheric-pressure argon plasma (APAP) is a promising non-thermal technology for microbial control and prevention minimally affecting quality of foods. Effect of APAP jet on the growth of bread molds, including two Aspergillus sp., Rhizopus stolonifer, and Penicillium roqueforti, isolated from white bread were investigated. The molds were isolated, verified, cultured to fully grown on potato dextrose agar (PDA), and subsequently treated with APAP jet using plasma generating power at 24 W for 5, 10, and 20 min, respectively. The inhibition of mold growth was investigated by comparing fungal dry weights and the effect on fungal cell structure was observed using compound light microscope. The results indicated that the 20-min treatment time is most effective in retarding the growth of the three bread molds. However, this level of generating power did not lead to destruction of the cellular structures for all the four fungi. Plasma generating power and treatment time are significant parameters determining the success of bread mold decontamination and further investigation on real bread matrix is needed.

In-liquid arc plasma jet and its application to phenol degradation

NASA Astrophysics Data System (ADS)

Liu, Jing-Lin; Park, Hyun-Woo; Hamdan, Ahmad; Cha, Min Suk

2018-03-01

We present a new method for achieving chemical reactions induced by plasmas with liquids—an in-liquid arc plasma jet system—designed to have a few advantages over the existing methods. High-speed imaging and optical emission spectroscopy were adopted to highlight the physical aspects of the in-liquid arc plasma jet system, and the feasibility of the system was investigated in a wastewater treatment case with phenol as the model contaminant. We found that the specific energy input is a reasonable parameter by which to characterize the overall process. The phenol removal reaction could be modeled as a pseudo-first-order reaction, and the reaction constant became smaller as the phenol concentration increased. However, complete decomposition of the phenol into water and carbon dioxide required very high energy because the final intermediate, oxalic acid, is relatively stable. Detailed chemical and physical analyses, including byproducts, ions, solution acidity, and conductivity, were conducted to evaluate this new method for use in the appropriate applications.

Modeling the Influence of Injection Modes on the Evolution of Solution Sprays in a Plasma Jet

NASA Astrophysics Data System (ADS)

Shan, Y.; Coyle, T. W.; Mostaghimi, J.

2010-01-01

Solution precursor plasma spraying (SPPS) is a novel technology with great potential for depositing finely structured ceramic coatings with nano- and sub-micrometric features. The solution is injected into the plasma jet either as a liquid stream or gas atomized droplets. Solution droplets or the stream interact with the plasma jet and break up into fine droplets. The solvent vaporizes very fast as the droplets travel downstream. Solid particles are finally formed, and the particle are heated up and accelerated to the substrate to generate the coating. The deposition process and the properties of coatings obtained are extremely sensitive to the process parameters, such as torch operating conditions, injection modes, injection parameters, and substrate temperatures. This article numerically investigates the effect of injection modes, a liquid stream injection and a gas-blast injection, on the size distribution of injected droplets. The particle/droplet size, temperature, and position distributions on the substrate are predicted for different injection modes.

Atmospheric-pressure plasma jet characterization and applications on melanoma cancer treatment (B/16-F10)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mashayekh, Shahriar; Rajaee, Hajar; Hassan, Zuhir M.

2015-09-15

A new approach in medicine is the use of cold plasma for various applications such as sterilization blood coagulation and cancer cell treatment. In this paper, a pin-to-hole plasma jet for biological applications has been designed and manufactured and characterized. The characterization includes power consumption via Lissajous method, thermal behavior of atmospheric-pressure plasma jet by using Infra-red camera as a novel method and using Speicair software to determine vibrational and transitional temperatures, and optical emission spectroscopy to determine the generated species. Treatment of Melanoma cancer cells (B16/F10) was also implemented, and tetrazolium salt dye (MTT assay) and flow cytometry weremore » used to evaluate viability. Effect of ultraviolet photons on cancerous cells was also observed using an MgF{sub 2} crystal with MTT assay. Finally, in-vivo studies on C57 type mice were also done in order to have a better understanding of the effects in real conditions.« less

Analysis of the effects of atomic mass, jet velocity, and radiative cooling on the dimensionless parameters of counter-propagating, weakly collisional plasma flows

NASA Astrophysics Data System (ADS)

Collins, Gilbert; Valenzuela, Julio; Beg, Farhat

2016-10-01

We have studied the collision of counter-propagating plasma flows using opposing conical wire arrays driven by the 200kA, 150ns rise-time `GenASIS' driver. These plasma flows produced weakly collisional, well-defined bow-shock structures. Varying initial parameters such as the opening angle of the array and the atomic mass of the wires allowed us to modify quantities such as the density contrast between jets, intra-jet mean free path (λmfp, scales with v, atomic mass A, and ionization state Zi-4) , Reynolds number (Re, scales with AZ), and the Peclet number (Pe, scales with Z). We calculate these dimensionless quantities using schlieren imagery, interferometry, and emission data, and determine whether they meet the scaling criteria necessary for the comparison to and subsequent study of astrophysical plasmas. This work was partially supported by the Department of Energy Grant Number DE-SC0014493.

One-Dimensional Burn Dynamics of Plasma-Jet Magneto-Inertial Fusion

NASA Astrophysics Data System (ADS)

Santarius, John

2009-11-01

This poster will discuss several issues related to using plasma jets to implode a Magneto-Inertial Fusion (MIF) liner onto a magnetized plasmoid and compress it to fusion-relevant temperatures [1]. The problem of pure plasma jet convergence and compression without a target present will be investigated. Cases with a target present will explore how well the liner's inertia provides transient plasma stability and confinement. The investigation uses UW's 1-D Lagrangian radiation-hydrodynamics code, BUCKY, which solves single-fluid equations of motion with ion-electron interactions, PdV work, table-lookup equations of state, fast-ion energy deposition, and pressure contributions from all species. Extensions to the code include magnetic field evolution as the plasmoid compresses plus dependence of the thermal conductivity and fusion product energy deposition on the magnetic field.[4pt] [1] Y.C. F. Thio, et al.,``Magnetized Target Fusion in a Spheroidal Geometry with Standoff Drivers,'' in Current Trends in International Fusion Research, E. Panarella, ed. (National Research Council of Canada, Ottawa, Canada, 1999), p. 113.

EDITORIAL: The interaction of radio-frequency fields with fusion plasmas: the JET experience The interaction of radio-frequency fields with fusion plasmas: the JET experience

NASA Astrophysics Data System (ADS)

Ongena, Jef

2012-07-01

The JET Task Force Heating is proud to present this special issue. It is the result of hard and dedicated work by everybody participating in the Task Force over the last four years and gives an overview of the experimental and theoretical results obtained in the period 2008-2010 with radio frequency heating of JET fusion plasmas. Topics studied and reported in this issue are: investigations into the operation of lower hybrid heating accompanied by new modeling results; new experimental results and insights into the physics of various ion cyclotron range of frequencies (ICRF) heating scenarios; progress in studies of intrinsic and ion cyclotron wave-induced plasma rotation and flows; a summary of the developments over the last years in designing an ion cyclotron radiofrequency heating (ICRH) system that can cope with the presence of fast load variations in the edge, as e.g. caused by pellets or edge localized modes (ELMs) during H-Mode operation; an overview of the results obtained with the ITER-like antenna operating in H-Mode with a packed array of straps and power densities close to those of the projected ITER ICRH antenna; and, finally, a summary of the results obtained in applying ion cyclotron waves for wall conditioning of the tokamak. This issue would not have been possible without the strong motivation and efforts (sometimes truly heroic) of all colleagues of the JET Task Force Heating. A sincere word of thanks, therefore, to all authors and co-authors involved in the experiments, analysis and compilation of the papers. It was a special privilege to work with all of them during the past very intense years. Thanks also to all other European and non-European scientists who contributed to the JET scientific programme, the operations team of JET and the colleagues of the Close Support Unit in Culham. Thanks also to the editors, Editorial Board and referees of Plasma Physics and Controlled Fusion, together with the publishing staff of IOPP, who have not only supported but also contributed very substantially to this initiative. Without their dedication this issue would not have been possible in its present form. A special word of thanks to Marie-Line Mayoral and Joelle Mailloux for their precious help and very active support in running the JET Task Force Heating over the last years. Without Joelle and Marie-Line itwould have been a much more daunting task to prepare JET operations, monitor progress during the experiments and edit the papers that are compiled here.

On factors influencing arc filament plasma actuator performance in control of high speed jets

NASA Astrophysics Data System (ADS)

Hahn, Casey; Kearney-Fischer, Martin; Samimy, Mo

2011-12-01

Localized arc filament plasma actuators (LAFPAs) have been developed and used at The Gas Dynamics and Turbulence Laboratory for the purpose of controlling high-speed and high Reynolds number jets. The ability of LAFPAs for use in both subsonic and supersonic jets has been explored, and experiments to date have shown that these actuators have significant potential for mixing enhancement and noise control applications. While it has been established that the actuators manipulate instabilities of the jet, the exact nature of how the actuation couples to the flow is still unclear. All of the results previously reported have been based on a nozzle extension that has an azimuthal groove of 1 mm width and 0.5 mm depth along the inner surface approximately 1 mm upstream of nozzle extension exit. The ring groove was initially added to shield the plasma arcs from the high-momentum flow. However, the effect of the ring groove on the actuation mechanism is not known. To explore this effect, a new nozzle extension is designed, which relocates the actuators to the nozzle extension face and eliminates the ring groove. Schlieren images, particle image velocimetry and acoustic results of a Mach 0.9 jet of Reynolds number ~6.1 × 105 show similar trends and magnitudes with and without a ring groove. Thus, it is concluded that the ring groove does not play a primary role in the LAFPAs' control mechanism. Furthermore, the effect of the duty cycle of the actuator input pulse on the LAFPAs' control authority is investigated. The results show that the minimum duty cycle that provides complete plasma formation has the largest control over the jet.

DBD Actuated Flow Control of Wall-Jet and Cross-Flow Interaction for Film Cooling Applications

NASA Astrophysics Data System (ADS)

Tirumala, Rakshit; Benard, Nicolas; Moreau, Eric; Fenot, Matthieu; Lalizel, Gildas; Dorignac, Eva

2014-11-01

In this work, we use surface DBD actuators to control the interaction between a wall jet and mainstream flow in film cooling applications. The intention of the study is to improve the contact of the jet with the wall and enhance the convective heat transfer coefficient downstream of the jet exit. A 2D wall jet (10 mm height) is injected into the mainstream flow at an angle of 30°. With an injected jet velocity (Ui) of 5 m/s, two blowing ratios M (=ρi Ui / ρ∞U∞) of 1.0 and 0.5 are studied corresponding to the mainstream flow velocity (U∞) of 5 m/s and 10 m/s respectively. Different configurations of the DBD actuator are studied, positioned both inside the jet and on the downstream side. PIV measurements are conducted to investigate the flow field of the interaction between the jet and cross flow. Streamwise velocity profiles at different downstream locations are compared to analyze the efficacy of the plasma actuator in improving the contact between the injected jet stream and the wall surface. Reynolds shear stress measurements are also conducted to study the mixing regions in the plasma-jet-mainstream flow interaction. Work was partially funded by the French government program ``Investissements d'avenir'' (LABEX INTERACTIFS, reference ANR-11-LABX-0017-01).

PHYSICAL PARAMETERS OF STANDARD AND BLOWOUT JETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pucci, Stefano; Romoli, Marco; Poletto, Giannina

2013-10-10

The X-ray Telescope on board the Hinode mission revealed the occurrence, in polar coronal holes, of much more numerous jets than previously indicated by the Yohkoh/Soft X-ray Telescope. These plasma ejections can be of two types, depending on whether they fit the standard reconnection scenario for coronal jets or if they include a blowout-like eruption. In this work, we analyze two jets, one standard and one blowout, that have been observed by the Hinode and STEREO experiments. We aim to infer differences in the physical parameters that correspond to the different morphologies of the events. To this end, we adoptmore » spectroscopic techniques and determine the profiles of the plasma temperature, density, and outflow speed versus time and position along the jets. The blowout jet has a higher outflow speed, a marginally higher temperature, and is rooted in a stronger magnetic field region than the standard event. Our data provide evidence for recursively occurring reconnection episodes within both the standard and the blowout jet, pointing either to bursty reconnection or to reconnection occurring at different locations over the jet lifetimes. We make a crude estimate of the energy budget of the two jets and show how energy is partitioned among different forms. Also, we show that the magnetic energy that feeds the blowout jet is a factor of 10 higher than the magnetic energy that fuels the standard event.« less

Measurement of atmospheric pressure microplasma jet with Langmuir probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Kunning G., E-mail: gabe.xu@uah.edu; Doyle, Steven J.

2016-09-15

A radio frequency argon microplasma jet at atmospheric-pressure is characterized using Langmuir probes. While optical methods are the typical diagnostic for these small scale plasmas, the simplicity and low cost of Langmuir probes makes them an attractive option. The plasma density and electron temperature are measured using existing high-pressure Langmuir probe theories developed for flames and arcs. The density and temperature vary from 1 × 10{sup 16} to 1 × 10{sup 19} m{sup −3} and 2.3 to 4.4 eV, respectively, depending on the operating condition. The density decreases while the electron temperature increases with axial distance from the jet exit. Themore » applicability of the probe theories as well as the effect of collisionality and jet mixing is discussed.« less

Analysis of ELM stability with extended MHD models in JET, JT-60U and future JT-60SA tokamak plasmas

NASA Astrophysics Data System (ADS)

Aiba, N.; Pamela, S.; Honda, M.; Urano, H.; Giroud, C.; Delabie, E.; Frassinetti, L.; Lupelli, I.; Hayashi, N.; Huijsmans, G.; JET Contributors, the; Research Unit, JT-60SA

2018-01-01

The stability with respect to a peeling-ballooning mode (PBM) was investigated numerically with extended MHD simulation codes in JET, JT-60U and future JT-60SA plasmas. The MINERVA-DI code was used to analyze the linear stability, including the effects of rotation and ion diamagnetic drift ({ω }* {{i}}), in JET-ILW and JT-60SA plasmas, and the JOREK code was used to simulate nonlinear dynamics with rotation, viscosity and resistivity in JT-60U plasmas. It was validated quantitatively that the ELM trigger condition in JET-ILW plasmas can be reasonably explained by taking into account both the rotation and {ω }* {{i}} effects in the numerical analysis. When deuterium poloidal rotation is evaluated based on neoclassical theory, an increase in the effective charge of plasma destabilizes the PBM because of an acceleration of rotation and a decrease in {ω }* {{i}}. The difference in the amount of ELM energy loss in JT-60U plasmas rotating in opposite directions was reproduced qualitatively with JOREK. By comparing the ELM affected areas with linear eigenfunctions, it was confirmed that the difference in the linear stability property, due not to the rotation direction but to the plasma density profile, is thought to be responsible for changing the ELM energy loss just after the ELM crash. A predictive study to determine the pedestal profiles in JT-60SA was performed by updating the EPED1 model to include the rotation and {ω }* {{i}} effects in the PBM stability analysis. It was shown that the plasma rotation predicted with the neoclassical toroidal viscosity degrades the pedestal performance by about 10% by destabilizing the PBM, but the pressure pedestal height will be high enough to achieve the target parameters required for the ITER-like shape inductive scenario in JT-60SA.

Role of Penning ionization in the enhancement of streamer channel conductivity and Ar(1s{sub 5}) production in a He-Ar plasma jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sands, Brian L.; Huang, Shih K.; Speltz, Jared W.

2013-04-21

Plasma jet devices that use a helium gas flow mixed with a small percentage of argon have been shown to operate with a larger discharge current and enhanced production of the Ar(1s{sub 5}) metastable state, particularly in the discharge afterglow. In this experiment, time-resolved quantitative measurements of He(2{sup 3}S{sub 1}) and Ar(1s{sub 5}) metastable species were combined with current and spectrally resolved emission measurements to elucidate the role of Penning ionization in a helium plasma jet with a variable argon admixture. The plasma jet was enclosed in a glass chamber through which a flowing nitrogen background was maintained at 600more » Torr. At 3%-5% Ar admixture, we observed a {approx}50% increase in the peak circuit current and streamer velocity relative to a pure helium plasma jet for the same applied voltage. The streamer initiation delay also decreased by {approx}20%. Penning ionization of ground-state argon was found to be the dominant quenching pathway for He(2{sup 3}S{sub 1}) up to 2% Ar and was directly correlated with a sharp increase in both the circuit current and afterglow production of Ar(1s{sub 5}) for Ar admixtures up to 1%, but not necessarily with the streamer velocity, which increased more gradually with Ar concentration. Ar(1s{sub 5}) was produced in the afterglow through recombination of Ar{sup +} and dissociative recombination of Ar{sub 2}{sup +} as the local mean electron energy decreased in the plasma channel behind the streamer head. The discharge current and argon metastable enhancement are contingent on the rapid production of He(2{sup 3}S{sub 1}) near the streamer head, >5 Multiplication-Sign 10{sup 12} cm{sup -3} in 30 ns under the conditions of this experiment.« less

Identifying Jets Using Artifical Neural Networks

NASA Astrophysics Data System (ADS)

Rosand, Benjamin; Caines, Helen; Checa, Sofia

2017-09-01

We investigate particle jet interactions with the Quark Gluon Plasma (QGP) using artificial neural networks modeled on those used in computer image recognition. We create jet images by binning jet particles into pixels and preprocessing every image. We analyzed the jets with a Multi-layered maxout network and a convolutional network. We demonstrate each network's effectiveness in differentiating simulated quenched jets from unquenched jets, and we investigate the method that the network uses to discriminate among different quenched jet simulations. Finally, we develop a greater understanding of the physics behind quenched jets by investigating what the network learnt as well as its effectiveness in differentiating samples. Yale College Freshman Summer Research Fellowship in the Sciences and Engineering.

Progress towards a laser produced relativistic electron-positron pair plasma

DOE PAGES

Chen, Hui; Bonlie, J.; Cauble, R.; ...

2016-04-01

Here, a set of experiments has been performed exploring unique characteristics of pair jets and plasmas at several energetic short-pulse laser facilities including Titan at Livermore and OMEGA EP in Rochester, as well as the Osaka LFEX and AWE Orion lasers. New results are summarized, including positron beam emittance, scaling of pair production vs. laser energy, and initial results on the pair jet collimation using electromagnetic fields.

X-ray spectroscopy diagnostics of a recombining plasma in laboratory astrophysics studies

NASA Astrophysics Data System (ADS)

Ryazantsev, S. N.; Skobelev, I. Yu.; Faenov, A. Ya.; Pikuz, T. A.; Grum-Grzhimailo, A. N.; Pikuz, S. A.

2015-12-01

The investigation of a recombining laser plasma is topical primarily because it can be used to simulate the interaction between plasma jets in astrophysical objects. It has been shown that the relative intensities of transitions of a resonance series of He-like multicharged ions can be used for the diagnostics of the recombining plasma. It has been found that the intensities of the indicated transitions for ions with the nuclear charge number Z n ~ 10 are sensitive to the plasma density in the range N e ~ 1016-1020 cm-3 at temperatures of 10-100 eV. The calculations performed for the F VIII ion have determined the parameters of plasma jets created at the ELFIE nanosecond laser facility (Ecole Polytechnique, France) in order to simulate astrophysical phenomena. The resulting universal calculation dependences can be used to diagnose different recombining plasmas containing helium-like fluorine ions.

Fully Implict Magneto-hydrodynamics Simulations of Coaxial Plasma Accelerators

DOE PAGES

Subramaniam, Vivek; Raja, Laxminarayan L.

2017-01-05

The resistive Magneto-Hydrodynamic (MHD) model describes the behavior of a strongly ionized plasma in the presence of external electric and magnetic fields. We developed a fully implicit MHD simulation tool to solve the resistive MHD governing equations in the context of a cell-centered finite-volume scheme. The primary objective of this study is to use the fully-implicit algorithm to obtain insights into the plasma acceleration and jet formation processes in Coaxial Plasma accelerators; electromagnetic acceleration devices that utilize self-induced magnetic fields to accelerate thermal plasmas to large velocities. We also carry out plasma-surface simulations in order to study the impact interactionsmore » when these high velocity plasma jets impinge on target material surfaces. Scaling studies are carried out to establish some basic functional relationships between the target-stagnation conditions and the current discharged between the coaxial electrodes.« less

Experimental Investigation of Laser-sustained Plasma in Supersonic Argon Flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sperber, David; Eckel, Hans-Albert; Moessinger, Peter

Laser-induced energy deposition is widely discussed as a flow control technique in supersonic transportation. In case of thermal laser-plasma upstream of a blunt body, a substantial adaptation of shock wave geometry and magnitude of wave drag is predicted. Related to the research on laser supported detonation, the paper describes the implementation of laser-sustained plasma in a supersonic Argon jet. The stable plasma state is generated by the intersection of a Q-switched Nd:YAG-laser and a continuous wave CO{sub 2}-laser beams, for ignition and maintenance of the plasma respectively. A miniature supersonic Ludwieg tube test facility generates a supersonic jet at velocitiesmore » of Mach 2.1. Modifications of the flow and plasma conditions are investigated and characterized by Schlieren flow visualisation, laser energy transmission and plasma radiation measurements. The results include the discussions of the flow field as well as the required laser and gas parameters.« less

DBD Plasma Actuators for Flow Control in Air Vehicles and Jet Engines - Simulation of Flight Conditions in Test Chambers by Density Matching

NASA Technical Reports Server (NTRS)

Ashpis, David E.; Thurman, Douglas R.

2011-01-01

Dielectric Barrier Discharge (DBD) Plasma actuators for active flow control in aircraft and jet engines need to be tested in the laboratory to characterize their performance at flight operating conditions. DBD plasma actuators generate a wall-jet electronically by creating weakly ionized plasma, therefore their performance is affected by gas discharge properties, which, in turn, depend on the pressure and temperature at the actuator placement location. Characterization of actuators is initially performed in a laboratory chamber without external flow. The pressure and temperature at the actuator flight operation conditions need to be simultaneously set in the chamber. A simplified approach is desired. It is assumed that the plasma discharge depends only on the gas density, while other temperature effects are assumed to be negligible. Therefore, tests can be performed at room temperature with chamber pressure set to yield the same density as in operating flight conditions. The needed chamber pressures are shown for altitude flight of an air vehicle and for jet engines at sea-level takeoff and altitude cruise conditions. Atmospheric flight conditions are calculated from standard atmosphere with and without shock waves. The engine data was obtained from four generic engine models; 300-, 150-, and 50-passenger (PAX) aircraft engines, and a military jet-fighter engine. The static and total pressure, temperature, and density distributions along the engine were calculated for sea-level takeoff and for altitude cruise conditions. The corresponding chamber pressures needed to test the actuators were calculated. The results show that, to simulate engine component flows at in-flight conditions, plasma actuator should be tested over a wide range of pressures. For the four model engines the range is from 12.4 to 0.03 atm, depending on the placement of the actuator in the engine. For example, if a DBD plasma actuator is to be placed at the compressor exit of a 300 PAX engine, it has to be tested at 12.4 atm for takeoff, and 6 atm for cruise conditions. If it is to be placed at the low-pressure turbine, it has to be tested at 0.5 and 0.2 atm, respectively. These results have implications for the feasibility and design of DBD plasma actuators for jet engine flow control applications. In addition, the distributions of unit Reynolds number, Mach number, and velocity along the engine are provided. The engine models are non-proprietary and this information can be used for evaluation of other types of actuators and for other purposes.

Mechanism and comparison of needle-type non-thermal direct and indirect atmospheric pressure plasma jets on the degradation of dyes

NASA Astrophysics Data System (ADS)

Attri, Pankaj; Yusupov, Maksudbek; Park, Ji Hoon; Lingamdinne, Lakshmi Prasanna; Koduru, Janardhan Reddy; Shiratani, Masaharu; Choi, Eun Ha; Bogaerts, Annemie

2016-10-01

Purified water supply for human use, agriculture and industry is the major global priority nowadays. The advanced oxidation process based on atmospheric pressure non-thermal plasma (NTP) has been used for purification of wastewater, although the underlying mechanisms of degradation of organic pollutants are still unknown. In this study we employ two needle-type atmospheric pressure non-thermal plasma jets, i.e., indirect (ID-APPJ) and direct (D-APPJ) jets operating at Ar feed gas, for the treatment of methylene blue, methyl orange and congo red dyes, for two different times (i.e., 20 min and 30 min). Specifically, we study the decolorization/degradation of all three dyes using the above mentioned plasma sources, by means of UV-Vis spectroscopy, HPLC and a density meter. We also employ mass spectroscopy to verify whether only decolorization or also degradation takes place after treatment of the dyes by the NTP jets. Additionally, we analyze the interaction of OH radicals with all three dyes using reactive molecular dynamics simulations, based on the density functional-tight binding method. This investigation represents the first report on the degradation of these three different dyes by two types of NTP setups, analyzed by various methods, and based on both experimental and computational studies.

Improving the fuel economy of stoichiometrically fueled S.I. engines by means of EGR and enhanced ignition -- A comparison of gasoline, methanol and natural gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neame, G.R.; Gardiner, D.P.; Mallory, R.W.

1995-12-31

This paper describes an experimental study in which the potential for fuel economy improvements with EGR was investigated using an automotive V6 engine. Steady state engine dynamometer tests were run at 2,000 rpm and 200 kPa Brake Mean Effective Pressure (BMEP). The engine was fueled with gasoline, methanol or natural gas. Plasma jet ignition was evaluated as a means of improving EGR tolerance. EGR tolerance with methanol was found to be better than with gasoline, while natural gas showed the poorest EGR tolerance. Plasma jet ignition extended EGR limits for all three fuels. Fuel economy benefits were realized with naturalmore » gas and gasoline at low EGR rates and without EGR but plasma jet ignition provided no improvements with methanol until over 10% EGR was used. Plasma jet ignition made stable operation possible with methanol at 40% EGR, where fuel economy improvements were ultimately limited by the slow burning associated with the high EGR rate. Both slow burning and high cyclic variation affected gasoline at high EGR rates, while stability limits to spark advance with natural gas caused fuel economy to degrade at relatively low EGR rates.« less

Magnetized Target Fusion Driven by Plasma Liners

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Cassibry, Jason; Eskridge, Richard; Kirkpatrick, Ronald C.; Knapp, Charles E.; Lee, Michael; Martin, Adam; Smith, James; Wu, S. T.; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

For practical applications of magnetized target fusion, standoff drivers to deliver the imploding momentum flux to the target plasma remotely are required. Quasi-spherically converging plasma jets have been proposed as standoff drivers for this purpose. The concept involves the dynamic formation of a quasi-spherical plasma liner by the merging of plasma jets, and the use of the liner so formed to compress a spheromak or a field reversed configuration (FRC). Theoretical analysis and computer modeling of the concept are presented. It is shown that, with the appropriate choice of the flow parameters in the liner and the target, the impact between the liner and the target plasma can be made to be shockless in the liner or to generate at most a very weak shock in the liner. Additional information is contained in the original extended abstract.

Simulation of rarefied low pressure RF plasma flow around the sample

NASA Astrophysics Data System (ADS)

Zheltukhin, V. S.; Shemakhin, A. Yu

2017-01-01

The paper describes a mathematical model of the flow of radio frequency plasma at low pressure. The hybrid mathematical model includes the Boltzmann equation for the neutral component of the RF plasma, the continuity and the thermal equations for the charged component. Initial and boundary conditions for the corresponding equations are described. The electron temperature in the calculations is 1-4 eV, atoms temperature in the plasma clot is (3-4) • 103 K, in the plasma jet is (3.2-10) • 102 K, the degree of ionization is 10-7-10-5, electron density is 1015-1019 m-3. For calculations plasma parameters is developed soft package on C++ program language, that uses the OpenFOAM library package. Simulations for the vacuum chamber in the presence of a sample and the free jet flow were carried out.

Quasi-phase-matching of high-order harmonics in plasma plumes: theory and experiment.

PubMed

Strelkov, V V; Ganeev, R A

2017-09-04

We theoretically analyze the phase-matching of high-order harmonic generation (HHG) in multi-jet plasmas and find the harmonic orders for which the quasi-phase-matching (QPM) is achieved depending on the parameters of the plasma and the generating beam. HHG by single- and two-color generating fields is analyzed. The QMP is studied experimentally for silver, indium and manganese plasmas using near IR and mid-IR laser fields. The theory is validated by comparison with our experimental observations, as well as published experimental data. In particular, the plasma densities and the harmonic phase coefficients reconstructed from the observed harmonic spectra using our theory agree with the corresponding parameters found using other methods. Our theory allows defining the plasma jet and the generating field properties, which can maximize the HHG efficiency due to QPM.

Isotope effects on L-H threshold and confinement in tokamak plasmas

NASA Astrophysics Data System (ADS)

Maggi, C. F.; Weisen, H.; Hillesheim, J. C.; Chankin, A.; Delabie, E.; Horvath, L.; Auriemma, F.; Carvalho, I. S.; Corrigan, G.; Flanagan, J.; Garzotti, L.; Keeling, D.; King, D.; Lerche, E.; Lorenzini, R.; Maslov, M.; Menmuir, S.; Saarelma, S.; Sips, A. C. C.; Solano, E. R.; Belonohy, E.; Casson, F. J.; Challis, C.; Giroud, C.; Parail, V.; Silva, C.; Valisa, M.; Contributors, JET

2018-01-01

The dependence of plasma transport and confinement on the main hydrogenic ion isotope mass is of fundamental importance for understanding turbulent transport and, therefore, for accurate extrapolations of confinement from present tokamak experiments, which typically use a single hydrogen isotope, to burning plasmas such as ITER, which will operate in deuterium-tritium mixtures. Knowledge of the dependence of plasma properties and edge transport barrier formation on main ion species is critical in view of the initial, low-activation phase of ITER operations in hydrogen or helium and of its implications on the subsequent operation in deuterium-tritium. The favourable scaling of global energy confinement time with isotope mass, which has been observed in many tokamak experiments, remains largely unexplained theoretically. Moreover, the mass scaling observed in experiments varies depending on the plasma edge conditions. In preparation for upcoming deuterium-tritium experiments in the JET tokamak with the ITER-like Be/W Wall (JET-ILW), a thorough experimental investigation of isotope effects in hydrogen, deuterium and tritium plasmas is being carried out, in order to provide stringent tests of plasma energy, particle and momentum transport models. Recent hydrogen and deuterium isotope experiments in JET-ILW on L-H power threshold, L-mode and H-mode confinement are reviewed and discussed in the context of past and more recent isotope experiments in tokamak plasmas, highlighting common elements as well as contrasting observations that have been reported. The experimental findings are discussed in the context of fundamental aspects of plasma transport models.

Plasma action on helium flow in cold atmospheric pressure plasma jet experiments

NASA Astrophysics Data System (ADS)

Darny, T.; Pouvesle, J.-M.; Fontane, J.; Joly, L.; Dozias, S.; Robert, E.

2017-10-01

In this work, helium flow modifications, visualized by schlieren imaging, induced by the plasma generated in a plasma jet have been studied in conditions used for biomedical treatments (jet being directed downwards with a low helium flow rate). It has been shown that the plasma action can shift up to few centimeters downstream the effects of buoyancy, which allows to the helium flow to reach a target below in conditions for which it is not the case when the plasma is off. This study reveals the critical role of large and long lifetime negative ions during repetitive operations in the kHz regime, inducing strong modifications in the gas propagation. The cumulative added streamwise momentum transferred to ambient air surrounding molecules resulting from a series of applied voltage pulses induces a gradual built up of a helium channel on tens of millisecond timescale. In some conditions, a remarkable stable cylindrical helium channel can be generated to the target with plasma supplied by negative polarity voltage pulses whereas a disturbed flow results from positive polarity operation. This has a direct effect on air penetration in the helium channel and then on the reactive species production over the target which is of great importance for biomedical applications. It has also been shown that with an appropriate combination of negative and positive polarity pulses, it is possible to benefit from both polarity features in order to optimize the plasma plume propagation and plasma delivery to a target.

The assessment of cold atmospheric plasma treatment of DNA in synthetic models of tissue fluid, tissue and cells

NASA Astrophysics Data System (ADS)

Szili, Endre J.; Gaur, Nishtha; Hong, Sung-Ha; Kurita, Hirofumi; Oh, Jun-Seok; Ito, Masafumi; Mizuno, Akira; Hatta, Akimitsu; Cowin, Allison J.; Graves, David B.; Short, Robert D.

2017-07-01

There is a growing literature database that demonstrates the therapeutic potential of cold atmospheric plasma (herein referred to as plasma). Given the breadth of proposed applications (e.g. from teeth whitening to cancer therapy) and vast gamut of plasma devices being researched, it is timely to consider plasma interactions with specific components of the cell in more detail. Plasma can produce highly reactive oxygen and nitrogen species (RONS) such as the hydroxyl radical (OH•), peroxynitrite (ONOO-) and superoxide (\\text{O}2- ) that would readily modify essential biomolecules such as DNA. These modifications could in principle drive a wide range of biological processes. Against this possibility, the reported therapeutic action of plasmas are not underpinned by a particularly deep knowledge of the potential plasma-tissue, -cell or -biomolecule interactions. In this study, we aim to partly address this issue by developing simple models to study plasma interactions with DNA, in the form of DNA-strand breaks. This is carried out using synthetic models of tissue fluid, tissue and cells. We argue that this approach makes experimentation simpler, more cost-effective and faster than compared to working with real biological materials and cells. Herein, a helium plasma jet source was utilised for these experiments. We show that the plasma jet readily induced DNA-strand breaks in the tissue fluid model and in the cell model, surprisingly without any significant poration or rupture of the phospholipid membrane. In the plasma jet treatment of the tissue model, DNA-strand breaks were detected in the tissue mass after pro-longed treatment (on the time-scale of minutes) with no DNA-strand breaks being detected in the tissue fluid model underneath the tissue model. These data are discussed in the context of the therapeutic potential of plasma.

Spheromaks and how plasmas may explain the ultra high energy cosmic ray mystery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fowler, T. Kenneth; Li, Hui

In recent papers, we show how accretion disks around massive black holes could act as dynamos producing magnetic jets similar to the jets that create spheromaks in the laboratory. In this paper, we discuss how these magnetic astrophysical jets might naturally produce runaway ion beams accelerated tomore » $$10^{20}$$ eV or more, finally ejected as ultra high energy cosmic rays (UHECRs) long regarded as one of the mysteries of astrophysics. The acceleration is mainly due to the drift cyclotron loss cone kinetic instability known from plasma research. Finally, experiments and simulations are suggested to verify the acceleration process.« less

Spheromaks and how plasmas may explain the ultra high energy cosmic ray mystery

DOE PAGES

Fowler, T. Kenneth; Li, Hui

2016-10-10

In recent papers, we show how accretion disks around massive black holes could act as dynamos producing magnetic jets similar to the jets that create spheromaks in the laboratory. In this paper, we discuss how these magnetic astrophysical jets might naturally produce runaway ion beams accelerated tomore » $$10^{20}$$ eV or more, finally ejected as ultra high energy cosmic rays (UHECRs) long regarded as one of the mysteries of astrophysics. The acceleration is mainly due to the drift cyclotron loss cone kinetic instability known from plasma research. Finally, experiments and simulations are suggested to verify the acceleration process.« less

Enhanced electron yield from laser-driven wakefield acceleration in high-Z gas jets.

PubMed

Mirzaie, Mohammad; Hafz, Nasr A M; Li, Song; Liu, Feng; He, Fei; Cheng, Ya; Zhang, Jie

2015-10-01

An investigation of the electron beam yield (charge) form helium, nitrogen, and neon gas jet plasmas in a typical laser-plasma wakefield acceleration experiment is carried out. The charge measurement is made by imaging the electron beam intensity profile on a fluorescent screen into a charge coupled device which was cross-calibrated with an integrated current transformer. The dependence of electron beam charge on the laser and plasma conditions for the aforementioned gases are studied. We found that laser-driven wakefield acceleration in low Z-gas jet targets usually generates high-quality and well-collimated electron beams with modest yields at the level of 10-100 pC. On the other hand, filamentary electron beams which are observed from high-Z gases at higher densities reached much higher yields. Evidences for cluster formation were clearly observed in the nitrogen gas jet target, where we received the highest electron beam charge of ∼1.7 nC. Those intense electron beams will be beneficial for the applications on the generation of bright X-rays, gamma rays radiations, and energetic positrons via the bremsstrahlung or inverse-scattering processes.

Study of the effect of collisionality and cooling on the interactions of counter-streaming plasma flows as a function of wire material

NASA Astrophysics Data System (ADS)

Collins, Gilbert; Valenzuela, Julio; Aybar, Nicholas; Conti, Fabio; Beg, Farhat

2017-10-01

We report on the effects wire material on collisionality and radiative cooling on the interactions of counter-streaming plasma jets produced by conical wire arrays on the 200 kA GenASIS driver. In these interactions, mean free path (λmfp) scales with jet velocity (vjet4),atomic mass (A2), and ionization (Z*-4), while cooling scales with atomic mass. By changing the material of the jets one can create slowly cooling, weakly collisional regimes using C, Al, or Cu, or strongly cooled, effectively collisionless plasmas using Mo or W. The former produced smooth shocks soon after the jets collide (near the peak current of 150 ns) that grew in size over time. Interactions of the latter produced multiple structures of a different shape, at a later time ( 300 ns) that dissipated rapidly compared to the lower Z materials. We will report on the scaleability of these different materials to astrophysical phenomena. This work was partially supported by the Department of Energy Grant Number DE-SC0014493.

Long wavelength perfect fluidity from short distance jet transport in quark-gluon plasmas

DOE PAGES

Xu, J.; Liao, J.; Gyulassy, M.

2015-12-01

Here, we build a new phenomenological framework that bridges the long wavelength bulk viscous transport properties of the strongly-coupled quark-gluon plasma (sQGP) and short distance hard jet transport properties in the QGP. The full nonperturbative chromo-electric (E) and chromo-magnetic (M) structure of the near “perfect fluid” like sQGP in the critical transition region are integrated into a semi-Quark-Gluon-Monopole Plasma (sQGMP) model lattice-compatibly and implemented into the new CUJET3.0 jet quenching framework. All observables computed from CUJET3.0 are found to be consistent with available data at RHIC and LHC simultaneously. Moreover, a quantitative connection between the shear viscosity and jet transportmore » parameter is rigorously established within this framework. Finally, we deduce the T = 160-600 MeV dependence of the QGP’s η/s: its near vanishing value in the near T c regime is determined by the composition of E and M charges, it increases as T rises, and its high T limit is fixed by color screening scales.« less

Arc plasma generator of atomic driver for steady-state negative ion source.

PubMed

Ivanov, A A; Belchenko, Yu I; Davydenko, V I; Ivanov, I A; Kolmogorov, V V; Listopad, A A; Mishagin, V V; Putvinsky, S V; Shulzhenko, G I; Smirnov, A

2014-02-01

The paper reviews the results of development of steady-state arc-discharge plasma generator with directly heated LaB6 cathode. This arc-discharge plasma generator produces a plasma jet which is to be converted into an atomic one after recombination on a metallic plate. The plate is electrically biased relative to the plasma in order to control the atom energies. Such an intensive jet of hydrogen atoms can be used in negative ion sources for effective production of negative ions on a cesiated surface of plasma grid. All elements of the plasma generator have an augmented water cooling to operate in long pulse mode or in steady state. The thermo-mechanical stresses and deformations of the most critical elements of the plasma generator were determined by simulations. Magnetic field inside the discharge chamber was optimized to reduce the local power loads. The first tests of the steady-state arc plasma generator prototype have performed in long-pulse mode.

Observations of supra-arcade fans: instabilities at the head of reconnection jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Innes, D. E.; Guo, L.-J.; Schmit, D.

2014-11-20

Supra-arcade fans are bright, irregular regions of emission that develop during eruptive flares above flare arcades. The underlying flare arcades are thought to be a consequence of magnetic reconnection along a current sheet in the corona. At the same time, theory predicts plasma jets from the reconnection sites which are extremely difficult to observe directly because of their low densities. It has been suggested that the dark supra-arcade downflows (SADs) seen falling through supra-arcade fans may be low-density jet plasma. The head of a low-density jet directed toward higher-density plasma would be Rayleigh-Taylor unstable, and lead to the development ofmore » rapidly growing low- and high-density fingers along the interface. Using Solar Dynamics Observatory/Atmospheric Imaging Assembly 131 Å images, we show details of SADs seen from three different orientations with respect to the flare arcade and current sheet, and highlight features that have been previously unexplained, such as the splitting of SADs at their heads, but are a natural consequence of instabilities above the arcade. Comparison with three-dimensional magnetohydrodynamic simulations suggests that SADs are the result of secondary instabilities of the Rayleigh-Taylor type in the exhaust of reconnection jets.« less

Dynamics and density distributions in a capillary-discharge waveguide with an embedded supersonic jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matlis, N. H., E-mail: nmatlis@gmail.com; Gonsalves, A. J.; Steinke, S.

We present an analysis of the gas dynamics and density distributions within a capillary-discharge waveguide with an embedded supersonic jet. This device provides a target for a laser plasma accelerator which uses longitudinal structuring of the gas-density profile to enable control of electron trapping and acceleration. The functionality of the device depends sensitively on the details of the density profile, which are determined by the interaction between the pulsed gas in the jet and the continuously-flowing gas in the capillary. These dynamics are captured by spatially resolving recombination light from several emission lines of the plasma as a function ofmore » the delay between the jet and the discharge. We provide a phenomenological description of the gas dynamics as well as a quantitative evaluation of the density evolution. In particular, we show that the pressure difference between the jet and the capillary defines three regimes of operation with qualitatively different longitudinal density profiles and show that jet timing provides a sensitive method for tuning between these regimes.« less

A Series of Jets that Drove Streamer-Puff CMEs from Giant Active Region of 2014

NASA Technical Reports Server (NTRS)

Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.

2016-01-01

We investigate characteristics of solar coronal jets that originated from active region NOAA 12192 and produced coronal mass ejections (CMEs). This active region produced many non­-jet major flare eruptions (X and M class) that made no CME. A multitude of jets occurred from the southeast edge of the active region, and in contrast to the major-­flare eruptions in the core, six of these jets resulted in CMEs. Our jet observations are from SDO/AIA EUV channels and from Hinode/XRT, and CME observations are from the SOHO/LASCO C2 coronograph. Each jet-­driven CME was relatively slow-­moving (approx. 200 - 300 km/s) compared to most CMEs; had angular width (20deg - 50deg) comparable to that of the streamer base; and was of the "streamer­-puff" variety, whereby a pre-existing streamer was transiently inflated but not removed (blown out) by the passage of the CME. Much of the chromospheric-­temperature plasma of the jets producing the CMEs escaped from the Sun, whereas relatively more of the chromospheric plasma in the non-CME-producing jets fell back to the solar surface. We also found that the CME-producing jets tended to be faster in speed and longer in duration than the non-CME-­producing jets. We expect that the jets result from eruptions of mini-filaments. We further propose that the CMEs are driven by magnetic twist injected into streamer-­base coronal loops when erupting twisted mini-filament field reconnects with the ambient field at the foot of those loops.

A Series of Jets that Drove Streamer-Puff CMEs from Giant Active Region of 2014

NASA Technical Reports Server (NTRS)

Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.

2016-01-01

We investigate characteristics of solar coronal jets that originated from active region NOAA 12192 and produced coronal mass ejections (CMEs). This active region produced many non-jet major flare eruptions (X and M class) that made no CME. A multiitude of jets occurred from the southeast edge of the active region, and in contrast to the major-flare eruptions in the core, six of these jets resulted in CMEs. Our jet observations are from multiple SDO/AIA EUV channels, including 304, 171 and 193 Angstrom, and CME observations are taken from SOHO/LASCO C2 coronograph. Each jet-driven CME was relatively slow-moving (approximately 200 - 300 km s(sup-1) compared to most CMEs; had angular width (20deg - 50deg) comparable to that of the streamer base; and was of the "streamer-puff" variety, whereby a preexisting streamer was transiently inflated but not removed (blown out) by the passage of the CME. Much of the chromospheric-temperature plasma of the jets producing the CMEs escaped from the Sun, whereas relatively more of the chromospheric plasma in the non-CME-producing jets fell back to the solar surface. We also found that the CME-producing jets tended to be faster in speed and longer in duration than the non-CME-producing jets. We expect that the jets result from eruptions of mini-filaments. We further propose that the CMEs are driven by magnetic twist injected into streamer-base coronal loops when erupting twisted mini-filament field reconnects with the ambient field at the foot of those loops.

The Trails of Superluminal Jet Components in 3C 111

NASA Technical Reports Server (NTRS)

Kadler, M.; Ros, E.; Perucho, M.; Kovalev, Y. Y.; Homan, D. C.; Agudo, I.; Kellermann, K. I.; Aller, M. F.; Aller, H. D.; Lister, M. L.;

Atmospheric pressure plasma jet treatment of Salmonella Enteritidis inoculated eggshells.

PubMed

Moritz, Maike; Wiacek, Claudia; Koethe, Martin; Braun, Peggy G

2017-03-20

Contamination of eggshells with Salmonella Enteritidis remains a food safety concern. In many cases human salmonellosis within the EU can be traced back to raw or undercooked eggs and egg products. Atmospheric pressure plasma is a novel decontamination method that can reduce a wide range of pathogens. The aim of this work was to evaluate the possibility of using an effective short time cold plasma treatment to inactivate Salmonella Enteritidis on the eggshell. Therefore, artificially contaminated eggshells were treated with an atmospheric pressure plasma jet under different experimental settings with various exposure times (15-300s), distances from the plasma jet nozzle to the eggshell surface (5, 8 or 12mm), feed gas compositions (Ar, Ar with 0.2, 0.5 or 1.0% O 2 ), gas flow rates (5 and 7slm) and different inoculations of Salmonella Enteritidis (10 1 -10 6 CFU/cm 2 ). Atmospheric pressure plasma could reduce Salmonella Enteritidis on eggshells significantly. Reduction factors ranged between 0.22 and 2.27 log CFU (colony-forming units). Exposure time and, particularly at 10 4 CFU/cm 2 inoculation, feed gas had a major impact on Salmonella reduction. Precisely, longer exposure times led to higher reductions and Ar as feed gas was more effective than ArO 2 mixtures. Copyright © 2017 Elsevier B.V. All rights reserved.

High-frequency counter-flow plasma synthetic jet actuator and its application in suppression of supersonic flow separation

NASA Astrophysics Data System (ADS)

Wang, Hongyu; Li, Jun; Jin, Di; Tang, Mengxiao; Wu, Yun; Xiao, Lianghua

2018-01-01

We come up with a control strategy for suppression of supersonic flow separation based on high-frequency Counter-flow Plasma Synthetic Jet Actuator (CPSJA). The main purpose of this investigation is to verify if its control authority can be enhanced by the jet/shock interaction. We use a blunt nose to generate a bow shock, a step on a flat plate to introduce a massive separation in a Mach 2 wind tunnel, and the CPSJA to generate Plasma Synthetic Jet (PSJ). In this study, pulsed capacitive discharge is provided for an array of CPSJAs, which makes the actuation (discharge) frequency f1 = 1 kHz, f2 = 2 kHz and f3 = 3 kHz. We use the high-speed schlieren imaging and fast response pressure transducers as well as a numerical simulation to investigate the quiescent PSJ properties, the interaction between the jet and bow shock, and its disturbance effect on the downstream separated region. The schlieren images show that PSJ is characterized by a succession of vortex rings; the jet strength weakens with the increase of frequency. A 4.5 mN jet thrust is found for all the frequencies. The simulation results show that jet/shock interaction produces vorticity in the vortex ring of the jet, enhancing turbulent mixing in PSJ so that a great deal of momentum is produced into the flow. We found the downstream flow is significantly disturbed by the enhanced actuation. Actuation with frequency of f2, f3 which is close to the natural frequency fn of the separation bubble suppresses the separation with the upstream laminar boundary layer being periodically attenuated, which has a better control effect than f1. The control effect is sensitive to the position where PSJ interacts with the shear layer, but the amount of energy deposited in one pulse is not crucial in a separation reduction in the experiment.

Invited Article: A novel calibration method for the JET real-time far infrared polarimeter and integration of polarimetry-based line-integrated density measurements for machine protection of a fusion plant.

PubMed

Boboc, A; Bieg, B; Felton, R; Dalley, S; Kravtsov, Yu

2015-09-01

In this paper, we present the work in the implementation of a new calibration for the JET real-time polarimeter based on the complex amplitude ratio technique and a new self-validation mechanism of data. This allowed easy integration of the polarimetry measurements into the JET plasma density control (gas feedback control) and as well as machine protection systems (neutral beam injection heating safety interlocks). The new addition was used successfully during 2014 JET Campaign and is envisaged that will operate routinely from 2015 campaign onwards in any plasma condition (including ITER relevant scenarios). This mode of operation elevated the importance of the polarimetry as a diagnostic tool in the view of future fusion experiments.

Invited Article: A novel calibration method for the JET real-time far infrared polarimeter and integration of polarimetry-based line-integrated density measurements for machine protection of a fusion plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boboc, A., E-mail: Alexandru.Boboc@ccfe.ac.uk; Felton, R.; Dalley, S.

2015-09-15

In this paper, we present the work in the implementation of a new calibration for the JET real-time polarimeter based on the complex amplitude ratio technique and a new self-validation mechanism of data. This allowed easy integration of the polarimetry measurements into the JET plasma density control (gas feedback control) and as well as machine protection systems (neutral beam injection heating safety interlocks). The new addition was used successfully during 2014 JET Campaign and is envisaged that will operate routinely from 2015 campaign onwards in any plasma condition (including ITER relevant scenarios). This mode of operation elevated the importance ofmore » the polarimetry as a diagnostic tool in the view of future fusion experiments.« less

Experimental investigation on a vectorized aerodynamic dielectric barrier discharge plasma actuator array

NASA Astrophysics Data System (ADS)

Neretti, Gabriele; Cristofolini, Andrea; Borghi, Carlo A.

2014-04-01

The Electro-Hydro-Dynamics (EHD) interaction, induced in atmospheric pressure still air by a surface dielectric barrier discharge (DBD) actuator, had been experimentally studied. A plasma aerodynamic actuator array, able to produce a vectorized jet, with the induced airflow oriented toward the desired direction, had been developed. The array was constituted by a sequence of single surface DBD actuators with kapton as dielectric material. An ac voltage in the range of 0-6 kV peak at 15 kHz had been used. The vectorization had been obtained by feeding the upper electrodes with different voltages and by varying the electrical connections. The lower electrodes had been connected either to ground or to the high voltage source, to produce the desired jet orientation and to avoid plasma formation acting in an undesired direction. Voltage and current measurements had been carried out to evaluate waveforms and to estimate the active power delivered to the discharge. Schlieren imaging allowed to visualize the induced jet and to estimate its orientation. Pitot measurements had been performed to obtain velocity profiles for all jet configurations. A proportional relation between the jet deflection angle and the applied voltage had been found. Moreover, a linear relation had been obtained between the maximum speed in the jet direction and the applied voltage. The active power of the discharge is approximated by both a power law function and an exponential function of the applied voltage.

In-situ monitoring of etching of bovine serum albumin using low-temperature atmospheric plasma jet

NASA Astrophysics Data System (ADS)

Kousal, J.; Shelemin, A.; Kylián, O.; Slavínská, D.; Biederman, H.

2017-01-01

Bio-decontamination of surfaces by means of atmospheric pressure plasma is nowadays extensively studied as it represents promising alternative to commonly used sterilization/decontamination techniques. The non-equilibrium atmospheric pressure plasmas were already reported to be highly effective in removal of a wide range of biological residual from surfaces. Nevertheless the kinetics of removal of biological contamination from surfaces is still not well understood as the majority of performed studies were based on ex-situ evaluation of etching rates, which did not allow investigating details of plasma action on biomolecules. This study therefore presents a real-time, in-situ ellipsometric characterization of removal of bovine serum albumin (BSA) from surfaces by low-temperature atmospheric plasma jet operated in argon. Non-linear and at shorter distances between treated samples and nozzle of the plasma jet also non-monotonic dependence of the removal rate on the treatment duration was observed. According to additional measurements focused on the determination of chemical changes of treated BSA as well as temperature measurements, the observed behavior is most likely connected with two opposing effects: the formation of a thin layer on the top of BSA deposit enriched in inorganic compounds, whose presence causes a gradual decrease of removal efficiency, and slight heating of BSA that facilitates its degradation and volatilization induced by chemically active radicals produced by the plasma.

Effect of corona discharge plasma jet on surface-borne microorganisms and sprouting of broccoli seeds.

PubMed

Kim, Je-Wook; Puligundla, Pradeep; Mok, Chulkyoon

2017-01-01

Different pathogenic microorganisms have been reported to cause sprouts-associated outbreaks. In order to sterilise and enhance the germination of seeds, non-thermal plasma has been increasingly investigated in the field of agricultural science as an alternative to the traditional pre-sowing seed treatments. This work aimed to evaluate the effect of corona discharge plasma jet (CDPJ) on disinfection of the natural bio-contaminants of broccoli seed and also studied the plasma effect on sprout seed germination rate and physico-chemical properties of sprouts. Aerobic bacteria, moulds and yeasts, B. cereus, E. coli, Salmonella spp. were detected on the broccoli seed surface. After 0-3 min treatment using CDPJ, the detected microorganisms were reduced in the range of 1.2-2.3 log units. Inactivation patterns were better explained using pseudo-first-order kinetics. The plasma treatment of seeds up to 2 min exhibited a positive effect on germination rate, seedling growth. The physico-chemical and sensory characteristics of sprouts were unaffected due to the CDPJ treatment of their respective seeds. Corona discharge plasma jet can potentially be used for microbial decontamination of broccoli seeds. In addition, the plasma treatment of broccoli sprout seeds has enabled a significant enhancement in their germination rate and seedling growth without compromising physico-chemical and sensory characteristics of their corresponding sprouts. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Stabilization of sawteeth with third harmonic deuterium ICRF-accelerated beam in JET plasmas

NASA Astrophysics Data System (ADS)

Girardo, Jean-Baptiste; Sharapov, Sergei; Boom, Jurrian; Dumont, Rémi; Eriksson, Jacob; Fitzgerald, Michael; Garbet, Xavier; Hawkes, Nick; Kiptily, Vasily; Lupelli, Ivan; Mantsinen, Mervi; Sarazin, Yanick; Schneider, Mireille

2016-01-01

Sawtooth stabilisation by fast ions is investigated in deuterium (D) and D-helium 3 (He3) plasmas of JET heated by deuterium Neutral Beam Injection combined in synergy with Ion Cyclotron Resonance Heating (ICRH) applied on-axis at 3rd beam cyclotron harmonic. A very significant increase in the sawtooth period is observed, caused by the ICRH-acceleration of the beam ions born at 100 keV to the MeV energy range. Four representative sawteeth from four different discharges are compared with Porcelli's model. In two discharges, the sawtooth crash appears to be triggered by core-localized Toroidal Alfvén Eigenmodes inside the q = 1 surface (also called "tornado" modes) which expel the fast ions from within the q = 1 surface, over time scales comparable with the sawtooth period. Two other discharges did not exhibit fast ion-driven instabilities in the plasma core, and no degradation of fast ion confinement was found in both modelling and direct measurements of fast ion profile with the neutron camera. The developed sawtooth scenario without fast ion-driven instabilities in the plasma core is of high interest for the burning plasmas. Possible causes of the sawtooth crashes on JET are discussed.

Characterization and optimization of the HyperV PLX- α coaxial-gun plasma jet

NASA Astrophysics Data System (ADS)

Case, Andrew; Brockington, Sam; Cruz, Edward; Witherspoon, F. Douglas

2017-10-01

We present results from characterizing and optimizing performance of the contoured gap coaxial plasma guns under development for the ARPA-E Accelerating Low-Cost Plasma Heating And Assembly (ALPHA) program. Plasma jet diagnostics include fast photodiodes for velocimetry and interferometry for line integrated density. Additionally we present results from spectroscopy, both time resolved high resolution spectroscopy using a novel detector and time integrated survey spectroscopy, for measurements of velocity and temperature as well as impurities. Fast imaging gives plume geometry and time integrated imaging gives overall light emission. Results from a novel long record length camera developed by HyperV will also be presented. Experimental results are compared to the desired target parameters for the plasma jets. The target values for the plasmoid are velocity of 50 km/s, mass of 3.5 mg, and length of 10 cm. The best results so far from the exploration of parameter space for gun operation are: 4 mg at >50 km/s, with a length of 10 cm. Peak axial density 34 cm downstream from the muzzle is 2 ×1016 cm-3. This work supported by the ARPA-E ALPHA Program under contract DE-AR0000566.

The National Shipbuilding Research Program: Solid Waste Segregation and Recycling

DTIC Science & Technology

1998-03-01

Shields , Recycling Coordinator D.C. Department of Public Works 65 K Street, NE Washington, DC 20002 202-727-5887 Task Three, Tab Three Page 42 George...SHEAR X FRONT END LOADERS = CONVEYORS X FORKLIFTS O WEIGHT SCALES X PROCESSING DROP-BALL BREAKAGE X CUTTING TORCHES GAS = PLASMA = POWDER = WATER-JET...Loaders Conveyors Forklifts Weight Scales Processing Drop-ball Breakage Cutting Torches Gas Plasma Powder Laser Water-jet Abrasive disk Shears Ferrous

Evaluation of the plasma hydrogen isotope content by residual gas analysis at JET and AUG

NASA Astrophysics Data System (ADS)

Drenik, A.; Alegre, D.; Brezinsek, S.; De Castro, A.; Kruezi, U.; Oberkofler, M.; Panjan, M.; Primc, G.; Reichbauer, T.; Resnik, M.; Rohde, V.; Seibt, M.; Schneider, P. A.; Wauters, T.; Zaplotnik, R.; ASDEX-Upgrade, the; EUROfusion MST1 Teams; contributors, JET

2017-12-01

The isotope content of the plasma reflects on the dynamics of isotope changeover experiments, efficiency of wall conditioning and the performance of a fusion device in the active phase of operation. The assessment of the isotope ratio of hydrogen and methane molecules is used as a novel method of assessing the plasma isotope ratios at JET and ASDEX-Upgrade (AUG). The isotope ratios of both molecules in general shows similar trends as the isotope ratio detected by other diagnostics. At JET, the absolute values of RGA signals are in relatively good agreement with each other and with spectroscopy data, while at AUG the deviation from neutral particle analyser data are larger, and the results show a consistent spatial distribution of the isotope ratio. It is further shown that the isotope ratio of the hydrogen molecule can be used to study the degree of dissociation of the injected gas during changeover experiments.

An evaluation of the electric arc spray and (HPPS) processes for the manufacturing of high power plasma spraying MCrAIY coatings

NASA Astrophysics Data System (ADS)

Sacriste, D.; Goubot, N.; Dhers, J.; Ducos, M.; Vardelle, A.

2001-06-01

The high power plasma torch (PlazJet) can be used to spray refractory ceramics with high spray rates and deposition efficiency. It can provide dense and hard coating with high bond strengths. When manufacturing thermal barrier coatings, the PlazJet gun is well adapted to spraying the ceramic top coat but not the MCrAIY materials that are used as bond coat. Arc spraying can compete with plasma spraying for metallic coatings since cored wires can be used to spray alloys and composites. In addition, the high production rate of arc spraying enables a significant decrease in coating cost. This paper discusses the performances of the PlazJet gun, and a twin-wire are spray system, and compares the properties and cost of MCrAIY coatings made with these two processes. For arc spraying, the use of air or nitrogen as atomizing gas is also investigated.

Atmospheric-pressure plasma jet system for silicon etching without fluorocarbon gas feed

NASA Astrophysics Data System (ADS)

Ohtsu, Yasunori; Nagamatsu, Kenta

2018-01-01

We developed an atmospheric-pressure plasma jet (APPJ) system with a tungsten rod electrode coated with C2F4 particles of approximately 0.3 µm diameter for the surface treatment of a silicon wafer. The APPJ was generated by dielectric barrier discharge with a driving frequency of 22 kHz using a He gas flow. The characteristics of the APPJ were examined under various experimental conditions. The plasma jet length increased proportionally to the electric field. It was found that the treatment area of the silicon wafer was approximately 1 mm in diameter. By atomic force microscopy analysis, minute irregularities with a maximum length of about 600 nm and part of a ring-shaped trench were observed. A Si etching rate of approximately 400 nm/min was attained at a low power of 6 W and a He flow rate of 1 L/min without introducing molecular gas including F atoms.

A Planar Source of Atmospheric-Pressure Plasma Jet

NASA Astrophysics Data System (ADS)

Zhdanova, O. S.; Kuznetsov, V. S.; Panarin, V. A.; Skakun, V. S.; Sosnin, E. A.; Tarasenko, V. F.

2018-01-01

In a single-barrier discharge with voltage sharpening and low gas consumption (up to 1 L/min), plane atmospheric pressure plasma jets with a width of up to 3 cm and length of up to 4 cm in air are formed in the slit geometry of the discharge zone. The energy, temperature, and spectral characteristics of the obtained jets have been measured. The radiation spectrum contains intense maxima corresponding to vibrational transitions of the second positive system of molecular nitrogen N2 ( C 3Π u → B 3Π g ) and comparatively weak transition lines of the first positive system of the N 2 + ion ( B 2Σ u + → X 2Σ g ). By an example of inactivation of the Staphylococcus aureus culture (strain ATCC 209), it is shown that plasma is a source of chemically active particles providing the inactivation of microorganisms.

STABILITY OF ROTATING MAGNETIZED JETS IN THE SOLAR ATMOSPHERE. I. KELVIN–HELMHOLTZ INSTABILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaqarashvili, Teimuraz V.; Zhelyazkov, Ivan; Ofman, Leon, E-mail: teimuraz.zaqarashvili@uni-graz.at

2015-11-10

Observations show various jets in the solar atmosphere with significant rotational motions, which may undergo instabilities leading to heat ambient plasma. We study the Kelvin–Helmholtz instability (KHI) of twisted and rotating jets caused by the velocity jumps near the jet surface. We derive a dispersion equation with appropriate boundary conditions for total pressure (including centrifugal force of tube rotation), which governs the dynamics of incompressible jets. Then, we obtain analytical instability criteria of KHI in various cases, which were verified by numerical solutions to the dispersion equation. We find that twisted and rotating jets are unstable to KHI when themore » kinetic energy of rotation is more than the magnetic energy of the twist. Our analysis shows that the azimuthal magnetic field of 1–5 G can stabilize observed rotations in spicule/macrospicules and X-ray/extreme-ultraviolet (EUV) jets. On the other hand, nontwisted jets are always unstable to KHI. In this case, the instability growth time is several seconds for spicule/macrospicules and a few minutes (or less) for EUV/X-ray jets. We also find that standing kink and torsional Alfvén waves are always unstable near the antinodes, owing to the jump of azimuthal velocity at the surface, while the propagating waves are generally stable. Kelvin–Helmholtz (KH) vortices may lead to enhanced turbulence development and heating of surrounding plasma; therefore, rotating jets may provide energy for chromospheric and coronal heating.« less

HOMOLOGOUS JET-DRIVEN CORONAL MASS EJECTIONS FROM SOLAR ACTIVE REGION 12192

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L., E-mail: navdeep.k.panesar@nasa.gov

We report observations of homologous coronal jets and their coronal mass ejections (CMEs) observed by instruments onboard the Solar Dynamics Observatory (SDO) and the Solar and Heliospheric Observatory (SOHO) spacecraft. The homologous jets originated from a location with emerging and canceling magnetic field at the southeastern edge of the giant active region (AR) of 2014 October, NOAA 12192. This AR produced in its interior many non-jet major flare eruptions (X- and M- class) that made no CME. During October 20 to 27, in contrast to the major flare eruptions in the interior, six of the homologous jets from the edgemore » resulted in CMEs. Each jet-driven CME (∼200–300 km s{sup −1}) was slower-moving than most CMEs, with angular widths (20°–50°) comparable to that of the base of a coronal streamer straddling the AR and were of the “streamer-puff” variety, whereby the preexisting streamer was transiently inflated but not destroyed by the passage of the CME. Much of the transition-region-temperature plasma in the CME-producing jets escaped from the Sun, whereas relatively more of the transition-region plasma in non-CME-producing jets fell back to the solar surface. Also, the CME-producing jets tended to be faster and longer-lasting than the non-CME-producing jets. Our observations imply that each jet and CME resulted from reconnection opening of twisted field that erupted from the jet base and that the erupting field did not become a plasmoid as previously envisioned for streamer-puff CMEs, but instead the jet-guiding streamer-base loop was blown out by the loop’s twist from the reconnection.« less

Electron magnetic reconnection without ion coupling in Earth's turbulent magnetosheath

NASA Astrophysics Data System (ADS)

Phan, T. D.; Eastwood, J. P.; Shay, M. A.; Drake, J. F.; Sonnerup, B. U. Ö.; Fujimoto, M.; Cassak, P. A.; Øieroset, M.; Burch, J. L.; Torbert, R. B.; Rager, A. C.; Dorelli, J. C.; Gershman, D. J.; Pollock, C.; Pyakurel, P. S.; Haggerty, C. C.; Khotyaintsev, Y.; Lavraud, B.; Saito, Y.; Oka, M.; Ergun, R. E.; Retino, A.; Le Contel, O.; Argall, M. R.; Giles, B. L.; Moore, T. E.; Wilder, F. D.; Strangeway, R. J.; Russell, C. T.; Lindqvist, P. A.; Magnes, W.

2018-05-01

Magnetic reconnection in current sheets is a magnetic-to-particle energy conversion process that is fundamental to many space and laboratory plasma systems. In the standard model of reconnection, this process occurs in a minuscule electron-scale diffusion region1,2. On larger scales, ions couple to the newly reconnected magnetic-field lines and are ejected away from the diffusion region in the form of bi-directional ion jets at the ion Alfvén speed3-5. Much of the energy conversion occurs in spatially extended ion exhausts downstream of the diffusion region6. In turbulent plasmas, which contain a large number of small-scale current sheets, reconnection has long been suggested to have a major role in the dissipation of turbulent energy at kinetic scales7-11. However, evidence for reconnection plasma jetting in small-scale turbulent plasmas has so far been lacking. Here we report observations made in Earth's turbulent magnetosheath region (downstream of the bow shock) of an electron-scale current sheet in which diverging bi-directional super-ion-Alfvénic electron jets, parallel electric fields and enhanced magnetic-to-particle energy conversion were detected. Contrary to the standard model of reconnection, the thin reconnecting current sheet was not embedded in a wider ion-scale current layer and no ion jets were detected. Observations of this and other similar, but unidirectional, electron jet events without signatures of ion reconnection reveal a form of reconnection that can drive turbulent energy transfer and dissipation in electron-scale current sheets without ion coupling.

Alfvén cascades in JET discharges with NBI-heating

NASA Astrophysics Data System (ADS)

Sharapov, S. E.; Alper, B.; Baranov, Yu. F.; Berk, H. L.; Borba, D.; Boswell, C.; Breizman, B. N.; Challis, C. D.; de Baar, M.; DeLa Luna, E.; Evangelidis, E. A.; Hacquin, S.; Hawkes, N. C.; Kiptily, V. G.; Pinches, S. D.; Sandquist, P.; Voitsekhovich, I.; Young, N. P.; Contributors, JET-EFDA

2006-10-01

Alfvén cascade (AC) eigenmodes excited by energetic ions accelerated with ion-cyclotron resonance heating in JET reversed-shear discharges are studied experimentally in high-density plasmas fuelled by neutral beam injection (NBI) and by deuterium pellets. The recently developed O-mode interferometry technique and Mirnov coils are employed for detecting ACs. The spontaneous improvements in plasma confinement (internal transport barrier (ITB) triggering events) and grand ACs are found to correlate within 0.2 s in JET plasmas with densities up to ~5 × 1019 m-3. Measurements with high time resolution show that ITB triggering events happen before 'grand' ACs in the majority of JET discharges, indicating that this improvement in confinement is likely to be associated with the decrease in the density of rational magnetic surfaces just before qmin(t) passes an integer value. Experimentally observed ACs excited by sub-Alfvénic NBI-produced ions with parallel velocities as low as V||NBI ap 0.2 · VA are found to be most likely associated with the geodesic acoustic effect that significantly modifies the shear-Alfvén dispersion relation at low frequency. Experiments were performed with a tritium NBI-blip (short time pulse) into JET plasmas with NBI-driven ACs. Although considerable NBI-driven AC activity was present, good agreement was found both in the radial profile and in the time evolution of DT neutrons between the neutron measurements and the TRANSP code modelling based on the Coulomb collision model, indicating the ACs have at most a small effect on fast particle confinement in this case.

Electron magnetic reconnection without ion coupling in Earth's turbulent magnetosheath.

PubMed

Phan, T D; Eastwood, J P; Shay, M A; Drake, J F; Sonnerup, B U Ö; Fujimoto, M; Cassak, P A; Øieroset, M; Burch, J L; Torbert, R B; Rager, A C; Dorelli, J C; Gershman, D J; Pollock, C; Pyakurel, P S; Haggerty, C C; Khotyaintsev, Y; Lavraud, B; Saito, Y; Oka, M; Ergun, R E; Retino, A; Le Contel, O; Argall, M R; Giles, B L; Moore, T E; Wilder, F D; Strangeway, R J; Russell, C T; Lindqvist, P A; Magnes, W

2018-05-01

Magnetic reconnection in current sheets is a magnetic-to-particle energy conversion process that is fundamental to many space and laboratory plasma systems. In the standard model of reconnection, this process occurs in a minuscule electron-scale diffusion region 1,2 . On larger scales, ions couple to the newly reconnected magnetic-field lines and are ejected away from the diffusion region in the form of bi-directional ion jets at the ion Alfvén speed 3-5 . Much of the energy conversion occurs in spatially extended ion exhausts downstream of the diffusion region 6 . In turbulent plasmas, which contain a large number of small-scale current sheets, reconnection has long been suggested to have a major role in the dissipation of turbulent energy at kinetic scales 7-11 . However, evidence for reconnection plasma jetting in small-scale turbulent plasmas has so far been lacking. Here we report observations made in Earth's turbulent magnetosheath region (downstream of the bow shock) of an electron-scale current sheet in which diverging bi-directional super-ion-Alfvénic electron jets, parallel electric fields and enhanced magnetic-to-particle energy conversion were detected. Contrary to the standard model of reconnection, the thin reconnecting current sheet was not embedded in a wider ion-scale current layer and no ion jets were detected. Observations of this and other similar, but unidirectional, electron jet events without signatures of ion reconnection reveal a form of reconnection that can drive turbulent energy transfer and dissipation in electron-scale current sheets without ion coupling.

Diagnostics for the plasma liner experiment.

PubMed

Lynn, A G; Merritt, E; Gilmore, M; Hsu, S C; Witherspoon, F D; Cassibry, J T

2010-10-01

The goal of the Plasma Liner Experiment (PLX) is to explore and demonstrate the feasibility of forming imploding spherical "plasma liners" via merging high Mach number plasma jets to reach peak liner pressures of ∼0.1 Mbar using ∼1.5 MJ of initial stored energy. Such a system would provide HED plasmas for a variety of fundamental HEDLP, laboratory astrophysics, and materials science studies, as well as a platform for experimental validation of rad-hydro and rad-MHD simulations. It could also prove attractive as a potential standoff driver for magnetoinertial fusion. Predicted parameters from jet formation to liner stagnation cover a large range of plasma density and temperature, varying from n(i)∼10(16) cm(-3), T(e)≈T(i)∼1 eV at the plasma gun mouth to n(i)>10(19) cm(-3), T(e)≈T(i)∼0.5 keV at stagnation. This presents a challenging problem for the plasma diagnostics suite which will be discussed.

Study and optimization of lower hybrid wave coupling in advanced scenario plasmas in JET

NASA Astrophysics Data System (ADS)

Pericoli Ridolfini, V.; Ekedahl, A.; Erents, S. K.; Mailloux, J.; Podda, S.; Sarazin, Y.; Tuccillo, A. A.; Workprogramme contributors, EFDA-JET

2004-02-01

Active current drive with lower hybrid (LH) waves in the advanced scenario plasmas at JET-EFDA was successful after a systematic study of the coupling problems that derive from the H-mode features of the edge plasma, namely very low density and ELM activity. The LH coupling has been improved compared to the past, by making the edge plasma in front of the LH launcher denser and more uniform. Injecting deuterated methane (CD4) from a nearby gas pipe increases the density in front of the LH launcher at least by a factor of 1.5, above the cut-off value for the LH frequency. A better matching of the plasma shape to that of the LH antenna makes the plasma ahead of the LH launcher more regular along the poloidal angle. These two techniques together have permitted a balanced supply of the three LH grills, with an average reflection below 4%, as in the previous L-mode operation. CD4 does not affect the performances nor does it contaminate the main plasma up to the maximum flow rate so far used, \\Phi_{CD_4}>10^{22}el\\,s^{-1} and now it is routinely applied in JET (up to 4 MW have been injected for longer than 8 s) with very encouraging results for LHCD. Even though CD4 is not suitable for ITER for tritium retention, the possibility of controlling locally and safely the scrape-off plasma density has been demonstrated.

Estimation of Flow Channel Parameters for Flowing Gas Mixed with Air in Atmospheric-pressure Plasma Jets

NASA Astrophysics Data System (ADS)

Yambe, Kiyoyuki; Saito, Hidetoshi

2017-12-01

When the working gas of an atmospheric-pressure non-equilibrium (cold) plasma flows into free space, the diameter of the resulting flow channel changes continuously. The shape of the channel is observed through the light emitted by the working gas of the atmospheric-pressure plasma. When the plasma jet forms a conical shape, the diameter of the cylindrical shape, which approximates the conical shape, defines the diameter of the flow channel. When the working gas flows into the atmosphere from the inside of a quartz tube, the gas mixes with air. The molar ratio of the working gas and air is estimated from the corresponding volume ratio through the relationship between the diameter of the cylindrical plasma channel and the inner diameter of the quartz tube. The Reynolds number is calculated from the kinematic viscosity of the mixed gas and the molar ratio. The gas flow rates for the upper limit of laminar flow and the lower limit of turbulent flow are determined by the corresponding Reynolds numbers estimated from the molar ratio. It is confirmed that the plasma jet length and the internal plasma length associated with strong light emission increase with the increasing gas flow rate until the rate for the upper limit of laminar flow and the lower limit of turbulent flow, respectively. Thus, we are able to explain the increasing trend in the plasma lengths with the diameter of the flow channel and the molar ratio by using the cylindrical approximation.

Plasma parameters of the cathode spot explosive electron emission cell obtained from the model of liquid-metal jet tearing and electrical explosion

NASA Astrophysics Data System (ADS)

Tsventoukh, M. M.

2018-05-01

A model has been developed for the explosive electron emission cell pulse of a vacuum discharge cathode spot that describes the ignition and extinction of the explosive pulse. The pulse is initiated due to hydrodynamic tearing of a liquid-metal jet which propagates from the preceding cell crater boundary and draws the ion current from the plasma produced by the preceding explosion. Once the jet neck has been resistively heated to a critical temperature (˜1 eV), the plasma starts expanding and decreasing in density, which corresponds to the extinction phase. Numerical and analytical solutions have been obtained that describe both the time behavior of the pulse plasma parameters and their average values. For the cell plasma, the momentum per transferred charge has been estimated to be some tens of g cm/(s C), which is consistent with the known measurements of ion velocity, ion erosion rate, and specific recoil force. This supports the model of the pressure-gradient-driven plasma acceleration mechanism for the explosive cathode spot cells. The ohmic electric field within the explosive current-carrying plasma has been estimated to be some tens of kV/cm, which is consistent with the known experimental data on cathode potential fall and explosive cell plasma size. This supports the model that assumes the ohmic nature of the cathode potential fall in a vacuum discharge.

Study of atmospheric plasma spray process with the emphasis on gas-shrouded nozzles

NASA Astrophysics Data System (ADS)

Jankovic, Miodrag M.

An atmospheric plasma spraying process is investigated in this work by using experimental approach and mathematical modelling. Emphasis was put on the gas shrouded nozzles, their design, and the protection against the mixing with the surrounding air, which they give to the plasma jet. First part of the thesis is dedicated to the analysis of enthalpy probe method, as a major diagnostic tool in this work. Systematic error in measuring the stagnation pressure, due to a big temperature difference between the plasma and the water-cooled probe, is investigated here. Parallel measurements with the enthalpy probe and an uncooled ceramic probe were performed. Also, numerical experiments were conducted, using the k-ɛ model of turbulence. Based on the obtained results, a compensating algorithm for the above error is suggested. Major objective of the thesis was to study the plasma spraying process, and potential benefits from using the gas shrouded nozzles. Mathematical modelling was used to perform the parametric study on the flow pattern inside these nozzles. Two nozzles were used: a commercial conical nozzle, and a custom-made curvilinear nozzle. The later is aimed towards elimination of the cold air entrainment, recorded for the conical nozzle. Also, parametric study on the shrouding gas and its interaction with the plasma jet was carried out. Two modes of the shrouding gas injection were tested: through sixteen injection ports, and through a continuous slot, surrounding the plasma jet. Both nozzles and both injection modes were thoroughly tested, experimentally and numerically. The curvilinear nozzle completely eliminates the cold air entrainment and yields significantly higher plasma temperature. Also, injection through the continuous slot resulted in a much better protection of the plasma jet. Both nozzles were used to perform the spraying tests. Obtained coatings were tested on porosity, adhesion strength, and micro- structure. These tests indicated better micro-structure of the coatings sprayed by the curvilinear nozzle. Also, their porosity was significantly lower, and the adhesion strength was higher for more than 25%. The overall results suggest that the curvilinear nozzles represent a much better solution for the gas shrouded plasma spraying.

Effects of the pulse width on the reactive species production and DNA damage in cancer cells exposed to atmospheric pressure microsecond-pulsed helium plasma jets

NASA Astrophysics Data System (ADS)

Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Kang, Tae Hong; Chung, T. H.

2017-08-01

Plasma-liquid and plasma-cell interactions were investigated using an atmospheric pressure dc microsecond-pulsed helium plasma jet. We investigated the effects of the electrical parameters such as applied voltage and pulse width (determined by the pulse frequency and duty ratio) on the production of reactive species in the gas/liquid phases and on the DNA damage responses in the cancer cells. The densities of reactive species including OH radicals were estimated inside the plasma-treated liquids using a chemical probe method, and the nitrite concentration was detected by Griess assay. Importantly, the more concentration of OH resulted in the more DNA base oxidation and breaks in human lung cancer A549 cells. The data are very suggestive that there is strong correlation between the production of OH in the plasmas/liquids and the DNA damage.

Radial Profiles of the Plasma Electron Characteristics in a 30 kW Arc Jet

NASA Technical Reports Server (NTRS)

Codron, Douglas A.; Nawaz, Anuscheh

2013-01-01

The present effort aims to strengthen modeling work conducted at the NASA Ames Research Center by measuring the critical plasma electron characteristics within and slightly outside of an arc jet plasma column. These characteristics are intended to give physical insights while assisting in the formulation of boundary conditions to validate full scale simulations. Single and triple Langmuir probes have been used to achieve estimates of the electron temperature (T(sub e)), electron number density (n(sub e)) and plasma potential (outside of the plasma column) as probing location is varied radially from the flow centerline. Both the electron temperature and electron number density measurements show a large dependence on radial distance from the plasma column centerline with T(sub e) approx. = (3 - 12 eV and n(sub e) approx. = 10(exp 12) - 10(exp 14)/cu cm.

Coanda-Assisted Spray Manipulation Collar for a Commercial Plasma Spray Gun

NASA Astrophysics Data System (ADS)

Mabey, K.; Smith, B. L.; Whichard, G.; McKechnie, T.

2011-06-01

A Coanda-assisted Spray Manipulation (CSM) collar was retrofitted to a Praxair SG-100 plasma spray gun. The CSM device makes it possible to change the direction of (vector) the plasma jet and powder without moving the gun. The two-piece retrofit device replaces the standard faceplate. Two separate collars were tested: one designed for small vector angles and one for larger vector angles. It was demonstrated that the small-angle device could modify the trajectory of zirconia powder up to several degrees. Doing so could realign the plasma with the powder resulting in increased powder temperature and velocity. The large-angle device was capable of vectoring the plasma jet up to 45°. However, the powder did not vector as much. Under large-angle vectoring, the powder velocity and temperature decreased steadily with vector angle. Both devices were tested using a supersonic configuration to demonstrate that CSM is capable of vectoring supersonic plasmas.

Design and characterization of an RF excited micro atmospheric pressure plasma jet for reference in plasma medicine

NASA Astrophysics Data System (ADS)

Schulz-von der Gathen, Volker

2015-09-01

Over the last decade a huge variety of atmospheric pressure plasma jets has been developed and applied for plasma medicine. The efficiency of these non-equilibrium plasmas for biological application is based on the generated amounts of reactive species and radiation. The gas temperatures stay within a range tolerable for temperature-sensitive tissues. The variety of different discharge geometries complicates a direct comparison. In addition, in plasma-medicine the combination of plasma with reactive components, ambient air, as well as biologic tissue - typically also incorporating fluids - results in a complex system. Thus, real progress in plasma-medicine requires a profound knowledge of species, their fluxes and processes hitting biological tissues. That will allow in particular the necessary tailoring of the discharge to fit the conditions. The complexity of the problem can only be overcome by a common effort of many groups and requires a comparison of their results. A reference device based on the already well-investigated micro-scaled atmospheric pressure plasma jet is presented. It is developed in the frame of the European COST initiative MP1101 to establish a publicly available, stable and reproducible source, where required plasma conditions can be investigated. Here we present the design and the ideas behind. The presentation discusses the requirements for the reference source and operation conditions. Biological references are also defined by the initiative. A specific part of the talk will be attributed to the reproducibility of results from various samples of the device. Funding by the DFG within the Package Project PAK816 ``Plasma Cell Interaction in Dermatology'' and the Research Unit FOR 1123 ``Physics of microplasmas'' is gratefully acknowledged.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vincena, Stephen

The aim of the original proposal was a basic plasma study to experimentally investigate the fundamental physics of how dense, fast-flowing, and field-aligned jets of plasma couple energy and momentum to a much larger, ambient, magnetized plasma. Coupling channels that were explored included bulk plasma heating and flow generation; shock wave production; and wave radiation, particularly in the form of shear and compressional Alfvén waves. The wave radiation, particularly to shear Alfvén waves was successfully modeled using the 3D Particle-In-Cell code, OSIRIS. Experimentally, these jets were produced via pulsed Nd:YAG laser ablation of solid carbon (graphite) rods, which were immersedmore » in the main plasma column of the Large Plasma Device (LaPD) at UCLA’s Basic Plasma Science Facility (BaPSF.) The axial expansion of the laser-produced plasma (LPP) was supersonic and with parallel expansion speeds approximately equal to the Alfvén speed. The project was renewed and refocused efforts to then utilize the laser-produced plasmas as a tool for the disruption and reconnection of current sheets in magnetized plasmas« less

Simultaneous Cotton-Mouton and Faraday rotation angle measurements on JET

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boboc, A.; Zabeo, L.; Murari, A.

The change in the ellipticity of a laser beam that passes through plasma due to the Cotton-Mouton effect can provide additional information on the plasma density. This approach, complementary to the more traditional interferometric methods, has been implemented recently using the JET interferometer-polarimeter with a new setup. Routine Cotton-Mouton phase shift measurements are made on the vertical central chords simultaneously with the Faraday rotation angle data. These new data are used to provide robust line-integrated density measurements in difficult plasma scenarios, with strong Edge Localized Modes (ELMs) or pellets. These always affect interferometry, causing fringe jumps and preventing good controlmore » of the plasma density. A comparison of line-integrated density from polarimetry and interferometry measurements shows an agreement within 10%. Moreover, in JET the measurements can be performed close to a reactor relevant range of parameters, in particular, at high densities and temperatures. This provides a unique opportunity to assess the quality of the Faraday rotation and Cotton-Mouton phase shift measurements where both effects are strong and mutual nonlinear interaction between the two effects takes place.« less

Proton acceleration by multi-terawatt interaction with a near-critical density hydrogen jet

NASA Astrophysics Data System (ADS)

Goers, Andy; Feder, Linus; Hine, George; Salehi, Fatholah; Woodbury, Daniel; Su, J. J.; Papadopoulos, Dennis; Zigler, Arie; Milchberg, Howard

2016-10-01

We investigate the high intensity laser interaction with thin, near critical density plasmas as a means of efficient acceleration of MeV protons. A promising mechanism is magnetic vortex acceleration, where the ponderomotive force of a tightly focused laser pulse drives a relativistic electron current which generates a strong azimuthal magnetic field. The rapid expansion of this azimuthal magnetic field at the back side of the target can accelerate plasma ions to MeV scale energies. Compared to typical ion acceleration experiments utilizing a laser- thin solid foil interaction, magnetic vortex acceleration in near critical density plasma may be realized in a high density gas jet, making it attractive for applications requiring high repetition rates. We present preliminary experiments studying laser-plasma interaction and proton acceleration in a thin (< 200 μm) near-critical density hydrogen gas jet delivering electron densities 1020 -1021 cm-3 . This research was funded by the United States Department of Energy and the Defense Advanced Research Projects Agency (DARPA) under Contract Number W911-NF-15-C-0217, issued by the Army Research Office.

On the magnetized disruption of inertially-confined plasma flows

NASA Astrophysics Data System (ADS)

Manuel, Mario; Kuranz, Carolyn; Rasmus, Alexander; Klein, Sallee; MacDonald, Michael; Trantham, Matt; Fein, Jeff; Belancourt, Patrick; Young, Rachel; Keiter, Paul; Drake, R. Paul; Pollock, Brad; Park, Jaebum; Hazi, Andrew; Williams, Jackson; Chen, Hui

2016-10-01

The creation and disruption of inertially-collimated plasma flows is investigated through experiment, simulation, and analytical modeling. Laser-generated plasma-jets are shown to be disrupted by an applied 5T B-field along the jet axis. An analytical model of the system describes the disruption mechanism through the competing effects of B-field advection and diffusion. These results indicate that for Rem 10-100, the ratio of inertial to magnetic pressures plays an important role in determining whether a jet is formed, but at high enough Rem , axial B-field amplification prevents inertial collimation altogether. This work is funded by the U.S. DOE, through the NNSA-DS and SC-OFES Joint Program in HED Laboratory Plasmas, Grant Number DE-NA0001840 and in collaboration with LLNL under contract DE-AC52-07NA27344. Support for this work was provided by NASA, under contract NAS8-03060, through Einstein Postdoctoral Fellowship Grant Number PF3-140111. Software used in this work was developed in part by the DOE NNSA ASC- and DOE Office of Science ASCR-supported Flash Center.

A key to improved ion core confinement in the JET tokamak: ion stiffness mitigation due to combined plasma rotation and low magnetic shear.

PubMed

Mantica, P; Angioni, C; Challis, C; Colyer, G; Frassinetti, L; Hawkes, N; Johnson, T; Tsalas, M; deVries, P C; Weiland, J; Baiocchi, B; Beurskens, M N A; Figueiredo, A C A; Giroud, C; Hobirk, J; Joffrin, E; Lerche, E; Naulin, V; Peeters, A G; Salmi, A; Sozzi, C; Strintzi, D; Staebler, G; Tala, T; Van Eester, D; Versloot, T

2011-09-23

New transport experiments on JET indicate that ion stiffness mitigation in the core of a rotating plasma, as described by Mantica et al. [Phys. Rev. Lett. 102, 175002 (2009)] results from the combined effect of high rotational shear and low magnetic shear. The observations have important implications for the understanding of improved ion core confinement in advanced tokamak scenarios. Simulations using quasilinear fluid and gyrofluid models show features of stiffness mitigation, while nonlinear gyrokinetic simulations do not. The JET experiments indicate that advanced tokamak scenarios in future devices will require sufficient rotational shear and the capability of q profile manipulation.

A Source for Fuel Supply to a Fusion Reactor Core

NASA Astrophysics Data System (ADS)

Voronin, A. V.; Bakharev, N. N.; Gusev, V. K.; Novokhatskii, A. N.; Ponyaev, S. A.

2018-05-01

We present the results of studies of the plasma source based on the coaxial accelerator with the slothole channel geometry for plasma acceleration and working gas inlet into the accelerator via the electrodynamic valve. The plasma parameters at the output of the accelerator are measured. The slot-hole channel of the accelerator created higher jet pressure, as compared to the coaxial channel, especially at large distances from the source. The jet pressure reached 106 N/m2 at a distance of 0.7 m. The source created moderately pure plasma for a current below 80 kA. The density was (2.5-5) × 1022 m-3, which was higher than the density obtained with the coaxial gun.

Runaway Electrons Modeling and Nanoparticle Plasma Jet Penetration into Tokamak Plasma

NASA Astrophysics Data System (ADS)

Galkin, S. A.; Bogatu, I. N.

2017-10-01

A novel idea to probe runaway electrons (REs) by superfast injection of high velocity nanoparticle plasma jet (NPPJ) from a plasma accelerator needs to be sustained by both RE dynamics modeling and simulation of NPPJ penetration through increasing tokamak magnetic field. We present our recent progress in both areas. RE simulation is based on the model, including Dreicer and ``avalanche'' mechanisms of RE generation, with emphasis on high Zeff effects. The high-density hyper-velocity C60 and BN NPPJ penetration through transversal B-field is conducted with the Hybrid Electro-Magnetic code (HEM-2D) in cylindrical coordinates, with 1/R B-field dependence for both DIII-D and ITER tokamaks. Work is supported in part by US DOE SBIR Grant.

Characteristic effects onto C13H12N2O3 molecule dissolved in solvents of argon plasma at atmospheric pressure

NASA Astrophysics Data System (ADS)

Tanışlı, Murat; Taşal, Erol

2017-07-01

We could easily argue that the decomposition of the chemical chain molecules is a compelling application when it comes to the atmospheric pressure plasma. In this paper, we have investigated the effect of the atmospheric pressure argon plasma on 4-((2-methoxyphenyl)diazenyl)benzene-1,3,-diol molecule (abbreviated as 4MBD) at room temperature. 4MBD molecule is one of the industrial dye molecules used widely. When considering the ecological life, this molecule is very harmful and dangerous. As such, we suggest a new decomposing method for such molecules. Atmospheric pressure plasma jet is principally treated for the breakdown of the molecule in question. Fourier transform infrared spectrometry and UV-Vis spectrophotometry tools are used to characterization of the molecules subsequent to the plasma applications to 4MBD molecule in ethanol and methanol solvents. The atmospheric-pressure plasma jet of argon (Ar) as non-equilibrium has been formed by ac-power generator with frequency—24 kHz and voltage—12 kV. Characterizations for solutions prepared with ethanol and methanol solvents of 4MBD molecule have been examined after applying ( duration 3 min) the atmospheric pressure plasma jet. The molecule is broken at 6C-7N-8N=9C stretching peak in consequence of the plasma treatment. The new plasma photo-products for ethanol and methanol solutions are produced as 6C-7N-8N=9C (strong, varying) and 12C=17O (strong, wide) stretching peaks. Also, the bathochromic drifts are discerned.

Qualification of tungsten coatings on plasma-facing components for JET

NASA Astrophysics Data System (ADS)

Maier, H.; Neu, R.; Greuner, H.; Böswirth, B.; Balden, M.; Lindig, S.; Matthews, G. F.; Rasinski, M.; Wienhold, P.; Wiltner, A.

2009-12-01

This contribution summarizes the work that has been performed to establish the industrial production of tungsten coatings on carbon fibre composite (CFC) for application within the ITER-like Wall Project at JET. This comprises the investigation of vacuum plasma-sprayed coatings, physical vapour deposited tungsten/rhenium multilayers, as well as coatings deposited by combined magnetron-sputtering and ion implantation. A variety of analysis tools were applied to investigate failures and oxide and carbide formation in these systems.

PHOTOSPHERIC ABUNDANCES OF POLAR JETS ON THE SUN OBSERVED BY HINODE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Kyoung-Sun; Brooks, David H.; Imada, Shinsuke, E-mail: lksun@solar.isas.jaxa.jp

2015-08-20

Many jets are detected at X-ray wavelengths in the Sun's polar regions, and the ejected plasma along the jets has been suggested to contribute mass to the fast solar wind. From in situ measurements in the magnetosphere, it has been found that the fast solar wind has photospheric abundances while the slow solar wind has coronal abundances. Therefore, we investigated the abundances of polar jets to determine whether they are the same as that of the fast solar wind. For this study, we selected 22 jets in the polar region observed by Hinode/EUV Imaging Spectroscopy (EIS) and X-ray Telescope (XRT)more » simultaneously on 2007 November 1–3. We calculated the First Ionization Potential (FIP) bias factor from the ratio of the intensity between high (S) and low (Si, Fe) FIP elements using the EIS spectra. The values of the FIP bias factors for the polar jets are around 0.7–1.9, and 75% of the values are in the range of 0.7–1.5, which indicates that they have photospheric abundances similar to the fast solar wind. The results are consistent with the reconnection jet model where photospheric plasma emerges and is rapidly ejected into the fast wind.« less

3-D RPIC simulations of relativistic jets: Particle acceleration, magnetic field generation, and emission

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.

2006-01-01

Nonthermal radiation observed from astrophysical systems containing (relativistic) jets and shocks, e.g., supernova remnants, active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the .shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. We will review recent PIC simulations which show particle acceleration in jets.

Lightweight Portable Plasma Medical Device - Plasma Engineering Research Laboratory

DTIC Science & Technology

2013-10-01

Engineering Research Laboratory has made a momentous advancement on meeting the proposed milestones. The project has two objectives, in which the ...pressure plasma jet based on a dielectric barrier discharge configuration. The plasma and biological testing and characterization are in progress...1(b). Direct exposure of plasma involves, exposure of plasma directly on to a target treatment surface whereas the indirect plasma exposure involves

Scaled laboratory experiments explain the kink behaviour of the Crab Nebula jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, C. K.; Tzeferacos, P.; Lamb, D.

X-ray images from the Chandra X-ray Observatory show that the South-East jet in the Crab nebula changes direction every few years. This remarkable phenomenon is also observed in jets associated with pulsar wind nebulae and other astrophysical objects, and therefore is a fundamental feature of astrophysical jet evolution that needs to be understood. Theoretical modeling and numerical simulations have suggested that this phenomenon may be a consequence of magnetic fields (B) and current-driven magnetohydrodynamic (MHD) instabilities taking place in the jet, but until now there has been no verification of this process in a controlled laboratory environment. Here we reportmore » the first such experiments, using scaled laboratory plasma jets generated by high-power lasers to model the Crab jet and monoenergetic-proton radiography to provide direct visualization and measurement of magnetic fields and their behavior. The toroidal magnetic field embedded in the supersonic jet triggered plasma instabilities and resulted in considerable deflections throughout the jet propagation, mimicking the kinks in the Crab jet. We also demonstrated that these kinks are stabilized by high jet velocity, consistent with the observation that instabilities alter the jet orientation but do not disrupt the overall jet structure. We successfully modeled these laboratory experiments with a validated three-dimensional (3D) numerical simulation, which in conjunction with the experiments provide compelling evidence that we have an accurate model of the most important physics of magnetic fields and MHD instabilities in the observed, kinked jet in the Crab nebula. The experiments initiate a novel approach in the laboratory for visualizing fields and instabilities associated with jets observed in various astrophysical objects, ranging from stellar to extragalactic systems. We expect that future work along this line will have important impact on the study and understanding of such fundamental astrophysical phenomena.« less

Scaled laboratory experiments explain the kink behaviour of the Crab Nebula jet

DOE PAGES

Li, C. K.; Tzeferacos, P.; Lamb, D.; ...

2016-10-07

X-ray images from the Chandra X-ray Observatory show that the South-East jet in the Crab nebula changes direction every few years. This remarkable phenomenon is also observed in jets associated with pulsar wind nebulae and other astrophysical objects, and therefore is a fundamental feature of astrophysical jet evolution that needs to be understood. Theoretical modeling and numerical simulations have suggested that this phenomenon may be a consequence of magnetic fields (B) and current-driven magnetohydrodynamic (MHD) instabilities taking place in the jet, but until now there has been no verification of this process in a controlled laboratory environment. Here we reportmore » the first such experiments, using scaled laboratory plasma jets generated by high-power lasers to model the Crab jet and monoenergetic-proton radiography to provide direct visualization and measurement of magnetic fields and their behavior. The toroidal magnetic field embedded in the supersonic jet triggered plasma instabilities and resulted in considerable deflections throughout the jet propagation, mimicking the kinks in the Crab jet. We also demonstrated that these kinks are stabilized by high jet velocity, consistent with the observation that instabilities alter the jet orientation but do not disrupt the overall jet structure. We successfully modeled these laboratory experiments with a validated three-dimensional (3D) numerical simulation, which in conjunction with the experiments provide compelling evidence that we have an accurate model of the most important physics of magnetic fields and MHD instabilities in the observed, kinked jet in the Crab nebula. The experiments initiate a novel approach in the laboratory for visualizing fields and instabilities associated with jets observed in various astrophysical objects, ranging from stellar to extragalactic systems. We expect that future work along this line will have important impact on the study and understanding of such fundamental astrophysical phenomena.« less

Atmospheric-pressure plasma jets: Effect of gas flow, active species, and snake-like bullet propagation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, S.; Wang, Z.; Huang, Q.

2013-02-15

Cold atmospheric-pressure plasma jets have recently attracted enormous interest owing to numerous applications in plasma biology, health care, medicine, and nanotechnology. A dedicated study of the interaction between the upstream and downstream plasma plumes revealed that the active species (electrons, ions, excited OH, metastable Ar, and nitrogen-related species) generated by the upstream plasma plume enhance the propagation of the downstream plasma plume. At gas flows exceeding 2 l/min, the downstream plasma plume is longer than the upstream plasma plume. Detailed plasma diagnostics and discharge species analysis suggest that this effect is due to the electrons and ions that are generatedmore » by the upstream plasma and flow into the downstream plume. This in turn leads to the relatively higher electron density in the downstream plasma. Moreover, high-speed photography reveals a highly unusual behavior of the plasma bullets, which propagate in snake-like motions, very differently from the previous reports. This behavior is related to the hydrodynamic instability of the gas flow, which results in non-uniform distributions of long-lifetime active species in the discharge tube and of surface charges on the inner surface of the tube.« less

An elevation of 0.1 light-seconds for the optical jet base in an accreting Galactic black hole system

NASA Astrophysics Data System (ADS)

Gandhi, P.; Bachetti, M.; Dhillon, V. S.; Fender, R. P.; Hardy, L. K.; Harrison, F. A.; Littlefair, S. P.; Malzac, J.; Markoff, S.; Marsh, T. R.; Mooley, K.; Stern, D.; Tomsick, J. A.; Walton, D. J.; Casella, P.; Vincentelli, F.; Altamirano, D.; Casares, J.; Ceccobello, C.; Charles, P. A.; Ferrigno, C.; Hynes, R. I.; Knigge, C.; Kuulkers, E.; Pahari, M.; Rahoui, F.; Russell, D. M.; Shaw, A. W.

2017-12-01

Relativistic plasma jets are observed in many systems that host accreting black holes. According to theory, coiled magnetic fields close to the black hole accelerate and collimate the plasma, leading to a jet being launched1-3. Isolating emission from this acceleration and collimation zone is key to measuring its size and understanding jet formation physics. But this is challenging because emission from the jet base cannot easily be disentangled from other accreting components. Here, we show that rapid optical flux variations from an accreting Galactic black-hole binary are delayed with respect to X-rays radiated from close to the black hole by about 0.1 seconds, and that this delayed signal appears together with a brightening radio jet. The origin of these subsecond optical variations has hitherto been controversial4-8. Not only does our work strongly support a jet origin for the optical variations but it also sets a characteristic elevation of ≲103 Schwarzschild radii for the main inner optical emission zone above the black hole9, constraining both internal shock10 and magnetohydrodynamic11 models. Similarities with blazars12,13 suggest that jet structure and launching physics could potentially be unified under mass-invariant models. Two of the best-studied jetted black-hole binaries show very similar optical lags8,14,15, so this size scale may be a defining feature of such systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Liping; He, Jiansen; Tu, Chuanyi

Observations with the space-based solar observatory Hinode show that small-scale magnetic structures in the photosphere are found to be associated with a particular class of jets of plasma in the chromosphere called anemone jets. The goal of our study is to conduct a numerical experiment of such chromospheric anemone jets related to the moving magnetic features (MMFs). We construct a 2.5 dimensional numerical MHD model to describe the process of magnetic reconnection between the MMFs and the pre-existing ambient magnetic field, which is driven by the horizontal motion of the magnetic structure in the photosphere. We include thermal conduction parallelmore » to the magnetic field and optically thin radiative losses in the corona to account for a self-consistent description of the evaporation process during the heating of the plasma due to the reconnection process. The motion of the MMFs leads to the expected jet and our numerical results can reproduce many observed characteristics of chromospheric anemone jets, topologically and quantitatively. As a result of the tearing instability, plasmoids are generated in the reconnection process that are consistent with the observed bright moving blobs in the anemone jets. An increase in the thermal pressure at the base of the jet is also driven by the reconnection, which induces a train of slow-mode shocks propagating upward. These shocks are a secondary effect, and only modulate the outflow of the anemone jet. The jet itself is driven by the energy input due to the reconnection of the MMFs and the ambient magnetic field.« less