Particle Simulation of Pulsed Plasma Thruster Plumes

National Research Council Canada - National Science Library

Boyd, Ian

2002-01-01

.... Our modeling had made progress in al aspects of simulating these complex devices including Teflon ablation, plasma formation, electro-magnetic acceleration, plume expansion, and particulate transport...

Laser-generated plasma plume expansion: Combined continuous-microscopic modeling

Science.gov (United States)

Itina, Tatiana E.; Hermann, Jörg; Delaporte, Philippe; Sentis, Marc

2002-12-01

The physical phenomena involved in the interaction of a laser-generated plasma plume with a background gas are studied numerically. A three-dimensional combined model is developed to describe the plasma plume formation and its expansion in vacuum or into a background gas. The proposed approach takes advantages of both continuous and microscopic descriptions. The simulation technique is suitable for the simulation of high-rate laser ablation for a wide range of background pressure. The model takes into account the mass diffusion and the energy exchange between the ablated and background species, as well as the collective motion of the ablated species and the background-gas particles. The developed approach is used to investigate the influence of the background gas on the expansion dynamics of the plume obtained during the laser ablation of aluminum. At moderate pressures, both plume and gas compressions are weak and the process is mainly governed by the diffusive mixing. At higher pressures, the interaction is determined by the plume-gas pressure interplay, the plume front is strongly compressed, and its center exhibits oscillations. In this case, the snowplough effect takes place, leading to the formation of a compressed gas layer in front of the plume. The background pressure needed for the beginning of the snowplough effect is determined from the plume and gas density profiles obtained at various pressures. Simulation results are compared with experimentally measured density distributions. It is shown that the calculations suggest localized formation of molecules during reactive laser ablation.

Laser-generated plasma plume expansion: Combined continuous-microscopic modeling

International Nuclear Information System (INIS)

Itina, Tatiana E.; Hermann, Joerg; Delaporte, Philippe; Sentis, Marc

2002-01-01

The physical phenomena involved in the interaction of a laser-generated plasma plume with a background gas are studied numerically. A three-dimensional combined model is developed to describe the plasma plume formation and its expansion in vacuum or into a background gas. The proposed approach takes advantages of both continuous and microscopic descriptions. The simulation technique is suitable for the simulation of high-rate laser ablation for a wide range of background pressure. The model takes into account the mass diffusion and the energy exchange between the ablated and background species, as well as the collective motion of the ablated species and the background-gas particles. The developed approach is used to investigate the influence of the background gas on the expansion dynamics of the plume obtained during the laser ablation of aluminum. At moderate pressures, both plume and gas compressions are weak and the process is mainly governed by the diffusive mixing. At higher pressures, the interaction is determined by the plume-gas pressure interplay, the plume front is strongly compressed, and its center exhibits oscillations. In this case, the snowplough effect takes place, leading to the formation of a compressed gas layer in front of the plume. The background pressure needed for the beginning of the snowplough effect is determined from the plume and gas density profiles obtained at various pressures. Simulation results are compared with experimentally measured density distributions. It is shown that the calculations suggest localized formation of molecules during reactive laser ablation

EM Modelling of RF Propagation Through Plasma Plumes

Science.gov (United States)

Pandolfo, L.; Bandinelli, M.; Araque Quijano, J. L.; Vecchi, G.; Pawlak, H.; Marliani, F.

2012-05-01

Electric propulsion is a commercially attractive solution for attitude and position control of geostationary satellites. Hall-effect ion thrusters generate a localized plasma flow in the surrounding of the satellite, whose impact on the communication system needs to be qualitatively and quantitatively assessed. An electromagnetic modelling tool has been developed and integrated into the Antenna Design Framework- ElectroMagnetic Satellite (ADF-EMS). The system is able to guide the user from the plume definition phases through plume installation and simulation. A validation activity has been carried out and the system has been applied to the plume modulation analysis of SGEO/Hispasat mission.

Numerical modeling of plasma plume evolution against ambient background gas in laser blow off experiments

International Nuclear Information System (INIS)

Patel, Bhavesh G.; Das, Amita; Kaw, Predhiman; Singh, Rajesh; Kumar, Ajai

2012-01-01

Two dimensional numerical modelling based on simplified hydrodynamic evolution for an expanding plasma plume (created by laser blow off) against an ambient background gas has been carried out. A comparison with experimental observations shows that these simulations capture most features of the plasma plume expansion. The plume location and other gross features are reproduced as per the experimental observation in quantitative detail. The plume shape evolution and its dependence on the ambient background gas are in good qualitative agreement with the experiment. This suggests that a simplified hydrodynamic expansion model is adequate for the description of plasma plume expansion.

Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures

Science.gov (United States)

Jia, Xianzhe; Kivelson, Margaret G.; Khurana, Krishan K.; Kurth, William S.

2018-05-01

The icy surface of Jupiter's moon, Europa, is thought to lie on top of a global ocean1-4. Signatures in some Hubble Space Telescope images have been associated with putative water plumes rising above Europa's surface5,6, providing support for the ocean theory. However, all telescopic detections reported were made at the limit of sensitivity of the data5-7, thereby calling for a search for plume signatures in in-situ measurements. Here, we report in-situ evidence of a plume on Europa from the magnetic field and plasma wave observations acquired on Galileo's closest encounter with the moon. During this flyby, which dropped below 400 km altitude, the magnetometer8 recorded an approximately 1,000-kilometre-scale field rotation and a decrease of over 200 nT in field magnitude, and the Plasma Wave Spectrometer9 registered intense localized wave emissions indicative of a brief but substantial increase in plasma density. We show that the location, duration and variations of the magnetic field and plasma wave measurements are consistent with the interaction of Jupiter's corotating plasma with Europa if a plume with characteristics inferred from Hubble images were erupting from the region of Europa's thermal anomalies. These results provide strong independent evidence of the presence of plumes at Europa.

Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures

Science.gov (United States)

Jia, Xianzhe; Kivelson, Margaret G.; Khurana, Krishan K.; Kurth, William S.

2018-06-01

The icy surface of Jupiter's moon, Europa, is thought to lie on top of a global ocean1-4. Signatures in some Hubble Space Telescope images have been associated with putative water plumes rising above Europa's surface5,6, providing support for the ocean theory. However, all telescopic detections reported were made at the limit of sensitivity of the data5-7, thereby calling for a search for plume signatures in in-situ measurements. Here, we report in-situ evidence of a plume on Europa from the magnetic field and plasma wave observations acquired on Galileo's closest encounter with the moon. During this flyby, which dropped below 400 km altitude, the magnetometer8 recorded an approximately 1,000-kilometre-scale field rotation and a decrease of over 200 nT in field magnitude, and the Plasma Wave Spectrometer9 registered intense localized wave emissions indicative of a brief but substantial increase in plasma density. We show that the location, duration and variations of the magnetic field and plasma wave measurements are consistent with the interaction of Jupiter's corotating plasma with Europa if a plume with characteristics inferred from Hubble images were erupting from the region of Europa's thermal anomalies. These results provide strong independent evidence of the presence of plumes at Europa.

Room-temperature atmospheric pressure plasma plume for biomedical applications

International Nuclear Information System (INIS)

Laroussi, M.; Lu, X.

2005-01-01

As low-temperature nonequilibrium plasmas come to play an increasing role in biomedical applications, reliable and user-friendly sources need to be developed. These plasma sources have to meet stringent requirements such as low temperature (at or near room temperature), no risk of arcing, operation at atmospheric pressure, preferably hand-held operation, low concentration of ozone generation, etc. In this letter, we present a device that meets exactly such requirements. This device is capable of generating a cold plasma plume several centimeters in length. It exhibits low power requirements as shown by its current-voltage characteristics. Using helium as a carrier gas, very little ozone is generated and the gas temperature, as measured by emission spectroscopy, remains at room temperature even after hours of operations. The plasma plume can be touched by bare hands and can be directed manually by a user to come in contact with delicate objects and materials including skin and dental gum without causing any heating or painful sensation

Modeling Laser and e-Beam Generated Plasma-Plume Experiments Using LASNEX

CERN Document Server

Ho, D

1999-01-01

The hydrodynamics code LASNEX is used to model the laser and e-beam generated plasma-plume experiments. The laser used has a wavelength of 1 (micro)m and the FWHM spot size is 1 mm. The total laser energy is 160 mJ. The simulation shows that the plume expands at a velocity of about 6 cm/(micro)s. The e-beam generated from the Experimental Test Accelerator (ETA) has 5.5 MeV and FWHM spot size ranges from 2 to 3.3 mm. From the simulations, the plasma plume expansion velocity ranges from about 3 to 6 mm/(micro)s and the velocity increases with decreasing spot size. All the simulation results reported here are in close agreement with experimental data.

Influence of the distance between target surface and focal point on the expansion dynamics of a laser-induced silicon plasma with spatial confinement

Science.gov (United States)

Zhang, Dan; Chen, Anmin; Wang, Xiaowei; Wang, Ying; Sui, Laizhi; Ke, Da; Li, Suyu; Jiang, Yuanfei; Jin, Mingxing

2018-05-01

Expansion dynamics of a laser-induced plasma plume, with spatial confinement, for various distances between the target surface and focal point were studied by the fast photography technique. A silicon wafer was ablated to induce the plasma with a Nd:YAG laser in an atmospheric environment. The expansion dynamics of the plasma plume depended on the distance between the target surface and focal point. In addition, spatially confined time-resolved images showed the different structures of the plasma plumes at different distances between the target surface and focal point. By analyzing the plume images, the optimal distance for emission enhancement was found to be approximately 6 mm away from the geometrical focus using a 10 cm focal length lens. This optimized distance resulted in the strongest compression ratio of the plasma plume by the reflected shock wave. Furthermore, the duration of the interaction between the reflected shock wave and the plasma plume was also prolonged.

A linear-field plasma jet for generating a brush-shaped laminar plume at atmospheric pressure

Energy Technology Data Exchange (ETDEWEB)

Li, Xuechen; Jia, Pengying, E-mail: plasmalab@126.com [College of Physics Science and Technology, Hebei University, Baoding 071002 (China); Key Laboratory of Photo-Electronics Information Materials of Hebei Province, Baoding 071002 (China); Li, Jiyuan; Chu, Jingdi; Zhang, Panpan [College of Physics Science and Technology, Hebei University, Baoding 071002 (China)

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 biomedical application.

Plasma Observations During the Mars Atmospheric Plume Event of March-April 2012

Science.gov (United States)

Andrews, D. J.; Barabash, S.; Edberg, N. J. T.; Gurnett, D. A.; Hall, B. E. S.; Holmstrom, M.; Lester, M.; Morgan, D. D.; Opgenoorth, H. J.; Ramstad, R.;

The role of the gas/plasma plume and self-focusing in a gas-filled capillary discharge waveguide for high-power laser-plasma applications

CERN Document Server

Ciocarlan, C.; Islam, M. R.; Ersfeld, B.; Abuazoum, S.; Wilson, R.; Aniculaesei, C.; Welsh, G. H.; Vieux, G.; Jaroszynski, D. A.; 10.1063/1.4822333

2013-01-01

The role of the gas/plasma plume at the entrance of a gas-filled capillary discharge plasma waveguide in increasing the laser intensity has been investigated. Distinction is made between neutral gas and hot plasma plumes that, respectively, develop before and after discharge breakdown. Time-averaged measurements show that the on-axis plasma density of a fully expanded plasma plume over this region is similar to that inside the waveguide. Above the critical power, relativistic and ponderomotive selffocusing lead to an increase in the intensity, which can be nearly a factor of 2 compared with the case without a plume. When used as a laser plasma wakefield accelerator, the enhancement of intensity can lead to prompt electron injection very close to the entrance of the waveguide. Self-focusing occurs within two Rayleigh lengths of the waveguide entrance plane in the region, where the laser beam is converging. Analytical theory and numerical simulations show that, for a density of 3.01018 cm3, the peak normalized...

Langmuir probe measurement of the bismuth plasma plume formed by an extreme-ultraviolet pulsed laser

International Nuclear Information System (INIS)

Pira, P; Burian, T; Kolpaková, A; Tichý, M; Kudrna, P; Daniš, S; Wild, J; Juha, L; Lančok, J; Vyšín, L; Civiš, S; Zelinger, Z; Kubát, P

2014-01-01

Properties of the plasma plume produced on a bismuth (Bi) target irradiated by a focused extreme-ultraviolet (XUV) capillary-discharge laser beam were investigated. Langmuir probes were used in both single- and double-probe arrangements to determine the electron temperature and the electron density, providing values of 1–3 eV and ∼10 13 –10 14  m −3 , respectively. Although the temperatures seem to be comparable with values obtained in ablation plasmas produced by conventional, long-wavelength lasers, the density is significantly lower. This finding indicates that the desorption-like phenomena are responsible for the plume formation rather than the ablation processes. A very thin Bi film was prepared on an MgO substrate by pulsed XUV laser deposition. The non-uniform, sub-monolayer character of the deposited bismuth film confirms the Langmuir probe's observation of the desorption-like erosion induced by the XUV laser on the primary Bi target. (paper)

Multi-Pulse DARHT Machine-Plasma Plume Problem

International Nuclear Information System (INIS)

Lauer, E J

2004-01-01

The plasma current decay time constant is predicted to be short compared to the pulse length and so self-focusing is predicted for most of the beam pulse. Four- pulse beam envelopes for a high dose case require mitigation, those for a low dose case do not. Methods of mitigation are summarized. Hose instability growth in the plume length is predicted to be minimal

Dependence of high order harmonics intensity on laser focal spot position in preformed plasma plumes

International Nuclear Information System (INIS)

Singhal, H.; Ganeev, R.; Naik, P. A.; Arora, V.; Chakravarty, U.; Gupta, P. D.

2008-01-01

The dependence of the high-order harmonic intensity on the laser focal spot position in laser produced plasma plumes is experimentally studied. High order harmonics up to the 59th order (λ∼13.5 nm) were generated by focusing 48 fs laser pulses from a Ti:sapphire laser system in silver plasma plume produced using 300 ps uncompressed laser radiation as the prepulse. The intensity of harmonics nearly vanished when the best focus was located in the plume center, whereas it peaked on either side with unequal intensity. The focal spot position corresponding to the peak harmonic intensity moved away from the plume center for higher order harmonics. The results are explained in terms of the variation of phase mismatch between the driving laser beam and harmonics radiation produced, relativistic drift of electrons, and defocusing effect due to radial ionization gradient in the plasma for different focal spot positions

Investigation of the vapour-plasma plume in the welding of titanium by high-power ytterbium fibre laser radiation

Energy Technology Data Exchange (ETDEWEB)

Bykovskiy, D P; Petrovskii, V N; Uspenskiy, S A [National Research Nuclear University ' MEPhI' (Russian Federation)

2015-03-31

The vapour-plasma plume produced in the welding of 6-mm thick VT-23 titanium alloy plates by ytterbium fibre laser radiation of up to 10 kW power is studied in the protective Ar gas medium. High-speed video filming of the vapour-plasma plume is used to visualise the processes occurring during laser welding. The coefficient of inverse bremsstrahlung by the welding plasma plume is calculated from the data of the spectrometric study. (interaction of laser radiation with matter)

Prediction of fluctuating pressure environments associated with plume-induced separated flow fields

Science.gov (United States)

Plotkin, K. J.

1973-01-01

The separated flow environment induced by underexpanded rocket plumes during boost phase of rocket vehicles has been investigated. A simple semi-empirical model for predicting the extent of separation was developed. This model offers considerable computational economy as compared to other schemes reported in the literature, and has been shown to be in good agreement with limited flight data. The unsteady pressure field in plume-induced separated regions was investigated. It was found that fluctuations differed from those for a rigid flare only at low frequencies. The major difference between plume-induced separation and flare-induced separation was shown to be an increase in shock oscillation distance for the plume case. The prediction schemes were applied to PRR shuttle launch configuration. It was found that fluctuating pressures from plume-induced separation are not as severe as for other fluctuating environments at the critical flight condition of maximum dynamic pressure.

The search for active Europa plumes in Galileo plasma particle detector data: the E12 flyby

Science.gov (United States)

Huybrighs, H.; Roussos, E.; Krupp, N.; Fraenz, M.; Futaana, Y.; Barabash, S. V.; Glassmeier, K. H.

2017-12-01

Hubble Space Telescope observations of Europa's auroral emissions and transits in front of Jupiter suggest that recurring water vapour plumes originating from Europa's surface might exist. If conclusively proven, the discovery of these plumes would be significant, because Europa's potentially habitable ocean could be studied remotely by taking in-situ samples of these plumes from a flyby mission. The first opportunity to collect in-situ evidence of the plumes will not arise before the early 2030's when ESA's JUICE mission or NASA's Europa Clipper are set to arrive. However, it may be possible that NASA's Galileo mission has already encountered the plumes when it was active in the Jupiter system from 1995 to 2003. It has been suggested that the high plasma densities and anomalous magnetic fields measured during one of the Galileo flybys of Europa (flyby E12) could be connected to plume activity. In the context of the search for Europa plume signatures in Galileo particle data we present an overview of the in-situ plasma particle data obtained by the Galileo spacecraft during the E12 flyby. Focus is in particular on the data obtained with the plasma particle instruments PLS (low energy ions and electrons) and EPD (high energy ions and electrons). We search for signs of an extended exosphere/ionosphere that could be consistent with ongoing plume activity. The PLS data obtained during the E12 flyby show an extended interaction region between Europa and the plasma from Jupiter's magnetosphere, hinting at the existence of an extended ionosphere and exosphere. Furthermore we show how the EPD data are analyzed and modelled in order to evaluate whether a series of energetic ion depletions can be attributed to losses on the moon's surface or its neutral exosphere.

Cascade generation in Al laser induced plasma

Science.gov (United States)

Nagli, Lev; Gaft, Michael; Raichlin, Yosef; Gornushkin, Igor

2018-05-01

We found cascade IR generation in Al laser induced plasma. This generation includes doublet transitions 3s 25s 2S1/2 → 3s24p 2P1/2,3/2 → 3s24s 2S1/2; corresponding to strong lines at 2110 and 2117 nm, and much weaker lines at 1312-1315 nm. The 3s25s2S 1/2 starting IR generation level is directly pumped from the 3s23p 2P3/2 ground level. The starting level for UV generation at 396.2 nm (transitions 3s24s 2S1/2 → 4p 2P3/2) is populated due to the fast collisional processes in the plasma plume. These differences led to different time and special dependences on the lasing in the IR and UV spectral range within the aluminum laser induced plasma.

High-order harmonic generation in laser plasma plumes

CERN Document Server

Ganeev, Rashid A

2013-01-01

This book represents the first comprehensive treatment of high-order harmonic generation in laser-produced plumes, covering the principles, past and present experimental status and important applications. It shows how this method of frequency conversion of laser radiation towards the extreme ultraviolet range matured over the course of multiple studies and demonstrated new approaches in the generation of strong coherent short-wavelength radiation for various applications. Significant discoveries and pioneering contributions of researchers in this field carried out in various laser scientific centers worldwide are included in this first attempt to describe the important findings in this area of nonlinear spectroscopy. "High-Order Harmonic Generation in Laser Plasma Plumes" is a self-contained and unified review of the most recent achievements in the field, such as the application of clusters (fullerenes, nanoparticles, nanotubes) for efficient harmonic generation of ultrashort laser pulses in cluster-containin...

Resonance-enhanced laser-induced plasma spectroscopy: ambient gas effects

International Nuclear Information System (INIS)

Lui, S.L.; Cheung, N.H.

2003-01-01

When performing laser-induced plasma spectroscopy for elemental analysis, the sensitivity could be significantly enhanced if the plume was resonantly rekindled by a dye laser pulse. The extent of the enhancement was found to depend on the ambient gas. Air, nitrogen, helium, argon and xenon at pressures ranging from vacuum to 1 bar were investigated. In vacuum, the analyte signal was boosted because of reduced cooling, but it soon decayed as the plume freely expanded. By choosing the right ambient gas at the right pressure, the expanding plume could be confined as well as thermally insulated to maximize the analyte signal. For instance, an ambient of 13 mbar xenon yielded a signal-to-noise ratio of 110. That ratio was 53 when the pellet was ablated in air, and decreased further to 5 if the dye laser was tuned off resonance

Tidally induced lateral dispersion of the Storfjorden overflow plume

Directory of Open Access Journals (Sweden)

F. Wobus

2013-10-01

Full Text Available We investigate the flow of brine-enriched shelf water from Storfjorden (Svalbard into Fram Strait and onto the western Svalbard Shelf using a regional set-up of NEMO-SHELF, a 3-D numerical ocean circulation model. The model is set up with realistic bathymetry, atmospheric forcing, open boundary conditions and tides. The model has 3 km horizontal resolution and 50 vertical levels in the sh-coordinate system which is specially designed to resolve bottom boundary layer processes. In a series of modelling experiments we focus on the influence of tides on the propagation of the dense water plume by comparing results from tidal and non-tidal model runs. Comparisons of non-tidal to tidal simulations reveal a hotspot of tidally induced horizontal diffusion leading to the lateral dispersion of the plume at the southernmost headland of Spitsbergen which is in close proximity to the plume path. As a result the lighter fractions in the diluted upper layer of the plume are drawn into the shallow coastal current that carries Storfjorden water onto the western Svalbard Shelf, while the dense bottom layer continues to sink down the slope. This bifurcation of the plume into a diluted shelf branch and a dense downslope branch is enhanced by tidally induced shear dispersion at the headland. Tidal effects at the headland are shown to cause a net reduction in the downslope flux of Storfjorden water into the deep Fram Strait. This finding contrasts previous results from observations of a dense plume on a different shelf without abrupt topography.

Plume splitting and oscillatory behavior in transient plasmas generated by high-fluence laser ablation in vacuum

Science.gov (United States)

Focsa, C.; Gurlui, S.; Nica, P.; Agop, M.; Ziskind, M.

2017-12-01

We present a short overview of studies performed in our research groups over the last decade on the characterization of transient plasma plumes generated by laser ablation in various temporal regimes, from nanosecond to femtosecond. New results are also presented along with this overview, both being placed in the context of similar studies performed by other investigators. Optical (fast gate intensified CCD camera imaging and space- and time-resolved emission spectroscopy) and electrical (mainly Langmuir probe) methods have been applied to experimentally explore the dynamics of the plasma plume and its constituents. Peculiar effects as plume splitting and sharpening or oscillations onset have been evidenced in vacuum at high laser fluence. New theoretical approaches have been developed to account for the experimental observations.

Influence of the reactive atmosphere on the formation of nanoparticles in the plasma plume induced by nanosecond pulsed laser irradiation of metallic targets at atmospheric pressure and high repetition rate

Energy Technology Data Exchange (ETDEWEB)

Girault, M. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Univ. Bourgogne Franche-Comté, 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex (France); Le Garrec, J.-L.; Mitchell, J.B.A. [Institut de Physique de Rennes, UMR 6251 CNRS-Université de Rennes 1, 35042 Rennes Cedex (France); Jouvard, J.-M. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Univ. Bourgogne Franche-Comté, 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex (France); Carvou, E. [Institut de Physique de Rennes, UMR 6251 CNRS-Université de Rennes 1, 35042 Rennes Cedex (France); Menneveux, J.; Yu, J. [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne Cedex (France); Ouf, F.-X. [Institut de Radioprotection et de Sureté Nucléaire IRSN/PSN-RES/SCA/LPMA BP 68, 91192 Gif-Sur-Yvette (France); Carles, S. [Institut de Physique de Rennes, UMR 6251 CNRS-Université de Rennes 1, 35042 Rennes Cedex (France); Potin, V.; Pillon, G.; Bourgeois, S. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Univ. Bourgogne Franche-Comté, 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex (France); Perez, J. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, F-91192 Gif-sur-Yvette Cedex (France); Marco de Lucas, M.C., E-mail: delucas@u-bourgogne.fr [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Univ. Bourgogne Franche-Comté, 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex (France); and others

2016-06-30

Highlights: • NPs formed in a plasma-plume during laser irradiation of metals (Al, Ti, Ag) were studied. • In situ SAXS and ex situ TEM, XRD and Raman spectra were measured. • NPs size decreased when increasing the O{sub 2} fraction in a controlled O{sub 2}+N{sub 2} atmosphere. • The oxidation of metal NPs in the plasma restricts the increase of the size of the NPs. - Abstract: The influence of a reactive atmosphere on the formation of nanoparticles (NPs) in the plasma plume generated by nanosecond pulsed laser irradiation of metal targets (Ti, Al, Ag) was probed in situ using Small Angle X-ray Scattering (SAXS). Air and different O{sub 2}–N{sub 2} gas mixtures were used as reactive gas within atmospheric pressure. SAXS results showed the formation of NPs in the plasma-plume with a mean radius varying in the 2–5 nm range. A decrease of the NPs size with increasing the O{sub 2} percentage in the O{sub 2}–N{sub 2} gas mixture was also showed. Ex situ observations by transmission electron microscopy and structural characterizations by X-ray diffraction and Raman spectroscopy were also performed for powders collected in experiments done using air as ambient gas. The stability of the different metal oxides is discussed as being a key parameter influencing the formation of NPs in the plasma-plume.

Low Density Supersonic Decelerator (LDSD) Supersonic Flight Dynamics Test (SFDT) Plume Induced Environment Modelling

Science.gov (United States)

Mobley, B. L.; Smith, S. D.; Van Norman, J. W.; Muppidi, S.; Clark, I

2016-01-01

Provide plume induced heating (radiation & convection) predictions in support of the LDSD thermal design (pre-flight SFDT-1) Predict plume induced aerodynamics in support of flight dynamics, to achieve targeted freestream conditions to test supersonic deceleration technologies (post-flight SFDT-1, pre-flight SFDT-2)

Sample and plume luminescence in fast heavy ion induced desorption

International Nuclear Information System (INIS)

Tuszynski, W.; Koch, K.; Hilf, E.R.

1996-01-01

The luminescence arising in 252 Cf-fission fragment induced desorption events has been measured using the time-correlated single photon counting technique. Photons emitted from the sample have been guided from a plasma desorption ion source to a photodetector by an optical fibre. Spectra and decay functions have been obtained using thin layers of Coronene or POPOP as samples. The results are strongly dependent on the acceleration field applied for ion extraction. Approximately 10 photons per fission fragment have been produced when applying no accelerating voltage. The results clearly show that these photons come from radiative electronic relaxations of molecules in the solid sample. Considerably more photons per fission fragment have been produced when applying a positive acceleration voltage. The intensity increases almost linearly for acceleration fields below 10 kV/cm and saturates at a nearly 10-fold higher value when compared to no acceleration. The intensity is also affected by the homogeneity of the accelerating field. These additional photons are attributed to radiative electronic relaxations of desorbed neutral molecules in the plume excited by inelastic collisions with accelerated positive ions. No additional photons have been observed when extracting negative ions. The negative ions produced do obviously not hit and/or excite desorbed neutral molecules, presumably due to their specific desorption characteristics. The experimental data have been analyzed by comparing with the cw and time-resolved sample luminescence obtained by optical excitation. The findings demonstrate that valuable information on ion-solid interactions, on specific desorption quantities and on processes in the plume can be obtained by measuring and analyzing the luminescence induced by the impact of high energy primary ions. (orig.)

Langmuir probe measurement of the bismuth plasma plume formed by an extreme-ultraviolet pulsed laser

Czech Academy of Sciences Publication Activity Database

Pira, P.; Burian, T.; Kolpaková, A.; Tichý, M.; Kudrna, P.; Daniš, S.; Juha, Libor; Lančok, Ján; Vyšín, Luděk; Civiš, Svatopluk; Zelinger, Zdeněk; Kubát, Pavel; Wild, J.

2014-01-01

Roč. 47, č. 40 (2014), 1-6 ISSN 0022-3727 R&D Projects: GA ČR(CZ) GAP108/11/1312 Institutional support: RVO:68378271 ; RVO:61388955 Keywords : XUV laser * pulsed laser deposition * Langmuir probe * plasma plume Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.721, year: 2014

[Study of enhancement effect of laser-induced crater on plasma radiation].

Science.gov (United States)

Chen, Jin-Zhong; Zhang, Xiao-Ping; Guo, Qing-Lin; Su, Hong-Xin; Li, Guang

2009-02-01

Single pulses exported from high-energy neodymium glass laser were used to act on the same position of soil sample surface repeatedly, and the plasma emission spectra generated from sequential laser pulse action were collected by spectral recording system. The experimental results show that the laser-induced soil plasma radiation was enhanced continuously under the confinement effect of the crater walls, and the line intensities and signal-to-background ratios both had different improvements along with increasing the number of acting pulses. The photographs of the plasma image and crater appearance were taken to study the plasma shape, laser-induced crater appearance, and the mass of the ablated sample. The internal mechanism behind that laser-induced crater enhanced plasma radiation was researched. Under the sequential laser pulse action, the forming plasma as a result enlarges gradually first, leading to distortion at the trail of plasma plume, and then, its volume diminishes slowly. And also, the color of the plasma changes from buff to white gradually, which implies that the temperature increases constantly. The laser-induced crater had a regular shape, that is, the diameter increased from its bottom to top gradually, thus forming a taper. The mass of the laser-ablated substance descends along with increasing the amount of action pulse. Atomization degree of vaporized substance was improved in virtue of the crater confinement effect, Fresnel absorption produced from the crater walls reflection, and the inverse bremsstrahlung, and the plasma radiation intensity was enhanced as a result.

Hybrid 3D model for the interaction of plasma thruster plumes with nearby objects

Science.gov (United States)

Cichocki, Filippo; Domínguez-Vázquez, Adrián; Merino, Mario; Ahedo, Eduardo

2017-12-01

This paper presents a hybrid particle-in-cell (PIC) fluid approach to model the interaction of a plasma plume with a spacecraft and/or any nearby object. Ions and neutrals are modeled with a PIC approach, while electrons are treated as a fluid. After a first iteration of the code, the domain is split into quasineutral and non-neutral regions, based on non-neutrality criteria, such as the relative charge density and the Debye length-to-cell size ratio. At the material boundaries of the former quasineutral region, a dedicated algorithm ensures that the Bohm condition is met. In the latter non-neutral regions, the electron density and electric potential are obtained by solving the coupled electron momentum balance and Poisson equations. Boundary conditions for both the electric current and potential are finally obtained with a plasma sheath sub-code and an equivalent circuit model. The hybrid code is validated by applying it to a typical plasma plume-spacecraft interaction scenario, and the physics and capabilities of the model are finally discussed.

Investigation on the role of air in the dynamical evolution and thermodynamic state of a laser-induced aluminium plasma by spatial- and time-resolved spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Cristoforetti, G., E-mail: gabriele.cristoforetti@cnr.i [National Institute of Optics, Research Area of National Research Council, Via G.Moruzzi, 1 - 56124 Pisa (Italy); Lorenzetti, G.; Legnaioli, S.; Palleschi, V. [Institute of Chemistry of Organometallic Compounds, Research Area of National Research Council, Via G.Moruzzi, 1 - 56124 Pisa (Italy)

2010-09-15

The amount and the spatial distribution of air atoms and ions in a laser-induced plasma in ambient air provide important information about the formation of the plasma and its successive evolution history. For this reason, in the present work, the air mixing in a laser-induced plasma in air at atmospheric pressure and its influence on its thermodynamic evolution were studied. Information about spatial distributions of atoms and ions from Al, N and O were achieved by Abel-inverted spectra in the plume. The occurrence of LTE in the plume was also assessed by the utilization of theoretical criteria, and by the analysis of experimental spectra. Aluminium atoms and ions were found to be in LTE, while nitrogen and oxygen were not because of their longer times of relaxation toward equilibrium. Nitrogen was found to be over-ionized with respect to Saha-Eggert equilibrium, indicating that the plasma is recombining. Experimental observations suggest that the concentration of air species in the plasma is larger than that of aluminium, even in the region closer to the target, where the aluminium lines are stronger. In the front part of the plume only emission lines from air species were observed. The results suggest that a Laser-Supported Detonation (LSD) regime occurs during the trailing part of the laser pulse, resulting in the strong inclusion into the plasma of air elements. In this scenario, also the thermodynamic history of the plume is affected by the predominance of air species.

Influence of sample temperature on the expansion dynamics and the optical emission of laser-induced plasma

Energy Technology Data Exchange (ETDEWEB)

Eschlböck-Fuchs, S.; Haslinger, M.J.; Hinterreiter, A.; Kolmhofer, P.; Huber, N. [Christian Doppler Laboratory for Laser-Assisted Diagnostics, Institute of Applied Physics, Johannes Kepler University Linz, A-4040 Linz (Austria); Rössler, R. [voestalpine Stahl GmbH, A-4031 Linz (Austria); Heitz, J. [Christian Doppler Laboratory for Laser-Assisted Diagnostics, Institute of Applied Physics, Johannes Kepler University Linz, A-4040 Linz (Austria); Pedarnig, J.D., E-mail: johannes.pedarnig@jku.at [Christian Doppler Laboratory for Laser-Assisted Diagnostics, Institute of Applied Physics, Johannes Kepler University Linz, A-4040 Linz (Austria)

2013-09-01

We investigate the influence of sample temperature on the dynamics and optical emission of laser induced plasma for various solid materials. Bulk aluminum alloy, silicon wafer, and metallurgical slag samples are heated to temperature T{sub S} ≤ 500 °C and ablated in air by Nd:YAG laser pulses (wavelength 1064 nm, pulse duration approx. 7 ns). The plasma dynamics is investigated by fast time-resolved photography. For laser-induced breakdown spectroscopy (LIBS) the optical emission of plasma is measured by Echelle spectrometers in combination with intensified CCD cameras. For all sample materials the temporal evolution of plume size and broadband plasma emission vary systematically with T{sub S}. The size and brightness of expanding plumes increase at higher T{sub S} while the mean intensity remains independent of temperature. The intensity of emission lines increases with temperature for all samples. Plasma temperature and electron number density do not vary with T{sub S}. We apply the calibration-free LIBS method to determine the concentration of major oxides in slag and find good agreement to reference data up to T{sub S} = 450 °C. The LIBS analysis of multi-component materials at high temperature is of interest for technical applications, e.g. in industrial production processes. - Highlights: • Size and emission of laser-induced plasma increase with sample temperature Ts. • Mean optical intensity of plasma is independent of Ts. • Plasma temperature and electron number density do not vary with Ts. • Major oxides in steel slag are quantified up to Ts = 450 °C. • Industrial steel slags are analyzed by calibration-free LIBS method.

Experimental studies of the effect target geometry on the evolution of laser produced plasma plumes

Science.gov (United States)

Beatty, Cuyler; Anderson, Austin; Iratcabal, Jeremy; Dutra, Eric; Covington, Aaron

2016-10-01

The expansion of the laser plumes was shown to be dependent on the initial target geometry. A 16 channel framing camera was used to record the plume shape and propagation speeds were determined from analysis of the images. Plastic targets were manufactured using different methods including 3D printing, CNC machining and vacuum casting. Preliminary target designs were made using a 3D printer and ABS plastic material. These targets were then tested using a 3 J laser with a 5 ns duration pulse. Targets with a deep conical depression were shown to produce highly collimated plumes when compared to flat top targets. Preliminary results of these experiments will be discussed along with planned future experiments that will use the indented targets with a 30 J laser with a 0.8 ns duration pulse in preparation for pinched laser plume experiments at the Nevada Terawatt Facility. Other polymers that are readily available in a deuterated form will also be explored as part of an effort to develop a cost effective plasma plume target for follow on neutron production experiments. Dr. Austin Anderson.

Resonance-enhanced laser-induced plasma spectroscopy for sensitive elemental analysis: Elucidation of enhancement mechanisms

International Nuclear Information System (INIS)

Lui, S.L.; Cheung, N.H.

2002-01-01

When performing laser-induced plasma spectroscopy for elemental analysis, the analyte signal-to-noise ratio increased from four to over fifty if the plume was reheated by a dye laser pulse tuned to resonant absorption. Time-resolved studies showed that the enhancement was not due to resonance photoionization. Rather, efficient and controlled rekindling of a larger plume volume was the key mechanism. The signal-to-noise ratio further increased to over a hundred if the atmosphere was replaced by a low-pressure heavy inert gas. The ambient gas helped confine and thermally insulate the expanding vapor

Investigating the Response and Expansion of Plasma Plumes in a Mesosonic Plasma Using the Situational Awareness Sensor Suite for the ISS (SASSI)

Science.gov (United States)

Gilchrist, Brian E.; Hoegy, W. R.; Krause, L. Habash; Minow, J. I.; Coffey, V. N.

2014-01-01

To study the complex interactions between the space environment surrounding the International Space Station (ISS) and the ISS space vehicle, we are exploring a specialized suite of plasma sensors, manipulated by the Space Station Remote Manipulator System (SSRMS) to probe the near-ISS mesosonic plasma ionosphere moving past the ISS. It is proposed that SASSI consists of the NASA Marshall Space Flight Center's (MSFC's) Thermal Ion Capped Hemispherical Spectrometer (TICHS), Thermal Electron Capped Hemispherical Spectrometer (TECHS), Charge Analyzer Responsive to Local Oscillations (CARLO), the Collimated PhotoElectron Gun (CPEG), and the University of Michigan Advanced Langmuir Probe (ALP). There are multiple expected applications for SASSI. Here, we will discuss the study of fundamental plasma physics questions associated with how an emitted plasma plume (such as from the ISS Plasma Contactor Unit (PCU)) responds and expands in a mesosonic magnetoplasma as well as emit and collect current. The ISS PCU Xe plasma plume drifts through the ionosphere and across the Earth's magnetic field, resulting in complex dynamics. This is of practical and theoretical interest pertaining to contamination concerns (e.g. energetic ion scattering) and the ability to collect and emit current between the spacecraft and the ambient plasma ionosphere. This impacts, for example, predictions of electrodynamic tether current performance using plasma contactors as well as decisions about placing high-energy electric propulsion thrusters on ISS. We will discuss the required measurements and connection to proposed instruments for this study.

A uniform laminar air plasma plume with large volume excited by an alternating current voltage

Science.gov (United States)

Li, Xuechen; Bao, Wenting; Chu, Jingdi; Zhang, Panpan; Jia, Pengying

2015-12-01

Using a plasma jet composed of two needle electrodes, a laminar plasma plume with large volume is generated in air through an alternating current voltage excitation. Based on high-speed photography, a train of filaments is observed to propagate periodically away from their birth place along the gas flow. The laminar plume is in fact a temporal superposition of the arched filament train. The filament consists of a negative glow near the real time cathode, a positive column near the real time anode, and a Faraday dark space between them. It has been found that the propagation velocity of the filament increases with increasing the gas flow rate. Furthermore, the filament lifetime tends to follow a normal distribution (Gaussian distribution). The most probable lifetime decreases with increasing the gas flow rate or decreasing the averaged peak voltage. Results also indicate that the real time peak current decreases and the real time peak voltage increases with the propagation of the filament along the gas flow. The voltage-current curve indicates that, in every discharge cycle, the filament evolves from a Townsend discharge to a glow one and then the discharge quenches. Characteristic regions including a negative glow, a Faraday dark space, and a positive column can be discerned from the discharge filament. Furthermore, the plasma parameters such as the electron density, the vibrational temperature and the gas temperature are investigated based on the optical spectrum emitted from the laminar plume.

Evolution of the plasma parameters in the expanding laser ablation plume of silver

DEFF Research Database (Denmark)

Christensen, Bo Toftmann; Schou, Jørgen; Hansen, T.N.

2002-01-01

The angular and radial variation of the ion density and electron temperature in the plasma plume produced by laser ablation of silver at fluences of 0.8-1.3 J cm(-2) at 355 nm have been studied using a time-resolving Langmuir probe. The angular dependence of the electron temperature...... and the magnitude of the ion flux, at the time when the ion flux is maximised, agree with the predictions of the self-similar isentropic model of the plasma expansion by Anisimov et al. (C) 2002 Elsevier Science B.V. All rights reserved....

The growth and decay of equatorial backscatter plumes

Science.gov (United States)

Tsunoda, R. T.

1980-02-01

During the past three years, a series of rocket experiments from the Kwajalein Atoll, Marshall Islands, were conducted to investigate the character of intense, scintillation-producing irregularities that occur in the nighttime equatorial ionosphere. Because the source mechanism of equatorial irregularities, believed to be the Rayleigh-Taylor instability, is analogous to that which generates plasma-density striations in a nuclear-induced environment, there is considerable interest in the underlying physics that controls the characteristics of these irregularities. A primary objective of ALTAIR investigations of equatorial irregularities is to seek an understanding of the underlying physics by establishing the relationship between meter-scale irregularities (detected by ALTAIR), and the large-scale plasma-density depletions (or 'bubbles') that contain the kilometer-scale, scintillation-producing irregularities. We describe the time evolution of backscatter 'plumes' produced by one meter equatorial field-aligned irregularities. Using ALTAIR, a fully steerable backscatter radar, to repeatedly map selected plumes, we characterize the dynamic behavior of plumes in terms of growth and a decay phase. Most of the observed characteristics are found to be consistent with equatorial-irregularity generation predicted by current theories of Rayleigh-Taylor and gradient-drift instabilities. However, other characteristics have been found that suggest key roles played by the eastward neutral wind and by altitude-modulation of the bottomside F layer in establishing the initial conditions for plume growth.

Fast photography of XeCl laser-induced plasma of graphite in vacuum and in nitrogen atmosphere

International Nuclear Information System (INIS)

Acquaviva, S; De Giorgi, M L

2003-01-01

Fast photography with a gated intensified close-coupled device camera was applied to provide a visualization of the temporal and spatial evolution of chemical species in a plasma induced by a 308 nm laser during graphite ablation, in vacuum and in nitrogen atmosphere. A sequence of frames of the luminous plume was recorded, using narrow interference filters, and plasma expansion velocity was estimated from the acquired images. Present observations agree with optical emission spectroscopic investigations performed under the same experimental conditions

Three-dimensional laser-induced fluorescence measurements of turbulent chemical plumes

Science.gov (United States)

True, Aaron; Crimaldi, John

2017-11-01

In order to find prey, mates, and suitable habitat, many organisms must navigate through complex chemical plume structures in turbulent flow environments. In this context, we investigate the spatial and temporal structure of chemical plumes released isokinetically into fractal-grid-generated turbulence in an open channel flow. We first utilized particle image velocimetry (PIV) to characterize flow conditions (mean free stream velocities, turbulence intensities, turbulent kinetic energy dissipation rates, Taylor Reynolds numbers). We then implemented a newly developed high-resolution, high-speed, volumetric scanning laser-induced fluorescence (LIF) system for near time-resolved measurements of three-dimensional chemical plume structures. We investigated cases with and without a cylinder wake, and compare statistical (mean, variance, intermittency, probability density functions) and spectral (power spectrum of concentration fluctuations) characteristics of the chemical plume structure. Stretching and folding of complex three-dimensional filament structures during chaotic turbulent mixing is greatly enhanced in the cylinder wake case. In future experiments, we will implement simultaneous PIV and LIF, enabling computation of the covariance of the velocity and chemical concentration fluctuations and thus estimation of turbulent eddy diffusivities. NSF PHY 1555862.

Temporal and spatial dynamics of laser-induced aluminum plasma in argon background at atmospheric pressure: Interplay with the ambient gas

International Nuclear Information System (INIS)

Ma, Q.L.; Motto-Ros, V.; Lei, W.Q.; Boueri, M.; Bai, X.S.; Zheng, L.J.; Zeng, H.P.; Yu, J.

2010-01-01

Laser ablation in background gas implies supplementary complexities with respect to what happens in the vacuum. It is however essential to understand in detail the involved mechanisms for a number of applications requiring the ablation to be performed in an ambient gas at relative high pressure, such as pulsed-laser deposition, or laser-induced breakdown spectroscopy. In this paper, the expansion of a vapor plume ablated from an aluminum target into an argon gas at atmospheric pressure is experimentally investigated using time- and space-resolved emission spectroscopy. The obtained results provide a detailed description of the interplay between the vapor and the gas. The electron density, the temperature and the number densities (and therefore the partial pressures) of aluminum vapor and argon gas have been measured in and surrounding the vapor plume. Our observations show a confinement of the vapor plume by the gas, which is expected as predicted by the usual hydrodynamics models. The result is a plasma core with quite uniform distributions in electron density, temperature and number densities. Such plasma core presents an ideal emission source for spectroscopic applications. It is however evidenced by our observations that a large amount of argon is mixed into the aluminum plume in the plasma core, which invalidates in the experimental conditions that we used, the hydrodynamic 'piston' model where the background gas is pushed out by the shock wave surrounding the vapor plume. Instead, other mechanisms such as laser-supported detonation wave should play important roles in the early stage of the expansion of the plasma for the determination of its morphology at longer delays.

Characterization and Comparison of Aluminum, Silicon, and Carbon Laser Ablation Plumes

Science.gov (United States)

Iratcabal, Jeremy; Swanson, Kyle; Covington, Aaron

2017-10-01

Laser ablation of solid targets produces plasma plumes with rapidly evolving temperature and density gradients. These gradients can be measured using laser interferometric techniques that allow for the study of the plasma as the plume expands from the target surface and the temperature and density decrease. A systematic study of the temperature and density of aluminum, silicon, and carbon plasma plumes produced with a 2 TW/cm2 laser using spectroscopic, interferometric, fast imaging, and charge diagnostics will be presented. Carbon, aluminum, and silicon plumes are of interest because they are closely grouped on the periodic table but have very different material characteristics. Temporally and spatially resolved data was collected to characterize the evolution of the plasma in the plume. To probe the plasmas produced from these materials, optical spectroscopy was employed to identify and measure the temperature of the coexisting neutral and ionized atomic and molecular species. A Mach-Zehnder interferometer was employed to measure electron density. ICCD imaging and shadowgraphy were used to image the plume dynamics. A comparison of plasma evolution for each element will also be presented and will provide data to benchmark plasma codes. This work was supported by the University of Nevada, Reno, the U.S. DOE /NNSA Cooperative Agreement No. DE-NA0002075, and National Securities Technologies, LLC under Contract No. DE-AC52-06NA25946/Subcontract No. 165819.

Charge dependence of the plasma travel length in atmospheric-pressure plasma

Energy Technology Data Exchange (ETDEWEB)

Yambe, Kiyoyuki; Konda, Kohmei; Masuda, Seiya [Graduate School of Science and Technology, Niigata University, Niigata 950-2181 (Japan)

2016-06-15

Plasma plume is generated using a quartz tube, helium gas, and foil electrode by applying AC high voltage under the atmosphere. The plasma plume is released into the atmosphere from inside of the quartz tube and is seen as the continuous movement of the plasma bullet. The travel length of plasma bullet is defined from plasma energy and force due to electric field. The drift velocity of plasma bullet has the upper limit under atmospheric-pressure because the drift velocity is determined from the balance between electric field and resistive force due to collisions between plasma and air. The plasma plume charge depends on the drift velocity. Consequently, in the laminar flow of helium gas flow state, the travel length of the plasma plume logarithmically depends on the plasma plume charge which changes with both the electric field and the resistive force.

Charge dependence of the plasma travel length in atmospheric-pressure plasma

International Nuclear Information System (INIS)

Yambe, Kiyoyuki; Konda, Kohmei; Masuda, Seiya

2016-01-01

Plasma plume is generated using a quartz tube, helium gas, and foil electrode by applying AC high voltage under the atmosphere. The plasma plume is released into the atmosphere from inside of the quartz tube and is seen as the continuous movement of the plasma bullet. The travel length of plasma bullet is defined from plasma energy and force due to electric field. The drift velocity of plasma bullet has the upper limit under atmospheric-pressure because the drift velocity is determined from the balance between electric field and resistive force due to collisions between plasma and air. The plasma plume charge depends on the drift velocity. Consequently, in the laminar flow of helium gas flow state, the travel length of the plasma plume logarithmically depends on the plasma plume charge which changes with both the electric field and the resistive force.

Autocorrelation analysis of plasma plume light emissions in deep penetration laser welding of steel

Czech Academy of Sciences Publication Activity Database

Mrňa, Libor; Šarbort, Martin; Řeřucha, Šimon; Jedlička, Petr

2017-01-01

Roč. 29, č. 1 (2017), s. 1-10, č. článku 012009. ISSN 1042-346X R&D Projects: GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : laser welding * plasma plume * light emissions * autocorrelation analysis * weld depth Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 1.492, year: 2016

Non-equilibrium modeling of UV laser induced plasma on a copper target in the presence of Cu{sup 2+}

Energy Technology Data Exchange (ETDEWEB)

Ait Oumeziane, Amina, E-mail: a.aitoumeziane@gmail.com; Liani, Bachir [Laboratoire de Physique Théorique, Abou Beker Blekaid University (Algeria); Parisse, Jean-Denis [IUSTI UMR CNRS 7343, Aix-Marseille University (France); French Air School, Salon de Provence (France)

2016-03-15

This work is a contribution to the understanding of UV laser ablation of a copper sample in the presence of Cu{sup 2+} species as well as electronic non-equilibrium in the laser induced plasma. This particular study extends a previous paper and develops a 1D hydrodynamic model to describe the behavior of the laser induced plume, including the thermal non-equilibrium between electrons and heavy particles. Incorporating the formation of doubly charged ions (Cu{sup 2+}) in such an approach has not been considered previously. We evaluate the effect of the presence of doubly ionized species on the characteristics of the plume, i.e., temperature, pressure, and expansion velocity, and on the material itself by evaluating the ablation depth and plasma shielding effects. This study evaluates the effects of the doubly charged species using a non-equilibrium hydrodynamic approach which comprises a contribution to the understanding of the governing processes of the interaction of ultraviolet nanosecond laser pulses with metals and the parameter optimization depending on the intended application.

Experimental determination of the temperature range of AlO molecular emission in laser-induced aluminum plasma in air

Energy Technology Data Exchange (ETDEWEB)

Bai, Xueshi; Motto-Ros, Vincent [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon Villeurbanne (France); Lei, Wenqi [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon Villeurbanne (France); State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062 (China); Zheng, Lijuan [State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062 (China); Yu, Jin, E-mail: jin.yu@univ-lyon1.fr [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon Villeurbanne (France); Key Laboratory for Laser Plasmas (Ministry of Education), Department of Physics and Astrophysics, Shanghai Jiao Tong University, Shanghai 200240 (China)

2014-09-01

Measurements with laser-induced breakdown spectroscopy (LIBS) usually take place in the atmospheric air. For quantitative analysis of metallic elements, oxidation may represent an important issue which can significantly modify the stoichiometry of the plasma. Molecule formation in plasma should be therefore studied and taken into account in the LIBS practice. In this work, we experimentally investigated the temporal evolution and transformation of the plasma induced on an aluminum target by a nanosecond infrared (1064 nm) laser in the atmospheric air, in terms of its temperatures over a large interval of time from hundreds of nanoseconds to tens of microseconds. Such evolution was then correlated to the temporal evolution of the emission intensity from AlO molecules in the ablation plume. In particular, for a given ablation laser pulse energy, the appearance of the molecular emission while the plume cools down allows determining a minimal delay, τ{sub min}, which corresponds to a maximal value of the temperature, T{sub max}, below which the molecular emission begins to be clearly observed and to grow as a function of the delay. Such delay or such temperature indicates the longest delay or the lowest temperature for laser-induced plasma to be suitable for a correct analysis of metallic elements without significant influence of the alternation of the stoichiometry by oxidation. In our experiment, the values of τ{sub min} and T{sub max} have been determined for a range of ablation laser pulse energies from 5 mJ to 50 mJ. These values lie respectively in the range of 3 to 15 μs for τ{sub min}, and 4500 K to 6600 K in terms of the molecule temperature for T{sub max}. Beyond the practical interest for LIBS, our results provide also insights to the kinetics of the AlO molecule formation in laser-induced plasma. - Highlights: • Determination of the temperatures in laser-induced plasma up to tens of microseconds • Determination of the molecule temperature by fitting

Investigation of excited states populations density of Hall thruster plasma in three dimensions by laser-induced fluorescence spectroscopy

Science.gov (United States)

Krivoruchko, D. D.; Skrylev, A. V.

2018-01-01

The article deals with investigation of the excited states populations distribution of a low-temperature xenon plasma in the thruster with closed electron drift at 300 W operating conditions were investigated by laser-induced fluorescence (LIF) over the 350-1100 nm range. Seven xenon ions (Xe II) transitions were analyzed, while for neutral atoms (Xe I) just three transitions were explored, since the majority of Xe I emission falls into the ultraviolet or infrared part of the spectrum and are difficult to measure. The necessary spontaneous emission probabilities (Einstein coefficients) were calculated. Measurements of the excited state distribution were made for points (volume of about 12 mm3) all over the plane perpendicular to thruster axis in four positions on it (5, 10, 50 and 100 mm). Measured LIF signal intensity have differences for each location of researched point (due to anisotropy of thruster plume), however the structure of states populations distribution persisted at plume and is violated at the thruster exit plane and cathode area. Measured distributions show that for describing plasma of Hall thruster one needs to use a multilevel kinetic model, classic model can be used just for far plume region or for specific electron transitions.

Plume-induced stress in pulsed-laser deposited CeO2 films

International Nuclear Information System (INIS)

Norton, D.P.; Park, C.; Budai, J.D.; Pennycook, S.J.; Prouteau, C.

1999-01-01

Residual compressive stress due to plume-induced energetic particle bombardment in CeO 2 films deposited by pulsed-laser deposition is reported. For laser ablation film growth in low pressures, stresses as high as 2 GPa were observed as determined by substrate curvature and four-circle x-ray diffraction. The amount of stress in the films could be manipulated by controlling the kinetic energies of the ablated species in the plume through gas-phase collisions with an inert background gas. The film stress decreased to near zero for argon background pressures greater than 50 mTorr. At these higher background pressures, the formation of nanoparticles in the deposited film was observed. copyright 1999 American Institute of Physics

Ultraviolet versus infrared: Effects of ablation laser wavelength on the expansion of laser-induced plasma into one-atmosphere argon gas

International Nuclear Information System (INIS)

Ma Qianli; Motto-Ros, Vincent; Laye, Fabrice; Yu Jin; Lei Wenqi; Bai Xueshi; Zheng Lijuan; Zeng Heping

2012-01-01

Laser-induced plasma from an aluminum target in one-atmosphere argon background has been investigated with ablation using nanosecond ultraviolet (UV: 355 nm) or infrared (IR: 1064 nm) laser pulses. Time- and space-resolved emission spectroscopy was used as a diagnostics tool to have access to the plasma parameters during its propagation into the background, such as optical emission intensity, electron density, and temperature. The specific feature of nanosecond laser ablation is that the pulse duration is significantly longer than the initiation time of the plasma. Laser-supported absorption wave due to post-ablation absorption of the laser radiation by the vapor plume and the shocked background gas plays a dominant role in the propagation and subsequently the behavior of the plasma. We demonstrate that the difference in absorption rate between UV and IR radiations leads to different propagation behaviors of the plasma produced with these radiations. The consequence is that higher electron density and temperature are observed for UV ablation. While for IR ablation, the plasma is found with lower electron density and temperature in a larger and more homogenous axial profile. The difference is also that for UV ablation, the background gas is principally evacuated by the expansion of the vapor plume as predicted by the standard piston model. While for IR ablation, the background gas is effectively mixed to the ejected vapor at least hundreds of nanoseconds after the initiation of the plasma. Our observations suggest a description by laser-supported combustion wave for the propagation of the plasma produced by UV laser, while that by laser-supported detonation wave for the propagation of the plasma produced by IR laser. Finally, practical consequences of specific expansion behavior for UV or IR ablation are discussed in terms of analytical performance promised by corresponding plasmas for application with laser-induced breakdown spectroscopy.

Effect of a transverse plasma jet on a shock wave induced by a ramp

Directory of Open Access Journals (Sweden)

Hongyu WANG

2017-12-01

Full Text Available We conducted experiments in a wind tunnel with Mach number 2 to explore the evolution of a transverse plasma jet and its modification effect on a shock wave induced by a ramp with an angle of 24°. The transverse plasma jet was created by arc discharge in a small cylindrical cavity with a 2 mm diameter orifice. Three group tests with different actuator arrangements in the spanwise or streamwise direction upstream from the ramp were respectively studied to compare their disturbances to the shock wave. As shown by a time-resolved schlieren system, an unsteady motion of the shock wave by actuation was found: the shock wave was significantly modified by the plasma jet with an upstream motion and a reduced angle. Compared to spanwise actuation, a more intensive impact was obtained with two or three streamwise actuators working together. From shock wave structures, the control effect of the plasma jet on the shock motion based on a thermal effect, a potential cause of shock modification, was discussed. Furthermore, we performed a numerical simulation by using the Improved Delayed Detached Eddy Simulation (IDDES method to simulate the evolution of the transverse plasma jet plume produced by two streamwise actuators. The results show that flow structures are similar to those identified in schlieren images. Two streamwise vortices were recognized, which indicates that the higher jet plume is the result of the overlap of two streamwise jets. Keywords: Flow control, Improved delayed detached eddy simulation (IDDES method, Plasma synthetic jet, Shock wave/boundary layer interaction, Time resolved schlieren system

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Spectroscopic investigation of thermodynamic parameters of a plasma plume formed by the action of cw CO2 laser radiation on a metal substrate

Science.gov (United States)

Vasil'chenko, Zh V.; Azharonok, V. V.; Filatova, I. I.; Shimanovich, V. D.; Golubev, V. S.; Zabelin, A. M.

1996-09-01

Emission spectroscopy methods were used in an investigation of thermodynamic parameters of a surface plasma formed by the action of cw CO2 laser radiation of (2-5)×106 W cm-2 intensity on stainless steel in a protective He or Ar atmosphere. The spatiotemporal structure and pulsation characteristics of the plasma plume were used to determine the fields of the plasma electron density and temperature.

Characteristics of indirect laser-induced plasma from a thin film of oil on a metallic substrate

Science.gov (United States)

Xiu, Jun-Shan; Bai, Xue-Shi; Motto-Ros, Vincent; Yu, Jin

2015-04-01

Optical emissions from the major and trace elements embodied in a transparent gel prepared from cooking oil were detected after the gel was spread in a thin film on a metallic substrate. Such emissions are due to the indirect breakdown of the coating layer. The generated plasma, a mixture of substances from the substrate, the layer, and the ambient gas, was characterized using emission spectroscopy. The characteristics of the plasma formed on the metal with and without the coating layer were investigated. The results showed that Al emission induced from the aluminum substrates coated with oil films extends away from the target surface to ablate the oil film. This finally formed a bifurcating circulation of aluminum vapor against a spherical confinement wall in the front of the plume, which differed from the evolution of the plasma induced from the uncoated aluminum target. The strongest emissions of elements from the oil films can be observed at 2 mm above the target after a detection delay of 1.0 μs. A high temperature zone has been observed in the plasma after the delay of 1.0 μs for the plasma induced from the coated metal. This higher temperature determined in the plasma allows the consideration of the sensitive detection of trace elements in liquids, gels, biological samples, or thin films.

Highly ionized plasma plume generation by long-pulse CO2 laser irradiation of solid targets in strong axial magnetic fields

International Nuclear Information System (INIS)

Hoffman, A.L.; Crawford, E.A.

1982-01-01

The present work utilizes high f number optics and is directed primarily at controlling the conditions in the magnetically confined plume. Typically, fully ionized carbon plasmas have been produced with 10 18 cm -3 electron densities and 100 to 150 eV electron temperatures. These carbon plasmas have been doped with high Z atoms in order to study ionization and emission rates at the above conditions

Comparative study of the expansion dynamics of laser-driven plasma and shock wave in in-air and underwater ablation regimes

Science.gov (United States)

Nguyen, Thao T. P.; Tanabe, Rie; Ito, Yoshiro

2018-03-01

We compared the expansion characteristics of the plasma plumes and shock waves generated in laser-induced shock process between the two ablation regimes: in air and under water. The observation was made from the initial moment when the laser pulse hit the target until 1.5 μs. The shock processes were driven by focusing a single laser pulse (1064 nm, FWHM = 13 ns) onto the surface of epoxy-resin blocks using a 40-mm focal length lens. The estimated laser intensity at the target plane is approximate to 9 ×109Wcm-2 . We used the fast-imaging technique to observe the expansion of the plasma plume and a custom-designed time-resolved photoelasticity imaging technique to observe the propagation of shock waves with the time resolution of nanoseconds. We found that at the same intensity of the laser beam, the plasma expansion during the laser pulse follows different mechanisms: the plasma plume that grows in air follows a radiation-wave model while a detonation-wave model can explain the expansion of the plasma plume induced in water. The ideal blast wave theory can be used to predict the decay of the shock wave in air but is not appropriate to describe the decay of the shock wave induced under water.

Understanding plume splitting of laser ablated plasma: A view from ion distribution dynamics

Energy Technology Data Exchange (ETDEWEB)

Wu, Jian; Li, Xingwen; Wei, Wenfu; Jia, Shenli; Qiu, Aici [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Shaanxi 710049 (China)

2013-11-15

Plume splitting in low-pressure ambient air was understood in view of ion distribution dynamics from the laser ablated Al plasma (1064 nm 0.57 J/mm{sup 2}) by combining fast photography and spatially resolved spectroscopy. In the beginning, the spectral lines were mainly from the Al III ion. Then, the Bragg peak in stopping power of the ambient gas to Al III could be the dominant reason for the enhanced emission from the fast moving part, and the recombination of Al III to Al I-II ions near the target surface was response to the radiations from the slow moving/stationary part. As the ambient gas pressure increased, stopping distances of the Al III decreased, and radiation from the air ions became pronounced. The laser shadowgraph image at 1100 Pa indicated that the shock wave front located between the fast moving and slow moving parts. Electron densities of the fast moving plasma, which peaked at the plasma front, were on the order of 10{sup 16} cm{sup −3}, and the electron temperatures were 2–3 eV.

Sheath and bulk expansion induced by RF bias in atmospheric pressure microwave plasma

Science.gov (United States)

Lee, Jimo; Nam, Woojin; Lee, Jae Koo; Yun, Gunsu

2017-10-01

A large axial volume expansion of microwave-driven plasma at atmospheric pressure is achieved by applying a low power radio frequency (RF) bias at an axial location well isolated from the original plasma bulk. The evolution of the plasma plume visualized by high speed ICCD imaging suggest that the free electrons drifting toward the bias electrode cause the prodigious expansion of the sheath, creating a stable plasma stream channel between the microwave and the RF electrodes. For argon plasma in ambient air, enhanced emissions of OH and N2 spectral lines are measured in the extended plume region, supporting the acceleration of electrons and subsequent generation of radical species. The coupling of RF bias with microwave provides an efficient way of enlarging the plasma volume and enhancing the production of radicals. Work supported by the National Research Foundation of Korea under BK21+ program and Grant No. 2015R1D1A1A01061556 (Ministry of Education).

Double pulse laser ablation and plasma: Laser induced breakdown spectroscopy signal enhancement

International Nuclear Information System (INIS)

Babushok, V.I.; DeLucia, F.C.; Gottfried, J.L.; Munson, C.A.; Miziolek, A.W.

2006-01-01

A review of recent results of the studies of double laser pulse plasma and ablation for laser induced breakdown spectroscopy applications is presented. The double pulse laser induced breakdown spectroscopy configuration was suggested with the aim of overcoming the sensitivity shortcomings of the conventional single pulse laser induced breakdown spectroscopy technique. Several configurations have been suggested for the realization of the double pulse laser induced breakdown spectroscopy technique: collinear, orthogonal pre-spark, orthogonal pre-heating and dual pulse crossed beam modes. In addition, combinations of laser pulses with different wavelengths, different energies and durations were studied, thus providing flexibility in the choice of wavelength, pulse width, energy and pulse sequence. The double pulse laser induced breakdown spectroscopy approach provides a significant enhancement in the intensity of laser induced breakdown spectroscopy emission lines up to two orders of magnitude greater than a conventional single pulse laser induced breakdown spectroscopy. The double pulse technique leads to a better coupling of the laser beam with the plasma plume and target material, thus providing a more temporally effective energy delivery to the plasma and target. The experimental results demonstrate that the maximum effect is obtained at some optimum separation delay time between pulses. The optimum value of the interpulse delay depends on several factors, such as the target material, the energy level of excited states responsible for the emission, and the type of enhancement process considered. Depending on the specified parameter, the enhancement effects were observed on different time scales ranging from the picosecond time level (e.g., ion yield, ablation mass) up to the hundred microsecond level (e.g., increased emission intensity for laser induced breakdown spectroscopy of submerged metal target in water). Several suggestions have been proposed to explain

Effect of ablation geometry on the formation of stagnation layer in laterally colliding plasmas

International Nuclear Information System (INIS)

Mondal, Alamgir; Singh, Rajesh K.; Kumar, Ajai

2015-01-01

Interaction between two parallel propagating plasma plumes have been investigated in two different ablation schemes e.g. laser-blow-off (LBO) of thin film and conventional laser ablation (LPP). Fast imagine technique is used to study the dynamical and geometrical aspect of seed plasmas and induced stagnation layer in between the two expanding seed plasmas. Interaction between the energetic particles, coming from the seed plasmas are responsible for formation of stagnation layer. It has been found that geometrical shape, size, kinetic energy and divergence of plasma plumes are highly dependent on the ablation geometry. These variations in seed plasmas initiate the significant differences in the stagnation layer formed by LBO and LPP geometry. In this presentation, characteristic feature of stagnation layer which includes density, initiation time, emissive life time and geometry in both LBO and LPP geometry are briefly discussed. A comparative study of present results suggests that the plume composition and directionality of seed plasma play crucial role in mechanistic aspect of stagnation layer. (author)

Comparison of pulsed Nd : YAG laser welding qualitative features with plasma plume thermal characteristics

International Nuclear Information System (INIS)

Sabbaghzadeh, J; Dadras, S; Torkamany, M J

2007-01-01

A spectroscopic approach was used to study the effects of different operating parameters on st14 sheet metal welding with a 400 W maximum average power pulsed Nd : YAG laser. The parameters included pulse duration and peak power and type and flow rate of the assist gas and welding speed. Weld quality, including penetration depth and melt width, has been compared with the FeI electron temperature obtained from spectroscopic observations of a plasma plume. A correlation between the standard deviation of the electron temperature and the quality of welding has also been found

Computational fluid dynamics and frequency-dependent finite-difference time-domain method coupling for the interaction between microwaves and plasma in rocket plumes

International Nuclear Information System (INIS)

Kinefuchi, K.; Funaki, I.; Shimada, T.; Abe, T.

2012-01-01

Under certain conditions during rocket flights, ionized exhaust plumes from solid rocket motors may interfere with radio frequency transmissions. To understand the relevant physical processes involved in this phenomenon and establish a prediction process for in-flight attenuation levels, we attempted to measure microwave attenuation caused by rocket exhaust plumes in a sea-level static firing test for a full-scale solid propellant rocket motor. The microwave attenuation level was calculated by a coupling simulation of the inviscid-frozen-flow computational fluid dynamics of an exhaust plume and detailed analysis of microwave transmissions by applying a frequency-dependent finite-difference time-domain method with the Drude dispersion model. The calculated microwave attenuation level agreed well with the experimental results, except in the case of interference downstream the Mach disk in the exhaust plume. It was concluded that the coupling estimation method based on the physics of the frozen plasma flow with Drude dispersion would be suitable for actual flight conditions, although the mixing and afterburning in the plume should be considered depending on the flow condition.

Computational fluid dynamics and frequency-dependent finite-difference time-domain method coupling for the interaction between microwaves and plasma in rocket plumes

Energy Technology Data Exchange (ETDEWEB)

Kinefuchi, K. [Department of Aeronautics and Astronautics, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Funaki, I.; Shimada, T.; Abe, T. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

2012-10-15

Under certain conditions during rocket flights, ionized exhaust plumes from solid rocket motors may interfere with radio frequency transmissions. To understand the relevant physical processes involved in this phenomenon and establish a prediction process for in-flight attenuation levels, we attempted to measure microwave attenuation caused by rocket exhaust plumes in a sea-level static firing test for a full-scale solid propellant rocket motor. The microwave attenuation level was calculated by a coupling simulation of the inviscid-frozen-flow computational fluid dynamics of an exhaust plume and detailed analysis of microwave transmissions by applying a frequency-dependent finite-difference time-domain method with the Drude dispersion model. The calculated microwave attenuation level agreed well with the experimental results, except in the case of interference downstream the Mach disk in the exhaust plume. It was concluded that the coupling estimation method based on the physics of the frozen plasma flow with Drude dispersion would be suitable for actual flight conditions, although the mixing and afterburning in the plume should be considered depending on the flow condition.

Composition of the excimer laser-induced plume produced during LASIK refractive surgery

Science.gov (United States)

Glickman, Randolph D.; Liu, Yun; Mayo, George L.; Baribeau, Alan D.; Starck, Tomy; Bankhead, Tom

2003-07-01

Because of concerns about potential hazards to surgical personnel of the plume associated with laser refractive surgery, this study was performed to characterize the composition of such plumes. Filter elements were removed from the smoke evacuator of a VISX S3 excimer laser (filter pore size ~0.3 microns) and from a Mastel Clean Room ( filter pore size ~0.2 microns) used with a LADARVISION excimer laser. The filters from both laser systems captured the laser-induced plumes from multiple, routine, LASIK patient procedures. Some filters were processed for scanning electron microscopy, while others were extracted with methanol and chloroform for biochemical analysis. Both the VISX "Final Air" filter and the Mastel "Clean Room" filter captured material that was not observed in filters that had clean operating room air only passed through them. In the VISX system, air flows through the filter unit parallel to the filter matrix. SEM analysis showed these filters captured discrete particles of 0.3 to 3.0 microns in size. In the Mastel Clean Room unit, air flows orthogonally through the filter, and the filter matrix was heavily layered with captured debris so that individual particles were not readily distinguished. Amino acid analysis and gel electrophoresis of extracted material revealed proteinaceous molecules as large as 5000 molecular weight. Such large molecules in the laser plume are not predicted by the existing theory of photochemical ablation. The presence of relatively large biomolecules may constitute a risk of allergenic reactions in personnel exposed to the plume, and also calls into question the precise mechanism of excimer laser photochemical ablation. Supported by the RMG Research Endowment, and Research to Prevent Blindness

A feasibility study and mission analysis for the Hybrid Plume Plasma Rocket

Science.gov (United States)

Sullivan, Daniel J.; Micci, Michael M.

1990-01-01

The Hybrid Plume Plasma Rocket (HPPR) is a high power electric propulsion concept which is being developed at the MIT Plasma Fusion Center. This paper presents a theoretical overview of the concept as well as the results and conclusions of an independent study which has been conducted to identify and categorize those technologies which require significant development before the HPPR can be considered a viable electric propulsion device. It has been determined that the technologies which require the most development are high power radio-frequency and microwave generation for space applications and the associated power processing units, low mass superconducting magnets, a reliable, long duration, multi-megawatt space nuclear power source, and long term storage of liquid hydrogen propellant. In addition to this, a mission analysis of a one-way transfer from low earth orbit (LEO) to Mars indicates that a constant acceleration thrust profile, which can be obtained using the HPPR, results in faster trip times and greater payload capacities than those afforded by more conventional constant thrust profiles.

Laser-induced plasmas in air studied using two-color interferometry

International Nuclear Information System (INIS)

Yang, Zefeng; Wu, Jian; Li, Xingwen; Han, Jiaxun; Jia, Shenli; Qiu, Aici; Wei, Wenfu

2016-01-01

Temporally and spatially resolved density profiles of Cu atoms, electrons, and compressed air, from laser-induced copper plasmas in air, are measured using fast spectral imaging and two-color interferometry. From the intensified CCD images filtered by a narrow-band-pass filter centered at 515.32 nm, the Cu atoms expansion route is estimated and used to determine the position of the fracture surface between the Cu atoms and the air. Results indicate that the Cu atoms density at distances closer to the target (0–0.4 mm) is quite low, with the maximum density appearing at the edge of the plasma's core being ∼4.6 × 10"2"4" m"−"3 at 304 ns. The free electrons are mainly located in the internal region of the plume, which is supposed to have a higher temperature. The density of the shock wave is (4–6) × 10"2"5" m"−"3, corresponding to air compression of a factor of 1.7–2.5.

Laser-induced plasmas in air studied using two-color interferometry

Energy Technology Data Exchange (ETDEWEB)

Yang, Zefeng; Wu, Jian, E-mail: jxjawj@mail.xjtu.edu.cn; Li, Xingwen; Han, Jiaxun; Jia, Shenli; Qiu, Aici [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Shaanxi 710049 (China); Wei, Wenfu [School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031 (China)

2016-08-15

Temporally and spatially resolved density profiles of Cu atoms, electrons, and compressed air, from laser-induced copper plasmas in air, are measured using fast spectral imaging and two-color interferometry. From the intensified CCD images filtered by a narrow-band-pass filter centered at 515.32 nm, the Cu atoms expansion route is estimated and used to determine the position of the fracture surface between the Cu atoms and the air. Results indicate that the Cu atoms density at distances closer to the target (0–0.4 mm) is quite low, with the maximum density appearing at the edge of the plasma's core being ∼4.6 × 10{sup 24 }m{sup −3} at 304 ns. The free electrons are mainly located in the internal region of the plume, which is supposed to have a higher temperature. The density of the shock wave is (4–6) × 10{sup 25 }m{sup −3}, corresponding to air compression of a factor of 1.7–2.5.

DSMC Simulations of Io's Pele Plume

Science.gov (United States)

McDoniel, William; Goldstein, D.; Varghese, P.; Trafton, L.

2012-10-01

Io’s Pele plume rises over 300km in altitude and leaves a deposition ring 1200km across on the surface of the moon. Material emerges from an irregularly-shaped vent, and this geometry gives rise to complex 3D flow features. The Direct Simulation Monte Carlo method is used to model the gas flow in the rarefied plume, demonstrating how the geometry of the source region is responsible for the asymmetric structure of the deposition ring and illustrating the importance of very small-scale vent geometry in explaining large observed features of interest. Simulations of small particles in the plume and comparisons to the black “butterfly wings” seen at Pele are used to constrain particle sizes and entrainment mechanisms. Preliminary results for the effects of plasma energy and momentum transfer to the plume will also be presented.

Spatial diagnostics of the laser induced lithium fluoride plasma

Energy Technology Data Exchange (ETDEWEB)

Baig, M. A.; Qamar, Aisha; Fareed, M. A.; Anwar-ul-Haq, M.; Ali, Raheel [Atomic and Molecular Physics Laboratory, Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan)

2012-06-15

We present spatial characteristics of the lithium fluoride plasma generated by the fundamental and second harmonic of a Nd:YAG laser. The plume emission has been recorded spatially using five spectrometers covering the spectral region from 200 nm to 720 nm. The electron density is measured from the Stark broadened line profile of the line at 610.37 nm, whereas the plasma temperature has been determined using the Boltzmann plot method including all the observed spectral lines of lithium. Both the plasma parameters; electron density and plasma temperature decrease with the increase of the distance from the target surface. The thermal conduction towards the target, the radiative cooling of the plasma, and the conversion of thermal energy into kinetic energy are the main mechanisms responsible for the spatially decrease of the plasma parameters.

Investigations on laser induced nickel and titanium plasmas

International Nuclear Information System (INIS)

Rahman, M.K.U.; Latif, A.; Bhatti, K.A.; Rafique, M.S.; Yousaf, M.K.

2011-01-01

Experiments were performed to find out plasma parameters for Nickel and Titanium metals which were irradiated in air (1 atm) to produce plasma plume using Q switched Nd: YAG pulsed laser of 1.1 MW, 10 m J, 1064 nm and 9-14 ns. Langmuir probe was used as a diagnostic tool. The signals at different probe voltages were recorded on digital storage oscilloscope. The information carried by the signals was utilized to calculate electron density, electron temperature, Debye's length and number of particles in Debye's sphere. The study shows that the calculated values of these parameters for Nickel and Titanium are different except Debye's length. Plasma parameters strongly depend on probe potentials, material used and ambient conditions. (author)

Formation of metal nanoparticles of various sizes in plasma plumes produced by Ti:sapphire laser pulses

International Nuclear Information System (INIS)

Chakravarty, U.; Naik, P. A.; Mukherjee, C.; Kumbhare, S. R.; Gupta, P. D.

2010-01-01

In this paper, an experimental study on generation of nanoparticle various sizes using Ti:sapphire laser pulses, is reported. Nanoparticle formation in plasma plumes of metals like silver and copper, expanding in vacuum, has been studied using stretched pulses of 300 ps duration [subnanoseconds (sub-ns)] from a Ti:sapphire laser. It has been compared with the nanoparticle formation (of the same materials) when compressed pulses of 45 fs duration were used under similar focusing conditions. Nanoparticle formation is observed at intensities as high as 2x10 16 W/cm 2 . The structural analysis of the nanoparticle deposition on a silicon substrate showed that, using 45 fs pulses, smaller nanoparticles of average size ∼20 nm were generated, whereas on using the sub-ns pulses, larger particles were produced. Also, the visible light transmission and reflection from the nanoparticle film of Ag on glass substrate showed surface plasmon resonance (SPR). The SPR curves of the films of nanoparticles deposited by femtosecond pulses were always broader and reflection/transmission was always smaller when compared with the films formed using the sub-ns pulses, indicating smaller size particle formation by ultrashort pulses. Thus, it has been demonstrated that variation in the laser pulse duration of laser offers a simple tool for varying the size of the nanoparticles generated in plasma plumes.

Ablation plume structure and dynamics in ambient gas observed by laser-induced fluorescence imaging spectroscopy

International Nuclear Information System (INIS)

Miyabe, M.; Oba, M.; Iimura, H.; Akaoka, K.; Khumaeni, A.; Kato, M.; Wakaida, I.

2015-01-01

The dynamic behavior of an ablation plume in ambient gas has been investigated by laser-induced fluorescence imaging spectroscopy. The second harmonic beam from an Nd:YAG laser (0.5–6 J/cm 2 ) was focused on a sintered oxide pellet or a metal chip of gadolinium. The produced plume was subsequently intersected with a sheet-shaped UV beam from a dye laser so that time-resolved fluorescence images were acquired with an intensified CCD camera at various delay times. The obtained cross-sectional images of the plume indicate that the ablated ground state atoms and ions of gadolinium accumulate in a hemispherical contact layer between the plume and the ambient gas, and a cavity containing a smaller density of ablated species is formed near the center of the plume. At earlier expansion stage, another luminous component also expands in the cavity so that it coalesces into the hemispherical layer. The splitting and coalescence for atomic plume occur later than those for ionic plume. Furthermore, the hemispherical layer of neutral atoms appears later than that of ions; however, the locations of the layers are nearly identical. This coincidence of the appearance locations of the layers strongly suggests that the neutral atoms in the hemispherical layer are produced as a consequence of three-body recombination of ions through collisions with gas atoms. The obtained knowledge regarding plume expansion dynamics and detailed plume structure is useful for optimizing the experimental conditions for ablation-based spectroscopic analysis. - Highlights: • Ablated ground-state species accumulated in a thin hemispherical boundary layer • Inside the layer, a cavity containing a small density of ablated species was formed. • The hemispherical layers of atoms and ions appeared at a nearly identical location. • The measured intensity peak variation was in good agreement with a model prediction. • We ascribed the dominant process for forming the layer to a three-body recombination

Kr II laser-induced fluorescence for measuring plasma acceleration.

Science.gov (United States)

Hargus, W A; Azarnia, G M; Nakles, M R

2012-10-01

We present the application of laser-induced fluorescence of singly ionized krypton as a diagnostic technique for quantifying the electrostatic acceleration within the discharge of a laboratory cross-field plasma accelerator also known as a Hall effect thruster, which has heritage as spacecraft propulsion. The 728.98 nm Kr II transition from the metastable 5d(4)D(7/2) to the 5p(4)P(5/2)(∘) state was used for the measurement of laser-induced fluorescence within the plasma discharge. From these measurements, it is possible to measure velocity as krypton ions are accelerated from near rest to approximately 21 km/s (190 eV). Ion temperature and the ion velocity distributions may also be extracted from the fluorescence data since available hyperfine splitting data allow for the Kr II 5d(4)D(7/2)-5p(4)P(5/2)(∘) transition lineshape to be modeled. From the analysis, the fluorescence lineshape appears to be a reasonable estimate for the relatively broad ion velocity distributions. However, due to an apparent overlap of the ion creation and acceleration regions within the discharge, the distributed velocity distributions increase ion temperature determination uncertainty significantly. Using the most probable ion velocity as a representative, or characteristic, measure of the ion acceleration, overall propellant energy deposition, and effective electric fields may be calculated. With this diagnostic technique, it is possible to nonintrusively characterize the ion acceleration both within the discharge and in the plume.

Spectroscopic and shadowgraphic analysis of laser induced plasmas in the orthogonal double pulse pre-ablation configuration

International Nuclear Information System (INIS)

Cristoforetti, G.; Legnaioli, S.; Pardini, L.; Palleschi, V.; Salvetti, A.; Tognoni, E.

2006-01-01

This work focuses on the study of the plumes obtained in the double pulse orthogonal Laser Induced Breakdown Spectroscopy (LIBS) in the pre-ablation configuration using both spectroscopic and shadowgraphic approaches. Single and double pulse LIBS experiments were carried out on a brass sample in air. Both the distance of the air plasma from the target surface and the interpulse delay were varied (respectively in the range 0.1-4.2 mm and up to 50 μs) revealing a significant variation of the plasma emission and of the plume-shock wave dynamical expansion in different cases. The intensity of both atomic and ionized zinc lines was measured in all the cases, allowing the calculation of the spatially averaged temperature and electron density and an estimation of the ablated mass. The line intensities and the thermodynamic parameters obtained by the spectroscopic measurements were discussed bearing in mind the dynamical expansion characteristics obtained from the shadowgraphic approach. All the data seem to be consistent with the model previously proposed for the double pulse collinear configuration where the line enhancement is mainly attributed to the ambient gas rarefaction produced by the first laser pulse, which causes a less effective shielding of the second laser pulse

Laser-induced carbon plasma emission spectroscopic measurements on solid targets and in gas-phase optical breakdown

International Nuclear Information System (INIS)

Nemes, Laszlo; Keszler, Anna M.; Hornkohl, James O.; Parigger, Christian

2005-01-01

We report measurements of time- and spatially averaged spontaneous-emission spectra following laser-induced breakdown on a solid graphite/ambient gas interface and on solid graphite in vacuum, and also emission spectra from gas-phase optical breakdown in allene C3H4 and helium, and in CO2 and helium mixtures. These emission spectra were dominated by CII (singly ionized carbon), CIII (doubly ionized carbon), hydrogen Balmer beta (H b eta), and Swan C2 band features. Using the local thermodynamic equilibrium and thin plasma assumptions, we derived electron number density and electron temperature estimates. The former was in the 1016 cm -3 range, while the latter was found to be near 20000 K. In addition, the vibration-rotation temperature of the Swan bands of the C2 radical was determined to be between 4500 and 7000 K, using an exact theoretical model for simulating diatomic emission spectra. This temperature range is probably caused by the spatial inhomogeneity of the laser-induced plasma plume. Differences are pointed out in the role of ambient CO2 in a solid graphite target and in gas-phase breakdown plasma

Modeling an Iodine Hall Thruster Plume in the Iodine Satellite (ISAT)

Science.gov (United States)

Choi, Maria

2016-01-01

An iodine-operated 200-W Hall thruster plume has been simulated using a hybrid-PIC model to predict the spacecraft surface-plume interaction for spacecraft integration purposes. For validation of the model, the plasma potential, electron temperature, ion current flux, and ion number density of xenon propellant were compared with available measurement data at the nominal operating condition. To simulate iodine plasma, various collision cross sections were found and used in the model. While time-varying atomic iodine species (i.e., I, I+, I2+) information is provided by HPHall simulation at the discharge channel exit, the molecular iodine species (i.e., I2, I2+) are introduced as Maxwellian particles at the channel exit. Simulation results show that xenon and iodine plasma plumes appear to be very similar under the assumptions of the model. Assuming a sticking coefficient of unity, iodine deposition rate is estimated.

SAMI3 Simulations of the Persistent May 1994 Plasmasphere Plume

Science.gov (United States)

Krall, J.; Huba, J.; Borovsky, J.

2017-12-01

We use the Naval Research Laboratory SAMI3 ionosphere/plasmasphere model[1] to explore the physics of a long-lived plasmasphere plume. A plasmasphere plume is a storm feature that extends the cold plasma that is normally trapped by the geomagnetic field (the plasmasphere) outward towards the bow shock. In the case of the May 1994 storm, the storm and the plume continued for 12 days. For the model storm, we imposed a Kp-driven Volland/Stern-Maynard/Chen potential [2-4]. Results are compared to measurements of the cold ion density from the 1989-046 spacecraft in geosynchronous orbit [5]. We find that many details of the observed plume are reproduced by SAMI3, but only if a background magnetosphere density is included as a boundary condition. We also find that high-speed, field aligned plasma flows contribute significantly to the observed plume density. [1] Huba, J. and J. Krall (2013), Modeling the plasmasphere with SAMI3, Geophys. Res. Lett., 40, 6-10, doi:10.1029/2012GL054300 [2] Volland, H. (1973), A semiempirical model of large-scale magnetospheric electric fields, Journal of Geophysical Research, 78, 171-180, doi:10.1029/JA078i001p00171 [3] Stern, D.P. (1975), The motion of a proton in the equatorial magnetosphere, Journal of Geophysical Research, 80, 595-599, doi:10.1029/JA080i004p00595 [4] Maynard, N.C., and A.J. Chen (1975), Isolated cold plasma regions: Observations and their relation to possible production mechanisms, Journal of Geophysical Research, 80, 1009-1013, doi:10.1029/JA080i007p01009 [5] Borovsky, J.E., D.T. Welling, M.F. Thomsen, and M.H. Denton (2014), Long-lived plasmaspheric drainage plumes: Where does the plasma come from?, Journal of Geophysical Research: Space Physics, 119, 6496-6520, doi:10.1002/2014JA020228 Research supported by NRL base funds.

Selective Killing Effects of Cold Atmospheric Pressure Plasma with NO Induced Dysfunction of Epidermal Growth Factor Receptor in Oral Squamous Cell Carcinoma.

Directory of Open Access Journals (Sweden)

Jung-Hwan Lee

Full Text Available The aim of this study is to investigate the effects of cold atmospheric pressure plasma (CAP-induced radicals on the epidermal growth factor receptor (EGFR, which is overexpressed by oral squamous cell carcinoma, to determine the underlying mechanism of selective killing. CAP-induced highly reactive radicals were observed in both plasma plume and cell culture media. The selective killing effect was observed in oral squamous cell carcinoma compared with normal human gingival fibroblast. Degradation and dysfunction of EGFRs were observed only in the EGFR-overexpressing oral squamous cell carcinoma and not in the normal cell. Nitric oxide scavenger pretreatment in cell culture media before CAP treatment rescued above degradation and dysfunction of the EGFR as well as the killing effect in oral squamous cell carcinoma. CAP may be a promising cancer treatment method by inducing EGFR dysfunction in EGFR-overexpressing oral squamous cell carcinoma via nitric oxide radicals.

Selective Killing Effects of Cold Atmospheric Pressure Plasma with NO Induced Dysfunction of Epidermal Growth Factor Receptor in Oral Squamous Cell Carcinoma.

Science.gov (United States)

Lee, Jung-Hwan; Om, Ji-Yeon; Kim, Yong-Hee; Kim, Kwang-Mahn; Choi, Eun-Ha; Kim, Kyoung-Nam

2016-01-01

The aim of this study is to investigate the effects of cold atmospheric pressure plasma (CAP)-induced radicals on the epidermal growth factor receptor (EGFR), which is overexpressed by oral squamous cell carcinoma, to determine the underlying mechanism of selective killing. CAP-induced highly reactive radicals were observed in both plasma plume and cell culture media. The selective killing effect was observed in oral squamous cell carcinoma compared with normal human gingival fibroblast. Degradation and dysfunction of EGFRs were observed only in the EGFR-overexpressing oral squamous cell carcinoma and not in the normal cell. Nitric oxide scavenger pretreatment in cell culture media before CAP treatment rescued above degradation and dysfunction of the EGFR as well as the killing effect in oral squamous cell carcinoma. CAP may be a promising cancer treatment method by inducing EGFR dysfunction in EGFR-overexpressing oral squamous cell carcinoma via nitric oxide radicals.

Laser-induced breakdown spectroscopy for the analysis of plasma facing components of tokamaks: parametric study and calibration-free measurements

International Nuclear Information System (INIS)

Mercadier, L.

2011-09-01

During the operation of a nuclear fusion device like the future reactor ITER, a fraction of tritium is trapped in the plasma facing components and has to be measured in order to fulfill nuclear safety requirements. Laser-induced breakdown spectroscopy (LIBS) is proposed to achieve this measurement. The laser plasma produced on carbon fibre composite tiles from the Tore Supra reactor is analyzed via a parametric study: it has to have a temperature over 10000 K and an electron density over 10 17 cm -3 to optimize the application. A calibration-free procedure that takes into account self-absorption is proposed to determine the relative concentration of hydrogen from the experimental spectra. The time- and space-resolved spectral emission of the plasma plume is investigated and reveals the presence of a temperature gradient from the core towards the periphery. This gradient is taken into account and the H/C concentration ratio is deduced. The accuracy of the results is evaluated and discussed. The study of the D/H isotopic ratio under low pressure argon reveals the presence of plume segregation that leads to an error of about 50%, error that can partially be reduced. Tungsten materials are investigated and difficulties related to spectroscopic databases are discussed. Finally, the feasibility of LIBS analysis with depth resolution is validated for multilayered metallic samples. (author)

Solar Coronal Plumes and the Fast Solar Wind Bhola N. Dwivedi1 ...

Indian Academy of Sciences (India)

Is there any contribution of plume plasma to the fast SW streams at all? ..... but to a slow diminution of the reconnection activity, presumably with the effect ... might think, even if the thermal energy could be dumped at the base of the plume,.

Liquid steel analysis by laser-induced plasma spectroscopy

International Nuclear Information System (INIS)

Gruber, J.

2002-11-01

When a nanosecond pulsed laser is focused onto a sample and the intensity exceeds a certain threshold, material is vaporized and a plasma is formed above the sample surface. The laser-light becomes increasingly absorbed by inverse bremsstrahlung and by photo-excitation and photo-ionization of atoms and molecules. The positive feedback, by which the number of energetic electrons for ionization is increased in an avalanche-like manner under the influence of laser-light, is the so-called optical breakdown. Radiating excited atoms and ions within the expanding plasma plume produce a characteristic optical emission spectrum. A spectroscopic analysis of this optical emission of the laser-induced plasma permits a qualitative and quantitative chemical analysis of the investigated sample. This technique is therefore often called laser-induced plasma spectroscopy (LIPS) or laser-induced breakdown spectroscopy (LIBS). LIPS is a fast non-contact technique, by which solid, liquid or gaseous samples can be analyzed with respect to their chemical composition. Hence, it is an appropriate tool for the rapid in-situ analysis of not easily accessible surfaces for process control in industrial environments. In this work, LIPS was studied as a technique to determine the chemical composition of solid and liquid steel. A LIPS set-up was designed and built for the remote and continuous in-situ analysis of the steel melt. Calibration curves were prepared for the LIPS analysis of Cr, Mn, Ni and Cu in solid steel using reference samples with known composition. In laboratory experiments an induction furnace was used to melt steel samples in crucibles, which were placed at a working distance of 1.5 m away from the LIPS apparatus. The response of the LIPS system was monitored on-line during the addition of pure elements to the liquid steel bath within certain concentration ranges (Cr: 0.11 - 13.8 wt%, Cu: 0.044 - 0.54 wt%, Mn: 1.38 - 2.5 wt%, Ni: 0.049 - 5.92 wt%). The analysis of an element

A buoyant plume adjacent to a headland-Observations of the Elwha River plume

Science.gov (United States)

Warrick, J.A.; Stevens, A.W.

2011-01-01

Small rivers commonly discharge into coastal settings with topographic complexities - such as headlands and islands - but these settings are underrepresented in river plume studies compared to more simplified, straight coasts. The Elwha River provides a unique opportunity to study the effects of coastal topography on a buoyant plume, because it discharges into the Strait of Juan de Fuca on the western side of its deltaic headland. Here we show that this headland induces flow separation and transient eddies in the tidally dominated currents (O(100. cm/s)), consistent with other headlands in oscillatory flow. These flow conditions are observed to strongly influence the buoyant river plume, as predicted by the "small-scale" or "narrow" dynamical classification using Garvine's (1995) system. Because of the transient eddies and the location of the river mouth on the headland, flow immediately offshore of the river mouth is directed eastward twice as frequently as it is westward. This results in a buoyant plume that is much more frequently "bent over" toward the east than the west. During bent over plume conditions, the plume was attached to the eastern shoreline while having a distinct, cuspate front along its westernmost boundary. The location of the front was found to be related to the magnitude and direction of local flow during the preceding O(1. h), and increases in alongshore flow resulted in deeper freshwater mixing, stronger baroclinic anomalies, and stronger hugging of the coast. During bent over plume conditions, we observed significant convergence of river plume water toward the frontal boundary within 1. km of the river mouth. These results show how coastal topography can strongly influence buoyant plume behavior, and they should assist with understanding of initial coastal sediment dispersal pathways from the Elwha River during a pending dam removal project. ?? 2010.

Morphological changes in ultrafast laser ablation plumes with varying spot size.

Science.gov (United States)

Harilal, S S; Diwakar, P K; Polek, M P; Phillips, M C

2015-06-15

We investigated the role of spot size on plume morphology during ultrafast laser ablation of metal targets. Our results show that the spatial features of fs LA plumes are strongly dependent on the focal spot size. Two-dimensional self-emission images showed that the shape of the ultrafast laser ablation plumes changes from spherical to cylindrical with an increasing spot size from 100 to 600 μm. The changes in plume morphology and internal structures are related to ion emission dynamics from the plasma, where broader angular ion distribution and faster ions are noticed for the smallest spot size used. The present results clearly show that the morphological changes in the plume with spot size are independent of laser pulse width.

Expansion of laser-produced plasmas into vacuum and ambient gases

International Nuclear Information System (INIS)

Williams, T.

2001-01-01

Presented in this thesis are observations recorded using optical absorption spectroscopy, laser induced fluorescence imaging and Langmuir probe techniques for a low temperature laser-produced plasma. The plasma was generated using a KrF (248 nm, 30ns) excimer laser system focused onto a solid target surface (Ti, Mg) housed within a vacuum chamber. Plasma studies were made within vacuum (x10 -5 mTorr) and low pressure ( 2 and Ar ambient gas environments. Experimental results from a volumetric integration technique for plasma species number densities are used to yield total plume content for a laser-produced plasma in vacuum. This was used to determine the threshold power density for titanium neutral species formation. Temporally resolved electron number densities were determined using a Langmuir probe technique, for a titanium plasma generated under 532 nm and 248 nm ablation, for similar power densities and spot geometries. In this case the ablation thresholds for titanium are determined in terms of average power density and peak power density. Plume opacity problems which limit OAS and LIF diagnostic techniques are minimised using novel ablations configurations. Both techniques used, the 'composite target' and the 'plasma-jet' configurations, rely on reducing the optical thickness of the plume. The plasma-jets produced were allowed to interact with an ambient argon background and the ion/neutral ratio of the plasma-jet determined. Laser-produced plasma interactions with a d.c. biased copper mesh ∼15 mm in front of the target surface are observed. Self-emission studies of plume interactions with the mesh are monitored for positive and negative biases. Also ground-state neutral and ion interactions with the mesh are observed using OAS and LIF techniques to study individual species effects. A simple model was used to predict the perturbations to charged species distributions resulting from positive and negative applied potentials, but more complex interaction

Evaluation of pressure in a plasma produced by laser ablation of steel

Science.gov (United States)

Hermann, Jörg; Axente, Emanuel; Craciun, Valentin; Taleb, Aya; Pelascini, Frédéric

2018-05-01

We investigated the time evolution of pressure in the plume generated by laser ablation with ultraviolet nanosecond laser pulses in a near-atmospheric argon atmosphere. These conditions were previously identified to produce a plasma of properties that facilitate accurate spectroscopic diagnostics. Using steel as sample material, the present investigations benefit from the large number of reliable spectroscopic data available for iron. Recording time-resolved emission spectra with an echelle spectrometer, we were able to perform accurate measurements of electron density and temperature over a time interval from 200 ns to 12 μs. Assuming local thermodynamic equilibrium, we computed the plasma composition within the ablated vapor material and the corresponding kinetic pressure. The time evolution of plume pressure is shown to reach a minimum value below the pressure of the background gas. This indicates that the process of vapor-gas interdiffusion has a negligible influence on the plume expansion dynamics in the considered timescale. Moreover, the results promote the plasma pressure as a control parameter in calibration-free laser-induced breakdown spectroscopy.

Rayleigh-Taylor analysis in a laser-induced plasma

International Nuclear Information System (INIS)

Marin, R A; Gonzales, C A; Riascos, H

2012-01-01

We report the conditions (plasma parameters) under which the Rayleigh-Taylor Instability (RTI) develops in an Al plasma produced by a Nd:Yag pulsed laser with a fluence range of 1 to 4 J/cm 2 , wavelength of 1064nm and 10Hz repetition rate. The used data correspond to different pressure values of the ambient N atmosphere. From previous works, we took the RTI growth rate form. From the perturbation theory the instability amplitude is proportional to e -ηt . Using the drag model, we calculated the plume dynamics equations integrating the instability term and plotted the instability growth profile with the delay time values to get critical numbers for it, in order to show under which conditions the RTI appears.

RMP-Flutter-Induced Pedestal Plasma Transport

Energy Technology Data Exchange (ETDEWEB)

Callen, J. D.; Hegna, C., E-mail: callen@engr.wisc.edu [University of Wisconsin, Madison (United States); Cole, A. J. [Columbia University, New York (United States)

2012-09-15

Full text: Plasma toroidal rotation can prevent or limit reconnection of externally applied resonant magnetic perturbation (RMP) fields {delta}B on rational magnetic flux surfaces. Hence, it causes the induced radial perturbations to vanish or be small there, and thereby inhibits magnetic island formation and stochasticity in the edge of high (H-mode) confinement tokamak plasmas. However, the radial component of the spatial magnetic flutter induced by RMP fields off rational surfaces causes a radial electron thermal diffusivity of (1/2)({delta}B{sub p}/B){sup 2} times a magnetic-shear-influenced effective parallel electron thermal diffusivity. The resultant RMP-flutter-induced electron thermal diffusivity can be comparable to experimentally inferred values at the top of H-mode pedestals. This process also causes a factor of about 3 smaller RMP-induced electron density diffusivity there. Because this electron density transport is non-ambipolar, it produces a toroidal torque on the plasma, which is usually in the co-current direction. Kinetic-based cylindrical screw-pinch and toroidal models of these RMP-flutter-induced plasma transport effects have been developed. The RMP-induced increases in these diffusive plasma transport processes are typically spatially inhomogeneous in that they are strongly peaked near the rational surfaces in low collisionality pedestals, which may lead to resonant sensitivities to the local safety factor q. The effects can be large enough to reduce the radially averaged gradients of the electron temperature and density at the top of H-mode edge pedestals, and modify the plasma toroidal rotation and radial electric field there. At high collisionality the various effects are less strongly peaked at rational surfaces and thus less likely to exhibit RMP-induced resonant behavior. These RMP-flutter-induced plasma transport processes provide a new paradigm for developing an understanding of how RMPs modify the pedestal structure to stabilize

Plume expansion dynamics during laser ablation of manganates in oxygen atmosphere

International Nuclear Information System (INIS)

Amoruso, S.; Sambri, A.; Wang, X.

2007-01-01

The effect of ambient gas on the expansion dynamics of the plasma plume generated by excimer laser ablation of a LaMnO 3 target is investigated by using fast photography and optical emission spectroscopy. The plume propagation in an oxygen environment is examined with pressure ranging from vacuum to few hundreds Pa. Imaging analysis of the plume emission has allowed following the changes in the plume front dynamics as a function of time and pressure. The expansion dynamics of the plume front is examined by means of a theoretical description of plume evolution and shock-wave propagation in dimensionless variables. Optical emission spectroscopy analysis showed that the oxides are mainly formed in the gas-phase through reaction of the ablated atomic species with ambient oxygen. Moreover, we observed that the formation of oxides is strongly favoured at a pressure level where the formation of a shock-wave occurs

Experimentally obtained values of electric field of an atmospheric pressure plasma jet impinging on a dielectric surface

NARCIS (Netherlands)

Sobota, A.; Guaitella, O.; Garcia-Caurel, E.

2013-01-01

We report on experimentally obtained values of the electric field magnitude on a dielectric surface induced by an impinging atmospheric pressure plasma jet. The plasma plume was striking the dielectric surface at an angle of 45¿, at 5mm from the surface measured at the axis of the jet. The results

Galileo observations of volcanic plumes on Io

Science.gov (United States)

Geissler, P.E.; McMillan, M.T.

2008-01-01

Io's volcanic plumes erupt in a dazzling variety of sizes, shapes, colors and opacities. In general, the plumes fall into two classes, representing distinct source gas temperatures. Most of the Galileo imaging observations were of the smaller, more numerous Prometheus-type plumes that are produced when hot flows of silicate lava impinge on volatile surface ices of SO2. Few detections were made of the giant, Pele-type plumes that vent high temperature, sulfur-rich gases from the interior of Io; this was partly because of the insensitivity of Galileo's camera to ultraviolet wavelengths. Both gas and dust spout from plumes of each class. Favorably located gas plumes were detected during eclipse, when Io was in Jupiter's shadow. Dense dust columns were imaged in daylight above several Prometheus-type eruptions, reaching heights typically less than 100 km. Comparisons between eclipse observations, sunlit images, and the record of surface changes show that these optically thick dust columns are much smaller in stature than the corresponding gas plumes but are adequate to produce the observed surface deposits. Mie scattering calculations suggest that these conspicuous dust plumes are made up of coarse grained “ash” particles with radii on the order of 100 nm, and total masses on the order of 106 kg per plume. Long exposure images of Thor in sunlight show a faint outer envelope apparently populated by particles small enough to be carried along with the gas flow, perhaps formed by condensation of sulfurous “snowflakes” as suggested by the plasma instrumentation aboard Galileo as it flew through Thor's plume [Frank, L.A., Paterson, W.R., 2002. J. Geophys. Res. (Space Phys.) 107, doi:10.1029/2002JA009240. 31-1]. If so, the total mass of these fine, nearly invisible particles may be comparable to the mass of the gas, and could account for much of Io's rapid resurfacing.

Emission study of alumina plasma produced by a KrF laser

Energy Technology Data Exchange (ETDEWEB)

Yahiaoui, K., E-mail: kyahiaoui@cdta.dz [Centre de Développement des Technologies Avancées, cité 20 aout 1956, BP 17, Baba Hassen, Alger (Algeria); Abdelli-Messaci, S.; Messaoud-Aberkane, S.; Kerdja, T. [Centre de Développement des Technologies Avancées, cité 20 aout 1956, BP 17, Baba Hassen, Alger (Algeria); Kellou, H. [Université des Sciences et de la Technologie Houari Boumediene, BP 32, El-Allia, 16111 Bab-Ezzouar, Alger (Algeria)

2014-03-01

We report on the plasma emission formed from an α-alumina target when irradiated by laser into vacuum and through oxygen gas. Two diagnostic tools have been used: ICCD camera fast imaging and optical emission spectroscopy. The alumina plasma was induced by a KrF laser beam at a wavelength of 248 nm and pulse duration of 25 ns. The laser fluence was set to 8 J/cm{sup 2} and the oxygen pressure was varied from 0.01 to 5 mbar. By using the ICCD camera, two dimensional images of the plasma expansion were taken at different times. Depending on oxygen pressure and time delay, the expansion behavior of the plasma showed free expansion, plume splitting, shock wave formation, hydrodynamic instability and deceleration of the plume. Using optical emission spectroscopy, the plasma emission revealed the presence of neutral Al I, Al II, Al III into vacuum and under oxygen ambiance. The molecular emission of aluminum oxide (AlO) was detected only in oxygen ambiance. It should be noted that no oxygen lines were observed. Finally, the evolution of the electronic temperature along the normal axis from the target surface, into vacuum, was estimated using the Boltzmann plot method. - Highlights: • Ablated mass measurements of α-alumina target irradiated by a laser in nanosecond regime. • Optical emission spectroscopy of alumina plasma. • Fast imaging diagnostic of alumina plume using ICCD camera.

Characterization and modeling of turbidity density plume induced into stratified reservoir by flood runoffs.

Science.gov (United States)

Chung, S W; Lee, H S

2009-01-01

In monsoon climate area, turbidity flows typically induced by flood runoffs cause numerous environmental impacts such as impairment of fish habitat and river attraction, and degradation of water supply efficiency. This study was aimed to characterize the physical dynamics of turbidity plume induced into a stratified reservoir using field monitoring and numerical simulations, and to assess the effect of different withdrawal scenarios on the control of downstream water quality. Three different turbidity models (RUN1, RUN2, RUN3) were developed based on a two-dimensional laterally averaged hydrodynamic and transport model, and validated against field data. RUN1 assumed constant settling velocity of suspended sediment, while RUN2 estimated the settling velocity as a function of particle size, density, and water temperature to consider vertical stratification. RUN3 included a lumped first-order turbidity attenuation rate taking into account the effects of particles aggregation and degradable organic particles. RUN3 showed best performance in replicating the observed variations of in-reservoir and release turbidity. Numerical experiments implemented to assess the effectiveness of different withdrawal depths showed that the alterations of withdrawal depth can modify the pathway and flow regimes of the turbidity plume, but its effect on the control of release water quality could be trivial.

Probing colliding Calcium plasmas with emission and VUV absorption imaging

International Nuclear Information System (INIS)

Kavanagh, K.D.; Hirsch, J.S.; Kennedy, E.T.; Costello, T.; Poletto, L.; Nicolosi, P.

2004-01-01

Full text: Laser produced plasmas are formed when a short pulse and high power laser is focused onto a surface. Applications range from VUV/X-ray sources for lithography, microscopy and radiography to X-ray lasers, thin film deposition, analytical spectroscopy and electron/ion beam generation (and even acceleration). A battery of particle and optical techniques are now used to diagnose laser plasmas. One highly successful technique is gated-CCD (Charged Coupled Device) imaging of plasma plumes. It provides critical data on the early (creation) and late (expansion) phases of plasma plumes. However, this technique is limited to detecting only the excited (emitting) species in the plume. Recently, we developed a vacuum-UV (VUV) photoabsorption imaging facility called VPIF which enables one can track the evolution of dark plume matter or non-emitting plasma species residing in ground and metastable states. Although much is known about the dynamics of single laser plasma plumes expanding freely, little is known about the overlap between colliding plasma plumes. We are currently performing combined conventional gated CCD imaging and spectroscopy with VUV absorption imaging to map the evolution of the overlap volume of two colliding and interpenetrating plasma plumes. We are specifically tracking ground state singly ionized calcium in the plasmas by tuning into the inner shell 3p to 3d transition at 33.2 eV while the excited state species are tracked using transitions in the UV -NIR spectral range. The experiment may be cast as a model system for atmospheric and/or astrophysical colliding systems, e.g., when tracer elements are injected into supersonic winds at high altitude or when supernovae eject plasma into the solar wind

Analysis of plasmaspheric plumes: CLUSTER and IMAGE observations

Directory of Open Access Journals (Sweden)

F. Darrouzet

2006-07-01

Full Text Available Plasmaspheric plumes have been routinely observed by CLUSTER and IMAGE. The CLUSTER mission provides high time resolution four-point measurements of the plasmasphere near perigee. Total electron density profiles have been derived from the electron plasma frequency identified by the WHISPER sounder supplemented, in-between soundings, by relative variations of the spacecraft potential measured by the electric field instrument EFW; ion velocity is also measured onboard these satellites. The EUV imager onboard the IMAGE spacecraft provides global images of the plasmasphere with a spatial resolution of 0.1 RE every 10 min; such images acquired near apogee from high above the pole show the geometry of plasmaspheric plumes, their evolution and motion. We present coordinated observations of three plume events and compare CLUSTER in-situ data with global images of the plasmasphere obtained by IMAGE. In particular, we study the geometry and the orientation of plasmaspheric plumes by using four-point analysis methods. We compare several aspects of plume motion as determined by different methods: (i inner and outer plume boundary velocity calculated from time delays of this boundary as observed by the wave experiment WHISPER on the four spacecraft, (ii drift velocity measured by the electron drift instrument EDI onboard CLUSTER and (iii global velocity determined from successive EUV images. These different techniques consistently indicate that plasmaspheric plumes rotate around the Earth, with their foot fully co-rotating, but with their tip rotating slower and moving farther out.

Magnetic Field Effects on Plasma Plumes

Science.gov (United States)

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

Magnetic-flutter-induced pedestal plasma transport

International Nuclear Information System (INIS)

Callen, J.D.; Hegna, C.C.; Cole, A.J.

2013-01-01

Plasma toroidal rotation can limit reconnection of externally applied resonant magnetic perturbation (RMP) fields δB on rational magnetic flux surfaces. Hence it causes the induced radial perturbations δB ρ to be small there, thereby inhibiting magnetic island formation and stochasticity at the top of pedestals in high (H-mode) confinement tokamak plasmas. However, the δB ρ s induced by RMPs increase away from rational surfaces and are shown to induce significant sinusoidal radial motion (flutter) of magnetic field lines with a radial extent that varies linearly with δB ρ and inversely with distance from the rational surface because of the magnetic shear. This produces a radial electron thermal diffusivity that is (1/2)(δB ρ /B 0 ) 2 times a kinetically derived, electron-collision-induced, magnetic-shear-reduced, effective parallel electron thermal diffusivity in the absence of magnetic stochasticity. These low collisionality flutter-induced transport processes and thin magnetic island effects are shown to be highly peaked in the vicinity of rational surfaces at the top of low collisionality pedestals. However, the smaller but finite level of magnetic-flutter-induced electron heat transport midway between rational surfaces is the primary factor that determines the electron temperature difference between rational surfaces at the pedestal top. The magnetic-flutter-induced non-ambipolar electron density transport can be large enough to push the plasma toward an electron density transport root. Requiring ambipolar density transport is shown to determine the radial electric field, the plasma toroidal rotation (via radial force balance), a reduced electron thermal diffusivity and increased ambipolar density transport in the pedestal. At high collisionality the various flutter effects are less strongly peaked at rational surfaces and generally less significant. They are thus less likely to exhibit flutter-induced resonant behaviour and transition toward an

Magnetic-flutter-induced pedestal plasma transport

Science.gov (United States)

Callen, J. D.; Hegna, C. C.; Cole, A. J.

2013-11-01

Plasma toroidal rotation can limit reconnection of externally applied resonant magnetic perturbation (RMP) fields δB on rational magnetic flux surfaces. Hence it causes the induced radial perturbations δBρ to be small there, thereby inhibiting magnetic island formation and stochasticity at the top of pedestals in high (H-mode) confinement tokamak plasmas. However, the δBρs induced by RMPs increase away from rational surfaces and are shown to induce significant sinusoidal radial motion (flutter) of magnetic field lines with a radial extent that varies linearly with δBρ and inversely with distance from the rational surface because of the magnetic shear. This produces a radial electron thermal diffusivity that is (1/2)(δBρ/B0)2 times a kinetically derived, electron-collision-induced, magnetic-shear-reduced, effective parallel electron thermal diffusivity in the absence of magnetic stochasticity. These low collisionality flutter-induced transport processes and thin magnetic island effects are shown to be highly peaked in the vicinity of rational surfaces at the top of low collisionality pedestals. However, the smaller but finite level of magnetic-flutter-induced electron heat transport midway between rational surfaces is the primary factor that determines the electron temperature difference between rational surfaces at the pedestal top. The magnetic-flutter-induced non-ambipolar electron density transport can be large enough to push the plasma toward an electron density transport root. Requiring ambipolar density transport is shown to determine the radial electric field, the plasma toroidal rotation (via radial force balance), a reduced electron thermal diffusivity and increased ambipolar density transport in the pedestal. At high collisionality the various flutter effects are less strongly peaked at rational surfaces and generally less significant. They are thus less likely to exhibit flutter-induced resonant behaviour and transition toward an electron

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

Science.gov (United States)

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.

EUV laser produced and induced plasmas for nanolithography

Science.gov (United States)

Sizyuk, Tatyana; Hassanein, Ahmed

2017-10-01

EUV produced plasma sources are being extensively studied for the development of new technology for computer chips production. Challenging tasks include optimization of EUV source efficiency, producing powerful source in 2 percentage bandwidth around 13.5 nm for high volume manufacture (HVM), and increasing the lifetime of collecting optics. Mass-limited targets, such as small droplet, allow to reduce contamination of chamber environment and mirror surface damage. However, reducing droplet size limits EUV power output. Our analysis showed the requirement for the target parameters and chamber conditions to achieve 500 W EUV output for HVM. The HEIGHTS package was used for the simulations of laser produced plasma evolution starting from laser interaction with solid target, development and expansion of vapor/plasma plume with accurate optical data calculation, especially in narrow EUV region. Detailed 3D modeling of mix environment including evolution and interplay of plasma produced by lasers from Sn target and plasma produced by in-band and out-of-band EUV radiation in ambient gas, used for the collecting optics protection and cleaning, allowed predicting conditions in entire LPP system. Effect of these conditions on EUV photon absorption and collection was analyzed. This work is supported by the National Science Foundation, PIRE project.

Elucidation of Metallic Plume and Spatter Characteristics Based on SVM During High-Power Disk Laser Welding

International Nuclear Information System (INIS)

Gao Xiangdong; Liu Guiqian

2015-01-01

During deep penetration laser welding, there exist plume (weak plasma) and spatters, which are the results of weld material ejection due to strong laser heating. The characteristics of plume and spatters are related to welding stability and quality. Characteristics of metallic plume and spatters were investigated during high-power disk laser bead-on-plate welding of Type 304 austenitic stainless steel plates at a continuous wave laser power of 10 kW. An ultraviolet and visible sensitive high-speed camera was used to capture the metallic plume and spatter images. Plume area, laser beam path through the plume, swing angle, distance between laser beam focus and plume image centroid, abscissa of plume centroid and spatter numbers are defined as eigenvalues, and the weld bead width was used as a characteristic parameter that reflected welding stability. Welding status was distinguished by SVM (support vector machine) after data normalization and characteristic analysis. Also, PCA (principal components analysis) feature extraction was used to reduce the dimensions of feature space, and PSO (particle swarm optimization) was used to optimize the parameters of SVM. Finally a classification model based on SVM was established to estimate the weld bead width and welding stability. Experimental results show that the established algorithm based on SVM could effectively distinguish the variation of weld bead width, thus providing an experimental example of monitoring high-power disk laser welding quality. (plasma technology)

Atmospheric-pressure plasma jets: Effect of gas flow, active species, and snake-like bullet propagation

Energy Technology Data Exchange (ETDEWEB)

Wu, S.; Wang, Z.; Huang, Q.; Tan, X.; Lu, X. [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Ostrikov, K. [CSIRO Materials Science and Engineering, PO Box 218, Lindfield NSW 2070 (Australia); School of Physics, University of Sydney, Sydney NSW 2006 (Australia); State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

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 generated 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.

Railgun system using a laser-induced plasma armature

International Nuclear Information System (INIS)

Onozuka, M.; Oda, Y.; Azuma, K.

1996-01-01

Development of an electromagnetic railgun system that utilizes a laser-induced plasma armature formation has been conducted to investigate the application of the railgun system for high-speed pellet injection into fusion plasmas. Using the laser-induced plasma formation technique, the required breakdown voltage was reduced by one-tenth compared with that for the spark-discharged plasma. The railgun system successfully accelerated the laser-induced plasma armature by an electromagnetic force that accelerated the pellet. The highest velocity of the solid hydrogen pellets, obtained so far, was 2.6 km/sec using a 2m-long railgun. copyright 1996 American Institute of Physics

Railgun system using a laser-induced plasma armature

Science.gov (United States)

Onozuka, Masanori; Oda, Yasushi; Azuma, Kingo

1996-05-01

Development of an electromagnetic railgun system that utilizes a laser-induced plasma armature formation has been conducted to investigate the application of the railgun system for high-speed pellet injection into fusion plasmas. Using the laser-induced plasma formation technique, the required breakdown voltage was reduced by one-tenth compared with that for the spark-discharged plasma. The railgun system successfully accelerated the laser-induced plasma armature by an electromagnetic force that accelerated the pellet. The highest velocity of the solid hydrogen pellets, obtained so far, was 2.6 km/sec using a 2m-long railgun.

Time resolved study of the emission enhancement mechanisms in orthogonal double-pulse laser-induced breakdown spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Sanginés, R., E-mail: roberto.sangines@ccadet.unam.mx; Sobral, H.

2013-10-01

The evolution of laser induced ablation plume on aluminum targets has been investigated in orthogonal pre-ablation double pulse scheme at atmospheric pressure from the earliest stages of plasma evolution. Time-resolved emission spectra from neutrals, singly- and doubly-ionized species obtained with the double pulse experiment have been compared with those from the single pulse configuration. Signal-to-noise enhancement reaches values of up to 15 depending on the analyzed species; and the lower the charge state the later its maximum signal-to-noise ratio is reached. Ablation plume dynamics was monitored from 10 ns after the plasma onset via shadowgraphy and fast-photography with narrow interference filters to follow the evolution of individual species. Results show that ionic species from the target are located at the plasma core while nitrogen from the background air is found at the plume peripheral. Initially both configurations exhibit similar ablation plume sizes and their expansions were successfully fitted with the strong explosion model for the first 500 ns. At later times a good agreement was obtained by using the drag model, which predicts that the plume expansion eventually stops due to interaction with the background gas particles. The emission enhancement measured in the double pulse scheme is discussed in terms of the models describing the plume dynamics. - Highlights: • Production of 2 + ions at the earliest stages of plasma evolution • The higher the charge state the inner the location within the ablation plume. • The expansion rate of the second (ablation) plume was measured. • Shock and drag models successfully fit the ablation shock front expansion.

Railgun system using a laser-induced plasma armature

Energy Technology Data Exchange (ETDEWEB)

Onozuka, M.; Oda, Y.; Azuma, K. [Mitsubishi Heavy Industries, Ltd., 3-3-1, Minatomirai, Nishi-ku, Yokohama 220-84 (Japan)

1996-05-01

Development of an electromagnetic railgun system that utilizes a laser-induced plasma armature formation has been conducted to investigate the application of the railgun system for high-speed pellet injection into fusion plasmas. Using the laser-induced plasma formation technique, the required breakdown voltage was reduced by one-tenth compared with that for the spark-discharged plasma. The railgun system successfully accelerated the laser-induced plasma armature by an electromagnetic force that accelerated the pellet. The highest velocity of the solid hydrogen pellets, obtained so far, was 2.6 km/sec using a 2m-long railgun. {copyright} {ital 1996 American Institute of Physics.}

Influence of external magnetic field on laser-induced gold nanoparticles fragmentation

International Nuclear Information System (INIS)

Serkov, A. A.; Rakov, I. I.; Simakin, A. V.; Kuzmin, P. G.; Shafeev, G. A.; Mikhailova, G. N.; Antonova, L. Kh.; Troitskii, A. V.; Kuzmin, G. P.

2016-01-01

Laser-assisted fragmentation is an efficient method of the nanoparticles size and morphology control. However, its exact mechanisms are still under consideration. One of the remaining problems is the plasma formation, inevitably occurring upon the high intensity laser irradiation. In this Letter, the role of the laser-induced plasma is studied via introduction of high-intensity external magnetic field (up to 7.5 T). Its presence is found to cause the plasma emission to start earlier regarding to a laser pulse, also increasing the plume luminosity. Under these conditions, the acceleration of nanoparticles fragmentation down to a few nanometers is observed. Laser-induced plasma interaction with magnetic field and consequent energy transfer from plasma to nanoparticles are discussed.

Experimental study of plume induced by nanosecond repetitively pulsed spark microdischarges in air at atmospheric pressure

Science.gov (United States)

Orriere, Thomas; Benard, Nicolas; Moreau, Eric; Pai, David

2016-09-01

Nanosecond repetitively pulsed (NRP) spark discharges have been widely studied due to their high chemical reactivity, low gas temperature, and high ionization efficiency. They are useful in many research areas: nanomaterials synthesis, combustion, and aerodynamic flow control. In all of these fields, particular attention has been devoted to chemical species transport and/or hydrodynamic and thermal effects for applications. The aim of this study is to generate an electro-thermal plume by combining an NRP spark microdischarge in a pin-to-pin configuration with a third DC-biased electrode placed a few centimeters away. First, electrical characterization and optical emission spectroscopy were performed to reveal important plasma processes. Second, particle image velocimetry was combined with schlieren photography to investigate the main characteristics of the generated flow. Heating processes are measured by using the N2(C ->B) (0,2) and (1,3) vibrational bands, and effects due to the confinement of the discharge are described. Moreover, the presence of atomic ions N+ and O+ is discussed. Finally, the electro-thermal plume structure is characterized by a flow velocity around 1.8 m.s-1, and the thermal kernel has a spheroidal shape.

On helicon wave induced radial plasma transport

International Nuclear Information System (INIS)

Petrzilka, V.

1993-04-01

Estimates of helicon wave induced radial plasma transport are presented. The wave induced transport grows or decreases in dependence on the sign of the azimuthal wave number; these changes in transport may play an important role in helicon wave plasma sources. (author) 5 figs., 18 refs

Vibrational emission analysis of the CN molecules in laser-induced breakdown spectroscopy of organic compounds

Energy Technology Data Exchange (ETDEWEB)

Fernández-Bravo, Ángel; Delgado, Tomás; Lucena, Patricia; Laserna, J. Javier, E-mail: laserna@uma.es

2013-11-01

Laser-induced breakdown spectroscopy (LIBS) of organic materials is based on the analysis of atomic and ionic emission lines and on a few molecular bands, the most important being the CN violet system and the C{sub 2} Swan system. This paper is focused in molecular emission of LIBS plasmas based on the CN (B{sup 2}Σ–X{sup 2}Σ) band, one of the strongest emissions appearing in all carbon materials when analyzed in air atmosphere. An analysis of this band with sufficient spectral resolution provides a great deal of information on the molecule, which has revealed that valuable information can be obtained from the plume chemistry and dynamics affecting the excitation mechanisms of the molecules. The vibrational emission of this molecular band has been investigated to establish the dependence of this emission on the molecular structure of the materials. The paper shows that excitation/emission phenomena of molecular species observed in the plume depend strongly on the time interval selected and on the irradiance deposited on the sample surface. Precise time resolved LIBS measurements are needed for the observation of distinctive CN emission. For the organic compounds studied, larger differences in the behavior of the vibrational emission occur at early stages after plasma ignition. Since molecular emission is generally more complex than that involving atomic emission, local plasma conditions as well as plume chemistry may induce changes in vibrational emission of molecules. As a consequence, alterations in the distribution of the emissions occur in terms of relative intensities, being sensitive to the molecular structure of every single material. - Highlights: • Vibrational emission of CN species in laser-induced plasmas has been investigated. • Distribution of vibrational emission of CN has been found to be time dependent. • Laser irradiance affects the vibrational distribution of the CN molecules. • Plume chemistry controls the excitation mechanisms of CN

High-order harmonic generation in a laser plasma: a review of recent achievements

International Nuclear Information System (INIS)

Ganeev, R A

2007-01-01

A review of studies of high-order harmonic generation in plasma plumes is presented. The generation of high-order harmonics (up to the 101st order, λ = 7.9 nm) of Ti:sapphire laser radiation during the propagation of short laser pulses through a low-excited, low-ionized plasma produced on the surfaces of different targets is analysed. The observation of considerable resonance-induced enhancement of a single harmonic (λ = 61.2 nm) at the plateau region with 10 -4 conversion efficiency in the case of an In plume can offer some expectations that analogous processes can be realized in other plasma samples in the shorter wavelength range. Recent achievements of single-harmonic enhancement at mid- and end-plateau regions are discussed. Various methods for the optimization of harmonic generation are analysed, such as the application of the second harmonic of driving radiation and the application of prepulses of different durations. The enhancement of harmonic generation efficiency during the propagation of femtosecond pulses through a nanoparticle-containing plasma is discussed. (topical review)

Reaction between laser ablation plume and ambient gas studied by laser-induced fluorescence imaging spectroscopy

International Nuclear Information System (INIS)

Sasaki, K; Watarai, H

2007-01-01

We visualized the density distributions of C 2 (plume), NO (ambient gas), and CN (reaction product) when a graphite target was ablated by irradiating YAG laser pulses at wavelengths of 1064 and 355 nm in ambient gas mixture of NO and He. It has been shown by the density distributions of C 2 and NO that the expansion of the plume removes the ambient gas and the plume and the ambient gas locate exclusively in both the cases at 1064 and 355 nm. A high CN density was observed at the interface between the plume and the ambient gas at 1064 nm, which is reasonable since chemical reactions between the plume and the ambient gas may occur only at their interface. On the other hand, in the case at 355 nm, we observed considerable CN inside the plume, indicating that the chemical reaction processes in the laser ablation at 355 nm is different from that expected from the density distributions of the plume and the ambient gas

An integral model of plume rise from high explosive detonations

International Nuclear Information System (INIS)

Boughton, B.A.; De Laurentis, J.M.

1987-01-01

A numerical model has been developed which provides a complete description of the time evolution of both the physical and thermodynamic properties of the cloud formed when a high explosive is detonated. This simulation employs the integral technique. The model equations are derived by integrating the three-dimensional conservation equations of mass, momentum and energy over the plume cross section. Assumptions are made regarding (a) plume symmetry; (b) the shape of profiles of velocity, temperature, etc. across the plume; and (c) the methodology for simulating entrainment and the effects of the crossflow induced pressure drag force on the plume. With these assumptions, the integral equations can be reduced to a set of ordinary differential equations on the plume centerline variables. Only the macroscopic plume characteristics, e.g., plume radius, centerline height, temperature and density, are predicted; details of the plume intrastructure are ignored. The model explicitly takes into account existing meteorology and has been expanded to consider the alterations in plume behavior which occur when aqueous foam is used as a dispersal mitigating material. The simulation was tested by comparison with field measurements of cloud top height and diameter. Predictions were within 25% of field observations over a wide range of explosive yield and atmospheric stability

Elemental analysis of bead samples using a laser-induced plasma at low pressure

International Nuclear Information System (INIS)

Lie, Tjung Jie; Kurniawan, Koo Hendrik; Kurniawan, Davy P.; Pardede, Marincan; Suliyanti, Maria Margaretha; Khumaeni, Ali; Natiq, Shouny A.; Abdulmadjid, Syahrun Nur; Lee, Yong Inn; Kagawa, Kiichiro; Idris, Nasrullah; Tjia, May On

2006-01-01

An Nd:YAG laser (1064 nm, 8 ns, 30 mJ) was focused on various types of fresh, fossilized white coral and giant shell samples, including samples of imitation shell and marble. Such samples are extremely important as material for preparing prayer beads that are extensively used in the Buddhist faith. The aim of this research was to develop a non-destructive method to distinguish original beads from their imitations by means of spectral measurements of the carbon, hydrogen, sodium and magnesium emission intensities and by measuring the hardness of the sample using the ratio between Ca (II) 396.8 nm and Ca (I) 422.6 nm. Based on these measurements, original fresh coral beads can be distinguished from any imitation made from hard wood. The same technique was also effective in distinguishing beads made of shell from its imitation. A spectral analysis of bead was also performed on a fossilized white coral sample and the result can be used to distinguish to some extent the fossilized white coral beads from any imitation made from marble. It was also found that the plasma plume should be generated at low ambient pressure to significantly improve the hydrogen and carbon emission intensity and also to avoid energy loss inside the crater during laser irradiation at atmospheric pressure. The results of this study confirm that operating the laser-induced plasma spectroscopy at reduced ambient pressure offers distinct advantage for bead analysis over the conventional laser-induced breakdown spectroscopy (LIBS) technique operated at atmospheric pressure

Elemental analysis of bead samples using a laser-induced plasma at low pressure

Energy Technology Data Exchange (ETDEWEB)

Lie, Tjung Jie [Research Center of Maju Makmur Mandiri Foundation, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630 (Indonesia); Kurniawan, Koo Hendrik [Research Center of Maju Makmur Mandiri Foundation, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630 (Indonesia)]. E-mail: kurnia18@cbn.net.id; Kurniawan, Davy P. [Research Center of Maju Makmur Mandiri Foundation, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630 (Indonesia); Pardede, Marincan [Research Center of Maju Makmur Mandiri Foundation, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630 (Indonesia); Suliyanti, Maria Margaretha [Graduate Program in Opto Electrotechniques and Laser Applications, Faculty of Engineering, The University of Indonesia, 4 Salemba Raya, Jakarta 10430 (Indonesia); Khumaeni, Ali [Department of Physics, Faculty of Mathematics and Natural Sciences, Diponegoro University, Tembalang Campus, Semarang 50275 (Indonesia); Natiq, Shouny A. [Department of Physics, Faculty of Mathematics and Natural Sciences, Diponegoro University, Tembalang Campus, Semarang 50275 (Indonesia); Abdulmadjid, Syahrun Nur [Department of Physics, Faculty of Mathematics and Natural Sciences, Syiah Kuala University, Darussalam, Banda Aceh 23116 (Indonesia); Lee, Yong Inn [Physics Department, Chonbuk National University, Chonju 561-756, South Korea (Korea); Kagawa, Kiichiro [Department of Physics, Faculty of Education and Regional Studies, Fukui University, 9-1 bunkyo 3-chome, Fukui 910-8507 (Japan); Idris, Nasrullah [Department of Physics, Faculty of Education and Regional Studies, Fukui University, 9-1 bunkyo 3-chome, Fukui 910-8507 (Japan); Tjia, May On [Department of Physics, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, 10 Ganesha, Bandung 40132 (Indonesia)

2006-01-15

An Nd:YAG laser (1064 nm, 8 ns, 30 mJ) was focused on various types of fresh, fossilized white coral and giant shell samples, including samples of imitation shell and marble. Such samples are extremely important as material for preparing prayer beads that are extensively used in the Buddhist faith. The aim of this research was to develop a non-destructive method to distinguish original beads from their imitations by means of spectral measurements of the carbon, hydrogen, sodium and magnesium emission intensities and by measuring the hardness of the sample using the ratio between Ca (II) 396.8 nm and Ca (I) 422.6 nm. Based on these measurements, original fresh coral beads can be distinguished from any imitation made from hard wood. The same technique was also effective in distinguishing beads made of shell from its imitation. A spectral analysis of bead was also performed on a fossilized white coral sample and the result can be used to distinguish to some extent the fossilized white coral beads from any imitation made from marble. It was also found that the plasma plume should be generated at low ambient pressure to significantly improve the hydrogen and carbon emission intensity and also to avoid energy loss inside the crater during laser irradiation at atmospheric pressure. The results of this study confirm that operating the laser-induced plasma spectroscopy at reduced ambient pressure offers distinct advantage for bead analysis over the conventional laser-induced breakdown spectroscopy (LIBS) technique operated at atmospheric pressure.

Current-driven ion-acoustic and potential-relaxation instabilities excited in plasma plume during electron beam welding

Energy Technology Data Exchange (ETDEWEB)

Trushnikov, D. N., E-mail: trdimitr@yandex.ru [The department for Applied Physics, Perm National Research Polytechnic University, Perm, 614990 (Russian Federation); Mladenov, G. M., E-mail: gmmladenov@abv.bg; Koleva, E. G., E-mail: eligeorg@abv.bg [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Shose, 1784, Sofia (Bulgaria); Technology Centre of Electron Beam and Plasma Technologies and Techniques, 68-70 Vrania, ap.10, Banishora,1309, Sofia (Bulgaria); Belenkiy, V. Ya., E-mail: mtf@pstu.ru; Varushkin, S. V., E-mail: stepan.varushkin@mail.ru [The department for Welding Production and Technology of Constructional Materials, Perm National Research Polytechnic University, Perm, 614990 (Russian Federation)

2014-04-15

Many papers have sought correlations between the parameters of secondary particles generated above the beam/work piece interaction zone, dynamics of processes in the keyhole, and technological processes. Low- and high-frequency oscillations of the current, collected by plasma have been observed above the welding zone during electron beam welding. Low-frequency oscillations of secondary signals are related to capillary instabilities of the keyhole, however; the physical mechanisms responsible for the high-frequency oscillations (>10 kHz) of the collected current are not fully understood. This paper shows that peak frequencies in the spectra of the collected high-frequency signal are dependent on the reciprocal distance between the welding zone and collector electrode. From the relationship between current harmonics frequency and distance of the collector/welding zone, it can be estimated that the draft velocity of electrons or phase velocity of excited waves is about 1600 m/s. The dispersion relation with the properties of ion-acoustic waves is related to electron temperature 10 000 K, ion temperature 2 400 K and plasma density 10{sup 16} m{sup −3}, which is analogues to the parameters of potential-relaxation instabilities, observed in similar conditions. The estimated critical density of the transported current for creating the anomalous resistance state of plasma is of the order of 3 A·m{sup −2}, i.e. 8 mA for a 3–10 cm{sup 2} collector electrode. Thus, it is assumed that the observed high-frequency oscillations of the current collected by the positive collector electrode are caused by relaxation processes in the plasma plume above the welding zone, and not a direct demonstration of oscillations in the keyhole.

High-Density Plasma-Induced Etch Damage of GaN

International Nuclear Information System (INIS)

Baca, A.G.; Han, J.; Lester, L.F.; Pearton, S.J.; Ren, F.; Shul, R.J.; Willison, C.G.; Zhang, L.; Zolper, J.C.

1999-01-01

Anisotropic, smooth etching of the group-III nitrides has been reported at relatively high rates in high-density plasma etch systems. However, such etch results are often obtained under high de-bias and/or high plasma flux conditions where plasma induced damage can be significant. Despite the fact that the group-III nitrides have higher bonding energies than more conventional III-V compounds, plasma-induced etch damage is still a concern. Attempts to minimize such damage by reducing the ion energy or increasing the chemical activity in the plasma often result in a loss of etch rate or anisotropy which significantly limits critical dimensions and reduces the utility of the process for device applications requiring vertical etch profiles. It is therefore necessary to develop plasma etch processes which couple anisotropy for critical dimension and sidewall profile control and high etch rates with low-damage for optimum device performance. In this study we report changes in sheet resistance and contact resistance for n- and p-type GaN samples exposed to an Ar inductively coupled plasma (ICP). In general, plasma-induced damage was more sensitive to ion bombardment energies as compared to plasma flux. In addition, p-GaN was typically more sensitive to plasma-induced damage as compared to n-GaN

Electrical model of cold atmospheric plasma gun

Science.gov (United States)

Slutsker, Ya. Z.; Semenov, V. E.; Krasik, Ya. E.; Ryzhkov, M. A.; Felsteiner, J.; Binenbaum, Y.; Gil, Z.; Shtrichman, R.; Cohen, J. T.

2017-10-01

We present an analytical model of cold atmospheric plasma formed by a dielectric barrier discharge (DBD), which is based on the lumped and distributed elements of an equivalent electric circuit of this plasma. This model is applicable for a wide range of frequencies and amplitudes of the applied voltage pulses, no matter whether or not the generated plasma plume interacts with a target. The model allows quantitative estimation of the plasma plume length and the energy delivered to the plasma. Also, the results of this model can be used for the design of DBD guns which efficiently generate cold atmospheric plasma. A comparison of the results of the model with those obtained in experiments shows a fairly good agreement.

The EUV Spectrum of Sunspot Plumes Observed by SUMER on ...

Indian Academy of Sciences (India)

tribpo

Abstract. We present results from sunspot observations obtained by. SUMER on SOHO. In sunspot plumes the EUV spectrum differs from the quiet Sun; continua are observed with different slopes and intensities; emission lines from molecular hydrogen and many unidentified species indicate unique plasma conditions ...

Quiescent Prominence Dynamics Observed with the Hinode Solar Optical Telescope. I. Turbulent Upflow Plumes

Science.gov (United States)

Berger, Thomas E.; Slater, Gregory; Hurlburt, Neal; Shine, Richard; Tarbell, Theodore; Title, Alan; Lites, Bruce W.; Okamoto, Takenori J.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Magara, Tetsuya; Suematsu, Yoshinori; Shimizu, Toshifumi

2010-06-01

Hinode/Solar Optical Telescope (SOT) observations reveal two new dynamic modes in quiescent solar prominences: large-scale (20-50 Mm) "arches" or "bubbles" that "inflate" from below into prominences, and smaller-scale (2-6 Mm) dark turbulent upflows. These novel dynamics are related in that they are always dark in visible-light spectral bands, they rise through the bright prominence emission with approximately constant speeds, and the small-scale upflows are sometimes observed to emanate from the top of the larger bubbles. Here we present detailed kinematic measurements of the small-scale turbulent upflows seen in several prominences in the SOT database. The dark upflows typically initiate vertically from 5 to 10 Mm wide dark cavities between the bottom of the prominence and the top of the chromospheric spicule layer. Small perturbations on the order of 1 Mm or less in size grow on the upper boundaries of cavities to generate plumes up to 4-6 Mm across at their largest widths. All plumes develop highly turbulent profiles, including occasional Kelvin-Helmholtz vortex "roll-up" of the leading edge. The flows typically rise 10-15 Mm before decelerating to equilibrium. We measure the flowfield characteristics with a manual tracing method and with the Nonlinear Affine Velocity Estimator (NAVE) "optical flow" code to derive velocity, acceleration, lifetime, and height data for several representative plumes. Maximum initial speeds are in the range of 20-30 km s-1, which is supersonic for a ~10,000 K plasma. The plumes decelerate in the final few Mm of their trajectories resulting in mean ascent speeds of 13-17 km s-1. Typical lifetimes range from 300 to 1000 s (~5-15 minutes). The area growth rate of the plumes (observed as two-dimensional objects in the plane of the sky) is initially linear and ranges from 20,000 to 30,000 km2 s-1 reaching maximum projected areas from 2 to 15 Mm2. Maximum contrast of the dark flows relative to the bright prominence plasma in SOT images

QUIESCENT PROMINENCE DYNAMICS OBSERVED WITH THE HINODE SOLAR OPTICAL TELESCOPE. I. TURBULENT UPFLOW PLUMES

International Nuclear Information System (INIS)

Berger, Thomas E.; Slater, Gregory; Hurlburt, Neal; Shine, Richard; Tarbell, Theodore; Title, Alan; Lites, Bruce W.; Okamoto, Takenori J.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Magara, Tetsuya; Suematsu, Yoshinori; Shimizu, Toshifumi

2010-01-01

Hinode/Solar Optical Telescope (SOT) observations reveal two new dynamic modes in quiescent solar prominences: large-scale (20-50 Mm) 'arches' or 'bubbles' that 'inflate' from below into prominences, and smaller-scale (2-6 Mm) dark turbulent upflows. These novel dynamics are related in that they are always dark in visible-light spectral bands, they rise through the bright prominence emission with approximately constant speeds, and the small-scale upflows are sometimes observed to emanate from the top of the larger bubbles. Here we present detailed kinematic measurements of the small-scale turbulent upflows seen in several prominences in the SOT database. The dark upflows typically initiate vertically from 5 to 10 Mm wide dark cavities between the bottom of the prominence and the top of the chromospheric spicule layer. Small perturbations on the order of 1 Mm or less in size grow on the upper boundaries of cavities to generate plumes up to 4-6 Mm across at their largest widths. All plumes develop highly turbulent profiles, including occasional Kelvin-Helmholtz vortex 'roll-up' of the leading edge. The flows typically rise 10-15 Mm before decelerating to equilibrium. We measure the flowfield characteristics with a manual tracing method and with the Nonlinear Affine Velocity Estimator (NAVE) 'optical flow' code to derive velocity, acceleration, lifetime, and height data for several representative plumes. Maximum initial speeds are in the range of 20-30 km s -1 , which is supersonic for a ∼10,000 K plasma. The plumes decelerate in the final few Mm of their trajectories resulting in mean ascent speeds of 13-17 km s -1 . Typical lifetimes range from 300 to 1000 s (∼5-15 minutes). The area growth rate of the plumes (observed as two-dimensional objects in the plane of the sky) is initially linear and ranges from 20,000 to 30,000 km 2 s -1 reaching maximum projected areas from 2 to 15 Mm 2 . Maximum contrast of the dark flows relative to the bright prominence plasma in

High-Resolution Spectroscopy of Laser Ablation Plumes Using Laser-Induced Fluorescence

Energy Technology Data Exchange (ETDEWEB)

Harilal, Sivanandan S.; LaHaye, Nicole L.; Phillips, Mark C.

2017-02-06

We used a CW laser as a narrow-band (~50kHz) tunable LIF excitation source to probe absorption from selected atomic transitions (Al, U etc. ) in a ns laser ablation plume. A comparison of fluorescence signal with respect to emission spectroscopy show significant increase in the magnitude and persistence from selected Al and U transitions in a LIBS plume. The high spectral resolution provided by the LIF measurement allows peaks to be easily separated even if they overlap in the emission spectra.

Velocity and texture of a plasma jet created in a plasma torch with fixed minimal arc length

International Nuclear Information System (INIS)

Vilotijevic, M; Dacic, B; Bozic, D

2009-01-01

A new plasma jet (PJ-100) plasma spraying torch with a fixed minimal arc length was tested and the basic working parameters were measured and evaluated. The velocity of the plasma exiting both the cylindrical and the conical anode nozzles was assessed by measuring the thrust generated by the plasma jet and by photographing the translation of plasma clouds (parts with different brightnesses) in the last third of the length of the plasma plume. The basic characteristics of the argon/hydrogen plasma jets (enthalpy, mean temperature, mean plasma velocity and effective exhaust thrust velocity) were determined for different working regimes, for both the cylindrical and the conical nozzles. The thermal efficiency of the new plasma torch is between 70% and 74% for the plasma generation power up to 90 kW. The plasma plume generated in the cylindrical nozzle has a homogeneous radial temperature (and velocity) distribution with a full laminar flow.

The planet beyond the plume hypothesis

Science.gov (United States)

Smith, Alan D.; Lewis, Charles

1999-12-01

but not counterflow, though convergent margin geometry may still induce propagating fractures which set up melting anomalies. Lateral migration of asthenospheric domains allows the sources of Pacific intraplate volcanism to be traced back to continental mantle eroded during the breakup of Gondwana and the amalgamation of Asia in the Paleozoic. Intraplate volcanism in the South Pacific therefore has a common Gondwanan origin to intraplate volcanism in the South Atlantic and Indian Oceans, hence the DUPAL anomaly is entirely of shallow origin. Such domains constitute a second order geochemical heterogeneity superimposed on a streaky/marble-cake structure arising from remixing of subducted crust with the convecting mantle. During the Proterozoic and Phanerozoic, remixing of slabs has buffered the evolution of the depleted mantle to a rate of 2.2 ɛNd units Ga -1, with fractionation of Lu from Hf in the sediment component imparting the large range in 176Hf/ 177Hf relative to 143Nd/ 144Nd observed in MORB. Only the high ɛNd values of some Archean komatiites are compatible with derivation from unbuffered mantle. The existence of a very depleted reservoir is attributed to stabilisation of a large early continental crust through either obduction tectonics or slab melting regimes which reduced the efficiency of crustal recycling back into the mantle. Generation of komatiite is therefore a consequence of mantle composition, and is permitted in ocean ridge environments and/or under hydrous melting conditions. Correspondingly, as intraplate volcanism depends on survival of volatile-bearing sources, its appearance in the Middle Proterozoic corresponds to the time in the Earth's thermal evolution at which minerals such as phlogopite and amphibole could survive in off-ridge environments in the shallow asthenosphere. The geodynamic evolution of the Earth was thus determined at convergent margins, not by plumes and hotspots, with the decline in thermal regime causing both a reduction

Experimental investigation of bubble plume structure instability

Energy Technology Data Exchange (ETDEWEB)

Marco Simiano; Robert Zboray; Francois de Cachard [Thermal-Hydraulics Laboratory, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Djamel Lakehal; George Yadigaroglu [Institute of Energy Technology, Swiss Federal Institute of Technology, ETH-Zentrum/CLT, 8092 Zurich (Switzerland)

2005-07-01

Full text of publication follows: The hydrodynamic properties of a 3D bubble plume in a large water pool are investigated experimentally. Bubble plumes are present in various industrial processes, including chemical plants, stirred reactors, and nuclear power plants, e.g. in BWR suppression pools. In these applications, the main issue is to predict the currents induced by the bubbles in the liquid phase, and to determine the consequent mixing. Bubble plumes, especially large and unconfined ones, present strong 3D effects and a superposition of different characteristic length scales. Thus, they represent relevant test cases for assessment and verification of 3D models in thermal-hydraulic codes. Bubble plumes are often unsteady, with fluctuations in size and shape of the bubble swarm, and global movements of the plume. In this case, local time-averaged data are not sufficient to characterize the flow. Additional information regarding changes in plume shape and position is required. The effect of scale on the 3D flow structure and stability being complex, there was a need to conduct studies in a fairly large facility, closer to industrial applications. Air bubble plumes, up to 30 cm in base diameter and 2 m in height were extensively studied in a 2 m diameter water pool. Homogeneously sized bubbles were obtained using a particular injector. The main hydrodynamic parameters. i.e., gas and liquid velocities, void fraction, bubble shape and size, plume shape and position, were determined experimentally. Photographic and image processing techniques were used to characterize the bubble shape, and double-tip optical probes to measure bubble size and void fraction. Electromagnetic probes measured the recirculation velocity in the pool. Simultaneous two-phase flow particle image velocimetry (STPFPIV) in a vertical plane containing the vessel axis provided instantaneous velocity fields for both phases and therefore the relative velocity field. Video recording using two CCD

Diurnal and Seasonal Statistical Characteristics of Well-formed Plasma Depletion and Enhancement Plumes under Quiet Solar Conditions

Science.gov (United States)

Haaser, R. A.

2011-12-01

The Ion Velocity Meter (IVM), a part of the Coupled Ion Neutral Dynamics Investigation (CINDI) aboard the Communication/ Navigation Outage Forecasting System (C/NOFS) satellite, is used to measure in situ ion densities and drifts at altitudes between 400 and 550 km during the nighttime hours from 2100 to 300 local time. A new approach to detecting and classifying well-formed ionospheric plasma depletion and enhancement plumes (bubbles and blobs) of scale sizes between 50 and 500 km is used to develop geophysical statistics for the summer, winter and equinox seasons of the quiet solar conditions during 2009 and 2010. Some diurnal and seasonal geomagnetic distribution characteristics confirm previous work on irregularities and scintillations, while others reveal new behaviors that require additional observations and modeling to promote full understanding.

Laser induced aluminiun plasma analysis by optical emission spectroscopy in a nitrogen background gas

International Nuclear Information System (INIS)

Chamorro, J C; Uzuriaga, J; Riascos, H

2012-01-01

We studied an Al plasma generated by a Nd:YAG laser with a laser fluence of 4 J/cm 2 , a wavelength of 1064 nm, energy pulse of 500 mJ and 10 Hz repetition rate. We studied their spectral characteristics at various ambient nitrogen pressures by optical emission spectroscopy (OES). The N 2 gas pressure was varied from 20 mTorr to 150 mTorr. In Al plume, both atomic and ionic spectra were observed. The electron temperature and electron number density of the plume as of the function ambient gas pressure were determined. The electron temperature was calculated by using the Boltzmann-plot method and the number density was calculated considering the stark effect as dominating on the emission lines.

Treatment of Streptococcus mutans bacteria by a plasma needle

International Nuclear Information System (INIS)

Zhang Xianhui; Huang Jun; Lv Guohua; Liu Xiaodi; Peng Lei; Guo Lihong; Chen Wei; Feng Kecheng; Yang Size

2009-01-01

A dielectric barrier discharge plasma needle was realized at atmospheric pressure with a funnel-shaped nozzle. The preliminary characteristics of the plasma plume and its applications in the inactivation of Streptococcus mutans (S. mutans), the most important microorganism causing dental caries, were presented in this paper. The temperature of the plasma plume does not reach higher than 315 K when the power is below 28 W. Oxygen was injected downstream in the plasma afterglow region through the powered steel tube. Its effect was studied via optical-emission spectroscopy, both in air and in agar. Results show that addition of 26 SCCM O 2 does not affect the plume length significantly (SCCM denotes cubic centimeter per minute at STP). The inactivation of S. mutans is primarily attributed to ultraviolet light emission, O, OH, and He radicals

Treatment of Streptococcus mutans bacteria by a plasma needle

Science.gov (United States)

Zhang, Xianhui; Huang, Jun; Liu, Xiaodi; Peng, Lei; Guo, Lihong; Lv, Guohua; Chen, Wei; Feng, Kecheng; Yang, Si-ze

2009-03-01

A dielectric barrier discharge plasma needle was realized at atmospheric pressure with a funnel-shaped nozzle. The preliminary characteristics of the plasma plume and its applications in the inactivation of Streptococcus mutans (S. mutans), the most important microorganism causing dental caries, were presented in this paper. The temperature of the plasma plume does not reach higher than 315 K when the power is below 28 W. Oxygen was injected downstream in the plasma afterglow region through the powered steel tube. Its effect was studied via optical-emission spectroscopy, both in air and in agar. Results show that addition of 26 SCCM O2 does not affect the plume length significantly (SCCM denotes cubic centimeter per minute at STP). The inactivation of S. mutans is primarily attributed to ultraviolet light emission, O, OH, and He radicals.

Dilution in Transition Zone between Rising Plumes and Surface Plumes

DEFF Research Database (Denmark)

Larsen, Torben

2004-01-01

The papers presents some physical experiments with the dilution of sea outfall plumes with emphasize on the transition zone where the relative fast flowing vertical plume turns to a horizontal surface plume following the slow sea surface currents. The experiments show that a considerable dilution...

The Influence of spot size on the expansion dynamics of nanosecond-laser-produced copper plasmas in atmosphere

International Nuclear Information System (INIS)

Li, Xingwen; Wei, Wenfu; Wu, Jian; Jia, Shenli; Qiu, Aici

2013-01-01

Laser produced copper plasmas of different spot sizes in air were investigated using fast photography and optical emission spectroscopy (OES). The laser energy was 33 mJ. There were dramatic changes in the plasma plume expansion into the ambient air when spot sizes changed from ∼0.1 mm to ∼0.6 mm. A stream-like structure and a hemispherical structure were, respectively, observed. It appeared that the same spot size resulted in similar expansion dynamics no matter whether the target was located in the front of or behind the focal point, although laser-induced air breakdown sometimes occurred in the latter case. Plasma plume front positions agree well with the classic blast wave model for the large spot-size cases, while an unexpected stagnation of ∼80 ns occurred after the laser pulse ends for the small spot size cases. This stagnation can be understood in terms of the evolution of enhanced plasma shielding effects near the plasma front. Axial distributions of plasma components by OES revealed a good confinement effect. Electron number densities were estimated and interpreted using the recorded Intensified Charge Coupled Device (ICCD) images.

Recent trends in atomic spectrometry with microwave-induced plasmas

International Nuclear Information System (INIS)

Broekaert, Jose A.C.; Siemens, Volker

2004-01-01

The state-of-the-art and trends of development in atomic spectrometry with microwave-induced plasmas (MIPs) since the 1998s are presented and discussed. This includes developments in devices for producing microwave plasma discharges, with reference also to miniaturized systems as well as to progress in sample introduction for microwave-induced plasmas, such as pneumatic and ultrasonic nebulization using membrane desolvation, to the further development of gaseous analyte species generation systems and to both spark and laser ablation (LA). The features of microwave-induced plasma mass spectrometry (MIP-MS) as an alternative to inductively coupled plasma (ICP)-MS are discussed. Recent work on the use of microwave-induced plasma atomic spectrometry for trace element determinations and monitoring, their use as tandem sources and for particle sizing are discussed. Recent applications of the coupling of gas chromatography and MIP atomic spectrometry for the determination of organometallic compounds of heavy metals such as Pb, Hg, Se and Sn are reviewed and the possibilities of trapping for sensitivity enhancement, as required for many applications especially in environmental work, are showed at the hand of citations from the recent literature

Analysis of laser ablation: Contribution of ionization energy to the plasma and shock wave properties

International Nuclear Information System (INIS)

Wen, S.-B.; Mao Xianglei; Greif, Ralph; Russo, Richard E.

2007-01-01

By fitting simulation results with experimentally measured trajectories of the shock wave and the vapor/background gas contact surface, we found that inclusion of ionization energy in the analysis leads to a change in the evolution of the pressure, mass density, electron number density, and temperature of the vapor plume. The contribution of ionization energy to both the plasma and shock wave has been neglected in most studies of laser ablation. Compared to previous simulations, the densities, pressures, and temperatures are lower shortly after the laser pulse ( 50 ns). The predicted laser energy conversion ratio also showed about a 20% increase (from 35% to 45%) when the ionization energy is considered. The changes in the evolution of the physical quantities result from the retention of the ionization energy in the vapor plume, which is then gradually transformed to kinetic and thermal energies. When ionization energy is included in the simulation, the vapor plume attains higher expansion speeds and temperatures for a longer time after the laser pulse. The better determination of the temperature history of the vapor plume not only improves the understanding of the expansion process of the laser induced vapor plume but also is important for chemical analysis. The accurate temperature history provides supplementary information which enhances the accuracy of chemical analysis based on spectral emission measurements (e.g., laser induced breakdown spectroscopy)

Dynamics of the plume produced by nanosecond ultraviolet laser ablation of metals

DEFF Research Database (Denmark)

Christensen, Bo Toftmann; Schou, Jørgen; Lunney, J.G.

2003-01-01

The dynamics of the ablation plume of a partially ionized plasma produced by a nanosecond UV laser with different irradiation spot geometries has been explored. We have used an ensemble of quartz crystal microbalances to make the first systematic and quantitative study of how the shape of the plume...... varies as the aspect ratio (b/a) of the elliptical laser spot is varied by about a factor of ten. The flip-over effect can be described by the adiabatic expansion model of Anisimov using a value of the adiabatic constant of about gamma = 1.4. We have also studied the forward peaking of the ablation plume...... for a large number of metals at the same laser fluence. Contrary to earlier reports, we find that the more refractory metals have the broader angular distributions....

Effect of ablation geometry on the dynamics, composition, and geometrical shape of thin film plasma

Science.gov (United States)

Mondal, Alamgir; Singh, R. K.; Kumar, Ajai

2018-01-01

The characteristics of plasma plume produced by front and back ablation of thin films have been investigated using fast imaging and optical emission spectroscopy. Ablation geometry dependence of the plume dynamics, its geometrical aspect and composition is emphasized. Also, the effect of an ambient environment and the beam diameter of an ablating laser on the front and back ablations is briefly discussed. Analysis of time resolved images and plasma parameters indicates that the energetic and spherical plasma formed by front ablation is strikingly different in comparison to the slow and nearly cylindrical plasma plume observed in the case of back ablation. Further shock formation, plume confinement, thermalization and validity of different expansion models in these two ablation geometries are also presented. The present study demonstrates the manipulation of kinetic energy, shape, ion/neutral compositions and directionality of the expanding plume by adjusting the experimental configuration, which is highly relevant to its utilization in various applications e.g., generation of energetic particles, tokamak edge plasma diagnostics, thin film deposition, etc.

[Investigation on the gas temperature of a plasma jet at atmospheric pressure by emission spectrum].

Science.gov (United States)

Li, Xue-chen; Yuan, Ning; Jia, Peng-ying; Niu, Dong-ying

2010-11-01

A plasma jet of a dielectric barrier discharge in coaxial electrode was used to produce plasma plume in atmospheric pressure argon. Spatially and temporally resolved measurement was carried out by photomultiplier tubes. The light emission signals both from the dielectric barrier discharge and from the plasma plume were analyzed. Furthermore, emission spectrum from the plasma plume was collected by high-resolution optical spectrometer. The emission spectra of OH (A 2sigma + --> X2 II, 307.7-308.9 nm) and the first negative band of N2+ (B2 sigma u+ --> X2 IIg+, 390-391.6 nm) were used to estimate the rotational temperature of the plasma plume by fitting the experimental spectra to the simulated spectra. The rotational temperature obtained is about 443 K by fitting the emission spectrum from the OH, and that from the first negative band of N2+ is about 450 K. The rotational temperatures obtained by the two method are consistent within 5% error band. The gas temperature of the plasma plume at atmospheric pressure was obtained because rotational temperature equals to gas temperature approximately in gas discharge at atmospheric pressure. Results show that gas temperature increases with increasing the applied voltage.

Observational evidence for turbulent effects on total suspended matter within the Pearl River plume

Science.gov (United States)

Chunhua, Qiu; Danyi, Su; Huabin, Mao; Jiaxue, Wu; Yongsheng, Cui; Dongxiao, Wang

2017-12-01

We observed the structure of the Pearl River plume and its turbulent characteristics, and investigated the turbulent effect on total suspended matter (TSM) within its ;far-field; region, based on in situ and satellite data collected in June 2015. A significant northeastward plume was created under southern monsoonal conditions. The in situ data provided the width, depth, and velocity of the plume, as inferred by salinity. Weaker turbulence occurred at the front surface position than in the plume zone. Stronger turbulence induced greater turbidity in the bottom boundary layer; however, the surface mixed layer differed. By estimating the turbidity budget, we found the lateral fluxes term was the largest term in the plume, turbulent fluxes comprised the second largest term, and the settling terms comprised the smallest term. We quantified the turbulent mechanisms and found that stronger river discharge induced greater TSM turbidity. Tidal and buoyancy fluxes had minor regulatory effects on TSM. Our observations suggest that TSM in the ;far field; region originated from the Pearl River and the coastal region.

Expansion dynamics and equilibrium conditions in a laser ablation plume of lithium: Modeling and experiment

International Nuclear Information System (INIS)

Stapleton, M.W.; McKiernan, A.P.; Mosnier, J.-P.

2005-01-01

The gas dynamics and atomic kinetics of a laser ablation plume of lithium, expanding adiabatically in vacuum, are included in a numerical model, using isothermal and isentropic self-similar analytical solutions and steady-state collisional radiative equations, respectively. Measurements of plume expansion dynamics using ultrafast imaging for various laser wavelengths (266-1064 nm), fluences (2-6.5 J cm -2 ), and spot sizes (50-1000 μm) are performed to provide input parameters for the model and, thereby, study the influence of laser spot size, wavelength, and fluence, respectively, on both the plume expansion dynamics and atomic kinetics. Target recoil pressure, which clearly affects plume dynamics, is included in the model. The effects of laser wavelength and spot size on plume dynamics are discussed in terms of plasma absorption of laser light. A transition from isothermal to isentropic behavior for spot sizes greater than 50 μm is clearly evidenced. Equilibrium conditions are found to exist only up to 300 ns after the plume creation, while complete local thermodynamic equilibrium is found to be confined to the very early parts of the expansion

Tracking of smokestack and cooling tower plumes using wind measurements at different levels

International Nuclear Information System (INIS)

Miller, R.L.; Patrinos, A.A.N.

1980-08-01

Relationships between cooling tower and smokestack plumes at the Bowen Electric Generating Plant in northwestern Georgia and wind direction measurements at levels from the surface at 850 mb (approx. 1.5 km) are examined. The wind measurements play an important role in estimating plume directions which in turn are utilized to establish control and target (upwind and downwind) areas for a study of plant-induced precipitation modification. Fifty-two plume observations were made during a three week period in December 1979. Results indicate that a windset (4.5 km from the plant) mounted at a level approximating that of the cooling tower plume is a better predictor of plume direction than surface windsets (1.0 km from the plant) or 850 mb level winds. However, an apparent topographical influence on the wind direction measurements at the plume-level windset site somewhat limits its plume tracking capability, at least for ambient winds from the SW quadrant

Non-Maxwellian electron energy probability functions in the plume of a SPT-100 Hall thruster

Science.gov (United States)

Giono, G.; Gudmundsson, J. T.; Ivchenko, N.; Mazouffre, S.; Dannenmayer, K.; Loubère, D.; Popelier, L.; Merino, M.; Olentšenko, G.

2018-01-01

We present measurements of the electron density, the effective electron temperature, the plasma potential, and the electron energy probability function (EEPF) in the plume of a 1.5 kW-class SPT-100 Hall thruster, derived from cylindrical Langmuir probe measurements. The measurements were taken on the plume axis at distances between 550 and 1550 mm from the thruster exit plane, and at different angles from the plume axis at 550 mm for three operating points of the thruster, characterized by different discharge voltages and mass flow rates. The bulk of the electron population can be approximated as a Maxwellian distribution, but the measured distributions were seen to decline faster at higher energy. The measured EEPFs were best modelled with a general EEPF with an exponent α between 1.2 and 1.5, and their axial and angular characteristics were studied for the different operating points of the thruster. As a result, the exponent α from the fitted distribution was seen to be almost constant as a function of the axial distance along the plume, as well as across the angles. However, the exponent α was seen to be affected by the mass flow rate, suggesting a possible relationship with the collision rate, especially close to the thruster exit. The ratio of the specific heats, the γ factor, between the measured plasma parameters was found to be lower than the adiabatic value of 5/3 for each of the thruster settings, indicating the existence of non-trivial kinetic heat fluxes in the near collisionless plume. These results are intended to be used as input and/or testing properties for plume expansion models in further work.

Laser-induced shockwave propagation from ablation in a cavity

International Nuclear Information System (INIS)

Zeng Xianzhong; Mao Xianglei; Mao, Samuel S.; Wen, S.-B.; Greif, Ralph; Russo, Richard E.

2006-01-01

The propagation of laser-induced shockwaves from ablation inside of cavities was determined from time-resolved shadowgraph images. The temperature and electron number density of the laser-induced plasma was determined from spectroscopic measurements. These properties were compared to those for laser ablation on the flat surface under the same energy and background gas condition. A theoretical model was proposed to determine the amount of energy and vaporized mass stored in the vapor plume based on these measurements

Observations of subauroral ionospheric dynamics during SED plume passage at Millstone Hill

Science.gov (United States)

Zhang, S.; Erickson, P. J.; Coster, A. J.

2017-12-01

Storm enhanced density (SED) is a characteristic ionospheric storm time structure, with a significant plasma density enhancement in a narrow zone. SED structures often (but not always) span the continental US with a base in the US northeast at the afternoon and dusk sector, extending westward or northwest into the high latitude dayside cusp region. It is a typical and repeatable space weather phenomenon occurring during the main phase of magnetic storms with intensity ranging from active to disturbed levels. Observations of stormtime ionospheric density enhancement at subauroral latitudes have a long history, and were termed the 'dusk effect' until relatively recently, when dense networks of GNSS receivers have allowed us to view this structure with much finer spatial and temporal resolution. The formation of a SED plume is a topic under intensive community investigation, but in general it is believed that stormtime ionospheric dynamics and processes within the coupling magnetosphere-ionosphere-thermosphere system are responsible. For instance, poleward and sunward plasma drifts at the edge of the expanded dusk sector high-latitude convection can be important. Subauroral polarization stream (SAPS) are often observed at the poleward edge of the SED plume where ionospheric conductivity is low. SAPS is a huge westward ion flow that can convect ionospheric plasma from the afternoon or evening sector where solar photoionization production is waning, creating low density or density troughs. Stormtime penetration electric fields also exist, creating enhanced low and mid latitude upward ion drifts that move ionospheric plasma upward from the low altitude region where they are produced. This provides another important ionization source to contribute to maintaining the SED plume. This paper will provide analysis of the relative strength of these factors by using joint datasets of current geospace storm events obtained with the Millstone Hill incoherent scatter radar, GNSS

High excitation of the species in nitrogen–aluminum plasma generated by electron cyclotron resonance microwave discharge of N2 gas and pulsed laser ablation of Al target

International Nuclear Information System (INIS)

Liang, Peipei; Li, Yanli; Cai, Hua; You, Qinghu; Yang, Xu; Huang, Feiling; Sun, Jian; Xu, Ning; Wu, Jiada

2014-01-01

A reactive nitrogen–aluminum plasma generated by electron cyclotron resonance (ECR) microwave discharge of N 2 gas and pulsed laser ablation of an Al target is characterized spectroscopically by time-integrated and time-resolved optical emission spectroscopy (OES). The vibrational and rotational temperatures of N 2 species are determined by spectral simulation. The generated plasma strongly emits radiation from a variety of excited species including ambient nitrogen and ablated aluminum and exhibits unique features in optical emission and temperature evolution compared with the plasmas generated by a pure ECR discharge or by the expansion of the ablation plume. The working N 2 gas is first excited by ECR discharge and the excitation of nitrogen is further enhanced due to the fast expansion of the aluminum plume induced by target ablation, while the excitation of the ablated aluminum is prolonged during the plume expansion in the ECR nitrogen plasma, resulting in the formation of strongly reactive nitrogen–aluminum plasma which contains highly excited species with high vibrational and rotational temperatures. The enhanced intensities and the prolonged duration of the optical emissions of the combined plasma would provide an improved analytical capability for spectrochemical analysis. - Highlights: • ECR discharge and pulsed laser ablation generate highly excited ECR–PLA plasma. • The expansion of PLA plasma results in excitation enhancement of ECR plasma species. • The ECR plasma leads to excitation prolongation of PLA plasma species. • The ECR–PLA plasma emits strong emissions from a variety of excited species. • The ECR–PLA plasma maintains high vibrational–rotational temperatures for a long time

Three Dimensional Simulation of Ion Thruster Plume-Spacecraft Interaction Based on a Graphic Processor Unit

International Nuclear Information System (INIS)

Ren Junxue; Xie Kan; Qiu Qian; Tang Haibin; Li Juan; Tian Huabing

2013-01-01

Based on the three-dimensional particle-in-cell (PIC) method and Compute Unified Device Architecture (CUDA), a parallel particle simulation code combined with a graphic processor unit (GPU) has been developed for the simulation of charge-exchange (CEX) xenon ions in the plume of an ion thruster. Using the proposed technique, the potential and CEX plasma distribution are calculated for the ion thruster plume surrounding the DS1 spacecraft at different thrust levels. The simulation results are in good agreement with measured CEX ion parameters reported in literature, and the GPU's results are equal to a CPU's. Compared with a single CPU Intel Core 2 E6300, 16-processor GPU NVIDIA GeForce 9400 GT indicates a speedup factor of 3.6 when the total macro particle number is 1.1×10 6 . The simulation results also reveal how the back flow CEX plasma affects the spacecraft floating potential, which indicates that the plume of the ion thruster is indeed able to alleviate the extreme negative floating potentials of spacecraft in geosynchronous orbit

Solar Coronal Plumes

Directory of Open Access Journals (Sweden)

Giannina Poletto

2015-12-01

Full Text Available Polar plumes are thin long ray-like structures that project beyond the limb of the Sun polar regions, maintaining their identity over distances of several solar radii. Plumes have been first observed in white-light (WL images of the Sun, but, with the advent of the space era, they have been identified also in X-ray and UV wavelengths (XUV and, possibly, even in in situ data. This review traces the history of plumes, from the time they have been first imaged, to the complex means by which nowadays we attempt to reconstruct their 3-D structure. Spectroscopic techniques allowed us also to infer the physical parameters of plumes and estimate their electron and kinetic temperatures and their densities. However, perhaps the most interesting problem we need to solve is the role they cover in the solar wind origin and acceleration: Does the solar wind emanate from plumes or from the ambient coronal hole wherein they are embedded? Do plumes have a role in solar wind acceleration and mass loading? Answers to these questions are still somewhat ambiguous and theoretical modeling does not provide definite answers either. Recent data, with an unprecedented high spatial and temporal resolution, provide new information on the fine structure of plumes, their temporal evolution and relationship with other transient phenomena that may shed further light on these elusive features.

Entrainment by turbulent plumes

Science.gov (United States)

Parker, David; Burridge, Henry; Partridge, Jamie; Linden, Paul

2017-11-01

Plumes are of relevance to nature and real consequence to industry. While the Morton, Taylor & Turner (1956) plume model is able to estimate the mean physical flux parameters, the process of entrainment is only parametrised in a time-averaged sense and a deeper understanding is key to understanding how they evolve. Various flow configurations, resulting in different entrainment values, are considered; we perform simultaneous PIV and plume-edge detection on saline plumes in water resulting from a point source, a line source and a line source where a vertical wall is placed immediately adjacent. Of particular interest is the effect the large scale eddies, forming at the edge of the plume and engulfing ambient fluid, have on the entrainment process. By using velocity statistics in a coordinate system based on the instantaneous scalar edge of the plume the significance of this large scale engulfment is quantified. It is found that significant mass is transported outside the plumes, in particular in regions where large scale structures are absent creating regions of relatively high-momentum ambient fluid. This suggests that the large scale processes, whereby ambient fluid is engulfed into the plume, contribute significantly to the entrainment.

NW Iberia Shelf Dynamics. Study of the Douro River Plume.

Directory of Open Access Journals (Sweden)

Isabel Iglesias

2014-06-01

Full Text Available River plumes are one of the most important mechanisms that transport the terrestrial materials to the coast and the ocean. Some examples of those materials are pollutants, essential nutrients, which enhance the phytoplankton productivity or sediments, which settle on the seabed producing modifications on the bathymetry affecting the navigation channels. The mixing between the riverine and the oceanic waters can induce instabilities, which might generate bulges, filaments, and buoyant currents over the continental shelf. Offshore, the buoyant riverine water could form a front with the oceanic waters often related with the occurrence of current-jets, eddies and strong mixing. The study and modelling of the river plumes is a key factor for the complete understanding of sediment transport mechanisms and patterns, and of coastal physics and dynamic processes. On this study the Douro River plume will be simulated. The Douro River is located on the north-west Iberian coast and its daily averaged freshwater discharge can range values from 0 to 13000 m3/s. This variability impacts the formation of the river plumes and its dispersion along the continental shelf. This study builds on the long-term objective of generate a Douro River plume forecasting system as part of the RAIA and RAIA.co projects. Satellite imagery was analyzed showing that the river Douro is one of the main sources of suspended particles, dissolved material and chlorophyll in the NW Iberian Shelf. The Regional Oceanic Modeling System (ROMS model was selected to reproduce scenarios of plume generation, retention and dispersion. Whit this model, three types of simulations were performed: (i schematic winds simulations with prescribed river flow, wind speed and direction; (ii multi-year climatological simulation, with river flow and temperature change for each month; (iii extreme case simulation, based on the Entre-os-Rios accident situation. The schematic wind case-studies suggest that the

Simulation of plume rise: Study the effect of stably stratified turbulence layer on the rise of a buoyant plume from a continuous source by observing the plume centroid

Science.gov (United States)

Bhimireddy, Sudheer Reddy; Bhaganagar, Kiran

2016-11-01

Buoyant plumes are common in atmosphere when there exists a difference in temperature or density between the source and its ambience. In a stratified environment, plume rise happens until the buoyancy variation exists between the plume and ambience. In a calm no wind ambience, this plume rise is purely vertical and the entrainment happens because of the relative motion of the plume with ambience and also ambient turbulence. In this study, a plume centroid is defined as the plume mass center and is calculated from the kinematic equation which relates the rate of change of centroids position to the plume rise velocity. Parameters needed to describe the plume are considered as the plume radius, plumes vertical velocity and local buoyancy of the plume. The plume rise velocity is calculated by the mass, momentum and heat conservation equations in their differential form. Our study focuses on the entrainment velocity, as it depicts the extent of plume growth. This entrainment velocity is made up as sum of fractions of plume's relative velocity and ambient turbulence. From the results, we studied the effect of turbulence on the plume growth by observing the variation in the plume radius at different heights and the centroid height reached before loosing its buoyancy.

Light-induced ion-acoustic instability of rarefied plasma

International Nuclear Information System (INIS)

Krasnov, I.V.; Sizykh, D.V.

1987-01-01

A new method of ion-acoustic instability excitation under the effect of coherent light, resonance to ion quantum transitions on collisionless plasma, is suggested. The light-induced ion-acoustic instability (LIIAI) considered is based on the induced progressive nonequilibrium resonance particles in the field of travelling electromagnetic wave. Principal possibility to use LIIAI in high-resolution spectroscopy and in applied problems of plasma physics, related to its instability, is pointed out

Fire analog: a comparison between fire plumes and energy center cooling tower plumes

Energy Technology Data Exchange (ETDEWEB)

Orgill, M.M.

1977-10-01

Thermal plumes or convection columns associated with large fires are compared to thermal plumes from cooling towers and proposed energy centers to evaluate the fire analog concept. Energy release rates of mass fires are generally larger than for single or small groups of cooling towers but are comparable to proposed large energy centers. However, significant physical differences exist between cooling tower plumes and fire plumes. Cooling tower plumes are generally dominated by ambient wind, stability and turbulence conditions. Fire plumes, depending on burning rates and other factors, can transform into convective columns which may cause the fire behavior to become more violent. This transformation can cause strong inflow winds and updrafts, turbulence and concentrated vortices. Intense convective columns may interact with ambient winds to create significant downwind effects such as wakes and Karman vortex streets. These characteristics have not been observed with cooling tower plumes to date. The differences in physical characteristics between cooling tower and fire plumes makes the fire analog concept very questionable even though the approximate energy requirements appear to be satisfied in case of large energy centers. Additional research is suggested in studying the upper-level plume characteristics of small experimental fires so this information can be correlated with similar data from cooling towers. Numerical simulation of fires and proposed multiple cooling tower systems could also provide comparative data.

Modeling of the near field plume of a Hall thruster

International Nuclear Information System (INIS)

Boyd, Iain D.; Yim, John T.

2004-01-01

In this study, a detailed numerical model is developed to simulate the xenon plasma near-field plume from a Hall thruster. The model uses a detailed fluid model to describe the electrons and a particle-based kinetic approach is used to model the heavy xenon ions and atoms. The detailed model is applied to compute the near field plume of a small, 200 W Hall thruster. Results from the detailed model are compared with the standard modeling approach that employs the Boltzmann model. The usefulness of the model detailed is assessed through direct comparisons with a number of different measured data sets. The comparisons illustrate that the detailed model accurately predicts a number of features of the measured data not captured by the simpler Boltzmann approach

ICRF induced edge plasma convection in ASDEX upgrade

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wei [Max Planck Institute for Plasma Physics, Garching/Greifswald (Germany); University of Ghent, Ghent (Belgium); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei (China); Feng, Yuehe; Lunt, Tilmann; Jacquot, Jonathan; Coster, David; Bilato, Roberto; Bobkov, Volodymyr; Ochoukov, Roman [Max Planck Institute for Plasma Physics, Garching/Greifswald (Germany); Noterdaeme, Jean-Marie [Max Planck Institute for Plasma Physics, Garching/Greifswald (Germany); University of Ghent, Ghent (Belgium); Colas, Laurent [CEA, IRFM, Saint-Paul-Lez-Durance (France); Collaboration: ASDEX Upgrade Team

2016-07-01

Ion Cyclotron Range of Frequency (ICRF) heating is one of the main auxiliary plasma heating methods in tokamaks. It relies on the fast wave to heat the plasma. However the slow wave can also be generated parasitically. The parallel electric field of the slow wave can induce large biased plasma potential through sheath rectification. The rapid variation of this rectified potential across the magnetic field can cause significant E x B convection in the Scrape-Off Layer (SOL). The ICRF induced convection can affect the SOL density, influence the ICRF power coupling and enhance the strength of plasma-wall interactions. To explore these physics, we not only show the experimental evidences in ASDEX Upgrade, but also present the associated simulation results with the 3D edge plasma fluid code EMC3-Eirene. Further simulations via combination of EMC3-Eirene and a sheath code SSWICH in an iterative and quasi self-consistent way can give good predictions for future experiments.

Multiprobe characterization of plasma flows for space propulsion

NARCIS (Netherlands)

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

2018-01-01

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

Magnetic Field Effects on the Plume of a Diverging Cusped-Field Thruster

KAUST Repository

Matlock, Taylor

2010-07-25

The Diverging Cusped-Field Thruster (DCFT) uses three permanent ring magnets of alternating polarity to create a unique magnetic topology intended to reduce plasma losses to the discharge chamber surfaces. The magnetic field strength within the DCFT discharge chamber (up to 4 kG on axis) is much higher than in thrusters of similar geometry, which is believed to be a driving factor in the high measured anode efficiencies. The field strength in the near plume region is large as well, which may bear on the high beam divergences measured, with peaks in ion current found at angles of around 30-35 from the thruster axis. Characterization of the DCFT has heretofore involved only one magnetic topology. It is then the purpose of this study to investigate changes to the near-field plume caused by altering the shape and strength of the magnetic field. A thick magnetic collar, encircling the thruster body, is used to lower the field strength outside of the discharge chamber and thus lessen any effects caused by the external field. Changes in the thruster plume with field topology are monitored by the use of normal Langmuir and emissive probes interrogating the near-field plasma. Results are related to other observations that suggest a unified conceptual framework for the important near-exit region of the thruster.

Plume-induced dynamic instabilities near cratonic blocks: Implications for P-T-t paths and metallogeny

NARCIS (Netherlands)

Guillou-Frottier, L.; Burov, E.; Cloetingh, S.; Le Goff, E.; Deschamps, Y.; Huet, B.; Bouchot, V.

2012-01-01

Plume head - lithosphere interactions around cratonic blocks result in thermo-mechanical disturbances that lead to heating and burial phases of crustal rocks. We present results from numerical models of plume head - cratonic blocks interactions where a free upper surface condition and realistic

Plume characteristics and dynamics of UV and IR laser-desorbed oligonucleotides.

Science.gov (United States)

Merrigan, Tony L; Timson, David J; Hunniford, C Adam; Catney, Martin; McCullough, Robert W

2012-05-01

Laser desorption of dye-tagged oligonucleotides was studied using laser-induced fluorescence imaging. Desorption with ultra violet (UV) and infra-red (IR) lasers resulted in forward directed plumes of molecules. In the case of UV desorption, the initial shot desorbed approximately seven-fold more material than subsequent shots. In contrast, the initial shot in IR desorption resulted in the ejection of less material compared to subsequent shots and these plumes had a component directed along the path of the laser. Thermal equilibrium of the molecules in the plume was achieved after approximately 25 μs with a spread in molecular temperature which was described by a modified Maxwell-Boltzmann equation. Copyright © 2012 Elsevier B.V. All rights reserved.

Numerical prediction of Plume Induced Flow Separation (PIFS) on launch vehicles

International Nuclear Information System (INIS)

Jeffries, D.K.; Ferguson, F.; Chandra, S.

2002-01-01

Lockheed Martin Astronautics designs and operates launch vehicles that deliver payloads into specific geosynchronous orbits for the government and the commercial market place. Lockheed's family Atlas Launch Vehicles are an industry leader in this very competitive business and remain in this position by continuously optimizing the Atlas design to increase its performance. However, the unknown overall effects of a phenomenon that occurs when aircraft operate at high altitudes is hindering the advancement of the vehicle. Engineers have known for years through observations and calculations that the exhaust plume from an aircraft's engine undergoes changes in shape and increases in size as the aircraft gains altitude and speed. The change in exhaust plum configuration typically leads to interaction between the exhaust gases and freestream air, which is the cause of the phenomenon know as Plume Induced Flow Separation (PIFS). PIFS separates the external flow from the surface of the vehicle allowing the hot exhaust gases to climb forward from the engines toward the aircraft's leading end. Long believed to harmlessly climb the outside surfaces of aircraft, the mostly unknown phenomenon in now feared to hamper the performance of today's launch vehicles. Lockheed Martin has contracted the research study of PIFS to better understand the flowfield and then use that information to optimize the design of their launch vehicles and mitigate ifs effects. A study of the phenomenon, its resulting flowfield and thermal environment, is greatly needed to add to the knowledge of bases of PIFS and aerospace flight. The study presented outlines the development of a numerical model, which was used to investigate the effects of PIFS on an Atlas IIIA Launch Vehicle by simulating the vehicle operating under flight conditions where PIFS is most likely to occur. The model was validated by comparing numerical results with experimental data and verified by reviewing the flow physics captured. The

Modelling of microwave induced plasmas : the interplay between electromagnetism, plasma chemistry and transport

NARCIS (Netherlands)

Jimenez-Diaz, M.

2011-01-01

In this thesis we report on a theoretical/numerical study that is concerned with Microwave Induced Plasmas (MIPs) in general, and the application of a MIP to the Plasma-activated Chemical Vapour Deposition (PCVD) process that is used at Draka Comteq for the production of optical fibres in

Interaction of cw CO2 laser radiation with plasma near-metallic substrate surface

Science.gov (United States)

Azharonok, V. V.; Astapchik, S. A.; Zabelin, Alexandre M.; Golubev, Vladimir S.; Golubev, V. S.; Grezev, A. N.; Filatov, Igor V.; Chubrik, N. I.; Shimanovich, V. D.

2000-07-01

Optical and spectroscopic methods were used in studying near-surface plasma that is formed under the effect CW CO2 laser of (2- 5)x106W/cm2 power density upon stainless steel in He and Ar shielding gases. The variation of plume spatial structure with time has been studied, the outflow of gas-vapor jets from the interaction area has been characterized. The spectra of plasma plume pulsations have been obtained for the frequency range Δf = 0-1 MHz. The temperature and electron concentration of plasma plume have been found under radiation effect upon the target of stainless steel. Consideration has been given to the most probable mechanisms of CW laser radiation-metal non-stationary interaction.

Seismic Imaging of Mantle Plumes

Science.gov (United States)

Nataf, Henri-Claude

The mantle plume hypothesis was proposed thirty years ago by Jason Morgan to explain hotspot volcanoes such as Hawaii. A thermal diapir (or plume) rises from the thermal boundary layer at the base of the mantle and produces a chain of volcanoes as a plate moves on top of it. The idea is very attractive, but direct evidence for actual plumes is weak, and many questions remain unanswered. With the great improvement of seismic imagery in the past ten years, new prospects have arisen. Mantle plumes are expected to be rather narrow, and their detection by seismic techniques requires specific developments as well as dedicated field experiments. Regional travel-time tomography has provided good evidence for plumes in the upper mantle beneath a few hotspots (Yellowstone, Massif Central, Iceland). Beneath Hawaii and Iceland, the plume can be detected in the transition zone because it deflects the seismic discontinuities at 410 and 660 km depths. In the lower mantle, plumes are very difficult to detect, so specific methods have been worked out for this purpose. There are hints of a plume beneath the weak Bowie hotspot, as well as intriguing observations for Hawaii. Beneath Iceland, high-resolution tomography has just revealed a wide and meandering plume-like structure extending from the core-mantle boundary up to the surface. Among the many phenomena that seem to take place in the lowermost mantle (or D''), there are also signs there of the presence of plumes. In this article I review the main results obtained so far from these studies and discuss their implications for plume dynamics. Seismic imaging of mantle plumes is still in its infancy but should soon become a turbulent teenager.

Plasma generation induced by triboelectrification

DEFF Research Database (Denmark)

Kusano, Yukihiro; Singh, Shailendra Vikram; Michelsen, Poul

2009-01-01

A gas discharge plasma can be induced by triboelectrification around a sliding contact. The detailed physical mechanism of triboelectrification is unknown, but an empirical classification scheme can be referred to in practice. It is reported that intense ultra-violet emission from a plasma...... is observed adjacent to the sliding contact, of which the location has a gap ranging from approximately 1 μm to 11 μm. When the gap is short enough, a theory predicts that the breakdown voltage can monotonically decrease with a decrease in the gap. However, when the gap is comparable to electron’s mean free...

Laboratory Study of Dispersion of Buoyant Surface Plumes

DEFF Research Database (Denmark)

Petersen, Ole; Larsen, Torben

1990-01-01

-differences. Other methods as infra-red sensing are used for visualizing purpose. The results are used to calibrate an integral model of the dispersion. Conclusions are that the dispersion of a buoyant surface plume can be treated the superposition of a buoyancy induced stretching and turbulent diffusion, reduced...

Cold plasma interactions with plants: Morphing and movements of Venus flytrap and Mimosa pudica induced by argon plasma jet.

Science.gov (United States)

Volkov, Alexander G; Xu, Kunning G; Kolobov, Vladimir I

2017-12-01

Low temperature (cold) plasma finds an increasing number of applications in biology, medicine and agriculture. In this paper, we report a new effect of plasma induced morphing and movements of Venus flytrap and Mimosa pudica. We have experimentally observed plasma activation of sensitive plant movements and morphing structures in these plants similar to stimulation of their mechanosensors in vivo. Application of an atmospheric pressure argon plasma jet to the inside or outside of a lobe, midrib, or cilia in Dionaea muscipula Ellis induces trap closing. Treatment of Mimosa pudica by plasma induces movements of pinnules and petioles similar to the effects of mechanical stimulation. We have conducted control experiments and simulations to illustrate that gas flow and UV radiation associated with plasma are not the primary reasons for the observed effects. Reactive oxygen and nitrogen species (RONS) produced by cold plasma in atmospheric air appear to be the primary reason of plasma-induced activation of phytoactuators in plants. Some of these RONS are known to be signaling molecules, which control plants' developmental processes. Understanding these mechanisms could promote plasma-based technology for plant developmental control and future use for plant protection from pathogens. Our work offers new insight into mechanisms which trigger plant morphing and movement. Copyright © 2017 Elsevier B.V. All rights reserved.

Coherent structures induced by dielectric barrier discharge plasma actuator

Science.gov (United States)

Zhang, Xin; Li, Huaxing; Choi, Kwing So; Song, Longfei

2017-11-01

The structures of a flow field induced by a plasma actuator were investigated experimentally in quiescent air using high-speed Particle Image Velocimetry (PIV) technology. The motivation behind was to figure out the flow control mechanism of the plasma technique. A symmetrical Dielectric Barrier Discharge (DBD) plasma actuator was mounted on the suction side of the SC (2)-0714 supercritical airfoil. The results demonstrated that the plasma jet had some coherent structures in the separated shear layer and these structures were linked to a dominant frequency of f0 = 39 Hz when the peak-to-peak voltage of plasma actuator was 9.8 kV. The high speed PIV measurement of the induced airflow suggested that the plasma actuator could excite the flow instabilities which lead to production of the roll-up vortex. Analysis of transient results indicated that the roll-up vortices had the process of formation, movement, merging and breakdown. This could promote the entrainment effect of plasma actuator between the outside airflow and boundary layer flow, which is very important for flow control applications.

Formation dynamics of UV and EUV induced hydrogen plasma

NARCIS (Netherlands)

Dolgov, A.A.; Lee, Christopher James; Yakushev, O.; Lopaev, D.V.; Abrikosov, A.; Krivtsun, V.M.; Zotovich, A.; Bijkerk, F.

2014-01-01

The comparative study of the dynamics of ultraviolet (UV) and extreme ultraviolet (EUV) induced hydrogen plasma was performed. It was shown that for low H2 pressures and bias voltages, the dynamics of the two plasmas are significantly different. In the case of UV radiation, the plasma above the

Asymmetric three-dimensional topography over mantle plumes.

Science.gov (United States)

Burov, Evgueni; Gerya, Taras

2014-09-04

The role of mantle-lithosphere interactions in shaping surface topography has long been debated. In general, it is supposed that mantle plumes and vertical mantle flows result in axisymmetric, long-wavelength topography, which strongly differs from the generally asymmetric short-wavelength topography created by intraplate tectonic forces. However, identification of mantle-induced topography is difficult, especially in the continents. It can be argued therefore that complex brittle-ductile rheology and stratification of the continental lithosphere result in short-wavelength modulation and localization of deformation induced by mantle flow. This deformation should also be affected by far-field stresses and, hence, interplay with the 'tectonic' topography (for example, in the 'active/passive' rifting scenario). Testing these ideas requires fully coupled three-dimensional numerical modelling of mantle-lithosphere interactions, which so far has not been possible owing to the conceptual and technical limitations of earlier approaches. Here we present new, ultra-high-resolution, three-dimensional numerical experiments on topography over mantle plumes, incorporating a weakly pre-stressed (ultra-slow spreading), rheologically realistic lithosphere. The results show complex surface evolution, which is very different from the smooth, radially symmetric patterns usually assumed as the canonical surface signature of mantle upwellings. In particular, the topography exhibits strongly asymmetric, small-scale, three-dimensional features, which include narrow and wide rifts, flexural flank uplifts and fault structures. This suggests a dominant role for continental rheological structure and intra-plate stresses in controlling dynamic topography, mantle-lithosphere interactions, and continental break-up processes above mantle plumes.

Destratification induced by bubble plumes as a means to reduce ...

African Journals Online (AJOL)

Qw = energy advected by evaporated water. ΔQ = change in reservoir energy. From the analysis performed by Hughes et al. (1975) 2 of the 9 parameters emerged as being dominant; these are Qe (evapora- tion latent heat) and Qv (the outflow component). Artificial destratification. To destratify a reservoir a bubble plume ...

Profiling an electrospray plume by laser-induced fluorescence and Fraunhofer diffraction combined to mass spectrometry: influence of size and composition of droplets on charge-state distributions of electrosprayed proteins.

Science.gov (United States)

Girod, Marion; Dagany, Xavier; Boutou, Véronique; Broyer, Michel; Antoine, Rodolphe; Dugourd, Philippe; Mordehai, Alex; Love, Craig; Werlich, Mark; Fjeldsted, John; Stafford, George

2012-07-14

We investigated how physico-chemical properties of charged droplets are affected by the electrospray process, using simultaneous in situ measurements by laser-induced fluorescence (LIF), Fraunhofer diffraction and mass spectrometry. For this purpose, we implemented a laser-induced-fluorescence profiling setup in conjunction with a fast, high-resolution particle sizing scheme on a modified Agilent Jet Stream electrospray source coupled to a single quadrupole mass analyser. The optical setup permits us to profile the solvent fractionation and the size of the droplets as they evaporate in an electrospray plume by measuring both the angular scattering pattern and emission spectra of a solvatochromic fluorescent dye. Mass spectra are recorded simultaneously. These mass spectrometry and optical spectroscopy investigations allow us to study the relation between the observed charge-state distributions of protein anions and physico-chemical properties of evaporating droplets in the spray plume. By mixing water with methanol, a refolding of cytochrome C is observed as the water percentage increases in the plume due to the preponderant evaporation of volatile methanol.

Characteristics of bubble plumes, bubble-plume bubbles and waves from wind-steepened wave breaking

NARCIS (Netherlands)

Leifer, I.; Caulliez, G.; Leeuw, G. de

2007-01-01

Observations of breaking waves, associated bubble plumes and bubble-plume size distributions were used to explore the coupled evolution of wave-breaking, wave properties and bubble-plume characteristics. Experiments were made in a large, freshwater, wind-wave channel with mechanical wind-steepened

Measurements at cooling tower plumes. Part 3. Three-dimensional measurements at cooling tower plumes

International Nuclear Information System (INIS)

Fortak, H.

An extended field experiment is described in which cooling tower plumes were studied by means of three-dimensional in situ measurements. The goal was to obtain input data for numerical models of cooling tower plumes. Of special interest were data for testing or developing assumptions for sub-grid parametrizations. Utilizing modern systems for high-resolution aerology and small aircraft, four measuring campaigns were conducted: two campaigns (1974) at the cooling towers of the RWE power station Neurath and also two (1975) at the single cooling tower of the RWE power station Meppen. Because of the broad spectrum of weather situations it can be assumed that the results are representative with regard to the interrelationship between structure of cooling tower plume and large-scale meteorological situation. A large number of flights with a powered glider crossing the plumes on orthogonal tracks was performed. All flights showed that the plume could be identified up to large downwind distances by discontinuous jumps of temperature and vapor pressure. Therefore, a definite geometry of the plume could always be defined. In all cross sections a vertical circulation could be observed. At the boundary, which could be defined by the mentioned jumps of temperature and vapor pressure, a maximum of downward vertical motion could be observed in most cases. Entrainment along the boundary of a cross section seems to be very small, except at the lower part of the plume. There, the mass entrainment is maximum and is responsible for plume rise as well as for enlargement of the cross section. The visible part of the plume (cloud) was only a small fraction of the whole plume. High-resolution aerology is necessary in order to explain the structure and behavior of such plumes. This is especially the case in investigations regarding the dynamic break-through of temperature inversions. Such cases were observed frequently under various meteorological conditions and are described

On predicting mantle mushroom plumes

Directory of Open Access Journals (Sweden)

Ka-Kheng Tan

2011-04-01

Top cooling may produce plunging plumes of diameter of 585 km and at least 195 Myr old. The number of cold plumes is estimated to be 569, which has not been observed by seismic tomography or as cold spots. The cold plunging plumes may overwhelm and entrap some of the hot rising plumes from CMB, so that together they may settle in the transition zone.

Laser ablated copper plasmas in liquid and gas ambient

Science.gov (United States)

Kumar, Bhupesh; Thareja, Raj K.

2013-05-01

The dynamics of copper ablated plasma plumes generated using laser ablation of copper targets in both liquid (de-ionized water) and gas (air) ambients is reported. Using time and space resolved visible emission spectroscopy (450-650 nm), the plasma plumes parameters are investigated. The electron density (ne) determined using Stark broadening of the Cu I (3d104d1 2D3/2-3d104p1 2P3/2 at 521.8 nm) line is estimated and compared for both plasma plumes. The electron temperature (Te) was estimated using the relative line emission intensities of the neutral copper transitions. Field emission scanning electron microscopy and energy dispersive x-ray spectral analysis of the ablated copper surface indicated abundance of spherical nanoparticles in liquid while those in air are amalgamates of irregular shapes. The nanoparticles suspended in the confining liquid form aggregates and exhibit a surface plasmon resonance at ˜590 nm.

Ovulation-inducing factor: a protein component of llama seminal plasma

Directory of Open Access Journals (Sweden)

Huanca Wilfredo

2010-05-01

Full Text Available Abstract Background Previously, we documented the presence of ovulation-inducing factor (OIF in the seminal plasma of llamas and alpacas. The purpose of the study was to define the biochemical characteristics of the molecule(s in seminal plasma responsible for inducing ovulation. Methods In Experiment 1, llama seminal plasma was centrifuged using filtration devices with nominal molecular mass cut-offs of 30, 10 and 5 kDa. Female llamas (n = 9 per group were treated i.m. with whole seminal plasma (positive control, phosphate-buffered saline (negative control, or the fraction of seminal plasma equal or higher than 30 kDa, 10 to 30 kDa, 5 to 10 kDa, or Results In Experiment 1, all llamas in the equal or higher than 30 kDa and positive control groups ovulated (9/9 in each, but none ovulated in the other groups (P Conclusions We conclude that ovulation-inducing factor (OIF in llama seminal plasma is a protein molecule that is resistant to heat and enzymatic digestion with proteinase K, and has a molecular mass of approximately equal or higher than 30 kDa.

Inductively Coupled Plasma-Induced Etch Damage of GaN p-n Junctions

International Nuclear Information System (INIS)

SHUL, RANDY J.; ZHANG, LEI; BACA, ALBERT G.; WILLISON, CHRISTI LEE; HAN, JUNG; PEARTON, S.J.; REN, F.

1999-01-01

Plasma-induced etch damage can degrade the electrical and optical performance of III-V nitride electronic and photonic devices. We have investigated the etch-induced damage of an Inductively Coupled Plasma (ICP) etch system on the electrical performance of mesa-isolated GaN pn-junction diodes. GaN p-i-n mesa diodes were formed by Cl 2 /BCl 3 /Ar ICP etching under different plasma conditions. The reverse leakage current in the mesa diodes showed a strong relationship to chamber pressure, ion energy, and plasma flux. Plasma induced damage was minimized at moderate flux conditions (≤ 500 W), pressures ≥2 mTorr, and at ion energies below approximately -275 V

Influence of the laser parameters on the space and time characteristics of an aluminum laser-induced plasma

International Nuclear Information System (INIS)

Barthelemy, O.; Margot, J.; Chaker, M.; Sabsabi, M.; Vidal, F.; Johnston, T.W.; Laville, S.; Le Drogoff, B.

2005-01-01

In this work, an aluminum laser plasma produced in ambient air at atmospheric pressure by laser pulses at a fluence of 10 J/cm 2 is characterized by time- and space-resolved measurements of electron density and temperature. Varying the laser pulse duration from 6 ns to 80 fs and the laser wavelength from ultraviolet to infrared only slightly influences the plasma properties. The temperature exhibits a slight decrease both at the plasma edge and close to the target surface. The electron density is found to be spatially homogeneous in the ablation plume during the first microsecond. Finally, the plasma expansion is in good agreement with the Sedov's model during the first 500 ns and it becomes subsonic, with respect to the velocity of sound in air, typically 1 μs after the plasma creation. The physical interpretation of the experimental results is also discussed to the light of a one-dimensional fluid model which provides a good qualitative agreement with measurements

The 2016 Case for Mantle Plumes and a Plume-Fed Asthenosphere (Augustus Love Medal Lecture)

Science.gov (United States)

Morgan, Jason P.

2016-04-01

The process of science always returns to weighing evidence and arguments for and against a given hypothesis. As hypotheses can only be falsified, never universally proved, doubt and skepticism remain essential elements of the scientific method. In the past decade, even the hypothesis that mantle plumes exist as upwelling currents in the convecting mantle has been subject to intense scrutiny; from geochemists and geochronologists concerned that idealized plume models could not fit many details of their observations, and from seismologists concerned that mantle plumes can sometimes not be 'seen' in their increasingly high-resolution tomographic images of the mantle. In the place of mantle plumes, various locally specific and largely non-predictive hypotheses have been proposed to explain the origins of non-plate boundary volcanism at Hawaii, Samoa, etc. In my opinion, this debate has now passed from what was initially an extremely useful restorative from simply 'believing' in the idealized conventional mantle plume/hotspot scenario to becoming an active impediment to our community's ability to better understand the dynamics of the solid Earth. Having no working hypothesis at all is usually worse for making progress than having an imperfect and incomplete but partially correct one. There continues to be strong arguments and strong emerging evidence for deep mantle plumes. Furthermore, deep thermal plumes should exist in a mantle that is heated at its base, and the existence of Earth's (convective) geodynamo clearly indicates that heat flows from the core to heat the mantle's base. Here I review recent seismic evidence by French, Romanowicz, and coworkers that I feel lends strong new observational support for the existence of deep mantle plumes. I also review recent evidence consistent with the idea that secular core cooling replenishes half the mantle's heat loss through its top surface, e.g. that the present-day mantle is strongly bottom heated. Causes for

Fast imaging of the laser-blow-off plume driven shock wave: Dependence on the mass and density of the ambient gas

Energy Technology Data Exchange (ETDEWEB)

George, Sony [ISP, Cochin University of Science and Tech., Cochin 682 022 (India); Singh, R.K., E-mail: rajesh@ipr.res.in [Institute for Plasma Research, Gandhinagar 382 428 (India); Nampoori, V.P.N. [ISP, Cochin University of Science and Tech., Cochin 682 022 (India); Kumar, Ajai [Institute for Plasma Research, Gandhinagar 382 428 (India)

2013-01-17

A systemic investigation of expansion dynamics of plasma plume, produced by laser-blow-off of LiF–C thin film has been done with emphasis on the formation of shock wave and their dependence on the pressure and nature of the ambient gas. The present results demonstrate that highly directional plume produces a strong shock wave in comparison to shock produced by the diverging plume. Shock-velocity, strength and its structure are strongly dependent on ambient environment; maximum shock velocity is observed in helium whereas shock strength is highest in argon environment. The role of chemically reactive processes was not observed in the present case as the plume structure is almost similar in argon and oxygen.

Thermal plumes in ventilated rooms

DEFF Research Database (Denmark)

Kofoed, Peter; Nielsen, Peter V.

1990-01-01

The design of a displacement ventilation system involves determination of the flow rate in the thermal plumes. The flow rate in the plumes and the vertical temperature gradient influence each other, and they are influenced by many factors. This paper shows some descriptions of these effects. Free...... above a point heat source cannot be used. This is caused either by the way of generating the plume including a long intermediate region or by the environmental conditions where vertical temperature gradients are present. The flow has a larger angle of spread and the entrainment factor is greather than...... turbulent plumes from different heated bodies are investigated. The measurements have taken place in a full-scale test room where the vertical temperature gradient have been changed. The velocity and the temperature distribution in the plume are measured. Large scale plume axis wandering is taken...

Characterization of plasma-induced cell membrane permeabilization: focus on OH radical distribution

International Nuclear Information System (INIS)

Sasaki, Shota; Honda, Ryosuke; Hokari, Yutaro; Takashima, Keisuke; Kaneko, Toshiro; Kanzaki, Makoto

2016-01-01

Non-equilibrium atmospheric-pressure plasma (APP) is used medically for plasma-induced cell permeabilization. However, how plasma irradiation specifically triggers permeabilization remains unclear. In an attempt to identify the dominant factor( s ), the distribution of plasma-produced reactive species was investigated, primarily focusing on OH radicals. A stronger plasma discharge, which produced more OH radicals in the gas phase, also produced more OH radicals in the liquid phase (OH aq ), enhancing the cell membrane permeability. In addition, plasma irradiation-induced enhancement of cell membrane permeability decreased markedly with increased solution thickness (<1 mm), and the plasma-produced OH aq decayed in solution (diffusion length on the order of several hundred micrometers). Furthermore, the horizontally center-localized distribution of OH aq corresponded with the distribution of the permeabilized cells by plasma irradiation, while the overall plasma-produced oxidizing species in solution (detected by iodine-starch reaction) exhibited a doughnut-shaped horizontal distribution. These results suggest that OH aq, among the plasma-produced oxidizing species, represents the dominant factor in plasma-induced cell permeabilization. These results enhance the current understanding of the mechanism of APP as a cell-permeabilization tool. (paper)

Life Cycle of Mantle Plumes: A perspective from the Galapagos Plume (Invited)

Science.gov (United States)

Gazel, E.; Herzberg, C. T.

2009-12-01

Hotspots are localized sources of heat and magmatism considered as modern-day evidence of mantle plumes. Some hotspots are related to massive magmatic production that generated Large Igneous Provinces (LIPS), an initial-peak phase of plume activity with a mantle source hotter and more magmatically productive than present-day hotspots. Geological mapping and geochronological studies have shown much lower eruption rates for OIB compared to lavas from Large Igneous Provinces LIPS such as oceanic plateaus and continental flood provinces. Our study is the first quantitative petrological comparison of mantle source temperatures and extent of melting for OIB and LIP sources. The wide range of primary magma compositions and inferred mantle potential temperatures for each LIP and OIB occurrence suggest that this rocks originated form a hotspot, a spatially localized source of heat and magmatism restricted in time. Extensive outcrops of basalt, picrite, and sometimes komatiite with circa 65-95 Ma ages occupy portions of the pacific shore of Central and South America included in the Caribbean Large Igneous Province (CLIP). There is general consensus of a Pacific-origin of CLIP and most studies suggest that it was produced by melting in the Galapagos mantle plume. The Galapagos connection is consistent with isotopic and geochemical similarities with lavas from the present-day Galapagos hotspot. A Galapagos link for rocks in South American oceanic complexes (eg. the island of Gorgona) is more controversial and requires future work. The MgO and FeO contents of lavas from the Galapagos related lavas and their primary magmas have decreased since the Cretaceous. From petrological modeling we infer that these changes reflect a cooling of the Galapagos mantle plume from a potential temperature of 1560-1620 C in the Cretaceous to 1500 C at the present time. These temperatures are higher than 1350 C for ambient mantle associated with oceanic ridges, and provide support for the mantle

Numerical modeling of the effects of fire-induced convection and fire-atmosphere interactions on wildfire spread and fire plume dynamics

Science.gov (United States)

Sun, Ruiyu

probabilistic prediction method is warranted. Of the two contributors to the variability in fire growth in the grass fire simulations in the ABL, fire-induced convection, as opposed to the turbulent ABL wind, appears to be the more important one. One mechanism associated with enhanced fire-induced flow is the downdraft behind the frontal fireline. The downdraft is the direct result of the random interaction between the fire plume and the large eddies in the ABL. This study indicates a connection between fire variability in rate of spread and area burnt and so-called convective velocity scale, and it may be possible to use this boundary-layer scale parameter to account for the effects of ABL turbulence on fire spread and fire behavior in today's operational fire prediction systems.

Two-dimensional nanoparticle self-assembly using plasma-induced Ostwald ripening

International Nuclear Information System (INIS)

Tang, J; Photopoulos, P; Tsoukalas, D; Tserepi, A

2011-01-01

In this work, a novel Ag nanoparticle self-assembly process based on plasma-induced two-dimensional Ostwald ripening is demonstrated. Ag nanoparticles are deposited on p-doped Si substrates using a DC magnetron sputtering process. With the assistance of O 2 /Ar plasma treatment, different sizes and patterns of Ag nanoparticles are formed, due to the Ostwald ripening. The evolution of plasma-induced nanoparticle ripening is studied and a clear increase in particle size and a decrease in particle density are observed with increasing plasma treatment. From the experiments, it is concluded that the initial nanoparticle density and the plasma gas mixture (Ar/O 2 ratio) are important factors that affect the ripening process. The proposed plasma-directed Ag nanoparticle self-assembly provides a rapid method of tailoring the nanoparticle distribution on substrates, with potential applications in the fields of solar cells, biosensors, and catalysis.

Influence of Penning effect on the plasma features in a non-equilibrium atmospheric pressure plasma jet

Energy Technology Data Exchange (ETDEWEB)

Chang, Zhengshi; Zhang, Guanjun [School of Electrical Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Jiang, Nan; Cao, Zexian, E-mail: zxcao@iphy.ac.cn [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2014-03-14

Non-equilibrium atmospheric pressure plasma jet (APPJ) is a cold plasma source that promises various innovative applications. The influence of Penning effect on the formation, propagation, and other physical properties of the plasma bullets in APPJ remains a debatable topic. By using a 10 cm wide active electrode and a frequency of applied voltage down to 0.5 Hz, the Penning effect caused by preceding discharges can be excluded. It was found that the Penning effect originating in a preceding discharge helps build a conductive channel in the gas flow and provide seed electrons, thus the discharge can be maintained at a low voltage which in turn leads to a smaller propagation speed for the plasma bullet. Photographs from an intensified charge coupled device reveal that the annular structure of the plasma plume for He is irrelevant to the Penning ionization process arising from preceding discharges. By adding NH{sub 3} into Ar to introduce Penning effect, the originally filamentous discharge of Ar can display a rather extensive plasma plume in ambient as He. These results are helpful for the understanding of the behaviors of non-equilibrium APPJs generated under distinct conditions and for the design of plasma jet features, especially the spatial distribution and propagation speed, which are essential for application.

Scaling for turbulent viscosity of buoyant plumes in stratified fluids: PIV measurement with implications for submarine hydrothermal plume turbulence

Science.gov (United States)

Zhang, Wei; He, Zhiguo; Jiang, Houshuo

2017-11-01

Time-resolved particle image velocimetry (PIV) has been used to measure instantaneous two-dimensional velocity vector fields of laboratory-generated turbulent buoyant plumes in linearly stratified saltwater over extended periods of time. From PIV-measured time-series flow data, characteristics of plume mean flow and turbulence have been quantified. To be specific, maximum plume penetration scaling and entrainment coefficient determined from the mean flow agree well with the theory based on the entrainment hypothesis for buoyant plumes in stratified fluids. Besides the well-known persistent entrainment along the plume stem (i.e., the 'plume-stem' entrainment), the mean plume velocity field shows persistent entrainment along the outer edge of the plume cap (i.e., the 'plume-cap' entrainment), thereby confirming predictions from previous numerical simulation studies. To our knowledge, the present PIV investigation provides the first measured flow field data in the plume cap region. As to measured plume turbulence, both the turbulent kinetic energy field and the turbulence dissipation rate field attain their maximum close to the source, while the turbulent viscosity field reaches its maximum within the plume cap region; the results also show that maximum turbulent viscosity scales as νt,max = 0.030(B/N)1/2, where B is source buoyancy flux and N is ambient buoyancy frequency. These PIV data combined with previously published numerical simulation results have implications for understanding the roles of hydrothermal plume turbulence, i.e. plume turbulence within the cap region causes the 'plume-cap' entrainment that plays an equally important role as the 'plume-stem' entrainment in supplying the final volume flux at the plume spreading level.

Surface hardening induced by high flux plasma in tungsten revealed by nano-indentation

Energy Technology Data Exchange (ETDEWEB)

Terentyev, D., E-mail: dterenty@sckcen.be [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, 2400 Mol (Belgium); Bakaeva, A. [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, 2400 Mol (Belgium); Department of Applied Physics, Ghent University, St. Pietersnieuwstraat 41, 9000 Ghent (Belgium); Pardoen, T.; Favache, A. [Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, Place Sainte Barbe 2 L5.02.02, 1348 Louvain-la-Neuve (Belgium); Zhurkin, E.E. [Department of Experimental Nuclear Physics K-89, Faculty of Physics and Mechanics, St. Petersburg State Polytechnical University, 29 Polytekhnicheskaya str., 195251 St. Petersburg (Russian Federation)

2016-08-01

Surface hardness of tungsten after high flux deuterium plasma exposure has been characterized by nanoindentation. The effect of plasma exposure was rationalized on the basis of available theoretical models. Resistance to plastic penetration is enhanced within the 100 nm sub-surface region, attributed to the pinning of geometrically necessary dislocations on nanometric deuterium cavities – signature of plasma-induced defects and deuterium retention. Sub-surface extension of thereby registered plasma-induced damage is in excellent agreement with the results of alternative measurements. The study demonstrates suitability of nano-indentation to probe the impact of deposition of plasma-induced defects in tungsten on near surface plasticity under ITER-relevant plasma exposure conditions.

Predicted and observed cooling tower plume rise and visible plume length at the John E. Amos power plant

Energy Technology Data Exchange (ETDEWEB)

Hanna, S R

1976-01-01

A one-dimensional numerical cloud growth model and several empirical models for plume rise and cloud growth are compared with twenty-seven sets of observations of cooling tower plumes from the 2900 MW John E. Amos power plant in West Virginia. The three natural draft cooling towers are 200 m apart. In a cross wind, the plumes begin to merge at a distance of about 500 m downwind. In calm conditions, with reduced entrainment, the plumes often do not merge until heights of 1000 m. The average plume rise, 750 m, is predicted well by the models, but day-to-day variations are simulated with a correlation coefficient of about 0.5. Model predictions of visible plume length agree, on the average, with observations for visible plumes of short to moderate length (less than about 1 km). The prediction of longer plumes is hampered by our lack of knowledge of plume spreading after the plumes level off. Cloud water concentrations predicted by the numerical model agree with those measured in natural cumulus clouds (about 0.1 to 1 g kg/sup -1/).

Turbulent buoyant jets and plumes

CERN Document Server

Rodi, Wolfgang

The Science & Applications of Heat and Mass Transfer: Reports, Reviews, & Computer Programs, Volume 6: Turbulent Buoyant Jets and Plumes focuses on the formation, properties, characteristics, and reactions of turbulent jets and plumes. The selection first offers information on the mechanics of turbulent buoyant jets and plumes and turbulent buoyant jets in shallow fluid layers. Discussions focus on submerged buoyant jets into shallow fluid, horizontal surface or interface jets into shallow layers, fundamental considerations, and turbulent buoyant jets (forced plumes). The manuscript then exami

Buoyant plumes from solute gradients generated by non-motile Escherichia coli

International Nuclear Information System (INIS)

Benoit, M R; Brown, R B; Todd, P; Klaus, D M; Nelson, E S

2008-01-01

The effect of hydrodynamic mixing in bacterial populations due to bacterial chemotaxis is a well-described phenomenon known as bioconvection. Here we report the observation of buoyant plumes that result in hydrodynamic mixing, but in contrast to bioconvection the plumes form in the absence of bacterial motility. We propose that the buoyant flow originates from solute gradients created by bacterial metabolism, similar to solute-induced buoyant flow around growing protein crystals. In our experiments, metabolically-active non-motile Escherichia coli were layered along the bottom of flat-bottomed containers. The E. coli consumed glucose in the medium creating a lighter fluid beneath a heavier fluid. The situation is an example of Rayleigh–Taylor instability, in which a lighter fluid pushes on a heavier one. We developed a numerical model to study the effect of E. coli nutrient consumption and by-product excretion on extracellular solute gradients. The model solutions showed reduced-density fluid along the bottom of the fluid domain leading to buoyant plumes, which were qualitatively similar to the experimental plumes. We also used scaling analyses to study the dependence of plume formation on container size and cell size, and to investigate the effect of reduced gravity, such as the microgravity conditions encountered during spaceflight

Geometrical effects in data collection and processing for calibration-free laser-induced breakdown spectroscopy

Science.gov (United States)

Shabanov, S. V.; Gornushkin, I. B.

2018-01-01

Data processing in the calibration-free laser-induced breakdown spectroscopy (LIBS) is usually based on the solution of the radiative transfer equation along a particular line of sight through a plasma plume. The LIBS data processing is generalized to the case when the spectral data are collected from large portions of the plume. It is shown that by adjusting the optical depth and width of the lines the spectra obtained by collecting light from an entire spherical homogeneous plasma plume can be least-square fitted to a spectrum obtained by collecting the radiation just along a plume diameter with a relative error of 10-11 or smaller (for the optical depth not exceeding 0.3) so that a mismatch of geometries of data processing and data collection cannot be detected by fitting. Despite the existence of such a perfect least-square fit, the errors in the line optical depth and width found by a data processing with an inappropriate geometry can be large. It is shown with analytic and numerical examples that the corresponding relative errors in the found elemental number densities and concentrations may be as high as 50% and 20%, respectively. Safe for a few found exceptions, these errors are impossible to eliminate from LIBS data processing unless a proper solution of the radiative transfer equation corresponding to the ray tracing in the spectral data collection is used.

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

Science.gov (United States)

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.

Time-Resolved Emission Spectroscopic Study of Laser-Induced Steel Plasmas

International Nuclear Information System (INIS)

Shah, M. L.; Pulhani, A. K.; Suri, B. M.; Gupta, G. P.

2013-01-01

Laser-induced steel plasma is generated by focusing a Q-switched Nd:YAG visible laser (532 nm wavelength) with an irradiance of ∼ 1 × 10 9 W/cm 2 on a steel sample in air at atmospheric pressure. An Echelle spectrograph coupled with a gateable intensified charge-coupled detector is used to record the plasma emissions. Using time-resolved spectroscopic measurements of the plasma emissions, the temperature and electron number density of the steel plasma are determined for many times of the detector delay. The validity of the assumption by the spectroscopic methods that the laser-induced plasma (LIP) is optically thin and is also in local thermodynamic equilibrium (LTE) has been evaluated for many delay times. From the temporal evolution of the intensity ratio of two Fe I lines and matching it with its theoretical value, the delay times where the plasma is optically thin and is also in LTE are found to be 800 ns, 900 ns and 1000 ns.

Decreased plasma levels of the endothelial protective sphingosine-1-phosphate are associated with dengue-induced plasma leakage

NARCIS (Netherlands)

Michels, M.; Japtok, L.; Alisjahbana, B.; Wisaksana, R.; Sumardi, U.; Puspita, M.; Kleuser, B.; Mast, Q. de; Ven, A.J.A.M. van der

2015-01-01

BACKGROUND: A transient endothelial hyperpermeability is a hallmark of severe dengue infections. Sphingosine-1-phosphate (S1P) maintains vascular integrity and protects against plasma leakage. We related plasma S1P levels to dengue-induced plasma leakage and studied mechanisms that may underlie the

Perspective: The physics, diagnostics, and applications of atmospheric pressure low temperature plasma sources used in plasma medicine

Science.gov (United States)

Laroussi, M.; Lu, X.; Keidar, M.

2017-07-01

Low temperature plasmas have been used in various plasma processing applications for several decades. But it is only in the last thirty years or so that sources generating such plasmas at atmospheric pressure in reliable and stable ways have become more prevalent. First, in the late 1980s, the dielectric barrier discharge was used to generate relatively large volume diffuse plasmas at atmospheric pressure. Then, in the early 2000s, plasma jets that can launch cold plasma plumes in ambient air were developed. Extensive experimental and modeling work was carried out on both methods and much of the physics governing such sources was elucidated. Starting in the mid-1990s, low temperature plasma discharges have been used as sources of chemically reactive species that can be transported to interact with biological media, cells, and tissues and induce impactful biological effects. However, many of the biochemical pathways whereby plasma affects cells remain not well understood. This situation is changing rather quickly because the field, known today as "plasma medicine," has experienced exponential growth in the last few years thanks to a global research community that engaged in fundamental and applied research involving the use of cold plasma for the inactivation of bacteria, dental applications, wound healing, and the destruction of cancer cells/tumors. In this perspective, the authors first review the physics as well as the diagnostics of the principal plasma sources used in plasma medicine. Then, brief descriptions of their biomedical applications are presented. To conclude, the authors' personal assessment of the present status and future outlook of the field is given.

On plasma ion beam formation in the Advanced Plasma Source

International Nuclear Information System (INIS)

Harhausen, J; Foest, R; Hannemann, M; Ohl, A; Brinkmann, R P; Schröder, B

2012-01-01

The Advanced Plasma Source (APS) is employed for plasma ion-assisted deposition (PIAD) of optical coatings. The APS is a hot cathode dc glow discharge which emits a plasma ion beam to the deposition chamber at high vacuum (p ≲ 2 × 10 −4 mbar). It is established as an industrial tool but to date no detailed information is available on plasma parameters in the process chamber. As a consequence, the details of the generation of the plasma ion beam and the reasons for variations of the properties of the deposited films are barely understood. In this paper the results obtained from Langmuir probe and retarding field energy analyzer diagnostics operated in the plasma plume of the APS are presented, where the source was operated with argon. With increasing distance to the source exit the electron density (n e ) is found to drop by two orders of magnitude and the effective electron temperature (T e,eff ) drops by a factor of five. The parameters close to the source region read n e ≳ 10 11 cm −3 and T e,eff ≳ 10 eV. The electron distribution function exhibits a concave shape and can be described in the framework of the non-local approximation. It is revealed that an energetic ion population leaves the source region and a cold ion population in the plume is build up by charge exchange collisions with the background neutral gas. Based on the experimental data a scaling law for ion beam power is deduced, which links the control parameters of the source to the plasma parameters in the process chamber. (paper)

Plasma extraction by centrifugo-pneumatically induced gating of flow

International Nuclear Information System (INIS)

Burger, Robert; Ducrée, Jens; Reis, Nuno; Da Fonseca, João Garcia

2013-01-01

We present a novel valving mechanism to implement plasma extraction from whole blood on a centrifugal microfluidic ‘lab-on-a-disc’ platform. The new scheme is based on pressure-induced deflection of a liquid membrane which gates the centrifugally driven flow through a microfluidic structure. Compared to conventional concepts such as capillary burst valves, siphons or sacrificial materials, the valving structure presented here is represented by a compact, small-footprint design which obviates the need for (local) surface functionalization or hybrid materials integration, thus significantly reducing the complexity (and hence cost) of manufacture. As a pilot study of this new centrifugal flow control element, we demonstrate here the efficient separation of metered plasma from whole blood. While the flow is stopped, blood is separated into plasma and its cellular constituents by centrifugally induced sedimentation. After completion, the flow resumes by elevating the spinning frequency, providing up to 80% of the original plasma content to an overflow chamber within a short, 2 min interval. The amount of residual cells in the plasma amounts to less than 20 cells μl −1 . (paper)

Electrical resistivity and induced polarization tomography in identifying the plume of chlorinated hydrocarbons in sedimentary formation: a case study in Rho (Milan - Italy).

Science.gov (United States)

Cardarelli, Ettore; Di Filippo, Gerardina

2009-09-01

Resistivity and induced polarization surveying were originally developed for mineral exploration but are now finding new applications in the field of environmental and engineering geophysics. The present article reports the results of a geophysical survey performed with the aim of identifying a plume of chlorinated hydrocarbons in sedimentary formations of the Pandania plain. The tested site is characterized by three sand and gravel aquifers containing a quantity of clay particles which influence the overall bulk resistivity and chargeability. According to data obtained using shallow boreholes, mainly dense non-aqueous phase liquids were found as contaminants in the first and second aquifer. The aforementioned geo-electrical methods were applied in both two- and three-dimensional approaches. Steel and copper electrodes were used in the process of field data acquisition and the results of the survey were compared. The geophysical survey revealed some anomalies that could be explained by the presence of dense non-aqueous phase liquids in the soil medium. The concept of normalized chargeability facilitates the interpretation of detected induced polarization anomalies. The shape of the plume was inferred from maps of resistivity and chargeability to a depth of 25 m below the surface of the ground.

Temperature dependence on plasma-induced damage and chemical reactions in GaN etching processes using chlorine plasma

Science.gov (United States)

Liu, Zecheng; Ishikawa, Kenji; Imamura, Masato; Tsutsumi, Takayoshi; Kondo, Hiroki; Oda, Osamu; Sekine, Makoto; Hori, Masaru

2018-06-01

Plasma-induced damage (PID) on GaN was optimally reduced by high-temperature chlorine plasma etching. Energetic ion bombardments primarily induced PID involving stoichiometry, surface roughness, and photoluminescence (PL) degradation. Chemical reactions under ultraviolet (UV) irradiation and chlorine radical exposure at temperatures higher than 400 °C can be controlled by taking into account the synergism of simultaneous photon and radical irradiations to effectively reduce PID.

Laser ablated copper plasmas in liquid and gas ambient

Energy Technology Data Exchange (ETDEWEB)

Kumar, Bhupesh; Thareja, Raj K. [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208 016 (India)

2013-05-15

The dynamics of copper ablated plasma plumes generated using laser ablation of copper targets in both liquid (de-ionized water) and gas (air) ambients is reported. Using time and space resolved visible emission spectroscopy (450-650 nm), the plasma plumes parameters are investigated. The electron density (n{sub e}) determined using Stark broadening of the Cu I (3d{sup 10}4d{sup 1} {sup 2}D{sub 3/2}-3d{sup 10}4p{sup 1} {sup 2}P{sub 3/2} at 521.8 nm) line is estimated and compared for both plasma plumes. The electron temperature (T{sub e}) was estimated using the relative line emission intensities of the neutral copper transitions. Field emission scanning electron microscopy and energy dispersive x-ray spectral analysis of the ablated copper surface indicated abundance of spherical nanoparticles in liquid while those in air are amalgamates of irregular shapes. The nanoparticles suspended in the confining liquid form aggregates and exhibit a surface plasmon resonance at ∼590 nm.

Global volcanic emissions: budgets, plume chemistry and impacts

Science.gov (United States)

Mather, T. A.

2012-12-01

Over the past few decades our understanding of global volcanic degassing budgets, plume chemistry and the impacts of volcanic emissions on our atmosphere and environment has been revolutionized. Global volcanic emissions budgets are needed if we are to make effective use of regional and global atmospheric models in order to understand the consequences of volcanic degassing on global environmental evolution. Traditionally volcanic SO2 budgets have been the best constrained but recent efforts have seen improvements in the quantification of the budgets of other environmentally important chemical species such as CO2, the halogens (including Br and I) and trace metals (including measurements relevant to trace metal atmospheric lifetimes and bioavailability). Recent measurements of reactive trace gas species in volcanic plumes have offered intriguing hints at the chemistry occurring in the hot environment at volcanic vents and during electrical discharges in ash-rich volcanic plumes. These reactive trace species have important consequences for gas plume chemistry and impacts, for example, in terms of the global fixed nitrogen budget, volcanically induced ozone destruction and particle fluxes to the atmosphere. Volcanically initiated atmospheric chemistry was likely to have been particularly important before biological (and latterly anthropogenic) processes started to dominate many geochemical cycles, with important consequences in terms of the evolution of the nitrogen cycle and the role of particles in modulating the Earth's climate. There are still many challenges and open questions to be addressed in this fascinating area of science.

Wave Glider Monitoring of Sediment Transport and Dredge Plumes in a Shallow Marine Sandbank Environment.

Science.gov (United States)

Van Lancker, Vera; Baeye, Matthias

2015-01-01

As human pressure on the marine environment increases, safeguarding healthy and productive seas increasingly necessitates integrated, time- and cost-effective environmental monitoring. Employment of a Wave Glider proved very useful for the study of sediment transport in a shallow sandbank area in the Belgian part of the North Sea. During 22 days, data on surface and water-column currents and turbidity were recorded along 39 loops around an aggregate-extraction site. Correlation with wave and tidal-amplitude data allowed the quantification of current- and wave-induced advection and resuspension, important background information to assess dredging impacts. Important anomalies in suspended particulate matter concentrations in the water column suggested dredging-induced overflow of sediments in the near field (i.e., dynamic plume), and settling of finer-grained material in the far field (i.e., passive plume). Capturing the latter is a successful outcome to this experiment, since the location of dispersion and settling of a passive plume is highly dependent on the ruling hydro-meteorological conditions and thus difficult to predict. Deposition of the observed sediment plumes may cause habitat changes in the long-term.

Wave Glider Monitoring of Sediment Transport and Dredge Plumes in a Shallow Marine Sandbank Environment.

Directory of Open Access Journals (Sweden)

Vera Van Lancker

Full Text Available As human pressure on the marine environment increases, safeguarding healthy and productive seas increasingly necessitates integrated, time- and cost-effective environmental monitoring. Employment of a Wave Glider proved very useful for the study of sediment transport in a shallow sandbank area in the Belgian part of the North Sea. During 22 days, data on surface and water-column currents and turbidity were recorded along 39 loops around an aggregate-extraction site. Correlation with wave and tidal-amplitude data allowed the quantification of current- and wave-induced advection and resuspension, important background information to assess dredging impacts. Important anomalies in suspended particulate matter concentrations in the water column suggested dredging-induced overflow of sediments in the near field (i.e., dynamic plume, and settling of finer-grained material in the far field (i.e., passive plume. Capturing the latter is a successful outcome to this experiment, since the location of dispersion and settling of a passive plume is highly dependent on the ruling hydro-meteorological conditions and thus difficult to predict. Deposition of the observed sediment plumes may cause habitat changes in the long-term.

Dynamics of plasma expansion in the pulsed laser material interaction

Indian Academy of Sciences (India)

at different ambient gas pressures using an adiabatic expansion model. ... Pulsed laser; plasma expansion; plasma ionization; plume dimension. 1. ...... De A, Shakhatov V A, Pascale De O 2001 Optical emission spectroscopy and modeling of.

East Asian SO2 pollution plume over Europe – Part 2: Evolution and potential impact

Directory of Open Access Journals (Sweden)

A. Stohl

2009-07-01

Full Text Available We report on the first observation-based case study of an aged East Asian anthropogenic SO2 pollution plume over Europe. Our airborne measurements in that plume detected highly elevated SO2 mole fractions (up to 900 pmol/mol between about 5000 and 7000 m altitude. Here, we focus on investigations of the origin, dispersion, evolution, conversion, and potential impact of the observed excess SO2. In particular, we investigate SO2 conversion to gas-phase sulfuric acid and sulfuric acid aerosols. Our FLEXPART and LAGRANTO model simulations, along with additional trace gas measurements, suggest that the plume originated from East Asian fossil fuel combustion sources and, 8–7 days prior to its arrival over Europe, ascended over the coast region of central East Asia to 9000 m altitude, probably in a cyclonic system with an associated warm conveyor belt. During this initial plume ascent a substantial fraction of the initially available SO2 must have escaped from removal by cloud processes. Hereafter, while mostly descending slowly, the plume experienced advection across the North Pacific, North America and the North Atlantic. During its upper troposphere travel, clouds were absent in and above the plume and OH-induced gas-phase conversion of SO2 to gas-phase sulfuric acid (GSA was operative, followed by GSA nucleation and condensation leading to sulfuric acid aerosol formation and growth. Our AEROFOR model simulations indicate that numerous large sulfuric acid aerosol particles were formed, which at least tempora-rily, caused substantial horizontal visibility degradation, and which have the potential to act as water vapor condensation nuclei in liquid water cloud formation, already at water vapor supersaturations as low as about 0.1%. Our AEROFOR model simulations also indicate that those fossil fuel combustion generated soot particles, which have survived cloud induced removal during the initial plume ascent, have experienced extensive H2SO4/H2O

Plasma diagnostics with a retarding potential analyzer

International Nuclear Information System (INIS)

Jack, T.M.

1996-01-01

The plasma rocket is located at NASA Johnson Space Center. To produce a thrust in space, an inert gas is ionized into a plasma and heated in the linear section of a tokamak fusion device. The magnetic field used to contain the plasma has a magnitude of 2--10 kGauss. The plasma plume has a variable thrust and specific impulse. A high temperature retarding potential analyzer (RPA) is being developed to characterize the plasma in the plume and at the edge of the magnetically contained plasma. The RPA measures the energy and density of ions or electrons entering into its solid angle of collection. An oscilloscope displays the ion flux versus the collected current. All measurements are made relative to the facility ground. Testing of this device involves the determination of its output parameters, sensitivity, and responses to a wide range of energies and densities. Each grid will be tested individually by changing only its voltage and observing the output from the RPA. To verify that the RPA is providing proper output, it is compared to the output from a Langmuir or Faraday probe

Particle Heating in Space and Laboratory Plasmas

Science.gov (United States)

Scime, E. E.; Keesee, A. M.; Aquirre, E.; Good, T.

2017-12-01

We report spatially resolved perpendicular and parallel ion velocity distribution function (IVDF) measurements in an expanding argon helicon plasma. The parallel IVDFs, obtained through laser induced fluorescence (LIF), show an ion beam with v ˜ 8 km/s flowing downstream that is confined to the center of the discharge. The ion beam is confined to within a few centimeters radially and is measurable for tens of centimeters axially before the LIF signal fades, likely a result of metastable quenching of the beam ions. The axial ion beam velocity slows in agreement with collisional processes. The perpendicular IVDFs show an ion population with a radially outward flow that increases with radial location. The DC electric field, electron temperature, and the plasma density in the double layer plume are all consistent with magnetic field aligned structures. The upstream and downstream electric field measurements show clear evidence of an ion hole that maps along the magnetic field at the edge of the plasma. Current theories and simulations of double layers, which are one-dimensional, completely miss these critically important two-dimensional features.

Plume rise from multiple sources

International Nuclear Information System (INIS)

Briggs, G.A.

1975-01-01

A simple enhancement factor for plume rise from multiple sources is proposed and tested against plume-rise observations. For bent-over buoyant plumes, this results in the recommendation that multiple-source rise be calculated as [(N + S)/(1 + S)]/sup 1/3/ times the single-source rise, Δh 1 , where N is the number of sources and S = 6 (total width of source configuration/N/sup 1/3/ Δh 1 )/sup 3/2/. For calm conditions a crude but simple method is suggested for predicting the height of plume merger and subsequent behavior which is based on the geometry and velocity variations of a single buoyant plume. Finally, it is suggested that large clusters of buoyant sources might occasionally give rise to concentrated vortices either within the source configuration or just downwind of it

A numerical study of the plume in Cape Fear River Estuary and adjacent coastal ocean

Science.gov (United States)

Xia, M.; Xia, L.; Pietrafesa, L. J.

2006-12-01

Cape Fear River Estuary (CFRE), located in southeast North Carolina, is the only river estuary system in the state which is directly connected to the Atlantic Ocean. It is also an important nursery for economically and ecologically important juvenile fish, crabs, shrimp, and other species because of the tidal influence and saline waters. In this study, Environmental Fluid Dynamic Code (EFDC) is used to simulate the salinity plume and trajectory distribution at the mouth of the CFRE and adjacent coastal ocean. Prescribed with the climatological freshwater discharge rates in the rivers, the modeling system was used to simulate the salinity plume and trajectory distribution distribution in the mouth of the CFRE under the influence of climatological wind conditions and tidal effect. We analyzed the plume formation processes and the strong relationship between the various plume distributions with respect to the wind and river discharge in the region. The simulations also indicate that strong winds tend to reduce the surface CFRE plume size and distorting the bulge region near the estuary mouth due to enhanced wind induced surface mixing. Even moderate wind speeds could fully reverse the buoyancy-driven plume structure in CFRE under normal river discharge conditions. Tide and the river discharge also are important factors to influence the plume structure. The comparions between the distribution of salinity plume and trajectory also are discussed in the study.

Sheared-flow induced confinement transition in a linear magnetized plasma

Science.gov (United States)

Zhou, S.; Heidbrink, W. W.; Boehmer, H.; McWilliams, R.; Carter, T. A.; Vincena, S.; Friedman, B.; Schaffner, D.

2012-01-01

A magnetized plasma cylinder (12 cm in diameter) is induced by an annular shape obstacle at the Large Plasma Device [W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875 (1991)]. Sheared azimuthal flow is driven at the edge of the plasma cylinder through edge biasing. Strong fluctuations of density and potential (δn /n~eδφ/kTe~0.5) are observed at the plasma edge, accompanied by a large density gradient (Ln=|∇lnn |-1~2cm) and shearing rate (γ ~300kHz). Edge turbulence and cross-field transport are modified by changing the bias voltage (Vbias) on the obstacle and the axial magnetic field (Bz) strength. In cases with low Vbias and large Bz, improved plasma confinement is observed, along with steeper edge density gradients. The radially sheared flow induced by E ×B drift dramatically changes the cross-phase between density and potential fluctuations, which causes the wave-induced particle flux to reverse its direction across the shear layer. In cases with higher bias voltage or smaller Bz, large radial transport and rapid depletion of the central plasma density are observed. Two-dimensional cross-correlation measurement shows that a mode with azimuthal mode number m =1 and large radial correlation length dominates the outward transport in these cases. Linear analysis based on a two-fluid Braginskii model suggests that the fluctuations are driven by both density gradient (drift wave like) and flow shear (Kelvin-Helmholtz like) at the plasma edge.

Sheared-flow induced confinement transition in a linear magnetized plasma

International Nuclear Information System (INIS)

Zhou, S.; Heidbrink, W. W.; Boehmer, H.; McWilliams, R.; Carter, T. A.; Vincena, S.; Friedman, B.; Schaffner, D.

2012-01-01

A magnetized plasma cylinder (12 cm in diameter) is induced by an annular shape obstacle at the Large Plasma Device [W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875 (1991)]. Sheared azimuthal flow is driven at the edge of the plasma cylinder through edge biasing. Strong fluctuations of density and potential (δn/n∼eδφ/kT e ∼0.5) are observed at the plasma edge, accompanied by a large density gradient (L n =∇lnn -1 ∼2cm) and shearing rate (γ∼300kHz). Edge turbulence and cross-field transport are modified by changing the bias voltage (V bias ) on the obstacle and the axial magnetic field (B z ) strength. In cases with low V bias and large B z , improved plasma confinement is observed, along with steeper edge density gradients. The radially sheared flow induced by ExB drift dramatically changes the cross-phase between density and potential fluctuations, which causes the wave-induced particle flux to reverse its direction across the shear layer. In cases with higher bias voltage or smaller B z , large radial transport and rapid depletion of the central plasma density are observed. Two-dimensional cross-correlation measurement shows that a mode with azimuthal mode number m=1 and large radial correlation length dominates the outward transport in these cases. Linear analysis based on a two-fluid Braginskii model suggests that the fluctuations are driven by both density gradient (drift wave like) and flow shear (Kelvin-Helmholtz like) at the plasma edge.

Simulation of river plume behaviors in a tropical region: Case study of the Upper Gulf of Thailand

Science.gov (United States)

Yu, Xiaojie; Guo, Xinyu; Morimoto, Akihiko; Buranapratheprat, Anukul

2018-02-01

River plumes are a general phenomenon in coastal regions. Most previous studies focus on river plumes in middle and high latitudes with few studies examining those in low latitude regions. Here, we apply a numerical model to the Upper Gulf of Thailand (UGoT) to examine a river plume in low latitudes. Consistent with observational data, the modeled plume has seasonal variation dependent on monsoon conditions. During southwesterly monsoons, the plume extends northeastward to the head of the gulf; during northeasterly monsoons, it extends southwestward to the mouth of the gulf. To examine the effects of latitude, wind and river discharge on the river plume, we designed several numerical experiments. Using a middle latitude for the UGoT, the bulge close to the river mouth becomes smaller, the downstream current flows closer to the coast, and the salinity in the northern UGoT becomes lower. The reduction in the size of the bulge is consistent with the relationship between the offshore distance of a bulge and the Coriolis parameter. Momentum balance of the coastal current is maintained by advection, the Coriolis force, pressure gradient and internal stresses in both low and middle latitudes, with the Coriolis force and pressure gradient enlarged in the middle latitude. The larger pressure gradient in the middle latitude is induced by more offshore freshwater flowing with the coastal current, which induces lower salinity. The influence of wind on the river plume not only has the advection effects of changing the surface current direction and increasing the surface current speed, but also decreases the current speed due to enhanced vertical mixing. Changes in river discharge influence stratification in the UGoT but have little effect on the behavior of the river plume.

Mathematical model of drift deposition from a bifurcated cooling tower plume

International Nuclear Information System (INIS)

Chen, N.C.J.; Jung, L.

1978-01-01

Cooling tower drift deposition modeling has been extended by including centrifugal force induced through plume bifurcation in a crosswind as a mechanism for drift droplet removal from the plume. The model, in its current state of development, is capable of predicting the trajectory of a single droplet from the stage of strong interaction with the vortex field soon after droplet emission at the tower top through the stage of droplet evaporation in an unsaturated atmosphere after droplet breakaway from the plume. The computer program developed from the mathematical formulation has been used to explore the dependency of the droplet trajectory on droplet size, vortex strength, point of droplet emission, drag coefficient, droplet efflux speed, and ambient conditions. A specific application to drift from a mechanical-draft cooling tower (for a wind speed twice the efflux speed, a relative humidity of 70 per cent, and an initial droplet radius of 100 μm) showed the droplet to follow a helical trajectory within the plume, with breakaway occurring at 2.5 tower diameters downwind and ground impact of the droplet (reduced through evaporation to 55 μm radius) at 11 tower diameters

Large plasma density enhancements occurring in the northern polar region during the 6 April 2000 superstorm

Science.gov (United States)

Horvath, Ildiko; Lovell, Brian C.

2014-06-01

We focus on the ionospheric response of northern high-latitude region to the 6 April 2000 superstorm and aim to investigate how the storm-enhanced density (SED) plume plasma became distributed in the regions of auroral zone and polar cap plus to study the resultant ionospheric features and their development. Multi-instrument observational results combined with model-generated, two-cell convection maps permitted identifying the high-density plasma's origin and the underlying plasma transportation processes. Results show the plasma density feature of polar cap enhancement (PCE; 600 × 103 i+/cm3) appearing for 7 h during the main phase and characterized by increases reaching up to 6 times of the quiet time values. Meanwhile, strong westward convections ( 17,500 m/s) created low plasma densities in a wider region of the dusk cell. Oppositely, small ( 750 m/s) but rigorous westward drifts drove the SED plume plasma through the auroral zone, wherein plasma densities doubled. As the SED plume plasma traveled along the convection streamlines and entered the polar cap, a continuous enhancement of the tongue of ionization (TOI) developed under steady convection conditions. However, convection changes caused slow convections and flow stagnations and thus segmented the TOI feature by locally depleting the plasma in the affected regions of the auroral zone and polar cap. From the strong correspondence of polar cap potential drop and subauroral polarization stream (SAPS), we conclude that the SAPS E-field strength remained strong, and under its prolonged influence, the SED plume provided a continuous supply of downward flowing high-density plasma for the development and maintenance of PCEs.

Plasma induced DNA damage: Comparison with the effects of ionizing radiation

Energy Technology Data Exchange (ETDEWEB)

Lazović, S.; Maletić, D.; Puač, N.; Malović, G.; Petrović, Z. Lj. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Leskovac, A.; Filipović, J.; Joksić, G. [Department of Physical Chemistry, Vinča Institute of Nuclear Sciences, University of Belgrade, 11001 Belgrade (Serbia)

2014-09-22

We use human primary fibroblasts for comparing plasma and gamma rays induced DNA damage. In both cases, DNA strand breaks occur, but of fundamentally different nature. Unlike gamma exposure, contact with plasma predominantly leads to single strand breaks and base-damages, while double strand breaks are mainly consequence of the cell repair mechanisms. Different cell signaling mechanisms are detected confirming this (ataxia telangiectasia mutated - ATM and ataxia telangiectasia and Rad3 related - ATR, respectively). The effective plasma doses can be tuned to match the typical therapeutic doses of 2 Gy. Tailoring the effective dose through plasma power and duration of the treatment enables safety precautions mainly by inducing apoptosis and consequently reduced frequency of micronuclei.

Evaluation of plume potential and plume abatement of evaporative cooling towers in a subtropical region

International Nuclear Information System (INIS)

Xu Xinhua; Wang Shengwei; Ma Zhenjun

2008-01-01

Hong Kong is a typical subtropical region with frequently high humidity in late spring and summer seasons. Plume from evaporative cooling towers, which service air-conditioning systems of civil buildings, has aroused public concerns since 2000 when the fresh water evaporative cooling towers were allowed to be used for high energy efficiency and environmental issues. This paper presents the evaluation of the plume potential and its effect on the sizing of the plume abatement system in a large commercial office building in Hong Kong for practical application. This evaluation was conducted based on a dynamic simulation platform using the typical meteorological year of Hong Kong since the occurrence of the plume heavily depends on the state conditions of the exhaust air from cooling towers and the ambient air, while the state condition of the exhaust air is determined by the total building cooling load and the control strategies of cooling towers employed mainly for improving energy efficiency. The results show that the control strategies have a significant effect on the plume potential and further affect the system design and sizing of the plume abatement system

High spatial resolution in laser-induced breakdown spectroscopy of expanding plasmas

International Nuclear Information System (INIS)

Siegel, J.; Epurescu, G.; Perea, A.; Gordillo-Vazquez, F.J.; Gonzalo, J.; Afonso, C.N.

2005-01-01

We report a technique that is able to achieve high spatial resolution in the measurement of the temporal and spectral emission characteristics of laser-induced expanding plasmas. The plasma is imaged directly onto the slit of an imaging spectrograph coupled to a time-gated intensified camera, with the plasma expansion direction being parallel to the slit extension. In this way, a single hybrid detection system is used to acquire the spatial, spectral and temporal characteristics of the laser induced plasma. The parallel acquisition approach of this technique ensures a much better spatial resolution in the expansion direction, reproducibility and data acquisition speed than commonly obtained by sequential measurements at different distances from the target. We have applied this technique to study the laser-induced plasma in LiNbO 3 and Bi 12 Ge 1 O 20 , revealing phenomena not seen in such detail with standard instruments. These include extreme line broadening up to a few nanometers accompanied by self-absorption near the target surface, as well as different ablation and expansion dynamics for the different species ejected. Overall, the high precision and wealth of quantitative information accessible with this technique open up new possibilities for the study of fundamental plasma expansion processes during pulsed laser ablation

Chemistry in aircraft plumes

Energy Technology Data Exchange (ETDEWEB)

Kraabol, A.G.; Stordal, F.; Knudsen, S. [Norwegian Inst. for Air Research, Kjeller (Norway); Konopka, P. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Wessling (Germany). Inst. fuer Physik der Atmosphaere

1997-12-31

An expanding plume model with chemistry has been used to study the chemical conversion of NO{sub x} to reservoir species in aircraft plumes. The heterogeneous conversion of N{sub 2}O{sub 5} to HNO{sub 3}(s) has been investigated when the emissions take place during night-time. The plume from an B747 has been simulated. During a ten-hour calculation the most important reservoir species was HNO{sub 3} for emissions at noon. The heterogeneous reactions had little impact on the chemical loss of NO{sub x} to reservoir species for emissions at night. (author) 4 refs.

Chemistry in aircraft plumes

Energy Technology Data Exchange (ETDEWEB)

Kraabol, A G; Stordal, F; Knudsen, S [Norwegian Inst. for Air Research, Kjeller (Norway); Konopka, P [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Wessling (Germany). Inst. fuer Physik der Atmosphaere

1998-12-31

An expanding plume model with chemistry has been used to study the chemical conversion of NO{sub x} to reservoir species in aircraft plumes. The heterogeneous conversion of N{sub 2}O{sub 5} to HNO{sub 3}(s) has been investigated when the emissions take place during night-time. The plume from an B747 has been simulated. During a ten-hour calculation the most important reservoir species was HNO{sub 3} for emissions at noon. The heterogeneous reactions had little impact on the chemical loss of NO{sub x} to reservoir species for emissions at night. (author) 4 refs.

Plasmid DNA damage induced by helium atmospheric pressure plasma jet

Science.gov (United States)

Han, Xu; Cantrell, William A.; Escobar, Erika E.; Ptasinska, Sylwia

2014-03-01

A helium atmospheric pressure plasma jet (APPJ) is applied to induce damage to aqueous plasmid DNA. The resulting fractions of the DNA conformers, which indicate intact molecules or DNA with single- or double-strand breaks, are determined using agarose gel electrophoresis. The DNA strand breaks increase with a decrease in the distance between the APPJ and DNA samples under two working conditions of the plasma source with different parameters of applied electric pulses. The damage level induced in the plasmid DNA is also enhanced with increased plasma irradiation time. The reactive species generated in the APPJ are characterized by optical emission spectra, and their roles in possible DNA damage processes occurring in an aqueous environment are also discussed.

The Alberta smoke plume observation study

Directory of Open Access Journals (Sweden)

K. Anderson

2018-02-01

Full Text Available A field project was conducted to observe and measure smoke plumes from wildland fires in Alberta. This study used handheld inclinometer measurements and photos taken at lookout towers in the province. Observations of 222 plumes were collected from 21 lookout towers over a 6-year period from 2010 to 2015. Observers reported the equilibrium and maximum plume heights based on the plumes' final levelling heights and the maximum lofting heights, respectively. Observations were tabulated at the end of each year and matched to reported fires. Fire sizes at assessment times and forest fuel types were reported by the province. Fire weather conditions were obtained from the Canadian Wildland Fire Information System (CWFIS. Assessed fire sizes were adjusted to the appropriate size at plume observation time using elliptical fire-growth projections. Though a logical method to collect plume observations in principle, many unanticipated issues were uncovered as the project developed. Instrument limitations and environmental conditions presented challenges to the investigators, whereas human error and the subjectivity of observations affected data quality. Despite these problems, the data set showed that responses to fire behaviour conditions were consistent with the physical processes leading to plume rise. The Alberta smoke plume observation study data can be found on the Canadian Wildland Fire Information System datamart (Natural Resources Canada, 2018 at http://cwfis.cfs.nrcan.gc.ca/datamart.

The Alberta smoke plume observation study

Science.gov (United States)

Anderson, Kerry; Pankratz, Al; Mooney, Curtis; Fleetham, Kelly

2018-02-01

A field project was conducted to observe and measure smoke plumes from wildland fires in Alberta. This study used handheld inclinometer measurements and photos taken at lookout towers in the province. Observations of 222 plumes were collected from 21 lookout towers over a 6-year period from 2010 to 2015. Observers reported the equilibrium and maximum plume heights based on the plumes' final levelling heights and the maximum lofting heights, respectively. Observations were tabulated at the end of each year and matched to reported fires. Fire sizes at assessment times and forest fuel types were reported by the province. Fire weather conditions were obtained from the Canadian Wildland Fire Information System (CWFIS). Assessed fire sizes were adjusted to the appropriate size at plume observation time using elliptical fire-growth projections. Though a logical method to collect plume observations in principle, many unanticipated issues were uncovered as the project developed. Instrument limitations and environmental conditions presented challenges to the investigators, whereas human error and the subjectivity of observations affected data quality. Despite these problems, the data set showed that responses to fire behaviour conditions were consistent with the physical processes leading to plume rise. The Alberta smoke plume observation study data can be found on the Canadian Wildland Fire Information System datamart (Natural Resources Canada, 2018) at http://cwfis.cfs.nrcan.gc.ca/datamart.

Desorption/ablation of lithium fluoride induced by extreme ultraviolet laser radiation

Directory of Open Access Journals (Sweden)

Blejchař Tomáš

2016-06-01

Full Text Available The availability of reliable modeling tools and input data required for the prediction of surface removal rate from the lithium fluoride targets irradiated by the intense photon beams is essential for many practical aspects. This study is motivated by the practical implementation of soft X-ray (SXR or extreme ultraviolet (XUV lasers for the pulsed ablation and thin film deposition. Specifically, it is focused on quantitative description of XUV laser-induced desorption/ablation from lithium fluoride, which is a reference large band-gap dielectric material with ionic crystalline structure. Computational framework was proposed and employed here for the reconstruction of plume expansion dynamics induced by the irradiation of lithium fluoride targets. The morphology of experimentally observed desorption/ablation craters were reproduced using idealized representation (two-zone approximation of the laser fluence profile. The calculation of desorption/ablation rate was performed using one-dimensional thermomechanic model (XUV-ABLATOR code taking into account laser heating and surface evaporation of the lithium fluoride target occurring on a nanosecond timescale. This step was followed by the application of two-dimensional hydrodynamic solver for description of laser-produced plasma plume expansion dynamics. The calculated plume lengths determined by numerical simulations were compared with a simple adiabatic expansion (blast-wave model.

Time-resolved resonance fluorescence spectroscopy for study of chemical reactions in laser-induced plasmas.

Science.gov (United States)

Liu, Lei; Deng, Leimin; Fan, Lisha; Huang, Xi; Lu, Yao; Shen, Xiaokang; Jiang, Lan; Silvain, Jean-François; Lu, Yongfeng

2017-10-30

Identification of chemical intermediates and study of chemical reaction pathways and mechanisms in laser-induced plasmas are important for laser-ablated applications. Laser-induced breakdown spectroscopy (LIBS), as a promising spectroscopic technique, is efficient for elemental analyses but can only provide limited information about chemical products in laser-induced plasmas. In this work, time-resolved resonance fluorescence spectroscopy was studied as a promising tool for the study of chemical reactions in laser-induced plasmas. Resonance fluorescence excitation of diatomic aluminum monoxide (AlO) and triatomic dialuminum monoxide (Al 2 O) was used to identify these chemical intermediates. Time-resolved fluorescence spectra of AlO and Al 2 O were used to observe the temporal evolution in laser-induced Al plasmas and to study their formation in the Al-O 2 chemistry in air.

Femtosecond self-reconfiguration of laser-induced plasma patterns in dielectrics

Science.gov (United States)

Déziel, Jean-Luc; Dubé, Louis J.; Messaddeq, Sandra H.; Messaddeq, Younès; Varin, Charles

2018-05-01

Laser-induced modification of transparent solids by intense femtosecond laser pulses allows fast integration of nanophotonic and nanofluidic devices with controlled optical properties. Experimental observations suggest that the local and dynamic nature of the interactions between light and the transient plasma plays an important role during fabrication. Current analytical models neglect these aspects and offer limited coverage of nanograting formation on dielectric surfaces. In this paper, we present a self-consistent dynamic treatment of the plasma buildup and its interaction with light within a three-dimensional electromagnetic framework. The main finding of this work is that local light-plasma interactions are responsible for the reorientation of laser-induced periodic plasma patterns with respect to the incident light polarization, when a certain energy density threshold is reached. Plasma reconfiguration occurs within a single laser pulse, on a femtosecond time scale. Moreover, we show that the reconfigured subwavelength plasma structures actually grow into the bulk of the sample, which agrees with the experimental observations of self-organized volume nanogratings. We find that mode coupling of the incident and transversely scattered light with the periodic plasma structures is sufficient to initiate the growth and self-organization of the pattern inside the medium with a characteristic half-wavelength periodicity.

Laser-induced plasmas as an analytical source for quantitative analysis of gaseous and aerosol systems: Fundamentals of plasma-particle interactions

Science.gov (United States)

Diwakar, Prasoon K.

2009-11-01

Laser-induced Breakdown Spectroscopy (LIBS) is a relatively new analytical diagnostic technique which has gained serious attention in recent past due to its simplicity, robustness, and portability and multi-element analysis capabilities. LIBS has been used successfully for analysis of elements in different media including solids, liquids and gases. Since 1963, when the first breakdown study was reported, to 1983, when the first LIBS experiments were reported, the technique has come a long way, but the majority of fundamental understanding of the processes that occur has taken place in last few years, which has propelled LIBS in the direction of being a well established analytical technique. This study, which mostly focuses on LIBS involving aerosols, has been able to unravel some of the mysteries and provide knowledge that will be valuable to LIBS community as a whole. LIBS processes can be broken down to three basic steps, namely, plasma formation, analyte introduction, and plasma-analyte interactions. In this study, these three steps have been investigated in laser-induced plasma, focusing mainly on the plasma-particle interactions. Understanding plasma-particle interactions and the fundamental processes involved is important in advancing laser-induced breakdown spectroscopy as a reliable and accurate analytical technique. Critical understanding of plasma-particle interactions includes study of the plasma evolution, analyte atomization, and the particle dissociation and diffusion. In this dissertation, temporal and spatial studies have been done to understand the fundamentals of the LIBS processes including the breakdown of gases by the laser pulse, plasma inception mechanisms, plasma evolution, analyte introduction and plasma-particle interactions and their influence on LIBS signal. Spectral measurements were performed in a laser-induced plasma and the results reveal localized perturbations in the plasma properties in the vicinity of the analyte species, for

Initiation of an early-stage plasma during picosecond laser ablation of solids

International Nuclear Information System (INIS)

Mao, Samuel S.; Mao, Xianglei; Greif, Ralph; Russo, Richard E.

2000-01-01

Picosecond time-resolved images of plasma initiation were recorded during pulsed-laser ablation of metal targets in an air atmosphere. An early-stage plasma was observed to form before the release of a material vapor plume. Close to the target surface, interferometry measurements indicate that the early-stage plasma has an electron number density on the order of 10 20 cm -3 . The longitudinal expansion of the ionization front for this plasma has a velocity 10 9 cm/s, during the laser pulse. In contrast, a material--vapor plume forms approximately 200 ps after the laser pulse, and it moves away from the target at 10 6 cm/s. The experimental observations of the early-stage plasma were simulated by using a theoretical model based on a two-fluids description of laser plasmas. The results indicate that the initiation of the plasma is due to air breakdown assisted by electron emission from the target

Plasma devices for hydrocarbon reformation

KAUST Repository

Cha, Min Suk

2017-02-16

Plasma devices for hydrocarbon reformation are provided. Methods of using the devices for hydrocarbon reformation are also provided. The devices can include a liquid container to receive a hydrocarbon source, and a plasma torch configured to be submerged in the liquid. The plasma plume from the plasma torch can cause reformation of the hydrocarbon. The device can use a variety of plasma torches that can be arranged in a variety of positions in the liquid container. The devices can be used for the reformation of gaseous hydrocarbons and/or liquid hydrocarbons. The reformation can produce methane, lower hydrocarbons, higher hydrocarbons, hydrogen gas, water, carbon dioxide, carbon monoxide, or a combination thereof.

Optical spectroscopy of laser-produced plasmas for standoff isotopic analysis

Energy Technology Data Exchange (ETDEWEB)

Harilal, Sivanandan S.; Brumfield, Brian E.; LaHaye, Nicole L.; Hartig, Kyle C.; Phillips, Mark C.

2018-04-20

This review article covers the present status of isotope detection through emission, absorption, and fluorescence spectroscopy of atoms and molecules in a laser-produced plasma formed from a solid sample. A description of the physics behind isotope shifts in atoms and molecules is presented, followed by the physics behind solid sampling of laser ablation plumes, optical methods for isotope measurements, the suitable physical conditions of laser-produced plasma plumes for isotopic analysis, and the current status. Finally, concluding remarks will be made on the existing gaps between previous works in the literature and suggestions for future work.

NW Iberia shelf dynamics and the behaviour of the Douro River plume

Science.gov (United States)

Iglesias, Isabel; Couvelard, Xavier; Avilez-Valente, Paulo; Caldeira, Rui M. A.

2015-04-01

The study and modelling of the river plumes is a key factor to complete understand the coastal physics and dynamic processes and sediment transport mechanisms. Some the terrestrial materials that they transport to the ocean are pollutants, essential nutrients, which enhance the phytoplankton productivity or sediments, which settle on the seabed producing bathymetric modifications. When the riverine water join the ocean several instabilities can be induced, generating bulges, filaments, and buoyant currents over the continental shelf. Offshore, the riverine water could form fronts that could be related with the occurrence of current-jets, eddies and strong mixing. This study focused on the Douro River plume simulation. This river is located on the north-west Iberian coast. Its daily averaged freshwater discharge can range values from 0 to 13000 m3/s, which impacts on the formation of the river plumes and its dispersion along the continental shelf. The Regional Oceanic Modeling System (ROMS) model was used to reproduce scenarios of plume generation, retention and dispersion (Shchepetkin and McWilliams, 2005). Three types of simulations were performed: schematic winds simulations with prescribed river flow, wind speed and direction; multi-year climatological simulation, with river flow and temperature change for each month; extreme case simulation. The schematic wind case-studies suggest that the plume is wind-driven. Important differences appear in its structure and dispersion pathways depending on the wind direction and strength. Northerly winds induce plumes with a narrow coastal current meanwhile southerly winds push the river water to the north finding water associated with the Douro River in the Galician Rías. The high surface salinity on the plume regions during strong wind events suggests that the wind enhances the vertical mixing. Extreme river discharges, associated with southerly winds, can transport debris to the Galician coast in about 60 h, helping to

Dual-wavelength differential spectroscopic imaging for diagnostics of laser-induced plasma

Energy Technology Data Exchange (ETDEWEB)

Motto-Ros, V., E-mail: vincent.motto-ros@univ-lyon1.fr [Universite de Lyon, F-69622, Lyon, Universite Lyon 1, Villeurbanne, CNRS, UMR5579, LASIM (France); Ma, Q.L. [Universite de Lyon, F-69622, Lyon, Universite Lyon 1, Villeurbanne, CNRS, UMR5579, LASIM (France); Gregoire, S. [CRITT Matriaux Alsace, 19 rue de St Junien, 67300 Schiltigheim (France); Lei, W.Q.; Wang, X.C. [Universite de Lyon, F-69622, Lyon, Universite Lyon 1, Villeurbanne, CNRS, UMR5579, LASIM (France); Pelascini, F.; Surma, F. [CRITT Matriaux Alsace, 19 rue de St Junien, 67300 Schiltigheim (France); Detalle, V. [Laboratoire de Recherche des Monuments Historiques, 29 rue de Paris, 77420 Champs-sur-Marne (France); Yu, J. [Universite de Lyon, F-69622, Lyon, Universite Lyon 1, Villeurbanne, CNRS, UMR5579, LASIM (France)

2012-08-15

A specific configuration for plasma fast spectroscopic imaging was developed, where a pair of narrowband filters, one fitting an emission line of a species to be studied and the other out of its emission line, allowed double images to be taken for a laser-induced plasma. A dedicated software was developed for the subtraction between the double images. The result represents therefore the monochromatic emission image of the species in the plasma. We have shown in this work that such configuration is especially efficient for the monitoring of a plasma generated under the atmospheric pressure at very short delays after the impact of the laser pulse on the target, when a strong continuum emission is observed. The efficiency of the technique has been particularly demonstrated in the study of laser-induced plasma on a polymer target. Molecular species, such as C{sub 2} and CN, as well as atomic species, such as C and N, were imaged starting from 50 ns after the laser impact. Moreover space segregation of different species, atomic or molecular, inside of the plasma was clearly observed. - Highlights: Black-Right-Pointing-Pointer Imaging to study species with time and space resolution in laser induced plasma. Black-Right-Pointing-Pointer Image display of multiple species is proposed based on RGB color model. Black-Right-Pointing-Pointer Molecular emission (CN and C{sub 2}) is observed at very short delays (50 ns). Black-Right-Pointing-Pointer Segregation of different species inside the plasma is clearly established.

Plasma dynamics study by fast imaging and Sm1-xNdxNiO3 thin film deposition

International Nuclear Information System (INIS)

Lafane, S.; Kerdja, T.; Abdelli-Messaci, S.; Malek, S.; Maaza, M.

2009-01-01

The plume expansion dynamics of an ablated target of Sm 2 O 3 , Nd 2 O 3 and NiO mixture oxides by KrF laser into 0.2 mbar oxygen atmosphere has been investigated using fast imaging. The study was carried out for two different laser fluences 2 and 3 J cm -2 . It was found that at early time delays, the expansion is still linear, independently of the laser fluence. However, as time evolves, the plume is decelerated and comes to rest. The plasma plume dynamics was analysed in the framework of Predtechensky and Mayorov model and drag model. It was found that Predtechensky and Mayorov model gives a general description of the plume expansion. However, at later time delays, it is rather the drag model which is valid. Furthermore, under the same conditions of pressure and fluences used for the plasma study, thin films were deposited at 4 cm from target surface and at temperature of 500 deg. C on (1 0 0) silicon substrates. The obtained layers were characterized by atomic force microscopy and electron dispersive X-ray spectroscopy diagnostics. A correlation between the films properties and the plasma plume dynamics was found.

Temporal and spatial effects of ablation plume on number density distribution of droplets in an aerosol measured by laser-induced breakdown

International Nuclear Information System (INIS)

Yashiro, H.; Kakehata, M.

2013-01-01

We proposed and experimentally demonstrated a novel method of evaluating the number density of droplets in an aerosol by laser-induced breakdown. The number density of droplets is evaluated from the volume in which the laser intensity exceeds the breakdown threshold intensity for droplets, and the number of droplets in this volume, which is evaluated by the experimentally observed breakdown probability. This measurement method requires a large number of laser shots for not only precise measurement but also highly temporally and spatially resolved density distribution in aerosol. Laser ablation plumes ejected from liquid droplets generated by breakdown disturb the density around the measurement points. Therefore, the recovery time of the density determines the maximum repetition rate of the probe laser irradiating a fixed point. The expansion range of the ablation plume determines the minimum distance at which the measurement points are unaffected by a neighboring breakdown when multiple laser beams are simultaneously irradiated. These laser irradiation procedures enable the measurement of the number density distribution of droplets in an aerosol at a large number of points within a short measurement time.

Temporal and spatial effects of ablation plume on number density distribution of droplets in an aerosol measured by laser-induced breakdown

Energy Technology Data Exchange (ETDEWEB)

Yashiro, H.; Kakehata, M. [Electronics and Photonics Research Institute (ESPRIT), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

2013-05-07

We proposed and experimentally demonstrated a novel method of evaluating the number density of droplets in an aerosol by laser-induced breakdown. The number density of droplets is evaluated from the volume in which the laser intensity exceeds the breakdown threshold intensity for droplets, and the number of droplets in this volume, which is evaluated by the experimentally observed breakdown probability. This measurement method requires a large number of laser shots for not only precise measurement but also highly temporally and spatially resolved density distribution in aerosol. Laser ablation plumes ejected from liquid droplets generated by breakdown disturb the density around the measurement points. Therefore, the recovery time of the density determines the maximum repetition rate of the probe laser irradiating a fixed point. The expansion range of the ablation plume determines the minimum distance at which the measurement points are unaffected by a neighboring breakdown when multiple laser beams are simultaneously irradiated. These laser irradiation procedures enable the measurement of the number density distribution of droplets in an aerosol at a large number of points within a short measurement time.

A forward model for the helium plume effect and the interpretation of helium charge exchange measurements at ASDEX Upgrade

Science.gov (United States)

Kappatou, A.; McDermott, R. M.; Pütterich, T.; Dux, R.; Geiger, B.; Jaspers, R. J. E.; Donné, A. J. H.; Viezzer, E.; Cavedon, M.; the ASDEX Upgrade Team

2018-05-01

The analysis of the charge exchange measurements of helium is hindered by an additional emission contributing to the spectra, the helium ‘plume’ emission (Fonck et al 1984 Phys. Rev. A 29 3288), which complicates the interpretation of the measurements. The plume emission is indistinguishable from the active charge exchange signal when standard analysis of the spectra is applied and its intensity is of comparable magnitude for ASDEX Upgrade conditions, leading to a significant overestimation of the He2+ densities if not properly treated. Furthermore, the spectral line shape of the plume emission is non-Gaussian and leads to wrong ion temperature and flow measurements when not taken into account. A kinetic model for the helium plume emission has been developed for ASDEX Upgrade. The model is benchmarked against experimental measurements and is shown to capture the underlying physics mechanisms of the plume effect, as it can reproduce the experimental spectra and provides consistent values for the ion temperature, plasma rotation, and He2+ density.

Liquid Booster Module (LBM) plume flowfield model

Science.gov (United States)

Smith, S. D.

1981-01-01

A complete definition of the LBM plume is important for many Shuttle design criteria. The exhaust plume shape has a significant effect on the vehicle base pressure. The LBM definition is also important to the Shuttle base heating, aerodynamics and the influence of the exhaust plume on the launch stand and environment. For these reasons a knowledge of the LBM plume characteristics is necessary. A definition of the sea level LBM plume as well as at several points along the Shuttle trajectory to LBM, burnout is presented.

Measurements on cooling tower plumes. Pt. 3

International Nuclear Information System (INIS)

Fortak, H.

1975-11-01

In this paper an extended field experiment is described in which cooling tower plumes were investigated by means of three-dimensional in situ measurements. The goal of this program was to obtain input data for numerical models of cooling tower plumes. Data for testing or developing assumptions for sub-grid parametrizations were of special interest. Utilizing modern systems for high-resolution aerology and small aircraft, four measuring campaigns were conducted: two campaigns (1974) at the cooling towers of the RWE power station at Neurath and also two (1975) at the single cooling tower of the RWE power station at Meppen. Because of the broad spectrum of weather situations, it can be assumed that the results are representative with regard to the interrelationship between the structure of cooling tower plumes and the large-scale meteorological situation. A large number of flights with a powered glider ASK 16 (more than 100 flight hours) crossing the plumes on orthogonal tracks was performed. All flights showed that the plume could be identified up to large downwind distances by discontinuous jumps of temperature and vapour pressure. Therefore a definite geometry of the plume could always be defined. In all cross sections a vertical circulation could be observed. At the plumes boundaries, which could be defined by the mentioned jumps of temperature and vapour pressure, a maximum of downward vertical motion was observed in most cases. Entrainment along the boundary of a cross section seems to be very small, except at the lower part of the plume. There, the mass entrainment is maximum and is responsible for plume rise as well as for enlargement of the cross section. The visible part of the plume (cloud) was only a small fraction of the whole plume. The discontinuities of temperature and vapour pressure show that the plume fills the space below the visible plume down to the ground. However, all effects decrease rapidly towards the ground. It turned out that high

Variations of helicon wave induced radial plasma transport in different experimental conditions

International Nuclear Information System (INIS)

Petrzilka, V.

1993-08-01

Variations of the helicon wave induced radial plasma transport are presented in dependence on values of the plasma radius, magnetostatic field, plasma density, frequency of the helicon wave and on the ion charge. 22 refs., 14 figs

Radioactive Plumes Monitoring Simulator

International Nuclear Information System (INIS)

Kapelushnik, I.; Sheinfeld, M.; Avida, R.; Kadmon, Y.; Ellenbogen, M.; Tirosh, D.

1999-01-01

The Airborne Radiation Monitoring System (ARMS) monitors air or ground radioactive contamination. The contamination source can be a radioactive plume or an area contaminated with radionuclides. The system is based on two major parts, an airborne unit carried by a helicopter and a ground station carried by a truck. The system enables real time measurement and analysis of radioactive plumes as well as post flight processing. The Radioactive Plumes Monitoring Simulator purpose is to create a virtual space where the trained operators experience full radiation field conditions, without real radiation hazard. The ARMS is based on a flying platform and hence the simulator allows a significant reduction of flight time costs

Toward 3-D E-field visualization in laser-produced plasma by polarization-spectroscopic imaging

International Nuclear Information System (INIS)

Kim, Yong W.

2004-01-01

A 3-D volume radiator such as laser-produced plasma (LPP) plumes is observed in the form of a 2-D projection of its radiative structure. The traditional approach to 3-D structure reconstruction relies on multiple projections but is not suitable as a general method for unsteady radiating objects. We have developed a general method for 3-D structure reconstruction for LPP plumes in stages of increasing complexity. We have chosen neutral gas-confined LPP plumes from an aluminum target immersed in high-density argon because the plasma experiences Rayleigh-Taylor instability. We make use of two time-resolved, mutually orthogonal side views of a LPP plume and a front-view snapshot. No symmetry assumptions are needed. Two scaling relations are invoked that connects the plasma temperature and pressure to local specific intensity at selected wavelength(s). Two mutually-orthogonal lateral luminosity views of the plume at each known distance from the target surface are compared with those computed from the trial specific intensity profiles and the scaling relations. The luminosity error signals are minimized to find the structure. The front-view snapshot is used to select the initial trial profile and as a weighting function for allocation of the error signal into corrections for specific intensities from the plasma cells along the line of sight. Full Saha equilibrium for multiple stages of ionization is treated, together with the self-absorption, in the computation of the luminosity. We show the necessary optics for determination of local electric fields through polarization-resolved imaging. (author)

Local thermodynamic equilibrium considerations in powerchip laser-induced plasmas

Energy Technology Data Exchange (ETDEWEB)

Merten, Jonathan A., E-mail: jmerten@astate.edu; Smith, Benjamin W., E-mail: bwsmith@chem.ufl.edu; Omenetto, Nicoló, E-mail: omenetto@chem.ufl.edu

2013-05-01

Time-resolved emission experiments are reported in the fast-decaying transient plasma induced by a microchip laser on an aluminum target in three different cover gases, i.e., air, argon and helium. The laser operates at 532 nm, with a repetition frequency of 1 kHz and a pulse width of less than 0.5 ns. The overall persistence of plasma emission is of the order of 100 ns. We examine the existence of local thermodynamic equilibrium (LTE) by evaluating the temporal criteria required (in addition to the McWhirter criterion), as recommended by Cristoforetti et al. (Spectrochim. Acta Part B 65, 2010, 86–95). The temporal criteria examine the evolution of temperature and electron number density and compare their rate of change to the rate at which electron collisions can thermalize the change. These considerations are used to determine time windows in which LTE may be present. Our results suggest that calibration-free LIBS measurements with these lasers may be possible for some elements at early times, especially under argon. - Highlights: ► Powerchip laser-induced plasma evolution is affected by cover gas. ► Plasma often out of LTE, despite fulfilling the McWhirter criterion ► Calibration-free LIBS may be possible with powerchip laser plasmas.

Local thermodynamic equilibrium considerations in powerchip laser-induced plasmas

International Nuclear Information System (INIS)

Merten, Jonathan A.; Smith, Benjamin W.; Omenetto, Nicoló

2013-01-01

Time-resolved emission experiments are reported in the fast-decaying transient plasma induced by a microchip laser on an aluminum target in three different cover gases, i.e., air, argon and helium. The laser operates at 532 nm, with a repetition frequency of 1 kHz and a pulse width of less than 0.5 ns. The overall persistence of plasma emission is of the order of 100 ns. We examine the existence of local thermodynamic equilibrium (LTE) by evaluating the temporal criteria required (in addition to the McWhirter criterion), as recommended by Cristoforetti et al. (Spectrochim. Acta Part B 65, 2010, 86–95). The temporal criteria examine the evolution of temperature and electron number density and compare their rate of change to the rate at which electron collisions can thermalize the change. These considerations are used to determine time windows in which LTE may be present. Our results suggest that calibration-free LIBS measurements with these lasers may be possible for some elements at early times, especially under argon. - Highlights: ► Powerchip laser-induced plasma evolution is affected by cover gas. ► Plasma often out of LTE, despite fulfilling the McWhirter criterion ► Calibration-free LIBS may be possible with powerchip laser plasmas

Localized electron density enhancements in the high-altitude polar ionosphere and their relationships with storm-enhanced density (SED plumes and polar tongues of ionization (TOI

Directory of Open Access Journals (Sweden)

Y. Kitanoya

2011-02-01

Full Text Available Events of localized electron density increase in the high-altitude (>3000 km polar ionosphere are occasionally identified by the thermal plasma instruments on the Akebono satellite. In this paper, we investigate the vertical density structure in one of such events in detail using simultaneous observations by the Akebono and DMSP F15 satellites, the SuperDARN radars, and a network of ground Global Positioning System (GPS receivers, and the statistical characteristics of a large number (>10 000 of such events using Akebono data over half of an 11-year solar cycle. At Akebono altitude, the parallel drift velocity is remarkably low and the O+ ion composition ratio remarkably high, inside the high plasma-density regions at high altitude. Detailed comparisons between Akebono, DMSP ion velocity and density, and GPS total electron content (TEC data suggest that the localized plasma density increase observed at high altitude on Akebono was likely connected with the polar tongue of ionization (TOI and/or storm enhanced density (SED plume observed in the F-region ionosphere. Together with the SuperDARN plasma convection map these data suggest that the TOI/SED plume penetrated into the polar cap due to anti-sunward convection and the plume existed in the same convection channel as the dense plasma at high altitude; in other words, the two were probably connected to each other by the convecting magnetic field lines. The observed features are consistent with the observed high-density plasma being transported from the mid-latitude ionosphere or plasmasphere and unlikely a part of the polar wind population.

Investigation of Balcony Plume Entrainment

OpenAIRE

Liu, F.; Nielsen, Peter V.; Heiselberg, Per; Brohus, Henrik; Li, B. Z.

2009-01-01

An investigation on the scenarios of the spill plume and its equation was presented in this paper. The study includes two aspects, i.e., the small-scale experiment and the numerical simulation. Two balcony spill plume models are assessed by comparing with the FDS (Fire Dynamic Simulation) and small scale model experiment results. Besides validating the spill model by experiments, the effect of different fire location on balcony plume is also discussed.The results show that the balcony equatio...

Generation of electromagnetic pulses from plasma channels induced by femtosecond light strings

OpenAIRE

Cheng, Chung-Chieh; Wright, E. M.; Moloney, J. V.

2000-01-01

We present a model that elucidates the physics underlying the generation of an electromagnetic pulse from a femtosecond laser induced plasma channel. The radiation pressure force from the laser pulse spatially separates the ionized electrons from the heavier ions and the induced dipole moment subsequently oscillates at the plasma frequency and radiates an electromagnetic pulse.

Laser-induced breakdown spectroscopy of tantalum plasma

International Nuclear Information System (INIS)

Khan, Sidra; Bashir, Shazia; Hayat, Asma; Khaleeq-ur-Rahman, M.; Faizan–ul-Haq

2013-01-01

Laser Induced Breakdown spectroscopy (LIBS) of Tantalum (Ta) plasma has been investigated. For this purpose Q-switched Nd: YAG laser pulses (λ∼ 1064 nm, τ∼ 10 ns) of maximum pulse energy of 100 mJ have been employed as an ablation source. Ta targets were exposed under the ambient environment of various gases of Ar, mixture (CO 2 : N 2 : He), O 2 , N 2 , and He under various filling pressure. The emission spectrum of Ta is observed by using LIBS spectrometer. The emission intensity, excitation temperature, and electron number density of Ta plasma have been evaluated as a function of pressure for various gases. Our experimental results reveal that the optical emission intensity, the electron temperature and density are strongly dependent upon the nature and pressure of ambient environment. The SEM analysis of the ablated Ta target has also been carried out to explore the effect of ambient environment on the laser induced grown structures. The growth of grain like structures in case of molecular gases and cone-formation in case of inert gases is observed. The evaluated plasma parameters by LIBS analysis such as electron temperature and the electron density are well correlated with the surface modification of laser irradiated Ta revealed by SEM analysis

Laser-induced breakdown spectroscopy of tantalum plasma

Energy Technology Data Exchange (ETDEWEB)

Khan, Sidra; Bashir, Shazia; Hayat, Asma; Khaleeq-ur-Rahman, M.; Faizan–ul-Haq [Centre for Advanced Studies in Physics, GC University, Lahore (Pakistan)

2013-07-15

Laser Induced Breakdown spectroscopy (LIBS) of Tantalum (Ta) plasma has been investigated. For this purpose Q-switched Nd: YAG laser pulses (λ∼ 1064 nm, τ∼ 10 ns) of maximum pulse energy of 100 mJ have been employed as an ablation source. Ta targets were exposed under the ambient environment of various gases of Ar, mixture (CO{sub 2}: N{sub 2}: He), O{sub 2}, N{sub 2}, and He under various filling pressure. The emission spectrum of Ta is observed by using LIBS spectrometer. The emission intensity, excitation temperature, and electron number density of Ta plasma have been evaluated as a function of pressure for various gases. Our experimental results reveal that the optical emission intensity, the electron temperature and density are strongly dependent upon the nature and pressure of ambient environment. The SEM analysis of the ablated Ta target has also been carried out to explore the effect of ambient environment on the laser induced grown structures. The growth of grain like structures in case of molecular gases and cone-formation in case of inert gases is observed. The evaluated plasma parameters by LIBS analysis such as electron temperature and the electron density are well correlated with the surface modification of laser irradiated Ta revealed by SEM analysis.

Influence of irradiation conditions on plasma evolution in laser-surface interaction

Science.gov (United States)

Hermann, J.; Boulmer-Leborgne, C.; Dubreuil, B.; Mihailescu, I. N.

1993-09-01

The plasma plume induced by pulsed CO2 laser irradiation of a Ti target at power densities up to 4×108 W cm-2 was studied by emission spectroscopy. Time- and space-resolved measurements were performed by varying laser intensity, laser temporal pulse shape, ambient gas pressure, and the nature of the ambient gas. Experimental results are discussed by comparison with usual models. We show that shock wave and plasma propagation depend critically on the ratio Ivap/Ii, Ivap being the intensity threshold for surface vaporization and Ii the plasma ignition threshold of the ambient gas. Spectroscopic diagnostics of the helium breakdown plasma show maximum values of electron temperature and electron density in the order of kTe˜10 eV and ne=1018 cm-3, respectively. The plasma cannot be described by local thermodynamic equilibrium modeling. Nevertheless, excited metal atoms appear to be in equilibrium with electrons, hence, they can be used like a probe to measure the electron temperature. In order to get information on the role of the plasma in the laser-surface interaction, Ti surfaces were investigated by microscopy after irradiation. Thus an enhanced momentum transfer from the plasma to the target due to the recoil pressure of the breakdown plasma could be evidenced.

Linking lowermost mantle structure, core-mantle boundary heat flux and mantle plume formation

Science.gov (United States)

Li, Mingming; Zhong, Shijie; Olson, Peter

2018-04-01

The dynamics of Earth's lowermost mantle exert significant control on the formation of mantle plumes and the core-mantle boundary (CMB) heat flux. However, it is not clear if and how the variation of CMB heat flux and mantle plume activity are related. Here, we perform geodynamic model experiments that show how temporal variations in CMB heat flux and pulses of mantle plumes are related to morphologic changes of the thermochemical piles of large-scale compositional heterogeneities in Earth's lowermost mantle, represented by the large low shear velocity provinces (LLSVPs). We find good correlation between the morphologic changes of the thermochemical piles and the time variation of CMB heat flux. The morphology of the thermochemical piles is significantly altered during the initiation and ascent of strong mantle plumes, and the changes in pile morphology cause variations in the local and the total CMB heat flux. Our modeling results indicate that plume-induced episodic variations of CMB heat flux link geomagnetic superchrons to pulses of surface volcanism, although the relative timing of these two phenomena remains problematic. We also find that the density distribution in thermochemical piles is heterogeneous, and that the piles are denser on average than the surrounding mantle when both thermal and chemical effects are included.

Are splash plumes the origin of minor hotspots?

Science.gov (United States)

Davies, J. H.; Bunge, H.-P.

2006-05-01

It has been claimed that focused hot cylindrical upwelling plumes cause many of the surface volcanic hotspots on Earth. It has also been argued that they must originate from thermal boundary layers. In this paper, we present spherical simulations of mantle circulation at close to Earth-like vigor with significant internal heating. These show, in addition to thermal boundary layer plumes, a new class of plumes that are not rooted in thermal boundary layers. These plumes develop as instabilities from the edge of bowls of hot mantle, which are produced by cold downwelling material deforming hot sheets of mantle. The resulting bowl and plume structure can look a bit like the “splash” of a water droplet. These splash plumes might provide an explanation for some hotspots that are not underlain by thermal boundary layer sourced plumes and not initiated by large igneous provinces. We suggest that in Earth's mantle, lithospheric instabilities or small pieces of subducting slab could play the role of the model downwelling material in initiating splash plumes. Splash plumes would have implications for interpreting ocean-island basalt geochemistry, plume fixity, excess plume temperature, and estimating core heat flux. Improved seismic imaging will ultimately test this hypothesis.

Marangoni flows induced by atmospheric-pressure plasma jets

International Nuclear Information System (INIS)

Berendsen, C W J; Van Veldhuizen, E M; Kroesen, G M W; Darhuber, A A

2015-01-01

We studied the interaction of atmospheric-pressure plasma jets of Ar or air with liquid films of an aliphatic hydrocarbon on moving solid substrates. The hydrodynamic jet-liquid interaction induces a track of lower film thickness. The chemical plasma-surface interaction oxidizes the liquid, leading to a local increase of the surface tension and a self-organized redistribution of the liquid film. We developed a numerical model that qualitatively reproduces the formation, instability and coarsening of the flow patterns observed in the experiments. Monitoring the liquid flow has potential as an in-situ, spatially and temporally resolved, diagnostic tool for the plasma-liquid surface interaction. (paper)

The effect of applied electric field on pulsed radio frequency and pulsed direct current plasma jet array

International Nuclear Information System (INIS)

Hu, J. T.; Liu, X. Y.; Liu, J. H.; Xiong, Z. L.; Liu, D. W.; Lu, X. P.; Iza, F.; Kong, M. G.

2012-01-01

Here we compare the plasma plume propagation characteristics of a 3-channel pulsed RF plasma jet array and those of the same device operated by a pulsed dc source. For the pulsed-RF jet array, numerous long life time ions and metastables accumulated in the plasma channel make the plasma plume respond quickly to applied electric field. Its structure similar as “plasma bullet” is an anode glow indeed. For the pulsed dc plasma jet array, the strong electric field in the vicinity of the tube is the reason for the growing plasma bullet in the launching period. The repulsive forces between the growing plasma bullets result in the divergence of the pulsed dc plasma jet array. Finally, the comparison of 309 nm and 777 nm emissions between these two jet arrays suggests the high chemical activity of pulsed RF plasma jet array.

Bioinspired algorithm for autonomous sensor-driven guidance in turbulent chemical plumes

International Nuclear Information System (INIS)

Webster, D R; Volyanskyy, K Y; Weissburg, M J

2012-01-01

We designed and implemented a control algorithm for sensor-mediated chemical plume tracking in a turbulent flow environment. In our design, we focused on development of a signal processing strategy capable of replicating behavioral responses of actively tracking blue crabs (Callinectes sapidus) to chemical stimuli. The control algorithm is evaluated in a hardware platform that allows motion in two directions (i.e. forward–back and left–right). The geometric arrangement of the sensor array is inspired by the location of blue crab sensor populations. Upstream motion is induced by a binary response to supra-threshold spikes of concentration, and cross-stream steering is controlled by contrast between bilaterally-separated sensors. Like animal strategies, the developed control algorithm is dynamic. This property allows the algorithm to function effectively in the highly irregular turbulent environment and produces adaptive adjustments of motion to minimize the distance to the source of a plume. Tracking trials indicate that roughly 80% of the tracks successfully stop near the plume source location. Both success rate and movement patterns of the tracker compare favorably to that of blue crabs searching for odorant plume sources, thus suggesting that our sensory-mediated behavior hypothesis are generally accurate and that the associated tracking mechanisms may be successfully implemented in hardware. (paper)

Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow

Energy Technology Data Exchange (ETDEWEB)

Hu, L.H., E-mail: hlh@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui 230026 (China); Huo, R.; Yang, D. [State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2009-07-15

The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons-a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.

Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow.

Science.gov (United States)

Hu, L H; Huo, R; Yang, D

2009-07-15

The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons--a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.

Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow

International Nuclear Information System (INIS)

Hu, L.H.; Huo, R.; Yang, D.

2009-01-01

The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons-a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.

Is the 'Fast Halo' around Hawaii as imaged in the PLUME experiment direct evidence for buoyant plume-fed asthenosphere?

Science.gov (United States)

Morgan, J. P.; Shi, C.; Hasenclever, J.

2010-12-01

An intriguing spatial pattern of variations in shear-wave arrival times has been mapped in the PLUME ocean bottom experiment (Wolfe et al., 2009) around Hawaii. The pattern consists of a halo of fast travel times surrounding a disk of slow arrivals from waves traveling up though the plume. We think it is directly sensing the pattern of dynamic uplift of the base of a buoyant asthenosphere - the buoyancy of the plume conduit lifting a 'rim' of the cooler, denser mantle that the plume rises through. The PLUME analysis inverted for lateral shear velocity variations beneath the lithosphere, after removing the assumed 1-D model velocity structure IASP91. They found that a slow plume-conduit extends to at least 1200 km below the Hawaiian hotspot. In this inversion the slow plume conduit is — quite surprisingly - surrounded by a fast wavespeed halo. A fast halo is impossible to explain as a thermal halo around the plume; this should lead to a slow wavespeed halo, not a fast one. Plume-related shearwave anisotropy also cannot simply explain this pattern — simple vertical strain around the plume conduit would result in an anisotropic slow shear-wavespeed halo, not a fast one. (Note the PLUME experiment’s uniform ‘fast-halo’ structure from 50-400km is likely to have strong vertical streaking in the seismic image; Pacific Plate-driven shear across a low-viscosity asthenosphere would be expected to disrupt and distort any cold sheet of vertical downwelling structure between 50-400km depths so that it would no longer be vertical as it is in the 2009 PLUME image with its extremely poor vertical depth control.) If the asthenosphere is plume-fed, hence more buoyant than underlying mantle, then there can be a simple explanation for this pattern. The anomaly would be due to faster traveltimes resulting from dynamic relief at the asthenosphere-mesosphere interface; uplift of the denser mesosphere by the buoyancy of the rising plume increases the distance a wave travels

Submarine Alkalic Lavas Around the Hawaiian Hotspot; Plume and Non-Plume Signatures Determined by Noble Gases

Science.gov (United States)

Hanyu, T.; Clague, D. A.; Kaneoka, I.; Dunai, T. J.; Davies, G. R.

2004-12-01

Noble gas isotopic ratios were determined for submarine alkalic volcanic rocks distributed around the Hawaiian islands to constrain the origin of such alkalic volcanism. Samples were collected by dredging or using submersibles from the Kauai Channel between Oahu and Kauai, north of Molokai, northwest of Niihau, Southwest Oahu, South Arch and North Arch volcanic fields. Sites located downstream from the center of the hotspot have 3He/4He ratios close to MORB at about 8 Ra, demonstrating that the magmas erupted at these sites had minimum contribution of volatiles from a mantle plume. In contrast, the South Arch, located upstream of the hotspot on the Hawaiian Arch, has 3He/4He ratios between 17 and 21 Ra, indicating a strong plume influence. Differences in noble gas isotopic characteristics between alkalic volcanism downstream and upstream of the hotspot imply that upstream volcanism contains incipient melts from an upwelling mantle plume, having primitive 3He/4He. In combination with lithophile element isotopic data, we conclude that the most likely source of the upstream magmatism is depleted asthenospheric mantle that has been metasomatised by incipient melt from a mantle plume. After major melt extraction from the mantle plume during production of magmas for the shield stage, the plume material is highly depleted in noble gases and moderately depleted in lithophile elements. Partial melting of the depleted mantle impregnated by melts derived from this volatile depleted plume source may explain the isotopic characteristics of the downstream alkalic magmatism.

Dynamics expansion of laser produced plasma with different materials in magnetic field

Energy Technology Data Exchange (ETDEWEB)

Rabia Qindeel; Noriah Bte Bidin; Yaacob Mat daud [Laser Technology Laboratory, Physics Department, Universiti Teknologi Malaysia, Skudai 81310, Johor (Malaysia)], E-mail: plasmaqindeel@yahoo.com

2008-12-01

The dynamics expansion of the plasma generated by laser ablation of different materials has been investigated. The dynamics and confinement of laser generated plasma plumes are expanding across variable magnetic fields. A Q-switched neodymium-doped yttrium aluminum garnet laser with 1064 nm, 8 ns pulse width and 0.125 J laser energy was used to generate plasma that was allowed to expand across variable magnetic within 0.1 - 0.8 T. The expansions of laser-produced plasma of different materials are characterized by using constant laser power. CCD video camera was used to visualize and record the activities in the focal region. The plasma plume length, width and area were measured by using Matrox Inpector 2.1 and video Test 0.5 software. Spectrums of plasma beam from different materials are studied via spectrometer. The results show that the plasma generated by aluminum target is the largest than Brass and copper. The optical radiation from laser generated plasma beam spectrums are obtained in the range of UV to visible light.

OClO and BrO observations in the volcanic plume of Mt. Etna - implications on the chemistry of chlorine and bromine species in volcanic plumes

Science.gov (United States)

Gliß, J.; Bobrowski, N.; Vogel, L.; Platt, U.

2014-10-01

mechanism in literature often referred to as "bromine explosion" and that OClO is formed in the "BrO + ClO"-reaction. BrO and OClO concentrations were estimated from the measured SCDs assuming a circular plume shape. In addition, mixing ratios of ClO were determined from the retrieved OClO and BrO-SCDs assuming chemical equilibrium between formation of OClO (BrO + ClO) and its destruction (photolysis). Mean abundances in the young plume (τBrO = 1.35 ppb, OClO = 300 ppt and ClO = 139 ppt with peak values of 600 ppt (OClO), 2.7 ppb (BrO) and 235 ppt (ClO) respectively. The prevailing Cl-atom concentrations in the plume could be estimated from the rate of increase of OClO and BrO in the young plume and the determined ClO and OClO concentrations. Values between 5.1 × 106 cm-3 (at 40 ppb O3) and 2.1 × 108 cm-3 (at 1 ppb O3) were found. Based on that, a potential - chlorine induced - depletion of tropospheric methane (CH4) in the plume was investigated. CH4-lifetimes between 13 h (at 1 ppb O3) and 23 days (at 40 ppb O3) were found. These are considerably small compared to the atmospheric lifetime of CH4. However, the impact of gaseous chlorine on the CH4-budget in the plume environment was assessed to be relatively small, mainly due to plume dispersion (decrease of Cl number densities) and permanent mixing of the plume with the surrounding atmosphere (net supply of O3 and CH4).

Polarized and persistent Ca²⁺ plumes define loci for formation of wall ingrowth papillae in transfer cells.

Science.gov (United States)

Zhang, Hui-Ming; Imtiaz, Mohammad S; Laver, Derek R; McCurdy, David W; Offler, Christina E; van Helden, Dirk F; Patrick, John W

2015-03-01

Transfer cell morphology is characterized by a polarized ingrowth wall comprising a uniform wall upon which wall ingrowth papillae develop at right angles into the cytoplasm. The hypothesis that positional information directing construction of wall ingrowth papillae is mediated by Ca(2+) signals generated by spatiotemporal alterations in cytosolic Ca(2+) ([Ca(2+)]cyt) of cells trans-differentiating to a transfer cell morphology was tested. This hypothesis was examined using Vicia faba cotyledons. On transferring cotyledons to culture, their adaxial epidermal cells synchronously trans-differentiate to epidermal transfer cells. A polarized and persistent Ca(2+) signal, generated during epidermal cell trans-differentiation, was found to co-localize with the site of ingrowth wall formation. Dampening Ca(2+) signal intensity, by withdrawing extracellular Ca(2+) or blocking Ca(2+) channel activity, inhibited formation of wall ingrowth papillae. Maintenance of Ca(2+) signal polarity and persistence depended upon a rapid turnover (minutes) of cytosolic Ca(2+) by co-operative functioning of plasma membrane Ca(2+)-permeable channels and Ca(2+)-ATPases. Viewed paradermally, and proximal to the cytosol-plasma membrane interface, the Ca(2+) signal was organized into discrete patches that aligned spatially with clusters of Ca(2+)-permeable channels. Mathematical modelling demonstrated that these patches of cytosolic Ca(2+) were consistent with inward-directed plumes of elevated [Ca(2+)]cyt. Plume formation depended upon an alternating distribution of Ca(2+)-permeable channels and Ca(2+)-ATPase clusters. On further inward diffusion, the Ca(2+) plumes coalesced into a uniform Ca(2+) signal. Blocking or dispersing the Ca(2+) plumes inhibited deposition of wall ingrowth papillae, while uniform wall formation remained unaltered. A working model envisages that cytosolic Ca(2+) plumes define the loci at which wall ingrowth papillae are deposited. © The Author 2014. Published by Oxford

Lithosphere erosion atop mantle plumes

Science.gov (United States)

Agrusta, R.; Arcay, D.; Tommasi, A.

2012-12-01

Mantle plumes are traditionally proposed to play an important role in lithosphere erosion. Seismic images beneath Hawaii and Cape Verde show a lithosphere-asthenosphere-boundary (LAB) up to 50 km shallower than the surroundings. However, numerical models show that unless the plate is stationary the thermo-mechanical erosion of the lithosphere does not exceed 30 km. We use 2D petrological-thermo-mechanical numerical models based on a finite-difference method on a staggered grid and marker in cell method to study the role of partial melting on the plume-lithosphere interaction. A homogeneous peridotite composition with a Newtonian temperature- and pressure-dependent viscosity is used to simulate both the plate and the convective mantle. A constant velocity, ranging from 5 to 12.5 cm/yr, is imposed at the top of the plate. Plumes are created by imposing a thermal anomaly of 150 to 350 K on a 50 km wide domain at the base of the model (700 km depth); the plate right above the thermal anomaly is 40 Myr old. Partial melting is modeled using batch-melting solidus and liquidus in anhydrous conditions. We model the progressive depletion of peridotite and its effect on partial melting by assuming that the melting degree only strictly increases through time. Melt is accumulated until a porosity threshold is reached and the melt in excess is then extracted. The rheology of the partially molten peridotite is determined using viscous constitutive relationship based on a contiguity model, which enables to take into account the effects of grain-scale melt distribution. Above a threshold of 1%, melt is instantaneously extracted. The density varies as a function of partial melting degree and extraction. Besides, we analyze the kinematics of the plume as it impacts a moving plate, the dynamics of time-dependent small-scale convection (SSC) instabilities developing in the low-viscosity layer formed by spreading of hot plume material at the lithosphere base, and the resulting thermal

Turbulent forces within river plumes affect spread

Science.gov (United States)

Bhattacharya, Atreyee

2012-08-01

When rivers drain into oceans through narrow mouths, hydraulic forces squeeze the river water into buoyant plumes that are clearly visible in satellite images. Worldwide, river plumes not only disperse freshwater, sediments, and nutrients but also spread pollutants and organisms from estuaries into the open ocean. In the United States, the Columbia River—the largest river by volume draining into the Pacific Ocean from North America—generates a plume at its mouth that transports juvenile salmon and other fish into the ocean. Clearly, the behavior and spread of river plumes, such as the Columbia River plume, affect the nation's fishing industry as well as the global economy.

Plume rise measurements at Turbigo

Energy Technology Data Exchange (ETDEWEB)

Anfossi, D

1982-01-01

This paper presents analyses of plume measurements obtained during that campaign by the ENEL ground-based Lidar. The five stacks of Turbigo Power Plant have different heights and emission parameters and their plumes usually combine, so a model for multiple sources was used to predict the plume rises. These predictions are compared with the observations. Measurements of sigma/sub v/ and sigma/sub z/ over the first 1000 m are compared with the curves derived from other observations in the Po Valley, using the no-lift balloon technique over the same range of downwind distance. Skewness and kurtosis distributions are shown, both along the vertical and the horizontal directions. In order to show the plume structure in more detail, we present two examples of Lidar-derived cross sections and the corresponding vertically and horizontally integrated concentration profiles.

Buildup of aerosol precursor gases and sulfur-induced activation of soot in nascent jet aircraft exhaust plumes

Energy Technology Data Exchange (ETDEWEB)

Kaercher, B.; Hirschberg, M.M.; Fabian, P. [Muenchen Univ. (Germany). Lehrstuhl fuer Bioklimatologie und Immissionsforschung; Gerz, T. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere

1997-12-31

Research issues concerning the chemical transformation of exhaust trace gases are summarized. The photochemical evolution of NO{sub x} early in the plume is strongly coupled to plume mixing. Substantial amounts of HNO{sub 3} are generated in nascent plumes even if no NO{sub 2} is emitted. The production of H{sub 2}SO{sub 4} becomes very efficient if part of the fuel sulfur is emitted as SO{sub 3}. Each emitted soot particle can acquire 1-10% by mass fully oxidized sulfur molecules prior to binary homogeneous nucleation, if a few percent of the exhaust SO{sub x} are emitted as SO{sub 3}, indicating an important activation pathway for soot, and leading to a marked enhancement of new aerosol formation and growth rates. (author) 11 refs.

Buildup of aerosol precursor gases and sulfur-induced activation of soot in nascent jet aircraft exhaust plumes

Energy Technology Data Exchange (ETDEWEB)

Kaercher, B; Hirschberg, M M; Fabian, P [Muenchen Univ. (Germany). Lehrstuhl fuer Bioklimatologie und Immissionsforschung; Gerz, T [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere

1998-12-31

Research issues concerning the chemical transformation of exhaust trace gases are summarized. The photochemical evolution of NO{sub x} early in the plume is strongly coupled to plume mixing. Substantial amounts of HNO{sub 3} are generated in nascent plumes even if no NO{sub 2} is emitted. The production of H{sub 2}SO{sub 4} becomes very efficient if part of the fuel sulfur is emitted as SO{sub 3}. Each emitted soot particle can acquire 1-10% by mass fully oxidized sulfur molecules prior to binary homogeneous nucleation, if a few percent of the exhaust SO{sub x} are emitted as SO{sub 3}, indicating an important activation pathway for soot, and leading to a marked enhancement of new aerosol formation and growth rates. (author) 11 refs.

Plume meander and dispersion in a stable boundary layer

Science.gov (United States)

Hiscox, April L.; Miller, David R.; Nappo, Carmen J.

2010-11-01

Continuous lidar measurements of elevated plume dispersion and corresponding micrometeorology data are analyzed to establish the relationship between plume behavior and nocturnal boundary layer dynamics. Contrasting nights of data from the JORNADA field campaign in the New Mexico desert are analyzed. The aerosol lidar measurements were used to separate the plume diffusion (plume spread) from plume meander (displacement). Mutiresolution decomposition was used to separate the turbulence scale (90 s). Durations of turbulent kinetic energy stationarity and the wind steadiness were used to characterize the local scale and submesoscale turbulence. Plume meander, driven by submesoscale wind motions, was responsible for most of the total horizontal plume dispersion in weak and variable winds and strong stability. This proportion was reduced in high winds (i.e., >4 m s-1), weakly stable conditions but remained the dominant dispersion mechanism. The remainder of the plume dispersion in all cases was accounted for by internal spread of the plume, which is a small eddy diffusion process driven by turbulence. Turbulence stationarity and the wind steadiness are demonstrated to be closely related to plume diffusion and plume meander, respectively.

Chesapeake Bay plume dynamics from LANDSAT

Science.gov (United States)

Munday, J. C., Jr.; Fedosh, M. S.

1981-01-01

LANDSAT images with enhancement and density slicing show that the Chesapeake Bay plume usually frequents the Virginia coast south of the Bay mouth. Southwestern (compared to northern) winds spread the plume easterly over a large area. Ebb tide images (compared to flood tide images) show a more dispersed plume. Flooding waters produce high turbidity levels over the shallow northern portion of the Bay mouth.

PLUME-MoM 1.0: A new integral model of volcanic plumes based on the method of moments

Science.gov (United States)

de'Michieli Vitturi, M.; Neri, A.; Barsotti, S.

2015-08-01

In this paper a new integral mathematical model for volcanic plumes, named PLUME-MoM, is presented. The model describes the steady-state dynamics of a plume in a 3-D coordinate system, accounting for continuous variability in particle size distribution of the pyroclastic mixture ejected at the vent. Volcanic plumes are composed of pyroclastic particles of many different sizes ranging from a few microns up to several centimeters and more. A proper description of such a multi-particle nature is crucial when quantifying changes in grain-size distribution along the plume and, therefore, for better characterization of source conditions of ash dispersal models. The new model is based on the method of moments, which allows for a description of the pyroclastic mixture dynamics not only in the spatial domain but also in the space of parameters of the continuous size distribution of the particles. This is achieved by formulation of fundamental transport equations for the multi-particle mixture with respect to the different moments of the grain-size distribution. Different formulations, in terms of the distribution of the particle number, as well as of the mass distribution expressed in terms of the Krumbein log scale, are also derived. Comparison between the new moments-based formulation and the classical approach, based on the discretization of the mixture in N discrete phases, shows that the new model allows for the same results to be obtained with a significantly lower computational cost (particularly when a large number of discrete phases is adopted). Application of the new model, coupled with uncertainty quantification and global sensitivity analyses, enables the investigation of the response of four key output variables (mean and standard deviation of the grain-size distribution at the top of the plume, plume height and amount of mass lost by the plume during the ascent) to changes in the main input parameters (mean and standard deviation) characterizing the

Fossil plume head beneath the Arabian lithosphere?

Science.gov (United States)

Stein, Mordechai; Hofmann, Albrecht W.

1992-12-01

Phanerozoic alkali basalts from Israel, which have erupted over the past 200 Ma, have isotopic compositions similar to PREMA ("prevalent mantle") with narrow ranges of initial ɛ Nd(T) = +3.9-+5.9; 87Sr/ 86Sr(T)= 0.70292-0.70334; 206Pb/ 204Pb(T)= 18.88-19.99; 207Pb/ 204Pb(T)= 15.58-15.70; and 208Pb/ 204Pb(T)= 38.42-39.57. Their Nb/U(43 ± 9) and Ce/Pb(26 ± 6) ratios are identical to those of normal oceanic basalts, demonstrating that the basalts are essentially free of crustal contamination. Overall, the basalts are chemically and isotopically indistinguishable from many ordinary plume basalts, but no plume track can be identified. We propose that these and other, similar, magmas from the Arabian plate originated from a "fossilized" head of a mantle plume, which was unable to penetrate the continental lithosphere and was therefore trapped and stored beneath it. The plume head was emplaced some time between the late Proterozoic crust formation and the initiation of the Phanerozoic magmatic cycles. Basalts from rift environments in other continental localities show similar geochemistry to that of the Arabian basalts and their sources may also represent fossil plume heads trapped below the continents. We suggest that plume heads are, in general, characterized by the PREMA isotopic mantle signature, because the original plume sources (which may have HIMU or EM-type composition) have been diluted by overlying mantle material, which has been entrained by the plume heads during ascent. On the Arabian plate, rifting and thinning of the lithosphere caused partial melting of the stored plume, which led to periodic volcanism. In the late Cenozoic, the lithosphere broke up and the Red Sea opened. N-MORB tholeiites are now erupting in the central trough of the Red Sea, where the lithosphere has moved apart and the fossil plume has been exhausted, whereas E-MORBs are erupting in the northern and southern troughs, still tapping the plume reservoir. Fossil plumes, which are

An experimental facility for microwave induced plasma processing of materials

International Nuclear Information System (INIS)

Patil, D.S.; Ramachandran, K.; Bhide, A.L.; Venkatramani, N.

1997-01-01

Microwave induced plasma processing offers many advantages over conventional processes. However this technology is in the development stage. This report gives a detailed information about a microwave plasma processing facility (2.45 GHz, 700 W) set up in the Laser and Plasma Technology Division. The equipment details and the results obtained on deposition of diamond like carbon (DLC) thin films and surface modification of polymer PET (polyethylene terephthalate) using this facility are given in this report. (author)

Buoyant plume calculations

International Nuclear Information System (INIS)

Penner, J.E.; Haselman, L.C.; Edwards, L.L.

1985-01-01

Smoke from raging fires produced in the aftermath of a major nuclear exchange has been predicted to cause large decreases in surface temperatures. However, the extent of the decrease and even the sign of the temperature change, depend on how the smoke is distributed with altitude. We present a model capable of evaluating the initial distribution of lofted smoke above a massive fire. Calculations are shown for a two-dimensional slab version of the model and a full three-dimensional version. The model has been evaluated by simulating smoke heights for the Hamburg firestorm of 1943 and a smaller scale oil fire which occurred in Long Beach in 1958. Our plume heights for these fires are compared to those predicted by the classical Morton-Taylor-Turner theory for weakly buoyant plumes. We consider the effect of the added buoyancy caused by condensation of water-laden ground level air being carried to high altitude with the convection column as well as the effects of background wind on the calculated smoke plume heights for several fire intensities. We find that the rise height of the plume depends on the assumed background atmospheric conditions as well as the fire intensity. Little smoke is injected into the stratosphere unless the fire is unusually intense, or atmospheric conditions are more unstable than we have assumed. For intense fires significant amounts of water vapor are condensed raising the possibility of early scavenging of smoke particles by precipitation. 26 references, 11 figures

PLUME and research sotware

Science.gov (United States)

Baudin, Veronique; Gomez-Diaz, Teresa

2013-04-01

The PLUME open platform (https://www.projet-plume.org) has as first goal to share competences and to value the knowledge of software experts within the French higher education and research communities. The project proposes in its platform the access to more than 380 index cards describing useful and economic software for this community, with open access to everybody. The second goal of PLUME focuses on to improve the visibility of software produced by research laboratories within the higher education and research communities. The "development-ESR" index cards briefly describe the main features of the software, including references to research publications associated to it. The platform counts more than 300 cards describing research software, where 89 cards have an English version. In this talk we describe the theme classification and the taxonomy of the index cards and the evolution with new themes added to the project. We will also focus on the organisation of PLUME as an open project and its interests in the promotion of free/open source software from and for research, contributing to the creation of a community of shared knowledge.

Broadening and attenuation of UV laser ablation plumes in background gases

DEFF Research Database (Denmark)

Amoruso, S.; Toftmann, B.; Schou, Jørgen

2005-01-01

The expansion of a laser-induced silver plume in a background gas has been studied in a variety of gases ranging from helium, oxygen and argon to xenon. We have measured the angular distribution of the total deposit of silver on an array of quartz crystal microbalances as well as the time...

Laser-induced incandescence applied to dusty plasmas

NARCIS (Netherlands)

van de Wetering, F.M.J.H.; Oosterbeek, W.; Beckers, J.; Nijdam, S.; Kovacevic, E.; Berndt, J.

2016-01-01

This paper reports on the laser heating of nanoparticles (diameters ≤1 μm) confined in a reactive plasma by short (150 ps) and intense (~63 mJ) UV (355 nm) laser pulses (laser-induced incandescence, LII). Important parameters such as the particle temperature and radius follow from analysis of the

Characterization of redox conditions in pollution plumes

DEFF Research Database (Denmark)

Christensen, Thomas Højlund; Bjerg, Poul Løgstrup; Banwart, Steven A.

2000-01-01

Evalution of redox conditions in groundwater pollution plumes is often a prerequisite for understanding the behviour of the pollutants in the plume and for selecting remediation approaches. Measuring of redox conditions in pollution plumes is, however, a fairly recent issue and yet relative few...

Turbulent structure of concentration plumes through application of video imaging

Energy Technology Data Exchange (ETDEWEB)

Dabberdt, W.F.; Martin, C. [National Center for Atmospheric Research, Boulder, CO (United States); Hoydysh, W.G.; Holynskyj, O. [Environmental Science & Services Corp., Long Island City, NY (United States)

1994-12-31

Turbulent flows and dispersion in the presence of building wakes and terrain-induced local circulations are particularly difficult to simulate with numerical models or measure with conventional fluid modeling and ambient measurement techniques. The problem stems from the complexity of the kinematics and the difficulty in making representative concentration measurements. New laboratory video imaging techniques are able to overcome many of these limitations and are being applied to study a range of difficult problems. Here the authors apply {open_quotes}tomographic{close_quotes} video imaging techniques to the study of the turbulent structure of an ideal elevated plume and the relationship of short-period peak concentrations to long-period average values. A companion paper extends application of the technique to characterization of turbulent plume-concentration fields in the wake of a complex building configuration.

Railgun pellet injection system using a laser-induced plasma armature

Energy Technology Data Exchange (ETDEWEB)

Onozuka, M.; Oda, Y.; Azuma, K. [Mitsubishi Heavy Industries Ltd., Yokohama (Japan). Advanced Technology Development Dept.; Kasai, S.; Hasegawa, K. [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan)

1996-06-01

An electromagnetic railgun pellet injection system that utilizes a laser-induced plasma armature formation has been developed for fusion experimental devices. Using the laser-induced plasma formation technique, the required breakdown voltage was reduced by one-tenth compared with that for the spark-discharged plasma. A small amount of hydrogen gas increased the breakdown voltage of helium gas. This effect is considered to be one of the reasons for lowering the energy conversion coefficient for hydrogen pellet acceleration. To compensate for the low pellet acceleration efficiency, a railgun with ceramic insulators and an augmented rail structure has been tested. The energy conversion coefficient using the augmented railgun was further increased from that using a single-rail structure with the plastic insulators. The average acceleration rate was almost doubled. The highest hydrogen pellet velocity was about 2.3 km s{sup -1}. (Author).

Railgun pellet injection system using a laser-induced plasma armature

International Nuclear Information System (INIS)

Onozuka, M.; Oda, Y.; Azuma, K.

1996-01-01

An electromagnetic railgun pellet injection system that utilizes a laser-induced plasma armature formation has been developed for fusion experimental devices. Using the laser-induced plasma formation technique, the required breakdown voltage was reduced by one-tenth compared with that for the spark-discharged plasma. A small amount of hydrogen gas increased the breakdown voltage of helium gas. This effect is considered to be one of the reasons for lowering the energy conversion coefficient for hydrogen pellet acceleration. To compensate for the low pellet acceleration efficiency, a railgun with ceramic insulators and an augmented rail structure has been tested. The energy conversion coefficient using the augmented railgun was further increased from that using a single-rail structure with the plastic insulators. The average acceleration rate was almost doubled. The highest hydrogen pellet velocity was about 2.3 km s -1 . (Author)

Io Pele plume

Science.gov (United States)

2000-01-01

Voyager 1 took this narrow-angle camera image on 5 March 1979 from a distance of 450,000 kilometers. At this geometry, the camera looks straight down through a volcanic plume at one of Io's most active volcanos, Pele. The large heart-shaped feature is the region where Pele's plume falls to the surface. At the center of the 'heart' is the small dark fissure that is the source of the eruption. The Voyager Project is managed by the Jet Propulsion Laboratory for NASA's Office of Space Science.

Io's Active Eruption Plumes: Insights from HST

Science.gov (United States)

Jessup, K. L.; Spencer, J. R.

2011-10-01

Taking advantage of the available data, we recently [10] completed a detailed analysis of the spectral signature of Io's Pele-type Tvashtar plume as imaged by the HST Wide Field and Planetary Camera 2 (HST/WFPC2) via absorption during Jupiter transit and via reflected sunlight in 2007, as well as HST/WFPC2 observations of the 1997 eruption of Io's Prometheus-type Pillan plume (Fig. 1). These observations were obtained in the 0.24-0.42 μm range, where the plumes gas absorption and aerosol scattering properties are most conspicuous. By completing a detailed analysis of these observations, several key aspects of the reflectance and the absorption properties of the two plumes have been revealed. Additionally, by considering the analysis of the HST imaging data in light of previously published spectral analysis of Io's Prometheus and Pele-type plumes several trends in the plume properties have been determined, allowing us to define the relative significance of each plume on the rate of re-surfacing occurring on Io and providing the measurements needed to better assess the role the volcanoes play in the stability of Io's tenuous atmosphere.

Small rocket exhaust plume data

Science.gov (United States)

Chirivella, J. E.; Moynihan, P. I.; Simon, W.

1972-01-01

During recent cryodeposit tests with an 0.18-N thruster, the mass flux in the plume back field was measured for the first time for nitrogen, carbon dioxide, and a mixture of nitrogen, hydrogen, and ammonia at various inlet pressures. This mixture simulated gases that would be generated by a hydrazine plenum attitude propulsion system. The measurements furnish a base upon which to build a mathematical model of plume back flow that will be used in predicting the mass distribution in the boundary region of other plumes. The results are analyzed and compared with existing analytical predictions.

Time-resolved diagnostics of excimer laser-generated ablation plasmas used for pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Geohegan, D.B.

1994-09-01

Characteristics of laser plasmas used for pulsed laser deposition (PLD) of thin films are examined with four in situ diagnostic techniques: Optical emission spectroscopy, optical absorption spectroscopy, ion probe studies, and gated ICCD (intensified charge-coupled-device array) fast photography. These four techniques are complementary and permit simultaneous views of the transport of ions, excited states, ground state neutrals and ions, and hot particulates following KrF laser ablation of YBCO, BN, graphite and Si in vacuum and background gases. The implementation and advantages of the four techniques are first described in order to introduce the key features of laser plasmas for pulsed laser deposition. Aspects of the interaction of the ablation plume with background gases (i.e., thermalization, attenuation, shock formation) and the collision of the plasma plume with the substrate heater are then summarized. The techniques of fast ICCD photography and gated photon counting are then applied to investigate the temperature, velocity, and spatial distribution of hot particles generated during KrF ablation of YBCO, BN, Si and graphite. Finally, key features of fast imaging of the laser ablation of graphite into high pressure rare gases are presented in order to elucidate internal reflected shocks within the plume, redeposition of material on a surface, and formation of hot nanoparticles within the plume.

Time-resolved diagnostics of excimer laser-generated ablation plasmas used for pulsed laser deposition

International Nuclear Information System (INIS)

Geohegan, D.B.

1994-01-01

Characteristics of laser plasmas used for pulsed laser deposition (PLD) of thin films are examined with four in situ diagnostic techniques: Optical emission spectroscopy, optical absorption spectroscopy, ion probe studies, and gated ICCD (intensified charge-coupled-device array) fast photography. These four techniques are complementary and permit simultaneous views of the transport of ions, excited states, ground state neutrals and ions, and hot particulates following KrF laser ablation of YBCO, BN, graphite and Si in vacuum and background gases. The implementation and advantages of the four techniques are first described in order to introduce the key features of laser plasmas for pulsed laser deposition. Aspects of the interaction of the ablation plume with background gases (i.e., thermalization, attenuation, shock formation) and the collision of the plasma plume with the substrate heater are then summarized. The techniques of fast ICCD photography and gated photon counting are then applied to investigate the temperature, velocity, and spatial distribution of hot particles generated during KrF ablation of YBCO, BN, Si and graphite. Finally, key features of fast imaging of the laser ablation of graphite into high pressure rare gases are presented in order to elucidate internal reflected shocks within the plume, redeposition of material on a surface, and formation of hot nanoparticles within the plume

Numerical studies of pulsating buoyant plume in isothermal and non isothermal situations

International Nuclear Information System (INIS)

Sharma, Pavan K.; Singh, R.K.; Mohanty, Ananya; Das, D.

2014-01-01

A computational study has been carried out for predicting the behaviour of buoyant plume in isothermal and non isothermal configuration. General simulation objectives of any buoyant flow simulation are macroscopic in nature and deals with the grass data in respect of buoyancy induced scalar transport. However, the accuracy of predicting such macroscopic parameters is a strong function of several other microscopic parameters which govern the overall macroscopic behaviour. Some of the microscopic parameters for analysis could be buoyancy induced stable/unstable flows, relative plume behaviour, baroclinic velocity distribution etc. Only the CFD based flow modelling approach is capable of calculating several of these aspects. LES based modelling scores over the conventional RANS based computational modelling. The primary objective of the present study was to model buoyant plume simulation of different types in order to explore the details regarding plume and flow structure, instabilities and puffing behaviour. One of the influencing parameters on the overall plume behaviour is the buoyancy resolution index i.e. fineness of chosen grid in relation to the buoyancy intensity and other hydrodynamic parameters. The grid sensitivity studies have been carried out to find out the optimum value grid size by way of buoyant pool fire simulations. Comparative simulation has also been made for a square and round pool fire and it was found that for engineering simulations equivalent area square pool modeling is sufficient. Using the optimum value of grid size and square pool shape simulations have been carried out for different value of fire intensity. The flame puffing frequency as calculated by the reported correlation was compared against the computationally observed puffing frequency and the agreement was generally found to be excellent. Besides these results the comparisons of predicted peak flames temperatures data for various case studies with the available experimental data

3-D spectral Induced Polarization (IP) imaging: Non-invasive characterization of contaminant plumes. Annual progress report, September 15, 1996 - September 14, 1997

International Nuclear Information System (INIS)

Frye, K.M.; Lesmes, D.P.; Morgan, F.D.; Rodi, W.; Shi, W.; Sturrock, J.

1997-01-01

'The objective of this project is to develop the scientific basis for characterizing contaminant plumes in the earth''s subsurface using field measurements of induced polarization (IP) effects. The first-year accomplishments are (1) laboratory experiments on fluid-saturated sandstones quantifying the dependence of spectral IP responses on solution chemistry and rock micro-geometry; (2) library research on the current understanding of electromagnetic coupling effects on IP data acquired in the field: and (3) development of prototype forward modeling and inversion algorithms for interpreting IP data in terms of 3-D models of complex resistivity.'

Thermal Plumes in Ventilated Rooms

DEFF Research Database (Denmark)

Kofoed, Peter; Nielsen, Peter V.

The design of a displacement ventilation system involves determination of the flow rate in the thermal plumes. The flow rate in the plumes and the vertical temperature gradient influence each other, and they are influenced by many factors. This paper shows some descriptions of these effects....

UV/IR Filaments for High Resolution Novel Spectroscopic Interrogation of Plumes on Nuclear Materials

Science.gov (United States)

2016-06-01

Raman spectroscopy of plumes created by a laser filament. The molecules to be detected are excited by the short pulse IR pulse, while the co-propagating... spectroscopy of gas samples has been demonstrated in IR filaments [32], using the fs pulse of the filament (800 nm) to vibrationally excite the components...Petit. Isotope ratio determination of uranium by optical emission spectroscopy on a laser -produced plasma; basic investigation and analytical results

Spectroscopic analysis of Zirconium plasma in different ambient and optimizing conditions for nanoclusters formation

International Nuclear Information System (INIS)

Yadav, Dheerendra; Thareja, Raj K.

2010-01-01

The laser produced zirconium plasma has been studied by emission spectroscopy and fast photography using intensified charged coupled device at different ambient pressures of nitrogen (0.1, 1.0 and 10 mbar). Formation of zirconium clusters are arising at ambient pressure of 1.0 mbar at the plume periphery due to the chemical reactions between the plasma plume and the ambient and confirmed using optical emission spectroscopy. The optimum parameters for existence cluster formation are reported. The ZrN clusters are deposited on silicon substrate and characterized by AFM, XRD and EDAX techniques. (author)

Effect of the atmospheric pressure nonequilibrium plasmas on the conformational changes of plasmid DNA

International Nuclear Information System (INIS)

Yan Xu; He Guangyuan; Shi Mengjun; Gao Xuan; Li Yin; Ma Fengyun; Yu Men; Wang Changdong; Wang Yuesheng; Yang Guangxiao; Zou Fei; Lu Xinpei; Xiong Qing; Xiong Zilan

2009-01-01

The cold atmospheric pressure plasma, which has been widely used for biomedical applications, may potentially affect the conformation of DNA. In this letter, an atmospheric pressure plasma plume is used to investigate its effects on the conformational changes of DNA of plasmid pAHC25. It is found that the plasma plume could cause plasmid DNA topology alteration, resulting in the percentage of the supercoiled plasmid DNA form decreased while that of the open circular and linearized form of plasmid DNA increased as detected by agrose gel electrophoresis. On the other hand, further investigation by using polymerase chain reaction method shows that the atmospheric pressure plasma jet treatments under proper conditions does not affect the genes of the plasmid DNA, which may have potential application in increasing the transformation frequency by genetic engineering.

A special cell morphology of saccharomyces cerevisiae induced by low-temperature plasma

International Nuclear Information System (INIS)

Ling Dajun; Cao Jinxiang

2003-01-01

A special cell morphology, cavity-like cells, was found in posterities of Saccharomyces cerevisiae treated by low-temperature air plasma with different powers. The feature of the special morphology indicates that the cavity-like cells may be formed by cellular mutation effect induced by the plasma, instead of direct cellular damage by the plasma. The results suggest that the cellular mutation effect of the low-temperature plasma is a complex process

Frequency domain and wavelet analysis of the laser-induced plasma shock waves

Energy Technology Data Exchange (ETDEWEB)

Burger, Miloš, E-mail: milosb@ff.bg.ac.rs; Nikolić, Zoran

2015-08-01

In addition to optical emission, another trace of interest that laser-induced plasma provides is a form of acoustic feedback. The acoustic emission (AE) signals were obtained using both microphone and piezo transducers. This kind of optoacoustic signals have some distinct features resembling the short, burst-like sounds, that may differ significantly depending mainly on the sample exposed and irradiance applied. Experiments were performed on atmospheric pressure by irradiating various metallic samples. The recorded waveforms were examined and numerically processed. Single-shot acoustical spectra have shown significant potential of providing valuable supplementary information regarding plasma propagation dynamics. Moreover, the general approach suggests the possibility of making the whole measurement system cost-effective and portable. - Highlights: • We report acoustical waveform, and acoustical spectroscopy measurements and analysis in a laser-induced plasma of a different metals in air. • Both piezo and microphone transducer were used. • The acoustical spectra of the emission were obtained when the sample (and plasma) were enclosed in experimental chamber. • The acquired acoustical spectra are time-integrated and the frequency peaks were sharp and relatively isolated. • Finally, both time and frequency resolved wavelet spectrogram present a novel method of observing laser-induced plasma behavior.

Rise of a cold plume

International Nuclear Information System (INIS)

Kakuta, Michio

1977-06-01

The rise of smoke from the stacks of two research reactors in normal operation was measured by photogrametric method. The temperature of effluent gas is less than 20 0 C higher than that of the ambient air (heat emission of the order 10 4 cal s -1 ), and the efflux velocity divided by the wind speed is between 0.5 and 2.8 in all 16 smoke runs. The field data obtained within downwind distance of 150m are compared with those by plume rise formulas presently available. Considering the shape of bending-over plume, the Briggs' formula for 'jet' gives a reasonable explanation of the observed plume rise. (auth.)

PLUME-MoM 1.0: a new 1-D model of volcanic plumes based on the method of moments

Science.gov (United States)

de'Michieli Vitturi, M.; Neri, A.; Barsotti, S.

2015-05-01

In this paper a new mathematical model for volcanic plumes, named PlumeMoM, is presented. The model describes the steady-state 1-D dynamics of the plume in a 3-D coordinate system, accounting for continuous variability in particle distribution of the pyroclastic mixture ejected at the vent. Volcanic plumes are composed of pyroclastic particles of many different sizes ranging from a few microns up to several centimeters and more. Proper description of such a multiparticle nature is crucial when quantifying changes in grain-size distribution along the plume and, therefore, for better characterization of source conditions of ash dispersal models. The new model is based on the method of moments, which allows description of the pyroclastic mixture dynamics not only in the spatial domain but also in the space of properties of the continuous size-distribution of the particles. This is achieved by formulation of fundamental transport equations for the multiparticle mixture with respect to the different moments of the grain-size distribution. Different formulations, in terms of the distribution of the particle number, as well as of the mass distribution expressed in terms of the Krumbein log scale, are also derived. Comparison between the new moments-based formulation and the classical approach, based on the discretization of the mixture in N discrete phases, shows that the new model allows the same results to be obtained with a significantly lower computational cost (particularly when a large number of discrete phases is adopted). Application of the new model, coupled with uncertainty quantification and global sensitivity analyses, enables investigation of the response of four key output variables (mean and standard deviation (SD) of the grain-size distribution at the top of the plume, plume height and amount of mass lost by the plume during the ascent) to changes in the main input parameters (mean and SD) characterizing the pyroclastic mixture at the base of the plume

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

Science.gov (United States)

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

Study on the effects of ion motion on laser-induced plasma wakes

International Nuclear Information System (INIS)

Zhou Suyun; Yu Wei; Yuan Xiao; Xu Han; Cao, L. H.; Cai, H. B.; Zhou, C. T.

2012-01-01

A 2D analytical model is presented for the generation of plasma wakes (or bubbles) with an ultra-intense laser pulse by taking into account the response of plasma ions. It is shown that the effect of ion motion becomes significant at the laser intensity exceeding 10 21 W/cm 2 and plasma background density below 10 19 cm −3 . In this regime, ion motion tends to suppress the electrostatic field induced by charge separation and makes the electron acceleration less effective. As a result, the assumption of immobile ions overestimates the efficiency of laser wake-field acceleration of electrons. Based on the analytical model, the dynamics of plasma ions in laser-induced wake field is investigated. It is found that only one bubble appears as the plasmas background density exceeds the resonant density and the deposited laser energy is concentrated into the bubble, resulting in the generation of an ion bunch with extremely high energy density.

Extreme ultraviolet emission and confinement of tin plasmas in the presence of a magnetic field

Energy Technology Data Exchange (ETDEWEB)

Roy, Amitava, E-mail: roy@fzu.cz, E-mail: aroy@barc.gov.in [School of Nuclear Engineering and Center for Materials Under Extreme Environment(CMUXE), Purdue University, West Lafayette, Indiana 47907 (United States); HiLASE Project, Department of Diode-pumped Lasers, Institute of Physics of the ASCR, Na Slovance 2, 18221 Prague (Czech Republic); Murtaza Hassan, Syed; Harilal, Sivanandan S.; Hassanein, Ahmed [School of Nuclear Engineering and Center for Materials Under Extreme Environment(CMUXE), Purdue University, West Lafayette, Indiana 47907 (United States); Endo, Akira; Mocek, Tomas [HiLASE Project, Department of Diode-pumped Lasers, Institute of Physics of the ASCR, Na Slovance 2, 18221 Prague (Czech Republic)

2014-05-15

We investigated the role of a guiding magnetic field on extreme ultraviolet (EUV) and ion emission from a laser produced Sn plasma for various laser pulse duration and intensity. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm, Nd:YAG laser pulses with varying pulse duration (5–15 ns) and intensity. A magnetic trap was fabricated with the use of two neodymium permanent magnets which provided a magnetic field strength ∼0.5 T along the plume expansion direction. Our results indicate that the EUV conversion efficiency do not depend significantly on applied axial magnetic field. Faraday Cup ion analysis of Sn plasma show that the ion flux reduces by a factor of ∼5 with the application of an axial magnetic field. It was found that the plasma plume expand in the lateral direction with peak velocity measured to be ∼1.2 cm/μs and reduced to ∼0.75 cm/μs with the application of an axial magnetic field. The plume expansion features recorded using fast photography in the presence and absence of 0.5 T axial magnetic field are simulated using particle-in-cell code. Our simulation results qualitatively predict the plasma behavior.

Remote triggering of high voltage systems by laser-induced plasmas

CSIR Research Space (South Africa)

West, NJ

2008-08-01

Full Text Available -induced plasma was found to play a significant role in the breakdown process – best results being obtained when the laser was focused in the centre of the gap. Finally, the shape of the laser-induced arc is dependant on the applied electric field. When the field...

Laser Induced Fluorescence Diagnostic for the Plasma Couette Experiment

Science.gov (United States)

Katz, Noam; Skiff, Fred; Collins, Cami; Weisberg, Dave; Wallace, John; Clark, Mike; Garot, Kristine; Forest, Cary

2010-11-01

The Plasma Couette Experiment (PCX) at U. Wisconsin-Madison consists of a rotating high-beta plasma and is well-suited to the study of flow-driven, astrophysically-relevant plasma phenomena. PCX confinement relies on alternating rings of 1kG permanent magnets and the rotation is driven by electrode rings, interspersed between the magnets, which provide an azimuthal ExB. I will discuss the development of a laser-induced fluorescence diagnostic (LIF) to characterize the ion distribution function of argon plasmas in PCX. The LIF system--which will be scanned radially--will be used to calibrate internal Mach probes, as well as to measure the time-resolved velocity profile, ion temperature and density non-perturbatively. These diagnostics will be applied to study the magneto-rotational instability in a plasma, as well as the buoyancy instability thought to be involved in producing the solar magnetic field. This work is supported by NSF and DOE.

Dynamics of the spatial electron density distribution of EUV-induced plasmas

Science.gov (United States)

van der Horst, R. M.; Beckers, J.; Osorio, E. A.; Banine, V. Y.

2015-11-01

We studied the temporal evolution of the electron density distribution in a low pressure pulsed plasma induced by high energy extreme ultraviolet (EUV) photons using microwave cavity resonance spectroscopy (MCRS). In principle, MCRS only provides space averaged information about the electron density. However, we demonstrate here the possibility to obtain spatial information by combining multiple resonant modes. It is shown that EUV-induced plasmas, albeit being a rather exotic plasma, can be explained by known plasma physical laws and processes. Two stages of plasma behaviour are observed: first the electron density distribution contracts, after which it expands. It is shown that the contraction is due to cooling of the electrons. The moment when the density distribution starts to expand is related to the inertia of the ions. After tens of microseconds, the electrons reached the wall of the cavity. The speed of this expansion is dependent on the gas pressure and can be divided into two regimes. It is shown that the acoustic dominated regime the expansion speed is independent of the gas pressure and that in the diffusion dominated regime the expansion depends reciprocal on the gas pressure.

Dynamics of the spatial electron density distribution of EUV-induced plasmas

International Nuclear Information System (INIS)

Van der Horst, R M; Beckers, J; Banine, V Y; Osorio, E A

2015-01-01

We studied the temporal evolution of the electron density distribution in a low pressure pulsed plasma induced by high energy extreme ultraviolet (EUV) photons using microwave cavity resonance spectroscopy (MCRS). In principle, MCRS only provides space averaged information about the electron density. However, we demonstrate here the possibility to obtain spatial information by combining multiple resonant modes. It is shown that EUV-induced plasmas, albeit being a rather exotic plasma, can be explained by known plasma physical laws and processes. Two stages of plasma behaviour are observed: first the electron density distribution contracts, after which it expands. It is shown that the contraction is due to cooling of the electrons. The moment when the density distribution starts to expand is related to the inertia of the ions. After tens of microseconds, the electrons reached the wall of the cavity. The speed of this expansion is dependent on the gas pressure and can be divided into two regimes. It is shown that the acoustic dominated regime the expansion speed is independent of the gas pressure and that in the diffusion dominated regime the expansion depends reciprocal on the gas pressure. (fast track communication)

A numerical study of the Magellan Plume

Science.gov (United States)

Palma, Elbio D.; Matano, Ricardo P.

2012-05-01

In this modeling study we investigate the dynamical mechanisms controlling the spreading of the Magellan Plume, which is a low-salinity tongue that extends along the Patagonian Shelf. Our results indicate that the overall characteristics of the plume (width, depth, spreading rate, etc.) are primarily influenced by tidal forcing, which manifests through tidal mixing and tidal residual currents. Tidal forcing produces a homogenization of the plume's waters and an offshore displacement of its salinity front. The interaction between tidal and wind-forcing reinforces the downstream and upstream buoyancy transports of the plume. The influence of the Malvinas Current on the Magellan Plume is more dominant north of 50°S, where it increases the along-shelf velocities and generates intrusions of saltier waters from the outer shelf, thus causing a reduction of the downstream buoyancy transport. Our experiments also indicate that the northern limit of the Magellan Plume is set by a high salinity discharge from the San Matias Gulf. Sensitivity experiments show that increments of the wind stress cause a decrease of the downstream buoyancy transport and an increase of the upstream buoyancy transport. Variations of the magnitude of the discharge produce substantial modifications in the downstream penetration of the plume and buoyancy transport. The Magellan discharge generates a northeastward current in the middle shelf, a recirculation gyre south of the inlet and a region of weak currents father north.

Ocean outfall plume characterization using an Autonomous Underwater Vehicle.

Science.gov (United States)

Rogowski, Peter; Terrill, Eric; Otero, Mark; Hazard, Lisa; Middleton, William

2013-01-01

A monitoring mission to map and characterize the Point Loma Ocean Outfall (PLOO) wastewater plume using an Autonomous Underwater Vehicle (AUV) was performed on 3 March 2011. The mobility of an AUV provides a significant advantage in surveying discharge plumes over traditional cast-based methods, and when combined with optical and oceanographic sensors, provides a capability for both detecting plumes and assessing their mixing in the near and far-fields. Unique to this study is the measurement of Colored Dissolved Organic Matter (CDOM) in the discharge plume and its application for quantitative estimates of the plume's dilution. AUV mission planning methodologies for discharge plume sampling, plume characterization using onboard optical sensors, and comparison of observational data to model results are presented. The results suggest that even under variable oceanic conditions, properly planned missions for AUVs equipped with an optical CDOM sensor in addition to traditional oceanographic sensors, can accurately characterize and track ocean outfall plumes at higher resolutions than cast-based techniques.

Electromagnetically induced transparency in high-temperature magnetoactive plasma

International Nuclear Information System (INIS)

Kryachko, A.Yu.; Litvak, A.G.; Tokman, M.D.

2002-01-01

The classical analog of the presently popular in the quantum electronics effect of the electromagnetically induced transparency (EIT) is studied. The EIT effect is considered for the electron-cyclotron waves in the plasma with the finite temperature. The expression for the effective index of the electromagnetic wave refraction is identified and the dispersion law and this wave absorption under the EIT conditions are studied. It is shown, that accounting for the thermal motion, which radically changes the behavior of the signal wave dispersion curves in the EIT area, as compared with the cold plasma case [ru

Axial- and radial-resolved electron density and excitation temperature of aluminum plasma induced by nanosecond laser: Effect of the ambient gas composition and pressure

Directory of Open Access Journals (Sweden)

Mahmoud S. Dawood

2015-11-01

Full Text Available The spatial variation of the characteristics of an aluminum plasma induced by a pulsed nanosecond XeCl laser is studied in this paper. The electron density and the excitation temperature are deduced from time- and space- resolved Stark broadening of an ion line and from a Boltzmann diagram, respectively. The influence of the gas pressure (from vacuum up to atmospheric pressure and compositions (argon, nitrogen and helium on these characteristics is investigated. It is observed that the highest electron density occurs near the laser spot and decreases by moving away both from the target surface and from the plume center to its edge. The electron density increases with the gas pressure, the highest values being occurred at atmospheric pressure when the ambient gas has the highest mass, i.e. in argon. The excitation temperature is determined from the Boltzmann plot of line intensities of iron impurities present in the aluminum target. The highest temperature is observed close to the laser spot location for argon at atmospheric pressure. It decreases by moving away from the target surface in the axial direction. However, no significant variation of temperature occurs along the radial direction. The differences observed between the axial and radial direction are mainly due to the different plasma kinetics in both directions.

The evolution of photochemical smog in a power plant plume

Science.gov (United States)

Luria, Menachem; Valente, Ralph J.; Tanner, Roger L.; Gillani, Noor V.; Imhoff, Robert E.; Mueller, Stephen F.; Olszyna, Kenneth J.; Meagher, James F. Present address: Aeronomy Laboratory, NOAA, 325 Broadway, Boulder CO 80303, USA.)

The evolution of photochemical smog in a plant plume was investigated with the aid of an instrumented helicopter. Air samples were taken in the plume of the Cumberland Power Plant, located in central Tennessee, during the afternoon of 16 July 1995 as part of the Southern Oxidants Study - Nashville Middle Tennessee Ozone Study. Twelve cross-wind air sampling traverses were made at six distance groups from 35 to 116 km from the source. During the sampling period the winds were from the west-northwest and the plume drifted towards the city of Nashville TN. Ten of the traverses were made upwind of the city, where the power plant plume was isolated, and two traverses downwind of the city when the plumes were possibly mixed. The results revealed that even six hours after the release, excess ozone production was limited to the edges of the plume. Only when the plume was sufficiently dispersed, but still upwind of Nashville, was excess ozone (up to 109 ppbv, 50-60 ppbv above background levels) produced in the center of the plume. The concentrations image of the plume and a Lagrangian particle model suggests that portions of the power plant plume mixed with the urban plume. The mixed urban power plant plume began to regenerate O 3 that peaked at 120 ppbv at a short distance (15-25 km) downwind of Nashville. Ozone productivity (the ratio of excess O 3 to NO y and NO z) in the isolated plume was significantly lower compared with that found in the city plume. The production of nitrate, a chain termination product, was significantly higher in the power plant plume compared to the mixed plume, indicating shorter chain length of the photochemical smog chain reaction mechanism.

The evolution of photochemical smog in a power plant plume

International Nuclear Information System (INIS)

Luria, M.; The Hebrew University, Jerusalem; Valente, R.J.; Tanner, R.L.; Imhoff, R.E.; Mueller, S.F.; Olszyna, K.J.; Meagher, J.F.; Gillani, N.V.; University of Alabama, Huntsville, AL

1999-01-01

The evolution of photochemical smog in a plant plume was investigated with the aid of an instrumented helicopter. Air samples were taken in the plume of the Cumberland Power Plant, located in central Tennessee, during the afternoon of 16 July 1995 as part of the Southern Oxidants Study - Nashville Middle Tennessee Ozone Study. Twelve cross-wind air sampling traverses were made at six distance groups from 35 to 116 km from the source. During the sampling period the winds were from the west-northwest and the plume drifted towards the city of Nashville TN. Ten of the traverses were made upwind of the city, where the power plant plume was isolated, and two traverses downwind of the city when the plumes were possibly mixed. The results revealed that even six hours after the release, excess ozone production was limited to the edges of the plume. Only when the plume was sufficiently dispersed, but still upwind of Nashville, was excess ozone (up to 109 ppbv, 50-60 ppbv above background levels) produced in the center of the plume. The concentrations image of the plume and a Lagrangian particle model suggests that portions of the power plant plume mixed with the urban plume. The mixed urban power plant plume began to regenerate O 3 that peaked at 120 ppbv at a short distance (15-25 km) downwind of Nashville. Ozone productivity (the ratio of excess O 3 to NO y and NO z ) in the isolated plume was significantly lower compared with that found in the city plume. The production of nitrate, a chain termination product, was significantly higher in the power plant plume compared to the mixed plume, indicating shorter chain length of the photochemical smog chain reaction mechanism. (author)

Analysis of relaxing laser-induced plasmas by absorption spectroscopy: Toward a new quantitative diagnostic technique

International Nuclear Information System (INIS)

Ribiere, M.; Cheron, B.G.

2010-01-01

Broad-band near UV absorption spectroscopy was used to analyze atmospheric laser-induced plasmas formed on metallic and refractory targets. When the common emission spectroscopy only provides the density of the radiating atomic excited states, the technique reported in this paper is able to achieve high spatial resolution in the measurement of absolute number densities in expanding laser-induced plasmas. The reliability and the versatility of this technique, which is based on the comparison between results of the numerical integration of the radiative transfer equation and experimental spectra, were tested on different targets. The evolutions in time and space of the absolute population of the plasma species originating from metallic alloys (Al-Mg and Cu-Ni) and refractory materials (C/SiC) were achieved over large time scales. Owing to its accuracy, this absorption technique (that we call 'LIPAS' for Laser Induced Plasma Absorption Spectroscopy) should bring a new and enhanced support to the validation of collisional-radiative models attempting to provide reliable evolutions of laser-induced plasmas.

Plume structure in high-Rayleigh-number convection

Science.gov (United States)

Puthenveettil, Baburaj A.; Arakeri, Jaywant H.

2005-10-01

Near-wall structures in turbulent natural convection at Rayleigh numbers of 10^{10} to 10^{11} at A Schmidt number of 602 are visualized by a new method of driving the convection across a fine membrane using concentration differences of sodium chloride. The visualizations show the near-wall flow to consist of sheet plumes. A wide variety of large-scale flow cells, scaling with the cross-section dimension, are observed. Multiple large-scale flow cells are seen at aspect ratio (AR)= 0.65, while only a single circulation cell is detected at AR= 0.435. The cells (or the mean wind) are driven by plumes coming together to form columns of rising lighter fluid. The wind in turn aligns the sheet plumes along the direction of shear. the mean wind direction is seen to change with time. The near-wall dynamics show plumes initiated at points, which elongate to form sheets and then merge. Increase in rayleigh number results in a larger number of closely and regularly spaced plumes. The plume spacings show a common log normal probability distribution function, independent of the rayleigh number and the aspect ratio. We propose that the near-wall structure is made of laminar natural-convection boundary layers, which become unstable to give rise to sheet plumes, and show that the predictions of a model constructed on this hypothesis match the experiments. Based on these findings, we conclude that in the presence of a mean wind, the local near-wall boundary layers associated with each sheet plume in high-rayleigh-number turbulent natural convection are likely to be laminar mixed convection type.

Evolution of sediment plumes in the Chesapeake bay and implications of climate variability.

Science.gov (United States)

Zheng, Guangming; DiGiacomo, Paul M; Kaushal, Sujay S; Yuen-Murphy, Marilyn A; Duan, Shuiwang

2015-06-02

Fluvial sediment transport impacts fisheries, marine ecosystems, and human health. In the upper Chesapeake Bay, river-induced sediment plumes are generally known as either a monotonic spatial shape or a turbidity maximum. Little is known about plume evolution in response to variation in streamflow and extreme discharge of sediment. Here we propose a typology of sediment plumes in the upper Chesapeake Bay using a 17 year time series of satellite-derived suspended sediment concentration. On the basis of estimated fluvial and wind contributions, we define an intermittent/wind-dominated type and a continuous type, the latter of which is further divided into four subtypes based on spatial features of plumes, which we refer to as Injection, Transport, Temporary Turbidity-Maximum, and Persistent Turbidity-Maximum. The four continuous types exhibit a consistent sequence of evolution within 1 week to 1 month following flood events. We also identify a "shift" in typology with increased frequency of Turbidity-Maximum types before and after Hurricane Ivan (2004), which implies that extreme events have longer-lasting effects upon estuarine suspended sediment than previously considered. These results can serve as a diagnostic tool to better predict distribution and impacts of estuarine suspended sediment in response to changes in climate and land use.

Simulating plasma production from hypervelocity impacts

Energy Technology Data Exchange (ETDEWEB)

Fletcher, Alex, E-mail: alexcf@stanford.edu; Close, Sigrid [Stanford University, Aeronautics and Astronautics, 496 Lomita Mall, Stanford, California 94305 (United States); Mathias, Donovan [NASA Ames Research Center, Bldg. 258, Moffett Field, California 94035 (United States)

2015-09-15

Hypervelocity particles, such as meteoroids and space debris, routinely impact spacecraft and are energetic enough to vaporize and ionize themselves and as well as a portion of the target material. The resulting plasma rapidly expands into the surrounding vacuum. While plasma measurements from hypervelocity impacts have been made using ground-based technologies such as light gas guns and Van de Graaff dust accelerators, some of the basic plasma properties vary significantly between experiments. There have been both ground-based and in-situ measurements of radio frequency (RF) emission from hypervelocity impacts, but the physical mechanism responsible and the possible connection to the impact-produced plasma are not well understood. Under certain conditions, the impact-produced plasma can have deleterious effects on spacecraft electronics by providing a new current path, triggering an electrostatic discharge, causing electromagnetic interference, or generating an electromagnetic pulse. Multi-physics simulations of plasma production from hypervelocity impacts are presented. These simulations incorporate elasticity and plasticity of the solid target, phase change and plasma formation, and non-ideal plasma physics due to the high density and low temperature of the plasma. A smoothed particle hydrodynamics method is used to perform a continuum dynamics simulation with these additional physics. By examining a series of hypervelocity impacts, basic properties of the impact produced plasma plume (density, temperature, expansion speed, charge state) are determined for impactor speeds between 10 and 72 km/s. For a large range of higher impact speeds (30–72 km/s), we find the temperature is unvarying at 2.5 eV. We also find that the plasma plume is weakly ionized for impact speeds less than 14 km/s and fully ionized for impact speeds greater than 20 km/s, independent of impactor mass. This is the same velocity threshold for the detection of RF emission in recent

Simulating Fine-Scale Marine Pollution Plumes for Autonomous Robotic Environmental Monitoring

Directory of Open Access Journals (Sweden)

Muhammad Fahad

2018-05-01

Full Text Available Marine plumes exhibit characteristics such as intermittency, sinuous structure, shape and flow field coherency, and a time varying concentration profile. Due to the lack of experimental quantification of these characteristics for marine plumes, existing work often assumes marine plumes exhibit behavior similar to aerial plumes and are commonly modeled by filament based Lagrangian models. Our previous field experiments with Rhodamine dye plumes at Makai Research Pier at Oahu, Hawaii revealed that marine plumes show similar characteristics to aerial plumes qualitatively, but quantitatively they are disparate. Based on the field data collected, this paper presents a calibrated Eulerian plume model that exhibits the qualitative and quantitative characteristics exhibited by experimentally generated marine plumes. We propose a modified model with an intermittent source, and implement it in a Robot Operating System (ROS based simulator. Concentration time series of stationary sampling points and dynamic sampling points across cross-sections and plume fronts are collected and analyzed for statistical parameters of the simulated plume. These parameters are then compared with statistical parameters from experimentally generated plumes. The comparison validates that the simulated plumes exhibit fine-scale qualitative and quantitative characteristics similar to experimental plumes. The ROS plume simulator facilitates future evaluations of environmental monitoring strategies by marine robots, and is made available for community use.

Amlodipine induced plasma cell granuloma of the gingiva: A novel case report.

Science.gov (United States)

Vishnudas, Bhandari; Sameer, Zope; Shriram, Bansode; Rekha, Kardile

2014-07-01

Drug-induced gingival overgrowth (DIGO) can be a serious concern for both patients and clinicians. DIGO is a well-documented side-effect of some pharmacologic agents, including, but not limited to, calcium channel blockers, phenytoin, and cyclosporine. Plasma cell granulomas (pseudotumors) are exceedingly rare, non-neoplastic, reactive tumor-like proliferation, primarily composed of plasma cells that manifest primarily in the lungs, but may occur in various anatomic locations. Intraoral plasma cell granulomas involving the lip, oral mucosa, tongue, and gingiva have been reported in the past. This is the first case report of amlodipine induced plasma cell granuloma of the gingiva in the medical literature presenting a 54 year-old female patient with hypertension, who received amlodipine (10 mg/day, single dose orally) for 2 years, sought medical attention because of developing maxillary anterior massive gingival overgrowth causing functional and esthetic problem, which was treated by excisional biopsy. Histologically, these lesions were composed of mature plasma cells, showing polyclonality for both lambda and kappa light chains and fibrovascular connective tissue stroma confirming a diagnosis of plasma cell granuloma. This case also highlights the need to biopsy for unusual lesions to rule out potential neoplasms.

Production and Characterization of Femtosecond-Laser-Induced Air Plasma

National Research Council Canada - National Science Library

Armbruster, David R

2008-01-01

.... A beam expander was used to expand the beam to a diameter of approximately 6.5 mm, and the beam was focused through a 25 mm focal length achromatic lens to produce laser-induced plasma in ambient air...

Analysis of dissolved benzene plumes and methyl tertiary butyl ether (MTBE) plumes in ground water at leaking underground fuel tank (LUFT) sites

International Nuclear Information System (INIS)

Happel, A.M.; Rice, D.; Beckenbach, E.; Savalin, L.; Temko, H.; Rempel, R.; Dooher, B.

1996-11-01

The 1990 Clean Air Act Amendments mandate the addition of oxygenates to gasoline products to abate air pollution. Currently, many areas of the country utilize oxygenated or reformulated fuel containing 15- percent and I I-percent MTBE by volume, respectively. This increased use of MTBE in gasoline products has resulted in accidental point source releases of MTBE containing gasoline products to ground water. Recent studies have shown MTBE to be frequently detected in samples of shallow ground water from urban areas throughout the United States (Squillace et al., 1995). Knowledge of the subsurface fate and transport of MTBE in ground water at leaking underground fuel tank (LUFT) sites and the spatial extent of MTBE plumes is needed to address these releases. The goal of this research is to utilize data from a large number of LUFT sites to gain insights into the fate, transport, and spatial extent of MTBE plumes. Specific goals include defining the spatial configuration of dissolved MTBE plumes, evaluating plume stability or degradation over time, evaluating the impact of point source releases of MTBE to ground water, and attempting to identify the controlling factors influencing the magnitude and extent of the MTBE plumes. We are examining the relationships between dissolved TPH, BTEX, and MTBE plumes at LUFT sites using parallel approaches of best professional judgment and a computer-aided plume model fitting procedure to determine plume parameters. Here we present our initial results comparing dissolved benzene and MTBE plumes lengths, the statistical significance of these results, and configuration of benzene and MTBE plumes at individual LUFT sites

Paducah Gaseous Diffusion Plant Northwest Plume interceptor system evaluation

International Nuclear Information System (INIS)

Laase, A.D.; Clausen, J.L.

1998-01-01

The Paducah Gaseous Diffusion Plant (PGDP) recently installed an interceptor system consisting of four wells, evenly divided between two well fields, to contain the Northwest Plume. As stated in the Northwest Plume Record of Decision (ROD), groundwater will be pumped at a rate to reduce further contamination and initiate control of the northwest contaminant plume. The objective of this evaluation was to determine the optimum (minimal) well field pumping rates required for plume hotspot containment. Plume hotspot, as defined in the Northwest Plume ROD and throughout this report, is that portion of the plume with trichloroethene (TCE) concentrations greater than 1,000 microg/L. An existing 3-dimensional groundwater model was modified and used to perform capture zone analyses of the north and south interceptor system well fields. Model results suggest that the plume hotspot is not contained at the system design pumping rate of 100 gallons per minute (gal/min) per well field. Rather, the modeling determined that north and south well field pumping rates of 400 and 150 gal/min, respectively, are necessary for plume hotspot containment. The difference between the design and optimal pumping rates required for containment can be attributed to the discovery of a highly transmissive zone in the vicinity of the two well fields

Follow the plume: the habitability of Enceladus.

Science.gov (United States)

McKay, Christopher P; Anbar, Ariel D; Porco, Carolyn; Tsou, Peter

2014-04-01

The astrobiological exploration of other worlds in our Solar System is moving from initial exploration to more focused astrobiology missions. In this context, we present the case that the plume of Enceladus currently represents the best astrobiology target in the Solar System. Analysis of the plume by the Cassini mission indicates that the steady plume derives from a subsurface liquid water reservoir that contains organic carbon, biologically available nitrogen, redox energy sources, and inorganic salts. Furthermore, samples from the plume jetting out into space are accessible to a low-cost flyby mission. No other world has such well-studied indications of habitable conditions. Thus, the science goals that would motivate an Enceladus mission are more advanced than for any other Solar System body. The goals of such a mission must go beyond further geophysical characterization, extending to the search for biomolecular evidence of life in the organic-rich plume. This will require improved in situ investigations and a sample return.

Dynamics of C2 formation in laser-produced carbon plasma in helium environment

International Nuclear Information System (INIS)

Al-Shboul, K. F.; Harilal, S. S.; Hassanein, A.; Polek, M.

2011-01-01

We investigated the role of helium ambient gas on the dynamics of C 2 species formation in laser-produced carbon plasma. The plasma was produced by focusing 1064 nm pulses from an Nd:YAG laser onto a carbon target. The emission from the C 2 species was studied using optical emission spectroscopy, and spectrally resolved and integrated fast imaging. Our results indicate that the formation of C 2 in the plasma plume is strongly affected by the pressure of the He gas. In vacuum, the C 2 emission zone was located near the target and C 2 intensity oscillations were observed both in axial and radial directions with increasing the He pressure. The oscillations in C 2 intensity at higher pressures in the expanding plume could be caused by various formation zones of carbon dimers.

Atmospheric-Pressure Non-Thermal Plasma Jet for biomedical and industrial applications

International Nuclear Information System (INIS)

Asenjo, J; Mora, J; Vargas, A; Brenes, L; Montiel, R; Arrieta, J; Vargas, VI

2015-01-01

In this work we present the development and evaluation of a low-cost DBD Plasma- JET reactor using Argon as carrier gas, this device is capable of generating a cold plasma plume several centimeters in length making it suitable for use directly in contact with objects and delicate materials, including living tissue. (paper)

Modeling Macro- and Micro-Scale Turbulent Mixing and Chemistry in Engine Exhaust Plumes

Science.gov (United States)

Menon, Suresh

1998-01-01

(that employed parabolic or temporal approximations) and the measured data. Finally to address the major uncertainty in the near-field plume modeling related to the plume processing of sulfur compounds and advanced model was developed to evaluate its impact on the chemical processes in the near wake. A comprehensive aerosol model is developed and it is coupled with chemical kinetics and the axisymmetric turbulent jet flow models. The integrated model is used to simulate microphysical processes in the near-field jet plume, including sulfuric acid and water binary homogeneous nucleation, coagulation, non-equilibrium heteromolecular condensation, and sulfur-induced soot activation. The formation and evolution of aerosols are computed and analyzed. The computed results show that a large number of ultra-fine (0.3--0.6 nm in radius) volatile HSO4 - HO embryos are generated in the near-field plume. These embryos further grow in size by self coagulation and condensation. Soot particles can be activated by both heterogeneous nucleation and scavenging of H2SO4-H2O aerosols. These activated soot particles can serve as water condensation nuclei for contrail formation. Conditions under which ice contrails can form behind aircrafts are studied. The sensitivities of the threshold temperature for contrail formation with respect to aircraft propulsion efficiency, relative humidity, and ambient pressure are evaluated. The computed aerosol properties for different extent of fuel sulfur conversion to S(VI) (SO3 and H2SO4) in engine are examined and the results are found to be sensitive to this conversion fraction.

A Nanosecond Pulsed Plasma Brush for Surface Decontamination

Science.gov (United States)

Neuber, Johanna; Malik, Muhammad; Song, Shutong; Jiang, Chunqi

2015-11-01

This work optimizes a non-thermal, atmospheric pressure plasma brush for surface decontamination. The generated plasma plumes with a maximum length of 2 cm are arranged in a 5 cm long, brush-like array. The plasma was generated in ambient air with Acinetobacter baumannii. Laminate surfaces inoculated with over-night cultured bacteria were subject to the plasma treatment for varying water concentrations in He, flow rates and discharge voltages. It was found that increasing the water content of the feed gas greatly enhanced the bactericidal effect. Emission spectroscopy was performed to identify the reactive plasma species that contribute to this variation. Additional affiliation: Frank Reidy Research Center for Bioelectrics

Birth, life, and death of a solar coronal plume

Energy Technology Data Exchange (ETDEWEB)

Pucci, Stefano; Romoli, Marco [Department of Physics and Astronomy, University of Firenze, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Poletto, Giannina [INAF-Arcetri Astrophysical Observatory, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Sterling, Alphonse C., E-mail: stpucci@arcetri.astro.it [Space Science Office, NASA/MSFC, Huntsville, AL 35812 (United States)

2014-10-01

We analyze a solar polar-coronal-hole (CH) plume over its entire ≈40 hr lifetime, using high-resolution Solar Dynamic Observatory Atmospheric Imaging Assembly (AIA) data. We examine (1) the plume's relationship to a bright point (BP) that persists at its base, (2) plume outflows and their possible contribution to the solar wind mass supply, and (3) the physical properties of the plume. We find that the plume started ≈2 hr after the BP first appeared and became undetectable ≈1 hr after the BP disappeared. We detected radially moving radiance variations from both the plume and from interplume regions, corresponding to apparent outflow speeds ranging over ≈(30-300) km s{sup –1} with outflow velocities being higher in the 'cooler' AIA 171 Å channel than in the 'hotter' 193 Å and 211 Å channels, which is inconsistent with wave motions; therefore, we conclude that the observed radiance variations represent material outflows. If they persist into the heliosphere and plumes cover ≈10% of a typical CH area, these flows could account for ≈50% of the solar wind mass. From a differential emission measure analysis of the AIA images, we find that the average electron temperature of the plume remained approximately constant over its lifetime, at T {sub e} ≈ 8.5 × 10{sup 5} K. Its density, however, decreased with the age of the plume, being about a factor of three lower when the plume faded compared to when it was born. We conclude that the plume died due to a density reduction rather than to a temperature decrease.

An analysis of millimetre-wave interferometry on Hall thruster plumes by finite difference time domain simulations

International Nuclear Information System (INIS)

Lee, Jungpyo; Cappelli, Mark A

2008-01-01

In this paper, we present finite difference time domain (FDTD) simulations of millimetre-wave propagation through the near-field plasma plume of low power Hall thrusters. The simulations are intended to address potential issues (collisions, magnetic fields) that may affect the validity of simple theory used for phase shift determination in the recent measurements of plasma density using microwave interferometry (Cappelli et al 2006 J. Phys. D: Appl. Phys. 39 4582). One-dimensional plane wave FDTD simulations indicate that plasma non-uniformities along the direction of wave propagation have only a minor effect on the phase shifts estimated from collisionless, non-magnetized wave propagation through a path-length averaged plasma slab. Three-dimensional FDTD simulations that also account for electron collisions and magnetic fields indicate that the departure from the use of usual simple models is no more than about 15%, well within the limits of uncertainty in the experimental measurements taken within the near field of these plasma sources

UV and IR laser ablation for inductively coupled plasma mass spectrometry

International Nuclear Information System (INIS)

Smith, M.R.; Koppenaal, D.W.; Farmer, O.T.

1993-06-01

Laser ablation particle plume compositions are characterized using inductively coupled plasma mass spectrometry (ICP/MS). This study evaluates the mass response characteristics peculiar to ICP/MS detection as a function of laser fluence and frequency. Evaluation of the ICP/MS mass response allows deductions to be made concerning how representative the laser ablation produced particle plume composition is relative to the targeted sample. Using a black glass standard, elemental fractionation was observed, primarily for alkalis and other volatile elements. The extent of elemental fractionation between the target sample and the sampled plume varied significantly as a function of laser fluences and IR and UV laser frequency

Production of organic compounds in plasmas - A comparison among electric sparks, laser-induced plasmas, and UV light

Science.gov (United States)

Scattergood, Thomas W.; Mckay, Christopher P.; Borucki, William J.; Giver, Lawrence P.; Van Ghyseghem, Hilde

1989-01-01

In order to ascertain the features of organic compound-production in planetary atmospheres under the effects of plasmas and shocks, various mixtures of N2, CH4, and H2 modeling the atmosphere of Titan were subjected to discrete sparks, laser-induced plasmas, and UV radiation. The experimental results obtained suggest that UV photolysis from the plasma is an important organic compound synthesis process, as confirmed by the photolysis of gas samples that were exposed to the light but not to the shock waves emitted by the sparks. The thermodynamic equilibrium theory is therefore incomplete in the absence of photolysis.

Emission Characteristics of Laser-Induced Plasma Using Collinear Long and Short Dual-Pulse Laser-Induced Breakdown Spectroscopy (LIBS).

Science.gov (United States)

Wang, Zhenzhen; Deguchi, Yoshihiro; Liu, Renwei; Ikutomo, Akihiro; Zhang, Zhenzhen; Chong, Daotong; Yan, Junjie; Liu, Jiping; Shiou, Fang-Jung

2017-09-01

Collinear long and short dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) was employed to clarify the emission characteristics from laser-induced plasma. The plasma was sustained and became stable by the long pulse-width laser with the pulse width of 60 μs under free running (FR) conditions as an external energy source. Comparing the measurement results of stainless steel in air using single-pulse LIBS (SP-LIBS) and DP-LIBS, the emission intensity was markedly enhanced using DP-LIBS. The temperature of plasma induced by DP-LIBS was maintained at a higher temperature under different gate delay time and short pulse-width laser power conditions compared with those measured using short SP-LIBS. Moreover, the variation rates of plasma temperatures measured using DP-LIBS were also lower. The superior detection ability was verified by the measurement of aluminum sample in water. The spectra were clearly detected using DP-LIBS, whereas it cannot be identified using SP-LIBS of short and long pulse widths. The effects of gate delay time and short pulse-width laser power were also discussed. These results demonstrate the feasibility and enhanced detection ability of the proposed collinear long and short DP-LIBS method.

Hydrogen production by thermal water splitting using a thermal plasma

International Nuclear Information System (INIS)

Boudesocque, N.; Lafon, C.; Girold, C.; Vandensteendam, C.; Baronnet, J.M.

2006-01-01

CEA has been working for more than 10 years in plasma technologies devoted to waste treatment: incineration, vitrification, gases and liquid treatment. Based on this experience, CEA experiments since several years an innovative route for hydrogen production by thermal water splitting, using a plasma as heat source. This new approach could be considered as an alternative to electrolysis for massive hydrogen production from water and electricity. This paper presents a brief state of the art of water thermal plasmas, showing the temperatures and quench velocity ranges technologically achievable today. Thermodynamic properties of a water plasma are presented and discussed. A kinetic computational model is presented, describing the behavior of splitted products during the quench in a plasma plume for various parameters, such as the quench rate. The model results are compared to gas analysis in the plasma plume obtained with in-situ sampling probe. The plasma composition measurements are issued from an Optical Emission Spectroscopic method (OES). The prediction of 30 % H 2 recovery with a 108 K.s -1 quench rate has been verified. A second experimentation has been performed: mass gas analysis, flowrate measurement and OES to study the 'behavior' and species in underwater electrical arc stricken between graphite electrodes. With this quench, a synthesis gas was produced with a content 55 % of hydrogen. (authors)

Influence of mode-beating pulse on laser-induced plasma

Science.gov (United States)

Nishihara, M.; Freund, J. B.; Glumac, N. G.; Elliott, G. S.

2018-04-01

This paper addresses the influence of mode-beating pulse on laser-induced plasma. The second harmonic of a Nd:YAG laser, operated either with the single mode or multimode, was used for non-resonant optical breakdown, and subsequent plasma development was visualized using a streak imaging system. The single mode lasing leads to a stable breakdown location and smooth envelopment of the plasma boundary, while the multimode lasing, with the dominant mode-beating frequency of 500-800 MHz, leads to fluctuations in the breakdown location, a globally modulated plasma surface, and growth of local microstructures at the plasma boundary. The distribution of the local inhomogeneity was measured from the elastic scattering signals on the streak image. The distance between the local structures agreed with the expected wavelength of hydrodynamic instability development due to the interference between the surface excited wave and transmitted wave. A numerical simulation, however, indicates that the local microstructure could also be directly generated at the peaks of the higher harmonic components if the multimode pulse contains up to the eighth harmonic of the fundamental cavity mode.

Smoke plumes: Emissions and effects

Science.gov (United States)

Susan O' Neill; Shawn Urbanski; Scott Goodrick; Sim Larkin

2017-01-01

Smoke can manifest itself as a towering plume rising against the clear blue sky-or as a vast swath of thick haze, with fingers that settle into valleys overnight. It comes in many forms and colors, from fluffy and white to thick and black. Smoke plumes can rise high into the atmosphere and travel great distances across oceans and continents. Or smoke can remain close...

Atmospheric pressure plasma jets interacting with liquid covered tissue: touching and not-touching the liquid

International Nuclear Information System (INIS)

Norberg, Seth A; Johnsen, Eric; Tian, Wei; Kushner, Mark J

2014-01-01

In the use of atmospheric pressure plasma jets in biological applications, the plasma-produced charged and neutral species in the plume of the jet often interact with a thin layer of liquid covering the tissue being treated. The plasma-produced reactivity must then penetrate through the liquid layer to reach the tissue. In this computational investigation, a plasma jet created by a single discharge pulse at three different voltages was directed onto a 200 µm water layer covering tissue followed by a 10 s afterglow. The magnitude of the voltage and its pulse length determined if the ionization wave producing the plasma plume reached the surface of the liquid. When the ionization wave touches the surface, significantly more charged species were created in the water layer with H 3 O + aq , O 3 − aq , and O 2 − aq being the dominant terminal species. More aqueous OH aq , H 2 O 2aq , and O 3aq were also formed when the plasma plume touches the surface. The single pulse examined here corresponds to a low repetition rate plasma jet where reactive species would be blown out of the volume between pulses and there is not recirculation of flow or turbulence. For these conditions, N x O y species do not accumulate in the volume. As a result, aqueous nitrites, nitrates, and peroxynitrite, and the HNO 3aq and HOONO aq , which trace their origin to solvated N x O y , have low densities. (paper)

Plume Splitting in a Two-layer Stratified Ambient Fluid

Science.gov (United States)

Ma, Yongxing; Flynn, Morris; Sutherland, Bruce

2017-11-01

A line-source plume descending into a two-layer stratified ambient fluid in a finite sized tank is studied experimentally. Although the total volume of ambient fluid is fixed, lower- and upper-layer fluids are respectively removed and added at a constant rate mimicking marine outfall through diffusers and natural and hybrid ventilated buildings. The influence of the plume on the ambient depends on the value of λ, defined as the ratio of the plume buoyancy to the buoyancy loss of the plume as it crosses the ambient interface. Similar to classical filling-box experiments, the plume can always reach the bottom of the tank if λ > 1 . By contrast, if λ < 1 , an intermediate layer eventually forms as a result of plume splitting. Eventually all of the plume fluid spreads within the intermediate layer. The starting time, tv, and the ending time, tt, of the transition process measured from experiments correlate with the value of λ. A three-layer ambient fluid is observed after transition, and the mean value of the measured densities of the intermediate layer fluid is well predicted using plume theory. Acknowledgments: Funding for this study was provided by NSERC.

Teaching the Mantle Plumes Debate

Science.gov (United States)

Foulger, G. R.

2010-12-01

There is an ongoing debate regarding whether or not mantle plumes exist. This debate has highlighted a number of issues regarding how Earth science is currently practised, and how this feeds into approaches toward teaching students. The plume model is an hypothesis, not a proven fact. And yet many researchers assume a priori that plumes exist. This assumption feeds into teaching. That the plume model is unproven, and that many practising researchers are skeptical, may be at best only mentioned in passing to students, with most teachers assuming that plumes are proven to exist. There is typically little emphasis, in particular in undergraduate teaching, that the origin of melting anomalies is currently uncertain and that scientists do not know all the answers. Little encouragement is given to students to become involved in the debate and to consider the pros and cons for themselves. Typically teachers take the approach that “an answer” (or even “the answer”) must be taught to students. Such a pedagogic approach misses an excellent opportunity to allow students to participate in an important ongoing debate in Earth sciences. It also misses the opportunity to illustrate to students several critical aspects regarding correct application of the scientific method. The scientific method involves attempting to disprove hypotheses, not to prove them. A priori assumptions should be kept uppermost in mind and reconsidered at all stages. Multiple working hypotheses should be entertained. The predictions of a hypothesis should be tested, and unpredicted observations taken as weakening the original hypothesis. Hypotheses should not be endlessly adapted to fit unexpected observations. The difficulty with pedagogic treatment of the mantle plumes debate highlights a general uncertainty about how to teach issues in Earth science that are not yet resolved with certainty. It also represents a missed opportunity to let students experience how scientific theories evolve, warts

Lidar sounding of volcanic plumes

Science.gov (United States)

Fiorani, Luca; Aiuppa, Alessandro; Angelini, Federico; Borelli, Rodolfo; Del Franco, Mario; Murra, Daniele; Pistilli, Marco; Puiu, Adriana; Santoro, Simone

2013-10-01

Accurate knowledge of gas composition in volcanic plumes has high scientific and societal value. On the one hand, it gives information on the geophysical processes taking place inside volcanos; on the other hand, it provides alert on possible eruptions. For this reasons, it has been suggested to monitor volcanic plumes by lidar. In particular, one of the aims of the FP7 ERC project BRIDGE is the measurement of CO2 concentration in volcanic gases by differential absorption lidar. This is a very challenging task due to the harsh environment, the narrowness and weakness of the CO2 absorption lines and the difficulty to procure a suitable laser source. This paper, after a review on remote sensing of volcanic plumes, reports on the current progress of the lidar system.

Plume collimation for laser ablation electrospray ionization mass spectrometry

Science.gov (United States)

Vertes, Akos; Stolee, Jessica A.

2014-09-09

In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

Global Modeling of Uranium Molecular Species Formation Using Laser-Ablated Plasmas

Science.gov (United States)

Curreli, Davide; Finko, Mikhail; Azer, Magdi; Armstrong, Mike; Crowhurst, Jonathan; Radousky, Harry; Rose, Timothy; Stavrou, Elissaios; Weisz, David; Zaug, Joseph

2016-10-01

Uranium is chemically fractionated from other refractory elements in post-detonation nuclear debris but the mechanism is poorly understood. Fractionation alters the chemistry of the nuclear debris so that it no longer reflects the chemistry of the source weapon. The conditions of a condensing fireball can be simulated by a low-temperature plasma formed by vaporizing a uranium sample via laser heating. We have developed a global plasma kinetic model in order to model the chemical evolution of U/UOx species within an ablated plasma plume. The model allows to track the time evolution of the density and energy of an uranium plasma plume moving through an oxygen atmosphere of given fugacity, as well as other relevant quantities such as average electron and gas temperature. Comparison of model predictions with absorption spectroscopy of uranium-ablated plasmas provide preliminary insights on the key chemical species and evolution pathways involved during the fractionation process. This project was sponsored by the DoD, Defense Threat Reduction Agency, Grant HDTRA1-16-1-0020. This work was performed in part under the auspices of the U.S. DoE by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Saharan dust plume charging observed over the UK

Science.gov (United States)

Harrison, R. Giles; Nicoll, Keri A.; Marlton, Graeme J.; Ryder, Claire L.; Bennett, Alec J.

2018-05-01

A plume of Saharan dust and Iberian smoke was carried across the southern UK on 16th October 2017, entrained into an Atlantic cyclone which had originated as Hurricane Ophelia. The dust plume aloft was widely noticed as it was sufficiently dense to redden the visual appearance of the sun. Time series of backscatter from ceilometers at Reading and Chilbolton show two plumes: one carried upwards to 2.5 km, and another below 800 m into the boundary layer, with a clear slot between. Steady descent of particles at about 50 cm s‑1 continued throughout the morning, and coarse mode particles reached the surface. Plumes containing dust are frequently observed to be strongly charged, often through frictional effects. This plume passed over atmospheric electric field sensors at Bristol, Chilbolton and Reading. Consistent measurements at these three sites indicated negative plume charge. The lower edge plume charge density was (‑8.0 ± 3.3) nC m‑2, which is several times greater than that typical for stratiform water clouds, implying an active in situ charge generation mechanism such as turbulent triboelectrification. A meteorological radiosonde measuring temperature and humidity was launched into the plume at 1412 UTC, specially instrumented with charge and turbulence sensors. This detected charge in the boundary layer and in the upper plume region, and strong turbulent mixing was observed throughout the atmosphere’s lowest 4 km. The clear slot region, through which particles sedimented, was anomalously dry compared with modelled values, with water clouds forming intermittently in the air beneath. Electrical aspects of dust should be included in numerical models, particularly the charge-related effects on cloud microphysical properties, to accurately represent particle behaviour and transport.

Experimental and numerical study of electromagnetically induced transparency in magnetized plasmas

International Nuclear Information System (INIS)

Kawamori, Eiichirou; Hsieh, Tung-Yuan; Nishida, Yasushi; Cheng, C-Z

2012-01-01

We present a demonstration of electromagnetically induced transparency (EIT) in magnetized plasmas by means of experiment and numerical simulation. EIT in magnetized plasmas is a phenomenon by which a plasma-absorbing electron cyclotron wave is rendered transparent by a pump wave, which is a classical analog to conventional quantum EIT although the plasma EIT is not a quantum-mechanics-based phenomenon. This paper describes an attempt to identify plasma oscillations excited by the mode coupling of a pump wave and a probe wave, which is a key mechanism for achieving magnetized plasma EIT, by an experiment and a particle-in-cell (PIC) simulation. A preliminary result of the longitudinal electric field measurement indicates an enhancement of the plasma oscillation in the vicinity of the beat frequency between the probe and pump waves. Also the PIC calculation, which simulated the real experiment, shows a plasma oscillation excited by the mode coupling between the probe and pump waves in the magnetized plasma EIT, showing agreement with theory and experiment. (paper)

Proceedings of plumes, plates and mineralisation symposium: an introduction

CSIR Research Space (South Africa)

Hatton, CJ

1997-12-01

Full Text Available of plume-theory. Mechanisms of magma formation are identified and plume positions and distances to their surface expression considered. Mantle plumes are considered as a heat and fluid source for the Witwatersrand gold deposits....

Simplified scheme or radioactive plume calculations

International Nuclear Information System (INIS)

Gibson, T.A.; Montan, D.N.

1976-01-01

A simplified mathematical scheme to estimate external whole-body γ radiation exposure rates from gaseous radioactive plumes was developed for the Rio Blanco Gas Field Nuclear Stimulation Experiment. The method enables one to calculate swiftly, in the field, downwind exposure rates knowing the meteorological conditions and γ radiation exposure rates measured by detectors positioned near the plume source. The method is straightforward and easy to use under field conditions without the help of mini-computers. It is applicable to a wide range of radioactive plume situations. It should be noted that the Rio Blanco experiment was detonated on May 17, 1973, and no seep or release of radioactive material occurred

Large potential change induced by pellet injection in JIPP T-IIU tokamak plasmas

International Nuclear Information System (INIS)

Hamada, Y.; Sato, K.N.; Sakakita, H.

1995-05-01

A large, rapid change in the local plasma potential is found to be induced by off-axis hydrogen ice-pellet injection into a tokamak plasma. The polarity of the rapid change is reversed when the pellet is injected into the upper and lower halves of the poloidal plasma cross-section. This change can be interpreted as being due to the gradient-B drift of particles in the high-density plasmas of the pellet cloud, before the increase of the plasma density due to the ablation becomes uniform on the magnetic surface. (author)

Hubble Captures Volcanic Eruption Plume From Io

Science.gov (United States)

1997-01-01

The Hubble Space Telescope has snapped a picture of a 400-km-high (250-mile-high) plume of gas and dust from a volcanic eruption on Io, Jupiter's large innermost moon.Io was passing in front of Jupiter when this image was taken by the Wide Field and Planetary Camera 2 in July 1996. The plume appears as an orange patch just off the edge of Io in the eight o'clock position, against the blue background of Jupiter's clouds. Io's volcanic eruptions blasts material hundreds of kilometers into space in giant plumes of gas and dust. In this image, material must have been blown out of the volcano at more than 2,000 mph to form a plume of this size, which is the largest yet seen on Io.Until now, these plumes have only been seen by spacecraft near Jupiter, and their detection from the Earth-orbiting Hubble Space Telescope opens up new opportunities for long-term studies of these remarkable phenomena.The plume seen here is from Pele, one of Io's most powerful volcanos. Pele's eruptions have been seen before. In March 1979, the Voyager 1 spacecraft recorded a 300-km-high eruption cloud from Pele. But the volcano was inactive when the Voyager 2 spacecraft flew by Jupiter in July 1979. This Hubble observation is the first glimpse of a Pele eruption plume since the Voyager expeditions.Io's volcanic plumes are much taller than those produced by terrestrial volcanos because of a combination of factors. The moon's thin atmosphere offers no resistance to the expanding volcanic gases; its weak gravity (one-sixth that of Earth) allows material to climb higher before falling; and its biggest volcanos are more powerful than most of Earth's volcanos.This image is a contrast-enhanced composite of an ultraviolet image (2600 Angstrom wavelength), shown in blue, and a violet image (4100 Angstrom wavelength), shown in orange. The orange color probably occurs because of the absorption and/or scattering of ultraviolet light in the plume. This light from Jupiter passes through the plume and is

Biogeochemistry of landfill leachate plumes

DEFF Research Database (Denmark)

Christensen, Thomas Højlund; Kjeldsen, Peter; Bjerg, Poul Løgstrup

2001-01-01

are relatively narrow and do not in terms of width exceed the width of the landfill. The concept of redox zones being present in the plume has been confirmed by the reported composition of the leachate contaminated groundwater at several landfills and constitutes an important framework for understanding...... the behavior of the contaminants in the plume as the leachate migrates away from the landfill. Diverse microbial communities have been identified in leachate plumes and are believed to be responsible for the redox processes. Dissolved organic C in the leachate, although it appears to be only slowly degradable...... to be subject to anaerobic oxidation, but the mechanisms are not yet understood. Heavy metals do not seem to constitute a significant pollution problem at landfills, partly because the heavy metal concentrations in the leachate often are low, and partly because of strong attenuation by sorption...

Investigation of local thermodynamic equilibrium of laser induced Al2O3–TiC plasma in argon by spatially resolved optical emission spectroscopy

Directory of Open Access Journals (Sweden)

K. Alnama

2016-06-01

Full Text Available Plasma plume of Al2O3–TiC is generated by third harmonic Q-switched Nd:YAG nanosecond laser. It is characterized using Optical Emission Spectroscopy (OES at different argon background gas pressures 10, 102, 103, 104 and 105 Pa. Spatial evolution of excitation and ionic temperatures is deduced from spectral data analysis. Temporal evolution of Ti I emission originated from different energy states is probed. The correlation between the temporal behavior and the spatial temperature evolution are investigated under LTE condition for the possibility to use the temporal profile of Ti I emission as an indicator for LTE validity in the plasma.

Non-thermal plasma instabilities induced by deformation of the electron energy distribution function

Science.gov (United States)

Dyatko, N. A.; Kochetov, I. V.; Napartovich, A. P.

2014-08-01

Non-thermal plasma is a key component in gas lasers, microelectronics, medical applications, waste gas cleaners, ozone generators, plasma igniters, flame holders, flow control in high-speed aerodynamics and others. A specific feature of non-thermal plasma is its high sensitivity to variations in governing parameters (gas composition, pressure, pulse duration, E/N parameter). This sensitivity is due to complex deformations of the electron energy distribution function (EEDF) shape induced by variations in electric field strength, electron and ion number densities and gas excitation degree. Particular attention in this article is paid to mechanisms of instabilities based on non-linearity of plasma properties for specific conditions: gas composition, steady-state and decaying plasma produced by the electron beam, or by an electric current pulse. The following effects are analyzed: the negative differential electron conductivity; the absolute negative electron mobility; the stepwise changes of plasma properties induced by the EEDF bi-stability; thermo-current instability and the constriction of the glow discharge column in rare gases. Some of these effects were observed experimentally and some of them were theoretically predicted and still wait for experimental confirmation.

DNA damage in oral cancer cells induced by nitrogen atmospheric pressure plasma jets

Science.gov (United States)

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.

Pulsed cold plasma-induced blood coagulation and its pilot application in stanching bleeding during rat hepatectomy

Science.gov (United States)

Keping, YAN; Qikang, JIN; Chao, ZHENG; Guanlei, DENG; Shengyong, YIN; Zhen, LIU

2018-04-01

This paper presents plasma-induced blood coagulation and its pilot application in rat hepatectomy by using a home-made pulsed cold plasma jet. Experiments were conducted on blood coagulation in vitro, the influence of plasma on tissue in vivo, and the pilot application of rat hepatectomy. Experimental results show that the cold plasma can lead to rapid blood coagulation. Compared with the control sample, the plasma-induced agglomerated layer of blood is thicker and denser, and is mostly composed of broken platelets. When the surface of the liver was treated by plasma, the influence of the plasma can penetrate into the liver to a depth of about 500 μm. During the rat hepatectomy, cold plasma was proved to be effective for stanching bleeding on incision. No obvious bleeding was found in the abdominal cavities of all six rats 48 h after the hepatectomy. This implies that cold plasma can be an effective modality to control bleeding during surgical operation.

Dynamics of the Sediment Plume Over the Yangtze Bank in the Yellow and East China Seas

Science.gov (United States)

Luo, Zhifa; Zhu, Jianrong; Wu, Hui; Li, Xiangyu

2017-12-01

A distinct sediment plume exists over the Yangtze Bank in the Yellow and East China Seas (YECS) in winter, but it disappears in summer. Based on satellite color images, there are two controversial viewpoints about the formation mechanism for the sediment plume. One viewpoint is that the sediment plume forms because of cross-shelf sediment advection of highly turbid water along the Jiangsu coast. The other viewpoint is that the formation is caused by local bottom sediment resuspension and diffused to the surface layer through vertical turbulent mixing. The dynamic mechanism of the sediment plume formation has been unclear until now. This issue was explored by using a numerical sediment model in the present paper. Observed wave, current, and sediment data from 29 December 2016 to 16 January 2017 were collected near the Jiangsu coast and used to validate the model. The results indicated that the model can reproduce the hydrodynamic and sediment processes. Numerical experiments showed that the bottom sediment could be suspended by the bottom shear stress and diffuse to the surface layer by vertical mixing in winter; however, the upward diffusion is restricted by the strong stratification in summer. The sediment plume is generated locally due to bottom sediment resuspension primarily via tide-induced bottom shear stress rather than by cross-shelf sediment advection over the Yangtze Bank.

Induced charge of spherical dust particle on plasma-facing wall in non-uniform electric field

International Nuclear Information System (INIS)

Tomita, Y.; Smirnov, R.; Zhu, S.

2005-01-01

Induced charge of a spherical dust particle on a plasma-facing wall is investigated analytically, where non-uniform electric field is applied externally. The one-dimensional non-uniform electrostatic potential is approximated by the polynomial of the normal coordinate toward the wall. The bipolar coordinate is introduced to solve the Laplace equation of the induced electrostatic potential. The boundary condition at the dust surface determines the unknown coefficients of the general solution of the Laplace equation for the induced potential. From the obtained potential the surface induced charge can be calculated. This result allows estimating the effect of the surrounding plasma, which shields the induced charge. (author)

The spatial and temporal patterns of odors sampled by lobsters and crabs in a turbulent plume.

Science.gov (United States)

Reidenbach, Matthew A; Koehl, M A R

2011-09-15

Odors are dispersed across aquatic habitats by turbulent water flow as filamentous, intermittent plumes. Many crustaceans sniff (take discrete samples of ambient water and the odors it carries) by flicking their olfactory antennules. We used planar laser-induced fluorescence to investigate how flicking antennules of different morphologies (long antennules of spiny lobsters, Panulirus argus; short antennules of blue crabs, Callinectes sapidus) sample fluctuating odor signals at different positions in a turbulent odor plume in a flume to determine whether the patterns of concentrations captured can provide information about an animal's position relative to the odor source. Lobster antennules intercept odors during a greater percentage of flicks and encounter higher peak concentrations than do crab antennules, but because crabs flick at higher frequency, the duration of odor-free gaps between encountered odor pulses is similar. For flicking antennules there were longer time gaps between odor encounters as the downstream distance to the odor source decreases, but shorter gaps along the plume centerline than near the edge. In contrast to the case for antennule flicking, almost all odor-free gaps were <500 ms at all positions in the plume if concentration was measured continuously at the same height as the antennules. Variance in concentration is lower and mean concentration is greater near the substratum, where leg chemosensors continuously sample the plume, than in the water where antennules sniff. Concentrations sampled by legs increase as an animal nears an odor source, but decrease for antennules. Both legs and antennules encounter higher concentrations near the centerline than at the edge of the plume.

Investigations of plasma induced effects on the surface properties of lignocellulosic natural coir fibres

Energy Technology Data Exchange (ETDEWEB)

Praveen, K.M., E-mail: praveenkmiiucnn@gmail.com [International and Inter University Centre for Nano Science and Nanotechnology (IIUCNN), Mahatma Gandhi University, Kottayam, Kerala (India); Centre de Recherche C.Huygens, LIMATB (Laboratoired’Ingénierie des Matériaux de Bretagne), Université De Bretagne-Sud, Rue stMaudé – BP 92116, Cedex Lorient 56321 Lorient (France); Thomas, Sabu [International and Inter University Centre for Nano Science and Nanotechnology (IIUCNN), Mahatma Gandhi University, Kottayam, Kerala (India); Grohens, Yves [Centre de Recherche C.Huygens, LIMATB (Laboratoired’Ingénierie des Matériaux de Bretagne), Université De Bretagne-Sud, Rue stMaudé – BP 92116, Cedex Lorient 56321 Lorient (France); Mozetič, Miran; Junkar, Ita; Primc, Gregor [Department of Surface Engineering, Jozef Stefan Institute, Jamovacesta 39, Ljubljana 1000 (Slovenia); Gorjanc, Marija [Faculty of Natural Sciences and Engineering, University of Ljubljana, Aškerčeva 12, Ljubljana 1000 (Slovenia)

2016-04-15

Graphical abstract: Plasma induced changes on the morphology of coir fibres (Viewed and Analysed using scanning electron microscopy, Jeol JSM 7600 FEG). The O{sub 2} plasma treated fibre possessed increased hydrophilicity due to the chemical and physical changes induced by plasma. - Highlights: • Plasma-induced effects on the surface properties of lignocellulosic natural coir fibres were investigated. • The morphological study using SEM analysis also confirmed the surface changes which were observed after plasma treatment. • The water absorption studies show an increase of water absorption from 39% to around 100%. • The topographic measurements done using atomic force microscopy (AFM) showed etching of fibre wall, and this is responsible for higher water absorption. • XPS analysis reveals that the oxygen content measured for samples treated at 50 Pa increased from initial 18 at% to about 32 at%. - Abstract: The development of lignocellulosic natural-fibre-reinforced polymers composites are constrained by two limitations: the upper temperature at which the fibre can be processed and the significant differences between the surface energy of the fibre and the polymer matrix. Since the fibres and matrices are chemically different, strong adhesion at their interface is needed for the effective transfer of stress and bond distribution throughout the interface. The present study investigated the plasma induced effects on the surface properties of natural coir fibres. Weakly ionized oxygen plasma was created in two different discharge chambers by an inductively coupled radiofrequency (RF) discharge. The water absorption studies showed an increase of water sorption from 39% to 100%. The morphological study using scanning electron microscopy (SEM) analysis also confirmed the surface changes which were observed after the plasma treatment. The topographic measurements and phase imaging done using atomic force microscopy (AFM) indicated difference in topographic

The controversy over plumes: Who is actually right?

Science.gov (United States)

Puchkov, V. N.

2009-01-01

The current state of the theory of mantle plumes and its relation to classic plate tectonics show that the “plume” line of geodynamic research is in a period of serious crisis. The number of publications criticizing this concept is steadily increasing. The initial suggestions of plumes’ advocates are disputed, and not without grounds. Questions have been raised as to whether all plumes are derived from the mantle-core interface; whether they all have a wide head and a narrow tail; whether they are always accompanied by uplifting of the Earth’s surface; and whether they can be reliably identified by geochemical signatures, e.g., by the helium-isotope ratio. Rather convincing evidence indicates that plumes cannot be regarded as a strictly fixed reference frame for moving lithospheric plates. More generally, the very existence of plumes has become the subject of debate. Alternative ideas contend that all plumes, or hot spots, are directly related to plate-tectonic mechanisms and appear as a result of shallow tectonic stress, subsequent decompression, and melting of the mantle enriched in basaltic material. Attempts have been made to explain the regular variation in age of volcanoes in ocean ridges by the crack propagation mechanism or by drift of melted segregations of enriched mantle in a nearly horizontal asthenospheric flow. In the author’s opinion, the crisis may be overcome by returning to the beginnings of the plume concept and by providing an adequate specification of plume attributes. Only mantle flows with sources situated below the asthenosphere should be referred to as plumes. These flows are not directly related to such plate-tectonic mechanisms as passive rifting and decompression melting in the upper asthenosphere and are marked by time-progressive volcanic chains; their subasthenospheric roots are detected in seismic tomographic images. Such plumes are mostly located at the margins of superswells, regions of attenuation of seismic waves at the

Integrating wildfire plume rises within atmospheric transport models

Science.gov (United States)

Mallia, D. V.; Kochanski, A.; Wu, D.; Urbanski, S. P.; Krueger, S. K.; Lin, J. C.

2016-12-01

Wildfires can generate significant pyro-convection that is responsible for releasing pollutants, greenhouse gases, and trace species into the free troposphere, which are then transported a significant distance downwind from the fire. Oftentimes, atmospheric transport and chemistry models have a difficult time resolving the transport of smoke from these wildfires, primarily due to deficiencies in estimating the plume injection height, which has been highlighted in previous work as the most important aspect of simulating wildfire plume transport. As a result of the uncertainties associated with modeled wildfire plume rise, researchers face difficulties modeling the impacts of wildfire smoke on air quality and constraining fire emissions using inverse modeling techniques. Currently, several plume rise parameterizations exist that are able to determine the injection height of fire emissions; however, the success of these parameterizations has been mixed. With the advent of WRF-SFIRE, the wildfire plume rise and injection height can now be explicitly calculated using a fire spread model (SFIRE) that is dynamically linked with the atmosphere simulated by WRF. However, this model has only been tested on a limited basis due to computational costs. Here, we will test the performance of WRF-SFIRE in addition to several commonly adopted plume parameterizations (Freitas, Sofiev, and Briggs) for the 2013 Patch Springs (Utah) and 2012 Baker Canyon (Washington) fires, for both of which observations of plume rise heights are available. These plume rise techniques will then be incorporated within a Lagrangian atmospheric transport model (STILT) in order to simulate CO and CO2 concentrations during NASA's CARVE Earth Science Airborne Program over Alaska during the summer of 2012. Initial model results showed that STILT model simulations were unable to reproduce enhanced CO concentrations produced by Alaskan fires observed during 2012. Near-surface concentrations were drastically

CALIOP-based Biomass Burning Smoke Plume Injection Height

Science.gov (United States)

Soja, A. J.; Choi, H. D.; Fairlie, T. D.; Pouliot, G.; Baker, K. R.; Winker, D. M.; Trepte, C. R.; Szykman, J.

2017-12-01

Carbon and aerosols are cycled between terrestrial and atmosphere environments during fire events, and these emissions have strong feedbacks to near-field weather, air quality, and longer-term climate systems. Fire severity and burned area are under the control of weather and climate, and fire emissions have the potential to alter numerous land and atmospheric processes that, in turn, feedback to and interact with climate systems (e.g., changes in patterns of precipitation, black/brown carbon deposition on ice/snow, alteration in landscape and atmospheric/cloud albedo). If plume injection height is incorrectly estimated, then the transport and deposition of those emissions will also be incorrect. The heights to which smoke is injected governs short- or long-range transport, which influences surface pollution, cloud interaction (altered albedo), and modifies patterns of precipitation (cloud condensation nuclei). We are working with the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) science team and other stakeholder agencies, primarily the Environmental Protection Agency and regional partners, to generate a biomass burning (BB) plume injection height database using multiple platforms, sensors and models (CALIOP, MODIS, NOAA HMS, Langley Trajectory Model). These data have the capacity to provide enhanced smoke plume injection height parameterization in regional, national and international scientific and air quality models. Statistics that link fire behavior and weather to plume rise are crucial for verifying and enhancing plume rise parameterization in local-, regional- and global-scale models used for air quality, chemical transport and climate. Specifically, we will present: (1) a methodology that links BB injection height and CALIOP air parcels to specific fires; (2) the daily evolution of smoke plumes for specific fires; (3) plumes transport and deposited on the Greenland Ice Sheet; and (4) compare CALIOP-derived smoke plume injection

On the relative motions of long-lived Pacific mantle plumes.

Science.gov (United States)

Konrad, Kevin; Koppers, Anthony A P; Steinberger, Bernhard; Finlayson, Valerie A; Konter, Jasper G; Jackson, Matthew G

2018-02-27

Mantle plumes upwelling beneath moving tectonic plates generate age-progressive chains of volcanos (hotspot chains) used to reconstruct plate motion. However, these hotspots appear to move relative to each other, implying that plumes are not laterally fixed. The lack of age constraints on long-lived, coeval hotspot chains hinders attempts to reconstruct plate motion and quantify relative plume motions. Here we provide 40 Ar/ 39 Ar ages for a newly identified long-lived mantle plume, which formed the Rurutu hotspot chain. By comparing the inter-hotspot distances between three Pacific hotspots, we show that Hawaii is unique in its strong, rapid southward motion from 60 to 50 Myrs ago, consistent with paleomagnetic observations. Conversely, the Rurutu and Louisville chains show little motion. Current geodynamic plume motion models can reproduce the first-order motions for these plumes, but only when each plume is rooted in the lowermost mantle.

Particulates reduction in laser-ablated YBa2Cu3O7-δ thin films by laser-induced plume heating

International Nuclear Information System (INIS)

Koren, G.; Baseman, R.J.; Gupta, A.; Lutwyche, M.I.; Laibowitz, R.B.

1990-01-01

Experimental demonstration of reduction in the number and size of particulates formed in the laser ablation deposition of YBa 2 Cu 3 O 7-δ thin films is obtained by the use of a second laser which further heats and fragments the blowoff material in the plume formed by the first laser. This results in a smoother film with higher critical current density as compared to that obtained without the second laser irradiation of the plume

Volcanic eruption plumes on Io

International Nuclear Information System (INIS)

Strom, R.G.; Terrile, R.J.; Masursky, H.; Hansen, C.

1979-01-01

The detection of an umbrella-shaped plume extending about 280 km above the bright limb of Io was one of the most important discoveries made during the Voyager 1 encounter with the jovian system. This discovery proves that Io is volcanically active at present, and the number and magnitude of these eruptions indicate that Io is the most volcanically active body so far discovered in the Solar System. Preliminary analyses of these eruptive plumes are presented. (U.K.)

A comparative study of the enhancement of molecular emission in a spatially confined plume through optical emission spectroscopy and probe beam deflection measurements

Energy Technology Data Exchange (ETDEWEB)

Ding, Dayu; Liang, Peipei; Wu, Jiada; Xu, Ning; Ying, Zhifeng; Sun, Jian, E-mail: jsun@fudan.edu.cn

2013-01-01

The spatial confinement effects of shock wave on the expansion of a carbon plume induced by pulsed laser ablation of graphite in air and the enhancement of the plume emission were studied by optical emission spectroscopy and probe beam deflection measurements. A metal disk was set in the way of the ablation-generated shock wave to block and reflect the supersonically propagating shock wave. The reflected shock wave propagated backwards and confined the expanding plume. The optical emission of CN molecules was enhanced in contrast to the case without the block disk and the emission enhancement was dependent on the position of the disk. Based on the results of time-integrated and -resolved optical emission spectroscopy, and the time- and space-resolved probe beam deflection measurements, the processes occurring in the plume were discussed and the mechanisms responsible for the enhancement of molecular emission in the spatially confined plume were investigated. - Highlights: ► Spatial confinement and optical emission enhancement of carbon plume were studied. ► Ablation-generated shockwave propagating in air was reflected by a block disk. ► The effects of reflected shockwave on the emission enhancement were confirmed. ► The reflect shockwave confined the carbon plume and enhanced the plume emission.

A comparative study of the enhancement of molecular emission in a spatially confined plume through optical emission spectroscopy and probe beam deflection measurements

International Nuclear Information System (INIS)

Ding, Dayu; Liang, Peipei; Wu, Jiada; Xu, Ning; Ying, Zhifeng; Sun, Jian

2013-01-01

The spatial confinement effects of shock wave on the expansion of a carbon plume induced by pulsed laser ablation of graphite in air and the enhancement of the plume emission were studied by optical emission spectroscopy and probe beam deflection measurements. A metal disk was set in the way of the ablation-generated shock wave to block and reflect the supersonically propagating shock wave. The reflected shock wave propagated backwards and confined the expanding plume. The optical emission of CN molecules was enhanced in contrast to the case without the block disk and the emission enhancement was dependent on the position of the disk. Based on the results of time-integrated and -resolved optical emission spectroscopy, and the time- and space-resolved probe beam deflection measurements, the processes occurring in the plume were discussed and the mechanisms responsible for the enhancement of molecular emission in the spatially confined plume were investigated. - Highlights: ► Spatial confinement and optical emission enhancement of carbon plume were studied. ► Ablation-generated shockwave propagating in air was reflected by a block disk. ► The effects of reflected shockwave on the emission enhancement were confirmed. ► The reflect shockwave confined the carbon plume and enhanced the plume emission

River plume patterns and dynamics within the Southern California Bight

Science.gov (United States)

Warrick, J.A.; DiGiacomo, P.M.; Weisberg, S.B.; Nezlin, N.P.; Mengel, M.; Jones, B.H.; Ohlmann, J.C.; Washburn, L.; Terrill, E.J.; Farnsworth, K.L.

2007-01-01

Stormwater river plumes are important vectors of marine contaminants and pathogens in the Southern California Bight. Here we report the results of a multi-institution investigation of the river plumes across eight major river systems of southern California. We use in situ water samples from multi-day cruises in combination with MODIS satellite remote sensing, buoy meteorological observations, drifters, and HF radar current measurements to evaluate the dispersal patterns and dynamics of the freshwater plumes. River discharge was exceptionally episodic, and the majority of storm discharge occurred in a few hours. The combined plume observing techniques revealed that plumes commonly detach from the coast and turn to the left, which is the opposite direction of Coriolis influence. Although initial offshore velocity of the buoyant plumes was ∼50 cm/s and was influenced by river discharge inertia (i.e., the direct momentum of the river flux) and buoyancy, subsequent advection of the plumes was largely observed in an alongshore direction and dominated by local winds. Due to the multiple day upwelling wind conditions that commonly follow discharge events, plumes were observed to flow from their respective river mouths to down-coast waters at rates of 20–40 km/d. Lastly, we note that suspended-sediment concentration and beam-attenuation were poorly correlated with plume salinity across and within the sampled plumes (mean r2=0.12 and 0.25, respectively), while colored dissolved organic matter (CDOM) fluorescence was well correlated (mean r2=0.56), suggesting that CDOM may serve as a good tracer of the discharged freshwater in subsequent remote sensing and monitoring efforts of plumes.

Characterization of redox conditions in groundwater contaminant plumes

Science.gov (United States)

Christensen, Thomas H.; Bjerg, Poul L.; Banwart, Steven A.; Jakobsen, Rasmus; Heron, Gorm; Albrechtsen, Hans-Jørgen

2000-10-01

Evaluation of redox conditions in groundwater pollution plumes is often a prerequisite for understanding the behaviour of the pollutants in the plume and for selecting remediation approaches. Measuring of redox conditions in pollution plumes is, however, a fairly recent issue and yet relative few cases have been reported. No standardised or generally accepted approach exists. Slow electrode kinetics and the common lack of internal equilibrium of redox processes in pollution plumes make, with a few exceptions, direct electrochemical measurement and rigorous interpretation of redox potentials dubious, if not erroneous. Several other approaches have been used in addressing redox conditions in pollution plumes: redox-sensitive compounds in groundwater samples, hydrogen concentrations in groundwater, concentrations of volatile fatty acids in groundwater, sediment characteristics and microbial tools, such as MPN counts, PLFA biomarkers and redox bioassays. This paper reviews the principles behind the different approaches, summarizes methods used and evaluates the approaches based on the experience from the reported applications.

Plasma contactor development for Space Station

Science.gov (United States)

Patterson, Michael J.; Hamley, John A.; Sarmiento, Charles J.; Manzella, David H.; Sarver-Verhey, Timothy; Soulas, George C.; Nelson, Amy

1993-01-01

Plasma contactors have been baselined for the Space Station (SS) to control the electrical potentials of surfaces to eliminate/mitigate damaging interactions with the space environment. The system represents a dual-use technology which is a direct outgrowth of the NASA electric propulsion program and, in particular, the technology development effort on ion thrustor systems. The plasma contactor subsystems include the plasma contactor unit, a power electronics unit, and an expellant management unit. Under this pre-flight development program these will all be brought to breadboard or engineering model status. Development efforts for the plasma contactor include optimizing the design and configuration of the contactor, validating its required lifetime, and characterizing the contactor plume and electromagnetic interference. The plasma contactor unit design selected for the SS is an enclosed keeper, xenon hollow cathode plasma source. This paper discusses the test results and development status of the plasma contactor unit subsystem for the SS.

Investigation of the effect of laser parameters on the target, plume and plasma behavior during and after laser-solid interaction

Science.gov (United States)

Stancalie, A.; Ciobanu, S. S.; Sporea, D.

2017-09-01

A detailed theoretical and experimental analysis is performed for a wide range of laser operating conditions, typical for laser induced breakdown spectroscopy (LIBS) and laser ablation (LA) experiments on copper metallic target. The plasma parameters were experimentally estimated from the line intensities ratio which reflects the relative population of neutral excited species in the plasma. In the case of LA experiments the highest temperature observed was 8210 ± 370 K. In case of LIBS measurements, a maximum temperature of 8123 K has been determined. The experimental results are in good agreement with a stationary, hydrodynamic model. We have theoretically investigated the plasma emission based on the generalized collisional-radiative model as implemented in the ADAS interconnected set of computer codes and data collections. The ionic population density distribution over the ground and excited states into the cooper plasma is graphically displayed as output from the code. The theoretical line intensity ratios are in good agreement with experimental values for the electron density and temperature range measured in our experiments.

Prepulse suppression using a self-induced, ultrashort pulse plasma mirror

International Nuclear Information System (INIS)

Gold, D.M.; Nathel, H.; Bolton, P.R.; White, W.E.; Van Woerkom, L.D.

1991-01-01

The plasma mirror is a self-induced, plasm-based optical element which can be inserted into existing experiments to reduce repulse energy without significant degradation of ultrashort pulse laser light. The authors have characteristics of the reflected pulse. The initial measurements indicate that the incident pulse reflects specularly from a high density, highly reflective plasma. The reflected pulse has a smoothed spatial profile and reduced pulsewidth. This paper outlines future work to characterize both the plasm mirror technique of repulse suppression and its reflected pulse

Mechanism of solid-state plasma-induced dewetting for formation of copper and gold nanoparticles.

Science.gov (United States)

Kwon, Soon-Ho; Choe, Han Joo; Lee, Hyo-Chang; Chung, Chin-Wook; Lee, Jung-Joong

2013-09-01

Cu and Au nanoparticles were fabricated by plasma treatment on Cu and Au films at 653 K. The nanoparticles were formed by dewetting the metallic films using plasma. Scanning electron microscopy and transmission electron microscopy investigations showed that the plasma-induced dewetting of the Cu and Au films proceeded through heterogeneous hole nucleation and growth along the grain boundaries to lower the surface energy. The amount of energy transferred to surface atoms by one Ar ion was calculated to be 16.1 eV, which was sufficient for displacing Cu and Au atoms. Compared to thermally activated dewetting, more uniform particles could be obtained by plasma-induced dewetting because a much larger number of holes with smaller sizes was generated. The plasma dewetting process is less sensitive to the oxidation of metallic films compared to the annealing process. As a result, Cu nanoparticles could be fabricated at 653 K, whereas the thermally activated dewetting was not possible.

Using satellite imagery for qualitative evaluation of plume transport in modeling the effects of the Kuwait oil fire smoke plumes

International Nuclear Information System (INIS)

Bass, A.; Janota, P.

1992-01-01

To forecast the behavior of the Kuwait oil fire smoke plumes and their possible acute or chronic health effects over the Arabian Gulf region, TASC created a comprehensive health and environmental impacts modeling system. A specially-adapted Lagrangian puff transport model was used to create (a) short-term (multiday) forecasts of plume transport and ground-level concentrations of soot and SO 2 ; and (b) long-term (seasonal and longer) estimates of average surface concentrations and depositions. EPA-approved algorithms were used to transform exposures to SO 2 and soot (as PAH/BaP) into morbidity, mortality and crop damage risks. Absent any ground truth, satellite imagery from the NOAA Polar Orbiter and the ESA Geostationary Meteosat offered the only opportunity for timely qualitative evaluation of the long-range plume transport and diffusion predictions. This paper shows the use of actual satellite images (including animated loops of hourly Meteosat images) to evaluate plume forecasts in near-real-time, and to sanity-check the meso- and long-range plume transport projections for the long-term estimates. Example modeled concentrations, depositions and health effects are shown

Field experimental observations of highly graded sediment plumes

DEFF Research Database (Denmark)

Hjelmager Jensen, Jacob; Saremi, Sina; Jimenez, Carlos

2015-01-01

A field experiment in the waters off the south-eastern coast of Cyprus was carried out to study near-field formation of sediment plumes from dumping. Different loads of sediment were poured into calm and limpid waters one at the time from just above the sea surface. The associated plumes......-bed positions gives unique insight into the dynamics of the descending plume and near-field dispersion processes, and enables good understanding of flow and sediment transport processes involved from-release-to-deposition of the load in a non-scaled environment. The high resolution images and footages...... are available through the link provided herein. Observations support the development of a detailed multi-fractional sediment plume model....

Laser induced plasma methodology for ignition control in direct injection sprays

International Nuclear Information System (INIS)

Pastor, José V.; García-Oliver, José M.; García, Antonio; Pinotti, Mattia

2016-01-01

Highlights: • Laser Induced Plasma Ignition system is designed and applied to a Diesel Spray. • A method for quantification of the system effectiveness and reliability is proposed. • The ignition system is optimized in atmospheric and engine-like conditions. • Higher system effectiveness is reached with higher ambient density. • The system is able to stabilize Diesel combustion compared to auto-ignition cases. - Abstract: New combustion modes for internal combustion engines represent one of the main fields of investigation for emissions control in transportation Industry. However, the implementation of lean fuel mixture condition and low temperature combustion in real engines is limited by different unsolved practical issues. To achieve an appropriate combustion phasing and cycle-to-cycle control of the process, the laser plasma ignition system arises as a valid alternative to the traditional electrical spark ignition system. This paper proposes a methodology to set-up and optimize a laser induced plasma ignition system that allows ensuring reliability through the quantification of the system effectiveness in the plasma generation and positional stability, in order to reach optimal ignition performance. For this purpose, experimental tests have been carried out in an optical test rig. At first the system has been optimized in an atmospheric environment, based on the statistical analysis of the plasma records taken with a high speed camera to evaluate the induction effectiveness and consequently regulate and control the system settings. The same optimization method has then been applied under engine-like conditions, analyzing the effect of thermodynamic ambient conditions on the plasma induction success and repeatability, which have shown to depend mainly on ambient density. Once optimized for selected engine conditions, the laser plasma induction system has been used to ignite a direct injection Diesel spray, and to compare the evolution of combustion

Volcanic Plume Measurements with UAV (Invited)

Science.gov (United States)

Shinohara, H.; Kaneko, T.; Ohminato, T.

2013-12-01

Volatiles in magmas are the driving force of volcanic eruptions and quantification of volcanic gas flux and composition is important for the volcano monitoring. Recently we developed a portable gas sensor system (Multi-GAS) to quantify the volcanic gas composition by measuring volcanic plumes and obtained volcanic gas compositions of actively degassing volcanoes. As the Multi-GAS measures variation of volcanic gas component concentrations in the pumped air (volcanic plume), we need to bring the apparatus into the volcanic plume. Commonly the observer brings the apparatus to the summit crater by himself but such measurements are not possible under conditions of high risk of volcanic eruption or difficulty to approach the summit due to topography etc. In order to overcome these difficulties, volcanic plume measurements were performed by using manned and unmanned aerial vehicles. The volcanic plume measurements by manned aerial vehicles, however, are also not possible under high risk of eruption. The strict regulation against the modification of the aircraft, such as installing sampling pipes, also causes difficulty due to the high cost. Application of the UAVs for the volcanic plume measurements has a big advantage to avoid these problems. The Multi-GAS consists of IR-CO2 and H2O gas analyzer, SO2-H2O chemical sensors and H2 semiconductor sensor and the total weight ranges 3-6 kg including batteries. The necessary conditions of the UAV for the volcanic plumes measurements with the Multi-GAS are the payloads larger than 3 kg, maximum altitude larger than the plume height and installation of the sampling pipe without contamination of the exhaust gases, as the exhaust gases contain high concentrations of H2, SO2 and CO2. Up to now, three different types of UAVs were applied for the measurements; Kite-plane (Sky Remote) at Miyakejima operated by JMA, Unmanned airplane (Air Photo Service) at Shinomoedake, Kirishima volcano, and Unmanned helicopter (Yamaha) at Sakurajima

Opacity and atomic analysis of double pulse laser ablated Li plasma

Science.gov (United States)

Sivakumaran, V.; Joshi, H. C.; Kumar, Ajai

2014-09-01

Opacity effects for neutral and ionic emission lines of lithium have been investigated by Atomic Data Analysis Structure (ADAS). Line ratios and opacity corrected photon emissivity coefficients are calculated over a wide range of electron temperatures and densities. The experimentally measured temporal evolution of the line profiles of the over dense Li plasma formed in the double pulse laser ablation experiment have been explained using the ADAS analysis and the plasma parameters of the plasma plume under consideration have been estimated. These results could be projected as a diagnostic tool to estimate plasma parameters of an over dense lithium plasma.

Calculation of doses received while crossing a plume of radioactive material

International Nuclear Information System (INIS)

Scherpelz, R.I.; Desrosiers, A.E.

1981-04-01

A method has been developed for determining the dose received by a person while crossing a plume of radioactive material. The method uses a Gaussian plume model to arrive at a dose rate on the plume centerline at the position of the plume crossing. This dose rate may be due to any external or internal dose pathway. An algebraic formula can then be used to convert the plume centerline dose rate to a total dose integrated over the total time of plume crossing. Correction factors are presented for dose pathways in which the dose rate is not normally distributed about the plume centerline. The method is illustrated by a study done at the Pacific Northwest Laboratory, and results of this study are presented

Qualitative and quantitative spectro-chemical analysis of dates using UV-pulsed laser induced breakdown spectroscopy and inductively coupled plasma mass spectrometry.

Science.gov (United States)

Mehder, A O; Habibullah, Y B; Gondal, M A; Baig, Umair

2016-08-01

Laser Induced Breakdown Spectroscopy (LIBS) is demonstrated for the spectral analysis of nutritional and toxic elements present in several varieties of date fruit samples available in the Saudi Arabia market. The method analyzes the optical emission of a test sample when subjected to pulsed laser ablation. In this demonstration, our primary focus is on calcium (Ca) and magnesium (Mg), as nutritional elements, and on chromium (Cr), as a toxic element. The local thermodynamic equilibrium (LTE) condition was confirmed prior to the elemental characterization of date samples to ensure accuracy of the LIBS analysis. This was achieved by measuring parameters associated with the plasma, such as the electron temperature and the electron number density. These plasma parameters aid interpretation of processes such as ionization, dissociation, and excitation occurring in the plasma plume formed by ablating the date palm sample. The minimum detection limit was established from calibration curves that involved plotting the LIBS signal intensity as a function of standard date samples with known concentrations. The concentration of Ca and Mg detected in different varieties of date samples was between 187 and 515 and 35-196mgL(-1) respectively, while Cr concentration measured between 1.72 and 7.76mgL(-1). In order to optimize our LIBS system, we have studied how the LIBS signal intensity depends on the incident laser energy and the delay time. In order to validate our LIBS analysis results, standard techniques such as inductively coupled plasma mass spectrometry (ICP-MS) were also applied on an identical (duplicate) date samples as those used for the LIBS analysis. The LIBS results exhibit remarkable agreement with those obtained from the ICP-MS analysis. In addition, the finger print wavelengths of other elements present in date samples were also identified and are reported here, which has not been previously reported, to the best of our knowledge. Copyright © 2016 Elsevier B

Poloidal rotation induced by injecting lower hybrid waves in tokamak plasma edge

International Nuclear Information System (INIS)

Jiao Yiming; Gao Qingdi; Shi Bingren

2001-01-01

The poloidal rotation of the magnetized edge plasma in tokamak driven by the ponderomotive force which is generated by injecting lower hybrid wave (LHW) electric field has been studied. The LHW is launched from a waveguide in the plasma edge, and by Brambilla's grill theory, analytic expressions for the wave electric field in the slab model of an inhomogeneous cold plasma have been derived. It is shown that a strong wave electric field will be generated in the plasma edge by injecting LH wave of the power in MW magnitude, and this electric field will induce a poloidal rotation with a sheared poloidal velocity

Argonne National Laboratory's thermal plume measurements: instruments and techniques

International Nuclear Information System (INIS)

Van Loon, L.S.; Frigo, A.A.; Paddock, R.A.

1977-12-01

Instrumentation and techniques were developed at Argonne National Laboratory for measuring the three-dimensional temperature structure of thermal plumes from power plants, along with the limnological, meteorological, and plant operating conditions affecting their behavior. The equipment and procedures were designed to provide field data for use in evaluating predictive models that describe thermal plume behavior, and over 100 sets of these data have been collected. The instrument systems and techniques employed in a typical thermal discharge survey are highly integrated. Continuous monitoring of ambient and plant conditions is coupled with plume mapping from a moving survey boat. The instantaneous location of the boat together with subsurface temperature measurements from a towed thermistor chain provide a quasisynoptic view of the plume structure. Real-time, onboard display of the boat path and vertical temperatures supply feedback to investigators for determining the extent and spatial resolution of measurements required. The unique design, reliability, accuracy, calibration, and historical development of the components of these integrated systems are described. Survey system interfaces with data handling and processing techniques are also explained. Special supportive studies to investigate plume dynamics, values of eddy diffusivities, time-temperature histories of water parcels in thermal plumes, and rapid changes in plume shape are also described along with instrumentation used

Numerical simulation for the influence of laser-induced plasmas addition on air mass capture of hypersonic inlet

Science.gov (United States)

Zhao, Wei; Dou, Zhiguo; Li, Qian

2012-03-01

The theory of laser-induced plasmas addition to hypersonic airflow off a vehicle to increase air mass capture and improve the performance of hypersonic inlets at Mach numbers below the design value is explored. For hypersonic vehicles, when flying at mach numbers lower than the design one, we can increase the mass capture ratio of inlet through laser-induced plasmas injection to the hypersonic flow upstream of cowl lip to form a virtual cowl. Based on the theory, the model of interaction between laser-induced plasmas and hypersonic flow was established. The influence on the effect of increasing mass capture ratio was studied at different positions of laser-induced plasmas region for the external compression hypersonic inlet at Mach 5 while the design value is 6, the power of plasmas was in the range of 1-8mJ. The main results are as follows: 1. the best location of the plasma addition region is near the intersection of the nose shock of the vehicle with the continuation of the cowl line, and slightly below that line. In that case, the shock generated by the heating is close to the shock that is a reflection of the vehicle nose shock off the imaginary solid surface-extension of the cowl. 2. Plasma addition does increase mass capture, and the effect becomes stronger as more energy is added, the peak value appeared when the power of plasma was about 4mJ, when the plasma energy continues to get stronger, the mass capture will decline slowly.

Plasma levels of cAMP, cGMP and CGRP in sildenafil-induced headache

DEFF Research Database (Denmark)

Kruuse, Christina Rostrup; Frandsen, E; Schifter, S

2004-01-01

Sildenafil, a selective inhibitor of the cyclic guanosine monophosphate (cGMP) degrading phosphodiestrase 5 (PDE5), induced migraine without aura in 10 of 12 migraine patients and in healthy subjects it induced significantly more headache than placebo. The aim of the present study was to determine...... whether the pain-inducing effects of sildenafil would be reflected in plasma levels of important signalling molecules in migraine: cGMP, cyclic adenosine monophosphate (cAMP) and calcitonin gene-related peptide (CGRP). Ten healthy subjects (four women, six men) and 12 patients (12 women) suffering from...... migraine without aura were included in two separate double-blind, placebo-controlled, cross-over studies in which placebo or sildenafil 100 mg was administered orally. Plasma levels of CGRP, cAMP and cGMP were determined in blood from the antecubital vein. Despite the ability of sildenafil to induce...

Enhancement and stabilization of plasma using collinear long-short double-pulse laser-induced breakdown spectroscopy

Science.gov (United States)

Cui, Minchao; Deguchi, Yoshihiro; Wang, Zhenzhen; Fujita, Yuki; Liu, Renwei; Shiou, Fang-Jung; Zhao, Shengdun

2018-04-01

A collinear long-short dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) method was employed to enhance and stabilize the laser-induced plasma from steel sample. The long-pulse-width laser beam with the pulse width of 60 μs was generated by a Nd: YAG laser which was operated at FR (free running) mode. The comparative experiments were carried out between single pulse LIBS (SP-LIBS) and long-short DP-LIBS. The recorded results showed that the emission intensities and the temperature of plasma were enhanced by long-short DP-LIBS. The plasma images showed that the plasma was bigger and had a longer lifetime in long-short DP-LIBS situation. Through the calculation of time-resolved plasma temperature and intensity ratio, it can be concluded that the plasma was stabilized by the long-pulse-width laser beam. The long-short DP-LIBS method also generated the stable plasma condition from the samples with different initial temperatures, which overcame the difficulties of LIBS in the online measurement for steel production line.

Experiments on Plume Spreading by Engineered Injection and Extraction

Science.gov (United States)

Mays, D. C.; Jones, M.; Tigera, R. G.; Neupauer, R.

2014-12-01

The notion that groundwater remediation is transport-limited emphasizes the coupling between physical (i.e., hydrodynamic), geochemical, and microbiological processes in the subsurface. Here we leverage this coupling to promote groundwater remediation using the approach of engineered injection and extraction. In this approach, inspired by the literature on chaotic advection, uncontaminated groundwater is injected and extracted through a manifold of wells surrounding the contaminated plume. The potential of this approach lies in its ability to actively manipulate the velocity field near the contaminated plume, generating plume spreading above and beyond that resulting from aquifer heterogeneity. Plume spreading, in turn, promotes mixing and reaction by chemical and biological processes. Simulations have predicted that engineered injection and extraction generates (1) chaotic advection whose characteristics depend on aquifer heterogeneity, and (2) faster rates and increased extent of groundwater remediation. This presentation focuses on a complimentary effort to experimentally demonstrate these predictions experimentally. In preparation for future work using refractive index matched (RIM) porous media, the experiments reported here use a Hele-Shaw apparatus containing silicone oil. Engineered injection and extraction is used to manipulate the geometry of an initially circular plume of black pigment, and photographs record the plume geometry after each step of injection of extraction. Image analysis, using complimentary Eulerian and Lagrangian approaches, reveals the thickness and variability of the dispersion zone surrounding the deformed plume of black pigment. The size, shape, and evolution of this dispersion zone provides insight into the interplay between engineered injection and extraction, which generates plume structure, and dispersion (here Taylor dispersion), which destroys plume structure. These experiments lay the groundwork for application of engineered

Production of organic compounds in plasmas: A comparison among electric sparks, laser-induced plasmas and UV light

Science.gov (United States)

Scattergood, T. W.; Mckay, C. P.; Borucki, W. J.; Giver, L. P.; Vanghyseghem, H.; Parris, J. E.; Miller, S. L.

1991-01-01

In order to study the production of organic compounds in plasmas (and shocks), various mixtures of N2, CH4, and H2, modeling the atmosphere of Titan, were exposed to discrete sparks, laser-induced plasmas (LIP) and ultraviolet light. The yields of HCN and simple hydrocarbons were measured and compared to those calculated from a simple quenched thermodynamic equilibrium model. The agreement between experiment and theory was fair for HCN and C2H2. However, the yields of C2H6 and other hydrocarbons were much higher than those predicted by the model. Our experiments suggest that photolysis by ultraviolet light from the plasma is an important process in the synthesis. This was confirmed by the photolysis of gas samples exposed to the light, but not to the plasma or shock waves. The results of these experiments demonstrate that, in addition to the well-known efficient synthesis of organic compounds in plasmas, the yields of saturated species, e.g., ethane, may be higher than predicted by theory and that LIP provide a convenient and clean way of simulating planetary lightning and impact plasmas in the laboratory.

Io with Loki Plume on Bright Limb

Science.gov (United States)

1990-01-01

Voyager 1 image of Io showing active plume of Loki on limb. Heart-shaped feature southeast of Loki consists of fallout deposits from active plume Pele. The images that make up this mosaic were taken from an average distance of approximately 490,000 kilometers (340,000 miles).

Metal surface nitriding by laser induced plasma

Science.gov (United States)

Thomann, A. L.; Boulmer-Leborgne, C.; Andreazza-Vignolle, C.; Andreazza, P.; Hermann, J.; Blondiaux, G.

1996-10-01

We study a nitriding technique of metals by means of laser induced plasma. The synthesized layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problem. The nitriding method is tested on the synthesis of titanium nitride which is a well-known compound, obtained at present by many deposition and diffusion techniques. In the method of interest, a laser beam is focused on a titanium target in a nitrogen atmosphere, leading to the creation of a plasma over the metal surface. In order to understand the layer formation, it is necessary to characterize the plasma as well as the surface that it has been in contact with. Progressive nitrogen incorporation in the titanium lattice and TiN synthesis are studied by characterizing samples prepared with increasing laser shot number (100-4000). The role of the laser wavelength is also inspected by comparing layers obtained with two kinds of pulsed lasers: a transversal-excited-atmospheric-pressure-CO2 laser (λ=10.6 μm) and a XeCl excimer laser (λ=308 nm). Simulations of the target temperature rise under laser irradiation are performed, which evidence differences in the initial laser/material interaction (material heated thickness, heating time duration, etc.) depending on the laser features (wavelength and pulse time duration). Results from plasma characterization also point out that the plasma composition and propagation mode depend on the laser wavelength. Correlation of these results with those obtained from layer analyses shows at first the important role played by the plasma in the nitrogen incorporation. Its presence is necessary and allows N2 dissociation and a better energy coupling with the target. Second, it appears that the nitrogen diffusion governs the nitriding process. The study of the metal nitriding efficiency, depending on the laser used, allows us to explain the differences observed in the layer features

Laser-induced plasma spectrometry: truly a surface analytical tool

International Nuclear Information System (INIS)

Vadillo, Jose M.; Laserna, J.

2004-01-01

For a long period, analytical applications of laser induced plasma spectrometry (LIPS) have been mainly restricted to overall and quantitative determination of elemental composition in bulk, solid samples. However, introduction of new compact and reliable solid state lasers and technological development in multidimensional intensified detectors have made possible the seeking of new analytical niches for LIPS where its analytical advantages (direct sampling from any material irrespective of its conductive status without sample preparation and with sensitivity adequate for many elements in different matrices) could be fully exploited. In this sense, the field of surface analysis could take advantage from the cited advantages taking into account in addition, the capability of LIPS for spot analysis, line scan, depth-profiling, area analysis and compositional mapping with a single instrument in air at atmospheric pressure. This review paper outlines the fundamental principles of laser-induced plasma emission relevant to sample surface studies, discusses the experimental parameters governing the spatial (lateral and in-depth) resolution in LIPS analysis and presents the applications concerning surface examination

Field experimental observations of highly graded sediment plumes.

Science.gov (United States)

Jensen, Jacob Hjelmager; Saremi, Sina; Jimenez, Carlos; Hadjioannou, Louis

2015-06-15

A field experiment in the waters off the south-eastern coast of Cyprus was carried out to study near-field formation of sediment plumes from dumping. Different loads of sediment were poured into calm and limpid waters one at the time from just above the sea surface. The associated plumes, gravitating towards the seafloor, were filmed simultaneously by four divers situated at different depths in the water column, and facing the plume at different angles. The processes were captured using GoPro-Hero-series cameras. The high-quality underwater footage from near-surface, mid-depth and near-bed positions gives unique insight into the dynamics of the descending plume and near-field dispersion processes, and enables good understanding of flow and sediment transport processes involved from-release-to-deposition of the load in a non-scaled environment. The high resolution images and footages are available through the link provided herein. Observations support the development of a detailed multi-fractional sediment plume model. Copyright © 2015 Elsevier Ltd. All rights reserved.

Destruction of α-synuclein based amyloid fibrils by a low temperature plasma jet

Science.gov (United States)

Karakas, Erdinc; Munyanyi, Agatha; Greene, Lesley; Laroussi, Mounir

2010-10-01

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.

Destruction of α-synuclein based amyloid fibrils by a low temperature plasma jet

International Nuclear Information System (INIS)

Karakas, Erdinc; Laroussi, Mounir; Munyanyi, Agatha; Greene, Lesley

2010-01-01

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.

Impact of biomass burning emission on total peroxy nitrates: fire plume identification during the BORTAS campaign

Directory of Open Access Journals (Sweden)

E. Aruffo

2016-11-01

Full Text Available Total peroxy nitrate ( ∑ PN concentrations have been measured using a thermal dissociation laser-induced fluorescence (TD-LIF instrument during the BORTAS campaign, which focused on the impact of boreal biomass burning (BB emissions on air quality in the Northern Hemisphere. The strong correlation observed between the  ∑ PN concentrations and those of carbon monoxide (CO, a well-known pyrogenic tracer, suggests the possible use of the  ∑ PN concentrations as marker of the BB plumes. Two methods for the identification of BB plumes have been applied: (1  ∑ PN concentrations higher than 6 times the standard deviation above the background and (2  ∑ PN concentrations higher than the 99th percentile of the  ∑ PNs measured during a background flight (B625; then we compared the percentage of BB plume selected using these methods with the percentage evaluated, applying the approaches usually used in literature. Moreover, adding the pressure threshold ( ∼  750 hPa as ancillary parameter to  ∑ PNs, hydrogen cyanide (HCN and CO, the BB plume identification is improved. A recurrent artificial neural network (ANN model was adapted to simulate the concentrations of  ∑ PNs and HCN, including nitrogen oxide (NO, acetonitrile (CH3CN, CO, ozone (O3 and atmospheric pressure as input parameters, to verify the specific role of these input data to better identify BB plumes.

Numerical simulation of inducing characteristics of high energy electron beam plasma for aerodynamics applications

Science.gov (United States)

Deng, Yongfeng; Jiang, Jian; Han, Xianwei; Tan, Chang; Wei, Jianguo

2017-04-01

The problem of flow active control by low temperature plasma is considered to be one of the most flourishing fields of aerodynamics due to its practical advantages. Compared with other means, the electron beam plasma is a potential flow control method for large scale flow. In this paper, a computational fluid dynamics model coupled with a multi-fluid plasma model is established to investigate the aerodynamic characteristics induced by electron beam plasma. The results demonstrate that the electron beam strongly influences the flow properties, not only in the boundary layers, but also in the main flow. A weak shockwave is induced at the electron beam injection position and develops to the other side of the wind tunnel behind the beam. It brings additional energy into air, and the inducing characteristics are closely related to the beam power and increase nonlinearly with it. The injection angles also influence the flow properties to some extent. Based on this research, we demonstrate that the high energy electron beam air plasma has three attractive advantages in aerodynamic applications, i.e. the high energy density, wide action range and excellent action effect. Due to the rapid development of near space hypersonic vehicles and atmospheric fighters, by optimizing the parameters, the electron beam can be used as an alternative means in aerodynamic steering in these applications.

Plume rise from stacks with scrubbers: a state-of-the-art review

International Nuclear Information System (INIS)

Schatzmann, M.; Policastro, A.J.

1984-01-01

The state of the art of predicting plume rise from stacks with scrubbers is evaluated critically. The significant moisture content of the scrubbed plume upon exit leads to important thermodynamic effects during plume rise that are unaccounted for in the usual dry plume rise theories. For example, under conditionally unstable atmospheres, a wet scrubbed plume treated as completely dry acts as if the atmosphere were stable, whereas in reality the scrubbed plume behaves instead as if the atmosphere were unstable. Even the use of moist plume models developed for application to cooling tower plume rise is not valid since these models 1) employ the Boussinesq approximation, 2) use a number of additional simplifying approximations that require small exit temperature differences between tower exit and ambient temperatures, and 3) are not calibrated to stack data

Low-temperature plasma-induced antiproliferative effects on multi-cellular tumor spheroids

International Nuclear Information System (INIS)

Plewa, Joseph-Marie; Yousfi, Mohammed; Eichwald, Olivier; Merbahi, Nofel; Frongia, Céline; Ducommun, Bernard; Lobjois, Valérie

2014-01-01

Biomedical applications of low-temperature plasmas are of growing interest, especially in the field of plasma-induced anti-tumor effects. The present work is aimed at investigating the regionalized antiproliferative effects of low-temperature plasmas on a multicellular tumor spheroid (MCTS), a model that mimics the 3D organization and regionalization of a microtumor region. We report that a low-temperature plasma jet, using helium flow in open air, inhibits HCT116 colon carcinoma MCTS growth in a dose-dependent manner. This growth inhibition is associated with the loss of Ki67, and the regionalized accumulation of DNA damage detected by histone H2AX phosphorylation. This regionalized genotoxic effect leads to massive cell death and loss of the MCTS proliferative region. The use of reactive oxygen species (ROS), scavenger N-acetyl cysteine (NAC) and plasma-conditioned media demonstrate that the ROS generated in the media after exposure to low-temperature plasma play a major role in these observed effects. These findings strengthen the interest in the use of MCTS for the evaluation of antiproliferative strategies, and open new perspectives for studies dedicated to demonstrate the potential of low-temperature plasma in cancer therapy

Low-temperature plasma-induced antiproliferative effects on multi-cellular tumor spheroids

Science.gov (United States)

Plewa, Joseph-Marie; Yousfi, Mohammed; Frongia, Céline; Eichwald, Olivier; Ducommun, Bernard; Merbahi, Nofel; Lobjois, Valérie

2014-04-01

Biomedical applications of low-temperature plasmas are of growing interest, especially in the field of plasma-induced anti-tumor effects. The present work is aimed at investigating the regionalized antiproliferative effects of low-temperature plasmas on a multicellular tumor spheroid (MCTS), a model that mimics the 3D organization and regionalization of a microtumor region. We report that a low-temperature plasma jet, using helium flow in open air, inhibits HCT116 colon carcinoma MCTS growth in a dose-dependent manner. This growth inhibition is associated with the loss of Ki67, and the regionalized accumulation of DNA damage detected by histone H2AX phosphorylation. This regionalized genotoxic effect leads to massive cell death and loss of the MCTS proliferative region. The use of reactive oxygen species (ROS), scavenger N-acetyl cysteine (NAC) and plasma-conditioned media demonstrate that the ROS generated in the media after exposure to low-temperature plasma play a major role in these observed effects. These findings strengthen the interest in the use of MCTS for the evaluation of antiproliferative strategies, and open new perspectives for studies dedicated to demonstrate the potential of low-temperature plasma in cancer therapy.

Mantle plumes on Venus revisited

Science.gov (United States)

Kiefer, Walter S.

1992-01-01

The Equatorial Highlands of Venus consist of a series of quasicircular regions of high topography, rising up to about 5 km above the mean planetary radius. These highlands are strongly correlated with positive geoid anomalies, with a peak amplitude of 120 m at Atla Regio. Shield volcanism is observed at Beta, Eistla, Bell, and Atla Regiones and in the Hathor Mons-Innini Mons-Ushas Mons region of the southern hemisphere. Volcanos have also been mapped in Phoebe Regio and flood volcanism is observed in Ovda and Thetis Regiones. Extensional tectonism is also observed in Ovda and Thetis Regiones. Extensional tectonism is also observed in many of these regions. It is now widely accepted that at least Beta, Atla, Eistla, and Bell Regiones are the surface expressions of hot, rising mantel plumes. Upwelling plumes are consistent with both the volcanism and the extensional tectonism observed in these regions. The geoid anomalies and topography of these four regions show considerable variation. Peak geoid anomalies exceed 90 m at Beta and Atla, but are only 40 m at Eistla and 24 m at Bell. Similarly, the peak topography is greater at Beta and Atla than at Eistla and Bell. Such a range of values is not surprising because terrestrial hotspot swells also have a side range of geoid anomalies and topographic uplifts. Kiefer and Hager used cylindrical axisymmetric, steady-state convection calculations to show that mantle plumes can quantitatively account for both the amplitude and the shape of the long-wavelength geoid and topography at Beta and Atla. In these models, most of the topography of these highlands is due to uplift by the vertical normal stress associated with the rising plume. Additional topography may also be present due to crustal thickening by volcanism and crustal thinning by rifting. Smrekar and Phillips have also considered the geoid and topography of plumes on Venus, but they restricted themselves to considering only the geoid-topography ratio and did not

Experimental simulation and analysis of off-normal heat loads accompanying plasma disruptions

International Nuclear Information System (INIS)

Laan, J.G. van der; Bakker, J.; Stad, R.C.L. van der; Klippel, H.T.

1990-12-01

The plasma disruption heat load is simulated experimentally using a pulsed laser beam with high energy density and short pulse duration (0.2-20 mm) covering a certain range of ITER design values. The present status of the laser heat flux test facility and new experimental tools are described. Spatial and time resolved profiles of the laser beam are given. Experimental results are presented including the variation of angle of incidence of the laser beam relative to the material surface. The nature and effects of the induced vapour plume are discussed. Materials studied are relevant to the ITER design. Experimental results are compared with numerical calculations. Some implications for the design of First Wall and Divertor of ITER are addressed. (author). 13 refs.; 5 figs