Plasma potentials and performance of the advanced electron cyclotron resonance ion source

International Nuclear Information System (INIS)

Xie, Z.Q.; Lyneis, C.M.

1994-01-01

The mean plasma potential was measured on the LBL advanced electron cyclotron resonance (AECR) ion source for a variety of conditions. The mean potentials for plasmas of oxygen, argon, and argon mixed with oxygen in the AECR were determined. These plasma potentials are positive with respect to the plasma chamber wall and are on the order of tens of volts. Electrons injected into the plasma by an electron gun or from an aluminum oxide wall coating with a very high secondary electron emission reduce the plasma potential as does gas mixing. A lower plasma potential in the AECR source coincides with enhanced production of high charged state ions indicating longer ion confinement times. The effect of the extra electrons from external injection or wall coatings is to lower the average plasma potential and to increase the n e τ i of the ECR plasma. With sufficient extra electrons, the need for gas mixing can be eliminated or reduced to a lower level, so the source can operate at lower neutral pressures. A reduction of the neutral pressure decreases charge exchange between ions and neutrals and enhances the production of high charge state ions. An aluminum oxide coating results in the lowest plasma potential among the three methods discussed and the best source performance

Time and space-correlated plasma potential measurements in the near field of a coaxial Hall plasma discharge

International Nuclear Information System (INIS)

Smith, A. W.; Cappelli, M. A.

2009-01-01

Space- and time-correlated measurements of floating and plasma potential are made in the near field, external flow cathode region of a coaxial Hall plasma discharge using an emissive probe synchronized to quasicoherent fluctuations in discharge current. The luminous axial feature frequently observed in the near field of operating plasma accelerators is found to be concomitant with a spike in the plasma potential (and electron temperature). The structure of the plasma potential allows for multiple avenues for back-streaming ions to accelerate toward the discharge front pole and may pull some classes of ions toward the central axis. The fluctuations in plasma properties exhibit a complex structure at frequencies on the order of the so-called 'breathing mode' ionization instability often seen in these types of discharges. Most notably, the plasma potential appears to fluctuate in a helical fashion, resembling tilted drift waves rotating about the central axis. A simple analysis of these waves draws attention to the possible role that they may play in driving anomalous cross-field electron transport in the near field region.

Analytic analysis on asymmetrical micro arcing in high plasma potential RF plasma systems

International Nuclear Information System (INIS)

Yin, Y; McKenzie, D R; Bilek, M M M

2006-01-01

We report experimental and analytical results on asymmetrical micro arcing in a RF (radio frequency) plasma. Micro arcing, resulting from high plasma potential, in RF plasma was found to occur only on the grounded electrode for a variety of electrode and surface configurations. The analytic derivation was based on a simple RF time-dependent Child-Langmuir sheath model and electric current continuity. We found that the minimum potential difference in one RF period across the grounded electrode sheath depends on the area ratio of the grounded electrode to the powered electrode. As the area ratio increases, the minimum potential difference across a sheath increases for the grounded electrode but not for the RF powered electrode. We showed that discharge time in micro arcing is more than 100 RF periods; thus the presence of a continuous high electric field in one RF cycle results in micro arcing on the grounded electrode. However, the minimum potential difference in one RF period across the powered electrode sheath is always small so that it prevents micro arcing occurring even though the average sheath voltage can be large. This simple analytic model is consistent with particle-in-cell simulation results

Methods for direct measurement of the plasma potential

DEFF Research Database (Denmark)

Andersen, S. A.; Christoffersen, G. B.; Jensen, Vagn Orla

1972-01-01

Reports on a simple experimental technique which can be used for determination of the plasma where the plasma potential prevails; these ions are accepted by the analyser plate when phi c= phi pl. Part of this technique has been used by Andersen, Jensen, Michelsen and Nielsen (1971) in measurements...

Fast potential change in sawteeth in JIPP T-IIU tokamak plasmas

International Nuclear Information System (INIS)

Hamada, Y.; Nishizawa, A.; Kawasumi, Y.

1994-12-01

Fast changes of electric potential with different polarities are observed during sawtooth oscillation in a core region of a tokamak plasma using a heavy ion beam probe. The potential change inside the inversion radius is found to be positive. The change is negative outside the inversion radius and shows clearly a propagation nature. The observed potential can be interpreted by the mixture of the potentials of two origins. One of them drives the fast MHD plasma motion through E/B drift and the other is a barrier potential induced by mixing of hot and cold plasmas at sawtooth crash. (author)

SCRIC: a code dedicated to the detailed emission and absorption of heterogeneous NLTE plasmas; application to xenon EUV sources

International Nuclear Information System (INIS)

Gaufridy de Dortan, F. de

2006-01-01

Nearly all spectral opacity codes for LTE and NLTE plasmas rely on configurations approximate modelling or even supra-configurations modelling for mid Z plasmas. But in some cases, configurations interaction (either relativistic and non relativistic) induces dramatic changes in spectral shapes. We propose here a new detailed emissivity code with configuration mixing to allow for a realistic description of complex mid Z plasmas. A collisional radiative calculation. based on HULLAC precise energies and cross sections. determines the populations. Detailed emissivities and opacities are then calculated and radiative transfer equation is resolved for wide inhomogeneous plasmas. This code is able to cope rapidly with very large amount of atomic data. It is therefore possible to use complex hydrodynamic files even on personal computers in a very limited time. We used this code for comparison with Xenon EUV sources within the framework of nano-lithography developments. It appears that configurations mixing strongly shifts satellite lines and must be included in the description of these sources to enhance their efficiency. (author)

Field-aligned plasma-potential structure formed by local electron cyclotron resonance

International Nuclear Information System (INIS)

Hatakeyama, Rikizo; Kaneko, Toshiro; Sato, Noriyoshi

2001-01-01

The significance of basic experiments on field-aligned plasma-potential structure formed by local electron cyclotron resonance (ECR) is claimed based on the historical development of the investigation on electric double layer and electrostatic potential confinement of open-ended fusion-oriented plasmas. In the presence of a single ECR point in simple mirror-type configurations of magnetic field, a potential dip (thermal barrier) appears around this point, being followed by a subsequent potential hump (plug potential) along a collisionless plasma flow. The observed phenomenon gives a clear-cut physics to the formation of field-aligned plug potential with thermal barrier, which is closely related to the double layer formation triggered by a negative dip. (author)

Status and potential of atmospheric plasma processing of materials

Energy Technology Data Exchange (ETDEWEB)

Pappas, Daphne [United States Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States)

2011-03-15

This paper is a review of the current status and potential of atmospheric plasma technology for materials processing. The main focus is the recent developments in the area of dielectric barrier discharges with emphasis in the functionalization of polymers, deposition of organic and inorganic coatings, and plasma processing of biomaterials. A brief overview of both the equipment being used and the physicochemical reactions occurring in the gas phase is also presented. Atmospheric plasma technology offers major industrial, economic, and environmental advantages over other conventional processing methods. At the same time there is also tremendous potential for future research and applications involving both the industrial and academic world.

Status and potential of atmospheric plasma processing of materials

International Nuclear Information System (INIS)

Pappas, Daphne

2011-01-01

This paper is a review of the current status and potential of atmospheric plasma technology for materials processing. The main focus is the recent developments in the area of dielectric barrier discharges with emphasis in the functionalization of polymers, deposition of organic and inorganic coatings, and plasma processing of biomaterials. A brief overview of both the equipment being used and the physicochemical reactions occurring in the gas phase is also presented. Atmospheric plasma technology offers major industrial, economic, and environmental advantages over other conventional processing methods. At the same time there is also tremendous potential for future research and applications involving both the industrial and academic world.

Direct measurements of the plasma potential in ELMy H-mode plasma with ball-pen probes on ASDEX Upgrade tokamak

Energy Technology Data Exchange (ETDEWEB)

Adamek, J., E-mail: adamek@ipp.cas.c [Institute of Plasma Physics, Association EURATOM/IPP.CR, Prague, Za Slovankou 3, 182 00, Prague 8 (Czech Republic); Rohde, V.; Mueller, H.W.; Herrmann, A. [Institute of Plasma Physics, Association EURATOM/IPP, Garching (Germany); Ionita, C.; Schrittwieser, R.; Mehlmann, F. [Institute for Ion Physics and Applied Physics, University of Innsbruck, Association EURATOM/OAW (Austria); Stoeckel, J.; Horacek, J.; Brotankova, J. [Institute of Plasma Physics, Association EURATOM/IPP.CR, Prague, Za Slovankou 3, 182 00, Prague 8 (Czech Republic)

2009-06-15

Experimental investigations of the plasma potential and electric field were performed for ELMy H-mode plasmas in the vicinity of the limiter shadow of ASDEX Upgrade. A fast reciprocating probe with a probe head containing four ball-pen probes (BPPs) [J. Adamek et al., Czech. J. Phys. 54 (2004) C95 - C99.] was used on the midplane manipulator. Different gradients of the plasma potential were observed during ELMs and in between them. The temporal resolution of the direct plasma potential measurements with BPP was determined by using power-spectra analysis.

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

NSTX Disruption Simulations of Detailed Divertor and Passive Plate Models by Vector Potential Transfer from OPERA Global Analysis Results

International Nuclear Information System (INIS)

Titus, P.H.; Avasaralla, S.; Brooks, A.; Hatcher, R.

2010-01-01

The National Spherical Torus Experiment (NSTX) project is planning upgrades to the toroidal field, plasma current and pulse length. This involves the replacement of the center-stack, including the inner legs of the TF, OH, and inner PF coils. A second neutral beam will also be added. The increased performance of the upgrade requires qualification of the remaining components including the vessel, passive plates, and divertor for higher disruption loads. The hardware needing qualification is more complex than is typically accessible by large scale electromagnetic (EM) simulations of the plasma disruptions. The usual method is to include simplified representations of components in the large EM models and attempt to extract forces to apply to more detailed models. This paper describes a more efficient approach of combining comprehensive modeling of the plasma and tokamak conducting structures, using the 2D OPERA code, with much more detailed treatment of individual components using ANSYS electromagnetic (EM) and mechanical analysis. This capture local eddy currents and resulting loads in complex details, and allows efficient non-linear, and dynamic structural analyses.

NSTX Disruption Simulations of Detailed Divertor and Passive Plate Models by Vector Potential Transfer from OPERA Global Analysis Results

Energy Technology Data Exchange (ETDEWEB)

P. H. Titus, S. Avasaralla, A.Brooks, R. Hatcher

2010-09-22

The National Spherical Torus Experiment (NSTX) project is planning upgrades to the toroidal field, plasma current and pulse length. This involves the replacement of the center-stack, including the inner legs of the TF, OH, and inner PF coils. A second neutral beam will also be added. The increased performance of the upgrade requires qualification of the remaining components including the vessel, passive plates, and divertor for higher disruption loads. The hardware needing qualification is more complex than is typically accessible by large scale electromagnetic (EM) simulations of the plasma disruptions. The usual method is to include simplified representations of components in the large EM models and attempt to extract forces to apply to more detailed models. This paper describes a more efficient approach of combining comprehensive modeling of the plasma and tokamak conducting structures, using the 2D OPERA code, with much more detailed treatment of individual components using ANSYS electromagnetic (EM) and mechanical analysis. This capture local eddy currents and resulting loads in complex details, and allows efficient non-linear, and dynamic structural analyses.

Potential around a dust grain in collisional plasma

Energy Technology Data Exchange (ETDEWEB)

Moulick, R., E-mail: moulick@gmail.com; Goswami, K. S. [Centre of Plasma Physics - Institute for Plasma Research Sonapur, Guwahati, Assam 782402 (India)

2015-04-15

The ion neutral collision can lead to interesting phenomena in dust charging, totally different from the expectations based on the traditional orbit motion limited theory. The potential around a dust grain is investigated for the collisional plasma considering the presence of ion neutral collisions. Fluid equations are solved for the one dimensional radial coordinate. It is observed that with the gradual increase in ion neutral collision, the potential structure around the dust grain changes its shape and is different from the usual Debye-Hückel potential. The shift however starts from a certain value of ion neutral collision and the electron-ion density varies accordingly. The potential variation is interesting and reconfirms the fact that there exists a region of attraction for negative charges. The collision modeling is done for the full range of plasma, i.e., considering the bulk and the sheath jointly. The potential variation with collision is also shown explicitly and the variation is found to cope up with the earlier observations.

Multi electron species and shielding potentials in plasmas

International Nuclear Information System (INIS)

Khan, Arroj A.; Murtaza, G.; Rasheed, A.; Jamil, M.

2012-01-01

The phenomenon of Debye shielding is investigated in electron ion plasmas using the approach of two temperature electrons. We get different profiles of potential for different parameters and observe that the potentials fall very slowly than the standard Coulomb and Debye potentials. The importance of work is pointed out in the introduction.

Floating potential and sheath thickness for cylindrical and spherical probes in electronegative plasmas

International Nuclear Information System (INIS)

Morales Crespo, R.; Fernandez Palop, J.I.; Hernandez, M.A.; Borrego del Pino, S.; Diaz-Cabrera, J.M.; Ballesteros, J.

2006-01-01

In this paper, the floating potential, for cylindrical and spherical Langmuir probes immersed into an electronegative plasma, is determined by using a radial model described in a previous paper. This floating potential is determined for several probe radius values and ranks of plasma electronegativity, from almost electropositive plasmas to high electronegative plasmas. The thickness of the positive ion sheath is also determined for this kind of probes in electronegative plasmas, as well as the analytical expressions fitting this thickness, showing its dependence on the probe radius and electric potential

Potential formation in the plasma confinement region of a radio-frequency plugged linear device

International Nuclear Information System (INIS)

Fujita, Hideki; Kumazawa, Ryuhei; Howald, A.M.; Okamura, Shoichi; Sato, Teruyuki; Adati, Keizo; Garner, H.R.; Nishimura, Kiyohiko.

1987-08-01

Plasma potential formation in an open-ended plasma confinement system with RF plugging (the RFC-XX-M device) is investigated. The plasma potential in the central confinement region is measured with a heavy ion beam probe system and potentials at the RF plug section are measured with multi-grid energy analyzers. The measured plasma potential is compared with that deduced from the generalized Pastukhov formula. Results show that the plasma potential develops as an ambipolar potential to equate ion and electron end losses. During RF plugging, electrons are heated by Landau damping, while ions are not heated since adiabatic conditions apply during ion plugging in this experiment. (author)

Ionization-potential depression and dynamical structure factor in dense plasmas

Science.gov (United States)

Lin, Chengliang; Röpke, Gerd; Kraeft, Wolf-Dietrich; Reinholz, Heidi

2017-07-01

The properties of a bound electron system immersed in a plasma environment are strongly modified by the surrounding plasma. The modification of an essential quantity, the ionization energy, is described by the electronic and ionic self-energies, including dynamical screening within the framework of the quantum statistical theory. Introducing the ionic dynamical structure factor as the indicator for the ionic microfield, we demonstrate that ionic correlations and fluctuations play a critical role in determining the ionization potential depression. This is, in particular, true for mixtures of different ions with large mass and charge asymmetry. The ionization potential depression is calculated for dense aluminum plasmas as well as for a CH plasma and compared to the experimental data and more phenomenological approaches used so far.

Direct measurements of the plasma potential by katsumata-type probes

Czech Academy of Sciences Publication Activity Database

Schrittwieser, R.; Ionita, C.; Adámek, Jiří; Stöckel, Jan; Brotánková, Jana; Martines, E.; Popa, G.; Costin, C.; van de Peppel, L.; Van Oost, G.

2006-01-01

Roč. 56, 8 suppl.B (2006), s. 145-150 ISSN 0011-4626. [Symposium on Plasma Physics and Technology /22nd./. Praha, 26.6.2006-29.6.2006] R&D Projects: GA AV ČR(CZ) KJB100430601 Institutional research plan: CEZ:AV0Z20430508 Keywords : toroidal plasma system * tokamak * probe diagnostics * plasma potential Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.568, year: 2006

Changes in plasma osmolality and anion gap: potential predictors of ...

African Journals Online (AJOL)

Changes in plasma osmolality and anion gap: potential predictors of ... PROMOTING ACCESS TO AFRICAN RESEARCH ... Objective: To determine the relationship of mortality to plasma osmolality and anion gap inpatients on haemodialysis.

Studies of Particle Wake Potentials in Plasmas

Science.gov (United States)

Ellis, Ian; Graziani, Frank; Glosli, James; Strozzi, David; Surh, Michael; Richards, David; Decyk, Viktor; Mori, Warren

2011-10-01

Fast Ignition studies require a detailed understanding of electron scattering, stopping, and energy deposition in plasmas with variable values for the number of particles within a Debye sphere. Presently there is disagreement in the literature concerning the proper description of these processes. Developing and validating proper descriptions requires studying the processes using first-principle electrostatic simulations and possibly including magnetic fields. We are using the particle-particle particle-mesh (PPPM) code ddcMD and the particle-in-cell (PIC) code BEPS to perform these simulations. As a starting point in our study, we examine the wake of a particle passing through a plasma in 3D electrostatic simulations performed with ddcMD and with BEPS using various cell sizes. In this poster, we compare the wakes we observe in these simulations with each other and predictions from Vlasov theory. Prepared by LLNL under Contract DE-AC52-07NA27344 and by UCLA under Grant DE-FG52-09NA29552.

Muzzle voltage and contact potential in plasma armature railguns

International Nuclear Information System (INIS)

Keefer, D.

1988-01-01

The voltages measured at the muzzle of a railgun have values greater than those calculated from the one-dimensional models for railgun plasma armatures. This excess voltage is attributed to the contact potential and has a value of several tens of volts. The use of experimentally measured muzzle voltage to determine plasma properties has required that this contact potential be subtracted in order to obtain meaningful results. A two-dimensional model of the plasma armature has been analyzed which shows that a portion of this excess voltage arises as a result of the reduced conductivity in the thermal boundary layer of the rail. Another portion arises from the speed voltage and is confined to a region near the rails within the velocity boundary layer thickness. The voltage drop in the boundary layer is not constant along the length of the armature, and the implications of this effect of the boundary conditions for one- and two-dimensional models of the railgun plasma armature are discussed

Scaling of laser-plasma interactions with laser wavelength and plasma size

International Nuclear Information System (INIS)

Max, C.E.; Campbell, E.M.; Mead, W.C.; Kruer, W.L.; Phillion, D.W.; Turner, R.E.; Lasinski, B.F.; Estabrook, K.G.

1983-01-01

Plasma size is an important parameter in wavelength-scaling experiments because it determines both the threshold and potential gain for a variety of laser-plasma instabilities. Most experiments to date have of necessity produced relatively small plasmas, due to laser energy and pulse-length limitations. We have discussed in detail three recent Livermore experiments which had large enough plasmas that some instability thresholds were exceeded or approached. Our evidence for Raman scatter, filamentation, and the two-plasmon decay instability needs to be confirmed in experiments which measure several instability signatures simultaneously, and which produce more quantitative information about the local density and temperature profiles than we have today

Scaling of laser-plasma interactions with laser wavelength and plasma size

Energy Technology Data Exchange (ETDEWEB)

Max, C.E.; Campbell, E.M.; Mead, W.C.; Kruer, W.L.; Phillion, D.W.; Turner, R.E.; Lasinski, B.F.; Estabrook, K.G.

1983-01-25

Plasma size is an important parameter in wavelength-scaling experiments because it determines both the threshold and potential gain for a variety of laser-plasma instabilities. Most experiments to date have of necessity produced relatively small plasmas, due to laser energy and pulse-length limitations. We have discussed in detail three recent Livermore experiments which had large enough plasmas that some instability thresholds were exceeded or approached. Our evidence for Raman scatter, filamentation, and the two-plasmon decay instability needs to be confirmed in experiments which measure several instability signatures simultaneously, and which produce more quantitative information about the local density and temperature profiles than we have today.

Plasma potential formation and measurement in TMX-U and MFTF-B

International Nuclear Information System (INIS)

Grubb, D.P.

1984-01-01

Tandem mirrors control the axial variation of the plasma potential to create electrostatic plugs that improve the axial confinement of central cell ions and, in a thermal barrier tandem mirror, control the electron axial heat flow. Measurements of the spatial and temporal variations of the plasma potential are, therefore, important to the understanding of confinement in a tandem mirror. In this paper we discuss potential formation in a thermal barrier tandem mirror and examine the diagnostics and data obtained on the TMX-U device, including measurements of the thermal barrier potential profile using a diagnostic neutral beam and charged particle energy-spectroscopy. We then describe the heavy ion beam probe and other new plasma potential diagnostics that are under development for TMX-U and MFTF-B and examine problem areas where additional diagnostic development is desirable

Dust removal in radio-frequency plasmas by a traveling potential modulation

International Nuclear Information System (INIS)

Li Yangfang; Jiang Ke; Thomas, Hubertus M.; Morfill, Gregor E.

2010-01-01

The dust contamination in plasma deposition processes plays a crucial role in the quality and the yield of the products. To improve the quality and the yield of plasma processing, a favorable way is to remove the dust particles actively from the plasma reactors.Our recent experiments in the striped electrode device show that a traveling plasma modulation allows for a systematic particle removal independent of the reactor size. Besides the rf powered electrode, the striped electrode device includes a segmented electrode that consists of 100 electrically insulated narrow stripes. A traveling potential profile is produced by the modulation of the voltage signals applied on the stripes. The dust particles are trapped in the potential wells and transported with the traveling of the potential profile.The particle-in-cell (PIC) simulation on the potential above the segmented electrode indicates that the traveling potential profile can be realized either by applying low-frequency (0.1-10 Hz) voltage signals with a fixed phase shift between adjacent stripes or high-frequency (10 kHz a circumflex AS 100 MHz) signals with the amplitudes modulated by a low-frequency envelope. The transportation of the dust particles is simulated with a two-dimensional molecular dynamics (MD) code with the potential profile obtained from the PIC simulation. The MD results reproduce the experimental observations successfully.This technology allows for an active removal of the contaminating particles in processing plasmas and it is independent of the reactor size. The removal velocity is controllable by adjusting the parameters for the modulation.

Monte Carlo simulations of ionization potential depression in dense plasmas

Energy Technology Data Exchange (ETDEWEB)

Stransky, M., E-mail: stransky@fzu.cz [Department of Radiation and Chemical Physics, Institute of Physics ASCR, Na Slovance 2, 182 21 Prague 8 (Czech Republic)

2016-01-15

A particle-particle grand canonical Monte Carlo model with Coulomb pair potential interaction was used to simulate modification of ionization potentials by electrostatic microfields. The Barnes-Hut tree algorithm [J. Barnes and P. Hut, Nature 324, 446 (1986)] was used to speed up calculations of electric potential. Atomic levels were approximated to be independent of the microfields as was assumed in the original paper by Ecker and Kröll [Phys. Fluids 6, 62 (1963)]; however, the available levels were limited by the corresponding mean inter-particle distance. The code was tested on hydrogen and dense aluminum plasmas. The amount of depression was up to 50% higher in the Debye-Hückel regime for hydrogen plasmas, in the high density limit, reasonable agreement was found with the Ecker-Kröll model for hydrogen plasmas and with the Stewart-Pyatt model [J. Stewart and K. Pyatt, Jr., Astrophys. J. 144, 1203 (1966)] for aluminum plasmas. Our 3D code is an improvement over the spherically symmetric simplifications of the Ecker-Kröll and Stewart-Pyatt models and is also not limited to high atomic numbers as is the underlying Thomas-Fermi model used in the Stewart-Pyatt model.

Monte Carlo simulations of ionization potential depression in dense plasmas

International Nuclear Information System (INIS)

Stransky, M.

2016-01-01

A particle-particle grand canonical Monte Carlo model with Coulomb pair potential interaction was used to simulate modification of ionization potentials by electrostatic microfields. The Barnes-Hut tree algorithm [J. Barnes and P. Hut, Nature 324, 446 (1986)] was used to speed up calculations of electric potential. Atomic levels were approximated to be independent of the microfields as was assumed in the original paper by Ecker and Kröll [Phys. Fluids 6, 62 (1963)]; however, the available levels were limited by the corresponding mean inter-particle distance. The code was tested on hydrogen and dense aluminum plasmas. The amount of depression was up to 50% higher in the Debye-Hückel regime for hydrogen plasmas, in the high density limit, reasonable agreement was found with the Ecker-Kröll model for hydrogen plasmas and with the Stewart-Pyatt model [J. Stewart and K. Pyatt, Jr., Astrophys. J. 144, 1203 (1966)] for aluminum plasmas. Our 3D code is an improvement over the spherically symmetric simplifications of the Ecker-Kröll and Stewart-Pyatt models and is also not limited to high atomic numbers as is the underlying Thomas-Fermi model used in the Stewart-Pyatt model

The Chemical Potential of Plasma Membrane Cholesterol: Implications for Cell Biology.

Science.gov (United States)

Ayuyan, Artem G; Cohen, Fredric S

2018-02-27

Cholesterol is abundant in plasma membranes and exhibits a variety of interactions throughout the membrane. Chemical potential accounts for thermodynamic consequences of molecular interactions, and quantifies the effective concentration (i.e., activity) of any substance participating in a process. We have developed, to our knowledge, the first method to measure cholesterol chemical potential in plasma membranes. This was accomplished by complexing methyl-β-cyclodextrin with cholesterol in an aqueous solution and equilibrating it with an organic solvent containing dissolved cholesterol. The chemical potential of cholesterol was thereby equalized in the two phases. Because cholesterol is dilute in the organic phase, here activity and concentration were equivalent. This equivalence allowed the amount of cholesterol bound to methyl-β-cyclodextrin to be converted to cholesterol chemical potential. Our method was used to determine the chemical potential of cholesterol in erythrocytes and in plasma membranes of nucleated cells in culture. For erythrocytes, the chemical potential did not vary when the concentration was below a critical value. Above this value, the chemical potential progressively increased with concentration. We used standard cancer lines to characterize cholesterol chemical potential in plasma membranes of nucleated cells. This chemical potential was significantly greater for highly metastatic breast cancer cells than for nonmetastatic breast cancer cells. Chemical potential depended on density of the cancer cells. A method to alter and fix the cholesterol chemical potential to any value (i.e., a cholesterol chemical potential clamp) was also developed. Cholesterol content did not change when cells were clamped for 24-48 h. It was found that the level of activation of the transcription factor STAT3 increased with increasing cholesterol chemical potential. The cholesterol chemical potential may regulate signaling pathways. Copyright © 2018. Published by

Heavy ion beam study of potential formation in bumpy torus plasma

International Nuclear Information System (INIS)

Takasugi, Keiichi.

1985-01-01

A heavy ion beam probe is constructed for the study of plasma confinement in Nagoya Bumpy Torus (NBT-1/1M). The measurement of the local plasma potential as well as the electron density profile is possible with good spatial (1 -- 2 cm) and temporal (-- 1 msec) resolutions. The feedback controlled detection technique and the time resolved fast detection technique are coupled to use, which enables us to measure local potential reliably even in the pulsed experiments. The process of the devlopment of concentric equipotential surface is observed. The cold and collisional plasma in bumpy torus is not in the equilibrium (C-mode), and the vertically polarized potential profile is produced by the toroidal drift. With the growth of warm collisionless electron component, the polarization is poloidally short-circuited, and the concentric equipotential surface is developed. The concentric negative potential well and its positive rim are observed in the standard operation. The position of the potential boundary (rim) moves with the second harmonic ECRH zone at the midplane of each mirror section, where the hot electron ring exists. The rim potential is formed by the direct loss of warm electrons. It is confirmed that the core electron heating is essential for the negative potential formation. The potential depth is much larger than the ion temperature Tsub(i), and cannot be explained by the existing neoclassical theory. A stable positive potential is observed near T-M transition. The positive potential is also observed in the ion heated plasma. Relating to the growth of the high energy component, the potential formation due to direct loss process is discussed. (author)

Plasma technology

International Nuclear Information System (INIS)

Drouet, M.G.

1984-03-01

IREQ was contracted by the Canadian Electrical Association to review plasma technology and assess the potential for application of this technology in Canada. A team of experts in the various aspects of this technology was assembled and each team member was asked to contribute to this report on the applications of plasma pertinent to his or her particular field of expertise. The following areas were examined in detail: iron, steel and strategic-metals production; surface treatment by spraying; welding and cutting; chemical processing; drying; and low-temperature treatment. A large market for the penetration of electricity has been identified. To build up confidence in the technology, support should be provided for selected R and D projects, plasma torch demonstrations at full power, and large-scale plasma process testing

Time evolution of plasma potential in pulsed operation of ECRIS

International Nuclear Information System (INIS)

Tarvainen, O.; Koivisto, H.; Ropponen, T.; Toivanen, V.; Higurashi, Y.; Nakagawa, T.

2012-01-01

The time evolution of plasma potential has been measured with a retarding field analyzer in pulsed operation mode with electron cyclotron resonance ion sources at JYFL and RIKEN. Three different ion sources with microwave frequencies ranging from 6.4 to 18 GHz were employed for the experiments. The plasma potential was observed to increase 10-75 % during the Pre-glow and 10-30 % during the afterglow compared to steady state. The paper is followed by the slides of the presentation. (authors)

Formation and control of plasma potentials in TMX upgrade

Energy Technology Data Exchange (ETDEWEB)

Simonen, T.C.; Orzechowski, T.J.; Porkolab, M.; Stallard, B.W.

1981-05-06

The methods to be employed to form and control plasma potentials in the TMX Upgrade tandem mirror with thermal barriers are described. ECRH-generated mirror -confined electron plasmas are used to establish a negative potential region to isolate the end-plug and central-cell celectrons. This thermal isolation will allow a higher end-plug electron temperature and an increased central-cell confining potential. Improved axial central-cell ion confinement results since higher temperature central-cell ions can be confined. This paper describes: (1) calculations of the sensitivity of barrier formation to vacuum conditions and to the presence of impurities in the neutral beams, (2) calculations of microwave penetration and absorption used to design the ECRH system, and (3) techniques to limit electron runaway to high energies by localized microwave beams and by relativistic detuning.

Formation and control of plasma potentials in TMX upgrade

International Nuclear Information System (INIS)

Simonen, T.C.; Orzechowski, T.J.; Porkolab, M.; Stallard, B.W.

1981-01-01

The methods to be employed to form and control plasma potentials in the TMX Upgrade tandem mirror with thermal barriers are described. ECRH-generated mirror -confined electron plasmas are used to establish a negative potential region to isolate the end-plug and central-cell celectrons. This thermal isolation will allow a higher end-plug electron temperature and an increased central-cell confining potential. Improved axial central-cell ion confinement results since higher temperature central-cell ions can be confined. This paper describes: (1) calculations of the sensitivity of barrier formation to vacuum conditions and to the presence of impurities in the neutral beams, (2) calculations of microwave penetration and absorption used to design the ECRH system, and (3) techniques to limit electron runaway to high energies by localized microwave beams and by relativistic detuning

Plasma potential measurements in the edge region of the ISTTOK plasma, using electron emissive probes

International Nuclear Information System (INIS)

Ionita, C.; Balan, P.; Schrittwieser, R.; Cabral, J.A.; Fernandes, H.; Figueiredo, H. F.C.; Varandas, C.

2001-01-01

We have recently started to use electron-emissive probes for direct measurements of the plasma potential and its fluctuations in the edge region of the plasma ring in the tokamak ISTTOK in Lisbon, Portugal. This method is based on the fact that the electron emission current of such a probe is able to compensate electron temperature variations and electron drifts, which can occur in the edge plasma region of magnetized fusion devices, and which are making measurements with cold probes prone to errors. In this contribution we present some of the first results of our investigations in ISTTOK.(author)

Relaxation of plasma potential and poloidal flows in the boundary of tokamak plasmas

International Nuclear Information System (INIS)

Hron, M.; Duran, I.; Stoeckel, J.; Hidalgo, C.; Gunn, J.

2003-01-01

The relaxation times of plasma parameters after a sudden change of electrode voltage have been measured in the plasma boundary during polarization experiments on the CASTOR tokamak (R = 0.4 m, a = 75 mm, B t = 1 T, I p ∼ 9 kA, q a ∼ 10). The time evolution of the floating potential after the biasing voltage switch-off can be well fitted by an exponential decay with characteristic time in the range of 10 - 20 μs. The poloidal flow shows a transient behaviour with a time scale of about 10 - 30 μs. These time scales are smaller than the expected damping time based on neoclassical parallel viscosity (which is in the range of 100 νs) and atomic physics via charge exchange (in the range of 100 - 1000 νs). But, they are larger than the correlation time of plasma turbulence (about 5 μs). These findings suggest that anomalous damping rate mechanisms for radial electric fields and poloidal flows may play a role in the boundary of tokamak plasmas. (authors)

Molecular Dynamic Studies of Particle Wake Potentials in Plasmas

Science.gov (United States)

Ellis, Ian; Graziani, Frank; Glosli, James; Strozzi, David; Surh, Michael; Richards, David; Decyk, Viktor; Mori, Warren

2010-11-01

Fast Ignition studies require a detailed understanding of electron scattering, stopping, and energy deposition in plasmas with variable values for the number of particles within a Debye sphere. Presently there is disagreement in the literature concerning the proper description of these processes. Developing and validating proper descriptions requires studying the processes using first-principle electrostatic simulations and possibly including magnetic fields. We are using the particle-particle particle-mesh (P^3M) code ddcMD to perform these simulations. As a starting point in our study, we examined the wake of a particle passing through a plasma. In this poster, we compare the wake observed in 3D ddcMD simulations with that predicted by Vlasov theory and those observed in the electrostatic PIC code BEPS where the cell size was reduced to .03λD.

Effective potential kinetic theory for strongly coupled plasmas

Science.gov (United States)

Baalrud, Scott D.; Daligault, Jérôme

2016-11-01

The effective potential theory (EPT) is a recently proposed method for extending traditional plasma kinetic and transport theory into the strongly coupled regime. Validation from experiments and molecular dynamics simulations have shown it to be accurate up to the onset of liquid-like correlation parameters (corresponding to Γ ≃ 10-50 for the one-component plasma, depending on the process of interest). Here, this theory is briefly reviewed along with comparisons between the theory and molecular dynamics simulations for self-diffusivity and viscosity of the one-component plasma. A number of new results are also provided, including calculations of friction coefficients, energy exchange rates, stopping power, and mobility. The theory is also cast in the Landau and Fokker-Planck kinetic forms, which may prove useful for enabling efficient kinetic computations.

Potential formation and confinement in high density plasma on the GAMMA 10 tandem mirror

International Nuclear Information System (INIS)

Yatsu, K.

2002-01-01

After the attainment of doubling of the density due to the potential confinement, GAMMA 10 experiments have been directed to realization of a high density plasma and also to study dependence of the confining potential and confinement time on the plasma density. These problems are important to understand the physics of potential formation in tandem mirrors and also for the development of a tandem mirror reactor. We reported high density plasma production by using an ion cyclotron range of frequency heating at a high harmonic frequency in the last IAEA Conference. However, the diamagnetic signal of the high density plasma decreased when electron cyclotron resonance heating (ECRH) was applied due to some instabilities. Recently, the high density plasma production was much improved by adjusting the spacing of the conducting plates installed in the anchor transition regions, which enabled us to produce a high density plasma without degradation of the diamagnetic signal with ECRH and also to study the density dependence. In this paper we report production of a high density plasma and dependence of the confining potential and the confinement time on the density. (author)

Relaxation of potential, flows, and density in the edge plasma of Castor tokamak

International Nuclear Information System (INIS)

Hron, M.; Weinzettl, V.; Dufkova, E.; Duran, I.; Stoeckel, J.; Hidalgo, C.

2004-01-01

Decay times of plasma flows and plasma profiles have been measured after a sudden biasing switch-off in experiments on the Castor tokamak. A biased electrode has been used to polarize the edge plasma. The edge plasma potential and flows have been characterized by means of Langmuir and Mach probes, the radiation was measured using an array of bolometers. Potential profiles and poloidal flows can be well fitted by an exponential decay time in the range of 10 - 30 μs when the electrode biasing is turned off in the Castor tokamak. The radiation shows a slower time scale (about 1 ms), which is linked to the evolution in the plasma density and particle confinement. (authors)

Circulating plasmablasts/plasma cells: a potential biomarker for IgG4-related disease.

Science.gov (United States)

Lin, Wei; Zhang, Panpan; Chen, Hua; Chen, Yu; Yang, Hongxian; Zheng, Wenjie; Zhang, Xuan; Zhang, Fengxiao; Zhang, Wen; Lipsky, Peter E

2017-02-10

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a multisystem fibroinflammatory disease. We previously reported that a circulating cell population expressing CD19 + CD24 - CD38 hi was increased in patients with IgG4-RD. In this study, we aimed to document that this cell population represented circulating plasmablasts/plasma cells, to identify the detailed phenotype and gene expression profile of these IgG4-secreting plasmablasts/plasma cells, and to determine whether this B-cell lineage subset could be a biomarker in IgG4-related disease (IgG4-RD). A total of 42 untreated patients with IgG4-RD were evaluated. Peripheral B-cell subsets, including CD19 + CD24 - CD38 hi plasmablasts/plasma cells, CD19 + CD24 + CD38 - memory B cells, CD19 + CD24 int CD38 int naïve B cells, and CD19 + CD24 hi CD38 hi regulatory B cells, were assessed and sorted by flow cytometry. Microarray analysis was used to measure gene expression of circulating B-cell lineage subsets. Further characterization of CD19 + CD24 - CD38 hi plasmablasts/plasma cells was carried out by evaluating additional surface markers, including CD27, CD95, and human leukocyte antigen (HLA)-DR, by flow cytometric assay. In addition, various B-cell lineage subsets were cultured in vitro and IgG4 concentrations were measured by cytometric bead array. In untreated patients with IgG4-RD, the peripheral CD19 + CD24 - CD38 hi plasmablast/plasma cell subset was increased and positively correlated with serum IgG4 levels, the number of involved organs, and the IgG4-related Disease Responder Index. It decreased after treatment with glucocorticoids. Characterization of the plasmablast/plasma cell population by gene expression profiling documented a typical plasmablast/plasma cell signature with higher expression of X-box binding protein 1 and IFN regulatory factor 4, but lower expression of paired box gene 5 and B-cell lymphoma 6 protein. In addition, CD27, CD95, and HLA-DR were highly expressed on CD19 + CD24 - CD38 hi

Time resolved measurements of plasma potential across an anode double layer

International Nuclear Information System (INIS)

Pohoata, V.; Popa, Gh.; Schrittwieser, R.; Ionita, Codrina

2002-01-01

Experimental results are presented on self-sustained oscillations produced by the dynamics of an anode double layer or fireball in a DP-machine. By additional ionisation processes the fireball is formed in front of an additional small plane anode inserted in the diffusive plasma. An annular (ring) electrode surrounds the anode. The thickness of the ion sheath in front of this ring affects the anode current by controlling its effective diameter during the fireball oscillations. The ring potential controls first the oscillation frequency of the anode current, but also other characteristics of the instability. The ring potential was chosen as a pulsed one so that only single anode double layer instability can be excited. The ring signal was used for triggering the data acquisition system. The spatial distribution of the plasma potential in front of the anode is presented as a time resolved measurement one. A negative drop potential was found that controls the charge flux particle across the double layer. Also the plasma density inside the fireball relaxes during the disrupting time controlled by ambipolar diffusion and also by the negative potential drop. (authors)

Holographic quark–antiquark potential in hot, anisotropic Yang–Mills plasma

International Nuclear Information System (INIS)

Chakraborty, Somdeb; Haque, Najmul

2013-01-01

Using the gauge/gravity duality we calculate the heavy quark–antiquark potential in a hot, anisotropic and strongly coupled Yang–Mills plasma in (3+1)-dimensions. As the anisotropic medium we take a deformed version of N=4 super Yang–Mills theory at finite temperature following a recent work where the dual type IIB supergravity solution is also proposed. We turn on a small value of the anisotropy parameter, for which the gravity dual is known analytically (perturbatively), and compute the velocity-dependent quark–antiquark interaction potential when the pair is moving through the plasma with a velocity v. By setting v=0 we recover the static quark–antiquark potential. We numerically study how the potential is modified in the presence of anisotropy. We further show numerically how the quark–antiquark separation (both in the static and the velocity-dependent case) and hence, the screening length gets modified by anisotropy. We discuss various cases depending upon the direction of the dipole and the direction of its propagation and make a comparative study of these cases. We are also able to obtain an analytical expression for the screening length of the dipole moving in a hot, anisotropic plasma in a special case

Potential Formation in Front of an Electron Emitting Electrode in a Two-Electron Temperature Plasma

International Nuclear Information System (INIS)

Gyergyek, T.; Cercek, M.; Erzen, D.

2003-01-01

Plasma potential formation in the pre-sheath region of a floating electron emitting electrode (collector) is studied theoretically in a two-electron-temperature plasma using a static kinetic plasma-sheath model. Dependence of the collector floating potential, the plasma potential in the pre-sheath region, and the critical emission coefficient on the hot electron density and temperature is calculated. It is found that for high hot to cool electron temperature ratio a double layer like solutions exist in a certain range of hot to cool electron densities

Potential and electron density calculated for freely expanding plasma by an electron beam

International Nuclear Information System (INIS)

Ho, C. Y.; Tsai, Y. H.; Ma, C.; Wen, M. Y.

2011-01-01

This paper investigates the radial distributions of potential and electron density in free expansion plasma induced by an electron beam irradiating on the plate. The region of plasma production is assumed to be cylindrical, and the plasma expansion is assumed to be from a cylindrical source. Therefore, the one-dimensional model in cylindrical coordinates is employed in order to analyze the radial distributions of the potential and electron density. The Runge-Kutta method and the perturbation method are utilized in order to obtain the numerical and approximate solutions, respectively. The results reveal that the decrease in the initial ion energy makes most of the ions gather near the plasma production region and reduces the distribution of the average positive potential, electron, and ion density along the radial direction. The oscillation of steady-state plasma along the radial direction is also presented in this paper. The ions induce a larger amplitude of oscillation along the radial direction than do electrons because the electrons oscillate around slowly moving ions due to a far smaller electron mass than ion mass. The radial distributions of the positive potential and electron density predicted from this study are compared with the available experimental data.

Estimate of electrical potential difference between plasmas with different degrees of ionization

Energy Technology Data Exchange (ETDEWEB)

Chang, Chong [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-01-12

The electrical potential difference has been estimated across the mixing region of two plasmas with different degrees of ionization. The estimation has been carried out in two different contexts of a charge neutral mixing region and a charge non-neutral sheath. Ion energy gained due to the potential difference has also been estimated. In both analyses, ion energy gain is proportional to the degree of ionization, and a fairly large ionization appears to be needed for overcoming the potential energy barrier of strongly coupled plasmas.

Plasma-potential diagnostic (PPD) hardware used on the Tandem Mirror Experiment-Upgrade (TMX-U)

International Nuclear Information System (INIS)

Steele, D.L.; Hornady, R.S.; Stever, R.D.; Coutts, G.W.; Nelson, D.H.

1985-01-01

The PPD is an instrument used to indirectly measure the potential of the center-cell plasma of TMX-U. Thallium ions are injected at energies of about 60 keV from an ion gun capable of 80 kV operation. The singly charged ions collide with plasma electrons and generate double-charged ions. Ions in the higher charge state exit the plasma and are detected in an electrostatic energy analyzer. From measurements of the injected ion energy and the output ion energy one can determine the plasma potential in the ionization region. The absolute potential measurements required careful calibrations of the energy analyzer. Hardware and techniques for calibration of the energy analyzer are discussed. 2 refs., 4 figs

Study of single and binary ion plasma expansion into laboratory-generated plasma wakes

International Nuclear Information System (INIS)

Wright, K.H. Jr.

1988-02-01

Plasma expansion into the wake of a large rectangular plate immersed in a collisionless, supersonic plasma was investigated in laboratory experiments. The experimental conditions address both single ion and binary ion plasma flows for the case of a body whose size is large in comparison with the Debye length, when the potential difference between the body and the plasma is relatively small. A new plasma source was developed to generate equi-velocity, binary ion plasma flows, which allows access to new parameter space that have previously been unavailable for laboratory studies. Specifically, the new parameters are the ionic mass ratio and the ionic component density ratio. In a series of experiments, a krypton-neon plasma is employed where the ambient density ratio of neon to krypton is varied more than an order of magnitude. The expansion in both the single ion and binary ion plasma cases is limited to early times, i.e., a few ion plasma periods, by the combination of plasma density, plasma drift speed, and vacuum chamber size, which prevented detailed comparison with self-similar theory

Shaping thin film growth and microstructure pathways via plasma and deposition energy: a detailed theoretical, computational and experimental analysis.

Science.gov (United States)

Sahu, Bibhuti Bhusan; Han, Jeon Geon; Kersten, Holger

2017-02-15

Understanding the science and engineering of thin films using plasma assisted deposition methods with controlled growth and microstructure is a key issue in modern nanotechnology, impacting both fundamental research and technological applications. Different plasma parameters like electrons, ions, radical species and neutrals play a critical role in nucleation and growth and the corresponding film microstructure as well as plasma-induced surface chemistry. The film microstructure is also closely associated with deposition energy which is controlled by electrons, ions, radical species and activated neutrals. The integrated studies on the fundamental physical properties that govern the plasmas seek to determine their structure and modification capabilities under specific experimental conditions. There is a requirement for identification, determination, and quantification of the surface activity of the species in the plasma. Here, we report a detailed study of hydrogenated amorphous and crystalline silicon (c-Si:H) processes to investigate the evolution of plasma parameters using a theoretical model. The deposition processes undertaken using a plasma enhanced chemical vapor deposition method are characterized by a reactive mixture of hydrogen and silane. Later, various contributions of energy fluxes on the substrate are considered and modeled to investigate their role in the growth of the microstructure of the deposited film. Numerous plasma diagnostic tools are used to compare the experimental data with the theoretical results. The film growth and microstructure are evaluated in light of deposition energy flux under different operating conditions.

Heavy ion beam probe investigations of plasma potential in ECRH and NBI in the TJ-II stellarator

International Nuclear Information System (INIS)

Melnikov, A.V.; Eliseev, L.; Perfilov, S.V.; Chmyga, A.A.; Dreval, N.; Khrebtov, S.M.; Komarov, A.D.; Kozachok, A.S.; Krupnik, L.; Alonso, A.; Pablos, J.L. de; Cappa, A.; Fernandez, A.; Fuentes, C.; Hidalgo, C.; Liniers, M.; Pedrosa, M.A.

2005-01-01

Direct measurements of electric potential and its fluctuations are of a primary importance in magnetic confinement systems. The Heavy Ion Beam Probe (HIBP) diagnostic is used in TJ-2 stellarator to study directly plasma electric potential profiles with spatial (up to 1cm) and temporal (up to 10 ∝s) resolution. The singly charged heavy ions Cs + with energies up to 125 keV are used to probe the plasma column from the edge to the core. Both ECRH and NBI heated plasmas (P ECRH = 200 - 400kW, P NBI = 400kW, E NBI = 28 kV) were studied. The significant improvement in the HIBP beam control system and the acquisition electronics leads us to increase the possibilities of the diagnostic. The most crucial one is the extension of the signal dynamic range, which allows us to have the reliable profiles from the plasma center to the plasma edge both in the high and low field side regions. Low density ECRH (n = 0.5-1.1.10 13 cm -3 ) plasmas in TJ-2 are characterised by core positive plasma potential of order of 500 - 1000 V and positive electric fields up to 50 V/cm. Edge radial electric fields remain positive at low densities and became negative at the threshold density that depends of plasma configuration. NBI plasmas are characterized by negative electric potential in the full plasma column and negative radial electric fields (in the range of 10 - 40 V/cm). The density rise during the NBI phase is accompanied by the decay of core plasma potential. When density is getting the level of n ∼ 2.0.10 13 cm -3 , the potential stops its evolution and remains constant. The evolution of plasma potential near density limit is under investigation. These observations, reported in different magnetic configurations, show the clear link between plasma potential and plasma density. (author)

Plasma kinetics issues in an ESA study for a plasma laboratory in space

International Nuclear Information System (INIS)

Annaratone, B M; Biancalani, A; Ceccherini, F; Pegoraro, F; Bruno, D; Capitelli, M; Pascale, O de; Longo, S; Daly, E; Hilgers, A; Diomede, P; D'Ammando, G; Marcuccio, S; Mendonca, J T; Nagnibeda, V; Sanmartin, J R

2008-01-01

A study supported by the European Space Agency (ESA), in the context of its General Studies Programme, performed an investigation of the possible use of space for studies in pure and applied plasma physics, in areas not traditionally covered by 'space plasma physics'. A set of experiments have been identified that can potentially provide access to new phenomena and to allow advances in several fields of plasma science. These experiments concern phenomena on a spatial scale (10 1 -10 4 m) intermediate between what is achievable on the ground and the usual solar system plasma observations. Detailed feasibility studies have been performed for three experiments: active magnetic experiments, large-scale discharges and long tether-plasma interactions. The perspectives opened by these experiments are discussed for magnetic reconnection, instabilities, MHD turbulence, atomic excited states kinetics, weakly ionized plasmas, plasma diagnostics, artificial auroras and atmospheric studies. The discussion is also supported by results of numerical simulations and estimates

Interpretation of fast measurements of plasma potential, temperature and density in SOL of ASDEX Upgrade

DEFF Research Database (Denmark)

Horacek, J.; Adamek, J.; Müller, H.W.

2010-01-01

This paper focuses on interpretation of fast (1 µs) and local (2–4 mm) measurements of plasma density, potential and electron temperature in the edge plasma of tokamak ASDEX Upgrade. Steady-state radial profiles demonstrate the credibility of the ball-pen probe. We demonstrate that floating...... potential fluctuations measured by a Langmuir probe are dominated by plasma electron temperature rather than potential. Spatial and temporal scales are found consistent with expectations based on interchange-driven turbulence. Conditionally averaged signals found for both potential and density are also...

The potential around a test charge in magnetized dusty plasmas

International Nuclear Information System (INIS)

Shukla, P.K.; Salimullah, M.

1996-01-01

The potential of a test dust particle in a magnetized dusty plasma is calculated, taking into account the dielectric constant associated with electrostatic ion-cyclotron waves. Besides the well-known Debye-Hueckel screening potential, an oscillatory potential distribution around a test dust particle is found, which strongly depends on the strength of the external magnetic field. copyright 1996 American Institute of Physics

Plane and hemispherical potential structures in magnetically expanding plasmas

International Nuclear Information System (INIS)

Takahashi, Kazunori; Igarashi, Yuichi; Fujiwara, Tamiya

2010-01-01

Two-dimensional potential structures are measured for different gas pressure in expanding argon plasma using permanent magnets, where the magnetic field is about 100 G in the source and several gauss in the diffusion chamber. The plane potential drop is observed near the source exit for 0.35 mTorr, while the potential structure becomes hemispherical when increasing up to 1 mTorr; the hemispherical structure results in the radial divergence of the ion beam. It is found that the trajectories of the accelerated ions and the electrons overcoming the potential drop are dominated by the potential structure and magnetic-field lines, respectively.

A direct indication of plasma potential diagnostic with fast time response and high accuracy based on a differential emissive probe

International Nuclear Information System (INIS)

Yao, W.E.; Hershkowitz; Intrator, T.

1985-01-01

The floating potential of the emissive probe has been used to directly measure the plasma potential. The authors have recently presented another method for directly indicating the plasma potential with a differential emissive probe. In this paper they describe the effects of probe size, plasma density and plasma potential fluctuation on plasma potential measurements and give methods for reducing errors. A control system with fast time response (α 20 μs) and high accuracy (the order of the probe temperature T/sub w//e) for maintaining a differential emissive probe at plasma potential has been developed. It can be operated in pulsed discharge plasma to measure plasma potential dynamic characteristics. A solid state optical coupler is employed to improve circuit performance. This system was tested experimentally by measuring the plasma potential in an argon plasma device an on the Phaedrus tandem mirror

A direct indication of plasma potential diagnostic with fast time response and high accuracy based on a differential emissive probe

International Nuclear Information System (INIS)

Yao, W.E.; Hershkowitz, N.; Intrator, T.

1985-01-01

The floating potential of the emissive probe has been used to directly measure the plasma potential. The authors have recently presented another method for directly indicating the plasma potential with a differential emissive probe. In this paper they describe the effects of probe size, plasma density and plasma potential fluctuation on plasma potential measurements and give methods for reducing errors. A control system with fast time response (≅ 20 μs) and high accuracy (the order of the probe temperature T/sub w//e) for maintaining a differential emissive probe at plasma potential has been developed. It can be operated in pulsed discharge plasma to measure plasma potential dynamic characteristics. A solid state optical coupler is employed to improve circuit performance. This system was tested experimentally by measuring the plasma potential in an argon plasma device and on the Phaedrus tandem mirror

A study of the potential of plasma processing in the chemical industry

International Nuclear Information System (INIS)

Estey, P.N.; Connolly, T.J.

1984-01-01

This work describes a systematic approach to determine the potential for plasma processing in the United States chemical industry. A model was developed that describes the physical inputs and outputs from a plasma based processing system. Based on these mass flows and the energy flows to the processor an economic assessment of the plasma processing system is made. This economic assessment which also includes the capital costs of the processor, can be used to determine if the plasma system is competitive with the conventional system

A study of single and binary ion plasma expansion into laboratory-generated plasma wakes

Science.gov (United States)

Wright, Kenneth Herbert, Jr.

1988-01-01

Plasma expansion into the wake of a large rectangular plate immersed in a collisionless, supersonic plasma was investigated in laboratory experiments. The experimental conditions address both single ion and binary ion plasma flows for the case of a body whose size is large in comparison with the Debye length, when the potential difference between the body and the plasma is relatively small. A new plasma source was developed to generate equi-velocity, binary ion plasma flows, which allows access to new parameter space that have previously been unavailable for laboratory studies. Specifically, the new parameters are the ionic mass ratio and the ionic component density ratio. In a series of experiments, a krypton-neon plasma is employed where the ambient density ratio of neon to krypton is varied more than an order of magnitude. The expansion in both the single ion and binary ion plasma cases is limited to early times, i.e., a few ion plasma periods, by the combination of plasma density, plasma drift speed, and vacuum chamber size, which prevented detailed comparison with self-similar theory.

Electroreflectance and the problem of studying plasma-surface interactions

International Nuclear Information System (INIS)

Preppernau, B.L.

1995-01-01

A long standing problem in low-temperature plasma discharge physics is to understand in detail the mutual interaction of real exposed surfaces (electrodes) with the reactive plasma environment. In particular, one wishes to discern the influence of these surfaces on the plasma parameters given their contributions from secondary electrons and ions. This paper briefly reviews the known surface interaction processes as well as currently available diagnostics to study the interface between plasmas and surfaces. Next comes a discussion describing the application of plasma-modulated electroreflectance to this research and some potential experimental techniques

Effect of confining wall potential on charged collimated dust beam in low-pressure plasma

International Nuclear Information System (INIS)

Kausik, S. S.; Kakati, B.; Saikia, B. K.

2013-01-01

The effect of confining wall potential on charged collimated dust beam in low-pressure plasma has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. Argon plasma is produced by hot cathode discharge method at a pressure of 5×10 −4 millibars and is confined by a full line cusped magnetic field confinement system. Silver dust grains are produced by gas-evaporation technique and move upward in the form of a collimated dust beam due to differential pressure maintained between the dust and plasma chambers. The charged grains in the beam after coming out from the plasma column enter into the diagnostic chamber and are deflected by a dc field applied across a pair of deflector plates at different confining potentials. Both from the amount of deflection and the floating potential, the number of charges collected by the dust grains is calculated. Furthermore, the collimated dust beam strikes the Faraday cup, which is placed above the deflector plates, and the current (∼pA) so produced is measured by an electrometer at different confining potentials. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains

Effect of confining wall potential on charged collimated dust beam in low-pressure plasma

Energy Technology Data Exchange (ETDEWEB)

Kausik, S. S.; Kakati, B.; Saikia, B. K. [Centre of Plasma Physics, Institute for Plasma Research, Sonapur 782 402 (India)

2013-05-15

The effect of confining wall potential on charged collimated dust beam in low-pressure plasma has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. Argon plasma is produced by hot cathode discharge method at a pressure of 5×10{sup −4} millibars and is confined by a full line cusped magnetic field confinement system. Silver dust grains are produced by gas-evaporation technique and move upward in the form of a collimated dust beam due to differential pressure maintained between the dust and plasma chambers. The charged grains in the beam after coming out from the plasma column enter into the diagnostic chamber and are deflected by a dc field applied across a pair of deflector plates at different confining potentials. Both from the amount of deflection and the floating potential, the number of charges collected by the dust grains is calculated. Furthermore, the collimated dust beam strikes the Faraday cup, which is placed above the deflector plates, and the current (∼pA) so produced is measured by an electrometer at different confining potentials. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains.

Effect of confining wall potential on charged collimated dust beam in low-pressure plasma

Science.gov (United States)

Kausik, S. S.; Kakati, B.; Saikia, B. K.

2013-05-01

The effect of confining wall potential on charged collimated dust beam in low-pressure plasma has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. Argon plasma is produced by hot cathode discharge method at a pressure of 5×10-4 millibars and is confined by a full line cusped magnetic field confinement system. Silver dust grains are produced by gas-evaporation technique and move upward in the form of a collimated dust beam due to differential pressure maintained between the dust and plasma chambers. The charged grains in the beam after coming out from the plasma column enter into the diagnostic chamber and are deflected by a dc field applied across a pair of deflector plates at different confining potentials. Both from the amount of deflection and the floating potential, the number of charges collected by the dust grains is calculated. Furthermore, the collimated dust beam strikes the Faraday cup, which is placed above the deflector plates, and the current (˜pA) so produced is measured by an electrometer at different confining potentials. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains.

Computer simulations of plasma-biomolecule and plasma-tissue interactions for a better insight in plasma medicine

Science.gov (United States)

Neyts, Erik C.; Yusupov, Maksudbek; Verlackt, Christof C.; Bogaerts, Annemie

2014-07-01

Plasma medicine is a rapidly evolving multidisciplinary field at the intersection of chemistry, biochemistry, physics, biology, medicine and bioengineering. It holds great potential in medical, health care, dentistry, surgical, food treatment and other applications. This multidisciplinary nature and variety of possible applications come along with an inherent and intrinsic complexity. Advancing plasma medicine to the stage that it becomes an everyday tool in its respective fields requires a fundamental understanding of the basic processes, which is lacking so far. However, some major advances have already been made through detailed experiments over the last 15 years. Complementary, computer simulations may provide insight that is difficult—if not impossible—to obtain through experiments. In this review, we aim to provide an overview of the various simulations that have been carried out in the context of plasma medicine so far, or that are relevant for plasma medicine. We focus our attention mostly on atomistic simulations dealing with plasma-biomolecule interactions. We also provide a perspective and tentative list of opportunities for future modelling studies that are likely to further advance the field.

Plasma-potentiated small molecules—possible alternative to antibiotics?

Science.gov (United States)

Bazaka, Kateryna; Bazaka, Olha; Levchenko, Igor; Xu, Shuyan; Ivanova, Elena P.; Keidar, Michael; (Ken Ostrikov, Kostya

2017-09-01

The efficacy of the existing arsenal of antibiotics is continuously compromised by their indiscriminative and often excessive use. The antibiotic arsenal can be expanded with agents that have different mechanisms of activity to conventional drugs, such as plant-derived natural antimicrobial small molecules, yet these often lack sufficient activity and selectivity to fulfill the antibiotics requirements and conventional thermochemical methods of their transient activation may not be compatible with biomedical applications. Here, non-equilibrium conditions of atmospheric-pressure plasma are used for rapid, single-step potentiation of activity of select terpenes without the use of chemicals or heating. Substantial potentiation of activity against Staphylococcus aureus cells in planktonic and biofilm states is observed in both inherently antibacterial terpenes, e.g. terpinen-4-ol, and compounds generally considered to have limited effect against S. aureus, e.g. γ-terpinene. The improved biological activity may arise, at least in part, from the changes in the physico-chemical properties of the terpenes induced by plasma-generated chemical species and physical effects, such as electric fields and UV irradiation. This activation approach is generic, and thus can potentially be applied to other molecules and their mixtures in an effort to expand the range of effective antimicrobial agents for deactivation of pathogenic organisms in hygiene, medical and food applications.

The vacuum-arc plasma motion in a toroidal magnetic field

International Nuclear Information System (INIS)

Timoshenko, A.I.; Gnybida, M.V.; Taran, V.S.; Tereshin, V.I.; Chechelnitskij, O.G.

2005-01-01

The separation of the vacuum-arc plasma from macro-particles in the curvilinear plasma filters allows obtaining coatings with especially high characteristics. However, inside such filters the significant plasma losses also have been occurred. At the same time, increasing in the filter's efficiency is a difficult task without an effective mathematical model that really would describe the vacuum-arc plasma motion in a toroidal magnetic field. The description based on the flax-tube model was in fact only the first approximation in the decision of this problem. According to detailed flax-tube analysis of ions passage through the quarter torus plasma guide, the efficiency of the filter should grow up to 85% as the positive potential U, applied to the body of the plasma guide, is on the increase. However, the experiment showed that maximum of transparency reach up to ∼ 12%, at potential about of +18 Volts, and comes down under the further increase in potential. Such big digression from experiment does not justify the use of flux-tube model for designing of curvilinear plasma filters. We offer the new approach to the description of the vacuum-arc plasma motion in a toroidal magnetic field based on the solutions of steady-state (∂/∂t=0) Vlasov-Maxwell equations for the long plasma column aligned parallel to a constant axial magnetic field. The relations for the self-consistent electric polarization fields, which appear due to displacement of the electron component from ionic one on the curvilinear part of motion, were derived within a framework of the drift approximation. The dynamics of the central part of the plasma flow in the electric polarization fields was considered in detail. The displacement of the plasma flow at the output of the plasma guide was calculated for the carbon and titanium plasmas. The good agreement with the experimental data was obtained. (author)

Mode suppression of a two-dimensional potential relaxation instability in a weakly magnetized discharge plasma

Science.gov (United States)

Gyergyek, T.; Čerček, M.; Jelić, N.; Stanojević, M.

1993-05-01

A potential relaxation instability (PRI) is modulated by an external signal using an additional grid to modulate the radial plasma potential profile in a magnetized plasma column in a linear magnetized discharge plasma device. It is observed that the electrode current oscillations follow the van der Pol equation with an external forcing term, and the linear growth rate of the instability is measured.

Measurement of plasma potential and electron temperature by ball-pen probes in RFX-MOD

International Nuclear Information System (INIS)

Brotankova, J.; Adamek, J.; Stockel, J.; Martines, E.; Spolaore, M.; Cavazzana, R.; Serianni, G.; Vianello, N.; Zuin, M.

2009-01-01

The ball-pen probe (BPP) is an innovative electric probe for direct measurements of the plasma potential. This probe was developed in IPP Prague and it is based on the Katsumata probe concept. Combined measurements of the plasma potential by a BPP and floating potential by a Langmuir probe provide also the value of the electron temperature. First test of the BPP on the RFX-mod reversed field pinch in Padova has been performed in November 2006. The BPP head, made of boron nitride, is equipped with four graphite collectors, which are positioned at four different radial positions h inside four shafts hollow into the probe head. The radial profile of the plasma potential and also the electron temperature were measured

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)

Direct measurement of the plasma potential in the edge of ASDEX Upgrade using a self emitting probe

International Nuclear Information System (INIS)

Rohde, V.; Laux, M.; Bachmann, P.; Herrmann, A.; Weinlich, M.

1997-01-01

In this paper we present first measurements of the plasma potential close to the separatrix in ASDEX Upgrade using a self emitting tip. The probe was inserted into the edge plasma of AUG using the midplane manipulator. Assuming Maxwellian plasmas, the observations agree with the predicted voltage drop in the plasma sheath, V pl ps -V fl =2.5T e , where V pl ps is the plasma potential at the presheath boundary and V fl the floating potential. Applying this technique a rapid change of the plasma potential was observed close to the separatrix during Ohmic discharges. From the gradient we derive a radial electric field E r of about -5 kV/m close to separatrix. Further out the field strength changes sign and we find up to +7 kV/m in the SOL. (orig.)

Ionization potential depression and optical spectra in a Debye plasma model

Science.gov (United States)

Lin, Chengliang; Röpke, Gerd; Reinholz, Heidi; Kraeft, Wolf-Dietrich

2017-11-01

We show how optical spectra in dense plasmas are determined by the shift of energy levels as well as the broadening owing to collisions with the plasma particles. In lowest approximation, the interaction with the plasma particles is described by the RPA dielectric function, leading to the Debye shift of the continuum edge. The bound states remain nearly un-shifted, their broadening is calculated in Born approximation. The role of ionization potential depression as well as the Inglis-Teller effect are shown. The model calculations have to be improved going beyond the lowest (RPA) approximation when applying to WDM spectra.

Automatic emissive probe apparatus for accurate plasma and vacuum space potential measurements

Science.gov (United States)

Jianquan, LI; Wenqi, LU; Jun, XU; Fei, GAO; Younian, WANG

2018-02-01

We have developed an automatic emissive probe apparatus based on the improved inflection point method of the emissive probe for accurate measurements of both plasma potential and vacuum space potential. The apparatus consists of a computer controlled data acquisition card, a working circuit composed by a biasing unit and a heating unit, as well as an emissive probe. With the set parameters of the probe scanning bias, the probe heating current and the fitting range, the apparatus can automatically execute the improved inflection point method and give the measured result. The validity of the automatic emissive probe apparatus is demonstrated in a test measurement of vacuum potential distribution between two parallel plates, showing an excellent accuracy of 0.1 V. Plasma potential was also measured, exhibiting high efficiency and convenient use of the apparatus for space potential measurements.

Electron cooling and finite potential drop in a magnetized plasma expansion

Energy Technology Data Exchange (ETDEWEB)

Martinez-Sanchez, M. [Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Navarro-Cavallé, J. [Escuela Técnica Superior de Ingeniería Aeronáutica y del Espacio, Universidad Politécnica de Madrid, Plaza Cardenal Cisneros 3, Madrid 28040 (Spain); Ahedo, E. [Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III de Madrid, Avda. Universidad 30, Leganés 28911, Madrid (Spain)

2015-05-15

The steady, collisionless, slender flow of a magnetized plasma into a surrounding vacuum is considered. The ion component is modeled as mono-energetic, while electrons are assumed Maxwellian upstream. The magnetic field has a convergent-divergent geometry, and attention is restricted to its paraxial region, so that 2D and drift effects are ignored. By using the conservation of energy and magnetic moment of particles and the quasi-neutrality condition, the ambipolar electric field and the distribution functions of both species are calculated self-consistently, paying attention to the existence of effective potential barriers associated to magnetic mirroring. The solution is used to find the total potential drop for a set of upstream conditions, plus the axial evolution of various moments of interest (density, temperatures, and heat fluxes). The results illuminate the behavior of magnetic nozzles, plasma jets, and other configurations of interest, showing, in particular, in the divergent plasma the collisionless cooling of electrons, and the generation of collisionless electron heat fluxes.

Ionization potential depression in an atomic-solid-plasma picture

Science.gov (United States)

Rosmej, F. B.

2018-05-01

Exotic solid density matter such as heated hollow crystals allow extended material studies while their physical properties and models such as the famous ionization potential depression are presently under renewed controversial discussion. Here we develop an atomic-solid-plasma (ASP) model that permits ionization potential depression studies also for single and multiple core hole states. Numerical calculations show very good agreement with recently available data not only in absolute values but also for Z-scaled properties while currently employed methods fail. For much above solid density compression, the ASP model predicts increased K-edge energies that are related to a Fermi surface rising. This is in good agreement with recent quantum molecular dynamics simulations. For hot dense matter a quantum number dependent optical electron finite temperature ion sphere model is developed that fits well with line shift and line disappearance data from dense laser produced plasma experiments. Finally, the physical transparency of the ASP picture allows a critical discussion of current methods.

Detailed-term-accounting approximation calculations of the radiative opacity of aluminum plasmas: A systematic study

International Nuclear Information System (INIS)

Zeng Jiaolong; Yuan Jianmin

2002-01-01

The spectrally resolved radiative opacity and the Rosseland and Planck mean opacities are calculated by using the detailed-term-accounting approximation for aluminum plasmas with varieties of density and temperature. The results are presented along a 40 eV isothermal sequence, a 0.01 g/cm 3 isodense sequence, and a sequence with average ionization degree Z*∼7.13. Particular attention is given to the influence of the detailed treatment of spectral lines on the Rosseland mean opacity under different thermodynamical conditions. The results show that at densities of 0.004 g/cm 3 and higher, the opacities are not very sensitive to the spectral linewidth within a reasonable range. As examples, the Rosseland mean opacity, which is most sensitive to the detailed linewidth, at 40 eV and 0.004 g/cm 3 changes no more than 15%, when we change the electron impact spectral linewidth artificially by reducing it by 50% or increasing it twice, and at 40 eV and 0.1 g/cm 3 it changes less than 5%. For comparison, we also carried out calculations by using an average atom model. For the Rosseland mean opacities, the two models show quite large differences, in particular at low densities, while for the Planck mean opacities the results of the two models are much closer

Investigation of tenuous plasma environment using Active Spacecraft Potential Control (ASPOC) on Magnetospheric Multiscale (MMS) Mission

Science.gov (United States)

Nakamura, Rumi; Jeszenszky, Harald; Torkar, Klaus; Andriopoulou, Maria; Fremuth, Gerhard; Taijmar, Martin; Scharlemann, Carsten; Svenes, Knut; Escoubet, Philippe; Prattes, Gustav; Laky, Gunter; Giner, Franz; Hoelzl, Bernhard

2015-04-01

The NASA's Magnetospheric Multiscale (MMS) Mission is planned to be launched on March 12, 2015. The scientific objectives of the MMS mission are to explore and understand the fundamental plasma physics processes of magnetic reconnection, particle acceleration and turbulence in the Earth's magnetosphere. The region of scientific interest of MMS is in a tenuous plasma environment where the positive spacecraft potential reaches an equilibrium at several tens of Volts. An Active Spacecraft Potential Control (ASPOC) instrument neutralizes the spacecraft potential by releasing positive charge produced by indium ion emitters. ASPOC thereby reduces the potential in order to improve the electric field and low-energy particle measurement. The method has been successfully applied on other spacecraft such as Cluster and Double Star. Two ASPOC units are present on each of the MMS spacecraft. Each unit contains four ion emitters, whereby one emitter per instrument is operated at a time. ASPOC for MMS includes new developments in the design of the emitters and the electronics enabling lower spacecraft potentials, higher reliability, and a more uniform potential structure in the spacecraft's sheath compared to previous missions. Model calculations confirm the findings from previous applications that the plasma measurements will not be affected by the beam's space charge. A perfectly stable spacecraft potential precludes the utilization of the spacecraft as a plasma probe, which is a conventional technique used to estimate ambient plasma density from the spacecraft potential. The small residual variations of the potential controlled by ASPOC, however, still allow to determine ambient plasma density by comparing two closely separated spacecraft and thereby reconstructing the uncontrolled potential variation from the controlled potential. Regular intercalibration of controlled and uncontrolled potentials is expected to increase the reliability of this new method.

Plasma heating

International Nuclear Information System (INIS)

Wilhelm, R.

1989-01-01

Successful plasma heating is essential in present fusion experiments, for the demonstration of DpT burn in future devices and finally for the fusion reactor itself. This paper discusses the common heating systems with respect to their present performance and their applicability to future fusion devices. The comparative discussion is oriented to the various function of heating, which are: - plasma heating to fusion-relevant parameters and to ignition in future machines, -non-inductive, steady-pstate current drive, - plasma profile control, -neutral gas breakdown and plasma build-up. In view of these different functions, the potential of neutral beam injection (NBI) and the various schemes of wave heating (ECRH, LH, ICRH and Alven wave heating) is analyzed in more detail. The analysis includes assessments of the present physical and technical state of these heating methods, and makes suggestions for future developments and about outstanding problems. Specific attention is given to the still critical problem of efficient current drive, especially with respect to further extrapolation towards an economically operating tokamak reactor. Remarks on issues such as reliability, maintenance and economy conclude this comparative overview on plasma heating systems. (author). 43 refs.; 13 figs.; 3 tabs

Response of the plasma to the size of an anode electrode biased near the plasma potential

International Nuclear Information System (INIS)

Barnat, E. V.; Laity, G. R.; Baalrud, S. D.

2014-01-01

As the size of a positively biased electrode increases, the nature of the interface formed between the electrode and the host plasma undergoes a transition from an electron-rich structure (electron sheath) to an intermediate structure containing both ion and electron rich regions (double layer) and ultimately forms an electron-depleted structure (ion sheath). In this study, measurements are performed to further test how the size of an electron-collecting electrode impacts the plasma discharge the electrode is immersed in. This is accomplished using a segmented disk electrode in which individual segments are individually biased to change the effective surface area of the anode. Measurements of bulk plasma parameters such as the collected current density, plasma potential, electron density, electron temperature and optical emission are made as both the size and the bias placed on the electrode are varied. Abrupt transitions in the plasma parameters resulting from changing the electrode surface area are identified in both argon and helium discharges and are compared to the interface transitions predicted by global current balance [S. D. Baalrud, N. Hershkowitz, and B. Longmier, Phys. Plasmas 14, 042109 (2007)]. While the size-dependent transitions in argon agree, the size-dependent transitions observed in helium systematically occur at lower electrode sizes than those nominally derived from prediction. The discrepancy in helium is anticipated to be caused by the finite size of the interface that increases the effective area offered to the plasma for electron loss to the electrode

Quantum-Mechanical Calculation of Ionization-Potential Lowering in Dense Plasmas

Directory of Open Access Journals (Sweden)

Sang-Kil Son (손상길

2014-07-01

Full Text Available The charged environment within a dense plasma leads to the phenomenon of ionization-potential depression (IPD for ions embedded in the plasma. Accurate predictions of the IPD effect are of crucial importance for modeling atomic processes occurring within dense plasmas. Several theoretical models have been developed to describe the IPD effect, with frequently discrepant predictions. Only recently, first experiments on IPD in Al plasma have been performed with an x-ray free-electron laser, where their results were found to be in disagreement with the widely used IPD model by Stewart and Pyatt. Another experiment on Al, at the Orion laser, showed disagreement with the model by Ecker and Kröll. This controversy shows a strong need for a rigorous and consistent theoretical approach to calculate the IPD effect. Here, we propose such an approach: a two-step Hartree-Fock-Slater model. With this parameter-free model, we can accurately and efficiently describe the experimental Al data and validate the accuracy of standard IPD models. Our model can be a useful tool for calculating atomic properties within dense plasmas with wide-ranging applications to studies on warm dense matter, shock experiments, planetary science, inertial confinement fusion, and nonequilibrium plasmas created with x-ray free-electron lasers.

Potentials of fissioning plasmas

International Nuclear Information System (INIS)

Karlheinz, Thom.

1979-01-01

Successful experiments with the nuclear pumping of lasers have demonstrated that in gaseous medium the kinetic energy of fission fragments can be converted directly into non-equilibrium optical radiation. This confirms the concept that the fissioning medium in a gas-phase nuclear reactor shows an internal structure such as a plasma in nearly thermal equilibrium varying up to a state of extreme-non-equilibrium. The accompanying variations of temperatures, pressure and radiative spectrum suggest wide ranges of applications. For example, in the gas-phase fission reactor concept enriched uranium hexafluoride or an uranium plasma replaces conventional fuel elements and permits operation above the melting point of solid materials. This potential has been motivation for the US National Aeronautics and Space Administration (NASA) to conduct relevant research for high specific impulse propulsion in space. The need to separate the high temperature gaseous fuel from the surfaces of a containing vessel and to protect them against thermal radiation has led to the concept of an externally moderated reactor in which the fissioning gaseous material is suspended by fluid dynamic means and the flow of opaque buffer gas removes the power. The gaseous nuclear fuel can slowly be circulated through the reactor for continuous on-site reprocessing including the annihilation of transuranium actinides at fission when being fed back into the reactor. An equilibrium of the generation and destruction of such actinides at fission when being fed back into the reactor. An equilibrium of the generation and destruction of such actinides can thus be achieved. These characteristics and the unique radiative properties led to the expectation that the gas-phase fission reactor could feature improved safety, safeguarding and economy, in addition to new technologies such as processing, photochemistry and the transmission of power over large distances in space

Structural instability of sheath potential distribution and its possible implications for the L/H transition in tokamak plasmas

International Nuclear Information System (INIS)

Yoshida, Zensho; Yamada, Hiroshi.

1988-07-01

The Bohm equation of electrostatic potential distributions in one-dimensional plasmas has been studied for various Mach numbers and plasma potentials. Solvability and structural stability have been discussed using the Sagdeev potential. Implications of the structural stability for the L/H transitions in tokamak plasmas has been also discussed. (author)

An extra contribution to the Mikheyev-Smirnov-Wolfenstein potential in a CP-nonsymmetric plasma

International Nuclear Information System (INIS)

Horvat, R.

1991-01-01

Owing to matter-induced electromagnetic properties of neutrinos, v L e - → v L e - electromagnetic scattering in a plasma becomes possible even in the standard model with massless left-handed neutrinos. Electric-charge screening in a plasma causes the contribution to the external potential for a left-handed neutrino field to be the same as the ordinary Mikheyev-Smirnov-Wolfenstein potential. (orig.)

Impact of Relativistic Electron Beam on Hole Acoustic Instability in Quantum Semiconductor Plasmas

Science.gov (United States)

Siddique, M.; Jamil, M.; Rasheed, A.; Areeb, F.; Javed, Asif; Sumera, P.

2018-01-01

We studied the influence of the classical relativistic beam of electrons on the hole acoustic wave (HAW) instability exciting in the semiconductor quantum plasmas. We conducted this study by using the quantum-hydrodynamic model of dense plasmas, incorporating the quantum effects of semiconductor plasma species which include degeneracy pressure, exchange-correlation potential and Bohm potential. Analysis of the quantum characteristics of semiconductor plasma species along with relativistic effect of beam electrons on the dispersion relation of the HAW is given in detail qualitatively and quantitatively by plotting them numerically. It is worth mentioning that the relativistic electron beam (REB) stabilises the HAWs exciting in semiconductor (GaAs) degenerate plasma.

Evaluation and Optimization of Paper-Based SERS Substrate for Potential Label-Free Raman Analysis of Seminal Plasma

Directory of Open Access Journals (Sweden)

Zufang Huang

2017-01-01

Full Text Available Characterization and optimization of paper SERS substrate were performed in detail, in which morphologies and distribution of silver nanoparticles (AgNPs on the paper substrate pretreated with different concentrations of NaCl and the subsequent soaking with colloidal AgNPs for different period of time were evaluated. Our results show that both NaCl concentration and soaking time with AgNPs have a significant influence on SERS enhancement, showing that an optimal EF of 2.27 × 107 was achieved when the paper substrate was treated with 20 mM NaCl and one-hour soak with AgNPs. Moreover, seminal plasma (SP was specifically selected to evaluate the performance of paper-based SERS substrate for potential clinical detection and diagnosis. The optimization of the paper SERS substrate demonstrates potential applications in reliable on-site detection of SP and clinical diagnosis of fertility-related diseases as well.

Plasma screening effects on the energies of hydrogen atom under the influence of velocity-dependent potential

International Nuclear Information System (INIS)

Bahar, M. K.

2014-01-01

In order to examine the plasma screening and velocity-dependent potential effects on the hydrogen atom, the Schrödinger equation including a more general exponential cosine screened Coulomb and velocity-dependent potential is solved numerically in the framework asymptotic iteration method. The more general exponential cosine screened Coulomb potential is used to model Debye and quantum plasma for the specific values of the parameters in its structure. However, in order to examine effects of velocity-dependent potential on energy values of hydrogen atom in Debye and quantum plasma, the isotropic form factor of velocity-dependent potential is given as harmonic oscillator type, ρ(r)=ρ o r 2 . Then, the energies of s and p states are calculated numerically without any approximation. In order to investigate thoroughly plasma screening effects and contribution of velocity-dependent potential on energy values of hydrogen atom, the corresponding calculations are carried out by using different values of parameters of more general exponential cosine screened Coulomb potential and isotropic dependence, results of which are discussed

Investigation of RF-enhanced plasma potentials on Alcator C-Mod

International Nuclear Information System (INIS)

Ochoukov, R.; Whyte, D.G.; Brunner, D.; Cziegler, I.; LaBombard, B.; Lipschultz, B.; Myra, J.; Terry, J.; Wukitch, S.

2013-01-01

Radio frequency (RF) sheath rectification is a leading mechanism suspected of causing anomalously high erosion of plasma facing materials in RF-heated plasmas on Alcator C-Mod. An extensive experimental survey of the plasma potential (Φ P ) in RF-heated discharges on C-Mod reveals that significant Φ P enhancement (>100 V) is found on outboard limiter surfaces, both mapped and not mapped to active RF antennas. Surfaces that magnetically map to active RF antennas show Φ P enhancement that is, in part, consistent with the recently proposed slow wave rectification mechanism. Surfaces that do not map to active RF antennas also experience significant Φ P enhancement, which strongly correlates with the local fast wave intensity. In this case, fast wave rectification is a leading candidate mechanism responsible for the observed enhancement

Potential profiles obtained from applied dust cloud perturbations

International Nuclear Information System (INIS)

Thomas, Edward Jr.

2002-01-01

This paper details an experimental investigation of the local potential structure within a cloud of suspended microparticles - a 'dusty' or 'complex' plasma - using particle image velocimetry (PIV) techniques. Applied perturbations, synchronized to the PIV measurements, are used to force a cloud of suspended microparticles to become unconfined. From the free-streaming motion of the particles during the loss of confinement and subsequent reformation of the dust cloud, an analysis of the potential is performed. Furthermore, a new method of analyzing the potential structure from the motion of free-streaming microparticles in the plasma is presented

Observation of floating potential asymmetry in the edge plasma of ...

Indian Academy of Sciences (India)

Floating potential; vertical magnetic field; vertical electric field reversal; vertical electric field reversal ... Similar exchange of behavior for bottom probe of figure 1 with top probe of ... In our case rate of rise of plasma currents and also the total ...

Plasma potential in a magnetic mirror with electron-cyclotron-resonance heating

International Nuclear Information System (INIS)

Smith, P.K.

1983-01-01

Experimental and theoretical studies of the ECRH plasma in the University of Wisconsin DE Machine magnetic mirror have been undertaken. Typical plasma parameters in these experiments were T/sub e/ - 10 to 30 eV, T/sub i/ - 4 eV, V/sub po/ (plasma potential at midplane) - 20 to 50 V, midplane plasma density n 0 - 10 16 m - 3 , B 0 (magnetic field strength on axis at midplane) - .005 to .01 T, mirror ratio R - 5 to 20. The principal experimental findings were the appearance of strong density peaks (approx. 2 x background) and notable V/sub f/ dips (approx. kT/sub e//e) in a narrow (approx. 1 cm) region near the axial positions of cyclotron resonance. The properties of these dips do not change greatly over the range of operating parameters, but are narrower at higher pressures

Investigation of RF-enhanced plasma potentials on Alcator C-Mod

Energy Technology Data Exchange (ETDEWEB)

Ochoukov, R., E-mail: ochoukov@psfc.mit.edu [PSFC MIT, NW17, 175 Albany Street, Cambridge, MA 02139 (United States); Whyte, D.G.; Brunner, D. [PSFC MIT, NW17, 175 Albany Street, Cambridge, MA 02139 (United States); Cziegler, I. [Center for Energy Research, UCSD, 9500 Gilman Drive, La Jolla, CA 92093 (United States); LaBombard, B.; Lipschultz, B. [PSFC MIT, NW17, 175 Albany Street, Cambridge, MA 02139 (United States); Myra, J. [Lodestar Research Corporation, 2400 Central Avenue P-5, Boulder, CO 80301 (United States); Terry, J.; Wukitch, S. [PSFC MIT, NW17, 175 Albany Street, Cambridge, MA 02139 (United States)

2013-07-15

Radio frequency (RF) sheath rectification is a leading mechanism suspected of causing anomalously high erosion of plasma facing materials in RF-heated plasmas on Alcator C-Mod. An extensive experimental survey of the plasma potential (Φ{sub P}) in RF-heated discharges on C-Mod reveals that significant Φ{sub P} enhancement (>100 V) is found on outboard limiter surfaces, both mapped and not mapped to active RF antennas. Surfaces that magnetically map to active RF antennas show Φ{sub P} enhancement that is, in part, consistent with the recently proposed slow wave rectification mechanism. Surfaces that do not map to active RF antennas also experience significant Φ{sub P} enhancement, which strongly correlates with the local fast wave intensity. In this case, fast wave rectification is a leading candidate mechanism responsible for the observed enhancement.

Quiescent plasma machine for beam-plasma interaction and wave studies

International Nuclear Information System (INIS)

Ferreira, J.L.

1994-01-01

A quiescent double plasma machine for beam-plasma interaction wave studies is described. A detailed description of several plasma diagnostics used for plasma and wave excitation detection is given. A beam-plasma wave dispersion relation is used to compare theoretical values with the experimentally measured Langmuir wave frequencies and wavelengths. (author). 14 refs, 10 figs

Development of negative heavy ion sources for plasma potential measurement

International Nuclear Information System (INIS)

Sasao, M.; Okabe, Y.; Fujisawa, A.; Iguchi, H.; Fujita, J.; Yamaoka, H.; Wada, M.

1991-10-01

A plasma sputter negative ion source was studied for its applicability to the potential measurement of a fusion plasma. Both the beam current density and the beam energy spread are key issues. Energy spectra of a self extracted Au - beam from the source were measured under the condition of a constant work function of the production surface. The full width of half maximum (FWHM) increases from 3 eV to 9 eV monotonically as the target voltage increases from 50 V to 300 V, independently from the target surface work function of 2.2 - 3 eV. (author)

Normal chemotaxis in Dictyostelium discoideum cells with a depolarized plasma membrane potential

NARCIS (Netherlands)

Duijn, Bert van; Vogelzang, Sake A.; Ypey, Dirk L.; Molen, Loek G. van der; Haastert, Peter J.M. van

1990-01-01

We examined a possible role for the plasma membrane potential in signal transduction during cyclic AMP-induced chemotaxis in the cellular slime mold Dictyostelium discoideum. Chemotaxis, cyclic GMP and cyclic AMP responses in cells with a depolarized membrane potential were measured. Cells can be

Plasma parameters, fluctuations and kinetics in a magnetic field line reconnection experiment

International Nuclear Information System (INIS)

Wild, N.C. Jr.

1983-01-01

The processes associated with reconnecting magnetic field lines have been studied in a large experimental laboratory plasma. Detailed time- and space-resolved probe measurements of the plasma density, temperature, potential and electric and magnetic fields are discussed. Plasma currents are seen to modify the vacuum magnetic field topology. A flat neutral sheet develops along the separatrix where magnetic flux is transferred from regions of private to common flux. Forced tearing and magnetic island formation are also observed. Rapid electron heating, density and temperature nonuniformities and plasma potential gradients are all observed. The pressure is found to peak at the two edges of the neutral sheet. The dissipation E.J is determined and analyzed in terms of particle heating and fluid acceleration. A consistent, detailed picture of the energy flow via Poynting's theorem is also described. Significant temporal fluctuations in the magnetic fields and electron velocity distribution are measured and seen to give rise to anomalously high values for the plasma resistivity, the ion viscosity and the cross-field thermal conductivity. Electron temperature fluctuations, double layers associated with partial current disruptions, and whistler wave magnetic turbulence have all been identified and studied during the course of the reconnection event

A Hartree-Fock-Slater-Boltzmann-Saha method for detailed atomic structure and equation of state of plasmas

International Nuclear Information System (INIS)

Jiang Minhao; Meng Xujun

2005-01-01

The effect of the free electron background in plasmas is introduced in Hartree-Fock-Slater self-consistent field atomic model to correct the single electron energies for each electron configuration, and to provide accurate atomic data for Boltzmann-Saha equation. In the iteration process chemical potential is adjusted to change the free electron background to satisfy simultaneously the conservation of the free electrons in Saha equation as well as in Hartree-Fock-Slater self-consistent field atomic model. As examples the equations of state of the carbon and aluminum plasmas are calculated to show the applicability of this method. (authors)

Plasma Extracellular Vesicles Enriched for Neuronal Origin: A Potential Window into Brain Pathologic Processes

Directory of Open Access Journals (Sweden)

Maja Mustapic

2017-05-01

Full Text Available Our team has been a pioneer in harvesting extracellular vesicles (EVs enriched for neuronal origin from peripheral blood and using them as a biomarker discovery platform for neurological disorders. This methodology has demonstrated excellent diagnostic and predictive performance for Alzheimer's and other neurodegenerative diseases in multiple studies, providing a strong proof of concept for this approach. Here, we describe our methodology in detail and offer further evidence that isolated EVs are enriched for neuronal origin. In addition, we present evidence that EVs enriched for neuronal origin represent a more sensitive and accurate base for biomarkers than plasma, serum, or non-enriched total plasma EVs. Finally, we proceed to investigate the protein content of EVs enriched for neuronal origin and compare it with other relevant enriched and non-enriched populations of plasma EVs. Neuronal-origin enriched plasma EVs contain higher levels of signaling molecules of great interest for cellular metabolism, survival, and repair, which may be useful as biomarkers and to follow response to therapeutic interventions in a mechanism-specific manner.

Helicon plasma potential measurements using a heavy ion beam probe

International Nuclear Information System (INIS)

P. Schoch; K. Connor; J. Si

2005-01-01

A Heavy Ion Beam Probe, HIBP, has been installed on a helicon plasma device. The objective was to measure plasma fluctuations at the 13.55MHz RF frequency. This offers a unique challenge for the HIBP, because the transit time of the probing ion is long compared to the fluctuations of interest. For previous HIBPs, the transit time has been short compared to the period of the fluctuations which permits one to assume that the magnetic and electric fields are static. Modeling has shown that the diagnostic will still accurately measure the average potential. The fluctuating potential was to be detected but the absolute magnitude is difficult to determine with signal from a single point. However, modeling indicates multipoint measurements will allow one to resolve the absolute fluctuation magnitude. Work supported by DOE Grant No. DE-FG02-99ER5452985 During the funding of this grant, a helicon plasma discharge device was built and operated. A Heavy Ion Beam Probe primary system was installed and operated. A primary beam detector was installed and primary beam was detected both with and without plasma. Attempts were made to detect secondary ions using the primary beam detector, without success. Given the lack of a detectable signal, the energy analyzer of the HIBP system was never installed. It is available for installation if there is a reason to do so in the future. Analysis of the system indicated that the plasma electron temperature, estimated to be a few eV, was the likely reason for the lack of detectable secondary ions. A change of ion species to either Boron or Magnesium would greatly increase the signal, but neither of these ions have been used in a HIBP system. The ion source used in this system is made by using a charge exchange process to create a zeolite loaded with the desired ion. Attempts were made to use charge exchange to load Magnesium into a zeolite, and were not successful. It is felt that Magnesium and/or Boron zeolite sources could be created, but

First HIBP Measurement of Plasma Potential During the H-Mode Transition on the TUMAN-3M Tokamak

International Nuclear Information System (INIS)

Askinazi, L.G.; Golant, V.E.; Kornev, V.A.; Lebedev, S.V.; Shevkin, E.A.; Tukachinsky, A.S.; Zhubr, N.A.; Chmyga, A.A.; Dreval, N.B.; Khrebtov, S.M.; Komarov, A.S.; Krupnik, L.I.; Oost, G. van; Tendler, M.

2003-01-01

The difficulty of Heavy Ion Beam Probe (HIBP) application on the TUMAN-3M (R=0.53m, a=0.22m, BT=0.8T, Ip=140kA, Te=0.5keV, n<4 1019m-3) -- significant toroidal shift of beam trajectory -- is caused by high ratio of poloidal field to toroidal one. Strong UV radiation from the plasma loads the energy analyzer's detector and complicates the problem even more. This paper presents the results of first measurement of plasma potential evolution in the discharges performed in ohmic H-mode using 80 keV K+ beam and a Proca-Green secondary ion energy analyzer. Spatial region covered by the diagnostic in the experiments discussed was 0< r<0.6a. Spatial scan was performed utilizing the toroidal field decrease due to capacity power supply battery discharge. The change in plasma potential of the order of 100V has been measured during the H-mode formation. The potential in core plasma (r<0.6a) starts to change simultaneously with L-H transition, and than changes during ∼6-8ms after the transition. Thus, the potential changes rather slowly in a comparison with L-H transition timescale (∼2ms for TUMAN-3M ohmic H-mode). Possible explanation to the slow change in central plasma potential may be a formation of potential well structure at the plasma edge, in which radial electric field changes direction. This kind of structure is beneficial for the edge turbulent transport suppression because of high |∂Er/∂r|, but not necessary requires a strong change in central plasma potential to occur immediately. The results from microwave reflectometry support this hypothesis

Bifurcation of space-charge wave in a plasma waveguide including the wake potential effect

Energy Technology Data Exchange (ETDEWEB)

Lee, Myoung-Jae [Department of Physics and Research Institute for Natural Sciences, Hanyang University, Seoul 04763 (Korea, Republic of); Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr [Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 15588, South Korea and Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590 (United States)

2016-09-15

The wake potential effects on the propagation of the space-charge dust ion-acoustic wave are investigated in a cylindrically bounded dusty plasma with the ion flow. The results show that the wake potential would generate the double frequency modes in a cylindrically bounded dusty plasma. It is found that the upper mode of the wave frequency with the root of higher-order is smaller than that with the root of lower-order in intermediate wave number domains. However, the lower mode of the scaled wave frequency with the root of higher-order is found to be greater than that with the root of lower-order. It is found that the influence in the order of the root of the Bessel function on the wave frequency of the space-charge dust-ion-acoustic wave in a cylindrically confined dusty plasma decreases with an increase in the propagation wave number. It is also found that the double frequency modes increase with increasing Mach number due to the ion flow in a cylindrical dusty plasma. In addition, it is found that the upper mode of the group velocity decreases with an increase in the scaled radius of the plasma cylinder. However, it is shown that the lower mode of the scaled group velocity of the space-charge dust ion acoustic wave increases with an increase in the radius of the plasma cylinder. The variation of the space-charge dust-ion-acoustic wave due to the wake potential and geometric effects is also discussed.

Plasma soluble prion protein, a potential biomarker for sport-related concussions: a pilot study.

Science.gov (United States)

Pham, Nam; Akonasu, Hungbo; Shishkin, Rhonda; Taghibiglou, Changiz

2015-01-01

Sport-related mild traumatic brain injury (mTBI) or concussion is a significant health concern to athletes with potential long-term consequences. The diagnosis of sport concussion and return to sport decision making is one of the greatest challenges facing health care clinicians working in sports. Blood biomarkers have recently demonstrated their potential in assisting the detection of brain injury particularly, in those cases with no obvious physical injury. We have recently discovered plasma soluble cellular prion protein (PrP(C)) as a potential reliable biomarker for blast induced TBI (bTBI) in a rodent animal model. In order to explore the application of this novel TBI biomarker to sport-related concussion, we conducted a pilot study at the University of Saskatchewan (U of S) by recruiting athlete and non-athlete 18 to 30 year-old students. Using a modified quantitative ELISA method, we first established normal values for the plasma soluble PrP(C) in male and female students. The measured plasma soluble PrP(C) in confirmed concussion cases demonstrated a significant elevation of this analyte in post-concussion samples. Data collected from our pilot study indicates that the plasma soluble PrP(C) is a potential biomarker for sport-related concussion, which may be further developed into a clinical diagnostic tool to assist clinicians in the assessment of sport concussion and return-to-play decision making.

Radio Frequency Enhanced Plasma Potential and Flows in the Scrap-Off Layer of an Active Antenna

Science.gov (United States)

Martin, Michael John

Ion cyclotron resonance heating (ICRH) systems are critical components of current and future tokamak experiments aimed at producing nuclear fusion energy. During ICRH a host of deleterious effects occur, including increased heat flux to plasma facing components and modification of launched wave power. A suspected root cause of these effects is the radio frequency (RF) rectification of the plasma potential. Interest in the antenna scrape-off layer (SOL) region has drawn increasing interest, as it is recognized that mitigating these effects is necessary to achieving fusion power. This dissertation investigates the RF rectification of the plasma potential and the resulting cross-field flows that form due to an active RF antenna. The experiment is performed in the Large Plasma Device (LAPD) utilizing a fast wave antenna and RF amplifier system developed for these studies. The RF system is capable of 150 kW output power for a 1 ms pulse that is repeated at the 1 Hz repetition rate of the LAPD plasma discharge. Upon application of the RF pulse to the antenna, the DC plasma potential, measured with an emissive probe, dramatically increases in certain spatial locations by a factor greater than 10 Te. The largest plasma potentials are observed at locations magnetically connected to the top and bottom of the antenna, and they exist only in the private SOL created between the antenna and a limiter placed 3.6 m away along the LAPD axis. The DC rectified potentials scale linearly with the antenna current over a factor of 12x in the applied current. These DC potentials increase plasma materials interactions (PMI), resulting in the sputtering of antenna materials whose presence is detected in the bulk plasma by the coatings that develop on probe diagnostics. The DC rectified potentials persist in the plasma long after the RF current in the antenna has rung down on the same time scales as the change in the density. At the top and bottom of the antenna are circular flows, often

Generalized model screening potentials for Fermi-Dirac plasmas

Science.gov (United States)

Akbari-Moghanjoughi, M.

2016-04-01

In this paper, some properties of relativistically degenerate quantum plasmas, such as static ion screening, structure factor, and Thomson scattering cross-section, are studied in the framework of linearized quantum hydrodynamic theory with the newly proposed kinetic γ-correction to Bohm term in low frequency limit. It is found that the correction has a significant effect on the properties of quantum plasmas in all density regimes, ranging from solid-density up to that of white dwarf stars. It is also found that Shukla-Eliasson attractive force exists up to a few times the density of metals, and the ionic correlations are seemingly apparent in the radial distribution function signature. Simplified statically screened attractive and repulsive potentials are presented for zero-temperature Fermi-Dirac plasmas, valid for a wide range of quantum plasma number-density and atomic number values. Moreover, it is observed that crystallization of white dwarfs beyond a critical core number-density persists with this new kinetic correction, but it is shifted to a much higher number-density value of n0 ≃ 1.94 × 1037 cm-3 (1.77 × 1010 gr cm-3), which is nearly four orders of magnitude less than the nuclear density. It is found that the maximal Thomson scattering with the γ-corrected structure factor is a remarkable property of white dwarf stars. However, with the new γ-correction, the maximal scattering shifts to the spectrum region between hard X-ray and low-energy gamma-rays. White dwarfs composed of higher atomic-number ions are observed to maximally Thomson-scatter at slightly higher wavelengths, i.e., they maximally scatter slightly low-energy photons in the presence of correction.

Potential of mean force for electrical conductivity of dense plasmas

Science.gov (United States)

Starrett, C. E.

2017-12-01

The electrical conductivity in dense plasmas can be calculated with the relaxation-time approximation provided that the interaction potential between the scattering electron and the ion is known. To date there has been considerable uncertainty as to the best way to define this interaction potential so that it correctly includes the effects of ionic structure, screening by electrons and partial ionization. Current approximations lead to significantly different results with varying levels of agreement when compared to bench-mark calculations and experiments. We present a new way to define this potential, drawing on ideas from classical fluid theory to define a potential of mean force. This new potential results in significantly improved agreement with experiments and bench-mark calculations, and includes all the aforementioned physics self-consistently.

Plasma-Potential Diagnostic (PPD) hardware used on the Tandem Mirror Experiment-Upgrade (TMX-U)

International Nuclear Information System (INIS)

Steele, D.L.; Hornady, R.S.; Stever, R.D.; Coutts, G.W.; Nelson, D.H.

1986-01-01

The PPD is an instrument used to indirectly measure the potential of the center-cell plasma of TMX-U. Thallium ions are injected at energies of about 60 keV from an ion gun capable of 80 kV operation. The singly charged ions collide with plasma electrons and generate double-charged ions. Ions in the higher charge state exit the plasma and are detected in an electrostatic energy analyzer. From measurements of the injected ion energy and the output ion energy one can determine the plasma potential in the ionization region. This paper discusses hardware and techniques for calibrating the energy analyzer on the PPD. Initially, calibrating the PPD analyzer required full operation of the TMX-U magnets to deflect the beam into the energy analyzer. Since it is a hazard to operate the magnets while personnel are in the pit area, calibration was done remotely. This was not only time consuming but also required magnet system operation personnel

Circuit Model Simulations for Ionospheric Plasma Response to High Potential System

Directory of Open Access Journals (Sweden)

Hwang-Jae Rhee

2000-06-01

Full Text Available When a deployed probe is biased by a high positive potential during a space experiment, the payload is induced to a negative voltage in order to balance the total current in the whole system. The return currents are due to the responding ions and secondary electrons on the payload surface. In order to understand the current collection mechanism, the process was simulated with a combination of resistor, inductor, and capacitor in SPICE program which was equivalent to the background plasma sheath. The simulation results were compared with experimental results from SPEAR-3 (Space Power Experiment Aboard Rocket-3. The return current curve in the simulation was compatible to the experimental result, and the simulation helped to predict the transient plasma response to a high voltage during the plasma sheath formation.

Plasma soluble prion protein, a potential biomarker for sport-related concussions: a pilot study.

Directory of Open Access Journals (Sweden)

Nam Pham

Full Text Available Sport-related mild traumatic brain injury (mTBI or concussion is a significant health concern to athletes with potential long-term consequences. The diagnosis of sport concussion and return to sport decision making is one of the greatest challenges facing health care clinicians working in sports. Blood biomarkers have recently demonstrated their potential in assisting the detection of brain injury particularly, in those cases with no obvious physical injury. We have recently discovered plasma soluble cellular prion protein (PrP(C as a potential reliable biomarker for blast induced TBI (bTBI in a rodent animal model. In order to explore the application of this novel TBI biomarker to sport-related concussion, we conducted a pilot study at the University of Saskatchewan (U of S by recruiting athlete and non-athlete 18 to 30 year-old students. Using a modified quantitative ELISA method, we first established normal values for the plasma soluble PrP(C in male and female students. The measured plasma soluble PrP(C in confirmed concussion cases demonstrated a significant elevation of this analyte in post-concussion samples. Data collected from our pilot study indicates that the plasma soluble PrP(C is a potential biomarker for sport-related concussion, which may be further developed into a clinical diagnostic tool to assist clinicians in the assessment of sport concussion and return-to-play decision making.

Generalized model screening potentials for Fermi-Dirac plasmas

International Nuclear Information System (INIS)

Akbari-Moghanjoughi, M.

2016-01-01

In this paper, some properties of relativistically degenerate quantum plasmas, such as static ion screening, structure factor, and Thomson scattering cross-section, are studied in the framework of linearized quantum hydrodynamic theory with the newly proposed kinetic γ-correction to Bohm term in low frequency limit. It is found that the correction has a significant effect on the properties of quantum plasmas in all density regimes, ranging from solid-density up to that of white dwarf stars. It is also found that Shukla-Eliasson attractive force exists up to a few times the density of metals, and the ionic correlations are seemingly apparent in the radial distribution function signature. Simplified statically screened attractive and repulsive potentials are presented for zero-temperature Fermi-Dirac plasmas, valid for a wide range of quantum plasma number-density and atomic number values. Moreover, it is observed that crystallization of white dwarfs beyond a critical core number-density persists with this new kinetic correction, but it is shifted to a much higher number-density value of n_0 ≃ 1.94 × 10"3"7 cm"−"3 (1.77 × 10"1"0 gr cm"−"3), which is nearly four orders of magnitude less than the nuclear density. It is found that the maximal Thomson scattering with the γ-corrected structure factor is a remarkable property of white dwarf stars. However, with the new γ-correction, the maximal scattering shifts to the spectrum region between hard X-ray and low-energy gamma-rays. White dwarfs composed of higher atomic-number ions are observed to maximally Thomson-scatter at slightly higher wavelengths, i.e., they maximally scatter slightly low-energy photons in the presence of correction.

Generalized model screening potentials for Fermi-Dirac plasmas

Energy Technology Data Exchange (ETDEWEB)

Akbari-Moghanjoughi, M. [Faculty of Sciences, Department of Physics, Azarbaijan Shahid Madani University, 51745-406 Tabriz, Iran and International Centre for Advanced Studies in Physical Sciences and Institute for Theoretical Physics, Ruhr University Bochum, D-44780 Bochum (Germany)

2016-04-15

In this paper, some properties of relativistically degenerate quantum plasmas, such as static ion screening, structure factor, and Thomson scattering cross-section, are studied in the framework of linearized quantum hydrodynamic theory with the newly proposed kinetic γ-correction to Bohm term in low frequency limit. It is found that the correction has a significant effect on the properties of quantum plasmas in all density regimes, ranging from solid-density up to that of white dwarf stars. It is also found that Shukla-Eliasson attractive force exists up to a few times the density of metals, and the ionic correlations are seemingly apparent in the radial distribution function signature. Simplified statically screened attractive and repulsive potentials are presented for zero-temperature Fermi-Dirac plasmas, valid for a wide range of quantum plasma number-density and atomic number values. Moreover, it is observed that crystallization of white dwarfs beyond a critical core number-density persists with this new kinetic correction, but it is shifted to a much higher number-density value of n{sub 0} ≃ 1.94 × 10{sup 37} cm{sup −3} (1.77 × 10{sup 10} gr cm{sup −3}), which is nearly four orders of magnitude less than the nuclear density. It is found that the maximal Thomson scattering with the γ-corrected structure factor is a remarkable property of white dwarf stars. However, with the new γ-correction, the maximal scattering shifts to the spectrum region between hard X-ray and low-energy gamma-rays. White dwarfs composed of higher atomic-number ions are observed to maximally Thomson-scatter at slightly higher wavelengths, i.e., they maximally scatter slightly low-energy photons in the presence of correction.

Analysis of magnetic-dipole transitions in tungsten plasmas using detailed and configuration-average descriptions

Science.gov (United States)

Na, Xieyu; Poirier, Michel

2017-06-01

This paper is devoted to the analysis of transition arrays of magnetic-dipole (M1) type in highly charged ions. Such transitions play a significant role in highly ionized plasmas, for instance in the tungsten plasma present in tokamak devices. Using formulas recently published and their implementation in the Flexible Atomic Code for M1-transition array shifts and widths, absorption and emission spectra arising from transitions inside the 3*n complex of highly-charged tungsten ions are analyzed. A comparison of magnetic-dipole transitions with electric-dipole (E1) transitions shows that, while the latter are better described by transition array formulas, M1 absorption and emission structures reveal some insufficiency of these formulas. It is demonstrated that the detailed spectra account for significantly richer structures than those predicted by the transition array formalism. This is due to the fact that M1 transitions may occur between levels inside the same relativistic configuration, while such inner configuration transitions are not accounted for by the currently available averaging expression. In addition, because of configuration interaction, transition processes involving more than one electron jump, such as 3p1/23d5/2 → 3p3/23d3/2, are possible but not accounted for in the transition array formulas. These missing transitions are collected in pseudo-arrays using a post-processing method described in this paper. The relative influence of inner- and inter-configuration transitions is carefully analyzed in cases of tungsten ions with net charge around 50. The need for an additional theoretical development is emphasized.

The measurement of potential distribution of plasma in MM-4 fusion device

International Nuclear Information System (INIS)

Tian Zhongyu; Ming Linzhou; Feng Xiaozhen; Feng Chuntang; Yi Youjun; Wang Jihai; Liu Yihua

1988-11-01

Some experimental results of the potential distribution in MM-4 fusion device are presented by measuring the floating potential of probe. The results showed that the distribution of axial potential is asymmetrical, but the radial potential is symmetrical. There are double ion potential wells in the plasma. The depth of the deepest potential well become deeper is the strength of the magnetic field and injection current are increasing. The location of the deepest well is moved towards the device center along with the increasing of injection energy. This is different from others results. The mechanism of causing this distribution in also discussed

Structure of pulsed plasma jets

International Nuclear Information System (INIS)

Cavolowsky, J.A.

1987-01-01

A pulsed plasma jet is a turbulent, inhomogeneous fluid mechanical discharge capable of initiating and enhancing combustion. Having shown the ability to ignite lean fuel mixtures, it now offers the potential for real-time control of combustion processes. This study explored the fluid-mechanical and chemical properties of such jets. The fluid-mechanical structure of the jet was examined using two optical diagnostic techniques. Self-light streak photography provided information on the motion of luminous gas particles in its core. It revealed that plasma jets behave either totally subsonic or embody a supersonic core. The turbulent, thermal evolution of the jet was explored using high-speed-laser schlieren cinematography. By examining plasma jet generators with both opaque and transparent plasma cavities, detailed information on plasma formation and jet structure, beginning with the electric arc discharge in the cavity, was obtained. These records revealed the production of thermal stratifications in the cavity that could account for the plasma particles in the jet core. After the electrical discharges ceased, the turbulent jet behaved as a self-similar plume. Molecular-beam mass spectrometry was used to determine temperature and species concentration in the jet. Both non-combustible and combustible jets were studied

E-detailing: information technology applied to pharmaceutical detailing.

Science.gov (United States)

Montoya, Isaac D

2008-11-01

E-detailing can be best described as the use of information technology in the field of pharmaceutical detailing. It is becoming highly popular among pharmaceutical companies because it maximizes the time of the sales force, cuts down the cost of detailing and increases physician prescribing. Thus, the application of information technology is proving to be beneficial to both physicians and pharmaceutical companies. When e-detailing was introduced in 1996, it was limited to the US; however, numerous other countries soon adopted this novel approach to detailing and now it is popular in many developed nations. The objective of this paper is to demonstrate the rapid growth of e-detailing in the field of pharmaceutical marketing. A review of e-detailing literature was conducted in addition to personal conversations with physicians. E-detailing has the potential to reduce marketing costs, increase accessibility to physicians and offer many of the advantages of face-to-face detailing. E-detailing is gaining acceptance among physicians because they can access the information of a pharmaceutical product at their own time and convenience. However, the drug safety aspect of e-detailing has not been examined and e-detailing remains a supplement to traditional detailing and is not yet a replacement to it.

Potential flow model for the hydromagnetic Rayleigh--Taylor instability in cylindrical plasmas

International Nuclear Information System (INIS)

Hwang, C.S.; Roderick, N.F.

1987-01-01

A potential flow model has been developed to study the linear behavior of the hydromagnetic equivalent of the Rayleigh--Taylor instability in imploding cylindrical plasmas. Ordinary differential equations are obtained for both (r,z) and (r,θ) disturbances. The model allows the study of the dynamic effects of the moving plasma on the development of the instability. The perturbation equations separate into a geometric part associated with the motion of the interface and a nongeometric part associated with the stability of the interface. In both planes the geometric part shows growth of perturbations for imploding plasmas. The surface is also unstable in both planes for plasmas being imploded by magnetic fields. Analytic solutions are obtained for constant acceleration. These show that the short wavelength perturbations that are most damaging in the (r,z) plane are not affected by the motion of the interface. In the (r,θ) plane the growth of longer wavelength disturbances is affected by the interface motion

Effects of dust grain charge fluctuation on obliquely propagating dust-acoustic potential in magnetized dusty plasmas

International Nuclear Information System (INIS)

Mamun, A.A.; Hassan, M.H.A.

1999-05-01

Effects of dust grain charge fluctuation, obliqueness and external magnetic field on finite amplitude dust-acoustic solitary potential in a magnetized dusty plasma, consisting of electrons, ions and charge fluctuating dust grains, have been investigated by the reductive perturbation method. It has been shown that such a magnetized dusty plasma system may support dust-acoustic solitary potential on a very slow time scale involving the motion of dust grains, whose charge is self-consistently determined by local electron and ion currents. The effects of dust grain charge fluctuation, external magnetic field and obliqueness are found to modify the properties of this dust-acoustic solitary potential significantly. The implications of these results to some space and astrophysical dusty plasma systems, especially to planetary ring-systems and cometary tails, are briefly mentioned. (author)

Characterization of plasma thiol redox potential in a common marmoset model of aging

Directory of Open Access Journals (Sweden)

James R. Roede

2013-01-01

Full Text Available Due to its short lifespan, ease of use and age-related pathologies that mirror those observed in humans, the common marmoset (Callithrix jacchus is poised to become a standard nonhuman primate model of aging. Blood and extracellular fluid possess two major thiol-dependent redox nodes involving cysteine (Cys, cystine (CySS, glutathione (GSH and glutathione disulfide (GSSG. Alteration in these plasma redox nodes significantly affects cellular physiology, and oxidation of the plasma Cys/CySS redox potential (EhCySS is associated with aging and disease risk in humans. The purpose of this study was to determine age-related changes in plasma redox metabolites and corresponding redox potentials (Eh to further validate the marmoset as a nonhuman primate model of aging. We measured plasma thiol redox states in marmosets and used existing human data with multivariate adaptive regression splines (MARS to model the relationships between age and redox metabolites. A classification accuracy of 70.2% and an AUC of 0.703 were achieved using the MARS model built from the marmoset redox data to classify the human samples as young or old. These results show that common marmosets provide a useful model for thiol redox biology of aging.

Two-dimensional spatial survey of the plasma potential and electric field in a pulsed bipolar magnetron discharge

International Nuclear Information System (INIS)

Vetushka, A.; Karkari, S.K.; Bradley, J.W.

2004-01-01

Emissive and Langmuir probe techniques have been used to obtain two-dimensional (2D) spatial maps of the plasma potential V p , electric field E, and ion trajectories in a pulsed bipolar magnetron discharge. The magnetron was pulsed at a frequency of 100 kHz, with a 50% duty cycle and operated at an argon pressure of 0.74 Pa. The pulse wave form was characterized by three distinct phases: the 'overshoot', 'reverse', and 'on' phases. In the 'on' phase of the pulse, when the cathode voltage is driven to -670 V, the 2D spatial distribution of V p has a similar form to that in dc magnetron, with significant axial and radial electric fields in the bulk plasma, accelerating ions to the sheath edge above the cathode racetrack region. During the 'overshoot' phase (duration 200 ns), V p is raised to values greater than +330 V, more than 100 V above the cathode potential, with E pointing away from the target. In the 'reverse' phase V p has a value of +45 V at all measured positions, 2 V more positive than the target potential. In this phase there is no electric field present in the plasma. In the bulk of the plasma, the results from Langmuir probe and the emissive probe are in good agreement, however, in one particular region of the plasma outside the radius of the cathode, the emissive probe measurements are consistently more positive (up to 45 V in the 'on' time). This discrepancy is discussed in terms of the different frequency response of the probes and their perturbation of the plasma. A simple circuit model of the plasma-probe system has been proposed to explain our results. A brief discussion of the effect of the changing plasma potential distribution on the operation of the magnetron is given

Thermal plasma spraying for SOFCs: Applications, potential advantages, and challenges

Energy Technology Data Exchange (ETDEWEB)

Hui, Rob; Wang, Zhenwei; Jankovic, Jasna; Yick, Sing; Maric, Radenka; Ghosh, Dave [National Research Council Institute for Fuel Cell Innovation, 4250 Wesbrook Mall, Vancouver, BC V6T 1W5 (Canada); Kesler, Olivera [National Research Council Institute for Fuel Cell Innovation, 4250 Wesbrook Mall, Vancouver, BC V6T 1W5 (Canada); Department of Mechanical Engineering, University of British Columbia, 2054-6250 Applied Science Lane, Vancouver, BC V6T 1Z4 (Canada); Rose, Lars [National Research Council Institute for Fuel Cell Innovation, 4250 Wesbrook Mall, Vancouver, BC V6T 1W5 (Canada); Department of Materials Engineering, University of British Columbia, 309-6350 Stores Road, Vancouver, BC V6T 1Z4 (Canada)

2007-07-10

In this article, the applications, potential advantages, and challenges of thermal plasma spray (PS) processing for nanopowder production and cell fabrication of solid oxide fuel cells (SOFCs) are reviewed. PS processing creates sufficiently high temperatures to melt all materials fed into the plasma. The heated material can either be quenched into oxide powders or deposited as coatings. This technique has been applied to directly deposit functional layers as well as nanopowder for SOFCs application. In particularly, low melting point and highly active electrodes can be directly fabricated on zirconia-based electrolytes. This is a simple processing technique that does not require the use of organic solvents, offering the opportunity for flexible adjustment of process parameters, and significant time saving in production of the cell and cost reduction compared with tape casting, screen printing and sintering processing steps. Most importantly, PS processing shows strong potential to enable the deposition of metal-supported SOFCs through the integrated fabrication of membrane-electrode assemblies (MEA) on porous metallic substrates with consecutive deposition steps. On the other hand, the application of PS processing to produce SOFCs faces some challenges, such as insufficient porosity of the electrodes, the difficulty of obtaining a thin (<10 {mu}m) and dense electrolyte layer. Fed with H{sub 2} as the fuel gas and oxygen as the oxidant gas, the plasma sprayed cell reached high power densities of 770 mW cm{sup -2} at 900 C and 430 mW cm{sup -2} at 800 C at a cell voltage of 0.7 V. (author)

Potential medical applications of the plasma focus in the radioisotope production for PET imaging

International Nuclear Information System (INIS)

Roshan, M.V.; Razaghi, S.; Asghari, F.; Rawat, R.S.; Springham, S.V.; Lee, P.; Lee, S.; Tan, T.L.

2014-01-01

Devices other than the accelerators are desired to be investigated for generating high energy particles to induce nuclear reaction and positron emission tomography (PET) producing radioisotopes. The experimental data of plasma focus devices (PF) are studied and the activity scaling law for External Solid Target (EST) activation is established. Based on the scaling law and the techniques to enhance the radioisotopes production, the feasibility of generating the required activity for PET imaging is studied. - Highlights: • Short lived radioisotopes for PET imaging are produced in plasma focus device. • The scaling law of the activity induced with plasma focus energy is established. • The potential medical applications of plasma focus are studied

Characterisation of Plasma Filled Rod Pinch electron beam diode operation

Science.gov (United States)

MacDonald, James; Bland, Simon; Chittenden, Jeremy

2016-10-01

The plasma filled rod pinch diode (aka PFRP) offers a small radiographic spot size and a high brightness source. It operates in a very similar to plasma opening switches and dense plasma focus devices - with a plasma prefill, supplied via a number of simple coaxial plasma guns, being snowploughed along a thin rod cathode, before detaching at the end. The aim of this study is to model the PFRP and understand the factors that affect its performance, potentially improving future output. Given the dependence on the PFRP on the prefill, we are making detailed measurements of the density (1015-1018 cm-3), velocity, ionisation and temperature of the plasma emitted from a plasma gun/set of plasma guns. This will then be used to provide initial conditions to the Gorgon 3D MHD code, and the dynamics of the entire rod pinch process studied.

The potential role of curcumin (diferuloylmethane in plasma cell dyscrasias/paraproteinemia

Directory of Open Access Journals (Sweden)

Terry Golombick

2008-03-01

Full Text Available Terry Golombick, Terry DiamondDepartment of Endocrinology, St George Hospital, Kogarah, AustraliaAbstract: Plasma cell dyscrasias, most commonly associated with paraproteinemia, are a diverse group of diseases. Monoclonal gammopathy of undefined significance (MGUS can precede multiple myeloma, a progressive neoplastic disease. MGUS occurs in association with a variety of other diseases and currently no treatment is recommended but rather “watchful waiting”. Given that the size of the M-protein is a risk factor for disease progression, early intervention with the aim of reducing the paraprotein load would provide an innovative therapeutic tool. Preliminary results from our pilot study show a drop of between 5% and 30% serum paraprotein in patients taking curcumin compared with patients on placebo. Curcumin is a diferuloylmethane present in extracts of the rhizome of the Curcuma longa plant. As a natural product, this has exciting potential in the treatment of plasma cell dyscrasias.Keywords: plasma cell dyscrasias, MGUS, myeloma, curcumin, paraproteinemia

Measurement of potentials in the wake region of an unmagnetized plasma by using a DC-heated emissive probe

International Nuclear Information System (INIS)

Jung, Yong Ho; Chung, Kyu Sun

1995-01-01

An emissive probe was designed and manufactured to measure the floating and the space potentials of a plasma in the wake region. The 'floating potential method', among various schemes, was used for the measurement and analysis. To generate the wake, a plane artificial satellite with a circular shape was introduced into a simply discharged argon plasma without a magnetic field. Potentials along the radial direction in and out of the wake region of the artificial satellite were measured, and the plasma parameters were compared in both regions. In the wake region, the floating potential was higher than that out of the wake; the space potential was approximately equal to that out of the wake; when a positive voltage was applied to the artificial satellite, the floating and the space potentials were lower than those out of the wake; and when a negative voltage was applied to the artificial satellite, the floating potential was higher and the space potential was lower than the corresponding potentials out of the wake. (author)

Plasma sheath in non-Maxwellian plasma

International Nuclear Information System (INIS)

Shimizu, Takuo; Horigome, Takashi

1992-01-01

Reviewing many theoretical and experimental works on the electron-energy distributions (EEDF) of various plasmas, we point out that many plasmas have EEDF of non-Maxwellian in shape. Therefore, the recent treatment of plasma sheath using the Maxwell-Boltzmann distribution approximation should be improved. To do this, we have adopted Rutcher's standard distribution as a generalized form in place of the traditional Maxwellian, and found that the minimum energy of ions entering the sheath edge (Bohm's criterion) varies largely, and have also shown the variation of Debye length with the shape of EEDF. The length is the most important parameter to proceed with more detailed analysis on plasma-sheaths, and also to control them in the future. (author)

Steady state behavior of rotating plasmas in a vacuum-arc centrifuge

International Nuclear Information System (INIS)

Bittencourt, J.A.; Ludwig, G.O.

1987-01-01

The steady state behaviour of the fully ionized, multiple species, rotating, magnetized plasma in a vacuum-arc plasma centrifuge is described in detail. The analysis is based on a multiple species fluid model which includes electromagnetic, pressure gradient, centrifugal and collisional forces, for each species, in cylindrical geometry. It is shown that there is a family of theoretically possible dynamical equilibrium configurations, which can be achieved by different combinations of ion rotation velocity, radial ion density distribution and radial dependence of internal electric potential. The parametric dependences of the various plasma parameters under equilibrium conditions, including the ion separation factor, are presented for a nickel-copper plasma. The numerical results are analysed and discussed in light of experimentally measured plasma characteristics in a vacuum-arc plasma centrifuge. (author)

Steady state behavior of rotating plasmas in a vacuum-arc centrifuge

International Nuclear Information System (INIS)

Bittencourt, J.A.; Ludwig, G.O.

1986-06-01

The steady state behavior of the fully ionized, multiple species, rotating, magnetized plasma in a vacuum-arc plasma centrifuge is described in detail. The analysis is based on a multiple species fluid model which includes electromagnetic, pressure gradient, centrifugal and collisional forces, for each species, in cylindrical geometry. It is showm that there is a family of theoretically possible dynamical equilibrium configurations, which can be achieved by different combinations of ion rotation velocity, radial ion density distribution and radial dependence of internal electric potential. The parametric dependences of the various plasma parameters under equilibrium conditions, including the ion separation factor, are presented for a nickel-copper plasma. The numerical results are analysed and discussed on light of experimentally measured plasma characteristics in a vacuum-arc plasma centrifuge. (Author) [pt

An interatomic potential model for molecular dynamics simulation of silicon etching by Br+-containing plasmas

International Nuclear Information System (INIS)

Ohta, H.; Iwakawa, A.; Eriguchi, K.; Ono, K.

2008-01-01

An interatomic potential model for Si-Br systems has been developed for performing classical molecular dynamics (MD) simulations. This model enables us to simulate atomic-scale reaction dynamics during Si etching processes by Br + -containing plasmas such as HBr and Br 2 plasmas, which are frequently utilized in state-of-the-art techniques for the fabrication of semiconductor devices. Our potential form is based on the well-known Stillinger-Weber potential function, and the model parameters were systematically determined from a database of potential energies obtained from ab initio quantum-chemical calculations using GAUSSIAN03. For parameter fitting, we propose an improved linear scheme that does not require any complicated nonlinear fitting as that in previous studies [H. Ohta and S. Hamaguchi, J. Chem. Phys. 115, 6679 (2001)]. In this paper, we present the potential derivation and simulation results of bombardment of a Si(100) surface using a monoenergetic Br + beam

Ionization-potential depression and other dense plasma statistical property studies - Application to spectroscopic diagnostics.

Science.gov (United States)

Calisti, Annette; Ferri, Sandrine; Mossé, Caroline; Talin, Bernard

2017-02-01

The radiative properties of an emitter surrounded by a plasma, are modified through various mechanisms. For instance the line shapes emitted by bound-bound transitions are broadened and carry useful information for plasma diagnostics. Depending on plasma conditions the electrons occupying the upper quantum levels of radiators no longer exist as they belong to the plasma free electron population. All the charges present in the radiator environment contribute to the lowering of the energy required to free an electron in the fundamental state. This mechanism is known as ionization potential depression (IPD). The knowledge of IPD is useful as it affects both the radiative properties of the various ionic states and their populations. Its evaluation deals with highly complex n-body coupled systems, involving particles with different dynamics and attractive ion-electron forces. A classical molecular dynamics (MD) code, the BinGo-TCP code, has been recently developed to simulate neutral multi-component (various charge state ions and electrons) plasma accounting for all the charge correlations. In the present work, results on IPD and other dense plasma statistical properties obtained using the BinGo-TCP code are presented. The study focuses on aluminum plasmas for different densities and several temperatures in order to explore different plasma coupling conditions.

Integrated modelling of the edge plasma and plasma facing components

International Nuclear Information System (INIS)

Coster, D.P.; Bonnin, X.; Mutzke, A.; Schneider, R.; Warrier, M.

2007-01-01

Modelling of the interaction between the edge plasma and plasma facing components (PFCs) has tended to place more emphasis on either the plasma or the PFCs. Either the PFCs do not change with time and the plasma evolution is studied, or the plasma is assumed to remain static and the detailed interaction of the plasma and the PFCs are examined, with no back-reaction on the plasma taken into consideration. Recent changes to the edge simulation code, SOLPS, now allow for changes in both the plasma and the PFCs to be considered. This has been done by augmenting the code to track the time-development of the properties of plasma facing components (PFCs). Results of standard mixed-materials scenarios (base and redeposited C; Be) are presented

Revisiting the plasma sheath—dust in plasma sheath

Energy Technology Data Exchange (ETDEWEB)

Das, G. C. [Mathematical Science Division, IASST, Guwahati 781014 (India); Deka, R.; Bora, M. P., E-mail: mpbora@gauhati.ac.in [Physics Department, Gauhati University, Guwahati 781014 (India)

2016-04-15

In this work, we have considered the formation of warm plasma sheath in the vicinity of a wall in a plasma with considerable presence of dust particles. As an example, we have used the parameters relevant in case of plasma sheath formed around surfaces of various solid bodies in space, though the results obtained in this work can be applied to any other physical situation such as laboratory plasma. In the ion-acoustic time scale, we neglect the dust dynamics. The dust particles affect the sheath dynamics by affecting the Poisson equation which determines the plasma potential in the sheath region. It is important to note that our calculations are valid only when the amount of dust particles is not sufficient so as to affect the plasma dynamics in the dust-acoustic time scale, but enough to affect the plasma sheath. We have assumed the current to a dust particle to be balanced throughout the analysis. This makes the grain potential dependent on plasma potential, which is then incorporated into the Poisson equation. The resultant numerical model becomes an initial value problem, which is described by a 1-D integro-differential equation, which is then solved self-consistently by incorporating the change in plasma potential caused by inclusion of the dust potential in the Poisson equation.

The experimental investigation on the properties of the plasma heated by waves in the mirror machine

Energy Technology Data Exchange (ETDEWEB)

Shuyun, Duan; Shiqing, Cheng; Xuemeng, Chen; Qing, Pan; Zhigang, Yang [Southwest Inst. of Physics, Leshan, SC (China)

1995-06-01

The application of ICRH (Ion Cyclotron Resonance Heating) in the MM-2U simple mirror plasma which is created and heated by ECRH (Electron Cyclotron Resonance Heating) can result in the increase of plasma temperature and density. The confinement performance of plasma also can be improved. The ion and electron temperatures and the plasma density are measured in detail by using the ISP (Ion Sensitive Probe). The plasma floating potential profile are measured in both the radial and the axial direction. The experimental results show that ICRF (Ion Cyclotron Radio Field) can be used for stabilizing ECRH plasma and for improving the confinement performance of plasma.

Characteristics of electron cyclotron waves creating field-aligned and transverse plasma-potential structures

International Nuclear Information System (INIS)

Takahashi, K; Kaneko, T; Hatakeyama, R; Fukuyama, A

2009-01-01

Characteristics of electromagnetic waves of azimuthal mode number m = ±1 are investigated experimentally, analytically and numerically when the waves triggering the field-aligned and transverse plasma-potential structure modification near an electron cyclotron resonance (ECR) point are injected into an inhomogeneously magnetized plasma with high-speed ion flow. The waves of m = +1 and -1 modes generate an electric double layer near the ECR point at the radially central and peripheral areas of the plasma column, respectively, and the transverse electric fields are consequently formed. At these areas the waves have a right-handed polarization and are absorbed through the ECR mechanism, where the experimental and analytical results do show the polarization reversal along the radial axis. The numerical results by plasma analysis by finite element method (FEM)/wave analysis by FEM (PAF/WF) code show that the wave-absorption area is localized at the radially central and peripheral areas for m = +1 and -1 mode waves, respectively, being consistent with the experimental and analytical ones.

Investigation on the Characteristics of Pellet Ablation in a Toroidal Plasma

Science.gov (United States)

Sato, K. N.; Sakakita, H.; Fujita, H.

2003-06-01

Characteristics of a cloud ablated from an ice pellet has been investigated in detail in the JIPP T-IIU tokamak plasma by utilizing a new scheme of pellet injection system, "the injection-angle controllable system". A long "helical tail" of ablation light has been observed using CCD cameras and a high speed framing photograph in the case of on-axis and off-axis injection with the injection angle smaller than a certain value. The direction of the helical tail is found to be independent to that of the total magnetic field lines of the torus. From the experiments with the combination of two toroildal filed directions and two plasma current directions, it is considered that the tail seems to rotate, in most cases, to the electron diamagnetic direction poloidally, and to the opposite to the plasma current direction toroidally. Consideration on various cross sections including charge exchange, ionization and elastic collisions leads us to the conclusion that the tail-shaped phenomena may come from the situation of charge exchange equilibrium of hydrogen ions and neutrals at extremely high density regime in the cloud. The relation of ablation behavior with plasma potential and rotation has also been studied. Potential measurements of pellet-injected plasmas using heavy ion beam probe (HIBP) method were carried out for the first time. In the case of an injection angle to be anti-parallel to the electron diamagnetic direction in the poloidal plane, the result shows that the direction of potential change is negative, and consequently the potential after the injection should be negative because it has been measured to be negative in usual ohmic plasmas without pellet injection. Thus, the direction of the "tail" structure seems to be consistent to that of the plasma potential measured, if it is considered that tail structure may be caused by the effect of the plasma potential and the rotation.

Investigation on the Characteristics of Pellet Ablation in a Toroidal Plasma

International Nuclear Information System (INIS)

Sato, K.N.; Sakakita, H.; Fujita, H.

2003-01-01

Characteristics of a cloud ablated from an ice pellet has been investigated in detail in the JIPP T-IIU tokamak plasma by utilizing a new scheme of pellet injection system, 'the injection-angle controllable system'. A long 'helical tail' of ablation light has been observed using CCD cameras and a high speed framing photograph in the case of on-axis and off-axis injection with the injection angle smaller than a certain value. The direction of the helical tail is found to be independent to that of the total magnetic field lines of the torus. From the experiments with the combination of two toroidal filed directions and two plasma current directions, it is considered that the tail seems to rotate, in most cases, to the electron diamagnetic direction poloidally, and to the opposite to the plasma current direction toroidally. Consideration on various cross sections including charge exchange, ionization and elastic collisions leads us to the conclusion that the tail-shaped phenomena may come from the situation of charge exchange equilibrium of hydrogen ions and neutrals at extremely high density regime in the cloud. The relation of ablation behavior with plasma potential and rotation has also been studied. Potential measurements of pellet-injected plasmas using heavy ion beam probe (HIBP) method were carried out for the first time. In the case of an injection angle to be anti-parallel to the electron diamagnetic direction in the poloidal plane, the result shows that the direction of potential change is negative, and consequently the potential after the injection should be negative because it has been measured to be negative in usual ohmic plasmas without pellet injection. Thus, the direction of the 'tail' structure seems to be consistent to that of the plasma potential measured, if it is considered that tail structure may be caused by the effect of the plasma potential and the rotation

Echo in a semibounded plasma confined by an inhomogeneous electrostatic potential

International Nuclear Information System (INIS)

Revenchuk, S.M.

1997-01-01

The effect of the shape of a confining potential (potential barrier) on linear and nonlinear echoes arising due to the reflection of charged particles by this potential is studied. The model of a plasma confined by a potential that is a monotonous power-law function of the space coordinate is used to study the problem. It is shown that a linear echo (the effect of a nonlocal reflection of waves) arises only for a square-law confining potential. The second-order nonlinear echo caused by two external perturbations with different frequencies can occur for potentials with both square-law and inverse power-law coordinate dependences: the frequency of this echo equals the difference of the frequencies of the externally applied perturbations. In the model considered, an echo at the frequency that is the sum of the frequencies of the external perturbations, which was predicted in the previous papers, does not occur

Examples of plasma horizons

International Nuclear Information System (INIS)

Hanni, R.S.

1975-01-01

The concept of the plasma horizon, defined as the boundary of the region in which an infinitely thin plasma can be supported against Coulomb attraction by a magnetic field, shows that the argument of selective accretion does not rule out the existence of charged black holes embedded in a conducting plasma. A detailed account of the covariant definition of plasma horizon is given and some examples of plasma horizons are presented. 7 references

SCRIC: a code dedicated to the detailed emission and absorption of heterogeneous NLTE plasmas; application to xenon EUV sources; SCRIC: un code pour calculer l'absorption et l'emission detaillees de plasmas hors equilibre, inhomogenes et etendus; application aux sources EUV a base de xenon

Energy Technology Data Exchange (ETDEWEB)

Gaufridy de Dortan, F. de

2006-07-01

Nearly all spectral opacity codes for LTE and NLTE plasmas rely on configurations approximate modelling or even supra-configurations modelling for mid Z plasmas. But in some cases, configurations interaction (either relativistic and non relativistic) induces dramatic changes in spectral shapes. We propose here a new detailed emissivity code with configuration mixing to allow for a realistic description of complex mid Z plasmas. A collisional radiative calculation. based on HULLAC precise energies and cross sections. determines the populations. Detailed emissivities and opacities are then calculated and radiative transfer equation is resolved for wide inhomogeneous plasmas. This code is able to cope rapidly with very large amount of atomic data. It is therefore possible to use complex hydrodynamic files even on personal computers in a very limited time. We used this code for comparison with Xenon EUV sources within the framework of nano-lithography developments. It appears that configurations mixing strongly shifts satellite lines and must be included in the description of these sources to enhance their efficiency. (author)

Transport coefficients of Quark-Gluon plasma with full QCD potential

Science.gov (United States)

J. P., Prasanth; Bannur, Vishnu M.

2018-05-01

The shear viscosity η, bulk viscosity ζ and their ratio with the entropy density, η / s, ζ / s have been studied in a quark-gluon plasma (QGP) within the cluster expansion method. The cluster expansion method allows us to include the interaction between the partons in the deconfined phase and to calculate the equation of state of quark-gluon plasma. It has been argued that the interactions present in the equation of state, the modified Cornell potential significantly contributes to the viscosity. The results obtained within our approaches agree with lattice quantum chromodynamics (LQCD) equation of state. We obtained η / s ≈ 0 . 128 within the temperature range T /Tc ∈ [ 0 . 9 , 1 . 5 ] which is very close to the theoretical lower bound η / s ≥ 1 /(4 π) in Yang-Mills theory. We also demonstrate that the effects of ζ / s at freezeout are possibly large.

Evolution of ion-acoustic potential well in a current-carrying plasma

International Nuclear Information System (INIS)

Maslov, V.I.

1990-01-01

Properties and evolution of nonlinear correlated collective disturbance of potential well in current-carrying limited plasma are described. Study shows, that potential well intensifies while exchanging energy with resonance electrons reflecting from it with distribution unstable function. In this case, electron deficiency occurs ahead of the well and electron excess - behined it due to asymmetry, relatively to well velocity, of distribution function of electrons injected at boundaries, in velocity space and due to their reflection from well. Quasineutrality is reduced by self-congruent formation of potential jump within well range. With amplitude growth at its essential values the well is braked. Similar pattern of localized disturbance evolution was observed during numerical and laboratory experiments

Plasma potential and electron temperature evaluated by ball-pen and Langmuir probes in the COMPASS tokamak.

Czech Academy of Sciences Publication Activity Database

Dimitrova, Miglena; Popov, Tsv.K.; Adámek, Jiří; Kovačič, J.; Ivanova, P.; Hasan, E.; López-Bruna, D.; Seidl, Jakub; Vondráček, Petr; Dejarnac, Renaud; Stöckel, Jan; Imríšek, Martin; Pánek, Radomír

2017-01-01

Roč. 59, č. 12 (2017), č. článku 125001. ISSN 0741-3335 R&D Projects: GA ČR(CZ) GA15-10723S; GA MŠk(CZ) LM2015045 Institutional support: RVO:61389021 Keywords : Plasma potential * electron temperature * bi-Maxwellian EEDF * ball-pen probe * Langmuir probe * COMPASS tokamak * last closed flux surface Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.392, year: 2016

Development of a test bed plasma and diagnostic methods for detailed K-shell spectroscopy

Czech Academy of Sciences Publication Activity Database

Hall, I.M.; Chambers, D.M.; Courtois, C.; Förster, E.; Gregory, C.D.; Howe, J.; Renner, Oldřich; Uschmann, I.; Woolsey, N.C.

2006-01-01

Roč. 133, - (2006), s. 1009-1011 ISSN 1155-4339 R&D Projects: GA MŠk LC528 Institutional research plan: CEZ:AV0Z10100523 Keywords : laser-produced plasmas * x-ray and optical emission * plasma modelling * plasma diagnostics Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.315, year: 2006

The current-voltage characteristic and potential oscillations of a double layer in a triple plasma device

International Nuclear Information System (INIS)

Carpenter, R.T.; Torven, S.

1986-07-01

The properties of a strong double layer in a current circuit with a capacitance and an inductance are investigated in a triple plasma device. The double layer gives rise to a region of negative differential resistance in the current-voltage characteristic of the device, and this gives non-linear oscillations in the current and the potential drop over the double layer (PhiDL). For a sufficiently large circuit inductance PhiDL reaches an amplitude given by the induced voltage (-LdI/dt) which is much larger than the circuit EMF due to the rapid current decrease when PhiDL increases. A variable potential minimum exists in the plasma on the low potential side of the double layer, and the depth of the minimum increases when PhiDL increases. An increasing fraction of the electrons incident at the double layer are then reflected, and this is found to be the main process giving rise to the negative differential resistance. A qualitative model for the variation of the minimum potential with PhiDL is also proposed. It is based on the condition that the minimum potential must adjust itself self-consistentely so that quasi-neutrality is maintained in the plasma region where the minimum is assumed. (authors)

Space plasmas 2

International Nuclear Information System (INIS)

Frankel, N.E.; Hines, K.C.; Kowalenko, V.

1981-01-01

The longitudinal dielectric response of an ultra-degenerate relativistic plasma composed of electrons and positrons is considered. The relativistic Hartree self-consistent field method is used to investigate the dispersion relations and damping parameters of such a plasma in the presence of a magnetic field. These properties must be studied in the various regimes appropriate for a relativistic plasma as detailed by Tsytovich and Jancovici

On the structure of pulsed plasma jets

Science.gov (United States)

Cavolowsky, John Arthur

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

Super-transition-arrays: A model for the spectral analysis of hot, dense plasma

International Nuclear Information System (INIS)

Bar-Shalom, A.; Oreg, J.; Goldstein, W.H.; Shvarts, D.; Zigler, A.

1989-01-01

A method is presented for calculating the bound-bound emission from a local thermodynamic equilibrium plasma. The total transition array of a specific single-electron transition, including all possible contributing configurations, is described by only a small number of super-transition-arrays (STA's). Exact analytic expressions are given for the first few moments of an STA. The method is shown to interpolate smoothly between the average-atom (AA) results and the detailed configuration accounting that underlies the unresolved transition array (UTA) method. Each STA is calculated in its own, optimized potential, and the model achieves rapid convergence in the number of STA's included. Comparisons of predicted STA spectra with the results of the AA and UTA methods are presented. It is shown that under certain plasma conditions the contributions of low-probability transitions can accumulate into an important component of the emission. In these cases, detailed configuration accounting is impractical. On the other hand, the detailed structure of the spectrum under such conditions is not described by the AA method. The application of the STA method to laser-produced plasma experiments is discussed

Microparticle injection effects on microwave transmission through an overly dense plasma layer

Energy Technology Data Exchange (ETDEWEB)

Gillman, Eric D., E-mail: eric.gillman@nrl.navy.mil; Amatucci, W. E. [Naval Research Laboratory, Washington, DC 20375 (United States); Williams, Jeremiah [Wittenberg University, Springfield, Ohio 45501 (United States); Compton, C. S. [Sotera Defense Solutions, Herndon, Virginia 20171 (United States)

2015-04-15

Microparticles injected into a plasma have been shown to deplete the free electron population as electrons are collected through the process of microparticles charging to the plasma floating potential. However, these charged microparticles can also act to scatter electromagnetic signals. These experiments investigate microwave penetration through a previously impenetrable overly dense plasma layer as microparticles are injected and the physical phenomena associated with the competing processes that occur due to electron depletion and microwave scattering. The timescales for when each of these competing processes dominates is analyzed in detail. It was found that while both processes play a significant and dominant role at different times, ultimately, transmission through this impenetrable plasma layer can be significantly increased with microparticle injection.

Increasing organ donation rates by revealing recipient details to families of potential donors.

Science.gov (United States)

Shaw, David; Gardiner, Dale

2018-02-01

Many families refuse to consent to donation from their deceased relatives or over-rule the consent given before death by the patient, but giving families more information about the potential recipients of organs could reduce refusal rates. In this paper, we analyse arguments for and against doing so, and conclude that this strategy should be attempted. While it would be impractical and possibly unethical to give details of actual potential recipients, generic, realistic information about the people who could benefit from organs should be provided to families before they make a decision about donation or attempt to over-rule it. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Charge and potential of a dust grain versus the intergrain distance and establishment of the latter in a low-pressure plasma

International Nuclear Information System (INIS)

Sysun, A. V.; Sysun, V. I.; Khakhaev, A. D.; Shelestov, A. S.

2008-01-01

Results from experimental studies of ordered dust structures in plasma are reviewed. The experimental conditions and the data on the grain size and intergrain distance in plasma dust crystals are analyzed. It is shown that intergrain distance is a function of the grain size. The range of the ratio of the dust grain size to the Debye radius within which plasma dust crystals can form is determined. A volume cell surrounding a dust grain in plasma is considered. It is found that the potential and charge of the grain depend substantially on the intergrain distance. The charge, potential, and potential energy of a dust grain in a plasma dust crystal, as well as the electrostatic force exerted by the plasma field on the grain, are calculated by the method of molecular dynamics as functions of the intergrain distance. The corresponding analytic approximations and the criterion for the establishment of a steady-state intergrain distance are proposed.

Detailed study of the plasma-activated catalytic generation of ammonia in N2-H2 plasmas

Science.gov (United States)

van Helden, J. H.; Wagemans, W.; Yagci, G.; Zijlmans, R. A. B.; Schram, D. C.; Engeln, R.; Lombardi, G.; Stancu, G. D.; Röpcke, J.

2007-02-01

We investigated the efficiency and formation mechanism of ammonia generation in recombining plasmas generated from mixtures of N2 and H2 under various plasma conditions. In contrast to the Haber-Bosch process, in which the molecules are dissociated on a catalytic surface, under these plasma conditions the precursor molecules, N2 and H2, are already dissociated in the gas phase. Surfaces are thus exposed to large fluxes of atomic N and H radicals. The ammonia production turns out to be strongly dependent on the fluxes of atomic N and H radicals to the surface. By optimizing the atomic N and H fluxes to the surface using an atomic nitrogen and hydrogen source ammonia can be formed efficiently, i.e., more than 10% of the total background pressure is measured to be ammonia. The results obtained show a strong similarity with results reported in literature, which were explained by the production of ammonia at the surface by stepwise addition reactions between adsorbed nitrogen and hydrogen containing radicals at the surface and incoming N and H containing radicals. Furthermore, our results indicate that the ammonia production is independent of wall material. The high fluxes of N and H radicals in our experiments result in a passivated surface, and the actual chemistry, leading to the formation of ammonia, takes place in an additional layer on top of this passivated surface.

Detailed balance method for chemical potential determination in Monte Carlo and molecular dynamics simulations

International Nuclear Information System (INIS)

Fay, P.J.; Ray, J.R.; Wolf, R.J.

1994-01-01

We present a new, nondestructive, method for determining chemical potentials in Monte Carlo and molecular dynamics simulations. The method estimates a value for the chemical potential such that one has a balance between fictitious successful creation and destruction trials in which the Monte Carlo method is used to determine success or failure of the creation/destruction attempts; we thus call the method a detailed balance method. The method allows one to obtain estimates of the chemical potential for a given species in any closed ensemble simulation; the closed ensemble is paired with a ''natural'' open ensemble for the purpose of obtaining creation and destruction probabilities. We present results for the Lennard-Jones system and also for an embedded atom model of liquid palladium, and compare to previous results in the literature for these two systems. We are able to obtain an accurate estimate of the chemical potential for the Lennard-Jones system at higher densities than reported in the literature

Concepual design of Langmuir probes for the diagnosis of plasma edge of Aditya-U

International Nuclear Information System (INIS)

Lachhvani, Lavkesh T.; Pandya, Shwetang N.; Iyer, Ramakrishnan B.; Barot, Akash; Patel, Kaushal M.; Jadeja, Kumarpalsinh; Gautam, Pramila; Joshi, Nishita H.; Ghosh, Joydeep; Raj, Harshita

2017-01-01

The role of the Tokamak edge plasma in influencing the fusion energy yield of Tokamaks is now widely recognized and is reflected in the increasing efforts devoted to the experimental and theoretical study of scrape-off layer (SOL) physics. Of particular concern are aspects of the plasma-surface interaction leading to impurity production and the subsequent impurity transport and contamination of the core plasma. The impurity transport depends strongly on the background properties of the SOL plasma, such as the plasma density, potential, electron and ion temperature, ion flows, flow velocity and their fluctuations and transport coefficients. The poster discusses the design considerations and technical details for variety of probes installed on Aditya-U

Plasma confinement

CERN Document Server

Hazeltine, R D

2003-01-01

Detailed and authoritative, this volume examines the essential physics underlying international research in magnetic confinement fusion. It offers readable, thorough accounts of the fundamental concepts behind methods of confining plasma at or near thermonuclear conditions. Designed for a one- or two-semester graduate-level course in plasma physics, it also represents a valuable reference for professional physicists in controlled fusion and related disciplines.

Calculation of coulomb correlation potential in a turbulent non-ideal plasma with reduced degrees of freedom

International Nuclear Information System (INIS)

Dwivedi, C.B.; Bhattacharjee, M.

1998-01-01

A simple but reasonable physical model has been developed to find out the correlation potential in a turbulent non-ideal plasma. It is assumed that the turbulent plasma state comprises of weakly interacting pseudo particles i.e. nonlinear coherent structures like solitons with random distribution in space and time. The calculation is based on the lowest order binary interacting model of the nonlinear normal modes (pseudo particles) of the weakly correlated plasmas. Its implication in the phase transition of the correlated Coulomb gas is discussed. (author)

Direct plasma potential measurements by ball-pen probe and self-emitting langmuir probe on COMPASS and ASDEX upgrade

Czech Academy of Sciences Publication Activity Database

Adámek, Jiří; Horáček, Jan; Seidl, Jakub; Müller, H.W.; Schrittwieser, R.; Mehlmann, F.; Vondráček, Petr; Pták, Svatopluk

2014-01-01

Roč. 54, č. 3 (2014), s. 279-284 ISSN 0863-1042 R&D Projects: GA ČR(CZ) GAP205/12/2327 Institutional support: RVO:61389021 ; RVO:61388998 Keywords : Tokamak * ball- pen probe * emissive probe * L-mode * plasma potential Subject RIV: BL - Plasma and Gas Discharge Physics; BL - Plasma and Gas Discharge Physics (UT-L) Impact factor: 0.838, year: 2014

Floating potential in electronegative plasmas for non-zero ion temperatures

Science.gov (United States)

Regodón, Guillermo Fernando; Fernández Palop, José Ignacio; Tejero-del-Caz, Antonio; Díaz-Cabrera, Juan Manuel; Carmona-Cabezas, Rafael; Ballesteros, Jerónimo

2018-02-01

The floating potential of a Langmuir probe immersed in an electronegative plasma is studied theoretically under the assumption of radial positive ion fluid movement for non-zero positive ion temperature: both cylindrical and spherical geometries are studied. The model is solvable exactly. The special characteristics of the electronegative pre-sheath are found and the influence of the stratified electronegative pre-sheath is shown to be very small in practical applications. It is suggested that the use of the floating potential in the measurement of negative ions population density is convenient, in view of the numerical results obtained. The differences between the two radial geometries, which become very important for small probe radii of the order of magnitude of the Debye length, are studied.

Two-fluid electromagnetic simulations of plasma-jet acceleration with detailed equation-of-state

International Nuclear Information System (INIS)

Thoma, C.; Welch, D. R.; Clark, R. E.; Bruner, N.; MacFarlane, J. J.; Golovkin, I. E.

2011-01-01

We describe a new particle-based two-fluid fully electromagnetic algorithm suitable for modeling high density (n i ∼ 10 17 cm -3 ) and high Mach number laboratory plasma jets. In this parameter regime, traditional particle-in-cell (PIC) techniques are challenging due to electron timescale and lengthscale constraints. In this new approach, an implicit field solve allows the use of large timesteps while an Eulerian particle remap procedure allows simulations to be run with very few particles per cell. Hall physics and charge separation effects are included self-consistently. A detailed equation of state (EOS) model is used to evolve the ion charge state and introduce non-ideal gas behavior. Electron cooling due to radiation emission is included in the model as well. We demonstrate the use of these new algorithms in 1D and 2D Cartesian simulations of railgun (parallel plate) jet accelerators using He and Ar gases. The inclusion of EOS and radiation physics reduces the electron temperature, resulting in higher calculated jet Mach numbers in the simulations. We also introduce a surface physics model for jet accelerators in which a frictional drag along the walls leads to axial spreading of the emerging jet. The simulations demonstrate that high Mach number jets can be produced by railgun accelerators for a variety of applications, including high energy density physics experiments.

Two-fluid electromagnetic simulations of plasma-jet acceleration with detailed equation-of-state

Energy Technology Data Exchange (ETDEWEB)

Thoma, C.; Welch, D. R.; Clark, R. E.; Bruner, N. [Voss Scientific, LLC, Albuquerque, New Mexico 87108 (United States); MacFarlane, J. J.; Golovkin, I. E. [Prism Computational Sciences, Inc., Madison, Wisconsin 53711 (United States)

2011-10-15

We describe a new particle-based two-fluid fully electromagnetic algorithm suitable for modeling high density (n{sub i} {approx} 10{sup 17} cm{sup -3}) and high Mach number laboratory plasma jets. In this parameter regime, traditional particle-in-cell (PIC) techniques are challenging due to electron timescale and lengthscale constraints. In this new approach, an implicit field solve allows the use of large timesteps while an Eulerian particle remap procedure allows simulations to be run with very few particles per cell. Hall physics and charge separation effects are included self-consistently. A detailed equation of state (EOS) model is used to evolve the ion charge state and introduce non-ideal gas behavior. Electron cooling due to radiation emission is included in the model as well. We demonstrate the use of these new algorithms in 1D and 2D Cartesian simulations of railgun (parallel plate) jet accelerators using He and Ar gases. The inclusion of EOS and radiation physics reduces the electron temperature, resulting in higher calculated jet Mach numbers in the simulations. We also introduce a surface physics model for jet accelerators in which a frictional drag along the walls leads to axial spreading of the emerging jet. The simulations demonstrate that high Mach number jets can be produced by railgun accelerators for a variety of applications, including high energy density physics experiments.

Poloidally asymmetric potential increases in tokamak scrape-off layer plasmas by radiofrequency power

International Nuclear Information System (INIS)

Diebold, D.A.; Majeski, R.; Tanaka, T.

1992-01-01

Langmuir probe data are presented which show poloidally asymmetric increases in floating potential, electron temperature and, hence, plasma potential on magnetic field lines which map to the Faraday shield of an ICRF antenna in a medium size tokamak, Phaedrus-T, during radiofrequency power injection. These data are consistent with and suggestive of the existence of radiofrequency generated sheath voltages on those field lines. (author). Letter-to-the-editor. 20 refs, 3 figs

Introduction to plasma engineering

International Nuclear Information System (INIS)

Roth, J.R.

1988-01-01

The author has begun writing a textbook entitled Introduction to Plasma Engineering, which is intended for upper division undergraduates or professionals who are entering the field. This paper features a detailed topical outline of all 20 chapters of the book. The text is organized so that the first five chapters cover plasma physics and basic principles; the next 13 chapters cover the most important engineering applications of plasmas, in order of increasing plasma energy/number density; and two final chapters cover plasma diagnostics and magnetic coil design

Potential formation in a collisionless plasma produced in an open magnetic field in presence of volume negative ion source

International Nuclear Information System (INIS)

Phukan, Ananya; Goswami, K. S.; Bhuyan, P. J.

2014-01-01

The electric potential near a wall for a multi-species plasma with volume produced negative ions in presence of axially varying magnetic field is studied following an analytical-numerical approach. A constant negative ion source is assumed throughout the plasma volume, along with finite temperature positive ions and Boltzmann electrons. The particles are assumed to be guided by an open magnetic field that has its maximum at the centre, and field strength decreasing towards the walls. The one dimensional (1D) Poisson equation is derived using an analytical approach, and then solved numerically to study the potential profiles. Effect of (a) negative ion production rate, (b) magnetic field profile, and (c) negative ion temperature on the potential profile has been investigated. A potential peak appears near the wall when the negative ion temperature and density are sufficiently high. Also, the presence of negative ions further decreases the potential in the plasma region for a finite Debye Length (λ D )

Dispersion relation and Landau damping of waves in high-energy density plasmas

International Nuclear Information System (INIS)

Zhu Jun; Ji Peiyong

2012-01-01

We present a theoretical investigation on the propagation of electromagnetic waves and electron plasma waves in high energy density plasmas using the covariant Wigner function approach. Based on the covariant Wigner function and Dirac equation, a relativistic quantum kinetic model is established to describe the physical processes in high-energy density plasmas. With the zero-temperature Fermi–Dirac distribution, the dispersion relation and Landau damping of waves containing the relativistic quantum corrected terms are derived. The relativistic quantum corrections to the dispersion relation and Landau damping are analyzed by comparing our results with those obtained in classical and non-relativistic quantum plasmas. We provide a detailed discussion on the Landau damping obtained in classical plasmas, non-relativistic Fermi plasmas and relativistic Fermi plasmas. The contributions of the Bohm potential, the Fermi statistics pressure and relativistic effects to the dispersion relation and Landau damping of waves are quantitatively calculated with real plasma parameters. (paper)

Plasma cross-gestational sphingolipidomic analyses reveal potential first trimester biomarkers of preeclampsia.

Directory of Open Access Journals (Sweden)

Aneta Dobierzewska

14:0 were significantly lower in first trimester plasma of PE patients when compared with their gestational-matched control samples (p = 0.009. Major plasma sphingomyelin species (SM 16:0, SM 18:1 and SM 24:0 tended to be higher in control pregnancies across gestation. However, in PE patients, SM 16:0, SM 18:0 and SM 18:1 showed significant up-regulation across gestation, pointing to atherogenic properties of the sphingomyelins and particularly the potential contribution of SM 18:0 to the disease development. In addition, two major sphingomyelins, SM 16:0 and SM 18:0, were significantly lower in first trimester plasma of PE patients versus first trimester samples of respective controls (p = 0.007 and p = 0.002, respectively.Cross-gestational analysis of maternal plasma of preeclamptic and normotensive women identifies differences in the biochemical profile of major sphingolipids (DH-S1P, sphingomyelins and ceramides between these two groups. In addition, first trimester maternal plasma sphingolipids (Cer 14:0, SM 16:0 and SM 18:0 may serve in the future as early biomarkers of PE occurrence and development.

The Potential for Ambient Plasma Wave Propulsion

Science.gov (United States)

Gilland, James H.; Williams, George J.

2016-01-01

A truly robust space exploration program will need to make use of in-situ resources as much as possible to make the endeavor affordable. Most space propulsion concepts are saddled with one fundamental burden; the propellant needed to produce momentum. The most advanced propulsion systems currently in use utilize electric and/or magnetic fields to accelerate ionized propellant. However, significant planetary exploration missions in the coming decades, such as the now canceled Jupiter Icy Moons Orbiter, are restricted by propellant mass and propulsion system lifetimes, using even the most optimistic projections of performance. These electric propulsion vehicles are inherently limited in flexibility at their final destination, due to propulsion system wear, propellant requirements, and the relatively low acceleration of the vehicle. A few concepts are able to utilize the environment around them to produce thrust: Solar or magnetic sails and, with certain restrictions, electrodynamic tethers. These concepts focus primarily on using the solar wind or ambient magnetic fields to generate thrust. Technically immature, quasi-propellantless alternatives lack either the sensitivity or the power to provide significant maneuvering. An additional resource to be considered is the ambient plasma and magnetic fields in solar and planetary magnetospheres. These environments, such as those around the Sun or Jupiter, have been shown to host a variety of plasma waves. Plasma wave propulsion takes advantage of an observed astrophysical and terrestrial phenomenon: Alfven waves. These are waves that propagate in the plasma and magnetic fields around and between planets and stars. The generation of Alfven waves in ambient magnetic and plasma fields to generate thrust is proposed as a truly propellantless propulsion system which may enable an entirely new matrix of exploration missions. Alfven waves are well known, transverse electromagnetic waves that propagate in magnetized plasmas at

On the non-linear dynamics of potential relaxation oscillations in bounded plasmas

International Nuclear Information System (INIS)

Krssak, M.; Skalny, J.D.; Gyergyek, T.; Cercek, M.

2007-01-01

Plasma in a 1-dimensional diode is studied theoretically and the computer simulations are used for verification of the theoretical model. When collector in the diode is biased positively, a double-layer is created in the system and consequently, we are able to observe oscillations of the potential, density and other plasma parameters. When external periodic forcing is applied, spectra of these oscillations are changed and effects of synchronisation and periodic pulling can be observed. Both of these effects are of non-linear nature and a good explanation is found using the analogy with Van der Pol oscillators. Following [1] and [2] approximate analytical solutions are found and then compared with computer simulations obtained using a 1-dimensional particle-in-cell code XPDP1. (author)

Plasma YKL-40: a potential new cancer biomarker?

DEFF Research Database (Denmark)

Johansen, Julia S; Schultz, Nicolai A; Jensen, Benny V

2009-01-01

tissue remodeling. Plasma levels of YKL-40 are elevated in a subgroup of patients with primary or advanced cancer compared with age-matched healthy subjects, but also in patients with many different diseases characterized by inflammation. Elevated plasma YKL-40 levels are an independent prognostic...... by inflammation. Large prospective, longitudinal clinical cancer studies are needed to determine if plasma YKL-40 is a new cancer biomarker, or is mainly a biomarker of inflammation....

Plasma biomarkers in juvenile marine fish provide evidence for endocrine modulation potential of organotin compounds.

Science.gov (United States)

Min, Byung Hwa; Kim, Bo-Mi; Kim, Moonkoo; Kang, Jung-Hoon; Jung, Jee-Hyun; Rhee, Jae-Sung

2018-08-01

Organotin compounds, such as tributyltin (TBT) and triphenyltin (TPT), have been widely used to control marine fouling. Here, we show that organotin stimulation reduces the hormone levels in the plasma of two economically important aquaculture fish. Blood plasma samples were collected from juvenile red seabream and black rockfish exposed to environmentally realistic concentrations of TBT and TPT for 14 days. The levels of two plasma biomarkers, namely the yolk protein precursor vitellogenin (VTG) and the sex steroid 17β-estradiol (E2), were measured to determine the endocrine disrupting potential of the organotin compounds. Both organotin compounds were dose-dependently accumulated in the blood of two fish. Exposure to waterborne TBT and TBT significantly decreased the plasma VTG levels in both the juvenile fish in a dose-dependent manner. In contrast, the treatment with E2, a well-known VTG inducer, significantly increased the plasma VTG levels in both the fish. In addition, the mRNA levels of vtg were also downregulated in the liver tissues of both the fish at 100 and/or 1000 ng L -1 of TBT or TPT exposure. The plasma E2 titers were significantly suppressed at 100 and/or 1000 ng L -1 of TBT or TPT exposure for 14 days compared to their titer in the control. Since estrogen directly regulates vtg gene expression and VTG synthesis, our results reveal the endocrine disrupting potential of organotin compounds, and subsequently the endocrine modulation at early stage of fish can trigger further fluctuations in sexual differentiation, maturation, sex ration or egg production. In addition, the results demonstrate their effects on non-target organisms, particularly on animals reared in aquaculture and fisheries. Copyright © 2018 Elsevier Inc. All rights reserved.

Plasma diagnostics discharge parameters and chemistry

CERN Document Server

Auciello, Orlando

1989-01-01

Plasma Diagnostics, Volume 1: Discharge Parameters and Chemistry covers seven chapters on the important diagnostic techniques for plasmas and details their use in particular applications. The book discusses optical diagnostic techniques for low pressure plasmas and plasma processing; plasma diagnostics for electrical discharge light sources; as well as Langmuir probes. The text also describes the mass spectroscopy of plasmas, microwave diagnostics, paramagnetic resonance diagnostics, and diagnostics in thermal plasma processing. Electrical engineers, nuclear engineers, microwave engineers, che

Plasma processing: Technologies and applications

International Nuclear Information System (INIS)

Naddaf, M.; Saloum, S.

2005-01-01

This study aims to present the fundamentals of physics of plasmas, methods of generation, diagnostics, and applications for processing of materials. The first chapter defines plasma in general as well as its main parameters, the most important differential equations in plasma physics, and classifies the types of plasmas. the various methods and techniques to create and sustain plasma are presented in the second chapter. Chapter 3 focuses on plasma diagnostic methods and tools. While chapter 4 deals with applications of plasma processing such as; surface modification of materials, plasma ashing and etching, plasma cutting, and the environmental applications of plasma. Plasma polymerization and its various applications have been presented in more details in the last chapter. (Author)

Introduction to dusty plasma physics

CERN Document Server

Shukla, PK

2001-01-01

Introduction to Dusty Plasma Physics contains a detailed description of the occurrence of dusty plasmas in our Solar System, the Earth''s mesosphere, and in laboratory discharges. The book illustrates numerous mechanisms for charging dust particles and provides studies of the grain dynamics under the influence of forces that are common in dusty plasma environments.

Stopping potential and ion beamlet control for micro-resistive patterning through sub-Debye length plasma apertures

Directory of Open Access Journals (Sweden)

Abhishek Chowdhury

2014-12-01

Full Text Available Focused multiple ion beamlets from a microwave plasma source is investigated for localized micron-scale modification of substrates in a patterned manner. Plasma electrodes (PE with an array of through apertures having aperture diameters of the order of plasma Debye length are investigated for generating the beamlets. Extraction through sub-Debye length apertures becomes possible when the PE is kept at floating potential. It is found that the current – voltage characteristics of the extracted beamlets exhibits interesting features such as a space-charge-limited region that has a different behaviour than the conventional Child-Langmuir’s law and an extraction-voltage-limited region that does not undergo saturation but exhibits a Schottky-like behaviour similar to that of a vacuum diode. A switching technique to control the motion of individual beamlets is developed and the stopping potential determined. The beamlets are thereafter used to create localized micro-resistive patterns. The experimental results are compared with simulations and reasonably good agreement is obtained.

An Experimental Study of a Pulsed Electromagnetic Plasma Accelerator

Science.gov (United States)

Thio, Y. C. Francis; Eskridge, Richard; Lee, Mike; Smith, James; Martin, Adam; Markusic, Tom E.; Cassibry, Jason T.; Rodgers, Stephen L. (Technical Monitor)

2002-01-01

Experiments are being performed on the NASA Marshall Space Flight Center (MSFC) pulsed electromagnetic plasma accelerator (PEPA-0). Data produced from the experiments provide an opportunity to further understand the plasma dynamics in these thrusters via detailed computational modeling. The detailed and accurate understanding of the plasma dynamics in these devices holds the key towards extending their capabilities in a number of applications, including their applications as high power (greater than 1 MW) thrusters, and their use for producing high-velocity, uniform plasma jets for experimental purposes. For this study, the 2-D MHD modeling code, MACH2, is used to provide detailed interpretation of the experimental data. At the same time, a 0-D physics model of the plasma initial phase is developed to guide our 2-D modeling studies.

Generating end plug potentials in tandem mirror plasma confinement by heating thermal particles so as to escape low density end stoppering plasmas

Science.gov (United States)

Baldwin, D.E.; Logan, B.G.

The invention provides a method and apparatus for raising the potential of a magnetic mirror cell by pumping charged particles of the opposite sign of the potential desired out of the mirror cell through excitation, with the pumping being done by an externally imposed field at the bounce frequence of the above charged particles. These pumped simple mirror cells then provide end stoppering for a center mirror cell for the tandem mirror plasma confinement apparatus. For the substantially complete pumping case, the end plugs of a tandem mirror can be up to two orders of magnitude lower in density for confining a given center mirror cell plasma than in the case of end plugs without pumping. As a result the decrease in recirculating power required to keep the system going, the technical state of the art required, and the capital cost are all greatly lowered.

Collisional effects on interaction potential in complex plasma in presence of magnetic field

International Nuclear Information System (INIS)

Bezbaruah, Pratikshya; Das, Nilakshi

2016-01-01

Interaction potential in complex plasma with streaming ions is derived analytically in presence of ion-neutral collision and magnetic field. The linear dielectric response function obtained describes the behavior of charged micron sized dust particles in strong collisional limit. A new type of repulsive potential is found to be operative among the dust grains apart from the normal Debye–Hückel potential. The amplitude and shielding length involved in the potential are substantially affected by the parameters describing ion cyclotron frequency, collision frequency among ions and neutrals, and ion streaming. It is also observed that the usual mechanism of ion focusing surrounding the grain is inhibited due to collision. As a result, the attractive wake potential structure is destroyed in the ion flow direction. The horizontal interaction involves only Debye–Hückel potential.

Collisional effects on interaction potential in complex plasma in presence of magnetic field

Energy Technology Data Exchange (ETDEWEB)

Bezbaruah, Pratikshya, E-mail: pratphd@tezu.ernet.in; Das, Nilakshi [Department of Physics, Tezpur University, Tezpur, Assam 784028 (India)

2016-04-15

Interaction potential in complex plasma with streaming ions is derived analytically in presence of ion-neutral collision and magnetic field. The linear dielectric response function obtained describes the behavior of charged micron sized dust particles in strong collisional limit. A new type of repulsive potential is found to be operative among the dust grains apart from the normal Debye–Hückel potential. The amplitude and shielding length involved in the potential are substantially affected by the parameters describing ion cyclotron frequency, collision frequency among ions and neutrals, and ion streaming. It is also observed that the usual mechanism of ion focusing surrounding the grain is inhibited due to collision. As a result, the attractive wake potential structure is destroyed in the ion flow direction. The horizontal interaction involves only Debye–Hückel potential.

Dynamics of Turbulence Suppression in a Helicon Plasma

Science.gov (United States)

Hayes, Tiffany; Gilmore, Mark

2012-10-01

Experiments are currently being conducted in the the Helicon-Cathode Device (HelCat) at the University of New Mexico. The goal is to the study in detail the transition from a turbulent to a non-turbulent state in the presence of flow shear. HelCat has intrinsic fluctuations that have been identified as drift-waves. Using simple electrode biasing, it has been found that these fluctuations can be completely suppressed. In some extreme cases, a different instability, possibly the Kelvin-Helmholtz instability, can be excited. Detailed studies are underway in order to understand the characteristics of each mode, and to elucidate the underlying physics that cause the change between an unstable plasma, and an instability-free plasma. Dynamics being observed include changes in flow profiles, both azimuthal and parallel, as well as changes in potential and temperature gradients. Further understanding is being sought using several computer codes developed at EPFL: a linear stability solver (LSS,footnotetextP. Ricci and B.N. Rogers (2009). Phys Plasmas 16, 062303. a one-dimensional PIC code/sheath solver, ODISEE,footnotetextJ. Loizu, P. Ricci, and C. Theiler (2011). Phys Rev E 83, 016406 and a global, 3D Braginski code, GBS.footnotetextRicci, Rogers (2009) A basic overview of results will be presented.

High beta capture and mirror confinement of laser produced plasmas. Final report

International Nuclear Information System (INIS)

Haught, A.F.; Tomlinson, R.G.; Ard, W.B.; Boedeker, L.R.; Churchill, T.L.; Fader, W.J.; Jong, R.A.; Mensing, A.E.; Polk, D.H.; Stufflebeam, J.H.

1977-12-01

The LITE fusion plasma research program at UTRC has been investigating the stabilization and confinement physics of a mirror plasma created by energetic neutral beam heating of a confined target plasma. During the period covered by this report work has been concentrated on the investigation of hot ion losses in a warm target plasma, development of a cryocondensation pump for the LITE beam line neutralizer, theoretical studies of ECRH modification of the ambipolar potential in mirror plasmas, and analysis of the effects of localized cold plasma on DCLC stabilization. The results of these investigations are summarized below and detailed in four papers which comprise the body of this report. Measurements of the lifetime of hot ions in a mirror confined warm plasma have been carried out by observations of the hot ion buildup time obtained with energetic neutral beam injection. A cryocondensation pump of novel design has been constructed and incorporated in the neutralizer chamber of the LITE neutral beam line. Calculations have been carried out to evaluate the sizes and shapes of ambipolar potential modification produced by electron cyclotron resonance heated electrons and to determine the spatial distribution and densities of cold ions trapped in the potential wells. The effects of the spatial distribution of the cold ions on their effectiveness for stabilizing the drift cyclotron loss cone instability has been studied numerically using the formulation of Pearlstein in which the dispersion relation for the DCLC mode is solved for finite-size plasmas containing hot and cold components

Diagnostics of laser-produced plasmas

Directory of Open Access Journals (Sweden)

Batani Dimitri

2016-12-01

Full Text Available We present the general challenges of plasma diagnostics for laser-produced plasmas and give a few more detailed examples: spherically bent crystals for X-ray imaging, velocity interferometers (VISAR for shock studies, and proton radiography.

On atmospheric-pressure non-equilibrium plasma jets and plasma bullets

International Nuclear Information System (INIS)

Lu, X; Laroussi, M; Puech, V

2012-01-01

Atmospheric-pressure non-equilibrium plasma jets (APNP-Js), which generate plasma in open space rather than in a confined discharge gap, have recently been a topic of great interest. In this paper, the development of APNP-Js will be reviewed. Firstly, the APNP-Js are grouped based on the type of gas used to ignite them and their characteristics are discussed in detail. Secondly, one of the most interesting phenomena of APNP-Js, the ‘plasma bullet’, is discussed and its behavior described. Thirdly, the very recent developments on the behavior of plasma jets when launched in a controlled environment and pressure are also introduced. This is followed by a discussion on the interaction between plasma jets. Finally, perspectives on APNP-J research are presented. (paper)

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

Energy Technology Data Exchange (ETDEWEB)

Topala, I., E-mail: ionut.topala@uaic.ro, E-mail: tmnagat@ipc.shizuoka.ac.jp [Alexandru Ioan Cuza University of Iasi, Faculty of Physics, Iasi Plasma Advanced Research Center (IPARC), Bd. Carol I No. 11, Iasi 700506 (Romania); Nagatsu, M., E-mail: ionut.topala@uaic.ro, E-mail: tmnagat@ipc.shizuoka.ac.jp [Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561 (Japan)

2015-02-02

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

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

Science.gov (United States)

Topala, I.; Nagatsu, M.

2015-02-01

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

Methods for the numerical calculation of the plasma potential from measured Langmuir probe characteristics

International Nuclear Information System (INIS)

Seifert, W.; Johanning, D.; Bankov, N.

1986-01-01

In a previous paper the results of the Langmuir probe experiment carried out on board of two INTERKOSMOS satellites have been described. The experiences have shown that the usage of high quality algorithms for analyzing the current-voltage-characteristics is necessary to yield real physical parameters. The key problem is the determination of the plasma potential. This paper reviews the different methods to determine the plasma potential especially under the circumstances of computer application. The test of the well developed methods shows, that for the evaluation of the applied methods a number of different factors, discussed in the following sections of this paper, has to be taken into account. The used test data are model values or real measurements obtained by the satellite missions IK-10, IK-18 and BULGARIA-1300. The computer procedures have been realized as FORTRAN-subroutines for the BESM 6 and ES 1040. (author)

New SUSYQM coherent states for Pöschl-Teller potentials: a detailed mathematical analysis

Science.gov (United States)

Bergeron, H.; Siegl, P.; Youssef, A.

2012-06-01

In a recent short note (Bergeron et al 2010 Europhys. Lett. 92 60003), we have presented the good properties of a new family of semi-classical states for Pöschl-Teller potentials. These states are built from a supersymmetric quantum mechanics (SUSYQM) approach and the parameters of these ‘coherent’ states are points in the classical phase space. In this paper, we develop all the mathematical aspects that have been left out of the previous paper (proof of the resolution of unity, detailed calculations of the quantized version of classical observables and mathematical study of the resulting operators: problems of domains, self-adjointness or self-adjoint extensions). Some additional questions such as asymptotic behavior are also studied. Moreover, the framework is extended to a larger class of Pöschl-Teller potentials. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’.

New SUSYQM coherent states for Pöschl–Teller potentials: a detailed mathematical analysis

International Nuclear Information System (INIS)

Bergeron, H; Siegl, P; Youssef, A

2012-01-01

In a recent short note (Bergeron et al 2010 Europhys. Lett. 92 60003), we have presented the good properties of a new family of semi-classical states for Pöschl–Teller potentials. These states are built from a supersymmetric quantum mechanics (SUSYQM) approach and the parameters of these ‘coherent’ states are points in the classical phase space. In this paper, we develop all the mathematical aspects that have been left out of the previous paper (proof of the resolution of unity, detailed calculations of the quantized version of classical observables and mathematical study of the resulting operators: problems of domains, self-adjointness or self-adjoint extensions). Some additional questions such as asymptotic behavior are also studied. Moreover, the framework is extended to a larger class of Pöschl–Teller potentials. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (paper)

One- and two-photon ionization of hydrogen atom embedded in Debye plasmas

International Nuclear Information System (INIS)

Chang, T. N.; Fang, T. K.; Ho, Y. K.

2013-01-01

We present a detailed analysis of the plasma-induced resonance-like atomic structures near the ionization threshold in one- and two-photon ionization of hydrogen atom. Such resonance-like structures result from the migration of the upper bound excited states of bound-bound atomic transitions into the continuum due to the less attractive screened Coulomb potential which simulates the external environmental effect for an atom embedded in Debye plasma. The change from the resonance-like narrow structures into broad continuous spectra as the plasma effect increases could be accounted for by the overlap between the respective wavefunctions of the atomic electron in the initial state and its corresponding outgoing ionized state in the continuum

Circulating Plasma Levels of MicroRNA-21 and MicroRNA-221 Are Potential Diagnostic Markers for Primary Intrahepatic Cholangiocarcinoma

Science.gov (United States)

Kemeny, Nancy; Kingham, T. Peter; Allen, Peter J.; D’Angelica, Michael I.; DeMatteo, Ronald P.; Betel, Doron; Klimstra, David; Jarnagin, William R.; Ventura, Andrea

2016-01-01

Background MicroRNAs (miRNAs) are potential biomarkers in various malignancies. We aim to characterize miRNA expression in intrahepatic cholangiocarcinoma (ICC) and identify circulating plasma miRNAs with potential diagnostic and prognostic utility. Methods Using deep-sequencing techniques, miRNA expression between tumor samples and non-neoplastic liver parenchyma were compared. Overexpressed miRNAs were measured in plasma from an independent cohort of patients with cholangiocarcinoma using RT-qPCR and compared with that healthy volunteers. The discriminatory ability of the evaluated plasma miRNAs between patients and controls was evaluated with receiving operating characteristic (ROC) curves. Results Small RNAs from 12 ICC and 11 tumor-free liver samples were evaluated. Unsupervised hierarchical clustering using the miRNA expression data showed clear grouping of ICC vs. non-neoplastic liver parenchyma. We identified 134 down-regulated and 128 upregulated miRNAs. Based on overexpression and high fold-change, miR21, miR200b, miR221, and miR34c were measured in plasma from an independent cohort of patients with ICC (n = 25) and healthy controls (n = 7). Significant overexpression of miR-21 and miR-221 was found in plasma from ICC patients. Furthermore, circulating miR-21 demonstrated a high discriminatory ability between patients with ICC and healthy controls (AUC: 0.94). Conclusion Among the differentially expressed miRNAs in ICC, miR-21 and miR-221 are overexpressed and detectable in the circulation. Plasma expression levels of these miRNAs, particularly miR-21, accurately differentiates patients with ICC from healthy controls and could potentially serve as adjuncts in diagnosis. Prospective validation and comparison with other hepatobiliary malignancies is required to establish their potential role as diagnostic and prognostic biomarkers. PMID:27685844

Ionic regulation of the plasma membrane potential of rainbow trout (Salmo gairdneri) spermatozoa: Role in the initiation of sperm motility

International Nuclear Information System (INIS)

Gatti, J.L.; Billard, R.; Christen, R.

1990-01-01

The ionic dependence of the trout sperm plasma membrane potential was analysed by measuring the accumulation of the lipophilic ions 3 H-tetraphenylphosphonium (TPP) and 14 C-thiocyanate (SCN) following dilution in artificial media isotonic to the seminal fluid. Our data showed that the trout sperm plasma membrane has a mixed conductance: the plasma membrane potential is sensitive upon the transmembrane gradients of K+, Na+, and H+. This potential is negative (less than -40 mV) in a 125 mM choline chloride media (ChM) at pH 8.5. Replacement of choline by sodium has a small depolarizing effect. The membrane potential is about -15 mV in a 125 mM potassium chloride and falls near zero mV only if valinomycin is added. In ChM changing the external pH (pHe) greatly affects the membrane potential: its value rises from less than -40 mV at pHe 9.0 to -17 mV at pHe 5.0. This pH effect is observed also in presence of sodium or potassium. A decrease in the transmembrane proton gradient produced by increasing internal pH without changing pHe induces also a depolarisation of the plasma membrane. In the different media in which trout sperm remain immotile after dilution (media with [K+] greater than 20-40 mM or a pH less than 7.5) the plasma membrane is more depolarized than in media allowing motility, suggesting a relationship between the state of membrane polarization and the intracellular effectors of the axonemal movement

Modeling plasma/material interactions during a tokamak disruption

International Nuclear Information System (INIS)

Hassanein, A.; Konkashbaev, I.

1994-10-01

Disruptions in tokamak reactors are still of serious concern and present a potential obstacle for successful operation and reliable design. Erosion of plasma-facing materials due to thermal energy dump during a disruption can severely limit the lifetime of these components, therefore diminishing the economic feasibility of the reactor. A comprehensive disruption erosion model which takes into account the interplay of major physical processes during plasma-material interaction has been developed. The initial burst of energy delivered to facing-material surfaces from direct impact of plasma particles causes sudden ablation of these materials. As a result, a vapor cloud is formed in front of the incident plasma particles. Shortly thereafter, the plasma particles are stopped in the vapor cloud, heating and ionizing it. The energy transmitted to the material surfaces is then dominated by photon radiation. It is the dynamics and the evolution of this vapor cloud that finally determines the net erosion rate and, consequently, the component lifetime. The model integrates with sufficient detail and in a self-consistent way, material thermal evolution response, plasma-vapor interaction physics, vapor hydrodynamics, and radiation transport in order to realistically simulate the effects of a plasma disruption on plasma-facing components. Candidate materials such as beryllium and carbon have been analyzed. The dependence of the net erosion rate on disruption physics and various parameters was analyzed and is discussed

Self-consistent electrostatic potential due to trapped plasma in the magnetosphere

International Nuclear Information System (INIS)

Miller, R.H.; Khazanov, G.V.

1993-01-01

The authors address the problem of the steady state confinement of plasma in a magnetic flux tube. They construct a steady state distribution function, under the assumption of no waves or collisions, using the kinematic constants of the motion, total energy and magnetic moment. The local particle densities are shown to be integrals over the equatorial distribution function for the particle of concern. The electric potential is determined by the imposition of quasineutrality. The authors show that their self consistent model produces potential drops which are consistent with the kinetic energy of the equatorially trapped particles. They comment on earlier work of Alfven and Faelthammar, and for a bi-Maxwellian distribution compare the results of the present model with the Alfven and Faelthammar model

MiOXSYS: a novel method of measuring oxidation reduction potential in semen and seminal plasma.

Science.gov (United States)

Agarwal, Ashok; Sharma, Rakesh; Roychoudhury, Shubhadeep; Du Plessis, Stefan; Sabanegh, Edmund

2016-09-01

To measure oxidative reduction potential (ORP) in semen and seminal plasma and to establish their reference levels. ORP levels were measured in semen and seminal plasma. Tertiary hospital. Twenty-six controls and 33 infertile men. None. Static ORP (sORP) and capacitance ORP (cORP) were measured in semen and seminal plasma at time 0 and 120 minutes. Correlation of ORP was assessed between [1] semen and seminal plasma and [2] time 0 and 120 minutes. The association with sperm parameters was studied in (a) controls and (b) infertile patients, and a receiver operating characteristic curve was generated to establish the sORP cutoff. Semen sORP and cORP levels were associated with seminal plasma levels at time 0 and time 120 minutes. In controls and infertile patients, an inverse relationship of sORP levels was established with concentration and total sperm count in semen as well as seminal plasma at time 0 and 120 minutes. Classification of subjects based on sperm motility showed that subjects with abnormal motility present with poor concentration, total count, morphology, and elevated levels of semen and seminal plasma sORP at time 120 minutes. The sORP cutoff of 1.48 in semen and 2.09 in seminal plasma based on motility was able to distinguish subjects with normal semen quality from those with abnormal semen quality. The MiOXSYS System can reliably measure ORP levels in semen and seminal plasma. ORP levels are not affected by semen age, making this new technology easy to employ in a clinical setting. Copyright © 2016 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

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)

Electric potential structures and propagation of electron beams injected from a spacecraft into a plasma

International Nuclear Information System (INIS)

Singh, Nagendra; Hwang, K.S.

1988-01-01

The propagation of electron beams injected from a spacecraft into an ambient plasma and the associated potential structures are investigated by one-dimensional Vlasov simulations. For moderate beams, for which the time average spacecraft potential (Φ sa ) lies in the range T e much-lt eΦ sa approx-lt W B , where T e is the electron temperature in energy units and W B is the average beam energy, a double layer forms near the beam head which propagates into the ambient plasma much more slowly than the initial beam velocity. The double layer formation is being reported for the first time. For weak beams, for which |eΦ sa | approx-lt T e , the beam propagates with the initial beam velocity, and no double layer formation occurs. On the other hand, for strong beams for which eΦ sa > W B , the bulk of the beam is returned to the spacecraft, and the main feature of the potential structure is a sheath formation with an intense electric field limited to distances d near the spacecraft surface. These features of the potential structures are compared with those seen in laboratory and space experiments on electron beam injections

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

technological solution in the early to late 1990s of confining atmospheric plasmas in a small volume of plasma generation (i.e. with a small volume-to-surface ratio) and then extending it towards a downstream sample [7]-[9]. These are among the first low-temperature atmospheric plasmas aimed particularly at the exploitation of their ability to invoke the active and rich reactive chemistry close to ambient temperature. The main applications of these early devices are precision surface modification of low-temperature dielectric materials, for example thin film deposition and etching [7]-[9]. Variations of the early plasma jets include atmospheric plasma sheet jets [10] for the treatment of largely planar objects (e.g. polymeric sheets) as well as large arrays of many plasma jets for the treatment of complex-structured objects (e.g. surgical tools and open human wounds) [11]. As a material processing technology, the sub-100oC atmospheric-pressure plasma jet has benefited over the years from many innovations. Whilst a detailed account and analysis of these is clearly outside the scope of this Editorial, it is worth stating that there are different avenues with which to maintain a moderate electron density at the plasma core so as to keep the gas temperature at the sample point below a ceiling level. Most of the early studies employed excitation at radio frequencies above 10 MHz, at which electrons are largely confined in the plasma generation region, and this limits the current flow to and gas heating in the plume region of the plasma jet. Other techniques of current limitation have since been shown to be effective, including the use of dielectric barriers across a very large frequency range of 1 kHz--50 MHz, sub-microsecond pulses sustained at kHz frequencies, pulse-modulated radio frequencies and dual-frequency excitation [12]-[15]. These and other techniques have considerably advanced the atmospheric-pressure plasma jet technology. The period of some 15 years since the above

Waves and Oscillations in Plasmas

CERN Document Server

Pecseli, Hans L

2012-01-01

The result of more than 15 years of lectures in plasma sciences presented at universities in Denmark, Norway, and the United States, Waves and Oscillations in Plasmas addresses central issues in modern plasma sciences. The book covers fluid models as well as kinetic plasma models, including a detailed discussion of, for instance, collisionless Landau damping. Offering a clear separation of linear and nonlinear models, the book can be tailored for readers of varying levels of expertise.Designed to provide basic training in linear as well as nonlinear plasma dynamics, and practical in areas as d

Plasma heating - a comparative overview for future applications

International Nuclear Information System (INIS)

Wilhelm, R.

1989-01-01

Successful plasma heating is essential in present fusion experiments, for the demonstration of D-T burn in future devices and finally for the fusion reactor itself. This paper discusses the common heating system with respect to their present performance and their applicability to future fusion devices. The comparative discussion is oriented to the various functions of heating, which are: Plasma heating to fusion-relevant parameters and to ignition in future machines, non-inductive, steady-state current drive, plasma profile control, neutral gas breakdown and plasma build-up. In view of these different functions, the potential of neutral beam injection (NBI) and the various schemes of wave heating (ECRH, LH, ICRH and Alfven wave heating) is analyzed in more detail. The analysis includes assessments of the present physical and technical state of these heating methods, and makes suggestions for future developments and about outstanding problems. Specific attention is given to the still critical problem of efficient current drive, especially with respect to further extrapolation towards an economically operating tokamak reactor. Remarks on issues such as reliability, maintenance and economy conclude this comparative overview on plasma heating systems. (orig.)

Combline antenna modeling for plasma heating

International Nuclear Information System (INIS)

Nelson, S.D.; Kamin, G.; Van Maren, R.; Poole, B.; Moeller, C.; Phelps, D.

1996-01-01

The combline antenna for plasma heating, as proposed by General Atomics(1), has unique potential for solving many plasma drive problems. The benefit of the combline design is the utilization of the coupling between elements that avoids a more cumbersome multidrive system. This design is being investigated using computational EM modeling codes in the 100 endash 400 MHz band using resources at General Atomics and LLNL. Preliminary experimental results, using a combline mockup, agree well with 3D modeling efforts including resonant frequency alignment and amplitudes. These efforts have been expanded into an endeavor to optimize the combline design using both time and frequency domain codes. This analysis will include plasma coupling but to date has been limited to antenna effects. The combline antenna system is modeled in 3D using a combination of computational tools in the time domain, for temporal feature isolation purposes, and in the frequency domain, for resonant structure analysis. Both time and frequency domain modeling details include the Faraday shield elements, the strap elements, and the feed structure. copyright 1996 American Institute of Physics

Two-extremum electrostatic potential of metal-lattice plasma and the work function of an electron

Directory of Open Access Journals (Sweden)

Surma S.A.

2015-06-01

Full Text Available Metal-lattice plasma is treated as a neutral two-component two-phase system of 2D surface and 3D bulk. Free electron density and bulk chemical potential are used as intensive parameters of the system with the phase boundary position determined in the crystalline lattice. A semiempirical expression for the electron screened electrostatic potential is constructed using the lattice-plasma polarization concept. It comprises an image term and three repulsion/attraction terms of second and fourth orders. The novel curve has two extremes and agrees with certain theoretical forms of potential. A practical formula for the electron work function of metals and a simplified schema of electronic structure at the metal/vacuum interface are proposed. This yields 10.44 eV for the Fermi energy of free electron gas; -5.817 eV for the Fermi energy level; 4.509 eV for the average work function of bcc tungsten. Selected data are also given for fcc Cu and hcp Re. For harmonic frequencies ~ 10E16 per s of the self-excited metal-lattice plasma, energy gaps of 14.54 and 8.02 eV are found, which correspond to the bulk and surface plasmons, respectively. Further extension of this thermodynamics and metal-lattice theory based approach may contribute to a better understanding of theoretical models which are employed in chemical physics, catalysis and materials science of nanostructures.

Detailed spectral simulations in support of PBFA-Z dynamic hohlraum Z-pinch experiments

International Nuclear Information System (INIS)

MacFarlane, J.J.; Wang, P.; Derzon, M.S.; Haill, A.; Nash, T.J.; Peterson, D.L.

1997-01-01

In PBFA-Z dynamic hohlraum Z-pinch experiments, 16--18 MA of current is delivered to a load comprises of a tungsten wire array surrounding a low-density cylindrical CH foam. The magnetic field accelerates the W plasma radially inward at velocities ∼ 40--60 cm/micros. The W plasma impacts into the foam, generating a high T R radiation field which diffuses into the foam. The authors are investigating several types of spectral diagnostics which can be used to characterize the time-dependent conditions in the foam. In addition, they are examining the potential ramifications of axial jetting on the interpretation of axial x-ray diagnostics. In the analysis, results from 2-D radiation-magnetohydrodynamics simulations are post-processed using a hybrid spectral analysis code in which low-Z material is treated using a detailed collisional-radiative atomic model, while high-Z material is modeled using LTE UTA (unresolved transition array) opacities. They will present results from recent simulations and discuss ramifications for x-ray diagnostics

Drag force in strongly coupled, anisotropic plasma at finite chemical potential

Energy Technology Data Exchange (ETDEWEB)

Chakraborty, Somdeb; Haque, Najmul [Theory Division, Saha Institute of Nuclear Physics,1/AF Bidhannagar, Kolkata-700 064 (India)

2014-12-30

We employ methods of gauge/string duality to analyze the drag force on a heavy quark moving through a strongly coupled, anisotropic N=4,SU(N) super Yang-Mills plasma in the presence of a finite U(1) chemical potential. We present numerical results valid for any value of the anisotropy parameter and the U(1) charge density and arbitrary direction of the quark velocity with respect to the direction of anisotropy. In the small anisotropy limit we are also able to furnish analytical results.

Enzymatic Modification of Plasma Low Density Lipoproteins in Rabbits: A Potential Treatment for Hypercholesterolemia

Science.gov (United States)

Labeque, Regine; Mullon, Claudy J. P.; Ferreira, Joao Paulo M.; Lees, Robert S.; Langer, Robert

1993-04-01

Phospholipase A_2 (EC 3.1.1.4) hydrolyzes certain phospholipids of low density lipoprotein (LDL). Plasma clearance of phospholipase A_2-modified human LDL is up to 17 times faster than that of native human LDL in hypercholesterolemic rabbits. Modification of blood lipoproteins of hypercholesterolemic rabbits was performed by using an extracorporeal circuit containing immobilized phospholipase A_2. After 90-min treatments, nearly 30% decreases in plasma cholesterol concentrations were observed. Erythrocyte, leukocyte, and platelet counts showed no net change after treatment. This technique does not require any fluid replacement or sorbent regeneration and offers a potential approach for lowering serum cholesterol and LDL levels.

Dynamic plasma screening effects on atomic collisions in dense plasmas

International Nuclear Information System (INIS)

Young-Dae Jung

1999-01-01

Dynamic plasma screening effects are investigated on electron-ion collisional excitation and Coulomb Bremsstrahlung processes in dense plasmas. The electron-ion interaction potential is considered by introduction of the plasma dielectric function. The straight-ling trajectory method is applied to the path of the projectile electron. The transition probability including the dynamic plasma screening effect is found to be always greater than that including the static plasma screening effects. It is found that the differential Bremsstrahlung radiation cross section including the dynamic plasma screening effect is also greater than that including the static plasma screening effect. When the projectile velocity is smaller than the electron thermal velocity, the dynamic polarization screening effect becomes the static plasma screening effect. However, when the projectile velocity is greater than the electron thermal velocity, the interaction potential is almost unshielded

Large amplitude ion-acoustic solitons in dusty plasmas

International Nuclear Information System (INIS)

Tiwari, R. S.; Jain, S. L.; Mishra, M. K.

2011-01-01

Characteristics of ion-acoustic soliton in dusty plasma, including the dynamics of heavily charged massive dust grains, are investigated following the Sagdeev Potential formalism. Retaining fourth order nonlinearities of electric potential in the expansion of the Sagdeev Potential in the energy equation for a pseudo particle and integrating the resulting energy equation, large amplitude soliton solution is determined. Variation of amplitude (A), half width (W) at half maxima and the product P = AW 2 of the Korteweg-deVries (KdV), dressed and large amplitude soliton as a function of wide range of dust concentration are numerically studied for recently observed parameters of dusty plasmas. We have also presented the region of existence of large amplitude ion-acoustic soliton in the dusty plasma by analyzing the structure of the pseudo potential. It is found that in the presence of positively charged dust grains, system supports only compressive solitons, on the other hand, in the presence of negatively charged dust grains, the system supports compressive solitons up to certain critical concentration of dust grains and above this critical concentration, the system can support rarefactive solitons also. The effects of dust concentration, charge, and mass of the dust grains, on the characteristics of KdV, dressed and large amplitude the soliton, i.e., amplitude (A), half width at half maxima (W), and product of amplitude (A) and half width at half maxima (P = AW 2 ), are discussed in detail

Plasma etching: Yesterday, today, and tomorrow

Energy Technology Data Exchange (ETDEWEB)

Donnelly, Vincent M.; Kornblit, Avinoam [Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204 (United States)

2013-09-15

The field of plasma etching is reviewed. Plasma etching, a revolutionary extension of the technique of physical sputtering, was introduced to integrated circuit manufacturing as early as the mid 1960s and more widely in the early 1970s, in an effort to reduce liquid waste disposal in manufacturing and achieve selectivities that were difficult to obtain with wet chemistry. Quickly, the ability to anisotropically etch silicon, aluminum, and silicon dioxide in plasmas became the breakthrough that allowed the features in integrated circuits to continue to shrink over the next 40 years. Some of this early history is reviewed, and a discussion of the evolution in plasma reactor design is included. Some basic principles related to plasma etching such as evaporation rates and Langmuir–Hinshelwood adsorption are introduced. Etching mechanisms of selected materials, silicon, silicon dioxide, and low dielectric-constant materials are discussed in detail. A detailed treatment is presented of applications in current silicon integrated circuit fabrication. Finally, some predictions are offered for future needs and advances in plasma etching for silicon and nonsilicon-based devices.

Plasma etching: Yesterday, today, and tomorrow

International Nuclear Information System (INIS)

Donnelly, Vincent M.; Kornblit, Avinoam

2013-01-01

The field of plasma etching is reviewed. Plasma etching, a revolutionary extension of the technique of physical sputtering, was introduced to integrated circuit manufacturing as early as the mid 1960s and more widely in the early 1970s, in an effort to reduce liquid waste disposal in manufacturing and achieve selectivities that were difficult to obtain with wet chemistry. Quickly, the ability to anisotropically etch silicon, aluminum, and silicon dioxide in plasmas became the breakthrough that allowed the features in integrated circuits to continue to shrink over the next 40 years. Some of this early history is reviewed, and a discussion of the evolution in plasma reactor design is included. Some basic principles related to plasma etching such as evaporation rates and Langmuir–Hinshelwood adsorption are introduced. Etching mechanisms of selected materials, silicon, silicon dioxide, and low dielectric-constant materials are discussed in detail. A detailed treatment is presented of applications in current silicon integrated circuit fabrication. Finally, some predictions are offered for future needs and advances in plasma etching for silicon and nonsilicon-based devices

A study of the transient plasma potential in a pulsed bi-polar dc magnetron discharge

International Nuclear Information System (INIS)

Bradley, J W; Karkari, S K; Vetushka, A

2004-01-01

The temporal evolution of the plasma potential, V p , in a pulsed dc magnetron plasma has been determined using the emissive probe technique. The discharge was operated in the 'asymmetric bi-polar' mode, in which the discharge voltage changes polarity during part of the pulse cycle. The probe measurements, with a time-resolution of 20 ns or better, were made along a line above the racetrack, normal to the plane of the cathode target, for a fixed frequency (100 kHz), duty cycle (50%), argon pressure (0.74 Pa) and discharge power (583 W). At all the measured positions, V p was found to respond to the large and rapid changes in the cathode voltage, V d , during the different phases of the pulse cycle, with V p always more positive than V d . At a typical substrate position (>80 mm from the target), V p remains a few volts above the most positive surface in the discharge at all times. In the 'on' phase of the pulse, the measurements show a significant axial electric field is generated in the plasma, with the plasma potential dropping by a total of about 30 V over a distance of 70 mm, from the bulk plasma to a position close to the beginning of the cathode fall. This is consistent with measurements made in the dc magnetron. During the stable 'reverse' phase of the discharge, for distances greater than 18 mm from the target, the axial electric field is found to collapse, with V p elevated uniformly to about 3 V above V d . Between the target and this field-free region an ion sheath forms, and the current flowing to the target is still an ion current in this 'reverse' period. During the initial 200 ns of the voltage 'overshoot' phase (between 'on' and 'reverse' phases), V d reached a potential of +290 V; however, close to the target, V p was found to attain a much higher value, namely +378 V. Along the line of measurement, the axial electric field reverses in direction in this phase, and an electron current of up to 9 A flows to the target. The spatial and temporal

Nonlinear relativistic plasma resonance: Renormalization group approach

Energy Technology Data Exchange (ETDEWEB)

Metelskii, I. I., E-mail: metelski@lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Kovalev, V. F., E-mail: vfkvvfkv@gmail.com [Dukhov All-Russian Research Institute of Automatics (Russian Federation); Bychenkov, V. Yu., E-mail: bychenk@lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

2017-02-15

An analytical solution to the nonlinear set of equations describing the electron dynamics and electric field structure in the vicinity of the critical density in a nonuniform plasma is constructed using the renormalization group approach with allowance for relativistic effects of electron motion. It is demonstrated that the obtained solution describes two regimes of plasma oscillations in the vicinity of the plasma resonance— stationary and nonstationary. For the stationary regime, the spatiotemporal and spectral characteristics of the resonantly enhanced electric field are investigated in detail and the effect of the relativistic nonlinearity on the spatial localization of the energy of the plasma relativistic field is considered. The applicability limits of the obtained solution, which are determined by the conditions of plasma wave breaking in the vicinity of the resonance, are established and analyzed in detail for typical laser and plasma parameters. The applicability limits of the earlier developed nonrelativistic theories are refined.

Effect of exchange correlation potential on dispersion properties of lower hybrid wave in degenerate plasma

Science.gov (United States)

Rimza, Tripti; Sharma, Prerana

2017-05-01

The dispersion properties of lower hybrid wave are studied in electron-iondegenerate plasma with exchange effect in non-relativistic regime. It is found that the combined effect of Bohm potential and exchange correlation potential significantly modifies the dispersion properties of lower hybrid wave. The graphical results explicitly show the influence of degeneracy pressure, Bohm force and exchange correlation potential on the frequency of the lower hybrid mode. Present work should be of relevance for the dense astrophysical environments like white dwarfs and for laboratory experiments.

Studies of the ablated plasma from experimental plasma gun disruption simulations

International Nuclear Information System (INIS)

Rockett, P.D.; Hunter, J.A.; Bradley, J.T. III; Gahl, J.M.; Litunovsky, V.N.; Ovchinnokov, I.B.; Ljublin, B.V.; Kuznetsov, B.E.; Titov, V.A.; Zhitlukhin, A.; Arkhipov, K.; Bakhtin, V.; Toporkov, D.

1995-01-01

Extensive simulations of tokamak disruptions have provided a picture of material erosion that is limited by the transfer of energy from the incident plasma to the armor solid surface through a dense plasma shield. Radiation spectra were recorded in the VUV and in the visible at the Efremov Laboratories on VIKA using graphite targets. The VUV data were recorded with a Sandia Labs transmission grating spectrograph, covering 1-40 nm. Plasma parameters were evaluated with incident plasma energy densities varying from 10-100 MJ/m 2 . A second transmission grating spectrograph was taken to 2MK-200 at TRINITI to study the plasma-material interface in magnetic cusp plasma. Target materials included POCO graphite, ATJ graphite, boron nitride, and plasma-sprayed tungsten. Detailed spectra were recorded with a spatial resolution of similar 1 mm. Time-resolved data with 40-200 ns resolution was also recorded. The data from both plasma gun facilities demonstrated that the hottest plasma region was sitting several millimeters above the armor tile surface. ((orig.))

Reconstruction of the time-averaged sheath potential profile in an argon RF plasma using the ion energy distribution

International Nuclear Information System (INIS)

Fivaz, M.; Brunner, S.; Schwarzenbach, W.; Howling, A.A.; Hollenstein, C.

1994-10-01

Charge-exchange collisions and radio-frequency excitation combine to give peaks in the ion energy distribution measured at the ground electrode of an argon plasma in a capacitive reactor. These peaks are used as a diagnostic to reconstruct the profile of the time-averaged potential in the sheath. Particle-In-Cell simulations show that the method is accurate. The method is applied to investigate the sheath thickness as a function of excitation frequency at constant plasma power. The time-averaged potential is found to be parabolic in both experimental measurements and numerical simulation. (author) 6 figs., 1 tab., 15 refs

Presheath profiles in simulated tokamak edge plasmas

International Nuclear Information System (INIS)

LaBombard, B.; Conn, R.W.; Hirooka, Y.; Lehmer, R.; Leung, W.K.; Nygren, R.E.; Ra, Y.; Tynan, G.

1988-04-01

The PISCES plasma surface interaction facility at UCLA generates plasmas with characteristics similar to those found in the edge plasmas of tokamaks. Steady state magnetized plasmas produced by this device are used to study plasma-wall interaction phenomena which are relevant to tokamak devices. We report here progress on some detailed investigations of the presheath region that extends from a wall surface into these /open quotes/simulated tokamak/close quotes/ edge plasma discharges along magnetic field lines

Plasma out of thermodynamical equilibrium: influence of the plasma environment on atomic structure and collisional cross sections

International Nuclear Information System (INIS)

Belkhiri, Madeny

2014-01-01

In hot dense plasmas, the free-electron and ion spatial distribution may strongly affect the atomic structure. To account for such effects we have implemented a potential correction based on the uniform electron gas model and on a Thomas-Fermi Approach in the Flexible Atomic Code (FAC). This code has been applied to obtain energies, wave-functions and radiative rates modified by the plasma environment. In hydrogen-like ions, these numerical results have been successfully compared to an analytical calculation based on first-order perturbation theory. In the case of multi-electron ions, we observe level crossings in agreement with another recent model calculation. Various methods for the collision cross-section calculations are reviewed. The influence of plasma environment on these cross-sections is analyzed in detail. Some analytical expressions are proposed for hydrogen-like ions in the limit where Born or Lotz approximations apply and are compared to the numerical results from the FAC code. Finally, from this work, we study the influence of the plasma environment on our collisional-radiative model so-called Foch. Because of this environment, the mean charge state of the ions increases. The line shift is observed on the bound-bound emission spectra. A good agreement is found between our work and experimental data on a Titanium plasma. (author) [fr

Bohm potential effect on the propagation of electrostatic surface wave in semi-bounded quantum plasmas

Energy Technology Data Exchange (ETDEWEB)

Lee, Myoung-Jae [Department of Physics, Hanyang University, Seoul 04763 (Korea, Republic of); Research Institute for Natural Sciences, Hanyang University, Seoul 04763 (Korea, Republic of); Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr [Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 15588 (Korea, Republic of); Department of Electrical and Computer Engineering, MC 0407, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0407 (United States)

2017-02-12

High frequency electrostatic wave propagation in a dense and semi-bounded electron quantum plasma is investigated with consideration of the Bohm potential. The dispersion relation for the surface mode of quantum plasma is derived and numerically analyzed. We found that the quantum effect enhances the frequency of the wave especially in the high wave number regime. However, the frequency of surface wave is found to be always lower than that of the bulk wave for the same quantum wave number. The group velocity of the surface wave for various quantum wave number is also obtained. - Highlights: • High frequency electrostatic wave propagation is investigated in a dense semi-bounded quantum plasma. • The dispersion relation for the surface mode of quantum plasma is derived and numerically analyzed. • The quantum effect enhances the frequency of the wave especially in the high wave number regime. • The frequency of surface wave is found to be always lower than that of the bulk wave. • The group velocity of the surface wave for various quantum wave number is also obtained.

Potential of electric discharge plasma methods in abatement of volatile organic compounds originating from the food industry.

Science.gov (United States)

Preis, S; Klauson, D; Gregor, A

2013-01-15

Increased volatile organic compounds emissions and commensurate tightening of applicable legislation mean that the development and application of effective, cost-efficient abatement methods are areas of growing concern. This paper reviews the last two decades' publications on organic vapour emissions from food processing, their sources, impacts and treatment methods. An overview of the latest developments in conventional air treatment methods is presented, followed by the main focus of the paper, non-thermal plasma technology. The results of the review suggest that non-thermal plasma technology, in its pulsed corona discharge configuration, is an emerging treatment method with potential for low-cost, effective abatement of a wide spectrum of organic air pollutants. It is found that the combination of plasma treatment with catalysis is a development trend that demonstrates considerable potential. The as yet relatively small number of plasma treatment applications is considered to be due to the novelty of pulsed electric discharge techniques and a lack of reliable pulse generators and reactors. Other issues acting as barriers to widespread adoption of the technique include the possible formation of stable oxidation by-products, residual ozone and nitrogen oxides, and sensitivity towards air humidity. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effects of inhomogeneity on the Shukla-Nambu-Salimullah and wake potentials in a streaming dusty magnetoplasma

International Nuclear Information System (INIS)

Salimullah, M.; Khan, M.I.U.; Amin, R.; Nitta, H.; Shukla, P.K.

2005-10-01

Detailed properties of the electrostatic Shukla-Nambu-Salimullah and the dynamical oscillatory wake potentials in an inhomogeneous dusty magnetoplasma in the presence of ion streaming, as in a laboratory discharge plasma, have been examined analytically. The potentials become sensitive functions of the external static magnetic field, the scale-length of inhomogeneity, and the deviation from the linear ion streaming velocity. For a decreasing ion density gradient, there is a limit of existence of the static modified shielding potential. For a strongly inhomogeneous dusty plasma, the effective length of the oscillatory wake potential increases with increasing deviation of the ion streaming velocity (u i0y ), but it does not depend on the external magnetic field. (author)

Investigation of plasma-related matrix effects in inductively coupled plasma-atomic emission spectrometry caused by matrices with low second ionization potentials-identification of the secondary factor

International Nuclear Information System (INIS)

Chan, George C.-Y.; Hieftje, Gary M.

2006-01-01

Plasma-related matrix effects induced by a comprehensive list of matrix elements (a total of fifty-one matrices) in inductively coupled plasma-atomic emission spectrometry were investigated and used to confirm that matrix effects caused by elements with a low second ionization potential are more severe than those from matrix elements having a low first ionization potential. Although the matrix effect is correlated unambiguously with the second ionization potential of a matrix, the correlation is not monotonic, which suggests that at least one other factor is operative. Through study of a large pool of matrix elements, it becomes possible to identify another critical parameter that defines the magnitude of the matrix effect; namely the presence of low-lying energy levels in the doubly charged matrix ion. Penning ionization by Ar excited states is proposed as the dominant mechanism for both analyte ionization/excitation and matrix effects; matrices with a low second ionization potential can effectively quench the population of Ar excited states through successive Penning ionization followed by ion-electron recombination and lead to more severe matrix effects

Generation of radiation by intense plasma and electromagnetic undulators

International Nuclear Information System (INIS)

Joshi, C.

1989-01-01

This is a second year progress report which details the work on the generation of radiation by intense plasma and electromagnetic undulators being carried out at UCLA. The status of the experimental work is described and the future directions are outlined. We have completed the first phase of experiments on the plasma wiggler generation and characterization. Suitability of a null-pinch as a plasma source was investigated in great detail. It is found that a w of a few percent can be excited but there are trapped magnetic fields within null-pinch plasma which hinder the injection of the electrons. A new more uniform and field-free plasma source is now being characterized

Generation of radiation by intense plasma and electromagnetic undulators

International Nuclear Information System (INIS)

Joshi, C.

1989-01-01

This is a second year progress report which details the work on the generation of radiation by intense plasma and electromagnetic undulators being carried out at UCLA. The status of the experimental work is described and the future directions are outlined. We have completed the first phase of experiments on the plasma wiggler generation and characterization. Suitability of a θ-pinch as a plasma source was investigated in great detail. It is found that a w of a few percent can be excited but there are trapped magnetic fields within θ-pinch plasma which hinder the injection of the electrons. A few more uniform and field-free plasma source is now being characterized. 8 refs., 5 figs

Equation of state of partially-ionized dense plasmas

International Nuclear Information System (INIS)

Rogers, F.J.

1989-01-01

This paper describes methods for calculating the equation of state of partially-ionized dense plasmas. The term dense plasma is used rather than strongly coupled plasma, since it is possible that at plasma conditions such that only a few levels can be observed spectroscopically the plasma coupling parameters are not large. Due mainly to their importance in theoretical astrophysics, the properties of partially ionized plasmas have been of interest for a long while. More recently, this interest has intensified due to the development of methods for producing partially ionized plasmas in the laboratory. This has opened up large programs of experimental investigation and of practical application. In this paper we consider detailed statistical mechanical methods that explicitly treat the distribution over ionic species and their energy level structure. These detailed approaches are generally characterized as being in the ''chemical picture'' when a free energy expression is minimized or in the ''physical picture'' when the starting point is the grand canonical ensemble. 52 refs., 2 tabs

Numerical simulations of a sounding rocket in ionospheric plasma: Effects of magnetic field on the wake formation and rocket potential

Science.gov (United States)

Darian, D.; Marholm, S.; Paulsson, J. J. P.; Miyake, Y.; Usui, H.; Mortensen, M.; Miloch, W. J.

2017-09-01

The charging of a sounding rocket in subsonic and supersonic plasma flows with external magnetic field is studied with numerical particle-in-cell (PIC) simulations. A weakly magnetized plasma regime is considered that corresponds to the ionospheric F2 layer, with electrons being strongly magnetized, while the magnetization of ions is weak. It is demonstrated that the magnetic field orientation influences the floating potential of the rocket and that with increasing angle between the rocket axis and the magnetic field direction the rocket potential becomes less negative. External magnetic field gives rise to asymmetric wake downstream of the rocket. The simulated wake in the potential and density may extend as far as 30 electron Debye lengths; thus, it is important to account for these plasma perturbations when analyzing in situ measurements. A qualitative agreement between simulation results and the actual measurements with a sounding rocket is also shown.

Thermal plasma waste treatment

International Nuclear Information System (INIS)

Heberlein, Joachim; Murphy, Anthony B

2008-01-01

Plasma waste treatment has over the past decade become a more prominent technology because of the increasing problems with waste disposal and because of the realization of opportunities to generate valuable co-products. Plasma vitrification of hazardous slags has been a commercial technology for several years, and volume reduction of hazardous wastes using plasma processes is increasingly being used. Plasma gasification of wastes with low negative values has attracted interest as a source of energy and spawned process developments for treatment of even municipal solid wastes. Numerous technologies and approaches exist for plasma treatment of wastes. This review summarizes the approaches that have been developed, presents some of the basic physical principles, provides details of some specific processes and considers the advantages and disadvantages of thermal plasmas in waste treatment applications. (topical review)

Momentum transfer to rotating magnetized plasma from gun plasma injection

International Nuclear Information System (INIS)

Shamim, Imran; Hassam, A. B.; Ellis, R. F.; Witherspoon, F. D.; Phillips, M. W.

2006-01-01

Numerical simulations are carried out to investigate the penetration and momentum coupling of a gun-injected plasma slug into a rotating magnetized plasma. An experiment along these lines is envisioned for the Maryland Centrifugal Experiment (MCX) [R. F. Ellis et al., Phys. Plasmas 8, 2057 (2001)] using a coaxial plasma accelerator gun developed by HyperV Technologies Corp. [F. D. Witherspoon et al., Bull. Am. Phys. Soc. 50, LP1 87 (2005)]. The plasma gun would be located in the axial midplane and fired off-axis into the rotating MCX plasma annulus. The numerical simulation is set up so that the initial momentum in the injected plasma slug is of the order of the initial momentum of the target plasma. Several numerical firings are done into the cylindrical rotating plasma. Axial symmetry is assumed. The slug is seen to penetrate readily and deform into a mushroom, characteristic of interchange deformations. It is found that up to 25% of the momentum in the slug can be transferred to the background plasma in one pass across a cylindrical chord. For the same initial momentum, a high-speed low density slug gives more momentum transfer than a low-speed high density slug. Details of the numerical simulations and a scaling study are presented

Plasma Nitriding of AISI 304 Stainless Steel in Cathodic and Floating Electric Potential: Influence on Morphology, Chemical Characteristics and Tribological Behavior

Science.gov (United States)

Li, Yang; He, Yongyong; Wang, Wei; Mao, Junyuan; Zhang, Lei; Zhu, Yijie; Ye, Qianwen

2018-03-01

In direct current plasma nitriding (DCPN), the treated components are subjected to a high cathodic potential, which brings several inherent shortcomings, e.g., damage by arcing and the edging effect. In active screen plasma nitriding (ASPN) processes, the cathodic potential is applied to a metal screen that surrounds the workload, and the component to be treated is placed in a floating potential. Such an electrical configuration allows plasma to be formed on the metal screen surface rather than on the component surface; thus, the shortcomings of the DCPN are eliminated. In this work, the nitrided experiments were performed using a plasma nitriding unit. Two groups of samples were placed on the table in the cathodic and the floating potential, corresponding to the DCPN and ASPN, respectively. The floating samples and table were surrounded by a steel screen. The DCPN and ASPN of the AISI 304 stainless steels are investigated as a function of the electric potential. The samples were characterized using scanning electron microscopy with energy-dispersive x-ray spectroscopy, x-ray diffraction, atomic force microscopy and transmission electron microscope. Dry sliding ball-on-disk wear tests were conducted on the untreated substrate, DCPN and ASPN samples. The results reveal that all nitrided samples successfully produced similar nitrogen-supersaturated S phase layers on their surfaces. This finding also shows the strong impact of the electric potential of the nitriding process on the morphology, chemical characteristics, hardness and tribological behavior of the DCPN and ASPN samples.

Studies of the ablated plasma from experimental plasma gun disruption simulations

International Nuclear Information System (INIS)

Rockett, P.D.; Hunter, J.A.; Bradley, J.T.

1994-01-01

Extensive simulations of Tokamak disruptions have provided a picture of material erosion that is limited by the transfer of energy from the incident plasma to the armor solid surface through a dense vapor shield. Radiation spectra were recorded in the VUV and in the visible at the Efremov Laboratories on VIKA using graphite targets. The VUV data were recorded with a Sandia Labs transmission grating spectrograph, covering 1--40 nm. Plasma parameters were evaluated with incident plasma energy densities varying from 1--10 kJ/cm 2 . A second transmission grating spectrograph was taken to 2MK-200 at TRINITI to study the plasma-material interface in magnetic cusp plasma. Target materials included POCO graphite, ATJ graphite, boron nitride, and plasma-sprayed tungsten. Detailed spectra were recorded with a spatial resolution of ∼1 mm resolution. Time-resolved data with 40--200 ns resolution was also recorded. The data from both plasma gun facilities demonstrated that the hottest plasma region was sitting several millimeters above the armor tile surface

Electrostatic interaction between Interball-2 and the ambient plasma. 1. Determination of the spacecraft potential from current calculations

Directory of Open Access Journals (Sweden)

M. Bouhram

2002-03-01

Full Text Available The Interball-2 spacecraft travels at altitudes extending up to 20 000 km, and becomes positively charged due to the low-plasma densities encountered and the photoemission on its sunlit surface. Therefore, a knowledge of the spacecraft potential Fs is required for correcting accurately thermal ion measurements on Interball-2. The determination of Fs  is based on the balance of currents between escaping photoelectrons and incoming plasma electrons. A three-dimensional model of the potential structure surrounding Interball-2, including a realistic geometry and neglecting the space-charge densities, is used to find, through particle simulations, current-voltage relations of impacting plasma electrons Ie (Fs and escaping photoelectrons Iph (Fs . The inferred relations are compared to analytic relationships in order to quantify the effects of the spacecraft geometry, the ambient magnetic field B0 and the electron temperature Te . We found that the complex geometry has a weak effect on the inferred currents, while the presence of B0 tends to decrease their values. Providing that the photoemission saturation current density Jph0 is known, a relation between Fs and the plasma density Ne can be derived by using the current balance. Since Jph0 is critical to this process, simultaneous measurements of Ne from Z-mode observations in the plasmapause, and data on the potential difference Fs  - Fp  between the spacecraft and an electric probe (p are used in order to reverse the process. A value Jph0 ~ = 32 µAm-2 is estimated, close to laboratory tests, but less than typical measurements in space. Using this value, Ne and Fs  can be derived systematically from electric field measurements without any additional calculation. These values are needed for correcting the distributions of low-energy ions measured by the Hyperboloid experiment on Interball-2. The effects of the potential structure on ion trajectories reaching Hyperboloid are discussed

Collisional processes in supersymmetric plasma

International Nuclear Information System (INIS)

Czajka, Alina; Mrowczynski, Stanislaw

2011-01-01

Collisional processes in ultrarelativistic N=1 supersymmetric QED plasma are studied and compared to those in an electromagnetic plasma of electrons, positrons and photons. Cross sections of all binary interactions which occur in the supersymmetric plasma at the order of e 4 are computed. Some processes, in particular, the Compton scattering on selectrons, appear to be independent of momentum transfer and thus they are qualitatively different from processes in an electromagnetic plasma. It suggests that the transport properties of the supersymmetric plasma are different than those of its nonsupersymmetric counterpart. Energy loss and momentum broadening of a particle traversing the supersymmetric plasma are discussed in detail and the characteristics are shown to be surprisingly similar to those of QED plasma.

Self-organization and oscillation of negatively charged dust particles in a 2-dimensional dusty plasma

Energy Technology Data Exchange (ETDEWEB)

Song, Y.L. [College of Science, China Agricultural University, Beijing 100083 (China); Huang, F., E-mail: huangfeng@cau.edu.cn [College of Science, China Agricultural University, Beijing 100083 (China); Chen, Z.Y., E-mail: chenzy@mail.buct.edu.cn [Department of Physics, Beijing University of Chemical Technology, Beijing 100029 (China); State Key Laboratory of Laser Propulsion & Application, Beijing 101416 (China); Liu, Y.H. [School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025 (China); Yu, M.Y. [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Institute for Theoretical Physics I, Ruhr University, D-44801 Bochum (Germany)

2016-02-22

Negatively charged dust particles immersed in 2-dimensional dusty plasma system are investigated by molecular dynamics simulations. The effects of the confinement potential and attraction interaction potential on dust particle self-organization are studied in detail and two typical dust particle distributions are obtained when the system reaches equilibrium. The average radial velocity (ARV), average radial force (ARF) and radial mean square displacement are employed to analyze the dust particles' dynamics. Both ARVs and ARFs exhibit oscillation behaviors when the simulation system reaches equilibrium state. The relationships between the oscillation and confinement potential and attraction potential are studied in this paper. The simulation results are qualitatively similar to experimental results. - Highlights: • Self-organization and oscillation of a 2-dimensional dusty plasma is investigated. • Effect of the confinement potential on dust self-organization and oscillation is given. • Effect of the attraction potential on dust self-organization and oscillation is studied.

Self-organization and oscillation of negatively charged dust particles in a 2-dimensional dusty plasma

International Nuclear Information System (INIS)

Song, Y.L.; Huang, F.; Chen, Z.Y.; Liu, Y.H.; Yu, M.Y.

2016-01-01

Negatively charged dust particles immersed in 2-dimensional dusty plasma system are investigated by molecular dynamics simulations. The effects of the confinement potential and attraction interaction potential on dust particle self-organization are studied in detail and two typical dust particle distributions are obtained when the system reaches equilibrium. The average radial velocity (ARV), average radial force (ARF) and radial mean square displacement are employed to analyze the dust particles' dynamics. Both ARVs and ARFs exhibit oscillation behaviors when the simulation system reaches equilibrium state. The relationships between the oscillation and confinement potential and attraction potential are studied in this paper. The simulation results are qualitatively similar to experimental results. - Highlights: • Self-organization and oscillation of a 2-dimensional dusty plasma is investigated. • Effect of the confinement potential on dust self-organization and oscillation is given. • Effect of the attraction potential on dust self-organization and oscillation is studied.

A study of density effects in plasmas using analytical approximations for the self-consistent potential

Science.gov (United States)

Poirier, M.

2015-06-01

Density effects in ionized matter require particular attention since they modify energies, wavefunctions and transition rates with respect to the isolated-ion situation. The approach chosen in this paper is based on the ion-sphere model involving a Thomas-Fermi-like description for free electrons, the bound electrons being described by a full quantum mechanical formalism. This permits to deal with plasmas out of thermal local equilibrium, assuming only a Maxwell distribution for free electrons. For H-like ions, such a theory provides simple and rather accurate analytical approximations for the potential created by free electrons. Emphasis is put on the plasma potential rather than on the electron density, since the energies and wavefunctions depend directly on this potential. Beyond the uniform electron gas model, temperature effects may be analyzed. In the case of H-like ions, this formalism provides analytical perturbative expressions for the energies, wavefunctions and transition rates. Explicit expressions are given in the case of maximum orbital quantum number, and compare satisfactorily with results from a direct integration of the radial Schrödinger equation. Some formulas for lower orbital quantum numbers are also proposed.

Differential proteomics of human seminal plasma: A potential target for searching male infertility marker proteins.

Science.gov (United States)

Tomar, Anil Kumar; Sooch, Balwinder Singh; Singh, Sarman; Yadav, Savita

2012-04-01

The clinical fertility tests, available in the market, fail to define the exact cause of male infertility in almost half of the cases and point toward a crucial need of developing better ways of infertility investigations. The protein biomarkers may help us toward better understanding of unknown cases of male infertility that, in turn, can guide us to find better therapeutic solutions. Many clinical attempts have been made to identify biomarkers of male infertility in sperm proteome but only few studies have targeted seminal plasma. Human seminal plasma is a rich source of proteins that are essentially required for development of sperm and successful fertilization. This viewpoint article highlights the importance of human seminal plasma proteome in reproductive physiology and suggests that differential proteomics integrated with functional analysis may help us in searching potential biomarkers of male infertility. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Numerical study of drift-kinetic evolution of collisional plasmas in tori

International Nuclear Information System (INIS)

Beasley, C.O. Jr.; Meier, H.K.; van Rij, W.I.; McCune, J.E.

1976-03-01

Preliminary numerical results for the dynamics of toroidally confined plasmas in the drift-kinetic, Fokker--Planck description are discussed. These solutions were obtained by using the techniques inherent to the collisional plasma model (CPM) described in detail elsewhere. An initial value problem is solved in the local approximation in which collisions and particle dynamics compete in a given magnetic field to set up a quasi-equilibrium. Both the plasma (guiding center) distribution function and many macroscopic quantities of interest are monitored. Good agreement with corresponding but more approximate theories is obtained over a wide range of collisionality, particularly with regard to the neoclassical particle flux. Encouraging confirmation of earlier results for the distribution function is achieved when due account is taken of the differing collisionality of particles with differing energies. These initial results indicate the potential importance of certain non-local effects as well as inclusion of self-consistency between fields and plasma currents and densities

The investigation of quark-antiquark potential in a plasma with hyperscaling violation background

Science.gov (United States)

Tahery, S.; Sadeghi, J.

2017-10-01

In this paper, we investigate the imaginary part of the potential for a moving quarkonia in plasma. In order to verify the validity of the imaginary part of the potential we employ a hyperscaling violation (HSV) metric background. In a quantum chromodynamics (QCD) system the imaginary part of the potential shows decay behaviour and the corresponding potential should be negative. The corresponding potential always appears in QCD as an exponential function. We find general constraints for Im{V}Q\\bar{Q} at the near horizon limit and apply them for some known cases. Finally, we find the suitable spatial dimensions d,z and θ, and also rapidity η for two interesting cases. Our calculation with the anti-de Sitter/conformal field theory guarantees the dynamical parameter as θ in an HSV metric background. We also present the HSV metric in this context very close to the Yang-Mills theory with finite temperature.

Study of plasma-material surface interaction using langmuir probe technique during plasma treatment

International Nuclear Information System (INIS)

Saloum, S.; Akel, M.

2012-01-01

In this study, we tried to understand the plasma-surface interactions by using Langmuir probes. Two different types of plasmas were studied, the first is the electropositive plasma in Argon and the second is the electronegative plasma in Sulfur Hexafluoride. In the first type, the effects of Argon gas pressure, the injection of Helium in the remote zone and the substrate bias on the measurements of the Electron Energy Probability Function (EEPF) and on the plasma parameters (electron density (n e ), effective electron temperature (T e ff), plasma potential (V p ) and floating potential (V f )) have been investigated. The obtained EEPFs and plasma parameters have been used to control two remote plasma processes. The first is the remote Plasma Enhanced Chemical Vapor Deposition (PE-CVD) of thin films, on silicon wafers, from Hexamethyldisiloxane (HMDSO) precursor diluted in the remote Ar-He plasma. The second is the pure Argon remote plasma treatment of polymethylmethacrylate (PMMA) polymer surface. In the second type, the plasma diagnostics were performed in the remote zone as a function of SF 6 flow rate, where relative concentrations of fluorine atoms were measured using actinometry optical emission spectroscopy; electron density, electron temperature and plasma potential were determined using single cylindrical Langmuir probe, positive ion flux and negative ion fraction were determined using an planar probe. The silicon etching process in SF 6 plasma was studied. (author)

Study of plasma-material surface interaction using Langmuir probe technique during plasma treatment

International Nuclear Information System (INIS)

Saloum, S.; Akel, M.

2009-06-01

In this study, we tried to understand the plasma-surface interactions by using Langmuir probes. Two different types of plasmas were studied, the first is the electropositive plasma in Argon and the second is the electronegative plasma in Sulfur Hexafluoride. In the first type, the effects of Argon gas pressure, the injection of Helium in the remote zone and the substrate bias on the measurements of the Electron Energy Probability Function (EEPF) and on the plasma parameters (electron density (n e ), effective electron temperature (T e ff), plasma potential (V p ) and floating potential (V f )) have been investigated. The obtained EEPFs and plasma parameters have been used to control two remote plasma processes. The first is the remote Plasma Enhanced Chemical Vapor Deposition (PE-CVD) of thin films, on silicon wafers, from Hexamethyldisoloxane (HMDSO) precursor diluted in the remote Ar-He plasma. The second is the pure Argon remote plasma treatment of polymethylmethacrylate (PMMA) polymer surface. In the second type, the plasma diagnostics were performed in the remote zone as a function of SF 6 flow rate, where relative concentrations of fluorine atoms were measured using actinometry optical emission spectroscopy; electron density, electron temperature and plasma potential were determined using single cylindrical Langmuir probe, positive ion flux and negative ion fraction were determined using an planar probe. The silicon etching process in SF 6 plasma was studied. (author)

Effect of asymmetric plasma potential in the SOL on the particle radial transport and heat flux broadening

International Nuclear Information System (INIS)

Hara, Junichiro; Uesugi, Yoshihiko; Miura, Yukitoshi; Kawashima, Hisato.

1997-01-01

The effective divertor heat-load relaxation using ExB induced convective cells in the SOL is studied. The ExB convective cells in the SOL are generated by the toroidally asymmetric divertor biasing, which can control the local plasma potential in the SOL. The preliminary experiment has been done in the JFT-2M tokamak with poloidal divertor. The helical SOL current flows along the magnetic field between the locally biased inboard plate and grounded outer plates, thereby modifying plasma potential in the vicinity of the local divertor current flow. The generation of the poloidal electric field reaching up to 1.5kV/m locally in the SOL and the modification of the heat flux profile on the divertor plate is observed. (author)

Author Details

African Journals Online (AJOL)

Legwaila, GM. Vol 12 (2003) - Articles Review of sweet sorghum: a potential cash and forage crop in Botswana Details. ISSN: 1021-0873. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about AJOL · AJOL's Partners · Terms and Conditions of Use · Contact ...

Lipid organization of the plasma membrane

NARCIS (Netherlands)

Ingólfsson, Helgi I; Melo, Manuel N; van Eerden, Floris J; Arnarez, Clément; Lopez, Cesar A; Wassenaar, Tsjerk A; Periole, Xavier; de Vries, Alex H; Tieleman, D Peter; Marrink, Siewert J

2014-01-01

The detailed organization of cellular membranes remains rather elusive. Based on large-scale molecular dynamics simulations, we provide a high-resolution view of the lipid organization of a plasma membrane at an unprecedented level of complexity. Our plasma membrane model consists of 63 different

Ozone dosing alters the biological potential and therapeutic outcomes of plasma rich in growth factors.

Science.gov (United States)

Anitua, E; Zalduendo, M M; Troya, M; Orive, G

2015-04-01

Until now, ozone has been used in a rather empirical way. This in-vitro study investigates, for the first time, whether different ozone treatments of plasma rich in growth factors (PRGF) alter the biological properties and outcomes of this autologous platelet-rich plasma. Human plasma rich in growth factors was treated with ozone using one of the following protocols: a continuous-flow method; or a syringe method in which constant volumes of ozone and PRGF were mixed. In both cases, ozone was added before, during and after the addition of calcium chloride. Three ozone concentrations, of the therapeutic range 20, 40 and 80 μg/mL, were tested. Fibrin clot properties, growth factor content and the proliferative effect on primary osteoblasts and gingival fibroblasts were evaluated. Ozone treatment of PRGF using the continuous flow protocol impaired formation of the fibrin scaffold, drastically reduced the levels of growth factors and significantly decreased the proliferative potential of PRGF on primary osteoblasts and gingival fibroblasts. In contrast, treatment of PRGF with ozone using the syringe method, before, during and after the coagulation process, did not alter the biological outcomes of the autologous therapy. These findings suggest that ozone dose and the way that ozone combines with PRGF may alter the biological potential and therapeutic outcomes of PRGF. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Cold Atmospheric Plasma Technology for Decontamination of Space Equipment

Science.gov (United States)

Thomas, Hubertus; Rettberg, Petra; Shimizu, Tetsuji; Thoma, Markus; Morfill, Gregor; Zimmermann, Julia; Müller, Meike; Semenov, Igor

2016-07-01

Cold atmospheric plasma (CAP) technology is very fast and effective in inactivation of all kinds of pathogens. It is used in hygiene and especially in medicine, since the plasma treatment can be applied to sensitive surfaces, like skin, too. In a first study to use CAP for the decontamination of space equipment we could show its potential as a quite promising alternative to the standard "dry heat" and H2O2 methods [Shimizu et al. Planetary and Space Science, 90, 60-71. (2014)]. In a follow-on study we continue the investigations to reach high application level of the technology. First, we redesign the actual setup to a plasma-gas circulation system, increasing the effectivity of inactivation and the sustainability. Additionally, we want to learn more about the plasma chemistry processes involved in the inactivation. Therefore, we perform detailed plasma and gas measurements and compare them to numerical simulations. The latter will finally be used to scale the decontamination system to sizes useful also for larger space equipment. Typical materials relevant for space equipment will be tested and investigated on surface material changes due to the plasma treatment. Additionally, it is planned to use electronic boards and compare their functionality before and after the CAP expose. We will give an overview on the status of the plasma decontamination project funded by the Bavarian Ministry of Economics.

The calculation of electron chemical potential and ion charge state and their influence on plasma conductivity in electrical explosion of metal wire

International Nuclear Information System (INIS)

Shi, Zongqian; Wang, Kun; Li, Yao; Shi, Yuanjie; Wu, Jian; Jia, Shenli

2014-01-01

The electron chemical potential and ion charge state (average ion charge and ion distribution) are important parameters in calculating plasma conductivity in electrical explosion of metal wire. In this paper, the calculating method of electron chemical potential and ion charge state is discussed at first. For the calculation of electron chemical potential, the ideal free electron gas model and Thomas-Fermi model are compared and analyzed in terms of the coupling constant of plasma. The Thomas-Fermi ionization model, which is used to calculate ion charge state, is compared with the method based on Saha equation. Furthermore, the influence of electron degenerated energy levels and ion excited states in Saha equation on the ion charge state is also analyzed. Then the influence of different calculating methods of electron chemical potential and ion charge state on plasma conductivity is discussed by applying them in the Lee-More conductivity model

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)

Physical processes in hot cosmic plasmas

International Nuclear Information System (INIS)

Fabian, A.G.; Giovannelli, F.

1990-01-01

The interpretation of many high energy astrophysical phenomena relies on a detailed knowledge of radiation and transport processes in hot plasmas. The understanding of these plasma properties is one of the aims of terrestrial plasma physics. While the microscopic properties of astrophysical plasmas can hardly be determined experimentally, laboratory plasmas are more easily accessible to experimental techniques, but transient phenomena and the interaction of the plasma with boundaries often make the interpretation of measurements cumbersome. This book contains the talks given at the NATO Advanced Research Workshop on astro- and plasma-physics in Vulcano, Sicily, May 29-June 2, 1989. The book focuses on three main areas: radiation transport processes in hot (astrophysical and laboratory) plasmas; magnetic fields; their generation, reconnection and their effects on plasma transport properties; relativistic and ultra-high density plasmas

Comparative measurements of plasma potential with ball-pen and Langmuir probe in low-temperature magnetized plasma

Czech Academy of Sciences Publication Activity Database

Zanáška, M.; Adámek, Jiří; Peterka, Matěj; Kudrna, P.; Tichý, M.

2015-01-01

Roč. 22, č. 3 (2015), č. článku 033516. ISSN 1070-664X Institutional support: RVO:61389021 Keywords : plasma * tokamak * ball- pen probe (BPP) Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.207, year: 2015 http://scitation.aip.org/content/aip/journal/pop/22/3/10.1063/1.4916572

Dynamic behavior of plasma-facing materials during plasma instabilities in tokamak reactors

International Nuclear Information System (INIS)

Hassanein, A.; Konkashbaev, I.

1997-01-01

Damage to plasma-facing and nearby components due to plasma instabilities remains a major obstacle to a successful tokamak concept. The high energy deposited on facing materials during plasma instabilities can cause severe erosion, plasma contamination, and structural failure of these components. Erosion damage can take various forms such as surface vaporization, spallation, and liquid ejection of metallic materials. Comprehensive thermodynamic and radiation hydrodynamic codes have been developed, integrated, and used to evaluate the extent of various damage to plasma-facing and nearby components. The eroded and splashed materials will be transported and then redeposited elsewhere on other plasma-facing components. Detailed physics of plasma/solid-liquid/vapor interaction in a strong magnetic field have been developed, optimized, and implemented in a self-consistent model. The plasma energy deposited in the evolving divertor debris is quickly and intensely reradiated, which may cause severe erosion and melting of other nearby components. Factors that influence and reduce vapor-shielding efficiency such as vapor diffusion and turbulence are also discussed and evaluated

[Does a lateral gradient of membrane potential on the plasma membrane of growing pollen tube of germinating pollen grain exist?].

Science.gov (United States)

Andreev, I M

2011-01-01

The data presented in the article by Breigina et al. (2009) "Changes in the membrane potential during pollen grain germination and pollen tube growth" (Tsitologiya. 51 (10): 815-823) and concerning the measurement of electric membrane potential (Delta Psi) on the plasma membrane of growing pollen tube of germinating pollen grain with the use of fluorescent potential-sensitive dye, di-4-ANEPPS, were critically analyzed in order to clarify whether a lateral gradient of Delta Psi on this membrane indeed exists. This analysis showed that the main conclusion of the authors of the above article on the existence of polar distribution of Delta Psi along the pollen tube plasma membrane is not in accordance with a number of known peculiarities of di-4-ANEPPS behavior in biological membranes and requires a significant revision. The findings in question reported by the authors, in my opinion, might be interpreted as evidence for the presence on the plasma membrane of growing pollen tube not only the membrane potential Delta Psi but also lateral gradient of so called intra-membrane dipole potential. Based on the comments made, another interpretation of the experimental results described by Breigina et al. has been offered. In addition, some drawbacks in the methodology used by the authors for measurement of Delta Psi with other fluorescent potential-sensitive dye, DiBAC3(3), are also shortly considered.

Properties of the Dense Plasma Produced in Plasma Focus

International Nuclear Information System (INIS)

Peacock, N.J.; Wilcock, P.D.; Speer, R.J.; Morgan, P.D.

1969-01-01

The plasma produced by the focus or quasi-cylindrical magnetic compression which occurs at the open end of a metal-walled, coaxial plasma gun has been studied, using the electrical waveforms and the electromagnetic and reaction particle, emission. The electromagnetic radiation in the XUV region of the spectrum has previously been briefly reported, and the present paper describes further more detailed analyses of the line emission at wavelengths shorter than 10 Å when impurities are added to the gas filling. The emission is characteristic of a plasma with a temperature of a few keV and a density greater than 10 19 cm -3 , while the appearance of optical transitions in highly stripped ions, e. g. A XVIII, gives a measure of the thermalization in the plasma. The stored electrical energy has been doubled and the scaling of the neutron emission with the applied voltage and the initial particle density is presented. The duration of the neutron and X-ray emission is considerably longer than the observed instability growth time in the plasma filament. Calculations of the mode of heating and the confinement of the plasma are compared with experimental observations. (author)

A numerical simulation study on active species production in dense methane-air plasma discharge

Science.gov (United States)

Gui, LI; Muyang, QIAN; Sanqiu, LIU; Huaying, CHEN; Chunsheng, REN; Dezhen, WANG

2018-01-01

Recently, low-temperature atmospheric pressure plasmas have been proposed as a potential type of ‘reaction carrier’ for the conversion of methane into value-added chemicals. In this paper, the multi-physics field coupling software of COMSOL is used to simulate the detailed discharge characteristics of atmospheric pressure methane-air plasma. A two-dimensional axisymmetric fluid model is constructed, in which 77 plasma chemical reactions and 32 different species are taken into account. The spatial density distributions of dominant charged ions and reactive radical species, such as {{{CH}}}4+, {{{CH}}}3+, {{{N}}}2+, {{{O}}}2+, H, O, CH3, and CH2, are presented, which is due to plasma chemical reactions of methane/air dissociation (or ionization) and reforming of small fragment radical species. The physicochemical mechanisms of methane dissociation and radical species recombination are also discussed and analyzed.

Plasma engineering: a perspective

International Nuclear Information System (INIS)

Gralnick, S.L.

1978-01-01

This review paper will present the authors perspective of the field of Plasma Engineering as it has evolved over the preceding five years. This embrionic discipline has grown in that period of time to the point where it is sufficiently mature to become part of the curriculum, and a speciality within, the discipline of Nuclear Engineering. Plasma Engineering can be distinguished from the underlying science of plasma physics in that in the pursuit of the latter, our goal is the understanding of the fundamental processes governing the behavior of plasmas while the former discipline seeks the embodiment of these concepts in useful devices. Consequent to this goal, the plasma engineer, of necessity, is concerned with the interfaces between a plasma configuration and the device by which it is produced and maintained. These interface problems, often referred to as kitchen physics are multidisciplinary in nature, and their solution requires careful attention to both plasma physics and machine engineering detail

Plasma engineering analyses of tokamak reactor operating space

International Nuclear Information System (INIS)

Houlberg, W.; Attenberger, S.E.

1981-01-01

A comprehensive method is presented for analyzing the potential physics operating regime of fusion reactor plasmas with detailed transport codes. Application is made to the tokamak Fusion Engineering Device (FED). The relationships between driven and ignited operation and supplementary heating requirements are examined. The reference physics models give a finite range of density and temperature over which physics objectives can be reached. Uncertainties in the confinement scaling and differences in supplementary heating methods can expand or contract this operating regime even to the point of allowing ignition with the more optimistic models

Proteomics and the dynamic plasma membrane

DEFF Research Database (Denmark)

Sprenger, Richard R; Jensen, Ole Nørregaard

2010-01-01

plasma membrane is of particular interest, by not only serving as a barrier between the "cell interior" and the external environment, but moreover by organizing and clustering essential components to enable dynamic responses to internal and external stimuli. Defining and characterizing the dynamic plasma...... the challenges in functional proteomic studies of the plasma membrane. We review the recent progress in MS-based plasma membrane proteomics by presenting key examples from eukaryotic systems, including mammals, yeast and plants. We highlight the importance of enrichment and quantification technologies required...... for detailed functional and comparative analysis of the dynamic plasma membrane proteome....

Influence of dense plasma on the energy levels and transition properties in highly charged ions

Science.gov (United States)

Chen, Zhan-Bin; Hu, Hong-Wei; Ma, Kun; Liu, Xiao-Bin; Guo, Xue-Ling; Li, Shuang; Zhu, Bo-Hong; Huang, Lian; Wang, Kai

2018-03-01

The studies of the influence of plasma environments on the level structures and transition properties for highly charged ions are presented. For the relativistic treatment, we implemented the multiconfiguration Dirac-Fock method incorporating the ion sphere (IS) model potential, in which the plasma screening is taken into account as a modified interaction potential between the electron and the nucleus. For the nonrelativistic treatment, analytical solutions of the Schrödinger equation with two types of the IS screened potential are proposed. The Ritz variation method is used with hydrogenic wave function as a trial wave function that contains two unknown variational parameters. Bound energies are derived from an energy equation, and the variational parameters are obtained from the minimisation condition of the expectation value of the energy. Numerical results for hydrogen-like ions in dense plasmas are presented as examples. A detailed analysis of the influence of relativistic effects on the energy levels and transition properties is also reported. Our results are compared with available results in the literature showing a good quantitative agreement.

Probing of flowing electron plasmas

International Nuclear Information System (INIS)

Himura, H.; Nakashima, C.; Saito, H.; Yoshida, Z.

2001-01-01

Probing of streaming electron plasmas with finite temperature is studied. For the first time, a current-voltage characteristic of an electric probe is measured in electron plasmas. Due to the fast flow of the electron plasmas, the characteristic curve spreads out significantly and exhibits a long tail. This feature can be explained calculating the currents collected to the probe. In flowing electron plasmas, the distribution function observed in the laboratory frame is non-Maxwellian even if the plasmas come to a state of thermal equilibrium. Another significant feature of the characteristic is that it determines a floating potential where the current equals zero, despite there being very few ions in the electron plasma. A high impedance probe, which is popularly used to determine the space potential of electron plasmas, outputs the potential. The method is available only for plasmas with density much smaller than the Brillouin limit

[Search for potential gastric cancer biomarkers using low molecular weight blood plasma proteome profiling by mass spectrometry].

Science.gov (United States)

Shevchenko, V E; Arnotskaia, N E; Ogorodnikova, E V; Davydov, M M; Ibraev, M A; Turkin, I N; Davydov, M I

2014-01-01

Gastric cancer, one of the most widespread malignant tumors, still lacks reliable serum/plasma biomarkers of its early detection. In this study we have developed, unified, and tested a new methodology for search of gastric cancer biomarkers based on profiling of low molecular weight proteome (LMWP) (1-17 kDa). This approach included three main components: sample pre-fractionation, matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS), data analysis by a bioinformatics software package. Applicability and perspectives of the developed approach for detection of potential gastric cancer markers during LMWP analysis have been demonstrated using 69 plasma samples from patients with gastric cancer (stages I-IV) and 238 control samples. The study revealed peptides/polypeptides, which may be potentially used for detection of this pathology.

An ECR table plasma generator

International Nuclear Information System (INIS)

Racz, R.; Palinkas, J.; Bin, S.

2012-01-01

A compact ECR plasma device was built in our lab using the 'spare parts' of the ATOMKI ECR ion source. We call it 'ECR Table Plasma Generator'. It consists of a relatively big plasma chamber (ID=10 cm, L=40 cm) in a thin NdFeB hexapole magnet with independent vacuum and gas dosing systems. For microwave coupling two low power TWTAs (Travelling Wave tube amplifier) can be applied individually or simultaneously, operating in the 6-18 GHz range. There is no axial magnetic trap and there is no extraction. The technical details of the plasma generator and preliminary plasma photo study results are shown. This paper is followed by the associated poster. (authors)

Interferometer for electron density measurement in exploding wire plasma

International Nuclear Information System (INIS)

Batra, Jigyasa; Jaiswar, Ashutosh; Kaushik, T.C.

2016-12-01

Mach-Zehnder Interferometer (MZI) has been developed for measuring electron density profile in pulsed plasmas. MZI is to be used for characterizing exploding wire plasmas for correlating electron density dynamics with x-rays emission. Experiments have been carried out for probing electron density in pulsed plasmas produced in our laboratory like in spark gap and exploding wire plasmas. These are microsecond phenomenon. Changes in electron density have been registered in interferograms with the help of a streak camera for specific time window. Temporal electron density profiles have been calculated by analyzing temporal fringe shifts in interferograms. This report deals with details of MZI developed in our laboratory along with its theory. Basic introductory details have also been provided for exploding wire plasmas to be probed. Some demonstrative results of electron density measurements in pulsed plasmas of spark gap and single exploding wires have been described. (author)

Observation of plasma hole in a rotating plasma

International Nuclear Information System (INIS)

Nagaoka, Kenichi; Ishihara, Tatsuzo; Okamoto, Atsushi; Yoshimura, Shinji; Tanaka, Masayoshi Y.

2001-01-01

Plasma hole, a cylindrical density cavity, formed in a rotating plasma has been investigated experimentally. The plasma hole is characterized by large aspect ratio (length/radius ≥ 30), steep boundary layer between the hole and the ambient plasma (10 ion Larmor radius), and extremely high positive potential (130 V). The flow velocity field associated with plasma hole structure has been measured, and is found to have interesting features: (1) plasma rotates in azimuthal direction at a maximum velocity of order of ion sound speed, (2) plasma flows radially inward across the magnetic field line, (3) there present an axial flow reversal between core and peripheral region. It is found that the flow pattern of the plasma hole is very similar to the that of well-developed typhoon with core. (author)

Pumping potential wells

International Nuclear Information System (INIS)

Hershkowitz, N.; Forest, C.; Wang, E.Y.; Intrator, T.

1987-01-01

Nonmonotonic plasma potential structures are a common feature of many double layers and sheaths. Steady state plasma potential wells separating regions having different plasma potentials are often found in laboratory experiments. In order to exist, such structures all must find a solution to a common problem. Ions created by charge exchange or ionization in the region of the potential well are electrostatically confined and tend to accumulate and fill up the potential well. The increase in positive charge should eliminate the well, but steady state structures are found in which the wells do not fill up. This means that it is important to take into account processes which 'pump' ions from the well. As examples of ion pumping of plasma wells, potential dips in front of a positively biased electron collecting anode in a relatively cold, low density multidipole plasma are considered. Pumping is provided by ion leaks from the edges of the potential dip or by oscillating the applied potential. In the former case the two dimensional character of the problem is shown to be important. (author)

Pumping potential wells

Science.gov (United States)

Hershkowitz, N.; Forest, C.; Wang, E. Y.; Intrator, T.

1987-01-01

Nonmonotonic plasma potential structures are a common feature of many double layers and sheaths. Steady state plasma potential wells separating regions having different plasma potentials are often found in laboratory experiments. In order to exist, such structures all must find a solution to a common problem. Ions created by charge exchange or ionization in the region of the potential well are electrostatically confined and tend to accumulate and fill up the potential well. The increase in positive charge should eliminate the well. Nevertheless, steady state structures are found in which the wells do not fill up. This means that it is important to take into account processes which 'pump' ions from the well. As examples of ion pumping of plasma wells, potential dips in front of a positively biased electro collecting anode in a relatively cold, low density multidipole plasma is considered. Pumping is provided by ion leaks from the edges of the potential dip or by oscillating the applied potential. In the former case the two dimensional character of the problem is shown to be important.

Pumping potential wells

International Nuclear Information System (INIS)

Hershkowitz, N.; Forest, C.; Wang, E.Y.; Intrator, T.

1987-01-01

Nonmonotonic plasma potential structures are a common feature of many double layers and sheaths. Steady state plasma potential wells separating regions having different plasma potentials are often found in laboratory experiments. In order to exist, all such structures must find a solution to a common problem. Ions created by charge exchange or ionization in the region of the potential well are electrostatically confined and tend to accumulate and fill up the potential well. The increase in positive charge should eliminate the well. Nevertheless, steady state structures are found in which the wells do not fill up. This means that it is important to take into account processes which pump ions from the well. As examples of ion pumping of plasma wells, potential dips in front of a positively biased electron collecting anode in a relatively cold, low density, multidipole plasma are considered. Pumping is provided by ion leaks from the edges of the potential dip or by oscillating the applied potential. In the former case the two-dimensional character of the problem is shown to be important

Influence of the helical resonant fields on the plasma potential in the TBR-1 Tokamak

International Nuclear Information System (INIS)

Ribeiro, C.; Silva, R.P. da; Caldas, I.L.; Fagundes, A.N.; Sanada, E.K.

1990-01-01

This work describes an experimental work that are in progress in TBR-1 tokamak about the influence of resonant helical fields on the plasma potential. TBR-1 is a small tokamak in operation in the Physics Institute of University of Sao Paulo and used for basic research, diagnostic development and personal formation. Its main parameters are: R(Major Radius) = 0.30 m; a v (Vessel Radius) = 0.11 m; a(Plasma Radius) = 0.08 m; R/a(Aspect Ratio) = 3.75; B φ (Toroidal Field) = 5 kG; n e0 (Central Electron Density) ≅ 7 x 10 18 m -3 ; T e0 (central electron temperature) ≅ 200 eV. (Author)

Transition in plasma fluctuation between attached and detached plasmas

International Nuclear Information System (INIS)

Okazaki, Katsuya; Ohno, Noriyasu; Kajita, Shin; Tanaka, Hirohiko

2012-01-01

The static and dynamic behaviors of detached plasmas have received considerable attention because the use of a detached divertor is thought to provide a promising method for reducing the heat flux to plasma-facing components. In this study, fluctuations were measured with an electrostatic probe as the plasma was changed from attached to detached states by increasing the neutral gas pressure. The transition from an attached plasma to a detached plasma was found to change the phase relation between the density and the potential. (author)

Plasma Epstein-Barr virus and Hepatitis B virus in non-Hodgkin lymphomas: Two lymphotropic, potentially oncogenic, latently occurring DNA viruses.

Science.gov (United States)

Sinha, Mahua; Rao, Clementina Rama; Premalata, C S; Shafiulla, Mohammed; Lakshmaiah, K C; Jacob, Linu Abraham; Babu, Govind K; Viveka, B K; Appaji, L; Subramanyam, Jayshree R

2016-01-01

There is a need to study potential infective etiologies in lymphomas. Lymphocyte-transforming viruses can directly infect lymphocytes, disrupt normal cell functions, and promote cell division. Epstein-Barr virus (EBV) is known to be associated with several lymphomas, especially Hodgkin lymphomas (HLs). And recently, the lymphocyte-transforming role of hepatitis B virus (HBV) has been emphasized. The aim of this study was to elucidate the association of two potentially oncogenic, widely prevalent latent DNA viruses, EBV and HBV, in non-HL (NHL). In this prospective study, we estimated plasma EBV and HBV DNA in NHL patients. Peripheral blood was obtained from newly diagnosed, treatment na ïve, histologically confirmed NHL patients. Plasma EBV DNA was quantified by real-time polymerase chain reaction (PCR) targeting Epstein-Barr Nucleic acid 1 while the plasma HBV DNA was detected using nested PCR targeting HBX gene. In a small subset of patients, follow-up plasma samples post-anticancer chemotherapy were available and retested for viral DNA. Of the 110 NHL patients, ~79% were B-cell NHL and ~21% were T-cell NHL. Plasma EBV-DNA was detected in 10% NHLs with a higher EBV association in Burkitt lymphoma (33.3%) than other subtypes. Pretherapy HBV DNA was detected in 21% NHLs; most of them being diffuse large B-cell lymphoma (DLBCL). Moreover, 42% of DLBCL patients had HBV DNA in plasma. Since all patients were HBV surface antigen seronegative at diagnosis, baseline plasma HBV-DNAemia before chemotherapy was indicative of occult hepatitis B infection. Our findings indicate a significant association of HBV with newly diagnosed DLBCL.

Acoustic nonlinear periodic waves in pair-ion plasmas

Science.gov (United States)

Mahmood, Shahzad; Kaladze, Tamaz; Ur-Rehman, Hafeez

2013-09-01

Electrostatic acoustic nonlinear periodic (cnoidal) waves and solitons are investigated in unmagnetized pair-ion plasmas consisting of same mass and oppositely charged ion species with different temperatures. Using reductive perturbation method and appropriate boundary conditions, the Korteweg-de Vries (KdV) equation is derived. The analytical solutions of both cnoidal wave and soliton solutions are discussed in detail. The phase plane plots of cnoidal and soliton structures are shown. It is found that both compressive and rarefactive cnoidal wave and soliton structures are formed depending on the temperature ratio of positive and negative ions in pair-ion plasmas. In the special case, it is revealed that the amplitude of soliton may become larger than it is allowed by the nonlinear stationary wave theory which is equal to the quantum tunneling by particle through a potential barrier effect. The serious flaws in the earlier published results by Yadav et al., [PRE 52, 3045 (1995)] and Chawla and Misra [Phys. Plasmas 17, 102315 (2010)] of studying ion acoustic nonlinear periodic waves are also pointed out.

Detailed analysis of hollow ions spectra from dense matter pumped by X-ray emission of relativistic laser plasma

International Nuclear Information System (INIS)

Hansen, S. B.; Colgan, J.; Abdallah, J.; Faenov, A. Ya.; Pikuz, S. A.; Skobelev, I. Yu.; Wagenaars, E.; Culfa, O.; Dance, R. J.; Tallents, G. J.; Rossall, A. K.; Woolsey, N. C.; Booth, N.; Lancaster, K. L.; Evans, R. G.; Gray, R. J.; McKenna, P.; Kaempfer, T.; Schulze, K. S.; Uschmann, I.

2014-01-01

X-ray emission from hollow ions offers new diagnostic opportunities for dense, strongly coupled plasma. We present extended modeling of the x-ray emission spectrum reported by Colgan et al. [Phys. Rev. Lett. 110, 125001 (2013)] based on two collisional-radiative codes: the hybrid-structure Spectroscopic Collisional-Radiative Atomic Model (SCRAM) and the mixed-unresolved transition arrays (MUTA) ATOMIC model. We show that both accuracy and completeness in the modeled energy level structure are critical for reliable diagnostics, investigate how emission changes with different treatments of ionization potential depression, and discuss two approaches to handling the extensive structure required for hollow-ion models with many multiply excited configurations

Atomic and molecular processes in fusion plasmas

Energy Technology Data Exchange (ETDEWEB)

Janev, R.K. [International Atomic Energy Agency, Vienna (Austria)

1997-01-01

The role of atomic and molecular processes in achieving and maintaining the conditions for thermonuclear burn in a magnetically confined fusion plasma is described. Emphasis is given to the energy balance and power and particle exhaust issues. The most important atomic and molecular processes which affect the radiation losses and impurity transport in the core plasma, the neutral particle transport in the plasma edge and the radiative cooling of divertor plasmas are discussed in greater detail. (author)

The near-Earth and interplanetary plasma

International Nuclear Information System (INIS)

Al'pert, Y.L.

1983-01-01

This monograph is an extensive revision and expansion of the original paper which first appeared in 1976 in the encyclopedia, Handbuch der Physik. It presents a detailed and comprehensive treatment of wave processes and of the motion of bodies through plasma around moving bodies such as artificial satellites, and with natural plasma waves and oscillations. Contents, abridged: General properties of the near-Earth and interplanetary plasma. Refractive indexes of cold magnetoplasma. Growth rates for the different oscillation branches. Nonlinear effects in a plasma. Group velocity, trajectories, and trapping of electromagnetic waves in a magnetoplasma. Indexes

Spectroscopic diagnostics of industrial plasmas

International Nuclear Information System (INIS)

Joshi, N.K.

2004-01-01

Plasmas play key role in modern industry and are being used for processing micro electronic circuits to the destruction of toxic waste. Characterization of industrial plasmas which includes both 'thermal plasmas' and non-equilibrium plasmas or 'cold plasmas' in industrial environment offers quite a challenge. Numerous diagnostic techniques have been developed for the measurement of these partially ionized plasma and/or particulate parameters. The 'simple' non-invasive spectroscopic methods for characterization of industrial plasmas will be discussed in detail in this paper. The excitation temperature in thermal (DC/RF) plasma jets has been determined using atomic Boltzmann technique. The central axis temperature of thermal plasma jets in a spray torch can be determined using modified atomic Boltzmann technique with out using Abel inversion. The Stark broadening of H β and Ar-I (430 nm) lines have been used to determine the electron number density in thermal plasma jets. In low-pressure non-equilibrium argon plasma, electron temperature has been measured using the Corona model from the ratio of line intensities of atomic and ionic transitions. (author)

Plasma response to electron energy filter in large volume plasma device

International Nuclear Information System (INIS)

Sanyasi, A. K.; Awasthi, L. M.; Mattoo, S. K.; Srivastava, P. K.; Singh, S. K.; Singh, R.; Kaw, P. K.

2013-01-01

An electron energy filter (EEF) is embedded in the Large Volume Plasma Device plasma for carrying out studies on excitation of plasma turbulence by a gradient in electron temperature (ETG) described in the paper of Mattoo et al. [S. K. Mattoo et al., Phys. Rev. Lett. 108, 255007 (2012)]. In this paper, we report results on the response of the plasma to the EEF. It is shown that inhomogeneity in the magnetic field of the EEF switches on several physical phenomena resulting in plasma regions with different characteristics, including a plasma region free from energetic electrons, suitable for the study of ETG turbulence. Specifically, we report that localized structures of plasma density, potential, electron temperature, and plasma turbulence are excited in the EEF plasma. It is shown that structures of electron temperature and potential are created due to energy dependence of the electron transport in the filter region. On the other hand, although structure of plasma density has origin in the particle transport but two distinct steps of the density structure emerge from dominance of collisionality in the source-EEF region and of the Bohm diffusion in the EEF-target region. It is argued and experimental evidence is provided for existence of drift like flute Rayleigh-Taylor in the EEF plasma

Positive zeta potential of a negatively charged semi-permeable plasma membrane

Science.gov (United States)

Sinha, Shayandev; Jing, Haoyuan; Das, Siddhartha

2017-08-01

The negative charge of the plasma membrane (PM) severely affects the nature of moieties that may enter or leave the cells and controls a large number of ion-interaction-mediated intracellular and extracellular events. In this letter, we report our discovery of a most fascinating scenario, where one interface (e.g., membrane-cytosol interface) of the negatively charged PM shows a positive surface (or ζ) potential, while the other interface (e.g., membrane-electrolyte interface) still shows a negative ζ potential. Therefore, we encounter a completely unexpected situation where an interface (e.g., membrane-cytosol interface) that has a negative surface charge density demonstrates a positive ζ potential. We establish that the attainment of such a property by the membrane can be ascribed to an interplay of the nature of the membrane semi-permeability and the electrostatics of the electric double layer established on either side of the charged membrane. We anticipate that such a membrane property can lead to such capabilities of the cell (in terms of accepting or releasing certain kinds of moieties as well regulating cellular signaling) that was hitherto inconceivable.

Heavy ion beam probe development for the plasma potential measurement on the TUMAN-3M tokamak

International Nuclear Information System (INIS)

Askinazi, L.G.; Kornev, V.A.; Lebedev, S.V.; Tukachinsky, A.S.; Zhubr, N.A.; Dreval, N.B.; Krupnik, L.I.

2004-01-01

The peculiarities of the heavy ion beam probe implementation on the small aspect ratio tokamak TUMAN-3M are analyzed. The toroidal displacement of beam trajectory due to the high I pl /B tor ratio is taken into account when designing the layout of the diagnostic. Numerical calculation of beam trajectories using realistic configuration of TUMAN-3M magnetic fields and parabolic plasma current profile resulted in proper adjustment of probing and detection parameters (probing ion material, energy, entrance angles, detector location, and orientation). Secondary ion energy analyzer gain functions G and F were measured in situ using neutral hydrogen puffed in the tokamak vessel as a target for secondary ions production. The detector unit featured split-plate design and had additional electrodes for secondary electron emission suppression. As a result, the diagnostic is now capable of plasma potential evolution measurement and is sensitive enough to trace the potential profile evolution at the L-H mode transition

Dynamic behavior of detached recombining plasmas during ELM-like plasma heat pulses in the divertor plasma simulator NAGDIS-II

International Nuclear Information System (INIS)

Uesugi, Y.; Hattori, N.; Nishijima, D.; Ohno, N.; Takamura, S.

2001-01-01

It has been recognized that the ELMs associated with a good confinement at the edge, such as H-mode, must bring an enormous energy to the divertor target plate through SOL and detached plasmas. The understanding of the ELM energy transport through SOL to the divertor target is rather poor at the moment, which leads to an ambiguous estimation of the deposited heat load on the divertor target in ITER. In the present work the ELM-like plasma heat pulse is generated by rf heating in a linear divertor plasma simulator. Energetic electrons with an energy range 10-40 eV are effectively generated by rf heating in low temperature plasmas with (T e )< ∼1 eV. It is observed experimentally that the energetic electrons ionize the highly excited Rydberg atoms quickly, bringing a rapid increase of the ion particle flux to the target, and make the detached plasmas attached to the target. Detailed physical processes about the interaction between the heat pulse with conduction and convection, and detached recombining plasmas are discussed

Hot-electron plasma formation and confinement in the Tandem Mirror Experiment-Upgrade

International Nuclear Information System (INIS)

Ress, D.B.

1988-01-01

Electron-cyclotron range-of-frequency heating (ECRH) at 28 GHz is used to create a population of mirror-confined hot electrons in the Tandem Mirror Experiment-Upgrade (TMX-U). Generation of a large fraction of such electrons within each end-cell of TMX-U is essential to the formation of the desired electrostatic potential profile of the thermal-barrier tandem mirror. The formation and confinement of the ECRH-generated hot-electron plasma was investigated with a variety of diagnostic instruments, including a novel instrumented limiter probe. The author characterized the spatial structure of the hot-electron plasma. Details of the heating process cause the plasma to separate into two regions: a halo, consisting entirely of energetic electrons, and a core, which is dominated by cooler electrons. The plasma structure forms rapidly under the action of second-harmonic ECRH. Fundamental ECRH, which is typically applied simultaneously, is only weakly absorbed and generally does not create energetic electrons. The ECRH-generated plasma displays several loss mechanisms. Hot electrons in the halo region, with T e ∼ 30 keV, are formed by localized ECRH near the plasma boundary, and are lost through a radial process involving open magnetic-curvature-drift surfaces

Large-scale structuring of a rotating plasma due to plasma macroinstabilities

International Nuclear Information System (INIS)

Kikuchi, Toshinori; Ikehata, Takashi; Sato, Naoyuki; Watahiki, Takeshi; Tanabe, Toshio; Mase, Hiroshi

1995-01-01

The formation of coherent structures during plasma macroinstabilities have been of interest in view of the nonlinear plasma physics. In the present paper, we have investigated in detail, the mechanism and specific features of large-scale structuring of a rotating plasma. In the case of weak magnetic field, the plasma ejected from a plasma gun has a high beta value (β > 1) so that it expands rapidly across the magnetic field excluding a magnetic flux from its interior. Then, the boundary between the expanding plasma and the magnetic field becomes unstable against Rayleigh-Taylor instability. This instability has the higher growth rate at the shorter wavelength and the mode appears as flute. These features of the instability are confirmed by the observation of radial plasma jets with the azimuthal mode number m=20-40 in the early time of the plasma expansion. In the case of strong magnetic field, on the other hand, the plasma little expands and rotates at two times the ion sound speed. Especially, we observe spiral jets of m=2 instead of short-wavelength radial jets. This mode appears only when a glass target is installed or a dense neutral gas is introduced around the plasma to give the plasma a frictional force. From these results and with reference to the theory of plasma instabilities, the centrifugal instability caused by a combination of the velocity shear and centrifugal force is concluded to be responsible for the formation of spiral jets. (author)

Bispectral analysis applied to coherent floating potential fluctuations obtained in the edge plasmas on JFT-2M

International Nuclear Information System (INIS)

Nagashima, Y; Itoh, K; Itoh, S-I; Fujisawa, A; Hoshino, K; Takase, Y; Yagi, M; Ejiri, A; Ida, K; Shinohara, K; Uehara, K; Kusama, Y

2006-01-01

This paper presents results of bispectral analysis applied to floating potential fluctuations in the edge region of ohmically heated plasmas in the JAERI Fusion Torus-2 Modified (JFT-2M) tokamak. Inside the outermost surface of plasmas, coherent mode fluctuations (CMs) in floating potential were observed around the frequency of the geodesic acoustic mode. The squared bicoherence shows significant nonlinear couplings between the CMs and background fluctuations. The biphase at the frequency of the CMs is localized around π, while that at frequencies of background fluctuations distributes in a wide range. The total bicoherence at the frequency of the CMs is proportional to the squared amplitude of the CMs. These observations are consistent with the theoretical prediction on the drift wave-zonal flow systems. Interpretation of the absolute value of the total bicoherence is also discussed

Two component plasma vortex approach to fusion

International Nuclear Information System (INIS)

Ikuta, Kazunari.

1978-09-01

Two component operation of the field reversed theta pinch plasma by injection of the energetic ion beam with energy of the order of 1 MeV is considered. A possible trapping scheme of the ion beam in the plasma is discussed in detail. (author)

RELATIVISTIC CYCLOTRON INSTABILITY IN ANISOTROPIC PLASMAS

Energy Technology Data Exchange (ETDEWEB)

López, Rodrigo A.; Moya, Pablo S.; Muñoz, Víctor; Valdivia, J. Alejandro [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Navarro, Roberto E.; Araneda, Jaime A. [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Viñas, Adolfo F., E-mail: rlopez186@gmail.com [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, MD 20771 (United States)

2016-11-20

A sufficiently large temperature anisotropy can sometimes drive various types of electromagnetic plasma micro-instabilities, which can play an important role in the dynamics of relativistic pair plasmas in space, astrophysics, and laboratory environments. Here, we provide a detailed description of the cyclotron instability of parallel propagating electromagnetic waves in relativistic pair plasmas on the basis of a relativistic anisotropic distribution function. Using plasma kinetic theory and particle-in-cell simulations, we study the influence of the relativistic temperature and the temperature anisotropy on the collective and noncollective modes of these plasmas. Growth rates and dispersion curves from the linear theory show a good agreement with simulations results.

Confinement of a neutral plasma using nested electric potential wells

International Nuclear Information System (INIS)

Ordonez, C.A.

1997-01-01

A self-consistent, two-dimensional analysis is presented on confining a region of neutral plasma with a Penning/Malmberg type plasma trap using a nested well configuration. It is found that a neutral plasma region having disparate electron and ion temperatures or having high charge state ions can be confined with static fields. For confining a neutral region comprised of electrons and equal temperature low charge state ions, a quasistatic approach appears promising. copyright 1997 American Institute of Physics

Spectroscopic analysis applied to temperature measurement in plasmas

International Nuclear Information System (INIS)

Fieffe-Prevost, P.

1978-01-01

The plasma temperature is defined only if the plasma is in a state near thermodynamic equilibrium. This plasma state is analysed in detail and spectroscopic methods for measuring the temperature are discussed. As an application the hydrogen arc of the National Institute of Metrology of the Conservatoire National des Arts et Metiers (Paris) is briefly described [fr

A new large-scale plasma source with plasma cathode

International Nuclear Information System (INIS)

Yamauchi, K.; Hirokawa, K.; Suzuki, H.; Satake, T.

1996-01-01

A new large-scale plasma source (200 mm diameter) with a plasma cathode has been investigated. The plasma has a good spatial uniformity, operates at low electron temperature, and is highly ionized under relatively low gas pressure of about 10 -4 Torr. The plasma source consists of a plasma chamber and a plasma cathode generator. The plasma chamber has an anode which is 200 mm in diameter, 150 mm in length, is made of 304 stainless steel, and acts as a plasma expansion cup. A filament-cathode-like plasma ''plasma cathode'' is placed on the central axis of this source. To improve the plasma spatial uniformity in the plasma chamber, a disk-shaped, floating electrode is placed between the plasma chamber and the plasma cathode. The 200 mm diameter plasma is measure by using Langmuir probes. As a result, the discharge voltage is relatively low (30-120 V), the plasma space potential is almost equal to the discharge voltage and can be easily controlled, the electron temperature is several electron volts, the plasma density is about 10 10 cm -3 , and the plasma density is about 10% variance in over a 100 mm diameter. (Author)

Comprehensive simulation of vertical plasma instability events and their serious damage to ITER plasma facing components

International Nuclear Information System (INIS)

Hassanein, A.; Sizyuk, T.

2008-01-01

Safe and reliable operation is still one of the major challenges in the development of the new generation of ITER-like fusion reactors. The deposited plasma energy during major disruptions, edge-localized modes (ELMs) and vertical displacement events (VDEs) causes significant surface erosion, possible structural failure and frequent plasma contamination. While plasma disruptions and ELM will have no significant thermal effects on the structural materials or coolant channels because of their short deposition time, VDEs having longer-duration time could have a destructive impact on these components. Therefore, modelling the response of structural materials to VDE has to integrate detailed energy deposition processes, surface vaporization, phase change and melting, heat conduction to coolant channels and critical heat flux criteria at the coolant channels. The HEIGHTS 3D upgraded computer package considers all the above processes to specifically study VDE in detail. Results of benchmarking with several known laboratory experiments prove the validity of HEIGHTS implemented models. Beryllium and tungsten are both considered surface coating materials along with copper structure and coolant channels using both smooth tubes with swirl tape insert. The design requirements and implications of plasma facing components are discussed along with recommendations to mitigate and reduce the effects of plasma instabilities on reactor components.

Time resolved plasma characterization in a long conduction time planar plasma opening switch

International Nuclear Information System (INIS)

Adler, L.K.; Greenly, J.B.; Qi, N.; Hammer, D.A.

1989-01-01

The authors discuss additional experiments in which the plasma dynamics and properties will be monitored in detail before and during opening. Space and time resolved density, temperature and motion information about the plasma and neutrals is given by emission spectroscopy and streak photography and correlated to the current and voltage traces. Specifically, we will look for the effects of neutrals evolving off of surfaces, stagnation of the switch plasma, and rvec J x rvec B motion of the plasma downstream of the switch. Diagnostics include current and voltage monitors, a multi-aperture biased Faraday cup, emission spectroscopy and streak photography. Pairs of B dot loops are positioned in the stripline just upstream and downstream of the POS. Also, two single B loops were placed further downstream to look for bulk plasma motion. An inductive monitor gives the voltage at the upstream side of the POS and the Faraday cup monitors the gun plasma consistency from shot to shot

Plasmon dispersion and dynamic exchange-correlation potential from two-pair excitations in degenerate plasmas

International Nuclear Information System (INIS)

Boehm, H.M.; Conti, S.; Tosi, M.P.

1995-11-01

Electron energy loss experiments have shown a rapid softening of the bulk plasmon dispersion across the series of the alkali metals. Motivated by these observations, we reconsider the evaluation of the dynamic, long-wavelength exchange-correlation potential f xc (ω) in the electron fluid, which is of interest for applications in time-dependent density functional theory. The value of Re[f xc (ω pl )] at the plasma frequency ω pl determines the exchange-correlation contribution to the leading plasmon dispersion coefficient in the homogeneous electron fluid. Whereas an interpolation scheme originally proposed by Gross and Kohn assumes a monotonic increase of Re[f xc (ω) - f xc (0)] across the plasma frequency, we examine the possibility of strongly non-monotonic behaviour arising from a resonance process between plasmons and two-pair excitations. This process is evaluated with the help of sum rules and selfconsistency requirements with a single-pole approximation of the dielectric function. The cases of a fermion plasma and of a boson plasma are treated in parallel and the reliability of the results for the fermion plasma at low coupling is tested by calculations within a random phase approximation for the dielectric function. In all cases it is found that the resonance process accumulates oscillator strength in the neighbourhood of 2ω pl , thus decreasing the value of Re[f xc (ω pl )] below the static value f xc (0) fixed by the compressibility sum rule. Although this lowering does not suffice to account by itself for the measured plasmon dispersion coefficient in the low-density alkali metals, our results provide useful input for combined band-structure and exchange-correlation calculations. (author). 40 refs, 9 figs, 2 tabs

Investigation of arcing on fiber-formed nanostructured tungsten by pulsed plasma during steady state plasma irradiation

Energy Technology Data Exchange (ETDEWEB)

Yajima, M., E-mail: yajima.miyuki@LHD.nifs.ac.jp [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, 509-5292 Japan (Japan); Ohno, N. [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kajita, S. [EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); De Temmerman, G. [ITER Organization, Route de Vinon sur Verdon, CS 90 046-13067 St Paul Lez Durance Cedex (France); Bystrov, K.; Bardin, S.; Morgan, T.W. [FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, Partner in the Trilateral Euregio Cluster, 5612 AJ Eindhoven (Netherlands); Masuzaki, S. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, 509-5292 Japan (Japan)

2016-11-15

Arcing on fiber-formed nanostructured tungsten samples during ELM-like pulses was investigated using the superimposition of high power pulsed plasma on a steady state plasma with hydrogen gas in the linear plasma device Pilot-PSI. The ignition of arcing was observed when the floating potential of the samples was less than −75 V with sufficient heat flux. The surface observation showed that the arc spots were not in the center, but in the peripheral area of the plasma column. Considering the plasma potential profile in the Pilot-PSI, the arcing occurred at the position where the heat flux and the sheath potential drop are sufficiently large.

SFRP Tumour Suppressor Genes Are Potential Plasma-Based Epigenetic Biomarkers for Malignant Pleural Mesothelioma

Directory of Open Access Journals (Sweden)

Yuen Yee Cheng

2017-01-01

Full Text Available Malignant pleural mesothelioma (MPM is associated with asbestos exposure. Asbestos can induce chronic inflammation which in turn can lead to silencing of tumour suppressor genes. Wnt signaling pathway can be affected by chronic inflammation and is aberrantly activated in many cancers including colon and MPM. SFRP genes are antagonists of Wnt pathway, and SFRPs are potential tumour suppressors in colon, gastric, breast, ovarian, and lung cancers and mesothelioma. This study investigated the expression and DNA methylation of SFRP genes in MPM cells lines with and without demethylation treatment. Sixty-six patient FFPE samples were analysed and have showed methylation of SFRP2 (56% and SFRP5 (70% in MPM. SFRP2 and SFRP5 tumour-suppressive activity in eleven MPM lines was confirmed, and long-term asbestos exposure led to reduced expression of the SFRP1 and SFRP2 genes in the mesothelium (MeT-5A via epigenetic alterations. Finally, DNA methylation of SFRPs is detectable in MPM patient plasma samples, with methylated SFRP2 and SFRP5 showing a tendency towards greater abundance in patients. These data suggested that SFRP genes have tumour-suppresive activity in MPM and that methylated DNA from SFRP gene promoters has the potential to serve as a biomarker for MPM patient plasma.

Computational plasma physics

International Nuclear Information System (INIS)

Killeen, J.

1975-08-01

The behavior of a plasma confined by a magnetic field is simulated by a variety of numerical models. Some models used on a short time scale give detailed knowledge of the plasma on a microscopic scale, while other models used on much longer time scales compute macroscopic properties of the plasma dynamics. In the last two years there has been a substantial increase in the numerical modelling of fusion devices. The status of MHD, transport, equilibrium, stability, Vlasov, Fokker-Planck, and Hybrid codes is reviewed. These codes have already been essential in the design and understanding of low and high beta toroidal experiments and mirror systems. The design of the next generation of fusion experiments and fusion test reactors will require continual development of these numerical models in order to include the best available plasma physics description and also to increase the geometric complexity of the model. (auth)

Proteomic Analysis of Plasma-Purified VLDL, LDL, and HDL Fractions from Atherosclerotic Patients Undergoing Carotid Endarterectomy: Identification of Serum Amyloid A as a Potential Marker

Directory of Open Access Journals (Sweden)

Antonio J. Lepedda

2013-01-01

Full Text Available Apolipoproteins are very heterogeneous protein family, implicated in plasma lipoprotein structural stabilization, lipid metabolism, inflammation, or immunity. Obtaining detailed information on apolipoprotein composition and structure may contribute to elucidating lipoprotein roles in atherogenesis and to developing new therapeutic strategies for the treatment of lipoprotein-associated disorders. This study aimed at developing a comprehensive method for characterizing the apolipoprotein component of plasma VLDL, LDL, and HDL fractions from patients undergoing carotid endarterectomy, by means of two-dimensional electrophoresis (2-DE coupled with Mass Spectrometry analysis, useful for identifying potential markers of plaque presence and vulnerability. The adopted method allowed obtaining reproducible 2-DE maps of exchangeable apolipoproteins from VLDL, LDL, and HDL. Twenty-three protein isoforms were identified by peptide mass fingerprinting analysis. Differential proteomic analysis allowed for identifying increased levels of acute-phase serum amyloid A protein (AP SAA in all lipoprotein fractions, especially in LDL from atherosclerotic patients. Results have been confirmed by western blotting analysis on each lipoprotein fraction using apo AI levels for data normalization. The higher levels of AP SAA found in patients suggest a role of LDL as AP SAA carrier into the subendothelial space of artery wall, where AP SAA accumulates and may exert noxious effects.

Resonant interaction of electromagnetic wave with plasma layer and overcoming the radiocommunication blackout problem

Science.gov (United States)

Bogatskaya, A. V.; Klenov, N. V.; Tereshonok, M. V.; Adjemov, S. S.; Popov, A. M.

2018-05-01

We present an analysis of the possibility of penetrating electromagnetic waves through opaque media using an optical-mechanical analogy. As an example, we consider the plasma sheath surrounding the vehicle as a potential barrier and analyze the overcoming of radiocommunication blackout problem. The idea is to embed a «resonator» between the surface on the vehicle and plasma sheath which is supposed to provide an effective tunneling of the signal to the receiving antenna. We discuss the peculiarities of optical mechanical analogy applicability and analyze the radio frequency wave tunneling regime in detail. The cases of normal and oblique incidence of radiofrequency waves on the vehicle surface are studied.

The assessment of cold atmospheric plasma treatment of DNA in synthetic models of tissue fluid, tissue and cells

Science.gov (United States)

Szili, Endre J.; Gaur, Nishtha; Hong, Sung-Ha; Kurita, Hirofumi; Oh, Jun-Seok; Ito, Masafumi; Mizuno, Akira; Hatta, Akimitsu; Cowin, Allison J.; Graves, David B.; Short, Robert D.

2017-07-01

There is a growing literature database that demonstrates the therapeutic potential of cold atmospheric plasma (herein referred to as plasma). Given the breadth of proposed applications (e.g. from teeth whitening to cancer therapy) and vast gamut of plasma devices being researched, it is timely to consider plasma interactions with specific components of the cell in more detail. Plasma can produce highly reactive oxygen and nitrogen species (RONS) such as the hydroxyl radical (OH•), peroxynitrite (ONOO-) and superoxide (\\text{O}2- ) that would readily modify essential biomolecules such as DNA. These modifications could in principle drive a wide range of biological processes. Against this possibility, the reported therapeutic action of plasmas are not underpinned by a particularly deep knowledge of the potential plasma-tissue, -cell or -biomolecule interactions. In this study, we aim to partly address this issue by developing simple models to study plasma interactions with DNA, in the form of DNA-strand breaks. This is carried out using synthetic models of tissue fluid, tissue and cells. We argue that this approach makes experimentation simpler, more cost-effective and faster than compared to working with real biological materials and cells. Herein, a helium plasma jet source was utilised for these experiments. We show that the plasma jet readily induced DNA-strand breaks in the tissue fluid model and in the cell model, surprisingly without any significant poration or rupture of the phospholipid membrane. In the plasma jet treatment of the tissue model, DNA-strand breaks were detected in the tissue mass after pro-longed treatment (on the time-scale of minutes) with no DNA-strand breaks being detected in the tissue fluid model underneath the tissue model. These data are discussed in the context of the therapeutic potential of plasma.

Dust in flowing magnetized plasma

International Nuclear Information System (INIS)

Pandey, Birendra P.; Samarian, Alex A.; Vladimirov, Sergey V.

2009-01-01

Plasma flows occur in almost every laboratory device and interactions of flowing plasmas with near-wall impurities and/or dust significantly affects the efficiency and lifetime of such devices. The charged dust inside the magnetized flowing plasma moves primarily under the influence of the plasma drag and electric forces. Here, the charge on the dust, plasma potential, and plasma density are calculated self-consistently. The electrons are assumed non-Boltzmannian and the effect of electron magnetization and electron-atom collisions on the dust charge is calculated in a self-consistent fashion. For various plasma magnetization parameters viz. the ratio of the electron and ion cyclotron frequencies to their respective collision frequencies, plasma-atom and ionization frequencies, the evolution of the plasma potential and density in the flow region is investigated. The variation of the dust charge profile is shown to be a sensitive function of plasma parameters. (author)

Hot-electron plasma formation and confinement in the tandem mirror experiment-upgrade

International Nuclear Information System (INIS)

Ress, D.B.

1988-06-01

The tandem mirror experiment-upgrade (TMX-U) at the Lawrence Livermore National Laboratory (LLNL) is the first experiment to investigate the thermal-barrier tandem-mirror concept. One attractive feature of the tandem magnetic mirror as a commercial power reactor is that the fusion reactions occur in an easily accessible center-cell. On the other hand, complicated end-cells are necessary to provide magnetohydrodynamic (MHD) stability and improved particle confinement of the center-cell plasma. In these end-cells, enhanced confinement is achieved with a particular axial potential profile that is formed with electron-cyclotron range-of-frequency heating (ECRF heating, ECRH). By modifying the loss rates of electrons at spatially distinct locations within the end-cells, the ECRH can tailor the plasma potential profile in the desired fashion. Specifically, the thermal-barrier concept requires generation of a population of energetic electrons near the midplane of each end-cell. To be effective, the transverse (to the magnetic field) spatial structure of the hot-electron plasma must be fairly uniform. In this dissertation we characterize the spatial structure of the ECRH-generated plasma, and determine how the structure builds up in time. Furthermore, the plasma should efficiently absorb the ECRF power, and a large fraction of the electrons must be well confined near the end-cell midplane. Therefore, we also examine in detail the ECRH power balance, determining how the ECRF power is absorbed by the plasma, and the processes through which that power is confined and lost. 43 refs., 69 figs., 6 tabs

The Potential of Cold Plasma for Safe and Sustainable Food Production.

Science.gov (United States)

Bourke, Paula; Ziuzina, Dana; Boehm, Daniela; Cullen, Patrick J; Keener, Kevin

2018-06-01

Cold plasma science and technology is increasingly investigated for translation to a plethora of issues in the agriculture and food sectors. The diversity of the mechanisms of action of cold plasma, and the flexibility as a standalone technology or one that can integrate with other technologies, provide a rich resource for driving innovative solutions. The emerging understanding of the longer-term role of cold plasma reactive species and follow-on effects across a range of systems will suggest how cold plasma may be optimally applied to biological systems in the agricultural and food sectors. Here we present the current status, emerging issues, regulatory context, and opportunities of cold plasma with respect to the broad stages of primary and secondary food production. Copyright © 2017 Elsevier Ltd. All rights reserved.

Asymptotic behavior of correlation functions for electric potential and field fluctuations in a classical one-component plasma

NARCIS (Netherlands)

Suttorp, L.G.

1992-01-01

The correlations of the electric potential fluctuations in a classical one-component plasma are studied for large distances between the observation points. The two-point correlation function for these fluctuations is known to decay slowly for large distances, even if exponential clustering holds for

Wake potential in a nonuniform self-gravitating dusty magnetoplasma in the presence of ion streaming

International Nuclear Information System (INIS)

Salimullah, M.; Ehsan, Z.; Zubia, K.; Shah, H. A.; Murtaza, G.

2007-01-01

A detailed investigation of the electrostatic asymmetric shielding potential and consequent generation of the dynamical oscillatory wake potential has been examined analytically in an inhomogeneous self-gravitating dusty magnetoplasma in the presence of uniform ion streaming. It is found that the wake potential depends significantly on the test particle speed, ambient magnetic field, ion streaming velocity, and the plasma inhomogeneity. The periodic oscillatory potential might lead to an alternative approach to the Jeans instability for the formation of dust agglomeration leading to gravitational collapse of the self-gravitating systems

Laser plasma focus produced in a ring target

International Nuclear Information System (INIS)

Saint-Hilaire, G.; Szili, Z.

1976-01-01

A new geometry for generating a laser-produced plasma is presented. A toroidal mirror is used to focus a CO 2 laser beam on the inside wall of a copper ring target. The plasma produced converges at the center of the ring where an axial plasma focus is formed. High-speed photography shows details of a plasma generated at a distance from the target surface. This new geometry could have important applications in the field of x-ray lasers

Solar wind and magnetosphere plasma diagnostics by spacecraft electrostatic potential measurements

Directory of Open Access Journals (Sweden)

A. Pedersen

1995-02-01

Full Text Available Several satellites (GEOS-1, GEOS-2, ISEE-1, Viking and CRRES carried electric field experiments on which probes were driven by a current from the satellite to be close to the plasma potential. The potential difference between an electric field probe and its spacecraft (with conductive surfaces can be used to determine the ambient electron density and/or electron flux with limited accuracy but with high time resolution, of the order of 10-100 ms. It is necessary for the development of this diagnostic method to understand the photoemission characteristics of probes and satellites. According to the electric field experiments on the above-mentioned satellites, all materials develop very similar photoemission properties when they are beyond the influence of atmospheric oxygen. The photoelectron yield steadily increases over the first few months in space and reaches values well above those measured on clean surfaces in the laboratory. The method can be used for solar radiation levels corresponding to distances from 0.4 to 5 AU from the Sun.

Detailed study of spontaneous rotation generation in diverted H-mode plasma using the full-f gyrokinetic code XGC1

Science.gov (United States)

Seo, Janghoon; Chang, C. S.; Ku, S.; Kwon, J. M.; Yoon, E. S.

2013-10-01

The Full-f gyrokinetic code XGC1 is used to study the details of toroidal momentum generation in H-mode plasma. Diverted DIII-D geometry is used, with Monte Carlo neutral particles that are recycled at the limiter wall. Nonlinear Coulomb collisions conserve particle, momentum, and energy. Gyrokinetic ions and adiabatic electrons are used in the present simulation to include the effects from ion gyrokinetic turbulence and neoclassical physics, under self-consistent radial electric field generation. Ion orbit loss physics is automatically included. Simulations show a strong co-Ip flow in the H-mode layer at outside midplane, similarly to the experimental observation from DIII-D and ASDEX-U. The co-Ip flow in the edge propagates inward into core. It is found that the strong co-Ip flow generation is mostly from neoclassical physics. On the other hand, the inward momentum transport is from turbulence physics, consistently with the theory of residual stress from symmetry breaking. Therefore, interaction between the neoclassical and turbulence physics is a key factor in the spontaneous momentum generation.

Transport processes in multicomponent plasma

International Nuclear Information System (INIS)

Zissis, G.

2002-01-01

Full text: This book treats in detail, as indicated in the title, the transport phenomena in multicomponent plasmas. Here, the term 'transport' applies to the study of mass and energy transfer in plasmas due to the interactions between pairs of particles only. Radiation is legitimately omitted; anyway, radiative transfer is another field of study. As the author himself mentions in the introduction, 'the term multicomponent plasma implies a partially or fully ionized mixture of arbitrary number of species of neutral and charged particles satisfying the condition of quasi-neutrality'. In fact, this book treats a large variety of plasmas applying to different systems ranging from low-pressure systems which may be far from local thermodynamic equilibrium (LTE) conditions, to thermal plasmas in LTE or near-LTE states with special attention to two-temperature systems; partially ionized plasmas with low ionization degree for which electron-neutral interactions are predominant, to systems with higher ionization degrees in which charged particle interactions are no more negligible. In addition, for all the above stated situations, the author treats both plasmas which are subjected to an external electromagnetic field and those which are not (homogeneous and inhomogeneous cases). Furthermore, in the last chapters a special discussion concerning molecular plasmas is presented. Taking into account the evolution of plasma modelling in the last few years, the subject is of current interest and the reader will find in the book a large amount of information necessary for a good understanding of transport phenomena in plasmas: for a plasma simulation specialist, this book may be regarded as reference text, which includes all necessary mathematical relations for his work. However, it should not be considered a simple formulary; the reader will also find here an excellent description of the theoretical basis necessary for the derivation of all given expressions. To this point of view

Influence of Glucose Deprivation on Membrane Potentials of Plasma Membranes, Mitochondria and Synaptic Vesicles in Rat Brain Synaptosomes.

Science.gov (United States)

Hrynevich, Sviatlana V; Pekun, Tatyana G; Waseem, Tatyana V; Fedorovich, Sergei V

2015-06-01

Hypoglycemia can cause neuronal cell death similar to that of glutamate-induced cell death. In the present paper, we investigated the effect of glucose removal from incubation medium on changes of mitochondrial and plasma membrane potentials in rat brain synaptosomes using the fluorescent dyes DiSC3(5) and JC-1. We also monitored pH gradients in synaptic vesicles and their recycling by the fluorescent dye acridine orange. Glucose deprivation was found to cause an inhibition of K(+)-induced Ca(2+)-dependent exocytosis and a shift of mitochondrial and plasma membrane potentials to more positive values. The sensitivity of these parameters to the energy deficit caused by the removal of glucose showed the following order: mitochondrial membrane potential > plasma membrane potential > pH gradient in synaptic vesicles. The latter was almost unaffected by deprivation compared with the control. The pH-dependent dye acridine orange was used to investigate synaptic vesicle recycling. However, the compound's fluorescence was shown to be enhanced also by the mixture of mitochondrial toxins rotenone (10 µM) and oligomycin (5 µg/mL). This means that acridine orange can presumably be partially distributed in the intermembrane space of mitochondria. Glucose removal from the incubation medium resulted in a 3.7-fold raise of acridine orange response to rotenone + oligomycin suggesting a dramatic increase in the mitochondrial pH gradient. Our results suggest that the biophysical characteristics of neuronal presynaptic endings do not favor excessive non-controlled neurotransmitter release in case of hypoglycemia. The inhibition of exocytosis and the increase of the mitochondrial pH gradient, while preserving the vesicular pH gradient, are proposed as compensatory mechanisms.

Turbulent transport in low-beta plasmas

DEFF Research Database (Denmark)

Nielsen, A.H.; Pécseli, H.L.; Juul Rasmussen, J.

1996-01-01

Low-frequency electrostatic fluctuations are studied experimentally in a low-P plasma, with particular attention to their importance for the anomalous plasma transport across magnetic field lines. The presence of large coherent structures in a turbulent background at the edge of the plasma column...... is demonstrated by a statistical analysis. The importance of these structures for the turbulent transport is investigated. The study is extended by a multichannel conditional analysis to illustrate detailed properties and parameter dependences of the turbulent transport. (C) 1996 American Institute of Physics....

Comparison of hollow cathode discharge plasma configurations

International Nuclear Information System (INIS)

Farnell, Casey C; Farnell, Cody C; Williams, John D

2011-01-01

Hollow cathodes used in plasma contactor and electric propulsion devices provide electrons for sustaining plasma discharges and enabling plasma bridge neutralization. Life tests show erosion on hollow cathodes exposed to the plasma environment produced in the region downstream of these devices. To explain the observed erosion, plasma flow field measurements are presented for hollow cathode generated plasmas using both directly immersed probes and remotely located plasma diagnostics. Measurements on two cathode discharge configurations are presented: (1) an open, no magnetic field configuration and (2) a setup simulating the discharge chamber environment of an ion thruster. In the open cathode configuration, large amplitude plasma potential oscillations, ranging from 20 to 85 V within a 34 V discharge, were observed using a fast response emissive probe. These oscillations were observed over a dc potential profile that included a well-defined potential hill structure. A remotely located electrostatic analyzer (ESA) was used to measure the energy of ions produced within the plasma, and energies were detected that met, and in some cases exceeded, the peak oscillatory plasma potentials detected by the emissive probe. In the ion thruster discharge chamber configuration, plasma potentials from the emissive probe again agreed with ion energies recorded by the remotely located ESA; however, much lower ion energies were detected compared with the open configuration. A simplified ion-transit model that uses temporal and spatial plasma property measurements is presented and used to predict far-field plasma streaming properties. Comparisons between the model and remote measurements are presented.

Analysis of plasma instabilities and verification of the BOUT code for the Large Plasma Device

International Nuclear Information System (INIS)

Popovich, P.; Carter, T. A.; Friedman, B.; Umansky, M. V.

2010-01-01

The properties of linear instabilities in the Large Plasma Device [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] are studied both through analytic calculations and solving numerically a system of linearized collisional plasma fluid equations using the three-dimensional fluid code BOUT[M. Umansky et al., Contrib. Plasma Phys. 180, 887 (2009)], which has been successfully modified to treat cylindrical geometry. Instability drive from plasma pressure gradients and flows is considered, focusing on resistive drift waves and the Kelvin-Helmholtz and rotational interchange instabilities. A general linear dispersion relation for partially ionized collisional plasmas including these modes is derived and analyzed. For Large Plasma Device relevant profiles including strongly driven flows, it is found that all three modes can have comparable growth rates and frequencies. Detailed comparison with solutions of the analytic dispersion relation demonstrates that BOUT accurately reproduces all characteristics of linear modes in this system.

Comprehensive physical models and simulation package for plasma/material interactions during plasma instabilities

International Nuclear Information System (INIS)

Hassanein, A.; Konkashbaev, I.

1999-01-01

Damage to plasma-facing components (PFCs) from plasma instabilities remains a major obstacle to a successful tokamak concept. The extent of the damage depends on the detailed physics of the disrupting plasma, as well as on the physics of plasma-material interactions. A comprehensive computer package called high energy interaction with general heterogeneous target systems (HEIGHTS) has been developed and consists of several integrated computer models that follow the beginning of a plasma disruption at the scrape-off layer (SOL) through the transport of the eroded debris and splashed target materials to nearby locations as a result of the deposited energy. The package can study, for the first time, plasma-turbulent behavior in the SOL and predict the plasma parameters and conditions at the divertor plate. Full two-dimensional (2-D) comprehensive radiation magnetohydrodynamic (MHD) models are coupled with target thermodynamics and liquid hydrodynamics to evaluate the integrated response of plasma-facing materials. Factors that influence the lifetime of plasma-facing and nearby components, such as loss of vapor cloud confinement and vapor removal due to MHD effects, damage to nearby components due to intense vapor radiation, melt splashing, and brittle destruction of target materials, are also modeled and discussed. (orig.)

Comprehensive physical models and simulation package for plasma/material interactions during plasma instabilities

International Nuclear Information System (INIS)

Hassanein, A.

1998-01-01

Damage to plasma-facing components (PFCS) from plasma instabilities remains a major obstacle to a successful tokamak concept. The extent of the damage depends on the detailed physics of the disrupting plasma, as well as on the physics of plasma-material interactions. A comprehensive computer package called High Energy Interaction with General Heterogeneous Target Systems (HEIGHTS) has been developed and consists of several integrated computer models that follow the beginning of a plasma disruption at the scrape-off layer (SOL) through the transport of the eroded debris and splashed target materials to nearby locations as a result of the deposited energy. The package can study, for the first time, plasma-turbulent behavior in the SOL and predict the plasma parameters and conditions at the divertor plate. Full two-dimensional (2-D) comprehensive radiation magnetohydrodynamic (MHD) models are coupled with target thermodynamics and liquid hydrodynamics to evaluate the integrated response of plasma-facing materials. Factors that influence the lifetime of plasma-facing and nearby components, such as loss of vapor-cloud confinement and vapor removal due to MHD effects, damage to nearby components due to intense vapor radiation, melt splashing, and brittle destruction of target materials, are also modeled and discussed

Study of the Spacecraft Potential Under Active Control and Plasma Density Estimates During the MMS Commissioning Phase

Science.gov (United States)

Andriopoulou, M.; Nakamura, R.; Torkar, K.; Baumjohann, W.; Torbert, R. B.; Lindqvist, P.-A.; Khotyaintsev, Y. V.; Dorelli, John Charles; Burch, J. L.; Russell, C. T.

2016-01-01

Each spacecraft of the recently launched magnetospheric multiscale MMS mission is equipped with Active Spacecraft Potential Control (ASPOC) Instruments, which control the spacecraft potential in order to reduce spacecraft charging effects. ASPOC typically reduces the spacecraft potential to a few volts. On several occasions during the commissioning phase of the mission, the ASPOC instruments were operating only on one spacecraft at a time. Taking advantage of such intervals, we derive photoelectron curves and also perform reconstructions of the uncontrolled spacecraft potential for the spacecraft with active control and estimate the electron plasma density during those periods. We also establish the criteria under which our methods can be applied.

Vortices, Reconnection and Turbulence in High Electron-Beta Plasmas

International Nuclear Information System (INIS)

Stenzel, R. L.

2004-01-01

Plasmas in which the kinetic energy exceeds the magnetic energy by a significant factor are common in space and in the laboratory. Such plasmas can convect magnetic fields and create null points in whose vicinity first the ions become unmagnetized, then the electrons. This project focuses on the detailed study of the transition regime of these plasmas

A flowing plasma model to describe drift waves in a cylindrical helicon discharge

International Nuclear Information System (INIS)

Chang, L.; Hole, M. J.; Corr, C. S.

2011-01-01

A two-fluid model developed originally to describe wave oscillations in the vacuum arc centrifuge, a cylindrical, rapidly rotating, low temperature, and confined plasma column, is applied to interpret plasma oscillations in a RF generated linear magnetized plasma [WOMBAT (waves on magnetized beams and turbulence)], with similar density and field strength. Compared to typical centrifuge plasmas, WOMBAT plasmas have slower normalized rotation frequency, lower temperature, and lower axial velocity. Despite these differences, the two-fluid model provides a consistent description of the WOMBAT plasma configuration and yields qualitative agreement between measured and predicted wave oscillation frequencies with axial field strength. In addition, the radial profile of the density perturbation predicted by this model is consistent with the data. Parameter scans show that the dispersion curve is sensitive to the axial field strength and the electron temperature, and the dependence of oscillation frequency with electron temperature matches the experiment. These results consolidate earlier claims that the density and floating potential oscillations are a resistive drift mode, driven by the density gradient. To our knowledge, this is the first detailed physics model of flowing plasmas in the diffusion region away from the RF source. Possible extensions to the model, including temperature nonuniformity and magnetic field oscillations, are also discussed.

Magnetic Field Analysis of Plasma Guide in Galathea Trimyx

Directory of Open Access Journals (Sweden)

Jin Xianji

2016-01-01

Full Text Available You Galathea Trimyx is a kind of small size, multipole magnetic confinement devices in controlled thermonuclear fusion. Plasma guide is one of important part in Galathea Trimyx which is responsible for transporting fast and slow plasma bunches ejected from plasma gun. The distribution and uniformity of magnetic field in completed plasma guide is analyzed in detail, including in x -axis direction and in z-axis direction. On the basis, the motion of plasma in the guide is discussed.

Corpuscular plasma diagnostics

International Nuclear Information System (INIS)

Afrosimov, V.; Petrov, M.

1984-01-01

An elementary explanation is presented of the physical principles and important methods of corpuscular plasma diagnostics. The invaluable role of corpuscular methods for measuring the hot plasma ion component in thermonuclear facilities, especially hydrogen ions in tokamaks, is emphasized. All corpuscular methods employ analysis of fast neutral atoms and therefore the mechanism of their creation inside a hot plasma is explained first. The ammount of information obtainable from spectra of fast neutrals is discussed. Multichannel analyzers developed at the FTI A.F. Ioffe in Leningrad are described in detail. Classical passive corpuscular diagnostics are examined as are active methods using artifitial beams of hydrogen atoms. The method used for obtaining local values of ion temperature and density is explained. Corpuscular spectroscopic diagnostics and its application for measuring impurities is mentioned. (J.U.)

Sensitivity of the Boundary Plasma to the Plasma-Material Interface

International Nuclear Information System (INIS)

Canik, John M.; Tang, X.-Z.

2017-01-01

While the sensitivity of the scrape-off layer and divertor plasma to the highly uncertain cross-field transport assumptions is widely recognized, the plasma is also sensitive to the details of the plasma-material interface (PMI) models used as part of comprehensive predictive simulations. Here in this paper, these PMI sensitivities are studied by varying the relevant sub-models within the SOLPS plasma transport code. Two aspects are explored: the sheath model used as a boundary condition in SOLPS, and fast particle reflection rates for ions impinging on a material surface. Both of these have been the study of recent high-fidelity simulation efforts aimed at improving the understanding and prediction of these phenomena. It is found that in both cases quantitative changes to the plasma solution result from modification of the PMI model, with a larger impact in the case of the reflection coefficient variation. Finally, this indicates the necessity to better quantify the uncertainties within the PMI models themselves, and perform thorough sensitivity analysis to propagate these throughout the boundary model; this is especially important for validation against experiment, where the error in the simulation is a critical and less-studied piece of the code-experiment comparison.

Plasma heating by adiabatic compression

International Nuclear Information System (INIS)

Ellis, R.A. Jr.

1972-01-01

These two lectures will cover the following three topics: (i) The application of adiabatic compression to toroidal devices is reviewed. The special case of adiabatic compression in tokamaks is considered in more detail, including a discussion of the equilibrium, scaling laws, and heating effects. (ii) The ATC (Adiabatic Toroidal Compressor) device which was completed in May 1972, is described in detail. Compression of a tokamak plasma across a static toroidal field is studied in this device. The device is designed to produce a pre-compression plasma with a major radius of 17 cm, toroidal field of 20 kG, and current of 90 kA. The compression leads to a plasma with major radius of 38 cm and minor radius of 10 cm. Scaling laws imply a density increase of a factor 6, temperature increase of a factor 3, and current increase of a factor 2.4. An additional feature of ATC is that it is a large tokamak which operates without a copper shell. (iii) Data which show that the expected MHD behavior is largely observed is presented and discussed. (U.S.)

Nonthermal Argon Plasma Generator and Some Potential Applications

Directory of Open Access Journals (Sweden)

Bunoiu M.

2015-12-01

Full Text Available A laboratory - made nonthermal plasma generator is presented. It has a diameter of 0.020 m and length of 0.155 m and contains two electrodes. The first electrode is a 2% Th-W alloy, 0.002 m in diameter bar, centred inside the generator’s body by means of a four channel teflon piece; the other three channels, 0.003 m in diameter, are used for Ar supply. The second electrode is a nozzle of 0.002 m - 0.008 m diameter and 0.005m length. A ~500 kV/m electric field is generated between the two electrodes by a high frequency source (13.56 MHz ±5%, equipped with a OT-1000 (Tungsram power triode. For Ar flows ranging from 0.00008 m3/s to 0.00056 m3/s, a plasma jet of length not exceeding 0.015 m and temperature below 315 K is obtained. Anthurium andraeanumis sample , blood matrix, human hair and textile fibers may be introduced in the plasma jet. For time periods of 30 s and 60 s, various effects like, cell detexturization, fast blood coagulation or textile fiber or hair cleaning and smoothing are obtained. These effects are presented and discussed in the paper.

Particle acceleration by plasma waves

International Nuclear Information System (INIS)

Joshi, C.

2006-01-01

In an advanced particle accelerator particles are driven near by light velocity through ionized gas. Such plasma devices are compact, cost efficient and usable in many fields. Examples are given in detail. (GL)

Plasma processing of nanomaterials

CERN Document Server

Sankaran, R Mohan

2014-01-01

CRC Press author R. Mohan Sankaran is the winner of the 2011 Peter Mark Memorial Award "… for the development of a tandem plasma synthesis method to grow carbon nanotubes with unprecedented control over the nanotube properties and chirality." -2011 AVS Awards Committee"Readers who want to learn about how nanomaterials are processed, using the most recent methods, will benefit greatly from this book. It contains very recent technical details on plasma processing and synthesis methods used by current researchers developing new nano-based materials, with all the major plasma-based processing techniques used today being thoroughly discussed."-John J. Shea, IEEE Electrical Insulation Magazine, May/June 2013, Vol. 29, No. 3.

Fundamental studies of fusion plasmas. Final report

International Nuclear Information System (INIS)

Aamodt, R.E.

1998-01-01

Lodestar has carried out a vigorous research program in the areas of rf, edge plasma and divertor physics, with emphasis largely geared towards improving the understanding and performance of ion-cyclotron heating and current drive (ICRF) systems. Additionally, a research program in the field of edge plasma and divertor modeling was initiated. Theoretical work on high power rf sheath formation for multi-strap rf arrays was developed and benchmarked against recent experimental data from the new JET A2 antennas. Sophisticated modeling tools were employed to understand the sheath formation taking into account realistic three-dimensional antenna geometry. A novel physics explanation of an observed anomaly in the low power loading of antennas was applied to qualitatively interpret data on DIII-D in terms of rf sheaths, and potential applications of the idea to develop a near-field sheath diagnostic were explored. Other rf-wave related topics were also investigated. Full wave ICRF modeling studies were carried out in support of ongoing and planned tokamaks experiments, including the investigation of low frequency plasma heating and current drive regimes for IGNITOR. In a cross-disciplinary study involving both MHD and ICRF physics, ponderomotive feedback stabilization by rf was investigated as a potential means of controlling external kink mode disruptions. In another study, the instability of the ion hybrid wave (IHW) in the presence of fusion alpha particles was studied. In the field of edge plasma and divertor modeling studies, Lodestar began the development of a theory of generalized ballooning and sheath instabilities in the scrape off layer (SOL) of divertor tokamaks. A detailed summary of the technical progress in these areas during the contract period is included, as well as where references to published work can be found. A separate listing of publications, meeting abstracts, and other presentations is also given at the end of this final report

Human Plasma Metabolomics Study across All Stages of Age-Related Macular Degeneration Identifies Potential Lipid Biomarkers.

Science.gov (United States)

Laíns, Inês; Kelly, Rachel S; Miller, John B; Silva, Rufino; Vavvas, Demetrios G; Kim, Ivana K; Murta, Joaquim N; Lasky-Su, Jessica; Miller, Joan W; Husain, Deeba

2018-02-01

To characterize the plasma metabolomic profile of patients with age-related macular degeneration (AMD) using mass spectrometry (MS). Cross-sectional observational study. We prospectively recruited participants with a diagnosis of AMD and a control group (>50 years of age) without any vitreoretinal disease. All participants underwent color fundus photography, used for AMD diagnosis and staging, according to the Age-Related Eye Disease Study classification scheme. Fasting blood samples were collected and plasma was analyzed by Metabolon, Inc. (Durham, NC), using ultrahigh-performance liquid chromatography (UPLC) and high-resolution MS. Metabolon's hardware and software were used to identify peaks and control quality. Principal component analysis and multivariate regression were performed to assess differences in the metabolomic profiles of AMD patients versus controls, while controlling for potential confounders. For biological interpretation, pathway enrichment analysis of significant metabolites was performed using MetaboAnalyst. The primary outcome measures were levels of plasma metabolites in participants with AMD compared with controls and among different AMD severity stages. We included 90 participants with AMD (30 with early AMD, 30 with intermediate AMD, and 30 with late AMD) and 30 controls. Using UPLC and MS, 878 biochemicals were identified. Multivariate logistic regression identified 87 metabolites with levels that differed significantly between AMD patients and controls. Most of these metabolites (82.8%; n = 72), including the most significant metabolites, belonged to the lipid pathways. Analysis of variance revealed that of the 87 metabolites, 48 (55.2%) also were significantly different across the different stages of AMD. A significant enrichment of the glycerophospholipids pathway was identified (P = 4.7 × 10 -9 ) among these metabolites. Participants with AMD have altered plasma metabolomic profiles compared with controls. Our data suggest

Magnum-PSI: A new plasma-wall interaction experiment

International Nuclear Information System (INIS)

Koppers, W.; Eck, H. van; Scholten, J.

2006-01-01

The FOM-Institute for Plasma Physics Rijnhuizen is preparing the construction of Magnum-PSI, a magnetized (3 T), steady-state, large area (diameter 10 cm), high-flux plasma (10 24 ions m -2 s -1 generator. The aim of the linear plasma device Magnum-PSI is to provide a controlled, highly accessible laboratory experiment in which the interaction of a magnetized plasma with different surfaces can be studied in detail. Plasma parameters can be varied over a wide range, in particular covering the high-density, low-temperature conditions expected for the detached divertor plasma of ITER. The target set-up will be extremely flexible allowing the investigation of different materials under a large variety of conditions (temperatures, inclination, biasing, coatings, etc.). A range of target materials will be used, including carbon, tungsten and other metals, and mixed materials. Because of the large plasma beam of 10 cm diameter and spacious vacuum tank, even the test of whole plasma-facing component mock-ups will be possible. Dedicated diagnostics will be installed to allow for detailed studies of the fundamental physics and chemistry of plasma-surface interaction, such as erosion and deposition, hydrogen recycling, retention and removal, dust and layer formation, plasma sheath physics and heat loads (steady-state or transient). Magnum-PSI will be a unique experiment to address the ITER divertor physics which will essentially differ from present day Tokamak and/or linear plasma generator physics. In this contribution, we will present the pre-design of the Magnum-PSI experiment. We will discuss the requirements on the vacuum system, 3T superconducting magnet, plasma source, target manipulator and additional plasma heating. In addition, we will briefly introduce the plasma and surface diagnostics that will be used in the Magnum-PSI experiment. (author)

Cold atmospheric-pressure plasma and bacteria: understanding the mode of action using vibrational microspectroscopy

International Nuclear Information System (INIS)

Kartaschew, Konstantin; Mischo, Meike; Bründermann, Erik; Havenith, Martina; Baldus, Sabrina; Awakowicz, Peter

2016-01-01

Cold atmospheric-pressure plasma show promising antimicrobial effects, however the detailed biochemical mechanism of the bacterial inactivation is still unknown. We investigated, for the first time, plasma-treated Gram-positive Bacillus subtilis and Gram-negative Escherichia coli bacteria with Raman and infrared microspectroscopy. A dielectric barrier discharge was used as a plasma source. We were able to detect several plasma-induced chemical modifications, which suggest a pronounced oxidative effect on the cell envelope, cellular proteins and nucleotides as well as a generation of organic nitrates in the treated bacteria. Vibrational microspectroscopy is used as a comprehensive and a powerful tool for the analysis of plasma interactions with whole organisms such as bacteria. Analysis of reaction kinetics of chemical modifications allow a time-dependent insight into the plasma-mediated impact. Investigating possible synergistic effects between the plasma-produced components, our observations strongly indicate that the detected plasma-mediated chemical alterations can be mainly explained by the particle effect of the generated reactive species. By changing the polarity of the applied voltage pulse, and hence the propagation mechanisms of streamers, no significant effect on the spectral results could be detected. This method allows the analysis of the individual impact of each plasma constituent for particular chemical modifications. Our approach shows great potential to contribute to a better understanding of plasma-cell interactions. (paper)

Dynamic plasma screening effects on semiclassical inelastic electron endash ion collisions in dense plasmas

International Nuclear Information System (INIS)

Jung, Y.

1997-01-01

In dense plasmas, dynamic plasma screening effects are investigated on 1s→2p dipole transition probabilities for electron-impact excitation of hydrogenic ions. The electron endash ion interaction potential is considered by introduction of the plasma dielectric function. A semiclassical straight-line trajectory method is applied to the path of the projectile electron in order to visualize the semiclassical transition probability as a function of the impact parameter, projectile energy, and plasma parameters. The transition probability including the dynamic plasma screening effect is always greater than that including the static plasma screening effect. When the projectile velocity is smaller than the electron thermal velocity, the dynamic polarization screening effect becomes the static plasma screening effect. When the projectile velocity is greater than the electron thermal velocity, then the interaction potential is almost unshielded. The difference between the dynamic and static plasma screening effects is more significant for low-energy projectiles. It is also found that the static plasma screening formula obtained by the Debye endash Hueckel model overestimates the plasma screening effects on the atomic excitation processes in dense plasmas. copyright 1997 American Institute of Physics

The viscous dynamics of a rotating plasma

International Nuclear Information System (INIS)

James, B.W.; Simpson, S.W.

1978-01-01

The rotational velocity of a high-density, partially-ionized neon plasma has been calculated as a function of time using a dynamical model in which J x B and viscous forces act on the plasma. The calculation of appropriate transport coefficients is discussed in detail. The model is used to predict measured voltages in a plasma centrifuge experiment. Observations of neon isotope separation in this experiment have been reported in a previous paper (James and Simpson 1976). (author)

LDA measurements under plasma conditions

International Nuclear Information System (INIS)

Lesinski, J.; Mizera-Lesinska, B.; Fanton, J.C.; Boulos, M.I.

1979-01-01

A study was made of the application of Laser Doppler Anemometry (LDA) for the measurement of the fluid and particle velocities under plasma conditions. The flow configuration, is that of a dc plasma jet called the principal jet, in which an alumina powder of a mean particle diameter of 115 μm and a standard deviation of 11.3 μm was injected using a secondary jet. The plasma jet immerged from a 7.1 mm ID nozzle while that of the secondary jet was 2 nm in diameter. The secondary jet was introduced at the nozzle level of the plasma jet directed 90 0 to its axis. Details of the nozzle and the gas flow system are shown in Figure 2

THERMODYNAMIC DEPRESSION OF IONIZATION POTENTIALS IN NONIDEAL PLASMAS: GENERALIZED SELF-CONSISTENCY CRITERION AND A BACKWARD SCHEME FOR DERIVING THE EXCESS FREE ENERGY

International Nuclear Information System (INIS)

Zaghloul, Mofreh R.

2009-01-01

Accurate and consistent prediction of thermodynamic properties is of great importance in high-energy density physics and in modeling stellar atmospheres and interiors as well. Modern descriptions of thermodynamic properties of such nonideal plasma systems are sophisticated and/or full of pitfalls that make it difficult, if not impossible, to reproduce. The use of the Saha equation modified at high densities by incorporating simple expressions for depression of ionization potentials is very convenient in that context. However, as it is commonly known, the incorporation of ad hoc or empirical expressions for the depression of ionization potentials in the Saha equation leads to thermodynamic inconsistencies. The problem of thermodynamic consistency of ionization potentials depression in nonideal plasmas is investigated and a criterion is derived, which shows immediately, whether a particular model for the ionization potential depression is self-consistent, that is, whether it can be directly related to a modification of the free-energy function, or not. A backward scheme is introduced which can be utilized to derive nonideality corrections to the free-energy function from formulas of ionization potentials depression derived from plasma microfields or in ad hoc or empirical fashion provided that the aforementioned self-consistency criterion is satisfied. The value and usefulness of such a backward method are pointed out and discussed. The above-mentioned criterion is applied to investigate the thermodynamic consistency of some historic models in the literature and an optional routine is introduced to recover their thermodynamic consistencies while maintaining the same functional dependence on the species densities as in the original models. Sample computational problems showing the effect of the proposed modifications on the computed plasma composition are worked out and presented.

Confinement properties of high energy density plasmas in the Wisconsin levitated octupole

International Nuclear Information System (INIS)

Twichell, J.C.

1984-08-01

The confinement of particles and energy is critically dependent on the plasma-wall interaction. Results of a study detailing this interaction are presented. High power ICRF heated and gun afterglow plasmas were studied to detail the mechanisms determining particle and energy confinement. An extensive zero-D simulation code is used to assist in interpreting the experimental data. Physically reasonable models for plasma surface interactions, time dependent coronal treatment of impurities and multiple region treatment of neutrals are used in modeling the plasma. Extensive diagnostic data are used to verify the model. Non-heated plasmas decay from 28 to 3 eV allowing clear identification of wall impact energy thresholds for desorption and particle reflection. The charge state distribution of impurities verifies the reflux to plasma diffusion rate ratio. Close agreement between the simulation and experimental data is found

Research briefing on contemporary problems in plasma science

International Nuclear Information System (INIS)

1991-01-01

An overview is presented of the broad perspective of all plasma science. Detailed discussions are given of scientific opportunities in various subdisciplines of plasma science. The first subdiscipline to be discussed is the area where the contemporary applications of plasma science are the most widespread, low temperature plasma science. Opportunities for new research and technology development that have emerged as byproducts of research in magnetic and inertial fusion are then highlighted. Then follows a discussion of new opportunities in ultrafast plasma science opened up by recent developments in laser and particle beam technology. Next, research that uses smaller scale facilities is discussed, first discussing non-neutral plasmas, and then the area of basic plasma experiments. Discussions of analytic theory and computational plasma physics and of space and astrophysical plasma physics are then presented

Monte Carlo simulations of ionization potential depression in dense plasmas

Czech Academy of Sciences Publication Activity Database

Stránský, Michal

2016-01-01

Roč. 23, č. 1 (2016), 1-5, č. článku 012708. ISSN 1070-664X R&D Projects: GA MŠk LG15013 Institutional support: RVO:68378271 Keywords : Monte Carlo methods * aluminium * plasma temperature * computer modeling * ionization Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.115, year: 2016

Optical orientation of atoms in plasma

Energy Technology Data Exchange (ETDEWEB)

Zhitnikov, R

1979-06-01

The results are summed up of experimental work on the optical orientation of atoms in a plasma conducted by the Atomic Radiospectroscopy Group at the AN SSSR Physical Technology Institute. The main methods of forming and observing the optical orientation of atoms in a helium plasma and an alkali metal plasma are described in detail. A quantum mechanical explanation is given of all observed phenomena. The most significant results include the discovery of the effect of the optical orientation of atoms in a plasma on the plasma optical and electrical properties, such as electric conductivity, emitted light intensity, ionization degree, and electron density. The phenomenon applies generally and is inherent to plasmas of different chemical compositions, at the optical orientation of atoms of different elements. The methods are indicated of the practical application of the phenomenon in designing principally new precision quantum magnetometers.

Preliminary Study of Plasma Exosomal Tau as a Potential Biomarker for Chronic Traumatic Encephalopathy.

Science.gov (United States)

Stern, Robert A; Tripodis, Yorghos; Baugh, Christine M; Fritts, Nathan G; Martin, Brett M; Chaisson, Christine; Cantu, Robert C; Joyce, James A; Shah, Sahil; Ikezu, Tsuneya; Zhang, Jing; Gercel-Taylor, Cicek; Taylor, Douglas D

2016-01-01

Chronic traumatic encephalopathy (CTE) is a tauopathy associated with prior exposure to repetitive head impacts, such as those incurred through American football and other collision sports. Diagnosis is made through neuropathological examination. Many of the clinical features of CTE are common in the general population, with and without a history of head impact exposure, making clinical diagnosis difficult. As is now common in the diagnosis of other neurodegenerative disorders, such as Alzheimer's disease, there is a need for methods to diagnose CTE during life through objective biomarkers. The aim of this study was to examine tau-positive exosomes in plasma as a potential CTE biomarker. Subjects were 78 former National Football League (NFL) players and 16 controls. Extracellular vesicles were isolated from plasma. Fluorescent nanoparticle tracking analysis was used to determine the number of vesicles staining positive for tau. The NFL group had higher exosomal tau than the control group (p <  0.0001). Exosomal tau discriminated between the groups, with 82% sensitivity, 100% specificity, 100% positive predictive value, and 53% negative predictive value. Within the NFL group, higher exosomal tau was associated with worse performance on tests of memory (p = 0.0126) and psychomotor speed (p = 0.0093). These preliminary findings suggest that exosomal tau in plasma may be an accurate, noninvasive CTE biomarker.

Tuning Surface Chemistry of Polyetheretherketone by Gold Coating and Plasma Treatment

Science.gov (United States)

Novotná, Zdeňka; Rimpelová, Silvie; Juřík, Petr; Veselý, Martin; Kolská, Zdeňka; Hubáček, Tomáš; Borovec, Jakub; Švorčík, Václav

2017-06-01

Polyetheretherketone (PEEK) has good chemical and biomechanical properties that are excellent for biomedical applications. However, PEEK exhibits hydrophobic and other surface characteristics which cause limited cell adhesion. We have investigated the potential of Ar plasma treatment for the formation of a nanostructured PEEK surface in order to enhance cell adhesion. The specific aim of this study was to reveal the effect of the interface of plasma-treated and gold-coated PEEK matrices on adhesion and spreading of mouse embryonic fibroblasts. The surface characteristics (polarity, surface chemistry, and structure) before and after treatment were evaluated by various experimental techniques (gravimetry, goniometry, X-ray photoelectron spectroscopy (XPS), and electrokinetic analysis). Further, atomic force microscopy (AFM) was employed to examine PEEK surface morphology and roughness. The biological response of cells towards nanostructured PEEK was evaluated in terms of cell adhesion, spreading, and proliferation. Detailed cell morphology was evaluated by scanning electron microscopy (SEM). Compared to plasma treatment, gold coating improved PEEK wettability. The XPS method showed a decrease in the carbon concentration with increasing time of plasma treatment. Cell adhesion determined on the interface between plasma-treated and gold-coated PEEK matrices was directly proportional to the thickness of a gold layer on a sample. Our results suggest that plasma treatment in a combination with gold coating could be used in biomedical applications requiring enhanced cell adhesion.

The Influence of Dietary Habits and Meat Consumption on Plasma 3‐Methylhistidine—A Potential Marker for Muscle Protein Turnover

Science.gov (United States)

Kochlik, Bastian; Gerbracht, Christiana; Grune, Tilman

2018-01-01

Scope 3‐Methylhistidine (3‐MH) as a potential biomarker for muscle protein turnover is influenced by meat intake but data on the impact of meat on plasma 3‐MH are scarce. We determined the association of plasma 3‐MH, 1‐methylhistidine (1‐MH), and creatinine with dietary habits and assessed the impact of a single white meat intervention during a meat‐free period. Methods and results Plasma 3‐MH, 1‐MH, and creatinine concentrations of healthy young omnivores (n = 19) and vegetarians (n = 16) were analyzed together with data on anthropometry, body composition, grip strength, and nutrition. After baseline measurements omnivores adhered to a meat‐free diet for 6 days and received a defined administration of chicken breast on day four. At baseline, omnivores had higher plasma 3‐MH and 1‐MH concentrations than vegetarians. White meat administration led to a slight increase in plasma 3‐MH in omnivores. The elevated 3‐MH concentrations significantly declined within 24 h after white meat intake. Conclusion 1‐MH concentrations in plasma seem to be suitable to display (white) meat consumption and its influence on 3‐MH plasma concentration. 3‐MH in plasma may be used as a biomarker for muscle protein turnover if subjects have not consumed meat in the previous 24 h. PMID:29573154

Plasma fluctuation measurements in tokamaks using beam-plasma interactions

International Nuclear Information System (INIS)

Fonck, R.J.; Duperrex, P.A.; Paul, S.F.

1990-01-01

High-frequency observations of light emitted from the interactions between plasma ions and injected neutral beam atoms allow the measurement of moderate-wavelength fluctuations in plasma and impurity ion densities. To detect turbulence in the local plasma ion density, the collisionally excited fluorescence from a neutral beam is measured either separately at several spatial points or with a multichannel imaging detector. Similarly, the role of impurity ion density fluctuations is measured using charge exchange recombination excited transitions emitted by the ion species of interest. This technique can access the relatively unexplored region of long-wavelength plasma turbulence with k perpendicular ρ i much-lt 1, and hence complements measurements from scattering experiments. Optimization of neutral beam geometry and optical sightlines can result in very good localization and resolution (Δx≤1 cm) in the hot plasma core region. The detectable fluctuation level is determined by photon statistics, atomic excitation processes, and beam stability, but can be as low as 0.2% in a 100 kHz bandwidth over the 0--1 MHz frequency range. The choices of beam species (e.g., H 0 , He 0 , etc.), observed transition (e.g., H α , L α , He I singlet or triplet transitions, C VI Δn=1, etc.) are dictated by experiment-specific factors such as optical access, flexibility of beam operation, plasma conditions, and detailed experimental goals. Initial tests on the PBX-M tokamak using the H α emissions from a heating neutral beam show low-frequency turbulence in the edge plasma region

How does the potential get from A to B in a plasma?

International Nuclear Information System (INIS)

Hershkowitz, N.

1993-01-01

This question--and the search for its many answers--have been a recurring theme in my work. It has important consequences for basic plasmas, plasmas in the earth's magnetosphere, plasmas in tandem mirrors and in tokamaks and plasmas used in plasma processing. In solving the problem, nature may have created auroras. The answer often depends on whether the reference frame is moving or stationary and on the dimensionality of the problem. Until recently, the answer made it impossible to carry out many rf experiments in tokamaks but provided a key ingredient to semiconductor etching and provided some axial plugging in tandem mirrors. The properties of the solutions and a simple measurement technique will be discussed

X-ray lasing in colliding plasmas

International Nuclear Information System (INIS)

Clark, R.W.; Davis, J.; Velikovich, A.L.; Whitney, K.G.

1997-01-01

Conditions favorable for the achievement of population inversion and large gains in short-pulse laser-heated selenium have been reported on previously [K. G. Whitney et al., Phys. Rev. E 50, 468 (1994)]. However, the required density profiles to minimize refraction and amplification losses can be difficult to achieve in conventional laser heated blowoff plasmas. The feasibility of accelerating plasma with a laser, and letting it collide with a solid density wall plasma has been explored. The density of the resulting shocked plasma can be controlled and refraction can be reduced in this design. A radiation hydrodynamics model is used to simulate the collision of the laser produced selenium plasma with the wall plasma. The heating of the stagnated plasma with a short-pulse laser is then simulated, providing the hydrodynamic response of the selenium plasma and detailed configuration nonequilibrium atomic populations. From the results of these calculations, it appears feasible to create an x-ray lasing selenium plasma with gains in the J=0 endash 1 line at 182 Angstrom in excess of 100cm -1 . copyright 1997 American Institute of Physics

Plasmas for medicine

Science.gov (United States)

von Woedtke, Th.; Reuter, S.; Masur, K.; Weltmann, K.-D.

2013-09-01

economic potential. This ambivalent situation fundamentally requires a responsible use of plasma sources, which are specifically designated for biomedical applications. To enable physicians as well as life scientists to decide whether a given plasma source is really suitable for medical applications or biological experiments, a meaningful and mandatory spectrum of indicators has to be compiled to allow for a basic estimation of the potential of this plasma source.

Simulation of the electric potential and plasma generation coupling in magnetron sputtering discharges

Science.gov (United States)

Trieschmann, Jan; Krueger, Dennis; Schmidt, Frederik; Brinkmann, Ralf Peter; Mussenbrock, Thomas

2016-09-01

Magnetron sputtering typically operated at low pressures below 1 Pa is a widely applied deposition technique. For both, high power impulse magnetron sputtering (HiPIMS) as well as direct current magnetron sputtering (dcMS) the phenomenon of rotating ionization zones (also referred to as spokes) has been observed. A distinct spatial profile of the electric potential has been associated with the latter, giving rise to low, mid, and high energy groups of ions observed at the substrate. The adherent question of which mechanism drives this process is still not fully understood. This query is approached using Monte Carlo simulations of the heavy particle (i.e., ions and neutrals) transport consistently coupled to a pre-specified electron density profile via the intrinsic electric field. The coupling between the plasma generation and the electric potential, which establishes correspondingly, is investigated. While the system is observed to strive towards quasi-neutrality, distinct mechanisms governing the shape of the electric potential profile are identified. This work is supported by the German Research Foundation (DFG) in the frame of the transregional collaborative research centre TRR 87.

Thermoelectric-Driven Liquid-Metal Plasma-Facing Structures (TELS) Final Report

Energy Technology Data Exchange (ETDEWEB)

Ruzic, David [Univ. of Illinois, Urbana-Champaign, IL (United States)

2016-12-17

The Thermoelectric-Driven Liquid-Metal Plasma-Facing Structures (TELS) project was able to establish the experimental conditions necessary for flowing liquid metal surfaces in order to be utilized as surfaces facing fusion relevant energetic plasma flux. The work has also addressed additional developments along with progressing along the timeline detailed in the proposal. A no-cost extension was requested to conduct other relevant experiment- specifically regarding the characterization droplet ejection during energetic plasma flux impact. A specially designed trench module, which could accommodate trenches with different aspect ratios was fabricated and installed in the TELS setup and plasma gun experiments were performed. Droplet ejection was characterized using high speed image acquisition and also surface mounted probes were used to characterize the plasma. The Gantt chart below had been provided with the original proposal, indicating the tasks to be performed in the third year of funding. These tasks are listed above in the progress report outline, and their progress status is detailed below.

Elements of plasma technology

CERN Document Server

Wong, Chiow San

2016-01-01

This book presents some fundamental aspects of plasma technology that are important for beginners interested to start research in the area of plasma technology . These include the properties of plasma, methods of plasma generation and basic plasma diagnostic techniques. It also discusses several low cost plasma devices, including pulsed plasma sources such as plasma focus, pulsed capillary discharge, vacuum spark and exploding wire; as well as low temperature plasmas such as glow discharge and dielectric barrier discharge which the authors believe may have potential applications in industry. The treatments are experimental rather than theoretical, although some theoretical background is provided where appropriate. The principles of operation of these devices are also reviewed and discussed.

Relativistic plasma dispersion functions

International Nuclear Information System (INIS)

Robinson, P.A.

1986-01-01

The known properties of plasma dispersion functions (PDF's) for waves in weakly relativistic, magnetized, thermal plasmas are reviewed and a large number of new results are presented. The PDF's required for the description of waves with small wave number perpendicular to the magnetic field (Dnestrovskii and Shkarofsky functions) are considered in detail; these functions also arise in certain quantum electrodynamical calculations involving strongly magnetized plasmas. Series, asymptotic series, recursion relations, integral forms, derivatives, differential equations, and approximations for these functions are discussed as are their analytic properties and connections with standard transcendental functions. In addition a more general class of PDF's relevant to waves of arbitrary perpendicular wave number is introduced and a range of properties of these functions are derived

Effects of dust-charge fluctuations on the potential of an array of projectiles in a partially ionized dusty plasma

International Nuclear Information System (INIS)

Ali, S.; Nasim, M.H.; Murtaza, G.

2003-01-01

The expressions for the Debye and the wake potential are derived by incorporating dust-charge fluctuations of a single projectile, as well as of an array of dust grain projectiles, propagating through a partially ionized dusty plasma with a constant velocity. Numerically, the effects of the dust-charge fluctuations and the dust-neutral collisions on the electrostatic potential for a single, three, six and ten projectiles are examined. The dust-charge relaxation rate modifies the shape of the Debye as well as the wake potential. For smaller values of the relaxation rates a potential well is formed instead of Debye potential

Complete plasma dropouts at Vela satellites during thinning of the plasma sheet

International Nuclear Information System (INIS)

Lui, A.T.Y.; Hones, E.W. Jr.; Venkatesan, D.; Akasofu, S.; Bame, S.J.

1975-01-01

Five satellite years of Vela data are examined for plasma sheet thinnings. Complete proton disappearances (plasma dropouts) are the main subject here. During such times, the Vela satellite is temporarily in the high-latitude tail lobe. The distribution of such plasma dropouts within the magnetotail suggests that the semithickness of the plasma sheet near midnight seldom reaches less than 1 R/sub E/ during substorms and that the dawn and dusk portions of the plasma sheet remain thicker than the midnight portion. But it is also shown that the plasma sheet occasionally becomes very thin near the dusk magnetopause. No such severe thinnings of the plasma sheet are found near the dawn magnetopause. Plasma dropouts can occur regardless of the sign of the Z component of the IMF, but their frequency of occurrence seems to be greater when the Z component is negative.Three plasma dropouts which occurred in the midnight sector at unusually large distances from the estimated position of the neutral sheet were observed during geomagnetic storms. It is likely that the midnight sector of the plasma sheet can become very thick (approx.18 R/sub E/) at certain times during the main phase of storms. Detailed measurements in the plasma sheet were obtained near the beginning of a geomagnetic storm whose sc triggered a substorm. A compression of the plasma sheet at X/sub SM/approx. =-15 R/sub E/ occurred about 10 min after the sc onset at the earth and about 5 min after the start of plasma sheet thinning associated with the sc-related substorm. If compression-thinning of the plasma sheet initiated this substorm, the triggering action must have occurred earthward of X/sub SM/approx. =-15 R/sub E/

Towards Plasma-Based Water Purification: Challenges and Prospects for the Future

Science.gov (United States)

Foster, John

2016-10-01

Freshwater scarcity derived from climate change, pollution, and over-development has led to serious consideration for water reuse. Advanced water treatment technologies will be required to process wastewater slated for reuse. One new and emerging technology that could potentially address the removal micropollutants in both drinking water as well as wastewater slated for reuse is plasma-based water purification. Plasma in contact with liquid water generates reactive species that attack and ultimately mineralize organic contaminants in solution. This interaction takes place in a boundary layer centered at the plasma-liquid interface. An understanding of the physical processes taking place at this interface, though poorly understood, is key to the optimization of plasma water purifiers. High electric field conditions, large density gradients, plasma-driven chemistries, and fluid dynamic effects prevail in this multiphase region. The region is also the source function for longer-lived reactive species that ultimately treat the water. Here, we review the need for advanced water treatment methods and in the process, make the case for plasma-based methods. Additionally, we survey the basic methods of interacting plasma with liquid water (including a discussion of breakdown processes in water), the current state of understanding of the physical processes taking place at the plasma-liquid interface, and the role that these processes play in water purification. The development of diagnostics usable in this multiphase environment along modeling efforts aimed at elucidating physical processes taking place at the interface are also detailed. Key experiments that demonstrate the capability of plasma-based water treatment are also reviewed. The technical challenges to the implementation of plasma-based water reactors are also discussed. NSF CBET 1336375 and DOE DE-SC0001939.

A Proton-Driven Plasma Wakefield Acceleration experiment at CERN

CERN Multimedia

The AWAKE Collaboration has been formed in order to demonstrate protondriven plasma wakefield acceleration for the first time. This technology could lead to future colliders of high energy but of a much reduced length compared to proposed linear accelerators. The SPS proton beam in the CNGS facility will be injected into a 10m plasma cell where the long proton bunches will be modulated into significantly shorter micro-bunches. These micro-bunches will then initiate a strong wakefield in the plasma with peak fields above 1 GV/m that will be harnessed to accelerate a bunch of electrons from about 20MeV to the GeV scale within a few meters. The experimental program is based on detailed numerical simulations of beam and plasma interactions. The main accelerator components, the experimental area and infrastructure required as well as the plasma cell and the diagnostic equipment are discussed in detail. First protons to the experiment are expected at the end of 2016 and this will be followed by an initial 3–4 yea...

Collective radio-emission from plasmas

International Nuclear Information System (INIS)

Papadopoulos, K.; Freund, H.P.

1979-01-01

Collective radiation processes operating in laboratory and space plasmas are reviewed with an emphasis towards astrophysical applications. Particular stress is placed on the physics involved in the various processes rather than in the detailed derivation of the formulas. Radiation processes from stable non-thermal, weakly turbulent and strongly turbulent magnetized and unmagnetized plasmas are discussed. The general theoretical ideas involved in amplification processes such as stimulated scattering are presented along with their application to free electron and plasma lasers. Direct radio-emission of electromagnetic waves by linear instabilities driven by beams or velocity anisotropies are shown to be of relevance in space applications. Finally, as an example of the computational state of the art pertaining to plasma radiation, a study of the type III solar radio bursts is presented. (orig.)

Optical orientation of atoms in plasma

International Nuclear Information System (INIS)

Zhitnikov, R.

1979-01-01

The results are summed up of experimental work on the optical orientation of atoms in a plasma conducted by the Atomic Radiospectroscopy Group at the AN SSSR Physical Technology Institute. The main methods of forming and observing the optical orientation of atoms in a helium plasma and an alkali metal plasma are described in detail. A quantum mechanical explanation is given of all observed phenomena. The most significant results include the discovery of the effect of the optical orientation of atoms in a plasma on the plasma optical and electrical properties, such as electric conductivity, emitted light intensity, ionization degree, and electron density. The phenomenon applies generally and is inherent to plasmas of different chemical compositions, at the optical orientation of atoms of different elements. The methods are indicated of the practical application of the phenomenon in designing principally new precision quantum magnetometers. (J.U.)

Pharmaceutical drug detailing in primary care: extent and methods

DEFF Research Database (Denmark)

Schramm, Jesper

The dimension and methods of pharmaceutical marketing towards 47 danish general practitioners is described. Conclusions: Pharmaceutical drug detailing possesses a huge potential to influence the prescription pattern of GP's.......The dimension and methods of pharmaceutical marketing towards 47 danish general practitioners is described. Conclusions: Pharmaceutical drug detailing possesses a huge potential to influence the prescription pattern of GP's....

Cutoff effects of electron velocity distribution to the properties of plasma parameters near the plasma-sheath boundary

International Nuclear Information System (INIS)

Jelic, N.

2011-01-01

The plasma properties under high thermodynamic non-equilibrium condition, established due to the presence of electrically biased electrode, are investigated. Assumption of electron cut-off velocity distribution function (VDF), as done by Andrews and Varey in their investigations of the sheath region [J. Phys. A 3, 413 (1970)], has been extended here to both plasma and sheath regions. Analytic expressions for the moments of electron VDF, as well as for the electron screening temperature function dependence on the plasma-sheath local potential are derived. In deriving the ion velocity distribution the ''standard'' assumption of strict plasma quasineutrality, or equivalently vanishing of the plasma Debye length, is employed, whereas the ions are assumed to be generated at rest over the plasma region. However, unlike the standard approach of solving the plasma equation, where pure Boltzmann electron density profile is used, here we employ modified Boltzmann's electron density profile, due to cutoff effect of the electron velocity distribution. It is shown that under these conditions the quasineutrality equation solution is characterised by the electric field singularity for any negative value of the electrode bias potential as measured with respect to the plasma potential. The point of singularity i.e., the plasma length and its dependence on the electrode bias and sheath potential is established for the particular case of ionization profile mechanism proportional to the local electron density. Relevant parameters for the kinetic Bohm criterion are explicitly calculated for both ions and electrons, for arbitrary electrode bias.

Electron acceleration using laser produced plasmas

CERN Multimedia

CERN. Geneva; Landua, Rolf

2005-01-01

Low density plasmas have long been of interest as a potential medium for particle acceleration since relativistic plasma waves are capable of supporting electric fields greater than 100 GeV/m. The physics of particle acceleration using plasmas will be reviewed, and new results will be discussed which have demonstrated that relatively narrow energy spread (<3%) beams having energies greater than 100 MeV can be produced from femtosecond laser plasma interactions. Future experiments and potential applications will also be discussed.

Internal oscillating current-sustained RF plasmas: Parameters, stability, and potential for surface engineering

DEFF Research Database (Denmark)

Ostrikov, K.; Tsakadze, E.L.; Tsakadze, Z.L.

2005-01-01

. Moreover, under certain conditions, the plasma becomes unstable due to spontaneous transitions between low-density (electrostatic, E) and high-density (electromagnetic, H) operating modes. Excellent uniformity of high-density plasmas makes the plasma reactor promising for various plasma processing...... applications and surface engineering. (c) 2005 Elsevier B.V. All rights reserved....

Design and construction of Keda Space Plasma Experiment (KSPEX) for the investigation of the boundary layer processes of ionospheric depletions.

Science.gov (United States)

Liu, Yu; Zhang, Zhongkai; Lei, Jiuhou; Cao, Jinxiang; Yu, Pengcheng; Zhang, Xiao; Xu, Liang; Zhao, Yaodong

2016-09-01

In this work, the design and construction of the Keda Space Plasma EXperiment (KSPEX), which aims to study the boundary layer processes of ionospheric depletions, are described in detail. The device is composed of three stainless-steel sections: two source chambers at both ends and an experimental chamber in the center. KSPEX is a steady state experimental device, in which hot filament arrays are used to produce plasmas in the two sources. A Macor-mesh design is adopted to adjust the plasma density and potential difference between the two plasmas, which creates a boundary layer with a controllable electron density gradient and inhomogeneous radial electric field. In addition, attachment chemicals can be released into the plasmas through a tailor-made needle valve which leads to the generation of negative ions plasmas. Ionospheric depletions can be modeled and simulated using KSPEX, and many micro-physical processes of the formation and evolution of an ionospheric depletion can be experimentally studied.

Modeling of EUV emission from xenon and tin plasma sources for nanolithography

Energy Technology Data Exchange (ETDEWEB)

Poirier, M. [Service Photons, Atomes, et Molecules, CEA Saclay, bat. 522, F91191 Gif/Yvette Cedex (France)]. E-mail: michel.poirier@cea.fr; Blenski, T. [Service Photons, Atomes, et Molecules, CEA Saclay, bat. 522, F91191 Gif/Yvette Cedex (France); Gaufridy de Dortan, F. de [Service Photons, Atomes, et Molecules, CEA Saclay, bat. 522, F91191 Gif/Yvette Cedex (France); Gilleron, F. [CEA-DAM, F91680 Bruyeres-le-Chatel (France)

2006-05-15

Over the last decade there has been a major effort devoted to the development of efficient extreme UV sources designed for nanolithography, operating in the 13.5-nm range. Possible sources include laser-produced plasmas and discharge-produced plasmas. This paper, devoted to the modeling of such emission, emphasizes the atomic physics effects and particularly the effects of configuration interaction. Two types of theoretical approaches are presented, one involving the detailed computation with the parametric potential code HULLAC, the other based on the superconfiguration code SCO. Computations of emission spectra in xenon and tin are presented. The possible influence of non-local thermodynamic equilibrium (NLTE) effects is investigated using populations given by the simple collisional-radiative formulas from Colombant and Tonon. Convergence to LTE is analyzed in the tin case.

A Method for Measuring Fast Time Evolutions of the Plasma Potential by Means of a Simple Emissive Probe

DEFF Research Database (Denmark)

Iizuka, S.; Michelsen, Poul; Juul Rasmussen, Jens

1981-01-01

potential is measured across a high resistance. During each sweep of the probe voltage, the changing of the sign of the probe current, which is sampled at a specific time, gives rise to a negative pulse, driving the pen-lift of an X-Y recorder. Since the real floating potential is measured where the probe......A method is presented for obtaining the temporal evolution of the plasma potential, which is assumed to be given by the floating potential of a simple emissive probe. The construction of the probe is also described. The method avoids the slow time response of the usual technique where the floating...

Molecular dynamics simulations of interactions between energetic dust and plasma-facing materials

International Nuclear Information System (INIS)

Niu, Guo-jian; Li, Xiao-chun; Xu, Qian; Yang, Zhong-shi; Luo, Guang-nan

2015-01-01

The interactions between dust and plasma-facing material (PFM) relate to the lifetime of PFM and impurity production. Series results have been obtained theoretically and experimentally but more detailed studies are needed. In present research, we investigate the evolution of kinetic, potential and total energy of plasma-facing material (PFM) in order to understand the dust/PFM interaction process. Three typical impacting energy are selected, i.e., 1, 10 and 100 keV/dust for low-, high- and hyper-energy impacting cases. For low impacting energy, dust particles stick on PFM surface without damaging it. Two typical time points exist and the temperature of PFM grows all the time but PFM structure experience a modifying process. Under high energy case, three typical points appear. The temperature curve fluctuates in the whole interaction process which indicates there are dust/PFM and kinetic/potential energy exchanges. In the hyper-energy case in present simulation, the violence dust/PFM interactions cause sputtering and crater investigating on energy evolution curves. We further propose the statistics of energy distribution. Results show that about half of impacting energy consumes on heating plasma-facing material meanwhile the other half on PFM structure deformation. Only a small proportion becomes kinetic energy of interstitial or sputtering atoms.

Molecular dynamics simulations of interactions between energetic dust and plasma-facing materials

Energy Technology Data Exchange (ETDEWEB)

Niu, Guo-jian, E-mail: niugj@ipp.ac.cn [Institute of Plasma Physics Chinese Academy of Sciences, Hefei (China); Li, Xiao-chun; Xu, Qian; Yang, Zhong-shi [Hefei Center Physical Science and Technology, Hefei (China); Luo, Guang-nan [Institute of Plasma Physics Chinese Academy of Sciences, Hefei (China); Hefei Center Physical Science and Technology, Hefei (China); Hefei Science Center of CAS, Hefei (China)

2015-11-15

The interactions between dust and plasma-facing material (PFM) relate to the lifetime of PFM and impurity production. Series results have been obtained theoretically and experimentally but more detailed studies are needed. In present research, we investigate the evolution of kinetic, potential and total energy of plasma-facing material (PFM) in order to understand the dust/PFM interaction process. Three typical impacting energy are selected, i.e., 1, 10 and 100 keV/dust for low-, high- and hyper-energy impacting cases. For low impacting energy, dust particles stick on PFM surface without damaging it. Two typical time points exist and the temperature of PFM grows all the time but PFM structure experience a modifying process. Under high energy case, three typical points appear. The temperature curve fluctuates in the whole interaction process which indicates there are dust/PFM and kinetic/potential energy exchanges. In the hyper-energy case in present simulation, the violence dust/PFM interactions cause sputtering and crater investigating on energy evolution curves. We further propose the statistics of energy distribution. Results show that about half of impacting energy consumes on heating plasma-facing material meanwhile the other half on PFM structure deformation. Only a small proportion becomes kinetic energy of interstitial or sputtering atoms.

Detailed spectra of high power broadband microwave radiation from interactions of relativistic electron beams with weakly magnetized plasmas

International Nuclear Information System (INIS)

Kato, K.G.; Benford, G.; Tzach, D.

1983-01-01

Prodigious quantities of microwave energy are observed uniformly across a wide frequency band when a relativistic electron beam (REB) penetrates a plasma. Measurement calculations are illustrated. A model of Compton-like boosting of ambient plasma waves by beam electrons, with collateral emission of high frequency photons, qualitatively explain the spectra. A transition in spectral behavior is observed from the weak to strong turbulence theories advocated for Type III solar burst radiation, and further into the regime the authors characterize as super-strong REB-plasma interactions

Viscosity of two-dimensional strongly coupled dusty plasma modified by a perpendicular magnetic field

Science.gov (United States)

Feng, Yan; Lin, Wei; Murillo, M. S.

2017-11-01

Transport properties of two-dimensional (2D) strongly coupled dusty plasmas have been investigated in detail, but never for viscosity with a strong perpendicular magnetic field; here, we examine this scenario using Langevin dynamics simulations of 2D liquids with a binary Yukawa interparticle interaction. The shear viscosity η of 2D liquid dusty plasma is estimated from the simulation data using the Green-Kubo relation, which is the integration of the shear stress autocorrelation function. It is found that, when a perpendicular magnetic field is applied, the shear viscosity of 2D liquid dusty plasma is modified substantially. When the magnetic field is increased, its viscosity increases at low temperatures, while at high temperatures its viscosity diminishes. It is determined that these different variational trends of η arise from the different behaviors of the kinetic and potential parts of the shear stress under external magnetic fields.

Plasma position control in TCABR Tokamak

International Nuclear Information System (INIS)

Galvao, R.M.O.; Kuznetsov, Yu. K.; Nascimento, I.C.; Fonseca, A.M.M.; Silva, R.P. da; Ruchko, L.F.; Tuszel, A.G.; Reis, A.P. dos; Sanada, E.K.

1998-01-01

The plasma control position in the TCABR tokamak is described. The TCA tokamak was transferred from the Centre de Recherches en Physique des Plasmas, Lausanne, to the Institute of Physics of University of Sao Paulo, renamed TCABR (α=0.18 m, R = 0.62 m, B = 1 T,I p = 100 kA). The control system was reconstructed using mainly components obtained from the TCA tokamak. A new method of plasma position determination is used in TCABR to improve its accuracy. A more detailed theoretical analysis of the feed forward and feedback control is performed as compared with. (author)

Detailed investigation of a time-of-flight neutron spectrometer

International Nuclear Information System (INIS)

Elevant, T.; Trostell, B.

1981-02-01

Properties of a neutron spectrometer and telescope, based on double neutron interaction in hydrogen based scintillators and neutron time-of-flight technique, have been investigated in detail. Theoretical scaling of the resolutions with the flight path length and scattering angle have been confirmed by experimental results. Important parameters in connection with calibration of the spectrometer are discussed and calculated relative resolutions of the ion temperature are shown when applied to a fusion deuterium plasma. (Auth.)

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

Science.gov (United States)

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

2018-03-01

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

Investigating plasma-rotation methods for the Space-Plasma Physics Campaign at UCLA's BAPSF.

Science.gov (United States)

Finnegan, S. M.; Koepke, M. E.; Reynolds, E. W.

2006-10-01

In D'Angelo et al., JGR 79, 4747 (1974), rigid-body ExB plasma flow was inferred from parabolic floating-potential profiles produced by a spiral ionizing surface. Here, taking a different approach, we report effects on barium-ion azimuthal-flow profiles using either a non-emissive or emissive spiral end-electrode in the WVU Q-machine. Neither electrode produced a radially-parabolic space-potential profile. The emissive spiral, however, generated controllable, radially-parabolic structure in the floating potential, consistent with a second population of electrons having a radially-parabolic parallel-energy profile. Laser-induced-fluorescence measurements of spatially resolved, azimuthal-velocity distribution functions show that, for a given flow profile, the diamagnetic drift of hot (>>0.2eV) ions overwhelms the ExB-drift contribution. Our experiments constitute a first attempt at producing controllable, rigid-body, ExB plasma flow for future experiments on the LArge-Plasma-Device (LAPD), as part of the Space-Plasma Physics Campaign (at UCLA's BAPSF).

Investigation of Plasmas Having Complex, Dynamic Evolving Morphology

Energy Technology Data Exchange (ETDEWEB)

Bellan, Paul M. [California Inst. of Technology (CalTech), Pasadena, CA (United States)

2017-01-03

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

Investigation of Plasmas Having Complex, Dynamic Evolving Morphology

International Nuclear Information System (INIS)

Bellan, Paul M.

2017-01-01

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

Numerical simulation of SMART-1 Hall-thruster plasma interactions

NARCIS (Netherlands)

Tajmar, Martin; Sedmik, René; Scharlemann, Carsten

2009-01-01

SMART-1 has been the first European mission using a Hall thruster to reach the moon. An onboard plasma diagnostic package allowed a detailed characterization of the thruster exhaust plasma and its interactions with the spacecraft. Analysis of in-flight data revealed, amongst others, an unpredicted

ECR plasma diagnostics with Langmuir probe

International Nuclear Information System (INIS)

Kenez, L.; Biri, S.; Valek, A.

2000-01-01

Complete text of publication follows. An Electron Cyclotron Resonance (ECR) Ion Source is a tool to generate highly charged ions. The ion beam is extracted from the plasma chamber of the ECRIS. Higher charge states and beam intensities are the main objectives of ECR research. The heart of an ion source is the confined plasma which should be well known to reach those objectives. Information about the plasma can be obtained by plasma diagnostics methods. Langmuir probes were successfully used in case of other plasmas, e.g. TOKAMAK. Until last year plasma diagnostics at the ATOMKI ECRIS was performed by X-ray and visible light measurements. While X-ray measurements give global information, the Langmuir probe method can give information on the local plasma parameters. This is an advantage because the local parameters are not known in detail. By Langmuir probe measurements it is possible to get information on plasma density, plasma potential and partly on the electron temperature. From the experimental point of view a Langmuir probe is very simple. However, the precise positioning of the probe in the plasma chamber (HV platform, strong magnetic field, RF waves) is a difficult task. Also the theory of probes is complicated: the ECR plasma is a special one because the confining magnetic field is inhomogeneous, beside hot electrons it contains cold ions with different charge states and it is heated with high frequency EM waves. What can be measured with a probe is a voltage-current (U-I) characteristics. Figure 1 shows a typical U-I curve measured in our lab. As it can be seen in the figure the diagram has three main parts. An ion saturation current region (I.), an electron saturation current region (III.) and a transition region (II.) between them. These measurements were performed using two different power supplies to bias the probe to positive and negative voltage. To perform more precise U-I measurements we need a special power supply which is presently being built in

Detailed spectra of high-power broadband microwave radiation from interactions of relativistic electron beams with weakly magnetized plasmas

International Nuclear Information System (INIS)

Kato, K.G.; Benford, G.; Tzach, D.

1983-01-01

Prodigious quantities of microwave energy distributed uniformly across a wide frequency band are observed when a relativistic electron beam (REB) penetrates a plasma. Typical measured values are 20 MW total for Δνapprox. =40 GHz with preliminary observations of bandwidths as large as 100 GHz. An intense annular pulsed REB (Iapprox. =128 kA; rapprox. =3 cm; Δrapprox. =1 cm; 50 nsec FWHM; γapprox. =3) is sent through an unmagnetized or weakly magnetized plasma column (n/sub plasma/approx.10 13 cm -3 ). Beam-to-plasma densities of 0.01 >ω/sub p/ and weak harmonic structure is wholly unanticipated from Langmuir scattering or soliton collapse models. A model of Compton-like boosting of ambient plasma waves by the beam electrons, with collateral emission of high-frequency photons, qualitatively explains these spectra. Power emerges largely in an angle approx.1/γ, as required by Compton mechanisms. As n/sub b//n/sub p/ falls, ω/sub p/-2ω/sub p/ structure and harmonic power ratios consistent with soliton collapse theories appear. With further reduction of n/sub b//n/sub p/ only the ω/sub p/ line persists

Effects of charge depletion in dusty plasmas

International Nuclear Information System (INIS)

Goertz, Imke; Greiner, Franko; Piel, Alexander

2011-01-01

The charge reduction effect is studied in dense dust clouds. The saturation currents of Langmuir probes are used to derive the density of ions and electrons, which are calibrated with the plasma oscillation method. The plasma potential inside the dust cloud is measured with an emissive probe, which also yields the floating potential in a heated nonemitting mode. The presence of the dust also affects the density and the plasma potential of the ambient plasma. The ion densities inside the dust cloud and in the ambient plasma are found equal, while the electron density is reduced inside the dust cloud. The measured potentials are compared with current models. Inclusion of the bi-Maxwellian distribution of the electrons leads to an improved description in the limit of low dust density. The strong increase of the floating and cloud potential for high dust density, predicted by the constant ion density model, is not confirmed.

Critical ionisation velocity effects in astrophysical plasmas

International Nuclear Information System (INIS)

Raadu, M.A.

1979-08-01

Critical ionisation velocity effects are relevant to astrophysical situations where neutral gas moves through a magnetised plasma. The experimental significance of the critical velocity is well established and the physical basis is now becoming clear. The underlying mechanism depends on the combined effects of electron impact ionisation and electron energisation by collective plasma interactions. For low density plasmas a theory based on a circular process involving electron heating through a modified two stream instability has been developed. Several applications of critical velocity effects to astrophysical plasmas have been discussed in the literature. The importance of the effect in any particular case may be determined from a detailed consideration of energy and momentum balance, using appropriate atomic rate coefficients and taking full account of collective plasma processes. (Auth.)

Plasma physics and instabilities

International Nuclear Information System (INIS)

Lashmore-Davies, C.N.

1981-01-01

These lectures procide an introduction to the theory of plasmas and their instabilities. Starting from the Bogoliubov, Born, Green, Kirkwood, and Yvon (BBGKY) hierarchy of kinetic equations, the additional concept of self-consistent fields leads to the fundamental Vlasov equation and hence to the warm two-fluid model and the one-fluid MHD, or cold, model. The properties of small-amplitude waves in magnetized (and unmagnetized) plasmas, and the instabilities to which they give rise, are described in some detail, and a complete chapter is devoted to Landau damping. The linear theory of plasma instabilities is illustrated by the current-driven electrostatic kind, with descriptions of the Penrose criterion and the energy principle of ideal MHD. There is a brief account of the application of feedback control. The non-linear theory is represented by three examples: quasi-linear velocity-space instabilities, three-wave instabilities, and the stability of an arbitrarily largeamplitude wave in a plasma. (orig.)

[Platelet rich plasma (PRP): potentialities and techniques of extraction].

Science.gov (United States)

Pacifici, L; Casella, F; Maggiore, C

2002-01-01

This paper describes the various techniques of platelet-rich plasma (PRP) extraction codified in recent years and their use potential is evaluated. PRP is one of the techniques with which at the moment it is attempted to modulate and facilitate the cure of a wound. The use of PRP is based on the theoretical premise that by concentrating platelets the effects of the growth factors (PDGF, TGF-beta, IGF-I and -II) so released will be increased. Marx's original technique is described above all. This prescribes the sampling of a unit of blood (450-500 ml) and the use of a cell separator. We then analysed the technique of Marx and Hannon in which the quantity of blood sampled is reduced to 150 ml, and the two simplified techniques of the Sacchi and Bellanda group. Finally, a new PRP extraction technique is described. We conclude that platelet gel allows access to autologous growth factors which by definition are neither toxic nor immunogenic and are capable of accelerating the normal processes of bone regeneration. PRP can thus be considered a useful instrument for increasing the quality and final quantity of regenerated bone in oral and maxillo-facial surgery operations.

Plasma fluctuation measurements in tokamaks using beam-plasma interactions (abstract)

International Nuclear Information System (INIS)

Fonck, R.J.; Duperrex, P.A.; Paul, S.F.

1990-01-01

High-frequency observations of light emitted from the interactions between plasma ions and injected neutral beam atoms allow the measurement of moderate-wavelength fluctuations in plasma and impurity ion densities. To detect turbulence in the local plasma ion density, the collisionally excited fluorescence from a neutral beam is measured either separately at several spatial points or with a multichannel imaging detector. Similarly, the role of impurity ion density fluctuations is measured using charge exchange recombination excited transitions emitted by the ion species of interest. This technique can access the relatively unexplored region of long-wavelength plasma turbulence with k perpendicular ρ i much-lt 1, and hence complements measurements from scattering experiments. Optimization of neutral beam geometry and optical sightlines can result in very good localization and resolution (Δx≤1 cm) in the hot plasma core region. The detectable fluctuation level is determined by photon statistics, atomic excitation processes, and beam stability, but can be as low as 0.2% in a 100 kHz bandwidth over the 0--1 MHz frequency range. The choices of beam species (e.g., H 0 , He 0 , etc.), observed transition (e.g., H α , L α , He I singlet or triplet transitions, C VI Δn=1, etc.) are dictated by experiment-specific factors such as optical access, flexibility of beam operation, plasma conditions, and detailed experimental goals. Initial tests on the PBX-M tokamak using the H α emissions from a heating neutral beam show low-frequency turbulence in the edge plasma region

ECR Plasma Photos

International Nuclear Information System (INIS)

Racz, R.; Biri, S.; Palinkas, J.

2009-01-01

we observed that some frequencies are 'better' than others for the point of view of plasma stability and brightness. There exist even frequencies where no plasma could be generated. Finally, a detailed study was carried out to analyze and understand the color of ECR plasmas. More photos can be found in the homepage of the ECRIS Laboratory.

Experimental high power plasma-filled backward wave oscillator results

International Nuclear Information System (INIS)

Minami, K.; Lou, W.R.; Destler, W.W.; Kehs, R.A.; Granatstein, V.L.; Carmel, Y.

1988-01-01

Previous results have indicated that a background gas can be used to increase the output microwave power of relativistic backward wave oscillators (BWOs) two or three times the vacuum case. In their experiments, two methods of plasma production are investigated in detail: the use of the electron beam to ionize a background gas, and the use of a plasma gun to inject a background plasma into the slow-wave structure of a BWO. It is found in the first case that there was a resonant increase in microwave power at a particular pressure of the background gas by a factor of ten. In the second case, power also increased compared with power production in vacuum. Detailed results are presented and the relative merits of the two approaches is discussed and compared with theoretical expectations

Downstream plasma transport and metal ionization in a high-powered pulsed-plasma magnetron

International Nuclear Information System (INIS)

Meng, Liang; Szott, Matthew M.; McLain, Jake T.; Ruzic, David N.; Yu, He

2014-01-01

Downstream plasma transport and ionization processes in a high-powered pulsed-plasma magnetron were studied. The temporal evolution and spatial distribution of electron density (n e ) and temperature (T e ) were characterized with a 3D scanning triple Langmuir probe. Plasma expanded from the racetrack region into the downstream region, where a high n e peak was formed some time into the pulse-off period. The expansion speed and directionality towards the substrate increased with a stronger magnetic field (B), largely as a consequence of a larger potential drop in the bulk plasma region during a relatively slower sheath formation. The fraction of Cu ions in the deposition flux was measured on the substrate using a gridded energy analyzer. It increased with higher pulse voltage. With increased B field from 200 to 800 Gauss above racetrack, n e increased but the Cu ion fraction decreased from 42% to 16%. A comprehensive model was built, including the diffusion of as-sputtered Cu flux, the Cu ionization in the entire plasma region using the mapped n e and T e data, and ion extraction efficiency based on the measured plasma potential (V p ) distribution. The calculations matched the measurements and indicated the main causes of lower Cu ion fractions in stronger B fields to be the lower T e and inefficient ion extraction in a larger pre-sheath potential.

Concept of a staged FEL enabled by fast synchrotron radiation cooling of laser-plasma accelerated beam by solenoidal magnetic fields in plasma bubble

Science.gov (United States)

Seryi, Andrei; Lesz, Zsolt; Andreev, Alexander; Konoplev, Ivan

2017-03-01

A novel method for generating GigaGauss solenoidal fields in a laser-plasma bubble, using screw-shaped laser pulses, has been recently presented. Such magnetic fields enable fast synchrotron radiation cooling of the beam emittance of laser-plasma accelerated leptons. This recent finding opens a novel approach for design of laser-plasma FELs or colliders, where the acceleration stages are interleaved with laser-plasma emittance cooling stages. In this concept paper, we present an outline of what a staged plasma-acceleration FEL could look like, and discuss further studies needed to investigate the feasibility of the concept in detail.

Electron beam production by a plasma focus

International Nuclear Information System (INIS)

Smith, J.R.; Luo, C.M.; Schneider, R.F.; Rhee, M.J.

1984-01-01

Operation of a plasma focus as a Compact Pulsed Accelerator (CPA) for ions has been previously reported. The CPA consists of: (1) a 15 μF, 3 kJ capacitor, (2) a triggered spark gap, (3) a coaxial transmission line, and (4) a Mather geometry plasma gun. Recently the authors have investigated application of the CPA as an accelerator for electrons. In the previously reported work using the standard Mather plasma gun geometry, ions were accelerated away from the plasma gun and were therefore conveniently extracted for analysis, but electrons were directed into the hollow anode where extraction is blocked by the coaxial transmission line. For investigation of accelerated electrons a new plasma gun design which allows extraction of electrons has been developed. Details of the new plasma gun design and further results of beam diagnostics are discussed

Heat loads to divertor nearby components from secondary radiation evolved during plasma instabilities

Energy Technology Data Exchange (ETDEWEB)

Sizyuk, V., E-mail: vsizyuk@purdue.edu; Hassanein, A., E-mail: hassanein@purdue.edu [Center for Materials under Extreme Environment, School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States)

2015-01-15

A fundamental issue in tokamak operation related to power exhaust during plasma instabilities is the understanding of heat and particle transport from the core plasma into the scrape-off layer and to plasma-facing materials. During abnormal and disruptive operation in tokamaks, radiation transport processes play a critical role in divertor/edge-generated plasma dynamics and are very important in determining overall lifetimes of the divertor and nearby components. This is equivalent to or greater than the effect of the direct impact of escaped core plasma on the divertor plate. We have developed and implemented comprehensive enhanced physical and numerical models in the upgraded HEIGHTS package for simulating detailed photon and particle transport in the evolved edge plasma during various instabilities. The paper describes details of a newly developed 3D Monte Carlo radiation transport model, including optimization methods of generated plasma opacities in the full range of expected photon spectra. Response of the ITER divertor's nearby surfaces due to radiation from the divertor-developed plasma was simulated by using actual full 3D reactor design and magnetic configurations. We analyzed in detail the radiation emission spectra and compared the emission of both carbon and tungsten as divertor plate materials. The integrated 3D simulation predicted unexpectedly high damage risk to the open stainless steel legs of the dome structure in the current ITER design from the intense radiation during a disruption on the tungsten divertor plate.

Cold plasmas

International Nuclear Information System (INIS)

Franz, G.

1990-01-01

This textbook discusses the following topics: Phenomenological description of a direct current glow discharge; the plasma (temperature distribution and measurement, potential variation, electron energy distribution function, charge neutralization, wall potentials, plasma oscillations); Production of charge carriers (ions, electrons, ionization in the cathode zone, negative glowing zone, Faraday dark space, positive column, anode zone, hollow cathode discharges); RF-discharges (charge carrier production, RF-Shields, scattering mechanisms); Sputtering (ion-surface interaction, kinetics, sputtering yield and energy distribution, systems and conditions, film formation and stresses, contamination, bias techniques, multicomponent film deposition, cohesion, magnetrons, triode systems, plasma enhanced chemical vapor deposition); Dry etching (sputter etching, reactive etching, topography, process control, quantitative investigations); Etching mechanisms (etching of Si and SiO 2 with CF 4 , of III/V-compound-semiconductors, combination of isotrope and anisotrope etching methods, surface cleaning); ion beam systems (applications, etching); Dyclotron-resonance-systems (electron cyclotron resonance systems, whistler-sources and 'resonant inductive plasma etching'); Appendix (electron energy distribution functions, Bohm's transition zone, plasma oscillations, scattering cross sections and mean free path, metastable states, Child-Langmuir-Schottky equation, loss mechanisms, charge carrier distribution in the positive column, breakdown at high frequencies, motion in a magnetic field, skin depth of an electric field for a HF-discharge, whistler waves, dispersion relations for plane wave propagation). (orig.) With 138 figs

Endobronchial Electrocautery and Argon Plasma Coagulation: A Practical Approach

Directory of Open Access Journals (Sweden)

Alain Tremblay

2004-01-01

Full Text Available The present review covers the technical and practical aspects of endobronchial electrocautery, including argon plasma coagulation, which have great potential for widespread use by pulmonologists around the world. The various electrocautery modes, power settings and electrode probes are described in detail, and the authors' clinical and technical approach is demonstrated with a narrative description and brief case presentations. Malignant airway obstruction, hemoptysis, web-like stenosis, stent related granulation tissue and early lung carcinomas are the most common indications for treatment. Advantages of electrocautery, such as low cost, rapid effect, safety and ease of use, are contrasted to other endobronchial therapeutic modalities. Published experience with electrocautery is reviewed.

Magnetic Configuration Control of ITER Plasmas

International Nuclear Information System (INIS)

Albanese, R.; Artaserse, G.; Mattei, M.; Ambrosino, G.; Crisanti, F.; Tommasi, G. de; Fresa, R.; Portone, A.; Sartori, F.; Villone, F.

2006-01-01

The aim of this paper is to review the capability of the ITER Poloidal Field (PF) system of controlling the broad range of plasma configurations presently forecasted during ITER operation. The attention is focused on the axi-symmetric aspects of plasma magnetic configuration control since they pose the greatest challenges in terms of control power and they have the largest impact on machine capital cost. The paper is broadly divided in two main sections devoted, respectively, to open loop (feed-forward) and closed loop (feedback) control. In the first part of the study the PF system is assessed with respect to the initiation, ramp-up, sustained burn, ramp-down phases of the main plasma inductive scenario. The limiter-to-divertor configuration transition phase is considered in detail with the aim of assessing the PF capability to form an X-point at the lowest possible current and, therefore, to relax the thermal load on the limiter surfaces. Moreover, during the sustained burn it is important to control plasmas with a broad range of current density profiles. In the second part of the study the plasma vertical feedback control requirements are assessed in details, in particular for the high elongation configurations achievable during the early limiter-to-X point transition phase. Non-rigid plasma displacement models are used to assess the control system voltage and current requirements of different radial field control circuits obtained, for example, by connecting the outermost PF coils, some CS coils, coils sub-sections etc. At last, the main 3D effects of the vessel ports are modeled and their impact of vertical stabilization evaluated. (author)

Dynamics and Melting of Finite Plasma Crystals

Science.gov (United States)

Ludwig, Patrick; K"Ahlert, Hanno; Baumgartner, Henning; Thomsen, Hauke; Bonitz, Michael

2009-11-01

Interacting few-particle systems in external trapping potentials are of strong current interest since they allow to realize and control strong correlation and quantum effects [1]. Here, we present our recent results on the structural and thermodynamic properties of the crystal-like Wigner phase of complex plasma confined in a 3D harmonic potential. We discuss the linear response of the strongly correlated system to external excitations, which can be described in terms of normal modes [2]. By means of first-principle simulations the details of the melting phase transitions of these mesoscopic systems are systematically analysed with the melting temperatures being determined by a modified Lindemann parameter for the pair distance fluctuations [3]. The critical temperatures turn out to be utmost sensitive to finite size effects (i.e., the exact particle number), and form of the (screened) interaction potential.[4pt] [1] PhD Thesis, P. Ludwig, U Rostock (2008)[0pt] [2] C. Henning et al., J. Phys. A 42, 214023 (2009)[0pt] [3] B"oning et al., Phys. Rev. Lett. 100, 113401 (2008)

Stopping power and polarization induced in a plasma by a fast charged particle in circular motion

Energy Technology Data Exchange (ETDEWEB)

Villo-Perez, Isidro [Departamento de Electronica, Tecnologia de las Computadoras y Proyectos, Universidad Politecnica de Cartagena, Cartagena (Spain); Arista, Nestor R. [Division Colisiones Atomicas, Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica, Bariloche (Argentina); Garcia-Molina, Rafael [Departamento de Fisica, Universidad de Murcia, Murcia (Spain)

2002-03-28

We describe the perturbation induced in a plasma by a charged particle in circular motion, analysing in detail the evolution of the induced charge, the electrostatic potential and the energy loss of the particle. We describe the initial transitory behaviour and the different ways in which convergence to final stationary solutions may be obtained depending on the basic parameters of the problem. The results for the stopping power show a resonant behaviour which may give place to large stopping enhancement values as compared with the case of particles in straight-line motion with the same linear velocity. The results also explain a resonant effect recently obtained for particles in circular motion in magnetized plasmas. (author)

On the potential of CARS spectroscopy in low-temperature plasma diagnostics

International Nuclear Information System (INIS)

Ambrazyavichyus, A.B.; Gladkov, S.M.; Grigajtis, Yu.P.; Koroteev, N.I.

1989-01-01

The principles of coherent anti-Stokes Raman spectroscopy (CARS) and its application to the diagnostics of technological plasmas are briefly discussed. THe CARS spectrometer is described, developed in IPTPE, Caunas for investigations of a nitrogen plasma stream generated by an industrial plasmatron, and several CARS spectra of nitrogen molecules are presented. As the CARS signal from vibrational-rotational energy levels decreases substantially at plasma temperatures above 2000 K, an alternative scheme using electronlevels of atoms or ions has to be used. To test the method, CARS signals from the lines of the first nitrogen ion were studied in a low-voltage spark discharge. (J.U.)

Semi-analytical wave functions in relativistic average atom model for high-temperature plasmas

International Nuclear Information System (INIS)

Guo Yonghui; Duan Yaoyong; Kuai Bin

2007-01-01

The semi-analytical method is utilized for solving a relativistic average atom model for high-temperature plasmas. Semi-analytical wave function and the corresponding energy eigenvalue, containing only a numerical factor, are obtained by fitting the potential function in the average atom into hydrogen-like one. The full equations for the model are enumerated, and more attentions are paid upon the detailed procedures including the numerical techniques and computer code design. When the temperature of plasmas is comparatively high, the semi-analytical results agree quite well with those obtained by using a full numerical method for the same model and with those calculated by just a little different physical models, and the result's accuracy and computation efficiency are worthy of note. The drawbacks for this model are also analyzed. (authors)

A fast spatial scanning combination emissive and mach probe for edge plasma diagnosis

International Nuclear Information System (INIS)

Lehmer, R.D.; LaBombard, B.; Conn, R.W.

1989-04-01

A fast spatially scanning emissive and mach probe has been developed for the measurement of plasma profiles in the PISCES facility at UCLA. A pneumatic cylinder is used to drive a multiple tip probe along a 15cm stroke in less than 400msec, giving single shot profiles while limiting power deposition to the probe. A differentially pumped sliding O-ring seal allows the probe to be moved between shots to infer two and three dimensional profiles. The probe system has been used to investigate the plasma potential, density, and parallel mach number profiles of the presheath induced by a wall surface and scrape-off-layer profile modifications in biased limiter simulation experiments. Details of the hardware, data acquisition electronics, and tests of probe reliability are discussed. 30 refs., 24 figs

Fluctuation characteristics in detached recombining plasmas

International Nuclear Information System (INIS)

Ohno, Noriyasu; Tanaka, Naoyuki; Takamura, Shuichi; Budaev, Viatcheslav

2002-01-01

Fluctuation in detached recombining plasmas has been investigated experimentally in the linear divertor plasma simulator, NAGDIS-II. As increasing neutral gas pressure, floating potential fluctuation of the target plate installed at the end of the NADIS-II device becomes larger and bursty negative spikes are observed in the signal associated with a transition from attached to detached a plasmas. The fluctuation property has been analyzed by using Fast Fourier Transform (FFT), probability distribution function (PDF) and wavelet transform. The PDF of the floating potential fluctuation in the attached plasma condition obeys the Gaussian distribution function, on the other hand, the PDF in detached plasma shows a strong deviation from the Gaussian distribution function, which can be characterized by flatness and skewness. Comparison of the fluctuation properties between the floating potential and the optical emission from the detached plasma has been done based on the wavelet transform to show that a strong correlation between them, which could indicate bursty transport of energetic electrons from upstream to downstream region along the magnetic field. (author)

Potential formation in a one-dimensional bounded plasma system containing a two-electron temperature plasma: Kinetic model and PIC simulation

International Nuclear Information System (INIS)

Gyergyek, T.; Jurcic-Zlobec, B.; Cercek, M.

2008-01-01

Potential formation in a bounded plasma system that contains electrons with a two-temperature velocity distribution and is terminated by a floating, electron emitting electrode (collector) is studied by a one-dimensional kinetic model. A method on how to determine the boundary conditions at the collector for the numerical solution of the Poisson equation is presented. The difference between the regular and the irregular numerical solutions of the Poisson equation is explained. The regular numerical solution of the Poisson equation fulfills the boundary conditions at the source and can be computed for any distance from the collector. The irregular solution does not fulfill the source boundary conditions and the computation breaks down at some distance from the collector. An excellent agreement of the values of the potential at the inflection point found from the numerical solution of the Poisson equation with the values predicted by the analytical model is obtained. Potential, electric field, and particle density profiles found by the numerical solution of the Poisson equation are compared to the profiles obtained with the particle in cell computer simulation. A very good quantitative agreement of the potential and electric field profiles is obtained. For certain values of the parameters the analytical model predicts three possible values of the potential at the inflection point. In such cases always only one of the corresponding numerical solutions of the Poisson equation is regular, while the other two are irregular. The regular numerical solution of the Poisson equation always corresponds to the solution of the model that predicts the largest ion flux to the collector

Nonlinear ion-acoustic structures in a nonextensive electron–positron–ion–dust plasma: Modulational instability and rogue waves

Energy Technology Data Exchange (ETDEWEB)

Guo, Shimin, E-mail: gsm861@126.com [School of Mathematics and Statistics, Xi’an Jiaotong University, Xi’an, 710049 (China); Research Group MAC, Centrum Wiskunde and Informatica, Amsterdam, 1098XG (Netherlands); Mei, Liquan, E-mail: lqmei@mail.xjtu.edu.cn [School of Mathematics and Statistics, Xi’an Jiaotong University, Xi’an, 710049 (China); Center for Computational Geosciences, Xi’an Jiaotong University, Xi’an, 710049 (China); Sun, Anbang [Research Group MAC, Centrum Wiskunde and Informatica, Amsterdam, 1098XG (Netherlands)

2013-05-15

The nonlinear propagation of planar and nonplanar (cylindrical and spherical) ion-acoustic waves in an unmagnetized electron–positron–ion–dust plasma with two-electron temperature distributions is investigated in the context of the nonextensive statistics. Using the reductive perturbation method, a modified nonlinear Schrödinger equation is derived for the potential wave amplitude. The effects of plasma parameters on the modulational instability of ion-acoustic waves are discussed in detail for planar as well as for cylindrical and spherical geometries. In addition, for the planar case, we analyze how the plasma parameters influence the nonlinear structures of the first- and second-order ion-acoustic rogue waves within the modulational instability region. The present results may be helpful in providing a good fit between the theoretical analysis and real applications in future spatial observations and laboratory plasma experiments. -- Highlights: ► Modulational instability of ion-acoustic waves in a new plasma model is discussed. ► Tsallis’s statistics is considered in the model. ► The second-order ion-acoustic rogue wave is studied for the first time.

Nonlinear ion-acoustic structures in a nonextensive electron–positron–ion–dust plasma: Modulational instability and rogue waves

International Nuclear Information System (INIS)

Guo, Shimin; Mei, Liquan; Sun, Anbang

2013-01-01

The nonlinear propagation of planar and nonplanar (cylindrical and spherical) ion-acoustic waves in an unmagnetized electron–positron–ion–dust plasma with two-electron temperature distributions is investigated in the context of the nonextensive statistics. Using the reductive perturbation method, a modified nonlinear Schrödinger equation is derived for the potential wave amplitude. The effects of plasma parameters on the modulational instability of ion-acoustic waves are discussed in detail for planar as well as for cylindrical and spherical geometries. In addition, for the planar case, we analyze how the plasma parameters influence the nonlinear structures of the first- and second-order ion-acoustic rogue waves within the modulational instability region. The present results may be helpful in providing a good fit between the theoretical analysis and real applications in future spatial observations and laboratory plasma experiments. -- Highlights: ► Modulational instability of ion-acoustic waves in a new plasma model is discussed. ► Tsallis’s statistics is considered in the model. ► The second-order ion-acoustic rogue wave is studied for the first time

Isotopic separation in a rotating neon plasma

International Nuclear Information System (INIS)

Cairns, J.B.S.

1976-01-01

The background to the use of rotating plasma as element and isotope separators is briefly reviewed. The principles of the process are outlined. The rotation in a plasma centrifuge is produced by passing a radial current across an axial magnetic field. The different mass spheres, if under the influence of azimuthal forces, may be separated by crossing the field. Details are given of the Vortex II experiment in which 22 Ne is separated from neon in a fully ionized rotating plasma. It was demonstrated that 22 Ne enrichments of approximately 15% could be achieved with the possibility of higher values when the design and operation of the plasma centrifuge have been optimised. (U.K.)

Excimer laser produced plasmas in copper wire targets and water droplets

Science.gov (United States)

Song, Kyo-Dong; Alexander, D. R.

1994-01-01

Elastically scattered incident radiation (ESIR) from a copper wire target illuminated by a KrF laser pulse at lambda = 248 nm shows a dinstinct two-peak structure which is dependent on the incident energy. The time required to reach the critical electron density (n(sub c) approximately = 1.8 x 10(exp 22) electrons/cu cm) is estimated at 11 ns based on experimental results. Detailed ESIR characteristics for water have been reported previously by the authors. Initiation of the broadband emission for copper plasma begins at 6.5 +/- 1.45 ns after the arrival of the laser pulse. However, the broadband emission occurs at 11 +/- 0.36 ns for water. For a diatomic substance such as water, the electron energy rapidly dissipates due to dissociation of water molecules, which is absent in a monatomic species such as copper. When the energy falls below the excitation energy of the lowest electron state for water, it becomes a subexcitation electron. Lifetimes of the subexcited electrons to the vibrational states are estimated to be of the order of 10(exp -9) s. In addition, the ionization potential of copper (440-530 nm) is approximately 6 eV, which is about two times smaller than the 13 eV ionization potential reported for water. The higher ionization potential contributes to the longer observed delay time for plasma formation in water. After initiation, a longer time is required for copper plasma to reach its peak value. This time delay in reaching the maximum intensity is attributed to the energy loss during the interband transition in copper.

The theory of hyrogenic plasmas and fluids

International Nuclear Information System (INIS)

Dharma-Wardana, M.W.C.

1978-01-01

A comprehensive theory of the transverse dielectric function, light absorption and other aspects of photon propagation as well as level shifts, the chemical potential and statistical mechanics of hydrogenic fluids ranging from the fully ionized plasma to the atomic fluid, is presented. A coulomb basis is used instead of the usual plane waves for second quantization. The commutation rules for these operators are discussed and a simplification valid for electron-ion systems is considered. The Coulomb basis simplifies the theory by replacing the six interaction potentials involving atoms, ions and electrons by a single term. The free bound and photo processes also reduce to a single term. As in the best available theory of the uniform electron gas we have calculated the mass operator contained in the polarization operator of the photon Green function to second order and included a partial summation of higher order effects via a screening function. The shifted and broadened energy levels, the chemical potential and the modified Saha equation are obtained from the one-particle Green function. The complex refractive index, the absorption profile, etc. contain terms in first order thus easily recovering effects not recovered in the existing theories. In the fully ionized plasma limit the results lead to the usual Geldart and Taylor type Fermi gas response theory. In the atomic fluid limit the polarizable atom models of, for example, Bullough et al., are compared with our microscopic theory. Explicit algebraic expressions together with details of the evaluation of the matrix elements are given for the final results. (Auth.)

Plasma heating by a relativistic electron beam

International Nuclear Information System (INIS)

Janssen, G.C.A.M.

1983-01-01

This thesis is devoted to the interaction of a Relativistic Electron Beam (REB) with a plasma. The goal of the experiment described herein is to study in detail the mechanism of energy transfer from the beam to the plasma. The beam particles have an energy of 800 keV, a current of 6 kA, a diameter of 3 cm and an adjustable pulse length of 50-150 ns. This beam is injected into cold hydrogen and helium plasmas with densities ranging from 10 18 to 10 20 m -3 . First, the technical aspects of the experiment are described. Then measurements on the hf fields excited by the REB-plasma are presented (optical line profiles and spectra of beam electrons). The final section is devoted to plasma heating. (Auth.)

PEPSI-Dock: a detailed data-driven protein-protein interaction potential accelerated by polar Fourier correlation.