Sample records for plasma sheet electrons

  1. Heliospheric plasma sheets

    Microsoft Academic Search

    N. U. Crooker; C.-L. Huang; S. M. Lamassa; D. E. Larson; S. W. Kahler; H. E. Spence

    2004-01-01

    As a high-beta feature on scales of hours or less, the heliospheric plasma sheet (HPS) encasing the heliospheric current sheet shows a high degree of variability. A study of 52 sector boundaries identified in electron pitch angle spectrograms in Wind data from 1995 reveals that only half concur with both high-beta plasma and current sheets, as required for an HPS.

  2. Energetic plasma sheet electrons and their relationship with the solar wind: A Cluster and Geotail study

    Microsoft Academic Search

    E. Burin des Roziers; X. Li; D. N. Baker; T. A. Fritz; R. Friedel; T. G. Onsager; I. Dandouras

    2009-01-01

    The statistical relationship between tens of kiloelectron volts plasma sheet electrons and the solar wind, as well as >2 MeV geosynchronous electrons, is investigated using plasma sheet measurements from Cluster (2001–2005) and Geotail (1998–2005) and concurrent solar wind measurements from ACE. Plasma sheet selection criteria from previous studies are compared, and this study selects a new combination of criteria that

  3. Energetic plasma sheet electrons and their relationship with the solar wind: A Cluster and Geotail study

    E-print Network

    Li, Xinlin

    Energetic plasma sheet electrons and their relationship with the solar wind: A Cluster and Geotail and the solar wind, as well as >2 MeV geosynchronous electrons, is investigated using plasma sheet measurements from Cluster (2001­2005) and Geotail (1998­2005) and concurrent solar wind measurements from ACE

  4. Experimental investigation of a 1 kA/cm2 sheet beam plasma cathode electron gun

    NASA Astrophysics Data System (ADS)

    Kumar, Niraj; Narayan Pal, Udit; Kumar Pal, Dharmendra; Prajesh, Rahul; Prakash, Ram

    2015-01-01

    In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ˜1 kA/cm2 from pseudospark based argon plasma for pulse length of ˜200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance in a drift space region maintaining sheet structure without assistance of any external magnetic field.

  5. Experimental investigation of a 1 kA/cm² sheet beam plasma cathode electron gun.

    PubMed

    Kumar, Niraj; Pal, Udit Narayan; Pal, Dharmendra Kumar; Prajesh, Rahul; Prakash, Ram

    2015-01-01

    In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ?1 kA/cm(2) from pseudospark based argon plasma for pulse length of ?200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance in a drift space region maintaining sheet structure without assistance of any external magnetic field. PMID:25638082

  6. Graphene sheets embedded carbon film prepared by electron irradiation in electron cyclotron resonance plasma

    SciTech Connect

    Wang Chao; Diao Dongfeng; Fan Xue; Chen Cheng [Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, School of Mechanical Engineering, Xi'an Jiaotong University, 710049 Xi'an (China)

    2012-06-04

    We used a low energy electron irradiation technique to prepare graphene sheets embedded carbon (GSEC) film based on electron cyclotron resonance plasma. The particular {pi} electronic structure of the GSEC film similar to bilayer graphene was verified by Raman spectra 2D band analyzing. The phase transition from amorphous carbon to GSEC was initiated when electron irradiation energy reached 40 eV, and the growth mechanism of GSEC was interpreted as inelastic scattering of low energy electrons. This finding indicates that the GSEC film obtained by low energy electron irradiation can be excepted for widely applications with outstanding electric properties.

  7. Thin Current Sheets and Associated Electron Heating in Turbulent Space Plasma

    NASA Astrophysics Data System (ADS)

    Chasapis, A.; Retinò, A.; Sahraoui, F.; Vaivads, A.; Khotyaintsev, Yu. V.; Sundkvist, D.; Greco, A.; Sorriso-Valvo, L.; Canu, P.

    2015-05-01

    Intermittent structures, such as thin current sheets, are abundant in turbulent plasmas. Numerical simulations indicate that such current sheets are important sites of energy dissipation and particle heating occurring at kinetic scales. However, direct evidence of dissipation and associated heating within current sheets is scarce. Here, we show a new statistical study of local electron heating within proton-scale current sheets by using high-resolution spacecraft data. Current sheets are detected using the Partial Variance of Increments (PVI) method which identifies regions of strong intermittency. We find that strong electron heating occurs in high PVI (>3) current sheets while no significant heating occurs in low PVI cases (<3), indicating that the former are dominant for energy dissipation. Current sheets corresponding to very high PVI (>5) show the strongest heating and most of the time are consistent with ongoing magnetic reconnection. This suggests that reconnection is important for electron heating and dissipation at kinetic scales in turbulent plasmas.

  8. Pulsed sheet electron beam plasma-assisted CVD of silicon films

    NASA Astrophysics Data System (ADS)

    Shaheen, Mohammad A.

    Pulsed Sheet Electron Beam Plasma-Assisted Chemical Vapor Deposition (PSEB-CVD) is a novel method of thin film deposition which is a variant on the conventional PECVD and an alternative to remote PECVD. PSEB-CVD uses a pulsed electron beam generated plasma, whose dimension is confined to a narrow sheet that passes over the substrate at a controllable height. Variations in plasma pulse width, cathode voltage, sheet beam-to-substrate distance, gas type and pressure can vary the type and energy of the species arriving at the substrate. Specifically, the ratio of SiHsb3/SiHsb2 flux to the substrate can be increased by a factor of 10 by placing the wafer at least 5 cm from the sheet beam and increased by 3 orders of magnitude by operating the plasma at a 10% duty cycle. The increased SiHsb3/SiHsb2 flux ratio results in better film quality due to the larger surface mobility of SiHsb3 when compared to SiHsb2. This improvement, however, is accompanied by a linear decrease in deposition rate, from 25 A/min for the dc case without a sheet beam, to 5 A/m for the 0.5 duty cycle case with the wafer at 5 cm from the substrate. A system based on the PSEB-CVD principles was designed and built to allow the creation of a sheet e-beam at a variable distance from a heated substrate in a 5% silane/He plasma. Also, a plasma-pulsing circuit that can deliver square pulses of widely varying shapes has been built and used to create a pulsed e-beam plasma with varying pulsing conditions. A model of the sheet e-beam plasma kinetics, silane chemistry and surface deposition is used to guide the choice of the experimental parameters so as to effectively select a specific radical for deposition. The pulsed plasma was characterized with Langmuir probe analysis which showed that for the case of a He plasma there was a sharp increase in electron density immediately after the pulse was turned off. For the pulsed silane/He plasma, this effect was not as large, but unlike the He plasma, the floating potential increased for a few ms's after initiating the pulse. The silane/He plasma may have had a strong e-beam component. A recipe was developed for the optimum operating conditions of the PSEB-CVD system based on an analysis of the system operating under a variety of conditions. Growth of Si films in the 100-600 A thickness range was demonstrated as a proof of principle of the PSEB-CVD method. The films were characterized for uniformity, impurity content and crystallinity by a variety of surface analysis techniques including Profilometer, AES, EBSD, SEM, XRD and AFM. The films grown were found to be pure to a detection limit of 0.2%. Diffraction data, as well as grain surface morphology, were used to characterize crystallinity. The films deposited without a sheet beam were found to be amorphous, while the ones grown in a sheet beam were partially polycrystalline (30%). An x-ray diffraction analysis on films deposited in pulsed (0.5 duty cycle) sheet beam (substrate height = 5 cm) indicated the possibility that the films could be preferentially oriented. The films were typically grown at temperatures of 370sp°C and 250 mTorr pressure. The Nm uniformity was also greatly improved with the use of the sheet e-beam configuration. The improved crystallinity confirms that deposition quality is improved as a result of beam confinement and plasma pulsing.

  9. Inner Magnetospheric Superthermal Electron Transport: Photoelectron and Plasma Sheet Electron Sources

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Liemohn, M. W.; Kozyra, J. U.; Moore, T. E.

    1998-01-01

    Two time-dependent kinetic models of superthermal electron transport are combined to conduct global calculations of the nonthermal electron distribution function throughout the inner magnetosphere. It is shown that the energy range of validity for this combined model extends down to the superthermal-thermal intersection at a few eV, allowing for the calculation of the en- tire distribution function and thus an accurate heating rate to the thermal plasma. Because of the linearity of the formulas, the source terms are separated to calculate the distributions from the various populations, namely photoelectrons (PEs) and plasma sheet electrons (PSEs). These distributions are discussed in detail, examining the processes responsible for their formation in the various regions of the inner magnetosphere. It is shown that convection, corotation, and Coulomb collisions are the dominant processes in the formation of the PE distribution function and that PSEs are dominated by the interplay between the drift terms. Of note is that the PEs propagate around the nightside in a narrow channel at the edge of the plasmasphere as Coulomb collisions reduce the fluxes inside of this and convection compresses the flux tubes inward. These distributions are then recombined to show the development of the total superthermal electron distribution function in the inner magnetosphere and their influence on the thermal plasma. PEs usually dominate the dayside heating, with integral energy fluxes to the ionosphere reaching 10(exp 10) eV/sq cm/s in the plasmasphere, while heating from the PSEs typically does not exceed 10(exp 8) eV/sq cm/s. On the nightside, the inner plasmasphere is usually unheated by superthermal electrons. A feature of these combined spectra is that the distribution often has upward slopes with energy, particularly at the crossover from PE to PSE dominance, indicating that instabilities are possible.

  10. The Inner Edge of the Plasma Sheet, REGION-2 Currents, and Electron Precipitation: Plasma Observations from ISEE 1.

    NASA Astrophysics Data System (ADS)

    Paterson, William Russell

    1990-01-01

    On 17 April, 29 April, and 4 June of 1978 the ISEE 1 spacecraft encountered the inner edge of the plasma sheet on the dusk side of Earth at radial distances of 6 to 9 R_{rm E}. Measurements obtained with a plasma analyzer aboard this spacecraft are examined in an effort to determine the source of Region -2 Birkeland currents. Near the inner edge it is found that the distributions of both electrons and positive ions have low-energy field-aligned components that apparently originate at low altitudes. In two cases it is also found that the low-energy electrons carry a current that is consistent in direction and magnitude with Region-2 currents observed at low altitude. Positive ions with energies per charge _sp{~}{<}1 kV also stream along the field and sometimes provide a current that is comparable in magnitude but opposite in direction to the electron current. The low-energy electrons are counterstreaming and appear to be backscattered secondaries produced by precipitation of keV plasma sheet electrons into the atmosphere. The source of low-energy ions is not determined but is probably related to the electron flow, possibly by wave-particle interactions. An analysis of electron distributions indicates that the inner edge is a drift boundary separating open and closed flow trajectories. However, shielding there is found to be more localized than the shielding assumed in standard convection models. This shielding may be provided by the low-energy field-aligned plasmas. It is also found that the electron distributions at the inner edge are strongly modified, apparently by pitch-angle diffusion which drives keV electrons into the loss cone and scatters secondary electrons out of the source cone, and modification of the distributions by pitch-angle diffusion may also play a role in producing the field-aligned currents. Thus, it is found that precipitation and pitch -angle diffusion play important roles in determining the structure of the inner magnetosphere and may serve to couple apparently diverse phenomena such as diffuse aurora, Region -2 currents, and formation of the inner edge.

  11. Magnetospheric protons and electrons encountered by the moon in the plasma sheet

    NASA Technical Reports Server (NTRS)

    Prakash, A.

    1975-01-01

    Results are summarized for a study of plasma-sheet particles (and their flow) encountered by the moon during its passage through the geomagnetic tail. The study is based on analysis of data obtained with a modulated Faraday cup on board the lunar-anchored spacecraft Explorer 35. It is shown that the electrons have a rapidly fluctuating non-Maxwellian energy distribution with a mean energy of several hundred electron volts and a density of approximately 0.2 per cu cm. Protons with energies of the order of 1 keV were usually detected above the instrument background when flowing towards earth at about 200 km/sec. It is suggested that strong terrestrial polar winds during the early history of the earth-moon system could have caused some erosion of the front side of the moon and that the relative smoothness of the same side could be explained in terms of gravitational shielding by the earth from the interplanetary rock flux.

  12. Magnetization of the plasma sheet

    Microsoft Academic Search

    Richard L. Kaufmann; W. R. Paterson; L. A. Frank

    2004-01-01

    Long-term-averaged three-dimensional data-based models were made of the ?30 < x < ?10, ?y? < 15, ?z? < 5 RE plasma sheet region. The average magnetic moments $\\\\langle$?$\\\\rangle$ and Chew-Goldberger-Low (CGL) double adiabatic parameters ?$\\\\perp$ and ?$\\\\parallel$ were evaluated for ions and electrons. It was shown that restricting the observations to those taken within 0.2 RE of the Bx =

  13. The plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Eastman, T. E.; Frank, L. A.; Peterson, W. K.; Lennartsson, W.

    1984-01-01

    A spatially distinct, temporally variable, transition region between the magnetotail lobes and the central plasma sheet designated the plasma sheet boundary layer has been identified from a survey of particle spectra and three-dimensional distributions as sampled by the ISEE 1 LEPEDEA. The instrumentation and data presentation are described, and the signatures of the magnetotail plasma regimes are presented and discussed for the central plasma sheet and lobe and the plasma sheet boundary layer. Comparisons of plasma parameters and distribution fucntions are made and the evolution of ion velocity distributions within the plasma sheet boundary layer is discussed. The spatial distribution of the plasma sheet boundary layer is considered and ion composition measurements are presented.

  14. Energetic ion and electron beams at the plasma-sheet boundary in the distant tail

    Microsoft Academic Search

    M. Scholer; B. Klecker; D. Hovestatd; G. Gloeckler; F. M. Ipavich; A. B. Galvin; D. N. Baker; B. T. Tsurutani

    1987-01-01

    Several energetic particle bursts observed by ISEE 3 in the distant tail are analyzed. The energetic particle data are supplemented by the electron plasma and magnetic field measurements. These bursts are characterized by large velocity-dispersion effects, with energetic electrons observed first, followed by ions with continuously lower velocities. Both ions and electrons stream in the tailward direction. Protons and alpha

  15. Simulation of electrostatic turbulence in the plasma sheet boundary layer with electron currents and bean-shaped ion beams

    NASA Astrophysics Data System (ADS)

    Nishikawa, K.-I.; Frank, L. A.; Huang, C. Y.

    1988-06-01

    Plasma data from ISEE-1 show the presence of electron currents as well as energetic ion beams in the plasma sheet boundary layer. Broadband electrostatic noise and low-frequency electromagnetic bursts are detected in the plasma sheet boundary layer, especially in the presence of strong ion flows, currents, and steep spacial gradients in the fluxes of few-keV electrons and ions. Particle simulations have been performed to investigate electrostatic turbulence driven by a cold electron beam and/or ion beams with a bean-shaped velocity distribution. The simulation results show that the counterstreaming ion beams as well as the counterstreaming of the cold electron beam and the ion beam excite ion acoustic waves with a given Doppler-shifted real frequency. However, the effect of the bean-shaped ion velocity distributions reduces the growth rates of ion acoustic instability. The simulation results also show that the slowing down of the ion bean is larger at the larger perpendicular velocity. The wave spectra of the electric fields at some points of the simulations show turbulence generated by growing waves.

  16. Simulation of electrostatic turbulence in the plasma sheet boundary layer with electron currents and bean-shaped ion beams

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Frank, L. A.; Huang, C. Y.

    1988-01-01

    Plasma data from ISEE-1 show the presence of electron currents as well as energetic ion beams in the plasma sheet boundary layer. Broadband electrostatic noise and low-frequency electromagnetic bursts are detected in the plasma sheet boundary layer, especially in the presence of strong ion flows, currents, and steep spacial gradients in the fluxes of few-keV electrons and ions. Particle simulations have been performed to investigate electrostatic turbulence driven by a cold electron beam and/or ion beams with a bean-shaped velocity distribution. The simulation results show that the counterstreaming ion beams as well as the counterstreaming of the cold electron beam and the ion beam excite ion acoustic waves with a given Doppler-shifted real frequency. However, the effect of the bean-shaped ion velocity distributions reduces the growth rates of ion acoustic instability. The simulation results also show that the slowing down of the ion bean is larger at the larger perpendicular velocity. The wave spectra of the electric fields at some points of the simulations show turbulence generated by growing waves.

  17. MHD Ballooning Instability in the Plasma Sheet

    SciTech Connect

    C.Z. Cheng; S. Zaharia

    2003-10-20

    Based on the ideal-MHD model the stability of ballooning modes is investigated by employing realistic 3D magnetospheric equilibria, in particular for the substorm growth phase. Previous MHD ballooning stability calculations making use of approximations on the plasma compressibility can give rise to erroneous conclusions. Our results show that without making approximations on the plasma compressibility the MHD ballooning modes are unstable for the entire plasma sheet where beta (sub)eq is greater than or equal to 1, and the most unstable modes are located in the strong cross-tail current sheet region in the near-Earth plasma sheet, which maps to the initial brightening location of the breakup arc in the ionosphere. However, the MHD beq threshold is too low in comparison with observations by AMPTE/CCE at X = -(8 - 9)R(sub)E, which show that a low-frequency instability is excited only when beq increases over 50. The difficulty is mitigated by considering the kinetic effects of ion gyrorad ii and trapped electron dynamics, which can greatly increase the stabilizing effects of field line tension and thus enhance the beta(sub)eq threshold [Cheng and Lui, 1998]. The consequence is to reduce the equatorial region of the unstable ballooning modes to the strong cross-tail current sheet region where the free energy associated with the plasma pressure gradient and magnetic field curvature is maximum.

  18. Correlation of Alfven wave Poynting flux in the plasma sheet at 47 RE with ionospheric electron energy flux

    E-print Network

    California at Berkeley, University of

    energy flux A. Keiling,1 J. R. Wygant,1 C. Cattell,1 W. Peria,2 G. Parks,2 M. Temerin,3 F. S. Mozer,3 C to the nominal plasma sheet. Previous studies of electric fields, using ISEE 1/2 [Mozer, 1981; Cattell et al that the fields do not only map like quasi-static electric fields, as shown by previous studies [Mozer, 1981

  19. Rapid loss of the plasma sheet energetic electrons associated with the growth of whistler mode waves inside the bursty bulk flows

    NASA Astrophysics Data System (ADS)

    Li, L. Y.; Yu, J.; Cao, J. B.

    During the interval 07:45:36- 07:54:24 UT on 24 August 2005, Cluster satellites (C1 and C3) observed an obvious loss of energetic electrons (3.2- 95keV) associated with the growth of whistler mode waves inside some bursty bulk flows (BBFs) in the midtail plasma sheet (X _{GSM}= -17.25 R _{E}). However, the fluxes of the higher-energy electrons (>128keV) and energetic ions (10- 160 keV) were relatively stable in the BBF-impacted regions. The energy-dependent electron loss inside the BBFs is mainly due to the energy-selective pitch angle scatterings by whistler mode waves within the time scales from several seconds to several minutes, and the electron scatterings in different pitch angle distributions are different in the wave growth regions. The plasma sheet energetic electrons have mainly a quasi-perpendicular pitch angle distribution (30(°) electrons, the low-energy electrons (0.073- 2.1keV) have initially a field-aligned pitch angle distribution (0(°) electrons inside the BBFs is not obvious in the presence of their large background fluxes. These observations indicate that the resonant electrons in an anisotropic pitch angle distribution mainly undergo the rapid pitch angle scattering loss during the wave-particle resonances.

  20. Region 2 field-aligned currents and earthward penetration of the electron and ion plasma sheet obtained from RCM simulations with a modified Dungey magnetic field solver, and comparison with observations in ionosphere and magnetosphere

    NASA Astrophysics Data System (ADS)

    Gkioulidou, M.; Wang, C.; Lyons, L. R.

    2011-12-01

    Ionospheric conductivity and field aligned currents (FAC) are two of the most important factors that control the magnetosphere - ionosphere (M-I) coupling. The relative location between conductivity and FAC strongly affect the spatial distribution of convection electric field, including the Harang reversal and Sub-Auroral Polarization Streams that are crucial to development of substorms and storms. The night-side conductivity strongly depends on electron precipitation, and thus the electron plasma sheet and precipitation rate. On the other hand, Region 2 (R2) FAC are associated with pressure gradients in the near-Earth magnetosphere built up by plasma sheet ions. To understand this aspect of M-I coupling, we have run simulations with the Rice Convection Model (RCM), integrated with a modified Dungey magnetic field solver for equatorial force balance, to investigate the earthward penetration of plasma sheet protons and electrons of different energies into the near-Earth magnetosphere under weak and enhanced convection. We have investigated in our simulations how different precipitation rate affects the relative locations of conductivity and FAC and the resulting M-I coupling. We evaluate these simulation results by comparing the plasma sheet ions and electrons and their relative earthward edges with in situ THEMIS statistical results, and by comparing the simulated precipitating electron energy fluxes, different ion and electron equatorward precipitation boundaries, as well as their locations relative to R2 FAC in ionosphere, with previous published statistical DMSP studies [Newell et al., 2009; Ohtani et al., 2010].

  1. The driving of the plasma sheet by the solar wind

    Microsoft Academic Search

    Joseph E. Borovsky; Michelle F. Thomsen; Richard C. Elphic

    1998-01-01

    The coupling of the plasma sheet to the solar wind is studied statistically using measurements from various satellite pairs: one satellite in the solar wind and one in either the magnetotail central plasma sheet or the near-Earth plasma sheet. It is found that the properties of the plasma sheet are highly correlated with the properties of the solar wind: specifically

  2. Laboratory Investigations of Current Sheets at the Electron Skin Depth Scale

    Microsoft Academic Search

    S. Vincena; W. Gekelman

    2005-01-01

    Laboratory Investigations of Current Sheets at the Electron Skin Depth Scale. Theoretical investigations, in situ spacecraft and rocket missions, and laboratory studies form an essential triad for understanding the variety of current sheet phenomena found in space plasmas. In the Large Plasma Device (LAPD) at UCLA, the formation dynamics, equilibrium state, and wave-mediated disruptions of current sheets can be studied

  3. Substorm Onset by Plasma Sheet Divergence

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Wang, C.; Nagai, T.

    2003-12-01

    It is necessary to understand current wedge formation in order to understand the cause of the substorm expansion phase. Geotail spacecraft observations have shown that the inner-plasma-sheet cross-tail current reduction within the current wedge results from a process that leads to a reduction in equatorial plasma pressure and a substantial reduction in flux tube ion content. We use the single-species continuity equation for plasma sheet particles to identify a plausible cause of these plasma reductions. We find that a convection reduction, which follows a growth phase period of enhanced convection, should cause a divergence of plasma sheet particles driven by diamagnetic drift that leads to flux tube content reduction. Such reduction in flux tube content is longitudinally localized to the pre-midnight to midnight region where the current wedge has been observed to initially form and must initiate within the region of the equatorial mapping of the Harang discontinuity, consistent with ionospheric observations of substorm onset. We also find that the reduction in flux tube content should initially develop slowly, and then develop more rapidly as the current wedge forms. This is consistent with observations which show that expansion phase aurora, and thus also the current wedge, develops slowly for a few minutes before brightening rapidly, and it is as required if plasma sheet divergence driven by diamagnetic drift leads to current wedge formation and initiation of the substorm expansion phase.

  4. Plasma-sheet structure and the onset of magnetospheric substorms

    Microsoft Academic Search

    T. W. Hill; A. J. Dessler

    1971-01-01

    A model is presented in which the plasma sheet is not confined by a closed magneticfield configuration. Instead, the plasma-sheet particles continually leak down the tail along open field lines; the loss rate is controlled by particle scattering with magnetic-field irregularities and waves, and the length of the plasma sheet is determined by loss of plasma-sheet particles to the neutral

  5. Current Sheets in the Earth Magnetotail: Plasma and Magnetic Field Structure with Cluster Project Observations

    NASA Astrophysics Data System (ADS)

    Petrukovich, Anatoli; Artemyev, Anton; Vasko, Ivan; Nakamura, Rumi; Zelenyi, Lev

    2015-05-01

    Thin current sheets having kinetic scales are an important plasma structure, where the magnetic energy dissipation and charged particle acceleration are the most effective. It is believed that such current sheets are self-consistently formed by the specific nonadiabatic dynamics of charged particles and play a critical role in many space plasma and astrophysical objects. Current sheets in the near-Earth plasma environment, e.g., the magnetotail current sheet, are readily available for in-situ investigations. The dedicated multi-spacecraft Cluster mission have revealed basic properties of this current sheet, which are presented in this review: typical spatial profiles of magnetic field and current density, distributions of plasma temperature and density, role of heavy ions and electron currents, etc. Being important for the Earth magnetosphere physics, the new knowledge also could provide the basis for advancement in general plasma physics as well as in plasma astrophysics.

  6. Thermomechanical processing of plasma sprayed intermetallic sheets

    DOEpatents

    Hajaligol, Mohammad R. (Midlothian, VA); Scorey, Clive (Cheshire, CT); Sikka, Vinod K. (Oak Ridge, TN); Deevi, Seetharama C. (Midlothian, VA); Fleischhauer, Grier (Midlothian, VA); Lilly, Jr., A. Clifton (Chesterfield, VA); German, Randall M. (State College, PA)

    2001-01-01

    A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

  7. Substorm onset by plasma sheet divergence

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Wang, C.-P.; Nagai, T.

    2003-12-01

    It is necessary to understand current wedge formation in order to understand the cause of the substorm expansion phase. In the companion paper we used Geotail spacecraft observations to show that the cross-tail current reduction within the inner-plasma-sheet current wedge results from a process that leads to a reduction in equatorial plasma pressure and a substantial reduction in flux tube ion content. Here we use the single-species continuity equation for plasma sheet particles to identify a plausible cause of these plasma reductions and thus for current wedge formation and the initiation of the substorm expansion phase. Specifically, we find that a convection reduction, which follows a growth phase period of enhanced convection, should cause a divergence of plasma sheet particles driven by diamagnetic drift that leads to flux tube content reduction. We find that the reduction in flux tube content should be longitudinally localized to the premidnight to midnight region where the current wedge has been observed to initially form and that the reduction must initiate within the region of the equatorial mapping of the Harang discontinuity, consistent with ionospheric observations of substorm onset. We also find that the reduction in flux tube content should initially develop slowly and then develop more rapidly as the current wedge forms. This is consistent with observations which show that expansion phase aurora, and thus also the current wedge, develops slowly for a few minutes before brightening rapidly, and it is as required if plasma sheet divergence driven by diamagnetic drift leads to current wedge formation and initiation of the substorm expansion phase.

  8. Relationship of dusk sector radial electric field to energy dispersion at the inner edge of the electron plasma sheet

    NASA Technical Reports Server (NTRS)

    Horwitz, J. L.

    1984-01-01

    It is shown that, by assuming that the magnetospheric particle boundaries are the result of steady state convection, the electron boundaries in the dusk sector are essentially sensitive to the local, not the global, electric field configuration. A simple, direct relationship is obtained between the dusk sector radial electric field and the inner edge of electron boundaries at various energies.

  9. Plasma dynamics in laboratory-produced current sheets

    SciTech Connect

    Frank, Anna G.; Kyrie, Natalya P.; Satunin, Sergey N. [A.M. Prokhorov Institute of General Physics of the Russian Academy of Sciences, 38 Vavilov Street, Moscow 119991 (Russian Federation)

    2011-11-15

    Evolution of currents and Ampere forces in current sheets are analyzed on the basis of magnetic measurements. Two new effects are observed in the current distributions at the later stage of the sheet evolution: first, a broadening of the current area at the side edges of the current sheet; second, a generation of reverse currents followed by their propagation from the edges to the center of the sheet. Super-thermal plasma flows moving across the width of the current sheet are observed by spectroscopic methods. The energies of plasma jets are consistent with the spatial structure and time dependences of the Ampere forces in the current sheets. The assumption is advanced that plasma acceleration may be more effective at the regions with lower plasma density, which are located at some distances from the sheet mid-plane. Generation of reverse currents provides an additional confirmation of transfer of energetic plasma jets toward the sheet edges.

  10. Evidence for kinetic Alfvén waves and parallel electron energization at 4-6 RE altitudes in the plasma sheet boundary layer

    Microsoft Academic Search

    J. R. Wygant; A. Keiling; C. A. Cattell; R. L. Lysak; M. Temerin; F. S. Mozer; C. A. Kletzing; J. D. Scudder; V. Streltsov; W. Lotko

    2002-01-01

    We present evidence based on measurements from the Polar spacecraft for the existence of small-scale, large-amplitude kinetic Alfvén waves\\/spikes at the plasma sheet boundary layer (PSBL) at altitudes of 4-6 RE. These structures coincide with larger-scale Alfvénic waves that carry a large net Poynting flux along magnetic field lines toward the Earth. Both structures are typically observed in the PSBL

  11. Plasma microwave electronics

    Microsoft Academic Search

    L. S. Bogdankevich; M. V. Kuzelev; Anri A. Rukhadze

    1981-01-01

    The theory of Cherenkov and cyclotron plasma sources of coherent microwave radiation excited by intense electron beams is reviewed systematically. The linear approximation of the theory yields the output frequency spectra, the wave growth rates, and the threshold electron beam currents required for exciting these sources. The general theory is illustrated for some particular devices: the forward-wave plasma Cherenkov source,

  12. Plasma relativistic microwave electronics

    Microsoft Academic Search

    M. V. Kuzelev; O. T. Loza; A. A. Rukhadze; P. S. Strelkov; A. G. Shkvarunets

    2001-01-01

    The principles of plasma relativistic microwave electronics based on the stimulated Cherenkov emission of electromagnetic\\u000a waves during the interaction of a relativistic electron beam with a plasma are formulated. A theory of relativistic Cherenkov\\u000a plasma microwave oscillators and amplifiers is developed, and model experimental devices are elaborated and investigated.\\u000a The emission mechanisms are studied theoretically. The efficiencies and frequency spectra

  13. Birkeland currents in the plasma sheet

    NASA Technical Reports Server (NTRS)

    Tsyganenko, Nikolai A.; Stern, David P.; Kaymaz, Zerefsan

    1993-01-01

    A search was conducted for the signatures of Birkeland currents in the Earth's magnetic tail, using observed values of B(sub x) and B(sub y) from large sets of spacecraft data. The data were binned by x and y for -10 greater than x(sub GSM) greater than -35 and absolute value of y(sub GSM) less than or equal to 20 R(sub E) (less than or equal to 30 R(sub E) for x(sub GSM) less than or equal to -25 R(sub E)) and in each bin their distribution in the (B(sub x), B(sub y)) plane was fitted by least squares to a piecewise linear function. That gave average x-y distributions of the flaring angle between B(sub xy) and the x direction, as well as that angle's variation across the thickness of the plasma sheet. Angles obtained in the central plasma sheet differed from those derived near the lobe boundary. That is the expected signature if earthward or tailward Birkeland current sheets are embedded in the plasma sheet, and from this dfiference we derived the dawn-dusk profiles of the tail Birkeland currents for several x(sub GSM) intervals. It was found that (1) the Birkeland currents have the sense of region 1 currents, when mapped to the ionosphere; (2) both the linear current density (kiloamperes/R(sub E)) and the net magnitude of the field-aligned currents decrease rapidly down the tail; (3) the total Birkeland current at x approximately equals -10 R(sub E) equals approximately equals 500-700 kA, which is approx. 30% of the net region 1 current observed at ionospheric altitudes, in agreement with model mapping results; and (4) the B(sub z) and B(sub y) components of the interplanetary magnetic field influence the distribution of Birkeland currents in the tail.

  14. Early results of microwave transmission experiments through an overly dense rectangular plasma sheet with microparticle injection

    SciTech Connect

    Gillman, Eric D., E-mail: eric.gillman.ctr@nrl.navy.mil [National Research Council Postdoctoral Associate at the U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Amatucci, W. E. [U.S. Naval Research Laboratory, Washington, DC 20375 (United States)

    2014-06-15

    These experiments utilize a linear hollow cathode to create a dense, rectangular plasma sheet to simulate the plasma layer surrounding vehicles traveling at hypersonic velocities within the Earth's atmosphere. Injection of fine dielectric microparticles significantly reduces the electron density and therefore lowers the electron plasma frequency by binding a significant portion of the bulk free electrons to the relatively massive microparticles. Measurements show that microwave transmission through this previously overly dense, impenetrable plasma layer increases with the injection of alumina microparticles approximately 60 ?m in diameter. This method of electron depletion is a potential means of mitigating the radio communications blackout experienced by hypersonic vehicles.

  15. Kinetic Theory of Dawson Plasma Sheet Model

    NASA Astrophysics Data System (ADS)

    Sano, Mitsusada M.; Kitahara, Kazuo

    2011-08-01

    A kinetic theory of one-dimensional plasma sheet model (Dawson model) is developed. The Vlasov equation, the Landau equation, and the Balescu--Lenard equation corresponding to this model are derived. For the Vlasov equation, it is shown that the linearized Vlasov equation exhibits a typical behavior of plasmas as in the three-dimensional space. The Landau collision term and the Balescu--Lenard collision term are identically zero. The fact of the vanishing collision term agrees with the behavior of generic one-dimesional systems. In an approximation that the system is in a thermal bath, the derived Landau equation and Balescu--Lenard equation are transformed into the Fokker--Planck equations. Some physical quantities such as thermal conductivity, relaxation rate, etc., are estimated. A discussion on physical meaning of these results, in particular, the zero collision terms, will be given.

  16. ISEE observations of the plasma sheet boundary, plasma sheet, and neutral sheet. I - Electric field, magnetic field, plasma, and ion composition

    NASA Technical Reports Server (NTRS)

    Cattell, C. A.; Mozer, F. S.; Hones, E. W., Jr.; Anderson, R. R.; Sharp, R. D.

    1986-01-01

    The first simultaneous study of dc and ac electric and magnetic fields, E x B velocity, plasma flows, ratio of plasma to magnetic field pressure, total energy density, energetic particles, and ion composition from the ISEE satellites and ground and interplanetary magnetic fields has been made to determine (1) the relationship of the previously observed electric fields at the plasma sheet boundary and at the neutral sheet to plasma parameters, and (2) whether the phenomena occurring during quiet and active times were consistent with the formation of a near-earth neutral line during substorms or with the boundary layer model. Five observations made during the study of two substorms were seen to be in agreement with the neutral-line model. The observations are consistent with the satellite being located at varying distances from the neutral line and diffusion region where reconnection and plasma acceleration were occurring. Although the z component (into or out of the ecliptic plane) of E x B convection was generally toward the neutral sheet, there were examples when it was consistent with the inferred motion of the plasma sheet past the satellite. A synthesis of previous reports on large electric fields at the plasma sheet boundary and variable fields at the neutral sheet including the associated plasma flows is also described.

  17. A pincer-shaped plasma sheet at Uranus

    NASA Technical Reports Server (NTRS)

    Hammond, C. Max; Walker, Raymond J.; Kivelson, Margaret G.

    1990-01-01

    An MHD simulation of the terrestrial magnetosphere, rescaled to represent the Uranian magnetotail, is carried out. The 3p immersion can be explained in terms of possible extreme departures from average plasma sheet shapes in the Uranian magnetosphere. The orientation of the Uranian dipole and rotation axes produce a dynamically curved plasma sheet which is an unusual feature of the Uranian magnetosphere.

  18. A two satellite study of nightside flux transfer events in the plasma sheet

    NASA Technical Reports Server (NTRS)

    Sergeev, V. A.; Elphic, R. C.; Mozer, F. S.; Saint-Marc, A.; Sauvaud, J. A.

    1992-01-01

    The short-term (about 1 min) events during two consecutive substorms on March 23 1979 have been studied using high time resolution measurements of magnetic and electric fields and of the kiloelectronvolt electron flux at X about -21 R(e). Data obtained make it possible to describe the localized magnetic structures transported or propagated within the plasma sheet and to identify these events as plasma sheet nightside magnetic flux transfer events (NFTEs). The best examples of the NFTEs found so far are all observed in a thin portion of plasma sheet where the contraction of the reconnected field lines dominates over the oppositely directed pressure gradient force. Systematic differences in the magnetic variations observed at ISEE-1 and 2 indicate current concentration at the outer plasma sheet boundary during the passage of a NFTE.

  19. Electric fields in the plasma sheet and plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Pedersen, A.; Knott, K.; Cattell, C. A.; Mozer, F. S.; Falthammar, C.-G.; Lindqvist, P.-A.; Manka, R. H.

    1985-01-01

    Results obtained by Forbes et al. (1981) on the basis of time delay measurements between ISEE 1 and ISEE 2 imply that the plasma flow and the boundary contracting velocity were nearly the same, whereas the expanding boundary velocity was not accompanied by any significant plasma sheet plasma motion. In the present study, this observation is discussed in conjunction with electric field data. The study is based on electric field data from the spherical double probe experiment on ISEE 1. Electric field data from GEOS 2 are used to some extent to monitor the electric fields near the geostationary orbit during the considered eve nts. Electric field data during CDAW 6 events are discussed, taking into account positions of ISEE 1/ISEE 2 and GEOS 2; March 22, 0600-1300 UT; and March 22, UT; and March 31, 1400-2400 UT.

  20. Experimental plasma relativistic microwave electronics

    Microsoft Academic Search

    Oleg T. Loza; Anatoly G. Shkvarunets; Pavel S. Strelkov

    1998-01-01

    The presence of plasma affects drastically the operation of microwave devices driven by high-current relativistic electron beams. Loading vacuum microwave oscillators with plasma changes the power and frequency band of the radiation. The Cherenkov plasma maser, that operates only with plasma inside, has both promising advantages and inherent disadvantages comparatively to the vacuum devices. Besides, plasma appears in a relativistic

  1. Convection-driven delivery of plasma sheet material to the inner magnetosphere.

    NASA Astrophysics Data System (ADS)

    Denton, M. H.; Thomsen, M. F.; Lavraud, B.; Skoug, R. M.; Henderson, M. G.; Funsten, H. O.; Jahn, J.; Pollock, C. J.; Weygand, J.

    2005-12-01

    We present data from the MENA instrument onboard the IMAGE satellite taken during a period of enhanced convection on 26 June 2001. During the interval, MENA observes energetic neutral atoms (ENAs) in the magnetotail and an Earthwards-propagating enhancement in their flux, at the same time as the convection strength increases (as measured by the Kp and MBI indices). Data from the magnetospheric plasma analyser (MPA) instrument onboard satellites in geosynchronous orbit indicate that enhanced ion and electron fluxes at plasma sheet energies (~1-45 keV) are detected at the same time as enhanced ENA flux are observed at the satellite location. We interpret the results as a convection-driven delivery of plasma sheet material, the ENA signature of which we observe with IMAGE/MENA. We use the rate of the propagation of the ENA enhancement to infer the speed of the plasma sheet delivery to the inner magnetosphere.

  2. Current Sheet in a non-Maxwellian collisionless plasma: Self-consistent theory, simulation, and comparison with spacecraft observations

    SciTech Connect

    Malova, Kh. V. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation); Zelenyi, L. M. [Russian Academy of Sciences, Institute for Space Research (Russian Federation); Mingalev, O. V.; Mingalev, I. V. [Russian Academy of Sciences, Polar Geophysics Institute, Kola Scientific Center (Russian Federation); Popov, V. Yu. [Russian Academy of Sciences, Institute for Space Research (Russian Federation); Artemyev, A. V. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation); Petrukovich, A. A. [Russian Academy of Sciences, Institute for Space Research (Russian Federation)

    2010-10-15

    A self-consistent theory is constructed of anisotropic current equilibria maintained in a non-Maxwellian plasma consisting of cold electrons and two hot ion components of different temperatures. The ion plasma components are described in the quasi-adiabatic approximation, and the plasma electrons, in the MHD approximation. Approximate steady solutions to the set of Vlasov-Maxwell equations are obtained and investigated parametrically. It is shown that the solutions can describe various current sheet profiles: from thin current structures with a maximum current density in the neutral sheet to comparatively 'thick' current sheets with two to three maxima of the current density. It is also shown that the electron plasma component predominates at the current sheet center and can maintain a narrow central peak in the current density. The ion plasma component predominates at the edge of the current sheet, thereby determining the characteristic sheet thickness. The results of numerical simulations of a two-temperature plasma by the macroparticle method are compared with the experimental data from the Cluster spacecraft. Good agreement between the theoretical, numerical, and experimental results leads to the conclusion that the theory developed here provides a fairly adequate description of collisionless current sheets in space plasmas.

  3. The dynamic expansion and contraction of the Jovian plasma sheet

    NASA Technical Reports Server (NTRS)

    Belcher, J. W.; Mcnutt, R. L., Jr.

    1980-01-01

    Observations suggesting the sequential expansion and compression of the Jovian plasma sheet are reported. Plasma flow in the vicinity of Jupiter was monitored by the four modulated-grid Faraday cups on board each of the Voyager spacecraft at times of closest Jupiter approach. Sensor measurements reveal the flow of magnetospheric plasma to be directed away from the equatorial current sheet near local noon and to be directed towards the sheet in the dusk to midnight sector. The observed flow patterns are interpreted in terms of short-time-scale perturbations of magnetic flux tubes due to the compression of the dayside magnetosphere by the solar wind. It is noted that such a dynamic motion is quite different from what would be expected of slower, quasi-static equilibrium plasma sheet expansion and contraction.

  4. Electrons, Ions and Plasmas

    NSDL National Science Digital Library

    Mendez, J.

    This series of web pages provides information on a range of topics regarding charged particles. Starting with the properties of atomic electrons, this material describes the Edison and photoelectric effects, the interaction between charged particles and magnetic fields, and the creation of plasmas and positive ions. Other topics, including the history of research on charges, are covered in linked pages. This is part of a series of non-mathematical, linked explorations of the Earth's Magnetosphere.

  5. Average electric wave spectra across the plasma sheet and their relation to ion bulk speed

    NASA Technical Reports Server (NTRS)

    Baumjohann, W.; Treumann, R. A.; Labelle, J.; Anderson, R. R.

    1989-01-01

    Using 4 months of tail data obtained by the ELF/MF spectrum analyzer of the wave experiment and the three-dimensional plasma instrument on board the AMPTE/IRM satellite, a statistical survey on the electric wave spectral density in the earth's plasma sheet has been conducted. More than 50,000 10-s-averaged electric wave spectra were analyzed with respect to differences between their values in the inner and outer central plasma sheet and the plasma sheet boundary layer as well as their dependence on radial distance and ion bulk speed. High-speed flows are dominated by broadband electrostatic noise with highest spectral densities in the plasma sheet boundary, where broadband electrostatic noise also exists during periods of low-speed flows. The broadband electrostatic noise has a typical spectral index of about -2. During low-speed flows the spectra in the central plasma sheet show distinct emissions at the electron cyclotron odd half-harmonic and upper hybrid frequency. Wave intensities during episodes of fast perpendicular flows are higher than those associated with fast parallel flows.

  6. Ballooning instability at the plasma sheet–lobe interface and its implications for polar arc formation

    Microsoft Academic Search

    I. V. Golovchanskaya; A. Kullen; Y. P. Maltsev; H. Biernat

    2006-01-01

    Huang et al. (1987, 1989) reported hot filaments of plasma sheet origin filling the magnetospheric lobes during northward interplanetary magnetic field (IMF). On the other hand, cold plasma transients of presumably lobe origin are often observed in the plasma sheet. These features can be interpreted in terms of plasma exchange at the plasma sheet–lobe interface (PSLI) proceeding in a filamentary

  7. Ballooning instability at the plasma sheet-lobe interface and its implications for polar arc formation

    Microsoft Academic Search

    I. V. Golovchanskaya; A. Kullen; Y. P. Maltsev; H. Biernat

    2006-01-01

    Huang et al. (1987, 1989) reported hot filaments of plasma sheet origin filling the magnetospheric lobes during northward interplanetary magnetic field (IMF). On the other hand, cold plasma transients of presumably lobe origin are often observed in the plasma sheet. These features can be interpreted in terms of plasma exchange at the plasma sheet-lobe interface (PSLI) proceeding in a filamentary

  8. Visualization of current sheet evolution in a pulsed plasma accelerator

    Microsoft Academic Search

    Thomas E. Markusic; John W. Berkery; Edgar Y. Choueiri

    2005-01-01

    High-speed photography and magnetic field probes were used to visualize and study the formation and propagation of current sheets in a pulsed plasma accelerator. Magnetic field measurements complement photographic records, as the latter indicate the location of the plasma but not necessarily current, whereas magnetic field data provide an unambiguous picture of the current location, but do not directly yield

  9. Properties and origin of subproton-scale magnetic holes in the terrestrial plasma sheet

    NASA Astrophysics Data System (ADS)

    Sundberg, T.; Burgess, D.; Haynes, C. T.

    2015-04-01

    Electron-scale magnetic depressions in the terrestrial plasma sheet are studied using Cluster multispacecraft data. The structures, which have an observed duration of ~5-10 s, are approximately 200-300 km wide in the direction of propagation, and they show an average reduction in the background magnetic field of 10-20%. A majority of the events are also associated with an increase in the high-energy high pitch angle electron flux, which indicates that the depressions are presumably generated by electrons with relatively high velocity perpendicular to the background magnetic field. Differences in the recorded electron spectra in the four spacecraft indicates a possible nongyrotropic structure. Multispacecraft measurements show that a subset of events are cylindrical, elongated along the magnetic field, and with a field-parallel scale size of at a minimum 500 km. Other events seem to be better described as electron-scale sheets, about 200-300 km thick. We find that no single formation mechanism can explain this variety of events observed. Instead, several processes may be operating in the plasma sheet, giving rise to similar magnetic field structures in the single-spacecraft data, but with different 3-D structuring. The cylindrical structures have several traits that are in agreement with the electron vortex magnetic holes observed in 2-D particle-in-cell simulations of turbulent relaxation, whereas the sheets, which show nearly identical signatures in the multispacecraft data, are better explained by propagating electron solitary waves.

  10. Ultrarelativistic Electron-Positron Plasma

    E-print Network

    Markus H. Thoma

    2008-10-06

    Ultrarelativistic electron-positron plasmas can be produced in high-intensity laser fields and play a role in various astrophysical situations. Their properties can be calculated using QED at finite temperature. Here we will use perturbative QED at finite temperature for calculating various important properties, such as the equation of state, dispersion relations of collective plasma modes of photons and electrons, Debye screening, damping rates, mean free paths, collision times, transport coefficients, and particle production rates, of ultrarelativistic electron-positron plasmas. In particular, we will focus on electron-positron plasmas produced with ultra-strong lasers.

  11. Plasma Sheet Velocity Measurement Techniques for the Pulsed Plasma Thruster SIMP-LEX

    NASA Technical Reports Server (NTRS)

    Nawaz, Anuscheh; Lau, Matthew

    2011-01-01

    The velocity of the first plasma sheet was determined between the electrodes of a pulsed plasma thruster using three measurement techniques: time of flight probe, high speed camera and magnetic field probe. Further, for time of flight probe and magnetic field probe, it was possible to determine the velocity distribution along the electrodes, as the plasma sheet is accelerated. The results from all three techniques are shown, and are compared for one thruster geometry.

  12. Microwave Reflections from a VUV Laser Produced Plasma Sheet

    Microsoft Academic Search

    K. L. Kelly; J. E. Scharer; G. Ding; M. Bettenhausen; D. Sinitsyn

    1996-01-01

    A Vacuum Ultra-Violet (VUV) Laser is utilized for creation of a plasma sheet in a low-ionization-energy organic gas. Microwaves from an X-band horn antenna impinge on the sheet where they are reflected. A bi-static antenna system is used for detecting the microwave radiation. Heterodyne and homodyne detection systems are investigated. Reflected signals are measured for amplitude and phase analysis. Comparable

  13. Microwave reflections from a VUV laser produced plasma sheet

    Microsoft Academic Search

    K. L. Kelly; J. E. Scharer; W. Shen; G. Ding; M. H. Bettenhausen; N. T. Lam

    1996-01-01

    Summary form only given. A Vacuum Ultra-Violet (VUV) laser pulse is used to create a plasma sheet in a low-ionization-energy organic gas. Microwaves from a highly directive X-band horn antenna impinge on the sheet where they are reflected. A bi-static antenna system is used for transmitting and receiving the microwave radiation. Both heterodyne and homodyne detection systems are investigated for

  14. Plasma sheet flow damping by oscillatory flow braking

    NASA Astrophysics Data System (ADS)

    Panov, Evgeny V.; Leontyeva, Olga S.; Baumjohann, Wolfgang; Nakamura, Rumi; Amm, Olaf; Angelopoulos, Vassilis; Glassmeier, Karl-Heinz; Kubyshkina, Marina V.; Petrukovich, Anatoli A.; Sergeev, Victor A.; Weygand, James M.

    2015-04-01

    Using simultaneous observations in the near-Earth plasma sheet by five Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes, conjugate ground all-sky camera observations from Canada, and magnetometer networks over North America, we show that auroral bulge dynamics is modulated by a recently discovered process known as oscillatory flow braking, which occurs at about 10 Earth radii down the Earth's magnetotail. In oscillatory flow breaking, plasma sheet flows oscillating with different periods at various distances collide, producing pressure forces that exert shear stresses on the magnetic field, transiently amplifying the vertical magnetic field component. Sporadic fast relief of these stresses through significant particle precipitations causes damping of plasma sheet fast flows.

  15. Low-temperature synthesis of thin graphite sheets using plasma-assisted thermal chemical vapor deposition system

    Microsoft Academic Search

    Byeong-Joo Lee; Taeg-Woo Lee; Serin Park; Han-Young Yu; Jeong-O Lee; Sung-Hwan Lim; Goo-Hwan Jeong

    2011-01-01

    We report the low-temperature synthesis of thin graphite sheets using a hybrid chemical vapor deposition (HCVD) system that combines plasma and thermal CVD (TCVD). Electron beam deposited Ni films were used as catalytic substrates, and methane was used as a carbon feedstock. The quartz tube was into two regions: core plasma region for efficient dissociation of methane and a TCVD

  16. Enhancement mechanism of H- production and suitable configurations for materials processing in a magnetized sheet plasma

    NASA Astrophysics Data System (ADS)

    Ramos, Henry J.; Villamayor, Michelle Marie S.; Mella, Aubrey Faith M.; Salamania, Janella Mae R.; Villanueva, Matthew Bryan P.; Viloan, Rommel Paulo B.

    2014-08-01

    A magnetized sheet plasma ion source was developed for steady state high density plasma with strong density and high temperature gradients. This feature provides efficient formation of negative hydrogen (H-) ions over a wide beam extraction area through the electron volume process. A hexapole confinement at the cathode, addition of argon and magnesium seeding led to the increase of H- yield. The device configuration is suitable for plasma based materials processing namely, synthesis of TiN, SiH, SnO2, and the formation of advanced MAX phase materials Ti2AlC, Ti2CdC and NbAlC.

  17. Plasma electron analysis: Voyager plasma science experiment

    NASA Technical Reports Server (NTRS)

    Sittler, E. C., Jr.

    1983-01-01

    The Plasma Science Experiment (PLS) on the Voyager spacecraft provide data on the plasma ions and electrons in the interplanetary medium and the magnetospheres of the giant planets Jupiter and Saturn. A description of the analysis used to obtain electron parameters (density, temperature, etc.) from the plasma science experiment PLS electron measurements which cover the energy range from 10 eV to 5950 eV is presented. The electron sensor (D cup) and its transmission characteristics are described. A derivation of the fundamental analytical expression of the reduced distribution function F(e) is given. The electron distribution function F(e), used in the moment integrations, can be derived from F(e). Positive ions produce a correction current (ion feedthrough) to the measured electron current, which can be important to the measurements of the suprathermal electron component. In the case of Saturn, this correction current, which can either add to or subtract from the measured electron current, is less than 20% of the measured signal at all times. Comments about the corrections introduced by spacecraft charging to the Saturn encounter data, which can be important in regions of high density and shadow when the spacecraft can become negatively charged are introduced.

  18. Plasma Propagation Through Porous Dielectric Sheets

    Microsoft Academic Search

    Mingmei Wang; John E. Foster; Mark J. Kushner

    2011-01-01

    TMOSPHERIC-PRESSURE plasmas (APPs) in dielectric barrier discharge (DBD) configurations are widely used for remediation of toxic gases. One such configuration is a packed-bed reactor where the plasma flows along the surface of high-dielectric-constant (?) beads where electric fields are intensified by the gradient in ? [1]. Typical DBD plasmas operate in air at atmospheric pressure at a few to tens

  19. Space Charge Effect in the Sheet and Solid Electron Beam

    NASA Astrophysics Data System (ADS)

    Song, Ho Young; Kim, Hyoung Suk; Ahn, Saeyoung

    1998-11-01

    We analyze the space charge effect of two different types of electron beam ; sheet and solid electron beam. Electron gun simulations are carried out using shadow and control grids for high and low perveance. Rectangular and cylindrical geometries are used for sheet and solid electron beam in planar and disk type cathode. The E-gun code is used to study the limiting current and space charge loading in each geometries.

  20. Contribution of low-energy ionospheric protons to the plasma sheet

    NASA Technical Reports Server (NTRS)

    Delcourt, D. C.; Moore, T. E.; Chappell, C. R.

    1994-01-01

    The magnetospheric transport of low-energy ionospheric ions is examined by means of three-dimensional particle codes. Emphasis is placed on the behavior of polar wind and cleft originating protons. It is demonstrated that, via nonadiabatic motion inside the neutral sheet, these ions can significantly contribute to the populations of the plasma sheet. The importance of this contribution is found to depend critically upon the dynamics of particles originating from the highest latitudes, as these possibly have access to the distant tail. Hence it is shown that polar wind H(+) expelled into the magnetosphere at very low energies (in the electron volt range) preferentially feed the plasma sheet during quiet times, experiencing accelerations up to several kiloelectron volts upon return into the inner magnetosphere. In contrast, during disturbed times, the intensifying magnetospheric convection confines this population to low L shells where it travels in a nearly adiabatic manner. As for the protons originating from the cleft fountain, the simulations reveal that they can be transported up to the vicinity of the distant neutral line in the nightside sector. Via interaction with the neutral sheet, these ionospheric ions are rapidly raised to the characteristic plasma sheet energy range. The density levels contributed by these populations are quite substantial when compared to those measured in situ. These simulations establish an active role of low-energy ionospheric ions in the overall magnetospheric dynamics.

  1. Tail plasma sheet models derived from Geotail particle data

    Microsoft Academic Search

    N. A. Tsyganenko; T. Mukai

    2003-01-01

    Simple analytical models have been derived for the first time, describing the 2-D distribution (along and across the Earth's magnetotail) of the central plasma sheet (CPS) ion temperature, density, and pressure, as functions of the incoming solar wind and interplanetary magnetic field (IMF) parameters, at distances between 10 and 50 RE. The models are based on a large set of

  2. Kinetic theory of the electron bounce instability in two dimensional current sheets—Full electromagnetic treatment

    SciTech Connect

    Tur, A.; Fruit, G.; Louarn, P. [Institut de Recherche en Astrophysique et Planétologie (IRAP), CNRS UMR5277/Université Paul Sabatier, Toulouse (France)] [Institut de Recherche en Astrophysique et Planétologie (IRAP), CNRS UMR5277/Université Paul Sabatier, Toulouse (France); Yanovsky, V. [Institute for Single Crystals, National Academy of Sciences of Ukraine, Kharkov 61001 (Ukraine)] [Institute for Single Crystals, National Academy of Sciences of Ukraine, Kharkov 61001 (Ukraine)

    2014-03-15

    In the general context of understanding the possible destabilization of a current sheet with applications to magnetospheric substorms or solar flares, a kinetic model is proposed for studying the resonant interaction between electromagnetic fluctuations and trapped bouncing electrons in a 2D current sheet. Tur et al. [A. Tur et al., Phys. Plasmas 17, 102905 (2010)] and Fruit et al. [G. Fruit et al., Phys. Plasmas 20, 022113 (2013)] already used this model to investigate the possibilities of electrostatic instabilities. Here, the model is completed for full electromagnetic perturbations. Starting with a modified Harris sheet as equilibrium state, the linearized gyrokinetic Vlasov equation is solved for electromagnetic fluctuations with period of the order of the electron bounce period. The particle motion is restricted to its first Fourier component along the magnetic field and this allows the complete time integration of the non local perturbed distribution functions. The dispersion relation for electromagnetic modes is finally obtained through the quasineutrality condition and the Ampere's law for the current density. It is found that for mildly strechted current, undamped modes oscillate at typical electron bounce frequency with wavelength of the order of the plasma sheet half thickness. As the stretching of the plasma sheet becomes more intense, the frequency of these normal modes decreases and beyond a certain threshold in ??=?B{sub z}/B{sub lobes}, the mode becomes explosive with typical growth rate of a few tens of seconds. The free energy contained in the bouncing motion of the electrons may trigger an electromagnetic instability able to disrupt the cross-tail current in a few seconds. This new instability–electromagnetic electron-bounce instability–may explain fast and global scale destabilization of current sheets as required to describe substorm phenomena.

  3. Comparison of plasma sheet ion composition with the IMF and solar wind plasma

    NASA Technical Reports Server (NTRS)

    Lennartsson, W.

    1988-01-01

    Plasma sheet energetic ion data (0.1- to 16 keV/e) obtained by the Plasma Composition Experiment on ISEE-1 between 10 and 23 earth radii are compared with concurrent IMF and solar wind plasma data. The densities of H(+) and He(++) ions in the plasma sheet are found to be the highest, and the most nearly proportional to the solar wind density, when the IMF B(z) is not northward. The density of terrestrial O(+) ions increases strongly with increasing magnitude of the IMF, in apparent agreement with the notion that the IMF plays a fundamental role in the electric coupling between the solar wind and the ionosphere.

  4. On the cause of X-line formation in the near-Earth plasma sheet: Results of adiabatic convection of plasma-sheet plasma

    NASA Astrophysics Data System (ADS)

    Erickson, G. M.

    Self-consistent, static-equilibrium solutions are presented for two-dimensional magnetospheric-magnetic-field configurations with isotropic thermal pressure. These solutions include a dipole field and are not restricted to the asymptotic theory. Adiabatic convection of plasma sheet flux tubes is modeled as a series of static-equilibrium solutions in which flux tubes conserve their PV? as they convect, which resulted in time dependent magnetospheric configurations. Specifically it is found that a deep minimum in the equatorial Bz develops in the inner plasma sheet, thereby causing the magneticfield configuration to become more stretched and tail-like in time. These results suggest X-line formation in the inner plasma sheet as a consequence of lossless, adiabatic convection of plasma sheet flux tubes.

  5. Transport of plasma sheet material to the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Denton, M. H.; Thomsen, M. F.; Lavraud, B.; Henderson, M. G.; Skoug, R. M.; Funsten, H. O.; Jahn, J.-M.; Pollock, C. J.; Weygand, J. M.

    2007-02-01

    The reaction of the plasma sheet in response to an increase in magnetospheric convection is examined using a combination of energetic neutral atom (ENA) imaging and in situ observations. Data from the IMAGE/MENA instrument are examined in conjunction with observations from the magnetospheric plasma analyzer (MPA) instrument onboard the Los Alamos 1994-084 satellite located in geosynchronous orbit. Examination of the MENA data during an enhanced convection event reveal that between 12:00 and 14:30 UT on 26 June 2001, ENA emissions from the plasma sheet material are observed to strengthen and move Earthwards. A simple calculation of the motion of the peak in ENA emissions following an increase in the convection gives an averaged speed of this sunward surge of around 8 km s-1 between 12:00 and 14:30 UT.

  6. Experimental study of XUV laser produced plasma sheet for microwave agile mirror application

    SciTech Connect

    Shen, W.; Scharer, J.E.; Porter, B.G.; Lam, N.T.; Kelly, K.L. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Electrical and Computer Engineering

    1995-12-31

    An excimer-laser ({lambda} = 193 nm, {tau} = 17 nS, E = 20 mJ) along with a cylindrical lens system is utilized to produce a sheet plasma in an organic gas (TMAE). The plasma has a peak density of 3.5 {times} 10{sup 13} cm{sup {minus}3} and a ``sheet`` like profile of 0.2--0.7 cm x 8 cm x 20 cm. The effect of the lens system on the plasma sheet thickness is examined. The triple probe measured plasma temperature agrees with the postulation of single-photon absorption-ionization process. The plasma density spatial decay along the laser beam, which is associated with TMAE photon absorption length, is measured. The absorption length is found to be a function of base pressure of the neutral working gas. The authors have obtained an optimal window of TMAE base pressure at 50--150 mTorr. Within this optimal pressure range a plasma formation can have a long absorption length, relatively high plasma density, and lifetime of 5 {micro}s. A 1-D plasma diffusion model is proposed and solved both analytically and numerically. Comparison of the modeling and the measured results yields accurate values for the plasma diffusion and recombination coefficients. The electron-ion recombination coefficient is determined to be 2.4 {times} 10{sup {minus}6} cm{sup 3} s{sup {minus}1}. This is within 30% of that previously reported measurement without a lens system. The study indicates that plasma dynamics is dominated by the recombination process except for a very short period after the laser pulse is turned off.

  7. Laboratory Investigations of Current Sheets at the Electron Skin Depth Scale

    NASA Astrophysics Data System (ADS)

    Vincena, S.; Gekelman, W.

    2005-12-01

    Laboratory Investigations of Current Sheets at the Electron Skin Depth Scale. Theoretical investigations, in situ spacecraft and rocket missions, and laboratory studies form an essential triad for understanding the variety of current sheet phenomena found in space plasmas. In the Large Plasma Device (LAPD) at UCLA, the formation dynamics, equilibrium state, and wave-mediated disruptions of current sheets can be studied with great spatial and temporal resolution using a variety of probes as well as non-invasive laser induced fluorescence and other optical diagnostics. The LAPD is aptly suited for studying current sheets flowing in a magnetized background plasma which is capable of supporting Alfvén waves. The cylindrical device is 20m long and one meter in diameter with a solenoidal magnetic field as high as 3000 Gauss. For the parameters in this experiment, the plasma column is ten shear Alfvén wavelengths along the field and 100 electron inertial lengths (?e) (or 200 ?i) in the perpendicular direction. An electron current sheet is created in the plasma by placing a thin copper plate in the plasma column at one end of the device and pulsing this plate positive with respect to the chamber wall. The current sheet extends for the length of the device and has an initial cross-field size of roughly 45 ?e by 0.5?e. A parallel flow of ions is observed with similar dimensions and moves in the same direction as the electrons in the current sheet with a velocity of 0.2 times the ion sound speed. A much weaker sheared perpendicular flow is also measured. Cross-sections of the ion flow are measured at several axial locations over a distance of six meters. Second, as the ion flow increases in magnitude, a much broader (8?i) density depletion (n=0.25nO) develops around the flow. The gradient scale length of the depletion shortens until the spontaneous growth of drift waves occurs. This disrupts the electron current and ion flow, and leads to cross-field transport of plasma and a relaxation of the density gradient. The process of steepening and disruption repeats during the bias pulse. Detailed two-dimensional correlation measurements reveal the density and magnetic field propagation of the waves and statistics on the wave fluctuations.

  8. Survey of the plasma electron environment of Jupiter: A view from Voyager

    NASA Technical Reports Server (NTRS)

    Scudder, J. D.; Sittler, E. C., Jr.; Bridge, H. S.

    1980-01-01

    The plasma environment within Jupiter's bow shock is considered in terms of the in situ, calibrated electron plasma measurements made between 10 eV and 5.95 keV by the Voyager plasma science experiment (PLS). Measurements were analyzed and corrected for spacecraft potential variations; the data were reduced to nearly model independent macroscopic parameters of the local electron density and temperature. It is tentatively concluded that the radial temperature profile within the plasma sheet is caused by the intermixing of two different electron populations that probably have different temporal histories and spatial paths to their local observation. The cool plasma source of the plasma sheet and spikes is probably the Io plasma torus and arrives in the plasma sheet as a result of flux tube interchange motions or other generalized transport which can be accomplished without diverting the plasma from the centrifugal equator. The hot suprathermal populations in the plasma sheet have most recently come from the sparse, hot mid-latitude "bath" of electrons which were directly observed juxtaposed to the plasma sheet.

  9. Development of a volume production type hydrogen negative ion source by using sheet plasma

    NASA Astrophysics Data System (ADS)

    Matsumoto, Satoki; Iijima, Takaaki; Tonegawa, Akira; Sato, Kohnosuke; Kawamura, Kazutaka

    2014-10-01

    Stationary production of negative ions are important to play an essential role in Neutral beam injection (NBI). Cesium seeded Surface-production of negative ion sources are used for NBI. However, Cesium seeded surface- production of negative ion sources are not desirable from the point of view of operating steady state ion sources. We carried out the development of negative ion sources by volume-production in hydrogen sheet plasma. Production of hydrogen negative ions through volume processes needs both high energy electron region and low energy electron region. The sheet plasma is suitable for the production of negative ions, because the electron temperature in the central region of the plasma as high as 10-15 eV, whereas in the periphery of the plasma, a low temperature of a few eV of obtained. The hydrogen negative ions density were detected using an omegatron mass analyzer, while the electron density and temperature were measured using a Langmuir probe. Negative ions current extracted from the grid are measured by Faraday-cup.

  10. Substorm-associated lower hybrid waves in the plasma sheet observed by ISEE 1

    NASA Technical Reports Server (NTRS)

    Cattell, C. A.; Mozer, F. S.

    1987-01-01

    Observations of the electric field at frequencies from 2-128 Hz, using the burst mode of the spherical double probe on ISEE 1, have been examined for a time period previously identified as containing the traversal of a near-earth neutral line past the satellite. Intense waves (3 to over 30 mV/m) at approximately half the lower hybrid frequency were observed throughout the plasma sheet from the neutral sheet to the boundary, but only during the period of the large dc electric field and E x B velocity associated with the substorm neutral line. The wave number deduced from linear fits of the data was comparable to the inverse electron gyroradius. These results are consistent with the lower-hybrid drift instability. Although peaks between the ion and electron plasma frequency were sometimes observed simultaneously, the integrated power below 100 Hz was usually at least one to two orders of magnitude greater than that above 100 Hz. Although theoretical work has suggested that the instability would be suppressed at the neutral sheet, the largest waves observed occurred right at the neutral sheet when the southward component of the magnetic field was 6 gamma. The observed waves could provide an anomalous resistivity of about (3-1000) x 10 to the -7th S (compared to the classical value of 1 x 10 to the -18th S).

  11. Sheet Fluorescence and Annular Analysis of Ultracold Neutral Plasmas

    SciTech Connect

    Castro, J.; Gao, H.; Killian, T. C. [Rice University, Department of Physics and Astronomy, 6100 Main St., Houston, Texas, 77005 (United States)

    2009-03-30

    Annular analysis of fluorescence imaging measurements on Ultracold Neutral Plasmas (UNPs) is demonstrated. Spatially-resolved fluorescence imaging of the strontium ions produces a spectrum that is Doppler-broadened due to the thermal ion velocity and shifted due to the ion expansion velocity. The fluorescence excitation beam is spatially narrowed into a sheet, allowing for localized analysis of ion temperatures within a volume of the plasma with small density variation. Annular analysis of fluorescence images permits an enhanced signal-to-noise ratio compared to previous fluorescence measurements done in strontium UNPs. Using this technique and analysis, plasma ion temperatures are measured and shown to display characteristics of plasmas with strong coupling such as disorder induced heating and kinetic energy oscillations.

  12. On the 3-dimensional structure of plasmoids. [in near-earth plasma sheets

    NASA Technical Reports Server (NTRS)

    Hughes, W. J.; Sibeck, D. G.

    1987-01-01

    The hypothesis that the IMF penetrates plasmoids causing them to be three- rather than two-dimensional is tested by comparing observations of By within plasmoids and related tail structures to upstream IMF By data. The magnetic topologies that result from the mergings of closed plasma sheet flux tubes and open tail lobe flux tubes at a near-earth neutral line, and merging near the tail flanks are described and studied. The particle signals and isotropic electron distributions are examined. It is observed that the IMF By penetrates plasmoids and that their structure is three-dimensional. In the three-dimensional model of plasmoids the reconnected plasma sheet field lines form a magnetic flux-ropelike structure. The three-dimensional model is utilized to analyze stagnant, slowly moving and earthward moving structures.

  13. Cluster observations of plasma sheet energy conversion near dipolarization fronts

    NASA Astrophysics Data System (ADS)

    Hamrin, M.; Norqvist, P.; Karlsson, T.; Nilsson, H.; Pitkänen, T.; Fu, H.; Marghitu, O.

    2013-12-01

    Bursty bulk flows (BBFs) play an important role for the mass, energy and magnetic flux transport in the plasma sheet. The flow pattern in and around a BBF is often rather complicated and it has important consequences for the localized energy conversion between the electromagnetic and plasma mechanical energy forms. A dipolarization front (DF) is often observed at the leading edge of a BBF, and a flux pileup region (FPR) behind the DFs. Return flows and plasma vortices are expected to exist at the the flanks of the main flow channel. Here we present Cluster measurements of the flow pattern and energy conversion near DFs observed in the plasma sheet. We discuss the energy conversion properties during various stages of the FPR evolution. By using a statistical data base of Cluster data we show that it is likely that an early stage FPR corresponds to a generator, consistent with the FPR build-up, while an FPR in its later stage corresponds to a load, as expected for the FPR decay.

  14. Evidence for lobe reconnection as a source mechanism for the cold dense plasma sheet

    Microsoft Academic Search

    Mark Wilber; James McFadden; Kristen Brown; Wenhui Li; Joachim Raeder

    2010-01-01

    Initial observations of cold, dense plasma sheet (CDPS) regions by equatorial spacecraft indicated that they occur during extended intervals of northward IMF near the low latitude boundary layer (LLBL). Since CDPS domains have plasma characteristics intermediate between the plasma sheet and the magnetosheath, the latter has long been considered a candidate source. During northward IMF the flanks of the LLBL

  15. Increases in plasma sheet temperature with solar wind driving during substorm growth phases

    NASA Astrophysics Data System (ADS)

    Forsyth, C.; Watt, C. E. J.; Rae, I. J.; Fazakerley, A. N.; Kalmoni, N. M. E.; Freeman, M. P.; Boakes, P. D.; Nakamura, R.; Dandouras, I.; Kistler, L. M.; Jackman, C. M.; Coxon, J. C.; Carr, C. M.

    2014-12-01

    During substorm growth phases, magnetic reconnection at the magnetopause extracts ~1015 J from the solar wind which is then stored in the magnetotail lobes. Plasma sheet pressure increases to balance magnetic flux density increases in the lobes. Here we examine plasma sheet pressure, density, and temperature during substorm growth phases using 9 years of Cluster data (>316,000 data points). We show that plasma sheet pressure and temperature are higher during growth phases with higher solar wind driving, whereas the density is approximately constant. We also show a weak correlation between plasma sheet temperature before onset and the minimum SuperMAG AL (SML) auroral index in the subsequent substorm. We discuss how energization of the plasma sheet before onset may result from thermodynamically adiabatic processes; how hotter plasma sheets may result in magnetotail instabilities, and how this relates to the onset and size of the subsequent substorm expansion phase.

  16. Increases in plasma sheet temperature with solar wind driving during substorm growth phases

    PubMed Central

    Forsyth, C; Watt, C E J; Rae, I J; Fazakerley, A N; Kalmoni, N M E; Freeman, M P; Boakes, P D; Nakamura, R; Dandouras, I; Kistler, L M; Jackman, C M; Coxon, J C; Carr, C M

    2014-01-01

    During substorm growth phases, magnetic reconnection at the magnetopause extracts ?1015?J from the solar wind which is then stored in the magnetotail lobes. Plasma sheet pressure increases to balance magnetic flux density increases in the lobes. Here we examine plasma sheet pressure, density, and temperature during substorm growth phases using 9 years of Cluster data (>316,000 data points). We show that plasma sheet pressure and temperature are higher during growth phases with higher solar wind driving, whereas the density is approximately constant. We also show a weak correlation between plasma sheet temperature before onset and the minimum SuperMAG AL (SML) auroral index in the subsequent substorm. We discuss how energization of the plasma sheet before onset may result from thermodynamically adiabatic processes; how hotter plasma sheets may result in magnetotail instabilities, and how this relates to the onset and size of the subsequent substorm expansion phase.

  17. Large scale instabilities and dynamics of the magnetotail plasma sheet

    SciTech Connect

    Birn, J.; Schindler, K.

    1986-01-01

    The stability properties of the magnetotail current sheet against large scale modes is reviewed in the framework of ideal MHD, resistive MHD, and collisionless Vlasov theory. It appears that the small deviations from a plane sheet pinch (in particular a magnetic field component normal to the sheet) are important to explain the transition of the tail from a quiet stable state to an unstable dynamic state. It is found that the tail is essentially stable in ideal MHD, but unstable in resistive MHD, while both stable and unstable configurations are found within collisionless theory. The results favor an interpretation where the onset of magnetotail dyanmics leading to a sudden thinning of the plasma sheet and the ejection of a plasmoid is caused by the onset of a collisionless instability that either directly leads to the growth of a collisionless tearing mode or via microscopic turbulence to the growth of a resistive mode. The actual onset conditions are not fully explored yet by rigorous methods. The onset may be triggered by local conditions as well as by boundary conditions at the ionosphere or at the magnetopause (resulting from solar wind conditions). 53 refs., 5 figs.

  18. Study of plasma flow reversal in the near-Earth plasma sheet using numerical computations

    NASA Astrophysics Data System (ADS)

    Kondoh, Koji; Shimizu, Tohru

    2014-12-01

    Tailward flow in the near-Earth plasma sheet associated with a rebound of the earthward bursty bulk flow (BBF) is investigated using three-dimensional magnetohydrodynamics simulations of magnetic reconnection in the magnetotail on the basis of the spontaneous fast reconnection model. In order to investigate the properties of this tailward flow, virtual satellites are located at different positions in the plasma sheet within the simulation region, so that we can directly observe the temporal variations of plasma quantities in accordance with the growth and preceding the flow reversal associated with the magnetic reconnection. The time profile of the plasma flow velocity in the course of the BBF depends on the satellite position. Furthermore, the time profile of the magnetic field strength in the course of the reverse flow depends on the satellite position in the dawn-dusk direction. As a result of the rebound of the earthward flow, the accumulation of the plasma density and the plasma pressure is observed at any position in the plasma sheet during the interval between the BBF and the reverse flow.

  19. Topological Features of a Compressible Plasma Vortex Sheet: 6 Cases

    NSDL National Science Digital Library

    Cindy Starr

    1993-12-17

    The Voyager and Pioneer Spacecraft have detected large-scale quasi-periodic plasma fluctuations in the outer heliosphere beyond 20 AU. A plasma vortex sheet model can explain these fluctuations and the observed correlations between various physical variables. The large scale outer heliosphere is modeled by solving the 3-D compressible magnetohydrodynamic equations involving three interacting shear layers. Computations were done on a Cray computer at the NASA Center for Computational Sciences. Six cases are animated: Weak magnetic field and strong magnetic field, each at three values of tau, the vortex street characteristic time. Contours of density are shown as dark transparent tubes. Critical points of the velocity field are represented by Glyphs. Vortex cores are shown in orange and blue.

  20. Kinetic electron bounce instability in a 2D current sheet - Implication for substorm dynamics

    NASA Astrophysics Data System (ADS)

    Fruit, G.; Tur, A.; Louarn, P.

    2013-12-01

    In the general context of understanding the possible destabilization of the magnetotail before a substorm, we propose a kinetic model for electromagnetic ballooning-type instabilities in resonant interaction with trapped bouncing electrons in a 2D current sheet. Tur et al. 2010 and Fruit et al. 2013 already used this model to investigate the possibilities of electrostatic instabilities. Here, we generalize the model for full electromagnetic perturbations. Starting with a modified Harris sheet as equilibrium state, the linearized gyrokinetic Vlasov equation is solved for electromagnetic fluctuations with period of the order of the electron bounce period. The particle motion is restricted to its first Fourier component along the magnetic field and this allows the complete time integration of the non local perturbed distribution functions. The dispersion relation for electromagnetic modes is finally obtained through the quasineutrality condition and the Ampere's law for the current density. It is found that for mildly stretched current sheet (Bz > 0.1 Blobes) undamped and stable modes oscillate at typical electron bounce frequency with wavelength (in y) of the order of the plasma sheet thickness. As the stretching of the plasma sheet becomes more intense, the frequency of these normal modes decreases and beyond a certain threshold in epsilon=Bz/Blobes < 0.05 typically, the mode becomes explosive (pure imaginary frequency) with typical growing rate of a few tens of seconds. The free energy contained in the electron bouncing motion could thus trigger and drive an electromagnetic instability able to disrupt the cross-tail current in a few seconds. The role of the temperature ratio Te/Ti is also evaluated.

  1. Tailward leap of multiple expansions of the plasma sheet during a moderately intense substorm: THEMIS observations

    E-print Network

    California at Berkeley, University of

    Tailward leap of multiple expansions of the plasma sheet during a moderately intense substorm as measured by different probes. The positions of the plasma sheet expansions have a tailward leap progression type is the dipolarization front which is associated with the bursty bulk flow (BBF). While the second

  2. Magnetized electron-positron plasmas

    E-print Network

    C. R. Stark; D. A. Diver; A. A. da Costa

    2006-12-22

    Electrostatic oscillations in cold electron-positron plasmas can be coupled to a propagating electromagnetic mode if the background magnetic field is inhomogeneous. Previous work considered this coupling in the quasi-linear regime, successfully simulating the electromagnetic mode. Here we present a stability analysis of the non-linear problem, perturbed from dynamical equilibrium, in order to gain some insight into the modes present in the system.

  3. Generation of microwave free-electron laser radiation using sheet electron beam and planar electromagnetic wiggler

    Microsoft Academic Search

    A. V. Ravi Kumar; K. K. Mohandas; K. K. Jain

    1998-01-01

    An experimental study of sheet electron beam propagation through a planar electromagnetic wiggler and generation of microwave radiation by free-electron laser action has been carried out. The space charge dominated sheet electron beam of energy ~100-200 keV, current 50-150 A, and pulsewidth of 100-150 ns was propagated through a 20-period planar electromagnetic wiggler. Significant enhancement in the beam transmission through

  4. Energy efficiency of electron plasma emitters

    SciTech Connect

    Zalesski, V. G., E-mail: V.Zalesski@mail.ru [Polotsk State University (Belarus)

    2011-12-15

    Electron emission influence from gas-discharge plasma on plasma emitter energy parameters is considered. It is shown, that electron emission from plasma is accompanied by energy contribution redistribution in the gas-discharge from plasma emitter supplies sources-the gas-discharge power supply and the accelerating voltage power supply. Some modes of electron emission as a result can be realized: 'a probe measurements mode,' 'a transitive mode,' and 'a full switching mode.'.

  5. Effects of plasma sheet condition on the evolution of shielding and the Harang reversal under weak convection: RCM simulations

    NASA Astrophysics Data System (ADS)

    Gkioulidou, M.; Lyons, L. R.; Wang, C.; Wolf, R. A.

    2007-12-01

    Shielding of the convection electric field and the Harang reversal associated with the region 2 field-aligned current system are fundamental manifestations of the large-scale plasma transport within the tail plasma sheet and the electrodynamic coupling of this transport to the ionosphere. However, how their formation and evolution is affected by the plasma sheet density and temperature is not well understood. We have used the RCM with Tsyganenko 96 magnetic field model to investigate this effect of plasma sheet conditions under weak convection. We have found that the existence of an overlap in local time of Region 2 upward and downward field aligned currents is necessary for the formation of the Harang reversal. The downward field aligned current in this overlap region is associated with electrons and low energy ions, while the upward field aligned current is associated with high-energy ions. Higher plasma sheet pressure can cause quicker shielding of the penetration electric field. If the time scale of the shielding is much shorter than the drift time scale of the low energy particles, these low energy particles cannot penetrate earthward enough to cause the overlap, thus preventing formation of the Harang reversal. Under the same plasma sheet pressure, higher auroral conductance can result in slower shielding. Higher plasma temperature enhances the upward field-aligned currents in the overlap region, therefore leading to a stronger Harang reversal. Currently we are running the simulation under different strengths of convection and with more realistic MLT dependent boundary conditions based on the Geotail observations.

  6. A Gridded Electron Gun for a Sheet Beam Klystron

    Microsoft Academic Search

    M. E. Read; G. Miram; R. L. Ives; V. Ivanov; A. Krasnykh

    2008-01-01

    This paper describes the development of an electron gun for a sheet beam klystron. Initially intended for accelerator applications, the gun can operate at a higher perveance than one with a cylindrically symmetric beam. Results of 2D and 3D simulations are discussed.

  7. A gridded electron gun for a sheet beam klystron

    Microsoft Academic Search

    M. E. Read; G. Miram; R. L. Ives; V. Ivanov; A. Krasnykh

    2003-01-01

    This paper describes the development of an electron gun for a sheet beam klystron. Initially intended for accelerator applications, the gun can operate at a higher perveance than one with a cylindrically symmetric beam. Results of 2D and 3D simulations are discussed.

  8. A gridded electron gun for a sheet beam klystron

    Microsoft Academic Search

    M. E. Read; G. Miram; R. L. Ives; V. Ivanov; A. Krasnykh

    2003-01-01

    In this paper we propose a gridded electron gun(dispenser-cathode gun) for sheet beam devices. The current generation of accelerators typically use klystrons with a cylindrical beam generated by a pierce-type electron gun. The gun design were used to determine the starting point for the electrodes to produce the compression. The use of grid was chosen for short pulse formation. The

  9. A reflector antenna for electron plasma waves

    Microsoft Academic Search

    Y. Morita; R. Kurati; S. Egashira

    1992-01-01

    Summary form only given. A linear antenna with a mesh reflector immersed in a plasma was studied in the frequency range where electron plasma waves can propagate. The electron plasma wave appears to be difficult to excite and to be buried in the noise level because it is damped by Landau damping except in a very small region of frequency

  10. PLASMA WAKEFIELD ACCELERATION UTILIZING MULTIPLE ELECTRON BUNCHES

    E-print Network

    Brookhaven National Laboratory

    PLASMA WAKEFIELD ACCELERATION UTILIZING MULTIPLE ELECTRON BUNCHES E. Kallos, T. Katsouleas, P investigate various plasma wakefield accelerator schemes that rely on multiple electron bunches to drive a large amplitude plasma wave, which are followed by a witness bunch at a phase where it will sample

  11. Plasma Wave Wigglers for Free Electron Lasers

    Microsoft Academic Search

    C. Joshi; F. F. Chen; J. M. Dawson; T. Katsouleas; Y. T. Yan

    1987-01-01

    We explore the possibility of using relativistic plasma density waves as wigglers for producing free electron laser radiation. Two possi- ble wave and beam geometries are explored. In the first, the wiggler is a purely electric wiggler with frequency ma (plasma frequency) but (approximately) zero wavenumber k,. If an electron beam is injected parallel to a wide plasma wave wavefront,

  12. Producing high current sheet electron beam with compact, repetitive Tesla generator

    Microsoft Academic Search

    Zhanliang Wang; Yubin Gong; Yanyu Wei; Zhaoyun Duan; Huarong Gong; Zhigang Lu; Lingna Yue; Hairong Yin; Jin Xu; Jinjun Feng

    2012-01-01

    Sheet electron beam device has the potential for high-power millimeter wave to terahertz regime radiation. A key part of this system is a high current sheet electron beam source. This paper introduces our currently ongoing program on producing high current, high aspect ratio sheet electron beam with compact, repetitive 160KV generator. In our experimental, a cathode which looks like a

  13. Electric fields in the plasma sheet and plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Pedersen, A.; Cattell, C. A.; Faelthammar, C. G.; Knott, K.; Lindqvist, P. A.; Manka, R. H.; Mozer, F. S.

    1984-01-01

    Data from the spherical double probe electric-field experiment on ISEE-1 were used to study plasmasheet/lobe boundary crossings during substorms, identified by plasma measurements and by using the electric field probes as a reference for measurements of the spacecraft potential. There are strong electric fields, with a dominant dawn-to-dusk component, throughout the boundary layer outside the plasmasheet for contracting and expanding motions of the plasmasheet and for different magnetic field directions. Characteristic amplitudes and durations are 5 to 10 mV/m and 5 to 15 min. The corresponding E x B vectors are always towards the plasmasheet.

  14. Laser frequency modulation with electron plasma

    NASA Technical Reports Server (NTRS)

    Burgess, T. J.; Latorre, V. R.

    1972-01-01

    When laser beam passes through electron plasma its frequency shifts by amount proportional to plasma density. This density varies with modulating signal resulting in corresponding modulation of laser beam frequency. Necessary apparatus is relatively inexpensive since crystals are not required.

  15. Poleward leaping auroras, the substorm expansive and recovery phases and the recovery of the plasma sheet

    SciTech Connect

    Hones, E.W.

    1992-01-01

    The auroral motions and geomagnetic changes the characterize the substorm's expansive phase, maximum epoch, and recovery phase are discussed in the context of their possible associations with the dropout and, especially, the recovery of the magnetotail plasma sheet. The evidence that there may be an inordinately sudden large poleward excursion or displacement (a poleward leap) of the electrojet and the auroras at the expansive phase-recovery phase transition is described. The close temporal association of these signatures with the recovery of the plasma sheet, observed on many occasions, suggests a causal relationship between substorm maximum epoch and recovery phase on the one hand and plasma sheet recovery on the other.

  16. Poleward leaping auroras, the substorm expansive and recovery phases and the recovery of the plasma sheet

    SciTech Connect

    Hones, E.W.

    1992-05-01

    The auroral motions and geomagnetic changes the characterize the substorm`s expansive phase, maximum epoch, and recovery phase are discussed in the context of their possible associations with the dropout and, especially, the recovery of the magnetotail plasma sheet. The evidence that there may be an inordinately sudden large poleward excursion or displacement (a poleward leap) of the electrojet and the auroras at the expansive phase-recovery phase transition is described. The close temporal association of these signatures with the recovery of the plasma sheet, observed on many occasions, suggests a causal relationship between substorm maximum epoch and recovery phase on the one hand and plasma sheet recovery on the other.

  17. A Gridded Electron Gun for a Sheet Beam Klystron

    Microsoft Academic Search

    M. E. Read; G. Miram; R. L. Ives; V. Ivanov; A. Krasnykh

    2003-01-01

    Calabazas Creek Research, Inc.(CCR) is developing rectangular, gridded, thermionic, dispenser-cathode guns for sheet beam devices. The first application is expected to be klystrons for advanced particle accelerators and colliders. The current generation of accelerators typically use klystrons with a cylindrical beam generated by a Pierce-type electron gun. As RF power is pushed to higher levels, space charge forces in the

  18. Plasmoid ejection and secondary current sheet generation from magnetic reconnection in laser-plasma interaction.

    PubMed

    Dong, Quan-Li; Wang, Shou-Jun; Lu, Quan-Ming; Huang, Can; Yuan, Da-Wei; Liu, Xun; Lin, Xiao-Xuan; Li, Yu-Tong; Wei, Hui-Gang; Zhong, Jia-Yong; Shi, Jian-Rong; Jiang, Shao-En; Ding, Yong-Kun; Jiang, Bo-Bin; Du, Kai; He, Xian-Tu; Yu, M Y; Liu, C S; Wang, Shui; Tang, Yong-Jian; Zhu, Jian-Qiang; Zhao, Gang; Sheng, Zheng-Ming; Zhang, Jie

    2012-05-25

    Reconnection of the self-generated magnetic fields in laser-plasma interaction was first investigated experimentally by Nilson et al. [Phys. Rev. Lett. 97, 255001 (2006)] by shining two laser pulses a distance apart on a solid target layer. An elongated current sheet (CS) was observed in the plasma between the two laser spots. In order to more closely model magnetotail reconnection, here two side-by-side thin target layers, instead of a single one, are used. It is found that at one end of the elongated CS a fanlike electron outflow region including three well-collimated electron jets appears. The (>1 MeV) tail of the jet energy distribution exhibits a power-law scaling. The enhanced electron acceleration is attributed to the intense inductive electric field in the narrow electron dominated reconnection region, as well as additional acceleration as they are trapped inside the rapidly moving plasmoid formed in and ejected from the CS. The ejection also induces a secondary CS. PMID:23003270

  19. The storm-time plasma sheet at geosynchronous orbit : CME- and CIR-dominated solar wind

    NASA Astrophysics Data System (ADS)

    Denton, M. H.; Thomsen, M. F.; Skoug, R. M.; Borovsky, J. E.; Henderson, M. G.; McPherron, R. L.; Pollock, C.

    2005-05-01

    The plasma sheet provides the primary source population for the storm-time ring current, and characteristic storm signatures are produced by the plasma sheet penetrating deep into the inner magnetosphere. Geosynchronous orbit offers an excellent vantage point from which to monitor the plasma sheet population that ultimately becomes the storm-time ring current. For well over a complete solar cycle, Los Alamos has been fielding magnetospheric plasma analyzers at geosynchronous orbit, creating an extensive multi-point database of plasma sheet conditions. Previous statistical analyses of these data have revealed important information about the access that the plasma sheet has to the inner magnetosphere. More recently, we have performed superposed epoch studies of the variation of plasma sheet properties as a function of storm phase. In the current study, we examine the storm-time behaviour for storms sorted according to the likely solar wind driver, i.e., CME-driven and CIR high-speed-stream-driven, and according to the phase of the solar cycle. We compare the geosynchronous data with data from the MENA instrument on-board the IMAGE satellite to investigate the global distribution of energetic ions in the inner magnetosphere during such events.

  20. Structure of the near-Earth plasma sheet during tailward flows

    NASA Astrophysics Data System (ADS)

    Runov, A.; Voronkov, I.; Asano, Y.; Baumjohann, W.; Fujimoto, M.; Nakamura, R.; Takada, T.; Volwerk, M.; Vörös, Z.; Meurant, M.; Fazakerley, A.; Rème, H.; Balogh, A.

    2008-03-01

    A detailed analysis of successive tailward flow bursts in the near-Earth magnetotail (X~-19 RE) plasma sheet is performed on the basis of in-situ multi-point observations by the Cluster spacecraft on 15 September 2001. The tailward flows were detected during a northward IMF interval, 2.5 h after a substorm expansion. Each flow burst (Vx<300 km/s) was associated with local auroral activation. Enhancements of the parallel and anti-parallel ~1 keV electron flux were detected during the flows. The spacecraft configuration enables to monitor the neutral sheet (Bx?0) and the level of Bx?10-15 nT simultaneously, giving a possibility to distinguish between closed plasmoid-like structures and open NFTE-like surges. The data analysis shows NFTE-like structures and localized current filaments embedded into the tailward plasma flow. 3-D shapes of the structures were reconstructed using the four-point magnetic filed measurements and the particle data.

  1. Growth model for plasma-CVD growth of carbon nano-tubes on Ni-sheets

    Microsoft Academic Search

    Wilfried Wunderlich

    2007-01-01

    The plasma enhanced chemical vapor deposition (PECVD) of carbon nano-tubes (CNT) on nickel sheets is considered as efficient production method of great technologically interest. Different morphologies of CNT on Ni-sheets can be achieved by a variation of the process parameters, like partial pressure of the acetylene and ammoniac inlet gas mixture, the total gas pressure, and temperature. The results are

  2. Dry etch damage in GaAs metal-semiconductor field-effect transistors exposed to inductively coupled plasma and electron cyclotron resonance Ar plasmas

    Microsoft Academic Search

    F. Ren; J. W. Lee; C. R. Abernathy; S. J. Pearton; C. Constantine; C. Barratt; R. J. Shul

    1997-01-01

    The effects of Ar plasma exposure on transconductance, channel sheet resistance, output resistance, and gate contact ideality factor of GaAs metal-semiconductor field-effect transistors (MESFETs) were investigated using two different high-density plasma sources, namely inductively coupled plasma and electron resonance plasma. Ion-induced damage is found to be reduced at moderate source powers (â¼200W) because of the reduction in cathode dc self-bias

  3. Nonlinear electron oscillations in a warm plasma

    SciTech Connect

    Sarkar, Anwesa; Maity, Chandan; Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700 064 (India)] [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700 064 (India)

    2013-12-15

    A class of nonstationary solutions for the nonlinear electron oscillations of a warm plasma are presented using a Lagrangian fluid description. The solution illustrates the nonlinear steepening of an initial Gaussian electron density disturbance and also shows collapse behavior in time. The obtained solution may indicate a class of nonlinear transient structures in an unmagnetized warm plasma.

  4. A magnetized sheet plasma source for the synthesis of TiN on stainless steel substrates

    Microsoft Academic Search

    Virginia R. Noguera; Henry J. Ramos

    2006-01-01

    A sheet plasma of several millimeters thickness and having dimensions 13×20 cm2 was used for wide area plasma-enhanced chemical vapor deposition of titanium nitride (TiN). A titanium disk placed at the anode of the source was sputtered by argon plasma produced at plasma current between 1.0 A to 4.5 A and a discharge potential between 85 V and 240 V.

  5. Io plasma torus electrons - Voyager 1

    NASA Astrophysics Data System (ADS)

    Sittler, E. C.; Strobel, D. F.

    1987-06-01

    A thermal Maxwellian component of the electron distribution function, together with a suprathermal, non-Maxwellian one, are featured in the present analysis of in situ plasma electron observations made by the Voyager 1 plasma science experiment in the Io plasma torus. A large difference in the hot electron pressure P(H) is noted between the inbound and the outbound data; this is interpreted as a latitudinal gradient, with P(H) being maximum at the magnetic equator. The presence of a neutral corona around Io is inferred from the observed decrease and symmetry with respect to Io of the cold electron temperature.

  6. Plasma behavior during energetic electron streaming events further evidence for substorm-associated magnetic reconnection

    NASA Technical Reports Server (NTRS)

    Bieber, J. W.; Stone, E. C.; Hones, E. W., Jr.; Baker, D. N.; Bame, S. J.

    1982-01-01

    A recent study showed that streaming energetic (more than 200 keV) electrons in earth's magnetotail are statistically associated with southward magnetic fields and with enhancements of the AE index. It is shown here that the streaming electrons characteristically are preceded by an approximately 15-minute period of tailward plasma flow and followed by a dropout of the plasma sheet, thus demonstrating a clear statistical association between substorms and the classical signatures of magnetic reconnection and plasmoid formation. Additionally, a brief upward surge of mean electron energy preceded plasma dropout in several of the events studied, providing direct evidence of localized, reconnection-associated heating processes.

  7. Substorm-related plasma sheet motions as determined from differential timing of plasma changes at the ISEE satellites

    NASA Technical Reports Server (NTRS)

    Forbes, T. G.; Hones, E. W., Jr.; Bame, S. J.; Asbridge, J. R.; Paschmann, G.; Sckopke, N.; Russell, C. T.

    1981-01-01

    From an ISEE survey of substorm dropouts and recoveries during the period February 5 to May 25, 1978, 66 timing events observed by the Los Alamos Scientific Laboratory/Max-Planck-Institut Fast Plasma Experiments were studied in detail. Near substorm onset, both the average timing velocity and the bulk flow velocity at the edge of the plasma sheet are inward, toward the center. Measured normal to the surface of the plasma sheet, the timing velocity is 23 + or - 18 km/s and the proton flow velocity is 20 + or - 8 km/s. During substorm recovery, the plasma sheet reappears moving outward with an average timing velocity of 133 + or - 31 km/s; however, the corresponding proton flow velocity is only 3 + or - 7 km/s in the same direction. It is suggested that the difference between the average timing velocity for the expansion of the plasma sheet and the plasma bulk flow perpendicular to the surface of the sheet during substorm recovery is most likely the result of surface waves moving past the position of the satellites.

  8. Short pulse, high power microwave radiation source with a laser-induced sheet plasma mirror

    SciTech Connect

    Higashiguchi, Takeshi; Yugami, Noboru [Graduate School of Engineering and Center for Optical Research and Education (CORE), Utsunomiya University, Yoto 7-1-2, Utsunomiya, Tochigi 321-8585 (Japan)

    2009-05-01

    We have demonstrated the short pulse, high power microwave radiation source using an ultraviolet laser-induced sheet plasma mirror in a gas-filled x-band rectangular waveguide from the conventional microwave sources and components. A laser-induced sheet plasma with an overdense plasma acts as a plasma mirror. The long pulse propagating in the gas-filled waveguide was sliced by the sheet plasma mirror at two different points along the waveguide. We observed about twice the power of the pulse by adding the two sliced microwave pulses produced by this scheme. A maximum peak power of 200 kW with a pulse duration of 10 ns (full width at half maximum) from the long microwave pulse source with a pulse duration of 0.8 mus was observed.

  9. Combination of platelet-rich plasma within periodontal ligament stem cell sheets enhances cell differentiation and matrix production.

    PubMed

    Xu, Qiu; Li, Bei; Yuan, Lin; Dong, Zhiwei; Zhang, Hao; Wang, Han; Sun, Jin; Ge, Song; Jin, Yan

    2014-09-01

    The longstanding goal of periodontal therapy is to regenerate periodontal tissues. Although platelet-rich plasma (PRP) has been gaining increasing popularity for use in the orofacial region, whether PRP is useful for periodontal regeneration is still unknown. The purpose of this study was to determine whether a mixture of periodontal ligament stem cell (PDLSC) sheets and PRP promoted bone regeneration, one of the most important measurement indices of periodontal tissue regenerative capability in vitro and in vivo. In this study, we evaluated the effects of different doses of PRP on the differentiation of human PDLSCs. Then cell sheet formation, extracellular matrix deposition and osteogenic gene expression in response to different doses of PRP treatment during sheet grafting was investigated. Furthermore, we implanted PDLSC sheets treated with 1% PRP subcutaneously into immunocompromised mice to evaluate their bone-regenerative capability. The results revealed that 1% PRP significantly enhanced the osteogenic differentiation of PDLSCs. Based on the production of extracellular matrix proteins, the results of scanning electron microscopy and the expression of the osteogenic genes ALP, Runx2, Col-1 and OCN, the provision of 1% PRP for PDLSC sheets was the most effective PRP administration mode for cell sheet formation. The results of in vivo transplantation showed that 1% PRP-mediated PDLSC sheets exhibited better periodontal tissue regenerative capability than those obtained without PRP intervention. These data suggest that a suitable concentration of PRP stimulation may enhance extracellular matrix production and positively affect cell behaviour in PDLSC sheets. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25186188

  10. Geotail observations of spiky electric fields and low-frequency waves in the plasma sheet and plasma sheet boundary

    NASA Technical Reports Server (NTRS)

    Cattell, C.; Mozer, F.; Tsuruda, K.; Hayakawa, H.; Nakamura, M.; Okada, T.; Kokubun, S.; Yamamoto, T.

    1994-01-01

    Electric field data from the Geotail spacecraft provide an opportunity to extend the observations of spiky fields made by International Sun Earth Explorer-1 (ISEE-1) to a region of the magnetosphere where quasistatic electric field measurements have not previously been msde, to examine their possible importance in the dynamics of the middle and distant tail, and to test some hypotheses about their formation. In this paper, examples of large fields in the plasma sheet and its boundary at radial distances up to approximately 90 R(sub E) are presented. It is shown that three different types of large electric fields can occur: (1) spiky fields; (2) 'DC' fields; and (3) waves at frequencies comparable to the lower hybrid frequency. There is usually a gradation between (1) and (3), and often large electric field spikes are embedded in regions of lower amplitude waves. The waves tend to occur in short (few to 10's of seconds) packets whose start and stop times are not always correlated with changes in the magnetic field and/or density (as indicated by the spacecraft potential). The peak frequency is often less than but comparable to the lower hybrid frequency in agreement with theories of lower hybrid drift waves in the magnetotail. The largest spikes are not always associated with the largest changes in the spacecraft potential and/or magnetic field. It is suggested that the spiky fields may represent the nonlinear development of the waves.

  11. Kelvin-Helmholtz instability in the plasma sheet of the earth magnetosphere

    Microsoft Academic Search

    V. G. Kirtskhaliia

    1985-01-01

    The effect of Kelvin-Helmholtz instability on the boundaries of the plasma sheet in the nightside magnetosphere is studied within the framework of a multilayered model. A generalized dispersion equation is obtained for the frequencies of natural oscillations in the layer system, taking into account the compressibility of the plasma.

  12. Modeling the transition of the inner plasma sheet from weak to enhanced convection

    Microsoft Academic Search

    Chih-Ping Wang; Larry R. Lyons; Margaret W. Chen; Frank R. Toffoletto

    2004-01-01

    We seek to determine whether the adiabatic plasma transport and energization resulting from electric and magnetic drift can quantitatively account for the plasma sheet under weak and enhanced convection observed by Geotail presented in the companion paper [Wang et al., 2004]. We use a modified Magnetospheric Specification Model to simulate the dynamics and distributions of protons originating from the deep

  13. Magnetosphere preconditioning by the formation of a cold-dense plasma sheet under northward IMF

    NASA Astrophysics Data System (ADS)

    Lavraud, B.; Thomsen, M. F.; Jordanova, V. K.; Borovsky, J. E.; Denton, M. H.; Pulkkinen, T. I.

    2009-04-01

    Motivated by recent observations and simulations of the formation of a cold and dense plasma sheet in the tail of the magnetosphere under northward interplanetary magnetic field (IMF) and of the direct influence of the plasma sheet density on the ring current strength, this study aims at (1) highlighting how the coupling of these effects may lead to a preconditioning of the magnetosphere under northward IMF and (2) performing first tests of the validity of this hypothesis. We performed both parametric kinetic ring current simulation studies to investigate how the density and temperature of the plasma sheet affect the ring current strength during geomagnetic storms, and superposed epoch analysis of various parameters to investigate the response of the magnetosphere (as indicated by the Dst index) to the passage of Coronal Mass Ejections (CMEs) and Corotating Interaction Regions (CIRs). The results all suggest that solar wind structures may be more geoeffective if preceded by a northward IMF interval, and they are consistent with the hypothesis of a preconditioning by a cold, dense plasma sheet. A colder and denser plasma sheet may lead to a stronger ring current when that plasma is convected inward during the main phase of an ensuing storm.

  14. Hierarchical regrowth of flowerlike nanographene sheets on oxygen-plasma-treated carbon nanowalls

    NASA Astrophysics Data System (ADS)

    Shimoeda, Hironao; Kondo, Hiroki; Ishikawa, Kenji; Hiramatsu, Mineo; Sekine, Makoto; Hori, Masaru

    2014-04-01

    Cauliflorous nanographene sheets were hierarchically regrown on the spearlike structures of carbon nanowalls (CNWs) produced by O2-plasma etching. The spears on the CNWs acted as a stem for the growth of flowerlike flaky nanographene sheets, where the root of the nanoflower was located at a defect or disordered site. The defects on the graphitic structures were induced by irradiation with oxygen-related radicals and ions in the O2-based plasmas and acted as sites for the nucleation of flowerlike nanographene. The porous carbon nanostructures regrown after O2-plasma treatment have a relatively higher surface area and are thus promising materials for electrochemical applications.

  15. Emission of electron Bernstein waves in plasmas

    NASA Astrophysics Data System (ADS)

    Ram, A. K.; Bers, A.; Lashmore-Davies, C. N.

    2002-02-01

    In previous publications [A. K. Ram and S. D. Schultz, Phys. Plasmas 7, 4084 (2000); A. Bers, A. K. Ram, and S. D. Schultz, in Proceedings of the Second Europhysics Topical Conference on RF Heating and Current Drive of Fusion Devices, edited by J. Jacquinot, G. Van Oost, and R. R. Weynants (European Physical Society, Petit-Lancy, 1998), Vol. 22A, pp. 237-240] it has been shown that, in overdense plasmas of the type encountered in spherical tori, electron Bernstein waves can be excited in a plasma by mode conversion of either an externally launched X mode or an O mode. The electron Bernstein waves are strongly absorbed by electrons in the region where the wave frequency matches the Doppler broadened electron cyclotron resonance frequency or its harmonics. The strong absorption also implies that electron Bernstein waves are emitted by a thermal plasma. These waves can then mode convert to the X mode and to the O mode and be observed external to the plasma. In this paper an approximate kinetic model describing the coupling between the X mode, the O mode, and the electron Bernstein waves is derived. This model is used to study the mode conversion properties of electron Bernstein wave emission from the plasma interior. It is shown, analytically and numerically, that the energy flow conversion efficiencies of the electron Bernstein wave to the X mode and to the O mode are the same as the energy flow conversion efficiency of the X mode to electron Bernstein waves and of the O mode to the electron Bernstein waves, respectively. This has important experimental consequences when designing experiments to heat overdense plasmas by electron Bernstein waves.

  16. Emission current formation in plasma electron emitters

    SciTech Connect

    Gruzdev, V. A.; Zalesski, V. G. [Polotsk State University (Belarus)

    2010-12-15

    A model of the plasma electron emitter is considered, in which the current redistribution over electrodes of the emitter gas-discharge structure and weak electric field formation in plasma are taken into account as functions of the emission current. The calculated and experimental dependences of the switching parameters, extraction efficiency, and strength of the electric field in plasma on the accelerating voltage and geometrical sizes of the emission channel are presented.

  17. Electron scattering in hot-dense plasmas

    NASA Astrophysics Data System (ADS)

    Zammit, Mark C.; Fursa, Dmitry V.; Bray, Igor

    2012-11-01

    Hot-dense plasmas have direct industrial applications in inertial confinement fusion. We have used the convergent close-coupling (CCC) method to investigate electron scattering off hydrogen and helium atoms in a hot-dense weakly coupled (Debye) plasma. The Yukawa-type Debye-Hückel potential has been used to describe the plasma screening effects. Integrated excitation, total ionization and total cross sections have been calculated over a broad range of energies and various Debye lengths, D.

  18. Creating standardized electronic data sheets for applications and devices

    NASA Astrophysics Data System (ADS)

    Hansen, L. J.; Lanza, D.

    The Air Force Research Laboratory (AFRL) continues to develop infrastructure to enable the modular construction of satellites using an open network architecture and off-the-shelf avionics for space systems. Recent efforts have included the refinement of an ontology to formalize a standard language for the exchange of data and commands between components, including hardware and software, which is still evolving. AFRL is also focusing effort on creating standard interfaces using electronic data sheets based on this recently defined ontology. This paper will describe the development of standard interfaces that are documented in terms of an electronic datasheet for a specific application. The datasheet will identify the standard interfaces between hardware devices and software applications that are needed for a specific satellite function, in this case, a spacecraft guidance, navigation, and control (GN& C) application for Sun pointing. Finally, the benefits of using standardized interfaces will be discussed.

  19. Spontaneous emission near the electron plasma frequency in a plasma with a runaway electron tail

    NASA Technical Reports Server (NTRS)

    Freund, H. P.; Lee, L. C.; Wu, C. S.

    1978-01-01

    Spontaneous emission of radiation with frequencies near the electron plasma frequency is studied for a plasma which consists of both thermal and runaway electrons. It is found that a substantial enhancement of the spontaneous radiation intensity can occur in this frequency regime via a Cherenkov resonance with the runaway electrons. Numerical analysis indicates that, for reasonable estimates of densities and energies, the plasma-frequency radiation can attain levels greater than the peak thermal emission at the second gyroharmonic.

  20. Plasma effects in a free electron laser

    Microsoft Academic Search

    VIPIN K. TRIPATHI; CHUAN SHENG LIU

    1990-01-01

    The introduction of a plasma and a strong guide magnetic field in a free electron laser (FEL) slows down the phase velocity of radiation, significantly reducing the requirements on beam energy for generating frequencies below the electron-cyclotron frequency (?1≲?c). Around plasma resonance (?1~?p), the FEL mode couples to two-stream instability (TSI), attaining a large growth rate, comparable to that of

  1. The generation of electrostatic noise in the plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Dusenbery, P. B.; Lyons, L. R.

    1985-01-01

    The one and two ion beam instability is considered as a possible explanation for the observations of broadband electrostatic noise in the plasma sheet region of the geomagnetic tail. When only hot streaming plasma sheet boundary layer ions are present, no broadband waves are excited. Cold, streaming ionospheric ions can generate electrostatic broadband waves propagating in the slow beam acoustic mode, but the growth rates of the waves are significantly enhanced when hot boundary layer ions are present. (Both the slow and fast beam acoustic modes can be excited, depending on the relative ion drift.) This model predicts that the wave intensity of the broad band noise should peak in the plasma sheet boundary layer. Observations of less intense electrostatic waves in the lobes and plasma sheet are likely a result of the absence of hot ion beams or large ion temperatures, respectively, which result in smaller growth rates. The ion beam instability may play an important role in the formation of the central plasma sheet.

  2. Tailward leap of multiple expansions of the plasma sheet during a moderately intense substorm: THEMIS observations

    NASA Astrophysics Data System (ADS)

    Ma, Yonghui; Shen, Chao; Angelopoulos, V.; Lui, A. T. Y.; Li, Xinlin; Frey, H. U.; Dunlop, M.; Auster, H. U.; McFadden, J. P.; Larson, D.

    2012-07-01

    A moderately intense substorm on 1 March 2008, from 0830 to 1000 UT, observed by THEMIS probes and the Ground Based Observatory (GBO) is examined to investigate the global evolution of substorm phenomena. During this interval, all five THEMIS probes are closely aligned along the tail axis near midnight covering a radial range from ˜9 Re to ˜18 Re. After the substorm onset, plasma sheet expansions take place successively at multiple locations in the magnetotail as measured by different probes. The positions of the plasma sheet expansions have a tailward leap progression with an average velocity of ˜36 km/s. There are two types of dipolarization detected in this substorm. The first type is the dipolarization front which is associated with the bursty bulk flow (BBF). While the second type, which we call ‘global dipolarization’, is associated with plasma sheet expansions. In the substorm studied, there are four intensifications as shown in the THEMIS AE index. We can detect the effects of localized and short-lived magnetic energy release processes occurring in the magnetotail corresponding to each of the four AE intensifications. Furthermore, the inner four probes can detect the global dipolarization signatures ˜4-15 min earlier than plasma sheet expansions, while the outermost probe (P1) cannot detect this before the plasma sheet expansion. These two phenomena are caused by the same process (magnetic energy release process) but the effects detected by probes locally appear delayed. The observations in this case are not sufficient to distinguish between the two competing substorm models.

  3. Development of plasma cathode electron guns

    NASA Astrophysics Data System (ADS)

    Oks, Efim M.; Schanin, Peter M.

    1999-05-01

    The status of experimental research and ongoing development of plasma cathode electron guns in recent years is reviewed, including some novel upgrades and applications to various technological fields. The attractiveness of this kind of e-gun is due to its capability of creating high current, broad or focused beams, both in pulsed and steady-state modes of operation. An important characteristic of the plasma cathode electron gun is the absence of a thermionic cathode, a feature which leads to long lifetime and reliable operation even in the presence of aggressive background gas media and at fore-vacuum gas pressure ranges such as achieved by mechanical pumps. Depending on the required beam parameters, different kinds of plasma discharge systems can be used in plasma cathode electron guns, such as vacuum arcs, constricted gaseous arcs, hollow cathode glows, and two kinds of discharges in crossed E×B fields: Penning and magnetron. At the present time, plasma cathode electron guns provide beams with transverse dimension from fractional millimeter up to about one meter, beam current from microamperes to kiloamperes, beam current density up to about 100 A/cm2, pulse duration from nanoseconds to dc, and electron energy from several keV to hundreds of keV. Applications include electron beam melting and welding, surface treatment, plasma chemistry, radiation technologies, laser pumping, microwave generation, and more.

  4. Investigation of a staged plasma-focus apparatus. [pinch construction and current sheet dynamics investigation

    NASA Technical Reports Server (NTRS)

    Lee, J. H.; Mcfarland, D. R.; Harries, W. L.

    1978-01-01

    A new staged plasma-focus geometry combining two Mather-type plasma-focus guns was constructed, and the current-sheet dynamics were investigated. The production of simultaneous pairs of plasma foci was achieved. The intensities of X-ray and fusion-neutron emission were measured and found to agree with the scaling law for a plasma focus. Advantages of this new geometry include the possibility of using plasma-focus type pinches in multiple arrays at power levels beyond the validity regime of the current scaling law for a single gun.

  5. Observation of a current-driven plasma instability at the outer zone-plasma sheet boundary.

    NASA Technical Reports Server (NTRS)

    Scarf, F. L.; Fredricks, R. W.; Russell, C. T.; Kivelson, M.; Neugebauer, M.; Chappell, C. R.

    1973-01-01

    Several spacecraft experimenters have reported on the detection of large temporal variations in trapped electron fluxes near L = 5 to 6 at midlatitudes in the night hemisphere. In this report we describe in detail the particle, wave, and field changes measured when Ogo 5 traversed an outer-zone trapping boundary of this type on September 7, 1968. It is shown that thermal proton concentrations and E greater than 50-keV electron fluxes abruptly decreased when electrons with (1-4) keV mean energy were detected. It is also shown that currents flowed along the average geomagnetic field direction near the plasma boundaries and that these were accompanied by intense VLF electrostatic waves. It is proposed that turbulent resistivity produced by current-driven plasma instabilities allows parallel dc electric fields to develop along this boundary.

  6. Understanding the near Earth plasma sheet instability responsible for substorm onset

    NASA Astrophysics Data System (ADS)

    Nishimura, T.; Lyons, L. R.; Pritchett, P. L.; Angelopoulos, V.; Donovan, E.

    2014-12-01

    Substorms are one of the most dramatic disturbances of the global magnetotail-ionosphere coupling system that release large amounts of solar wind energy accumulated in the magnetotail and are associated with auroral activations. A critical, long-standing problem in substorm research is to identify what physical mechanism leads to substorm auroral onset. It has been suggested that pre-onset waves with ~1-2 min periodicity are an important facet of the instability in the near-Earth region that leads to substorm onset and auroral beads. It is thus critical to determine if, and if so how, pre-onset waves in the near-Earth plasma sheet evolve to substorm onset waves. We found using the THEMIS satellite-imager conjunction events that westward-propagating pre-onset waves evolve to the beginning part of onset waves soon after auroral streamers, indicating an importance of the coupling process between incoming flows and pre-existing waves to substorm onset. On the other hand, a portion of the onset waves propagates eastward in contrast to westward propagation of the pre-onset waves and part of the onset waves. These unique propagation characteristics as well as the wavelength and periodicity can be used to identify a possible mechanism of near-Earth plasma sheet instability. We have compared the observation results with 3-D kinetic simulations with a localized tailward entropy gradient. This initial condition induces weak waves propagating westward that can be interpreted as due to kinetic ballooning/interchange instability and electromagnetic current-driven ion cyclotron instability. Part of those waves grows much larger in amplitude and propagated eastward and earthward due to charge separations between magnetized electrons and unmagnetized ions, indicating that kinetic effects are responsible for the onset wave propagation. These propagation features of simulated waves are consistent with the observations, and therefore suggest that these kinetic waves may play an important role in initiating the instability responsible for substorm expansion phase onset.

  7. Fast magnetic reconnection in thin current sheets: effects of different current profiles and electron inertia in Ohm's law.

    NASA Astrophysics Data System (ADS)

    Pucci, Fulvia; Del Sarto, Daniele; Tenerani, Anna; Velli, Marco

    2015-04-01

    By examining sheets with thicknesses scaling as different powers of the Lundquist number S, we previously showed (Pucci and Velli, 2014) that the growth rate of the tearing mode increases as current sheets thin and, once the inverse aspect ratio reaches a scaling a/L = S-1/3, the time-scale for the instability to develop becomes of the order of the Alfvén time. That means that a fast instability sets in well before Sweet-Parker type current sheets can form. In addition, such an instability produces many islands in the sheet, leading to fast nonlinear evolution and most probably a turbulent disruption of the sheet itself. This has fundamental implications for magnetically driven reconnection throughout the corona, and in particular for coronal heating and the triggering of coronal mass ejections. Here we extend the study of reconnection instabilities to magnetic fields of grater complexity, displaying different current structures such as, for example, multiple or asymmetric current layers. We also consider the possibility of a ?' dependence on wave-number k-p for different values of p, studying analogies and variations of the trigger scaling relation a/L ~ S-1/3 with respect to the Harris current sheet equilibrium. At large Lundquist numbers in typical Heliospheric plasmas kinetic effects become more important in Ohm's law: we consider the effects of electron skin depth reconnection, showing that we can define a trigger relation similar to the resistive case. The results are important to the transition to fast reconnection in the solar corona, solar wind, magnetosphere as well as laboratory plasmas. F. Pucci and M. Velli, "Reconnection of quasi-singular current sheets: the 'ideal" tearing mode" ApJ 780:L19, 2014.

  8. Thermal Structure and Dynamics in Supra-arcade Downflows and Flare Plasma Sheets

    NASA Astrophysics Data System (ADS)

    Reeves, K.; Hanneman, W.; Freed, M.; McKenzie, D. E.

    2014-12-01

    During a long duration solar flare, a hot plasma sheet is commonly formed above the flare loops. Often produced within this sheet are down-flowing voids referred to as supra-arcade downflows, thought to be the products of a patchy reconnection process. Models differ on the question of whether the downflows should be hotter than the surrounding plasma or not. We use imaging data from Hinode/XRT and SDO/AIA to determine the thermal structure of the plasma sheet and downflows. We find that the temperatures of the plasma within the downflows are either roughly the same as or lower than the surrounding fan plasma. This result implies that a mechanism for forming the voids that involves a sunward directed hydrodynamic shock pattern combined with perpendicular magnetic shock is unlikely. Additionally, we use the high cadence AIA data to trace the velocity fields in these regions through the use of a local correlation tracking algorithm. Through these measurements, we can determine areas of diverging velocity fields, as well as velocity shear fields and correlate them with temperature changes in order to understand the heating mechanisms in the plasma sheet. This work is supported by under contract SP02H1701R from Lockheed-Martin to SAO, contract NNM07AB07C from NASA to SAO and NASA grant numbers NNX13AG54G and NNX14AD43G

  9. Vortex and ULF wave structures in the plasma sheet of the Earth magnetosphere

    NASA Astrophysics Data System (ADS)

    Saliuk, D. A.; Agapitov, O. V.

    2013-08-01

    We studied the ULF wave packet propagation in the Earth plasma sheet making use of the magnetic field measurements from FGM detector and plasma properties from CORRAL detector aboard the Interball-Tail spacecraft. The MHD vortex structures were observed simultaneously with the Pc5 ULF waves. The vortex spatial scale was found to be about 1200-3600 km and the velocity is 4-16 km/s transverse to the background magnetic field. We studied numerically the dynamics of the initial vortex perturbations in the plasma system with parameters observed in the Earth plasma sheet. The system with the vector nonlinearity was processed making use of the full reduction scheme. The good agreement of the experimental value of the vortex structure velocity with numerical results was obtained. The velocity was found to be close to the local plasma drift velocity.

  10. A Theoretical Model of a Thinning Current Sheet in the Low-? Plasmas

    NASA Astrophysics Data System (ADS)

    Takeshige, Satoshi; Takasao, Shinsuke; Shibata, Kazunari

    2015-07-01

    Magnetic reconnection is an important physical process in various explosive phenomena in the universe. In previous studies, it was found that fast reconnection takes place when the thickness of a current sheet becomes on the order of a microscopic length such as the ion Larmor radius or the ion inertial length. In this study, we investigated the pinching process of a current sheet by the Lorentz force in a low-? plasma using one-dimensional magnetohydrodynamics (MHD) simulations. It is known that there is an exact self-similar solution for this problem that neglects gas pressure. We compared the non-linear MHD dynamics with the analytic self-similar solution. From the MHD simulations, we found that with the gas pressure included the implosion process deviates from the analytic self-similar solution as t\\to {t}0, where t0 is the explosion time when the thickness of a current sheet of the analytic solution becomes 0. We also found that a pair of MHD fast-mode shocks is generated and propagates after the formation of the pinched current sheet as t\\to {t}0. On the basis of the Rankine–Hugoniot relations, we derived the scaling law of the physical quantities with respect to the initial plasma beta in the pinched current sheet. Our study could help us estimate the physical quantities in the pinched current sheet formed in a low-? plasma.

  11. Ballooning instability of the earth's plasma sheet region in the presence of parallel flow

    NASA Technical Reports Server (NTRS)

    Lakhina, G. S.; Hameiri, E.; Mond, M.

    1990-01-01

    Stability of the plasma sheet and plasma sheet boundary layer against the ballooning mode instability is investigated. The equilibrium state of a two-dimensional plasma sheet configuration with parallel sheared flow is modeled. This equilibrium is shown to be ballooning unstable when delta-W is not positive definite, where delta-W is the potential energy. The eigenmode structure of the ballooning mode is found by imposing the boundary conditions that the waves are totally reflected from the ionosphere, and that no waves are coming in from infinity. The eigenmode structure of the unstable balloning modes is highly oscillatory, extending beyond about 100 R(E). The ballooning modes are thus a possible candidate for explaining the MHD waves and other dynamical events observed in the magnetotail by ISEE 3 and other spacecraft.

  12. Ion and electron heating during magnetic reconnection in weakly collisional plasmas

    NASA Astrophysics Data System (ADS)

    Numata, Ryusuke; Loureiro, N. F.; Loureiro

    2015-04-01

    Magnetic reconnection and associated heating of ions and electrons in strongly magnetized, weakly collisional plasmas are studied by means of gyrokinetic simulations. It is shown that an appreciable amount of the released magnetic energy is dissipated to yield (irreversible) electron and ion heating via phase mixing. Electron heating is mostly localized to the magnetic island, not the current sheet, and occurs after the dynamical reconnection stage. Ion heating is comparable to electron heating only in high-? plasmas, and results from both parallel and perpendicular phase mixing due to finite Larmor radius (FLR) effects; in space, ion heating is mostly localized to the interior of a secondary island (plasmoid) that arises from the instability of the current sheet.

  13. Electron plasma oscillations in the Venus foreshock

    SciTech Connect

    Crawford, G.K.; Strangeway, R.J.; Russell, C.T. (Univ. of California, Los Angeles (USA)

    1990-10-01

    Plasma waves are observed in the solar wind upstream of the Venus bow shock by the Pioneer Venus Orbiter. These wave signatures occur during periods when the interplanetary magnetic field through the spacecraft position intersects the bow shock, thereby placing the spacecraft in the foreshock region. The electron foreshock boundary is clearly evident in the data as a sharp onset in wave activity and a peak in intensity. Wave intensity is seen to drop rapidly with increasing penetration into the foreshock. The peak wave electric field strength at the electron foreshock boundary is found to be similar to terrestrial observations. A normalized wave spectrum was constructed using measurements of the electron plasma frequency and the spectrum was found to be centered about this value. These results, along with polarization studies showing the wave electric field to be field aligned, are consistent with the interpretation of the waves as electron plasma oscillations.

  14. Electron Beam Diagnostics in Plasmas Based on Electron Beam Ionization

    NASA Astrophysics Data System (ADS)

    Leonhardt, Darrin; Leal-Quiros, Edbertho; Blackwell, David; Walton, Scott; Murphy, Donald; Fernsler, Richard; Meger, Robert

    2001-10-01

    Over the last few years, electron beam ionization has been shown to be a viable generator of high density plasmas with numerous applications in materials modification. To better understand these plasmas, we have fielded electron beam diagnostics to more clearly understand the propagation of the beam as it travels through the background gas and creates the plasma. These diagnostics vary greatly in sophistication, ranging from differentially pumped systems with energy selective elements to metal 'hockey pucks' covered with thin layers of insulation to electrically isolate the detector from the plasma but pass high energy beam electrons. Most importantly, absolute measurements of spatially resolved beam current densities are measured in a variety of pulsed and continuous beam sources. The energy distribution of the beam current(s) will be further discussed, through experiments incorporating various energy resolving elements such as simple grids and more sophisticated cylindrical lens geometries. The results are compared with other experiments of high energy electron beams through gases and appropriate disparities and caveats will be discussed. Finally, plasma parameters are correlated to the measured beam parameters for a more global picture of electron beam produced plasmas.

  15. Microwave reflections from a vacuum ultraviolet laser produced plasma sheet

    E-print Network

    Scharer, John E.

    as the plasma. A computer model is developed to interpret and optimize the plasma conditions which provide been several studies1­4 of a plasma as a mi- crowave reflector or absorber based on its application wave at a dielectric boundary is given by the Fresnel reflection coef- ficient, Ereflected Eincident p

  16. Plasma sheet instability related to the westward traveling surge

    SciTech Connect

    Roux, A.; Perraut, S.; Robert, P.; Morane, A. (Centre National d'Etudes des Telecommunications, Issy-les-Moulineaux (France)); Pedersen, A. (European Space Research and Technology Centre, Noordwijk (Netherlands)); Korth, A.; Kremser, G. (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (West Germany)); Aparicio, B. (Swedish Inst. of Space Physics, Kiruna (Sweden)); Rodgers, D. (University College, London (England)); Pellinen, R. (Finnish Meteorological Inst., Helsinki (Finland))

    1991-10-01

    The detailed analysis of an isolated dispersionless substorm is performed on the basis of field and particle data collected in situ by the geostationary satellite GEOS 2 and of data from ground-based instruments installed close to the GEOS 2 magnetic footprint. These data give evidence for (1) quasi-periodic variations of the magnetic field configuration, which is alternatively taillike and dipolelike, (2) in-phase oscillations of the flux of energetic electrons, which is high when the configuration is dipolelike and vice versa, (3) a gradient in the flux of energetic ions, which is, on the average, earthward but undergoes large fluctuations around this average direction, and (4) large transient fluctuations of the quasi-dc electric field, which reverses its direction from eastward to westward. It is shown that these results are consistent with the development of an instability which leads to a westward propagating wave. The source of the instability is the differential drift of energetic electrons and ions in a highly stressed magnetic field configuration (in a high {beta} plasma). Evidence is given for a system of localized field-aligned currents flowing alternately earthward and equatorward at the leading and trailing edges of the westward propagating wave. This current system resulting from the temporal development of the instability produces the so-called Pi 2 pulsations, at the ionospheric level. The closure of this current system in the equatorial region leads to a current antiparallel to the tail current, and therefore to its reduction or cancellation. This reduction/cancellation of the tail current restores the dipole magnetic field (dipolarization) and generates a large westward directed induced electric field (injection).

  17. Dynamic Harris current sheet thickness from Cluster current density and plasma measurements

    NASA Technical Reports Server (NTRS)

    Thompson, S. M.; Kivelson, M. G.; Khurana, K. K.; McPherron, R. L.; Weygand, J. M.; Balogh, A.; Reme, H.; Kistler, L. M.

    2005-01-01

    We use the first accurate measurements of current densities in the plasma sheet to calculate the half-thickness and position of the current sheet as a function of time. Our technique assumes a Harris current sheet model, which is parameterized by lobe magnetic field B(o), current sheet half-thickness h, and current sheet position z(sub o). Cluster measurements of magnetic field, current density, and plasma pressure are used to infer the three parameters as a function of time. We find that most long timescale (6-12 hours) current sheet crossings observed by Cluster cannot be described by a static Harris current sheet with a single set of parameters B(sub o), h, and z(sub o). Noting the presence of high-frequency fluctuations that appear to be superimposed on lower frequency variations, we average over running 6-min intervals and use the smoothed data to infer the parameters h(t) and z(sub o)(t), constrained by the pressure balance lobe magnetic field B(sub o)(t). Whereas this approach has been used in previous studies, the spatial gnuhen& now provided by the Cluster magnetometers were unavailable or not well constrained in earlier studies. We place the calculated hdf&cknessa in a magnetospheric context by examining the change in thickness with substorm phase for three case study events and 21 events in a superposed epoch analysis. We find that the inferred half-thickness in many cases reflects the nominal changes experienced by the plasma sheet during substorms (i.e., thinning during growth phase, thickening following substorm onset). We conclude with an analysis of the relative contribution of (Delta)B(sub z)/(Delta)X to the cross-tail current density during substorms. We find that (Delta)B(sub z)/(Delta)X can contribute a significant portion of the cross-tail c m n t around substorm onset.

  18. Visualization of Current Sheet Canting in a Pulsed Plasma Accelerator

    E-print Network

    Choueiri, Edgar

    normal). Ion conduction current, electrode erosion, magnetic field asymmetry, and the Hall effect be amenable to analyt- 1 #12;2 MARKUSIC, CHOUEIRI: CURRENT SHEET CANTING TOP VIEW SIDE VIEW COPPER PYREX 60 cm loading, one- dimensional magnetic and electric fields, etc.). It was decided that a parallel plate

  19. Kinetic theory of plasma sheaths surrounding electron-emitting surfaces.

    PubMed

    Sheehan, J P; Hershkowitz, N; Kaganovich, I D; Wang, H; Raitses, Y; Barnat, E V; Weatherford, B R; Sydorenko, D

    2013-08-16

    A one-dimensional kinetic theory of sheaths surrounding planar, electron-emitting surfaces is presented which accounts for plasma electrons lost to the surface and the temperature of the emitted electrons. It is shown that ratio of plasma electron temperature to emitted electron temperature significantly affects the sheath potential when the plasma electron temperature is within an order of magnitude of the emitted electron temperature. The sheath potential goes to zero as the plasma electron temperature equals the emitted electron temperature, which can occur in the afterglow of an rf plasma and some low-temperature plasma sources. These results were validated by particle in cell simulations. The theory was tested by making measurements of the sheath surrounding a thermionically emitting cathode in the afterglow of an rf plasma. The measured sheath potential shrunk to zero as the plasma electron temperature cooled to the emitted electron temperature, as predicted by the theory. PMID:23992073

  20. Characterization of electron cyclotron resonance hydrogen plasmas

    SciTech Connect

    Outten, C.A. (Michigan Univ., Ann Arbor, MI (USA). Dept. of Nuclear Engineering); Barbour, J.C.; Wampler, W.R. (Sandia National Labs., Albuquerque, NM (USA))

    1990-01-01

    Electron cyclotron resonance (ECR) plasmas yield low energy and high ion density plasmas. The characteristics downstream of an ECR hydrogen plasma were investigated as a function of microwave power and magnetic field. A fast-injection Langmuir probe and a carbon resistance probe were used to determine plasma potential (V{sub p}), electron density (N{sub e}), electron temperature (T{sub e}), ion energy (T{sub i}), and ion fluence. Langmuir probe results showed that at 17 cm downstream from the ECR chamber the plasma characteristics are approximately constant across the center 7 cm of the plasma for 50 Watts of absorbed power. These results gave V{sub p} = 30 {plus minus} 5 eV, N{sub e} = 1 {times} 10{sup 8} cm{sup {minus}3}, and T{sub e} = 10--13 eV. In good agreement with the Langmuir probe results, carbon resistance probes have shown that T{sub i} {le} 50 eV. Also, based on hydrogen chemical sputtering of carbon, the hydrogen (ion and energetic neutrals) fluence rate was determined to be 1 {times} 10{sup 16}/cm{sup 2}-sec. at a pressure of 1 {times} 10{sup {minus}4} Torr and for 50 Watts of absorbed power. 19 refs.

  1. The evolution of flux pileup regions in the plasma sheet: Cluster observations

    NASA Astrophysics Data System (ADS)

    Hamrin, M.; Norqvist, P.; Karlsson, T.; Nilsson, H.; Fu, H. S.; Buchert, S.; André, M.; Marghitu, O.; Pitkänen, T.; Klecker, B.; Kistler, L. M.; Dandouras, I.

    2013-10-01

    Bursty bulk flows (BBFs) play an important role for the mass, energy, and magnetic flux transport in the plasma sheet, and the flow pattern in and around a BBF has important consequences for the localized energy conversion between the electromagnetic and plasma mechanical energy forms. The plasma flow signature in and around BBFs is often rather complicated. Return flows and plasma vortices are expected to exist at the flanks of the main flow channel, especially near the inner plasma sheet boundary, but also farther down-tail. A dipolarization front (DF) is often observed at the leading edge of a BBF, and a flux pileup region (FPR) behind the DF. Here we present Cluster data of three FPRs associated with vortex flows observed in the midtail plasma sheet on 15 August 2001. According to the principles of Fu et al. (2011, 2012c), two of the FPRs are considered to be in an early stage of evolution (growing FPRs). The third FPR is in a later stage of evolution (decaying FPR). For the first time, the detailed energy conversion properties during various stages of the FPR evolution have been measured. We show that the later stage FPR has a more complex vortex pattern than the two earlier stage FPRs. The two early stage FPR correspond to generators, E·J<0, while the later stage FPR only shows weak generator characteristics and is instead dominated by load signatures at the DF, E·J>0. Moreover, to our knowledge, this is one of the first times BBF-related plasma vortices have been observed to propagate over the spacecraft in the midtail plasma sheet at geocentric distances of about 18RE. Our observations are compared to recent simulation results and previous observations.

  2. A Gridded Electron Gun for a Sheet Beam Klystron

    NASA Astrophysics Data System (ADS)

    Read, M. E.; Miram, G.; Ives, R. L.; Ivanov, V.; Krasnykh, A.

    2003-12-01

    Calabazas Creek Research, Inc.(CCR) is developing rectangular, gridded, thermionic, dispenser-cathode guns for sheet beam devices. The first application is expected to be klystrons for advanced particle accelerators and colliders. The current generation of accelerators typically use klystrons with a cylindrical beam generated by a Pierce-type electron gun. As RF power is pushed to higher levels, space charge forces in the electron beam limit the amount of current that can be transmitted at a given voltage. The options are to increase the beam voltage, leading to problems with X-Ray shielding and modulator and power supply design, or to develop new techniques for lowering the space charge forces in the electron beam. In this device, the beam has a rectangular cross section. The thickness is constrained as it would in a normal, cylindrically symmetric klystron with a Pierce gun. However, the width of the beam is many times the thickness, and the resulting cross sectional area is much larger than in the conventional device. This allows much higher current and/or a lower voltage before space charge forces become too high. The current program addresses issues related to beam formation at the emitter surface, design and implementation of shadow and control grids in a rectangular geometry. It is directed toward a robust, cost-effective, and reliable mechanical design. A prototype device will be developed that will operate at 415 kV, 250 A for an 80 MW, X-Band, sheet-beam klystron. The cathode will have 100 cm2 of cathode area with an average cathode current loading of 2.5 A/cm2. For short pulse formation, the use of a grid was chosen. The gun has been designed with a combination of 2-D and 3-D codes. 2-D codes were used to determine the starting point for the electrodes to produce the compression (which is in only 1 direction.) These results showed that a very high quality beam could be achieved even in the presence of the shadow grid. 3-D results have shown that the quality can be maintained for the actual geometry. Final designs of the gun are being completed, and fabrication is expected to begin in the spring of 2003. Details of the design will be reported.

  3. RICHTMYER-MESHKOV-TYPE INSTABILITY OF A CURRENT SHEET IN A RELATIVISTICALLY MAGNETIZED PLASMA

    SciTech Connect

    Inoue, Tsuyoshi, E-mail: inouety@phys.aoyama.ac.jp [Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara, Kanagawa 252-5258 (Japan)

    2012-11-20

    The linear stability of a current sheet that is subject to an impulsive acceleration due to shock passage with the effect of a guide magnetic field is studied. We find that a current sheet embedded in relativistically magnetized plasma always shows a Richtmyer-Meshkov-type instability, while the stability depends on the density structure in the Newtonian limit. The growth of the instability is expected to generate turbulence around the current sheet, which can induce the so-called turbulent reconnection, the rate of which is essentially free from plasma resistivity. Thus, the instability can be applied as a triggering mechanism for rapid magnetic energy release in a variety of high-energy astrophysical phenomena such as pulsar wind nebulae, gamma-ray bursts, and active galactic nuclei, where the shock wave is thought to play a crucial role.

  4. Formation of the Harang reversal and its dependence on plasma sheet conditions: Rice convection model simulations

    E-print Network

    Lyons, Larry

    Formation of the Harang reversal and its dependence on plasma sheet conditions: Rice convection of this paper is to understand the formation of the Harang reversal and its association with the region 2 field for the formation of the Harang reversal. In the overlap region the downward FAC, which is located at lower

  5. Comment on the group velocity of surface waves on the plasma sheet boundary

    Microsoft Academic Search

    P. Nenovski

    1985-01-01

    In the recent estimation by Maltsev and Lyatsky (1984) of the group velocity of surface waves on the inner boundary of the plasma sheet, the effect of the curvature of the field lines of the ambient magnetic field of the earth on the spectrum has been assessed. The authors have not accounted for the fact, however, that the group velocity

  6. Penetration of the Interplanetary Magnetic Field B(sub y) into Earth's Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Hau, L.-N.; Erickson, G. M.

    1995-01-01

    There has been considerable recent interest in the relationship between the cross-tail magnetic field component B(sub y) and tail dynamics. The purpose of this paper is to give an overall description of the penetration of the interplanetary magnetic field (IMF) B(sub y) into the near-Earth plasma sheet. We show that plasma sheet B(sub y) may be generated by the differential shear motion of field lines and enhanced by flux tube compression. The latter mechanism leads to a B(sub y) analogue of the pressure-balance inconsistency as flux tubes move from the far tail toward the Earth. The growth of B(sub y), however, may be limited by the dawn-dusk asymmetry in the shear velocity as a result of plasma sheet tilting. B(sub y) penetration into the plasma sheet implies field-aligned currents flowing between hemispheres. These currents together with the IMF B(sub y) related mantle field-aligned currents effectively shield the lobe from the IMF B(sub y).

  7. Equilibrium electron-ion bunches in plasma

    SciTech Connect

    Krasovitskii, V.B. [Rostov State Univ., Rostov-na-Donu (Russian Federation); Naguchev, O.Yu. [Space Research Institute, Moscow (Russian Federation)

    1994-12-31

    The criteria of the laminated electron-ion beam electrostatic equilibrium are found, the modulated beams with the modulation frequency lower than the Langmuir plasma frequency being treated. A self-focusing mechanism is shown to exist for both electron and ion bunches. The phenomenon also occurs in the external longitudinal magnetic field. In an external transverse magnetic field the action of the Lorenz force onto electrons and ions results in the particle escaping from the potential wells, in the edge regions of the beam cross-section. However, the polarization electric field, originating from the beam charge lamination, partially compensates the Lorenz force. This, in turn, results in the enhanced transport conditions of the layered beams trough a dense plasma as compared to the case of bunched electron beams. 4 refs., 2 figs.

  8. Electron beam-plasma interaction in a dusty plasma with excess suprathermal electrons

    SciTech Connect

    Danehkar, A. [Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109 (Australia); Saini, N. S. [Department of Physics, Guru Nanak Dev University, Amritsar-143005 (India); Hellberg, M. A. [School of Physics, University of KwaZulu-Natal, Durban 4000 (South Africa); Kourakis, I. [Department of Physics and Astronomy, Queen's University Belfast, BT7 1NN (United Kingdom)

    2011-11-29

    The existence of large-amplitude electron-acoustic solitary structures is investigated in an unmagnetized and collisionless two-temperature dusty plasma penetrated by an electron beam. A nonlinear pseudopotential technique is used to investigate the occurrence of stationary-profile solitary waves, and their parametric dependence on the electron beam and dust perturbation is discussed.

  9. The structure of the plasma sheet-lobe boundary in the Earth's magnetotail

    NASA Technical Reports Server (NTRS)

    Orsini, S.; Candidi, M.; Formisano, V.; Balsiger, H.; Ghielmetti, A.; Ogilvie, K. W.

    1982-01-01

    The structure of the magnetotail plasma sheet-plasma lobe boundary was studied by observing the properties of tailward flowing O+ ion beams, detected by the ISEE 2 plasma experiment inside the boundary during three time periods. The computed value of the north-south electric field component as well as the O+ parameters are shown to change at the boundary. The results are related to other observations made in this region. The O+ parameters and the Ez component behavior are shown to be consistent with that expected from the topology of the electric field lines in the tail as mapped from the ionosphere.

  10. The structure of the plasma sheet-lobe boundary in the earth's magnetotail

    NASA Technical Reports Server (NTRS)

    Orsini, S.; Candidi, M.; Formisano, V.; Balsiger, H.; Ghielmetti, A.; Ogilvie, K. W.

    1984-01-01

    The structure of the magnetotail plasma sheet-plasma lobe boundary was studied by observing the properties of tailward flowing O+ ion beams, detected by the ISEE 2 plasma experiment inside the boundary during three time periods. The computed value of the north-south electric field component as well as the O+ parameters are shown to change at the boundary. The results are related to other observations made in this region. The O+ parameters and the Ez component behavior are shown to be consistent with that expected from the topology of the electric field lines in the tail as mapped from the ionosphere. Previously announced in STAR as N84-13049

  11. Thermal catastrophe in the plasma sheet boundary layer. [in substorm models

    NASA Technical Reports Server (NTRS)

    Smith, Robert A.; Goertz, Christoph K.; Grossmann, William

    1986-01-01

    This letter presents a first step towards a substorm model including particle heating and transport in the plasma sheet boundary layer (PSBL). The heating mechanism discussed is resonant absorption of Alfven waves. For some assumed MHD perturbation incident from the tail lobes onto the plasma sheet, the local heating rate in the PSBL has the form of a resonance function of the one-fluid plasma temperature. Balancing the local heating by convective transport of the heated plasma toward the central plasma sheet, an 'equation of state" is found for the steady-state PSBL whose solution has the form of a mathematical catastrophe: at a critical value of a parameter containing the incident power flux, the local density, and the convection velocity, the equilibrium temperature jumps discontinuously. Associating this temperature increase with the abrupt onset of the substorm expansion phase, the catastrophe model indicates at least three ways in which the onset may be triggered. Several other consequences related to substorm dynamics are suggested by the simple catastrophe model.

  12. Boron Sheet Adsorbed on Metal Surfaces: Structures and Electronic L. Z. Zhang,

    E-print Network

    Gao, Hongjun

    Boron Sheet Adsorbed on Metal Surfaces: Structures and Electronic Properties L. Z. Zhang, Q. B. Yan of monolayer boron sheets (BSs) on different metal (Mg, Al, Ti, Au, and Ag) surfaces. We find that, when according to the interactions between boron and metal: (1) h-BS on Mg(0001), Al(111), or Ti(0001) shows

  13. Confinement of Pure Ion Plasma in a Cylindrical Current Sheet

    SciTech Connect

    C.K. Phillips; E.H. Chao; R.C. Davidson; S.F. Paul

    1999-12-10

    A novel method for containing a pure ion plasma at thermonuclear densities and temperatures has been modeled. The method combines the confinement properties of a Penning-Malmberg trap and some aspects of the magnetic field geometry of a pulsed theta-pinch. A conventional Penning trap can confine a uniform-density plasma of about 5x1011 cm-3 with a 30-Tesla magnetic field. However, if the axial field is ramped, a much higher local ion density can be obtained. Starting with a 107 cm-3 trapped deuterium plasma in a conventional Penning-Malmberg trap at the Brillouin limit (B = 0.6 Tesla), the field is ramped to 30 Tesla. Because the plasma is comprised of particles of only one sign of charge, transport losses are very low, i.e., the conductivity is high. As a result, the ramped field does not penetrate the plasma and a diamagnetic surface current is generated, with the ions being accelerated to relativistic velocities. To counteract the inward j x B forces from this induced current, additional ions are injected into the plasma along the axis to increase the density (and mutual electrostatic repulsion) of the target plasma. In the absence of the higher magnetic field in the center, the injected ions drift outward until a balance is established between the outward driving forces (centrifugal, electrostatic, pressure gradient) and the inward j x B force. An equilibrium calculation using a relativistic, 1-D, cold-fluid model shows that a plasma can be trapped in a hollow, 49-cm diameter, 0.2-cm thick cylinder with a density exceeding 4 x 1014 cm-3.

  14. Kink-like mode of a double gradient instability in a compressible plasma current sheet

    PubMed Central

    Korovinskiy, D.B.; Ivanova, V.V.; Erkaev, N.V.; Semenov, V.S.; Ivanov, I.B.; Biernat, H.K.; Zellinger, M.

    2011-01-01

    A linear MHD instability of the electric current sheet, characterized by a small normal magnetic field component, varying along the sheet, is investigated. The tangential magnetic field component is modeled by a hyperbolic function, describing Harris-like variations of the field across the sheet. For this problem, which is formulated in a 3D domain, the conventional compressible ideal MHD equations are applied. By assuming Fourier harmonics along the electric current, the linearized 3D equations are reduced to 2D ones. A finite difference numerical scheme is applied to examine the time evolution of small initial perturbations of the plasma parameters. This work is an extended numerical study of the so called “double gradient instability”, – a possible candidate for the explanation of flapping oscillations in the magnetotail current sheet, which has been analyzed previously in the framework of a simplified analytical approach for an incompressible plasma. The dispersion curve is obtained for the kink-like mode of the instability. It is shown that this curve demonstrates a quantitative agreement with the previous analytical result. The development of the instability is investigated also for various enhanced values of the normal magnetic field component. It is found that the characteristic values of the growth rate of the instability shows a linear dependence on the square root of the parameter, which scales uniformly the normal component of the magnetic field in the current sheet. PMID:22053125

  15. Superposed Epoch Analysis of Cold, Dense Plasma Sheet Access to Geosynchronous Orbit

    NASA Astrophysics Data System (ADS)

    Lavraud, B.; Denton, M. H.; Thomsen, M. F.; Borovsky, J. E.

    2005-05-01

    We report on the occurrence of cold, dense plasma access to geosynchronous orbit. We performed a superposed epoch analysis of 1952 events of dense (> 2 /cc at onset) plasma observed by the MPA instruments onboard the Los Alamos satellites, for the period 1990-2002. The results show the temporal evolution of various plasma parameters as a function of local time. We show that dense plasma access to geosynchronous orbit mostly occurs near local midnight. Such access is also observed at slightly later times on the dawnside of geosynchronous orbit. We demonstrate that this latter population is, however, not the result of the dawnward transport of the population detected near midnight. The dense plasma population observed in the midnight region is shown to be freshly injected from the mid-tail region, colder than the typical plasma sheet and composed of a relatively small O+ component. This population is thus probably the result of cold, dense plasma sheet (CDPS) injection from the mid-tail region. The population observed on the dawnside of geosynchronous orbit is possibly the result of inward motion of the low-latitude boundary layer (LLBL). The observation of an enhanced Kp index around the arrival of the CDPS at geosynchronous orbit shows that the inward transport of these populations is allowed by an enhanced magnetospheric convection.

  16. High resolution measurements of density structures in the Jovian plasma sheet

    NASA Technical Reports Server (NTRS)

    Ansher, J. A.; Kurth, W. S.; Gurnett, D. A.; Goertz, C. K.

    1991-01-01

    A recent effort to digitize the plasma density by using the low frequency cutoff of trapped continuum radiation in the vicinity of the Jovian plasma sheet has revealed the existence of sharply defined density structures in the plasma sheet. These structures typically have a plasma density which is relatively constant but of order 50 percent greater or less than in the surrounding plasma. At the boundaries of these structures, the transitions from low to high density occur on time scales of about ten seconds, which correspond to spatial dimensions on the order of a few ion Larmor radii. The structures themselves last for intervals from less than a minute to more than five minutes, corresponding to size scales from a fraction of a Jovian radius to more than a Jovian radius, depending of the velocity of the structure relative to the spacecraft. In view of the importance of near corotation plasma flows, these structures are likely to be limited in both the longitudinal and radial dimensions and, therefore, could represent flux tubes with greatly varying plasma content. These observations are presented as among the first to directly address the theoretically proposed interchange instability.

  17. Electron Boltzmann equation in nonthermal plasmas

    NASA Technical Reports Server (NTRS)

    Kunc, J. A.; Soon, W. H.

    1991-01-01

    Numerical and analytical solutions of the electron Boltzmann equation for a two-temperature steady-state He plasma are examined in a broad range of conditions, i.e., atom temperature ranging from 5000 K to 20,000 K; electron temperature ranging from 10,000 K to 20,000 K; and atom density ranging from 10 to the 10th to 10 to the 18th per cu cm. The WKB analytical solution is shown to be satisfactory in most situations. Attention is also given to the deviation of the electron distribution from Maxwellian, and to the possibility of raising the tail of the distribution.

  18. Electron Beam Generation by an Electron Cyclotron Resonance Plasma

    Microsoft Academic Search

    Max Light; Tsitsi G. Madziwa-Nussinov; Patrick Colestock; Ronald Kashuba

    2009-01-01

    Electron guns based on a plasma, instead of a thermionic material cathode, are gaining more attention due to their ability to generate beams of a variety of sizes for both pulsed and steady state operation. These guns have a major advantage in that they have no material cathode, can drive current densities larger than their thermionic counterparts, and can operate

  19. An electron gun for a sheet beam klystron

    Microsoft Academic Search

    M. E. Read; G. Miram; R. L. Ives; V. Ivanov; A. Krasnykh

    2002-01-01

    Calabazas Creek Research, Inc.(CCR) is developing a rectangular, gridded, thermionic, dispenser-cathode gun for sheet beam devices. We present the preliminary design of a 415 kV, 250 A gridded gun for a sheet beam klystron, giving results from 2D and 3D simulations.

  20. Electron cyclotron emission from nonthermal tokamak plasmas

    SciTech Connect

    Harvey, R.W.; O'Brien, M.R.; Rozhdestvensky, V.V.; Luce, T.C.; McCoy, M.G.; Kerbel, G.D. (General Atomics, San Diego, California 92186-9784 (United States))

    1993-02-01

    Electron cyclotron emission can be a sensitive indicator of nonthermal electron distributions. A new, comprehensive ray-tracing and cyclotron emission code that is aimed at predicting and interpreting the cyclotron emission from tokamak plasmas is described. The radiation transfer equation is solved along Wentzel--Kramers--Brillouin (WKB) rays using a fully relativistic calculation of the emission and absorption from electron distributions that are gyrotropic and toroidally symmetric, but may be otherwise arbitrary functions of the constants of motion. Using a radial array of electron distributions obtained from a bounce-averaged Fokker--Planck code modeling dc electron field and electron cyclotron heating effects, the cyclotron emission spectra are obtained. A pronounced strong nonthermal cyclotron emission feature that occurs at frequencies relativistically downshifted to second harmonic cyclotron frequencies outside the tokamak is calculated, in agreement with experimental results from the DIII-D [J. L. Luxon and L. G. Davies, Fusion Technol. [bold 8], 441 (1985)] and FT-1 [D. G. Bulyginsky [ital et] [ital al]., in [ital Proceedings] [ital of] [ital the] 15[ital th] [ital European] [ital Conference] [ital on] [ital Controlled] [ital Fusion] [ital and] [ital Plasma] [ital Heating], Dubrovnik, 1988 (European Physical Society, Petit-Lancy, 1988), Vol. 12B, Part II, p. 823] tokamaks. The calculations indicate the presence of a strong loss mechanism that operates on electrons in the 100--150 keV energy range.

  1. Turbulent electron thermal transport in fusion plasmas

    NASA Astrophysics Data System (ADS)

    Kim, Juhyung

    Electron heat transport at the scale of electron gyroradius are investigated via numerical simulation of a fluid model and a role of E x B shear flow with intermediate E x B shearing rate is explored in Euler's equation. The anomalous transport, enhanced transport due to turbulent electromagnetic fields caused by plasma instabilities, has been a focus of the international fusion research communities. Among the instabilities, the drift-type instabilities from the pressure-gradient universal in magnetic fusion devices are considered responsible for the anomalous transport. In the current status of wide use of wave heating on electrons and subsequent high core electron temperature, the turbulent heat loss through electrons has one of the most important science element in preventing the large fusion tokamaks from reaching breakeven in the past decade. The Electron Temperature Gradient fluid model consists of electrostatic potential, toroidal magnetic flux function and electron temperature (or pressure) describing electron drift waves. The fluid model proves to be highly useful to electron heat flux analysis in fusion machines. We analyze the discharges in National Spherical Tokamak eXperiment(NSTX) and Tokamak Configuration Variable (TCV) and found that the electron thermal diffusivities can be explained in terms of the mixing length argument based on electron gyroradius, linear theory and our nonlinear fluid simulation. The nonlinear fluid model predicts reasonable heat flux observed in the experiments. Based on the analysis, we investigate the dependences of the dynamics on the ratio of electron and ion temperature Te/Ti and plasma beta betae . The nonlinear dynamics such as saturation mechanism of the ETG turbulence and the electromagnetic dynamics in terms of micro-tearing at the scale of electron gyroradius are discussed briefly. In most of plasma confinement devices, the equilibrium radial electric field exists and the turbulence-generated electric field is observed. The coherent structure, called as zonal flow, has been know to be effective to suppress the micro-turbulence. But at intermediate E x B shear, where the vortex eddy turn-over time is comparable to E x B shearing rate, the suppression is weak and the flow shear can leads to vortex amplification through interaction of nonlinear dynamics and shear flow.

  2. Electron acoustic surface waves in a two-electron component plasma

    SciTech Connect

    Bharuthram, R.; Misthry, S.S.; Yu, M.Y. (Department of Physics, University of Durban-Westville, Durban 4000 ( ) Plasma Physics Research Institute, University of Natal, Durban 4001 (South Africa))

    1993-12-01

    Surface electron acoustic waves on a two-electron component plasma in a semi-infinite half-space are investigated. The dispersion relation of these waves differs considerably from that of the surface electron plasma waves.

  3. Electron Scattering in Hot/Warm Plasmas

    SciTech Connect

    Rozsnyai, B F

    2008-01-18

    Electrical and thermal conductivities are presented for aluminum, iron and copper plasmas at various temperatures, and for gold between 15000 and 30000 Kelvin. The calculations are based on the continuum wave functions computed in the potential of the temperature and density dependent self-consistent 'average atom' (AA) model of the plasma. The cross sections are calculated by using the phase shifts of the continuum electron wave functions and also in the Born approximation. We show the combined effect of the thermal and radiative transport on the effective Rosseland mean opacities at temperatures from 1 to 1000 eV. Comparisons with low temperature experimental data are also presented.

  4. Silicone Coating on Polyimide Sheet

    NASA Technical Reports Server (NTRS)

    Park, J. J.

    1985-01-01

    Silicone coatings applied to polyimide sheeting for variety of space-related applications. Coatings intended to protect flexible substrates of solar-cell blankets from degradation by oxygen atoms, electrons, plasmas, and ultraviolet light in low Earth orbit and outer space. Since coatings are flexible, generally useful in forming flexible laminates or protective layers on polyimide-sheet products.

  5. Theoretical predictions on the electronic structure and charge carrier mobility in 2D Phosphorus sheets

    PubMed Central

    Xiao, Jin; Long, Mengqiu; Zhang, Xiaojiao; Ouyang, Jun; Xu, Hui; Gao, Yongli

    2015-01-01

    We have investigated the electronic structure and carrier mobility of four types of phosphorous monolayer sheet (?-P, ?-P,?-P and ?-P) using density functional theory combined with Boltzmann transport method and relaxation time approximation. It is shown that ?-P, ?-P and ?-P are indirect gap semiconductors, while ?-P is a direct one. All four sheets have ultrahigh carrier mobility and show anisotropy in-plane. The highest mobility value is ~3?×?105?cm2V?1s?1, which is comparable to that of graphene. Because of the huge difference between the hole and electron mobilities, ?-P, ?-P and ?-P sheets can be considered as n-type semiconductors, and ?-P sheet can be considered as a p-type semiconductor. Our results suggest that phosphorous monolayer sheets can be considered as a new type of two dimensional materials for applications in optoelectronics and nanoelectronic devices. PMID:26035176

  6. Theoretical predictions on the electronic structure and charge carrier mobility in 2D Phosphorus sheets.

    PubMed

    Xiao, Jin; Long, Mengqiu; Zhang, Xiaojiao; Ouyang, Jun; Xu, Hui; Gao, Yongli

    2015-01-01

    We have investigated the electronic structure and carrier mobility of four types of phosphorous monolayer sheet (?-P, ?-P,?-P and ?-P) using density functional theory combined with Boltzmann transport method and relaxation time approximation. It is shown that ?-P, ?-P and ?-P are indirect gap semiconductors, while ?-P is a direct one. All four sheets have ultrahigh carrier mobility and show anisotropy in-plane. The highest mobility value is ~3?×?10(5)?cm(2)V(-1)s(-1), which is comparable to that of graphene. Because of the huge difference between the hole and electron mobilities, ?-P, ?-P and ?-P sheets can be considered as n-type semiconductors, and ?-P sheet can be considered as a p-type semiconductor. Our results suggest that phosphorous monolayer sheets can be considered as a new type of two dimensional materials for applications in optoelectronics and nanoelectronic devices. PMID:26035176

  7. Connections Between Plasma Sheet Transport, Region 2 Currents, and Entropy Changes During Substorms and SMCs

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Wang, C.; Nagai, T.

    2007-12-01

    Modeling shows that energy-dependent magnetic drift leads to a divergence of particles and particle energy flux that gives significant violation of entropy conservation along the direction of the plasma bulk velocity. This is of critical importance to understanding the formation of the substorm growth-phase plasma sheet and the maintenance of a stable plasma sheet during SMC periods of prolonged enhanced convection. The particle divergence also is a divergence of the cross tail current, leading to the field-aligned currents that form the Region 2 system. Thus the Region 2 current system provides direct evidence that the modeled variations in entropy are reasonable. Shielding of the convection electric field from the inner magnetosphere is an aspect of the Region 2 system, so that the well-known development of shielding after a convection enhancement can be viewed as an additional signature of violation of entropy conservation. Region 2 field-aligned currents dramatically enhance during the substorm expansion phase in the vicinity of the Harang electric field reversal, signaling a region of greatly enhanced plasma sheet particle and current divergence. This enhanced divergence should also be a region of greatly enhanced divergence of particle energy flux, which should lead to significant reduction of plasma sheet entropy and pressure within the substorm current wedge, and such a reduction has been observed with Geotail. The observations also show a reduction of the flux tube content of particles over a broad range of invariant energies, despite the apparent injections of energetic particles inferred from fluxes measured at fixed particle energies. Evidence suggests that a reduction in the strength of earthward convection can initiate the enhanced divergence within the current wedge. Observations from the new ground radars and THEMIS will provide critical information for the evaluation and further understanding of the above processes.

  8. Formation of electron clouds during particle acceleration in a 3D current sheet

    Microsoft Academic Search

    Valentina V. Zharkova; Taras Siversky

    2011-01-01

    Acceleration of protons and electrons in a reconnecting current sheet (RCS) is investigated with the test particle and particle-in-cell (PIC) approaches in the 3D magnetic configuration including the guiding field. PIC simulations confirm a spatial separation of electrons and protons towards the midplane and reveal that this separation occur as long as protons are getting accelerated. During this time electrons

  9. Plasma parameters controlled by remote electron shower in a double plasma device

    NASA Astrophysics Data System (ADS)

    Mishra, M. K.; Phukan, A.

    2012-07-01

    The principal feature of this experiment is the electron showers consisting of three tungsten wires embedded by the plasma, which are heated up consequently emitting electrons inside the diffused plasma to control the plasma parameters in the discharge section of a double plasma device. These cold electrons emitted by the heated filament are free from maintenance of discharge which is sustained in the source section. The target plasma, where electrons are injected is produced as a result of diffusion from the source section. It is found that, plasma density and plasma potential can be effectively controlled in this way.

  10. Free electron laser with small period wiggler and sheet electron beam: A study of the feasibility of operation at 300 GHz with 1 MW CW output power

    SciTech Connect

    Booske, J.H.; Granatstein, V.L.; Antonsen, T.M. Jr.; Destler, W.W.; Finn, J.; Latham, P.E.; Levush, B.; Mayergoyz, I.D.; Radack, D.; Rodgers, J.

    1988-01-01

    The use of a small period wiggler (/ell//sub ..omega../ < 1 cm) together with a sheet electron beam has been proposed as a low cost source of power for electron cyclotron resonance heating (ECRH) in magnetic fusion plasmas. Other potential applications include space-based radar systems. We have experimentally demonstrated stable propagation of a sheet beam (18 A. 1 mm /times/ 20 mm) through a ten-period wiggler electromagnet with peak field of 1.2 kG. Calculation of microwave wall heating and pressurized water cooling have also been carried out, and indicate the feasibility of operating a near-millimeter, sheet beam FEL with an output power of 1 MW CW (corresponding to power density into the walls of 2 kW/cm/sup 2/). Based on these encouraging results, a proof-of-principle experiment is being assembled, and is aimed at demonstrating FEL operating at 120 GHz with 300 kW output power in 1 ..mu..s pulses: electron energy would be 410 keV. Preliminary design of a 300 GHz 1 MW FEL with an untapered wiggler is also presented. 10 refs., 5 figs., 3 tabs.

  11. Collisional damping of plasma waves on a pure electron plasma column M. W. Anderson and T. M. O'Neil

    E-print Network

    California at San Diego, University of

    Collisional damping of plasma waves on a pure electron plasma column M. W. Anderson and T. M. O of electron plasma waves or Trivelpiece­Gould waves on a pure electron plasma column is discussed. The damping in a pure electron plasma differs from that in a neutral plasma, since there are no ions to provide

  12. Understanding Turbulence in the Plasma Sheet and Its Role in Transport

    NASA Astrophysics Data System (ADS)

    El-Alaoui, M.; Ashour-Abdalla, M.; Lapenta, G.; Richard, R. L.

    2014-12-01

    In this study the nature and implications of turbulence in the plasma sheet is explored with emphasis on large scale and meso-scale processes. The relationship between turbulence and reconnection, and its contribution to magnetospheric transport and dynamics will be evaluated. Observational studies to date have shown that the magnetotail rarely exhibits simple steady convection; instead, flows in the magnetotail have a high level of fluctuations. Flows driven on the scale of the entire system are well described by MHD and break up into structures that cascade to smaller scales. MHD simulation studies have shown the presence of realistic fluctuation spectra both in case studies where direct comparisons to observations have been made and in idealized test cases which have been compared to the statistical studies of observed events. The simulations do a good job of representing the effects of dissipation and yield dissipative scale lengths that are comparable to those inferred from observations. At intermediate, meso-scales, which receive energy from both large and small scales, turbulent processes are important in the plasma sheet, in particular around dipolarization fronts. We will explore the interaction between large-scale and smaller-scale fluctuations and their contributions to the magnetotail current sheet structure. We will use a global MHD simulation and a two dimensional version of the iPIC3Dimplicit particle in cell simulation separately to examine how turbulence is related to global and local processes involved in the current sheet.

  13. RCM-E simulation of bimodal transport in the plasma sheet

    NASA Astrophysics Data System (ADS)

    Yang, Jian; Wolf, Richard A.; Toffoletto, Frank R.; Sazykin, Stanislav; Wang, Chih-Ping

    2014-03-01

    Plasma sheet transport is bimodal, consisting of both large-scale adiabatic convection and intermittent bursty flows in both earthward and tailward directions. We present two comparison simulations with the Rice Convection Model—Equilibrium (RCM-E) to investigate how those high-speed flows affect the average configuration of the magnetosphere and its coupling to the ionosphere. One simulation represents pure large-scale slow-flow convection with time-independent boundary conditions; in addition to the background convection, the other simulation randomly imposes bubbles and blobs through the tailward boundary to a degree consistent with observed statistical properties of flows. Our results show that the bursty flows can significantly alter the magnetic and entropy profiles in the plasma sheet as well as the field-aligned current distributions in the ionosphere, bringing them into much better agreement with average observations.

  14. Plasma sheet access to the inner magnetosphere during bursty bulk flows

    NASA Astrophysics Data System (ADS)

    Elkington, S. R.; Wiltberger, M. J.; Jaynes, A. N.; Malaspina, D.

    2014-12-01

    Energetic particles in the plasma sheet and near-Earth magnetotail can be transported sunward by large-scale magnetospheric convective processes, allowing some populations to be trapped inside the 'Alfven Layer' on close drift paths in the inner magnetosphere. These newly-trapped particles may contribute directly to the seed populations that are subsequently heated to ring current and radiation belt energies, and may also provide a source of free energy for the generation of electromagnetic waves that affect the dynamic variations of the outer radiation belts. In this work, we examine the access of plasma sheet particles to the inner magnetosphere using a combination of global MHD/test particle simulations and observations from geosynchronous, THEMIS, and the Van Allen probes. We focus in particular on transient events associated with substorm activity and bursty bulk flows, and contrast particle access to geosynchronous orbit during these events with that observed during steady driving of the magnetosphere.

  15. Electron kinetics in a cooling plasma

    SciTech Connect

    Helander, P.; Smith, H.; Fueloep, T.; Eriksson, L.-G. [Euratom/UKAEA Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Department of Electromagnetics, Chalmers University of Technology, 412 96 Goeteborg (Sweden); Association Euratom-CEA, CEA/DSM/DRFC, Centre de Cadarache, 13108 Saint-Paul lez Durance (France)

    2004-12-01

    The distribution function of suprathermal electrons in a slowly cooling plasma is calculated by an asymptotic expansion in the cooling rate divided by the collision frequency. Since the collision frequency decreases with increasing velocity, a high-energy tail forms in the electron distribution function as the bulk population cools down. Under certain simplifying assumptions (slow cooling, constant density, Born approximation of cross sections), the distribution function evolves to a self-similar state where the tail is inversely proportional to the cube of the velocity. Its practical consequences are discussed briefly.

  16. Superthermal electron production from hot underdense plasmas

    SciTech Connect

    Aithal, S.; Lavigne, P.; Pepin, H.; Johnston, T.W.; Estabrook, K.

    1987-12-01

    Very-high-energy electrons of up to an energy of approx.2.3 MeV have been observed to be emitted from the hot underdense exploding thin foil plasmas created by 10.6 ..mu..m CO/sub 2/ laser radiation at intensity levels up to approx.4 x 10/sup 14/ W/cm/sup 2/. As a supplement to the electron measurements the forward and backward scattered light components were also measured. Correlation of these measurements shows that either Raman scattering or the high-temperature version of two-plasmon decay or both, manifesting themselves near the quarter-critical density region, are responsible for the production of a hot (T/sub h/approx.135 keV) tail of electrons at least up to energies of 1 MeV. There are no indications that the Raman forward scattering (as distinct from Raman backward scattering) at lower densities plays any significant role. These experimental results are consistent with the results from a l 1/2 -dimensional particle-in-cell code simulation with a parabolic density profile resembling the experimental conditions. An apparent anomaly is discussed, which is that hot electrons are produced (both in experiments and simulations) at energies higher than the trapping value appropriate to electron plasma waves whose phase velocity is equal to the matching value (C/(3)/sup 1/2/) at the turning point for the light of half the laser frequency.

  17. Density effect on relativistic electron beams in a plasma fiber

    SciTech Connect

    Zhou, C. T.; He, X. T. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Wang, X. G. [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Wu, S. Z. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Cai, H. B. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Wang, F. [Center for Applied Physics and Technology, Peking University, Beijing 100871 (China)

    2010-11-15

    Intense short-petawatt-laser driven relativistic electron beams in a hollow high-Z plasma fiber embedded in low-Z plasmas of different densities are studied. When the plasma is of lower density than the hollow fiber, resistive filamentation of the electron beam is observed. It is found that the electron motion and the magnetic field are highly correlated with tens of terahertz oscillation frequency. Depending on the material property around the hollow fiber and the plasma density, the beam electrons can be focused or defocused as it propagates in the plasma. Relativistic electron transport and target heating are also investigated.

  18. Plasma plume oscillations during welding of thin metal sheets with a CW CO2 laser

    Microsoft Academic Search

    Z. Szymanski; J. Hoffman; J. Kurzyna

    2001-01-01

    An analysis is presented of the oscillations of keyhole pressure and plasma radiation emitted during welding with a continuous wave (CW) CO2 laser. Welding was done with a CW CO2 laser, Photon Sources VFA 2500, operating at the power of 1.75 kW. The welded materials were mild and stainless steel sheets, 0.8-2 mm thick. The shielding gas was argon or

  19. Formation of the Harang reversal and its dependence on plasma sheet conditions: Rice convection model simulations

    NASA Astrophysics Data System (ADS)

    Gkioulidou, Matina; Wang, Chih-Ping; Lyons, Larry R.; Wolf, Richard A.

    2009-07-01

    The goal of this paper is to understand the formation of the Harang reversal and its association with the region 2 field-aligned current (FAC) system, which couples the plasma sheet transport to the ionosphere. We have run simulations with the Rice convection model (RCM) using the Tsyganenko 96 magnetic field model and realistic plasma sheet particle boundary conditions on the basis of Geotail observations. Our results show that the existence of an overlap in magnetic local time (MLT) of the region 2 upward and downward FAC is necessary for the formation of the Harang reversal. In the overlap region the downward FAC, which is located at lower latitudes, is associated with low-energy ions that penetrate closer to Earth toward the dawn side, while the upward FAC, which is located at higher latitudes, is associated with high-energy ions. Under the same enhanced convection we compare the Harang reversal resulting from a hotter and more tenuous plasma sheet with the one resulting from a colder and denser plasma sheet. For the former case the shielding of the convection electric field is less efficient than for the latter case, allowing low-energy protons to penetrate further earthward, resulting in a Harang reversal that extends to lower latitudes, expands wider in MLT, and is located further equatorward than the upward FAC peak and the conductivity peak. The return flows of the Harang reversal in the hot and tenuous case are located in a low conductivity region. This leads to an enhancement of these westward flows, resulting in subauroral polarization streams (SAPS).

  20. THEMIS observations of plasma bubbles associated with energetic electron acceleration in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Tang, C. L.

    2014-12-01

    Using Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations, we study the plasma bubbles associated with a transient increase of the magnetic field Bz component in the inner magnetosphere during the substorm expansion phase. Except small electric field, the main characteristics of these plasma bubbles are similar with those associated with dipolarization front (DF) in the mid-tail and near-Earth tail. Based on the different dipolarization of the magnetic field, we defined the plasma bubble with no dipolarization phenomenon as "no dipolarization bubble" (NDB), the plasma bubble with dipolarization phenomenon as "dipolarization bubble" (DB). We find that these plasma bubbles in the inner magnetosphere accompany the energetic electron acceleration. Some pancake-type distributions of energetic electrons inside the NDB in the inner magnetosphere are caused by drift betatron acceleration, other pancake-type distributions of energetic electrons inside the NDB are caused by gyrobetatron acceleration. For the DB in the inner magnetosphere, the cigar-type distributions of energetic electrons are attributed to Fermi acceleration. Our observations suggest that the inner magnetosphere may be a very important source region for energetic electrons, except for a reconnection site in the mid-tail and the plasma sheet in the near-Earth tail.

  1. A statistical study of plasma sheet dynamics using ISEE 1 and 2 energetic particle flux data

    NASA Technical Reports Server (NTRS)

    Dandouras, J.; Reme, H.; Saint-Marc, A.; Sauvaud, J. A.; Parks, G. K.

    1986-01-01

    Plasma sheet dynamics during substorms are studied by analyzing 461 cases of transient dropout events of the 1.5 and 6-keV particle fluxes detected by ISEE 1 and 2 satellites. The instruments for detecting low- and high-energy particles are described. The spatial distribution of flux dropout events, and the events' relationship to magnetospheric activity level are examined. Substorm events without observed flux dropout events are investigated. The data reveal that the flux dropout distribution is isotropic, between 12-23 earth radii, and is present in the entire nightside plasma sheet; and the substorms without flux dropout are more frequent near earth and magnetospheric flanks. It is observed that tailward of 12 earth radii the flux dropout events and substorms without flux dropout are similar. The Chao et al. (1977) MHD rarefaction wave propagation model and the Hones (1973, 1980) near-tail, X-type magnetic neutral line formation model are discussed and compared to the experimental data. It is noted that neither model explains the plasma sheet dynamics observed.

  2. Electron-acoustic solitons in an electron-beam plasma system with kappa-distributed electrons

    NASA Astrophysics Data System (ADS)

    Danehkar, A.; Kourakis, I.; Hellberg, M. A.

    2014-05-01

    Interaction of a stream of high-energy electrons with the background plasma plays an important role in the astrophysical phenomena such as interplanetary and stellar bow shock and Earth's foreshock emission. It is not yet fully understood how electrostatic solitary waves are produced at the bow shock. Interestingly, a population of energetic suprathermal electrons were also found to exist in those environments. Previously, we have studied the properties of negative electrostatic potential solitary structures exist in such a plasma with excess suprathermal electrons. In the present study, we investigate the existence conditions and propagation properties of electron-acoustic solitary waves in a plasma consisting of an electron beam fluid, a cold electron fluid, and hot suprathermal electrons modeled by a kappa-distribution function. The Sagdeev pseudopotential method was used to investigate the occurrence of stationary-profile solitary waves. We have determined how the electron-acoustic soliton characteristics depend on the electron beam parameters. It is found that the existence domain for solitons becomes narrower with an increase in the suprathermality of hot electrons, increasing the beam speed, decreasing the beam-to-cold electron population ratio. These results lead to a better understanding of the formation of electron-acoustic solitary waves observed in those space plasma systems characterized by kappa-distributed electrons and inertial drifting (beam) electrons.

  3. Effect of Electron Beam Irradiation on the Tensile Properties of Carbon Nanotubes Sheets and Yarns

    NASA Technical Reports Server (NTRS)

    Williams, Tiffany S.; Miller, Sandi G.; Baker, James S.; McCorkle, Linda S.; Meador, Michael A.

    2013-01-01

    Carbon nanotube sheets and yarns were irradiated using electron beam (e-beam) energy to determine the effect of irradiation dose on the tensile properties. Results showed that a slight change in tensile strength occurred after irradiating as-received CNT sheets for 20 minutes, and a slight decrease in tensile strength as the irradiation time approached 90 minutes. On the other hand, the addition of small molecules to the CNT sheet surface had a greater effect on the tensile properties of e-beam irradiated CNT sheets. Some functionalized CNT sheets displayed up to a 57% increase in tensile strength following 90 minutes of e-beam exposure. In addition, as-received CNT yarns showed a significant increase in tensile strength as the irradiation time increased.

  4. High conductivity magnetic tearing instability. [of neutral plasma sheets

    NASA Technical Reports Server (NTRS)

    Cross, M. A.; Van Hoven, G.

    1976-01-01

    Linearized equations of magnetohydrodynamics are used to investigate the tearing mode, for arbitrary values of the conductivity, through a consideration of the additional effect of the electron-inertia contribution to Ohm's law. A description is provided of the equilibrium and subsequent instability in the magnetohydrodynamic approximation. A method for solving the perturbation equations in the linear approximation is discussed and attention is given to the results in the high conductivity limit.

  5. Probing Runaway Electrons with Nanoparticle Plasma Jet

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    The injection of C60/C nanoparticle plasma jet (NPPJ) into tokamak plasma during a major disruption has the potential to probe the runaway electrons (REs) during different phases of their dynamics and diagnose them through spectroscopy of C ions visible/UV lines. A C60/C NPPJ of ~75 mg, high-density (>1023 m-3), hyper-velocity (>4 km/s), and uniquely fast response-to-delivery time (~1 ms) has been demonstrated on a test bed. It can rapidly and deeply deliver enough mass to increase electron density to ~2.4 × 1021 m-3, ~60 times larger than typical DIII-D pre-disruption value. We will present the results of our investigations on: 1) C60 fragmentation and gradual release of C atoms along C60 NPPJ penetration path through the RE carrying residual cold plasma, 2) estimation of photon emissivity coefficient for the lines of the C ions, and 3) simulation of C60/C PJ penetration to the RE beam location in equivalent conditions to the characteristic ~1 T B-field of DIII-D. The capabilities of this injection technique provide a unique possibility in understanding and controlling the RE beam, which is a critical problem for ITER. Work supported by US DOE DE-SC0011864 Grant.

  6. Angular anisotropy of electron energy distributions in inductively coupled plasmas

    E-print Network

    Kushner, Mark

    Angular anisotropy of electron energy distributions in inductively coupled plasmas Alex V of Physics. DOI: 10.1063/1.1614428 I. INTRODUCTION Low- and intermediate-pressure inductively coupled plasmas coupled plasmas ICPs has the potential to produce highly anisotropic angle-dependent electron energy

  7. Graphene electron cannon: High-current edge emission from aligned graphene sheets

    SciTech Connect

    Liu, Jianlong; Li, Nannan; Guo, Jing; Fang, Yong; Deng, Jiang [National Key Laboratory of Science and Technology on Vacuum Electronics, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Zeng, Baoqing, E-mail: bqzeng@uestc.edu.cn [National Key Laboratory of Science and Technology on Vacuum Electronics, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); State Key Laboratory of Electronic Thin Films and Integrated Devices Zhongshan Lab, Department of Electronic Engineering, University of Electronic Science and Technology of China Zhongshan Institute, Zhongshan 528402 (China); Wang, Wenzhong; Li, Jiangnan; Hao, Chenchun [School of Science, Minzu University of China, Beijing 100081 (China)

    2014-01-13

    High-current field emitters are made by graphene paper consist of aligned graphene sheets. Field emission luminance pattern shows that their electron beams can be controlled by rolling the graphene paper from sheet to cylinder. These specific electron beams would be useful to vacuum devices and electron beam lithograph. To get high-current emission, the graphene paper is rolled to array and form graphene cannon. Due to aligned emission array, graphene cannon have high emission current. Besides high emission current, the graphene cannon is also tolerable with excellent emission stability. With good field emission properties, these aligned graphene emitters bring application insight.

  8. Ion mixing in the plasma sheet boundary layer by drift instabilities

    NASA Technical Reports Server (NTRS)

    Horton, W.; Dong, J. Q.; Su, X. N.; Tajima, T.

    1993-01-01

    The linear stability properties of collisionless drift instabilities are analyzed in a Harris equilibrium model of the plasma sheet boundary layer (PSBL). The strearmng ions with drift-type instabilities driven in the PSBL are considered. The fluid approximation leads to growth but predicts that the mode width approaches the gyroradius of the energetic ions. Thus an integral equation theory for the modes is developed taking into account that in the PSBL the curvature drift is weak compared with the grad-B drift. The exact wave particle resonance is kept in the nonlocal response functions. Plasma density, temperature, and magnetic gradient drift motions are taken into account. The drift modes produce an anomalous cross-field momentum transport mixing the PSBL ions on the time scale of tens of seconds. A nonlinear simulation is performed which shows the coalescence of the small scale, fast growing modes into large-scale vortices. The relation between these collective modes and plasma sheet transport phenomena is discussed including the comparison with the competing plasma mixing from single-particle stochasticity.

  9. Experimental investigation of a Cerenkov grating amplifier for implementation with a sheet electron beam

    Microsoft Academic Search

    M. A. Basten; J. Joe; A. H. Kumbasar; J. H. Booske; J. E. Scharer; B. D. McVey; R. True

    1993-01-01

    Summary form only given. A new facility to investigate the feasibility and physics of low-voltage sheet-beam Cerenkov amplifiers is described. While work progresses on the design of a suitable sheet beam source and periodic magnetic focusing system, initial experiments near 14 GHz will be conducted using a pencil beam from a 10-kV, 0.25 A Piece electron source matched into a

  10. Effect of Electron Beam Irradiation, EPDM and Azodicarbonamide on the Foam Properties of LDPE Sheet

    Microsoft Academic Search

    Magdy M. Senna; Hussein A. Youssef; Hannan M. Eyssa

    2007-01-01

    The effect of electron beam irradiation, EPDM blending, and Azodicarbonamide (ACA) concentration on the foaming properties of LDPE sheet was investigated. The studied properties are foaming degree, cell densities, mechanical properties and thermal decomposition properties. The data showed that the increasing of foaming agent (ACA) concentration reduces the mechanical properties and increases the gel content. Also, electron beam irradiation has

  11. Diagnosis of Unmagnetized Plasma Electron Number Density and Electron-neutral Collision Frequency by Using Microwave

    Microsoft Academic Search

    Zhongcai Yuan; Jiaming Shi; Bo Xu

    2005-01-01

    The plasma diagnostic method using the transmission attenuation of microwaves at double frequencies (PDMUTAMDF) indicates that the frequency and the electron-neutral collision frequency of the plasma can be deduced by utilizing the transmission attenuation of microwaves at two neighboring frequencies in a non-magnetized plasma. Then the electron density can be obtained from the plasma frequency. The PDMUTAMDF is a simple

  12. Connections between large-scale transport to the inner magnetosphere from the distant plasma sheet, region 2 coupling to the ionosphere, and substorm and storm dynamics (Invited)

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Wang, C.; Zou, S.; Gkioulidou, M.; Nishimura, Y.; Shi, Y.; Kim, H.; Xing, X.; Nicolls, M. J.; Heinselman, C. J.

    2009-12-01

    Studies using a variety of ground-based and spacecraft observations, as well as the Rice Convection Model, have taught us much about the connection between plasma sheet transport and particle distributions within the inner plasma sheet. These studies have shown that plasma moves earthward (equatorward in the ionosphere) after enhancements in convection to reach the near-Earth plasma sheet, leading to the enhancements in plasma sheet pressure that are responsible for the growth phase of substorms and the partial ring current. The highest inner plasma sheet pressures likely occur in the subauroral polarization streams (SAPS) region of the evening-side convection cell, lying equatorward of the Harang reversal. Both the Harang reversal and SAPS are manifestations of the region 2 (R2) electrodynamical coupling, so that transport to the near-Earth plasma sheet is strongly influenced by the R2 magnetosphere-ionosphere coupling. Modeling results show that this transport, together with the concurrent R2 coupling, is also strongly dependent on the plasma distributions that enter the plasma sheet. However, the entering plasma distribution is expected to have substantial spatial and temporal structure, which should impart substantial spatial structure and time dependencies to the inner plasma sheet particle distributions. In addition, very recent analyses indicate that the temporal variations of the particle distribution entering the plasma sheet, and the ensuing transport of new particle distributions within the plasma sheet, is fundamental to understanding the substorm expansion phase. Taken together, the above results indicate that an important understanding of inner magnetosphere particle distributions and their dynamics, as well as of major geomagnetic disturbances, is likely to come from integrated studies of plasma sheet particle entry, particle transport, and electrodynamical coupling to the ionosphere.

  13. Self-organized criticality in the substorm phenomenon and its relation to localized reconnection in the magnetospheric plasma sheet

    Microsoft Academic Search

    A. J. Klimas; J. A. Valdivia; D. Vassiliadis; D. N. Baker; M. Hesse; J. Takalo

    2000-01-01

    Evidence is presented that suggests that there is a significant self-organized criticality (SOC) component in the dynamics of substorms in the magnetosphere. We assume that observations of bursty bulk flows, fast flows, localized dipolarizations, plasma turbulence, etc. show that multiple localized reconnection sites provide the basic avalanche phenomenon in the establishment of SOC in the plasma sheet. First results are

  14. Electron Recombination in a Dense Hydrogen Plasma

    SciTech Connect

    Jana, M.R.; Johnstone, C.; Kobilarcik, T.; Koizumi, G.M.; Moretti, A.; Popovic, M.; Tollestrup, A.V.; Yonehara, K.; /Fermilab; Leonova, M.A.; Schwarz, T.A.; /Fermilab; Chung, M.; /Unlisted /IIT, Chicago /Fermilab /MUONS Inc., Batavia /Turin Polytechnic

    2012-05-01

    A high pressure hydrogen gas filled RF cavity was subjected to an intense proton beam to study the evolution of the beam induced plasma inside the cavity. Varying beam intensities, gas pressures and electric fields were tested. Beam induced ionized electrons load the cavity, thereby decreasing the accelerating gradient. The extent and duration of this degradation has been measured. A model of the recombination between ionized electrons and ions is presented, with the intent of producing a baseline for the physics inside such a cavity used in a muon accelerator. Analysis of the data taken during the summer of 2011 shows that self recombination takes place in pure hydrogen gas. The decay of the number of electrons in the cavity once the beam is turned off indicates self recombination rather than attachment to electronegative dopants or impurities. The cross section of electron recombination grows for larger clusters of hydrogen and so at the equilibrium of electron production and recombination in the cavity, processes involving H{sub 5}{sup +} or larger clusters must be taking place. The measured recombination rates during this time match or exceed the analytic predicted values. The accelerating gradient in the cavity recovers fully in time for the next beam pulse of a muon collider. Exactly what the recombination rate is and how much the gradient degrades during the 60 ns muon collider beam pulse will be extrapolated from data taken during the spring of 2012.

  15. Nonlocal electron kinetics in collisional gas discharge plasmas

    Microsoft Academic Search

    Vladimir I. Kolobov; Valery A. Godyak

    1995-01-01

    Nonlocal phenomena in electron kinetics of collisional gas discharge plasmas, their kinetic treatment by a nonlocal approach, and relevant experimental results are reviewed in this paper. Using the traditional two-term approximation for the electron distribution function, a general method to analyze electron kinetics in nonuniform plasmas in DC and RF fields for atomic gases is presented for the nonlocal case,

  16. Studies of Cryogenic Electron Plasmas in Magnetic Mirror Fields

    E-print Network

    Fajans, Joel

    Studies of Cryogenic Electron Plasmas in Magnetic Mirror Fields by Ramesh Gopalan A.B. (University: Chair Date Date Date University of California at Berkeley 1998 #12;Studies of Cryogenic Electron Plasmas in Magnetic Mirror Fields Copyright 1998 by Ramesh Gopalan #12;1 Abstract Studies of Cryogenic Electron

  17. Electron Beam Emission Characteristics from Plasma Focus Devices

    SciTech Connect

    Zhang, T.; Patran, A.; Wong, D.; Hassan, S.M.; Springham, S.V.; Tan, T.L.; Lee, P.; Lee, S.; Rawat, R.S. [Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University (Singapore)

    2006-01-05

    In this paper we observed the characteristics of the electron beam emission from our plasma focus machine filling neon, argon, helium and hydrogen. Rogowski coil and CCD based magnetic spectrometer were used to obtain temporal and energy distribution of electron emission. And the preliminary results of deposited FeCo thin film using electron beam from our plasma focus device were presented.

  18. A plasma-cathode electron source designed for industrial use

    Microsoft Academic Search

    Igor Osipov; Nikolai Rempe

    2000-01-01

    The article presents a description of the principle of operation, the design, and the performance data of a plasma-cathode electron source. Plasma is produced in a hollow-cathode reflex discharge operating in an axial magnetic field. The discharge unit is filamentless. Air is used as the working gas. The electron source generates a focused continuous electron beam of current up to

  19. Effects of emitted electron temperature on the plasma sheath

    SciTech Connect

    Sheehan, J. P., E-mail: sheehanj@umich.edu [Department of Aerospace Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Kaganovich, I. D.; Wang, H.; Raitses, Y. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Sydorenko, D. [Physics Department, University of Alberta, Edmonton, Alberta T6G 2E9 (Canada); Hershkowitz, N. [Department of Engineering Physics, University of Wisconsin–Madison, Madison, Wisconsin 53706 (United States)

    2014-06-15

    It has long been known that electron emission from a surface significantly affects the sheath surrounding that surface. Typical fluid theory of a planar sheath with emitted electrons assumes that the plasma electrons follow the Boltzmann relation and the emitted electrons are emitted with zero energy and predicts a potential drop of 1.03T{sub e}/e across the sheath in the floating condition. By considering the modified velocity distribution function caused by plasma electrons lost to the wall and the half-Maxwellian distribution of the emitted electrons, it is shown that ratio of plasma electron temperature to emitted electron temperature significantly affects the sheath potential when the plasma electron temperature is within an order of magnitude of the emitted electron temperature. When the plasma electron temperature equals the emitted electron temperature the emissive sheath potential goes to zero. One dimensional particle-in-cell simulations corroborate the predictions made by this theory. The effects of the addition of a monoenergetic electron beam to the Maxwellian plasma electrons were explored, showing that the emissive sheath potential is close to the beam energy only when the emitted electron flux is less than the beam flux.

  20. Detection of steel fatigue cracks with strain sensing sheets based on large area electronics.

    PubMed

    Yao, Yao; Glisic, Branko

    2015-01-01

    Reliable early-stage damage detection requires continuous monitoring over large areas of structure, and with sensors of high spatial resolution. Technologies based on Large Area Electronics (LAE) can enable direct sensing and can be scaled to the level required for Structural Health Monitoring (SHM) of civil structures and infrastructure. Sensing sheets based on LAE contain dense arrangements of thin-film strain sensors, associated electronics and various control circuits deposited and integrated on a flexible polyimide substrate that can cover large areas of structures. This paper presents the development stage of a prototype strain sensing sheet based on LAE for crack detection and localization. Two types of sensing-sheet arrangements with size 6 × 6 inch (152 × 152 mm) were designed and manufactured, one with a very dense arrangement of sensors and the other with a less dense arrangement of sensors. The sensing sheets were bonded to steel plates, which had a notch on the boundary, so the fatigue cracks could be generated under cyclic loading. The sensors within the sensing sheet that were close to the notch tip successfully detected the initialization of fatigue crack and localized the damage on the plate. The sensors that were away from the crack successfully detected the propagation of fatigue cracks based on the time history of the measured strain. The results of the tests have validated the general principles of the proposed sensing sheets for crack detection and identified advantages and challenges of the two tested designs. PMID:25853407

  1. Detection of Steel Fatigue Cracks with Strain Sensing Sheets Based on Large Area Electronics

    PubMed Central

    Yao, Yao; Glisic, Branko

    2015-01-01

    Reliable early-stage damage detection requires continuous monitoring over large areas of structure, and with sensors of high spatial resolution. Technologies based on Large Area Electronics (LAE) can enable direct sensing and can be scaled to the level required for Structural Health Monitoring (SHM) of civil structures and infrastructure. Sensing sheets based on LAE contain dense arrangements of thin-film strain sensors, associated electronics and various control circuits deposited and integrated on a flexible polyimide substrate that can cover large areas of structures. This paper presents the development stage of a prototype strain sensing sheet based on LAE for crack detection and localization. Two types of sensing-sheet arrangements with size 6 × 6 inch (152 × 152 mm) were designed and manufactured, one with a very dense arrangement of sensors and the other with a less dense arrangement of sensors. The sensing sheets were bonded to steel plates, which had a notch on the boundary, so the fatigue cracks could be generated under cyclic loading. The sensors within the sensing sheet that were close to the notch tip successfully detected the initialization of fatigue crack and localized the damage on the plate. The sensors that were away from the crack successfully detected the propagation of fatigue cracks based on the time history of the measured strain. The results of the tests have validated the general principles of the proposed sensing sheets for crack detection and identified advantages and challenges of the two tested designs. PMID:25853407

  2. Field Theoretic Description of Ultrarelativistic Electron-Positron Plasmas

    E-print Network

    Markus H. Thoma

    2009-07-06

    Ultrarelativistic electron-positron plasmas can be produced in high-intensity laser fields and play a role in various astrophysical situations. Their properties can be calculated using QED at finite temperature. Here we will use perturbative QED at finite temperature for calculating various important properties, such as the equation of state, dispersion relations of collective plasma modes of photons and electrons, Debye screening, damping rates, mean free paths, collision times, transport coefficients, and particle production rates, of ultrarelativistic electron-positron plasmas. In particular, we will focus on electron-positron plasmas produced with ultra-strong lasers.

  3. Three-dimensional particle-in-cell simulations of energetic electron generation and transport with relativistic laser pulses in overdense plasmas.

    PubMed

    Sentoku, Y; Mima, K; Sheng, Z M; Kaw, P; Nishihara, K; Nishikawa, K

    2002-04-01

    The interaction of relativistic laser light with overdense plasmas is studied by three-dimensional particle-in-cell simulations. Generation of layered current sheets and quasistatic magnetic fields is observed near the target surface owing to anisotropic laser filamentation and Weibel instabilities. Later these current sheets tear into filaments that partially merge with each other to form isolated magnetic channels penetrating into the dense plasmas. It is found that fast electron energy flow is not only inside the magnetic channels but also it is widely distributed outside the channels. This is possible because of electron anomalous diffusion across self-generated magnetic fields. Consequently, the total hot electron current exceeds a few hundred kiloamperes and is much larger than the Alfvén current. Hence a considerable amount of energy flows towards the plasma core. Significant heating of the bulk plasma electrons is also observed. PMID:12006024

  4. A research of W-band folded waveguide traveling wave tube with elliptical sheet electron beam

    SciTech Connect

    Guo Guo; Wei Yanyu; Yue Lingna; Gong Yubin; Zhao Guoqing; Huang Minzhi; Tang Tao; Wang Wenxiang [National Key Laboratory of Science and Technology on Vacuum Electronics, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2012-09-15

    Folded waveguide (FWG) traveling wave tube (TWT), which shows advantages in high power capacity, moderate bandwidth, and low-cost fabrication, has become the focus of vacuum electronics recently. Sheet electron beam devices are better suited for producing radiation sources with large power in millimeter wave spectrum due to their characteristics of relatively low space charge fields and large transport current. A FWG TWT with elliptical sheet beam working in W-band is presented in this paper, with the analysis of its dispersion characteristics, coupling impedance, transmission properties, and interaction characteristics. A comparison is also made with the traditional FWG TWT. Simulation results lead to the conclusion that the FWG TWT with elliptical sheet beam investigated in this paper can make full use of relatively large electric fields and thus generate large output power with the same electric current density.

  5. Observations of a nonthermal ion layer at the plasma sheet boundary during substorm recovery

    NASA Technical Reports Server (NTRS)

    Moebius, E.; Scholer, M.; Hovestadt, D.; Klecker, B.; Ipavich, F. M.; Gloeckler, G.

    1980-01-01

    Measurements of the energy and angular distributions of energetic protons and alpha particles (not less than 30 keV/charge) in the geomagnetic tail are presented. The measurements were made during the recovery phase of a geomagnetic substorm on Apr. 19, 1978, with the Max-Planck-Institut/University of Maryland sensor system on the Isee 1 satellite. The measurements were also correlated with plasma observations made by the LASL/MPE instrument on Isee 1. The data reveal the presence of a thin nonthermal layer of protons and alpha particles at the plasma sheet boundary. The particles have their maximum flux at 60 keV/charge and are streaming highly collimated in the earthward direction. The alpha particle layer is confined within the proton layer. Many aspects of the observations are in agreement with an acceleration model near the neutral line proposed by Jaeger and Speiser (1974)

  6. Topological Features of a Compressible Plasma Vortex Sheet - a Model of the Outer Heliospheric Wind

    NSDL National Science Digital Library

    Cindy Starr

    1993-12-17

    The Voyager and Pioneer Spacecraft have detected large-scale quasi-periodic plasma fluctuations in the outer heliosphere beyond 20 AU. A plasma vortex sheet model can explain these fluctuations and the observed correlations between various physical variables. The large scale outer heliosphere is modeled by solving the 3-D compressible magnetohydrodynamic equations involving three interacting shear layers. Computations were done on a Cray computer at the NASA Center for Computational Sciences. Six cases are animated: Weak magnetic field and strong magnetic field, each at three values of tau, the vortex street characteristic time. Contours of density are shown as dark transparent tubes. Critical points of the velocity field are represented by Glyphs. Vortex cores are shown in orange and blue.

  7. Influence of the renormalization plasma screening on the electron-atom collision in partially ionized plasmas

    SciTech Connect

    Hong, Woo-Pyo [Department of Electronics Engineering, Catholic University of Daegu, Hayang 712-702 (Korea, Republic of); Jung, Young-Dae [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of)

    2012-02-13

    The renormalization plasma screening effects on the elastic electron-atom collision are investigated in partially ionized dense hydrogen plasmas using the eikonal method. It is found that the renormalization plasma screening suppresses the eikonal phase shift and cross section for the elastic electron-atom collision in partially ionized plasmas. It is also found that the renormalization plasma screening effect on the elastic electron-atom collision process increases with an increasing impact parameter. In addition, it is found that the maximum position of the differential cross section is receded from the center of the atom with an increase of the Debye length.

  8. Attachment of alginate microcapsules onto plasma-treated PDMS sheet for retrieval after transplantation.

    PubMed

    Shin, Soojeong; Shin, Jeong Eun; Yoo, Young Je

    2013-01-01

    Although transplantation of microencapsulated islets has been proposed as a therapy for the treatment of diabetes mellitus, limited retrievability of the cells has impeded its medical usage. To achieve retrieval of microencapsulated islets, capsules were attached to polydimethylsiloxane (PDMS) with a biocompatible adhesive. Because the hydrophobic nature of the PDMS surface prevents attachment, surface modification is essential. Alginate microcapsules were attached to modified PDMS sheets, and the mechanical stability of the resulting constructs was determined. Acrylic acid (AA) and acrylamide (AM) mixtures were grafted on the surfaces of PDMS sheets using a two-step oxygen plasma treatment (TSPT). TSPT-PDMS was characterized according to water contact angle and zeta-potential measurements. The contact angle was altered by changing the ratio of AM to AA to generate hydrophilic surface. Evaluation of the surface charge at pH 2, 7, and 12 confirmed the presence of polar groups on the modified surface. Microcapsules were attached to TSPT-PDMS using Histoacryl® and shown to be in a monolayered and half-exposed state. The shear stress resistance of alginate capsules attached to the PDMS sheet indicates the possibility of transplantation of encapsulated cells without scattering in vivo. This method is applicable to retrieve microencapsulated porcine islets when required. PMID:23668815

  9. The 3 DLE instrument on ATS-5. [plasma electron counter

    NASA Technical Reports Server (NTRS)

    Deforest, S. E.

    1973-01-01

    The performance and operation of the DLE plasma electron counter on board the ATS 5 are described. Two methods of data presentation, microfilm line plots and spectrograms, are discussed along with plasma dynamics, plasma flow velocity, electrostatic charging, and wave-particle interactions.

  10. Guided and surface electron drift waves in plasmas

    SciTech Connect

    Dragila, R.; Vukovic, S.

    1988-04-11

    The existence of guided and surface electron drift waves in magnetoactive plasmas is demonstrated. The conditions for each of these modes to exist are found It is shown that the surface mode is unstable if the gradients of the plasma density and of the externally applied dc magnetic field are parallel within a localized region of the plasma.

  11. Nonlinear electromagnetic waves in electron-positron plasmas

    Microsoft Academic Search

    N. F. Cramer

    Plasmas with unequal numbers of electrons and positrons are of interest for pulsar magnetospheres and laboratory pair plasma experiments. Here the dispersion relation for electromagnetic waves in such a plasma is discussed, and the types of nonlinear waves that arise on the various branches of the dispersion curves. An excess of one type of charge carrier leads to circular and

  12. Vortex stabilized electron beam compressed fusion grade plasma

    SciTech Connect

    Hershcovitch, Ady [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.

    2014-03-19

    Most inertial confinement fusion schemes are comprised of highly compressed dense plasmas. Those schemes involve short, extremely high power, short pulses of beams (lasers, particles) applied to lower density plasmas or solid pellets. An alternative approach could be to shoot an intense electron beam through very dense, atmospheric pressure, vortex stabilized plasma.

  13. The trajectory of an electron in a plasma Arnaud Beck

    E-print Network

    Demoulin, Pascal

    of the supposedly typical trajectory of a plasma particle. We present here trajectories of electrons in a weakly with a large number of distant particles via the Coulomb electric field, so that its trajectory experiences trajectories in a weakly coupled plasma, obtained from plasma particle simulations using N-body techniques

  14. Effect of Plasma Sheet Conditions and Induced Electric Fields on Geomagnetic Storm Development

    NASA Astrophysics Data System (ADS)

    Zaharia, S. G.; Jordanova, V. K.; Welling, D. T.

    2010-12-01

    We present numerical simulation results of the storm-time near-Earth magnetosphere obtained with our newly improved self-consistent model, RAM-SCB. The model represents a 2-way coupling of the kinetic ring current-atmosphere interactions model (RAM) with an Euler potential-based 3D plasma equilibrium code. In our approach, the magnetic field is computed in force balance with the anisotropic pressures in RAM (anisotropy being critically important for the excitation of EMIC waves), and then returned to RAM to guide the particle dynamics. RAM-SCB thus properly treats both the kinetic drift physics crucial in the inner magnetosphere (where gradient/curvature drifts are important) and the self-consistent interaction between plasma and magnetic field (required due to the strong depressions in the field during geomagnetic storms, depressions that affect the plasma evolution). Recent improvements in RAM-SCB are the expansion of the model boundary from geosynchronous location outward and the inclusion of the induced electric fields. The RAM-SCB boundary has been expanded to 9 RE from Earth, with plasma pressure and magnetic field boundary conditions prescribed there from observations or other models (empirical or first principles). The full inclusion of the induced electric fields arising from the time changing magnetic field has been greatly facilitated by our Euler potential magnetic field representation. This presentation will analyze, using storm-time simulations of the near-Earth magnetosphere with the improved model, the effects on ring current development of the following factors: 1). plasma sheet conditions (density, temperature, local time variation, shape of distribution function), 2). self-consistent feedback between plasma and fields, and 3). induced vs. convective electric fields. We will also compare model results with observations (including global indices such as Dst, but also plasma and field observations from available spacecraft, such as POLAR, CLUSTER, and GOES).

  15. Generating electron cyclotron resonance plasma using distributed scheme

    SciTech Connect

    Huang, C. C. [Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan (China); Chung-Shan Institute of Science and Technology, Lung-Tan, Taoyuan, Taiwan (China); Chang, T. H.; Chen, N. C.; Chao, H. W. [Department of Physics, National Tsing Hua University, Hsinchu, Taiwan (China); Chen, C. C. [Chung-Shan Institute of Science and Technology, Lung-Tan, Taoyuan, Taiwan (China); Chou, S. F. [Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan (China)

    2012-08-06

    This study employs a distributed microwave input system and permanent magnets to generate large-area electron cyclotron resonance (ECR) plasma. ECR plasmas were generated with nitrogen gas, and the plasma density was measured by Langmuir probe. A uniform ECR plasma with the electron density fluctuation of {+-}9.8% over 500 mm Multiplication-Sign 500 mm was reported. The proposed idea of generating uniform ECR plasma can be scaled to a much larger area by using n Multiplication-Sign n microwave input array system together with well-designed permanent magnets.

  16. Whistler Solitons in Plasma with Anisotropic Hot Electron Admixture

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Krivorutsky, E. N.; Gallagher, D. L.

    1999-01-01

    The longitudinal and transverse modulation instability of whistler waves in plasma, with a small admixture of hot anisotropic electrons, is discussed. If the hot particles temperature anisotropy is positive, it is found that, in such plasma, longitudinal perturbations can lead to soliton formation for frequencies forbidden in cold plasma. The soliton is enriched by hot particles. The frequency region unstable to transverse modulation in cold plasma in the presence of hot electrons is divided by stable domains. For both cases the role of hot electrons is more significant for whistlers with smaller frequencies.

  17. UV laser ionization and electron beam diagnostics for plasma lenses

    SciTech Connect

    Govil, R.; Volfbeyn, P.; Leemans, W.

    1995-04-01

    A comprehensive study of focusing of relativistic electron beams with overdense and underdense plasma lenses requires careful control of plasma density and scale lengths. Plasma lens experiments are planned at the Beam Test Facility of the LBL Center for Beam Physics, using the 50 MeV electron beam delivered by the linac injector from the Advanced Light Source. Here we present results from an interferometric study of plasmas produced in tri-propylamine vapor with a frequency quadrupled Nd:YAG laser at 266 nm. To study temporal dynamics of plasma lenses we have developed an electron beam diagnostic using optical transition radiation to time resolve beam size and divergence. Electron beam ionization of the plasma has also been investigated.

  18. Progress on a gridded electron gun for a sheet beam klystron

    Microsoft Academic Search

    M. E. Read; G. Miram; V. Jabotinski; R. L. Ives

    2004-01-01

    Calabazas Creek Research Inc. (CCR) is developing rectangular, gridded, thermionic dispenser-cathode guns for sheet beam devices. The first application is expected to be klystrons for advanced particle accelerators and colliders. The current generation of accelerators typically use klystrons with a cylindrical beam generated by a Pierce-type electron gun. As RF power is pushed to higher levels, space charge forces in

  19. Reception Characteristics of Monopole Antennas for Electron Plasma Waves

    Microsoft Academic Search

    Yoshiharu Nakamura; Masaharu Nakamura; Tomizo Itoh

    1973-01-01

    The radiation patterns of a longitudinal electron plasma wave excited in a warm unbounded plasma by a grid and parallel plane grids and the reception patterns for wire antennas and the grid having a grounded plate were measured experimentally. The results agreed well with theoretically predicted radiation patterns based on a fluid model description for electrons. The dependence of the

  20. Plasma Cleaning and Its Applications for Electron Microscopy

    Microsoft Academic Search

    Thomas C. Isabell; Paul E. Fischione; Catherine O'Keefe; Murat U. Guruz; Vinayak P. Dravid

    1999-01-01

    The effectiveness of applying a high-frequency, low-energy, reactive gas plasma for the removal of hydrocarbon contamination from specimens and components for electron microscopy has been investigated with a variety of analytical techniques. Transmission electron microscopy (TEM) analysis of specimens that have been plasma cleaned shows an elimination of the carbonaceous contamination from the specimen. With extended cleaning times the removal

  1. Low frequency waves in plasmas with spatially varying electron temperature

    E-print Network

    Paris-Sud XI, Université de

    Low frequency waves in plasmas with spatially varying electron temperature P. Guio1,* , S. Bùrve2 frequency electrostatic waves are studied in magnetized plasmas with an electron temperature which varies with position in a direction perpendicular to the magnetic ®eld. For wave frequencies below the ion cyclotron

  2. Multiscale Auroral Emission Statistics as Evidence of Turbulent Reconnection in Earth's Midtail Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Klimas, Alex; Uritsky, Vadim; Donovan, Eric

    2010-01-01

    We provide indirect evidence for turbulent reconnection in Earth's midtail plasma sheet by reexamining the statistical properties of bright, nightside auroral emission events as observed by the UVI experiment on the Polar spacecraft and discussed previously by Uritsky et al. The events are divided into two groups: (1) those that map to absolute value of (X(sub GSM)) < 12 R(sub E) in the magnetotail and do not show scale-free statistics and (2) those that map to absolute value of (X(sub GSM)) > 12 R(sub E) and do show scale-free statistics. The absolute value of (X(sub GSM)) dependence is shown to most effectively organize the events into these two groups. Power law exponents obtained for group 2 are shown to validate the conclusions of Uritsky et al. concerning the existence of critical dynamics in the auroral emissions. It is suggested that the auroral dynamics is a reflection of a critical state in the magnetotail that is based on the dynamics of turbulent reconnection in the midtail plasma sheet.

  3. Electron current to a probe in a magnetized, collisional plasma

    NASA Astrophysics Data System (ADS)

    Charro, M.; Sanmartín, J. R.

    2000-06-01

    A collisional analysis of electron collection by a probe in a strongly magnetized, fully ionized plasma is carried out. A solution to the complete set of macroscopic equations with classical transport coefficients that is wholly consistent in the domain 1?R2/le?2?(mi/me)3/2 is determined; R and le? are probe radius and electron gyroradius, respectively. If R2/le?2 is large compared with mi/3me (probe large compared with ion gyroradius), ion-electron energy exchange—rather than electron heat diffusion—keeps electrons isothermal. For smaller probes at negative bias, however, electron cooling occurs in the plasma beyond the sheath, with a potential overshoot lying well away from it. The probe characteristic in the electron-retarding range may then mimic the characteristic for a two electron-temperature plasma and lead to an overestimate of electron temperature; the validity of these results for other transport models is discussed.

  4. Loaded two-element ring antenna for electron plasma waves

    Microsoft Academic Search

    Y. Morita; S. Egashira; M. Honjoh

    1989-01-01

    A short, coil-loaded two-element ring antenna including a transmission line, immersed in a warm, isotropic plasma, is investigated as a boundary value problem in the frequency range where electron plasma waves exist. The wave potential of electron plasma waves launched from a two-element ring antenna has been enhanced by a factor of 4-6 in comparison with the case of an

  5. Proton Beam Tests of an Electron Plasma Target

    Microsoft Academic Search

    R. Pollock; D. Stoller; A. Sarrazine; H. Gerberich; T. Sloan

    1996-01-01

    Stored protons of 45 MeV striking a non-neutral electron plasma have shown the stability of a beam-target system. The plasma had a length of 0.5 m, with 10^10 electrons maintained in a steady state by torque from a rotating electric quadrupole field and thermal energy from a noise source. A plasma temperature of a few eV allowed ionization of background

  6. Electron energy distribution function control in gas discharge plasmas

    SciTech Connect

    Godyak, V. A. [Electrical Engineering and Computer Science Department, University of Michigan, Ann Arbor, Michigan 48109, USA and RF Plasma Consulting, Brookline, Massachusetts (United States)] [Electrical Engineering and Computer Science Department, University of Michigan, Ann Arbor, Michigan 48109, USA and RF Plasma Consulting, Brookline, Massachusetts (United States)

    2013-10-15

    The formation of the electron energy distribution function (EEDF) and electron temperature in low temperature gas discharge plasmas is analyzed in frames of local and non-local electron kinetics. It is shown, that contrary to the local case, typical for plasma in uniform electric field, there is the possibility for EEDF modification, at the condition of non-local electron kinetics in strongly non-uniform electric fields. Such conditions “naturally” occur in some self-organized steady state dc and rf discharge plasmas, and they suggest the variety of artificial methods for EEDF modification. EEDF modification and electron temperature control in non-equilibrium conditions occurring naturally and those stimulated by different kinds of plasma disturbances are illustrated with numerous experiments. The necessary conditions for EEDF modification in gas discharge plasmas are formulated.

  7. Plasma response to electron energy filter in large volume plasma device

    SciTech Connect

    Sanyasi, A. K.; Awasthi, L. M.; Mattoo, S. K.; Srivastava, P. K.; Singh, S. K.; Singh, R.; Kaw, P. K. [Institute for Plasma Research, Gandhinagar, 382 428 Gujarat (India)] [Institute for Plasma Research, Gandhinagar, 382 428 Gujarat (India)

    2013-12-15

    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.

  8. Slant Slot Antenna-Type Electron Cyclotron Resonance Plasma Source

    Microsoft Academic Search

    Seiichi Watanabe; Hitoshi Tamura; Masahiro Sumiya; Muneo Furuse; Sunao Kawasaki

    1998-01-01

    A new compact electron cyclotron resonance (ECR) plasma source, which is termed slant-slot antenna-type ECR plasma source, is presented. Using this plasma source an ion saturation current density Iis of 6.2 mA\\/cm2±5.2% was obtained over a diameter of 300 mm under ambient conditions of Cl2 gas at 0.7 Pa. The features of the plasma source are an independent circular TM011

  9. Electromagnetic solitons in degenerate relativistic electron–positron plasma

    NASA Astrophysics Data System (ADS)

    Berezhiani, V. I.; Shatashvili, N. L.; Tsintsadze, N. L.

    2015-06-01

    The existence of soliton-like electromagnetic (EM) distributions in a fully degenerate electron–positron plasma is studied applying relativistic hydrodynamic and Maxwell equations. For a circularly polarized wave it is found that the soliton solutions exist both in relativistic as well as nonrelativistic degenerate plasmas. Plasma density in the region of soliton pulse localization is reduced considerably. The possibility of plasma cavitation is also shown.

  10. Physics of laser-driven plasma-based electron accelerators

    SciTech Connect

    Esarey, E.; Schroeder, C. B.; Leemans, W. P. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2009-07-15

    Laser-driven plasma-based accelerators, which are capable of supporting fields in excess of 100 GV/m, are reviewed. This includes the laser wakefield accelerator, the plasma beat wave accelerator, the self-modulated laser wakefield accelerator, plasma waves driven by multiple laser pulses, and highly nonlinear regimes. The properties of linear and nonlinear plasma waves are discussed, as well as electron acceleration in plasma waves. Methods for injecting and trapping plasma electrons in plasma waves are also discussed. Limits to the electron energy gain are summarized, including laser pulse diffraction, electron dephasing, laser pulse energy depletion, and beam loading limitations. The basic physics of laser pulse evolution in underdense plasmas is also reviewed. This includes the propagation, self-focusing, and guiding of laser pulses in uniform plasmas and with preformed density channels. Instabilities relevant to intense short-pulse laser-plasma interactions, such as Raman, self-modulation, and hose instabilities, are discussed. Experiments demonstrating key physics, such as the production of high-quality electron bunches at energies of 0.1-1 GeV, are summarized.

  11. Theoretical study of the adsorption of CHO radicals on hexagonal boron nitride sheet: Structural and electronic changes

    NASA Astrophysics Data System (ADS)

    Tian, Yu; Pan, Xiao-fan; Liu, Yue-jie; Zhao, Jing-xiang

    2014-03-01

    It is well known that pristine hexagonal boron nitride sheet (h-BN sheet) exhibits large insulating band gap, thus hindering its application to some extent. In this regard, surface chemisorption of certain groups on h-BN sheet is shown to be the most popular method to tune its band gap and thus modify its electronic properties. In the present work, we performed density functional theory (DFT) calculations to study the adsorption of CHO radicals with different coverages on h-BN sheet. Particular attention is paid to explore the effects of CHO adsorption on the geometrical structures and electronic properties of h-BN sheet. The results indicate that the adsorption of a single CHO radical on pristine h-BN sheet is very weak with a negligible adsorption energy (-0.09 eV). In contrast, upon adsorption of more CHO radicals on h-BN sheet, these adsorbates prefer to adsorb in pairs on the B and the nearest N atoms from both sides of h-BN sheet. An energy diagram of the average adsorption energy of CHO radicals on h-BN sheet as a function of its coverage indicates that up to 20 CHO radicals (40%) can be attached to h-BN sheet with the adsorption energy of -0.29 eV. More importantly, the adsorption of CHO radicals can induce certain impurity states within the band gap of h-BN sheet, thus reducing the band gap and enhancing its electrical conductivity.

  12. Electronically swept millimetre-wave interferometer for spatially resolved measurement of plasma electron

    E-print Network

    Howard, John

    electron density John Howard and David Oliver Plasma Research Laboratory, Research School of Physical, located in the Plasma Research Laboratory at the Australian National University, is a flexible, medium

  13. Electron and ion thermal forces in complex (dusty) plasmas

    SciTech Connect

    Khrapak, Sergey A. [Max-Planck-Institut fuer extraterrestrische Physik, D-85741 Garching (Germany)

    2013-01-15

    Expressions for the ion and electron thermal forces acting on a charged grain, suspended in a weakly ionized plasma subject to temperature gradients, are derived. The main emphasize is on the conditions pertinent to the investigations of complex (dusty) plasmas in gas discharges. Estimates show that for the electron temperature gradients {approx}O(eV/cm) typically encountered in laboratory gas discharges, the electron thermal force can become an important player among other forces acting on micron-size grains.

  14. Electron energy distribution function and plasma parameters across magnetic filters

    SciTech Connect

    Aanesland, A.; Bredin, J.; Chabert, P. [Laboratoire de Physique des Plasmas, CNRS--Ecole Polytechnique, 91128 Palaiseau Cedex (France); Godyak, V. [RF Plasma Consulting, Brookline, Massachusetts 02446 (United States)

    2012-01-23

    The electron energy distribution function (EEDF) is measured across a magnetic filter in inductively coupled plasmas. The measured EEDFs are found to be Maxwellian in the elastic energy range with the corresponding electron temperature monotonously decreasing along the positive gradient of the magnetic field. At the maximum of the magnetic field, the electron temperature reaches its minimum and remains nearly constant in the area of the negative gradient of the field, where the plasma density distribution exhibits a local minimum.

  15. Pepperpot emittance measurement of laser-plasma wakefield accelerated electrons

    Microsoft Academic Search

    R. P. Shanks; M. P. Anania; E. Brunetti; S. Cipiccia; B. Ersfeld; J. G. Gallacher; R. C. Issac; M. R. Islam; G. Vieux; G. H. Welsh; S. M. Wiggins; D. A. Jaroszynski

    2009-01-01

    The transverse emittance is an important parameter governing the brightness of an electron beam. Here we present the first pepper-pot measurement of the transverse emittance for a mono-energetic electron beam from a laser-plasma wakefield accelerator, carried out on the Advanced Laser-Plasma High Energy Accelerators towards X-Rays (ALPHA-X) beam line. Mono-energetic electrons are passed through an array of 52 mum diameter

  16. Cold plasma stabilization of a mirror-confined, hot-electron plasma

    Microsoft Academic Search

    I. G. Brown; A. J. Lichtenberg; M. A. Lieberman; N. C. Wyeth

    1976-01-01

    The stabilization of a hot-electron plasma in a simple mirror geometry is investigated. Controlled quantities of neutral gas generate a cold plasma through hot-electron ionization. Increasing stability is found with increasing gas pressure. The pressure required for stabilization is found to be inversely proportional to the ionization cross section of the type of neutral gas, indicating that the number of

  17. Multifunctional bulk plasma source based on discharge with electron injection

    SciTech Connect

    Klimov, A. S.; Medovnik, A. V. [Tomsk State University of Control Systems and Radioelectronics, Tomsk 634050 (Russian Federation); Tyunkov, A. V. [Tomsk State University of Control Systems and Radioelectronics, Tomsk 634050 (Russian Federation); Institute of High Current Electronics, Tomsk 634055 (Russian Federation); Savkin, K. P.; Shandrikov, M. V.; Vizir, A. V. [Institute of High Current Electronics, Tomsk 634055 (Russian Federation)

    2013-01-15

    A bulk plasma source, based on a high-current dc glow discharge with electron injection, is described. Electron injection and some special design features of the plasma arc emitter provide a plasma source with very long periods between maintenance down-times and a long overall lifetime. The source uses a sectioned sputter-electrode array with six individual sputter targets, each of which can be independently biased. This discharge assembly configuration provides multifunctional operation, including plasma generation from different gases (argon, nitrogen, oxygen, acetylene) and deposition of composite metal nitride and oxide coatings.

  18. Progress toward positron-electron pair plasma experiments

    NASA Astrophysics Data System (ADS)

    Stenson, E. V.; Saitoh, H.; Stanja, J.; Niemann, H.; Hergenhahn, U.; Pedersen, T. Sunn; Marx, G. H.; Schweikhard, L.; Danielson, J. R.; Surko, C. M.; Hugenschmidt, C.

    2015-06-01

    Electron-positron plasmas have been of theoretical interest for decades, due to the unique plasma physics that arises from all charged particles having precisely identical mass. It is only recently, though, that developments in non-neutral plasma physics (both in linear and toroidal geometries) and in the flux of sources for cold positrons have brought the goal of conducting electron-positron pair plasma experiments within reach. The APEX/PAX collaboration is working on a number of projects in parallel toward that goal; this paper provides an overview of recent, current, and upcoming activities.

  19. Multifunctional bulk plasma source based on discharge with electron injection.

    PubMed

    Klimov, A S; Medovnik, A V; Tyunkov, A V; Savkin, K P; Shandrikov, M V; Vizir, A V

    2013-01-01

    A bulk plasma source, based on a high-current dc glow discharge with electron injection, is described. Electron injection and some special design features of the plasma arc emitter provide a plasma source with very long periods between maintenance down-times and a long overall lifetime. The source uses a sectioned sputter-electrode array with six individual sputter targets, each of which can be independently biased. This discharge assembly configuration provides multifunctional operation, including plasma generation from different gases (argon, nitrogen, oxygen, acetylene) and deposition of composite metal nitride and oxide coatings. PMID:23387642

  20. Multifunctional bulk plasma source based on discharge with electron injection

    NASA Astrophysics Data System (ADS)

    Klimov, A. S.; Medovnik, A. V.; Tyunkov, A. V.; Savkin, K. P.; Shandrikov, M. V.; Vizir, A. V.

    2013-01-01

    A bulk plasma source, based on a high-current dc glow discharge with electron injection, is described. Electron injection and some special design features of the plasma arc emitter provide a plasma source with very long periods between maintenance down-times and a long overall lifetime. The source uses a sectioned sputter-electrode array with six individual sputter targets, each of which can be independently biased. This discharge assembly configuration provides multifunctional operation, including plasma generation from different gases (argon, nitrogen, oxygen, acetylene) and deposition of composite metal nitride and oxide coatings.

  1. Influence of Electron Evaporative Cooling on Ultracold Plasma Expansion

    E-print Network

    Wilson, Truman; Roberts, Jacob

    2013-01-01

    The expansion of ultracold neutral plasmas (UCP) is driven primarily by the thermal pressure of the electron component and is therefore sensitive to the electron temperature. At lower densities (less than 10$^8$ /cm$^3$), evaporative cooling has a significant influence on the UCP expansion rate. We studied the effect of electron evaporation in this density range. Owing to the low density, the effects of three-body recombination were negligible. We modeled the expansion by taking into account the change in electron temperature owing to evaporation as well as adiabatic expansion and found good agreement with our data. We also developed a simple model for initial evaporation over a range of ultracold plasma densities, sizes, and electron temperatures to determine over what parameter range electron evaporation is expected to have a significant effect. We also report on a signal calibration technique, which relates the signal at our detector to the total number of ions and electrons in the ultracold plasma.

  2. Plasma Chemistry and Plasma Processing, Vol. 22, No. 2, June 2002 ( 2002) Electron Density and Energy Distributions in

    E-print Network

    Chen, Junhong

    Plasma Chemistry and Plasma Processing, Vol. 22, No. 2, June 2002 ( 2002) Electron Density in the corona plasma is required to quantify the chemical processes. In this paper, the electron density- ness of the plasma and the electron energy distribution are not affected. Smaller electrodes produce

  3. One-step synthesis of N-doped graphene quantum sheets from monolayer graphene by nitrogen plasma.

    PubMed

    Moon, Joonhee; An, Junghyun; Sim, Uk; Cho, Sung-Pyo; Kang, Jin Hyoun; Chung, Chul; Seo, Jung-Hye; Lee, Jouhahn; Nam, Ki Tae; Hong, Byung Hee

    2014-06-01

    High-quality N-doped graphene quantum sheets are successfully fabricated from as-grown monolayer graphene on Cu using nitrogen plasma, which can be transferred as a film-like layer or easily dispersed in an organic solvent for further optoelectronic or photoelectrochemical applications. PMID:24664667

  4. Correction to ``Three-dimensional analyses of electric currents and pressure anisotropies in the plasma sheet'' by Richard L. Kaufmann,

    E-print Network

    Kaufmann, Richard L.

    Correction to ``Three-dimensional analyses of electric currents and pressure anisotropies. Paterson, and L. A. Frank, Correction to ``Three-dimensional analyses of electric currents and pressure] In the paper ``Three-dimensional analyses of electric currents and pressure anisotropies in the plasma sheet

  5. Level shifts and inelastic electron scattering in dense plasmas

    NASA Technical Reports Server (NTRS)

    Davis, J.; Blaha, M.

    1982-01-01

    A completely quantum mechanical formalism has been developed to describe the high density plasma effects on fundamental atomic parameters. Both the bound and free electrons are treated by a method which in principle is similar to Hartree's self-consistent field method. The free plasma electrons' wavefunction is obtained from the Schroedinger equation with the effective potential representing the spherically averaged Coulomb interaction with bound and free electrons. Results are given for level shifts, coefficients of transition probabilities, and electron collision cross sections of Ne(9+) for temperatures of 200 and 500 eV for an electron density range of 1-6 x 10 to the 24th per cu cm.

  6. Excitation of surface plasma waves by an electron beam in a magnetized dusty plasma

    Microsoft Academic Search

    Ved Prakash; Suresh C. Sharma

    2009-01-01

    An electron beam drives surface plasma waves to instability on a vacuum magnetized dusty plasma interface and in a magnetized dusty plasma cylinder via Cerenkov and fast cyclotron interaction. The dispersion relation of a surface plasma wave has been derived and it has been shown that the phase velocity of waves increases with increase in relative density delta(=ni0\\/ne0), where ni0

  7. Solitary and shock waves in magnetized electron-positron plasma

    NASA Astrophysics Data System (ADS)

    Lu, Ding; Li, Zi-Liang; Abdukerim, Nuriman; Xie, Bai-Song

    2014-02-01

    An Ohm's law for electron-positron (EP) plasma is obtained. In the framework of EP magnetohydrodynamics, we investigate nonrelativistic nonlinear waves' solutions in a magnetized EP plasma. In the collisionless limit, quasistationary propagating solitary wave structures for the magnetic field and the plasma density are obtained. It is found that the wave amplitude increases with the Mach number and the Alfvén speed. However, the dependence on the plasma temperature is just the opposite. Moreover, for a cold EP plasma, the existence range of the solitary waves depends only on the Alfvén speed. For a hot EP plasma, the existence range depends on the Alfvén speed as well as the plasma temperature. In the presence of collision, the electromagnetic fields and the plasma density can appear as oscillatory shock structures because of the dissipation caused by the collisions. As the collision frequency increases, the oscillatory shock structure becomes more and more monotonic.

  8. Energy loss of fast electrons and positrons in a plasma.

    NASA Technical Reports Server (NTRS)

    Gould, R. J.

    1972-01-01

    Calculation of the stopping power of a plasma for fast electrons and positrons. First the classical limit is considered where beta = v/c is much less than alpha is the fine structure constant. Then the nonrelativistic Born-approximation formulas are derived; this domain corresponds to alpha much less than beta much less than 1. Finally, the general case of relativistic electrons and positrons is treated; in the relativistic case the scattering cross sections of Moller (electron-electron) and Bhabha (positron-electron) are used in the calculation. In all three energy domains the problem is broken up into cases of small and large momentum transfers. For large q, scattering off individual plasma electrons is considered, while in the limit of very small q for the quantum-mechanical domain, excitation of quantized plasma oscillations contributes to dE/dx; in the classical limit for small q the polarizability of the plasma provides the effective cutoff. The formulas for the stopping power differ slightly from those for a heavy ion going through a plasma because there are exchange effects and the fast electrons and positrons can lose a large fraction of their energy in one scattering off a plasma electron.

  9. Fluctuations in a Plasma I: Ion-Electron Temperature Relaxation

    Microsoft Academic Search

    Osamu Aono

    1961-01-01

    Fluctuations of the electric field in a plasma are treated on the basis of the fluctuation-dissipation theorem. The treatment is applied to the relaxation between ion and electron temperatures. The interaction between ion and electron which causes the relaxation is reduced to the interaction between the ion and the fluctuating electric field caused by the surrounding electrons. The short range

  10. Influence of electron injection on electron cyclotron resonance plasma properties and reflected mode electrons (abstract)

    NASA Astrophysics Data System (ADS)

    Ovsyannikov, V. P.; Ullmann, F.; Zschornack, G.

    2000-02-01

    The injection of an additional strong focused electron beam from a special designed electron gun into a magnetic electron cyclotron resonance (ECR) confinement field is studied. The electron gun uses a cathode with a long lifetime and resistiveness providing high emission current densities with electron currents up to 50 mA and voltages up to 4 keV. A sequence of aluminum foils is used to investigate the trajectories of the electrons in the magnetic field without plasma. The high density electron beam passes through the foils, welds them, and prints its image into the foils. Details of this technique are described in Ref. 1. Using this technique we see that before the electrons enter the sextupole region the beam moves along the magnetic straight lines preserving its structure. Only a central beam passes through the sextupole region, thereby changing its form due to the interaction with radial components of the magnetic field. A new operation method at our 14.5 GHz ECR ion source is based on so-called reflection mode electrons (RMEs) analogous to a known electron beam ion source operation regime.2 The basic idea is that electrons, which traveling from the cathode in a strong axial field, meet an anticathode potential, are reflected from it, move back to the cathode, and will be reflected again and so on. It can be supposed that the electrons will make reflections up to the moment when the anode aperture of the gun is fulfilled and the electrons will be collected on the anode electrode. Investigations are performed extracting nitrogen ions using the RME beam. As a result we got a clear increase in the beam current of the extracted ions (e.g., at 10 mA electron injection an increase of the current of N5+ ions up to 400%) and a shift of the measured ion charge state distribution to higher mean ionization stages. Measured x-ray spectra from a neon loaded plasma show for the case of RME operation increasing energy shifts to the high energy side of the spectra, i.e., the mean ionization degree of the ions in the plasma increases. They also increase the intensity of the neon K x rays (more than 100% increase for RME injection of Ee=4 keV and Ie=10 mA) indicating that for the same operation parameters the mean density of energetic electrons rises at RME injection, i.e., there are more electrons with energies high enough to ionize K-shell electrons in neon.

  11. Electron plasma oscillations associated with type 3 radio emissions and solar electrons

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Frank, L. A.

    1975-01-01

    An extensive study of the IMP-6 and IMP-8 plasma and radio wave data was performed to try to find electron plasma oscillations associated with type III radio noise bursts and low-energy solar electrons. It is shown that electron plasma oscillations are seldom observed in association with solar electron events and type III radio bursts at 1.0 AU. For the one case in which electron plasma oscillations are definitely produced by the electrons ejected by the solar flare the electric field strength is relatively small. Electromagnetic radiation, believed to be similar to the type III radio emission, is observed coming from the region of the more intense electron plasma oscillations upstream. Quantitative calculations of the rate of conversion of the plasma oscillation energy to electromagnetic radiation are presented for plasma oscillations excited by both solar electrons and electrons from the bow shock. These calculations show that neither the type III radio emissions nor the radiation from upstream of the bow shock can be adequately explained by a current theory for the coupling of electron plasma oscillations to electromagnetic radiation.

  12. Data-Model Comparisons of Plasma Sheet Ion Temperatures during Moderate Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Keesee, A. M.; Ilie, R.; Liemohn, M. W.; Trigo, B.; Robison, G.; Carr, J., Jr.

    2014-12-01

    Ion heating occurs during geomagnetic storms as a result of many physical processes, including magnetic reconnection and adiabatic heating. Ion temperatures calculated from TWINS energetic neutral atom (ENA) data provide a global view of regions of heated ions in the plasma sheet. Two storms of similar, moderate magnitude are analyzed, a coronal mass ejection (CME)-driven storm that occurred on 26 September 2011 and a high speed stream (HSS)-driven storm on 13 October 2012. We present a comparison of the ion temperatures during the storms to patterns observed in a superposed epoch analysis of ion temperatures [Keesee et al., 2013] and compare the October storm to a previously analyzed HSS-driven storm [Keesee et al., 2012]. We also present a comparison of observed ion temperatures to those calculated from a simulation of each storm using the Space Weather Modeling Framework, including the BATS-R-US MHD model coupled with the HEIDI inner magnetosphere model.

  13. Energetic neutral atom images of a narrow flow channel from the plasma sheet: Astrid-1 observations

    NASA Astrophysics Data System (ADS)

    C:Son Brandt, P.; Ebihara, Y.; Barabash, S.; Roelof, E. C.

    2002-10-01

    We present two energetic neutral atom (ENA) images in the energy range 26-37 keV from the ENA imager on board the Swedish microsatellite Astrid-1. The images are taken 24 hours apart from below the ring current at 0300 magnetic local time (MLT) around the equator at 1000 km altitude and show a narrow region of ENA emissions extending along the field lines in the postmidnight region. A parameterized model of the ring current is used to extract the ion distribution. The extracted ion distribution is 25° wide in longitude within L = 4 - 6 with an almost isotropic pitch angle distribution (PAD). One ENA image from a polar vantage point shows that the loss cones of the PAD are partially filled. The z component of the interplanetary magnetic field (IMF) was +2 and -3 nT at the times of the two observations. For IMF Bz = -3 nT the ENA flux is stronger than that for the observation when IMF Bz = +2 nT. We use a kinetic ring current model to show that the morphology of the extracted ion distribution can be explained by a narrow flow channel from the plasma sheet at L = 10 and 0200-0300 MLT to L = 5 and 0100-0200 MLT for 26 keV protons. In order to match the absolute flux of the extracted ion distribution with the results from the kinetic model, the plasma sheet density at L = 10 had to be set to 10 cm-3. This value is unreasonably high, and we discuss some scenarios that may justify a more reasonable value. During the previous 5 days the Dst had been between -50 and -15 nT, and the interplanetary magnetic field Bz had been fluctuating between -10 and +10 nT.

  14. Acceleration of electrons in strong beam-plasma interactions

    NASA Technical Reports Server (NTRS)

    Wilhelm, K.; Bernstein, W.; Kellogg, P. J.; Whalen, B. A.

    1984-01-01

    The effects of strong beam-plasma interactions on the electron population of the upper atmosphere have been investigated in an electron acceleration experiment performed with a sounding rocket. The rocket carried the Several Complex Experiments (SCEX) payload which included an electron accelerator, three disposable 'throwaway' detectors (TADs), and a stepped electron energy analyzer. The payload was launched in an auroral arc over the rocket at altitudes of 157 and 178 km, respectively. The performance characteristics of the instruments are discussed in detail. The data are combined with the results of laboratory measurements and show that electrons with energies of at least two and probably four times the injection energy of 2 keV were observed during strong beam-plasma interaction events. The interaction events occurred at pitch angles of 54 and 126 degrees. On the basis of the data it is proposed that the superenergization of the electrons is correlated with the length of the beam-plasma interaction region.

  15. Quantum tunneling resonant electron transfer process in Lorentzian plasmas

    NASA Astrophysics Data System (ADS)

    Hong, Woo-Pyo; Jung, Young-Dae

    2014-08-01

    The quantum tunneling resonant electron transfer process between a positive ion and a neutral atom collision is investigated in nonthermal generalized Lorentzian plasmas. The result shows that the nonthermal effect enhances the resonant electron transfer cross section in Lorentzian plasmas. It is found that the nonthermal effect on the classical resonant electron transfer cross section is more significant than that on the quantum tunneling resonant charge transfer cross section. It is shown that the nonthermal effect on the resonant electron transfer cross section decreases with an increase of the Debye length. In addition, the nonthermal effect on the quantum tunneling resonant electron transfer cross section decreases with increasing collision energy. The variation of nonthermal and plasma shielding effects on the quantum tunneling resonant electron transfer process is also discussed.

  16. Microwave radiation measurements near the electron plasma frequency of the NASA Lewis Bumpy Torus plasma

    NASA Technical Reports Server (NTRS)

    Mallavarpu, R.; Roth, J. R.

    1978-01-01

    Microwave emission near the electron plasma frequency of the NASA Lewis Bumpy Torus plasma has been observed, and its relation to the average electron density and the dc toroidal magnetic field was examined. The emission was detected using a spectrum analyzer and a 50-ohm miniature coaxial probe. The radiation appeared as a broad amplitude peak that shifted in frequency as the plasma parameters were varied. The observed radiation scanned an average plasma density ranging from 20 billion to 800 billion per cu cm. A linear relation was observed between the density calculated from the emission frequency and the average plasma density measured with a microwave interferometer. With the aid of a relative density profile measurement of the plasma, it was determined that the emissions occurred from the outer periphery of the plasma.

  17. Plasma actuator electron density measurement using microwave perturbation method

    SciTech Connect

    Mirhosseini, Farid; Colpitts, Bruce [Electrical and Computer Engineering, University of New Brunswick, Fredericton, New Brunswick E3B 5A3 (Canada)

    2014-07-21

    A cylindrical dielectric barrier discharge plasma under five different pressures is generated in an evacuated glass tube. This plasma volume is located at the center of a rectangular copper waveguide cavity, where the electric field is maximum for the first mode and the magnetic field is very close to zero. The microwave perturbation method is used to measure electron density and plasma frequency for these five pressures. Simulations by a commercial microwave simulator are comparable to the experimental results.

  18. Electron beam welding, laser beam welding and gas tungsten arc welding of titanium sheet

    Microsoft Academic Search

    Qi Yunlian; Deng Ju; Hong Quan; Zeng Liying

    2000-01-01

    Microstructures, properties and technical parameters of welding specimen of 0.5 mm thick sheets of commercial purity titanium (C.P. Ti) have been studied via high vacuum electron beam welding (EBW-HV), CO2 laser beam welding (LBW) and gas tungsten arc welding (TIG), as well as optical microscope (OM) observation and microhardness measuring. The results indicate that the EBW is more suitable for

  19. Electromagnetic solitary pulses in a magnetized electron-positron plasma

    SciTech Connect

    Shukla, P. K. [RUB International Chair, International Centre for Advanced Studies in Physical Sciences, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Eliasson, B. [Institut fuer Theoretische Physik, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Stenflo, L. [Department of Physics, Linkoeping University, SE-58183 Linkoeping (Sweden)

    2011-03-15

    A theory for large amplitude compressional electromagnetic solitary pulses in a magnetized electron-positron (e-p) plasma is presented. The pulses, which propagate perpendicular to the external magnetic field, are associated with the compression of the plasma density and the wave magnetic field. Here the solitary wave magnetic field pressure provides the restoring force, while the inertia comes from the equal mass electrons and positrons. The solitary pulses are formed due to a balance between the compressional wave dispersion arising from the curl of the inertial forces in Faraday's law and the nonlinearities associated with the divergence of the electron and positron fluxes, the nonlinear Lorentz forces, the advection of the e-p fluids, and the nonlinear plasma current densities. The compressional solitary pulses can exist in a well-defined speed range above the Alfven speed. They can be associated with localized electromagnetic field excitations in magnetized laboratory and space plasmas composed of electrons and positrons.

  20. Electron Bernstein wave current drive modeling in toroidal plasma confinement

    E-print Network

    Decker, Joan, 1977-

    2005-01-01

    The steady-state confinement of tokamak plasmas in a fusion reactor requires non-inductively driven toroidal currents. Radio frequency waves in the electron cyclotron (EC) range of frequencies can drive localized currents ...

  1. Measurement of electron density and temperature in plasmas

    NASA Technical Reports Server (NTRS)

    Billman, K. W.; Rowley, P. D.; Presley, L. L.; Stallcop, J.

    1972-01-01

    Application of two laser wavelengths passing through plasma measures electron density and temperature. Function depends on determining absorption of light at two wavelengths. Nature of reaction is explained and schematic diagram of equipment is included.

  2. Neutrino-electron processes in a strongly magnetized thermal plasma

    E-print Network

    Stephen J. Hardy; Markus H. Thoma

    2000-11-15

    We present a new method of calculating the rate of neutrino-electron interactions in a strong magnetic field based on finite temperature field theory. Using this method, in which the effect of the magnetic field on the electron states is taken into account exactly, we calculate the rates of all of the lowest order neutrino-electron interactions in a plasma. As an example of the use of this technique, we explicitly calculate the rate at which neutrinos and antineutrinos annihilate in a highly magnetized plasma, and compare that to the rate in an unmagnetized plasma. The most important channel for energy deposition is the gyromagnetic absorption of a neutrino-antineutrino pair on an electron or positron in the plasma ($\

  3. Ponderomotive Acceleration of Hot Electrons in Tenuous Plasmas

    SciTech Connect

    V.I. Geyko and G.M. Fraiman, I.Y. Dodin and N.J. Fisch

    2009-02-17

    The oscillation-center Hamiltonian is derived for a relativistic electron injected with an arbitrary momentum in a linearly polarized laser pulse propagating in tenuous plasma, assuming that the pulse length is smaller than the plasma wavelength. For hot electrons generated at collisions with ions under intense laser drive, multiple regimes of ponderomotive acceleration are identified and the laser dispersion is shown to affect the process at plasma densities down to 1017 cm?3. Assuming a/?g << 1, which prevents net acceleration of the cold plasma, it is also shown that the normalized energy ? of hot electrons accelerated from the initial energy ?o < , ? does not exceed ? ~ a?g, where a is the normalized laser field, and ?g is the group velocity Lorentz factor. Yet ? ~ ? is attained within a wide range of initial conditions; hence a cutoff in the hot electron distribution is predicted.

  4. Alfvenic Solitons in Ultrarelativistic Electron-Position Plasmas

    NASA Technical Reports Server (NTRS)

    Verheest, G. S. Lakhina F.

    1997-01-01

    In electron-positron plasmas some of the plasma modes are decoupled due to the equal charge-to-mass ratio of both species. We derive the dispersion law for a low-frequency, generalized X-mode, which exists at all angles of propagation with respect to the static magnetic field.

  5. Electron temperature and density fluctuations during improved confinement plasmas

    Microsoft Academic Search

    E. Parke; H. D. Stephens; D. J. den Hartog; J. A. Reusch; Y. M. Yang; W. S. Harris; A. F. Falkowski; C. P. Kasten

    2010-01-01

    We plan to present initial results of Thomson scattering measurements of Te and ne fluctuations associated with electrostatic transport during improved confinement plasmas (PPCD). Recent upgrades to the MST Thomson scattering diagnostic have allowed detailed measurements of electron temperature fluctuations in a variety of plasmas. For example, previous studies have mapped temperature fluctuations to magnetic perturbations, observing remnant island structures

  6. Mating Electron Beam Columns to Plasma Window Apertures

    NASA Astrophysics Data System (ADS)

    Hershcovitch, Ady

    2001-10-01

    The Plasma Window is a novel apparatus that utilizes a stabilized plasma arc as an interface between vacuum and atmosphere without solid material. In addition to sustaining a vacuum atmosphere interface, the plasma window has a lensing effect on charged particles. The plasma current generates an azimuthal magnetic field, which exerts a radial Lorentz force on charged particles moving parallel to the current channel. With proper orientation of the current direction, the Lorentz force is radially inward. This feature can be used to focus beams to a very small spot size, and to overcome beam dispersion due to scattering by atmospheric atoms and molecules. Consequently, for a number of particle beam applications, the plasma window is an attractive alternative to differential pumping. Two such applications are non-vacuum electron beam welding and hypersonic wind tunnel heating. Design issues that are presently under consideration involve electron beam optics due to plasma window lensing effects, and preventing ions and electrons from entering the beam structure. Matching electron beam columns to plasma windows while shielding accelerating and focusing elements from plasma particles to prevent breakdowns is to be discussed in the presentation.

  7. Visible Light Emission of Electron Cyclotron Resonance Plasmas

    Microsoft Academic Search

    Richárd Racz; Sándor Biri; József Palinkas

    2011-01-01

    Electron cyclotron resonance (ECR) plasmas gener- ated by microwave and confined by magnetic field are, in most cases, generated for highly charged ion production followed by injection of them into an accelerator. The ECR plasma itself usually cannot be seen because it is deeply hidden in the center of the facility. In the Institute of Nuclear Research (ATOMKI), the ECR

  8. Electron-temperature evolution in expanding ultracold neutral plasmas.

    PubMed

    Gupta, P; Laha, S; Simien, C E; Gao, H; Castro, J; Killian, T C; Pohl, T

    2007-08-17

    We have used the free expansion of ultracold neutral plasmas as a time-resolved probe of electron temperature. A combination of experimental measurements of the ion expansion velocity and numerical simulations characterize the crossover from an elastic-collision regime at low initial Gamma(e), which is dominated by adiabatic cooling of the electrons, to the regime of high Gamma(e) in which inelastic processes drastically heat the electrons. We identify the time scales and relative contributions of various processes, and we experimentally show the importance of radiative decay and disorder-induced electron heating for the first time in ultracold neutral plasmas. PMID:17930904

  9. Electron Hole Generation and Propagation in an Inhomogeneous Collisionless Plasma

    SciTech Connect

    Califano, F. [Istituto di Fisica del Plasma, EURATOM-ENEA-CNR (Italy); Physics Department, University of Pisa (Italy); Lontano, M. [Istituto di Fisica del Plasma, EURATOM-ENEA-CNR (Italy)

    2005-12-09

    The generation of 'trains' of electron holes in phase space due to an external electrostatic disturbance is investigated by using a Vlasov-Ampere code with open boundary conditions. Electron holes are produced mostly during the initial phase of the wave-plasma interaction, with a given drift velocity which is maintained until they exit the integration box, even in the presence of plasma inhomogeneities. They present macroscopic features, a dipolar electrostatic field and an electron density perturbation, which can be exploited for diagnostic purposes. Their equilibrium is intrinsically kinetic, in that they are accompanied by a stationary hole in the electron distribution function.

  10. Study on electron beam in a low energy plasma focus

    NASA Astrophysics Data System (ADS)

    Khan, Muhammad Zubair; Ling, Yap Seong; San, Wong Chiow

    2014-03-01

    Electron beam emission was investigated in a low energy plasma focus device (2.2 kJ) using copper hollow anode. Faraday cup was used to estimate the energy of the electron beam. XR100CR X-ray spectrometer was used to explore the impact of the electron beam on the target observed from top-on and side-on position. Experiments were carried out at optimized pressure of argon gas. The impact of electron beam is exceptionally notable with two different approaches using lead target inside hollow anode in our plasma focus device.

  11. Study on electron beam in a low energy plasma focus

    SciTech Connect

    Khan, Muhammad Zubair, E-mail: mzubairkhan-um76@yahoo.com [Plasma Technology Research Center, Department of Physics, Faculty of Science, University Malaya, 50603 Kuala Lumpur, Malaysia and Department of Physics, Federal Urdu University of Arts, Science and Technology, 45320 Islamabad (Pakistan); Ling, Yap Seong; San, Wong Chiow [Plasma Technology Research Center, Department of Physics, Faculty of Science, University Malaya, 50603 Kuala Lumpur (Malaysia)

    2014-03-05

    Electron beam emission was investigated in a low energy plasma focus device (2.2 kJ) using copper hollow anode. Faraday cup was used to estimate the energy of the electron beam. XR100CR X-ray spectrometer was used to explore the impact of the electron beam on the target observed from top-on and side-on position. Experiments were carried out at optimized pressure of argon gas. The impact of electron beam is exceptionally notable with two different approaches using lead target inside hollow anode in our plasma focus device.

  12. Properties of trapped electron bunches in a plasma wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Kirby, Neil Allen

    Plasma-based accelerators use the propagation of a drive bunch through plasma to create large electric fields. Recent plasma wakefield accelerator (PWFA) experiments, carried out at the Stanford Linear Accelerator Center (SLAC), successfully doubled the energy for some of the 42 GeV drive bunch electrons in less than a meter; this feat would have required 3 km in the SLAC linac. This dissertation covers one phenomenon associated with the PWFA, electron trapping. Recently it was shown that PWFAs, operated in the nonlinear bubble regime, can trap electrons that are released by ionization inside the plasma wake and accelerate them to high energies. These trapped electrons occupy and can degrade the accelerating portion of the plasma wake, so it is important to understand their origins and how to remove them. Here, the onset of electron trapping is connected to the drive bunch properties. Additionally, the trapped electron bunches are observed with normalized transverse emittance divided by peak current, epsilonN,x/I t, below the level of 0.2 microm/kA. A theoretical model of the trapped electron emittance, developed here, indicates that the emittance scales inversely with the square root of the plasma density in the nonlinear "bubble" regime of the PWFA. This model and simulations indicate that the observed values of epsilonN,x/It result from multi-GeV trapped electron bunches with emittances of a few mum and multi-kA peak currents. These properties make the trapped electrons a possible particle source for next generation light sources. This dissertation is organized as follows. The first chapter is an overview of the PWFA, which includes a review of the accelerating and focusing fields and a survey of the remaining issues for a plasma-based particle collider. Then, the second chapter examines the physics of electron trapping in the PWFA. The third chapter uses theory and simulations to analyze the properties of the trapped electron bunches. Chapters four and five present the experimental diagnostics and measurements for the trapped electrons. Next, the sixth chapter introduces suggestions for future trapped electron experiments. Then, Chapter seven contains the conclusions. In addition, there is an appendix chapter that covers a topic which is extraneous to electron trapping, but relevant to the PWFA. This chapter explores the feasibility of one idea for the production of a hollow channel plasma, which if produced could solve some of the remaining issues for a plasma-based collider.

  13. Dynamical Casimir effect for TE and TM modes in a resonant cavity bisected by a plasma sheet

    E-print Network

    Wade Naylor; S. Matsuki; Tomoaki Nishimura; Yoshiaki Kido

    2010-01-18

    Parametric photon creation via the dynamical Casimir effect (DCE) is evaluated numerically, in a three-dimensional rectangular resonant cavity bisected by a semiconductor diaphragm (SD), which is irradiated by a pulsed laser with frequency of GHz order. The aim of this paper is to determine some of the optimum conditions required to detect DCE photons relevant to a novel experimental detection system. We expand upon the thin plasma sheet model [Crocce et al., Phys. Rev. A 70 033811 (2004)] to estimate the number of photons for both TE and TM modes at any given SD position. Numerical calculations are performed considering up to 51 inter-mode couplings by varying the SD location, driving period and laser power without any perturbations. It is found that the number of photons created for TE modes strongly depends on SD position, where the strongest enhancement occurs at the midpoint (not near the cavity wall); while TM modes have weak dependence on SD position. Another important finding is the fact that significant photon production for TM$_{111}$ modes still takes place at the midpoint even for a low laser power of 0.01 micro J/pulse, although the number of TE$_{111}$ photons decreases almost proportionately with laser power. We also find a relatively wide tuning range for both TE and TM modes that is correlated with the frequency variation of the instantaneous mode functions caused by the interaction between the cavity photons and conduction electrons in the SD excited by a pulsed laser.

  14. Dynamical Casimir effect for TE and TM modes in a resonant cavity bisected by a plasma sheet

    NASA Astrophysics Data System (ADS)

    Naylor, W.; Matsuki, S.; Nishimura, T.; Kido, Y.

    2009-10-01

    Parametric photon creation via the dynamical Casimir effect (DCE) is evaluated numerically, in a three-dimensional rectangular resonant cavity bisected by a semiconductor diaphragm (SD), which is irradiated by a pulsed laser with frequency of GHz order. The aim of this paper is to determine some of the optimum conditions required to detect DCE photons relevant to an experimental detection system. We expand upon the thin plasma sheet model [M. Crocce , Phys. Rev. A 70, 033811 (2004)] to estimate the number of photons for both transverse electric (TE) and transverse magnetic (TM) modes at any given SD position. Numerical calculations are performed considering up to 51 intermode couplings by varying the SD location, driving period and laser power without any perturbations. It is found that the number of photons created for TE modes strongly depends on SD position, where the strongest enhancement occurs at the midpoint (not near the cavity wall); while TM modes have weak dependence on SD position. Another important finding is the fact that significant photon production for TM111 modes still takes place at the midpoint even for a low-laser power of 0.01?J/pulse , although the number of TE111 photons decreases almost proportionately with laser power. We also find a relatively wide tuning range for both TE and TM modes that is correlated with the frequency variation in the instantaneous mode functions caused by the interaction between the cavity photons and conduction electrons in the SD excited by a pulsed laser.

  15. Transport of internal electronic energy in atomic hydrogen thermal plasmas

    SciTech Connect

    Bruno, D.; Capitelli, M.; Catalfamo, C.; Laricchiuta, A. [Istituto di Metodologie Inorganiche e dei Plasmi del C.N.R., via G. Amendola 122/D, 70126 Bari (Italy) and Istituto di Metodologie Inorganiche e dei Plasmi del C.N.R., via G. Amendola 122/D, 70126 Bari (Italy) and Dipartimento di Chimica, Universita di Bari, via E. Orabona 4, 70126 Bari (Italy); Dipartimento di Chimica, Universita di Bari, via E. Orabona 4, 70126 Bari (Italy); Istituto di Metodologie Inorganiche e dei Plasmi del C.N.R., via G. Amendola 122/D, 70126 Bari (Italy)

    2007-07-15

    Reactive and internal thermal conductivities for equilibrium hydrogen plasma have been calculated by the Chapman-Enskog method. The equilibrium composition of the plasma is determined by taking consistently into account the number of allowed atomic electronic excited states (EES) as determined by the average interparticle distance. The coefficients depend on the inclusion of realistic cross sections for the interactions with EES. In particular, the interplay between the two coefficients that describe the transport of electronic and ionization energy is analyzed.

  16. Large amplitude solitary electromagnetic waves in electron-positron plasmas

    Microsoft Academic Search

    Frank Verheest; Tom Cattaert

    2004-01-01

    Waves in electron-positron plasmas have fundamentally different dispersion characteristics due to the equal charge-to-mass ratios between negative and positive charges, which mix different timescales, and are of interest in understanding aspects of pulsars and active galactic nuclei, where astrophysical electron-positron plasmas occur. Earlier systematic nonlinear treatments of parallel propagating electromagnetic waves via a reductive perturbation analysis had indicated unusual results,

  17. Ascorbate and plasma membrane electron transport—Enzymes vs efflux

    Microsoft Academic Search

    Alfons Lawen

    2009-01-01

    Transplasma membrane electron transport (tPMET) systems transfer electrons across the plasma membrane, resulting in the net reduction of extracellular oxidants (e.g., ferricyanide) at the expense of intracellular reductants such as NADH and ascorbate. In mammalian tPMET systems, the major proximal electron donor is ascorbate. The classical description of ascorbate-dependent tPMET views ascorbate as a restrictively intracellular electron donor to a

  18. Plasma parameters and electron energy distribution functions in a magnetically focused plasma

    SciTech Connect

    Samuell, C. M.; Blackwell, B. D.; Howard, J.; Corr, C. S. [Plasma Research Laboratory, Research School of Physics and Engineering, Australian National University, Canberra (Australia)

    2013-03-15

    Spatially resolved measurements of ion density, electron temperature, floating potential, and the electron energy distribution function (EEDF) are presented for a magnetically focused plasma. The measurements identify a central plasma column displaying Maxwellian EEDFs at an electron temperature of about 5 eV indicating the presence of a significant fraction of electrons in the inelastic energy range (energies above 15 eV). It is observed that the EEDF remains Maxwellian along the axis of the discharge with an increase in density, at constant electron temperature, observed in the region of highest magnetic field strength. Both electron density and temperature decrease at the plasma radial edge. Electron temperature isotherms measured in the downstream region are found to coincide with the magnetic field lines.

  19. Oscillating plasma bubbles. III. Internal electron sources and sinks

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

    2012-08-15

    An internal electron source has been used to neutralize ions injected from an ambient plasma into a spherical grid. The resultant plasma is termed a plasma 'bubble.' When the electron supply from the filament is reduced, the sheath inside the bubble becomes unstable. The plasma potential of the bubble oscillates near but below the ion plasma frequency. Different modes of oscillations have been observed as well as a subharmonic and multiple harmonics. The frequency increases with ion density and decreases with electron density. The peak amplitude occurs for an optimum current and the instability is quenched at large electron densities. The frequency also increases if Langmuir probes inside the bubble draw electrons. Allowing electrons from the ambient plasma to enter, the bubble changes the frequency dependence on grid voltage. It is concluded that the net space charge density in the sheath determines the oscillation frequency. It is suggested that the sheath instability is caused by ion inertia in an oscillating sheath electric field which is created by ion bunching.

  20. Demonstration of a 100kW Solenoidally Focused Sheet Electron Beam for Millimeter-Wave Amplifiers

    Microsoft Academic Search

    John Pasour; Khanh Nguyen; Edward Wright; Adam Balkcum; John Atkinson; Michael Cusick; Baruch Levush

    2011-01-01

    The design and development of a high-perveance sheet electron beam is reported. A beamstick that employs a novel sheet beam gun together with a permanent magnet solenoid has been fabricated and tested up to 4.8 A at 22 kV. At the nominal operating point of 19.5 kV and 3.3 A, this beamstick has transported 98.5% of the emitted electron current

  1. Temporal evolution of electron-positron plasmas

    SciTech Connect

    Brinkmann, W.

    1983-01-01

    Recently it has become increasingly clear that e/sup -/e/sup +/ pairs can play an important role in various high-energy astrophysical phenomena and there has been growing interest in understanding these plasmas. In spherical accretion flows and in accretion discs the pairs created close to the Schwarzschild radius have a strong influence on the overall dynamics of the flow, and the spectrum of the emitted high energy radiation shows the typical signature of the pair component. In ..gamma..-ray bursters, where the physics of the primary energy release is not fully understood the observed radiation reflects the temporal evolution of the trans-relativistic pair plasma. Zdziarski and Ramaty and Meszaros performed Monte Carlo calculations to obtain the annihilation radiation spectra from relativistic plasmas. Gould and Lightman determined the equilibrium properties and relaxation rates of e/sup -/e/sup +/ pair plasmas qualitatively and Svensson was able to give analytical expressions for the differential cross sections for annihilation rate and emissivity in isotropic plasmas, leaving only the integrations over the distribution functions of the particles. Nearly all these papers dealt with plasmas having (thermal) Maxwellian distribution functions. It is known from classical plasma physics that this assumption allows to obtain fairly good estimates of the relevant plasma parameters. Nevertheless, for a detailed description of a non-equilibrium plasma one has to solve the transport equation for the system. In particular, in situations where the dynamics of the whole system depends on the actual form of the particle distribution functions (e.g. in accretion flows), a better knowledge of the temporal evolution of pair plasmas is required. 5 references, 1 figure.

  2. Magnetic suppression of secondary electrons in plasma immersion ion implantation

    SciTech Connect

    Tan, I.H.; Ueda, Mario; Dallaqua, Renato S.; Rossi, Jose O. [Instituto Nacional de Pesquisas Espaciais, Laboratorio Associado de Plasmas, Av. Dos Astronautas 1758, CEP 12227-010, Sao Jose dos Campos (Brazil)

    2005-01-10

    In this work, magnetic suppression of secondary electrons in plasma immersion ion implantation is demonstrated experimentally in a vacuum arc system. Secondary electrons emitted normally to a copper sample surface were detected by a Faraday cup, whose signal exhibited large negative spikes coincident with high voltage pulses when aluminum ions of an unmagnetized plasma were implanted. When a 12.5 mT magnetic field parallel to the sample's surface is applied, these spikes are not seen, showing that secondary electrons were magnetically suppressed. Another cup, oriented to detect electrons that flow along the field lines, does not exhibit such negative spikes in either unmagnetized or magnetized plasmas, indicating that a virtual cathode was formed by the trapped secondary electrons.

  3. Influence of electron velocity distribution on the plasma expansion features

    SciTech Connect

    Shokoohi, R.; Abbasi, H. [Faculty of Physics, Amirkabir University of Technology, P. O. Box 15875-4413, Tehran (Iran, Islamic Republic of)

    2009-08-01

    Collisionless plasma expansion into vacuum is addressed emphasizing on the kinetic effects associated with the plasma electrons. It is an important issue since there are situations in which the plasmas are in nonequilibrium state. Thus, the electron distribution function (DF) that is generally non-Maxwellian has to be modeled. For this purpose, the generalized Lorentzian (kappa) DF is used to simulate the electron DF. The Maxwellian and kappa distributions differ substantially in a high-energy tail. Thus, the electron dynamics is studied by the Vlasov equation. Neglecting the ion temperatures, fluid equations are used for them. It is shown that by increasing the population of energetic electrons, the expansion takes place faster, the resulting electric field is stronger, and the ions are accelerated to higher energy.

  4. Nonlocal collisionless and collisional electron transport in low temperature plasmas

    NASA Astrophysics Data System (ADS)

    Kaganovich, Igor

    2009-10-01

    The purpose of the talk is to describe recent advances in nonlocal electron kinetics in low-pressure plasmas. A distinctive property of partially ionized plasmas is that such plasmas are always in a non-equilibrium state: the electrons are not in thermal equilibrium with the neutral species and ions, and the electrons are also not in thermodynamic equilibrium within their own ensemble, which results in a significant departure of the electron velocity distribution function from a Maxwellian. These non-equilibrium conditions provide considerable freedom to choose optimal plasma parameters for applications, which make gas discharge plasmas remarkable tools for a variety of plasma applications, including plasma processing, discharge lighting, plasma propulsion, particle beam sources, and nanotechnology. Typical phenomena in such discharges include nonlocal electron kinetics, nonlocal electrodynamics with collisionless electron heating, and nonlinear processes in the sheaths and in the bounded plasmas. Significant progress in understanding the interaction of electromagnetic fields with real bounded plasma created by this field and the resulting changes in the structure of the applied electromagnetic field has been one of the major achievements of the last decade in this area of research [1-3]. We show on specific examples that this progress was made possible by synergy between full scale particle-in-cell simulations, analytical models, and experiments. In collaboration with Y. Raitses, A.V. Khrabrov, Princeton Plasma Physics Laboratory, Princeton, NJ, USA; V.I. Demidov, UES, Inc., 4401 Dayton-Xenia Rd., Beavercreek, OH 45322, USA and AFRL, Wright-Patterson AFB, OH 45433, USA; and D. Sydorenko, University of Alberta, Edmonton, Canada. [4pt] [1] D. Sydorenko, A. Smolyakov, I. Kaganovich, and Y. Raitses, IEEE Trans. Plasma Science 34, 895 (2006); Phys. Plasmas 13, 014501 (2006); 14 013508 (2007); 15, 053506 (2008). [0pt] [2] I. D. Kaganovich, Y. Raitses, D. Sydorenko, and A. Smolyakov, Phys. Plasmas 14, 057104 (2007). [0pt] [3] V.I. Demidov, C.A. DeJoseph, and A.A. Kudryavtsev, Phys. Rev. Lett. 95, 215002 (2005); V.I. Demidov, C.A. DeJoseph, J. Blessington, and M.E. Koepke, Europhysics News, 38, 21 (2007).

  5. Probing the electronic structure of graphene sheets with various thicknesses by scanning transmission X-ray microscopy

    SciTech Connect

    Bai, Lili; Liu, Jinyin; Zhao, Guanqi; Gao, Jing; Sun, Xuhui, E-mail: xhsun@suda.edu.cn, E-mail: jzhong@suda.edu.cn; Zhong, Jun, E-mail: xhsun@suda.edu.cn, E-mail: jzhong@suda.edu.cn [Soochow University-Western University Centre for Synchrotron Radiation Research, Institute of Functional Nano and Soft Materials Laboratory (FUNSOM) and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123 (China)] [Soochow University-Western University Centre for Synchrotron Radiation Research, Institute of Functional Nano and Soft Materials Laboratory (FUNSOM) and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123 (China)

    2013-12-16

    The electronic structure of an aggregation of graphene sheets with various thicknesses was probed by scanning transmission X-ray microscopy. A uniform oxidation of the graphene sheets in the flat area was observed regardless of the thickness, while in the folded area the result could be strongly affected by the geometry. Moreover, thick parts of the aggregation showed strong angle-dependence to the incident X-ray, while thin parts showed less angle-dependence, which might be related to the surface wrinkles and ripples. The electronic structure differences due to the geometry and thickness suggest a complicated situation in the aggregation of graphene sheets.

  6. Investigation of the Effects of IMF Orientation Upon Delivery of Plasma Sheet Material to the Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Denton, M. H.; Thomsen, M. F.; Skoug, R. M.; Henderson, M. G.; Pollock, C. J.

    2004-12-01

    The orientation of the interplanetary magnetic field (IMF) is known to strongly control the entry of solar wind material into the Earth's magnetosphere. Within the magnetosphere various plasma properties and parameters are known to be IMF dependent. In this study we use Magnetospheric Plasma Analyser (MPA) data from the LANL constellation of satellites located in geosynchronous orbit, in conjunction with the imaging capabilities of the Medium Energy Neutral Atom (MENA) imager on-board the IMAGE satellite, to determine the effects of IMF orientation on the transport of plasma from the plasma sheet into the inner magnetosphere. A statistical study of MPA data is performed to determine bulk plasma properties at geosynchronous orbit in relation to IMF-By and IMF-Bz. In a parallel statistical study we use MENA data to determine the location of the peak nightside energetic neutral atom (ENA) emissons and to investigate whether this peak, which may indicate substorm injection regions, is IMF-dependent.

  7. A plasma-cathode electron source designed for industrial use

    NASA Astrophysics Data System (ADS)

    Osipov, Igor; Rempe, Nikolai

    2000-04-01

    The article presents a description of the principle of operation, the design, and the performance data of a plasma-cathode electron source. Plasma is produced in a hollow-cathode reflex discharge operating in an axial magnetic field. The discharge unit is filamentless. Air is used as the working gas. The electron source generates a focused continuous electron beam of current up to 0.3 A at an accelerating voltage of up to 60 kV. Owing to the absence of hot electrodes, the system operates reliably under severe gas conditions with a long lifetime. The electron source is currently used as a component of electron-beam welding flow lines. The use of the electron source for electron-beam facing of composite powdered materials is also discussed.

  8. Secondary-electrons-induced cathode plasma in a relativistic magnetron

    SciTech Connect

    Queller, T.; Gleizer, J. Z.; Krasik, Ya. E. [Physics Department, Technion, Haifa 32000 (Israel)

    2012-11-19

    Results of time- and space-resolved spectroscopic studies of cathode plasma during a S-band relativistic magnetron operation and a magnetically insulated diode having an identical interelectrode gap are presented. It was shown that in the case of the magnetron operation, one obtains an earlier, more uniform plasma formation due to energetic electrons' interaction with the cathode surface and ionization of desorbed surface monolayers. No differences were detected in the cathode's plasma temperature between the magnetron and the magnetically insulated diode operation, and no anomalous fast cathode plasma expansion was observed in the magnetron at rf power up to 350 MW.

  9. Microwave radiation measurements near the electron plasma frequency of the NASA Lewis bumpy torus plasma

    NASA Technical Reports Server (NTRS)

    Mallavarpu, R.; Roth, J. R.

    1978-01-01

    Microwave emission near the electron plasma frequency was observed, and its relation to the average electron density and the dc toroidal magnetic field was examined. The emission was detected using a spectrum analyzer and a 50 omega miniature coaxial probe. The radiation appeared as a broad amplitude peak that shifted in frequency as the plasma parameters were varied. The observed radiation scanned an average plasma density ranging from 10 million/cu cm to 8 hundred million/cu cm. A linear relation was observed betweeen the density calculated from the emission frequency and the average plasma density measured with a microwave interferometer. With the aid of a relative density profile measurement of the plasma, it was determined that the emissions occurred from the outer periphery of the plasma.

  10. Enhanced confinement in electron cyclotron resonance ion source plasma

    SciTech Connect

    Schachter, L.; Dobrescu, S. [National Institute for Physics and Nuclear Engineering, Bucharest (Romania); Stiebing, K. E. [Institut fuer Kernphysik der J. W. Goethe-Universitaet, Frankfurt/Main (Germany)

    2010-02-15

    Power loss by plasma-wall interactions may become a limitation for the performance of ECR and fusion plasma devices. Based on our research to optimize the performance of electron cyclotron resonance ion source (ECRIS) devices by the use of metal-dielectric (MD) structures, the development of the method presented here, allows to significantly improve the confinement of plasma electrons and hence to reduce losses. Dedicated measurements were performed at the Frankfurt 14 GHz ECRIS using argon and helium as working gas and high temperature resistive material for the MD structures. The analyzed charge state distributions and bremsstrahlung radiation spectra (corrected for background) also clearly verify the anticipated increase in the plasma-electron density and hence demonstrate the advantage by the MD-method.

  11. Three-wave coupling in electron-positron-ion plasmas

    SciTech Connect

    Tinakiche, N.; Annou, R. [Faculty of Physics, U.S.T.H.B. Algiers 16111 (Algeria); Tripathi, V. K. [Physics Department, I.T.T Delhi, New-Delhi 16 (India)

    2012-07-15

    The three-wave coupling processes in electron-positron-ion plasmas are investigated. The non-linear dispersion relation is derived along with the non-linear growth rate in both resonant and non resonant processes. It is shown that the inclusion of positron affects the dielectric properties of the plasma as well as the nonlinear growth rates of parametric processes. As one increases the positron density to electron density ratio from 0 to 1, maintaining quasi neutrality of the plasma, the growth rates of stimulated Raman, Brillouin, and Compton scattering processes in an isothermal plasma tend to zero due to the ponderomotive forces acting on electrons and positrons due the pump and scattered waves being equal.

  12. Electron energy distributions in a magnetized inductively coupled plasma

    SciTech Connect

    Song, Sang-Heon, E-mail: ssongs@umich.edu, E-mail: Sang-Heon.Song@us.tel.com [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, Michigan 48109-2104 (United States); Yang, Yang, E-mail: yang-yang@amat.com [Applied Materials Inc., 974 E. Arques Avenue, M/S 81312, Sunnyvale, California 94085 (United States); Chabert, Pascal, E-mail: pascal.chabert@lpp.polytechnique.fr [LPP, CNRS, Ecole Polytechnique, UPMC, Paris XI, 91128 Palaiseau (France); Kushner, Mark J., E-mail: mjkush@umich.edu [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109-2122 (United States)

    2014-09-15

    Optimizing and controlling electron energy distributions (EEDs) is a continuing goal in plasma materials processing as EEDs determine the rate coefficients for electron impact processes. There are many strategies to customize EEDs in low pressure inductively coupled plasmas (ICPs), for example, pulsing and choice of frequency, to produce the desired plasma properties. Recent experiments have shown that EEDs in low pressure ICPs can be manipulated through the use of static magnetic fields of sufficient magnitudes to magnetize the electrons and confine them to the electromagnetic skin depth. The EED is then a function of the local magnetic field as opposed to having non-local properties in the absence of the magnetic field. In this paper, EEDs in a magnetized inductively coupled plasma (mICP) sustained in Ar are discussed with results from a two-dimensional plasma hydrodynamics model. Results are compared with experimental measurements. We found that the character of the EED transitions from non-local to local with application of the static magnetic field. The reduction in cross-field mobility increases local electron heating in the skin depth and decreases the transport of these hot electrons to larger radii. The tail of the EED is therefore enhanced in the skin depth and depressed at large radii. Plasmas densities are non-monotonic with increasing pressure with the external magnetic field due to transitions between local and non-local kinetics.

  13. PIC modeling of fast electron transport in plasmas

    NASA Astrophysics Data System (ADS)

    Mishra, R.; Yabuuchi, T.; Wei, M. S.; Sentoku, Y.; Stephens, R. B.; Beg, F. N.

    2011-10-01

    Understanding fast electron transport in plasma is crucial for fast ignition. A recent experiment using the OMEGA EP laser (1 kJ/10 ps) study of fast electrons transport from the Au layer into hot (40 eV) dense (30 mg/cc) plasma created by shock heating of CH foam sandwiched between Au and Cu tracer layer, showed a strong reduction (20 ×) in Cu K ? yield compared to the cold target with a uniform and weak K ? spot. To understand this transport experiment, 2D collisional PIC simulations, using the PICLS code, are performed to model fast electron transport in such plasma transport target. Simulations show a significant increase in fast electron divergence going from high density Au to less dense plasma transport layer due to strong B-fields generated at the Au/CH plasma interface. Fine B-field structures in plasma are also observed, possibly responsible for further electron scattering resulting in poor K ? yield. Supported by US DOE under contracts DE-FC02-04ER54789 and DE-FG02-05ER54834.

  14. Field Emission Properties of Carbon Nanotube Fibers and Sheets for a High Current Electron Source

    NASA Astrophysics Data System (ADS)

    Christy, Larry

    Field emission (FE) properties of carbon nanotube (CNT) fibers from Rice University and the University of Cambridge have been studied for use within a high current electron source for a directed energy weapon. Upon reviewing the performance of these two prevalent CNT fibers, cathodes were designed with CNT fibers from the University of Cincinnati Nanoworld Laboratory. Cathodes composed of a single CNT fiber, an array of three CNT fibers, and a nonwoven CNT sheet were investigated for FE properties; the goal was to design a cathode with emission current in excess of 10 mA. Once the design phase was complete, the cathode samples were fabricated, characterized, and then analyzed to determine FE properties. Electrical conductivity of the CNT fibers was characterized with a 4-probe technique. FE characteristics were measured in an ultra-high vacuum chamber at Wright-Patterson Air Force Base. The arrayed CNT fiber and the enhanced nonwoven CNT sheet emitter design demonstrated the most promising FE properties. Future work will include further analysis and cathode design using this nonwoven CNT sheet material to increase peak current performance during electron emission.

  15. Electron transfer from sulfate-reducing becteria biofilm promoted by reduced graphene sheets

    NASA Astrophysics Data System (ADS)

    Wan, Yi; Zhang, Dun; Wang, Yi; Wu, Jiajia

    2012-01-01

    Reduced graphene sheets (RGSs) mediate electron transfer between sulfate-reducing bacteria (SRB) and solid electrodes, and promote the development of microbial fuel cells (MFC). We have investigated RSG-promoted electron transfer between SRB and a glassy carbon (GC) electrode. The RGSs were produced at high yield by a chemical sequence involving graphite oxidation, ultrasonic exfoliation of nanosheets, and N2H4 reduction. Cyclic voltammetric testing showed that the characteristic anodic peaks (around 0.3 V) might arise from the combination of bacterial membrane surface cytochrome c3 and the metabolic products of SRB. After 6 d, another anodic wave gradually increased to a maximum current peak and a third anodic signal became visible at around 0 V. The enhancements of two characteristic anodic peaks suggest that RSGs mediate electron-transfer kinetics between bacteria and the solid electrode. Manipulation of these recently-discovered electron-transport mechanisms will lead to significant advances in MFC engineering.

  16. Low-frequency mobility response functions for the central plasma sheet with application to tearing modes

    NASA Technical Reports Server (NTRS)

    Hernandez, J.; Horton, W.; Tajima, T.

    1993-01-01

    Consideration is given to the effect of constant cross-tail magnetic field By on the collisionless conductivity produced by chaotic scattering and stochastic diffusion of particles in the current sheet for a parabolic geometry. It is shown that the correlation time scales as (By/Bz)-squared, and from this strong By scaling a strong tendency toward stabilization of the linear tearing modes with increasing values of By is inferred. This effect of increased dawn-dusk mobility is particularly dramatic when electrons are introduced in the calculation, and is in agreement with the results of kinetic particle simulations. The collisionless conductivity is expressed in terms of the ensemble-averaged power spectrum of the single particle trajectories, which makes it possible to calculate directly the linear conductivity instead of deriving it from the calculation of the irreversible heating rates.

  17. Fundamental processes in pair plasmas. [electron-positron relativistic plasmas in quasars and active galaxies

    NASA Technical Reports Server (NTRS)

    Lightman, A. P.

    1983-01-01

    The various processes that produce and destroy electron-positron pairs are reviewed, and the timescales of these processes are compared to thermalization, accretion, and cooling timescales. The various radiation spectra produced by relativistic, thermal plasmas are considered. Recent results for the equilibria available to finite, thermal relativistic plasmas with and without embedded magnetic fields are reviewed. Such plasmas, in steady state, have maximum temperatures, luminosities, and field strengths, useful diagnostics for interpreting quasars and active galaxies.

  18. Paper-like electronic displays: Large-area rubber-stamped plastic sheets of electronics and microencapsulated electrophoretic inks

    PubMed Central

    Rogers, John A.; Bao, Zhenan; Baldwin, Kirk; Dodabalapur, Ananth; Crone, Brian; Raju, V. R.; Kuck, Valerie; Katz, Howard; Amundson, Karl; Ewing, Jay; Drzaic, Paul

    2001-01-01

    Electronic systems that use rugged lightweight plastics potentially offer attractive characteristics (low-cost processing, mechanical flexibility, large area coverage, etc.) that are not easily achieved with established silicon technologies. This paper summarizes work that demonstrates many of these characteristics in a realistic system: organic active matrix backplane circuits (256 transistors) for large (?5 × 5-inch) mechanically flexible sheets of electronic paper, an emerging type of display. The success of this effort relies on new or improved processing techniques and materials for plastic electronics, including methods for (i) rubber stamping (microcontact printing) high-resolution (?1 ?m) circuits with low levels of defects and good registration over large areas, (ii) achieving low leakage with thin dielectrics deposited onto surfaces with relief, (iii) constructing high-performance organic transistors with bottom contact geometries, (iv) encapsulating these transistors, (v) depositing, in a repeatable way, organic semiconductors with uniform electrical characteristics over large areas, and (vi) low-temperature (?100°C) annealing to increase the on/off ratios of the transistors and to improve the uniformity of their characteristics. The sophistication and flexibility of the patterning procedures, high level of integration on plastic substrates, large area coverage, and good performance of the transistors are all important features of this work. We successfully integrate these circuits with microencapsulated electrophoretic “inks” to form sheets of electronic paper. PMID:11320233

  19. Paper-like electronic displays: large-area rubber-stamped plastic sheets of electronics and microencapsulated electrophoretic inks.

    PubMed

    Rogers, J A; Bao, Z; Baldwin, K; Dodabalapur, A; Crone, B; Raju, V R; Kuck, V; Katz, H; Amundson, K; Ewing, J; Drzaic, P

    2001-04-24

    Electronic systems that use rugged lightweight plastics potentially offer attractive characteristics (low-cost processing, mechanical flexibility, large area coverage, etc.) that are not easily achieved with established silicon technologies. This paper summarizes work that demonstrates many of these characteristics in a realistic system: organic active matrix backplane circuits (256 transistors) for large ( approximately 5 x 5-inch) mechanically flexible sheets of electronic paper, an emerging type of display. The success of this effort relies on new or improved processing techniques and materials for plastic electronics, including methods for (i) rubber stamping (microcontact printing) high-resolution ( approximately 1 microm) circuits with low levels of defects and good registration over large areas, (ii) achieving low leakage with thin dielectrics deposited onto surfaces with relief, (iii) constructing high-performance organic transistors with bottom contact geometries, (iv) encapsulating these transistors, (v) depositing, in a repeatable way, organic semiconductors with uniform electrical characteristics over large areas, and (vi) low-temperature ( approximately 100 degrees C) annealing to increase the on/off ratios of the transistors and to improve the uniformity of their characteristics. The sophistication and flexibility of the patterning procedures, high level of integration on plastic substrates, large area coverage, and good performance of the transistors are all important features of this work. We successfully integrate these circuits with microencapsulated electrophoretic "inks" to form sheets of electronic paper. PMID:11320233

  20. The effect of electron beam on the electron hole in a plasma

    SciTech Connect

    Sayal, V.K.; Jain, S.L.; Sharma, S.R. (Department of Physics, University of Rajasthan, Jaipur (India))

    1994-11-01

    An electron hole is discussed theoretically in an electron beam--plasma system. The nonlinear dispersion relation for the electron hole along with the conditions on the existence of the electron hole is investigated numerically. It is found that depending upon the beam parameters and radial boundary there are two regions where the electron hole can be formed. It is also seen that the upper limit on Mach number of the electron hole does not vanish even in the presence of the electron beam. The electron holes of high Mach number are possible only in the presence of an electron beam.

  1. Coupled electron and ion nonlinear oscillations in a collisionless plasma

    SciTech Connect

    Karimov, A. R. [Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya 13/19, Moscow 127412, Russia and Department of Electrophysical Facilities, National Research Nuclear University MEPhI, Kashirskoye shosse 31, Moscow 115409 (Russian Federation)] [Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya 13/19, Moscow 127412, Russia and Department of Electrophysical Facilities, National Research Nuclear University MEPhI, Kashirskoye shosse 31, Moscow 115409 (Russian Federation)

    2013-05-15

    Dynamics of coupled electrostatic electron and ion nonlinear oscillations in a collisionless plasma is studied with reference to a kinetic description. Proceeding from the exact solution of Vlasov-Maxwell equations written as a function of linear functions in the electron and ion velocities, we arrive at the two coupled nonlinear equations which describe the evolution of the system.

  2. Coupled electron and ion nonlinear oscillations in a collisionless plasma

    NASA Astrophysics Data System (ADS)

    Karimov, A. R.

    2013-05-01

    Dynamics of coupled electrostatic electron and ion nonlinear oscillations in a collisionless plasma is studied with reference to a kinetic description. Proceeding from the exact solution of Vlasov-Maxwell equations written as a function of linear functions in the electron and ion velocities, we arrive at the two coupled nonlinear equations which describe the evolution of the system.

  3. PLASMA WAKEFIELD ACCELERATION EXPERIMENTS USING TWO SUBPICOSECOND ELECTRON BUNCHES*

    E-print Network

    Brookhaven National Laboratory

    PLASMA WAKEFIELD ACCELERATION EXPERIMENTS USING TWO SUBPICOSECOND ELECTRON BUNCHES* P. Muggli,#,1 W, USA 3 Brookhaven National Laboratory, Upton, NY, USA Abstract Two subpicosecond electron bunches (PWFA) model indicates the net wakefield produced by the bunches will depend on their relative charge

  4. Electron and proton transport across the plasma membrane

    Microsoft Academic Search

    Frederick L. Crane; Iris L. Sun; Rita Barr; Hans Löw

    1991-01-01

    Transplasma membrane electron transport in both plant and animal cells activates proton release. The nature and components of the electron transport system and the mechanism by which proton release is activated remains to be discovered. Reduced pyridine nucleotides are substrates for the plasma membrane dehydrogenases. Both plant and animal membranes have unusual cyanide-insensitive oxidases so oxygen can be the natural

  5. Numerical model of the plasma formation at electron beam welding

    NASA Astrophysics Data System (ADS)

    Trushnikov, D. N.; Mladenov, G. M.

    2015-01-01

    The model of plasma formation in the keyhole in liquid metal as well as above the electron beam welding zone is described. The model is based on solution of two equations for the density of electrons and the mean electron energy. The mass transfer of heavy plasma particles (neutral atoms, excited atoms, and ions) is taken into account in the analysis by the diffusion equation for a multicomponent mixture. The electrostatic field is calculated using the Poisson equation. Thermionic electron emission is calculated for the keyhole wall. The ionization intensity of the vapors due to beam electrons and high-energy secondary and backscattered electrons is calibrated using the plasma parameters when there is no polarized collector electrode above the welding zone. The calculated data are in good agreement with experimental data. Results for the plasma parameters for excitation of a non-independent discharge are given. It is shown that there is a need to take into account the effect of a strong electric field near the keyhole walls on electron emission (the Schottky effect) in the calculation of the current for a non-independent discharge (hot cathode gas discharge). The calculated electron drift velocities are much bigger than the velocity at which current instabilities arise. This confirms the hypothesis for ion-acoustic instabilities, observed experimentally in previous research.

  6. ELECTRON ACCELERATION AND PLASMA INSTABILITIES IN THE TRANSITION REGION

    Microsoft Academic Search

    F. L. Scarf; W. Bernstein; R. W. Fredricks

    1965-01-01

    It is proposed that after a solar wind enhancement the wind-magnetosphere in- terface becomes unstable with respect to production of ion acoustic waves. The high frequency electric oscillations then allow plasma to diffuse across the magnetic field, and the waves interact with the electron population via the cyclotron resonance. A small fraction of the electrons are accelerated to key energies,

  7. Beam loading by electrons in nonlinear plasma wakes

    Microsoft Academic Search

    M. Tzoufras; W. Lu; F. S. Tsung; C. Huang; W. B. Mori; T. Katsouleas; J. Vieira; R. A. Fonseca; L. O. Silva

    2009-01-01

    An analytical theory for the interaction of an electron bunch with a nonlinear plasma wave is developed to make it possible to design efficient laser- and\\/or beam-driven accelerators that generate high quality monoenergetic electron beams. This theory shows how to choose the charge, the shape, and the placing of the bunch so that the conversion efficiency from the fields of

  8. Possible control of plasma transport in the near-Earth plasma sheet via current-driven Alfvén waves (f~=fH+)

    NASA Astrophysics Data System (ADS)

    Le Contel, O.; Roux, A.; Perraut, S.; Pellat, R.; Holter, Ø.; Pedersen, A.; Korth, A.

    2001-06-01

    Two time periods, each covering both quiet and disturbed conditions (growth phase, breakup, and postbreakup phase), are studied. Electric and magnetic field measurements, carried out in the near-Earth plasma sheet (NEPS), are used to calculate the two components (radial and azimuthal) of the electric E×B/B2 drift. These calculations are compared with independent estimates of the ion flow direction deduced from ion flux measurements. During active periods, the two flow directions coincide to a large degree. Evidence is given for two regimes of transport: (1) During the growth phase, and after the active phase, the electric field (radial and azimuthal) and hence the azimuthal and radial flow velocities are small in the near-equatorial region. This is interpreted as the consequence of an electrostatic field that tends to shield the induced electric field associated with time-varying external conditions. (2) During active phases (breakup and pseudobreakup), however, large-amplitude bursts in E×B/B2 radial and azimuthal components (interpreted as flow bursts), with typical velocities of the order of 100 kms-1, are observed. The direction of these flow bursts is somewhat arbitrary, and in particular, for the two substorm events described here, sudden reversals in the flow direction are observed. These fast flow bursts coincide with intense low-frequency electromagnetic fluctuations: current-driven Alfvén waves (CDA waves) with frequency f~=fH+, the proton gyrofrequency. CDA waves produce ``anomalous'' collisions on timescales shorter than the electron bounce period, thus violating the second adiabatic invariant for electrons. As a consequence, the electrostatic shielding is destroyed, which leads to enhanced radial transport. Thus the transport in the NEPS seems to be controlled by a microscopic current-driven instability.

  9. Method for generating a plasma wave to accelerate electrons

    DOEpatents

    Umstadter, D.; Esarey, E.; Kim, J.K.

    1997-06-10

    The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention. 21 figs.

  10. Revisiting plasma hysteresis with an electronically compensated Langmuir probe

    NASA Astrophysics Data System (ADS)

    Srivastava, P. K.; Singh, S. K.; Awasthi, L. M.; Mattoo, S. K.

    2012-09-01

    The measurement of electron temperature in plasma by Langmuir probes, using ramped bias voltage, is seriously affected by the capacitive current of capacitance of the cable between the probe tip and data acquisition system. In earlier works a dummy cable was used to balance the capacitive currents. Under these conditions, the measured capacitive current was kept less than a few mA. Such probes are suitable for measurements in plasma where measured ion saturation current is of the order of hundreds of mA. This paper reports that controlled balancing of capacitive current can be minimized to less than 20 ?A, allowing plasma measurements to be done with ion saturation current of the order of hundreds of ?A. The electron temperature measurement made by using probe compensation technique becomes independent of sweep frequency. A correction of ?45% is observed in measured electron temperature values when compared with uncompensated probe. This also enhances accuracy in the measurement of fluctuation in electron temperature as ?Tpk-pk changes by ˜30%. The developed technique with swept rate ?100 kHz is found accurate enough to measure both the electron temperature and its fluctuating counterpart. This shows its usefulness in measuring accurately the temperature fluctuations because of electron temperature gradient in large volume plasma device plasma with frequency ordering ?50 kHz.

  11. Method for generating a plasma wave to accelerate electrons

    DOEpatents

    Umstadter, Donald (Ann Arbor, MI); Esarey, Eric (Chevy Chase, MD); Kim, Joon K. (Ann Arbor, MI)

    1997-01-01

    The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention.

  12. Relativistic plasma microwave electronics: studies of high power plasma filled backward wave oscillators

    Microsoft Academic Search

    Y. Carmel; W. R. Lou; J. Rodgers; B. Levush; J. Tate; W. W. Destler; V. L. Granatstein

    1992-01-01

    Summary form only given, as follows. The area of relativistic plasma microwave electronics has recently generated renewed interest in the microwave and millimeter-wave device community. The authors have obtained experimental data demonstrating that the presence of a low-density background plasma in a relativistic backward wave oscillator leads to several beneficial effects, including enhanced interaction efficiency (40%), operation at very low

  13. Nonlinear evolution of three-dimensional instabilities of thin and thick electron scale current sheets: Plasmoid formation and current filamentation

    SciTech Connect

    Jain, Neeraj; Büchner, Jörg [Max Planck/Princeton Center for Plasma Physics, Göttingen (Germany); Max Planck Institute for Solar System Research, Justus-Von-Liebig-Weg-3, Göttingen (Germany)

    2014-07-15

    Nonlinear evolution of three dimensional electron shear flow instabilities of an electron current sheet (ECS) is studied using electron-magnetohydrodynamic simulations. The dependence of the evolution on current sheet thickness is examined. For thin current sheets (half thickness =d{sub e}=c/?{sub pe}), tearing mode instability dominates. In its nonlinear evolution, it leads to the formation of oblique current channels. Magnetic field lines form 3-D magnetic spirals. Even in the absence of initial guide field, the out-of-reconnection-plane magnetic field generated by the tearing instability itself may play the role of guide field in the growth of secondary finite-guide-field instabilities. For thicker current sheets (half thickness ?5?d{sub e}), both tearing and non-tearing modes grow. Due to the non-tearing mode, current sheet becomes corrugated in the beginning of the evolution. In this case, tearing mode lets the magnetic field reconnect in the corrugated ECS. Later thick ECS develops filamentary structures and turbulence in which reconnection occurs. This evolution of thick ECS provides an example of reconnection in self-generated turbulence. The power spectra for both the thin and thick current sheets are anisotropic with respect to the electron flow direction. The cascade towards shorter scales occurs preferentially in the direction perpendicular to the electron flow.

  14. Radiative recombination of ions with electrons in cold magnetized plasma

    NASA Astrophysics Data System (ADS)

    Pajek, M.; Bana?, D.; Brandau, C.; Gumberidze, A.; Jagodzi?ski, P.; Kozhuharov, Ch; Surzhykov, A.; Stöhlker, Th

    2012-11-01

    New interpretation of the enhancement effect in the radiative recombination (RR) of bare ions with with cooling electrons in cooler/storage rings is proposed which explains this effect by the transverse collisions with large impact parameter, in the ?m range, in the magnetized anisotropic plasma in the electron cooler. The developed simplified approach, called the semiclassical geometrical model (SGM), predicts for a weak magnetic fields the scaling of RR excess rate which agrees with experimental observations. Detailed Monte Carlo simulations of the RR in the magnetized electron-cooler plasma based on the proposed SGM model explains the enhancement observed in ion storage rings in RR experiments.

  15. Kinetic description of electron plasma waves with orbital angular momentum

    NASA Astrophysics Data System (ADS)

    Mendonça, J. T.

    2012-11-01

    We describe the kinetic theory of electron plasma waves with orbital angular momentum or twisted plasmons. The conditions for a twisted Landau resonance to exist are established, and this concept is introduced for the first time. Expressions for the kinetic dispersion relation and for the electron Landau damping are derived. The particular case of a Maxwellian plasma is examined in detail. The new contributions to wave dispersion and damping due the orbital angular momentum are discussed. It is shown that twisted plasmons can be excited by rotating electron beams.

  16. Kinetic description of electron plasma waves with orbital angular momentum

    SciTech Connect

    Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

    2012-11-15

    We describe the kinetic theory of electron plasma waves with orbital angular momentum or twisted plasmons. The conditions for a twisted Landau resonance to exist are established, and this concept is introduced for the first time. Expressions for the kinetic dispersion relation and for the electron Landau damping are derived. The particular case of a Maxwellian plasma is examined in detail. The new contributions to wave dispersion and damping due the orbital angular momentum are discussed. It is shown that twisted plasmons can be excited by rotating electron beams.

  17. Suprathermal electrons produced by beam-plasma-discharge

    NASA Technical Reports Server (NTRS)

    Sharp, W. E.

    1982-01-01

    Experiments conducted with a low energy plasma lens, HARP, in the electron beam of the large vacuum chamber at Johnson Space Center indicate that an enhanced population of 50 to 300 volt electrons appear when the beam goes into the Beam-Plasma Discharge (BPD) mode. Below the BPD instability the electron distribution appears to be characterized as non-energized single particle scattering and energy loss. At 100 cm from the beam core in the BPD mode the fluxes parallel to the beam are reduced by a factor of 20 with respect to the fluxes at 25 cm. Some evidence for isotropy near the beam core is presented.

  18. Linear analysis of a rectangular waveguide cyclotron maser with a sheet electron beam

    SciTech Connect

    Zhao Ding; Ding Yaogen; Wang Yong; Ruan Cunjun [Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China)

    2010-11-15

    A linear theory for a rectangular waveguide cyclotron maser with a sheet electron beam is developed by using the Laplace transformation approach. This theory can be applied to any TE{sub mn} rectangular waveguide mode. The corresponding equations for the TM{sub mn} mode in the rectangular waveguide are also derived as a useful reference. Especially, the effect from the coupling between degenerate modes, which is induced by the nonideal rectangular waveguide walls, on the dispersion relation is considered in order to provide a more accurate model for the real devices. Through numerical calculations, the linear growth rate, launching loss, and spontaneous oscillations (caused by the absolute instability and backward wave oscillation) of this new structure can be analyzed in detail. It is worthwhile to point out that the operation at higher power levels of the rectangular waveguide sheet beam system is possible.

  19. Two-dimensional-spatial distribution measurement of electron temperature and plasma density in low temperature plasmas

    SciTech Connect

    Kim, Young-Cheol [Department of Nanoscale Semiconductor Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Jang, Sung-Ho; Oh, Se-Jin; Lee, Hyo-Chang; Chung, Chin-Wook [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

    2013-05-15

    A real-time measurement method for two-dimensional (2D) spatial distribution of the electron temperature and plasma density was developed. The method is based on the floating harmonic method and the real time measurement is achieved with little plasma perturbation. 2D arrays of the sensors on a 300 mm diameter wafer-shaped printed circuit board with a high speed multiplexer circuit were used. Experiments were performed in an inductive discharge under various external conditions, such as powers, gas pressures, and different gas mixing ratios. The results are consistent with theoretical prediction. Our method can measure the 2D spatial distribution of plasma parameters on a wafer-level in real-time. This method can be applied to plasma diagnostics to improve the plasma uniformity of plasma reactors for plasma processing.

  20. Effect of Time Dependent Bending of Current Sheets in Response to Generation of Plasma Jets and Reverse Currents

    NASA Astrophysics Data System (ADS)

    Frank, Anna

    Magnetic reconnection is a basis for many impulsive phenomena in space and laboratory plasmas accompanied by effective transformation of magnetic energy. Reconnection processes usually occur in relatively thin current sheets (CSs), which separate magnetic fields of different or opposite directions. We report on recent observations of time dependent bending of CSs, which results from plasma dynamics inside the sheet. The experiments are carried out with the CS-3D laboratory device (Institute of General Physics RAS, Moscow) [1]. The CS magnetic structure with an X line provides excitation of the Hall currents and plasma acceleration from the X line to both side edges [2]. In the presence of the guide field By the Hall currents give rise to bending of the sheet: the peripheral regions located away from the X line are deflected from CS middle plane (z=0) in the opposite directions ±z [3]. We have revealed generation of reverse currents jy near the CS edges, i.e. the currents flowing in the opposite direction to the main current in the sheet [4]. There are strong grounds to believe that reverse currents are generated by the outflow plasma jets [5], accelerated inside the sheet and penetrated into the regions with strong normal magnetic field component Bz [4]. An impressive effect of sudden change in the sign of the CS bend has been disclosed recently, when analyzing distributions of plasma density [6] and current away from the X line, in the presence of the guide field By. The CS configuration suddenly becomes opposite from that observed at the initial stage, and this effect correlates well with generation of reverse currents. Consequently this effect can be related to excitation of the reverse Hall currents owing to generation of reverse currents jy in the CS. Hence it may be concluded that CSs may exhibit time dependent vertical z-displacements, and the sheet geometry depends on excitation of the Hall currents, acceleration of plasma jets and generation of reverse currents. The work was supported in part by the Program (OFN-15) “Plasma Processes in Space and Laboratory” of the Division of Physical Sciences of the Russian Academy of Sciences. 1. Frank A.G., Bogdanov S.Yu., Markov V.S. et al. // Phys. Plasmas 2005. 12, 052316(1-11). 2. Frank A.G., Bugrov S.G., Markov V.S. // Phys. Plasmas 2008. 15, 092102 (1-10). 3. Frank A.G., Bogdanov S.Yu., Dreiden G.V. et al. // Phys. Lett. A 2006. 348, 318-325. 4. Frank A.G., Kyrie N.P., Satunin S.N. // Phys. Plasmas 2011. 18, 111209 (1-9). 5. Kyrie N.P., Markov V.S., Frank A.G. // Plasma Phys. Reports 2010. 36, 357-364; JETP Lett. 2012. 95, 14-19. 6. Ostrovskaya G.V., Frank A.G. // Plasma Phys. Reports 2014. 40, 21-33.

  1. Ion composition of the near-Earth plasma sheet in storm and quiet intervals: Geotail\\/EPIC measurements

    Microsoft Academic Search

    M. Nosé; S. Ohtani; K. Takahashi; A. T. Y. Lui; R. W. McEntire; D. J. Williams; S. P. Christon; K. Yumoto

    2001-01-01

    We investigate the ion composition of the near-Earth plasma sheet in storm and quiet intervals, using energetic (9-210 keV) particle flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on the Geotail spacecraft. In 1998 four magnetic storms (minimum Dst=-10RE). For each of the storms, we have selected a

  2. Ultra-low-frequency waves and associated wave vectors observed in the plasma sheet boundary layer by Cluster

    Microsoft Academic Search

    M. C. Broughton; M. J. Engebretson; K.-H. Glassmeier; Y. Narita; A. Keiling; K.-H. Fornaçon; G. K. Parks

    2008-01-01

    Waves in the Pc1–Pc2 frequency range (0.1–5 Hz) are studied using Cluster magnetic field data. In the plasma sheet boundary layer, Cluster observed harmonically related waves with the fundamental near the local proton cyclotron frequency (?p). These waves had components both parallel and perpendicular to the local magnetic field (B0). Application of the wave telescope yielded the full wave vector

  3. DE particle and field observations during the poleward expansion of an auroral surge through the plasma sheet

    NASA Astrophysics Data System (ADS)

    Anderson, P. C.; Lyons, L. R.

    A substorm surge on September 25, 1981 was observed by the imagers on the high-altitude DE-1 spacecraft and encountered by the coplanar, low-altitude DE-2 spacecraft. This case is unique among those that we examined in that DE-2 traversed the surge during the ˜10-15 min period of its rapid poleward motion through the plasma sheet. Because of this, the DE-2 measurements provide a critical test for the recent proposal that the substorm expansion phase is due to an anti-sunward-propagating reduction in the large-scale magnetospheric electric field imparted to the magnetosphere from the solar wind [Lyons, 1995]. A specific prediction of this theory is that the electric field reduction in the equatorial magnetosphere maps to the ionosphere as a poleward-moving electric field reduction. In the ionosphere, large growth-phase electric fields are expected poleward of the active surge aurora, and significantly weaker electric fields are expected equatorward of the active aurora. This electric field pattern is expected to propagate poleward through the plasma sheet with the surge. The DE-2 measurements show significant southwestward electric fields within the portion of the plasma sheet poleward of the active auroral region, and greatly reduced electric fields within, the heated central plasma sheet that was left behind by the narrow region of poleward-moving, active aurora. We also find weak electric fields equatorward of the region of active aurora in typical DE-2 passes over auroral surges, where the region of active aurora had moved poleward to very near the magnetic separatrix prior to the satellite pass. These observations agree strongly with the Lyons [1995] predictions. Consistent with previous observations, the DE-2 measurements also show strong and variable electric fields within the region of active surge; however these fields are not specifically addressed by the theory.

  4. Possible control of plasma transport in the near-Earth plasma sheet via current-driven Alfvén waves (f~=fH+)

    Microsoft Academic Search

    O. Le Contel; A. Roux; S. Perraut; R. Pellat; Ø. Holter; A. Pedersen; A. Korth

    2001-01-01

    Two time periods, each covering both quiet and disturbed conditions (growth phase, breakup, and postbreakup phase), are studied. Electric and magnetic field measurements, carried out in the near-Earth plasma sheet (NEPS), are used to calculate the two components (radial and azimuthal) of the electric E×B\\/B2 drift. These calculations are compared with independent estimates of the ion flow direction deduced from

  5. Electron densities in the upper ionosphere of Mars from the excitation of electron plasma oscillations

    E-print Network

    Gurnett, Donald A.

    Electron densities in the upper ionosphere of Mars from the excitation of electron plasma to remote radio sounding of the ionosphere of Mars, the MARSIS (Mars Advanced Radar for Subsurface and Ionospheric Sounding) instrument on the Mars Express spacecraft is also able to measure the in situ electron

  6. Emission of electron Bernstein waves in plasmas

    Microsoft Academic Search

    A. K. Ram; A. Bers; C. N. Lashmore-Davies

    2002-01-01

    In previous publications [A. K. Ram and S. D. Schultz, Phys. Plasmas 7, 4084 (2000); A. Bers, A. K. Ram, and S. D. Schultz, in Proceedings of the Second Europhysics Topical Conference on RF Heating and Current Drive of Fusion Devices, edited by J. Jacquinot, G. Van Oost, and R. R. Weynants (European Physical Society, Petit-Lancy, 1998), Vol. 22A, pp.

  7. Entry of plasma sheet particles into the inner magnetosphere as observed by Polar/CAMMICE

    NASA Astrophysics Data System (ADS)

    Ganushkina, N. Yu.; Pulkkinen, T. I.; Sergeev, V. A.; Kubyshkina, M. V.; Baker, D. N.; Turner, N. E.; Grande, M.; Kellett, B.; Fennell, J.; Roeder, J.; Sauvaud, J.-A.; Fritz, T. A.

    2000-11-01

    Statistical results are presented from Polar/CAMMICE measurements of events during which the plasma sheet ions have penetrated deeply into the inner magnetosphere. Owing to their characteristic structure in energy-time spectrograms, these events are called ``intense nose events.'' Almost 400 observations of such structures were made during 1997. Intense nose events are shown to be more frequent in the dusk than in the dawn sector. They typically penetrate well inside L=4, the deepest penetration having occurred around midnight and noon. The intense nose events are associated with magnetic (substorm) activity. However, even moderate activity (AE=150-250nT) resulted in formation of these structures. In a case study of November 3, 1997, three sequential inner magnetosphere crossings of the Polar and Interball Auroral spacecraft are shown, each of which exhibited signatures of intense nose-like structures. Using the innermost boundary determinations from these observations, it is demonstrated that a large-scale convective electric field alone cannot account for the inward motion of the structure. It is suggested that the intense nose structures are caused by short-lived intense electric fields (in excess of ~1 mV/m) in the inner tail at L=4-5.

  8. Effect of electron extraction from a grid plasma cathode on the generation of emission plasma

    NASA Astrophysics Data System (ADS)

    Devyatkov, V. N.; Koval, N. N.

    2014-11-01

    The paper describes the operating mode of a plasma electron source based on a low- pressure arc discharge with grid stabilization of the plasma emission boundary which provides a considerable (up to twofold) increase in discharge and beam currents at an Ar pressure in the vacuum chamber p = 0.02-0.05 Pa, accelerating voltages of up to U = 10 kV, and longitudinal magnetic field of up to Bz = 0.1 T. The discharge and beam currents are increased on electron extraction from the emission plasma through meshes of a fine metal grid due to the energy of a high-voltage power supply which ensures electron emission and acceleration. The electron emission from the plasma cathode and arrival of ions from the acceleration gap in the discharge changes the discharge plasma parameters near the emission grid, thus changing the potential of the emission grid electrode with respect to the discharge cathode. The load is not typical and changes the voltage polarity of the electrode gap connected to the discharge power supply, which is to be taken into account in its calculation and design. The effect of electron emission from the plasma cathode on the discharge system can not only change the discharge and beam current pulse shapes but can also lead to a breakdown of the acceleration gap and failure of semiconductor elements in the discharge power supply unit.

  9. Plasma properties in electron-bombardment ion thrusters

    NASA Technical Reports Server (NTRS)

    Matossian, J. N.; Beattie, J. R.

    1987-01-01

    The paper describes a technique for computing volume-averaged plasma properties within electron-bombardment ion thrusters, using spatially varying Langmuir-probe measurements. Average values of the electron densities are defined by integrating the spatially varying Maxwellian and primary electron densities over the ionization volume, and then dividing by the volume. Plasma properties obtained in the 30-cm-diameter J-series and ring-cusp thrusters are analyzed by the volume-averaging technique. The superior performance exhibited by the ring-cusp thruster is correlated with a higher average Maxwellian electron temperature. The ring-cusp thruster maintains the same fraction of primary electrons as does the J-series thruster, but at a much lower ion production cost. The volume-averaged predictions for both thrusters are compared with those of a detailed thruster performance model.

  10. Plasma properties in electron-bombardment ion thrusters

    SciTech Connect

    Matossian, J.N.; Beattie, J.R.

    1987-05-01

    The paper describes a technique for computing volume-averaged plasma properties within electron-bombardment ion thrusters, using spatially varying Langmuir-probe measurements. Average values of the electron densities are defined by integrating the spatially varying Maxwellian and primary electron densities over the ionization volume, and then dividing by the volume. Plasma properties obtained in the 30-cm-diameter J-series and ring-cusp thrusters are analyzed by the volume-averaging technique. The superior performance exhibited by the ring-cusp thruster is correlated with a higher average Maxwellian electron temperature. The ring-cusp thruster maintains the same fraction of primary electrons as does the J-series thruster, but at a much lower ion production cost. The volume-averaged predictions for both thrusters are compared with those of a detailed thruster performance model. 20 references.

  11. Anomalous electron mobility in a coaxial Hall discharge plasma.

    PubMed

    Meezan, N B; Hargus, W A; Cappelli, M A

    2001-02-01

    A comprehensive analysis of measurements supporting the presence of anomalous cross-field electron mobility in Hall plasma accelerators is presented. Nonintrusive laser-induced fluorescence measurements of neutral xenon and ionized xenon velocities, and various electrostatic probe diagnostic measurements are used to locally determine the effective electron Hall parameter inside the accelerator channel. These values are then compared to the classical (collision-driven) Hall parameters expected for a quiescent magnetized plasma. The results indicate that in the vicinity of the anode, where there are fewer plasma instabilities, the electron-transport mechanism is likely elastic collisions with the background neutral xenon. However, we find that in the vicinity of the discharge channel exit, where the magnetic field is the strongest and where there are intense fluctuations in the plasma properties, the inferred Hall parameter departs from the classical value, and is close to the Bohm value of (omega(ce)tau)(eff) approximately 16. These results are used to support a simple model for the Hall parameter that is based on the scalar addition of the electron collision frequencies (elastic collision induced plus fluctuation induced), as proposed by Boeuf and Garrigues [J. Appl. Phys. 84, 3541 (1998)]. The results also draw attention to the possible role of fluctuations in enhancing electron transport in regions where the electrons are highly magnetized. PMID:11308588

  12. Particle Simulations for Electron Beam-Plasma Interactions

    NASA Astrophysics Data System (ADS)

    Zhou, Guo-cheng; G, Zhou C.; Li, Yang; Cao, Jin-bin; J, Cao B.; Wang, Xue-yi; X, Wang Y.

    1998-12-01

    The computer simulations of high-frequency instabilities excited by the high density electron beam and their nonlinear effect are presented. One-dimensional electromagnetic particle simulations are performed with different values of the electron beam-to-plasma density ratio. The results show that for the high electron beam-to-background plasma density ratio, all the Langmuir waves and two electromagnetic waves with left-hand and right-hand circular polarizations (i.e., the "L-O mode" and the "R-X mode") propagating parallel to the magnetic field can be generated and the maximum values of wave electric fields are nearly the same. The electron beam and background plasma are diffused and a part of energetic background electrons are obviously accelerated by the wave-particle interactions. The heating of the beam and background plasma is mainly due to the electrostatic (Langmuir) wave-particle interactions, but the accelerations of a part of energetic background electrons may be mainly due to the electromagnetic wave-particle interactions.

  13. Collisionless reconnection in an electron-positron plasma.

    PubMed

    Bessho, N; Bhattacharjee, A

    2005-12-01

    Electromagnetic particle-in-cell simulations of fast collisionless reconnection in a two-dimensional electron-positron plasma (without an equilibrium guide field) are presented. A generalized Ohm's law in which the Hall current cancels out exactly is given. It is suggested that the key to fast reconnection in this plasma is the localization caused by the off-diagonal components of the pressure tensors, which produce an effect analogous to a spatially localized resistivity. PMID:16384388

  14. Influence of electron injection into 27 cm audio plasma cell on the plasma diagnostics

    SciTech Connect

    Haleem, N. A.; Ragheb, M. S.; Zakhary, S. G. [Accelerators Department, Nuclear Research Center, AEA, Cairo 13759 (Egypt)] [Accelerators Department, Nuclear Research Center, AEA, Cairo 13759 (Egypt); El Fiki, S. A.; Nouh, S. A. [Faculty of Science, Ain Shams University, Cairo 11566 (Egypt)] [Faculty of Science, Ain Shams University, Cairo 11566 (Egypt); El Disoki, T. M. [Faculty of Girls, Ain Shams University, Cairo 11566 (Egypt)] [Faculty of Girls, Ain Shams University, Cairo 11566 (Egypt)

    2013-08-15

    In this article, the plasma is created in a Pyrex tube (L = 27 cm, ?= 4 cm) as a single cell, by a capacitive audio frequency (AF) discharge (f = 10–100 kHz), at a definite pressure of ?0.2 Torr. A couple of tube linear and deviating arrangements show plasma characteristic conformity. The applied AF plasma and the injection of electrons into two gas mediums Ar and N{sub 2} revealed the increase of electron density at distinct tube regions by one order to attain 10{sup 13}/cm{sup 3}. The electrons temperature and density strengths are in contrast to each other. While their distributions differ along the plasma tube length, they show a decaying sinusoidal shape where their peaks position varies by the gas type. The electrons injection moderates electron temperature and expands their density. The later highest peak holds for the N{sub 2} gas, at electrons injection it changes to hold for the Ar. The sinusoidal decaying density behavior generates electric fields depending on the gas used and independent of tube geometry. The effect of the injected electrons performs a responsive impact on electrons density not attributed to the gas discharge. Analytical tools investigate the interaction of the plasma, the discharge current, and the gas used on the electrodes. It points to the emigration of atoms from each one but for greater majority they behave to a preferred direction. Meanwhile, only in the linear regime, small percentage of atoms still moves in reverse direction. Traces of gas atoms revealed on both electrodes due to sheath regions denote lack of their participation in the discharge current. In addition, atoms travel from one electrode to the other by overcoming the sheaths regions occurring transportation of particles agglomeration from one electrode to the other. The electrons injection has contributed to increase the plasma electron density peaks. These electrons populations have raised the generated electrostatic fields assisting the elemental ions emigration to a preferred electrode direction. Regardless of plasma electrodes positions and plasma shape, ions can be departed from one electrode to deposit on the other one. In consequence, as an application the AF plasma type can enhance the metal deposition from one electrode to the other.

  15. Strongly turbulent stabilization of electron beam-plasma interactions

    NASA Technical Reports Server (NTRS)

    Freund, H. P.; Haber, I.; Palmadesso, P.; Papadopoulos, K.

    1980-01-01

    The stabilization of electron beam interactions due to strongly turbulent nonlinearities is studied analytically and numerically for a wide range of plasma parameters. A fluid mode coupling code is described in which the effects of electron and ion Landau damping and linear growth due to the energetic electron beam are included in a phenomenological manner. Stabilization of the instability is found to occur when the amplitudes of the unstable modes exceed the threshold of the oscillating two-stream instability. The coordinate space structure of the turbulent spectrum which results clearly shows that soliton-like structures are formed by this process. Phenomenological models of both the initial stabilization and the asymptotic states are developed. Scaling laws between the beam-plasma growth rate and the fluctuations in the fields and plasma density are found in both cases, and shown to be in good agreement with the results of the simulation.

  16. Numerical study of a dust-contaminated electron plasma

    NASA Astrophysics Data System (ADS)

    Maero, Giancarlo; Romé, Massimiliano; Lepreti, Fabio; Cavenago, Marco

    2014-10-01

    The collective behaviour of dusty plasmas is heavily affected by the presence of a small fraction of micrometric or sub-micrometric dust particles which collect a large surface charge. While dusty plasmas under study are usually quasi-neutral, we propose here an investigation on a magnetized nonneutral plasma (a situation found for example in Penning traps) where a conventional plasma with a single sign of charge (e.g. electrons) is contaminated by a dust population. We simulate the two-dimensional dynamics of such a plasma in the plane orthogonal to a homogeneous magnetic field with a tailored Particle-In-Cell code implementing a mass-less fluid (drift-Poisson) approximation for electrons and a kinetic description for the dust component, including gravity effects. Simulations with a range of initial conditions are performed to observe the influence of dust on the diocotron instability developing in the electron plasma. The early stage of the growth of diocotron modes is analyzed by Fourier decomposition. The fully non-linear evolution is studied by means of a statistical analysis of probability density functions and flatness of spatial vorticity increments in order to characterize the intermittency properties of the turbulence. Contribution to the Topical Issue "Theory and Applications of the Vlasov Equation", edited by Francesco Pegoraro, Francesco Califano, Giovanni Manfredi and Philip J. Morrison.

  17. Design of a gridded gun and PPM-focusing structure for a high-power sheet electron beam

    Microsoft Academic Search

    Michael E. Read; Vadim Jabotinski; George Miram; Lawrence Ives

    2005-01-01

    We describe the design of a gridded electron gun and periodic permanent magnet (ppm)-focusing structure to create and guide a 415-kV, 250-A sheet beam with a cross section of 100 mm × 8 mm. The gun is intended for use with a 40-MW X- band sheet beam klystron for driving accelerators. Using the three-dimensional (3-D) code suite AMAZE, we designed

  18. Two-plane focusing of high-space-charge sheet electron beams using periodically cusped magnetic fields

    Microsoft Academic Search

    M. A. Basten; J. H. Booske

    1999-01-01

    Numerical and theoretical analyses show that stable, two-plane focusing of finite width, elliptical cross section, sheet electron beams with high space charge (low voltage, high current density) can be accomplished using periodically cusped-magnetic (PCM) fields. Magnetic field strength requirements for focusing high-space-charge sheet beams are within technological capabilities of modern permanent magnet technology. Both an offset-pole PCM stack and a

  19. Thermal effects on the electron density fluctuations in ICF plasmas

    NASA Astrophysics Data System (ADS)

    Rozmus, Wojciech; Chapman, T.; Berger, R.; Brantov, A.; Bychenkov, V.; Tzoufras, M.

    2013-10-01

    We have examined modifications of the electron distribution functions (EDF) due to thermal gradients in the ignition-scale ICF plasmas. In particular, given the high background temperatures of such plasmas the heat-carrying electrons have energies (20 - 40 keV) that are close to kinetic energies of the electrons that are resonant with Langmuir waves produced by parametric instabilities, such as stimulated Raman scattering. We have found that under these conditions the modifications of the EDF introduce anisotropy in the plasma response that manifests itself in the significant reduction (increase) of the Landau damping of Langmuir waves propagating along (against) the temperature gradient. Similarly there is strong anisotropy in the fluctuation spectra of the electron plasma waves that modifies Thomson scattering cross-section. The EDF have been calculated and compared using the standard Spitzer-Harm theory, numerical solutions to the Fokker-Planck equations and analytical solutions of the kinetic equation. An impact of this theory on the observations of scattering instabilities and Thomson scattering experiments in ICF plasmas will be discussed.

  20. Applicability of Electron Emissive Probes for Plasma Potential and Electric Field Measurements in Magnetized Plasmas

    NASA Astrophysics Data System (ADS)

    Schrittwieser, R.; Adámek, J.; Balan, P.; Cabral, J. A.; Fernandes, H.; Figueiredo, H. F. C.; Hidalgo, C.; Hron, M.; IoniÅ£?, C.; Martines, E.; Pedrosa, M. A.; Stöckel, J.; Tichý, M.; Van Oost, G.; Varandas, C.

    2003-06-01

    In the edge region of magnetised fusion experiments hitherto mainly cold probes were used in order to determine the plasma potential and thereby parameters like electric field turbulence. However, this method causes problems when the electron temperature varies and when the electrons are drifting. We have therefore used electron-emissive probes in (i) the tokamak ISTTOK in Lisbon, Portugal, (ii) the CASTOR tokamak in Prague, Czech Republic, and (iii) the TJ-II stellarator in Madrid, Spain. Our method has the advantage that in principle the electron emission current compensates temperature variations and electron drifts. We discuss the applicability, the advantages and the limits of emissive probes for measurements of the plasma potential and the electric field, taking into account especially the effect of a space charge around the probe wire, formed by the emitted electrons.

  1. Dynamical Casimir effect for TE and TM modes in a resonant cavity bisected by a plasma sheet

    SciTech Connect

    Naylor, W.; Matsuki, S.; Kido, Y. [Department of Physics, Ritsumeikan University, Kusatsu, Shiga 525-8577 (Japan); Nishimura, T. [Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan)

    2009-10-15

    Parametric photon creation via the dynamical Casimir effect (DCE) is evaluated numerically, in a three-dimensional rectangular resonant cavity bisected by a semiconductor diaphragm (SD), which is irradiated by a pulsed laser with frequency of GHz order. The aim of this paper is to determine some of the optimum conditions required to detect DCE photons relevant to an experimental detection system. We expand upon the thin plasma sheet model [M. Crocce et al., Phys. Rev. A 70, 033811 (2004)] to estimate the number of photons for both transverse electric (TE) and transverse magnetic (TM) modes at any given SD position. Numerical calculations are performed considering up to 51 intermode couplings by varying the SD location, driving period and laser power without any perturbations. It is found that the number of photons created for TE modes strongly depends on SD position, where the strongest enhancement occurs at the midpoint (not near the cavity wall); while TM modes have weak dependence on SD position. Another important finding is the fact that significant photon production for TM{sub 111} modes still takes place at the midpoint even for a low-laser power of 0.01 {mu}J/pulse, although the number of TE{sub 111} photons decreases almost proportionately with laser power. We also find a relatively wide tuning range for both TE and TM modes that is correlated with the frequency variation in the instantaneous mode functions caused by the interaction between the cavity photons and conduction electrons in the SD excited by a pulsed laser.

  2. PEACE: A PLASMA ELECTRON AND CURRENT EXPERIMENT

    Microsoft Academic Search

    A. D. Johnstone; C. Alsop; S. Burge; P. J. Carter; A. J. Coates; A. J. Coker; A. N. Fazakerley; M. Grande; R. A. Gowen; C. Gurgiolo; B. K. Hancock; B. Narheim; A. Preece; P. H. Sheather; J. D. Winningham; R. D. Woodliffe

    1997-01-01

    An electron analyser to measure the three-dimensional velocity distribution of electrons in the energy range from 0.59 eV to 26.4 keV on the four spacecraft of the Cluster mission is described. The instrument consists of two sensors with hemispherical electrostatic energy analysers with a position-sensitive microchannel plate detectors placed to view radially on opposite sides of the spacecraft. The intrinsic

  3. Electron cooling in decaying low-pressure plasmas.

    PubMed

    Celik, Yusuf; Tsankov, Tsanko V; Aramaki, Mitsutoshi; Yoshimura, Shinji; Luggenhölscher, Dirk; Czarnetzki, Uwe

    2012-04-01

    A simple analytical fluid dynamic model is developed for evaporative electron cooling in a low-pressure decaying plasma and compared to a two-dimensional simulation and experimental data for the particular case of argon. Measured electron temperature and density developments are fully reproduced by the ab initio model and the simulation. Further, it is shown that in the late afterglow thermalization of electrons occurs by coupling to the ion fluid via Coulomb collisions at sufficiently high electron densities and not by coupling to the neutral background. PMID:22680586

  4. Effect of electron thermal motion on plasma heating in a magnetized inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Aman-ur-Rehman, Pu, Yi-Kang

    2007-06-01

    Power absorbed inside the magnetized inductively coupled plasma (MICP) is calculated using three different warm MICP models and is then compared with the result of the cold MICP model. The comparison shows that in the propagating region (?plasma heating Swarm is significantly less than the cold plasma heating Scold, unless the distance traveled by the electrons due to their thermal motion, during the effective wave period, becomes significantly less than the wavelength of the cavity wave. Furthermore, in the propagating region, when ? ???e?, there appears a valley on the plot of ?(? )=Swarm/Scold versus ? showing the negative effect of electron thermal motion on plasma heating. This valley widens and gets smoother with an increase in the plasma length. In the nonpropagating region (?>??e?), the maximum value of ?(? ) exists when ? -??e??vth/?, showing that, in the presence of the external magnetic field, the thermal motion of the electrons leads to a Doppler shift of the frequencies, at which collisionless heating is the dominant mode of electron heating. Furthermore, in the nonpropagating region, when ? ???e?, the skin depth of the right circularly polarized electric field decreases with magnetic field. This decrease in the skin depth results in an increase of collisionless heating under the Doppler-shifted wave particle resonant condition of ? -??e??vth/?. It is also observed that, for large plasma length, the results of all the three warm MICP models are consistent with each other.

  5. Charge transport in micas: The kinetics of FeII/III electron transfer in the octahedral sheet

    SciTech Connect

    Rosso, Kevin M.; Ilton, Eugene S.

    2003-11-01

    The two principal FeII/III electron exchange reactions underlying charge transport in the octahedral sheet of ideal end-member annite were modeled using a combination of ab initio calculations and Marcus electron transfer theory. A small polaron model was applied which yielded electron hopping activation energies that agree well with the limited available experimental data. A small ab initio cluster model successfully reproduced several important structural, energetic, and magnetic characteristics of the M1 and M2 Fe sites in the annite octahedral sheet. The cluster enabled calculation of the internal reorganization energy and electronic coupling matrix elements for the M2-M2 and M1-M2 electron transfer reactions. The M2-M2 electron transfer is symmetric with a predicted forward/reverse electron hopping rate of 106 s-1. The M1-M2 electron transfers are asymmetric due to the higher ionization potential by 0.46 eV of FeII in the M1 site. The electronic coupling matrix elements for these reactions are predicted to be small and of similar magnitude, suggesting the possibility that the coupling is essentially direction independent amongst hopping directions in the octahedral sheet. M1 Fe sites are predicted to be efficient electron traps and charge transport should occur by nearest-neighbor electron hops along the M2 Fe sublattice.

  6. Electron series resonance plasma discharges: Unmagnetized and magnetized

    NASA Astrophysics Data System (ADS)

    Qiu, Weiguang

    2001-08-01

    This thesis explores high frequency electron series resonance in unmagnetized and magnetized bounded plasmas. Special interest is focused on low temperature plasmas in planar systems as such are useful for material processing and fusion devices. Chapter 1, Chapter 2 and Chapter 3 describe simulation studies of unmagnetized electron series resonance (ESR) sustained discharges with comparisons to theory and experiment. These plasmas have many desirable characteristics. The input resistance is small and the drive voltage and current are in phase. The drive voltage is small (˜Te) and the time average plasma potential is low (˜10Te). A strong kinetic phase space bunching process is shown to provide electrons of sufficient energy for ionization, which allows discharge operation at low neutral pressure and low electron temperatures. At low pressure, the ion flux to the wall has a narrow angular spread about the normal and the ion bombarding energy distribution has a sharp peak at the plasma potential. Scaling laws at fixed pressure nr?w3RF ,s¯?w -1RF are shown to hold when RF frequency is varied smoothly ("chirping") demonstrating continuous density control. Research on magnetized electron series resonance (MESR) discharges is described in Chapter 4, Chapter 5 and Chapter 6. The resonant frequency is derived from cold plasma theory and shows two resonant modes. Simulations verify these modes to be the natural oscillatory frequencies of weakly magnetized plasmas in a planar plasma diode. A global model is established for magnetized resonant discharges. The interrelations among the plasma parameters and the drive terms are formulated for both resonant modes. The initiation of a MESR discharge and its steady state properties are discussed and compared to the unmagnetized case. Weak lock-on of MESR frequency to the drive frequency is observed in simulation. Similar V - I characteristics as those in ESR are found both in theory and in simulation. Different from the ESR discharges, MESR discharges show strong bulk heating. The scaling laws from the analytical model are also tested by simulation. The results show that we may control the plasma discharge parameters by the applied magnetic field: its magnitude and tilted angle; two more external controls than the ESR discharges.

  7. Glow plasma trigger for electron cyclotron resonance ion sourcesa)

    NASA Astrophysics Data System (ADS)

    Vodopianov, A. V.; Golubev, S. V.; Izotov, I. V.; Nikolaev, A. G.; Oks, E. M.; Savkin, K. P.; Yushkov, G. Yu.

    2010-02-01

    Electron cyclotron resonance ion sources (ECRISs) are particularly useful for nuclear, atomic, and high energy physics, as unique high current generators of multicharged ion beams. Plasmas of gas discharges in an open magnetic trap heated by pulsed (100 ?s and longer) high power (100 kW and higher) high-frequency (greater than 37.5 GHz) microwaves of gyrotrons is promising in the field of research in the development of electron cyclotron resonance sources for high charge state ion beams. Reaching high ion charge states requires a decrease in gas pressure in the magnetic trap, but this method leads to increases in time, in which the microwave discharge develops. The gas breakdown and microwave discharge duration becomes greater than or equal to the microwave pulse duration when the pressure is decreased. This makes reaching the critical plasma density initiate an electron cyclotron resonance (ECR) discharge during pulse of microwave gyrotron radiation with gas pressure lower than a certain threshold. In order to reduce losses of microwave power, it is necessary to shorten the time of development of the ECR discharge. For fast triggering of ECR discharge under low pressure in an ECRIS, we initially propose to fill the magnetic trap with the plasmas of auxiliary pulsed discharges in crossed ExB fields. The glow plasma trigger of ECR based on a Penning or magnetron discharge has made it possible not only to fill the trap with plasma with density of 1012 cm-3, required for a rapid increase in plasma density and finally for ECR discharge ignition, but also to initially heat the plasma electrons to Te?20 eV.

  8. Glow plasma trigger for electron cyclotron resonance ion sources

    SciTech Connect

    Vodopianov, A. V.; Golubev, S. V.; Izotov, I. V. [Institute of Applied Physics, Russian Academy of Science, Nizhniy Novgorod 603950 (Russian Federation); Nikolaev, A. G.; Oks, E. M.; Savkin, K. P.; Yushkov, G. Yu. [High Current Electronics Institute, Siberian Division, Russian Academy of Science, Tomsk 634055 (Russian Federation)

    2010-02-15

    Electron cyclotron resonance ion sources (ECRISs) are particularly useful for nuclear, atomic, and high energy physics, as unique high current generators of multicharged ion beams. Plasmas of gas discharges in an open magnetic trap heated by pulsed (100 {mu}s and longer) high power (100 kW and higher) high-frequency (greater than 37.5 GHz) microwaves of gyrotrons is promising in the field of research in the development of electron cyclotron resonance sources for high charge state ion beams. Reaching high ion charge states requires a decrease in gas pressure in the magnetic trap, but this method leads to increases in time, in which the microwave discharge develops. The gas breakdown and microwave discharge duration becomes greater than or equal to the microwave pulse duration when the pressure is decreased. This makes reaching the critical plasma density initiate an electron cyclotron resonance (ECR) discharge during pulse of microwave gyrotron radiation with gas pressure lower than a certain threshold. In order to reduce losses of microwave power, it is necessary to shorten the time of development of the ECR discharge. For fast triggering of ECR discharge under low pressure in an ECRIS, we initially propose to fill the magnetic trap with the plasmas of auxiliary pulsed discharges in crossed ExB fields. The glow plasma trigger of ECR based on a Penning or magnetron discharge has made it possible not only to fill the trap with plasma with density of 10{sup 12} cm{sup -3}, required for a rapid increase in plasma density and finally for ECR discharge ignition, but also to initially heat the plasma electrons to T{sub e}{approx_equal}20 eV.

  9. Glow plasma trigger for electron cyclotron resonance ion sources.

    PubMed

    Vodopianov, A V; Golubev, S V; Izotov, I V; Nikolaev, A G; Oks, E M; Savkin, K P; Yushkov, G Yu

    2010-02-01

    Electron cyclotron resonance ion sources (ECRISs) are particularly useful for nuclear, atomic, and high energy physics, as unique high current generators of multicharged ion beams. Plasmas of gas discharges in an open magnetic trap heated by pulsed (100 micros and longer) high power (100 kW and higher) high-frequency (greater than 37.5 GHz) microwaves of gyrotrons is promising in the field of research in the development of electron cyclotron resonance sources for high charge state ion beams. Reaching high ion charge states requires a decrease in gas pressure in the magnetic trap, but this method leads to increases in time, in which the microwave discharge develops. The gas breakdown and microwave discharge duration becomes greater than or equal to the microwave pulse duration when the pressure is decreased. This makes reaching the critical plasma density initiate an electron cyclotron resonance (ECR) discharge during pulse of microwave gyrotron radiation with gas pressure lower than a certain threshold. In order to reduce losses of microwave power, it is necessary to shorten the time of development of the ECR discharge. For fast triggering of ECR discharge under low pressure in an ECRIS, we initially propose to fill the magnetic trap with the plasmas of auxiliary pulsed discharges in crossed ExB fields. The glow plasma trigger of ECR based on a Penning or magnetron discharge has made it possible not only to fill the trap with plasma with density of 10(12) cm(-3), required for a rapid increase in plasma density and finally for ECR discharge ignition, but also to initially heat the plasma electrons to T(e) approximately = 20 eV. PMID:20192326

  10. Excitation of surface plasma waves by an electron beam in a magnetized dusty plasma

    SciTech Connect

    Prakash, Ved; Sharma, Suresh C. [Department of Physics, Maharaja Agrasen Institute of Technology, PSP Area Plot No. 1, Sector 22, Rohini, Delhi 110086 (India)

    2009-09-15

    An electron beam drives surface plasma waves to instability on a vacuum magnetized dusty plasma interface and in a magnetized dusty plasma cylinder via Cerenkov and fast cyclotron interaction. The dispersion relation of a surface plasma wave has been derived and it has been shown that the phase velocity of waves increases with increase in relative density {delta}(=n{sub i0}/n{sub e0}), where n{sub i0} is the ion plasma density and n{sub e0} is the electron plasma density of negatively charged dust grains. The frequency and the growth rate of the unstable wave instability also increases with {delta}. The growth rate of the instability increases with beam density and scales as the one-third power of the beam density in Cerenkov interaction and is proportional to the square root of beam density in fast cyclotron interaction. The dispersion relation of surface plasma waves has been retrieved from the derived dispersion relation by considering that the beam is absent and there is no dust in the plasma cylinder.

  11. Electron dynamics in a plasma focus. [electron acceleration

    NASA Technical Reports Server (NTRS)

    Hohl, F.; Gary, S. P.; Winters, P. A.

    1977-01-01

    Results are presented of a numerical integration of the three-dimensional relativistic equations of motion of electrons subject to given electric and magnetic fields deduced from experiments. Fields due to two different models are investigated. For the first model, the fields are those due to a circular distribution of axial current filaments. As the current filaments collapse toward the axis, large azimuthal magnetic and axial electric fields are induced. These fields effectively heat the electrons to a temperature of approximately 8 keV and accelerate electrons within the radius of the filaments to high axial velocities. Similar results are obtained for the current-reduction phase of focus formation. For the second model, the fields are those due to a uniform current distribution. Both the current-reduction and the compression phases were studied. These is little heating or acceleration of electrons during the compression phase because the electrons are tied to the magnetic field. However, during the current-reduction phase, electrons near the axis are accelerated toward the center electrode and reach energies of 100 keV. A criterion is obtained which limits the runaway electron current to about 400 A.

  12. Negative ion production in cesium seeded high electron temperature plasmas

    SciTech Connect

    Inoue, T.; Tobari, H.; Takado, N.; Hanada, M.; Kashiwagi, M.; Hatayama, A.; Wada, M.; Sakamoto, K. [Japan Atomic Energy Agency (JAEA), Fusion Research and Development Directorate, Naka 311-0193 (Japan); Keio University, Yokohama 223-8522 (Japan); Japan Atomic Energy Agency (JAEA), Fusion Research and Development Directorate, Naka 311-0193 (Japan); Keio University, Yokohama 223-8522 (Japan); Doshisha University, Kyotanabe 610-0394 (Japan); Japan Atomic Energy Agency (JAEA), Fusion Research and Development Directorate, Naka 311-0193 (Japan)

    2008-02-15

    In experiments on uniformity improvement in a large negative ion source, steep gradients have been observed in the profiles of electron temperature and H{sup -} ion beam intensity. It has been observed that the gradient in the H{sup -} ion beam intensity is altered by seeding cesium, though the electron temperature distribution is not affected by Cs. Thus in the Cs seeded condition, the H{sup -} ion beam intensity is enhanced in local area illuminated by high electron temperature plasmas. A brief analysis suggests possible advantages of high electron temperature plasmas for the negative ion surface production, by enhancement of dissociation to yield proton or atoms as parent particles of the negative ions.

  13. Electron energy distribution produced by beam-plasma discharge

    NASA Technical Reports Server (NTRS)

    Anderson, H. R.; Gordeuk, J.; Jost, R. J.

    1982-01-01

    In an investigation of a beam-plasma discharge (BPD), the electron energy distribution of an electron beam moving through a partially ionized gas is analyzed. Among other results, it is found that the occurrence of BPD heats the initially cold electron beam from the accelerator. The directional intensity of electrons measured outside the beam core indicates that most particles suffer a single scattering in energy and pitch angle. At low currents this result is expected as beam particles collide with the neutral atmosphere, while in BPD the majority of particles is determined to still undergo a single scattering near the original beam core. The extended energy spectra at various beam currents show two rather distinct plasma populations, one centered at the initial beam energy (approximately 1500 eV) and the other at approximately 150 eV.

  14. Effects of plasma composition on backscatter, hot electron production, and propagation in underdense plasmas

    NASA Astrophysics Data System (ADS)

    Stevenson, R. M.; Suter, L. J.; Oades, K.; Kruer, W.; Slark, G. E.; Fournier, K. B.; Meezan, N.; Kauffman, R.; Miller, M.; Glenzer, S.; Niemann, C.; Grun, J.; Davis, J.; Back, C.; Thomas, B.

    2004-05-01

    A series of underdense laser plasma interaction experiments performed on the Helen laser [M. J. Norman et al., Appl. Opt. 41, 3497 (2002)] at the Atomic Weapons Establishment (AWE), U.K., using 2? light have uncovered a strong dependence of laser backscatter and hot electron production on plasma composition. Using low-Z materials, we find a behavior familiar from previous 3? work, the interchange of stimulated Raman scattering for Brillouin scattering as we change from gases that have high ion wave damping (e.g., C5H12) to gases with low ion wave damping (e.g., CO2). However, as Z is increased, we find that Brillouin scattering drops while Raman scattering remains low. For gases with Z greater than 18, it is possible to have long scalelength, underdense plasmas with both low Brillouin and Raman backscatter losses. Complementary measurements of hot electron production show efficient production of hot electrons in C5H12 plasmas approaching 0.25ncr, but changing the plasma composition can greatly suppress the hot electron production, even near 0.25ncr. Additional experiments indicate that by adding small amounts of high Z dopant, significant changes to the backscatter and hot electron production in C5H12 targets may be produced.

  15. Comparison of Ar electron-cyclotron-resonance plasmas in three magnetic field configurations. I. Electron temperature and plasma density

    SciTech Connect

    Junck, K.L. (Department of Nuclear Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States)); Getty, W.D. (Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109 (United States))

    1994-09-01

    Optical emission spectroscopy, Langmuir probe, and microwave interferometry measurements have been used to characterize the electron temperature and plasma density of electron-cyclotron-resonance (ECR) heated Ar plasmas in a magnetic-mirror plasma tool. The magnetic field was operated in a symmetric mirror, asymmetric mirror, and minimum-B configuration. The dependency of the plasma parameters upon microwave power, pressure, and magnetic field configuration have been examined. Plasma densities up to 2[times]10[sup 12] cm[sup [minus]3] at the midplane and 5[times]10[sup 12] cm[sup [minus]3] at the ECR zone for a symmetric mirror configuration of the magnetic field have been measured. Operation of the minimum-B magnetic field configuration was found to increase the plasma stability with comparable plasma density while an asymmetric mirror magnetic field configuration, similar to other devices recently studied, yielded densities in the 2--8[times]10[sup 11] cm[sup [minus]3] range. Radial uniformity was found to be [plus minus]25% over the 4 cm radius of the microwave window.

  16. Electron beam transport analysis of W-band sheet beam klystron

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Xun; Barnett, Larry R.; Luhmann, Neville C.; Shin, Young-Min; Humphries, Stanley

    2010-04-01

    The formation and transport of high-current density electron beams are of critical importance for the success of a number of millimeter wave and terahertz vacuum devices. To elucidate design issues and constraints, the electron gun and periodically cusped magnet stack of the original Stanford Linear Accelerator Center designed W-band sheet beam klystron circuit, which exhibited poor beam transmission (?55%), have been carefully investigated through theoretical and numerical analyses taking advantage of three-dimensional particle tracking solvers. The re-designed transport system is predicted to exhibit 99.76% (cold) and 97.38% (thermal) beam transmission, respectively, under space-charge-limited emission simulations. The optimized design produces the required high aspect ratio (10:1) sheet beam with 3.2 A emission current with highly stable propagation. In the completely redesigned model containing all the circuit elements, more than 99% beam transmission is experimentally observed at the collector located about 160 mm distant from the cathode surface. Results are in agreement of the predictions of two ray-tracing simulators, CST PARTICLE STUDIO and OMNITRAK which also predict the observed poor transmission in the original design. The quantitative analysis presents practical factors in the modeling process to design a magnetic lens structure to stably transport the elliptical beam along the long drift tube.

  17. Electron backscatter diffraction applied to lithium sheets prepared by broad ion beam milling.

    PubMed

    Brodusch, Nicolas; Zaghib, Karim; Gauvin, Raynald

    2015-01-01

    Due to its very low hardness and atomic number, pure lithium cannot be prepared by conventional methods prior to scanning electron microscopy analysis. Here, we report on the characterization of pure lithium metallic sheets used as base electrodes in the lithium-ion battery technology using electron backscatter diffraction (EBSD) and X-ray microanalysis using energy dispersive spectroscopy (EDS) after the sheet surface was polished by broad argon ion milling (IM). No grinding and polishing were necessary to achieve the sufficiently damage free necessary for surface analysis. Based on EDS results the impurities could be characterized and EBSD revealed the microsctructure and microtexture of this material with accuracy. The beam damage and oxidation/hydration resulting from the intensive use of IM and the transfer of the sample into the microscope chamber was estimated to be <50 nm. Despite the fact that the IM process generates an increase of temperature at the specimen surface, it was assumed that the milling parameters were sufficient to minimize the heating effect on the surface temperature. However, a cryo-stage should be used if available during milling to guaranty a heating artefact free surface after the milling process. PMID:25280344

  18. Appearance of relativistic electrons in stochastic plasma heating

    SciTech Connect

    Krasovitskii, V.B.

    1980-03-01

    Plasma heating by an electromagnetic pulse propagating along the external magnetic field is analyzed. When there are field harmonics with a phase velocity near the speed of light, electrons are accelerated to relativistic energies. The velocity-space distribution of the fast electrons and their number are found. The characteristic acceleration time is also found; it is determined by the particle diffusion time in momentum space.

  19. Beltrami-Bernoulli Equilibria in Plasmas with Degenerate Electrons

    E-print Network

    Berezhiani, V I; Mahajan, S M

    2014-01-01

    A new class of Double Beltrami-Bernoulli equilibria, sustained by electron degeneracy pressure, are investigated. It is shown that due to electron degeneracy, a nontrivial Beltrami-Bernoulli equilibrium state is possible even for a zero temperature plasma. These states are, conceptually, studied to show the existence of new energy transformation pathways converting, for instance, the degeneracy energy into fluid kinetic energy. Such states may be of relevance to compact astrophysical objects like white dwarfs, neutron stars etc.

  20. Electron temperature measurements of x-ray laser plasmas

    SciTech Connect

    Young, B.K.F.; Osterheld, A.L.; Shepherd, R.L.; Shimkaveg, G.M.; Cerjan, C.J.; Goldstein, W.H.; Rosen, M.D.; Walling, R.S.; Stewart, R.E.

    1992-08-06

    We present results of recent experiments at the NOVA laser to measure the electron temperature of neon-like yttrium X-my laser plasmas. Trace amounts of aluminum were introduced into yttrium exploding-foil targets. Time resolved electron temperatures were determined by comparing the measured aluminum K-shell spectra with detailed quasi-steady state calculations and are compared to 2D LASNEX hydrodynamics simulations.

  1. Laser light backscattering off an electron beam-plasma system

    Microsoft Academic Search

    H. H. Szu

    1983-01-01

    An analysis of the stimulated Raman backscattering instability combined with a Buneman instability was performed for a head-on collision of a 10.6 micron CO2 laser beam with a nonrelativistic electron beam. The electron beam was directed through a laser-induced plasma with a density of up to 10 to the 16th\\/cu cm, which was originally produced by the CO2 laser beam.

  2. Multiple-satellite studies of magnetospheric substorms: Plasma sheet recovery and the poleward leap of auroral-zone activity

    NASA Technical Reports Server (NTRS)

    Pytte, T.; Mcpherron, R. L.; Kivelson, M. G.; West, H. I., Jr.; Hones, E. W., Jr.

    1977-01-01

    Particle observations from pairs of satellites (Ogo 5, Vela 4A and 5B, Imp 3) during the recovery of plasma sheet thickness late in substorms were examined. Six of the nine events occurred within about 5 min in locations near the estimated position of the neutral sheet, but over wide ranges of east-west and radial separations. The time of occurrence and spatial extent of the recovery were related to the onset (defined by ground Pi 2 pulsations) and approximate location (estimated from ground mid-latitude magnetic signatures) of substorm expansions. It was found that the plasma sheet recovery occurred 10 - 30 min after the last in a series of Pi bursts, which were interpreted to indicate that the recovery was not due directly to a late, high latitude substorm expansion. The recovery was also observed to occur after the substorm current wedge had moved into the evening sector and to extend far to the east of the center of the last preceding substorm expansion.

  3. Collisionless forced magnetic reconnection in an electron-positron plasma

    SciTech Connect

    Hosseinpour, M.; Vekstein, G. [Jodrel Bank Center for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom)

    2008-02-15

    Collisionless forced magnetic reconnection in an electron-positron plasma, where the mechanism of the magnetic field breaking is inertia of plasma particles, is considered. The model under analytical investigation is the so-called Taylor problem: a tearing stable slab plasma equilibrium with a magnetic field reversal is subjected to a small-amplitude boundary perturbation that drives magnetic reconnection at the neutral surface within the plasma. It is shown that forced collisionless reconnection has a direct analogy with its collisional (resistive) counterpart investigated by T. S. Hahm and R. M. Kulsrud [Phys. Fluids 28, 2412 (1985)], with the role of the inverse Lundquist number S{sup -1}<<1 of the resistive magnetohydrodynamics now being played by the normalized inertia skin depth d{identical_to}(c/{omega}{sub p}a)<<1 ({omega}{sub p} is the electron-positron plasma frequency, and a is a width of the plasma slab). The transition between the collisionless and resistive regimes of forced reconnection is also considered.

  4. Classification of fast flows in central plasma sheet: Superposed epoch analysis based on THEMIS observations

    NASA Astrophysics Data System (ADS)

    Li, H.; Wang, C.; Fu, S. Y.

    2014-09-01

    A statistical survey of 560 fast flows in midnight central plasma sheet is performed based on Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations during its first two tail phases. From superposed epoch analysis, no significant substorm activities are found to be associated with the occurrence of fast flows beyond X=-15 Re. Considering the associations with substorm activities, the fast flows inside of X=-15 Re can be classified into two obvious classes: short duration (< 2.0 min) and long duration (> 4.0 min). Substorm breakups are shown to be more closely correlated to short-duration fast flows. Furthermore, the onset of short-duration fast flows in the dipolarization region (X=-9 to -11 Re) is almost simultaneous with the onset of substorm breakups and dipolarizations. On the other hand, time delays of 2-4 min are both found in the near-Earth region (X=-7 to -9 Re) and in the near-tail region (X=-11 to -15 Re). Assuming that short-duration fast flows are generated by the force imbalance caused by cross-tail current disruption, these features are consistent with the predictions made by the cowling electrojet current loop and the cross-tail current disruption substorm models. In comparison, although more magnetic flux is transported toward Earth for long-duration fast flows, no clear substorm breakup is closely associated with them. The analysis of 2-D ion velocity distribution further shows some differences. For short-duration fast flows, multiple crescent-shaped ion populations are found. However, for long-duration fast flows, there exists only a single crescent-shaped ion population. The difference may be an important signature for distinguishing these two classes of fast flows.

  5. Sudden pressure enhancement and tailward retreat in the near-Earth plasma sheet: THEMIS observation and MHD simulation

    NASA Astrophysics Data System (ADS)

    Yao, Y.; Ebihara, Y.; Tanaka, T.

    2015-01-01

    enhancement of the plasma pressure in the near-Earth plasma sheet is one of the common manifestations of substorms and is thought to play an important role in relevant disturbances in the magnetosphere and ionosphere. On 1 March 2008, four of the Time History of Events and Macroscale Interactions during Substorms probes observed the sudden enhancement of the plasma pressure around 15:40 UT. The four probes were almost aligned along the Sun-Earth line, which was suitable for investigating spatial-temporal evolution of the near-Earth plasma sheet around the substorm onset. The four probes were located off the equatorial plane, according to a magnetic field model. The plasma pressure suddenly increased at the innermost probe first (at ~7.2 Re), followed by the outer probes (at ~7.5, ~8.3, and ~10.4 Re), that could be seen as a tailward propagation (or retreat) of high-pressure region (HPR). After comparing with results of a global magnetohydrodynamic simulation, we found that only the tailward propagation of the HPR could be seen at off equator. Near the equatorial plane, the HPR propagates earthward from the magnetotail region, then it retreats tailward. In the course of the tailward retreat, the HPR also propagates away from the equatorial plane. As a consequence, the innermost probe observed the pressure enhancement first, followed by the outer probes. The propagation of the HPR in the ZGSM direction is understood to be a combination of the convergence of the plasma flow (the divergence of bulk velocity along the ZGSM axis) and the pressure gradient force.

  6. Magnetically Controlled Optical Plasma Waveguide for Electron Acceleration

    SciTech Connect

    Pollock, B B; Froula, D H; Tynan, G R; Divol, L; Davis, P; Palastro, J P; Price, D; Glenzer, S H

    2008-08-28

    In order to produce multi-Gev electrons from Laser Wakefield Accelerators, we present a technique to guide high power laser beams through underdense plasma. Experimental results from the Jupiter Laser Facility at the Lawrence Livermore National Laboratory that show density channels with minimum plasma densities below 5 x 10{sup 17} cm{sup -3} are presented. These results are obtained using an external magnetic field (<5 T) to limit the radial heat flux from a pre-forming laser beam. The resulting increased plasma pressure gradient produces a parabolic density gradient which is tunable by changing the external magnetic field strength. These results are compared with 1-D hydrodynamic simulations, while quasi-static kinetic simulations show that for these channel conditions 90% of the energy in a 150 TW short pulse beam is guided over 5 cm and predict electron energy gains of 3 GeV.

  7. Radiation fields of helical antenna in compressible electron plasma

    Microsoft Academic Search

    V. L. TALEKAR; K. R. SONI

    1974-01-01

    Expressions for the radiation fields in a compressible electron plasma medium are derived pertaining to the helical antenna of finite size immersed in it. The current distribution on the helical antenna is assumed to be an out-going travelling wave with an arbitrary phase propagation constant. From these general expressions fields of circular loop and linear antennas can be deduced as

  8. Collisional Cooling of Pure Electron Plasmas W. Bertsche

    E-print Network

    Fajans, Joel

    into the vacuum chamber via a leak valve and monitored with an ion gauge and residual gas analyzer. For mea thermal energy. Motivated by an examination of spectroscopic data, calculations of electron-CO2 scattering thermal equilibrium giving T T. The plasma temper- ature with no buffer gas (base pressure 5·10-10 torrto

  9. Plasma-screening effects on the electron-impact excitation of hydrogenic ions in dense plasmas

    NASA Technical Reports Server (NTRS)

    Jung, Young-Dae

    1993-01-01

    Plasma-screening effects are investigated on electron-impact excitation of hydrogenic ions in dense plasmas. Scaled cross sections Z(exp 4) sigma for 1s yields 2s and 1s yields 2p are obtained for a Debye-Hueckel model of the screened Coulomb interaction. Ground and excited bound wave functions are modified in the screened Coulomb potential (Debye-Hueckel model) using the Ritz variation method. The resulting atomic wave functions and their eigenenergies agree well with the numerical and high-order perturbation theory calculations for the interesting domain of the Debye length not less than 10. The Born approximation is used to describe the continuum states of the projectile electron. Plasma screening effects on the atomic electrons cannot be neglected in the high-density cases. Including these effects, the cross sections are appreciably increased for 1s yields 2s transitions and decreased for 1s yields 2p transitions.

  10. The solvation of electrons by an atmospheric-pressure plasma.

    PubMed

    Rumbach, Paul; Bartels, David M; Sankaran, R Mohan; Go, David B

    2015-01-01

    Solvated electrons are typically generated by radiolysis or photoionization of solutes. While plasmas containing free electrons have been brought into contact with liquids in studies dating back centuries, there has been little evidence that electrons are solvated by this approach. Here we report direct measurements of solvated electrons generated by an atmospheric-pressure plasma in contact with the surface of an aqueous solution. The electrons are measured by their optical absorbance using a total internal reflection geometry. The measured absorption spectrum is unexpectedly blue shifted, which is potentially due to the intense electric field in the interfacial Debye layer. We estimate an average penetration depth of 2.5±1.0?nm, indicating that the electrons fully solvate before reacting through second-order recombination. Reactions with various electron scavengers including H(+), NO2(-), NO3(-) and H2O2 show that the kinetics are similar, but not identical, to those for solvated electrons formed in bulk water by radiolysis. PMID:26088017

  11. Stochastic electron motion driven by space plasma waves

    NASA Astrophysics Data System (ADS)

    Khazanov, G. V.; Tel'nikhin, A. A.; Kronberg, T. K.

    2014-01-01

    Stochastic motion of relativistic electrons under conditions of the nonlinear resonance interaction of particles with space plasma waves is studied. Particular attention is given to the problem of the stability and variability of the Earth's radiation belts. It is found that the interaction between whistler-mode waves and radiation-belt electrons is likely to involve the same mechanism that is responsible for the dynamical balance between the accelerating process and relativistic electron precipitation events. We have also considered the efficiency of the mechanism of stochastic surfing acceleration of cosmic electrons at the supernova remnant shock front, and the accelerating process driven by a Langmuir wave packet in producing cosmic ray electrons. The dynamics of cosmic electrons is formulated in terms of a dissipative map involving the effect of synchrotron emission. We present analytical and numerical methods for studying Hamiltonian chaos and dissipative strange attractors, and for determining the heating extent and energy spectra.

  12. Thin Film Deposition of MAX Phase Nb-Al-C Compounds on Stainless Steel Substrates Using a Magnetized Sheet Plasma Source

    NASA Astrophysics Data System (ADS)

    Salamania, Janella Mae; Ramos, Henry

    2013-09-01

    Thin films of the Nb-Al-C system were deposited on stainless steel substrates through the magnetron sputtering mode of the Magnetized Sheet Plasma Facility from elemental source of Nb, Al metals and reactive gas CH4. Niobium and aluminum targets were first sputtered using argon plasma and were deposited together with CH4 gas onto the substrates. Various parameters such as target bias, time, filling pressure and extraction current were varied. Synthesized thin films were then characterized using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX) and Raman Spectroscopy. XRD spectra of the samples show that MAX phases of the Nb-Al-C family are present on the films, specifically, the 413 phase (Nb4AlC3) . EDX and Raman spectra confirm the presence of the elemental niobium, aluminum and carbon in the films. Raman spectra show that excess carbon formed fine graphite crystallites. SEM surface images show that the resulting films follow the contours of the SS substrate. The cross-sectional images show micron scale thickness deposited above the SS substrates. Thin films of the Nb-Al-C system were deposited on stainless steel substrates through the magnetron sputtering mode of the Magnetized Sheet Plasma Facility from elemental source of Nb, Al metals and reactive gas CH4. Niobium and aluminum targets were first sputtered using argon plasma and were deposited together with CH4 gas onto the substrates. Various parameters such as target bias, time, filling pressure and extraction current were varied. Synthesized thin films were then characterized using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX) and Raman Spectroscopy. XRD spectra of the samples show that MAX phases of the Nb-Al-C family are present on the films, specifically, the 413 phase (Nb4AlC3) . EDX and Raman spectra confirm the presence of the elemental niobium, aluminum and carbon in the films. Raman spectra show that excess carbon formed fine graphite crystallites. SEM surface images show that the resulting films follow the contours of the SS substrate. The cross-sectional images show micron scale thickness deposited above the SS substrates. We would like to thank the Department of Science and Technology for the funding of this project.

  13. Emittance Measurement Of An Electron Beam Extracted From A Plasma Edge Cathode

    Microsoft Academic Search

    Roman Stemprok; Klaus W. Zieher

    1994-01-01

    current density of 100 A\\/cm2 [1,31. The Plasma Edge Cathode concept can possibly produce high electron current densities while avoiding or delaying plasma closure of the extraction gap of an electron source. An obstacle partially intercepts the plasma jet emitted from a spark plug and causes a stationary transverse plasma boundary from which electrons are extracted. The plasma should experience

  14. Determining electron temperature and density in a hydrogen microwave plasma

    NASA Technical Reports Server (NTRS)

    Scott, Carl D.; Farhat, Samir; Gicquel, Alix; Hassouni, Khaled; Lefebvre, Michel

    1993-01-01

    A three-temperature thermo-chemical model is developed for analyzing the chemical composition and energy states of a hydrogen microwave plasma used for studying diamond deposition. The chemical and energy exchange rate coefficients are determined from cross section data, assuming Maxwellian velocity distributions for electrons. The model is reduced to a zero-dimensional problem to solve for the electron temperature and ion mole fraction, using measured vibrational and rotational temperatures. The calculations indicate that the electron temperature may be determined to within a few percent error even though the uncertainty in dissociation fraction is many times larger.

  15. Electron-Ion Streaming Instabilities of AN Electromagnetically Accelerated Plasma.

    NASA Astrophysics Data System (ADS)

    Choueiri, Edgar Yazid

    This dissertation addresses the linear and nonlinear plasma physics associated with electron-ion streaming instabilities of an electromagnetically accelerated plasma. Specifically, the microinstabilities and related wave-particle transport in the working plasma of the Lorentz force accelerator (LFA) or magnetoplasmadynamic (MPD) thruster are investigated. The stability analysis required the derivation of a general dispersion tensor from kinetic theory for a magnetoactive plasma including the effects of a cross-field current, collisions, flowing plasma and arbitrary polarization. The inclusion of the last effect was necessitated by the finite beta (ratio of thermal to magnetic pressures) of such plasmas. While analytical solutions were only possible for some simplified situations the full electromagnetic problem including collisions required detailed numerical studies to reveal the nature, dependences and trends of the thresholds, frequencies, temporal and spatial growth rates, phase velocities and polarization of the unstable modes. The dominant instability was found to be the lower hybrid current-driven instability (LHCDI), which is the finite-beta generalization of the modified two-stream instability (MTSI). The effects of collisions, spatial evolution and plasma beta on the instability were studied parametrically. While the resulting dispersion relations describing the unstable waves in their linear growth stage were helpful to the design and interpretation of active wave injection experiments, the ultimate goal was an assessment of the importance of microturbulent transport namely the anomalous resistivity and heating rates engendered by the saturated unstable waves. For this purpose, finite -beta expressions for the anomalous resistivity and the anomalous heating rates of both ions and electrons were derived within the framework of a quasilinear weak turbulence formalism. Using the potential representation of the dielectric tensor it was possible to express the anomalous rates as an electrostatic contribution and a finite-beta (electromagnetic) correction. It was demonstrated through calculations in the region of parameter-space typical of the LFA plasma that the finite-beta correction can be significant and that the dominance of anomalous transport over classical dissipation is conditioned by large values of the electron Hall parameter. If the instabilities saturate by trapping the ions, the calculations show that significant enhancement to the local resistivity of the plasma can result in regions of low collisionality leading to the substantial thermalization, which would adversely impact the efficiency of plasma acceleration.

  16. Langmuir solitons in a plasma with inhomogeneous electron temperature

    NASA Astrophysics Data System (ADS)

    Gromov, Evgeny M.; Malomed, Boris A.

    2015-06-01

    Dynamics of Langmuir solitons is considered in plasmas with spatially inhomogeneous electron temperature. An underlying Zakharov-type system of two unidirectional equations for the Langmuir and ion-sound fields is reduced to an inhomogeneous nonlinear Schrödinger equation with spatial variation of the second-order dispersion and self-phase modulation coefficients, induced by a spatially inhomogeneous profile of the electron temperature. Analytical trajectories of motion of a soliton in the plasma with an electron-temperature hole, barrier, or cavity between two barriers are found, using the method of integral moments. The possibility of the soliton to pass a high-temperature barrier is shown too. Analytical results are well corroborated by numerical simulations.

  17. Electron energy spectrum in circularly polarized laser irradiated overdense plasma

    NASA Astrophysics Data System (ADS)

    Liu, C. S.; Tripathi, V. K.; Shao, Xi; Kumar, Pawan

    2014-10-01

    A circularly polarized laser normally impinged on an overdense plasma thin foil target is shown to accelerate the electrons in the skin layer towards the rear, converting the quiver energy into streaming energy exactly if one ignores the space charge field. The energy distribution of electrons is close to Maxwellian with an upper cutoff ?max=m c2(1 +a02) 1 /2-1 ] , where a02=(1 +(2 ?2/?p2)|ai n|2) 2-1 , |ai n| is the normalized amplitude of the incident laser of frequency ?, and ?p is the plasma frequency. The energetic electrons create an electrostatic sheath at the rear and cause target normal sheath acceleration of protons. The energy gain by the accelerated ions is of the order of ?max .

  18. Fast collisionless reconnection and electron heating in strongly magnetized plasmas.

    PubMed

    Loureiro, N F; Schekochihin, A A; Zocco, A

    2013-07-12

    Magnetic reconnection in strongly magnetized (low-beta), weakly collisional plasmas is investigated by using a novel fluid-kinetic model [Zocco and Schekochihin, Phys. Plasmas 18, 102309 (2011)] which retains nonisothermal electron kinetics. It is shown that electron heating via Landau damping (linear phase mixing) is the dominant dissipation mechanism. In time, electron heating occurs after the peak of the reconnection rate; in space, it is concentrated along the separatrices of the magnetic island. For sufficiently large systems, the peak reconnection rate is cE(?)(max) ? 0.2v(A)B(y,0), where v(A) is the Alfvén speed based on the reconnecting field B(y,0). The island saturation width is the same as in magnetohydrodynamics models except for small systems, when it becomes comparable to the kinetic scales. PMID:23889411

  19. Measurement of an electron beam extracted from the plasma edge cathode

    Microsoft Academic Search

    Roman Stemprok; T. G. Engel

    1995-01-01

    The plasma edge cathode concept can produce high electron current densities while avoiding or delaying plasma closure of the extraction gap of an electron source. A plasma beam is generated by surface flashover from a spark plug. An obstacle partially intercepts the emitted plasma jet at a distance of about 150 mm from the source and causes a stationary transverse

  20. Ascorbate and plasma membrane electron transport--enzymes vs efflux.

    PubMed

    Lane, Darius J R; Lawen, Alfons

    2009-09-01

    Transplasma membrane electron transport (tPMET) systems transfer electrons across the plasma membrane, resulting in the net reduction of extracellular oxidants (e.g., ferricyanide) at the expense of intracellular reductants such as NADH and ascorbate. In mammalian tPMET systems, the major proximal electron donor is ascorbate. The classical description of ascorbate-dependent tPMET views ascorbate as a restrictively intracellular electron donor to a transplasma membrane enzymatic activity that transfers electrons across the plasma membrane to various physiological acceptors (e.g., ferric iron and the ascorbyl radical). Candidate proteins involved in this process include members of the cytochrome b(561) family (e.g., duodenal cytochrome b). However, mounting evidence suggests that cellular export of ascorbate (and concomitant import of its two-electron oxidation product, dehydroascorbate) may constitute a novel and physiologically relevant form of ascorbate-dependent tPMET. As with enzymatic tPMET, cellular ascorbate export results in net electron transfer from the cytoplasm to the extracellular space. The mechanisms of ascorbate release from cells are ill-defined, though volume-sensitive anion channels and exocytosis remain promising candidates. Cellular ascorbate release is implicated in various homeostatic processes including ascorbate maintenance in blood and brain, and the uptake of non-transferrin-bound iron by cells. Recent insights into the "duality" of ascorbate-dependent tPMET are discussed. PMID:19501649

  1. Nonlinear propagation of Electron-acoustic waves in a nonextensive electron-positron-ion plasma

    NASA Astrophysics Data System (ADS)

    Rahman, M. M.; Rafat, A.; Alam, M. S.; Mamun, A. A.

    2015-03-01

    Electron-acoustic shock waves (EASWs) in an unmagnetized electron-positron-ion plasma system (consisting of a cold mobile viscous electron fluid, hot electrons and positrons following the q-nonextensive distribution, and immobile positive ions) are studied analytically. The Burgers equation is derived by using the well-known reductive perturbation method. The basic features (viz. polarity, amplitude, width, phase speed, etc.) of EASWs are briefly addressed. The basic features of EASWs are found to be significantly modified by the effects of nonextensivity of the hot electrons and positrons, the relative number density and temperature ratios, and the kinematic viscosity of the cold electrons. The present investigation can be useful in understanding the fundamental characteristics of EASWs in various space plasmas.

  2. High-resolution Sensing Sheet for Structural-health Monitoring via Scalable Interfacing of Flexible Electronics with High-performance ICs

    E-print Network

    are patterned on both the LAE sheet and on the flex-tape packaging of the ICs. We achieve assembly via sheet Electronics with High-performance ICs Yingzhe Hu, Warren Rieutort-Louis, Josue Sanz-Robinson, Katherine Song that combines high-performance ICs with flexible electronics, allowing bonding to such surfaces. The flexi ble

  3. Suprathermal Electrons in the Plasma Environments of Mars and Venus

    NASA Astrophysics Data System (ADS)

    Brain, D. A.

    2014-12-01

    Suprathermal electrons have been measured in situ at every planet in the solar system, as well as at many smaller solar system bodies. They are hallmarks of heating, acceleration, or non-equilibrium processes occurring in any plasma, and planets are no exception. After introducing the many planetary measurements that have been made over time, this presentation will focus on a subset of electron measurements from Mars and Venus made over the last decade. At Mars, suprathermal electrons are used as diagnostics of auroral acceleration in small-scale crustal fields, and the magnetic topology of the crustal fields. At Venus, electron energy distributions are used to map the ionosphere, revealing previously unknown asymmetries. The presentation will close with a brief discussion of prospects for future and ongoing planetary electron measurements.

  4. Spontaneous synchrotron emission from a plasma with an energetic runaway electron tail

    NASA Technical Reports Server (NTRS)

    Freund, H. P.; Dillenburg, D.; Wu, C. S.; Lee, L. C.

    1978-01-01

    The emissivity of spontaneous synchrotron radiation is computed for a plasma consisting of a background thermal plasma in addition to an energetic runaway electron component. The analysis is performed for both the ordinary and extraordinary modes, for frequencies in the vicinity of the electron plasma frequency and the higher harmonics of the electron gyrofrequency, and for the case when the electron plasma frequency is approximately the same as or smaller than the cyclotron frequency. The relativistic gyroresonance with the runaway electrons is found to result in a level of spontaneous emission which, for frequencies in the neighborhood of the electron plasma frequency, is significantly enhanced over the thermal radiation.

  5. Calculation of electronic transport coefficients of Ag and Au plasma

    SciTech Connect

    Apfelbaum, E. M. [Joint Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya Street 13, Building 2, Moscow 125412 (Russian Federation)

    2011-12-15

    The thermoelectric transport coefficients of silver and gold plasma have been calculated within the relaxation-time approximation. We considered temperatures of 10-100 kK and densities of {rho} < or approx. 1 g/cm{sup 3}. The plasma composition was calculated using a corresponding system of coupled mass action laws, including the atom ionization up to +4. For momentum cross sections of electron-atom scattering we used the most accurate expressions available. The results of our modeling have been compared with other researchers' data whenever possible.

  6. Cathode Plasma Formation in High Intensity Electron Beam Diodes

    NASA Astrophysics Data System (ADS)

    Johnston, Mark; Kiefer, Mark; Oliver, Bryan; Bennett, Nichelle; Droemer, Darryl; Bernshtam, V.; Doron, R.; Maron, Yitzhak

    2013-10-01

    This talk will detail the experimental results and conclusions obtained for cathode plasma formation on the Self-Magnetic Pinch (SMP) diode fielded on the RITS-6 accelerator (4-7.5 MeV) at Sandia National Laboratories. The SMP diode utilizes a hollowed metal cathode to produce high power (TW), focused electron beams (<3 mm diameter) which are used for flash x-ray radiography applications. Optical diagnostics include high speed (<10 ns) framing cameras, optical streak cameras, and spectroscopy. The cathode plasma in this high electric (MV/cm) and magnetic (>10 Tesla) field environment forms well-defined striations. These striations have been examined for a number of different cathode sizes, vacuum gap spacings, and diode voltages. Optical streak images have been taken to determine the time evolution of the plasma, and optical spectroscopy has been employed to determine its constituents as well as their densities and temperatures inferred from detailed time-dependent, collisional-radiative (CR) and radiation transport modelings. Comments will be made as to the overall effect of the cathode plasma in regards to the diode impedance and electron beam focusing. This talk will detail the experimental results and conclusions obtained for cathode plasma formation on the Self-Magnetic Pinch (SMP) diode fielded on the RITS-6 accelerator (4-7.5 MeV) at Sandia National Laboratories. The SMP diode utilizes a hollowed metal cathode to produce high power (TW), focused electron beams (<3 mm diameter) which are used for flash x-ray radiography applications. Optical diagnostics include high speed (<10 ns) framing cameras, optical streak cameras, and spectroscopy. The cathode plasma in this high electric (MV/cm) and magnetic (>10 Tesla) field environment forms well-defined striations. These striations have been examined for a number of different cathode sizes, vacuum gap spacings, and diode voltages. Optical streak images have been taken to determine the time evolution of the plasma, and optical spectroscopy has been employed to determine its constituents as well as their densities and temperatures inferred from detailed time-dependent, collisional-radiative (CR) and radiation transport modelings. Comments will be made as to the overall effect of the cathode plasma in regards to the diode impedance and electron beam focusing. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  7. Arbitrary amplitude slow electron-acoustic solitons in three-electron temperature space plasmas

    NASA Astrophysics Data System (ADS)

    Mbuli, L. N.; Maharaj, S. K.; Bharuthram, R.; Singh, S. V.; Lakhina, G. S.

    2015-06-01

    We examine the characteristics of large amplitude slow electron-acoustic solitons supported in a four-component unmagnetised plasma composed of cool, warm, hot electrons, and cool ions. The inertia and pressure for all the species in this plasma system are retained by assuming that they are adiabatic fluids. Our findings reveal that both positive and negative potential slow electron-acoustic solitons are supported in the four-component plasma system. The polarity switch of the slow electron-acoustic solitons is determined by the number densities of the cool and warm electrons. Negative potential solitons, which are limited by the cool and warm electron number densities becoming unreal and the occurrence of negative potential double layers, are found for low values of the cool electron density, while the positive potential solitons occurring for large values of the cool electron density are only limited by positive potential double layers. Both the lower and upper Mach numbers for the slow electron-acoustic solitons are computed and discussed.

  8. Potential hill electron-acoustic solitons and double layers in plasmas with two electron species

    SciTech Connect

    Cattaert, Tom; Verheest, Frank; Hellberg, Manfred A. [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, B-9000 Gent (Belgium); Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, B-9000 Gent (Belgium) and School of Physics (Howard College Campus), University of KwaZulu-Natal, Durban 4041 (South Africa); School of Physics (Howard College Campus), University of KwaZulu-Natal, Durban 4041 (South Africa)

    2005-04-15

    In the description of (high-frequency) electron-acoustic solitons in a plasma consisting of positive ions, cool electrons, and hot electrons, the dynamics of the ions plays no essential role and can be eliminated from the treatment, the ions merely providing a constant positive background. It is widely believed that in such a plasma only potential dip solitary waves can be generated. In a potential dip the cooler electrons are compressed and the hotter electrons rarefied, both being driven towards their sonic points, the cooler ones from above, the hotter ones from below. This transonic feature gives rise to the solitary wave. However, it is shown that the restriction to potential dip solitons is due to the neglect of the inertia of the hot electrons, implicitly or explicitly assumed by most authors. If hot electron inertia is retained, there exists a parameter range where potential hill solitary waves are formed, with both electron species being driven away from their sonic points. This has important consequences for the reinterpretation of several astrophysical phenomena involving two-electron plasmas.

  9. Ion- and electron-acoustic solitons in two-electron temperature space plasmas

    SciTech Connect

    Lakhina, G. S.; Kakad, A. P.; Singh, S. V. [Indian Institute of Geomagnetism, New Panvel (West), Navi Mumbai-410 218 (India); Verheest, F. [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, B-9000 Gent (Belgium); School of Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000 (South Africa)

    2008-06-15

    Properties of ion- and electron-acoustic solitons are investigated in an unmagnetized multicomponent plasma system consisting of cold and hot electrons and hot ions using the Sagdeev pseudopotential technique. The analysis is based on fluid equations and the Poisson equation. Solitary wave solutions are found when the Mach numbers exceed some critical values. The critical Mach numbers for the ion-acoustic solitons are found to be smaller than those for electron-acoustic solitons for a given set of plasma parameters. The critical Mach numbers of ion-acoustic solitons increase with the increase of hot electron temperature and the decrease of cold electron density. On the other hand, the critical Mach numbers of electron-acoustic solitons increase with the increase of the cold electron density as well as the hot electron temperature. The ion-acoustic solitons have positive potentials for the parameters considered. However, the electron-acoustic solitons have positive or negative potentials depending whether the fractional cold electron density with respect to the ion density is greater or less than a certain critical value. Further, the amplitudes of both the ion- and electron-acoustic solitons increase with the increase of the hot electron temperature. Possible application of this model to electrostatic solitary waves observed on the auroral field lines by the Viking spacecraft is discussed.

  10. Anti-bias voltage electron-Kondo transport in a quantum dot device driven by a graphene sheet

    NASA Astrophysics Data System (ADS)

    Chen, Xiongwen; Shi, Zhengang; Zhang, Shunru; Song, Kehui; Zhou, Guanghui

    2015-01-01

    We theoretically investigate the manipulation of electron-Kondo transport through a single-quantum dot (QD) two-electrode device by introducing a side-coupled graphene sheet. It is shown that with increase of coupling strength between the QD and the zero-potential graphene sheet, the anti-bias voltage capability of the QD-electrode Kondo resonance is improved obviously. This causes a high-conductance QD-electrode channel to be opened up for electron transport within a wide bias voltage range. Moreover, the conductance/current of the Kondo channel can be accurately controlled by adjusting the potential of the graphene sheet. These results may be useful for the observation of nonequilibrium Kondo effect and the design of high-conductance control device.

  11. Effect of suprathermal electrons on the intensity and Doppler frequency of electron plasma lines

    NASA Astrophysics Data System (ADS)

    Guio, P.; Lilensten, J.

    1999-07-01

    In an incoherent scattering radar experiment, the spectral measurement of the so-called up- and downshifted electron plasma lines provides information about their intensity and their Doppler frequency. These two spectral lines correspond, in the backscatter geometry, to two Langmuir waves travelling towards and away from the radar. In the daytime ionosphere, the presence of a small percentage of photoelectrons produced by the solar EUV of the total electron population can excite or damp these Langmuir waves above the thermal equilibrium, resulting in an enhancement of the intensity of the lines above the thermal level. The presence of photo-electrons also modifies the dielectric response function of the plasma from the Maxwellian and thus influences the Doppler frequency of the plasma lines. In this paper, we present a high time-resolution plasma-line data set collected on the Eiscat VHF radar. The analysed data are compared with a model that includes the effect of a suprathermal electron population calculated by a transport code. By comparing the intensity of the analysed plasma lines data to our model, we show that two sharp peaks in the electron suprathermal distribution in the energy range 20-30 eV causes an increased Landau damping around 24.25 eV and 26.25 eV. We have identified these two sharp peaks as the effect of the photoionisation of N2 and O by the intense flux of monochromatic HeII radiation of wavelength 30.378 nm (40.812 eV) created in the chromospheric network and coronal holes. Furthermore, we see that what would have been interpreted as a mean Doppler drift velocity for a Maxwellian plasma is actually a shift of the Doppler frequency of the plasma lines due to suprathermal electrons.

  12. Collimated fast electron beam generation in critical density plasma

    NASA Astrophysics Data System (ADS)

    Iwawaki, T.; Habara, H.; Baton, S.; Morita, K.; Fuchs, J.; Chen, S.; Nakatsutsumi, M.; Rousseaux, C.; Filippi, F.; Nazarov, W.; Tanaka, K. A.

    2014-11-01

    Significantly collimated fast electron beam with a divergence angle 10° (FWHM) is observed when an ultra-intense laser pulse (I = 1014 W/cm2, 300 fs) irradiates a uniform critical density plasma. The uniform plasma is created through the ionization of an ultra-low density (5 mg/c.c.) plastic foam by X-ray burst from the interaction of intense laser (I = 1014 W/cm2, 600 ps) with a thin Cu foil. 2D Particle-In-Cell (PIC) simulation well reproduces the collimated electron beam with a strong magnetic field in the region of the laser pulse propagation. To understand the physical mechanism of the collimation, we calculate energetic electron motion in the magnetic field obtained from the 2D PIC simulation. As the results, the strong magnetic field (300 MG) collimates electrons with energy over a few MeV. This collimation mechanism may attract attention in many applications such as electron acceleration, electron microscope and fast ignition of laser fusion.

  13. Electron temperature and average density in spherical laser-produced plasmas - Ultraviolet plasma spectroscopy

    NASA Technical Reports Server (NTRS)

    Goldsmith, S.; Seely, J. F.; Feldman, U.; Behring, W. E.; Cohen, L.

    1985-01-01

    The average values of the electron temperature Te and the electron density Ne in the corona plasmas of spherically irradiated high-Z targets have been estimated. Targets composed of the elements Cu through Br, Rb, and Mo were irradiated using the fundamental (1.06 microns) and the frequency-tripled (351 nm) output of the Omega laser system. Spectra were recorded in the wavelength region 15-200 A. Using various extreme ultraviolet spectroscopic techniques, it is found that for the case of a Mo plasma produced by frequency-tripled laser irradiation, Te = 2600 + or - 600 eV and Ne is greater than 6 x 10 to the 20th/cu cm. This is consistent with a 'flux limit' smaller than 0.1. The estimated values of Te and Ne are lower in the corona plasmas produced using the fundamental (1.06 micron) irradiation.

  14. Non-ambipolar radio-frequency plasma electron source and systems and methods for generating electron beams

    DOEpatents

    Hershkowitz, Noah (Madison, WI); Longmier, Benjamin (Madison, WI); Baalrud, Scott (Madison, WI)

    2009-03-03

    An electron generating device extracts electrons, through an electron sheath, from plasma produced using RF fields. The electron sheath is located near a grounded ring at one end of a negatively biased conducting surface, which is normally a cylinder. Extracted electrons pass through the grounded ring in the presence of a steady state axial magnetic field. Sufficiently large magnetic fields and/or RF power into the plasma allow for helicon plasma generation. The ion loss area is sufficiently large compared to the electron loss area to allow for total non-ambipolar extraction of all electrons leaving the plasma. Voids in the negatively-biased conducting surface allow the time-varying magnetic fields provided by the antenna to inductively couple to the plasma within the conducting surface. The conducting surface acts as a Faraday shield, which reduces any time-varying electric fields from entering the conductive surface, i.e. blocks capacitive coupling between the antenna and the plasma.

  15. Non-ambipolar radio-frequency plasma electron source and systems and methods for generating electron beams

    NASA Technical Reports Server (NTRS)

    Hershkowitz, Noah (Inventor); Longmier, Benjamin (Inventor); Baalrud, Scott (Inventor)

    2011-01-01

    An electron generating device extracts electrons, through an electron sheath, from plasma produced using RF fields. The electron sheath is located near a grounded ring at one end of a negatively biased conducting surface, which is normally a cylinder. Extracted electrons pass through the grounded ring in the presence of a steady state axial magnetic field. Sufficiently large magnetic fields and/or RF power into the plasma allow for helicon plasma generation. The ion loss area is sufficiently large compared to the electron loss area to allow for total non-ambipolar extraction of all electrons leaving the plasma. Voids in the negatively-biased conducting surface allow the time-varying magnetic fields provided by the antenna to inductively couple to the plasma within the conducting surface. The conducting surface acts as a Faraday shield, which reduces any time-varying electric fields from entering the conductive surface, i.e. blocks capacitive coupling between the antenna and the plasma.

  16. Non-ambipolar radio-frequency plasma electron source and systems and methods for generating electron beams

    NASA Technical Reports Server (NTRS)

    Hershkowitz, Noah (Inventor); Longmier, Benjamin (Inventor); Baalrud, Scott (Inventor)

    2009-01-01

    An electron generating device extracts electrons, through an electron sheath, from plasma produced using RF fields. The electron sheath is located near a grounded ring at one end of a negatively biased conducting surface, which is normally a cylinder. Extracted electrons pass through the grounded ring in the presence of a steady state axial magnetic field. Sufficiently large magnetic fields and/or RF power into the plasma allow for helicon plasma generation. The ion loss area is sufficiently large compared to the electron loss area to allow for total non-ambipolar extraction of all electrons leaving the plasma. Voids in the negatively-biased conducting surface allow the time-varying magnetic fields provided by the antenna to inductively couple to the plasma within the conducting surface. The conducting surface acts as a Faraday shield, which reduces any time-varying electric fields from entering the conductive surface, i.e. blocks capacitive coupling between the antenna and the plasma.

  17. Effect of self-consistent magnetic field on plasma sheet penetration to the inner magnetosphere: Rice convection model simulations combined with modified Dungey force-balanced magnetic field solver

    NASA Astrophysics Data System (ADS)

    Gkioulidou, Matina; Wang, Chih-Ping; Lyons, Larry R.

    2011-12-01

    Transport of plasma sheet particles into the inner magnetosphere is crucial to the development of the region 2 (R2) field-aligned current system (FAC), which results in the shielding of the penetration electric field and the formation of subauroral polarization streams (SAPS) and the Harang reversal, phenomena closely associated with storms and substorms. In addition to the electric field, this transport is also strongly affected by the magnetic field, which changes with plasma pressure and is distinctly different from the dipole field in the inner plasma sheet. To determine the feedback of force-balanced magnetic field to the transport, we have integrated the Rice convection model (RCM) with a modified Dungey magnetic field solver to obtain the required force balance in the equatorial plane. Comparing our results with those from a RCM run using a T96 magnetic field, we find that transport under a force-balanced magnetic field results in weaker pressure gradients and thus weaker R2 FAC in the near-Earth region and weaker shielding of the penetration electric field. As a result, plasma sheet protons and electrons penetrate farther earthward, and their inner edges become closer together and more azimuthally symmetric than in the T96 case. The Harang reversal extends farther dawnward, and the SAPS become more confined in radial and latitudinal extents. The magnitudes of azimuthal pressure gradient, the inner edges of thermal protons and electrons, the latitudinal range of the Harang reversal, and the radial and latitudinal widths of the SAPS from the force-balanced run are found to be more consistent with observations.

  18. Effect of electron thermal motion on plasma heating in a magnetized inductively coupled plasma

    SciTech Connect

    Aman-ur-Rehman; Pu Yikang [Department of Engineering Physics, Tsinghua University, 100084 Beijing, China and Pakistan Institute of Engineering and Applied Sciences, P.O. Nilore Islamabad (Pakistan); Department of Engineering Physics, Tsinghua University, 100084 Beijing (China)

    2007-06-15

    Power absorbed inside the magnetized inductively coupled plasma (MICP) is calculated using three different warm MICP models and is then compared with the result of the cold MICP model. The comparison shows that in the propagating region ({omega}< vertical bar {omega}{sub e} vertical bar), under the cavity resonance conditions, warm plasma heating S{sub warm} is significantly less than the cold plasma heating S{sub cold}, unless the distance traveled by the electrons due to their thermal motion, during the effective wave period, becomes significantly less than the wavelength of the cavity wave. Furthermore, in the propagating region, when {omega}{approx_equal} vertical bar {omega}{sub e} vertical bar, there appears a valley on the plot of {eta}({omega})=S{sub warm}/S{sub cold} versus {omega} showing the negative effect of electron thermal motion on plasma heating. This valley widens and gets smoother with an increase in the plasma length. In the nonpropagating region ({omega}> vertical bar {omega}{sub e} vertical bar), the maximum value of {eta}({omega}) exists when {omega}- vertical bar {omega}{sub e} vertical bar {approx_equal}v{sub th}/{delta}, showing that, in the presence of the external magnetic field, the thermal motion of the electrons leads to a Doppler shift of the frequencies, at which collisionless heating is the dominant mode of electron heating. Furthermore, in the nonpropagating region, when {omega}{approx_equal} vertical bar {omega}{sub e} vertical bar, the skin depth of the right circularly polarized electric field decreases with magnetic field. This decrease in the skin depth results in an increase of collisionless heating under the Doppler-shifted wave particle resonant condition of {omega}- vertical bar {omega}{sub e} vertical bar {approx_equal}v{sub th}/{delta}. It is also observed that, for large plasma length, the results of all the three warm MICP models are consistent with each other.

  19. First-principles study of the stability and electronic properties of sheets and nanotubes of elemental boron

    E-print Network

    Pandey, Ravi

    of elemental boron Kah Chun Lau a , Ranjit Pati a , Ravindra Pandey a,*, Andrew C. Pineda b,c a Department The structural and electronic properties of sheets and nanotubes of boron are investigated using density Elsevier B.V. All rights reserved. Boron holds a unique place among the elements of the periodic table

  20. Interaction of ion-acoustic solitons with electron beam in warm plasmas with superthermal electrons

    E-print Network

    Esfandyari-Kalejahi, A R

    2012-01-01

    Propagation of ion-acoustic solitary waves (IASWs) is studied using the hydrodynamic equations coupled with the Poisson equation in a warm plasma consisting of adiabatic ions and superthermal (Kappa distributed) electrons in presence of an electron-beam component. In the linear limit, the dispersion relation for ion-acoustic (IA) waves is obtained by linearizing of basic equations. On the other hand, in the nonlinear analysis, an energy-balance like equation involving Sagdeev's pseudo-potential is derived in order to investigate arbitrary amplitude IA solitons. The Mach number range is determined in which, propagation and characteristics of IA solitons are analyzed both parametrically and numerically. The variation of amplitude and width of electrostatic (ES) excitations as a result of superthermality (via) and also the physical parameters (ion temperature, soliton speed, electron-beam density and electron-beam velocity) are examined. A typical interaction between IASWs and the electron-beam in plasma is conf...

  1. Oblique modulation of electron-acoustic waves in a Fermi electron-ion plasma

    SciTech Connect

    Bhowmik, C.; Misra, A. P.; Shukla, P. K. [Department of Mathematics, Siksha Bhavana, Visva-Bharati University, Santiniketan-731 235 (India); Institut fuer Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultaet fuer Physik and Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum, Germany and School of Physics, University of KwaZulu-Natal, Durban 4000 (South Africa)

    2007-12-15

    The oblique modulational instability (MI) of electron-acoustic waves (EAWs) in a quantum plasma whose components are two distinct groups of electrons (one inertial cold electrons and other inertialess hot electrons) and immobile ions is investigated, by using a quantum hydrodynamic model. The analysis is carried out through the derivation of the nonlinear Schroedinger equation for the modulated EAW packets. The effects of obliqueness, the quantum diffraction (H), and the equilibrium density ratio of the cold to hot electron component ({delta}) on the MI of EAWs are numerically examined. At quantum scales, these parameters are found to significantly modify the MI domain in the plane of wave number and the angle ({theta}) between the modulation and the propagation direction. The relevance of our results in astrophysical environments, as well as in intense laser-solid density plasma interaction experiments is discussed.

  2. Amplitude saturation effect of a laser-driven plasma beat-wave on electron accelerations

    NASA Astrophysics Data System (ADS)

    Gupta, D. N.; Singh, Mamta; Suk, H.

    2015-06-01

    A large-amplitude plasma beat-wave driven by two lasers (differing in frequencies equal to the plasma frequency) can accelerate the plasma electrons to a higher energy level. As the plasma beat-wave grows, it becomes susceptible to oscillating two-stream instability. The decayed sideband plasma wave couples with the pump wave to divert its energy by the instability, and saturates it. The saturated amplitude of the plasma beat-wave traps the electrons more effectively to accelerate them to higher energy. The saturation of plasma beat-wave amplitude is shown to have a significant effect in an electron energy gain.

  3. The specific entropy of the plasma sheet as a controlling factor for the injection of a storm-time ring current

    NASA Astrophysics Data System (ADS)

    Lemon, C. L.; Wolf, R. A.; Hill, T. W.; Sazykin, S.; Spiro, R. W.; Toffoletto, F. R.; Birn, J.; Hesse, M.

    2004-12-01

    Simulation results are presented which explore the importance of the inner plasma sheet specific entropy (pV5/3, where p is pressure and V = ? ds/B is the flux tube volume) for controlling the strength and depth of ring current particle injections during magnetic storms. The simulation model is the RCM--E (Rice Convection Model -- Equilibrium), which calculates the energy-dependent magnetic and electric drifts of particles within self-consistently computed magnetic and electric fields. The results demonstrate that inner plasma sheet reductions in the specific entropy can drive region 1 Birkeland currents that enhance the westward electric field in the depletion region; the strong electric field then propels plasma earthward, into the ring current. In contrast, earthward convection of heavily loaded (insufficiently depleted) plasma sheet flux tubes is impeded by the immense pressure gradient that would result from squeezing that much plasma into the much smaller volume of a ring current flux tube. In other words, insufficient depletion disallows the flux tubes from taking on the quasi-dioplar shape necessary to penetrate into the ring current. Flux tube content reductions are observed during the substorm expansion phase, suggesting one potential process (though perhaps not the only one) that could lead to ring current injection. The ability of the plasma sheet specific entropy to influence the injection of ring current particles, and the implications for understanding the differences between SMC and Sawtooth events will be examined.

  4. Analysis of electron beam damage of exfoliated MoS? sheets and quantitative HAADF-STEM imaging.

    PubMed

    Garcia, Alejandra; Raya, Andres M; Mariscal, Marcelo M; Esparza, Rodrigo; Herrera, Miriam; Molina, Sergio I; Scavello, Giovanni; Galindo, Pedro L; Jose-Yacaman, Miguel; Ponce, Arturo

    2014-11-01

    In this work we examined MoS? sheets by aberration-corrected scanning transmission electron microscopy (STEM) at three different energies: 80, 120 and 200 kV. Structural damage of the MoS? sheets has been controlled at 80 kV according a theoretical calculation based on the inelastic scattering of the electrons involved in the interaction electron-matter. The threshold energy for the MoS? material has been found and experimentally verified in the microscope. At energies higher than the energy threshold we show surface and edge defects produced by the electron beam irradiation. Quantitative analysis at atomic level in the images obtained at 80 kV has been performed using the experimental images and via STEM simulations using SICSTEM software to determine the exact number of MoS2? layers. PMID:24929924

  5. Observations of underdense plasma lens focusing of relativistic electron beams

    SciTech Connect

    Thompson, M.C.; /UCLA /LLNL, Livermore; Badakov, H.; Rosenzweig, J.B.; Travish, G.; /UCLA; Fliller, R.; Kazakevich, G.M.; Piot, P.; Santucci, J.; /Fermilab; Li, J.; Tikhoplav, R.; /Rochester U.

    2007-06-01

    Focusing of a 15 MeV, 19 nC electron bunch by an underdense plasma lens operated just beyond the threshold of the underdense condition has been demonstrated in experiments at the Fermilab NICADD Photoinjector Laboratory (FNPL). The strong 1.9 cm focal-length plasma-lens focused both transverse directions simultaneously and reduced the minimum area of the beam spot by a factor of 23. Analysis of the beam-envelope evolution observed near the beam waist shows that the spherical aberrations of this underdense lens are lower than those of an overdense plasma lens, as predicted by theory. Correlations between the beam charge and the properties of the beam focus corroborate this conclusion.

  6. Trapped Electron Mode Turbulence Driven Intrinsic Rotation in Tokamak Plasmas

    SciTech Connect

    Wang, W. X.; Hahm, T. S.; Ethier, S.; Zakharov, L. E.; Diamond, P. H. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States)] [University of California, San Diego, La Jolla, California 92093 (United States)

    2011-02-25

    Progress from global gyrokinetic simulations in understanding the origin of intrinsic rotation in toroidal plasmas is reported. The turbulence-driven intrinsic torque associated with nonlinear residual stress generation due to zonal flow shear induced asymmetry in the parallel wave number spectrum is shown to scale close to linearly with plasma gradients and the inverse of the plasma current, qualitatively reproducing experimental empirical scalings of intrinsic rotation. The origin of current scaling is found to be enhanced k{sub ||} symmetry breaking induced by the increased radial variation of the safety factor as the current decreases. The intrinsic torque is proportional to the pressure gradient because both turbulence intensity and zonal flow shear, which are two key ingredients for driving residual stress, increase with turbulence drive, which is R/L{sub T{sub e}} and R/L{sub n{sub e}} for the trapped electron mode.

  7. Plasma electron temperature and the entropy effect on hydrogen production

    NASA Astrophysics Data System (ADS)

    Chakartnarodom, Parinya

    The thesis is that the interaction between the microwave induced electric field and a conductive material will produce plasma with high effective temperature such that it is thermodynamically and kinetically possible to produce small molecules from large molecules. The high effective temperature increases the potency of the entropy term such that small molecules are produced from large molecules even though the enthalpy for the process is positive. This hypothesis will be tested in several reactions for which the entropy change is positive. The plasma enhanced chemical reactions examined here may also be important in the practical application of alternative fuel production. The specific reactions of interest to this thesis are: (1) H 2O?H2 + 1/2 O2; DeltaGo ( kJ) = 247.5--0.056T, (2) 1/2 N2 + H2O? H2 + NO; DeltaGo (kJ) = 338.45--0.069T, (3) C + H2O ?Fe H2 + CO; Delta Go(kJ) = 135.8--0.143 T, (4) C6H 10O5 ? 5H2 + C + 5CO; DeltaGo( kJ) = 711.3--2.48T. Experiments are carried out to examine the chemical species present within the plasma by the optical emission spectrometer (OES) and in the resultant gas outflow by the flue gas analyzer as a function of incoming gas composition and composition of the solid materials at the point of plasma initiation. The chemical and plasma reactions observed experimentally will be compared to thermodynamic calculations as a method to test the hypothesis. In addition, hydrogen production from water and from water and nitrogen at elevated effective temperature produces products, which recombine with negative free energy change at lower temperatures. Based on our initial results, it is also necessary to hypothesize that spatiotemporal plasma discharges can produce molecular hydrogen and an associated oxidant at an elevated effective temperature such that the mixture is 'quenched' to a lower temperature where said mixture is kinetically stabilized against spontaneous recombination. In all experiments, the results from OES show that atomic hydrogen is produced in the plasma, and the results from flue-gas analyzer show that H 2 is a product from the reaction in the plasma. From the experimental results, the yield of H2 is increased with the increasing of the electron temperature in gas/gas plasma reactions having positive entropy. For solid/gas plasma reactions which DeltaSo is either positive or negative, there is no correlation between H2 yield and electron temperature. However, H2 yield from all plasma reactions is lower than the prediction from the van't Hoff equation. Based on an analysis of the Saha equation, the effective temperature of the chemical species in the plasma may be lower than the electron temperature, thus rationalizing our observation of reduced H2 yield. An alternative hypothesis is that the quenching rates of the products from the plasma are not fast enough to avoid recombination of the reaction products at low temperature, where the enthalpy term dominates.

  8. Progress toward positron-electron pair plasma experiments

    NASA Astrophysics Data System (ADS)

    Stanja, J.; Hergenhahn, U.; Niemann, H.; Paschkowski, N.; Sunn Pedersen, T.; Saitoh, H.; Stenson, E. V.; Hugenschmidt, Ch.; Marx, G. H.; Schweikhard, L.; Danielson, J. R.; Surko, C. M.

    2014-10-01

    Matter-antimatter pair plasmas have been of great theoretical and astrophysical interest for a long time. A Positron-Electron Experiment (APEX) aims for the creation and study of such a plasma in the laboratory. It will be operated at the NEPOMUC facility which provides a cold and high-intensity positron beam. To achieve at least 10 Debye length within APEX's flux surfaces the beam needs to initially pass through several stages of manipulation. Presented here is an overview of work from the APEX team. Topics include E-> × B-> beam handling for separation into multiple beams in order to reduce the energy spread of the positron beam; injection and trapping of electrons in a prototype dipole field device with a permanent magnet; and design plans for the next generation of confinement device. on behalf of the APEX/PAX Team and Collaborators.

  9. A novel electron density reconstruction method for asymmetrical toroidal plasmas

    SciTech Connect

    Shi, N.; Ohshima, S.; Minami, T.; Nagasaki, K.; Yamamoto, S.; Mizuuchi, T.; Okada, H.; Kado, S.; Kobayashi, S.; Konoshima, S.; Sano, F. [Institute of Advanced Energy, Kyoto University, Gokasyo, Uji (Japan)] [Institute of Advanced Energy, Kyoto University, Gokasyo, Uji (Japan); Tanaka, K. [National Institute for Fusion Science, Toki (Japan)] [National Institute for Fusion Science, Toki (Japan); Ohtani, Y.; Zang, L.; Kenmochi, N. [Graduate School of Energy Science, Kyoto University, Uji (Japan)] [Graduate School of Energy Science, Kyoto University, Uji (Japan)

    2014-05-15

    A novel reconstruction method is developed for acquiring the electron density profile from multi-channel interferometric measurements of strongly asymmetrical toroidal plasmas. It is based on a regularization technique, and a generalized cross-validation function is used to optimize the regularization parameter with the aid of singular value decomposition. The feasibility of method could be testified by simulated measurements based on a magnetic configuration of the flexible helical-axis heliotron device, Heliotron J, which has an asymmetrical poloidal cross section. And the successful reconstruction makes possible to construct a multi-channel Far-infrared laser interferometry on this device. The advantages of this method are demonstrated by comparison with a conventional method. The factors which may affect the accuracy of the results are investigated, and an error analysis is carried out. Based on the obtained results, the proposed method is highly promising for accurately reconstructing the electron density in the asymmetrical toroidal plasma.

  10. Neoclassical electron and ion transport in toroidally rotating plasmas

    SciTech Connect

    Sugama, H. [National Institute for Fusion Science, Nagoya 464-01 (Japan)] [National Institute for Fusion Science, Nagoya 464-01 (Japan); Horton, W. [Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712 (United States)] [Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712 (United States)

    1997-06-01

    Neoclassical transport processes of electrons and ions are investigated in detail for toroidally rotating axisymmetric plasmas with large flow velocities on the order of the ion thermal speed. The Onsager relations for the flow-dependent neoclassical transport coefficients are derived from the symmetry properties of the drift kinetic equation with the self-adjoint collision operator. The complete neoclassical transport matrix with the Onsager symmetry is obtained for the rotating plasma consisting of electrons and single-species ions in the Pfirsch{endash}Schl{umlt u}ter and banana regimes. It is found that the inward banana fluxes of particles and toroidal momentum are driven by the parallel electric field, which are phenomena coupled through the Onsager symmetric off-diagonal coefficients to the parallel currents caused by the radial thermodynamic forces conjugate to the inward fluxes, respectively. {copyright} {ital 1997 American Institute of Physics.}

  11. Optical Guiding and Electron Acceleration in Programmably Modulated Plasma Waveguides

    NASA Astrophysics Data System (ADS)

    Hine, George; Goers, Andrew; Elle, Jennifer; Feder, Linus; Milchberg, Howard

    2014-10-01

    We demonstrate the guiding of relativistically intense laser pulses through programmably structured plasma waveguides. The structure of the waveguide is dictated electronically using a Spatial Light Modulator (SLM). The waveguides are generated by sending a radially patterned intense laser pulse through an axicon in a clustered gas medium, efficiently ionizing and heating a column of plasma which expands to form an optical guiding structure. Intensity modulations at the line focus produce density modulations as the waveguide evolves. Patterning of the intense laser pulse is achieved using the SLM in an interferometric configuration. This SLM patterning technique allows for in situ sculpting of waveguides with arbitrary density structures. Density ramps are generated for electron injection, and periodic structures are formed to quasi-phasematch laser wakefield acceleration and direct laser acceleration. This work is supported by the DoE and DTRA.

  12. Electron trajectories and growth rates of the plasma wave pumped free-electron laser

    NASA Astrophysics Data System (ADS)

    Jafari, S.; Jafarinia, F.; Nilkar, M.; Amiri, M.

    2014-12-01

    A theory for a plasma wave wiggler has been described which employs the plasma whistler wave for producing laser radiation in a free-electron laser (FEL). While electromagnetically pumped FELs have been proven to be an effective means generating short wavelengths, practical difficulties occur in the design of these wigglers. For this reason, it is found that a plasma wave wiggler can be employed in concept with an electromagnetic wave wiggler due to both higher tunability and holding the focus of pump wave and e-beam over a significant distance to achieve a suitable amplification. Plasma in the presence of static magnetic field supports a plasma whistler wave. The plasma wiggler period can be tuned by varying the plasma density and/or ambient magnetic field. Electron trajectories have been analyzed using single particle dynamics and regimes of orbital stability have been demonstrated. A polynomial dispersion relation for electromagnetic and space-charge waves has then been derived, analytically. Numerical studies of the dispersion relation reveal that the growth rates are sensitive functions of the cyclotron frequency. It has been shown that by increasing the axial magnetic field strength (or cyclotron frequency), the growth rate for groups I and III orbits increases, while a growth decrement has been obtained for groups II and IV orbits.

  13. Optical Spectroscopy of High Intensity Electron Beam Plasmas^1

    NASA Astrophysics Data System (ADS)

    Johnston, Mark; Oliver, Bryan; Bruner, Nichelle; Welch, Dale; Maron, Yitzhak

    2012-10-01

    This talk will be an overview of spectroscopic results obtained on the RITS-6 accelerator at Sandia National Laboratories on the Self-Magnetic Pinch (SMP) electron beam diode. The SMP diode produces a focused (<3mm diameter), e-beam at 7MeV and 150kA, which is used as an intense, flash x-ray source. During the ˜45ns electron beam pulse, plasmas are generated on the electrode surfaces which propagate into the A-K vacuum gap, affecting the diode impedance, x-ray spectrum, and pulse-width. These plasmas are measured using a series of optical diagnostics including: streak cameras, ICCD cameras, and avalanche photodetectors. Visible spectroscopy is used to gather time and space information on these plasmas. Density and temperature calculations are made using detailed, time-dependent, collisional-radiative (CR) and radiation transport modelings. The results are then used in conjunction with hybrid PIC/fluid simulations to model the overall plasma behavior. Details regarding the data collection, system calibration, analyses, and interpretation of results will be presented. [4pt] ^1Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  14. The spatial evolution of energetic electrons and plasma waves during the steady state beam plasma discharge

    NASA Technical Reports Server (NTRS)

    Llobet, X.; Bernstein, W.; Kondradi, A.

    1985-01-01

    Experiments, involving the injection of energetic (keV) electron beams into the ionosphere-upper atmosphere system from rocket-borne electron guns, have provided evidence for the occurrence of strong beam-plasma interactions (BPI) both near to and remote from the injection point. However, the flight experiments have not provided clear and unambiguous evidence for the basic physical processes which produce the variety of confusing signatures. A laboratory experimental program was initiated to clarify some of a number of ambiguities regarding the obtained results. The present investigation is concerned with some experimental studies of the evolution of both the beam energy spectrum and the local wave amplitude-frequency spectrum at increasing axial distances from the electron gun for a variety of experimental conditions. The results of the studies show that the high frequency beam-plasma interaction represents the most important process.

  15. Whistler mode plasma waves observed on Electron Echo 2

    NASA Technical Reports Server (NTRS)

    Monson, S. J.; Kellogg, P. J.; Cartwright, D. G.

    1976-01-01

    Observations of whistler-mode waves associated with beams of electrons injected into the ionosphere are reported. The measurements are from the plasma-wave experiments carried on the Electron Echo 2 sounding rocket launched on September 24, 1972. Over 2000 electron injections were made with durations of 8 ms and 64 ms and pitch angles from 0 to 180 deg. The electric field receivers carried on the ejected nose cone observed strong whistler waves in the range from less than 100 kHz up to the electron cyclotron frequency of 1400 kHz. The whistler characteristics fall into four distinct types depending on pitch angle and gun energy. Both frequency and amplitude showed strong dependence on time from the start of the pulse and pitch angle. Cases of enhancement at the leading edge of a gun pulse, growth during a pulse, and echoes after the end of a pulse were all observed.

  16. Plasma jet braking: energy dissipation and nonadiabatic electrons.

    PubMed

    Khotyaintsev, Yu V; Cully, C M; Vaivads, A; André, M; Owen, C J

    2011-04-22

    We report in situ observations by the Cluster spacecraft of wave-particle interactions in a magnetic flux pileup region created by a magnetic reconnection outflow jet in Earth's magnetotail. Two distinct regions of wave activity are identified: lower-hybrid drift waves at the front edge and whistler-mode waves inside the pileup region. The whistler-mode waves are locally generated by the electron temperature anisotropy, and provide evidence for ongoing betatron energization caused by magnetic flux pileup. The whistler-mode waves cause fast pitch-angle scattering of electrons and isotropization of the electron distribution, thus making the flow braking process nonadiabatic. The waves strongly affect the electron dynamics and thus play an important role in the energy conversion chain during plasma jet braking. PMID:21599373

  17. Ultrafast Diagnostics for Electron Beams from Laser Plasma Accelerators

    SciTech Connect

    Matlis, N. H.; Bakeman, M.; Geddes, C. G. R.; Gonsalves, T.; Lin, C.; Nakamura, K.; Osterhoff, J.; Plateau, G. R.; Schroeder, C. B.; Shiraishi, S.; Sokollik, T.; van Tilborg, J.; Toth, Cs.; Leemans, W. P.

    2010-06-01

    We present an overview of diagnostic techniques for measuring key parameters of electron bunches from Laser Plasma Accelerators (LPAs). The diagnostics presented here were chosen because they highlight the unique advantages (e.g., diverse forms of electromagnetic emission) and difficulties (e.g., shot-to-shot variability) associated with LPAs. Non destructiveness and high resolution (in space and time and energy) are key attributes that enable the formation of a comprehensive suite of simultaneous diagnostics which are necessary for the full characterization of the ultrashort, but highly-variable electron bunches from LPAs.

  18. Plasma modeling in an electron-cyclotron-resonance ion source

    SciTech Connect

    Pesic, S.; Vukovic, M. (Institute for Research in Physics, Boris Kidric'' Institute, P.O. Box 522, 11001 Beograd (Yugoslavia))

    1990-09-15

    Modeling calculations of an electron-cyclotron-resonance ion source (ECRIS) are presented. The adopted model is described through an analysis of the impact of ECR heating, transport, and atomic-collision processes on the particle balance in an ECRIS. On the basis of the obtained numerical results, general relationships among externally controllable parameters, and plasma and ion-beam characteristics are derived. Comparison with experimental results that use the electron energy as the only fitting parameter supports the applied model. The predicted general trends provide some basis for future experiments.

  19. Laser driven electron acceleration in vacuum, gases and plasmas

    SciTech Connect

    Sprangle, P.; Esarey, E.; Krall, J.

    1996-04-19

    This paper discusses some of the important issues pertaining to laser acceleration in vacuum, neutral gases and plasmas. The limitations of laser vacuum acceleration as they relate to electron slippage, laser diffraction, material damage and electron aperture effects, are discussed. An inverse Cherenkov laser acceleration configuration is presented in which a laser beam is self guided in a partially ionized gas. Optical self guiding is the result of a balance between the nonlinear self focusing properties of neutral gases and the diffraction effects of ionization. The stability of self guided beams is analyzed and discussed. In addition, aspects of the laser wakefield accelerator are presented and laser driven accelerator experiments are briefly discussed.

  20. Helicity Injection by Knotted Antennas into Electron Magnetohydrodynamical Plasmas

    Microsoft Academic Search

    C. L. Rousculp; R. L. Stenzel

    1997-01-01

    A fully three-dimensional computer simulation of an ideal electron magnetohydrodynamical plasma is performed. By introducing various pulsed inductive antenna sources, magnetic helicity ( H = A˙B dV) injection is studied. Confirming experimental results, a simple loop provides no net helicity injection. Linked and knotted antennas, however, do inject helicity and preferentially radiate whistler wave packets parallel or antiparallel to the

  1. Modulation of continuous electron beams in plasma wake-fields

    SciTech Connect

    Rosenzweig, J.B.

    1988-09-08

    In this paper we discuss the interaction of a continuous electron beam with wake-field generated plasma waves. Using a one-dimensional two fluid model, a fully nonlinear analytical description of the interaction is obtained. The phenomena of continuous beam modulation and wave period shortening are discussed. The relationship between these effects and the two-stream instability is also examined. 12 refs., 1 fig.

  2. Electron temperature measurements in an argon\\/cesium plasma diode

    Microsoft Academic Search

    Michael J. Ward

    1987-01-01

    Line intensity measurements in an argon\\/cesium plasma diode were made at various locations within the discharge, yielding a spatially resolved electron temperature distribution. This device operated at 0.9 Torr argon, 0.04 Torr cesium, and at a current density of 1.05 mA\\/sq cm. Observations of the spectral line intensities of the 6P greater than nS and 6P greater than nD transitions

  3. Electron density determination of aluminium laser-induced plasma

    NASA Astrophysics Data System (ADS)

    Surmick, D. M.; Parigger, C. G.

    2015-06-01

    We present temporally and spatially resolved electron density results of laser-induced plasma initiated on the surface of an aluminium target. Aluminium 394.4 and 396.15 nm lines were fit to Lorentzian profiles to evaluate Stark widths and shifts. Experimentally determined electron density versus line width and shift relationships were applied. Fitting to the aluminium lines indicates an electron density of 1.9 ± 0.2 and 3.2+/- 0.4× {{10}18} c{{m}-3} for Stark widths and 1.7 ± 0.5 and 1.7+/- 0.5× {{10}18} c{{m}-3} for Stark shifts at a 0.3 ?s time delay following plasma initiation for the aluminium Al i 394.4 and 396.15 nm transitions, respectively. Simultaneous observations of the singly ionized nitrogen line, N ii, at 395.5 nm were also fit for a time delay of 0.2 ?s, indicating an electron density of 1.8+/- 1.0× {{10}18} c{{m}-3}. The differences between the nitrogen and aluminium electron densities show evidence of self absorption.

  4. Temperature diagnostics of ECR plasma by measurement of electron bremsstrahlung.

    PubMed

    Kasthurirangan, S; Agnihotri, A N; Desai, C A; Tribedi, L C

    2012-07-01

    The x-ray bremsstrahlung spectrum emitted by the electron population in a 14.5 GHz ECR plasma source has been measured using a NaI(Tl) detector, and hence the electron temperature of the higher energy electron population in the plasma has been determined. The x-ray spectra for Ne and Ar gases have been systematically studied as a function of inlet gas pressure from 7 × 10(-7) mbar to 7 × 10(-5) mbar and for input microwave power ?1 W to ?300 W. At the highest input power and optimum pressure conditions, the end point bremsstrahlung energies are seen to reach ?700 keV. The estimated electron temperatures (T(e)) were found to be in the range 20 keV-80 keV. The T(e) is found to be peaking at a pressure of 1 × 10(-5) mbar for both gases. The T(e) is seen to increase with increasing input power in the intermediate power region, i.e., between 100 and 200 W, but shows different behaviour for different gases in the low and high power regions. Both gases show very weak dependence of electron temperature on inlet gas pressure, but the trends in each gas are different. PMID:22852675

  5. Ion boundary conditions in semi-infinite fluid models of electron beam-plasma interaction

    SciTech Connect

    Levko, Dmitry [LAPLACE (Laboratoire Plasma et Conversion d'Energie), Universite de Toulouse, UPS, INPT Toulouse, 118 route de Narbonne, F-31062 Toulouse cedex 9 (France)

    2014-10-15

    The modified Bohm criterion is derived for the plasma consisting of the monoenergetic electron beam and thermal electrons. This criterion allows us to define the accurate ion boundary conditions for semi-infinite collisionless fluid models of electron beam–plasma interaction. In the absence of electron beam, these boundary conditions give the classical sheath parameters. When the monoenergetic electron beam propagates through the plasma, the fluid model with proposed boundary conditions gives the results, which are in qualitative agreement with the results obtained earlier in M. Sharifian and B. Shokri, Phys. Plasmas 14, 093503 (2007). However, dynamics and parameters of the plasma sheath are different.

  6. Spatial measurements of electron energy distribution and plasma parameters in a weakly magnetized inductive discharge

    SciTech Connect

    Kim, Young-Do; Lee, Young-Kwang; Lee, Hyo-Chang; Chung, Chin-Wook [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

    2013-02-15

    Spatial characteristics of plasma parameters such as electron temperature, plasma density, plasma potential, and electron energy distribution (EED) were studied in inductively coupled plasma with an axial dc magnetic field. With dc magnetic field, the measured EEDs in the total electron energy scale are spatially coincided except cutting of the low electron energy part indicating the conserved non-local electron kinetics in an axial direction, even though the dc magnetic field is applied. Spatial distributions of the plasma densities at axial positions have almost same trends with various magnetic field strengths. We also discuss the reduction of the ambipolar potential along the axial direction as the applied magnetic field increased.

  7. Thin current sheets in the Jovian magnetotail

    NASA Astrophysics Data System (ADS)

    Artemyev, A. V.; Vasko, I. Y.; Kasahara, S.

    2014-06-01

    In this paper we investigate the fine structure of the current sheet located at the dawn side (and the central region) of the Jovian magnetotail (magnetodisk). We consider observational data collected by Galileo spacecraft (our dataset includes 226 current sheet crossings). Measurements of spectra of electric field fluctuations allow us to estimate the electron density. The plasma temperature is estimated from the vertical stress balance in the current sheet. To determine the vertical structure of the current sheet we use magnetic field measurements and the model of the neutral plane vertical motion. The current sheet vertical structure includes two spatial scales: the thin current sheet with the thickness around two Larmor radii of thermal sulfur ions is embedded into the thick current sheet with the thickness around one Jupiter radius, RJ. The vertical stress balance in the thin current sheet can be partially supported by the local maximum of the shear magnetic field. The amplitude of the corresponding field-aligned current density is comparable with the amplitude of the total current density. The drop of the plasma (electron) density across the thick current sheet is about 50-80% of the density peak value. We investigate horizontal (along the tail) distributions of magnetic field amplitudes B0 measured at the boundary of the current sheet and magnitudes of the normal component measured in the vicinity of the central region, Bn0. For r>50RJ both B0 and Bn0 vary with the radial distance r as ~r-1, and the ratio Bn0/B0~0.05-0.2 is almost constant along the tail (up to 120RJ). The amplitude of the current density jm0 and the plasma (electron) density (averaged across the current sheet) decrease with the same rate ~r-1. Thus, the current bulk velocity vD=jm0/e?100 km/s is almost constant along the tail. We compare properties of the Jovian magnetotail current sheet with the corresponding properties of current sheets observed in the Earth's magnetotail. Current sheet (CS) in the Jupiter magnetotail has been investigated. The magnetotail includes thin CS (thickness <0.25RJ) and thick CS (thickness ~1RJ). Thin CS thickness is only about two Larmor radius of thermal sulfur ions. Current density in thin CS cannot be described by diamagnetic currents.

  8. Spatial distributions of ion pitch angle anisotropy in the near-Earth magnetosphere and tail plasma sheet

    NASA Astrophysics Data System (ADS)

    Wang, Chih-Ping; Zaharia, Sorin G.; Lyons, Larry R.; Angelopoulos, Vassilis

    2013-01-01

    We have quantified anisotropy of ion pitch angle distributions observed by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft and determined statistically how anisotropy varies with particle energy, as well as spatial distributions and dependences on geomagnetic activity. In the tail plasma sheet, ions from a few keV to a few tens of keV are mostly isotropic. The locations and energy ranges for these isotropic ions and their changes with Dst are consistent with ions being isotropized by current sheet scattering predicted using empirical magnetic field models. Ions of a few hundreds of keV in the tail have cigar-shaped or unidirectional pitch angle distribution (PAD) and are likely a result of Speiser motion. The majority of ions in the near-Earth magnetosphere are expected to conserve their first and second adiabatic invariants as they move with pitch angle dependent drift. This gives drift shell splitting, which plays an important role in generating pancake-shaped PAD observed from ~1 keV up to hundreds of keV. The magnetic local time of the pancake PAD rotates with increasing energy. Loss of near 90° ions due to magnetopause shadowing can further explain the butterfly-shaped PAD observed at the postmidnight sector at energies above 30 keV. For ions below a few hundreds of eV in the tail plasma sheet and the near-Earth magnetosphere, their PAD is dominantly bidirectional, which is likely due to ionosphere outflow. High-energy ions on the dayside become less anisotropic during higher AE, when pitch angle scattering by electromagnetic ion cyclotron waves may play an important role.

  9. Fast electron studies in the ZT-40M edge plasma

    SciTech Connect

    Ingraham, J.C.; Ellis, R.F.; Downing, J.N.; Miller, G.; Munson, C.P.; Pickrell, M.M.; Schoenberg, K.F.; Weber, P.G.; Wurden, G.A.

    1990-01-01

    Measurements of the edge plasma on the ZT-40M Reversed Field Pinch (RFP) show the presence of a dilute (1 to 10 per cent of the edge density), fast (T{sub H} {approx equal} (2 {minus} 3)T{sub {epsilon}0}) electron tail with a nearly unidirectional flow along B in a toroidal sense that is against the external applied electric field force. These studies have been extended over a wide range of operating conditions including high density and krypton-injected radiation-dominated (P{sub RAD} {approx equal} 0.9 P{sub IN}) discharges. In all cases the current density of the fast electrons is sufficient to account for the current density required to maintain the RFP. For low current 60 kA discharges this result has been confirmed in to a depth 20 mm inside of the reversal surface suggesting that the source of the fast electrons is the core of the discharge. The fast electrons also carry a large power flux parallel to B (several hundreds of MW/m{sup 2}, typically), and radial transport measurements of the fast electrons in the shadow of a movable limiter for 120 kA standard discharges indicate that the fast electrons are the primary electron energy loss channel. The fast electrons are a significant energy loss channel for a broad range of other cases as well. The collisionality of the fast electrons varies widely over the range of cases studied and it is noted that a small backflowing component of fast electrons increases in relative size as the collisionality increases. An estimate of the magnetic field stochastic diffusivity at the edge is made from the fast electron limiter shadow measurements and shows that the stochasticity of the magnetic field is low at the edge relative to the core, in agreement with magnetic fluctuation diffusivity measurements and MHD simulations. 35 refs., 10 figs.

  10. Two-plane focusing of high-space-charge sheet electron beams using periodically cusped magnetic fields

    NASA Astrophysics Data System (ADS)

    Basten, M. A.; Booske, J. H.

    1999-05-01

    Numerical and theoretical analyses show that stable, two-plane focusing of finite width, elliptical cross section, sheet electron beams with high space charge (low voltage, high current density) can be accomplished using periodically cusped-magnetic (PCM) fields. Magnetic field strength requirements for focusing high-space-charge sheet beams are within technological capabilities of modern permanent magnet technology. Both an offset-pole PCM stack and a PCM stack combined with a periodic quadrupole magnet (PQM) edge array are shown to be effective for two-plane sheet beam confinement. The PCM-PQM hybrid configuration offers inherent advantages for independent adjustment of confinement fields to achieve beam matching (minimum ripple) in both transverse dimensions. The offset-pole configuration offers the advantage of open-side access for applications such as vacuum electronic microwave devices. It is also shown that PCM-focused sheet beam envelope stability obeys criteria equivalent to that previously identified for round-cross-section electron beams in periodic permanent magnet focusing.

  11. Bernstein-Greene-Kruskal electron solitary waves in collisionless plasmas

    NASA Astrophysics Data System (ADS)

    Chen, Li-Jen

    2002-07-01

    In this thesis, the theory of one-dimensional Berstein- Greene-Kruskal (BGK) electron solitary waves has been studied and extended to three dimensions. We find that the positive core of a 1D BGK electron solitary wave is screened by electrons trapped and oscillating inside the solitary wave potential, and not achieved by the thermal screening from ambient electrons as previously thought. An important consequence of this new finding is that the size of 1D BGK electron solitary waves need not be larger than the Debye length. Another finding is that the relationship between the solitary potential amplitude and width is governed by an inequality rather than an equality. This inequality resolves the discrepancy in the width-amplitude relations found earlier by Turikov [1] and Schamel [2]. The extension to three-dimensional space is accomplished by incorporating three-dimensional electric interaction for magnetized plasmas assuming the gyroradii of electrons are much smaller than all other relevant scale lengths. This permits us to construct azimuthally symmetric BGK electron solitary waves. The solutions here predict that the size of the azimuthally symmetric solitary waves can be smaller than one Debye length (as in the 1D case), and show that the solitary waves with Gaussian potentials have to be either spherical or elongated along the magnetic field. For both the spherical and parallel elongated cases, the relationship between the scale sizes and the potential amplitude is of an inequality type. The inequality indicates that the parallel width-amplitude relation depends on the perpendicular size. This dependence, together with observational data, can yield an estimate of the typical perpendicular size of the observed solitary waves, and an estimate of the amount of electrostatic energy that is transported by the solitary waves. The last theory developed in this thesis concerns the 3D solitary waves in unmagnetized plasmas. This theory is relevant for plasmas in vanishing magnetic fields or in field reversal regions where the magnetic field is zero. We open both the velocity and position space to 3D, and solve the Vlasov-Poisson equations. We find that positive-potential pulse solitary wave solutions do exist, but there does not exist a physical parameter range for the solutions to be physical. The non-existence of a physical solution is attributed to the collisionless screening processes in 3D plasmas.

  12. Laser Thomson scattering measurements of electron properties in glow discharge plasmas

    Microsoft Academic Search

    K. Muraoka

    1999-01-01

    Thomson scattering is a technique to send a powerful laser into plasmas, and detect scattered spectra and their intensities to yield electron properties, such as electron density and electron temperature (or, more generally, electron energy distribution functions, EEDF). Until recently, the main area of its application has been to high density plasmas, with density of above 1018 m3 for fusion

  13. Development of Plasma Electron Guns to Produce Narrow Focusing Beams Under the Higher Operation Pressure

    Microsoft Academic Search

    V. Burdovitsin; M. Eroshkin; I. Osipov; N. Rempe; I. Zhirkov; E. Oks

    2005-01-01

    Summary form only given. One of the main advantages of the plasma cathode electron guns is its ability to produce electron beam under the higher operation pressure up to fore-pump pressure range. Present work is devoted to plasma electron guns that were designed especially to generate narrow focusing electron beams under the high pressure. To produce narrow focusing beam two

  14. CURRENT SHEET REGULATION OF SOLAR NEAR-RELATIVISTIC ELECTRON INJECTION HISTORIES

    SciTech Connect

    Agueda, N.; Sanahuja, B. [Departament d'Astronomia i Meteorologia, Institut de Ciencies del Cosmos, Universitat de Barcelona (Spain); Vainio, R. [Department of Physics, University of Helsinki (Finland); Dalla, S. [Jeremiah Horrocks Institute, University of Central Lancashire (United Kingdom); Lario, D. [Applied Physics Laboratory, Johns Hopkins University (United States)

    2013-03-10

    We present a sample of three large near-relativistic (>50 keV) electron events observed in 2001 by both the ACE and the Ulysses spacecraft, when Ulysses was at high-northern latitudes (>60 Degree-Sign ) and close to 2 AU. Despite the large latitudinal distance between the two spacecraft, electrons injected near the Sun reached both heliospheric locations. All three events were associated with large solar flares, strong decametric type II radio bursts and accompanied by wide (>212 Degree-Sign ) and fast (>1400 km s{sup -1}) coronal mass ejections (CMEs). We use advanced interplanetary transport simulations and make use of the directional intensities observed in situ by the spacecraft to infer the electron injection profile close to the Sun and the interplanetary transport conditions at both low and high latitudes. For the three selected events, we find similar interplanetary transport conditions at different heliolatitudes for a given event, with values of the mean free path ranging from 0.04 AU to 0.27 AU. We find differences in the injection profiles inferred for each spacecraft. We investigate the role that sector boundaries of the heliospheric current sheet (HCS) have on determining the characteristics of the electron injection profiles. Extended injection profiles, associated with coronal shocks, are found if the magnetic footpoints of the spacecraft lay in the same magnetic sector as the associated flare, while intermittent sparse injection episodes appear when the spacecraft footpoints are in the opposite sector or a wrap in the HCS bounded the CME structure.

  15. Relativistic warm plasma theory of nonlinear laser-driven electron plasma waves

    SciTech Connect

    Schroeder, Carl B.; Esarey, Eric

    2010-06-30

    A relativistic, warm fluid model of a nonequilibrium, collisionless plasma is developed and applied to examine nonlinear Langmuir waves excited by relativistically-intense, short-pulse lasers. Closure of the covariant fluid theory is obtained via an asymptotic expansion assuming a non-relativistic plasma temperature. The momentum spread is calculated in the presence of an intense laser field and shown to be intrinsically anisotropic. Coupling between the transverse and longitudinal momentum variances is enabled by the laser field. A generalized dispersion relation is derived for langmuir waves in a thermal plasma in the presence of an intense laser field. Including thermal fluctuations in three velocity-space dimensions, the properties of the nonlinear electron plasma wave, such as the plasma temperature evolution and nonlinear wavelength, are examined, and the maximum amplitude of the nonlinear oscillation is derived. The presence of a relativistically intense laser pulse is shown to strongly influence the maximum plasma wave amplitude for non-relativistic phase velocities owing to the coupling between the longitudinal and transverse momentum variances.

  16. Relativistic modulational instability of electron-acoustic waves in an electron-pair ion plasma

    SciTech Connect

    Misra, A. P. [Department of Mathematics, Siksha Bhavana, Visva-Bharati University, Santiniketan-731 235 (India); Shukla, P. K. [Institut fuer Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultaet fuer Physik and Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum, Germany and School of Physics, University of KwaZulu-Natal, 4000 Durban (South Africa)

    2008-12-15

    The modulational instability of finite amplitude electron-acoustic waves (EAWs) along the external magnetic field is studied in an electron-pair ion plasma. Accounting for the relativistic electron mass variation nonlinearity and the Boltzmann distribution of both positive and negative ions, new regimes for the relativistic modulational instability (MI) for the low frequency (below the electron gyrofrequency) short-wavelength (in comparison with the ion gyroradius) modes are obtained numerically. It is found that the presence of a significant fraction of negative ions suppresses the MI growth/decay rate for the modulated EAW packets. The results could be of important for understanding the origin of amplitude modulated EAW packets in space (e.g., Earth's magnetotail) as well as in laboratory plasmas.

  17. Electron Heating in a Relativistic, Weibel-unstable Plasma

    NASA Astrophysics Data System (ADS)

    Kumar, Rahul; Eichler, David; Gedalin, Michael

    2015-06-01

    The dynamics of two initially unmagnetized relativistic counter-streaming homogeneous ion–electron plasma beams are simulated in two dimensions (2D) using the particle-in-cell (PIC) method. It is shown that current filaments, which form due to the Weibel instability, develop a large-scale longitudinal electric field in the direction opposite to the current carried by the filaments as predicted by theory. This field, which is partially inductive and partially electrostatic, is identified as the main source of net electron acceleration, greatly exceeding that due to magnetic field decay at later stages. The transverse electric field, although larger than the longitudinal field, is shown to play a smaller role in heating electrons, contrary to previous claims. It is found that in one dimension, the electrons become strongly magnetized and are not accelerated beyond their initial kinetic energy. Rather, the heating of the electrons is enhanced by the bending and break up of the filaments, which releases electrons that would otherwise be trapped within a single filament and slow the development of the Weibel instability (i.e., the magnetic field growth) via induction as per Lenz’s law. In 2D simulations, electrons are heated to about one quarter of the initial kinetic energy of ions. The magnetic energy at maximum is about 4%, decaying to less than 1% by the end of the simulation. The ions are found to gradually decelerate until the end of the simulation, by which time they retain a residual anisotropy of less than 10%.

  18. Basic theoretical formulation of plasma microwave electronics. II. Kinetic theory of electron beam-wave interactions

    Microsoft Academic Search

    Shenggang Liu; Robert J. Barker; Yung Yan; Dajun Zhu

    2000-01-01

    For pt.I see ibid., vol.28, no.6, p.2135-51 (2000) Building upon the theoretical foundations presented in Part I of this paper, the kinetic theory of electron-beam-wave interactions in a magnetized plasma-filled waveguide (MPW) is presented in this second part. This kinetic theory treatment is more generally applicable to cases of less-intense electron-beams (Montgomery and Tidman, 1964). The dispersion relations for longitudinal

  19. Enhanced electron field emission from plasma-nitrogenated carbon nanotips

    SciTech Connect

    Wang, B. B. [College of Chemistry and Chemical Engineering, Chongqing University of Technology, 69 Hongguang Rd, Lijiatuo, Banan District, Chongqing 400054 (China); Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P. O. Box 218, Lindfield, NSW 2070 (Australia); Cheng, Q. J.; Ostrikov, K. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P. O. Box 218, Lindfield, NSW 2070 (Australia); Plasma Nanoscience, Complex Systems, School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia); Zhong, X. X. [Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China); Wang, Y. Q. [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Chen, Y. A. [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China)

    2012-02-15

    Nitrogenated carbon nanotips (NCNTPs) are synthesized by plasma-enhanced hot filament chemical vapor deposition from the hydrogen, methane, and nitrogen gas mixtures with different flow rate ratios of hydrogen to nitrogen. The morphological, structural, compositional, and electron field emission (EFE) properties of the NCNTPs were investigated by field emission scanning electron microscopy, Raman spectroscopy, x ray photoelectron spectroscopy, and EFE high-vacuum system. It is shown that the NCNTPs deposited at an intermediate flow rate ratio of hydrogen to nitrogen feature the best size/shape and pattern uniformity, the highest nanotip density, the highest nitrogen concentration, as well as the best electron field emission performance. Several factors that come into play along with the nitrogen incorporation, such as the combined effect of the plasma sputtering and etching, the transition of sp{sup 3} carbon clusters to sp{sup 2} carbon clusters, the increase of the size of the sp{sup 2} clusters, as well as the reduction of the work function, have been examined to interpret these experimental findings. Our results are highly relevant to the development of the next generation electron field emitters, flat panel displays, atomic force microscope probes, and several other advanced applications.

  20. Localized electron heating and density peaking in downstream helicon plasma

    NASA Astrophysics Data System (ADS)

    Ghosh, Soumen; Barada, K. K.; Chattopadhyay, P. K.; Ghosh, J.; Bora, D.

    2015-06-01

    Localized electron temperature and density peaking at different axial locations in the downstream helicon plasma have been observed in a linear helicon device with both geometrical and magnetic expansion. The discharge is produced with an m=+1 right helical antenna powered by a RF source operating at 13.56 MHz. Axial wave field measurement shows the presence of damped helicon waves with standing wave character folded into it even at low densities (? {{10}16} m-3 ). The measured helicon wavelength is just about twice the antenna length and the phase velocity ?ft({{v}p}\\right) is almost the speed required for electron impact ionization. These experimental observations strongly advocate the Landau damping heating and density production by the helicon waves, particularly in low density plasma such as ours. The electron temperature maximizes at 35–45?cm away from the antenna center in our experiments indicating a local source of heating at those locations. Different mechanisms responsible for this additional heating at a particular spatial location have been discussed for their possible roles. Further downstream from the location of the maximum electron temperature, a density peak located 55–65?cm away from the antenna is observed. This downstream density peaking can be explained through pressure balance in the system.

  1. Electron density measurements in a slot antenna microwave plasma source by means of the plasma oscillation method

    NASA Astrophysics Data System (ADS)

    Schwabedissen, A.; Soll, C.; Brockhaus, A.; Engemann, J.

    1999-08-01

    The absolute electron density in the downstream region of a 2.45 GHz microwave plasma source has been measured by the plasma oscillation method. In the plasma oscillation method a weak electron beam injected into the plasma excites electrostatic electron waves oscillating at the electron plasma frequency, which is proportional to the square root of the electron density. The plasma source is a slot antenna (SLAN) type, that is the microwave power is coupled from a ring resonator through equidistantly positioned resonant coupling slots into the plasma chamber which is made of quartz. The results of the plasma oscillation method are compared with the results of single and double Langmuir probe (LP) measurements. In Ar and Ar:O2 mixtures reasonable agreement between the two diagnostic methods is found. However, in depositing plasmas traditional LPs cannot be used with confidence. We studied Ar:O2 gas mixtures with hexamethyldisiloxane (HMDSO) added downstream for the deposition of quartz-like films. We found that even a small amount of HMDSO in the gas mixture leads to erroneous LP measurements due to probe surface coating, while the plasma oscillation method is still applicable here.

  2. Directional velocity analyzer for measuring electron distribution functions in plasmas

    SciTech Connect

    Stenzel, R.L.; Gekelman, W.; Wild, N.; Urrutia, J.M.; Whelan, D.

    1983-10-01

    A directional velocity analyzer has been developed for measuring electron distribution functions in plasmas. It contains a collimating aperture which selects particles from a narrow cone in velocity space and a retarding potential analyzer. The distribution function f(v, theta, phi) is obtained from a large number of analyzer traces taken at different angles theta, phi. In addition, the small analyzer can be moved in space and the measurements are time resolved so as to obtain the complete phase space information f (v, r, t). The large data flow of this seven-variable function is processed with a high-speed digital data-acquisition system. The new electron velocity analyzer is applicable over a wide parameter range in electron energies and densities. Various cases of anisotropic distributions such as beams, shells, tails, and drifts have been successfully investigated.

  3. Directional velocity analyzer for measuring electron distribution functions in plasmas

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.; Gekelman, W.; Wild, N.; Urrutia, J. M.; Whelan, D.

    1983-01-01

    A directional velocity analyzer has been developed for measuring electron distribution functions in plasmas. It contains a collimating aperture which selects particles from a narrow cone in velocity space and a retarding potential analyzer. The distribution function f(v, theta, phi) is obtained from a large number of analyzer traces taken at different angles theta, phi. In addition, the small analyzer can be moved in space and the measurements are time resolved so as to obtain the complete phase space information f(v,r,t). The large data flow of this seven-variable function is processed with a high-speed digital data-acquisition system. The new electron velocity analyzer is applicable over a wide parameter range in electron energies and densities. Various cases of anisotropic distributions such as beams, shells, tails, and drifts have been successfully investigated.

  4. Effect of suprathermal electrons on the intensity and Doppler frequency of electron plasma lines

    Microsoft Academic Search

    P. Guio; J. Lilensten

    1999-01-01

    In an incoherent scattering radar experiment, the spectral measurement of the so-called up- and downshifted electron plasma lines provides information about their intensity and their Doppler frequency. These two spectral lines correspond, in the backscatter geometry, to two Langmuir waves travelling towards and away from the radar. In the daytime ionosphere, the presence of a small percentage of photoelectrons produced

  5. Eect of suprathermal electrons on the intensity and Doppler frequency of electron plasma lines

    E-print Network

    Paris-Sud XI, Université de

    and coronal holes. Furthermore, we see that what would have been interpreted as a mean Doppler drift velocity. In the daytime ionosphere, the presence of a small percentage of photoelectrons produced by the solar EUV-electrons also modi®es the dielectric response function of the plasma from the Maxwellian and thus in

  6. Microwave heating of electrons of a dense plasma column at frequencies higher than electron cyclotron frequency

    Microsoft Academic Search

    J. ?atlov; R. Klíma; L. Kryška; V. N. Budnikov; O. N. Scherbinin

    1973-01-01

    In the overdense collisionless plasma column inserted through the narrow sides of a rectangular waveguide, the excited electron cyclotron harmonic waves (CHWs) are studied by means of two movable probes and a phase interferometer in the range of parameters of 2 >?\\/?ce>1; 0·5 ?pe\\/?)2 < 15.

  7. Microwave free-electron laser applications for electron cyclotron heating of plasmas

    SciTech Connect

    Thomassen, K.I.

    1990-01-01

    Millimeter wave power may be the ideal source of heat for a plasma, but advances in technology are needed to meet requirements of next generation fusion devices. Free electron lasers (FEL) are one candidate for such sources, and this paper reviews the progress, issues of physics and technology, and potential benefits for fusion from these devices. 15 refs., 13 figs.

  8. Determining electron temperature and electron density in moderate pressure H2/CH4 microwave plasma

    NASA Astrophysics Data System (ADS)

    Derkaoui, N.; Rond, C.; Gries, T.; Henrion, G.; Gicquel, A.

    2014-05-01

    The electron temperature and electron density are measured in a microwave (MW) plasma-assisted chemical vapour diamond deposition reactor for different experimental conditions by varying the substrate temperature, methane content and MW power density. Optical emission spectroscopy (OES) and MW interferometry are used to probe the discharge generated in a stainless steel resonant cavity excited at a frequency of 2.45 GHz. Changing the substrate temperature from 630 to 900 °C does not show any significant influence on the electron temperature or on the electron density. Increasing the methane content from 0 to 10% does not lead to any modification of the electron temperature or density. However between 10% and 20% CH, a decrease of the electron density is observed which may be attributed to soot particle formation. The electron density increases in the range of (1.2-10) × 1011 cm-3 from moderate power density conditions (50 hPa/1000 W) to high power density conditions (250 hPa/3500 W). OES measurements show that the electron temperature exhibits a flat axial profile in the plasma bulk and ranges from 14?000 K at (25 hPa/600 W) to 10 500 K at (400 hPa/3000 W).

  9. Self-Similar Decay of Enstrophy in an Electron Plasma

    NASA Astrophysics Data System (ADS)

    Rodgers, Douglas; Servidio, Sergio; Matthaeus, William; Mitchell, Travis

    2009-11-01

    The similarity solution for energy decay in 3D hydrodynamic turbulence, due to Taylor and von Karman [1], based on the self preservation hypothesis for the shape of the two point correlation, implies that the energy E decays as dE/dt = - a Z^3/L, where a is a constant, Z is the turbulence amplitude and L is a similarity length scale. Extensions of this idea to MHD [2] have been of great utility in solar wind and coronal heating studies. While the hydrodynamic case is well studied experimentally, we are not aware that similarity decay has been examined in a laboratory plasma. Here we conduct an experimental study of this idea in the context of two dimensional electron plasma turbulence. Specifically, we propose an expression for the decay of enstrophy of a single-signed-vorticity fluid which is analogous to the von Karman decay of energy in 3D turbulence, and compare this to the dynamical relaxation of a pure electron plasma in a Malmberg-Penning (MP) trap [3]. Results show good agreement between the proposed decay law and the MP experiments. [1] G. I. Taylor, Proc. Roy. Soc. Lon. A, 151:421, 1935; T. de Karman and L. Howarth, Proc. Roy. Soc. Lon. A, 164:192, 1938. [2] W. H. Matthaeus, G. P. Zank and S. Oughton. J. Plas. Phys., 56:659, 1996. [3] D. J. Rodgers et al, Phys. Rev. Lett., 102(24):244501, 2009.

  10. Relativistic, perpendicular shocks in electron-positron plasmas

    NASA Technical Reports Server (NTRS)

    Gallant, Yves A.; Hoshino, Masahiro; Langdon, A. B.; Arons, Jonathan; Max, Claire E.

    1992-01-01

    One-dimensional particle-in-cell plasma simulations are used to examine the mechanical structure and thermalization properties of collisionless relativistic shock waves in electron-positron plasmas. Shocks propagating perpendicularly to the magnetic field direction are considered. It is shown that these shock waves exist, and that they are completely parameterized by the ratio of the upstream Poynting flux to the upstream kinetic energy flux. The way in which the Rankine-Hugoniot shock jump conditions are modified by the presence of wave fluctuations is shown, and they are used to provide a macroscopic description of these collisionless shock flows. The results of a 2D simulation that demonstrates the generality of these results beyond the assumption of the 1D case are discussed. It is suggested that the thermalization mechanism is the formation of a synchrotron maser by the coherently reflected particles in the shock front. Because the downstream medium is thermalized, it is argued that perpendicular shocks in pure electron-positron plasmas are not candidates as nonthermal particle accelerators.

  11. Wakefields generated by collisional neutrinos in neutral-electron-positron plasma

    SciTech Connect

    Tinakiche, Nouara [Faculty of Physics, U.S.T.H.B., Algiers 16111 (Algeria)

    2013-02-15

    A classical fluid description is adopted to investigate nonlinear interaction between an electron-type neutrino beam and a relativistic collisionless unmagnetized neutral-electron-positron plasma. In this work, we consider the collisions of the neutrinos with neutrals in the plasma and study their effect on the generation of wakefields in this plasma.

  12. A Parametric Study of Electron Extraction from a Low Frequency Inductively Coupled RF-Plasma Source

    E-print Network

    A Parametric Study of Electron Extraction from a Low Frequency Inductively Coupled RF-Plasma Source: The electron extraction from a low-frequency (2 MHz) inductively-coupled rf-plasma cathode is characterized and Nathaniel J. Fisch 3 Princeton University Plasma Physics Laboratory, Princeton, NJ 08540, USA Abstract

  13. Electron Impact Ionization of Molecules for Plasma Processing

    NASA Astrophysics Data System (ADS)

    Schmidt, Martin

    1999-10-01

    Plasma processing is successfully used in plasma etching, thin film deposition, surface cleaning and surface treatment. One fundamental process in low temperature plasmas is the electron impact ionization of molecules and atoms. This report deals with the methods and results of measurements of the partial and total ionization cross sections of precursor molecules used in plasma etching (halocarbons, fluorine-bearing compounds: CF_4, C_2F_6, NF_3) and thin film deposition (silicon-bearing compounds SiH_4, Si(CH_3)_4, Si(OC_2H_5)_4, Si_2O(CH_3)6 and metal-containing compounds TiCl_4, (C_5H_5)Pt(CH_3)_3, (CH_3C_5H_4)_2Fe, (CH_3C_5H_4)_2Ru). The measurement of partial ionization cross sections requires the application of mass spectrometry (or some other means of mass selection). Here results received with a double focussing E-B mass spectrometer and with a time-of-flight instrument are presented. The influence of kinetic excess energies of the fragment ions and of pyrolytic decomposition of the target gas on the cross section measurements are discussed. A short review of cross section measurements of free radicals with the fast-beam-technique is given. The results are compared with calculations of the total ionization cross section using additivity rules, semi-classical and semi-empirical formulae, and the BEB method. note

  14. Comparing Different Models for Fast Earthward Flows in the Magnetotail: Moving Flux Ropes, Unsteady Reconnection, Pressure-Depleted Plasma Bubbles, and Atypical Currents Sheets

    NASA Astrophysics Data System (ADS)

    Sitnov, M. I.; Runov, A. V.; Ohtani, S.

    2007-12-01

    The physics of fast earthward flows or BBFs, a major mechanism of bursty transfer of the plasma and magnetic flux in the terrestrial magnetotail, remains uncertain and controversial. A part of observations can be explained as signatures of earthward moving flux ropes or secondary plasmoids dragged by the earthward part a larger-scale reconnection region [Slavin et al., 2003]. The statistics of variations of the z-component of the magnetospheric magnetic field in the central plasma sheet [Ohtani et al., 2004] suggest no changes of the magnetic field topology for another group of BBFs. These observations can be explained as signatures of either unsteady reconnection, which remains located tailward of the spacecraft, or other phenomena that are connected but not identical to reconnection in its active phase. These are the plasma bubbles, flux tubes with the reduced specific entropy that may move earthward faster than the neighboring flux tubes due to the buoyancy force. However, the original model of bubbles arising from local reductions of the plasma pressure [Pontius and Wolf, 1990] also explains only a part of observations. Another part [Angelopoulos et al., 1992] reveals no reduction of the plasma pressure in BBFs. One more model, which explains both missing magnetic topology changes and no reduction of the plasma pressure [Sitnov et al., 2005] describes the bubble as a seam in the body of the tail plasma, which appears after the formation and tailward retreat of a small plasmoid, and which is composed of atypical, embedded and bifurcated thin current sheets. Signatures of such atypical current sheets have been convincingly demonstrated recently in CLUSTER observations [Runov et al., 2003]. In this presentation we elaborate the BBF models and compare them with 2001 and 2002 tail CLUSTER observations in the central plasma sheet. These include full-particle simulations of the secondary plasmoid formation in tail-like systems, two- and three- dimensional features and dynamical properties of atypical current sheets that constitute plasma bubbles. Comparison with data is focused on the distinction between plasma flows moving in the earthward part of a neutral line (which may be both stable and moving earthward or tailward) and similar motions of plasma and magnetic field structures associated with plasma bubbles.

  15. Beam loading by electrons in nonlinear plasma wakesa)

    NASA Astrophysics Data System (ADS)

    Tzoufras, M.; Lu, W.; Tsung, F. S.; Huang, C.; Mori, W. B.; Katsouleas, T.; Vieira, J.; Fonseca, R. A.; Silva, L. O.

    2009-05-01

    An analytical theory for the interaction of an electron bunch with a nonlinear plasma wave is developed to make it possible to design efficient laser- and/or beam-driven accelerators that generate high quality monoenergetic electron beams. This theory shows how to choose the charge, the shape, and the placing of the bunch so that the conversion efficiency from the fields of the bubble to the accelerating electrons reaches nearly 100% and the beam quality is optimized. For intense drivers the nonlinear wake is described by the shape of the bubble and beam loading arises when the radial space-charge force of the beam acts back on the electron sheath surrounding the ion channel. The modification of the wake due to the presence of flat-top electron bunches is studied and it is shown that the energy spread of an externally injected flat-top electron bunch can be kept low. The bunch profile that leads to zero energy spread is also derived.

  16. Magnetosheath and plasma sheet observations by GEOTAIL during the low-density solar wind event on 24-25 May 2002

    Microsoft Academic Search

    M. N. Nishino; T. Terasawa; M. Hoshino; M. Fujimoto; T. Mukai; Y. Kasaba; H. Kojima

    2002-01-01

    During the low-density solar wind interval in May 2002, when the density in the solar wind was extremely low (0.1-0.3\\/cc), GEOTAIL was mostly in the dusk magnetosheath but went into the plasma sheet several times. Of particular interest are the plasma\\/field conditions in these regions when the solar wind seemed to become sub-Alfvénic intermittently (12 UT on 24 May -

  17. Almost-parallel electromagnetic wave propagation at frequencies near the electron plasma frequency

    Microsoft Academic Search

    S. S. Sazhin

    1988-01-01

    An approximate dispersion equation for almost-parallel electromagnetic wave propagation in a weakly relativistic plasma at frequencies near the electron plasma frequency is derived and investigated both analytically and numerically. It is pointed out that the cold plasma approximation cannot be applied to the analysis of these waves in any realistic (e.g., magnetospheric or astrophysical) plasma.

  18. FAST MAGNETIC RECONNECTION AND PARTICLE ACCELERATION IN RELATIVISTIC LOW-DENSITY ELECTRON-POSITRON PLASMAS WITHOUT GUIDE FIELD

    SciTech Connect

    Bessho, Naoki; Bhattacharjee, A., E-mail: naoki.bessho@unh.edu [Center for Integrated Computation and Analysis of Reconnection and Turbulence, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824 (United States)

    2012-05-10

    Magnetic reconnection and particle acceleration in relativistic Harris sheets in low-density electron-positron plasmas with no guide field have been studied by means of two-dimensional particle-in-cell simulations. Reconnection rates are of the order of one when the background density in a Harris sheet is of the order of 1% of the density in the current sheet, which is consistent with previous results in the non-relativistic regime. It has been demonstrated that the increase of the Lorentz factors of accelerated particles significantly enhances the collisionless resistivity needed to sustain a large reconnection electric field. It is shown analytically and numerically that the energy spectrum of accelerated particles near the X-line is the product of a power law and an exponential function of energy, {gamma}{sup -1/4}exp (- a{gamma}{sup 1/2}), where {gamma} is the Lorentz factor and a is a constant. However, in the low-density regime, while the most energetic particles are produced near X-lines, many more particles are energized within magnetic islands. Particles are energized in contracting islands by multiple reflection, but the mechanism is different from Fermi acceleration in magnetic islands for magnetized particles in the presence of a guide field. In magnetic islands, strong core fields are generated and plasma beta values are reduced. As a consequence, the fire-hose instability condition is not satisfied in most of the island region, and island contraction and particle acceleration can continue. In island coalescence, reconnection between two islands can accelerate some particles, however, many particles are decelerated and cooled, which is contrary to what has been discussed in the literature on particle acceleration due to reconnection in non-relativistic hydrogen plasmas.

  19. Electron beam transport in weak plasma and plasma heating by electron beams

    SciTech Connect

    Tascione, T.F.

    1982-01-01

    Today, the earth's intrinsic magnetic field prevents the streaming solar wind plasma from directly interacting with the terrestrial atmosphere. Periodically the geomagnetic field reverses direction, and during the transition period, the earth's magnetic barrier is thought to disappear. In the past, studies about the atmospheric-solar wind interaction dynamics were hindered by a scarcity of observational data. However, since December 1978, the Pioneer-Venus Orbiter has been providing daily observations of the atmospheric dynamics produced by the direct solar wind interaction with the atmosphere of Venus (the only planet known to lack an intrinsic magnetic field). This thesis develops the first three dimensional magnetohydrodynamic (MHD) theory of this interaction. Within the ionosphere of Venus analytic solutions to the MHD equations are possible because of a favorable geometry between the induced ionospheric magnetic fields and the ionospheric plasma motions. It is shown that variations in the solar wind speed and interplanetary magnetic vector direction cause variations in the dayside ionospheric plasma flows and the induced magnetic field configuration, and that these changes can account for the variety of magnetic structures observed by Pioneer-Venus. Portions of the Venus ionosphere are shown to be susceptible to the Kelvin-Helmholtz shear instability. The unusual shape of the computed region of stability is shown to be an important key to understanding the highly variable Pioneer-Venus observations.

  20. Electron temperature gradient driven instability in the tokamak boundary plasma

    SciTech Connect

    Xu, X.Q.; Rosenbluth, M.N.; Diamond, P.H.

    1992-12-15

    A general method is developed for calculating boundary plasma fluctuations across a magnetic separatrix in a tokamak with a divertor or a limiter. The slab model, which assumes a periodic plasma in the edge reaching the divertor or limiter plate in the scrape-off layer(SOL), should provide a good estimate, if the radial extent of the fluctuation quantities across the separatrix to the edge is small compared to that given by finite particle banana orbit. The Laplace transform is used for solving the initial value problem. The electron temperature gradient(ETG) driven instability is found to grow like t{sup {minus}1/2}e{sup {gamma}mt}.

  1. Fluid aspects of electron streaming instability in electron-ion plasmas

    SciTech Connect

    Jao, C.-S. [Institute of Space Science, National Central University, Jhongli, Taiwan (China)] [Institute of Space Science, National Central University, Jhongli, Taiwan (China); Hau, L.-N. [Institute of Space Science, National Central University, Jhongli, Taiwan (China) [Institute of Space Science, National Central University, Jhongli, Taiwan (China); Department of Physics, National Central University, Jhongli, Taiwan (China)

    2014-02-15

    Electrons streaming in a background electron and ion plasma may lead to the formation of electrostatic solitary wave (ESW) and hole structure which have been observed in various space plasma environments. Past studies on the formation of ESW are mostly based on the particle simulations due to the necessity of incorporating particle's trapping effects. In this study, the fluid aspects and thermodynamics of streaming instabilities in electron-ion plasmas including bi-streaming and bump-on-tail instabilities are addressed based on the comparison between fluid theory and the results from particle-in-cell simulations. The energy closure adopted in the fluid model is the polytropic law of d(p?{sup ??})/dt=0 with ? being a free parameter. Two unstable modes are identified for the bump-on-tail instability and the growth rates as well as the dispersion relation of the streaming instabilities derived from the linear theory are found to be in good agreement with the particle simulations for both bi-streaming and bump-on-tail instabilities. At the nonlinear saturation, 70% of the electrons are trapped inside the potential well for the drift velocity being 20 times of the thermal velocity and the p?{sup ??} value is significantly increased. Effects of ion to electron mass ratio on the linear fluid theory and nonlinear simulations are also examined.

  2. Kinetic modelling of runaway electron avalanches in tokamak plasmas

    E-print Network

    Nilsson, E; Peysson, Y; Granetz, R S; Saint-Laurent, F; Vlainic, M

    2015-01-01

    Runaway electrons (REs) can be generated in tokamak plasmas if the accelerating force from the toroidal electric field exceeds the collisional drag force due to Coulomb collisions with the background plasma. In ITER, disruptions are expected to generate REs mainly through knock-on collisions, where enough momentum can be transferred from existing runaways to slow electrons to transport the latter beyond a critical momentum, setting off an avalanche of REs. Since knock-on runaways are usually scattered off with a significant perpendicular component of the momentum with respect to the local magnetic field direction, these particles are highly magnetized. Consequently, the momentum dynamics require a full 3-D kinetic description, since these electrons are highly sensitive to the magnetic non-uniformity of a toroidal configuration. A bounce-averaged knock-on source term is derived. The generation of REs from the combined effect of Dreicer mechanism and knock-on collision process is studied with the code LUKE, a s...

  3. The Ion Composition of the Plasma Sheet at 15-19 Re as a function of the IMF and the Solar Wind conditions

    Microsoft Academic Search

    C. Mouikis; L. M. Kistler; Y. Liu; B. Klecker; A. Korth; I. S. Dandouras

    2010-01-01

    Recent observational and simulation studies have reported a close correlation of the ionospheric outflow and the IMF and Solar Wind conditions. In this study we use the ion composition data from the CIS\\/CODIF instrument on Cluster to determine how the H+, He+ and O+ contributions to the plasma sheet density change as a function of certain IMF and Solar Wind

  4. Electron-acoustic solitary waves in dense quantum electron-ion plasmas

    SciTech Connect

    Misra, A. P.; Shukla, P. K.; Bhowmik, C. [Department of Mathematics, Siksha Bhavana, Visva-Bharati University, Santiniketan-731 235 (India); Institut fuer Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultaet fuer Physik and Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum, Germany, and School of Physics, University of KwaZulu-Natal, Durban 4000 (South Africa); Barisha High School, Barisha, Kolkata-700 008 (India)

    2007-08-15

    A quantum hydrodynamic (QHD) model is used to investigate the propagation characteristics of nonlinear electron-acoustic solitary waves (EASWs) in a dense quantum plasma whose constituents are two groups of electrons: one inertial cold electrons and other inertialess hot electrons, and the stationary ions which form the neutralizing background. By using the standard reductive perturbation technique, a Kadomtsev-Petviashvili (KP) equation, which governs the dynamics of EASWs, is derived in both spherical and cylindrical geometry. The effects of cold electrons and the density correlations due to quantum fluctuations on the profiles of the amplitudes and widths of the solitary structures are examined numerically. The nondimensional parameter {delta}=n{sub c0}/n{sub h0}, which is the equilibrium density ratio of the cold to hot electron component, is shown to play a vital role in the formation of both bright and dark solitons. It is also found that the angular dependence of the physical quantities and the presence of cold electrons in a quantum plasma lead to the coexistence of some new interesting novel solitary structures quite distinctive from the classical ones.

  5. Review of Electron Interaction Data for Plasma Processing Gases

    NASA Astrophysics Data System (ADS)

    Olthoff, James

    1998-10-01

    To assess the behavior of gases in their uses in manufacturing semiconductor devices and other applications, and to promote the modeling of these processes, it is necessary to have accurate information on the fundamental interactions of low energy (< 100 eV) electrons with process gases. In support of this effort, we have undertaken the assessment and evaluation of the available information on cross sections and rate coefficients for collisional interactions of electrons with three groups of gases: those used in etching, deposition, or cleaning (e.g., CF_4, CHF_3, C_2F_6, C_3F_8, Cl_2, SF_6, NF3 and HBr), those used as buffer gases (e.g., Ar, He), and those that are present in practical systems as impurities (e.g., O_2, N_2, H_2O). In this talk we summarize our assessed data on cross sections and rate coefficients for the gases whose review is completed: CF4 , CHF_3, C_2F6 , C_3F_8, and Cl_2. We also indicate specific electron-interaction data needs for these gases. In this regard, knowledge is lacking on two important basic processes, namely, dissociation into neutral fragments by electron impact and electron interactions with vibrationally and electronically excited species. In addition, with the sole exception of the electron-impact ionization of radicals from CF_4, there are few published data on the interactions of slow electrons with the radicals of these plasma processing gases. The recommended data for the reviewed gases and CCl_2F2 are available via the World Wide Web at http://www.eeel.nist.gov/811/refdata.

  6. 2005 Workshop on NCETIP 1 Kinetic of plasma particles and electron

    E-print Network

    Kaganovich, Igor

    action on metals. · Ablative plasma accelerators · MHD power conversion. · Vacuum arc Cathode spot · Unipolar arcs in Tokamaks. KINETIC OF A CONDENSED MATERIAL VAPORIZATION INTO VACUUM · Langmuir approach · Plasma in vacuum arc cathode spot. Electron transport · Cathode evaporation DIFFERENT CATHODE MATERIALS

  7. Measurement of temperature and electrons density distribution of atmospheric arc plasma by moiré deflectometry technique

    NASA Astrophysics Data System (ADS)

    Salimi Meidanshahi, Fatemeh; Madanipour, Khosro; Shokri, Babak

    2013-04-01

    In the present paper, the refractive index, electron density and temperature distribution of atmospheric arc plasmas are measured by moiré deflectometry. The deflection angle of rays passing through the plasma is obtained by moiré fringe analysis. Then by using inverse Abel transform integral for this axisymmetric plasma, the refractive index distribution is obtained in different points of plasma and environment. Considering the relation between plasma temperature and refractive index, the spatial temperature distribution of the arc plasma is evaluated. Also, in contrast to conventional models to obtain electron number density, in which the refractive index of plasmas is approximately assumed equal to the electron refractive index, a model is used for accurate and absolute measurement of the electron density profile. This technique is especially suitable for measuring axially symmetric plasma parameters.

  8. Deposition of diamondlike films by electron cyclotron resonance microwave plasmas

    NASA Technical Reports Server (NTRS)

    Pool, F. S.; Shing, Y. H.

    1990-01-01

    Hard a-C:H films have been deposited through electron cyclotron resonance (ECR) microwave plasma decomposition of CH4 diluted with H2 gas. It has been found that hard diamondlike films could only be produced under a RF-induced negative self-bias of the substrate stage. Raman spectra indicate the deposition of two distinct film types: one film type exhibiting well-defined bands at 1360 and 1580/cm and another displaying a broad Raman peak centered at approximately 1500/cm. Variation of the mirror magnetic-field profile of the ECR system was examined, demonstrating the manipulation of film morphology through the extraction of different ion energies.

  9. Electron beam driven lower hybrid waves in a dusty plasma

    NASA Astrophysics Data System (ADS)

    Prakash, Ved; Vijayshri; Sharma, Suresh C.; Gupta, Ruby

    2013-05-01

    An electron beam propagating through a magnetized dusty plasma drives electrostatic lower hybrid waves to instability via Cerenkov interaction. A dispersion relation and the growth rate of the instability for this process have been derived taking into account the dust charge fluctuations. The frequency and the growth rate of the unstable wave increase with the relative density of negatively charged dust grains. Moreover, the growth rate of the instability increases with beam density and scales as the one-third power of the beam density. In addition, the dependence of the growth rate on the beam velocity is also discussed.

  10. Electron beam driven lower hybrid waves in a dusty plasma

    SciTech Connect

    Prakash, Ved; Vijayshri [School of Sciences, Indira Gandhi National Open University, Maidan Garhi, New Delhi-110 068 (India)] [School of Sciences, Indira Gandhi National Open University, Maidan Garhi, New Delhi-110 068 (India); Sharma, Suresh C. [Department of Applied Physics, Delhi Technological University, Shahbad Daulatpur, Bawana Road, Delhi-110 042 (India)] [Department of Applied Physics, Delhi Technological University, Shahbad Daulatpur, Bawana Road, Delhi-110 042 (India); Gupta, Ruby [Department of Physics, Swami Shraddhanand College, University of Delhi, Alipur, Delhi-110 036 (India)] [Department of Physics, Swami Shraddhanand College, University of Delhi, Alipur, Delhi-110 036 (India)

    2013-05-15

    An electron beam propagating through a magnetized dusty plasma drives electrostatic lower hybrid waves to instability via Cerenkov interaction. A dispersion relation and the growth rate of the instability for this process have been derived taking into account the dust charge fluctuations. The frequency and the growth rate of the unstable wave increase with the relative density of negatively charged dust grains. Moreover, the growth rate of the instability increases with beam density and scales as the one-third power of the beam density. In addition, the dependence of the growth rate on the beam velocity is also discussed.

  11. Characteristics of InGaP/InGaAs pseudomorphic high electron mobility transistors with triple delta-doped sheets

    SciTech Connect

    Chu, Kuei-Yi [National Cheng-Kung University, Institute of Microelectronics, Department of Electrical Engineering (China); Chiang, Meng-Hsueh, E-mail: mhchiang@niu.edu.tw; Cheng, Shiou-Ying, E-mail: sycheng@niu.edu.tw [National II an University, Department of Electronic Engineering (China); Liu, Wen-Chau [National Cheng-Kung University, Institute of Microelectronics, Department of Electrical Engineering (China)

    2012-02-15

    Fundamental and insightful characteristics of InGaP/InGaAs double channel pseudomorphic high electron mobility transistors (DCPHEMTs) with graded and uniform triple {delta}-doped sheets are coomprehensively studied and demonstrated. To gain physical insight, band diagrams, carrier densities, and direct current characteristics of devices are compared and investigated based on the 2D semiconductor simulator, Atlas. Due to uniform carrier distribution and high electron density in the double InGaAs channel, the DCPHEMT with graded triple {delta}-doped sheets exhibits better transport properties, higher and linear transconductance, and better drain current capability as compared with the uniformly triple {delta}-doped counterpart. The DCPHEMT with graded triple {delta}-doped structure is fabricated and tested, and the experimental data are found to be in good agreement with simulated results.

  12. Probe measurements of the electron distribution function in an electron-beam-produced ytterbium plasma

    SciTech Connect

    Bobrova, A. A.; Dubinov, A. E.; Esin, M. I.; Zolotov, S. V.; Maksimov, A. N.; Selemir, V. D.; Sidorov, I. I.; Shubin, A. Yu. [Russian Federal Nuclear Center, All-Russia Research Institute of Experimental Physics (Russian Federation)

    2011-01-15

    A nonequilibrium anisotropic plasma produced by an electron beam in the residual air with a low content of ytterbium vapor was investigated by the probe method. It is found that a minor (at a level of a few ppm) admixture of ytterbium to low-pressure air substantially modifies the electron energy distribution function (EEDF): the main peak corresponding to thermal electrons broadens, and new peaks appear. It is shown that the observed change in the EEDF is caused by the low ionization energy of ytterbium, due to which one beam electron can ionize several ytterbium atoms. The new peaks in the EEDF correspond to the final energies of a beam electron after each subsequent ionizing collision with ytterbium atoms.

  13. Temperature and anisotropic-temperature relaxation measurements in cold, pure-electron plasmas

    E-print Network

    California at San Diego, University of

    Temperature and anisotropic-temperature relaxation measurements in cold, pure-electron plasmas B. R not be equal, and, when unequal, we have measured the relaxation rate at which electron­electron collisions; accepted 3 January 1996 Plasma temperatures in the range 25 to 2 106 K have been measured using a cryogenic

  14. Electron Density Oscillations in CC-RF Oxygen Plasma Investigated by Gaussian Beam Microwave Interferometry

    Microsoft Academic Search

    Christian Kullig; Kristian Dittmann; Jürgen Meichsner

    2011-01-01

    Gaussian beam microwave interferometry (160 GHz, beam waist of 5 mm) is applied to study the electron density in capacitively coupled radio-frequency (RF) oxygen plasma. The mi- crowave interferometry provides immediately the line-integrated electron density without model assumptions. In the considered range of RF power and total pressure, the investigations have shown that the oxygen plasma is dominated by electron

  15. Propagation modes for a dusty plasma ionization instability under electron beam injection

    Microsoft Academic Search

    J. M. Donoso; L. Conde

    2008-01-01

    The low frequency electrostatic linear modes of a dusty plasma penetrated by an energized electron beam are investigated in the frame of a one-dimensional multifluid equations. This plasma contains with thermal and non-thermal electrons, ions and charged dust grains. The stable and unstable modes of the ionization instability are examined in relation to the injected electron beam current density. We

  16. X-ray spectroscopy application for magnetic field and electron beam measurements in laser produced plasma

    Microsoft Academic Search

    E. O. Baronova; G. Sholin

    1998-01-01

    Temperature and density gradients, parametric instabilities which are common to laser produced plasma, can lead to both spontaneous magnetic field and electron beam generation. Strong magnetic field splits lines, suprathermal electrons are of great importance in energy transition processes and in plasma emission spectra formation. The paper presents magnetic field strength and suprathermal electron energy measurement methods, based on investigation

  17. Influence of electron injection on electron cyclotron resonance plasma properties and reflected mode electrons (abstract)

    Microsoft Academic Search

    V. P. Ovsyannikov; F. Ullmann; G. Zschornack

    2000-01-01

    The injection of an additional strong focused electron beam from a special designed electron gun into a magnetic electron cyclotron resonance (ECR) confinement field is studied. The electron gun uses a cathode with a long lifetime and resistiveness providing high emission current densities with electron currents up to 50 mA and voltages up to 4 keV. A sequence of aluminum

  18. Parameter manipulation in the Synthesis of Ti-Cd-C Films via Reactive Sputtering in a Magnetized Sheet Plasma Facility

    NASA Astrophysics Data System (ADS)

    Villanueva, Matthew Bryan; Ramos, Henry

    2013-09-01

    Titanium-cadmium-carbon (Ti-Cd-C) deposits were achieved through reactive sputtering in a magnetized sheet plasma facility (MSPF). Titanium and cadmium metals (99.9% purity) were used as sputter targets, and high purity methane as the reactive gas. Parameters investigated were target bias, deposition duration, filling pressure, gas ratio, gas type such as acetylene, and magnetic configuration. Through X-ray diffractometry, peak signals at 2 ? = 23.3° for the treatment which implemented an independent sputtering step at -200 V target bias, and 2 ? = 12.34° for direct reactive sputtering only with -800 V target bias were recorded. Both XRD results are indicative of the formation of Ti2CdC, a theorized solid solution of Mn+1AXn phase variety. Titanium-cadmium-carbon (Ti-Cd-C) deposits were achieved through reactive sputtering in a magnetized sheet plasma facility (MSPF). Titanium and cadmium metals (99.9% purity) were used as sputter targets, and high purity methane as the reactive gas. Parameters investigated were target bias, deposition duration, filling pressure, gas ratio, gas type such as acetylene, and magnetic configuration. Through X-ray diffractometry, peak signals at 2 ? = 23.3° for the treatment which implemented an independent sputtering step at -200 V target bias, and 2 ? = 12.34° for direct reactive sputtering only with -800 V target bias were recorded. Both XRD results are indicative of the formation of Ti2CdC, a theorized solid solution of Mn+1AXn phase variety. Department of Science and Technology for the project grant.

  19. A 2-D empirical plasma sheet pressure model for substorm growth phase using the Support Vector Regression Machine

    NASA Astrophysics Data System (ADS)

    Yue, Chao; Wang, Chih-Ping; Lyons, Larry; Wang, Yongli; Hsu, Tung-Shin; Henderson, Michael; Angelopoulos, Vassilis; Lui, A. T. Y.; Nagai, Tsugunobu

    2015-03-01

    The plasma sheet pressure and its spatial structure during the substorm growth phase are crucial to understanding the development and initiation of substorms. In this paper, we first statistically analyzed the growth phase pressures using Geotail and Time History of Events and Macroscale Interactions during Substorms data and identified that solar wind dynamic pressure (PSW), energy loading, and sunspot number as the three primary factors controlling the growth phase pressure change. We then constructed a 2-D equatorial empirical pressure model and an error model within r ? 20 RE using the Support Vector Regression Machine with the three factors as input. The model predicts the plasma sheet pressure accurately with median errors of 5%, and predicted pressure gradients agree reasonably well with observed gradients obtained from two-probe measurements. The model shows that pressure increases linearly as PSW increases, and the PSW effect is stronger under lower energy loading. However, the pressure responses to energy loading and sunspot number are nonlinear. The pressure increases first with increasing loading or sunspot number, then remains relatively constant after reaching a peak value at ~8000 kV min loading or sunspot number of ~80. The loading effect is stronger when PSW is lower and the pressure variations are stronger near midnight than away from midnight. The sunspot number effect is clearer at smaller r. The pressure model can also be applied to understand the pressure changes observed during a substorm event by providing evaluations of the effects of energy loading and PSW, as well as the temporal and spatial effects along the spacecraft trajectory.

  20. Suprathermal electron transport in laser-produced plasmas

    SciTech Connect

    Mason, R.J.

    1981-01-01

    A self-consistent, collisional, particle-in-cell scheme has been developed to model the one dimensional transport of suprathermal electrons in laser produced plasmas. This full Monte Carlo approach was taken, since earlier, simpler models have failed to explain an experimentally almost universal anomalous inhibition of thermal transport. The Monte Carlo scheme allows for free-streaming, ion scatter, and self thermalization of the electrons, which are moved in self-consistent E-fields computed with the aid of implicit fluid moments. PIC hydrodynamics for the ions, ponderomotive forces, and resonance and inverse-bremsstrahlung absorption of the light are all accommodated. In application to the anomalous inhibition problem, use of the scheme demonstrates that intrinsic differences in the Monte Carlo, and conventional flux-limited diffusion modelling of the transport results in apparent and real inhibition, explaining the need for strong flux-limiting in the simpler diffusion modelling of experiments.

  1. Confinement of pure electron plasmas in the CNT stellarator

    SciTech Connect

    Pedersen, T. Sunn; Berkery, J. W.; Boozer, A. H.; Brenner, P. W.; Hahn, M.; Durand de Gevigney, B.; Martin, X. Sarasola [Columbia University, New York, NY 10027 (United States); Marksteiner, Q. R. [Columbia University, New York, NY 10027 (United States); Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2009-03-30

    The Columbia Non-neutral Torus is a stellarator devoted to non-neutral and electron-positron plasma research. Confinement and transport processes have been studied in some detail now, and an understanding of these processes has emerged. Transport is driven in two ways: The presence of internal rods, and the presence of neutrals. Both transport processes are clearly distinguished experimentally, and a model of the rod driven transport has been developed, yielding very good agreement with experimental data. The neutral driven transport is faster than originally expected and indicates the presence of unconfined orbits in CNT. Numerical modeling of the electron orbits in CNT confirms the existence of loss orbits and shows that a flux surface conforming electrostatic boundary will greatly improve confinement. Such a boundary has now been installed in CNT, with initial results showing an order of magnitude improvement in confinement.

  2. Theoretical study on the electron energy distribution function and electron transport parameters of argon plasma

    NASA Astrophysics Data System (ADS)

    Zhang, Yachun; He, Xiang; Chen, Jianping; Lu, Jian; Ni, Xiaowu; Shen, Zhonghua

    2015-05-01

    Fluid model of argon plasma require the input of transport parameters that depend on the electron energy distribution function (EEDF). The EEDF and electron transport parameters of reduced field and electric field frequency in argon plasma are investigated by solving the Boltzmann equation with the two-term approximation. It is found that the EEDF closes to Druyvesteyn distribution and decreases sharply after several eV when the reduced field is less than 10Td. The low energy part of EEDF flats with the reduced field, and the high energy tail of EEDF increases with the reduced field. The EEDF approaches to dual temperature Maxwellian distribution when the reduced field is larger than 50Td. When the reduced field is larger than 300Td, the high energy tail of EEDF decreases more slowly than Maxwellian distribution, and the shape of EEDF tends to concave. The electron mobility decreases with the reduced field, and tends to a const . The electron diffusion coefficient increases with the reduced field, but exists a local minimum at 50Td. The relationship between EEDF and electric field frequency shows that the EEDF approaches to Maxwellian distribution in a high frequency field because of the collision with electrons and neutral particles. In this case, the electron mobility and diffusion coefficient are complex number, and the imaginary parts raise with the field frequency. The absolute value of transport parameters decrease with the field frequency.

  3. Electron self-injection in the proton-driven-plasma-wakefield acceleration

    SciTech Connect

    Hu, Zhang-Hu; Wang, You-Nian [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)] [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

    2013-12-15

    The self-injection process of plasma electrons in the proton-driven-plasma-wakefield acceleration scheme is investigated using a two-dimensional, electromagnetic particle-in-cell method. Plasma electrons are self-injected into the back of the first acceleration bucket during the initial bubble formation period, where the wake phase velocity is low enough to trap sufficient electrons. Most of the self-injected electrons are initially located within a distance of the skin depth c/?{sub pe} to the beam axis. A decrease (or increase) in the beam radius (or length) leads to a significant reduction in the total charges of self-injected electron bunch. Compared to the uniform plasma, the energy spread, emittance and total charges of the self-injected bunch are reduced in the plasma channel case, due to a reduced injection of plasma electrons that initially located further away from the beam axis.

  4. Perturbed optical emission and electron heating in capacitively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Barroy, Pierre; Goodyear, Alec; Braithwaite, Nick

    2002-10-01

    Studies have been conducted to observe directly the dominant heating processes in a capacitively coupled plasma (GEC reference cell). The ground electrode incorporates a 25 mm diameter planar embedded test surface flush with the electrode face. Controlled pulses of radio-frequency voltage were applied to the test surface in addition to the main 13.56 MHz reactor driving voltage. Spatially resolved measurements, adjacent to the test surface, of the enhanced optical emission that coincides with the RF excitation were made using an intensified CCD camera [1]. Correlation between the parameters of the controlled perturbation and enhanced emission give insight into heating processes within the plasma. To distinguish between stochastic processes, ohmic heating and heating through secondary electrons, the effects of the amplitude, frequency, phase and timing of the perturbing RF pulses are being examined. [1] PRJ Barroy, A Goodyear, and N St J Braithwaite, IEEE Trans Plasma Science Vol 30, 148-149, 2002 Work supported by the EPSRC, Grant No. GR/L82380.

  5. Nonlocal control of electron temperature in short direct current glow discharge plasma

    SciTech Connect

    Demidov, V. I. [Department of Optics and Spectroscopy, St. Petersburg State University, St. Petersburg 199034 (Russian Federation); International Laboratory “Nonlocal Plasma in Nanotechnology and Medicine”, ITMO University, Kronverkskiy pr. 49, St. Petersburg 197101 (Russian Federation); Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506 (United States); Kudryavtsev, A. A.; Stepanova, O. M. [Department of Optics and Spectroscopy, St. Petersburg State University, St. Petersburg 199034 (Russian Federation); Kurlyandskaya, I. P. [International Laboratory “Nonlocal Plasma in Nanotechnology and Medicine”, ITMO University, Kronverkskiy pr. 49, St. Petersburg 197101 (Russian Federation); St. Petersburg University of State Fire Service of EMERCOM RF, Murmansk Branch, Murmansk 183040 (Russian Federation)

    2014-09-15

    To demonstrate controlling the electron temperature in nonlocal plasma, experiments have been performed on a short (without positive column) dc glow discharge with a cold cathode by applying different voltages to the conducting discharge wall. The experiments have been performed for low-pressure noble gas discharges. The applied voltage can modify trapping the energetic electrons emitted from the cathode sheath and arising from the atomic and molecular processes in the plasma within the device volume. This phenomenon results in the energetic electrons heating the slow plasma electrons, which consequently modifies the electron temperature. Furthermore, a numerical model of the discharge has demonstrated the electron temperature modification for the above case.

  6. Elastic Cross Sections for Electron Collisions with Molecules Relevant to Plasma Processing

    Microsoft Academic Search

    J.-S. Yoon; M.-Y. Song; H. Kato; M. Hoshino; H. Tanaka; M. J. Brunger; S. J. Buckman; H. Cho

    2010-01-01

    Absolute electron-impact cross sections for molecular targets, including their radicals, are important in developing plasma reactors and testing various plasma processing gases. Low-energy electron collision data for these gases are sparse and only the limited cross section data are available. In this report, elastic cross sections for electron-polyatomic molecule collisions are compiled and reviewed for 17 molecules relevant to plasma

  7. Wakefield acceleration in atmospheric plasmas: a possible source of MeV electrons

    E-print Network

    Arrayás, M; Seviour, R; Trueba, J L

    2015-01-01

    Intense electromagnetic pulses interacting with a plasma can create a wake of plasma oscillations. Electrons trapped in such oscillations can be accelerated under certain conditions to very high energies. We study the conditions for the wakefield acceleration to produce MeV electrons in atmospheric plasmas. This mechanism may explain the origin of MeV or runaway electrons needed in the current theories for the production of Terrestrial Gamma ray Flashes.

  8. Anomalous Resistivity Resulting from MeV-Electron Transport in Overdense Plasma

    Microsoft Academic Search

    Y. Sentoku; K. Mima; P. Kaw; K. Nishikawa

    2003-01-01

    Laser produced hot electron transport in an overdense plasma is studied by three-dimensional particle-in-cell simulations. Hot electron currents into the plasma generate neutralizing return currents in the cold plasma electrons, leading to a configuration which is unstable to electromagnetic Weibel and tearing instabilities. The resulting current filaments self-organize through a coalescence process finally settling into a single global current channel.

  9. Observation of plasma instabilities related to dust particle growth mechanisms in electron cyclotron resonance plasmas

    NASA Astrophysics Data System (ADS)

    Drenik, A.; Yuryev, P.; Vesel, A.; Margot, J.; Clergereaux, R.

    2013-10-01

    Instabilities are observed in the self-bias voltage measured on a probe immersed in microwave plasma excited at Electron Cyclotron Resonance (ECR). Observed in the MHz range, they were systematically measured in dust-free or dusty plasmas (obtained for different conditions of applied microwave powers and acetylene flow rates). Two characteristic frequencies, well described as lower hybrid oscillations, can be defined. The first one, in the 60-70 MHz range, appears as a sharp peak in the frequency spectra and is observed in every case. Attributed to ions, its position shift observed with the output power highlights that nucleation process takes place in the dusty plasma. Attributed to lower hybrid oscillation of powders, the second broad peak in the 10-20 MHz range leads to the characterization of dust particles growth mechanisms: in the same way as in capacitively coupled plasmas, accumulation of nucleus confined near the probe in the magnetic field followed by aggregation takes place. Then, the measure of electrical instabilities on the self-bias voltage allows characterizing the discharge as well as the chemical processes that take place in the magnetic field region and their kinetics.

  10. Multi-point observations of the inner boundary of the plasma sheet during geomagnetic disturbances

    E-print Network

    California at Berkeley, University of

    of the equatorial dusk-side plasma in the string-of-pearls configuration, allowing the dynamics of particle- sphere in a string-of-pearls configuration, successively crossing geostationary orbit, allowing

  11. Electron Beam Charge Diagnostics for Laser Plasma Accelerators

    SciTech Connect

    Nakamura, Kei; Gonsalves, Anthony; Lin, Chen; Smith, Alan; Rodgers, David; Donahue, Rich; Byrne, Warren; Leemans, Wim

    2011-06-27

    A comprehensive study of charge diagnostics is conducted to verify their validity for measuring electron beams produced by laser plasma accelerators (LPAs). First, a scintillating screen (Lanex) was extensively studied using subnanosecond electron beams from the Advanced Light Source booster synchrotron, at the Lawrence Berkeley National Laboratory. The Lanex was cross calibrated with an integrating current transformer (ICT) for up to the electron energy of 1.5 GeV, and the linear response of the screen was confirmed for charge density and intensity up to 160 pC/mm{sup 2} and 0.4 pC/(ps mm{sup 2}), respectively. After the radio-frequency accelerator based cross calibration, a series of measurements was conducted using electron beams from an LPA. Cross calibrations were carried out using an activation-based measurement that is immune to electromagnetic pulse noise, ICT, and Lanex. The diagnostics agreed within {+-}8%, showing that they all can provide accurate charge measurements for LPAs.

  12. Electron hole structure and its stability depending on plasma magnetization

    NASA Astrophysics Data System (ADS)

    Singh, Nagendra; Loo, Sin M.; Wells, Earl

    2001-10-01

    Observations from Polar have revealed that electron hole (e-hole) structure critically depends on the plasma magnetization determined by the ratio ?=?e/?pe, where ?e and ?pe are the electron cyclotron and plasma frequencies, respectively. Using three-dimensional parallel particle-in-cell) simulations, we have studied the formation and structure of e-holes by varying ? showing that (1) for ?<1 e-holes are highly transitory while for ?<1 long-lasting e-holes form, especially when ?>=2, (2) in the transitory e-holes for ?<1, the e-holes are essentially planar with parallel electric fields E?>>E?, the perpendicular field, (3) when ?>=2 a variety of structures are possible ranging from spheroidal structures with Ex~Ey~E? to a planar one with Ex~Ey<plasma waves. An e-hole with long transverse structure is effective in radiating high-frequency whistler waves which have long perpendicular wavelengths. When such waves are radiated out, the remnant structure is transversely modulated and has relatively short scale length. On the other hand, the fragments with the short perpendicular scale lengths are effective in radiating the LH waves. These findings from the simulations are compared with findings from the data from Polar [Franz et al., 2000].

  13. Stabilization of electron emission from nanoneedles with two dimensional graphene sheet structure in a high residual pressure region

    NASA Astrophysics Data System (ADS)

    Matsumoto, Takahiro; Neo, Yoichiro; Mimura, Hidenori; Tomita, Makoto; Minami, Nariyuki

    2007-03-01

    A stable field emission (FE) under a high residual pressure (10-5Torr) was obtained by the thermal field operation of a nanoneedle cathode with a two dimensional graphene sheet structure. A high brightness electron emission of the order of 1012Asr-1m-2, as well as stable emission, was achieved. The performance of the stabilized cathode was demonstrated by the construction of a compact FE scanning electron microscope (SEM) system, and clear FE-SEM images were obtained at a residual pressure above 10-5Torr. The emission current fluctuation as a function of cathode temperature was discussed based on the Poisson distribution.

  14. Theoretical study on strain induced variations in electronic properties of 2H-MoS{sub 2} bilayer sheets

    SciTech Connect

    Dong, Liang; Dongare, Avinash M., E-mail: dongare@uconn.edu [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Namburu, Raju R. [Computational and Information Sciences Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States); O'Regan, Terrance P.; Dubey, Madan [Sensors and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, Maryland 20783 (United States)

    2014-02-03

    The strain dependence of the electronic properties of bilayer sheets of 2H-MoS{sub 2} is studied using ab initio simulations based on density functional theory. An indirect band gap for bilayer MoS{sub 2} is observed for all variations of strain along the basal plane. Several transitions for the indirect band gap are observed for various strains for the bilayer structure. The variation of the band gap and the carrier effective masses for the holes and the electrons for the bilayer MoS{sub 2} structure under conditions of uniaxial strain, biaxial strain, as well as uniaxial stress is investigated.

  15. Study of the substrate bias in plasma depositions using an electron cyclotron resonance plasma

    SciTech Connect

    Shirai, K.; Gonda, S. (The Institute of Scientific and Industrial Research, Osaka University, 8-1, Mihogaoka, Ibaraki, Osaka 567 (Japan))

    1990-10-15

    A variety of effects of substrate bias upon an electron cyclotron resonance plasma deposition have been studied, taking the deposition of amorphous boron carbide films as an example. First, the impact energy of ions incident on substrates was studied through the variation of the sheath potentials formed on insulating and conducting substrates. For this purpose, the plasma potential ({ital V}{sub {ital p}}) was measured by the bias current-voltage ({ital I}{sub {ital b}}-{ital V}{sub {ital b}}) analysis, and the floating potential ({ital V}{sub {ital f}}) was measured by the Langmuir probe method. These analyses show that the plasma potential is sufficiently influenced by the substrate bias for positive biases even if the area of the bias electrode is small. The energy of ions incident on conducting substrates is not effectively changed by imposing a positive bias. This effect can be explained in terms of the global balance of the electron and ion currents. This consideration leads to the criterion for the area of bias electrode at which the substrate bias perturbs the plasma potential. Next, the effects of the substrate bias upon the deposition processes and properties of the deposited films were studied through the variations of the deposition rates and the infrared absorption due to the atomic vibrations in the films. The deposition rates vary with the substrate bias according to the variation of sheath potentials: {ital V}{sub {ital p}}{minus}{ital V}{sub {ital f}} for insulating substrates and {ital V}{sub {ital p}}{minus}{ital V}{sub {ital b}} for conducting substrates. As the substrate bias increases negatively, the deposition rate on conducting substrates increases. This increase is hardly explained by the direct contribution of ions to the deposition.

  16. Analysis of electron energy distribution function in a magnetically filtered complex plasma

    NASA Astrophysics Data System (ADS)

    M, K. Deka; H, Bailung; N, C. Adhikary

    2013-04-01

    The electron energy distribution function (EEDF) for a magnetically filtered dusty plasma is studied in a dusty double plasma device where the electron energy can be varied from 0.15 eV to ~ 2.8 eV and plasma density from 106 cm-3 to 109 cm-3. The characteristics of EEDF for these ranges of plasma parameters are investigated in a pristine plasma as well as in a dusty plasma. The results show that in the presence of dust, there is a drastic modification in EEDF patterns in a plasma with higher electron temperature and density than those in a low temperature and low density plasma produced by the magnetic filter.

  17. Thomson scattering from near-solid density plasmas using soft x-ray free electron lasers

    SciTech Connect

    Holl, A; Bornath, T; Cao, L; Doppner, T; Dusterer, S; Forster, E; Fortmann, C; Glenzer, S H; Gregori, G; Laarmann, T; Meiwes-Broer, K H; Przystawik, A; Radcliffe, P; Redmer, R; Reinholz, H; Ropke, G; Thiele, R; Tiggesbaumker, J; Toleikis, S; Truong, N X; Tschentscher, T; Uschmann, I; Zastrau, U

    2006-11-21

    We propose a collective Thomson scattering experiment at the VUV free electron laser facility at DESY (FLASH) which aims to diagnose warm dense matter at near-solid density. The plasma region of interest marks the transition from an ideal plasma to a correlated and degenerate many-particle system and is of current interest, e.g. in ICF experiments or laboratory astrophysics. Plasma diagnostic of such plasmas is a longstanding issue. The collective electron plasma mode (plasmon) is revealed in a pump-probe scattering experiment using the high-brilliant radiation to probe the plasma. The distinctive scattering features allow to infer basic plasma properties. For plasmas in thermal equilibrium the electron density and temperature is determined from scattering off the plasmon mode.

  18. Coherent kilo-electron-volt backscattering from plasma-wave boosted relativistic electron mirrors

    SciTech Connect

    Li, F. Y.; Chen, M., E-mail: minchen@sjtu.edu.cn; Liu, Y.; Zhang, J. [Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Sheng, Z. M., E-mail: zhengming.sheng@strath.ac.uk, E-mail: zmsheng@sjtu.edu.cn [Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Wu, H. C. [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Meyer-ter-Vehn, J. [Max-Planck-Institut für Quantenoptik, D-85748 Garching (Germany); Mori, W. B. [University of California, Los Angeles, California 90095-1547 (United States)

    2014-10-20

    A different parameter regime of laser wakefield acceleration driven by sub-petawatt femtosecond lasers is proposed, which enables the generation of relativistic electron mirrors further accelerated by the plasma wave. Integrated particle-in-cell simulation, including both the mirror formation and Thomson scattering, demonstrates that efficient coherent backscattering up to keV photon energy can be obtained with moderate driving laser intensities and high density gas targets.

  19. Electron density and electron temperature in pulsed atmospheric pressure air plasmas

    Microsoft Academic Search

    F. Leipold; K. H. Schoenbach

    2002-01-01

    The use of atmospheric pressure air plasmas as reflectors for microwave radiation with frequencies up to 30 GHz requires electron densities of approximately 1013 cm-3. It has been shown, that direct current microhollow cathode sustained (MCS) discharges meet this requirement. However, the power consumption of such air glow discharges of 5 kW\\/cm3 does not permit scaling to large volumes. Pulsing

  20. Studies of a Pure Electron Plasma to Investigate Electron Mobility in Hall Thrusters

    NASA Astrophysics Data System (ADS)

    Fossum, Emily; King, Lyon

    2007-11-01

    Excessive cross-field electron mobility in Hall thrusters has a negative effect on thruster efficiency and has been shown experimentally to be much larger than predicted by classical theory. An electron trapping apparatus was constructed in order to study electron dynamics in the defining electric and magnetic fields of a Hall-effect thruster in a highly controlled environment. Electrons are confined using only electric and magnetic fields without ions and dielectric walls, which are present in a typical Hall thruster. Mobility studies on a non-neutral plasma provide several advantages over a Hall thuster's quasi-neutral plasma, including a well-defined electric field and the ability to take internal electrostatic probe measurements. Cross-field electron mobility was investigated in response to magnetic and electric field strengths and background neutral density. Experimental design considerations including loading mechanisms, trapping potential, field design, and diagnostic techniques are presented along with experimental results. In this investigation, measured cross-field mobility appears to be consistent with Bohm-like mobility rather than classical mobility.