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Sample records for plasma electron temperature

  1. Electron temperature measurement in an ultracold plasma

    NASA Astrophysics Data System (ADS)

    Afrousheh, K.; Bohlouli, P. Z.; Fedorov, M.; Mugford, A.; Martin, J. D. D.

    2004-05-01

    There has been growing interest in recent years in studying ultracold plasmas. These cold plasmas are produced by photoionizing a sample of cold atoms in a MOT. Of interest is the evolution of electron temperature in these plasmas. Strong correlation due to low initial temperature, as well as lack of correlation due to rapid heating are two possible scenarios. We will present a unique experimental method for measuring electron temperature in a cold plasma, as well as our calculation of the feasibility of the proposed method. In this process, which we call stimulated photoattachment, we stimulate the transition of free electrons from the continuum to bound states of nearby atoms by a laser beam. The negative ions produced can be observed with a microchannel plate detector. For electrons with well-defined energy this is a resonant process. The width of the resonance indicates the electron temperature. This technique has advantage of high temporal resolution of the evolution of electron temperature after the plasma is formed.

  2. Collisionless Plasma Shocks in Striated Electron Temperatures

    SciTech Connect

    Guio, P.; Pecseli, H. L.

    2010-02-26

    The existence of low frequency waveguide modes of ion acoustic waves is demonstrated in magnetized plasmas for electron temperatures striated along the magnetic field lines. At higher frequencies, in a band between the ion cyclotron and the ion plasma frequency, radiative modes develop and propagate obliquely to the field away from the striation. Arguments for the subsequent formation and propagation of electrostatic shock are presented and demonstrated numerically. For such plasma conditions, the dissipation mechanism is the 'leakage' of the harmonics generated by the wave steepening.

  3. New Electron Temperature Diagnostic for Low Temperature Plasmas

    NASA Astrophysics Data System (ADS)

    Boivin, Robert; Loch, Stuart

    2004-11-01

    A new line ratio diagnostic design to measure electron temperature in plasma is presented. Unlike previous diagnostics, this new technique features emission lines originating from levels with different principal quantum numbers. A significant advantage of this approach is that the line ratio varies considerably with temperature in the 1 to 20 eV range. Another advantage is that both transitions are optically thin even for plasma density up to 1 E 14 cm-3. The drawbacks are: a large difference in the line intensities and the significant difference in wavelength. The event of high sensitivity CCD camera combine with precise calibration can to a large extent minimize these latest two issues. The diagnostic is tested on the ASTRAL (Auburn Steady sTate Research fAciLity) helicon plasma source. ASTRAL is a 2.3 m long helicon source designed to investigate basic plasma and space plasma processes. The device produces plasmas with the following typical parameters ne = 1 E9 to 1 E13 cm-3, Te = 2 to 20 eV and Ti = 0.03 to 0.3 eV. A series of 8 large coils produce an axial magnetic field up to 1.2 kGauss. Operating pressure varies from 0.1 to 100 mTorr. A water cooled fractional helix antenna is used to introduce RF power up to 2 kwatt through a standard matching circuit. The line ratio temperatures are measured by means of a 0.33 m McPherson Criss-Cross Scanning monochromator instrumented with a SPH5 Apogee CCD camera. The line ratio temperatures are compared to electron temperatures measured by a rf compensated Langmuir Probe. To validate the diagnostic, a new collisional radiative model that makes use of the latest excitation cross-section values is presented. The model is also used to predict the potential range of this new diagnostic both in terms of electron temperature and plasma density.

  4. Effects of emitted electron temperature on the plasma sheath

    SciTech Connect

    Sheehan, J. P.; Kaganovich, I. D.; Wang, H.; Raitses, Y.; Sydorenko, D.; Hershkowitz, N.

    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.

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

    SciTech Connect

    Kim, Young-Cheol; Jang, Sung-Ho; Oh, Se-Jin; Lee, Hyo-Chang; Chung, Chin-Wook

    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.

  6. Laboratory plasma with cold electron temperature of the lower ionosphere

    NASA Astrophysics Data System (ADS)

    Dickson, Shannon; Robertson, Scott

    2009-10-01

    For the first time, plasma with cold electron temperatures less than 300K has been created continuously in the laboratory. The plasma is created in a cylindrical double-walled vacuum chamber in which the inner chamber (18cm in diameter and 30cm long) is wrapped in copper tubing through which vapor from liquid nitrogen flows, providing a cooling mechanism for the neutral gas. The inner chamber has two negatively-biased filaments for plasma generation and a platinum wire Langmuir probe for diagnostic measurements. Neutral gas pressures of 1.6mTorr and a total filament emission current of 2mA are used to obtain plasma densities near 4 x 10^8 cm-3. When carbon monoxide is used as the working gas, decreasing the neutral gas temperature also decreases the cold electron temperatures, yielding cold electrons with 21meV (240K) when the neutral CO is at 150K. The same experiment conducted with H2, He, or Ar results in a doubling of the cold electron temperatures, yielding 80meV (930K) when the neutral gas is at 150K. The lower electron temperature with CO is attributed to the asymmetric CO molecule having a nonzero electric dipole moment which increases the cross section for electron energy exchange. Nitric oxide, a dominant constituent of the ionosphere, has a similar dipole moment and collision cross section as carbon monoxide and is likely to be equally effective at cooling electrons.

  7. Electron temperature and density measurements of laser induced germanium plasma

    NASA Astrophysics Data System (ADS)

    Shakeel, Hira; Arshad, Saboohi; Haq, S. U.; Nadeem, Ali

    2016-05-01

    The germanium plasma produced by the fundamental harmonics (1064 nm) of Nd:YAG laser in single and double pulse configurations have been studied spectroscopically. The plasma is characterized by measuring the electron temperature using the Boltzmann plot method for neutral and ionized species and electron number density as a function of laser irradiance, ambient pressure, and distance from the target surface. It is observed that the plasma parameters have an increasing trend with laser irradiance (9-33 GW/cm2) and with ambient pressure (8-250 mbar). However, a decreasing trend is observed along the plume length up to 4.5 mm. The electron temperature and electron number density are also determined using a double pulse configuration, and their behavior at fixed energy ratio and different interpulse delays is discussed.

  8. Atomic precision etch using a low-electron temperature plasma

    NASA Astrophysics Data System (ADS)

    Dorf, L.; Wang, J.-C.; Rauf, S.; Zhang, Y.; Agarwal, A.; Kenney, J.; Ramaswamy, K.; Collins, K.

    2016-03-01

    Sub-nm precision is increasingly being required of many critical plasma etching processes in the semiconductor industry. Accurate control over ion energy and ion/radical composition is needed during plasma processing to meet these stringent requirements. Described in this work is a new plasma etch system which has been designed with the requirements of atomic precision plasma processing in mind. In this system, an electron sheet beam parallel to the substrate surface produces a plasma with an order of magnitude lower electron temperature Te (~ 0.3 eV) and ion energy Ei (< 3 eV without applied bias) compared to conventional radio-frequency (RF) plasma technologies. Electron beam plasmas are characterized by higher ion-to-radical fraction compared to RF plasmas, so a separate radical source is used to provide accurate control over relative ion and radical concentrations. Another important element in this plasma system is low frequency RF bias capability which allows control of ion energy in the 2-50 eV range. Presented in this work are the results of etching of a variety of materials and structures performed in this system. In addition to high selectivity and low controllable etch rate, an important requirement of atomic precision etch processes is no (or minimal) damage to the remaining material surface. It has traditionally not been possible to avoid damage in RF plasma processing systems, even during atomic layer etch. The experiments for Si etch in Cl2 based plasmas in the aforementioned etch system show that damage can be minimized if the ion energy is kept below 10 eV. Layer-by-layer etch of Si is also demonstrated in this etch system using electrical and gas pulsing.

  9. Optical Diagnostics of Electron Energy Distributions in Low Temperature Plasmas

    NASA Astrophysics Data System (ADS)

    Wendt, Amy

    2011-05-01

    Passive, non-invasive optical emission measurements provide a means of probing important plasma parameters without introducing contaminants into plasma systems. We investigate the electron energy distribution function (EEDF) in argon containing inductively-coupled plasmas due to dominant role in rates of gas-phase reactions for processing plasmas. EEDFs are determined using measurements of 3p5 4 p --> 3p5 4 s emissions in the 650-1150 nm wavelength range and measured metastable and resonant level concentrations, in conjunction with a radiation model that includes contributions from often neglected but critical processes such as radiation trapping and electron-impact excitation from metastable and resonant levels. Measurements over a wide range of operating conditions (pressure, RF power, Ar/Ne/N2 gas mixtures) show a depletion of the EEDF relative to the Maxwell- Boltzmann form at higher electron energy, in good agreement with measurements made with Langmuir probes and predictions of a global discharge model. This result is consistent with predictions of electron kinetics and can be explained in terms of reduced life times for energetic electrons due to wall losses and inelastic collisions. This example highlights the potential utility of this method as a tool for probing kinetics of many types of low-temperature plasma systems, which are typically characterized by non-Maxwellian EEDFs. This work was supported by the Wisconsin Alumni Research Foundation (WARF) and by NSF Grant CBET 0714600.

  10. Plasma electron temperature and the entropy effect on hydrogen production

    NASA Astrophysics Data System (ADS)

    Chakartnarodom, Parinya

    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.

  11. Temperature evolution of strongly coupled electron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Tiwari, Sanat Kumar; Shaffer, Nathaniel; Baalrud, Scott D.

    2015-11-01

    Molecular dynamics simulations of electron-ion plasmas have been carried out, focusing on the classical strongly coupled regime relevant to ultracold neutral plasmas. The interaction of oppositely charged species is modeled using a pseudopotential with a repulsive core at a specified distance ɛ in units of average interparticle spacing. This parameter distinguishes classical from quantum statistical regimes. Simulations are initiated with an equilibration phase in which ions and electrons are held to fixed independent temperatures using a thermostat. Subsequently, the thermostats are removed and the system is allowed to evolve. Two effects are observed: (1) For sufficiently small values of ɛ, the plasma rapidly heats, (2) electrons and ions equilibrate on a longer time scale. The critical ɛ value for the onset of heating and the temperature equilibration rate are compared with existing theory. Excess pressure is calculated in each case based on the equilibrium radial distribution functions obtained during the equilibration phase. The Γ - ɛ phase space is explored, revealing qualitative differences in the temperature evolution due to electron-ion interactions in the classical and quantum regimes. The authors gratefully acknowledge support from NSF grant PHY-1453736.

  12. Temperature diagnostics of ECR plasma by measurement of electron bremsstrahlung

    SciTech Connect

    Kasthurirangan, S.; Agnihotri, A. N.; Desai, C. A.; Tribedi, L. C.

    2012-07-15

    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 Multiplication-Sign 10{sup -7} mbar to 7 Multiplication-Sign 10{sup -5} mbar and for input microwave power {approx}1 W to {approx}300 W. At the highest input power and optimum pressure conditions, the end point bremsstrahlung energies are seen to reach {approx}700 keV. The estimated electron temperatures (T{sub e}) were found to be in the range 20 keV-80 keV. The T{sub e} is found to be peaking at a pressure of 1 Multiplication-Sign 10{sup -5} mbar for both gases. The T{sub 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.

  13. To the problem of electron temperature control in plasma

    SciTech Connect

    Galechyan, G.A.; Anna, P.R.

    1995-12-31

    One of the main problems in low temperature plasma is control plasma parameters at fixed values of current and gas pressure in the discharge. It is known that an increase in the intensity of sound wave directed along the positive column to values in excess of a definite threshold leads to essential rise of the temperature of electrons. However, no less important is the reduction of electron temperature in the discharge down to the value less than that in plasma in the absence external influence. It is known that to reduce the electron temperature in the plasma of CO{sub 2} laser, easily ionizable admixture are usually introduced in the discharge area with the view of increasing the overpopulation. In the present work we shall show that the value of electron temperature can be reduced by varying of sound wave intensity at its lower values. The experiment was performed on an experimental setup consisted of the tube with length 52 cm and diameter 9.8 cm, two electrodes placed at the distance of 27 cm from each other. An electrodynamical radiator of sound wave was fastened to one of tube ends. Fastened to the flange at the opposite end was a microphone for the control of sound wave parameters. The studies were performed in range of pressures from 40 to 180 Torr and discharge currents from 40 to 110 mA. The intensity of sound wave was varied from 74 to 92 dB. The measurement made at the first resonance frequency f = 150 Hz of sound in the discharge tube, at which a quarter of wave length keep within the length of the tube. The measurement of longitudinal electric field voltage in plasma of positive column was conducted with the help of two probes according to the compensation method. Besides, the measurement of gas temperature in the discharge were taken. Two thermocouple sensors were arranged at the distance of 8 cm from the anode, one of them being installed on the discharge tube axis, the second-fixed the tube wall.

  14. Modelling electron transport in magnetized low-temperature discharge plasmas

    NASA Astrophysics Data System (ADS)

    Hagelaar, G. J. M.

    2007-02-01

    Magnetic fields are sometimes used to confine the plasma in low-pressure low-temperature gas discharges, for example in magnetron discharges, Hall-effect-thruster discharges, electron-cyclotron-resonance discharges and helicon discharges. We discuss how these magnetized discharges can be modelled by two-dimensional self-consistent models based on electron fluid equations. The magnetized electron flux is described by an anisotropic drift diffusion equation, where the electron mobility is much smaller perpendicular to the magnetic field than parallel to it. The electric potential is calculated either from Poisson's equation or from the electron equations, assuming quasineutrality. Although these models involve many assumptions, they are appropriate to study the main effects of the magnetic field on the charged particle transport and space charge electric fields in realistic two-dimensional discharge configurations. We demonstrate by new results that these models reproduce known phenomena such as the establishment of the Boltzmann relation along magnetic field lines, the penetration of perpendicular applied electric fields into the plasma bulk and the decrease in magnetic confinement by short-circuit wall currents. We also present an original method to prevent numerical errors arising from the extreme anisotropy of the electron mobility, which tend to invalidate model results from standard numerical methods.

  15. 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}.

  16. Ion- and electron-acoustic solitons in two-electron temperature space plasmas

    SciTech Connect

    Lakhina, G. S.; Kakad, A. P.; Singh, S. V.; Verheest, F.

    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.

  17. Sustenance of inhomogeneous electron temperature in a magnetized plasma column

    SciTech Connect

    Karkari, S. K. Mishra, S. K.; Kaw, P. K.

    2015-09-15

    This paper presents the equilibrium properties of a magnetized plasma column sustained by direct-current (dc) operated hollow cathode discharge in conjunction with a conducting end-plate, acting as the anode. The survey of radial plasma characteristics, performed in argon plasma, shows hotter plasma in the periphery as compared to the central plasma region; whereas the plasma density peaks at the center. The off-centered peak in radial temperature is attributed due to inhomogeneous power deposition in the discharge volume in conjunction with short-circuiting effect by the conducting end plate. A theoretical model based on particle flux and energy balance is given to explain the observed characteristics of the plasma column.

  18. 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

  19. 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.

  20. Nonlocal control of electron temperature in short direct current glow discharge plasma

    SciTech Connect

    Demidov, V. I.; Kudryavtsev, A. A.; Stepanova, O. M.; Kurlyandskaya, I. P.

    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.

  1. Nonlinear Mirror Modes in a Plasma with Nonzero Electron Temperature

    SciTech Connect

    Istomin, Ya. N.; Pokhotelov, O. A.; Balikhin, M. A.

    2009-11-10

    The nonlinear theory of magnetic mirror instability (MI) accounting for the nonzero electron temperature effect is developed. Using our previous low-frequency approach to the analysis of this instability but including nonzero electron temperature effect a set of equations describing nonlinear dynamics of mirror modes was derived. In the linear limit a Fourier transform of these equations recovers the linear MI growth rate in which the finite ion Larmor radius and nonzero electron temperature effects are taken into account. When the electron temperature T{sub e} becomes of the same order as the parallel ion temperature T{sub parallel} the growth rate of the mirror instability is reduced by the presence of the parallel electric field. The latter arises because the electrons are dragged by nonresonant ions which are mirror accelerated from regions of high into regions of low parallel magnetic flux. The nonzero electron temperature effect also substantially modifies the mirror mode nonlinear dynamics. It is found that when T{sub e}{approx_equal}T{sub parallel} the transition from the linear to nonlinear regime occurs already for the wave amplitude twice smaller than that inherent to the cold electron temperature limit. The further nonlinear dynamics develops with the explosive formation of the magnetic holes and then ends with the saturated state in the form of solitary structures or cnoidal waves. It is shown that incorporation of nonzero temperature results in a weak decreases of the spatial dimensions of the holes and increase of their depth.

  2. Measuring the electron density, temperature, and electronegativity in electron beam-generated plasmas produced in argon/SF6 mixtures

    NASA Astrophysics Data System (ADS)

    Boris, D. R.; Fernsler, R. F.; Walton, S. G.

    2015-04-01

    This paper presents measurements of electron density (ne0), electron temperature (Te), and electronegativity (α) in electron beam-generated plasmas produced in mixtures of argon and SF6 using Langmuir probes and plasma resonance spectroscopy. Langmuir probe measurements are analyzed using a model capable of handling multi-component plasmas with both positive and negative ions. Verification of the model is provided through plasma frequency resonance measurements of ne0. The results suggest a simple approach to ascertaining α in negative-ion-containing plasmas using Langmuir probes alone. In addition, modest amounts of SF6 are shown to produce sharp increases in both Te and α in electron beam generated plasmas.

  3. 2-D Imaging of Electron Temperature in Tokamak Plasmas

    SciTech Connect

    T. Munsat; E. Mazzucato; H. Park; C.W. Domier; M. Johnson; N.C. Luhmann Jr.; J. Wang; Z. Xia; I.G.J. Classen; A.J.H. Donne; M.J. van de Pol

    2004-07-08

    By taking advantage of recent developments in millimeter wave imaging technology, an Electron Cyclotron Emission Imaging (ECEI) instrument, capable of simultaneously measuring 128 channels of localized electron temperature over a 2-D map in the poloidal plane, has been developed for the TEXTOR tokamak. Data from the new instrument, detailing the MHD activity associated with a sawtooth crash, is presented.

  4. Two dimensional electron cyclotron emission imaging study of electron temperature profiles and fluctuations in Tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Deng, Bihe

    An innovative plasma diagnostic technique, electron cyclotron emission imaging (ECEI), was successfully developed and implemented on the TEXT-U and RTP tokamaks for the study of plasma electron temperature profiles and fluctuations. Due to the high spatial and temporal resolution of this new diagnostic, plasma filamentation was observed during high power electron cyclotron resonance heating (ECRH) in TEXT-U, and was identified as multiple rotating magnetic islands. In RTP, under special plasma conditions, evidence for magnetic bubbling was first observed, which is characterized by the flattening of the electron temperature and pressure profiles over a small annular region of about 1-2 cm extent near the q = 2 surface. More important results arose from the detailed study of the broadband plasma turbulence in TEXT-U and RTP. With the first measurements of poloidal wavenumbers and dispersion relations, turbulent Te fluctuations in the confinement region of TEXT-U plasmas were identified as electron drift wave turbulence. The fluctuation amplitude is found to follow the mixing length scaling, and the fluctuation-induced conducted- heat flux can account for the observed anomalous energy transport in TEXT-U. In RTP, detailed ECEI study of broadband Te fluctuations has shown that many characteristics of the observed fluctuations are consistent with the predictions of toroidal ηi mode theory. These include the global dependence of the fluctuation frequency and amplitude on the plasma density and current. The measured isotope and impurity scalings quantitatively match the predictions of toroidal ηi mode theory. The ECEI measurements in combination with ECRH modification of T e profiles argue against the Te gradients serving as the driving force of the turbulence. With the detailed 2- D measurements of the fluctuation distribution over the plasma minor cross-section, large scale, coherent structures similar to the eigenmode structures predicted by toroidal ηi mode theory

  5. Electron temperature measurement in Maxwellian non-isothermal beam plasma of an ion thruster

    NASA Astrophysics Data System (ADS)

    Zhang, Zun; Tang, Haibin; Kong, Mengdi; Zhang, Zhe; Ren, Junxue

    2015-02-01

    Published electron temperature profiles of the beam plasma from ion thrusters reveal many divergences both in magnitude and radial variation. In order to know exactly the radial distributions of electron temperature and understand the beam plasma characteristics, we applied five different experimental approaches to measure the spatial profiles of electron temperature and compared the agreement and disagreement of the electron temperature profiles obtained from these techniques. Experimental results show that the triple Langmuir probe and adiabatic poly-tropic law methods could provide more accurate space-resolved electron temperature of the beam plasma than other techniques. Radial electron temperature profiles indicate that the electrons in the beam plasma are non-isothermal, which is supported by a radial decrease (˜2 eV) of electron temperature as the plume plasma expands outward. Therefore, the adiabatic "poly-tropic law" is more appropriate than the isothermal "barometric law" to be used in electron temperature calculations. Moreover, the calculation results show that the electron temperature profiles derived from the "poly-tropic law" are in better agreement with the experimental data when the specific heat ratio (γ) lies in the range of 1.2-1.4 instead of 5/3.

  6. Electron temperature measurement in Maxwellian non-isothermal beam plasma of an ion thruster

    SciTech Connect

    Zhang, Zun; Tang, Haibin Kong, Mengdi; Zhang, Zhe; Ren, Junxue

    2015-02-15

    Published electron temperature profiles of the beam plasma from ion thrusters reveal many divergences both in magnitude and radial variation. In order to know exactly the radial distributions of electron temperature and understand the beam plasma characteristics, we applied five different experimental approaches to measure the spatial profiles of electron temperature and compared the agreement and disagreement of the electron temperature profiles obtained from these techniques. Experimental results show that the triple Langmuir probe and adiabatic poly-tropic law methods could provide more accurate space-resolved electron temperature of the beam plasma than other techniques. Radial electron temperature profiles indicate that the electrons in the beam plasma are non-isothermal, which is supported by a radial decrease (∼2 eV) of electron temperature as the plume plasma expands outward. Therefore, the adiabatic “poly-tropic law” is more appropriate than the isothermal “barometric law” to be used in electron temperature calculations. Moreover, the calculation results show that the electron temperature profiles derived from the “poly-tropic law” are in better agreement with the experimental data when the specific heat ratio (γ) lies in the range of 1.2-1.4 instead of 5/3.

  7. Electron temperature measurement in Maxwellian non-isothermal beam plasma of an ion thruster.

    PubMed

    Zhang, Zun; Tang, Haibin; Kong, Mengdi; Zhang, Zhe; Ren, Junxue

    2015-02-01

    Published electron temperature profiles of the beam plasma from ion thrusters reveal many divergences both in magnitude and radial variation. In order to know exactly the radial distributions of electron temperature and understand the beam plasma characteristics, we applied five different experimental approaches to measure the spatial profiles of electron temperature and compared the agreement and disagreement of the electron temperature profiles obtained from these techniques. Experimental results show that the triple Langmuir probe and adiabatic poly-tropic law methods could provide more accurate space-resolved electron temperature of the beam plasma than other techniques. Radial electron temperature profiles indicate that the electrons in the beam plasma are non-isothermal, which is supported by a radial decrease (∼2 eV) of electron temperature as the plume plasma expands outward. Therefore, the adiabatic "poly-tropic law" is more appropriate than the isothermal "barometric law" to be used in electron temperature calculations. Moreover, the calculation results show that the electron temperature profiles derived from the "poly-tropic law" are in better agreement with the experimental data when the specific heat ratio (γ) lies in the range of 1.2-1.4 instead of 5/3. PMID:25725841

  8. Thermal and Nonthermal Electron-ion Bremsstrahlung Spectrum from High-Temperature Plasmas

    NASA Technical Reports Server (NTRS)

    Jung, Young-Dae

    1994-01-01

    Electron-ion bremsstrahlung radiation from high-temperature plasmas is investigated. The first- and second-order Coulomb corrections in the nonrelativistic bremsstrahlung radiation power are obtained by the Elwert-Sommerfeld factor. In this paper, two cases of the electron distributions, the thermal and nonthermal power-law distributions, are considered. The inclusion of Coulomb corrections is necessary in deducing correctly the electron distribution function from radiation data. These results provide the correct information of electron distributions in high-temperature plasmas, such as in inertial confinement fusion plasmas and in the astrophysical hot thermal and nonthermal x-ray sources.

  9. Probing plasma turbulence by modulating the electron temperature gradient

    SciTech Connect

    DeBoo, J. C.; Petty, C. C.; Holland, C.; Rhodes, T. L.; Schmitz, L.; Wang, G.; Doyle, E. J.; Hillesheim, J.; Peebles, W. A.; Zeng, L.; White, A. E.; Austin, M. E.; Yan, Z.

    2010-05-15

    The local value of a/L{sub Te}, a turbulence drive term, was modulated with electron cyclotron heating in L-mode discharges on DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] and the density and electron temperature fluctuations in low, intermediate, and high-k regimes were measured and compared with nonlinear gyrokinetic turbulence simulations using the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)]. The local drive term at rhoapprox0.6 was reduced by up to 50%, which produced comparable reductions in electron temperature fluctuations at low-k. At intermediate k, k{sub t}hetaapprox4 cm{sup -1} and k{sub t}hetarho{sub s}approx0.8, a very interesting and unexpected result was observed where density fluctuations increased by up to 10% when the local drive term was decreased by 50%. Initial comparisons of simulations from GYRO with the thermal diffusivity from power balance analysis and measured turbulence response are reported. Simulations for the case with the lowest drive term are challenging as they are near the marginal value of a/L{sub Te} for trapped electron mode activity.

  10. Potential Formation in a Bounded Two-Electron Temperature Plasma System with Floating Collector That Emits Electrons

    NASA Astrophysics Data System (ADS)

    Gyergyek, Tomaž; Čerček, Milan

    2004-04-01

    Formation of the plasma potential in a plasma that contains energetic electrons and is bounded by a floating collector that emits electrons is studied theoretically. The problem is treated by a static. kinetic plasma-sheath model of Schwager and Birdsall [Phys. Fluids B 2 (1990) 1057], which we have extended in order to include additional energetic electron population. The distribution of these electrons is assumed to be a high-temperature Maxwellian. They are called hot electrons. In the paper we study effects of the density and temperature of the hot electrons on the formation of the plasma potential. The model shows that for certain densities and temperatures of the hot electron population plasmas with two different plasma potentials can coexist in the system. These two plasmas are separated spatially by a double layer. For the case when there is no emission of electrons from the collector, results of the model are compared with computer simulation and very good agreement between the model and the simulation is found. The simulation also confirms existence of two plasmas with two different potentials separated by a double layer.

  11. Local Measurement of Electron Density and Temperature in High Temperature Laser Plasma Using the Ion-Acoustic Dispersion

    SciTech Connect

    Froula, D H; Davis, P; Ross, S; Meezan, N; Divol, L; Price, D; Glenzer, S H; Rousseaux, C

    2005-09-20

    The dispersion of ion-acoustic fluctuations has been measured using a novel technique that employs multiple color Thomson-scattering diagnostics to measure the frequency spectrum for two separate thermal ion-acoustic fluctuations with significantly different wave vectors. The plasma fluctuations are shown to become dispersive with increasing electron temperature. We demonstrate that this technique allows a time resolved local measurement of electron density and temperature in inertial confinement fusion plasmas.

  12. Height variation of electron temperature associated with equatorial plasma bubbles - some recent rocket observations

    NASA Astrophysics Data System (ADS)

    Muralikrishna, P.; Batista, I. S.; Domingos, S.; Aquino, M. G.

    2013-05-01

    In-situ measurements made from Brazil recently using rocket-borne swept-bias Langmuir Probes show that the electron temperatures in the valley region between the equatorial E and F regions get modified before the onset of plasma bubbles. During one of the post sunset launches made on 18-th December 1995 from the equatorial rocket launching station CLA in Alcântara, Brazil the Langmuir probe measured abnormally large electron temperatures below the F-region just before the onset of plasma bubbles but temperatures became normal soon after the onset of bubbles. Later on 2-nd December 2011 a Brazilian VS-30 single stage rocket was launched from the equatorial rocket launching station CLBI in Natal, Brazil carrying a Langmuir probe operating alternately in swept and constant bias modes to measure both electron temperature and electron density respectively. The ground equipments operated before and during the rocket launch clearly showed the presence of plasma bubbles above the F-region. At the time of launch the bubble activity was at its peak. The electron density and temperature height profiles could be estimated from the LP data up to the rocket apogee altitude of 139km. During the rocket upleg and downleg the valley region showed the presence electron temperatures as high as 2000 degree K while the temperatures expected from the existing models are around 500 degree K. A two stage VS-30/Orion rocket was launched on 8-th December soon after sunset carrying a Langmuir Probe operating alternately in swept and constant bias modes to measure the electron density and electron temperature, mainly in the valley between the E and F regions. At the time of launch ground equipments operated at equatorial stations showed ionospheric conditions favorable for the generation of plasma bubbles. These profiles are compared with model electron density and temperature profiles as well as with electron density and temperature profiles observed under conditions of no plasma bubbles.

  13. Evolution of the electron temperature profile of ohmically heated plasmas in TFTR

    SciTech Connect

    Taylor, G.; Efthimion, P.C.; Arunasalam, V.; Goldston, R.J.; Grek, B.; Hill, K.W.; Johnson, D.W.; McGuire, K.; Ramsey, A.T.; Stauffer, F.J.

    1985-08-01

    Blackbody electron cyclotron emission was used to ascertain and study the evolution and behavior of the electron temperature profile in ohmically heated plasmas in the Tokamak Fusion Test Reactor (TFTR). The emission was measured with absolutely calibrated millimeter wavelength radiometers. The temperature profile normalized to the central temperature and minor radius is observed to broaden substantially with decreasing limiter safety factor q/sub a/, and is insensitive to the plasma minor radius. Sawtooth activity was seen in the core of most TFTR discharges and appeared to be associated with a flattening of the electron temperature profile within the plasma core where q less than or equal to 1. Two types of sawtooth behavior were identified in large TFTR plasmas (minor radius, a less than or equal to 0.8 m) : a typically 35 to 40 msec period ''normal'' sawtooth, and a ''compound'' sawtooth with 70 to 80 msec period.

  14. Experimental observation of electron-temperature-gradient turbulence in a laboratory plasma.

    PubMed

    Mattoo, S K; Singh, S K; Awasthi, L M; Singh, R; Kaw, P K

    2012-06-22

    We report the observation of electron-temperature-gradient (ETG) driven turbulence in the laboratory plasma of a large volume plasma device. The removal of unutilized primary ionizing and nonthermal electrons from uniform density plasma and the imposition and control of the gradient in the electron temperature (T[Symbol: see text] T(e)) are all achieved by placing a large (2 m diameter) magnetic electron energy filter in the middle of the device. In the dressed plasma, the observed ETG turbulence in the lower hybrid range of frequencies ν = (1-80 kHz) is characterized by a broadband with a power law. The mean wave number k perpendicular ρ(e) = (0.1-0.2) satisfies the condition k perpendicular ρ(e) ≤ 1, where ρ(e) is the electron Larmor radius. PMID:23004612

  15. Arbitrary amplitude kinetic Alfven solitary waves in two temperature electron superthermal plasma

    NASA Astrophysics Data System (ADS)

    Singh, Manpreet; Singh Saini, Nareshpal; Ghai, Yashika

    2016-07-01

    Through various satellite missions it is observed that superthermal velocity distribution for particles is more appropriate for describing space and astrophysical plasmas. So it is appropriate to use superthermal distribution, which in the limiting case when spectral index κ is very large ( i.e. κ→∞), shifts to Maxwellian distribution. Two temperature electron plasmas have been observed in auroral regions by FAST satellite mission, and also by GEOTAIL and POLAR satellite in the magnetosphere. Kinetic Alfven waves arise when finite Larmor radius effect modifies the dispersion relation or characteristic perpendicular wavelength is comparable to electron inertial length. We have studied the kinetic Alfven waves (KAWs) in a plasma comprising of positively charged ions, superthermal hot electrons and Maxwellian distributed cold electrons. Sagdeev pseudo-potential has been employed to derive an energy balance equation. The critical Mach number has been determined from the expression of Sagdeev pseudo-potential to see the existence of solitary structures. It is observed that sub-Alfvenic compressive solitons and super-Alfvenic rarefactive solitons exist in this plasma model. It is also observed that various parameters such as superthermality of hot electrons, relative concentration of cold and hot electron species, Mach number, plasma beta, ion to cold electron temperature ratio and ion to hot electron temperature ratio have significant effect on the amplitude and width of the KAWs. Findings of this investigation may be useful to understand the dynamics of coherent non-linear structures (i.e. KAWs) in space and astrophysical plasmas.

  16. Measurement of Electron Temperature and Plasma Density via Thomson Scattering and Electric Probe in Low Temperature Plasmas

    NASA Astrophysics Data System (ADS)

    Woo, Hyun-Jong; Chung, Kyu-Sun; Lho, Taihyeop

    2011-10-01

    Laser Thomson scattering system has been developed for the measurements of electron temperature and plasma density in low temperature plasma by means of the Q-switched Nd:YAG laser with 2nd Harmonics (250 mJ at 532 nm, repetition rate of 20 Hz), triple grating spectrometer and ICCD camera. The triple grating spectrometer is composed of 3 grating (1800 gr/mm and 100 x 100 mm dimensions), 6 achromatic doublet lens (f=400 mm and 100 mm diameter) for reducing the abbreviation effect, two slits (entrance and exitance), opto- mechanical instruments, etc. The alignment and calibration of TGS system were performed by a diode laser and diffraction optics, Ne lamp (wavelength) and metal halide lamp (intensity), respectively. The LTS measurements were done wide ranges of 1 Plasma Simulator-II (DiPS-II) and it compared with the single probe measurements.

  17. Analysis of Electron Temperature in DC Ar/SF6 Plasma Using Cylindrical and Planar Probes

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Woo; Cho, Soon-Gook; Bae, Min-Keun; Kim, Hyung-Jin; Chung, Tae Hun; Chung, Kyu-Sun

    2013-11-01

    Electronegative plasmas are generated by adding SF6 gas to a background argon (Ar) DC plasma with parameters of n0 = 1×1010 cm3 and Te = 2 eV. The heating current of the thoriated filament was in the range of 20.5-21.5 A and the plasmas were generated under a discharge condition of 100 V/0.4 A. The amount of negative ions was controlled by adjusting the ratio of flow rate of SF6 = 0-10% to that of Ar. Plasma parameters were measured using cylindrical and planar electric probes. The behavior of electrons, which means the change in a parameter due to negative ion production, is characterized by measuring the floating and plasma potentials, and electron temperature. Electron temperature seems to increase and the potentials decrease with SF6 flow rate.

  18. Threefold Increase of the Bulk Electron Temperature of Plasma Discharges in a Magnetic Mirror Device

    NASA Astrophysics Data System (ADS)

    Bagryansky, P. A.; Shalashov, A. G.; Gospodchikov, E. D.; Lizunov, A. A.; Maximov, V. V.; Prikhodko, V. V.; Soldatkina, E. I.; Solomakhin, A. L.; Yakovlev, D. V.

    2015-05-01

    This Letter describes plasma discharges with a high temperature of bulk electrons in the axially symmetric high-mirror-ratio (R =35 ) open magnetic system gas dynamic trap (GDT) in the Budker Institute (Novosibirsk). According to Thomson scattering measurements, the on-axis electron temperature averaged over a number of sequential shots is 660 ±50 eV with the plasma density being 0.7 ×1 019 m-3 ; in few shots, electron temperature exceeds 900 eV. This corresponds to at least a threefold increase with respect to previous experiments both at GDT and at other comparable machines, thus, demonstrating the highest quasistationary (about 1 ms) electron temperature achieved in open traps. The breakthrough is made possible by application of a new 0.7 MW /54.5 GHz electron cyclotron resonance heating system in addition to standard 5 MW heating by neutral beams, and application of a radial electric field to mitigate the flute instability.

  19. Effect of two-temperature electrons distribution on an electrostatic plasma sheath

    NASA Astrophysics Data System (ADS)

    Ou, Jing; Xiang, Nong; Gan, Chunyun; Yang, Jinhong

    2013-06-01

    A magnetized collisionless plasma sheath containing two-temperature electrons is studied using a one-dimensional model in which the low-temperature electrons are described by Maxwellian distribution (MD) and high-temperature electrons are described by truncated Maxwellian distribution (TMD). Based on the ion wave approach, a modified sheath criterion including effect of TMD caused by high-temperature electrons energy above the sheath potential energy is established theoretically. The model is also used to investigate numerically the sheath structure and energy flux to the wall for plasmas parameters of an open divertor tokamak-like. Our results show that the profiles of the sheath potential, two-temperature electrons and ions densities, high-temperature electrons and ions velocities as well as the energy flux to the wall depend on the high-temperature electrons concentration, temperature, and velocity distribution function associated with sheath potential. In addition, the results obtained in the high-temperature electrons with TMD as well as with MD sheaths are compared for the different sheath potential.

  20. Reduced electron temperature in a magnetized inductively-coupled plasma with internal coil

    SciTech Connect

    Arancibia Monreal, J.; Chabert, P.; Godyak, V.

    2013-10-15

    The effect of magnetic filtering on the electron energy distribution function is studied in an inductive discharge with internal coil coupling. The coil is placed inside the plasma and driven by a low-frequency power supply (5.8 MHz) which leads to a very high power transfer efficiency. A permanent dipole magnet may be placed inside the internal coil to produce a static magnetic field around 100 Gauss. The coil and the matching system are designed to minimize the capacitive coupling to the plasma. Capacitive coupling is quantified by measuring the radiofrequency (rf) plasma potential with a capacitive probe. Without the permanent magnet, the rf plasma potential is significantly smaller than the electron temperature. When the magnet is present, the rf plasma potential increases. The electron energy distribution function is measured as a function of space with and without the permanent magnet. When the magnet is present, electrons are cooled down to low temperature in the downstream region. This region of low electron temperature may be useful for plasma processing applications, as well as for efficient negative ion production.

  1. Oblique shock waves in a two electron temperature superthermally magnetized plasma

    NASA Astrophysics Data System (ADS)

    Bains, A. S.; Panwar, A.; Ryu, C. M.

    2015-11-01

    A study is presented for the oblique propagation of low-frequency ion acoustic ( IA) shock waves in a magnetized plasma consisting of cold ions and two temperature superthermally distributed electrons. A nonlinear Korteweg de-Vries-Burger ( KdV-Burger) equation is obtained by using the reductive perturbation method (RPM) which governs the dynamics of the IA shock wave. Using the solution of KdV-Burger equation, the characteristics of the IA shock wave have been studied for various plasma parameters. The combined effects of the cold to hot electron temperature ratio (σ), the density ratio of hot electrons to ions (f), the superthermality of cold and hot electrons (κc, κh), the strength of the magnetic field (ω_{ci}), and the obliqueness (θ), significantly influence the profile of the shock wave. The findings in the present study could be important for the electrostatic wave structures in the Saturn's magnetosphere, where two temperature electrons exist with a kappa distribution.

  2. Quantum Cohesion Oscillation of Electron Ground State in Low Temperature Laser Plasma

    NASA Technical Reports Server (NTRS)

    Zhao, Qingxun; Zhang, Ping; Dong, Lifang; Zhang, Kaixi

    1996-01-01

    The development of radically new technological and economically efficient methods for obtaining chemical products and for producing new materials with specific properties requires the study of physical and chemical processes proceeding at temperature of 10(exp 3) to 10(exp 4) K, temperature range of low temperature plasma. In our paper, by means of Wigner matrix of quantum statistical theory, a formula is derived for the energy of quantum coherent oscillation of electron ground state in laser plasma at low temperature. The collective behavior would be important in ion and ion-molecule reactions.

  3. Simultaneous measurement of electron temperature and density by a line pair method in the RFP plasma

    NASA Astrophysics Data System (ADS)

    Watanabe, Masayuki; Shimizu, S.; Ogawa, H.; Shinohara, T.

    2009-11-01

    A line-pair-method has been applied for a simultaneous measurement of the electron temperature and density in ATRAS RFP plasma. Three helium spectrum lines (668nm, 706nm, 728nm) were measured during the discharge at the same time and the electron temperature and density is estimated by using a Collision-Radiation model. To get the signal of the helium impunity line from the RFP discharge, the RFP plasma in the hydrogen gas with a few mixed helium gas was formed. In the typical ATRAS RFP discharge of the plasma current of 60kA, the electron temperature was approximately 50-150 eV and the electron density is the order of 10^18 m-3. During the discharge, the change of the temperature and density are mutually related and this correlation was the almost reverse phase. The periodically change of the temperature and density were also observed. This change synchronizes with a periodically increase of the averaged toroidal magnetic field, which is caused by the toroidal rotation of the increase of the toroidal magnetic field. This rotation, which is deeply related with dynamo effect, makes the plasma energy lose and particles also diffuse toward the plasma edge. As a result, the recycling of the particle and energy are occurred at the same time.

  4. Comparative electron temperature measurements of Thomson scattering and electron cyclotron emission diagnostics in TCABR plasmas

    SciTech Connect

    Alonso, M. P.; Figueiredo, A. C. A.; Berni, L. A.; Machida, M.

    2010-10-15

    We present the first simultaneous measurements of the Thomson scattering and electron cyclotron emission radiometer diagnostics performed at TCABR tokamak with Alfven wave heating. The Thomson scattering diagnostic is an upgraded version of the one previously installed at the ISTTOK tokamak, while the electron cyclotron emission radiometer employs a heterodyne sweeping radiometer. For purely Ohmic discharges, the electron temperature measurements from both diagnostics are in good agreement. Additional Alfven wave heating does not affect the capability of the Thomson scattering diagnostic to measure the instantaneous electron temperature, whereas measurements from the electron cyclotron emission radiometer become underestimates of the actual temperature values.

  5. Effects of relativistic electron temperature on parametric instabilities for intense laser propagation in underdense plasma

    SciTech Connect

    Zhao, Yao; Zheng, Jun; Chen, Min; Yu, Lu-Le; Weng, Su-Ming; Ren, Chuang; Liu, Chuan-Sheng; Sheng, Zheng-Ming E-mail: zhengming.sheng@strath.ac.uk

    2014-11-15

    Effects of relativistic electron temperature on stimulated Raman scattering and stimulated Brillouin scattering instabilities for high intensity lasers propagating in underdense plasma are studied theoretically and numerically. The dispersion relations for these instabilities are derived from the relativistic fluid equation. For a wide range of laser intensity and electron temperature, it is found that the maximum growth rate and the instability region in k-space can be reduced at relativistic electron temperature. Particle-in-cell simulations are carried out, which confirm the theoretical analysis.

  6. Estimations of electron densities and temperatures in He-3 dominated plasmas. [in nuclear pumped lasers

    NASA Technical Reports Server (NTRS)

    Depaola, B. D.; Marcum, S. D.; Wrench, H. K.; Whitten, B. L.; Wells, W. E.

    1979-01-01

    It is very useful to have a method of estimation for electron temperature and electron densities in nuclear pumped plasmas because measurements of such quantities are very difficult. This paper describes a method, based on rate equation analysis of the ionized species in the plasma and the electron energy balance. In addition to the ionized species, certain neutral species must also be calculated. Examples are given for pure helium and a mixture of helium and argon. In the HeAr case, He(+), He2(+), He/2 3S/, Ar(+), Ar2(+), and excited Ar are evaluated.

  7. Arbitrary amplitude slow electron-acoustic solitons in three-electron temperature space plasmas

    SciTech Connect

    Mbuli, L. N.; Maharaj, S. K.; Bharuthram, R.; Singh, S. V.; Lakhina, G. S.

    2015-06-15

    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. Electron density and temperature profile diagnostics for C-2 field reversed configuration plasmas

    SciTech Connect

    Deng, B. H.; Kinley, J. S.; Schroeder, J.

    2012-10-15

    The 9-point Thomson scattering diagnostic system for the C-2 field reversed configuration plasmas is improved and the measured electron temperature profiles are consistent with theoretical expectations. Rayleigh scattering revealed a finite line width of the ruby laser emission, which complicates density calibration. Taking advantage of the plasma wobble motion, density profile reconstruction accuracy from the 6-chord two-color CO{sub 2}/HeNe interferometer data is improved.

  9. Electron energy distribution function, effective electron temperature, and dust charge in the temporal afterglow of a plasma

    NASA Astrophysics Data System (ADS)

    Denysenko, I. B.; Kersten, H.; Azarenkov, N. A.

    2016-05-01

    Analytical expressions describing the variation of electron energy distribution function (EEDF) in an afterglow of a plasma are obtained. Especially, the case when the electron energy loss is mainly due to momentum-transfer electron-neutral collisions is considered. The study is carried out for different EEDFs in the steady state, including Maxwellian and Druyvesteyn distributions. The analytical results are not only obtained for the case when the rate for momentum-transfer electron-neutral collisions is independent on electron energy but also for the case when the collisions are a power function of electron energy. Using analytical expressions for the EEDF, the effective electron temperature and charge of the dust particles, which are assumed to be present in plasma, are calculated for different afterglow durations. An analytical expression for the rate describing collection of electrons by dust particles for the case when the rate for momentum-transfer electron-neutral collisions is independent on electron energy is also derived. The EEDF profile and, as a result, the effective electron temperature and dust charge are sufficiently different in the cases when the rate for momentum-transfer electron-neutral collisions is independent on electron energy and when the rate is a power function of electron energy.

  10. Optical emission spectroscopy for simultaneous measurement of plasma electron density and temperature in a low-pressure microwave induced plasma

    SciTech Connect

    Konjevic, N.; Jovicevic, S.; Ivkovic, M.

    2009-10-15

    The simple optical emission spectroscopy technique for diagnostics of low pressure microwave induced plasma (MIP) in hydrogen or in MIP seeded with hydrogen is described and tested. This technique uses the Boltzmann plot of relative line intensities along Balmer spectral series in conjunction with the criterion for partial local thermodynamic equilibrium for low electron density (N{sub e}) plasma diagnostics. The proposed technique is tested in a low pressure MIP discharge for simultaneous determination of electron density N{sub e} (10{sup 17}-10{sup 18} m{sup -3}) and temperature T{sub e}.

  11. Measurements of Electron Temperature and Density, in an AC Pulsed Oxygen Plasma Discharge

    NASA Astrophysics Data System (ADS)

    Yousif, Farook; Martinez, Horacio; Castillo, Fermin

    2007-06-01

    Emission and analytical spectroscopy was applied to investigate O2 plasma, which was generated by an AC discharge between 0.15 and 0.5 Torr pressure. For the diagnostic study, a double Langmuir probe was employed. The derivation of plasma parameters is based on a theoretical description of the double-probe current-voltage characterization in the Thick Sheath Limit (TSL) region [1]. Electron temperature of Te = 1.09 eV and an ion density of ni= 2.08 x 10^10 cm-3 were evaluated at 2 Torr. We present electron temperature and ion density as a function of the pressure at 3 different power discharge levels. Also we present emission spectroscopy in the wavelength range of 200-1100 nm as a function of the pressure. [1] J.D. Swift and J. R. Schwar, Electric Probes for Plasma Diagnostics (New York: Elsevier) 1971.

  12. Ion-Scale Electrostatic Nonplanar Shock Waves in Dusty Plasmas with Two-Temperature Superthermal Electrons

    NASA Astrophysics Data System (ADS)

    Alam, M. S.; Masud, M. M.; Mamun, A. A.

    2015-02-01

    The basic properties of nonplanar (viz. cylindrical and spherical) dust-ion-acoustic (DIA) shock waves in an unmagnetized dusty plasma system [consisting of inertial ions, negatively charged immobile dust, and superthermal electrons with two distinct temperatures] are investigated by employing the reductive perturbation method. The modified Burgers equation is derived and is numerically analyzed in order to examine the basic properties of DIA shock structures. The effects of nonplanar geometry, electron superthermality, and ion kinematic viscosity on the basic features of DIA shock waves are discussed. It is found that the properties of the cylindrical and spherical DIA shock waves in dusty plasmas with two-temperature superthermal electrons significantly differ from those of one-dimensional planar shocks. The implications of our results in space plasmas [viz. star formation, supernovae explosion, solar wind, pulsar magnetosphere, Saturn's outer magnetosphere (R ˜13-18 R S , where R S is the radius of Saturn), Saturn's inner magnetosphere (R <9 R S , etc.)] and laboratory plasmas (viz. laser-induced implosion, capsule implosion, shock tube, etc.), where superthermal electrons with two distinct temperatures occurs, are briefly discussed.

  13. 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.

  14. Improved electron collisional line broadening for low-temperature ions and neutrals in plasma modeling

    SciTech Connect

    Johns, H. M.; Kilcrease, D. P.; Colgan, J.; Judge, E. J.; Barefield II, J. E.; Wiens, R. C.; Clegg, S. M.

    2015-09-29

    In this study, electron collisional broadening of observed spectral lines depends on plasma electron temperature and density. Including this effect in models of measured spectra is necessary to determine plasma conditions; however, computational limits make accurate line broadening treatments difficult to implement in large-scale plasma modeling efforts. In this paper, we report on improvements to the treatment of electron collisional line broadening and illustrate this with calculations using the Los Alamos ATOMIC code. We implement the Dimitrijevic and Konjevic modified semi-empirical model Dimitrijevic and Konjevic (1986 Astron. and Astrophy. 163 297 and 1987 Astron. Astrophys. 172 345), which we amend by employing oscillator strengths from Hartree–Fock calculations. This line broadening model applies to near-neutral plasmas with electron temperatures of Te ~ 1 eV and electron densities of Ne ~1017 cm-3. We evaluate the D.K.-inspired model against the previous hydrogenic approach in ATOMIC through comparison to NIST-rated measurements for selected neutral and singly-ionized Ca, O, Fe, and Sn lines using both fine-structure and configuration-averaged oscillator strengths. The new D.K.-inspired model is significantly more accurate than the previous hydrogenic model and we find the use of configuration-averaged oscillator strengths a good approximation for applications such as LIBS (laser induced breakdown spectroscopy), for which we demonstrate the use of the D.K.-inspired model.

  15. Improved electron collisional line broadening for low-temperature ions and neutrals in plasma modeling

    DOE PAGESBeta

    Johns, H. M.; Kilcrease, D. P.; Colgan, J.; Judge, E. J.; Barefield II, J. E.; Wiens, R. C.; Clegg, S. M.

    2015-09-29

    In this study, electron collisional broadening of observed spectral lines depends on plasma electron temperature and density. Including this effect in models of measured spectra is necessary to determine plasma conditions; however, computational limits make accurate line broadening treatments difficult to implement in large-scale plasma modeling efforts. In this paper, we report on improvements to the treatment of electron collisional line broadening and illustrate this with calculations using the Los Alamos ATOMIC code. We implement the Dimitrijevic and Konjevic modified semi-empirical model Dimitrijevic and Konjevic (1986 Astron. and Astrophy. 163 297 and 1987 Astron. Astrophys. 172 345), which we amendmore » by employing oscillator strengths from Hartree–Fock calculations. This line broadening model applies to near-neutral plasmas with electron temperatures of Te ~ 1 eV and electron densities of Ne ~1017 cm-3. We evaluate the D.K.-inspired model against the previous hydrogenic approach in ATOMIC through comparison to NIST-rated measurements for selected neutral and singly-ionized Ca, O, Fe, and Sn lines using both fine-structure and configuration-averaged oscillator strengths. The new D.K.-inspired model is significantly more accurate than the previous hydrogenic model and we find the use of configuration-averaged oscillator strengths a good approximation for applications such as LIBS (laser induced breakdown spectroscopy), for which we demonstrate the use of the D.K.-inspired model.« less

  16. Electron density and temperature measurement by continuum radiation emitted from weakly ionized atmospheric pressure plasmas

    SciTech Connect

    Park, Sanghoo; Choe, Wonho; Youn Moon, Se; Park, Jaeyoung

    2014-02-24

    The electron-atom neutral bremsstrahlung continuum radiation emitted from weakly ionized plasmas is investigated for electron density and temperature diagnostics. The continuum spectrum in 450–1000 nm emitted from the argon atmospheric pressure plasma is found to be in excellent agreement with the neutral bremsstrahlung formula with the electron-atom momentum transfer cross-section given by Popović. In 280–450 nm, however, a large discrepancy between the measured and the neutral bremsstrahlung emissivities is observed. We find that without accounting for the radiative H{sub 2} dissociation continuum, the temperature, and density measurements would be largely wrong, so that it should be taken into account for accurate measurement.

  17. Generalized Lenard-Balescu calculations of electron-ion temperature relaxation in beryllium plasma.

    PubMed

    Fu, Zhen-Guo; Wang, Zhigang; Li, Da-Fang; Kang, Wei; Zhang, Ping

    2015-09-01

    The problem of electron-ion temperature relaxation in beryllium plasma at various densities (0.185-18.5g/cm^{3}) and temperatures [(1.0-8)×10^{3} eV] is investigated by using the generalized Lenard-Balescu theory. We consider the correlation effects between electrons and ions via classical and quantum static local field corrections. The numerical results show that the electron-ion pair distribution function at the origin approaches the maximum when the electron-electron coupling parameter equals unity. The classical result of the Coulomb logarithm is in agreement with the quantum result in both the weak (Γ_{ee}<10^{-2}) and strong (Γ_{ee}>1) electron-electron coupling ranges, whereas it deviates from the quantum result at intermediate values of the coupling parameter (10^{-2}<Γ_{ee}<1). We find that with increasing density of Be, the Coulomb logarithm will decrease and the corresponding relaxation rate ν_{ie} will increase. In addition, a simple fitting law ν_{ie}/ν_{ie}^{(0)}=a(ρ_{Be}/ρ_{0})^{b} is determined, where ν_{ie}^{(0)} is the relaxation rate corresponding to the normal metal density of Be and ρ_{0}, a, and b are the fitting parameters related to the temperature and the degree of ionization 〈Z〉 of the system. Our results are expected to be useful for future inertial confinement fusion experiments involving Be plasma. PMID:26465571

  18. Study of transport properties with relativistic ponderomotive effect in two-electron temperature plasma

    SciTech Connect

    Sen, Sonu Dubey, A.; Varshney, Meenu Asthana; Varshney, Dinesh

    2014-04-24

    In the present paper we make an analytical investigation to study transport properties with relativistic ponderomotive effect in two-electron temperature plasma. Using fluid model the two-electron temperature are introduced through relativistic ponderomotive force for the transportation of two species of electrons. Applying WKB and paraxial ray approximation the nonlinear dielectric constant and self-focusing equation is evaluated and analyzed with experimental relevance. Numerical calculations are made for different concentration of electron density (10{sup 19}−10{sup 21} per cm{sup 3}) at arbitrary values of laser intensity in the range 10{sup 18}−10{sup 21} W/cm{sup 2}. For a minimum radius depending on the initial conditions it is oscillating between a minimum and maximum value. The hot electrons leading to the increase of the on-axis transportation and favorable effect on relativistic self-focusing.

  19. Measurements of plasma quasi-thermal noise on STEREO spacecraft and plasma temperature deduction using antenna electron shot noise model

    NASA Astrophysics Data System (ADS)

    Martinović, M.; Zaslavsky, A.; Maksimovic, M.; Zouganelis, Y.

    2014-12-01

    Quasi-thermal noise spectroscopy is very accurate technique for in situ measurements of electron density and temperature in space plasmas. This technique uses the voltage fluctuation spectrum, which is ubiquitous in interplanetary space, obtained by an electric antenna. It is independent of antenna orientation if velocity distribution function of plasma particles is considered to be isotropic. On STEREO/WAVES antennas electron shot noise spectrum dominates because of large antenna surface area, especially at lower frequencies. This feature of antennas disables simultaneous measurements of electron density and temperature. However, technique may work accurately in high-density filamentary structures, where Debye length is small. In this paper, it has been illustrated on magnetic clouds. Obtained results have been used to recalibrate the data of PLASTIC instrument. Further on, in unperturbed solar wind, electron shot noise has been used to infer electron temperature. Electron density data, necessary in data processing, has been estimated from recalibrated PLASTIC data. For this purpose, data of both STEREO A and STEREO B spacecraft have been processed by selecting only spectra from free solar wind.

  20. Surface electronic states of low-temperature H-plasma-exposed Ge(100)

    NASA Astrophysics Data System (ADS)

    Cho, Jaewon; Nemanich, R. J.

    1992-11-01

    The surface of low-temperature H-plasma-cleaned Ge(100) was studied by angle-resolved UV-photoemission spectroscopy and low-energy electron diffraction (LEED). The surface was prepared by an ex situ preclean followed by an in situ H-plasma exposure at a substrate temperature of 150-300 °C. Auger-electron spectroscopy indicated that the in situ H-plasma clean removed the surface contaminants (carbon and oxygen) from the Ge(100) surface. The LEED pattern varied from a 1×1 to a sharp 2×1, as the substrate temperature was increased. The H-induced surface state was identified at ~5.6 eV below EF, which was believed to be mainly due to the ordered or disordered monohydride phases. The annealing dependence of the spectra showed that the hydride started to dissociate at a temperature of 190 °C, and the dangling-bond surface state was identified. A spectral shift upon annealing indicated that the H-terminated surfaces were unpinned. After the H-plasma clean at 300 °C the dangling-bond surface state was also observed directly with no evidence of H-induced states.

  1. Threefold Increase of the Bulk Electron Temperature of Plasma Discharges in a Magnetic Mirror Device.

    PubMed

    Bagryansky, P A; Shalashov, A G; Gospodchikov, E D; Lizunov, A A; Maximov, V V; Prikhodko, V V; Soldatkina, E I; Solomakhin, A L; Yakovlev, D V

    2015-05-22

    This Letter describes plasma discharges with a high temperature of bulk electrons in the axially symmetric high-mirror-ratio (R=35) open magnetic system gas dynamic trap (GDT) in the Budker Institute (Novosibirsk). According to Thomson scattering measurements, the on-axis electron temperature averaged over a number of sequential shots is 660±50  eV with the plasma density being 0.7×10^{19}  m^{-3}; in few shots, electron temperature exceeds 900 eV. This corresponds to at least a threefold increase with respect to previous experiments both at GDT and at other comparable machines, thus, demonstrating the highest quasistationary (about 1 ms) electron temperature achieved in open traps. The breakthrough is made possible by application of a new 0.7  MW/54.5  GHz electron cyclotron resonance heating system in addition to standard 5 MW heating by neutral beams, and application of a radial electric field to mitigate the flute instability. PMID:26047233

  2. Ion-acoustic supersolitons in plasmas with two-temperature electrons: Boltzmann and kappa distributions

    SciTech Connect

    Verheest, Frank; Hellberg, Manfred A.; Kourakis, Ioannis

    2013-08-15

    Acoustic supersolitons arise when a plasma model is able to support three consecutive local extrema of the Sagdeev pseudopotential between the undisturbed conditions and an accessible root. This leads to a characteristic electric field signature, where a simple bipolar shape is enriched by subsidiary maxima. Large-amplitude nonlinear acoustic modes are investigated, using a pseudopotential approach, for plasmas containing two-temperature electrons having Boltzmann or kappa distributions, in the presence of cold fluid ions. The existence domains for positive supersolitons are derived in a methodological way, both for structure velocities and amplitudes, in terms of plasma compositional parameters. In addition, typical pseudopotentials, soliton, and electric field profiles have been given to illustrate that positive supersolitons can be found in the whole range of electron distributions from Maxwellian to a very hard nonthermal spectrum in kappa. However, it is found that the parameter ranges that support supersolitons vary significantly over the wide range of kappa considered.

  3. Zakharov-Kuznetsov equation in a magnetized plasma with two temperature superthermal electrons

    SciTech Connect

    Saini, N. S. Chahal, B. S.; Bains, A. S.; Bedi, C.

    2014-02-15

    A nonlinear Zakharov-Kuznetsov (ZK) equation for ion-acoustic solitary waves (IASWs) in a magnetized plasmas containing kappa distributed cold and hot electrons is derived by using reductive perturbation method. From the solution of ZK equation, the characteristics of IASWs have been studied under the influence of various plasma parameters. Existence domain of physical parameters is determined. It has been observed that the present plasma system supports the existence of both positive as well as negative potential solitons. The combined effects of cold to hot electron temperature ratio (σ), density ratio of cold electrons to ions (f), superthermality of cold and hot electrons (κ{sub c},κ{sub h}), strength of magnetic field (via Ω{sub i}), and obliqueness (θ) significantly influence the profile of IASWs. The physical parameters play a great role to modify the width and amplitude of the solitary structures. The stability analysis is also presented in this investigation and parametric range is determined to check the presence of stable and unstable solitons. The findings of this study are important to the physics of electrostatic wave structures in the Saturn's magnetosphere where two temperature electrons with kappa distribution exist.

  4. High and low frequency instabilities driven by a single electron beam in two-electron temperature space plasmas

    SciTech Connect

    Mbuli, L. N.; Maharaj, S. K.; Bharuthram, R.

    2013-12-15

    In an attempt to understand the excitation mechanisms of broadband electrostatic noise, beam-generated electrostatic instabilities are investigated using kinetic theory in a four-component magnetised plasma model composed of beam electrons (magnetic field-aligned), background hot and cool electrons and ions. All species are fully magnetised and considered to be Maxwellian. The dependence of the instability growth rates and real frequencies on various plasma parameters such as beam speed, particle densities and temperatures, magnetic field strength, wave propagation angle, and temperature anisotropy of the beam are examined. In this study we have found that the electron-acoustic, electron beam-resonant and ion-acoustic instabilities are excited. Our studies have focused on three velocity regimes, namely, the low (v{sub dbz}2 C{sub h}) regimes, where v{sub dbz} (C{sub h}) is the electron beam drift speed (thermal speed of the hot electrons). Plasma parameters from satellite measurements are used where applicable to provide realistic predictions.

  5. Improvement of Electron Field Emission in Patterned Carbon Nanotubes by High Temperature Hydrogen Plasma Treatment

    PubMed Central

    Wang, Sigen; Sellin, Paul. J.; Lian, Jun; Özsan, Ersin; Chang, Sha

    2009-01-01

    In this paper, we report a significant improvement of electron field emission property in patterned carbon nanotubes films by using a high temperature (650 °C) hydrogen plasma treatment. This treatment was found to greatly increase the emission current, emission uniformity and stability. The mechanism study showed that these enhanced properties are attributed to the lowering of the potential barrier and the creation of geometrical features through the removal of amorphous carbon, catalyst particles and the saturation of dangling bonds after such a hydrogen plasma treatment. PMID:19946566

  6. Finite electron temperature effects on interferometric and polarimetric measurements in fusion plasmas

    NASA Astrophysics Data System (ADS)

    Mirnov, V. V.; Ding, W. X.; Brower, D. L.; Van Zeeland, M. A.; Carlstrom, T. N.

    2007-10-01

    Finite electron temperature effects on interferometry and polarimetry measurements for burning plasma are considered with particular focus on analytically understanding the role of weakly relativistic effects. Development of a new iterative technique, in the limit when the probing wave frequency is much higher than the electron cyclotron frequency, yields the dispersion relation to lowest (linear) order in Te/mec2≪1. Perturbative treatment of the wave phase and polarization is presented in a form suitable for interpretation of experimental data. Previous analysis of the problem included nonrelativistic calculations only. Herein, it is shown that relativistic effects are equally important. Theoretical results are in agreement with computations and can be used for benchmarking of ray tracing codes. The implication of finite temperature effects on future burning plasma interferometer diagnostics is discussed.

  7. Theory of coupled whistler-electron temperature gradient mode in high beta plasma: Application to linear plasma device

    SciTech Connect

    Singh, S. K.; Awasthi, L. M.; Singh, R.; Kaw, P. K.; Jha, R.; Mattoo, S. K.

    2011-10-15

    This paper presents a theory of coupled whistler (W) and electron temperature gradient (ETG) mode using two-fluid model in high beta plasma. Non-adiabatic ion response, parallel magnetic field perturbation ({delta}B{sub z}), perpendicular magnetic flutter ({delta}B{sub perpendicular}), and electron collisions are included in the treatment of theory. A linear dispersion relation for whistler-electron temperature gradient (W-ETG) mode is derived. The numerical results obtained from this relation are compared with the experimental results observed in large volume plasma device (LVPD) [Awasthi et al., Phys. Plasma 17, 42109 (2010)]. The theory predicts that the instability grows only where the temperature gradient is finite and the density gradient flat. For the parameters of the experiment, theoretically estimated frequency and wave number of W-ETG mode match with the values corresponding to the peak in the power spectrum observed in LVPD. By using simple mixing length argument, estimated level of fluctuations of W-ETG mode is in the range of fluctuation level observed in LVPD.

  8. Effects of Anomalous Electron Cross-Field Transport in a Low Temperature Magnetized Plasma

    NASA Astrophysics Data System (ADS)

    Raitses, Yevgeny

    2014-10-01

    The application of the magnetic field in a low pressure plasma can cause a spatial separation of low and high energy electrons. This so-called magnetic filter effect is used for many plasma applications, including ion and neutral beam sources, plasma processing of semiconductors and nanomaterials, and plasma thrusters. In spite of successful practical applications, the magnetic filter effect is not well understood. In this work, we explore this effect by characterizing the electron and ion energy distribution functions in a plasma column with crossed electric and magnetic fields. Experimental results revealed a strong dependence of spatial variations of plasma properties on the gas pressure. For xenon and argon gases, below ~ 1 mtorr, the increase of the magnetic field leads to a more uniform profile of the electron temperature. This surprising result is due to anomalously high electron cross-field transport that causes mixing of hot and cold electrons. High-speed imaging and probe measurements revealed a coherent structure rotating in E cross B direction with frequency of a few kHz. Theory and simulations describing this rotating structure has been developed and points to ionization and electrostatic instabilities as their possible cause. Similar to spoke oscillations reported for Hall thrusters, this rotating structure conducts the large fraction of the cross-field current. The use of segmented electrodes with an electrical feedback control is shown to mitigate these oscillations. Finally, a new feature of the spoke phenomenon that has been discovered, namely a sensitive dependence of the rotating oscillations on the gas pressure, can be important for many applications. This work was supported by DOE Contract DE-AC02-09CH11466.

  9. Oblique ion-acoustic cnoidal waves in two temperature superthermal electrons magnetized plasma

    SciTech Connect

    Panwar, A. Ryu, C. M.; Bains, A. S.

    2014-12-15

    A study is presented for the oblique propagation of ion acoustic cnoidal waves in a magnetized plasma consisting of cold ions and two temperature superthermal electrons modelled by kappa-type distributions. Using the reductive perturbation method, the nonlinear Korteweg de-Vries equation is derived, which further gives the solutions with a special type of cnoidal elliptical functions. Both compressive and rarefactive structures are found for these cnoidal waves. Nonlinear periodic cnoidal waves are explained in terms of plasma parameters depicting the Sagdeev potential and the phase curves. It is found that the density ratio of hot electrons to ions μ significantly modifies compressive/refractive wave structures. Furthermore, the combined effects of superthermality of cold and hot electrons κ{sub c},κ{sub h}, cold to hot electron temperature ratio σ, angle of propagation and ion cyclotron frequency ω{sub ci} have been studied in detail to analyze the height and width of compressive/refractive cnoidal waves. The findings in the present study could have important implications in understanding the physics of electrostatic wave structures in the Saturn's magnetosphere where two temperature superthermal electrons are present.

  10. Electrostatic wave structures in a magnetized superthermal plasma with two-temperature electrons

    SciTech Connect

    Shahmansouri, M.; Alinejad, H.

    2013-08-15

    The linear and nonlinear excitation of arbitrary amplitude ion-acoustic (IA) solitary waves in a magnetized plasma comprising two-temperature electrons and cold ions are studied. The oblique propagation properties of two possible modes (in the linear regime) are investigated. It is found that the electron superthermality reduces the phase velocities of both modes, whereas obliqueness leads to an increase in the separation between two modes. In the nonlinear regime, an energy-like equation describes the evolution of IA solitary waves in the present model. The combined effects of the electron superthermality, magnitude of magnetic field, obliqueness and electron population are incorporated in the study of the existence domain of solitary waves and the soliton characteristics. It is shown that the small values of the hot electron population shift the permitted interval of Mach number to the lower values. Both compressive and rarefactive solitary structures are found to exist in the presence of two temperature electrons. The present investigation contributes to the physics of electrostatic wave structures in Saturn's magnetosphere in which two temperature electrons with kappa distribution exist.

  11. The Jupiter hot plasma torus - Observed electron temperature and energy flows

    NASA Technical Reports Server (NTRS)

    Brown, R. A.

    1981-01-01

    The detection of the optical emission /O I/ 6300 A (8 + or - 4 R) and /S III/ 6312 A (48 + or - 5 R) is reported. It is noted that these emissions are indicators of the ion source morphology and the plasma physical state and that the S III emitters have a kinetic temperature of approximately 10 to the 6th K. When combined with observations of UV lines from the same species, the optical measurements separately imply effective electron temperatures for radiative processes that are mutually consistent (approximately 50,000 K).

  12. Secondary Electron Emission Properties of Plasma Facing Ceramic Materials at High Temperatures

    NASA Astrophysics Data System (ADS)

    Raitses, Yevgeny; Dourbal, Paul; Spektor, Rostislav

    2015-11-01

    The plasma-wall interaction in the presence of strong secondary electron emission (SEE) has been studied theoretically and experimentally both as a basic phenomenon and in relation to numerous plasma applications such as, for example, fusion devices and Hall thrusters. Herein, we report on SEE measurements for boron nitride (BN) ceramics, which are commonly used as channel wall materials for Hall thrusters. Measurements were conducted for BN ceramics of three different grades with different fractions (0, 1% and 40%) and phases of different binder additions (calcium borate, silicon oxide) and as a function of the sample temperature relevant to the thruster operation (about 600K). For all three grades, the energy at which the yield equals to 1 at room temperature was measured to be near 40 V. This result is in agreement with previous measurements. At the elevated temperature, the yield was slightly different for these ceramics, but lower than at the room temperature. This temperature effect was not as strong as measured in. Analysis of these results and their implication on plasma-surface interactions in Hall thrusters and other related devices are presented. This work was partially supported by the Aerospace Corporation and by DOE contract DE-AC02-09CH11466.

  13. The LXCat project: Electron scattering cross sections and swarm parameters for low temperature plasma modeling

    NASA Astrophysics Data System (ADS)

    Pancheshnyi, S.; Biagi, S.; Bordage, M. C.; Hagelaar, G. J. M.; Morgan, W. L.; Phelps, A. V.; Pitchford, L. C.

    2012-04-01

    LXCat is a dynamic, open-access, website for collecting, displaying, and downloading ELECtron SCATtering cross sections and swarm parameters (mobility, diffusion coefficient, reaction rates, etc.) required for modeling low temperature, non-equilibrium plasmas. Contributors set up individual databases, and the available databases, indicated by the contributor's chosen title, include mainly complete sets of electron-neutral scattering cross sections, although the option for introducing partial sets of cross sections exists. A database for measured swarm parameters is also part of LXCat, and this is a growing activity. On-line tools include options for browsing, plotting, and downloading cross section data. The electron energy distribution functions (edfs) in low temperature plasmas are in general non-Maxwellian, and LXCat provides an option for execution of an on-line Boltzmann equation solver to calculate the edf in homogeneous electric fields. Thus, the user can obtain electron transport and rate coefficients (averages over the edfs) in pure gases or gas mixtures over a range of values of the reduced electric fields strength, E/N, the ratio of the electric field strength to the neutral density, using cross sections from the available databases. New contributors are welcome and anyone wishing to create a database and upload data can request a username and password. LXCat is part of a larger, community-wide effort aimed at collecting, evaluating, and sharing data relevant to modeling low temperature plasmas. To illustrate the utility of LXCat in this context, we compare electron swarm parameters in argon calculated using the different compilations of cross sections presently available on LXCat. These compilations include quite different groupings of excited states, yet lead to swarm parameters in good agreement. LXCat is available at http://www.lxcat.laplace.univ-tlse.fr.

  14. Parametric decays in relativistic magnetized electron-positron plasmas with relativistic temperatures

    SciTech Connect

    Lopez, Rodrigo A.; Munoz, Victor; Asenjo, Felipe A.; Alejandro Valdivia, J.

    2012-08-15

    The nonlinear evolution of a circularly polarized electromagnetic wave in an electron-positron plasma propagating along a constant background magnetic field is considered, by studying its parametric decays. Relativistic effects, of the particle motion in the wave field and of the plasma temperature, are included to obtain the dispersion relation of the decays. The exact dispersion relation of the pump wave has been previously calculated within the context of a relativistic fluid theory and presents two branches: an electromagnetic and an Alfven one. We investigate the parametric decays for the pump wave in these two branches, including the anomalous dispersion zone of the Alfven branch where the group velocity is negative. We solve the nonlinear dispersion relation for different pump wave amplitudes and plasma temperatures, finding various resonant and nonresonant wave couplings. We are able to identify these couplings and study their behavior as we modify the plasma parameters. Some of these couplings are suppressed for larger amplitudes or temperatures. We also find two kinds of modulational instabilities, one involving two sideband daughter waves and another involving a forward-propagating electroacoustic mode and a sideband daughter wave.

  15. Parametric decays in relativistic magnetized electron-positron plasmas with relativistic temperatures

    NASA Astrophysics Data System (ADS)

    López, Rodrigo A.; Asenjo, Felipe A.; Muñoz, Víctor; Alejandro Valdivia, J.

    2012-08-01

    The nonlinear evolution of a circularly polarized electromagnetic wave in an electron-positron plasma propagating along a constant background magnetic field is considered, by studying its parametric decays. Relativistic effects, of the particle motion in the wave field and of the plasma temperature, are included to obtain the dispersion relation of the decays. The exact dispersion relation of the pump wave has been previously calculated within the context of a relativistic fluid theory and presents two branches: an electromagnetic and an Alfvén one. We investigate the parametric decays for the pump wave in these two branches, including the anomalous dispersion zone of the Alfvén branch where the group velocity is negative. We solve the nonlinear dispersion relation for different pump wave amplitudes and plasma temperatures, finding various resonant and nonresonant wave couplings. We are able to identify these couplings and study their behavior as we modify the plasma parameters. Some of these couplings are suppressed for larger amplitudes or temperatures. We also find two kinds of modulational instabilities, one involving two sideband daughter waves and another involving a forward-propagating electroacoustic mode and a sideband daughter wave.

  16. Small amplitude electron-acoustic double layers and solitons in fully relativistic plasmas of two-temperature electrons

    SciTech Connect

    Lee, Nam C.

    2009-04-15

    A Korteweg-de Vries (KdV) equation for fully relativistic one dimensional plasmas of arbitrarily large streaming speed and temperature is derived by using the reductive perturbation method. For plasmas with more than two species of particles, the coefficient representing quadratic nonlinearity in KdV can vanish at critical values of certain parameters. To describe the nonlinear evolution at this critical parameter, a modified KdV (mKdV) equation that contains a cubic nonlinear term is obtained. Furthermore, a mixed mKdV equation pertaining to parameters in the vicinity of the critical values is also derived, in which the quadratic and cubic nonlinearities are both present. As an illustration of the results, the mixed mKdV equation is applied to a plasma comprised of cold ions and electrons having cold (T=0) and finite temperature components. For warm temperature T<electron-acoustic nonlinear waves in the shape of double layer (kink) and solitary waves can exist, which have phase speed {radical}(3T/(4+{alpha})m{sub e}) in the rest frame of plasma, where {alpha} is the polytropic index of the equation of state of the warm electrons. The thickness of the transitional layer of the kink structure is of the order of Debye length {lambda}{sub D}. For extremely high temperature T>>m{sub e}c{sup 2}, it is also found that double layer and soliton-type solutions can exist with phase speed {radical}({alpha}-1)c, which is equal to the well known relativistic sound speed c/{radical}(3) for {alpha}=4/3. The thickness of the transition layer scales as {delta}{approx}T{sup -1/4}, which is different from the T<

  17. Electron temperature diagnostics of aluminium plasma in a z-pinch experiment at the “QiangGuang-1" facility

    NASA Astrophysics Data System (ADS)

    Li, Mo; Wu, Jian; Wang, Liang-Ping; Wu, Gang; Han, Juan-Juan; Guo, Ning; Qiu, Meng-Tong

    2012-12-01

    Two curved crystal spectrometers are set up on the “QiangGuang-1" generator to measure the z-pinch plasma spectra emitted from planar aluminum wire array loads. Kodak Biomax-MS film and an IRD AXUVHS5# array are employed to record time-integrated and time-resolved free-bound radiation, respectively. The photon energy recorded by each detector is ascertained by using the L-shell lines of molybdenum plasma. Based on the exponential relation between the continuum power and photon energies, the aluminum plasma electron temperatures are measured. For the time-integrated diagnosis, several “bright spots" indicate electron temperatures between (450 eV ~ 520 eV) ± 35%. And for the time-resolved ones, the result shows that the electron temperature reaches about 800 eV ± 30% at peak power. The system satisfies the demand of z-pinch plasma electron temperature diagnosis on a ~ 1 MA facility.

  18. Ion-acoustic Gardner Solitons in electron-positron-ion plasma with two-electron temperature distributions

    NASA Astrophysics Data System (ADS)

    Rehman, Momin A.; Mishra, M. K.

    2016-01-01

    The ion-acoustic solitons in collisionless plasma consisting of warm adiabatic ions, isothermal positrons, and two temperature distribution of electrons have been studied. Using reductive perturbation method, Korteweg-de Vries (K-dV), the modified K-dV (m-KdV), and Gardner equations are derived for the system. The soliton solution of the Gardner equation is discussed in detail. It is found that for a given set of parameter values, there exists a critical value of β=Tc/Th, (ratio of cold to hot electron temperature) below which only rarefactive KdV solitons exist and above it compressive KdV solitons exist. At the critical value of β, both compressive and rarefactive m-KdV solitons co-exist. We have also investigated the soliton in the parametric regime where the KdV equation is not valid to study soliton solution. In this region, it is found that below the critical concentration the system supports rarefactive Gardner solitons and above it compressive Gardner solitons are found. The effects of temperature ratio of two-electron species, cold electron concentration, positron concentration on the characteristics of solitons are also discussed.

  19. Instability of field-aligned electron-cyclotron waves in a magnetic mirror plasma with anisotropic temperature

    NASA Astrophysics Data System (ADS)

    Grishanov, N. I.; Azarenkov, N. A.

    2016-08-01

    > Dispersion characteristics have been analysed for field-aligned electron-cyclotron waves (also known as right-hand polarized waves, extraordinary waves or whistlers) in a cylindrical magnetic mirror plasma including electrons with anisotropic temperature. It is shown that the instability of these waves is possible only in the range below the minimal electron-cyclotron frequency, which is much lower than the gyrotron frequency used for electron-cyclotron resonance power input into the plasma, under the condition where the perpendicular temperature of the resonant electrons is larger than their parallel temperature. The growth rates of whistler instability in the two magnetized plasma models, where the stationary magnetic field is either uniform or has a non-uniform magnetic mirror configuration, are compared.

  20. Linear and nonlinear dynamics of electron temperature gradient mode in non-Maxwellian plasmas

    SciTech Connect

    Zakir, U.; Qamar, A.; Haque, Q.

    2013-05-15

    The effect of non-Maxwellian distributed ions on electron temperature gradient mode is investigated. The linear dispersion relation of η{sub e}−mode is obtained which shows that the behavior of this mode changes in the presence of superthermal ions. The growth rate of η{sub e}−mode driven linear instability is found and is observed to modify due to nonthermal ions. However, it is found that this leaves the electron energy transport coefficient unchanged. In the nonlinear regime, a dipolar vortex solution is derived which indicates that the dynamic behavior of the vortices changes with the inclusion of kappa distributed ions. The importance of present study with respect to space and laboratory plasmas is also pointed out.

  1. Reduced model prediction of electron temperature profiles in microtearing-dominated NSTX plasmas

    NASA Astrophysics Data System (ADS)

    Kaye, S. M.; Guttenfelder, W.; Bell, R.; Gerhardt, S.; Leblanc, B.; Maingi, R.

    2014-10-01

    A representative H-mode discharge from the National Spherical Torus Experiment (NSTX) is studied in detail as a basis for a time-evolving prediction of the electron temperature profile using an appropriate reduced transport model. The time evolution of characteristic plasma variables such as βe, νe*, the MHD α parameter and the gradient scale lengths of Te, Ti and ne were examined prior to performing linear gyrokinetic calculations to determine the fastest growing microinstability at various times and locations throughout the discharge. The inferences from the parameter evolutions and the linear stability calculations were consistent. Early in the discharge, when βe and νe* were relatively low, ballooning parity modes were dominant. As both βe and νe* increased with time, microtearing became the dominant low-kθmode, especially in the outer half of the plasma. There are instances in time and radius where other modes, at higher-kθ, may be important for driving electron transport. The Rebut-Lallia-Watkins (RLW) electron thermal diffusivity model, which is based on microtearing-induced transport, was used to predict the time-evolving electron temperature across most of the profile. The results indicate that RLW does a good job of predicting Te for times and locations where microtearing was determined to be important, but not as well when microtearing was predicted to be stable or subdominant. This work has been supported by U.S. Dept of Energy contracts DE-AC02-09CH11466.

  2. Localized Electronic Excitation Temperature Measurements in an Air Microwave Plasma Torch at Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Green, K. M.; Flores, G. J., III; Woskov, P. P.; Hadidi, K.; Thomas, P.

    1999-10-01

    The Microwave Plasma Continuous Emissions Monitor, currently under development, uses atomic emission spectroscopy for trace metals pollution monitoring of stack exhaust. Operating at 2.45 GHz, the 1.5 kW magnetron sustains the plasma in a shorted WR-284 waveguide. Air flows through a 25.4 mm i.d. fused quartz tube traversing the waveguide. A pneumatic nebulizer introduces an iron nitrate solution into the axial gas flow. Radial profile measurements of atomic excitation temperature inside the waveguide have been obtained by Abel inversion of Fe I emission lines in the 367 nm to 377 nm range. An optical system with image magnification lenses and a fiber optic cable on a translation stage scans the radial intensity profile along 66 chords. Intensity and temperature profiles show peaked values on axis with a FWHM of 11 mm. An electronic excitation temperature of 6551 K ± 349 K is measured with an axial flow of 12 l/min and a swirl flow of 10 l/min.

  3. Theoretical and experimental study of the microwave cut-off probe for electron density measurements in low-temperature plasmas

    SciTech Connect

    Li Bin; Li Hong; Wang Huihui; Xie Jinlin; Liu Wandong

    2011-10-01

    The microwave cut-off probe for the electron density measurement in low-temperature plasmas is described in this article. It is based on the wave cutoff in an unmagnetized plasma. The measurement principle is analyzed theoretically using a model of plasma slab. Because of the high-pass characteristic of plasma, the waves above the cut-off frequency can penetrate the plasma slab, whereas the lower frequency waves are reflected from the cut-off layer. Therefore, an obvious critical point can be observed in the wave transmission spectrum. The abscissa of the critical point indicates the cut-off frequency, which is directly related to the maximum electron density between transmitting/receiving antennas of the cut-off probe. The measured electron densities are in agreement with the data obtained by the Langmuir probe. Experimental results show that the microwave cut-off probe can be used to diagnose the plasmas with a wide range of parameters.

  4. Electron density and temperature measurements in a magnetized expanding hydrogen plasma.

    PubMed

    Leyte-González, R; Palomares, J M; Schram, D C; Engeln, R

    2016-08-01

    We report measurements of electron densities, n_{e}, and temperatures, T_{e}, in a magnetized expanding hydrogen plasma performed using Thomson scattering. The effects of applying an axial magnetic field and changing the background pressure in the plasma vessel on n_{e} and T_{e} along the expansion axis are reported. Magnetic field strengths (B field) up to 170 mT were applied, which are one order of magnitude larger than previously reported. The main effect of the applied B field is the plasma confinement, which leads to higher n_{e}. At B fields larger than 88 mT the electron density along the expansion axis does not depend strongly on the magnetic field strength. However, T_{e} is susceptible to the B field and reaches at 170 mT a maximum of 2.5 eV at a distance of 1.5 cm from the exit of the cascaded arc. To determine also the effect of the arc current through the arc, measurements were performed with arc currents of 45, 60, and 75 A at background pressures of 9.7 and 88.3 Pa. At constant magnetic field n_{e} decreases from the exit of the arc along the expansion axis when the arc current is decreased. At 88.3 Pa n_{e} shows a higher value close to the exit of the arc, but a faster decay along the expansion axis with respect to the 9.7 Pa case. T_{e} is overall higher at lower pressure reaching a maximum of 3.2 eV at the lower arc current of 45 A. The results of this study complement our understanding and the characterization of expanding hydrogen plasmas. PMID:27627401

  5. Electron density and temperature measurements in a magnetized expanding hydrogen plasma

    NASA Astrophysics Data System (ADS)

    Leyte-González, R.; Palomares, J. M.; Schram, D. C.; Engeln, R.

    2016-08-01

    We report measurements of electron densities, ne, and temperatures, Te, in a magnetized expanding hydrogen plasma performed using Thomson scattering. The effects of applying an axial magnetic field and changing the background pressure in the plasma vessel on ne and Te along the expansion axis are reported. Magnetic field strengths (B field) up to 170 mT were applied, which are one order of magnitude larger than previously reported. The main effect of the applied B field is the plasma confinement, which leads to higher ne. At B fields larger than 88 mT the electron density along the expansion axis does not depend strongly on the magnetic field strength. However, Te is susceptible to the B field and reaches at 170 mT a maximum of 2.5 eV at a distance of 1.5 cm from the exit of the cascaded arc. To determine also the effect of the arc current through the arc, measurements were performed with arc currents of 45, 60, and 75 A at background pressures of 9.7 and 88.3 Pa. At constant magnetic field ne decreases from the exit of the arc along the expansion axis when the arc current is decreased. At 88.3 Pa ne shows a higher value close to the exit of the arc, but a faster decay along the expansion axis with respect to the 9.7 Pa case. Te is overall higher at lower pressure reaching a maximum of 3.2 eV at the lower arc current of 45 A. The results of this study complement our understanding and the characterization of expanding hydrogen plasmas.

  6. Studies of Electron Temperature Fluctuations in the Core of Alcator C-Mod Plasmas via Correlation ECE

    NASA Astrophysics Data System (ADS)

    Oi, C.; Sung, C.; Howard, N.; White, A. E.; Irby, J.; Leccacorvi, R.; Vieira, R.; Rice, J.; Gao, C.

    2012-10-01

    A correlation electron cyclotron emission (CECE) diagnostic has been designed and installed at the Alcator C-Mod tokamak to measure long wavelength fluctuations in electron temperature [C. Sung, this conference, C-Mod oral session]. It is important to characterize turbulent fluctuations in the plasma in order to better understand and predict transport, since the cross-magnetic field transport of particles and energy in fusion plasmas exceeds the values predicted by neoclassical theory. The first electron temperature fluctuation data collected from Alcator C-Mod ohmic plasmas has shown that as the ohmic confinement regime transitions from Linear Ohmic Confinement (LOC) to Saturated Ohmic Confinement (SOC) there is a decrease in the core electron temperature fluctuation level. The edge electron temperature fluctuations are similar between the two modes, suggesting that mainly the core turbulence characteristics change when there is a shift between LOC and SOC regimes. In both ohmic and ICRH plasmas, the measured spectrum is seen to broaden in response to increases in plasma rotation; and fluctuation level increases with radius. A description of the C-Mod CECE diagnostic will be presented, along with the initial measurements of turbulent electron temperature fluctuations.

  7. Electron temperature in transient plasmas from quasi-steady ratio of isoelectronic lines: application to picosecond and subpicosecond plasmas

    NASA Astrophysics Data System (ADS)

    Marjoribanks, R. S.; Budnik, F. W.; Chen, H.; Meyerhofer, D. D.

    1996-02-01

    We have extended the technique of plasma temperature measurement by ratio of isoelectronic lines, recently developed with nanosecond laser plasmas, to the diagnosis of picosecond and subpicosecond plasmas. We have found a major benefit-particularly for short-pulse laser plasmas-that even where level populations are far from steady-state values, the ratio of isoelectronic lines may be nearly steady state, which considerably simplifies interpretation. We describe theoretical and experimental investigations for plasmas created from solid targets by 100-fs-10-ps high-intensity laser pulses and report the experimental application of the technique to lambda =1.05 - mu m laser pulses at 1016 W cm -2 .

  8. Transitional properties of supersolitons in a two electron temperature warm multi-ion plasma

    NASA Astrophysics Data System (ADS)

    Varghese, Steffy S.; Ghosh, S. S.

    2016-08-01

    The existence domain of an ion acoustic supersoliton and its transition to a regular kind of solitary wave have been explored in detail using Sagdeev pseudopotential technique for a two electron temperature warm multi-ion plasma having two species of ions. It was found that both the cold to hot electron temperature ratio and their respective ambient densities play a deterministic role for the existence of a supersoliton, as well as its transitional processes to a regular solitary wave. Analogous to a double layer solution, which often marks the boundary of the existence domain of a regular solitary wave, a "curve of inflection" determines the boundary of the existence domain of a supersoliton. The characteristics of the "curve of inflection," in turn, depend on the respective concentrations of the two ion species. It is observed that the supersolitons are actually a subset of a more general kind of solutions which are characterized by a fluctuation in the corresponding charge separation which precedes their maximum amplitude. It is also observed that these novel kinds of solitary structures, including supersolitons, occur only for a very narrow range of parameters near constant amplitude beyond which the wave breaks.

  9. A new method for in situ electron temperature determinations from plasma wave phenomena

    NASA Technical Reports Server (NTRS)

    Oya, H.; Benson, R. F.

    1972-01-01

    A discrepancy has been reported between the values of the electron temperature t sub e deduced from satellite electrostatic probe measurements and ground based radar backscatter measurements. This discrepancy (radar backscatter temperature less than the probe temperature) is not present when the probe experiment is flown on a rocket to lower altitudes but reappears when the rocket probe attains higher altitudes. There is a need for an independent radio wave method for making in-situ t sub e measurements in order to help resolve this problem. A new method of determining t sub e from the satellite resonant phenomena is presented. It is based on the splitting (observed at high latitudes) of the diffuse resonance which occurs at the frequency f sub d1 between f sub h and 2 f sub h. The advantage of this method over the other methods involving ionospheric resonances is the simplicity of the required calculations. There is, however, the limitation of plasma conditions where the f sub d1 resonance can be observed and the limitation to mid-to-high latitudes where the splitting is observed.

  10. Research on soft x-rays in high-current plasma-focus discharges and estimation of plasma electron temperature

    NASA Astrophysics Data System (ADS)

    Skladnik-Sadowska, E.; Zaloga, D.; Sadowski, M. J.; Kwiatkowski, R.; Malinowski, K.; Miklaszewski, R.; Paduch, M.; Surala, W.; Zielinska, E.; Tomaszewski, K.

    2016-09-01

    The paper presents results of experimental studies of dense and high-temperature plasmas, which were produced by pulsed high-current discharges within a modernised PF-1000U facility operated at different initial gas conditions, and supplied from a condenser bank which delivered energy of about 350 kJ. The investigated discharges were performed at the initial deuterium filling under pressure of 1.6–2.0 hPa, with or without an additional puffing of pure deuterium (1 cm3, under pressure 0.15 MPa, at instants 1.5–2 ms before the main discharge initiation). For a comparison discharges were also performed at the initial neon filling under pressure of 1.1–1.3 hPa, with or without the addition of deuterium puffing. The recorded discharge current waveforms, laser interferometric images, signals of hard x-rays and fusion neutrons, as well as time-integrated x-ray pinhole images and time-resolved x-ray signals were compared. From a ratio of the x-ray signals recorded behind beryllium filters of different thickness there were estimated values of a plasma electron temperature (T e) in a region at the electrode outlets. For pure deuterium discharges an averaged T e value amounted to 150–170 eV, while for neon discharges with the deuterium puffing it reached 330–880 eV (with accuracy of  ±20%).

  11. Quantification of the error induced on Langmuir probe determined electron temperature and density due to an RF plasma potential

    NASA Astrophysics Data System (ADS)

    Kafle, Nischal; Donovan, David; Martin, Elijah

    2015-11-01

    An RF plasma potential can significantly effect the IV characteristic of a Langmuir probe if not properly compensated. A substantial research effort in the low temperature plasma community has been carried out to determine this effect and how to achieve the required compensation for accurate measurements. However, quantification of the error induced on the extracted electron temperature and density from an uncompensated Langmuir probe due to an RF plasma potential has not been explored. The research presented is the first attempt to quantify this error in terms of RF plasma potential magnitude, electron temperature, and electron density. The Langmuir probe IV characteristic was simulated using empirical formulas fitted to the Laframboise simulation results. The RF effected IV characteristic was simulated by adding a sinusoidal variation to the plasma potential and computing the time average numerically. The error induced on the electron temperature and density was determined by fitting the RF effected IV characteristic to the empirical formulas representing the standard Laframboise simulation results. Experimental results indicating the accuracy of this quantification will be presented.

  12. Estimation of Electron Temperature and Frequency Components in a Dual Frequency Capacitively-Coupled Plasma Processing Reactor

    NASA Astrophysics Data System (ADS)

    Ito, Toru; Mo, Yun; Masahiro, Horigome

    2008-10-01

    The measurement of electron temperature in RF plasma sources with Langmuir probes is difficult because of the influence of rf noise. We attempted to estimate the electron temperature in a capacitively-coupled plasma processing reactor with a Surface Wave Probe [1] which employs microwaves. We also estimated the frequency spectrum with the sensitive PAP [1, 2]. We measured the harmonics which appeared in the bulk plasma for various experimental conditions in the dual-frequency [60 MHz and 2MHz] capacitively-coupled plasma processing reactor. We estimated RF power spectra for several experimental conditions like RF power [500-2000W], gas pressure [3-20Pa], and gas species [Ar, CF4]. The measurement results suggest the existence of energy transport among several frequency spectrum. [1ex] [1] K. Nakamura, M. Ohata, and H. Sugai: J. Vac. Sci. Technol. A 21, 325 (2003). [0pt] [2] T. Shirakawa and H. Sugai : Jpn. J. Appl. Phys. 32, 5129 (1993).

  13. Simultaneous measurement of electron and heavy particle temperatures in He laser-induced plasma by Thomson and Rayleigh scattering

    SciTech Connect

    Dzierzega, K.; Mendys, A.; Zawadzki, W.; Pokrzywka, B.; Pellerin, S.

    2013-04-01

    Thomson and Rayleigh scattering methods were applied to quantify the electron and heavy particle temperatures, as well as electron number density, in a laser spark in helium at atmospheric pressure. Plasma was created using 4.5 ns, 25 mJ pulses from Nd:YAG laser at 532 nm. Measurements, performed for the time interval between 20 ns and 800 ns after breakdown, show electron density and temperature to decrease from 7.8 Multiplication-Sign 10{sup 23} m{sup -3} to 2.6 Multiplication-Sign 10{sup 22} m{sup -3} and from 95 900 K to 10 350 K, respectively. At the same time, the heavy particle temperature drops from only 47 000 K down to 4100 K which indicates a two temperature plasma out of local isothermal equilibrium.

  14. Boundary conditions at the walls with thermionic electron emission in two temperature modeling of “thermal” plasmas

    SciTech Connect

    Pekker, Leonid; Hussary, Nakhleh

    2015-08-15

    In this paper, we propose new boundary conditions for the electric potential, the electron energy equation, and the energy equation for heavy particles (ions and neutrals) at the hot walls with thermionic electron emission for two-temperature thermal arc models. The derived boundary conditions assume that the walls are made from refractory metals and, consequently, the erosion of the wall is small and can be neglected. In these boundary conditions, the plasma sheath formed at the electrode is viewed as the interface between the plasma and the wall. The derived boundary conditions allow the calculation of the heat flux to the walls from the plasma. This allows the calculation of the thermionic electron current that makes the model of electrode-plasma interaction self-consistent.

  15. Spectroscopic and probe measurements of the electron temperature in the plasma of a pulse-periodic microwave discharge in argon

    NASA Astrophysics Data System (ADS)

    Andreev, V. V.; Vasileska, I.; Korneeva, M. A.

    2016-07-01

    A pulse-periodic 2.45-GHz electron-cyclotron resonance plasma source on the basis of a permanent- magnet mirror trap has been constructed and tested. Variations in the discharge parameters and the electron temperature of argon plasma have been investigated in the argon pressure range of 1 × 10-4 to 4 × 10-3 Torr at a net pulsed input microwave power of up to 600 W. The plasma electron temperature in the above ranges of gas pressures and input powers has been measured by a Langmuir probe and determined using optical emission spectroscopy (OES) from the intensity ratios of spectral lines. The OES results agree qualitatively and quantitatively with the data obtained using the double probe.

  16. Effects of rf power on electron density and temperature, neutral temperature, and T{sub e} fluctuations in an inductively coupled plasma

    SciTech Connect

    Camparo, James; Fathi, Gilda

    2009-05-15

    Atomic clocks that fly on global-navigation satellites such as global positioning system (GPS) and Galileo employ light from low-temperature, inductively coupled plasmas (ICPs) for atomic signal generation and detection (i.e., alkali/noble-gas rf-discharge lamps). In this application, the performance of the atomic clock and the capabilities of the navigation system depend sensitively on the stability of the ICP's optical emission. In order to better understand the mechanisms that might lead to instability in these rf-discharge lamps, and hence the satellite atomic clocks, we studied the optical emission from a Rb/Xe ICP as a function of the rf power driving the plasma. Surprisingly, we found that the electron density in the plasma was essentially independent of increases in rf power above its nominal value (i.e., 'rf-power gain') and that the electron temperature was only a slowly varying function of rf-power gain. The primary effect of rf power was to increase the temperature of the neutrals in the plasma, which was manifested by an increase in Rb vapor density. Interestingly, we also found evidence for electron temperature fluctuations (i.e., fluctuations in the plasma's high-energy electron content). The variance of these fluctuations scaled inversely with the plasma's mean electron temperature and was consistent with a simple model that assumed that the total electron density in the discharge was independent of rf power. Taken as a whole, our results indicate that the electrons in alkali/noble-gas ICPs are little affected by slight changes in rf power and that the primary effect of such changes is to heat the plasma's neutral species.

  17. Weibel instability for a streaming electron, counterstreaming e-e, and e-p plasmas with intrinsic temperature anisotropy

    SciTech Connect

    Ghorbanalilu, M.; Sadegzadeh, S.; Ghaderi, Z.; Niknam, A. R.

    2014-05-15

    The existence of Weibel instability for a streaming electron, counterstreaming electron-electron (e-e), and electron-positron (e-p) plasmas with intrinsic temperature anisotropy is investigated. The temperature anisotropy is included in the directions perpendicular and parallel to the streaming direction. It is shown that the beam mean speed changes the instability mode, for a streaming electron beam, from the classic Weibel to the Weibel-like mode. The analytical and numerical solutions approved that Weibel-like modes are excited for both counterstreaming e-e and e-p plasmas. The growth rates of the instabilities in e-e and e-p plasmas are compared. The growth rate is larger for e-p plasmas if the thermal anisotropy is small and the opposite is true for large thermal anisotropies. The analytical and numerical solutions are in good agreement only in the small parallel temperature and wave number limits, when the instability growth rate increases linearly with normalized wave number kc∕ω{sub p}.

  18. Two-dimensional quasi-double-layers in two-electron-temperature, current-free plasmas

    NASA Astrophysics Data System (ADS)

    Merino, Mario; Ahedo, Eduardo

    2013-02-01

    The expansion of a plasma with two disparate electron populations into vacuum and channeled by a divergent magnetic nozzle is analyzed with an axisymmetric model. The purpose is to study the formation and two-dimensional shape of a current-free double-layer in the case when the electric potential steepening can still be treated within the quasineutral approximation. The properties of this quasi-double-layer are investigated in terms of the relative fraction of the high-energy electron population, its radial distribution when injected into the nozzle, and the geometry and intensity of the applied magnetic field. The two-dimensional double layer presents a curved shape, which is dependent on the natural curvature of the equipotential lines in a magnetically expanded plasma and the particular radial distribution of high-energy electrons at injection. The double layer curvature increases the higher the nozzle divergence is, the lower the magnetic strength is, and the more peripherally hot electrons are injected. A central application of the study is the operation of a helicon plasma thruster in space. To this respect, it is shown that the curvature of the double layer does not increment the thrust, it does not modify appreciably the downstream divergence of the plasma beam, but it increases the magnetic-to-pressure thrust ratio. The present study does not attempt to cover current-free double layers involving plasmas with multiple populations of positive ions.

  19. Two-dimensional quasi-double-layers in two-electron-temperature, current-free plasmas

    SciTech Connect

    Merino, Mario; Ahedo, Eduardo

    2013-02-15

    The expansion of a plasma with two disparate electron populations into vacuum and channeled by a divergent magnetic nozzle is analyzed with an axisymmetric model. The purpose is to study the formation and two-dimensional shape of a current-free double-layer in the case when the electric potential steepening can still be treated within the quasineutral approximation. The properties of this quasi-double-layer are investigated in terms of the relative fraction of the high-energy electron population, its radial distribution when injected into the nozzle, and the geometry and intensity of the applied magnetic field. The two-dimensional double layer presents a curved shape, which is dependent on the natural curvature of the equipotential lines in a magnetically expanded plasma and the particular radial distribution of high-energy electrons at injection. The double layer curvature increases the higher the nozzle divergence is, the lower the magnetic strength is, and the more peripherally hot electrons are injected. A central application of the study is the operation of a helicon plasma thruster in space. To this respect, it is shown that the curvature of the double layer does not increment the thrust, it does not modify appreciably the downstream divergence of the plasma beam, but it increases the magnetic-to-pressure thrust ratio. The present study does not attempt to cover current-free double layers involving plasmas with multiple populations of positive ions.

  20. Effects of positron concentration, ion temperature, and plasma {beta} value on linear and nonlinear two-dimensional magnetosonic waves in electron-positron-ion plasmas

    SciTech Connect

    Mushtaq, A.; Shah, H.A.

    2005-01-01

    Magnetosonic waves are intensively studied due to their importance in space plasmas and also in fusion plasmas where they are used in particle acceleration and heating experiments. This work considers magnetosonic waves propagating obliquely at an angle {theta} to an external magnetic field in an electron-positron-ion plasma, using the effective one-fluid magnetohydrodynamic model. Two separate modes (fast and slow) for the waves are discussed in the linear approximation, and the Kadomstev-Petviashvilli soliton equation is derived by using reductive perturbation scheme for these modes in the nonlinear regime. It is observed that for both the modes the angle {theta}, positron concentration, ion temperature, and plasma {beta}-value affect the propagation properties of solitary waves and behave differently from the simple electron-ion plasmas. Likewise, current density, electric field, and magnetic field for these waves are investigated, for their dependence on the above mentioned parameters.

  1. Electron Temperature and Density Variation Due To Temporal Evolution of Nano Particle Growth in RF Silane Plasma

    SciTech Connect

    Chai, K. B.; Seon, C. R.; Choe, W.; Park, S.; Chung, C. W.

    2008-09-07

    Nano particles, generated in various processing plasmas, have been extensively studied for applications in the fabrication of microelectronics devices. However, studies to find the relation between the particle parameters (particle size and density) and the plasma parameters (electron temperature and density) have been limited because of the availability of the appropriate diagnostic method. The utilization of Langmuir probes are limited in many cases due to the probe tip contamination and the presence of abundant negative ions and particles. In this work, measurements of electron temperature and ion density were performed in rf silane plasmas using a floating probe, which allows an accurate measurement even under harsh plasma environments. The size and density of nano particles were measured by the laser light scattering and the laser extinction method at various gas pressures. It was found that the temporal evolution of the particle growth played a significant role in changing the plasma parameters due to the electron and ion fluxes to the particles. The relation between the plasma parameters and the particle parameters was described by a power balance equation including the power loss to the particle surface.

  2. Electronic excitation and isentropic coefficients of high temperature planetary atmosphere plasmas

    SciTech Connect

    Colonna, Gianpiero; Capitelli, Mario

    2012-07-15

    In this paper, we have discussed the effects of electronically excited states of atomic species in affecting the isentropic coefficients of plasmas, focusing on mixtures representing the atmospheres of Jupiter, Mars, and Earth. General behaviors have been rationalized on the basis of simplified approaches. The contribution of the electronically excited states has been evidenced by comparing results obtained considering only the ground state and those obtained using either Fermi or Griem cutoff criteria.

  3. Comparison of plasma temperature and electron density on nanosecond laser ablation of Cu and nano-Cu

    SciTech Connect

    Chen, Anmin; Jiang, Yuanfei; Wang, Tingfeng; Shao, Junfeng; Jin, Mingxing

    2015-03-15

    Laser-induced breakdown spectroscopy is performed through the collection of spectra by spectral detection equipment at different delay times and distances from targets composed of Cu and nano-Cu, which are ablated using a Nd:YAG laser (532 nm, 10 ns, 10 Hz) in our experiments. The measured wavelength range is from 475 nm to 525 nm. Using the local thermodynamic equilibrium model, we analyze the characteristics of the plasma temperature and the electron number density for different distances between the target surface and the lens. The results show that when compared with the nano-Cu plasma case, the temperature of the Cu plasma is higher, while its electron number density is lower.

  4. METHES: A Monte Carlo collision code for the simulation of electron transport in low temperature plasmas

    NASA Astrophysics Data System (ADS)

    Rabie, M.; Franck, C. M.

    2016-06-01

    We present a freely available MATLAB code for the simulation of electron transport in arbitrary gas mixtures in the presence of uniform electric fields. For steady-state electron transport, the program provides the transport coefficients, reaction rates and the electron energy distribution function. The program uses established Monte Carlo techniques and is compatible with the electron scattering cross section files from the open-access Plasma Data Exchange Project LXCat. The code is written in object-oriented design, allowing the tracing and visualization of the spatiotemporal evolution of electron swarms and the temporal development of the mean energy and the electron number due to attachment and/or ionization processes. We benchmark our code with well-known model gases as well as the real gases argon, N2, O2, CF4, SF6 and mixtures of N2 and O2.

  5. New Electron Temperature Measurements During Local Helicity Injection and H-mode Plasmas at the Pegasus Toroidal Experiment

    NASA Astrophysics Data System (ADS)

    Schlossberg, D. J.; Bodner, G. M.; Fonck, R. J.; Reusch, J. A.; Winz, G. R.

    2015-11-01

    Extrapolation of non-solenoidal startup via local helicity injection (LHI) to larger devices depends critically on confinement during the injection process. To begin quantifying confinement regimes, the Thomson scattering diagnostic on the Pegasus ST was upgraded to include 12 radial positions and high temperature (0.1 electron distributions, with central Te = 150 eV. In the low-density LHI startup plasmas shot-to-shot averaging of data improves background measurements and increases signal-to-noise ratio. Initial core measurements during the drive phase of LHI suggest average Te of several hundred eV for plasmas with ne ~ 3x1018 m-3 and Ip ~ 0.15 MA. Experiments are underway to verify these unexpectedly high electron temperatures. If verified, these temperatures may reflect the dominance of high-energy electrons via fueling with LHI current streams with average energy ~1 keV. Further investigations will explore the dependence of the inferred electron distribution on fueling source, density, and electron injection potential. The upgraded Thomson scattering diagnostic will also be applied to Ohmic H-mode plasmas in Pegasus. Work supported by US DOE grant DE-FG02-96ER54375.

  6. Comparison of analytical methods to determine the electron density and temperature for a laser-based atmospheric plasma jet

    NASA Astrophysics Data System (ADS)

    Schwander, M.; Kwiatkowski, P.; Prieske, M.

    2016-09-01

    Highly dependent on plasma properties and the energy range, different approaches are used for plasma diagnostics. Measurements of the plasma potential, electron density, electron temperature are imperative for a full characterisation. However, when comparing published studies it seems that different measuring systems produce different results for the same plasma. In order to show that by using different measurement methods varied results are achieved, the following analytical methods are applied for a high-energy laser-based thermal plasma: Langmuir probe measurement, bottleneck equation, emission spectroscopy by Finkelnburg and emission spectroscopy by the Saha equation. The electron density and temperature are determined between 1017-1020 m-3 and 1.1-1.8 eV by the use of Langmuir probes and 1.3•1021 m-3 and 1.0-3.5 eV using emission spectroscopy. Comparison to other studies shows that our results are in the same range, according to the method of analysis. It is conspicuous that the choice of a measurement method predetermines the results in a certain range. This indicates that the chosen method has a huge impact on the resulting outcomes.

  7. Electron Temperature Measurement by a Helium Line Intensity Ratio Method in Helicon Plasmas

    NASA Astrophysics Data System (ADS)

    Boivin, R. F.; Balkey, M. M.; Blackburn, M. A.; Keiter, P. A.; Kline, J. L.; Scime, E. E.; Spangler, R.

    1999-10-01

    Te measurements in helicon plasmas are not an easy task. The presence of intense RF fields complicates the interpretation of the Langmuir probe curves. A spectroscopy technique based on the relative intensities of He I lines is used to measure Te in the HELIX plasmas. This non-intrusive diagnostic is based on the fact that the dependence on the electron energy of the excitation rate differs between singlet and triplet lines of the He atom. This method has been applied to measure Te in many plasma conditions and, lately has been extended to high-density, fusion edge plasmas. The validity of this technique to measure Te in RF plasmas has not yet been established. The wide range in density that can generated by HELIX (10^10 to 10^13 cm-3) makes it an ideal source to verify if this diagnostic can be used in such RF plasmas. At low density, this diagnostic is believed to be very reliable since the population of the emitting levels can be accurately estimated by assuming that all excitation originate from the ground state. At higher density, secondary processes become important and can seriously affect the validity of the diagnostic. We measured the excitation rate for many He lines and compared them to the excitation rate from ground state previously published. The validity density range for the diagnostic is presented together with the apparent excitation rate observed for the different transitions.

  8. Ion acoustic solitary waves and double layers in a plasma with two temperature electrons featuring Tsallis distribution

    SciTech Connect

    Shalini, Saini, N. S.

    2014-10-15

    The propagation properties of large amplitude ion acoustic solitary waves (IASWs) are studied in a plasma containing cold fluid ions and multi-temperature electrons (cool and hot electrons) with nonextensive distribution. Employing Sagdeev pseudopotential method, an energy balance equation has been derived and from the expression for Sagdeev potential function, ion acoustic solitary waves and double layers are investigated numerically. The Mach number (lower and upper limits) for the existence of solitary structures is determined. Positive as well as negative polarity solitary structures are observed. Further, conditions for the existence of ion acoustic double layers (IADLs) are also determined numerically in the form of the critical values of q{sub c}, f and the Mach number (M). It is observed that the nonextensivity of electrons (via q{sub c,h}), concentration of electrons (via f) and temperature ratio of cold to hot electrons (via β) significantly influence the characteristics of ion acoustic solitary waves as well as double layers.

  9. Effects of suprathermal electrons on the proton temperature anisotropy in space plasmas: Electromagnetic ion-cyclotron instability

    NASA Astrophysics Data System (ADS)

    Shaaban, S. M.; Lazar, M.; Poedts, S.; Elhanbaly, A.

    2016-06-01

    In collision-poor plasmas from space, e.g., the solar wind and planetary magnetospheres, the kinetic anisotropy of the plasma particles is expected to be regulated by the kinetic instabilities. Driven by an excess of ion (proton) temperature perpendicular to the magnetic field (T_{perp}>T_{allel}), the electromagnetic ion-cyclotron (EMIC) instability is fast enough to constrain the proton anisotropy, but the observations do not conform to the instability thresholds predicted by the standard theory for bi-Maxwellian models of the plasma particles. This paper presents an extended investigation of the EMIC instability in the presence of suprathermal electrons which are ubiquitous in these environments. The analysis is based on the kinetic (Vlasov-Maxwell) theory assuming that both species, protons and electrons, may be anisotropic, and the EMIC unstable solutions are derived numerically providing an accurate description for conditions typically encountered in space plasmas. The effects of suprathermal populations are triggered by the electron anisotropy and the temperature contrast between electrons and protons. For certain conditions the anisotropy thresholds exceed the limits of the proton anisotropy measured in the solar wind considerably restraining the unstable regimes of the EMIC modes.

  10. Consistent multi-internal-temperature models for vibrational and electronic nonequilibrium in hypersonic nitrogen plasma flows

    SciTech Connect

    Guy, Aurélien Bourdon, Anne Perrin, Marie-Yvonne

    2015-04-15

    In this work, a state-to-state vibrational and electronic collisional model is developed to investigate nonequilibrium phenomena behind a shock wave in an ionized nitrogen flow. In the ionization dynamics behind the shock wave, the electron energy budget is of key importance and it is found that the main depletion term corresponds to the electronic excitation of N atoms, and conversely the major creation terms are the electron-vibration term at the beginning, then replaced by the electron ions elastic exchange term. Based on these results, a macroscopic multi-internal-temperature model for the vibration of N{sub 2} and the electronic levels of N atoms is derived with several groups of vibrational levels of N{sub 2} and electronic levels of N with their own internal temperatures to model the shape of the vibrational distribution of N{sub 2} and of the electronic excitation of N, respectively. In this model, energy and chemistry source terms are calculated self-consistently from the rate coefficients of the state-to-state database. For the shock wave condition studied, a good agreement is observed on the ionization dynamics as well as on the atomic bound-bound radiation between the state-to-state model and the macroscopic multi-internal temperature model with only one group of vibrational levels of N{sub 2} and two groups of electronic levels of N.

  11. Low frequency solitons and double layers in a magnetized plasma with two temperature electrons

    SciTech Connect

    Rufai, O. R.; Bharuthram, R.; Singh, S. V.; Lakhina, G. S.

    2012-12-15

    Finite amplitude non-linear ion-acoustic solitary waves and double layers are studied in a magnetized plasma with cold ions fluid and two distinct groups of Boltzmann electrons, using the Sagdeev pseudo-potential technique. The conditions under which the solitary waves and double layers can exist are found both analytically and numerically. We have shown the existence of negative potential solitary waves and double layers for subsonic Mach numbers, whereas in the unmagnetized plasma they can only in the supersonic Mach number regime. For the plasma parameters in the auroral region, the electric field amplitude of the solitary structures comes out to be 49 mV/m which is in agreement of the Viking observations in this region.

  12. The multipole resonance probe: A concept for simultaneous determination of plasma density, electron temperature, and collision rate in low-pressure plasmas

    SciTech Connect

    Lapke, M.; Mussenbrock, T.; Brinkmann, R. P.

    2008-08-04

    A diagnostic concept is presented which enables the simultaneous determination of plasma density, electron temperature, and collision rate in low-pressure gas discharges. The proposed method utilizes a radio-frequency driven probe of particular spherical design which is immersed in the plasma to excite a family of spatially bounded surface resonances. An analysis of the measured absorption spectrum S({omega}) of the probe provides information on the distribution of the plasma in its vicinity, from which the values of the plasma parameters can be inferred. In its simplest realization, the probe consists of two dielectrically shielded, conducting hemispheres, which are symmetrically driven by an radio-frequency source, and the excited resonances can be classified as multipole fields, which allows an analytical evaluation of the measured signal. The proposed method is robust, calibration free, economical, and can be used for ideal and reactive plasmas alike.

  13. Non-invasive probe diagnostic method for electron temperature and ion current density in atmospheric pressure plasma jet source

    SciTech Connect

    Kim, Young-Cheol; Kim, Yu-Sin; Lee, Hyo-Chang; Moon, Jun-Hyeon; Chung, Chin-Wook; Kim, Yunjung; Cho, Guangsup

    2015-08-15

    The electrical probe diagnostics are very hard to be applied to atmospheric plasmas due to severe perturbation by the electrical probes. To overcome this, the probe for measuring electron temperature and ion current density is indirectly contacted with an atmospheric jet source. The plasma parameters are obtained by using floating harmonic analysis. The probe is mounted on the quartz tube that surrounds plasma. When a sinusoidal voltage is applied to a probe contacting on a quartz tube, the electrons near the sheath at dielectric tube are collected and the probe current has harmonic components due to probe sheath nonlinearity. From the relation of the harmonic currents and amplitude of the sheath voltage, the electron temperature near the wall can be obtained with collisional sheath model. The electron temperatures and ion current densities measured at the discharge region are in the ranges of 2.7–3.4 eV and 1.7–5.2 mA/cm{sup 2} at various flow rates and input powers.

  14. Electron temperature profile invariance on OH, L- and H-mode plasmas and consequences for the anomalous transport

    NASA Astrophysics Data System (ADS)

    Becker, G.

    1992-01-01

    The shapes of the electron temperature and electron density profiles in the OH, L- and H-mode confinement regimes of ASDEX are explored by statistical analysis. It is shown that the shape of Te(r) is conserved in the outer half of the plasma in these regimes and that it is invariant with respect to heating power, heating profile, density, density scale length, q value and ion mass. These results suggest that microturbulence constrains the shape of the temperature profile by adjusting the electron heat diffusivity χe(r). No such invariance is found for the temperature profile in the inner half of the plasma and for the density profile over the whole cross-section. Properties of the empirical electron heat diffusivity and the diffusion coefficient in different regimes can be described by Te profile invariance. The improved confinement with peaked density profiles, the reduction of χe in the bulk of H-mode plasmas and the power dependence of χe in the L-regime are discussed

  15. Effect of a novel nonlinearity, viz., electron temperature dependence of electron-ion recombination on electromagnetic wave. Plasma interaction: Nonlinear propagation in the E-layer

    NASA Astrophysics Data System (ADS)

    Sodha, Mahendra Singh; Mishra, Rashmi; Srivastava, Sweta

    2016-03-01

    In this paper, we consider the nonlinearity in the propagation of electromagnetic (e.m.) waves in a plasma caused by the electron temperature dependence of the coefficient of recombination of electrons with ions; specifically, the ionospheric E layer has been investigated. The enhancement in electron temperature by an intense electromagnetic wave causes reduction of the electron-ion recombination coefficient and thereby enhancement of electron density, the electron collision frequency also gets enhanced. The equations for number and energy balance of electrons and the wave equation have been used to predict the dependence of electron density/collision frequency and the nonlinear refractive index and absorption coefficient on αE02 (proportional to wave irradiance). The dependence of the propagation parameters on αE02 has been used to investigate the nonlinear electromagnetic wave propagation in the ionosphere. The study concludes that the electron temperature dependence of the recombination coefficient should be considered in all analyses of nonlinear plasma-e.m. wave interaction.

  16. Kinetic Temperature and Electron Density Measurement in an Inductively Coupled Plasma Torch using Degenerate Four-Wave Mixing

    NASA Technical Reports Server (NTRS)

    Schafer, Julia; Lyons, Wendy; Tong, WIlliam G.; Danehy, Paul M.

    2008-01-01

    Laser wave mixing is presented as an effective technique for spatially resolved kinetic temperature measurements in an atmospheric-pressure radio-frequency inductively-coupled plasma. Measurements are performed in a 1 kW, 27 MHz RF plasma using a continuous-wave, tunable 811.5-nm diode laser to excite the 4s(sup 3)P2 approaches 4p(sup 3)D3 argon transition. Kinetic temperature measurements are made at five radial steps from the center of the torch and at four different torch heights. The kinetic temperature is determined by measuring simultaneously the line shape of the sub-Doppler backward phase-conjugate degenerate four-wave mixing and the Doppler-broadened forward-scattering degenerate four-wave mixing. The temperature measurements result in a range of 3,500 to 14,000 K+/-150 K. Electron densities measured range from 6.1 (+/-0.3) x 10(exp 15)/cu cm to 10.1 (+/-0.3) x 10(exp 15)/cu cm. The experimental spectra are analyzed using a perturbative treatment of the backward phase-conjugate and forward-geometry wave-mixing theory. Stark width is determined from the collisional broadening measured in the phase-conjugate geometry. Electron density measurements are made based on the Stark width. The kinetic temperature of the plasma was found to be more than halved by adding deionized water through the nebulizer.

  17. TOPICAL REVIEW: Optical emission spectroscopy in low-temperature plasmas containing argon and nitrogen: determination of the electron temperature and density by the line-ratio method

    NASA Astrophysics Data System (ADS)

    Zhu, Xi-Ming; Pu, Yi-Kang

    2010-10-01

    This article reviews a variety of methods to obtain the electron temperature and density by the emission line ratios for low-temperature plasmas containing argon or nitrogen gas. Based on the collisional-radiative model of excited particles, the underlying principle of each of these methods is described, along with the criterion on how to select an appropriate line-ratio method according to the discharge conditions. Limitations on the application of each line-ratio technique are also discussed.

  18. The effects of nonthermal electron distributions on ion-temperature-gradient driven drift-wave instabilities in electron-ion plasma

    SciTech Connect

    Batool, Nazia; Masood, W.; Mirza, Arshad M.

    2012-08-15

    The effects of nonthermal electron distributions on electrostatic ion-temperature-gradient (ITG) driven drift-wave instabilities in the presence of equilibrium density, temperature, and magnetic field gradients are investigated here. By using Braginskii's transport equations for ions and Cairns as well as Kappa distribution for electrons, the coupled mode equations are derived. The modified ITG driven modes are derived, and it is found both analytically as well as numerically that the nonthermal distribution of electrons significantly modify the real frequencies as well as the growth rate of the ITG driven drift wave instability. The growth rate of ion-temperature-gradient driven instability is found to be maximum for Cairns, intermediate for Kappa, and minimum for the Maxwellian distributed electron case. The results of present investigation might be helpful to understand several wave phenomena in space and laboratory plasmas in the presence of nonthermal electrons.

  19. Electron Temperature Fluctuations Associated with the Weakly Coherent Mode in the Edge of I-mode Plasmas

    NASA Astrophysics Data System (ADS)

    White, A. E.; Phillips, P.; Whyte, D. G.; Hubbard, A. E.; Sung, C.; Hughes, J. W.; Dominguez, A.; Terry, J.; Cziegler, I.

    2012-03-01

    New measurements of electron temperature fluctuations associated with the weakly coherent mode (WCM) during improved mode, or I-mode plasmas at Alcator C-Mod are presented in this poster [A. E. White, et al. Nuclear Fusion, 51, 113005 (2011)]. The measurements are made with a 32-channel, high-resolution profile ECE radiometer. The WCM electron temperature fluctuations are localized to a 1 cm region inside the last closed flux surface. The WCM electron temperature fluctuation level is measured in several different I-mode discharges and is in the range 1-2%, which is up to an order of magnitude smaller than the WCM density fluctuation level. The WCM edge fluctuations observed in I-mode are believed to play a role in increasing particle transport but not energy transport in the edge of I-mode plasmas. The large difference between normalized density and electron temperature fluctuation amplitudes provides new evidence that the WCM fluctuations can separately affect energy and particle transport.

  20. Cylindrical and spherical dust-ion-acoustic modified Gardner solitons in dusty plasmas with two-temperature superthermal electrons

    SciTech Connect

    Alam, M. S.; Masud, M. M.; Mamun, A. A.

    2013-12-15

    A rigorous theoretical investigation has been performed on the propagation of cylindrical and spherical Gardner solitons (GSs) associated with dust-ion-acoustic (DIA) waves in a dusty plasma consisting of inertial ions, negatively charged immobile dust, and two populations of kappa distributed electrons having two distinct temperatures. The well-known reductive perturbation method has been used to derive the modified Gardner (mG) equation. The basic features (amplitude, width, polarity, etc.) of nonplanar DIA modified Gardner solitons (mGSs) have been thoroughly examined by the numerical analysis of the mG equation. It has been found that the characteristics of the nonplanar DIA mGSs significantly differ from those of planar ones. It has been also observed that kappa distributed electrons with two distinct temperatures significantly modify the basic properties of the DIA solitary waves and that the plasma system under consideration supports both compressive and rarefactive DIA mGSs. The present investigation should play an important role for understanding localized electrostatic disturbances in space and laboratory dusty plasmas where stationary negatively charged dust, inertial ions, and superthermal electrons with two distinct temperatures are omnipresent ingredients.

  1. Temperature and density evolution during decay in a 2.45 GHz hydrogen electron cyclotron resonance plasma: Off-resonant and resonant cases

    NASA Astrophysics Data System (ADS)

    Cortázar, O. D.; Megía-Macías, A.; Vizcaíno-de-Julián, A.

    2013-09-01

    Time resolved electron temperature and density measurements during the decay stage in a hydrogen electron cyclotron resonance (ECR) plasma are presented for a resonance and off-resonance magnetic field configurations. The measurements are conducted on a ECR plasma generator excited at 2.45 GHz denominated test-bench for ion-sources plasma studies at ESS Bilbao. The plasma parameters evolution is studied by Langmuir probe diagnostic with synchronized sample technique developed for repetitive pulsed plasmas with a temporal resolution of 200 ns in typical decay processes of about 40 μs. An afterglow transient is clearly observed in the reflected microwave power signal from the plasma. Simultaneously, the electron temperature evolution shows rebounding peaks that may be related to the interplay between density drop and microwave coupling with deep impact on the Electron Energy Distribution Function. The correlation of such structures with the plasma absorbed power and the coupling quality is also reported.

  2. Temperature and electron density distributions of laser-induced plasmas generated with an iron sample at different ambient gas pressures

    NASA Astrophysics Data System (ADS)

    Aguilera, J. A.; Aragón, C.

    2002-09-01

    Intensity, temperature and electron density distributions of laser-induced plasmas (LIPs) have been measured by emission spectroscopy with two-dimensional spatial resolution and temporal resolution. The plasmas have been generated with an iron sample at different pressures of air, in the range 10-1000 mbar. An experimental system based in an imaging spectrometer equipped with an intensified CCD detector has been used to obtain the spectra with two-dimensional spatial resolution. The evolution of the intensity distributions is described by the blast wave model only at initial times. The temperature distributions are shown to correspond to a slight difference between the intensity distributions of two Fe I emission lines that have a high difference of their upper energy levels (3.38 eV). The electron density distributions have similar features to those of the temperature distributions. The features of the intensity and temperature distributions show a significant change with the ambient gas pressure: they have separated maxima in the plasmas generated at pressures below 100 mbar, whereas at higher pressures, the maxima of the two distributions coincide.

  3. Plasma temperatures in Saturn's ionosphere

    NASA Astrophysics Data System (ADS)

    Moore, Luke; Galand, Marina; Mueller-Wodarg, Ingo; Yelle, Roger; Mendillo, Michael

    2008-10-01

    We have calculated self-consistent electron and ion temperatures in Saturn's ionosphere using a series of coupled fluid and kinetic models developed to help interpret Cassini observations and to examine the energy budget of Saturn's upper atmosphere. Electron temperatures in the midlatitude topside ionosphere during solar maximum are calculated to range between 500 and 560 K during the Saturn day, approximately 80-140 K above the neutral temperature. Ion temperatures, calculated for only the major ions H+ and H3+, are nearly equal to the neutral temperature at altitudes near and below the height of peak electron density, while they can reach 500 K during the day at the topside. Plasma scale heights of the dusk electron density profile from radio occultation measurements of the Voyager 2 flyby of Saturn have been used to estimate plasma temperature as a comparison. Such an estimate agrees well with the temperatures calculated here, although there is a topside enhancement in electron density that remains unexplained by ionospheric calculations that include photochemistry and plasma diffusion. Finally, parameterizations of the heating rate from photoelectrons and secondary electrons to thermal, ambient electrons have been developed. They may apply for other conditions at Saturn and possibly at other giant planets and exoplanets as well.

  4. Ion-acoustic solitons in negative ion plasma with two-electron temperature distributions

    SciTech Connect

    Mishra, M. K.; Tiwari, R. S.; Chawla, J. K.

    2012-06-15

    Ion-acoustic solitons in a warm positive and negative ion species with different masses, concentrations, and charge states with two electron temperature distributions are studied. Using reductive perturbation method, Korteweg de-Vries (KdV) and modified-KdV (m-KdV) equations are derived for the system. The soliton solution of the KdV and m-KdV equations is discussed in detail. It is found that if the ions have finite temperatures, then there exist two types of modes, namely slow and fast ion-acoustic modes. It is also investigated that the parameter determining the nature of soliton (i.e., whether the system will support compressive or rarefactive solitons) is different for slow and fast modes. For the slow mode, the parameter is the relative temperature of the two ion species; whereas for the fast mode, it is the relative concentration of the two ion species. At a critical concentration of negative ions, both compressive and rarefactive solitons coexist. The amplitude and width of the solitons are discussed in detail at critical concentration for m-KdV solitons. The effect of the relative temperature of the two-electron and cold-electron concentration on the characteristics of the solitons are also discussed.

  5. Effect of ion temperature on ion-acoustic solitary waves in a magnetized plasma in presence of superthermal electrons

    SciTech Connect

    Singh, S. V.; Devanandhan, S.; Lakhina, G. S.; Bharuthram, R.

    2013-01-15

    Obliquely propagating ion-acoustic soliatry waves are examined in a magnetized plasma composed of kappa distributed electrons and fluid ions with finite temperature. The Sagdeev potential approach is used to study the properties of finite amplitude solitary waves. Using a quasi-neutrality condition, it is possible to reduce the set of equations to a single equation (energy integral equation), which describes the evolution of ion-acoustic solitary waves in magnetized plasmas. The temperature of warm ions affects the speed, amplitude, width, and pulse duration of solitons. Both the critical and the upper Mach numbers are increased by an increase in the ion temperature. The ion-acoustic soliton amplitude increases with the increase in superthermality of electrons. For auroral plasma parameters, the model predicts the soliton speed, amplitude, width, and pulse duration, respectively, to be in the range of (28.7-31.8) km/s, (0.18-20.1) mV/m; (590-167) m, and (20.5-5.25) ms, which are in good agreement with Viking observations.

  6. What is the electron temperature in a plasma which evolves from a sample of ultra-cold Rydberg atoms?

    NASA Astrophysics Data System (ADS)

    Tate, Duncan; Forest, Gabriel; Ward, Edwin; Goodsell, Anne

    2016-05-01

    Dense samples of cold Rydberg atoms evolve rapidly to an ultra-cold neutral plasma (UNP) due to ionizing collisions mediated by dipole forces, and other mechanisms. The subsequent plasma evolution is mediated by three-body recombination (TBR) of electrons and ions, and electron-Rydberg collisions, which can lead to de-excitation, excitation, and ionization of the Rydberg atoms. However, in contrast with UNPs formed by direct photoionization, the plasma evolves in the presence of a large reservoir of Rydberg atoms, and we have been investigating how this affects the UNP dynamics. Specifically, we excite cold Rb atoms in a MOT to a selected Rydberg state using a tuneable pulsed laser. We then measure the UNP expansion velocity using the ion time-of-flight spectra, as a function of the binding energy of the initial Rydberg state (Eb = 0 - 400 K), and the initial Rydberg density. Preliminary results show that the UNP expansion velocity, which is a manifestation of the effective electron temperature, has only a weak sensitivity to Eb, but is strongly dependent on the Rydberg density. Research supported by Colby College and NSF.

  7. Effects of ion-temperature on propagation of the large-amplitude ion-acoustic solitons in degenerate electron-positron-ion plasmas

    SciTech Connect

    Akbari-Moghanjoughi, M.

    2010-08-15

    Large-amplitude ion-acoustic solitary wave (IASW) propagation and matching criteria of existence of such waves are investigated in a degenerate dense electron-positron-ion plasma considering the ion-temperature as well as electron/positron degeneracy effects. It is shown that the ion-temperature effects play an important role in the existence criteria and allowed Mach-number range in such plasmas. Furthermore, a fundamental difference is remarked in the existence of supersonic IASW propagations between degenerate plasmas with nonrelativistic and ultrarelativistic electrons and positrons. Current study may be helpful in astrophysical as well as the laboratory inertial confinement fusion-research.

  8. Computational Study of Electron-Molecule Collisions Related to Low-Temperature Plasmas

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Partridge, Harry (Technical Monitor)

    1997-01-01

    Computational study of electron-molecule collisions not only complements experimental measurements, but can also be used to investigate processes not readily accessible experimentally. A number of ab initio computational methods are available for these types of calculations. Here we describe a recently developed technique, the finite element Z-matrix method, Analogous to the R-matrix, method, it partitions the space into regions and employs real matrix elements. However, unlike the implementation of the R-matrix method commonly used in atomic and molecular physics, the Z-matrix method is fully variational. In the present implementation, a mixed basis of finite elements and Gaussians is used to represent the continuum electron, thus offering full flexibility without imposing fixed boundary conditions. Numerical examples include the electron-impact dissociation of N2 via the metastable A3Su+ state, a process which may be important in the lower thermosphere, and the dissociation of the CF radical, a process of interest to plasma etching. To understand the dissociation pathways, large scale quantum chemical calculations have been carried out for all target states which dissociate to the lowest five limits in the case of N2, and to the lowest two limits in the case of CF. For N2, the structural calculations clearly show the preference for predissociation if the initial state is the ground X1 Sg+ state, but direct dissociation appears to be preferable if the initial state is the A3Su+ state. Multi-configuration SCF target functions are used in the collisional calculation.

  9. Improvements in electron temperature measurements from soft x-rays in MST plasmas

    NASA Astrophysics Data System (ADS)

    Reusch, L. M.; Franz, P.; Galante, M. E.; Goetz, J.; den Hartog, D. J.; McGarry, M. B.; Stephens, H. D.

    2015-11-01

    The MST is equipped with a two-color soft x-ray tomography (SXT) diagnostic that is capable of making electron temperature measurements via the double-foil technique. Discrepancies between the double-foil temperature and Thomson scattering (TS) have been confirmed to be due to impurities present in the Be filters used to block visible light and select the energy range for soft x-ray detection. Namely, contamination from Zr led to a larger effective thickness for all filters. Furthermore, the distribution of Zr particles was highly non-uniform, making accurate accounting of the contaminated filters impossible and leading to different effective thicknesses between different probes in the SXT system. We have installed new confirmed 99.9% purity Be filters and assessed their effect on the brightness profiles and on the two-foil temperature measurements. Results show consistent amplitudes for brightness profiles from all four probes, and the double-foil temperature measurement from SXT matches TS within uncertainty, both spatially and temporally. In addition, empirical measurements of the transmission function versus energy for the Be filters contaminated with Zr will allow us to accurately characterize data using the contaminated Be filters. This work was supported by the US DOE.

  10. Self-modulation of nonlinear waves in a weakly magnetized relativistic electron-positron plasma with temperature.

    PubMed

    Asenjo, Felipe A; Borotto, Felix A; Chian, Abraham C-L; Muñoz, Víctor; Valdivia, J Alejandro; Rempel, Erico L

    2012-04-01

    We develop a nonlinear theory for self-modulation of a circularly polarized electromagnetic wave in a relativistic hot weakly magnetized electron-positron plasma. The case of parallel propagation along an ambient magnetic field is considered. A nonlinear Schrödinger equation is derived for the complex wave amplitude of a self-modulated wave packet. We show that the maximum growth rate of the modulational instability decreases as the temperature of the pair plasma increases. Depending on the initial conditions, the unstable wave envelope can evolve nonlinearly to either periodic wave trains or solitary waves. This theory has application to high-energy astrophysics and high-power laser physics. PMID:22680585

  11. Plasma heating power dissipation in low temperature hydrogen plasmas

    SciTech Connect

    Komppula, J. Tarvainen, O.

    2015-10-15

    A theoretical framework for power dissipation in low temperature plasmas in corona equilibrium is developed. The framework is based on fundamental conservation laws and reaction cross sections and is only weakly sensitive to plasma parameters, e.g., electron temperature and density. The theory is applied to low temperature atomic and molecular hydrogen laboratory plasmas for which the plasma heating power dissipation to photon emission, ionization, and chemical potential is calculated. The calculated photon emission is compared to recent experimental results.

  12. Determination of the time evolution of the electron-temperature profile of reactor-like plasmas from the measurement of blackbody electron-cyclotron emission

    SciTech Connect

    Efthimion, P.C.; Arunasalam, V.; Bitzer, R.A.; Hosea, J.C.

    1982-04-01

    Plasma characteristics (i.e., n/sub e/ greater than or equal to 1 x 10/sup 13/ cm/sup -3/, T/sub e/ greater than or equal to 10/sup 7/ /sup 0/K, B/sub psi/ greater than or equal to 20 kG) in present and future magnetically confined plasma devices, e.g., Princeton Large Torus (PLT) and Tokamak Fusion Test Reactor (TFTR), meet the conditions for blackbody emission near the electron cyclotron frequency and at few harmonics. These conditions, derived from the hot plasma dielectric tensor, have been verified by propagation experiments on PLT and the Princeton Model-C Stellarator. Blackbody emission near the fundamental electron cyclotron frequency and the second harmonic have been observed in PLT and is routinely measured to ascertain the time evolution of the electron temperature profile. These measurements are especially valuable in the study of auxiliary heating of tokamak plasma. Measurement and calibration techniques will also be discussed with special emphasis on our fast-scanning heterodyne receiver concept.

  13. Measurements of electron density and temperature profiles in plasma produced by Nike KrF laser for laser plasma instability research

    NASA Astrophysics Data System (ADS)

    Oh, Jaechul; Weaver, J. L.; Karasik, M.; Chan, L. Y.

    2015-08-01

    A grid image refractometer (GIR) has been implemented at the Nike krypton fluoride laser facility of the Naval Research Laboratory. This instrument simultaneously measures propagation angles and transmissions of UV probe rays (λ = 263 nm, Δt = 10 ps) refracted through plasma. We report results of the first Nike-GIR measurement on a CH plasma produced by the Nike laser pulse (˜1 ns FWHM) with the intensity of 1.1 × 1015 W/cm2. The measured angles and transmissions were processed to construct spatial profiles of electron density (ne) and temperature (Te) in the underdense coronal region of the plasma. Using an inversion algorithm developed for the strongly refracted rays, the deployed GIR system probed electron densities up to 4 × 1021 cm-3 with the density scale length of 120 μm along the plasma symmetry axis. The resulting ne and Te profiles are verified to be self-consistent with the measured quantities of the refracted probe light.

  14. Measurements of electron density and temperature profiles in plasma produced by Nike KrF laser for laser plasma instability research.

    PubMed

    Oh, Jaechul; Weaver, J L; Karasik, M; Chan, L Y

    2015-08-01

    A grid image refractometer (GIR) has been implemented at the Nike krypton fluoride laser facility of the Naval Research Laboratory. This instrument simultaneously measures propagation angles and transmissions of UV probe rays (λ = 263 nm, Δt = 10 ps) refracted through plasma. We report results of the first Nike-GIR measurement on a CH plasma produced by the Nike laser pulse (∼1 ns FWHM) with the intensity of 1.1 × 10(15) W/cm(2). The measured angles and transmissions were processed to construct spatial profiles of electron density (ne) and temperature (Te) in the underdense coronal region of the plasma. Using an inversion algorithm developed for the strongly refracted rays, the deployed GIR system probed electron densities up to 4 × 10(21) cm(-3) with the density scale length of 120 μm along the plasma symmetry axis. The resulting n(e) and T(e) profiles are verified to be self-consistent with the measured quantities of the refracted probe light. PMID:26329186

  15. Reduced model prediction of electron temperature profiles in microtearing-dominated National Spherical Torus eXperiment plasmas

    NASA Astrophysics Data System (ADS)

    Kaye, S. M.; Guttenfelder, W.; Bell, R. E.; Gerhardt, S. P.; LeBlanc, B. P.; Maingi, R.

    2014-08-01

    A representative H-mode discharge from the National Spherical Torus eXperiment is studied in detail to utilize it as a basis for a time-evolving prediction of the electron temperature profile using an appropriate reduced transport model. The time evolution of characteristic plasma variables such as β e , νe ∗ , the MHD α parameter, and the gradient scale lengths of Te, Ti, and ne were examined as a prelude to performing linear gyrokinetic calculations to determine the fastest growing micro instability at various times and locations throughout the discharge. The inferences from the parameter evolutions and the linear stability calculations were consistent. Early in the discharge, when βe and νe ∗ were relatively low, ballooning parity modes were dominant. As time progressed and both βe and νe ∗ increased, microtearing became the dominant low-kθ mode, especially in the outer half of the plasma. There are instances in time and radius, however, where other modes, at higher-kθ, may, in addition to microtearing, be important for driving electron transport. Given these results, the Rebut-Lallia-Watkins (RLW) electron thermal diffusivity model, which is based on microtearing-induced transport, was used to predict the time-evolving electron temperature across most of the profile. The results indicate that RLW does a good job of predicting Te for times and locations where microtearing was determined to be important, but not as well when microtearing was predicted to be stable or subdominant.

  16. Reduced model prediction of electron temperature profiles in microtearing-dominated National Spherical Torus eXperiment plasmas

    SciTech Connect

    Kaye, S. M.; Guttenfelder, W.; Bell, R. E.; Gerhardt, S. P.; LeBlanc, B. P.; Maingi, R.

    2014-08-01

    A representative H-mode discharge from the National Spherical Torus eXperiment is studied in detail to utilize it as a basis for a time-evolving prediction of the electron temperature profile using an appropriate reduced transport model. The time evolution of characteristic plasma variables such as βe, ν*e, the MHD α parameter, and the gradient scale lengths of Te, Ti, and ne were examined as a prelude to performing linear gyrokinetic calculations to determine the fastest growing micro instability at various times and locations throughout the discharge. The inferences from the parameter evolutions and the linear stability calculations were consistent. Early in the discharge, when βe and ν*e were relatively low, ballooning parity modes were dominant. As time progressed and both βe and ν*e increased, microtearing became the dominant low-κθ mode, especially in the outer half of the plasma. There are instances in time and radius, however, where other modes, at higher-κθ, may, in addition to microtearing, be important for driving electron transport. Given these results, the Rebut-Lallia-Watkins (RLW) electron thermal diffusivity model, which is based on microtearing-induced transport, was used to predict the time-evolving electron temperature across most of the profile. The results indicate that RLW does a good job of predicting Te for times and locations where microtearing was determined to be important, but not as well when microtearing was predicted to be stable or subdominant.

  17. Reduced model prediction of electron temperature profiles in microtearing-dominated National Spherical Torus eXperiment plasmas

    SciTech Connect

    Kaye, S. M. Guttenfelder, W.; Bell, R. E.; Gerhardt, S. P.; LeBlanc, B. P.; Maingi, R.

    2014-08-15

    A representative H-mode discharge from the National Spherical Torus eXperiment is studied in detail to utilize it as a basis for a time-evolving prediction of the electron temperature profile using an appropriate reduced transport model. The time evolution of characteristic plasma variables such as β{sub e}, ν{sub e}{sup ∗}, the MHD α parameter, and the gradient scale lengths of T{sub e}, T{sub i}, and n{sub e} were examined as a prelude to performing linear gyrokinetic calculations to determine the fastest growing micro instability at various times and locations throughout the discharge. The inferences from the parameter evolutions and the linear stability calculations were consistent. Early in the discharge, when β{sub e} and ν{sub e}{sup ∗} were relatively low, ballooning parity modes were dominant. As time progressed and both β{sub e} and ν{sub e}{sup ∗} increased, microtearing became the dominant low-k{sub θ} mode, especially in the outer half of the plasma. There are instances in time and radius, however, where other modes, at higher-k{sub θ}, may, in addition to microtearing, be important for driving electron transport. Given these results, the Rebut-Lallia-Watkins (RLW) electron thermal diffusivity model, which is based on microtearing-induced transport, was used to predict the time-evolving electron temperature across most of the profile. The results indicate that RLW does a good job of predicting T{sub e} for times and locations where microtearing was determined to be important, but not as well when microtearing was predicted to be stable or subdominant.

  18. Electron Bernstein wave electron temperature profile diagnostic

    SciTech Connect

    G. Taylor; P. Efthimion; B. Jones; T. Munsat; J. Spaleta; J. Hosea; R. Kaita; R. Majeski; J. Menard

    2000-07-20

    Electron cyclotron emission (ECE) has been employed as a standard electron temperature profile diagnostic on many tokamaks and stellarators, but most magnetically confined plasma devices cannot take advantage of standard ECE diagnostics to measure temperature. They are either overdense, operating at high density relative to the magnetic field (e.g. where the plasma frequency is much greater than the electron cyclotron frequency, as in a spherical torus) or they have insufficient density and temperature to reach the blackbody condition. Electron Bernstein waves (EBWs) are electrostatic waves that can propagate in overdense plasmas and have a high optical thickness at the electron cyclotron resonance layers, as a result of their large perpendicular wavenumber. This paper reports on measurements of EBW emission on the CDX-U spherical torus, where B{sub o} {approximately} 2 kG, {approximately}10{sup 13} cm{sup {minus}3} and T{sub e} {approx} to 10 -- 200 eV. Results are presented for electromagnetic measurements of EBW emission, mode-converted near the plasma edge. The EBW emission was absolutely calibrated and compared to the electron temperature profile measured by a multi-point Thomson scattering diagnostic. Depending on the plasma conditions, the mode converted EBW radiation temperature was found to be less than or equal to T{sub e} and the emission source was determined to be radially localized at the electron cyclotron resonance layer. A Langmuir triple probe and a 140 GHz interferometer were employed to measure changes in edge density profile in the vicinity of the upper hybrid resonance, where the mode conversion of the EBWs is expected to occur. Initial results suggest EBW emission and EBW heating are viable concepts for overdense plasmas.

  19. Experiments on the Scaling of Ionization Balance vs. Electron and Radiation Temperature in Non-LTE Gold Plasmas

    SciTech Connect

    Heeter, R F; Hansen, S B; Beiersdorfer, P; Foord, M E; Fournier, K B; Froula, D H; Mackinnon, A J; May, M J; Schneider, M B; Young, B F

    2004-06-25

    Understanding and predicting the behavior of high-Z non-LTE plasmas is important for developing indirect-drive inertial confinement fusion. Extending earlier work from the Nova laser, we present results from experiments using the Omega laser to study the ionization balance of gold as a function of electron and radiation temperature. In these experiments, gold samples embedded in Be disks expand under direct laser heating to n{sub e} {approx} 10{sup 21} cm{sup -3}, with T{sub e} varying from 0.8 to 2.5 keV. An additional finite radiation field with effective temperature T{sub r} up to 150 eV is provided by placing the gold-Be disks inside truncated 1.2 mm diameter tungsten-coated cylindrical hohlraums with full laser entrance holes. Densities are measured by imaging of plasma expansion. Electron temperatures are diagnosed with either 2 {omega} or 4 {omega} Thomson scattering, and also K-shell spectroscopy of KCl tracers co-mixed with the gold. Hohlraum flux and effective radiation temperature are measured using an absolutely-calibrated multichannel filtered diode array. Spectroscopic measurements of the M-shell gold emission in the 2.9-4 keV spectral range provide ionization balance and charge state distribution information. The spectra show strong variation with T{sub e}, strong variation with the applied T{sub r} at T{sub e} below 1.6 keV, and relatively little variation with T{sub r} at higher T{sub e} (upwards of 2 keV). We summarize our most recent spectral analyses and discuss emerging and outstanding issues.

  20. Temperature and Electron Density Determination on Laser-Induced Breakdown Spectroscopy (LIBS) Plasmas: A Physical Chemistry Experiment

    ERIC Educational Resources Information Center

    Najarian, Maya L.; Chinni, Rosemarie C.

    2013-01-01

    This laboratory is designed for physical chemistry students to gain experience using laser-induced breakdown spectroscopy (LIBS) in understanding plasma diagnostics. LIBS uses a high-powered laser that is focused on the sample causing a plasma to form. The emission of this plasma is then spectrally resolved and detected. Temperature and electron…

  1. Galectin expression in healing wounded skin treated with low-temperature plasma: Comparison with treatment by electronical coagulation.

    PubMed

    Akimoto, Yoshihiro; Ikehara, Sanae; Yamaguchi, Takashi; Kim, Jaeho; Kawakami, Hayato; Shimizu, Nobuyuki; Hori, Masaru; Sakakita, Hajime; Ikehara, Yuzuru

    2016-09-01

    Low-temperature plasma is useful for the care of wounded skin. It accelerates wound healing. However, the mechanism of this effect has not been fully elucidated yet. Galectin-1 is reported to accelerate wound healing via the Smad signaling pathway. In the present study to clarify whether or not galectins were expressed during the process of wound healing in the plasma-treated skin, we examined the effect of low-temperature plasma on galectin expression in the healing skin. We compared the effects of low-temperature plasma on the expression of galectin-1, -2, and -3 in the healing skin with those of electrocoagulation conducted with a high-frequency electrical coagulator. Immediately after the start of low-temperature plasma treatment following the incision made in the skin, a membrane-like structure was formed on the surface of the wound. Immunoelectron microscopy showed that these galectins were localized in the membrane-like structure of the plasma-treated skin. The expressions of these galectins were increased by the low-temperature plasma treatment, whereas they were inhibited by the electrocoagulation. These results suggest that galectins were involved in the wound healing of low-temperature plasma-treated skin. Galectins will thus be good markers for further examination of the effects of low-temperature plasma on the healing of wounded skin. PMID:26827730

  2. Imaging spectroscopy diagnosis of internal electron temperature and density distributions of plasma cloud surrounding hydrogen pellet in the Large Helical Device

    SciTech Connect

    Motojima, G.; Sakamoto, R.; Goto, M.; Matsuyama, A.; Yamada, H.; Mishra, J. S.

    2012-09-15

    To investigate the behavior of hydrogen pellet ablation, a novel method of high-speed imaging spectroscopy has been used in the Large Helical Device (LHD) for identifying the internal distribution of the electron density and temperature of the plasma cloud surrounding the pellet. This spectroscopic system consists of a five-branch fiberscope and a fast camera, with each objective lens having a different narrow-band optical filter for the hydrogen Balmer lines and the background continuum radiation. The electron density and temperature in the plasma cloud are obtained, with a spatial resolution of about 6 mm and a temporal resolution of 5 Multiplication-Sign 10{sup -5} s, from the intensity ratio measured through these filters. To verify the imaging, the average electron density and temperature also have been measured from the total emission by using a photodiode, showing that both density and temperature increase with time during the pellet ablation. The electron density distribution ranging from 10{sup 22} to 10{sup 24} m{sup -3} and the temperature distribution around 1 eV have been observed via imaging. The electron density and temperature of a 0.1 m plasma cloud are distributed along the magnetic field lines and a significant electron pressure forms in the plasma cloud for typical experimental conditions of the LHD.

  3. Coulomb collisions in the Boltzmann equation for electrons in low-temperature gas discharge plasmas

    NASA Astrophysics Data System (ADS)

    Hagelaar, G. J. M.

    2016-02-01

    This paper investigates the effects of electron-electron and electron-ion Coulomb collisions on the electron distribution function and transport coefficients obtained from the Boltzmann equation for simple dc gas discharge conditions. Expressions are provided for the full Coulomb collision terms acting on both the isotropic and anisotropic parts of the electron distribution function, which are then incorporated in the freeware Boltzmann equation solver BOLSIG+. Different Coulomb collision effects are demonstrated and discussed on the basis of BOLSIG+  results for argon gas. It is shown that the anisotropic part of the electron-electron collision term, neglected in previous work, can in certain cases have a large effect on the electron mobility and is essential when describing the transition towards the Coulomb-collision dominated regime characterized by Spitzer transport coefficients. Finally, a brief overview is presented of the discharge conditions for which different Coulomb collision effects occur in different gases.

  4. Low Temperature Plasma Medicine

    NASA Astrophysics Data System (ADS)

    Graves, David

    2013-10-01

    Ionized gas plasmas near room temperature are used in a remarkable number of technological applications mainly because they are extraordinarily efficient at exploiting electrical power for useful chemical and material transformations near room temperature. In this tutorial address, I will focus on the newest area of low temperature ionized gas plasmas (LTP), in this case operating under atmospheric pressure conditions, in which the temperature-sensitive material is living tissue. LTP research directed towards biomedical applications such as sterilization, surgery, wound healing and anti-cancer therapy has seen remarkable growth in the last 3-5 years, but the mechanisms responsible for the biomedical effects have remained mysterious. It is known that LTP readily create reactive oxygen species (ROS) and reactive nitrogen species (RNS). ROS and RNS (or RONS), in addition to a suite of other radical and non-radical reactive species, are essential actors in an important sub-field of aerobic biology termed ``redox'' (or oxidation-reduction) biology. I will review the evidence suggesting that RONS generated by plasmas are responsible for their observed therapeutic effects. Other possible bio-active mechanisms include electric fields, charges and photons. It is common in LTP applications that synergies between different mechanisms can play a role and I will review the evidence for synergies in plasma biomedicine. Finally, I will address the challenges and opportunities for plasma physicists to enter this novel, multidisciplinary field.

  5. Effects of finite beam and plasma temperature on the growth rate of a two-stream free electron laser with background plasma

    SciTech Connect

    Mahdizadeh, N.; Aghamir, F. M.

    2013-02-28

    A fluid theory is used to derive the dispersion relation of two-stream free electron laser (TSFEL) with a magnetic planar wiggler pump in the presence of background plasma (BP). The effect of finite beams and plasma temperature on the growth rate of a TSFEL has been verified. The twelve order dispersion equation has been solved numerically. Three instabilities, FEL along with the TS and TS-FEL instabilities occur simultaneously. The analysis in the case of cold BP shows that when the effect of the beam temperature is taken into account, both instable bands of wave-number and peak growth rate in the TS instability increase, but peak growth of the FEL and TS-FEL instabilities decreases. Thermal motion of the BP causes to diminish the TS instability and it causes to decrease the FEL and TS-FEL instabilities. By increasing the beam densities and lowering initial velocities (in the collective Raman regime), growth rate of instabilities increases; however, it has opposite behavior in the Campton regime.

  6. Electron temperature measurements inside the ablating plasma of gas-filled hohlraums at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Barrios, M. A.; Liedahl, D. A.; Schneider, M. B.; Jones, O.; Brown, G. V.; Regan, S. P.; Fournier, K. B.; Moore, A. S.; Ross, J. S.; Landen, O.; Kauffman, R. L.; Nikroo, A.; Kroll, J.; Jaquez, J.; Huang, H.; Hansen, S. B.; Callahan, D. A.; Hinkel, D. E.; Bradley, D.; Moody, J. D.

    2016-05-01

    The first measurement of the electron temperature (Te) inside a National Ignition Facility hohlraum is obtained using temporally resolved K-shell X-ray spectroscopy of a mid-Z tracer dot. Both isoelectronic- and interstage-line ratios are used to calculate the local Te via the collisional-radiative atomic physics code SCRAM [Hansen et al., High Energy Density Phys 3, 109 (2007)]. The trajectory of the mid-Z dot as it is ablated from the capsule surface and moves toward the laser entrance hole (LEH) is measured using side-on x-ray imaging, characterizing the plasma flow of the ablating capsule. Data show that the measured dot location is farther away from the LEH in comparison to the radiation-hydrodynamics simulation prediction using HYDRA [Marinak et al., Phys. Plasmas 3, 2070 (1996)]. To account for this discrepancy, the predicted simulation Te is evaluated at the measured dot trajectory. The peak Te, measured to be 4.2 keV ± 0.2 keV, is ˜0.5 keV hotter than the simulation prediction.

  7. Singlet oxygen in the low-temperature plasma of an electron-beam-sustained discharge

    SciTech Connect

    Vagin, N. P.; Ionin, A. A.; Klimachev, Yu. M.; Kotkov, A. A.; Kochetov, I. V.; Napartovich, A. P.; Podmar'kov, Yu. P.; Rulev, O. A.; Seleznev, L. V.; Sinitsyn, D. V.; Frolov, M. P.; Yuryshev, N. N.

    2006-05-15

    Results are presented from experimental and theoretical studies of the production of singlet delta oxygen in a pulsed electron-beam-sustained discharge ignited in a large ({approx}18-1) volume at a total gas mixture pressure of up to 210 Torr. The measured yield of singlet oxygen reaches 10.5%. It is found that varying the reduced electric field from {approx}2 to {approx}11 kV/(cm atm) slightly affects singlet oxygen production. It is shown experimentally that an increase in the gas mixture pressure or the specific input energy reduces the duration of singlet oxygen luminescence. The calculated time evolution of the singlet oxygen concentration is compared with experimental results.

  8. Time-fractional KdV equation for plasma of two different temperature electrons and stationary ion

    SciTech Connect

    El-Wakil, S. A.; Abulwafa, Essam M.; El-Shewy, E. K.; Mahmoud, Abeer A.

    2011-09-15

    Using the time-fractional KdV equation, the nonlinear properties of small but finite amplitude electron-acoustic solitary waves are studied in a homogeneous system of unmagnetized collisionless plasma. This plasma consists of cold electrons fluid, non-thermal hot electrons, and stationary ions. Employing the reductive perturbation technique and the Euler-Lagrange equation, the time-fractional KdV equation is derived and it is solved using variational method. It is found that the time-fractional parameter significantly changes the soliton amplitude of the electron-acoustic solitary waves. The results are compared with the structures of the broadband electrostatic noise observed in the dayside auroral zone.

  9. Parametric dependence of ion temperature and electron density in the SUMMA hot-ion plasma using laser light scattering and emission spectroscopy

    NASA Technical Reports Server (NTRS)

    Snyder, A.; Patch, R. W.; Lauver, M. R.

    1980-01-01

    Hot-ion plasma experiments were conducted in the NASA Lewis SUMMA facility. A steady-state modified Penning discharge was formed by applying a radially inward dc electric field of several kilovolts near the magnetic mirror maxima. Results are reported for a hydrogen plasma covering a wide range in midplane magnetic flux densities from 0.5 to 3.37 T. Input power greater than 45 kW was obtained with water-cooled cathodes. Steady-state plasmas with ion kinetic temperatures from 18 to 830 eV were produced and measured spectroscopically. These ion temperatures were correlated with current, voltage, and magnetic flux density as the independent variables. Electron density measurements were made using an unusually sensitive Thomson scattering apparatus. The measured electron densities range from 2.1 x 10 to the 11th to 6.8 x 10 to the 12th per cu cm.

  10. Effect of ion temperature on ion-acoustic solitary waves in a plasma with a q-nonextensive electron velocity distribution

    SciTech Connect

    Roy, Kaushik; Saha, Taraknath; Chatterjee, Prasanta

    2012-10-15

    The effect of ion temperature on the existence of arbitrary amplitude ion-acoustic solitary waves is studied in a two component plasma in presence of a q-nonextensive velocity distributed electrons by using Sagdeev's pseudo potential technique. The range of relevent parameters for which solitons may exist is discussed. It is observed that both q, the nonextensive parameter and the ion temperature {sigma}, play significant roles in the formation and existence of solitons.

  11. Deposition temperature dependence of the deep defect density for a-Si:H films grown by electron cyclotron resonance microwave plasma

    NASA Technical Reports Server (NTRS)

    Essick, J. M.; Pool, F. S.; Shing, Y. H.

    1992-01-01

    The dependence on deposition temperature of the mobility gap density of states has been determined for hydrogenated amorphous silicon (a-Si:H) films grown by electron cyclotron resonance (ECR) microwave plasma CVD. A minimum in the integrated deep defect density of 1 x 10 exp 16/cu cm was found to occur at a temperature of approximately 250 C, while an Urbach slope minimum of 52 meV was observed at 175 C under our deposition conditions. Based on these measurements the ECR-grown films were found to be of excellent device quality and comparable to a-Si:H films grown by RF plasma-enhanced CVD.

  12. Cyclic evolution of the electron temperature and density in dusty low-pressure radio frequency plasmas with pulsed injection of hexamethyldisiloxane

    SciTech Connect

    Garofano, V.; Stafford, L. E-mail: kremena.makasheva@laplace.univ-tlse.fr; Despax, B.; Clergereaux, R.; Makasheva, K. E-mail: kremena.makasheva@laplace.univ-tlse.fr

    2015-11-02

    Optical emission spectroscopy was used to analyze the very-low-frequency cyclic evolution of the electron energy and density caused by repetitive formation and loss of dust nanoparticles in argon plasmas with pulsed injection of hexamethyldisiloxane (HMDSO, [CH{sub 3}]{sub 6}Si{sub 2}O). After elaborating a Boltzmann diagram for Ar high-lying levels and a collisional-radiative model for Ar 2p (Paschen notation) states, temperatures characterizing the low- and high-energy parts of the electron population were calculated. Relative electron densities were also estimated from relative line emission intensities. Both temperatures increase when the dust occupation increases, and then decrease when dust is lost. The opposite trend was observed for the electron density. Such cyclic behaviors of the electron energy and electron density in the HMDSO-containing plasmas are in good agreement with the evolution processes in dusty plasmas, in which the formation of negative ions followed by an electron attachment on the surfaces of the nanoparticles is a critical phenomenon driving dust growth.

  13. Marshall N. Rosenbluth Outstanding Doctoral Thesis Award Talk: Simultaneous Measurement of Electron Temperature and Density Fluctuations in the Core of DIII-D Plasmas

    NASA Astrophysics Data System (ADS)

    White, A. E.

    2009-11-01

    Multi-field fluctuation measurements provide opportunities for rigorous comparison between experiment and nonlinear gyrokinetic turbulence simulations. A unique set of diagnostics on DIII-D allows for simultaneous study of local, long-wavelength (0 < kθρs< 0.5) electron temperature and density fluctuations in the core plasma (0.4 < ρ< 0.8). Previous experiments in L-mode indicate that normalized electron temperature fluctuation levels (40 < f < 400,kHz) increase with radius from ˜0.4% at ρ= 0.5 to ˜2% at ρ=0.8, similar to simultaneously measured density fluctuations. Electron cyclotron heating (ECH) is used to increase Te, which increases electron temperature fluctuation levels and electron heat transport in the experiments. In contrast, long wavelength density fluctuation levels change very little. The different responses are consistent with increased TEM drive relative to ITG-mode drive. A new capability at DIII-D is the measurement of phase angle between electron temperature and density fluctuations using coupled correlation electron cyclotron emission radiometer and reflectometer diagnostics. Linear and nonlinear GYRO runs have been used to design validation experiments that focus on measurements of the phase angle. GYRO shows that if Te and ∇Te increase 50% in a beam-heated L-mode plasma (ρ=0.5), then the phase angle between electron temperature and density fluctuations decreases 30%-50% and electron temperature fluctuation levels increase a factor of two more than density fluctuations. Comparisons between these predictions and experimental results will be presented.

  14. High temperature electronics

    NASA Astrophysics Data System (ADS)

    Seng, Gary T.

    1991-03-01

    In recent years, the aerospace propulsion and space power communities have acknowledged a growing need for electronic devices that are capable of sustained high-temperature operation. Aeropropulsion applications for high-temperature electronic devices include engine ground test instrumentation such as multiplexers, analog-to-digital converters, and telemetry systems capable of withstanding hot section engine temperatures in excess of 600 C. Uncooled operation of control and condition monitoring systems in advanced supersonic aircraft would subject the electronics to temperatures in excess of 300 C. Similarly, engine-mounted integrated electronic sensors could reach temperatures which exceed 500 C. In addition to aeronautics, there are many other areas that could benefit from the existence of high-temperature electronic devices. Space applications include power electronic devices for space platforms and satellites. Since power electronics require radiators to shed waste heat, electronic devices that operate at higher temperatures would allow a reduction in radiator size. Terrestrial applications include deep-well drilling instrumentation, high power electronics, and nuclear reactor instrumentation and control. To meet the needs of the applications mentioned previously, the high-temperature electronics (HTE) program at the Lewis Research Center is developing silicon carbide (SiC) as a high-temperature semiconductor material. Research is focused on developing the crystal growth, growth modeling, characterization, and device fabrication technologies necessary to produce a family of SiC devices. Interest in SiC has grown dramatically in recent years due to solid advances in the technology. Much research remains to be performed, but SiC appears ready to emerge as a useful semiconductor material.

  15. Rotation dependence of a phase delay between plasma edge electron density and temperature fields due to a fast rotating, resonant magnetic perturbation field

    SciTech Connect

    Stoschus, H.; Schmitz, O.; Frerichs, H.; Unterberg, B.; Abdullaev, S. S.; Clever, M.; Coenen, J. W.; Kruezi, U.; Schega, D.; Samm, U.; Jakubowski, M. W.

    2010-06-15

    Measurements of the plasma edge electron density n{sub e} and temperature T{sub e} fields during application of a fast rotating, resonant magnetic perturbation (RMP) field show a characteristic modulation of both, n{sub e} and T{sub e} coherent to the rotation frequency of the RMP field. A phase delay PHI between the n{sub e}(t) and T{sub e}(t) waveforms is observed and it is demonstrated that this phase delay PHI is a function of the radius with PHI(r) depending on the relative rotation of the RMP field and the toroidal plasma rotation. This provides for the first time direct experimental evidence for a rotation dependent damping of the external RMP field in the edge layer of a resistive high-temperature plasma which breaks down at low rotation and high resonant field amplitudes.

  16. Existence domains of arbitrary amplitude nonlinear structures in two-electron temperature space plasmas. II. High-frequency electron-acoustic solitons

    SciTech Connect

    Maharaj, S. K.; Bharuthram, R.; Singh, S. V.; Lakhina, G. S.

    2012-12-15

    A three-component plasma model composed of ions, cool electrons, and hot electrons is adopted to investigate the existence of large amplitude electron-acoustic solitons not only for the model for which inertia and pressure are retained for all plasma species which are assumed to be adiabatic but also neglecting inertial effects of the hot electrons. Using the Sagdeev potential formalism, the Mach number ranges supporting the existence of large amplitude electron-acoustic solitons are presented. The limitations on the attainable amplitudes of electron-acoustic solitons having negative potentials are attributed to a number of different physical reasons, such as the number density of either the cool electrons or hot electrons ceases to be real valued beyond the upper Mach number limit, or, alternatively, a negative potential double layer occurs. Electron-acoustic solitons having positive potentials are found to be supported only if inertial effects of the hot electrons are retained and these are found to be limited only by positive potential double layers.

  17. Electron temperature gradient mode instability and stationary vortices with elliptic and circular boundary conditions in non-Maxwellian plasmas

    SciTech Connect

    Haque, Q.; Zakir, U.; Qamar, A.

    2015-12-15

    Linear and nonlinear dynamics of electron temperature gradient mode along with parallel electron dynamics is investigated by considering hydrodynamic electrons and non-Maxwellian ions. It is noticed that the growth rate of η{sub e}-mode driven linear instability decreases by increasing the value of spectral index and increases by reducing the ion/electron temperature ratio along the magnetic field lines. The eigen mode dispersion relation is also found in the ballooning mode limit. Stationary solutions in the form of dipolar vortices are obtained for both circular and elliptic boundary conditions. It is shown that the dynamics of both circular and elliptic vortices changes with the inclusion of inhomogeneity and non-Maxwellian effects.

  18. Changes in core electron temperature fluctuations across the ohmic energy confinement transition in Alcator C-Mod plasmas

    NASA Astrophysics Data System (ADS)

    Sung, C.; White, A. E.; Howard, N. T.; Oi, C. Y.; Rice, J. E.; Gao, C.; Ennever, P.; Porkolab, M.; Parra, F.; Mikkelsen, D.; Ernst, D.; Walk, J.; Hughes, J. W.; Irby, J.; Kasten, C.; Hubbard, A. E.; Greenwald, M. J.; the Alcator C-Mod Team

    2013-08-01

    The first measurements of long wavelength (kyρs < 0.3) electron temperature fluctuations in Alcator C-Mod made with a new correlation electron cyclotron emission diagnostic support a long-standing hypothesis regarding the confinement transition from linear ohmic confinement (LOC) to saturated ohmic confinement (SOC). Electron temperature fluctuations decrease significantly (∼40%) crossing from LOC to SOC, consistent with a change from trapped electron mode (TEM) turbulence domination to ion temperature gradient (ITG) turbulence as the density is increased. Linear stability analysis performed with the GYRO code (Candy and Waltz 2003 J. Comput. Phys. 186 545) shows that TEMs are dominant for long wavelength turbulence in the LOC regime and ITG modes are dominant in the SOC regime at the radial location (ρ ∼ 0.8) where the changes in electron temperature fluctuations are measured. In contrast, deeper in the core (ρ < 0.8), linear stability analysis indicates that ITG modes remain dominant across the LOC/SOC transition. This radial variation suggests that the robust global changes in confinement of energy and momentum occurring across the LOC/SOC transition are correlated to local changes in the dominant turbulent mode near the edge.

  19. A low-temperature growth process of GaAs by electron-cyclotron-resonance plasma-excited molecular-beam-epitaxy (ECR-MBE)

    NASA Astrophysics Data System (ADS)

    Kondo, Naoto; Nanishi, Yasushi

    1988-09-01

    Taking advantage of plasma excitation, surface cleaning and growth process are realized at low temperatures by electron-cyclotron-resonance (ECR) plasma-excited molecular-beam-epitaxy (MBE). Prior to growth, substrates are cleaned by exposure to hydrogen plasma at temperatures ranging from 300 to 550°C. Arsine gas is introduced and cracked in an ECR plasma generation chamber. Gallium is supplied either as trimethylgallium (TMG) or as metallic Ga. Epitaxial films are successfully grown at substrate temperatures low as 430°C for the TMG-arsine system and 350°C for the metallic Ga-arsine system. The growth rate for the TMG-arsine system is found to be governed by a balance between TMG decomposition and surface atom desorption. By contrast, the metallic Ga-arsine system is only governed by the desorption process. Exposure to plasma is found to promote desorption of atoms migrating on the substrate surface. The interface between the substrate and the epitaxial layer produced by the ECR-MBE process is found to be clean without piling up of impurity.

  20. Propagation of ion-acoustic solitons in an electron beam-superthermal plasma system with finite ion-temperature: Linear and fully nonlinear investigation

    SciTech Connect

    Saberian, E.; Esfandyari-Kalejahi, A.; Rastkar-Ebrahimzadeh, A.; Afsari-Ghazi, M.

    2013-03-15

    The propagation of ion-acoustic (IA) solitons is studied in a plasma system, comprised of warm ions and superthermal (Kappa distributed) electrons in the presence of an electron-beam by using a hydrodynamic model. In the linear analysis, it is seen that increasing the superthermality lowers the phase speed of the IA waves. On the other hand, in a fully nonlinear investigation, the Mach number range and characteristics of IA solitons are analyzed, parametrically and numerically. It is found that the accessible region for the existence of IA solitons reduces with increasing the superthermality. However, IA solitons with both negative and positive polarities can coexist in the system. Additionally, solitary waves with both subsonic and supersonic speeds are predicted in the plasma, depending on the value of ion-temperature and the superthermality of electrons in the system. It is examined that there are upper critical values for beam parameters (i.e., density and velocity) after which, IA solitary waves could not propagate in the plasma. Furthermore, a typical interaction between IA waves and the electron-beam in the plasma is confirmed.

  1. Measurements of Electron Temperature and Density Profiles of Plasmas Produced by Nike KrF Laser for Laser Plasma Instability (LPI) Research

    NASA Astrophysics Data System (ADS)

    Oh, Jaechul; Weaver, J. L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Karasik, M.; Chan, L.-Y.; Serlin, V.; Phillips, L.

    2012-10-01

    ExperimentsfootnotetextJ. Oh, et al, GO5.4, APS DPP (2010).^,footnotetextJ. L. Weaver, et al, GO5.3, APS DPP (2010). using Nike KrF laser observed LPI signatures from CH plasmas at the laser intensities above ˜1x10^15 W/cm^2. Knowing spatial profiles of temperature (Te) and density (ne) in the underdense coronal region (0 < n < nc/4) of the plasma is essential to understanding the LPI observation. However, numerical simulation was the only way to access the profiles for the previous experiments. In the current Nike LPI experiment, a side-on grid imaging refractometer (GIR)footnotetextR. S. Craxton, et al, Phys. Fluids B 5, 4419 (1993). is being deployed for measuring the underdense plasma profiles. The GIR will resolve Te and ne in space taking a 2D snapshot of probe laser (λ= 263 nm, δt = 10 psec) beamlets (50μm spacing) refracted by the plasma at a selected time during the laser illumination. Time-resolved spectrometers with an absolute-intensity-calibrated photodiode array and a streak camera will simultaneously monitor light emission from the plasma in spectral ranges relevant to Raman (SRS) and two plasmon decay (TDP) instabilities. The experimental study of effects of the plasma profiles on the LPI initiation will be presented.

  2. Characterization of Electron Temperature and Density Profiles of Plasmas Produced by Nike KrF Laser for Laser Plasma Instability (LPI) Research

    NASA Astrophysics Data System (ADS)

    Oh, Jaechul; Weaver, J. L.; Phillips, L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Chan, L.-Y.; Serlin, V.

    2011-10-01

    Previous experiments with Nike KrF laser (λ = 248 nm , Δν ~ 1 THz) observed LPI signatures near quarter critical density (nc / 4) in CH plasmas, however, detailed measurement of the temperature (Te) and density (ne) profiles was missing. The current Nike LPI campaign will perform experimental determination of the plasma profiles. A side-on grid imaging refractometer (GIR) is the main diagnostic to resolve Te and ne in space taking 2D snapshots of probe laser (λ = 266 nm , Δt = 8 psec) beamlets (50 μm spacing) refracted by the plasma at laser peak time. Ray tracing of the beamlets through hydrodynamically simulated (FASTRAD3D) plasma profiles estimates the refractometer may access densities up to ~ 0 . 2nc . With the measured Te and ne profiles in the plasma corona, we will discuss analysis of light data radiated from the plasmas in spectral ranges relevant to two plasmon decay and convective Raman instabilities. Validity of the (Te ,ne) data will also be discussed for the thermal transport study. Work supported by DoE/NNSA and ONR and performed at NRL.

  3. High-temperature plasma physics

    SciTech Connect

    Furth, H.P.

    1988-03-01

    Both magnetic and inertial confinement research are entering the plasma parameter range of fusion reactor interest. This paper reviews the individual and common technical problems of these two approaches to the generation of thermonuclear plasmas, and describes some related applications of high-temperature plasma physics.

  4. Numerical studies of independent control of electron density and gas temperature via nonlinear coupling in dual-frequency atmospheric pressure dielectric barrier discharge plasmas

    NASA Astrophysics Data System (ADS)

    Zhang, Z. L.; Nie, Q. Y.; Wang, Z. B.; Gao, X. T.; Kong, F. R.; Sun, Y. F.; Jiang, B. H.

    2016-07-01

    Dielectric barrier discharges (DBDs) provide a promising technology of generating non-equilibrium cold plasmas in atmospheric pressure gases. For both application-focused and fundamental studies, it is important to explore the strategy and the mechanism for enabling effective independent tuning of key plasma parameters in a DBD system. In this paper, we report numerical studies of effects of dual-frequency excitation on atmospheric DBDs, and modulation as well as separate tuning mechanism, with emphasis on dual-frequency coupling to the key plasma parameters and discharge evolution. With an appropriately applied low frequency to the original high frequency, the numerical calculation demonstrates that a strong nonlinear coupling between two frequencies governs the process of ionization and energy deposition into plasma, and thus raises the electron density significantly (e.g., three times in this case) in comparisons with a single frequency driven DBD system. Nevertheless, the gas temperature, which is mainly determined by the high frequency discharge, barely changes. This method then enables a possible approach of controlling both averaged electron density and gas temperature independently.

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

    SciTech Connect

    Dawood, Mahmoud S.; Hamdan, Ahmad E-mail: Joelle.margot@umontreal.ca; Margot, Joëlle E-mail: Joelle.margot@umontreal.ca

    2015-11-15

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

  6. Effects of the parallel electron dynamics and finite ion temperature on the plasma blob propagation in the scrape-off layer

    SciTech Connect

    Jovanovic, D.; Shukla, P. K.; Pegoraro, F.

    2008-11-15

    A new three-dimensional model for the warm-ion turbulence at the tokamak edge plasma and in the scrape-off layer is proposed, and used to study the dynamics of plasma blobs in the scrape-off layer. The model is based on the nonlinear interchange mode, coupled with the nonlinear resistive drift mode, in the presence of the magnetic curvature drive, the density inhomogeneity, the electron dynamics along the open magnetic field lines, and the electron-ion and electron-neutral collisions. Within the present model, the effect of the sheath resistivity decreases with the distance from the wall, resulting in the bending and the break up of the plasma blob structure. Numerical solutions exhibit the coupling of interchange modes with nonlinear drift modes, causing the collapse of the blob in the lateral direction, followed by a clockwise rotation and radial propagation. The symmetry breaking, caused both by the parallel resistivity and the finite ion temperature, introduces a poloidal component in the plasma blob propagation, while the overall stability properties and the speed are not affected qualitatively.

  7. Electron temperature differences and double layers

    NASA Technical Reports Server (NTRS)

    Chan, C.; Hershkowitz, N.; Lonngren, K. E.

    1983-01-01

    Electron temperature differences across plasma double layers are studied experimentally. It is shown that the temperature differences across a double layer can be varied and are not a result of thermalization of the bump-on-tail distribution. The implications of these results for electron thermal energy transport in laser-pellet and tandem-mirror experiments are also discussed.

  8. Effect of dust charge fluctuations on dust acoustic structures in magnetized dusty plasma containing nonextensive electrons and two-temperature isothermal ions

    NASA Astrophysics Data System (ADS)

    Araghi, F.; Dorranian, D.

    2016-02-01

    Effect of dust electrical charge fluctuations on the nature of dust acoustic solitary waves (DASWs) in a four-species magnetized dusty plasma containing nonextensive electrons and two-temperature isothermal ions has been investigated. In this model, the negative dust electric charge is considered to be proportional to the plasma space potential. The nonlinear Zakharov-Kuznetsov (ZK) and modified Zakharov-Kuznetsov (mZK) equations are derived for DASWs by using the standard reductive perturbation method. The combined effects of electron nonextensivity and dust charge fluctuations on the DASW profile are analyzed. The different ranges of the nonextensive q-parameter are considered. The results show that solitary waves the amplitude and width of which depend sensitively on the nonextensive q-parameter can exist. Due to the electron nonextensivity and dust charge fluctuation rate, our dusty plasma model can admit both positive and negative potential solitons. The results show that the amplitude of the soliton increases with increasing electron nonextensivity, but its width decreases. Increasing the electrical charge fluctuations leads to a decrease in both the amplitude and width of DASWs.

  9. 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.

  10. Higher order nonlinear equations for the dust-acoustic waves in a dusty plasma with two temperature-ions and nonextensive electrons

    SciTech Connect

    Emamuddin, M.; Yasmin, S.; Mamun, A. A.

    2013-04-15

    The nonlinear propagation of dust-acoustic waves in a dusty plasma whose constituents are negatively charged dust, Maxwellian ions with two distinct temperatures, and electrons following q-nonextensive distribution, is investigated by deriving a number of nonlinear equations, namely, the Korteweg-de-Vries (K-dV), the modified Korteweg-de-Vries (mK-dV), and the Gardner equations. The basic characteristics of the hump (positive potential) and dip (negative potential) shaped dust-acoustic (DA) Gardner solitons are found to exist beyond the K-dV limit. The effects of two temperature ions and electron nonextensivity on the basic features of DA K-dV, mK-dV, and Gardner solitons are also examined. It has been observed that the DA Gardner solitons exhibit negative (positive) solitons for qq{sub c}) (where q{sub c} is the critical value of the nonextensive parameter q). The implications of our results in understanding the localized nonlinear electrostatic perturbations existing in stellar polytropes, quark-gluon plasma, protoneutron stars, etc. (where ions with different temperatures and nonextensive electrons exist) are also briefly addressed.

  11. High-temperature electronics

    NASA Technical Reports Server (NTRS)

    Matus, Lawrence G.; Seng, Gary T.

    1990-01-01

    To meet the needs of the aerospace propulsion and space power communities, the high temperature electronics program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. This program supports a major element of the Center's mission - to perform basic and developmental research aimed at improving aerospace propulsion systems. Research is focused on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of SiC devices.

  12. High-temperature electronics

    NASA Astrophysics Data System (ADS)

    Matus, Lawrence G.; Seng, Gary T.

    1990-02-01

    To meet the needs of the aerospace propulsion and space power communities, the high temperature electronics program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. This program supports a major element of the Center's mission - to perform basic and developmental research aimed at improving aerospace propulsion systems. Research is focused on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of SiC devices.

  13. Relativistic Electron-Electron Bremsstrahlung in Fusion Plasma

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Jia; Kawai, Norio; Kawamura, Takaichi; Maegauchi, Tetsuo; Narumi, Hajime

    1982-05-01

    Transition matrices and differential cross sections for electron-electron bremsstrahlung in relativistic energy region are calculated by the lowest-order perturbation theory of quantum electrodynamics. The bremsstrahlung spectra and emission rates are evaluated for relativistic Maxwellian plasma. The results are discussed in comparison with those obtained by non-relativistic and extreme-relativistic approximations and it is noted that the relativistic effect becomes appreciable above the order of 10 keV for the electron temperature.

  14. Plasma Temperatures in the Ionosphere of Saturn

    NASA Astrophysics Data System (ADS)

    Moore, Luke; Galand, M.; Mendillo, M.; Müller-Wodarg, I.

    2007-10-01

    Using a one-dimensional version of the Saturn Thermosphere Ionosphere Model (STIM), we perform calculations of the ion and electron temperatures in the ionosphere of Saturn. There are no direct measurements of plasma temperatures in Saturn's atmosphere published to date, but they are often estimated from the topside plasma scale heights of radio occultation measurements of electron density. Based on Pioneer, Voyager, and now Cassini data, those estimates range from 625 K to 1700 K. Our preliminary calculations reproduce the lower level of that range, with an electron temperature peak value of just over 600 K at midlatitudes near dawn and dusk. Our calculations also suggest a diurnal variation of more than 200 K. Finally, our results allow an assessment of the reliability of estimating plasma temperatures from altitude profiles of electron density, which are also computed in STIM. By applying a range of background conditions (e.g., neutral atmosphere, solar flux) we explore the parameter space of possible variability of plasma temperatures on Saturn. STIM development at Boston University was funded by the NASA Planetary Atmospheres program. LM acknowledges support from a NASA Graduate Student Researchers Program fellowship, IM-W is supported by a British Royal Society Fellowship.

  15. Central electron temperature estimations of TJ-II neutral beam injection heated plasmas based on the soft x ray multi-foil technique

    SciTech Connect

    Baiao, D.; Varandas, C.

    2012-05-15

    The core electron temperature (T{sub e0}) of neutral beam heated plasmas is determined in TJ-II stellarator by using soft x ray detectors with beryllium filters of different thickness, based on the method known as the foil absorption technique. T{sub e0} estimations are done with the impurity code IONEQ, making use of complementary information from the TJ-II soft x ray tomography and the VUV survey diagnostics. When considering the actual electron density and temperature profile shapes, an acceptable agreement is found with Thomson scattering measurements for 8 different magnetic configurations. The impact of the use of both neutral beam injectors on the T{sub e0} measurements is addressed. Also, the behaviour of T{sub e0} during spontaneous profile transitions is presented.

  16. Implementation of a multichannel soft x-ray diagnostic for electron temperature measurements in TJ-II high-density plasmas

    SciTech Connect

    Baiao, D.; Varandas, C.; Molinero, A.; Chercoles, J.

    2012-10-15

    Based on the multi-foil technique, a multichannel soft x-ray diagnostic for electron temperature measurements has been recently implemented in the TJ-II stellarator. The diagnostic system is composed by four photodiodes arrays with beryllium filters of different thickness. An in-vacuum amplifier board is coupled to each array, aiming at preventing induced noise currents. The Thomson scattering and the vacuum ultraviolet survey diagnostics are used for assessing plasma profiles and composition, being the analysis carried out with the radiation code IONEQ. The electron temperature is determined through the different signal-pair ratios with temporal and spatial resolution. The design and preliminary results from the diagnostic are presented.

  17. High-temperature electronics

    NASA Astrophysics Data System (ADS)

    Seng, Gary T.

    1987-11-01

    In recent years, there was a growing need for electronics capable of sustained high-temperature operation for aerospace propulsion system instrumentation, control and condition monitoring, and integrated sensors. The desired operating temperature in some applications exceeds 600 C, which is well beyond the capability of currently available semiconductor devices. Silicon carbide displays a number of properties which make it very attractive as a semiconductor material, one of which is the ability to retain its electronic integrity at temperatures well above 600 C. An IR-100 award was presented to NASA Lewis in 1983 for developing a chemical vapor deposition process to grow single crystals of this material on standard silicon wafers. Silicon carbide devices were demonstrated above 400 C, but much work remains in the areas of crystal growth, characterization, and device fabrication before the full potential of silicon carbide can be realized. The presentation will conclude with current and future high-temperature electronics program plans. Although the development of silicon carbide falls into the category of high-risk research, the future looks promising, and the potential payoffs are tremendous.

  18. High temperature electronics technology

    NASA Astrophysics Data System (ADS)

    Dening, J. C.; Hurtle, D. E.

    1984-03-01

    This report summarizes the barrier metallization developments accomplished in a program intended to develop 300 C electronic controls capability for potential on-engine aircraft engine application. In addition, this report documents preliminary life test results at 300 C and above and discusses improved design practices required for high temperature integrated injection logic semiconductors. Previous Phase 1 activities focused on determining the viability of operating silicon semiconductor devices over the -55 C to +300 C temperature range. This feasibility was substantiated but the need for additional design work and process development was indicated. Phase 2 emphasized the development of a high temperature metallization system as the primary development need for high temperature silicon semiconductor applications.

  19. Temperature Diffusion Waves in Magnetized Plasmas

    NASA Astrophysics Data System (ADS)

    Reynolds, M. A.; Morales, G. J.; Maggs, J. E.

    2002-11-01

    Fluctuations of localized heat sources manifest themselves as temperature diffusion waves throughout the plasma surrounding the source, with anisotropic propagation characteristics due to the anisotropic nature of the thermal conductivity. In fact, fluctuations in electron temperature have been observed experimentally in studies of heat transport in magnetized temperature filaments (Burke et al., Phys. Plasmas, 7, 1397, 2000) where the anisotropic nature was of paramount interest. Here, the theory of temperature diffusion waves in a magnetized plasma is presented, and the properties of these waves are investigated both analytically and numerically. Results from the one-dimensional (parallel), linear theory of diffusion waves are used to shed light on the results obtained by a two-dimensional (parallel and perpendicular) transport code. Features that are investigated include the spatial structure of wave amplitude and phase, the effect that the size of the source region has on the spatial structure (i.e., radial localization), and the strongly nonlinear (large amplitude source fluctuations) limit.

  20. High confinement in fusion oriented plasmas with kV-order potential, ion, and electron temperatures with controlled radial turbulent transport in GAMMA 10

    NASA Astrophysics Data System (ADS)

    Cho, Teruji

    2007-11-01

    The tandem mirror system has achieved improved energy confinement times (> 60-90 ms) with radial transport dominating the Pastukhov axial energy confinement time (> 100 ms). This high confinement regime establishes a proof of principle that the combination of electrostatic and magnetic mirror confinement can successfully insulate electrons from thermal ions. ECH controlled hot-layer formation facilitates plasma-rotation profile formation with a radially localized high-vorticity layer. In the vicinity of the layer, a radial transport barrier is formed [1], showing similar properties to ITB in toroidal plasmas. Coaxially nested intense E(r)xB sheared flow [2] in the GAMMA 10 core plasma realizes an upgraded stable regime having (i) > 0.75 keV bulk central electron temperature with (ii) an achievement of larger stored energy for axially potential-confined ions exceeding that (i.e., diamagnetism) for central magnetically confined ions ( 7 keV). The radially sheared flow having peak-on-axis high vorticity guards and improves whole core plasma confinement, and is controlled by (iii) improved 3 kV ion-confining potential due to simultaneous central and plug ECH. X-ray imaging of the suppression of turbulent structures [1-3] will be shown [1,2]. [1] T. Cho et al., Phys. Rev. Lett. 97, 055001 (2006). [2] T. Cho et al., Phys. Rev. Lett. 94, 085002 (2005). [3] J. Pratt and W. Horton, Phys. Plasmas 13, 042513 (2006). Collaborators; W. Horton^1, J. Pratt^1, M. Hirata, J. Kohagura, T. Numakura, H. Hojo, M. Ichimura, A. Itakura, T. Kariya, I. Katanuma, R. Minami, Y. Nakashima, M. Yoshikawa, Y. Miyata, Y. Yamaguchi, T. Imai, V. P. Pastukhov^2, S. Miyoshi, GAMMA 10 Group (^1IFS, Univ. Texas at Austin, ^2Kurchatov Institute, Russia)

  1. Electron cyclotron resonance plasma photos

    SciTech Connect

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

    2010-02-15

    In order to observe and study systematically the plasma of electron cyclotron resonance (ECR) ion sources (ECRIS) we made a high number of high-resolution visible light plasma photos and movies in the ATOMKI ECRIS Laboratory. This required building the ECR ion source into an open ECR plasma device, temporarily. An 8MP digital camera was used to record photos of plasmas made from Ne, Ar, and Kr gases and from their mixtures. We studied and recorded the effect of ion source setting parameters (gas pressure, gas composition, magnetic field, and microwave power) to the shape, color, and structure of the plasma. The analysis of the photo series gave us many qualitative and numerous valuable physical information on the nature of ECR plasmas.

  2. Solitary waves in asymmetric electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    > By solving the coupled equations of the electromagnetic field and electrostatic potential, we investigate solitary waves in an asymmetric electron-positron plasma and/or electron-positron-ion plasmas with delicate features. It is found that the solutions of the coupled equations can capture multipeak structures of solitary waves in the case of cold plasma, which are left out by using the long-wavelength approximation. By considering the effect of ion motion with respect to non-relativistic and ultra-relativistic temperature plasmas, we find that the ions' mobility can lead to larger-amplitude solitary waves; especially, this becomes more obvious for a high-temperature plasma. The effects of asymmetric temperature between electrons and positrons and the ion fraction on the solitary waves are also studied and presented. It is shown that the amplitudes of solitary waves decrease with positron temperature in asymmetric temperature electron-positron plasmas and decrease also with ion concentration.

  3. Statistical modeling of deconvolution procedures for improving the resolution of measuring electron temperature profiles in tokamak plasmas by Thomson scattering lidar

    NASA Astrophysics Data System (ADS)

    Dreischuh, Tanja N.; Gurdev, Ljuan L.; Stoyanov, Dimitar V.

    2010-10-01

    The potentialities are investigated, by statistical modeling, of deconvolution techniques for high-resolution restoration of electron temperature profiles in fusion plasma reactors like Joint European Torus (JET) measured by Thomson scattering lidar using the center-of-mass wavelength approach. The sensing laser pulse shape and the receiving-system response function are assumed to be exponentially-shaped. The plasma light background influence is taken into account as well as the Poisson fluctuations of the photoelectron number after the photocathode enhanced in the process of cascade multiplying in the employed microchannel photomultiplier tube. It is shown that the Fourier-deconvolution of the measured long-pulse (lidar-response-convolved) lidar profiles, at relatively high and low signal-to-noise ratios, ensures a higher accuracy of recovering the electron temperature profiles with three times higher range resolution compared to the case without deconvolution. The final resolution scale is determined by the width of the window of an optimum monotone sharp-cutoff digital noise-suppressing (noise-controlling) filter applied to the measured lidar profiles.

  4. Energy Transfer via Ion-Beam Driven Weibel and Two-stream instabilities in Two-Temperature Electron-Ion Plasmas

    NASA Astrophysics Data System (ADS)

    Park, Jaehong; Ren, Chuang; Blackman, Eric; Kong, Xianglong

    2009-11-01

    Whether a collisionless faster-than-Coulomb energy transfer mechanism exists in two-temperature accretion flows is an open question. Using 2D PIC simulations, we generalize Ren et al.2007 (Phy.Plasmas 012901) into counter-streaming ion beam-driven oblique instabilities where Weibel, two-stream, and oblique modes coexist. We explain in detail the evolution patterns in both linear and non-linear regimes, and how to reach saturation. To compare with simulations, we solve a set of 1+1D quasi-linear calculations. In a real mass ratio, M/m=1836, we estimate that electrons gain 3.2% of initial ion energy for the case, Te=0.2KeV, Ti=375KeV, and vid=0.7c. While this gain of 3.2% does not threaten the existence of two-temperature accretion flow models per se, one might ask whether it threatens the subset of models (Narayan et al.1998 (ApJ492,554)) which employ less than this percentage of energy to be transferred from ions to electrons on an infall time scales. However, in the solution of Narayan et al.1998, the electron and ion temperature are much larger than ours and ion beam drifts as high as 0.7c would probably occur at most in localized regions. As a result, the electron-ion coupling could be smaller than 3.2%. At present, our results do not therefore definitively rule out existing two-temperature accretion solutions.

  5. CONFINEMENT OF HIGH TEMPERATURE PLASMA

    DOEpatents

    Koenig, H.R.

    1963-05-01

    The confinement of a high temperature plasma in a stellarator in which the magnetic confinement has tended to shift the plasma from the center of the curved, U-shaped end loops is described. Magnetic means are provided for counteracting this tendency of the plasma to be shifted away from the center of the end loops, and in one embodiment this magnetic means is a longitudinally extending magnetic field such as is provided by two sets of parallel conductors bent to follow the U-shaped curvature of the end loops and energized oppositely on the inside and outside of this curvature. (AEC)

  6. Temperature Relaxation in Non-Ideal Plasmas

    NASA Astrophysics Data System (ADS)

    Gericke, Dirk O.; Murillo, Michael S.

    2001-10-01

    The equilibration process of multi-temperature plasmas, i.e., the energy transfer between electrons and ions, is investigated for the case of hot electrons and cold ions. Such non-equilibrium plasmas occur in various experiments, including the creation and heating of plasmas with short-pulse lasers and intense ion beams. Temperature separation occurs since these drivers couple almost entirely to the electrons. The standard approach to the equilibration rates goes back to the early works of Landau and Spitzer. However, this approach is only valid for systems where the Coulomb logarithm is larger than three, which clearly fails for strongly coupled plasmas. We first generalize this approach by considering hyperbolic orbits for the particle trajectories. Then we calculate the energy transfer rates using a quantal kinetic equation of the Boltzmann type which allows an exact (T-matrix) treatment of close collisions. On this basis, we demonstrate the importance of hyperbolic orbits, quantum defraction effects on the scattering cross section, a correct treatment of the distribution, dynamic screening effects, and the influence of the plasma composition.

  7. TG wave autoresonant control of plasma temperature

    SciTech Connect

    Kabantsev, A. A. Driscoll, C. F.

    2015-06-29

    The thermal correction term in the Trivelpiece-Gould (TG) wave’s frequency has been used to accurately control the temperature of electron plasma, by applying a swept-frequency continuous drive autoresonantly locked in balance with the cyclotron cooling. The electron temperature can be either “pegged” at a desired value (by constant drive frequency); or varied cyclically (following the tailored frequency course), with rates limited by the cooling time (on the way down) and by chosen drive amplitude (on the way up)

  8. A search for the Sunyaev-Zel'dovich effect at millimeter wavelengths. [cosmic background photon energy increase due to Compton scattering by high temperature galactic cluster plasma electrons

    NASA Technical Reports Server (NTRS)

    Meyer, S. S.; Jeffries, A. D.; Weiss, R.

    1983-01-01

    It is believed that X-ray emission from clusters of galaxies represents thermal bremsstrahlung from a hot plasma. According to Sunyaev and Zel'dovich (1972), the plasma column density and temperature derived from this model imply a measurable distortion of the cosmic background radiation (CBR) in the cluster direction. This distortion results from the Compton scattering of the CBR photons by the electrons in the plasma, resulting in an average increase of each photon. This process, known as the Sunyaev-Zel'dovich effect, is photon conserving and 'shifts' the CBR spectrum to higher frequencies. The result is a decrease of flux at frequencies below 7.5 per cm (the Rayleigh-Jeans region), and an increase above. The investigation is concerned with measurements of the Sunyaev-Zel'dovich effect at frequencies in the range from 3 to 10 per cm. Attention is given to the employed observing and analysis technique, and an initial null result for the cluster Abell 1795.

  9. On the use of the double floating probe method to infer the difference between the electron and the heavy particles temperatures in an atmospheric pressure, vortex-stabilized nitrogen plasma jet

    SciTech Connect

    Prevosto, L. Mancinelli, B. R.; Kelly, H.

    2014-05-15

    Sweeping double probe measurements in an atmospheric pressure direct current vortex-stabilized plasma jet are reported (plasma conditions: 100 A discharge current, N{sub 2} gas flow rate of 25 Nl/min, thoriated tungsten rod-type cathode, copper anode with 5 mm inner diameter). The interpretation of the double probe characteristic was based on a generalization of the standard double floating probe formulae for non-uniform plasmas coupled to a non-equilibrium plasma composition model. Perturbations caused by the current to the probe together with collisional and thermal processes inside the probe perturbed region were taken into account. Radial values of the average electron and heavy particle temperatures as well as the electron density were obtained. The calculation of the temperature values did not require any specific assumption about a temperature relationship between different particle species. An electron temperature of 10 900 ± 900 K, a heavy particle temperature of 9300 ± 900 K, and an electron density of about 3.5 × 10{sup 22} m{sup −3} were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found toward the outer border of the plasma jet. These results showed good agreement with those previously reported by the authors by using a single probe technique. The calculations have shown that this method is particularly useful for studying spraying-type plasma torches operated at power levels of about 15 kW.

  10. Flute-interchange stability in a hot electron plasma

    SciTech Connect

    Dominguez, R.R.

    1980-01-01

    Several topics in the kinetic stability theory of flute-interchange modes in a hot electron plasma are discussed. The stability analysis of the hot-electron, curvature-driven flute-interchange mode, previously performed in a slab geometry, is extended to a cylindrical plasma. The cold electron concentration necessary for stability differs substantially from previous criteria. The inclusion of a finite temperature background plasma in the stability analysis results in an ion curvature-driven flute-interchange mode which may be stabilized by either hot-electron diamagnetic effects, hot-electron plasma density, or finite (ion) Larmor radius effects.

  11. Existence domains of arbitrary amplitude nonlinear structures in two-electron temperature space plasmas. I. Low-frequency ion-acoustic solitons

    SciTech Connect

    Maharaj, S. K.; Bharuthram, R.; Singh, S. V.; Lakhina, G. S.

    2012-07-15

    Using the Sagdeev pseudopotential technique, the existence of large amplitude ion-acoustic solitons is investigated for a plasma composed of ions, and hot and cool electrons. Not only are all species treated as adiabatic fluids but the model for which inertial effects of the hot electrons is neglected whilst retaining inertia and pressure for the ions and cool electrons has also been considered. The focus of this investigation has been on identifying the admissible Mach number ranges for large amplitude nonlinear ion-acoustic soliton structures. The lower Mach number limit yields a minimum velocity for the existence of ion-acoustic solitons. The upper Mach number limit for positive potential solitons is found to coincide with the limiting value of the potential (positive) beyond which the ion number density ceases to be real valued, and ion-acoustic solitons can no longer exist. Small amplitude solitons having negative potentials are found to be supported when the temperature of the cool electrons is negligible.

  12. 30-cm electron cyclotron plasma generator

    NASA Technical Reports Server (NTRS)

    Goede, Hank

    1987-01-01

    Experimental results on the development of a 30-cm-diam electron cyclotron resonance plasma generator are presented. This plasma source utilizes samarium-cobalt magnets and microwave power at a frequency of 4.9 GHz to produce a uniform plasma with densities of up to 3 x 10 to the 11th/cu cm in a continuous fashion. The plasma generator contains no internal structures, and is thus inherently simple in construction and operation and inherently durable. The generator was operated with two different magnetic geometries. One used the rare-earth magnets arranged in an axial line cusp configuration, which directly showed plasma production taking place near the walls of the generator where the electron temperature was highest but with the plasma density peaking in the central low B-field regions. The second configuration had magnets arranged to form azimuthal line cusps with approximately closed electron drift surfaces; this configuration showed an improved electrical efficiency of about 135 eV/ion.

  13. Spectroscopic diagnostics of high temperature plasmas

    SciTech Connect

    Moos, W.

    1990-01-01

    A three-year research program for the development of novel XUV spectroscopic diagnostics for magnetically confined fusion plasmas is proposed. The new diagnostic system will use layered synthetic microstructures (LSM) coated, flat and curved surfaces as dispersive elements in spectrometers and narrow band XUV filter arrays. In the framework of the proposed program we will develop impurity monitors for poloidal and toroidal resolved measurements on PBX-M and Alcator C-Mod, imaging XUV spectrometers for electron density and temperature fluctuation measurements in the hot plasma core in TEXT or other similar tokamaks and plasma imaging devices in soft x-ray light for impurity behavior studies during RF heating on Phaedrus T and carbon pellet ablation in Alcator C-Mod. Recent results related to use of multilayer in XUV plasma spectroscopy are presented. We also discuss the latest results reviewed to q{sub o} and local poloidal field measurements using Zeeman polarimetry.

  14. Analysis of experimental observations of electron temperatures in the near wake of a model in a laboratory-simulated solar wind plasma

    NASA Technical Reports Server (NTRS)

    Intriligator, D. S.; Steele, G. R.

    1985-01-01

    In the present paper, the results are presented of the first laboratory experiments in a high-energy plasma which investigate the electron temperature Te in the body wake. A large number of Te samples in the very near- and near-wake regions downstream from a conducting body are employed. The obtained results are compared with the experimental findings of Oran et al. (1975), Stone (1981), and others. The findings are discussed in the more general context of theoretical studies and of other relevant considerations. Attention is also given to the possible relevance of the results to the maintenance of the nightside ionosphere of Venus, and suggestions are made regarding some specific spacecraft observations which should be carried out using the Pioneer Venus orbiter.

  15. Electron Bernstein wave electron temperature profile diagnostic (invited)

    SciTech Connect

    Taylor, G.; Efthimion, P.; Jones, B.; Munsat, T.; Spaleta, J.; Hosea, J.; Kaita, R.; Majeski, R.; Menard, J.

    2001-01-01

    Electron cyclotron emission (ECE) has been employed as a standard electron temperature profile diagnostic on many tokamaks and stellarators, but most magnetically confined plasma devices cannot take advantage of standard ECE diagnostics to measure temperature. They are either ''overdense,'' operating at high density relative to the magnetic field (e.g., {omega}{sub pe}>>{Omega}{sub ce} in a spherical torus) or they have insufficient density and temperature to reach the blackbody condition ({tau}>2). Electron Bernstein waves (EBWs) are electrostatic waves that can propagate in overdense plasmas and have a high optical thickness at the electron cyclotron resonance layers as a result of their large k{sub perp}. In this article we report on measurements of EBW emission on the CDX-U spherical torus, where B{sub 0}{approx}2kG, {approx}10{sup 13}cm{sup -3} and T{sub e}{approx}10--200eV. Results are presented for electromagnetic measurements of EBW emission, mode converted near the plasma edge. The EBW emission was absolutely calibrated and compared to the electron temperature profile measured by a multipoint Thomson scattering diagnostic. Depending on the plasma conditions, the mode-converted EBW radiation temperature was found to be {<=}T{sub e} and the emission source was determined to be radially localized at the electron cyclotron resonance layer. A Langmuir triple probe and a 140 GHz interferometer were employed to measure changes in the edge density profile in the vicinity of the upper hybrid resonance where the mode conversion of the EBWs is expected to occur. Initial results suggest EBW emission and EBW heating are viable concepts for plasmas where {omega}{sub pe}>>{Omega}{sub ce}.

  16. Measurement of plasma temperature and density using laser absorption

    NASA Technical Reports Server (NTRS)

    Billman, K. W.; Stallcop, J. R.

    1973-01-01

    A laser radiation absorption technique, suitable for temporal measurement of the electron density, the temperature, or a simultaneous determination of both, in an LTE plasma, is discussed. The theoretical calculation of the absorption coefficient for a hydrogen plasma is outlined; some results are presented for visible wavelengths. Measurements of electron density and temperature are presented and shown to be in good agreement with those values obtained by other methods. Finally, the possible use of the argon ion laser for simultaneous electron density and temperature measurement is discussed, and the theoretical curves necessary for its application to hydrogen plasma diagnostics are shown.

  17. Implementation of a new atomic basis for the He I equilibrium line ratio technique for electron temperature and density diagnostic in the SOL for H-mode plasmas in DIII-D

    NASA Astrophysics Data System (ADS)

    Muñoz Burgos, J. M.; Schmitz, O.; Unterberg, E. A.; Loch, S. D.; Ballance, C. P.

    2011-08-01

    Evaluating the ratio of selected helium lines allows for measurement of electron densities and temperatures. This technique is applied for L-mode plasmas at TEXTOR (O. Schmitz et al., Plasma Phys. Control. Fusion 50 (2008) 115004). We report our first efforts to extend it to H-mode plasma diagnostics in DIII-D. This technique depends on the accuracy of the atomic data used in the collisional radiative model (CRM). We present predictions for the electron temperatures and densities by using recently calculated R-Matrix With Pseudostates (RMPS) and Convergent Close-Coupling (CCC) electron-impact excitation and ionization data. We include contributions from higher Rydberg states by means of the projection matrix. These effects become significant for high electron density conditions, which are typical in H-mode. We apply a non-equilibrium model for the time propagation of the ionization balance to predict line emission profiles from experimental H-mode data from DIII-D.

  18. Controlling electron energy distributions for plasma technologies

    NASA Astrophysics Data System (ADS)

    Kushner, Mark

    2009-10-01

    The basic function of low temperature plasmas in society benefiting technologies is to channel power into specific modes of atoms and molecules to excite desired states or produce specified radicals. This functionality ultimately depends on the ability to craft an electron energy distribution (EED) to match cross sections. Given electric fields, frequencies, gas mixtures and pressures, predicting EEDs and excitation rates can in large part be reliably done. The inverse problem, specifying the conditions that produce a given EED, is less well understood. Early strategies to craft EEDs include adjusting gas mixtures, such as the rare gas-Hg mixtures in fluorescent lamps, and externally sustained discharges, such as electron-beam sustained plasmas for molecular lasers. More recent strategies include spiker-sustainer circuitry which produces desired EEDs in non-self-sustained plasmas; and adjusting frequency in capacitively coupled plasmas. In this talk, past strategies for customizing EEDs in low pressure plasmas will be reviewed and prospects for improved control of plasma kinetics will be discussed using results from 2-dimensional computer models.

  19. Electron density measurements for plasma adaptive optics

    NASA Astrophysics Data System (ADS)

    Neiswander, Brian W.

    Over the past 40 years, there has been growing interest in both laser communications and directed energy weapons that operate from moving aircraft. As a laser beam propagates from an aircraft in flight, it passes through boundary layers, turbulence, and shear layers in the near-region of the aircraft. These fluid instabilities cause strong density gradients which adversely affect the transmission of laser energy to a target. Adaptive optics provides corrective measures for this problem but current technology cannot respond quickly enough to be useful for high speed flight conditions. This research investigated the use of plasma as a medium for adaptive optics for aero-optics applications. When a laser beam passes through plasma, its phase is shifted proportionally to the electron density and gas heating within the plasma. As a result, plasma can be utilized as a dynamically controllable optical medium. Experiments were carried out using a cylindrical dielectric barrier discharge plasma chamber which generated a sub-atmospheric pressure, low-temperature plasma. An electrostatic model of this design was developed and revealed an important design constraint relating to the geometry of the chamber. Optical diagnostic techniques were used to characterize the plasma discharge. Single-wavelength interferometric experiments were performed and demonstrated up to 1.5 microns of optical path difference (OPD) in a 633 nm laser beam. Dual-wavelength interferometry was used to obtain time-resolved profiles of the plasma electron density and gas heating inside the plasma chamber. Furthermore, a new multi-wavelength infrared diagnostic technique was developed and proof-of-concept simulations were conducted to demonstrate the system's capabilities.

  20. Temperature equilibration in strongly coupled plasma

    SciTech Connect

    Thode, L. E.; Chang, C. H.; Snell, C. M.; Daughton, W. S.; Csanak, G. Y.

    2002-01-01

    A laser-driven experiment investigating electron-ion equilibration in strongly coupled plasma was performed in 1995. At that time, standard estimates for the electron-ion equilibration time were two-to-three orders of magnitude faster than observed experimentally. As a result, the electron-ion equilibration time was taken as a fitting parameter to understand the experimental results. Based upon guidance from nonequilibrium molecular dynamics mixture calculations 121 and comparison with strongly coupled resistivity experiments, we have developed a consistent binary collision model to understand the electron-ion equilibration experiment. The model has been implemented in a newly developed multi-species, multi-temperature physics code, which was used for simulation of the experiment. The resulting electron-ion exchange rate is close to the experiment, which is about three orders-of-magnitude slower than given by standard estimates, most of which is the result of a modified coulomb logarithm.

  1. Dynamics of energetic plasma sheet electrons

    NASA Astrophysics Data System (ADS)

    Burin Des Roziers, Edward

    2009-06-01

    The dynamics of energetic plasma sheet electrons plays an important role in many geomagnetic processes. The intent of this thesis is to extend the current understanding of the relationship between the solar wind and energetic plasma sheet electrons (~> 40 keV ), as well as the variability of these electrons within the plasma sheet. The statistical relationship between tens of keV 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. Statistically, plasma sheet electron flux variations are compared to solar wind velocity, density, dynamic pressure, IMF B z , and solar wind energetic electrons, as well as > 2 MeV electrons at geosynchronous orbit. Several new results are revealed: (1) there is a strong positive correlation between energetic plasma sheet electrons and solar wind velocity; (2) this correlation is valid throughout the plasma sheet and extends to distances of X GSM =-30 R E ; (3) there is evidence of a weak negative correlation between energetic plasma sheet electrons and solar wind density; (4) energetic plasma sheet electrons are enhanced during times of southward interplanetary magnetic field (IMF); (5) there is no clear correlation between energetic plasma sheet electrons and solar wind electrons of comparable energies; and (6) there is a strong correlation between energetic electrons in the plasma sheet and > 2 MeV electrons at geosynchronous orbit measured 2 days later. In addition, the variability of energetic electron fluxes within the plasma sheet is explored. Interesting events were found using a combination of automated methods and visual inspection. Events are classified into 4 main types: (1) plasma sheet empty of energetic electrons; (2) decreasing plasma sheet energetic electron fluxes; (3) increasing plasma sheet energetic electron fluxes; and (4) sharp

  2. 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.

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  4. Optical plasma torch electron bunch generation in plasma wakefield accelerators

    NASA Astrophysics Data System (ADS)

    Wittig, G.; Karger, O.; Knetsch, A.; Xi, Y.; Deng, A.; Rosenzweig, J. B.; Bruhwiler, D. L.; Smith, J.; Manahan, G. G.; Sheng, Z.-M.; Jaroszynski, D. A.; Hidding, B.

    2015-08-01

    A novel, flexible method of witness electron bunch generation in plasma wakefield accelerators is described. A quasistationary plasma region is ignited by a focused laser pulse prior to the arrival of the plasma wave. This localized, shapeable optical plasma torch causes a strong distortion of the plasma blowout during passage of the electron driver bunch, leading to collective alteration of plasma electron trajectories and to controlled injection. This optically steered injection is more flexible and faster when compared to hydrodynamically controlled gas density transition injection methods.

  5. Temperature relaxation in a magnetized plasma

    SciTech Connect

    Dong, Chao; Ren, Haijun; Cai, Huishan; Li, Ding

    2013-10-15

    A magnetic field greatly affects the relaxation phenomena in a plasma when the particles’ thermal gyro-radii are smaller than the Debye length. Its influence on the temperature relaxation (TR) is investigated through consideration of binary collisions between charged particles in the presence of a uniform magnetic field within a perturbation theory. The relaxation times are calculated. It is shown that the electron-electron (e-e) and ion-ion (i-i) TR rates first increase and then decrease as the magnetic field grows, and the doubly logarithmic term contained in the electron-ion (e-i) TR rate results from the exchange between the electron parallel and the ion perpendicular kinetic energies.

  6. Electron energy distribution in a dusty plasma: analytical approach.

    PubMed

    Denysenko, I B; Kersten, H; Azarenkov, N A

    2015-09-01

    Analytical expressions describing the electron energy distribution function (EEDF) in a dusty plasma are obtained from the homogeneous Boltzmann equation for electrons. The expressions are derived neglecting electron-electron collisions, as well as transformation of high-energy electrons into low-energy electrons at inelastic electron-atom collisions. At large electron energies, the quasiclassical approach for calculation of the EEDF is applied. For the moderate energies, we account for inelastic electron-atom collisions in the dust-free case and both inelastic electron-atom and electron-dust collisions in the dusty plasma case. Using these analytical expressions and the balance equation for dust charging, the electron energy distribution function, the effective electron temperature, the dust charge, and the dust surface potential are obtained for different dust radii and densities, as well as for different electron densities and radio-frequency (rf) field amplitudes and frequencies. The dusty plasma parameters are compared with those calculated numerically by a finite-difference method taking into account electron-electron collisions and the transformation of high-energy electrons at inelastic electron-neutral collisions. It is shown that the analytical expressions can be used for calculation of the EEDF and dusty plasma parameters at typical experimental conditions, in particular, in the positive column of a direct-current glow discharge and in the case of an rf plasma maintained by an electric field with frequency f=13.56MHz. PMID:26465570

  7. 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.

  8. Temperature peaking at beginning of breakdown in 2.45 GHz pulsed off-resonance electron cyclotron resonance ion source hydrogen plasma

    SciTech Connect

    Cortazar, O. D.

    2012-10-15

    An experimental study of temperature and density evolution during breakdown in off-resonance ECR hydrogen plasma is presented. Under square 2.45 GHz microwave excitation pulses with a frequency of 50 Hz and relative high microwave power, unexpected transient temperature peaks that reach 18 eV during 20 {mu}s are reported at very beginning of plasma breakdown. Decays of such peaks reach final stable temperatures of 5 eV at flat top microwave excitation pulse. Evidence of interplay between incoming power and duty cycle giving different kind of plasma parameters evolutions engaged to microwave coupling times is observed. Under relative high power conditions where short microwave coupling times are recorded, high temperature peaks are measured. However, for lower incoming powers and longer coupling times, temperature evolves gradually to a higher final temperature without peaking. On the other hand, the early instant where temperature peaks are observed also suggest a possible connection with preglow processes during breakdown in ECRIS plasmas.

  9. Finite temperature static charge screening in quantum plasmas

    NASA Astrophysics Data System (ADS)

    Eliasson, B.; Akbari-Moghanjoughi, M.

    2016-07-01

    The shielding potential around a test charge is calculated, using the linearized quantum hydrodynamic formulation with the statistical pressure and Bohm potential derived from finite temperature kinetic theory, and the temperature effects on the force between ions is assessed. The derived screening potential covers the full range of electron degeneracy in the equation of state of the plasma electrons. An attractive force between shielded ions in an arbitrary degenerate plasma exists below a critical temperature and density. The effect of the temperature on the screening potential profile qualitatively describes the ion-ion bound interaction strength and length variations. This may be used to investigate physical properties of plasmas and in molecular-dynamics simulations of fermion plasma. It is further shown that the Bohm potential including the kinetic corrections has a profound effect on the Thomson scattering cross section in quantum plasmas with arbitrary degeneracy.

  10. Electron plasma orbits from competing diocotron drifts.

    PubMed

    Hurst, N C; Danielson, J R; Baker, C J; Surko, C M

    2014-07-11

    The perpendicular dynamics of a pure electron plasma column are investigated when the plasma spans two Penning-Malmberg traps with noncoinciding axes. The plasma executes noncircular orbits described by competing image-charge electric-field (diocotron) drifts from the two traps. A simple model is presented that predicts a set of nested orbits in agreement with observed plasma trajectories. PMID:25062198

  11. Revisiting plasma hysteresis with an electronically compensated Langmuir probe

    SciTech Connect

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

    2012-09-15

    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 {mu}A, allowing plasma measurements to be done with ion saturation current of the order of hundreds of {mu}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 {delta}T{sub pk-pk} changes by {approx}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.

  12. Radiation temperature of non-equilibrium plasmas

    SciTech Connect

    Arunasalam, V.

    1991-07-01

    In fusion devices measurements of the radiation temperature T{sub r} ({omega}, k) near the electron cyclotron frequency {omega}{sub C} and the second harmonic 2{omega}{sub C} in directions nearly perpendicular to the confining magnetic field B (i.e., k {approx} k {perpendicular}) serve to map out the electron temperature profiles T{sub e}(r,t). For optically thick plasma at thermodynamic equilibrium T{sub r} = T{sub e}. However, there is increasing experimental evidence for the presence of non-equilibrium electron distributions (such as a drifting Maxwellian with appreciable values of the streaming parameter {omicron} = v{sub d}/v{sub t}, a bi- Maxwellian, and anisotropic Maxwellian with T {perpendicular} {ne} T {parallel}, etc.,) in tokamak plasmas, especially in the presence of radio-frequency heating. Here, we examine (both non-relativistically and relativistically) the dependence of T{sub r} on {omicron}, T{perpendicular}/T{parallel}, T{sub h}/T{sub b}, n{sub h}/n{sub b}etc., where n{sub b}, n{sub h}, T{sub b}, T{sub h} are the densities and temperatures, respectively, of the bulk and the hot components of the bi-Maxwellian plasma. Our bi-Maxwellian results predict that the ratio T{sub r}/T{sub e} is a very sensitive function of the ratios n{sub h}/n{sub b} and T{sub h}/T{sub b}. Further, these relativistic and non-relativistic results satisfy the well-known limit c {yields} {infinity} correspondence principle'', showing that the intensity of the emission and absorption line is independent of the line broadening mechanism. 44 refs., 2 figs.

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

    SciTech Connect

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

    2014-02-15

    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.

  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. Temperature profile determination in an absorbing plasma.

    NASA Technical Reports Server (NTRS)

    Usher, J. L.; Campbell, H. D.

    1972-01-01

    A new method has been developed to determine the temperature profile of an optically-non-thin plasma. The technique is essentially an extension of the brightness-emissivity method to the case of a cylindrically-symmetric plasma.

  16. Low Temperature Atmospheric Pressure Plasma Sterilization Shower

    NASA Astrophysics Data System (ADS)

    Gandhiraman, R. P.; Beeler, D.; Meyyappan, M.; Khare, B. N.

    2012-10-01

    Low-temperature atmospheric pressure plasma sterilization shower to address both forward and backward biological contamination issues is presented. The molecular effects of plasma exposure required to sterilize microorganisms is also analysed.

  17. Electron temperature probe onboard Japan's Mars orbiter

    NASA Astrophysics Data System (ADS)

    Oyama, K.; Abe, T.; Schlegel, K.; Nagy, A.; Kim, J.; Marubashi, K.

    1999-12-01

    Japan' s first Mars spacecraft PLANET-B was successfully launched on 4th of July, 1998 and was named "NOZOMI" after the launch. One of the scientific instruments is a unique electron temperature probe which was developed in Japan and has been used for more than 20 years on sounding rockets as well as on scientific satellites (Oyama, 1991). The electron temperature probe dubbed PET (Probe for Electron Temperature measurements) consists of two planar electrodes, 150 mm in diameter, placed at the edges of the two solar cell panels of the "NOZOMI" spacecraft. Electron temperatures can be measured in plasmas with densities exceeding 1000 cm-1 with sufficient accuracy. The maximum sampling rate of 8 data points per satellite spin for each probe allows high resolution measurements (i.e., an angular resolution around the spin axis of 23 degrees). Additionally, the probe can measure the anisotropy of the electron temperature, if it exists. It is also possible to infer the existence of nonthermal electrons.

  18. Electron density and electron temperature measurement in a bi-Maxwellian electron distribution using a derivative method of Langmuir probes

    SciTech Connect

    Choi, Ikjin; Chung, ChinWook; Youn Moon, Se

    2013-08-15

    In plasma diagnostics with a single Langmuir probe, the electron temperature T{sub e} is usually obtained from the slope of the logarithm of the electron current or from the electron energy probability functions of current (I)-voltage (V) curve. Recently, Chen [F. F. Chen, Phys. Plasmas 8, 3029 (2001)] suggested a derivative analysis method to obtain T{sub e} by the ratio between the probe current and the derivative of the probe current at a plasma potential where the ion current becomes zero. Based on this method, electron temperatures and electron densities were measured and compared with those from the electron energy distribution function (EEDF) measurement in Maxwellian and bi-Maxwellian electron distribution conditions. In a bi-Maxwellian electron distribution, we found the electron temperature T{sub e} obtained from the method is always lower than the effective temperatures T{sub eff} derived from EEDFs. The theoretical analysis for this is presented.

  19. Measurements of laser-induced plasma temperature field in deep penetration laser welding

    NASA Astrophysics Data System (ADS)

    Chen, Genyu; Zhang, Mingjun; Zhao, Zhi; Zhang, Yi; Li, Shichun

    2013-02-01

    Laser-induced plasma in deep penetration laser welding is located inside or outside the keyhole, namely, keyhole plasma or plasma plume, respectively. The emergence of laser-induced plasma in laser welding reveals important information of the welding technological process. Generally, electron temperature and electron density are two important characteristic parameters of plasma. In this paper, spectroscopic measurements of electron temperature and electron density of the keyhole plasma and plasma plume in deep penetration laser welding conditions were carried out. To receive spectra from several points separately and simultaneously, an Optical Multi-channel Analyser (OMA) was developed. On the assumption that the plasma was in local thermal equilibrium, the temperature was calculated with the spectral relative intensity method. The spectra collected were processed with Abel inversion method to obtain the temperature fields of keyhole plasma and plasma plume.

  20. Collector and source sheaths of a finite ion temperature plasma

    SciTech Connect

    Schwager, L.A.; Birdsall, C.K. )

    1990-05-01

    The region between a Maxwellian plasma source and an absorbing surface is described theoretically with a static, kinetic plasma--sheath model and modeled numerically with a dynamic, electrostatic particle simulation. In the kinetic theory, Poisson's equation and Vlasov equations govern the non-Maxwellian velocity distribution of the ions and electrons. The results in this paper for collector potential and plasma transport agree with the bounded model of Emmert {ital et} {ital al}. (Phys. Fluids {bold 23}, 803 (1980)). However, this approach differs from those using traditional Bohm sheath analysis by {plus minus}0.25 (in units of electron temperature) for potential drop through the collector sheath of a hydrogen plasma. In both the theory and simulation, the plasma source injects equal fluxes of ions and electrons with half-Maxwellian velocities and various mass and temperature ratios and is assumed to have a zero electric field. The potential change within a spatially distributed, full Maxwellian source region is represented with the source sheath potential drop that depends primarily on temperature ratio. This source sheath evolves over a few Debye lengths from the source to neutralize the injected plasma. The plasma flows to an electrically floating collector where the more familiar electron-repelling collector sheath appears. The collector potential {psi}{sub {ital C}} and source sheath potential drop {psi}{sub {ital P}} (in units of electron temperature) are evaluated as a function of mass and temperature ratio. The velocity moments of density, drift velocity, temperature, kinetic energy flux, and heat flux are also derived as a function of {psi}{sub {ital C}} and {psi}{sub {ital P}}. Comparisons with electrostatic particle simulations are shown for the ion/electron mass ratios of 40 and 100 and temperature ratios of 0.1, 1, and 10.

  1. Estimation of Electron Temperature on Glass Spherical Tokamak (GLAST)

    NASA Astrophysics Data System (ADS)

    Hussain, S.; Sadiq, M.; Shah, S. I. W.; GLAST Team

    2015-03-01

    Glass Spherical Tokamak (GLAST) is a small spherical tokamak indigenously developed in Pakistan with an insulating vacuum vessel. A commercially available 2.45 GHz magnetron is used as pre-ionization source for plasma current startup. Different diagnostic systems like Rogowski coils, magnetic probes, flux loops, Langmuir probe, fast imaging and emission spectroscopy are installed on the device. The plasma temperature inside of GLAST, at the time of maxima of plasma current, is estimated by taking into account the Spitzer resistivity calculations with some experimentally determined plasma parameters. The plasma resistance is calculated by using Ohm's law with plasma current and loop voltage as experimentally determined inputs. The plasma resistivity is then determined by using length and area of the plasma column. Finally, the average plasma electron temperature is predicted to be 12.65eV for taking neon (Ne) as a working gas.

  2. Thermally excited modes in a pure electron plasma.

    PubMed

    Anderegg, F; Shiga, N; Danielson, J R; Dubin, D H E; Driscoll, C F; Gould, R W

    2003-03-21

    Thermally excited plasma modes are observed in near-thermal-equilibrium pure electron plasmas over a temperature range of 0.05plasma-antenna coupling calibration uniquely determine the temperature. This calibration is obtained from the spectra themselves when absorption of the receiver-generated noise is significant, or from kinetic theory. This nondestructive temperature diagnostic agrees well with standard diagnostics and may be useful for expensive species such as antimatter. PMID:12688935

  3. Electron Temperature Gradient Mode Transport

    SciTech Connect

    Horton, W.; Kim, J.-H.; Hoang, G. T.; Park, H.; Kaye, S. M.; LeBlanc, B. P.

    2008-05-14

    Anomalous electron thermal losses plays a central role in the history of the controlled fusion program being the first and most persistent form of anomalous transport across all toroidal magnetic confinement devices. In the past decade the fusion program has made analysis and simulations of electron transport a high priority with the result of a clearer understanding of the phenomenon, yet still incomplete. Electron thermal transport driven by the electron temperature gradient is examined in detail from theory, simulation and power balance studies in tokamaks with strong auxiliary heating.

  4. Electron heat transport down steep temperature gradients

    SciTech Connect

    Matte, J.P.; Virmont, J.

    1982-12-27

    Electron heat transport is studied by numerically solving the Fokker-Planck equation, with a spherical harmonic representation of the distribution function. The first two terms (f/sub 0/, f/sub 1/) suffice, even in steep temperature gradients. Deviations from the Spitzer-Haerm law appear for lambda/L/sub T/ ((mean free path)/(temperature gradient length))> or approx. =0.01, as a result of non-Maxwellian f/sub 0/. For lambda/L/sub T/> or approx. =1, the heat flux is (1/3) of the free-streaming value. In intermediate cases, a harmonic law describes well the hottest part of the plasma.

  5. Plasma lenses for focusing relativistic electron beams

    SciTech Connect

    Govil, R.; Wheeler, S.; Leemans, W.

    1997-04-01

    The next generation of colliders require tightly focused beams with high luminosity. To focus charged particle beams for such applications, a plasma focusing scheme has been proposed. Plasma lenses can be overdense (plasma density, n{sub p} much greater than electron beam density, n{sub b}) or underdense (n{sub p} less than 2 n{sub b}). In overdense lenses the space-charge force of the electron beam is canceled by the plasma and the remaining magnetic force causes the electron beam to self-pinch. The focusing gradient is nonlinear, resulting in spherical aberrations. In underdense lenses, the self-forces of the electron beam cancel, allowing the plasma ions to focus the beam. Although for a given beam density, a uniform underdense lens produces smaller focusing gradients than an overdense lens, it produces better beam quality since the focusing is done by plasma ions. The underdense lens can be improved by tapering the density of the plasma for optimal focusing. The underdense lens performance can be enhanced further by producing adiabatic plasma lenses to avoid the Oide limit on spot size due to synchrotron radiation by the electron beam. The plasma lens experiment at the Beam Test Facility (BTF) is designed to study the properties of plasma lenses in both overdense and underdense regimes. In particular, important issues such as electron beam matching, time response of the lens, lens aberrations and shot-to-shot reproducibility are being investigated.

  6. Transition of electron kinetics in weakly magnetized inductively coupled plasmas

    SciTech Connect

    Kim, Jin-Yong; Lee, Hyo-Chang; Kim, Young-Do; Chung, Chin-Wook; Kim, Young-Cheol

    2013-10-15

    Transition of the electron kinetics from nonlocal to local regime was studied in weakly magnetized solenoidal inductively coupled plasma from the measurement of the electron energy probability function (EEPF). Without DC magnetic field, the discharge property was governed by nonlocal electron kinetics at low gas pressure. The electron temperatures were almost same in radial position, and the EEPFs in total electron energy scale were radially coincided. However, when the DC magnetic field was applied, radial non-coincidence of the EEPFs in total electron energy scale was observed. The electrons were cooled at the discharge center where the electron heating is absent, while the electron temperature was rarely changed at the discharge boundary with the magnetic field. These changes show the transition from nonlocal to local electron kinetics and the transition is occurred when the electron gyration diameter was smaller than the skin depth. The nonlocal to local transition point almost coincided with the calculation results by using nonlocal parameter and collision parameter.

  7. Multi electron species and shielding potentials in plasmas

    SciTech Connect

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

    2012-11-15

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

  8. Plasma-wall interaction in an electrostatic sheath of plasma containing a monoenergetic electron beam

    NASA Astrophysics Data System (ADS)

    Ou, Jing; Zhao, Xiaoyun; Gan, Chunyun

    2016-04-01

    The plasma-wall interaction in the presence of a monoenergetic electron beam has been studied by taking into account the self-consistency among plasma transport in a collisionless electrostatic sheath, deposited energy flux at the wall and material thermal response for carbon and tungsten as wall materials. The variations of the potential drop across the sheath, ion velocity at the sheath edge, and surface temperature of material as a function of electron beam flux are explored in the presence of the electron emission. It is found that when electron beam does not dominate the sheath, potential drop across the sheath depends strongly on the material properties due to the impact of electron emission while the surface temperature of material shows monotonic variation. In the case of carbon wall, the electron beam may dominate the sheath at a certain electron beam concentration or energy. Under this circumstance, both the potential drop across the sheath and surface temperature of material demonstrate the sharp increasing transition. The development of local hot spot on the plasma facing material is caused by the enhanced ion energy flux instead of the electron beam energy flux. If the electron emission is not taken into account, as a smaller electron beam flux, both the potential drop across the sheath and surface temperature of material display the significant change and then it may be easier to develop for the local hot spot on the plasma facing material.

  9. Nonlinear electron oscillations in a warm plasma

    SciTech Connect

    Sarkar, Anwesa; Maity, Chandan; Chakrabarti, Nikhil

    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.

  10. Ion temperature evolution in an ultracold neutral plasma

    SciTech Connect

    McQuillen, P. Strickler, T.; Langin, T.; Killian, T. C.

    2015-03-15

    We study the long-time evolution of the ion temperature in an expanding ultracold neutral plasma using spatially resolved, laser-induced-fluorescence spectroscopy. Adiabatic cooling reduces the ion temperature by an order of magnitude during the plasma expansion, to temperatures as low as 0.2 K. Cooling is limited by heat exchange between ions and the much hotter electrons. We also present evidence for an additional heating mechanism and discuss possible sources. Data are described by a model of the plasma evolution, including the effects of ion-electron heat exchange. We show that for appropriate initial conditions, the degree of Coulomb coupling of ions in the plasma increases during expansion.

  11. Atomic processes in high temperature plasmas

    SciTech Connect

    Hahn, Y.

    1991-07-01

    This is the final report on the project Atomic Processes in High Temperature Plasmas', which has been completed in June 30, 1991. The original contract started in 1978. The dielectronic recombination (DR) rate coefficients were calculated for ions with the number of electrons N = 1, 2, 3, 4, 5, 10, 11, and 12. The result was then used to construct a new and improved rate formula. Other important resonant processes, which are closely related to DR, were also studied to interpret experiments and to test the DR theory. The plasma field and the density effects on the rate coefficients was found to be important, and a consistent correction procedure is being developed. The available data on the DR rates and their accuracy do not yet fully meet the requirement for plasma modeling; there are serious gaps in the available data, and the currently adopted theoretical procedure needs improvements. Critical assessment of the current status of the DR problem is presented, and possible future work needed is summarized.

  12. Electron density and plasma dynamics of a colliding plasma experiment

    NASA Astrophysics Data System (ADS)

    Wiechula, J.; Schönlein, A.; Iberler, M.; Hock, C.; Manegold, T.; Bohlender, B.; Jacoby, J.

    2016-07-01

    We present experimental results of two head-on colliding plasma sheaths accelerated by pulsed-power-driven coaxial plasma accelerators. The measurements have been performed in a small vacuum chamber with a neutral-gas prefill of ArH2 at gas pressures between 17 Pa and 400 Pa and load voltages between 4 kV and 9 kV. As the plasma sheaths collide, the electron density is significantly increased. The electron density reaches maximum values of ≈8 ṡ 1015 cm-3 for a single accelerated plasma and a maximum value of ≈2.6 ṡ 1016 cm-3 for the plasma collision. Overall a raise of the plasma density by a factor of 1.3 to 3.8 has been achieved. A scaling behavior has been derived from the values of the electron density which shows a disproportionately high increase of the electron density of the collisional case for higher applied voltages in comparison to a single accelerated plasma. Sequences of the plasma collision have been taken, using a fast framing camera to study the plasma dynamics. These sequences indicate a maximum collision velocity of 34 km/s.

  13. Effect of fast drifting electrons on electron temperature measurement with a triple Langmuir probe

    SciTech Connect

    Biswas, Subir Chowdhury, Satyajit; Pal, Rabindranath

    2015-08-14

    Triple Langmuir Probe (TLP) is a widely used diagnostics for instantaneous measurement of electron temperature and density in low temperature laboratory plasmas as well as in edge region of fusion plasma devices. Presence of a moderately energetic flowing electron component, constituting only a small fraction of the bulk electrons, is also a generally observed scenario in plasma devices, where plasmas are produced by electron impact ionization of neutrals. A theoretical analysis of its effect on interpretation of the TLP data for bulk electron temperature measurement is presented here assuming electron velocity distribution is not deviating substantially from a Maxwellian. The study predicts conventional expression from standard TLP theory to give overestimated value of bulk electron temperature. Correction factor is significant and largely depends on population density, temperature, and energy of the fast component. Experimental verification of theoretical results is obtained in the magnetized plasma linear experimental device of Saha Institute of Nuclear Physics where plasma is produced by an electron cyclotron resonance method and known to have a fast flowing electron component.

  14. Implementation of a new atomic basis for the He I equilibrium line ratio technique for electron temperature and density diagnostic in the SOL for H-mode plasmas in DIII-D

    SciTech Connect

    Burgos, JMM; Schmitz, O.; Unterberg, Ezekial A; Loch, S. D.; Ballance, C. P.

    2011-01-01

    Evaluating the ratio of selected helium lines allows for measurement of electron densities and temperatures. This technique is applied for L-mode plasmas at TEXTOR (O. Schmitz et al., Plasma Phys. Control. Fusion 50 (2008) 115004). We report our first efforts to extend it to H-mode plasma diagnostics in DIII-D. This technique depends on the accuracy of the atomic data used in the collisional radiative model (CRM). We present predictions for the electron temperatures and densities by using recently calculated R-Matrix With Pseudostates (RMPS) and Convergent Close-Coupling (CCC) electron-impact excitation and ionization data. We include contributions from higher Rydberg states by means of the projection matrix. These effects become significant for high electron density conditions, which are typical in H-mode. We apply a non-equilibrium model for the time propagation of the ionization balance to predict line emission profiles from experimental H-mode data from DIII-D. (C) 2010 Elsevier B.V. All rights reserved.

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

    SciTech Connect

    Queller, T.; Gleizer, J. Z.; Krasik, Ya. E.

    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.

  16. Correlation of growth temperature with stress, defect states and electronic structure in an epitaxial GaN film grown on c-sapphire via plasma MBE.

    PubMed

    Krishna, Shibin; Aggarwal, Neha; Mishra, Monu; Maurya, K K; Singh, Sandeep; Dilawar, Nita; Nagarajan, Subramaniyam; Gupta, Govind

    2016-03-21

    The relationship of the growth temperature with stress, defect states, and electronic structure of molecular beam epitaxy grown GaN films on c-plane (0001) sapphire substrates is demonstrated. A minimum compressively stressed GaN film is grown by tuning the growth temperature. The correlation of dislocations/defects with the stress relaxation is scrutinized by high-resolution X-ray diffraction and photoluminescence measurements which show a high crystalline quality with significant reduction in the threading dislocation density and defect related bands. A substantial reduction in yellow band related defect states is correlated with the stress relaxation in the grown film. Temperature dependent Raman analysis shows the thermal stability of the stress relaxed GaN film which further reveals a downshift in the E2 (high) phonon frequency owing to the thermal expansion of the lattice at elevated temperatures. Electronic structure analysis reveals that the Fermi level of the films is pinned at the respective defect states; however, for the stress relaxed film it is located at the charge neutrality level possessing the lowest electron affinity. The analysis demonstrates that the generated stress not only affects the defect states, but also the crystal quality, surface morphology and electronic structure/properties. PMID:26916430

  17. Laser Thomson Scattering Diagnostics in the Low-Temperature Plasmas

    NASA Astrophysics Data System (ADS)

    Woo, Hyun-Jong; Chung, Kyu-Sun

    2008-10-01

    Laser Thomson Scattering (LTS) is the non-invasive method for measuring the electron temperature and its density, which can be used for the calibrations of electric probes within collisional and magnetized plasmas. For LTS diagnostics in the low-temperature plasmas, one need to special optics for detection of the scattered light with restricting the Rayleigh and Stray lights. For this, one uses the Triple Grating Spectrometer (TGS), which is composed of Rayleigh block (notch filter for Rayleigh light) and double grating filter (DGF). All focusing lenses are used with achromatic doublet configuration for reducing the non-linear optical effects such as spherical aberration, coma, etc. The specifications of the grating and achromatic doublet lens are 1800 gr/mm with the dimensions of 84 mm x 84 mm and 400 mm of focal length with the diameter of 100 mm, respectively. In this configurations, the linear dispersion is given as 1.006 nm/mm. Considering the dimension of Charged Coupled Device (CCD) with the linear dispersion, the LTS system can be measure the electron temperatures of less than 10 eV (in most laboratory plasmas). The initial measurement of LTS measurement and comparative study with single probe are done in Divertor Plasma Simulator (DiPS) with the following plasma parameters; plasma density of 10^11-10^13 cm-3, electron temperature of 1-4 eV, and the magnetic field of 0.2-1 kG, respectively.

  18. Thomson scattering in dense plasmas with density and temperature gradients

    NASA Astrophysics Data System (ADS)

    Fortmann, C.; Thiele, R.; Fäustlin, R. R.; Bornath, Th.; Holst, B.; Kraeft, W.-D.; Schwarz, V.; Toleikis, S.; Tschentscher, Th.; Redmer, R.

    2009-09-01

    Collective X-ray Thomson scattering has become a versatile tool for the diagnostics of dense plasmas. Assuming homogeneous density and temperature throughout the target sample, these parameters can be determined directly from the plasmon dispersion and the ratio of plasmon amplitudes via detailed balance. In inhomogeneous media, the scattering signal is an average of the density and temperature dependent scattering cross-section weighted with the density and temperature profiles. We analyse Thomson scattering spectra in the XUV range from near solid density hydrogen targets generated by free electron laser radiation. The influence of plasma inhomogeneities on the scattering spectrum is investigated by comparing density and temperature averaged scattering signals to calculations assuming homogeneous targets. We find discrepancies larger than 10% between the mean electron density and the effective density as well as between the mean temperature and the effective temperature.

  19. Ionization and Cooling of a Hot Plasma with Temperature Fluctuations

    NASA Astrophysics Data System (ADS)

    Kholtygin, A. F.; Bratsev, V. F.; Ochkur, V. I.

    2002-01-01

    Cooling functions for a stationary plasma are calculated in a wide temperature range from 5·103 K to 108 K, both for a plasma with the solar abundances of elements and for a plasma with an anomalous chemical composition typical of Wolf—Rayet stars. The HILYS project is described, with the aim of calculating cross sections and rates of excitation by electron collision of atoms and ions with a charge Z 26 and principal electron quantum numbers n 10, needed to calculate the ionization and thermal states of a plasma and the development of methods of calculating the plasma's spectrum in the visible, UV, and x-ray ranges. The results of a calculation of cross sections and effective collision strengths obtained within the framework of the project are given. The influence of temperature fluctuations (T/T 0.16) on the relative ion abundances and the total cooling function is studied. It is shown that the presence of such fluctuations considerably increases the temperature range in which the abundances of ions of a given degree of ionization are not negligible, while the cooling function can differ considerably from that calculated for a one-temperature plasma. The contribution of dielectronic recombination to the total cooling function is investigated, and it proves to be significant only for a plasma with high abundances of heavy elements. The x-ray spectrum of the bright supergiant Pup is analyzed.

  20. Quantitative diagnostics of reactive, multicomponent low-temperature plasmas

    NASA Astrophysics Data System (ADS)

    Schwarz-Selinger, Thomas

    2013-09-01

    The special emphasis in this work is put on the quantitative determination of the plasma composition of an inductively coupled low temperature plasma (ICP). Several standard plasma diagnostic techniques were applied. As a test case for a multi-component low-temperature plasma argon-hydrogen as well as argon-hydrogen-nitrogen mixed plasmas were investigated. For steady-state plasma operation the ion density and electron temperature were determined with a single tip Langmuir probe. A multi-grid miniature retarding-field analyzer was used to measure the mass integrated ion flux. An energy-dispersive mass spectrometer - a so-called plasma monitor (PM) - was applied to sample ions from the plasma to derive the ion composition. The degree of dissociation of hydrogen and the gas temperature were derived from optical emission spectroscopy. The gas temperature was estimated by the rotational distribution of the Q-branch lines of the hydrogen Fulcher- α diagonal band for the argon-hydrogen mixed plasmas and from the second positive system of N2 in argon-hydrogen-nitrogen mixed plasmas. The degree of dissociation of hydrogen was measured by actinometry. The influence of the substrate material of the counter electrode (stainless steel, copper, tungsten, Macor, and aluminium) on the atomic hydrogen concentration was investigated by OES. In addition, ionization-threshold mass spectrometry (ITMS) was used to determine the densities of atomic nitrogen (N) and atomic hydrogen (H and D). Pulsed plasma operation was applied to directly measure the loss rate of H, D and N in the afterglow from the temporal decay of the ITMS signal. From these data the wall loss probability of atomic hydrogen was determined. Furthermore, a zero-dimensional rate equation model was devised to explain the ion composition in these mixed plasmas with different admixture ratios. In addition to the experimental data on electron density, gas temperature, total pressure, atomic hydrogen density, and Ar, H2

  1. dc-plasma-sprayed electronic-tube device

    DOEpatents

    Meek, T.T.

    1982-01-29

    An electronic tube and associated circuitry which is produced by dc plasma arc spraying techniques is described. The process is carried out in a single step automated process whereby both active and passive devices are produced at very low cost. The circuitry is extremely reliable and is capable of functioning in both high radiation and high temperature environments. The size of the electronic tubes produced are more than an order of magnitude smaller than conventional electronic tubes.

  2. Ion Temperature Control of the Io Plasma Torus

    NASA Technical Reports Server (NTRS)

    Delamere, P. A.; Schneider, N. M.; Steffl, A. J.; Robbins, S. J.

    2005-01-01

    We report on observational and theoretical studies of ion temperature in the Io plasma torus. Ion temperature is a critical factor for two reasons. First, ions are a major supplier of energy to the torus electrons which power the intense EUV emissions. Second, ion temperature determines the vertical extent of plasma along field lines. Higher temperatures spread plasma out, lowers the density and slows reaction rates. The combined effects can play a controlling role in torus energetics and chemistry. An unexpected tool for the study of ion temperature is the longitudinal structure in the plasma torus which often manifests itself as periodic brightness variations. Opposite sides of the torus (especially magnetic longitudes 20 and 200 degrees) have been observed on numerous occasions to have dramatically different brightness, density, composition, ionization state, electron temperature and ion temperature. These asymmetries must ultimately be driven by different energy flows on the opposite sides, presenting an opportunity to observe key torus processes operating under different conditions. The most comprehensive dataset for the study of longitudinal variations was obtained by the Cassini UVIS instrument during its Jupiter flyby. Steffl (Ph.D. thesis, 2005) identified longitudinal variations in all the quantities listed above wit the exception of ion temperature. We extend his work by undertaking the first search for such variation in the UVIS dataset. We also report on a 'square centimeter' model of the torus which extend the traditional 'cubic centimeter' models by including the controlling effects of ion temperature more completely.

  3. Production of a large diameter hot-electron plasma by electron cyclotron resonance heating

    SciTech Connect

    Kawai, Y.; Sakamoto, K.

    1982-05-01

    A large diameter hot-electron plasma is produced by electron cyclotron resonance heating, using a slotted Lisitano coil as a launcher. It is found from detailed measurements of the plasma parameters that n/sub e/< or approx. =3 x 10/sup 11/ cm/sup -3/ and T/sub e/< or approx. =40 eV, with a diameter roughly-equal14 cm. High-energy tails with temperatures of more than 100 eV are observed.

  4. Production of a large diameter hot-electron plasma by electron cyclotron resonance heating

    NASA Astrophysics Data System (ADS)

    Kawai, Y.; Sakamoto, K.

    1982-05-01

    A large diameter hot-electron plasma is produced by electron cyclotron resonance heating, using a slotted Lisitano coil as a launcher. It is found from detailed measurements of the plasma parameters that ne≲3×1011 cm-3 and Te≲40 eV, with a diameter ≊14 cm. High-energy tails with temperatures of more than 100 eV are observed.

  5. Collector and source sheaths of a finite ion temperature plasma

    SciTech Connect

    Schwager, L.A.; Birdsall, C.K.

    1988-04-13

    The region between a Maxwellian plasma source and an absorbing surface is modeled with an electrostatic particle simulation and with a kinetic plasma-sheath model. In the kinetic model, Poisson's equation and Vlasov equations govern the velocity distribution of the ions and electrons. Our numerical and theoretical results for collector potential and plasma transport agree with the bounded model of Emmert et al., but differ somewhat from those using traditional Bohm sheath analysis. The plasma source injects equal fluxes of half-Maxwellian ions and electrons with specified mass and temperature ratios and is assumed to have a zero electric field. Representing the potential change within a distributed full-Maxwellian source region, the source potential drop depends primarily on temperature ratio and evolves a few Debye lengths from the source to neutralize the injected plasma. The plasma flows to an electrically floating collector where the more familiar electron-repelling collector sheath appears. Profiles of potential, density, drift velocity, temperature, kinetic energy flux, and heat flux are shown from simulation; all compare very well with theory. 24 refs., 7 figs., 1 tab.

  6. Industrial Applications of Low Temperature Plasmas

    SciTech Connect

    Bardsley, J N

    2001-03-15

    The use of low temperature plasmas in industry is illustrated by the discussion of four applications, to lighting, displays, semiconductor manufacturing and pollution control. The type of plasma required for each application is described and typical materials are identified. The need to understand radical formation, ionization and metastable excitation within the discharge and the importance of surface reactions are stressed.

  7. Plasma production for electron acceleration by resonant plasma wave

    NASA Astrophysics Data System (ADS)

    Anania, M. P.; Biagioni, A.; Chiadroni, E.; Cianchi, A.; Croia, M.; Curcio, A.; Di Giovenale, D.; Di Pirro, G. P.; Filippi, F.; Ghigo, A.; Lollo, V.; Pella, S.; Pompili, R.; Romeo, S.; Ferrario, M.

    2016-09-01

    Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (10-100 GV/m), enabling acceleration of electrons to GeV energy in few centimeter. However, the quality of the electron bunches accelerated with this technique is still not comparable with that of conventional accelerators (large energy spread, low repetition rate, and large emittance); radiofrequency-based accelerators, in fact, are limited in accelerating field (10-100 MV/m) requiring therefore hundred of meters of distances to reach the GeV energies, but can provide very bright electron bunches. To combine high brightness electron bunches from conventional accelerators and high accelerating fields reachable with plasmas could be a good compromise allowing to further accelerate high brightness electron bunches coming from LINAC while preserving electron beam quality. Following the idea of plasma wave resonant excitation driven by a train of short bunches, we have started to study the requirements in terms of plasma for SPARC_LAB (Ferrario et al., 2013 [1]). In particular here we focus on hydrogen plasma discharge, and in particular on the theoretical and numerical estimates of the ionization process which are very useful to design the discharge circuit and to evaluate the current needed to be supplied to the gas in order to have full ionization. Eventually, the current supplied to the gas simulated will be compared to that measured experimentally.

  8. Approximate equations of state in two-temperature plasma mixtures

    SciTech Connect

    Ramshaw, John D.; Cook, Andrew W.

    2014-02-15

    Approximate thermodynamic state relations for multicomponent atomic and molecular gas mixtures are often constructed by artificially partitioning the mixture into its constituent materials and requiring the separated materials to be in temperature and pressure equilibrium. Iterative numerical algorithms have been employed to enforce this equilibration and compute the resulting approximate state relations in single-temperature mixtures. In partially ionized gas mixtures, there is both theoretical and empirical evidence that equilibrating the chemical potentials, number densities, or partial pressures of the free electrons is likely to produce more accurate results than equilibrating the total pressures. Moreover, in many situations of practical interest the free electrons and heavy particles have different temperatures. In this paper, we present a generalized algorithm for equilibrating the heavy-particle and electron temperatures and a third user-specified independent thermodynamic variable in a two-temperature plasma mixture. Test calculations based on the equilibration of total pressure vs. electron pressure are presented for three different mixtures.

  9. Effects of interhemisphere transport on plasma temperatures at low latitudes.

    NASA Technical Reports Server (NTRS)

    Bailey, G. J.; Moffett, R. J.; Hanson, W. B.; Sanatani, S.

    1973-01-01

    The thermal balance of the equatorial plasma between 300 and 800 km is examined. Steady state nighttime calculations are made for O+, H+, and electrons. The following features are included: collisional heat transfer between ions, electrons, and neutrals; ion and electron thermal conduction along the field lines; curvature of the field lines; nonlinear advection due to field-aligned ion and electron motions; and convective compression or expansion due to field-aligned and E x B motions. The ion velocities necessary to calculate the effects of convection are obtained from the work of Moffett and Hanson, who include a meridional wind across the magnetic equator in their calculations. It is shown that field-aligned interhemisphere plasma flows appreciably affect the plasma temperatures.

  10. Electron density measurements in highly electronegative plasmas

    NASA Astrophysics Data System (ADS)

    Rafalskyi, D.; Lafleur, T.; Aanesland, A.

    2016-08-01

    In this paper we present experimental measurements of the electron density in very electronegative ‘ion–ion’ Ar–SF6 plasmas where previous investigations using Langmuir probes have observed electronegativities of up to 5000. The electron density is measured using a short matched dipole probe technique that provides a tolerance better than  ±2 · 1013 m‑3. The results demonstrate that the electron density in the low pressure plasma source (which contains a magnetic filter) can be reduced to around 2.7 · 1013 m‑3 with a corresponding plasma electronegativity of about 4000; close to that from fluid simulation predictions. The highest electronegativity, and lowest electron density, is achieved with a pure SF6 plasma, while adding only 6% SF6 to Ar allows the electronegativity to be increased from 0 to a few hundred with a corresponding decrease in the electron density by more than a thousand. The impedance probe based on a short matched dipole appears to be a practical diagnostic that can be used for independent measurements of the electron density in very electronegative plasmas, and opens up the possibility to further investigate and optimize electronegative plasma sources.

  11. 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.

  12. Electron heating in capacitively coupled plasmas revisited

    NASA Astrophysics Data System (ADS)

    Lafleur, T.; Chabert, P.; Booth, J. P.

    2014-06-01

    We revisit the problem of electron heating in capacitively coupled plasmas (CCPs), and propose a method for quantifying the level of collisionless and collisional heating in plasma simulations. The proposed procedure, based on the electron mechanical energy conservation equation, is demonstrated with particle-in-cell simulations of a number of single and multi-frequency CCPs operated in regimes of research and industrial interest. In almost all cases tested, the total electron heating is comprised of collisional (ohmic) and pressure heating parts. This latter collisionless component is in qualitative agreement with the mechanism of electron heating predicted from the recent re-evaluation of theoretical models. Finally, in very electrically asymmetric plasmas produced in multi-frequency discharges, we observe an additional collisionless heating mechanism associated with electron inertia.

  13. Etching with electron beam generated plasmas

    SciTech Connect

    Leonhardt, D.; Walton, S.G.; Muratore, C.; Fernsler, R.F.; Meger, R.A.

    2004-11-01

    A modulated electron beam generated plasma has been used to dry etch standard photoresist materials and silicon. Oxygen-argon mixtures were used to etch organic resist material and sulfur hexafluoride mixed with argon or oxygen was used for the silicon etching. Etch rates and anisotropy were determined with respect to gas compositions, incident ion energy (from an applied rf bias) and plasma duty factor. For 1818 negative resist and i-line resists the removal rate increased nearly linearly with ion energy (up to 220 nm/min at 100 eV), with reasonable anisotropic pattern transfer above 50 eV. Little change in etch rate was seen as gas composition went from pure oxygen to 70% argon, implying the resist removal mechanism in this system required the additional energy supplied by the ions. With silicon substrates at room temperature, mixtures of argon and sulfur hexafluoride etched approximately seven times faster (1375 nm/min) than mixtures of oxygen and sulfur hexafluoride ({approx}200 nm/min) with 200 eV ions, the difference is attributed to the passivation of the silicon by involatile silicon oxyfluoride (SiO{sub x}F{sub y}) compounds. At low incident ion energies, the Ar-SF{sub 6} mixtures showed a strong chemical (lateral) etch component before an ion-assisted regime, which started at {approx}75 eV. Etch rates were independent of the 0.5%-50% duty factors studied in this work.

  14. Self-effect in expanding electron beam plasma

    SciTech Connect

    Garcia, M

    1999-05-07

    An analytical model of plasma flow from a metal plate hit by an intense, pulsed, electron beam aims to bridge the gap between radiation-hydrodynamics simulations and experiments, and to quantify the self-effect of the electron beam penetrating the flow. Does the flow disrupt the tight focus of the initial electron bunch, or later pulses in a train? This work aims to model the spatial distribution of plasma speed, density, degree of ionization, and magnetization to inquire. The initial solid density, several eV plasma expands to 1 cm and 10{sup {minus}4} relative density by 2 {micro}s, beyond which numerical simulations are imprecise. Yet, a Faraday cup detector at the ETA-II facility is at 25 cm from the target and observes the flow after 50 {micro}s. The model helps bridge this gap. The expansion of the target plasma into vacuum is so rapid that the ionized portion of the flow departs from local thermodynamic equilibrium. When the temperature (in eV) in a parcel of fluid drops below V{sub i} x [(2{gamma} - 2)/(5{gamma} + 17)], where V{sub i} is the ionization potential of the target metal (7.8 eV for tantalum), and {gamma} is the ratio of specific heats (5/3 for atoms), then the fractional ionization and electron temperature in that parcel remain fixed during subsequent expansion. The freezing temperature as defined here is V{sub i}/19. The balance between the self-pinching force and the space charge repulsion of an electron beam changes on penetrating a flow: (i) the target plasma cancels the space-charge field, (ii) internal eddy currents arise to counter the magnetization of relativistic electrons, and (iii) electron beam heating alters the flow magnetization by changing the plasma density gradient and the magnitude of the conductivity.

  15. Non-thermal plasma mills bacteria: Scanning electron microscopy observations

    NASA Astrophysics Data System (ADS)

    Lunov, O.; Churpita, O.; Zablotskii, V.; Deyneka, I. G.; Meshkovskii, I. K.; Jäger, A.; Syková, E.; Kubinová, Š.; Dejneka, A.

    2015-02-01

    Non-thermal plasmas hold great promise for a variety of biomedical applications. To ensure safe clinical application of plasma, a rigorous analysis of plasma-induced effects on cell functions is required. Yet mechanisms of bacteria deactivation by non-thermal plasma remain largely unknown. We therefore analyzed the influence of low-temperature atmospheric plasma on Gram-positive and Gram-negative bacteria. Using scanning electron microscopy, we demonstrate that both Gram-positive and Gram-negative bacteria strains in a minute were completely destroyed by helium plasma. In contrast, mesenchymal stem cells (MSCs) were not affected by the same treatment. Furthermore, histopathological analysis of hematoxylin and eosin-stained rat skin sections from plasma-treated animals did not reveal any abnormalities in comparison to control ones. We discuss possible physical mechanisms leading to the shred of bacteria under non-thermal plasma irradiation. Our findings disclose how helium plasma destroys bacteria and demonstrates the safe use of plasma treatment for MSCs and skin cells, highlighting the favorability of plasma applications for chronic wound therapy.

  16. Time-resolved aluminium laser-induced plasma temperature measurements

    NASA Astrophysics Data System (ADS)

    Surmick, D. M.; Parigger, C. G.

    2014-11-01

    We seek to characterize the temperature decay of laser-induced plasma near the surface of an aluminium target from laser-induced breakdown spectroscopy measurements of aluminium alloy sample. Laser-induced plasma are initiated by tightly focussing 1064 nm, nanosecond pulsed Nd:YAG laser radiation. Temperatures are inferred from aluminium monoxide spectra viewed at systematically varied time delays by comparing experimental spectra to theoretical calculations with a Nelder Mead algorithm. The temperatures are found to decay from 5173 ± 270 to 3862 ± 46 Kelvin from 10 to 100 μs time delays following optical breakdown. The temperature profile along the plasma height is also inferred from spatially resolved spectral measurements and the electron number density is inferred from Stark broadened Hβ spectra.

  17. Electron temperature and density relationships in coronal mass ejections

    NASA Technical Reports Server (NTRS)

    Hammond, C. M.; Phillips, J. L.; Balogh, A.

    1995-01-01

    We examine 10 coronal mass ejections from the in-ecliptic portion of the Ulysses mission. Five of these CMEs are magnetic clouds. In each case we observe an inverse relationship between electron temperature and density. For protons this relationship is less clear. Earlier work has shown a similar inverse relationship for electrons inside magnetic clouds and interpreted it to mean that the polytropic index governing the expansion of electrons is less than unity. This requires electrons to be heated as the CME expands. We offer an alternative view that the inverse relationship between electron temperature and density is caused by more rapid cooling of the denser plasma through collisions. More rapid cooling of denser plasma has been shown for 1 AU measurements in the solar wind. As evidence for this hypothesis we show that the denser plasma inside the CMEs tends to be more isotropic indicating a different history of collisions for the dense plasma. Thus, although the electron temperature inside CMEs consistently shows an inverse correlation with the density, this is not an indication of the polytropic index of the plasma but instead supports the idea of collisional modification of the electrons during their transit from the sun.

  18. 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

    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.

  19. Influence of electron evaporative cooling on ultracold plasma expansion

    SciTech Connect

    Wilson, Truman; Chen, Wei-Ting; Roberts, Jacob

    2013-07-15

    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. For typical UCP spatial extents, evaporative cooling has a significant influence on the UCP expansion rate at lower densities (less than 10{sup 8}/cm{sup 3}). 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.

  20. Effect of secondary electron emission on the plasma sheath

    SciTech Connect

    Langendorf, S. Walker, M.

    2015-03-15

    In this experiment, plasma sheath potential profiles are measured over boron nitride walls in argon plasma and the effect of secondary electron emission is observed. Results are compared to a kinetic model. Plasmas are generated with a number density of 3 × 10{sup 12} m{sup −3} at a pressure of 10{sup −4} Torr-Ar, with a 1%–16% fraction of energetic primary electrons. The sheath potential profile at the surface of each sample is measured with emissive probes. The electron number densities and temperatures are measured in the bulk plasma with a planar Langmuir probe. The plasma is non-Maxwellian, with isotropic and directed energetic electron populations from 50 to 200 eV and hot and cold Maxwellian populations from 3.6 to 6.4 eV and 0.3 to 1.3 eV, respectively. Plasma Debye lengths range from 4 to 7 mm and the ion-neutral mean free path is 0.8 m. Sheath thicknesses range from 20 to 50 mm, with the smaller thickness occurring near the critical secondary electron emission yield of the wall material. Measured floating potentials are within 16% of model predictions. Measured sheath potential profiles agree with model predictions within 5 V (∼1 T{sub e}), and in four out of six cases deviate less than the measurement uncertainty of 1 V.

  1. Effect of secondary electron emission on the plasma sheath

    NASA Astrophysics Data System (ADS)

    Langendorf, S.; Walker, M.

    2015-03-01

    In this experiment, plasma sheath potential profiles are measured over boron nitride walls in argon plasma and the effect of secondary electron emission is observed. Results are compared to a kinetic model. Plasmas are generated with a number density of 3 × 1012 m-3 at a pressure of 10-4 Torr-Ar, with a 1%-16% fraction of energetic primary electrons. The sheath potential profile at the surface of each sample is measured with emissive probes. The electron number densities and temperatures are measured in the bulk plasma with a planar Langmuir probe. The plasma is non-Maxwellian, with isotropic and directed energetic electron populations from 50 to 200 eV and hot and cold Maxwellian populations from 3.6 to 6.4 eV and 0.3 to 1.3 eV, respectively. Plasma Debye lengths range from 4 to 7 mm and the ion-neutral mean free path is 0.8 m. Sheath thicknesses range from 20 to 50 mm, with the smaller thickness occurring near the critical secondary electron emission yield of the wall material. Measured floating potentials are within 16% of model predictions. Measured sheath potential profiles agree with model predictions within 5 V (˜1 Te), and in four out of six cases deviate less than the measurement uncertainty of 1 V.

  2. Principle of radial transport in low temperature annular plasmas

    SciTech Connect

    Zhang, Yunchao Charles, Christine; Boswell, Rod

    2015-07-15

    Radial transport in low temperature annular plasmas is investigated theoretically in this paper. The electrons are assumed to be in quasi-equilibrium due to their high temperature and light inertial mass. The ions are not in equilibrium and their transport is analyzed in three different situations: a low electric field (LEF) model, an intermediate electric field (IEF) model, and a high electric field (HEF) model. The universal IEF model smoothly connects the LEF and HEF models at their respective electric field strength limits and gives more accurate results of the ion mobility coefficient and effective ion temperature over the entire electric field strength range. Annular modelling is applied to an argon plasma and numerical results of the density peak position, the annular boundary loss coefficient and the electron temperature are given as functions of the annular geometry ratio and Paschen number.

  3. Nonextensive statistical mechanics approach to electron trapping in degenerate plasmas

    NASA Astrophysics Data System (ADS)

    Mebrouk, Khireddine; Gougam, Leila Ait; Tribeche, Mouloud

    2016-06-01

    The electron trapping in a weakly nondegenerate plasma is reformulated and re-examined by incorporating the nonextensive entropy prescription. Using the q-deformed Fermi-Dirac distribution function including the quantum as well as the nonextensive statistical effects, we derive a new generalized electron density with a new contribution proportional to the electron temperature T, which may dominate the usual thermal correction (∼T2) at very low temperatures. To make the physics behind the effect of this new contribution more transparent, we analyze the modifications arising in the propagation of ion-acoustic solitary waves. Interestingly, we find that due to the nonextensive correction, our plasma model allows the possibility of existence of quantum ion-acoustic solitons with velocity higher than the Fermi ion-sound velocity. Moreover, as the nonextensive parameter q increases, the critical temperature Tc beyond which coexistence of compressive and rarefactive solitons sets in, is shifted towards higher values.

  4. Experimental study of hot electrons in LECR2M plasma

    SciTech Connect

    Zhao, H. Y.; Zhao, H. W.; Ma, X. W.; Wang, H.; Zhang, X. Z.; Sun, L. T.; Ma, B. H.; Li, X. X.; Sha, S.; Zhu, Y. H.; Lu, W.; Shang, Y.

    2008-02-15

    In order to investigate the hot electron component in electron cyclotron resonance (ECR) plasmas, the volume bremsstrahlung spectra in the x-ray photon energy range were measured with a high-purity germanium detector on Lanzhou ECR Ion Source No. 2 Modified (LECR2M). A collimation system similar to Bernhardi's was used to focus at the central part of the plasma. The ion source was operated under various source conditions with argon; sometimes oxygen was added to enhance high charge state ion beam intensities. The spectral temperature of hot electrons T{sub spe} was derived from the measured bremsstrahlung spectra. The evolution of the deduced temperature of hot electrons T{sub spe} with the ion source parameters, such as the rf frequency, power, and the magnetic confinement configuration, was investigated.

  5. Kinetic effects on streaming instabilities in electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Shan, S. Ali; Saleem, H.

    2009-02-01

    Streaming instabilities in electron-positron-ion plasmas are investigated using kinetic approach in several different limits. The effects of the variation of background temperatures of electrons Teo and positrons Tpo on the growth rates are also presented for the case of ion beam streaming into electron-positron plasmas and positrons beam streaming into electron-ion plasmas. It is noticed that the increase of number density of positrons gives a destabilizing trend to the electrostatic perturbations in the system.

  6. A new electron temperature diagnostic of critical surface based on the ion acoustic decay instability in hot, high density plasma relevant to laser fusion. Semiannual report, April 1--September 29, 1994

    SciTech Connect

    Mizuno, K.; DeGroot, J.S.; Drake, R.P.; Seka, W.; Craxton, R.S.; Estabrook, K.G.

    1994-12-31

    The authors made analysis of the IADI experiments previously made using OMEGA laser system. They obtained two important new results: the first direct observation of the epw excited by the Ion Acoustic Decay Instability, and the first study of the IADI in a plasma that approaches laser-fusion conditions, in the sense of having a density scale length of order 1 mm and an electron temperature, T{sub e}, in excess of 1 keV. Previous observations of the epw`s have been based on the second harmonic emission, from which little can be inferred because the emission is produced by unknown pairs of epw`s, integrated in a complicated way over wavenumber space and real space. In contrast, they have directly observed the epw by using the 90{degree}, collective Thomson scattering (CTS) of a UV laser (at the third harmonic of the pump) from the epw`s. Because the ratio of probe frequency to electron plasma frequency is only about three, the scattering is collective (i.e. k{sub epw}{lambda}{sub De} is small, where k{sub epw} is the epw wave number and {lambda}{sub De} is the Debye length),m even though the scattering angle is large. The electron temperature can then be deduced from the ion sound velocity, obtained from the measurement of the frequency at which growth is maximum at the scattering wavenumber.

  7. Influence of emitter temperature on the energy deposition in a low-pressure plasma

    NASA Astrophysics Data System (ADS)

    Levko, Dmitry; Raja, Laxminarayan L.

    2016-03-01

    The influence of emitter temperature on the energy deposition into low-pressure plasma is studied by the self-consistent one-dimensional Particle-in-Cell Monte Carlo Collisions model. Depending on the emitter temperature, different modes of discharge operation are obtained. The mode type depends on the plasma frequency and does not depend on the ratio between the densities of beam and plasma electrons. Namely, plasma is stable when the plasma frequency is small. For this plasma, the energy transfer from emitted electrons to plasma electrons is inefficient. The increase in the plasma frequency results first in the excitation of two-stream electron instability. However, since the thermal velocity of plasma electrons is smaller than the electrostatic wave velocity, the resonant wave-particle interaction is inefficient for the energy deposition into the plasma. Further increase in the plasma frequency leads to the distortion of beam of emitted electrons. Then, the electrostatic wave generated due to two-stream instability decays into multiple slower waves. Phase velocities of these waves are comparable with the thermal velocity of plasma electrons which makes possible the resonant wave-particle interaction. This results in the efficient energy deposition from emitted electrons into the plasma.

  8. Monte Carlo Collision method for low temperature plasma simulation

    NASA Astrophysics Data System (ADS)

    Taccogna, Francesco

    2015-01-01

    This work shows the basic foundation of the particle-based representation of low temperature plasma description. In particular, the Monte Carlo Collision (MCC) recipe has been described for the case of electron-atom and ion-atom collisions. The model has been applied to the problem of plasma plume expansion from an electric Hall-effect type thruster. The presence of low energy secondary electrons from electron-atom ionization on the electron energy distribution function (EEDF) have been identified in the first 3 mm from the exit plane where, due to the azimuthal heating the ionization continues to play an important role. In addition, low energy charge-exchange ions from ion-atom electron transfer collisions are evident in the ion energy distribution functions (IEDF) 1 m from the exit plane.

  9. High temperature UF6 and plasma research

    NASA Technical Reports Server (NTRS)

    Roman, W. C.

    1979-01-01

    Research currently under way on technology for uranium plasma core reactors is reviewed. A feeder system to provide a controlled and steady flow of UF6 at rates up to 5 g/sec and temperatures up to 500 K into rf plasma test chambers operating at pressures of up to 20 atm has been developed. Plasma emission and dye laser absorption measurements have been used to estimate the radial distribution of uranium atom number density within the plasma. X-ray absorption equipment and techniques have also been employed to measure the amount of uranium in the plasma, and dc plasma torch experiments have shown variations in plasma VUV emission with temperature. Analysis of residues deposited on various test-chamber components after plasma tests reveals traces of several uranium oxides, including UO2F2, and various exhaust duct configurations with flow augmentation are under investigation as means of preventing uranium deposition. Other areas of research include off- and on-line exhaust gas diagnostics, and a UF6/Ar injection, separation and recirculation system.

  10. Beltrami–Bernoulli equilibria in plasmas with degenerate electrons

    SciTech Connect

    Berezhiani, V. I.; Shatashvili, N. L.; Mahajan, S. M.

    2015-02-15

    A new class of Double Beltrami–Bernoulli equilibria, sustained by electron degeneracy pressure, is 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.

  11. Spatial Distributions of Electron, CF, and CF2 Radical Densities and Gas Temperature in DC-Superposed Dual-Frequency Capacitively Coupled Plasma Etch Reactor Employing Cyclic-C4F8/N2/Ar Gas

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tsuyoshi; Kimura, Tetsuya; Koshimizu, Chishio; Takeda, Keigo; Kondo, Hiroki; Ishikawa, Kenji; Sekine, Makoto; Hori, Masaru

    2011-05-01

    On a plasma etch reactor for a wafer of 300 mm in diameter, the spatial distributions of the absolute densities of CF and CF2 radicals, electron density (ne), and the gas temperature (Tg) of N2 were measured employing the dual frequency of negative dc voltage superposed to a very high frequency (VHF) of 60 MHz capacitively coupled plasma (DS-2f-CCP) with the cyclic- (c-)C4F8/Ar/N2 gas mixture. The dc bias was superposed on the upper electrode with a frequency of 60 MHz. The distributions of electron and radical densities were uniform within a diameter of about 260 mm, and took a monotonic decay in regions outside a diameter of 260 mm on the reactor for 300 mm wafers in the reactor. It was found that only CF2 density at the radial position between 150 and 180 mm, corresponding to the position of the Si focus ring, dropped, while CF density took a uniform distribution over a diameter of 260 mm. Additionally, at this position, the rotational temperature of N2 gas increased to be 100 K larger than that at the center position. CF2 radical density was markedly affected by the modified surface loss probability of the material owing to coupling with surface temperature.

  12. A predictive model for the temperature relaxation rate in dense plasmas

    SciTech Connect

    Daligault, Jerome; Dimonte, Guy

    2008-01-01

    We present and validate a simple model for the electron-ion temperature relaxation rate in plasmas that applies over a wide range of plasma temperatures and densities, including weakly-coupled, non-degenerate as well as strongly-coupled, degenerate plasmas. Electron degeneracy and static correlation effects between electrons and ions are shown to play a cumulative role that, at low temperature, lead to relaxation rates a few times smaller than when these effects are neglected. We predict the evolution of the relaxation in dense hydrogen plasmas from the fully degenerate to the non-degenerate limit.

  13. Non-thermal plasma mills bacteria: Scanning electron microscopy observations

    SciTech Connect

    Lunov, O. Churpita, O.; Zablotskii, V.; Jäger, A.; Dejneka, A.; Deyneka, I. G.; Meshkovskii, I. K.; Syková, E.; Kubinová, Š.

    2015-02-02

    Non-thermal plasmas hold great promise for a variety of biomedical applications. To ensure safe clinical application of plasma, a rigorous analysis of plasma-induced effects on cell functions is required. Yet mechanisms of bacteria deactivation by non-thermal plasma remain largely unknown. We therefore analyzed the influence of low-temperature atmospheric plasma on Gram-positive and Gram-negative bacteria. Using scanning electron microscopy, we demonstrate that both Gram-positive and Gram-negative bacteria strains in a minute were completely destroyed by helium plasma. In contrast, mesenchymal stem cells (MSCs) were not affected by the same treatment. Furthermore, histopathological analysis of hematoxylin and eosin–stained rat skin sections from plasma–treated animals did not reveal any abnormalities in comparison to control ones. We discuss possible physical mechanisms leading to the shred of bacteria under non-thermal plasma irradiation. Our findings disclose how helium plasma destroys bacteria and demonstrates the safe use of plasma treatment for MSCs and skin cells, highlighting the favorability of plasma applications for chronic wound therapy.

  14. 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.

  15. 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.

  16. Characteristics of surface sterilization using electron cyclotron resonance plasma

    NASA Astrophysics Data System (ADS)

    Yonesu, Akira; Hara, Kazufumi; Nishikawa, Tatsuya; Hayashi, Nobuya

    2016-07-01

    The characteristics of surface sterilization using electron cyclotron resonance (ECR) plasma were investigated. High-energy electrons and oxygen radicals were observed in the ECR zone using electric probe and optical emission spectroscopic methods. A biological indicator (BI), Geobacillus stearothermophilus, containing 1 × 106 spores was sterilized in 120 s by exposure to oxygen discharges while maintaining a temperature of approximately 55 °C at the BI installation position. Oxygen radicals and high-energy electrons were found to be the sterilizing species in the ECR region. It was demonstrated that the ECR plasma could be produced in narrow tubes with an inner diameter of 5 mm. Moreover, sterilization tests confirmed that the spores present inside the narrow tube were successfully inactivated by ECR plasma irradiation.

  17. Electron vortex magnetic holes: A nonlinear coherent plasma structure

    NASA Astrophysics Data System (ADS)

    Haynes, Christopher T.; Burgess, David; Camporeale, Enrico; Sundberg, Torbjorn

    2015-01-01

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.

  18. Electron vortex magnetic holes: A nonlinear coherent plasma structure

    SciTech Connect

    Haynes, Christopher T. Burgess, David; Sundberg, Torbjorn; Camporeale, Enrico

    2015-01-15

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.

  19. Electron Bernstein waves in spherical torus plasmas

    SciTech Connect

    Saveliev, A. N.

    2006-11-30

    Propagation and absorption of the electron Bernstein waves (EBWs) in spherical tokamaks (STs) have been intensively discussed in recent years because the EBWs coupled with an externally launched electromagnetic beam seem to be the only opportunity for microwave plasma heating and current drive in the electron cyclotron (EC) frequency range in the STs. The whole problem of the electron Bernstein heating and current drive (EBWHCD) in spherical plasmas is naturally divided into three major parts: coupling of incident electromagnetic waves (EMWs) to the EBWs near the upper hybrid resonance (UHR) surface, propagation and absorption of the EBWs in the plasma interior and generation of noninductive current driven by the EBWs. The present paper is a brief survey of the most important theoretical and numerical results on the issue of EBWs.

  20. Controlled thermonuclear fusion, high temperature plasma physics

    NASA Astrophysics Data System (ADS)

    1985-05-01

    The primary source of nuclear energy comes from the fission process of heavy nuclei. To utilize the energy released by a thermonuclear fusion process, methods of controlling the fusion reaction were studied. This is controlled thermonuclear fusion technology. The fuel used in a thermonuclear fusion process are isotopes of hydrogen: deuterium and tritium. They can be extracted from the almost unlimited seawater. Nuclear fusion also produces very little radioactive waste. Thermonuclear fusion is a promising energy source with an almost unlimited supply; it is economical, safe, and relatively clean. Ways to raise plasma temperature to a very high level and to maintain it to allow fusion reactions to take place are studied. The physical laws of high temperature plasma was studied to reach this goal which resulted in the development of high temperature plasma physics.

  1. Plasma-Catalysis During Temperature Transient Testing

    SciTech Connect

    Hoard, John

    2001-08-05

    A combination of catalysts is used together with nonthermal plasma in simulated diesel exhaust, while the gas temperature is varied. The catalysts both store and convert pollutants. As a result, pollutant concentrations during temperature ramps are different than those at steady state conditions. The data are presented for plasma followed by BaY, alumina, and Pt catalysts in simulated exhaust. When temperature ramps from high to low, apparent NOx conversion is quite high. However, when temperature is ramped from low to high, lower apparent conversions are seen. In a typical test cycle, average NOx conversion between 100 and 400 C is 60%. Peak conversion during the down ramp is over 90%, and minimum conversion during the up ramp is 30%. The composition of the effluent gas also varies during the temperature cycle. Intermediates such as methyl nitrate and hydrogen cyanide are not present following the combination of catalysts.

  2. 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.; El Fiki, S. A.; Nouh, S. A.; El Disoki, T. M.

    2013-08-15

    In this article, the plasma is created in a Pyrex tube (L = 27 cm, φ= 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

  3. Relativistic thermal electron scale instabilities in sheared flow plasma

    NASA Astrophysics Data System (ADS)

    Miller, Evan D.; Rogers, Barrett N.

    2016-04-01

    > The linear dispersion relation obeyed by finite-temperature, non-magnetized, relativistic two-fluid plasmas is presented, in the special case of a discontinuous bulk velocity profile and parallel wave vectors. It is found that such flows become universally unstable at the collisionless electron skin-depth scale. Further analyses are performed in the limits of either free-streaming ions or ultra-hot plasmas. In these limits, the system is highly unstable in the parameter regimes associated with either the electron scale Kelvin-Helmholtz instability (ESKHI) or the relativistic electron scale sheared flow instability (RESI) recently highlighted by Gruzinov. Coupling between these modes provides further instability throughout the remaining parameter space, provided both shear flow and temperature are finite. An explicit parameter space bound on the highly unstable region is found.

  4. Relativistic thermal electron scale instabilities in sheared flow plasma

    NASA Astrophysics Data System (ADS)

    Miller, Evan D.; Rogers, Barrett N.

    2016-02-01

    > The linear dispersion relation obeyed by finite-temperature, non-magnetized, relativistic two-fluid plasmas is presented, in the special case of a discontinuous bulk velocity profile and parallel wave vectors. It is found that such flows become universally unstable at the collisionless electron skin-depth scale. Further analyses are performed in the limits of either free-streaming ions or ultra-hot plasmas. In these limits, the system is highly unstable in the parameter regimes associated with either the electron scale Kelvin-Helmholtz instability (ESKHI) or the relativistic electron scale sheared flow instability (RESI) recently highlighted by Gruzinov. Coupling between these modes provides further instability throughout the remaining parameter space, provided both shear flow and temperature are finite. An explicit parameter space bound on the highly unstable region is found.

  5. 100 eV electron temperatures in the Maryland centrifugal experiment observed using electron Bernstein emission

    SciTech Connect

    Reid, R. R.; Romero-Talamás, C. A.; Young, W. C.; Ellis, R. F.; Hassam, A. B.

    2014-06-15

    Thermal electron Bernstein emission has been observed at the second harmonic of the electron cyclotron frequency at the mid-plane of the Maryland Centrifugal eXperiment. The emission is received in the X-mode polarization and coupled to the Bernstein wave by the B-X mode conversion process. The average B-X coupling efficiency is approximately 20%. The observed emission indicates thermal electron temperatures an excess of 100 eV in the core of the rotating plasma. The measured electron temperature is consistent with recent ion temperature measurements and indicates that the total energy confinement time exceeds 500 μs.

  6. Plasma heating with crossing relativistic electron beams

    NASA Astrophysics Data System (ADS)

    Ratan, Naren; Sircombe, Nathan; Ceurvorst, Luke; Kasim, Muhammad; Sadler, James; Bingham, Robert; Trines, Raoul; Norreys, Peter

    2015-11-01

    Plasma heating by relativistic electron beams is a powerful tool with applications including the heating of inertial confinement fusion targets and the study of matter in extreme conditions. We discuss the use of two relativistic electron beams to efficiently heat the plasma ions where the beams cross by using beam-plasma instabilities and non-linear wave coupling between Langmuir and ion-acoustic waves. Energy from the electron beams is coupled to the plasma ions as the beams become unstable and drive Langmuir waves which couple non-linearly to ion-acoustic waves which are then damped . Results of linear growth rate calculations are presented for the system of two crossing electron beams demonstrating a broad spectrum of unstable modes. Relativistic Vlasov-Maxwell simulations in two space and two momentum dimensions have been performed which demonstrate the non-linear coupling of the electron beam energy into ion-acoustic waves and the energy cascade to the background ions. Time-frequency analysis is applied to analyze the non-linear coupling between Langmuir and ion-acoustic waves in wave phase space. Structural properties of the strong turbulence produced at late times are analyzed.

  7. Pure electron plasmas in asymmetric traps*

    NASA Astrophysics Data System (ADS)

    Chu, R.; Wurtele, J. S.; Notte, J.; Peurrung, A. J.; Fajans, J.

    1993-07-01

    Pure electron plasmas are routinely confined within cylindrically symmetric Penning traps. In this paper the static and dynamic properties of plasmas confined in traps with applied electric field asymmetries are investigated. Simple analytical theories are derived and used to predict the shapes of the stable noncircular plasma equilibria observed in experiments. Both analytical and experimental results agree with those of a vortex-in-cell simulation. For an l=1 diocotron mode in a cylindrically symmetric trap, the plasma rotates as a rigid column in a circular orbit. In contrast, plasmas in systems with electric field asymmetries are shown to have an analog to the l=1 mode in which the shape of the plasma changes as it rotates in a noncircular orbit. These bulk plasma features are studied with a Hamiltonian model. It is seen that, for a small plasma, the area enclosed by the orbit of the center of charge is an invariant when electric field perturbations are applied adiabatically. This invariant has been observed experimentally. The breaking of the invariant is also studied. The dynamic Hamiltonian model is also used to predict the shape and frequency of the large amplitude l=1 and l=2 diocotron modes in symmetric traps.

  8. Turbulent electron transport in edge pedestal by electron temperature gradient turbulence

    SciTech Connect

    Singh, R.; Jhang, Hogun; Diamond, P. H.

    2013-11-15

    We present a model for turbulent electron thermal transport at the edge pedestal in high (H)-mode plasmas based on electron temperature gradient (ETG) turbulence. A quasi-linear analysis of electrostatic toroidal ETG modes shows that both turbulent electron thermal diffusivity and hyper-resistivity exhibits the Ohkawa scaling in which the radial correlation length of turbulence becomes the order of electron skin depth. Combination of the Ohkawa scales and the plasma current dependence results in a novel confinement scaling inside the pedestal region. It is also shown that ETG turbulence induces a thermoelectric pinch, which may accelerate the density pedestal formation.

  9. Ion Temperature Anisotropies in Helicon Plasmas

    NASA Astrophysics Data System (ADS)

    Balkey, Matthew M.; Boiven, Robert; Keiter, Paul; Kline, John; Scime, Earl; Spangler, Robert

    1999-11-01

    Laser induced fluorescence measurements of the ion temperature in an argon helicon plasma indicate a substantial ion temperature anisotropy (perpendicular over parallel). The perpendicular ion temperature scales linearly with the applied magnetic field strength and also depends on the RF driving frequency and amplitude. We will present measurements of the ion temperature as a function of magnetic field, RF amplitude, and RF frequency. We will also present measurements of the electromagnetic fluctuation spectrum in the source. Preliminary measurements suggest that the RF driving wave may parametrically decay into waves that can couple to the ions, thus providing a path for RF energy directly into the ions.

  10. Numerical Simulation of the Self-Heating Effect Induced by Electron Beam Plasma in Atmosphere

    NASA Astrophysics Data System (ADS)

    Deng, Yongfeng; Tan, Chang; Han, Xianwei; Tan, Yonghua

    2012-02-01

    For exploiting advantages of electron beam air plasma in some unusual applications, a Monte Carlo (MC) model coupled with heat transfer model is established to simulate the characteristics of electron beam air plasma by considering the self-heating effect. Based on the model, the electron beam induced temperature field and the related plasma properties are investigated. The results indicate that a nonuniform temperature field is formed in the electron beam plasma region and the average temperature is of the order of 600 K. Moreover, much larger volume pear-shaped electron beam plasma is produced in hot state rather than in cold state. The beam ranges can, with beam energies of 75 keV and 80 keV, exceed 1.0 m and 1.2 m in air at pressure of 100 torr, respectively. Finally, a well verified formula is obtained for calculating the range of high energy electron beam in atmosphere.

  11. Electron density and temperature of gas-temperature-dependent cryoplasma jet

    SciTech Connect

    Noma, Yuri; Hyuk Choi, Jai; Muneoka, Hitoshi; Terashima, Kazuo

    2011-03-01

    A microsize cryoplasma jet was developed and analyzed at plasma gas temperatures ranging from room temperature down to 5 K. Experimental results obtained from optical emission spectroscopy and current-voltage measurements indicate that the average electron density and electron temperature of the cryoplasma jet depend on the gas temperature. In particular, the electron temperature in the cryoplasma starts to decrease rapidly near 60 K from about 13 eV at 60 K to 2 eV at 5 K, while the electron density increases from about 10{sup 9} to approximately 10{sup 12} cm{sup -3} from room temperature to 5 K. This phenomenon induces an increase in the Coulomb interaction between electrons, which can be explained by the virial equation of state.

  12. Three-temperature plasma shock solutions with gray radiation diffusion

    NASA Astrophysics Data System (ADS)

    Johnson, B. M.; Klein, R. I.

    2016-04-01

    The effects of radiation on the structure of shocks in a fully ionized plasma are investigated by solving the steady-state fluid equations for ions, electrons, and radiation. The electrons and ions are assumed to have the same bulk velocity but separate temperatures, and the radiation is modeled with the gray diffusion approximation. Both electron and ion conduction are included, as well as ion viscosity. When the material is optically thin, three-temperature behavior occurs. When the diffusive flux of radiation is important but radiation pressure is not, two-temperature behavior occurs, with the electrons strongly coupled to the radiation. Since the radiation heats the electrons on length scales that are much longer than the electron-ion Coulomb coupling length scale, these solutions resemble radiative shock solutions rather than plasma shock solutions that neglect radiation. When radiation pressure is important, all three components are strongly coupled. Results with constant values for the transport and coupling coefficients are compared to a full numerical simulation with a good match between the two, demonstrating that steady shock solutions constitute a straightforward and comprehensive verification test methodology for multi-physics numerical algorithms.

  13. Spectroscopic diagnostics of high temperature plasmas. [Annual report

    SciTech Connect

    Moos, W.

    1990-12-31

    A three-year research program for the development of novel XUV spectroscopic diagnostics for magnetically confined fusion plasmas is proposed. The new diagnostic system will use layered synthetic microstructures (LSM) coated, flat and curved surfaces as dispersive elements in spectrometers and narrow band XUV filter arrays. In the framework of the proposed program we will develop impurity monitors for poloidal and toroidal resolved measurements on PBX-M and Alcator C-Mod, imaging XUV spectrometers for electron density and temperature fluctuation measurements in the hot plasma core in TEXT or other similar tokamaks and plasma imaging devices in soft x-ray light for impurity behavior studies during RF heating on Phaedrus T and carbon pellet ablation in Alcator C-Mod. Recent results related to use of multilayer in XUV plasma spectroscopy are presented. We also discuss the latest results reviewed to q{sub o} and local poloidal field measurements using Zeeman polarimetry.

  14. Nonquasineutral electron vortices in nonuniform plasmas

    SciTech Connect

    Angus, J. R.; Richardson, A. S.; Swanekamp, S. B.; Schumer, J. W.; Ottinger, P. F.

    2014-11-15

    Electron vortices are observed in the numerical simulation of current carrying plasmas on fast time scales where the ion motion can be ignored. In plasmas with nonuniform density n, vortices drift in the B × ∇n direction with a speed that is on the order of the Hall speed. This provides a mechanism for magnetic field penetration into a plasma. Here, we consider strong vortices with rotation speeds V{sub ϕ} close to the speed of light c where the vortex size δ is on the order of the magnetic Debye length λ{sub B}=|B|/4πen and the vortex is thus nonquasineutral. Drifting vortices are typically studied using the electron magnetohydrodynamic model (EMHD), which ignores the displacement current and assumes quasineutrality. However, these assumptions are not strictly valid for drifting vortices when δ ≈ λ{sub B}. In this paper, 2D electron vortices in nonuniform plasmas are studied for the first time using a fully electromagnetic, collisionless fluid code. Relatively large amplitude oscillations with periods that correspond to high frequency extraordinary modes are observed in the average drift speed. The drift speed W is calculated by averaging the electron velocity field over the vorticity. Interestingly, the time-averaged W from these simulations matches very well with W from the much simpler EMHD simulations even for strong vortices with order unity charge density separation.

  15. 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.

  16. Characterization of electron kinetics regime with electron energy probability functions in inductively coupled hydrogen plasmas

    NASA Astrophysics Data System (ADS)

    Kim, June Young; Cho, Won-Hwi; Dang, Jeong-Jeung; Chung, Kyoung-Jae; Hwang, Y. S.

    2016-02-01

    Electron kinetics regime is characterized with the evolution of electron energy probability functions (EEPFs) in inductively coupled hydrogen plasmas. Measurements on EEPFs are carried out with a radio-frequency-compensated single Langmuir probe at the center of a planar-type hydrogen plasma driven by 13.56 MHz wave frequency. Measured EEPFs deviate considerably from the Maxwellian distribution only at relatively high pressures (15-40 mTorr), and the effective electron temperature steeply decreases as the gas pressure increases. Such evolution of the EEPF shapes with pressures is discussed in the consideration of the electron energy relaxation length and various characteristic frequencies. It is found that the EEPFs show locally depleted electron energy distribution where the electron-molecule vibrational collision frequency exceeds the electron-electron collision frequency at the local kinetics regime, while the measured EEPF is not dependent on the vibrational collision frequency at the non-local kinetics regime. Variation of the EEPF shape with distance from the heating region at the local kinetics regime is also well explained in the context of the energy relaxation length and electron-molecule collision frequencies. This study indicates that the control of electron energy distribution should be carried out in the consideration of electron kinetic regime depending on the energy relaxation length for various hydrogen plasma sources.

  17. 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

  18. Simultaneous measurement of core electron temperature and density fluctuations during electron cyclotron heating on DIII-D

    SciTech Connect

    White, A. E.; Schmitz, L.; Peebles, W. A.; Rhodes, T. L.; Carter, T. A.; McKee, G. R.; Shafer, M. W.; Staebler, G. M.; Burrell, K. H.; DeBoo, J. C.; Prater, R.

    2010-02-15

    New measurements show that long-wavelength (k{sub t}hetarho{sub s}<0.5) electron temperature fluctuations can play an important role in determining electron thermal transport in low-confinement mode (L-mode) tokamak plasmas. In neutral beam-heated L-mode tokamak plasmas, electron thermal transport and the amplitude of long-wavelength electron temperature fluctuations both increase in cases where local electron cyclotron heating (ECH) is used to modify the plasma profiles. In contrast, the amplitude of simultaneously measured long-wavelength density fluctuations does not significantly increase. Linear stability analysis indicates that the ratio of the trapped electron mode (TEM) to ion temperature gradient (ITG) mode growth rates increases in the cases with ECH. The increased importance of the TEM drive relative to the ITG mode drive in the cases with ECH may be associated with the increases in electron thermal transport and electron temperature fluctuations.

  19. Characterization of Secondary Electron Emission Properties of Plasma Facing Materials

    NASA Astrophysics Data System (ADS)

    Patino, Marlene I.; Capece, Angela M.; Raitses, Yevgeny; Koel, Bruce E.

    2015-11-01

    The behavior of wall-bounded plasmas is significantly affected by the plasma-wall interactions, including the emission of secondary electrons (SEE) from the wall materials due to bombardment by primary electrons. The importance of SEE has prompted previous investigations of SEE properties of materials especially with applications to magnetic fusion, plasma thrusters, and high power microwave devices. In this work, we present results of measurements of SEE properties of graphite and lithium materials relevant for the divertor region of magnetic fusion devices. Measurements of total SEE yield (defined as the number of emitted secondary electrons per incident primary electron) for lithium are extended up to 5 keV primary electron energy, and the energy distributions of secondary electrons are provided for graphite and lithium. Additionally, the effect of contamination on the total SEE yield of lithium was explored by exposing the material to water vapor. Auger electron spectroscopy (AES) was used to determine surface composition and temperature programmed desorption (TPD) was used to determine lithium film thickness. Results show an order of magnitude increase in total SEE yield for lithium exposed to water vapor. This work was supported by DOE contract DE-AC02-09CH11466; AFOSR grants FA9550-14-1-0053, FA9550-11-1-0282, and AF9550-09-1-0695; and DOE Office of Science Graduate Student Research Program.

  20. EUV induced low temperature SF6-based plasma

    NASA Astrophysics Data System (ADS)

    Bartnik, A.; Wachulak, P.; Fiedorowicz, H.; Skrzeczanowski, W.; Jarocki, R.; Fok, T.; Węgrzyński, Ł.

    2016-03-01

    In this work spectral investigations of low temperature F-rich photoionized plasmas were performed. The photoionized plasmas were created by irradiation of SF6 gas with intense EUV (extreme ultraviolet) radiation pulses. Two laser plasma EUV sources of different parameters used in the experiments were based on 0.8 J /4ns and 10 J/ 10 ns Nd:YAG lasers respectively. Both sources operated at 10 Hz repetition rate. The EUV radiation was focused using a dedicated reflective collector onto the gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Irradiation of the SF6 gas resulted in dissociative ionization of the molecules, leading to creation of SFn+ ions and fluorine atoms. Further photo- or electron impact ionization and excitation processes allow for formation of photoionized plasmas emitting radiation in the wide spectral range. Emission spectra were measured in the EUV and optical ranges. The EUV spectra contained multiple spectral lines, originating from F II, F III and S II ions. The UV/VIS spectra were composed of spectral lines corresponding to radiative transitions in F II, F I and S II species. A computer simulation of the F II spectrum was performed using a collisional-radiative PrismSPECT code. Parameters of the photoionized plasmas were estimated by fitting the spectrum obtained from the simulations to the experimental one. Apart from that, the electron temperature was estimated employing Boltzmann plots based on the UV/VIS spectrum.

  1. Rotating structures in low temperature magnetized plasmas - Insight from particle simulations

    NASA Astrophysics Data System (ADS)

    Boeuf, Jean-Pierre

    2014-12-01

    The EXB configuration of various low temperature plasma devices is often responsible for the formation of rotating structures and instabilities leading to anomalous electron transport across the magnetic field. In these devices, electrons are strongly magnetized while ions are weakly or not magnetized and this leads to specific physical phenomena that are not present in fusion plasmas where both electrons and ions are strongly magnetized. In this paper we describe basic phenomena involving rotating plasma structures in simple configurations of low temperature EXB plasma devices on the basis of PIC-MCC (Particle-In-Cell Monte Carlo Collisions) simulations. We focus on three examples: rotating electron vortices and rotating spokes in cylindrical magnetrons, and azimuthal electron-cyclotron drift instability in Hall thrusters. The simulations are not intended to give definite answers to the many physics issues related to low temperature EXB plasma devices but are used to illustrate and discuss some of the basic questions that need further studies.

  2. Electron properties and air mixing in radio frequency driven argon plasma jets at atmospheric pressure

    SciTech Connect

    Gessel, Bram van; Bruggeman, Peter; Brandenburg, Ronny

    2013-08-05

    A time modulated radio frequency (RF) plasma jet operated with an Ar mixture is investigated by measuring the electron density and electron temperature using Thomson scattering. The measurements have been performed spatially resolved for two different electrode configurations and as a function of the plasma dissipated power and air concentration admixed to the Ar. Time resolved measurements of electron densities and temperatures during the RF cycle and after plasma power switch-off are presented. Furthermore, the influence of the plasma on the air entrainment into the effluent is studied using Raman scattering.

  3. Electron-positron pair equilibrium in strongly magnetized plasmas

    SciTech Connect

    Harding, A.K.

    1984-11-01

    Steady states of thermal electron-positron pair plasmas at mildly relativistic temperatures and in strong magnetic fields are investigated. The pair density in steady-state equilibrium, where pair production balances annihilation, is found as a function of temperature, magnetic field strength and source size, by a numerical calculation which includes pair production attenuation and Compton scattering of the photons. It is found that there is a maximum pair density for each value of temperature and field strength, and also a source size above which optically thin equilibrium states do not exist. (ESA)

  4. Generation of uniform electron beam plasma in a dielectric flask at fore-vacuum pressures

    NASA Astrophysics Data System (ADS)

    Zolotukhin, D. B.; Burdovitsin, V. A.; Oks, E. M.

    2016-02-01

    We describe a system for the generation of spatially uniform and homogeneous dense plasma in a dielectric flask using a forevacuum-pressure plasma-cathode electron beam source. At optimum beam energy and gas pressure, the non-uniformity in plasma density distribution along the length of the flask is less than 10%, and the plasma density and electron temperature in the flask are greater than for the plasma produced in the vacuum chamber with no flask. The measured parameters of the beam plasma in the flask are compared to the predictions of a model based on balance equations.

  5. Electron decoherence at low temperatures

    NASA Astrophysics Data System (ADS)

    Mohanty, Pritiraj

    2001-03-01

    Electron decoherence is fundamental to condensed matter physics. Our understanding of metals and insulators in the Fermi-liquid framework relies entirely on a diverging decoherence rate 1/τ_φ at low temperatures, which is expected to vanish at T=0. However, recent experiments find that 1/τ_φ saturates at low temperatures [1-2]. We review these measurements on a variety of mesoscopic systems (in 0D, 1D, 2D and 3D) as well as the control experiments used to check for various artifacts [1-3]. We emphasize the connection between the temperature-independent decoherence rate and persistent current in normal metals [4]. We briefly discuss decoherence induced by dynamic defects or two-level systems [5,6], including its relevance--or lack thereof---to the experiments on metallic wires [2]. Saturation of decohrence rate is argued to be present in---and relevant to---the following phenomena: metal-insulator transition in 2D [7,8], superconductor-insulator transition in 2D [9], quantum-Hall-insulator transition [10], transport through superconductor/normal-metal hybrid junctions [11], normal-state resistivity of high Tc superconductors [12], persistent current in normal metals [4], and energy relaxation in normal metals [13]. [1] P. Mohanty, Physica B 280, 446 (2000). [2] P. Mohanty, E.M.Q. Jariwala, R. Webb, PRL 78, 3366 (1997); PRB 55, R13542 (1997). [3] P. Mohanty, R. Webb, PRL 84, 4481 (2000). [4] P. Mohanty, Ann. Phys. 8, 549 (1999). [5] P. Mohanty, M.L. Roukes (to be published). [6] K. Ahn, P. Mohanty, cond-mat/ 0011139. [7] S. Kravchenko et al. PRB 50, 8039 (1994). [8] G. Brunthaler, A. Prinz, G. Bauer, V. Pudalov, cond-mat/0007230. [9] A. Kapitulnik, N. Mason, S. Kivelson, S. Chakravarty, cond-mat/0008005. [10] D. Shahar, D. Tsui, M. Shayegan, J. Cunningham, E. Shimsoni, S. Sondhi, SSC. 102, 817 (1997). [11] A. Vaknin, A. Frydman, Z. Ovadyahu, PRB 61, 13037 (2000). [12] P. Fournier et al., PRB 62, R11993 (2000). [13] A. Gougam, F. Pierre, H. Pothier, D. Esteve, N

  6. Improved Magnetic Field Generation Efficiency and Higher Temperature Spheromak Plasmas

    SciTech Connect

    Wood, R D; Hill, D N; McLean, H S; Hooper, E B; Hudson, B F; Moller, J M; Romero-Talamas, C A

    2008-09-15

    New understanding of the mechanisms governing the observed magnetic field generation limits on the sustained spheromak physics experiment has been obtained. Extending the duration of magnetic helicity injection during the formation of a spheromak and optimizing the ratio of injected current to bias flux produce higher magnetic field plasmas with record spheromak electron temperatures. To explore magnetic field buildup efficiency limits, the confinement region geometry was varied resulting in improved field buildup efficiencies.

  7. Three-temperature plasma shock solutions with gray radiation diffusion

    DOE PAGESBeta

    Johnson, Bryan M.; Klein, Richard I.

    2016-04-19

    Here we discuss the effects of radiation on the structure of shocks in a fully ionized plasma are investigated by solving the steady-state fluid equations for ions, electrons, and radiation. The electrons and ions are assumed to have the same bulk velocity but separate temperatures, and the radiation is modeled with the gray diffusion approximation. Both electron and ion conduction are included, as well as ion viscosity. When the material is optically thin, three-temperature behavior occurs. When the diffusive flux of radiation is important but radiation pressure is not, two-temperature behavior occurs, with the electrons strongly coupled to the radiation.more » Since the radiation heats the electrons on length scales that are much longer than the electron–ion Coulomb coupling length scale, these solutions resemble radiative shock solutions rather than plasma shock solutions that neglect radiation. When radiation pressure is important, all three components are strongly coupled. Results with constant values for the transport and coupling coefficients are compared to a full numerical simulation with a good match between the two, demonstrating that steady shock solutions constitute a straightforward and comprehensive verification test methodology for multi-physics numerical algorithms.« less

  8. Nonlinear electrostatic solitary waves in electron-positron plasmas

    NASA Astrophysics Data System (ADS)

    Lazarus, I. J.; Bharuthram, R.; Moolla, S.; Singh, S. V.; Lakhina, G. S.

    2016-02-01

    The generation of nonlinear electrostatic solitary waves (ESWs) is explored in a magnetized four component two-temperature electron-positron plasma. Fluid theory is used to derive a set of nonlinear equations for the ESWs, which propagate obliquely to an external magnetic field. The electric field structures are examined for various plasma parameters and are shown to yield sinusoidal, sawtooth and bipolar waveforms. It is found that an increase in the densities of the electrons and positrons strengthen the nonlinearity while the periodicity and nonlinearity of the wave increases as the cool-to-hot temperature ratio increases. Our results could be useful in understanding nonlinear propagation of waves in astrophysical environments and related laboratory experiments.

  9. Observations of the dissipative trapped electron instability in a mirror plasma produced by electron-cyclotron resonance

    NASA Astrophysics Data System (ADS)

    Suetsugu, Y.; Kawai, Y.

    1986-02-01

    The dissipative trapped electron instability driven by the finite Larmor radius effects is observed in a mirror plasma produced by electron-cyclotron resonance using the Lisitano coil. The effect of the radial electron temperature gradient on the excitation of this mode is studied theoretically and experimentally. It is found that the electron temperature gradient opposite to the density gradient tends to stabilize this mode.

  10. Rotating structures and vortices in low temperature plasmas

    NASA Astrophysics Data System (ADS)

    Boeuf, Jean-Pierre

    2014-10-01

    Rotating structures are present in a number of low temperature EXB devices such as Hall thrusters, magnetrons, Penning discharges etc...Some aspects of the physics of these rotating instabilities are specific to low temperature plasmas because of the relatively large collisionality, the role of ionization, and the fact that ions are often non-magnetized. On the basis of fully kinetic simulations (Particle-In-Cell Monte Carlo Collisions) we describe the formation of a rotating instability associated with an ionization front (``rotating spoke'') and driven by a cross-field current in a self-sustained cylindrical magnetron discharge at gas pressure on the order of 1 Pa. The rotating spoke is a strong double layer (electrostatic sheath) moving towards the higher potential region at a velocity close to the critical ionization velocity, a concept proposed by Alfvén in the context of the formation of the solar system. The mechanisms of cross-field electron transport induced by this instability are analyzed. At lower pressure (<0.01 Pa) the plasma of a magnetron discharge is non-neutral and the simulations predict the formation of electron vortices rotating in the azimuthal direction and resulting from the diocotron instability. The properties of these vortices are specific since they form in a self-sustained discharge where ionization (and losses at the ends of the plasma column) play an essential role in contrast with the electron vortices in pure electron plasmas. We discuss and analyze the mechanisms leading to the generation, dynamics and merging of these self-sustained electron vortices, and to the periodic ejection of fast electrons at the column ends (consistent with previous experimental observations).

  11. Diagnostic techniques for measuring suprathermal electron dynamics in plasmas (invited)

    SciTech Connect

    Coda, S.

    2008-10-15

    Plasmas, both in the laboratory and in space, are often not in thermodynamic equilibrium, and the plasma electron distribution function is accordingly non-Maxwellian. Suprathermal electron tails can be generated by external drives, such as rf waves and electric fields, or internal ones, such as instabilities and magnetic reconnection. The variety and importance of the phenomena in which suprathermal electrons play a significant role explains an enduring interest in diagnostic techniques to investigate their properties and dynamics. X-ray bremsstrahlung emission has been studied in hot magnetized plasmas for well over two decades, flanked progressively by electron-cyclotron emission in geometries favoring the high-energy end of the distribution function (high-field-side, vertical, oblique emission), by electron-cyclotron absorption, by spectroscopic techniques, and at lower temperatures, by Langmuir probes and electrostatic analyzers. Continuous progress in detector technology and in measurement and analysis techniques, increasingly sophisticated layouts (multichannel and tomographic systems, imaging geometries), and highly controlled suprathermal generation methods (e.g., perturbative rf modulation) have all been brought to bear in recent years on an increasingly detailed, although far from complete, understanding of suprathermal electron dynamics.

  12. Laser-driven electron acceleration in an inhomogeneous plasma channel

    SciTech Connect

    Zhang, Rong; Cheng, Li-Hong; Xue, Ju-Kui

    2015-12-15

    We study the laser-driven electron acceleration in a transversely inhomogeneous plasma channel. We find that, in inhomogeneous plasma channel, the developing of instability for electron acceleration and the electron energy gain can be controlled by adjusting the laser polarization angle and inhomogeneity of plasma channel. That is, we can short the accelerating length and enhance the energy gain in inhomogeneous plasma channel by adjusting the laser polarization angle and inhomogeneity of the plasma channel.

  13. Laser Plasma Coupling for High Temperature Hohlraums

    SciTech Connect

    Kruer, W.

    1999-11-04

    Simple scaling models indicate that quite high radiation temperatures can be achieved in hohlraums driven with the National Ignition Facility. A scaling estimate for the radiation temperature versus pulse duration for different size NIF hohlraums is shown in Figure 1. Note that a radiation temperature of about 650 ev is projected for a so-called scale 1 hohlraum (length 2.6mm, diameter 1.6mm). With such high temperature hohlraums, for example, opacity experiments could be carried out using more relevant high Z materials rather than low Z surrogates. These projections of high temperature hohlraums are uncertain, since the scaling model does not allow for the very strongly-driven laser plasma coupling physics. Lasnex calculations have been carried out to estimate the plasma and irradiation conditions in a scale 1 hohlraum driven by NIF. Linear instability gains as high as exp(100) have been found for stimulated Brillouin scattering, and other laser-driven instabilities are also far above their thresholds. More understanding of the very strongly-driven coupling physics is clearly needed in order to more realistically assess and improve the prospects for high temperature hohlraums. Not surprisingly, this regime has been avoided for inertial fusion applications and so is relatively unexplored.

  14. Short wavelength trapped electron modes in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Zhang, N.; Gong, X. Y.; Dong, J. Q.; Huang, Q. H.; Gong, L.; Li, J. C.

    2016-04-01

    The collisionless trapped electron modes in the short wavelength region k⊥ρs>1 (SWTEMs) are studied with the gyrokinetic integral eigenmode equation in tokamak plasmas. Here, we present a systematic study of the correlation between the SWTEMs and short wavelength ion temperature gradient (SWITG) modes. The kθρs spectra of TEM have double humps in the short wavelength and long wavelength regions, respectively. The SWITG modes with trapped electron effects taking into account have broader kθρs spectra. Dependences of growth rate and real frequency of SWTEMs on the various parameters, such as ion temperature gradient (ηi), the temperature gradient of trapped electrons (ηe), toroidicity (ɛn), magnetic shear ( s ̂ ), safety factor (q), and the ratio of temperature (Te/Ti), are investigated in detail. It is found that the SWTEMs propagate in the electron diamagnetic drift direction and require temperature gradient of trapped electrons ηe exceeding thresholds. Moreover, the ion temperature gradient has a strong stabilizing effect on the SWTEMs. The SWTEMs become stable in both regimes of toroidicity ɛn > 0.1 and magnetic shear s ̂>0.5 regardless of the fraction of trapped electrons. In addition, the properties of short wavelength ITG (SWITG) modes are discussed with different ratio of trapped electrons. It is found that trapped electrons of greater fraction have a stronger destabilizing effect on the SWTEM and SWITG modes. These results are significant for the electrons anomalous transport experiments in the future.

  15. Electron-vibration relaxation in oxygen plasmas

    NASA Astrophysics Data System (ADS)

    Laporta, V.; Heritier, K. L.; Panesi, M.

    2016-06-01

    An ideal chemical reactor model is used to study the vibrational relaxation of oxygen molecules in their ground electronic state, X3 Σg-, in presence of free electrons. The model accounts for vibrational non-equilibrium between the translational energy mode of the gas and the vibrational energy mode of individual molecules. The vibrational levels of the molecules are treated as separate species, allowing for non-Boltzmann distributions of their population. The electron and vibrational temperatures are varied in the range [0-20,000] K. Numerical results show a fast energy transfer between oxygen molecules and free electron, which causes strong deviation of the vibrational distribution function from Boltzmann distribution, both in heating and cooling conditions. Comparison with Landau-Teller model is considered showing a good agreement for electron temperature range [2000-12,000] K. Finally analytical fit of the vibrational relaxation time is given.

  16. Electron kinetics in a cooling plasma

    SciTech Connect

    Helander, P.; Smith, H.; Fueloep, T.; Eriksson, L.-G.

    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.

  17. Center for High Temperature Plasma Physics certified

    NASA Astrophysics Data System (ADS)

    Hu, Maolian

    1985-05-01

    The construction and functions of a research center for high temperature plasma physics and controlled thermonuclear fusion are discussed. It has four of China's largest d.c. pulse generators capable of producing 80 megawatts of power, an induction coil capable of storing 200 million joules of electric energy, and a capacitor bank that can store 8 million joules of energy. It has equipment for producing deionized water, low temperature equipment, a cooling system using refrigerated circulating water, and a heat supply system. The center is one of China's important bases for thermonuclear fusion research.

  18. Material for electrodes of low temperature plasma generators

    DOEpatents

    Caplan, Malcolm; Vinogradov, Sergel Evge'evich; Ribin, Valeri Vasil'evich; Shekalov, Valentin Ivanovich; Rutberg, Philip Grigor'evich; Safronov, Alexi Anatol'evich; Shiryaev, Vasili Nikolaevich

    2010-03-02

    Material for electrodes of low temperature plasma generators. The material contains a porous metal matrix impregnated with a material emitting electrons. The material uses a mixture of copper and iron powders as a porous metal matrix and a Group IIIB metal component such as Y.sub.2O.sub.3 is used as a material emitting electrons at, for example, the proportion of the components, mass %: iron:3-30; Y.sub.2O.sub.3:0.05-1; copper: the remainder. Copper provides a high level of heat conduction and electric conductance, iron decreases intensity of copper evaporation in the process of plasma creation providing increased strength and lifetime, Y.sub.2O.sub.3 provides decreasing of electronic work function and stability of arc burning. The material can be used for producing the electrodes of low temperature AC plasma generators used for destruction of liquid organic wastes, medical wastes, municipal wastes as well as for decontamination of low level radioactive waste, the destruction of chemical weapons, warfare toxic agents, etc.

  19. Material for electrodes of low temperature plasma generators

    DOEpatents

    Caplan, Malcolm; Vinogradov, Sergel Evge'evich; Ribin, Valeri Vasil'evich; Shekalov, Valentin Ivanovich; Rutberg, Philip Grigor'evich; Safronov, Alexi Anatol'evich

    2008-12-09

    Material for electrodes of low temperature plasma generators. The material contains a porous metal matrix impregnated with a material emitting electrons. The material uses a mixture of copper and iron powders as a porous metal matrix and a Group IIIB metal component such as Y.sub.2O.sub.3 is used as a material emitting electrons at, for example, the proportion of the components, mass %: iron: 3-30; Y.sub.2O.sub.3:0.05-1; copper: the remainder. Copper provides a high level of heat conduction and electric conductance, iron decreases intensity of copper evaporation in the process of plasma creation providing increased strength and lifetime, Y.sub.2O.sub.3 provides decreasing of electronic work function and stability of arc burning. The material can be used for producing the electrodes of low temperature AC plasma generators used for destruction of liquid organic wastes, medical wastes, and municipal wastes as well as for decontamination of low level radioactive waste, the destruction of chemical weapons, warfare toxic agents, etc.

  20. 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.

  1. Radial Profiles of the Plasma Electron Characteristics in a 30 kW Arc Jet

    NASA Technical Reports Server (NTRS)

    Codron, Douglas A.; Nawaz, Anuscheh

    2013-01-01

    The present effort aims to strengthen modeling work conducted at the NASA Ames Research Center by measuring the critical plasma electron characteristics within and slightly outside of an arc jet plasma column. These characteristics are intended to give physical insights while assisting in the formulation of boundary conditions to validate full scale simulations. Single and triple Langmuir probes have been used to achieve estimates of the electron temperature (T(sub e)), electron number density (n(sub e)) and plasma potential (outside of the plasma column) as probing location is varied radially from the flow centerline. Both the electron temperature and electron number density measurements show a large dependence on radial distance from the plasma column centerline with T(sub e) approx. = (3 - 12 eV and n(sub e) approx. = 10(exp 12) - 10(exp 14)/cu cm.

  2. Modeling of free electronic state density in hydrogenic plasmas based on nearest neighbor approximation

    SciTech Connect

    Nishikawa, Takeshi

    2014-07-15

    Most conventional atomic models in a plasma do not treat the effect of the plasma on the free-electron state density. Using a nearest neighbor approximation, the state densities in hydrogenic plasmas for both bound and free electrons were evaluated and the effect of the plasma on the atomic model (especially for the state density of the free electron) was studied. The model evaluates the electron-state densities using the potential distribution formed by the superposition of the Coulomb potentials of two ions. The potential from one ion perturbs the electronic state density on the other. Using this new model, one can evaluate the free-state density without making any ad-hoc assumptions. The resulting contours of the average ionization degree, given as a function of the plasma temperature and density, are shifted slightly to lower temperatures because of the effect of the increasing free-state density.

  3. Thermal equilibrium of a cryogenic magnetized pure electron plasma

    NASA Technical Reports Server (NTRS)

    Dubin, D. H. E.; Oneil, T. M.

    1986-01-01

    The thermal equilibrium correlation properties of a magnetically confined pure electron plasma (McPEP) are related to those of a one-component plasma (OCP). The N-particle spatial distribution rho sub s and the Helmholtz free energy F are evaluated for the McPEP to O(lambda sub d-squared/a-squared), where lambda sub d is the thermal de Broglie wavelength and is an interparticle spacing. The electron gyromotion is allowed to be fully quantized while the guiding center motion is quasi-classical. The distribution rho sub s is shown to be identical to that of a classical OCP with a slightly modified potential. To O(lambda sub d-squared/a-squared) this modification does not affect that part of F that is caused by correlations, as long as certain requirements concerning the size of the plasma are met. This theory is motivated by a current series of experiments that involve the cooling of a magnetically confined pure electron plasma to the cryogenic temperature range.

  4. Plasma-Surface Interactions and Impact on Electron Energy Distribution Function

    NASA Astrophysics Data System (ADS)

    Fox-Lyon, N. A.; Oehrlein, G. S.; Ning, N.; Graves, D. B.; Godyak, V.

    2011-10-01

    The goal of this work is to explore the role of surface processes in influencing characteristic electron energy distribution functions (EEDF).As a model system, we use a well characterized, inductively coupled plasma system to examine Ar/H2 (or D2) discharges interacting with a-C:H films. The modification/erosion of a-C:H surfaces is monitored in real time by ellipsometry and the effects of gas mixtures and surface generated carbon on plasma parameters (Te, plasma density, EEDF) are probed with Langmuir probe measurements. We find that plasma density decreased greatly (from 1011 to 109 per cm3) with small H2 additions to Ar plasma (conditions: 10-30 mTorr, 300-600 W source power). The electron temperature was shown to increase with H2 flow. At high H2 flows, the electron energy distribution transitions from Maxwellian distribution to a two-temperature distribution. The addition of 1-20 % CH4 into H2 plasma shows an increase in plasma density and a change in the electron temperature. The hydrocarbon erosion products of a-C:H films in H2 plasma are found to cause a similar effect on plasma properties as CH4 addition. These observations indicate that prediction/control of EEDF for plasmas interacting with reactive bounding surfaces requires an understanding of the consequences of the plasma-surface interactions.

  5. Kinetic modelling of runaway electron avalanches in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Nilsson, E.; Decker, J.; Peysson, Y.; Granetz, R. S.; Saint-Laurent, F.; Vlainic, M.

    2015-09-01

    relative importance of the avalanche mechanism is investigated as a function of the key parameters for runaway electron formation, namely the plasma temperature and the electric field strength. In agreement with theoretical predictions, the LUKE simulations show that in low temperature and electric field the knock-on collisions becomes the dominant source of runaway electrons and can play a significant role for runaway electron generation, including in non-disruptive tokamak scenarios.

  6. Low temperature plasma biomedicine: A tutorial review

    SciTech Connect

    Graves, David B.

    2014-08-15

    Gas discharge plasmas formed at atmospheric pressure and near room temperature have recently been shown to be potentially useful for surface and wound sterilization, antisepsis, bleeding cessation, wound healing, and cancer treatment, among other biomedical applications. This tutorial review summarizes the field, stressing the likely role of reactive oxygen and nitrogen species created in these plasmas as the biologically and therapeutically active agents. Reactive species, including radicals and non-radical compounds, are generated naturally within the body and are now understood to be essential for normal biological functions. These species are known to be active agents in existing therapies for wound healing, infection control, and cancer treatment. But they are also observed at elevated levels in persons with many diseases and are associated with aging. The physical and chemical complexity of plasma medical devices and their associated biochemical effects makes the development of safe, effective plasma medical devices and procedures a challenge, but encouragingly rapid progress has been reported around the world in the last several years.

  7. Low temperature plasma biomedicine: A tutorial reviewa)

    NASA Astrophysics Data System (ADS)

    Graves, David B.

    2014-08-01

    Gas discharge plasmas formed at atmospheric pressure and near room temperature have recently been shown to be potentially useful for surface and wound sterilization, antisepsis, bleeding cessation, wound healing, and cancer treatment, among other biomedical applications. This tutorial review summarizes the field, stressing the likely role of reactive oxygen and nitrogen species created in these plasmas as the biologically and therapeutically active agents. Reactive species, including radicals and non-radical compounds, are generated naturally within the body and are now understood to be essential for normal biological functions. These species are known to be active agents in existing therapies for wound healing, infection control, and cancer treatment. But they are also observed at elevated levels in persons with many diseases and are associated with aging. The physical and chemical complexity of plasma medical devices and their associated biochemical effects makes the development of safe, effective plasma medical devices and procedures a challenge, but encouragingly rapid progress has been reported around the world in the last several years.

  8. Implicit two-fluid simulation of electron transport in a plasma erosion opening switch

    SciTech Connect

    Mason, R.J.; Wallace, J.M.; Lee, K.

    1986-01-01

    The two-dimensional implicit code ANTHEM is used to model electron transport in Plasma Opening Switches. We look at low density (approx.4 x 10/sup 12/cm/sup -3/) switches at initial plasma temperatures as low as 5 eV. Two-fluid modeling (ions and electrons with inertia) and implicit determination of the fields is employed to allow time steps well in excess of the inverse plasma period, and cell sizes much larger than a Debye length - with the avoidance of the finite grid anomalous plasma heating characteristic of particle codes. Features indicative of both erosion and E > B plasma drift are manifest in the simulations.

  9. 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.

  10. Relativistic warm plasma theory of nonlinear laser-driven electron plasma waves.

    PubMed

    Schroeder, C B; Esarey, E

    2010-05-01

    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 nonrelativistic 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 nonrelativistic phase velocities owing to the coupling between the longitudinal and transverse momentum variances. PMID:20866340

  11. Electron plasma oscillations at arbitrary Debye lengths

    NASA Astrophysics Data System (ADS)

    Lehnert, B.

    1991-06-01

    A solution is presented for electron plasma oscillations in a thermalized plasma, at arbitrary ratios of the Debye length AλD and the perturbation wavelength λ. The limit λDλ corresponds to the conventional fluid-like theory of small particle excursions, whereas λDλ corresponds to the free-streaming limit of strong kinetic phase mixing due to large particle excursions. A strong large-Debye-distance (LDD) effect already appears when λD λ. The initial amplitude of the fluid-like contribution to the macroscopic density perturbation then becomes small compared with the contribution from the free-streaming part. As a consequence, only a small fraction of the density perturbation remains after a limited number of kinetic damping times of the free-streaming part. The present analysis can be considered as a first exercise in an attempt to tackle the far more difficult problem of large-Larmor-radius (LLR) effects in a magnetized plasma. The analysis further shows that a representation in terms of normal modes of the form exp (— iωt) leads to amplitude factors of these modes that are related to each other and that depend on the combined free-streaming and fluid behaviour of the plasma. Consequently, these modes are coupled and cannot be treated as independent of each other.

  12. Low-temperature atmospheric-pressure plasma sources for plasma medicine.

    PubMed

    Setsuhara, Yuichi

    2016-09-01

    In this review paper, fundamental overviews of low-temperature atmospheric-pressure plasma generation are provided and various sources for plasma medicine are described in terms of operating conditions and plasma properties. PMID:27109191

  13. Positron-acoustic solitary waves in a magnetized electron-positron-ion plasma with nonthermal electrons and positrons

    NASA Astrophysics Data System (ADS)

    Rahman, M. M.; Alam, M. S.; Mamun, A. A.

    2015-05-01

    Obliquely propagating positron-acoustic solitary waves (PASWs) in a magnetized electron-positron-ion plasma (containing nonthermal hot positrons and electrons, inertial cold positrons, and immobile positive ions) are precisely investigated by deriving the Zakharov-Kuznetsov equation. It is found that the characteristics of the PASWs are significantly modified by the effects of external magnetic field, obliqueness, nonthermality of hot positrons and electrons, temperature ratio of hot positrons and electrons, and respective number densities of hot positrons and electrons. The findings of our results can be employed in understanding the localized electrostatic structures and the characteristics of PASWs in various space and laboratory plasmas.

  14. Modulational instability of ion acoustic wave with warm ions in electron-positron-ion plasmas

    SciTech Connect

    Mahmood, S.; Siddiqui, Sadiya; Jehan, Nusrat

    2011-05-15

    The nonlinear amplitude modulation of ion acoustic wave is studied in the presence of warm ions in unmagnetized electron-positron-ion plasmas. The Krylov-Bogoliubov-Mitropolsky (KBM) method is used to derive the nonlinear Schroedinger equation. The dispersive and nonlinear coefficients are obtained which depends on the ion temperature and positron density in electron-positron-ion plasmas. The modulationally stable and unstable regions are studied numerically for a wide range of wave number. It is found that both ion temperature and positron density play a significant role in the formation of bright and dark envelope solitons in electron-positron-ion plasmas.

  15. Excitation of Plasma Waves in Aurora by Electron Beams

    NASA Technical Reports Server (NTRS)

    daSilva, C. E.; Vinas, A. F.; deAssis, A. S.; deAzevedo, C. A.

    1996-01-01

    In this paper, we study numerically the excitation of plasma waves by electron beams, in the auroral region above 2000 km of altitude. We have solved the fully kinetic dispersion relation, using numerical method and found the real frequency and the growth rate of the plasma wave modes. We have examined the instability properties of low-frequency waves such as the Electromagnetic Ion Cyclotron (EMIC) wave as well as Lower-Hybrid (LH) wave in the range of high-frequency. In all cases, the source of free energy are electron beams propagating parallel to the geomagnetic field. We present some features of the growth rate modes, when the cold plasma parameters are changed, such as background electrons and ions species (H(+) and O(+)) temperature, density or the electron beam density and/or drift velocity. These results can be used in a test-particle simulation code, to investigate the ion acceleration and their implication in the auroral acceleration processes, by wave-particle interaction.

  16. Electron-helium scattering in Debye plasmas

    SciTech Connect

    Zammit, Mark C.; Fursa, Dmitry V.; Bray, Igor; Janev, R. K.

    2011-11-15

    Electron-helium scattering in weakly coupled hot-dense (Debye) plasma has been investigated using the convergent close-coupling method. The Yukawa-type Debye-Hueckel potential has been used to describe plasma Coulomb screening effects. Benchmark results are presented for momentum transfer cross sections, excitation, ionization, and total cross sections for scattering from the ground and metastable states of helium. Calculations cover the entire energy range up to 1000 eV for the no screening case and various Debye lengths (5-100 a{sub 0}). We find that as the screening interaction increases, the excitation and total cross sections decrease, while the total ionization cross sections increase.

  17. Plasma treatment for producing electron emitters

    DOEpatents

    Coates, Don Mayo; Walter, Kevin Carl

    2001-01-01

    Plasma treatment for producing carbonaceous field emission electron emitters is disclosed. A plasma of ions is generated in a closed chamber and used to surround the exposed surface of a carbonaceous material. A voltage is applied to an electrode that is in contact with the carbonaceous material. This voltage has a negative potential relative to a second electrode in the chamber and serves to accelerate the ions toward the carbonaceous material and provide an ion energy sufficient to etch the exposed surface of the carbonaceous material but not sufficient to result in the implantation of the ions within the carbonaceous material. Preferably, the ions used are those of an inert gas or an inert gas with a small amount of added nitrogen.

  18. Measurements of low-energy electron reflection at a plasma boundary

    SciTech Connect

    Demidov, V. I.; Adams, S. F.; Kaganovich, I. D.; Koepke, M. E.; Kurlyandskaya, I. P.

    2015-10-15

    It is demonstrated that low-energy (<3 eV) electron reflection from a solid surface in contact with a low-temperature plasma can have significant variation with time. An uncontaminated, i.e., “clean,” metallic surface (just after heating up to glow) in a plasma environment may have practically no reflection of low-energy incident electrons. However, a contaminated, i.e., “dirty,” surface (in some time after cleaning by heating) that has a few monolayers of absorbent can reflect low-energy incident electrons and therefore significantly affect the net electron current collected by the surface. This effect may significantly change plasma properties and should be taken into account in plasma experiments and models. A diagnostic method is demonstrated for measurements of low-energy electron absorption coefficient in plasmas with a mono-energetic electron group.

  19. Dynamics of runaway electrons in magnetized plasmas

    SciTech Connect

    Moghaddam-Taaheri, E.

    1986-01-01

    The evolution of a runaway electron tail driven by a subcritical dc electric field in a magnetized plasma is studied numerically using a quasi-linear numerical code (2-D in v- and k-space) based on the Ritz-Galerkin method and finite elements. Three different regimes in the evolution of the runaway tail depending on the strength of the dc electric field and the ratio of plasma to gyrofrequency, were found. The tail can be (a) stable and the electrons are accelerated to large parallel velocities, (b) unstable to the Cerenkov resonance due to the formation of a positive slope on the runaway tail, (c) unstable to the anomalous Doppler resonance instability driven by the large velocity anisotropy in the tail. Once an instability is triggered (Cerenkov or anomalous Doppler resonance) the tail relaxes into an isotropic distribution resulting in less acceleration. The synchrotron emission of the runaway electrons shows large enhancement in the radiation level at the high-frequency end of the spectrum during the pitch-angle scattering of the fast particles. The results are relevant to recent experimental data from the Princeton Large Torus (PLT) during current-drive experiments and to the microwave bursts observed during solar flares.

  20. Thermalization of electrons in decaying extreme ultraviolet photons induced low pressure argon plasma

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    We monitored—in the pressure range: 0.5–15 Pa—the electron temperature in decaying plasmas induced in argon gas by pulsed irradiation with extreme ultraviolet (EUV) photons with wavelengths closely around 13.5 nm. For this purpose, temporal measurements of the space-averaged and electric field weighted electron density after pulsed EUV irradiation are combined with an ambipolar diffusion model of the plasma. Results demonstrate that electrons are thermalized to room temperature before the plasma has fully expanded to the chamber walls for pressures of 3 Pa and higher. At pressures below 3 Pa, the electron temperature was found to be up to 0.1 eV above room temperature which is explained by the fact that plasma expansion is too quick for the electrons to fully thermalize. The comparison between plasma expansion duration towards a surface, plasma decay at a surface and time needed for thermalization and cooling of electrons is essential for designers of EUV lithography tools and EUV sources since the temperature of electrons dictates many fundamental physical processes.

  1. Cylindrical and Spherical Electron-Acoustic Shock Waves in Electron-Positron-Ion Plasmas with Nonextensive Electrons and Positrons

    NASA Astrophysics Data System (ADS)

    Rafat, A.; M. M., Rahman; M. S., Alam; A. A., Mamun

    2015-02-01

    Electron-acoustic shock waves (EASWs) in an unmagnetized four-component plasma (containing hot electrons and positrons following the q-nonextensive distribution, cold mobile viscous electron fluid, and immobile positive ions) are studied in nonplanar (cylindrical and spherical) geometry. With the help of the reductive perturbation method, the modified Burgers equation is derived. Analytically, the effects of nonplanar geometry, nonextensivity, relative number density and temperature ratios, and cold electron kinematic viscosity on the basic properties (viz. amplitude, width, speed, etc.) of EASWs are discussed. It is examined that the EASWs in nonplanar geometry significantly differ from those in planar geometry. The results of this investigation can be helpful in understanding the nonlinear features of EASWs in various astrophysical plasmas.

  2. New electron cyclotron emission diagnostic for measurement of temperature based upon the electron Bernstein wave

    SciTech Connect

    Efthimion, P.C.; Hosea, J.C.; Kaita, R.; Majeski, R.; Taylor, G.

    1999-01-01

    Most magnetically confined plasma devices cannot take advantage of standard electron cyclotron emission (ECE) diagnostics to measure temperature. They either operate at high density relative to their magnetic field (e.g., {omega}{sub p}{gt}{Omega}{sub c} in spherical tokamaks) or they do not have sufficient density and temperature to reach the blackbody condition ({tau}{gt}2). The standard ECE technique measures the electromagnetic waves emanating from the plasma. Here we propose to measure electron Bernstein waves (EBW) to ascertain the local electron temperature in these plasmas. The optical thickness of EBW is extremely high because it is an electrostatic wave with a large k{sub i}. For example, the National Spherical Torus Experiment (NSTX) will have an optical thickness {tau}{approx}3000 and CDX-U will have {tau}{approx}300. One can reach the blackbody condition with a plasma density {approx}10{sup 11}thinspcm{sup {minus}3} and T{sub e}{approx}1thinspeV. This makes it attractive to most plasma devices. The serious issue with using EBW is the wave accessibility for the emission measurement. Simple accessibility arguments indicate the wave may be accessible by either direct coupling or mode conversion through an extremely narrow layer ({approx}1{endash}2 mm). EBW experiments on the Current Drive Experiment-Upgrade (CDX-U) will test the accessibility properties of the spherical tokamak configuration. {copyright} {ital 1999 American Institute of Physics.}

  3. Simulating Electron Cyclotron Resonance Heating in Kinetic and Dielectric Plasma Models with VORPAL

    NASA Astrophysics Data System (ADS)

    Roark, Christine; Smithe, David; Stoltz, Peter; Tech-X Corporation Team

    2011-10-01

    We present results of electron cyclotron resonance heating (ECRH) in a plasma sustained by microwaves using VORPAL. Specifically, we look at the electron temperature, sheath size, rate of plasma formation and power absorbed for simulations with an argon gas at 10s of mTorr pressure and 2.45 GHz. We look at the effects of including elastic, inelastic and ionizing Monte Carlo collisions on the formation of the kinetic plasma. We also discuss the use of higher-order particle algorithms for smoothing out the particle current and charge which can help reduce unphysical heating in PIC simulations of high pressure, low temperature plasmas and the effect this has on sheath size and electron temperature. We then compare these simulations to a method replacing the kinetic particles with an equivalent plasma dielectric model.

  4. Profile modification and hot electron temperature from resonant absorption at modest intensity

    SciTech Connect

    Albritton, J.R.; Langdon, A.B.

    1980-10-13

    Resonant absorption is investigated in expanding plasmas. The momentum deposition associated with the ejection of hot electrons toward low density via wavebreaking readily exceeds that of the incident laser radiation and results in significant modification of the density profile at critical. New scaling of hot electron temperature with laser and plasma parameters is presented.

  5. Electron microscopy methods for studying plasma membranes.

    PubMed

    Beckett, Alison J; Prior, Ian A

    2015-01-01

    Electron microscopy allows direct visualization of the underlying organization of cell surface components on a nano-scale. Immuno-gold labelling of isolated plasma membranes generates point patterns that enable mapping of protein and lipid distributions. 2D spatial statistics reveals the extent to which these distributions are clustered or dispersed and allows the extent of co-localization between different cell surface components to be precisely determined. This approach has been successfully applied to the study of signalling network organization and the consequences of physiological changes in modulating cell surface function. PMID:25331134

  6. 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.; Leonova, M.A.; Schwarz, T.A.; 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.

  7. High temperature electronic gain device

    DOEpatents

    McCormick, J. Byron; Depp, Steven W.; Hamilton, Douglas J.; Kerwin, William J.

    1979-01-01

    An integrated thermionic device suitable for use in high temperature, high radiation environments. Cathode and control electrodes are deposited on a first substrate facing an anode on a second substrate. The substrates are sealed to a refractory wall and evacuated to form an integrated triode vacuum tube.

  8. Spatial plasma potentials and electron energy distributions in inductively and capacitively coupled plasmas under a weakly collisional and nonlocal electron kinetic regime

    NASA Astrophysics Data System (ADS)

    Lee, Hyo-Chang; Chung, Chin-Wook

    2012-10-01

    Spatial profiles of the plasma potential and electron energy distribution function (EEDF) were measured in inductively and capacitively coupled plasmas (ICP and CCP) under weakly collisional and nonlocal electron kinetic regimes [1]. The measured EEDF at the discharge center was a bi-Maxwellain distribution with low (T1) and high (T2) electron temperature groups at both the ICP and the CCP, while the EEDF at the radial boundary was closely Maxwellian distribution in the ICP due to cutting of the low energy electrons by relatively large ambipolar potential in this discharge regime. The ambipolar potential in the entire radial region was in the scale of Teff -1.5 Teff, where Teff is the effective electron temperature. At the boundary region with the ion mean free path scale, the ambipolar potential increased abruptly and was about Teff,edge/2, where the Teff,edge is the effective electron temperature at the boundary, which corresponds to the presheath scale. These results of the ICP, which are contrary to the ambipolar potential of the CCP in a nearly free-fall regime [2], are caused by relatively high T1 and a small portion of low energy electron group density to total electron density in the ICP under the weakly collisional and nonlocal electron kinetic regimes. [4pt] [1] H. C. Lee and C. W. Chung, Phys. Plasmas 19 033514 (2012).[0pt] [2] V. A. Godyak, V. P. Meytlis, and H. R. Strauss, IEEE Trans. Plasma Sci. 23 728 (1995).

  9. Energy Measurements of Trapped Electrons from a Plasma Wakefield Accelerator

    SciTech Connect

    Kirby, Neal; Auerbach, David; Berry, Melissa; Blumenfeld, Ian; Clayton, Christopher E.; Decer, Franz-Josef; Hogan, Mark J.; Huang, Chengkun; Ischebeck, Rasmus; Iverson, Richard; Johnson, Devon; Joshi, Chadrashekhar; Katsouleas, Thomas; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; Muggli, Patric; Oz, Erdem; Siemann, Robert H.; Walz, Dieter; Zhou, Miaomiao; /SLAC /UCLA /Southern California U.

    2007-01-03

    Recent electron beam driven plasma wakefield accelerator experiments carried out at SLAC indicate trapping of plasma electrons. More charge came out of than went into the plasma. Most of this extra charge had energies at or below the 10 MeV level. In addition, there were trapped electron streaks that extended from a few GeV to tens of GeV, and there were mono-energetic trapped electron bunches with tens of GeV in energy.

  10. Hydrodynamic theory of diffusion in two-temperature multicomponent plasmas

    SciTech Connect

    Ramshaw, J.D.; Chang, C.H.

    1995-12-31

    Detailed numerical simulations of multicomponent plasmas require tractable expressions for species diffusion fluxes, which must be consistent with the given plasma current density J{sub q} to preserve local charge neutrality. The common situation in which J{sub q} = 0 is referred to as ambipolar diffusion. The use of formal kinetic theory in this context leads to results of formidable complexity. We derive simple tractable approximations for the diffusion fluxes in two-temperature multicomponent plasmas by means of a generalization of the hydrodynamical approach used by Maxwell, Stefan, Furry, and Williams. The resulting diffusion fluxes obey generalized Stefan-Maxwell equations that contain driving forces corresponding to ordinary, forced, pressure, and thermal diffusion. The ordinary diffusion fluxes are driven by gradients in pressure fractions rather than mole fractions. Simplifications due to the small electron mass are systematically exploited and lead to a general expression for the ambipolar electric field in the limit of infinite electrical conductivity. We present a self-consistent effective binary diffusion approximation for the diffusion fluxes. This approximation is well suited to numerical implementation and is currently in use in our LAVA computer code for simulating multicomponent thermal plasmas. Applications to date include a successful simulation of demixing effects in an argon-helium plasma jet, for which selected computational results are presented. Generalizations of the diffusion theory to finite electrical conductivity and nonzero magnetic field are currently in progress.

  11. Deriving large electron temperatures and small electron densities with the Cassini Langmuir probe at Saturn

    NASA Astrophysics Data System (ADS)

    Garnier, Philippe; Wahlund, Jan-Erik; Holmberg, Mika; Lewis, Geraint; Schippers, Patricia; Rochel Grimald, Sandrine; Gurnett, Donald; Coates, Andrew; Dandouras, Iannis; Waite, Hunter

    2014-05-01

    The Langmuir Probes (LPs) are commonly used to investigate the cold plasma characteristics in planetary ionospheres/magnetospheres. The LPs performances are limited to low temperatures (i.e. below 5-10 eV at Saturn) and large densities (above several particles/cm3). A strong sensitivity of the Cassini LP measurements to energetic electrons (hundreds eV) may however be observed at Saturn in the L Shell range L=6-10 RS. These electrons impact the surface of the probe and generate a detectable current of secondary electrons. We investigate the influence of such electrons on the current-voltage (I-V) characteristics (for negative potentials), and manage to reproduce the observations with a reasonable precision through empirical and theoretical methods. Conversely, the modelling allows us to derive useful information about the energetic electrons from the LP observations : some information about their pitch angle anisotropy (if combined with the data from a single CAPS ELS anode), as well as an estimate of the electron temperature (in the range 100-300 eV) and of the electron density (above 0.1 particles/cm3). This enlarges the LP measurements capabilities when the influence of the energetic electrons is large (essentially near L=6-10 RS at Saturn). We finally show that a significant influence of the energetic electrons (larger than the contribution of thermal ions) is also expected in various plasma environments of the Solar System, such as at Jupiter (i.e near Ganymede, Europa, Callisto and Io), or even at Earth (in the plasmasheet, the magnetosheath or in plasma cavities). Large electron temperatures and small electron densities could potentially be derived in these environments, which may be of interest for Langmuir Probes in the Earth magnetosphere or onboard the future JUICE mission at Jupiter.

  12. 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.

  13. Status of Plasma Electron Hose Instability Studies in FACET

    SciTech Connect

    Adli, Erik; England, Robert Joel; Frederico, Joel; Hogan, Mark; Li, Selina Zhao; Litos, Michael Dennis; Nosochkov, Yuri; An, Weiming; Mori, Warren; /UCLA

    2011-12-13

    In the FACET plasma-wakefield acceleration experiment a dense 23 GeV electron beam will interact with lithium and cesium plasmas, leading to plasma ion-channel formation. The interaction between the electron beam and the plasma sheath-electrons may lead to a fast growing electron hose instability. By using optics dispersion knobs to induce a controlled z-x tilt along the beam entering the plasma, we investigate the transverse behavior of the beam in the plasma as function of the tilt. We seek to quantify limits on the instability in order to further explore potential limitations on future plasma wakefield accelerators due to the electron hose instability. The FACET plasma-wakefield experiment at SLAC will study beam driven plasma wakefield acceleration. A dense 23 GeV electron beam will interact with lithium or cesium plasma, leading to plasma ion-channel formation. The interaction between the electron beam and the plasma sheath-electrons drives the electron hose instability, as first studied by Whittum. While Ref. [2] indicates the possibility of a large instability growth rate for typical beam and plasma parameters, other studies including have shown that several physical effects may mitigate the hosing growth rate substantially. So far there has been no quantitative benchmarking of experimentally observed hosing in previous experiments. At FACET we aim to perform such benchmarking by for example inducing a controlled z-x tilt along the beamentering the plasma, and observing the transverse behavior of the beam in the plasma as function. The long-term objective of these studies is to quantify potential limitations on future plasma wakefield accelerators due to the electron hose instability.

  14. Experimental and Theoretical Determination of Temperature in Plasmas

    SciTech Connect

    Zmerli, Besma; Ben Nessib, Nebil; Dimitrijevic, Milan S.

    2007-09-28

    When plasma is in thermodynamic equilibrium, all species have the same kinetic temperature. In practice, plasmas are generally not in equilibrium, so different temperatures can be obtained. We investigated here temperature dependence of Stark widths for neutral atom spectral lines in order to find a more precise method for scaling with temperature.

  15. High temperature power electronics for space

    NASA Technical Reports Server (NTRS)

    Hammoud, Ahmad N.; Baumann, Eric D.; Myers, Ira T.; Overton, Eric

    1991-01-01

    A high temperature electronics program at NASA Lewis Research Center focuses on dielectric and insulating materials research, development and testing of high temperature power components, and integration of the developed components and devices into a demonstrable 200 C power system, such as inverter. An overview of the program and a description of the in-house high temperature facilities along with experimental data obtained on high temperature materials are presented.

  16. Ion temperature in the ASTRAL helicon plasma source

    NASA Astrophysics Data System (ADS)

    Boivin, Robert

    2005-10-01

    Ion temperature is measured in the ASTRAL (Auburn Steady sTate Research fAciLity) helicon plasma source by means of a diode laser based Laser Induced Fluorescence (LIF) diagnostic. ASTRAL produces plasmas with the following parameters: ne = 10^10 to 10^13 cm-3, Te = 2 to 15 eV and Ti = 0.03 to 0.5 eV. A series of 7 large coils produce an axial magnetic field up to 1.3 kGauss. A fractional helix antenna is used to introduce rf power up to 2 kWatt. The 1.5 MHz bandwidth diode laser has a Littrow external cavity with a mode-hop free tuning range up to 15 GHz and with a total power output of about 15 mW. The wavelength is measured by a wavemeter and frequent monitoring prevents wavelength drift. For Ar plasma, the laser tuned at 668.61 nm, is used to pump the 3d^4F7/2 Ar II metastable level to the 4p^4D5/2 level. The fluorescence radiation between the 4p^4D5/2 and the 4s^4P3/2 levels (442.6 nm) is monitored by a PMT. Other diagnostics are presently installed on the plasma device. They included a RF compensated Langmuir probe which is used to measure both electron temperature and plasma density. A spectrometer which features a 0.33 m Criss-Cross Scanning monochromator and a CCD camera is used for spectroscopy studies of the plasma.

  17. Electron Temperature Measurements on BCTX using Thomson Scattering

    NASA Astrophysics Data System (ADS)

    Morse, E.; Coomer, E.

    1997-11-01

    The Berkeley Compact Toroid Experiment (BCTX) is a spheromak configuration with a 70 cm diameter flux conserver. Studies have been undertaken to determine the core energy transport in the spheromak by investigation of the scaling of the core electron temperature (as measured by single point Thomson scattering) with various parameters. Elevated temperatures have been observed with lower core electron densities, as observed by the Thomson system. Careful studies of the magnetic decay have been undertaken using ten edge magnetic field B -dot coils. Density control has been achieved using a Penning discharge mode for the initial gas breakdown in the Marshall gun. A 20 MW lower hybrid heating pulse ( 430 MHz ) was used to study tranisent heating effects on the core plasma. Methods of controlling breakdown at the antenna will be presented, along with data for RF-heated plasma experiments. Comparison with recent theoretical work on spheromak energy transport by T. K. Fowler will be presented.

  18. The Empowerment of Plasma Modeling by Fundamental Electron Scattering Data

    NASA Astrophysics Data System (ADS)

    Kushner, Mark J.

    2015-09-01

    Modeling of low temperature plasmas addresses at least 3 goals - investigation of fundamental processes, analysis and optimization of current technologies, and prediction of performance of as yet unbuilt systems for new applications. The former modeling may be performed on somewhat idealized systems in simple gases, while the latter will likely address geometrically and electromagnetically intricate systems with complex gas mixtures, and now gases in contact with liquids. The variety of fundamental electron and ion scattering data (FSD) required for these activities increases from the former to the latter, while the accuracy required of that data probably decreases. In each case, the fidelity, depth and impact of the modeling depends on the availability of FSD. Modeling is, in fact, empowered by the availability and robustness of FSD. In this talk, examples of the impact of and requirements for FSD in plasma modeling will be discussed from each of these three perspectives using results from multidimensional and global models. The fundamental studies will focus on modeling of inductively coupled plasmas sustained in Ar/Cl2 where the electron scattering from feed gases and their fragments ultimately determine gas temperatures. Examples of the optimization of current technologies will focus on modeling of remote plasma etching of Si and Si3N4 in Ar/NF3/N2/O2 mixtures. Modeling of systems as yet unbuilt will address the interaction of atmospheric pressure plasmas with liquids Work was supported by the US Dept. of Energy (DE-SC0001939), National Science Foundation (CHE-124752), and the Semiconductor Research Corp.

  19. Helical temperature perturbations associated with tearing modes in tokamak plasmas

    SciTech Connect

    Fitzpatrick, R.

    1994-06-01

    An investigation is made into the electron temperature perturbations associated with tearing modes in tokamak plasmas, with a view to determining the mode structure using Electron Cyclotron Emission (ECE) data. It is found that there is a critical magnetic island width below which the conventional picture where the temperature is flattened inside the separatrix is invalid. This effect comes about because of the stagnation of magnetic field lines in the vicinity of the rational surface and the finite parallel thermal conductivity of the plasma. For islands whose widths lie below the critical value there is no flattening of the electron temperature inside the separatrix. Such islands have quite different ECE signatures to conventional magnetic islands. In fact the two island types could, in principle, be differentiated experimentally. It should also be possible to map out the outer ideal magnetohydrodynamical eigenfunctions using ECE data. Islands whose widths are much less than the critical value are not destabilized by the perturbed bootstrap current, unlike conventional magnetic islands. This effect is found to have a number of very interesting consequences and may, indeed, provide an explanation for some puzzling experimental results regarding error field induced magnetic reconnection. All islands whose widths are much greater than the critical width possess a boundary layer on the separatrix which enables heat to be transported from one side of the island to the other via the X-point region. The structure of this boundary layer is described in some detail. Finally, the critical island width is found to be fairly substantial in conventional tokamak plasmas, provided that the long mean free path nature of parallel heat transport and the anomalous nature of perpendicular heat transport are taken into account in the calculation.

  20. Cold pulse experiments in plasma with an electron internal transport barrier on LHD

    NASA Astrophysics Data System (ADS)

    Inagaki, S.; Ida, K.; Tamura, N.; Shimozuma, T.; Kubo, S.; Nagayama, Y.; Kawahata, K.; Sudo, S.; Ohkubo, K.; LHD Experimental Group

    2004-05-01

    Transient transport experiments are performed in LHD plasma with electron internal transport barrier (e-ITB). Evidence for a reduction of electron heat diffusivity inside the ITB is observed from cold and heat pulse propagations. The observed enhancement of the cold pulse peak is explained by the temperature dependent electron heat diffusivity. The heat diffusivity inside the ITB decreases with an increase in the electron temperature in LHD. A preliminary version of this study was presented in the 29th EPS Conf. on Plasma Phys. and Control. Fusion (Montreux, Switzerland, 17 21 June 2002) [1].

  1. The behavior of the electron plasma boundary in ultraintense laser–highly overdense plasma interaction

    SciTech Connect

    Sánchez-Arriaga, G.; Sanz, J.; Debayle, A.; Lehmann, G.

    2014-12-15

    The structural stability of the laser/plasma interaction is discussed, for the case of a linearly polarized laser beam interacting with a solid at normal incidence. Using a semi-analytical cold fluid model, the dynamics of the electron plasma boundary (EPB), usually related to the high-order harmonic generation and laser absorption, are presented. While the well-known J × B plasma oscillations at two times the laser frequency are recovered by the model, several other periodic in time stable solutions exist for exactly the same value of the physical parameters. This novel behavior highlights the importance of the laser pulse history among other factors. Some important features, such as the synchronization between the incident laser and the EPB oscillation, depend on the solution under consideration. A description of the possible types of stable oscillations in a parametric plane involving plasma density and laser amplitude is presented. The semi-analytical model is compared with particle-in-cell and semi-Lagrangian Vlasov simulations. They show that, among all the stable solutions, the plasma preferentially evolves to a state with the EPB oscillating twice faster than the laser. The effect of the plasma temperature and the existence of a ramp in the ion density profile are also discussed.

  2. 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.

  3. Plasma temperature rise toward the plasma-facing surface

    NASA Astrophysics Data System (ADS)

    Nishijima, D.; Doerner, R. P.; Seraydarian, R. P.; De Temmerman, G.; van der Meiden, H. J.

    2015-08-01

    Detailed measurements of axial electron temperature, Te, profiles in the presheath region were carried out using a Langmuir probe and the line intensity ratio technique for both He I (728.1 nm/706.5 nm) and Be II (467.3 nm/313.1 nm). The results show that Te increases toward the material surface, which contradicts the standard picture that Te is constant along the magnetic field in the sheath-limited regime. While no target bias voltage, Vb, dependence is seen, the Te rise becomes more prominent with decreasing neutral pressure. Similarly, the ion temperature, Ti, evaluated from Doppler broadening of a He II line emission at 468.6 nm is found to increase toward the surface, but also does not depend on Vb. Possible mechanisms of the Te and Ti rise as well as validity of the line intensity ratio technique near the material surface are discussed.

  4. Generation of anomalously energetic suprathermal electrons by an electron beam interacting with a nonuniform plasma

    SciTech Connect

    Sydorenko, D.; Kaganovich, I. D.; Chen, L.; Ventzek, P. L. G.

    2015-12-15

    Generation of anomalously energetic suprathermal electrons was observed in simulation of a high-voltage dc discharge with electron emission from the cathode. An electron beam produced by the emission interacts with the nonuniform plasma in the discharge via a two-stream instability. The energy transfer from the beam to the plasma electrons is ensured by the plasma nonuniformity. The electron beam excites plasma waves whose wavelength and phase speed gradually decrease towards anode. The waves with short wavelength near the anode accelerate plasma bulk electrons to suprathermal energies. The sheath near the anode reflects some of the accelerated electrons back into the plasma. These electrons travel through the plasma, reflect near the cathode, and enter the accelerating area again but with a higher energy than before. Such particles are accelerated to energies much higher than after the first acceleration. This mechanism plays a role in explaining earlier experimental observations of energetic suprathermal electrons in similar discharges.

  5. Characteristics of wall sheath and secondary electron emission under different electron temperature in Hall thruster

    NASA Astrophysics Data System (ADS)

    Duan, Ping; Qin, Haijuan; Cao, Anning; Zhou, Xinwei; Chen, Long; Gao, Hong

    2013-09-01

    Characteristics of discharge channel wall plasma sheath in Hall thruster have great effects on its performance. In this paper, we establish a two-dimensional physical model in Hall thruster sheath area to investigate the influences of the different electron temperature, propellant and particle weight on sheath potential and secondary electron emission in Hall thruster, by the method of Particle In Cell (PIC) simulation. And the electric field at the particle position is obtained by solving the Poisson's equation. The numerical results show that when the electron temperature is low, the change of sheath potential drop is bigger than that with electrons at high temperature, the surface potential maintains a stable value and the stability of the sheath is good. When the electron temperature is high, the surface potential maintains persistent oscillation, and the stability of the sheath is reduced. Along with the increase of electron temperature, the coefficient of secondary electron emission in wall reduce after the first increasing. For three kinds of propellant (Ar, Kr, Xe), with the increase of ion mass, sheath potential and the secondary electron emission coefficient in turn reduce.

  6. Density and temperature scaling of disorder-induced heating in ultracold plasmas

    SciTech Connect

    Bergeson, S. D.; Denning, A.; Lyon, M.; Robicheaux, F.

    2011-02-15

    We report measurements and simulations of disorder-induced heating in ultracold neutral plasmas. Fluorescence from plasma ions is excited using a detuned probe laser beam while the plasma relaxes from its initially disordered nonequilibrium state. This method probes the wings of the ion velocity distribution. The simulations yield information on time-evolving plasma parameters that are difficult to measure directly and make it possible to connect the fluorescence signal to the rms velocity distribution. The disorder-induced heating signal can be used to estimate the electron and ion temperatures {approx}100 ns after the plasma is created. This is particularly interesting for plasmas in which the electron and ion temperatures are not known.

  7. Electron Cyclotron Current Drive at High Electron Temperature on DIII-D

    SciTech Connect

    Petty, C. C.; Lohr, J.; Luce, T. C.; Prater, R.; Austin, M. E.; Harvey, R. W.; Makowski, M. A.

    2007-09-28

    Experiments on DIII-D have measured the electron cyclotron current drive (ECCD) efficiency for co- and counter-injection in low density plasmas with radiation temperatures from electron cyclotron emission (ECE) above 20 keV. The radiation temperature is generally higher than the Thomson scattering temperature, indicating that there is a significant population of non-thermal electrons. The experimental ECCD profile measured with motional Stark effect (MSE) polarimetry is found to agree with quasi-linear theory except for the highest power density cases (Q{sub EC}/n{sub e}{sup 2}>>1). Radial transport of the energetic electrons with diffusion coefficients of {approx}0.4 m{sup 2}/s is needed to model the broadened ECCD profile at high power density.

  8. The effect of quantum correction on plasma electron heating in ultraviolet laser interaction

    SciTech Connect

    Zare, S.; Sadighi-Bonabi, R. Anvari, A.; Yazdani, E.; Hora, H.

    2015-04-14

    The interaction of the sub-picosecond UV laser in sub-relativistic intensities with deuterium is investigated. At high plasma temperatures, based on the quantum correction in the collision frequency, the electron heating and the ion block generation in plasma are studied. It is found that due to the quantum correction, the electron heating increases considerably and the electron temperature uniformly reaches up to the maximum value of 4.91 × 10{sup 7 }K. Considering the quantum correction, the electron temperature at the laser initial coupling stage is improved more than 66.55% of the amount achieved in the classical model. As a consequence, by the modified collision frequency, the ion block is accelerated quicker with higher maximum velocity in comparison with the one by the classical collision frequency. This study proves the necessity of considering a quantum mechanical correction in the collision frequency at high plasma temperatures.

  9. Inactivation of Microcystis aeruginosa using dielectric barrier discharge low-temperature plasma

    NASA Astrophysics Data System (ADS)

    Pu, Sichuan; Chen, Jierong; Wang, Gang; Li, Xiaoyong; Ma, Yun

    2013-05-01

    The efficiency of Microcystis aeruginosa plasma inactivation was investigated using dielectric barrier discharge low-temperature plasma. The inactivation efficiency was characterized in terms of optical density. The influence of electrical and physicochemical parameters on M. aeruginosa inactivation was studied to determine the optimal experimental conditions. The influence of active species was studied. The proliferation of the M. aeruginosa cells was significantly decreased under plasma exposure. The morphologic changes in M. aeruginosa were characterized under scanning electron microscopy. These results suggest that the low-temperature plasma technology is a promising method for water pollution control.

  10. Inactivation of Microcystis aeruginosa using dielectric barrier discharge low-temperature plasma

    SciTech Connect

    Pu, Sichuan; Chen, Jierong; Wang, Gang; Li, Xiaoyong; Ma, Yun

    2013-05-13

    The efficiency of Microcystis aeruginosa plasma inactivation was investigated using dielectric barrier discharge low-temperature plasma. The inactivation efficiency was characterized in terms of optical density. The influence of electrical and physicochemical parameters on M. aeruginosa inactivation was studied to determine the optimal experimental conditions. The influence of active species was studied. The proliferation of the M. aeruginosa cells was significantly decreased under plasma exposure. The morphologic changes in M. aeruginosa were characterized under scanning electron microscopy. These results suggest that the low-temperature plasma technology is a promising method for water pollution control.

  11. Advanced simulation of electron heat transport in fusion plasmas

    SciTech Connect

    Lin, Zhihong; Xiao, Y.; Klasky, Scott A; Lofstead, J.

    2009-01-01

    Electron transport in burning plasmas is more important since fusion products first heat electrons. First-principles simulations of electron turbulence are much more challenging due to the multi-scale dynamics of the electron turbulence, and have been made possible by close collaborations between plasma physicists and computational scientists. The GTC simulations of collisionless trapped electron mode (CTEM) turbulence show that the electron heat transport exhibits a gradual transition from Bohm to gyroBohm scaling when the device size is increased. The deviation from the gyroBohm scaling can be induced by large turbulence eddies, turbulence spreading, and non-diffusive transport processes. Analysis of radial correlation function shows that CTEM turbulence eddies are predominantly microscopic but with a significant tail in the mesoscale. A comprehensive analysis of kinetic and fluid time scales shows that zonal flow shearing is the dominant decorrelation mechanism. The mesoscale eddies result from a dynamical process of linear streamers breaking by zonal flows and merging of microscopic eddies. The radial profile of the electron heat conductivity only follows the profile of fluctuation intensity on a global scale, whereas the ion transport tracks more sensitively the local fluctuation intensity. This suggests the existence of a nondiffusive component in the electron heat flux, which arises from the ballistic radial E x B drift of trapped electrons due to a combination of the presence of mesoscale eddies and the weak de-tuning of the toroidal precessional resonance that drives the CTEM instability. On the other hand, the ion radial excursion is not affected by the mesoscale eddies due to a parallel decorrelation, which is not operational for the trapped electrons because of a bounce averaging process associated with the electron fast motion along magnetic field lines. The presence of the nondiffusive component raises question on the applicability of the usual

  12. Advanced Simulation of Electron Heat Transport in Fusion Plasmas

    SciTech Connect

    Lin, Z.; Xiao, Y.; Holod, I.; Zhang, W. L.; Deng, Wenjun; Klasky, Scott A; Lofstead, J.; Kamath, Chandrika; Wichmann, Nathan

    2009-01-01

    Electron transport in burning plasmas is more important since fusion products first heat electrons. First-principles simulations of electron turbulence are much more challenging due to the multi-scale dynamics of the electron turbulence, and have been made possible by close collaborations between plasma physicists and computational scientists. The GTC simulations of collisionless trapped electron mode (CTEM) turbulence show that the electron heat transport exhibits a gradual transition from Bohm to gyroBohm scaling when the device size is increased. The deviation from the gyroBohm scaling can be induced by large turbulence eddies, turbulence spreading, and non-diffusive transport processes. Analysis of radial correlation function shows that CTEM turbulence eddies are predominantly microscopic but with a significant tail in the mesoscale. A comprehensive analysis of kinetic and fluid time scales shows that zonal flow shearing is the dominant decorrelation mechanism. The mesoscale eddies result from a dynamical process of linear streamers breaking by zonal flows and merging of microscopic eddies. The radial profile of the electron heat conductivity only follows the profile of fluctuation intensity on a global scale, whereas the ion transport tracks more sensitively the local fluctuation intensity. This suggests the existence of a nondiffusive component in the electron heat flux, which arises from the ballistic radial E x B drift of trapped electrons due to a combination of the presence of mesoscale eddies and the weak de-tuning of the toroidal precessional resonance that drives the CTEM instability. On the other hand, the ion radial excursion is not affected by the mesoscale eddies due to a parallel decorrelation, which is not operational for the trapped electrons because of a bounce averaging process associated with the electron fast motion along magnetic field lines. The presence of the nondiffusive component raises question on the applicability of the usual

  13. Electron plasma dynamics during autoresonant excitation of the diocotron mode

    SciTech Connect

    Baker, C. J. Danielson, J. R. Hurst, N. C. Surko, C. M.

    2015-02-15

    Chirped-frequency autoresonant excitation of the diocotron mode is used to move electron plasmas confined in a Penning-Malmberg trap across the magnetic field for advanced plasma and antimatter applications. Plasmas of 10{sup 8} electrons, with radii small compared to that of the confining electrodes, can be moved from the magnetic axis to ≥90% of the electrode radius with near unit efficiency and reliable angular positioning. Translations of ≥70% of the wall radius are possible for a wider range of plasma parameters. Details of this process, including phase and displacement oscillations in the plasma response and plasma expansion, are discussed, as well as possible extensions of the technique.

  14. Electronic ceramics in high temperature environments

    SciTech Connect

    Searcy, A.W.; Meschi, D.J.

    1980-11-01

    Simple thermodynamic means are described for understanding and predicting the influence of temperature changes in various environments on electronic properties of ceramics. Thermal gradients, thermal cycling and vacuum annealing are discussed, as well as the variations of activities and solubilities with temperature.

  15. Picosecond imaging of low-density plasmas by electron deflectometry.

    PubMed

    Centurion, M; Reckenthaeler, P; Krausz, F; Fill, E E

    2009-02-15

    We have imaged optical-field ionized plasmas with electron densities as low as 10(13) cm(-3) on a picosecond timescale using ultrashort electron pulses. Electric fields generated by the separation of charges are imprinted on a 20 keV probe electron pulse and reveal a cloud of electrons expanding away from a positively charged plasma core. Our method allows for a direct measurement of the electron energy required to escape the plasma and the total charge. Simulations reproduce the main features of the experiment and allow determination of the energy of the electrons. PMID:19373367

  16. Positron plasma diagnostics and temperature control for antihydrogen production.

    PubMed

    Amoretti, M; Amsler, C; Bonomi, G; Bouchta, A; Bowe, P D; Carraro, C; Cesar, C L; Charlton, M; Doser, M; Filippini, V; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Jørgensen, L V; Lagomarsino, V; Landua, R; Lindelöf, D; Rizzini, E Lodi; Macrí, M; Madsen, N; Manuzio, G; Montagna, P; Pruys, H; Regenfus, C; Rotondi, A; Testera, G; Variola, A; van der Werf, D P

    2003-08-01

    Production of antihydrogen atoms by mixing antiprotons with a cold, confined, positron plasma depends critically on parameters such as the plasma density and temperature. We discuss nondestructive measurements, based on a novel, real-time analysis of excited, low-order plasma modes, that provide comprehensive characterization of the positron plasma in the ATHENA antihydrogen apparatus. The plasma length, radius, density, and total particle number are obtained. Measurement and control of plasma temperature variations, and the application to antihydrogen production experiments are discussed. PMID:12906600

  17. Deep Trek High Temperature Electronics Project

    SciTech Connect

    Bruce Ohme

    2007-07-31

    This report summarizes technical progress achieved during the cooperative research agreement between Honeywell and U.S. Department of Energy to develop high-temperature electronics. Objects of this development included Silicon-on-Insulator (SOI) wafer process development for high temperature, supporting design tools and libraries, and high temperature integrated circuit component development including FPGA, EEPROM, high-resolution A-to-D converter, and a precision amplifier.

  18. Electron dynamics and ion acceleration in expanding-plasma thrusters

    NASA Astrophysics Data System (ADS)

    Lafleur, T.; Cannat, F.; Jarrige, J.; Elias, P. Q.; Packan, D.

    2015-12-01

    In most expanding-plasma thrusters, ion acceleration occurs due to the formation of ambipolar-type electric fields; a process that depends strongly on the electron dynamics of the discharge. The electron properties also determine the heat flux leaving the thruster as well as the maximum ion energy, which are important parameters for the evaluation of thruster performance. Here we perform an experimental and theoretical investigation with both magnetized, and unmagnetized, low-pressure thrusters to explicitly determine the relationship between the ion energy, E i , and the electron temperature, T e0. With no magnetic field a relatively constant value of {{E}i}/{{T}e0}≈ 6 is found for xenon, while when a magnetic nozzle is present, {{E}i}/{{T}e0} is between about 4-5. These values are shown to be a function of both the magnetic field strength, as well as the electron energy distribution function, which changes significantly depending on the mass flow rate (and hence neutral gas pressure) used in the thruster. The relationship between the ion energy and electron temperature allows estimates to be made for polytropic indices of use in a number of fluid models, as well as estimates of the upper limits to the performance of these types of systems, which for xenon and argon result in maximum specific impulses of about 2500 s and 4500 s respectively.

  19. Dust-ion-acoustic solitons in plasmas with non-Maxwellian electron distribution function

    SciTech Connect

    Pajouh, H. Hakimi; Abbasi, H.

    2008-10-15

    Stationary dust-ion-acoustic (DIA) solitons in plasma with non-Maxwellian electron distribution function (DF) are studied. This is an important issue in low-pressure electrical gas discharges that the particle DF is generally non-Maxwellian. In the discharge plasmas, the electron temperature is usually much greater than the ion temperature. Thus, neglecting the ions velocity distribution, the electron DF is modeled by the generalized Lorentzian ({kappa})-DF. The formalism is derived near the ion-plasma frequency. In this range of frequency, the ion dynamics is considerable and the dust-ion-acoustic solitons are the stationary solution of the governing equations. Electron trapping is included in the model as the result of nonlinear resonant interaction of the DIA soliton with electrons. The solitons attributes and influence of the non-Maxwellian electrons are studied.

  20. Secondary electron emission and the bifurcation of the heat flux to the targets in fusion plasmas

    SciTech Connect

    Lee, Wonjae; Krasheninnikov, Sergei I.

    2013-12-15

    The presence of secondary electron emission (SEE) from plasma facing components in fusion devices can result in a strong localization of the heat flux from plasma to the wall and subsequent wall erosion. Usually, the impact of the SEE is considered assuming the Maxwellian distribution of the electrons coming to the surface. As a result, the SEE coefficient only depends on the temperature of primary electrons. However, the tail of primary electron distribution function in the scrape off layer (SOL) of fusion devices can be far from Maxwellian due to preferential loss of fast electrons. Consequently, it is shown that the SEE coefficient will depend on the wall potential and multiple solutions can be possible corresponding to different regimes of plasma flow to the wall: with and without SEE effects. This effect can cause two-slope electron temperature profiles in the SOL, which are often seen in experiments.

  1. Measuring electron temperature in the extended corona

    NASA Technical Reports Server (NTRS)

    Hassler, Donald M.; Gardner, L. D.; Kohl, John L.

    1992-01-01

    A technique for measuring electron temperature in the extended corona from the line profile of the electron scattered component of coronal H I Ly alpha produced by Thomson scattering of chromospheric Ly alpha emission is discussed. Because of the high thermal velocity of electrons at coronal temperatures (approximately 6800 km/s at T(sub e) = 1,500,000 K) the effect of nonthermal velocities and solar wind flows on the electron velocity distribution are negligible. However, the low electron mass which is responsible for the high thermal velocity also results in a very wide profile (approximately equal to 50 A). This wide profile, together with an intensity that is three orders of magnitude weaker than the resonantly scattered component of Ly alpha makes the direct measurement of T(sub e) a challenging observational problem. An evaluation of this technique based on simulated measurements is presented and the subsequent instrumental requirements necessary to make a meaningful determination of the electron temperature are discussed. Estimates of uncertainties in the measured electron temperature are related to critical instrument parameters such as grating stray light suppression.

  2. Existence of a virtual cathode close to a strongly electron emissive wall in low density plasmas

    NASA Astrophysics Data System (ADS)

    Tierno, S. P.; Donoso, J. M.; Domenech-Garret, J. L.; Conde, L.

    2016-01-01

    The interaction between an electron emissive wall, electrically biased in a plasma, is revisited through a simple fluid model. We search for realistic conditions of the existence of a non-monotonic plasma potential profile with a virtual cathode as it is observed in several experiments. We mainly focus our attention on thermionic emission related to the operation of emissive probes for plasma diagnostics, although most conclusions also apply to other electron emission processes. An extended Bohm criterion is derived involving the ratio between the two different electron densities at the potential minimum and at the background plasma. The model allows a phase-diagram analysis, which confirms the existence of the non-monotonic potential profiles with a virtual cathode. This analysis shows that the formation of the potential well critically depends on the emitted electron current and on the velocity at the sheath edge of cold ions flowing from the bulk plasma. As a consequence, a threshold value of the governing parameter is required, in accordance to the physical nature of the electron emission process. The latter is a threshold wall temperature in the case of thermionic electrons. Experimental evidence supports our numerical calculations of this threshold temperature. Besides this, the potential well becomes deeper with increasing electron emission, retaining a fraction of the released current which limits the extent of the bulk plasma perturbation. This noninvasive property would explain the reliable measurements of plasma potential by using the floating potential method of emissive probes operating in the so-called strong emission regime.

  3. Cavity Enhanced Thomson Scattering for Low Temperature Plasmas

    NASA Astrophysics Data System (ADS)

    Yalin, Azer; Friss, Adam; Lee, Brian; Franka, Isaiah

    2013-09-01

    This contribution describes the design, simulation, and initial experimental development of a novel laser Thomson scattering (LTS) system for measurement of weakly-ionized low temperature plasmas. The LTS approach uses a high power intra-cavity beam of power ~10-100 kW to provide increased scattered photon counts and sensitivity as compared to conventional LTS experiments that use light sources with orders of magnitude lower average power. The high power intra-cavity beam is generated by locking a narrow linewidth source laser to a high-finesse optical cavity via Pound-Drever-Hall locking. The plasma (to be studied) is housed with the high-finesse optical cavity. The high-power source is combined with a detection system comprised of a high-suppression triple monochromator and a low-noise photomultiplier tube used in photon counting mode. We present simulations of signal strengths and scattering spectra including elastic scatter background, detector dark counts, and random (counting) noise contributions. Expected experimental performance is assessed from fits to the simulated data. The number density and electron temperature of a 1010 cm-3 plasma should be accurately measurable with standard deviation of <5% in a measurement time of 5 minutes per wavelength channel. We also present experimental development including characterization of laser locking, and initial Rayleigh and Raman signals which will be used to calibrate the Thomson system.

  4. Low-Temperature Electronic Components Being Developed

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Hammond, Ahmad

    1999-01-01

    In many future NASA missions, such as deep space planetary exploration and the Next Generation Space Telescope, electrical components and systems must operate reliably and efficiently in extremely low temperature environments. Most modern electronic components cannot operate below moderately low operating temperatures (-40 to -55 C). The low-temperature electronics program at the NASA Lewis Research Center is focusing on the development and characterization of low-temperature components and the integration of the developed devices into demonstrable very low-temperature (-200 C) power systems such as dc-dc converters. Such low-temperature electronics will not only tolerate hostile environments but also will reduce system size and weight by eliminating radioisotope heating units, thereby reducing launch cost, improving reliability and lifetime, and increasing energy densities. Low-temperature electronic components will also have a great influence on terrestrial applications such as medical instrumentation, magnetic levitation transportation systems, and arctic and antarctic exploration. Lewis researchers are now performing extensive evaluations of commercially available as well as custom-made devices. These include various types of energy storage and signal capacitors, power switching devices, magnetic and superconducting materials, and primary lithium batteries, to name a few.

  5. Two dimensional electrostatic shock waves in relativistic electron positron ion plasmas

    SciTech Connect

    Masood, W.; Rizvi, H.

    2010-05-15

    Ion-acoustic shock waves (IASWs) are studied in an unmagnetized plasma consisting of electrons, positrons and hot ions. In this regard, Kadomtsev-Petviashvili-Burgers (KPB) equation is derived using the small amplitude perturbation expansion method. The dependence of the IASWs on various plasma parameters is numerically investigated. It is observed that ratio of ion to electron temperature, kinematic viscosity, positron concentration, and the relativistic ion streaming velocity affect the structure of the IASW. Limiting case of the KPB equation is also discussed. Stability of KPB equation is also presented. The present investigation may have relevance in the study of electrostatic shock waves in relativistic electron-positron-ion plasmas.

  6. Fundamentals and applications of a plasma-processing system based on electron-beam ionization

    SciTech Connect

    Leonhardt, D.; Walton, S. G.; Fernsler, R. F.

    2007-05-15

    Plasmas generated from moderate energy (2-5 keV) electron beams (e-beam) have unique, attractive characteristics that are ideal for materials processing applications. These plasmas possess low electron temperatures (<0.5 eV), variable plasma densities (10{sup 9}-10{sup 12} cm{sup -3}) with an improved control of plasma species generation, and perhaps most importantly, a direct scalability to processing areas exceeding one square meter. These characteristics are due to the plasma ionization being driven by the e-beam instead of an external electromagnetic field as used in conventional processing plasma sources. Theoretical and experimental system details are discussed in terms of plasma operating conditions applied to three different surface modification approaches: metal nitriding, negative ion etching, and polymer surface energy tailoring.

  7. Electron density measurement of inductively coupled plasmas by terahertz time-domain spectroscopy (THz-TDS)

    SciTech Connect

    Ando, Ayumi; Kurose, Tomoko; Kitano, Katsuhisa; Hamaguchi, Satoshi; Reymond, Vivien; Kitahara, Hideaki; Takano, Keisuke; Hangyo, Masanori; Tani, Masahiko

    2011-10-01

    The electron densities of argon inductively coupled plasmas were measured by terahertz time-domain spectroscopy (THz-TDS). At a low pressure, the electron densities were also measured with a Langmuir-type double probe and the validity of THz-TDS electron-density measurement in a plasma has been corroborated. As the input radio-frequency (RF) power increases, the plasma density and gas temperature increase, which makes the probe measurement less reliable or even impossible, due to the large heat load to the probe surface. On the contrary, the THz-TDS measurement is unaffected by the gas temperature and becomes more reliable due to the higher electron density at higher input power for plasma generation.

  8. Microwave plasma burner and temperature measurements in its flames

    SciTech Connect

    Hong, Yong Cheol; Cho, Soon Cheon; Bang, Chan Uk; Shin, Dong Hun; Kim, Jong Hun; Uhm, Han Sup; Yi, Won Ju

    2006-05-15

    An apparatus for generating flames and more particularly the microwave plasma burner for generating high-temperature large-volume plasma flame was presented. The plasma burner is operated by injecting liquid hydrocarbon fuels into a microwave plasma torch in air discharge and by mixing the resultant gaseous hydrogen and carbon compounds with air or oxygen gas. The microwave plasma torch can instantaneously vaporize and decompose the hydrogen and carbon containing fuels. It was observed that the flame volume of the burner was more than 50 times that of the torch plasma. While the temperature of the torch plasma flame was only 550 K at a measurement point, that of the plasma-burner flame with the addition of 0.025 lpm (liters per minute) kerosene and 20 lpm oxygen drastically increased to about 1850 K. A preliminary experiment was carried out, measuring the temperature profiles of flames along the radial and axial directions.

  9. Plasma Cleaning and Its Applications for Electron Microscopy

    NASA Astrophysics Data System (ADS)

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

    1999-03-01

    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 of existing carbon contamination debris due to previously conducted microanalysis is shown. Following plasma cleaning, specimens may be examined in the electron microscope for several hours without exhibiting evidence of recontamination. The effectiveness of plasma cleaning is not limited to applications for TEM specimens. Scanning electron microscopy (SEM) specimens that have been plasma cleaned likewise show an elimination of carbonaceous contamination. Furthermore, other electron microscopy parts and accessories, such as aperture strips, specimen clamping rings, and Wehnelts, among others, can benefit from plasma cleaning.

  10. Electronics Demonstrated for Low- Temperature Operation

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Hammond, Ahmad; Gerber, Scott S.

    2000-01-01

    The operation of electronic systems at cryogenic temperatures is anticipated for many NASA spacecraft, such as planetary explorers and deep space probes. For example, an unheated interplanetary probe launched to explore the rings of Saturn would experience an average temperature near Saturn of about 183 C. Electronics capable of low-temperature operation in the harsh deep space environment also would help improve circuit performance, increase system efficiency, and reduce payload development and launch costs. An ongoing research and development program on low-temperature electronics at the NASA Glenn Research Center at Lewis Field is focusing on the design of efficient power systems that can survive and exploit the advantages of low-temperature environments. The targeted systems, which are mission driven, include converters, inverters, controls, digital circuits, and special-purpose circuits. Initial development efforts successfully demonstrated the low-temperature operation and cold-restart of several direct-current/direct-current (dc/dc) converters based on different types of circuit design, some with superconducting inductors. The table lists some of these dc/dc converters with their properties, and the photograph shows a high-voltage, high-power dc/dc converter designed for an ion propulsion system for low-temperature operation. The development efforts of advanced electronic systems and the supporting technologies for low-temperature operation are being carried out in-house and through collaboration with other Government agencies, industry, and academia. The Low Temperature Electronics Program supports missions and development programs at NASA s Jet Propulsion Laboratory and Goddard Space Flight Center. The developed technologies will be transferred to commercial end users for applications such as satellite infrared sensors and medical diagnostic equipment.

  11. Effect of re-heating on the hot electron temperature

    SciTech Connect

    Estabrook, K.; Rosen, M.

    1980-06-17

    Resonant absorption is the direct conversion of the transverse laser light to longitudinal electron plasma waves (epw) at the critical density (10/sup 21/ (1.06 ..mu..m/lambda/sub 0/)/sup 2/ cm/sup -3/). The oscillating longitudinal electric field of the epw heats the electrons by accelerating them down the density gradient to a temperature of approximately 21T/sub e//sup 0/ /sup 25/ ((I(W/cm/sup 2/)/10/sup 16/)(lambda/sub 0//1.06 ..mu..m)/sup 2/)/sup 0/ /sup 4/. This section extends the previous work by studying the effects of magnetic fields and collisions (albedo) which return the heated electrons for further heating. A magnetic field increases their temperature and collisions do not.

  12. Analysis of Electron Trajectories in Magnetized High Power Plasmas

    NASA Astrophysics Data System (ADS)

    Krueger, Dennis; Gallian, Sara; Trieschmann, Jan; Brinkmann, Ralf Peter

    2015-09-01

    High Power Impulse Magnetron Sputtering (HiPIMS) is an important example of magnetized technological plasmas. With HiPIMS the focus lies on the generation of a high density plasma with a remarkably high degree of ionization. It can be used for the deposition of thin films with superior density and quality. Theoretical approaches to the regime of magnetized low temperature plasmas encounter some fundamental difficulties, for example concerning the details of the magnetic field configuration, the strongly varying degree of magnetization, and the frequent wall interactions. A kinetic single particle model is used for the investigations. Single electron trajectories are analyzed with the widely used Boris algorithm within the magnetized zone above the target (racetrack). We further examine a configuration where symmetry breaking occurs due to a potential bump, which is rotating azimuthally around the racetrack (spoke). Observing the effects of this structure on the single electron motion may allow us to obtain further insight into this phenomenon. This work is supported by the German Research Foundation in the frame of the Collaborative Research Centre TRR 87.

  13. High-Temperature Passive Power Electronics

    NASA Technical Reports Server (NTRS)

    1997-01-01

    In many future NASA missions - such as deep-space exploration, the National AeroSpace Plane, minisatellites, integrated engine electronics, and ion or arcjet thrusters - high-power electrical components and systems must operate reliably and efficiently in high-temperature environments. The high-temperature power electronics program at the NASA Lewis Research Center focuses on dielectric and insulating material research, the development and characterization of high-temperature components, and the integration of the developed components into a demonstrable 200 C power system - such as an inverter. NASA Lewis has developed high-temperature power components through collaborative efforts with the Air Force Wright Laboratory, Northrop Grumman, and the University of Wisconsin. Ceramic and film capacitors, molypermalloy powder inductors, and a coaxially wound transformer were designed, developed, and evaluated for high-temperature operation.

  14. Performance of large electron energy filter in large volume plasma device

    SciTech Connect

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

    2014-03-15

    This paper describes an in-house designed large Electron Energy Filter (EEF) utilized in the Large Volume Plasma Device (LVPD) [S. K. Mattoo, V. P. Anita, L. M. Awasthi, and G. Ravi, Rev. Sci. Instrum. 72, 3864 (2001)] to secure objectives of (a) removing the presence of remnant primary ionizing energetic electrons and the non-thermal electrons, (b) introducing a radial gradient in plasma electron temperature without greatly affecting the radial profile of plasma density, and (c) providing a control on the scale length of gradient in electron temperature. A set of 19 independent coils of EEF make a variable aspect ratio, rectangular solenoid producing a magnetic field (B{sub x}) of 100 G along its axis and transverse to the ambient axial field (B{sub z} ∼ 6.2 G) of LVPD, when all its coils are used. Outside the EEF, magnetic field reduces rapidly to 1 G at a distance of 20 cm from the center of the solenoid on either side of target and source plasma. The EEF divides LVPD plasma into three distinct regions of source, EEF and target plasma. We report that the target plasma (n{sub e} ∼ 2 × 10{sup 11} cm{sup −3} and T{sub e} ∼ 2 eV) has no detectable energetic electrons and the radial gradients in its electron temperature can be established with scale length between 50 and 600 cm by controlling EEF magnetic field. Our observations reveal that the role of the EEF magnetic field is manifested by the energy dependence of transverse electron transport and enhanced transport caused by the plasma turbulence in the EEF plasma.

  15. Experimental investigation of ultraviolet laser induced plasma density and temperature evolution in air

    SciTech Connect

    Thiyagarajan, Magesh; Scharer, John

    2008-07-01

    We present measurements and analysis of laser induced plasma neutral densities and temperatures in dry air by focusing 200 mJ, 10 MW high power, 193 nm ultraviolet ArF (argon fluoride) laser radiation to a 30 {mu}m radius spot size. We examine these properties that result from multiphoton and collisional cascade processes for pressures ranging from 40 Torr to 5 atm. A laser shadowgraphy diagnostic technique is used to obtain the plasma electron temperature just after the shock front and this is compared with optical emission spectroscopic measurements of nitrogen rotational and vibrational temperatures. Two-color laser interferometry is employed to measure time resolved spatial electron and neutral density decay in initial local thermodynamic equilibrium (LTE) and non-LTE conditions. The radiating species and thermodynamic characteristics of the plasma are analyzed by means of optical emission spectroscopy (OES) supported by SPECAIR, a special OES program for air constituent plasmas. Core plasma rotational and vibrational temperatures are obtained from the emission spectra from the N{sub 2}C-B(2+) transitions by matching the experimental spectrum results with the SPECAIR simulation results and the results are compared with the electron temperature just behind the shock wave. The plasma density decay measurements are compared with a simplified electron density decay model that illustrates the dominant three-and two-body recombination terms with good correlation.

  16. Experimental investigation of ultraviolet laser induced plasma density and temperature evolution in air

    NASA Astrophysics Data System (ADS)

    Thiyagarajan, Magesh; Scharer, John

    2008-07-01

    We present measurements and analysis of laser induced plasma neutral densities and temperatures in dry air by focusing 200 mJ, 10 MW high power, 193 nm ultraviolet ArF (argon fluoride) laser radiation to a 30 μm radius spot size. We examine these properties that result from multiphoton and collisional cascade processes for pressures ranging from 40 Torr to 5 atm. A laser shadowgraphy diagnostic technique is used to obtain the plasma electron temperature just after the shock front and this is compared with optical emission spectroscopic measurements of nitrogen rotational and vibrational temperatures. Two-color laser interferometry is employed to measure time resolved spatial electron and neutral density decay in initial local thermodynamic equilibrium (LTE) and non-LTE conditions. The radiating species and thermodynamic characteristics of the plasma are analyzed by means of optical emission spectroscopy (OES) supported by SPECAIR, a special OES program for air constituent plasmas. Core plasma rotational and vibrational temperatures are obtained from the emission spectra from the N2C-B(2+) transitions by matching the experimental spectrum results with the SPECAIR simulation results and the results are compared with the electron temperature just behind the shock wave. The plasma density decay measurements are compared with a simplified electron density decay model that illustrates the dominant three-and two-body recombination terms with good correlation.

  17. Effects of electron temperature and electron flow on O-X conversion

    SciTech Connect

    Jia, Guo-Zhang; Gao, Zhe; Zhao, Ai-Hui

    2013-10-15

    Effects of electron temperature and electron flow on Ordinary-Extraordinary (O-X) conversion in the range of electron cyclotron frequency are investigated. The modified optimal parallel refraction index, N{sub zc}, and the conversion coefficient are obtained analytically from the kinetic dispersion relation. The presence of finite electron temperature shifts the O-X conversion layer towards a region of lower density and increases the value of N{sub zc}; while the effect of electron flow depends on its direction with respect to the parallel wave vector. When the electron flow is along the parallel wave vector, N{sub zc} will be increased and the effects of finite electron temperature and finite electron flow accumulate. As a result, a more oblique incidence angle is required for efficient O-X conversion. For typical Tokamak plasmas, the efficiency of O-X conversion will decrease without the consideration of the two effects. When the electron flow is in the direction opposite to the parallel wave vector, the two effects compete, even cancel each other.

  18. Integration issues of a plasma contactor Power Electronics Unit

    NASA Technical Reports Server (NTRS)

    Pinero, Luis R.; York, Kenneth W.; Bowers, Glen E.

    1995-01-01

    A hollow cathode-based plasma contactor is baselined on International Space Station Alpha (ISSA) for spacecraft charge control. The plasma contactor system consists of a hollow cathode assembly (HCA), a power electronics unit (PEU), and an expellant management unit (EMU). The plasma contactor has recently been required to operate in a cyclic mode to conserve xenon expellant and extend system life. Originally, a DC cathode heater converter was baselined for a continuous operation mode because only a few ignitions of the hollow cathode were expected. However, for cyclic operation, a DC heater supply can potentially result in hollow cathode heater component failure due to the DC electrostatic field. This can prevent the heater from attaining the proper cathode tip temperature for reliable ignition of the hollow cathode. To mitigate this problem, an AC cathode heater supply was therefore designed, fabricated, and installed into a modified PEU. The PEU was tested using resistive loads and then integrated with an engineering model hollow cathode to demonstrate stable steady-state operation. Integration issues such as the effect of line and load impedance on the output of the AC cathode heater supply and the characterization of the temperature profile of the heater under AC excitation were investigated.

  19. Temperature measurement systems in wearable electronics

    NASA Astrophysics Data System (ADS)

    Walczak, S.; Gołebiowski, J.

    2014-08-01

    The aim of this paper is to present the concept of temperature measurement system, adapted to wearable electronics applications. Temperature is one of the most commonly monitored factor in smart textiles, especially in sportswear, medical and rescue products. Depending on the application, measured temperature could be used as an initial value of alert, heating, lifesaving or analysis system. The concept of the temperature measurement multi-point system, which consists of flexible screen-printed resistive sensors, placed on the T-shirt connected with the central unit and the power supply is elaborated in the paper.

  20. Electron Temperature Measurements and Energy Transport in SSPX

    NASA Astrophysics Data System (ADS)

    Hudson, B. F.; Casper, T. A.; Hooper, E. B.; Jayakumar, R. J.; Lodestro, L. L.; McLean, H. S.; Moller, J. M.; Romero-Talamas, C. A.; Wood, R. D.

    2007-11-01

    Time-resolved measurements (<100 μs) have been made with a multi-pulse Thomson scattering diagnostic in the SSPX spheromak experiment, to obtain radial electron density and temperature profile during plasma formation and sustainment. In most discharges three regimes are observed with respect to Te and ne evolution. Initially there is a cold (<100 eV) formation phase, followed by a hollow Te profile with maximum temperatures 100-200 eV, and a final heat-up and cool-down phase where we obtain the highest plasma temperatures (350+ eV). The transition from hollow to peaked Te is quite sharp (˜50 μs) and the recent upgrade to double-pulse Thomson scattering (˜40 μs between pulses) facilitates capturing this transition. We also present simulations using the CORSICA code where the equilibrium is kept fixed and the discharge is evolved to observe the change in temperature profiles for different transport coefficients. In addition, electron transport and heating will be correlated with measured MHD mode activity. Temperature and density measurements during multi-pulse coaxial gun-current operation will also be presented. * Work performed under the auspices of the US DOE by University of California Lawrence Livermore National Laboratory under contract W--7405--ENG--48.

  1. Aperiodic ion temperature variations in the Io plasma torus

    NASA Astrophysics Data System (ADS)

    Eviatar, A.; Mekler, Y.

    1984-03-01

    The observed aperiodic variations of S III temperature reported by ground-based observers, which take place on time scales short in comparison with the radiation and electron collision relaxation times, are considered. It is suggested that ion-ion charge exchange processes are responsible for the heating and ion-atom collisions are the source of the cooling. The fluctuations are attributed to random strong variations in the output of neutral matter from the volcanoes and surface of Io. Freshly ionized sulfur that will have near full corotation gyro-energy will undergo charge exchange with thermal doubly ionized sulfur and oxygen, thus producing hot S III. Newly injected neutral atoms can cool the ambient hot plasma by collisions on a time scale comparable to their lifetime against ionization processes. Analytic solutions of the temperature rate equations, including the time variation of the neutral and ionized matter density are found to reproduce the observed fluctuations for reasonable values of initial densities.

  2. Integrated discharge scenario for high-temperature helical plasma in LHD

    NASA Astrophysics Data System (ADS)

    Nagaoka, K.; Takahashi, H.; Murakami, S.; Nakano, H.; Takeiri, Y.; Tsuchiya, H.; Osakabe, M.; Ida, K.; Yokoyama, M.; Yoshinuma, M.; Morita, S.; Goto, M.; Oishi, T.; Pablant, N.; Fujii, K.; Tanaka, K.; Tamura, N.; Nakamura, Y.; Du, X.; Ido, T.; Shimizu, A.; Kubo, S.; Igami, H.; Seki, R.; Suzuki, C.; Suzuki, Y.; Tsumori, K.; Ikeda, K.; Kisaki, M.; Yoshimura, Y.; Shimozuma, T.; Seki, T.; Saito, K.; Kasahara, H.; Kamio, S.; Mutoh, T.; Kaneko, O.; Yamada, H.; Komori, A.

    2015-09-01

    The discharge scenario of high temperature plasma with a helical configuration has significantly progressed. The increase of central ion temperature due to the reduction of wall recycling was clearly observed. The peaking of the ion heating profile and the reduction of charge exchange loss of energetic ions play an important role for further improvement of ion heat transport in the ion internal transport barrier (ITB) core. The ion ITB and electron ITB have been successfully integrated due to the superposition of centrally focused electron cyclotron heating to the ion ITB plasma, and the high temperature regime of the ion temperature comparable to the electron temperature (Ti ~ Te) has been significantly extended. The width of the ion ITB formed with electron ITB is wider than the width of electron ITB. The positive radial electric field was observed in the integrated ITB plasma by a heavy ion beam probe, while the negative radial electric field was observed in ion ITB plasmas. The ion temperature gradient decreases with the increase of the temperature ratio (Te /Ti).

  3. Electron-acoustic solitary waves in a nonextensive plasma

    SciTech Connect

    Tribeche, Mouloud; Djebarni, Lyes

    2010-12-15

    The problem of arbitrary amplitude electron-acoustic solitary waves (EASWs) in a plasma having cold fluid electrons, hot nonextensive electrons, and stationary ions is addressed. It is found that the 'Maxwellianization' process of the hot nonextensive component does not favor the propagation of the EASWs. In contrast to superthermality, nonextensivity makes the electron-acoustic solitary structure less spiky. Our theoretical analysis brings a possibility to develop more refined theories of nonlinear solitary structures in astrophysical plasmas.

  4. Radial Temperature Profile Measurements in a Microwave Plasma at Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Green, K. M.; Borras, M. C.; Flores, G. J., III; Woskov, P. P.; Hadidi, K.; Thomas, P.

    1998-11-01

    Radial profile measurements of the electronic excitation and rotational temperature are obtained for a Microwave Plasma Continuous Emissions Monitor (MP-CEM). The MP-CEM, employed in monitoring trace metals in furnace exhausts using atomic emission spectroscopy, operates at atmospheric pressure with air as the working gas. An iron solution is introduced into the plasma, and the intensity of the atomic emission spectrum of the Fe I excited levels is measured. The relative intensities of these lines give the electronic excitation temperature. Rotational temperatures are obtained through molecular emission spectroscopy in nitrogen plasmas. To collect the profile measurements, an optical detection system equipped with a collimator lens scans the plasma. By applying Abel inversion techniques to the integrated signals from the scanned plasma chords, the radial temperature profile is determined. For a plasma maintained at 1.5 kW by a 2.45 GHz microwave source with an axial flow of 10 scfh and a swirl flow of 20 scfh, a core electronic excitation temperature in air of 5300 K ± 600 K is measured, and a rotational temperature in nitrogen of 5100 K ± 300 K has been determined.

  5. 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.

  6. Vortex stabilized electron beam compressed fusion grade plasma

    SciTech Connect

    Hershcovitch, Ady

    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.

  7. Vortices, Reconnection and Turbulence in High Electron-Beta Plasmas

    SciTech Connect

    Stenzel, R. L.

    2004-08-31

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

  8. A relativistic solitary wave in electron-positron ion plasma

    SciTech Connect

    Berezhiani, V.I.; Mahajan, S.M. |

    1994-03-01

    The nonlinear propagation of circularly polarized electromagnetic (CPEM) waves with relativistically strong amplitude in an unmagnetized cold electron-positron ion plasma is investigated. The possibility of finding soliton solutions in such a plasma is explored. In one- and two-dimensions it is shown that the presence of a small fraction of massive ions in the plasma leads to stable localized solutions.

  9. Thermodiffusion of high-density electron-hole plasmas in semiconductors

    SciTech Connect

    Mahler, G.; Maier, G.; Forchel, A.; Laurich, B.; Sanwald, H.; Schmid, W.

    1981-12-21

    The spatial distributions of temperature and density in electron-hole plasmas in surface-excited semiconductors are investigated with use of linear irreversible thermodynamics and a microscopic plasma theory. Above a certain threshold the density distribution is dominated by a characteristic density, which increases with temperature. Experimental results for Ge, unstressed Si, and Si under high uniaxial stress are in agreement with the theory.

  10. Low-Temperature Power Electronics Program

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Dickman, John E.; Hammoud, Ahmad; Gerber, Scott

    1997-01-01

    Many space and some terrestrial applications would benefit from the availability of low-temperature electronics. Exploration missions to the outer planets, Earth-orbiting and deep-space probes, and communications satellites are examples of space applications which operate in low-temperature environments. Space probes deployed near Pluto must operate in temperatures as low as -229 C. Figure 1 depicts the average temperature of a space probe warmed by the sun for various locations throughout the solar system. Terrestrial applications where components and systems must operate in low-temperature environments include cryogenic instrumentation, superconducting magnetic energy storage, magnetic levitation transportation system, and arctic exploration. The development of electrical power systems capable of extremely low-temperature operation represents a key element of some advanced space power systems. The Low-Temperature Power Electronics Program at NASA Lewis Research Center focuses on the design, fabrication, and characterization of low-temperature power systems and the development of supporting technologies for low-temperature operations such as dielectric and insulating materials, power components, optoelectronic components, and packaging and integration of devices, components, and systems.

  11. X-ray emission from high temperature plasmas

    NASA Technical Reports Server (NTRS)

    Harries, W. L.

    1977-01-01

    The physical processes occurring in plasma focus devices were investigated with particular emphasis on X-ray emission. Topics discussed include: trajectories of high energy electrons; detection of ion trajectories; spatial distribution of neutron emission; space and time resolved emission of hard X-rays from a plasma focus; the staged plasma focus as a variation of the hypocloidal pinch; formation of current sheets in a staged plasma focus; and X-ray and neutron emission from a staged plasma focus. The possibility of operating dense plasma-focus type devices in multiple arrays beyond the scaling law for a single gun is discussed.

  12. Weakly nonlinear ion waves in striated electron temperatures

    NASA Astrophysics Data System (ADS)

    Guio, P.; Pécseli, H. L.

    2016-04-01

    The existence of low-frequency waveguide modes of electrostatic ion acoustic waves is demonstrated in magnetized plasmas for cases where the electron temperature is striated along magnetic field lines. For low frequencies, the temperature striation acts as waveguide that supports a trapped mode. For conditions where the ion cyclotron frequency is below the ion plasma frequency we find a dispersion relation having also a radiative frequency band, where waves can escape from the striation. Arguments for the formation and propagation of an equivalent of electrostatic shocks are presented and demonstrated numerically for these conditions. The shock represents here a balance between an external energy input maintained by ion injection and a dissipation mechanism in the form of energy leakage of the harmonics generated by nonlinear wave steepening. This is a reversible form for energy loss that can replace the time-irreversible losses in a standard Burgers equation.

  13. Effects of nonthermal electrons on plasma expansion into vacuum

    SciTech Connect

    Bennaceur-Doumaz, D. Bara, D.; Benkhelifa, E.; Djebli, M.

    2015-01-28

    The expansion of semi-infinite plasma into vacuum is analyzed with a hydrodynamic model for cold ions assuming electrons modelled by a kappa-type distribution. Similarly to Mora study of a plasma expansion into vacuum [P. Mora, Phys. Rev. Lett. 90, 185002 (2003)], we formulated empirical expressions for the electric field strength, velocity, and position of the ion front in one-dimensional nonrelativistic, collisionless isothermally expanding plasma. Analytic expressions for the maximum ion energy and the spectrum of the accelerated ions in the plasma were derived and discussed to highlight the electron nonthermal effects on enhancing the ion acceleration in plasma expansion into vacuum.

  14. Electron Energization During m=0 Magnetic Bursts in MST plasmas

    NASA Astrophysics Data System (ADS)

    Young, W. C.; den Hartog, D. J.; Morton, L. A.; MST Team

    2015-11-01

    MST reversed-field pinch plasmas develop magnetic modes with both a core-resonant poloidal mode m=1 structure and edge-resonant m=0 structure on the reversal surface. The impact of the m=0 modes on electron energization has been observed with Thomson scattering under plasma conditions with suppressed m=1 modes. Under such conditions, the m=0 modes undergo brief (~100 μs) bursts of localized magnetic activity. These bursts show a localized 4% heating of electrons above a 600-900 eV background temperature, associated with a reduction of magnetic energy. An inward propagating cold pulse follows after the heating as a result of reduced confinement. Ensembles of hundreds of bursts are required to measure small relative heating, however single-shot results from MST's high repetition Thomson scattering diagnostic support the ensemble results. Analysis of Thomson scattering data also provides constraints on non-Maxwellian distributions and upcoming upgrades will improve the ability to resolve electron currents associated with the magnetic bursts. This work is supported by the US DOE and NSF.

  15. Electronics for Low Temperature Space Exploration Missions

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Hammoud, Ahmad; Elbuluk, Malik

    2007-01-01

    Exploration missions to outer planets and deep space require spacecraft, probes, and on-board data and communication systems to operate reliably and efficiently under severe harsh conditions. On-board electronics, in particular those in direct exposures to the space environment without any shielding or protection, will encounter extreme low temperature and thermal cycling in their service cycle in most of NASA s upcoming exploration missions. For example, Venus atmosphere, Jupiter atmosphere, Moon surface, Pluto orbiter, Mars, comets, Titan, Europa, and James Webb Space Telescope all involve low-temperature surroundings. Therefore, electronics for space exploration missions need to be designed for operation under such environmental conditions. There are ongoing efforts at the NASA Glenn Research Center (GRC) to establish a database on the operation and reliability of electronic devices and circuits under extreme temperature operation for space applications. This work is being performed under the Extreme Temperature Electronics Program with collaboration and support of the NASA Electronic Parts and Packaging (NEPP) Program. The results of these investigations will be used to establish safe operating areas and to identify degradation and failure modes, and the information will be disseminated to mission planners and system designers for use as tools for proper part selection and in risk mitigation. An overview of this program along with experimental data will be presented.

  16. Pulse propagation and electron acceleration in a corrugated plasma channel.

    PubMed

    Palastro, J P; Antonsen, T M; Morshed, S; York, A G; Milchberg, H M

    2008-03-01

    A preformed plasma channel provides a guiding structure for laser pulses unbound by the intensity thresholds of standard waveguides. The recently realized corrugated plasma channel [Layer, Phys. Rev. Lett. 99, 035001 (2007)] allows for the guiding of laser pulses with subluminal spatial harmonics. These spatial harmonics can be phase matched to high energy electrons, making the corrugated plasma channel ideal for the acceleration of electrons. We present a simple analytic model of pulse propagation in a corrugated plasma channel and examine the laser-electron beam interaction. Simulations show accelerating gradients of several hundred MeV/cm for laser powers much lower than required by standard laser wakefield schemes. PMID:18517531

  17. The Conference on High Temperature Electronics

    NASA Technical Reports Server (NTRS)

    Hamilton, D. J.; Mccormick, J. B.; Kerwin, W. J.; Narud, J. A.

    1981-01-01

    The status of and directions for high temperature electronics research and development were evaluated. Major objectives were to (1) identify common user needs; (2) put into perspective the directions for future work; and (3) address the problem of bringing to practical fruition the results of these efforts. More than half of the presentations dealt with materials and devices, rather than circuits and systems. Conference session titles and an example of a paper presented in each session are (1) User requirements: High temperature electronics applications in space explorations; (2) Devices: Passive components for high temperature operation; (3) Circuits and systems: Process characteristics and design methods for a 300 degree QUAD or AMP; and (4) Packaging: Presently available energy supply for high temperature environment.

  18. Terahertz rectification by periodic two-dimensional electron plasma

    SciTech Connect

    Popov, V. V.

    2013-06-24

    The physics of terahertz rectification by periodic two-dimensional electron plasma is discussed. Two different effects yielding terahertz rectification are studied: the plasmonic drag and plasmonic ratchet. Ultrahigh responsivity of terahertz rectification by periodic two-dimensional electron plasma in semiconductor heterostructures and graphene is predicted.

  19. Electron acceleration by a laser pulse in a plasma

    SciTech Connect

    McKinstrie, C.J.; Startsev, E.A.

    1996-08-01

    The acceleration of an electron by a circularly polarized laser pulse in a plasma is studied. It appears possible to increase significantly the energy of a preaccelerated electron. Although the pulse tends to generate a plasma wake, to which it loses energy, one can eliminate the wake by choosing the duration of the pulse judiciously. {copyright} {ital 1996 The American Physical Society.}

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

    SciTech Connect

    Esarey, E.; Schroeder, C. B.; Leemans, W. P.

    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.

  1. Plasma and ion barrier for electron beam spot stability

    SciTech Connect

    Kwan, T.J.T.; Snell, C.M.

    1999-04-01

    The concept of a self-biased target to spatially confine the ions generated by the bombardment of intense electron beams on bremsstrahlung conversion targets has been predicted by computer simulation and further verified by experiments at the Integrated Test Stand for DARHT at Los Alamos National Laboratory. This technical article reports an alternative method of containing the plasmas and ions from the bremsstrahlung conversion target if the energy density of the electron beam is below a certain threshold. With the proposed changes of the electron beam parameters of the second axis of DARHT, the authors are able to show that a thin (0.5 mm) metallic barrier such as pure beryllium, or boron carbide with desirable thermal properties, is sufficiently transparent to the 20 MeV DARHT beam and at the same time able to confine the ions between the target and the barrier foil. The temperature rise in the foil due to energy deposited by the electron beam is expected to be below the melting point of the materials for the first three pulses. More important, they have shown in their time dependent particle-in-cell simulations that the deployment of a barrier situated 1 to 2 cm away from the converter target can achieve the ion confinement needed for the stability of the electron beam spot.

  2. Influence of microwave driver coupling design on plasma density at Testbench for Ion sources Plasma Studies, a 2.45 GHz Electron Cyclotron Resonance Plasma Reactor

    SciTech Connect

    Megía-Macías, A.; Vizcaíno-de-Julián, A.; Cortázar, O. D.

    2014-03-15

    A comparative study of two microwave driver systems (preliminary and optimized) for a 2.45 GHz hydrogen Electron Cyclotron Resonance plasma generator has been conducted. The influence on plasma behavior and parameters of stationary electric field distribution in vacuum, i.e., just before breakdown, along all the microwave excitation system is analyzed. 3D simulations of resonant stationary electric field distributions, 2D simulations of external magnetic field mapping, experimental measurements of incoming and reflected power, and electron temperature and density along the plasma chamber axis have been carried out. By using these tools, an optimized set of plasma chamber and microwave coupler has been designed paying special attention to the optimization of stationary electric field value in the center of the plasma chamber. This system shows a strong stability on plasma behavior allowing a wider range of operational parameters and even sustaining low density plasma formation without external magnetic field. In addition, the optimized system shows the capability to produce values of plasma density four times higher than the preliminary as a consequence of a deeper penetration of the magnetic resonance surface in relative high electric field zone by keeping plasma stability. The increment of the amount of resonance surface embedded in the plasma under high electric field is suggested as a key factor.

  3. Influence of microwave driver coupling design on plasma density at Testbench for Ion sources Plasma Studies, a 2.45 GHz electron cyclotron resonance plasma reactor.

    PubMed

    Megía-Macías, A; Cortázar, O D; Vizcaíno-de-Julián, A

    2014-03-01

    A comparative study of two microwave driver systems (preliminary and optimized) for a 2.45 GHz hydrogen Electron Cyclotron Resonance plasma generator has been conducted. The influence on plasma behavior and parameters of stationary electric field distribution in vacuum, i.e., just before breakdown, along all the microwave excitation system is analyzed. 3D simulations of resonant stationary electric field distributions, 2D simulations of external magnetic field mapping, experimental measurements of incoming and reflected power, and electron temperature and density along the plasma chamber axis have been carried out. By using these tools, an optimized set of plasma chamber and microwave coupler has been designed paying special attention to the optimization of stationary electric field value in the center of the plasma chamber. This system shows a strong stability on plasma behavior allowing a wider range of operational parameters and even sustaining low density plasma formation without external magnetic field. In addition, the optimized system shows the capability to produce values of plasma density four times higher than the preliminary as a consequence of a deeper penetration of the magnetic resonance surface in relative high electric field zone by keeping plasma stability. The increment of the amount of resonance surface embedded in the plasma under high electric field is suggested as a key factor. PMID:24689578

  4. Impurity effects on trapped electron mode in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Du, Huarong; Wang, Zheng-Xiong; Dong, J. Q.

    2016-07-01

    The effects of impurity ions on the trapped electron mode (TEM) in tokamak plasmas are numerically investigated with the gyrokinetic integral eigenmode equation. It is shown that in the case of large electron temperature gradient ( η e ), the impurity ions have stabilizing effects on the TEM, regardless of peaking directions of their density profiles for all normalized electron density gradient R / L n e . Here, R is the major radius and L n e is the electron density gradient scale length. In the case of intermediate and/or small η e , the light impurity ions with conventional inwardly (outwardly) peaked density profiles have stabilizing effects on the TEM for large (small) R / L n e , while the light impurity ions with steep inwardly (outwardly) peaked density profiles can destabilize the TEM for small (large) R / L n e . Besides, the TEM driven by density gradient is stabilized (destabilized) by the light carbon or oxygen ions with inwardly (outwardly) peaked density profiles. In particular, for flat and/or moderate R / L n e , two independent unstable modes, corresponding respectively to the TEM and impurity mode, are found to coexist in plasmas with impurity ions of outwardly peaked density profiles. The high Z tungsten impurity ions play a stronger stabilizing role in the TEM than the low Z impurity ions (such as carbon and oxygen) do. In addition, the effects of magnetic shear and collision on the TEM instability are analyzed. It is shown that the collisionality considered in this work weakens the trapped electron response, leading to a more stable TEM instability, and that the stabilizing effects of the negative magnetic shear on the TEM are more significant when the impurity ions with outwardly peaked density profile are taken into account.

  5. Survey of low energy plasma electrons in Saturn's magnetosphere: Voyagers 1 and 2

    NASA Technical Reports Server (NTRS)

    Sittler, E. C., Jr.; Ogilvie, K. W.; Scudder, J. D.

    1983-01-01

    The low energy plasma electron environment within Saturn's magnetosphere was surveyed by the Plasma Science Experiment (PLS) during the Voyager encounters with Saturn. Over the full energy range of the PLS instrument (10 eV to 6 keV) the electron distribution functions are clearly non-Maxwellian in character; they are composed of a cold (thermal) component with Maxwellian shape and a hot (suprathermal) non-Maxwellian component. A large scale positive radial gradient in electron temperature is observed, increasing from less than 1 eV in the inner magnetosphere to as high as 800 eV in the outer magnetosphere. Three fundamentally different plasma regimes were identified from the measurements: (1) the hot outer magnetosphere, (2) the extended plasma sheet, and (3) the inner plasma torus.

  6. High temperature electronics applications in space exploration

    NASA Technical Reports Server (NTRS)

    Jurgens, R. F.

    1981-01-01

    The extension of the range of operating temperatures of electronic components and systems for planetary exploration is examined. In particular, missions which utilize balloon-borne instruments to study the Venusian and Jovian atmospheres are discussed. Semiconductor development and devices including power sources, ultrastable oscillators, transmitters, antennas, electromechanical devices, and deployment systems are addressed.

  7. Density Gradient Stabilization of Electron Temperature Gradient Driven Turbulence in a Spherical Tokamak

    SciTech Connect

    Ren, Y; Mazzucato, E; Guttenfelder, W; Bell, R E; Domier, C W; LeBlanc, B P; Lee, K C; Luhmann Jr, N C; Smith, D R

    2011-03-21

    In this letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k⊥ρs ≤10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in the plasma effective thermal diffusivity.

  8. Density gradient stabilization of electron temperature gradient driven turbulence in a spherical tokamak.

    PubMed

    Ren, Y; Kaye, S M; Mazzucato, E; Guttenfelder, W; Bell, R E; Domier, C W; LeBlanc, B P; Lee, K C; Luhmann, N C; Smith, D R; Yuh, H

    2011-04-22

    In this Letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k(⊥)ρ(s) ≲ 10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of 2 decrease in the plasma effective thermal diffusivity. PMID:21599377

  9. Electron Acoustic Waves in Pure Ion Plasmas

    NASA Astrophysics Data System (ADS)

    Anderegg, F.; Affolter, M.; Driscoll, C. F.; O'Neil, T. M.; Valentini, F.

    2012-10-01

    Electron Acoustic Waves (EAWs) are the low-frequency branch of near-linear Langmuir (plasma) waves: the frequency is such that the complex dielectric function (Dr, Di) has Dr= 0; and ``flattening'' of f(v) near the wave phase velocity vph gives Di=0 and eliminates Landau damping. Here, we observe standing axisymmetric EAWs in a pure ion column.footnotetextF. Anderegg, et al., Phys. Rev. Lett. 102, 095001 (2009). At low excitation amplitudes, the EAWs have vph˜1.4 v, in close agreement with near-linear theory. At moderate excitation strengths, EAW waves are observed over a range of frequencies, with 1.3 v < vph< 2.1 v. Here, the final wave frequency may differ from the excitation frequency since the excitation modifies f (v); and recent theory analyzes frequency shifts from ``corners'' of a plateau at vph.footnotetextF. Valentini et al., arXiv:1206.3500v1. Large amplitude EAWs have strong phase-locked harmonic content, and experiments will be compared to same-geometry simulations, and to simulations of KEENfootnotetextB. Afeyan et al., Proc. Inertial Fusion Sci. and Applications 2003, A.N.S. Monterey (2004), p. 213. waves in HEDLP geometries.

  10. Diamond switches for high temperature electronics

    SciTech Connect

    Prasad, R.R.; Rondeau, G.; Qi, Niansheng

    1996-04-25

    Diamond switches are well suited for use in high temperature electronics. Laboratory feasibility of diamond switching at 1 kV and 18 A was demonstrated. DC blocking voltages up to 1 kV were demonstrated. A 50 {Omega} load line was switched using a diamond switch, with switch on-state resistivity {approx}7 {Omega}-cm. An electron beam, {approx}150 keV energy, {approx}2 {mu}s full width at half maximum was used to control the 5 mm x 5 mm x 100 {mu}m thick diamond switch. The conduction current temporal history mimics that of the electron beam. These data were taken at room temperature.

  11. Sheath structure in plasmas with nonextensively distributed electrons and thermal ions

    SciTech Connect

    Hatami, M. M.

    2015-02-15

    Sheath region of an electropositive plasma consisting of q-nonextensive electrons and singly charged positive ions with finite temperature is modeled. Using Sagdeev's pseudo potential technique to derive the modified sheath formation criterion, it is shown that the velocity of ions at the sheath edge is directly proportional to the ion temperatures and inversely proportional to the degree of nonextensivity of electrons (q-parameter). Using the modified Bohm criterion, effect of degree of nonextensivity of electrons and temperature of positive ions on the characteristics of the sheath region are investigated numerically. It is shown that an increase in the ion temperature gives rise to an increase in the electrostatic potential and the velocity of ions in the sheath regardless of the value of q. Furthermore, it is seen that the sheath width and the density distribution of the charged particles decrease by increasing the temperature of positive ions. In addition, it is found that the positive ion temperature is less effective on the sheath structure for higher values of the q-parameter. Finally, the results obtained for a thermal plasma with nonextensively distributed electrons are compared with the results of a cold plasma with nonextensive electrons and an extensive (Maxwellian) plasma with thermal ions.

  12. Transport Processes in High Temperature QCD Plasmas

    NASA Astrophysics Data System (ADS)

    Hong, Juhee

    The transport properties of high temperature QCD plasmas can be described by kinetic theory based on the Boltzmann equation. At a leading-log approximation, the Boltzmann equation is reformulated as a Fokker-Planck equation. First, we compute the spectral densities of Tµν and Jµ by perturbing the system with weak gravitational and electromagnetic fields. The spectral densities exhibit a smooth transition from free-streaming quasi-particles to hydrodynamics. This transition is analyzed with hydrodynamics and diffusion equation up to second order. We determine all of the first and second order transport coefficients which characterize the linear response in the hydrodynamic regime. Second, we simulate the wake of a heavy quark moving through the plasmas. At long distances, the energy density and flux distributions show sound waves and a diffusion wake. The kinetic theory calculations based on the Boltzmann equation at weak coupling are compared to the strong coupling results given by the AdS/CFT correspondence. By using the hard-thermal-loop effective theory, we determine the photon emission rate at next-to-leading order (NLO), i.e., at order g2mD /T. There are three mechanisms which contribute to the leading-order photon emission: (2 ↔ 2) elastic scatterings, (1 ↔ 2) collinear bremsstrahlung, and (1 ↔ 1) quark-photon conversion due to soft fermion exchange. At NLO, these three mechanisms are not completely independent. When the transverse momentum between quark and photon becomes soft, the Compton scattering with a soft gluon reduces to wide-angle bremsstrahlung. Similarly, bremsstrahlung reduces to the quark-photon conversion process when the photon carries most of the incoming momentum. Therefore, the rates should be matched to determine the wide-angle NLO correction. Collinear bremsstrahlung can be accounted for by solving an integral

  13. Whistler-mode phenomena in electron MHD plasmas

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.

    2003-12-01

    While the linear properties of plane whistler waves are well known, many new phenomena of bounded wavepackets and nonlinear effects are worth to describe. The present talk will review laboratory observations of whistler filaments, whistler vortices, whistler wings, whistler-sound modes in high-beta plasmas, nonlinear whistlers forming magnetic null points, and magnetic reconnection in EMHD plasmas. The time-varying magnetic field of a spatially bounded whistler wave packet consists of 3-D vortices. Each vortex can be decomposed into linked toroidal and poloidal field components. The self-helicity is positive for propagation along the field, negative for opposite propagation. Helicity injection from a suitable source produces unidirectional propagation. Magnetic helicity changes sign, i.e., is not conserved, when the propagation direction along B changes, for example due to reflection or propagation through a magnetic null point. In ideal EMHD the electric and magnetic forces on the electrons are equal, -n e E +J x B=0, i.e., the electron fluid is not compressed. Force-free vortices do not interact during collisions. Vortices are excited with pulsed magnetic antennas or pulsed electrodes. Both transient currents and fields can form vortices that propagate in the whistler mode. Moving dc magnets or dc current systems can also induce whistler modes in a magnetized plasma. These form a Cherenkov-like radiation pattern, a ``whistler wing.'' Nonlinear phenomena arise from wave-induced modifications of the electron temperature, density and magnetic field. In collisional plasmas electrons are heated by strong whistlers. Modifications of the classical conductivity leads to current filamentation. On a slower time scale density modifications arise from ambipolar fields associated with electron heating. In a filamentation instability a strong whistler wave is ducted along a narrow field-aligned density depression. The ion density is also modified by the ac electric field of

  14. Sheath Effects on Electron Density Measurements in Frequency Shift Probe and their Application to Electron Temperature Measurements

    NASA Astrophysics Data System (ADS)

    Nakamura, Keiji; Zhang, Qi; Sugai, Hideo

    2009-10-01

    Technologies of plasma monitoring are important for accurate plasma control. We have developed a frequency shift probe, and the probe enables us to measure an electron density from variation of resonance frequency of the probe head similarly to the hairpin probe. A plane structure of the probe head make it possible to minimizes disturbance to the processing plasma, and the probe is applicable to a reactive polymer-deposition plasmas since the polymer has no significant effects on the resonance frequency. The electron density is usually obtained from a plasma-induced shift of the probe resonance frequency, however influences of a sheath around the probe should been considered for more precise density measurements. In this work, sheath effects on the frequency shift probe were investigated, and the frequency shift probe was applied to measure a electron temperature using the sheath effects. As the sheath thickness increased, the resonance frequency decreased, and the sheath effect is enhanced depending on probe structure. Since the sheath width is proportional to Debye length, the probe resonance frequency depends on electron density and electron temperature, suggesting that resonance frequencies obtained in two probes having different sheath dependence gives an unique solution of the density and temperature of electrons.

  15. Theory of interparticle correlations in dense, high-temperature plasmas. V - Electric and thermal conductivities

    NASA Technical Reports Server (NTRS)

    Ichimaru, S.; Tanaka, S.

    1985-01-01

    Ichimaru et al. (1985) have developed a general theory in which the interparticle correlations in dense, high-temperature multicomponent plasmas were formulated systematically over a wide range of plasma parameters. The present paper is concerned with an extension of this theory, taking into account the problems of the electronic transport in such high-density plasmas. It is shown that the resulting theory is capable of describing the transport coefficients accurately over a wide range of the density and temperature parameters. Attention is given to electric and thermal conductivities, generalized Coulomb logarithms, a comparison of the considered theory with other theories, and a comparison of the theory with experimental results.

  16. Gyrokinetic stability theory of electron-positron plasmas

    NASA Astrophysics Data System (ADS)

    Helander, P.; Connor, J. W.

    2016-06-01

    > The linear gyrokinetic stability properties of magnetically confined electron-positron plasmas are investigated in the parameter regime most likely to be relevant for the first laboratory experiments involving such plasmas, where the density is small enough that collisions can be ignored and the Debye length substantially exceeds the gyroradius. Although the plasma beta is very small, electromagnetic effects are retained, but magnetic compressibility can be neglected. The work of a previous publication (Helander, Phys. Rev. Lett., vol. 113, 2014a, 135003) is thus extended to include electromagnetic instabilities, which are of importance in closed-field-line configurations, where such instabilities can occur at arbitrarily low pressure. It is found that gyrokinetic instabilities are completely absent if the magnetic field is homogeneous: any instability must involve magnetic curvature or shear. Furthermore, in dipole magnetic fields, the stability threshold for interchange modes with wavelengths exceeding the Debye radius coincides with that in ideal magnetohydrodynamics. Above this threshold, the quasilinear particle flux is directed inward if the temperature gradient is sufficiently large, leading to spontaneous peaking of the density profile.

  17. Determination of Plasma Electron Density from Optical Measurements

    NASA Astrophysics Data System (ADS)

    Neiswander, Brian; Matlis, Eric; Corke, Thomas

    2009-11-01

    Plasma has been shown to be effective in many flow control applications, but now may also find use in adaptive optics. Plasma's index of refraction is coupled with it's electron density which may be adjusted for adaptive control. An experimental setup to verify the relation between plasma electron density, pressure, and voltage is presented. A non-thermal DBD plasma cell is created by evacuating air and applying a voltage potential between two conducting glass slides. Plasma forms in the chamber between the glass and the applied voltage potential controls the electron density. A HeNe laser is passed through the plasma cell and then focused onto a duo-lateral position sensing device (PSD). The plasma cell is oriented at an angle to the laser's beam and so changes in the plasma's index of refraction produce lateral translations in the beam position. Differences in the PSD output with and without plasma provides for the calculation of the electron density averaged over the beam spot area. The data from this experiment will be used to further develop an adaptive plasma lens for wavefront aberration corrections.

  18. Analysis of density effects in plasmas and their influence on electron-impact cross sections

    NASA Astrophysics Data System (ADS)

    Belkhiri, M.; Poirier, M.

    2014-12-01

    Density effects in plasmas are analyzed using a Thomas-Fermi approach for free electrons. First, scaling properties are determined for the free-electron potential and density. For hydrogen-like ions, the first two terms of an analytical expansion of this potential as a function of the plasma coupling parameter are obtained. In such ions, from these properties and numerical calculations, a simple analytical fit is proposed for the plasma potential, which holds for any electron density, temperature, and atomic number, at least assuming that Maxwell-Boltzmann statistics is applicable. This allows one to analyze perturbatively the influence of the plasma potential on energies, wave functions, transition rates, and electron-impact collision rates for single-electron ions. Second, plasmas with an arbitrary charge state are considered, using a modified version of the Flexible Atomic Code (FAC) package with a plasma potential based on a Thomas-Fermi approach. Various methods for the collision cross-section calculations are reviewed. The influence of plasma density on these cross sections is analyzed in detail. Moreover, it is demonstrated that, in a given transition, the radiative and collisional-excitation rates are differently affected by the plasma density. Some analytical expressions are proposed for hydrogen-like ions in the limit where the Born or Lotz approximation applies and are compared to the numerical results from the FAC.

  19. Electron cyclotron emission measurements on JET: Michelson interferometer, new absolute calibration, and determination of electron temperature.

    PubMed

    Schmuck, S; Fessey, J; Gerbaud, T; Alper, B; Beurskens, M N A; de la Luna, E; Sirinelli, A; Zerbini, M

    2012-12-01

    At the fusion experiment JET, a Michelson interferometer is used to measure the spectrum of the electron cyclotron emission in the spectral range 70-500 GHz. The interferometer is absolutely calibrated using the hot/cold technique and, in consequence, the spatial profile of the plasma electron temperature is determined from the measurements. The current state of the interferometer hardware, the calibration setup, and the analysis technique for calibration and plasma operation are described. A new, full-system, absolute calibration employing continuous data acquisition has been performed recently and the calibration method and results are presented. The noise level in the measurement is very low and as a result the electron cyclotron emission spectrum and thus the spatial profile of the electron temperature are determined to within ±5% and in the most relevant region to within ±2%. The new calibration shows that the absolute response of the system has decreased by about 15% compared to that measured previously and possible reasons for this change are presented. Temperature profiles measured with the Michelson interferometer are compared with profiles measured independently using Thomson scattering diagnostics, which have also been recently refurbished and recalibrated, and agreement within experimental uncertainties is obtained. PMID:23282107

  20. Instability of Interaction of a Coherent Electron Beam and Plasma

    NASA Astrophysics Data System (ADS)

    Matveev, A. I.

    2015-12-01

    Nonlinear interaction of a beam with finite density of electrons, whose velocity is greater than the phase velocity of a plasma wave, with homogeneous collisionless plasma is described. It is shown that a positive feedback arises between plasma oscillations and the wave of longitudinal electron density of the beam if the phase of this wave is 90° ahead of the phase of plasma oscillations. An increase in the energies of plasma and beam oscillations is accompanied by a decrease in the kinetic beam energy until the moment when the beam velocity becomes equal to the plasma wave phase velocity. Since the beam velocity can be greater than the plasma wave phase velocity, such energy conversion is very efficient.

  1. Electron acceleration in long scale laser - plasma interactions

    NASA Astrophysics Data System (ADS)

    Kamperidis, Christos; Mangles, Stuart P. D.; Nagel, Sabrina R.; Bellei, Claudio; Krushelnick, Karl; Najmudin, Zulfikar; Bourgeois, Nicola; Marques, Jean Raphael; Kaluza, Malte C.

    2006-10-01

    Broad energy electron bunches are produced through the Self-Modulated Laser Wakefield Acceleration scheme at the 30J, 300 fsec laser, LULI, France, with long scale underdense plasmas, created in a He filled gas cell and in He gas jet nozzles of various lengths. With c.τlaser>>λplasma, electrons reached Emax ˜ 200MeV. By carefully controlling the dynamics of the interaction and by simultaneous observations of the electron energy spectra and the forward emitted optical spectrum, we found that a plasma density threshold (˜5.10^18 cm-3) exists for quasi-monoenergetic (˜30MeV) features to appear. The overall plasma channel size was inferred from the collected Thomson scattered light. 2D PIC simulations indicate that the main long laser pulse breaks up into small pulselets that eventually get compressed and tightly focused inside the first few plasma periods, leading to a bubble like acceleration of electron bunches.

  2. Resonance between heat-carrying electrons and Langmuir waves in inertial confinement fusion plasmas

    NASA Astrophysics Data System (ADS)

    Rozmus, W.; Chapman, T.; Brantov, A.; Winjum, B. J.; Berger, R. L.; Brunner, S.; Bychenkov, V. Yu.; Tableman, A.; Tzoufras, M.; Glenzer, S.

    2016-01-01

    In ignition scale hot plasmas, temperature gradients and thermal transport modify electron distributions in a velocity range resonant with Langmuir waves typical of those produced by stimulated Raman scattering. We examine the resultant changes to the Landau damping experienced by these Langmuir waves and the levels of thermal plasma fluctuations. The form factor and Thomson scattering cross-section in such plasmas display unique characteristics of the background conditions. A theoretical model and high-order Vlasov-Fokker-Planck simulations are used in our analysis. An experiment to measure changes in thermal plasma fluctuation levels due to a thermal gradient is proposed.

  3. Laser scattering for temporal and spatial diagnostic of low temperature plasmas

    NASA Astrophysics Data System (ADS)

    Palomares Linares, Jose Maria

    2012-10-01

    Many recent industrial and technological applications like surface etching, inorganic films deposition, polymerization of surfaces or sterilization are developed within the field of low temperature plasmas. To study, monitor and model plasma processes is of great importance to have diagnostic tools that can provide reliable information on different plasma parameters. In general, laser scattering techniques provide a direct and accurate method for plasma diagnostic with spatial and temporal resolution. Laser Thomson scattering is used for the diagnostic of electron density and temperature, two of the most important parameters in low temperature discharges. With a similar setup Rayleigh and Raman scattering techniques are used for the diagnostic of gas density and temperature. In this contribution we deal with the different technical and theoretical aspects that are required for the application of these laser scattering techniques. Of special importance are the detection limit, laser stray light rejection and laser perturbations of the plasma. The present study is performed on different low temperature microwave discharges, both at low and atmospheric pressure. The laser scattering techniques provide information on the spatial distribution of the mentioned plasma parameters over different discharge conditions, including small micro-plasmas. Similarly, the temporal evolution of pulsed plasmas is studied, unraveling the features of the switching on and off phases of the discharges.

  4. Public Data Set: Impedance of an Intense Plasma-Cathode Electron Source for Tokamak Plasma Startup

    DOE Data Explorer

    Hinson, Edward T. [University of Wisconsin-Madison] (ORCID:000000019713140X); Barr, Jayson L. [University of Wisconsin-Madison] (ORCID:0000000177685931); Bongard, Michael W. [University of Wisconsin-Madison] (ORCID:0000000231609746); Burke, Marcus G. [University of Wisconsin-Madison] (ORCID:0000000176193724); Fonck, Raymond J. [University of Wisconsin-Madison] (ORCID:0000000294386762); Perry, Justin M. [University of Wisconsin-Madison] (ORCID:0000000171228609)

    2016-05-31

    This data set contains openly-documented, machine readable digital research data corresponding to figures published in E.T. Hinson et al., 'Impedance of an Intense Plasma-Cathode Electron Source for Tokamak Plasma Startup,' Physics of Plasmas 23, 052515 (2016).

  5. Plasma diagnostics of low pressure high power impulse magnetron sputtering assisted by electron cyclotron wave resonance plasma

    SciTech Connect

    Stranak, Vitezslav; Herrendorf, Ann-Pierra; Drache, Steffen; Bogdanowicz, Robert; Hippler, Rainer; Cada, Martin; Hubicka, Zdenek; Tichy, Milan

    2012-11-01

    This paper reports on an investigation of the hybrid pulsed sputtering source based on the combination of electron cyclotron wave resonance (ECWR) inductively coupled plasma and high power impulse magnetron sputtering (HiPIMS) of a Ti target. The plasma source, operated in an Ar atmosphere at a very low pressure of 0.03 Pa, provides plasma where the major fraction of sputtered particles is ionized. It was found that ECWR assistance increases the electron temperature during the HiPIMS pulse. The discharge current and electron density can achieve their stable maximum 10 {mu}s after the onset of the HiPIMS pulse. Further, a high concentration of double charged Ti{sup ++} with energies of up to 160 eV was detected. All of these facts were verified experimentally by time-resolved emission spectroscopy, retarding field analyzer measurement, Langmuir probe, and energy-resolved mass spectrometry.

  6. Radial convection of finite ion temperature, high amplitude plasma blobs

    SciTech Connect

    Wiesenberger, M. Kendl, A.; Madsen, J.

    2014-09-15

    We present results from simulations of seeded blob convection in the scrape-off-layer of magnetically confined fusion plasmas. We consistently incorporate high fluctuation amplitude levels and finite Larmor radius (FLR) effects using a fully nonlinear global gyrofluid model. This is in line with conditions found in tokamak scrape-off-layers (SOL) regions. Varying the ion temperature, the initial blob width, and the initial amplitude, we found an FLR dominated regime where the blob behavior is significantly different from what is predicted by cold-ion models. The transition to this regime is very well described by the ratio of the ion gyroradius to the characteristic gradient scale length of the blob. We compare the global gyrofluid model with a partly linearized local model. For low ion temperatures, we find that simulations of the global model show more coherent blobs with an increased cross-field transport compared to blobs simulated with the local model. The maximal blob amplitude is significantly higher in the global simulations than in the local ones. When the ion temperature is comparable to the electron temperature, global blob simulations show a reduced blob coherence and a decreased cross-field transport in comparison with local blob simulations.

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

    SciTech Connect

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

    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.

  8. Progress toward positron-electron pair plasma experiments

    SciTech Connect

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

    2015-06-29

    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.

  9. Transport and fluctuations in high temperature spheromak plasmas

    NASA Astrophysics Data System (ADS)

    McLean, Harry

    2005-10-01

    A systematic analysis is presented of thermal transport in a driven spheromak that extends well into the collisionless regime and spans a wide range of magnetic fluctuation levels. The relationship between internal fluctuations and energy/helicity transport is of fundamental interest to many self-organized configurations in laboratory and space plasmas and the subject of ongoing multi-institutional collaborations. With the recent achievement on the SSPX spheromak[1] of electron temperature Te˜350eV in the core, and good confinement (core electron thermal diffusivity χe<10m^2/ for Te>200eV), we are now comparing heat transport in the experiment with a variety of models including classical, Bohm, and stochastic[2]/diffusive[3]/open[4] field lines. Using Thomson scattering to measure Te, ne profiles and the CORSICA equilibrium code to calculate internal current profiles from magnetic probe fits, we find that χe decreases as Te increases, a scaling behavior more classical-like than Bohm or open field line models would indicate. Lower Te and higher χe is observed in the transition region between the core and the separatrix where NIMROD 3d resistive MHD calculations[5] show the possible existence of chaotic field lines. We will also discuss plans including multi-pulse Thomson scattering and neutral beam heating. [1] E.B. Hooper, et al., Nucl. Fusion 39, 863 (1999). [2] A.B. Rechester and M.N. Rosenbluth, Phys. Rev. Lett. 40, 38 (1978). [3] J.D. Callen, Phys. Rev. Lett. 94, 055002 (2005). [4] R.W. Moses, et al., Phys. Plasmas 8, 4839 (2001). [5] B.I. Cohen, et al., Phys. Plasmas 12, 056106 (2005). This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

  10. An Exact Calculation of Electron-Ion Energy Splitting in a Hot Plasma

    SciTech Connect

    Singleton, Robert L

    2012-09-10

    In this brief report, I summarize the rather involved recent work of Brown, Preston, and Singleton (BPS). In Refs. [2] and [3], BPS calculate the energy partition into ions and electrons as a charged particle traverses a non-equilibrium two-temperature plasma. These results are exact to leading and next-to-leading order in the plasma coupling g, and are therefore extremely accurate in a weakly coupled plasma. The new BPS calculations are compared with the more standard work of Fraley et al. [12]. The results differ substantially at higher temperature when T{sub I} {ne} T{sub e}.

  11. Electron-ion plasma modification of Al-based alloys

    NASA Astrophysics Data System (ADS)

    Ivanov, Yurii; Rygina, Mariya; Petrikova, Elizaveta; Krysina, Olga; Teresov, Anton; Ivanova, Olga; Ikonnikova, Irina

    2016-01-01

    The paper reports on the study where we analyzed the surface structure and strength properties of coated Al alloys modified by electron-ion plasma treatment. The Al alloys were deposited with a thin (≈0.5 μm) TiCu film coating (TiCu-Al system) and with a hard TiCuN coating (TiCuN-AlSi system) on a TRIO vacuum setup in the plasma of low-pressure arc discharges. The temperature fields and phase transformations in the film-substrate system were estimated by numerical simulation in a wide range of electron energy densities (5-30 J/cm2) and pulse durations (50-200 μs). The calculations allowed us to determine the threshold energy density and pulse duration at which the surface structure of the irradiated Al-based systems is transformed in a single-phase state (solid or liquid) and in a two-phase state (solid plus liquid). The elemental composition, defect structure, phase state, and lattice state in the modified surface layers were examined by optical, scanning, and transmission electron microscopy, and by X-ray diffraction analysis. The mechanical characteristics of the modified layers were studied by measuring the hardness and Young's modulus. The tribological properties of the modified layers were analyzed by measuring the wear resistance and friction coefficient. It is shown that melting and subsequent high-rate crystallization of the TiCu-Al system makes possible a multiphase Al-based surface structure with the following characteristics: crystallite size ranging within micrometer, microhardness of more than 3 times that in the specimen bulk, and wear resistance ≈1.8 times higher compared to the initial material. Electron beam irradiation of the TiCuN-AlSi system allows fusion of the coating into the substrate, thus increasing the wear resistance of the material ≈2.2 times at a surface hardness of ˜14 GPa.

  12. Oxidation Degradation of Aqueous Carbofuran Induced by Low Temperature Plasma

    NASA Astrophysics Data System (ADS)

    Pu, Lumei; Gao, Jinzhang; Hu, Yusen; Liang, Huiguang; Xiao, Wen; Wang, Xingmin

    2008-06-01

    The oxidative degradation of aqueous carbofuran, a heavily used toxic carbamate insecticide by low temperature plasma, was investigated. The results show that the treatment efficiency increases with the increase in initial concentration. Raising the treatment temperature and changing the pH value can result in enhanced degradation of carbofuran in solution. The results also show that low temperature plasma treatment can effectively remove chemical oxygen demand (COD) of carbofuran in the solution.

  13. Electron anions and the glass transition temperature.

    PubMed

    Johnson, Lewis E; Sushko, Peter V; Tomota, Yudai; Hosono, Hideo

    2016-09-01

    Properties of glasses are typically controlled by judicious selection of the glass-forming and glass-modifying constituents. Through an experimental and computational study of the crystalline, molten, and amorphous [Ca12Al14O32](2+) ⋅ (e(-))2, we demonstrate that electron anions in this system behave as glass modifiers that strongly affect solidification dynamics, the glass transition temperature, and spectroscopic properties of the resultant amorphous material. The concentration of such electron anions is a consequential control parameter: It invokes materials evolution pathways and properties not available in conventional glasses, which opens a unique avenue in rational materials design. PMID:27559083

  14. Experimental measurement of plasma parameters and electron energy distribution in ferrite-core side type Ar/He inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Han, Duksun; Bang, Jin-Young; Lee, Hyo-Chang; Chung, Chin-Wook

    2012-10-01

    Spatial distributions of a plasma density and an effective electron temperature (Teff) were studied from the measurement of an electron energy probability function (EEPF) in the side type ferrite-core inductively coupled plasma with an argon-helium mixture. As the helium gas was diluted at the fixed total gas pressure of 5 mTorr in an argon discharge, the distribution of the plasma density was changed from a concave to a flat, and finally became a convex, while all spatial profiles of Teff were the hollow shapes with the helium dilution. This evolution of the plasma uniformity with the helium gas could be explained by the increased energy relaxation length and the changed plasma potential, indicating the transition of the electron kinetics from the local to non-local kinetics. From this result, it is expected that the addition of helium gas could be applied as a method to control the plasma uniformity in a large area plasma processing.

  15. Hopkins Ultraviolet Telescope determination of the Io torus electron temperature

    NASA Technical Reports Server (NTRS)

    Hall, D. T.; Bednar, C. J.; Durrance, S. T.; Feldman, P. D.; Mcgrath, M. A.; Moos, H. W.; Strobel, D. F.

    1994-01-01

    Sulfur ion emissions from the Io plasma torus observed by the Hopkins Ultraviolet Telescope (HUT) in 1990 December have been analyzed to determine the effective temperature of the exciting electrons. Spectra were obtained with a long slit that extended from 3.1 to 8.7 Jupiter radii R(sub J) on both dawn and dusk torus ansae. The average temperature of electrons exciting S(2+) emissions from the dawn ansa is (4800 +/- 2400) K lower than on the dusk ansa, a dawn-dusk asymmetry comparable in both sign and magnitude to that measured by the Voyager Ultraviolet Spectrograph (UVS) experiment. Emissions from S(2+) ions are generated in a source region with electron temperatures in the range 32,000-56,000 K; S(3+) ion emissions are excited by electrons that average 20,000-40,000 K hotter. This distinct difference suggests that the S(3+) emission source region is spatially separate from the S(2+) source region. Estimated relative aperture filling factors suggest that the S(3+) emissions originate from a region more extended out of the centrifugal plane than the S(2+) emissions.

  16. Electron Gyro-scale Fluctuation Measurements in National Spherical Torus Experiment H-mode Plasmas

    SciTech Connect

    Smith, D R; Lee, W; Mazzucato, E; Park, H K; Bell, R E; Domier, C W; LeBlanc, B P; Levinton, F M; Luhmann, N C; Menard, J E

    2009-08-10

    A collective scattering system has measured electron gyro-scale fluctuations in National Spherical Torus Experiment (NSTX) H-mode plasmas to investigate electron temperature gradient (ETG) turbulence. Observations and results pertaining to fluctuation measurements in ETGstable regimes, the toroidal field scaling of fluctuation amplitudes, the relation between between fluctuation amplitudes and transport quantities, and fluctuation magnitudes and k-spectra are presented. Collectively, the measurements provide insight and guidance for understanding ETG turbulence and anomalous electron thermal transport.

  17. Electron-ion energy partition when a charged particle slows in a plasma: results.

    PubMed

    Brown, Lowell S; Preston, Dean L; Singleton, Robert L

    2012-07-01

    This paper concerns plasmas in which the electrons and ions may have different temperatures. This is a case that must be examined because nuclear fusion processes, such as those that appear in ICF capsules, have ions whose temperature runs away from the electron temperature. A fast charged particle traversing a plasma--such as the α particle created in deuterium-tritium fusion--loses its energy to both the electrons and the ions in the plasma. In this paper, we present and discuss the results for the energy partition, the fractions E(e)/E(0) and E(I)/E(0) of the initial energy E(0) of this projectile particle that are deposited into the electrons and ions when it has slowed to its minimum energy distribution. The calculations, performed in the following paper [Brown, Preston, and Singleton Jr., Phys. Rev. E 86, 016407 (2012)], use a well-defined Fokker-Planck equation for the phase-space distribution of the charged projectiles in a weakly to moderately coupled plasma. The Fokker-Planck equation holds to first subleading order in the dimensionless plasma coupling constant, which translates to computing to order n ln n (leading) and n (subleading) in the plasma density n. We present an examination of the energy partition for the general case, in which the temperatures of the ions and electrons in the background plasma are not equal. The energy partitions for a background plasma in thermal equilibrium have been previously computed, but the order n terms have not been calculated, only estimated. Our Fokker-Planck formulation provides an unambiguous, precise definition of the energy fractions. PMID:23005549

  18. Potential applications of an electron cyclotron resonance multicusp plasma source

    SciTech Connect

    Tsai, C.C.; Berry, L.A.; Gorbatkin, S.M.; Haselton, H.H.; Roberto, J.B.; Stirling, W.L.

    1989-01-01

    An electron cyclotron resonance (ECR) multicusp plasmatron has been developed by feeding a multicusp bucket arc chamber with a compact ECR plasma source. This novel source produced large (about 25-cm-diam), uniform (to within {plus minus}10%), dense (>10{sup 11}-cm{sup -3}) plasmas of argon, helium, hydrogen, and oxygen. It has been operated to produce an oxygen plasma for etching 12.7-cm (5-in.) positive photoresist-coated silicon wafers with uniformity within {plus minus}8%. Results and potential applications of this new ECR plasma source for plasma processing of thin films are discussed. 21 refs., 10 figs.

  19. Plasma two-temperature equilibration rate.

    PubMed

    Chang, Yongbin; Ordonez, C A

    2004-03-01

    A theory is developed that is suitable for describing a two-species thermalization process in a plasma with parameters suitable for recombination to take place. Recombining plasmas have recently been produced using positrons and antiprotons [M. Amoretti et al., Nature (London) 419, 456 (2002); G. Gabrielse et al., Phys. Rev. Lett. 89, 213401 (2002)]. The theory is not restricted to large Coulomb logarithm values, and correspondence with prior theory is shown in the limit of large Coulomb logarithm values. The theory applies for two plasma species, each having a Maxwellian velocity distribution and being weakly correlated. PMID:15089448

  20. Thermoemission (dust-electron) plasmas: theory of neutralizing charges.

    PubMed

    Vishnyakov, V I; Dragan, G S

    2006-09-01

    Thermoemission plasma--i.e., a system consisting of dust grains and electrons--is studied. In the proposed model, it is assumed that the major part of the electronic gas is uniformly distributed in space and the spatial inhomogeneities of electronic density exist only near the dust grains. The experimental data, well described by the proposed theory, are given. PMID:17025751

  1. Nonplanar positron-acoustic Gardner solitary waves in electron-positron-ion plasmas with superthermal electrons and positrons

    SciTech Connect

    Uddin, M. J. Alam, M. S.; Mamun, A. A.

    2015-02-15

    Nonplanar (cylindrical and spherical) positron-acoustic (PA) Gardner solitary waves (SWs) in an unmagnetized plasma system consisting of immobile positive ions, mobile cold positrons, and superthermal (kappa distributed) hot positrons and electrons are investigated. The modified Gardner equation is derived by using the reductive perturbation technique. The effects of cylindrical and spherical geometries, superthermal parameter of hot positrons and electrons, relative temperature ratios, and relative number density ratios on the PA Gardner SWs are studied by using the numerical simulations. The implications of our results in various space and laboratory plasma environments are briefly discussed.

  2. Radio Emissions from Plasma with Electron Kappa-Distributions

    NASA Astrophysics Data System (ADS)

    Fleishman, G. D.; Kuznetsov, A. A.

    2015-12-01

    Gregory Fleishman (New Jersey Institute of Technology, Newark, USA)Alexey Kuznetsov (Institute of Solar-Terrestrial Physics, Irkutsk, Russia), Currently there is a concern about the ability of the classical thermal (Maxwellian) distribution to describe quasisteady-state plasma in the solar atmosphere, including active regions. In particular, other distributions have been proposed to better fit observations, for example, kappa-distributions. If present, these distributions will generate radio emissions with different observable properties compared with the classical gyroresonance (GR) or free-free emission, which implies a way of remotely detecting these kappa distributions in the radio observations. Here we present analytically derived GR and free-free emissivities and absorption coefficients for the kappa-distribution, and discuss their properties, which are in fact remarkably different from the classical Maxwellian plasma. In particular, the radio brightness temperature from a gyrolayer increases with the optical depth τ for kappa-distribution. This property has a remarkable consequence allowing a straightforward observational test: the GR radio emission from the non-Maxwellian distributions is supposed to be noticeably polarized even in the optically thick case, where the emission would have strictly zero polarization in the case of Maxwellian plasma. This offers a way of remote probing the plasma distribution in astrophysical sources, including solar active regions as a vivid example. In this report, we present analytical formulae and computer codes to calculate the emission parameters. We simulate the gyroresonance emission under the conditions typical of the solar active regions and compare the results for different electron distributions. We discuss the implications of our findings for interpretation of radio observations. This work was supported in part by NSF grants AGS-1250374 and AGS-1262772, NASA grant NNX14AC87G to New Jersey Institute of Technology

  3. Effect of antenna size on electron kinetics in inductively coupled plasmas

    SciTech Connect

    Lee, Hyo-Chang; Chung, Chin-Wook

    2013-10-15

    Spatially resolved measurements of electron energy distribution functions (EEDFs) are investigated in inductively coupled plasmas with two planar antenna coils. When the plasma is sustained by the antenna with a diameter of 18 cm, the nonlocal kinetics is preserved in the argon gas pressure range from 2 mTorr to 20 mTorr. However, electron kinetics transit from nonlocal kinetics to local kinetics in discharge sustained by the antenna coil with diameter 34 cm. The results suggest that antenna size as well as chamber length are important parameters for the transition of the electron kinetics. Spatial variations of plasma potential, effective electron temperature, and EEDF in terms of total electron energy scale are also presented.

  4. Energy exchange in strongly coupled plasmas with electron drift

    SciTech Connect

    Akbari-Moghanjoughi, M.; Ghorbanalilu, M.

    2015-11-15

    In this paper, the generalized viscoelastic collisional quantum hydrodynamic model is employed in order to investigate the linear dielectric response of a quantum plasma in the presence of strong electron-beam plasma interactions. The generalized Chandrasekhar's relativistic degeneracy pressure together with the electron-exchange and Coulomb interaction effects are taken into account in order to extend current research to a wide range of plasma number density relevant to big planetary cores and astrophysical compact objects. The previously calculated shear viscosity and the electron-ion collision frequencies are used for strongly coupled ion fluid. The effect of the electron-beam velocity on complex linear dielectric function is found to be profound. This effect is clearly interpreted in terms of the wave-particle interactions and their energy-exchange according to the sign of the imaginary dielectric function, which is closely related to the wave attenuation coefficient in plasmas. Such kinetic effect is also shown to be in close connection with the stopping power of a charged-particle beam in a quantum plasma. The effect of many independent plasma parameters, such as the ion charge-state, electron beam-velocity, and relativistic degeneracy, is shown to be significant on the growing/damping of plasma instability or energy loss/gain of the electron-beam.

  5. Energy exchange in strongly coupled plasmas with electron drift

    NASA Astrophysics Data System (ADS)

    Akbari-Moghanjoughi, M.; Ghorbanalilu, M.

    2015-11-01

    In this paper, the generalized viscoelastic collisional quantum hydrodynamic model is employed in order to investigate the linear dielectric response of a quantum plasma in the presence of strong electron-beam plasma interactions. The generalized Chandrasekhar's relativistic degeneracy pressure together with the electron-exchange and Coulomb interaction effects are taken into account in order to extend current research to a wide range of plasma number density relevant to big planetary cores and astrophysical compact objects. The previously calculated shear viscosity and the electron-ion collision frequencies are used for strongly coupled ion fluid. The effect of the electron-beam velocity on complex linear dielectric function is found to be profound. This effect is clearly interpreted in terms of the wave-particle interactions and their energy-exchange according to the sign of the imaginary dielectric function, which is closely related to the wave attenuation coefficient in plasmas. Such kinetic effect is also shown to be in close connection with the stopping power of a charged-particle beam in a quantum plasma. The effect of many independent plasma parameters, such as the ion charge-state, electron beam-velocity, and relativistic degeneracy, is shown to be significant on the growing/damping of plasma instability or energy loss/gain of the electron-beam.

  6. Spectroscopic measurement of plasma gas temperature of the atmospheric-pressure microwave induced nitrogen plasma torch

    NASA Astrophysics Data System (ADS)

    Chen, Chuan-Jie; Li, Shou-Zhe

    2015-06-01

    Atmospheric-pressure microwave induced N2 plasma is diagnosed by optical emission spectroscopy with respect to the plasma gas temperature. The spectroscopic measurement of plasma gas temperature is discussed with respect to the spectral line broadening of Ar I and the various emission rotational-vibrational band systems of N2(B-A), N2(C-B) and \\text{N}2+(\\text{B-X}). It is found that the Boltzmann plot of the selective spectral lines from \\text{N}2+(\\text{B-X}) at 391.4 nm is preferable to others with an accuracy better than 5% for an atmospheric-pressure plasma of high gas temperature. On the basis of the thermal balance equation, the dependences of the plasma gas temperature on the absorbed power, the gas flow rate, and the gas composition are investigated experimentally with photographs recording the plasma morphology.

  7. Temperature of solid particles in colloidal plasmas in space

    NASA Technical Reports Server (NTRS)

    De, B. R.

    1977-01-01

    Lehnert (1970) has investigated the question of the relationship between the kinetic temperature and the internal temperature at which a solid coexists with a plasma in a thermal steady state. The reported investigation is a more refined version of Lehnert's preliminary analysis of this relationship. The electric potential of grains is considered along with the ambient radiation field and the grain temperatures in the thermal steady state. An illustrative calculation is conducted of the grain temperatures in the dense regions of the primordial circumsolar colloidal plasma envelope such as envisioned in the Alfven-Arrhenius model (1976) of the origin of the solar system. It is shown that under certain conditions the solid grains can coexist with the plasma phase up to fairly high plasma densities and temperatures.

  8. Electron acceleration by a nonlinear wakefield generated by ultrashort (23-fs) high-peak-power laser pulses in plasma.

    PubMed

    Kando, M; Masuda, S; Zhidkov, A; Yamazaki, A; Kotaki, H; Kondo, S; Homma, T; Kanazawa, S; Nakajima, K; Hayashi, Y; Mori, M; Kiriyama, H; Akahane, Y; Inoue, N; Ueda, H; Nakai, Y; Tsuji, K; Yamamoto, Y; Yamakawa, K; Koga, J; Hosokai, T; Uesaka, M; Tajima, T

    2005-01-01

    We study experimentally the interaction of the shortest at present (23-fs) , relativistically intense (20-TW), tightly focused laser pulses with underdense plasma. MeV electrons constitute a two-temperature distribution due to different plasma wave-breaking processes at a plasma density of 10(20) cm(-3). These two groups of electrons are shown numerically to constitute bunches with very distinctive time durations. PMID:15697651

  9. Magnetohydrodynamic spin waves in degenerate electron-positron-ion plasmas

    SciTech Connect

    Mushtaq, A.; Maroof, R.; Ahmad, Zulfiaqr; Qamar, A.

    2012-05-15

    Low frequency magnetosonic waves are studied in magnetized degenerate electron-positron-ion plasmas with spin effects. Using the fluid equations of magnetoplasma with quantum corrections due to the Bohm potential, temperature degeneracy, and spin magnetization energy, a generalized dispersion relation for oblique magnetosonic waves is derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. For three different values of angle {theta}, the generalized dispersion relation is reduced to three different relations under the low frequency magnetohydrodynamic assumptions. It is found that the effect of quantum corrections in the presence of positron concentration significantly modifies the dispersive properties of these modes. The importance of the work relevant to compact astrophysical bodies is pointed out.

  10. Plasma scale-length effects on electron energy spectra in high-irradiance laser plasmas

    NASA Astrophysics Data System (ADS)

    Culfa, O.; Tallents, G. J.; Rossall, A. K.; Wagenaars, E.; Ridgers, C. P.; Murphy, C. D.; Dance, R. J.; Gray, R. J.; McKenna, P.; Brown, C. D. R.; James, S. F.; Hoarty, D. J.; Booth, N.; Robinson, A. P. L.; Lancaster, K. L.; Pikuz, S. A.; Faenov, A. Ya.; Kampfer, T.; Schulze, K. S.; Uschmann, I.; Woolsey, N. C.

    2016-04-01

    An analysis of an electron spectrometer used to characterize fast electrons generated by ultraintense (1020W cm-2 ) laser interaction with a preformed plasma of scale length measured by shadowgraphy is presented. The effects of fringing magnetic fields on the electron spectral measurements and the accuracy of density scale-length measurements are evaluated. 2D EPOCH PIC code simulations are found to be in agreement with measurements of the electron energy spectra showing that laser filamentation in plasma preformed by a prepulse is important with longer plasma scale lengths (>8 μ m ).

  11. Large amplitude double layers in a positively charged dusty plasma with nonthermal electrons

    SciTech Connect

    Djebli, M.; Marif, H.

    2009-06-15

    A pseudopotential approach is used to investigate large amplitude dust-acoustic solitary structures for a plasma composed of positively charged dust, cold electrons, and nonthermal hot electrons. Numerical investigation for an adiabatic situation is conducted to examine the existence region of the wave. The negative potential of the double layers is found to be dependent on nonthermal parameters, Mach number, and electrons temperature. A range of the nonthermal parameters values exists for which two possible double layers for the same plasma mix at different Mach numbers and with significant different amplitudes. The present model is used to investigate localized structures in the lower-altitude Earth's ionosphere.

  12. Relativistic electromagnetic waves in an electron-ion plasma

    NASA Technical Reports Server (NTRS)

    Chian, Abraham C.-L.; Kennel, Charles F.

    1987-01-01

    High power laser beams can drive plasma particles to relativistic energies. An accurate description of strong waves requires the inclusion of ion dynamics in the analysis. The equations governing the propagation of relativistic electromagnetic waves in a cold electron-ion plasma can be reduced to two equations expressing conservation of energy-momentum of the system. The two conservation constants are functions of the plasma stream velocity, the wave velocity, the wave amplitude, and the electron-ion mass ratio. The dynamic parameter, expressing electron-ion momentum conversation in the laboratory frame, can be regarded as an adjustable quantity, a suitable choice of which will yield self-consistent solutions when other plasma parameters were specified. Circularly polarized electromagnetic waves and electrostatic plasma waves are used as illustrations.

  13. Quantum tunneling resonant electron transfer process in Lorentzian plasmas

    SciTech Connect

    Hong, Woo-Pyo; Jung, Young-Dae

    2014-08-15

    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.

  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. Observation of warm, higher energy electrons transiting a double layer in a helicon plasma

    SciTech Connect

    Sung, Yung-Ta Li, Yan; Scharer, John E.

    2015-03-15

    Measurements of an inductive RF helicon argon plasma double layer with two temperature electron distributions including a fast (>80 eV) tail are observed at 0.17 mTorr Ar pressure. The fast, untrapped electrons observed downstream of the double layer have a higher temperature (13 eV) than the trapped (T{sub e} = 4 eV) electrons. The reduction of plasma potential and density observed in the double layer region would require an upstream temperature ten times the measured 4 eV if occurring via Boltzmann ambipolar expansion. The experimental observation in Madison helicon experiment indicates that fast electrons with substantial density fractions can be created at low helicon operating pressures.

  16. Monitoring Temperature in High Enthalpy Arc-heated Plasma Flows using Tunable Diode Laser Absorption Spectroscopy

    NASA Technical Reports Server (NTRS)

    Martin, Marcel Nations; Chang, Leyen S.; Jeffries, Jay B.; Hanson, Ronald K.; Nawaz, Anuscheh; Taunk, Jaswinder S.; Driver, David M.; Raiche, George

    2013-01-01

    A tunable diode laser sensor was designed for in situ monitoring of temperature in the arc heater of the NASA Ames IHF arcjet facility (60 MW). An external cavity diode laser was used to generate light at 777.2 nm and laser absorption used to monitor the population of electronically excited oxygen atoms in an air plasma flow. Under the assumption of thermochemical equilibrium, time-resolved temperature measurements were obtained on four lines-of-sight, which enabled evaluation of the temperature uniformity in the plasma column for different arcjet operating conditions.

  17. A fluid description for the discharge equilibrium of a divergent electron cyclotron resonance plasma source

    SciTech Connect

    Guan, G.; Mauel, M.E. ); Holber, W.M.; Caughman, J.B.O. )

    1992-12-01

    A fluid description of the presheath of a magnetized plasma is used to model a divergent electron cyclotron resonance (ECR) plasma source. The fluid equations are moments of the time-independent Boltzman equation when cross-field particle motion occurs only through a static {bold E}{times}{bold B} drift. Closure is obtained by neglecting third-order moments. The electrons are assumed to have constant temperature along the magnetic field, to obey a Maxwell--Boltzmann potential-density relationship, and to be warmer than the ions. Interactions between plasma and neutral gas are included by specifying the profile of the gas density along the magnetic field and collision cross sections. A form of the equations is derived that can be used to study ions with anisotropic temperatures. The model is used to estimate the axial profiles of the density, ion flow, and ion temperature of an ECR plasma source. The calculated global relationships between (1) the electron temperature and the equilibrium neutral gas density, and (2) the absorbed microwave power and the equilibrium plasma density are comparable with experimental measurements. Furthermore, the calculated ion temperature is comparable to recently reported measurements (Appl. Phys. Lett. {bold 57}, 661 (1990) and Appl. Phys. Lett. {bold 58}, 458 (1991)).

  18. Ion and electron temperatures in the SUMMA mirror device by emission spectroscopy

    NASA Technical Reports Server (NTRS)

    Patch, R. W.; Voss, D. E.; Reinmann, J. J.; Snyder, A.

    1974-01-01

    Ion and electron temperatures, and ion drift were measured in a superconducting magnetic mirror apparatus by observing the Doppler-broadened charge-exchange component of the 667.8 and 587.6 nanometer He lines in He plasma, and the H sub alpha and H sub beta lines in H2 plasma. The second moment of the line profiles was used as the parameter for determining ion temperature. Corrections for magnetic splitting, fine structure, monochromator slit function, and variation in charge-exchange cross section with energy are included. Electron temperatures were measured by the line ratio method for the corona model, and correlations of ion and electron temperatures with plasma parameters are presented.

  19. The effect of non-thermal electrons on obliquely propagating electron acoustic waves in a magnetized plasma

    NASA Astrophysics Data System (ADS)

    Singh, Satyavir; Bharuthram, Ramashwar

    2016-07-01

    Small amplitude electron acoustic solitary waves are studied in a magnetized plasma consisting of hot electrons following Cairn's type non-thermal distribution function and fluid cool electrons, cool ions and an electron beam. Using reductive perturbation technique, the Korteweg-de-Vries-Zakharov-Kuznetsov (KdV-ZK) equation is derived to describe the nonlinear evolution of electron acoustic waves. It is observed that the presence of non-thermal electrons plays an important role in determining the existence region of solitary wave structures. Theoretical results of this work is used to model the electrostatic solitary structures observed by Viking satellite. Detailed investigation of physical parameters such as non-thermality of hot electrons, beam electron velocity and temperature, obliquity on the existence regime of solitons will be discussed.

  20. Annular vortex merging processes in non-neutral electron plasmas

    SciTech Connect

    Kaga, Chikato Ito, Kiyokazu; Higaki, Hiroyuki; Okamoto, Hiromi

    2015-06-29

    Non-neutral electron plasmas in a uniform magnetic field are investigated experimentally as a two dimensional (2D) fluid. Previously, it was reported that 2D phase space volume increases during a vortex merging process with viscosity. However, the measurement was restricted to a plasma with a high density. Here, an alternative method is introduced to evaluate a similar process for a plasma with a low density.

  1. Plasma actuator electron density measurement using microwave perturbation method

    SciTech Connect

    Mirhosseini, Farid; Colpitts, Bruce

    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.

  2. Alkylation of lignites and peat in low-temperature plasma

    SciTech Connect

    L.I. Shchukin; S.I. Zherebtsov; M.V. Kornievich; O.A. Skutina

    2007-02-15

    The alkylation of lignites and peat was carried out at 50-270{sup o}C in different plasmas. The degree of conversion determined as the yield of the alcohol-benzene extract increases on passing from methane to alcohol plasma. The dependence of the extract yield on the plasma temperature, treatment time, and sample grinding degree was studied. 5 refs., 4 figs., 2 tabs.

  3. Interaction of two solitary waves in quantum electron-positron-ion plasma

    SciTech Connect

    Xu Yanxia; Lin Maimai; Shi Yuren; Duan Wenshan; Liu Zongming; Chen Jianmin

    2011-05-15

    The collision between two ion-acoustic solitary waves with arbitrary colliding angle {theta} in an unmagnetized, ultracold quantum three-component e-p-i plasma has been investigated. By using the extended Poincare-Lighthill-Kuo (PLK) perturbation method, we obtain the KdV equations and the analytical phase shifts after the collision of two solitary waves in this three-component plasma. The effects of the quantum parameter H, the ratio of Fermi positron temperature to Fermi electron temperature {sigma}, the ratio of Fermi positron number density to Fermi electron number density {mu}, and the ratio of Fermi ion temperature to Fermi electron temperature {rho} on the phase shifts are studied. It is found that these parameters can significantly influence the phase shifts of the solitons.

  4. Ponderomotive Acceleration of Hot Electrons in Tenuous Plasmas

    SciTech Connect

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

    2009-02-01

    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/Υg << 1, which prevents net acceleration of the cold plasma, it is also shown that the normalized energy Υ of hot electrons accelerated from the initial energy Υo < , Γ does not exceed Γ ~ aΥg, where a is the normalized laser field, and Υg is the group velocity Lorentz factor. Yet Υ ~ Γ is attained within a wide range of initial conditions; hence a cutoff in the hot electron distribution is predicted.

  5. Controlling electron injection in laser plasma accelerators using multiple pulses

    SciTech Connect

    Matlis, N. H.; Geddes, C. G. R.; Plateau, G. R.; Esarey, E.; Schroeder, C.; Bruhwiler, D.; Cormier-Michel, E.; Chen, M.; Yu, L.; Leemans, W. P.

    2012-12-21

    Use of counter-propagating pulses to control electron injection in laser-plasma accelerators promises to be an important ingredient in the development of stable devices. We discuss the colliding pulse scheme and associated diagnostics.

  6. Electron transport in a collisional plasma with multiple ion species

    SciTech Connect

    Simakov, Andrei N. Molvig, Kim

    2014-02-15

    A generalization of the Braginskii electron fluid description [S. I. Braginskii, Sov. Phys. JETP 6, 358 (1958)] to the case of an unmagnetized collisional plasma with multiple ion species is presented. A description of the plasma ions with disparate masses is also discussed.

  7. 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.

  8. Ideal laser-beam propagation through high-temperature ignition Hohlraum plasmas.

    PubMed

    Froula, D H; Divol, L; Meezan, N B; Dixit, S; Moody, J D; Neumayer, P; Pollock, B B; Ross, J S; Glenzer, S H

    2007-02-23

    We demonstrate that a blue (3omega, 351 nm) laser beam with an intensity of 2 x 10(15) W cm(-2) propagates nearly within the original beam cone through a millimeter scale, T(e)=3.5 keV high density (n(e)=5 x 10(20) cm(-3)) plasma. The beam produced less than 1% total backscatter at these high temperatures and densities; the resulting transmission is greater than 90%. Scaling of the electron temperature in the plasma shows that the plasma becomes transparent for uniform electron temperatures above 3 keV. These results are consistent with linear theory thresholds for both filamentation and backscatter instabilities inferred from detailed hydrodynamic simulations. This provides a strong justification for current inertial confinement fusion designs to remain below these thresholds. PMID:17359104

  9. Role of ionization and electron drift velocity profile to Rayleigh instability in a Hall thruster plasma

    SciTech Connect

    Singh, Sukhmander; Malik, Hitendra K.

    2012-07-01

    Role of ionization to Rayleigh instability is clarified in a Hall thruster plasma under the variety of profiles of electron drift velocity, namely, step-like profile (SLP) and two different super-Gaussian profiles (SGP1 and SGP2). For this, a relevant Rayleigh equation is derived and solved numerically using fourth-order Runge-Kutta method. Interestingly, an upper cutoff frequency of oscillations {omega}{sub max} is realized for the occurrence of the instability that shows dependence on the ionization rate {alpha}, electron drift velocity u{sub 0}, electron cyclotron frequency {Omega}, azimuthal wave number k{sub y}, plasma density n{sub 0}, density gradient {partial_derivative}n{sub 0}/{partial_derivative}x, ion (electron) thermal speed V{sub thI}(V{sub thE}), and ion (electron) plasma frequency {omega}{sub pi}({omega}{sub pe}). The frequency {omega}{sub max} follows the trend {omega}{sub max} (for SGP2) >{omega}{sub max} (for SLP) >{omega}{sub max} (for SGP1) and shows a similar behaviour with ionization for all types of the velocity profiles. The instability is found to grow faster for the higher {alpha} and the ion temperature but it acquires lower rate under the effect of the higher electron temperature; the perturbed potential also varies in accordance with the growth rate. The electron temperature influences the growth rate and cutoff frequency less significantly in comparison with the ion temperature.

  10. Electron acceleration during the decay of nonlinear Whistler waves in low-beta electron-ion plasma

    SciTech Connect

    Umeda, Takayuki; Saito, Shinji; Nariyuki, Yasuhiro E-mail: saito@stelab.nagoya-u.ac.jp

    2014-10-10

    Relativistic electron acceleration through dissipation of a nonlinear, short-wavelength, and monochromatic electromagnetic whistler wave in low-beta plasma is investigated by utilizing a one-dimensional fully relativistic electromagnetic particle-in-cell code. The nonlinear (large-amplitude) parent whistler wave decays through the parametric instability which enhances electrostatic ion acoustic waves and electromagnetic whistler waves. These waves satisfy the condition of three-wave coupling. Through the decay instability, the energy of electron bulk velocity supporting the parent wave is converted to the thermal energy perpendicular to the background magnetic field. Increase of the perpendicular temperature triggers the electron temperature anisotropy instability which generates broadband whistler waves and heats electrons in the parallel direction. The broadband whistler waves are inverse-cascaded during the relaxation of the electron temperature anisotropy. In lower-beta conditions, electrons with a pitch angle of about 90° are successively accelerated by inverse-cascaded whistler waves, and selected electrons are accelerated to over a Lorentz factor of 10. The result implies that the nonlinear dissipation of a finite-amplitude and short-wavelength whistler wave plays an important role in producing relativistic nonthermal electrons over a few MeV especially at lower beta plasmas.

  11. Electrostatic Nonplanar Positron-Acoustic Shock Waves in Superthermal Electron-Positron-Ion Plasmas

    NASA Astrophysics Data System (ADS)

    M. J., Uddin; M. S., Alam; A. A., Mamun

    2015-06-01

    The basic properties of the nonlinear propagation of the nonplanar (cylindrical and spherical) positron-acoustic (PA) shock waves (SHWs) in an unmagnetized electron-positron-ion (e-p-i) plasma containing immobile positive ions, mobile cold positrons, and superthermal (kappa distributed) hot positrons and electrons are investigated both analytically and numerically. The modified Burgers equation (mBE) is derived by using the reductive perturbation method. The basic features of PA SHWs are significantly modified by the cold positron kinematic viscosity (η), superthermal parameter of electrons (κe), superthermal parameter of hot positrons (κp), the ratio of the electron temperature to hot positron temperature (σ), the ratio of the electron number density to cold positron number density and the ratio of the hot positron number density to cold positron number density (μph). This study could be useful to identify the basic properties of nonlinear electrostatic disturbances in dissipative space and laboratory plasmas.

  12. Low-Temperature Sterilization with Surface-Wave-Excited Oxygen Plasma

    NASA Astrophysics Data System (ADS)

    Nagatsu, Masaaki; Terashita, Fumie; Koide, Yukio

    2003-07-01

    Low-temperature plasma sterilization has been experimentally demonstrated using surface-wave plasma excited by a 2.45 GHz microwave. With the spores of Bacillus stearothermophilus and Bacillus subtilis as biological indicators, we have carried out the plasma sterilization experiments by varying the irradiation period of oxygen plasma discharges. It was experimentally confirmed that the spores with a population of 1.5 × 106 were sterilized by irradiating them with oxygen plasma discharges generated with a microwave power of 700 W at a pressure of 60-80 mTorr for 3 min or longer. From the scanning electron microscopy (SEM) analysis of the spores, we found that the sterilized spores clearly had different sizes and shapes compared with those before the plasma irradiation. Furthermore, present experiments suggested that the changes of spore shapes were mainly attributed to the reactive interactions with oxygen radicals.

  13. Electron beam manipulation, injection and acceleration in plasma wakefield accelerators by optically generated plasma density spikes

    NASA Astrophysics Data System (ADS)

    Wittig, Georg; Karger, Oliver S.; Knetsch, Alexander; Xi, Yunfeng; Deng, Aihua; Rosenzweig, James B.; Bruhwiler, David L.; Smith, Jonathan; Sheng, Zheng-Ming; Jaroszynski, Dino A.; Manahan, Grace G.; Hidding, Bernhard

    2016-09-01

    We discuss considerations regarding a novel and robust scheme for optically triggered electron bunch generation in plasma wakefield accelerators [1]. In this technique, a transversely propagating focused laser pulse ignites a quasi-stationary plasma column before the arrival of the plasma wake. This localized plasma density enhancement or optical "plasma torch" distorts the blowout during the arrival of the electron drive bunch and modifies the electron trajectories, resulting in controlled injection. By changing the gas density, and the laser pulse parameters such as beam waist and intensity, and by moving the focal point of the laser pulse, the shape of the plasma torch, and therefore the generated trailing beam, can be tuned easily. The proposed method is much more flexible and faster in generating gas density transitions when compared to hydrodynamics-based methods, and it accommodates experimentalists needs as it is a purely optical process and straightforward to implement.

  14. Low Temperature Atmospheric Argon Plasma: Diagnostics and Medical Applications

    NASA Astrophysics Data System (ADS)

    Ermolaeva, Svetlana; Petrov, Oleg; Zigangirova, Nailya; Vasiliev, Mikhail; Sysolyatina, Elena; Antipov, Sergei; Alyapyshev, Maxim; Kolkova, Natalia; Mukhachev, Andrei; Naroditsky, Boris; Shimizu, Tetsuji; Grigoriev, Anatoly; Morfill, Gregor; Fortov, Vladimir; Gintsburg, Alexander

    This study was devoted to diagnostic of low temperature plasma produced by microwave generator and investigation of its bactericidal effect against bacteria in biofilms and within eukaryotic cells. The profile of gas temperature near the torch outlet was measured. The spectrum in a wide range of wavelengths was derived by the method of optical emission spec-troscopy. Probe measurements of the floating potential of plasma were car-ried out. The estimation and adaptation of parameters of plasma flow (tem-perature, velocity, ion number density) according to medico-technical requirements were produced. The model of immersed surface-associated biofilms formed by Gram-negative bacteria, Pseudomonas aeruginosa and Burkholderia cenocepacia, and Gram-positive bacteria, Staphylococcus aureus, was used to assess bactericidal effects of plasma treatment. Reduction in the concentration of live bacteria in biofilms treated with plasma for 5 min was demonstrated by measuring Live/Dead fluorescent labeling and using direct plating. The intracellular infection model with the pathogenic bacterium, Chlamydia trachomatis, was used to study the efficacy of microwave argon plasma against intracellular parasites. A 2 min plasma treatment of mouse cells infected with C. trachomatis reduced infectious bacteria by a factor of 2×106. Plasma treatment diminished the number of viable host cells by about 20%. When the samples were covered with MgF2 glass to obstruct active particles and UV alone was applied, the bactericidal effect was re-duced by 5×104 fold compared to the whole plasma.

  15. Ground State and Excited State H-Atom Temperatures in a Microwave Plasma Diamond Deposition Reactor

    NASA Astrophysics Data System (ADS)

    Gicquel, A.; Chenevier, M.; Breton, Y.; Petiau, M.; Booth, J. P.; Hassouni, K.

    1996-09-01

    Ground electronic state and excited state H-atom temperatures are measured in a microwave plasma diamond deposition reactor as a function of a low percentage of methane introduced in the feed gas and the averaged input microwave power density. Ground state H-atom temperatures (T_H) and temperature of the H-atom in the n=3 excited state (T_{Hα}) are obtained from the measurements respectively of the excitation profile by Two-photon Allowed transition Laser Induced Fluorescence (TALIF) and the Hα line broadening by Optical Emission Spectroscopy (OES). They are compared to gas temperatures calculated with a 1D diffusive non equilibrium H{2} plasma flow model and to ground electronic state rotational temperatures of molecular hydrogen measured previously by Coherent Anti-Stokes Raman Spectroscopy.

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

    SciTech Connect

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

    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.

  17. Vacuum polarization and electron-positron plasma oscillations

    SciTech Connect

    Ruffini, R.; Vereshchagin, G. V.; Xue, S.-S.

    2008-01-03

    We study plasma oscillations of electrons-positron pairs created by the vacuum polarization in an uniform electric field. Our treatment, encompassing also the case of E>E{sub c}, shows the existence in both cases of a maximum Lorentz factor acquired by electrons and positrons and allows determination of the a maximal length of oscillation. We quantitatively estimate how plasma oscillations reduce the rate of pair creation and increase the time scale of the pair production.

  18. Properties of Trapped Electron Bunches in a Plasma Wakefield Accelerator

    SciTech Connect

    Kirby, Neil; /SLAC

    2009-10-30

    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, {epsilon}{sub N,x}/I{sub t}, below the level of 0.2 {micro}m/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 non-linear 'bubble' regime of the PWFA. This model and simulations indicate that the observed values of {epsilon}{sub N,x}/I{sub t} result from multi-GeV trapped electron bunches with emittances of a few {micro}m 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

  19. Temperature profile measurements and equilibrium calculations in a non-neutral plasma.

    NASA Astrophysics Data System (ADS)

    Hart, Grant W.; Peterson, Bryan G.

    2004-11-01

    In 1992 Eggleston, et.al.^1 developed a technique for measuring the radial temperature profile in a pure electron plasma by partially dumping the plasma onto a charge collector. They used a model which described the plasma as a flat-ended cylinder to determine the midplane potential of the plasma and ignored the plasma's contribution to the confining potential hill. These assumptions are fine if the plasma is long and the ring to which the confining potential is applied is also fairly long. For short plasmas and short confining rings, a more general calculation is needed. In this paper we present a variation on the standard equilibrium calculation that allows us to use dumped charge vs. confining potential data to calculate the temperature profile of a pure electron plasma. The fact that part of the Maxwellian velocity distribution has escaped forces a generalization of the form of the equilibrium condition from the usual e^-q φ/kT. Experimental data and results will be discussed. A simplified measurement similar to the simple r=0 velocity-tail measurement of Eggleston will also be discussed. ^1D.L.Eggleston, C.F. Driscoll, B.R. Beck, A.W. Hyatt and J.H. Malmberg, Phys. Fluids B 4, 3432 (1992).

  20. The Influence of Energetic Electrons on the Cassini Langmuir Probe at Saturn : Deriving Large Electron Temperatures and Small Electron Densities

    NASA Astrophysics Data System (ADS)

    Garnier, P.; Wahlund, J.; Holmberg, M.; Lewis, G.; Schippers, P.; Thomsen, M. F.; Rochel Grimald, S.; Gurnett, D. A.; Coates, A. J.; Dandouras, I. S.; Waite, J. H.

    2013-12-01

    The Langmuir probes (LPs) are commonly used to investigate the cold plasma characteristics in planetary ionospheres/magnetospheres. The LPs performances are limited to low temperatures (i.e. below 5-10 eV at Saturn) and large densities (above several particles/cm3). A strong sensitivity of the Cassini LP measurements to energetic electrons (hundreds eV) may however be observed at Saturn in the L Shell range L=6-10 RS. These electrons impact the surface of the probe and generate a detectable current of secondary electrons. We investigated the influence of such electrons on the current-voltage (I-V) characteristics (for negative potentials), showing that both the DC level and slope of the I-V curve are modified. The influence of energetic electrons may be interpreted in terms of the critical and anticritical temperatures concept that is important for spacecraft charging studies. Estimations of the maximum secondary yield value for the LP surface are obtained without using laboratory measurements. Empirical and theoretical methods were developed to reproduce the influence of the energetic electrons with a reasonable precision. Conversely, this modelling allows us to derive useful information about the energetic electrons from the LP observations : some information about their pitch angle anisotropy (if combined with the data from a single CAPS ELS anode), as well as an estimate of the electron temperature (in the range 100-300 eV) and of the electron density (above 0.1 particles/cm3). This enlarges the LP measurements capabilities when the influence of the energetic electrons is large (essentially near L=6-10 RS at Saturn). The understanding of this influence may be used for other missions using Langmuir probes, such as the future missions JUICE at Jupiter, BepiColombo at Mercury, or even the probes in the Earth magnetosphere.