Sample records for ion drift velocity

  1. Ion acoustic solitons in a plasma with finite temperature drifting ions: Limit on ion drift velocity

    Microsoft Academic Search

    H. K. Malik; Sanjay Singh; R. P. Dahiya

    1994-01-01

    Propagation of ion acoustic solitons in a plasma consisting of finite temperature drifting ions and nondrifting electrons has been studied. It is shown that in addition to the electron inertia and weak relativistic effects, the ion temperature also modifies the soliton behavior. By including the finite ion temperature, limit for the ion drift velocity [ital u][sub 0] for which the

  2. Ion drift velocities in gaseous mixtures at arbitrary field strengths.

    NASA Technical Reports Server (NTRS)

    Mason, E. A.; Hahn, H.-S.

    1972-01-01

    A momentum-transfer theory is used to obtain an expression for the drift velocity of an ion in a multicomponent gas mixture. This is combined with an approximate calculation of the partition of the ion energy in the mixture to yield a formula for the drift velocity in terms of the drift velocities in the pure component gases. Positive deviations from Blanc's law at high fields are predicted, of magnitudes that should be easily measured experimentally.

  3. Negative hydrogen ion densities and drift velocities in a multicusp ion source

    SciTech Connect

    Eenshuistra, P.J.; Gochitashvilli, M.; Becker, R.; Kleyn, A.W.; Hopman, H.J. (Association EURATOM-FOM, FOM-Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam (The Netherlands))

    1990-01-01

    We have determined densities of negative hydrogen ions in a discharge by a laser detachment technique. We measured the electron density, the electron temperature, and the positive ion density using a Langmuir probe. We also performed extraction measurements. Combination of H{sup {minus}} density measurements and extraction measurements yields information about the H{sup {minus}} drift velocity. It was found that the velocity scaled with the square root of the electron temperature. All measurements were done as a function of discharge voltage, discharge current, and gas pressure. The densities are compatible with a semiquantitative model in which H{sup {minus}} is produced by dissociative attachment of plasma electrons to vibrationally excited molecules and destroyed by wall collisions at very low pressure and collisions with H atoms, positive ions and/or hot thermal electrons at higher pressure.

  4. Ion Drift Velocities at Sheath\\/Presheath Boundary in Weakly Collisional Plasmas with Two Ion Species

    Microsoft Academic Search

    Noah Hershkowitz; Eunsuk Ko; Xu Wang; Greg Severn

    2002-01-01

    The concept of presheaths, i.e. weak plasma potential gradients provide ion acceleration to the Bohm velocity at the sheath\\/plasma boundary, works in single ion species plasmas. When two ion species are present and ion-neutral collision lengths are small compared to chamber dimensions and large compared to Debye lengths, it is not clear that an appropriate presheath potential profile can provide

  5. Calculation of poloidal velocity in the tokamak plasma with allowance for density inhomogeneity and diamagnetic drift of ions

    SciTech Connect

    Shurygin, R. V. [National Research Centre Kurchatov Institute, Institute of Tokamak Physics (Russian Federation)

    2012-02-15

    A one-dimensional evolution equation for the angle-averaged poloidal momentum of the tokamak plasma is derived in the framework of reduced magnetohydrodynamics with allowance for density inhomogeneity and diamagnetic drift of ions. In addition to fluctuations of the E Multiplication-Sign B drift velocity, the resulting turbulent Reynolds stress tensor includes fluctuations of the ion density and ion pressure, as well as turbulent radial fluxes of particles and heat. It is demonstrated numerically by using a particular example that the poloidal velocity calculated using the refined one-dimensional evolution equation differs substantially from that provided by the simplified model. When passing to the new model, both the turbulent Reynolds force and the Stringer-Winsor force increase, which leads to an increase in the amplitude of the ion poloidal velocity. This, in turn, leads to a decrease in turbulent fluxes of particles and heat due to the effect of shear decorrelation.

  6. The role of external electric fields in enhancing ion mobility, drift velocity, and drift-diffusion rates in aqueous electrolyte solutions

    NASA Astrophysics Data System (ADS)

    Murad, Sohail

    2011-03-01

    Molecular simulations have been carried out using the method of molecular dynamics to investigate the role of external electric fields on the ion mobility, drift velocity, and drift-diffusion rate of ions in aqueous electrolyte solutions. These properties are critical for a range of processes including electrodialysis, electro-deionization, electrophoresis, and electroosmosis. Our results show that external electric fields relax the hydrated ion structure at significantly larger time scales (between 300 and 800 ps), than most other relaxation processes in solutions (generally of the order of 1 ps). Previous studies that did not account for the much longer relaxation times did not observe this behavior for ions even with very high electric fields. External electric fields must also overcome several (at least two or more) activation energy barriers to significantly change the structure of hydrated ions. As a result, the dynamic behavior changes almost in bands as a function of electric field strengths, rather than linearly. Finally, the effect of the field is much less dramatic on water than the ions. Thus electric fields will be of more significance in processes that involve the transport of ions (such as electro-deionization) than the transport of water (electroosmosis).

  7. Ion Drift Meter for Dynamics Explorer

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.; Hanson, W. B.; Lippincott, C. R.; Zuccaro, D. R.

    1982-01-01

    The ion drift meter for Dynamics Explorer B is discussed. It measures two mutually perpendicular angles of arrival of thermal ions with respect to the sensor look directions. These angles lie in the vertical and horizontal planes and may be thought of as pitch and yaw in the conventional aerodynamic sense. The components of the ion drift velocity along vertical and horizontal axes through the spacecraft body are derived to first order from knowledge of the spacecraft velocity vector and more accurately with additional knowledge of the component of ion drift along the sensor look direction.

  8. Remote-sensing observations of F-region ion drift velocities using Dynamics Explorer-2 Doppler measurements of the O+(2P) 732.0 nm emission

    NASA Technical Reports Server (NTRS)

    Carr, S. S.; Killeen, T. L.; Coley, W. R.

    1992-01-01

    Limb-scan observations of Doppler line profiles from the O+(2P) 732.0 nm emission at F-region altitudes, made with the Fabry-Perot interferometer (FPI) on the Dynamics Explorer-2 (DE-2) spacecraft, have been analyzed to provide measurements of the meridional component of the ion convection velocity along the instrument line-of-sight. The initial DE-2 results presented here demonstrate the first spaceborne use of the remote-sensing Doppler technique for measurements of ionospheric convection. The FPI meridional ion drift measurements have been compared with nearly simultaneous in situ ion drift measurements from the Retarding Potential Analyzer on DE 2. Once allowance is made for the temporal lag between the in situ and remote measurements, the results from the two techniques are in good agreement. The results of a simulation study demonstrate that the spaceborne interferometric technique has future utility for 2D imaging of the quasi-instantaneous ion convection pattern.

  9. The Ion Drift Meter for Dynamics Explorer-B

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.; Hanson, W. B.; Lippincott, C. R.; Zuccaro, D. R.; Harmon, L. H.; Holt, B. J.; Doherty, J. E.; Power, R. A.

    1981-01-01

    The Ion Drift Meter on Dynamics Explorer-B measures two mutually perpendicular angles of arrival of thermal ions with respect to the sensor look direction. These measurements are used to derive two components of the ambient thermal ion drift velocity, which together with the third component from the Retarding Potential Analyzer instrument provide the total velocity. The Ion Drift Meter technique yields high temporal resolution measurements essential in the studies of the convection pattern and energy deposition in the ionosphere.

  10. Effects of ion drift on small-amplitude ion-acoustic solitons

    Microsoft Academic Search

    H. H. Kuehl; C. Y. Zhang

    1991-01-01

    Some properties of small-amplitude ion-acoustic solitons in a plasma consisting of nondrifting electrons and drifting ions are investigated. Electron inertia effects are shown to be considerably more important than relativistic effects. It is also shown that ion-acoustic soliton solutions exist only if the ion drift velocity is less than the electron thermal velocity.

  11. Prediction of ion drift effects on spacecraft floating potentials

    NASA Technical Reports Server (NTRS)

    Chang, J. S.; Prokopenko, S. M. L.; Godard, R.; Laframboise, J. G.

    1979-01-01

    The plasma environment of high altitude spacecraft was observed to involve ion drift velocities which sometimes become comparable to ion mean thermal speeds. Such drifts may cause an electrically isolated spacecraft surface to float at a substantially increased negative potential if it is simultaneously shaded and downstream relative to the drift direction. The results showed that: (1) the ion speed ratio at which drift effects become important (i.e. change the floating potential by at least 10 percent) can be as low as 0.1, and may be decreased if the ambient electrons are non-Maxwellian; (2) the effects of ion speed ratio increase with increasing ion-to-electron temperature ratio; and (3) negative floating potentials for drifting Maxwellian ion velocity distributions with speed ratio unity are typically about twice as large as the corresponding potentials for nondrifting conditions.

  12. Nonlinear drift waves in electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Saleem, H.; Haque, Q.; Vranjes, J.

    2003-05-01

    It is suggested that low-frequency drift waves can play an important role in the dynamics of electron-positron plasmas comprising some concentration of ions. In the electromagnetic case the drift wave couples with the shear Alfvén wave in an electron-positron-ion plasma. The drift wave frequency can be very low in such plasmas depending on the concentration and density scale lengths of the plasma components. In the nonlinear regime these waves can give rise to dipolar vortices in both electrostatic and electromagnetic limits. The velocity of the nonlinear structure turns out to be different compared to the case of an electron-ion plasma.

  13. Dimethylether: a low velocity, low diffusion drift chamber gas

    SciTech Connect

    Villa, F.

    1983-01-01

    There are two main motivations to look for a low electron mobility gas: the first is that a low drift velocity relaxes the need to measure drift times with nanosecond (or even subnanosecond) precision; the second is that (in an ideal drift geometry), the capability of resolving two closely spaced tracks depends upon the ratio of electron mobility to ion mobility ..mu../sub e//..mu../sub i/. Since ..mu../sub i/ is rather constant, the way to separate two tracks is to slow down the electrons. Many other properties are required besides low mobility and low drifting electron temperature: the gas should have a large (> 10/sup 3/) stable gain; it must be chemically stable and not oxic; it should not attack materials commonly used to fabricate drift chambers, etc. With these requirements in mind, we have tried a few promising (on paper) gases, either pure or in admixture with Argon. One of the gases examined, dimethylether ((CH/sub 3/)/sub 2/)), has shown interesting characteristics.

  14. Drift Velocity Calibration for the CLAS Drift Chamber System

    Microsoft Academic Search

    Stephen L. Levy; Gerard P. Gilfoyle; Mac Mestayer

    1996-01-01

    The University of Richmond Physics Department is responsible for projects being developed for the Continuous Electron Beam Accelerator Facility (CEBAF). We have constructed a prototype of the bow section of the Region 3 drift chambers of Hall B, called the nose cone prototype. Cosmic rays travel through the chamber and ionize atoms from its argon\\/ethane gas mixture. The displaced electrons

  15. Electrostatic drift shocks and drift wave instability in inhomogeneous rotating electron-positron-ion plasmas

    SciTech Connect

    Haque, Q. [Theoretical Plasma Physics Division, PINSTECH P. O. Nilore, Islamabad (Pakistan) and National Centre for Physics, Islamabad (Pakistan)

    2012-09-15

    The electrostatic drift wave shocks are studied in inhomogeneous rotating e-p-i plasma of the pulsar atmosphere. In this regard, the dissipation due to ion-neutral collisions is considered, which facilitate the formation of shock structures. It is noticed that these structures can move with the velocity of the drift wave which is not possible without considering the rotational effects. Several limiting cases are also discussed. In addition, the drift wave instability is obtained when electrons and positrons could not cancel out the space charge effects along the magnetic field lines in the presence of electron-ion and positron-ion collisions. Further, it is found that this instability is sensitive to rotational frequency of the object. The importance of the results with relevance to astrophysical plasmas is also pointed out.

  16. Two-stream instability with time-dependent drift velocity

    DOE PAGESBeta

    Qin, Hong [PPPL; Davidson, Ronald C. [PPPL

    2014-01-01

    The classical two-stream instability driven by a constant relative drift velocity between two plasma components is extended to the case with time-dependent drift velocity. A solution method is developed to rigorously define and calculate the instability growth rate for linear perturbations relative to the time-dependent unperturbed two-stream motions. Stability diagrams for the oscillating two-stream instability are presented over a large region of parameter space. It is shown that the growth rate for the classical two-stream instability can be significantly reduced by adding an oscillatory component to the relative drift velocity.

  17. Drift compression of an intense neutralized ion beam

    SciTech Connect

    Roy, P.K.; Yu, S.S.; Henestroza, E.; Anders, A.; Bieniosek, F.M.; Coleman, J.; Eylon, S.; Greenway, W.G.; Leitner, M.; Logan, B.G.; Waldron, W.L.; Welch, D.R.; Thoma, C.; Sefkow, A.B.; Gilson, E.P.; Efthimion, P.C.; Davidson, R.C.

    2004-10-25

    Longitudinal compression of a tailored-velocity, intense neutralized ion beam has been demonstrated. The compression takes place in a 1-2 m drift section filled with plasma to provide space-charge neutralization. An induction cell produces a head-to-tail velocity ramp that longitudinally compresses the neutralized beam, enhancing the beam peak current by a factor of 50 and producing a pulse duration of about 3 ns. this measurement has been confirmed independently with two different diagnostic systems.

  18. Separation of motile bacteria using drift velocity in a microchannel.

    PubMed

    Ishikawa, Takuji; Shioiri, Tatsuya; Numayama-Tsuruta, Keiko; Ueno, Hironori; Imai, Yohsuke; Yamaguchi, Takami

    2014-03-01

    Separation of certain bacteria from liquids is important in the food, water quality management, bioengineering, and pharmaceutical industries. In this study, we developed a microfluidic device for the hydrodynamic separation of motile bacteria (Escherichia coli) using drift velocity. We first investigated drift tendencies of bacteria and found that cells tended to move in a spanwise direction with similar velocities regardless of the flow rate. When the drift distance was small compared to the wetted perimeter of the cross section, the cells were not separated efficiently. We then investigated the drift phenomenon in more detail using a numerical simulation. Interestingly, the drift phenomenon was observed even without a wall boundary, indicating that drift was caused mainly by the interaction of moving cells with the background shear flow. Finally, we developed a microfluidic device to separate motile bacteria from tracer particles or less motile cells. By decreasing the channel height, the device could successfully separate motile bacteria from other particles or cells with a separation efficiency of about 40%. Connecting microchannels in a series was also found to be effective, which achieved the separation efficiency of about 60%. The knowledge obtained in this study will facilitate the development of other microfluidics devices for use with bacteria. PMID:24448484

  19. Linear and nonlinear coupled drift and ion acoustic waves in collisional pair ion-electron magnetoplasma

    SciTech Connect

    Mushtaq, A. [Theoretical Plasma Physics Division, Pakistan Institute of Nuclear Science and Technology (PINSTECH), Nilore, Islamabad 45660 (Pakistan); School of Physics, University of Sydney, New South Wales 2006 (Australia); Saeed, R.; Haque, Q. [Theoretical Plasma Physics Division, Pakistan Institute of Nuclear Science and Technology (PINSTECH), Nilore, Islamabad 45660 (Pakistan)

    2011-04-15

    Linear and nonlinear coupled electrostatic drift and ion acoustic waves are studied in inhomogeneous, collisional pair ion-electron plasma. The Korteweg-de Vries-Burgers (KdVB) equation for a medium where both dispersion and dissipation are present is derived. An attempt is made to obtain exact solution of KdVB equation by using modified tanh-coth method for arbitrary velocity of nonlinear drift wave. Another exact solution for KdVB is obtained, which gives a structure of shock wave. Korteweg-de Vries (KdV) and Burgers equations are derived in limiting cases with solitary and monotonic shock solutions, respectively. Effects of species density, magnetic field, obliqueness, and the acoustic to drift velocity ratio on the solitary and shock solutions are investigated. The results discussed are useful in understanding of low frequency electrostatic waves at laboratory pair ion plasmas.

  20. Height dependence of spread F bubble drift velocities

    NASA Technical Reports Server (NTRS)

    Hudson, M. K.; Balsley, B. B.

    1979-01-01

    Vertical bubble velocities in equatorial spread F have been investigated analytically by Ott (1978), Osakow and Chaturvedi (1978), all of whom found a proportionality of the vertical velocity to bubble depletion density. The paper presents radar data from two equatorial sites which support theoretical predictions that vertical drift velocities of spread F bubbles increase with height on the bottomside of the F layer. This increase is shown to result from the proportionality of bubble drift velocity to density depletion amplitude, which itself increases with height. The measured rate of increase is found to be dU/dh equals about 2 m/s km. It is concluded that this is consistent with numerical simulation results within a factor of 2.

  1. Coupled nonlinear drift and ion acoustic waves in dense dissipative electron-positron-ion magnetoplasmas

    SciTech Connect

    Masood, W.; Siddiq, M. [TPPD, PINSTECH, P.O. Nilore, 44000 Islamabad (Pakistan); Karim, S.; Shah, H. A. [Department of Physics, GC University, 54000 Lahore (Pakistan)

    2009-11-15

    Linear and nonlinear propagation characteristics of drift ion acoustic waves are investigated in an inhomogeneous electron-positron-ion (e-p-i) quantum magnetoplasma with neutrals in the background using the well known quantum hydrodynamic model. In this regard, Korteweg-de Vries-Burgers (KdVB) and Kadomtsev-Petviashvili-Burgers (KPB) equations are obtained. Furthermore, the solutions of KdVB and KPB equations are presented by using the tangent hyperbolic (tanh) method. The variation in the shock profile with the quantum Bohm potential, collision frequency, and the ratio of drift to shock velocity in the comoving frame, v{sub *}/u, is also investigated. It is found that increasing the positron concentration and collision frequency decreases the strength of the shock. It is also shown that when the localized structure propagates with velocity greater than the diamagnetic drift velocity (i.e., u>v{sub *}), the shock strength decreases. However, the shock strength is observed to increase when the localized structure propagates with velocity less than that of drift velocity (i.e., u

  2. Transmission of different ions through a drift tube

    NASA Astrophysics Data System (ADS)

    Shamlouei, Hamid R.; Tabrizchi, Mahmoud

    2008-06-01

    Transmission through a drift tube has been measured for different types of ions. Various ions were injected at the same rate at the start of the drift tube. Then, the transmitted currents were measured at the end of the drift tube. The results show that transmission depends linearly on the inverse of the drift time. Factors influencing the drift time, such as pressure, temperature, and electric field, were also investigated and shown to affect the transmission efficiency in a similar manner as the type of ion. A simple model based on kinetics of two parallel processes (loss or transmission) is proposed to explain the results. Since slow-moving ions are lost more often than fast-moving ones, the intensity of ion peaks decreases as drift time increases. This can be easily corrected by transforming the y-axis to y × x (i.e., intensity × drift time).

  3. Test particle study of ion transport in drift type turbulence

    SciTech Connect

    Vlad, M.; Spineanu, F. [National Institute of Laser, Plasma and Radiation Physics, Association EURATOM-MEdC, Atomistilor 409, 077125 Magurele, Bucharest (Romania)] [National Institute of Laser, Plasma and Radiation Physics, Association EURATOM-MEdC, Atomistilor 409, 077125 Magurele, Bucharest (Romania)

    2013-12-15

    Ion transport regimes in drift type turbulence are determined in the frame of a realistic model for the turbulence spectrum based on numerical simulations. The model includes the drift of the potential with the effective diamagnetic velocity, turbulence anisotropy, and dominant waves. The effects of the zonal flow modes are also analyzed. A semi-analytical method that is able to describe trajectory stochastic trapping or eddying is used for obtaining the transport coefficients as function of the parameters of the turbulence. Analytical approximations of the transport coefficients are derived from the results. They show the transition from Bohm to gyro-Bohm scaling as plasma size increases in very good agreement with the numerical simulations.

  4. Filament velocity scaling laws for warm ions

    SciTech Connect

    Manz, P. [Physik-Department E28, Technische Universität München, James-Franck-Str. 1, 85748 Garching (Germany) [Physik-Department E28, Technische Universität München, James-Franck-Str. 1, 85748 Garching (Germany); Max-Planck-Institut für Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany); Carralero, D.; Birkenmeier, G.; Müller, H. W.; Scott, B. D. [Max-Planck-Institut für Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany)] [Max-Planck-Institut für Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany); Müller, S. H. [Center for Momentum Transport and Flow Organization, University of California at San Diego, San Diego 92093 (United States)] [Center for Momentum Transport and Flow Organization, University of California at San Diego, San Diego 92093 (United States); Fuchert, G. [Insitut für Grenzflächenverfahrenstechnik und Plasmatechnologie, Universität Stuttgart, 70569 Stuttgart (Germany)] [Insitut für Grenzflächenverfahrenstechnik und Plasmatechnologie, Universität Stuttgart, 70569 Stuttgart (Germany); Stroth, U. [Max-Planck-Institut für Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany) [Max-Planck-Institut für Plasmaphysik, EURATOM Assoziation, Boltzmannstr. 2, 85748 Garching (Germany); Physik-Department E28, Technische Universität München, James-Franck-Str. 1, 85748 Garching (Germany)

    2013-10-15

    The dynamics of filaments or blobs in the scrape-off layer of magnetic fusion devices are studied by magnitude estimates of a comprehensive drift-interchange-Alfvén fluid model. The standard blob models are reproduced in the cold ion case. Even though usually neglected, in the scrape-off layer, the ion temperature can exceed the electron temperature by an order of magnitude. The ion pressure affects the dynamics of filaments amongst others by adding up to the interchange drive and the polarisation current. It is shown how both effects modify the scaling laws for filament velocity in dependence of its size. Simplifications for experimentally relevant limit regimes are given. These are the sheath dissipation, collisional, and electromagnetic regime.

  5. Role of ionization and electron drift velocity profile to Rayleigh instability in a Hall thruster plasma

    SciTech Connect

    Singh, Sukhmander; Malik, Hitendra K. [Plasma Waves and Particle Acceleration Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110 016 (India)

    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.

  6. Development of Ion Drift-Chemical Ionization Mass Spectrometry

    E-print Network

    Development of Ion Drift-Chemical Ionization Mass Spectrometry Edward C. Fortner, Jun Zhao An ion drift-chemical ionization mass spectrometry (ID- CIMS) technique has been developed to detect in laboratory kinetic investigations and field measurements. Chemical ionization mass spectrometry (CIMS) has

  7. Ion Collection by a Sphere in a Drifting Collisional Plasma

    SciTech Connect

    Haakonsen, Christian Bernt; Hutchinson, Ian H. [Plasma Science and Fusion Center and Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2011-11-29

    SCEPTIC3D now includes charge-exchange collisions, and is used to examine ion collection by a floating conducting sphere (small compared to the electron debye length) in the presence of a background neutral drift. The enhancement of ion collection at moderate collisionalities seen for the stationary case is weakened as the drift speed increases from the ion thermal speed to the ion sound speed, above which no enhancement is seen.

  8. Dominance of the diurnal mode of horizontal drift velocities at F-region heights

    NASA Technical Reports Server (NTRS)

    Kirchhoff, V. W. J. H.; Carpenter, L. A.

    1975-01-01

    Drift measurements perpendicular to the magnetic field are examined, taking into account also some nighttime measurements. Nighttime measurements of drift velocities are more difficult because densities are lower. However, the uncertainty in the drift velocities can be optimized by making use of an approach reported by Kirchhoff (1973). The approach involves a careful selection of the elevation angle of the radar antenna. Measured velocities are discussed along with the magnetospheric perturbation effect. The measurements are compared with conclusions of the dynamo theories.

  9. In situ measurements of plasma drift velocity and enhanced NO/+/ in the auroral electrojet by the Bennett spectrometer on AE-C. [Atmosphere Explorer-C satellite

    NASA Technical Reports Server (NTRS)

    Brinton, H. C.

    1975-01-01

    Simultaneous measurements of ion composition and plasma drift velocity by the Bennett mass spectrometer on the Atmosphere Explorer-C satellite reveal a direct correlation between enhancements in NO(+) concentration and ion drift velocity in the southern auroral oval. Low altitude (137 to 250 km) data obtained between 1700 and 2400 hr magnetic local time on October 22, 1974, reveal a region of westward plasma flow at velocities up to 1.3 km/s between 62 and 68 deg invariant latitude, with corresponding NO(+) enhancements of up to a factor of 20. A narrow region of reverse flow at about 0.9 km/s was also measured. These drift observations are consistent with convective flow patterns derived from electric field measurements, and their correlation with NO(+) appears to support the suggestion that NO(+) enhancements would be expected in regions of drift owing to the dependence on ion energy of the reaction O(+) + N2 yields NO(+) + N.

  10. In situ measurements of plasma drift velocity and enhanced NO(+) in the auroral electroject by the Bennett spectrometer on AE-C

    NASA Technical Reports Server (NTRS)

    Brinton, H. C.

    1974-01-01

    Simultaneous measurements of ion composition and plasma drift velocity by the Bennett mass spectrometer on the Atmosphere Explorer-C satellite reveal a direct correlation between enhancements in NO(+) concentration and ion drift velocity in the southern auroral oval. Low altitude (137 to 250 km) nighttime data reveal a region of westward plasma flow at velocities up to 1.3 km/s between 62 deg and 68 deg invariant latitude, with corresponding NO(+) enhancements of up to a factor of 25. A narrow region of reverse flow at approximately 0.9 km/s was also measured. These drift observations are consistent with convective flow patterns derived from electric field measurements, and their correlation with NO(+) appears to support the suggestion that NO(+) enhancements would be expected in regions of drift owing to the dependence on ion energy of the reaction O(+) + N2 yields NO(+) + N.

  11. Explaining the subpulse drift velocity of pulsar magnetosphere within the space-charge limited flow model

    NASA Astrophysics Data System (ADS)

    Morozova, Viktoriya S.; Ahmedov, Bobomurat J.; Zanotti, Olindo

    2014-10-01

    We try to explain the subpulse drift phenomena adopting the space-charge limited flow model and comparing the plasma drift velocity in the inner region of pulsar magnetospheres with the observed velocity of drifting subpulses. We apply the approach described in a recent paper of van Leeuwen & Timokhin, where it was shown that the standard estimation of the subpulse drift velocity through the total value of the scalar potential drop in the inner gap gives inaccurate results, while the exact expression relating the drift velocity to the gradient of the scalar potential should be used instead. After considering a selected sample of sources taken from the catalogue of Weltevrede et al. with coherently drifting subpulses and reasonably known observing geometry, we show that their subpulse drift velocities would correspond to the drift of the plasma located very close or above the pair formation front. Moreover, a detailed analysis of PSR B0826-34 and PSR B0818-41 reveals that the variation of the subpulse separation with the pulse longitude can be successfully explained by the dependence of the plasma drift velocity on the angular coordinates.

  12. Low Pressure Negative Ion Drift Chamber for Dark Matter Search

    E-print Network

    D. P. Snowden-Ifft; C. J. Martoff; J. M. Burwell

    1999-04-06

    Weakly Interacting Massive Particles (WIMPs) are an attractive candidate for the dark matter thought to make up the bulk of the mass of our universe. We explore here the possibility of using a low pressure negative ion drift chamber to search for WIMPs. The innovation of drifting ions, instead of electrons, allows the design of a detector with exceptional sensitivity to, background rejection from, and signature of WIMPs.

  13. Drift ion acoustic shock waves in an inhomogeneous two-dimensional quantum magnetoplasma

    SciTech Connect

    Masood, W.; Siddiq, M. [TPPD, PINSTECH, P. O. Nilore, Islamabad 54000 (Pakistan); Karim, S.; Shah, H. A. [Department of Physics, GC University, Lahore 54000 (Pakistan)

    2009-04-15

    Linear and nonlinear propagation characteristics of drift ion acoustic waves are investigated in an inhomogeneous quantum plasma with neutrals in the background employing the quantum hydrodynamics (QHD) model. In this regard, a quantum Kadomtsev-Petviashvili-Burgers (KPB) equation is derived for the first time. It is shown that the ion acoustic wave couples with the drift wave if the parallel motion of ions is taken into account. Discrepancies in the earlier works on drift solitons and shocks in inhomogeneous plasmas are also pointed out and a correct theoretical framework is presented to study the one-dimensional as well as the two-dimensional propagation of shock waves in an inhomogeneous quantum plasma. Furthermore, the solution of KPB equation is presented using the tangent hyperbolic (tanh) method. The variation of the shock profile with the quantum Bohm potential, collision frequency, and ratio of drift to shock velocity in the comoving frame, v{sub *}/u, are also investigated. It is found that increasing the number density and collision frequency enhances the strength of the shock. It is also shown that the fast drift shock (i.e., v{sub *}/u>0) increases, whereas the slow drift shock (i.e., v{sub *}/u<0) decreases the strength of the shock. The relevance of the present investigation with regard to dense astrophysical environments is also pointed out.

  14. Drift Compression and Final Focus Options for Heavy Ion Fusion

    SciTech Connect

    Hong Qin; Ronald C. Davidson; John J. Barnard; Edward P. Lee

    2005-02-14

    A drift compression and final focus lattice for heavy ion beams should focus the entire beam pulse onto the same focal spot on the target. We show that this requirement implies that the drift compression design needs to satisfy a self-similar symmetry condition. For un-neutralized beams, the Lie symmetry group analysis is applied to the warm-fluid model to systematically derive the self-similar drift compression solutions. For neutralized beams, the 1-D Vlasov equation is solved explicitly, and families of self-similar drift compression solutions are constructed. To compensate for the deviation from the self-similar symmetry condition due to the transverse emittance, four time-dependent magnets are introduced in the upstream of the drift compression such that the entire beam pulse can be focused onto the same focal spot.

  15. Ion behavior and interelectrode breakdown voltage of a drift tube

    E-print Network

    Geng, Hao; Duan, Yixiang

    2015-01-01

    We experimentally studied ion behavior and interelectrode breakdown voltage. The ion behavior of a drift tube directly influences the detection of ion intensity, and then influences the detection sensitivity of a system. Interelectrode voltage and pressure directly influence the ion behavior. Gas discharge between electrodes influences the adjustments required for interelectrode voltage. The experimental results show: ion intensity increases exponentially with the increment of voltage between drift electrodes; ion intensity decreases exponentially as pressure increases; with the increment of pressure, the breakdown voltage at first decreases, and then increases; ion injection has a significant influence on breakdown voltage, and this influence depends on the pressure and shapes of the electrodes. We explain the results above through assumptions and by mathematical methods.

  16. Drift and ion acoustic wave driven vortices with superthermal electrons

    SciTech Connect

    Ali Shan, S. [Theoretical Plasma Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); National Centre For Physics (NCP), Shahdra Valley Road, QAU Campus, 44000 Islamabad (Pakistan); Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad (Pakistan); Haque, Q. [Theoretical Plasma Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); National Centre For Physics (NCP), Shahdra Valley Road, QAU Campus, 44000 Islamabad (Pakistan)

    2012-08-15

    Linear and nonlinear analysis of coupled drift and acoustic mode is presented in an inhomogeneous electron-ion plasma with {kappa}-distributed electrons. A linear dispersion relation is found which shows that the phase speed of both the drift wave and the ion acoustic wave decreases in the presence of superthermal electrons. Several limiting cases are also discussed. In the nonlinear regime, stationary solutions in the form of dipolar and monopolar vortices are obtained. It is shown that the condition for the boundedness of the solution implies that the speed of drift wave driven vortices reduces with increase in superthermality effect. Ignoring density inhomogeniety, it is investigated that the lower and upper limits on the speed of the ion acoustic driven vortices spread with the inclusion of high energy electrons. The importance of results with reference to space plasmas is also pointed out.

  17. Drift velocity and gain in argon- and xenon-based mixtures

    Microsoft Academic Search

    A. Andronic; S. Biagi; P. Braun-Munzinger; C. Garabatos; G. Tsiledakis

    2004-01-01

    We present measurements of drift velocities and gains in gas mixtures based on Ar and Xe, with CO2, CH4, and N2 as quenchers, and compare them with calculations. In particular, we show the dependence of Ar- and Xe–CO2 drift velocities and gains on the amount of nitrogen contamination in the gas, which in real experiments may build up through leaks.

  18. Momentum transfer cross section of argon deduced from electron drift velocity data

    Microsoft Academic Search

    M. Suzuki; T. Taniguchi; H. Tagashira

    1990-01-01

    The momentum transfer cross section of argon is deduced from experimental electron drift velocity data over the energy range from 0.02 to 100 eV. A method proposed earlier by Suzuki et al. (1989) which is improved by adding a minimising procedure of the fractional difference between calculated and experimental electron drift velocities, is used. In an E\\/N range below 0.1

  19. Lower-hybrid drift instability in a thin current sheet with {kappa} velocity distribution

    SciTech Connect

    Huang Feng; Chen Yinhua; Shi Guifen; Hu Zuquan; Peng Haiou; Zheng Jugao [Key Laboratory of Basic Physics, USTC, Chinese Academy of Sciences, 230026 Hefei (China) and Department of Modern Physics, University of Science and Technology of China, 230026 Hefei (China); Yu, M. Y. [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, 310027 Hangzhou (China)

    2009-04-15

    The lower-hybrid drift instability (LHDI) in a thin current sheet in the intermediate-wavelength (k{sub y}{radical}({rho}{sub i}{rho}{sub e}){approx}1, where k{sub y}, {rho}{sub e}, and {rho}{sub i} are the wave vector and the electron and ion gyroradii, respectively) regime for particles with {kappa} velocity distribution is studied. The latter is more suitable for describing nonthermal distributions with an enhanced high-energy tail and includes the Maxwellian as a limiting case. It is shown that linear electromagnetic LHDI can be excited near the center of the current sheet. The growth rate decreases, but the electromagnetic component of the LHD mode increases with increase in hot particles.

  20. Shear-flow-driven ion cyclotron and ion sound-drift instabilities of cylindrical inhomogeneous plasma

    SciTech Connect

    Mikhailenko, V. S.; Chibisov, D. V. [Kharkov National University, 61108, Kharkov (Ukraine)

    2007-08-15

    The effects of the shear flow along the magnetic field on the development of the ion cyclotron, ion sound, and drift instabilities in the radially inhomogeneous cylindrical plasma are studied on the ground of a kinetic approach. It is shown that flow shear not only modifies the frequencies and growth rates of known current driven electrostatic ion cyclotron, ion sound, and drift instabilities, but is the source of the development of specific shear-flow-driven ion cyclotron, ion sound, and drift instabilities. These instabilities are excited at the levels of current along the ambient magnetic field which is below the critical value for the development of the modified by flow shear current driven ion cyclotron, ion sound, and drift instabilities.

  1. Electrostatic drift-wave instability in a nonuniform quantum magnetoplasma with parallel velocity shear flows

    SciTech Connect

    Tariq, Sabeen; Mirza, Arshad M. [Department of Physics, Theoretical Plasma Physics Group, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Masood, W. [Theoretical Plasma Physics Division, PINSTECH, P.O. Box. Nilore, Islamabad 44000, Pakistan and National Center for Physics (NCP), Islamabad 45320 (Pakistan)

    2010-10-15

    The propagation of high and low frequency (in comparison with the cyclotron frequency) electrostatic drift-waves is investigated in a nonuniform, dense magnetoplasma (composed of electrons and ions), in the presence of parallel shear flow, by employing the quantum magnetohydrodynamic (QMHD) model. Using QMHD model, a new set of equations is presented in order to investigate linear properties of electrostatic drift-waves with sheared plasma flows for dense plasmas. In this regard, dispersion relations for coupled electron-thermal and drift-ion acoustic modes are derived and several interesting limiting cases are discussed. For instance, it is found that sheared ion flow parallel to the external magnetic field can drive the quantum drift-ion acoustic wave unstable, etc. The present investigation may have relevance in dense astrophysical environments where quantum effects are significant.

  2. Spatially limited ion acoustic drift soliton in electron-positron-ion magnetoplasma

    SciTech Connect

    Mushtaq, A. [Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan)

    2008-08-15

    Ion acoustic drift solitary wave with intermediate parametric range in both linear and nonlinear regimes has been studied in electron-positron-ion magnetoplasma. In the spatially limited region dispersion relation in the linear and Zakharov-Kuznetsov-type equation in the nonlinear regime are derived, respectively. Both equations show the coupling of electrostatic drift and ion acoustic waves. The stationary soliton solution for oblique drift solitary waves with the effect of positron concentration and temperature has been discussed analytically and graphically. The results are relevant for astrophysical observations and diagnostics of laboratory electron-positron-ion magnetoplasmas.

  3. Effect of burst ions on the excitation of ion-acoustic solitons in a drifting plasma

    Microsoft Academic Search

    De-Long Xiao; J. X. Ma; Yi-Ren Li; Yang-Fang Li; M. Y. Yu

    2007-01-01

    The characteristics of fast burst ions and ion-acoustic solitons in a drifting plasma, as well as their interaction, are investigated experimentally. It is shown that the soliton evolves from the normal fast ion-beam mode excited locally in the presheath region of an excitation grid. The burst ions are created by applying a positive ramp voltage to the grid. Adjusting the

  4. Transient ion-drift-induced capacitance signals in semiconductors

    SciTech Connect

    Heiser, T. [Universite Louis Pasteur, Laboratoire de Physique et Applications des Semiconducteurs, CNRS, BP 20, F-67037 Strasbourg Cedex 2 (France)] [Universite Louis Pasteur, Laboratoire de Physique et Applications des Semiconducteurs, CNRS, BP 20, F-67037 Strasbourg Cedex 2 (France); Weber, E.R. [Department of Material Science and Mineral Engineering, University of California at Berkeley, Berkeley, California 94720 (United States)] [Department of Material Science and Mineral Engineering, University of California at Berkeley, Berkeley, California 94720 (United States)

    1998-08-01

    A theoretical model is developed that describes capacitance signals induced by drift of mobile ions in the space charge region of a Schottky diode. Pairing between the diffusing ion and the doping impurities is taken into account. The coupled partial differential equations are resolved numerically and the influence of key parameters on the signal shape is analyzed. Special emphasis is put on those features that enable transient ion-drift- (TID-) induced signals to be distinguished from capacitance transients caused by deep-level carrier emission processes. Relaxation kinetics and reverse bias dependence of the signal shape represent two reliable tools to verify the ion-drift nature of the signals. Methods for extracting quantitative information on both diffusion and pairing properties of the mobile ions are described. The question of whether pairing or diffusion is limiting the process is addressed. The influence of the doping level on the signal time constant is used to evaluate whether or not the diffusion is trap limited. A semiempirical model is described that permits the estimation of diffusion and pairing coefficients without resolving numerically the differential equations. Experiments are performed on interstitial copper in {ital p}-type silicon to test the predictions of the theoretical model. An overall agreement is found between theory and experiments. {copyright} {ital 1998} {ital The American Physical Society}

  5. Calculated nighttime eastward plasma drift velocities at low latitudes and their solar cycle dependence

    NASA Technical Reports Server (NTRS)

    Anderson, D. N.; Heelis, R. A.; Mcclure, J. P.

    1987-01-01

    After calculating ambient electron densities as a function of altitude, latitude and local time, a simplified expression is used to calculate F-region eastward plasma drifts given a zonal neutral wind model. The derived eastward plasma drift on a magnetic flux tube is examined as a function of the flux tube apex height. If the neutral wind is assumed to be independent of latitude the plasma drift maximizes along the flux tube which intercepts the F-region peak concentration at the Appleton anomaly. Above this altitude the velocity decreases to reflect a decrease in the flux tube integrated F-region Pedersen conductivity. For a latitude dependent wind the plasma drift tends to maximize along the flux tube which intercepts the F-peak at the dip equator. Above this altitude the drift decreases to reflect the latitude distribution of the wind.

  6. Drift ion acoustic solitons in an inhomogeneous 2-D quantum magnetoplasma

    Microsoft Academic Search

    W. Masood

    2009-01-01

    Linear and nonlinear propagation characteristics of quantum drift ion acoustic waves are investigated in an inhomogeneous two-dimensional plasma employing the quantum hydrodynamic (QHD) model. In this regard, the dispersion relation of the drift ion acoustic waves is derived and limiting cases are discussed. In order to study the drift ion acoustic solitons, nonlinear quantum Kadomstev–Petviashvilli (KP) equation in an inhomogeneous

  7. Cross-tail ion drift in a realistic model magnetotail

    NASA Technical Reports Server (NTRS)

    Propp, K.; Beard, D. B.

    1984-01-01

    By integrating the exact equations of motion, particle orbits have been followed in a good model magnetospheric field consisting of a planetary dipole, forward magnetosphere, and magnetotail current system. Proton energies from 2 eV to 20 keV were used for the full range of equatorial pitch angles and phase. Despite considerable pitch angle scattering in the equatorial plane crossings, it is found, first, that the bounce-averaged cross-tail drift velocity is approximately independent of pitch angle. Second, it is found that, averaged over initial gyrophase, the drift velocity (due to field curvature and gradient) is proportional to proton energy and is given to good approximation by adiabatic approximations, even up to 20 keV, despite the extreme lack of meeting the adiabatic criteria.

  8. Instability of a magnetic drift wave in the vicinity of the dust-ion hybrid resonance

    SciTech Connect

    Prudskikh, V. V. [South Federal University, Institute of Physics (Russian Federation)

    2012-06-15

    Low-frequency electromagnetic waves propagating perpendicular to the gradients of the density and magnetic field in an inhomogeneous dusty plasma whose mass density is determined primarily by the dust component are analyzed. It is shown that, in analyzing the dispersion properties of inhomogeneous plasma, it is important to take into account the dynamic properties of ions in the vicinity of the dust-ion hybrid resonance. The conditions for the onset of instability of a magnetic drift wave are investigated for different relations between parameters of the inhomogeneity and the value of the Alfven velocity. The differences from the previous results, as well as possible astrophysical applications, are discussed.

  9. Drift Compression of an Intense Neutralized Ion Beam

    SciTech Connect

    Roy, P.K.; Yu, S.S.; Henestroza, E.; Anders, A.; Bieniosek, F.M.; Coleman, J.; Eylon, S.; Greenway, W.G.; Leitner, M.; Logan, B.G.; Waldron, W.L. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California, 94720 (United States); Welch, D. R.; Thoma, C. [ATK Mission Research, Albuquerque, New Mexico 87110-3946 (United States); Sefkow, A.B.; Gilson, E.P.; Efthimion, P.C.; Davidson, R.C. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543-0451 (United States)

    2005-12-02

    Longitudinal compression of a velocity-tailored, intense neutralized K{sup +} beam at 300 keV, 25 mA has been demonstrated. The compression takes place in a 1-2 m drift section filled with plasma to provide space-charge neutralization. An induction cell produces a head-to-tail velocity ramp that longitudinally compresses the neutralized beam, enhancing the beam peak current by a factor of 50 and producing a pulse duration of about 3 ns. This measurement has been confirmed independently with two different diagnostic systems.

  10. Drift compression of an intense neutralized ion beam

    SciTech Connect

    Roy, P.K.; Yu, S.S.; Henestroza, E.; Anders, A.; Bieniosek, F.M.; Coleman, J.; Eylon, S.; Greenway, W. G.; Leitner, M.; Logan, B.G.; Waldron, W.L.; Welch, D.R.; Thoma, C.; Sefkow, A.B.; Gilson, E.P.; Efthimion, P.C.; Davidson, R.C.

    2005-09-08

    Longitudinal compression of a velocity-tailored, intense neutralized K{sup +} beam at 300 keV, 25 mA has been demonstrated. The compression takes place in a 1-2 m drift section filled with plasma to provide space-charge neutralization. An induction cell produces a head-to-tail velocity ramp that longitudinally compresses the neutralized beam, enhancing the beam peak current by a factor of 50 and producing a pulse duration of about 3 ns. This measurement has been confirmed independently with two different diagnostic systems.

  11. Drift velocity and gain in argon- and xenon-based mixtures

    E-print Network

    Andronic, A; Braun-Munzinger, P; Garabatos, C; Tsiledakis, G

    2004-01-01

    We present measurements of drift velocities and gains in gas mixtures based on Ar and Xe, with CO2, CH4, and N2 as quenchers, and compare them with calculations. In particular, we show the dependence of Ar- and Xe-CO2 drift velocities and gains on the amount of nitrogen contamination in the gas, which in real experiments may build up through leaks. A quantification of the Penning mechanism which contributes to the Townsend coefficients of a given gas mixture is proposed.

  12. Direct measurements of plasma drift velocities at high magnetic latitudes.

    NASA Technical Reports Server (NTRS)

    Doupnik, J. R.; Banks, P. M.; Baron, M. J.; Rino, C. L.; Petriceks, J.

    1972-01-01

    Description of an incoherent scatter radar experiment performed at the 23-cm radar facility in Chatanika, Alaska. The experiment has provided a direct method for measuring the ionospheric plasma transport velocity vector over long periods with relatively good time resolution. Since the F-region transport at this site is closely associated with magnetospheric convection, particularly at night, the radar can provide important information about the behavior of the magnetosphere.

  13. Measurement of the drift velocities of electrons and holes in high-ohmic silicon

    E-print Network

    Scharf, Christian

    2015-01-01

    Measurements of the drift velocities of electrons and holes as functions of electric field and temperature in high-purity n- and p-type silicon with orientation are presented. The measurements cover electric field values between 2.5 and 50 kV/cm and temperatures between 233 and 333 K. For both electrons and holes differences of more than 15 % are found between our results and the drift velocities from literature, which are frequently also used for simulating sensors. For electrons, the results agree with previous measurements, however, for holes differences between 5 to 15 % are observed for fields above 10 kV/cm. Combining our results with published data of low-field mobilities, we derive parametrizations of the drift velocities in high-ohmic silicon for electrons and holes for fields between 0 and 50 kV/cm, and temperatures between 233 and 333 K. In addition, new parametrizations for the drift velocities for electrons and holes are introduced, which provide somewhat better descriptions of existing da...

  14. 2-D Drift Velocities from the IMAGE EUV Plasmaspheric Imager

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.

    2006-01-01

    The IMAGE Mission extreme ultraviolet imager (EW) observes He(+) plasmaspheric ions throughout the inner magnetosphere. Limited by ionizing radiation and viewing close to the Sun, images of the He(+) distribution are available every 10 minutes for many hours as the spacecraft passes through apogee in its highly elliptical orbit. As a consistent constituent at about 15%, He(+) is an excellent surrogate for monitoring all of the processes that control the dynamics of plasmaspheric plasma. In particular, the motion of He' transverse to the ambient magnetic field is a direct indication of convective electric fields. The analysis of boundary motions has already achieved new insights into the electrodynamic coupling processes taking place between energetic magnetospheric plasmas and the ionosphere. Yet to be fulfilled, however, is the original promise that global E W images of the plasmasphere might yield two-dimensional pictures of mesoscale to macro-scale electric fields in the inner magnetosphere. This work details the technique and initial application of an IMAGE EUV analysis that appears capable of following thermal plasma motion on a global basis.

  15. 2-D Drift Velocities from the IMAGE EUV Plasmaspheric Imager

    NASA Technical Reports Server (NTRS)

    Gallagher, D.; Adrian, M.

    2007-01-01

    The IMAGE Mission extreme ultraviolet imager (EUY) observes He+ plasmaspheric ions throughout the inner magnetosphere. Limited by ionizing radiation and viewing close to the Sun, images of the He+ distribution are available every 10 minutes for many hours as the spacecraft passes through apogee in its highly elliptical orbit. As a consistent constituent at about 15%, He+ is an excellent surrogate for monitoring all of the processes that control the dynamics of plasmaspheric plasma. In particular, the motion ofHe+ transverse to the ambient magnetic field is a direct indication of convective electric fields. The analysis of boundary motions has already achieved new insights into the electrodynamic coupling processes taking place between energetic magnetospheric plasmas and the ionosphere. Yet to be fulfilled, however, is the original promise that global EUY images of the plasmasphere might yield two-dimensional pictures of meso-scale to macro-scale electric fields in the inner magnetosphere. This work details the technique and initial application of an IMAGE EUY analysis that appears capable of following thermal plasma motion on a global basis.

  16. Coupled ion acoustic and drift waves in magnetized superthermal electron-positron-ion plasmas

    SciTech Connect

    Adnan, Muhammad; Qamar, Anisa [Institute of Physics and Electronics, University of Peshawar, Peshawar 25000 (Pakistan); National Center for Physics, Quaid-i-Azam University Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Mahmood, S. [National Center for Physics, Quaid-i-Azam University Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Theoretical Physics Division, PINSTECH P.O. Nilore Islamabad 44000 (Pakistan); Physics Institute, Federal University of Rio Grande do Sul (UFRGS), 915051-970, Porto Alegre, RS (Brazil)

    2014-09-15

    Linear and nonlinear coupled drift-ion acoustic waves are investigated in a nonuniform magnetoplasma having kappa distributed electrons and positrons. In the linear regime, the role of kappa distribution and positron content on the dispersion relation has been highlighted; it is found that strong superthermality (low value of ?) and addition of positrons lowers the phase velocity via decreasing the fundamental scalelengths of the plasmas. In the nonlinear regime, first, coherent nonlinear structure in the form of dipoles and monopoles are obtained and the boundary conditions (boundedness) in the context of superthermality and positron concentrations are discussed. Second, in case of scalar nonlinearity, a Korteweg–de Vries-type equation is obtained, which admit solitary wave solution. It is found that both compressive and rarefactive solitons are formed in the present model. The present work may be useful to understand the low frequency electrostatic modes in inhomogeneous electron positron ion plasmas, which exist in astrophysical plasma situations such as those found in the pulsar magnetosphere.

  17. Ion trapping for ion mobility spectrometry measurements in a cyclical drift tube.

    PubMed

    Glaskin, Rebecca S; Ewing, Michael A; Clemmer, David E

    2013-08-01

    A new ion trapping technique, involving the accumulation of ions in a cyclical drift tube, as a means of enhancing ion signals for scanning ion cyclotron mobility measurements has been modeled by computational simulations and demonstrated experimentally. In this approach, multiple packets of ions are periodically released from a source region into the on ramp region of the cyclical drift tube and these pulses are accumulated prior to initiation of the mobility measurements. Using this ion trapping approach, it was possible to examine ions that traversed between 1.83 and 182.86 m (from 1 to 100 cycles). Overall, we observe that instrumental resolving power improves with increasing cycle numbers; at 100 cycles, a resolving power in excess of 1000 can be achieved. The utility of this method as a means of distinguishing between analytes is demonstrated by examining the well-characterized model peptides substance P, angiotensin II, and bradykinin. PMID:23855480

  18. Investigation of a Drifting Plasma Containing Negative Ions by Cylindrical Langmuir Probe Ion Mass Spectrometer

    Microsoft Academic Search

    F. M. Ragab

    1975-01-01

    The study of drifting plasma in the laboratory or the ionsphere is not a straightforward problem because of the many variables such plasma will encounter. The presence of negative ions will add to the complication due to the detachment mechanism and other physical processes. It is not easy to separate the negative ion current component from the electron current component.

  19. Analysis of a drift tube at ambient pressure: Models and precise measurements in ion mobility spectrometry

    NASA Astrophysics Data System (ADS)

    Eiceman, G. A.; Nazarov, E. G.; Rodriguez, J. E.; Stone, J. A.

    2001-09-01

    Mobility spectra for positive ions, created from a 63Ni foil in purified air at ambient pressure (660 Torr) with 0.15 ppm moisture, were obtained with a drift tube with a discrete drift ring design at 250 °C as electric fields for components were individually and independently varied. Peak area, peak width, baseline intensity, drift times, and reduced mobilities (Ko) were used to measure the function and performance of each component and findings were interpreted using a model for the transport of thermalized ions in weak electric fields at ambient pressure. Transit times and intensities for ions in drift tubes at ambient pressure can be understood through a detailed knowledge of the fields local to a component and derivations from theory of ion transport. Prolonged ion residence in the drift region resulted in ion transformations even for highly purified gases of low moisture at high temperature. These findings suggest that mobility spectra may be obtained with uniformly high quality and reproducibility only under conditions when ion residence time is the primary point of reference in obtaining spectra. Other regions of the drift tube were optimized and newly observed chemistry occurred in the aperture to detector region. The sampling of ions by such an ion shutter was found to inherently bias the ion distributions and alter actual lengths of drift regions. Consequently, drift lengths measured from physical configurations of drift tubes will be inadequate for precise measurements of drift times. These studies establish baseline measurements for evaluating drift tubes that should be generally applicable for optimizing performance in other drift tubes with discrete drift ring designs. Also, these results demonstrate that precise measurements in ion mobility spectrometry (IMS) will require attention to detail not heretofore carefully regarded in modern analytical IMS.

  20. Intersaccadic drift velocity is sensitive to short-term hypobaric hypoxia.

    PubMed

    Di Stasi, Leandro L; Cabestrero, Raúl; McCamy, Michael B; Ríos, Francisco; Catena, Andrés; Quirós, Pilar; Lopez, Jose A; Saez, Carolina; Macknik, Stephen L; Martinez-Conde, Susana

    2014-04-01

    Hypoxia, defined as decreased availability of oxygen in the body's tissues, can lead to dyspnea, rapid pulse, syncope, visual dysfunction, mental disturbances such as delirium or euphoria, and even death. It is considered to be one of the most serious hazards during flight. Thus, early and objective detection of the physiological effects of hypoxia is critical to prevent catastrophes in civil and military aviation. The few studies that have addressed the effects of hypoxia on objective oculomotor metrics have had inconsistent results, however. Thus, the question of whether hypoxia modulates eye movement behavior remains open. Here we examined the effects of short-term hypobaric hypoxia on the velocity of saccadic eye movements and intersaccadic drift of Spanish Air Force pilots and flight engineers, compared with a control group that did not experience hypoxia. Saccadic velocity decreased with time-on-duty in both groups, in correlation with subjective fatigue. Intersaccadic drift velocity increased in the hypoxia group only, suggesting that acute hypoxia diminishes eye stability, independently of fatigue. Our results suggest that intersaccadic drift velocity could serve as a biomarker of acute hypoxia. These findings may also contribute to our understanding of the relationship between hypoxia episodes and central nervous system impairments. PMID:24877213

  1. Ion acoustic and drift wave vortices in electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Haque, Q.; Saleem, H.

    2003-09-01

    It is shown that two-dimensional large amplitude ion acoustic waves can give rise to dipolar vortex structures in magnetized homogeneous electron-positron-ion plasmas. In nonuniform plasmas they can couple with drift waves and similar structures can again be produced. A comparison with earlier works on pulse-like soliton formation of these waves in magnetized and unmagnetized electron-positron-ion plasmas is also presented.

  2. East-west ion drifts at mid-latitudes observed by Dynamics Explorer 2

    SciTech Connect

    Heelis, R.A.; Coley, W.R. (Univ. of Texas, Richardson (United States))

    1992-12-01

    Zonal ion drifts measured from the polar orbiting DE 2 spacecraft are examined to determine the effects of dynamo electric fields and penetration of high latitude electric fields at middle latitudes. Construction of a local time distribution from satellite data results in a mixture of local time and season as well as a range of magnetic activity encompassing Kp [le] 2 and Kp [ge] 3. Thus some combination of magnetospheric effects, expected to dominate during disturbed times, are seen during both quiet and disturbed times and solar tidal influences are most easily observed during quiet times. During quiet times, at invariant latitudes near 25[degrees], the solar diurnal tide dominates the local time distribution of the ion drift. At latitudes above 50[degrees] a diurnal component of comparable magnitude is also present, but its magnetospheric origin produces a shift in phase of almost 180[degrees] from the lower latitude diurnal tide. In the intervening region, between 20[degrees] and 50[degrees] invariant latitude, semidurnal and terdiurnal components in the local time distribution of the drift velocity are also seen. These components are generally larger than those seen by ground based radars during quiet times and may be attributable in part to a difference in solar activity and in part to a combination of the solar tides and magnetospheric penetration fields.

  3. Optimum Drift Velocity for Single Molecule Fluorescence Bursts in Micro/Nano-Fluidic Channels

    E-print Network

    Lazar L. Kish; Jun Kameoka; Claes G. Granqvist; Laszlo B. Kish

    2012-03-12

    Photonic burst histograms can be used to identify single protein molecules in micro/nano-fluidic channels provided the width of the histogram is narrow. Photonic shot noise and residence time fluctuations, caused by longitudinal diffusion, are the major sources of the histogram width. This Communication is a sequel to an earlier Letter of ours [L. L. Kish et al., Appl. Phys. Lett. 99, 143121 (2011)] and demonstrates that, for a given diffusion coefficient, an increase of the drift velocity enhances the relative shot noise and decreases the relative residence time fluctuations. This leads to an optimum drift velocity which minimizes the histogram width and maximizes the ability to identify single molecules, which is an important result for applications.

  4. Drift Velocities of Slow Electrons in Helium, Neon, Argon, Hydrogen, and Nitrogen

    Microsoft Academic Search

    J. L. Pack; A. V. Phelps

    1961-01-01

    The drift velocities of electrons in helium, neon, argon, hydrogen, and nitrogen have been measured for Ep values between 10-4 and 10 volt\\/cm-mm Hg at temperatures between 77°K and 373°K. The data were obtained from measurements of electron transit time in an improved version of the double-shutter tube developed by Bradbury and Nielsen. By applying sufficiently small voltage pulses to

  5. Resolute Bay CADI ionosonde drifts, PolarDARN HF velocities, and cross polar cap potential

    NASA Astrophysics Data System (ADS)

    Mori, D.; Koustov, A. V.; Jayachandran, P. T.; Nishitani, N.

    2012-01-01

    In this study, velocities measured by the Rankin Inlet and Inuvik PolarDARN HF radars over Resolute Bay (RB) are compared with measurements from the RB CADI ionosonde to investigate the consistency of the measurements. Two types of comparisons are performed: 1-D, where each PolarDARN radar line-of-sight velocity is plotted against CADI velocity projected onto appropriate radar beam, and 2-D, where the PolarDARN merged velocity is compared with the full CADI vector. In both cases, velocities were found to statistically agree. For the 1-D comparison, the velocities were comparable in ˜85% of cases. For the 2-D comparison, a minor tendency for larger PolarDARN merge velocities (˜60 m/s) was noticed. The second task performed is a comparison of the SuperDARN cross polar cap potential (CPCP) and the CADI-based CPCP and their dependence on the CADI velocity. Linear dependences were found allowing for inter-conversion between these parameters. For large plasma drifts, the SuperDARN CPCPs were found to be much smaller than the CADI-based CPCPs hinting that the separation between the foci of a large-scale convection pattern is often underestimated in the SuperDARN convection mapping.

  6. Drift velocity of the ionospheric irregularities measured by closely-spaced GNSS receivers in Tromsoe, Norway

    NASA Astrophysics Data System (ADS)

    Ito, Y.; Otsuka, Y.; Shiokawa, K.; Hosokawa, K.; Ogawa, Y.

    2013-12-01

    A radio signal passing through small-scale irregularities in the ionospheric electron density fluctuates in amplitude and phase because the irregularities act as diffraction gratings. This phenomenon is known as scintillation. The GNSS (Global Navigation Satellite System) scintillation is caused by irregularities with a scale-size of several hundred meters. In this study, we use three GNSS receivers at the EISCAT radar site in Tromsoe, Norway, where optical and radio measurements are carried out. On January, 2012, we have installed a GNSS receiver at EISCAT radar site in Tromsoe, Norway. The receiver measures phase and signal-to-noise ratio of the radio wave from the GNSS satellites at dual frequency (L1 and L2) at 50 Hz, so that total electron content (TEC) and phase and amplitude scintillations of the ionosphere can be obtained. On September, 2012, we have installed two more receivers at Tromsoe. The distances between the three GNSS receivers are 172m, 242m and 218m, respectively. Drift velocities of irregularities can be measured using cross-correlation analysis for the time series of the GNSS signal intensity and phase obtained from the three receivers. Weak scintillation with an S4 index of 0.15 was observed at 1545 - 1605 UT on November 20, 2012. Period of the signal intensity variation was approximately 0.5 seconds. Since the scale-size of the irregularity causing the GPS scintillation, which corresponds to the Fresnel scale, is approximately 200 m, drift velocity of the irregularity causing the scintillation is estimated 400 m/s. On the other hand, the drift velocity was also estimated to be 350-400 m/s west-northwestward using cross-correlation analysis with the time series of the GPS signal intensity obtained from the three receivers. This velocity is similar to that estimated from the period of the signal intensity variation. The direction of aurora movement observed simultaneously using a digital camera at Tromsoe is also similar to that of the velocity estimated from the closely-spaced GNSS receivers. In this presentation, we discuss relationship of the irregularity drift velocity with aurora structure and movement based on these observations.

  7. A study of vacuum arc ion velocities using a linear set of probes

    SciTech Connect

    Hohenbild, Stefan; Grubel, Christoph; Yushkov, Georgy Yu.; Oks, Efim M.; Anders, Andre

    2008-07-15

    The most likely velocity of ions moving away from vacuum arc cathode spots was measured using a set of probes along the path of plasma expansion. The goal was to determine how much, if any, change of the ion drift velocity occurs in the expanded plasma. The arc discharge current was perturbed to create plasma density markers whose travel is picked up by the set of probes. It was found that the perturbation with current oscillations did not result in consistent data because ion current maxima and minima are not only determined by the plasma production but by the transients of the arc pulse and by the asymmetry of the ion velocity distribution function. Perturbation with a short current spike was more conclusive. The ion velocity was measured to be slightly reduced with increasing distance from the cathode, which can be explained by collisions of ions with the background of neutrals. The ion velocity was increased when the arc current was increased, which correlated with enhanced arc voltage and power dissipation. The ion velocity could be enhanced when the plasma was produced in a non-uniform magnetic field.

  8. Self-consistent analysis of high drift velocity measurements with the STARE system

    NASA Technical Reports Server (NTRS)

    Reinleitner, L. A.; Nielsen, E.

    1985-01-01

    The use of the STARE and SABRE coherent radar systems as valuable tools for geophysical research has been enhanced by a new technique called the Superimposed-Grid-Point method. This method permits an analysis of E-layer plasma irregularity phase velocity versus flow angle utilizing only STARE or SABRE data. As previous work with STARE has indicated, this analysis has clearly shown that the cosine law assumption breaks down for velocities near and exceeding the local ion acoustic velocities. Use of this method is improving understanding of naturally-occurring plasma irregularities in the E-layer.

  9. Graphene, a material for high temperature devices – intrinsic carrier density, carrier drift velocity, and lattice energy

    PubMed Central

    Yin, Yan; Cheng, Zengguang; Wang, Li; Jin, Kuijuan; Wang, Wenzhong

    2014-01-01

    Heat has always been a killing matter for traditional semiconductor machines. The underlining physical reason is that the intrinsic carrier density of a device made from a traditional semiconductor material increases very fast with a rising temperature. Once reaching a temperature, the density surpasses the chemical doping or gating effect, any p-n junction or transistor made from the semiconductor will fail to function. Here, we measure the intrinsic Fermi level (|EF| = 2.93?kBT) or intrinsic carrier density (nin = 3.87 × 106?cm?2K?2·T2), carrier drift velocity, and G mode phonon energy of graphene devices and their temperature dependencies up to 2400?K. Our results show intrinsic carrier density of graphene is an order of magnitude less sensitive to temperature than those of Si or Ge, and reveal the great potentials of graphene as a material for high temperature devices. We also observe a linear decline of saturation drift velocity with increasing temperature, and identify the temperature coefficients of the intrinsic G mode phonon energy. Above knowledge is vital in understanding the physical phenomena of graphene under high power or high temperature. PMID:25044003

  10. Graphene, a material for high temperature devices - intrinsic carrier density, carrier drift velocity, and lattice energy

    NASA Astrophysics Data System (ADS)

    Yin, Yan; Cheng, Zengguang; Wang, Li; Jin, Kuijuan; Wang, Wenzhong

    2014-07-01

    Heat has always been a killing matter for traditional semiconductor machines. The underlining physical reason is that the intrinsic carrier density of a device made from a traditional semiconductor material increases very fast with a rising temperature. Once reaching a temperature, the density surpasses the chemical doping or gating effect, any p-n junction or transistor made from the semiconductor will fail to function. Here, we measure the intrinsic Fermi level (|EF| = 2.93 kBT) or intrinsic carrier density (nin = 3.87 × 106 cm-2K-2.T2), carrier drift velocity, and G mode phonon energy of graphene devices and their temperature dependencies up to 2400 K. Our results show intrinsic carrier density of graphene is an order of magnitude less sensitive to temperature than those of Si or Ge, and reveal the great potentials of graphene as a material for high temperature devices. We also observe a linear decline of saturation drift velocity with increasing temperature, and identify the temperature coefficients of the intrinsic G mode phonon energy. Above knowledge is vital in understanding the physical phenomena of graphene under high power or high temperature.

  11. The Influence of Drift Gas Composition on the Separation Mechanism in Traveling Wave Ion Mobility Spectrometry: Insight from Electrodynamic Simulations

    PubMed Central

    May, Jody C.; McLean, John A.

    2013-01-01

    The influence of three different drift gases (helium, nitrogen, and argon) on the separation mechanism in traveling wave ion mobility spectrometry is explored through ion trajectory simulations which include considerations for ion diffusion based on kinetic theory and the electrodynamic traveling wave potential. The model developed for this work is an accurate depiction of a second-generation commercial traveling wave instrument. Three ion systems (cocaine, MDMA, and amphetamine) whose reduced mobility values have previously been measured in different drift gases are represented in the simulation model. The simulation results presented here provide a fundamental understanding of the separation mechanism in traveling wave, which is characterized by three regions of ion motion: (1) ions surfing on a single wave, (2) ions exhibiting intermittent roll-over onto subsequent waves, and (3) ions experiencing a steady state roll-over which repeats every few wave cycles. These regions of ion motion are accessed through changes in the gas pressure, wave amplitude, and wave velocity. Resolving power values extracted from simulated arrival times suggest that momentum transfer in helium gas is generally insufficient to access regions (2) and (3) where ion mobility separations occur. Ion mobility separations by traveling wave are predicted to be effectual for both nitrogen and argon, with slightly lower resolving power values observed for argon as a result of band-broadening due to collisional scattering. For the simulation conditions studied here, the resolving power in traveling wave plateaus between regions (2) and (3), with further increases in wave velocity contributing only minor improvements in separations. PMID:23888124

  12. Nonlinear propagation of electromagnetic ion-cyclotron waves in an electron-ion plasma in the presence of ion temperature gradient drift

    Microsoft Academic Search

    G. Murtaza; M. Nadeem; P. K. Shukla

    1993-01-01

    Nonlinear coupling between the electromagnetic ion cyclotron waves and the background ion-temperature gradient drift modes is investigated in an electron-ion plasma. This interaction is governed by a system of two coupled equations consisting of a nonlinear Schrödinger equation for the electromagnetic wave envelopes and a dynamical equation, derived from the Braginskii's fluid model, for the drift fluctuations. A general dispersion

  13. Visualization of Trajectories of Electron Beams Emitted by an IonSource with Closed Electron Drift

    SciTech Connect

    Institue of Physics, National Academy of Sciences of Ukraine; Brown, Ian G.; Bordenjuk, Ian V.; Panchenko, Oleg A.; Sologub, Sergei V.; Brown, Ian G.

    2007-10-01

    Trajectories of electron beams emitted by an ion source with an anode layer and Hall electron closed drift orbits were visualized using light emission from a working gas excited by electrons. Gas discharge of magnetron type, arising in the beam drift region under the influence of an electric field of a target bias potential, was visualized.

  14. Electron drift velocities in He and water mixtures: measurements and an assessment of the water vapour cross-section sets.

    PubMed

    de Urquijo, J; Basurto, E; Juárez, A M; Ness, K F; Robson, R E; Brunger, M J; White, R D

    2014-07-01

    The drift velocity of electrons in mixtures of gaseous water and helium is measured over the range of reduced electric fields 0.1-300 Td using a pulsed-Townsend technique. Admixtures of 1% and 2% water to helium are found to produce negative differential conductivity (NDC), despite NDC being absent from the pure gases. The measured drift velocities are used as a further discriminative assessment on the accuracy and completeness of a recently proposed set of electron-water vapour cross-sections [K. F. Ness, R. E. Robson, M. J. Brunger, and R. D. White, J. Chem. Phys. 136, 024318 (2012)]. A refinement of the momentum transfer cross-section for electron-water vapour scattering is presented, which ensures self-consistency with the measured drift velocities in mixtures with helium to within approximately 5% over the range of reduced fields considered. PMID:25005290

  15. Electron drift velocities in He and water mixtures: Measurements and an assessment of the water vapour cross-section sets

    SciTech Connect

    Urquijo, J. de; Juárez, A. M. [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, 62251, Cuernavaca, Mor. (Mexico); Basurto, E. [División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana, Av. San Pablo 180, 02200, México, D.F. (Mexico); Ness, K. F.; Robson, R. E.; White, R. D. [School of Engineering and Physical Sciences, James Cook University, Townsville 4810 (Australia); Brunger, M. J. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001 (Australia); Institute of Mathematical Sciences, University of Malaya, 5063 Kuala Lumpur (Malaysia)

    2014-07-07

    The drift velocity of electrons in mixtures of gaseous water and helium is measured over the range of reduced electric fields 0.1–300 Td using a pulsed-Townsend technique. Admixtures of 1% and 2% water to helium are found to produce negative differential conductivity (NDC), despite NDC being absent from the pure gases. The measured drift velocities are used as a further discriminative assessment on the accuracy and completeness of a recently proposed set of electron-water vapour cross-sections [K. F. Ness, R. E. Robson, M. J. Brunger, and R. D. White, J. Chem. Phys. 136, 024318 (2012)]. A refinement of the momentum transfer cross-section for electron-water vapour scattering is presented, which ensures self-consistency with the measured drift velocities in mixtures with helium to within approximately 5% over the range of reduced fields considered.

  16. Electron drift velocities in He and water mixtures: Measurements and an assessment of the water vapour cross-section sets

    NASA Astrophysics Data System (ADS)

    de Urquijo, J.; Basurto, E.; Juárez, A. M.; Ness, K. F.; Robson, R. E.; Brunger, M. J.; White, R. D.

    2014-07-01

    The drift velocity of electrons in mixtures of gaseous water and helium is measured over the range of reduced electric fields 0.1-300 Td using a pulsed-Townsend technique. Admixtures of 1% and 2% water to helium are found to produce negative differential conductivity (NDC), despite NDC being absent from the pure gases. The measured drift velocities are used as a further discriminative assessment on the accuracy and completeness of a recently proposed set of electron-water vapour cross-sections [K. F. Ness, R. E. Robson, M. J. Brunger, and R. D. White, J. Chem. Phys. 136, 024318 (2012)]. A refinement of the momentum transfer cross-section for electron-water vapour scattering is presented, which ensures self-consistency with the measured drift velocities in mixtures with helium to within approximately 5% over the range of reduced fields considered.

  17. On Relationships Between Horizontal Velocity Structure and Thermal Ion Upwellings at High Latitudes

    NASA Technical Reports Server (NTRS)

    Kivanc, O.; Heelis, R. A.

    1999-01-01

    Recent studies indicate that the vertical velocity of F region ion upwellings cannot be explained by frictional heating in the horizontal plane alone but requires additional energization sources. Processes involving velocity shear have recently been put forward as alternate mechanisms that can provide the energization in regions of smaller convection speeds. Studies show that structured flows can also give rise to significant upwelling of ions by seeding plasma waves that can potentially cause ion heating while Joule heating is relatively small. We provide a statistical analysis of the Dynamics Explorer 2 vertical and horizontal ion drift measurements that show further evidence for the significance of plasma wave energization process in regions of varying levels of Joule heating.

  18. Drift mode in a bounded plasma having two-ion species

    SciTech Connect

    Ahmad, Ali; Sajid, M.; Saleem, H. [Theoretical Plasma Physics Division, Pakistan Institute of Nuclear Science and Technology (PINSTECH), Islamabad, Pakistan and Department of Physics, COMSATS Institute of Information Technology (CIIT), Islamabad (Pakistan); Theoretical Plasma Physics Division, Pakistan Institute of Nuclear Science and Technology (PINSTECH), Islamabad (Pakistan); Theoretical Plasma Physics Division, Pakistan Institute of Nuclear Science and Technology (PINSTECH), Islamabad, Pakistan and Department of Physics, COMSATS Institute of Information Technology (CIIT), Islamabad (Pakistan)

    2008-01-15

    The drift wave is investigated in a two-ion species plasma in several different cases. The global drift mode is studied in a plasma bounded in a cylinder having Gaussian density profile corresponding to different poloidal wavenumbers. The frequency of the mode becomes a little larger when it is investigated without including the ion cyclotron wave dynamics. The effect of magnetic shear on the wave propagation along the density gradient is studied in a Cartesian geometry assuming absorbing boundary. It is found that the wave amplitude is reduced when two-ion species are present (with the same concentration) compared to pure electron-ion plasma.

  19. Observations of Counter-Streaming Ion Velocity Distributions in LLBL

    NASA Technical Reports Server (NTRS)

    Vaisberg, O. L.; Avanonv, L. A.; Smirnov, V. N.; Moore, T. E.

    2003-01-01

    We analyze ion velocity distributions observed by Interball-Tail at two LLBL crossings under southward and variable magnetosheath magnetic field. These magnetic conditions lead to highly structured LLBL. D-shape ion velocity distributions were observed within LLBL structures along with other reconnection signatures. Another type of the ion velocity distributions observed within LLBL structures consists of two counter-streaming magnetosheath-type components. We consider two possible scenarios that may lead to development of these counterstreaming ion components: reflection of transmitted magnetosheath ions from the ionosphere and creation of these velocity distributions during formation of the LLBL. We argue that observed counter-streaming component could not be due to ionospheric reflection. The observations of these ion velocity distributions are in favor of the multiple reconnections between magnetosheath and magnetospheric flux tubes.

  20. EARLY-TIME VELOCITY AUTOCORRELATION FOR CHARGED PARTICLES DIFFUSION AND DRIFT IN STATIC MAGNETIC TURBULENCE

    SciTech Connect

    Fraschetti, F.; Giacalone, J. [Department of Planetary Sciences and Astronomy, University of Arizona, Tucson, AZ 85721 (United States)

    2012-08-20

    Using test-particle simulations, we investigate the temporal dependence of the two-point velocity correlation function for charged particles scattering in a time-independent spatially fluctuating magnetic field derived from a three-dimensional isotropic turbulence power spectrum. Such a correlation function allowed us to compute the spatial coefficients of diffusion both parallel and perpendicular to the average magnetic field. Our simulations confirm the dependence of the perpendicular diffusion coefficient on turbulence energy density and particle energy predicted previously by a model for early-time charged particle transport. Using the computed diffusion coefficients, we exploit the particle velocity autocorrelation to investigate the timescale over which the particles 'decorrelate' from the solution to the unperturbed equation of motion. Decorrelation timescales are evaluated for parallel and perpendicular motions, including the drift of the particles from the local magnetic field line. The regimes of strong and weak magnetic turbulence are compared for various values of the ratio of the particle gyroradius to the correlation length of the magnetic turbulence. Our simulation parameters can be applied to energetic particles in the interplanetary space, cosmic rays at the supernova shocks, and cosmic-rays transport in the intergalactic medium.

  1. Electron Drift Velocity in the BooNE TPC Qing He and Kirk T. McDonald

    E-print Network

    McDonald, Kirk

    of these measurements was made by Walkowiak [6], as shown in fig. 1. Kalinin et al., and also Walkowiak, fit al. [3], and fits to measurements by Kalinin et al. [5]. Temperature (K) 86 88 90 92 94 s: Ratio of the fits of form (1) to the drift velocity by Kalinin et al. [5] and [6] as a function

  2. Effects of errors in velocity tilt on maximum longitudinal compression during neutralized drift compression of intense beam pulses

    E-print Network

    Kaganovich, Igor

    compresses as it drifts in the focusing section. The beam current can increase by more than a factor of 100 that the compression ratio is determined by the relative errors in the velocity tilt. That is, one-percent errors may

  3. Vertical Drift Velocities and East-West Electric Fields at the Magnetic Equator

    Microsoft Academic Search

    Ronald F. Woodman

    1970-01-01

    Incoherent scatter observations of vertical drifts taken at Jicamarca (2 ø dip) are presented. Vertical drifts are found to be nearly constant as a function of height. These vertical drifts can also be taken as a direct measurement of the east-west electric fields at the magnetic equator. Their daily and seasonal behavior is presented. The effect of geomagnetic activity is

  4. Pulse line ion accelerator based design for the neutralized drift chamber experiment

    Microsoft Academic Search

    C. Y. Ling; S. S. Yu; E. Henestroza; D. P. Grote; A. Friedman

    2009-01-01

    The pulse line ion accelerator (PLIA) is a promising approach to accelerating heavy ion beams to regimes of interest for the study of high energy density physics (HEDP) and warm dense matter in a cost effective way. In this paper we demonstrate a PLIA-based design for a proposed HEDP machine, the neutralized drift compression experiment II. The simulation results from

  5. Li+ alumino-silicate ion source development for the neutralized drift compression experiment

    Microsoft Academic Search

    Prabir K. Roy; Wayne G. Greenway; Joe W. Kwan; Peter A. Seidl; William L. Waldron; James K. Wu

    2011-01-01

    We report results on lithium alumino-silicate ion source development in preparation for warm dense matter heating experiments on the new neutralized drift compression experiment II. The practical limit to the current density for a lithium alumino-silicate source is determined by the maximum operating temperature that the ion source can withstand before running into problems of heat transfer, melting of the

  6. Solar wind bulk velocity fluctuations acting as velocity space diffusion on comoving ions

    NASA Astrophysics Data System (ADS)

    Fahr, H.-J.; Chashei, I. V.; Siewert, M.

    2012-01-01

    From most in-situ plasma observations made in the outer heliosphere it became evident that above the injection border of pick-up ions (?1 keV), an extended suprathermal ion tail is found which in most cases can be fitted by a power law with velocity power indices of (-6) ? ?v ? (-4). As has been shown by theory such energetic ion tails cannot be explained by Fermi-2 type velocity diffusion, since in the outer heliosphere both Alfvenic and magnetoacoustic turbulences become too weak. Here we come to a new solution of this unsolved problem by studying the action of solar wind bulk velocity fluctuations on ions co-moving with the wind. As we show the passage of such fluctuations results in energization of each individual ion and systematic evolution of the ion distribution function towards suprathermal tails. From the basic knowledge that we can obtain on this process we can calculate the velocity divergence of the ion phasespace flow and thus can derive a velocity diffusion operator. As we can show here this operator leads to a velocity diffusion coefficient proportional to the square of the ion velocity and, when employed in the phasespace transport equation, together with terms for convective changes, cooling processes and pick-up ion injection, interestingly enough, permits to find solutions for suprathermal power law tails with power indices of ?v ? -5 as very often observed.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  8. Stationary Plasma Thruster Ion Velocity Distribution

    NASA Technical Reports Server (NTRS)

    Manzella, David H.

    1994-01-01

    A nonintrusive velocity diagnostic based on laser induced fluorescence of the 5d4F(5/2)-6p4D(5/2) singly ionized xenon transition was used to interrogate the exhaust of a 1.5 kW Stationary Plasma Thruster (SPT). A detailed map of plume velocity vectors was obtained using a simplified, cost-effective, nonintrusive, semiconductor laser based scheme. Circumferential velocities on the order of 250 m/s were measured which implied induced momentum torques of approximately 5 x 10(exp -2) N-cm. Axial and radial velocities were evaluated one mm downstream of the cathode at several locations across the width of the annular acceleration channel. Radial velocities varied linearly with radial distance. A maximum radial velocity of 7500 m/s was measured 8 mm from the center of the channel. Axial velocities as large as 16,500 m/s were measured.

  9. Simultaneous observations of field-aligned currents and plasma drift velocities by Atmosphere Explorer C

    NASA Technical Reports Server (NTRS)

    Bythrow, P. F.; Heelis, R. A.; Hanson, W. B.; Power, R. A.

    1980-01-01

    The three-axis flux gate magnetometer on board the Atmosphere Explorer C (AE-C) has provided an additional magnetic field data set to the already broad spectrum of AE-C measurement. The results of an investigation into the feasibility of using the magnetometer for scientific purposes are described. It is shown that within the limitations inherent in the device and in the data reduction technique used, meaningful results can be obtained when the spacecraft is in the spinning mode. From a comparison between the field-aligned current signatures and the simultaneously observed ion convection velocity, it proved possible to locate regions of ionospheric conductivity gradients.

  10. Drift compression and final focus systems for heavy ion inertial fusion

    SciTech Connect

    de Hoon, M.J.L.

    2001-05-01

    Longitudinal compression of space-charge dominated beams can be achieved by imposing a head-to-tail velocity tilt on the beam. This tilt has to be carefully tailored, such that it is removed by the longitudinal space-charge repulsion by the time the beam reaches the end of the drift compression section. The transverse focusing lattice should be designed such that all parts of the beam stay approximately matched, while the beam smoothly expands transversely to the larger beam radius needed in the final focus system following drift compression. In this thesis, several drift compression systems were designed within these constraints, based on a given desired pulse shape at the end of drift compression systems were designed within these constraints, based on a given desired pulse shape at the end of drift compression. The occurrence of mismatches due to a rapidly increasing current was analyzed. In addition, the sensitivity of drift compression to errors in the initial velocity tilt and current profile was studied. These calculations were done using a new computer code that accurately calculates the longitudinal electric field in the space-charge dominated regime.

  11. A Study of Ion Velocities Observed by TIDE and How It Relates to Magnetospheric Circulation

    NASA Technical Reports Server (NTRS)

    Elliott, H. A.; Comfort, R. H.; Craven, P. D.; Chandler, M. O.; Moore, T. E.

    1998-01-01

    The high-latitude ion velocities measured by the Thermal Ion Dynamics Experiment (TIDE) instrument on the Polar spacecraft will be examined in relation to magnetospheric circulation. TIDE derives ion velocities from moments of measured distribution functions. Hydrogen and oxygen ions are E X B drifting in the polar cap and cleft regions with a speed of about 5-20 km/s at apogee (approximately 9 Re) and a speed of 1-2 km/s at perigee (approximately 1.8 Re). At perigee 0+ is typically seen flowing down in the polar cap and outflowing from the cleft. At the transition from downflowing to upflowing there is also seen a reversal in the ion convection. The convection at perigee is consistent with standard ionospheric convection models for given Interplanetary Magnetic Field (IMF) conditions. Convection at high altitude (approximately 8.9 Re) polar regions has not been studied very much since there have not been many satellites in this region. Unlike previous missions to this region TIDE in conjunction the Plasma Source Instrument (PSI) can measure ions with as low an energy as several electron Volts. The outflowing ions observed by TIDE at apogee are believed to be important to the overall circulation of the magnetosphere. The convection of these outflowing ions at apogee will be related to the IMF. This study tries to answer the question of how the IMF response of the convection influences the overall circulation of the magnetosphere.

  12. First simultaneous measurements of thermospheric winds and zonal ion drifts from the Jicamarca Radio Observatory

    NASA Astrophysics Data System (ADS)

    Meriwether, John; Baker, Brooke; Twork, Greg; Chau, Jorge; Veliz, Oskar; Woodman, Ronald; Hedden, Russell; Hysell, David

    The first simultaneous observations of thermospheric winds and zonal ion drifts have been ob-tained at the Jicamarca Radio Observatory using a new Fabry-Perot interferometer observatory installed on a mountain ridge overlooking the valley where the JRO radar is located. The re-sults show that the neutral winds and ion drifts generally have the same speed and temporal variation characteristics. These results illustrate the simultaneous detection of the midnight temperature maximum as well. The paper will also describe efforts to obtain common volume measurements of thermospheric winds and temperatures utilizing the FPI Arequipa observatory which is located 4 degrees south of the geomagnetic equator.

  13. MOBILITIES OF POSITIVE IONS IN SOME GAS MIXTURES USED IN PROPORTIONAL AND DRIFT CHAMBERS

    E-print Network

    Paris-Sud XI, Université de

    de Blanc est vérifiée pour tous les mélanges gazeux étudiés, sauf dans le cas des mélanges argon-isobutane methylal concentration in argon-isobutane-methylal. The law permits the calculation of ion mobility in any proportional chambers or drift chambers with gas mixtures, using isobutane as a quencher. The positive ions

  14. Li+ alumino-silicate ion source development for the Neutralized Drift Compression Experiment (NDCX)

    Microsoft Academic Search

    Prabir K. Roy; Wayne G. Greenway; Joe W. Kwan; Peter A. Seidl; William L. Waldron; James K. Wu

    2010-01-01

    We report results on lithium alumino-silicate ion source development in preparation for warmdense-matter heating experiments on the new Neutralized Drift Compression Experiment (NDCXII). The practical limit to the current density for a lithium alumino-silicate source is determined by the maximum operating temperature that the ion source can withstand before running into problems of heat transfer, melting of the alumino-silicate material,

  15. Ion velocities in a micro-cathode arc thruster

    SciTech Connect

    Zhuang Taisen; Shashurin, Alexey; Keidar, Michael [The George Washington University, Washington, DC 22202 (United States); Beilis, Isak [Tel Aviv University, Tel Aviv (Israel)

    2012-06-15

    Ion velocities in the plasma jet generated by the micro-cathode arc thruster are studied by means of time-of-flight method using enhanced ion detection system (EIDS). The EIDS triggers perturbations (spikes) on arc current waveform, and the larger current in the spike generates denser plasma bunches propagating along with the mainstream plasma. The EIDS utilizes double electrostatic probes rather than single probes. The average Ti ion velocity is measured to be around 2 Multiplication-Sign 10{sup 4} m/s without a magnetic field. It was found that the application of a magnetic field does not change ion velocities in the interelectrode region while leads to ion acceleration in the free expanding plasma plume by a factor of about 2. Ion velocities of about 3.5 Multiplication-Sign 10{sup 4} m/s were detected for the magnetic field of about 300 mT at distance of about 100-200 mm from the cathode. It is proposed that plasma is accelerated due to Lorentz force. The average thrust is calculated using the ion velocity measurements and the cathode mass consumption rate, and its increase with the magnetic field is demonstrated.

  16. Prediction of peptide drift time in ion mobility mass spectrometry from sequence-based features

    PubMed Central

    2013-01-01

    Background Ion mobility-mass spectrometry (IMMS), an analytical technique which combines the features of ion mobility spectrometry (IMS) and mass spectrometry (MS), can rapidly separates ions on a millisecond time-scale. IMMS becomes a powerful tool to analyzing complex mixtures, especially for the analysis of peptides in proteomics. The high-throughput nature of this technique provides a challenge for the identification of peptides in complex biological samples. As an important parameter, peptide drift time can be used for enhancing downstream data analysis in IMMS-based proteomics. Results In this paper, a model is presented based on least square support vectors regression (LS-SVR) method to predict peptide ion drift time in IMMS from the sequence-based features of peptide. Four descriptors were extracted from peptide sequence to represent peptide ions by a 34-component vector. The parameters of LS-SVR were selected by a grid searching strategy, and a 10-fold cross-validation approach was employed for the model training and testing. Our proposed method was tested on three datasets with different charge states. The high prediction performance achieve demonstrate the effectiveness and efficiency of the prediction model. Conclusions Our proposed LS-SVR model can predict peptide drift time from sequence information in relative high prediction accuracy by a test on a dataset of 595 peptides. This work can enhance the confidence of protein identification by combining with current protein searching techniques. PMID:23815343

  17. In situ ERDA studies of ion drift processes during anodic bonding of alkali-borosilicate glass to metal

    Microsoft Academic Search

    U. Kreissig; S. Grigull; K. Lange; P. Nitzsche; B. Schmidt

    1998-01-01

    Although anodic bonding is widely used to join silicon wafers or metals and glass the underlying ion-drift mechanism and interface bonding process are not yet clarified in detail. In situ ERDA with 35 MeV Cl ions was used to study the ion-drift of sodium, oxygen and hydrogen in glass. Three particle identifying detection techniques were used to separate the scattered

  18. Observation of Anomalous Ion Heating by Broadband Drift-Wave Turbulence

    SciTech Connect

    Enge, S.; Birkenmeier, G.; Manz, P.; Ramisch, M.; Stroth, U. [Institut fuer Plasmaforschung, Universitaet Stuttgart, 70569 Stuttgart (Germany)

    2010-10-22

    Using laser induced fluorescence and passive spectroscopy on a magnetically confined low-temperature plasma, anomalous ion heating is observed which exceeds collisional heating from the electrons by a factor of up to five. Direct wave heating due to the 2.45 GHz microwave as well as stochastic heating by large-amplitude fluctuations could be ruled out as explanations. Good quantitative agreement is found when comparing the missing power in the ion species with heating power due to the dissipation of drift-wave turbulence. This turbulent energy transfer into the ion channel could have important consequences for the interpretation of transport in fusion plasmas.

  19. Pulse line ion accelerator based design for the neutralized drift chamber experiment

    NASA Astrophysics Data System (ADS)

    Ling, C. Y.; Yu, S. S.; Henestroza, E.; Grote, D. P.; Friedman, A.

    2009-04-01

    The pulse line ion accelerator (PLIA) is a promising approach to accelerating heavy ion beams to regimes of interest for the study of high energy density physics (HEDP) and warm dense matter in a cost effective way. In this paper we demonstrate a PLIA-based design for a proposed HEDP machine, the neutralized drift compression experiment II. The simulation results from the injector to the exit of the accelerator using the particle-in-cell code WARP are presented. We show how the traveling wave structure of PLIA suggests straightforward strategies in controlling the longitudinal and transverse dynamics of the ion beam.

  20. Lithium-ion drifting: Application to the study of point defects in floating-zone silicon

    SciTech Connect

    Walton, J.T.; Wong, Y.K. [Lawrence Berkeley National Lab., CA (United States); Zulehner, W. [Wacker-Siltronic GmbH, Burghausen (Germany)] [and others

    1997-04-01

    The use of lithium-ion (Li{sup +}) drifting to study the properties of point defects in p-type Floating-Zone (FZ) silicon crystals is reported. The Li{sup +} drift technique is used to detect the presence of vacancy-related defects (D defects) in certain p-type FZ silicon crystals. SUPREM-IV modeling suggests that the silicon point defect diffusivities are considerably higher than those commonly accepted, but are in reasonable agreement with values recently proposed. These results demonstrate the utility of Li{sup +} drifting in the study of silicon point defect properties in p-type FZ crystals. Finally, a straightforward measurement of the Li{sup +} compensation depth is shown to yield estimates of the vacancy-related defect concentration in p-type FZ crystals.

  1. Lithium-ion drifting: Application to the study of point defects in floating-zone silicon

    NASA Technical Reports Server (NTRS)

    Walton, J. T.; Wong, Y. K.; Zulehner, W.

    1997-01-01

    The use of lithium-ion (Li(+)) drifting to study the properties of point defects in p-type Floating-Zone (FZ) silicon crystals is reported. The Li(+) drift technique is used to detect the presence of vacancy-related defects (D defects) in certain p-type FZ silicon crystals. SUPREM-IV modeling suggests that the silicon point defect diffusivities are considerably higher than those commonly accepted, but are in reasonable agreement with values recently proposed. These results demonstrate the utility of Li(+) drifting in the study of silicon point defect properties in p-type FZ crystals. Finally, a straightforward measurement of the Li(+) compensation depth is shown to yield estimates of the vacancy-related defect concentration in p-type FZ crystals.

  2. Electrostatic ion cyclotron velocity shear instability

    NASA Technical Reports Server (NTRS)

    Lemons, D. S.; Winske, D.; Gary, S. P.

    1992-01-01

    A local electrostatic dispersion equation is derived for a shear flow perpendicular to an ambient magnetic field, which includes all kinetic effects and involves only one important parameter. The dispersion equation is cast in the form of Gordeyev integrals and is solved numerically. Numerical solutions indicate that an ion cyclotron instability is excited. The instability occurs roughly at multiples of the ion cyclotron frequency (modified by the shear), with the growth rate or the individual harmonics overlapping in the wavenumber. At large values of the shear parameter, the instability is confined to long wavelengths, but at smaller shear, a second distinct branch at shorter wavelengths also appears. The properties of the instability obtained are compared with those obtained in the nonlocal limit by Ganguli et al. (1985, 1988).

  3. Laser induced fluorescence observation of ion velocity distribution functions in a plasma sheath

    NASA Astrophysics Data System (ADS)

    Claire, Nicolas; Bachet, Gerard; Stroth, Ulrich

    2005-10-01

    New experimental results obtained by laser induced fluorescence on metastable ion velocity distribution functions (MIVDFs) in electrostatic presheaths and sheaths in multipolar Argon plasmas are presented. The laser power broadening of the MIVDFs has been observed when there is no ion drift. The MIVDFs parallel to the plate in front of which the sheath is formed are Maxwellian with the ions at exactly the ambient temperature. The MIVDFs perpendicular to the plate (PMIVDFs) are in qualitative agreement, for the presheath, with Emmert's predictions: a Maxwellian profile at the center of the device where the potential is zero, with an ion temperature equal to the ambient temperature (0.027 eV), and a profile made of three pieces at the beginning of the pre-sheath. The PMIVDFs point out that their width is related to the neutral pressure. In the sheath, where the theory is no more valid, the PMIVDFs recover a Maxwellian profile. This ``ion thermalization'' has never been observed in published simulations. The velocity and potential profiles for different plasma conditions have also been measured.

  4. Spectral anomalies of the light-induced drift effect caused by the velocity dependence of the collision broadening and shift of the absorption line

    SciTech Connect

    Parkhomenko, A I; Shalagin, Anatolii M [Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2013-02-28

    We have theoretically investigated the spectral features of the light-induced drift (LID) effect, arising due to the dependence of the collision broadening {gamma} and shift {Delta} of the absorption line on the velocity of resonance particles, {nu}. It is shown that under certain conditions, account of this dependence can radically change the spectral shape of the LID signal, up to the appearance of additional zeros in the dependence of the drift velocity on the radiation frequency. (nonlinear optical phenomena)

  5. In situ ERDA studies of ion drift processes during anodic bonding of alkali-borosilicate glass to metal

    NASA Astrophysics Data System (ADS)

    Kreissig, U.; Grigull, S.; Lange, K.; Nitzsche, P.; Schmidt, B.

    1998-03-01

    Although anodic bonding is widely used to join silicon wafers or metals and glass the underlying ion-drift mechanism and interface bonding process are not yet clarified in detail. In situ ERDA with 35 MeV Cl ions was used to study the ion-drift of sodium, oxygen and hydrogen in glass. Three particle identifying detection techniques were used to separate the scattered ions and target recoils with respect to their energy and atomic number or mass. The thermally activated drift of sodium ions has been characterized quantitatively up to a depth of about 1 ?m by means of a TOF-E telescope. Activation energies, drift rates and depletion layer thicknesses were determined. A Bragg Ionization Chamber with an energy resolution of {?E}/{E} = 1.1% was used to determine the slight oxygen buildup in the metal layer near the interface to the glass. Hydrogen depth profiles up to a depth of 600 nm were measured by a Si detector with a 17 ?m Al range foil. A considerable drift of hydrogen from the "leached" glass surface was found which is strongly correlated with the sodium drift. The simultaneous oxygen drift gives rise to the assumption that a (OH) --drift takes place. A reaction path for the anodic oxidation process at the metal-glass interface is proposed.

  6. Closed electron drift in a self-magnetically insulated ion diode

    SciTech Connect

    Pushkarev, A. I.; Isakova, Y. I. [Tomsk Polytechnic University, 2a Lenin Ave., Tomsk 634050 (Russian Federation)] [Tomsk Polytechnic University, 2a Lenin Ave., Tomsk 634050 (Russian Federation)

    2013-05-15

    The paper investigates a spiral geometry self-magnetically insulated ion diode with an explosive-emission cathode made from graphite. The experiments have been carried out using the TEMP-4M accelerator, with the accelerator configured to operate in double-pulse mode: the first negative pulse (300–500 ns, 100–150 kV) and the second positive pulse (150 ns, 250–300 kV). The ion beam energy density was 0.4–0.8 J/cm{sup 2} and the beam was composed of carbon ions (80%–85%) and protons. In order to increase the efficiency of ion current generation, we have developed a new diode with a spiral-shaped grounded electrode. Using this geometry, it seems possible to realize closed electron drift in a diode with self-magnetic insulation. In the spiral diode, the efficiency of accelerated ions is increased from 5%–9% (conventional self-insulated diodes) up to 30%–40%. The realization of closed electron drift in the diode increases the efficiency of C{sup +} ion generation up to 40–50 times the Childe-Langmuir limit, which is more than 4 times higher than with other known constructions of self-magnetically insulated diodes.

  7. Distributed drift chamber design for rare particle detection in relativistic heavy ion collisions

    SciTech Connect

    Bellwied, R.; Bennett, M.J.; Bernardo, V.; Caines, H.; Christie, W.; Costa, S.; Crawford, H.J.; Cronqvist, M.; Debbe, R.; Dinnwiddie, R.; Engelage, J.; Flores, I.; Fuzesy, R.; Greiner, L.; Hallman, T.; Hoffmann, G.; Huang, H.Z.; Jensen, P.; Judd, E.G.; Kainz, K.; Kaplan, M.; Kelly, S.; Lindstrom, P.J; Llope, W.J.; LoCurto, G.; Longacre, R.; Milosevich, Z.; Mitchell, J.T.; Mitchell, J.W.; Mogavero, E.; Mutchler, G.; Paganis, S.; Platner, E.; Potenza, R.; Rotondo, F.; Russ, D.; Sakrejda, I.; Saulys, A.; Schambach, J.; Sheen, J.; Smirnoff, N.; Stokeley, C.; Tang, J.; Trattner, A.L.; Trentalange, S.; Visser, G.; Whitfield, J.P.; Witharm, F.; Witharm, R.; Wright, M.

    2001-10-02

    This report describes a multi-plane drift chamber that was designed and constructed to function as a topological detector for the BNL AGSE896 rare particle experiment. The chamber was optimized for good spatial resolution, two track separation, and a high uniform efficiency while operating in a 1.6 Tesla magnetic field and subjected to long term exposure from a 11.6 GeV/nucleon beam of 10**6 Au ions per second.

  8. The Performance and Plume Characterization of a Laboratory Gridless Ion Thruster with Closed Electron Drift Acceleration

    Microsoft Academic Search

    Peter Y. Peterson; Alec D. Gallimore

    The design and characteristics of a laboratory-model two-stage gridless ion thruster with closed electron drift are presented. The scaling and design of the electron bombardment ionization stage and the acceleration stage are described. The performance characterization of the thruster in single and two-stage is presented and discussed. The thruster plume was characterized with an ExB probe and gridded Faraday probe.

  9. Two-dimensional spectroscopy of sunspots. II. Search for propagating waves and drifting velocity filaments in photospheric layers

    NASA Astrophysics Data System (ADS)

    Balthasar, H.; Schleicher, H.

    2008-04-01

    Aims: Running penumbral waves are often reported from observations in chromospheric lines or lines formed in the upper photosphere. In this work we investigate whether they can be detected in a line formed in the mid to lower photosphere. Methods: We used time series of two-dimensional spectra of an iron line that is insensitive to the magnetic field and that is formed in the lower to mid photosphere. Results: No running penumbral waves are detected in this line formed in the lower and mid photosphere. In the moat, outward moving velocity features are detected. They are slightly faster than the plasma motions but much slower than running penumbral waves. Conclusions: Running penumbral waves are a phenomenon occurring in higher layers, i.e. the lower chromosphere and the upper photosphere, but not in the mid photosphere or below. In the moat, we found long-living filamentary velocity features drifting outwards.

  10. Pickup Ion Velocity Distributions at Titan: Effects of Spatial Gradients

    NASA Technical Reports Server (NTRS)

    Hartle, R. E.; Sittler, E. C.

    2004-01-01

    The principle source of pickup ions at Titan is its neutral exosphere, extending well above the ionopause into the magnetosphere of Saturn or the solar wind, depending on the moon's orbital position. Thermal and nonthermal processes in the thermosphere generate the distribution of neutral atoms and molecules in the exosphere. The combination of these processes and the range of mass numbers, 1 to over 28, contribute to an exospheric source structure that produces pickup ions with gyroradii that are much larger or smaller than the corresponding scale heights of their neutral sources. The resulting phase space distributions are dependent on the spatial structure of the exosphere as well as that of the magnetic field and background plasma. When the pickup ion gyroradius is less than the source gas scale height, the pickup ion velocity distribution is characterized by a sharp cutoff near the maximum speed, which is twice that of the ambient plasma times the sine of the angle between the magnetic field and the flow velocity. This was the case for pickup H(sup +) ions identified during the Voyager 1 flyby. In contrast, as the gyroradius becomes much larger than the scale height, the peak of the velocity distribution in the source region recedes from the maximum speed. Iri addition, the amplitude of the distribution near the maximum speed decreases. These more beam like distributions of heavy ions were not observed from Voyager 1 , but should be observable by more sensitive instruments on future spacecraft, including Cassini. The finite gyroradius effects in the pickup ion velocity distributions are studied by including in the analysis the possible range of spatial structures in the neutral exosphere and background plasma.

  11. Electron-ion hybrid mode due to transverse velocity shear

    NASA Technical Reports Server (NTRS)

    Ganguli, G.; Lee, Y. C.; Palmadesso, P. J.

    1988-01-01

    Cases in which the velocity shear scale length is larger than the electron gyroradius but much smaller than the ion gyroradius are considered. In this situation, it is found that a hybrid mode with short wavelength and high frequency can be excited.

  12. Kinetic effects on the Kelvin–Helmholtz instability in ion-to-magnetohydrodynamic scale transverse velocity shear layers: Particle simulations

    PubMed Central

    Nakamura, T. K. M.; Hasegawa, H.; Shinohara, I.

    2010-01-01

    Ion-to-magnetohydrodynamic scale physics of the transverse velocity shear layer and associated Kelvin–Helmholtz instability (KHI) in a homogeneous, collisionless plasma are investigated by means of full particle simulations. The shear layer is broadened to reach a kinetic equilibrium when its initial thickness is close to the gyrodiameter of ions crossing the layer, namely, of ion-kinetic scale. The broadened thickness is larger in B??<0 case than in B??>0 case, where ? is the vorticity at the layer. This is because the convective electric field, which points out of (into) the layer for B??<0 (B??>0), extends (reduces) the gyrodiameters. Since the kinetic equilibrium is established before the KHI onset, the KHI growth rate depends on the broadened thickness. In the saturation phase of the KHI, the ion vortex flow is strengthened (weakened) for B??<0 (B??>0), due to ion centrifugal drift along the rotational plasma flow. In ion inertial scale vortices, this drift effect is crucial in altering the ion vortex size. These results indicate that the KHI at Mercury-like ion-scale magnetospheric boundaries could show clear dawn-dusk asymmetries in both its linear and nonlinear growth. PMID:20838425

  13. Equatorial plasma bubble zonal velocity using 630.0 nm airglow observations and plasma drift modeling over Ascension Island

    NASA Astrophysics Data System (ADS)

    Chapagain, Narayan P.; Taylor, Michael J.; Makela, Jonathan J.; Duly, Timothy M.

    2012-06-01

    We present OI (630.0 nm) airglow image data from Ascension Island (geographic: 7.9°S, 14.4°W dip latitude: 16°S) in the southern Atlantic Ocean taken with the Utah State University all-sky CCD camera during 20 March to 7 April 1997 in order to study plasma bubbles occurring in the low-latitude nighttime ionosphere. The initial plasma bubble onset occurs in the early evening hours at ˜19:15-20:00 LST and is followed by eastward propagation with an average speed of ˜90-120 m/s prior to local midnight, rapidly decreasing around the midnight and postmidnight periods. The Ascension results are compared with similar observations from Christmas Island in order to examine the longitudinal variations of EPB development and propagation. The observed EPB velocities from Ascension Island are also compared with the results of a plasma drift model. In a case study during the night of 4-5 April, the velocity reveals unusual latitudinal shear, up to 0.12 m/s/km, with a reversal to westward flow at low latitudes while eastward flow is maintained at higher latitudes. Consequently, the bubble rotates counterclockwise and tilts eastward, significantly away from alignment with the geomagnetic field lines. The westward reversal of the drift motion near the geomagnetic equator is most likely the result of a reversal in the F region dynamo or from a large increase in the altitude of the shear node in the F region plasma drift at the geomagnetic equator.

  14. Graphene, a material for high temperature devices--intrinsic carrier density, carrier drift velocity, and lattice energy.

    PubMed

    Yin, Yan; Cheng, Zengguang; Wang, Li; Jin, Kuijuan; Wang, Wenzhong

    2014-01-01

    Heat has always been a killing matter for traditional semiconductor machines. The underlining physical reason is that the intrinsic carrier density of a device made from a traditional semiconductor material increases very fast with a rising temperature. Once reaching a temperature, the density surpasses the chemical doping or gating effect, any p-n junction or transistor made from the semiconductor will fail to function. Here, we measure the intrinsic Fermi level (|EF| = 2.93 kBT) or intrinsic carrier density (nin = 3.87 × 10(6) cm(-2)K(-2)· T(2)), carrier drift velocity, and G mode phonon energy of graphene devices and their temperature dependencies up to 2400 K. Our results show intrinsic carrier density of graphene is an order of magnitude less sensitive to temperature than those of Si or Ge, and reveal the great potentials of graphene as a material for high temperature devices. We also observe a linear decline of saturation drift velocity with increasing temperature, and identify the temperature coefficients of the intrinsic G mode phonon energy. Above knowledge is vital in understanding the physical phenomena of graphene under high power or high temperature. PMID:25044003

  15. Superconducting accelerating structures for very low velocity ion beams.

    SciTech Connect

    Xu, J.; Shepard, K. W.; Ostroumov, P. N.; Fuerst, J. D.; Waldschmidt, G.; Gonin, I. V.; FNAL

    2008-03-01

    This paper presents designs for four types of very-low-velocity superconducting (SC) accelerating cavity capable of providing several MV of accelerating potential per cavity, and suitable for particle velocities in the range 0.006ion beams. SC linacs can be formed as an array of independently phased cavities, enabling a variable velocity profile to maximize the output energy for each of a number of different ion species. Several laboratories in the U.S. and Europe are planning exotic beam facilities based on SC linacs. The cavity designs presented here are intended for the front end of such linacs, particularly for the postacceleration of rare isotopes of low charge state. Several types of SC cavities have been developed recently to cover particle velocities above 0.06c. Superconducting four-gap quarter-wave resonators for velocities 0.008<{beta}=v/c<0.05 were developed about two decades ago and have been successfully operated at the ATLAS SC linac at Argonne National Laboratory. Since that time, progress in simulation tools, cavity fabrication, and processing have increased SC cavity gradients by a factor of 3-4. This paper applies these tools to optimize the design of a four-gap quarter-wave resonator for exotic beam facilities and other low-velocity applications.

  16. Superconducting accelerating structures for very low velocity ion beams

    NASA Astrophysics Data System (ADS)

    Xu, J.; Shepard, K. W.; Ostroumov, P. N.; Fuerst, J. D.; Waldschmidt, G.; Gonin, I. V.

    2008-03-01

    This paper presents designs for four types of very-low-velocity superconducting (SC) accelerating cavity capable of providing several MV of accelerating potential per cavity, and suitable for particle velocities in the range 0.006ion beams. SC linacs can be formed as an array of independently phased cavities, enabling a variable velocity profile to maximize the output energy for each of a number of different ion species. Several laboratories in the U.S. and Europe are planning exotic beam facilities based on SC linacs. The cavity designs presented here are intended for the front end of such linacs, particularly for the postacceleration of rare isotopes of low charge state. Several types of SC cavities have been developed recently to cover particle velocities above 0.06c. Superconducting four-gap quarter-wave resonators for velocities 0.008velocity applications.

  17. Superconducting accelerating structures for very low velocity ion beams

    SciTech Connect

    Xu, J.; Shepard, K.W.; Ostroumov, P.N.; Fuerst, J.D.; Waldschmidt, G.; /Argonne; Gonin, I.V.; /Fermilab

    2008-01-01

    This paper presents designs for four types of very-low-velocity superconducting accelerating cavity capable of providing several MV of accelerating potential per cavity, and suitable for particle velocities in the range 0.006 < v/c < 0.06. Superconducting TEM-class cavities have been widely applied to CW acceleration of ion beams. SC linacs can be formed as an array of independently-phased cavities, enabling a variable velocity profile to maximize the output energy for each of a number of different ion species. Several laboratories in the US and Europe are planning exotic beam facilities based on SC linacs. The cavity designs presented here are intended for the front-end of such linacs, particularly for the post-acceleration of rare isotopes of low charge state. Several types of SC cavities have been developed recently to cover particle velocities above 0.06c. Superconducting four-gap quarter-wave resonators for velocities 0.008 < {beta} = v/c < 0.05 were developed about two decades ago and have been successfully operated at the ATLAS SC linac at Argonne National Laboratory. Since that time, progress in simulation tools, cavity fabrication and processing have increased SC cavity gradients by a factor of 3-4. This paper applies these tools to optimize the design of a four-gap quarter-wave resonator for exotic beam facilities and other low-velocity applications.

  18. Dynamics Explorer observations of equatorial spread F - Evidence for drift waves

    NASA Technical Reports Server (NTRS)

    Hoegy, W. R.; Curtis, S. A.; Brace, L. H.; Maynard, N. C.; Heelis, R. A.

    1982-01-01

    Recent DE-2 data from the Langmuir probe, vector electric field, and ion drift meter instruments are employed to study equatorial spread F in the frequency regime of the low frequency drift and the lower hybrid drift instabilities. Strong electron density gradients topside equatorial F region correspond to regions of high electric field waves and large ion drift velocities. The electric field waves are seen in two distinct wavelength ranges which correspond to the parameter regimes of the low frequency drift and the lower hybrid drift instabilities. In the smaller of the two wavelength ranges the lower hybrid drift instability is found to be unstable, based on the ion drift velocity and the other plasma parameters measured on DE-2, and using published theory. Thus there is experimental evidence that the lower hybrid drift instability may produce the observed short wavelength waves without invoking a cascading mechanism.

  19. Beam dynamics of the Neutralized Drift Compression Experiment-II (NDCX-II),a novel pulse-compressing ion accelerator

    SciTech Connect

    Friedman, A.; Barnard, J.J.; Cohen, R.H.; Grote, D.P.; Lund, S.M.; Sharp, W.M.; Faltens, A.; Henestroza, E.; Jung, J.-Y.; Kwan, J.W.; Lee, E.P.; Leitner, M.A.; Logan, B.G.; Vay, J.-L.; Waldron, W.L.; Davidson, R.C.; Dorf, M.; Gilson, E.P.; Kaganovich, I.D.

    2009-12-19

    Intense beams of heavy ions are well suited for heating matter to regimes of emerging interest. A new facility, NDCX-II, will enable studies of warm dense matter at {approx}1 eV and near-solid density, and of heavy-ion inertial fusion target physics relevant to electric power production. For these applications the beam must deposit its energy rapidly, before the target can expand significantly. To form such pulses, ion beams are temporally compressed in neutralizing plasma; current amplification factors of {approx}50-100 are routinely obtained on the Neutralized Drift Compression Experiment (NDCX) at LBNL. In the NDCX-II physics design, an initial non-neutralized compression renders the pulse short enough that existing high-voltage pulsed power can be employed. This compression is first halted and then reversed by the beam's longitudinal space-charge field. Downstream induction cells provide acceleration and impose the head-to-tail velocity gradient that leads to the final neutralized compression onto the target. This paper describes the discrete-particle simulation models (1-D, 2-D, and 3-D) employed and the space-charge-dominated beam dynamics being realized.

  20. Beam dynamics of the Neutralized Drift Compression Experiment-II (NDCX-II), a novel pulse-compressing ion accelerator

    SciTech Connect

    Friedman, A; Barnard, J J; Cohen, R H; Grote, D P; Lund, S M; Sharp, W M; Faltens, A; Henestroza, E; Jung, J; Kwan, J W; Lee, E P; Leitner, M A; Logan, B G; Vay, J; Waldron, W L; Davidson, R C; Dorf, M; Gilson, E P; Kaganovich, I

    2009-11-19

    Intense beams of heavy ions are well suited for heating matter to regimes of emerging interest. A new facility, NDCX-II, will enable studies of warm dense matter at {approx}1 eV and near-solid density, and of heavy-ion inertial fusion target physics relevant to electric power production. For these applications the beam must deposit its energy rapidly, before the target can expand significantly. To form such pulses, ion beams are temporally compressed in neutralizing plasma; current amplification factors of {approx}50-100 are routinely obtained on the Neutralized Drift Compression Experiment (NDCX) at LBNL. In the NDCX-II physics design, an initial non-neutralized compression renders the pulse short enough that existing high-voltage pulsed power can be employed. This compression is first halted and then reversed by the beam's longitudinal space-charge field. Downstream induction cells provide acceleration and impose the head-to-tail velocity gradient that leads to the final neutralized compression onto the target. This paper describes the discrete-particle simulation models (1-D, 2-D, and 3-D) employed and the space-charge-dominated beam dynamics being realized.

  1. A Monte Carlo simulation of the effect of ion self-collisions on the ion velocity distribution function in the high-latitude F-region

    NASA Technical Reports Server (NTRS)

    Barghouthi, I. A.; Barakat, A. R.; Schunk, R. W.

    1994-01-01

    Non-Maxwellian ion velocity distribution functions have been theoretically predicted and confirmed by observations, to occur at high latitudes. These distributions deviate from Maxwellian due to the combined effect of the E x B drift and ion-neutral collisions. At high altitude and/or for solar maximum conditions, the ion-to-neutral density ratio increases and, hence, the role of ion self-collisions becomes appreciable. A Monte Carlo simulation was used to investigate the behavior of O(+) ions that are E x B-drifting through a background of neutral O, with the effect of O(+) (Coulomb) self-collisions included. Wide ranges of the ion-to-neutral density ratio n(sub i)/n(sub n) and the electrostatic field E were considered in order to investigate the change of ion behavior with solar cycle and with altitude. For low altitudes and/or solar minimum (n(sub i)/n(sub n) less than or equal to 10(exp -5)), the effect of self-collisions is negligible. For higher values of n(sub i)/n(sub n), the effect of self-collisions becomes significant and, hence, the non-Maxwellian features of the O(+) distribution are reduced. The Monte Carlo results were compared to those that used simplified collision models in order to assess their validity. In general, the simple collision models tend to be more accurate for low E and for high n(sub i)/n(sub n).

  2. Low Velocity Ion Stopping in Binary Ionic Mixtures

    NASA Astrophysics Data System (ADS)

    Deutsch, Claude; Ceban, Victor; Fromy, Patrice; Tashev, Bekbolat

    2011-11-01

    We investigate the basic features underlying the low ion velocity (Vp) slowing down (LIVSD) in multicomponent and dense target plasmas built of quasi-classical electron fluids neutralizing binary ionic mixtures (BIM)such as deuterium-tritium of current fusion interest,proton-heliumlike iron in the solar interior or proton-helium ions considered in planetology, as well as other mixtures of fiducial concern in the heavy ion beam production of warm dense matter (WDM) at Bragg peak conditions [1]. The target plasma is taken in a multicomponent dielectric Fried-Conte formulation. We also focus attention on so-called critical Vp values featuring same LIVSD on target ions and electrons,respectively. BIM including negative hydrogen are also given attention [2].[4pt] [1] B. Tashev, F. Baimbetov, C. Deutsch and P. Fromy, PoP 15, 102701 (2008)[0pt] [2] B. Tashev, P. Fromy and C. Deutsch, PRSTAB 13, 10130 (2010)

  3. Coulomb explosion at low and high ion velocities

    NASA Astrophysics Data System (ADS)

    Szenes, G.

    2013-03-01

    The ion-induced electric field is calculated for estimating the effect of the Coulomb explosion (CE) mechanism. The increase of the kinetic energy of lattice ions in the electric field of the track core is ?? ? (q(0))4, where q(r) is the induced initial charge density. Estimates are made for the irradiation of SiO2 by 2 MeV/nucleon Kr beam: the mean energy of lattice ions reaches 8.1 eV within 4 fs in the track core. The Lorentzian and Gaussian charge density distributions lead to similar results. The type of solids affects ?? through the charge neutralization time. As a result of the decrease of q(0), ?? is reduced by about an order of magnitude in the range 2-8 MeV/nucleon. The projectile velocity may affect the formation of ion-induced tracks by the CE mechanism.

  4. Properties of ion temperature gradient drift instabilities in H-mode plasmas

    SciTech Connect

    Hahm, T.S.; Tang, W.M.

    1988-11-01

    Experimental results from tokamaks such as DIII-D and JET have indicated that the electron density profile in H-mode (''high- confinement'') discharges can be nearly flat over most of the plasma, and, in some cases, even inverted (outwardly peaked). These conditions have very interesting implications for pictures of anomalous thermal transport based on the presence of ion temperature gradient drift instabilities. The present paper includes a new derivation of the ion temperature gradient threshold for weak density gradient /eta//sub i/ modes when ion transit resonances are taken into account; and the first derivation of threshold conditions for the onset of /eta//sub i/-modes when /eta//sub i/ is negative along with the properties of these negative /eta//sub i/ instabilities when the thresholds are exceeded. Possible consequences for confinement in H-mode plasmas are discussed. 32 refs., 8 figs.

  5. Li{sup +} alumino-silicate ion source development for the neutralized drift compression experiment

    SciTech Connect

    Roy, Prabir K.; Greenway, Wayne G.; Kwan, Joe W.; Seidl, Peter A.; Waldron, William L.; Wu, James K. [Lawrence Berkeley National Laboratory (LBNL), One Cyclotron Road, Berkeley, California 94720 (United States)

    2011-01-15

    We report results on lithium alumino-silicate ion source development in preparation for warm dense matter heating experiments on the new neutralized drift compression experiment II. The practical limit to the current density for a lithium alumino-silicate source is determined by the maximum operating temperature that the ion source can withstand before running into problems of heat transfer, melting of the alumino-silicate material, and emission lifetime. Using small prototype emitters, at a temperature of {approx_equal}1275 deg. C, a space-charge limited Li{sup +} beam current density of J {approx_equal}1 mA/cm{sup 2} was obtained. The lifetime of the ion source was {approx_equal}50 h while pulsing at a rate of 0.033 Hz with a pulse duration of 5-6 {mu}s.

  6. Li+ alumino-silicate ion source development for the Neutralized Drift Compression Experiment (NDCX)

    SciTech Connect

    Roy, Prabir K.; Greenway, Wayne G.; Kwan, Joe W.; Seidl, Peter A.; Waldron, William L.; Wu, James K.

    2010-10-01

    We report results on lithium alumino-silicate ion source development in preparation for warmdense-matter heating experiments on the new Neutralized Drift Compression Experiment (NDCXII). The practical limit to the current density for a lithium alumino-silicate source is determined by the maximum operating temperature that the ion source can withstand before running into problems of heat transfer, melting of the alumino-silicate material, and emission lifetime. Using small prototype emitters, at a temperature of ~;;1275 oC, a space-charge-limited Li+ beam current density of J ~;;1 mA/cm2 was obtained. The lifetime of the ion source was ~;;50 hours while pulsing at a rate of 0.033 Hz with a pulse duration of 5-6 mu s.

  7. Li+ alumino-silicate ion source development for the neutralized drift compression experiment.

    PubMed

    Roy, Prabir K; Greenway, Wayne G; Kwan, Joe W; Seidl, Peter A; Waldron, William L; Wu, James K

    2011-01-01

    We report results on lithium alumino-silicate ion source development in preparation for warm dense matter heating experiments on the new neutralized drift compression experiment II. The practical limit to the current density for a lithium alumino-silicate source is determined by the maximum operating temperature that the ion source can withstand before running into problems of heat transfer, melting of the alumino-silicate material, and emission lifetime. Using small prototype emitters, at a temperature of ?1275 °C, a space-charge limited Li(+) beam current density of J ?1 mA/cm(2) was obtained. The lifetime of the ion source was ?50 h while pulsing at a rate of 0.033 Hz with a pulse duration of 5-6 ?s. PMID:21280822

  8. The effects of hyper-velocity dust-particle impacts on the LOFT Silicon Drift Detectors

    NASA Astrophysics Data System (ADS)

    Zampa, G.; Del Monte, E.; Perinati, E.; Rashevskaya, I.; Rachevski, A.; Zampa, N.; Bugiel, S.; Kendziorra, E.; Tenzer, C.; Feroci, M.; Santangelo, A.; Vacchi, A.

    2014-07-01

    Solid-state detectors that operate in orbit are required to withstand harsh space environment conditions. Among the various phenomena able to damage the sensors, X-ray detectors are subjected to impacts of orbital debris and micrometeoroids whenever, to be sensitive to low energy photons, they need to be ``directly'' exposed to the sky. The LOFT mission, proposed for the M3 class opportunity of the ESA Cosmic Vision, has a very-large sensitive area (greater than 10 m2) made of Silicon Drift Detectors (SDD). Moreover, the satellite includes an X-ray Wide-Field Monitor based on the same SDD detectors. Here we present the results of a test campaign at the Cosmic Dust Accelerator Facility at MPIK in Heidelberg aimed at the space qualification of the detectors with respect to this phenomenon.

  9. Electron mobility and drift velocity in selectively doped InAlAs/InGaAs/InAlAs heterostructures

    SciTech Connect

    Vasil'evskii, I. S., E-mail: pozela@pfi.lt; Galiev, G. B.; Klimov, E. A. [MEPHI National Nuclear Research University (Russian Federation); Pozela, K.; Pozela, J.; Juciene, V.; Suziedelis, A.; Zurauskiene, N.; Kersulis, S.; Stankevic, V. [Center for Physical Sciences and Technology, Semiconductor Physics Institute (Lithuania)

    2011-09-15

    An increase in the electron mobility and drift velocity in high electric fields in quantum wells of selectively doped InAlAs/InGaAs/InAsAs heterostructures is obtained experimentally via controlling the composition of semiconductors forming the interface. The electron mobility at the interface in the In{sub 0.8}Ga{sub 0.2}As/In{sub 0.7}Al{sub 0.3}As metamorphic structure with a high molar fraction of In (0.7-0.8) is as high as 12.3 Multiplication-Sign 10{sup 3} cm{sup 2} V{sup -1} s{sup -1} at room temperature. An increase in the electron mobility by a factor of 1.1-1.4 is attained upon the introduction of thin (1-3 nm) InAs layers into a quantum well of selectively doped In{sub 0.53}Ga{sub 0.47}As/In{sub 0.52}Al{sub 0.48}As heterostructures. A maximal drift velocity attains 2.5 Multiplication-Sign 10{sup 7} cm/s in electric fields of 2-5 kV/cm. The threshold field F{sub th} for the intervalley {Gamma}-L electron transfer (the Gunn effect) in the InGaAs quantum well is higher than in the bulk material by a factor of 2.5-3. The effect of two- to threefold decrease in the threshold field F{sub th} in the InGaAs quantum well is established upon increasing the molar fraction of In in the InAlAs barrier, as well as upon the introduction of thin InAs inserts into the InGaAs quantum well.

  10. Amplification of ion acoustic wave in an inhomogeneous plasma through nonlinear wave-particle interaction with drift wave turbulence

    SciTech Connect

    Deka, P. N.; Borgohain, A. [Department of Mathematics, Dibrugarh University, Dibrugarh-786004, Assam (India)

    2011-04-15

    A study on the amplification of ion acoustic wave in an inhomogeneous plasma has been made on the basis of a nonlinear wave-particle interaction process called plasma maser effect. The drift wave instability, which is a universal phenomenon of an inhomogeneous confined plasma system, is found to be strongly in phase relation with thermal particles and may transfer its wave energy nonlinearly through a modulated field to ion acoustic wave. Considering a Maxwellian distribution function model for inhomogeneous plasmas under the standard local approximation, we have estimated the growth rate for ion acoustic wave, which is obtained by using the nonlinear dispersion relation. It has been found that amplification of ion acoustic wave is possible at the expense of drift wave turbulent energy. This result may be particularly important for stability of various drift modes in magnetically confined plasma as well as for transport of momentum and energy in such inhomogeneous systems.

  11. Drift orbit topology of fast ions in tokamaks Plasma Science and Fusion Centre, Massachusetts Institute of Technology,

    E-print Network

    Egedal, Jan

    Drift orbit topology of fast ions in tokamaks J. Egedal Plasma Science and Fusion Centre methods are developed by which the guiding centre orbit topology of fast ions in tokamaks is e magnetic profiles. The orbit topology is obtained simply by studying the contours of the magnitude

  12. Drift orbit topology of fast ions in tokamaks Plasma Science and Fusion Centre, Massachusetts Institute of Technology,

    E-print Network

    Egedal, Jan

    Drift orbit topology of fast ions in tokamaks J. Egedal Plasma Science and Fusion Centre methods are developed by which the guiding centre orbit topology of fast ions in tokamaks is efficiently magnetic profiles. The orbit topology is obtained simply by studying the contours of the magnitude

  13. A gated atmospheric pressure drift tube ion mobility spectrometer-time-of-flight mass spectrometer.

    PubMed

    Heptner, Andre; Reinecke, Tobias; Langejuergen, Jens; Zimmermann, Stefan

    2014-08-22

    Identifying the compounds of an unknown gas mixture by using an ion mobility spectrometer (IMS) is a difficult task, because several ion species can be generated in the ionization process. One method to analyze the occurring peaks in an IMS spectrum is coupling an IMS to a mass spectrometer (MS). In our setup we coupled a (3)H drift tube IMS to a Bruker micrOTOF II. Therefore, the detector plate of the IMS is pierced and a transfer capillary is inserted. The ions are transferred via gas flow and electric fields into the MS. The transmission of the ions through the transfer capillary can be shuttered very precisely by increasing the electric potential of the detector generating a repulsive electric field. Thus, it is possible to transfer single ion clouds of generated IMS spectra into the mass spectrometer where a corresponding mass spectrum is generated. In this work we analyze the positive and negative IMS spectra of single analytes as well as gas mixtures and characterize the occurring ion species. PMID:25015244

  14. Error Sources for Velocity Moments Obtained by Imaging Ion Spectrographs

    NASA Astrophysics Data System (ADS)

    Burchill, J.; Knudsen, D.

    2008-12-01

    Imaging ion spectrography is a unique method of producing two-dimensional maps of low-energy (<20 eV) ion distribution functions. It was first tested in the Freja Cold Plasma Analyzer, following which a new, CCD- based detector scheme was developed to allow very high resolution in space, time, and velocity space. The Suprathermal Ion Imager has since flown successfully five times including on the GEODESIC, Cusp, JOULE and Japanese S-520-23 sounding rocket missions, demonstrating its ability to make very sensitive measurements of 2-D bulk ion flow (tens of m/s) at rates of over 100 vectors per second. As the technique becomes more widespread, it is necessary that the devices not only be reliable, but also that the data reduction techniques be accurate and robust. We have undertaken a detailed analysis of sources of error in velocity and temperature measurements from CCD imaging spectrographs, specifically the Canadian Electric Field Instrument that will be flown on each of the three Swarm satellites in 2010. The main sources of error come from uncertainties in the instrument transfer functions, the sensor-to-plasma potential difference, particle Poisson noise, and galactic cosmic ray events. We discuss also the challenge of calibrating the instruments with the aid of computer simulations, and the merits and limitations of on-ground and in-flight calibration strategies.

  15. Storm-Time Ion Velocity Distributions in the Generalized Polar Wind

    NASA Astrophysics Data System (ADS)

    Barakat, A. R.; Schunk, R. W.

    2009-12-01

    At high latitudes the plasma escapes along geomagnetic field lines from the high pressure ionosphere into the low pressure magnetosphere. As the plasma flows upwards, it goes through transitions from collision-dominated to collisionless conditions, from subsonic to supersonic flows, and form O+-dominated to H+-dominated compositions. Meanwhile, the plasma E×B drifts across the cusp, the polar cap, the auroral oval, and the subauroral regions, where it is exposed to different intensities of physical factors, e.g. wave-particle interactions, magnetospheric particle precipitation, and centrifugal acceleration. Moreover, during geomagnetic activity these effects vary significantly with time. We used a 3-D generalized polar wind (GPW) model in order to simulate the plasma behavior during a geomagnetic storm. The northern polar region was modeled with 1000 convecting trajectories and about one billion simulation particles. Special attention was given to investigating the interplay between the different mechanisms regarding their influence on the velocity distributions of the O+ and H+ ions at different altitudes, latitudes and storm phases. We present the evolution of the ion velocity distributions and how they depend on space and time. The results will be compared with previous results from simpler models.

  16. Modeling of impurity effect on drift instabilities in plasmas with many ion species

    SciTech Connect

    Moradi, S. [Department of Statistical and Plasma Physics, Universite Libre de Bruxelles, 1050 Brussels (Belgium); Tokar, M. Z. [Institute fuer Energieforschung-Plasmaphysik, Forschungszentrum Juelich, Association EURATOM-FZJ, Trilateral Euregio Cluster, 52425 Juelich (Germany); Weyssow, B. [EFDA-CSU, D-85748 Garching, Muenchen (Germany)

    2010-01-15

    Drift microinstabilities, being the main cause of anomalous transport of charged particles and energy in fusion plasmas, can be strongly influenced by the presence of impurities. Normally a large amount of different ion species from diverse charge states and chemical elements is present. An approach, providing a possibility to take into account an arbitrary number of ion species in analysis of instabilities, is proposed and applied to study the impurity effect on unstable modes due to ion temperature gradient and trapped electrons described in a linear fluid approximation. The method is validated by comparing with the results from direct calculations in a one impurity ion case. The dependence of instability characteristics and anomalous transport coefficients on the absolute level and radial gradient of impurity density is investigated. Plasmas with several impurity ion species, including C{sup +6}, N{sup +7}, O{sup +8}, Ne{sup +10}, and Ar{sup +18} whose density peaking factors are determined self-consistently from the impurity zero flux condition, are considered as an example of applications.

  17. Scavenging of atmospheric ions and aerosols by drifting snow in Antarctica

    E-print Network

    Kamra, A K; Pant, Vimlesh; 10.1016/j.atmosres.2008.02.018

    2009-01-01

    Measurements of the small,intermediate, and large ion concentrations and the airearth current density along with simultaneous measurements of the concentration and size-distribution of aerosol particles in the size ranges 4.4 to 163 nm and 0.5 to 20 micrometer diameters are reported for a drifting snow period after the occurrence of a blizzard at a coastal station, Maitri, Antarctica. Ion concentrations of all categories and the airearth current simultaneously decrease by approximately an order of magnitude as the wind speed increases from 5 to 10 meter per sec. The rate of decrease is the highest for large ions, lowest for small ions and in between the two for intermediate ions. Total aerosol number concentration decreases in the 4.4 to 163 nm size range but increases in 0.5 to 20 micrmetr size range with wind speed. Size distribution of the nanometer particles show a dominant maximum at 30 nm diameter throughout the period of observations and the height of the maximum decreases with wind speed. However, lar...

  18. A mass- and velocity-broadband ion deflector for off-axis ion injection into a cyclotron resonance ion trap

    SciTech Connect

    Guan, S.; Marshall, A.G. [Center for Interdisciplinary Magnetic Resonance, National High Magnetic Field Lab, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, Florida 32306-4005 (United States)] [Center for Interdisciplinary Magnetic Resonance, National High Magnetic Field Lab, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, Florida 32306-4005 (United States)

    1996-02-01

    Off-axis ion injection into an FT-ICR ion trap is desirable for capturing ions from a continuously generated beam (e.g., electrospray). A conventional {bold E{times}B} (Wien) filter focuses ions of a {ital single} velocity (independent of mass). Here we show that by segmenting opposed flat electrodes into small sections, the electric field may be tailored to produce well-focused ion trajectories over a wide range of ion velocity and mass-to-charge ratio, {ital m}/{ital z}. In the limit of infinitely extended deflector electrodes, small {ital m}/{ital z}, and/or high {bold B}, ion trajectories vary as powers or roots of distance. {copyright} {ital 1996 American Institute of Physics.}

  19. Effects of drift gas on collision cross sections of a protein standard in linear drift tube and traveling wave ion mobility mass spectrometry.

    PubMed

    Jurneczko, Ewa; Kalapothakis, Jason; Campuzano, Iain D G; Morris, Michael; Barran, Perdita E

    2012-10-16

    There has been a significant increase in the use of ion mobility mass spectrometry (IM-MS) to investigate conformations of proteins and protein complexes following electrospray ionization. Investigations which employ traveling wave ion mobility mass spectrometry (TW IM-MS) instrumentation rely on the use of calibrants to convert the arrival times of ions to collision cross sections (CCS) providing "hard numbers" of use to structural biology. It is common to use nitrogen as the buffer gas in TW IM-MS instruments and to calibrate by extrapolating from CCS measured in helium via drift tube (DT) IM-MS. In this work, both DT and TW IM-MS instruments are used to investigate the effects of different drift gases (helium, neon, nitrogen, and argon) on the transport of multiply charged ions of the protein myoglobin, frequently used as a standard in TW IM-MS studies. Irrespective of the drift gas used, recorded mass spectra are found to be highly similar. In contrast, the recorded arrival time distributions and the derived CCS differ greatly. At low charge states (7 ? z ? 11) where the protein is compact, the CCS scale with the polarizability of the gas; this is also the case for higher charge states (12 ? z ? 22) where the protein is more unfolded for the heavy gases (neon, argon, and nitrogen) but not the case for helium. This is here interpreted as a different conformational landscape being sampled by the lighter gas and potentially attributable to increased field heating by helium. Under nanoelectrospray ionization (nESI) conditions, where myoglobin is sprayed from an aqueous solution buffered to pH 6.8 with 20 mM ammonium acetate, in the DT IM-MS instrument, each buffer gas can yield a different arrival time distribution (ATD) for any given charge state. PMID:22974196

  20. Very Low velocity Ion Slowing Down in Binary Ionic Mixtures

    NASA Astrophysics Data System (ADS)

    Fromy, Patrice; Tashev, Bekbolat; Deutsch, Claude

    2010-11-01

    Binary ionic mixtures (BIM) in dense and hot plasmas of specific concern for inertial confinement fusion (ICF) and white dwarf crust are considered as targets for incoming light ions with a velocity smaller than thermal electron one in target.The given BIM formalism worked out within a dielectric approach [1] is specifically investigated in terms of charge-and mass-asymmetry in the target BIM components.Results are scanned w.r.t density, temperature and relative BIM composition as well.A certain attention is paid to the so-called critical regime when target electron stopping equals the target ion contribution. [4pt] [1] B.Tashev et al, Phys.Plasmas 15,102701(2008) and NIMA 606,218(2009)

  1. Unexpected transverse velocity component of Xe{sup +} ions near the exit plane of a Hall thruster

    SciTech Connect

    Bourgeois, G.; Mazouffre, S. [ICARE, CNRS, 1C Avenue de la Recherche Scientifique, 45071 Orleans (France); Sadeghi, N. [LSP, Joseph Fourier University and CNRS, 140 Ave. de la Physique, 38402 St. Martin d'Heres (France)

    2010-11-15

    The velocity component of singly charged xenon ions in a plane perpendicular to the thrust axis of the 1 kW-class PPS100-ML Hall effect thruster is deduced from laser induced fluorescence measurements on the 5d {sup 2}F{sub 7/2}{yields}6p {sup 2}D{sub 5/2}{sup 0} electronic transition at 834.72 nm. Measurements are carried out at several locations in the near field of the channel exhaust. Thruster operating parameters, such as magnetic field strength, discharge voltage, and xenon mass flow rate, are varied over a wide range. The initial aim of this work was to measure the azimuthal velocity of the ions due to their weak magnetic deflection. Surprisingly, experimental results cannot be explained by the one and only Lorentz force acting on Xe{sup +} ions. A realistic picture of the ion trajectory in the ExB drift plane is obtained when adding a velocity component directed toward the external cathode.

  2. Kinetic water-bag model of global collisional drift waves and ion temperature gradient instabilities in cylindrical geometry

    SciTech Connect

    Gravier, E. [Institut Jean Lamour, UMR 7198 CNRS-Universite de Lorraine, Bd des Aiguillettes, 54 506 Vandoeuvre-les-Nancy Cedex (France); Plaut, E. [LEMTA, UMR 7563 CNRS-Universite de Lorraine, 2, av. de la Foret de Haye, 54 518 Vandoeuvre-les-Nancy Cedex (France)

    2013-04-15

    Collisional drift waves and ion temperature gradient (ITG) instabilities are studied using a linear water-bag kinetic model [P. Morel et al., Phys. Plasmas 14, 112109 (2007)]. An efficient spectral method, already validated in the case of drift waves instabilities [E. Gravier et al., Eur. Phys. J. D 67, 7 (2013)], allows a fast solving of the global linear problem in cylindrical geometry. The comparison between the linear ITG instability properties thus computed and the ones given by the COLUMBIA experiment [R. G. Greaves et al., Plasma Phys. Controlled Fusion 34, 1253 (1992)] shows a qualitative agreement. Moreover, the transition between collisional drift waves and ITG instabilities is studied theoretically as a function of the ion temperature profile.

  3. Analysis of heterogeneous uptake by nanoparticles via differential mobility analysis-drift tube ion mobility spectrometry.

    PubMed

    Oberreit, Derek R; McMurry, Peter H; Hogan, Christopher J

    2014-04-21

    Improved methods are needed to study sorption of vapor molecules by particles in the gas phase (heterogeneous uptake), which is an important process in both natural and engineered environments. Here, a new measurement system, composed of a differential mobility analyzer (DMA) and drift tube ion mobility spectrometer (DTIMS) in series, is used to examine the heterogeneous uptake of water vapor by 2.85-7.6 nm particles composed of lithium and sodium iodide. The extent of heterogeneous uptake is determined by controlling the relative humidity of the drift region in the DTIMS in the 0-30% range (in air at atmospheric pressure and room temperature), and is quantified via the dimensionless growth factor (GF), i.e. the ratio of the mobility diameter of particles at a prescribed relative humidity relative to their mobility diameter under dry conditions. The precision in GF estimation of the DMA-DTIMS system is shown to be below 0.2%. An analytical equation to calculate the growth factor, based upon predictions of the equilibrium constants for the successive uptake of vapor molecules by particles, is also presented. While the equation is sufficiently general to enable comparison between measured GFs and predictions from any theoretical expression for equilibrium constants, we specifically compare measurements to GF predictions based on the classical Kelvin-Thomson-Raoult (KTR) model for the vapor pressure of a small particle, with consideration of the influence of the ion-dipole potential on water vapor-nanoparticle collisions. It is shown that KTR calculations drastically underpredict the extent of heterogeneous uptake for the examined nanoparticles. PMID:24600691

  4. Mobility-Resolved Ion Selection in Uniform Drift Field Ion Mobility Spectrometry/Mass Spectrometry; Dynamic Switching in Structures for Lossless Ion Manipulations

    SciTech Connect

    Webb, Ian K.; Garimella, Venkata BS; Tolmachev, Aleksey V.; Chen, Tsung-Chi; Zhang, Xinyu; Cox, Jonathan T.; Norheim, Randolph V.; Prost, Spencer A.; Lamarche, Brian L.; Anderson, Gordon A.; Ibrahim, Yehia M.; Smith, Richard D.

    2014-09-26

    A Structures for Lossless Ion Manipulations (SLIM) module that allows ion mobility separations and the switching of ions between alternative drift paths is described. The SLIM switch component has a “Tee” configuration and allows switching of ions between a linear path and a 90-degree bend. By controlling switching times, ions can be deflected to an alternative channel as a function of their mobilities. In the initial evaluation the switch is used in a static mode and shown compatible with high performance ion mobility separations at 4 torr. In the “dynamic mode” we show that mobility-selected ions can be switched into the alternative channel, and that various ion species can be independently selected based on their mobilities for time-of-flight mass spectrometer (TOF MS) IMS detection and mass analysis. This development also provides the basis for e.g. the selection of specific mobilities for storage and accumulation, and key modules for the assembly of SLIM devices enabling much more complex sequences of ion manipulations.

  5. Effective ionization coefficients and electron drift velocities in gas mixtures of SF6 with He, Xe, CO2 and N2 from Boltzmann analysis

    Microsoft Academic Search

    M. J. Pinheiro; J. Loureiro

    2002-01-01

    The effective reduced electron ionization coefficients (alpha-eta)\\/N, with alpha and eta denoting the first Townsend ionization and attachment coefficients, respectively, and the drift velocities are calculated for different mixture compositions of SF6 with He, Xe, CO2 and N2, by solving the electron Boltzmann equation, under the two-term approximation, in a steady-state Townsend discharge. It is shown that a self-contained equation

  6. Theoretical relationship between maximum value of the post-sunset drift velocity and peak-to-valley ratio of anomaly TEC

    Microsoft Academic Search

    B. Basu; J. M. Retterer; O. de La Beaujardière; C. E. Valladares; E. Kudeki

    2004-01-01

    Theoretical study of electron density distribution in the nighttime equatorial ionosphere shows that linear relationships with statistically significant correlation coefficients exist between the maximum value of the post-sunset plasma drift velocity and the peak-to-valley ratio of anomaly TEC. The study is based on the low-latitude density model of Air Force Research Laboratory (AFRL) and the obtained relationships are valid for

  7. Influence of the interplanetary magnetic field orientation on polar cap ion trajectories - Energy gain and drift effects

    NASA Technical Reports Server (NTRS)

    Delcourt, D. C.; Horwitz, J. L.; Swinney, K. R.

    1988-01-01

    The influence of the interplanetary magnetic field (IMF) orientation on the transport of low-energy ions injected from the ionosphere is investigated using three-dimensional particle codes. It is shown that, unlike the auroral zone outflow, the ions originating from the polar cap region exhibit drastically different drift paths during southward and northward IMF. During southward IMF orientation, a 'two-cell' convection pattern prevails in the ionosphere, and three-dimensional simulations of ion trajectories indicate a preferential trapping of the light ions H(+) in the central plasma sheet, due to the wide azimuthal dispersion of the heavy ions, O(+). In contrast, for northward IMF orientation, the 'four-cell' potential distribution predicted in the ionosphere imposes a temporary ion drift toward higher L shells in the central polar cap. In this case, while the light ions can escape into the magnetotail, the heavy ions can remain trapped, featuring more intense acceleration (from a few electron volts up to the keV range) followed by precipitation at high invariant latitudes, as a consequence of their further travel into the tail.

  8. Li+ alumino-silicate ion source development for the Neutralized Drift Compression Experiment (NDCX-II)

    SciTech Connect

    LBNL; Roy, P.K.; Greenway, W.; Kwan, J.W.; Seidl, P.A.; Waldron, W.

    2011-04-20

    To heat targets to electron-volt temperatures for the study of warm dense matter with intense ion beams, low mass ions, such as lithium, have an energy loss peak (dE/dx) at a suitable kinetic energy. The Heavy Ion Fusion Sciences (HIFS) program at Lawrence Berkeley National Laboratory will carry out warm dense matter experiments using Li{sup +} ion beam with energy 1.2-4 MeV in order to achieve uniform heating up to 0.1-1 eV. The accelerator physics design of Neutralized Drift Compression Experiment (NDCX-II) has a pulse length at the ion source of about 0.5 {micro}s. Thus for producing 50 nC of beam charge, the required beam current is about 100 mA. Focusability requires a normalized (edge) emittance {approx}2 {pi}-mm-mrad. Here, lithium aluminosilicate ion sources, of {beta}-eucryptite, are being studied within the scope of NDCX-II construction. Several small (0.64 cm diameter) lithium aluminosilicate ion sources, on 70%-80% porous tungsten substrate, were operated in a pulsed mode. The distance between the source surface and the mid-plane of the extraction electrode (1 cm diameter aperture) was 1.48 cm. The source surface temperature was at 1220 C to 1300 C. A 5-6 {micro}s long beam pulsed was recorded by a Faraday cup (+300 V on the collector plate and -300 V on the suppressor ring). Figure 1 shows measured beam current density (J) vs. V{sup 3/2}. A space-charge limited beam density of {approx}1 mA/cm{sup 2} was measured at 1275 C temperature, after allowing a conditioning time of about {approx} 12 hours. Maximum emission limited beam current density of {ge} 1.8mA/cm{sup 2} was recorded at 1300 C with 10-kV extractions. Figure 2 shows the lifetime of two typical sources with space-charge limited beam current emission at a lower extraction voltage (1.75 kV) and at temperature of 1265 {+-} 7 C. These data demonstrate a constant, space-charge limited beam current for 20-50 hours. The lifetime of a source is determined by the loss of lithium from the alumino-silicate material either as ions or as neutral atoms. Our measurements suggest that for the low duty factor ({approx}10{sup -8}) required for NDCX-II, the lifetime of an emitter depends mostly on the duration that the emitter spends at elevated temperature, that is, at {ge} 1250 C. At this temperature, lithium loss is due mostly to neutral loss (not charged ion extraction). Extension of the lifetime of the source may be possible by lowering the temperature between beam pulses, when the idling time is sufficiently long between shots. The NDCX-II design seeks to operate the ion source at the maximum current density without running into heat management and lifetime problems. In preparation to fabricate a large (10.9 cm in diameter) source for the NDCXII experiment, recently a 7.6 cm diameter source has been fabricated. The method of fabrication of this larger source is similar to that of fabrication of a 6.3mm diameter source, except a longer furnace heating time was used due to mass differences. NDCX-II construction is in progress. Progress of lithium source study for NDCX-II is available in literature.

  9. Deciphering drift time measurements from travelling wave ion mobility spectrometry-mass spectrometry studies.

    PubMed

    Smith, David P; Knapman, Tom W; Campuzano, Iain; Malham, Richard W; Berryman, Joshua T; Radford, Sheen E; Ashcroft, Alison E

    2009-01-01

    Detailed knowledge of the tertiary and quaternary structure of proteins and protein complexes is of immense importance in understanding their functionality. Similarly, variations in the conformational states of proteins form the underlying mechanisms behind many biomolecular processes, numerous of which are disease-related. Thus, the availability of reliable and accurate biophysical techniques that can provide detailed information concerning these issues is of paramount importance. Ion mobility spectrometry (IMS) coupled to mass spectrometry (MS) offers a unique opportunity to separate multi-component biomolecular entities and to measure the molecular mass and collision cross-section of individual components in a single, rapid (ion mobility spectrometry (TWIMS)-mass spectrometer using known cross-sectional areas determined for a range of biomolecules by conventional IMS-MS. Using this method of calibration, we have analysed a range of proteins of differing mass and 3D architecture in their native conformations by ESI-TWIMS-MS and found that the cross-sectional areas measured in this way compare extremely favourably with cross-sectional areas calculated using an in-house computing method based on Protein Data Bank NMR-derived co-ordinates. This not only provides a high degree of confidence in the calibration method, but also suggests that the gas phase ESI- TWIMS-MS measurements relate well to solution-based measurements derived from other biophysical techniques. In order to determine which instrumental parameters affect the ESI-TWIMS-MS cross-sectional area calibration, a systematic study of the parameters used to optimise TWIMS drift time separations has been carried out, observing the effect each parameter has on drift times and IMS resolution. Finally, the ESI-TWIMS-MS cross-sectional area calibration has been applied to the analysis of the amyloidogenic protein beta(2)-microglobulin and measurements for three co-populated conformational families, present under denaturing conditions, have been made: the folded, partially unfolded and unfolded states. PMID:19423898

  10. Computation of the Drift Velocity of Spiral Waves using Response Functions I.V. Biktasheva and A.J. Foulkes

    E-print Network

    Biktashev, Vadim N.

    '' drift caused by (approx­ imately) periodic modulation of medium properties through external forcing [20 reactions [21], a spatial gradient of medium properties [22--25] and pinning (anchoring, trapping

  11. Computation of the Drift Velocity of Spiral Waves using Response Functions I.V. Biktasheva and A.J. Foulkes

    E-print Network

    Biktashev, Vadim N.

    " drift caused by (approx- imately) periodic modulation of medium properties through external forcing [20 reactions [21], a spatial gradient of medium properties [22­25] and pinning (anchoring, trapping

  12. Spectroscopic measurement of ion temperature and ion velocity distributions in the flux-coil generated FRC

    SciTech Connect

    Gupta, D.; Gota, H.; Hayashi, R.; Kiyashko, V.; Morehouse, M.; Primavera, S. [Tri Alpha Energy, Inc., Rancho Santa Margarita, California 92688 (United States); Bolte, N. [Tri Alpha Energy, Inc., Rancho Santa Margarita, California 92688 (United States); Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Marsili, P. [Department of Physics, University of Pisa, Largo B. Pontecorvo 3, 56127 Pisa (Italy); Roche, T. [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Wessel, F. [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Tri Alpha Energy, Inc., Rancho Santa Margarita, California 92688 (United States)

    2010-10-15

    One aim of the flux-coil generated field reversed configuration at Tri Alpha Energy (TAE) is to establish the plasma where the ion rotational energy is greater than the ion thermal energy. To verify this, an optical diagnostic was developed to simultaneously measure the Doppler velocity-shift and line-broadening using a 0.75 m, 1800 groves/mm, spectrometer. The output spectrum is magnified and imaged onto a 16-channel photomultiplier tube (PMT) array. The individual PMT outputs are coupled to high-gain, high-frequency, transimpedance amplifiers, providing fast-time response. The Doppler spectroscopy measurements, along with a survey spectrometer and photodiode-light detector, form a suite of diagnostics that provide insights into the time evolution of the plasma-ion distribution and current when accelerated by an azimuthal-electric field.

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

    SciTech Connect

    Batool, Nazia [Theoretical Plasma Physics Group, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); National Center of Physics (NCP), Quaid-i-Azam University campus, Islamabad (Pakistan); Masood, W. [National Center of Physics (NCP), Quaid-i-Azam University campus, Islamabad (Pakistan); Theoretical Plasma Physics Division, PINSTECH P. O. Nilore, Islamabad (Pakistan); Mirza, Arshad M. [Theoretical Plasma Physics Group, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

    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.

  14. Drift Compression and Final Focus for Intense Heavy Ion Beams with Non-periodic, Time-dependent Lattice

    SciTech Connect

    Hong Qin; Ronald C. Davidson; John J. Barnard; Edward P. Lee

    2005-02-14

    In the currently envisioned configurations for heavy ion fusion, it is necessary to longitudinally compress the beam bunches by a large factor after the acceleration phase. Because the space-charge force increases as the beam is compressed, the beam size in the transverse direction will increase in a periodic quadrupole lattice. If an active control of the beam size is desired, a larger focusing force is needed to confine the beam in the transverse direction, and a non-periodic quadrupole lattice along the beam path is necessary. In this paper, we describe the design of such a focusing lattice using the transverse envelope equations. A drift compression and final focus lattice should focus the entire beam pulse onto the same focal spot on the target. This is difficult with a fixed lattice, because different slices of the beam may have different perveance and emittance. Four time-dependent magnets are introduced in the upstream of drift compression to focus the entire pulse onto the sam e focal spot. Drift compression and final focusing schemes are developed for a typical heavy ion fusion driver and for the Integrated Beam Experiment (IBX) being designed by the Heavy Ion Fusion Virtual National Laboratory.

  15. An Effective Approach for Coupling Direct Analysis in Real Time with Atmospheric Pressure Drift Tube Ion Mobility Spectrometry

    NASA Astrophysics Data System (ADS)

    Keelor, Joel D.; Dwivedi, Prabha; Fernández, Facundo M.

    2014-09-01

    Drift tube ion mobility spectrometry (DTIMS) has evolved as a robust analytical platform routinely used for screening small molecules across a broad suite of chemistries ranging from food and pharmaceuticals to explosives and environmental toxins. Most modern atmospheric pressure IM detectors employ corona discharge, photoionization, radioactive, or electrospray ion sources for efficient ion production. Coupling standalone DTIMS with ambient plasma-based techniques, however, has proven to be an exceptional challenge. Device sensitivity with near-ground ambient plasma sources is hindered by poor ion transmission at the source-instrument interface, where ion repulsion is caused by the strong electric field barrier of the high potential ion mobility spectrometry (IMS) inlet. To overcome this shortfall, we introduce a new ion source design incorporating a repeller point electrode used to shape the electric field profile and enable ion transmission from a direct analysis in real time (DART) plasma ion source. Parameter space characterization studies of the DART DTIMS setup were performed to ascertain the optimal configuration for the source assembly favoring ion transport. Preliminary system capabilities for the direct screening of solid pharmaceuticals are briefly demonstrated.

  16. Experimental studies of the two-ion species flow in the plasma presheath

    Microsoft Academic Search

    X. Wang; N. Hershkowitz

    2006-01-01

    The ion flow created in the presheath of weakly ionized He+Ar plasma is studied experimentally. Ion acoustic wave measurements combined with previous LIF measurements [Phys. Rev. Lett. 90, 145001 (2003)] suggest that the Ar ion and He ion drift velocities approach each other near the sheath-presheath boundary. Their common velocity is the ion sound velocity of the system. The Ar

  17. Helium cluster ions RgHe{\\/x +} (Rg=Ne, Ar and Kr, x≦14) formed in a drift tube cooled by liquid helium

    Microsoft Academic Search

    T. M. Kojima; N. Kobayashi; Y. Kaneko

    1992-01-01

    Rare gas ions Ne+, Ar+ and Kr+ are injected into a drift tube which is filled with helium gas and cooled by liquid helium. Helium cluster ions RgHe{\\/x +} (Rg=Ne, Ar and Kr, x≦14) are observed as products. Information regarding the stability of RgHe{\\/x +} is obtained from drift field dependence of the size distribution of the clusters, and magic

  18. Ion velocity distributions in the vicinity of the current sheet in Earth`s distant magnetotail

    SciTech Connect

    Frank, L.A.; Paterson, W.R.; Ackerson, K.L.; Kokubun, S.; Kivelson, M.G.; Yamamoto, T.; Fairfield, D.H.

    1994-04-01

    Observations of the three-dimensional velocity distributions of positive ions and electrons have been recently gained for the first time in Earth`s distant magnetotail with the Galileo and Geotail spacecraft. For this brief discussion of these exciting results the focus is on the overall character of the ion velocity distributions during substorm activity. The ion velocity distributions within and near the magnetotail current sheet are not accurately described as convecting, isotropic Maxwellians. The observed velocity distributions are characterized by at least two robust types. The first type is similar to the `lima bean`-shaped velocity distributions that are expected from the nonadiabatic acceleration of ions which execute Speiser-type trajectories in the current sheet. The second distribution is associated with the presence of cold ion beams that presumably also arise from the acceleration of plasma mantle ions in the electric and weak magnetic fields in the current sheet. The ion velocity distributions in a magnetic field structure that is similar to that for plasmoids are also examined. Again the velocity distributions are not Maxwellian but are indicative of nonadiabatic acceleration. An example of the pressure tensor within the plasmoid-like event is also presented because it is anticipated that the off-diagonal elements are important in a description of magnetotail dynamics. Thus the concept of magnetotail dynamics must advance from the present assumption of co-moving electron and ion Maxwellian distributions into reformulations in terms of global kinematical models and nonadiabatic particle motion.

  19. Ion velocity distributions in the vicinity of the current sheet in Earth's distant magnetotail

    NASA Technical Reports Server (NTRS)

    Frank, L. A.; Paterson, W. R.; Ackerson, K. L.; Kokubun, S.; Kivelson, M. G.; Yamamoto, T.; Fairfield, D. H.

    1994-01-01

    Observations of the three-dimensional velocity distributions of positive ions and electrons have been recently gained for the first time in Earth's distant magnetotail with the Galileo and Geotail spacecraft. For this brief discussion of these exciting results the focus is on the overall character of the ion velocity distributions during substorm activity. The ion velocity distributions within and near the magnetotail current sheet are not accurately described as convecting, isotropic Maxwellians. The observed velocity distributions are characterized by at least two robust types. The first type is similar to the 'lima bean'-shaped velocity distributions that are expected from the nonadiabatic acceleration of ions which execute Speiser-type trajectories in the current sheet. The second distribution is associated with the presence of cold ion beams that presumably also arise from the acceleration of plasma mantle ions in the electric and weak magnetic fields in the current sheet. The ion velocity distributions in a magnetic field structure that is similar to that for plasmoids are also examined. Again the velocity distributions are not Maxwellian but are indicative of nonadiabatic acceleration. An example of the pressure tensor within the plasmoid-like event is also presented because it is anticipated that the off-diagonal elements are important in a description of magnetotail dynamics. Thus our concept of magnetotail dynamics must advance from the present assumption of co-moving electron and ion Maxwellian distributions into reformulations in terms of global kinematical models and nonadiabatic particle motion.

  20. Effects of errors in velocity tilt on maximum longitudinal compression during neutralized drift compression of intense beam pulses: I. general description

    SciTech Connect

    Kaganovich, Igor D.; Massidda, Scottt; Startsev, Edward A.; Davidson, Ronald C.; Vay, Jean-Luc; Friedman, Alex

    2012-06-21

    Neutralized drift compression offers an effective means for particle beam pulse compression and current amplification. In neutralized drift compression, a linear longitudinal velocity tilt (head-to-tail gradient) is applied to the non-relativistic beam pulse, so that the beam pulse compresses as it drifts in the focusing section. The beam current can increase by more than a factor of 100 in the longitudinal direction. We have performed an analytical study of how errors in the velocity tilt acquired by the beam in the induction bunching module limit the maximum longitudinal compression. It is found that the compression ratio is determined by the relative errors in the velocity tilt. That is, one-percent errors may limit the compression to a factor of one hundred. However, a part of the beam pulse where the errors are small may compress to much higher values, which are determined by the initial thermal spread of the beam pulse. It is also shown that sharp jumps in the compressed current density profile can be produced due to overlaying of different parts of the pulse near the focal plane. Examples of slowly varying and rapidly varying errors compared to the beam pulse duration are studied. For beam velocity errors given by a cubic function, the compression ratio can be described analytically. In this limit, a significant portion of the beam pulse is located in the broad wings of the pulse and is poorly compressed. The central part of the compressed pulse is determined by the thermal spread. The scaling law for maximum compression ratio is derived. In addition to a smooth variation in the velocity tilt, fast-changing errors during the pulse may appear in the induction bunching module if the voltage pulse is formed by several pulsed elements. Different parts of the pulse compress nearly simultaneously at the target and the compressed profile may have many peaks. The maximum compression is a function of both thermal spread and the velocity errors. The effects of the finite gap width of the bunching module on compression are analyzed analytically.

  1. Thermal iron ions in high speed solar wind streams. II - Temperatures and bulk velocities

    NASA Technical Reports Server (NTRS)

    Mitchell, D. G.; Roelof, E. C.; Feldman, W. C.; Bame, S. J.; Williams, D. J.

    1981-01-01

    Mitchel and Roelof (1980) reported the detection of iron in high speed solar wind flows using the small, but finite sensitivity of solid state detectors to Fe ions in the low energy (50-200 keV protons) L1 channel of the NOAA/JHU energetic particle experiment (EPE). In the current investigation, the EPE response is modeled to a convected Maxwellian to obtain the thermal velocity, flow angle, and bulk velocity of the iron distribution. It is assumed that the iron bulk flow velocity can be represented as a vector sum of the hydrogen bulk velocity and an interplanetary magnetic field (IMF) aligned velocity increment. It is found that the velocity increment is smaller than the local Alfven speed in magnitude, and that the iron thermal velocity is comparable with or greater than the proton thermal velocity, with the 'thermal' velocity defined as the square root of 2kT/m.

  2. Ion wind drag reduction

    NASA Technical Reports Server (NTRS)

    Malik, M. R.; Weinstein, L. M.; Hussaini, M. Y.

    1983-01-01

    In order to study the effect of ion wind on viscous drag, the equations of electrogasdynamics are solved numerically assuming the flow is incompressible, the electric field is steady and that the fluid velocity is negligible compared to ion drift velocity. The results obtained to date in a continuing theoretical and experimental research program are presented.

  3. Nonequilibrium velocity distribution and reaction rate in ion-molecule reactions

    Microsoft Academic Search

    Katsuhisa Koura

    1981-01-01

    The nonequilibrium velocity distribution and reaction rate in fast ion-molecule reactions with non-Langevin reaction cross sections are studied using the Monte Carlo simulation in steady-state systems where ions are diluted in heat-bath reactant molecules and ion sources compensate the loss of ions due to the reaction. The non-Langevin reaction cross sections are taken as the power and exponential dependences on

  4. Comparative analysis of nocturnal vertical plasma drift velocities inferred from ground-based ionosonde measurements of hmF2 and h?F

    NASA Astrophysics Data System (ADS)

    Adebesin, B. O.; Adeniyi, J. O.; Adimula, I. A.; Oladipo, O. A.; Olawepo, A. O.; Reinisch, B. W.

    2015-01-01

    Variations in the evening/nighttime ionosonde vertical plasma drift velocities inferred from the time rate of change of both the base of the F-layer height (Vz(h?F)) and height of the peak electron density (Vz(hmF2)) from an equatorial station were compared for better description of the E×B drifts. For better interpretation, both results were compared with the Incoherent Scatter (IS) radar observations (Vz(ISR)) which is taken to be the most accurate method of measuring drift, and therefore the data of reference level. An equinoctial maximum and June solstice minimum in post-sunset pre-reversal enhancement (PRE) was observed for Vz(hmF2), Vz(ISR), and Vz(h?F). The percentage correlation between VzhmF2 and Vzh?F ranges within 55-70%. While PRE for Vz(hmF2) peaked at 19 LT for all seasons, Vz(h?F) peaked at 18 LT for September equinox and December solstice, and start earlier. The nighttime downward reversal peak magnitudes for Vz(hmF2) and Vz(h?F) are respectively within the range of -4 to -14 and -2 to -14 m/s; whereas Vz(ISR) ranges within -12 and -34 m/s; and the peak time was reached earlier with the ionosonde observations than for the ISR. The PRE peak magnitude for Vz(hmF2), Vz(h?F) and Vz(ISR) varies between 3-14, 2-14, and 4-14 m/s for the entire seasons. Our results revealed higher drift correlation coefficients in both Vz(hmF2) vs. Vz(ISR) (0.983) and Vz(h?F) vs. Vz(ISR) (0.833) relationships during the equinoxes between 16-20 LT, at which time the F-layer altitude is higher than the 300 km threshold value; and lower for solstice period (0.326 and 0.410 in similar order). A better linear relationship between Vz(hmF2) and Vz(h?F2) was observed during the reversal (19-21 LT) phase period. PRE velocity was shown to be seasonal and solar activity dependent. Both VzhmF2 and Vzh?F compares almost equally with the ISR measurement. However, the PRE peak magnitude for the drift inferred using h?F2 is closer to the corresponding ISR magnitude during the equinoxes; whereas the drift inferred from hmF2 best represent the ISR magnitude for solstices. We established that both VzhmF2 and Vzh?F are governed by the same mechanism at nighttime, and as such any of them can be used to infer vertical drift as long as the 300 km threshold value condition is considered, otherwise chemical correction may be required for the F-layer uplift.

  5. Superconducting twin quarter wave resonator for acceleration of low velocity heavy ions

    Microsoft Academic Search

    H. Kabumoto; S. Takeuchi; M. Matsuda; N. Ishizaki; Y. Otokawa

    2010-01-01

    We have designed and fabricated a superconducting twin quarter wave resonator (Twin-QWR) made of niobium and copper for the acceleration of low velocity heavy ions. The resonator has two inner conductors and three acceleration gaps, which give a resonant frequency of 129.8MHz and an optimum beam velocity of 6% of the light velocity. Each inner conductor resonates like in a

  6. Phase velocities of irregularities in the equatorial electrojet.

    NASA Technical Reports Server (NTRS)

    Cohen, R.

    1973-01-01

    Spectral decomposition of the power spectrum of radar echoes at 50 MHz from the equatorial electrojet reveals information as to the phase velocities of several classes of electron density irregularities and permits inferences as to the electron drift velocity and the electron and ion temperatures in the electrojet. In particular, it is shown that the phase velocity of two-stream irregularities is comparable to the ion-acoustic speed and independent of the horizontal phase velocity of coexistent non-two-stream irregularities. The latter can exceed the ion-acoustic speed and is probably a measure of the electron drift velocity. Thus a probable inference is that the electron drift velocity can itself be supersonic, contrary to some existing theoretical opinions.

  7. A velocity map imaging spectrometer for electron?ion and ion?ion coincidence experiments with synchrotron radiation

    SciTech Connect

    Advanced Light Source; Kilcoyne, Arthur L; Rolles, D.; Pesic, Z.D.; Perri, M.; Bilodeau, R.C.; Ackerman, G.D.; Rude, B.S.; Kilcoyne, A.L.D.; Bozek, J.D.; Berrah, N.

    2007-04-27

    We have built a velocity imaging (VMI) spectrometer optimized for angle-resolved photoionization experiments with synchrotron radiation (SR) in the VUV and soft X-tay range. The spectrometer is equiped with four electrostatic lenses that focus the charged photoionization products onto a position-sensitive multi-hit delay-line anode. The use of two additional electrostatic lens elements as compared to the standard design of Eppink and Parker [T.J.B. Eppink and D.H. Parker, Rev. Sci. Instrum. 68 (1997) 3477]provides better focusing of an extended interaction region, which is crucial for most SR applications. Furthermore, the apparatus is equipped with a second micro-channel plate detector opposite to the VMI spectrometer, enabling electron-ion coincidence experiments and thereby mass-resolved ion spectroscopy independent of the time structure of the synchrotron radiation. First results for the photofragmentation of CO2 molecules are presented.

  8. Ion velocities in direct current arc plasma generated from compound cathodes

    SciTech Connect

    Zhirkov, I.; Rosen, J. [Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden)] [Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Eriksson, A. O. [Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden) [Thin Film Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Oerlikon Balzers Coating AG, Iramali 18, 9496 Balzers (Liechtenstein)

    2013-12-07

    Arc plasma from Ti-C, Ti-Al, and Ti-Si cathodes was characterized with respect to charge-state-resolved ion energy. The evaluated peak velocities of different ion species in plasma generated from a compound cathode were found to be equal and independent on ion mass. Therefore, measured difference in kinetic energies can be inferred from the difference in ion mass, with no dependence on ion charge state. The latter is consistent with previous work. These findings can be explained by plasma quasineutrality, ion acceleration by pressure gradients, and electron-ion coupling. Increasing the C concentration in Ti-C cathodes resulted in increasing average and peak ion energies for all ion species. This effect can be explained by the “cohesive energy rule,” where material and phases of higher cohesive energy generally result in increasing energies (velocities). This is also consistent with the here obtained peak velocities around 1.37, 1.42, and 1.55 (10{sup 4} m/s) for ions from Ti{sub 0.84}Al{sub 0.16}, Ti{sub 0.90}Si{sub 0.10}, and Ti{sub 0.90}C{sub 0.10} cathodes, respectively.

  9. Electrostatic ion-cyclotron waves driven by parallel velocity shear R. L. Merlinoa)

    E-print Network

    Merlino, Robert L.

    Electrostatic ion-cyclotron waves driven by parallel velocity shear R. L. Merlinoa) Department cyclotron frequency propagating at large angles to the ambient magnetic field can be excited in a magnetized in determining the stability of shear-driven electrostatic ion-cyclotron EIC modes is also considered

  10. Mass loading and velocity diffusion models for heavy pickup ions at comet Grigg-Skjellerup

    NASA Technical Reports Server (NTRS)

    Huddleston, D. E.; Coates, A. J.; Johnstone, A. D.; Neubauer, Fritz M.

    1993-01-01

    We compare model predictions of cometary water group ion densities and the solar wind slow down with measurements made by the Giotto Johnstone plasma analyzer implanted ion sensor at the encounter with comet Grigg-Skjellerup (G-S) on July 10, 1992. The observed slope of the ion density profile on approach to the comet is unexpectedly steep. Possible explanations for this are discussed. We present also a preliminary investigation of the quasilinear velocity-space diffusion of the implanted heavy ion population at G-S using a transport equation including souce, convection, adiabatic compression, and velocity diffusion terms. Resulting distributions are anisotropic, in agreement with observations. We consider theoretically the waves that may be generated by the diffusion process for the observed solar wind conditions. At initial ion injections, waves are generated at omega approximately Omega(sub i) the ion gyrofrequency, and lower frequencies are predicted for diffusion toward a bispherical shell.

  11. Kr II and Xe II axial velocity distribution functions in a cross-field ion source

    SciTech Connect

    Lejeune, A.; Bourgeois, G.; Mazouffre, S. [ICARE, CNRS, 1C Avenue de la Recherche Scientifique, 45071 Orlans Cedex 2 (France)

    2012-07-15

    Laser induced fluorescence measurements were carried out in a cross-field ion source to examine the behaviour of the axial ion velocity distribution functions (VDFs) in the expanding plasma. In the present paper, we focus on the axial VDFs of Kr II and Xe II ions. We examine the contourplots in a 1D-phase space (x,v{sub x}) representation in front of the exhaust channel and along the centerline of the ion source. The main ion beam, whose momentum corresponds to the ions that are accelerated through the whole potential drop, is observed. A secondary structure reveals the ions coming from the opposite side of the channel. We show that the formation of the neutralized ion flow is governed by the annular geometry. The assumption of a collisionless shock or a double layer due to supersonic beam interaction is not necessary. A non-negligible fraction of slow ions originates in local ionization or charge-exchange collision events between ions of the expanding plasma and atoms of the background residual gas. Slow ions that are produced near the centerline in the vicinity of the exit plane are accelerated toward the source body with a negative velocity leading to a high sputtering of front face. On the contrary, the ions that are produced in the vicinity of the channel exit plane are partially accelerated by the extended electric field.

  12. SIMULATIONS OF HIGH-VELOCITY CLOUDS. II. ABLATION FROM HIGH-VELOCITY CLOUDS AS A SOURCE OF LOW-VELOCITY HIGH IONS

    SciTech Connect

    Henley, David B.; Kwak, Kyujin; Shelton, Robin L., E-mail: dbh@physast.uga.edu, E-mail: rls@physast.uga.edu, E-mail: kkwak@kasi.re.kr [Department of Physics and Astronomy, University of Georgia, Athens, GA 30602 (United States)

    2012-07-01

    In order to determine if the material ablated from high-velocity clouds (HVCs) is a significant source of low-velocity high ions (C IV, N V, and O VI) such as those found in the Galactic halo, we simulate the hydrodynamics of the gas and the time-dependent ionization evolution of its carbon, nitrogen, and oxygen ions. Our suite of simulations examines the ablation of warm material from clouds of various sizes, densities, and velocities as they pass through the hot Galactic halo. The ablated material mixes with the environmental gas, producing an intermediate-temperature mixture that is rich in high ions and that slows to the speed of the surrounding gas. We find that the slow mixed material is a significant source of the low-velocity O VI that is observed in the halo, as it can account for at least {approx}1/3 of the observed O VI column density. Hence, any complete model of the high ions in the halo should include the contribution to the O VI from ablated HVC material. However, such material is unlikely to be a major source of the observed C IV, presumably because the observed C IV is affected by photoionization, which our models do not include. We discuss a composite model that includes contributions from HVCs, supernova remnants, a cooling Galactic fountain, and photoionization by an external radiation field. By design, this model matches the observed O VI column density. This model can also account for most or all of the observed C IV, but only half of the observed N V.

  13. Flute mode waves near the lower hybrid frequency excited by ion rings in velocity space

    NASA Technical Reports Server (NTRS)

    Cattell, C.; Hudson, M.

    1982-01-01

    Discrete emissions at the lower hybrid frequency are often seen on the S3-3 satellite. Simultaneous observation of perpendicularly heated ions suggests that these ions may provide the free energy necessary to drive the instability. Studies of the dispersion relation for flute modes excited by warm ion rings in velocity space show that waves are excited with real frequencies near the lower hybrid frequency and with growth rates ranging from about 0.01 to 1 times the ion cyclotron frequency. Numerical results are therefore consistent with the possibility that the observed ions are the free energy source for the observed waves.

  14. Low-velocity ion slowing-down in strongly asymmetric and binary ionic mixtures

    NASA Astrophysics Data System (ADS)

    Fromy, P.; Tashev, B.; Deutsch, C.

    2010-10-01

    Attention is focused on the low-ion-velocity stopping mechanisms in multicomponent and dense target plasmas built of quasi-classical electron fluids neutralizing binary ionic mixtures. The target plasma is taken in a multicomponent dielectric formulation à la Fried-Conte. The occurrence of projectile ion velocities (so-called critical) for which target electron slowing-down equals that of given target ion components is also considered. We emphasize the strongly asymmetric BIM targets such as the proton-boron 11 of thermonuclear concern and the strongly mass-asymmetric proton-U238+.

  15. Plasma structuring by the gradient drift instability at high latitudes and comparison with velocity shear driven processes

    NASA Technical Reports Server (NTRS)

    Basu, Sunanda; Mackenzie, E.; Basu, S.; Coley, W. R.; Sharber, J. R.; Hoegy, W. R.

    1990-01-01

    Using results of the in situ measurements made by the DE 2 satellite, the nature of plasma structuring at high latitudes, caused by the gradient drift instability process, is described. Using noon-midnight and dawn-dusk orbits of the DE 2 satellite, it was possible to examine the simultaneous density and electric field spectra of convecting large-scale plasma density enhancements in the polar cap known as 'patches', in directions parallel and perpendicular to their antisunward convection. The results provide evidence for the existence of at least two generic classes of instabilities operating in the high-latitude ionosphere: one driven by large-scale density gradients in a homogeneous convection field with respect to the neutrals, and the other driven by the structured convection field itself in an ambient ionosphere where density fluctuations are ubiquitous.

  16. Kinetic theory and atomic physics corrections for determination of ion velocities from charge-exchange spectroscopy

    NASA Astrophysics Data System (ADS)

    Muñoz Burgos, J. M.; Burrell, K. H.; Solomon, W. M.; Grierson, B. A.; Loch, S. D.; Ballance, C. P.; Chrystal, C.

    2013-09-01

    Charge-exchange spectroscopy is a powerful diagnostic tool for determining ion temperatures, densities and rotational velocities in tokamak plasmas. This technique depends on detailed understanding of the atomic physics processes that affect the measured apparent velocities with respect to the true ion rotational velocities. These atomic effects are mainly due to energy dependence of the charge-exchange cross-sections, and in the case of poloidal velocities, due to gyro-motion of the ion during the finite lifetime of the excited states. Accurate lifetimes are necessary for correct interpretation of measured poloidal velocities, specially for high density plasma regimes on machines such as ITER, where l-mixing effects must be taken into account. In this work, a full nl-resolved atomic collisional radiative model coupled with a full kinetic calculation that includes the effects of electric and magnetic fields on the ion gyro-motion is presented for the first time. The model directly calculates from atomic physics first principles the excited state lifetimes that are necessary to evaluate the gyro-orbit effects. It is shown that even for low density plasmas where l-mixing effects are unimportant and coronal conditions can be assumed, the nl-resolved model is necessary for an accurate description of the gyro-motion effects to determine poloidal velocities. This solution shows good agreement when compared to three QH-mode shots on DIII-D, which contain a wide range of toroidal velocities and high ion temperatures where greater atomic corrections are needed. The velocities obtained from the model are compared to experimental velocities determined from co- and counter-injection of neutral beams on DIII-D.

  17. Ion collection by a conducting sphere in a magnetized or drifting collisional plasma

    E-print Network

    Haakonsen, Christian Bernt, 1985-

    2011-01-01

    Ion collection by dust grains and probes in plasmas with a neutral background is of interest in the study of both space and terrestrial plasmas, where charge-exchange collisions can play an important role in ion collection. ...

  18. Pick-up ion energization in the outer heliosphere due to bulk velocity fluctuations

    NASA Astrophysics Data System (ADS)

    Fahr, H.-J.; Siewert, M.

    2012-04-01

    At large solar distances beyond 10 AU MHD turbulence amplitudes are decreasing and even selfgenerated turbulences by pick-up ions will not support effectively enough energy diffusion processes driven by nonlinear wave-particle interactions. This should suppress the evolution of suprathermal ion tails beyond the pick-up ion injection border, though at distances beyond 10 AU such tails have been observed by spacecraft like Voyager-1/2, Cassini, and Horizon. We want to show here that an effective process of ion energy diffusion is driven by solar wind bulk velocity fluctuations passing over co-moving ions. Describing such fluctuations as traveling MHD shocks we describe kinetically the ion processing in momentum space and can identify this with an energy diffusion process with a distance-independent diffusion coefficient. As we show this process will lead to the appearance of suprathermal ion power law tails as observed by in-situ spectral ion observations.

  19. Verifying effects of instability enhanced ion–ion Coulomb collisions on ion velocity distribution functions near the sheath edge in low temperature plasmas

    NASA Astrophysics Data System (ADS)

    Yip, Chi-Shung; Hershkowitz, Noah; Severn, Greg

    2015-02-01

    Experiments have shown that ion velocity distribution functions (ivdfs) with non-Maxwellian tails created by ion–neutral collisions and ionizations along pre-sheaths in weakly collisional plasmas can be thermalized into Maxwellian distributions near the sheath edge. A recent theory suggests that ion–ion collisions enhanced by ion-acoustic instabilities can rapidly thermalize ions near the sheath edge into Maxwellian distributions and that increasing either electron temperature or neutral pressure of a plasma suppresses the growth of instabilities and eliminates the thermalization process. Measurements of ivdfs by laser induced fluorescence showed qualitative agreement between experimental data and a marginal stability curve inferred from the new theory.

  20. Velocity dependence of heavy-ion stopping below the maximum

    NASA Astrophysics Data System (ADS)

    Sigmund, P.; Schinner, A.

    2015-01-01

    In the slowing-down of heavy ions in materials, the standard description by Lindhard and Scharff assumes the electronic stopping cross section to be proportional to the projectile speed v up to close to a stopping maximum, which is related to the Thomas-Fermi speed vTF . It is well known that strict proportionality with v is rarely observed, but little is known about the systematics of observed deviations. In this study we try to identify factors that determine positive or negative curvature of stopping cross sections on the basis of experimental data and of binary stopping theory. We estimate the influence of shell structure of the target and of the equilibrium charge of the ion and comment the role of dynamic screening.

  1. Ion Velocity Distribution Function Investigated Inside an Unstable Magnetized Plasma Exhibiting a Rotating Nonlinear Structure

    NASA Astrophysics Data System (ADS)

    Rebont, C.; Claire, N.; Pierre, Th.; Doveil, F.

    2011-06-01

    The frequent situation where a strongly nonlinear rotating structure develops in a linear magnetized plasma column is investigated experimentally with emphasis on the ion velocity distribution function (IVDF). Most often, a mode m=2 appears exhibiting a large density and potential perturbation with angular frequency slightly above the ion cyclotron frequency. For the first time the spatiotemporal evolution of the IVDF is studied using time-resolved laser induced fluorescence to explore the ion’s interaction with the nonlinear wave propagating inside the column and at the origin of plasma transport outside the limiter. The ion fluid exhibits an alternance from azimuthal to radial velocity due to the electric field inside the rotating structure. A fluid model also allows us to locally reconstruct the self-consistent electric field evolution which contradicts all existing theories.

  2. Two-fluid magnetic island dynamics in slab geometry: III -Influence of drift-wave resonances on island propagation

    E-print Network

    Fitzpatrick, Richard

    Two-fluid magnetic island dynamics in slab geometry: III - Influence of drift-wave resonances- , magnetic island propagating through a two-fluid, drift-MHD (magneto- hydrodynanical) plasma in slab fluid velocities. However, in the supersonic limit, resonant interac- tion of the ion and electron

  3. Regulation of Ion Drifts and Anisotropies by Parametrically Unstable Finite-amplitude Alfvén-cyclotron Waves in the Fast Solar Wind

    NASA Astrophysics Data System (ADS)

    Maneva, Y. G.; Araneda, J. A.; Marsch, E.

    2014-03-01

    We study the preferential heating and differential acceleration of minor ions by dissipation of ion-acoustic waves (IAWs) generated by parametric instabilities of a finite-amplitude monochromatic Alfvén-cyclotron pump wave. We consider the associated kinetic effects of Landau damping and nonlinear pitch-angle scattering of protons and ? particles in the tenuous plasma of coronal holes and the fast solar wind. Various data collected by Wind spacecraft show signatures for a local transverse heating of the minor ions, presumably by Alfvén-cyclotron wave dissipation, and an unexpected parallel heating by a so far unknown mechanism. Here, we present the results from a set of 1.5 dimensional hybrid simulations in search for a plausible explanation for the observed field-aligned kinetic features in the fast solar wind minor ions. We investigate the origin and regulation of ion relative drifts and temperature anisotropies in low plasma ?, fast solar wind conditions. Depending on their initial drifts, both ion species can heat up not only transversely through cyclotron resonance and non-resonant wave-particle interactions, but also strongly in the parallel direction by Landau damping of the daughter IAWs. We discuss the dependence of the relative ion drifts and temperature anisotropies on the plasma ? of the individual species and we describe the effect of the pump wave amplitude on the ion heating and acceleration.

  4. A Novel pH-dependent Drift Improvement Method for Zirconium Dioxide Gated pH-Ion Sensitive Field Effect Transistors

    PubMed Central

    Chang, Kow-Ming; Chang, Chih-Tien; Chao, Kuo-Yi; Lin, Chia-Hung

    2010-01-01

    A novel compensation method for Zirconium dioxide gated Ion Sensitive Field Effect Transistors (ISFETs) to improve pH-dependent drift was demonstrated. Through the sequential measurements for both the n-channel and p-channel ISFETs, 75–100% pH-dependent drift could be successfully suppressed for the first seven hours. As a result, a nearly constant drift rate versus pH value was obtained, which increases the accuracy of pH measurements. Meanwhile, the drawback of the hyperbolic-like change with time of the common drift behavior for ISFETs was improved. A state-of-the-art integrated scheme adopting this method was also illustrated. PMID:22399897

  5. Photons from Heavy-Ion Collisions at Fermi Velocity

    E-print Network

    Ko, Che Ming; Alchelin, J.

    1987-01-01

    - cludes both the mean field and the Pauli blocking of nucleon-nucleon collisions has been introduced recently to describe heavy-ion collisions at intermediate energies. ' Important information about the properties of dense nu- clear matter has been...-frequency limit since for high frequencies, some terms in Eq. (1) will not contribute due to the Pauli blocking of the final nucleon states and, furthermore, each term in Eq. (1) will have to be weighted diA'erently according to the density of 1976 1987...

  6. Ionization of highly charged iodine ions near the Bohr velocity

    NASA Astrophysics Data System (ADS)

    Zhou, Xianming; Cheng, Rui; Lei, Yu; Sun, Yuanbo; Ren, Jieru; Liu, Shidong; Deng, Jiachuan; Zhao, Yongtao; Xiao, Guoqing

    2015-01-01

    We have measured the L-shell X-rays of iodine from the collisions of 3 MeV Iq+(q=15,20,22,25,26) ions with an iron target. It is found that the X-ray yield decreases with the increasing initial charge state. The energy of the subshell X-ray has a blue shift, which is independent of the projectile charge state. In addition, the relative intensity ratios of L?1,3,4 and L?2,15 to L?1,2 X-ray are obtained and compared with the theoretical calculations. That they are larger than for a singly ionized atom can be understood by the multiple ionization effect of the outer-shell electrons.

  7. On the nonlinear stability of a quasi-two-dimensional drift kinetic model for ion temperature gradient turbulence

    E-print Network

    Plunk, G G

    2015-01-01

    We study a quasi-two-dimensional electrostatic drift kinetic system as a model for near-marginal ion temperature gradient (ITG) driven turbulence. A proof is given of the nonlinear stability of this system under conditions of linear stability. This proof is achieved using a transformation that diagonalizes the linear dynamics and also commutes with nonlinear $E\\times B$ advection. For the case when linear instability is present, a corollary is found that forbids nonlinear energy transfer between appropriately defined sets of stable and unstable modes. It is speculated that this may explain the preservation of linear eigenmodes in nonlinear gyrokinetic simulations. Based on this property, a dimensionally reduced ($\\infty\\times\\infty \\rightarrow 1$) system is derived that may be useful for understanding dynamics around the critical gradient of Dimits.

  8. Ion velocity and plasma potential measurements of a cylindrical cusped field thruster

    SciTech Connect

    MacDonald, N. A.; Young, C. V.; Cappelli, M. A. [Stanford Plasma Physics Laboratory, Stanford University, Stanford, California 94305 (United States); Hargus, W. A. Jr. [Spacecraft Propulsion Branch, Air Force Research Laboratory, Edwards AFB, California 93524 (United States)

    2012-05-01

    Measurements of the most probable time-averaged axial ion velocities and plasma potential within the acceleration channel and in the plume of a straight-channeled cylindrical cusped field thruster operating on xenon are presented. Ion velocities for the thruster are derived from laser-induced fluorescence measurements of the 5d[4]{sub 7/2}-6p[3]{sub 5/2} xenon ion excited state transition centered at {lambda}=834.72nm. Plasma potential measurements are made using a floating emissive probe with a thoriated-tungsten filament. The thruster is operated in a power matched condition with 300 V applied anode potential for comparison to previous krypton plasma potential measurements, and a low power condition with 150 V applied anode potential. Correlations are seen between the plasma potential drop outside of the thruster and kinetic energy contours of the accelerating ions.

  9. Ion Velocity Distribution Function Investigated Inside an Unstable Magnetized Plasma Exhibiting a Rotating Nonlinear Structure

    SciTech Connect

    Rebont, C.; Claire, N.; Pierre, Th.; Doveil, F. [PIIM, UMR6633 CNRS/Universite de Provence, case 321, centre universitaire de Saint-Jerome, 13397 Marseille (France)

    2011-06-03

    The frequent situation where a strongly nonlinear rotating structure develops in a linear magnetized plasma column is investigated experimentally with emphasis on the ion velocity distribution function (IVDF). Most often, a mode m=2 appears exhibiting a large density and potential perturbation with angular frequency slightly above the ion cyclotron frequency. For the first time the spatiotemporal evolution of the IVDF is studied using time-resolved laser induced fluorescence to explore the ion's interaction with the nonlinear wave propagating inside the column and at the origin of plasma transport outside the limiter. The ion fluid exhibits an alternance from azimuthal to radial velocity due to the electric field inside the rotating structure. A fluid model also allows us to locally reconstruct the self-consistent electric field evolution which contradicts all existing theories.

  10. Positive ion distributions in the morning auroral zone - local acceleration and drift effects

    SciTech Connect

    Sauvaud, J.A.; Bosqued, J.M.; Kovrazhkin, R.A.; Delcourt, D.; Berthelier, J.J.

    1985-01-01

    The typical structure of the large-scale ion precipitation in the morning sector of the auroral zone and associated low-frequency electromagnetic waves are examined on the basis of Aureole-3 satellite data. Two main precipitation regions are distinguished. In the poleward part of the auroral zone, the latitudinal variations of the average energy or temperature of the precipitated ions (mainly H+) indicate that they are adiabatically accelerated in the outer magnetosphere. In addition, a drastic change in the ion characteristics is observed near the boundary between discrete and diffuse electron auroras. The flux of energetic precipitated H(+) ions is sharply reduced, which suggests the formation of an Alfven layer; however, intense fluxes of precipitated H(+), O(+), and He(+) ions with energies below 3 keV are observed equatorward of the Alfven layer, coinciding with the diffuse aurora and associated with quasi-monochromatic electromagnetic waves with frequencies around the proton gyrofrequency. It is suggested that the precipitation of ionospheric ions inside the diffuse aurora results from convection and corotation of ions accelerated to suprathermal energies at higher latitudes. 13 references.

  11. Negative ion productions in high velocity collision between small carbon clusters and Helium atom target

    NASA Astrophysics Data System (ADS)

    M, Chabot; K, Béroff; T, Pino; G, Féraud; N, Dothi; Padellec A, Le; G, Martinet; S, Bouneau; Y, Carpentier

    2012-11-01

    We measured absolute double capture cross section of Cn+ ions (n=1,5) colliding, at 2.3 and 2.6 a.u velocities, with an Helium target atom and the branching ratios of fragmentation of the so formed electronically excited anions Cn-*. We also measured absolute cross section for the electronic attachment on neutral Cn clusters colliding at same velocities with He atom. This is to our knowledge the first measurement of neutral-neutral charge exchange in high velocity collision.

  12. 2D He+ pickup ion velocity distribution functions: STEREO PLASTIC observations

    NASA Astrophysics Data System (ADS)

    Drews, C.; Berger, L.; Taut, A.; Peleikis, T.; Wimmer-Schweingruber, R. F.

    2015-03-01

    Context. He+ pickup ions are either born from the ionization of interstellar neutral helium inside our heliosphere, the so-called interstellar pickup ions, or through the interaction of solar wind ions with small dust particles, the so-called inner source of pickup ions. Until now, most observations of pickup ions were limited to reduced 1D velocity spectra, which are insufficient to study certain characteristics of the He+ velocity distribution function (VDF). Aims: It is generally assumed that rapid pitch-angle scattering of freshly created pickup ions quickly leads to a fully isotropic He+ VDF. In light of recent observations, this assumption has found to be oversimplified and needs to be reinvestigated. Methods: Using He+ pickup ion data from the PLASTIC instrument on board the STEREO A spacecraft, we reconstruct a reduced form of the He+ VDF in two dimensions. This allows us to study relative changes of the 2D He+ VDF as a function of the configuration of the heliospheric magnetic field. Results: Our observations show that the He+ VDF is highly anisotropic and even indicates that, at least for certain configurations of B, it is not fully gyrotropic. Our results further suggest, that the observed velocity and pitch angle of He+ depends strongly on the local solar magnetic field vector, B, the ecliptic longitude, ?, the solar wind speed, vsw, and the global distribution of B. Conclusions: We found two distinct signatures that systematically change as a function of the alignment of B: (1) a ring beam distribution that is most pronounced at wsw> 0.5 and likely attributed to interstellar He+; (2) a beam signature aligned parallel to B that is most pronounced at wsw < 0.5 and attributed to inner-source He+. The strong anisotropy and the aforementioned dependencies of the He+ VDF also imply that observations of 1D velocity spectra of He+ pickup ions are potentially deceiving.

  13. Electron-ion hybrid instabilities driven by velocity shear in a magnetized plasma

    NASA Technical Reports Server (NTRS)

    Romero, H.; Ganguli, G.; Lee, Y. C.; Palmadesso, P. J.

    1992-01-01

    The stability of a magnetized plasma is investigated in which a sheared electron flow channel is present. The flow's peak velocity and shear scale length are denoted by V and L, respectively. If the velocity channel is perpendicular to the confining magnetic field and L is less than the ion Larmor radius, an electrostatic instability develops whose frequency is on the order of the lower hybrid frequency. It is concluded that velocity shear is the only source of free energy. Further, it is shown that density gradients do not stabilize this mode. It follows that the mode presented in this work can not be identified with the well-known modified two-stream instability. If the velocity channel is parallel to the confining magnetic field and the plasma is weakly magnetized, an instability driven by velocity shear is shown to exist.

  14. Nonlinear electrostatic drift waves in dense electron-positron-ion plasmas

    SciTech Connect

    Haque, Q.; Mahmood, S.; Mushtaq, A. [Theoretical Plasma Physics Division, PINSTECH, P.O. Nilore Islamabad (Pakistan)

    2008-08-15

    The Korteweg-de Vries-Burgers (KdVB)-type equation is obtained using the quantum hydrodynamic model in an inhomogeneous electron-positron-ion quantum magnetoplasma with neutral particles in the background. The KdV-type solitary waves, Burgers-type monotonic, and oscillatory shock like solutions are discussed in different limits. The quantum parameter is also dependent on the positron concentration in dense multicomponent plasmas. It is found that both solitary hump and dip are formed and their amplitude and width are dependent on percentage presence of positrons in electron-ion plasmas. The height of the monotonic shock is decreased with the increase of positron concentration and it is independent of the quantum parameter in electron-positron-ion magnetized quantum plasmas. However, the amplitude of the oscillatory shock is dependent on positron concentration and quantum parameter in electron-positron-ion plasmas.

  15. MAVEN Observations of Escaping Planetary Ions from the Martian Atmosphere: Mass, Velocity, and Spatial Distributions

    NASA Astrophysics Data System (ADS)

    Dong, Yaxue; Fang, Xiaohua; Brain, D. A.; McFadden, James P.; Halekas, Jasper; Connerney, Jack

    2015-04-01

    The Mars-solar wind interaction accelerates and transports planetary ions away from the Martian atmosphere through a number of processes, including ‘pick-up’ by electromagnetic fields. The MAVEN spacecraft has made routine observations of escaping planetary ions since its arrival at Mars in September 2014. The SupraThermal And Thermal Ion Composition (STATIC) instrument measures the ion energy, mass, and angular spectra. It has detected energetic planetary ions during most of the spacecraft orbits, which are attributed to the pick-up process. We found significant variations in the escaping ion mass and velocity distributions from the STATIC data, which can be explained by factors such as varying solar wind conditions, contributions of particles from different source locations and different phases during the pick-up process. We also study the spatial distributions of different planetary ion species, which can provide insight into the physics of ion escaping process and enhance our understanding of atmospheric erosion by the solar wind. Our results will be further interpreted within the context of the upstream solar wind conditions measured by the MAVEN Solar Wind Ion Analyzer (SWIA) instrument and the magnetic field environment measured by the Magnetometer (MAG) instrument. Our study shows that the ion spatial distribution in the Mars-Sun-Electric-Field (MSE) coordinate system and the velocity space distribution with respect to the local magnetic field line can be used to distinguish the ions escaping through the polar plume and those through the tail region. The contribution of the polar plume ion escape to the total escape rate will also be discussed.

  16. Effect of ion excape velocity and conversion surface material on H- production

    SciTech Connect

    Johnson, Kenneth F [Los Alamos National Laboratory; Tarvainen, Olli A [Los Alamos National Laboratory; Geros, E. [Los Alamos National Laboratory; Stelzer, J. [Los Alamos National Laboratory; Rouleau, G. [Los Alamos National Laboratory; Kalvas, T. [UNIV OF JYVASKYLA; Komppula, J. [UNIV OF JYASKYLA; Carmichael, J. [ORNL

    2010-10-05

    According to generally accepted models surface production of negative ions depends on ion escape velocity and work function of the surface. We have conducted an experimental study addressing the role of the ion escape velocity on H{sup -} production. A converter-type ion source at Los Alamos Neutron Science Center was employed for the experiment. The ion escape velocity was changed by varying the bias voltage of the converter electrode. It was observed that due to enhanced stripping of H{sup -} no direct gain of extracted beam current can be achieved by increasing the converter voltage. At the same time the conversion efficiency of H{sup -} was observed to vary with converter voltage and follow the existing theories in qualitative manner. We discuss the role of surface material on H{sup -} formation probability and present calculations predicting relative H{sup -} yields from different cesiated surfaces. These calculations are compared with experimental observations from different types of H{sup -} ion sources. The effects caused by varying cesium coverage are also discussed. Finally, we present a novel idea of utilizing materials exhibiting so-called negative electron affinity in H{sup -}/D{sup -} production under UV-light exposure.

  17. Velocity and Density of Low Energy Ions in High-Latitude Magnetosphere

    NASA Technical Reports Server (NTRS)

    Elliott, Heather A.; Comfort, Richard H.; Chandler, M. O.; Craven, P. D.; Moore, T. E.

    1999-01-01

    This study examines the characteristics of low energy ions at the polar cap boundary and within the polar cap in relationship to the convection velocity. The source of low energy ions in the magnetosphere could be driven by solar wind/IMF (interplanetary magnetic fields) interactions affecting energization processes of ionospheric ions. The IMF also influences the convection pattern which is in part responsible for determining the path ions take as they leave the ionosphere and contribute to magnetospheric populations. The primary source of data for this study is the Thermal Ion Dynamics Experiment (TIDE) on board the Polar satellite. TIDE can measure 3-D velocities and covers an energy range ideal for examining the polar cap plasma (0-450 eV). Due to certain limitations, this study uses H+ measurements at apogee and O+ measurements at perigee. At apogee H+ is very field-aligned and outflowing, and at perigee O+ is often moving downward in the polar cap proper. The path highly field-aligned flows take across the polar cap are also affected by changes in the magnetic field line topology which varies with geophysical conditions. Convection near the polar cap boundary is of particular interest since often the convection there is highly structured, and convection reversals may play a role in causing ion outflow. This study will examine in particular the density structures of ions in relationship to the convection velocity. Examining such relationships may provide insight into understanding the consequences of the 3-D flow on the density of ions in the polar cap, and transport of ions across the polar cap.

  18. Effects of a magnetic field gradient on the lower hybrid drift instability

    NASA Technical Reports Server (NTRS)

    Huba, J. D.; Wu, C. S.

    1976-01-01

    The effect of a magnetic field gradient on the lower hybrid drift instability is examined in the low drift velocity regime (i.e., of the order of the ion thermal velocity). The theoretical model includes density and temperature gradients, and considers only waves propagating perpendicular to the ambient magnetic field with wavelengths of the order of the electron Larmor radius. It is found, for the case of a finite ratio of the electron pressure to the magnetic field pressure, that a magnetic gradient drift-wave resonance can be important and is stabilizing or destabilizing depending upon the physical conditions. Substantial plasma heating and a large anomalous resistivity can also occur.

  19. Ultrafast spectroscopy diagnostic to measure localized ion temperature and toroidal velocity fluctuations

    SciTech Connect

    Uzun-Kaymak, I. U.; Fonck, R. J.; McKee, G. R.; Schoenbeck, N.; Smith, D.; Winz, G.; Yan, Z. [Engineering Physics, University of Wisconsin-Madison, Wisconsin 53706 (United States)

    2010-10-15

    A dual-channel high-efficiency, high-throughput custom spectroscopic system has been designed and implemented at DIII-D to measure localized ion thermal fluctuations associated with drift wave turbulence. A large-area prism-coupled transmission grating and high-throughput collection optics are employed to observe C VI emission centered near {lambda}=529 nm. The diagnostic achieves 0.25 nm resolution over a 2.0 nm spectral band via eight discrete spectral channels. A turbulence-relevant time resolution of 1 {mu}s is achieved using cooled high-speed avalanche photodiodes and ultralow-noise preamplifiers. The system sensitivity is designed to provide measurements of normalized ion temperature fluctuations on the order of {delta}T{sub i}/T{sub i}{<=}1%.

  20. Analogous saturation mechanisms of the ion and electron temperature gradient drift wave turbulence.

    PubMed

    Sokolov, V; Sen, A K

    2014-08-29

    New experimental results and theoretical arguments indicate that a novel saturation mechanism of the electron temperature gradient modes is related to its coupling to a damped ion acoustic mode. The experimental bicoherence data show multimode coupling between two high frequency radial harmonics of electron temperature gradient in the vicinity of (?2??MHz) and one low frequency ion acoustic (?45??kHz) mode. A unique feedback diagnostic also verifies this coupling. It is pointed out that a near identical mechanism is responsible for ITG mode saturation [V. Sokolov, and A.?K. Sen, Phys. Rev. Lett. 92, 165002 (2004)], indicating its plausible generic nature. PMID:25215988

  1. Velocity distribution of ions incident on a radio-frequency biased wafer

    NASA Astrophysics Data System (ADS)

    Wakayama, G.; Nanbu, K.

    2001-08-01

    The ion velocity distribution (IVD) is important in plasma etching of microfeatures. IVD at a rf biased wafer is studied, first analytically using probability theory and then numerically by using a particle simulation method. The analytic expression shows that IVD is governed by the parameter qVrf/mi?l, where q is the charge of ion, Vrf is the rf bias amplitude, ? is the rf bias angular frequency, l is the penetration depth of bias potential, and mi is the mass of ion. The analytical expression is applicable to the case when the ion collisions in the penetration depth are negligibly few and the rf period of biasing is much shorter than the time that ions take in traversing the depth l. The IVDs for general conditions are also examined using the self-consistent particle-in-cell/Monte Carlo simulation.

  2. Inversion technique to obtain local rotation velocity and ion temperature from line-integrated measurements for elongated tokamak plasmaa)

    NASA Astrophysics Data System (ADS)

    Shi, Y. J.; Lee, S. G.; Hill, K. W.; Bitter, M.

    2012-10-01

    An inversion technique is presented to calculate local toroidal and poloidal rotation velocity and ion temperature from line-integrated measurements of impurity lines by a matrix method. The effects of the rotation velocity on the ion temperature are analyzed in particular. An accurate inversion formula for the ion temperature is obtained. Several experimental geometries or configurations of line-integrated diagnostics in tokamaks are presented. For a plasma that is up-down symmetric, both the toroidal rotation velocity and poloidal rotation velocity can be deduced from one special line-integrated measurement.

  3. Computed versus measured ion velocity distribution functions in a Hall effect thruster

    SciTech Connect

    Garrigues, L. [Universite de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d'Energie), 118 route de Narbonne, F-31062 Toulouse cedex 9 (France); CNRS, LAPLACE, F-31062 Toulouse (France); Mazouffre, S.; Bourgeois, G. [ICARE (Institut de Combustion, Aerothermique, Reactivite et Environnement), 1 C avenue de la recherche scientifique, 45071 Orleans (France)

    2012-06-01

    We compare time-averaged and time-varying measured and computed ion velocity distribution functions in a Hall effect thruster for typical operating conditions. The ion properties are measured by means of laser induced fluorescence spectroscopy. Simulations of the plasma properties are performed with a two-dimensional hybrid model. In the electron fluid description of the hybrid model, the anomalous transport responsible for the electron diffusion across the magnetic field barrier is deduced from the experimental profile of the time-averaged electric field. The use of a steady state anomalous mobility profile allows the hybrid model to capture some properties like the time-averaged ion mean velocity. Yet, the model fails at reproducing the time evolution of the ion velocity. This fact reveals a complex underlying physics that necessitates to account for the electron dynamics over a short time-scale. This study also shows the necessity for electron temperature measurements. Moreover, the strength of the self-magnetic field due to the rotating Hall current is found negligible.

  4. Initial Velocity Distribution of MALDI/LDI Ions Measured by Internal MALDI Source Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Chagovets, Vitaliy; Frankevich, Vladimir; Zenobi, Renato

    2014-08-01

    A new method for measuring the ion velocity distribution using an internal matrix-assisted laser desorption/ionization (MALDI) source Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer is described. The method provides the possibility of studying ion velocities without any influence of electric fields in the direction of the instrument axis until the ions reach the ICR cell. It also allows to simultaneously account for and to estimate not only the velocity distribution but the angular distribution as well. The method was demonstrated using several types of compounds in laser desorption/ionization (LDI) mode.

  5. Initial velocity distribution of MALDI/LDI ions measured by internal MALDI source Fourier-transform ion cyclotron resonance mass spectrometry.

    PubMed

    Chagovets, Vitaliy; Frankevich, Vladimir; Zenobi, Renato

    2014-11-01

    A new method for measuring the ion velocity distribution using an internal matrix-assisted laser desorption/ionization (MALDI) source Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer is described. The method provides the possibility of studying ion velocities without any influence of electric fields in the direction of the instrument axis until the ions reach the ICR cell. It also allows to simultaneously account for and to estimate not only the velocity distribution but the angular distribution as well. The method was demonstrated using several types of compounds in laser desorption/ionization (LDI) mode. PMID:25146958

  6. Double-modulation spectroscopy of molecular ions - Eliminating the background in velocity-modulation spectroscopy

    NASA Technical Reports Server (NTRS)

    Lan, Guang; Tholl, Hans Dieter; Farley, John W.

    1991-01-01

    Velocity-modulation spectroscopy is an established technique for performing laser absorption spectroscopy of molecular ions in a discharge. However, such experiments are often plagued by a coherent background signal arising from emission from the discharge or from electronic pickup. Fluctuations in the background can obscure the desired signal. A simple technique using amplitude modulation of the laser and two lock-in amplifiers in series to detect the signal is demonstrated. The background and background fluctuations are thereby eliminated, facilitating the detection of molecular ions.

  7. Theoretical investigations on plasma processes in the Kaufman thruster. [electron and ion velocity distribution

    NASA Technical Reports Server (NTRS)

    Wilhelm, H. E.

    1974-01-01

    An analysis of the sputtering of metal surfaces and grids by ions of medium energies is given and it is shown that an exact, nonlinear, hyperbolic wave equation for the temperature field describes the transient transport of heat in metals. Quantum statistical and perturbation theoretical analysis of surface sputtering by low energy ions are used to develop the same expression for the sputtering rate. A transport model is formulated for the deposition of sputtered atoms on system components. Theoretical efforts in determining the potential distribution and the particle velocity distributions in low pressure discharges are briefly discussed.

  8. Temperature dependent sound velocity in hydrodynamic equations for relativistic heavy-ion collisions

    E-print Network

    Mikolaj Chojnacki

    2007-09-11

    We analyze the effects of different forms of the sound-velocity function cs(T) on the hydrodynamic evolution of matter formed in the central region of relativistic heavy-ion collisions. At high temperatures (above the critical temperature Tc) the sound velocity is calculated from the recent lattice simulations of QCD, while in the low temperature region it is obtained from the hadron gas model. In the intermediate region we use different interpolations characterized by the values of the sound velocity at the local maximum (at T = 0.4 Tc) and local minimum (at T = Tc). In all considered cases the temperature dependent sound velocity functions yield the entropy density, which is consistent with the lattice QCD simulations at high temperature. Our calculations show that the presence of a distinct minimum of the sound velocity leads to a very long (about 20 fm/c) evolution time of the system, which is not compatible with the recent estimates based on the HBT interferometry. Hence, we conclude that the hydrodynamic description is favored in the case where the cross-over phase transition renders the smooth sound velocity function with a possible shallow minimum at Tc.

  9. Measurements of Nitrous Acid (HONO) Using Ion Drift - Chemical Ionization Mass Spectrometry during the 2009 SHARP Field Campaign

    NASA Astrophysics Data System (ADS)

    Levy, M. E.; Zhang, R.

    2013-12-01

    During the 2009 SHARP Field Campaign in Houston, TX, measurements of HONO were continuously conducted from May 1 to June 1 at a site located on the campus of the University of Houston. We have developed a novel approach for ambient measurements of nitrous acid (HONO) using ion drift - chemical ionization mass spectrometry (ID-CIMS). In our innovative method, HONO is ionized using the sulfur hexafluoride anion, representing the first application of this reagent ion under humid tropospheric conditions. In this presentation, we will discuss the temporal trends and sources of HONO, as well as, as the involvement of HONO in the formation of key atmospheric constituents, such as ozone. Diurnally, HONO concentration accumulates in the late afternoon, reaches a nighttime maximum, and declines rapidly after sunrise; the averaged daytime and nighttime concentrations are 0.15 × 0.05 and 0.26 × 0.04, respectively. The nighttime measured HONO peaks show strong correlations with the NO2 concentration, particle surface area, and soot mass concentration, indicating that the aerosol-phase chemistry represents a significant contributor to the HONO yield. A higher nighttime HONO peak concentration consistently precedes a higher and earlier ozone peak concentration of the following day, by about 20 ppb higher and four hours earlier than those with a lower preceding HONO peak concentration do. Using a kinetic approach, we estimate an uptake coefficient in the range of 6 x 10-4 to 2 x 10-3 for the heterogeneous conversion of NO2 to HONO on aerosol surfaces, which is necessary to account for the measured nighttime HONO peaks. Our results underscore the importance of aerosol heterogeneous chemistry in HONO production and the contributions of this non-photolytic HONO source to the radical budget and the photochemical ozone production in this region. Furthermore, because of its high detection sensitivity and fast-responding time, the ID-CIMS method described in this work may greatly facilitate HONO detection under typical tropospheric conditions.

  10. Apparent Velocity Threshold in the Electronic Stopping of Slow Hydrogen Ions in LiF

    SciTech Connect

    Draxler, M.; Chenakin, S.P.; Markin, S.N.; Bauer, P. [Institut fuer Experimentalphysik, Johannes-Kepler Universitaet, Altenbergerstr. 69, A-4040 Linz (Austria)

    2005-09-09

    The electronic energy loss of hydrogen ions (protons and deuterons) in thin supported films of LiF has been studied in backscattering geometry for specific energies from 700 eV/u to 700 keV/u, using Rutherford backscattering spectroscopy and time-of-flight low-energy ion scattering spectroscopy. For specific energies below 8 keV/u, our data confirm velocity proportionality for the stopping cross section {epsilon} (like in a metal) down to 3.8 keV/u, as observed previously for protons and antiprotons despite the large band gap (14 eV) of LiF. Below 3.8 keV/u, the present results indicate an apparent velocity threshold at about 0.1 a.u. for the onset of electronic stopping.

  11. Edge Ion Velocity and Temperature Measurements in NSTX T.M. Biewer, R.E. Bell, D. W. Johnson

    E-print Network

    Biewer, Theodore

    Edge Ion Velocity and Temperature Measurements in NSTX T.M. Biewer, R.E. Bell, D. W. JohnsonBeam Trajectories RF antenna Ion dynamics from C III, C IV, and He II are studied. C III triplet 47.88 eV ionization Waves (HHFW) are launched by the RF antenna into similar plasmas, a two-population distribution of ions

  12. Very low velocity ion slowing down in binary ionic mixtures: Charge- and mass-asymmetry effects

    NASA Astrophysics Data System (ADS)

    Fromy, Patrice; Tashev, Bekbolat; Deutsch, Claude

    2010-10-01

    A binary ionic mixture (BIM) in dense and hot plasmas of specific concern for inertial confinement fusion and white dwarf crust is considered as a target for incoming light ions with a velocity smaller than the thermal electron one. The given target stopping power, mostly BIM monitored, is specifically studied in terms of charge and mass asymmetry in its ionic component. The classical plasma target is worked out within a dielectric framework, and scanned with respect to density, temperature, and BIM composition.

  13. Importance of subshell coupling in L-shell ionization by low-velocity heavy ions

    Microsoft Academic Search

    M. Sarkar; D. Bhattacharya; M. B. Chatterjee; P. Sen; G. Kuri; D. P. Mahapatra; G. Lapicki

    1995-01-01

    Data for available L-subshell ionization caused by slow and heavy ions (Z1 = 6, 7 and 8) are compiled and compared with the prdictions of the ECPSSR theory with and without the intra-shell (IS) coupling. It has been observed that the standard ECPSSR without Is is inadequate to predict quantitatively the L-subshell cross section data at low projectile velocities. The

  14. Superconducting twin quarter wave resonator for acceleration of low velocity heavy ions

    NASA Astrophysics Data System (ADS)

    Kabumoto, H.; Takeuchi, S.; Matsuda, M.; Ishizaki, N.; Otokawa, Y.

    2010-01-01

    We have designed and fabricated a superconducting twin quarter wave resonator (Twin-QWR) made of niobium and copper for the acceleration of low velocity heavy ions. The resonator has two inner conductors and three acceleration gaps, which give a resonant frequency of 129.8 MHz and an optimum beam velocity of 6% of the light velocity. Each inner conductor resonates like in a coaxial quarter-wave line resonator. The resonator was designed to have a separable structure so that we could treat the inner conductor's part fully made of high purity niobium apart from the outer conductor made of niobium and copper. We obtained an acceleration field gradient of 5.8 MV/m at an RF power input of 4 W.

  15. Experimental studies of the two-ion species flow in the plasma presheath

    SciTech Connect

    Wang, X.; Hershkowitz, N. [Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

    2006-05-15

    The ion flow created in the presheath of weakly ionized He+Ar plasma is studied experimentally. Ion acoustic wave measurements combined with previous LIF measurements [Phys. Rev. Lett. 90, 145001 (2003)] suggest that the Ar ion and He ion drift velocities approach each other near the sheath-presheath boundary. Their common velocity is the ion sound velocity of the system. The Ar ion and He ion drift velocities are also calculated assuming mobility-limited flow, including symmetric and asymmetric ion-neutral collisions, combined with the measured plasma potential profile. Comparing these calculations to the wave and LIF data shows that both ion species drift in the presheath with mobility-limited flow until very close to the sheath edge.

  16. Superconducting low-velocity linac for the Argonne positive-ion injector

    SciTech Connect

    Shepard, K.W.; Markovich, P.K.; Zinkann, G.P.; Clifft, B.; Benaroya, R.

    1989-01-01

    A low-velocity superconducting linac has been developed as part of a positive-ion injector system, which is replacing a 9 MV tandem as the injector for the ATLAS accelerator. The linac consists of an independently phased array of resonators, and is designed to accelerate various ions over a velocity range .008 < v/c < .06. The resonator array is formed of four different types of superconducting interdigital structures. The linac is being constructed in three phases, each of which will cover the full velocity range. Successive phases will increase the total accelerating potential and permit heavier ions to be accelerated. Assembly of the first phase was completed in early 1989. In initial tests with beam, a five-resonator array provided approximately 3.5 MV of accelerating potential and operated without difficulty for several hundred hours. The second phase is scheduled for completion in late 1989, and will increase the accelerating potential to more than 8 MV. 5 refs., 2 figs., 1 tab.

  17. Investigation of localized 2D convection mapping based on artificially generated Swarm ion drift data

    NASA Astrophysics Data System (ADS)

    Fiori, R. A. D.; Boteler, D. H.; Koustov, A. V.; Knudsen, D.; Burchill, J. K.

    2014-07-01

    Ionospheric plasma flow is an indicator of the interconnection between the solar wind, interplanetary magnetic field (IMF), and Earth’s magnetosphere. Ionospheric convection has been mapped in the past using either a widespread data set for instantaneous convection mapping over a short time period or data from an instrument measuring convection in a spatially confined region over a long time period for the purpose of building a statistically averaged convection pattern. This study explores convection mapping using a spherical cap harmonic analysis (SCHA) technique within a localized spherical cap based on data that will be available from the Swarm three-satellite constellation. Convection is mapped in the vicinity of hypothetical Swarm satellite tracks where it is adequately constrained by data. By using statistical models to emulate Swarm measurements, we demonstrate that such mapping can be successful based on data from the Swarm A and Swarm B satellites. Convection is divided into well constrained and poorly constrained subsets to determine parameters characterizing goodness-of-fit based on known quantities. Using the subset of well constrained maps, it is determined that convection is best mapped for a spherical cap having an angular radius of ?c=10°. The difference between the maximum mapped convection and the maximum velocity measured along the satellite track (?v) is introduced to evaluate goodness-of-fit. For the examples presented in this paper, we show that a threshold value of ?v=281 m/s successfully differentiates between well and poorly constrained maps 77.6% of the time. It is shown that convection can be represented over a larger region through the use of multiple spherical caps.

  18. The role of Nonlinear Ion Temperature Gradient Driven Drift Modes in a Reversed Field Pinch Plasma

    NASA Astrophysics Data System (ADS)

    Tangri, Varun; Terry, Paul; Waltz, R. E.

    2009-11-01

    The Ion Temperature gradient (ITG) mode has been rarely investigated in Reversed Field pinch (RFP) plasmas, although its role tokamak turbulence has been studied extensively. In this work, we investigate if it is plausible that ITG may play a role in particle and heat confinement in such devices. The linear stability and nonlinear saturation of ITG is investigated in the RFP geometry by modifying the gyrokinetic code GYROfootnotetextJ. Candy and R.E. Waltz, J. Comp. Phys. 186, 545 (2003). in a low beta, collisionless limit with and without non-adiabatic electrons. A simple toroidal equilibrium has been devised that is specified by just two parameters: the pinch parameter and the radial position. The level of transport is shown to be sensitive to temperature and density gradients and the threshold is found. To determine the nature of the instability, we study parametric scaling and also compare results with the well-known CYCLONE base case for tokamak simulations. We also estimate mixing level transport for MST parameters using linear simulations to determine if the instability is relevant to the small-scale turbulence observed in MST.

  19. Drifting Continents

    NSDL National Science Digital Library

    Integrated Teaching and Learning Program,

    This activity is a teacher-led demonstration of continental drift and includes a math worksheet for students involving the calculation of continental drift over time. Students will understand what continental drift is, why it occurs, and how earthquakes occur because of it.

  20. Parallel and perpendicular velocity sheared flows driven tripolar vortices in an inhomogeneous electron-ion quantum magnetoplasma

    SciTech Connect

    Mirza, Arshad M. [Theoretical Plasma Physics Group, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Masood, W. [TPPD, PINSTECH, P.O. Nilore, Islamabad (Pakistan) and National Centre for Physics (NCP), Shahdara Valley Road, 44000 Islamabad (Pakistan)

    2011-12-15

    Nonlinear equations governing the dynamics of finite amplitude drift-ion acoustic-waves are derived by taking into account sheared ion flows parallel and perpendicular to the ambient magnetic field in a quantum magnetoplasma comprised of electrons and ions. It is shown that stationary solution of the nonlinear equations can be represented in the form of a tripolar vortex for specific profiles of the equilibrium sheared flows. The tripolar vortices are, however, observed to form on very short scales in dense quantum plasmas. The relevance of the present investigation with regard to dense astrophysical environments is also pointed out.

  1. High Resolution Ion Mobility Spectrometry with Increased Ion Transmission: Exploring the Analytical Utility of Periodic-Focusing DC Ion Guide Drift Cells

    E-print Network

    Blase, Ryan Christopher

    2012-02-14

    collision cross sections, requiring higher resolution ion mobility spectrometers. Resolution in IMS is of utmost importance for the separation of complex mixtures, e.g. crude oil samples, proteolytic digests, positional isomers, and ion conformers. However...

  2. Ion Bernstein waves in a plasma with a kappa velocity distribution

    NASA Astrophysics Data System (ADS)

    Nsengiyumva, F.; Mace, R. L.; Hellberg, M. A.

    2013-10-01

    Using a Vlasov-Poisson model, a numerical investigation of the dispersion relation for ion Bernstein waves in a kappa-distributed plasma has been carried out. The dispersion relation is found to depend significantly on the spectral index of the ions, ?i, the parameter whose smallness is a measure of the departure from thermal equilibrium of the distribution function. Over all cyclotron harmonics, the typical Bernstein wave curves are shifted to higher wavenumbers (k) if ?i is reduced. For waves whose frequency lies above the lower hybrid frequency, ?LH, an increasing excess of superthermal particles (decreasing ?i) reduces the frequency, ?peak, of the characteristic peak at which the group velocity vanishes, while the associated kpeak is increased. As the ratio of ion plasma to cyclotron frequency (?pi/?ci) is increased, the fall-off of ? at large k is smaller for lower ?i and curves are shifted towards larger wavenumbers. In the lower hybrid frequency band and harmonic bands above it, the frequency in a low-?i plasma spans only a part of the intraharmonic space, unlike the Maxwellian case, thus exhibiting considerably less coupling between adjacent bands for low ?i. It is suggested that the presence of the ensuing stopbands may be a useful diagnostic for the velocity distribution characteristics. The model is applied to the Earth's plasma sheet boundary layer in which waves propagating perpendicularly to the ambient magnetic field at frequencies between harmonics of the ion cyclotron frequency are frequently observed.

  3. Specularly reflected ions, shock foot thicknesses, and shock velocity determinations in space

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.; Thomsen, M. F.

    1985-01-01

    The magnetic foot of a quasi-perpendicular, supercritical collisionless shock is spatially coincident with and caused by gyrating ions nearly specularly reflected from the shock. The reflected ions are turned around by the upstream magnetic field and returned to the shock after completing a partial gyration. An expression is derived for the turnaround distance of specularly reflected ions for arbitrary orientations of the incident velocity vector and the upstream magnetic field. This expression is then used to derive a formula for calculating the shock speed in the spacecraft frame from a single point measurement of the time required for the magnetic foot to transit a spacecraft. The derived formulas for turnaround distance and shock speed differ from previously published equations for these parameters and in some geometries give quantitatively very different results.

  4. Absorption Spectroscopy Measurements of Ion Velocity Distribution Functions in Argon Plasmas.

    NASA Astrophysics Data System (ADS)

    Scime, Earl; Przybysz, William S.

    2007-11-01

    The scarcity of strong absorption lines in accessible tuning ranges along with plasma saturation due to low ion population densities makes absorption spectroscopy of helium ions notoriously difficult. Helicon plasmas, with their characteristically high ion densities, are a good candidate for initial helium ion spectroscopy experiments. However, preliminary measurements of Doppler broadened ion velocity distribution functions (ivdf) involving injecting a tunable infrared diode laser, tuned to 1012.36 nm and chopped roughly at 1kHz, along the axis of a 1.5m long helicon plasma have yielded erratic and irreproducible measurements. Here we present absorption spectroscopy measurements of ivdfs in argon helicon plasma using a tunable diode laser at 668.43 nm to pump the Ar II metastable 3d^4F7/2 level to the 4p^4D5/2 level. The optimized multi-pass optical configuration and the ratioing detector will be described and initial measurements presented. Once the absorption measurement technique is optimized for the well-known and more easily diagnosed Ar II transition, the same experimental configuration will then be used for the infrared helium ion absorption measurement

  5. Modeling and prediction of peptide drift times in ion mobility spectrometry using sequence-based and structure-based approaches.

    PubMed

    Zhang, Yiming; Jin, Quan; Wang, Shuting; Ren, Ren

    2011-05-01

    The mobile behavior of 1481 peptides in ion mobility spectrometry (IMS), which are generated by protease digestion of the Drosophila melanogaster proteome, is modeled and predicted based on two different types of characterization methods, i.e. sequence-based approach and structure-based approach. In this procedure, the sequence-based approach considers both the amino acid composition of a peptide and the local environment profile of each amino acid in the peptide; the structure-based approach is performed with the CODESSA protocol, which regards a peptide as a common organic compound and generates more than 200 statistically significant variables to characterize the whole structure profile of a peptide molecule. Subsequently, the nonlinear support vector machine (SVM) and Gaussian process (GP) as well as linear partial least squares (PLS) regression is employed to correlate the structural parameters of the characterizations with the IMS drift times of these peptides. The obtained quantitative structure-spectrum relationship (QSSR) models are evaluated rigorously and investigated systematically via both one-deep and two-deep cross-validations as well as the rigorous Monte Carlo cross-validation (MCCV). We also give a comprehensive comparison on the resulting statistics arising from the different combinations of variable types with modeling methods and find that the sequence-based approach can give the QSSR models with better fitting ability and predictive power but worse interpretability than the structure-based approach. In addition, though the QSSR modeling using sequence-based approach is not needed for the preparation of the minimization structures of peptides before the modeling, it would be considerably efficient as compared to that using structure-based approach. PMID:21439562

  6. Patterns of equatorial drifts according to diverse observational probes

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi S.

    We examine morphological patterns of observational results of the equatorial vertical E×B drifts obtained from different probing methods (VHF radar at Jicamarca, Ion Drift Meter on the AE-E satellite, drifts derived from ionosonde h’F data at Ibadan (Nigeria) over 1-year, and HF Doppler at Trivandrum (India)) during the evening and nighttime periods for geomagnetic quiet-day and high solar activity conditions (F10.7 ranges from ~160-208 sfu) for three different seasonal periods. A direct comparison between these measurements and the International Reference Ionosphere 2007 (IRI-2007) model-predictions of equatorial vertical plasma drifts are also made. Our results show that while VHF, AE-E and ionosonde-inferred drifts generally exhibit the typical characteristic features of quiet-time equatorial electrodynamics but reveal substantial disparities in the observational techniques of F-region vertical drifts. The trends in the experimental data agree reasonably with the Scherliess-Fejer climatological curves for the three seasons. In contrast, an IRI representation grossly overestimates and show large departure from the Ibadan and Trivandrum Doppler drift patterns between 1500-0100 LT. The model peak velocity occurs at about two hours earlier than the ionosonde and HF-Doppler velocity peaks. The magnitudes of the velocity peak differ by approximately 28 percent. The dusk reversal times fluctuate significantly and occur between about 1800-2200 LT for all the drift techniques. On the other hand, reversal times near sunrise show less variation. The essential feature of equatorial electrodynamics is the evening prereversal enhancement (PRE) peak velocity; a key parameter required to trigger postsunset ionospheric irregularities. We demonstrate that the simulated PRE ranges between about 20-50 m/s with average value (standard deviation) of roughly 37+/-11 m/s; whereas Ibadan ionosonde PRE velocities vary from about 20 to 45 m/s, with typical average value (standard deviation) of about 29+/-6 m/s. Assessment of the association between model and ionosonde PRE velocities with solar F10.7 and geomagnetic Ap indices illustrate that both IRI and ionosonde-inferred PRE peak velocities illustrate no noticeable link with solar flux, but correlate well with geomagnetic activity. This high correlation is an unexpected result which might shed new light on sources of quiet-time variability of the equatorial PRE peak vertical plasma velocities.

  7. MEASUREMENTS OF ANISOTROPIC ION TEMPERATURES, NON-THERMAL VELOCITIES, AND DOPPLER SHIFTS IN A CORONAL HOLE

    SciTech Connect

    Hahn, M.; Savin, D. W. [Columbia Astrophysics Laboratory, Columbia University, MC 5247, 550 West 120th Street, New York, NY 10027 (United States)] [Columbia Astrophysics Laboratory, Columbia University, MC 5247, 550 West 120th Street, New York, NY 10027 (United States)

    2013-02-15

    We present a new diagnostic allowing one to measure the anisotropy of ion temperatures and non-thermal velocities, as well as Doppler shifts with respect to the ambient magnetic field. This method provides new results, as well as an independent test for previous measurements obtained with other techniques. Our spectral data come from observations of a low-latitude, on-disk coronal hole. A potential field source surface model was used to calculate the angle between the magnetic field lines and the line of sight for each spatial bin of the observation. A fit was performed to determine the line widths and Doppler shifts parallel and perpendicular to the magnetic field. For each line width component we derived ion temperatures T {sub i,} and T {sub i, Parallel-To} and non-thermal velocities v {sub nt,} and v {sub nt, Parallel-To }. T {sub i,} was cooler than off-limb polar coronal hole measurements, suggesting increasing collisional cooling with decreasing height. T {sub i, Parallel-To} is consistent with a uniform temperature of (1.8 {+-} 0.2) Multiplication-Sign 10{sup 6} K for each ion. Since parallel ion heating is expected to be weak, this ion temperature should reflect the proton temperature. A comparison between our results and others implies a large proton temperature gradient around 1.02 R {sub Sun }. The non-thermal velocities are thought to be proportional to the amplitudes of various waves. Our results for v {sub nt,} agree with Alfven wave amplitudes inferred from off-limb polar coronal hole line width measurements. Our v {sub nt, Parallel-To} results are consistent with slow magnetosonic wave amplitudes inferred from Fourier analysis of time-varying intensity fluctuations. Doppler shift measurements yield outflows of Almost-Equal-To 5 km s{sup -1} for ions formed over a broad temperature range. This differs from other studies that found a strong Doppler shift dependence on formation temperature.

  8. The stopping of heavy ions in the low-to-intermediate energy range: The apparent velocity threshold

    NASA Astrophysics Data System (ADS)

    Lifschitz, A. F.; Arista, N. R.

    2013-12-01

    We present a non-linear study of the energy loss of heavy ions in solids, which is based on the transport cross section (TCS) and the extension of the Friedel sum rule (EFSR) for moving ions. We apply this approach to study the velocity dependence of the energy loss of heavy ions in the energy region below the stopping power maximum. With this formulation we are able to explain some striking effects in the energy loss of heavy ions which have been experimentally observed long time ago (Brown and Moak (1972) [14]), but have not been explained so far by the existing theoretical models: the deviations from the proportionality with ion velocity (predicted by alternative models in the low energy range), and the "apparent velocity threshold".

  9. Laser-induced-fluorescence observation of ion velocity distribution functions in a plasma sheath

    NASA Astrophysics Data System (ADS)

    Claire, N.; Bachet, G.; Stroth, U.; Doveil, F.

    2006-06-01

    Experimental results obtained by laser-induced-fluorescence on metastable ion velocity distribution functions (MIVDF) in electrostatic presheaths and sheaths in argon plasmas produced by the thermoionic effect in a multipolar dc discharge are presented. The shape of the measured MIVDF are in qualitative agreement, for the presheath, with Emmert's model and exhibit: (1) a Maxwellian profile at the center of the device where the potential is zero; (2) a distribution function's shape made of three distinct parts at the entrance of the presheath. Inside the sheath the recorded MIVDF recovers a Maxwellian profile with a width unexpectedly related to the background neutral pressure. The velocity and potential profiles that can be deduced from the measured MIVDF show a strong influence of the primary electrons emitted by the filaments.

  10. Deviations of the K ?/K ? intensity ratio of Ti upon impact with low velocity ions

    NASA Astrophysics Data System (ADS)

    Wijsman, W. E.; Vis, R. D.

    1999-04-01

    Deviations of the branching ratio of the decay of K-vacancies in Ti have been observed during bombardment with low velocity ions of H, He and N. Beams of these ions have been used for various applications in which resonant nuclear reactions were used as the main analytical technique, whereas the X-ray signal could conveniently be used for monitoring the accumulated charge. During the evaluation of this monitoring signal, it was observed that the commonly made assumption that the K ?/K ? intensity ratio is a constant can easily be off by 30% or more. Also a few data of L-shell ionisation cross sections has been measured on Au to establish if the onset of deviations in the branching ratio parallels the onset of deviations from the ECPSSR theory for inner shell ionisation.

  11. Ion Bernstein waves in a plasma with a kappa velocity distribution

    SciTech Connect

    Nsengiyumva, F.; Mace, R. L.; Hellberg, M. A. [School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4000 (South Africa)] [School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4000 (South Africa)

    2013-10-15

    Using a Vlasov-Poisson model, a numerical investigation of the dispersion relation for ion Bernstein waves in a kappa-distributed plasma has been carried out. The dispersion relation is found to depend significantly on the spectral index of the ions, ?{sub i}, the parameter whose smallness is a measure of the departure from thermal equilibrium of the distribution function. Over all cyclotron harmonics, the typical Bernstein wave curves are shifted to higher wavenumbers (k) if ?{sub i} is reduced. For waves whose frequency lies above the lower hybrid frequency, ?{sub LH}, an increasing excess of superthermal particles (decreasing ?{sub i}) reduces the frequency, ?{sub peak}, of the characteristic peak at which the group velocity vanishes, while the associated k{sub peak} is increased. As the ratio of ion plasma to cyclotron frequency (?{sub pi}/?{sub ci}) is increased, the fall-off of ? at large k is smaller for lower ?{sub i} and curves are shifted towards larger wavenumbers. In the lower hybrid frequency band and harmonic bands above it, the frequency in a low-?{sub i} plasma spans only a part of the intraharmonic space, unlike the Maxwellian case, thus exhibiting considerably less coupling between adjacent bands for low ?{sub i}. It is suggested that the presence of the ensuing stopbands may be a useful diagnostic for the velocity distribution characteristics. The model is applied to the Earth's plasma sheet boundary layer in which waves propagating perpendicularly to the ambient magnetic field at frequencies between harmonics of the ion cyclotron frequency are frequently observed.

  12. Global equatorial ionospheric vertical plasma drifts measured by the AE-E satellite

    NASA Technical Reports Server (NTRS)

    Fejer, B. G.; De Paula, E. R.; Heelis, R. A.; Hanson, W. B.

    1995-01-01

    Ion drift meter observations from the Atmosphere Explorer E (AE-E) satellite during the period of January 1977 to December 1979 are used to study the dependence of equatorial (dip latitudes less than or equal to 7.5 deg) F region vertical plasma drifts (east-west electric fields) on solar activity, season, and longitude. The satellite-observed ion drifts show large day-to-day and seasonal variations. Solar cycle effects are most pronounced near the dusk sector with a large increase of the prereversal velocity enhancement from solar minimum to maximum. The diuurnal, seasonal, and solar cycle dependence of the logitudinally averaged drifts are consistent with results from the Jicamarca radar except near the June solstice when the AE-E nighttime downward velocities are significantly smaller than those observed by the radar. Pronounced presunrise downward drift enhancements are often observed over a large longituudinal range but not in the Peruvian equatorial region. The satellite data indicate that longitudinal variations are largest near the June solstice, particularly near dawn and dusk but are virtually absent during equinox. The longitudinal dependence of the AE-E vertical drifts is consistent with results from ionosonde data. These measurements were also used to develop a description of equatorial F region vertical drifts in four longitudinal sectors.

  13. Ion Beam Heating in the Auroral Zone

    NASA Technical Reports Server (NTRS)

    Schriver, David; Ashour-Abdalla, Maha; Collin, Henry; Lallande, Nicole

    1990-01-01

    Recent satellite observations at high altitudes (greater than 5000 km) in the auroral zone have shown the existence of hybrid or bimodal ion beam distributions that are evidence of both parallel and perpendicular ion acceleration. Acceleration parallel to the magnetic field is most likely due to quasi-static electric fields (double layers) which can create outflowing ion beams; since ions of different mass will have different drift speeds due to this acceleration, a plasma configuration unstable to the ion-ion two-stream acoustic mode develops. When the net drift velocity (U) between the two ion species is greater than the sound speed (C(sub 0)), the ion-ion instability has maximum growth at oblique wave propagation. To study the nonlinear effects of the ion-ion instability in terms of plasma heating, a numerical simulation parametric study has been performed. It was found that the parallel acceleration that forms the ion beams occurs on a time scale faster than ion- ion wave growth at low drifts; thus ion-ion wave growth is expected to occur primarily for higher drift speeds (U greater than C(sub 0)) which results in strong oblique heating of the ions (both hydrogen and oxygen) forming elevated ion conics (sometimes called 'bowl' distributions). Also, strong parallel electron heating in the direction of the ion beams can occur, and electrons near the top of the acceleration region may attain a net upward drift along with the elevated ion conics. Variation of the oxygen density greatly affects the ion heating due to the ion-ion instability; as the oxygen density decreases, oxygen heating increases, in agreement with observations (Collin et al., 1987). Ion-ion electrostatic wave properties and the plasma heating that results over a wide range of auroral zone parameters are included.

  14. Interpretation of neutral particle analyzer measurements on plasmas having azimuthal drift

    NASA Technical Reports Server (NTRS)

    Englert, G. W.; Reinmann, J. J.; Lauver, M. R.

    1975-01-01

    The theoretical model accounts for drift and cyclotron components of ion motion in a partially ionized plasma. Density and velocity distributions are systematically prescribed. The flux into the neutral particle analyzer (NPA) from this plasma is determined by summing over all charge exchange neutrals in phase space which are directed into apertures. Calculation of the process is continued through the NPA using appropriate cross section data to obtain analyzer output distributions. Theoretical results were compared with NPA measurements on four plasma heating devices having radial electric, E, and axial magnetic, B, fields. Drift velocity, in the azimuthal direction is identified with E/B. Selection of randomized cyclotron velocity distributions about mean azimuthal drift yield energy distributions which compare well with experiment.

  15. Physics of a magnetic filter for negative ion sources. II. E Multiplication-Sign B drift through the filter in a real geometry

    SciTech Connect

    Boeuf, J. P.; Claustre, J.; Chaudhury, B.; Fubiani, G. [LAboratoire PLAsma et Conversion d'Energie (LAPLACE), Universite de Toulouse, Bt. 3R2, 118 Route de Narbonne, F-31062 Toulouse Cedex 9 (France)

    2012-11-15

    The physics of a magnetic filter under conditions similar to those of the negative ion source for the ITER neutral beam injector is analyzed with the help of a two-dimensional particle-in-cell Monte Carlo Collisions model. A detailed analysis of the different terms of the electron momentum equations shows how diamagnetic and drift currents can be dominant in different regions of the filter. Electron transport through the filter is due to an E Multiplication-Sign B drift current on one side of the chamber induced by the presence of the chamber walls perpendicular to the electron diamagnetic current. The filter design of the ITER negative ion source, which does not allow a closed electron diamagnetic current, induces an asymmetry of the plasma that is analyzed with the particle model. It is shown that electron transport through the filter in this geometry is very different from the transport in an ideal, one-dimensional magnetic filter often considered in the literature and described in detail in the companion paper [Boeuf et al., Phys. Plasmas 19, 113509 (2012)].

  16. Drift wave vortices in nonuniform plasmas with sheared magnetic fields

    SciTech Connect

    Su, X.N.; Horton, W.; Morrison, P.J.

    1991-11-01

    Nonlinear coherent structures governed by the coupled drift wave-ion acoustic mode equations in nonuniform plasmas with sheared magnetic fields are studied analytically and numerically. A solitary vortex equation that includes the effects of density and temperature gradients, and magnetic shear is derived and analyzed. The analytic and numerical studies show that for a plasma in a sheared magnetic field, even without the temperature and drift velocity gradients, solitary vortex solutions are possible; however, these solutions are not exponentially localized due to the presence of a nonstructurally stable perturbative tail that connects to the core of the vortex. The new coherent vortex structures are dipole-like in their symmetry, but are not the modons of Larichev and Reznik. In the presence of a small temperature or drift velocity gradient, the new shear-induced dipole can not survive and will separate into monopoles, like the case of the modon in a sheared drift velocity as studied in Su et al. The solitary solutions are found from the nonlinear eigenvalue problem for the effective potential in a quasi-one-dimensional approximation. The numerical simulations are performed in 2-D with the coupled vorticity and parallel mass flow equations.

  17. Drift waves in the corona: heating and acceleration of ions at frequencies far below the gyro frequency

    E-print Network

    Vranjes, J

    2010-01-01

    In the solar corona, several mechanisms of the drift wave instability can make the mode growing up to amplitudes at which particle acceleration and stochastic heating by the drift wave take place. The stochastic heating, well known from laboratory plasma physics where it has been confirmed in numerous experiments, has been completely ignored in past studies of coronal heating. However, in the present study and in our very recent works it has been shown that the inhomogeneous coronal plasma is, in fact, a perfect environment for fast growing drift waves. As a matter of fact, the large growth rates are typically of the same order as the plasma frequency. The consequent heating rates may exceed the required values for a sustained coronal heating by several orders of magnitude. Some aspects of these phenomena are investigated here. In particular the analysis of the particle dynamics within the growing wave is compared with the corresponding fluid analysis. While both of them predict the stochastic heating, the th...

  18. Influence Of Finite Larmor Radius Effects On Development Of Drift Flute Turbulence With The Presence Of Ion Temperature Gradient

    Microsoft Academic Search

    Essam Yasin; V. Sotnikov; J. Kindel; O. G. Onishchnko; J. N. Leboeuf

    2010-01-01

    Investigation of flute mode instability in the presence of ion temperature gradient effects will be presented. The approached used in this study allows to analyze spatial scales comparable with the ion Larmor radius. Linear analysis of this system shows that the range of unstable wavelengths in a plasma with large ion charge numbers extends into the region of spatial scales

  19. Wind Drift Compensation in Migrating Dragonflies Pantala (Odonata: Libellulidae)

    Microsoft Academic Search

    Robert B. Srygley

    2003-01-01

    Tailwind drift compensation serves to maximize a migrant's flight distance on a given amount of energy, and crosswind drift compensation serves to hold a course true and minimize the distance flown. With full or part compensation, airspeeds are predicted to increase with greater crosswind drift. To test whether migrating dragonflies compensated for wind drift, I measured the velocity and heading

  20. Wind Drift Compensation in Migrating Dragonfiles Pantala (Odonata: Libellulidae)

    Microsoft Academic Search

    Robert B. Srygley

    2003-01-01

    Q1 Tailwind drift compensation serves to maximize a migrant's flight distance on a given amount of energy, and crosswind drift compensation serves to hold a course true and minimize the distance flown. With full or part com- pensation, airspeeds are predicted to increase with greater crosswind drift. To test whether migrating dragonflies compensated for wind drift, I measured the velocity

  1. Ionic liquid lubrication: influence of ion structure, surface potential and sliding velocity.

    PubMed

    Li, Hua; Rutland, Mark W; Atkin, Rob

    2013-09-21

    Colloid probe atomic force microscopy (AFM) has been employed to investigate the nanotribology of the ionic liquid (IL)-Au(111) interface. Data is presented for four ILs, 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([EMIM] FAP), 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([BMIM] FAP), 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM] FAP) and 1-butyl-3-methylimidazolium iodide ([BMIM] I), at different Au(111) surface potentials. Lateral forces vary as a function of applied surface potential and ion structure because the composition of the confined ion layer changes from cation-enriched (at negative potentials) to mixed (at 0 V), and to anion-enriched (at positive potentials). ILs with FAP(-) anions all exhibit similar nanotribology: low friction at negative potentials and higher friction at positive potentials. [BMIM] I displays the opposite behaviour, as an I(-) anion-enriched layer is more lubricating than either the [BMIM](+) or FAP(-) layers. The effect of cation charged group (charge-delocalised versus charged-localised) was investigated by comparing [BMIM] FAP with 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([Py(1,4)] FAP). [BMIM] FAP is less lubricating at negative potentials, but more lubricating at positive potentials. This indicated that even at positive potentials the cation concentration in the boundary layer is sufficiently high to influence lubricity. The influence of sliding velocity on lateral force was investigated for the [EMIM] FAP-Au(111) system. At neutral potentials the behaviour is consistent with a discontinuous sliding process. When a positive or negative potential bias is applied, this effect is less pronounced as the colloid probe slides along a better defined ion plane. PMID:23836254

  2. Generation of lower hybrid and whistler waves by an ion velocity ring distribution

    SciTech Connect

    Winske, D.; Daughton, W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2012-07-15

    Using fully kinetic simulations in two and three spatial dimensions, we consider the generation and nonlinear evolution of lower hybrid waves produced by a cold ion ring velocity distribution in a low beta plasma. We show that the initial development of the instability is very similar in two and three dimensions and not significantly modified by electromagnetic effects, consistent with linear theory. At saturation, the level of electric field fluctuations is a small fraction of the background thermal energy; the electric field and corresponding density fluctuations consist of long, field-aligned striations. Energy extracted from the ring goes primarily into heating the background ions and the electrons at comparable rates. The initial growth and saturation of the magnetic components of the lower hybrid waves are related to the electric field components, consistent with linear theory. As the growing electric field fluctuations saturate, parallel propagating whistler waves develop by the interaction of two lower hybrid waves. At later times, these whistlers are replaced by longer wavelength, parallel propagating whistlers that grow through the decay of the lower hybrid fluctuations. Wave matching conditions demonstrate these conversion processes of lower hybrid waves to whistler waves. The conversion efficiency (=ratio of the whistler wave energy to the energy in the saturated lower hybrid waves) is computed and found to be significant ({approx}15%) for the parameters of the three-dimensional simulation (and even larger in the two-dimensional simulation), although when normalized in terms of the initial kinetic energy in the ring ions the overall efficiency is very small (<10{sup -4}). The results are compared with relevant linear and nonlinear theory.

  3. 2-dimensional ion velocity distributions measured by laser-induced fluorescence above a radio-frequency biased silicon wafer

    SciTech Connect

    Moore, Nathaniel B.; Gekelman, Walter; Pribyl, Patrick [Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States)] [Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States); Zhang, Yiting; Kushner, Mark J. [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109-2122 (United States)] [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109-2122 (United States)

    2013-08-15

    The dynamics of ions traversing sheaths in low temperature plasmas are important to the formation of the ion energy distribution incident onto surfaces during microelectronics fabrication. Ion dynamics have been measured using laser-induced fluorescence (LIF) in the sheath above a 30 cm diameter, 2.2 MHz-biased silicon wafer in a commercial inductively coupled plasma processing reactor. The velocity distribution of argon ions was measured at thousands of positions above and radially along the surface of the wafer by utilizing a planar laser sheet from a pulsed, tunable dye laser. Velocities were measured both parallel and perpendicular to the wafer over an energy range of 0.4–600 eV. The resulting fluorescence was recorded using a fast CCD camera, which provided resolution of 0.4 mm in space and 30 ns in time. Data were taken at eight different phases during the 2.2 MHz cycle. The ion velocity distributions (IVDs) in the sheath were found to be spatially non-uniform near the edge of the wafer and phase-dependent as a function of height. Several cm above the wafer the IVD is Maxwellian and independent of phase. Experimental results were compared with simulations. The experimental time-averaged ion energy distribution function as a function of height compare favorably with results from the computer model.

  4. The Three-dimensional Evolution of Ion-scale Current Sheets: Tearing and Drift-kink Instabilities in the Presence of Proton Temperature Anisotropy

    NASA Astrophysics Data System (ADS)

    Gingell, P. W.; Burgess, D.; Matteini, L.

    2015-03-01

    We present the first three-dimensional (3D) hybrid simulations of the evolution of ion-scale current sheets, with an investigation of the role of temperature anisotropy and associated kinetic instabilities on the growth of the tearing instability and particle heating. We confirm the ability of the ion cyclotron and firehose instabilities to enhance or suppress reconnection, respectively. The simulations demonstrate the emergence of persistent 3D structures, including patchy reconnection sites and the fast growth of a narrow-band drift-kink instability, which suppresses reconnection for thin current sheets with weak guide fields. Potential observational signatures of the 3D evolution of solar wind current sheets are also discussed. We conclude that kinetic instabilities, arising from non-Maxwellian ion populations, are significant to the evolution of 3D current sheets, and two-dimensional studies of heating rates by reconnection may therefore over-estimate the ability of thin, ion-scale current sheets to heat the solar wind by reconnection.

  5. Following the movement of Cu ions in a SSZ-13 zeolite during dehydration, reduction and adsorption: a combined in situ TP-XRD, XANES/DRIFTS study

    SciTech Connect

    Kwak, Ja Hun; Varga, Tamas; Peden, Charles HF; Gao, Feng; Hanson, Jonathan C.; Szanyi, Janos

    2014-05-05

    Cu-SSZ-13 has been shown to possess high activity and superior N2 formation selectivity in the selective catalytic reduction of NOx under oxygen rich conditions. Here, a combination of synchrotron-based (XRD and XANES) and vibrational (DRIFTS) spectroscopy tools have been used to follow the changes in the location and coordination environment of copper ions in a Cu-SSZ-13 zeolite during calcinations, reduction with CO, and adsorption of CO and H2O. XANES spectra collected during these procedures provides critical information not only on the variation in the oxidation state of the copper species in the zeolite structure, but also on the changes in the coordination environment around these ions as they interact with the framework, and with different adsorbates (H2O and CO). Time-resolved XRD data indicate the movement of copper ions and the consequent variation of the unit cell parameters during dehydration. DRIFT spectra provide information about the adsorbed species present in the zeolite, as well as the oxidation states of and coordination environment around the copper ions. A careful analysis of the asymmetric T-O-T vibrations of the CHA framework perturbed by copper ions in different coordination environments proved to be especially informative. The results of this study will aid the identification of the location, coordination and oxidation states of copper ions obtained during in operando catalytic studies. Financial support was provided by the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program. Part of this work (sample preparation) was performed in the Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory (PNNL). The EMSL is a national scientific user facility supported by the US DOE, Office of Biological and Environmental Research. PNNL is a multi-program national laboratory operated for the US DOE by Battelle. All of the spectroscopy work reported here was carried out at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL). NSLS is a national scientific user facility supported by the US DOE.

  6. Broadband Velocity Modulation Spectroscopy of Molecular Ions for Use in the Jila Electron Edm Experiment

    NASA Astrophysics Data System (ADS)

    Gresh, Daniel N.; Cossel, Kevin C.; Cornell, Eric A.; Ye, Jun

    2013-06-01

    The JILA electron electric dipole moment (eEDM) experiment will use a low-lying, metastable ^3?_1 state in trapped molecular ions of HfF^+ or ThF^+. Prior to this work, the low-lying states of these molecules had been investigated by PFI-ZEKE spectroscopy. However, there were no detailed studies of the electronic structure. The recently developed technique of frequency comb velocity modulation spectroscopy (VMS) provides broad-bandwidth, high-resolution, ion-sensitive spectroscopy, allowing the acquisition of 150 cm^{-1} of continuous spectra in 30 minutes over 1500 simultaneous channels. By supplementing this technique with cw-laser VMS, we have investigated the electronic structure of HfF^+ in the frequency range of 9950 to 14600 cm^{-1}, accurately fitting and assigning 16 rovibronic transitions involving 8 different electronic states including the X^1?^+ and a^3?_1 states. In addition, an observed ^3?_{0+} state with coupling to both the X and a states has been used in the actual eEDM experiment to coherently transfer population from the rovibronic ground state of HfF^+ to the eEDM science state. Furthermore, we report on current efforts of applying frequency comb VMS at 700 - 900 nm to the study of ThF^+, which has a lower energy ^3?_1 state and a greater effective electric field, and will provide increased sensitivity for a measurement of the eEDM. A. E. Leanhardt et. al., Journal of Molecular Spectroscopy 270, 1-25 (2011). B. J. Barker, I. O. Antonov, M. C. Heaven, K. A. Peterson, Journal of Chemical Physics 136, 104305 (2012). L. C. Sinclair, K. C. Cossel, T. Coffey, J. Ye, E. A. Cornell, Physical Review Letters 107, 093002 (2011). K.C. Cossel et. al., Chemical Physics Letters 546, 1-11 (2012).

  7. An Analytic Study of the Perpendicularly Propagating Electromagnetic Drift Instabilities in the Magnetic Reconnection Experiment

    SciTech Connect

    Wang, Y., Kulsrud, R., Ji, H

    2008-12-03

    A local linear theory is proposed for a perpendicularly propagating drift instability driven by relative drifts between electrons and ions. The theory takes into account local cross-field current, pressure gradients and modest collisions as in the Magnetic Reconnection Experiment (MRX) [10]. The unstable waves have very small group velocities in the direction of the pressure gradient, but have a large phase velocity near the relative drift velocity between electrons and ions in the direction of cross-field current. By taking into account the electron-ion collisions and applying the theory in the Harris sheet, we establish that this instability could be excited near the center of the Harris sheet and have enough efoldings to grow to large amplitude before it propagates out of the unstable region. Comparing with the other magnetic reconnection related instabilities (LHDI, MTSI et.) studied previously, we believe the instability we find is a favorable candidate to produce anomalous resistivity because of its unique wave characteristics, such as electromagnetic component, large phase velocity, and small group velocity in the cross current layer direction.

  8. Genetic Drift

    NSDL National Science Digital Library

    Scott Cooper

    In this biology simulation, students use a mathematical simulation of genetic drift to answer questions about the factors that influence this evolutionary process. Students run a series of simulations varying allele frequency and population size and then analyze their data and propose a model to explain their results.

  9. The Relation between Relaxation Time, Mean Free Path, Collision Time and Drift Velocity--Pitfalls and a Proposal for an Approach Illustrating the Essentials

    ERIC Educational Resources Information Center

    Jakoby, Bernhard

    2009-01-01

    The collision model is frequently introduced to describe electronic conductivity in solids. Depending on the chosen approach, the introduction of the collision time can lead to erroneous results for the average velocity of the electrons, which enters the expression for the electrical conductivity. In other textbooks, correct results are obtained…

  10. Excitation of ion-acoustic-like waves by subcritical currents in a plasma having equal electron and ion temperatures.

    PubMed

    Agrimson, E; D'Angelo, N; Merlino, R L

    2001-06-01

    The effect of a magnetic-field-aligned plasma flow with a transverse velocity gradient on the excitation of current-driven ion-acoustic-like waves in a plasma having equal electron and ion temperatures (T(e) = T(i)) was investigated experimentally. In agreement with theoretical predictions, the presence of sheared plasma flow substantially reduces the critical electron drift velocity needed to produce the ion-acoustic instability. PMID:11384478

  11. Ion temperature gradient driven mode in presence of transverse velocity-shear in magnetized plasmas

    E-print Network

    confined plasmas is the anomaly of particle and heat transport by plasma convection across the magnetic described by various drift wave models3,4 . Several experiments2,5,6 have revealed the existence calculations8,9 predict that unstable modes in tokamaks may be stabilized by a critical shear flow. Also, fully

  12. Notched velocity profiles and the radial electric field in high ion temperature plasmas in the Tokamak Fusion Test Reactor

    SciTech Connect

    Ernst, D.R. [Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States)] [Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Bell, M.G.; Bell, R.E.; Bush, C.E.; Chang, Z.; Fredrickson, E.; Grisham, L.R.; Hill, K.W.; Jassby, D.L.; Mansfield, D.K.; McCune, D.C.; Park, H.K.; Ramsey, A.T.; Scott, S.D.; Strachan, J.D.; Synakowski, E.J.; Taylor, G.; Thompson, M.; Wieland, R.M. [Princeton Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States)

    1998-03-01

    A large {open_quotes}notch,{close_quotes} or non-monotonic feature, appears in measured toroidal velocity profiles of the carbon impurity in the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Fusion {bold 26}, 11 (1984)], centered near the radius of strongest ion temperature gradient. This is explained as a consequence of radial momentum transport dominated by anomalous diffusion together with parallel heat friction on the impurity ions arising from the hydrogenic neoclassical parallel heat flow. The toroidal velocity profile of the hydrogenic species is predicted to be monotonic, from measurements of the impurity toroidal velocity, consistent with the anomalous radial diffusion of toroidal momentum. This supports a neoclassical calculation of the radial electric field for near-balanced beam injection. In supershot plasmas [Phys. Rev. Lett. {bold 58}, 1004 (1987)], a well structure in the radial electric field profile is found in the enhanced confinement region. An associated shear layer separates the core, where the local confinement trends are favorable, from the degraded outer region. This provides a mechanism for the nonlinear coupling of the ion temperature gradient, ion thermal confinement, and the radial electric field, which may help explain the favorable core confinement trends of very high temperature supershot plasmas. {copyright} {ital 1998 American Institute of Physics.}

  13. Effect of Cross-Field Drifts and Core Rotation on Flows in the Main Scrape-Off Layer of DIII-D L-mode Plasmas

    SciTech Connect

    Groth, M; Boedo, J A; Brooks, N H; Isler, R C; Leonard, A W; Porter, G D; Watkins, J G; West, W P; Bray, B D; Fenstermacher, M E; Groebner, R J; Moyer, R A; Rudakov, D L; Yu, J H; Zeng, L

    2008-10-13

    The flow velocities of deuterons and low charge-state carbon ions have been measured simultaneously for the first time at the crown of the main SOL for low-density plasmas in DIII-D. The dependences of the flow fields on the direction of the cross-field drifts (E x B and B x {del}B) and core plasma rotation were investigated. The measurements indicate that the carbon ion flow direction and magnitude along the magnetic field lines are not necessarily determined by the deuteron flow field, but other physics must also play a role. The deuteron velocities at the plasma crown are high (20-30 km/s) in configurations with the ion B x {del}B drift toward the divertor X-point, while nearly zero in configurations with the opposite B x {del}B drift direction. The flow velocities of doubly charged carbon ions are independent of the ion B x {del}B drift direction, and the measurements suggest a stagnation point in the flow field at the crown of the plasma. Both deuteron and carbon ion flow velocities in the SOL were found to be independent of the direction of core plasma rotation. Simulations with the UEDGE code have been carried out to better understand the underlying physics processes. Including the cross-field drifts in the simulations produced divertor solutions that are in significantly closer agreement with the measurements. They do not, however, reproduce the measured flow fields at the crown for the configuration with the ion B x {del}B drift toward the divertor X-point.

  14. The effect of vertical drift on the equatorial F-region stability

    NASA Technical Reports Server (NTRS)

    Hanson, W. B.; Cragin, B. L.; Dennis, A.

    1986-01-01

    Time-dependent ionospheric model calculations for day-time and night-time solutions are presented. The behavior of the growth rate and ion-electron recombination rate for the Rayleigh-Taylor instability on the F-region bottomside is examined as a function of the vertical eastward electric field-magnetic field strength drift velocity. It is observed that on the bottomside F-layer the growth rate exceeds the ion-electron recombination rate even without vertical drift; however, an eastward electric field-magnetic field strength drift can produce an increase in the growth rate by an order of magnitude. The calculated data are compared with previous research and good correlation is detected. The formation of bubbles from a seeding mechanism is investigated.

  15. Invertebrate drift — A review

    Microsoft Academic Search

    John E. Brittain; Tor Jan Eikeland

    1988-01-01

    This paper reviews the literature on invertebrate drift in running waters, emphasising papers published during the last 10–15 years. The terms constant drift, catastrophic drift, behavioural drift, active drift and distributional drift are defined, but their use should be limited as much confusion has arisen. Sampling methods are briefly reviewed.

  16. Evidence for the incoming-velocity effect on negative fluorine ions scattering from a highly-oriented-pyrolytic-graphite surface

    NASA Astrophysics Data System (ADS)

    Chen, Lin; Ding, Bin; Li, Yuan; Qiu, Shunli; Xiong, Feifei; Zhou, Hu; Guo, Yanling; Chen, Ximeng

    2013-10-01

    Negative-ion fractions depending on incident energies and angles have been measured for keV-energy fluorine negative ions scattering on a graphite surface at a scattering angle of 38°. For specular scattering, the fraction increases monotonously with increasing incident energy. A specific feature is the nonmonotonic angular dependence of the fraction with the variation of incident angles. It strongly indicates the interaction-time-dependent electron transfer process. The incident-velocity effect has been taken into account to analyze the experimental results, in which an exponential scaling is found.

  17. High-velocity, multistage, nozzled, ion driven wind generator and method of operation of the same adaptable to mesoscale realization

    NASA Technical Reports Server (NTRS)

    Dunn-Rankin, Derek (Inventor); Rickard, Matthew J. A. (Inventor)

    2011-01-01

    Gas flows of modest velocities are generated when an organized ion flux in an electric field initiates an ion-driven wind of neutral molecules. When a needle in ambient air is electrically charged to a potential sufficient to produce a corona discharge near its tip, such a gas flow can be utilized downstream of a ring-shaped or other permeable earthed electrode. In view of the potential practical applications of such devices, as they represent blowers with no moving parts, a methodology for increasing their flow velocities includes exploitation of the divergence of electric field lines, avoidance of regions of high curvature on the second electrode, control of atmospheric humidity, and the use of linear arrays of stages, terminating in a converging nozzle. The design becomes particularly advantageous when implemented in mesoscale domains.

  18. Background and pickup ion velocity distribution dynamics in Titan's plasma environment: 3D hybrid simulation and comparison with CAPS T9 observations

    Microsoft Academic Search

    A. S. Lipatov; E. C. Sittler; R. E. Hartle; J. F. Cooper; D. G. Simpson

    2011-01-01

    In this report we discuss the ion velocity distribution dynamics from the 3D hybrid simulation. In our model the background, pickup, and ionospheric ions are considered as a particles, whereas the electrons are described as a fluid. Inhomogeneous photoionization, electron-impact ionization and charge exchange are included in our model. We also take into account the collisions between the ions and

  19. DRIFT BOTTLE RELEASES DRIFT BOTTLE RELEASES

    E-print Network

    DRIFT BOTTLE RELEASES #12;#12;DRIFT BOTTLE RELEASES OFF NEW JERSEY- A Preliminary Report Service Albert U* Day, Director Special Scientific Report - Fisheries No. 10 DRIFT BOTTLE RELEASES OFF NEW !· Drift Bottle inserts ·····e».*.«««o«oo»o 2 2* Balanus releases of July 27-28, 1948 .

  20. Deconvolution of ion velocity distributions from laser-induced fluorescence spectra of xenon electrostatic thruster plumes

    Microsoft Academic Search

    Timothy B. Smith

    2003-01-01

    This thesis presents a method for extracting singly-ionized xenon (Xe II) velocity distribution estimates from single-point laser-induced fluorescence (LIF) spectra at 605.1 nm. Unlike currently-popular curve-fitting methods for extracting bulk velocity and temperature data from LIF spectra, this method makes no assumptions about the velocity distribution, and thus remains valid for non-equilibrium and counterstreaming plasmas. The well-established hyperfine structure and

  1. Continental Drift

    NSDL National Science Digital Library

    This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on Alfred Wegener's theory of Continental Drift and the evidence used to support it. Using fossil types and maps, students view similarities between continents that led Wegener to conclude that they had once been together as a supercontinent, Pangea. Included are objectives, materials, procedures, discussion questions, evaluation ideas, suggested readings, and vocabulary. There are videos available to order which complement this lesson, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

  2. Time-evolution of the ion velocity distribution function in the discharge of a Hall effect thruster

    E-print Network

    Mazouffre, S; Sadeghi, N

    2009-01-01

    The temporal characteristics of the Xe$^+$ ion axial Velocity Distribution Function (VDF) were recorded in the course of low-frequency discharge current oscillations ($\\sim$~14 kHz) of the 5 kW-class PPS$\\circledR$X000 Hall thruster. The evolution in time of the ion axial velocity component is monitored by means of a laser induced fluorescence diagnostic tool with a time resolution of 100 ns. As the number of fluorescence photons is very low during such a short time period, a hom-made pulse-counting lock-in system was used to perform real-time discrimination between background photons and fluorescence photons. The evolution in time of the ion VDF was observed at three locations along the thruster channel axis after a fast shut down of the thruster power. The anode discharge current is switched off at 2 kHz during 5 $\\mu$s without any synchronization with the current oscillation cycle. This approach allows to examine the temporal behavior of the ion VDF during decay and ignition of the discharge as well as dur...

  3. Long wavelength gradient drift instability in Hall plasma devices. II. Applications

    SciTech Connect

    Frias, Winston; Smolyakov, Andrei I. [Department of Physics and Engineering Physics, University of Saskatchewan, 116 Science Place, Saskatoon SK S7N 5E2 (Canada)] [Department of Physics and Engineering Physics, University of Saskatchewan, 116 Science Place, Saskatoon SK S7N 5E2 (Canada); Kaganovich, Igor D.; Raitses, Yevgeny [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

    2013-05-15

    Hall plasma devices with electron E × B drift are subject to a class of long wavelength instabilities driven by the electron current, gradients of plasma density, temperature, and magnetic field. In the first companion paper [Frias et al., Phys. Plasmas 19, 072112 (2012)], the theory of these modes was revisited. In this paper, we apply analytical theory to show that modern Hall thrusters exhibit azimuthal and axial oscillations in the frequency spectrum from tens KHz to few MHz, often observed in experiments. The azimuthal phase velocity of these modes is typically one order of magnitude lower than the E × B drift velocity. The growth rate of these modes scales inversely with the square root of the ion mass, ?1/?(m){sub i}. It is shown that several different thruster configurations share the same common feature: the gradient drift instabilities are localized in two separate regions, near the anode and in the plume region, and absent in the acceleration region. Our analytical results show complex interaction of plasma and magnetic field gradients and the E × B drift flow as the sources of the instability. The special role of plasma density gradient is revealed and it is shown that the previous theory is not applicable in the region where the ion flux density is not uniform. This is particularly important for near anode region due to ionization and in the plume region due to diverging ion flux.

  4. Long wavelength gradient drift instability in Hall plasma devices. II. Applications

    NASA Astrophysics Data System (ADS)

    Frias, Winston; Smolyakov, Andrei I.; Kaganovich, Igor D.; Raitses, Yevgeny

    2013-05-01

    Hall plasma devices with electron E × B drift are subject to a class of long wavelength instabilities driven by the electron current, gradients of plasma density, temperature, and magnetic field. In the first companion paper [Frias et al., Phys. Plasmas 19, 072112 (2012)], the theory of these modes was revisited. In this paper, we apply analytical theory to show that modern Hall thrusters exhibit azimuthal and axial oscillations in the frequency spectrum from tens KHz to few MHz, often observed in experiments. The azimuthal phase velocity of these modes is typically one order of magnitude lower than the E × B drift velocity. The growth rate of these modes scales inversely with the square root of the ion mass, ˜1/?m i. It is shown that several different thruster configurations share the same common feature: the gradient drift instabilities are localized in two separate regions, near the anode and in the plume region, and absent in the acceleration region. Our analytical results show complex interaction of plasma and magnetic field gradients and the E × B drift flow as the sources of the instability. The special role of plasma density gradient is revealed and it is shown that the previous theory is not applicable in the region where the ion flux density is not uniform. This is particularly important for near anode region due to ionization and in the plume region due to diverging ion flux.

  5. Fast ion collective Thomson scattering diagnostic for ITER S.B. Korsholm1,2, H. Bindslev1, F. Leipold1, F. Meo1, P.K. Michelsen1,

    E-print Network

    Fast ion collective Thomson scattering diagnostic for ITER S.B. Korsholm1,2, H. Bindslev1, F, 2007 Outline of the talk · ITER measurement requirements for confined fast ions · Overview of the 60 to misalignment · Measurements of fuel ion ratio and bulk ion drift velocity by CTS · Future work #12;ITPA

  6. Method for enhancing the resolving power of ion mobility separations over a limited mobility range

    DOEpatents

    Shvartsburg, Alexandre A; Tang, Keqi; Smith, Richard D

    2014-09-23

    A method for raising the resolving power, specificity, and peak capacity of conventional ion mobility spectrometry is disclosed. Ions are separated in a dynamic electric field comprising an oscillatory field wave and opposing static field, or at least two counter propagating waves with different parameters (amplitude, profile, frequency, or speed). As the functional dependencies of mean drift velocity on the ion mobility in a wave and static field or in unequal waves differ, only single species is equilibrated while others drift in either direction and are mobility-separated. An ion mobility spectrum over a limited range is then acquired by measuring ion drift times through a fixed distance inside the gas-filled enclosure. The resolving power in the vicinity of equilibrium mobility substantially exceeds that for known traveling-wave or drift-tube IMS separations, with spectra over wider ranges obtainable by stitching multiple segments. The approach also enables low-cutoff, high-cutoff, and bandpass ion mobility filters.

  7. Search for auroral belt E-parallel fields with high-velocity barium ion injections

    NASA Technical Reports Server (NTRS)

    Heppner, J. P.; Ledley, B. G.; Miller, M. L.; Marionni, P. A.; Pongratz, M. B.

    1989-01-01

    In April 1984, four high-velocity shaped-charge Ba(+) injections were conducted from two sounding rockets at 770-975 km over northern Alaska under conditions of active auroral and magnetic disturbance. Spatial ionization (brightness) profiles of high-velocity Ba(+) clouds from photometric scans following each release were found to be consistent with the 28-sec theoretical time constant for Ba photoionization determined by Carlsten (1975). These observations therefore revealed no evidence of anomalous fast ionization predicted by the Alfven critical velocity hypothesis.

  8. Electron capture dissociation and drift tube ion mobility-mass spectrometry coupled with site directed mutations provide insights into the conformational diversity of a metamorphic protein.

    PubMed

    Harvey, Sophie R; Porrini, Massimiliano; Tyler, Robert C; MacPhee, Cait E; Volkman, Brian F; Barran, Perdita E

    2015-04-01

    Ion mobility mass spectrometry can be combined with data from top-down sequencing to discern adopted conformations of proteins in the absence of solvent. This multi-technique approach has particular applicability for conformationally dynamic systems. Previously, we demonstrated the use of drift tube ion mobility-mass spectrometry (DT IM-MS) and electron capture dissociation (ECD) to study the metamorphic protein lymphotactin (Ltn). Ltn exists in equilibrium between distinct monomeric (Ltn10) and dimeric (Ltn40) folds, both of which can be preserved and probed in the gas-phase. Here, we further test this mass spectrometric framework, by examining two site directed mutants of Ltn, designed to stabilise either distinct fold in solution, in addition to a truncated form consisting of a minimum model of structure for Ltn10. The truncated mutant has similar collision cross sections to the wild type (WT), for low charge states, and is resistant to ECD fragmentation. The monomer mutant (CC3) presents in similar conformational families as observed previously for the WT Ltn monomer. As with the WT, the CC3 mutant is resistant to ECD fragmentation at low charge states. The dimer mutant W55D is found here to exist as both a monomer and dimer. As a monomer W55D exhibits similar behaviour to the WT, but as a dimer presents a much larger charge state and collision cross section range than the WT dimer, suggesting a smaller interaction interface. In addition, ECD on the W55D mutant yields greater fragmentation than for the WT, suggesting a less stable ?-sheet core. The results highlight the power of MS to provide insight into dynamic proteins, providing further information on each distinct fold of Ltn. In addition we observe differences in the fold stability following single or double point mutations. This approach, therefore, has potential to be a useful tool to screen for the structural effects of mutagenesis, even when sample is limited. PMID:25805055

  9. Radiative charge exchange in ion atom collisions at intermediate impact velocities: spectral characteristics and possibilities of experimental studies

    NASA Astrophysics Data System (ADS)

    Mihajlov, A. A.; Ermolaev, A. M.; Ignjatovi?, Lj M.; Sakan, N. M.

    2004-09-01

    The radiative charge exchange processes in H+ + H(1s) and He+(1s) + H(1s2) collisions at intermediate ion-atom impact velocities were treated in this paper from a spectroscopic aspect as new sources of UV and VUV emission. These processes were characterized by the cross-section spectral densities. In the case of hydrogen the corresponding spectral density was calculated for the wavelength lgr and impact velocity v in the ranges 1.823 nm les lgr les 217.537 nm and 0.141v0 les v les 1.414v0 where v0 is the atomic unit velocity. Based on these calculations the photon fluxes, generated due to the interaction of weakly ionized low pressure hydrogen plasma with H+ ion beams, were estimated. It was shown that these fluxes in the UV and VUV domain were strong enough for the spectroscopic measurement. In the case of helium the photon fluxes were estimated in the range lgr > 30 nm. It was found that they are smaller than those in the case of hydrogen but still at a substantial level.

  10. Dissociation of internal energy-selected methyl bromide ion revealed from threshold photoelectron-photoion coincidence velocity imaging

    SciTech Connect

    Tang, Xiaofeng [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China) [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Zhou, Xiaoguo, E-mail: xzhou@ustc.edu.cn, E-mail: yanbing@jlu.edu.cn; Liu, Shilin [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China) [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Sun, Zhongfa [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China)] [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Liu, Fuyi; Sheng, Liusi [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China)] [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Yan, Bing, E-mail: xzhou@ustc.edu.cn, E-mail: yanbing@jlu.edu.cn [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China)] [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China)

    2014-01-28

    Dissociative photoionization of methyl bromide (CH{sub 3}Br) in an excitation energy range of 10.45–16.90 eV has been investigated by using threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging. The coincident time-of-flight mass spectra indicate that the ground state X{sup 2}E of CH{sub 3}Br{sup +} is stable, and both A{sup 2}A{sub 1} and B{sup 2}E ionic excited states are fully dissociative to produce the unique fragment ion of CH{sub 3}{sup +}. From TPEPICO 3D time-sliced velocity images of CH{sub 3}{sup +} dissociated from specific state-selected CH{sub 3}Br{sup +} ion, kinetic energy release distribution (KERD) and angular distribution of CH{sub 3}{sup +} fragment ion are directly obtained. Both spin-orbit states of Br({sup 2}P) atom can be clearly observed in fast dissociation of CH{sub 3}Br{sup +}(A{sup 2}A{sub 1}) ion along C–Br rupture, while a KERD of Maxwell-Boltzmann profile is obtained in dissociation of CH{sub 3}Br{sup +}(B{sup 2}E) ion. With the aid of the re-calculated potential energy curves of CH{sub 3}Br{sup +} including spin-orbit coupling, dissociation mechanisms of CH{sub 3}Br{sup +} ion in A{sup 2}A{sub 1} and B{sup 2}E states along C–Br rupture are revealed. For CH{sub 3}Br{sup +}(A{sup 2}A{sub 1}) ion, the CH{sub 3}{sup +} + Br({sup 2}P{sub 1/2}) channel is occurred via an adiabatic dissociation by vibration, while the Br({sup 2}P{sub 3/2}) formation is through vibronic coupling to the high vibrational level of X{sup 2}E state followed by rapid dissociation. C–Br bond breaking of CH{sub 3}Br{sup +}(B{sup 2}E) ion can occur via slow internal conversion to the excited vibrational level of the lower electronic states and then dissociation.

  11. Filamentation instability of nonextensive current-driven plasma in the ion acoustic frequency range

    NASA Astrophysics Data System (ADS)

    Khorashadizadeh, S. M.; Rastbood, E.; Niknam, A. R.

    2014-12-01

    The filamentation and ion acoustic instabilities of nonextensive current-driven plasma in the ion acoustic frequency range have been studied using the Lorentz transformation formulas. Based on the kinetic theory, the possibility of filamentation instability and its growth rate as well as the ion acoustic instability have been investigated. The results of the research show that the possibility and growth rate of these instabilities are significantly dependent on the electron nonextensive parameter and drift velocity. Besides, the increase of electrons nonextensive parameter and drift velocity lead to the increase of the growth rates of both instabilities. In addition, the wavelength region in which the filamentation instability occurs is more stretched in the presence of higher values of drift velocity and nonextensive parameter. Finally, the results of filamentation and ion acoustic instabilities have been compared and the conditions for filamentation instability to be dominant mode of instability have been presented.

  12. Single-fluid stability of stationary plasma equilibria with velocity shear and magnetic shear

    SciTech Connect

    Miura, Akira [Department of Earth and Planetary Science, University of Tokyo, Tokyo 113-0033 (Japan)

    2009-10-15

    By using incompressible single-fluid equations with a generalized Ohm's law neglecting the electron inertia, a linear eigenmode equation for a magnetic field perturbation is derived for stationary equilibria in a slab geometry with velocity and magnetic shears. The general eigenmode equation contains a fourth-order derivative of the perturbation in the highest order and contains Alfven and whistler mode components for a homogeneous plasma. The ratio of the characteristic ion inertia length to the characteristic inhomogeneity scale length is chosen as a small parameter for expansion. Neglecting whistler mode in the lowest order, the eigenmode equation becomes a second-order differential equation similar to the ideal magnetohydrodynamic eigenmode equation except for the fact that the unperturbed perpendicular velocity contains both electric and ion diamagnetic drifts. A sufficient condition for stability against the Kelvin-Helmholtz instability driven by shear in the ion diamagnetic drift velocity is derived and then applied to tokamaks.

  13. Influence of the Proton Pressure Tensor on the Turbulent Velocity Spectrum at Ion Kinetic Scales

    NASA Astrophysics Data System (ADS)

    Vasquez, B. J.; Markovskii, S.

    2011-12-01

    Numerical hybrid simulations with particle protons and fluid electrons are presented for turbulent fluctuations with spatial variations in a plane perpendicular to the background magnetic field. The steepened portion of the proton bulk velocity spectrum is found at smaller wavenumbers for larger background proton temperature. The velocity spectrum is determined, in part, by the proton pressure tensor. The proton pressure tensor is shown to possess non-gyrotropic and finite off-diagonal components in the places where the turbulent fluctuations have developed strong gradients. Proton demagnetization at these places is a factor in the departure from a Maxwellian velocity distribution function. How demagnetization could connect with both reversible and effectively irreversible aspects of the pressure tensor is considered. The effectively irreversible aspect corresponds to the net heating of the protons and to the dissipation of the turbulent energy cascade.

  14. Pitch angle and velocity diffusions of newborn ions by turbulence in the solar wind

    NASA Technical Reports Server (NTRS)

    Ziebell, L. F.; Yoon, Peter H.

    1990-01-01

    The temporal evolution of the distribution function of newborn ions under the influence of intrinsic low-frequency solar wind turbulences is studied. In particular, an initial ring-beam distribution of newborn ions under the influence of hydromagnetic waves is considered. A simplified treatment of the resonance broadening effect is given, and its role in the pickup process is discussed. Two different configurations of wave polarization amd direction of propagation are considered. The conditions that lead either to the formation of anisotropic shells as a long-duration transient state or to rapid isotropization of the ion pitch angle distribution are discussed, as are the conditions which lead to significant acceleration of the ions.

  15. Predicted Z/sub 2/ structure and gas-solid difference in low-velocity stopping power of light ions

    SciTech Connect

    Oddershede, J.; Sabin, J.R.; Sigmund, P.

    1983-10-10

    Atomic stopping cross sections for low-velocity light ions have been evaluated for the atomic numbers 1< or =Z/sub 2/< or =36 on the basis of the kinetic theory of electronic stopping. Valence electrons make the main contribution. A pronounced Z/sub 2/ structure in stopping cross sections is found, with minima for noble gases where our estimates agree well with experimental results and with the Lindhard-Scharff formula. Pronounced maxima are predicted for alkalis, where large gas-solid differences are to be expected.

  16. Time-resolved ion velocity distribution in a cylindrical Hall thruster: Heterodyne-based experiment and modeling.

    PubMed

    Diallo, A; Keller, S; Shi, Y; Raitses, Y; Mazouffre, S

    2015-03-01

    Time-resolved variations of the ion velocity distribution function (IVDF) are measured in the cylindrical Hall thruster using a novel heterodyne method based on the laser-induced fluorescence technique. This method consists in inducing modulations of the discharge plasma at frequencies that enable the coupling to the breathing mode. Using a harmonic decomposition of the IVDF, one can extract each harmonic component of the IVDF from which the time-resolved IVDF is reconstructed. In addition, simulations have been performed assuming a sloshing of the IVDF during the modulation that show agreement between the simulated and measured first order perturbation of the IVDF. PMID:25832228

  17. Time-resolved ion velocity distribution in a cylindrical Hall thruster: Heterodyne-based experiment and modeling

    NASA Astrophysics Data System (ADS)

    Diallo, A.; Keller, S.; Shi, Y.; Raitses, Y.; Mazouffre, S.

    2015-03-01

    Time-resolved variations of the ion velocity distribution function (IVDF) are measured in the cylindrical Hall thruster using a novel heterodyne method based on the laser-induced fluorescence technique. This method consists in inducing modulations of the discharge plasma at frequencies that enable the coupling to the breathing mode. Using a harmonic decomposition of the IVDF, one can extract each harmonic component of the IVDF from which the time-resolved IVDF is reconstructed. In addition, simulations have been performed assuming a sloshing of the IVDF during the modulation that show agreement between the simulated and measured first order perturbation of the IVDF.

  18. Drift reduction with drift control adjuvants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Numerous drift reduction adjuvants and spray deposition aids are available to applicators of crop production and protection chemicals. Performance of many of the newly introduced drift control adjuvants has not been well documented for aerial application. Four new drift control adjuvants were sele...

  19. Drift reduction with drift control adjuvants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Numerous drift reduction adjuvants and spray deposition aids are available to applicators of crop production and protection chemicals. Performance of many of the newly introduced drift control adjuvants has not been well documented for aerial application. Five new drift control adjuvants were sele...

  20. Temporal evolution of drift Alfvén waves and instabilities in an inhomogeneous plasma with homogeneous shear flow.

    PubMed

    Mikhailenko, Vladimir S; Mikhailenko, Vladimir V; Heyn, Martin F; Mahajan, Swadesh M

    2002-12-01

    The temporal evolution of drift Alfvén waves in an inhomogeneous plasma of low and finite pressure with homogeneous shear flow is studied as an initial value problem without the use of spectral expansion in time. The cases of plasma with cold and hot ions, weak and strong flow shear are considered separately. It is shown that the conventional modal structure of the stable and unstable drift and Alfvén waves holds only for a limited time in the initial stage of its evolution. For larger times, nonmodal effects due to the velocity shear define the development of drift Alfvén waves and drift Alfvén instabilities. For the regimes of low flow shear, which corresponds to the period of the low-to-high transition, the long time evolution of these instabilities as well as their saturation are determined by the nonlinear effects such as the nonlinear decorrelation effect. In contrast, the plasma with strong flow shear, which corresponds to the regime of the developed transport barriers, is stable against the development hydrodynamic drift Alfvén and resistive drift Alfvén instabilities. The frequency increase caused by the shear flow brings the Alfvén wave phase speed close to the electron thermal speed where strong electron Landau damping occurs. At this stage, a kinetic approach for the description of these waves becomes necessary. PMID:12513414

  1. Frictional coefficients of ion-implanted alumina against ion-implanted beta-titanium in the low load, low velocity, single pass regime.

    PubMed

    Kusy, R P; Tobin, E J; Whitley, J Q; Sioshansi, P

    1992-05-01

    The frictional coefficients were measured for four wire alloys against the flats of polycrystalline alumina cylinders using a low load, low velocity, single pass device. Ion-implantations of titanium into polycrystalline alumina flats and nitrogen into beta-titanium wires reduced the static and kinetic coefficients from 0.50 and 0.44 before implantation to 0.20 and 0.25 after implantation, respectively. These results are similar in magnitude to frictional coefficients for unimplanted, control couples of stainless steel, cobalt-chromium, and nickel titanium wires against polycrystalline alumina flats. For orthodontic applications, we conclude that more efficient and reproducible appliances can be engineered for tooth movement if ion-implantation is used to reduce the abrasion of beta-titanium by polycrystalline alumina. PMID:1521704

  2. Velocity oscillations in the outer heliosphere: A signature of pickup ion temperature variability?

    E-print Network

    Richardson, John

    unusual long-wavelength, low- frequency velocity oscillations in the solar wind with periods of $2.3 days and peak to trough amplitudes that ranged from $10 km/s to 20 km/s [Paularena et al., 1996-Helmholtz instabilities at the boundaries of fast and slow solar wind streams, which occur at solar minimum when

  3. Shear driven electromagnetic drift-waves in a nonuniform dense magnetoplasma

    SciTech Connect

    Tariq, Sabeen; Mirza, Arshad M. [Theoretical Plasma Physics Group, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Masood, Waqas [Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad 44000 (Pakistan); National Center for Physics (NCP), Islamabad 44000 (Pakistan)

    2011-08-15

    Linear characteristic properties of high- and low-frequency (in comparison with the cyclotron frequency) electromagnetic drift-waves are studied in a nonuniform, dense magnetoplasma (composed of electrons and ions), in the presence of parallel (magnetic field-aligned) velocity shear, by using quantum magnetohydrodynamic model. By applying the drift-approximation (viz., |{partial_derivative} {sub t}|<<{omega}{sub ci}<<{omega}{sub ce}) to the quantum momentum equations, together with the continuity equations and the Poisson equation, we derive the governing equations for electromagnetic drift-waves with the shear flow. These linear equations are then Fourier transformed to obtain the dispersion relation in both high-frequency and low-frequency regimes. The dispersion relations are then discussed under various limiting cases.

  4. Determination of plasma ion velocity distribution via charge-exchange recombination spectroscopy

    SciTech Connect

    Fonck, R.J.; Darrow, D.S.; Jaehnig, K.P.

    1983-12-01

    Spectroscopy of line radiation from plasma impurity ions excited by charge-exchange recombination reactions with energetic neutral beam atoms is rapidly becoming recognized as a powerful technique for measuring ion temperature, bulk plasma motion, impurity transport, and more exotic phenomena such as fast alpha particle distributions. In particular, this diagnostic offers the capability of obtaining space- and time-resolved ion temperature and toroidal plasma rotation profiles with relatively simple optical systems. Cascade-corrected excitation rate coefficients for use in both fully stripped impurity density studies and ion temperature measurements have been calculated to the principal ..delta..n = 1 transitions of He+, C/sup 5 +/, and O/sup 7 +/ with neutral beam energies of 5 to 100 keV/amu. A fiber optically coupled spectrometer system has been used on PDX to measure visible He/sup +/ radiation excited by charge exchange. Central ion temperatures up to 2.4 keV and toroidal rotation speeds up to 1.5 x 10/sup 7/ cm/s were observed in diverted discharges with P/sub INJ/ less than or equal to 3.0 MW.

  5. Background and Pickup Ion Velocity Distribution Dynamics in Titan's Plasma Environment: 3D Hybrid Simulation and Comparison with CAPS T9 Observations

    NASA Technical Reports Server (NTRS)

    Lipatov, A. S.; Sittler, E. C., Jr.; Hartle, R. E.; Cooper, J. F.; Simpson, D. G.

    2011-01-01

    In this report we discuss the ion velocity distribution dynamics from the 3D hybrid simulation. In our model the background, pickup, and ionospheric ions are considered as a particles, whereas the electrons are described as a fluid. Inhomogeneous photoionization, electron-impact ionization and charge exchange are included in our model. We also take into account the collisions between the ions and neutrals. The current simulation shows that mass loading by pickup ions H(+); H2(+), CH4(+) and N2(+) is stronger than in the previous simulations when O+ ions are introduced into the background plasma. In our hybrid simulations we use Chamberlain profiles for the atmospheric components. We also include a simple ionosphere model with average mass M = 28 amu ions that were generated inside the ionosphere. The moon is considered as a weakly conducting body. Special attention will be paid to comparing the simulated pickup ion velocity distribution with CAPS T9 observations. Our simulation shows an asymmetry of the ion density distribution and the magnetic field, including the formation of the Alfve n wing-like structures. The simulation also shows that the ring-like velocity distribution for pickup ions relaxes to a Maxwellian core and a shell-like halo.

  6. Hermite expansions with hypercollisionality for velocity space degrees of freedom in ion-temperature-gradient driven instabilities

    NASA Astrophysics Data System (ADS)

    Parker, Joseph; Dellar, Paul

    2012-03-01

    We study a 1+1 dimensional model for instabilities driven by ion density and temperature gradients. We use a truncated Hermite expansion in velocity space, and an iterated Fokker--Planck collision operator. This selectively damps the highest terms in the Hermite expansion, analogous to the hyperviscous dissipation used in Fourier spectral simulations of Navier--Stokes turbulence. Our approach accurately captures the full range of growing and decaying modes with only a few tens of Hermite coefficients in velocity space, and is insensitive to parameter values in the collision operator. Without hypercollisions, hundreds of Hermite coefficients are required to capture the growing modes. Decaying modes (due to Landau damping in the original kinetic equation) are completely absent without some form of collisionality, or other source of dissipation. We also derive an partial differential equation for the flow of relative entropy in Hermite space. Solutions of this equation are in excellent agreeement with computed Hermite spectra. The approach developed here extends to more general kinetic equations, and should improve the accuracy of large-scale gyrokinetic simulations, for which only modest numbers of degrees of freedom in velocity space are computationally feasible.

  7. Effect of ion orbit loss on the structure in the H-mode tokamak edge pedestal profiles of rotation velocity, radial electric field, density, and temperature

    SciTech Connect

    Stacey, Weston M. [Fusion Research Center, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)] [Fusion Research Center, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

    2013-09-15

    An investigation of the effect of ion orbit loss of thermal ions and the compensating return ion current directly on the radial ion flux flowing in the plasma, and thereby indirectly on the toroidal and poloidal rotation velocity profiles, the radial electric field, density, and temperature profiles, and the interpretation of diffusive and non-diffusive transport coefficients in the plasma edge, is described. Illustrative calculations for a high-confinement H-mode DIII-D [J. Luxon, Nucl. Fusion 42, 614 (2002)] plasma are presented and compared with experimental results. Taking into account, ion orbit loss of thermal ions and the compensating return ion current is found to have a significant effect on the structure of the radial profiles of these quantities in the edge plasma, indicating the necessity of taking ion orbit loss effects into account in interpreting or predicting these quantities.

  8. Dynamics of positive probes in underdense, strongly magnetized, E×B drifting plasma: Particle-in-cell simulations

    SciTech Connect

    Heinrich, Jonathon R.; Cooke, David L. [Air Force Research Laboratory, Kirtland Air Force Base, New Mexico 87117 (United States)] [Air Force Research Laboratory, Kirtland Air Force Base, New Mexico 87117 (United States)

    2013-09-15

    Electron trapping, electron heating, space-charge wings, wake eddies, and current collection by a positive probe in E×B drifting plasma were studied in three-dimensional electromagnetic particle-in-cell simulations. In these simulations, electrons and ions were magnetized with respect to the probe and the plasma was underdense (?{sub pe}drift velocity (Mach 4.5 with respect to the ion acoustic speed) between the plasma and probe was created with background electric and magnetic fields. Four distinct regions developed in the presences of the positive probe: a quasi-trapped electron region, an electron-depletion wing, an ion-rich wing, and a wake region. We report on the observations of strong electron heating mechanisms, space-charge wings, ion cyclotron charge-density eddies in the wake, electron acceleration due to a magnetic presheath, and the current-voltage relationship.

  9. Non-linear zonal dynamics of drift and drift-Alfven turbulence in tokamak plasmas

    E-print Network

    Lin, Zhihong

    Non-linear zonal dynamics of drift and drift-Alfv´en turbulence in tokamak plasmas L. Chen, Z. Lina. The present work addresses the issue of identifying the major non-linear physics processes which may regulate of the non-linear gyrokinetic equation for both electrons and ions, an analytic theory is presented for non-linear

  10. Multi-point, high-speed passive ion velocity distribution diagnostic on the Pegasus Toroidal Experiment

    SciTech Connect

    Burke, M. G.; Fonck, R. J.; Bongard, M. W.; Schlossberg, D. J.; Winz, G. R. [Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)

    2012-10-15

    A passive ion temperature polychromator has been deployed on Pegasus to study power balance and non-thermal ion distributions that arise during point source helicity injection. Spectra are recorded from a 1 m F/8.6 Czerny-Turner polychromator whose output is recorded by an intensified high-speed camera. The use of high orders allows for a dispersion of 0.02 A/mm in 4th order and a bandpass of 0.14 A ({approx}13 km/s) at 3131 A in 4th order with 100 {mu}m entrance slit. The instrument temperature of the spectrometer is 15 eV. Light from the output of an image intensifier in the spectrometer focal plane is coupled to a high-speed CMOS camera. The system can accommodate up to 20 spatial points recorded at 0.5 ms time resolution. During helicity injection, stochastic magnetic fields keep T{sub e} low ({approx}100 eV) and thus low ionization impurities penetrate to the core. Under these conditions, high core ion temperatures are measured (T{sub i} Almost-Equal-To 1.2 keV, T{sub e} Almost-Equal-To 0.1 keV) using spectral lines from carbon III, nitrogen III, and boron IV.

  11. Bulk properties and velocity distributions of water group ions at Comet Halley - Giotto measurements

    NASA Technical Reports Server (NTRS)

    Coates, A. J.; Johnstone, A. D.; Wilken, B.; Jockers, K.; Glassmeier, K.-H.

    1990-01-01

    In the region upstream of Comet Halley, pickup heavy ions of cometary origin were directly observed by the implanted ion spectrometer on Giotto. Diffusion of this population in pitch angle and in energy, during the approach to the comet and on the outbound leg is discussed. The two data sets are compared and qualitative ideas on scattering timescales are inferred. In addition the bulk parameters of these distributions have been computed and a comparison of the observed speed in the solar wind frame and the observed density with expectations is presented. Pitch angle scattering occurs more slowly than expected with filled shells appearing at 2,500,000 km, and significant energy diffusion does not occur until the bow shock region. Also the shell distributions downstream of the shock flow at the bispherical bulk speed (related to the Alfven speed) along the magnetic field with respect to the solar wind in accordance with conservation of energy between the pickup ions and the wave turbulence.

  12. Verification of continuum drift kinetic equation solvers in NIMROD

    NASA Astrophysics Data System (ADS)

    Held, E. D.; Kruger, S. E.; Ji, J.-Y.; Belli, E. A.; Lyons, B. C.

    2015-03-01

    Verification of continuum solutions to the electron and ion drift kinetic equations (DKEs) in NIMROD [C. R. Sovinec et al., J. Comp. Phys. 195, 355 (2004)] is demonstrated through comparison with several neoclassical transport codes, most notably NEO [E. A. Belli and J. Candy, Plasma Phys. Controlled Fusion 54, 015015 (2012)]. The DKE solutions use NIMROD's spatial representation, 2D finite-elements in the poloidal plane and a 1D Fourier expansion in toroidal angle. For 2D velocity space, a novel 1D expansion in finite elements is applied for the pitch angle dependence and a collocation grid is used for the normalized speed coordinate. The full, linearized Coulomb collision operator is kept and shown to be important for obtaining quantitative results. Bootstrap currents, parallel ion flows, and radial particle and heat fluxes show quantitative agreement between NIMROD and NEO for a variety of tokamak equilibria. In addition, velocity space distribution function contours for ions and electrons show nearly identical detailed structure and agree quantitatively. A ?-centered, implicit time discretization and a block-preconditioned, iterative linear algebra solver provide efficient electron and ion DKE solutions that ultimately will be used to obtain closures for NIMROD's evolving fluid model.

  13. Ion kinetics in a helicon plasma source reactor

    SciTech Connect

    Chatain, F.; Boswell, R.; Dalaire, A. [Universite Joseph Fourier, Saint Martin d`Heres (France)] [and others

    1995-12-31

    In this contribution we present correlated measurements of plasma optical emission, plasma potential and density, and ion axial and radial drift velocities in an extended {open_quotes}helicon{close_quotes} source/diffusion chamber system. This enables us to have insights about plasma excitation, transport and loss processes in this low pressure, high density plasma source.

  14. Heavy ion beam driven warm dense matter experiments

    Microsoft Academic Search

    F. M. Bieniosek; M. A. Leitner; B. G. Logan; R. M. More; P. K. Roy; J. J. Barnard; L. R. Grisham

    2006-01-01

    We describe near term heavy-ion beam-driven warm dense matter (WDM) experiments. Initial experiments are at low beam velocity, below the Bragg peak, increasing toward the Bragg peak in subsequent versions of the accelerator. The WDM conditions are envisioned to be achieved by combined longitudinal and transverse neutralized drift compression to provide a hot spot on the target with a beam

  15. Magnetic island evolution in hot ion plasmas

    SciTech Connect

    Ishizawa, A.; Nakajima, N. [National Institute for Fusion Science, Toki 509-5292 (Japan); Waelbroeck, F. L.; Fitzpatrick, R.; Horton, W. [Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States)

    2012-07-15

    Effects of finite ion temperature on magnetic island evolution are studied by means of numerical simulations of a reduced set of two-fluid equations which include ion as well as electron diamagnetism in slab geometry. The polarization current is found to be almost an order of magnitude larger in hot than in cold ion plasmas, due to the strong shear of ion velocity around the separatrix of the magnetic islands. As a function of the island width, the propagation speed decreases from the electron drift velocity (for islands thinner than the Larmor radius) to values close to the guiding-center velocity (for islands of order 10 times the Larmor radius). In the latter regime, the polarization current is destabilizing (i.e., it drives magnetic island growth). This is in contrast to cold ion plasmas, where the polarization current is generally found to have a healing effect on freely propagating magnetic island.

  16. Drift Instability in Collisionless Alkali Metal Plasmas

    Microsoft Academic Search

    Peter A. Politzer

    1971-01-01

    Measurements of low-frequency (?≪?i) oscillations in collisionless, low-?, alkali metal Q-device plasmas are reported. These oscillations are conclusively identified as density-gradient-driven drift waves by the agreement between experiment and the predictions of the linear theory with regard to frequency, wave-number, and stabilization by ion Landau damping. The linear theory of collisionless drift waves is modified to take into account effects

  17. The effect of altitude- and velocity-dependent wave particle interactions on the H+ and O+ outflows in the auroral region

    NASA Astrophysics Data System (ADS)

    Barghouthi, I. A.; Doudin, N. M.; Saleh, A. A.; Pierrard, V.

    2008-06-01

    The formation of H+ and O+ toroids at high altitudes in the auroral region are discussed in terms of altitude- and velocity-dependent wave-particle interactions (WPI), and special attention is given to the peaked nature of the velocity diffusion coefficient D[perpendicular]. The effects of altitude- and velocity-dependent WPI are taken into account by perturbing the ion velocity with random increment [Delta]v[perpendicular], such that <([Delta]v[perpendicular])2>=4D[perpendicular][Delta]t, where the time step is [Delta]t. To model the heating process, we specify a model for the velocity diffusion coefficient as a function of the ion perpendicular velocity and position along the auroral geomagnetic field line. The ion velocity distribution is described by a quasi-linear diffusion equation, which is solved by the Monte Carlo technique. The Monte Carlo model includes the effects of altitude- and velocity-dependent WPI, gravity, polarization electrostatic field, and the divergence of the geomagnetic field within the simulation tube (1.2-10 earth radii, RE). These effects were included self-consistently in the computations. The peaked nature of D[perpendicular] reflects the way in which altitude- and velocity-dependent WPI lead to the formation of H+ and O+ toroids at high altitudes in the auroral region, rather than simple bulk heating process. Because D[perpendicular] falls to zero at small perpendicular velocities, the bulk of the ion velocity distribution is unaffected by interaction with the waves (electromagnetic turbulence). However, near the phase velocity v0, D[perpendicular] begins to become appreciable, and the diffusion process begins to affect ions. Because there are initially more ions at lower velocities than at higher velocities, the net escape flux in velocity space is toward higher velocities, leading to the formation of ion toroids. At large perpendicular velocities, D[perpendicular] falls to zero and consequently, the effect of WPI is negligible. As the heated ions drift upward along geomagnetic field lines due to the mirror geometry of the Earth's magnetic field, they eventually leave the primary heating region and form a ring "donuts". The heating process is found to be self-limiting, and this explains the saturation of the ion velocity distributions at high altitudes. The altitude profiles of ion density, drift velocity, parallel and perpendicular temperatures are also discussed. We find that including the effect of velocity-dependent WPI in addition to the effect of altitude-dependent WPI produce realistic ion temperatures that are, qualitatively, comparable to the observations. The model produces simulation results similar to the observed toroids.

  18. Dynamics of pickup ion velocity distribution function in Titan's plasma environment (TA encounter): 3D hybrid kinetic modeling and comparison with CAPS observations

    NASA Astrophysics Data System (ADS)

    Simpson, D. G.; Lipatov, A. S.; Sittler, E. C.; Hartle, R. E.; Cooper, J. F.

    2013-12-01

    Wave-particle interactions play a very important role in the plasma dynamics near Titan: mass loading, excitation of the low-frequency waves and the formation of the particle velocity distribution function, e.g. ring/shell-like distributions, etc. The kinetic approach is important for estimation of the collision processes e.g. a charge exchange. The particle velocity distribution function also plays a key role for understanding the observed particle fluxes. In this report we discuss the ion velocity distribution function dynamics from 3D hybrid modeling. The modeling is based on recent analysis of the Cassini Plasma Spectrometer (CAPS) ion measurements during the TA flyby. In our model the background ions, all pickup ions, and ionospheric ions are considered as particles, whereas the electrons are described as a fluid. Inhomogeneous photoionization, electron-impact ionization and charge exchange are included in our model. The temperatures of the background electrons and pickup electrons were also included into the generalized Ohm's law. We also take into account the collisions between the ions and neutrals. We use Chamberlain profiles for the exosphere's components and include a simple ionosphere model with M=28 ions that were generated inside the ionosphere. The moon is considered as a weakly conducting body. Our modeling shows that interaction between background plasma and pickup ions H+, H2+, CH4+ and N2+ has a more complicated structure than was observed in the T9 flyby and modeling due to the large gyroradius of the background O+ ions [1,2,3,4]. Special attention will be paid to comparing the simulated pickup ion velocity distribution with CAPS TA observations. We also compare our kinetic modeling with other hybrid and MHD modeling of Titan's environment. References [1] Sittler, E.C., et al., Energy Deposition Processes in Titan's Upper Atmosphere and Its Induced Magnetosphere. In: Titan from Cassini-Huygens, Brown, R.H., Lebreton J.P., Waite, J.H., Eds., Springer, (Dordrecht, Heidelberg, London, New York, pp. 393-455, 2009). [2] Sittler, E.C., et al., Saturn's Magnetospheric Interaction with Titan as Defined by Cassini Encounters T9 and T18: New Results, Planet. Space Sci., doi.10.1016/j.pss.2009.09.017. [3] Coates, A.J., Interaction of Titan's ionosphere with Saturn's magnetosphere. Phil. Trans. R. Soc. A (2009) 367, 773-788, doi: 10.1098/rsta.2008.0248. [4] Lipatov, A.S., et al., Background and pickup ion velocity distribution dynamics in Titan's plasma environment: 3D hybrid simulation and comparison with CAPS T9 observations. Adv. Space Res. 48, 1114-1125, 2011.

  19. Adiabatic particle motion in a nearly drift-free magnetic field - Application to the geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Stern, D. P.

    1978-01-01

    An investigation is made of the adiabatic particle motion occurring in an almost drift-free magnetic field. The dependence of the mean drift velocity on the equatorial pitch angle and the variation of the local drift velocity along the trajectories is studied. The fields considered are two-dimensional and resemble the geomagnetic tail. Derivations are presented for instantaneous and average drift velocities, bounce times, longitudinal invariants, and approximations to the adiabatic Hamiltonian. As expected, the mean drift velocity is significantly smaller than the instantaneous drift velocities found at typical points on the trajectory. The slow drift indicates that particles advance in the dawn-dusk direction rather slowly in the plasma sheet of the magnetospheric tail.

  20. L-subshell ionization of Bi, Au, and Yb induced by F ions at intermediate velocities

    NASA Astrophysics Data System (ADS)

    Singh, Y. P.; Mitra, D.; Tribedi, Lokesh C.; Tandon, P. N.

    2001-01-01

    We have measured the absolute cross sections for the L-subshell ionization for Yb, Au, and Bi induced by intermediate and low-energy F ions. A comparative study of the different methods of extracting the vacancy production cross sections from the L x-ray line intensities is presented. The measured cross sections are compared with the available theoretical calculations based on the perturbed stationary state (PSS) approximation including the effects due to the increased binding energy, Coulomb (C) deflection, energy (E) loss, and the relativistic (R) wave function (ECPSSR). In the case of Yb and Au targets, the ratio of the subshell ionization cross section for L1 to that for L2 is found to be larger than 1.0 contrary to theoretical predictions, whereas the ratio is less than 1.0 for Bi, as expected. Similar ratios for the L2 to L3 subshells are, however, in agreement with the theoretical predictions for all three targets. These observations can be understood in terms of the multiple vacancies in the outer shells and their effect on the fluorescence yields and Coster-Kronig transitions. In the case of L1 ionization, the ECPSSR calculations are found to fall much below the experimental data for Yb and Au, and a part of the deviation is understood to be due to the existence of multiple vacancies in the outer shells and the interplay between the Coster-Kronig and radiative transition probability. Quantitative estimates on the enhancement in the effective fluorescence yields of the L1 subshell are also provided for all three targets.

  1. The response of a spherical tissue-equivalent proportional counter to different heavy ions having similar velocities

    PubMed Central

    Taddei, Phillip J.; Borak, Thomas B.; Guetersloh, Stephen B.; Gersey, Brad B.; Zeitlin, Cary; Heilbronn, Lawrence; Miller, Jack; Murakami, Takeshi; Iwata, Yoshiyuki

    2008-01-01

    A tissue-equivalent proportional counter (TEPC) has been used as a dosimeter in mixed radiation fields. Since it does not measure LET directly, the response function must be characterized in order to estimate quality factor and thus equivalent dose for the incident radiation. The objectives of this study were to measure the response of a spherical TEPC for different high-energy heavy ions (HZE) having similar velocity and to determine how quality factors can be determined. Data were obtained at the HIMAC heavy ion accelerator for 4He and 12C at 220 ± 5 MeV/nucleon (? = 0.59) and 12C, 16O, 28Si and 56Fe at 376 ± 15 MeV/nucleon (? = 0.70). A particle spectrometer recorded the charge and position of each incident beam particle. Events with low energy deposition were observed for particles that passed through the wall of the TEPC but not through the sensitive volume. The frequency averaged lineal energy, ?f, was always less than the LET of the incident particles. The dose averaged lineal energy, ?D, was approximately equal to LET for particles with LET greater than 10 keV/?m, whereas ?D was larger than LET for the lighter particles with lower LET. Part of this effect is due to detector resolution and energy straggling that increases the variance of the response function. Although the TEPC is not a LET spectrometer, it can provide real time measurements of dose and provide estimates of quality factors for HZE particles using averaged values of lineal energy. PMID:19079798

  2. Stability of ion acoustic solitary waves in a magnetized plasma consisting of warm adiabatic ions and non-thermal electrons having vortex-like velocity distribution

    NASA Astrophysics Data System (ADS)

    Das, Jayasree; Bandyopadhyay, Anup; Das, K. P.; Das

    2014-02-01

    Schamel's modified Korteweg-de Vries-Zakharov-Kuznetsov (S-ZK) equation, governing the behavior of long wavelength, weak nonlinear ion acoustic waves propagating obliquely to an external uniform static magnetic field in a plasma consisting of warm adiabatic ions and non-thermal electrons (due to the presence of fast energetic electrons) having vortex-like velocity distribution function (due to the presence of trapped electrons), immersed in a uniform (space-independent) and static (time-independent) magnetic field, admits solitary wave solutions having a sech 4 profile. The higher order stability of this solitary wave solution of the S-ZK equation has been analyzed with the help of multiple-scale perturbation expansion method of Allen and Rowlands (Allen, M. A. and Rowlands, G. 1993 J. Plasma Phys. 50, 413; 1995 J. Plasma Phys. 53, 63). The growth rate of instability is obtained correct to the order k 2, where k is the wave number of a long wavelength plane wave perturbation. It is found that the lowest order (at the order k) instability condition is strongly sensitive to the angle of propagation (?) of the solitary wave with the external uniform static magnetic field, whereas at the next order (at the order k 2) the solitary wave solutions of the S-ZK equation are unstable irrespective of ?. It is also found that the growth rate of instability up to the order k 2 for the electrons having Boltzmann distribution is higher than that of the non-thermal electrons having vortex-like distribution for any fixed ?.

  3. A time-resolved laser induced fluorescence study on the ion velocity distribution function in a Hall thruster after a fast current disruption

    SciTech Connect

    Mazouffre, S.; Gawron, D. [ICARE, CNRS, 1C avenue de la Recherche Scientifique, 45071 Orleans (France); Sadeghi, N. [LSP, Joseph Fourier University, CNRS, 140 Av. de la Physique, 38402 St. Martin d'Hueres (France)

    2009-04-15

    The temporal characteristics of the Xe{sup +} ion axial velocity distribution function (VDF) were recorded in the course of low-frequency discharge current oscillations ({approx}14 kHz) of the 5 kW class PPS X000 Hall thruster. The evolution in time of the ion axial velocity component is monitored by means of a laser induced fluorescence diagnostic tool with a time resolution of 100 ns. As the number of fluorescence photons is very low during such a short time period, a homemade pulse-counting lock-in system was used to perform real-time discrimination between background photons and fluorescence photons. The evolution in time of the ion VDF was observed at three locations along the thruster channel axis after a fast shutdown of the thruster power. The anode discharge current is switched off at 2 kHz during 5 {mu}s without any synchronization with the current oscillation cycle. This approach allows to examine the temporal behavior of the ion VDF during decay and ignition of the discharge as well as during forced and natural plasma oscillations. Measurements show that the distribution function of the axial component of the Xe{sup +} ion does change periodically in time with a frequency close to the current oscillation frequency in both forced and natural cases. The ion density and the mean velocity are found to oscillate, whereas the velocity dispersion stays constant, which indicates that ionization and acceleration layers have identical dynamics. Finally, variations over time in the electric field are for the first time experimentally evidenced in a crossed-field discharge.

  4. Collisional effects on nonlinear ion drag force for small grains

    SciTech Connect

    Hutchinson, I. H.; Haakonsen, C. B. [Plasma Science and Fusion Center and Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Plasma Science and Fusion Center and Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2013-08-15

    The ion drag force arising from plasma flow past an embedded spherical grain is calculated self-consistently and non-linearly using particle in cell codes, accounting for ion-neutral collisions. Using ion velocity distribution appropriate for ion drift driven by a force field gives wake potential and force greatly different from a shifted Maxwellian distribution, regardless of collisionality. The low-collisionality forces are shown to be consistent with estimates based upon cross-sections for scattering in a Yukawa (shielded) grain field, but only if non-linear shielding length is used. Finite collisionality initially enhances the drag force, but only by up to a factor of 2. Larger collisionality eventually reduces the drag force. In the collisional regime, the drift distribution gives larger drag than the shift distribution even at velocities where their collisionless drags are equal. Comprehensive practical analytic formulas for force that fit the calculations are provided.

  5. Adiabatic particle motion in a nearly drift-free magnetic field: Application to the geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Stern, D. P.

    1977-01-01

    The guiding center motion of particles in a nearly drift free magnetic field is analyzed in order to investigate the dependence of mean drift velocity on equatorial pitch angle, the variation of local drift velocity along the trajectory, and other properties. The mean drift for adiabatic particles is expressed by means of elliptic integrals. Approximations to the twice-averaged Hamiltonian W near z = O are derived, permitting simple representation of drift paths if an electric potential also exists. In addition, the use of W or of expressions for the longitudinal invariant allows the derivation of the twice averaged Liouville equation and of the corresponding Vlasov equation. Bounce times are calculated (using the drift-free approximation), as are instantaneous guiding center drift velocities, which are then used to provide a numerical check on the formulas for the mean drift.

  6. Ion heating mechanism in a modified Penning discharge

    NASA Technical Reports Server (NTRS)

    Roth, J. R.

    1972-01-01

    Ions with Maxwellian energy distributions and kinetic temperatures ranging from 20 eV to 7 keV have been observed in a modified Penning discharge operating in the steady state. Investigation of the plasma revealed two distinct spoke-like concentrations of charge rotating with different velocities in the sheath between the plasma and the anode ring. The faster spoke consists of electrons rotating with the E/B drift velocity, where E is the electric field and B is the magnetic field strength. The slow spoke consists of ions, the thermal velocity of which is observed to be proportional to the spoke velocity. The experimental data are consistent with a model whereby the ion drift velocity in this spoke, corresponding to kilovolt ion energies, is Maxwellianized by strong electrostatic turbulence in the sheath. Theoretical expressions are derived for the frequency of the electron and ion spoke rotation, for the ion kinetic temperature, and for the ion heating efficiency as functions of the discharge parameters. These expressions are shown to be consistent with extensive experimental data.

  7. Ion acceleration in plasmas emerging from a helicon-heated magnetic-mirror device

    Microsoft Academic Search

    S. A. Cohen; N. S. Siefert; S. Stange; R. F. Boivin; E. E. Scime; F. M. Levinton

    2003-01-01

    Using laser-induced fluorescence, measurements have been made of metastable argon-ion, Ar+*(3d4F7\\/2), velocity distributions on the major axis of an axisymmetric magnetic-mirror device whose plasma is sustained by helicon wave absorption. Within the mirror, these ions have sub-eV temperature and, at most, a subthermal axial drift. In the region outside the mirror coils, conditions are found where these ions have a

  8. Ion beams from laser-generated plasmas

    NASA Astrophysics Data System (ADS)

    Hughes, R. H.; Anderson, R. J.; Gray, L. G.; Rosenfeld, J. P.; Manka, C. K.; Carruth, M. R.

    1980-08-01

    The paper describes the space-charge-limited beams produced by the plasma blowoffs generated by 20-MW bursts of 1.06-micron radiation from an active Q-switched Nd:YAG laser. Laser power densities near 10 to the 11th/sq cm on solid targets generate thermalized plasma plumes which drift to a 15-kV gridded extraction gap where the ions are extracted, accelerated, and electrostatically focused; the spatially defined ion beams are then magnetically analyzed to determine the charge state content in the beams formed from carbon, aluminum, copper, and lead targets. This technique preserves time-of-flight (TOF) information in the plasma drift region, which permits plasma ion temperatures and mass flow velocities to be determined from the Maxwellian ion curve TOF shapes for the individual charge species.

  9. Dike/Drift Interactions

    SciTech Connect

    E. Gaffiney

    2004-11-23

    This report presents and documents the model components and analyses that represent potential processes associated with propagation of a magma-filled crack (dike) migrating upward toward the surface, intersection of the dike with repository drifts, flow of magma in the drifts, and post-magma emplacement effects on repository performance. The processes that describe upward migration of a dike and magma flow down the drift are referred to as the dike intrusion submodel. The post-magma emplacement processes are referred to as the post-intrusion submodel. Collectively, these submodels are referred to as a conceptual model for dike/drift interaction. The model components and analyses of the dike/drift interaction conceptual model provide the technical basis for assessing the potential impacts of an igneous intrusion on repository performance, including those features, events, and processes (FEPs) related to dike/drift interaction (Section 6.1).

  10. A silicon drift photodiode

    SciTech Connect

    Avset, B.S.; Evensen, L.; Ellison, J.A.; Hall, G.; Roe, S.; Wheadon, R.; Hansen, T.E.

    1989-02-01

    A low capacitance photodiode based on the principle of the solid state drift chamber has been constructed and tested. The device is based on a cellular design with an anode at the centre of each of five cells allowing electrons liberated by ionisation to drift up to 1mm to the read out strip. Results on the performance of the detector, including leakage current, capacitance and drift properties, are presented and compared with simulations.

  11. Gradient drift eigenmodes in the equatorial electrojet

    NASA Technical Reports Server (NTRS)

    Wang, X.-H.; Bhattacharjee, A.

    1994-01-01

    The problem of kilometer-scale irregularities in the daytime equatorial electrojet is revisited by means of an eigenmode analysis of the gradient drift instability. Realistic physical parameters are used, including the modeled altitude variations of ion and electron collision frequencies and mobilities. The full fourth-order system of two coupled differential equations (each of second order) for the denisty and electrostatic potential perturbations is solved numerically by a relaxation technique. Under some approximations, the fourth-order system can be shown to reduce to a second-order differential equation for the perturbed potential or density. The latter is solved using a shooting technique and provides initial guesses for numerical solutions to the full problem. It is shown that the linear growth rate peaks for kilometer-scale waves, contrary to the findings of recent initial-value studies. This occurs because the equilibrium velocity shear is much more effective as a damping mechanism for short-wavelength modes than it is for the longer, kilometer-scale modes. These results provide a natural qualitative explanation for the observed dominance of kilometer-scale structures in the daytime electrojet spectrum.

  12. Magnetotail acceleration using generalized drift theory - A kinetic merging scenario

    NASA Technical Reports Server (NTRS)

    Whipple, E. C.; Rosenberg, M.; Brittnacher, M.

    1990-01-01

    It is possible to describe particle behavior in the magnetotail, including particle energization, by means of generalized drift theory. Generalized drift velocities are obtained by using the generalized first invariant which has been shown to be useful in such current sheet configurations. Particles whose generalized invariant is preserved gain energy entirely in the field-aligned direction. The form of the accelerated particle velocity distribution is obtained and self-consistency conditions are derived.

  13. Dike/Drift Interactions

    SciTech Connect

    E.S. Gaffney

    2003-10-08

    This report documents the model of events associated with a potential intrusion of magma from a volcanic dike into a drift or drifts in the Yucca Mountain Nuclear Waste Repository. The following topics are included in this report: (1) A discussion of dike propagation, which provides the basis for describing the path that a representative dike, or swarm of dikes, would follow during an event. (2) A discussion of magma flow, which evaluates the interaction at the junction of the propagating dike with the drift and the movement of magmatic products into and down drifts and, potentially, through a drift to the surface by way of access drift or a secondary dike opened up along the drift. (3) A discussion of gas flow and conductive cooling of a magma-filled drift, describing how an adjacent drift that has not been intersected by a dike could be affected by post-intrusion phenomena. Note that a gas flow analysis is also addressed in ''Igneous Intrusion Impacts on Waste Form and Waste Packages'' (BSC 2003 [DIRS 161810]), and those results are consistent with the results presented in this report.

  14. Free Drifting Buoys

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Information was exchanged between people directly involved with the development, use, and/or potential use of free drifting buoys. Tracking systems and techniques, where methods and accuracy of optical, radio, radar, satellite, and sonic tracking of free-drifting buoys were discussed. Deployment and retrieval covering methods currently used or planned in the deployment and retrieval of free-drifting buoys from boats, ships, helicopters, fixed platforms, and fixed-wing aircraft were reported. Simulation, sensors, and data emphasizing the status of water circulation modeling, and sensors useful on free-drifting buoys, and data display and analysis were described.

  15. Lower hybrid drift instability at a dipolarization front

    NASA Astrophysics Data System (ADS)

    Divin, A.; Khotyaintsev, Yu. V.; Vaivads, A.; André, M.

    2015-02-01

    We present observations of a reconnection jet front detected by the Cluster satellites in the magnetotail of Earth, which are commonly referred to as dipolarization fronts. We investigate in detail electric field structures observed at the front which have frequency in the lower hybrid range and amplitudes reaching 40 mV/m. We determine the frequency and phase velocity of these structures in the reference frame of the front and identify them as a manifestation of the lower hybrid drift instability (LHDI) excited at the sharp density gradient at the front. The LHDI is observed in the nonlinear stage of its evolution as the electrostatic potential of the structures is comparable to ˜ 10% of the electron temperature. The front appears to be a coherent structure on ion and MHD scales, suggesting existence of a dynamic equilibrium between excitation of the LHDI and recovery of the steep density gradient at the front.

  16. Generation of electromagnetic structures via modulational instability of drift waves

    SciTech Connect

    Smolyakov, A. I. [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada); Nuclear Fusion Institute, Russian Research Center 'Kurchatov Institute', 1 Kurchatov Square, 123182, Moscow (Russian Federation); Krasheninnikov, S. I. [University of California at San Diego, 9500 Gilman Dr., La Jolla, California 92093 (United States)

    2008-07-15

    Generation mechanism for large scale electromagnetic structures (blobs) is considered by employing the technique of four-wave interactions (modulational instability). It is shown that primary electrostatic turbulence may generate elongated electromagnetic structures with poloidal modulations. Such structures are principally related to drift-Alfven waves. The analysis fully takes into account finite ion temperature effects and associated diamagnetic contributions to Reynolds stress. The turbulent generation of blobs has instability growth rates which scale similar to the zonal flow instabilities, {gamma}{approx}, where q is a characteristic wave vector of large scale modes, and V-tilde is a characteristic amplitude of the velocity of turbulent fluctuations. This analysis is shown to be fully consistent with results of an earlier analysis by using the wave kinetic equation.

  17. Origins of ion irradiation-induced Ga nanoparticle motion on GaAs surfaces

    SciTech Connect

    Kang, M.; Wu, J. H.; Chen, H. Y.; Thornton, K.; Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)] [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Sofferman, D. L. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States) [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States); Department of Physics, Adelphi University, Garden City, New York 11530-0701 (United States); Beskin, I. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)] [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)

    2013-08-12

    We have examined the origins of ion irradiation-induced nanoparticle (NP) motion. Focused-ion-beam irradiation of GaAs surfaces induces random walks of Ga NPs, which are biased in the direction opposite to that of ion beam scanning. Although the instantaneous NP velocities are constant, the NP drift velocities are dependent on the off-normal irradiation angle, likely due to a difference in surface non-stoichiometry induced by the irradiation angle dependence of the sputtering yield. It is hypothesized that the random walks are initiated by ion irradiation-induced thermal fluctuations, with biasing driven by anisotropic mass transport.

  18. Experimental study of grad-B drift-electron transport

    SciTech Connect

    Lee, J.R.; Hartmann, J.R.

    1982-11-01

    We have experimentally studied electron-beam transport via gradient-B drift in the applied magnetic field generated by a current-carrying wire. The electron beam transported 89 cm to a tantalum target. The measured drift velocity was 4.12 +- .26 cm/nsec for .83-MV electrons with a 75-kamp wire current, in good agreement with the theoretically expected value of 3.83 cm/nsec. We studied x-ray production in the tantalum target as a function of the wire current, the target thickness, the gas pressure in the drift tube, and the length of a beam-expansion gap preceding the drift region.

  19. Gyrokinetic theory of electrostatic lower-hybrid drift instabilities in a current sheet with guide field

    NASA Astrophysics Data System (ADS)

    Tummel, K.; Chen, L.; Wang, Z.; Wang, X. Y.; Lin, Y.

    2014-05-01

    A kinetic electrostatic eigenvalue equation for the lower-hybrid drift instability (LHDI) in a thin Harris current sheet with a guide field is derived based on the gyrokinetic electron and fully kinetic ion(GeFi) description. Three-dimensional nonlocal analyses are carried out to investigate the influence of a guide field on the stabilization of the LHDI by finite parallel wavenumber, k?. Detailed stability properties are first analyzed locally, and then as a nonlocal eigenvalue problem. Our results indicate that at large equilibrium drift velocities, the LHDI is further destabilized by finite k? in the short-wavelength domain. This is demonstrated in a local stability analysis and confirmed by the peak in the eigenfunction amplitude. We find the most unstable modes localized at the current sheet edges, and our results agree well with simulations employing the GeFi code developed by Lin et al. [Plasma Phys. Controlled Fusion 47, 657 (2005); Plasma Phys. Controlled Fusion 53, 054013 (2011)].

  20. Drift Degradation Analysis

    SciTech Connect

    Dwayne C. Kicker

    2001-09-28

    A statistical description of the probable block sizes formed by fractures around the emplacement drifts has been developed for each of the lithologic units of the repository host horizon. A range of drift orientations with the drift azimuth varied in 15{sup o} increments has been considered in the static analysis. For the quasi-static seismic analysis, and the time-dependent and thermal effects analysis, two drift orientations have been considered: a drift azimuth of 105{sup o} and the current emplacement drift azimuth of 75{sup o}. The change in drift profile resulting from progressive deterioration of the emplacement drifts has been assessed both with and without backfill. Drift profiles have been determined for four different time increments, including static (i.e., upon excavation), 200 years, 2,000 years, and 10,000 years. The effect of seismic events on rock fall has been analyzed. Block size distributions and drift profiles have been determined for three seismic levels, including a 1,000-year event, a 5,000-year event, and a 10,000-year event. Data developed in this modeling and analysis activity have been entered into the TDMS (DTN: MO0109RDDAAMRR.003). The following conclusions have resulted from this drift degradation analysis: (1) The available fracture data are suitable for supporting a detailed key block analysis of the repository host horizon rock mass. The available data from the north-south Main Drift and the east-west Cross Drift provide a sufficient representative fracture sample of the repository emplacement drift horizon. However, the Tptpln fracture data are only available from a relatively small section of the Cross Drift, resulting in a smaller fracture sample size compared to the other lithologic units. This results in a lower degree of confidence that the key block data based on the Tptpln data set is actually representative of the overall Tptpln key block population. (2) The seismic effect on the rock fall size distribution for all events analyzed is relatively minor. (3) The analysis of thermal and time-dependent effects on rock fall in this study is based on a reduction in the joint cohesion. Joint cohesion has been conservatively reduced from a laboratory test value of 0.86 MPa to a value of 0.01 MPa after 10,000 years. The results from this analysis indicate that time-dependent and thermal effects have a minor impact on rock fall. (4) Both the 75 percentile and the worst-case drift degradation profiles have been provided in this analysis for the current emplacement drift azimuth of approximately 75{sup o}. Most of the emplacement drift openings were not affected by rock fall. For the current emplacement drift alignment, the highest percentage of drift affected by rock fall was 8% in the Tptpmn unit. The Tptpmn unit produced the highest frequency of key blocks per kilometer compared to the other lithologic units (Tables 26 and 41). (5) This key block analysis has shown that the current drift alignment is relatively favorable in terms of reducing the potential maximum size rock block compared to most drift orientations.

  1. Radar and satellite global equatorial F region vertical drift model

    Microsoft Academic Search

    L. Scherliess

    1999-01-01

    We present the first global empirical model for the quiet time F region equatorial vertical drifts based on combined incoherent scatter radar observations at Jicamarca and Ion Drift Meter observations on board the Atmospheric Explorer E satellite. This analytical model, based on products of cubic-B splines and with nearly conservative electric fields, describes the diurnal and seasonal variations of the

  2. Development of A Cryogenic Drift Cell Spectrometer and Methods for Improving the Analytical Figures of Merit for Ion Mobility-Mass Spectrometry Analysis

    E-print Network

    May, Jody C.

    2010-10-12

    A cryogenic (325-80 K) ion mobility-mass spectrometer was designed and constructed in order to improve the analytical figures-of-merit for the chemical analysis of small mass analytes using ion mobility-mass spectrometry. The instrument incorporates...

  3. Particle drift in the Earth's plasma sheet

    NASA Technical Reports Server (NTRS)

    Wolf, R. A.; Pontius, D. H., Jr.

    1993-01-01

    We generalize the derivation of the average gradient/curvature-drift for a flux tube filled with an isotropic distribution of particles at specified kinetic energy. The present treatment is restricted to a two-dimensional magnetic field with zero electric field, but it includes all chaotic and Speiser orbits, which do not correspond to the simple picture of gradient/curvature drift. We assume that particles are evenly distributed throughout the regions of phase space allowed by their energy and canonical momentum. This assumption is closely related but not exactly equivalent to the assumption of isotropic pitch-angle distribution. Our derivation assumes that the maximum Larmor radius is small compared to the scale length for equatorial variations in the flux tube volume, but it does not involve any restrictions on the curvature of the field line. The resulting expression for the drift rate is valid for situations where the particle drift velocity is comparable to the thermal speed in some regions. The apparent implication of this generalized treatment is that the existence of very complex non-adiabatic particle trajectories in the plasma sheet may not invalidate previous estimates of the average rate of particle drift out the sides of the tail, estimates that were made under the assumption of simple guiding-center drifts.

  4. Drift Bottles: A Vehicle for the Teaching of Earth-Science Topics.

    ERIC Educational Resources Information Center

    Akers, Brian N.

    1992-01-01

    Describes an extended problem-solving activity utilizing drift-bottles that encourages students to deduce probable and great-circle drift-bottle routes, to use logic based on unit calculations, and to estimate the distance traveled and the minimum velocity of these drift-bottles. Includes materials needed, learning objectives, procedures,…

  5. Development of a High Resolution X-Ray Imaging Crystal Spectrometer for Measurement of Ion-Temperature and Rotation-Velocity Profiles in Fusion Energy Research Plasmas

    SciTech Connect

    Hill, K W; Broennimann, Ch; Eikenberry, E F; Ince-Cushman, A; Lee, S G; Rice, J E; Scott, S

    2008-02-27

    A new imaging high resolution x-ray crystal spectrometer (XCS) has been developed to measure continuous profiles of ion temperature and rotation velocity in fusion plasmas. Following proof-of-principle tests on the Alcator C-Mod tokamak and the NSTX spherical tokamak, and successful testing of a new silicon, pixilated detector with 1MHz count rate capability per pixel, an imaging XCS is being designed to measure full profiles of Ti and v? on C-Mod. The imaging XCS design has also been adopted for ITER. Ion-temperature uncertainty and minimum measurable rotation velocity are calculated for the C-Mod spectrometer. The affects of x-ray and nuclear-radiation background on the measurement uncertainties are calculated to predict performance on ITER.

  6. Relativistic wave-function effect on the K-shell ionization of Sb, Gd, Yb, Au, and Bi by low- to intermediate-velocity F ions

    Microsoft Academic Search

    D. Mitra; Yeshpal Singh; Lokesh C. Tribedi; P. N. Tandon; D. Trautmann

    2001-01-01

    We have measured absolute cross sections for the K-shell ionization of medium- and high-Z targets of Sb, Gd, Yb, Au, and Bi induced by low- to intermediate-velocity F ions having energies between 2.5 and 5.8 MeV\\/u. Our main interest is to see the effect of the relativistic nature of the K-shell electrons of these target atoms on the ionization cross

  7. Note on the electric splitting of drift shells. [in magnetospheric convection electric field

    NASA Technical Reports Server (NTRS)

    Kivelson, M. G.; Southwood, D. J.

    1975-01-01

    A nonrelativistic analysis is presented for the deviation of a particle from its dipole magnetic drift shell in the presence of an electric field. An alternative definition of weak shell splitting is introduced in which the corotation drift velocity need not be small with respect to the azimuthal magnetic drift velocity. Approximate explicit solutions are obtained for the asymmetry of drift shells in the strong shell splitting case, i.e., for the case where the cross-magnetosphere potential drop is not small compared to particle kinetic energy. Upper limits to drift shell asymmetry are obtained from considerations of the Alfven layer.

  8. Abstraction of Drift Seepage

    SciTech Connect

    J.T. Birkholzer

    2004-11-01

    This model report documents the abstraction of drift seepage, conducted to provide seepage-relevant parameters and their probability distributions for use in Total System Performance Assessment for License Application (TSPA-LA). Drift seepage refers to the flow of liquid water into waste emplacement drifts. Water that seeps into drifts may contact waste packages and potentially mobilize radionuclides, and may result in advective transport of radionuclides through breached waste packages [''Risk Information to Support Prioritization of Performance Assessment Models'' (BSC 2003 [DIRS 168796], Section 3.3.2)]. The unsaturated rock layers overlying and hosting the repository form a natural barrier that reduces the amount of water entering emplacement drifts by natural subsurface processes. For example, drift seepage is limited by the capillary barrier forming at the drift crown, which decreases or even eliminates water flow from the unsaturated fractured rock into the drift. During the first few hundred years after waste emplacement, when above-boiling rock temperatures will develop as a result of heat generated by the decay of the radioactive waste, vaporization of percolation water is an additional factor limiting seepage. Estimating the effectiveness of these natural barrier capabilities and predicting the amount of seepage into drifts is an important aspect of assessing the performance of the repository. The TSPA-LA therefore includes a seepage component that calculates the amount of seepage into drifts [''Total System Performance Assessment (TSPA) Model/Analysis for the License Application'' (BSC 2004 [DIRS 168504], Section 6.3.3.1)]. The TSPA-LA calculation is performed with a probabilistic approach that accounts for the spatial and temporal variability and inherent uncertainty of seepage-relevant properties and processes. Results are used for subsequent TSPA-LA components that may handle, for example, waste package corrosion or radionuclide transport.

  9. Computation of two-dimensional electric field from the ion laser induced fluorescence measurements

    SciTech Connect

    Spektor, Rostislav [Aerospace Corporation, P.O. Box 92957-M2-341, Los Angeles, California 90009-2957 (United States)

    2010-09-15

    This paper presents a method of computing two-dimensional electric field from ion laser induced fluorescence (LIF) measurements in a plasma flow. The expression for the field is derived by taking velocity moments of the Boltzmann equation for ions. It was found that the pressure tensor, related to the width of the ion velocity distribution, plays a critical role in the computation of the electric field. Even with the assumption of cold ion flow, the pressure tensor contribution may be significant when velocity spread is caused by other forces. Such a situation occurs in the flow of a Hall thruster, where velocity spread is caused by the ions born at different potentials. LIF measurements of the cylindrical hall thruster plume were used to demonstrate practical application of the derived method. Whenever the pressure tensor components are small as compared to the mean ion drift velocity, the electric field calculations reduce to a simple expression given in terms of mean ion drift velocity and its divergence.

  10. Fast Faraday cup to measure neutralized drift compression in intense ion charge bunches A. B. Sefkow, R. C. Davidson, P. C. Efthimion, and E. P. Gilson

    E-print Network

    Gilson, Erik

    . Greenway, E. Henestroza, J. W. Kwan, D. L. Vanecek, and W. L. Waldron Lawrence Berkeley National Laboratory. INTRODUCTION One of the more significant challenges in developing heavy ion drivers is found in the final

  11. Synthesis of time models of the drifts of a triaxial gyrostabilizer

    NASA Astrophysics Data System (ADS)

    Sokolov, S. V.; Marinenko, I. N.

    Equations are obtained which describe changes with time of the instantaneous rotational velocity of a gyrostabilized platform. The time dependences of the projections of the drift velocity of a gyrostabilized platform are determined analytically.

  12. Synthesis of time models of the drifts of a triaxial gyrostabilizer

    Microsoft Academic Search

    S. V. Sokolov; I. N. Marinenko

    1991-01-01

    Equations are obtained which describe changes with time of the instantaneous rotational velocity of a gyrostabilized platform. The time dependences of the projections of the drift velocity of a gyrostabilized platform are determined analytically.

  13. Search for the best timing strategy in high-precision drift chambers

    SciTech Connect

    Va'vra, J.

    1983-06-01

    Computer simulated drift chamber pulses are used to investigate various possible timing strategies in the drift chambers. In particular, the leading edge, the multiple threshold and the flash ADC timing methods are compared. Although the presented method is general for any drift geometry, we concentrate our discussion on the jet chambers where the drift velocity is about 3 to 5 cm/..mu..sec and the individual ionization clusters are not resolved due to a finite speed of our electronics.

  14. Gradient and curvature drifts in magnetic fields with arbitrary spatial variation. [charged particle distribution in plasmas

    NASA Technical Reports Server (NTRS)

    Isenberg, P. A.; Jokipii, J. R.

    1979-01-01

    It is shown that, for a magnetic field of arbitrary spatial variation, a nearly isotropic distribution of charged particles drifts with a velocity given by the usual first-order orbit theory drifts averaged over pitch angle. It is assumed that the near-isotropy brought about by scattering, but conclusions concerning drift are insensitive to the details of the scattering process. It is found that this drift velocity is correct even for arbitrarily large ratios of particle gyroradius to magnetic spatial scale, although this velocity must, like all drift effects, be viewed on a scale larger than a gyroradius. Hence for many astrophysical applications, such as cosmic rays, where anisotropies are small, the usual drift velocities provide a valid approximation to convective motions even if the magnetic field scales are very small.

  15. Origin of hot ions observed in a modified Penning discharge.

    NASA Technical Reports Server (NTRS)

    Roth, J. R.

    1971-01-01

    Ions with a Maxwellian energy distribution and kinetic temperatures ranging from below 100 eV to several keV have been observed in a steady-state modified Penning discharge. Observations in the plasma, with capacitive probes at several azimuthal locations, are consistent with the existence of two distinct spokes rotating with different velocities in the sheath between the plasma and the anode ring. The faster (0.5-10 MHz) spoke consists of electrons rotating with the E/B drift velocity. The slow (0.1-1.0 MHz) spoke consists of ions, the measured thermal velocity of which is directly proportional to the spoke velocity. The interaction of the two spokes is apparently responsible for the observed electrostatic ?turbulence' and ion thermalization. The anode sheath thickness is smaller than the ion gyrodiameter in this plasma. Thus the ions are in the electric field of the sheath for only a fraction of their orbit, and their E/B drift (spoke) velocity is smaller than that of the electrons.

  16. Origin of hot ions observed in a modified Penning discharge

    NASA Technical Reports Server (NTRS)

    Roth, J. R.

    1971-01-01

    Ions with a Maxwellian energy distriubtion and kinetic temperatures ranging from below 100 eV to several keV are observed in a steady state modified Penning discharge. Observations in the plasma, with capacitive probes at several azimuthal locations, are consistent with the existence of two distinct spokes rotating with different velocities in the sheath between the plasma and the anode ring. The faster (0.5 to 10 MHz) spoke consists of electrons rotating with the E/B drift velocity. The slow (0.1 to 1.0 MHz) spoke consists of ions whose measured thermal velocity is directly proportional to the spoke velocity. The interaction of the two spokes is apparently responsible for the observed electrostatic turbulence and ion thermalization. The anode sheath thickness is smaller than the ion gyrodiameter in this plasma. Thus the ions are in the electric field of the sheath for only a fraction of their orbit, and their E/B drift (spoke) velocity is smaller than that of the electrons.

  17. Lithium drifted germanium system

    Microsoft Academic Search

    E. J. Fjarlie

    1969-01-01

    General characteristics of the lithium-drifted germanium photodiode-Dewar-preamplifier system and particular operating instructions for the device are given. Information is included on solving operational problems.

  18. Background and pickup ion velocity distribution dynamics in Titan's plasma environment: 3D hybrid simulation and comparison with CAPS's observations

    Microsoft Academic Search

    Alexander Lipatov; Edward Sittler; Richard Hartle; David Simpson

    2010-01-01

    The wave-particle interactions play very important role in the plasma dynamics near Titan: mass loading, excitation of the low-frequency waves and the formation of the particle velocity distribution function, e.g. ring\\/shell-like distributions, etc. The kinetic approach is important for estimation of the collision processes e.g. a charge exchange. The particle velocity distri-bution also plays a key role for understanding the

  19. Dynamics of pickup ion velocity distribution in Titan's plasma environment: 3D hybrid simulation and comparison with CAPS's observations

    Microsoft Academic Search

    D. G. Simpson; A. S. Lipatov; E. C. Sittler; R. E. Hartle; J. F. Cooper

    2010-01-01

    The wave-particle interactions play a very important role in the plasma dynamics near Titan: mass loading, excitation of the low-frequency waves and the formation of the particle velocity distribution function, e.g. ring\\/shell-like distributions, etc. The kinetic approach is important for estimation of the collision processes e.g. a charge exchange. The particle velocity distribution also plays a key role for understanding

  20. Auroral Electron and Ion Accelerations by Large-scale Alfven waves

    NASA Astrophysics Data System (ADS)

    Singh, Nagendra

    Alfven waves with large perpendicular wavelengths deposit a large amount of electromagnetic energy in the auroral plasma. Dissipation of this energy resulting into electron and ion accelerations remains a challenging problem in space physics. We find that an effective mechanism for the dissipation is the cross-field instabilities (CFI) driven by the relative drifts between electrons and ions generated in the fields of the Alfven waves. Specifically the polarization drift of the ions plays a crucial role in CFI. If the plasma is sufficiently cold, the CFI driven by the ion polarization drift generates lower hybrid (LH) and electrostatic ion cyclotron (EIC) waves. These electrostatic waves are found to be very effective in causing perpendicular ion heating and parallel electron acceleration. The parallel acceleration of electrons by the LH waves has features of electrons observed in association of Alfven waves. The accelerated electrons in the LH waves powered by the shear Alfven waves have average drifts determined by the group velocity of the shear Alfven waves, and not its phase velocity, as commonly believed when the acceleration occurs directly in the parallel electric fields of transversely small-scale shear Alfven waves.

  1. The influence of finite ion temperature on plasma blob dynamics

    NASA Astrophysics Data System (ADS)

    Manz, P.; Birkenmeier, G.; Carralero, D.; Fuchert, G.; Müller, H. W.; Müller, S. H.; Scott, B. D.; Stroth, U.; Ribeiro, T. T.; Wolfrum, E.

    2015-01-01

    In the scrape-off layer of magnetically confined fusion devices, the ion temperature is at least as high as the electron temperature and usually even much higher. The effects of the finite ion temperature enhance the blob drive and modify the vorticity. Recently developed scaling laws for blob velocity independent of its size, based on the full drift-interchange-Alfvén fluid equations are compared with recent experiments on the ASDEX Upgrade tokamak and gyrofluid simulations, showing remarkable agreement for the blob sizes and reasonable agreement for the blob velocities.

  2. Numerical simulation of drifting snow sublimation in the saltation layer

    PubMed Central

    Dai, Xiaoqing; Huang, Ning

    2014-01-01

    Snow sublimation is an important hydrological process and one of the main causes of the temporal and spatial variation of snow distribution. Compared with surface sublimation, drifting snow sublimation is more effective due to the greater surface exposure area of snow particles in the air. Previous studies of drifting snow sublimation have focused on suspended snow, and few have considered saltating snow, which is the main form of drifting snow. In this study, a numerical model is established to simulate the process of drifting snow sublimation in the saltation layer. The simulated results show 1) the average sublimation rate of drifting snow particles increases linearly with the friction velocity; 2) the sublimation rate gradient with the friction velocity increases with increases in the environmental temperature and the undersaturation of air; 3) when the friction velocity is less than 0.525?m/s, the snowdrift sublimation of saltating particles is greater than that of suspended particles; and 4) the snowdrift sublimation in the saltation layer is less than that of the suspended particles only when the friction velocity is greater than 0.625?m/s. Therefore, the drifting snow sublimation in the saltation layer constitutes a significant portion of the total snow sublimation. PMID:25312383

  3. A method for calculating plasma rotation velocity due to internal and external sources

    SciTech Connect

    Taguchi, M. [College of Industrial Technology, Nihon University, Narashino 275-8576 (Japan)

    2011-10-15

    A method for calculating the plasma rotation velocity caused by the effect of fluctuations due to instabilities and/or by externally imposed sources is presented for multiple ion species plasmas in a general toroidal magnetic field. The rotation velocity is shown to be obtained by solving generalized Spitzer equations, accompanied with the drift kinetic equations employing the pitch-angle-scattering and Krook collision terms. This method reduces to the moment equation approach in the conventional neoclassical transport theory when the source term can be approximated by a momentum source.

  4. Origin of hot ions observed in a modified Penning discharge.

    NASA Technical Reports Server (NTRS)

    Roth, J. R.

    1973-01-01

    Ions with a Maxwellian energy distribution and kinetic temperatures ranging from below 100 eV to several keV have been observed in a steady-state modified Penning discharge. Observations in the plasma, with capacitive probes at several azimuthal locations, are consistent with the existence of two distinct spokes rotating with different velocities in the sheath between the plasma and the anode ring. The faster (0.3-10 MHz) spoke consists of electrons rotating with the E/B drift velocity. The slow (0.06-0.8 MHz) spoke consists of ions, the measured thermal velocity of which is directly proportional to the spoke velocity. The interaction of the two spokes is apparently responsible for the observed electrostatic turbulence and ion thermalization.

  5. Bifurcation in electrostatic resistive drift wave turbulence

    SciTech Connect

    Numata, Ryusuke; Ball, Rowena; Dewar, Robert L. [Department of Theoretical Physics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200 (Australia)

    2007-10-15

    The Hasegawa-Wakatani equations, coupling plasma density, and electrostatic potential through an approximation to the physics of parallel electron motions, are a simple model that describes resistive drift wave turbulence. Numerical analyses of bifurcation phenomena in the model are presented, that provide new insights into the interactions between turbulence and zonal flows in the tokamak plasma edge region. The simulation results show a regime where, after an initial transient, drift wave turbulence is suppressed through zonal flow generation. As a parameter controlling the strength of the turbulence is tuned, this zonal-flow-dominated state is rapidly destroyed and a turbulence-dominated state re-emerges. The transition is explained in terms of the Kelvin-Helmholtz stability of zonal flows. This is the first observation of an upshift of turbulence onset in the resistive drift wave system, which is analogous to the well-known Dimits shift in turbulence driven by ion temperature gradients.

  6. P-type silicon drift detectors

    SciTech Connect

    Walton, J.T.; Krieger, B.; Krofcheck, D.; O`Donnell, R.; Odyniec, G.; Partlan, M.D.; Wang, N.W.

    1995-06-01

    Preliminary results on 16 CM{sup 2}, position-sensitive silicon drift detectors, fabricated for the first time on p-type silicon substrates, are presented. The detectors were designed, fabricated, and tested recently at LBL and show interesting properties which make them attractive for use in future physics experiments. A pulse count rate of approximately 8 {times} l0{sup 6} s{sup {minus}1} is demonstrated by the p-type silicon drift detectors. This count rate estimate is derived by measuring simultaneous tracks produced by a laser and photolithographic mask collimator that generates double tracks separated by 50 {mu}m to 1200 {mu}m. A new method of using ion-implanted polysilicon to produce precise valued bias resistors on the silicon drift detectors is also discussed.

  7. Drift Scale THM Model

    SciTech Connect

    J. Rutqvist

    2004-10-07

    This model report documents the drift scale coupled thermal-hydrological-mechanical (THM) processes model development and presents simulations of the THM behavior in fractured rock close to emplacement drifts. The modeling and analyses are used to evaluate the impact of THM processes on permeability and flow in the near-field of the emplacement drifts. The results from this report are used to assess the importance of THM processes on seepage and support in the model reports ''Seepage Model for PA Including Drift Collapse'' and ''Abstraction of Drift Seepage'', and to support arguments for exclusion of features, events, and processes (FEPs) in the analysis reports ''Features, Events, and Processes in Unsaturated Zone Flow and Transport and Features, Events, and Processes: Disruptive Events''. The total system performance assessment (TSPA) calculations do not use any output from this report. Specifically, the coupled THM process model is applied to simulate the impact of THM processes on hydrologic properties (permeability and capillary strength) and flow in the near-field rock around a heat-releasing emplacement drift. The heat generated by the decay of radioactive waste results in elevated rock temperatures for thousands of years after waste emplacement. Depending on the thermal load, these temperatures are high enough to cause boiling conditions in the rock, resulting in water redistribution and altered flow paths. These temperatures will also cause thermal expansion of the rock, with the potential of opening or closing fractures and thus changing fracture permeability in the near-field. Understanding the THM coupled processes is important for the performance of the repository because the thermally induced permeability changes potentially effect the magnitude and spatial distribution of percolation flux in the vicinity of the drift, and hence the seepage of water into the drift. This is important because a sufficient amount of water must be available within a drift to transport any exposed radionuclides out of the drift to the groundwater below, and eventually to people within the accessible environment. Absent sufficient water, radionuclides cannot be transported and there would be no significant health effect on people, even if radioactive waste containers were damaged or corroded to such an extent that radionuclides were exposed to water.

  8. Alternative dust-ion acoustic waves in a magnetized charge varying dusty plasma with nonthermal electrons having a vortex-like velocity distribution

    NASA Astrophysics Data System (ADS)

    Hadjaz, Idir; Tribeche, Mouloud

    2014-06-01

    Alternative localized dust-ion acoustic waves are investigated in a magnetized charge varying dusty plasma with nonthermal electrons having a vortex-like velocity distribution. The correct non-Maxwellian charging currents are obtained based on the well-known orbit limited motion theory. Following the standard reductive perturbation technique, a Schamel-Zakharov Kuznetsov Burgers (S-ZKB) equation is derived. It is shown that due to an interplay between trapping and nonthermality, our dusty plasma model may support solitary as well as shock waves the main quantities (phase velocity, amplitude and width) of which are drastically influenced by trapping, nonthermality and charge variation. Due to the flexibility provided by the outlined distribution function (two concepts of non isothermality), we stress that our model should provide a good fit of the space observations.

  9. drift and selection a) selection, no genetic drift b) large population, drift + selection

    E-print Network

    Dever, Jennifer A.

    1 drift and selection a) selection, no genetic drift b) large population, drift + selection c) small population, drift + selection nonrandom mating affects genotypic frequencies of a population continental "mainland" population to a smaller island population pt+1 = pt + m (pm - pt ) p = pt+1 - pt = m

  10. A Spatially Resolving X-ray Crystal Spectrometer for Measurement of Ion-temperature and Rotation-velocity Profiles on the AlcatorC-Mod Tokamak

    SciTech Connect

    Hill, K. W.; Bitter, M. L.; Scott, S. D.; Ince-Cushman, A.; Reinke, M.; Rice, J. E.; Beiersdorfer, P.; Gu, M. F.; Lee, S. G.; Broennimann, C. H.; Eikenberry, E. F.

    2009-03-24

    A new spatially resolving x-ray crystal spectrometer capable of measuring continuous spatial profiles of high resolution spectra (?/d? > 6000) of He-like and H-like Ar K? lines with good spatial (~1 cm) and temporal (~10 ms) resolutions has been installed on the Alcator C-Mod tokamak. Two spherically bent crystals image the spectra onto four two-dimensional Pilatus II pixel detectors. Tomographic inversion enables inference of local line emissivity, ion temperature (Ti), and toroidal plasma rotation velocity (v?) from the line Doppler widths and shifts. The data analysis techniqu

  11. Study of plasma meniscus and beam halo in negative ion sources using three dimension in real space and three dimension in velocity space particle in cell model

    SciTech Connect

    Nishioka, S., E-mail: nishioka@ppl.appi.keio.ac.jp; Goto, I.; Hatayama, A. [Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)] [Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Miyamoto, K. [School of Natural and Living Sciences Education, Naruto University of Education, 748 Nakashima, Takashima, Naruto-cho, Naruto-shi, Tokushima 772-8502 (Japan)] [School of Natural and Living Sciences Education, Naruto University of Education, 748 Nakashima, Takashima, Naruto-cho, Naruto-shi, Tokushima 772-8502 (Japan); Okuda, S.; Fukano, A. [Toshiba, 33 Isogo-chou, Isogo-ku, Yokohama-shi, Kanagawa 235-001 (Japan)] [Toshiba, 33 Isogo-chou, Isogo-ku, Yokohama-shi, Kanagawa 235-001 (Japan)

    2014-02-15

    Our previous study by two dimension in real space and three dimension in velocity space-particle in cell model shows that the curvature of the plasma meniscus causes the beam halo in the negative ion sources. The negative ions extracted from the periphery of the meniscus are over-focused in the extractor due to the electrostatic lens effect, and consequently become the beam halo. The purpose of this study is to verify this mechanism with the full 3D model. It is shown that the above mechanism is essentially unchanged even in the 3D model, while the fraction of the beam halo is significantly reduced to 6%. This value reasonably agrees with the experimental result.

  12. Study of plasma meniscus and beam halo in negative ion sources using three dimension in real space and three dimension in velocity space particle in cell model.

    PubMed

    Nishioka, S; Miyamoto, K; Okuda, S; Goto, I; Hatayama, A; Fukano, A

    2014-02-01

    Our previous study by two dimension in real space and three dimension in velocity space-particle in cell model shows that the curvature of the plasma meniscus causes the beam halo in the negative ion sources. The negative ions extracted from the periphery of the meniscus are over-focused in the extractor due to the electrostatic lens effect, and consequently become the beam halo. The purpose of this study is to verify this mechanism with the full 3D model. It is shown that the above mechanism is essentially unchanged even in the 3D model, while the fraction of the beam halo is significantly reduced to 6%. This value reasonably agrees with the experimental result. PMID:24593471

  13. Drift Degradation Analysis

    SciTech Connect

    D. Kicker

    2004-09-16

    Degradation of underground openings as a function of time is a natural and expected occurrence for any subsurface excavation. Over time, changes occur to both the stress condition and the strength of the rock mass due to several interacting factors. Once the factors contributing to degradation are characterized, the effects of drift degradation can typically be mitigated through appropriate design and maintenance of the ground support system. However, for the emplacement drifts of the geologic repository at Yucca Mountain, it is necessary to characterize drift degradation over a 10,000-year period, which is well beyond the functional period of the ground support system. This document provides an analysis of the amount of drift degradation anticipated in repository emplacement drifts for discrete events and time increments extending throughout the 10,000-year regulatory period for postclosure performance. This revision of the drift degradation analysis was developed to support the license application and fulfill specific agreement items between the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Department of Energy (DOE). The earlier versions of ''Drift Degradation Analysis'' (BSC 2001 [DIRS 156304]) relied primarily on the DRKBA numerical code, which provides for a probabilistic key-block assessment based on realistic fracture patterns determined from field mapping in the Exploratory Studies Facility (ESF) at Yucca Mountain. A key block is defined as a critical block in the surrounding rock mass of an excavation, which is removable and oriented in an unsafe manner such that it is likely to move into an opening unless support is provided. However, the use of the DRKBA code to determine potential rockfall data at the repository horizon during the postclosure period has several limitations: (1) The DRKBA code cannot explicitly apply dynamic loads due to seismic ground motion. (2) The DRKBA code cannot explicitly apply loads due to thermal stress. (3) The DRKBA code, which determines structurally controlled key-block failure, is not applicable for stress-controlled failure in the lithophysal units. To address these limitations, additional numerical codes have been included that can explicitly apply seismic and thermal loads, providing significant improvements to the analysis of drift degradation and extending the validity of drift degradation models.

  14. Spiral silicon drift detectors

    SciTech Connect

    Rehak, P.; Gatti, E.; Longoni, A.; Sampietro, M.; Holl, P.; Lutz, G.; Kemmer, J.; Prechtel, U.; Ziemann, T.

    1988-01-01

    An advanced large area silicon photodiode (and x-ray detector), called Spiral Drift Detector, was designed, produced and tested. The Spiral Detector belongs to the family of silicon drift detectors and is an improvement of the well known Cylindrical Drift Detector. In both detectors, signal electrons created in silicon by fast charged particles or photons are drifting toward a practically point-like collection anode. The capacitance of the anode is therefore kept at the minimum (0.1pF). The concentric rings of the cylindrical detector are replaced by a continuous spiral in the new detector. The spiral geometry detector design leads to a decrease of the detector leakage current. In the spiral detector all electrons generated at the silicon-silicon oxide interface are collected on a guard sink rather than contributing to the detector leakage current. The decrease of the leakage current reduces the parallel noise of the detector. This decrease of the leakage current and the very small capacities of the detector anode with a capacitively matched preamplifier may improve the energy resolution of Spiral Drift Detectors operating at room temperature down to about 50 electrons rms. This resolution is in the range attainable at present only by cooled semiconductor detectors. 5 refs., 10 figs.

  15. Parallel and oblique proton fire hose instabilities in the presence of alpha/proton drift: Hybrid simulations

    NASA Astrophysics Data System (ADS)

    Hellinger, Petr; TráVní?Ek, Pavel

    2006-01-01

    Parallel and oblique proton fire hose instabilities are investigated in the presence of a small abundance of alpha particles with a nonzero drift velocity with respect to protons. Both instabilities scatter protons and alpha particles in the perpendicular direction with respect to the ambient magnetic field and decelerate both species with respect each other; especially the oblique fire hose effectively diffuses ions owing to its non-quasi-linear evolution. Linear Vlasov theory predicts that the presence of the alpha/proton drift enhances the maximum growth rates of the two instabilities in a similar way and that the parallel fire hose is typically the dominant instability. On the other hand, the oblique fire hose has often the maximum growth rate comparable to that of the parallel one and hybrid simulations show that the oblique instability may be active even when the parallel one is marginally stable. Consequently, both instabilities are relevant in the solar wind context.

  16. Ion soliton observation with laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Claire, N.; Bachet, G.; Skiff, F.

    2002-12-01

    A laser-induced fluorescence observation of ion-acoustic waves in a collisionless unmagnetized double plasma multipolar device is presented. The optical pumping effect is found to be critical for the interpretation of fast changes of the ion velocity distribution functions induced by the propagation of a soliton. To take this effect into account, the continuity equation is used. The laser-induced fluorescence diagnostic shows that the separation of solitons requires a small plasma drift in the backward direction (reverse direction of the soliton propagation) and that the precursor ions are in fact a precursor wave.

  17. Measuring the effect of ion-induced drift-gas polarization on the electrical mobilities of multiply-charged ionic liquid nanodrops in air.

    PubMed

    Fernández-García, Juan; Fernández de la Mora, Juan

    2013-12-01

    The electrical mobilities of multiply-charged nanodrops of the ionic liquid 1-ethyl, 3-methylimidazolium dicyanamide (EMI-N[CN]2) were accurately measured in air at 20 °C for mass-selected clusters of composition [EMI-N[CN]2] n [EMI(+)] z , with 2 ? n ? 369 and 1 ? z ? 10. We confirm prior reports that the mobility Z of a globular ion of mass m is given approximately by the modified Stokes-Millikan law for spheres, Z? = ?Z SM,mod (d m ? + ?d g ,?z,?m), where d m ? = ?(6m/??)(1/3) is the nanodrop mass-diameter based on the density ? of the liquid (corrected for the capillary compression and electrostatic deformation of the nanodrop), and d g is an effective air molecule diameter. There is however a measurable (up to 7%) and systematic z-dependent departure of Z from Z SM,mod . As theoretically expected at small ? (*) , this effect is accurately described by a simple correction factor of the form Z/Z SM,mod ? = ??(1? - ??? (*)), where kT? (*) is the potential energy due to the ion-induced dipole (polarization) attraction between a perfectly-conducting charged nanodrop and a polarized neutral gas-molecule at a distance (d m ? + ?d g )/2 from its center. An excellent fit of this model to hundreds of data points is found for d g ? 0.26 nm, ? ? 0.36, and ? ? 0.954. Accounting for the effect of polarization decreases d g considerably with respect to values inferred from earlier nanodrop measurements that ignored this effect. In addition, and in spite of ambiguities in the mobility calibration scale, the measured constant ? smaller than unity increases Millikan's drag enhancement factor from the accepted value ? m ? 1.36 to the new value ? ? ? m /? ? 1.42? ± 0.03. PMID:24048890

  18. Effects of particle drifts on the solar modulation of galactic cosmic rays

    NASA Technical Reports Server (NTRS)

    Jokipii, J. R.; Levy, E. H.

    1977-01-01

    Gradient and curvature drifts in an Archimedean-spiral magnetic field are shown to produce a significant effect on the modulation of galactic cosmic rays by the solar wind. The net modulation, heliocentric radial gradient, and average energy change of particles which reach the inner solar system are significantly reduced. The effects of drifts are due to the fact that cosmic rays for which the drift velocity is comparable to the wind velocity or larger, have more rapid access to the inner solar system than in the absence of drifts.

  19. Drift wave instability in the Io plasma torus

    NASA Technical Reports Server (NTRS)

    Huang, T. S.; Hill, T. W.

    1991-01-01

    A linear normal mode analysis of the drift wave instability in the Io plasma torus was carried out on the basis of the Richmond (1973) and Huang et al. (1990) analyses of drift waves in the vicinity of the earth's plasmapause. Results indicate that the outer torus boundary is linearly unstable to the growth of electrostatic drift waves. It is shown that the linear growth rate is proportional to the ion drift frequency and to the ratio of the flux tube charge content to the Jovian ionospheric Pedersen conductance. It is also shown that various theoretical models of global radial transport in Jupiter's atmosphere (including corotating convection, interchange diffusion, and transient flux tube convection) can be understood as plausible nonlinear evolutions of electrostatic drift waves.

  20. Laced permanent magnet quadrupole drift tube magnets

    Microsoft Academic Search

    B. Feinberg; G. U. Behrsing; K. Halbach; J. S. Marks; M. E. Morrison; D. H. Nelson

    1989-01-01

    Twenty-three laced permanent magnet quadrupole drift tube magnets have been constructed, tested, and installed in the SuperHILAC heavy ion linear accelerator at LBL (Lawrence Berkeley Laboratory), marking the first accelerator use of this new type of quadrupole. The magnets consist of conventional tape-wound quadrupole electromagnets, using iron pole-pieces, with permanent magnet material (samarium cobalt) inserted between the poles to reduce

  1. High-Resolution Ion Cyclotron Mobility Spectrometry

    PubMed Central

    Merenbloom, Samuel I.; Glaskin, Rebecca S.; Henson, Zachary B.; Clemmer, David E.

    2009-01-01

    A novel ion mobility spectrometry instrument incorporating a cyclotron geometry drift tube is presented. The drift tube consists of eight regions, four curved drift tubes and four ion funnels. Packets of ions are propagated around the drift tube by changing the drift field at a frequency that is resonant with the ion’s drift time through each region. The approach trims each packet of ions as it leaves and enters each new region. An electrostatic gate allows ions to be kept in the drift tube for numerous cycles, increasing the ability to resolve specified ions. We demonstrate the approach by isolating the [M+2H]2+ or [M+3H]3+ charge state of substance P as well as individual trisaccharide isomers from a mixture of melezitose and raffinose. Resolving powers in excess of 300 are obtainable with this approach. PMID:19143495

  2. Laser initiated reactions in N{sub 2}O clusters studied by time-sliced ion velocity imaging technique

    SciTech Connect

    Honma, Kenji [Graduate School of Material Science, University of Hyogo, 3-2-1 Kohto, Kamigori, Hyogo 678-1297 (Japan)] [Graduate School of Material Science, University of Hyogo, 3-2-1 Kohto, Kamigori, Hyogo 678-1297 (Japan)

    2013-07-28

    Laser initiated reactions in N{sub 2}O clusters were studied by a time-sliced velocity imaging technique. The N{sub 2}O clusters, (N{sub 2}O){sub n}, generated by supersonic expansion were irradiated by an ultraviolet laser around 204 nm to convert reactant pairs, O({sup 1}D{sub 2})-(N{sub 2}O){sub n?1}. The NO molecules formed from these reactant pairs were ionized by the same laser pulse and their velocity distribution was determined by the time-sliced velocity imaging technique. At low nozzle pressure, lower than 1.5 atm, the speed distribution in the frame moving with the clusters consists of two components. These components were ascribed to the products appeared in the backward and forward directions in the center-of-mass frame, respectively. The former consists of the vibrational ground state and the latter consists of highly vibrational excited states. At higher nozzle pressure, a single broad speed distribution became dominant for the product NO. The pressure and laser power dependences suggested that this component is attributed to the product formed in the clusters larger than dimer, (N{sub 2}O){sub n} (n ? 3)

  3. Influence of plasma beta on the generation of lower hybrid and whistler waves by an ion velocity ring distribution

    NASA Astrophysics Data System (ADS)

    Winske, D.; Daughton, W.

    2015-02-01

    We present results of three-dimensional electromagnetic particle-in-cell simulations of the lower hybrid ion ring instability, similar to our earlier results [D. Winske and W. Daughton, Phys. Plasma 19, 072109 (2012)], but at higher electron beta (?e = ratio of electron thermal pressure to magnetic pressure = 0.06, rather than at 0.006) with Ti = Te. At higher electron beta, the level of lower hybrid waves at saturation normalized to the ion thermal energy (?i = 0.06 also) is only slightly smaller, but the corresponding magnetic fluctuations are about an order of magnitude larger, consistent with linear theory. After saturation, the waves evolve into whistler waves, through a number of possible mechanisms, with an average growth rate considerably smaller than the linear growth rate of the lower hybrid waves, to a peak fluctuation level that is about 20% above the lower hybrid wave saturation level. The ratio of the peak magnetic fluctuations associated with the whistler waves relative to those of the saturated lower hybrid waves, the ratio of the nonlinear growth rate of whistlers relative to the linear growth rate of lower hybrid waves, the amount of energy extracted from the ring, and the amount of heating of the background ions and electrons are comparable to those in the lower electron beta 3D simulation. This suggests that even at higher electron beta, the linear and nonlinear physics of the lower hybrid ion ring instability is dominated by electrostatic, wave-particle rather than wave-wave interactions.

  4. Negative ion production rates in rare gas-halide lasers

    Microsoft Academic Search

    K. J. Nygaard; H. L. Brooks; S. R. Hunter

    1979-01-01

    This paper reports on dissociative electron attachment in F2, NF3, Cl2, and I2. The principle of the method is to produce a short burst of photoelectrons from a photocathode by means of light from an argon-fluoride laser. Subsequently, by studying the motion of electrons and negative ions in a constant electric field (E) region, information is obtained about drift velocities

  5. HIV envelope drift

    SciTech Connect

    Myers, G.

    1988-01-01

    The consensus sequences for (HIV) the Human Immunodeficiency Virus,envelope proteins can also be examined with regard to what might be called differential drift. Conserved and hypervariable regions, or domains, of the envelope were defined in 1986, when the extent of conspicuous HIV variation began to be noticed. Although a large fraction of the envelope residues are subject to drift, once substition at some particular site begins, constraints will most likely naturally arise in relation to which residues will admit of substitution thereafater. Thus, we should not expect that the type 1 and type 2 HIVs will manifest identical patterns of conservation and hypervariability. They already reveal significant differences in the number of cysteine residues, for example; although it is far less obvious, there is some indication that with the sequences analyzed thus far that the Zairean and North American HIVs may be differentially drifting as a direct consequence of their high rates of diversification. What makes this case of drift so extraordinary is the rapid pace which appears to be characteristic of the HIV speciation, stemming from not merely the high mutation rate, but also from proliferation in what might be for these viruses a relatively new ecological niche. 3 figs.

  6. IN DRIFT CORROSION PRODUCTS

    SciTech Connect

    D.M. Jolley

    1999-12-02

    As directed by a written development plan (CRWMS M&O 1999a), a conceptual model for steel and corrosion products in the engineered barrier system (EBS) is to be developed. The purpose of this conceptual model is to assist Performance Assessment Operations (PAO) and its Engineered Barrier Performance Department in modeling the geochemical environment within a repository drift, thus allowing PAO to provide a more detailed and complete in-drift geochemical model abstraction and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near-Field Environment (NFE) Revision 2 (NRC 1999). This document provides the conceptual framework for the in-drift corrosion products sub-model to be used in subsequent PAO analyses including the EBS physical and chemical model abstraction effort. This model has been developed to serve as a basis for the in-drift geochemical analyses performed by PAO. However, the concepts discussed within this report may also apply to some near and far-field geochemical processes and may have conceptual application within the unsaturated zone (UZ) and saturated zone (SZ) transport modeling efforts.

  7. A photodissociation study of CH2BrCl in the A-band using the time-sliced ion velocity imaging method

    NASA Astrophysics Data System (ADS)

    Zhou, Jingang; Lau, Kai-Chung; Hassanein, Elsayed; Xu, Haifeng; Tian, Shan-Xi; Jones, Brant; Ng, C. Y.

    2006-01-01

    Employing a high-resolution (velocity resolution ?? /?<1.5%) time-sliced ion velocity imaging apparatus, we have examined the photodissociation of CH2BrCl in the photon energy range of 448.6-618.5kJ/mol (193.3-266.6nm). Precise translational and angular distributions for the dominant Br (P3/22) and Br(P1/22) channels have been determined from the ion images observed for Br (P3/22) and Br (P1/22). In confirmation with the previous studies, the kinetic-energy distributions for the Br (P1/22) channel are found to fit well with one Gaussian function, whereas the kinetic- energy distributions for the Br (P3/22) channel exhibit bimodal structures and can be decomposed into a slow and a fast Gaussian component. The observed kinetic-energy distributions are consistent with the conclusion that the formation of the Br (P3/22) and Br (P1/22) channels takes place on a repulsive potential-energy surface, resulting in a significant fraction (0.40-0.47) of available energy to appear as translational energy for the photofragments. On the basis of the detailed kinetic-energy distributions and anisotropy parameters obtained in the present study, together with the specific features and relative absorption cross sections of the excited 2A', 1A?, 3A', 4A', and 2A? states estimated in previous studies, we have rationalized the dissociation pathways of CH2BrCl in the A-band, leading to the formation of the Br (P3/22) and Br(P1/22) channels. The analysis of the ion images observed at 235nm for Cl (P3/2,1/22) provides strong evidence that the formation of Cl mainly arises from the secondary photodissociation process CH2Cl+h??CH2+Cl.

  8. Experimental study of K-shell ionization of low-Z solids in collisions with intermediate-velocity carbon ions and the local plasma approximation

    NASA Astrophysics Data System (ADS)

    Kadhane, U.; Montanari, C. C.; Tribedi, Lokesh C.

    2003-07-01

    K-shell vacancy production in low-atomic-number (Zt = 17-29) solid targets has been measured in collisions of highly charged carbon ions with energies of 1.5-6 MeV u-1. The K-shell ionization cross sections of Cl, K, Ti, Fe and Cu are derived from the measured K x-ray cross sections. The present data-set has been used to test the predictions of a theoretical model based on the local plasma approximation (LPA). This theory takes into account the response of solid core electrons working within the dielectric formalism. We find that this ab initio ion-solid model gives very good agreement with the measured data for Fe and Cu targets, while it tends to under-estimate the data for the most symmetric collision systems studied here. We discuss the range of validity of the LPA in terms of the symmetry parameter and the impact velocity. On the other hand, a model based on the perturbed stationary state approximation, designed for ion-atom collisions (ECPSSR) is found to give excellent agreement with the measured data for all target elements over the whole energy range. All the measured cross sections for different targets are found to follow a universal scaling rule predicted by the ECPSSR.

  9. Experimental limits on the velocities of sodium atoms sputtered from solid surfaces by hydrogen ions. [Na cloud production around Io

    NASA Technical Reports Server (NTRS)

    Stoner, J. O., Jr.

    1976-01-01

    Optical emission at 589.0 nm by sodium atoms sputtered from solid targets by hydrogen molecular ions was observed, and no accompanying broadening or shifts of this line could be detected relative to that from a laboratory lamp. This allowed an upper limit of about 500,000 cm/sec on the mean speed of ejected sodium atoms to be calculated. The results are consistent with the hypothesis that the atomic sodium cloud surrounding Io is produced by this mechanism.

  10. Microsaccade and drift dynamics reflect mental fatigue.

    PubMed

    Di Stasi, Leandro L; McCamy, Michael B; Catena, Andrés; Macknik, Stephen L; Cañas, José J; Martinez-Conde, Susana

    2013-08-01

    Our eyes are always in motion. Even during periods of relative fixation we produce so-called 'fixational eye movements', which include microsaccades, drift and tremor. Mental fatigue can modulate saccade dynamics, but its effects on microsaccades and drift are unknown. Here we asked human subjects to perform a prolonged and demanding visual search task (a simplified air traffic control task), with two difficulty levels, under both free-viewing and fixation conditions. Saccadic and microsaccadic velocity decreased with time-on-task whereas drift velocity increased, suggesting that ocular instability increases with mental fatigue. Task difficulty did not influence eye movements despite affecting reaction times, performance errors and subjective complexity ratings. We propose that variations in eye movement dynamics with time-on-task are consistent with the activation of the brain's sleep centers in correlation with mental fatigue. Covariation of saccadic and microsaccadic parameters moreover supports the hypothesis of a common generator for microsaccades and saccades. We conclude that changes in fixational and saccadic dynamics can indicate mental fatigue due to time-on-task, irrespective of task complexity. These findings suggest that fixational eye movement dynamics have the potential to signal the nervous system's activation state. PMID:23675850

  11. Toroidal universal drift instability: A global gyrokinetic study

    SciTech Connect

    Chowdhury, J.; Ganesh, R. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India); Brunner, S.; Vaclavik, J.; Villard, L. [CRPP, Association EURATOM-Confederation Suisse, EPFL, 1015 Lausanne (Switzerland)

    2010-10-15

    An electron density gradient driven instability identified as the toroidal branch of the universal drift instability is studied using a global gyrokinetic model treating both electrons and ions fully nonadiabatically and valid at all orders in the ratio of the Larmor radius to the wavelength. The physics of the magnetic drift resonance, Landau resonance and transit resonance, which are considered to be important for the toroidal universal mode, are kept for both species. A systematic parametric study is carried out for the mode. The toroidal universal drift mode is observed to sustain finite temperature gradient and can thus coexist with the temperature gradient driven modes and may contribute to the observed particle transport along with other drift modes. Especially at intermediate scales between the ion temperature gradient driven mode and electron temperature gradient driven mode, this branch of the drift instability can also be a plausible candidate for the observed particle loss. The effect of magnetic fluctuations on the mode is also investigated. In contrast to the slab mode, the toroidal branch of the universal drift mode is found to be strongly stabilized by electromagnetic effects at finite plasma {beta}. Finally, the effect of trapped electrons on the universal mode is studied and compared with the other possible modes in the same parameter regime, namely, ion temperature gradient mode in the presence of trapped electrons and pure trapped electron modes.

  12. Gyrokinetic simulation of momentum transport with residual stress from diamagnetic level velocity shears

    SciTech Connect

    Waltz, R. E.; Staebler, G. M. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Solomon, W. M. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543-0451 (United States)

    2011-04-15

    Residual stress refers to the remaining toroidal angular momentum (TAM) flux (divided by major radius) when the shear in the equilibrium fluid toroidal velocity (and the velocity itself) vanishes. Previously [Waltz et al., Phys. Plasmas 14, 122507 (2007); errata 16, 079902 (2009)], we demonstrated with GYRO [Candy and Waltz, J. Comp. Phys. 186, 545 (2003)] gyrokinetic simulations that TAM pinching from (ion pressure gradient supported or diamagnetic level) equilibrium ExB velocity shear could provide some of the residual stress needed to support spontaneous toroidal rotation against normal diffusive loss. Here we show that diamagnetic level shear in the intrinsic drift wave velocities (or ''profile shear'' in the ion and electron density and temperature gradients) provides a comparable residual stress. The individual signed contributions of these small (rho-star level) ExB and profile velocity shear rates to the turbulence level and (rho-star squared) ion energy transport stabilization are additive if the rates are of the same sign. However because of the additive stabilization effect, the contributions to the small (rho-star cubed) residual stress is not always simply additive. If the rates differ in sign, the residual stress from one can buck out that from the other (and in some cases reduce the stabilization.) The residual stress from these diamagnetic velocity shear rates is quantified by the ratio of TAM flow to ion energy (power) flow (M/P) in a global GYRO core simulation of a ''null'' toroidal rotation DIII-D [Mahdavi and Luxon, Fusion Sci. Technol. 48, 2 (2005)] discharge by matching M/P profiles within experimental uncertainty. Comparison of global GYRO (ion and electron energy as well as particle) transport flow balance simulations of TAM transport flow in a high-rotation DIII-D L-mode quantifies and isolates the ExB shear and parallel velocity (Coriolis force) pinching components from the larger ''diffusive'' parallel velocity shear driven component and the much smaller profile shear residual stress component.

  13. Gyrokinetic simulation of momentum transport with residual stress from diamagnetic level velocity shears

    NASA Astrophysics Data System (ADS)

    Waltz, R. E.; Staebler, G. M.; Solomon, W. M.

    2011-04-01

    Residual stress refers to the remaining toroidal angular momentum (TAM) flux (divided by major radius) when the shear in the equilibrium fluid toroidal velocity (and the velocity itself) vanishes. Previously [Waltz et al., Phys. Plasmas 14, 122507 (2007); errata 16, 079902 (2009)], we demonstrated with GYRO [Candy and Waltz, J. Comp. Phys. 186, 545 (2003)] gyrokinetic simulations that TAM pinching from (ion pressure gradient supported or diamagnetic level) equilibrium E ×B velocity shear could provide some of the residual stress needed to support spontaneous toroidal rotation against normal diffusive loss. Here we show that diamagnetic level shear in the intrinsic drift wave velocities (or "profile shear" in the ion and electron density and temperature gradients) provides a comparable residual stress. The individual signed contributions of these small (rho-star level) E ×B and profile velocity shear rates to the turbulence level and (rho-star squared) ion energy transport stabilization are additive if the rates are of the same sign. However because of the additive stabilization effect, the contributions to the small (rho-star cubed) residual stress is not always simply additive. If the rates differ in sign, the residual stress from one can buck out that from the other (and in some cases reduce the stabilization.) The residual stress from these diamagnetic velocity shear rates is quantified by the ratio of TAM flow to ion energy (power) flow (M/P) in a global GYRO core simulation of a "null" toroidal rotation DIII-D [Mahdavi and Luxon, Fusion Sci. Technol. 48, 2 (2005)] discharge by matching M/P profiles within experimental uncertainty. Comparison of global GYRO (ion and electron energy as well as particle) transport flow balance simulations of TAM transport flow in a high-rotation DIII-D L-mode quantifies and isolates the E ×B shear and parallel velocity (Coriolis force) pinching components from the larger "diffusive" parallel velocity shear driven component and the much smaller profile shear residual stress component.

  14. Ion cyclotron and spin-flip emissions from fusion products in tokamaks

    SciTech Connect

    Arunasalam, V.; Greene, G.J.; Young, K.M.

    1993-02-01

    Power emission by fusion products of tokamak plasmas in their ion cyclotron range of frequencies (ICRF) and at their spin-flip resonance frequency is calculated for some specific model fusion product velocity-space distribution functions. The background plasma of say deuterium (D) is assumed to be in equilibrium with a Maxwellian distribution both for the electrons and ions. The fusion product velocity distributions analyzed here are: (1) A monoenergetic velocity space ring distribution. (2) A monoenergetic velocity space spherical shell distribution. (3) An anisotropic Maxwellian distribution with T [perpendicular] [ne] T[parallel]and with appreciable drift velocity along the confining magnetic field. Single dressed'' test particle spontaneous emission calculations are presented first and the radiation temperature for ion cyclotron emission (ICE) is analyzed both for black-body emission and nonequilibrium conditions. Thresholds for instability and overstability conditions are then examined and quasilinear and nonlinear theories of the electromagnetic ion cyclotron modes are discussed. Distinctions between kinetic or causal instabilities'' and hydrodynamic instabilities'' are drawn and some numerical estimates are presented for typical tokamak parameters. Semiquantitative remarks are offered on wave accessibility, mode conversion, and parametric decay instabilities as possible for spatially localized ICE. Calculations are carried out both for k[parallel] = 0 for k[parallel] [ne] 0. The effects of the temperature anisotropy and large drift velocities in the parallel direction are also examined. Finally, proton spin-flip resonance emission and absorption calculations are also presented both for thermal equilibrium conditions and for an inverted'' population of states.

  15. Ion cyclotron and spin-flip emissions from fusion products in tokamaks

    SciTech Connect

    Arunasalam, V.; Greene, G.J.; Young, K.M.

    1993-02-01

    Power emission by fusion products of tokamak plasmas in their ion cyclotron range of frequencies (ICRF) and at their spin-flip resonance frequency is calculated for some specific model fusion product velocity-space distribution functions. The background plasma of say deuterium (D) is assumed to be in equilibrium with a Maxwellian distribution both for the electrons and ions. The fusion product velocity distributions analyzed here are: (1) A monoenergetic velocity space ring distribution. (2) A monoenergetic velocity space spherical shell distribution. (3) An anisotropic Maxwellian distribution with T {perpendicular} {ne} T{parallel}and with appreciable drift velocity along the confining magnetic field. Single ``dressed`` test particle spontaneous emission calculations are presented first and the radiation temperature for ion cyclotron emission (ICE) is analyzed both for black-body emission and nonequilibrium conditions. Thresholds for instability and overstability conditions are then examined and quasilinear and nonlinear theories of the electromagnetic ion cyclotron modes are discussed. Distinctions between ``kinetic or causal instabilities`` and ``hydrodynamic instabilities`` are drawn and some numerical estimates are presented for typical tokamak parameters. Semiquantitative remarks are offered on wave accessibility, mode conversion, and parametric decay instabilities as possible for spatially localized ICE. Calculations are carried out both for k{parallel} = 0 for k{parallel} {ne} 0. The effects of the temperature anisotropy and large drift velocities in the parallel direction are also examined. Finally, proton spin-flip resonance emission and absorption calculations are also presented both for thermal equilibrium conditions and for an ``inverted`` population of states.

  16. Drifts of electron orbits induced by toroidal electric field in tokamaks

    NASA Astrophysics Data System (ADS)

    Abdullaev, S. S.

    2015-03-01

    The drifts of electron orbits induced by the toroidal electric field in tokamaks are analyzed. Based on the relativistic Hamiltonian equations for guiding centre motion, the formula for the drift velocity vdr is derived. It describes the outward drift of passing particles as well as the inward drift (the Ware pinch) of trapped particles. Unlike the approximate formula for vdr given in Guan et al. [Phys. Plasmas 17, 092502 (2010)] for circular electron orbits, it describes qualitatively new features of the outward drift of electron orbits. Particularly, the new formula describes the evolution of the orbit's shape, the formation of X-point and the associated separatrix. It is shown that the outward drift velocity is proportional to the inverse aspect ratio of tokamaks.

  17. Molecular Communication Using Brownian Motion with Drift

    E-print Network

    Kadloor, Sachin; Eckford, Andrew W

    2010-01-01

    Inspired by biological communication systems, molecular communication has been proposed as a viable scheme to communicate between nano-sized devices separated by a very short distance. Here, molecules are released by the transmitter into the medium, which are then sensed by the receiver. This paper develops a preliminary version of such a communication system focusing on the release of either one or two molecules into a fluid medium with drift. We analyze the mutual information between transmitter and the receiver when information is encoded in the time of release of the molecule. Simplifying assumptions are required in order to calculate the mutual information, and theoretical results are provided to show that these calculations are upper bounds on the true mutual information. Furthermore, optimized degree distributions are provided, which suggest transmission strategies for a variety of drift velocities.

  18. Coupled-cavity drift-tube linac

    DOEpatents

    Billen, James H. (Los Alamos, NM)

    1996-01-01

    A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the .pi.-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is .beta..lambda., where .lambda. is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a .pi./2 structure mode so the coupling cavities are nominally unexcited. The CCDTL configuration provides an rf structure with high shunt impedance for intermediate velocity charged particles, i.e., particles with energies in the 20-200 MeV range.

  19. Quantum-limited velocity readout and quantum feedback cooling of a trapped ion via electromagnetically induced transparency

    NASA Astrophysics Data System (ADS)

    Rabl, P.; Steixner, V.; Zoller, P.

    2005-10-01

    We discuss continuous observation of the momentum of a single atom by employing the high velocity sensitivity of the index of refraction in a driven ? -system based on electromagnetically induced transparency. In the ideal limit of unit collection efficiency this provides a quantum-limited measurement with minimal backaction on the atomic motion. A feedback loop, which drives the atom with a force proportional to measured signal, provides a cooling mechanism for the atomic motion. We derive the master equation which describes the feedback cooling and show that in the Lamb-Dicke limit the steady state energies are close to the ground state, limited only by the photon collection efficiency. Outside of the Lamb-Dicke regime the predicted temperatures are well below the Doppler limit.

  20. Summary The ARGUS Drift

    E-print Network

    H. Hasemann

    The use of pure heavy hydrocarbons like propane or isobutane has some advantages for drift chaders that measure the specific ionisation for particle identification. With a prototype of the ARGUS drift chamber various gases were tested with a 3 GeV/c electron beam. We found a dE/dx resolution for propane of Fwhm = 10.4% and for isobutane Fwhm = 9.9X, by a factor of + 1.6 better than that for argon-methane (92:8) mixture with Fwhm = 16.4%. This improvement corresponds to an increase in effective gas length by a factor of 4 compared to pure argon. In isobutane and propane we found a broadening of the 55Fe-pulseheight spectrum with increasing gas amplification,showing in isobutane a clear two peak structure for gas amplifications above-3 l 104. However, neither gas showed a broadening of the truncated Landau distribution for electrons.

  1. {ital L}{sub 3}-subshell alignment in gold and bismuth induced by low-velocity carbon ions

    SciTech Connect

    Mitra, D.; Sarkar, M.; Bhattacharya, D.; Chatterjee, M.B.; Sen, P. [Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Calcutta 700064 (India)] [Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Calcutta 700064 (India); Kuri, G.; Mahapatra, D.P. [Institute of Physics, Bhubaneswar, Orissa 751005 (India)] [Institute of Physics, Bhubaneswar, Orissa 751005 (India); Lapicki, G. [Department of Physics, East Carolina University, Greenville, North Carolina 27858 (United States)] [Department of Physics, East Carolina University, Greenville, North Carolina 27858 (United States)

    1996-04-01

    Angular distribution of the {ital L}{sub {ital l}} x-ray line (3{ital s}{sub 1/2}{r_arrow}2{ital p}{sub 3/2}) in Au and Bi induced by 3{endash}9 MeV carbon ions has been measured. Values of the alignment parameter ({ital A}{sub 2}) of the {ital L}{sub 3}(2{ital p}{sub 3/2}) subshell have been obtained from the data as a function of the carbon ion energy. The data have been compared with the calculations of the standard perturbed-stationary-state (PSS) theory with energy-loss (E), Coulomb deflection (C), and relativistic (R) corrections (ECPSSR) and ECPSSR with the intrashell (IS) effect included as a multiplicative factor. From this comparison it is evident that an account for the IS coupling substantially improves agreement between theory and measurement. The effect of simultaneous multiple ionization of the {ital M} and higher shells on the measured {ital A}{sub 2} values is discussed. {copyright} {ital 1996 The American Physical Society.}

  2. A spatially resolving x-ray crystal spectrometer for measurement of ion-temperature and rotation-velocity profiles on the Alcator C-Mod tokamak.

    PubMed

    Hill, K W; Bitter, M L; Scott, S D; Ince-Cushman, A; Reinke, M; Rice, J E; Beiersdorfer, P; Gu, M-F; Lee, S G; Broennimann, Ch; Eikenberry, E F

    2008-10-01

    A new spatially resolving x-ray crystal spectrometer capable of measuring continuous spatial profiles of high resolution spectra (lambda/d lambda>6000) of He-like and H-like Ar K alpha lines with good spatial (approximately 1 cm) and temporal (approximately 10 ms) resolutions has been installed on the Alcator C-Mod tokamak. Two spherically bent crystals image the spectra onto four two-dimensional Pilatus II pixel detectors. Tomographic inversion enables inference of local line emissivity, ion temperature (T(i)), and toroidal plasma rotation velocity (upsilon(phi)) from the line Doppler widths and shifts. The data analysis techniques, T(i) and upsilon(phi) profiles, analysis of fusion-neutron background, and predictions of performance on other tokamaks, including ITER, will be presented. PMID:19044482

  3. Fermilab drift tube Linac revisited

    SciTech Connect

    Milorad Popovic

    2004-05-12

    Using the PARMILA code running under PC-WINDOWS, the present performance of the Fermilab Drift Tube Linac has been analyzed in the light of new demands on the Linac/Booster complex (the Proton Source). The Fermilab Drift Tube Linac (DTL) was designed in the sixties as a proton linac with a final energy of 200 MeV and a peak current of 100mA. In the seventies, in order to enable multi-turn charge exchange injection into the Booster, the ion source was replaced by an H- source with a peak beam current of 25mA. Since then the peak beam current was steadily increased up to 55mA. In the early nineties, part of the drift tube structure was replaced with a side-coupled cavity structure in order to increase the final energy to 400 MeV. The original and still primary purpose of the linac is to serve as the injector for the Booster. As an added benefit, the Neutron Therapy Facility (NTF) was built in the middle seventies. It uses 66MeV protons from the Linac to produce neutrons for medical purposes. The Linac/Booster complex was designed to run at a fundamental cycling rate of 15Hz, but beam is accelerated on every cycle only when NTF is running. Until recently the demand from the High Energy Physics program resulted in an average linac beam repetition rate of order 1 Hz. With the MiniBoone experiment and the NuMI program, the demands on the Proton Source have changed, with emphasis on higher beam repetition rates up to 7.5Hz. Historically the beam losses in the linac were small, localized at one spot, so activation was not an important issue. With higher beam rate, this has the potential to become the dominant issue. Until today all tuning in the linac and Proton Source was governed by two goals: to maximize the peak beam current out of the linac and to minimize the beam losses in the linac. If maximal peak current from the linac is no longer a primary goal, then the linac quadrupoles can be adjusted differently to achieve different goals.

  4. Drift in supported membranes

    NASA Astrophysics Data System (ADS)

    Prasad, Ashok; Kondev, Jané; Stone, Howard A.

    2007-11-01

    An object moving in a fluid transports the fluid along the direction of its motion. Using the concept of drift, i.e., the net motion of a small volume of fluid or a tracer particle due to a moving body, we quantify this entrainment for an inclusion in a supported lipid bilayer membrane. Our analysis demonstrates that a moving object in a supported membrane transports a small volume of fluid by a significant distance only when the initial position of the fluid volume in question is within a distance ? from the line of motion, where ? is the screening length of the membrane. The total area swept out by a line of such fluid volume elements, initially at rest and oriented perpendicular to the direction of motion, is the drift area. We show that the drift area is related quadratically to the screening length. These calculations suggest that dynamic domains of entrained lipids of size ? form spontaneously around moving objects in supported membranes due to hydrodynamic interactions. This effect is potentially important for transport processes in biological and artificial membranes.

  5. Macroinvertebrate drift in a Rocky Mountain stream

    Microsoft Academic Search

    J. David Allan

    1987-01-01

    An extensive series of drift collections from a Rocky Mountain stream was used to investigate quantitative patterns in the taxonomic composition of drift throughout spring, summer and fall for 1975–1978. Drift was estimated by drift rate, the number of organisms drifting past a point per 24 h; and by drift density, the numbers of organisms collected per 100 m3 of

  6. Emplacement Drift System Description Document

    SciTech Connect

    Eric Loros

    2001-07-31

    The Emplacement Drift System is part of the Engineered Barrier System and provides the interface between the various waste package (WP) systems and the Ground Control System. In conjunction with the various WPs, the Emplacement Drift System limits the release and transport of radionuclides from the WP to the Natural Barrier following waste emplacement. Collectively, the Emplacement Drift System consists of the structural support hardware (emplacement drift invert and WP emplacement pallet) and any performance-enhancing barriers (drip shields and invert ballast) installed or placed in the emplacement drifts. The Emplacement Drift System is entirely located within the emplacement drifts in the subsurface portion of the Monitored Geologic Repository (MGR); specifically, it is physically bounded by the Subsurface Facility System, the Ground Support System, and the Natural Barrier. The Emplacement Drift System supports the key MGR functions of limiting radionuclide release to the Natural Barrier, minimizing the likelihood of a criticality external to the WPs, limiting natural and induced environmental effects, and providing WP support. The Emplacement Drift System limits radionuclide release to the Natural Barrier by controlling the movement of radionuclides within the emplacement drift and to the Natural Barrier, and by limiting water contact with the WPs. The Emplacement Drift System provides physical support and barriers for emplaced WPs that reduce water contact. The Emplacement Drift WP spacing supports the thermal loading performance by complimenting drift layout and orientation as described in the system description document for the Subsurface Facility System. The Emplacement Drift System supports the WP and also provides an environment that aids in enhancing WP confinement performance. As part of the Engineered Barrier System, the Emplacement Drift System interfaces with the WP systems. The Emplacement Drift System also interfaces with the Natural Barrier, Subsurface Facility System, and Ground Control System for the space and location of emplaced WPs, for the controlled release of radionuclides, and for controlling the heat, chemical, and physical effects that interact between these systems. The Emplacement Drift System interfaces with the Subsurface Ventilation System for preclosure heat removal from WPs. The Emplacement Drift System interfaces with the Waste Emplacement/Retrieval System and the Performance Confirmation Emplacement Drift Monitoring System for equipment clearance for the emplacement, retrieval, and monitoring of waste.

  7. The Electron Drift Technique for Measuring Electric and Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Paschmann, G.; McIlwain, C. E.; Quinn, J. M.; Torbert, R. B.; Whipple, E. C.; Christensen, John (Technical Monitor)

    1998-01-01

    The electron drift technique is based on sensing the drift of a weak beam of test electrons that is caused by electric fields and/or gradients in the magnetic field. These quantities can, by use of different electron energies, in principle be determined separately. Depending on the ratio of drift speed to magnetic field strength, the drift velocity can be determined either from the two emission directions that cause the electrons to gyrate back to detectors placed some distance from the emitting guns, or from measurements of the time of flight of the electrons. As a by-product of the time-of-flight measurements, the magnetic field strength is also determined. The paper describes strengths and weaknesses of the method as well as technical constraints.

  8. Pulsed-laser deposition of diamond-like carbon: Relations between laser fluence, velocity of carbon ions, and bonding in the films

    NASA Astrophysics Data System (ADS)

    Koivusaari, K. J.; Levoska, J.; Leppävuori, S.

    1999-03-01

    In the pulsed-laser deposition process, high intensity laser pulses expel material from a solid target and form expanding plasma near the solid surface. The expansion of the plasma produces a forward-directed beam of ionized and neutral species with typical energies of 1-100 eV. In this study, amorphous diamond-like carbon (DLC) thin films were deposited onto silicon substrates at room temperature using an XeCl excimer laser (wavelength 308 nm, pulse length 20 ns) with laser fluences in the range 5-45 J cm-2, on a pyrolytic graphite target. The effect of laser fluence on the velocity and kinetic energy distribution of carbon ions was measured by time-of-flight (TOF) spectrometry using a system based on a Faraday cup with biased grids, and a multichannel plate based particle detector. We have found high kinetic energies, up to 500 eV, for expelled atomic species. In order to study the effect of the energy of the arriving ions on the structure of DLC, the bonding of carbon atoms in films, deposited under similar conditions as in the TOF measurements, was studied by x-ray absorption near-edge structure.

  9. Pre-sheath density drop induced by ion-neutral friction along plasma blobs and implications for blob velocities

    SciTech Connect

    Furno, I.; Chabloz, V.; Fasoli, A.; Loizu, J. [Centre de Recherches en Physique des Plasmas-Ecole Polytechnique Fédérale de Lausanne, Association EURATOM-Confédération Suisse, CH-1015 Lausanne (Switzerland)] [Centre de Recherches en Physique des Plasmas-Ecole Polytechnique Fédérale de Lausanne, Association EURATOM-Confédération Suisse, CH-1015 Lausanne (Switzerland); Theiler, C. [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States)] [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States)

    2014-01-15

    The pre-sheath density drop along the magnetic field in field-aligned, radially propagating plasma blobs is investigated in the TORPEX toroidal experiment [Fasoli et al., Plasma Phys. Controlled Fusion 52, 124020 (2010)]. Using Langmuir probes precisely aligned along the magnetic field, we measure the density n{sub se} at a poloidal limiter, where blobs are connected, and the upstream density n{sub 0} at a location half way to the other end of the blobs. The pre-sheath density drop n{sub se}/n{sub 0} is then computed and its dependence upon the neutral background gas pressure is studied. At low neutral gas pressures, the pre-sheath density drop is ?0.4, close to the value of 0.5 expected in the collisionless case. In qualitative agreement with a simple model, this value decreases with increasing gas pressure. No significant dependence of the density drop upon the radial distance into the limiter shadow is observed. The effect of reduced blob density near the limiter on the blob radial velocity is measured and compared with predictions from a blob speed-versus-size scaling law [Theiler et al., Phys. Rev. Lett. 103, 065001 (2009)].

  10. Effects of Variable Flows on Invertebrate Drift in Two Spring Runs in Comal Springs, Texas, USA

    NASA Astrophysics Data System (ADS)

    Arsuffi, T.; Norris, C. W.

    2005-05-01

    Comal Springs, TX, the largest spring in the western U.S., experiences anthropogenic flow reductions. Drift sampling evaluated the effects of fluctuating flow on quantitative patterns and taxonomic composition of invertebrate drift. The composition, abundance, and seasonal patterns of drift varied between runs. Invertebrate drift was greater (2x) at night than by day and marked crepuscular peaks in drift activity, common in streams throughout the world, were observed in only one spring run. Multiple regression analysis of the total drift rate and drift density in each spring run was performed with water depth, current velocity, and Julian day as independent variables. Significant relationships were found in spring run 1, but not in spring run 3. Simple linear correlations between drift of individual taxa in each spring run and the three independent variables showed significant negative relationships to current velocity and water depth, while drift rate and density of several taxa in spring run 3 showed significant positive relationships to current velocity. This indicates differences in habitat and organism ecology between the spring runs may cause different responses to variable flows. Such insects may be used as indicators of hydrological change and used to predict critical flow levels and aquifer management targets.

  11. Quaternary contourite drifts of the Western Spitsbergen margin

    NASA Astrophysics Data System (ADS)

    Rebesco, Michele; Wåhlin, Anna; Laberg, Jan Sverre; Schauer, Ursula; Beszczynska-Möller, Agnieszka; Lucchi, Renata Giulia; Noormets, Riko; Accettella, Daniela; Zarayskaya, Yulia; Diviacco, Paolo

    2013-09-01

    The study of contourite drifts is an increasingly used tool for understanding the climate history of the oceans. In this paper we analyse two contourite drifts along the continental margin west of Spitsbergen, just south of the Fram Strait where significant water mass exchanges impact the Arctic climate. We detail the internal geometry and the morphologic characteristics of the two drifts on the base of multichannel seismic reflection data, sub-bottom profiles and bathymetry. These mounded features, that we propose to name Isfjorden and Bellsund drifts, are located on the continental slope between 1200 and 1800 m depth, whereas the upper slope is characterized by reduced- or non-deposition. The more distinct Isfjorden Drift is about 25 km wide and 45 km long, and over 200 ms TWT thick. We revise the 13 years-long time series of velocity, temperature, and salinity obtained from a mooring array across the Fram Strait. Two distinct current cores are visible in the long-term average. The shallower current core has an average northward velocity of about 20 cm/s, while the deeper bottom current core at about 1450 m depth has an average northward velocity of about 9 cm/s. We consider Norwegian Sea Deep Water episodically ventilated by relatively dense and turbid shelf water from the Barents Sea responsible for the accumulation of the contourites. The onset of the drift growth west of Spitsbergen is inferred to be about 1.3 Ma and related to the Early Pleistocene glacial expansion recorded in the area. The lack of mounded contouritic deposits on the continental slope of the Storfjorden is related to consecutive erosion by glacigenic debris flows. The Isfjorden and Bellsund drifts are inferred to contain the record of the regional palaeoceanography and glacial history and may constitute an excellent target of future scientific drilling.

  12. Electromagnetic nonlinear gyrokinetics with polarization drift

    SciTech Connect

    Duthoit, F.-X. [SNU Division of Graduate Education for Sustainabilization of Foundation Energy, Seoul National University, Gwanak-ro 1, Gwanak-gu, 151-744 Seoul (Korea, Republic of); Hahm, T. S., E-mail: tshahm@snu.ac.kr [Department of Nuclear Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, 151-744 Seoul (Korea, Republic of); Wang, Lu [College of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

    2014-08-15

    A set of new nonlinear electromagnetic gyrokinetic Vlasov equation with polarization drift and gyrokinetic Maxwell equations is systematically derived by using the Lie-transform perturbation method in toroidal geometry. For the first time, we recover the drift-kinetic expression for parallel acceleration [R. M. Kulsrud, in Basic Plasma Physics, edited by A. A. Galeev and R. N. Sudan (North-Holland, Amsterdam, 1983)] from the nonlinear gyrokinetic equations, thereby bridging a gap between the two formulations. This formalism should be useful in addressing nonlinear ion Compton scattering of intermediate-mode-number toroidal Alfvén eigenmodes for which the polarization current nonlinearity [T. S. Hahm and L. Chen, Phys. Rev. Lett. 74, 266 (1995)] and the usual finite Larmor radius effects should compete.

  13. Laced permanent magnet quadrupole drift tube magnets

    SciTech Connect

    Feinberg, B.; Behrsing, G.U.; Halbach, K.; Marks, J.S.; Morrison, M.E.; Nelson, D.H.

    1989-03-01

    Twenty-three laced permanent magnet quadrupole drift tube magnets have been constructed, tested, and installed in the SuperHILAC heavy ion linear accelerator at LBL, marking the first accelerator use of this new type of quadrupole. The magnets consist of conventional tape-wound quadrupole electromagnets, using iron pole-pieces, with permanent magnet material (samarium cobalt) inserted between the poles to reduce the effects of saturation. The iron is preloaded with magnetic flux generated by the permanent magnet material, resulting in an asymmetrical saturation curve. Since the polarity of the individual quadrupole magnets in a drift tube linac is never reversed, we can take advantage of this asymmetrical saturation to provide about 20% greater focusing strength than is available with conventional quadrupoles, while replacing the vanadium permendur poletips with iron poletips. Comparisons between these magnets and conventional tape-wound quadrupoles will be presented. 3 refs., 5 figs.

  14. Electromagnetic nonlinear gyrokinetics with polarization drift

    NASA Astrophysics Data System (ADS)

    Duthoit, F.-X.; Hahm, T. S.; Wang, Lu

    2014-08-01

    A set of new nonlinear electromagnetic gyrokinetic Vlasov equation with polarization drift and gyrokinetic Maxwell equations is systematically derived by using the Lie-transform perturbation method in toroidal geometry. For the first time, we recover the drift-kinetic expression for parallel acceleration [R. M. Kulsrud, in Basic Plasma Physics, edited by A. A. Galeev and R. N. Sudan (North-Holland, Amsterdam, 1983)] from the nonlinear gyrokinetic equations, thereby bridging a gap between the two formulations. This formalism should be useful in addressing nonlinear ion Compton scattering of intermediate-mode-number toroidal Alfvén eigenmodes for which the polarization current nonlinearity [T. S. Hahm and L. Chen, Phys. Rev. Lett. 74, 266 (1995)] and the usual finite Larmor radius effects should compete.

  15. Drift of domain walls of the ab type in weak ferromagnets

    Microsoft Academic Search

    V. S. Gerasimchuk; A. A. Shitov

    2002-01-01

    The drift motion of 180° domain walls of the ab type in a weak ferromagnet in an elastic stress field created by a sound wave propagating parallel or perpendicular to the plane of the domain wall is investigated. The dependence of the domain-wall drift velocity on the direction, amplitude, and polarization of the sound wave is found. The conditions for

  16. Effect of vertical drifts on the electron concentration distribution in the ionosphere F region

    Microsoft Academic Search

    A. G. Khantadze; R. G. Gachechiladze; B. Ia. Chekhoshvili

    1976-01-01

    Results of computer numerical integration of the continuity equation for electrons, with vertical drift independent of height or of time taken into account, are reported. Simplifications gained by assuming a height dependence of the continuity equation are put aside for the more involved and more exact numerical solution. Electron density profiles are plotted for assigned drift velocities as a function

  17. A Gyrostabilizer Drift Model: Autonomous Identification by the Inverse Sensitivity Method

    Microsoft Academic Search

    I. V. Shcherban’; O. G. Shcherban’

    2005-01-01

    The concept of the inverse sensitivity problem is used to design a method for autonomous (on-board) identification of the drift velocity of a gyrostabilizer when there is no possibility for laboratory experimentation. Results obtained by this method on identification of the drift of a three-degree gyrostabilizer are given.

  18. Drift-diffusion kinetics of a confined colloid Yves Leroyer and Alois Wrger

    E-print Network

    Paris-Sud XI, Université de

    Drift-diffusion kinetics of a confined colloid Yves Leroyer and Alois Würger CPMOH, Université. As a possible application, we discuss confined colloidal suspensions subject to an external field. I coef- ficient or drift velocity affect the mean first-passage time [5--7]. In colloid science

  19. Magnetic conjugate point observations of kilometer and hundred-meter scale irregularities and zonal drifts

    NASA Astrophysics Data System (ADS)

    de Paula, E. R.; Muella, M. T. A. H.; Sobral, J. H. A.; Abdu, M. A.; Batista, I. S.; Beach, T. L.; Groves, K. M.

    2010-08-01

    The Conjugate Point Equatorial Experiment (COPEX) campaign was carried out in Brazil, between October and December 2002, to study the conjugate nature of plasma bubble irregularities and to investigate their generation mechanisms, development characteristics, spatial-temporal distribution, and dynamics. In this work we will focus mainly on the zonal spaced GPS (1.575 GHz) and VHF (250 MHz) receivers' data collected simultaneously at two magnetic conjugate sites of the COPEX geometry: Boa Vista and Campo Grande. These GPS/VHF receivers were set up to detect the equatorial scintillations and to measure ionospheric scintillation pattern velocities. Then, the zonal irregularity drift velocities were estimated by applying a methodology that corrects the effects caused by vertical drifts and geometrical factors. The results reveal the coexistence of kilometer- (VHF) and hundred-meter-scale (GPS L-band) irregularities into the underlying depletion structure. Over the conjugate site of Campo Grande, the average zonal velocity at VHF seems to be consistently larger than the estimated GPS velocities until ˜0200 UT, whereas over Boa Vista the irregularities detected from both techniques are drifting with comparable velocities. The hundred-meter-scale structures causing L-band scintillations appear to be drifting with comparable velocities over both the conjugate sites, whereas the kilometer-scale structures are drifting over Campo Grande with larger average velocities (before 0300 UT). Complementary data of ionospheric parameters scaled from collocated digital ionosondes are used in the analysis to explain differences/similarities on the scintillation/zonal drift results.

  20. Ion soliton observation with laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Claire, N.; Bachet, G.; Skiff, F.

    2003-12-01

    Many theoretical and experimental studies of solitons in plasma have been performed [Phys. Fluids 16 (1973) 1668; Plasma Phys. 25 (1983) 943; IEEE Trans. Plasma Phys. PS 10 (1982) 180; Plasma Phys. 5 (1998) 4144] and most of the properties such as the relation between the amplitude, the velocity and the width, for soliton or soliton-dust interaction, have been obtained. The agreement between experiment and theoretical model is not always good [Phil. Mag. Ser. 39 (1895) 422; Phys. Rev. Lett. 17 (1966) 996; Phys. Rev. E 51 (1995) 4796]. The experimental observations typically involve Langmuir probes. However, the ion acoustic soliton propagation can be observed by laser induced fluorescence (LIF) in double plasma device. This direct observation of ion perturbation with LIF points out the importance of the optical pumping effect [Rev. Sci. Instrum. 72 (2001) 4372] in the measurement of fast velocity propagation of ion phenomena like solitons are. With the LIF we discovered that a train of soliton propagates easier in the device if a weak backward ion flux plasma, having a drift velocity in the range of 200 m/s is present; as faster the ion flux is, as close to the grid the solitons separation occurs; the precursors ions is in fact a collective phenomenon.

  1. Relationship between vertical ExB drift and F2-layer characteristics in the equatorial ionosphere at solar minimum conditions

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi S.

    2012-07-01

    Equatorial and low-latitude electrodynamics plays a dominant role in determining the structure and dynamics of the equatorial and low-latitude ionospheric F-region. Thus, they constitute essential input parameters for quantitative global and regional modeling studies. In this work, hourly median value of ionosonde measurements namely, peak height F2-layer (hmF2), F2-layer critical frequency (foF2) and propagation factor M(3000)F2 made at near equatorial dip latitude, Ouagadougou, Burkina Faso (12oN, 1.5oW; dip: 1.5oN) and relevant F2-layer parameters such as thickness parameter (Bo), electron temperature (Te), ion temperature (Ti), total electron content (TEC) and electron density (Ne, at the fixed altitude of 300 km) provided by the International Reference Ionosphere (IRI) model for the longitude of Ouagadougou are contrasted with the IRI vertical drift model to explore in detail the monthly climatological behavior of equatorial ionosphere and the effects of equatorial vertical plasma drift velocities on the diurnal structure of F2-layer parameters. The analysis period covers four months representative of solstitial and equinoctial seasonal periods during solar minimum year of 1987 for geomagnetically quiet-day. We show that month-by-month morphological patterns between vertical E×B drifts and F2-layer parameters range from worst to reasonably good and are largely seasonally dependent. A cross-correlation analysis conducted between equatorial drift and F2-layer characteristics yield statistically significant correlations for equatorial vertical drift and IRI-Bo, IRI-Te and IRI-TEC, whereas little or no acceptable correlation is obtained with observational evidence. Assessment of the association between measured foF2, hmF2 and M(3000)F2 illustrates consistent much more smaller correlation coefficients with no systematic linkage. In general, our research indicates strong departure from simple electrodynamically controlled behavior.

  2. Describing Velocity

    NSDL National Science Digital Library

    The Concord Consortium

    2012-02-07

    Learn to connect position-time and velocity-time graphs. Explore velocity using an animated car icon connected to either a position-time or a velocity-time graph, or both. Then investigate other motion graphs. Describing Velocity is the fourth of five SmartGraphs activities designed for a typical physical science unit of study on the motion of objects.

  3. The DRIFT Dark Matter Experiments

    Microsoft Academic Search

    E. Daw; A. Dorofeev; J. R. Fox; J.-L. Gauvreau; C. Ghag; L. J. Harmon; J. L. Harton; M. Gold; E. R. Lee; D. Loomba; E. H. Miller; A. St. J. Murphy; S. M. Paling; J. M. Landers; N. Phan; M. Pipe; K. Pushkin; M. Robinson; S. W. Sadler; D. P. Snowden-Ifft; N. J. C. Spooner; D. Walker; D. Warner

    2011-01-01

    The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Boulby Mine is presented, including the latest limits on the WIMP spin-dependent cross-section from 1.5 kg days of running with a mixture of CS2 and CF4. Planned upgrades to DRIFT IId are detailed, along with ongoing work towards DRIFT III, which aims to be the world's first

  4. Inhomogeneity scale lengths in a magnetized, low-temperature, collisionless, Q-machine plasma column containing perpendicular-velocity shear

    SciTech Connect

    Reynolds, E. W.; Koepke, M. E.; Carroll, J. J.; Shinohara, S. [Department of Physics, West Virginia University, Morgantown, West Virginia 26505-6315 (United States); Department of Physics and Astronomy, Eastern Michigan University, Ypsilanti, Michigan 48197 (United States); Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan)

    2006-09-15

    Radial inhomogeneity scale lengths for radial electric field, ion density, and magnetic-field-aligned (parallel) electron-drift velocity have been measured and interpreted in magnetized, low-temperature, collisionless plasma. The effect of a narrow layer of inhomogeneity in these parameters on the excitation of electrostatic ion-cyclotron waves is investigated. When the ion Larmor radius {rho}{sub i} is on the order of, or larger than, the half-width at half-maximum {sigma}{sub r}{l_brace}E{sub r}{r_brace} of the Gaussian-like, radially localized, radial electric-field profile E{sub r}(r), the radial profile of the azimuthal ion rotation velocity, measured using laser-induced fluorescence (LIF), has a peak that, because of finite-Larmor-radius effects, is significantly lower than the peak of the combined radial profile of the ExB and diamagnetic drift velocities. Results of an experimentally validated test-particle simulation are presented and applied using experimentally relevant electric-field profiles. Two experimental configurations are explored for which the ions enter into the electric field at different rates. In one configuration, the ions experience an effectively adiabatic increase in electric-field strength. In the other configuration, the increase in electric-field strength is effectively instantaneous. The simulation reproduces both the main features of the radial profile of LIF-measured ion flow and the observed density depletion in regions of relatively high plasma potential for experimental conditions in which no waves were observed. The density depletion is interpreted as resulting from the finite-Larmor-radius ion orbits in the presence of an inhomogeneous electric field with radial scale length {sigma}{sub r}{l_brace}E{sub r}{r_brace}{approx_equal}{rho}{sub i}.

  5. Interferometric phase velocity measurements

    NASA Technical Reports Server (NTRS)

    Kintner, P. M.; Labelle, J.; Kelley, M. C.; Cahill, L. J., Jr.; Moore, T.; Arnoldy, R.

    1984-01-01

    Phase velocities of plasma waves near the lower hybrid frequency were measured with an interferometer composed of two spatially separated electron-density probes. The plasma waves were produced in the F-region ionosphere by an argon ion beam. By calculating the normalized cross spectrum of the plasma waves a coherency of .98 was estimated along with a maximum phase difference of pi/3 radians between the two probes. This implies that the wavelength was 6 meters compared to an O(+) gyroradius of 3.8 meters, and that the phase velocity was 45 km/sec compared to an ion-beam velocity of 12.4 km/sec. These numbers compare favorably with recent predictions of a nonresonant mode produced by a dense ion beam.

  6. Drift-Scale Radionuclide Transport

    SciTech Connect

    J. Houseworth

    2004-09-22

    The purpose of this model report is to document the drift scale radionuclide transport model, taking into account the effects of emplacement drifts on flow and transport in the vicinity of the drift, which are not captured in the mountain-scale unsaturated zone (UZ) flow and transport models ''UZ Flow Models and Submodels'' (BSC 2004 [DIRS 169861]), ''Radionuclide Transport Models Under Ambient Conditions'' (BSC 2004 [DIRS 164500]), and ''Particle Tracking Model and Abstraction of Transport Process'' (BSC 2004 [DIRS 170041]). The drift scale radionuclide transport model is intended to be used as an alternative model for comparison with the engineered barrier system (EBS) radionuclide transport model ''EBS Radionuclide Transport Abstraction'' (BSC 2004 [DIRS 169868]). For that purpose, two alternative models have been developed for drift-scale radionuclide transport. One of the alternative models is a dual continuum flow and transport model called the drift shadow model. The effects of variations in the flow field and fracture-matrix interaction in the vicinity of a waste emplacement drift are investigated through sensitivity studies using the drift shadow model (Houseworth et al. 2003 [DIRS 164394]). In this model, the flow is significantly perturbed (reduced) beneath the waste emplacement drifts. However, comparisons of transport in this perturbed flow field with transport in an unperturbed flow field show similar results if the transport is initiated in the rock matrix. This has led to a second alternative model, called the fracture-matrix partitioning model, that focuses on the partitioning of radionuclide transport between the fractures and matrix upon exiting the waste emplacement drift. The fracture-matrix partitioning model computes the partitioning, between fractures and matrix, of diffusive radionuclide transport from the invert (for drifts without seepage) into the rock water. The invert is the structure constructed in a drift to provide the floor of the drift. The reason for introducing the fracture-matrix partitioning model is to broaden the conceptual model for flow beneath waste emplacement drifts in a way that does not rely on the specific flow behavior predicted by a dual continuum model and to ensure that radionuclide transport is not underestimated. The fracture-matrix partitioning model provides an alternative method of computing the partitioning of radionuclide releases from drifts without seepage into rock fractures and rock matrix. Drifts without seepage are much more likely to have a significant fraction of radionuclide releases into the rock matrix, and therefore warrant additional attention in terms of the partitioning model used for TSPA.

  7. Electron current drive by fusion-product-excited lower hybrid drift instability

    E-print Network

    Cook, J W S; Dendy, R O

    2010-01-01

    We present first principles simulations of the direct collisionless coupling of the free energy of fusion-born ions into electron current in a magnetically confined fusion plasma. These simulations demonstrate, for the first time, a key building block of some "alpha channelling" scenarios for tokamak experiments. A fully self-consistent electromagnetic 1D3V particle-in-cell code is used to evolve a parallel drifting ring-beam distribution of 3MeV protons in a 10keV thermal deuterium-electron plasma with realistic mass ratio. Collective instability gives rise to electromagnetic field activity in the lower hybrid range of frequencies. These spontaneously excited obliquely propagating waves undergo Landau damping on resonant electrons, drawing out an asymmetric tail in the distribution of electron parallel velocities, which carries a current.

  8. Effect of solenoidal magnetic field on drifting laser plasma

    SciTech Connect

    Takahashi, Kazumasa; Sekine, Megumi [Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Okamura, Masahiro [Brookhaven National Laboratory, Upton, NY 11973 (United States) and RIKEN, Wako-shi, Saitama 351-0198 (United States); Cushing, Eric [Pennsylvania State University, University Park, PA 16802 (United States); Jandovitz, Peter [Cornell University, Ithaca, NY 14853 (United States)

    2013-04-19

    An ion source for accelerators requires to provide a stable waveform with a certain pulse length appropriate to the application. The pulse length of laser ion source is easy to control because it is expected to be proportional to plasma drifting distance. However, current density decay is proportional to the cube of the drifting distance, so large current loss will occur under unconfined drift. We investigated the stability and current decay of a Nd:YAG laser generated copper plasma confined by a solenoidal field using a Faraday cup to measure the current waveform. It was found that the plasma was unstable at certain magnetic field strengths, so a baffle was introduced to limit the plasma diameter at injection and improve the stability. Magnetic field, solenoid length, and plasma diameter were varied in order to find the conditions that minimize current decay and maximize stability.

  9. Strange Attractors in Drift Wave Turbulence

    SciTech Connect

    Jerome L.V. Lewandowski

    2003-09-03

    There are growing experimental, numerical and theoretical evidences that the anomalous transport observed in tokamaks and stellarators is caused by slow, drift-type modes (such as trapped electron modes and ion-temperature gradient-driven modes). Although typical collision frequencies in hot, magnetized fusion plasmas can be quite low in absolute values, collisional effects are nevertheless important since they act as dissipative sinks. As it is well known, dissipative systems with many (strictly speaking more than two) degrees of freedom are often chaotic and may evolve towards a so-called attractor.

  10. Effects of grids in drift tubes

    SciTech Connect

    Okamura M.; Yamauchi, H.

    2012-05-20

    In 2011, we upgraded a 201 MHz buncher in the proton injector for the alternating gradient synchrotron (AGS) - relativistic heavy ion collider (RHIC) complex. In the buncher we installed four grids made of tungsten to improve the transit time factor. The grid installed drift tubes have 32 mm of inner diameter and the each grid consists of four quadrants. The quadrants were cut out precisely from 1mm thick tungsten plates by a computerized numerically controlled (CNC) wire cutting electrical discharge machining (EDM). The 3D electric field of the grid was simulated.

  11. Comparison of drift wave models with fluctuation data from the interior of the TEXT tokamak

    Microsoft Academic Search

    David W. Ross; R. V. Bravenec; Ch. P. Ritz; M. L. Sloan; J. R. Thompson; A. J. Wootton; P. M. Schoch; J. W. Heard; T. P. Crowley; R. L. Hickok; V. Simcic; D. L. Brower; W. A. Peebles; N. C. Luhmann Jr.

    1991-01-01

    Experimental evidence for and against drift waves as the origin of the observed fluctuations and anomalous transport in the plasma interior is reviewed. Fluctuation spectra observed by far-infrared (FIR) scattering and a heavy ion beam probe (HIBP) are compared. The FIR system observes broad S(k,?), which are spatially resolved at large k and readily identified with electron drift waves. At

  12. A parametric study of the drift-tearing mode using an extended-magnetohydrodynamic model

    SciTech Connect

    King, J. R.; Kruger, S. E. [Tech-X Corporation, 5621 Arapahoe Ave. Suite A Boulder, Colorado 80303 (United States)

    2014-10-15

    The linear, collisional, constant-? drift-tearing mode is analyzed for different regimes of the plasma-?, ion-skin-depth parameter space with an unreduced, extended-magnetohydrodynamic model. New dispersion relations are found at moderate plasma ? and previous drift-tearing results are classified as applicable at small plasma ?.

  13. 40 CFR 1065.550 - Gas analyzer range validation, drift validation, and drift correction.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 2011-07-01 false Gas analyzer range validation, drift validation, and drift...Duty Cycles § 1065.550 Gas analyzer range validation, drift validation, and drift correction. (a) Range validation. If an analyzer...

  14. An experimental test and models of drift and dispersal processes of pallid sturgeon (Scaphirhynchus albus) free embryos in the Missouri River

    USGS Publications Warehouse

    Braaten, P.J.; Fuller, D.B.; Lott, R.D.; Ruggles, M.P.; Brandt, T.F.; Legare, R.G.; Holm, R.J.

    2012-01-01

    Free embryos of wild pallid sturgeon Scaphirhynchus albus were released in the Missouri River and captured at downstream sites through a 180-km reach of the river to examine ontogenetic drift and dispersal processes. Free embryos drifted primarily in the fastest portion of the river channel, and initial drift velocities for all age groups (mean?=?0.66–0.70 m?s?1) were only slightly slower than mean water column velocity (0.72 m?s?1). During the multi-day long-distance drift period, drift velocities of all age groups declined an average of 9.7% day?1. Younger free embryos remained in the drift upon termination of the study; whereas, older age groups transitioned from drifting to settling during the study. Models based on growth of free embryos, drift behavior, size-related variations in drift rates, and channel hydraulic characteristics were developed to estimate cumulative distance drifted during ontogenetic development through a range of simulated water temperatures and velocity conditions. Those models indicated that the average free embryo would be expected to drift several hundred km during ontogenetic development. Empirical data and model results highlight the long-duration, long-distance drift and dispersal processes for pallid sturgeon early life stages. In addition, results provide a likely mechanism for lack of pallid sturgeon recruitment in fragmented river reaches where dams and reservoirs reduce the length of free-flowing river available for pallid sturgeon free embryos during ontogenetic development.

  15. ATLAS Muon Drift Tube Electronics

    Microsoft Academic Search

    Y. Arai; B. Ball; M. Beretta; H. Boterenbrood; G. W. Brandenburg; F. Ceradini; J. W. Chapman; T. Dai; C. Ferretti; T. Fries; J. Gregory; J. Guimarães da Costa; S. Harder; E. Hazen; J. Huth; P. P. M. Jansweijer; L. E. Kirsch; A. C. König; A. Lanza; G. Mikenberg; J. Oliver; C. Posch; R. Richter; W. Riegler; E. Spiriti; F. E. Taylor; J. C. Vermeulen; B. Wadsworth; T. A. M. Wijnen

    2008-01-01

    This paper describes the electronics used for the ATLAS monitored drift tube (MDT) chambers. These chambers are the main component of the precision tracking system in the ATLAS muon spectrometer. The MDT detector system consists of 1,150 chambers containing a total of 354,000 drift tubes. It is capable of measuring the sagitta of muon tracks to an accuracy of 60

  16. Drift waves in rotating plasmas

    SciTech Connect

    Horton, W.; Liu, J.

    1983-09-01

    The stability of the electron drift wave is investigated in the presence of E x B plasma rotation typical of the central cell plasma in tandem mirrors. It is shown that a rotationally-driven drift wave may occur at low azimuthal mode numbers. Conditions for rotational instabilities are derived. Quasilinear formulas are given for the anomalous transport associated with the unstable fluctuations.

  17. Drift Wave Simulation in Toroidal Geometry.

    NASA Astrophysics Data System (ADS)

    Lebrun, Maurice Joseph, III

    1988-12-01

    The drift wave, a general category of plasma behavior arising from a plasma inhomogeneity, is studied using the particle simulation method. In slab geometry, the drift wave (or universal mode) is stabilized by any finite amount of magnetic shear. In toroidal geometry, however, the coupling of the poloidal harmonics gives rise to a new branch of drift wave eigenmodes called the toroidicity -induced mode, which is predicted to be unstable in some regimes. The drift wave in a toroidal system is intrinsically three-dimensional, and is sensitive to the handling of the parallel electron dynamics, the (nearly) perpendicular wave dynamics, and the radial variation of magnetic field vector (shear). A simulation study must therefore be kinetic in nature, motivating the extension of particle simulation techniques to complex geometries. From this effort a three dimensional particle code in a toroidal coordinate system has been developed and applied to the toroidal drift wave problem. The code uses an (r,theta,phi) -type coordinate system, and a nonuniform radial grid that increases resolution near the mode-rational surfaces. Full ion dynamics and electron guiding center dynamics are employed. Further, the algorithm incorporates a straightforward limiting process to cylindrical geometry and slab geometry, enabling comparison to the theoretical results in these regimes. Simulations of the density-driven modes in toroidal geometry retain a single toroidal mode number (n = 9). In this regime, the poloidal harmonics are expected to be strongly coupled, giving rise to the marginally unstable toroidicity-induced drift mode. Analysis of the simulation data reveals a strong, low-frequency response that peaks near each mode rational surface. Further, the characteristic oscillation frequencies persist from one mode rational surface to the next, which identifies them as multiple harmonics of the toroidicity-induced mode. The lowest harmonic occurs at a frequency of omega/ omega^{*} ~ 0.26, which is reasonably close to the prediction of linear theory. Interferogram analysis of these modes indicates a "ballooning" structure toward the outside of the torus. The amplitude of the potential is observed to grow exponentially for the m = 8 through m = 10 poloidal mode numbers, with a growth rate of approximately gamma/omega ^{*} ~ 0.075. Saturation occurs at time t ~ 1000 Omega_sp{i}{-1}, and may be caused by quasilinear flattening of the density profile.

  18. East-west ionospheric drifts at the magnetic equator.

    NASA Technical Reports Server (NTRS)

    Woodman, R. F.

    1972-01-01

    A technique has been developed to measure the electromagnetic east-west drift velocity of the F region ionosphere by means of the Jicamarca incoherent scatter radar. Results show a fairly consistent behavior from day to day even during a magnetically disturbed day. Velocities are westward with a maximum of the order of 50 m/sec during the day, and eastward with a maximum of the order of 135 m/sec during the night. They are shown as experimental evidence for the superrotation of the neutral atmosphere at equatorial latitudes, but with a velocity smaller than the values inferred from satellite drag.

  19. Ion Soliton Observation in Plasma with Laser Induced

    NASA Astrophysics Data System (ADS)

    Claire, Nicolas; Bachet, Gerard; Skiff, Fred

    2003-10-01

    The aim of this talk is to show that the ion acoustic soliton propagation in double plasma device can be observed by laser induced fluorescence (LIF). Comparison between LIF and Langmuir probe measurements demonstrate that the pumping effect has to be taken into account by using a classical fluid model. One main contribution of the LIF has been to show that a train of soliton propagates easier in the device if a weak backward ion flux plasma having a drift velocity in the range of 200 m/s is present; as faster the ion flux is, the closer to the grid the soliton separation occurs. The other contribution of the LIF concerns the bump observed in front of the first soliton edge which was generally identified as precursors ions : in fact this bump results from a collective motion of the argon ions.

  20. High Performance Ion Mobility Spectrometry Using Hourglass Electrodynamic Funnel And Internal Ion Funnel

    DOEpatents

    Smith, Richard D. (Richland, WA); Tang, Keqi (Richland, WA); Shvartsburg, Alexandre A. (Richland, WA)

    2005-11-22

    A method and apparatus enabling increased sensitivity in ion mobility spectrometry/mass spectrometry instruments which substantially reduces or eliminates the loss of ions in ion mobility spectrometer drift tubes utilizing a device for transmitting ions from an ion source which allows the transmission of ions without significant delay to an hourglass electrodynamic ion funnel at the entrance to the drift tube and/or an internal ion funnel at the exit of the drift tube. An hourglass electrodynamic funnel is formed of at least an entry element, a center element, and an exit element, wherein the aperture of the center element is smaller than the aperture of the entry element and the aperture of the exit elements. Ions generated in a relatively high pressure region by an ion source at the exterior of the hourglass electrodynamic funnel are transmitted to a relatively low pressure region at the entrance of the hourglass funnel through a conductance limiting orifice. Alternating and direct electrical potentials are applied to the elements of the hourglass electrodynamic funnel thereby drawing ions into and through the hourglass electrodynamic funnel thereby introducing relatively large quantities of ions into the drift tube while maintaining the gas pressure and composition at the interior of the drift tube as distinct from those at the entrance of the electrodynamic funnel and allowing a positive gas pressure to be maintained within the drift tube, if desired. An internal ion funnel is provided within the drift tube and is positioned at the exit of said drift tube. The advantage of the internal ion funnel is that ions that are dispersed away from the exit aperture within the drift tube, such as those that are typically lost in conventional drift tubes to any subsequent analysis or measurement, are instead directed through the exit of the drift tube, vastly increasing the amount of ions exiting the drift tube.

  1. Theory of semicollisional drift-interchange modes in cylindrical plasmas

    SciTech Connect

    Hahm, T.S.; Chen, L.

    1985-01-01

    Resistive interchange instabilities in cylindrical plasmas are studied, including the effects of electron diamagnetic drift, perpendicular resistivity, and plasma compression. The analyses are pertinent to the semicollisional regime where the effective ion gyro-radius is larger than the resistive layer width. Both analytical and numerical results show that the modes can be completely stabilized by the perpendicular plasma transport. Ion sound effects, meanwhile, are found to be negligible in the semicollisional regime.

  2. Interferometric phase velocity measurements in the auroral electrojet

    NASA Technical Reports Server (NTRS)

    Labelle, J.; Kintner, P. M.; Kelley, M. C.

    1986-01-01

    A double-probe electric field detector and two spatially separated fixed-bias Langmuir probes were flown on a Taurus-Tomahawk sounding rocket launched from Poker Flat Research Range in March 1982. Interesting wave data have been obtained from about 10s of the downleg portion of the flight during which the rocket passed through the auroral electrojet. Here the electric field receiver and both density fluctuation (delta-n/n) receivers responded to a broad band of turbulence centered at 105 km-altitude and at frequencies generally below 4 kHz. Closer examination of the two delta-n/n turbulent waveforms reveals that they are correlated; from the phase difference between the two signals, the phase velocity of the waves in the rocket reference frame is inferred. The magnitude and direction of the observed phase velocity are consistent either with waves which travel at the ion sound speed or with waves which travel at the electron drift velocity. The observed phase velocity varies by about 50 percent over a 5 km altitude range, an effect which probably results from shear in the zonal neutral wind, although, unfortunately, no simultaneous neutral wind measurements exist to confirm this.

  3. Helium, hydrogen, and oxygen velocities observed on isee-3

    Microsoft Academic Search

    K. W. Ogilvie; M. A. Coplan; R. D. Zwickl

    1982-01-01

    The velocities of hydrogen, helium, and oxygen ions over a full range of solar wind conditions were recorded by the ion composition instrument and Los Alamos National Laboratory plasma instrument aboard the International Sun Earth Explorer. Interspecie velocity differences were observed frequently. For solar wind velocities between 300 and 400 km s(-1) the helium velocity exceeded the hydrogen velocity by

  4. ON PLASMA ROTATION AND DRIFTING SUBPULSES IN PULSARS: USING ALIGNED PULSAR B0826-34 AS A VOLTMETER

    SciTech Connect

    Van Leeuwen, J. [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo (Netherlands); Timokhin, A. N., E-mail: leeuwen@astron.nl, E-mail: andrey.timokhin@nasa.gov [Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2012-06-20

    We derive the exact drift velocity of plasma in the pulsar polar cap, in contrast to the order-of-magnitude expressions presented by Ruderman and Sutherland and generally used throughout the literature. We emphasize that the drift velocity depends not on the absolute value, as is generally used, but on the variation of the accelerating potential across the polar cap. If we assume that drifting subpulses in pulsars are indeed due to this plasma drift, several observed subpulse-drift phenomena that are incompatible with the Ruderman and Sutherland family of models can now be explained: we show that variations of drift rate, outright drift reversals, and the connection between drift rates and mode changes have natural explanations within the frame of the 'standard' pulsar model, when derived exactly. We apply this model for drifting subpulses to the case of PSR B0826-34, an aligned pulsar with two separate subpulse-drift regions emitted at two different colatitudes. Careful measurement of the changing and reversing drift rate in each band independently sets limits on the variation of the accelerating potential drop. The derived variation is small, {approx}10{sup -3} times the vacuum potential drop voltage. We discuss the implications of this result for pulsar modeling.

  5. Drift-Kinetic Simulations of Neoclassical Transport

    SciTech Connect

    Belli, E. A.; Candy, J. [General Atomics, P.O. Box 85608, San Diego, CA 92186-5608 (United States)

    2008-11-01

    We present results from numerical studies of neoclassical transport for multi-species plasmas. The code, NEO, provides a first-principles based calculation of the neoclassical transport coefficients directly from solution of the distribution function by solving a hierarchy of equations derived by expanding the fundamental drift-kinetic equation in powers of {rho}{sub *i}, the ratio of the ion gyroradius to system size. It extends previous studies by including the self-consistent coupling of electrons and multiple ion species and strong toroidal rotation effects. Systematic calculations of the second-order particle and energy fluxes and first-order plasma flows and bootstrap current and comparisons with existing theories are given for multi-species plasmas. The ambipolar relation {sigma}{sub a}z{sub a}{gamma}{sub a} = 0, which can only be maintained with complete cross-species collisional coupling, is confirmed. The effects of plasma shaping are also explored.

  6. Effects of Solar Energetic Particle deceleration due to drift

    NASA Astrophysics Data System (ADS)

    Dalla, Silvia; Marsh, Micheal S.; Laitinen, Timo

    2015-04-01

    Solar Energetic Particles (SEPs) experience deceleration during their propagation through the interplanetary magnetic field (IMF). Adiabatic deceleration has been known for decades to be an important process that influences SEP intensity profiles and spectra, and needs to be properly accounted for in models.Recently we have shown that drifts due to the gradient and curvature of the large scale Parker IMF cause SEP cross-field transport of a nearly symmetric nature in the heliolongitudinal direction and asymmetric in the heliolatitudinal one. As a result of the latitudinal drift, SEPs move in the direction opposite to that of the solar wind electric field and experience deceleration.Drift-induced deceleration is not accounted for by focussed transport approaches that neglect drift velocities within their spatial convection term, i.e. it is not included in the majority of current SEP models, on which interpretations of SEP data are based.Here we use 3D full orbit test particle simulations to demonstrate the effect of drift-induced deceleration on SEP populations injected near the Sun at different energies. Protons injected at 100 MeV experience latitudinal drifts of about 5 to 10 degrees and the associated deceleration reduces their kinetic energy by between 20 and 55% of the initial value, after four days. At lower energies (1 MeV) the spatial drift is of the order of 0.1 of a degree, however the effect of drift-induced deceleration is stronger, with particles losing between 35 and 90% of the initial kinetic energy during the same time.We show that the magnitude of drift-induced deceleration is similar to that of standard adiabatic deceleration, indicating that it needs to be accounted for in models. While adiabatic energy change is strongly influenced by the scattering conditions, the dependence of drift-induced deceleration on the level of pitch-angle scattering is weak. We discuss ways in which deceleration associated with drift could be included within SEP models.

  7. Saturn's magnetosphere interaction with Titan for T9 encounter. Pickup ion velocity distribution: 3D hybrid simulation and comparison with CAPS's observations

    Microsoft Academic Search

    Alexander S. Lipatov; Edward C. Sittler Jr.; Richard E. Hartle; David G. Simpson

    2010-01-01

    We discuss the results of the hybrid simulation of Titan's environment in case of T9 encounter. The simulations are based on recent analysis of the Cassini Plasma Spectrometer (CAPS) ion measurements during the T9 flyby through the induced magnetic tail of Titan [1]. In our model the background ions, all pickup ions, and ionospheric ions are considered as a particles,

  8. Electrostatic ion-acoustic-like instabilities in the solar wind with a backstreaming alpha particle beam

    SciTech Connect

    Gomberoff, L. [Departamento de Fisica, Facultad de Ciencias, Universidad de Chile, Santiago (Chile); Gomberoff, K. [Department of Physics, Technion, Haifa 32000 (Israel); Deutsch, A. [Rafael, P.O. Box 2250, Haifa 31021 (Israel)

    2010-06-15

    Nonlinear electrostatic instabilities have been shown to occur frequently and under very different conditions in plasma with two ion beams such as the fast solar wind. These instabilities can be triggered when the phase velocity of electrostatic ion-acoustic waves propagating forward and backward relative to the interplanetary magnetic field overlaps due to the presence of a finite amplitude of circularly polarized wave. The instabilities can be triggered by waves supported by the same ion component, or by waves supported by different ion components. By assuming a beam of alpha particles moving backward relative to the external magnetic field, as observed in some events in the fast solar wind, it is shown that a very small negative drift velocity of the alpha particle beam relative to the core plasma--a few percent of the local Alfven velocity--can trigger a very rich variety of nonlinear electrostatic acousticlike instabilities. Their growth rates can be rather large and they persist for larger negative alpha particles drift velocities and temperatures.

  9. Hall thruster plasma fluctuations identified as the E×B electron drift instability: Modeling and fitting on experimental data

    SciTech Connect

    Cavalier, J.; Lemoine, N.; Bonhomme, G. [IJL, Université de Lorraine, CNRS (UMR 7198), BP 70239, 54506 Vandoeuvre-lès-Nancy (France)] [IJL, Université de Lorraine, CNRS (UMR 7198), BP 70239, 54506 Vandoeuvre-lès-Nancy (France); Tsikata, S. [ICARE, CNRS (UPR 3021), 1C av. de la Recherche Scientifique, 45071 Orléans (France)] [ICARE, CNRS (UPR 3021), 1C av. de la Recherche Scientifique, 45071 Orléans (France); Honoré, C.; Grésillon, D. [LPP, CNRS (UMR 7648), École Polytechnique, 91128 Palaiseau (France)] [LPP, CNRS (UMR 7648), École Polytechnique, 91128 Palaiseau (France)

    2013-08-15

    Microturbulence has been implicated in anomalous transport at the exit of the Hall thruster, and recent simulations have shown the presence of an azimuthal wave which is believed to contribute to the electron axial mobility. In this paper, the 3D dispersion relation of this E×B electron drift instability is numerically solved. The mode is found to resemble an ion acoustic mode for low values of the magnetic field, as long as a non-vanishing component of the wave vector along the magnetic field is considered, and as long as the drift velocity is small compared to the electron thermal velocity. In these conditions, an analytical model of the dispersion relation for the instability is obtained and is shown to adequately describe the mode obtained numerically. This model is then fitted on the experimental dispersion relation obtained from the plasma of a Hall thruster by the collective light scattering diagnostic. The observed frequency-wave vector dependences are found to be similar to the dispersion relation of linear theory, and the fit provides a non-invasive measurement of the electron temperature and density.

  10. Hall thruster plasma fluctuations identified as the E ×B electron drift instability: Modeling and fitting on experimental data

    NASA Astrophysics Data System (ADS)

    Cavalier, J.; Lemoine, N.; Bonhomme, G.; Tsikata, S.; Honoré, C.; Grésillon, D.

    2013-08-01

    Microturbulence has been implicated in anomalous transport at the exit of the Hall thruster, and recent simulations have shown the presence of an azimuthal wave which is believed to contribute to the electron axial mobility. In this paper, the 3D dispersion relation of this E ×B electron drift instability is numerically solved. The mode is found to resemble an ion acoustic mode for low values of the magnetic field, as long as a non-vanishing component of the wave vector along the magnetic field is considered, and as long as the drift velocity is small compared to the electron thermal velocity. In these conditions, an analytical model of the dispersion relation for the instability is obtained and is shown to adequately describe the mode obtained numerically. This model is then fitted on the experimental dispersion relation obtained from the plasma of a Hall thruster by the collective light scattering diagnostic. The observed frequency-wave vector dependences are found to be similar to the dispersion relation of linear theory, and the fit provides a non-invasive measurement of the electron temperature and density.

  11. Anisotropy of electromigration-induced void and island drift.

    PubMed

    Latz, A; Sindermann, S P; Brendel, L; Dumpich, G; Meyer zu Heringdorf, F-J; Wolf, D E

    2014-02-01

    By means of our novel self-learning kinetic Monte Carlo model (Latz et al 2012 J. Phys.: Condens. Matter 24 485005) we study the electromigration-induced drift of monolayer voids and islands on unpassivated surfaces of single crystalline Ag(111) and Ag(001) films at the atomic scale. Regarding the drift velocity, we find a non-monotonic size dependence for small voids. The drift direction is aligned with the electromigration force only along high symmetry directions, while halfway between, the angle enclosed by them is maximal. The magnitude of these directional deviations strongly depends on the system parameter, which are investigated in detail. The simulation results are in accordance with void motion observed in experiments performed on Ag(111). PMID:24356088

  12. Conformation and drift of a telechelic chain in porous media

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Aniket

    2004-11-01

    The conformation and drift properties of a telechelic chain moving through a porous host of randomly distributed static obstacles are studied using Brownian dynamics simulation for a Grest-Kremer bead-spring model of polymer. Static chain conformations exhibit non-monotonic behaviour as a function of the impurity density ?imp at zero bias. The chain initially shrinks due to an entropic barrier as the density of the obstacles ?imp is increased. In the presence of the obstacles it requires only a tiny bias for a long chain to be mostly stretched. We then study the drift property of the chain as a function of the bias and impurity density. The drift velocity of the chain saturates beyond a threshold bias Fxcrit. This observation can be useful in designing DNA sequencing methods based on electrophoretic mobility.

  13. Quantum diffusion with drift and the Einstein relation. I

    SciTech Connect

    De Roeck, Wojciech, E-mail: wojciech.deroeck@fys.kuleuven.be [Institute for Theoretical Physics, K.U. Leuven, 3001 Leuven (Belgium); Fröhlich, Jürg, E-mail: juerg.froehlich@itp.phys.ethz.ch [Institute for Theoretical Physics, ETH Zürich, 8093 Zürich (Switzerland); Schnelli, Kevin, E-mail: skevin@math.harvard.edu [Department of Mathematics, Harvard University, Cambridge, Massachusetts 02138 (United States)

    2014-07-15

    We study the dynamics of a quantum particle hopping on a simple cubic lattice and driven by a constant external force. It is coupled to an array of identical, independent thermal reservoirs consisting of free, massless Bose fields, one at each site of the lattice. When the particle visits a site x of the lattice it can emit or absorb field quanta of the reservoir at x. Under the assumption that the coupling between the particle and the reservoirs and the driving force are sufficiently small, we establish the following results: The ergodic average over time of the state of the particle approaches a non-equilibrium steady state describing a non-zero mean drift of the particle. Its motion around the mean drift is diffusive, and the diffusion constant and the drift velocity are related to one another by the Einstein relation.

  14. Production of Magnetic Turbulence by Cosmic Rays Drifting Upstream of Supernova Remnant Shocks

    NASA Technical Reports Server (NTRS)

    Stroman, Thomas; Niemiec, Jacek; Pohl, Martin; Nishikawa, Ken-ichi

    2008-01-01

    I will present results of our recent two- and three-dimensional Particle-In-Cell simulations of magnetic-turbulence production by cosmic-ray ions drifting upstream of supernova remnant shocks. These studies' aim is twofold: test recent predictions of strong amplification in short wavelength, non-resonant wave modes, and study the subsequent evolution of the magnetic turbulence, including its backreaction on cosmic-ray trajectories. We confirm that the drifting cosmic rays give rise to a turbulent magnetic field, but show that an oblique filamentary mode grows more rapidly than the non-resonant parallel modes found in analytical theory. The field perturbations grow more slowly than estimated using a quasi-linear analytical approach for the parallel plane-wave mode, and saturate in amplitude at deltaB/B approximately equal to 1. The backreaction of the magnetic turbulence on the particles leads to an alignment of the bulk-flow velocities of the cosmic rays and the background medium. This is an essential characteristic of cosmic ray-modified shocks: the upstream flow speed is continuously changed by the cosmic rays. The reduction of relative drift between cosmic rays and background medium accounts for the saturation of the instability at only moderate magnetic-field amplitudes. It is possible that the prolonged magnetic field growth observed in recent MHD simulations results from a cosmic-ray current assumed to be constant and thus immune to the backreaction from the turbulent field. We speculate that the parallel plane-wave mode found in analytical treatments very quickly leads co filamentation, which we observe in our PIC modeling and is also apparent in the MHD simulations.

  15. SPIV measurements around the DELFT 372 catamaran in steady drift

    NASA Astrophysics Data System (ADS)

    Falchi, M.; Felli, M.; Grizzi, S.; Aloisio, G.; Broglia, R.; Stern, F.

    2014-11-01

    The present work concerns the experimental measurements of the velocity field around a catamaran advancing in static drift. The main aim of the paper was to investigate the dynamics of the vortices generated by catamaran hulls with particular emphasis on the mechanisms of generation, detachment, downstream evolution and destabilization. In this context, a Stereo-PIV campaign has been performed to map the velocity fields on some cross-planes along and downstream of the catamaran. Froude numbers equal to 0.4 and 0.5 at drift angles as large as 6° and 9° have been selected as testing conditions. In all the tests, the model has been fixed at the dynamical values of trim and sinkage, measured in a preliminary static drift experiments. Major geometrical and kinematical characteristics of the keel vortices have been documented in the paper through the analysis of the mean and fluctuating components of the velocity and vorticity field. Vortex interaction with the wave pattern has been investigated as well through the use of a conditional average technique of the velocity snapshots with the free surface elevation. As a secondary, but important, outcome, a valuable experimental dataset for CFD benchmarking in severe off-design conditions has been collected.

  16. Drift solitons and shocks in inhomogeneous quantum magnetoplasmas

    SciTech Connect

    Haque, Q.; Mahmood, S. [Theoretical Plasma Physics Division, Pakistan Institute of Nuclear Science and Technology, P.O. Nilore, Islamabad, 45320 (Pakistan)

    2008-03-15

    Linear and nonlinear drift waves are studied in inhomogeneous electron-ion quantum magnetoplasma with neutrals in the background. The Korteweg-de Vries-Burgers equation is derived by using the quantum hydrodynamic model for nonlinear drift waves with quantum corrections. Both soliton and shock solutions are obtained in different limits. It is noticed that the width of the solitary hump is decreased with the increase in the quantum parameter. However this effect is reversed for the solitary dip case. It is also found that oscillatory shock wave is dependent on the quantum parameter. However, the monotonic shock formation is independent of the quantum parameter.

  17. THE 15 LAYER SILICON DRIFT DETECTOR TRACKER IN EXPERIMENT 896.

    SciTech Connect

    PANDY,S.U.

    1998-11-08

    Large linear silicon drift detectors have been developed and are in production for use in several experiments. Recently 15 detectors were used as a tracking device in BNL-AGS heavy ion experiment (E896). The detectors were successfully operated in a 6.2 T magnetic field. The behavior of the detectors, such as drift uniformity, resolution, and charge collection efficiency are presented. The effect of the environment on the detector performance is discussed. Some results from the experimental run are presented. The detectors performed well in an experimental environment. This is the first tracking application of these detectors.

  18. Relativistic wave-function effect on the K-shell ionization of Sb, Gd, Yb, Au, and Bi by low- to intermediate-velocity F ions

    NASA Astrophysics Data System (ADS)

    Mitra, D.; Singh, Yeshpal; Tribedi, Lokesh C.; Tandon, P. N.; Trautmann, D.

    2001-07-01

    We have measured absolute cross sections for the K-shell ionization of medium- and high-Z targets of Sb, Gd, Yb, Au, and Bi induced by low- to intermediate-velocity F ions having energies between 2.5 and 5.8 MeV/u. Our main interest is to see the effect of the relativistic nature of the K-shell electrons of these target atoms on the ionization cross sections. The information on the degree of relativistic effect has been obtained by comparing the measured data with different theoretical calculations with and without including the relativistic corrections. A comparative study of the two different models such as SCA (semiclassical approximation) and ECPSSR [perturbed stationary state (PSS) including the corrections for energy (E) loss, Coulomb (C) deflection, and relativistic (R) effects] is presented. It is shown that the SCA calculations with the relativistic wave function predict an ionization cross section that is at least an order of magnitude higher compared to that given by the nonrelativistic calculation for Bi target. This factor is reduced to about 2 in the case of Sb. The ECPSSR, however, predicts lower ratios for the relativistic to nonrelativistic calculations. The experimental results, in general, are in good agreement with the SCA calculations using relativistic wave functions as well as with the ECPSSR model. For high-Z targets the SCA gives slightly better agreement with the data compared to the ECPSSR. In addition, it is shown that in the ECPSSR formalism the ionization cross sections of high-Z (with large relativistic effect) as well as low-Z targets (with less relativistic effect) can be scaled approximately to follow a universal curve after including the relativistic correction.

  19. Time-dependent drift Hamiltonian

    SciTech Connect

    Boozer, A.H.

    1983-03-01

    The lowest-order drift equations are given in a canonical magnetic coordinate form for time-dependent magnetic and electric fields. The advantages of the canonical Hamiltonian form are also discussed.

  20. Managing “Pollen Drift ” to Minimize

    E-print Network

    unknown authors

    Corn is a cross-pollinating crop in which most pollination results from pollen dispersed by wind and gravity. Pollen drift in corn has received considerable attention in recent years as the result of the development and widespread adoption of new seed technologies containing transgenes or genetically modified organisms (GMOs). Managing pollen drift has always been a major concern in the production of hybrid seed (to ensure genetic purity of inbreds) and specialty corn (to optimize expression of valueadded traits, like high oil content). Pollen drift has now become an important consideration in the production of non-GMO corn as an Identity-Preserved (IP) grain crop. Producers of IP non-GMO grain are concerned that pollen drift from GMO hybrids will contaminate, by cross-pollination, nearby non-GMO corn. Farmers growing GMO hybrids approved for export also want to avoid contamination of their crops by GMO corns that have not

  1. Asymmetric particle fluxes from drifting ionization zones in sputtering magnetrons

    NASA Astrophysics Data System (ADS)

    Panjan, Matjaž; Franz, Robert; Anders, André

    2014-04-01

    Electron and ion fluxes from direct current and high-power impulse magnetron sputtering (dcMS and HiPIMS) plasmas were measured in the plane of the target surface. Biased collector probes and a particle energy and mass analyzer showed asymmetric emission of electrons and of singly and doubly charged ions. For both HiPIMS and dcMS discharges, higher fluxes of all types of particles were observed in the direction of the electrons' E × B drift. These results are put in the context with ionization zones that drift over the magnetron's racetrack. The measured currents of time-resolving collector probes suggest that a large fraction of the ion flux originates from drifting ionization zones, while energy-resolving mass spectrometry indicates that a large fraction of the ion energy is due to acceleration by an electric field. This supports the recently proposed hypothesis that each ionization zone is associated with a negative-positive-negative space charge structure, thereby producing an electric field that accelerates ions from the location where they were formed.

  2. Density and velocity of H{sup -} in the extraction region of a negative ion source estimated from the change in H{sup -} beam current due to a pulse laser injection

    SciTech Connect

    Matsumoto, Y.; Nishiura, M.; Matsuoka, K.; Wada, M.; Sasao, M.; Yamaoka, H. [National Institute for Fusion Science (NIFS), Toki, Gifu 509-5292 (Japan); Department of Electronics, Doshisha University, Kyotanabe, Kyoto 610-0321 (Japan); Tohoku University, Sendai 980-8579 (Japan); Harima Institute, RIKEN -Institute of Physical and Chemical Research, Hyogo 679-5148 (Japan)

    2006-03-15

    A method to estimate H{sup -} density and velocity in the extraction region of a negative ion source plasma without a Langmuir probe is developed. It utilizes the laser photodetachment with a Faraday cup (PD-FC). The H{sup -} parameters estimated by PD-FC are compared to the results measured by laser-photodetachment with a Langmuir probe (PD-LP). The result shows that H{sup -} velocity estimated by PD-FC is in good agreement with the PD-LP result. Meanwhile, H{sup -} density estimated by PD-FC is twice larger than the PD-LP result. Though a more detailed research, including more effects that are ignored in this study, is needed for H{sup -} density measurement, PD-FC will be a very useful tool for H{sup -} measurements especially near an extraction hole in negative ion sources.

  3. Self?convection of floating heat sources: A model for continental drift

    Microsoft Academic Search

    L. N. Howard; W. V. R. Malkus; J. A. Whitehead

    1970-01-01

    Two models of floating heat sources are studied. In the first model the motion of two line heat sources constrained to float at an arbitrary depth in a viscous fluid is determined in the limit of small convection velocities. It is found that the sources drift apart and at great separation attain a constant velocity proportional to the square root

  4. Origin of Lagrangian intermittency in drift-wave turbulence , W.J.T. Bos2

    E-print Network

    Boyer, Edmond

    , France and 2 LMFA, CNRS UMR 5509, Ecole Centrale de Lyon - Universit´e de Lyon, Ecully, France The Lagrangian velocity statistics of dissipative drift-wave turbulence are investigated. For large values-dimensional fluid turbulence it is now well established that the velocity displays near Gaussian statistics

  5. Comparison between African equatorial station ground-based inferred vertical E × B drift, Jicamarca direct measured drift, and IRI model

    NASA Astrophysics Data System (ADS)

    Adeniyi, J. O.; Adebesin, B. O.; Adimula, I. A.; Oladipo, O. A.; Olawepo, A. O.; Ikubanni, S. O.; Reinisch, B. W.

    2014-10-01

    The Incoherent Scatter Radar measurement over Jicamarca, together with the IRI model-2007 measurements were compared with ground-based digisonde inferred E × B drift over Ilorin in the African region during year of solar minima (F10.7 = 81). Seasonally, Ilorin pre-reversal enhancement (PRE) had peak drift velocities of 7.2, 3.7 and 7.9 m/s for March equinox, September equinox and December solstice respectively, while Jicamarca drifts indicated 13.0, 10.5 and 5.2 m/s; as well as the IRI model with 14.3, 8.4 and 0.7 m/s in similar order. PRE value was insignificant during June solstice. The PRE magnitude of the IRI-model during the equinoxes is twice the value obtained at Ilorin. The daytime E × B drift peaked over Ilorin 1-2 h earlier than both the modeled and Jicamarca observations. This could be due to the difference in sunset time at the conjugate points corresponding to the altitude of the observation. During the evening time PRE, the respective correlation coefficients (R) for Vz-F10.7 relation over Jicamarca, Ilorin and the modeled observations are -0.5559, 0.4796 and -0.4979. Similarly, the Vz-Ap relation exhibit excellent anti-correlation coefficient (R = -0.8637) for the IRI-model, -0.4827 over Jicamarca and 0.3479 for Ilorin. Annual mean drift velocities over Jicamarca, Ilorin and IRI model measurements respectively are 10, 5.6 and 10 m/s for the peak PRE observation; 15, 16 and 21 m/s for the daytime pre-sunrise peak values; and -21, -9 and -16 m/s for the nighttime downward reversals. The root-mean square (RMS) deviation between IRI-model and the Ilorin drift between 2000 and 0500 h is 4.37, 2.03, 3.71 and 2.42 m/s for March equinox, June solstice, September equinox and December solstice respectively. For Jicamarca-Ilorin drift relation, RMS deviation is 5.48, 2.30, 3.47 and 1.27 m/s in the same order respectively. Annual hmF2 inferred drift over Ilorin during daytime is higher by a factor of ?2 and 3 at Jicamarca and IRI model measurements respectively; and by a factor of ?5 for both during the night-time period. The limitations in using hmF2 to infer drifts are discussed.

  6. High-Performance Ion Mobility Spectrometry Using Hourglass Electrodynamic Funnel And Internal Ion Funnel

    DOEpatents

    Smith, Richard D. (Richland, WA); Tang, Keqi (Richland, WA); Shvartsburg, Alexandre A. (Richland, WA)

    2004-11-16

    A method and apparatus enabling increased sensitivity in ion mobility spectrometry/mass spectrometry instruments which substantially reduces or eliminates the loss of ions in ion mobility spectrometer drift tubes utilizing an hourglass electrodynamic ion funnel at the entrance to the drift tube and/or an internal ion funnel at the exit of the drift tube. An hourglass electrodynamic funnel is formed of at least an entry element, a center element, and an exit element, wherein the aperture of the center element is smaller than the aperture of the entry element and the aperture of the exit elements. Ions generated in a relatively high pressure region by an ion source at the exterior of the hourglass electrodynamic funnel are transmitted to a relatively low pressure region at the entrance of the hourglass funnel through a conductance limiting orifice. Alternating and direct electrical potentials are applied to the elements of the hourglass electrodynamic funnel thereby drawing ions into and through the hourglass electrodynamic funnel thereby introducing relatively large quantities of ions into the drift tube while maintaining the gas pressure and composition at the interior of the drift tube as distinct from those at the entrance of the electrodynamic funnel and allowing a positive gas pressure to be maintained within the drift tube, if desired. An internal ion funnel is provided within the drift tube and is positioned at the exit of said drift tube. The advantage of the internal ion funnel is that ions that are dispersed away from the exit aperture within the drift tube, such as those that are typically lost in conventional drift tubes to any subsequent analysis or measurement, are instead directed through the exit of the drift tube, vastly increasing the amount of ions exiting the drift tube.

  7. Effect of drift waves on plasma blob dynamics.

    PubMed

    Angus, Justin R; Umansky, Maxim V; Krasheninnikov, Sergei I

    2012-05-25

    Most of the work to date on plasma blobs found in the edge region of magnetic confinement devices is limited to 2D theory and simulations which ignore the variation of blob parameters along the magnetic field line. However, if the 2D convective rate of blobs is on the order of the growth rate of unstable drift waves, then drift wave turbulence can drastically alter the dynamics of blobs from that predicted by 2D theory. The density gradients in the drift plane that characterize the blob are mostly depleted during the nonlinear stage of drift waves resulting in a much more diffuse blob with a greatly reduced radial velocity. Sheath connected plasma blobs driven by effective gravity forces are considered in this Letter and it is found that the effects of resistive drift waves occur at earlier stages in the 2D motion for smaller blobs and in systems with a smaller effective gravity force. These conclusions are supported numerically by a direct comparison of 2D and 3D seeded blob simulations. PMID:23003271

  8. Surface Drift of RAFOS Floats in the California Current System

    NASA Astrophysics Data System (ADS)

    Gates, D. C.; Collins, C. A.; Margolina, T.

    2011-12-01

    The patterns of surface drift of ninety RAFOS floats in the California Current System have been studied. The floats were launched in the California Undercurrent during 1992-2010 and were tracked by the ARGOS system when they surfaced at the end of their subsurface mission. The float hulls were glass cylinders which were 8.6 cm wide by 1.52 m long and floated with the upper 30 cm of the hull above water. The surface drift of these floats was typically equatorward in the California Current. However, some floats would flow poleward, others would drift westward into the North Pacific Gyre, and others with orbital cyclonic and/or anti-cyclonic motions. The duration of surface trajectories varied from as short as a period of days to approximately ten months. Forces on the floats included wind stress on the exposed hull and the drag of ocean currents on the subsurface hull. The latter included the Stokes drift associated with surface wind waves, Ekman flow caused by the stress of the wind on the ocean surface, and the currents associated with the general circulation of the ocean. Surface currents can be explained by calculating current direction and velocity from wind stress data. As a first step, the relationship between observed wind stress and the motion of the float is determined by assuming Ekman balance. Mesoscale effects, including eddies, are also considered in explaining the surface drift of the floats.

  9. Towards a complete parametrization of the ordinary-mode electromagnetic instability in counterstreaming plasmas. II. Ion effects

    SciTech Connect

    Ibscher, D.; Schlickeiser, R. [Institut fuer Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

    2013-04-15

    The linear marginal instability analysis of the ordinary perpendicular mode instability of drifting bi-Maxwellian plasma particle distributions with and without temperature anisotropy is extended by including the modifications of heavier ion species. For general values of the temperature anisotropy, the streaming velocity, and the parallel plasma beta, accurate marginal stability conditions are derived, which enable a better understanding of the interplay of counterstreaming and temperature anisotropy.

  10. Snow particle speeds in drifting snow

    NASA Astrophysics Data System (ADS)

    Nishimura, Kouichi; Yokoyama, Chika; Ito, Yoichi; Nemoto, Masaki; Naaim-Bouvet, Florence; Bellot, Hervé; Fujita, Koji

    2014-08-01

    Knowledge of snow particle speeds is necessary for deepening our understanding of the internal structures of drifting snow. In this study, we utilized a snow particle counter (SPC) developed to observe snow particle size distributions and snow mass flux. Using high-frequency signals from the SPC transducer, we obtained the sizes of individual particles and their durations in the sampling area. Measurements were first conducted in the field, with more precise measurements being obtained in a boundary layer established in a cold wind tunnel. The obtained results were compared with the results of a numerical analysis. Data on snow particle speeds, vertical velocity profiles, and their dependence on wind speed obtained in the field and in the wind tunnel experiments were in good agreement: both snow particle speed and wind speed increased with height, and the former was always 1 to 2 m s-1 less than the latter below a height of 1 m. Thus, we succeeded in obtaining snow particle speeds in drifting snow, as well as revealing the dependence of particle speed on both grain size and wind speed. The results were verified by similar trends observed using random flight simulations. However, the difference between the particle speed and the wind speed in the simulations was much greater than that observed under real conditions. Snow transport by wind is an aeolian process. Thus, the findings presented here should be also applicable to other geophysical processes relating to the aeolian transport of particles, such as blown sand and soil.

  11. Linear electronic field time-of-flight ion mass spectrometers

    DOEpatents

    Funsten, Herbert O. (Los Alamos, NM)

    2010-08-24

    Time-of-flight mass spectrometer comprising a first drift region and a second drift region enclosed within an evacuation chamber; a means of introducing an analyte of interest into the first drift region; a pulsed ionization source which produces molecular ions from said analyte of interest; a first foil positioned between the first drift region and the second drift region, which dissociates said molecular ions into constituent atomic ions and emits secondary electrons; an electrode which produces secondary electrons upon contact with a constituent atomic ion in second drift region; a stop detector comprising a first ion detection region and a second ion detection region; and a timing means connected to the pulsed ionization source, to the first ion detection region, and to the second ion detection region.

  12. Internal physics of the ion-sensitive probe

    NASA Astrophysics Data System (ADS)

    Sullivan, R. M.; Ochoukov, R.; Whyte, D. G.

    2013-07-01

    Due to its usefulness as a diagnostic for high-density magnetized plasmas, a complete picture of particle motion and potential surfaces within the Ion-Sensitive Probe (ISP) is desired. To that end, results from an ISP with a segmented collector are presented. Asymmetry in the electron current to the collector is found to be in the ExB drift direction, consistent with previous numerical studies of the probe. Asymmetry in the ion current is found to be due to geometric "shadowing" of parts of the collector surface. Additionally, insight into the ion velocity distribution function (IVDF) is gained by comparing Ti,? to the thermal energy required for an ion to overcome the potential barrier inside the probe.

  13. Conditions and growth rate of Rayleigh instability in a Hall thruster under the effect of ion temperature.

    PubMed

    Malik, Hitendra K; Singh, Sukhmander

    2011-03-01

    Rayleigh instability is investigated in a Hall thruster under the effect of finite temperature and density gradient of the plasma species. The instability occurs only when the frequency of the oscillations ? falls within a frequency band described by k{y}u?+1/k_{y}?²u_{0}/?x²+?/k_{y}n_{0}?n?/?x??drift velocity of the electrons, ? is their gyration frequency under the effect of the magnetic field, k{y} is the wave propagation constant, n? is the plasma density together with ?n?/?x as the density gradient, and T{i}(T{e}), M(m), Y{i}(Y{e}), and ?{p}{i}(?{p}{e}) are the temperature, mass, specific heat ratio, and plasma frequency of the ions (electrons), respectively. A relevant Rayleigh equation is derived and solved numerically using the fourth-order Runge-Kutta method for investigating the perturbed potential under the effect of electron drift velocity, channel length, magnetic field, ion temperature, and electron temperature. The instability grows faster because of the magnetic field, ion temperature, and drift velocity of the electrons but its growth rate is reduced because of the electron temperature, channel length, and also its far distances from the anode. PMID:21517603

  14. Drift coefficients of motor proteins moving along sidesteps

    NASA Astrophysics Data System (ADS)

    Li, Jing-Hui

    2014-10-01

    In the paper, we investigate two motor proteins moving along the sidesteps: a motor protein moving along a two-dimensional sidestep and another protein moving along a three-dimensional sidestep. The drift coefficients (or stationary average velocities) of these two motor proteins are calculated. We believe that our investigation of the motor proteins moving along the sidesteps in the present paper can benefit the investigation of the transport of the motor proteins to some extent.

  15. The Drifting Star

    NASA Astrophysics Data System (ADS)

    2008-04-01

    By studying in great detail the 'ringing' of a planet-harbouring star, a team of astronomers using ESO's 3.6-m telescope have shown that it must have drifted away from the metal-rich Hyades cluster. This discovery has implications for theories of star and planet formation, and for the dynamics of our Milky Way. ESO PR Photo 09a/08 ESO PR Photo 09a/08 Iota Horologii The yellow-orange star Iota Horologii, located 56 light-years away towards the southern Horologium ("The Clock") constellation, belongs to the so-called "Hyades stream", a large number of stars that move in the same direction. Previously, astronomers using an ESO telescope had shown that the star harbours a planet, more than 2 times as large as Jupiter and orbiting in 320 days (ESO 12/99). But until now, all studies were unable to pinpoint the exact characteristics of the star, and hence to understand its origin. A team of astronomers, led by Sylvie Vauclair from the University of Toulouse, France, therefore decided to use the technique of 'asteroseismology' to unlock the star's secrets. "In the same way as geologists monitor how seismic waves generated by earthquakes propagate through the Earth and learn about the inner structure of our planet, it is possible to study sound waves running through a star, which forms a sort of large, spherical bell," says Vauclair. The 'ringing' from this giant musical instrument provides astronomers with plenty of information about the physical conditions in the star's interior. And to 'listen to the music', the astronomers used one of the best instruments available. The observations were conducted in November 2006 during 8 consecutive nights with the state-of-the-art HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla. Up to 25 'notes' could be identified in the unique dataset, most of them corresponding to waves having a period of about 6.5 minutes. These observations allowed the astronomers to obtain a very precise portrait of Iota Horologii: its temperature is 6150 K, its mass is 1.25 times that of the Sun, and its age is 625 million years. Moreover, the star is found to be more metal-rich than the Sun by about 50%. ESO PR Photo 09b/08 ESO PR Photo 09b/08 Constellations "These results show the power of asteroseismology when using a very precise instrument such as HARPS," says Vauclair. "It also shows that Iota Horologii has the same metal abundance and age as the Hyades cluster and this cannot be a coincidence." The Hyades is an ensemble of stars that is seen with the unaided eye in the Northern constellation Taurus ("The Bull"). This open cluster, located 151 light-years away, contains stars that were formed together 625 million years ago. The star Iota Horologii must have thus formed together with the stars of the Hyades cluster but must have slowly drifted away, being presently more than 130 light-years away from its original birthplace. This is an important result to understand how stars move on the galactic highways of the Milky Way. This also means that the amount of metals present in the star is due to the original cloud from which it formed and not because it engulfed planetary material. "The chicken and egg question of whether the star got planets because it is metal-rich, or whether it is metal-rich because it made planets that were swallowed up is at least answered in one case," says Vauclair. More information The astronomers' study is being published as a Letter to the Editor in Astronomy and Astrophysics ("The exoplanet-host star iota Horologii: an evaporated member of the primordial Hyades cluster", by S. Vauclair et al.). The team is composed of Sylvie Vauclair, Marion Laymand, Gérard Vauclair, Alain Hui Bon Hoa, and Stéphane Charpinet (LATT, Toulouse, France), François Bouchy (IAP, Paris, France), and Michaël Bazot (University of Porto, Portugal).

  16. Impact of drift time variation on the Compton image from large-volume CdZnTe crystals

    NASA Astrophysics Data System (ADS)

    Kim, Jae Cheon; Kaye, William R.; Wang, Weiyi; Zhang, Feng; He, Zhong

    2012-08-01

    In pixelated CdZnTe detectors, multiple interaction gamma-ray events are critical because they permit Compton imaging. However, in large-volume CdZnTe crystals, the depth of multiple interaction events is often poorly reconstructed due to significant nonuniformity of electron drift velocity while the depth of single interaction events can be accurately reconstructed using signal ratios. The nonuniformity of the drift velocity is likely due to nonuniformity in the electric field within the detector. This causes variation in the drift time even amongst events that occur at the same depth of interaction in the same pixel. The degradation in the depth reconstruction results in poorer imaging performance. The electron drift velocity at each depth is measured using 241Am alpha particles incident on the entire cathode surface of each detector. Cathode waveforms are recorded for events collected by each element in the 11×11 array of anode pixels. To illustrate the impact of electron drift time variation, two CdZnTe crystals fabricated by Redlen Technologies with similar spectral performance, but significantly different Compton imaging performance are selected. The detector with poorer imaging performance demonstrated significant nonuniformity of the electron drift velocity. This work clearly shows that even CdZnTe crystals with 1% FWHM energy resolution at 662 keV can have a nonuniform electron drift velocity, on the sub-pixel scale, which seriously degrades the Compton imaging performance of pixelated detectors.

  17. Non-gyrotropic proton and alpha-particle velocity distributions in the solar wind: TAUS observations and stability analysis

    NASA Technical Reports Server (NTRS)

    Astudillo, H. F.; Marsch, E.; Livi, S.; Rosenbauer, H.

    1995-01-01

    Ion velocity distribution functions have been measured with high time resolution by the TAUS plasma instrument on the PHOBOS mission to Mars in 1989. The unambiguous separation of protons and alpha-particles by TAUS enabled us to study the nonthermal features of their distributions separately and to analyze the stability of the distributions against excitation of waves in the cyclotron-frequency domain. Typical nonthermal features include temperature anisotropies, with T(sub perpendicular) larger than T(sub parallel), and ion beam populations drifting along the local magnetic field direction. Also, distinctly non-gyrotropic alpha-particle velocity distributions were sometimes found. Non-gyrotropy strongly changes the wave dispersion and gives rise to new growing modes, related to the coupling of the standard wave modes existing in gyrotropic plasma. It is found that for the measured non-gyrotropic ion distributions the right-hand polarized wave can also be excited by a temperature anistropy instead of the usual beam drift.

  18. ISEE-1 and -2 observations of laminar bow shocks - Velocity and thickness

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Hoppe, M. M.; Livesey, W. A.; Gosling, J. T.; Bame, S. J.

    1982-01-01

    The ISEE-1 and -2 spacecraft have provided the opportunity for studying the thickness and velocity of the bow shock on a regular basis. There are two models for the thickness of quasi-perpendicular laminar shocks. Galeev (1976) has calculated the thickness of the nearly perpendicular laminar bow shock by means of a weak ion sound turbulence (WIST) approach. Morse and Greenstadt (1976), on the other hand, assume that the shock thickness adjust itself to stay close to the drift velocity for marginal stability of current driven electrostatic waves. The present investigation is concerned with an evaluation of the competing theories, taking into account ISEE-1 and -2 observations of laminar bow shocks. It is found that the formula used by Morse and Greenstadt does not predict the observed thicknesses as well as the formula given by Galeev.

  19. Multi-payload measurement of transverse velocity shears in the topside ionosphere

    NASA Astrophysics Data System (ADS)

    Lundberg, E. T.; Kintner, P. M.; Lynch, K. A.; Mella, M. R.

    2012-01-01

    Using a multi-payload sounding rocket mission, we present the first direct measurement of velocity shear in the topside auroral ionosphere. In regions of large, ˜200 mV/m, transient electric fields we directly measure differences in the plasma drift velocity. From these differences, shear frequencies reaching ±6Hz are measured. These directly measured shears are compared with the shear inferred from single payload measurements. It is shown this traditional measurement of shear overestimates the shear frequency by a factor of two for this event, highlighting the importance of the temporal component of near-DC electric field structures. Coincident with these strong fields and shears are enhanced emissions of broadband, extremely low frequency (BB-ELF) plasma waves, and a narrowband wave emission near the H+-O+ bi-ion resonant frequency.

  20. Measurement of the ion drag force on falling dust particles in a low-pressure plasma

    NASA Astrophysics Data System (ADS)

    Nosenko, Vladimir; Fisher, Ross; Merlino, Robert; Miller, Michael

    2006-10-01

    The ion drag force on falling dust particles in a low-pressure discharge was measured experimentally. The plasma was produced in a multidipole hot-filament discharge using argon gas at pressures below 1 mTorr. The plasma density, electron temperature and space potential were measured using a planar Langmuir probe. Typically, the electron density was in the range of 10^15 -10^16 m-3, and the electron temperature in the 2 -- 5 eV range. A weak electric field, present along the axis of the plasma, induced a drift motion of the argon ions to velocities several times the ion thermal velocity. Glass micro-balloons (mean diameter 40 or 59 micron), dropped into the plasma using a dust shaker, were deflected by the horizontally-directed drag force produced by the drifting ions. The ion drag force was deduced from measurements of the deflection angles of the particle trajectories which were observed by laser light illumination and recorded by a CCD camera. The measurements will be compared to theoretical models of the ion drag force.

  1. STATUS OF THE NEUTRALIZED DRIFT COMPRESSION EXPERIMENT (NDCX-II)

    SciTech Connect

    Waldron, W.L.; Kwan, J.W.

    2011-04-21

    The Neutralized Drift Compression Experiment (NDCX-II) is an 11 M$ induction accelerator project currently in construction at Lawrence Berkeley National Laboratory for warm dense matter (WDM) experiments investigating the interaction of ion beams with matter at elevated temperature and pressure. The machine consists of a lithium injector, induction accelerator cells, diagnostic cells, a neutralized drift compression line, a final focus solenoid, and a target chamber. The induction cells and some of the pulsed power systems have been reused from the decommissioned Advanced Test Accelerator at Lawrence Livermore National Laboratory after refurbishment and modification. The machine relies on a sequence of acceleration waveforms to longitudinally compress the initial ion pulse from 600 ns to less than 1 ns in {approx} 12 m. Radial confinement of the beam is achieved with 2.5 T pulsed solenoids. In the initial hardware configuration, 50 nC of Li{sup +} will be accelerated to 1.25 MeV and allowed to drift-compress to a peak current of {approx}40 A. The project started in the summer of 2009. Construction of the accelerator will be completed in the fall of 2011 and will provide a worldwide unique opportunity for ion-driven warm dense matter experiments as well as research related to novel beam manipulations for heavy ion fusion drivers.

  2. In-Drift Microbial Communities

    SciTech Connect

    D. Jolley

    2000-11-09

    As directed by written work direction (CRWMS M and O 1999f), Performance Assessment (PA) developed a model for microbial communities in the engineered barrier system (EBS) as documented here. The purpose of this model is to assist Performance Assessment and its Engineered Barrier Performance Section in modeling the geochemical environment within a potential repository drift for TSPA-SR/LA, thus allowing PA to provide a more detailed and complete near-field geochemical model and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near Field Environment (NFE) Revision 2 (NRC 1999). This model and its predecessor (the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document, CRWMS M and O 1998a) was developed to respond to the applicable KTIs. Additionally, because of the previous development of the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a), the M and O was effectively able to resolve a previous KTI concern regarding the effects of microbial processes on seepage and flow (NRC 1998). This document supercedes the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a). This document provides the conceptual framework of the revised in-drift microbial communities model to be used in subsequent performance assessment (PA) analyses.

  3. Velocity diagrams

    NASA Technical Reports Server (NTRS)

    Whitney, W. J.; Stewart, W. L.

    1972-01-01

    The selection and design of velocity diagrams for axial flow turbines are considered. Application is treated in two parts which includes: (1) mean-section diagrams, and (2) radial variation of diagrams. In the first part, the velocity diagrams occurring at the mean section are assumed to represent the average conditions encountered by the turbine. The different types of diagrams, their relation to stage efficiency, and their selection when staging is required are discussed. In the second part, it is shown that in certain cases the mean-section diagrams may or may not represent the average flow conditions for the entire blade span. In the case of relatively low hub- to tip-radius ratios, substantial variations in the velocity diagrams are encountered. The radial variations in flow conditions and their effect on the velocity diagrams are considered.

  4. Application of a drift-flux model to flashing in straight pipes

    Microsoft Academic Search

    C. W. Hirt

    1976-01-01

    A computer program, SOLA-DF, was written to solve the unsteady, two-dimensional equations of motion for a two-phase mixture. The equations solved are based on the drift-flux approximation and include a phase transition model and a general drift velocity calculation. The SOLA-DF code is used for a study of the blowdown of straight pipes initially filled with water at high temperature

  5. Effects of particle drift on cosmic-ray transport. I. General properties, application to solar modulation

    Microsoft Academic Search

    J. R. Jokipii; E. H. Levy; W. B. Hubbard

    1977-01-01

    Although gradient and curvature drifts are explicitly contained in the general equations of cosmic-ray transport, they have been almost universally neglected in applications of these equations. We evaluate the drifts explicitly for the Parker spiral magnetic field and show that, for particles with rigidities greater than approx.0.3 GV in the solar wind, they are larger than the solar-wind velocity over

  6. The ion experiment onboard the Interball-Aurora satellite; initial results on velocity-dispersed structures in the cleft and inside the auroral oval

    Microsoft Academic Search

    J. A. Sauvaud; H. Barthe; C. Aoustin; J. J. Thocaven; J. Rouzaud; E. Penou; D. Popescu; R. A. Kovrazhkin; K. G. Afanasiev

    1998-01-01

    The Toulouse ION experiment flown on the Russian Interball-Aurora mission performs simultaneous ion and electron measurements. Two mass spectrometers looking in opposing directions perpendicular to the satellite spin axis, which points toward the sun, measure ions in the mass and energy ranges 1–32 amu and ~0-14 000 eV. Two electron spectrometers also looking in opposing directions perform measurements in the

  7. Closed-drift thruster investigations

    NASA Technical Reports Server (NTRS)

    Robinson, Raymond S.; Schemmel, Terry D.; Patterson, Michael J.

    1986-01-01

    Recent data obtained from a second generation closed-drift thruster design, employing Hall current acceleration is outlined. This type device is emphasized for electric propulsion for geocentric mission applications. Because geocentric mission profiles are best achieved with a specific impulse range of 1000 to 2000 s, closed-drift thrusters are well suited for this application, permitting time payload compromises intermediate of those possible with either electrothermal or electrostatic devices. A discussion is presented of the potential advantages of using a 1000 to 2000 s device for one way orbit raising of nonpower payloads. Because closed-drift thruster operation is not space charge limited, and requires only one power circuit for steady state operation, their application is technically advantageous. Beam, plasma and thrust characteristics are detailed for a range of operating conditions.

  8. Unconventional Ballooning Structures for Toroidal Drift Waves

    E-print Network

    Xie, H S

    2015-01-01

    The conventional ballooning structures for toroidal drift waves peak in the outboard mid-plane of tokamaks. With strong gradients in the pedestal of H-mode plasmas, gyrokinetic simulations are carried out for the trapped electron and ion temperature gradient modes. General unconventional mode structures that can localize at arbitrary poloidal positions or with multiple peaks are found. By solving the eigenvalue problem of a simplified model equation, it is found that series eigen solutions exist. At weak gradient (L-mode), the most unstable solution is usually the ground eigen state, which corresponds to a conventional mode structure. However, at strong gradient (H-mode), the most unstable solutions usually are not the ground eigen state and the mode structures are general. This result implies that the transport properties of H-mode can be significantly different from those of L-mode.

  9. Propagation of cylindrical lower hybrid drift solitary wave in an inhomogeneous plasma

    SciTech Connect

    Liu Haifeng; Wang Shiqing; Fazhan Yang [Southwestern Institute of Physics, Chengdu 610041 (China); Engineering and Technical College of Chengdu University of Technology, Leshan 614000 (China); Li Kehua; Wang Zhanhe; Zhang Weibing; Wang Zhilong; Qiangxiang; Kaihuang; Yaoliu; Silili; Lanchang [Engineering and Technical College of Chengdu University of Technology, Leshan 614000 (China)

    2013-04-15

    The nonlinear cylindrical lower hybrid drift solitary wave in an inhomogeneous, magnetized plasma with the combined effects of electron density inhomogeneity and electron temperature inhomogeneity is investigated in a two-fluid model. The amplitude and width of the solitary wave are found to decrease as the electronic density inhomogeneity increases. When the electron temperature inhomogeneity grows, the amplitude of the soliton decays and the width never changes. It is noted that the decrease of diamagnetic drift velocity will strengthen the cylindrical lower hybrid drift solitary wave height and width.

  10. Preferential heating of light ions during an ionospheric AR(+) injection experiment

    NASA Technical Reports Server (NTRS)

    Pollock, C. J.; Moore, T. E.; Arnoldy, R. L.; Kintner, P. M.; Cahill, L. J., Jr.

    1994-01-01

    The ARCS 4 sounding rocket was launched northward into high altitude from Poker Flat Research Range on February 23, 1990. The vehicle crossed geomagnetic field lines containing discrete auroral activity. An instrumented subpayload released 100 ev and 200 ev Ar(+) ion beams sequentially, in a direction largely perpendicular to both the local geomagnetic field and the subpayload spin axis. The instrumented main payload was separated along field lines from the beam emitting subpayload by a distance which increased at a steady rate of approx. 2.4 m/s. Three-dimensional mass spectrometric ion observations of ambient H(+) and O(+) ions, obtained onboard the main payload, are presented. Main payload electric field observations in the frequency range 0-16 kHz, are also presented. These observations are presented to demonstrate the operation of transverse ion acceleration, that was differential with respect to ion mass, primarily during 100-ev beam operations. The preferential transverse acceleration of ambient H(+) ions, as compared with ambient O(+) ions during the second, third, fourth, and fifth 100-ev beam operations, is attributed to a resonance at the injected the beam drift velocity among the thermal H(+) ions and plasma waves generated by the injected beam and propagating at the beam drift speed. This work provides experimental support of processes predicted by previously published theory and simulations.

  11. The Great Continental Drift Mystery

    NSDL National Science Digital Library

    This unit introduces students to the development of the theory of continental drift. They will examine the early work of Alfred Wegener and Alexander DuToit, investigate lines of evidence that resulted in the development of the theory, and learn about the final lines of evidence that resulted in the theory's acceptance. There is a set of activities in which the students construct a map of Pangea using Wegener's clues, familiarize themselves with some important geographic locations, and investigate how fossil distribution can be used to enhance the study of continental drift. Study questions and a bibliography are included.

  12. Particle Acceleration in Plasmoid Ejections Derived from Radio Drifting Pulsating Structures

    NASA Astrophysics Data System (ADS)

    Nishizuka, N.; Karlický, M.; Janvier, M.; Bárta, M.

    2015-02-01

    We report observations of slowly drifting pulsating structures (DPSs) in the 0.8-4.5 GHz frequency range of the RT4 and RT5 radio spectrographs at Ond?ejov Observatory, between 2002 and 2012. We found 106 events of DPSs, which we classified into four cases: (I) single events with a constant frequency drift (12 events), (II) multiple events occurring in the same flare with constant frequency drifts (11 events), (III) single or multiple events with increasing or decreasing frequency drift rates (52 events), and (IV) complex events containing multiple events occurring at the same time in a different frequency range (31 events). Many DPSs are associated with hard X-ray (HXR) bursts (15-25 keV) and soft X-ray (SXR) gradient peaks, as they typically occurred at the beginning of HXR peaks. This indicates that DPS events are related to the processes of fast energy release and particle acceleration. Furthermore, interpreting DPSs as signatures of plasmoids, we measured their ejection velocity, their width, and their height from the DPS spectra, from which we also estimated the reconnection rate and the plasma beta. In this interpretation, constant frequency drift indicates a constant velocity of a plasmoid, and an increasing/decreasing frequency drift indicates a deceleration/acceleration of a plasmoid ejection. The reconnection rate shows a good positive correlation with the plasmoid velocity. Finally we confirmed that some DPS events show plasmoid counterparts in Solar Dynamics Observatory/Atmospheric Imaging Assembly images.

  13. Experimental study of particle formation by ion-ion recombination

    NASA Astrophysics Data System (ADS)

    Nagato, Kenkichi; Nakauchi, Masataka

    2014-10-01

    Particle formation by ion-ion recombination has been studied using an ion-ion recombination drift tube (IIR-DT). IIR-DT uses two DC corona ionizers to produce positive and negative ions at the ends of the drift tube. The ions of different polarity move in opposite directions along the electric field in the drift tube. We observed significant particle formation using ions generated in purified air containing H2O, SO2, and NH3. Particle formation was suppressed when no drift field was applied. We also observed few particles when we used a single discharge (positive or negative only). These results clearly show that particle formation observed in the IIR-DT was caused by nucleation by ion-ion recombination. Positive and negative ion species produced by corona ionizers were investigated using an atmospheric pressure ionization mass spectrometer. The ions involved in the particle formation were suggested to include H3O+(H2O)n and NH4+(H2O)n for positive ions and sulfur-based ions such as SO5-, SO5-NO2, and HSO4- for negative ions.

  14. Commissioning Results of the Upgraded Neutralized Drift Compression Experiment

    SciTech Connect

    Lidia, S.M.; Roy, P.K.; Seidl, P.A.; Waldron, W.L.; Gilson, E.P.

    2009-04-30

    Recent changes to the NDCX beamline offer the promise of higher charge compressed bunches (>15nC), with correspondingly large intensities (>500kW/cm2), delivered to the target plane for ion-beam driven warm dense matter experiments. We report on commissioning results of the upgraded NDCX beamline that includes a new induction bunching module with approximately twice the volt-seconds and greater tuning flexibility, combined with a longer neutralized drift compression channel.

  15. Nonlinear oblique whistlers: Their relevance to nonthermal coupling of ions and electrons in accretion flow and supercritical quasi-perpendicular collisionless shocks

    Microsoft Academic Search

    T. Chang

    1989-01-01

    It is demonstrated that oblique whistlers may be effective in coupling and energizing plasma populations during accretion flow onto massive central objects such as black holes. These plasma collective modes could be excited by inverse ion-populations in perpendicular velocity space such as the ring-like and loss-cone type of distributions, or cross-field drifts induced by the gravitational and magnetic fields, reflection

  16. Helium, hydrogen, and oxygen velocities observed on ISEE-3

    NASA Technical Reports Server (NTRS)

    Ogilvie, K. W.; Coplan, M. A.; Zwicki, R. D.

    1982-01-01

    The velocities of hydrogen, helium, and oxygen ions over a full range of solar wind conditions were recorded by the ion composition instrument and Los Alamos National Laboratory plasma instrument aboard the International Sun Earth Explorer. Interspecie velocity differences were observed frequently. For solar wind velocities between 300 and 400 km s(-1) the helium velocity exceeded the hydrogen velocity by 5 km s(-1) the average difference was 14 km s(-1), however no evidence was found for a nonzero average velocity difference between helium and oxygen ions even at the higher velocities. Velocity differences were examined in a number of streams and across a number of interplanetary shocks. Generally helium hydrogen velocity differences are bounded by the Alfven speed. Velocity differences show abrupt changes across interplanetary discontinuities, presumably tangential. The electrostatic potential change across a shock produces differences between the velocities of ions having different charges.

  17. The relation between invertebrate drift and two primary controls, discharge and benthic densities, in a large regulated river

    USGS Publications Warehouse

    Kennedy, Theodore A.; Yackulic, Charles B.; Cross, Wyatt F.; Grams, Paul E.; Yard, Michael D.; Copp, Adam J.

    2014-01-01

    1. Invertebrate drift is a fundamental process in streams and rivers. Studies from laboratory experiments and small streams have identified numerous extrinsic (e.g. discharge, light intensity, water quality) and intrinsic factors (invertebrate life stage, benthic density, behaviour) that govern invertebrate drift concentrations (# m?3), but the factors that govern invertebrate drift in larger rivers remain poorly understood. For example, while large increases or decreases in discharge can lead to large increases in invertebrate drift, the role of smaller, incremental changes in discharge is poorly described. In addition, while we might expect invertebrate drift concentrations to be proportional to benthic densities (# m?2), the benthic–drift relation has not been rigorously evaluated. 2. Here, we develop a framework for modelling invertebrate drift that is derived from sediment transport studies. We use this framework to guide the analysis of high-resolution data sets of benthic density and drift concentration for four important invertebrate taxa from the Colorado River downstream of Glen Canyon Dam (mean daily discharge 325 m3 s?1) that were collected over 18 months and include multiple observations within days. Ramping of regulated flows on this river segment provides an experimental treatment that is repeated daily and allowed us to describe the functional relations between invertebrate drift and two primary controls, discharge and benthic densities. 3. Twofold daily variation in discharge resulted in a >10-fold increase in drift concentrations of benthic invertebrates associated with pools and detritus (i.e. Gammarus lacustris and Potamopyrgus antipodarum). In contrast, drift concentrations of sessile blackfly larvae (Simuliium arcticum), which are associated with high-velocity cobble microhabitats, decreased by over 80% as discharge doubled. Drift concentrations of Chironomidae increased proportional to discharge. 4. Drift of all four taxa was positively related to benthic density. Drift concentrations of Gammarus, Potamopyrgus and Chironomidae were proportional to benthic density. Drift concentrations of Simulium were positively related to benthic density, but the benthic–drift relation was less than proportional (i.e. a doubling of benthic density only led to a 40% increase in drift concentrations). 5. Our study demonstrates that invertebrate drift concentrations in the Colorado River are jointly controlled by discharge and benthic densities, but these controls operate at different timescales. Twofold daily variation in discharge associated with hydropeaking was the primary control on within-day variation in invertebrate drift concentrations. In contrast, benthic density, which varied 10- to 1000-fold among sampling dates, depending on the taxa, was the primary control on invertebrate drift concentrations over longer timescales (weeks to months).

  18. Some remarks on continental drift

    Microsoft Academic Search

    L. Egyed

    1960-01-01

    Summary The continental drift may be explained by an expanding Earth only. In fact, there is a differences in the rate of heat flow between continents and oceans. Principially, there is a possibility of deriving the value of ancient radii by palaeomagnetic and age measurements.

  19. Developing the Theory: Continental Drift

    NSDL National Science Digital Library

    This document outlines the development of the theory of contintental drift and how many lines of evidence collected over several decades by various researchers were brought together to explain how the seafloor spreads and the continents move about. Links to additional information are included.

  20. Continuous drifting games Yoav Freund

    E-print Network

    Freund, Yoav

    Continuous drifting games Yoav Freund AT&T Labs Research Shannon Laboratory 180 Park Avenue, Room that describes the core of the problem. 1 Introduction In [7], Freund shows that boosting is closely related of the recursive formula. 1 #12;Second, in [8], Freund derives an adaptive version of the boost

  1. Continuous drifting games Yoav Freund

    E-print Network

    Freund, Yoav

    Continuous drifting games Yoav Freund AT&T Labs\\Gamma Research Shannon Laboratory 180 Park Avenue that describes the core of the problem. 1 Introduction In [7], Freund shows that boosting is closely related of the recursive formula. 1 #12; Second, in [8], Freund derives an adaptive version of the boost

  2. Primordial Ooze and Continental Drift

    NSDL National Science Digital Library

    In this lesson, students will learn that continental plates drift and this affects the layers of the earth. Following a directed reading and discussion, they will perform an experiment in which they use chocolate frosting and graham crackers to simulate tectonic plates sliding about on the mantle.

  3. Rotating field mass and velocity analyzer

    NASA Technical Reports Server (NTRS)

    Smith, Steven Joel (Inventor); Chutjian, Ara (Inventor)

    1998-01-01

    A rotating field mass and velocity analyzer having a cell with four walls, time dependent RF potentials that are applied to each wall, and a detector. The time dependent RF potentials create an RF field in the cell which effectively rotates within the cell. An ion beam is accelerated into the cell and the rotating RF field disperses the incident ion beam according to the mass-to-charge (m/e) ratio and velocity distribution present in the ion beam. The ions of the beam either collide with the ion detector or deflect away from the ion detector, depending on the m/e, RF amplitude, and RF frequency. The detector counts the incident ions to determine the m/e and velocity distribution in the ion beam.

  4. Electron and ion inertia effects on current-driven collisional dust acoustic, dust ion acoustic, and ion acoustic instabilities

    E-print Network

    Merlino, Robert L.

    Electron and ion inertia effects on current-driven collisional dust acoustic, dust ion acoustic, and ion acoustic instabilities Robert L. Merlino and Nicola D'Angelo Department of Physics and Astronomy online 20 April 2005 Ion acoustic waves can be excited by electrons drifting relative to the ions

  5. Fast non-explosive gases for drift chambers

    SciTech Connect

    Green, D.; Haggerty, H.; Oshima, N.; Yamada, R.

    1988-05-01

    Typical gases which are stock at Fermilab are Ar:C/sub 2/H/sub 6/(50:50) and Ar:CO/sub 2/ (80:20). Argon:Ethane has the virtue of high gas gain and a saturated drift velocity. In fact, parametrizing the drift velocity as a function of electric field we find v/sub d/(E) = v/sub o/(1/minus/e/sup -E/E/o) with v/sub o/ approx. = 5.4 cm/..mu..sec and E/sub o/ = 160 V/cm. However, safety considerations make this gas somewhat inconvenient. The addition of alcohol as quencher also raises the saturation field to, for example, E/sub o/ approx. = 500 V/cm for 1.5% added alcohol. This gas also tends to break up in a high-beam flux environment and leave carbon deposits. The addition of alcohol to avoid such aging often takes a unit cell out of saturation over its entire volume. Finally, for collider applications it is useful to exclude free protons from the gas in order to reduce the sensitivity to the sea of slow neutrons which are present in the collider environment. In contrast, Ar:CO/sub 2/ (80:20) is a gas with more moderate gas gain. The drift velocity at high field is v/sub d/(E > 1.5 kV/cm) approx. = 5.8 cm/..mu..sec. For most field configurations this gas does not saturate, causing a long tail in the drift time distrubtion due to low field regions in the unit cell. The virtues of this gas mixture are that it is cheap, not flammable, and stable under high-beam flux. However as the Collider Upgrade progresses, we wish to find a gas which is faster than 5.0 cm/..mu..sec since the time separation between collisions will at some point be less than drift time of 1..mu..sec for drift distance of 5 cm. 3 refs., 5 figs.

  6. An ion mobility mass spectrometer for investigating photoisomerization and photodissociation of molecular ions

    NASA Astrophysics Data System (ADS)

    Adamson, B. D.; Coughlan, N. J. A.; Markworth, P. B.; Continetti, R. E.; Bieske, E. J.

    2014-12-01

    An ion mobility mass spectrometry apparatus for investigating the photoisomerization and photodissociation of electrosprayed molecular ions in the gas phase is described. The device consists of a drift tube mobility spectrometer, with access for a laser beam that intercepts the drifting ion packet either coaxially or transversely, followed by a quadrupole mass filter. An ion gate halfway along the drift region allows the instrument to be used as a tandem ion mobility spectrometer, enabling mobility selection of ions prior to irradiation, with the photoisomer ions being separated over the second half of the drift tube. The utility of the device is illustrated with photoisomerization and photodissociation action spectra of carbocyanine molecular cations. The mobility resolution of the device for singly charged ions is typically 80 and it has a mass range of 100-440 Da, with the lower limit determined by the drive frequency for the ion funnels, and the upper limit by the quadrupole mass filter.

  7. Incoherent scatter ion line enhancements and auroral arc-induced Kelvin-Helmholtz turbulence

    NASA Astrophysics Data System (ADS)

    Ekeberg, J.; Stasiewicz, K.; Wannberg, G.; Sergienko, T.; Eliasson, L.

    2015-01-01

    We present two cases of incoherent-scatter ion line enhancements in conjunction with auroral arcs drifting through the radar beam. The up- and downshifted ion line shoulders as well as the spectral region between them are enhanced equally and simultaneously. The power enhancements are one order of magnitude above the thermal level and are concentrated in less than 15 km wide altitude ranges at the ionospheric F region peak. The auroral arc passages are preceded by significantly enhanced ion temperatures in the E region, assumed to be caused by transient electric fields associated with velocity shears. We use a Hall MHD model of velocity shears perpendicular to the geomagnetic field and show that a Kelvin-Helmholtz instability will grow for the two presented cases.

  8. Impact of incoherent pumping field and Er3+ ion concentration on group velocity and index of refraction in an Er3+-doped YAG crystal

    NASA Astrophysics Data System (ADS)

    Jafarzadeh, Hossein; Asadpour, Seyyed Hossein; Rahimpour Soleimani, H.

    2015-03-01

    The effect of Er3+ ion concentration and incoherent pumping field on the refractive index and group index in an Er3+: YAG crystal is investigated. It is shown that under different concentrations of Er3+ ion in the crystal, the index of refraction and absorption can be changed and a high index of refraction is accompanied by amplification in the medium. Also, it is shown that with the switching from subluminal to superluminal, or vice versa, light propagation can be obtained by different concentrations of Er3+ ions in the crystal.

  9. Evolution: drift will tear us apart.

    PubMed

    Maderspacher, Florian

    2012-11-01

    That the widely scattered geographical distribution of some animals could be due to continental drift is a neat idea. Now, cave animals provide evidence for extreme long-term persistence on continents drifting apart. PMID:23137684

  10. Performance of drift tubes under high radiation

    E-print Network

    Shi, Yue, S.B. Massachusetts Institute of Technology

    2005-01-01

    In this thesis, the aging and the rejuvenation of an ATLAS proportional drift tube are described. Firstly, the Diethorn model of gain is tested using pressure and sense-wire voltage measurements. The drift tube was then ...

  11. Drift correction for scanning-electron microscopy

    E-print Network

    Snella, Michael T

    2010-01-01

    Scanning electron micrographs at high magnification (100,000x and up) are distorted by motion of the sample during image acquisition, a phenomenon called drift. We propose a method for correcting drift distortion in images ...

  12. Ultraviolet laser calibration of drift chambers

    E-print Network

    Elliott, Grant (Grant Andrew)

    2006-01-01

    We demonstrate the use of a focused ultraviolet laser as a track calibration source in drift chambers, and specifically in a small time projection chamber (TPC). Drift chambers such as TPCs reconstruct the trajectories of ...

  13. Systematic drift of a triaxial gyrostabilizer

    Microsoft Academic Search

    T. K. Gadelshin

    1974-01-01

    Systematic drift of triaxial gyrostabilizers as a function of the parameters of the gyrostabilizer and the external harmonic disturbing moments was evaluated. The effects of external harmonic perturbation on systematic drift was also considered.

  14. Comparison of drift wave models with fluctuation data from the interior of the TEXT tokamak

    Microsoft Academic Search

    D. W. Ross; R. V. Bravenec; C. P. Ritz; M. L. Sloan; J. R. Thompson; A. J. Wootton; P. M. Schoch; J. W. Heard; T. P. Crowley; R. L. Hickok; V. Simcic; D. L. Brower; W. A. Peebles; N. C. Jr. Luhmann

    1990-01-01

    Experimental evidence for and against drift waves as the origin of the observed fluctuations and anomalous transport in the plasma interior is reviewed. Fluctuation spectra observed by far-infrared scattering and a heavy ion beam probe (HIBP) are compared. The FIR system observes broad S(k,(omega)), which are spatially resolved at large k and readily identified with electron drift waves. At higher

  15. New advances in the partial-reflection-drifts experiment using microprocessors

    NASA Technical Reports Server (NTRS)

    Ruggerio, R. L.; Bowhill, S. A.

    1982-01-01

    Improvements to the partial reflection drifts experiment are completed. The results of the improvements include real time processing and simultaneous measurements of the D region with coherent scatter. Preliminary results indicate a positive correlation between drift velocities calculated by both methods during a two day interval. The possibility now exists for extended observations between partial reflection and coherent scatter. In addition, preliminary measurements could be performed between partial reflection and meteor radar to complete a comparison of methods used to determine velocities in the D region.

  16. Cross-B convection of artificially created, negative-ion clouds and plasma depressions - Low-speed flow

    NASA Technical Reports Server (NTRS)

    Bernhardt, Paul A.

    1988-01-01

    A negative-ion, positive-ion plasma produced by the release of an electron attachment chemical into the F region becomes electrically polarized by collisions with neutrals moving across magnetic field lines. The resulting electric field causes E x B drift of the two ion species and the residual electrons. The cross-field flow of the modified ionosphere is computed using a two-dimensional numerical simulation which includes electron attachment and mutual neutralization chemistry, self-consistent electric fields, and three-species plasma transport. The velocity of the plasma is initially in the direction of the neutral wind because the negative-ion cloud is a Pedersen conductivity enhancement. As the positive and negative ions react, the Pedersen conductivity becomes depressed below the ambient value and the velocity of the plasma reverses direction. A plasma hole remains after the positive and negative ions have mutually neutralized. The E x B gradient drift instability produces irregularities on the upwind edge of the hole.

  17. Response of macrofauna to drifting tidal sediments

    NASA Astrophysics Data System (ADS)

    Zühlke, R.; Reise, K.

    1994-06-01

    The effect of hydrodynamically-mobilized sediment on abundance and vertical distribution of macrobenthic fauna was studied in Königshafen, a sheltered tidal bay at the northern end of the Island of Sylt (North Sea). Sediment drift tended to increase from high towards low tide level, while abundance of nearly all species decreased (with the polychaete Spio filicornis as a notable exception). To test whether this decrease could be attributed to water currents affecting sediment stability, experimental flumes with funnels at both ends were set up to enhance sediment mobility by increasing tidal current velocities. Abundance and vertical distribution of fauna inside and outside the flumes were compared. Responses of individual species depended on their vertical position in the sediment, and resembled those observed along the gradient of sediment drift between high and low tide levels. Mainly juveniles of Pygospio elegans, Scoloplos armiger, Hydrobia ulvae and Macoma balthica, and the small polychaete Microphthalmus sczelkowii were washed out of the sediment. No effect of increased erosion inside the flume was found on the numbers of Capitella capitata and the oligochaetes Tubificoides benedii and T. pseudogaster. These oligochaetes probably migrated downwards with increasing erosion in the flumes. Numbers decreased in the upper cm and tended to increase below. A storm had a similar effect on oligochaete vertical distribution, while under conditions of permanently high sediment mobility near low tide level, these species were rare or absent. It is concluded that even under sheltered conditions, differential degrees of sediment mobility may have effects on the zonation of the tidal flat macrofauna.

  18. Branching ratio measurements of the predissociation of 12C16O by time-slice velocity-map ion imaging in the energy region from 108 000 to 110 500 cm-1

    NASA Astrophysics Data System (ADS)

    Gao, Hong; Song, Yu; Yang, Lei; Shi, Xiaoyu; Yin, Qing-Zhu; Ng, C. Y.; Jackson, William M.

    2012-07-01

    Direct branching ratio measurements of the three lowest dissociation channels of 12C16O that produce C(3P) + O(3P), C(1D) + O(3P), and C(3P) + O(1D) are reported in the vacuum ultraviolet region from 108 000 cm-1 (92.59 nm) to 110 500 cm-1 (90.50 nm) using the time-slice velocity-map ion imaging and nonlinear resonant four-wave mixing techniques. Rotationally, resolved carbon ion yield spectra for both 1?+ and 1? bands of CO in this region have been obtained. Our measurements using this technique show that the branching ratio in this energy region, especially the relative percentages of the two spin-forbidden channels, is strongly dependent on the particular electronic and vibrational energy levels of CO that are excited.

  19. First background-free limit from a directional dark matter experiment: results from a fully fiducialised DRIFT detector

    E-print Network

    J. B. R. Battat; J. Brack; E. Daw; A. Dorofeev; A. C. Ezeribe; J. -L. Gauvreau; M. Gold; J. L. Harton; J. M. Landers; E. Law; E. R. Lee; D. Loomba; A. Lumnah; J. A. J. Matthews; E. H. Miller; A. Monte; F. Mouton; A. StJ. Murphy; S. M. Paling; N. Phan; M. Robinson; S. W. Sadler; A. Scarff; F. Schuckman; D. P. Snowden-Ifft; N. J. C. Spooner; S. Telfer; S. E. Vahsen; D. Walker; D. Warner; L. Yuriev

    2014-12-02

    The addition of O2 to gas mixtures in time projection chambers containing CS2 has recently been shown to produce multiple negative ions that travel at slightly different velocities. This allows a measurement of the absolute position of ionising events in the z (drift) direction. In this work, we apply the z-fiducialisation technique to a directional dark matter search. In particular, we present results from a 46.3 live-day source-free exposure of the DRIFT-IId detector run in this completely new mode. With full-volume fiducialisation, we have achieved the first background-free operation of a directional detector. The resulting exclusion curve for spin-dependent WIMP-proton interactions reaches 1.1 pb at 100 GeV/c2, a factor of 2 better than our previous work. We describe the automated analysis used here, and argue that detector upgrades, implemented after the acquisition of these data, will bring an additional factor of >3 improvement in the near future.

  20. Spray drift mitigation with spray mix adjuvants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Numerous drift reduction adjuvants and spray deposition aids are available to applicators of crop production and protection chemicals. Performance of many of the newly introduced drift control adjuvants has not been well documented for aerial application. Four new drift control adjuvants were sele...