Sample records for ion drift velocity

  1. Negative Ion Drift Velocity and Longitudinal Diffusion in Mixtures of Carbon Disulfide and Methane

    NASA Technical Reports Server (NTRS)

    Dion, Michael P.; Son, S.; Hunter, S. D.; deNolfo, G. A.

    2011-01-01

    Negative ion drift velocity and longitudinal diffusion has been measured for gas mixtures of carbon disulfide (CS2) and methane (CH4)' Measurements were made as a function of total pressure, CS2 partial pressure and electric field. Constant mobility and thermal-limit longitudinal diffusion is observed for all gas mixtures tested. Gas gain for some of the mixtures is also included.

  2. 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).

  3. 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.

  4. Drift Velocity Calibration for the CLAS Drift Chamber System

    NASA Astrophysics Data System (ADS)

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

    1996-05-01

    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 drift toward sense wires due to the force exerted by an electric field. Using electronics to measure this drift time, we then compute the distance of closest approach of the track to the sense wire. These distances of closest approach allow us to reconstruct a track showing the trajectory of the cosmic ray. A major problem encountered with the prototype was that changing environmental conditions like the atmospheric pressure and other factors degraded its performance. The changes reduced the accuracy of the drift-time-to-drift-distance formula; leading to worse resolution. However, we have determined that accounting for the change in the maximum drift time can help us regain our accuracy. Data obtained from the drift time spectrum enables us to obtain an accurate value of this parameter. Using this updated value in a calibration file maintains the drift velocity function and the resolution.

  5. Variation of type 1 plasma wave phase velocity with electron drift velocity in the equatorial electrojet

    NASA Astrophysics Data System (ADS)

    Ravindran, Sudha; Reddy, C. A.

    1993-12-01

    Using a 54.95-MHz coherent backscatter radar at Thumba (8.5 deg N, 77 deg E; 0.5 deg N dip angle), the phase velocity variations of type 1 plasma waves generated by the modified two-stream instability process in the equatorial electrojet have been measured on several occasions of large and rapid electric field flunctuations associated with geomagnetic substorms and storms. The measurements show a clear linear variation of type 1 wave phase velocity (VIp) over a considerable range with the simultaneously measured phase velocity (VIIp) of gradient drift instability-generated type 2 plasma waves. Since VIIp is porportional to the drift velocity of electrons, the observed variations of VIp with VIIp mean that VIp varies in step with the variations of the electron drift velocity Vey. The observed variation of VIp with Vey is consistent with the current theoretical understanding that the plasma wave-associated electric fields cause anomalous electron diffusion and heating which result in the stabilization of the type 1 wave phase velocity near the increased value of the ion-acoustic velocity. The enhanced electron temperatures estimated from the largest values of the observed VIp are found to be 2.0 - 2.4 times the ambient value in the absence of waves.

  6. 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.

  7. 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

  8. Longitudinal structure of the vertical E × B drift and ion density seen from ROCSAT-1

    Microsoft Academic Search

    Hyosub Kil; S.-J. Oh; M. C. Kelley; L. J. Paxton; S. L. England; E. Talaat; K.-W. Min; S.-Y. Su

    2007-01-01

    We investigate the longitudinal distribution of the vertical E × B drift velocity and ion density in the low-latitude ionosphere using the first Republic of China Satellite (ROCSAT-1) data acquired during 1999–2004. The ROCSAT-1 observations during daytime demonstrate the presence of the longitudinally periodic patterns of the vertical E × B drift and plasma density on the topside F region

  9. 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.

  10. Filament velocity scaling laws for warm ions

    NASA Astrophysics Data System (ADS)

    Manz, P.; Carralero, D.; Birkenmeier, G.; Müller, H. W.; Müller, S. H.; Fuchert, G.; Scott, B. D.; Stroth, U.

    2013-10-01

    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.

  11. 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.

  12. A first comparison of STARE and EISCAT electron drift velocity measurements

    Microsoft Academic Search

    E. Nielsen; K. Schlegel

    1983-01-01

    The accuracy of Scandinavian Twin Auroral Radar Experiment (STARE) estimates of ionospheric electron drift velocities has been tested by comparison with simultaneous velocity measurements of the European Incoherent Scatter facility (EISCAT). While STARE estimated drift velocity magnitudes are in agreement with EISCAT figures for velocities smaller than 700 m\\/sec, the estimates become too low with increasing velocity. Agreement is obtained

  13. Longitudinal and seasonal variations of the equatorial ionospheric density and drift velocities during solar minimum

    NASA Astrophysics Data System (ADS)

    Mohapatra, S.; Earle, G. D.

    2010-12-01

    The C/NOFS satellite sensors measure the ion density, electric and magnetic fields, ion drift, ion and electron temperatures, neutral wind, total electron content and ionsopheric scintillation. The extended solar minimum prevailing during C/NOFS mission allow us to establish a baseline model of the seasonal variations of the topside equatorial ionosphere. The 13-degree inclination of the C/NOFS orbit causes the perigee to advances through all local times in about 66 days. This allows seasonal sampling of the ionsopheric density and drift velocity as a function of local time, magnetic latitude, altitude, and longitude. Measurements taken near the spacecraft's perigee at about 420 km altitude indicate an unusually cold low-density ionosphere with an O+ to H+ ratio of approximately 4 during nighttime conditions. Our analysis focuses on the behavior of the longitudinal structure of the equatorial ionospheric density and velocity at all the local times during the equinox months (August 21 to October 21st, February 21 to April 21st), northern summer months (April 21 to August 21st) and northern winter (October 21 to February 21) months for the year 2008 and 2009 near the perigee. The systematic study of the ion velocity and ion density with longitude will reveal new characteristics of the low latitude ionosphere during extreme solar minimum conditions.

  14. Ion Trapping for Ion Mobility Spectrometry Measurements in a Cyclical Drift Tube

    E-print Network

    Clemmer, David E.

    Ion Trapping for Ion Mobility Spectrometry Measurements in a Cyclical Drift Tube Rebecca S. Glaskin in a cyclical drift tube, as a means of enhancing ion signals for scanning ion cyclotron mobility measurements of the cyclical drift tube and these pulses are accumulated prior to initiation of the mobility measurements

  15. Electron-drift driven ion-acoustic mode in a dusty plasma with collisional effects

    E-print Network

    Singh, R

    2000-01-01

    Instabilities of ion-acoustic waves in a dusty plasma with electron-drift, collisional, and dust charge fluctuations effects, have been investigated. The regimes are clearly marked out where the theory is applicable. The critical electron-drift velocity required to drive the instability is predicted. It is also shown that electron thermal conductivity and charged grains concentration enhance the growth of the ion-acoustic mode whereas ion-viscosity, ion-thermal conductivity, and dust charge fluctuations have a stabilizing effect.

  16. 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.

  17. 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.

  18. On Ion Drifts and Neutral Winds in Titan's Thermosphere

    NASA Astrophysics Data System (ADS)

    Shebanits, Oleg; Wahlund, Jan-Erik; Edberg, Niklas J. T.; Andrews, David J.; Crary, Frank J.; Wellbrock, Anne; Coates, Andrew; Mandt, Kathleen E.; Waite, J. Hunter, Jr.

    2015-04-01

    Saturn's largest moon Titan hosts an atmosphere with complex organic chemistry initiated in the ionosphere. The nightside chemistry may be influenced by the ion transport from the dayside ionosphere. In turn, ion transport (ion drifts) may be affected by the neutral winds, which cannot be measured directly by Cassini. In this study we derive the ion drifts along the spacecraft trajectories based on analysis of in-situ measurements of electron and ion fluxes, positive and negative ion masses and the magnetic field. Data from Titan flybys TA to T100 was included (Oct 2005 - Apr 2014), of which 55 flybys were below 1400 km and 48 below 1200 km altitude. From the electron and ion flux measurements three regions were observed: 1) above 1600 km, ions are ExB-drifting (frozen into the fields), 2) 1100-1600 km altitudes, dynamo-region, ions drift in opposite directions (perpendicular to B) and 3) 880-1100 km altitude (upper limit depends on convection electric field strength), ions are following neutrals and ion drifts translate to neutral winds of 0.5-2.5 km/s with weaker winds on the dayside of Titan's ionosphere.

  19. Drift Compression of an Intense Neutralized Ion Beam P. K. Roy,1

    E-print Network

    Gilson, Erik

    Drift Compression of an Intense Neutralized Ion Beam P. K. Roy,1 S. S. Yu,1 E. Henestroza,1 A Jersey 08543-0451, USA (Received 9 September 2005; published 29 November 2005) Longitudinal compression of a velocity-tailored, intense neutralized K beam at 300 keV, 25 mA has been demonstrated. The compression

  20. 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.

  1. Electronic and positronic guiding-center drift ions.

    PubMed

    Dubin, Daniel H E

    2004-05-14

    A novel type of guiding-center drift ion is described. These ions occur only in strong magnetic fields. They consist of a neutral atom to which either an electron or positron is weakly bound, at a sufficiently large radius that it may be described by ExB drift dynamics. Such ions may occur naturally in astrophysical plasmas and may have been formed in recent antihydrogen experiments, where their presence would provide proof that deeply bound H atoms are being created. PMID:15169411

  2. 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.

  3. The longitudinal variability of equatorial electrojet and vertical drift velocity in the African and American sectors

    NASA Astrophysics Data System (ADS)

    Yizengaw, E.; Moldwin, M. B.; Zesta, E.; Biouele, C. M.; Damtie, B.; Mebrahtu, A.; Rabiu, B.; Valladares, C. F.; Stoneback, R.

    2014-03-01

    While the formation of equatorial electrojet (EEJ) and its temporal variation is believed to be fairly well understood, the longitudinal variability at all local times is still unknown. This paper presents a case and statistical study of the longitudinal variability of dayside EEJ for all local times using ground-based observations. We found EEJ is stronger in the west American sector and decreases from west to east longitudinal sectors. We also confirm the presence of significant longitudinal difference in the dusk sector pre-reversal drift, using the ion velocity meter (IVM) instrument onboard the C/NOFS satellite, with stronger pre-reversal drift in the west American sector compared to the African sector. Previous satellite observations have shown that the African sector is home to stronger and year-round ionospheric bubbles/irregularities compared to the American and Asian sectors. This study's results raises the question if the vertical drift, which is believed to be the main cause for the enhancement of Rayleigh-Taylor (RT) instability growth rate, is stronger in the American sector and weaker in the African sector - why are the occurrence and amplitude of equatorial irregularities stronger in the African sector?

  4. Simulation of drift-cyclotron-loss-cone modes in tandem mirrors with sloshing ions

    SciTech Connect

    Cohen, B.I.; Maron, N.; Nevins, W.M.

    1984-03-01

    Particle simulations of drift-cyclotron-loss-cone modes in a tandem-mirror end cell confirm that sloshing-ion distributions and the concomitant trapping of low-energy ions by a depression in the ambipolar potential lead to improved microstablity. The simulations study the influences of neutral-beam-injection angle, the magnetic-mirror ratio, the size of the depression in the ambipolar potential, and warm streaming plasma on both plasma confinement and drift-cone instability. A simple nonlinear theory of velocity-space transport predicts wave amplitudes and end-loss rates at steady state that are reasonably consistent with the simulation results. This study supports both the basic strategy for sloshing-ion operation of tandem mirrors and corroborates the first measurements of ion-cyclotron modes in the TMX-Upgrade experiment at the Lawrence Livermore National Laboratory.

  5. EFFECT OF ION B DRIFT DIRECTION ON TURBULENCE FLOW AND FLOW SHEAR

    SciTech Connect

    FENZI,C; McKEE,G.R; BURRELL,K.H; CARLSTROM,T.N; FONCK,R.J; GROEBNER,R.J

    2003-07-01

    The divertor magnetic geometry has a significant effect on the poloidal flow and resulting flow shear of turbulence in the outer region of L-mode tokamak plasmas, as determined via two-dimensional measurements of density fluctuations with Beam Emission Spectroscopy on DIII-D. Plasmas with similar parameters, except that in one case the ion {del}B drift points towards the divertor X-point (lower single-null, LSN), and in the other case, the ion {del}B drift points away from the divertor X-point (upper single-null, USN), are compared. Inside of r/a=0.9, the turbulence characteristics (amplitude, flow direction, correlation lengths) are similar in both cases, while near r/a=0.92, a dramatic reversal of the poloidal flow of turbulence relative to the core flow direction is observed in plasmas with the ion {del}B drift pointing towards the divertor X-point. No such flow reversal is observed in plasmas with the ion {del}B drift pointing away from the divertor X-point. This poloidal flow reversal results in a significantly larger local shear in the poloidal turbulence flow velocity in plasmas with the ion {del}B drift pointing towards the divertor X-point. Additionally, these plasmas locally exhibit significant dispersion, with two distinct and counter-propagating turbulence modes. Likewise, the radial correlation length of the turbulence is reduced in these plasmas, consistent with biorthogonal decomposition measurements of dominant turbulence structures. The naturally occurring turbulence flow shear in these LSN plasmas may facilitate the LH transition that occurs at an input power of roughly one-half to one-third that of corresponding plasmas with the ion {del}B drift pointing away from the X-point.

  6. Ion Mobility Spectrometry – Mass Spectrometry Performance Using Electrodynamic Ion Funnels and Elevated Drift Gas Pressures

    SciTech Connect

    Baker, Erin Shammel; Clowers, Brian H.; Li, Fumin; Tang, Keqi; Tolmachev, Aleksey V.; Prior, David C.; Belov, Mikhail E.; Smith, Richard D.

    2007-06-28

    The ability of ion mobility spectrometry coupled with mass spectrometry (IMS-MS) to characterize biological mixtures has been illustrated over the past eight years. However, the challenges posed by the extreme complexity of many biological samples have demonstrated the need for higher resolution IMS-MS measurements. We have developed a higher resolution ESI-IMS-TOF MS by utilizing high pressure electrodynamic ion funnels at both ends of the IMS drift cell and operating the drift cell at an elevated pressure compared to a previous design. The ESI-IMS-TOF MS instrument consists of an ESI source, an hourglass ion funnel used for ion accumulation/injection into an 88 cm drift cell followed by a 10 cm ion funnel and a commercial orthogonal time-of-flight mass spectrometer providing high mass measurement accuracy. It was found that the rear (exit) ion funnel could be effectively operated as an extension of the drift cell when the DC fields were matched, allowing the instrument to have an effective drift region of 98 cm. Two differentially pumped quadrupole regions were used to couple the IMS and TOF MS to focus and minimize the ion transient time between the stages. The resolution of the instrument was evaluated at pressures ranging from 4 to12 Torr and ion mobility drift voltages of 16 V/cm (4 Torr) to 43 V/cm (12 Torr). An increase in resolution from 55 to 80 was observed from 4 to 12 Torr nitrogen drift gas with no loss in sensitivity. Given the increased usage of ion funnels prior to ion mobility separations, additional attention was directed towards the influence of drift gas on the observed ion populations trapped and transmitted using an electrodynamic ion funnel. The choice of drift gas was shown to influence the degree of ion heating and relative trapping efficiency within the ion funnel.

  7. Identity confirmation of drugs and explosives in ion mobility spectrometry using a secondary drift gas

    Microsoft Academic Search

    Abu B. Kanu; Herbert H. Hill

    2007-01-01

    This work demonstrated the potential of using a secondary drift gas of differing polarizability from the primary drift gas for confirmation of a positive response for drugs or explosives by ion mobility spectrometry (IMS). The gas phase mobilities of response ions for selected drugs and explosives were measured in four drift gases. The drift gases chosen for this study were

  8. A Split-Field Drift Tube for Separation and Efficient Fragmentation of Biomolecular Ions

    E-print Network

    Clemmer, David E.

    A Split-Field Drift Tube for Separation and Efficient Fragmentation of Biomolecular Ions Stephen J in their mobilities in a 20-cm-long low-field (5 V cm-1) region of a drift tube. As the ions approach the drift tube collisionally activated and dissociate as they exit the drift tube. We have demon- strated this approach

  9. Ion drifts in a snowflake divertor

    SciTech Connect

    Ryutov, D. D.; Umansky, M. V. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

    2010-01-15

    Prompt losses of ions having turning points in the vicinity of the poloidal field null of a snowflake divertor are analyzed. Classification of the ion trajectories is presented. It is concluded that prompt losses in a snowflake affect a broader zone than in the standard X-point divertor. The size of the phase-space 'hole' produced by prompt losses is evaluated.

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

    E-print Network

    Merlino, Robert L.

    treatment of the Kelvin­Helmholtz KH instability in a fully ionized plasma in a magnetic field of shear can, in some cases, drastically reduce the necessary critical drift velocities for the excitationElectrostatic ion-cyclotron waves driven by parallel velocity shear R. L. Merlinoa) Department

  11. Ion source with closed drift anode layer plasma acceleration

    Microsoft Academic Search

    V. Dudnikov; A. Westner

    2002-01-01

    Several versions of ion sources with closed drift anode layer plasma acceleration (ALPA sources) were built and tested. Robust, ``all iron'' design and water cooling permeate an unlimited operation with oxygen and with other high reactive gases. Long time operation of discharges in oxygen, nitrogen, argon, water vapor, propane, acetone, ethyl alcohol vapors, and in different gas cocktails has been

  12. Oblique ion collection in the drift approximation: How magnetized Mach probes really work

    SciTech Connect

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

    2008-12-15

    The anisotropic fluid equations governing a frictionless obliquely flowing plasma around an essentially arbitrarily shaped three-dimensional ion-absorbing object in a strong magnetic field are solved analytically in the quasineutral drift approximation, neglecting parallel temperature gradients. The effects of transverse displacements traversing the magnetic presheath are also quantified. It is shown that the parallel collection flux density dependence upon the external Mach number is n{sub {infinity}}c{sub s} exp[-1-(M{sub parallel}{infinity}-M{sub perpendicular}cot {theta})], where {theta} is the angle (in the plane of field and drift velocity) of the object-surface to the magnetic-field and M{sub parallel{infinity}} is the external parallel flow. The perpendicular drift, M{sub perpendicular}, appearing here consists of the external E and B drift plus a weighted sum of the ion and electron diamagnetic drifts that depends upon the total angle of the surface to the magnetic field. It is that somewhat counterintuitive combination that an oblique (transverse) Mach probe experiment measures.

  13. An empirical model of the drift velocity of equatorial plasma depletions

    NASA Astrophysics Data System (ADS)

    England, S. L.; Immel, T. J.

    2012-12-01

    The Far-Ultraviolet Imager on the IMAGE spacecraft (IMAGE-FUV) has been used to observe O+plasma depletions in the post-sunset equatorial ionosphere. Small-scale density irregularities associated with such depletions are believed to adversely affect trans-ionospheric radio signals such as GPS. Prediction of the motion of these plasma depletions is a necessary component of the ability to forecast the occurrence of such radio signal interference. An automated method has recently been developed to identify and track the position and zonal drift velocity of these depletions. Here we use this method to create a large database of the zonal drift velocities of these depletions. We present an empirical model based on these observations that describes the observed drift velocities as a function of both local time and magnetic latitude, which is essential to represent their behavior. A comparison of the observed drift velocities with zonal winds from both an empirical model (Horizontal Wind Model; HWM07) and a first-principles model (the TIEGCM) reveals that the plasma depletions' drift velocities have a latitudinal gradient that cannot be explained solely by the F-region dynamo in the post-sunset period, at least by these climatological models. This suggests that these plasma depletions may not simply drift with the background F-region plasma. It has previously been suggested that vertical polarization electric fields associated with the plasma depletions are responsible for their zonal drifts exceeding the background flow, which may explain the previously-observed discrepancy in the drift velocities and the discrepancy in their gradients reported here.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

    Geng, Hao; Zhao, Zhong-Jun; Duan, Yi-Xiang

    2015-05-01

    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. Supported by Financial Support from the National Major Scientific Instruments and Equipment Development Special Funds (2011YQ030113), National Recruitment Program of Global Experts (NRPGE), the Hundred Talents Program of Sichuan Province (HTPSP) and the Startup Funding of Sichuan University for Setting up the Research Center of Analytical Instrumentation

  16. Asymptotic velocity of one dimensional diffusions with periodic drift

    E-print Network

    P. Collet S. Martinez

    2007-05-10

    We consider the asymptotic behaviour of the solution of one dimensional stochastic differential equations and Langevin equations in periodic backgrounds with zero average. We prove that in several such models, there is generically a non vanishing asymptotic velocity, despite of the fact that the average of the background is zero.

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

    E-print Network

    Biktashev, Vadim N.

    wave rotation frequency, and spatial drift, that is slow movement of the spiral's rotation centre'' drift caused by (approx­ imately) periodic modulation of medium properties through external forcing [20Computation of the Drift Velocity of Spiral Waves using Response Functions I.V. Biktasheva and A

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

    E-print Network

    Biktashev, Vadim N.

    wave rotation frequency, and spatial drift, that is slow movement of the spiral's rotation centre" drift caused by (approx- imately) periodic modulation of medium properties through external forcing [20Computation of the Drift Velocity of Spiral Waves using Response Functions I.V. Biktasheva and A

  19. 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...

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

    E-print Network

    Christian Scharf; Robert Klanner

    2015-03-30

    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 data for silicon, than the standard parametrization.

  1. 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.

  2. Current-driven drift wave instability in a collisional dusty negative ion plasma

    NASA Astrophysics Data System (ADS)

    Rosenberg, M.; Rosenberg

    2013-12-01

    The excitation of drift waves by an electron current parallel to the magnetic field is investigated in a nonuniform plasma composed of electrons, positive ions, negative ions, and massive, negatively charged dust. Electrostatic drift waves with frequencies smaller than the ion gyrofrequencies and wavelengths larger than the ion gyroradii are considered. Linear kinetic theory is used, and collisions of charged particles with neutrals are taken into account. The present results may be relevant to laboratory collisional magnetoplasmas containing negative ions and dust.

  3. 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

    Drift tube ion mobility spectrometry (IMS) is a powerful, post-ionization separation that yields structural information of ions through an ion-neutral collision cross section. The ion-neutral collision cross section is governed by the collision...

  4. 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

  5. Ion mobility mass spectrometry of peptide ions: effects of drift gas and calibration strategies.

    PubMed

    Bush, Matthew F; Campuzano, Iain D G; Robinson, Carol V

    2012-08-21

    One difficulty in using ion mobility (IM) mass spectrometry (MS) to improve the specificity of peptide ion assignments is that IM separations are performed using a range of pressures, gas compositions, temperatures, and modes of separation, which makes it challenging to rapidly extract accurate shape parameters. We report collision cross section values (?) in both He and N(2) gases for 113 peptide ions determined directly from drift times measured in a low-pressure, ambient temperature drift cell with radio-frequency (rf) ion confinement. These peptide ions have masses ranging from 231 to 2969 Da, ?(He) of 89-616 Å(2), and ?(N(2)) of 151-801 Å(2); thus, they are ideal for calibrating results from proteomics experiments. These results were used to quantify the errors associated with traveling-wave ? measurements of peptide ions and the errors concomitant with using drift times measured in N(2) gas to estimate ?(He). More broadly, these results enable the rapid and accurate determination of calibrated ? for peptide ions, which could be used as an additional parameter to increase the specificity of assignments in proteomics experiments. PMID:22845859

  6. Sudden appearance of sub-keV structured ions in the inner magnetosphere within one hour: drift simulation

    NASA Astrophysics Data System (ADS)

    Yamauchi, Masatoshi; Ebihara, Yusuke; Dandouras, Iannis; Nilsson, Hans

    2014-05-01

    Energy-latitude dispersed structured sub-keV ions in the inner magnetosphere drifts very slowly in the noon-to-afternoon sectors because the eastward corotation and the westward magnetic drift balances to each other there. However, majority of Cluster ion observation by the Cluster Ion Spectrometry (CIS) COmposition DIstribution Function (CODIF) instrument during 2001-2006 showed significant development or intensification (by more than factor of 3) within 1-2 h in that sector during the Cluster perigee traversals that quickly scans latitudinal structure at a fixed local time (Yamauchi et al., 2013). The frequent observations of significant inbound-outbound differences in the wedge-like dispersed ions by Cluster indicates either new injections or high eastward drift velocity even in the afternoon sector. To examine the former possibility, i.e., whether such sudden appearances in the dayside can be explained by the drift motion of ions that are formed during substorm-related injections, we numerically simulated two such examples, one at noon (8 September 2002) and the other in the afternoon (9 July 2001), based on the same ion drift simulation model that has successfully reproduced the ion pattern of an inbound-outbound symmetric event at 5 MLT observed by the Cluster CIS/CODIF instrument. The model uses backward phase-space mapping to a boundary at the nightside 8 Earth radii and forward numerical simulation using re-constructed distribution function at that boundary. For both examples, the ion drift model with finite duration (limited to 1-2 hours) of proton source in the nightside can explain the observed large inbound-outbound differences in the sub-keV proton population without any new sources. Ion drift motion is thus able to cause rapid changes of complicated ion populations, at remote places from the source long time after the substorm activities, although this result does not eliminate the possibility of having independent ionospheric sources. References: Yamauchi, M. et al.: Cluster observation of few-hour-scale evolution of structured plasma in the inner magnetosphere, Ann. Geophys., 31, 1569-1578, doi:10.5194/angeo-31-1569-2013, 2013.

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

    E-print Network

    Kaganovich, Igor

    compression is a standard technique used to increase the beam intensity in various accelerators [1]. PreviousEffects of errors in velocity tilt on maximum longitudinal compression during neutralized drift compression of intense beam pulses: II. Analysis of experimental data of the Neutralized Drift Compression e

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

    E-print Network

    Kaganovich, Igor

    intensity in various accelerators [1]. Long- itudinal compression during neutralized drift is achievedEffects of errors in velocity tilt on maximum longitudinal compression during neutralized drift compression of intense beam pulses: I. general description Igor D. Kaganovich a,n , Scott Massidda a , Edward

  10. A large enhancement of the maximum drift velocity of electrons in the channel of a field-effect heterotransistor

    SciTech Connect

    Pozela, J. K. [Semiconductor Physics Institute (Lithuania)], E-mail: pozela@spi.pfi.lt; Mokerov, V. G. [Russian Academy of Sciences, Institute of the Microwave Semiconductor Electronics (Russian Federation)

    2006-03-15

    It is shown that the optical-phonon momentum quantization in a GaAs quantum well resulting from the introduction of an InAs quantum-dot barrier layer provides for the elimination of inelastic scattering of electrons by optical phonons and, thus, makes the acceleration of electrons above the saturation drift velocity possible. It is shown experimentally that the maximum drift velocity of electrons in high electric fields in AlGaAs/GaAs heterostructure with InAs quantum-dot barriers introduced into the GaAs quantum well exceeds the saturation drift velocity in bulk GaAs by as much as a factor of 10. Such a rise in the maximum drift velocity of electrons ensures increased maximum current density, transconductance, and cutoff frequency of the heterostructure field-effect transistor with quantum dots.

  11. Fast Faraday cup to measure neutralized drift compression in intense ion charge bunches

    Microsoft Academic Search

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

    2006-01-01

    Heavy ion drivers for heavy ion fusion and high energy density physics applications use space-charge-dominated ion beams which must undergo longitudinal bunch compression in order to meet the requisite beam intensities desired at the target. The Neutralized Drift Compression Experiment-1A (NDCX-1A) at Lawrence Berkeley National Laboratory is used to determine the effective limits of neutralized drift compression, which occurs due

  12. Precession Drift Velocity Shear and the Origin of Electron Transport Barriers

    NASA Astrophysics Data System (ADS)

    Katt, L. T.; Katt, D. T.; Diamond, P. H.

    1997-11-01

    The origin and dynamics of electron transport barriers are the premier unsolved problems in magnetic confinement theory today. Here, we propose a novel mechanism for enhanced decorrelation of short wavelength trapped electron modes (i.e. with ?_bot? _i>1), which are a likely and theoretically plausible agent of anomalous electron transport. The electron temperature and q(r) dependence of the trapped electron magnetic precession drift induce rapid decorrelation when coupled to radial scattering, so that a BDT-like model can be constructed. Note that for sufficiently strong shear, a positive feedback loop can result, leading to the formation of an electron transport barrier supported by drift velocity shear. Critical electron heating power levels can be predicted and will be compared to results from Tore-Supra and JT-60U.

  13. Dayside/nightside asymmetry of ion densities and velocities in Saturn's inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Holmberg, M. K. G.; Wahlund, J.-E.; Morooka, M. W.

    2014-06-01

    We present Radio and Plasma Wave Science Langmuir probe measurements from 129 Cassini orbits, which show a day/night asymmetry in both ion density and ion velocity in the radial region 4-6 RS (1 RS = 60,268 km) from the center of Saturn. The ion densities ni vary from an average of ˜35 cm-3 around noon up to ˜70 cm-3 around midnight. The ion velocities vi,? vary from ˜28-32 km/s at the lowest dayside values to ˜36-40 km/s at the highest nightside values. The day/night asymmetry is suggested to be due to the radiation pressure force acting on negatively charged nanometer-sized dust of the E ring. This force will introduce an extra grain and ion drift component equivalent to the force of an additional electric field of 0.1-2 mV/m for 10-50 nm sized grains.

  14. 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.

  15. Ion velocity distribution function measurements in a helium helicon plasma

    Microsoft Academic Search

    E. Scime; R. Murphy; I. Biloiu; C. Compton

    2006-01-01

    Summary form only given. The scarcity of strong absorption lines in accessible tuning ranges along with plasma saturation due to low ion population densities makes laser absorption spectroscopy of helium ions in plasma notoriously difficult. Helicon plasmas, with their characteristically high ion densities are a good candidate for helium ion spectroscopy experiments. Initial measurements of Doppler broadened ion velocity distribution

  16. Ion drift meter calibration and photoemission correction for the C/NOFS satellite

    NASA Astrophysics Data System (ADS)

    Stoneback, R. A.; Davidson, R. L.; Heelis, R. A.

    2012-08-01

    The Ion Drift Meter (IDM) onboard the Communication/Navigation Outage Forecasting System (C/NOFS) measures ion arrival angles transverse to the satellite path and requires precise attitude determination for proper conversion to ambient ion drift. Low ionospheric densities during the 2008/9 solar minimum restricted quality measurements to altitudes near perigee, limiting the daily local time coverage of the satellite. As the primary ionospheric boundary condition available to calibrate the IDM requires that the integral of meridional (vertical) ion drifts be zero over all local times and longitudes, the limited daily local time coverage necessitated a new calibration procedure. A procedure is presented that utilizes the median meridional drift over all local times determined over a 67 day perigee precession period to calibrate the instrument. Offsets are isolated for both measurement directions by exploiting the different symmetry relationships that the spacecraft orientation has with respect to the meridional direction as a function of magnetic latitude. The low ionospheric densities along with the equatorial orbit of C/NOFS also allowed photoemission currents within the instrument to be detected. A numerical model of photoemission within the drift meter is presented in detail and used to generate a first order software correction to remove a large portion of this error from measurements. Both the photoemission correction and the drift meter calibration procedure are supported by a comparison to vertical ion drifts measured by the Jicamarca Radar Observatory.

  17. Designing Neutralized Drift Compression for Focusing of Intense Ion Beam Pulses in a Background Plasma

    SciTech Connect

    Kaganovich, I.D.; Davidson, R.C.; Dorf, M.; Startsev, E.A.; Barnard, J.J.; Friedman, A.; Lee, E.P.; Lidia, S.M.; Logan, B.G.; Roy, P.K.; Seidl, P.A.; Welch, D.R.; Sefkow, A.B.

    2009-04-28

    Neutralized drift compression offers an effective method for particle beam focusing and current amplification. In neutralized drift compression, a linear radial and longitudinal velocity drift is applied to a beam pulse, so that the beam pulse compresses as it drifts in the drift-compression section. The beam intensity can increase more than a factor of 100 in both the radial and longitudinal directions, resulting in more than 10,000 times increase in the beam number density during this process. The self-electric and self-magnetic fields can prevent tight ballistic focusing and have to be neutralized by supplying neutralizing electrons. This paper presents a survey of the present theoretical understanding of the drift compression process and plasma neutralization of intense particle beams. The optimal configuration of focusing and neutralizing elements is discussed in this paper.

  18. Electronic and Positronic Guiding-Center Drift Ions Daniel H. E. Dubin

    E-print Network

    California at San Diego, University of

    fields [2], and while there has been work on the properties of negative ions in such fields, little-center hydrogen atoms, where an electron E B drifts in the Coulomb potential of a central proton [7]. Antimatter

  19. 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

  20. Fluid and drift-kinetic description of a magnetized plasma with low collisionality and slow dynamics orderings. II. Ion theory

    SciTech Connect

    Ramos, J. J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States)

    2011-10-15

    The ion side of a closed, fluid and drift-kinetic theoretical model to describe slow and macroscopic plasma processes in a fusion-relevant, low collisionality regime is presented. It follows the ordering assumptions and the methodology adopted in the companion electron theory [Ramos, Phys. Plasmas 17, 082502 (2010)]. To reach the frequency scale where collisions begin to play a role, the drift-kinetic equation for the ion distribution function perturbation away from a Maxwellian must be accurate to the second order in the Larmor radius. The macroscopic density, flow velocity and temperature are accounted for in the Maxwellian, and are evolved by a fluid system which includes consistently the gyroviscous part of the stress tensor and second-order contributions to the collisionless perpendicular heat flux involving non-Maxwellian fluid moments. The precise compatibility among these coupled high-order fluid and drift-kinetic equations is made manifest by showing that the evolution of the non-Maxwellian part of the distribution function is such that its first three velocity moments remain equal to zero.

  1. Estimating drift velocity of polar cap patches with all-sky airglow imager at Resolute Bay, Canada

    Microsoft Academic Search

    K. Hosokawa; K. Shiokawa; Y. Otsuka; A. Nakajima; T. Ogawa; J. D. Kelly

    2006-01-01

    Highly sensitive all-sky airglow imager has been operative at Resolute Bay, Canada (74.73°N, 265.07°E AACGM latitude 82.9°) since January 2005. We present, as a first result from the imager, an event of polar cap patches drifting anti-sunward during the southward IMF conditions. Magnitude and direction of patch drift velocities are computed with a temporal resolution of 2 min by using

  2. Rapidly changing distribution of velocity and suspended materials under the drifting Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Ha, Ho Kyung; Im, Jungho; Kim, Yong Hoon; Yae Son, Eun; Lee, Sanggyun

    2015-04-01

    In two summer seasons of 2011 and 2014, the short-term (1-4 days) ice-camp study has been conducted on the drifting Arctic sea ice. In particular, in 2014, the international collaboration with the Marginal Ice Zone program (sponsored by Office of Naval Research) has been integrated. The mooring package comprises the acoustic Doppler velocity profiler, holographic imaging camera, and conductivity-temperature-depth profiler, which are used to understand the dynamic behavior of sea ice and spatial-temporal variation of mixing layer (ML) and suspended particulate matters under the sea ice. Mooring data clearly shows the mixing and entrainment pattern in the upper ML in the marginal ice zone. When ice floes drift toward the pack ice, the upward entrainment from the seasonal pycnocline to sea ice-water boundary was induced by shear across ML and seasonal pycnocline. The entrainment speed was in the range of 0.25-2 m/hr, which matches well with thickening and thinning rate of ML during the near-inertial period (~12 hr). When ice floes drift toward the open ocean, the turbulent wakes at the advancing edge of ice were combined with the entrainment caused by near-inertial motion, which results in a complex mixing pattern of both upward and downward fluxes in the ML. Also, the acoustic backscatter observed by the acoustic Doppler current profiler and beam attenuation from transmissometer revealed the increased concentration of suspended particulate materials in the ML, which can be direct evidence visualizing the mixing pattern. Results suggest that the mixing and entrainment found in our study sustain particulate matters in suspension within the upper ML for a few months.

  3. Effects of ion diamagnetic drift on the m?n = 1 high-order harmonic modes in rotating tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Fan, Dong-Mei; Wang, Zheng-Xiong; Wei, Lai

    2014-06-01

    The effects of ion diamagnetic drift on the m/n=1 high-order harmonic modes in rotating tokamak plasmas are numerically investigated by using a cylindrical reduced magnetohydrodynamic model. It is found that the ion diamagnetic drift has a stabilizing effect on the high-order tearing modes in the small ion diamagnetic drift regime and can excite the m/n=1 high-order Kelvin-Helmholtz (KH) instability in the large ion diamagnetic drift regime. The effects of ion diamagnetic drift flow on the tearing modes are different from those of the poloidal E\\times B shear flow. Moreover, the combined effect of the two flows on tearing modes and KH modes depends on their relative direction. The eigenmode structures of the tearing modes and KH modes under the influence of ion diamagnetic drift flow are also presented. Finally, the numerical results are verified reasonably by the scalings on resistivity.

  4. Electron drift driven nonlinear ion-acoustic instability in a dusty plasma

    NASA Astrophysics Data System (ADS)

    Bora, Madhurjya Prosad; Goswami, Rajita

    In this work, we report the investigation of nonlinear ion-acoustic instability in complex plasma with electron drift in the presence of collisional effects. We have analysed the parameter regime, which can be very well realisable in laboratory and space plasma. The dust particles are negatively charged and their influence on the ion-acoustic instability is modelled through the charge fluctuation term.

  5. Measurement of ion swarm distribution functions in miniature low-temperature co-fired ceramic ion mobility spectrometer drift tubes.

    PubMed

    Pfeifer, Kent B; Rumpf, Arthur N

    2005-08-15

    Measurements of the performance of a miniature, portable 12-mm-diameter, 57-mm-length low-temperature cofired ceramic (LTCC) ion mobility spectrometer drift tube were undertaken to verify models of ion transport and determine the physical shape of the ion "swarms" in the LTCC tube. Simplified two-dimensional Gaussian models of ion swarm shape were fit to measured data to extract geometrical shape parameters. Results indicate that tube-transfer function effects that produce asymmetric ion swarms are minimized in the tube reducing temporal dispersion. Data are presented that illustrate the swarm shape as a function of gate time, electric field magnitude, and total charge in the ion swarm. Characterization and understanding of the ion transport mechanisms and effects that limit the resolution and other performance parameters of miniature IMS drift tubes is essential to the development of practical, robust, portable systems for "first responder" and homeland security missions. PMID:16097761

  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. Investigation of drift gas selectivity in high resolution ion mobility spectrometry with mass spectrometry detection

    Microsoft Academic Search

    Laura M. Matz; Luther W. Beegle; Isik Kanik

    2002-01-01

    Recent studies in electrospray ionization (ESI)\\/ion mobility spectrometry (IMS) have focussed on employing different drift\\u000a gases to alter separation efficiency for some molecules. This study investigates four structurally similar classes of molecules\\u000a (cocaine and metabolites, amphetamines, benzodiazepines, and small peptides) to determine the effect of structure on relative\\u000a mobility changes in four drift gases (helium, nitrogen, argon, carbon dioxide). Collision

  8. Optimal transport of two ions under slow spring-constant drifts

    E-print Network

    Xiao-Jing Lu; Mikel Palmero; Andreas Ruschhaupt; Xi Chen; Juan Gonzalo Muga

    2015-02-05

    We investigate the effect of slow spring-constant drifts of the trap used to shuttle two ions of different mass. We design transport protocols to suppress or mitigate the final excitation energy by applying invariant-based inverse engineering, perturbation theory, and a harmonic dynamical normal-mode approximation. A simple, explicit trigonometric protocol for the trap trajectory is found to be robust with respect to the spring-constant drifts.

  9. Optimal transport of two ions under slow spring-constant drifts

    NASA Astrophysics Data System (ADS)

    Lu, Xiao-Jing; Palmero, Mikel; Ruschhaupt, Andreas; Chen, Xi; Gonzalo Muga, Juan

    2015-06-01

    We investigate the effect of slow spring-constant drifts of the trap used to shuttle two ions of different mass. We design transport protocols to suppress or mitigate the final excitation energy by applying invariant-based inverse engineering, perturbation theory, and a harmonic dynamical normal-mode approximation. A simple, explicit trigonometric protocol for the trap trajectory is found to be robust with respect to the spring-constant drifts.

  10. 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.

  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. Ionic Drift Velocity Measurements on A Nano-composite Polymer Electrolyte: 95[90PEO: 10AgNO3]: 5SiO2

    NASA Astrophysics Data System (ADS)

    Chandra, Angesh; Chandra, Archana; Thakur, S. S.; Chakrawarti, V.

    2011-11-01

    Ionic drift velocity (vd) measurements on a hot-press synthesized nano-composite polymer electrolyte (NCPE) membrane: 95[90PEO: 10AgNO3]: 5SiO2, are reported. The ionic transference number (tion) values were determined using dc polarization Transient Ionic Current (TIC) technique for vd measurement at different temperatures. The drift energy (Ed), involved in the thermally activated process was determined from the temperature dependent studies on ionic drift velocity using the log vd vs 1/T Arrhenius plot. At all the temperatures, the ionic drift velocity is directly proportional to the ionic mobility (?) at a fixed value of applied dc potential.

  13. 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

  14. Ion beam energy effects on structure and properties of diamond like carbon films deposited by closed drift ion source

    Microsoft Academic Search

    Š. Meškinis; V. Kopustinskas; A. Tamulevi?ien?; S. Tamulevi?ius; G. Niaura; J. Jankauskas; R. Gudaitis

    2010-01-01

    In the present study DLC films deposited from acetylene gas by a closed drift ion source were investigated. Ion beam energy effects on structure as well as optical and electrical properties of the synthesized films were studied. Non-monotonic dependence of structure of the DLC films on ion beam energy was observed. The highest sp3\\/sp2 ratio as well as highest optical

  15. Ion-implanted drift field silicon solar cell

    Microsoft Academic Search

    H. Y. Lee; J. K. Kim; Y. S. Kim

    1977-01-01

    Development of a single-side drift-field silicon solar cell with the structure p(+)-p-n is discussed. The p-n junction is obtained by use of a gas discharge and heating implanter, which deposits dopant atoms onto the substrate by the processes of radiation-enhanced diffusion and, secondarily, hot implantation. The open-circuit voltage of the experimental solar cells is 0.44 V and the conversion efficiency

  16. Drift Compression and Final Focus Systems for Heavy Ion Inertial Fusion

    NASA Astrophysics Data System (ADS)

    de Hoon, M. J. L.; Littlejohn, R. G.; Wurtele, J. S.; Peterson, P. F.

    2001-04-01

    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. The occurrence of mismatches due to a rapidly increasing current was analyzed.

  17. Beam dynamics of the Neutralized Drift Compression Experiment-II, a novel pulse-compressing ion accelerator

    E-print Network

    Gilson, Erik

    Beam dynamics of the Neutralized Drift Compression Experiment-II, a novel pulse-compressing ion accelerator A. Friedman, J. J. Barnard, R. H. Cohen, D. P. Grote, S. M. Lund et al. Citation: Phys. Plasmas 17 dynamics of the Neutralized Drift Compression Experiment-II, a novel pulse-compressing ion acceleratora

  18. Drift wave stabilized by an additional streaming ion or plasma population

    E-print Network

    Bashir, M F

    2015-01-01

    It is shown that the universally unstable kinetic drift wave in an electron-ion plasma can very effectively be suppressed by adding an extra flowing ion (or plasma) population. The effect of the flow of the added ions is essential, their response is of the type (vph-vf0) exp[-(vph-vf0)^2], where vf0 is the flow speed and vph phase speed parallel to the magnetic field vector. The damping is strong and it is mainly due to this ion exponential term, and this remains so for vf0 < vph.

  19. Non-contact Measurement of Electrostatic Fields: Verification of Modeled Potentials within Ion Mobility Spectrometer Drift Tube Designs

    SciTech Connect

    Jill R. Scott; Paul L. Tremblay

    2007-03-01

    The heart of an ion mobility spectrometer is the drift region where the ion separation occurs. While the electrostatic potentials within a drift tube design can be modeled, no method for validating the electrostatic field has previously been reported. Two basic drift tube designs were modeled using SIMION 7.0 to reveal the expected electrostatic fields: 1) a traditional “stacked” alternating electrodes and insulators and 2) a truly linear drift tube. One version of the stacked electrode/insulator drift tube and two versions of linear drift tubes were then fabricated. The stacked alternating electrodes/insulators were connected through a resistor network to generate the electrostatic gradient in the drift tube. The two linear drift tube designs consisted of two types of resistive drift tubes with one tube consisting of a resistive coating within an insulating tube and the other tube composed of semiconducting ferrites. The electrostatic fields within each type of drift tube were then evaluated using a non-contact method using a Kelvin-Zisman type electrostatic voltmeter and probe. The experimental results were then compared with the electrostatic fields predicted by SIMION. Both the modeling and experimental measurements reveal that the electrostatic fields within a stacked IMS drift tube are only pseudo-linear, while the electrostatic fields within a resistive drift tube can approach perfect linearity.

  20. Ion flux energy distributions in a hydrogen-filled drift tube at high E\\/N

    Microsoft Academic Search

    Arthur Phelps

    2008-01-01

    Ion flux energy distributions are calculated for H^+, H2^+, and H3^+ ions in H2 for low-current, uniform-electric-field drift tubes at 1 kTd < E\\/N < 10 kTd and 5x10^20 <=N d <=3x10^21 m^2, where E is the electric field, N is the gas density, and d is the electrode separation. We use updated cross sections in a multi-beam model of

  1. 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.

  2. Optically Induced Measurement of Electron and Hole Drift Velocities in a Germanium <100> CDMS Detector at 50 mK

    NASA Astrophysics Data System (ADS)

    Phipps, A.; Sundqvist, K. M.; Lam, A.; Sadoulet, B.

    2012-06-01

    We report on precise drift velocity measurements of electrons and holes in 50 mK, ultrapure (?1010 net shallow impurities per cm3) germanium <100> CDMS dark matter detectors as a function of electric field up to 4 V/cm. A laser diode connected to an optical fiber extending from room-temperature to the detector creates electron-hole pairs on one surface of the crystal. High-speed electronics measure the drift current as the generated carriers travel to the opposite face of the crystal. CDMS detectors measure the ionization and phonon response of particle interactions within the crystal. Stable charge collection is necessary for successful background discrimination when looking for a possible dark matter signal. While biased, however, ionization performance degrades over time due to the build-up of space charge. Free electrons and holes created by particle interactions are subject to drift-diffusion dynamics occurring simultaneously with the trapping of carriers to localized surface and bulk states. The combination of these processes determine the evolution of space charge within the crystal, making it important that we understand carrier transport under our unique operating condition of low-temperature and low-field. We find good agreement between our measured drift velocities and our theoretical predictions, indicating carrier scattering is dominated by spontaneous phonon emission. In addition, we present preliminary measurements of effective longitudinal carrier trapping lengths for both n-type and p-type crystals at 50 mK.

  3. Low velocity ion stopping in binary ionic mixtures

    SciTech Connect

    Tashev, Bekbolat; Baimbetov, Fazylkhan [Department of Physics, Kazakh National University, Tole Bi 96, Almaty 480012 (Kazakhstan); Deutsch, Claude [LPGP (UMR-CNRS 8578), Universite Paris XI, 91405 Orsay (France); Fromy, Patrice [Direction de l'Informatique, Universite Paris XI, 91405 Orsay (France)

    2008-10-15

    Attention is focused on the low ion velocity stopping mechanisms in multicomponent and dense target plasmas built of quasiclassical electron fluids neutralizing binary ionic mixtures, 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 at Bragg peak conditions. The target plasma is taken in a multicomponent dielectric formulation a 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. The corresponding multiquadrature computations, albeit rather heavy, can be monitored analytical through a very compact code operating a PC cluster. Slowing down results are systematically scanned with respect to target temperature and electron density, as well as ion composition.

  4. The functional response of drift-feeding Arctic grayling: the effects of prey density, water velocity, and location efficiency

    Microsoft Academic Search

    W. John O'Brien; Michael Barfield; Karen Sigler

    2001-01-01

    An important aspect of a predator-prey system is the functional response of the predator to changing prey densities. We studied the feeding rate response of drift-feeding Arctic grayling ( Thymallus arcticus) on a small inverte- brate prey, Daphnia middendorffiana, at densities ranging from 0.01 L-1 to 1.8 L-1 and current velocities of 25, 32, and 40 cm·s-1. We videotaped the

  5. Velocity-dependent isotope fractionation in secondary-ion emission

    SciTech Connect

    Gnaser, H.; Hutcheon, I.D.

    1987-01-15

    The formation of secondary ions is subject to isotopic fractionation (differing ionization probabilities for two isotopes) that depends linearly on the inverse velocity of the ejected ions. Theoretically, such a correlation follows directly from an exponential dependence of the ionization probability P on v/sup -1/, Pproportionalexp(-v/sub 0//v). The parameter v/sub 0/, derived from the experiment, amounts to --2 x 10/sup 6/ cm/sec for B, Si, and Ca ions.

  6. 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.

  7. 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.

  8. Analysis of drifting electron concentration in a self-magnetically insulated ion diode

    NASA Astrophysics Data System (ADS)

    Pushkarev, A. I.; Pak, V. G.

    2015-02-01

    The drifting electron concentration in a self-magnetically insulated ion diode is analyzed using a TEMP-4M accelerator operating in a double bipolar pulse regime with the first pulse (300-600 ns and 150-200 kV) being negative and the second (120 ns and 250-300 kV) being positive. The electron concentration in the drift region is shown to be 1013-1014 cm-3. It is established that the Lorentz force acting on electrons in crossed electric and magnetic fields is 150-200 times greater than the Coulomb repulsion force, which ensures a higher electron concentration in the drift region as compared with the space charge region.

  9. 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).

  10. Anomalous electron-ion energy coupling in electron drift wave turbulence

    NASA Astrophysics Data System (ADS)

    Zhao, Lei

    Turbulence is a ubiquitous phenomenon in nature, and it is well known that turbulence couples energy input to dissipation by cascade processes. Plasma turbulence play a critical role in tokamak confinement. Magnetized plasma turbulence is quasi 2D, anisotropic, wave like and two fluid (i.e. electrons and ions) in structure. Thus, weakly collisional plasma turbulence can mediate electron and ion energy transfer. The issue of anomalous electron and ion energy coupling is particularly important for low collisionality, electron heated plasmas, such as ITER. In this work, we reconsider the classic problem of turbulent heating and energy transfer pathways in drift wave turbulence. The total turbulent heating, composed of quasilinear electron cooling, quasilinear ion heating, nonlinear ion heating and zonal flow frictional heating, is analyzed. In Chapter 2, the electron and ion energy exchange via linear wave and particle resonance will be computed. To address net heating, we show the turbulent heating in an annulus arises due to a wave energy flux differential across this region. We show this net heating is proportional to the Reynolds work on the zonal flow. Zonal flow friction heats ions, thus the turbulence and zonal flow interaction enters as an important energy transfer channel. Since zonal flows are nonlinearly generated, it follows that we should apply weak turbulence theory to calculate the nonlinear ion turbulent heating via the virtual mode resonance in the electron drift wave turbulence, which will be discussed in Chapter 3. We defines a new collisionless turbulent energy transfer channel through nonlinear Landau damping in the electron and ion energy coupling process. The result shows that nonlinear ion heating can exceed quasilinear ion heating, so that nonlinear heating becomes the principal collisionless wave energy dissipation channel in electron drift wave turbulence. This follows since the beat mode resonates with the bulk of the ion distribution, in contrast to the linear resonance which is located on the tail. This result also suggests that zonal flow shearing is not necessarily the only saturation mechanism of importance, especially for very low collisionality. This observation brings a new perspective on electron heat transport where ions, play a role as an energy "sink" in a collisionless plasma, such as ITER. In addition, it is shown that the electron turbulent energy transfer to ions in a collisionless plasma can be the same order as electron heat transport losses. Thus, it is necessary to consider the influence of collisionless energy transfer to determine the total energy budget in ITER.

  11. Drift-velocity and electron-density measurements in electron-beam-irradiated Ar-F2 gas mixtures subjected to an external electric field

    Microsoft Academic Search

    Z. Rozenberg; M. Lando; M. Rokni

    1988-01-01

    Measurements of drift velocity and electron density in electron-beam-irradiated Ar-F2 gas mixtures which have been subjected to an externally applied electric field are reported. The electron density was measured by time-resolved infrared interferometry. The drift velocity was derived from discharge-current-density measurements. Experiments were performed for gas mixtures with various fluorine concentrations between 0.025% and 2% and total mixture pressures between

  12. 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)

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

    NASA Astrophysics Data System (ADS)

    Pushkarev, A. I.; Isakova, Y. I.

    2013-05-01

    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/cm2 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+ 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.

  14. 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.

  15. Poloidal velocity of impurity ions in neoclassical theory

    SciTech Connect

    Wong, S. K.; Chan, V. S. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Solomon, W. M. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

    2008-08-15

    A formula for the poloidal velocity of impurity ions in a two-species plasma is derived from neoclassical theory in the banana regime, with corrections from the boundary layer separating the trapped and transiting ions. The formula is applicable to plasmas with toroidal rotations that can approach the thermal speeds of the ions. Using the formula to determine the poloidal velocity of C{sup +6} ions in a recently reported experiment [W. M. Solomon et al., Phys. Plasmas 13, 056116 (2006)] leads to agreement in the direction of the central region when it is otherwise from theories without strong toroidal rotations. Comparisons among these theories are made, demonstrating the degree of uncertainty of theoretical predictions.

  16. Equatorial F-region vertical ion drifts during quiet solar maximum

    Microsoft Academic Search

    O. S. Oyekola

    2009-01-01

    Median values of ionosonde h?F data acquired at Ibadan (Geographic:7.4°N, 3.9°E, Magnetic: dip 6°S, and magnetic declination, 3°W), Nigeria, West Africa, have been used to determine vertical ion drift (electric field) characteristics in the postsunset ionosphere in the African region during a time of high solar activity (average F10.7 ?208). The database spans from January and December 1958 during the

  17. Solar and geomagnetic trends of equatorial evening and nighttime F region vertical ion drifts

    Microsoft Academic Search

    O. S. Oyekola; C. O. Oluwafemi

    2008-01-01

    F region vertical ion drifts were inferred from the evening and nighttime ionosonde data for two magnetic equatorial stations in West Africa: Ouagadougou (geographic: 12°N, 1.5°W; 5.9°N dip) and Ibadan (geographic: 7.9°N, 3.9°E; 6°S dip). We examine and discuss the short-term patterns of behavior of ionospheric variability over Ouagadougou for 1986–1987 years of low solar activity (F10.7 = 80) and

  18. Equatorial F-region vertical ion drifts during quiet solar maximum

    Microsoft Academic Search

    O. S. Oyekola

    2009-01-01

    Median values of ionosonde h'F data acquired at Ibadan (Geographic:7.4°N, 3.9°E, Magnetic: dip 6°S, and magnetic declination, 3°W), Nigeria, West Africa, have been used to determine vertical ion drift (electric field) characteristics in the postsunset ionosphere in the African region during a time of high solar activity (average F10.7 -208). The database spans from January and December 1958 during the

  19. Photons from Heavy-Ion Collisions at Fermi Velocity

    E-print Network

    Ko, Che Ming; Alchelin, J.

    1987-01-01

    'I ~ (+l Ii & & .~ I + I I 'f Il I I PHYSICAL REVIEW C VOLUME 35, NUMBER 5 MAY 1987 Photons from heavy-ion collisions at Fermi velocity Che Ming Ko Center for Theoretical Physics, Physics Department and Cyclotron Institute, Texas Ad... December 1986) The production of photons from heavy-ion collisions at intermediate energies is studied in the model based on the Boltzmann-Uehling-Uhlenbeck equation. Taking into account photon produc- tion from nucleon-nucleon collisions...

  20. The distribution of velocities for Ba+ ions in Ar gas

    Microsoft Academic Search

    Larry A. Viehland; Denise S. Hampt

    1992-01-01

    The ground-state potential for singly-charged barium ions interacting with argon atoms is inferred from laser-induced fluorescence measurements of the gaseous ion transport coefficients. The potential is used to compute velocity component distribution functions and fluorescence spectra. Comparison with the measured spectra provides insight into the accuracy with which the potential can be inferred and with which the distribution function and

  1. Nuclear Instruments and Methods in Physics Research A 526 (2004) 409412 GEM operation in negative ion drift gas mixtures

    E-print Network

    2004-01-01

    elements in negative ion gas mixtures is reported. Gains up to several thousand were obtained from single. Negative ion drift gases (NI-gases) are another innovation in gas detector technology which are just or TPC device to be transported to the gain elements in the form of negative molecular ions [10

  2. High-velocity tails on the velocity distribution of solar wind ions

    SciTech Connect

    Ogilvie, K.W. (Goddard Space Flight Center, Greenbelt, MD (United States)); Geiss, J. (Univ. of Bern (Swaziland)); Gloeckler, G. (Univ. of Maryland, College Park (United States)); Berdichevsky, D. (Highes-STX, Lanham, MD (United States)); Wilken, B. (Max-Plank-Institut fuer Aeronomie Katlenburg-Lindau (Germany))

    1993-03-01

    Recent observations of the solar wind using the SWICS instrument on the Ulysses spacecraft have shown the presence of high-velocity [open quotes]tails[close quotes] on the velocity distribution of protons. Similar features have also been observed on the velocity distributions of helium and oxygen ions. Of the order of 1% of the solar wind density is involved in these tails, which are approximately exponential in shape and persist to V = V[sub B] + 10V[sub th] or beyond, where V[sub B] is the bulk velocity and V[sub th] the thermal velocity of the solar wind. This paper contains a preliminary description of the phenomenon. It is clear that it is ultimately connected with the passage of interplanetary shocks past the spacecraft and that particle acceleration at oblique shocks is involved. 21 refs., 6 figs., 2 tabs.

  3. 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

  4. Solvable Examples of Drift and Diffusion of Ions in Non-uniform Electric Fields

    SciTech Connect

    Cahn, Robert; Cahn, Robert N.; Jackson, John David

    2008-05-30

    The drift and diffusion of a cloud of ions in a fluid are distorted by an inhomogeneous electric field. If the electric field carries the center of the distribution in a straight line and the field configuration is suitably symmetric, the distortion can be calculated analytically. We examine the specific examples of fields with cylindrical and spherical symmetry in detail assuming the ion distributions to be of a generally Gaussian form. The effects of differing diffusion coefficients in the transverse and longitudinal directions are included.

  5. Lower hybrid drift instability in a neutral sheet with O+ ions.

    PubMed

    Huang, Feng; Chen, Yinhua; Peng, Hai-Ou; Zheng, Ju-Gao; Shi, Gui-Fen; Hu, Zu-Quan; Yu, M Y

    2009-11-01

    The electromagnetic lower-hybrid drift instability (LHDI) in the intermediate-wavelength regime k_(y)sqrt[rho_(i)rho_(e)] approximately 1 , where k_(y) and rho_(e,i) are the wave vector and the electron and ion gyroradii, respectively, in a thin plasma sheet containing electrons and H+ and O+ ions is examined using kinetic theory. It is shown that the growth rate of the LHDI first decreases and then increases with increase in the O+ content and temperature, with a minimum at a moderate level of the latter. The results can be relevant to understanding magnetic reconnection in the presence of LHDI. PMID:20365077

  6. 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.

  7. 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).

  8. Ion concentrations and velocity profiles in nanochannel electroosmotic flows

    NASA Astrophysics Data System (ADS)

    Qiao, R.; Aluru, N. R.

    2003-03-01

    Ion distributions and velocity profiles for electroosmotic flow in nanochannels of different widths are studied in this paper using molecular dynamics and continuum theory. For the various channel widths studied in this paper, the ion distribution near the channel wall is strongly influenced by the finite size of the ions and the discreteness of the solvent molecules. The classical Poisson-Boltzmann equation fails to predict the ion distribution near the channel wall as it does not account for the molecular aspects of the ion-wall and ion-solvent interactions. A modified Poisson-Boltzmann equation based on electrochemical potential correction is introduced to account for ion-wall and ion-solvent interactions. The electrochemical potential correction term is extracted from the ion distribution in a smaller channel using molecular dynamics. Using the electrochemical potential correction term extracted from molecular dynamics (MD) simulation of electroosmotic flow in a 2.22 nm channel, the modified Poisson-Boltzmann equation predicts the ion distribution in larger channel widths (e.g., 3.49 and 10.00 nm) with good accuracy. Detailed studies on the velocity profile in electro-osmotic flow indicate that the continuum flow theory can be used to predict bulk fluid flow in channels as small as 2.22 nm provided that the viscosity variation near the channel wall is taken into account. We propose a technique to embed the velocity near the channel wall obtained from MD simulation of electroosmotic flow in a narrow channel (e.g., 2.22 nm wide channel) into simulation of electroosmotic flow in larger channels. Simulation results indicate that such an approach can predict the velocity profile in larger channels (e.g., 3.49 and 10.00 nm) very well. Finally, simulation of electroosmotic flow in a 0.95 nm channel indicates that viscosity cannot be described by a local, linear constitutive relationship that the continuum flow theory is built upon and thus the continuum flow theory is not applicable for electroosmotic flow in such small channels.

  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. 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

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

    NASA Astrophysics Data System (ADS)

    de Hoon, Michiel Jan Laurens

    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. 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. In final focus, the beam is usually expanded transversely before it is focused onto a small spot. This may cause third-order aberrations to significantly affect the beam quality. Previously, it has been suggested that octupoles be used to correct these aberrations. However, it is shown that for modest convergence angles of the beam, a considerable improvement can be achieved by rematching the quadrupoles in the final focus system, if these aberrations are taken into account in the rematching process. For larger convergence angles, third-order aberrations cause a significant halo formation. Detailed particle-in-cell simulations were performed to better understand the experimental results from the Scaled Final Focus Experiment at LBNL, which is a replica of a driver-scale final focus system. The simulations showed that expanding beams may suffer a substantial emittance increase due to their nonlinear space-charge field. Phase-space comparisons between the experiment and simulations showed reasonable agreement. Of particular interest was the beam rotation that has been measured in the experiment. Simulations showed that this may have been caused by a minor rotation of one or more of the quadrupoles in the experiment.

  12. Argon Ion Velocity Distribution in an ICP Reactor

    Microsoft Academic Search

    N. Sadeghi; M. van de Grift; D. Vender; G. M. W. Kroesen; F. J. de Hoog

    1996-01-01

    Doppler Shifted Laser Induced Fluorescence technique was used to determine the distribution functions of the radial and axial velocity components of the Ar^+*(^2G_9\\/2) metastable ions on the axis of an ICP reactor (phi=15 cm, h=4 cm; RF up to 500 W; p_Ar=2.5 to 80 mTorr ). To avoid metal sputtering, the internal walls of the reactor are covered by a

  13. A method for determining the drift velocity of plasma depletions in the equatorial ionosphere using far-ultraviolet spacecraft observations: initial results

    NASA Astrophysics Data System (ADS)

    England, S. L.; Immel, T. J.; Park, S. H.; Frey, H. U.; Mende, S. B.

    2007-12-01

    The Far-Ultraviolet Imager (IMAGE-FUV) on-board the NASA IMAGE satellite has been used to observe plasma depletions in the nightside equatorial ionosphere. Observations from periods around spacecraft apogee, during which equatorial regions are visible for several hours, have allowed the velocity of these plasma depletions to be determined. A new method for determining the velocity of these depletions using an image analysis technique, Tracking Of Airglow Depletions (TOAD), has been developed. TOAD allows the objective identification and tracking of depletions. The automation of this process has also allowed for the tracking of a greater number of depletions than previously achieved without requiring any human input, which shows that TOAD is suitable for use with large data sets and for future routine monitoring of the ionosphere from space. Furthermore, this allows the drift velocities of each depletion to be determined as a function of magnetic latitude as well as local time. Previous ground-based airglow observations from a small number of locations have indicated that the drift velocities of depletions may vary rapidly with magnetic latitude. Here we shall present the first results from TOAD of this shear in drift velocities from our global sample of depletion drift velocities.

  14. High-power millimeter wave IMPATT oscillators with both hole and electron drift spaces made by ion implantation

    Microsoft Academic Search

    T. E. Seidel; D. L. Scharfetter

    1970-01-01

    CW powers of 640 mW at 50 GHz have been obtained from double-drift region IMPATT diodes. This result represents the highest product of CW power times frequency squared obtained to date from any IMPATT diode. The diodes are p+pnn+structures and have both hole and electron drift spaces. The systematic fabrication (by ion implantation) and the evaluation of the dc and

  15. Preferential acceleration of heavy ions from thermal velocities D. B. MELROSE

    E-print Network

    Melrose, Don

    Preferential acceleration of heavy ions from thermal velocities D. B. MELROSE #12;Preferential acceleration of heavy ions from thermal velocities1 D. B. MELROSE Belfer Graduate School of Science, Yeshiva University, New York, N.Y., U.S.A. Received June 15, 1967 The acceleration of ions from thermal velocities

  16. A method for determining the drift velocity of plasma depletions in the equatorial ionosphere using far-ultraviolet spacecraft observations

    NASA Astrophysics Data System (ADS)

    Park, S. H.; England, S. L.; Immel, T. J.; Frey, H. U.; Mende, S. B.

    2007-11-01

    The Far-Ultraviolet Imager (IMAGE-FUV) on board the NASA IMAGE satellite has been used to observe plasma depletions in the nightside equatorial ionosphere. Observations from periods around spacecraft apogee, during which equatorial regions are visible for several hours, have allowed the velocity of these plasma depletions to be determined. A new method for determining the velocity of these depletions using an image analysis technique, Tracking Of Airglow Depletions (TOAD), has been developed. TOAD allows the objective identification and tracking of depletions. The automation of this process has also allowed for the tracking of a greater number of depletions than previously achieved without requiring any human input, which shows that TOAD is suitable for use with large data sets and for future routine monitoring of the ionosphere from space. Furthermore, this automation allows the drift velocities of each bubble to be determined as a function of magnetic latitude, which will give us the capability of retrieving geophysically important parameters such as the electric field, which are believed to vary rapidly with magnetic latitude.

  17. 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.}

  18. Two-dimensional drift velocities from the IMAGE EUV plasmaspheric imager

    Microsoft Academic Search

    D. L. Gallagher; Mark L. Adrian

    2007-01-01

    The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) Mission extreme ultraviolet (EUV) imager 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 10min for many hours as the spacecraft passes through apogee in its highly elliptical orbit. As a consistent constituent at about 15%,

  19. Observations of the velocity distribution of solar wind ions

    NASA Technical Reports Server (NTRS)

    Ogilvie, K. W.; Bochsler, P.; Geiss, J.; Coplan, M. A.

    1980-01-01

    Measurements made by the Isee 3 ion composition experiment have been used to determine the kinetic temperatures of 3He(++), 4He(++), 16O(6+), and 16O(7+) in the solar wind. It is found that these temperatures generally obey the relation that T(i)/m(i) equals const, but fluctuations, some of which are caused by dynamical effects in the flow, are observed. The temperature of oxygen sometimes rises above 10 K, which is very strong evidence for heating outside the collisional region of the corona. The tendency toward equal temperatures per nucleon occurs everywhere where collisions are unimportant, suggesting that the temperatures are set up close to the sun rather than elsewhere in the interplanetary medium. The velocity distribution function of helium is observed to be non-Maxwellian, with a pronounced high velocity tail.

  20. 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

  1. Photons from Heavy-Ion Collisions at Fermi Velocity 

    E-print Network

    Ko, Che Ming; Alchelin, J.

    1987-01-01

    the phase space in- tegral over the final state and obtain the following factor: mp3$F I pi ?p2 I Ei&2 I p'&4 ?&3p3 p. I (2) In the above, p& and E & are, respectively, the momentum and energy of the proton of mass m before the collision with another...'I ~ (+l Ii & & .~ I + I I 'f Il I I PHYSICAL REVIEW C VOLUME 35, NUMBER 5 MAY 1987 Photons from heavy-ion collisions at Fermi velocity Che Ming Ko Center for Theoretical Physics, Physics Department and Cyclotron Institute, Texas Ad...

  2. A study of the performance of an ion shutter for drift tubes in atmospheric pressure ion mobility spectrometry: Computer models and experimental findings

    SciTech Connect

    Tadjimukhamedov, Fatkhulla K.; Eiceman, Gary A. [Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003 (United States); Puton, Jaroslaw [Department of Environmental Sciences, Laboratory of Applied Environmental Chemistry, University of Kuopio, Mikkeli FIN-50100 (Finland); Stone, John A. [Department of Chemistry, Queens University, Kingston, Ontario K7L 3N6 (Canada)

    2009-10-15

    Ion mobility spectra are initiated when ions, derived from a sample, are pulsed or injected through ion shutters into a drift region. The effect on signal intensity from electric fields arising from the shutter grids (E{sub s}) and a superimposed electric field of the drift tube (E{sub d}) was determined experimentally and simulated computationally for ion motion at ambient pressure. The combination of these two fields influenced shutter performance in three ways: (1) intensity of an ion peak was suppressed by increased current in the baseline due to continuous leakage of ions into the drift region from insufficient E{sub s} to block ion motion when needed, at a given value of E{sub d}; (2) the ion shutter provided maximum peak intensity with some optimal ratio of E{sub s}/E{sub d} when ions were fully blocked except using the injection time; (c) the signal intensity was reduced when the blocking voltage of the ion shutter exceeded this optimal E{sub s}/E{sub d} ratio from ion depletion at the shutter grids. The optimal ratio from the computer models was equal to 1.50, whereas a value of 2.50 was obtained from the experimental findings. This difference was attributed to nonideal geometry with the grids of the shutter and the conducting elements in the drift tube establishing both E{sub s} and E{sub d}. As both the experimental and modeling results demonstrated, a mobility dependence of ion yield from the ionization source was found to cause a mobility dependent ion signal at the collector electrode.

  3. Ion mobility spectrometry—mass spectrometry performance using electrodynamic ion funnels and elevated drift gas pressures

    Microsoft Academic Search

    Erin Shammel Baker; Brian H. Clowers; Fumin Li; Keqi Tang; Aleksey V. Tolmachev; David C. Prior; Mikhail E. Belov; Richard D. Smith

    2007-01-01

    The ability of ion mobility spectrometry coupled with mass spectrometry (IMS-MS) to characterize biological mixtures has been\\u000a illustrated over the past eight years. However, the challenges posed by the extreme complexity of many biological samples\\u000a have demonstrated the need for higher resolution IMS-MS measurements. We have developed a higher resolution ESI-IMS-TOF MS\\u000a by utilizing high-pressure electrodynamic ion funnels at both

  4. Measurements of transport coefficients for lithium ions in argon and helium ions in helium with a drift-tube mass spectrometer

    Microsoft Academic Search

    T. Stefansson; T. Berge; R. Lausund; H. R. Skullerud

    1988-01-01

    A drift-tube mass spectrometer for precision measurements of transport coefficients for ions in gases is described. The apparatus has been used to determine the ratio DT\\/ mu between the transverse diffusion coefficient and the mobility for He+ ions in the helium at 294 K and 15ions. The apparatus

  5. Observations of the velocity distribution of solar wind ions

    SciTech Connect

    Ogilvie, K.W.; Bochsler, P.; Geiss, J.; Coplan, M.A.

    1980-11-01

    Measurements made by the Isee 3 ion composition experiment have been used to determine the kinetic temperatures of /sup 3/He/sup + +/, /sup 4/He/sup + +/, /sup 16/O/sup 6 +/, and /sup 16/O/sup 7 +/ in the solar wind. It is found that these temperatures generally obey the relation that T/sub i//m/sub i/=const, but fluctuations, some of which are caused by dynamical effects in the flow, are observed. Whether this relation applies to ions with masses greater than 16 requires more analysis to determine. The temperature of oxygen sometimes rises above 10/sup 6/ /sup 0/K, which is very strong evidence for heating outside the collisional region of the corona. The tendency toward equal temperatures per nucleon occurs everywhere where collisions are unimportant, suggesting that the temperatures are set up close to the sun rather than elsewhere in the interplanetary medium. The velocity distribution function of helium is observed to be non-Maxwellian, with a pronounced high velocity tail. As this is one condition for heating by wave dissipation, this mechanism must still be considered as a heating mechanism.

  6. Mobility-resolved ion selection in uniform drift field ion mobility spectrometry/mass spectrometry: dynamic switching in structures for lossless ion manipulations.

    PubMed

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

    2014-10-01

    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 the efficient switching of ions between a linear path and a 90-degree bend. By controlling switching times, ions can be efficiently directed 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 of, for example, the selection of specific mobilities for storage and accumulation, and the key component of modules for the assembly of SLIM devices enabling much more complex sequences of ion manipulations. PMID:25222548

  7. Analysis of the effect of artificial ion masses on current-driven electrostatic instabilities

    Microsoft Academic Search

    Anssi Malkki

    1994-01-01

    The electrostatic ion cyclotron (EIC) and ion acoustic (IA) waves can be driven unstable by an electron current. The critical drift velocity of the electrons, at which the wave modes become unstable, depends on the parallel and perpendicular temperatures of the electrons and ions, and on the ion mass. We show that in plasma simulations the critical drift velocity for

  8. Ion flux energy distributions in a hydrogen-filled drift tube at high E/N

    NASA Astrophysics Data System (ADS)

    Phelps, Arthur

    2008-10-01

    Ion flux energy distributions are calculated for H^+, H2^+, and H3^+ ions in H2 for low-current, uniform-electric-field drift tubes at 1 kTd < E/N < 10 kTd and 5x10^20 <=N d <=3x10^21 m^2, where E is the electric field, N is the gas density, and d is the electrode separation. We use updated cross sections in a multi-beam model of the spatial and energy dependent particle fluxes. Calculated distributions at the cathode are compared with experiments by Rao et al. and detailed theory by Bretagne et al. Hypothetical large increases in the total momentum transfer cross sections for H^+ and H3^+ at 100 to 1000 eV yield approximate fits to the relative experimental distributions at high energies at moderate E/N. However, these fitted distributions are much too small at low ion energies. Similar discrepancies occur for analytic solutions of the Boltzmann equations using simplified reaction cross sections and the almost free-fall conditions for H^+ at 10 kTd.

  9. JOURNAL DE PHYSIQUE Colloque C7, suppl&menl; au n07, Tome 40, JuiZZet 1979, pa@ C7-6 3 MONTE CARL0 SIMULATIONS OF ELECTRON DRIFT VELOCITIES INTHE NOBLE GASES AND THEIR MIXTURES

    E-print Network

    Boyer, Edmond

    , can be 1 found . This problem has stimulated the investigation of drift velocities in noble gas SIMULATIONS OF ELECTRON DRIFT VELOCITIES INTHE NOBLE GASES AND THEIR MIXTURES A.J. Davies, J. Dutton, C the respective cross-sections of 1 2 Mixtures of noble and molecular gases a r e widely used the gaseous

  10. Added discussion of ``Observations of fast anisotropic ion heating, ion cooling, and ion recycling in large-amplitude drift waves''

    Microsoft Academic Search

    S. J. Sanders; R. F. Boivin; P. M. Bellan; R. A. Stern

    1999-01-01

    A recent paper [S. J. Sanders, P. M. Bellan, and R. A. Stern, Phys. Plasmas 5, 716, (1998)] identified neutral particle recycling as one important aspect of severe heating and cooling cycles observed in large-amplitude drift waves. An apparent inconsistency in the ionization mean free path of these neutrals, left as an open question in the original paper, is resolved

  11. Added discussion of “Observations of fast anisotropic ion heating, ion cooling, and ion recycling in large-amplitude drift waves”

    Microsoft Academic Search

    S. J. Sanders; R. F. Boivin; P. M. Bellan; R. A. Stern

    1999-01-01

    A recent paper [S. J. Sanders, P. M. Bellan, and R. A. Stern, Phys. Plasmas 5, 716, (1998)] identified neutral particle recycling as one important aspect of severe heating and cooling cycles observed in large-amplitude drift waves. An apparent inconsistency in the ionization mean free path of these neutrals, left as an open question in the original paper, is resolved

  12. Drift tube measurements on Na+ ions and clusters using the 24mNa+ tracer

    NASA Astrophysics Data System (ADS)

    Kasuya, A.; Abmayr, B.; Ohtsuki, T.; Masumoto, K.; Kotajima, H.; Huenges, E.; Morinaga, H.

    1997-06-01

    Mobilities of sodium ions and their clusters in different gases have been measured by gamma-ray spectrometry using the 20 ms isomeric state of 24Na as tracer. This isomer is obtained through the ?-decay of 24Ne, which was produced by bombarding 22Ne with the 7 MeV triton beam of a cyclotron. This new technique of measurement allows us to determine the mobility of sodium ions in non-reacting gases of a pressure above 1 mbar. Measurements have been carried out in gases of pressures ranging from 6 mbar to 1000 mbar under an electric field up to 250 V/cm at room temperature. The measured mobility of 24Na+ in pure neon gas at 1000 mbar was determined to be 3.2 cm2/Vs. This value is lower than the zero field mobility of about 8.5 cm2/Vs measured by Tyndall and Akridge. A small amount of polar molecules such as water or ethanol introduced into the drift tube causes their clustering with the sodium ions through monopole-dipole interaction, resulting in a strong decrease in the mobility. This clustering effect has been studied for various combinations of polar molecules and inert gases. The usable pressure range from 1 mbar to high pressures in the range of some hundred bars is interesting because most other methods for cluster studies cannot be done at such high pressures. With this method it is possible to measure the mobility change of sodium ions towards the condensation point and eventually even towards the critical point.

  13. Simulation of temporal characteristics of ion-velocity susceptibility to single event upset effect

    NASA Astrophysics Data System (ADS)

    Geng, Chao; Xi, Kai; Liu, Tian-Qi; Gu, Song; Liu, Jie

    2014-08-01

    Using a Monte Carlo simulation tool of the multi-functional package for SEEs Analysis (MUFPSA), we study the temporal characteristics of ion-velocity susceptibility to the single event upset (SEU) effect, including the deposited energy, traversed time within the device, and profile of the current pulse. The results show that the averaged dposited energy decreases with the increase of the ion-velocity, and incident ions of 209Bi have a wider distribution of energy deposition than 132Xe at the same ion-velocity. Additionally, the traversed time presents an obvious decreasing trend with the increase of ion-velocity. Concurrently, ion-velocity certainly has an influence on the current pulse and then it presents a particular regularity. The detailed discussion is conducted to estimate the relevant linear energy transfer (LET) of incident ions and the SEU cross section of the testing device from experiment and simulation and to critically consider the metric of LET.

  14. SIMULATIONS OF HIGH-VELOCITY CLOUDS. I. HYDRODYNAMICS AND HIGH-VELOCITY HIGH IONS

    SciTech Connect

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

    2011-09-20

    We present hydrodynamic simulations of high-velocity clouds (HVCs) traveling through the hot, tenuous medium in the Galactic halo. A suite of models was created using the FLASH hydrodynamics code, sampling various cloud sizes, densities, and velocities. In all cases, the cloud-halo interaction ablates material from the clouds. The ablated material falls behind the clouds where it mixes with the ambient medium to produce intermediate-temperature gas, some of which radiatively cools to less than 10,000 K. Using a non-equilibrium ionization algorithm, we track the ionization levels of carbon, nitrogen, and oxygen in the gas throughout the simulation period. We present observation-related predictions, including the expected H I and high ion (C IV, N V, and O VI) column densities on sightlines through the clouds as functions of evolutionary time and off-center distance. The predicted column densities overlap those observed for Complex C. The observations are best matched by clouds that have interacted with the Galactic environment for tens to hundreds of megayears. Given the large distances across which the clouds would travel during such time, our results are consistent with Complex C having an extragalactic origin. The destruction of HVCs is also of interest; the smallest cloud (initial mass {approx} 120 M{sub sun}) lost most of its mass during the simulation period (60 Myr), while the largest cloud (initial mass {approx} 4 x 10{sup 5} M{sub sun}) remained largely intact, although deformed, during its simulation period (240 Myr).

  15. Drift Tube Studies of Ion-Molecule Reactions at Low Collision Energies.

    NASA Astrophysics Data System (ADS)

    Chatterjee, Barun Kumar

    This thesis presents experimental studies of ion -molecule reactions at low collision energies using two drift tube mass spectrometer apparatus. The reactions studied are (i) proton transfer from HeH^+ to ArH^+, (ii) charge and ion transfer reactions of O_2^{2+ } with NO, CO_2, Ne and of O_2^+(^4pi_ {rm u}) with CO_2 , (iii) oxidation reactions of Zr^+ and ZrO^+ with NO, CO _2 and O_2, (iv) vibrational quenching reactions of H_3^+ with He, (v) termolecular clustering reactions of H _2CN^+ and H _2CN^+(HCN) (with He as the third body), (vi) three body association reactions of H^+ and D^+ with He (with He as the third body) and (vii) termolecular association reaction of NO^+ with NO (with Ne as third body). All the reactions were studied at thermal energies (at room temperature), reactions of O_2^{2+} with NO and CO_2, Zr^+ with NO/CO_2/O_2 were also studied at center-of-mass energies higher than thermal and the association reactions of H _2CN^+/H_2 CN^+(HCN) with HCN and H ^+/D^+ with He were studied at low temperatures. In addition, the thesis presents model calculations for the "sweep-out" effect which is an instrumental effect. A "super Langevin" rate constant is introduced which is a higher-order correction to the Langevin model. A theoretical model for the "three-body ion-atom association" rate constant is presented in the appendix of the thesis.

  16. 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.

  17. Ion acceleration in Ar-Xe and Ar-He plasmas. II. Ion velocity distribution functions

    SciTech Connect

    Biloiu, Ioana A.; Scime, Earl E. [Department of Physics, West Virginia University, Morgantown, West Virginia 26506 (United States)

    2010-11-15

    Ion velocity distribution functions (ivdfs) are investigated by laser induced fluorescence in Ar-Xe and Ar-He expanding helicon plasmas as a function of gas composition. In the case of Ar-Xe plasma, it was found that in the helicon source, both the Ar{sup +} and Xe{sup +} vdfs are unimodal. Their parallel speeds are subsonic and unaffected by changes in gas composition. At the end of the source, the argon ivdf shows a bimodal structure indicative of an electric double layer upstream of the measurement location. The fast argon ion component parallel velocity increases with Xe fraction from 6.7 to 8 km/s as the Xe fraction increases from 0% to 4%. In the expansion region, the bimodal character of Ar ivdf is maintained with a supersonic fast component reaching parallel speeds of 10.5 km/s. For all the studied plasma conditions and different spatial locations, the Xe{sup +} vdf exhibits a unimodal structure with a maximum parallel flow velocity of 2.2 km/s at the end of the source. For Ar-He plasma, the Ar ivdf is bimodal with the fast ion component parallel velocity increasing from 5.2 to 7.8 km/s as the He fraction increases from 0% to 30%. For the same He fraction range, the slow argon ion population distribution changes from a single Gaussian to a wide distribution extending all the way from the speed of the fast population to 0 m/s.

  18. Ion acceleration in Ar-Xe and Ar-He plasmas. II. Ion velocity distribution functions

    Microsoft Academic Search

    Ioana A. Biloiu; Earl E. Scime

    2010-01-01

    Ion velocity distribution functions (ivdfs) are investigated by laser induced fluorescence in Ar-Xe and Ar-He expanding helicon plasmas as a function of gas composition. In the case of Ar-Xe plasma, it was found that in the helicon source, both the Ar+ and Xe+ vdfs are unimodal. Their parallel speeds are subsonic and unaffected by changes in gas composition. At the

  19. Neoclassical polarization drift of collisionless single ions in a sheared radial electric field in a tokamak magnetic geometry

    SciTech Connect

    Baek, Hoyul; Ku, Seunghoe; Chang, C. S. [Department of Physics, Korea Advanced Institute of Science and Technology, Yusong-Ku, Daejon, 305-701 (Korea, Republic of); Department of Physics, Korea Advanced Institute of Science and Technology, Yusong-Ku, Daejon, 305-701 (Korea, Republic of) and Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, New York 10012 (United States)

    2006-01-15

    Neoclassical polarization drift is known to play critical role in the dynamical behavior of a sheared radial electric field E{sub r} in a toroidal confinement device. However, basic studies on the effect of radial electric shear on neoclassical polarization drift have not yet appeared in the literature. In the present report, the neoclassical polarization drift speed V{sub NP} of collisionless single ions is studied using a guiding-center code in a time-varying, spatially sheared E{sub r} in a realistic tokamak geometry. It is found numerically that the V{sub NP} for single ions is not only a function of the time derivative {partial_derivative}E{sub r}/{partial_derivative}t, but also a strong function of the radial shear {delta}r{partial_derivative}E{sub r}/{partial_derivative}r if the shear length is on the same order as the ion banana width {delta}r. Comparison with an analytic investigation reveals that this effect is simply due to the finite banana modification to the orbital average E{sub r}. An approximate analytic formula has been presented for collisionless single banana ions in a conventional tokamak magnetic geometry. The trapped-passing boundary layer physics is not treated.

  20. Maximum drift velocity of electrons in selectively doped InAlAs/InGaAs/InAlAs heterostructures with InAs inserts

    SciTech Connect

    Silenas, A.; Pozela, Yu., E-mail: pozela@pfi.lt; Pozela, K.; Juciene, V. [Center for Physical Sciences and Technology, Semiconductor Physics Institute (Lithuania); Vasil'evskii, I. S.; Galiev, G. B.; Pushkarev, S. S.; Klimov, E. A. [Russian Academy of Sciences, Institute of Microwave Semiconductor Electronics (Russian Federation)

    2013-03-15

    The dependence of the electron mobility and drift velocity on the growth conditions, thickness, and doping of an InAs insert placed at the center of the quantum well in a selectively doped InAlAs/InGaAs/InAlAs heterostructure has been investigated. Record enhancement of the maximum drift velocity to (2-4) Multiplication-Sign 10{sup 7} cm/s in an electric field of 5 Multiplication-Sign 10{sup 3} V/cm has been obtained in a 17-nm-wide quantum well with an undoped 4-nm-thick InAs insert. In the structures with additional doping of the InAs insert, which facilitates an increase in the density of electrons in the quantum well to 4.0 Multiplication-Sign 10{sup 12} cm{sup -2}, the maximum drift velocity is as high as 2 Multiplication-Sign 10{sup 7} cm/s in an electric field of 7 Multiplication-Sign 10{sup 3} V/cm.

  1. Low energy electron and nuclear recoil thresholds in the DRIFT-II negative ion TPC for dark matter searches

    Microsoft Academic Search

    S. Burgos; E. Daw; J. Forbes; C. Ghag; M. Gold; C. Hagemann; V. A. Kudryavtsev; T. B. Lawson; D. Loomba; P. Majewski; D. Muna; A. St. J. Murphy; S. M. Paling; A. Petkov; S. J. S. Plank; M. Robinson; N. Sanghi; D. P. Snowden-Ifft; N. J. C. Spooner; J. Turk; E. Tziaferi

    2009-01-01

    Understanding the ability to measure and discriminate particle events at the lowest possible energy is an essential requirement in developing new experiments to search for weakly interacting massive particle (WIMP) dark matter. In this paper we detail an assessment of the potential sensitivity below 10 keV in the 1 m3 DRIFT-II directionally sensitive, low pressure, negative ion time projection chamber

  2. 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.

  3. 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

    parallel [24] Cyclic Drift Tube Mobility Spectrometry scanning / filtering Radially Symmetric; Cyclic Ion Path Electrodynamic DC parallel [25] Differential Mobility Analysis (DMA) Gas-phase Electrophoretic Mobility Molecular Analyzer (GEMMA...

  4. Linear dependence of the postsunset equatorial anomaly electron density on solar flux and its relation to the maximum prereversal E × B drift velocity through its dependence on solar flux

    Microsoft Academic Search

    James A. Whalen

    2004-01-01

    The postsunset equatorial ionization anomaly, with maximum F layer electron density, Nemax, occurring near 2100 LT, has been found during solar maximum to be a linear function of the maximum prereversal E × B drift velocity (E × B drift). In order to examine this relation at all levels of solar flux, Nemax is measured during 13 years of an

  5. 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.

  6. 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.

  7. Performance evaluation of a miniature ion mobility spectrometer drift cell for application in hand-held explosives detection ion mobility spectrometers

    Microsoft Academic Search

    J. S. Babis; R. P. Sperline; A. K. Knight; D. A. Jones; C. A. Gresham; M. B. Denton

    2009-01-01

    The implementation of hand-held ion mobility spectrometers (IMS) requires the development and evaluation of miniature drift\\u000a cells providing high sensitivity while maintaining reasonable resolution. This manuscript describes the construction of a\\u000a miniature IMS designed for such an application and its characterization by evaluation of the detection limits and resolution\\u000a of the system with seven explosive compounds including trinitrotoluene (TNT), cyclotrimethylenetrinitramine

  8. Double-drift-region ion-implanted millimeter-wave IMPATT diodes

    Microsoft Academic Search

    THOMAS E. SEIDEL; RONALD E. DAVIS; DAVID E. IGLESIAS

    1971-01-01

    A detailed experimental comparison between double-drift-region (DDR) and single-drift-region (SDR) millimeter-wave avalanche diodes is presented. For 50-GHz CW operation, DDR diodes have given a maximum of 1-W output power compared to 0.53 W for the SDR diodes, while maximum efficiencies of 14.2 percent for the DDR and 10.3 percent for the SDR diodes have been obtained. These results are in

  9. Hypersonic drift-tearing magnetic islands in tokamak plasmas R. Fitzpatrick and F. L. Waelbroeck

    E-print Network

    Fitzpatrick, Richard

    Hypersonic drift-tearing magnetic islands in tokamak plasmas R. Fitzpatrick and F. L. Waelbroeck of long wavelength, hypersonic, drift-tearing magnetic islands in low-collisionality, low- plasmas. Isolated hypersonic islands propagate with a velocity that lies between those of the unperturbed local ion

  10. Seasonal cycle of velocity in the Atlantic North Equatorial Countercurrent as measured by surface drifters, current meters, and ship drifts

    Microsoft Academic Search

    P. L. Richardson; G. Reverdin

    1987-01-01

    This report describes the general circulation and seasonal variation of currents in the equatorial Atlantic, concentrating on the North Equatorial Countercurrent (NECC), using data collected as part of the Seasonal Response of the Equatorial Atlantic and Programme Français Océan et Climat dans l'Atlantique Equatorial experiments plus historical ship drifts. During 1983-1985 the Lagrangian circulation was studied by launching and tracking

  11. Energy of secondary ions desorbed from insulating films by MeV heavy ions as a function of projectile velocity

    Microsoft Academic Search

    O. Becker; K. Wien

    1986-01-01

    The influence of projectile velocity on the axial energy distribution and mean axial energy of secondary ions was measured with a double-field time-of-flight method at the GSI accelerator-system. The secondary ions were ejected from thin layers ( ~ 150 nm) of CsI, MgO, CaF2, valine and phenylalanine irradiated with Sn and U projectiles. The mean energy of ions like Cs+

  12. Measurements of velocity shear and ion viscosity profile in a magnetohydrodynamic plasma jet

    SciTech Connect

    Dorf, L. A.; Intrator, T.; Sun, X.; Hendryx, J.; Wurden, G. A.; Furno, I; Lapenta, G. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2010-10-15

    Time-dependent, two-dimensional profiles of the axial flow velocity, density, electron temperature, and magnetic field components are measured at two axial locations in a screw pinch plasma column of the reconnection scaling experiment. The results show that the ion momentum flux for a given column radius is dissipated by the ion-ion Coulomb scattering viscosity due to a significant radial shear of the axial velocity. By comparing the terms of the magnetohydrodynamic momentum balance equation, radial profile of ion viscosity is determined. Chord-integrated ion temperature measurements performed at several radial locations using Doppler broadening spectroscopy show ion temperature of about 1 eV. Measured ion viscosity agrees within a factor of 2 with the classical Braginskii expectations.

  13. 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.

  14. Velocity dependence of the transient hyperfine field at Pd ions swiftly recoiling through magnetized Fe

    SciTech Connect

    Stuchbery, A.E.; Ryan, C.G.; Bolotin, H.H.; Sie, S.H.

    1981-04-01

    The velocity dependence of the transient hyperfine magnetic field manifest at nuclei of /sup 108/Pd ions recoiling through magnetized Fe was investigated to a velocity higher than previously examined for the heavier nuclides. The state of interest (2/sup +//sub 1/) was populated by Coulomb excitation using beams of 80-MeV /sup 32/S and 180-MeV /sup 58/Ni ions and precessed ..gamma..-ray angular distribution measurements were carried out in coincidence with backscattered projectiles. These results, when combined with prior lower-velocity measurements for /sup 106/Pd, yield a transient field velocity dependence v/sup p/, p=0.41 +- 0.15, for Pd isotopes over the extended velocity range 1.74< or =< or =7.02 (v/sub 0/=c/137); a result incompatible with a linear velocity dependence.

  15. Electrostatic instabilities driven by velocity gradients

    Microsoft Academic Search

    A. Hirose; I. Alexeff

    1973-01-01

    It is shown that cross-field gradients of guiding-center drift velocities can excite several high-frequency (? > ?ci ) electrostatic instabilities. The instabilities can enhance effective interelectron and\\/or electron-ion collisions which in turn destory the velocity gradients. In pulsed, turbulent heating experiments, this effect is expected to appear as anomalously rapid current penetration (anomalous skin effect).

  16. Relation between the occurrence rate of ESF and the equatorial vertical plasma drift velocity at sunset derived from global observations

    Microsoft Academic Search

    C. Stolle; H. Lühr

    2008-01-01

    In this study, we investigate two global climatological data sets; the occurrence rate of Equatorial Spread-F (ESF), associated with equatorial plasma irregularities, at ~400 km altitude obtained from CHAMP observations, and the evening equatorial vertical plasma drift, vz, from ROCSAT-1 measurements. First, as retrieved for a solar flux level of F10.7=150, the longitudinal variation of the two independently derived quantities

  17. A method for determining the drift velocity of plasma depletions in the equatorial ionosphere using far-ultraviolet spacecraft observations

    Microsoft Academic Search

    S. H. Park; S. L. England; T. J. Immel; H. U. Frey; S. B. Mende

    2007-01-01

    The Far-Ultraviolet Imager (IMAGE-FUV) on board the NASA IMAGE satellite has been used to observe plasma depletions in the nightside equatorial ionosphere. Observations from periods around spacecraft apogee, during which equatorial regions are visible for several hours, have allowed the velocity of these plasma depletions to be determined. A new method for determining the velocity of these depletions using an

  18. Sensitive detection of black powder by stand-alone ion mobility spectrometer with chlorinated hydrocarbon modifiers in drift gas.

    PubMed

    Liang, Xixi; Wang, Xin; Wang, Weiguo; Zhou, Qinghua; Chen, Chuang; Peng, Liying; Wen, Meng; Qu, Tuanshuai; Wang, Zhenxin; Zhao, Kun; Li, Jinghua; Li, Haiyang

    2014-04-01

    This paper introduces a simple method for selective and sensitive detection of black powder by adding chlorinated hydrocarbons in the drift gas instead of changing the structure of conventional ion mobility spectrometer (IMS). The function of chloride modifiers was to substitute Cl(-)(H?O)n for [O?? (H?O)(n)] in the drift region so as to avoid the overlap between O?? (H?O)(n) and sulfur ion peaks. Among CH?Cl?, CHCl? and CCl?, CCl? was chosen as the modifier due to the best peak-to-peak resolution and stability towards the fluctuation of modifier concentration. With 1.4 ppm CCl? as the modifier, the minimum detectable quantity of 0.1 ng for sulfur was achieved. Moreover, this method showed the ability for detection of common explosives at sub-nanogram level, such as black powder (BP), ammonium nitrate fuel oil (ANFO), 2,4,6-trinitrotoluene (TNT), and pentaerythritol tetranitrate (PETN). In summary, this method requiring no configuration modification has high sensitivity and selectivity, and consumes trace amount of modifier. And these characteristics make it easy to be adopted in current deployed IMS to detect black powder explosives. PMID:24607130

  19. Measurements of the parallel ion velocity distribution at the plasma-sheath interface

    NASA Astrophysics Data System (ADS)

    Ko?an, M.; Gunn, J. P.; Fuchs, V.; Müller, H. W.; ASDEX Upgrade Team

    2013-07-01

    The ion velocity distribution parallel to magnetic field lines, f is extracted from retarding field analyzer (RFA) measurements in the ASDEX Upgrade scrape-off layer. The RFA ion current-voltage characteristic is transformed into a system of linear equations, from which f is unfolded using a standard regularization method. The algorithm is validated on numerically generated data. The experimentally measured f compares favorably with the ion velocity distributions calculated from a quasi-neutral kinetic simulation of the plasma pre-sheath. The technique can be used to measure f by RFAs in plasma processing, high-energy particle accelerators or by satellite-born RFAs.

  20. Nonadiabatic ion acceleration at the nightside highlatitude magnetopause: Fine structure of the velocity distribution function

    NASA Astrophysics Data System (ADS)

    Vaisberg, O.; Artemyev, A.; Avanov, L.

    2015-06-01

    In this paper we use Interball-tail observations and numerical modeling to investigate ion acceleration in reconnected nightside magnetopause. We consider magnetic field configuration corresponding to the superposition of the magnetopause current sheet and reconnected fluxtube, which moves tailward. This fluxtube creates normal component of the magnetic field and the transverse electric field component. Initial current sheet geometry includes tangential and shear components of the magnetic field. Interaction of cold magnetosheath ions with the reconnected current sheet results in particle acceleration and transition through the magnetopause. Reflected and transited ions form velocity distributions with a halo in the (v?,v?) plane. Numerical modeling reproduce these velocity distributions quite well. Comparison of numerical results and spacecraft observation indicates that nonadibatic ion acceleration plays essential role in formation of such velocity distributions.

  1. 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.

  2. Isotropic ion distribution functions triggered by consecutive solar wind bulk velocity jumps: a new equilibrium state

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    Context. Throughout the heliosphere, ion power spectra have been found in observations to exhibit suprathermal tails that follow power laws. Ion power-law spectra, though having a broad range of spectral indices 4.4 ? ?v ? 6.6, perhaps favourably seem to have velocity power indices of ?v ? (-5), a phenomenon that can more or less ubiquitously be found in heliospheric space plasmas. This is probably indicative of an as yet unidentified quasi-equilibrium state of collisionless space plasmas. Aims: We develop the idea that these forms of ion spectra could be produced by a continuous back- and forth- shuffling of wind convected ions in consecutive jumps from fast to slow, and vice-versa, bulk velocity regimes. Methods: The appearance of a quasi-equilibrium state due to this shuffling and re-shuffling, as we show, naturally results in ion distribution functions that are superpositions of a series of weighted Maxwellians resulting into power laws beyond a critical velocity border. Spectral intensities thereby anticorrelate with bulk velocities, but power indices depend only slightly on bulk velocity. Results: The fully developed equilibrium state is shown here, however, to be characterized by a power law with power index ?v = ( - 3), instead of 4.4 ? ?v ? 6.6. These latter states, which generally show up in observations, thus may characterize an off-equilibrium state as we discuss in this paper.

  3. Observations of the velocity distribution of solar wind ions

    Microsoft Academic Search

    K. W. Ogilvie; P. Bochsler; J. Geiss; M. A. Coplan

    1980-01-01

    Measurements made by the Isee 3 ion composition experiment have been used to determine the kinetic temperatures of ³He\\/sup + +\\/, ⁴He\\/sup + +\\/, ¹⁶O\\/sup 6 +\\/, and ¹⁶O\\/sup 7 +\\/ in the solar wind. It is found that these temperatures generally obey the relation that T\\/sub i\\/\\/m\\/sub i\\/=const, but fluctuations, some of which are caused by dynamical effects in

  4. 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.

  5. Regulation of ion drifts and anisotropies by parametrically unstable finite-amplitude Alfvén-cyclotron waves in the fast solar wind

    SciTech Connect

    Maneva, Y. G. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Araneda, J. A. [Departamento de Física, Universidad de Concepción, 4070386 (Chile); Marsch, E., E-mail: yana.g.maneva@nasa.gov [Institute for Experimental and Applied Physics, Christian Albrechts University at Kiel, D-24118 Kiel (Germany)

    2014-03-10

    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.

  6. An experimental study of ion-induced nucleation using a drift tube ion mobility spectrometer\\/mass spectrometer and a cluster-differential mobility analyzer\\/Faraday cup electrometer

    Microsoft Academic Search

    Kenkichi Nagato; Chan Soo Kim; Motoaki Adachi; Kikuo Okuyama

    2005-01-01

    An experimental system employing a drift tube ion mobility spectrometer\\/mass spectrometer (DT-IMS\\/MS) and a cluster-differential mobility analyzer with Faraday cup electrometer (C-DMA\\/FCE) was developed for the study of ion-induced nucleation. Using this, both the time scales and size scales of ions to be measured can be extended significantly. The system offers the potential for tracing the entire process of ion-induced

  7. Onset, growth, and saturation of the current-driven ion cyclotron instability

    Microsoft Academic Search

    D. L. Correll; N. Rynn

    1975-01-01

    The temporal evolution of the current-driven electrostatic ion cyclotron instability was investigated experimentally. The critical destabilizing electron drift velocity for different values of mode phase velocity was measured. The phase velocity was changed by varying the effective plasma column length and hence the parallel wavelength. Ion cyclotron damping was observed to dominate over electron Landau damping at low phase velocities.

  8. Nonlinear evolution of drift instabilities

    SciTech Connect

    Lee, W.W.; Krommes, J.A.; Oberman, C.R.; Smith, R.A.

    1984-01-01

    The nonlinear evolution of collisionless drift instabilities in a shear-free magnetic field has been studied by means of gyrokinetic particle simulation as well as numerical integration of model mode-coupling equations. The purpose of the investigation is to identify relevant nonlinear mechanisms responsible for the steady-state drift wave fluctuations. It is found that the saturation of the instability is mainly caused by the nonlinear E x B convection of the resonant electrons and their associated velocity space nonlinearity. The latter also induces energy exchange between the competing modes, which, in turn, gives rise to enhanced diffusion. The nonlinear E x B convection of the ions, which contributes to the nonlinear frequency shift, is also an important ingredient for the saturation.

  9. Acceleration Gap Effects on the Longitudinal Compression of Intense Ion Beams in the Neutralized Drift Compression Experiment

    NASA Astrophysics Data System (ADS)

    Sefkow, Adam; Davidson, Ronald

    2007-11-01

    Longitudinal compression of space-charge-dominated ion beams to high currents in nanosecond pulses for warm dense matter and heavy ion fusion applications is achieved by imposing a time-dependent velocity tilt to the charge bunch across the acceleration gap of a linear induction accelerator. The subsequent neutralization of the beam by a pre-formed plasma allows the intense charge bunch to compress above the traditional space-charge limit for quiescent propagation and longitudinal focusing. The detailed physics and implications of acceleration-gap effects and focusing aberration on optimum current compression are reviewed. Quantitative examples using particle-in-cell simulations explore the dependency of the axial compression on effects such as the finite-size acceleration gap, voltage waveform, and the beam's initial temperature, pulse length, intended fractional velocity tilt, kinetic energy uncertainty, and distribution function.

  10. One year variations in the near earth solar wind ion density and bulk flow velocity

    NASA Technical Reports Server (NTRS)

    Bolton, Scott J.

    1990-01-01

    One-year periodic variations in the near earth solar wind ion density and bulk flow velocity are reported. The variations show an inverse relationship between the ion velocity and density. The peak strength of the observed density variation ranges from 50-100 percent over the background. These variations imply either large scale mass loading inside the earth's orbit or intrinsic solar modulations. Analyses of both near earth and Pioneer Venus Orbiter spacecraft data provide a comparison at two different heliocentric distances. Several explanations for these variations are discussed.

  11. Asymmetry in electron and ion charge collection in a drifting plasma bunch

    SciTech Connect

    Belloni, F.; Lorusso, A.; Nassisi, V. [Laboratory of Applied Electronics, Department of Physics, University of Lecce and INFN-sect. of Lecce, C.P. 193, via Arnesano, 73100 Lecce, Italy and European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe (Germany); Laboratory of Applied Electronics, Department of Physics, University of Lecce and INFN-sect. of Lecce, C.P. 193, via Arnesano, 73100 Lecce (Italy)

    2007-05-01

    We report on the different behavior of electron and ion currents recorded by a Faraday cup in a plasma bunch generated via laser ablation. An excimer laser was employed to irradiate a Ge target. The current signals were recorded equipping the Faraday cup collector by a set of diaphragms. We found that the electron time-of-flight spectra were fairly similar to the ion ones, but the collected charge yield for electrons was up to 200 times larger than the corresponding ion yield. We ascribed such a discrepancy to the different cup collection efficiency for ions and electrons forming the plasma which was heavily influenced by the plume geometry, the energy of the particles, as well as the diaphragm size. Our findings would suggest that the overall electron charge 'tended' to be collected, unlike the ion charge which scaled upon the collection solid angle.

  12. Dust acoustic instability driven by drifting ions and electrons in the dust plasma with Lorentzian kappa distribution

    SciTech Connect

    Liu Zhipeng; Du Jiulin [Department of Physics, School of Science, Tianjin University, Tianjin 300072 (China)

    2009-12-15

    The instability of the dust acoustic waves driven by drifting electrons and ions in a dusty plasma is investigated by the kinetic theory. All the plasma components (electrons, ions, and dust particles) are assumed to be the Lorentzian kappa (kappa) distributions. The spectral indices kappa of the kappa-distributions for the three plasma components are different from each other. The obtained instability growth rate depends on the physical quantities of the plasma not only, but on the spectral indices. The numerical results for the kappa-effect on the instability growth rate show that, if the normalized wave number is small, the index of electrons has a stabilized effect on the dust acoustic waves and the index of ions has an instability effect on the waves, but if the normalized wave number is large, they both nearly have no any effect on the waves. In reverse, the index of dust grains has nearly no any effect on the instability growth rate if the normalized wave number is small, but it has a stabilized effect on the dust waves if the normalized wave number is large.

  13. 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.

  14. Velocity and Energy Distributions of Water Group Ion Around the Enceladus Plume

    NASA Astrophysics Data System (ADS)

    Sakai, S.; Cravens, T.; Pothapragada, S.; Kumar, A.

    2014-12-01

    Enceladus has a dynamic plume on its south pole which is emitting gas, including water vapor, and dust. The gas is ionized by solar EUV radiation and by electron impacts and extends throughout the inner magnetosphere of Saturn. The dust is negatively charged and forms the E ring. Hence, the inner magnetosphere within 10 RS contains a complex mixture of plasma, neutral gas and dust. Cassini observations show that the plasma velocities are less than the co-rotation velocity. The velocity and energy distributions of this need to be explained in order to understand the inner magnetospheric plasma physics. We have investigated the velocity and energy distributions of water group ions in the vicinity of Enceladus using test particle and Monte Carlo methods including collisional processes such as charge exchange and ion-neutral chemical reaction. The model results will be constrained by neutral and ion composition data from the Cassini Ion and Neutral Mass Spectrometer and ion energy spectra from the Plasma Spectrometer (CAPS). We will also discuss related plasma processed in the Enceladus torus.

  15. An Implication of Ether Drift

    E-print Network

    Hong-Yi Zhou

    1998-05-25

    The experimental results of the two-photon absorption(TPA) and M\\"{o}ssbauer-rotor(MR) for testing the isotropy of the speed of light are explained in an ether drift model with a drift velocity of $\\sim 10^{-3}c$. Further tests of the ether drift assumption are suggested.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Plasma immersion ion implantation characteristics with q-nonextensive electron velocity distribution

    NASA Astrophysics Data System (ADS)

    Safa, N. Navab; Ghomi, H.; Niknam, A. R.

    2015-06-01

    The plasma immersion ion implantation process is investigated in the presence of q-nonextensive electrons by using a one-dimensional fluid model. The effect of the nonextensivity parameter, q, on the plasma parameters and sheath dynamics during the implantation process is studied. The results show that the implantation dose can be enhanced in the presence of energetic electrons at the tail of the distribution function. Different parameters of plasma such as sheath thickness, ion velocity and ion density show more change at the larger values of the q-parameter. Furthermore, the results of simulation tend to what is predicted by the Maxwellian electron distribution function (q = 1).

  1. A simulation study on the impact of altitudinal dependent vertical plasma drift on the equatorial ionosphere in the evening

    NASA Astrophysics Data System (ADS)

    Qian, Cheng; Lei, Jiuhou; Wang, Wenbin

    2015-04-01

    We carry out a simulation study on the impact of altitudinal dependent plasma drift on the equatorial ionosphere in the evening, under geomagnetically quiet conditions. Our study used the vertical plasma drift velocity data measured by an incoherent scatter radar at Jicamarca (11.95°S, 76.87°W). The data covered the local sunset period on 15 and 16 November 2004. The plasma drift had significant altitudinal variations in the vertical component, which is perpendicular to the magnetic field. We employed SAMI2 (SAMI2 is another model of the ionosphere) to evaluate the effect of the altitude-dependent ion drift on the equatorial ionosphere. Three types of plasma drift velocity inputs were used in our simulations. The first input is calculated from an empirical model, the second is a height-averaged drift obtained from the observed drift velocity, and the third one corresponds to the observed altitudinal dependent drift data. A strong equatorial ionization anomaly occurred in the results of all numerical experiments. Additional layers (F3 layers) in electron densities over the equatorial F region and "arch" latitudinal structures extending to lower middle latitudes were seen in the simulations driven by the observed altitudinal dependent drift. We further show that neutral winds do not have a significant effect on the simulated F3 layers. The results of our numerical experiments suggest that the simulated additional ionospheric layers and arch structures are associated with the altitudinal gradients in the vertical plasma drift velocity.

  2. Simultaneous energy distribution and ion fraction measurements using a linear time-of-flight analyzer with a floatable drift tube

    E-print Network

    -of-flight analyzer with a floatable drift tube V. A. Morozov and F. W. Meyer Physics Division, Oak Ridge National-of-flight analyzer with a floatable drift tube is described. Analytical expressions for the relative collection and eventually reaching the detector when voltage U is applied to the drift tube , and D(Ed ,q) is the detector

  3. The mobilities of NO+(CH3CN)n cluster ions (n=0–3) drifting in helium and in helium–acetonitrile mixtures

    Microsoft Academic Search

    Joost A. de Gouw; Li Ning Ding; M. Krishnamurthy; Hack Sung Lee; Eric B. Anthony; Veronica M. Bierbaum; Stephen R. Leone

    1996-01-01

    The mobilities of NO+(CH3CN)n cluster ions (n=0–3) drifting in helium and in mixtures of helium and acetonitrile (CH3CN) are measured in a flow-drift tube. The mobilities in helium decrease with cluster size [the mobility at zero field, K(0)0, is 22.4±0.5 cm2 V?1 s?1 for NO+, 12.3±0.3 cm2 V?1 s?1 for NO+(CH3CN), 8.2±0.2 cm2 V?1 s?1 for NO+(CH3CN)2 and 7.5±0.5 cm2

  4. Head-to-tail velocity tilt in an ion induction linac

    SciTech Connect

    Kim, C.H.; Judd, D.L.; Laslett, L.J.; Smith, L.; Warwick, A.I.

    1986-06-01

    In the earleir stages of acceleration in a heavy-ion-induction linac, acceleration and bunching rates are constrained by the allowable value of head-to-tail velocity tilt at a given location. If focusing parameters at a given location are fixed, the velocity tilt should be less than a certain upper bound to avoid too much envelope variation and consequent beam losses. For space charge dominated beams, we found some favorable particle distributions in longitudinal phase space for which the maximum-matched-beam envelope at a given location is almost constant with respect to time, in spite of the presence of a large velocity tilt. Mismatch oscillations can be reduced by slow variation of the velocity tilt and slow current amplification. Under these circumstances, the velocity tilt can be as large as allowed by the usable range of sigma/sub o/. Behavior of Cs ion beams with very large velocity tilts (up to 40%) are studied experimentally in MBE-4 and the results are presented.

  5. Conformational ordering of biomolecules in the gas phase: nitrogen collision cross sections measured on a prototype high resolution drift tube ion mobility-mass spectrometer.

    PubMed

    May, Jody C; Goodwin, Cody R; Lareau, Nichole M; Leaptrot, Katrina L; Morris, Caleb B; Kurulugama, Ruwan T; Mordehai, Alex; Klein, Christian; Barry, William; Darland, Ed; Overney, Gregor; Imatani, Kenneth; Stafford, George C; Fjeldsted, John C; McLean, John A

    2014-02-18

    Ion mobility-mass spectrometry measurements which describe the gas-phase scaling of molecular size and mass are of both fundamental and pragmatic utility. Fundamentally, such measurements expand our understanding of intrinsic intramolecular folding forces in the absence of solvent. Practically, reproducible transport properties, such as gas-phase collision cross-section (CCS), are analytically useful metrics for identification and characterization purposes. Here, we report 594 CCS values obtained in nitrogen drift gas on an electrostatic drift tube ion mobility-mass spectrometry (IM-MS) instrument. The instrument platform is a newly developed prototype incorporating a uniform-field drift tube bracketed by electrodynamic ion funnels and coupled to a high resolution quadrupole time-of-flight mass spectrometer. The CCS values reported here are of high experimental precision (±0.5% or better) and represent four chemically distinct classes of molecules (quaternary ammonium salts, lipids, peptides, and carbohydrates), which enables structural comparisons to be made between molecules of different chemical compositions for the rapid "omni-omic" characterization of complex biological samples. Comparisons made between helium and nitrogen-derived CCS measurements demonstrate that nitrogen CCS values are systematically larger than helium values; however, general separation trends between chemical classes are retained regardless of the drift gas. These results underscore that, for the highest CCS accuracy, care must be exercised when utilizing helium-derived CCS values to calibrate measurements obtained in nitrogen, as is the common practice in the field. PMID:24446877

  6. Conformational Ordering of Biomolecules in the Gas Phase: Nitrogen Collision Cross Sections Measured on a Prototype High Resolution Drift Tube Ion Mobility-Mass Spectrometer

    PubMed Central

    2014-01-01

    Ion mobility-mass spectrometry measurements which describe the gas-phase scaling of molecular size and mass are of both fundamental and pragmatic utility. Fundamentally, such measurements expand our understanding of intrinsic intramolecular folding forces in the absence of solvent. Practically, reproducible transport properties, such as gas-phase collision cross-section (CCS), are analytically useful metrics for identification and characterization purposes. Here, we report 594 CCS values obtained in nitrogen drift gas on an electrostatic drift tube ion mobility-mass spectrometry (IM-MS) instrument. The instrument platform is a newly developed prototype incorporating a uniform-field drift tube bracketed by electrodynamic ion funnels and coupled to a high resolution quadrupole time-of-flight mass spectrometer. The CCS values reported here are of high experimental precision (±0.5% or better) and represent four chemically distinct classes of molecules (quaternary ammonium salts, lipids, peptides, and carbohydrates), which enables structural comparisons to be made between molecules of different chemical compositions for the rapid “omni-omic” characterization of complex biological samples. Comparisons made between helium and nitrogen-derived CCS measurements demonstrate that nitrogen CCS values are systematically larger than helium values; however, general separation trends between chemical classes are retained regardless of the drift gas. These results underscore that, for the highest CCS accuracy, care must be exercised when utilizing helium-derived CCS values to calibrate measurements obtained in nitrogen, as is the common practice in the field. PMID:24446877

  7. Ion velocity distribution at the termination shock: 1-D PIC simulation

    NASA Astrophysics Data System (ADS)

    Lu, Quanming; Yang, Zhongwei; Lembège, Bertrand

    2012-11-01

    The Voyager 2 (V2) plasma observations of the proton temperature downstream of the quasi-perpendicular heliospheric termination shock (TS) showed that upstream thermal solar wind ions played little role in the shock dissipation mechanism and their downstream temperature is an order of magnitude smaller than predicted by MHD Rankine-Hugoniot conditions. While pickup ions (PUI) are generally expected to play an important role in energy dissipation at the shock, the details remain unclear. Here, one-dimensional (1-D) Particle-in-cell (PIC) code is used to examine kinetic properties and downstream velocity distribution functions of pickup ions (the hot supra-thermal component) and solar wind protons (SWs, the cold component) at the perpendicular heliospheric termination shock. The code treats the pickup ions self-consistently as a third component. Present results show that: (1) both of the incident SWs and PUIs can be separated into two parts: reflected (R) ions and directly transmitted (DT) ions, the energy gain of the R ions at the shock front is much larger than that of the DT ions; (2) the fraction of reflected SWs and their downstream temperature decrease with the relative percentage PUI%; (3) no matter how large the PUI% is, the downstream ion velocity distribution function always can be separated into three parts: 1. a high energy tail (i.e. the wings) dominated by the reflected PUIs, 2. a low energy core mainly contributed by the directly transmitted SWs, and 3. a middle energy part which is a complicated superposition of reflected SWs and directly transmitted PUIs. The significance of the presence of pickup ions on shock front micro-structure and nonstationarity is also discussed.

  8. Ion velocity distribution at the termination shock: 1-D PIC simulation

    SciTech Connect

    Lu Quanming; Yang Zhongwei; Lembege, Bertrand [CAS Key Laboratory of Basic Plasma Physics, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026 (China); SOA Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai 200136 (China); LATMOS-UVSQ-IPSL-CNRS, Guyancourt 78280 (France)

    2012-11-20

    The Voyager 2 (V2) plasma observations of the proton temperature downstream of the quasi-perpendicular heliospheric termination shock (TS) showed that upstream thermal solar wind ions played little role in the shock dissipation mechanism and their downstream temperature is an order of magnitude smaller than predicted by MHD Rankine-Hugoniot conditions. While pickup ions (PUI) are generally expected to play an important role in energy dissipation at the shock, the details remain unclear. Here, one-dimensional (1-D) Particle-in-cell (PIC) code is used to examine kinetic properties and downstream velocity distribution functions of pickup ions (the hot supra-thermal component) and solar wind protons (SWs, the cold component) at the perpendicular heliospheric termination shock. The code treats the pickup ions self-consistently as a third component. Present results show that: (1) both of the incident SWs and PUIs can be separated into two parts: reflected (R) ions and directly transmitted (DT) ions, the energy gain of the R ions at the shock front is much larger than that of the DT ions; (2) the fraction of reflected SWs and their downstream temperature decrease with the relative percentage PUI%; (3) no matter how large the PUI% is, the downstream ion velocity distribution function always can be separated into three parts: 1. a high energy tail (i.e. the wings) dominated by the reflected PUIs, 2. a low energy core mainly contributed by the directly transmitted SWs, and 3. a middle energy part which is a complicated superposition of reflected SWs and directly transmitted PUIs. The significance of the presence of pickup ions on shock front micro-structure and nonstationarity is also discussed.

  9. Non-solar UV produced ions observed optically from the 'Crit I' critical velocity ionization experiment

    NASA Technical Reports Server (NTRS)

    Stenbaek-Nielsen, H. C.; Wescott, E. M.; Rees, D.; Valenzuela, A.; Brenning, N.

    1990-01-01

    A critical velocity ionization experiment was carried out with a heavily instrumented rocket launched from Wallops Island on May 13, 1986. Two neutral barium beams were created by explosive shaped charges released from the rocket and detonated at 48 deg to B at altitudes near 400 km and below the solar UV cutoff. Critical velocity ionization was expected to form a detectable ion jet along the release field line, but, instead, an ion cloud of fairly uniform intensity was observed stretching from the release field line across to where the neutral barium jet reached sunlight. The process creating these ions must have been present from the time of the release; the efficiency is estimated to be equivalent to an ionization time constant of 1800 sec. This ionization is most likely from collisions between the neutral barium jet and the ambient atmospheric oxygen, and, if so, the cross section for collisional ionization is 9 x 10 to the -18th sq cm.

  10. Baseline resolution of isomers by traveling wave ion mobility mass spectrometry: investigating the effects of polarizable drift gases and ionic charge distribution.

    PubMed

    Lalli, Priscila M; Corilo, Yuri E; Fasciotti, Maíra; Riccio, Maria Francesca; de Sa, Gilberto F; Daroda, Romeu J; Souza, Gustavo H M F; McCullagh, Michael; Bartberger, Michael D; Eberlin, Marcos N; Campuzano, Iain D G

    2013-09-01

    We have studied the behavior of isomers and analogues by traveling wave ion mobility mass spectrometry (TWIM-MS) using drift-gases with varying masses and polarizabilities. Despite the reduced length of the cell (18?cm), a pair of constitutional isomers, N-butylaniline and para-butylaniline, with theoretical collision cross-section values in helium (?He ) differing by as little as 1.2?Å(2) (1.5%) but possessing contrasting charge distribution, showed baseline peak-to-peak resolution (Rp-p ) for their protonated molecules, using carbon dioxide (CO2), nitrous oxide (N2O) and ethene (C2H4 ) as the TWIM drift-gas. Near baseline Rp-p was also obtained in CO2 for a group of protonated haloanilines (para-chloroaniline, para-bromoaniline and para-iodoaniline) which display contrasting masses and theoretical ?He , which differ by as much as 15.7?Å(2) (19.5%) but similar charge distributions. The deprotonated isomeric pair of trans-oleic acid and cis-oleic acid possessing nearly identical theoretical ?He and ?N2 as well as similar charge distributions, remained unresolved. Interestingly, an inversion of drift-times were observed for the 1,3-dialkylimidazolium ions when comparing He, N2 and N2O. Using density functional theory as a means of examining the ions electronic structure, and He and N2-based trajectory method algorithm, we discuss the effect of the long-range charge induced dipole attractive and short-range Van der Waals forces involved in the TWIM separation in drift-gases of differing polarizabilities. We therefore propose that examining the electronic structure of the ions under investigation may potentially indicate whether the use of more polarizable drift-gases could improve separation and the overall success of TWIM-MS analysis. PMID:24078238

  11. 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.

  12. Stokes Drift for Random Gravity Waves

    Microsoft Academic Search

    Kern E. Kenyon

    1969-01-01

    Introduction. The modified form of the Stokes drift velocity [Stokes, 1847] for a random sea is briefly considered. For a statistically stationary and horizontally homogeneous wave field, the total wave drift is the sum of the drifts of the individual wave components. The expression for the Stokes drift, given here in terms of the full two-dimensionM energy spectrum for arbitrary

  13. Initial Velocity Distributions of MALDI Ions Desorbed from Single Crystals Ragnar Dworschak, Werner Ens, and Kenneth G Standing

    E-print Network

    Ens, Werner

    Initial Velocity Distributions of MALDI Ions Desorbed from Single Crystals Ragnar Dworschak, Werner desorption/ionization (MALDI). Here we present some observations from initial velocity measurements made with polystyrene. Previous measurements of initial velocities in MALDI have shown that for high fluence the initial

  14. Positive/negative ion velocity mapping apparatus for electron-molecule reactions

    SciTech Connect

    Wu Bin; Xia Lei; Li Hongkai; Zeng Xianjin; Tian Shanxi [Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2012-01-15

    In molecular dissociative ionization by electron collisions and dissociative electron attachment to molecule, the respective positively and negatively charged fragments are the important products. A compact ion velocity mapping apparatus is developed for the angular distribution measurements of the positive or negative fragments produced in the electron-molecule reactions. This apparatus consists of a pulsed electron gun, a set of ion velocity mapping optic lenses, a two-dimensional position detector including two pieces of micro-channel plates, and a phosphor screen, and a charge-coupled-device camera for data acquisition. The positive and negative ion detections can be simply realized by changing the voltage polarity of ion optics and detector. Velocity sliced images can be directly recorded using a narrow voltage pulse applied on the rear micro-channel plate. The efficient performance of this system is evaluated by measuring the angular distribution of O{sup -} from the electron attachments to NO at 7.3 and 8.3 eV and O{sup +} from the electron collision with CO at 40.0 eV.

  15. Inverting ion images without Abel inversion: maximum entropy reconstruction of velocity maps.

    PubMed

    Dick, Bernhard

    2014-01-14

    A new method for the reconstruction of velocity maps from ion images is presented, which is based on the maximum entropy concept. In contrast to other methods used for Abel inversion the new method never applies an inversion or smoothing to the data. Instead, it iteratively finds the map which is the most likely cause for the observed data, using the correct likelihood criterion for data sampled from a Poissonian distribution. The entropy criterion minimizes the information content in this map, which hence contains no information for which there is no evidence in the data. Two implementations are proposed, and their performance is demonstrated with simulated and experimental data: Maximum Entropy Velocity Image Reconstruction (MEVIR) obtains a two-dimensional slice through the velocity distribution and can be compared directly to Abel inversion. Maximum Entropy Velocity Legendre Reconstruction (MEVELER) finds one-dimensional distribution functions Q(l)(v) in an expansion of the velocity distribution in Legendre polynomials P((cos ?) for the angular dependence. Both MEVIR and MEVELER can be used for the analysis of ion images with intensities as low as 0.01 counts per pixel, with MEVELER performing significantly better than MEVIR for images with low intensity. Both methods perform better than pBASEX, in particular for images with less than one average count per pixel. PMID:24172596

  16. Effects of projectile track charging on the H - secondary ion velocity distribution

    NASA Astrophysics Data System (ADS)

    Iza, P.; Farenzena, L. S.; da Silveira, E. F.

    2007-03-01

    The bombardment of insulating targets by MeV projectiles produces a positive track delivering secondary electrons to the solid. These electrons are eventually captured by adsorbed hydrogen-containing molecules, inducing fragmentation and initiating the H - secondary ion emission. The dynamics of this process is very sensitive to the track electric field and depends on the emission site and on the H - initial velocity. In this work, a model, based on a time-depending track potential followed by secondary electron induced desorption - SEID, is employed to describe the production and dynamics of H - secondary ion emission. It is shown that depending on how fast the track neutralization occurs, the movement of H - ions may be accelerated, decelerated or even aborted. Trajectories, angular distributions and energy distributions are predicted and compared with experimental data obtained for water ice bombarded by 1.7 MeV nitrogen ions.

  17. Electron impact ionization and attachment, drift velocities and longitudinal diffusion in CF3I and CF3I N2 mixtures

    NASA Astrophysics Data System (ADS)

    de Urquijo, J.; Juárez, A. M.; Basurto, E.; Hernández-Ávila, J. L.

    2007-04-01

    This paper reports the measurement of the electron drift velocity ve, the longitudinal diffusion coefficient NDL and the density-normalized effective ionization coefficient (? - ?)/N in pure CF3I and in the CF3I-N2 mixtures, where ? and ? are the electron impact ionization and attachment coefficients, respectively, and N is the gas density. The E/N range covered was 100-850 Td (1 Td = 10-17 V cm2). The present results were derived from a pulsed Townsend experiment. For pure CF3I, the values of ve and (? - ?)/N were found to increase linearly with E/N. Moreover, the E/N value at which ionization equals attachment, commonly referred to as the limiting field strength, was found to be E/Nlim = 437 Td, which is greater than that of SF6 (360 Td), a widely used insulating gas. For the CF3I-N2 mixture with 70% CF3I, this E/Nlim value was found to be essentially the same as that for pure SF6.

  18. The effective ionization coefficients and electron drift velocities in gas mixtures of CF3I with N2 and CO2 obtained from Boltzmann equation analysis

    NASA Astrophysics Data System (ADS)

    Deng, Yun-Kun; Xiao, Deng-Ming

    2013-03-01

    The electron swarm parameters including the density-normalized effective ionization coefficients (?-?)/N and the electron drift velocities Ve are calculated for a gas mixture of CF3I with N2 and CO2 by solving the Boltzmann equation in the condition of a steady-state Townsend (SST) experiment. The overall density-reduced electric field strength is from 100 Td to 1000 Td (1 Td = 10-17 V·cm2), while the CF3I content k in the gas mixture can be varied over the range from 0% to 100%. From the variation of (?-?)/N with the CF3I mixture ratio k, the limiting field strength (E/N)lim for each CF3I concentration is derived. It is found that for the mixtures with 70% CF3I, the values of (E/N)lim are essentially the same as that for pure SF6. Additionally, the global warming potential (GWP) and the liquefaction temperature of the gas mixtures are also taken into account to evaluate the possibility of application in the gas insulation of power equipment.

  19. Velocity map ion imaging applied to studies of molecularfragementation with synchrotron radiation

    SciTech Connect

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

    2006-12-01

    A novel apparatus has been employed to investigate molecularfragmentation following inner-shell photoionization by synchrotronradiation.A modified design of the velocity map imaging spectrometer,first introduced by Eppink and Parker [A.T.J.B. Eppink, D.H. Parker, Rev.Sci. Instrum. 68 (1997) 3477], provides high detection efficiency andgood focusing properties for an extended interaction region, while theuse of atime and position resolving anode allows electron ion and ion ioncoincidence measurements. We discuss overall capabilities of thespectrometerand present first results for the C(1s) photoionization ofCO2. Special emphasis is placed on the analysis of time and vectorcorrelations betweenions detected in coincidence.

  20. 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.

  1. Energy-conserving finite-{beta} electromagnetic drift-fluid equations

    SciTech Connect

    Brizard, A.J. [Department of Chemistry and Physics, Saint Michael's College, Colchester, Vermont 05439 (United States)

    2005-09-15

    Nonlinear energy-conserving drift-fluid equations that are suitable to describe self-consistent finite-{beta} low-frequency electromagnetic (drift-Alfven) turbulent fluctuations in a nonuniform, anisotropic, magnetized plasma are derived from a variational principle. The variational principle is based on a drift-fluid Lagrangian that contains linear and nonlinear ExB velocities derived directly from the corresponding single-particle finite-{beta} gyrocenter Hamiltonian (in the zero-Larmor-radius limit). Covariant electromagnetic effects introduce a magnetic generalization to the standard ion polarization density as well as introduce a new ion magnetization current, which appear in finite-{beta} gyrokinetic theory [T. S. Hahm, W. W. Lee, and A. J. Brizard, Phys. Fluids 31, 1940 (1988)] but are both missing from existing gyrofluid and drift-fluid Poisson-Ampere equations. An exact energy conservation law is also derived directly from the drift-fluid Lagrangian by application of the Noether method.

  2. Phase-Resolved Measurements of Ion Velocity in a Radio-Frequency Sheath Brett Jacobs,1,* Walter Gekelman,1

    E-print Network

    California at Los Angles, University of

    Phase-Resolved Measurements of Ion Velocity in a Radio-Frequency Sheath Brett Jacobs,1,* Walter plasma rotation [5] and low-frequency waves [6]. Since then, many basic plasma physics experiments have upon the ratio of the ion transit time through the sheath to the rf period (ion=rf) [11]. In the high-frequency

  3. Low Energy Electron and Nuclear Recoil Thresholds in the DRIFT-II Negative Ion TPC for Dark Matter Searches

    E-print Network

    S. Burgos; E. Daw; J. Forbes; C. Ghag; M. Gold; C. Hagemann; V. A. Kudryavtsev; T. B. Lawson; D. Loomba; P. Majewski; D. Muna; A. St. J. Murphy; S. M. Paling; A. Petkov; S. J. S. Plank; M. Robinson; N. Sanghi; D. P. Snowden-Ifft; N. J. C. Spooner; J. Turk; E. Tziaferi

    2009-03-30

    Understanding the ability to measure and discriminate particle events at the lowest possible energy is an essential requirement in developing new experiments to search for weakly interacting massive particle (WIMP) dark matter. In this paper we detail an assessment of the potential sensitivity below 10 keV in the 1 m^3 DRIFT-II directionally sensitive, low pressure, negative ion time projection chamber (NITPC), based on event-by-event track reconstruction and calorimetry in the multiwire proportional chamber (MWPC) readout. By application of a digital smoothing polynomial it is shown that the detector is sensitive to sulfur and carbon recoils down to 2.9 and 1.9 keV respectively, and 1.2 keV for electron induced events. The energy sensitivity is demonstrated through the 5.9 keV gamma spectrum of 55Fe, where the energy resolution is sufficient to identify the escape peak. The effect a lower energy sensitivity on the WIMP exclusion limit is demonstrated. In addition to recoil direction reconstruction for WIMP searches this sensitivity suggests new prospects for applications also in KK axion searches.

  4. 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.

  5. Velocity Map Ion Imaging Applied to Studies of Molecular Fragmentation With Synchrotron Radiation

    SciTech Connect

    Pesic, Z.D.; Rolles, D.; Perri, M.; Bilodeau, R.C.; /Western Michigan U.; Ackerman, G.D.; Rude, B.S.; Kilcoyne, A.L.D.; /LBNL, ALS; Bozek, J.D.; Berrah, N.; /SLAC

    2007-06-11

    We have built a velocity map imaging (VMI) spectrometer optimized for angle-resolved photoionization experiments with synchrotron radiation (SR) in the VUV and soft x-ray range. The spectrometer is equipped with four electrostatic lenses, that focus the charged photoionization products on 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 provides better focusing of an extended interaction region, which is crucial for most SR applications. Furthermore, the apparatus is equipped with a second microchannelplate 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 CO{sub 2} molecules are presented, including measurements of velocity and angular distributions as well as momentum correlations between coincident fragments.

  6. Argon ion velocity distributions in a helicon discharge measured by laser induced fluorescence

    Microsoft Academic Search

    D. Luggenhölscher; Y. Celik; Y. K. Pu; U. Czarnetzki

    2010-01-01

    A Helicon discharge in argon at low gas pressure of 0.1 Pa is generated with a flat coil antenna operated with 13.56 MHz. The power coupled into the discharge is around 1 kW which leads to an electron density of 1012 cm-3. The velocity and temperature of the argon ions is measured by laser induced fluorescence (LIF) spatially resolved in

  7. Giotto-IMS observations of ion flow velocities and temperatures outside the contact surface of Comet Halley. [Ion Mass Spectrometer (IMS)

    NASA Technical Reports Server (NTRS)

    Goldstein, B. E.; Neugebauer, M.; Balsiger, H.; Drake, J.; Fuselier, S. A.; Goldstein, R.; Ip, WING-H.; Rettenmund, U.; Rosenbauer, H.; Schwenn, R.

    1986-01-01

    Fluid parameters for He(++) ions obtained from the Giotto ion mass spectrometer are presented. Proton densities and velocities and thermal speeds of protons, alpha particles, and heavy ions in the hour before closest approach are discussed. A region of enhanced He(++) ion densities, and velocity, and decreased temperature is observed from 20:26 to 21:45. Sharp decreases in the proton density are observed at 23:30 and at 23:41. There is a relative flow velocity between alpha particles and oxygen ions of 30 km/sec during a period from 22:55 to 23:30; the difference in flow velocity is less than the experimental uncertainities. The flow properties of protons observed during this period are also discussed.

  8. Measurement of ion temperature and flow velocity by using LIF and electric probe methods in K2H and DiPS propulsion simulators

    NASA Astrophysics Data System (ADS)

    Choi, Geun-Sig; Chung, Kyu-Sun; Woo, Hyun-Jong; Seo, Young Jun; Lee, Myoung-Jae; Lho, Taihyeop; Jung, Yong Ho; Lee, Bong Ju

    2006-10-01

    Ion temperature, plasma flow velocity and plasma density are measured in DiPS (Diversified Plasma Simulator) and K2H (KBSI-KAIST-Hanyang University) propulsion simulators by a laser induced fluorescence (LIF) method and a fast scanning electric probe system, which consists of an rf-compensated single probe and a Mach probe. In both devices helicon plasmas were stably generated with m=+1 right-helical antenna at 13.56 MHz with powers of 1 - 3kW (DiPS) and 0.5 - 1kW (K2H), and open ended magnetic configurations are utilized. The measured plasma parameters are as follows: plasma densities of 10^11 -- 10^13 cm-3 (K2H) and 10^12 -- 10^13 cm-3 (DiPS), electron temperatures of 3 -- 9 eV (K2H) and 2 -- 4 eV (DiPS), ion temperatures of 0.14 -- 0. 17 eV (K2H) and 0.05 -- 0.2 eV (DiPS) and drift velocities of 0.8 -- 1.6 km/s (k2H) and 0.2 -- 0.5 km/s (DiPS).

  9. 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.

  10. Doppler spectroscopic measurements of sheath ion velocities in radio-frequency plasmas

    SciTech Connect

    Woodcock, B.K.; Busby, J.R.; Freegarde, T.G.; Hancock, G. [Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ (United Kingdom)] [Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ (United Kingdom)

    1997-05-01

    We have measured the distributions of N{sub 2}{sup +} ion velocity components parallel and perpendicular to the electrode in the sheath of a radio-frequency nitrogen reactive ion etching discharge, using pulsed laser-induced fluorescence. Parallel to the electrode, the ions have throughout a thermal distribution that is found to be consistent with the rotational temperature of 355 K. In the perpendicular direction, we see clearly the acceleration of the ions towards the electrode, and our results agree well with theoretical predictions although an unexpected peak of unaccelerated ions persists. We have also determined the absolute ion concentrations in the sheath, which we have calibrated by analyzing the decay in laser-induced fluorescence in the plasma bulk after discharge extinction. At 20 mTorr, the bulk concentration of 1.0{times}10{sup 10} cm{sup {minus}3} falls to around 2{times}10{sup 8} cm{sup {minus}3} at 2 mm from the electrode. {copyright} {ital 1997 American Institute of Physics.}

  11. Asymmetry of velocity distributions in peripheral reactions with heavy ions at Fermi energies

    NASA Astrophysics Data System (ADS)

    Mikhailova, T. I.; Erdemchimeg, B.; Kaminski, G.; Artyukh, A. G.; Colonna, M.; Toro, M.; Mikhailov, I. N.; Sereda, Yu. M.; Wolter, H. H.

    2009-07-01

    Asymmetry of the velocity distributions of projectile like fragments produced in heavy-ion collisions is discussed. The calculations made in transport model approach (the solution of Vlasov kinetic equation with the collisions term) are compared with experimental data for the reactions $^{22}Ne$ ($40 A\\cdot$MeV) + $^{9}$Be and $^{18}$O ($35 A\\cdot$MeV) + $^9$Be ($^{181}$Ta) at forward angles. It is found that the velocity distributions appear to be composed of two contributions: a direct component centered at beam velocity and a dissipative component at lower energies, leading to an asymmetry of the velocity distributions. The direct component is interpreted empirically in the Goldhaber model, and the widths and centroids of the distributions are extracted. The remaining dissipative (also called deep-inelastic) contributions are then well described by the transport calculations. It is shown that the ratio of yields of direct and dissipative contributions, which determines the asymmetry of velocity distribution, depends on the shape of the deflection function.

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

    E-print Network

    to misalignment · Measurements of fuel ion ratio and bulk ion drift velocity by CTS · Future work #12;ITPA (dispersion effects). · Robustness of the overlap against variations of density such as sawteeth · Robustness

  13. Drifting Continents

    NSDL National Science Digital Library

    2014-09-18

    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.

  14. Atomic collision studies at moderate projectile velocities using highly charged, decelerated heavy ions from the GSI-UNILAC

    Microsoft Academic Search

    P. M. Mokler; D. H. H. Hoffmann; W. A. Schönfeldt; D. Maor; W. E. Meyerhof; Z. Stachura

    1984-01-01

    Beams of highly ionized, very heavy atoms at moderate velocities have been produced at the UNILAC using the acceleration-stripping-deceleration method. The available ion species range from Kr33+ to U66+ in the energy region between 2 and 5 MeV\\/u. A survey on first experiments at GSI using these moderate velocity, few electron, heavy ion beams is given. The effectiveness of the

  15. Calculation of the Ion Distribution Function over Transverse Velocities under ICR Heating Conditions and Separation Parameters of a Collector of Heated Ions

    SciTech Connect

    Karchevskii, A.I.; Potanin, E.P. [Institute of Molecular Physics, Russian Research Centre Kurchatov Institute, pl. Kurchatova 1, Moscow, 123182 (Russian Federation)

    2004-12-15

    The ion distribution function over transverse velocities and the ion heating efficiency (which is defined as the fraction {eta} of ions heated above a certain energy W{sub min}) are calculated in the context of a plasma method for isotope separation on the basis of ion cyclotron resonance heating. The ion distribution function over longitudinal velocities is assumed to be linear in the range of low velocities. It is shown that, when the ions are heated to high energies, the averaged ion distribution function over transverse velocities becomes highly nonequilibrium and has two peaks. Results are presented from calculations of the ion heating efficiency {eta} for W{sub min} = 40 eV and for different values of the parameter p that characterizes the ratio of the wavelength {lambda} of the antenna electric field to the length L of the heating region. The relative roles of the time-of-flight and the Doppler broadening are analyzed, and the separation parameters of a collector of heated ions are estimated.

  16. Design and test of a superconducting structure for high-velocity ions

    SciTech Connect

    Delayen, J.R.; Kennedy, W.L.; Roche, C.T.

    1992-10-01

    Following the successful development of a niobium coaxial half-wave structure we have designed, built and tested a new half-wave geometry: the spoke resonator. This geometry is better suited for high frequency resonators and for the acceleration of high velocity ions. The prototype cavity is a 2-gap structure resonating at 855 MHz, and optimized for particle velocity of 0.30 c. It is easier to manufacture than the coaxial half-wave resonator and the geometry can be straightforwardly extended to multigap designs. Rf-tests have been performed on this cavity both prior to and after high temperature annealing. An accelerating gradient of 7.2 MV/m (cw) and 7.8 MV/m (pulsed) was observed at 4.2 K. After annealing, a low power Q{sub 0} of 1.2 {times}10{sup 8} was observed with small Q degradation due to field emission at high accelerating fields.

  17. Design and test of a superconducting structure for high-velocity ions

    SciTech Connect

    Delayen, J.R.; Kennedy, W.L.; Roche, C.T.

    1992-01-01

    Following the successful development of a niobium coaxial half-wave structure we have designed, built and tested a new half-wave geometry: the spoke resonator. This geometry is better suited for high frequency resonators and for the acceleration of high velocity ions. The prototype cavity is a 2-gap structure resonating at 855 MHz, and optimized for particle velocity of 0.30 c. It is easier to manufacture than the coaxial half-wave resonator and the geometry can be straightforwardly extended to multigap designs. Rf-tests have been performed on this cavity both prior to and after high temperature annealing. An accelerating gradient of 7.2 MV/m (cw) and 7.8 MV/m (pulsed) was observed at 4.2 K. After annealing, a low power Q{sub 0} of 1.2 {times}10{sup 8} was observed with small Q degradation due to field emission at high accelerating fields.

  18. Atomic physics effects on tokamak edge drift-tearing modes

    SciTech Connect

    Hahm, T.S.

    1993-03-01

    The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold [Delta][sup Th], produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

  19. Atomic physics effects on tokamak edge drift-tearing modes

    SciTech Connect

    Hahm, T.S.

    1993-03-01

    The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold {Delta}{sup Th}, produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

  20. Absolute Wavelength Calibration of the IDSII Spectrometer for Impurity Ion Velocity Measurements in the MST

    NASA Astrophysics Data System (ADS)

    Baltzer, M.; Craig, D.; den Hartog, D. J.; Nornberg, M. D.; MST Team

    2014-10-01

    The MST operates two Ion Doppler Spectrometers (IDS) for high time-resolution passive and active measurements of impurity ion emission. Absolutely calibrated measurements of flow are difficult because the spectrometers record data within 0.3 nm of the line of interest, and commercial calibration lamps do not produce lines in this narrow range . Four calibration methods were investigated. First, emission along the chord bisecting the poloidal plane was measured as it should have no time-averaged Doppler shift. Second, a calibrated CCD spectrometer and the IDSII were used to observe the same plasma from opposing sides so as to measure opposite Doppler shifts. The unshifted line is located halfway between the two opposing measurements. Third, the two fibers of the IDSI were positioned to take absolute flow measurements using opposing views. Substituting the IDSII for one of the IDSI fibers, absolute measurements of flow from the IDSI were used to calibrate the IDSII. Finally, an optical system was designed to filter an ultraviolet LED, providing a known wavelength source within the spectral range covered by the IDSII. The optical train is composed of an air-gapped etalon and fused silica lenses. The quality of calibration for each of these methods is analyzed and their results compared. Preliminary impurity ion velocity measurements are shown. This work has been supported by the US DOE and the NSF.

  1. Drift-tearing magnetic islands in tokamak plasmas

    SciTech Connect

    Fitzpatrick, R.; Waelbroeck, F. L. [Institute for Fusion Studies, Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)

    2008-01-15

    A systematic fluid theory of nonlinear magnetic island dynamics in conventional low-{beta}, large aspect-ratio, circular cross-section tokamak plasmas is developed using an extended magnetohydrodynamics model that incorporates diamagnetic flows, ion gyroviscosity, fast parallel electron heat transport, the ion sound wave, the drift wave, and average magnetic field-line curvature. The model excludes the compressible Alfven wave, geodesic field-line curvature, neoclassical effects, and ion Landau damping. A collisional closure is used for plasma dynamics parallel to the magnetic field. Two distinct branches of island solutions are found, namely the 'sonic' and 'hypersonic' branches. Both branches are investigated analytically, using suitable ordering schemes, and in each case the problem is reduced to a relatively simple set of nonlinear differential equations that can be solved numerically via iteration. The solution determines the island phase velocity, relative to the plasma, and the effect of local currents on the island stability. Sonic islands are relatively wide, flatten both the temperature and density profiles, and tend to propagate close to the local ion fluid velocity. Hypersonic islands, on the other hand, are relatively narrow, only flatten the temperature profile, radiate drift-acoustic waves, and tend to propagate close to the local electron fluid velocity. The hypersonic solution branch ceases to exist above a critical island width. Under normal circumstances, both types of island are stabilized by local ion polarization currents.

  2. 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)].

  3. A new crossed molecular beam apparatus using time-sliced ion velocity imaging technique

    SciTech Connect

    Wu Guorong; Zhang Weiqing; Pan Huilin; Shuai Quan; Jiang Bo; Dai Dongxu; Yang Xueming [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 (China)

    2008-09-15

    A new crossed molecular beam apparatus has been constructed for investigating polyatomic chemical reactions using the time-sliced ion velocity map imaging technique. A unique design is adopted for one of the two beam sources and allows us to set up the molecular beam source either horizontally or vertically. This can be conveniently used to produce versatile atomic or radical beams from photodissociation and as well as electric discharge. Intensive H-atom beam source with high speed ratio was produced by photodissociation of the HI molecule and was reacted with the CD{sub 4} molecule. Vibrational-state resolved HD product distribution was measured by detecting the CD{sub 3} product. Preliminary results were also reported on the F+SiH{sub 4} reaction using the discharged F atom beam. These results demonstrate that this new instrument is a powerful tool for investigating chemical dynamics of polyatomic reactions.

  4. Transport of argon ions in an inductively coupled high-density plasma reactor

    Microsoft Academic Search

    N. Sadeghi; Grift van der M; D. Vender; G. M. W. Kroesen; F. J. de Hoog

    1997-01-01

    The first direct observation of the velocity distribution of the metastable Ar{sup +}{sup *}(²Gââ) ions in the presheath of an inductively coupled plasma has been achieved by using the Doppler shifted laser induced fluorescence technique. Drift of the ions along the electric field in the presheath is observed and distribution functions of the velocity in both parallel and perpendicular directions,

  5. 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

  6. 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.

  7. Velocity fluctuations of a heavy particle interacting with a hot and cold gas: Applications to molecular ion traps

    NASA Astrophysics Data System (ADS)

    Vaca, Christian; Bruinsma, Robijn; Levine, Alex J.

    2014-03-01

    Understanding the stochastic motion of a heavy particle in a gas of lighter ones is a classic problem in statistical mechanics. Alkemade, MacDonald, and Van Kampen (AMvK) analyzed this problem in one dimension, computing the velocity distribution function of the heavy particle in a perturbation expansion using the ratio of mass of the light to the heavy particle as a small parameter. Novel tests of this theory are now being provided by modern molecular ion traps [arXiv:1310.5190]. In such experiments, the heavy molecular ion interacts with a cold gas used for sympathetic cooling and low density hot gasses that leak into the system. Thus, the heavy ion is maintained in a complex nonequilibrium state due to its interactions with the hot and cold gasses. In this talk, we present an extension of the AMvK model appropriate to these experiments. Using new analytic and computational techniques, we explore the time-dependent velocity distribution function of the molecular ion interacting with the gasses including higher order perturbative corrections necessary to discuss the case in which the ion's mass is not significantly larger than that of the other two species. Using this analysis we address the experimental observation of non-Gaussian velocity distributions of the heavy ions.

  8. 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.

  9. 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.

  10. 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).

  11. Shields to Reduce Spray Drift

    Microsoft Academic Search

    HE Ozkan; A Miralles; C Sinfort; H Zhu

    1997-01-01

    The effects of several spray-boom shield designs and ‘‘low-drift ’’ nozzles on spray drift are presented. Results are based on experiments conducted in a wind tunnel. Performances of all experimental shields were evaluated under two spray pressures (0·15 and 0·3MPa), and two air velocities (2·75 and 4·80m\\/s) in the wind tunnel. The distance to the centre of mass of the

  12. A method for determining the drift velocity of plasma depletions in the equatorial ionosphere using far-ultraviolet spacecraft observations: initial results

    Microsoft Academic Search

    S. L. England; T. J. Immel; S. H. Park; H. U. Frey; S. B. Mende

    2007-01-01

    The Far-Ultraviolet Imager (IMAGE-FUV) on-board the NASA IMAGE satellite has been used to observe plasma depletions in the nightside equatorial ionosphere. Observations from periods around spacecraft apogee, during which equatorial regions are visible for several hours, have allowed the velocity of these plasma depletions to be determined. A new method for determining the velocity of these depletions using an image

  13. Doppler Shift and Ion Mobility Measurements of ArH+ in a He dc Glow Discharge by Infrared Laser Spectroscopy

    Microsoft Academic Search

    Nathan N. Haese; Fu-Shih Pan; Takeshi Oka

    1983-01-01

    A new, infrared-laser-spectroscopic method for in situ ion drift-velocity and mobility measurements in a dc glow discharge is reported, a method sensitive to quantum effects in the ion transport process. Excellent agreement with earlier drift-tube studies for the mobility of ArH+ in He is obtained. While no ion rotational energy dependence was observed in preliminary measurements, a vibrational dependence was

  14. Beam dynamics of the Neutralized Drift Compression Experiment-II, a novel pulse-compressing ion accelerator

    Microsoft Academic Search

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

    2010-01-01

    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 ~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

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

    Microsoft Academic Search

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

    2009-01-01

    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 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

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

    Microsoft Academic Search

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

    2009-01-01

    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 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

  17. Influence of H{sup -} velocity on H{sup -} extraction probability from a negative ion source

    SciTech Connect

    Matsumoto, Y. [Tokushima Bunri University, Nishihama, Yamashiro-cho, Tokushima 770-8514 (Japan); Nishiura, M. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Shinto, K. [Japan Atomic Energy Agency, Rokkasho, Aomori 039-3212 (Japan); Yamaoka, H. [Harima Institute, RIKEN, Hyogo 679-5148 (Japan); Sasao, M. [Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Wada, M. [Graduate School of Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321 (Japan)

    2010-02-15

    We investigate influence of H{sup -} initial transport direction and kinetic energy on H{sup -} extraction probability with three-dimensional Monte Carlo calculation. As a result, lower energy H{sup -} ions are strongly trapped by the electrical potential structure, so that initial condition of H{sup -} transport direction is cancelled by alignment of the electric field; thus, it has lower influence for H{sup -} extraction probability. Besides, the potential hill induced by the beam extraction voltage more effectively enhances H{sup -} extraction probability for the lower energy H{sup -} ions. The correlation between the magnitude of the local plasma potential near the extraction region and the mean velocity of H{sup -} ions in the region should determine the H{sup -} extraction probability from the ion source.

  18. 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.

  19. 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.

  20. 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…

  1. 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

  2. Volume 122. number 1.2 CHEMICAL PHYSICS LEl-l-ERS 29 November 1985 ELECTRONIC SPIk-I-ROSCOPY OF MOLECULAR IONS BY VE&OCITY MODULATION

    E-print Network

    Cohen, Ronald C.

    glow discharge. In these ac discharges the component of the ion drift velocity along the axis-I-ROSCOPY OF MOLECULAR IONS BY VE&OCITY MODULATION WITH cw DYE LASERS: A NON-INTRUSIVE, IN SITU STATE-SELECTIVE PROBE environments by velocity modulation laser spectroscopy. Tbrsc experiments rcvral rotational state

  3. 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.

  4. Pick-up ion transport under conservation of particle invariants: how important are velocity diffusion and cooling processes?

    NASA Astrophysics Data System (ADS)

    Fahr, H. J.; Fichtner, H.

    2011-09-01

    Context. The phase space transport of pick-up ions (PUIs) in the heliosphere has been studied for the cases that these particles are experiencing a second-order Fermi process, i.e. velocity diffusion, a convection with the solar wind, and adiabatic or "magnetic" cooling, i.e. cooling connected with the conservation of the magnetic moment. Aims: The study aims at a quantification of the process of "magnetic cooling" that has recently been introduced as a modification of adiabatic cooling in the presence of frozen-in magnetic fields. Methods: The isotropic PUI velocity distributions are obtained as numerical solutions of a Fokker-Planck phase space transport equation. Results: It is demonstrated that this newly discussed process is, like adiabatic energy changes, not limited to cooling but can also, depending on the shape of the distribution function, result in heating. For pure cooling with negligible velocity diffusion a v-5 velocity power law is found for magnetic cooling, thus confirming earlier analytical results. For non-negligible second-order Fermi acceleration, the tails of the distribution functions exhibit different shapes, which in special cases are also close to the prominent v-5 behaviour, which is often found in observations. Conclusions: The existence of an exact v-5 power law of PUI distribution functions can be confirmed for insignificant velocity diffusion and its approximate validity for specific choices of the velocity dependence of the diffusion coefficient.

  5. Velocity dependence of free ion production in K(np)-C2Cl4, CS2, and O2 collisions: Internal-to-translational energy transfer

    NASA Astrophysics Data System (ADS)

    Popple, R. A.; Dionne, M. A.; Smith, K. A.; Dunning, F. B.

    1994-10-01

    The rates for free ion production through electron transfer in collisions between K(np) Rydberg atoms and C2Cl4, CS2, and O2 are measured as a function of Rydberg atom velocity for intermediate values of n, 13?n?21. The data show that postattachment interactions between the product positive and negative ions are important and can lead to conversion of internal energy from the negative ion, which is formed in an excited state, into translational energy of the product ion pair. This energy conversion occurs without ion-ion neutralization and can stabilize the negative ion against dissociation or autodetachment.

  6. 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.

  7. Number-conserving linear-response study of low-velocity ion stopping in a collisional magnetized classical plasma

    SciTech Connect

    Nersisyan, Hrachya B. [Institute of Radiophysics and Electronics, 0203 Ashtarak (Armenia); Centre of Strong Fields Physics, Yerevan State University, Alex Manoogian Street 1, 0025 Yerevan (Armenia); Deutsch, Claude [LPGP - UMR-CNRS 8578, Universite Paris XI, F-91405 Orsay (France); Das, Amal K. [Department of Physics, Dalhousie University, Halifax, Nova Scotia B3H 3J5 (Canada)

    2011-03-15

    The results of a theoretical investigation of the low-velocity stopping power of ions in a magnetized collisional and classical plasma are reported. The stopping power for an ion is calculated through the linear-response (LR) theory. The collisions, which lead to a damping of the excitations in the plasma, are taken into account through a number-conserving relaxation time approximation in the LR function. In order to highlight the effects of collisions and magnetic field, we present a comparison of our analytical and numerical results obtained for nonzero damping or magnetic field with those for vanishing damping or magnetic field. It is shown that the collisions remove the anomalous friction obtained previously [Nersisyan et al., Phys. Rev. E 61, 7022 (2000)] for the collisionless magnetized plasmas at low ion velocities. One of the major objectives of this paper is to compare and to contrast our theoretical results with those obtained through a diffusion coefficient formulation based on the Dufty-Berkovsky relation evaluated for a magnetized one-component plasma modeled with target ions and electrons.

  8. 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.

  9. Diogene pictorial drift chamber

    NASA Astrophysics Data System (ADS)

    Gosset, J.

    1984-02-01

    A pictorial drift chamber, called DIOGENE, has been installed at Saturne in order to study central collisions of high energy heavy ions. It has been adapted from the JADE internal detector, with two major differences to be taken into account. First, the center-of-mass of these collisions is not identical to the laboratory reference frame. Second, the energy loss and the momentum ranges of the particles to be detected are different from the ones in JADE. It was also tried to keep the cost as small as possible, hence the choice of minimum size and minimum number of sensitive wires. Moreover the wire planes are shifted from the beam axis: this trick helps very much to quickly reject the bad tracks caused by the ambiguity of measuring drift distances (positive or negative) through times (always positive).

  10. Diogene pictorial drift chamber

    SciTech Connect

    Gosset, J.

    1984-01-01

    A pictorial drift chamber, called DIOGENE, has been installed at Saturne in order to study central collisions of high energy heavy ions. It has been adapted from the JADE internal detector, with two major differences to be taken into account. First, the center-of-mass of these collisions is not identical to the laboratory reference frame. Second, the energy loss and the momentum ranges of the particles to be detected are different from the ones in JADE. It was also tried to keep the cost as small as possible, hence the choice of minimum size and minimum number of sensitive wires. Moreover the wire planes are shifted from the beam axis: this trick helps very much to quickly reject the bad tracks caused by the ambiguity of measuring drift distances (positive or negative) through times (always positive).

  11. Diffusion behavior of chloride ions in concrete

    Microsoft Academic Search

    Tiewei Zhang; Odd E. Gjørv

    1996-01-01

    In the present paper, an analysis of the diffusion behavior of chloride ions in concrete is presented. In concentrated electrolytic aqueous solutions such as seawater or that typically used in laboratory experiments, the effect of ionic interaction may significantly reduce the chemical potential and thus the driving force of the diffusing species. Because of different drift velocities of the cations

  12. 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.

  13. 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.

  14. Hypersonic drift-tearing magnetic islands in tokamak plasmas

    SciTech Connect

    Fitzpatrick, R.; Waelbroeck, F. L. [Institute for Fusion Studies, Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)

    2007-12-15

    A two-fluid theory of long wavelength, hypersonic, drift-tearing magnetic islands in low-collisionality, low-{beta} plasmas possessing relatively weak magnetic shear is developed. The model assumes both slab geometry and cold ions, and neglects electron temperature and equilibrium current gradient effects. The problem is solved in three asymptotically matched regions. The 'inner region' contains the island. However, the island emits electrostatic drift-acoustic waves that propagate into the surrounding 'intermediate region', where they are absorbed by the plasma. Since the waves carry momentum, the inner region exerts a net force on the intermediate region, and vice versa, giving rise to strong velocity shear in the region immediately surrounding the island. The intermediate region is matched to the surrounding 'outer region', in which ideal magnetohydrodynamic holds. Isolated hypersonic islands propagate with a velocity that lies between those of the unperturbed local ion and electron fluids, but is much closer to the latter. The ion polarization current is stabilizing, and increases with increasing island width. Finally, the hypersonic branch of isolated island solutions ceases to exist above a certain critical island width. Hypersonic islands whose widths exceed the critical width are hypothesized to bifurcate to the so-called 'sonic' solution branch.

  15. Dust magneto-gravitational drift wave in g ×B configuration

    NASA Astrophysics Data System (ADS)

    Salahshoor, M.; Niknam, A. R.

    2014-11-01

    The dispersion relation of electrostatic waves in a magnetized complex plasma under gravity is presented. It is assumed that the waves propagate perpendicular to the external fields. The effects of weak electric field, neutral drag force, and ion drag force are also taken into account. The dispersion relation is numerically examined in an appropriate parameter space in which the gravity plays the dominant role in the dynamics of magnetized microparticles. The numerical results show that an unstable low frequency drift wave can be developed in the long wavelength limit. This unstable mode is transformed into an aperiodic stationary structure at a cut-off wavenumber. Furthermore, the influence of the external fields on the dispersion properties is analyzed. It is shown that the instability is essentially due to the E ×B drift motion of plasma particles. However, in the absence of weak electric field, the g ×B drift motion of microparticles can cause the instability in a wide range of wavenumbers. It is also found that by increasing the magnetic field strength, the wave frequency is first increased and then decreased. This behaviour is explained by the existence of an extremum point in the dust magneto-gravitational drift velocity.

  16. 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.

  17. Latitudinal variation in the occurrence of GPS L-band scintillations associated with the day-to-day changes in TEC, h'F and the E×B drift velocity and their impact on GPS satellite signals

    NASA Astrophysics Data System (ADS)

    Venkatesh, K.; Rao, P. V. S. Rama; Seemala, Gopi K.; Prasad, D. S. V. V. D.

    2015-04-01

    The present study describes the day-to-day variations in the occurrence of GPS L-band scintillations from equator to the anomaly crest location associated with the changes in TEC, hF and E ×B drift velocities. The GPS-TEC and S4 index data from an equatorial station, Trivandrum (8.47?N, 76.91?E), a low latitude station, Waltair (17.7?N, 83.3?E) and an anomaly crest location Kolkata (22.6?N, 88.4?E) during the low solar activity years of 2004 and 2005 are used. It is observed that the day-time ambient TEC is higher during scintillation days compared to that during the days on which there are no scintillations at the three different locations mentioned above. Further, the diurnal variation of TEC shows a rapid decay during 1700-2000 hr LT over the three different locations during scintillation days which is observed to be comparatively much less during no scintillation days. The average height of the F-layer in the post-sunset hours over Trivandrum is found to be higher, around 350 km during scintillation days while it is around 260 km during the days on which there is no scintillation activity. The average pre-reversal E ×B drift velocity observed around 19:00 hr LT is higher (20 m/s) during scintillation days, whereas during no scintillation days, it is found to be much less (7 m/s). Further, it is observed that the GPS receivers lose their locks whenever the S4 index exceeds 0.5 (>10 dB power level) and these loss of lock events are observed to be more around the anomaly crest location (Kolkata). It may be inferred from the present observations that the level of ambient ionization around noon-time, and a fast decay (collapse) of the ionization during afternoon hours followed by rapid increase in the height of the F-layer contributes significantly to the occurrence of scintillations. The present study further indicates that the S4 index at L-band frequencies increases with an increase in latitude maximizing around the crest of the equatorial ionization anomaly during the post-sunset hours resulting in more loss of lock events in the GPS receiver signals around the EIA crest region.

  18. Latitudinal variation in the occurrence of GPS L-band scintillations associated with the day-to-day changes in TEC, h'F and the E×B drift velocity and their impact on GPS satellite signals

    NASA Astrophysics Data System (ADS)

    Venkatesh, K.; Rao, P. V. S. Rama; Seemala, Gopi K.; Prasad, D. S. V. V. D.

    2015-04-01

    The present study describes the day-to-day variations in the occurrence of GPS L-band scintillations from equator to the anomaly crest location associated with the changes in TEC, h ^' }F and E ×B drift velocities. The GPS-TEC and S4 index data from an equatorial station, Trivandrum (8.47?N, 76.91?E), a low latitude station, Waltair (17.7?N, 83.3?E) and an anomaly crest location Kolkata (22.6?N, 88.4?E) during the low solar activity years of 2004 and 2005 are used. It is observed that the day-time ambient TEC is higher during scintillation days compared to that during the days on which there are no scintillations at the three different locations mentioned above. Further, the diurnal variation of TEC shows a rapid decay during 1700-2000 hr LT over the three different locations during scintillation days which is observed to be comparatively much less during no scintillation days. The average height of the F-layer in the post-sunset hours over Trivandrum is found to be higher, around 350 km during scintillation days while it is around 260 km during the days on which there is no scintillation activity. The average pre-reversal E ×B drift velocity observed around 19:00 hr LT is higher (20 m/s) during scintillation days, whereas during no scintillation days, it is found to be much less (7 m/s). Further, it is observed that the GPS receivers lose their locks whenever the S4 index exceeds 0.5 (>10 dB power level) and these loss of lock events are observed to be more around the anomaly crest location (Kolkata). It may be inferred from the present observations that the level of ambient ionization around noon-time, and a fast decay (collapse) of the ionization during afternoon hours followed by rapid increase in the height of the F-layer contributes significantly to the occurrence of scintillations. The present study further indicates that the S4 index at L-band frequencies increases with an increase in latitude maximizing around the crest of the equatorial ionization anomaly during the post-sunset hours resulting in more loss of lock events in the GPS receiver signals around the EIA crest region.

  19. Spherical and Cylindrical Ion Acoustic Shock Structures in Plasmas with q-Nonextensive Electron Velocity Distribution

    NASA Astrophysics Data System (ADS)

    Eslami, Parvin; Pakzad, Hamid Reza; Mottaghizadeh, Marzieh

    2012-12-01

    The propagation of ion acoustic shock waves in cylindrical and spherical geometries has been investigated. The plasma system consists of cold ions, nonextensive electrons and thermal positrons. Spherical and cylindrical Korteweg-de Vries-Burger equations have been derived by reductive perturbation method and their shock behavior is studied by employing finite difference method. It is found that shock waves can be produced in this medium. The important effects of the q-nonextensive electron on the properties of ion acoustic waves are discussed. Furthermore, it is observed that the positron concentration, ratio of electron to positron temperature, geometry parameter and the plasma kinematic viscosity significantly modifies the shock structure.

  20. 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.

  1. Ion acoustic double layers in the presence of positrons beam and q-nonextensive velocity distributed electrons

    NASA Astrophysics Data System (ADS)

    Ali Shan, S.; Mushtaq, A.; Akhtar, N.

    2013-12-01

    Linear and nonlinear studies are presented for an electron-ion plasma system which is being energized with an external beam of positrons. The electrons are assumed to follow the q-nonextensive velocity distribution. The growth rates of instability due to positron beam are analyzed numerically. The compressive and rarefactive double layers are studied in the system and it is found that by varying the entropic index parameter q, positron beam speed v po and concentration of positrons p, the dynamics of nonlinear profile is changing quite effectively. The relevance of the work regarding to astrophysical space plasma is pointed out.

  2. Track reconstruction and performance of DRIFT directional dark matter detectors using alpha particles

    Microsoft Academic Search

    S. Burgos; J. Forbes; C. Ghag; M. Gold; V. A. Kudryavtsev; T. B. Lawson; D. Loomba; P. Majewski; D. Muna; A. St J. Murphy; G. G. Nicklin; S. M. Paling; A. Petkov; S. J. S. Plank; M. Robinson; N. Sanghi; N. J. T. Smith; D. P. Snowden-Ifft; N. J. C. Spooner; T. J. Sumner; J. Turk; E. Tziaferi; T. Tziaferi

    2008-01-01

    First results are presented from an analysis of data from the DRIFT-IIa and DRIFT-IIb directional dark matter detectors at Boulby Mine in which alpha particle tracks were reconstructed and used to characterise detector performance—an important step towards optimising directional technology. The drift velocity in DRIFT-IIa was 59.3±0.2(stat)±7.5(sys)ms-1 based on an analysis of naturally occurring alpha-emitting background. The drift velocity in

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

    NASA Astrophysics Data System (ADS)

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

    1990-12-01

    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.

  4. Calibration with relativistic and low velocity ions of a CR39 nuclear track detector

    Microsoft Academic Search

    P. Baiocchi; S. Cecchini; H. Dekhissi; V. Garutti; G. Giacomelli; G. G. Giani; E. Katsavounidis; G. Iori; L. Patrizii; V. Popa; P. Serra; V. Togo; E. Vilela

    1995-01-01

    We present experimental results on the calibration of the CR9 nuclear track detector, manufactured by the Intercast Europe Co., of Parma (Italy). The calibration was performed with several ions of different kinetic energies: from 50 keV protons to 11.3 A GeV gold ions; ?=v\\/c ranges from about 4·10?3 to about 1. We find that a single curve of the reduced

  5. Calibration with relativistic and low-velocity ions of a CR39 nuclear track detector

    Microsoft Academic Search

    S. Cecchini; H. Dekhissi; V. Garutti; G. Giacomelli; E. Katsavounidis; G. Mandrioli; A. R. Margiotta-Neri; L. Patrizir; V. Popa; P. Serra; M. Spurio; V. Togo; U. Valdre; E. Vilela

    1996-01-01

    Summary  We present experimental results on the calibration of the CR39 nuclear track detector, manufactured by the Intercast Europe\\u000a Co., of Parma (Italy). The calibration was performed with several ions of different kinetic energies: from 50 keV protons\\u000a to 11.3A GeV gold ions; ?=v\\/c ranges from about 4·10?3 to about 1. We find that a single curve of the reduced etch

  6. A DRIFT ORDERED SHORT MEAN-FREE DESCRIPTION FOR PARTIALLY IONIZED MAGNETIZED PLASMA

    SciTech Connect

    SIMAKOV, ANDERI N. [Los Alamos National Laboratory

    2007-02-08

    Effects of neutral particles, most prominently the associated heat flux and viscosity, can be very important or even dominant at the edge of a tokamak and so must be self-consistently accounted for in a description of magnetized tokamak edge plasma. To the best of our knowledge, this has only been done so far for short mean-free path plasma under MHD-like Braginskii's orderings i.e. assuming that species velocities are on the order of the ion thermal speed. Since plasma flows in modern tokamaks are usually slow compared with the ion thermal speed (at least in the absence of strong external momentum sources) it is more appropriate to use drift orderings in which the plasma flow velocity is instead comparable with the diamagnetic heat flow divided by pressure. Employing drift orderings and evaluating species distribution functions through second order in the small gyroradius and mean-free path expansion parameters allows accounting for the important effects of heat fluxes on species momentum transport (viscosities), which are missing from the large flow ordered treatments. In this work we consider short mean-free path plasma consisting of electrons and single species of singly-charged ions and neutrals. We neglect neutral-neutral and elastic electron-neutral collisions and approximate the neutral-ion charge-exchange cross-section with a constant. We employ drift orderings to evaluate ion, neutral, and electron heat fluxes, viscosity tensors, and momentum and energy exchange terms and formulate a self-consistent system of electron, ion, and neutral fluid equations, thereby generalizing the drift-ordered treatment of fully ionized plasma.

  7. Diffusion behavior of chloride ions in concrete

    SciTech Connect

    Zhang, T.; Gjoerv, O.E. [Norwegian Univ. of Science and Technology, Trondheim (Norway). Div. of Building Materials] [Norwegian Univ. of Science and Technology, Trondheim (Norway). Div. of Building Materials

    1996-06-01

    In the present paper, an analysis of the diffusion behavior of chloride ions in concrete is presented. In concentrated electrolytic aqueous solutions such as seawater or that typically used in laboratory experiments, the effect of ionic interaction may significantly reduce the chemical potential and thus the driving force of the diffusing species. Because of different drift velocities of the cations and chloride ions in the solution, the lagging motion of the cations will also retard the drift velocity of the chlorides. In addition, both the electrical double layer forming on the solid surface and the chemical binding may significantly interfere with the transport of the chloride ions. As a result, the diffusion behavior of the chloride ions in concrete is a more complex and complicated transport process than what can be described by Fick`s law of diffusion.

  8. Continuous wave cavity ring down spectroscopy measurements of velocity distribution functions of argon ions in a helicon plasma.

    PubMed

    Chakraborty Thakur, Saikat; McCarren, Dustin; Carr, Jerry; Scime, Earl E

    2012-02-01

    We report continuous wave cavity ring down spectroscopy (CW-CRDS) measurements of ion velocity distribution functions (VDFs) in low pressure argon helicon plasma (magnetic field strength of 600 G, T(e) ? 4 eV and n ? 5 × 10(11) cm(-3)). Laser induced fluorescence (LIF) is routinely used to measure VDFs of argon ions, argon neutrals, helium neutrals, and xenon ions in helicon sources. Here, we describe a CW-CRDS diagnostic based on a narrow line width, tunable diode laser as an alternative technique to measure VDFs in similar regimes but where LIF is inapplicable. Being an ultra-sensitive, cavity enhanced absorption spectroscopic technique; CW-CRDS can also provide a direct quantitative measurement of the absolute metastable state density. The proof of principle CW-CRDS measurements presented here are of the Doppler broadened absorption spectrum of Ar II at 668.6138 nm. Extrapolating from these initial measurements, it is expected that this diagnostic is suitable for neutrals and ions in plasmas ranging in density from 1 × 10(9) cm(-3) to 1 × 10(13) cm(-3) and target species temperatures less than 20 eV. PMID:22380092

  9. Stability analysis of self-gravitational electrostatic drift waves for a streaming nonuniform quantum dusty magnetoplasma

    NASA Astrophysics Data System (ADS)

    Bashir, M. F.; Jamil, M.; Murtaza, G.; Salimullah, M.; Shah, H. A.

    2012-04-01

    Using the quantum hydrodynamic model of plasmas, the stability analysis of self-gravitational electrostatic drift waves for a streaming non-uniform quantum dusty magnetoplasma is presented. For two different frequency domains, i.e., ?0d??drift waves, which incorporates the effects of density inhomogeneity ?n0?, streaming velocity v0? due to magnetic field inhomogeneity ?B0, Bohm potential, and the Fermi degenerate pressure. For both frequency domains, the effect of density inhomogeneity gives rise to real oscillations while the ions streaming velocity v0i as well as the effective electron quantum velocity vFe' make these oscillations propagate perpendicular to the ambient magnetic field. This oscillatory behavior of self-gravitational drift waves increases with increase in inhomogeneities and quantum effects while it decreases with increase in the gravitational potential. However, only for the unmagnetized case, the drift waves may become unstable under appropriate conditions giving rise to Jeans instability. The modified threshold condition is also determined for instability by using the intersection method for solving the cubic equation. We note that the inhomogeneity in magnetic field (equilibrium density) through streaming velocity (diamagnetic drift velocity) suppress the Jeans instability depending upon the characteristic scale length of these inhomogeneities. On the other hand, the dust-lower-hybrid wave and the quantum mechanical effects of electrons tend to reduce the growth rate as expected. A number of special cases are also discussed.

  10. Time-Dependent Ion Velocity Distribution: A novel Heterodyne Laser-Induced Fluorescence with Coupled

    E-print Network

    velocity distribution (IVDF) in a Hall thruster. This approach is motivated by studies of low frequency-called breathing oscillations. In this paper, we present the first successful application of this method to an axial mode, by driving coherent breathing oscillations. Staff Research Scientist, Princeton Plasma

  11. 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.

  12. Measurement of Time-Dependent Ion Velocity Distribution Function by Laser Induced Fluorescence in a Cylindrical Hall Thruster with Driven Spoke

    NASA Astrophysics Data System (ADS)

    Shi, Yuan; Diallo, Ahmed; Raitses, Yevgeny; Mazouffre, Stephane

    2013-09-01

    This paper reports, for the first time, effects of spoke on ion velocity distribution function measured by time-resolving laser induced fluorescence. To scan ion speed, the 5d4F5/2-6p4D5/2 transition of Xe + is excited using tunable diode laser. Photons from 6p4D5/2-6s4P3/2 transition are collected by a photomultiplier tube and counted by a multichannel scaler. To subtract background, a mechanical chopper is used to generate laser pulses whose power is monitored by a photodiode. To achieve phase-locked accumulation of fluorescence photons, spoke is driven using successively phase-shifted square waves on anode segments and the driving signal is used to synchronize photon accumulation to spoke in data post processing. To resolve three ion velocity components, two laser beams are established, with one beam measuring axial velocity and the other beam measuring some linear combination of radial and azimuthal velocities, depending on the position of collection volume with respect to thruster plume. Measurements shows ion distribution function oscillates with spoke. Along the thruster axis, ion density is strongly modulated while axial ion velocities are not affected. Off-axis effects of spoke will also be discussed.

  13. Measurement of Time-Dependent Ion Velocity Distribution Function by Laser Induced Fluorescence in a Cylindrical Hall Thruster with Driven Spoke

    NASA Astrophysics Data System (ADS)

    Shi, Yuan; Raitses, Yevgeny; Diallo, Ahmed; Mazouffre, Stephane; Htx Team; Icare-Cnrs Collaboration

    2013-10-01

    This paper reports, for the first time, effects of spoke on ion velocity distribution function measured by time-resolving laser induced fluorescence. To scan ion speed, the 5d 4 F -6p 4 5/2 D 5/2 transition of Xe+ is excited using tunable diode laser. Photons from 6p 4 D -6s 4 5/2 P 3/2 transition are collected by a photomultiplier tube and counted by a multichannel scaler. To subtract background, a mechanical chopper is used to generate laser pulses whose power is monitored by a photodiode. To achieve phase-locked accumulation of fluorescence photons, spoke is driven using successively phase-shifted square waves on anode segments and the driving signal is used to synchronize photon accumulation to spoke in data post processing. To resolve three ion velocity components, two laser beams are established, with one beam measuring axial velocity and the other beam measuring some linear combination of radial and azimuthal velocities, depending on the position of collection volume with respect to thruster plume. Measurements shows ion distribution function oscillates with spoke. Along the thruster axis, ion density is strongly modulated while axial ion velocities are not affected. Off-axis effects of spoke will also be discussed.

  14. 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.

  15. Current driven electromagnetic ion cyclotron instability

    Microsoft Academic Search

    D. W. Forslund; J. M. Kindel; M. A. Stroscio

    1979-01-01

    A detailed investigation of the electron-current-driven electro-magnetic ion cyclotron instability is presented which extends the original work on the subject by Stix (1962). An infinite uniform collisionless Maxwellian plasma embedded in a constant dc magnetic field is assumed. Analytical derivation of the critical drift velocity spans the range of ion-beta from about 0.001 to 0.1. An important result is that

  16. Focusing of negative ions by vortices in rotating 3He-A

    Microsoft Academic Search

    J. T. Simola; K. K. Nummila; A. Hirai; J. S. Korhonen; W. Schoepe; L. Skrbek

    1986-01-01

    Experiments with negative ions in rotating superfluid 3A show strong retardation and deformation of ion pulses drifting parallel to the angular velocity Omega. This is caused by the interaction between the ions and the l texture in the soft cores of A-phase vortices. The interaction is mediated by the anisotropic ion mobility: v=mu?E-Deltamu(E.l)l. The (Omega,T) dependence of the retardation is

  17. JOURNAL.DE PHYSIQUE Colloque C6, suppliment au no 8, Tome 39, aoiit 1978, page C6-174 RINGS AMONG THE ROTONS : MEASUREMENTS OF THE VORTEX NUCLEATION RATE FOR NEGATIVE IONS

    E-print Network

    Boyer, Edmond

    THE ROTONS : MEASUREMENTS OF THE VORTEX NUCLEATION RATE FOR NEGATIVE IONS WHOSE DRIFT VELOCITIES ARE LIMITED vortex ring nucleation rates v for negative ions moving in He I1 under the influence of electric fields 0 of the current i reaching-the collector C performed /I/ is for negative ions moving in He I1 depends on : (i

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

    SciTech Connect

    Chakrabarti, Nikhil; Rasmussen, Jens Juul; Michelsen, Poul [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700 064 (India); Association EURATOM-Riso National Laboratory, Optics and Plasma Research, OPL-128 Riso, P.O. Box 49, DK 4000 Roskilde (Denmark)

    2005-07-15

    The effect of sheared poloidal flow on the toroidal branch of the ion temperature gradient driven mode of magnetized nonuniform plasma is studied. A novel 'nonmodal' calculation is used to analyze the problem. It is shown that the transverse shear flow considerably reduced the growth of the instability. A small but finite amount of viscosity and/or diffusion enhanced the stabilization process.

  19. VELOCITY PHASE SPACE STUDIES OF ION DYNAMICS IN THE VASIMR ENGINE

    Microsoft Academic Search

    Edgar A. Bering; Franklin R. Chang Díaz; Jared P. Squire; Timothy W. Glover; Roger D. Bengtson; Michael Brukardt

    The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is a high power, radio frequency-driven magnetoplasma rocket, capable of Isp\\/thrust modulation at constant power. The physics and engineering of this device have been under study since 1980. The plasma is produced by an integrated helicon discharge. However, the bulk of the plasma energy is added in a separate downstream stage by ion

  20. Ion Velocity Phase Space Studies of the VASIMR Engine Exhaust Plasma

    Microsoft Academic Search

    Bering III; F. R. Chang-Diaz; J. Squire; V. Jacobson; A. Tarditi; R. D. Bengtson; T. W. Glover; M. Brukardt; G. E. McCaskill

    2004-01-01

    The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is a high power engine capable of Isp\\/thrust modulation at constant power. The plasma is produced by helicon discharge. The bulk of the energy is added by ion cyclotron resonance heating (ICRH.) Axial momentum is obtained by adiabatic expansion of the plasma in a magnetic nozzle. Thrust\\/specific impulse ratio control in the VASIMR

  1. Ultra-Violet Line Intensities of High Ions Predicted from Simulations of Turbulent Mixing Layers and High Velocity Clouds

    NASA Astrophysics Data System (ADS)

    Kwak, Kyujin; Shelton, R. L.

    2013-01-01

    We present the ultra-violet line intensities of high ions predicted from our hydrodynamic simulations of turbulent mixing layers and high velocity clouds. We compare these predictions with observations and predictions from other models such as analytic models of turbulent mixing layers and simulations of thermal conduction fronts. Our model predictions compare better with the observations than the other model predictions do. We also discuss the validity of the current method commonly used to estimate the thermal pressure of high-ion-rich gas from the ratio of the observed emission intensity to the observed column density. When applied to our simulations, this method tends to underestimate the thermal pressure by as much as a factor of a few, suggesting that it also underestimates the true thermal pressure of the interstellar medium by a similar factor. We propose a more realistic spatial distribution of high-ion-rich gas in the Milky Way, consisting of dense but compact regions near the disk and sparse but extended regions in the halo.

  2. Laboratory study of velocity shear-driven electromagnetic ion cyclotron waves

    Microsoft Academic Search

    E. M. Tejero

    2011-01-01

    Laboratory observations of electromagnetic ion cyclotron waves generated by a localized transverse dc electric field are reported. Experiments indicate that these waves result from a strong E×B flow inhomogeneity in a mildly collisional plasma with sub-critical magnetic field-aligned current. The wave amplitude scales with the magnitude of the applied radial dc electric field. The electromagnetic signatures become stronger with increasing

  3. 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.

  4. 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.

  5. Relative drifts and temperature anisotropies of protons and ? particles in the expanding solar wind: 2.5D hybrid simulations

    NASA Astrophysics Data System (ADS)

    Maneva, Y. G.; Ofman, L.; Viñas, A.

    2015-06-01

    Context. We perform 2.5D hybrid simulations to investigate the origin and evolution of relative drift speeds between protons and ? particles in the collisionless turbulent low- tilde? solar wind plasma. Aims: We study the generation of differential streaming by wave-particle interactions and absorption of turbulent wave spectra. Next we focus on the role of the relative drifts for the turbulent heating and acceleration of ions in the collisionless fast solar wind streams. Methods: The energy source is given by an initial broad-band spectrum of parallel propagating Alfvén-cyclotron waves, which co-exists with the plasma and is self-consistently coupled to the perpendicular ion bulk velocities. We include the effect of a gradual solar wind expansion, which cools and decelerates the minor ions. We here consider for the first time the combined effect of self-consistently initialized dispersive turbulent Alfvénic spectra with differentially streaming protons and ? particles in the expanding solar wind outflows within a 2.5D hybrid simulation study. Results: For differential streaming of V?p < 0.5VA, the selected initial wave spectrum accelerates the minor ions in the non-expanding wind. At V?p = 0.5VA the relative drift speed remains nearly steady. For ions that stream below this threshold value, the waves act to increase the magnitude of the relative drift speed. Ions that stream faster than the threshold value become subject to a nonlinear streaming instability, and as the system evolves, their bulk velocities decrease. We find that the solar wind expansion strongly affects the relative drift speed and significantly slows down both ion species for all values of the relative drift speeds considered in this study. The initial nonresonant wave spectra interact with the particles, resulting in preferential and anisotropic heating for the minor ions with a prominent increase of their perpendicular temperature, which overcomes the effect of the double-adiabatic cooling that is due to the solar wind expansion. Finally, the initial parallel spectra undergo a micro-turbulent nonlinear cascade during which oblique waves are generated, whose intensity depends on the value of the relative drift speed.

  6. 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.

  7. Transport of argon ions in an inductively coupled high-density plasma reactor

    Microsoft Academic Search

    N. Sadeghi; M. van de Grift; D. Vender; G. M. W. Kroesen; F. J. de Hoog

    1997-01-01

    The first direct observation of the velocity distribution of the metastable Ar+*(2G9\\/2) ions in the presheath of an inductively coupled plasma has been achieved by using the Doppler shifted laser induced fluorescence technique. Drift of the ions along the electric field in the presheath is observed and distribution functions of the velocity in both parallel and perpendicular directions, relative to

  8. A NOVEL X-RAY IMAGING CRYSTAL SPECTROMETER FOR DOPPLER MEASUREMENTS OF ION TEMPERATURE AND PLASMA ROTATION VELOCITY PROFILES

    SciTech Connect

    Bitter, M; Hill, K W; Scott, S; Ince-Cushman, A; Reinke, M; Rice, J E; Beiersdorfer, P; Gu, M F; Lee, S G; Broennimann, C; Eikenberry, E F

    2008-06-06

    A new type of X-ray imaging crystal spectrometer has been implemented on Alcator CMod for Doppler measurements of ion temperature and plasma rotation velocity profiles. The instrument consists of two spherically bent (102)-quartz crystals with radii of curvature of 1444 and 1385 mm and four 'PILATUS II' detector modules. It records spectra of He-like argon from the entire, 72 cm high, elongated plasma cross-section and spectra of H-like argon from a 20 cm high, central region of the plasma, with a spatial resolution of 1.3 cm and a time resolution of less than 20 ms. The new spectrometer concept is also of interest for the diagnosis of burning plasmas on future machines. This paper presents recent experimental results from Aclator C-Mod and discusses challenges in X-ray spectroscopy for the diagnosis of fusion plasmas on future machines.

  9. Laser probing of transport properties and rotational alignment of N(2)(+) drifted in He

    NASA Astrophysics Data System (ADS)

    Anthony, Eric Baxley

    1998-09-01

    Results of transport property and rotational alignment experiments of the atmospherically important molecule N2+ are presented, as measured in a flow-drift apparatus using the technique of single-frequency laser- induced fluorescence (LIF). A trace amount of N2+ is drifted in helium as a buffer gas; the external axial electric field of the drift tube varies the center-of-mass collision energy of the ion-neutral pair. The net effect over hundreds of buffer gas collisions is to establish a steady-state anisotropic ion velocity distribution, the precise character of which is determined by the ion-neutral interaction potential, mass ratio, and field strength. A single-frequency ring dye laser is used to probe Doppler profiles of various rotational lines of the (/nu/sp/prime,?/prime') = (0,0) band in the B/ [2?u+] - X/ [2?g+] system at 390 nm. The single-frequency cw laser technique allows one to measure the velocity component distribution function (VCDF) along the laser propagation direction k; the VCDF is a projection of the complete ion velocity distribution function. Additionally, the rotational alignment of the ions as a function of one component of sub-Doppler laboratory velocity is probed by polarized LIF. Drift velocities and ion mobilities are determined from the shift of the first moments of the coaxial LIF Doppler profiles, while perpendicular and parallel translational temperatures are determined from the widths or second central moments of the profiles in the direction probed. Drift velocities measured up to a field strength of 16 Td appear to be in good agreement with data derived from earlier arrival-time measurements. A small but definite increase in mobility with increasing rotational state from J = 13.5 to J = 22.5 is observed. A significant difference of over 100 K between the parallel and perpendicular temperatures is measured at the highest field strength employed (16 Td). A small degree of positive skewness or third central moment is observed as well in the parallel VCDF's, which is of particular interest since a high-velocity tail has not been previously reported for any molecular ion system. Additionally, by probing with linearly polarized light and measuring the degree of polarization of the resultant LIF, the collision-induced quadrupole rotational alignment parameter A0(2) is determined as a function of field strength and velocity subgroup. A strong correlation is found between the degree of rotational alignment and the velocity subgroup when probed parallel to the field direction, with the alignment parameters generally increasing monotonically across the distribution. A dramatic difference in velocity-selected alignment as a function of rotational state is observed as well, for experiments conducted on various rotational lines at a fixed field strength of 12 Td. For sufficiently low rotational state (J about 9), it appears that A0(2) changes sign across the Doppler profile.

  10. An investigation of the velocity spectrum of excited particles by fast ions from a solid as a means to study its electronic level structure

    Microsoft Academic Search

    V. V. Gritsyna; T. S. Kijan; A. G. Koval; Ya. M. Fogel

    1972-01-01

    In this work is shown that by measurement of the velocity of excited particles ejected by a beam of fast ions from the surface of a solid, some characteristics of its electronic level structure may be determined. The velocity spectrum of Ti, Na and Li atoms ejected respectively from targets of titanium and NaCl- and LiF-crystals by a beam of

  11. The neutral lithium velocity distribution of an AMPTE solar wind release as inferred from lithium ion measurements on the UKS spacecraft

    NASA Astrophysics Data System (ADS)

    Chapman, S. C.; Cowley, S. W. H.; Johnstone, A. D.

    As part of the AMPTE mission on September 20, 1984 a neutral lithium release was made in the quiet solar wind. The MSSL ion instrument on board the AMPTE-UKS spacecraft that was positioned about 30 km from the release center enabled measurements of significant fluxes of lithium ions to be made for about 3 min after the release; that is, long after the effects of the initial local perturbation to the field and flow had died away. These lithium test ions move in cycloidal orbits in the steady ambient fields, so that measurements of their fluxes at the UKS can be used to infer the velocity distribution function of the collisionless neutral cloud over a restricted region in velocity space. These restrictions are such that the ion data can show that significant anisotropy is present.

  12. Parallel ion velocity shear driven electromagnetic fluctuations and associated particle transport in partially ionized plasmas

    NASA Astrophysics Data System (ADS)

    Shukla, P. K.; Mirza, Arshad M.; Faria, R. T.

    1998-05-01

    A nonuniform partially ionized magnetized plasma is shown to be unstable against electromagnetic perturbations. The source of free energy for the instability is sheared magnetic-field-aligned ion flow, which is coupled to the electromagnetic waves via charged particle-neutral collisions. Analytical expressions for the growth rate and threshold are obtained. Numerical studies for the ionospheric parameters suggest that electromagnetic waves grow faster than their electrostatic counterparts. Furthermore, linearly excited electromagnetic waves in partially ionized collisional plasmas are shown to cause nonthermal cross-field transport of plasma particles. The results can have relevance to the current filamentation and the plasma diffusion in the ionosphere of the Earth, as well as in low-temperature laboratory plasmas.

  13. Dissipative drift instability in dusty plasma

    NASA Astrophysics Data System (ADS)

    Das, Nilakshi; Baruah, Swati

    2012-03-01

    An investigation has been done on the very low-frequency electrostatic drift waves in a collisional dusty plasma. The dust density gradient is taken perpendicular to the magnetic field overrArr{B0}, which causes the drift wave. In this case, low-frequency drift instabilities can be driven by overrArr{E1}× overrArr{B0} and diamagnetic drifts, where overrArr{E1} is the perturbed electric field. Dust charge fluctuation is also taken into consideration for our study. The dust- neutral and ion-neutral collision terms have been included in equations of motion. It is seen that the low-frequency drift instability gets damped in such a system. Both dust charging and collision of plasma particles with the neutrals may be responsible for the damping of the wave. Both analytical and numerical techniques have been used while developing the theory.

  14. Drift waves in stellarator geometry

    SciTech Connect

    Persson, M.; Nadeem, M.; Lewandowski, J.L.V.; Gardner, H.J.

    2000-02-07

    Drift waves are investigated in a real three-dimensional stellarator geometry. A linear system, based on the cold ion fluid model and a ballooning mode formalism, is solved numerically in the geometry of the stellarator H1-NF. The spectra of stable and unstable modes, as well as localization, are discussed. The dependence of the spectrum of the unstable modes on the wavevector, plasma density variation, and the location in the plasma is presented.

  15. The DRIFT Directional Dark Matter Experiments

    NASA Astrophysics Data System (ADS)

    Harton, John

    2014-03-01

    The DRIFT dark matter collaboration aims to detect the sidereal modulation of the dark matter signal through measurement of spatial components of the recoil nucleus direction from WIMP-nucleon interactions. DRIFT uses low-pressure negative-ion time projection chambers to measure recoil nuclei, and the recoiling nuclei, from a standard WIMP halo, would typically leave a millimeter-scale ionization track in the chamber. The rotation of the Earth on its axis combined with the motion of the solar system through the WIMP halo creates the sidereal modulation. This sidereal (``daily'') modulation is the change in average direction of the recoils over the course of the sidereal day, which for the DRIFT detector, located in England, changes from generally down to south once a (sidereal) day. Recent advances in background rejection are allowing DRIFT-IId to run background free. And measurement of the interaction location along the ion drift direction has recently been enabled by adding a small amount of oxygen to the drift gas. This talk will report on these recent advances and show current limits, as well as describe plans for future DRIFT detectors. Supported by the US Department of Energy and the National Science Foundation.

  16. Kinetic instability of ion acoustic mode in permeating plasmas

    SciTech Connect

    Vranjes, J.; Poedts, S. [Center for Plasma Astrophysics and Leuven Mathematical Modeling and Computational Science Center (LMCC), K. U. Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); Ehsan, Zahida [Salam Chair in Department of Physics, GC University, Lahore 54000, Pakistan and Plasma Physics Group, Blackett Laboratory, Imperial College, London SW7 2AZ (United Kingdom)

    2009-07-15

    In plasmas with electron drift (current) relative to static ions, the ion acoustic wave is subject to the kinetic instability which takes place if the directed electron speed exceeds the ion acoustic speed. The instability threshold becomes different in the case of one quasineutral electron-ion plasma propagating through another static quasineutral (target) plasma. The threshold velocity of the propagating plasma may be well below the ion acoustic speed of the static plasma. Such a currentless instability may frequently be expected in space and astrophysical plasmas.

  17. General ignition requirements in TMR's with drift pumping

    SciTech Connect

    Logan, B.G.

    1983-01-01

    Drift pumping of collisionally trapped DT ions and thermal alpha ash in the transitions and thermal barriers of TMR plugs can be shown by simple models to dominate the central cell energy losses, requiring in fact more radial ion loss by drift pumping than axial ion loss through the potential plugs, and setting a minimum central cell length for ignition. Induced electron transport due to drift pumping is shown to be small, so grids are not needed on the direct converter to separate ion and electron currents.

  18. 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.

  19. Reduction effect of neutral density on the excitation of turbulent drift waves in a linear magnetized plasma with flow

    SciTech Connect

    Saitou, Y.; Yonesu, A.; Shinohara, S.; Ignatenko, M. V.; Kasuya, N.; Kawaguchi, M.; Terasaka, K.; Nishijima, T.; Nagashima, Y.; Kawai, Y.; Yagi, M.; Itoh, S.-I.; Azumi, M.; Itoh, K. [Faculty of Engineering, Utsunomiya University, Utsunomiya, Tochigi 321-8585 (Japan); Faculty of Engineering, Ryukyu University, Nishihara, Okinawa 903-0213 (Japan); Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Japan Atomic Energy Agency, Naka, Ibaraki 319-1184 (Japan); National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan)

    2007-07-15

    The importance of reducing the neutral density to reach strong drift wave turbulence is clarified from the results of the extended magnetohydrodynamics and Monte Carlo simulations in a linear magnetized plasma. An upper bound of the neutral density relating to the ion-neutral collision frequency for the excitation of drift wave instability is shown, and the necessary flow velocity to excite this instability is also estimated from the neutral distributions. Measurements of the Mach number and the electron density distributions using Mach probe in the large mirror device (LMD) of Kyushu University [S. Shinohara et al., Plasma Phys. Control. Fusion 37, 1015 (1995)] are reported as well. The obtained results show a controllability of the neutral density and provide the basis for neutral density reduction and a possibility to excite strong drift wave turbulence in the LMD.

  20. Thermal Electron Contributions to Current-Driven Instabilities: SCIFER Observations in the 1400-km Cleft Ion Fountain and Their Implications to Thermal Ion Energization

    NASA Technical Reports Server (NTRS)

    Adrian, Mark L.; Pollock, C. J.; Moore, T. E.; Kintner, P. M.; Arnoldy, R. L.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    SCIFER TECHS observations of the variations in the thermal electron distribution in the 1400-km altitude cleft are associated with periods of intense ion heating and field-aligned currents. Energization of the thermal ion plasma in the mid-altitude cleft occurs within density cavities accompanied by enhanced thermal electron temperatures, large field-aligned thermal electron plasma flows and broadband low-frequency electric fields. Variations in the thermal electron contribution to field-aligned current densities indicate small scale (approximately 100's m) filamentary structure embedded within the ion energization periods. TECHS observations of the field-aligned drift velocities and temperatures of the thermal electron distribution are presented to evaluate the critical velocity thresholds necessary for the generation of electrostatic ion cyclotron and ion acoustic instabilities. This analysis suggests that, during periods of thermal ion energization, sufficient drift exists in the thermal electron distribution to excite the electrostatic ion cyclotron instability. In addition, brief periods exist within the same interval where the drift of the thermal electron distribution is sufficient to marginally excite the ion acoustic instability. In addition, the presence an enhancement in Langmuir emission at the plasma frequency at the center of the ion energization region, accompanied by the emission's second-harmonic, and collocated with observations of high-frequency electric field solitary structures suggest the presence of electron beam driven decay of Langmuir waves to ion acoustic modes as an additional free energy source for ion energization.

  1. The Westward Drift of the Earth's Magnetic Field

    Microsoft Academic Search

    E. C. Bullard; Cynthia Freedman; H. Gellman; Jo Nixon

    1950-01-01

    The westward drift of the non-dipole part of the earth's magnetic field and of its secular variation is investigated for the period 1907-45 and the uncertainty of the results discussed. It is found that a real drift exists having an angular velocity which is independent of latitude. For the non-dipole field the rate of drift is 0.18± 0.015 o \\/year,

  2. Time-Resolved Laser-Induced Fluorescence Measurements of the Ion Velocity Distribution in the H6 Hall Thruster Plume

    NASA Astrophysics Data System (ADS)

    Durot, Christopher; Gallimore, Alec

    2013-09-01

    We developed a technique to measure time-resolved laser-induced fluorescence signals in plasma sources that have a relatively constant spectrum of oscillations in steady-state operation but are not periodically pulsed, such as Hall thrusters. We present the first results using the new technique to capture oscillations in a Hall Thruster. The ion velocity distribution function in the plume of the H6 Hall thruster is interrogated during breathing mode oscillations. The breathing mode is characterized by an oscillating depletion and replenishment of neutrals at a frequency of about 10-25 kHz. We use laser modulation on the order of megahertz, well above the time scale of interest (about 0.1 ms). Band-pass filtering and phase-sensitive detection (with a time constant on the order of microseconds) raise the signal-to-noise ratio and demodulate the signal while preserving time-resolved information. Following phase-sensitive detection, we average over transfer functions to finish recovering the signal. This technique has advantages such as a shorter dwell time than other techniques and the lack of a need for triggering for averaging in the time domain.

  3. 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.

  4. Effects of centrifugal drift on hurricane structure and intensity

    Microsoft Academic Search

    G. J. Tripoli; T. Hashino; W. Lewis

    2009-01-01

    High (1km) resolution simulations of the 2005 hurricane Wilma were conducted using the UW-NMS which models the effect of horizontal precipitation drift due to centrifugal force. The extremely tight nature of Wilma's vortex suggests that there should be a measurable horizontal drift of precipitation, comparable to the vertical motion, that is due to centrifugal terminal velocity. These effects would likely

  5. Dust ion acoustic instability with q-distribution in nonextensive statistics

    NASA Astrophysics Data System (ADS)

    Dai, Jin-Wei; Chen, Xiao-Chang; Li, Xiao-Qing

    2013-07-01

    The instability of dust ion acoustic waves (DIAWs) driven by ions and electrons with different drift velocities in an unmagnetized, collisionless, isotropic dusty plasma was investigated. The electrons, ions and dust particles are assumed to be the generalized q-nonextensive distributions. The spectral indices of the q-distributions for the three plasma components are different from each other. Based on kinetic theory, the dispersion relation and the instability growth rate of DIAWs are obtained. It is found that the presence of the nonextensive distribution electrons and ions significantly modify the domain of the instability growth rate, as well as the ion-electron density ratio ( ?) and drifting-thermal velocity ratio ( u i0/ v Te ). In reverse, the index of dust grains has nearly no any effect on the instability growth rate. Furthermore, the effects of these parameters on the growth rate have also been discussed in detail.

  6. Drift distance survey in DPIS for high current beam production

    SciTech Connect

    Kanesue,T.; Okamura, M.; Kondo, K.; Tamura, J.; Kashiwagi, H.; Zhang, Z.

    2009-09-20

    In a laser ion source, plasma drift distance is one of the most important design parameters. Ion current density and beam pulse width are defined by plasma drift distance between laser target and beam extraction position. In direct plasma injection scheme (DPIS), which uses a laser ion source and Radio Frequency Quadrupole (RFQ) linac, we can apply relatively higher electric field at the beam extraction due to the unique shape of a positively biased electrode. However, when we aim at very high current acceleration like several tens of mA, we observed mismatched beam extraction conditions. We tested three different ion current at ion extraction region by changing plasma drift distance to study better extraction condition. In this experiment, C{sup 6+} beam was accelerated. We confirmed that the matching condition can be improved by controlling plasma drift distance.

  7. 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.

  8. Determination of low latitude plasma drift speeds from FUV images

    Microsoft Academic Search

    Thomas J. Immel; Stephen B. Mende; Harald U. Frey; Laura M. Peticolas; Eiichi Sagawa

    2003-01-01

    Thousands of images of the nighttime equatorial airglow arcs have been obtained by the Far-Ultraviolet Imager (FUV) on-board the NASA IMAGE satellite. Imaging periods lasting several hours around the time of satellite apogee allow for the determination of the velocity of drifting plasma density depletions occurring within the airglow arcs. These velocities reflect the E × B drift of low-latitude

  9. Determination of low latitude plasma drift speeds from FUV images

    Microsoft Academic Search

    Thomas J. Immel; Stephen B. Mende; Harald U. Frey; Laura M. Peticolas; Eiichi Sagawa

    2003-01-01

    Thousands of images of the nighttime equatorial airglow arcs have been obtained by the far-ultraviolet imager (FUV) on-board the NASA IMAGE satellite. Imaging periods lasting several hours around the time of satellite apogee allow for the determination of the velocity of drifting plasma density depletions occurring within the airglow arcs. These velocities re?ect the ExB drift of low-latitude plasma under

  10. Time-Resolved Laser-Induced Fluorescence Measurements of the Ion Velocity Distribution in the H6 Hall Thruster Plume

    NASA Astrophysics Data System (ADS)

    Durot, Christopher; Gallimore, Alec

    2013-10-01

    We developed a technique to recover time-resolved laser-induced fluorescence signals from strong background emission in plasma sources that have a relatively constant spectrum of oscillations in steady-state operation but are not periodically pulsed, such as Hall thrusters. The system was previously validated using a hollow cathode plasma source with forced discharge current oscillations. We present the first results using the new technique to capture oscillations in a Hall thruster. The ion velocity distribution function in the plume of the H6 Hall thruster is interrogated during breathing mode oscillations, which are characterized by an oscillating depletion and replenishment of neutrals at a frequency of 10-25 kHz. We use laser modulation on the order of megahertz, well above the time scale of interest (about 0.1 ms). A combination of band-pass filtering, phase-sensitive detection (with a time constant on the order of microseconds), and averaging over transfer functions is used to recover the signal. This technique has advantages such as a shorter dwell time than other techniques and the lack of a need for triggering averaging in the time domain. The ultimate bandwidth of the system that we implemented is approximately 1 MHz, limited by the speed of the AOM and signal photon rate collected. We developed a technique to recover time-resolved laser-induced fluorescence signals from strong background emission in plasma sources that have a relatively constant spectrum of oscillations in steady-state operation but are not periodically pulsed, such as Hall thrusters. The system was previously validated using a hollow cathode plasma source with forced discharge current oscillations. We present the first results using the new technique to capture oscillations in a Hall thruster. The ion velocity distribution function in the plume of the H6 Hall thruster is interrogated during breathing mode oscillations, which are characterized by an oscillating depletion and replenishment of neutrals at a frequency of 10-25 kHz. We use laser modulation on the order of megahertz, well above the time scale of interest (about 0.1 ms). A combination of band-pass filtering, phase-sensitive detection (with a time constant on the order of microseconds), and averaging over transfer functions is used to recover the signal. This technique has advantages such as a shorter dwell time than other techniques and the lack of a need for triggering averaging in the time domain. The ultimate bandwidth of the system that we implemented is approximately 1 MHz, limited by the speed of the AOM and signal photon rate collected. This work was supported by AFOSR and AFRL through the MACEEP center of excellence grant number FA9550-09-1-0695.

  11. 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).

  12. Determination of the interstitial electron density in liquid metals: Basic quantity to calculate the ion collective-mode velocity and related properties

    NASA Astrophysics Data System (ADS)

    Sani, L.; Petrillo, C.; Sacchetti, F.

    2014-07-01

    Considering that various investigations identified a correlation between the interstitial electron density in crystalline metals and some ground-state properties, including the compressibility, we propose a procedure to estimate the interstitial electron density in liquid metals starting from the experimental static structure factor. From the calculated electron density, starting from the standard approximation, which describes a liquid metal as made up of a homogeneous classic ion plasma with Coulomb interaction and a homogeneous interacting electron gas, we determine the ion collective mode velocity. The so-derived collective mode velocity is compared to the experimental data and a coherent view in different metallic systems at the melting point is obtained. Some guess about the collective mode damping is also presented because of the connection to the local static fluctuations of the interstitial electron density.

  13. 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

    2008-01-29

    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 1 MHz 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 uclear-radiation background on the measurement uncertainties are calculated to predict performance on ITER.

  14. 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.

  15. The complex mixed Wentzel-Kramers-Brillouin-full-wave approach and its application to the two dimensional mode structure analysis of ion temperature gradient/collisionless trapped electron mode drift waves

    NASA Astrophysics Data System (ADS)

    Lu, Z. X.

    2015-05-01

    The complex mixed Wentzel-Kramers-Brillouin (WKB)-full-wave approach is applied to the 2D mode structure analysis of ion temperature gradient/collisionless trapped electron mode drift waves in tokamak plasmas. The parallel mode structure is calculated with the full-wave approach, while the radial envelope is calculated with the complex WKB method. The tilting of the global mode structure along radius is demonstrated analytically. The effects of the phase and amplitude variation of the radial envelope on the parallel mode structure are included in terms of a complex radial wave vector in the parallel mode equation. It is shown that the radial equilibrium non-uniformity leads to the asymmetry of the parallel mode structure not only in configuration space but also in spectrum space. The mixed approach provides a practical way to analyze the asymmetric component of the global mode structure due to radial equilibrium non-uniformity.

  16. 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.

  17. Drift and reactions of positive tetratomic ions in dry, atmospheric air: Their effects on the dynamics of primary and secondary streamers

    Microsoft Academic Search

    A. Bekstein; M. Yousfi; M. Benhenni; O. Ducasse; O. Eichwald

    2010-01-01

    The ion swarm data, namely, the reduced mobility, diffusion, and reaction rates of the positive tetratomic ions O4+ and N2O2+ in N2 and O2 have been determined from a Monte Carlo simulation using calculated and fitted elastic and inelastic cross sections. The elastic momentum transfer cross sections have been determined from a semiclassical Jeffreys-Wentzell-Kramers-Brilouin (JWKB) approximation based on a rigid

  18. Dust acoustic wave growth measured in a drifting, moderately coupled, quiescent dusty plasma

    NASA Astrophysics Data System (ADS)

    Heinrich, J. R.; Kim, S. H.; Meyer, J. R.; Merlino, R. L.

    2011-10-01

    By introducing a grid with a variable bias potential far from the anode of a dc-glow discharge device we developed a technique to produce a drifting dusty plasma. The biased mesh trapped a secondary dust cloud that was released when the grid was returned to its floating potential. The secondary dust suspension then drifted toward the anode, and when it reached a certain distance from the grid, dust acoustic waves (DAW) spontaneously appeared in the suspension. The DAWs began growing at the location where the ion drift velocity was presumably high enough to excite the ion-dust streaming instability. The observed DAWs grew from thermal density fluctuations in a dust cloud that was large enough to support many wavelengths. The amplitude of the DAWs were measured over time to obtain the growth rate. As the wave growth saturated, a transition from linear to nonlinear waves was observed. The measured wave frequencies, wavelengths and growth rates are compared with theoretical values obtained from both fluid and kinetic theory. Work supported by DOE Grant No. DE-FG01-04ER54795.

  19. A kinetic theory for the drift-kink instability

    Microsoft Academic Search

    Giovanni Lapenta; J. U. Brackbill

    1997-01-01

    We have developed a linear two-dimensional kinetic theory, which is motivated by recent results for the drift-kink instability. The theory predicts plasma instability for large values of ion-electron temperature ratios, Ti\\/Te, moderate drift speeds, and large ion-electron mass ratios, mi\\/me, corresponding to conditions in the near-Earth region of the magnetotail neutral sheet. The growth rate predicted by the theory is

  20. 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.

  1. Meridional drift in the large-scale solar magnetic field pattern

    Microsoft Academic Search

    S. Latushko

    1994-01-01

    A method of two-dimensional correlation functions has been applied to a sequence of synoptic maps of the large-scale magnetic field to obtain the meridional drift pattern of field structures. The meridional drift profile obtained is antisymmetric about the equator. The meridional drift is directed from the equator to the poles at latitudes below 45°. A maximum drift velocity of 11–13

  2. Ion acceleration by an electron beam with neutral gas ionization by an external source

    NASA Astrophysics Data System (ADS)

    Kucherov, Victor I.; Kurilko, Victor I.; Ostrovsky, Alexey O.

    1995-02-01

    The theoretical results for ion acceleration by a high current relativistic electron beam (REB) at the neutral-gas ionization front are presented. For a significant increase in the ion energy it is necessary to control the drift velocity of the ionization front so that it is close to the synchronous particle velocity. The most feasible way for such a control is gas ionization by an external source moving in synchronism with the accelerated particles. This work is devoted to estimating the characteristics of such a source. The space-time distribution of accelerating field is also analyzed and the dynamics of accelerated ion bunch formation is studied.

  3. Electrostatic ion-cyclotron waves in a nonuniform magnetic field

    NASA Technical Reports Server (NTRS)

    Cartier, S. L.; Dangelo, N.; Merlino, R. L.

    1985-01-01

    The properties of electrostatic ion-cyclotron waves excited in a single-ended cesium Q machine with a nonuniform magnetic field are described. The electrostatic ion-cyclotron waves are generated in the usual manner by drawing an electron current to a small exciter disk immersed in the plasma column. The parallel and perpendicular (to B) wavelengths and phase velocities are determined by mapping out two-dimensional wave phase contours. The wave frequency f depends on the location of the exciter disk in the nonuniform magnetic field, and propagating waves are only observed in the region where f is approximately greater than fci, where fci is the local ion-cyclotron frequency. The parallel phase velocity is in the direction of the electron drift. From measurements of the plasma properties along the axis, it is inferred that the electron drift velocity is not uniform along the entire current channel. The evidence suggests that the waves begin being excited at that axial position where the critical drift velocity is first exceeded, consistent with a current-driven excitation mechanism.

  4. Selected ion flow drift tube studies of the reactions of Si + (2P) with HCl, H2O, H2S, and NH3: Reactions which produce atomic hydrogen

    NASA Astrophysics Data System (ADS)

    Glosík, J.; Zakou?il, P.; Lindinger, W.

    1995-10-01

    The reaction rate coefficients, k, for the reactions of ground-state Si+(2P) with HCl, H2O, H2S, and NH3, have been measured as a function of reactant ion/reactant neutral center-of-mass kinetic energy, KECM, in a selected ion flow drift tube (SIFDT) apparatus, operated with helium at a temperature 298±2 K. The values k of the studied reactions have very pronounced, negative energy dependencies; the rate coefficients decrease by about 1 order of magnitude as KECM increase from near thermal values to ˜2 eV. The results are interpreted in terms of a simple model assuming the reactions to proceed via the formation of long-lived complexes. These intermediate complexes decompose back to reactants or forward to products, the unimolecular decomposition rate coefficients for these reactions being k1 and k2, respectively. It is found that a power law of the form k-1/k2=const(KECM)m closely describes each reaction.

  5. A Benign, Low Z Electron Capture Agent for Negative Ion TPCs

    NASA Technical Reports Server (NTRS)

    Martoff, C. J.; Dion, M. P.; Hosack, M.; Barton, D.; Black, J. K.

    2008-01-01

    We have identified nitromethane (CH3NO2) as an effective electron capture agent for negative ion TPCs (NITPCs). We present drift velocity and longitudinal diffusion measurements for negative ion gas mixtures using nitromethane as the capture agent. Not only is nitromethane substantially more benign than the only other identified capture agent, CS2, but its low atomic number will enable the use of the NITPC as a photoelectric X-ray polarimeter in the 1-10 keV band.

  6. SRA: a new ion accelerator scheme

    SciTech Connect

    Choe, J.Y.; Uhm, H.S.

    1983-08-01

    The space-charge resonance accelerator consists of a relativistic electron beam propagating through a dielectric loaded drift tube. In a range of physical parameters, the phase velocity of a self-growing space-charge wave increases slowly from zero to a large beam velocity as it propagates into the downstream region, thereby trapping and accelerating ions with its electric field. The self-growing mechanism of the space-charge wave is a typical Cherenkov radiation. This paper presents schematics and calculation methods which describe the accelerator, its dynamics, and its fields.

  7. Dust ion-acoustic shock waves in charge varying dusty plasmas with electrons having vortexlike velocity distribution

    Microsoft Academic Search

    H. Alinejad; M. Tribeche

    2010-01-01

    A weakly nonlinear analysis is carried out to investigate the properties of dust ion-acoustic shock waves in a charge varying dusty plasma with vortexlike electron distribution. We use the ionization model, hot ions with equilibrium streaming speed and a trapped electron charging current derived from the well-known orbit limited motion theory. A new modified Burger equation is derived. Besides nonlinear

  8. The Role of Electric Fields in the Occurence, Structure, and Drift of Thin Metallic Ion Layers in the High-Latitude Ionosphere

    Microsoft Academic Search

    David Franklin Bedey

    1996-01-01

    Metallic ions deposited in the upper atmosphere through the process of meteoroid ablation can, on occasion, be forced into dense layers at altitudes of 90-120 km with a thickness of <2 km. These layers result from a combination of appropriately directed neutral winds and electric fields. The objective of this thesis is to gain new insights into several poorly understood

  9. 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

  10. 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

  11. Lithium drifted germanium system

    NASA Technical Reports Server (NTRS)

    Fjarlie, E. J.

    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.

  12. 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

  13. 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

    condensed phase to the gas phase duty cycle the time interval in which an instrument is doing useful analysis dynamic range the linear response range of an instrument or detector. ESI Electrospray Ionization EI Electron Ionization (synonymous... billion (1 part in 10 8 ) ppm parts per million (1 part in 10 6 ) ix RF Radio Frequency (i.e., a temporally dynamic potential) swarm a (usually low) density of ions within a neutral gas throughput an instrument?s measurement rate, quantified...

  14. DC Electric Fields, Associated Plasma Drifts, and Irregularities Observed on the C/NOFS Satellite

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Klenzing, J.

    2011-01-01

    Results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. Compared to data obtained during more active solar conditions, the ambient DC electric fields and their associated E x B drifts are variable and somewhat weak, typically < 1 mV/m. Although average drift directions show similarities to those previously reported, eastward/outward during day and westward/downward at night, this pattern varies significantly with longitude and is not always present. Daytime vertical drifts near the magnetic equator are largest after sunrise, with smaller average velocities after noon. Little or no pre-reversal enhancement in the vertical drift near sunset is observed, attributable to the solar minimum conditions creating a much reduced neutral dynamo at the satellite altitude. The nighttime ionosphere is characterized by larger amplitude, structured electric fields, even where the plasma density appears nearly quiescent. Data from successive orbits reveal that the vertical drifts and plasma density are both clearly organized with longitude. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. The VEFI data represents a new set of measurements that are germane to numerous fundamental aspects of the electrodynamics and irregularities inherent to the Earth s low latitude ionosphere.

  15. 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

  16. 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.

  17. 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

  18. Electron drift in alkali-metal vapours

    Microsoft Academic Search

    I. I. Fabrikant

    1992-01-01

    Electron drift velocities in sodium, potassium, rubidium and caesium vapours are calculated using theoretical momentum-transfer cross sections for electron-atom scattering. The results strongly disagree with experimental data for saturated vapours at low values of E\\/N (ratio of electric field to vapour number density). The author shows using the case of sodium as an example, that the disagreement could be explained

  19. Tidal decomposition of zonal neutral and ion flows in the earth's upper equatorial thermosphere

    NASA Technical Reports Server (NTRS)

    Herrero, F. A.; Mayr, H. G.

    1986-01-01

    Evidence is presented for strong coupling between the diurnal components of zonal neutral winds and ion drifts, suggesting that the relative importance of the E- and F-region dynamos be reevaluated. Measurements of zonal neutral winds in the equatorial region of the earth's thermosphere at an average altitude of about 350 km show that the nighttime zonal winds are very similar to the zonal ion-drifts. That similarity is examined, comparing the corresponding tidal components of the 24 hr variations of these two parameters. The amplitude spectrum of the neutral winds exhibits primary and secondary maxima at the diurnal and ter-diurnal frequencies respectively, while the ion-drift spectrum shows only the diurnal maximum. It is found that the simularity between neutral winds and ion-drifts is strongest in the diurnal mode where the phases differ by less than one half hour, the amplitude of the ion-drift being between 70 percent and 80 percent that of the neutral wind, suggesting a first-order relation between the two quantities. The largest difference is found in the steady component representing superrotation; under similar conditions of solar activity, the ions superrotate with a velocity of about 30 m/s and the neutrals with 10 m/s. For the ions, the steady component, the phase of the semi-diurnal component and the amplitude of the ter-diurnal component appear to be sensitive to solar activity and are responsible for the observed solar cycle variations in the times of eastward-to-westward reversals between 0400 and 0700 LT. The ion-drift diurnal amplitude and phase are relatively insensitive to changes in solar activity.

  20. Negative ion production rates in rare gas-halide lasers

    Microsoft Academic Search

    KAARE J. NYGAARD; HOWARD L. BROOKS; SCOTT 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

  1. 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

  2. Confinement Regime Transition, Spontaneous Rotation and Phase Velocity Inversion of Edge Modes*

    NASA Astrophysics Data System (ADS)

    di Sanzo, C.; Coppi, B.; Landreman, M.

    2007-04-01

    The transition from the L-confinement regime to the H-regime is associated with the inversion of the phase velocity of collisional ballooningootnotetextCoppi, B., et. al., 33rd E.P.S. Plasma Conf., Paper O4.017 (2006) modes excited at the edge of the plasma column and driven by the pressure gradient. Electron-ion, ion-ion and ion-ion neutral collisions are involved in an essential way. The phase velocity inversion from the electron diamagnetic velocity direction (L-regime) to the ion's occurs when i-i collisions and i-n collisions begin to prevailootnotetextB. Coppi, MIT(LNS) Report HEP 06/12 and in Paper TH/P6-21, 2006 Intern. Fusion Energy Conf. (IAEA, Vienna) and is very similar to the one found originally,ootnotetextCoppi, B., H. Hendel, et al., Report MATT- 523 (P.P.P.L., 1967); Intern. Conf. on Phys. of Quiescent Plasmas (Frascati, 1967) in order to identify collisional electron drift modes in Q-machine experiments. The quality of confinement is associated with the effective rate of expulsion of angular momentum in the same direction as the mode phase velocity, toward the surrounding material wall, and rotation of the main plasma column resulting from recoil.ootnotetextCoppi, B., Nucl. Fusion 42, 1 (2002)*Sponsored in part by the U.S. D.O.E.

  3. Mapping climatological seasonal variations of surface currents in the tropical Atlantic using ship drifts

    Microsoft Academic Search

    Philip L. Richardson; David Walsh

    1986-01-01

    The seasonal variability of current velocities in the tropical Atlantic was studied by grouping ship drift velocity observations into 2°×5° boxes and calculating monthly mean velocity values. These values were used to calculate and map the annual mean velocity, the seasonal variation about the mean, the annual and semiannual harmonics, and the first two empirical orthogonal functions (EOFs).The seasonal variation

  4. Designing Neutralized Driftes g g Neu ed Compression for Focusing of

    E-print Network

    Kaganovich, Igor

    Designing Neutralized Driftes g g Neu ed Compression for Focusing of I I B P l iIntense Ion Beam;#2 Neutralized drift compression can reach 300x300 = 105 combined longitudinal and transverse compression of ion Vacuum arc source #12;#3 OutlineOutline Longitudinal compressionLongitudinal compression Radial

  5. Dust ion-acoustic shock waves in charge varying dusty plasmas with electrons having vortexlike velocity distribution

    NASA Astrophysics Data System (ADS)

    Alinejad, H.; Tribeche, M.

    2010-12-01

    A weakly nonlinear analysis is carried out to investigate the properties of dust ion-acoustic shock waves in a charge varying dusty plasma with vortexlike electron distribution. We use the ionization model, hot ions with equilibrium streaming speed and a trapped electron charging current derived from the well-known orbit limited motion theory. A new modified Burger equation is derived. Besides nonlinear trapping, this equation involves two kinds of dissipation (the anomalous one inherent to nonadiabatic dust charge fluctuation and the one due to the particle loss and ionization). These two kinds of dissipation can act concurrently. The traveling wave solution has been acquired by employing the modified extended tanh-function method. The shocklike solution is numerically analyzed based on the typical numerical data from laboratory dusty plasma devices. It is found that ion temperature, trapped particles, and weak dissipations significantly modify the shock structures.

  6. Cross-field potential hill arisen eccentrically in toroidal electron cyclotron resonance plasmas in the Low Aspect ratio Torus Experiment device to regulate electron and ion flows from source to boundary

    NASA Astrophysics Data System (ADS)

    Kuroda, Kengoh; Wada, Manato; Uchida, Masaki; Tanaka, Hitoshi; Maekawa, Takashi

    2015-07-01

    We have investigated the electron and ion flows in toroidal electron cyclotron resonance (ECR) plasmas maintained by a 2.45 GHz microwave power around 1 kW under a simple toroidal field in the low aspect ratio torus experiment (LATE) device. We have found that a vertically uniform ridge of electron pressure that also constitutes the source belt of electron impact ionization is formed along just lower field side of the ECR layer and a cross-field potential hill ({{V}S}\\cong 30?V while {{T}e}\\cong 10?eV), eccentrically shifted toward the corner formed by the top panel and the ECR layer, arises. Combination of the hill-driven E× B drift and the vertical drift due to the field gradient and curvature, being referred to as vacuum toroidal field (VTF) drift, realizes steady flows of electrons and ions from the source to the boundary. In particular, the ions, of which VTF drift velocity is much slower than the electron VTF drift velocity near the source belt, are carried by the E× B drift around the hill to the vicinity of the top panel, where the ion VTF drift is enhanced on the steep down slope of potential toward the top panel. On the other hand the electron temperature strongly decreases in this area. Thus the carrier of VTF drift current is replaced from the electrons to the ions before the top panel, enabling the current circulation through the top and bottom panels and the vessel (electrons mainly to the bottom and ions mainly to the top) that keeps the charge neutrality very high. A few percent of electrons from the source turn around the hill by 360 degree and reentry the source belt from the high field side as seed electrons for the impact ionization, keeping the discharge stable.

  7. Time-Resolved Laser-Induced Fluorescence Measurements of Ion Velocity Distribution in the Plume of a 6 kW Hall Thruster with Unperturbed Discharge Oscillations

    NASA Astrophysics Data System (ADS)

    Durot, Christopher; Gallimore, Alec

    2014-10-01

    We present laser-induced fluorescence (LIF) measurements of the time-resolved ion velocity distribution in the plume of a 6 kW laboratory Hall thruster. To our knowledge, these are the first measurements of time-resolved ion velocity distribution on completely unperturbed Hall thruster operating conditions. To date, time-resolved LIF measurements have been made on Hall thrusters with oscillations driven or perturbed to be amenable to averaging techniques that assume a periodic oscillation. Natural Hall thruster breathing and spoke oscillations, however, are not periodic due to chaotic variations in amplitude and frequency. Although the system averages over many periods of nonperiodic oscillation, it recovers the time-resolved signal in part by assuming that a constant transfer function exists relating discharge current and LIF signal and averaging over the transfer function itself (http://dx.doi.org/10.1063/1.4856635). The assumption of a constant transfer function has been validated for a Hall thruster and the technique is now applied to a Hall thruster for the first time.

  8. Effects of bias potential upon H- density near a plasma grid of a negative ion source

    NASA Astrophysics Data System (ADS)

    Takahashi, H.; Kasuya, T.; Wada, M.

    2006-03-01

    A molybdenum plasma grid was installed in a 30-cm-long 16-cm-diam 16-pole magnetic multicusp ion source to simulate the effect of a plasma electrode bias of a negative ion source. Effects caused by the bias voltage applied to the electrode upon the plasma parameters, the density of negative hydrogen ions (H-), and the drift velocity of plasma perturbed by the photodetachment of H- were investigated with the direct current laser photodetachment method. The electron density at the distance of 0.5 cm from the plasma grid decreased from 8×1010 to 4×1010cm-3 by increasing the grid bias from 0 to +4V, while the H- density increased from 8×108 to 4.5×109cm-3. The drift velocity of plasma perturbation was changed by a factor of 3 corresponding with the gradient of the plasma potential near the electrode.

  9. Ions

    MedlinePLUS

    ... Ions with a positive charge are called cations. Ions with a negative charge are called anions. Many normal substances exist in the body as ions. Common examples include sodium, potassium, calcium, chloride, and ...

  10. Laboratory Experiments on Parallel Velocity Shear

    Microsoft Academic Search

    Robert L. Merlino; Su-Hyun Kim; Erick Agrimson; Nicola D'Angelo

    The results of experimental investigations of the effect of parallel velocity shear (ion flow parallel to the magnetic field with a transverse velocity gradient) on ion acoustic (IA) and electrostatic ion cyclotron instabilities (EIC) will be presented. (1) For nearly 40 years, satellite observations of ion-acoustic-like waves and waves near the ion- cyclotron frequency and its harmonics have been associated

  11. The simulation of slow-drift motions of offshore structures

    Microsoft Academic Search

    O. J. Emmerhoff; P. D. Sclavounos

    1996-01-01

    The large amplitude surge-sway-yaw ‘slow-drift’ motions of a floating body constrained by weak restoring forces in random waves are considered. A multiple time scales approximation is employed to separate the fast time scale associated with the linear motions from the slowly varying motions. The ideal fluid free surface flow is approximated by a perturbation series expansion for small slow-drift velocities

  12. Lower Hybrid Drift in Simulations of Hypersonic Plasma

    NASA Astrophysics Data System (ADS)

    Niehoff, D.; Ashour-Abdalla, M.; Niemann, C.; Schriver, D.; Sotnikov, V. I.; Lapenta, G.

    2014-12-01

    It has been shown experimentally that hypersonic plasma (defined as moving with a bulk flow velocity of more than 5 to 10 times the Mach speed) traveling through a magnetic field will create a diamagnetic cavity, or bubble [1]. At the edge of the bubble, opposing field and density gradients can drive the lower hybrid drift instability [2]. We will explore two and a half dimensional (2 space and 3 velocity dimensions) simulations of hypersonic plasma within a parameter regime motivated by the aforementioned diamagnetic bubble experiments, wherein we find oscillations excited near the lower hybrid frequency propagating perpendicular to the bulk motion of the plasma and the background magnetic field. The simulations are run using the implicit PIC code iPIC3D so that we are able to capture dynamics of the plasma below ion scales, but not be forced to resolve all electron scales [3]. [1] Niemann et al, Phys. Plasmas 20, 012108 (2013) [2] Davidson et al, Phys. Fluids, Vol. 20, No. 2, February 1977 [3] S. Markidis et al, Math. Comput. Simul. (2009), doi 10.1016/j.matcom.2009.08.038

  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. Effects of centrifugal drift on hurricane structure and intensity

    NASA Astrophysics Data System (ADS)

    Tripoli, G. J.; Hashino, T.; Lewis, W.

    2009-04-01

    High (1km) resolution simulations of the 2005 hurricane Wilma were conducted using the UW-NMS which models the effect of horizontal precipitation drift due to centrifugal force. The extremely tight nature of Wilma's vortex suggests that there should be a measurable horizontal drift of precipitation, comparable to the vertical motion, that is due to centrifugal terminal velocity. These effects would likely unload the updraft in the central core of the storm. Explicit calculations of this effect will be presented at the oral presentation and implications of centrifugal horizontal drift to the general 3D structure of a tropical cyclone will be discussed.

  15. The relationship between oblique double layers, ion cyclotron waves, ion phase space holes and cold ion beams

    NASA Astrophysics Data System (ADS)

    Main, D. S.; Newman, D. L.

    2012-12-01

    Observations of Earth's auroral upward current region (UCR) indicate the presence of many non-linear structures including a transition region (TR) separating the ionosphere from the auroral cavity, ion phase space holes and ion cyclotron waves. In addition, the UCR is characterized by a cold, anti-earthward traveling ion beam with typical drift energies of ~sim 1000 eV. Observations indicate that the TR is 2D with an inferred U-shaped potential profile, abrupt drop in density and simultaneous parallel (E?) and perpendicular (E?) electric fields. In 1D, E? and the density cavity are well modeled by a double layer (DL). However, in 2D it is not clear how the U-shaped potential profile forms and evolves. In this paper, we study oblique DLs and the resulting waves using a Particle-in-Cell (PIC) simulation initialized with two different methods. In method 1, we initialize a 2D PIC simulation with a non-oblique density cavity (i.e. the initial density drop has no perpendicular dependence), resulting in a U-shaped 2D DL whose obliqueness angle can evolve with time. The drift velocity of the anti-earthward ions is given a perpendicular velocity shear so that the drift velocity is largest at the ? borders and smallest at the center of the simulation domain. In method 2, we initialize a 2D PIC simulation with a magnetic field that lies oblique to an initial density drop resulting in an oblique DL whose angle is fixed with respect to earth's magnetic field. In both methods, the initial plasma is composed of hot magnetospheric electrons and H+ ions, cold ionospheric electrons, and cold ionospheric H + and O + ions which have an anti-earthward drift (all initially Maxwellian). In method 1, we show that as the U-shaped DL evolves, strong cyclotron waves initially form. As the simulation progresses, ion holes form which are localized both perpendicular and parallel to earth's magnetic field. Method 2 also results in the formation of strong cyclotron waves. We compare/contrast both methods with homogeneous simulations in which no DL is included and only the auroral cavity is included in the simulation domain. The homogeneous simulations represent a more typical linear scenario in which some linear instability leads to non-linear waves. We show that including an oblique DL in the simulation leads to much stronger cyclotron waves and more localized phase space holes (in the perpendicular direction) compared with homogeneous simulations. We also show that including the low altitude DL results in more coherent ion beams compared with homogenous simulations, consistent with FAST observations.

  16. 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

  17. Measuring the Effect of Ion-Induced Drift-Gas Polarization on the Electrical Mobilities of Multiply-Charged Ionic Liquid Nanodrops in Air

    NASA Astrophysics Data System (ADS)

    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 = (6 m/ ??)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.

  18. Thermal ion observations of depletion and refilling in the plasmaspheric trough

    SciTech Connect

    Watanabe, S.; Whalen, B.A.; Yau, A.W. (National Research Council of Canada, Ottawa, Ontario (Canada))

    1992-02-01

    Thermal (0-25 eV) ion observations in the altitude range 5,000 km to 10,000 km and ar invariant latitudes greater than {approximately} 60{degree}, made by the Superthermal Ion Mass Spectrometer (SMS) on the EXOS-D satellite, are used to estimate temperatures, densities, composition, and drift velocities of the local major thermal ion population during a 22-day period in February 1990. This preliminary study indicates that equatorward of a high-latitude boundary, higher-density cold ions corotate with Earth and field-aligned drift velocities are low (<1 km/s). These observations are consistent with a plasmaspheric origin for these ions; however, densities measured near the boundary (10-100 cm{sup {minus}3}) suggest that this boundary lies in or near the trough region. Poleward of this boundary, convection patterns, consistent with a polar wind like source mechanism, are detected. Typically, parallel drift velocities of 12, 7, and 3 km/s for H{sup +}, He{sup +}, and O{sup +} are observed. Correlations of these plasma parameters, which were obtained approximately once per day, with magnetic activity (Kp) suggest response times of 2-3 days between the onset of Kp changes and the establishment of new, large-scale, steady state conditions. The implications of these results with regard to ionospheric plasma dynamics associated with depletion and replenish of high-latitude flux tubes are discussed.

  19. Drift Dynamics of Larval Pallid Sturgeon and Shovelnose Sturgeon in a Natural Side Channel of the Upper Missouri River, Montana

    Microsoft Academic Search

    Patrick J. Braaten; David B. Fuller; Landon D. Holte; Ryan D. Lott; William Viste; Tyrel F. Brandt; Robert G. Legare

    2008-01-01

    The drift dynamics of larval shovelnose sturgeon Scaphirhynchus platorynchus (1, 2, 6, and 10 d posthatch (dph)) and pallid sturgeon S. albus (1, 2, 5, 9, 11, and 17 dph) were examined in a natural side channel of the Missouri River to quantify the vertical drift location of larvae in the water column, determine the drift velocity of larvae relative

  20. 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)

  1. 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.

  2. 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.

  3. Differences in drift behavior between drouged and undrogued satellite-tracked drifting buoys

    NASA Astrophysics Data System (ADS)

    Brügge, B.; Dengg, J.

    1991-04-01

    Drift behavior of drogued and undrogued Hermes-type buoys is studied. After drogue loss, an increase in drift speed and acceleration is observed as well as improved correlations between drift and wind in both speed and direction. With these criteria, a method for the separation of large data sets into a drogued and an undrogued part has been developed. In most areas of the North Atlantic this works very well; problems arise in regions with strong surface currents and/or light winds. A statistical analysis is performed in a selected area to demonstrate the errors that can be caused by indiscriminate use of drogued and undrogued drifters. Mean and rms velocities as well as kinetic energies change significantly when undrogued buoys are considered. Therefore caution is essential when using surface drifters without drogues.

  4. 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.

  5. New theoretical treatment of ion resonance phenomena.

    PubMed

    Vincze, G; Szasz, A; Liboff, A R

    2008-07-01

    Despite experimental evidence supporting ICR-like interactions in biological systems, to date there is no reasonable theoretical explanation for this phenomenon. The parametric resonance approach introduced by Lednev has enjoyed limited success in predicting the response as a function of the ratio of AC magnetic intensity to that of the DC field, explaining the results in terms of magnetically induced changes in the transition probability of calcium binding states. In the present work, we derive an expression for the velocity of a damped ion with arbitrary q/m under the influence of the Lorentz force. Series solutions to the differential equations reveal transient responses as well as resonance-like terms. One fascinating result is that the expressions for ionic drift velocity include a somewhat similar Bessel function dependence as was previously obtained for the transition probability in parametric resonance. However, in the present work, not only is there an explicit effect due to damping, but the previous Bessel dependence now occurs as a subset of a more general solution, including not only the magnetic field AC/DC ratio as an independent variable, but also the ratio of the cyclotronic frequency Omega to the applied AC frequency omega. In effect, this removes the necessity to explain the ICR interaction as stemming from ion-protein binding sites. We hypothesize that the selectively enhanced drift velocity predicted in this model can explain ICR-like phenomena as resulting from increased interaction probabilities in the vicinity of ion channel gates. PMID:18288680

  6. A Fast Faraday Cup for the Neutralized Drift Compression Experiment

    Microsoft Academic Search

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

    2005-01-01

    Heavy ion drivers for high energy density physics applications and inertial fusion energy use space-charge-dominated beams which require longitudinal bunch compression in order to achieve sufficiently high beam intensity at the target. The Neutralized Drift Compression Experiment-1A (NDCX-1A) at Lawrence Berkeley National Laboratory (LBNL) is used to determine the effective limits of neutralized drift compression. NDCX-1A investigates the physics of

  7. Streamers generation by small-scale drift-Alfvén waves

    SciTech Connect

    Zhao, J. S. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Yu, M. Y. [Institute for Fusion Theory and Simulation and Department of Physics, Zhejiang University, Hangzhou 310027, China and Institute for Theoretical Physics I, Ruhr University, D-44780 Bochum (Germany)

    2014-10-15

    Excitation of streamers by modulationally unstable small-scale drift-Alfvén wave (SSDAW) is investigated. It is found that the excitation depends strongly on the propagation direction of the SSDAW, and the ion and electron diamagnetic drift waves are both unstable due to the generation of streamers. It is also shown that zonal flows can be effectively excited by the SSDAW with the propagation direction different from that for streamer excitation.

  8. Drift resistive interchange and tearing modes in cylindrical geometry

    SciTech Connect

    Finn, J.M.; Manheimer, W.M.; Antonsen, T.M. Jr.

    1982-04-13

    Resistive interchange and tearing modes are studied including the effects of electron parrallel pressure gradient and ion polarization drift (Hall terms) as well as finite plasma compressibility and perpendicular resistivity. It is found that for unfavorable curvature and weak tearing forces (positive but small ..delta..') all modes are stabilized provided the effects of the Hall (drift) terms are large enough. The principal stabilizing influences are plasma compression and coupling to outgoing drift waves. The relevance to reversed field pinch and spheromak experiments is discussed.

  9. Drift wave instability in a nonuniform quantum dusty magnetoplasma

    SciTech Connect

    Salimullah, M.; Jamil, M.; Zeba, I.; Uzma, Ch.; Shah, H. A. [Department of Physics, GC University, Lahore 54000 (Pakistan)

    2009-03-15

    Using the quantum hydrodynamic model of plasmas and with quantum effects arising through the Bohm potential and the Fermi degenerate pressure, the possible drift waves and their instabilities have been investigated in considerable detail in a nonuniform dusty magnetoplasma. It is found that in the presence of a nonuniform ambient magnetic field, the drift waves grow in amplitude by taking energy from the streaming ions and density inhomogeneity. The implication of the drift wave instability for nonthermal electrostatic fluctuations to laboratory and astrophysical environments is also pointed out.

  10. 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.

  11. Visualizing concept drift

    Microsoft Academic Search

    Kevin B. Pratt; Gleb Tschapek

    2003-01-01

    We describe a visualization technique that uses brushed, parallel histograms to aid in understanding concept drift in multidimensional problem spaces. This technique illustrates the relationship between changes in distributions of multiple antecedent feature values and the outcome distribution. We can also observe effects on the relative utilization of predictive rules. Our parallel histogram technique solves the over-plotting difficulty of parallel

  12. 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.

  13. Transfer impedance of a probe in a drifting plasma

    NASA Astrophysics Data System (ADS)

    Fiala, V.; Blahak, F.

    1984-06-01

    The transfer impedance of a probe comprising a small spherical monopole antenna excited by a constant-amplitude constant-sweep-frequency RF generator and located on a line with and equidistant from the spherical poles of a dipole is computed theoretically for small drift velocities, extending the analysis of Fiala and Blahak (1983) to conditions such as those in the solar wind or distant magnetosphere. The numerical results are presented graphically, and it is found that the technique permits the determination of plasma density, temperature, and drift velocity from a single frequency sweep if the impedance curve of the probe is known with sufficient accuracy.

  14. Population of n, l States in Electron-Capture Collisions Between Highly Charged, Medium-Velocity Ions and H2

    NASA Astrophysics Data System (ADS)

    Hvelplund, P.; Samsoe, E.; Andersen, L. H.; Haugen, H. K.; Knudsen, H.

    1983-01-01

    The formation of excited states resulting from electron capture by Auq+ ions (q from 12 to 18, v = 2v0) colliding with H2 has been measured by means of optical methods. The capture cross sections into various n, l states are derived from measured emission cross sections by applying a simplified cascade correction. It is found that high l states are preferentially populated and that a large number of n states contributes to the total capture process. The general picture, which emerges from the present study, is in reasonable agreement with theoretical calculations by Olson, by Ryufuku and Watanabe, and by Crothers.

  15. Modulational instability of ion-acoustic waves in a plasma with a q-nonextensive electron velocity distribution

    SciTech Connect

    Bains, A. S.; Gill, T. S. [Department of Physics, Guru Nanak Dev University, Amritsar 143005 (India); Tribeche, Mouloud [Plasma Physics Group (PPG), Theoretical Physics Laboratory (TPL), Faculty of Sciences-Physics, University of Bab-Ezzouar, U.S.T.H.B, B.P. 32, El Alia, Algiers 16111 (Algeria)

    2011-02-15

    The modulational instability (MI) of ion-acoustic waves (IAWs) in a two-component plasma is investigated in the context of the nonextensive statistics proposed by Tsallis [J. Stat. Phys. 52, 479 (1988)]. Using the reductive perturbation method, the nonlinear Schroedinger equation (NLSE) which governs the MI of the IAWs is obtained. The presence of the nonextensive electron distribution is shown to influence the MI of the waves. Three different ranges of the nonextensive q-parameter are considered and in each case the MI sets in under different conditions. Furthermore, the effects of the q-parameter on the growth rate of MI are discussed in detail.

  16. Effect of drift-acoustic waves on magnetic island stability in slab geometry R. Fitzpatrick and F. L. Waelbroeck

    E-print Network

    Fitzpatrick, Richard

    Effect of drift-acoustic waves on magnetic island stability in slab geometry R. Fitzpatrick and F island width evolution equation in the presence of drift-acoustic waves. The calculation is fully to emit drift-acoustic waves. Wave emission gives rise to rapid oscillations in the ion polarization term

  17. Particle and wave observations of low-altitude ionospheric ion acceleration events

    NASA Technical Reports Server (NTRS)

    Yau, A. W.; Whalen, B. A.; Mcnamara, A. G.; Kellogg, P. J.; Bernstein, W.

    1983-01-01

    Two sounding rockets were launched into the expansive phases of two auroral substorms and passed through source regions of transversely accelerated ionospheric ions. Energetic ion and electron, wave, and ambient plasma observations were made. The events were observed in the 400-600 km range and resulted in the ion energization of hundreds of electron volts. In the acceleration region the ionospheric ion velocity distribution function in the direction perpendicular to the local magnetic field showed a non-Maxwellian, high-energy tail. Plasma density was lower than theoretical quiescent values. Strong thermal ion drift was observed only in the perpendicular direction. Large-amplitude, low-frequency fluctuations in plasma density were present along with a number of different wave modes. The characteristics of the ion energy spectra agreed with a model of ion cyclotron acceleration and energy loss due to ion-neutral collisions.

  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. Coupled-cavity drift-tube linac

    DOEpatents

    Billen, J.H.

    1996-11-26

    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. 5 figs.

  20. Ion Loss as Intrinsic Momentum Source in Tokamaks

    NASA Astrophysics Data System (ADS)

    Boedo, J. A.

    2013-10-01

    Measurements of D+ parallel velocity at the DIII-D edge are consistent with the kinetic loss of thermal ions as the mechanism for edge momentum generation. Edge velocity profiles exhibit a co-Ip peak velocity of 40-60 km/s in OH, L- and H-mode. The flow layer acts as a robust boundary value not affected by NBI injection. D+ velocity measurements are compared to a first-principles, collisionless, kinetic model predicting the existence of a loss-cone distribution in velocity space resulting in a co-Ip directed velocity. A fine Er structure, found by probes, has 10-20 kV/m peaks in the scrape-off layer (SOL) and LCFS and when incorporated in the kinetic model, results in: 1) ~30%-50% increase in the peak parallel velocity over the zero field case and, 2) broadened rotation profile into the SOL. The model-data agreement shows this mechanism is important, competing with pre-sheath acceleration and Pfirsch-Schluter drives. Computations with XGC0, a full-f particle-in-cell drift-kinetic solver with collisional kinetic ions and electrons, and NEO, a drift kinetic code with multiple species and linearized F-P collisions confirms the relevance of the ion orbit loss the impact of kinetic effects on Er and the measured C6+ and D+ velocities inside the LCFS. Measurements of D+ parallel velocity at the DIII-D edge are consistent with the kinetic loss of thermal ions as the mechanism for edge momentum generation. Edge velocity profiles exhibit a co-Ip peak velocity of 40-60 km/s in OH, L- and H-mode. The flow layer acts as a robust boundary value not affected by NBI injection. D+ velocity measurements are compared to a first-principles, collisionless, kinetic model predicting the existence of a loss-cone distribution in velocity space resulting in a co-Ip directed velocity. A fine Er structure, found by probes, has 10-20 kV/m peaks in the scrape-off layer (SOL) and LCFS and when incorporated in the kinetic model, results in: 1) ~30%-50% increase in the peak parallel velocity over the zero field case and, 2) broadened rotation profile into the SOL. The model-data agreement shows this mechanism is important, competing with pre-sheath acceleration and Pfirsch-Schluter drives. Computations with XGC0, a full-f particle-in-cell drift-kinetic solver with collisional kinetic ions and electrons, and NEO, a drift kinetic code with multiple species and linearized F-P collisions confirms the relevance of the ion orbit loss the impact of kinetic effects on Er and the measured C6+ and D+ velocities inside the LCFS. Work supported by the US DOE under DE-FG02-07ER54917, DE-FC02-08ER54977, & DE-FC02-04ER54698.

  1. 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

  2. Adaptation to Drifting Concepts

    Microsoft Academic Search

    Gladys Castillo; João Gama; Pedro Medas

    2003-01-01

    Most of supervised learning algorithms assume the stability of the target concept over time.Nevertheless in many real-user modeling systems, where the data is collected over an extended period of time, the learning task can be complicated by changes in the distribution under- lying the data.This problem is known in machine learning as concept drift.The main idea behind Statistical Quality Control

  3. Particle-in-cell simulations of the critical ionization velocity effect in finite size clouds

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Lu, G.; Goertz, C. K.; Nishikawa, K. - I.

    1994-01-01

    The critical ionization velocity (CIV) mechanism in a finite size cloud is studied with a series of electrostatic particle-in-cell simulations. It is observed that an initial seed ionization, produced by non-CIV mechanisms, generates a cross-field ion beam which excites a modified beam-plasma instability (MBPI) with frequency in the range of the lower hybrid frequency. The excited waves accelerate electrons along the magnetic field up to the ion drift energy that exceeds the ionization energy of the neutral atoms. The heated electrons in turn enhance the ion beam by electron-neutral impact ionization, which establishes a positive feedback loop in maintaining the CIV process. It is also found that the efficiency of the CIV mechanism depends on the finite size of the gas cloud in the following ways: (1) Along the ambient magnetic field the finite size of the cloud, L (sub parallel), restricts the growth of the fastest growing mode, with a wavelength lambda (sub m parallel), of the MBPI. The parallel electron heating at wave saturation scales approximately as (L (sub parallel)/lambda (sub m parallel)) (exp 1/2); (2) Momentum coupling between the cloud and the ambient plasma via the Alfven waves occurs as a result of the finite size of the cloud in the direction perpendicular to both the ambient magnetic field and the neutral drift. This reduces exponentially with time the relative drift between the ambient plasma and the neutrals. The timescale is inversely proportional to the Alfven velocity. (3) The transvers e charge separation field across the cloud was found to result in the modulation of the beam velocity which reduces the parallel heating of electrons and increases the transverse acceleration of electrons. (4) Some energetic electrons are lost from the cloud along the magnetic field at a rate characterized by the acoustic velocity, instead of the electron thermal velocity. The loss of energetic electrons from the cloud seems to be larger in the direction of plasma drift relative to the neutrals, where the loss rate is characterized by the neutral drift velocity. It is also shown that a factor of 4 increase in the ambient plasma density, increases the CIV ionization yield by almost 2 orders of magnitude at the end of a typical run. It is concluded that a larger ambient plasma density can result in a larger CIV yield because of (1) larger seed ion production by non-CIV mechanisms, (2) smaller Alfven velocity and hence weak momentum coupling, and (3) smaller ratio of the ion beam density to the ambient ion density, and therefore a weaker modulation of the beam velocity. The simulation results are used to interpret various chemical release experiments in space.

  4. Flow shear induced Compton scattering of electron drift instability

    SciTech Connect

    Hahm, T.S.

    1992-02-01

    Plasma flow shear effects on nonlinear saturation of electron drift waves are analyzed in the weak turbulence regime. Flow shear can enhance ion Compton scattering of long wavelength electron drift waves not only by modifying the beat wave-ion resonance condition, but also via the radial dependence of linear susceptibility. A nonlinear dispersion relation is obtained as a solution of the radially nonlocal nonlinear eigenmode equation. At nonlinear saturation, the spectral intensity of the fluctuations scales with flow shear as ({partial derivative}V{var phi}/{partial derivative}r){sup {minus}2} in addition to the linear dependence on the linear growth rate.

  5. Flow shear induced Compton scattering of electron drift instability

    SciTech Connect

    Hahm, T.S.

    1992-02-01

    Plasma flow shear effects on nonlinear saturation of electron drift waves are analyzed in the weak turbulence regime. Flow shear can enhance ion Compton scattering of long wavelength electron drift waves not only by modifying the beat wave-ion resonance condition, but also via the radial dependence of linear susceptibility. A nonlinear dispersion relation is obtained as a solution of the radially nonlocal nonlinear eigenmode equation. At nonlinear saturation, the spectral intensity of the fluctuations scales with flow shear as ({partial_derivative}V{var_phi}/{partial_derivative}r){sup {minus}2} in addition to the linear dependence on the linear growth rate.

  6. 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

  7. 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.

  8. 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.

  9. Fast Correction Optics to Reduce Chromatic Aberrations in Longitudinally Compressed Ion Beams

    SciTech Connect

    Lidia, S.M.; Lee, E.P.; Ogata, D.; Seidl, P.A.; Waldron, W.L.; Lund, S.M.

    2009-04-30

    Longitudinally compressed ion beam pulses are currently employed in ion-beam based warm dense matter studies [1]. Compression arises from an imposed time-dependent longitudinal velocity ramp followed by drift in a neutralized channel. Chromatic aberrations in the final focusing system arising from this chirp increase the attainable beam spot and reduce the effective fluence on target. We report recent work on fast correction optics that remove the time-dependent beam envelope divergence and minimizes the beam spot on target. We present models of the optical element design and predicted ion beam fluence.

  10. 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.

  11. Imaging and Rapid-Scanning Ion Mass Spectrometer (IRM) for the CASSIOPE e-POP Mission

    NASA Astrophysics Data System (ADS)

    Yau, Andrew W.; Howarth, Andrew; White, Andrew; Enno, Greg; Amerl, Peter

    2015-06-01

    The imaging and rapid-scanning ion mass spectrometer (IRM) is part of the Enhanced Polar Outflow Probe (e-POP) instrument suite on the Canadian CASSIOPE small satellite. Designed to measure the composition and detailed velocity distributions of ions in the ˜1-100 eV/q range on a non-spinning spacecraft, the IRM sensor consists of a planar entrance aperture, a pair of electrostatic deflectors, a time-of-flight (TOF) gate, a hemispherical electrostatic analyzer, and a micro-channel plate (MCP) detector. The TOF gate measures the transit time of each detected ion inside the sensor. The hemispherical analyzer disperses incident ions by their energy-per-charge and azimuth in the aperture plane onto the detector. The two electrostatic deflectors may be optionally programmed to step through a sequence of deflector voltages, to deflect ions of different incident elevation out of the aperture plane and energy-per-charge into the sensor aperture for sampling. The position and time of arrival of each detected ion at the detector are measured, to produce an image of 2-dimensional (2D), mass-resolved ion velocity distribution up to 100 times per second, or to construct a composite 3D velocity distribution by combining successive images in a deflector voltage sequence. The measured distributions are then used to investigate ion composition, density, drift velocity and temperature in polar ion outflows and related acceleration and transport processes in the topside ionosphere.

  12. A drift chamber telescope for high-Z particles

    SciTech Connect

    Isbert, J. [Louisiana State Univ., Baton Rouge, LA (United States)]| [Siegen Univ. (Gesamthochschule) (Germany, F.R.); Crawford, H.J.; Mathis, K.D. [California Univ., Berkeley, CA (United States). Space Sciences Lab.; Guzik, T.G.; Mitchell, J.W.; Wefel, J.P. [Louisiana State Univ., Baton Rouge, LA (United States); Hof, M.; Neuhaus, J.; Simon, M. [Siegen Univ. (Gesamthochschule) (Germany, F.R.)

    1990-02-01

    Drift chambers are one of the position sensing technologies used in cosmic ray balloon and satellite experiments with potential application to the next generation of detectors for space flight. A low mass TPC type drift chamber, employing 8 distinct drift regions within a single gas volume has been built, tested and used at the LBL Bevalac. From the drift time X-coordinate, spatial resolutions below 100 {mu}m are obtained for a variety of heavy ions with selected trigger modes. The Y-coordinate is determined by pickup pads located behind the anode wire, thereby providing both X and Y coordinates from the same avalanche. Results from different timing schemes, {delta}-ray effects and the pickup pad resolution are presented. 6 refs., 5 figs.

  13. An ion-neutral species collision model for particle simulation of glow discharge

    Microsoft Academic Search

    K. Nanbu; Y. Kitatani

    1995-01-01

    An ion-neutral species collision model with charge exchange is developed for use in particle simulation of a glow discharge based on an extension of the theory of Langevin (1905) and Hasse (1926). The validity of the model is checked by Monte Carlo calculation of drift velocity for He+-He, Ne+-Ne, Ar+-Ar and Kr+-Kr collisions. The results show good agreement with the

  14. Drift dynamics of larval pallid sturgeon and shovelnose sturgeon in a natural side channel of the Upper Missouri River, Montana

    USGS Publications Warehouse

    Braaten, P.J.; Fuller, D.B.; Holte, L.D.; Lott, R.D.; Viste, W.; Brandt, T.F.; Legare, R.G.

    2008-01-01

    The drift dynamics of larval shovelnose sturgeon Scaphirhynchus platorynchus (1, 2, 6, and 10 d posthatch [dph]) and pallid sturgeon S. albus (1, 2, 5, 9, 11, and 17 dph) were examined in a natural side channel of the Missouri River to quantify the vertical drift location of larvae in the water column, determine the drift velocity of larvae relative to water velocity, and simulate the cumulative distance (km) drifted by larvae during ontogenetic development. Larvae were released at the side-channel inlet and sampled at points 100, 500, 900, and 1,300 m downstream. Larvae drifted primarily near the riverbed, as 58-79% of recaptured shovelnose sturgeon and 63-89% of recaptured pallid sturgeon were sampled in the lower 0.5 m of the water column. The transition from the drifting to the benthic life stage was initiated at 6 dph (mean length, 15.6 mm) for shovelnose sturgeon and at 11-17 dph (mean length, 18.1-20.3 mm) for pallid sturgeon. Across ages, the drift rates of larval shovelnose sturgeon averaged 0.09-0.16 m/s slower than the mean water column velocity. The drift rates of pallid sturgeon were similar to or slightly slower (0.03-0.07 m/s) than the mean water column velocity for 1-11-dph larvae. Conversely, 17-dph larval pallid sturgeon dispersed downstream at a much slower rate (mean, 0.20 m/s slower than the mean water column velocity) owing to their transition to benthic habitats. Drift simulations indicated that the average larval shovelnose sturgeon may drift from 94 to 250 km and the average larval pallid sturgeon may drift from 245 to 530 km, depending on water velocity. Differences in larval drift dynamics between species provide a possible explanation for differences in recruitment between shovelnose sturgeon and pallid sturgeon in the upper Missouri River. ?? Copyright by the American Fisheries Society 2008.

  15. A magnetospheric critical velocity experiment - Particle results

    NASA Technical Reports Server (NTRS)

    Torbert, R. B.; Newell, P. T.

    1986-01-01

    In March of 1983, a barium injection sounding rocket experiment (The Star of Lima) was conducted to investigate Alfven's critical ionization velocity (CIV) hypothesis in space. Included in the instrumented payload was a particle detection experiment consisting of five retarding potential analyzers. Despite conditions that appeared to be optimal for the critical velocity effect, the particle data, in agreement with optical observations, indicates that a fractional ionization of only approximately .0005 was observed, indicating that the conditions required for the effect to occur are still not well understood. However many of the required phenomena associated with the CIV effect were observed; in particular a superthermal electron population was formed at the expense of ion drift kinetic energy in the presence of intense electrostatic waves near the lower hybrid frequency. The amount of ionization produced is plausibly consistent with the observed electron flux, but could also be accounted for by residual solar UV at the injection point. It is shown based on the data set that one obvious explanation for the low ionization efficiency, namely that the ionizing superthermal electrons may rapidly escape along field lines, can be ruled out.

  16. Nonlinear Evolution of the Lower-hybrid Drift Instability in a Current Sheet Wiliam Daughton1

    E-print Network

    Sitnov, Mikhail I.

    -hybrid drift instability (LHDI) is driven by the diamagnetic current in the presence of inhomo- geneitiesNonlinear Evolution of the Lower-hybrid Drift Instability in a Current Sheet Wiliam Daughton1, 2004) The evolution of an ion-scale current sheet is simulated with a fully kinetic approach using

  17. Linux-PC based 1024Channel Transient Digitizer System for the DRIFT Experiment Acquisition System

    Microsoft Academic Search

    R. Ayad; Z. Hanson-Hart; M. Hyatt; M. Katz-Hyman; P. Maher; C. J. Martoff; A. Posner; D. Freytag; M. Freytag; G. Haller; D. Nelson

    2003-01-01

    The DRIFT Experiment [1] is an underground search for WIMP Dark Matter using a novel detector invented for this purpose: the Negative Ion TPC (NITPC). The data acquisition system for DRIFT had to allow acquisition of long duration time digitized data from the 1024 analog channels at an affordable price. This was accomplished with a system based on a Linux

  18. 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 ?.

  19. An obliquely propagating electromagnetic drift instability in the lower hybrid frequency range

    E-print Network

    Ji, Hantao

    An obliquely propagating electromagnetic drift instability in the lower hybrid frequency range-fluid theory, we investigate an obliquely propagating electromagnetic instability in the lower hybrid frequency in the electron frame and the forward propagating sound (slow) wave in the ion frame when the relative drifts

  20. Gyrokinetic particle simulation of drift-compressional modes in dipole geometry

    E-print Network

    Lin, Zhihong

    Gyrokinetic particle simulation of drift-compressional modes in dipole geometry Peter Porazika magnetic dipole geometry. The compressional component is formulated in a scalar form of the parallel drift-compressional modes in the dipole geometry with kinetic ions find that finite Larmor radius (FLR

  1. 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.

  2. 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.

  3. Pulsed discharge ionization source for miniature ion mobility spectrometers

    DOEpatents

    Xu, Jun; Ramsey, J. Michael; Whitten, William B.

    2004-11-23

    A method and apparatus is disclosed for flowing a sample gas and a reactant gas (38, 43) past a corona discharge electrode (26) situated at a first location in an ion drift chamber (24), applying a pulsed voltage waveform comprising a varying pulse component and a dc bias component to the corona discharge electrode (26) to cause a corona which in turn produces ions from the sample gas and the reactant gas, applying a dc bias to the ion drift chamber (24) to cause the ions to drift to a second location (25) in the ion drift chamber (24), detecting the ions at the second location (25) in the drift chamber (24), and timing the period for the ions to drift from the corona discharge electrode to the selected location in the drift chamber.

  4. 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.

  5. 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.

  6. 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.

  7. The DRIFT-II Directional Dark Matter Detector

    Microsoft Academic Search

    2007-01-01

    The DRIFT-II detector is a negative ion time projection chamber (NITPC) with the ability to measure nuclear recoils for the purpose of detecting dark matter, reconstruct three dimensional tracks of nuclear recoils, and has the potential to set competitive limits. The directional information provides powerful background discrimination and a means to robustly verify a dark matter signal as extraterrestrial in

  8. 40 CFR 1065.550 - Gas analyzer range validation, drift validation, and drift correction.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 2010-07-01 false Gas analyzer range validation, drift validation, and drift correction. 1065.550 Section...Duty Cycles § 1065.550 Gas analyzer range validation, drift validation, and drift correction....

  9. 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 correction. 1065.550 Section...Duty Cycles § 1065.550 Gas analyzer range validation, drift validation, and drift correction....

  10. 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.

  11. A statistical analysis of systematic errors in temperature and ram velocity estimates from satellite-borne retarding potential analyzers

    SciTech Connect

    Klenzing, J. H.; Earle, G. D.; Heelis, R. A.; Coley, W. R. [William B. Hanson Center for Space Sciences, University of Texas at Dallas, 800 W. Campbell Rd. WT15, Richardson, Texas 75080 (United States)

    2009-05-15

    The use of biased grids as energy filters for charged particles is common in satellite-borne instruments such as a planar retarding potential analyzer (RPA). Planar RPAs are currently flown on missions such as the Communications/Navigation Outage Forecast System and the Defense Meteorological Satellites Program to obtain estimates of geophysical parameters including ion velocity and temperature. It has been shown previously that the use of biased grids in such instruments creates a nonuniform potential in the grid plane, which leads to inherent errors in the inferred parameters. A simulation of ion interactions with various configurations of biased grids has been developed using a commercial finite-element analysis software package. Using a statistical approach, the simulation calculates collected flux from Maxwellian ion distributions with three-dimensional drift relative to the instrument. Perturbations in the performance of flight instrumentation relative to expectations from the idealized RPA flux equation are discussed. Both single grid and dual-grid systems are modeled to investigate design considerations. Relative errors in the inferred parameters for each geometry are characterized as functions of ion temperature and drift velocity.

  12. Repository Drift Backfilling Demonstrator

    SciTech Connect

    Londe, I.; Dubois, J.Ph.; Bauer, C. [Agence Nationale pour la Gestion des Dechets Radioactifs (ANDRA), 92 - Chatenay Malabry (France)

    2008-07-01

    The 'Backfilling Demonstrator' is one of the technological demonstrators developed by ANDRA in the framework of the feasibility studies for a geological repository for high-level long-lived (HL-LL waste) within a clay formation. The demonstrator concerns the standard and supporting backfills as defined in Andra's 2005 design. The standard backfill is intended to fill up almost all drifts of the underground repository in order to limit any deformation of the rock after the degradation of the drift lining. The supporting backfill only concerns a small portion of the volume to be backfilled in order to counter the swelling pressure of the swelling clay contained in the sealing structures. The first objective of the demonstrator was to show the possibility of manufacturing a satisfactory backfill, in spite of the exiguity of the underground structures, and of reusing as much as possible the argillite muck. For the purpose of this experiment, the argillite muck was collected on Andra's work-site for the implementation of an underground research laboratory. Still ongoing, the second objective is to follow up the long-term evolution of the backfill. Approximately 200 m{sup 3} of compacted backfill material have been gathered in a large concrete tube simulating a repository drift. The standard backfill was manufactured exclusively with argillite. The supporting backfill was made by forming a mixture of argillite and sand. Operations were carried out mostly at Richwiller, close to Mulhouse, France. The objectives of the demonstrator were met: an application method was tested and proven satisfactory. The resulting dry densities are relatively high, although the moduli of deformation do not always reach the set goal. The selected objective for the demonstrator was a dry density corresponding to a relatively high compaction level (95% of the standard Proctor optimum [SPO]), for both pure argillite and the argillite-sand mixture. The plate-percussion compaction technique was used and proved satisfactory. The measured dry densities are higher than the 95%-SPO objective. The implementation rates remain very low due to the experimental conditions involved. The metal supply mode would need to be revised before any industrial application is contemplated. The Demonstrator Program started in August 2004 and is followed up today over the long term. With that objective in mind, sensors and a water-saturation system have been installed. (author)

  13. 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,

  14. Gyrokinetic theory of electrostatic lower-hybrid drift instabilities in a current sheet with guide field

    SciTech Connect

    Tummel, K., E-mail: tummel08@gmail.com [Department of Physics and Astronomy, University of California at Irvine, Irvine, California 92697 (United States); Chen, L. [Institute for Fusion Theory and Simulation and Department of Physics, ZheJiang University, Hang Zhou, ZheJiang 310058 (China) [Institute for Fusion Theory and Simulation and Department of Physics, ZheJiang University, Hang Zhou, ZheJiang 310058 (China); Department of Physics and Astronomy, University of California at Irvine, Irvine, California 92697 (United States); Wang, Z.; Wang, X. Y.; Lin, Y. [Department of Physics, Auburn University, Auburn, Alabama 36849 (United States)] [Department of Physics, Auburn University, Auburn, Alabama 36849 (United States)

    2014-05-15

    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{sub ?}. 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{sub ?} 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)].

  15. 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.

  16. A laboratory study of ion energization by EIC waves and subsequent upstreaming along diverging magnetic field lines

    NASA Technical Reports Server (NTRS)

    Cartier, S. L.; Dangelo, N.; Merlino, R. L.

    1986-01-01

    A laboratory study related to energetic upstreaming ions in the ionosphere-magnetosphere system is described. The experiment was carried out in a cesium Q machine plasma with a region of nonuniform magnetic field. Electrostatic ion cyclotron waves were excited by drawing an electron current to a small biased exciter electrode. In the presence of the instability, ions are heated in the direction perpendicular to B. Using a gridded retarding potential ion energy analyzer, the evolution of the ion velocity distribution was followed as the ions passed through the heating region and subsequently flowed out along the diverging B field lines. As expected, the heated ions transfer their energy from perpendicular to parallel motion as they move through the region of diverging B field. Both their parallel thermal energy and the parallel drift energy increase at the expense of the perpendicular energy.

  17. 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.

  18. 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.

  19. CuI, gamma modification: electron mobility, drift velocity

    NASA Astrophysics Data System (ADS)

    Hönerlage, B.

    This document is part of Volume 44 `Semiconductors', Subvolume A `New Data and Updates for I-VII, III-V, III-VI and IV-VI Compounds' of Landolt-Börnstein Group III `Condensed Matter'. It contains data on CuI (cuprous iodide), Element System Cu-I.

  20. 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.

  1. Electrodeless drift chambers with 50-cm drift distance

    SciTech Connect

    Ayres, D.S.; Price, L.E.

    1982-08-01

    The electrodeless drift-chamber technique is potentially very useful in applications requiring the drifting of ionization in gas over long distances in narrow channels. Chamber construction is simple and cheap; the technique is well suited to very large detectors operating in low-rate environments. Prototype tests on planar chambers reveal excellent drifting characteristics after the initial charging, but show a substantial degradation of pulse height from cosmic rays over a two-week period. The loss of efficiency appears to be caused by excess charge buildup on the dielectric surfaces of the chamber. Several solutions are suggested.

  2. Ion Collision, Theory

    SciTech Connect

    Shukla, Anil K.

    2013-09-11

    The outcome of a collision between an ion and neutral species depends on the chemical and physical properties of the two reactants, their relative velocities, and the impact parameter of their trajectories. These include elastic and inelastic scattering of the colliding particles, charge transfer (including dissociative charge transfer), atom abstraction, complex formation and dissociation of the colliding ion. Each of these reactions may be characterized in terms of their energy-dependent rate coefficients, cross sections and reaction kinetics. A theoretical framework that emphasizes simple models and classical mechanics is presented for these processes. Collision processes are addressed in two categories of low-energy and high-energy collisions. Experiments under thermal or quasi-thermal conditions–swarms, drift tubes, chemical ionization and ion cyclotron resonance are strongly influenced by long-range forces and often involve collisions in which atom exchange and extensive energy exchange are common characteristics. High-energy collisions are typically impulsive, involve short-range intermolecular forces and are direct, fast processes.

  3. Dust-lower-hybrid drift instabilities with dust charge fluctuations in an inhomogeneous dusty magnetoplasma.

    PubMed

    Salimullah, M; Rizwan, A M; Nambu, M; Nitta, H; Shukla, P K

    2004-08-01

    Effects of a uniform magnetic field, the plasma inhomogeneity, and dust charge fluctuations on low-frequency dust-lower-hybrid drift waves have been investigated. Charging currents of electrons and ions to a spherical dust grain in a nonuniform magnetized dusty plasma have been calculated to study the charge fluctuation induced damping or growth of low-frequency drift waves. It is found that for strongly magnetized electrons and ions, the charge fluctuation damping is reduced significantly from that of an unmagnetized plasma. For sufficiently hot electrons, the drift wave exhibits instability in the absence of dust charge fluctuation damping. PMID:15447598

  4. Effects of finite plasma beta on the lower-hybrid-drift instability

    NASA Technical Reports Server (NTRS)

    Davidson, R. C.; Gladd, N. T.; Wu, C. S.; Huba, J. D.

    1977-01-01

    The local dispersion relation for the lower-hybrid-drift (LHD) instability is derived and analyzed, taking into account the finite-beta effects associated with transverse electromagnetic perturbations as well as with resonant and nonresonant electron-orbit modifications due to magnetic-field gradients. The influence of finite-beta effects on the LHD instability is calculated in a fully self-consistent manner for arbitrary values of electron-ion temperature ratio, local beta, cross-field ExB velocity/ion thermal speed ratio, and other plasma parameters. Stability properties are investigated analytically for the case of cold electrons, and the local dispersion relation is solved numerically in the parameter regime of most interest for high-density plasma pinches. The results show that for all parameter regimes studied, the net effect of finite plasma beta is to reduce the maximum growth rate of the LHD instability, although the details can vary, depending on the plasma parameters. Except in the limit where the electron/ion temperature ratio tends to zero, it is found that there is a critical value of plasma beta above which the LHD instability is completely stabilized.

  5. Quasicrystallization of vortices in drift-wave turbulence

    SciTech Connect

    Kukharkin, N.; Orszag, S.A.; Yakhot, V. [Fluid Dynamics Research Center, Princeton University, Princeton, New Jersey 08544 (United States)] [Fluid Dynamics Research Center, Princeton University, Princeton, New Jersey 08544 (United States)

    1995-09-25

    The formation and dynamics of coherent vortices in the Hasegawa-Mima two-dimensional model of drift-wave turbulence is studied numerically. The effect of ``vortex shielding`` due to the presence of a characteristic length scale (ion Larmor radius {rho}{sub {ital s}}) leads to important differences between self-organization in drift-wave and Navier-Stokes fluid turbulence. While it may not be surprising that a finite deformation radius leads to the formation of coherent vortices, we show here that it also results in the appearance of long-range order in the system, i.e., the formation of a vortical ``quasicrystal.``

  6. 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.

  7. 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.

  8. 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

  9. Superluminal apparent velocities of relativistic electron beams in the solar corona

    NASA Astrophysics Data System (ADS)

    Klassen, A.; Karlický, M.; Mann, G.

    2003-10-01

    We present spectral and imaging observations of high frequency type III bursts appearing in pairs: a primary fast drifting component and a secondary ``normal" drifting component. The primary bursts have generally higher frequency drift and start at higher frequencies. They show superluminal velocities up to 2.5 c (c, speed of light), while the secondary component shows the usual <0.5 c velocity expected for type III burst exciters. These superluminal velocities are explained as apparent velocities of relativistic electron beams propagating nearly along the line of sight towards the observer with velocities close to the speed of light. A model of type III burst pairs consisting of subsequent fast drifting and ``normal" drifting components is presented.

  10. 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

  11. Ion Trap/Ion Mobility/Quadrupole/Time-of-Flight Mass Spectrometry for Peptide Mixture Analysis

    E-print Network

    Clemmer, David E.

    Ion Trap/Ion Mobility/Quadrupole/Time-of-Flight Mass Spectrometry for Peptide Mixture Analysis IN, 47405 An ion trap/ion mobility/quadrupole/time-of-flight mass spectrometer has been developed tube where ions separate ac- cording to differences in gas-phase ion mobilities. Upon exiting the drift

  12. New concepts for drift pumping a thermal barrier with rf

    SciTech Connect

    Barter, J.D.; Baldwin, D.; Chen, Y.; Poulsen, P.

    1985-05-09

    Pump neutral beams, which are directed into the loss cone of the TMX-U plugs, are normally used to pump ions from the thermal barriers. Because these neutral beams introduce cold gas that reduces pumping efficiency, and require a straight line entrance and exit from the plug, alternate methods are being investigated to provide barrier pumping. To maintain the thermal barrier, either of two classes of particles can be pumped. First, the collisionally trapped ions can be pumped directly. In this case, the most promising selection criterion is the azimuthal drift frequency. Second, the excess sloshing-ion density can be removed, allowing the use of increased sloshing-beam density to pump the trapped ions. The selection mechanism in this case is the Doppler-shifted ion-cyclotron resonance of the high-energy sloshing-ions (3 keV less than or equal to U/sub parallel/ less than or equal to 10 keV).

  13. Positron drift in molecular hydrogen

    Microsoft Academic Search

    N. Bose; D. A. L. Paul; J.-S. Tsai

    1981-01-01

    Measurements of positron drift in H2 gas have been made in the pressure range 10-200 Torr between 0 and 4 Td. A shape analysis gives a universal function W\\/Zeff. Using the annihilation parameter Zeff=13.6, the drift speed W increases linearly up to 2.9*105 cm s-1 at 1 Td. Above 1.4 Td there is evidence for positronium formation. These are the

  14. Pulsed Drift Tube Accelerator

    SciTech Connect

    Faltens, A.

    2004-10-25

    The pulsed drift-tube accelerator (DTA) concept was revived by Joe Kwan and John Staples and is being considered for the HEDP/WDM application. It could be used to reach the full energy or as an intermediate accelerator between the diode and a high gradient accelerator such as multi-beam r.f. In the earliest LBNL HIF proposals and conceptual drivers it was used as an extended injector to reach energies where an induction linac with magnetic quadrupoles is the best choice. For HEDP, because of the very short pulse duration, the DTA could provide an acceleration rate of about 1MV/m. This note is divided into two parts: the first, a design based on existing experience; the second, an optimistic extrapolation. The first accelerates 16 parallel K{sup +} beams at a constant line charge density of 0.25{micro} C/m per beam to 10 MeV; the second uses a stripper and charge selector at around 4MeV followed by further acceleration to reach 40 MeV. Both benefit from more compact sources than the present 2MV injector source, although that beam is the basis of the first design and is a viable option. A pulsed drift-tube accelerator was the first major HIF experiment at LBNL. It was designed to produce a 2{micro}s rectangular 1 Ampere C{sub s}{sup +} beam at 2MeV. It ran comfortably at 1.6MeV for several years, then at lower voltages and currents for other experiments, and remnants of that experiment are in use in present experiments, still running 25 years later. The 1A current, completely equivalent to 1.8A K{sup +}, was chosen to be intermediate between the beamlets appropriate for a multi-beam accelerator, and a single beam of, say, 10A, at injection energies. The original driver scenarios using one large beam on each side of the reactor rapidly fell out of favor because of the very high transverse and longitudinal fields from the beam space charge, circa 1MV/cm and 250 kV/cm respectively, near the chamber and because of aberrations in focusing a large diameter beam down to a 1mm radius spot at a distance of 10m. Almost all subsequent work and the present concept have invoked multiple beams. For HEDP the major differences are that the focal distance can be centimeters instead of meters, provided strong-enough lenses exist and they do, thereby allowing much higher transverse and longitudinal emittances than driver concepts, and focusing parallel small beams is easier than one big beam.

  15. Using multiple windows to track concept drift

    Microsoft Academic Search

    Mihai Lazarescu; Svetha Venkatesh; Hung Hai Bui

    2004-01-01

    In this paper we present a multiple window incremental learning algorithm that distin- guishes between virtual concept drift and real concept drift. The algorithm is unsupervised and uses a novel approach to tracking concept drift that involves the use of competing windows to interpret the data. Unlike previous methods which use a single window to determine the drift in the

  16. 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.

  17. Sunward Propagating Alfvén Waves in Association with Sunward Drifting Proton Beams in the Solar Wind

    NASA Astrophysics Data System (ADS)

    He, Jiansen; Pei, Zhongtian; Wang, Linghua; Tu, Chuanyi; Marsch, Eckart; Zhang, Lei; Salem, Chadi

    2015-06-01

    Using measurements from the WIND spacecraft, here we report the observation of sunward propagating Alfvén waves (AWs) in solar wind that is magnetically disconnected from the Earth's bow shock. In the sunward magnetic field sector, we find a period lasting for more than three days in which there existed (during most time intervals) a negative correlation between the flow velocity and magnetic field fluctuations, thus indicating that the related AWs are mainly propagating sunward. Simultaneous observations of counter-streaming suprathermal electrons suggest that these sunward AWs may not simply be due to the deflection of an open magnetic field line. Moreover, no interplanetary coronal mass ejection appears to be associated with the counter-streaming suprathermal electrons. As the scale goes from the magnetohydrodynamic down to the ion kinetic regime, the wave vector of magnetic fluctuations usually becomes more orthogonal to the mean magnetic field direction, and the fluctuations become increasingly compressible, which are both features consistent with quasi-perpendicular kinetic AWs. However, in the case studied here, we find clear signatures of quasi-parallel sunward propagating ion-cyclotron waves. Concurrently, the solar wind proton velocity distribution reveals a sunward field-aligned beam that drifts at about the local Alfvén speed. This beam is found to run in the opposite direction of the normally observed (anti-sunward) proton beam, and is apparently associated with sunward propagating Alfvén/ion-cyclotron waves. The results and conclusions of this study enrich our knowledge of solar wind turbulence and foster our understanding of proton heating and acceleration within a complex magnetic field geometry.

  18. Apparatus and method for laser velocity interferometry

    DOEpatents

    Stanton, Philip L. (Bernalillo County, NM); Sweatt, William C. (Albuquerque, NM); Crump, Jr., O. B. (Albuquerque, NM); Bonzon, Lloyd L. (Albuquerque, NM)

    1993-09-14

    An apparatus and method for laser velocity interferometry employing a fixed interferometer cavity and delay element. The invention permits rapid construction of interferometers that may be operated by those non-skilled in the art, that have high image quality with no drift or loss of contrast, and that have long-term stability even without shock isolation of the cavity.

  19. Filamental quenching of the current-driven ion-cyclotron instability

    NASA Technical Reports Server (NTRS)

    Cartier, S. L.; Dangelo, N.; Merlino, R. L.; Krumm, P. H.

    1985-01-01

    Since their discovery by D'Angelo and Motley (1962), ion-cyclotron waves have been an area of active research. Drummond and Rosenbluth (1962) have first conducted a theoretical analysis of the current-driven ion-cyclotron wave instability, taking into account a uniform, magnetized plasma, without magnetic shear, in which electrons drift along B field lines with the same drift velocity at all points in the plasma. Bakshi et al. (1983) have found conditions for which the instability is completely quenched. This phenomenon has been referred to as filamental quenching. The present investigation is concerned with a systematic test of the filamental quenching effect. It is found that filamental quenching operates at widths of the current channel comparable to the local Larmor radius, in agreement with the conclusions of Bakshi et al.

  20. Local drift parameter, j/n/sub e/ and resistivity anomaly measurements in CTX spheromaks

    SciTech Connect

    Hoida, H.W.; Barnes, C.W.; Henins, I.; Jarboe, T.R.; Buchenauer, C.J.; Marklin, G.J.

    1985-01-01

    The ratio of the electron drift velocity to the electron thermal velocity, also known as the drift parameter (streaming parameter), and j/n/sub e/(approx.V/sub d/) have been measured locally at the magnetic axis in CTX spheromaks at Los Alamos. The drift parameter and j/n/sub e/ appear to be correlated with local measurements of the resistivity anomaly (eta/eta/sub Spitz/) at the magnetic axis. The drift parameter and j/n/sub e/ are varied by changing the background fill pressure. Data is presented for three cases: high density (6mT fill), medium density (4mT fill) and low density (0mT fill).

  1. Structure of parallel-velocity-shear-driven mode in toroidal plasmas

    NASA Astrophysics Data System (ADS)

    Dong, J. Q.; Xu, W. B.; Zhang, Y. Z.; Horton, W.

    1998-12-01

    It is shown that the Fourier-ballooning representation is appropriate for the study of short-wavelength drift-like perturbation in toroidal plasmas with a parallel velocity shear (PVS). The radial structure of the mode driven by a PVS is investigated in a torus. The Reynolds stress created by PVS turbulence, and proposed as one of the sources for a sheared poloidal plasma rotation, is analyzed. It is demonstrated that a finite ion temperature may strongly enhance the Reynolds stress creation ability from PVS-driven turbulence. The correlation of this observation with the requirement that ion heating power be higher than a threshold value for the formation of an internal transport barrier is discussed.

  2. 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).

  3. 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

  4. A method of estimation of the results of reconstruction of the trajectories of drifting buoys

    Microsoft Academic Search

    A. P. Tolstosheev

    2009-01-01

    A method for the estimation of the results of reconstruction of the trajectories of drifting buoys is proposed. It is based\\u000a on the comparison of the estimates of power spectral densities for the components of current velocity computed according to\\u000a three data sets: the data set of the coordinates of a drifting buoy with a built-in GPS receiver, the data

  5. Effect of drift-acoustic waves on magnetic island stability in slab R. Fitzpatrick and F.L. Waelbroeck

    E-print Network

    Fitzpatrick, Richard

    Effect of drift-acoustic waves on magnetic island stability in slab geometry R. Fitzpatrick and F evolution equation in the presence of drift-acoustic waves. The calculation is fully nonlinear, includes- acoustic waves. Wave emission gives rise to rapid oscillations in the ion polarization term as the island

  6. 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.

  7. Particle and wave observations of low-altitude ionospheric ion acceleration events

    SciTech Connect

    Yau, A.W.; Whalen, B.A.; McNamara, A.G.; Kellogg, P.J.; Bernstein, W.

    1983-01-01

    We report energetic ion and electron, wave, and ambient plasma observations from two sounding rockets which were launched from Churchill, Canada, into the expansive phases of two auroral substorms and which passed through source regions of transversely accelerated ionospheric ions (TAI). The two events were observed at low altitude (400--600 km) and resulted in ion energization of hundreds of electron volts. In the acceleration region, the ionospheric ion velocity distribution function in the direction perpendicular to the local magnetic field (perpendicularB) displayed a distinct, non-Maxwellian, high-energy tail, suggesting ion cyclotron heating. The plasma density was lower than theoretical quiescent values, by as much as 2 decades in the stronger event. Strong thermal ion drift was observed in the perpendicular (perpendicularB) direction, but was absent in the parallel (parallelB) direction. Large-amplitude, low-frequency fluctuations in plasma density were present, and a number of wave modes were observed, including upper hybrid and Langmuir waves, and whistler, ion acoustic, and ion cyclotron waves. No consistent correlation existed between the energetic particle precipitation and the TAI. However, strong field-aligned electron enchancements were observed at times coincident with the TAI acceleration region. The characteristics of the TAI ion energy spectra were consistent with a simple model of ion cyclotron acceleration and energy loss due to ion-neutral collisions. These observations are discussed in terms of current theories on electrostatic ion cyclotron acceleration and lower hybrid acceleration.

  8. Neoclassical electron and ion transport in toroidally rotating plasmas

    SciTech Connect

    Sugama, H. [National Institute for Fusion Science, Nagoya 464-01 (Japan)] [National Institute for Fusion Science, Nagoya 464-01 (Japan); Horton, W. [Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712 (United States)] [Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712 (United States)

    1997-06-01

    Neoclassical transport processes of electrons and ions are investigated in detail for toroidally rotating axisymmetric plasmas with large flow velocities on the order of the ion thermal speed. The Onsager relations for the flow-dependent neoclassical transport coefficients are derived from the symmetry properties of the drift kinetic equation with the self-adjoint collision operator. The complete neoclassical transport matrix with the Onsager symmetry is obtained for the rotating plasma consisting of electrons and single-species ions in the Pfirsch{endash}Schl{umlt u}ter and banana regimes. It is found that the inward banana fluxes of particles and toroidal momentum are driven by the parallel electric field, which are phenomena coupled through the Onsager symmetric off-diagonal coefficients to the parallel currents caused by the radial thermodynamic forces conjugate to the inward fluxes, respectively. {copyright} {ital 1997 American Institute of Physics.}

  9. Helium, hydrogen, and oxygen velocities observed on isee-3

    SciTech Connect

    Ogilvie, K.W. (Maryland Univ., College Park); Coplan, M.A. (LASL)

    1982-03-01

    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.

  10. The Transpolar Drift in the Central Arctic Ocean as Measured by AON Observations

    NASA Astrophysics Data System (ADS)

    Morison, J.; Andersen, R.; Kwok, R.; Smethie, W. M., Jr.; Rigor, I. G.; Alkire, M. B.; Newton, R.; Schlosser, P.; Steele, M.

    2014-12-01

    The Transpolar Drift of sea ice across Arctic Ocean was arguably the first major element of Arctic Ocean circulation to be discovered. Nansen's plan for his pioneering Fram expedition was based on the observation of the drift of the wreckage of the De Long's ill-fated Jeanette from near Wrangle Island to the southern coast of Greenland. In this context the Transpolar Drift characterizes the large-scale motion of sea ice, but the term can be applied to the geostrophic circulation of the upper ocean as well. The Transpolar Drift of sea ice and upper ocean are related because both are driven, at least in part, by the gradient in dynamic ocean topography (DOT, sea surface height - geoid) associated with the Transpolar Front between Pacific and Atlantic-derived waters. Starting in the 1990s, major changes in direction of the ocean and ice transpolar drifts characterized shifts between anticyclonic and cyclonic ocean circulation. These affect the dominant pathways of ice, freshwater, and chemical constituents through Arctic Basin. Consequently, tracking behavior of the Transpolar Drift has been a high priority for the AON North Pole Environmental Observatory (NPEO). Recent hydrographic sections across the 90°E (from NPEO) and 90°W (from the Switchyard Project) longitude lines mainly straddle the Drift so that dynamic heights derived from the hydrography can be used as a proxy for DOT, and annual sections of geostrophic velocity determined. Sections along 0° and 180° longitude usually cross the Transpolar Front and Drift at a more oblique angle but provide a measure of Transpolar Drift direction. Hydrography results will be compared with DOT from satellite remote sensing, optimally interpolated satellite and buoy-derived ice drift, and changes in chemical constituents to describe the significance of and recent changes in the Transpolar Drift.

  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. Renormalized non-modal theory of the kinetic drift instability of plasma shear flows

    SciTech Connect

    Mikhailenko, V. S.; Mikhailenko, V. V. [Department of Physics and Technology, V. N. Karazin Kharkov National University, 61108 Kharkov (Ukraine); Stepanov, K. N. [National Science Center, 'Kharkov Institute of Physics and Technology', 61108 Kharkov (Ukraine)

    2011-06-15

    The linear and renormalized nonlinear kinetic theory of drift instability of plasma shear flow across the magnetic field, which has the Kelvin's method of shearing modes or the so-called non-modal approach as its foundation, is developed. The developed theory proves that the time-dependent effect of the finite ion Larmor radius is the key effect, which is responsible for the suppression of drift turbulence in an inhomogeneous electric field. This effect leads to the non-modal decrease of the frequency and growth rate of the unstable drift perturbations with time. We find that turbulent scattering of the ion gyrophase is the dominant effect which determines the extremely rapid suppression of drift turbulence in shear flow.

  13. Behavior of N2+ Ions in He Microplasma Jet at Atmospheric Pressure Measured by Laser Induced Fluorescence Spectroscopy

    NASA Astrophysics Data System (ADS)

    Urabe, Keiichiro; Ito, Yosuke; Tachibana, Kunihide; Ganguly, Biswa N.

    2008-06-01

    The behavior of N2+ ions in a low-frequency driven atmospheric pressure He plasma jet effused into ambient air was analyzed from laser induced fluorescence (LIF) spectroscopy measurements. The gas temperature derived from the rotational distribution was kept near room temperature and the drift velocity of N2+ ions estimated from the line shape was almost zero as compared to the apparent speed of the plasma bunch given by the spatiotemporal intensity profile. This shows that the mechanism of moving plasma bunches can be attributed to the ionization wave propagation similar to the streamer in positive corona discharge.

  14. Velocity determination from velocity spectra

    E-print Network

    Yang, Sung Jin

    1973-01-01

    . correction values, ms Sp no. correction values, ms 1 2 3 4 5 6 7 8 9 10 ll 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 source 30 30 32 27 27 27 33 33 32 29 25 25 29 27 25 25 25 26 31 40 23 23... Figure 14. CDP gathers at some shot points. . . Figure 15. Velocity spectra at SP 12. 5 and 20. 5. . 30 Figure 16. Velocity spectra at SP 28. 5 and 39. . 31 Figure 17. Velocity spectra at SP 43 and 52. . Figure 18. Stacked section. 37 Figure 19...

  15. Velocity determination from velocity spectra 

    E-print Network

    Yang, Sung Jin

    1973-01-01

    . on from Velocity Spectra (December 1973) Sung Jin Yang, B. S. Seoul National University; Korea Directed by: Dr. Anthony F. Gangi The reflected signals on the traces of a common-depth-point (CDP) gather appear along a hyperbolic curve which is a...VELOCITY DETERMINATION FRON VELOCITY SPECTRA A Thesis by SUNG JIN YANG Submutted to the Graduate C:lleEe of Texas ASM University in partial fulfill sent of requirement for the degree of EASTER GF SCIENCE December 1973 Naj or Subject...

  16. Effect of ion temperature on arbitrary amplitude Kinetic Alfvén solitons in a plasma with a q-nonextensive electron velocity distribution

    NASA Astrophysics Data System (ADS)

    Ahmed, M. K.; Sah, O. P.

    2014-09-01

    Taking into account of ion temperature effect, existence conditions of arbitrary amplitude solitary Kinetic Alfvén Waves (KAWs) in a plasma with q-nonextensive electrons are investigated by the conventional Sagdeev pseudo potential method. It is found that only solitons with density hump can exist, the amplitude of which depends sensitively on the parameter q, ion temperature () and plasma ?. There is an upper limit of solitary wave amplitude which decreases with increase of q, ? and ?. The amplitude of solitary KAWs is found to increase with increase in ion temperature. The results obtained in the framework of Maxwellian distribution are reproduced when q?1.

  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. Ion-beam-driven electrostatic ion cyclotron instabilities

    SciTech Connect

    Miura, A.; Okuda, H.; Ashour-Abdalla, M.

    1982-10-01

    We present results of numerical simulations on the electrostatic ion cyclotron instabilities driven by the ion beam parallel to the magnetic field. For the beam speed exceeding the thermal speed of background ions and the beam temperature much lower than the background ion temperature, it is found that the instability results in strong perpendicular heating and slowing down of parallel drift of the beam ions, leading to the saturation of the instability. Applications to plasma heating and space plasma physics are discussed.

  19. First Principles Based Reactive Atomistic Simulations to Understand the Effects of Molecular Hyper Velocity Impact on Cassini's Ion and Neutral Mass Spectrometer

    NASA Astrophysics Data System (ADS)

    Jaramillo-Botero, A.; Cheng, M. J.; Cvicek, V.; Beegle, L. W.; Hodyss, R.; Goddard, W. A.

    2011-03-01

    We have used the recently developed electron force field (eFF) and ReaxFF reactive force field to simulate the hypervelocity impacts experienced by the Cassini ion and neutral mass spectrometer during the Enceladus and Titian encounters.

  20. Theory for the critical ionization velocity phenomenon

    Microsoft Academic Search

    T. Abe

    1984-01-01

    The critical velocity for the explosive ionization of a neutral gas flowing in a magnetic field and a background plasma is formulated using a macroscopic theory, assuming an unstable velocity distribution for the newly formed ions (NFI) and electron heating by the resulting fluctuating electric field. The initial conditions under which the critical velocity can operate are defined, and the

  1. The Continental Drift Convection Cell

    NASA Astrophysics Data System (ADS)

    Whitehead, J. A.; Behn, M. D.

    2014-12-01

    Continents on Earth periodically assemble to form supercontinents, and then break up again into smaller continental blocks (the Wilson Cycle). Highly developed but realistic numerical models cannot resolve if continents respond passively to mantle convection or whether they modulate flow. Our simplified numerical model addresses this problem: A thermally insulating continent floats on a stress-free surface for infinite Prandtl number cellular convection with constant material properties in a chamber 8 times longer than its depth. The continent moves back and forth across the chamber driven by a "continental drift convection cell" of a form not previously described. Subduction exists at the upstream end with cold slabs dipping at an angle beneath the moving continent. Fluid moves with the continent in the upper region of this cell with return flow near the bottom. Many continent/subduction regions on Earth have these features. The drifting cell enhances vertical heat transport by approximately 30% compared to a fixed continent, especially at the core-mantle boundary, and significantly decreases lateral mantle temperature differences. However, continent drift or fixity has smaller effects on profiles of horizontally averaged temperature. Although calculations are done at Rayleigh numbers lower than expected for Earth's mantle (2x105 and 106), the drift speed extrapolates to reasonable Wilson Cycle speeds for larger Ra.

  2. 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.

  3. 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.

  4. 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.

  5. 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 ...

  6. 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

  7. 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 ...

  8. 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 ...

  9. 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.

  10. Improved sliced velocity map imaging apparatus optimized for H photofragments.

    PubMed

    Ryazanov, Mikhail; Reisler, Hanna

    2013-04-14

    Time-sliced velocity map imaging (SVMI), a high-resolution method for measuring kinetic energy distributions of products in scattering and photodissociation reactions, is challenging to implement for atomic hydrogen products. We describe an ion optics design aimed at achieving SVMI of H fragments in a broad range of kinetic energies (KE), from a fraction of an electronvolt to a few electronvolts. In order to enable consistently thin slicing for any imaged KE range, an additional electrostatic lens is introduced in the drift region for radial magnification control without affecting temporal stretching of the ion cloud. Time slices of ?5 ns out of a cloud stretched to ?50 ns are used. An accelerator region with variable dimensions (using multiple electrodes) is employed for better optimization of radial and temporal space focusing characteristics at each magnification level. The implemented system was successfully tested by recording images of H fragments from the photodissociation of HBr, H2S, and the CH2OH radical, with kinetic energies ranging from <0.4 eV to >3 eV. It demonstrated KE resolution ?1%-2%, similar to that obtained in traditional velocity map imaging followed by reconstruction, and to KE resolution achieved previously in SVMI of heavier products. We expect it to perform just as well up to at least 6 eV of kinetic energy. The tests showed that numerical simulations of the electric fields and ion trajectories in the system, used for optimization of the design and operating parameters, provide an accurate and reliable description of all aspects of system performance. This offers the advantage of selecting the best operating conditions in each measurement without the need for additional calibration experiments. PMID:24981528

  11. A note on electrostatic ion\\/dust cyclotron instabilities in dusty plasmas

    Microsoft Academic Search

    V. W. Chow; M. Rosenberg

    1998-01-01

    The electrostatic dust cyclotron instability (EDC) in dusty plasmas is somewhat analogous to the electrostatic ion cyclotron instability (EIC) in electron-ion plasmas, negative ion plasmas, and dusty plasmas. While the EIC instability can be driven by an electron drift along the magnetic field, the EDC instability can be driven by an ion drift along B in a plasma with negatively

  12. Vlasov-Maxwell kinetic simulations of radio-frequency-driven ion flows in magnetized plasmas.

    PubMed

    Marchetto, Chiara; Califano, Francesco; Lontano, Maurizio

    2003-02-01

    The generation of a coherent ion flow due to the injection in a plasma of a purely electrostatic wave of finite amplitude, propagating at right angle with the ambient uniform magnetic field, is investigated making use of a kinetic code which solves the fully nonlinear Vlasov equations for electrons and ions, coupled with the Maxwell equations, in one spatial and two velocity dimensions. A uniformly magnetized slab plasma is considered. The wave frequency is assumed in the range of the fourth harmonic of the ion cyclotron frequency, and the wave vector is chosen in order to model the propagation of an ion Bernstein wave. The computation of the first-order moment of the ion distribution function shows that indeed a quasistationary transverse average ion drift velocity is produced. The time evolution of the ion distribution function undergoes a "resonant" interaction of Cherenkov type, even if the plasma ions are magnetized (omega(ci)/omega(pi) approximately 0.5). During the wave-plasma interaction, the electron distribution function remains Gaussian-like, while increasing its energy content. PMID:12636820

  13. MACROINVERTEBRATE STREAM DRIFT - AN AUSTRALIAN EXAMPLE

    Microsoft Academic Search

    D. P. THORNTON

    The flow of organisms in lotic environments is known as Macroinvertebrate Stream Drift: a phenomenon that has long fascinated freshwater ecologists. Stream-dwelling organisms are often transported downstream in the water column in substantial numbers. Because they have limited swimming ability and the movement is apparently passive, the process is referred to as drift. This study assesses drift fauna in a

  14. 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...

  15. Categorizing and mining concept drifting data streams

    Microsoft Academic Search

    Peng Zhang; Xingquan Zhu; Yong Shi

    2008-01-01

    Mining concept drifting data streams is a defining challenge for data mining research. Recent years have seen a large body of work on detecting changes and building prediction models from stream data, with a vague understanding on the types of the concept drifting and the impact of different types of concept drifting on the mining algorithms. In this paper, we

  16. Tracking Drifting Concepts by Time Window Optimisation

    E-print Network

    Koychev, Ivan

    the training dataset. This problem is known in the area of machine learning as concept drift. We develop to detect concept drift and then optimizes the size of the time window, aiming to maximise to be `forgotten'. This problem is known as concept drift [16]. A prominent example of a system that should adapt

  17. Adaptive Concept Drift Detection Anton Dries

    E-print Network

    Morik, Katharina

    to detect concept drift in data streams is to perform statistical hypothesis testing on the multivariateAdaptive Concept Drift Detection Anton Dries Ulrich R¨uckert Abstract An established method- based tests outperform the multivariate Wald-Wolfowitz test for concept drift detection. We also show

  18. Terminal Velocity

    NSDL National Science Digital Library

    Michael Horton

    2009-05-30

    This lab is an inquiry activity in that students have not been exposed to the idea of terminal velocity, though they are using skills that they already have to analyze the balloon's motion. The lab is both a review of graphing and translating distance ver

  19. Temperature, humidity and air flow in the emplacement drifts using convection and dispersion transport models

    SciTech Connect

    Danko, G.; Birkholzer, J.T.; Bahrami, D.; Halecky, N.

    2009-10-01

    A coupled thermal-hydrologic-airflow model is developed, solving for the transport processes within a waste emplacement drift and the surrounding rockmass together at the proposed nuclear waste repository at Yucca Mountain. Natural, convective air flow as well as heat and mass transport in a representative emplacement drift during post-closure are explicitly simulated, using the MULTIFLUX model. The conjugate, thermal-hydrologic transport processes in the rockmass are solved with the TOUGH2 porous-media simulator in a coupled way to the in-drift processes. The new simulation results show that large-eddy turbulent flow, as opposed to small-eddy flow, dominate the drift air space for at least 5000 years following waste emplacement. The size of the largest, longitudinal eddy is equal to half of the drift length, providing a strong axial heat and moisture transport mechanism from the hot to the cold drift sections. The in-drift results are compared to those from simplified models using a surrogate, dispersive model with an equivalent dispersion coefficient for heat and moisture transport. Results from the explicit, convective velocity simulation model provide higher axial heat and moisture fluxes than those estimated from the previously published, simpler, equivalent-dispersion models, in addition to showing differences in temperature, humidity and condensation rate distributions along the drift length. A new dispersive model is also formulated, giving a time- and location-variable function that runs generally about ten times higher in value than the highest dispersion coefficient currently used in the Yucca Mountain Project as an estimate for the equivalent dispersion coefficient in the emplacement drift. The new dispersion coefficient variation, back-calculated from the convective model, can adequately describe the heat and mass transport processes in the emplacement drift example.

  20. Drift of a polymer chain in disordered media

    E-print Network

    Semjon Stepanow; Michael Schulz

    1999-07-20

    We consider the drift of a polymer chain in a disordered medium, which is caused by a constant force applied to the one end of the polymer, under neglecting the thermal fluctuations. In the lowest order of the perturbation theory we have computed the transversal fluctuations of the centre of mass of the polymer, the transversal and the longitudinal size of the polymer, and the average velocity of the polymer. The corrections to the quantities under consideration, which are due to the interplay between the motion and the quenched forces, are controlled by the driving force and the degree of polymerization. The transversal fluctuations of the Brownian particle and of the centre of mass of the polymer are obtained to be diffusive. The transversal fluctuations studied in the present Letter may also be of relevance for the related problem of the drift of a directed polymer in disordered media and its applications.

  1. Measurements of radial profiles of the ion temperature and the plasma rotation velocity with the TFTR vertical x-ray crystal spectrometer

    Microsoft Academic Search

    M. Bitter; H. Hsuan; J. E. Rice; K. W. Hill; M. Diesso; B. Grek; R. Hulse; D. W. Johnson; L. C. Johnson; S. von Goeler

    1988-01-01

    The TFTR vertical x-ray crystal spectrometer has now been operating with three crystals and position-sensitive detectors according to the original design specifications. The observed spectra of heliumlike Ti xxi, Cr xxiii, Fe xxv, and Ni xxvii have permitted a detailed comparison with the predictions from atomic theories, and they have provided data on the radial profiles of the ion temperature

  2. Measurements of radial profiles of the ion temperature and the plasma rotation velocity with the TFTR vertical x-ray crystal spectrometer (abstract)

    Microsoft Academic Search

    M. Bitter; H. Hsuan; J. E. Rice; K. W. Hill; M. Diesso; B. Grek; R. Hulse; D. W. Johnson; L. C. Johnson; S. von Goeler

    1988-01-01

    The TFTR vertical x-ray crystal spectrometer has now been operating with three crystals and position-sensitive detectors according to the original design specifications. The observed spectra of heliumlike Ti xxi, Cr xxiii, Fe xxv, and Ni xxvii have permitted a detailed comparison with the predictions from atomic theories, and they have provided data on the radial profiles of the ion temperature

  3. Numerical velocity distributions of positive and negative ions incident on a wafer in a pulsed 2f-CCP in CF_4/Ar for SiO2 etching

    NASA Astrophysics Data System (ADS)

    Yagisawa, T.; Maeshige, K.; Makabe, T.

    2002-10-01

    Charging damage during plasma etching of insulator will be still interesting issue with further decreasing the size of elements of ULSI. Recently, we reported the experimental evidence of the reduction of charging voltage during etching by using a pulsed two-frequency capacitively coupled plasma(2f-CCP)(T.Fujita and T.Makabe; Plasma Sources Sci.Technol.11),142 (2002) T.Ohmori et al ; submitted . In this work, we will focus on the charging free plasma etching in a pulsed 2f-CCP system with rf sources used for sustaining a high density plasma at VHF (100MHz) and biasing a wafer at high energy positive ion at LF (1MHz). A particle trace method (Monte Carlo simulation) is used to estimate a time-dependent ion velocity distribution, on the basis of the 2D-t plasma structure predicted by the RCT model(K.Maeshige,G.Washio,T.Yagisawa,T.Makabe;J.Appl.Phys. 91),9494(2002) (T.Makabe and K.Maeshige; Appl.Surf.Sci. 192),176(2002). Typical velocity distribution with non-linear time-dependence, modulated at low frequency bias power at 1MHz or 500kHz is shown. The characteristics of the impact energy and angle, which act as the element to reduce charges accumulated inside the hole/trench in SiO2 with high aspect ratio, are discussed for positive and negative ions in a pulsed 2f-CCP in CF_4(5%)/Ar.

  4. Measurements of the ion fraction and mobility of alpha and beta decay products in liquid xenon using EXO-200

    E-print Network

    J. B. Albert; D. J. Auty; P. S. Barbeau; D. Beck; V. Belov; M. Breidenbach; T. Brunner; A. Burenkov; G. F. Cao; C. Chambers; B. Cleveland; M. Coon; A. Craycraft; T. Daniels; M. Danilov; S. J. Daugherty; C. G. Davis; J. Davis; S. Delaquis; A. Der Mesrobian-Kabakian; R. DeVoe; T. Didberidze; A. Dolgolenko; M. J. Dolinski; M. Dunford; W. Fairbank Jr.; J. Farine; W. Feldmeier; P. Fierlinger; D. Fudenberg; R. Gornea; K. Graham; G. Gratta; C. Hall; M. Hughes; M. J. Jewell; X. S. Jiang; A. Johnson; T. N. Johnson; S. Johnston; A. Karelin; L. J. Kaufman; R. Killick; T. Koffas; S. Kravitz; A. Kuchenkov; K. S. Kumar; D. S. Leonard; C. Licciardi; Y. H. Lin; J. Ling; R. MacLellan; M. G. Marino; B. Mong; D. Moore; R. Nelson; K. O'Sullivan; A. Odian; I. Ostrovskiy; A. Piepke; A. Pocar; C. Y. Prescott; A. Robinson; P. C. Rowson; J. J. Russell; A. Schubert; D. Sinclair; E. Smith; V. Stekhanov; M. Tarka; T. Tolba; R. Tsang; K. Twelker; J. -L. Vuilleumier; A. Waite; J. Walton; T. Walton; M. Weber; L. J. Wen; U. Wichoski; J. D. Wright; J. Wood; L. Yang; Y. -R. Yen; O. Ya. Zeldovich

    2015-06-01

    Alpha decays in the EXO-200 detector are used to measure the fraction of charged $^{218}\\mathrm{Po}$ and $^{214}\\mathrm{Bi}$ daughters created from alpha and beta decays, respectively. $^{222}\\mathrm{Rn}$ alpha decays in liquid xenon (LXe) are found to produce $^{218}\\mathrm{Po}^{+}$ ions $50.3 \\pm 3.0\\%$ of the time, while the remainder of the $^{218}\\mathrm{Po}$ atoms are neutral. The fraction of $^{214}\\mathrm{Bi}^{+}$ from $^{214}\\mathrm{Pb}$ beta decays in LXe is found to be $76.4 \\pm 5.7\\%$, inferred from the relative rates of $^{218}\\mathrm{Po}$ and $^{214}\\mathrm{Po}$ alpha decays in the LXe. The average velocity of $^{218}\\mathrm{Po}$ ions is observed to decrease for longer drift times. Initially the ions have a mobility of $0.390 \\pm 0.006~\\mathrm{cm}^2/(\\mathrm{kV}~\\mathrm{s})$, and at long drift times the mobility is $0.219 \\pm 0.004~\\mathrm{cm}^2/(\\mathrm{kV}~\\mathrm{s})$. Time constants associated with the change in mobility during drift of the $^{218}\\mathrm{Po}^{+}$ ions are found to be proportional to the electron lifetime in the LXe.

  5. Measurements of the ion fraction and mobility of alpha and beta decay products in liquid xenon using EXO-200

    E-print Network

    Albert, J B; Barbeau, P S; Beck, D; Belov, V; Breidenbach, M; Brunner, T; Burenkov, A; Cao, G F; Chambers, C; Cleveland, B; Coon, M; Craycraft, A; Daniels, T; Danilov, M; Daugherty, S J; Davis, C G; Davis, J; Delaquis, S; Der Mesrobian-Kabakian, A; DeVoe, R; Didberidze, T; Dolgolenko, A; Dolinski, M J; Dunford, M; Fairbank, W; Farine, J; Feldmeier, W; Fierlinger, P; Fudenberg, D; Gornea, R; Graham, K; Gratta, G; Hall, C; Hughes, M; Jewell, M J; Jiang, X S; Johnson, A; Johnson, T N; Johnston, S; Karelin, A; Kaufman, L J; Killick, R; Koffas, T; Kravitz, S; Kuchenkov, A; Kumar, K S; Leonard, D S; Licciardi, C; Lin, Y H; Ling, J; MacLellan, R; Marino, M G; Mong, B; Moore, D; Nelson, R; O'Sullivan, K; Odian, A; Ostrovskiy, I; Piepke, A; Pocar, A; Prescott, C Y; Robinson, A; Rowson, P C; Russell, J J; Schubert, A; Sinclair, D; Smith, E; Stekhanov, V; Tarka, M; Tolba, T; Tsang, R; Twelker, K; Vuilleumier, J -L; Waite, A; Walton, J; Walton, T; Weber, M; Wen, L J; Wichoski, U; Wright, J D; Wood, J; Yang, L; Yen, Y -R; Zeldovich, O Ya

    2015-01-01

    Alpha decays in the EXO-200 detector are used to measure the fraction of charged $^{218}\\mathrm{Po}$ and $^{214}\\mathrm{Bi}$ daughters created from alpha and beta decays, respectively. $^{222}\\mathrm{Rn}$ alpha decays in liquid xenon (LXe) are found to produce $^{218}\\mathrm{Po}^{+}$ ions $50.3 \\pm 3.0\\%$ of the time, while the remainder of the $^{218}\\mathrm{Po}$ atoms are neutral. The fraction of $^{214}\\mathrm{Bi}^{+}$ from $^{214}\\mathrm{Pb}$ beta decays in LXe is found to be $76.4 \\pm 5.7\\%$, inferred from the relative rates of $^{218}\\mathrm{Po}$ and $^{214}\\mathrm{Po}$ alpha decays in the LXe. The average velocity of $^{218}\\mathrm{Po}$ ions is observed to decrease for longer drift times. Initially the ions have a mobility of $0.390 \\pm 0.006~\\mathrm{cm}^2/(\\mathrm{kV}~\\mathrm{s})$, and at long drift times the mobility is $0.219 \\pm 0.004~\\mathrm{cm}^2/(\\mathrm{kV}~\\mathrm{s})$. Time constants associated with the change in mobility during drift of the $^{218}\\mathrm{Po}^{+}$ ions are found to be propor...

  6. Integrated simulation of an ion-driven warm dense matter experiment

    NASA Astrophysics Data System (ADS)

    Welch, Dale R.; Rose, David V.; Thoma, Carsten; Sefkow, Adam B.; Kaganovich, Igor D.; Seidl, Peter A.; Yu, Simon S.; Barnard, John J.; Roy, Prabir K.

    2007-07-01

    Longitudinal compression factors in excess of 50 of a 300-keV, 20-mA K + ion beam have been demonstrated in the Neutralized Drift Compression Experiment (NDCX) in agreement with LSP particle-in-cell simulations using the experimental tilt voltage waveform. Here, pre-formed plasma provides beam neutralization for a 1-2-m drift length. To achieve simultaneous transverse and longitudinal compression, we must understand and account for the impact of the applied velocity tilt on the transverse phase space of the beam. Of equal importance to achieving warm dense matter and heavy ion fusion conditions, is quantifying the effect of beam plasma interactions, including stability and neutralization, on the beam transport throughout the drift section up to the target. Critical new issues relate to transverse focusing of the axially compressing ion beam in a high-field (3-15 T) solenoid that is filled with plasma. Integrated LSP simulations that include modeling of the diode, magnetic transport, induction bunching module, plasma neutralized transport, solenoidal focusing and beam target interaction, are assisting in the design of a near-term warm dense matter experiment. We discuss the simulation algorithms and present calculations of designs for such an experiment that will heat an aluminum target up to roughly 1-eV temperature.

  7. On the determination of the poloidal velocity and the shear layer in the scrape-off layer of ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Schrittwieser, Roman; Costea, Stefan; Mehlmann, Franz; Nielsen, Anders Henry; Naulin, Volker; Rasmussen, Jens Juul; Mueller, Hans Werner; Vianello, Nicola; Carralero, Daniel; Rohde, Volker; Lux, Christian; Ionita, Codrina; ASDEX Upgrade Team

    2013-10-01

    We have determined the poloidal velocity in the scrape-off layer (SOL) of ASDEX Upgrade (AUG) and further inside with three different methods, which are critically compared. The methods take use of a reciprocating probe with six pins by which the radial electric field and the cross-correlation (CC) of signals was determined in the SOL up to the shear layer (SL) and a few mm inside it. The poloidal velocity was determined (i) from the ExB drift, (ii) from the CC of the ion saturation currents of two poloidally separated negatively biased probes and (iii) from the CC of two poloidally separated floating probes. By use of synthetic data, obtained from simulations with AUG parameters applying the ESEL code, a detailed benchmarking was carried out. Based on the probe data we have also determined the position of the shear layer. We have determined the poloidal velocity in the scrape-off layer (SOL) of ASDEX Upgrade (AUG) and further inside with three different methods, which are critically compared. The methods take use of a reciprocating probe with six pins by which the radial electric field and the cross-correlation (CC) of signals was determined in the SOL up to the shear layer (SL) and a few mm inside it. The poloidal velocity was determined (i) from the ExB drift, (ii) from the CC of the ion saturation currents of two poloidally separated negatively biased probes and (iii) from the CC of two poloidally separated floating probes. By use of synthetic data, obtained from simulations with AUG parameters applying the ESEL code, a detailed benchmarking was carried out. Based on the probe data we have also determined the position of the shear layer. EURATOM/EFDA, Austrian Science Fund (FWF).

  8. High-resolution ion mobility measurements

    NASA Astrophysics Data System (ADS)

    Dugourd, Ph.; Hudgins, R. R.; Clemmer, D. E.; Jarrold, M. F.

    1997-02-01

    Gas phase ion mobility measurements can resolve structural isomers for polyatomic ions and provide information about their geometries. A new experimental apparatus for performing high-resolution ion mobility measurements is described. The apparatus consists of a pulsed laser vaporization/desorption source coupled through an ion gate to a 63-cm-long drift tube. The ion gate is a critical component that prevents the diffusion of neutral species from the source into the drift tube. Ions travel along the drift tube under the influence of a uniform electric field. At the end of the drift tube some of the ions exit through a small aperture. They are focused into a quadrupole mass spectrometer, where they are mass analyzed, and then detected by an off-axis collision dynode and by dual microchannel plates. The apparatus is operated with a drift voltage of up to 14 000 V and a helium buffer gas pressure of around 500 Torr. The resolving power for ion mobility measurements is over an order of magnitude higher than has been achieved using conventional injected-ion drift tube techniques. Examples of the application of the new apparatus in resolving isomers of laser desorbed metallofullerenes, in studying silicon clusters generated by laser vaporization, and in following the isomerization of small nanocrystalline (NaCl)nCl- clusters as a function of temperature, are presented.

  9. Drift-Kinetic Alfven Waves Observed near a Reconnection X Line in the Earth's Magnetopause

    SciTech Connect

    Chaston, C.C.; Phan, T.D.; Bonnell, J.W.; Mozer, F.S. [Space Science Laboratory, University of California, Berkeley, California 94720 (United States); Acuna, M.; Goldstein, M.L. [NASA Goddard Space Flight Center, Greenbelt, Maryland (United States); Balogh, A. [Imperial College, London (United Kingdom); Andre, M. [Swedish Institute of Space Physics, Uppsala (Sweden); Reme, H. [CESR, Toulouse (France); Fazakerley, A. [Mullard Space Science Laboratory, Dorking (United Kingdom)

    2005-08-05

    We identify drift-kinetic Alfven waves in the vicinity of a reconnection X line on the Earth's magnetopause. The dispersive properties of these waves have been determined using wavelet interferometric techniques applied to multipoint observations from the Cluster spacecraft. Comparison of the observed wave dispersion with that expected for drift-kinetic Alfven waves shows close agreement. The waves propagate outwards from the X line suggesting that reconnection is a kinetic Alfven wave source. Energetic O{sup +} ions observed in these waves indicate that reconnection is a driver of auroral ion outflow.

  10. Inner vacuum gap formation and drifting subpulses in pulsars

    NASA Astrophysics Data System (ADS)

    Gil, J. A.; Melikidze, G. I.

    The problem of formation of the inner vacuum gap in neutron stars with Omega\\cdot{B}<0 is considered. It is argued by means of the condition Ti/Ts > 1, where Ti is the melting temperature of surface 5626 Fe ions and Ts is the actual temperature of the polar cap surface, that the inner vacuum gap can form, provided that the actual surface magnetic field is extremaly strong (Bs>˜ 1013 G) and curved ( R < 10 < SUP>6 cm), irrespective of the value of dipolar component measured from the pulsar spin down rate. The calculations are carried out for pulsars with drifting subpulses and/or periodic intensity modulations, in which the existence of the quasi steady vacuum gap discharging via E x B drifting sparks is almost unavoidable.

  11. A Double Take at 'Serpent' Drift

    NASA Technical Reports Server (NTRS)

    2004-01-01

    NASA's Mars Exploration Rover Spirit took this microscopic imager picture of the drift dubbed 'Serpent' on Spirit's 73rd martian day on Mars after successfully digging into the side of the drift. The image is the first-ever microscopic look inside a drift. It captures only the scuffed interior of the Serpent drift and is dominated by larger pea-shaped particles. These grains are not natural to the inside of the drift, but are crust particles that have tumbled into the scuffed area as a result of the digging. These grains lost their dust cover in the process of falling into the scuff, giving scientists clues about the strength -- or lack of strength -- of the bond between the dust and sand particles.

    Most interesting to scientists are the fine grains making up the interior of Serpent drift. The grains of sand found within drifts or dunes on Earth are usually about 200 micrometers (.008 inches) in diameter -- much like sand on a beach. On Earth, dunes are formed when sand particles of this size are bounced across a surface by wind and collect together as drifts. Smaller particles, like the ones making up Serpent drift, would not necessarily collect into a dune on Earth, but would more likely be distributed across the surface like dust. The fine grains making up the interior of Serpent drift are no larger than 50 or 60 micrometers (.002 inches) and can be compared to silt on Earth.

    How did this very fine material manage to accumulate into a drift? Earth-based tests that simulate the wind speed and atmospheric density of Mars have found it difficult to reproduce dunes with grain particles as small as those found in the Serpent drift. However, Earth-based tests cannot duplicate the gravity of Mars, which is one-third that of the gravity on Earth. This environmental factor is a likely contributor to the diminutive material making up Serpent drift.

  12. Equinoctial asymmetry of ionospheric vertical plasma drifts and its effect on F-region plasma density

    Microsoft Academic Search

    Zhipeng Ren; Weixing Wan; Libo Liu; Yiding Chen; Huijun Le

    2011-01-01

    The equinoctial asymmetry of the ionospheric vertical E × B plasma drift velocity (V$\\\\perp$) in the equatorial F region is investigated based on observations from ROCSAT-1 during 1999 to 2004. It is found that the observed asymmetry exhibits obvious local time dependence with three noticeable features. First, in the Eastern Hemisphere during the interval between 0900 and 1300 LT, V$\\\\perp$

  13. An Implicit "Drift-Lorentz" Mover for Plasma and Beam Simulations

    SciTech Connect

    Cohen, R H; Friedman, A; Grote, D P; Vay, J

    2009-02-12

    In order to efficiently perform particle simulations in systems with widely varying magnetization, we developed a drift-Lorentz mover, which interpolates between full particle dynamics and drift kinetics in such a way as to preserve a physically correct gyroradius and particle drifts for both large and small ratios of the timestep to the cyclotron period. In order to extend applicability of the mover to systems with plasma frequency exceeding the cyclotron frequency such as one may have with fully neutralized drift compression of a heavy-ion beam we have developed an implicit version of the mover. A first step in this direction, in which the polarization charge was added to the field solver, was described previously. Here we describe a fully implicit algorithm (which is analogous to the direct-implicit method for conventional particle-in-cell simulation), summarize a stability analysis of it, and describe several tests of the resultant code.

  14. AN IMPLICIT"DRIFT-LORENTZ" PARTICLE MOVER FOR PLASMA AND BEAM SIMULATIONS

    SciTech Connect

    Friedman, A.; Grote, D.P.; Vay, J.-L; Cohen, R.H.

    2008-07-15

    In order to efficiently perform particle simulations in systems with widely varying magnetization, we developed a drift-Lorentz mover, which interpolates between full particle dynamics and drift kinetics in such a way as to preserve a physically correct gyroradius and particle drifts for both large and small ratios of the timestep to the cyclotron period. In order to extend applicability of the mover to systems with plasma frequency exceeding the cyclotron frequency such as one may have with fully neutralized drift compression of a heavy-ion beam we have developed an implicit version of the mover. A first step in this direction, in which the polarization charge was added to the field solver, was described previously. Here we describe a fully implicit algorithm (which is analogous to the direct-implicit method for conventionalparticle-in-cell simulation), summarize a stability analysis of it, and describe several tests of the resultant code.

  15. Modulation of drift-wave envelopes in a nonuniform quantum magnetoplasma

    SciTech Connect

    Misra, A. P., E-mail: apmisra@visva-bharati.ac.in, E-mail: apmisra@gmail.com [Department of Mathematics, Siksha Bhavana, Visva-Bharati University, Santiniketan-731 235, West Bengal (India)

    2014-04-15

    We study the amplitude modulation of low-frequency, long-wavelength electrostatic drift-wave envelopes in a nonuniform quantum magnetoplasma consisting of cold ions and degenerate electrons. The effects of tunneling associated with the quantum Bohm potential and the Fermi pressure for nonrelativistic degenerate electrons, as well as the equilibrium density and magnetic field inhomogeneities are taken into account. Starting from a set of quantum magnetohydrodynamic equations, we derive a nonlinear Schrödinger equation (NLSE) that governs the dynamics of the modulated quantum drift-wave packets. The NLSE is used to study the modulational instability (MI) of a Stoke's wave train to a small plane wave perturbation. It is shown that the quantum tunneling effect as well as the scale length of inhomogeneity plays crucial roles for the MI of the drift-wave packets. Thus, the latter can propagate in the form of bright and dark envelope solitons or as drift-wave rogons in degenerate dense magnetoplasmas.

  16. Time-spatial drift of decelerating electromagnetic pulses.

    PubMed

    Nerukh, Alexander G; Nerukh, Dmitry A

    2013-07-15

    A time dependent electromagnetic pulse generated by a current running laterally to the direction of the pulse propagation is considered in paraxial approximation. It is shown that the pulse envelope moves in the time-spatial coordinates on the surface of a parabolic cylinder for the Airy pulse and a hyperbolic cylinder for the Gaussian. These pulses propagate in time with deceleration along the dominant propagation direction and drift uniformly in the lateral direction. The Airy pulse stops at infinity while the asymptotic velocity of the Gaussian is nonzero. PMID:23938583

  17. Low frequency electrostatic waves in a magnetized plasma with heavy negative ions

    NASA Astrophysics Data System (ADS)

    Kim, Su-Hyun; Meyer, John K.; Merlino, Robert L.

    2012-10-01

    We have observed large amplitude, low frequency (well below any cyclotron or plasma frequencies) electrostatic waves in a magnetized Q-machine plasma containing positive potassium ions (39 amu), electrons, and heavy negative ions (350 amu). The negative ions were produced by leaking C7F14 (perfluoromethylcyclohexane) vapor into the Q-machine. C7F14 has a large attachment rate for low energy electrons (in the Q-machine, Te 0.2,eV), so that a relatively large fraction (n- / n- ne . - ne>10^3) of magnetized C7F14^- negative ions are formed at neutral pressures 10-5Torr. The waves propagate in the azimuthal direction of the cylindrical plasma column. The frequency spectrum of the waves contains narrow features at the fundamental (m=1) and several harmonics. Possible excitation mechanisms being considered are the negative ion-modified drift instability driven by the radial density gradient, and radial shear in the azimuthal (ExB) drift velocity.

  18. Excitation of poloidal standing Alfvén waves through drift resonance wave-particle interaction

    NASA Astrophysics Data System (ADS)

    Dai, Lei; Takahashi, Kazue; Wygant, John R.; Chen, Liu; Bonnell, John; Cattell, Cynthia A.; Thaller, Scott; Kletzing, Craig; Smith, Charles W.; MacDowall, Robert J.; Baker, Daniel N.; Blake, J. Bernard; Fennell, Joseph; Claudepierre, Seth; Funsten, Herbert O.; Reeves, Geoffrey D.; Spence, Harlan E.

    2013-08-01

    Drift-resonance wave-particle interaction is a fundamental collisionless plasma process studied extensively in theory. Using cross-spectral analysis of electric field, magnetic field, and ion flux data from the Van Allen Probe (Radiation Belt Storm Probes) spacecraft, we present direct evidence identifying the generation of a fundamental mode standing poloidal wave through drift-resonance interactions in the inner magnetosphere. Intense azimuthal electric field (E?) oscillations as large as 10mV/m are observed, associated with radial magnetic field (Br) oscillations in the dawn-noon sector near but south of the magnetic equator at L˜5. The observed wave period, E?/Br ratio and the 90° phase lag between Br and E? are all consistent with fundamental mode standing Poloidal waves. Phase shifts between particle fluxes and wave electric fields clearly demonstrate a drift resonance with ˜90 keV ring current ions. The estimated earthward gradient of ion phase space density provides a free energy source for wave generation through the drift-resonance instability. A similar drift-resonance process should occur ubiquitously in collisionless plasma systems. One specific example is the "fishbone" instability in fusion plasma devices. In addition, our observations have important implications for the long-standing mysterious origin of Giant Pulsations.

  19. Electric currents through ion tracks in silicon devices

    Microsoft Academic Search

    Larry D. Edmonds

    1998-01-01

    A modified form of Ohm's law, describing electric currents through ion tracks, is presented as a tool for future theoretical modeling efforts related to charge collection from ion tracks in silicon devices. The equation is rigorously derived from the drift\\/diffusion equations and accounts for all currents (electron and hole, drift, and diffusion). While only one quantitative result is given, a

  20. Development of a Spatially Resolving X-Ray Crystal Spectrometer (XCS) for Measurement of Ion-Temperature (Ti) and Rotation-Velocity (v) Profiles in ITER

    SciTech Connect

    Hill, K W; Delgado-Aprico, L; Johnson, D; Feder, R; Beiersdorfer,; Dunn, J; Morris, K; Wang, E; Reinke, M; Podpaly, Y; Rice, J E; Barnsley, R; O'Mullane, M; Lee, S G

    2010-05-21

    Imaging XCS arrays are being developed as a US-ITER activity for Doppler measurement of Ti and v profiles of impurities (W, Kr, Fe) with ~7 cm (a/30) and 10-100 ms resolution in ITER. The imaging XCS, modeled after a PPPL-MIT instrument on Alcator C-Mod, uses a spherically bent crystal and 2d x-ray detectors to achieve high spectral resolving power (E/dE>6000) horizontally and spatial imaging vertically. Two arrays will measure Ti and both poloidal and toroidal rotation velocity profiles. Measurement of many spatial chords permits tomographic inversion for inference of local parameters. The instrument design, predictions of performance, and results from C-Mod will be presented.