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Sample records for field asymmetric ion

  1. Mass spectrometric characterization of a high-field asymmetric waveform ion mobility spectrometer

    NASA Astrophysics Data System (ADS)

    Purves, Randy W.; Guevremont, Roger; Day, Stephen; Pipich, Charles W.; Matyjaszczyk, Matthew S.

    1998-12-01

    Ion mobility spectrometry (IMS) has become an important method for the detection of many compounds because of its high sensitivity and amenability to miniaturization for field-portable monitoring; applications include detection of narcotics, explosives, and chemical warfare agents. High-field asymmetric waveform ion mobility spectrometry (FAIMS) differs from IMS in that the electric fields are applied using a high-frequency periodic asymmetric waveform, rather than a dc voltage. Furthermore, in FAIMS the compounds are separated by the difference in the mobility of ions at high electric field relative to low field, rather than by compound to compound differences in mobility at low electric field (IMS). We report here the first cylindrical-geometry-FAIMS interface with mass spectrometry (FAIMS-MS) and the MS identification of the peaks observed in a FAIMS compensation voltage (CV) spectrum. Using both an electrometer-based-FAIMS (FAIMS-E) and FAIMS-MS, several variables that affect the sensitivity of ion detection were examined for two (polarity reversed) asymmetric waveforms (modes 1 and 2) each of which yields a unique spectrum. An increase in the dispersion voltage (DV) was found to improve the sensitivity and separation observed in the FAIMS CV spectrum. This increase in sensitivity and the unexpected dissimilarity in modes 1 and 2 suggest that atmospheric pressure ion focusing is occurring in the FAIMS analyzer. The sensitivity and peak locations in the CV spectra were affected by temperature, gas flow rates, operating pressure, and analyte concentration.

  2. Two-Scale Ion Meandering Caused by the Polarization Electric Field During Asymmetric Reconnection

    NASA Technical Reports Server (NTRS)

    Wang, Shan; Chen, Li-Jen; Hesse, Michael; Bessho, Naoki; Gershman, Daniel J.; Dorelli, John; Giles, Barbara L.; Torbert, Roy B.; Pollock, Craig J.; Strangeway, Robert; Ergun, Robert E.; Burch, James L.; Avanov, Levon; Lavraud, Benoit; Moore, Thomas E.; Saito, Yoshifumi

    2016-01-01

    Ion velocity distribution functions (VDFs) from a particle-in-cell simulation of asymmetric reconnection are investigated to reveal a two-scale structure of the ion diffusion region (IDR). Ions bouncing in the inner IDR are trapped mainly by the electric field normal to the current sheet (N direction), while those reaching the outer IDR are turned back mainly by the magnetic force. The resulting inner layer VDFs have counter-streaming populations along N with decreasing counter-streaming speeds away from the midplane while maintaining the out-of-plane speed, and the outer layer VDFs exhibit crescent shapes toward the out-of-plane direction. Observations of the above VDF features and the normal electric fields provide evidence for the two-scale meandering motion.

  3. Asymmetric Ion-Pairing Catalysis

    PubMed Central

    Brak, Katrien

    2014-01-01

    Charged intermediates and reagents are ubiquitous in organic transformations. The interaction of these ionic species with chiral neutral, anionic, or cationic small molecules has emerged as a powerful strategy for catalytic, enantioselective synthesis. This review describes developments in the burgeoning field of asymmetric ion-pairing catalysis with an emphasis on the insights that have been gleaned into the structural and mechanistic features that contribute to high asymmetric induction. PMID:23192886

  4. Asymmetric ion trap

    DOEpatents

    Barlow, S.E.; Alexander, M.L.; Follansbee, J.C.

    1997-12-02

    An ion trap having two end cap electrodes disposed asymmetrically about a center of a ring electrode is disclosed. The inner surface of the end cap electrodes are conformed to an asymmetric pair of equipotential lines of the harmonic formed by the application of voltages to the electrodes. The asymmetry of the end cap electrodes allows ejection of charged species through the closer of the two electrodes which in turn allows for simultaneously detecting anions and cations expelled from the ion trap through the use of two detectors charged with opposite polarity. 4 figs.

  5. Asymmetric ion trap

    DOEpatents

    Barlow, Stephan E.; Alexander, Michael L.; Follansbee, James C.

    1997-01-01

    An ion trap having two end cap electrodes disposed asymmetrically about a center of a ring electrode. The inner surface of the end cap electrodes are conformed to an asymmetric pair of equipotential lines of the harmonic formed by the application of voltages to the electrodes. The asymmetry of the end cap electrodes allows ejection of charged species through the closer of the two electrodes which in turn allows for simultaneously detecting anions and cations expelled from the ion trap through the use of two detectors charged with opposite polarity.

  6. Peak deconvolution in high-field asymmetric waveform ion mobility spectrometry (FAIMS) to characterize macromolecular conformations

    NASA Astrophysics Data System (ADS)

    Robinson, Errol W.; Sellon, Rachel E.; Williams, Evan R.

    2007-01-01

    Protonated poly(ethylene glycol), produced by electrospray ionization (ESI), with molecular weights ranging from 0.3 to 5 kDa and charge states from 1+ to 7+ were characterized using high-field asymmetric waveform ion mobility spectrometry (FAIMS). Results for all but some of the 3+ and 4+ charge states are consistent with a single gas-phase conformer or family of unresolved conformers for each of these charge states. The FAIMS compensation voltage scans resulted in peaks that could be accurately fit with a single Gaussian for each peak. The peak widths increase linearly with compensation voltage for maximum ion transmission but do not depend on m/z or molecular weight. Fitting parameters obtained from the poly(ethylene glycol) data were used to analyze conformations of oxidized and reduced lysozyme formed from different solutions. For oxidized lysozyme formed from a buffered aqueous solution, a single conformer (or group of unresolved conformers) was observed for the 7+ and 8+ charge states. Two conformers were observed for the 9+ and 10+ charge states formed from more denaturing solutions. Data for the fully reduced form indicate the existence of up to three different conformers for each charge state produced directly by ESI and a general progression from a more extended to a more folded structure with decreasing charge state. These results are consistent with those obtained previously by proton-transfer reactivity and drift tube ion mobility experiments, although more conformers were identified for the fully reduced form of lysozyme using FAIMS.

  7. Enhancing Biological Analyses with Three Dimensional Field Asymmetric Ion Mobility, Low Field Drift Tube Ion Mobility and Mass Spectrometry (μFAIMS/IMS-MS) Separations

    PubMed Central

    Zhang, Xing; Ibrahim, Yehia M.; Chen, Tsung-Chi; Kyle, Jennifer E.; Norheim, Randolph V.; Monroe, Matthew E.; Smith, Richard D.; Baker, Erin S.

    2015-01-01

    Multidimensional high throughput separations are ideal for analyzing distinct ion characteristics simultaneously in one analysis. We report on the first evaluation of a platform coupling a high speed field asymmetric ion mobility spectrometry microchip (μFAIMS) with drift tube ion mobility and mass spectrometry (IMS-MS). The μFAIMS/IMS-MS platform was used to analyze biological samples and simultaneously acquire multidimensional FAIMS compensation fields, IMS drift times, and accurate ion masses for the detected features. These separations thereby increased the overall measurement separation power, resulting in greater information content and more complete characterization of the complex samples. The separation conditions were optimized for sensitivity and resolving power by the selection of gas compositions and pressures in the FAIMS and IMS separation stages. The resulting performance provided three dimensional separations, benefitting both broad complex mixture studies and targeted analyses by improving isomeric separations and allowing detection of species obscured by interfering peaks. PMID:26140287

  8. Enhancing Biological Analyses with Three Dimensional Field Asymmetric Ion Mobility, Low Field Drift Time Ion Mobility and Mass Spectrometry (µFAIMS/IMS-MS) Separations

    SciTech Connect

    Zhang, Xing; Ibrahim, Yehia M.; Chen, Tsung-Chi; Kyle, Jennifer E.; Norheim, Randolph V.; Monroe, Matthew E.; Smith, Richard D.; Baker, Erin Shammel

    2015-06-30

    We report the first evaluation of a platform coupling a high speed field asymmetric ion mobility spectrometry microchip (µFAIMS) with drift tube ion mobility and mass spectrometry (IMS-MS). The µFAIMS/IMS-MS platform was used to analyze biological samples and simultaneously acquire multidimensional information of detected features from the measured FAIMS compensation fields and IMS drift times, while also obtaining accurate ion masses. These separations thereby increase the overall separation power, resulting increased information content, and provide more complete characterization of more complex samples. The separation conditions were optimized for sensitivity and resolving power by the selection of gas compositions and pressures in the FAIMS and IMS separation stages. The resulting performance provided three dimensional separations, benefitting both broad complex mixture studies and targeted analyses by e.g. improving isomeric separations and allowing detection of species obscured by “chemical noise” and other interfering peaks.

  9. Separation of Opiate Isomers Using Electrospray Ionization and Paper Spray Coupled to High-Field Asymmetric Waveform Ion Mobility Spectrometry

    NASA Astrophysics Data System (ADS)

    Manicke, Nicholas E.; Belford, Michael

    2015-05-01

    One limitation in the growing field of ambient or direct analysis methods is reduced selectivity caused by the elimination of chromatographic separations prior to mass spectrometric analysis. We explored the use of high-field asymmetric waveform ion mobility spectrometry (FAIMS), an ambient pressure ion mobility technique, to separate the closely related opiate isomers of morphine, hydromorphone, and norcodeine. These isomers cannot be distinguished by tandem mass spectrometry. Separation prior to MS analysis is, therefore, required to distinguish these compounds, which are important in clinical chemistry and toxicology. FAIMS was coupled to a triple quadrupole mass spectrometer, and ionization was performed using either a pneumatically assisted heated electrospray ionization source (H-ESI) or paper spray, a direct analysis method that has been applied to the direct analysis of dried blood spots and other complex samples. We found that FAIMS was capable of separating the three opiate structural isomers using both H-ESI and paper spray as the ionization source.

  10. Asymmetrical field emitter

    DOEpatents

    Fleming, J.G.; Smith, B.K.

    1995-10-10

    A method is disclosed for providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure. 17 figs.

  11. Asymmetrical field emitter

    DOEpatents

    Fleming, James G.; Smith, Bradley K.

    1995-01-01

    Providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure.

  12. Comprehensive theoretical analysis and experimental exploration of ultrafast microchip-based high-field asymmetric ion mobility spectrometry (FAIMS) technique.

    PubMed

    Li, Lingfeng; Wang, Yonghuan; Chen, Chilai; Wang, Xiaozhi; Luo, Jikui

    2015-06-01

    High-field asymmetric ion mobility spectrometry (FAIMS) has become an efficient technique for separation and characterization of gas-phase ions at ambient pressure, which utilizes the mobility differences of ions at high and low fields. Micro FAIMS devices made by micro-electromechanical system technology have small gaps of the channels, high electric field and good installation precision, as thus they have received great attentions. However, the disadvantage of relatively low resolution limits their applications in some areas. In this study, theoretical analysis and experimental exploration were carried out to overcome the disadvantage. Multiple scans, characteristic decline curves of ion transmission and pattern recognitions were proposed to improve the performance of the microchip-based FAIMS. The results showed that although micro FAIMS instruments as a standalone chemical analyzer suffer from low resolution, by using one or more of the methods proposed, they can identify chemicals precisely and provide quantitative analysis with low detection limit in some applications. Copyright © 2015 John Wiley & Sons, Ltd.

  13. Enhanced analyte detection using in-source fragmentation of field asymmetric waveform ion mobility spectrometry-selected ions in combination with time-of-flight mass spectrometry.

    PubMed

    Brown, Lauren J; Smith, Robert W; Toutoungi, Danielle E; Reynolds, James C; Bristow, Anthony W T; Ray, Andrew; Sage, Ashley; Wilson, Ian D; Weston, Daniel J; Boyle, Billy; Creaser, Colin S

    2012-05-01

    Miniaturized ultra high field asymmetric waveform ion mobility spectrometry (FAIMS) is used for the selective transmission of differential mobility-selected ions prior to in-source collision-induced dissociation (CID) and time-of-flight mass spectrometry (TOFMS) analysis. The FAIMS-in-source collision induced dissociation-TOFMS (FISCID-MS) method requires only minor modification of the ion source region of the mass spectrometer and is shown to significantly enhance analyte detection in complex mixtures. Improved mass measurement accuracy and simplified product ion mass spectra were observed following FAIMS preselection and subsequent in-source CID of ions derived from pharmaceutical excipients, sufficiently close in m/z (17.7 ppm mass difference) that they could not be resolved by TOFMS alone. The FISCID-MS approach is also demonstrated for the qualitative and quantitative analysis of mixtures of peptides with FAIMS used to filter out unrelated precursor ions thereby simplifying the resulting product ion mass spectra. Liquid chromatography combined with FISCID-MS was applied to the analysis of coeluting model peptides and tryptic peptides derived from human plasma proteins, allowing precursor ion selection and CID to yield product ion data suitable for peptide identification via database searching. The potential of FISCID-MS for the quantitative determination of a model peptide spiked into human plasma in the range of 0.45-9.0 μg/mL is demonstrated, showing good reproducibility (%RSD < 14.6%) and linearity (R(2) > 0.99).

  14. High-Field Asymmetric-Waveform Ion Mobility Spectrometry and Electron Detachment Dissociation of Isobaric Mixtures of Glycosaminoglycans

    NASA Astrophysics Data System (ADS)

    Kailemia, Muchena J.; Park, Melvin; Kaplan, Desmond A.; Venot, Andre; Boons, Geert-Jan; Li, Lingyun; Linhardt, Robert J.; Amster, I. Jonathan

    2013-11-01

    High-field asymmetric waveform ion mobility spectrometry (FAIMS) is shown to be capable of resolving isomeric and isobaric glycosaminoglycan negative ions and to have great utility for the analysis of this class of molecules when combined with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and tandem mass spectrometry. Electron detachment dissociation (EDD) and other ion activation methods for tandem mass spectrometry can be used to determine the sites of labile sulfate modifications and for assigning the stereochemistry of hexuronic acid residues of glycosaminoglycans (GAGs). However, mixtures with overlapping mass-to-charge values present a challenge, as their precursor species cannot be resolved by a mass analyzer prior to ion activation. FAIMS is shown to resolve two types of mass-to-charge overlaps. A mixture of chondroitin sulfate A (CSA) oligomers with 4-10 saccharides units produces ions of a single mass-to-charge by electrospray ionization, as the charge state increases in direct proportion to the degree of polymerization for these sulfated carbohydrates. FAIMS is shown to resolve the overlapping charge. A more challenging type of mass-to-charge overlap occurs for mixtures of diastereomers. FAIMS is shown to separate two sets of epimeric GAG tetramers. For the epimer pairs, the complexity of the separation is reduced when the reducing end is alkylated, suggesting that anomers are also resolved by FAIMS. The resolved components were activated by EDD and the fragment ions were analyzed by FTICR-MS. The resulting tandem mass spectra were able to distinguish the two epimers from each other.

  15. Analysis of Supramolecular Complexes of 3-Methylxanthine with Field Asymmetric Waveform Ion Mobility Spectrometry Combined with Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Arthur, Kayleigh L.; Eiceman, Gary A.; Reynolds, James C.; Creaser, Colin S.

    2016-05-01

    Miniaturised field asymmetric waveform ion mobility spectrometry (FAIMS), combined with mass spectrometry (MS), has been applied to the study of self-assembling, noncovalent supramolecular complexes of 3-methylxanthine (3-MX) in the gas phase. 3-MX forms stable tetrameric complexes around an alkali metal (Na+, K+) or ammonium cation, to generate a diverse array of complexes with single and multiple charge states. Complexes of (3-MX)n observed include: singly charged complexes where n = 1-8 and 12 and doubly charged complexes where n = 12-24. The most intense ions are those associated with multiples of tetrameric units, where n = 4, 8, 12, 16, 20, 24. The effect of dispersion field on the ion intensities of the self-assembled complexes indicates some fragmentation of higher order complexes within the FAIMS electrodes (in-FAIMS dissociation), as well as in-source collision induced dissociation within the mass spectrometer. FAIMS-MS enables charge state separation of supramolecular complexes of 3-MX and is shown to be capable of separating species with overlapping mass-to-charge ratios. FAIMS selected transmission also results in an improvement in signal-to-noise ratio for low intensity complexes and enables the visualization of species undetectable without FAIMS.

  16. A 2D ion chamber array audit of wedged and asymmetric fields in an inhomogeneous lung phantom

    SciTech Connect

    Lye, Jessica; Dunn, Leon Alves, Andrew; Kenny, John; Lehmann, Joerg; Williams, Ivan; Kron, Tomas; Cole, Andrew

    2014-10-15

    Purpose: The Australian Clinical Dosimetry Service (ACDS) has implemented a new method of a nonreference condition Level II type dosimetric audit of radiotherapy services to increase measurement accuracy and patient safety within Australia. The aim of this work is to describe the methodology, tolerances, and outcomes from the new audit. Methods: The ACDS Level II audit measures the dose delivered in 2D planes using an ionization chamber based array positioned at multiple depths. Measurements are made in rectilinear homogeneous and inhomogeneous phantoms composed of slabs of solid water and lung. Computer generated computed tomography data sets of the rectilinear phantoms are supplied to the facility prior to audit for planning of a range of cases including reference fields, asymmetric fields, and wedged fields. The audit assesses 3D planning with 6 MV photons with a static (zero degree) gantry. Scoring is performed using local dose differences between the planned and measured dose within 80% of the field width. The overall audit result is determined by the maximum dose difference over all scoring points, cases, and planes. Pass (Optimal Level) is defined as maximum dose difference ≤3.3%, Pass (Action Level) is ≤5.0%, and Fail (Out of Tolerance) is >5.0%. Results: At close of 2013, the ACDS had performed 24 Level II audits. 63% of the audits passed, 33% failed, and the remaining audit was not assessable. Of the 15 audits that passed, 3 were at Pass (Action Level). The high fail rate is largely due to a systemic issue with modeling asymmetric 60° wedges which caused a delivered overdose of 5%–8%. Conclusions: The ACDS has implemented a nonreference condition Level II type audit, based on ion chamber 2D array measurements in an inhomogeneous slab phantom. The powerful diagnostic ability of this audit has allowed the ACDS to rigorously test the treatment planning systems implemented in Australian radiotherapy facilities. Recommendations from audits have led to

  17. Analysis of paralytic shellfish toxins using high-field asymmetric waveform ion mobility spectrometry with liquid chromatography-mass spectrometry.

    PubMed

    Beach, Daniel G; Melanson, Jeremy E; Purves, Randy W

    2015-03-01

    The analysis of paralytic shellfish toxins (PSTs) by liquid chromatography-mass spectrometry remains a challenge because of their high polarity, large number of analogues and the complex matrix in which they occur. Here we investigate the potential utility of high-field asymmetric waveform ion mobility spectrometry (FAIMS) as a gas-phase ion separation tool for analysis of PSTs by mass spectrometry. We investigate the separation of PSTs using FAIMS with two divergent goals: using FAIMS as a primary separation tool for rapid screening by electrospray ionization (ESI)-FAIMS-MS or combined with LC in a multidimensional LC-ESI-FAIMS-MS separation. First, a survey of the parameters that affect the sensitivity and selectivity of PST analysis by FAIMS was carried out using ESI-FAIMS-MS. In particular, the use of acetonitrile as a gas additive in the carrier gas flow offered good separation of all PST epimeric pairs. A second set of FAIMS conditions was also identified, which focussed PSTs to a relatively narrow CV range allowing development of an LC-ESI-FAIMS-MS method for analysis of PST toxins in complex mussel tissue extracts. The quantitative capabilities of this method were evaluated by analysing a PST containing mussel tissue matrix material. Results compared favourably with analysis by an established LC-post-column oxidation-fluorescence method with recoveries ranging from 70 to 106%, although sensitivity was somewhat reduced. The current work represents the first successful separation of PST isomers using ion mobility and shows the promise of FAIMS as a tool for analysis of algal biotoxins in complex samples and outlines some critical requirements for its future improvement.

  18. Detection of potato storage disease via gas analysis: a pilot study using field asymmetric ion mobility spectrometry.

    PubMed

    Rutolo, Massimo; Covington, James A; Clarkson, John; Iliescu, Daciana

    2014-08-28

    Soft rot is a commonly occurring potato tuber disease that each year causes substantial losses to the food industry. Here, we explore the possibility of early detection of the disease via gas/vapor analysis, in a laboratory environment, using a recent technology known as FAIMS (Field Asymmetric Ion Mobility Spectrometry). In this work, tubers were inoculated with a bacterium causing the infection, Pectobacterium carotovorum, and stored within set environmental conditions in order to manage disease progression. They were compared with controls stored in the same conditions. Three different inoculation time courses were employed in order to obtain diseased potatoes showing clear signs of advanced infection (for standard detection) and diseased potatoes with no apparent evidence of infection (for early detection). A total of 156 samples were processed by PCA (Principal Component Analysis) and k-means clustering. Results show a clear discrimination between controls and diseased potatoes for all experiments with no difference among observations from standard and early detection. Further analysis was carried out by means of a statistical model based on LDA (Linear Discriminant Analysis) that showed a high classification accuracy of 92.1% on the test set, obtained via a LOOCV (leave-one out cross-validation).

  19. Liquid Extraction Surface Analysis Mass Spectrometry Coupled with Field Asymmetric Waveform Ion Mobility Spectrometry for Analysis of Intact Proteins from Biological Substrates.

    PubMed

    Sarsby, Joscelyn; Griffiths, Rian L; Race, Alan M; Bunch, Josephine; Randall, Elizabeth C; Creese, Andrew J; Cooper, Helen J

    2015-07-07

    Previously we have shown that liquid extraction surface analysis (LESA) mass spectrometry is suitable for the analysis of intact proteins from a range of biological substrates. Here we show that LESA mass spectrometry may be coupled with high field asymmetric waveform ion mobility spectrometry (FAIMS) for top-down protein analysis directly from thin tissue sections (mouse liver, mouse brain) and from bacterial colonies (Escherichia coli) growing on agar. Incorporation of FAIMS results in significant improvements in signal-to-noise and reduced analysis time. Abundant protein signals are observed in single scan mass spectra. In addition, FAIMS enables gas-phase separation of molecular classes, for example, lipids and proteins, enabling improved analysis of both sets of species from a single LESA extraction.

  20. Trace level impurity method development with high-field asymmetric waveform ion mobility spectrometry: systematic study of factors affecting the performance.

    PubMed

    Champarnaud, Elodie; Laures, Alice M-F; Borman, Phil J; Chatfield, Marion J; Kapron, James T; Harrison, Mark; Wolff, Jean-Claude

    2009-01-01

    For the determination of trace level impurities, analytical chemists are confronted with complex mixtures and difficult separations. New technologies such as high-field asymmetric waveform ion mobility spectrometry (FAIMS) have been developed to make their work easier; however, efficient method development and troubleshooting can be quite challenging if little prior knowledge of the factors or their settings is available. We present the results of an investigation performed in order to obtain a better understanding of the FAIMS technology. The influence of eight factors (polarity of dispersion voltage, outer bias voltage, total gas flow rate, composition of the carrier gas (e.g. %He), outer electrode temperature, ratio between the temperatures of the inner and outer electrodes, flow rate and composition of the make-up mobile phase) was assessed. Five types of responses were monitored: value of the compensation voltage (CV), intensity, width and asymmetry of the compensation voltage peak, and resolution between two peaks. Three types of studies were performed using different test mixtures and various ionisation modes to assess whether the same conclusions could be drawn across these conditions for a number of different types of compounds. To extract the maximum information from as few experiments as possible, a Design of Experiment (DoE) approach was used. The results presented in this work provide detailed information on the factors affecting FAIMS separations and therefore should enable the user to troubleshoot more effectively and to develop efficient methods.

  1. ASYMMETRIC DIFFUSION OF MAGNETIC FIELD LINES

    SciTech Connect

    Beresnyak, Andrey

    2013-04-20

    Stochasticity of magnetic field lines is important for particle transport properties. Magnetic field lines separate faster than diffusively in turbulent plasma, which is called superdiffusion. We discovered that this superdiffusion is pronouncedly asymmetric, so that the separation of field lines along the magnetic field direction is different from the separation in the opposite direction. While the symmetry of the flow is broken by the so-called imbalance or cross-helicity, the difference between forward and backward diffusion is not directly due to imbalance, but a non-trivial consequence of both imbalance and non-reversibility of turbulence. The asymmetric diffusion perpendicular to the mean magnetic field entails a variety of new physical phenomena, such as the production of parallel particle streaming in the presence of perpendicular particle gradients. Such streaming and associated instabilities could be significant for particle transport in laboratory, space, and astrophysical plasmas.

  2. Bio-inspired smart single asymmetric hourglass nanochannels for continuous shape and ion transport control.

    PubMed

    Zhang, Huacheng; Hou, Xu; Yang, Zhe; Yan, Dadong; Li, Lin; Tian, Ye; Wang, Huanting; Jiang, Lei

    2015-02-18

    Inspired by biological asymmetric ion channels, new shape-tunable and pH-responsive asymmetric hourglass single nanochannel systems demonstrate unique ion-transport properties. It is found that the change in shape and pH cooperatively control the ion transport within the nanochannel ranging from asymmetric shape with asymmetric ion transport, to asymmetric shape with symmetric ion transport and symmetric shape with symmetric ion transport.

  3. Quantitation of amphetamine, methamphetamine, and their methylenedioxy derivatives in urine by solid-phase microextraction coupled with electrospray ionization-high-field asymmetric waveform ion mobility spectrometry-mass spectrometry.

    PubMed

    McCooeye, Margaret A; Mester, Zoltán; Ells, Barbara; Barnett, David A; Purves, Randy W; Guevremont, Roger

    2002-07-01

    Amphetamine, methamphetamine, and their methylenedioxy derivatives have been identified and measured in a human urine matrix using solid-phase microextraction (SPME) and high-field asymmetric waveform ion mobility spectrometry (FAIMS) in combination with electrospray ionization (ESI) and mass spectrometric detection (MS). Limits of detection in human urine between 200 pg/mL and 7.5 ng/mL have been achieved. The use of a simple extraction method, SPME, combined with the high sensitivity and selectivity of ESI-FAIMS-MS eliminates the need for chromatographic separation and allows for very rapid sample processing.

  4. Recycling asymmetric hydrogenation catalysts by their immobilization onto ion-exchange resins.

    PubMed

    Barbaro, Pierluigi

    2006-07-24

    Ion-exchange resins can be used as supports for the preparation of single-site, heterogenised asymmetric hydrogenation catalysts. The immobilised catalysts obtained can be efficiently and conveniently recovered and recycled. This article reviews the significant contributions in the field including the main concepts behind the design and the applications of this type of catalyst.

  5. Polarization dependent switching of asymmetric nanorings with a circular field

    NASA Astrophysics Data System (ADS)

    Pradhan, Nihar R.; Tuominen, Mark T.; Aidala, Katherine E.

    2016-01-01

    We experimentally investigated the switching from onion to vortex states in asymmetric cobalt nanorings by an applied circular field. An in-plane field is applied along the symmetric or asymmetric axis of the ring to establish domain walls (DWs) with symmetric or asymmetric polarization. A circular field is then applied to switch from the onion state to the vortex state, moving the DWs in the process. The asymmetry of the ring leads to different switching fields depending on the location of the DWs and direction of applied field. For polarization along the asymmetric axis, the field required to move the DWs to the narrow side of the ring is smaller than the field required to move the DWs to the larger side of the ring. For polarization along the symmetric axis, establishing one DW in the narrow side and one on the wide side, the field required to switch to the vortex state is an intermediate value.

  6. The dominance of small ions in the electric double layer of size- and charge-asymmetric electrolytes: a mean-field study on the charge reversal and surface charge amplification

    NASA Astrophysics Data System (ADS)

    Angélica Barrios-Contreras, Evelyn; González-Tovar, Enrique; Iván Guerrero-García, Guillermo

    2015-05-01

    The dominance of counterions in the electric double layer of size-asymmetric semi-punctual ions was proposed more than 30 years ago by Valleau and Torrie. According to their theoretical prescription, at large colloidal surface charges, the double layer properties of a fully asymmetric binary electrolyte become similar to those of a completely symmetric electrolyte if the properties of counterions are the same in both instances. In the same theoretical framework, we propose here that, for a fixed concentration of the smallest ionic species and weakly/moderate colloidal surface charges, the valence of small ions rules or mainly determines the structural and thermodynamic properties of the electric double layer regardless of the colloidal polarity. In other words, we show that the characteristics of the small ions dominate the double layer structure of non-highly charged colloids, independently if the small ions are coions or counterions. This is illustrated by a comprehensive analysis of the ionic and integrated charge profiles around a spherical macroion immersed in a fully size- and charge-asymmetric semi-punctual electrolyte. Charge reversal and surface charge amplification are observed in the regime of low/medium colloidal surface charge densities. The origin of these counterintuitive phenomena, and their corresponding localisation properties in the Helmholtz zone, are explained in terms of the electric double layer structure.

  7. An asymmetric approach to modeling ion channels using finite element analysis.

    PubMed

    Siksik, M; Krishnamurthy, V

    2009-01-01

    Biological ion channels are water filled pores in the cell membrane. They regulate the flow of ions in and out of the cell. Modeling the dynamics of these channels and relating their structure to functionality is crucial in understanding the mechanisms by which they conduct. This paper proposes a novel Finite Element Method (FEM) based simulation framework for modeling of ion channels that does not assume channel symmetry. This is the first framework that allows the use of multiple dielectric constants inside such channels without assuming geometrical symmetry thus providing a more realistic model of the channel. Due to the run-time complexity of the problem, lookup tables must be constructed in memory to store pre-calculated electric potential information. The large number of elements involved in FEM and channel resolution requirements can potentially result in very large lookup tables leading to a performance "bottleneck". This paper answers the following question: Does the accuracy introduced by using an asymmetric model outweigh the inaccuracy caused by having to reduce the size and resolution of electric-field look-up tables? This paper compares the memory footprint of an ion channel simulator that assumes a symmetric channel model versus an asymmetric model. We show that currently available personal computers are sufficient for attaining reasonable levels of accuracy for both. Our results show diminishing returns in accuracy with tables sized greater than 8.5 GB for the asymmetric model.

  8. Micro/nanofluidic Diode using Asymmetric Ion Concentration Polarization Layer

    NASA Astrophysics Data System (ADS)

    Sohn, Seoyun; Cho, Inhee; Kim, Sung Jae

    2016-11-01

    Recent developments of ion concentration polarization (ICP) theory would suggest that an over-limiting conductance (OLC) of the device is subject to the morphology of ICP layer and a micro-structure is able to alter the morphology. In this study, we demonstrated an ion rectification resulted only from asymmetric microscale structures, while conventional nanofluidic diode applications have usually employed a nanoscale asymmetry which requires sophisticate and expensive fabrication processes. We designed two dead-end microchannels incorporated with the nanoporous membrane. The difference in width of the microchannels was designed to yield asymmetry to the device. Cyclic voltammetry measurement was conducted to investigate the OLC behaviors on both forward and reverse bias. The diodic characteristics on I-V responses were observed at various ratio of the different microchannel width. In addition, we experimentally verified the logarithmical linearity between the ratios and the rectification ratios of OLC. This quantitative analysis would guide the further application utilizing microscale asymmetric diode device that now can be realized with minimum fabrication endeavors.

  9. A mean-field theory on the differential capacitance of asymmetric ionic liquid electrolytes.

    PubMed

    Han, Yining; Huang, Shanghui; Yan, Tianying

    2014-07-16

    The size of ions significantly influences the electric double layer structure of room temperature ionic liquid (IL) electrolytes and their differential capacitance (Cd). In this study, we extended the mean-field theory (MFT) developed independently by Kornyshev (2007J. Phys. Chem. B 111 5545-57) and Kilic, Bazant, and Ajdari (2007 Phys. Rev. E 75 021502) (the KKBA MFT) to take into account the asymmetric 1:1 IL electrolytes by introducing an additional parameter ξ for the anion/cation volume ratio, besides the ionic compressibility γ in the KKBA MFT. The MFT of asymmetric ions becomes KKBA MFT upon ξ = 1, and further reduces to Gouy-Chapman theory in the γ → 0 limit. The result of the extended MFT demonstrates that the asymmetric ILs give rise to an asymmetric Cd, with the higher peak in Cd occurring at positive polarization for the smaller anionic size. At high potential, Cd decays asymptotically toward KKBA MFT characterized by γ for the negative polarization, and characterized by ξγ for the positive polarization, with inverse-square-root behavior. At low potential, around the potential of zero charge, the asymmetric ions cause a higher Cd, which exceeds that of Gouy-Chapman theory.

  10. Laboratory study of ion and electron dynamics during asymmetric magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Yoo, J.; Jara-Almonte, J.; Yamada, M.; Ji, H.; Fox, W. R., II; Chen, L. J.; Roytershteyn, V.; Na, B.

    2015-12-01

    Magnetic reconnection at the dayside magnetopause has a large density asymmetry across the current sheet. To study effects of the density asymmetry on the ion and electron dynamics, plasmas with a significant (~10) density asymmetry are created in the Magnetic Reconnection Experiment (MRX) [1]. The density asymmetry affects the ion flow pattern by changing the in-plane electrostatic field such that the potential decrease on the high-density side becomes much smaller than that on the low-density side [2]. The ion inflow stagnation point is shifted toward the low-density side and the maximum ion outflow velocity is observed on the low-density side. The density asymmetry also makes the electron temperature profile asymmetric, which has a higher temperature near the low-density-side separatrices. The bulk electron heating is proportional to the total incoming magnetic energy per particle. The electron energization process during asymmetric reconnection is studied via numerical simulations. By comparing 2D simulations with corresponding 3D simulations, we find that the overall energization process does not depend on variations along the third dimension. Where and how electrons are energized during asymmetric reconnection will be discussed by using data from 2D numerical simulations. Finally, the scaling of the reconnection rate and the ion outflow speed given by the Cassak and Shay 2007 [3] is tested by systematically varying the density ratio. The measured ion outflow speed is about 40% of the theoretical values and the measured reconnection rate agrees with the scaling only with the measured density in the exhaust region. [1] M. Yamada et al., Phys. Plasmas 4, 1936 (1997). [2] J. Yoo et al., Phys. Rev. Lett. 113, 095002 (2014). [3] P. Cassak and M. Shay, Phys. Plasmas 14, 102114 (2007).

  11. Asymmetric ion transport through ion-channel-mimetic solid-state nanopores.

    PubMed

    Guo, Wei; Tian, Ye; Jiang, Lei

    2013-12-17

    Both scientists and engineers are interested in the design and fabrication of synthetic nanofluidic architectures that mimic the gating functions of biological ion channels. The effort to build such structures requires interdisciplinary efforts at the intersection of chemistry, materials science, and nanotechnology. Biological ion channels and synthetic nanofluidic devices have some structural and chemical similarities, and therefore, they share some common features in regulating the traverse ionic flow. In the past decade, researchers have identified two asymmetric ion transport phenomena in synthetic nanofluidic structures, the rectified ionic current and the net diffusion current. The rectified ionic current is a diode-like current-voltage response that occurs when switching the voltage bias. This phenomenon indicates a preferential direction of transport in the nanofluidic system. The net diffusion current occurs as a direct product of charge selectivity and is generated from the asymmetric diffusion through charged nanofluidic channels. These new ion transport phenomena and the elaborate structures that occur in biology have inspired us to build functional nanofluidic devices for both fundamental research and practical applications. In this Account, we review our recent progress in the design and fabrication of biomimetic solid-state nanofluidic devices with asymmetric ion transport behavior. We demonstrate the origin of the rectified ionic current and the net diffusion current. We also identify several influential factors and discuss how to build these asymmetric features into nanofluidic systems by controlling (1) nanopore geometry, (2) surface charge distribution, (3) chemical composition, (4) channel wall wettability, (5) environmental pH, (6) electrolyte concentration gradient, and (7) ion mobility. In the case of the first four features, we build these asymmetric features directly into the nanofluidic structures. With the final three, we construct

  12. Digital field ion microscopy

    SciTech Connect

    Sijbrandij, S.J.; Russell, K.F.; Miller, M.K.; Thomson, R.C.

    1998-01-01

    Due to environmental concerns, there is a trend to avoid the use of chemicals needed to develop negatives and to process photographic paper, and to use digital technologies instead. Digital technology also offers the advantages that it is convenient, as it enables quick access to the end result, allows image storage and processing on computer, allows rapid hard copy output, and simplifies electronic publishing. Recently significant improvements have been made to the performance and cost of camera-sensors and printers. In this paper, field ion images recorded with two digital cameras of different resolution are compared to images recorded on standard 35 mm negative film. It should be noted that field ion images exhibit low light intensity and high contrast. Field ion images were recorded from a standard microchannel plate and a phosphor screen and had acceptance angles of {approximately} 60{degree}. Digital recordings were made with a Digital Vision Technologies (DVT) MICAM VHR1000 camera with a resolution of 752 x 582 pixels, and a Kodak DCS 460 digital camera with a resolution of 3,060 x 2,036 pixels. Film based recordings were made with Kodak T-MAX film rated at 400 ASA. The resolving power of T-MAX film, as specified by Kodak, is between 50 and 125 lines per mm, which corresponds to between 1,778 x 1,181 and 4,445 x 2,953 pixels, i.e. similar to that from the DCS 460 camera. The intensities of the images were sufficient to be recorded with standard fl:1.2 lenses with exposure times of less than 2 s. Many digital cameras were excluded from these experiments due to their lack of sensitivity or the inability to record a full frame image due to the fixed working distance defined by the vacuum system. The digital images were output on a Kodak Digital Science 8650 PS dye sublimation color printer (300 dpi). All field ion micrographs presented were obtained from a Ni-Al-Be specimen.

  13. Dipolophoresis of dielectric spheroids under asymmetric fields

    NASA Astrophysics Data System (ADS)

    Frankel, Itzchak; Yossifon, Gilad; Miloh, Touvia

    2012-01-01

    Non-spherical particles are common in colloidal science. Spheroidal shapes are particularly convenient for the analysis of the pertinent electrostatic and hydrodynamic problems and are thus widely used to model the manipulation of biological cells as well as deformed drops and bubbles. We study the rotary motion of a dielectric spheroidal micro-particle which is freely suspended in an unbounded electrolyte solution in the presence of a uniform applied electric field, assuming a thin Debye layer. For the common case of a uniform distribution of the native surface-charge density, the rotary motion of the particle is generated by the contributions of the induced-charge electro-osmotic (ICEO) slip and the dielectrophoresis associated with the distribution of the Maxwell stress, respectively. Series solutions are obtained by using spheroidal (prolate or oblate) coordinates. Explicit results are presented for the angular velocity of particles spanning the entire spectrum from rod-like to disk-like shapes. These results demonstrate the non-monotonic variation of the angular speed with the eccentricity of particle shape and the singularity of the multiple limits corresponding to conducting (ideally polarizable) particles of extreme eccentricity (e ≈ 1). The non-monotonic variation of the angular speed with the particle dielectric permittivity is related to the induced-charge contribution. We apply these results to describe the motion of particles subject to a uniform field rotating in the plane. For a sufficiently slow rotation rate, prolate particles eventually become "locked" to the external field with their stationary relative orientation in the plane of rotation being determined by the particle eccentricity and dielectric constant. This effect may be of potential use in the manipulation of poly-disperse suspensions of dielectric non-spherical particles. Oblate spheroids invariably approach a uniform orientation with their symmetry axes directed normal to the external-field

  14. Effects of a Guide Field on the Larmor Electric Field in Collisionless Asymmetric Reconnection

    NASA Astrophysics Data System (ADS)

    Ruffolo, D. J.; Malakit, K.; Ek-In, S.; Shay, M. A.; Cassak, P.

    2014-12-01

    Recently it has been pointed out that when the inflow conditions of magnetic reconnection are asymmetric, a new in-plane electric field can arise from the physics of finite ion Larmor radius, called the Larmor electric field. It is located next to the Hall electric field structure, making it a potential indicator of proximity to the diffusion region. However, the properties of the Larmor electric field have not previously been explored for the case of a nonzero guide field, which could occur for many reconnection sites, including the day-side magnetopause. In this study, we therefore further explore the properties of the Larmor electric field by adding guide fields with different strengths into our simulations. The results show that the width of the Larmor electric field structure will be smaller, but the strength of the field will be stronger as the guide field increases, consistent with what we expect from the existing theory. Moreover, we show that in the region where the Larmor electric field occurs, there also appears an electron anisotropy. The widths of the electron anisotropy and Larmor electric field structures are found to be similar, suggesting that observing the combination of these two signatures provides a useful indicator of proximity to a reconnection site. Partially supported by a Mahidol University Postdoctoral Fellowship and the Thailand Research Fund. This research was supported by the postdoctoral research sponsorship of Mahidol University (K. M.), the Thailand Research Fund (D. R.), NSF Grants No. ATM-0645271 (M. A. S.) and No. AGS-0953463 (P.A. C.), NASA Grants No. NNX08A083G—MMS IDS, No. NNX11AD69G, and No. NNX13AD72G(M. A. S.).

  15. The Asymmetric Top Molecule In An Electric Field

    NASA Astrophysics Data System (ADS)

    Pittman, Suzanne; Almaguer, Jose; Heller, Eric; Heller Group Team

    2014-03-01

    The quantum and classical behavior of the asymmetric top has been studied in a variety of different contexts, and is known for its dynamical complexity due to have greater than 2 DOF. In this presentation the focus will be on the classical dynamics of an asymmetric top molecule with a dipole moment in an electric field (a non-integrable system), and how the underlying classical phase space structures, such as resonances, can impact the behavior of its quantum analog. Specifically, we will be presenting results from a classical simulation, which highlights both chaotic and regular regions for small electric fields depending on initial conditions. Department of Physics and Harvard, I7 Oxford St., Harvard University, Cambridge, Massachusetts 02138.

  16. Stacking and Electrostatic Interactions Drive the Stereoselectivity of Silylium-Ion Asymmetric Counteranion-Directed Catalysis.

    PubMed

    Seguin, Trevor J; Wheeler, Steven E

    2016-12-19

    Computational analysis shows that the enantioselectivity of asymmetric Lewis-acid organocatalysis of the Diels-Alder cycloaddition of cyclopentadiene to cinnamates arises from stacking interactions that favor the addition of the diene to the more hindered face of the dienophile, while electrostatic interactions control the diastereoselectivity by selectively stabilizing the endo transition state. These results not only explain the stereoselectivity of these silylium-ion-ACDC reactions but should also guide the development of more effective ion-pairing asymmetric organocatalysts.

  17. Electro-responsive asymmetric nanopores in polyimide with stable ion-current signal

    NASA Astrophysics Data System (ADS)

    Siwy, Z.; Dobrev, D.; Neumann, R.; Trautmann, C.; Voss, K.

    For the preparation of a single asymmetrically shaped nanopore in a polyimide membrane, Kapton foils were irradiated with single heavy ions and subsequently etched from one side in sodium hypochlorite (NaOCl). The other side of the membrane was protected from etching by a stopping medium containing a reducing agent for hypochlorite ions (OCl-). The resulting conical nanopore rectified ion current and exhibited a stable ion-current flow.

  18. A New Electric Field in Asymmetric Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Malakit, K.; Shay, M. A.; Cassak, P.; Ruffolo, D. J.

    2013-12-01

    Magnetic reconnection is an important plasma process that drives the dynamics of the plasma in the magnetosphere and plays a crucial role in the interaction between magnetospheric and magnetosheath plasma. It has been shown that when a reconnection occurs in a collisionless plasma, it exhibits the Hall electric field, an in-plane electric field structure pointing toward the X-line. In this work, we show that when the reconnection has asymmetric inflow conditions such as the reconnection at the day-side magnetopause, a new in-plane electric field structure can exist. This electric field points away from the X-line and is distinct from the known Hall electric field. We argue that the origin of the electric field is associated with the physics of finite Larmor radius. A theory and predictions of the electric field properties are presented and backed up by results from fully kinetic particle-in-cell simulations of asymmetric reconnection with various inflow conditions. Under normal day-side reconnection inflow conditions, the electric field is expected to occur on the magnetospheric side of the X-line pointing Earthward. Hence, it has a potential to be used as a signature for satellites, such as the upcoming Magnetospheric Multi-Scale (MMS) mission, to locate the reconnection sites at the day-side magnetopause. This research was supported by the postdoctoral research sponsorship of Mahidol University (KM), NSF grants ATM-0645271 - Career Award (MAS) and AGS-0953463 (PAC), NASA grants NNX08A083G - MMS IDS, NNX11AD69G, and NNX13AD72G (MAS) and NNX10AN08A (PAC), and the Thailand Research Fund (DR).

  19. Electric-field-driven polymer entry into asymmetric nanoscale channels.

    PubMed

    Nikoofard, Narges; Fazli, Hossein

    2012-02-01

    The electric-field-driven entry process of flexible charged polymers such as single-stranded DNA (ssDNA) into asymmetric nanoscale channels such as the α-hemolysin protein channel is studied theoretically and using molecular dynamics simulations. Dependence of the height of the free-energy barrier on the polymer length, the strength of the applied electric field, and the channel entrance geometry is investigated. It is shown that the squeezing effect of the driving field on the polymer and the lateral confinement of the polymer before its entry to the channel crucially affect the barrier height and its dependence on the system parameters. The attempt frequency of the polymer for passing the channel is also discussed. Our theoretical and simulation results support each other and describe related data sets of polymer translocation experiments through the α-hemolysin protein channel reasonably well.

  20. Asymmetric field-aligned currents in the conjugate hemispheres

    NASA Astrophysics Data System (ADS)

    Reistad, J. P.; Ostgaard, N.; Oksavik, K.; Laundal, K. M.

    2012-12-01

    Earlier studies using simultaneous imaging from space of the Aurora Borealis (Northern Hemisphere) and Aurora Australis (Southern Hemisphere) have revealed that the aurora can experience a high degree of asymmetry between the two hemispheres. Using 19 hours of simultaneous global imaging from both hemispheres (IMAGE satellite in north and Polar satellite in south) in conjunction with the entire IMAGE WIC database, we investigate the importance of various mechanisms thought to generate the asymmetries seen in global imaging. In terms of asymmetric or interhemispheric field-aligned currents, three candidate mechanisms have been suggested: 1) Hemispheric differences in solar wind dynamo efficiency mainly controlled by IMF Bx leading to asymmetric region 1 currents; 2) conductivity differences in conjugate areas; and 3) penetration of IMF By into the closed magnetosphere possibly generating a pair of oppositely directed interhemispheric currents. From the 19 hour conjugate dataset we find that the solar wind dynamo is likely to be the most important controlling mechanism for asymmetric bright aurora in the polar part of the nightside oval. Here we present statistical analyses of candidates 1) and 3). Using the entire IMAGE WIC database, a statistical analysis of the auroral brightness distribution along and across the Northern Hemisphere oval is carried out. For each candidate, two extreme cases (+/- IMF Bx for 1) and +/- IMF By for 3)) are compared during times non-favorable for the other two mechanisms. Our results indicate that solar wind dynamo induced currents play an important role for the nightside auroral brightness in an average sense. Also, signatures of interhemispheric currents due to IMF By penetration are seen in our statistics, although this effect is somehow weaker.

  1. Ion track symmetric and asymmetric nanopores in polyethylene terephthalate foils for versatile applications

    NASA Astrophysics Data System (ADS)

    Apel, P. Yu.; Blonskaya, I. V.; Dmitriev, S. N.; Orelovich, O. L.; Sartowska, B. A.

    2015-12-01

    In this report we present several fabrication methods which allow production of ion track nanopore membranes with different pore configurations. Polymer foils, typically polyethylene terephthalate with a thickness of 5-23 μm, are irradiated with accelerated heavy ions (energy of 1-10 MeV/u) and then subjected to different physico-chemical treatments. Depending on the procedure, symmetric or asymmetric pores with nanoscale-sized narrowing are obtained. The asymmetric configurations include conical, funnel-like and bullet-like shapes. In electrolyte solutions the asymmetric nanopores exhibit diode-like properties which strongly depend on the pore shape. The peculiar features of such pores provide a basis for various applications.

  2. Concentrating membrane proteins using asymmetric traps and AC electric fields.

    PubMed

    Cheetham, Matthew R; Bramble, Jonathan P; McMillan, Duncan G G; Krzeminski, Lukasz; Han, Xiaojun; Johnson, Benjamin R G; Bushby, Richard J; Olmsted, Peter D; Jeuken, Lars J C; Marritt, Sophie J; Butt, Julea N; Evans, Stephen D

    2011-05-04

    Membrane proteins are key components of the plasma membrane and are responsible for control of chemical ionic gradients, metabolite and nutrient transfer, and signal transduction between the interior of cells and the external environment. Of the genes in the human genome, 30% code for membrane proteins (Krogh et al. J. Mol. Biol.2001, 305, 567). Furthermore, many FDA-approved drugs target such proteins (Overington et al. Nat. Rev. Drug Discovery 2006, 5, 993). However, the structure-function relationships of these are notably sparse because of difficulties in their purification and handling outside of their membranous environment. Methods that permit the manipulation of membrane components while they are still in the membrane would find widespread application in separation, purification, and eventual structure-function determination of these species (Poo et al. Nature 1977, 265, 602). Here we show that asymmetrically patterned supported lipid bilayers in combination with AC electric fields can lead to efficient manipulation of charged components. We demonstrate the concentration and trapping of such components through the use of a "nested trap" and show that this method is capable of yielding an approximately 30-fold increase in the average protein concentration. Upon removal of the field, the material remains trapped for several hours as a result of topographically restricted diffusion. Our results indicate that this method can be used for concentrating and trapping charged membrane components while they are still within their membranous environment. We anticipate that our approach could find widespread application in the manipulation and study of membrane proteins.

  3. Observation of mass-asymmetric fission of mercury nuclei in heavy ion fusion

    NASA Astrophysics Data System (ADS)

    Prasad, E.; Hinde, D. J.; Ramachandran, K.; Williams, E.; Dasgupta, M.; Carter, I. P.; Cook, K. J.; Jeung, D. Y.; Luong, D. H.; McNeil, S.; Palshetkar, C. S.; Rafferty, D. C.; Simenel, C.; Wakhle, A.; Khuyagbaatar, J.; Düllmann, Ch. E.; Lommel, B.; Kindler, B.

    2015-06-01

    Background: Mass-asymmetric fission has been observed in low energy fission of 180Hg . Calculations predicted the persistence of asymmetric fission in this region even at excitation energies of 30-40 MeV. Purpose: To investigate fission mass distributions by populating different isotopes of Hg using heavy ion fusion reactions. Methods: Fission fragment mass-angle distributions have been measured for two reactions, 40Ca+142Nd and 13C+182W , populating 182Hg and 195Hg , respectively, using the Heavy Ion Accelerator Facility and CUBE spectrometer at the Australian National University. Measurements were made at beam energies around the capture barrier for the two reactions and mass ratio distributions were obtained using the kinematic reconstruction method. Results: Asymmetric fission has been observed following the population of 182Hg at an excitation energy of 22.8 MeV above the saddle point. A symmetric peaked mass ratio distribution was observed for 195Hg nuclei at a similar excitation energy above the saddle point. Conclusions: Mass-asymmetric fission has been observed in neutron deficient Hg nuclei populated via heavy ion fusion for the first time. The results are consistent with observations from beta-delayed fission measurements and provide a proof-of-principle for expanding experimental studies of the influence of shell effects on the fission processes.

  4. Delayed rectifier current of bullfrog sympathetic neurons: ion-ion competition, asymmetrical block and effects of ions on gating.

    PubMed Central

    Block, B M; Jones, S W

    1997-01-01

    1. The delayed rectifier (DR) K+ channel pore was probed using different permeant and blocking ions applied intra- and extracellularly. Currents were recorded from bullfrog sympathetic neurons using whole-cell patch-clamp techniques. 2. With intra- and extracellular Cs+ (0 K+), there were large, tetraethylammonium (TEA)-sensitive currents. Adding K+ back to the extracellular solution revealed that the current with Cs+i was K+ selective (permeability ratio PCs/PK = 0.17 +/- 0.02, n = 4) and showed a strong anomalous mole fraction effect. 3. There were also large non-inactivating currents with Na+i and Na+o (0 K+). The current with Na+i was K+ selective (Na+o vs. K+o: PNa/PK = 0.022 +/- 0.005, n = 5), and was TEA sensitive with K+o but not with Na+o. 4. Permeant ions affected gating kinetics. DR currents activated faster in K+ than in Cs+, and activated faster with increasing concentrations of either K+ or Cs+. Deactivation was slowed by increased K+ or Cs+ concentration, with no difference between K+ and Cs+. 5. The pore was also characterized using intracellular blocking ions. A wide variety of monovalent cations (TEA, N-methyl-D-glucamine, arginine, choline, CH3NH3+, Li+, Cs+ and Na+) blocked DR channels from the inside in a voltage-dependent manner: KD at 0 mV was 2.9 mM for TEA and 134-487 mM for the others, at apparent electrical distances (delta) of 0.33-0.79. There was no detectable block by 10 mM Mgi2+. Apart from TEA, the organic cations did not block from the outside. 6. The permeability to Na+ in the absence of K+, and the strong anomalous mole fraction effects observed for Cs+o + K+o mixtures, suggest that DR channels select for K+ using ion-ion competition. The block by large intracellular cations shows that the pore is asymmetrical. The loss of high affinity TEAo block with Na+i and Na+o, and the effects of permeant ions on gating, suggest that channel conformation may be affected by ions in the pore. PMID:9080370

  5. Delayed rectifier current of bullfrog sympathetic neurons: ion-ion competition, asymmetrical block and effects of ions on gating.

    PubMed

    Block, B M; Jones, S W

    1997-03-01

    1. The delayed rectifier (DR) K+ channel pore was probed using different permeant and blocking ions applied intra- and extracellularly. Currents were recorded from bullfrog sympathetic neurons using whole-cell patch-clamp techniques. 2. With intra- and extracellular Cs+ (0 K+), there were large, tetraethylammonium (TEA)-sensitive currents. Adding K+ back to the extracellular solution revealed that the current with Cs+i was K+ selective (permeability ratio PCs/PK = 0.17 +/- 0.02, n = 4) and showed a strong anomalous mole fraction effect. 3. There were also large non-inactivating currents with Na+i and Na+o (0 K+). The current with Na+i was K+ selective (Na+o vs. K+o: PNa/PK = 0.022 +/- 0.005, n = 5), and was TEA sensitive with K+o but not with Na+o. 4. Permeant ions affected gating kinetics. DR currents activated faster in K+ than in Cs+, and activated faster with increasing concentrations of either K+ or Cs+. Deactivation was slowed by increased K+ or Cs+ concentration, with no difference between K+ and Cs+. 5. The pore was also characterized using intracellular blocking ions. A wide variety of monovalent cations (TEA, N-methyl-D-glucamine, arginine, choline, CH3NH3+, Li+, Cs+ and Na+) blocked DR channels from the inside in a voltage-dependent manner: KD at 0 mV was 2.9 mM for TEA and 134-487 mM for the others, at apparent electrical distances (delta) of 0.33-0.79. There was no detectable block by 10 mM Mgi2+. Apart from TEA, the organic cations did not block from the outside. 6. The permeability to Na+ in the absence of K+, and the strong anomalous mole fraction effects observed for Cs+o + K+o mixtures, suggest that DR channels select for K+ using ion-ion competition. The block by large intracellular cations shows that the pore is asymmetrical. The loss of high affinity TEAo block with Na+i and Na+o, and the effects of permeant ions on gating, suggest that channel conformation may be affected by ions in the pore.

  6. A study of ion acceleration, asymmetric optical pumping and low frequency waves in two expanding helicon plasmas

    NASA Astrophysics Data System (ADS)

    Sun, Xuan

    This work concerns measurements of parallel ion flow, optical pumping, and low frequency waves in expanding plasmas generated by two different helicon plasma sources. The measurements confirm numerical predictions of the formation of a current-free double layer in a region of diverging magnetic field. With laser-induced fluorescence (LIF), the double layer structure in both helicon plasma sources was investigated through measurements of the bulk parallel ion flow speed. Both double layers have a total potential drop of 3-4 kTe and length scales smaller than ion-neutral mean-free-path. A stronger double layer, with a potential drop of ˜ 6kTe , was created in a uniform magnetic field region with a plasma limiting aperture plate. During the investigations of ion acceleration in expanding plasmas, a new phenomenon, asymmetrical optical pumping (AOP) due to the acceleration of ions in magnetic field gradient, was observed. The signature of AOP is a difference in the LIF emission amplitude from a pair of Zeeman-split ion states. A model that reproduces the dependence of the AOP on magnetic-field and ion-velocity gradients is described. With magnetic fluctuation probes, low frequency, transverse, electromagnetic waves were also identified in the expanding helicon plasma. The wave is localized to the vicinity of the maximum plasma density gradient and appears only at low neutral pressure. Based on the scaling of the wave frequency and amplitude with magnetic field strength, the wave was identified as the resistive drift Alfven wave.

  7. Comparison between hybrid and fully kinetic models of asymmetric magnetic reconnection: Coplanar and guide field configurations

    SciTech Connect

    Aunai, Nicolas; Hesse, Michael; Kuznetsova, Maria; Black, Carrie; Evans, Rebekah; Zenitani, Seiji; Smets, Roch

    2013-02-15

    Magnetic reconnection occurring in collisionless environments is a multi-scale process involving both ion and electron kinetic processes. Because of their small mass, the electron scales are difficult to resolve in numerical and satellite data, it is therefore critical to know whether the overall evolution of the reconnection process is influenced by the kinetic nature of the electrons, or is unchanged when assuming a simpler, fluid, electron model. This paper investigates this issue in the general context of an asymmetric current sheet, where both the magnetic field amplitude and the density vary through the discontinuity. A comparison is made between fully kinetic and hybrid kinetic simulations of magnetic reconnection in coplanar and guide field systems. The models share the initial condition but differ in their electron modeling. It is found that the overall evolution of the system, including the reconnection rate, is very similar between both models. The best agreement is found in the guide field system, which confines particle better than the coplanar one, where the locality of the moments is violated by the electron bounce motion. It is also shown that, contrary to the common understanding, reconnection is much faster in the guide field system than in the coplanar one. Both models show this tendency, indicating that the phenomenon is driven by ion kinetic effects and not electron ones.

  8. An analytical method to calculate equivalent fields to irregular symmetric and asymmetric photon fields

    SciTech Connect

    Tahmasebi Birgani, Mohamad J.; Chegeni, Nahid; Zabihzadeh, Mansoor; Hamzian, Nima

    2014-04-01

    Equivalent field is frequently used for central axis depth-dose calculations of rectangular- and irregular-shaped photon beams. As most of the proposed models to calculate the equivalent square field are dosimetry based, a simple physical-based method to calculate the equivalent square field size was used as the basis of this study. The table of the sides of the equivalent square or rectangular fields was constructed and then compared with the well-known tables by BJR and Venselaar, et al. with the average relative error percentage of 2.5 ± 2.5% and 1.5 ± 1.5%, respectively. To evaluate the accuracy of this method, the percentage depth doses (PDDs) were measured for some special irregular symmetric and asymmetric treatment fields and their equivalent squares for Siemens Primus Plus linear accelerator for both energies, 6 and 18 MV. The mean relative differences of PDDs measurement for these fields and their equivalent square was approximately 1% or less. As a result, this method can be employed to calculate equivalent field not only for rectangular fields but also for any irregular symmetric or asymmetric field.

  9. Asymmetric Functional Conversion of Eubacterial Light-driven Ion Pumps.

    PubMed

    Inoue, Keiichi; Nomura, Yurika; Kandori, Hideki

    2016-05-06

    In addition to the well-known light-driven outward proton pumps, novel ion-pumping rhodopsins functioning as outward Na(+) and inward Cl(-) pumps have been recently found in eubacteria. They convert light energy into transmembrane electrochemical potential difference, similar to the prototypical archaeal H(+) pump bacteriorhodopsin (BR) and Cl(-) pump halorhodopsin (HR). The H(+), Na(+), and Cl(-) pumps possess the conserved respective DTE, NDQ, and NTQ motifs in the helix C, which likely serve as their functional determinants. To verify this hypothesis, we attempted functional interconversion between selected pumps from each category by mutagenesis. Introduction of the proton-pumping motif resulted in successful Na(+) → H(+) functional conversion. Introduction of the respective characteristic motifs with several additional mutations leads to successful Na(+) → Cl(-) and Cl(-) → H(+) functional conversions, whereas remaining conversions (H(+) → Na(+), H(+) → Cl(-), Cl(-) → Na(+)) were unsuccessful when mutagenesis of 4-6 residues was used. Phylogenetic analysis suggests that a H(+) pump is the common ancestor of all of these rhodopsins, from which Cl(-) pumps emerged followed by Na(+) pumps. We propose that successful functional conversions of these ion pumps are achieved exclusively when mutagenesis reverses the evolutionary amino acid sequence changes. Dependence of the observed functional conversions on the direction of evolution strongly suggests that the essential structural mechanism of an ancestral function is retained even after the gain of a new function during natural evolution, which can be evoked by a few mutations. By contrast, the gain of a new function needs accumulation of multiple mutations, which may not be easily reproduced by limited mutagenesis in vitro.

  10. Manipulating antiferromagnets with magnetic fields: Ratchet motion of multiple domain walls induced by asymmetric field pulses

    NASA Astrophysics Data System (ADS)

    Gomonay, O.; Kläui, M.; Sinova, J.

    2016-10-01

    Future applications of antiferromagnets (AFs) in many spintronics devices rely on the precise manipulation of domain walls. The conventional approach using static magnetic fields is inefficient due to the low susceptibility of AFs. Recently proposed electrical manipulation with spin-orbit torques is restricted to metals with a specific crystal structure. Here, we propose an alternative, broadly applicable approach: using asymmetric magnetic field pulses to induce controlled ratchet motion of AF domain walls. The efficiency of this approach is based on three peculiarities of AF dynamics. First, a time-dependent magnetic field couples with an AF order parameter stronger than a static magnetic field, which leads to higher mobility of the domain walls. Second, the rate of change of the magnetic field couples with the spatial variation of the AF order parameter inside the domain, and this enables a synchronous motion of multiple domain walls with the same structure. Third, tailored asymmetric field pulses in combination with static friction can prevent backward motion of domain walls and thus lead to the desired controlled ratchet effect. The proposed use of an external field, rather than internal spin-orbit torques, avoids any restrictions on size, conductivity, and crystal structure of the AF material. We believe that our approach paves a way for the development of AF-based devices based on the controlled motion of AF domain walls.

  11. Generation of circularly polarized attosecond pulses by intense ultrashort laser pulses from extended asymmetric molecular ions

    SciTech Connect

    Yuan, Kai-Jun; Bandrauk, Andre D.

    2011-08-15

    We present a method for generation of single circularly polarized attosecond pulses in extended asymmetric HHe{sup 2+} molecular ions. By employing an intense ultrashort circularly polarized laser pulse with intensity 4.0x10{sup 14} W/cm{sup 2}, wavelength 400 nm, and duration 10 optical cycles, molecular high-order-harmonic generation (MHOHG) spectra with multiple plateaus exhibit characters of circular polarization. Using a classical laser-induced collision model, double collisions of continuum electrons first with neighboring ions and then second with parent ions are presented at a particular internuclear distance and confirmed from numerical solutions of a time-dependent Schroedinger equation. We analyze the MHOHG spectra with a Gabor time window and find that, due to the asymmetry of HHe{sup 2+}, a single collision trajectory of continuum electrons with ions can produce circularly polarized harmonics, leading to single circularly polarized attosecond pulses for specific internuclear distances.

  12. Detection, identification, and occurrence of thiotetronic acids in drinking water from underground sources by electrospray ionization-high field asymmetric waveform ion mobility spectrometry-quadrupole time-of-flight-mass spectrometry.

    PubMed

    Lyczko, Jadwiga; Beach, Daniel; Gabryelski, Wojciech

    2015-10-06

    This paper demonstrates that electrospray ionization (ESI) with differential ion mobility spectroscopy (FAIMS) and "soft" mass spectrometry (MS) provide unique analytical capabilities that led to the discovery of sulfur-containing polar congeners of thiotetronic acid (TA) in drinking water from underground sources in Canada and the United States. Polar TAs accumulate in underground aquifers and appear to be the most abundant class of organic compounds in bottled water but cannot be detected by conventional mass spectrometry methods. We show that normally stable TAs are converted into very reactive ions in ESI which have to be analyzed using special conditions in ESI-FAIMS-MS to avoid extensive dissociation and ion/molecule reactions. De novo identification of 10 TAs was accomplished by the comparative tandem mass spectrometry analysis of authentic TA derivatives from groundwater samples and synthetic TA analogues prepared for this study. We present highlights of gas phase ion chemistry of polar TAs to explain their unique properties and reactivity. TA derivatives were originally isolated from soil bacteria and are of interest in the pharmaceutical industry due to their potent activity against a broad spectrum of pathogenic bacteria and negligible toxicity to mammals. We suspect that TAs are natural disinfection agents protecting groundwater from bacterial contamination, but these compound undergo modifications or decompose during an ozonation water treatment.

  13. Investigation of the asymmetric distributions of RF transmission and reception fields at high static field.

    PubMed

    Watanabe, Hidehiro

    2012-01-01

    When radiofrequency (RF) transmission field represents B(1)(+), the reception field represents B(1)(-)*. The distribution of those maps demonstrates asymmetric features at high field magnetic resonance (MR) imaging. Both maps are in mirror symmetry to one another. Almost symmetric distribution of the B(1) field was expected on the laboratory frame in a symmetric sample loaded inside the RF coil designed to achieve a homogeneous B(1) field. Then, a simple change was made in the coordinate transformation equation of RF fields between the rotating and laboratory frames in both linear and quadrature modes to investigate the source of this feature of asymmetry. The magnitude of rotating frame components, B(1)(+) and B(1)(-), consists of the magnitude and the phase difference of the laboratory frame components. The rotating frame components differ in the sign of the sinusoidal phase difference. B(1)(+) is equal to B(1)(-) at lower field because phase changes that depend on position can be ignored. At higher fields, the magnitude component has a symmetric profile, and distribution in the phase component is antisymmetric. Thus, the distributions of B(1)(+) and B(1)(-) maps demonstrate mirror symmetry. Maps of magnitude and phase components were examined in the laboratory frame. Their maps were computed from B(1)(+) and B(1)(-) maps of the human brain and of a spherical saline phantom measured at 4.7T. It was concluded from these analytical and experimental results that the asymmetric and mirror symmetric distributions in B(1)(+) and B(1)(-) are derived from the phase difference in the laboratory frame.

  14. Ion pairing and phase behaviour of an asymmetric restricted primitive model of ionic liquids

    NASA Astrophysics Data System (ADS)

    Lu, Hongduo; Li, Bin; Nordholm, Sture; Woodward, Clifford E.; Forsman, Jan

    2016-12-01

    An asymmetric restricted primitive model (ARPM) of electrolytes is proposed as a simple three parameter (charge q, diameter d, and charge displacement b) model of ionic liquids and solutions. Charge displacement allows electrostatic and steric interactions to operate between different centres, so that orientational correlations arise in ion-ion interactions. In this way the ionic system may have partly the character of a simple ionic fluid/solid and of a polar fluid formed from ion pairs. The present exploration of the system focuses on the ion pair formation mechanism, the relative concentration of paired and free ions and the consequences for the cohesive energy, and the tendency to form fluid or solid phase. In contrast to studies of similar (though not identical) models in the past, we focus on behaviours at room temperature. By MC and MD simulations of such systems composed of monovalent ions of hard-sphere (or essentially hard-sphere) diameter equal to 5 Å and a charge displacement ranging from 0 to 2 Å from the hard-sphere origin, we find that ion pairing dominates for b larger than 1 Å. When b exceeds about 1.5 Å, the system is essentially a liquid of dipolar ion pairs with a small presence of free ions. We also investigate dielectric behaviours of corresponding liquids, composed of purely dipolar species. Many basic features of ionic liquids appear to be remarkably consistent with those of our ARPM at ambient conditions, when b is around 1 Å. However, the rate of self-diffusion and, to a lesser extent, conductivity is overestimated, presumably due to the simple spherical shape of our ions in the ARPM. The relative simplicity of our ARPM in relation to the rich variety of new mechanisms and properties it introduces, and to the numerical simplicity of its exploration by theory or simulation, makes it an essential step on the way towards representation of the full complexity of ionic liquids.

  15. Realization of near-field linear nano-polarizer by asymmetric nanoaperture and bowtie nanoantenna.

    PubMed

    Li, Jianxiong; Chen, Shuqi; Yu, Ping; Cheng, Hua; Duan, Xiaoyang; Tian, Jianguo

    2013-04-22

    We present a linear nano-polarizer composed of asymmetric nanoaperture and bowtie nanoantenna, which provides a new way to freely control the polarization azimuth of the translated optical field in the near-field. It can not only generate large localized field enhancement and outstanding spatial confinement, but also maintain the polarization azimuth of linearly polarized optical field excited by arbitrary linearly, circularly or elliptically polarized lights. The response wavelength of the linear nano-polarizer can be easily tuned in a wide range by adjusting the geometrical parameters of asymmetric nanoaperture. This offers a further step in developing integrated optical devices for polarization manipulation.

  16. Using heavy-ion collisions to elucidate the asymmetric equation-of-state

    NASA Astrophysics Data System (ADS)

    Yennello, Sherry; McIntosh, Alan

    2016-06-01

    The nuclear equation-of-state impacts a number of nuclear properties as well as astrophysical processes. The asymmetric term of the equation-of-state, which describes the behavior away from N=Z, has significant uncertainty. Giant resonances and nuclear masses can elucidate the asymmetry energy for cold normal-density nuclei. Heavy-ion collisions can be used to probe nuclear matter at higher temperatures and densities away from saturation density. The temperatures that are attained in these nuclear collisions are predicted to depend on the isospin asymmetry. In this work we present evidence of the asymmetry dependence of the nuclear caloric curve.

  17. Laser ion source with solenoid field

    SciTech Connect

    Kanesue, Takeshi; Fuwa, Yasuhiro; Kondo, Kotaro; Okamura, Masahiro

    2014-11-12

    Pulse length extension of highly charged ion beam generated from a laser ion source is experimentally demonstrated. In this study, the laser ion source (LIS) has been recognized as one of the most powerful heavy ion source. However, it was difficult to provide long pulse beams. By applying a solenoid field (90 mT, 1 m) at plasma drifting section, a pulse length of carbon ion beam reached 3.2 μs which was 4.4 times longer than the width from a conventional LIS. The particle number of carbon ions accelerated by a radio frequency quadrupole linear accelerator was 1.2 × 1011, which was provided by a single 1 J Nd-YAG laser shot. A laser ion source with solenoid field could be used in a next generation heavy ion accelerator.

  18. Laser ion source with solenoid field

    DOE PAGES

    Kanesue, Takeshi; Fuwa, Yasuhiro; Kondo, Kotaro; ...

    2014-11-12

    Pulse length extension of highly charged ion beam generated from a laser ion source is experimentally demonstrated. In this study, the laser ion source (LIS) has been recognized as one of the most powerful heavy ion source. However, it was difficult to provide long pulse beams. By applying a solenoid field (90 mT, 1 m) at plasma drifting section, a pulse length of carbon ion beam reached 3.2 μs which was 4.4 times longer than the width from a conventional LIS. The particle number of carbon ions accelerated by a radio frequency quadrupole linear accelerator was 1.2 × 1011, whichmore » was provided by a single 1 J Nd-YAG laser shot. A laser ion source with solenoid field could be used in a next generation heavy ion accelerator.« less

  19. Laser ion source with solenoid field

    NASA Astrophysics Data System (ADS)

    Kanesue, Takeshi; Fuwa, Yasuhiro; Kondo, Kotaro; Okamura, Masahiro

    2014-11-01

    Pulse length extension of highly charged ion beam generated from a laser ion source is experimentally demonstrated. The laser ion source (LIS) has been recognized as one of the most powerful heavy ion source. However, it was difficult to provide long pulse beams. By applying a solenoid field (90 mT, 1 m) at plasma drifting section, a pulse length of carbon ion beam reached 3.2 μs which was 4.4 times longer than the width from a conventional LIS. The particle number of carbon ions accelerated by a radio frequency quadrupole linear accelerator was 1.2 × 1011, which was provided by a single 1 J Nd-YAG laser shot. A laser ion source with solenoid field could be used in a next generation heavy ion accelerator.

  20. Isotopic effect on ion mobility and separation of isotopomers by high-field ion mobility spectrometry.

    PubMed

    Shvartsburg, Alexandre A; Clemmer, David E; Smith, Richard D

    2010-10-01

    Distinguishing and separating isotopic molecular variants is important across many scientific fields. However, discerning such variants, especially those producing no net mass difference, has been challenging. For example, single-stage mass spectrometry is broadly employed to analyze isotopes but is blind to isotopic isomers (isotopomers) and, except at very high resolution, species of the same nominal mass (isobars). Here, we report separation of isotopic ions, including isotopomers and isobars, using ion mobility spectrometry (IMS), specifically, the field asymmetric waveform IMS (FAIMS). The effect is not based on the different reduced masses of ion-gas molecule pairs previously theorized to cause isotopic separations in conventional IMS, but appears related to the details of energetic ion-molecule collisions in strong electric fields. The observed separation qualitatively depends on the gas composition and may be improved using gas mixtures. Isotopic shifts depend on the position of the labeled site, which allows its localization and contains information about the ion geometry, potentially enabling a new approach to molecular structure characterization.

  1. Dynamics of a reconnection-driven runaway ion tail in a reversed field pinch plasma

    NASA Astrophysics Data System (ADS)

    Anderson, J. K.; Kim, J.; Bonofiglo, P. J.; Capecchi, W.; Eilerman, S.; Nornberg, M. D.; Sarff, J. S.; Sears, S. H.

    2016-05-01

    While reconnection-driven ion heating is common in laboratory and astrophysical plasmas, the underlying mechanisms for converting magnetic to kinetic energy remain not fully understood. Reversed field pinch discharges are often characterized by rapid ion heating during impulsive reconnection, generating an ion distribution with an enhanced bulk temperature, mainly perpendicular to magnetic field. In the Madison Symmetric Torus, a subset of discharges with the strongest reconnection events develop a very anisotropic, high energy tail parallel to magnetic field in addition to bulk perpendicular heating, which produces a fusion neutron flux orders of magnitude higher than that expected from a Maxwellian distribution. Here, we demonstrate that two factors in addition to a perpendicular bulk heating mechanism must be considered to explain this distribution. First, ion runaway can occur in the strong parallel-to-B electric field induced by a rapid equilibrium change triggered by reconnection-based relaxation; this effect is particularly strong on perpendicularly heated ions which experience a reduced frictional drag relative to bulk ions. Second, the confinement of ions varies dramatically as a function of velocity. Whereas thermal ions are governed by stochastic diffusion along tearing-altered field lines (and radial diffusion increases with parallel speed), sufficiently energetic ions are well confined, only weakly affected by a stochastic magnetic field. High energy ions traveling mainly in the direction of toroidal plasma current are nearly classically confined, while counter-propagating ions experience an intermediate confinement, greater than that of thermal ions but significantly less than classical expectations. The details of ion confinement tend to reinforce the asymmetric drive of the parallel electric field, resulting in a very asymmetric, anisotropic distribution.

  2. A Systematic Investigation of Quaternary Ammonium Ions as Asymmetric Phase Transfer Catalysts. Application of Quantitative Structure Activity/Selectivity Relationships

    PubMed Central

    Denmark, Scott E.; Gould, Nathan D.; Wolf, Larry M.

    2011-01-01

    While the synthetic utility of asymmetric phase transfer catalysis continues to expand, the number of proven catalyst types and design criteria remains limited. At the origin of this scarcity is a lack in understanding of how catalyst structural features affect the rate and enantioselectivity of phase transfer catalyzed reactions. Described in this paper is the development of quantitative structure-activity relationships (QSAR) and -selectivity relationships (QSSR) for the alkylation of a protected glycine imine with libraries of quaternary ammonium ion catalysts. Catalyst descriptors including ammonium ion accessibility, interfacial adsorption affinity, and partition coefficient were found to correlate meaningfully with catalyst activity. The physical nature of the descriptors was rationalized through differing contributions of the interfacial and extraction mechanisms to the reaction under study. The variation in the observed enantioselectivity was rationalized employing a comparative molecular field analysis (CoMFA) using both the steric and electrostatic fields of the catalysts. A qualitative analysis of the developed model reveals preferred regions for catalyst binding to afford both configurations of the alkylated product. PMID:21446723

  3. Self-assembled asymmetric membrane containing micron-size germanium for high capacity lithium ion batteries

    SciTech Connect

    Byrd, Ian; Chen, Hao; Webber, Theron; Li, Jianlin; Wu, Ji

    2015-10-23

    We report the formation of novel asymmetric membrane electrode containing micron-size (~5 μm) germanium powders through a self-assembly phase inversion method for high capacity lithium ion battery anode. 850 mA h g-1 capacity (70%) can be retained at a current density of 600 mA g-1 after 100 cycles with excellent rate performance. Such a high retention rate has rarely been seen for pristine micron-size germanium anodes. Moreover, scanning electron microscope studies reveal that germanium powders are uniformly embedded in a networking porous structure consisting of both nanopores and macropores. It is believed that such a unique porous structure can efficiently accommodate the ~260% volume change during germanium alloying and de-alloying process, resulting in an enhanced cycling performance. Finally, these porous membrane electrodes can be manufactured in large scale using a roll-to-roll processing method.

  4. Self-assembled asymmetric membrane containing micron-size germanium for high capacity lithium ion batteries

    DOE PAGES

    Byrd, Ian; Chen, Hao; Webber, Theron; ...

    2015-10-23

    We report the formation of novel asymmetric membrane electrode containing micron-size (~5 μm) germanium powders through a self-assembly phase inversion method for high capacity lithium ion battery anode. 850 mA h g-1 capacity (70%) can be retained at a current density of 600 mA g-1 after 100 cycles with excellent rate performance. Such a high retention rate has rarely been seen for pristine micron-size germanium anodes. Moreover, scanning electron microscope studies reveal that germanium powders are uniformly embedded in a networking porous structure consisting of both nanopores and macropores. It is believed that such a unique porous structure can efficientlymore » accommodate the ~260% volume change during germanium alloying and de-alloying process, resulting in an enhanced cycling performance. Finally, these porous membrane electrodes can be manufactured in large scale using a roll-to-roll processing method.« less

  5. Mean-field analysis for parallel asymmetric exclusion process with anticipation effect.

    PubMed

    Hao, Qing-Yi; Jiang, Rui; Hu, Mao-Bin; Wu, Qing-Song

    2010-08-01

    This paper studies an extended parallel asymmetric exclusion process, in which the anticipation effect is taken into account. The fundamental diagram of the model has been investigated via cluster mean field analysis. Different from previous mean field analysis, in which the n -cluster probabilities P(σ{i},…,σ{i+n-1}) involve the (n+2) -cluster probabilities P(τ{i-1},…,τ{i+n}) , our mean-field analysis is asymmetric because the three-cluster probabilities P(σ{i},σ{i+1},σ{i+2}) involve the six-cluster probabilities P(τ{i-1},…,τ{i+4}) . We find an excellent agreement between Monte Carlo simulations and cluster mean field analysis, which indicates that the mean field analysis might give the exact expression.

  6. Negative-Refractive Bicrystal with Broken Symmetry Produces Asymmetric Electromagnetic Fields in Guided-Wave Heterostructures

    NASA Astrophysics Data System (ADS)

    Krowne, Clifford M.

    2004-07-01

    Heterostructure arrangements of uniaxial bicrystals have been discovered to produce electromagnetic fields with asymmetric distributions in guide wave structures. The property behind this remarkable phenomenon is the broken crystalline symmetry which allows the new physics to be seen in unsymmetric distributions. Here the theory behind this phenomenon is presented, numerical calculations are performed using an ab initio anisotropic Green’s function approach, and the results provided at 10 GHz for a realistic crystal system with nominal permittivity of 5. Asymmetric distributions seen here are one facet of the broken symmetry property which generates negative refraction for impinging waves on a bicrystal.

  7. Asymmetric Reconnection at the Magnetopause Under the Presence of Low-Energy Ions of Magnetospheric Origin

    NASA Astrophysics Data System (ADS)

    Toledo Redondo, S.; Vaivads, A.; Andre, M.; Khotyaintsev, Y. V.

    2014-12-01

    Magnetic reconnection at the magnetopause is characterized by asymmetry of the plasmas involved. On one side, there is the shocked plasma of the sheath coming from the solar wind, and, on the other, the energetic plasma drifting from the magnetosphere towards the magnetopause. Recent studies have pointed that, in addition to the high-energy (~104 eV) ions from the latter plasma, relevant amounts of positive low-energy ions (with energies below the equivalent spacecraft potential, i.e. below ~5-10 eV) are frequently present on the magnetospheric side of reconnection layer. These ions have small enough gyroradius to ExB drift inside the thin separatrix layer, and can modify processes in the layer. We use Cluster observations near the subsolar point to study the role of these low-energy ions at the magnetopause when reconnection is occurring. The presence of low-energy ions can be detected by observing a local wake electric field caused by a supersonic flow of low-energy ions passed a charged spacecraft. The density of these ions can be estimated by comparing the total density obtained from the plasma frequency or the spacecraft potential with observations by particle detectors of ions with high enough energy to reach the spacecraft. The dataset employed (2008) permits to resolve the current at scales below the ion inertial length (c/ωpi) in the direction normal to the magnetopause. The terms jxB/en, -vxB and ∇ pe/en are compared in the thin layers with strong En fields observed during the magnetopause crossings. It is clear that the presence of low-energy ions modifies the reconnection process, since in some cases they are able to balance the whole En term via the -vxB drift without the need of jxB/en.

  8. Angular Dependence of Vortex Annihilation Fields in Asymmetric Co Dots

    DTIC Science & Technology

    2009-07-15

    eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars...a dynamic research platform to scholars worldwide. the half loop and the vortex chirality can be well controlled. At intermediate angles the chirality...and the changing energy landscape during field cycling. The vortex annihilation along the half loop faces a higher energy barrier than along the

  9. Asymmetric catalytic formation of quaternary carbons by iminium ion trapping of radicals

    NASA Astrophysics Data System (ADS)

    Murphy, John J.; Bastida, David; Paria, Suva; Fagnoni, Maurizio; Melchiorre, Paolo

    2016-04-01

    An important goal of modern organic chemistry is to develop new catalytic strategies for enantioselective carbon-carbon bond formation that can be used to generate quaternary stereogenic centres. Whereas considerable advances have been achieved by exploiting polar reactivity, radical transformations have been far less successful. This is despite the fact that open-shell intermediates are intrinsically primed for connecting structurally congested carbons, as their reactivity is only marginally affected by steric factors. Here we show how the combination of photoredox and asymmetric organic catalysis enables enantioselective radical conjugate additions to β,β-disubstituted cyclic enones to obtain quaternary carbon stereocentres with high fidelity. Critical to our success was the design of a chiral organic catalyst, containing a redox-active carbazole moiety, that drives the formation of iminium ions and the stereoselective trapping of photochemically generated carbon-centred radicals by means of an electron-relay mechanism. We demonstrate the generality of this organocatalytic radical-trapping strategy with two sets of open-shell intermediates, formed through unrelated light-triggered pathways from readily available substrates and photoredox catalysts—this method represents the application of iminium ion activation (a successful catalytic strategy for enantioselective polar chemistry) within the realm of radical reactivity.

  10. Improvement of infrared near-field spectrum by asymmetric interferometer configuration

    NASA Astrophysics Data System (ADS)

    Ikemoto, Yuka; Okamura, Hidekazu; Moriwaki, Taro; Suto, Hitoshi; Kinoshita, Toyohiko

    2015-08-01

    Infrared synchrotron radiation (IR-SR) is a highly brilliant white light source. We are developing an infrared near-field spectroscopy system with an IR-SR light source. The near-field spectroscopy system previously reported comprised an atomic force microscope (AFM) and a commercial Fourier transform infrared (FTIR) spectrometer. In the present study, the configuration of the FTIR interferometer has been modified to an asymmetric one. In the asymmetric interferometer, one beam split by a beamsplitter is focused onto the tip of an AFM probe, and the other beam goes to a movable mirror. The scattered light from the probe and the light reflected by the movable mirror interfere with each other. The near-field signal is extracted by a modulation method with an AFM oscillation frequency. The signal-to-noise ratio has been improved 6-fold and the signal-to-background ratio is improved 8-fold compared with those observed in the previous system.

  11. Bending and growth of entrained air filament under converging and asymmetric rotational fields

    NASA Astrophysics Data System (ADS)

    Kumar, Parmod; Das, Arup K.; Mitra, Sushanta K.

    2017-02-01

    Here we have proposed the increase of the entrainment rate by extruding an air filament under the action of convergent but asymmetric rotational field. By varying the source speed and the diameter of rotational fields, we showed the bending of an air filament towards the higher strength direction of the asymmetric inertia. Interfacial profiles like bubble ejection from the air filament and non-collapsible entrainment with air accumulation in a stagnant zone are obtained in finite volume based numerical simulations, on gradual increase of average rotational fields. Physical understanding of bent interface profile reveals the presence of multiple stages in filament growth depending upon the inertia of surrounding medium. Accumulation of air in the stagnant zone is found to be more prominent in case of rotational speed based asymmetry in contrast to its counterpart having diametric asymmetry of imposing sources. Relative comparison between these two methods of producing asymmetric field showed faster growth of filament upon varying the source diameter, while keeping the speed same. In case of extreme retardation and enhancement of rotational asymmetry, film pinch off and formation of bubble train have been reported. The shape of ejected bubbles is governed by the inertia of the surrounding medium, and bubbles have taken elliptical shapes with their major axis aligned parallel to the adjacent velocity field.

  12. Asymmetric kinetic equilibria: Generalization of the BAS model for rotating magnetic profile and non-zero electric field

    NASA Astrophysics Data System (ADS)

    Dorville, Nicolas; Belmont, Gérard; Aunai, Nicolas; Dargent, Jérémy; Rezeau, Laurence

    2015-09-01

    Finding kinetic equilibria for non-collisional/collisionless tangential current layers is a key issue as well for their theoretical modeling as for our understanding of the processes that disturb them, such as tearing or Kelvin Helmholtz instabilities. The famous Harris equilibrium [E. Harris, Il Nuovo Cimento Ser. 10 23, 115-121 (1962)] assumes drifting Maxwellian distributions for ions and electrons, with constant temperatures and flow velocities; these assumptions lead to symmetric layers surrounded by vacuum. This strongly particular kind of layer is not suited for the general case: asymmetric boundaries between two media with different plasmas and different magnetic fields. The standard method for constructing more general kinetic equilibria consists in using Jeans theorem, which says that any function depending only on the Hamiltonian constants of motion is a solution to the steady Vlasov equation [P. J. Channell, Phys. Fluids (1958-1988) 19, 1541 (1976); M. Roth et al., Space Sci. Rev. 76, 251-317 (1996); and F. Mottez, Phys. Plasmas 10, 1541-1545 (2003)]. The inverse implication is however not true: when using the motion invariants as variables instead of the velocity components, the general stationary particle distributions keep on depending explicitly of the position, in addition to the implicit dependence introduced by these invariants. The standard approach therefore strongly restricts the class of solutions to the problem and probably does not select the most physically reasonable. The BAS (Belmont-Aunai-Smets) model [G. Belmont et al., Phys. Plasmas 19, 022108 (2012)] used for the first time the concept of particle accessibility to find new solutions: considering the case of a coplanar-antiparallel magnetic field configuration without electric field, asymmetric solutions could be found while the standard method can only lead to symmetric ones. These solutions were validated in a hybrid simulation [N. Aunai et al., Phys. Plasmas (1994-present) 20

  13. Asymmetric kinetic equilibria: Generalization of the BAS model for rotating magnetic profile and non-zero electric field

    SciTech Connect

    Dorville, Nicolas Belmont, Gérard; Aunai, Nicolas; Dargent, Jérémy; Rezeau, Laurence

    2015-09-15

    Finding kinetic equilibria for non-collisional/collisionless tangential current layers is a key issue as well for their theoretical modeling as for our understanding of the processes that disturb them, such as tearing or Kelvin Helmholtz instabilities. The famous Harris equilibrium [E. Harris, Il Nuovo Cimento Ser. 10 23, 115–121 (1962)] assumes drifting Maxwellian distributions for ions and electrons, with constant temperatures and flow velocities; these assumptions lead to symmetric layers surrounded by vacuum. This strongly particular kind of layer is not suited for the general case: asymmetric boundaries between two media with different plasmas and different magnetic fields. The standard method for constructing more general kinetic equilibria consists in using Jeans theorem, which says that any function depending only on the Hamiltonian constants of motion is a solution to the steady Vlasov equation [P. J. Channell, Phys. Fluids (1958–1988) 19, 1541 (1976); M. Roth et al., Space Sci. Rev. 76, 251–317 (1996); and F. Mottez, Phys. Plasmas 10, 1541–1545 (2003)]. The inverse implication is however not true: when using the motion invariants as variables instead of the velocity components, the general stationary particle distributions keep on depending explicitly of the position, in addition to the implicit dependence introduced by these invariants. The standard approach therefore strongly restricts the class of solutions to the problem and probably does not select the most physically reasonable. The BAS (Belmont-Aunai-Smets) model [G. Belmont et al., Phys. Plasmas 19, 022108 (2012)] used for the first time the concept of particle accessibility to find new solutions: considering the case of a coplanar-antiparallel magnetic field configuration without electric field, asymmetric solutions could be found while the standard method can only lead to symmetric ones. These solutions were validated in a hybrid simulation [N. Aunai et al., Phys. Plasmas (1994-present

  14. Electromagnetically induced transparency in an asymmetric double quantum well under non-resonant, intense laser fields

    NASA Astrophysics Data System (ADS)

    Niculescu, E. C.

    2017-02-01

    Electromagnetically induced transparency in an asymmetric double quantum well subjected to a non-resonant, intense laser field is theoretically investigated. We found that the energy levels configuration could be switched between a Λ-type and a ladder-type scheme by varying the non-resonant radiation intensity. This effect is due to the laser-induced electron tunneling between the wells and it allows a substantial flexibility in the manipulation of the optical properties. The dependence of the susceptibilities on the control field Rabi frequency, intensity of the nonresonant laser, and the control field detuning for both configurations are discussed and compared.

  15. Inner field compensation as a tool for the characterization of asymmetric membranes and Peptide-membrane interactions.

    PubMed

    Hagge, Sven O; Wiese, Andre; Seydel, Ulrich; Gutsmann, Thomas

    2004-02-01

    Symmetric and asymmetric planar lipid bilayers prepared according to the Montal-Mueller method are a powerful tool to characterize peptide-membrane interactions. Several electrical properties of lipid bilayers such as membrane current, membrane capacitance, and the inner membrane potential differences and their changes can be deduced. The time-resolved determination of peptide-induced changes in membrane capacitance and inner membrane potential difference are of high importance for the characterization of peptide-membrane interactions. Intercalation and accumulation of peptides lead to changes in membrane capacitance, and membrane interaction of charged peptides induces changes in the charge distribution within the membrane and with that to changes in the membrane potential profile. In this study, we establish time-resolved measurements of the capacitance minimization potential DeltaPsi on various asymmetric planar lipid bilayers using the inner field compensation method. The results are compared to the respective ones of inner membrane potential differences DeltaPhi determined from ion carrier transport measurements. Finally, the time courses of membrane capacitances and of DeltaPsi have been used to characterize the interaction of cathelicidins with reconstituted lipid matrices of various Gram-negative bacteria.

  16. Asymmetrical flow field-flow fractionation of white wine chromophoric colloidal matter.

    PubMed

    Coelho, Christian; Parot, Jérémie; Gonsior, Michael; Nikolantonaki, Maria; Schmitt-Kopplin, Philippe; Parlanti, Edith; Gougeon, Régis D

    2017-04-01

    Two analytical separation methods-size-exclusion chromatography and asymmetrical flow field-flow fractionation-were implemented to evaluate the integrity of the colloidal composition of Chardonnay white wine and the impact of pressing and fermentations on the final macromolecular composition. Wine chromophoric colloidal matter, representing UV-visible-absorbing wine macromolecules, was evaluated by optical and structural measurements combined with the description of elution profiles obtained by both separative techniques. The objective of this study was to apply these two types of fractionation on a typical Chardonnay white wine produced in Burgundy and to evaluate how each of them impacted the determination of the macromolecular chromophoric content of wine. UV-visible and fluorescence measurements of collected fractions were successfully applied. An additional proteomic study revealed that grape and microorganism proteins largely impacted the composition of chromophoric colloidal matter of Chardonnay wines. Asymmetrical flow field-flow fractionation appeared to be more reliable and less invasive with respect to the native chemical environment of chromophoric wine macromolecules, and hence is recommended as a tool to fractionate chromophoric colloidal matter in white wines. Graphical Abstract An innovative macromolecular separation method based on Asymmetrical Flow Field-Flow Fractionation was developed to better control colloidal dynamics across Chardonnay white winemaking.

  17. Impact of flows on ion temperatures inferred from neutron spectra in asymmetrically driven OMEGA DT implosions

    NASA Astrophysics Data System (ADS)

    Gatu Johnson, M.; Frenje, J. A.; Seguin, F. H.; Petrasso, R. D.; Aappelbe, B.; Chittenden, J.; Walsh, C.; Knauer, J. P.; Glebov, V. Yu.; Forrest, C.; Marshall, F.; Michel, T.; Stoeckl, C.; Sangster, T. C.; Zylstra, A.

    2016-10-01

    Ion temperatures (Tion) in Inertial Confinement Fusion (ICF) experiments have traditionally been inferred from the broadening of primary neutron spectra. Directional motion (flow) of the fuel at burn, expected to arise due to asymmetries imposed by engineering features (such as stalks, fill tubes, tents, or capsule imperfections) or drive non-uniformity, also impacts broadening and may lead to artificially inflated ``Tion'' values. Flow due to low-mode asymmetries is expected to give rise to line-of-sight variations in measured Tion, as observed in OMEGA cryogenic DT implosions but not in similar experiments at the NIF. In this presentation we report on an OMEGA experiment with intentionally asymmetric drive, designed to test the ability to accurately predict and measure line-of-sight differences in apparent Tion due to low-mode asymmetry-seeded flows. The results provide insight into the complexity of hot-spot dynamics, which is a problem that must be mastered to achieve ICF ignition. This work was supported in part by LLE, the U.S. DoE (NNSA, NLUF) and LLNL.

  18. Effects of electromagnetic fields on the nonlinear optical properties of asymmetric double quantum well under intense laser field

    NASA Astrophysics Data System (ADS)

    Yesilgul, U.; Sari, H.; Ungan, F.; Martínez-Orozco, J. C.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.; Sökmen, I.

    2017-03-01

    In this study, the effects of electric and magnetic fields on the optical rectification and second and third harmonic generation in asymmetric double quantum well under the intense non-resonant laser field is theoretically investigated. We calculate the optical rectification and second and third harmonic generation within the compact density-matrix approach. The theoretical findings show that the influence of electric, magnetic, and intense laser fields leads to significant changes in the coefficients of nonlinear optical rectification, second and third harmonic generation.

  19. Asymmetric Synthesis of Chiral Bimetallic [Ag28Cu12(SR)24](4-) Nanoclusters via Ion Pairing.

    PubMed

    Yan, Juanzhu; Su, Haifeng; Yang, Huayan; Hu, Chengyi; Malola, Sami; Lin, Shuichao; Teo, Boon K; Häkkinen, Hannu; Zheng, Nanfeng

    2016-10-05

    In this work, a facile ion-pairing strategy for asymmetric synthesis of optically active negatively charged chiral metal nanoparticles using chiral ammonium cations is demonstrated. A new thiolated chiral three-concentric-shell cluster, [Ag28Cu12(SR)24](4-), was first synthesized as a racemic mixture and characterized by single-crystal X-ray structure determination. Mass spectrometric measurements revealed relatively strong ion-pairing interactions between the anionic nanocluster and ammonium cations. Inspired by this observation, the as-prepared racemic mixture was separated into enantiomers by employing chiral quaternary ammonium salts as chiral resolution agents. Subsequently, direct asymmetric synthesis of optically active enantiomers of [Ag28Cu12(SR)24](4-) was achieved by using appropriate chiral ammonium cations (such as N-benzylcinchoninium vs N-benzylcinchonidinium) in the cluster synthesis. These simple strategies, ion-pairing enantioseparation and direct asymmetric synthesis using chiral counterions, may be of general use in preparing chiral metal nanoparticles.

  20. The second harmonic generation in symmetrical and asymmetrical Gaussian potential quantum wells with applied electric field

    NASA Astrophysics Data System (ADS)

    Yuan, Jian-Hui; Chen, Ni; Mo, Hua; Zhang, Yan; Zhang, Zhi-Hai

    2015-12-01

    A detailed investigation of the second harmonic generation in symmetrical and asymmetrical Gaussian potential quantum wells under the influence of applied electric field by using the compact-density-matrix approach and the finite difference method. The results show that the second-harmonic generation susceptibility obtained in two cases can reach the magnitude of 10-4 m/V, which depend dramatically on the applied electric field and the structural parameters. Finally, the resonant peak and its corresponding to the resonant energy are also taken into account.

  1. Meeting in Florida: Using Asymmetric Flow Field-Flow Fractionation (AF4) to Determine C60 Colloidal Size Distributions

    EPA Science Inventory

    The study of nanomaterials in environmental systems requires robust and specific analytical methods. Analytical methods which discriminate based on particle size and molecular composition are not widely available. Asymmetric Flow Field-Flow Fractionation (AF4) is a separation...

  2. Resonance fluorescence from an asymmetric quantum dot dressed by a bichromatic electromagnetic field

    NASA Astrophysics Data System (ADS)

    Kryuchkyan, G. Yu.; Shahnazaryan, V.; Kibis, O. V.; Shelykh, I. A.

    2017-01-01

    We present the theory of resonance fluorescence from an asymmetric quantum dot driven by a two-component electromagnetic field with two different frequencies, polarizations, and amplitudes (bichromatic field) in the regime of strong light-matter coupling. It follows from the elaborated theory that the broken inversion symmetry of the driven quantum system and the bichromatic structure of the driving field result in unexpected features of the resonance fluorescence, including the infinite set of Mollow triplets, the quench of fluorescence peaks induced by the dressing field, and the oscillating behavior of the fluorescence intensity as a function of the dressing field amplitude. These quantum phenomena are of general physical nature and, therefore, can take place in various double-driven quantum systems with broken inversion symmetry.

  3. On the Electron Diffusion Region in Asymmetric Reconnection with a Guide Magnetic Field

    NASA Technical Reports Server (NTRS)

    Hesse, Michael; Liu, Yi-Hsin; Chen, Li-Jen; Bessho, Naoki; Kuznetsova, Masha; Birn, Joachim; Burch, James L.

    2016-01-01

    Particle-in-cell simulations in a 2.5-D geometry and analytical theory are employed to study the electron diffusion region in asymmetric reconnection with a guide magnetic field. The analysis presented here demonstrates that similar to the case without guide field, in-plane flow stagnation and null of the in-plane magnetic field are well separated. In addition, it is shown that the electric field at the local magnetic X point is again dominated by inertial effects, whereas it remains dominated by nongyrotropic pressure effects at the in-plane flow stagnation point. A comparison between local electron Larmor radii and the magnetic gradient scale lengths predicts that distribution should become nongyrotropic in a region enveloping both field reversal and flow stagnation points. This prediction is verified by an analysis of modeled electron distributions, which show clear evidence of mixing in the critical region.

  4. On the electron diffusion region in asymmetric reconnection with a guide magnetic field

    NASA Astrophysics Data System (ADS)

    Hesse, Michael; Liu, Yi-Hsin; Chen, Li-Jen; Bessho, Naoki; Kuznetsova, Masha; Birn, Joachim; Burch, James L.

    2016-03-01

    Particle-in-cell simulations in a 2.5-D geometry and analytical theory are employed to study the electron diffusion region in asymmetric reconnection with a guide magnetic field. The analysis presented here demonstrates that similar to the case without guide field, in-plane flow stagnation and null of the in-plane magnetic field are well separated. In addition, it is shown that the electric field at the local magnetic X point is again dominated by inertial effects, whereas it remains dominated by nongyrotropic pressure effects at the in-plane flow stagnation point. A comparison between local electron Larmor radii and the magnetic gradient scale lengths predicts that distribution should become nongyrotropic in a region enveloping both field reversal and flow stagnation points. This prediction is verified by an analysis of modeled electron distributions, which show clear evidence of mixing in the critical region.

  5. Selective charge asymmetric distribution in heteronuclear diatomic molecules in strong laser fields

    NASA Astrophysics Data System (ADS)

    Lai, Wei; Guo, Chunlei

    2015-07-01

    In this paper we study double-ionization-induced charge asymmetric dissociation (CAD) in heteronuclear diatomic molecules. In CO we find a selective charge distribution in two CAD channels, i.e., C2 ++O is abundantly produced but C +O2 + is nearly nonexistent. This cannot be explained by the ionization energy difference between the two channels alone. Our study shows that the C2 ++O channel is sequentially formed through an intermediate state C++O and the selective charge distribution is the result of electron distribution in CO when exposed to intense laser fields.

  6. Electrical characteristics of tunneling field-effect transistors with asymmetric channel thickness

    NASA Astrophysics Data System (ADS)

    Kim, Jungsik; Oh, Hyeongwan; Kim, Jiwon; Meyyappan, M.; Lee, Jeong-Soo

    2017-02-01

    Effects of using asymmetric channel thickness in tunneling field-effect transistors (TFET) are investigated in sub-50 nm channel regime using two-dimensional (2D) simulations. As the thickness of the source side becomes narrower in narrow-source wide-drain (NSWD) TFETs, the threshold voltage (V th) and the subthreshold swing (SS) decrease due to enhanced gate controllability of the source side. The narrow source thickness can make the band-to-band tunneling (BTBT) distance shorter and induce much higher electric field near the source junction at the on-state condition. In contrast, in a TFET with wide-source narrow-drain (WSND), the SS shows almost constant values and the V th slightly increases with narrowing thickness of the drain side. In addition, the ambipolar current can rapidly become larger with smaller thickness on the drain side because of the shorter BTBT distance and the higher electric-field at the drain junction. The on-current of the asymmetric channel TFET is lower than that of conventional TFETs due to the volume limitation of the NSWD TFET and high series resistance of the WSND TFET. The on-current is almost determined by the channel thickness of the source side.

  7. The measurement of 3-D asymmetric temperature field by using real time laser interferometric tomography

    NASA Astrophysics Data System (ADS)

    Wang, Dezhong; Zhuang, Tiange

    2001-09-01

    A real time nondestructive temperature measurement technique based on laser holographic interference tomography technique is presented. An He-Ne laser is used as light source, and a CCD video camera is used to grab the interferogram. This laser holographic tomography technique is applied to the measurement of the temperature fields generated by two heated rods. Since data error is inevitable in engineering measurement, it is necessary to study the reconstruction techniques for reconstructing the temperature field. Three techniques including convolution back projection (CBP), algebra reconstruction technique (ART) and simultaneous iterative reconstruction technique (SIRT) are studied. Based on the reconstruction techniques and experimental situation, ART is used to reconstruct the asymmetric temperature fields. The thermocouples are used to measure the temperatures of the two heated rods. Comparing the reconstructed result with the measured temperature value, a satisfactory result is obtained.

  8. Surface potential at a ferroelectric grain due to asymmetric screening of depolarization fields

    SciTech Connect

    Genenko, Yuri A. Hirsch, Ofer; Erhart, Paul

    2014-03-14

    Nonlinear screening of electric depolarization fields, generated by a stripe domain structure in a ferroelectric grain of a polycrystalline material, is studied within a semiconductor model of ferroelectrics. It is shown that the maximum strength of local depolarization fields is rather determined by the electronic band gap than by the spontaneous polarization magnitude. Furthermore, field screening due to electronic band bending and due to presence of intrinsic defects leads to asymmetric space charge regions near the grain boundary, which produce an effective dipole layer at the surface of the grain. This results in the formation of a potential difference between the grain surface and its interior of the order of 1 V, which can be of either sign depending on defect transition levels and concentrations. Exemplary acceptor doping of BaTiO{sub 3} is shown to allow tuning of the said surface potential in the region between 0.1 and 1.3 V.

  9. Particle Diffusion in Chaotic Magnetic Fields Generated by Asymmetric Current Configurations

    NASA Astrophysics Data System (ADS)

    Ram, A. K.; Dasgupta, B.

    2008-12-01

    The observed cross-field diffusion of charged particles in cosmic rays is assumed to be due to the chaotic nature of the interplanetary/intergalactic magnetic fields. Among the classic works on this subject have been those of Parker [1] and Jokipii [2]. Parker considered the passage of cosmic ray particles and energetic solar particles in a large scale magnetic field containing small scale irregularities. In the context of cosmic ray propagation, Jokipii considered a small fluctuating component, added on to a uniform magnetic field, to study the spatial transport of particles. In these studies the irregular component of the magnetic field is prescribed in an ad hoc fashion. In contrast, we consider asymmetric, nonlinear, steady-state magnetic fields, in three spatial dimensions, generated by currents flowing in circular loops and straight lines [3]. These magnetic fields are completely deterministic and, for certain range of parameters, chaotic. We will present analytical and numerical studies on the spatial characteristics of these fields. The motion of charged particles in the nonlinear and chaotic magnetic fields is determined using the Lorentz equation. A particle moving in a deterministic chaotic magnetic field superposed on a uniform background magnetic field is found to undergo spatial transport. This shows that chaotic magnetic fields generated by simple current configurations can produce cross-field diffusion. A detailed analysis of particle motion and diffusion along with application to space plasmas will be presented. [1] E.N. Parker, Planet. Space Sci. 13, 9 (1965). [2] J.R. Jokipii, Astrophys. J. 146, 480 (1966), and J.R. Jokipii, Astrophys. J. 149, 405 (1967). [3] A.K. Ram and B. Dasgupta, Eos Trans. AGU 87 (52), Fall Meet. Suppl. Abstract NG31B-1593 (2006); and Eos Trans. AGU 88 (52), Fall Meet. Suppl. Abstract NG21B-0522 (2007).

  10. The non-dominance of counterions in charge-asymmetric electrolytes: non-monotonic precedence of electrostatic screening and local inversion of the electric field by multivalent coions.

    PubMed

    Guerrero-García, Guillermo Iván; González-Tovar, Enrique; Quesada-Pérez, Manuel; Martín-Molina, Alberto

    2016-08-03

    The asymptotic convergence of the thermodynamic and structural properties of unequally-sized charge-symmetric ions in strong electric fields was postulated more than thirty years ago by Valleau and Torrie as the dominance of counterions via the non-linear Poisson-Boltzmann theory [Valleau and Torrie, J. Chem. Phys., 1982, 76, 4623]. According to this mean field prescription, the properties of the electrical double layer near a highly charged electrode immersed in a size-asymmetric binary electrolyte converge to those of a size-symmetric electrolyte if the properties of counterions are the same in both instances. On the other hand, some of the present authors have shown that, in fact, counterions do not dominate the electrical properties of a spherical macroion in the presence of unequally-sized ions, symmetric in valence, if ion correlations and ionic excluded volume effects are taken into account consistently. These ingredients are neglected in the classical Poisson-Boltzmann picture. In the present work, we show the occurrence of the non-dominance of counterions in the opposite scenario, that is, when ions are equally-sized but asymmetric in valence. This is performed in the presence of highly charged colloidal surfaces of spherical and planar geometries for different ionic volume fractions. In addition to the phenomenon of non-dominance of counterions, our simulations and theoretical data also exhibit a non-monotonic order or precedence in the mean electrostatic potential, or electrostatic screening, at the Helmholtz plane of a charged colloid. This interesting behaviour is analyzed as a function of the coion's valence, the ionic volume fraction, and the charge and size of the colloidal particle. All these phenomena are explained in terms of the decay of the electric field near the colloidal surface, and by the appearance of a local inversion of both the electric field and the integrated surface charge density of the colloidal particle in the presence of

  11. Dynamics of a reconnection-driven runaway ion tail in a reversed field pinch plasma

    NASA Astrophysics Data System (ADS)

    Anderson, Jay

    2015-11-01

    Non-collisional heating and energization of ions is a powerful process in reversed-field pinch (RFP) plasmas and in many astrophysical settings. Tearing activity in the RFP (including linearly and nonlinearly driven modes which span the plasma column) saturates through dynamo-like feedback on the current density profile, rapidly releasing magnetic energy and inducing a strong impulsive, parallel-to-B electric field as poloidal magnetic flux is converted to toroidal flux. The global reconnection leads to strong ion heating with a known anisotropy in temperature (T⊥ >T| |), suggestive of a perpendicular bulk heating mechanism. In the subset of strongest reconnection events, multiple mechanisms combine to create a most interesting ion distribution. Runaway of the reduced-friction naturally-heated ions generates an asymmetric ion tail with E|| >>E⊥ . The tail is reinforced by a confinement asymmetry where runaway ions approach the limit of classical cross-field transport despite magnetic stochasticity from the broad spectrum of tearing modes. Confinement is lower in other regions of the v⊥ /v| | plane and reduces to Rechester-Rosenbluth-like transport experienced by thermal particles. Experiments with neutral beam injection elegantly confirm the ion runaway process and fast ion confinement characteristics in MST. Neutral particle analyzers measure an unrestricted parallel acceleration of the fast test particle distribution during the reconnection event. The energy gain is larger for higher initial ion energy (reduced drag), and deceleration is observed with reversed electric field (counter-current injection) according to runaway dynamics and confirmed with Fokker-Planck modeling. Full orbit test particle tracing in the 3D time evolving electric and magnetic fields (from visco-resistive MHD simulations) corroborates the understanding of fast ion confinement. Work supported by by US DoE and NSF.

  12. Integrated field emission array for ion desorption

    DOEpatents

    Resnick, Paul J; Hertz, Kristin L; Holland, Christopher; Chichester, David; Schwoebel, Paul

    2013-09-17

    An integrated field emission array for ion desorption includes an electrically conductive substrate; a dielectric layer lying over the electrically conductive substrate comprising a plurality of laterally separated cavities extending through the dielectric layer; a like plurality of conically-shaped emitter tips on posts, each emitter tip/post disposed concentrically within a laterally separated cavity and electrically contacting the substrate; and a gate electrode structure lying over the dielectric layer, including a like plurality of circular gate apertures, each gate aperture disposed concentrically above an emitter tip/post to provide a like plurality of annular gate electrodes and wherein the lower edge of each annular gate electrode proximate the like emitter tip/post is rounded. Also disclosed herein are methods for fabricating an integrated field emission array.

  13. Integrated field emission array for ion desorption

    DOEpatents

    Resnick, Paul J; Hertz, Kristin L.; Holland, Christopher; Chichester, David

    2016-08-23

    An integrated field emission array for ion desorption includes an electrically conductive substrate; a dielectric layer lying over the electrically conductive substrate comprising a plurality of laterally separated cavities extending through the dielectric layer; a like plurality of conically-shaped emitter tips on posts, each emitter tip/post disposed concentrically within a laterally separated cavity and electrically contacting the substrate; and a gate electrode structure lying over the dielectric layer, including a like plurality of circular gate apertures, each gate aperture disposed concentrically above an emitter tip/post to provide a like plurality of annular gate electrodes and wherein the lower edge of each annular gate electrode proximate the like emitter tip/post is rounded. Also disclosed herein are methods for fabricating an integrated field emission array.

  14. Ion beam probing of electrostatic fields

    NASA Technical Reports Server (NTRS)

    Persson, H.

    1979-01-01

    The determination of a cylindrically symmetric, time-independent electrostatic potential V in a magnetic field B with the same symmetry by measurements of the deflection of a primary beam of ions is analyzed and substantiated by examples. Special attention is given to the requirements on canonical angular momentum and total energy set by an arbitrary, nonmonotone V, to scaling laws obtained by normalization, and to the analogy with ionospheric sounding. The inversion procedure with the Abel analysis of an equivalent problem with a one-dimensional fictitious potential is used in a numerical experiment with application to the NASA Lewis Modified Penning Discharge. The determination of V from a study of secondary beams of ions with increased charge produced by hot plasma electrons is also analyzed, both from a general point of view and with application to the NASA Lewis SUMMA experiment. Simple formulas and geometrical constructions are given for the minimum energy necessary to reach the axis, the whole plasma, and any point in the magnetic field. The common, simplifying assumption that V is a small perturbation is critically and constructively analyzed; an iteration scheme for successively correcting the orbits and points of ionization for the electrostatic potential is suggested.

  15. Magnetomigration of rare-earth ions in inhomogeneous magnetic fields.

    PubMed

    Franczak, Agnieszka; Binnemans, Koen; Jan Fransaer

    2016-10-05

    The effects of external inhomogenous (gradient) magnetic fields on the movement of the rare-earth ions: Dy(3+), Gd(3+) and Y(3+), in initially homogeneous aqueous solutions have been investigated. Differences in the migration of rare-earth ions in gradient magnetic fields were observed, depending on the magnetic character of the ions: paramagnetic ions of Dy(3+) and Gd(3+) move towards regions of the sample where the magnetic field gradient is the strongest, while diamagnetic ions of Y(3+) move in the opposite direction. It has been showed that the low magnetic field gradients, such the ones generated by permanent magnets, are sufficient to observe the magnetomigration effects of the ions in solution. The present work clearly establishes the behavior of magnetically different ions in initially homogeneous aqueous solutions exposed to magnetic field gradients. To this avail, a methodology for measuring the local concentration differences of metal ions in liquid samples was developed.

  16. Dynamical simulation of energy dissipation in asymmetric heavy-ion induced fission of {sup 200}Pb, {sup 213}Fr, and {sup 251}Es

    SciTech Connect

    Mirfathi, S. M.; Pahlavani, M. R.

    2008-12-15

    The dynamical model based on the asymmetric mass division has been applied to calculate pre-scission neutron multiplicity from heavy-ion induced fusion-fission reactions. Links between the pre-scission neutron multiplicity, excitation energy, and asymmetric mass distribution are clarified based on the Monte Carlo simulation and Langevin dynamics. The pre-scission neutron multiplicity is calculated and compared with the respective experimental data over a wide range of excitation energy and nonconstant viscosity. The analysis indicates a different effect for the application of asymmetric mass division in different energy regions of such processes.

  17. The influence of intense electric fields on three-dimensional asymmetric magnetic reconnection

    SciTech Connect

    Pritchett, P. L.

    2013-06-15

    A three-dimensional particle-in-cell simulation of magnetic reconnection in an asymmetric configuration without a guide field and with temperature ratio T{sub i}/T{sub e}>1 demonstrates that intense perpendicular electric fields are produced on the low-density side of the current layer where there is a strong gradient in the plasma density. The simulation shows that the 3-D reconnection rate is unaffected by these intense electric fields, that the electron current layer near the X line remains coherent and does not break up, but that localized regions of strong energy dissipation exist along the low-density separatrices. Near the X line the dominant term in the generalized Ohm's law for the reconnection electric field remains the off-diagonal electron pressure gradient ∂P{sub exy}/∂x. On the low-beta separatrix, however, the anomalous drag −<δnδE{sub y}>/ makes an equally important contribution to that of the pressure gradient to the average E{sub y} field.

  18. Nanoparticle separation with a miniaturized asymmetrical flow field-flow fractionation cartridge

    PubMed Central

    Müller, David; Cattaneo, Stefano; Meier, Florian; Welz, Roland; de Mello, Andrew J.

    2015-01-01

    Asymmetrical Flow Field-Flow Fractionation (AF4) is a separation technique applicable to particles over a wide size range. Despite the many advantages of AF4, its adoption in routine particle analysis is somewhat limited by the large footprint of currently available separation cartridges, extended analysis times and significant solvent consumption. To address these issues, we describe the fabrication and characterization of miniaturized AF4 cartridges. Key features of the down-scaled platform include simplified cartridge and reagent handling, reduced analysis costs and higher throughput capacities. The separation performance of the miniaturized cartridge is assessed using certified gold and silver nanoparticle standards. Analysis of gold nanoparticle populations indicates shorter analysis times and increased sensitivity compared to conventional AF4 separation schemes. Moreover, nanoparticulate titanium dioxide populations exhibiting broad size distributions are analyzed in a rapid and efficient manner. Finally, the repeatability and reproducibility of the miniaturized platform are investigated with respect to analysis time and separation efficiency. PMID:26258119

  19. A three-dimensional body-fitted coordinate system for flow field calculations on asymmetric nosetips

    NASA Technical Reports Server (NTRS)

    Hall, D. W.

    1980-01-01

    A three dimensional body-fitted coordinate system developed for use in the calculation of inviscid flows over ablated, asymmetric reentry vehicle nosetips is described. Because of the potential geometric asymmetries, no standard coordinate system (e.g., spherical, axisymmetric reference surface-normal) is capable of being closely aligned with the nosetip surface. To generate a 3-D, body-fitted coordinate system an analytic mapping procedure is applied that is conformal within each meridional plane of the nosetip; these transformations are then coupled circumferentially to yield a three dimensional coordinate system. The mappings used are defined in terms of hinge points, which are points selected to approximate the body contours in each meridional plane. The selection of appropriate hinge points was automated to facilitate the use of the resulting nosetip flow field code.

  20. Bashful Ballerina: The asymmetric global solar magnetic field viewed from the heliosphere

    NASA Astrophysics Data System (ADS)

    Mursula, Kalevi

    Long-term observations of the heliospheric magnetic field (HMF) at 1 AU have depicted interesting systematic hemispheric and longitudinal asymmetries that have far-reaching implications for the understanding of solar magnetism. It has been found that the HMF sector of the northern solar hemisphere dominates the observed HMF sector occurrence in the heliosphere for about three years during the late declining to minimum phase of the solar cycle. This leads to a persistent southward shift or coning of the heliospheric current sheet at these times, which has been described by the concept of the bashful ballerina. Measurements of the solar surface fields have verified that, at these times, the average field intensity is smaller and the area larger in the northern than in the southern solar hemisphere. They have also shown that a persistent global quadrupole moment, oppositely oriented with respect to the dipole moment, appears at these times. Long-term observations of the geomagnetic field can yield information on the HMF sector structure in the pre-satellite era, and show that the ballerina was bashful at least since 1930s. In addition to the hemispheric asymmetries, the Sun is systematically asymmetric in longitude. The HMF has persistent active longitudes whose dominance depicts an oscillation with a period of about 3.2 years. Similar flip-flopping is also seen in the longitudinal distribution of sunspots and stellar observations show that this is a general pattern for sun-like cool stars. We describe these phenomena and discuss their theoretical implications.

  1. Bashful Ballerina: The asymmetric global solar magnetic field viewed from the heliosphere

    NASA Astrophysics Data System (ADS)

    Mursula, K.

    2008-05-01

    Long-term observations of the heliospheric magnetic field (HMF) at 1 AU have depicted interesting systematic hemispheric and longitudinal asymmetries that have far-reaching implications for the understanding of solar magnetism. It has been found that the HMF sector of the northern solar hemisphere dominates the observed HMF sector occurrence in the heliosphere for about three years during the late declining to minimum phase of the solar cycle. This leads to a persistent southward shift or coning of the heliospheric current sheet at these times, which has been described by the concept of the bashful ballerina. Measurements of the solar surface fields have verified that, at these times, the average field intensity is smaller and the area larger in the northern than in the southern solar hemisphere. They have also shown that a persistent global quadrupole moment, oppositely oriented with respect to the dipole moment, appears at these times. Long-term observations of the geomagnetic field can yield information on the HMF sector structure in the pre- satellite era, and show that the ballerina was bashful at least since 1930s. In addition to the hemispheric asymmetries, the Sun is systematically asymmetric in longitude. The HMF has persistent active longitudes whose dominance depicts an oscillation with a period of about 3.2 years. Similar flip-flopping is also seen in the longitudinal distribution of sunspots and stellar observations show that this is a general pattern for sun-like cool stars. We describe these phenomena and discuss their theoretical implications.

  2. Biological dose optimization with multiple ion fields.

    PubMed

    Gemmel, A; Hasch, B; Ellerbrock, M; Weyrather, W K; Krämer, M

    2008-12-07

    We describe a method to irradiate arbitrarily shaped target volumes with simultaneously optimized multiple fields of fast carbon ions, explicitly taking into account sparing of organs at risk. The method was developed with realistic technical boundary conditions in mind, so that irradiations can be executed with devices like the GSI raster scanner or its successors at the upcoming dedicated ion-beam radiotherapy facilities. By virtue of the local effect model (LEM) biological effects are fully taken into account. Several minimization algorithms were investigated, and plain gradient search was found to be more effective than methods based on conjugate gradients or Newton's root finding algorithm. Two sets of cell survival experiments for the experimental verification of patient-like treatment plans were performed. Chinese hamster cells were used for quasi two-dimensional biological dosimetry. The plans combine a very good target conformation with an excellent sparing of organs-at-risk which was verified by the measurements. The results are compared to predictions of the local effect model in its original formulation and a modified version taking additional effects of clustered DNA damage into account. The new method is implemented in GSI's TRiP98 treatment planning system. It has already been applied clinically for planning and irradiating selected patients within the GSI pilot project.

  3. Polycrystalline silicon ion sensitive field effect transistors

    NASA Astrophysics Data System (ADS)

    Yan, F.; Estrela, P.; Mo, Y.; Migliorato, P.; Maeda, H.; Inoue, S.; Shimoda, T.

    2005-01-01

    We report the operation of polycrystalline silicon ion sensitive field effect transistors. These devices can be fabricated on inexpensive disposable substrates such as glass or plastics and are, therefore, promising candidates for low cost single-use intelligent multisensors. In this work we have developed an extended gate structure with a Si3N4 sensing layer. Nearly ideal pH sensitivity (54mV /pH) and stable operation have been achieved. Temperature effects have been characterized. A penicillin sensor has been fabricated by functionalizing the sensing area with penicillinase. The sensitivity to penicillin G is about 10mV/mM, in solutions with concentration lower than the saturation value, which is about 7 mM.

  4. Nonlinear and asymmetric open channel characteristics of an ion-selective porin in planar membranes.

    PubMed Central

    Mathes, A; Engelhardt, H

    1998-01-01

    The open channel characteristics of the bacterial porin Omp32 from Comamonas acidovorans were investigated by means of conductance measurements in planar lipid bilayers of the Montal-Mueller type. Particularly at low salt conditions (< or = 30 mM KCl) Omp32 exhibited some unusual asymmetric and nonlinear functional properties. Current-voltage relationship measurements showed that conductance depends on the orientation of porin molecules and is a nonlinear function of the applied membrane potential. Conductance also depends on the salt concentration in a manner not common to porins and the salt concentration modulates the nonlinearity of conductance-voltage relationships. Omp32 is strongly anion-selective. The nonlinear and asymmetric conductance of the open channel is a new observation in porins. PMID:9726928

  5. Ion heating perpendicular to the magnetic field. Technical report

    SciTech Connect

    Andre, M.; Chang, T.

    1994-03-28

    Several theories of ion heating perpendicular to the geomagnetic field are briefly reviewed and assessed. Perpendicular heating of ions leading to the formation of ion conics is common in the ionosphere and magnetosphere. Ion conics at altitudes above a few thousand kilometers are often associated with waves around the ion gyrofrequency. It is concluded that the majority of these ion conics that are locally heated or generated over extended altitude regimes, may be best explained by ion cyclotron resonance heating. At lower altitudes, particularly in the region of discrete auroras, energization by turbulence around the lower hybrid frequency seems to be an important heating mechanism.

  6. Nonmonotonous variation of DNA angular separation during asymmetric pulsed field electrophoresis.

    PubMed

    Nazemifard, Neda; Bhattacharjee, Subir; Masliyah, Jacob H; Harrison, D Jed

    2013-09-01

    Asymmetric pulsed field electrophoresis within crystalline arrays is used to generate angular separation of DNA molecules. Four regimes of the frequency response are observed, a low frequency rise in angular separation, a plateau, a subsequent decline, and a second plateau at higher frequencies. It is shown that the frequency response for different sized DNA is governed by the relation between pulse time and the reorientation time of DNA molecules. The decline in angular separation at higher frequencies has not previously been analyzed. Real-time videos of single DNA molecules migrating under high frequency-pulsed electric field show the molecules no longer follow the head to tail switching, ratchet mechanism seen at lower frequencies. Once the pulse period is shorter than the reorientation time, the migration mechanism changes significantly. The molecule reptates along the average direction of the two electric fields, which reduces the angular separation. A freely jointed chain model of DNA is developed where the porous structure is represented with a hexagonal array of obstacles. The model qualitatively predicts the variation of DNA angular separation with respect to frequency.

  7. Evidence for a sedimentary fingerprint of an asymmetric flow field surrounding a short seamount

    NASA Astrophysics Data System (ADS)

    Turnewitsch, Robert; Reyss, Jean-Louis; Chapman, David C.; Thomson, John; Lampitt, Richard S.

    2004-06-01

    Physical oceanographic modeling and field studies have shown that kilometer-scale seafloor elevations of comparable breadth and width (abyssal hills, knolls, seamounts) are surrounded by complex flow fields. Asymmetric flow fields, reversed flow and closed streamlines around the topographic feature (Taylor caps), and resonantly amplified tidal currents around the seamount rim potentially control near-bottom particle dynamics, particle deposition at the seafloor and, consequently, the formation of the sedimentary record. We combine numerical modeling and field data to study how such topographically controlled flow-field features are reflected in the sedimentary record. Sediment deposition on a topographically isolated abyssal knoll (height: 900 m) on the Porcupine Abyssal Plain in the Northeast Atlantic (water depth above the abyssal plain: 4850 m) was studied, (1) by comparing the spatial distribution of 210Pb fluxes, calculated from inventories of sedimentary excess 210Pb, with 210Pb input from the water column as recorded by sediment traps; and (2) by comparing sedimentary grain-size distributions and Zr/Al ratios (an indicator for contents of the heavy mineral zircon) at slope, summit and far-field sites. Given Rossby numbers ≥0.23, a fractional seamount height of ˜0.2, and the absence of diurnal tides it is concluded that an asymmetric flow field without Taylor cap and without amplified tidal currents around the seamount rim is the principal flow-field feature at this knoll. The results and conclusions are as follows: (1) Geochemical and grain-size patterns in the sedimentary record largely agree with the predicted pattern of flow intensity around the topographic elevation: with increasing current strength (erosiveness) there is evidence for a growing discrepancy between water column-derived and sediment-derived 210Pb fluxes, and for increasing contents of larger and heavier particles. The topographically controlled flow field distorts a homogeneous particle

  8. METHOD AND APPARATUS FOR TRAPPING IONS IN A MAGNETIC FIELD

    DOEpatents

    Luce, J.S.

    1962-04-17

    A method and apparatus are described for trapping ions within an evacuated container and within a magnetic field utilizing dissociation and/or ionization of molecular ions to form atomic ions and energetic neutral particles. The atomic ions are magnetically trapped as a result of a change of charge-to- mass ratio. The molecular ions are injected into the container and into the path of an energetic carbon arc discharge which dissociates and/or ionizes a portion of the molecular ions into atomic ions and energetic neutrals. The resulting atomic ions are trapped by the magnetic field to form a circulating beam of atomic ions, and the energetic neutrals pass out of the system and may be utilized in a particle accelerator. (AEC)

  9. Field applications of ion-mobility spectrometry

    NASA Astrophysics Data System (ADS)

    Brown, Patricia A.

    1997-02-01

    Ion mobility spectrometry (IMS) is an excellent tool for detection of controlled substances under field conditions. Plasmagrams and tables showing the results of field applications will be discussed. Residues of drugs, such as cocaine and heroin, can be left anywhere including vehicles, boats, and houses. In houses, the carpets, walls, and floors are good locations for residues to adhere. Individual clothing can also be contaminated with drug residue. Vehicles that are suspected of having previously smuggled illegal substances can be vacuumed and screened. Tablets that look similar and respond the same when screened with the Marquis reagent can be differentiated by IMS. With Southern California being the 'methamphetamine capital of the world' and the resurgence of phencyclidine, IMS has proven extremely valuable in the screening of abandoned clandestine laboratory sites and vehicles in which the clandestine laboratories; chemicals and glassware were transported. IMS is very responsive to ephedrine/pseudophedrine, a precursor of methamphetamine and 1-piperidinocyclohexanecarbonitrile, an intermediate of phencyclidine. Once residues are detected, vacuum samples, and/or methanol wipes are collected and analyzed at the DEA Laboratory for confirmation of the suspected substance using GC-IRD or Mass Spectrometry.

  10. Misfit strain-temperature phase diagrams and domain stability of asymmetric ferroelectric capacitors: Thermodynamic calculation and phase-field simulation

    SciTech Connect

    Chen, W. J.; Zheng, Yue Wu, C. M.; Wang, B. Ma, D. C.

    2014-03-07

    Thermodynamic calculation and phase-field simulation have been conducted to investigate the misfit strain-temperature phase diagrams, dielectric property, and domain stability of asymmetric ferroelectric capacitors (FCs), with considering the effects of dissimilar screening properties and work function steps at the two interfaces. The distinct features of asymmetric FCs from their symmetric counterparts have been revealed and discussed. Polar states with nonzero out-of-plane polarization in parallel with the built-in field are found preferential to form in asymmetric FCs. Meanwhile, the built-in field breaks the degeneracy of states with out-of-plane polarization in anti-directions. This leads to the necessity of redefining phases according to the bistability of out-of-plane polarization. Moreover, the phase stability as well as the dielectric behavior can be significantly controlled by the properties of electrodes, misfit strain, and temperature. The phase-field simulation result also shows that polydomain instability would happen in asymmetric FCs as the equivalence of domain stability in anti-directions is destroyed.

  11. Determining Aqueous Fullerene Particle Size Distributions by Asymmetric Flow Field-Flow Fractionation (AF4) without Surfactants

    EPA Science Inventory

    To determine the behavior of nanoparticles in environmental systems, methods must be developed to measure nanoparticle size. Asymmetric Flow Field Flow Fractionation (AF4) is an aqueous compatible size separation technique which is able to separate particles from 1 nm to 10 µm in...

  12. Corneal Biomechanical Parameters and Asymmetric Visual Field Damage in Patients with Untreated Normal Tension Glaucoma

    PubMed Central

    Li, Bai-Bing; Cai, Yu; Pan, Ying-Zi; Li, Mei; Qiao, Rong-Hua; Fang, Yuan; Tian, Tian

    2017-01-01

    Background: High intraocular pressure (IOP) and low central corneal thickness (CCT) are important validated risk factors for glaucoma, and some studies also have suggested that eyes with more deformable corneas may be in higher risk of the development and worsening of glaucoma. In the present study, we aimed to evaluate the association between corneal biomechanical parameters and asymmetric visual field (VF) damage using a Corvis-ST device in patients with untreated normal tension glaucoma (NTG). Methods: In this observational, cross-sectional study, 44 newly diagnosed NTG patients were enrolled. Of these, 31 had asymmetric VF damage, which was defined as a 5-point difference between the eyes according to the Advanced Glaucoma Intervention Study scoring system. Corneal biomechanical parameters were obtained using a Corvis-ST device, such as time from start until the first and second applanation is reached (time A1 and time A2, respectively), cord length of the first and second applanation (length A1 and length A2, respectively), corneal speed during the first and second applanation (velocity A1 and velocity A2, respectively), time from start until highest concavity is reached (time HC), maximum amplitude at the apex of highest concavity (def ampl HC), distance between the two peaks at highest concavity (peak dist HC), and central concave curvature at its highest concavity (radius HC). Results: Time A1 (7.19 ± 0.28 vs. 7.37 ± 0.41 ms, P = 0.010), length A1 (1.73 [1.70–1.76] vs. 1.78 [1.76–1.79] mm, P = 0.007), length A2 (1.58 [1.46–1.70] vs. 1.84 [1.76–1.92] mm, P < 0.001), peak dist HC (3.53 [3.08–4.00] vs. 4.33 [3.92–4.74] mm, P = 0.010), and radius HC (6.20 ± 0.69 vs. 6.59 ± 1.18 mm, P = 0.032) were significantly lower in the worse eyes than in the better eyes, whereas velocity A1 and def ampl HC were significantly higher (0.156 [0.149–0.163] vs. 0.145 [0.138–0.152] m/s, P = 0.002 and 1.19 ± 0.13 vs. 1.15 ± 0.13 mm, P = 0.005, respectively

  13. Modeling of complex antibody elution behavior under high protein load densities in ion exchange chromatography using an asymmetric activity coefficient.

    PubMed

    Huuk, Thiemo C; Hahn, Tobias; Doninger, Katharina; Griesbach, Jan; Hepbildikler, Stefan; Hubbuch, Jürgen

    2017-03-01

    A main requirement for the implementation of model-based process development in industry is the capability of the model to predict high protein load densities. The frequently used steric mass action isotherm assumes a thermodynamically ideal system and, hence constant activity coefficients. In this manuscript, an industrial antibody purification problem under high load conditions is considered where this assumption does not hold. The high protein load densities, as commonly applied in industrial downstream processing, may lead to complex elution peak shapes. Using Mollerup's generalized ion-exchange isotherm (GIEX), the observed elution peak shapes could be modeled. To this end, the GIEX isotherm introduced two additional parameters to approximate the asymmetric activity coefficient. The effects of these two parameters on the curvature of the adsorption isotherm and the resulting chromatogram are investigated. It could be shown that they can be determined by inverse peak fitting and conform with the mechanistic demands of model-based process development.

  14. Characterization Of Commonly Encountered Explosives Using Highfield Asymmetric Waveform Ion Mobility Spectrometry Coupled With Mass Spectrometry

    DTIC Science & Technology

    2007-05-01

    a second nitro group. In other words, the predominant fragment ion peak shown here is the same elemental composition as the [M]- ion for... composition X) was developed as an explosive during the 1930s and was used widely during World War II. This explosive is found in many mixtures (such as...which is Composition C-4 (RDX with polyisobutylene and di(2-ethylhexyl)sebacate as the binder and plasticizer). RDX is stable at room temperature

  15. Precise determination of nonlinear function of ion mobility for explosives and drugs at high electric fields for microchip FAIMS.

    PubMed

    Guo, Dapeng; Wang, Yonghuan; Li, Lingfeng; Wang, Xiaozhi; Luo, Jikui

    2015-01-01

    High-field asymmetric waveform ion mobility spectrometry (FAIMS) separates ions by utilizing the characteristics of nonlinear ion mobility at high and low electric fields. Accurate ion discrimination depends on the precise solution of nonlinear relationships and is essential for accurate identification of ion species for applications. So far, all the nonlinear relationships of ion mobility obtained are based at low electric fields (E/N <65 Td). Microchip FAIMS (μ-FAIMS) with small dimensions has high electric field up to E/N = 250 Td, making the approximation methods and conclusions for nonlinear relationships inappropriate for these systems. In this paper, we deduced nonlinear functions based on the first principle and a general model. Furthermore we considered the hydrodynamics of gas flow through microchannels. We then calculated the specific alpha coefficients for cocaine, morphine, HMX, TNT and RDX, respectively, based on their FAIMS spectra measured by μ-FAIMS system at ultra-high fields up to 250 Td. The results show that there is no difference in nonlinear alpha functions obtained by the approximation and new method at low field (<120 Td), but the error induced by using approximation method increases monotonically with the increase in field, and could be as much as 30% at a field of 250 Td.

  16. Enantiospecific bromonium ion generation and intramolecular capture: a model system for asymmetric bromonium ion-induced polyene cyclisations.

    PubMed

    Braddock, D Christopher; Marklew, Jared S; Thomas, Alexander J F

    2011-08-28

    Scalemic bromonium ions generated enantiospecifically by the action of catalytic triflic acid on scalemic regioisomeric bromohydrin derivatives are trapped intramolecularly, enantiospecifically and regioselectively to give bicyclic brominated carbocycles in excellent yield and high enantiomeric excess. This enantiospecific pathway is not significantly perturbed by the addition of a trisubstituted alkene.

  17. Tunnel field-effect transistor with asymmetric gate dielectric and body thickness

    NASA Astrophysics Data System (ADS)

    Kwon, Dae Woong; Park, Byung-Gook

    2017-04-01

    Tunnel field-effect transistor (TFET) with asymmetric gate dielectric and body thickness (TFETAsy) is proposed. The TFETAsy not only reduces the tunneling resistance by using the thinner source-side gate dielectric and body, but also suppresses the ambipolar current (I ambipolar) and the degradation of alternating current (AC) switching performances with the thicker drain-side gate dielectric and body. Technology computer aided design process and device/circuit simulations are performed to verify the validity of the TFETAsy in terms of fabrication process and electrical characteristics. From the simulation results, it is revealed that the thinner source-side gate dielectric and body can be simply formed by oxide wet-etching after the selective oxidation of the source-side body. Moreover, the thinner source-side SiGe body can be also formed by using Ge condensation process instead of the oxidation. Additionally, it is confirmed that the TFETAsy has higher on-current, steeper subthreshold swing, lower I ambipolar and improved AC switching characteristics as compared to those of conventional TFET with symmetric structure.

  18. Asymmetrical flow field-flow fractionation for the analysis of PEG-asparaginase.

    PubMed

    John, C; Herz, T; Boos, J; Langer, K; Hempel, G

    2016-01-01

    Monomethoxypolyethylene glycol L-asparaginase (PEG-ASNASE) is the PEGylated version of the enzyme L-asparaginase (ASNASE). Both are used for remission induction in acute lymphoblastic leukemia (ALL) and non-Hodgkin's lymphoma (NHL). The treatment control is generally carried out by performing activity assays, though methods to determine the actual enzyme rather than its activity are rare. Using asymmetrical flow field-flow fractionation (AF4) offered the chance to develop a method capable of simultaneously measuring PEG-ASNASE and PEG. A method validation was performed in accordance with FDA guidelines for PEG-ASNASE from non-biological solutions. The method unfolded a linearity of 15-750 U/mL with coefficients of correlation of r(2)>0.99. The coefficients of variation (CV) for within-run and between-run variability were 1.18-10.15% and 2.43-8.73%, respectively. Furthermore, the method was used to perform stability tests of the product Oncaspar® (PEG-ASNASE) and estimation of the molecular weight by multi-angle light scattering (MALS) of stressed samples to correlate them with the corresponding activity. The findings indicate that Oncaspar® stock solution should not be stored any longer than 24 h at room temperature and cannot be frozen in pure aqueous media. The validated method might be useful for the pharmaceutical industry and its quality control of PEG-ASNASE production.

  19. Analysis of plant ribosomes with asymmetric flow field-flow fractionation.

    PubMed

    Pitkänen, Leena; Tuomainen, Päivi; Eskelin, Katri

    2014-02-01

    Ribosome profiling is a technique used to separate ribosomal subunits, 80S ribosomes (monosomes), and polyribosomes (polysomes) from other RNA-protein complexes. It is traditionally performed in sucrose gradients. In this study, we used asymmetric flow field-flow fractionation (AsFlFFF) to characterize ribosome profiles of Nicotiana benthamiana plants. With the optimized running conditions, we were able to separate free molecules from ribosomal subunits and intact ribosomes. We used various chemical and enzymatic treatments to validate the positions of subunits, monosomes, and polysomes in the AsFlFFF fractograms. We also characterized the protein and RNA content of AsFlFFF fractions by gel electrophoresis and western blotting. The reverse transcription polymerase chain reaction (RT-PCR) analysis showed that ribosomes remained bound to messenger RNAs (mRNAs) during the analysis. Therefore, we conclude that AsFlFFF can be used for ribosome profiling to study the mRNAs that are being translated. It can also be used to study the protein composition of ribosomes that are active in translation at that particular moment.

  20. High-Resolution Differential Ion Mobility Separations Using Planar Analyzers at Elevated Dispersion Field

    PubMed Central

    Prior, David C.; Tang, Keqi; Smith, Richard D.

    2010-01-01

    The ion mobility spectrometry (IMS) methods are grouped into conventional IMS, based on the absolute ion mobility, and differential or field asymmetric waveform IMS (FAIMS), based on the mobility difference in strong and weak electric fields. A key attraction of FAIMS is substantial orthogonality to mass spectrometry (MS). Although several FAIMS/MS platforms were commercialized, their utility was limited by FAIMS resolving power, typically ∼10 - 20. Recently, gas mixtures comprising up to 75% He has enabled resolving power >100 that permits separation of numerous heretofore “co-eluting” isomers. This performance opens major new proteomic and other biological applications. Here, we show that raising the separation field by ∼35% over the previous 21 kV/cm provides similar or better resolution (with resolving powers of >200 for multiply-charged peptides) using only 50% He, which avoids problems due to elevated pressure and He content in the mass spectrometer. The heating of ions by the separation field in this regime exceeds that at higher He content but weaker field, inducing greater izomerization of labile species. PMID:20666414

  1. Energetic-particle-driven instabilities and induced fast-ion transport in a reversed field pinch

    SciTech Connect

    Lin, L.; Brower, D. L.; Ding, W. X.; Anderson, J. K.; Capecchi, W.; Eilerman, S.; Forest, C. B.; Koliner, J. J.; Nornberg, M. D.; Reusch, J.; Sarff, J. S.; Liu, D.

    2014-05-15

    Multiple bursty energetic-particle (EP) driven modes with fishbone-like structure are observed during 1 MW tangential neutral-beam injection in a reversed field pinch (RFP) device. The distinguishing features of the RFP, including large magnetic shear (tending to add stability) and weak toroidal magnetic field (leading to stronger drive), provide a complementary environment to tokamak and stellarator configurations for exploring basic understanding of EP instabilities. Detailed measurements of the EP mode characteristics and temporal-spatial dynamics reveal their influence on fast ion transport. Density fluctuations exhibit a dynamically evolving, inboard-outboard asymmetric spatial structure that peaks in the core where fast ions reside. The measured mode frequencies are close to the computed shear Alfvén frequency, a feature consistent with continuum modes destabilized by strong drive. The frequency pattern of the dominant mode depends on the fast-ion species. Multiple frequencies occur with deuterium fast ions compared to single frequency for hydrogen fast ions. Furthermore, as the safety factor (q) decreases, the toroidal mode number of the dominant EP mode transits from n=5 to n=6 while retaining the same poloidal mode number m=1. The transition occurs when the m=1, n=5 wave-particle resonance condition cannot be satisfied as the fast-ion safety factor (q{sub fi}) decreases. The fast-ion temporal dynamics, measured by a neutral particle analyzer, resemble a classical predator-prey relaxation oscillation. It contains a slow-growth phase arising from the beam fueling followed by a rapid drop when the EP modes peak, indicating that the fluctuation-induced transport maintains a stiff fast-ion density profile. The inferred transport rate is strongly enhanced with the onset of multiple EP modes.

  2. Energetic-particle-driven instabilities and induced fast-ion transport in a reversed field pincha)

    NASA Astrophysics Data System (ADS)

    Lin, L.; Anderson, J. K.; Brower, D. L.; Capecchi, W.; Ding, W. X.; Eilerman, S.; Forest, C. B.; Koliner, J. J.; Liu, D.; Nornberg, M. D.; Reusch, J.; Sarff, J. S.

    2014-05-01

    Multiple bursty energetic-particle (EP) driven modes with fishbone-like structure are observed during 1 MW tangential neutral-beam injection in a reversed field pinch (RFP) device. The distinguishing features of the RFP, including large magnetic shear (tending to add stability) and weak toroidal magnetic field (leading to stronger drive), provide a complementary environment to tokamak and stellarator configurations for exploring basic understanding of EP instabilities. Detailed measurements of the EP mode characteristics and temporal-spatial dynamics reveal their influence on fast ion transport. Density fluctuations exhibit a dynamically evolving, inboard-outboard asymmetric spatial structure that peaks in the core where fast ions reside. The measured mode frequencies are close to the computed shear Alfvén frequency, a feature consistent with continuum modes destabilized by strong drive. The frequency pattern of the dominant mode depends on the fast-ion species. Multiple frequencies occur with deuterium fast ions compared to single frequency for hydrogen fast ions. Furthermore, as the safety factor (q) decreases, the toroidal mode number of the dominant EP mode transits from n =5 to n =6 while retaining the same poloidal mode number m =1. The transition occurs when the m =1, n =5 wave-particle resonance condition cannot be satisfied as the fast-ion safety factor (qfi) decreases. The fast-ion temporal dynamics, measured by a neutral particle analyzer, resemble a classical predator-prey relaxation oscillation. It contains a slow-growth phase arising from the beam fueling followed by a rapid drop when the EP modes peak, indicating that the fluctuation-induced transport maintains a stiff fast-ion density profile. The inferred transport rate is strongly enhanced with the onset of multiple EP modes.

  3. Energetic-particle-driven instabilities and induced fast-ion transport in a reversed field pinch

    NASA Astrophysics Data System (ADS)

    Lin, Liang

    2013-10-01

    Multiple bursty energetic-particle (EP) modes with fishbone-like structures are observed during 1 MW tangential neutral-beam injection into MST reversed field pinch (RFP) plasmas. The distinguishing features of the RFP, including large magnetic shear (tending to add stability) and weak toroidal magnetic field (leading to large fast ion beta and stronger drive), provide a complementary environment to tokamak and stellarator configurations for exploring basic understanding of these instabilities. Detailed measurements of the EP mode characteristics and temporal-spatial dynamics reveal their influence on fast ion transport and interaction with global tearing modes. Internal magnetic field fluctuations associated with the EP modes are directly observed for the first time by Faraday-effect polarimetry (frequency ~ 90 kHz and amplitude ~ 2 G). Simultaneously measured density fluctuations exhibit a dynamically evolving and asymmetric spatial structure that peaks near the core where fast ions reside and shifts outward as the instability evolves. Furthermore, the EP mode frequencies appear at ~k∥VA , consistent with continuum modes destabilized by strong drive. The fast-ion temporal dynamics, measured by a neutral particle analyzer, resemble a classical predator-prey relaxation oscillation. It contains a slow-growing phase arising from the beam fueling followed by a rapid drop (~ 15 %) when the EP modes peak, indicating the fluctuation-induced transport maintains a stiff fast-ion density profile. The inferred transport rate is strongly enhanced (× 2) with the onset of multiple nonlinearly-interacting EP modes. The fast ions also impact global tearing modes, reducing their amplitudes by up to 65%. This mode reduction is lessened following the EP-bursts, further evidence for fast ion redistribution that weakens the suppression mechanism. Possible tearing mode suppression mechanisms will be discussed. Work supported by US DoE.

  4. Helium in chirped laser fields as a time-asymmetric atomic switch

    SciTech Connect

    Kaprálová-Žďánská, Petra Ruth; Moiseyev, Nimrod

    2014-07-07

    Tuning the laser parameters exceptional points in the spectrum of the dressed laser helium atom are obtained. The weak linearly polarized laser couples the ground state and the doubly excited P-states of helium. We show here that for specific chirped laser pulses that encircle an exceptional point one can get the time-asymmetric phenomenon, where for a negative chirped laser pulse the ground state is transformed into the doubly excited auto-ionization state, while for a positive chirped laser pulse the resonance state is not populated and the neutral helium atoms remains in the ground state as the laser pulse is turned off. Moreover, we show that the results are very sensitive to the closed contour we choose. This time-asymmetric state exchange phenomenon can be considered as a time-asymmetric atomic switch. The optimal time-asymmetric switch is obtained when the closed loop that encircles the exceptional point is large, while for the smallest loops, the time-asymmetric phenomenon does not take place. A systematic way for studying the effect of the chosen closed contour that encircles the exceptional point on the time-asymmetric phenomenon is proposed.

  5. Measurement of ultra-low ion energy of decelerated ion beam using a deflecting electric field

    NASA Astrophysics Data System (ADS)

    Thopan, P.; Suwannakachorn, D.; Tippawan, U.; Yu, L. D.

    2015-12-01

    In investigation on ultra-low-energy ion bombardment effect on DNA, an ion beam deceleration lens was developed for high-quality ultra-low-energy ion beam. Measurement of the ion energy after deceleration was necessary to confirm the ion beam really decelerated as theoretically predicted. In contrast to conventional methods, this work used a simple deflecting electrostatic field after the deceleration lens to bend the ion beam. The beam bending distance depended on the ion energy and was described and simulated. A system for the measurement of the ion beam energy was constructed. It consisted of a pair of parallel electrode plates to generate the deflecting electrical field, a copper rod measurement piece to detect ion beam current, a vernier caliper to mark the beam position, a stepping motor to translate the measurement rod, and a webcam-camera to read the beam bending distance. The entire system was installed after the ion-beam deceleration lens inside the large chamber of the bioengineering vertical ion beam line. Moving the measurement rod across the decelerated ion beam enabled to obtain beam profiles, from which the beam bending distance could be known and the ion beam energy could be calculated. The measurement results were in good agreement with theoretical and simulated results.

  6. Ion trap electric field measurements using slab coupled optical sensors

    NASA Astrophysics Data System (ADS)

    Shumway, L.; Chadderdon, S.; Powell, A.; Li, A.; Austin, D.; Hawkins, A.; Selfridge, R.; Schultz, S.

    2014-03-01

    Ion traps are widely used in the field of mass spectrometry. These devices use high electric fields to mass-selectively trap, eject, and count the particles of a material, producing a mass spectrum of the given material. Because of their usefulness, technology pushes for smaller, more portable ion traps for field use. Making internal ion trap field measurements not yet feasible because current electric field sensors are often too bulky or their metallic composition perturbs field measurements. Using slab coupled optical sensor (SCOS) technology, we are able to build sensors that are compatible with the spacing constraints of the ion trap. These sensors are created by attaching a nonlinear crystal slab waveguide to an optical fiber. When a laser propagates through the fiber, certain wavelengths of light couple out of the fiber via the crystal and create "resonances" in the output light spectrum. These resonances shift in proportion to a given applied electric field, and by measuring that shift, we can approximate the electric field. Developing a sensor that can effectively characterize the electric fields within an ion trap will greatly assist in ion trap design, fabrication, and troubleshooting techniques.

  7. Asymmetrical distribution of ion channels in canine and human left-ventricular wall: epicardium versus midmyocardium.

    PubMed

    Szabó, Gergely; Szentandrássy, Norbert; Bíró, Tamás; Tóth, Balázs I; Czifra, Gabriella; Magyar, János; Bányász, Tamás; Varró, András; Kovács, László; Nánási, Péter P

    2005-08-01

    The aim of the present study was to compare the distribution of ion currents and the major underlying ion channel proteins in canine and human subepicardial (EPI) and midmyocardial (MID) left-ventricular muscle. Ion currents and action potentials were recorded from canine cardiomyocytes derived from the very superficial EPI and central MID regions of the left ventricle. Amplitude, duration and the maximum velocity of depolarization of the action potential were significantly greater in MID than EPI myocytes, whereas phase-1 repolarization was more pronounced in the EPI cells. Amplitudes of the transient outwards K+ current (29.5+/-1.5 vs. 19.0+/-2.3 pA/pF at +50 mV) and the slow component of the delayed rectifier K+ current (10.3+/-2.3 vs. 6.5+/-1.0 pA/pF at +50 mV) were significantly larger in EPI than in MID myocytes under whole-cell voltage-clamp conditions. The densities of the inwards rectifier K+ current, rapid delayed rectifier K+ current and L-type Ca2+ current were similar in both cell types. Expression of channel proteins in both canine and human ventricular myocardium was determined by Western blotting. In the canine heart, the expression of Kv4.3, Kv1.4, KChIP2 and KvLQT1 was significantly higher, and that of Nav1.5 and MinK much lower, in EPI than in MID. No significant EPI-MID differences were observed in the expression of the other channel proteins studied (Kir2.1, alpha1C, HERG and MiRP1). Similar results were obtained in human hearts, although the HERG was more abundant in the EPI than in the MID layer. In the canine heart, the EPI-MID differences in ion current densities were proportional to differences in channel protein expression. Except for the density of HERG, the pattern of EPI-MID distribution of ion-channel proteins was identical in canine and human ventricles.

  8. Energy partitioning of gaseous ions in an electric field.

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    The partitioning of ion energy among thermal energy, drift energy, and random-field energy is studied by solution of the Boltzmann equation. An expansion in powers of the square of the electric field strength is obtained by Kihara's method. Numerical calculations for several ion-neutral force laws show that Wannier's constant mean-free-time model gives a reasonable first approximation. The formal extension to multicomponent mixtures is also given. The matrix elements obtained are tabulated, and can be used to study the field dependence of other moments of the ion-distribution function.

  9. Application of asymmetric flow-field flow fractionation to the characterization of colloidal dispersions undergoing aggregation.

    PubMed

    Lattuada, Marco; Olivo, Carlos; Gauer, Cornelius; Storti, Giuseppe; Morbidelli, Massimo

    2010-05-18

    The characterization of complex colloidal dispersions is a relevant and challenging problem in colloidal science. In this work, we show how asymmetric flow-field flow fractionation (AF4) coupled to static light scattering can be used for this purpose. As an example of complex colloidal dispersions, we have chosen two systems undergoing aggregation. The first one is a conventional polystyrene latex undergoing reaction-limited aggregation, which leads to the formation of fractal clusters with well-known structure. The second one is a dispersion of elastomeric colloidal particles made of a polymer with a low glass transition temperature, which undergoes coalescence upon aggregation. Samples are withdrawn during aggregation at fixed times, fractionated with AF4 using a two-angle static light scattering unit as a detector. We have shown that from the analysis of the ratio between the intensities of the scattered light at the two angles the cluster size distribution can be recovered, without any need for calibration based on standard elution times, provided that the geometry and scattering properties of particles and clusters are known. The nonfractionated samples have been characterized also by conventional static and dynamic light scattering to determine their average radius of gyration and hydrodynamic radius. The size distribution of coalescing particles has been investigated also through image analysis of cryo-scanning electron microscopy (SEM) pictures. The average radius of gyration and the average hydrodynamic radius of the nonfractionated samples have been calculated and successfully compared to the values obtained from the size distributions measured by AF4. In addition, the data obtained are also in good agreement with calculations made with population balance equations.

  10. Optimization and evaluation of asymmetric flow field-flow fractionation of silver nanoparticles.

    PubMed

    Loeschner, Katrin; Navratilova, Jana; Legros, Samuel; Wagner, Stephan; Grombe, Ringo; Snell, James; von der Kammer, Frank; Larsen, Erik H

    2013-01-11

    Asymmetric flow field-flow fractionation (AF(4)) in combination with on-line optical detection and mass spectrometry is one of the most promising methods for separation and quantification of nanoparticles (NPs) in complex matrices including food. However, to obtain meaningful results regarding especially the NP size distribution a number of parameters influencing the separation need to be optimized. This paper describes the development of a separation method for polyvinylpyrrolidone-stabilized silver nanoparticles (AgNPs) in aqueous suspension. Carrier liquid composition, membrane material, cross flow rate and spacer height were shown to have a significant influence on the recoveries and retention times of the nanoparticles. Focus time and focus flow rate were optimized with regard to minimum elution of AgNPs in the void volume. The developed method was successfully tested for injected masses of AgNPs from 0.2 to 5.0 μg. The on-line combination of AF(4) with detection methods including ICP-MS, light absorbance and light scattering was helpful because each detector provided different types of information about the eluting NP fraction. Differences in the time-resolved appearance of the signals obtained by the three detection methods were explained based on the physical origin of the signal. Two different approaches for conversion of retention times of AgNPs to their corresponding sizes and size distributions were tested and compared, namely size calibration with polystyrene nanoparticles (PSNPs) and calculations of size based on AF(4) theory. Fraction collection followed by transmission electron microscopy was performed to confirm the obtained size distributions and to obtain further information regarding the AgNP shape. Characteristics of the absorbance spectra were used to confirm the presence of non-spherical AgNP.

  11. Asymmetric flow field flow fractionation with light scattering detection - an orthogonal sensitivity analysis.

    PubMed

    Galyean, Anne A; Filliben, James J; Holbrook, R David; Vreeland, Wyatt N; Weinberg, Howard S

    2016-11-18

    Asymmetric flow field flow fractionation (AF(4)) has several instrumental factors that may have a direct effect on separation performance. A sensitivity analysis was applied to ascertain the relative importance of AF(4) primary instrument factor settings for the separation of a complex environmental sample. The analysis evaluated the impact of instrumental factors namely, cross flow, ramp time, focus flow, injection volume, and run buffer concentration on the multi-angle light scattering measurement of natural organic matter (NOM) molar mass (MM). A 2((5-1)) orthogonal fractional factorial design was used to minimize analysis time while preserving the accuracy and robustness in the determination of the main effects and interactions between any two instrumental factors. By assuming that separations resulting in smaller MM measurements would be more accurate, the analysis produced a ranked list of effects estimates for factors and interactions of factors based on their relative importance in minimizing the MM. The most important and statistically significant AF(4) instrumental factors were buffer concentration and cross flow. The least important was ramp time. A parallel 2((5-2)) orthogonal fractional factorial design was also employed on five environmental factors for synthetic natural water samples containing silver nanoparticles (NPs), namely: NP concentration, NP size, NOM concentration, specific conductance, and pH. None of the water quality characteristic effects or interactions were found to be significant in minimizing the measured MM; however, the interaction between NP concentration and NP size was an important effect when considering NOM recovery. This work presents a structured approach for the rigorous assessment of AF(4) instrument factors and optimal settings for the separation of complex samples utilizing efficient orthogonal factional factorial design and appropriate graphical analysis.

  12. Quantum dot agglomerates in biological media and their characterization by asymmetrical flow field-flow fractionation.

    PubMed

    Moquin, Alexandre; Neibert, Kevin D; Maysinger, Dusica; Winnik, Françoise M

    2015-01-01

    The molecular composition of the biological environment of nanoparticles influences their physical properties and changes their pristine physicochemical identity. In order to understand, or predict, the interactions of cells with specific nanoparticles, it is critical to know their size, shape, and agglomeration state not only in their nascent state but also in biological media. Here, we use asymmetrical flow field-flow fractionation (AF4) with on-line multiangle light scattering (MALS), dynamic light scattering (DLS) and UV-Visible absorption detections to determine the relative concentration of isolated nanoparticles and agglomerates in the case of three types of semi-conductor quantum dots (QDs) dispersed in Dulbecco's Modified Eagle Media (DMEM) containing 10% of fetal bovine serum (DMEM-FBS). AF4 analysis also yielded the size and size distribution of the agglomerates as a function of the time of QDs incubation in DMEM-FBS. The preferred modes of internalization of the QDs are assessed for three cell-types, N9 microglia, human hepatocellular carcinoma cells (HepG2) and human embryonic kidney cells (Hek293), by confocal fluorescence imaging of live cells, quantitative determination of the intracellular QD concentration, and flow cytometry. There is an excellent correlation between the agglomeration status of the three types of QDs in DMEM-FBS determined by AF4 analysis and their preferred mode of uptake by the three cell lines, which suggests that AF4 yields an accurate description of the nanoparticles as they encounter cells and advocates its use as a means to characterize particles under evaluation.

  13. Comment on "Effects of Magnetic Field Gradient on Ion Beam Current in Cylindrical Hall Ion Source

    SciTech Connect

    Raitses, Y.; Smirnov A.; Fisch, N.J.

    2008-08-29

    It is argued that the key difference of the cylindrical Hall thruster (CHT) as compared to the end-Hall ion source cannot be exclusively attributed to the magnetic field topology [Tang et al. J. Appl. Phys., 102, 123305 (2007)]. With a similar mirror-type topology, the CHT configuration provides the electric field with nearly equipotential magnetic field surfaces and a better suppression of the electron cross-field transport, as compared to both the end-Hall ion source and the cylindrical Hall ion source of Tang et al.

  14. Effects of H+, He+ ion reflection at the lunar surface and pickup ion dynamics in case of oblique/quasi-parallel magnetic field: 3-D hybrid kinetic modeling

    NASA Astrophysics Data System (ADS)

    Lipatov, A. S.; Cooper, J. F.; Sittler, E. C.; Hartle, R. E.; Sarantos, M.

    2013-12-01

    The hybrid kinetic model used here supports comprehensive simulation of the interaction between different spatial and energetic elements of the moon-solar wind-magnetosphere of the Earth system. This involves variable upstream magnetic field and solar wind plasma, including energetic ions, electrons, and neutral atoms. This capability is critical to improved interpretation of existing measurements for surface and atmospheric composition from previous missions and planning future missions. Recently, MAP-PAGE-IMA (Plasma energy Angle and Composition Experiment, and Ion Mass Analyzer) onboard Japanese lunar orbiter SELENE (KAGUYA) detected Moon originating ions at 100 km altitude. Ion species of H+, He++, He+, C+, O+, Na+, K+, and Ar+ were definitively identified. The first portion of our modeling devotes to a study of the H+, H2+, He+, Na+ pickup ion dynamics in cases of flow with a oblique and quasi-parallel magnetic field. In the second series of modeling we also take into account collisions between ions and the surface of the moon and further sputtering of fragments from the surface of the moon. The ion reflection at the lunar surface is also responsible for wave activity in the upstream flow. The solar wind parameters are chosen from ARTEMIS observations. The hybrid kinetic model allows us to take into account the finite gyroradius effects of pickup ions and to estimate correctly the ions velocity distribution and the fluxes along the magnetic field. Modeling shows the asymmetric Mach cone, pickup and reflected ion tails, and presents another type of lunar-solar wind interaction. Our simulation may be also important for the study of the interaction between the solar wind and very weak comets, Mercury and Pluto.

  15. Quantum Simulation of Quantum Field Theories in Trapped Ions

    SciTech Connect

    Casanova, J.; Lamata, L.; Egusquiza, I. L.; Gerritsma, R.; Roos, C. F.; Garcia-Ripoll, J. J.; Solano, E.

    2011-12-23

    We propose the quantum simulation of fermion and antifermion field modes interacting via a bosonic field mode, and present a possible implementation with two trapped ions. This quantum platform allows for the scalable add up of bosonic and fermionic modes, and represents an avenue towards quantum simulations of quantum field theories in perturbative and nonperturbative regimes.

  16. Quantum simulation of quantum field theories in trapped ions.

    PubMed

    Casanova, J; Lamata, L; Egusquiza, I L; Gerritsma, R; Roos, C F; García-Ripoll, J J; Solano, E

    2011-12-23

    We propose the quantum simulation of fermion and antifermion field modes interacting via a bosonic field mode, and present a possible implementation with two trapped ions. This quantum platform allows for the scalable add up of bosonic and fermionic modes, and represents an avenue towards quantum simulations of quantum field theories in perturbative and nonperturbative regimes.

  17. Corona discharges in asymmetric electric fields and its impact on ionic wind generation

    NASA Astrophysics Data System (ADS)

    Tirumala, Rakshit

    configurations that induce asymmetric electric fields in the discharge space. Multiple collector configurations are a particular subset of these and are studied in more detail to characterize their fundamental behavior and to understand the differences from traditional discharges involving a single collecting electrode. The configurations are shown to present characteristics that are suitable for mitigating some of the problems encountered in device miniaturization. The three-electrode configurations are shown to reduce the onset potentials for device operation, increase the total current production, and present a favorable redistribution of current to the various collectors. Traditional corona modeling procedures are demonstrated to have significant shortcomings in asymmetric configurations and an alternative modeling procedure is developed for application in these conditions. The multi-electrode configurations were adapted to the development of an ionic wind blower. In a laboratory setup, these configurations are shown to improve flow rates by a factor of ˜3x and reduce power consumption by up to 0.5x. A prototype fabricated within the constraints imposed by handheld electronic systems on size and operating potential is described. The performance of the prototype-installed system is compared to the baseline system for flow and acoustic characteristics and is shown to be comparable in terms of the flow rates generated and significantly better in the acoustic signature levels. The technology presented in this dissertation has been patented [1].

  18. Electron jet of asymmetric reconnection

    NASA Astrophysics Data System (ADS)

    Khotyaintsev, Yu. V.; Graham, D. B.; Norgren, C.; Eriksson, E.; Li, W.; Johlander, A.; Vaivads, A.; André, M.; Pritchett, P. L.; Retinò, A.; Phan, T. D.; Ergun, R. E.; Goodrich, K.; Lindqvist, P.-A.; Marklund, G. T.; Le Contel, O.; Plaschke, F.; Magnes, W.; Strangeway, R. J.; Russell, C. T.; Vaith, H.; Argall, M. R.; Kletzing, C. A.; Nakamura, R.; Torbert, R. B.; Paterson, W. R.; Gershman, D. J.; Dorelli, J. C.; Avanov, L. A.; Lavraud, B.; Saito, Y.; Giles, B. L.; Pollock, C. J.; Turner, D. L.; Blake, J. D.; Fennell, J. F.; Jaynes, A.; Mauk, B. H.; Burch, J. L.

    2016-06-01

    We present Magnetospheric Multiscale observations of an electron-scale current sheet and electron outflow jet for asymmetric reconnection with guide field at the subsolar magnetopause. The electron jet observed within the reconnection region has an electron Mach number of 0.35 and is associated with electron agyrotropy. The jet is unstable to an electrostatic instability which generates intense waves with E∥ amplitudes reaching up to 300 mV m-1 and potentials up to 20% of the electron thermal energy. We see evidence of interaction between the waves and the electron beam, leading to quick thermalization of the beam and stabilization of the instability. The wave phase speed is comparable to the ion thermal speed, suggesting that the instability is of Buneman type, and therefore introduces electron-ion drag and leads to braking of the electron flow. Our observations demonstrate that electrostatic turbulence plays an important role in the electron-scale physics of asymmetric reconnection.

  19. Theoretical description of the mixed-field orientation of asymmetric-top molecules: A time-dependent study

    NASA Astrophysics Data System (ADS)

    Omiste, Juan J.; González-Férez, Rosario

    2016-12-01

    We present a theoretical study of the mixed-field-orientation of asymmetric-top molecules in tilted static electric field and nonresonant linearly polarized laser pulse by solving the time-dependent Schrödinger equation. Within this framework, we compute the mixed-field orientation of a state-selected molecular beam of benzonitrile (C7H5N ) and compare with the experimental observations [J. L. Hansen et al., Phys. Rev. A 83, 023406 (2011), 10.1103/PhysRevA.83.023406] and with our previous time-independent descriptions [J. J. Omiste et al., Phys. Chem. Chem. Phys. 13, 18815 (2011), 10.1039/c1cp21195a]. For an excited rotational state, we investigate the field-dressed dynamics for several field configurations as those used in the mixed-field experiments. The nonadiabatic phenomena and their consequences on the rotational dynamics are analyzed in detail.

  20. Role of ions in a crossed-field diode.

    PubMed

    Lau, Y Y; Luginsland, J W; Cartwright, K L; Haworth, M D

    2007-01-05

    The effect of ions in a magnetically insulated crossed-field gap is studied using a single particle orbit model, shear flow model, and particle-in-cell simulation. It is found that, in general, the presence of ions in a crossed-field gap always increases the electrons' excursion toward the anode region, regardless of the location of the ions. Thus, the rate at which the electrons migrate toward the anode, which is a measure of the diode closure rate, is related to the rate at which ions are introduced into the crossed-field gap. This anode migration of electrons is unrelated to crossed-field ambipolar diffusion. The implications of these findings are explored, such as pulse shortening in relativistic magnetrons and bipolar flows in pulsed-power systems.

  1. Role of Ions in a Crossed-Field Diode

    SciTech Connect

    Lau, Y. Y.; Luginsland, J. W.; Cartwright, K. L.; Haworth, M. D.

    2007-01-05

    The effect of ions in a magnetically insulated crossed-field gap is studied using a single particle orbit model, shear flow model, and particle-in-cell simulation. It is found that, in general, the presence of ions in a crossed-field gap always increases the electrons' excursion toward the anode region, regardless of the location of the ions. Thus, the rate at which the electrons migrate toward the anode, which is a measure of the diode closure rate, is related to the rate at which ions are introduced into the crossed-field gap. This anode migration of electrons is unrelated to crossed-field ambipolar diffusion. The implications of these findings are explored, such as pulse shortening in relativistic magnetrons and bipolar flows in pulsed-power systems.

  2. Driving toroidally asymmetric current through the tokamak scrape-off layer, Part II: Magnetic field structure and spectrum

    SciTech Connect

    Joseph, I

    2009-04-08

    The structure of the magnetic field perturbations due to non-axisymmetric field-aligned currents in the tokamak scrape-off layer (SOL) are analytically calculated near the X-point. Part I [I. Joseph, et al., submitted to Phys. Plasmas (2008)] demonstrated that biasing divertor target plates in a toroidally asymmetric fashion can generate an appreciable toroidally asymmetric parallel current density in the SOL along the separatrix. Here, the magnetic field perturbation caused by a SOL current channel of finite width and step-wise constant amplitude at the target plate is derived. Flux expansion amplifies the magnetic perturbation near the X-point, while phase interference causes the SOL amplitude to be reduced at large toroidal mode number. Far enough from the current channel, the magnetic field can be approximated as arising from a surface current near the separatrix with differing amplitudes in the SOL and the divertor leg. The perturbation spectrum and resonant components of this field are computed analytically asymptotically close to the separatrix in magnetic flux coordinates. The size of the stochastic layer due to the applied perturbation that would result without self-consistent plasma shielding is also estimated. If enough resonant field is generated, control of the edge pressure gradient may allow stabilization of edge localized modes.

  3. Asymmetric magnetic bubble expansion under in-plane field in Pt/Co/Pt: Effect of interface engineering

    NASA Astrophysics Data System (ADS)

    Lavrijsen, R.; Hartmann, D. M. F.; van den Brink, A.; Yin, Y.; Barcones, B.; Duine, R. A.; Verheijen, M. A.; Swagten, H. J. M.; Koopmans, B.

    2015-03-01

    We analyze the impact of growth conditions on the asymmetric magnetic bubble expansion under an in-plane field in ultrathin Pt/Co/Pt films. Specifically, using sputter deposition, we vary the Ar pressure during the growth of the top Pt layer. This induces a large change in the interfacial structure as evidenced by a factor three change in the effective perpendicular magnetic anisotropy. Strikingly, a discrepancy between the current theory for domain-wall propagation based on a simple domain-wall energy density and our experimental results is found. This calls for further theoretical development of domain-wall creep under in-plane fields and varying structural asymmetry.

  4. The Effects of Ion heating in Martian Magnetic Crustal Fields: Particle Tracing and Ion Distributions

    NASA Astrophysics Data System (ADS)

    Fowler, C. M.; Andersson, L.

    2014-12-01

    Ion heating is a process that may allow low energy ions within the Martian ionosphere to be accelerated and escape. Ion heating can be especially efficient if the ions stay in the heating region for long time durations. With this in mind, the magnetic crustal field regions on Mars are particularly interesting. We focus on ions present within these regions, where changes in magnetic field strength and direction can heat these ions. Since crustal magnetic fields can maintain a trapped particle population it is unclear how efficiently plasma can be built up that can later escape to space. We investigate here two drivers: rotation of the planet and the solar wind pressure. As crustal fields rotate from the wake of the planet to the sub solar point and back, they experience compression and expansion over time scales of ~24 hours. The solar wind pressure on the other hand can cause variations over much shorter time scales (minutes). The effect of these two drivers using a particle tracing simulation that solves the Lorentz force is presented. O+ ions are seeded within the simulation box. The magnetic environment is a linear sum of a dipole field and a solar wind magnetic field. The dipole field represents the magnetic crustal field and the dipole strength is chosen to be consistent with MGS magnetometer observations of Martian crustal field regions. By increasing the solar wind strength the magnetic dipole is compressed. Decreasing solar wind strength allows the dipole to expand. Small magnitude, short time scale variations can be imposed over the top of this larger variation to represent short time scale solar wind variations. Since the purpose of this analysis is to understand the changes of the ion distribution inside the crustal field, simplistic assumptions of the field outside the crustal field can be made. Initial results are presented, with the focus on two main questions: (a) can low energy ions be heated and escape the closed dipole field lines as a result of

  5. Electric field by pick-up ions and electrons

    NASA Astrophysics Data System (ADS)

    Yamauchi, Masatoshi; Behar, Etienne; Nilsson, Hans; Holmstrom, Mats

    2016-04-01

    Observations by the Rosetta Plasma Consortium (RPC) showed increasing distortion of the solar wind flow as Rosetta approached the Sun, i.e., as the density of the newly born ions increased. This indicates azimuthal momentum transfer from the solar wind to the newly born ions because they are displaced by the solar wind electric field up to the ion gyroradius this the solar wind velocity, and conservation of the momentum (center of the mass) makes the solar wind to azimuthally shift by "counter action" of these pick-up ion motions. To understand this azimuthal momentum transfer, it is inevitable to model the electric field by the displacement of these pick-up ions and electrons. Although the E×B drift does not make charge separation when the scale size is larger than the ion gyroradius, ions and electrons move in the opposite direction to each other within the short distance up to a gyroradius, and therefore, the charge separation occurs. Thus, the newly-ionized neutrals (ion-electron pairs) create the electric field in the opposite (shielding) direction to the solar wind electric field (like the ionopause of Venus and Mars). However, such a newly induced "shielding" electric field will simultaneously be weakened by the solar wind electrons because the solar wind is also moved by this shielding electric field to reduce it, in the same way as the plasma oscillation (time scale of about 10-4 s). In other words, the solar wind tries to maintain the solar wind electric field as far as the momentum allows. These two opposite effects must be combined when modelling the azimuthal electric field, and resultant ion/electron motions within a gyroradius, like the case for ROSETTA. Furthermore, the effect of the induced electric field by the pick-up ions and electrons will be different when the newly born ions are created as the result of photo-ionization and of the charge exchange because the electron effect is different between them. In the presentation, we model the

  6. Linear electric field time-of-flight ion mass spectrometer

    DOEpatents

    Funsten, Herbert O.; Feldman, William C.

    2008-06-10

    A linear electric field ion mass spectrometer having an evacuated enclosure with means for generating a linear electric field located in the evacuated enclosure and means for injecting a sample material into the linear electric field. A source of pulsed ionizing radiation injects ionizing radiation into the linear electric field to ionize atoms or molecules of the sample material, and timing means determine the time elapsed between ionization of atoms or molecules and arrival of an ion out of the ionized atoms or molecules at a predetermined position.

  7. Evolution of perturbed rotations of an asymmetric Gyro in a gravitational field and a resisting medium

    NASA Astrophysics Data System (ADS)

    Akulenko, L. D.; Leshchenko, D. D.; Rachinskaya, A. L.; Shchetinina, Yu. S.

    2016-07-01

    We study the fast rotational motion of a dynamically asymmetric satellite with a spherical cavity filled with a highly viscous liquid about the center of mass under the action of gravitational torque and medium drag torques. The system obtained by averaging over the Euler-Poinsotmotion and by using a modified averaging method is analyzed. An analytic study and numerical analysis are carried out.

  8. Directional deprotonation ionization of acetylene in asymmetric two-color laser fields

    NASA Astrophysics Data System (ADS)

    Song, Qiying; Gong, Xiaochun; Ji, Qinying; Lin, Kang; Pan, Haifeng; Ding, Jingxin; Zeng, Heping; Wu, Jian

    2015-05-01

    We experimentally investigate the deprotonation dissociative double ionization of an acetylene molecule by an asymmetric two-color laser pulse. We find that the ejection direction of the proton, and hence the directional C-H bond breaking of a polyatomic hydrocarbon molecule, can be controlled by finely tuning the phase of a two-color laser pulse.

  9. Membrane curvature generated by asymmetric depletion layers of ions, small molecules, and nanoparticles

    NASA Astrophysics Data System (ADS)

    RóŻycki, Bartosz; Lipowsky, Reinhard

    2016-08-01

    Biomimetic and biological membranes consist of molecular bilayers with two leaflets that are typically exposed to different aqueous solutions. We consider solutions of "particles" that experience effectively repulsive interactions with these membranes and form depletion layers in front of the membrane leaflets. The particles considered here are water-soluble, have a size between a few angstrom and a few nanometers as well as a rigid, more or less globular shape, and do neither adsorb onto the membranes nor permeate these membranes. Examples are provided by ions, small sugar molecules, globular proteins, or inorganic nanoparticles with a hydrophilic surface. We first study depletion layers in a hard-core system based on ideal particle solutions as well as hard-wall interactions between these particles and the membrane. For this system, we obtain exact expressions for the coverages and tensions of the two leaflets as well as for the spontaneous curvature of the bilayer membrane. All of these quantities depend linearly on the particle concentrations. The exact results for the hard-core system also show that the spontaneous curvature can be directly deduced from the planar membrane geometry. Our results for the hard-core system apply both to ions and solutes that are small compared to the membrane thickness and to nanoparticles with a size that is comparable to the membrane thickness, provided the particle solutions are sufficiently dilute. We then corroborate the different relationships found for the hard-core system by extensive simulations of a soft-core particle system using dissipative particle dynamics. The simulations confirm the linear relationships obtained for the hard-core system. Both our analytical and our simulation results show that the spontaneous curvature induced by a single particle species can be quite large. When one leaflet of the membrane is exposed, e.g., to a 100 mM solution of glucose, a lipid bilayer can acquire a spontaneous curvature of ±1

  10. Visualization of lithium ions by annular bright field imaging.

    PubMed

    Oshima, Yoshifumi; Lee, Soyeon; Takayanagi, Kunio

    2016-10-14

    The detection of lithium ions is required for characterization of lithium ion batteries, since the movement of lithium ions in the battery is one of the key ways to improve the performance. Annular bright field (ABF) imaging enables us to visualize individual lithium atomic columns simultaneously with heavy elements. Furthermore, it has been found that the number of lithium ions at the column is countable when the specimen is thin. These results suggest that movement of lithium ions in the material can be observed by taking consecutive ABF images during operation or in situ ABF observation. Actually, the spinel structure of L2V4O crystals was directly observed to be transformed into the defective NaCl structure at the moment when lithium ions were extracted from the original position during electron beam irradiation. We clarify the features of ABF imaging by comparing it with HAADF imaging in order to understand what information can be obtained by ABF imaging directly.

  11. Trapped energetic ion dynamics affected by localized electric field perturbations

    NASA Astrophysics Data System (ADS)

    Nishimura, Seiya

    2016-01-01

    Trapped energetic ion orbits in helical systems are numerically simulated using the Lorentz model. Simulation results of precession drift frequencies of trapped energetic ions are benchmarked by those of analytic solutions. The effects of the electric field perturbation localized at the rational surface on trapped energetic ions are examined, where the perturbation has an arbitrary rotation frequency and an amplitude fixed in time. It is found that the trapped energetic ions resonantly interact with the perturbation, when the rotation frequency of the perturbation is comparable to the precession drift frequencies of trapped energetic ions. The simulation results are suggestive to a mechanism of the energetic-ion-induced interchange mode, which might be associated with the fishbone mode observed in helical systems.

  12. Asymmetric hydration structure around calcium ion restricted in micropores fabricated in activated carbons

    NASA Astrophysics Data System (ADS)

    Ohkubo, Takahiro; Kusudo, Tomoko; Kuroda, Yasushige

    2016-11-01

    The adsorbed phase and hydration structure of an aqueous solution of Ca(NO3)2 restricted in micropores fabricated in activated carbons (ACs) having different average pore widths (0.63 and 1.1 nm) were investigated with the analysis of adsorption isotherms and x-ray absorption fine structure (XAFS) spectra on Ca K-edge. The adsorbed density of Ca2+ per unit micropore volume in the narrower pore was higher than in the wider pore, while the adsorbed amount per unit mass of carbon with the narrower pore was half of the amount of ACs with the larger pore. On the other hand, variations in the bands assigned to double-electron (KM I) and 1s  →  3d excitations in XAFS spectra demonstrate the formation of a distorted hydration cluster around Ca2+ in the micropore, although the structural parameters of hydrated Ca2+ in the micropores were almost consistent with the bulk aqueous solution, as revealed by the analysis of extended XAFS (EXAFS) spectra. In contrast to the hydration structure of monovalent ions such as Rb+, which generally presents a dehydrated structure in smaller than 1 nm micropores in ACs, the present study clearly explains that the non-spherically-symmetric structure of hydrated Ca2+ restricted in carbon micropores whose sizes are around 1 nm is experimentally revealed where any dehydration phenomena from the first hydration shell around Ca2+ could not be observed.

  13. Atom probe field ion microscopy and related topics: A bibliography 1991

    SciTech Connect

    Russell, K.F.; Miller, M.K.

    1993-01-01

    This report contains a bibliography for 1991 on the following topics: Atom probe field ion microscopy; field desorption mass spectrometry; field emission; field ion microscopy; and field emission theory.

  14. Ion Beam Neutralization Using FEAs and Mirror Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Nicolaescu, Dan; Sakai, Shigeki; Gotoh, Yasuhito; Ishikawa, Junzo

    2011-01-01

    Advanced implantation systems used for semiconductor processing require transportation of ion beams which are quasi-parallel and have low energy, such as (11B+,31P+,75As+) with energy in the range Eion = 200-1000 eV. Compensation of ion beam divergence may be obtained through electron injection and confinement in regions of non-uniform magnetic fields. Field emitter arrays with special properties are used as electron sources. The present study shows that electron confinement takes place in regions of gradient magnetic field, such as nearby analyzing, collimator and final energy magnets of the ion beam line. Modeling results have been obtained using Opera3D/Tosca/Scala. In regions of gradient magnetic field, electrons have helical trajectories which are confined like a cloud inside curved "magnetic bottles". An optimal range of positions with respect to the magnet for placing electron sources in gradient magnetic field has been shown to exist.

  15. Measuring Fast Ion Losses in a Reversed Field Pinch Plasma

    NASA Astrophysics Data System (ADS)

    Bonofiglo, P. J.; Anderson, J. K.; Almagri, A. F.; Kim, J.; Clark, J.; Capecchi, W.; Sears, S. H.

    2015-11-01

    The reversed field pinch (RFP) provides a unique environment to study fast ion confinement and transport. The RFP's weak toroidal field, strong magnetic shear, and ability to enter a 3D state provide a wide range of dynamics to study fast ions. Core-localized, 25 keV fast ions are sourced into MST by a tangentially injected hydrogen/deuterium neutral beam. Neutral particle analysis and measured fusion neutron flux indicate enhanced fast ion transport in the plasma core. Past experiments point to a dynamic loss of fast ions associated with the RFP's transition to a 3D state and with beam-driven, bursting magnetic modes. Consequently, fast ion transport and losses in the RFP have garnered recent attention. Valuable information on fast-ion loss, such as energy and pitch distributions, are sought to provide a better understanding of the transport mechanisms at hand. We have constructed and implemented two fast ion loss detectors (FILDs) for use on MST. The FILDs have two, independent, design concepts: collecting particles as a function of v⊥ or with pitch greater than 0.8. In this work, we present our preliminary findings and results from our FILDs on MST. This research is supported by US DOE.

  16. Combination of Metal Coordination Tetrahedra and Asymmetric Coordination Geometries of Sb(III) in the Organically Directed Chalcogenidometalates: Structural Diversity and Ion-exchange Properties.

    PubMed

    Feng, Mei-Ling; Wang, Kai-Yao; Huang, Xiao-Ying

    2016-04-01

    Chalcogenidometalates exhibit rich and diverse structures and properties applicable to ion exchange, thermoelectrics, photocatalysis, nonlinear optics, and so on. This personal account summarizes our recent progress in constructing chalcogenidometalates by combining metal coordination tetrahedra and the asymmetric coordination geometries of Sb(3+) in the presence of organic species (typically organic amines and metal-organic amine complexes), which has been demonstrated as an effective strategy for synthesizing chalcogenidometalates with diversified structures and interesting properties. The linkage modes of asymmetric SbQn (n = 3, 4) geometries and group 13 (or 14) metal coordination tetrahedra are analyzed, and the secondary building units (SBUs), with different compositions and architectures, are clarified. The crucial role and function of organic species in the formation of chalcogenidometalates are explored, with an emphasis on their powerful structure-directing features. In particular, some chalcogenidometalates in this family exhibit excellent ion-exchange properties for Cs(+) and/or Sr(2+) ions; the factors affecting ion-exchange properties are discussed to understand the underlying ion-exchange mechanism.

  17. Simulating Geomagnetic Depth Sounding using a Time-domain Finite Element Method: Effects of Asymmetric External Source Fields

    NASA Astrophysics Data System (ADS)

    Ribaudo, J. T.; Constable, C.

    2010-12-01

    The commercial finite element software FlexPDE has been successfully used to simulate electromagnetic induction in Earth's mantle and lithosphere and validated by several previously published results. Estimates of Earth's frequency-dependent electromagnetic response calculated from satellite data are known to be influenced by the local time of the observing frame. We use time-stepping methods scripted within FlexPDE to investigate the hypothesis that this bias results from the rotation of Earth through the asymmetric and highly variable magnetic field associated with the magnetospheric ring current. We evaluate local-time response functions at periods of a few hours to a few months. These are calculated from long 3-dimensional, time-domain simulations of geomagnetic induction and using the magnetic data similar to those gathered by low earth orbiting satellite missions. The spatial structure of the external field is imposed in the form of a time-varying spherical harmonic representation in a geomagnetic coordinate system that rotates with respect to Earth. The symmetric part of the field is controlled by the dipole (degree 1, order 0) term and the asymmetric part controlled by a quadrupole (degree 2, order 1) term. Time variations in the magnitude of the external field are controlled by a high-resolution magnetic index such as the new 1-minute USGS Dst, subsampled at 15 minute intervals.

  18. On the Electrons Dynamics during Rapid Island Coalescence in Asymmetric Magnetic Reconnection: Case With and With No Guide Field

    NASA Astrophysics Data System (ADS)

    Cazzola, E.; Innocenti, M. E.; Markidis, S.; Goldman, M. V.; Newman, D. L.; Lapenta, G.

    2015-12-01

    We present a set of fully kinetic 2.5D simulations of electron dynamics during rapid magnetic islands coalescence in asymmetric conditions. Simulations are performed using the massively parallel fully kinetic implicit moment method code iPIC3D (Markidis et al. 2010). The domain is a double periodic box with two current sheets initially representing two different reconnection conditions with the same asymmetric ratio. In the upper sheet the conventional hyperbolic continuous functions for magnetic field and density are initialised across the layer (e.g. Pritchett 2008). In the lower layer the same asymmetric conditions are used the presence of an extremely steep gradient describing a pure tangential discontinuity.Cases with and without guide field are compared. While the upper layer shows the typical reconnection evolution of an asymmetric configuration, the lower layer very soon develops not-uniformly distributed multiple reconnection points which rapidly evolve in a series of magnetic islands. Quick islands coalescence follows. Even though the electrons dynamics during island merging has been studied in both symmetric and asymmetric conditions (e.g. Pritchett 2007, 2008b, Drake et al. 2006, Oka et al. 2010, Huang et al. 2014), these simulations show new interesting features such as the presence of three distinct regions, here named X, M and D, with very different properties. Regions X and M manifest typical signatures of ongoing reconnection, distinguishable thanks to the direct comparison with the outcomes of the upper layer. In particular, M-type regions are different because reconnection occurs between two merging islands in a vertical fashion with respect to the direction of the current sheets initially set. In contrast, regions D present a quite diverse features, not showing the typical signatures of a occurring reconnection. The present work is supported by the NASA MMS Grant NNX08AO84G. Additional support for the KULeuven team is provided by the European

  19. Cusped magnetic field mercury ion thruster. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Beattie, J. R.

    1976-01-01

    The importance of a uniform current density profile in the exhaust beam of an electrostatic ion thruster is discussed in terms of thrust level and accelerator system lifetime. A residence time approach is used to explain the nonuniform beam current density profile of the divergent magnetic field thruster. Mathematical expressions are derived which relate the thruster discharge power loss, propellant utilization, and double to single ion density ratio to the geometry and plasma properties of the discharge chamber. These relationships are applied to a cylindrical discharge chamber model of the thruster. Experimental results are presented for a wide range of the discharge chamber length. The thruster designed for this investigation was operated with a cusped magnetic field as well as a divergent field geometry, and the cusped field geometry is shown to be superior from the standpoint of beam profile uniformity, performance, and double ion population.

  20. Quantum Molecular Interaction Field Models of Substrate Enantioselection in Asymmetric Processes

    PubMed Central

    Kozlowski, Marisa C.; Ianni, James C.

    2010-01-01

    Computational models correlating substrate structure to enantioselection with asymmetric catalysts using the QMQSAR program are described. In addition to rapidly providing predictions that could be used to facilitate the screening of catalysts for novel substrates, the QMQSAR program identifies the portions of the substrate that most directly influence the enantioselectivity. The lack underlying relationship between all the substrates in one case, requires two quantitative structure selectivity relationships (QSSR) models to describe all of the experimental results. PMID:20676382

  1. Retarding field energy analyser ion current calibration and transmission

    NASA Astrophysics Data System (ADS)

    Denieffe, K.; Mahony, C. M. O.; Maguire, P. D.; Gahan, D.; Hopkins, M. B.

    2011-02-01

    Accurate measurement of ion current density and ion energy distributions (IEDs) is often critical for plasma processes in both industrial and research settings. Retarding field energy analysers (RFEAs) have been used to measure IEDs because they are considered accurate, relatively simple and cost effective. However, their usage for critical measurement of ion current density is less common due to difficulties in estimating the proportion of incident ion current reaching the current collector through the RFEA retarding grids. In this paper an RFEA has been calibrated to measure ion current density from an ion beam at pressures ranging from 0.5 to 50.0 mTorr. A unique method is presented where the currents generated at each of the retarding grids and the RFEA upper face are measured separately, allowing the reduction in ion current to be monitored and accounted for at each stage of ion transit to the collector. From these I-V measurements a physical model is described. Subsequently, a mathematical description is extracted which includes parameters to account for grid transmissions, upper face secondary electron emission and collisionality. Pressure-dependent calibration factors can be calculated from least mean square best fits of the collector current to the model allowing quantitative measurement of ion current density.

  2. Analysis of the light-field intensity dependence of catastrophic optical damage in high-power AlGaInP lasers using an asymmetrical tapered laser

    NASA Astrophysics Data System (ADS)

    Bou Sanayeh, Marwan

    2016-04-01

    Catastrophic optical damage (COD) in semiconductor lasers is a major limiting effect for high-power operation. Several techniques like microphotoluminescence (μPL) mapping, focused ion beam (FIB) microscopy, and micro- Raman spectroscopy were employed to reveal the physics behind catastrophic optical damage, its related temperature dynamics, as well as associated defect and near-field patterns. High-resolution μPL images demonstrated that during COD, nonradiative dark line defects (DLDs) originate from the front mirror of the laser and propagate deep inside the cavity. Furthermore, FIB microscopy identified the epitaxial layers affected by COD, revealing that the DLDs are confined to the active region. In addition, deep-etching uncovered the DLDs by making them visible, and showed that they are composed of complex dislocation networks. Lasers that underwent a spontaneous breakdown where also studied. One missing piece to complete the characterization of COD is to analyze if the DLDs actually follow certain crystal direction lines inside the laser cavity, which are in general perpendicular to the output facet, or follow the path of the light-field intensity-maximum. Using a specially designed innovative device, namely an asymmetrical AlGaInP tapered laser, it is proven in this study that the COD is strongly dependent on the light-field intensity inside the laser cavity and not on certain crystal direction lines.

  3. Extending the Ion Capacity of a Linear Ion Trap Using Nonlinear Radio Frequency Fields.

    PubMed

    Guna, Mircea

    2015-12-01

    Mass selective axial ejection (MSAE) from a low pressure linear ion trap (LIT) is investigated in the presence of added auxiliary nonlinear radio frequency (rf) fields. Nonlinear rf fields allow ions to be ejected with high sensitivity at large excitation amplitudes and reduced deleterious effects of space charge. These permit the operation of the LIT at ion populations considerably larger than the space charge limit usually observed in the absence of the nonlinear fields while maintaining good spectral resolution and mass accuracy. Experimental data show that the greater the strength of the nonlinear field, the less the effects of space charge on mass assignment and peak width. The only deleterious effect is a slight broadening of the mass spectral peaks at the highest values of added nonlinear fields used. Graphical Abstract ᅟ.

  4. Sharpening of field emitter tips using high-energy ions

    DOEpatents

    Musket, Ronald G.

    1999-11-30

    A process for sharpening arrays of field emitter tips of field emission cathodes, such as found in field-emission, flat-panel video displays. The process uses sputtering by high-energy (more than 30 keV) ions incident along or near the longitudinal axis of the field emitter to sharpen the emitter with a taper from the tip or top of the emitter down to the shank of the emitter. The process is particularly applicable to sharpening tips of emitters having cylindrical or similar (e.g., pyramidal) symmetry. The process will sharpen tips down to radii of less than 12 nm with an included angle of about 20 degrees. Because the ions are incident along or near the longitudinal axis of each emitter, the tips of gated arrays can be sharpened by high-energy ion beams rastered over the arrays using standard ion implantation equipment. While the process is particularly applicable for sharpening of arrays of field emitters in field-emission flat-panel displays, it can be effectively utilized in the fabrication of other vacuum microelectronic devices that rely on field emission of electrons.

  5. Generation of macroscopic magnetic-field-aligned electric fields by the convection surge ion acceleration mechanism

    NASA Technical Reports Server (NTRS)

    Mauk, B. H.

    1989-01-01

    The 'convection surge' model for ion acceleration, designed by Mauk (1986) to explain the observed ion distributions and the field-aligned character of middle magnetospheric ion distributions during the expansion phase of a substorm, was extended to include the self-consistent generation of magnetic-field-aligned electric fields. Results from the modified model show that the convection surge mechanism leads to the generation of dynamical macroscopic magnetic field-aligned electric fields that begin their strongest developments very near the magnetic equator and then propagate to higher latitudes. Potential drops as high as 1 to 10 kV might be expected, depending on the mass species of the ions and on the electron temperatures. It is speculated that the convection surge mechanism could be a key player in the transient field-aligned electromagnetic processes observed to operate within the middle magnetosphere.

  6. Correcting the fundamental ion mobility equation for field effects.

    PubMed

    Siems, William F; Viehland, Larry A; Hill, Herbert H

    2016-11-14

    The fundamental ion mobility equation computes the energy-averaged collision cross section as a function of measured drift velocity, electric field strength, ion and neutral masses, and drift gas state parameters. As field strength approaches zero, in particular when the drift velocity drops below about 4% of the average ion-neutral thermal speed, the fundamental equation takes on an especially simple form because the collision frequency and average momentum transfer become indistinguishable from their thermal values. However, in modern high-performance IMS-MS instruments, ion drift velocities may be 10-50% or more of thermal speed, and analysis using the zero-field equation gives rise to erroneously large cross sections. We address this problem by developing correction factors for the zero-field equation from an improved momentum-transfer (MT) theory for ion mobility, corrected and completed herein, and from the well-known two-temperature (2T) theory. The corrected and uncorrected equations are compared by their ability to recover known hard-sphere cross sections from accurately-computed mobility data. Both MT and 2T expressions adjust for the field-driven increase in collision frequency and are noticeably superior to zero-field expression whenever the ion drift velocity is greater than ∼4% of thermal speed. The MT expression also adjusts for the mass and field dependent change in average momentum transfer, and is more accurate than the 2T first approximation whenever the mass of the ionic species is greater than about four times that of drift gas molecules, as is the case in most analytical applications of IMS coupled to MS.

  7. A study of electric-field-induced second-harmonic generation in asymmetrical Gaussian potential quantum wells

    NASA Astrophysics Data System (ADS)

    Zhai, Wangjian

    2014-12-01

    Electric-field-induced second-harmonic generation in asymmetrical Gaussian potential quantum wells is investigated using the effective mass approximation employing the compact density matrix method and the iterative approach. Our results show that the absolute value, the real part and the imaginary part of second-harmonic generation are greatly affected by the height of the Gaussian potential quantum wells, the range of the Gaussian confinement potential and the applied electric field. The relationship between the absolute value and the imaginary part of second-harmonic generation together with the relationship between the absolute value and the real part of second-harmonic generation is studied. It is found that no matter how the height of the Gaussian potential quantum wells, the range of the Gaussian confinement potential and the applied electric field vary, the resonant peaks of the absolute value of second-harmonic generation do not originate from the imaginary part but from the real part.

  8. Fast Ion Transport in the MST Reversed Field Pinch

    NASA Astrophysics Data System (ADS)

    Bonofiglo, P. J.; Anderson, J. K.; Capecchi, W.; Kim, J.; Sears, S. H.; Egedal, J.

    2016-10-01

    The reversed field pinch (RFP) provides a unique environment to study fast ion confinement and transport. The magnetic topology of the RFP establishes guiding center drifts along flux surfaces, resulting in naturally well-confined fast ions. Past experiments reveal reduced confinement and a redistribution of fast ions with beam-driven instabilities or transition to a 3D equilibrium state. A fast ion transport model characterized by a temporally and spatially dependent diffusion profile describes the fast ion evolution. The diffusion coefficient varies as the square of the measured mode amplitude, and the width is inferred from comparison with correlated density fluctuations. In studying multiple interacting modes, the model reproduces the dynamic NPA-measured 20 % drop in core fast ion concentration. In the case of long-lived frequency chirping modes, there is a consistent time evolution of the fast ion distribution and measured mode frequency on a spatially varying Alfven continuum. Additional studies probe the dynamics of energetic particle modes (EPMs) during the growth of the core-localized kink mode and the rapid loss of fast ion confinement as a transition to a 3D equilibrium occurs. This research is supported by US DOE.

  9. Exciton-related nonlinear optical properties in cylindrical quantum dots with asymmetric axial potential: combined effects of hydrostatic pressure, intense laser field, and applied electric field

    PubMed Central

    2012-01-01

    The exciton binding energy of an asymmetrical GaAs-Ga1−xAlxAs cylindrical quantum dot is studied with the use of the effective mass approximation and a variational calculation procedure. The influence on this quantity of the application of a direct-current electric field along the growth direction of the cylinder, together with that of an intense laser field, is particularly considered. The resulting states are used to calculate the exciton-related nonlinear optical absorption and optical rectification, whose corresponding resonant peaks are reported as functions of the external probes, the quantum dot dimensions, and the aluminum molar fraction in the potential barrier regions. PMID:22971418

  10. Inhomogeneous Magnetic Field Geometry Light Ion Helicon Plasma Source

    NASA Astrophysics Data System (ADS)

    Mori, Yoshitaka; Nakashima, Hideki; Goulding, R. H.; Carter Baity, M. D., Jr.; Sparks, D. O.; Barber, G. C.; White, K. F.; Jaeger, E. F.; Chang-Díaz, F. R.; Squire, J. P.

    2002-11-01

    Helicon plasma source is a well-known high-density plasma source for many applications including plasma processing and fusion. However, most helicon research has been focused on a uniform static magnetic field and relatively heavy ions. Light ion helicon operation is more sensitive to magnetic field strength and geometry than heavy ions. The axially inhomogeneous Mini-Radio Frequency Test Facility (Mini-RFTF) has a capability for controlling static magnetic fields then is applicative for light ion source plasma operation. Inhomogeneous static magnetic field geometry also can procedure a high velocity to plasma exhaust when combined with ICRF heating enabling the possibility of use in plasma propulsion. In this poster, we will show how the source has been optimized for a hydrogen operation and a specific plasma propulsion concept: The Variable Specific Impulse Magnetoplasma Rocket (VASIMR). Measurements of the rf magnetic fields and profile of plasma parameters for several magnetic field strengths and geometries will be discussed. Comparisons with a RF modeling code EMIR3 also will be reported here.

  11. Effect of magnetic field inhomogeneity on ion cyclotron motion coherence at high magnetic field.

    PubMed

    Vladimirov, Gleb; Kostyukevich, Yury; Hendrickson, Christopher L; Blakney, Greg T; Nikolaev, Eugene

    2015-01-01

    A three-dimensional code based on the particle-in-cell algorithm modified to account for the inhomogeneity of the magnetic field was applied to determine the effect of Z(1), Z(2), Z(3), Z(4), X, Y, ZX, ZY, XZ(2) YZ(2), XY and X(2)-Y(2) components of an orthogonal magnetic field expansion on ion motion during detection in an FT-ICR cell. Simulations were performed for magnetic field strengths of 4.7, 7, 14.5 and 21 Tesla, including experimentally determined magnetic field spatial distributions for existing 4.7 T and 14.5 T magnets. The effect of magnetic field inhomogeneity on ion cloud stabilization ("ion condensation") at high numbers of ions was investigated by direct simulations of individual ion trajectories. Z(1), Z(2), Z(3) and Z(4) components have the largest effect (especially Z(1)) on ion cloud stability. Higher magnetic field strength and lower m/z demand higher relative magnetic field homogeneity to maintain cloud coherence for a fixed time period. The dependence of mass resolving power upper limit on Z(1) inhomogeneity is evaluated for different magnetic fields and m/z. The results serve to set the homogeneity requirements for various orthogonal magnetic field components (shims) for future FT-ICR magnet design.

  12. Energetic Ions and Magnetic Fields Upstream From the Kronian Magnetosphere

    NASA Astrophysics Data System (ADS)

    Krimigis, S. M.; Sarris, E.; Sergis, N.; Dialynas, K.; Mitchell, D. G.; Hamilton, D. C.; Dougherty, M.

    2008-12-01

    The existence of energetic particle events to ~200 Rs upstream and ~1300 Rs downstream of Saturn was established during the Voyager 1, 2 flybys in 1980 and 1981, respectively. The origin of the events could not be determined with certainty because of lack of particle charge state and species measurements at lower (<300 keV) energies, which dominate the spectra. High sensitivity observations of energetic ion directional intensities, energy spectra, and ion composition were obtained by the Ion and Neutral Camera (INCA) of the MIMI instrument complement with a geometry factor of ~2.5 cm2 sr and some capability of separating light (H, He) and heavier (C, N, O) ion groups (henceforth referred to as "hydrogen" and "oxygen" respectively). Charge state information was provided where possible by the Charge-Energy-Mass-Spectrometer (CHEMS) over the range ~3 to 220 keV per charge, and magnetic field (IMF) data by the MAG instrument on Cassini. The observations revealed the presence of distinct upstream bursts of energetic hydrogen and oxygen ions whenever the IMF connected the spacecraft to the planetary bow shock, up to distances of 135 RS. The events exhibited the following characteristics: (1) Hydrogen ion bursts are observed in the energy range 3 to 220 keV (and occasionally to E > 220 keV) and oxygen ion bursts in the energy range 32 to -300 keV. (2) Particle onsets are nearly field-aligned, but the distribution tends to isotropize as the event progresses in time. (3) The duration of the ion bursts is several minutes up to 4 hrs. (4) The events are of varying composition, with some exhibiting significant fluxes of oxygen. (5) The bursts have a filamentary structure with some exhibiting distinct signatures of "velocity- filtering effects" at the edges of convecting IMF filaments. (6) Some ion bursts are accompanied by distinct diamagnetic field depressions and exhibit wave structures consistent with ion cyclotron waves for H+, and O+. Given the repeated magnetic field

  13. Rotational state dependence of rate constants for the reaction of ions with asymmetric top molecules at very low temperatures: application to the N+/H2O system

    NASA Astrophysics Data System (ADS)

    Dubernet, M. L.; McCarroll, R.

    1990-12-01

    The adiabatic rotational state method is applied to the study of reactions between ions and polar asymmetric top molecules at very low temperatures. Detailed results of the calculated rate coefficients for the reaction of N+ with H2O are presented. A strong dependence of the rate coefficients on the initial rotational state is observed at low temperatures. In the case of a thermal distribution of rotational states, where the rate constants are summed over a Boltzman distribution, the replacement of the asymmetric top by an average symmetric top, which leads to a considerable simplification of the calculations, appears to be satisfactory. On the other hand, for a non thermal distribution, no such simplifying assumption can be made. In particular, the rate coefficient for a specific initial rotational state is quite sensitive to the orientation of the dipole moment.

  14. Analysis of the effect of symmetric/asymmetric CUSP magnetic fields on melt/crystal interface during Czochralski silicon growth

    NASA Astrophysics Data System (ADS)

    Daggolu, Parthiv; Ryu, Jae Woo; Galyukov, Alex; Kondratyev, Alexey

    2016-10-01

    With the use of 300 mm silicon wafers for industrial semiconductor device manufacturing, the Czochralski (Cz) crystal growth process has to be optimized to achieve higher quality and productivity. Numerical studies based on 2D global thermal models combined with 3D simulation of melt convection are widely used today to save time and money in the process development. Melt convection in large scale Cz Si growth is controlled by a CUSP or transversal magnetic field (MF) to suppress the melt turbulence. MF can be optimized to meet necessary characteristics of the growing crystal, in terms of point defects, as MF affects the melt/crystal interface geometry and allows adjustment of the pulling rate. Among the different knobs associated with the CUSP magnetic field, the nature of its configuration, going from symmetric to asymmetric, is also reported to be an important tool for the control of crystallization front. Using a 3D unsteady model of the CGSim software, we have studied these effects and compared with several experimental results. In addition, physical mechanisms behind these observations are explored through a detailed modeling analysis of the effect of an asymmetric CUSP MF on convection features governing the heat transport in the silicon melt.

  15. Effects of long-term sensory deprivation on asymmetric synapses in the whisker barrel field of the adult rat.

    PubMed

    Machín, Raquel; Pérez-Cejuela, César G; Bjugn, Roger; Avendaño, Carlos

    2006-08-30

    Whisker trimming deprives the cortical barrel field from the patterned sensory input that derives from active touch but leaves passive tactile signals unaltered. We have studied in the rat barrel field, by stereological procedures, the effects of a sustained period of unilateral deprivation by whisker clipping during adolescence and early adulthood on (1) the surface density (SV) of asymmetric synapses, as determined from measuring the presynaptic membrane specializations, and (2) the numerical density of asymmetric synaptic profiles (NA), classified according to their postsynaptic target and their apparent curvature. Compared to control rats, the procedure did not change the overall volume of the region, the volume fraction occupied by each cortical layer, or the volume fraction occupied by unmyelinated axons and boutons. However, the deprived barrel cortex displayed an increase in SV in layers I and II, and an increase in NA in layer I and in the cortex as a whole, mainly due to an increase in profiles with a convex shape. Layer IV was the least affected by the deprivation. These results point to a net increase, rather than a decrease, of excitatory synapses in the deprived cortex, which could result from a deprivation-induced decrease in the rate of normal synapse loss. This effect occurs specifically in superficial layers, more involved in intracortical and cortico-cortical, rather than thalamo-cortical, processing.

  16. The inhomogeneous ion temperature anisotropy instabilities of magnetic-field-aligned plasma sheared flow

    NASA Astrophysics Data System (ADS)

    Mikhailenko, V. V.; Mikhailenko, V. S.; Lee, Hae June

    2016-11-01

    The stability of the magnetic field aligned sheared flow with anisotropic ion temperatures, which have the anisotropic spatial inhomogeneities across the magnetic field and are comparable with or are above the electron temperature, is investigated numerically and analytically. The ion temperatures gradients across the magnetic field affect the instability development only when the inhomogeneous is the ion temperature along the magnetic field irrespective the inhomogeneity of the ion temperature across the magnetic field. In this case, the instability is developed due to the combined effect of the ion Landau damping, velocity shear, ion temperature anisotropy, and anisotropy of the ion temperature gradients. In the case when the ion temperature along the magnetic field is homogeneous, but the ion temperature across the magnetic field is inhomogeneous, the short wavelength instability develops with the wave length less than the thermal ion Larmor radius. This instability excites due to the coupled effect of the ion Landau damping, velocity shear and ion temperature anisotropy.

  17. Ion transferring in polyelectrolyte networks in electric fields

    NASA Astrophysics Data System (ADS)

    Li, Honghao; Erbas, Aykut; Zwanikken, Jos; Olvera de La Cruz, Monica

    Ion-conducting polyelectrolyte gels have drawn the attention of many researchers in the last few decades as they have wide applications not only in lithium batteries but also as stretchable, transparent ionic conductor or ionic cables devices. However, ion dynamics in polyelectrolyte gels has been much less studied analytically or computationally due to the complicated interplay of long-range electrostatic and short-range interactions. Here we propose a coarse-grained non-equilibrium molecular dynamics simulation to study the ion dynamics in polyelectrolyte gels under external electric fields. We found a nonlinear response region where the molar conductivity of polyelectrolyte gels increases with external fields. We propose counterion redistribution under electric fields as the driving mechanism. We also found the ionic conductivity to be modulated by changing polylelectrolyte network topology such as the chain length. Our discovery reveals the essential difference of ion dynamics between electrolytes and polyelectrolyte gels. These results will expand our understanding in charged polymeric systems and help in designing ion-conducting devices with higher conductivity.

  18. Electron-Ion collisions in relativistically strong laser fields

    SciTech Connect

    Balakin, A. A.

    2008-04-15

    Electron-ion collisions in relativistically strong electromagnetic fields are considered. Analytical and numerical analyses both show that all qualitative effects characteristic of collisions in nonrelativistic strong fields [1-3] occur at relativistic intensities of an electromagnetic wave as well. Expressions for Joule plasma heating and for the energy distributions of fast particles are derived from simple analytic considerations and are confirmed by numerical simulations. It is found, in particular, that, due to the relativistic increase in the mass of a scattered electron, Joule heating in ultrarelativistic fields becomes more intense as the field amplitude grows.

  19. Influence of electrical fields and asymmetric application of mucilage on curvature of primary roots of Zea mays.

    PubMed

    Marcum, H; Moore, R

    1990-04-01

    Primary roots of Zea mays cv. Yellow Dent growing in an electric field curve towards the anode. Roots treated with EDTA and growing in electric field do not curve. When root cap mucilage is applied asymmetrically to tips of vertically-oriented roots, the roots curve toward the mucilage. Roots treated with EDTA curve toward the side receiving mucilage and toward blocks containing 10 mM CaCl2, but not toward "empty" agar blocks or the cut surfaces of severed root tips. These results suggest that 1) free calcium (Ca) is necessary for root electrotropism, 2) mucilage contains effector(s) that induce gravitropiclike curvature, and 3) mucilage can replace gravitropic effectors chelated by EDTA. These results are consistent with the hypothesis that the downward movement of gravitropic effectors to the lower sides of tips of horizontally-oriented roots occurs at least partially in the apoplast.

  20. Influence of electrical fields and asymmetric application of mucilage on curvature of primary roots of Zea mays

    NASA Technical Reports Server (NTRS)

    Marcum, H.; Moore, R.

    1990-01-01

    Primary roots of Zea mays cv. Yellow Dent growing in an electric field curve towards the anode. Roots treated with EDTA and growing in electric field do not curve. When root cap mucilage is applied asymmetrically to tips of vertically-oriented roots, the roots curve toward the mucilage. Roots treated with EDTA curve toward the side receiving mucilage and toward blocks containing 10 mM CaCl2, but not toward "empty" agar blocks or the cut surfaces of severed root tips. These results suggest that 1) free calcium (Ca) is necessary for root electrotropism, 2) mucilage contains effector(s) that induce gravitropiclike curvature, and 3) mucilage can replace gravitropic effectors chelated by EDTA. These results are consistent with the hypothesis that the downward movement of gravitropic effectors to the lower sides of tips of horizontally-oriented roots occurs at least partially in the apoplast.

  1. The influence of stray magnetic fields on ion beam neutralization

    NASA Technical Reports Server (NTRS)

    Feng, Y.-C.; Wilbur, P. J.

    1982-01-01

    An experimental investigation is described of a comparison between the ion beam neutralization characteristics of a local neutralizer (within approximately 5 cm of the beam edge) and those associated with a distant one (approximately 1 meter away from the thruster). The influence of magnetic fields in the vicinity of the neutralizer cathode orifice which are either parallel or normal to the neutralizer axis is assessed. The plasma property profiles which reflect the influence of the magnetic fields are measured. The results suggest that magnetic fields at the region of a neutralizer cathode orifice influence its ability to couple to the ion beam. They reveal that there is a potential jump from the neutralizer cathode orifice to the plasma which exists close to the orifice. This potential drop is found to increase as the axial component of magnetic flux density increases. A magnetic field perpendicular to the neutralizer axis induces a potential rise a few centimeters downstream from the neutralizer cathode.

  2. Atom probe field ion microscopy of titanium aluminides

    SciTech Connect

    Larson, D.J.; Miller, M.K.

    1998-01-01

    Titanium aluminides have a number of potential high temperature applications due to their good elevated-temperature mechanical properties, low density, and good creep and oxidation resistance. However, fabrication of commercial components of these materials has been impeded by their poor mechanical properties at ambient temperatures. Significant efforts with various degrees of success have been made to improve the mechanical properties of these TiAl alloys by doping them with a variety of different elements including B, C, Cr, Er, Fe, Mn, Mo, Ni, Nb, P, Si, Ta, V and W. One of the optimum analytical tools for investigating the effects of these additions on the microstructure is the atom probe field ion micro scope. However, relatively few studies of titanium aluminides, compared to some other intermetallic compounds, have performed by atom probe field ion microscopy. This lack of attention can be attributed to the brittle nature of the material, in-situ transformations that occur during the field ion microscopy and preferential evaporation problems that were encountered in some of the early studies. The atom probe field ion microscope used for the current experiments has a low base pressure ({approximately} 2 {times} 10{sup 9} Pa) and careful attention was paid to optimizing the experimental parameters. All the examples shown were obtained from specimens prepared by standard electropolishing techniques. To demonstrate the suitability of the technique to these materials, several different titanium aluminides have been characterized in the atom probe.

  3. Magnetic Field Would Reduce Electron Backstreaming in Ion Thrusters

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2003-01-01

    The imposition of a magnetic field has been proposed as a means of reducing the electron backstreaming problem in ion thrusters. Electron backstreaming refers to the backflow of electrons into the ion thruster. Backstreaming electrons are accelerated by the large potential difference that exists between the ion-thruster acceleration electrodes, which otherwise accelerates positive ions out of the engine to develop thrust. The energetic beam formed by the backstreaming electrons can damage the discharge cathode, as well as other discharge surfaces upstream of the acceleration electrodes. The electron-backstreaming condition occurs when the center potential of the ion accelerator grid is no longer sufficiently negative to prevent electron diffusion back into the ion thruster. This typically occurs over extended periods of operation as accelerator-grid apertures enlarge due to erosion. As a result, ion thrusters are required to operate at increasingly negative accelerator-grid voltages in order to prevent electron backstreaming. These larger negative voltages give rise to higher accelerator grid erosion rates, which in turn accelerates aperture enlargement. Electron backstreaming due to accelerator-gridhole enlargement has been identified as a failure mechanism that will limit ionthruster service lifetime. The proposed method would make it possible to not only reduce the electron backstreaming current at and below the backstreaming voltage limit, but also reduce the backstreaming voltage limit itself. This reduction in the voltage at which electron backstreaming occurs provides operating margin and thereby reduces the magnitude of negative voltage that must be placed on the accelerator grid. Such a reduction reduces accelerator- grid erosion rates. The basic idea behind the proposed method is to impose a spatially uniform magnetic field downstream of the accelerator electrode that is oriented transverse to the thruster axis. The magnetic field must be sufficiently

  4. Ion temperature fluctuation measurements using a retarding field analyzer

    SciTech Connect

    Nedzelskiy, I. S.; Silva, C.; Duarte, P.; Fernandes, H.

    2011-04-15

    The retarding field analyzer (RFA) is a widely used diagnostic tool for the ion temperature measurement in the scrape-off-layer (SOL) of the thermonuclear plasma devices. However, the temporal resolution in the standard RFA application is restricted to the ms timescale. In this paper, a dc operation of the RFA is considered, which allows for the measurement of the plasma ion temperature fluctuations. The method is based on the relation for the RFA current-voltage (I-V) characteristic resulted from a common RFA model of shifted Maxwellian distribution of the analyzed ions, and the measurements of two points on the exponentially decaying region of the I-V characteristic with two differently dc biased RFA electrodes. The method has been tested and compared with conventional RFA measurements of the ion temperature in the tokamak ISTTOK SOL plasma. An ion temperature of T{sub i}= 17 eV is obtained near the limiter position. The agreement between the results of the two methods is within {approx}25%. The amplitude of the ion temperature fluctuations is found to be around 5 eV at this location. The method has been validated by taking into account the effect of fluctuations in the plasma potential and the noise contamination, proving the reliability of the results obtained. Finally, constrains to the method application are discussed that include a negligible electron emission from the RFA grids and the restriction to operate in the exponentially decaying region of the I-V characteristic.

  5. Ion temperature fluctuation measurements using a retarding field analyzer.

    PubMed

    Nedzelskiy, I S; Silva, C; Duarte, P; Fernandes, H

    2011-04-01

    The retarding field analyzer (RFA) is a widely used diagnostic tool for the ion temperature measurement in the scrape-off-layer (SOL) of the thermonuclear plasma devices. However, the temporal resolution in the standard RFA application is restricted to the ms timescale. In this paper, a dc operation of the RFA is considered, which allows for the measurement of the plasma ion temperature fluctuations. The method is based on the relation for the RFA current-voltage (I-V) characteristic resulted from a common RFA model of shifted Maxwellian distribution of the analyzed ions, and the measurements of two points on the exponentially decaying region of the I-V characteristic with two differently dc biased RFA electrodes. The method has been tested and compared with conventional RFA measurements of the ion temperature in the tokamak ISTTOK SOL plasma. An ion temperature of T(i) = 17 eV is obtained near the limiter position. The agreement between the results of the two methods is within ∼25%. The amplitude of the ion temperature fluctuations is found to be around 5 eV at this location. The method has been validated by taking into account the effect of fluctuations in the plasma potential and the noise contamination, proving the reliability of the results obtained. Finally, constrains to the method application are discussed that include a negligible electron emission from the RFA grids and the restriction to operate in the exponentially decaying region of the I-V characteristic.

  6. Ion Thruster Discharge Performance Per Magnetic Field Topography

    NASA Technical Reports Server (NTRS)

    Wirz, Richard E.; Goebel, Dan

    2006-01-01

    DC-ION is a detailed computational model for predicting the plasma characteristics of rain-cusp ion thrusters. The advanced magnetic field meshing algorithm used by DC-ION allows precise treatment of the secondary electron flow. This capability allows self-consistent estimates of plasma potential that improves the overall consistency of the results of the discharge model described in Reference [refJPC05mod1]. Plasma potential estimates allow the model to predict the onset of plasma instabilities, and important shortcoming of the previous model for optimizing the design of discharge chambers. A magnetic field mesh simplifies the plasma flow calculations, for both the ions and the secondary electrons, and significantly reduces numerical diffusion that can occur with meshes not aligned with the magnetic field. Comparing the results of this model to experimental data shows that the behavior of the primary electrons, and the precise manner of their confinement, dictates the fundamental efficiency of ring-cusp. This correlation is evident in simulations of the conventionally sized NSTAR thruster (30 cm diameter) and the miniature MiXI thruster (3 cm diameter).

  7. Single-ion microwave near-field quantum sensor

    NASA Astrophysics Data System (ADS)

    Wahnschaffe, M.; Hahn, H.; Zarantonello, G.; Dubielzig, T.; Grondkowski, S.; Bautista-Salvador, A.; Kohnen, M.; Ospelkaus, C.

    2017-01-01

    We develop an intuitive model of 2D microwave near-fields in the unusual regime of centimeter waves localized to tens of microns. Close to an intensity minimum, a simple effective description emerges with five parameters that characterize the strength and spatial orientation of the zero and first order terms of the near-field, as well as the field polarization. Such a field configuration is realized in a microfabricated planar structure with an integrated microwave conductor operating near 1 GHz. We use a single 9 Be+ ion as a high-resolution quantum sensor to measure the field distribution through energy shifts in its hyperfine structure. We find agreement with simulations at the sub-micron and few-degree level. Our findings give a clear and general picture of the basic properties of oscillatory 2D near-fields with applications in quantum information processing, neutral atom trapping and manipulation, chip-scale atomic clocks, and integrated microwave circuits.

  8. Ion reflection by shock waves and pulse generation by cross-field ion beams

    NASA Astrophysics Data System (ADS)

    Ohsawa, Yukiharu

    2017-02-01

    Comparisons are made of two different particle simulations: one for the study of plasma-based accelerators (Gueroult & Fisch, Phys. Plasmas, vol. 23, 2016, 032113) and the other for the study of shock formation in the interstellar medium (Yamauchi & Ohsawa, Phys. Plasmas, vol. 14, 2007, 053110). In the former, shock waves used for plasma density control create ion beams by reflection. In the latter, a fast and dense beam of exploding ions penetrates a surrounding plasma. In both simulations, magnetic bumps are generated from the motion of ion beams perpendicular to a magnetic field. Despite the apparent differences of their purposes, configurations and spatial scales, the two simulations show strong similarities in the generation processes and effects of the bumps, suggesting that these are not rare plasma phenomena. The bump created by the exploding ions develops into backward and forward magnetosonic pulses.

  9. Test results of distributed ion pump designs for the PEP-II Asymmetric B-Factory collider

    SciTech Connect

    Calderon, M.; Holdener, F.; Peterson, D.

    1994-07-01

    The testing facility measurement methods and results of prototype distributed ion pump (DIP) designs for the PEP-II B-Factory High Energy Ring are presented. Two basic designs with 5- or 7-anode plates were tested at LLNL with penning cell sizes of 15, 18, and 21 mm. Direct comparison of 5- and 7-plate anodes with 18 mm holes shows increased pumping speed with the 7-plate design. The 5-plate, 18 mm and 7-plate, 15 mm designs both gave an average pumping speed of 135 1/s/m at 1 {times} 10{sup {minus}8} Torr nitrogen base pressure in a varying 0.18 T peak B-field. Comparison of the three hole sizes indicates that cells smaller than the 15 mm tested can be efficiently used to obtain higher pumping speeds for the same anode plate sizes used.

  10. Characterisation of cationic potato starch by asymmetrical flow field-flow fractionation. Influence of ionic strength and degree of substitution.

    PubMed

    Santacruz, Stalin

    2014-06-15

    The properties of a paper sheet depend on the absorption together with the physico-chemical properties of additives used in the paper processing. The effect of ionic strength and degree of substitution of cationic potato starch on the elution pattern of asymmetrical flow field-flow fractionation was analysed. The effect of starch derivatisation, in either dry or wet phase, was also investigated. Average molar mass showed no difference between the starches obtained from the two derivatisation processes. Apparent densities showed that dry cationic starch had higher density than wet cationic starch for a hydrodynamic radius between 50 and 100 nm. Elution times of native and three cationic starches increased when the ionic strength increased from 50 to 100mM. No differences in the molar mass among cationic starches with different degree of substitution suggested no degradation due to a derivatisation process. Large sample loads can be used at 100mM without overloading.

  11. Pulsed magnetic field-electron cyclotron resonance ion source operation

    SciTech Connect

    Muehle, C.; Ratzinger, U.; Joest, G.; Leible, K.; Schennach, S.; Wolf, B.H.

    1996-03-01

    The pulsed magnetic field (PuMa)-electron cyclotron resonance (ECR) ion source uses a pulsed coil to improve the peak current by opening the magnetic bottle along the beam axis. After demonstration of the principle of the pulsed magnetic extraction, the ion source was tested with different gases. We received promising results from helium to krypton. The influence of the current in the pulsed coil on the analyzed ion current was measured. With increased current levels within the pulsed coil not only the pulse height of the PuMa pulse, but the pulse length can also be controlled. By using the pulsed coil the maximum of the charge state distribution can be shifted to higher charge states. {copyright} {ital 1996 American Institute of Physics.}

  12. Near-surface density profiling of Fe ion irradiated Si (100) using extremely asymmetric x-ray diffraction by variation of the wavelength

    SciTech Connect

    Khanbabaee, B. Pietsch, U.; Facsko, S.; Doyle, S.

    2014-10-20

    In this work, we report on correlations between surface density variations and ion parameters during ion beam-induced surface patterning process. The near-surface density variations of irradiated Si(100) surfaces were investigated after off-normal irradiation with 5 keV Fe ions at different fluences. In order to reduce the x-ray probing depth to a thickness below 5 nm, the extremely asymmetrical x-ray diffraction by variation of wavelength was applied, exploiting x-ray refraction at the air-sample interface. Depth profiling was achieved by measuring x-ray rocking curves as function of varying wavelengths providing incidence angles down to 0°. The density variation was extracted from the deviations from kinematical Bragg angle at grazing incidence angles due to refraction of the x-ray beam at the air-sample interface. The simulations based on the dynamical theory of x-ray diffraction revealed that while a net near-surface density decreases with increasing ion fluence which is accompanied by surface patterning, there is a certain threshold of ion fluence to surface density modulation. Our finding suggests that the surface density variation can be relevant with the mechanism of pattern formation.

  13. Laser measurement of H{sup -} ions in a field-effect-transistor based radio frequency ion source

    SciTech Connect

    Tanaka, N.; Matsuno, T.; Funaoi, T.; Ando, A.; Tauchi, Y.; Nakano, H.; Tsumori, K.; Takeiri, Y.

    2012-02-15

    Hydrogen negative ion density measurements are required to clarify the characteristics of negative ion production and ion source performance. Both of laser photodetachment and cavity ring down (CRD) measurements have been implemented to a field-effect-transistor based radio-frequency ion source. The density ratio of negative hydrogen ions to electrons was successfully measured by laser photodetachment and effect of magnetic filter field on negative ion density was confirmed. The calculated CRD signal showed that CRD mirrors with >99.990% reflectivity are required and loss of reflectivity due to cesium contamination should be minimized.

  14. Carbon-coated LiCrTiO4 electrode material promoting phase transition to reduce asymmetric polarization for lithium-ion batteries.

    PubMed

    Yang, Jianwen; Yan, Bo; Ye, Jing; Li, Xue; Liu, Yansheng; You, Haiping

    2014-02-21

    In this work, carbon-free and carbon-coated spinel LiCrTiO4 oxides were synthesized by a conventional solid state reaction. The lithium-ion diffusion coefficient and electronic conductivity of prepared electrode materials were systematically investigated using the galvanostatic intermittent titration technique (GITT), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The rate performances of the prepared materials were evaluated by galvanostatic charge-discharge. Carefully comparing the charge-discharge polarization potential of both materials, we unexpectedly discovered that the pristine LiCrTiO4 electrode demonstrated asymmetric polarization during the charging-discharging process, which is possibly attributed to the nonuniform electron conductivity between the endmember of a two-phase reaction, whereas carbon coating could level this phenomenon. Additionally, using an asymmetric core-shell model from the microscopic point of view can easily explain this common phenomenon. Meanwhile, this new research perspective can be extended to other active materials in lithium ion batteries.

  15. Trapped-Ion Quantum Logic with Global Radiation Fields

    NASA Astrophysics Data System (ADS)

    Weidt, S.; Randall, J.; Webster, S. C.; Lake, K.; Webb, A. E.; Cohen, I.; Navickas, T.; Lekitsch, B.; Retzker, A.; Hensinger, W. K.

    2016-11-01

    Trapped ions are a promising tool for building a large-scale quantum computer. However, the number of required radiation fields for the realization of quantum gates in any proposed ion-based architecture scales with the number of ions within the quantum computer, posing a major obstacle when imagining a device with millions of ions. Here, we present a fundamentally different approach for trapped-ion quantum computing where this detrimental scaling vanishes. The method is based on individually controlled voltages applied to each logic gate location to facilitate the actual gate operation analogous to a traditional transistor architecture within a classical computer processor. To demonstrate the key principle of this approach we implement a versatile quantum gate method based on long-wavelength radiation and use this method to generate a maximally entangled state of two quantum engineered clock qubits with fidelity 0.985(12). This quantum gate also constitutes a simple-to-implement tool for quantum metrology, sensing, and simulation.

  16. Trapped-Ion Quantum Logic with Global Radiation Fields.

    PubMed

    Weidt, S; Randall, J; Webster, S C; Lake, K; Webb, A E; Cohen, I; Navickas, T; Lekitsch, B; Retzker, A; Hensinger, W K

    2016-11-25

    Trapped ions are a promising tool for building a large-scale quantum computer. However, the number of required radiation fields for the realization of quantum gates in any proposed ion-based architecture scales with the number of ions within the quantum computer, posing a major obstacle when imagining a device with millions of ions. Here, we present a fundamentally different approach for trapped-ion quantum computing where this detrimental scaling vanishes. The method is based on individually controlled voltages applied to each logic gate location to facilitate the actual gate operation analogous to a traditional transistor architecture within a classical computer processor. To demonstrate the key principle of this approach we implement a versatile quantum gate method based on long-wavelength radiation and use this method to generate a maximally entangled state of two quantum engineered clock qubits with fidelity 0.985(12). This quantum gate also constitutes a simple-to-implement tool for quantum metrology, sensing, and simulation.

  17. Quantifying vorticity in magnetic particle suspensions driven by symmetric and asymmetric multiaxial fields.

    SciTech Connect

    Martin, James E.; Solis, Kyle Jameson

    2015-08-07

    We recently reported two methods of inducing vigorous fluid vorticity in magnetic particle suspensions. The first method employs symmetry-breaking rational fields. These fields are comprised of two orthogonal ac components whose frequencies form a rational number and an orthogonal dc field that breaks the symmetry of the biaxial ac field to create the parity required to induce deterministic vorticity. The second method is based on rational triads, which are fields comprised of three orthogonal ac components whose frequency ratios are rational (e.g., 1 : 2 : 3). For each method a symmetry theory has been developed that enables the prediction of the direction and sign of vorticity as functions of the field frequencies and phases. However, this theory has its limitations. It only applies to those particular phase angles that give rise to fields whose Lissajous plots, or principal 2-d projections thereof, have a high degree of symmetry. Nor can symmetry theory provide a measure of the magnitude of the torque density induced by the field. In this paper a functional of the multiaxial magnetic field is proposed that not only is consistent with all of the predictions of the symmetry theories, but also quantifies the torque density. This functional can be applied to fields whose Lissajous plots lack symmetry and can thus be used to predict a variety of effects and trends that cannot be predicted from the symmetry theories. These trends include the dependence of the magnitude of the torque density on the various frequency ratios, the unexpected reversal of flow with increasing dc field amplitude for certain symmetry-breaking fields, and the existence of off-axis vorticity for rational triads, such as 1 : 3 : 5, that do not have the symmetry required to analyze by symmetry theory. As a result, experimental data are given that show the degree to which this functional is successful in predicting observed trends.

  18. Quantifying vorticity in magnetic particle suspensions driven by symmetric and asymmetric multiaxial fields.

    PubMed

    Martin, James E; Solis, Kyle J

    2015-09-28

    We recently reported two methods of inducing vigorous fluid vorticity in magnetic particle suspensions. The first method employs symmetry-breaking rational fields. These fields are comprised of two orthogonal ac components whose frequencies form a rational number and an orthogonal dc field that breaks the symmetry of the biaxial ac field to create the parity required to induce deterministic vorticity. The second method is based on rational triads, which are fields comprised of three orthogonal ac components whose frequency ratios are rational (e.g., 1 : 2 : 3). For each method a symmetry theory has been developed that enables the prediction of the direction and sign of vorticity as functions of the field frequencies and phases. However, this theory has its limitations. It only applies to those particular phase angles that give rise to fields whose Lissajous plots, or principal 2-d projections thereof, have a high degree of symmetry. Nor can symmetry theory provide a measure of the magnitude of the torque density induced by the field. In this paper a functional of the multiaxial magnetic field is proposed that not only is consistent with all of the predictions of the symmetry theories, but also quantifies the torque density. This functional can be applied to fields whose Lissajous plots lack symmetry and can thus be used to predict a variety of effects and trends that cannot be predicted from the symmetry theories. These trends include the dependence of the magnitude of the torque density on the various frequency ratios, the unexpected reversal of flow with increasing dc field amplitude for certain symmetry-breaking fields, and the existence of off-axis vorticity for rational triads, such as 1 : 3 : 5, that do not have the symmetry required to analyze by symmetry theory. Experimental data are given that show the degree to which this functional is successful in predicting observed trends.

  19. Quantifying vorticity in magnetic particle suspensions driven by symmetric and asymmetric multiaxial fields.

    DOE PAGES

    Martin, James E.; Solis, Kyle Jameson

    2015-08-07

    We recently reported two methods of inducing vigorous fluid vorticity in magnetic particle suspensions. The first method employs symmetry-breaking rational fields. These fields are comprised of two orthogonal ac components whose frequencies form a rational number and an orthogonal dc field that breaks the symmetry of the biaxial ac field to create the parity required to induce deterministic vorticity. The second method is based on rational triads, which are fields comprised of three orthogonal ac components whose frequency ratios are rational (e.g., 1 : 2 : 3). For each method a symmetry theory has been developed that enables the predictionmore » of the direction and sign of vorticity as functions of the field frequencies and phases. However, this theory has its limitations. It only applies to those particular phase angles that give rise to fields whose Lissajous plots, or principal 2-d projections thereof, have a high degree of symmetry. Nor can symmetry theory provide a measure of the magnitude of the torque density induced by the field. In this paper a functional of the multiaxial magnetic field is proposed that not only is consistent with all of the predictions of the symmetry theories, but also quantifies the torque density. This functional can be applied to fields whose Lissajous plots lack symmetry and can thus be used to predict a variety of effects and trends that cannot be predicted from the symmetry theories. These trends include the dependence of the magnitude of the torque density on the various frequency ratios, the unexpected reversal of flow with increasing dc field amplitude for certain symmetry-breaking fields, and the existence of off-axis vorticity for rational triads, such as 1 : 3 : 5, that do not have the symmetry required to analyze by symmetry theory. As a result, experimental data are given that show the degree to which this functional is successful in predicting observed trends.« less

  20. Robust ion current oscillations under a steady electric field: An ion channel analog

    NASA Astrophysics Data System (ADS)

    Yan, Yu; Wang, Yunshan; Senapati, Satyajyoti; Schiffbauer, Jarrod; Yossifon, Gilad; Chang, Hsueh-Chia

    2016-08-01

    We demonstrate a nonlinear, nonequilibrium field-driven ion flux phenomenon, which unlike Teorell's nonlinear multiple field theory, requires only the application of one field: robust autonomous current-mass flux oscillations across a porous monolith coupled to a capillary with a long air bubble, which mimics a hydrophobic protein in an ion channel. The oscillations are driven by the hysteretic wetting dynamics of the meniscus when electro-osmotic flow and pressure driven backflow, due to bubble expansion, compete to approach zero mass flux within the monolith. Delayed rupture of the film around the advancing bubble cuts off the electric field and switches the monolith mass flow from the former to the latter. The meniscus then recedes and repairs the rupture to sustain an oscillation for a range of applied fields. This generic mechanism shares many analogs with current oscillations in cell membrane ion channel. At sufficiently high voltage, the system undergoes a state transition characterized by appearance of the ubiquitous 1 /f power spectrum.

  1. Galactic heavy-ion shielding using electrostatic fields

    NASA Technical Reports Server (NTRS)

    Townsend, L. W.

    1984-01-01

    The shielding of spacecraft against galactic heavy ions, particularly high-energy Fe(56) nuclei, by electrostatic fields is analyzed for an arrangement of spherical concentric shells. Vacuum breakdown considerations are found to limit the minimum radii of the spheres to over 100 m. This limitation makes it impractical to use the fields for shielding small spacecraft. The voltages necessary to repel these Fe(56) nuclei exceed present electrostatic generating capabilities by over 2 orders of magnitude and render the concept useless as an alternative to traditional bulk-material shielding methods.

  2. Unveiling the intricacies of the curved-field ion mirror.

    PubMed

    Maechler, Lars; Fillipov, Igor; Derrick, Peter J

    2015-01-01

    In time-of-flight (ToF) mass spectrometry, non-linear ion mirrors, i.e. mirrors that produce a non-linear potential in which the ions fly, can focus ions exhibiting a very broad kinetic energy distribution. Besides the quadratic potential, the so-called curved field has been used in mirrors as a non-linear potential over the past 20 years. The curved field has, however, only been loosely defined. The focusing properties of the curved field appear to have never been mathematically investigated and explained. In this work, we put forward a rigid definition of the curved field and investigate the properties of it in terms of focusing and transmission. This rigid definition shows the curved field as a two-parameter function for a given mirror length and maximum potential, which can be optimized in terms of ToF distribution/resolution. Such an optimization was performed in one- dimension (1D) by solving the ToF integral equation numerically. The characteristics of optimized configurations arrived at through a comparison with mirrors with polynomial distance-potential relationships are assessed. These optimised solutions cannot be approximated in 1D by a common set of polynomial terms. There are optimised configurations affording ideal energy focussing, but on closer inspection, these potential distributions are found to be, in fact, quadratic potentials. There are other optimised solutions that afford good energy focussing in cases of there being significant field-free regions between the source/detector and the entrance to the mirror. Some of these configurations are approximated by a linear plus a quadratic term, others need higher-order terms to be approximated. To facilitate 3D investigation, the optimised solutions in 1D were used to set the initial voltages on electrodes in a rotationally symmetric mirror, which was modelled with the computer package SIMION 8.0. The SIMION ion-flight simulations revealed that the other optimised solutions with higher-order terms

  3. Ion-Sensitive Field-Effect Transistor for Biological Sensing

    PubMed Central

    Lee, Chang-Soo; Kim, Sang Kyu; Kim, Moonil

    2009-01-01

    In recent years there has been great progress in applying FET-type biosensors for highly sensitive biological detection. Among them, the ISFET (ion-sensitive field-effect transistor) is one of the most intriguing approaches in electrical biosensing technology. Here, we review some of the main advances in this field over the past few years, explore its application prospects, and discuss the main issues, approaches, and challenges, with the aim of stimulating a broader interest in developing ISFET-based biosensors and extending their applications for reliable and sensitive analysis of various biomolecules such as DNA, proteins, enzymes, and cells. PMID:22423205

  4. Mechanism of DNA Trapping in Nanoporous Structures during Asymmetric Pulsed-Field Electrophoresis

    NASA Astrophysics Data System (ADS)

    Zhou, Ya; Harrison, D. Jed

    2014-03-01

    DNA molecules (>100kbp) are trapped in separation sieves when high electric fields are applied in pulsed field electrophoresis, seriously limiting the speed of separation. Using crystalline particle arrays, to generate interstitial pores for molecular sieving, allows higher electric fields than in gels, (e.g 40 vs 5 V/cm), however trapping still limits the field strength. Using reverse pulses, which release DNA from being fully-stretched, allows higher fields (140 V/cm). We investigate the trapping mechanism of individual DNA molecules in ordered nanoporous structures. Two prerequisites for trapping are revealed by the dynamics of single trapped DNA, hernia formation and fully-stretched U/J shapes. Fully stretched DNA has longer unhooking times than expected by simple models. We propose a dielectrophoretic (DEP) force reduces the mobility of segments at the apex of the U or J, where field gradients are highest, based on simulations. A modified model for unhooking time is obtained after the DEP force is introduced. The new model explains the unhooking time data by predicting an infinite trapping time when the ratio of arm length differences (of the U or J) to molecule length Δx / L < β . β is a DEP parameter that is found to strongly increase with electric field. The work was supported by grant from Natural Sciences and Engineering Research Council of Canada (NSERC) and the National Institute for Nanotechnology (NINT).

  5. Numerical Modeling of Ion Dynamics in a Carbon Nanotube Field-Ionized Thruster

    DTIC Science & Technology

    2011-12-01

    ION SOURCES Ions may be produced by several methods: photo-ionization, electron bombardment, field ionization, surface ionization, and thermionic ...OF ION DYNAMICS IN A CARBON NANOTUBE FIELD -IONIZED ION THRUSTER by Sarah F. Michael December 2011 Thesis Advisors: Dragoslav Grbovic...December 2011 3. REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE Numerical Modeling of Ion Dynamics in a Carbon Nanotube Field

  6. LETTER TO THE EDITOR: Anisotropy of ion temperature in a reversed-field-pinch plasma

    NASA Astrophysics Data System (ADS)

    Sasaki, K.; Hörling, P.; Fall, T.; Brzozowski, J. H.; Brunsell, P.; Hokin, S.; Tennfors, E.; Sallander, J.; Drake, J. R.; Inoue, N.; Morikawa, J.; Ogawa, Y.; Yoshida, Z.

    1997-03-01

    Anomalous heating of ions has been observed in the EXTRAP-T2 reversed-field-pinch (RFP) plasma. Ions are heated primarily in the parallel direction (with respect to the magnetic field), resulting in an appreciable anisotropy of the ion temperature. This observation suggests that the magnetohydrodynamic fluctuations are dissipated primarily by the ion viscosity.

  7. Effects of 3D Toroidally Asymmetric Magnetic Field on Tokamak Magnetic Surfaces

    NASA Astrophysics Data System (ADS)

    Lao, L. L.

    2005-10-01

    The effects of 3D error magnetic field on magnetic surfaces are investigated using the DIII-D internal coils (I-Coils). Slowly rotating n=1 traveling waves at 5 Hz and various amplitudes were applied to systematically perturb the edge surfaces by programming the I-Coil currents. The vertical separatrix location difference between EFIT magnetic reconstructions that assumes toroidal symmetry and Thomson scattering Te measurements responds in phase to the applied perturbed field. The oscillation amplitudes increase with the strength of the applied field but are much smaller than those expected from the applied field alone. The results indicate that plasma response is important. Various plasma response models based on results from the MHD codes MARS and GATO are being developed and compared to the experimental observations. To more accurately evaluate the effects of magnetic measurement errors, a new form of the magnetic uncertainty matrix is also being implemented into EFIT. Details will be presented.

  8. Isotopic Effect on Ion Mobility and Separation of Isotopomers by High-Field Ion Mobility Spectrometry

    SciTech Connect

    Shvartsburg, Alexandre A.; Clemmer, David E.; Smith, Richard D.

    2010-10-01

    Since early 1900-s, when vacuum techniques and ion detectors first enabled investigations of gas-phase ions, two approaches to their separation and characterization have emerged - mass spectrometry (MS) and ion mobility spectrometry (IMS).1,2 Though both exploit that distinct charged species move in electric fields differently, MS is performed in vacuum and is based only on the ion mass/charge (m/q) ratio while IMS involves sufficiently dense buffer gases and relies on ion transport properties. The first major discovery enabled by MS was the existence of isotopes by Thomson and Aston,3 and isotopic analyses have since been integral to MS. In particular, the preparative separation of U isotopes using Lawrence’s Calutron was the first industrial application of MS,4 and isotopic labeling is key to MS quantification methods. With IMS, the issue of isotopes was largely ignored as the resolving power (R) was generally too low for their separation. Here, we demonstrate that recently developed high-resolution differential IMS can separate isotopic molecular ions, including nominal isobars with different isotopic content and isotopomers. This capability may enable a new method for isotope separation in a small-scale format at ambient pressure and aid localization of labeled sites in various molecules. Perhaps most importantly, the isotopic shifts depend on the labeled atom position and thus may contain the kind of detailed structural information that is available in solution or solid state using tools such as NMR but has not generally been obtainable for gas-phase ions.

  9. Behavior of molecules and molecular ions near a field emitter

    NASA Astrophysics Data System (ADS)

    Gault, Baptiste; Saxey, David W.; Ashton, Michael W.; Sinnott, Susan B.; Chiaramonti, Ann N.; Moody, Michael P.; Schreiber, Daniel K.

    2016-03-01

    The cold emission of particles from surfaces under intense electric fields is a process which underpins a variety of applications including atom probe tomography (APT), an analytical microscopy technique with near-atomic spatial resolution. Increasingly relying on fast laser pulsing to trigger the emission, APT experiments often incorporate the detection of molecular ions emitted from the specimen, in particular from covalently or ionically bonded materials. Notably, it has been proposed that neutral molecules can also be emitted during this process. However, this remains a contentious issue. To investigate the validity of this hypothesis, a careful review of the literature is combined with the development of new methods to treat experimental APT data, the modeling of ion trajectories, and the application of density-functional theory simulations to derive molecular ion energetics. It is shown that the direct thermal emission of neutral molecules is extremely unlikely. However, neutrals can still be formed in the course of an APT experiment by dissociation of metastable molecular ions. This work is a partial contribution of the US Government and therefore is not subject to copyright in the United States.

  10. Asymmetric cancer-cell filopodium growth induced by electric-fields in a microfluidic culture chip.

    PubMed

    Wang, Chun-Chieh; Kao, Yu-Chiu; Chi, Pei-Yin; Huang, Ching-Wen; Lin, Jiunn-Yuan; Chou, Chia-Fu; Cheng, Ji-Yen; Lee, Chau-Hwang

    2011-02-21

    We combine a micro-fluidic electric-field cell-culture (MEC) chip with structured-illumination nano-profilometry (SINAP) to quantitatively study the variations of cancer cell filopodia under external direct-current electric field (dcEF) stimulations. Because the lateral resolution of SINAP is better than 150 nm in bright-field image modality, filopodia with diameters smaller than 200 nm can be observed clearly without fluorescent labeling. In the MEC chip, a homogeneous EF is generated inside the culture area that simulates the endogenous EF environment. With this MEC chip-SINAP system, we directly observe and quantify the biased growth of filopodia of lung cancer cells toward the cathode. The epidermal growth factor receptors around the cell edges are also redistributed to the cathodal side. These results suggest that cancer-cell filopodia respond to the changes in EFs in the microenvironment.

  11. 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.

  12. Asymmetric masks for large field-of-view and high-energy X-ray phase contrast imaging

    NASA Astrophysics Data System (ADS)

    Endrizzi, M.; Astolfo, A.; Price, B.; Haig, I.; Olivo, A.

    2016-12-01

    We report on a large field of view, laboratory-based X-ray phase-contrast imaging setup. The method is based upon the asymmetric mask design that enables the retrieval of the absorption, refraction and scattering properties of the sample without the need to move any component of the imaging system. This can be thought of as a periodic repetition of a group of three (or more) apertures arranged in such a way that each laminar beam, defined by the apertures, produces a different illumination level when analysed with a standard periodic set of apertures. The sample is scanned through the imaging system, also removing possible aliasing problems that might arise from partial sample illumination when using the edge illumination technique. This approach preserves the incoherence and achromatic properties of edge illumination, removes the problems related to aliasing and it naturally adapts to those situations in clinical, industrial and security imaging where the image is acquired by scanning the sample relative to the imaging system. These concepts were implemented for a large field-of-view set of masks (20 cm × 1.5 cm and 15 cm × 1.2 cm), designed to work with a tungsten anode X-ray source operated up to 80-100 kVp, from which preliminary experimental results are presented.

  13. Field Emitter Arrays and Displays Produced by Ion Tracking Lithography

    SciTech Connect

    Felter, T E; Musket, R G; Bernhardt, A F

    2004-12-28

    When ions of sufficient electronic energy loss traverse a dielectric film or foil, they alter the chemical bonding along their nominally straight path within the material. A suitable etchant can quickly dissolve these so-called latent tracks leaving holes of small diameter ({approx}10nm) but long length - several microns. Continuing the etching process gradually increases the diameter reproducibly and uniformly. The trackable medium can be applied as a uniform film onto large substrates. The small, monodisperse holes produced by this track etching can be used in conjunction with additional thin film processing to create functional structures attached to the substrate. For example, Lawrence Livermore National Laboratory and Candescent Technologies Corporation (CTC) co-developed a process to make arrays of gated field emitters ({approx}100nm diameter electron guns) for CTC's ThinCRT{trademark} displays, which have been fabricated to diagonal dimensions > 13. Additional technological applications of ion tracking lithography will be briefly covered.

  14. Experimental studies on ion acceleration and stream line detachment in a diverging magnetic field

    PubMed Central

    Terasaka, K.; Yoshimura, S.; Ogiwara, K.; Aramaki, M.; Tanaka, M. Y.

    2010-01-01

    The flow structure of ions in a diverging magnetic field has been experimentally studied in an electron cyclotron resonance plasma. The flow velocity field of ions has been measured with directional Langmuir probes calibrated with the laser induced fluorescence spectroscopy. For low ion-temperature plasmas, it is concluded that the ion acceleration due to the axial electric field is important compared with that of gas dynamic effect. It has also been found that the detachment of ion stream line from the magnetic field line takes place when the parameter |fciLB∕Vi| becomes order unity, where fci, LB, and Vi are the ion cyclotron frequency, the characteristic scale length of magnetic field inhomogeneity, and the ion flow velocity, respectively. In the detachment region, a radial electric field is generated in the plasma and the ions move straight with the E×B rotation driven by the radial electric field. PMID:20838424

  15. Solenoidal Fields for Ion Beam Transport and Focusing

    SciTech Connect

    Lee, Edward P.; Leitner, Matthaeus

    2007-11-01

    In this report we calculate time-independent fields of solenoidal magnets that are suitable for ion beam transport and focusing. There are many excellent Electricity and Magnetism textbooks that present the formalism for magnetic field calculations and apply it to simple geometries [1-1], but they do not include enough relevant detail to be used for designing a charged particle transport system. This requires accurate estimates of fringe field aberrations, misaligned and tilted fields, peak fields in wire coils and iron, external fields, and more. Specialized books on magnet design, technology, and numerical computations [1-2] provide such information, and some of that is presented here. The AIP Conference Proceedings of the US Particle Accelerator Schools [1-3] contain extensive discussions of design and technology of magnets for ion beams - except for solenoids. This lack may be due to the fact that solenoids have been used primarily to transport and focus particles of relatively low momenta, e.g. electrons of less than 50 MeV and protons or H- of less than 1.0 MeV, although this situation may be changing with the commercial availability of superconducting solenoids with up to 20T bore field [1-4]. Internal reports from federal laboratories and industry treat solenoid design in detail for specific applications. The present report is intended to be a resource for the design of ion beam drivers for Inertial Fusion Energy [1-5] and Warm Dense Matter experiments [1-6], although it should also be useful for a broader range of applications. The field produced by specified currents and material magnetization can always be evaluated by solving Maxwell's equations numerically, but it is also desirable to have reasonably accurate, simple formulas for conceptual system design and fast-running beam dynamics codes, as well as for general understanding. Most of this report is devoted to such formulas, but an introduction to the Tosca{copyright} code [1-7] and some numerical

  16. Magnetized retarding field energy analyzer measuring the particle flux and ion energy distribution of both positive and negative ions.

    PubMed

    Rafalskyi, Dmytro; Dudin, Stanislav; Aanesland, Ane

    2015-05-01

    This paper presents the development of a magnetized retarding field energy analyzer (MRFEA) used for positive and negative ion analysis. The two-stage analyzer combines a magnetic electron barrier and an electrostatic ion energy barrier allowing both positive and negative ions to be analyzed without the influence of electrons (co-extracted or created downstream). An optimal design of the MRFEA for ion-ion beams has been achieved by a comparative study of three different MRFEA configurations, and from this, scaling laws of an optimal magnetic field strength and topology have been deduced. The optimal design consists of a uniform magnetic field barrier created in a rectangular channel and an electrostatic barrier consisting of a single grid and a collector placed behind the magnetic field. The magnetic barrier alone provides an electron suppression ratio inside the analyzer of up to 6000, while keeping the ion energy resolution below 5 eV. The effective ion transparency combining the magnetic and electrostatic sections of the MRFEA is measured as a function of the ion energy. It is found that the ion transparency of the magnetic barrier increases almost linearly with increasing ion energy in the low-energy range (below 200 eV) and saturates at high ion energies. The ion transparency of the electrostatic section is almost constant and close to the optical transparency of the entrance grid. We show here that the MRFEA can provide both accurate ion flux and ion energy distribution measurements in various experimental setups with ion beams or plasmas run at low pressure and with ion energies above 10 eV.

  17. Magnetized retarding field energy analyzer measuring the particle flux and ion energy distribution of both positive and negative ions

    SciTech Connect

    Rafalskyi, Dmytro; Aanesland, Ane; Dudin, Stanislav

    2015-05-15

    This paper presents the development of a magnetized retarding field energy analyzer (MRFEA) used for positive and negative ion analysis. The two-stage analyzer combines a magnetic electron barrier and an electrostatic ion energy barrier allowing both positive and negative ions to be analyzed without the influence of electrons (co-extracted or created downstream). An optimal design of the MRFEA for ion-ion beams has been achieved by a comparative study of three different MRFEA configurations, and from this, scaling laws of an optimal magnetic field strength and topology have been deduced. The optimal design consists of a uniform magnetic field barrier created in a rectangular channel and an electrostatic barrier consisting of a single grid and a collector placed behind the magnetic field. The magnetic barrier alone provides an electron suppression ratio inside the analyzer of up to 6000, while keeping the ion energy resolution below 5 eV. The effective ion transparency combining the magnetic and electrostatic sections of the MRFEA is measured as a function of the ion energy. It is found that the ion transparency of the magnetic barrier increases almost linearly with increasing ion energy in the low-energy range (below 200 eV) and saturates at high ion energies. The ion transparency of the electrostatic section is almost constant and close to the optical transparency of the entrance grid. We show here that the MRFEA can provide both accurate ion flux and ion energy distribution measurements in various experimental setups with ion beams or plasmas run at low pressure and with ion energies above 10 eV.

  18. Distribution of plasma and magnetic field in the Venus induced magnetosphere is strongly asymmetrical

    NASA Astrophysics Data System (ADS)

    Dubinin, E.; Fraenz, M.; Zhang, T.-L.; Woch, J.; Wei, Y.; Fedorov, A.; Barabash, S.; Lundin, R.

    2013-09-01

    Venus Express spacecraft have provided us a wealth of in-situ observations of characteristics of induced magnetosphere of Venus. One of its important features is a distinct asymmetry in plasma and field characteristics between the hemisphere pointed in the direction of the motional electric field and the opposite hemisphere. Asymmetry starts from formation of the magnetic barrier, then continues to low altitudes where effects of finite conductivity become important and further to the near Venus tail where the magnetic tail and plasma sheet are formed. As a result, the structure and dynamics of the induced magnetosphere in both hemispheres occur different. We present different aspects of such an asymmetry and discuss possible mechanisms of its appearance.

  19. Distribution of plasma and magnetic field in the Venus induced magnetosphere is strongly asymmetrical

    NASA Astrophysics Data System (ADS)

    Dubinin, E.; Fraenz, M.; Zhang, T.; Woch, J. G.; Wei, Y.; Fedorov, A.; Barabash, S. V.; Lundin, R. N.

    2013-12-01

    Venus Express spacecraft have provided us a wealth of in-situ observations of characteristics of induced magnetosphere of Venus. One of its important features is a distinct asymmetry in plasma and field characteristics between the hemisphere pointed in the direction of the motional electric field and the opposite hemisphere. Asymmetry starts from formation of the magnetic barrier, then continues to low altitudes where effects of finite conductivity become important and further to the near Venus tail where the magnetic tail and plasma sheet are formed. As a result, the structure and dynamics of the induced magnetosphere in both hemispheres occur different. We present different aspects of such an asymmetry and discuss possible mechanisms of its appearance.

  20. Simulation of Ions Confined by Quadrupole Electric Fields

    NASA Astrophysics Data System (ADS)

    Cummings, Michael David

    Computer simulations are routinely used to develop physical insight into ionic systems confined by static and time-varying quadrupole electric fields. However, after nearly 30 years of numerical exploration, three questions remain: which numerical techniques produce accurate simulations for the least computational expense? How can thermal equilibrium initial conditions be generated? How should temperature be calculated? Trapped ion simulations generally employ molecular dynamics techniques, where ion trajectories are numerically calculated at discrete points in time. While many numerical methods have been applied to these systems, it is unclear which technique is fastest or what time-step is required. In this work, the computational speed of and time-step for 11 commonly used techniques are assessed through analysis of four numerical error components. The most rapid method and required step-size depend strongly on the system parameters, with any one of the Beeman, Gear6, 5th-order Adams-Bashforth-Moulton, or 4th-order Runge-Kutta algorithms proving most appropriate. The 11 algorithms are then applied to a realistic multi-ion system and verify that the four tests accurately predict the required step size. When equilibrium properties are desired, simulations should commence from initial conditions that conform closely to thermal equilibrium; however little has been published on initial condition generation and assessment for the multi-ion system. A method is presented for generating thermal equilibrium via laser cooling and recoil heating, a ramp-down stage, where the heating and cooling are gradually reduced, and an equilibration phase where the ensemble is evolved under only the trapping forces. Furthermore, it is demonstrated that thermal equilibrium can be assessed using well-known tests of distribution normality. When time-varying fields are present, temperature calculation becomes difficult, as the ion motion contains both thermal and nonthermal components. The

  1. ac-Field-induced fluid pumping in microsystems with asymmetric temperature gradients.

    PubMed

    Holtappels, Moritz; Stubbe, Marco; Gimsa, Jan

    2009-02-01

    We present two different designs of electrohydrodynamic micropumps for microfluidic systems. The micropumps have no movable parts, and their simple design allows for fabrication by microsystems technology. The pumps are operated by ac voltages from 1 to 60 V and were tested with aqueous solutions in the conductivity range of 1-112 mS m(-1). The pump effect is induced by an ac electric field across a fluid medium with an inhomogeneous temperature distribution. It is constant over a wide range of the ac field frequency with a conductivity-dependent drop-off at high frequencies. The temperature-dependent conductivity and permittivity distributions in the fluid induce space charges that interact with the electric field and induce fluid motion. The temperature distribution can be generated either by Joule heating in the medium or by external heating. We present experimental results obtained with two prototypes featuring Joule heating and external heating by a heating filament. Experimental and numerical results are compared with an analytical model.

  2. Strong parallel magnetic field effects on the hydrogen molecular ion

    NASA Astrophysics Data System (ADS)

    Guan, Xiaoxu; Li, Baiwen; Taylor, K. T.

    2003-09-01

    Equilibrium distances, binding energies and dissociation energies for the ground and low-lying states of the hydrogen molecular ion in a strong magnetic field parallel to the internuclear axis are calculated and refined, by using the two-dimensional pseudospectral method. High-precision results are presented for the binding energies over a wider field regime than already given in the literature (Kravchenko and Liberman 1997 Phys. Rev. A 55 2701). The present work removes a long-standing discrepancy for the Req value in the 1sigmau state at a field strength of 1.0 × 106 T. The dissociation energies of the antibonding 1pig state induced by magnetic fields are determined accurately. We have also observed that the antibonding 1pig potential energy curve develops a minimum if the field is sufficiently strong. Some unreliable results in the literature are pointed out and discussed. A way to efficiently treat vibrational processes and coupling between the nuclear and the electronic motions in magnetic fields is also suggested within a three-dimensional pseudospectral scheme.

  3. Paired Ion Chamber Constants for Fission Gamma-Neutron Fields

    DTIC Science & Technology

    1984-12-01

    energy E. For neutrons with energies distributed over a spectrum, the above theory must be extended to define a spectrum-averaged neutron W-value...733, 1979. 21. DLC-31/(DPL-1/FEWG1), 37- neutrOn , 21-gamma ray coupled, P3, multigroup library in ANISN Format. ORNL/TM-4840. Oak Ridge National...ragMD©/^ ^i[p@^¥ Paired ion chamber constants for fission gamma- neutron fields G. H.Zeman K. P. Ferlic DEFENSE NUCLEAR AGENCY ARMED FORCES

  4. Ion-wake field inside a glass box

    NASA Astrophysics Data System (ADS)

    Chen, Mudi; Dropmann, Michael; Zhang, Bo; Matthews, Lorin S.; Hyde, Truell W.

    2016-09-01

    The confinement provided by a glass box is proving ideal for the formation of vertically aligned structures and a convenient method for controlling the number of dust particles comprising these dust structures as well as their sizes and shapes. In this paper, the electronic confinement of the glass box is mapped, and the particle interactions between the particle pairs inside the glass box are measured. The ion-wake field is shown to exist within the glass box, and its vertical and horizontal extents are measured.

  5. Fractionating power and outlet stream polydispersity in asymmetrical flow field-flow fractionation. Part I: isocratic operation.

    PubMed

    Williams, P Stephen

    2016-05-01

    Asymmetrical flow field-flow fractionation (As-FlFFF) has become the most commonly used of the field-flow fractionation techniques. However, because of the interdependence of the channel flow and the cross flow through the accumulation wall, it is the most difficult of the techniques to optimize, particularly for programmed cross flow operation. For the analysis of polydisperse samples, the optimization should ideally be guided by the predicted fractionating power. Many experimentalists, however, neglect fractionating power and rely on light scattering detection simply to confirm apparent selectivity across the breadth of the eluted peak. The size information returned by the light scattering software is assumed to dispense with any reliance on theory to predict retention, and any departure of theoretical predictions from experimental observations is therefore considered of no importance. Separation depends on efficiency as well as selectivity, however, and efficiency can be a strong function of retention. The fractionation of a polydisperse sample by field-flow fractionation never provides a perfectly separated series of monodisperse fractions at the channel outlet. The outlet stream has some residual polydispersity, and it will be shown in this manuscript that the residual polydispersity is inversely related to the fractionating power. Due to the strong dependence of light scattering intensity and its angular distribution on the size of the scattering species, the outlet polydispersity must be minimized if reliable size data are to be obtained from the light scattering detector signal. It is shown that light scattering detection should be used with careful control of fractionating power to obtain optimized analysis of polydisperse samples. Part I is concerned with isocratic operation of As-FlFFF, and part II with programmed operation.

  6. Observations of asymmetric velocity fields and gas cooling in the NGC 4636 galaxy group X-ray halo

    NASA Astrophysics Data System (ADS)

    Ahoranta, Jussi; Finoguenov, Alexis; Pinto, Ciro; Sanders, Jeremy; Kaastra, Jelle; de Plaa, Jelle; Fabian, Andrew

    2016-08-01

    Aims: This study aims to probe the thermodynamic properties of the hot intragroup medium (IGM) plasma in the core regions of the NGC 4636 galaxy group by detailed measurements of several emission lines and their relative intensities. Methods: We analyzed deep XMM-Newton Reflection Grating Spectrometer (RGS) data in five adjacent spectral regions in the central parts of the NGC 4636 galaxy group. We examined the suppression of the Fe xvii resonance line (15.01 Å) as compared to the forbidden lines of the same ion (17.05 Å and 17.10 Å). The presence and radial dependence of the cooling flow was investigated through spectral modeling. Parallel analysis with deep Chandra Advances CCD Imaging Spectrometer (ACIS) data was conducted to gain additional information about the thermodynamical properties of the IGM. Results: The plasma at the group center to the north shows efficient Fe xvii ion resonant scattering, yielding (Iλ17.05 + Iλ17.10) /Iλ15.01 line ratios up to 2.9 ± 0.4, corresponding toabout twice the predicted line ratio. In contrast, no resonant scattering was detected at the south side. The regions featuring resonant scattering coincide with those embodying large amounts of cool (kT ≲ 0.4 keV) gas phases, and the spectral imprints of cooling gas with a total mass deposition rate of ~0.8 M⊙ yr-1 within the examined region of 2.4' × 5.0'. Conclusions: We interpret the results as possible evidence of asymmetric turbulence distribution in the NGC 4636 IGM: turbulence dominates the gas dynamics to the south, while collective gas motions characterize the dynamics to the north. X-ray images show imprints of energetic AGN at both sides, yet we find evidence of turbulence heating at the south and gas cooling at the north of the core. We infer that the observed asymmetry may be the result of the specific observation angle to the source, or arise from the turbulence driven by core sloshing at south side.

  7. Observation of synchronized atomic motions in the field ion microscope.

    PubMed

    Rahman, Fhm F; Notte, John A; Livengood, Richard H; Tan, Shida

    2013-03-01

    For over half a century, the field ion microscope (FIM) has been used to visualize atomic structures at the apex of a sharpened needle by way of the ion beams which are created at the most protruding atoms. In this paper we used a conventional FIM to study the emission characteristics of the neon ion beams produced within the FIM. The neon emission pattern is observed to be relatively short lived and subject to temporal and angular fluctuations. The nature of these fluctuations is complex, often with different parts of the emission pattern changing in a synchronized fashion over timescales spanning from milliseconds to a few tens of seconds. In this paper, we characterize the observed instability of the neon emission. We also offer a simple model of adsorbed atom mobility that explains much of these observations. And finally, we present a method by which the stability can be greatly improved so that the produced neon beam can be used effectively for nanomachining applications.

  8. Study on steric transition in asymmetrical flow field-flow fractionation and application to characterization of high-energy material.

    PubMed

    Dou, Haiyang; Lee, Yong-Ju; Jung, Euo Chang; Lee, Byung-Chul; Lee, Seungho

    2013-08-23

    In field-flow fractionation (FFF), there is the 'steric transition' phenomenon where the sample elution mode changes from the normal to steric/hyperlayer mode. Accurate analysis by FFF requires understanding of the steric transition phenomenon, particularly when the sample has a broad size distribution, for which the effect by combination of different modes may become complicated to interpret. In this study, the steric transition phenomenon in asymmetrical flow FFF (AF4) was studied using polystyrene (PS) latex beads. The retention ratio (R) gradually decreases as the particle size increases (normal mode) and reaches a minimum (Ri) at diameter around 0.5μm, after which R increases with increasing diameter (steric/hyperlayer mode). It was found that the size-based selectivity (Sd) tends to increase as the channel thickness (w) increases. The retention behavior of cyclo-1,3,5-trimethylene-2,4,6-trinitramine (commonly called 'research department explosive' (RDX)) particles in AF4 was investigated by varying experimental parameters including w and flow rates. AF4 showed a good reproducibility in size determination of RDX particles with the relative standard deviation of 4.1%. The reliability of separation obtained by AF4 was evaluated by transmission electron microscopy (TEM).

  9. Hydrodynamic radius determination with asymmetrical flow field-flow fractionation using decaying cross-flows. Part II. Experimental evaluation.

    PubMed

    Magnusson, Emma; Håkansson, Andreas; Janiak, John; Bergenståhl, Björn; Nilsson, Lars

    2012-08-31

    In this study we investigate the effect of programmed cross-flows on the error in the hydrodynamic radii (r(h)) determination with asymmetrical flow field-flow fractionation (AsFlFFF). Three different standard polystyrene particles (nominal radii of 30 and 40 and 50 nm) are fractionated with exponentially and linearly decaying cross-flows with different decay rates. Hydrodynamic radii are calculated according to retention theory including steric effects. Rapid decay is expected to give rise to systematic deviations in r(h) determination. The error in r(h) was found to be small when decay rates with half-lives longer than 6 min were used, whereas steeper decays could give rise to errors as high as 16% of the particle size. The error is often explained in terms of secondary relaxation. However, comparisons show that experimental errors are significantly larger than what would be expected due to secondary relaxation, suggesting that other factors also have to be considered in order to fully understand deviations for rapidly decaying cross-flow.

  10. Expression of picogram sensitive bending modes in piezoelectric cantilever sensors with nonuniform electric fields generated by asymmetric electrodes

    NASA Astrophysics Data System (ADS)

    Johnson, Blake N.; Mutharasan, Raj

    2010-12-01

    Single-layer uniform cross-sectioned piezoelectric macro-cantilevers fabricated with an asymmetric electrode configuration enabled electrical measurement of picogram-sensitive resonant bending modes in liquids. Bending modes were otherwise not electrically measurable without excitation by a nonuniform electric field created by the geometric asymmetry in electrode design used. Electrode modification was confirmed by energy-dispersive X-ray spectroscopy (EDS). Mass-change sensitivity was tested using both bulk density changes and surface chemisorption experiments in a continuous flow apparatus. Significant response to density changes as small as 0.004 g/mL was measured. A sensitivity limit of ˜1 picogram in liquid was determined from 1-dodecanethiol chemisorption experiments. The sensitivity decreased with chemisorbed mass and was log-linear over five orders of magnitude. The observed resonance responses were in agreement with previously reported models of resonating cantilever sensors. This work demonstrates experimentally for the first time that introducing electrode asymmetry enables measurement of bending modes in cantilevers containing only a single piezoelectric layer.

  11. Study on aggregation behavior of Cytochrome C-conjugated silver nanoparticles using asymmetrical flow field-flow fractionation.

    PubMed

    Kim, Sun Tae; Lee, Yong-Ju; Hwang, Yu-Sik; Lee, Seungho

    2015-01-01

    In this study, 40 nm silver nanoparticles (AgNPs) were synthesized using the citrate reduction method and then the surface of AgNPs was modified by conjugating Cytochrome C (Cyto C) to improve stability and to enhance bioactivity and biocompatibility of AgNPs. It is known that Cyto C may undergo conformational changes under various conditions of pH, temperature, ionic strength, etc., resulting in aggregation of the particles. These parameters also affect the size and size distribution of Cyto C-conjugated AgNPs (Cyto C-AgNP). ζ-potential measurement revealed that the adsorption of Cyto C on the surface of AgNPs is saturated at the molar ratio [Cyto C]/[AgNPs] above about 300. Asymmetrical flow field-flow fractionation (AsFlFFF) analysis showed that hydrodynamic diameter of AgNPs increases by about 4 nm when the particle is saturated by Cyto C. The aggregation behavior of Cyto C-AgNP at various conditions of pH, temperature and ionic strength were investigated using AsFlFFF and UV-vis spectroscopy. It was found that the aggregation of Cyto C-AgNP increases with decreasing pH, increasing temperature and ionic strength due to denaturation of Cyto C on AgNPs and reduction in the thickness of electrostatic double layer on the surface of Cyto C-AgNP.

  12. Fractionating power and outlet stream polydispersity in asymmetrical flow field-flow fractionation. Part II: programmed operation.

    PubMed

    Williams, P Stephen

    2017-01-01

    Asymmetrical flow field-flow fractionation (As-FlFFF) is a widely used technique for analyzing polydisperse nanoparticle and macromolecular samples. The programmed decay of cross flow rate is often employed. The interdependence of the cross flow rate through the membrane and the fluid flow along the channel length complicates the prediction of elution time and fractionating power. The theory for their calculation is presented. It is also confirmed for examples of exponential decay of cross flow rate with constant channel outlet flow rate that the residual sample polydispersity at the channel outlet is quite well approximated by the reciprocal of four times the fractionating power. Residual polydispersity is of importance when online MALS or DLS detection are used to extract quantitative information on particle size or molecular weight. The theory presented here provides a firm basis for the optimization of programmed flow conditions in As-FlFFF. Graphical abstract Channel outlet polydispersity remains significant following fractionation by As-FlFFF under conditions of programmed decay of cross flow rate.

  13. Development and evaluation of methods for starch dissolution using asymmetrical flow field-flow fractionation. Part II: Dissolution of amylose.

    PubMed

    Perez-Rea, Daysi; Bergenståhl, Björn; Nilsson, Lars

    2016-02-01

    In this paper, we investigate whether dissolution in water under autoclaving conditions (140 °C, 20 min) or in dimethyl sulfoxide, DMSO (100 °C, 1 h), is preferable for characterization of amylose. Two types of amylose, potato and maize, were dissolved either in water using an autoclave or in DMSO. On the aqueous solutions obtained, the extent of molecular dissolution of the sample (referred to as the dissolution yield) was determined by enzymatic analysis as well as the molecular properties, such as molar mass and root-mean-square radius, obtained with asymmetrical flow field-flow fractionation coupled to multi-angle light scattering and differential refractive index detection (AF4-MALS-dRI). The results showed that both dissolution methods are efficient at dissolving amylose. However, AF4-MALS-dRI analysis revealed substantial differences. Amylose aqueous solutions obtained by dissolution in DMSO were relatively stable over time, but the dissolution method in autoclave caused some degradation of the molecules, and their solutions display a high tendency to retrograde.

  14. Ultraviolet-B radiation mobilizes uranium from uranium-dissolved organic carbon complexes in aquatic systems, demonstrated by asymmetrical flow field-flow fractionation.

    PubMed

    Nehete, Sachin Vilas; Christensen, Terje; Salbu, Brit; Teien, Hans-Christian

    2017-03-21

    Humic substances have a tendency to form complexes with metal ions in aquatic medium, impacting the metal mobility, decreasing bioavailability and toxicity. Ultraviolet-B (UV-B) radiation exposure degrades the humic substance, changes their molecular weight distribution and their metal binding capacity in aquatic medium. In this study, we experimented the effect of UV-B radiation on the uranium complexed with fulvic acids and humic acids in a soft water system at different pH, uranium concentrations and radiant exposure. The concentration and distribution of uranium in a complexed form were investigated by asymmetrical flow field-flow fractionation coupled to multi detection technique (AsFlFFF-UV-ICP-MS). The major concentration of uranium present in complexes was primarily associated with average and higher molecular weight fulvic and humic acids components. The concentration of uranium in a complexed form increased with increasing fulvic and humic acid concentrations as well as pH of the solution. The higher molecular weight fraction of uranium was degraded due to the UV-B exposure, transforming about 50% of the uranium-dissolved organic carbon complexes into low molecular weight uranium species in complex form with organic ligands and/or free form. The result also suggests AsFlFFF-UV-ICP-MS to be an important separation and detection technique for understanding the interaction of radionuclides with dissolved organic matter, tracking size distribution changes during degradation of organic complexes for understanding mobility, bioavailability and ecosystem transfer of radionuclides as well as metals.

  15. Fragmentation of negative ions in a strong laser field

    NASA Astrophysics Data System (ADS)

    Berry, Ben; Jochim, Bethany; Severt, T.; Feizollah, Peyman; Rajput, Jyoti; Hayes, D.; Carnes, K. D.; Esry, B. D.; Ben-Itzhak, I.

    2016-05-01

    The fragmentation of negative ions in a strong laser field can provide a testing ground for a variety of unique phenomena. For example, anions with a loosely bound electron allow for the study of rescattering phenomena at lower laser intensities than for neutral targets. We study the behavior of keV anion beams in an ultrafast, intense laser field. The use of a fast-beam target facilitates the measurement of neutral fragments. This capability allows us to explore laser-induced dynamics in both ionic and neutral charge states. Using a coincidence 3D momentum imaging technique, we obtain the full 3D momentum of all nuclear fragments. In this preliminary work, we study atomic (H-) and molecular (H2-,F2-)systems with the goal of identifying and controlling their fragmentation pathways. This work was supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

  16. Ion distribution function in a plasma with uniform electric field

    SciTech Connect

    Lampe, M.; Joyce, G.; Roecker, T. B.; Zhdanov, S. K.; Ivlev, A. V.; Morfill, G. E.

    2012-11-15

    For a homogeneous partially ionized plasma subject to a uniform electric field E, several methods and models are used to calculate the distribution function f(v) for ions subject to charge-exchange collisions. The exact solution for f(v), based on the energy-dependent cross section for Ar, is obtained by Monte Carlo (MC) simulation. This is compared to the MC results for f(v), based on either a constant cross section {sigma} or a constant collision frequency {nu}. The constant-{sigma} model is found to accurately represent f(v) for any value of E, whereas the constant-{nu} results are qualitatively incorrect for large fields. Under the constant-{sigma} assumption, a simple, easily solvable ordinary differential equation is obtained which reproduces the MC results with good accuracy.

  17. Classical trajectories in polar-asymmetric laser fields: Synchronous THz and XUV emission.

    PubMed

    Gragossian, Aram; Seletskiy, Denis V; Sheik-Bahae, Mansoor

    2016-10-19

    The interaction of intense near- and mid-infrared laser pulses with rare gases has produced bursts of radiation with spectral content extending into the extreme ultraviolet and soft x-ray region of electromagnetic spectrum. On the other end of the spectrum, laser-driven gas plasmas has been shown to produce coherent sub-harmonic optical waveforms, covering from terahertz (THz) to mid- and near-infrared frequency spectral band. Both processes can be enhanced via a combination of a driving field and its second harmonic. Despite this striking similarity, only limited experimental and theoretical attempts have been made to address these two regimes simultaneously. Here we present systematic experiments and a unifying picture of these processes, based on our extension of the semi-classical three-step model. Further understanding of the generation and coherent control of time-synchronized transients with photon energies from meV to 1 keV can lead to numerous technological advances and to an intriguing possibilities of ultra-broadband investigations into complex condensed matter systems.

  18. Classical trajectories in polar-asymmetric laser fields: Synchronous THz and XUV emission

    PubMed Central

    Gragossian, Aram; Seletskiy, Denis V.; Sheik-Bahae, Mansoor

    2016-01-01

    The interaction of intense near- and mid-infrared laser pulses with rare gases has produced bursts of radiation with spectral content extending into the extreme ultraviolet and soft x-ray region of electromagnetic spectrum. On the other end of the spectrum, laser-driven gas plasmas has been shown to produce coherent sub-harmonic optical waveforms, covering from terahertz (THz) to mid- and near-infrared frequency spectral band. Both processes can be enhanced via a combination of a driving field and its second harmonic. Despite this striking similarity, only limited experimental and theoretical attempts have been made to address these two regimes simultaneously. Here we present systematic experiments and a unifying picture of these processes, based on our extension of the semi-classical three-step model. Further understanding of the generation and coherent control of time-synchronized transients with photon energies from meV to 1 keV can lead to numerous technological advances and to an intriguing possibilities of ultra-broadband investigations into complex condensed matter systems. PMID:27756903

  19. Density Fluctuation in Asymmetric Nozzle Plumes and Correlation with Far Field Noise

    NASA Technical Reports Server (NTRS)

    Panda, J.; Zaman, K. B. M. Q.

    2001-01-01

    A comparative experimental study of air density fluctuations in the unheated plumes of a circular, 4-tabbed-circular, chevron-circular and 10-lobed rectangular nozzles was performed at a fixed Mach number of 0.95 using a recently developed Rayleigh scattering based technique. Subsequently, the flow density fluctuations are cross-correlated with the far field sound pressure fluctuations to determine sources for acoustics emission. The nearly identical noise spectra from the baseline circular and the chevron nozzles are found to be in agreement with the similarity in spreading, turbulence fluctuations, and flow-sound correlations measured in the plumes. The lobed nozzle produced the least low frequency noise, in agreement with the weakest overall density fluctuations and flow-sound correlation. The tabbed nozzle took an intermediate position in the hierarchy of noise generation, intensity of turbulent fluctuation and flow-sound correlation. Some of the features in the 4-tabbed nozzle are found to be explainable in terms of splitting of the jet in a central large core and 4 side jetlets.

  20. Classical trajectories in polar-asymmetric laser fields: Synchronous THz and XUV emission

    NASA Astrophysics Data System (ADS)

    Gragossian, Aram; Seletskiy, Denis V.; Sheik-Bahae, Mansoor

    2016-10-01

    The interaction of intense near- and mid-infrared laser pulses with rare gases has produced bursts of radiation with spectral content extending into the extreme ultraviolet and soft x-ray region of electromagnetic spectrum. On the other end of the spectrum, laser-driven gas plasmas has been shown to produce coherent sub-harmonic optical waveforms, covering from terahertz (THz) to mid- and near-infrared frequency spectral band. Both processes can be enhanced via a combination of a driving field and its second harmonic. Despite this striking similarity, only limited experimental and theoretical attempts have been made to address these two regimes simultaneously. Here we present systematic experiments and a unifying picture of these processes, based on our extension of the semi-classical three-step model. Further understanding of the generation and coherent control of time-synchronized transients with photon energies from meV to 1 keV can lead to numerous technological advances and to an intriguing possibilities of ultra-broadband investigations into complex condensed matter systems.

  1. CINEMA (Cubesat for Ion, Neutral, Electron, MAgnetic fields)

    NASA Astrophysics Data System (ADS)

    Lin, R. P.; Parks, G. K.; Halekas, J. S.; Larson, D. E.; Eastwood, J. P.; Wang, L.; Sample, J. G.; Horbury, T. S.; Roelof, E. C.; Lee, D.; Seon, J.; Hines, J.; Vo, H.; Tindall, C.; Ho, J.; Lee, J.; Kim, K.

    2009-12-01

    The NSF-funded CINEMA mission will provide cutting-edge magnetospheric science and critical space weather measurements, including high sensitivity mapping and high cadence movies of ring current, >4 keV Energetic Neutral Atom (ENA), as well as in situ measurements of suprathermal electrons (>~2 keV) and ions (>~ 4 keV) in the auroral and ring current precipitation regions, all with ~1 keV FWHM resolution and uniform response up to ~100 keV. A Suprathermal Electron, Ion, Neutral (STEIN) instrument adds an electrostatic deflection system to the STEREO STE (SupraThermal Electron) 4-pixel silicon semiconductor sensor to separate ions from electrons and from ENAs up to ~20 keV. In addition, inboard and outboard (on an extendable 1m boom) magnetoresistive sensor magnetometers will provide high cadence 3-axis magnetic field measurements. A new attitude control system (ACS) uses torque coils, a solar aspect sensor and the magnetometers to de-tumble the 3u CINEMA spacecraft, then spin it up to ~1 rpm with the spin axis perpendicular to the ecliptic, so STEIN can sweep across most of the sky every minute. Ideally, CINEMA will be placed into a high inclination low earth orbit that crosses the auroral zone and cusp. An S-band transmitter will be used to provide > ~8 kbps orbit-average data downlink to the ~11m diameter antenna of the Berkeley Ground Station. Two more identical CINEMA spacecraft will be built by Kyung Hee University (KHU) in Korea under their World Class University (WCU) program, to provide stereo ENA imaging and multi-point in situ measurements. Furthermore, CINEMA’s development of miniature particle and magnetic field sensors, and cubesat-size spinning spacecraft will be important for future nanosatellite space missions.

  2. Characterization of colloidal phosphorus species in drainage waters from a clay soil using asymmetric flow field-flow fractionation.

    PubMed

    Regelink, Inge C; Koopmans, Gerwin F; van der Salm, Caroline; Weng, Liping; van Riemsdijk, Willem H

    2013-01-01

    Phosphorus transport from agricultural land contributes to eutrophication of surface waters. Pipe drain and trench waters from a grassland field on a heavy clay soil in the Netherlands were sampled before and after manure application. Phosphorus speciation was analyzed by physicochemical P fractionation, and the colloidal P fraction in the dissolved fraction (<0.45 μm) was analyzed by asymmetric flow field-flow fractionation (AF4) coupled to high-resolution inductively coupled plasma-mass spectrometry and ultraviolet diode array detector. When no manure was applied for almost 7 mo, total P (TP) concentrations were low (<21 μmol L), and TP was almost evenly distributed among dissolved reactive P (DRP), dissolved unreactive P (DUP), and particulate P (PP). Total P concentrations increased by a factor of 60 and 4 when rainfall followed shortly after application of cattle slurry or its solid fraction, respectively. Under these conditions, DRP contributed 50% or more to TP. The P speciation within the DUP and PP fractions varied among the different sampling times. Phosphorus associated with dissolved organic matter, probably via cation bridging, comprised a small fraction of DUP at all sampling times. Colloidal P coeluted with clay particles when P application was withheld for almost 7 mo and after application of the solid cattle slurry fraction. At these sampling times, PP correlated well with particulate Fe, Al, and Si, indicating that P is associated with colloidal clay particles. After cattle slurry application, part of DUP was probably present as phospholipids. Physicochemical fractionation combined with AF4 analysis is a promising tool to unravel the speciation of colloidal P in environmental water samples.

  3. Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

    DTIC Science & Technology

    2008-07-22

    fragmented ions of FC-43 were measured for all investigated quadrupole transmission energies ...observed ions that are produced with internal energies above the dissociation limit, and to substantiate the present interpretation that ion field... ions with internal energies exceeding the binding energy , we determine the unimolecular dissociation rate using a RRKM approach, following

  4. Asymmetric dipolar ring

    DOEpatents

    Prosandeev, Sergey A.; Ponomareva, Inna V.; Kornev, Igor A.; Bellaiche, Laurent M.

    2010-11-16

    A device having a dipolar ring surrounding an interior region that is disposed asymmetrically on the ring. The dipolar ring generates a toroidal moment switchable between at least two stable states by a homogeneous field applied to the dipolar ring in the plane of the ring. The ring may be made of ferroelectric or magnetic material. In the former case, the homogeneous field is an electric field and in the latter case, the homogeneous field is a magnetic field.

  5. ASYMMETRIC MAGNETIC RECONNECTION IN WEAKLY IONIZED CHROMOSPHERIC PLASMAS

    SciTech Connect

    Murphy, Nicholas A.; Lukin, Vyacheslav S.

    2015-06-01

    Realistic models of magnetic reconnection in the solar chromosphere must take into account that the plasma is partially ionized and that plasma conditions within any two magnetic flux bundles undergoing reconnection may not be the same. Asymmetric reconnection in the chromosphere may occur when newly emerged flux interacts with pre-existing, overlying flux. We present 2.5D simulations of asymmetric reconnection in weakly ionized, reacting plasmas where the magnetic field strengths, ion and neutral densities, and temperatures are different in each upstream region. The plasma and neutral components are evolved separately to allow non-equilibrium ionization. As in previous simulations of chromospheric reconnection, the current sheet thins to the scale of the neutral–ion mean free path and the ion and neutral outflows are strongly coupled. However, the ion and neutral inflows are asymmetrically decoupled. In cases with magnetic asymmetry, a net flow of neutrals through the current sheet from the weak-field (high-density) upstream region into the strong-field upstream region results from a neutral pressure gradient. Consequently, neutrals dragged along with the outflow are more likely to originate from the weak-field region. The Hall effect leads to the development of a characteristic quadrupole magnetic field modified by asymmetry, but the X-point geometry expected during Hall reconnection does not occur. All simulations show the development of plasmoids after an initial laminar phase.

  6. Novel symmetric diimine-Schiff bases and asymmetric triimine-Schiff bases as chemosensors for the detection of various metal ions

    NASA Astrophysics Data System (ADS)

    Özdemir, Özlem

    2016-12-01

    In this study, two symmetric diimine-Schiff bases (D1, D2) containing nitro group were synthesized by a simple one-pot condensation of 4-nitro-o-phenylenediamine with substituted-salicylaldehyde (5-Cl, 5-CH3) in 1:2 ratio. After the selective reduction of nitro group to amino group by using sodium dithionite and forming the new imine bond by adding substituted-salicylaldehyde or 2-hydroxy-1-naphthaldehyde, four asymmetric triimine-Schiff bases (T1s, T1n, T2s, and T2n) were obtained. Results of the newly synthesized compounds established by elemental analyses, FT-IR, UV-vis, 2D NMR (HMQC), 1H-NMR, 13C-NMR and TOF-mass spectroscopic experiments were consistent with their chemical structures. The tautomeric equilibria were also studied. The sensor properties of all Schiff bases were examined upon addition of the metal ions, such as Cr3+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, and Pb2+. The interactions between receptors and ions are easily monitored by UV-vis method. The receptor D2 showed colour changes from yellow to intense deep orange colour for Cu2+, a orange colour for Co2+ and dark yellow colour for other ions. Although metal ions caused no change in colour of T2s, the main absorption band of receptor shifted from 351 nm to 343-372 nm T2n underwent colour changes from yellow to light yellow on gradual addition of Fe3+.

  7. Asymmetrical flow field-flow fractionation with multi-angle light scattering and quasi-elastic light scattering for characterization of polymersomes: comparison with classical techniques.

    PubMed

    Till, Ugo; Gaucher-Delmas, Mireille; Saint-Aguet, Pascale; Hamon, Glenn; Marty, Jean-Daniel; Chassenieux, Christophe; Payré, Bruno; Goudounèche, Dominique; Mingotaud, Anne-Françoise; Violleau, Frédéric

    2014-12-01

    Polymersomes formed from amphiphilic block copolymers, such as poly(ethyleneoxide-b-ε-caprolactone) (PEO-b-PCL) or poly(ethyleneoxide-b-methylmethacrylate), were characterized by asymmetrical flow field-flow fractionation coupled with quasi-elastic light scattering (QELS), multi-angle light scattering (MALS), and refractive index detection, leading to the determination of their size, shape, and molecular weight. The method was cross-examined with more classical ones, like batch dynamic and static light scattering, electron microscopy, and atomic force microscopy. The results show good complementarities between all the techniques; asymmetrical flow field-flow fractionation being the most pertinent one when the sample exhibits several different types of population.

  8. Near-field plume properties of an ion beam formed by alternating extraction and acceleration of oppositely charged ions

    NASA Astrophysics Data System (ADS)

    Oudini, N.; Aanesland, A.; Chabert, P.; Lounes-Mahloul, S.; Bendib, A.

    2016-10-01

    This paper is devoted to study the expansion of a beam composed of packets of positively and negatively charged ions generated by alternating extraction and acceleration. This beam is extracted from an ion-ion plasma, i.e. the electron density is negligible compared to the negative ion density. The alternating acceleration of ions is ensured by two grids placed in the ion-ion plasma region. The screen grid in contact with the plasma is biased with a square voltage waveform while the acceleration grid is grounded. A two-dimensional particle-in-cell (2D-PIC) code and an analytical model are used to study the properties of the near-field plume downstream of the acceleration grid. It is shown that the possible operating bias frequency is delimited by an upper limit and a lower one that are in the low MHz range. The simulations show that alternating acceleration with bias frequencies close to the upper frequency limit for the system can achieve high ion exhaust velocities, similar to traditional gridded ion thrusters, and with lower beam divergence than in classical systems. Indeed, ion-ion beam envelope might be reduced to 15° with 70% of ion flux contained within an angle of 3°. Thus, this alternating acceleration method is promising for electric space propulsion.

  9. The quantum mechanics of ion-enhanced field emission and how it influences microscale gas breakdown

    SciTech Connect

    Li, Yingjie; Go, David B.

    2014-09-14

    The presence of a positive gas ion can enhance cold electron field emission by deforming the potential barrier and increasing the tunneling probability of electrons—a process known as ion-enhanced field emission. In microscale gas discharges, ion-enhanced field emission produces additional emission from the cathode and effectively reduces the voltage required to breakdown a gaseous medium at the microscale (<10 μm). In this work, we enhance classic field emission theory by determining the impact of a gaseous ion on electron tunneling and compute the effect of ion-enhanced field emission on the breakdown voltage. We reveal that the current density for ion-enhanced field emission retains the same scaling as vacuum cold field emission and that this leads to deviations from traditional breakdown theory at microscale dimensions.

  10. Fixed Field Alternating Gradient recirculator for heavy ion fusion

    SciTech Connect

    Paul, A.C.; Neil, V.K.

    1991-03-01

    A heavy ion fusion driver is considered in which a beam is passed repeatedly through a LIA (linear induction accelerator) by recirculating with two spiral sector FFAG (Fixed Field Alternating Gradient) 180 degree bends. The driver consists of three such rings: a 10--100 MeV low energy ring (LER), a 100--1000 MeV medium energy ring (MER), and a 1--10 GeV high energy ring (HER). Using a scaling field of 14 kG and taking the length of the straight sections to equal the path length in the bends, the circumference of the three rings would be 187, 590, and 1890 meters. Four matching sections in each of the three rings provide the interface between the two straight sections accommodating the LIA and the FFAG bends. These matching sections consist of dipoles which provide a dispersion free match between the linear induction accelerator and the energy dependent equilibrium orbits of the FFAG ring. The advantage in the use of the spiral sector FFAG over other recirculator concepts is that the fields are time invariant. This removes the problems associated with time dependent field penetration into the vacuum chamber and the large amount of energy which must be expended to change the magnetic field on the small time scale associated with the required pulse repetition frequency. The disadvantage, as we show in this work is the relatively weak alternating gradient focusing. The FFAG will not accommodate the level of beam current possible in a separate function lattice of bending magnets and quadrupoles.

  11. Nano-textured high sensitivity ion sensitive field effect transistors

    SciTech Connect

    Hajmirzaheydarali, M.; Sadeghipari, M.; Akbari, M.; Shahsafi, A.; Mohajerzadeh, S.

    2016-02-07

    Nano-textured gate engineered ion sensitive field effect transistors (ISFETs), suitable for high sensitivity pH sensors, have been realized. Utilizing a mask-less deep reactive ion etching results in ultra-fine poly-Si features on the gate of ISFET devices where spacing of the order of 10 nm and less is achieved. Incorporation of these nano-sized features on the gate is responsible for high sensitivities up to 400 mV/pH in contrast to conventional planar structures. The fabrication process for this transistor is inexpensive, and it is fully compatible with standard complementary metal oxide semiconductor fabrication procedure. A theoretical modeling has also been presented to predict the extension of the diffuse layer into the electrolyte solution for highly featured structures and to correlate this extension with the high sensitivity of the device. The observed ultra-fine features by means of scanning electron microscopy and transmission electron microscopy tools corroborate the theoretical prediction.

  12. Field performance of GCL under ion exchange conditions

    SciTech Connect

    James, A.N.; Fullerton, D.; Drake, R.

    1997-10-01

    Five Victorian reservoirs of brick pillar and arch construction were renovated using geosynthetic clay liners (also called bentonite/geosynthetic composites) (GCL) as roof sealing materials. The GCL was predominantly sodium bentonite and contained some 2% of calcite. GCLs were laid on leveled, original puddled clay packed between and above the brick arches. There was an overlying gravel layer connected to a drainage system that, in turn, was covered with soil and seeded with grass. Leaks through roofs into stored potable water were discovered. Excavation and exposure of the GCL showed that they were finely cracked in many places. Samples of the GCL bentonite from several locations at each of five sites had a high moisture content. Also, the GCL had a much reduced exchangeable sodium and increased exchangeable calcium content when compared to the dry unused GCL. Laboratory experiments, lasting for a limited period, were carried out to simulate operating conditions of the GCL whereby water falling on the ground and reaching the GCL flowed across the GCL in the overlying gravel layer to collector drains. Similar but less extensive ion exchange, calcium for sodium, was found here also. The evidence demonstrates that calcium from calcite, contained in the GCL bentonite, exchanged with sodium and, in so doing, contributed to shrinkage and cracking. Supplementary sources of calcium for ion exchange probably came from overlying calcareous soil and water from firehoses used to field test the integrity of the GCL.

  13. Modeling of asymmetric degradation based on a non-uniform electric field and temperature in amorphous In–Ga–Zn–O thin film transistors

    NASA Astrophysics Data System (ADS)

    In Kim, Jong; Jeong, Chan-Yong; Kwon, Hyuck-In; Jung, Keum Dong; Park, Mun Soo; Kim, Ki Hwan; Seo, Mi Seon; Lee, Jong-Ho

    2017-03-01

    We propose a new local degradation model based on a non-uniform increase in donor-like traps (DLTs) determined by distributions of an electric field and measured device temperature in amorphous In–Ga–Zn–O (a-IGZO) thin film transistors (TFTs). A systematic investigation of the degradation model reveals that vertical field-dependent DLTs are essential for modeling of measured asymmetric electrical characteristics between the source and drain after positive gate and drain bias stressing. An increased temperature due to self-heating is found to play a role in intensifying the asymmetric degradation. From the individual simulation of measured transfer curves at different stress times, the model parameters and an asymmetry index as a function of stress time are extracted. It is expected that this novel methodology will provide new insight into asymmetric degradation and be utilized to predict the influence of electric field and heat on degradation under various bias-stress conditions in a-IGZO TFTs.

  14. Ion orbit loss and the poloidal electric field in a tokamak

    SciTech Connect

    Xiao, H.; Hazeltine, R.D.; Valanju, P.M.

    1994-07-29

    Monte Carlo simulation studies for ion orbit loss in limiter tokamaks show a poloidal asymmetry in ion loss arising from differences in ion orbit geometry. Since electron loss to the limiter is uniformly distributed because of its tiny orbit width, the nonuniform ion loss could cause a poloidal electric field that would tend to make the ion loss to the limiter more uniform. A simple analytical derivation of this poloidal electric field and a discussion of its effects ion movement and transport are also presented.

  15. Design and construction of cage environments for air ion and electric field research

    NASA Astrophysics Data System (ADS)

    Yost, M. G.; Kellogg, E. W.

    1987-06-01

    This report describes the design and construction of cage environments suitable for chronic exposures of large groups of mice to air ions and electric fields. These environments provide defined and reproducible ion densities, ion flux, DC electric fields, sound levels, air temperature and air quality. When used during a 2 year study, these cage environments served as a durable and reliable continuous exposure system. Three environmental chambers (cubicles) housed a total of 12 cages and provided control of air temperature, air purity and lighting. Exposure cages had grounded metal exterior walls, a plexiglass door and interior walls lined with formica. An internal isolated field plate supplemented with guard wires, energized with ca 1000 VDC, created about a 2 kV/m electric field at the grounded cage floor. Air ions resulted from the beta emission of sealed tritium foils mounted on the field plate. Cages provided high ion (1.3×105 ions/cc), low ion (1.6×103 ions/cc) and field only (ion depleted < 50 ions/cc) conditions for both polarities with similar electric fields in ionized and field only cages. Detailed mapping of the floor level ion flux using 100 cm2 flat probes gave average fluxes of 880 fA cm-2 in high ion cages and 10 fA cm-2 in low ion cages. Whole body currents measured using live anesthethized mice in high ion cages averaged 104±63 pA. Both ion flux and whole body currents remained constant over time, indicating no charge accumulation on body fur or cage wall surfaces in this exposure system.

  16. Atom probe field ion microscopy and related topics: A bibliography 1992

    SciTech Connect

    Russell, K.F.; Godfrey, R.D.; Miller, M.K.

    1993-12-01

    This bibliography contains citations of books, conference proceedings, journals, and patents published in 1992 on the following types of microscopy: atom probe field ion microscopy (108 items); field emission microscopy (101 items); and field ion microscopy (48 items). An addendum of 34 items missed in previous bibliographies is included.

  17. Asymmetric magnetoimpedance effect in CoFeSiB amorphous ribbons by combination of field and current annealing for sensor applications

    NASA Astrophysics Data System (ADS)

    Hajiali, Mohammadreza; Mohseni, S. Majid; Roozmeh, S. Ehsan; Moradi, Mehrdad

    2016-08-01

    The roles of applied magnetic field during the current annealing of Co68.15Fe4.35Si12.5B15 soft magnetic amorphous ribbons are studied. Samples heat treated by Joule heating effect in open air and simultaneously in the present of longitudinal external magnetic field showed asymmetric magnetoimpedance (AMI) behavior. The AMI profile can be related to the exchange bias interaction between the soft magnetic amorphous material and a harder magnetic crystalline phase formed on the surface of the ribbon. This effect stems from thermal effect, the transverse Oe field generated from the annealing current which is thickness dependent and the longitudinal external field. The single peak AMI with the field sensitivity of 101%/Oe for DC annealing current is achieved. Our results could address a simple way to achieve the AMI response toward developing high sensitive magnetic field sensors.

  18. Ion heating by kinetic cross-field streaming instability due to reflected ions at a quasiperpendicular shock

    NASA Technical Reports Server (NTRS)

    Yoon, Peter H.; Wu, C. S.; Mandt, M. E.

    1992-01-01

    The present paper shows that the reflected ion at a supercritical quasi-perpendicular shock wave can excite a purely growing mode propagating parallel to the ambient magnetic field. To discuss the ion heating by such an unstable mode, the self-consistent quasi-linear kinetic equation is solved with the assumption that the present purely growing mode is the dominant unstable mode in the system. In the quasi-linear analysis of the instability, two particular cases are considered: the case of low initial ion beta and that of a high initial ion beta.

  19. Atom probe field-ion microscopy and related topics: A bibliography, 1988

    SciTech Connect

    Miller, M.K.; Hawkins, A.R.

    1989-10-01

    This bibliography includes references related to the following topics: field-ion microscopy (FIM), field emission microscopy (FEM), atom probe field-ion microscopy (APFIM), and liquid metal ion sources (LMIS). Technique-orientated studies and applications are included. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications. To reduce the length of this document, the references have been reduced to the minimum necessary to locate the articles.

  20. Atom probe field ion microscopy and related topics: A bibliography 1989

    SciTech Connect

    Miller, M.K.; Hawkins, A.R.; Russell, K.F.

    1990-12-01

    This bibliography includes references related to the following topics: atom probe field ion microscopy (APFIM), field ion spectroscopy (FIM), field emission microscopy (FEM), liquid metal ion sources (LMIS), scanning tunneling microscopy (STM), and theory. Technique-orientated studies and applications are included. This bibliography covers the period 1989. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications.

  1. (In)validity of the constant field and constant currents assumptions in theories of ion transport.

    PubMed Central

    Syganow, A; von Kitzing, E

    1999-01-01

    Constant electric fields and constant ion currents are often considered in theories of ion transport. Therefore, it is important to understand the validity of these helpful concepts. The constant field assumption requires that the charge density of permeant ions and flexible polar groups is virtually voltage independent. We present analytic relations that indicate the conditions under which the constant field approximation applies. Barrier models are frequently fitted to experimental current-voltage curves to describe ion transport. These models are based on three fundamental characteristics: a constant electric field, negligible concerted motions of ions inside the channel (an ion can enter only an empty site), and concentration-independent energy profiles. An analysis of those fundamental assumptions of barrier models shows that those approximations require large barriers because the electrostatic interaction is strong and has a long range. In the constant currents assumption, the current of each permeating ion species is considered to be constant throughout the channel; thus ion pairing is explicitly ignored. In inhomogeneous steady-state systems, the association rate constant determines the strength of ion pairing. Among permeable ions, however, the ion association rate constants are not small, according to modern diffusion-limited reaction rate theories. A mathematical formulation of a constant currents condition indicates that ion pairing very likely has an effect but does not dominate ion transport. PMID:9929480

  2. Linear electronic field time-of-flight ion mass spectrometers

    DOEpatents

    Funsten, Herbert O.

    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.

  3. Dark-Field Scanning Transmission Ion Microscopy via Detection of Forward-Scattered Helium Ions with a Microchannel Plate.

    PubMed

    Woehl, Taylor J; White, Ryan M; Keller, Robert R

    2016-06-01

    A microchannel plate was used as an ion sensitive detector in a commercial helium ion microscope (HIM) for dark-field transmission imaging of nanomaterials, i.e. scanning transmission ion microscopy (STIM). In contrast to previous transmission HIM approaches that used secondary electron conversion holders, our new approach detects forward-scattered helium ions on a dedicated annular shaped ion sensitive detector. Minimum collection angles between 125 mrad and 325 mrad were obtained by varying the distance of the sample from the microchannel plate detector during imaging. Monte Carlo simulations were used to predict detector angular ranges at which dark-field images with atomic number contrast could be obtained. We demonstrate atomic number contrast imaging via scanning transmission ion imaging of silica-coated gold nanoparticles and magnetite nanoparticles. Although the resolution of STIM is known to be degraded by beam broadening in the substrate, we imaged magnetite nanoparticles with high contrast on a relatively thick silicon nitride substrate. We expect this new approach to annular dark-field STIM will open avenues for more quantitative ion imaging techniques and advance fundamental understanding of underlying ion scattering mechanisms leading to image formation.

  4. Control of Magnetic Field for Sustainment of Ion Production and Uniform Ion Flux to Substrate in Neutral Loop Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Yoshida, Takuhei; Sakurai, Yohei; Sugawara, Hirotake; Murayama, Akihiro

    We simulated the electron and ion motions in a neutral loop discharge plasma under the control of the foot of separatrix sweeping over a substrate and the neutral loop moving within a short distance from the RF antenna by a Monte Carlo method. We analyzed the distributions of ion production and ion flux to the substrate. We revealed that ion production is sensitive to the gradient of magnetic field rather than the electric field strength. Moreover, by superposing the flux distributions weighted by the passage time of the foot of separatrix on the substrate, we obtained a uniform time-averaged distribution of ion flux to the substrate in a radius range of r = 4.0-14.0 cm with σ/m = 0.25% (m: the average, σ: the standard deviation).

  5. Renormalized theory of ion temperature gradient instability of the magnetic-field-aligned plasma shear flow with hot ions

    SciTech Connect

    Mikhailenko, V. V. Mikhailenko, V. S.; Lee, Hae June

    2015-10-15

    The developed kinetic theory for the stability of a magnetic-field-aligned (parallel) shear flow with inhomogeneous ion temperature [Mikhailenko et al., Phys. Plasmas 21, 072117 (2014)] predicted that a kinetic instability arises from the coupled reinforcing action of the flow velocity shear and ion temperature gradient in the cases where comparable ion and electron temperatures exist. In the present paper, the nonlinear theory was developed for the instability caused by the combined effects of ion-temperature-gradient and shear-flow (ITG–SF). The level of the electrostatic turbulence is determined for the saturation state of the instability on the basis of the nonlinear dispersion equation, which accounts for a nonlinear scattering of ions by the developed turbulence in a sheared flow. The renormalized quasilinear equation for the ion distribution function, which accounts for the turbulent scattering of ions by ITG–SF driven turbulence, was derived and employed for the estimation of the turbulent ion viscosity, the anomalous ion thermal conductivity, and anomalous ion heating rate at the saturation state of the instability.

  6. Freja observations of electromagnetic ion cyclotron ELF waves and transverse oxygen ion acceleration on auroral field lines

    SciTech Connect

    Erlandson, R.E.; Zanetti, L.J.; Acuna, M.H.; Eliasson, L.; Boehm, M.H.; Blomberg, L.G.

    1994-08-15

    Extremely low-frequency (ELF) magnetic and electric field plasma wave emissions were recorded on 2 October 1993 on auroral field lines by the Magnetic Field Experiment during Freja orbit 4770. The ELF wave frequencies were below the local oxygen gyrofrequency (25 Hz) and between the helium and proton gyrofrequencies (100 to 400 Hz). The ELF waves, interpreted as electromagnetic ion cyclotron (EMIC) waves, were observed in a region of inverted-V-type electron precipitation. The EMIC waves were correlated over time with auroral and lower energy ({approximately} 100 eV) electrons, which are both possible sources of free energy, and also with transversely accelerated oxygen ions. The waves above the helium gyrofrequency were more closely correlated with the transverse oxygen ion acceleration than the waves below the oxygen gyrofrequency. These observations are consistent with a scenario in which electron beams generate EMIC waves, which then produce transverse oxygen ion acceleration through a gyroresonant interaction. 16 refs., 4 figs.

  7. ALTERATIONS IN CALCIUM ION ACTIVITY BY ELF AND RF ELECTROMAGNETIC FIELDS

    EPA Science Inventory



    Alterations in calcium ion activity by ELF and RF electromagnetic fields

    Introduction

    Calcium ions play many important roles in biological systems. For example, calcium ion activity can be used as an indicator of second-messenger signal-transduction processe...

  8. Feasibility of asymmetric flow field-flow fractionation coupled to ICP-MS for the characterization of wear metal particles and metalloproteins in biofluids from hip replacement patients.

    PubMed

    Loeschner, Katrin; Harrington, Chris F; Kearney, Jacque-Lucca; Langton, David J; Larsen, Erik H

    2015-06-01

    Hip replacements are used to improve the quality of life of people with orthopaedic conditions, but the use of metal-on-metal (MoM) arthroplasty has led to poor outcomes for some patients. These problems are related to the generation of micro- to nanosized metal wear particles containing Cr, Co or other elements, but the current analytical methods used to investigate the processes involved do not provide sufficient information to understand the size or composition of the wear particles generated in vivo. In this qualitative feasibility study, asymmetric flow field-flow fractionation (AF(4)) coupled with inductively coupled plasma mass spectrometry (ICP-MS) was used to investigate metal protein binding and the size and composition of wear metal particles present in serum and hip aspirates from MoM hip replacement patients. A well-established HPLC anion exchange chromatography (AEC) separation system coupled to ICP-MS was used to confirm the metal-protein associations in the serum samples. Off-line single particle ICP-MS (spICP-MS) analysis was used to confirm the approximate size distribution indicated by AF(4) of the wear particles in hip aspirates. In the serum samples, AF(4) -ICP-MS suggested that Cr was associated with transferrin (Tf) and Co with albumin (Alb) and an unidentified species; AEC-ICP-MS confirmed these associations and also indicated an association of Cr with Alb. In the hip aspirate sample, AF(4)-ICP-MS suggested that Cr was associated with Alb and Tf and that Co was associated with Alb and two unidentified compounds; AEC analysis confirmed the Cr results and the association of Co with Alb and a second compound. Enzymatic digestion of the hip aspirate sample, followed by separation using AF(4) with detection by UV absorption (280 nm), multi-angle light scattering and ICP-MS, suggested that the sizes of the Cr-, Co- and Mo-containing wear particles in a hip aspirate sample were in the range 40-150 nm. Off-line spICP-MS was used to confirm these

  9. Linear and total intersubband transitions in the step-like GaAs/GaAlAs asymmetric quantum well as dependent on intense laser field

    NASA Astrophysics Data System (ADS)

    Ozturk, Emine

    2015-11-01

    In this study, for a step-like GaAs- Ga_{1-x}AlxAs asymmetric quantum well (AQW) the linear and total intersubband optical absorption coefficients and the refractive index changes are calculated as dependent on the intense laser field (ILF) and the right quantum well (RQW) width. Our results show that the location and the magnitude of all absorption coefficients and refractive index changes depend on ILF and the asymmetric parameter ( d=LR/LL). Also, we showed that both ILF and d provide an important effect on the electronic and optical properties of step-like quantum well, and the changes of the energy levels, the dipole moment matrix elements and the resonant peak values of the absorption coefficients are dependent on the shape of the confinement potential. While for different asymmetric parameters the intersubband absorption spectrum shows blue shift up to the different critical ILF values, this spectrum shows red shift for ILF values greater than certain values. By considering the variation of the energy difference as dependent on the RQW width, for step-like QW the absorption spectrum shows blue or red shift. Especially, step-like QWs are used for producing terahertz radiation from intersubband transitions and they have more tunable structure parameters (the left (right) quantum well width, LL(LR), and the confinement potential in the left (right) hand side, VL (VR) with respect to other asymmetric QWs (in the present study we used LR=LL/2, LL, 3 L L/2 and V R = 2 V L/3 values). This case provides a new degree of freedom for controlling the optical properties in quantum wells (QWs). In addition, the nonlinear optics underlying the application of the ILF to asymmetric potential heterostructures becomes a subject of present-day interest. In conclusion: i) The electronic and optical properties of the step-like AQW vary by increasing ILF. ii) ILF leads to major modifications on the shape of the confining potential. iii) The position and the size of all absorption

  10. Ion adsorption and its influence on direct current electric field induced deformations of flexoelectric nematic layers

    NASA Astrophysics Data System (ADS)

    Derfel, Grzegorz; Buczkowska, Mariola

    2011-07-01

    The influence of ion adsorption on the behavior of the nematic liquid crystal layers is studied numerically. The homeotropic flexoelectric layer subjected to the dc electric field is considered. Selective adsorption of positive ions is assumed. The analysis is based on the free energy formalism for ion adsorption. The distributions of director orientation angle, electric potential, and ion concentrations are calculated by numerical resolving of suitable torques equations and Poisson equation. The threshold voltages for the deformations are also determined. It was shown that adsorption affects the distributions of both cations and anions. Sufficiently large number of adsorbed ions leads to spontaneous deformation arising without any threshold if the total number of ions creates sufficiently strong electric field with significant field gradients in the neighborhood of electrodes. The spontaneous deformations are favored by strong flexoelectricity, large thickness, large ion concentrations, weak anchoring, and large adsorption energy.

  11. Possible role of external radial electric field on ion heating in an FRC

    NASA Astrophysics Data System (ADS)

    Gupta, Deepak; Trask, E.; Korepanov, S.; Granstedt, E.; Osin, D.; Roche, T.; Deng, B.; Beall, M.; Zhai, K.; TAE Team

    2016-10-01

    In C-2/C-2U FRCs, a radial electric field is applied by either plasma guns or biased electrodes inside the divertors, at both ends of the machine. The electric field plays an important role in stabilizing the FRC; thus, providing a favorable target condition to a neutral beam injection. In addition, it is also observed that the application of radial electric field may lead to a heating of ions. Radial profile of impurity ion emission, azimuthal velocity and temperature are measured under different configurations. The conditions and evidences of ion heating due to the electric field biasing will be presented and discussed. Radial momentum balance equation of oxygen impurity ions is used with these measurements to estimate the radial electric field profile. Parameters affecting the ion heating due to biasing will also be discussed with some correlations. The external radial electric field is planned to be applied by biased electrodes and plasma guns in C-2W inner/outer divertors.

  12. Ion drift in a magnetic field under the combined action of LID and light pressure

    SciTech Connect

    Parkhomenko, A I

    2002-06-30

    The effect of magnetic field on the ion drift in a weakly ionised gas under the combined action of light-induced drift (LID) and light pressure is theoretically investigated. It is shown that the imposition of an external magnetic field may give rise to a velocity component of light-induced ion drift orthogonal to the direction of radiation propagation. The effect of light pressure in sufficiently strong magnetic fields is found to prevail over the LID effect, while the reverse is true for weak magnetic fields. The dependence of the ion drift velocity on the frequency detuning drastically changes in the magnetic field when ions experience the Lorenz force. It is predicted that the projection of the ion drift velocity on the direction of radiation propagation should change its sign with increasing magnetic field, and an anomalous LID can be observed. (laser applications and other topics in quantum electronics)

  13. Gas field ion source current stability for trimer and single atom terminated W(111) tips

    SciTech Connect

    Urban, Radovan; Wolkow, Robert A.; Pitters, Jason L.

    2012-06-25

    Tungsten W(111) oriented trimer-terminated tips as well as single atom tips, fabricated by a gas and field assisted etching and evaporation process, were investigated with a view to scanning ion microscopy and ion beam writing applications. In particular, ion current stability was studied for helium and neon imaging gases. Large ion current fluctuations from individual atomic sites were observed when a trimer-terminated tip was used for the creation of neon ion beam. However, neon ion current was stable when a single atom tip was employed. No such current oscillations were observed for either a trimer or a single atom tip when imaged with helium.

  14. On Alfvenic Waves and Stochastic Ion Heating with 1Re Observations of Strong Field-aligned Currents, Electric Fields, and O+ ions

    NASA Technical Reports Server (NTRS)

    Coffey, Victoria; Chandler, Michael; Singh, Nagendra

    2008-01-01

    The role that the cleft/cusp has in ionosphere/magnetosphere coupling makes it a very dynamic region having similar fundamental processes to those within the auroral regions. With Polar passing through the cusp at 1 Re in the Spring of 1996, we observe a strong correlation between ion heating and broadband ELF (BBELF) emissions. This commonly observed relationship led to the study of the coupling of large field-aligned currents, burst electric fields, and the thermal O+ ions. We demonstrate the role of these measurements to Alfvenic waves and stochastic ion heating. Finally we will show the properties of the resulting density cavities.

  15. Influence of Heat Source, Thermal Radiation and Inclined Magnetic Field on Peristaltic Flow of a Hyperbolic Tangent Nanofluid in a Tapered Asymmetric Channel.

    PubMed

    Kothandapani, Munirathinam; Prakash, Jayavel

    2014-10-31

    In the present analytic thinking, we have modeled the governing equations of a two dimensional peristaltic transport of a Hyperbolic tangent nanofluid in the presence of a heat source/sink with the combined effects of thermal radiation and inclined magnetic field in a tapered asymmetric channel. The propagation of waves on the non-uniform walls to have different amplitudes and phase but the same wave speed is produced the tapered asymmetric channel. The equations of dimensionless temperature and nanoparticle concentration are solved analytically under assumptions of long wavelength and low Reynolds number. The governing equations of momentum of a hyperbolic tangent nanofluid for the tapered asymmetric channel have also been solved analytically using the regular perturbation method. The expression for average rise in pressure has been figured using numerical integrations. The effects of various physical parameters entering into the problem are discussed numerically and graphically. The phenomenon of trapping is also investigated. Furthermore, the received results show that the maximum pressure rise gets increased in case of non-Newtonian fluid when equated with Newtonian fluid.

  16. Improved two-dimensional electron mobility in asymmetric barrier delta-doped GaAs/AlGaAs modulation-doped field-effect transistor structures

    NASA Astrophysics Data System (ADS)

    Das, Sudhakar; Mohapatra, Meryleen; Nayak, Rasmita K.; Panda, Ajit K.; Sahu, Trinath

    2017-03-01

    We study the enhancement of electron mobility μ in barrier delta-doped GaAs/AlGaAs quantum-well-based modulation-doped field-effect transistor (MODFET) structures. We asymmetrically vary the doping concentrations N d1 and N d2 in the barriers on the substrate and surface sides, respectively, to obtain a nonlinear enhancement of μ as a function of the well width w through multi-subband effects. We show that an increase in doping concentration increases the surface electron density N s, which in turn enhances μ. Interchanging N d1 and N d2 leads to no change in N s but rather, an enhancement of μ as a function of w for N d2 > N d1 owing to asymmetric variation of subband wave functions, thereby implying a higher channel conductivity in a surface-doped structure than in an inverted doped structure. By keeping (N d1 + N d2) unchanged, the conductivity of a single-channel MODFET, N d1 (N d2) ≠ 0 and N d2 (N d1) = 0, can be enhanced by considering a MODFET based on an asymmetrically doped (N d1 ≠ N d2 ≠ 0) quantum well structure. We show that the highest N s and μ product for these structures occurs almost before the onset of the occupation of the second subband. Our analysis of the effect of asymmetric doping profiles on channel conductivity can be utilized for the performance improvement of MODFET-like devices.

  17. Ion acoustic turbulence and transport in a plasma in a strong electric field

    NASA Astrophysics Data System (ADS)

    Bychenkov, V. Iu.; Gradov, O. M.; Silin, V. P.

    1984-01-01

    A theory is derived for the nonlinear state which is established in a plasma when the ion acoustic instability is suppressed by nonlinear induced wave scattering by ions, and there is a quasi-linear relaxation of electrons among turbulent fluctuations. The behavior of the ion acoustic noise spectrum and of transport processes in strong fields, where the anomalous plasma resistance is a square-root function of the field intensity, is found. In this region of electric fields there is a universal distribution of the ion acoustic fluctuations in the magnitude of the wave vector and in angle for the turbulence spectrum.

  18. Field screening of volatile organochlorine compounds using ion mobility spectrometry

    SciTech Connect

    Stach, J.; Brodacki, M.; Doering, H.R.; Flachowsky, J.

    1995-12-31

    Chlorinated alkanes and alkenes produce due to a dissociative charge transfer reaction strong signals of Cl{sup {minus}} ions in ion mobility spectra. This reaction can be used to analyze these compounds in on site analyses. The method is applicable to dump gases, soil air or soil using head space techniques and volatile halogen compounds dissolved in organic solvents. The results obtained by ion mobility spectrometry correlate with GC/MS or AOX measurements in most cases.

  19. Optimization of operation conditions for extracting lithium ions from calcium chloride-type oil field brine

    NASA Astrophysics Data System (ADS)

    Yang, Hong-jun; Li, Qing-hai; Li, Bing; Guo, Feng-qin; Meng, Qing-fen; Li, Wu

    2012-04-01

    Al(OH)3 was prepared to extract lithium ions from calcium chloride-type oil field brine. The influences of four factors, namely temperature, Al3+/Li+ molar ratio, OH-/Al3+ molar ratio, and contact time between Al(OH)3 and the brine, on the yield of lithium ions were investigated. It is found that their optimal values are 35°C, 4.5, 2.6, and 6 h, respectively. In the course of the experiment, the apparent pH value was observed. The results reveal that the apparent pH value has no remarkable influence on the yield of lithium ions. Meanwhile, the effects of the concentrations of calcium ions and magnesium ions in the brine on lithium recovery were studied. The results indicate that calcium ions have minor negative influence on the yield of lithium ions under optimal conditions, and magnesium ions slightly influence the yield of lithium ions.

  20. Simulation of RF power and multi-cusp magnetic field requirement for H- ion sources

    NASA Astrophysics Data System (ADS)

    Pathak, Manish; Senecha, V. K.; Kumar, Rajnish; Ghodke, Dharmraj. V.

    2016-12-01

    A computer simulation study for multi-cusp RF based H- ion source has been carried out using energy and particle balance equation for inductively coupled uniformly dense plasma considering sheath formation near the boundary wall of the plasma chamber for RF ion source used as high current injector for 1 Gev H- Linac project for SNS applications. The average reaction rates for different reactions responsible for H- ion production and destruction have been considered in the simulation model. The RF power requirement for the caesium free H- ion source for a maximum possible H- ion beam current has been derived by evaluating the required current and RF voltage fed to the coil antenna using transformer model for Inductively Coupled Plasma (ICP). Different parameters of RF based H- ion source like excited hydrogen molecular density, H- ion density, RF voltage and current of RF antenna have been calculated through simulations in the presence and absence of multicusp magnetic field to distinctly observe the effect of multicusp field. The RF power evaluated for different H- ion current values have been compared with the experimental reported results showing reasonably good agreement considering the fact that some RF power will be reflected from the plasma medium. The results obtained have helped in understanding the optimum field strength and field free regions suitable for volume emission based H- ion sources. The compact RF ion source exhibits nearly 6 times better efficiency compare to large diameter ion source.

  1. Ion heating in the field-reversed configuration (FRC) by rotating magnetic fields (RMF) near cyclotron resonance

    SciTech Connect

    Samuel A. Cohen; Alan H. Glasser

    2000-07-20

    The trajectories of ions confined in a Solovev FRC equilibrium magnetic geometry and heated with a small-amplitude, odd-parity rotating magnetic field, have been studied with a Hamiltonian computer code. When the RMF frequency is in the ion-cyclotron range, explosive heating occurs. Higher-energy ions are found to have betatron-type orbits, preferentially localized near the FRC midplane. These results are relevant to a compact magnetic-fusion-reactor design.

  2. Electric field measurement in microwave discharge ion thruster with electro-optic probe.

    PubMed

    Ise, Toshiyuki; Tsukizaki, Ryudo; Togo, Hiroyoshi; Koizumi, Hiroyuki; Kuninaka, Hitoshi

    2012-12-01

    In order to understand the internal phenomena in a microwave discharge ion thruster, it is important to measure the distribution of the microwave electric field inside the discharge chamber, which is directly related to the plasma production. In this study, we proposed a novel method of measuring a microwave electric field with an electro-optic (EO) probe based on the Pockels effect. The probe, including a cooling system, contains no metal and can be accessed in the discharge chamber with less disruption to the microwave distribution. This method enables measurement of the electric field profile under ion beam acceleration. We first verified the measurement with the EO probe by a comparison with a finite-difference time domain numerical simulation of the microwave electric field in atmosphere. Second, we showed that the deviations of the reflected microwave power and the beam current were less than 8% due to inserting the EO probe into the ion thruster under ion beam acceleration. Finally, we successfully demonstrated the measurement of the electric-field profile in the ion thruster under ion beam acceleration. These measurements show that the electric field distribution in the thruster dramatically changes in the ion thruster under ion beam acceleration as the propellant mass flow rate increases. These results indicate that this new method using an EO probe can provide a useful guide for improving the propulsion of microwave discharge ion thrusters.

  3. Electric field measurement in microwave discharge ion thruster with electro-optic probe

    NASA Astrophysics Data System (ADS)

    Ise, Toshiyuki; Tsukizaki, Ryudo; Togo, Hiroyoshi; Koizumi, Hiroyuki; Kuninaka, Hitoshi

    2012-12-01

    In order to understand the internal phenomena in a microwave discharge ion thruster, it is important to measure the distribution of the microwave electric field inside the discharge chamber, which is directly related to the plasma production. In this study, we proposed a novel method of measuring a microwave electric field with an electro-optic (EO) probe based on the Pockels effect. The probe, including a cooling system, contains no metal and can be accessed in the discharge chamber with less disruption to the microwave distribution. This method enables measurement of the electric field profile under ion beam acceleration. We first verified the measurement with the EO probe by a comparison with a finite-difference time domain numerical simulation of the microwave electric field in atmosphere. Second, we showed that the deviations of the reflected microwave power and the beam current were less than 8% due to inserting the EO probe into the ion thruster under ion beam acceleration. Finally, we successfully demonstrated the measurement of the electric-field profile in the ion thruster under ion beam acceleration. These measurements show that the electric field distribution in the thruster dramatically changes in the ion thruster under ion beam acceleration as the propellant mass flow rate increases. These results indicate that this new method using an EO probe can provide a useful guide for improving the propulsion of microwave discharge ion thrusters.

  4. Enhancement of hypersensitive transitions of rare-earth ions in the near field of nanoobjects

    NASA Astrophysics Data System (ADS)

    Pukhov, K. K.; Sekatskii, S. K.

    2014-05-01

    The change of intensities of optical transitions of atoms, molecules, and their ions in the near field of nanoobjects is of interest for researchers from both basic and applied points of view. The concept of a near field was used as early as the 1960s to study the mechanisms of hypersensitive transitions of rare-earth (RE) ions. In this work, it is once more emphasized that, precisely for these transitions, changes in characteristics under the action of local properties of the medium are especially strong and, correspondingly, these transitions are especially promising for use. The Judd method for the calculation of the intensities of hypersensitive transitions of RE ions taking into account the inhomogeneous ligand field is extended to RE ions in the near field of nanoobjects. A simple analytical expression for the Judd-Ofelt intensity parameter Ω2 for RE ions in the field of spherical nanoparticles of a subwavelength size is derived.

  5. Effect of axial magnetic field on a 2.45 GHz permanent magnet ECR ion source

    SciTech Connect

    Nakamura, T. Wada, H.; Furuse, M.; Asaji, T.

    2016-02-15

    Herein, we conduct a fundamental study to improve the generation efficiency of a multi-charged ion source using argon. A magnetic field of our electron cyclotron resonance ion source is composed of a permanent magnet and a solenoid coil. Thereby, the axial magnetic field in the chamber can be tuned. Using the solenoid coil, we varied the magnetic field strength in the plasma chamber and measured the ion beam current extracted at the electrode. We observed an approximately three times increase in the Ar{sup 4+} ion beam current when the magnetic field on the extractor-electrode side of the chamber was weakened. From our results, we can confirm that the multi-charged ion beam current changes depending on magnetic field intensity in the plasma chamber.

  6. Field-Reversal Source for Negative Halogen Ions

    NASA Technical Reports Server (NTRS)

    Chutjian, A.; Orient, O. J.; Aladzhadzhyan, S. H.

    1987-01-01

    Large zero-energy electron-attachment cross sections result in intense ion beams. Concept for producing negative halogen ions takes advantage of large cross sections at zero kinetic energy for dissociative attachment of electrons to such halogen-containing gases as SF6, CFCI3, and CCI4.

  7. Magnetic field design for a Penning ion source for a 200 keV electrostatic accelerator

    NASA Astrophysics Data System (ADS)

    Fathi, A.; Feghhi, S. A. H.; Sadati, S. M.; Ebrahimibasabi, E.

    2017-04-01

    In this study, the structure of magnetic field for a Penning ion source has been designed and constructed with the use of permanent magnets. The ion source has been designed and constructed for a 200 keV electrostatic accelerator. With using CST Studio Suite, the magnetic field profile inside the ion source was simulated and an appropriate magnetic system was designed to improve particle confinement. Designed system consists of two ring magnets with 9 mm distance from each other around the anode. The ion source was constructed and the cylindrical magnet and designed magnetic system were tested on the ion source. The results showed that the ignition voltage for ion source with the designed magnetic system is almost 300 V lower than the ion source with the cylindrical magnet. Better particle confinement causes lower voltage discharge to occur.

  8. Electrostatic ion instabilities in the presence of parallel currents and transverse electric fields

    NASA Technical Reports Server (NTRS)

    Ganguli, G.; Palmadesso, P. J.

    1988-01-01

    The electrostatic ion instabilities are studied for oblique propagation in the presence of magnetic field-aligned currents and transverse localized electric fields in a weakly collisional plasma. The presence of transverse electric fields result in mode excitation for magnetic field aligned current values that are otherwise stable. The electron collisions enhance the growth while ion collisions have a damping effect. These results are discussed in the context of observations of low frequency ion modes in the auroral ionosphere by radar and rocket experiments.

  9. Atom probe field ion microscopy and related topics: A bibliography 1990

    SciTech Connect

    Russell, K.F.; Miller, M.K.

    1991-12-01

    This bibliography includes references related to the following topics: atom probe field ion microscopy (APFIM), field ion microscopy (FIM), field emission (FE), ion sources, and field desorption mass microscopy (FDMM). Technique-orientated studies and applications are included. The bibliography covers the period 1990. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications. To reduce the length of this document, the references have been reduced to the minimum necessary to locate the articles. The references, listed alphabetically by authors, are subdivided into the categories listed in paragraph one above. An Addendum of references missed in previous bibliographies is included.

  10. Ion mobility sensor system

    DOEpatents

    Xu, Jun; Watson, David B.; Whitten, William B.

    2013-01-22

    An ion mobility sensor system including an ion mobility spectrometer and a differential mobility spectrometer coupled to the ion mobility spectrometer. The ion mobility spectrometer has a first chamber having first end and a second end extending along a first direction, and a first electrode system that generates a constant electric field parallel to the first direction. The differential mobility spectrometer includes a second chamber having a third end and a fourth end configured such that a fluid may flow in a second direction from the third end to the fourth end, and a second electrode system that generates an asymmetric electric field within an interior of the second chamber. Additionally, the ion mobility spectrometer and the differential mobility spectrometer form an interface region. Also, the first end and the third end are positioned facing one another so that the constant electric field enters the third end and overlaps the fluid flowing in the second direction.

  11. The nonlinear optical rectification and second harmonic generation in asymmetrical Gaussian potential quantum well: Effects of hydrostatic pressure, temperature and magnetic field

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Zou, LiLi; Liu, Chenglin; Zhang, Zhi-Hai; Yuan, Jian-Hui

    2016-03-01

    In the present work, the effects of hydrostatic pressure, temperature, and magnetic field on the nonlinear optical rectification (OR) and second-harmonic generation (SHG) in asymmetrical Gaussian potential quantum well (QW) have been investigated theoretically. Here, the expressions for the optical properties are calculated by the compact-density-matrix approach and iterative method. Simultaneously, the energy eigenvalues and their corresponding eigenfunctions have been obtained by using the finite difference method. The energy eigenvalues and the shape of the confined potential are modulated by the hydrostatic pressure, temperature, and magnetic field. So the results of a number of numerical experiments indicate that the nonlinear OR and SHG strongly depends on the hydrostatic pressure, temperature, and magnetic field. This gives a new degree of freedom in various device applications based on the intersubband transitions of electrons.

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

    NASA Astrophysics Data System (ADS)

    Lejeune, A.; Bourgeois, G.; Mazouffre, S.

    2012-07-01

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

  13. Measurement of deposition rate and ion energy distribution in a pulsed dc magnetron sputtering system using a retarding field analyzer with embedded quartz crystal microbalance.

    PubMed

    Sharma, Shailesh; Gahan, David; Scullin, Paul; Doyle, James; Lennon, Jj; Vijayaraghavan, Rajani K; Daniels, Stephen; Hopkins, M B

    2016-04-01

    A compact retarding field analyzer with embedded quartz crystal microbalance has been developed to measure deposition rate, ionized flux fraction, and ion energy distribution arriving at the substrate location. The sensor can be placed on grounded, electrically floating, or radio frequency (rf) biased electrodes. A calibration method is presented to compensate for temperature effects in the quartz crystal. The metal deposition rate, metal ionization fraction, and energy distribution of the ions arriving at the substrate location are investigated in an asymmetric bipolar pulsed dc magnetron sputtering reactor under grounded, floating, and rf biased conditions. The diagnostic presented in this research work does not suffer from complications caused by water cooling arrangements to maintain constant temperature and is an attractive technique for characterizing a thin film deposition system.

  14. The onset of ion heating during magnetic reconnection with a strong guide field

    SciTech Connect

    Drake, J. F.; Swisdak, M.

    2014-07-15

    The onset of the acceleration of ions during magnetic reconnection is explored via particle-in-cell simulations in the limit of a strong ambient guide field that self-consistently and simultaneously follow the motions of protons and α particles. Heating parallel to the local magnetic field during reconnection with a guide field is strongly reduced compared with the reconnection of anti-parallel magnetic fields. The dominant heating of thermal ions during guide field reconnection results from pickup behavior of ions during their entry into reconnection exhausts and dominantly produces heating perpendicular rather than parallel to the local magnetic field. Pickup behavior requires that the ion transit time across the exhaust boundary (with a transverse scale of the order of the ion sound Larmor radius) be short compared with the ion cyclotron period. This translates into a threshold in the strength of reconnecting magnetic field that favors the heating of ions with high mass-to-charge. A simulation with a broad initial current layer produces a reconnecting system in which the amplitude of the reconnecting magnetic field just upstream of the dissipation region increases with time as reconnection proceeds. The sharp onset of perpendicular heating when the pickup threshold is crossed is documented. A comparison of the time variation of the parallel and perpendicular ion heating with that predicted based on the strength of the reconnecting field establishes the scaling of ion heating with ambient parameters both below and above the pickup threshold. The relevance to observations of ion heating in the solar corona is discussed.

  15. Ion trap simulations of quantum fields in an expanding universe.

    PubMed

    Alsing, Paul M; Dowling, Jonathan P; Milburn, G J

    2005-06-10

    We propose an experiment in which the phonon excitation of ion(s) in a trap, with a trap frequency exponentially modulated at rate kappa, exhibits a thermal spectrum with an "Unruh" temperature given by k(B)T=Planck kappa. We discuss the similarities of this experiment to the response of detectors in a de Sitter universe and the usual Unruh effect for uniformly accelerated detectors. We demonstrate a new Unruh effect for detectors that respond to antinormally ordered moments using the ion's first blue sideband transition.

  16. Confinement and dynamics of neutral beam injected fast ions in the MST Reversed Field Pinch

    NASA Astrophysics Data System (ADS)

    Liu, D.; Almagri, F.; Anderson, J. K.; den Hartog, D. J.; Nornberg, M. D.; Sarff, J. S.; Waksman, J.; Fiksel, G.; Deichuli, P.; Davydenko, V. I.; Ivanov, A. A.; Polosatkin, S. V.; Stupishin, N.; Andre, R.; McCune, D.

    2010-11-01

    The new 1MW neutral beam injector (97% H, 3% D) on MST provides a good test-bed for study of fast ions in the RFP. Analysis of the D-D fusion neutron flux decay at beam turn-off reveals that the confinement time of the fast ions is at least 10 ms, ten-fold larger than the thermal conferment times for particles and energy in standard stochastic plasmas. Also, the fast ion confinement increases with magnetic field strength. Dependence of fast ion confinement on plasma parameters, beam energy, and injection direction will be characterized and compared with TRANSP simulations. In addition, an advanced neutral particle analyzer and a prototype of fast ion charge exchange spectroscopy are under construction to measure neutralized fast ions and induced Doppler-shifted Hα light, respectively, thereby resolving fast ion density and energy distribution. Initial measurements of fast-ion dynamics during magnetic reconnection events will be presented.

  17. Radioelectric asymmetric conveyed fields and human adipose-derived stem cells obtained with a nonenzymatic method and device: a novel approach to multipotency.

    PubMed

    Maioli, Margherita; Rinaldi, Salvatore; Santaniello, Sara; Castagna, Alessandro; Pigliaru, Gianfranco; Delitala, Alessandro; Bianchi, Francesca; Tremolada, Carlo; Fontani, Vania; Ventura, Carlo

    2014-01-01

    Human adipose-derived stem cells (hASCs) have been recently proposed as a suitable tool for regenerative therapies for their simple isolation procedure and high proliferative capability in culture. Although hASCs can be committed into different lineages in vitro, the differentiation is a low-yield and often incomplete process. We have recently developed a novel nonenzymatic method and device, named Lipogems, to obtain a fat tissue derivative highly enriched in pericytes/mesenchymal stem cells by mild mechanical forces from human lipoaspirates. When compared to enzymatically dissociated cells, Lipogems-derived hASCs exhibited enhanced transcription of vasculogenic genes in response to provasculogenic molecules, suggesting that these cells may be amenable for further optimization of their multipotency. Here we exposed Lipogems-derived hASCs to a radioelectric asymmetric conveyer (REAC), an innovative device asymmetrically conveying radioelectric fields, affording both enhanced differentiating profiles in mouse embryonic stem cells and efficient direct multilineage reprogramming in human skin fibroblasts. We show that specific REAC exposure remarkably enhanced the transcription of prodynorphin, GATA-4, Nkx-2.5, VEGF, HGF, vWF, neurogenin-1, and myoD, indicating the commitment toward cardiac, vascular, neuronal, and skeletal muscle lineages, as inferred by the overexpression of a program of targeted marker proteins. REAC exposure also finely tuned the expression of stemness-related genes, including NANOG, SOX-2, and OCT-4. Noteworthy, the REAC-induced responses were fashioned at a significantly higher extent in Lipogems-derived than in enzymatically dissociated hASCs. Therefore, REAC-mediated interplay between radioelectric asymmetrically conveyed fields and Lipogems-derived hASCs appears to involve the generation of an ideal "milieu" to optimize multipotency expression from human adult stem cells in view of potential improvement of future cell therapy efforts.

  18. Measurements accounting for the impediment of ion spin-up in rotating magnetic field driven field reversed configurations

    SciTech Connect

    Deards, C. L.; Hoffman, A. L.; Steinhauer, L. C.

    2011-11-15

    Improved vacuum hygiene, wall conditioning, and reduced recycling in the rotating magnetic field (RMF) driven translation, confinement, and sustainment-upgrade (TCSU) field reversed configuration experiment have made possible a more accurate assessment of the forces affecting ion spin-up. This issue is critical in plasmas sustained by RMFs, such as TCSU since ion spin-up can substantially reduce or cancel the RMF current drive effect. Several diagnostics are brought to bear, including a 3-axis translatable magnetic probe allowing the first experimental measurement of the end shorting effect. These results show that the ion rotation is determined by a balance between electron-ion friction, the end shorting effect, and ion drag against neutrals.

  19. Dynamics of ions in a water drop using the AMOEBA polarizable force field

    NASA Astrophysics Data System (ADS)

    Thaunay, Florian; Ohanessian, Gilles; Clavaguéra, Carine

    2017-03-01

    Various ions carrying a charge from -2 to +3 were confined in a drop of 100 water molecules as a way to model coordination properties inside the cluster and at the interface. The behavior of the ions has been followed by molecular dynamics with the AMOEBA polarizable force field. Multiply charged ions and small singly charged ions are found to lie inside the droplet, while bigger monovalent ions sit near the surface. The results provide a coherent picture of average structural properties as well as residence times for which a general trend is proposed, especially for the anions.

  20. A single-atom sharp iridium tip as an emitter of gas field ion sources

    NASA Astrophysics Data System (ADS)

    Kuo, Hong-Shi; Hwang, Ing-Shouh; Fu, Tsu-Yi; Hwang, Ying-Siang; Lu, Yi-Hsien; Lin, Chun-Yueh; Hou, Jin-Long; Tsong, Tien T.

    2009-08-01

    We report a reliable method for preparing a pure Ir single-atom tip by thermal treatment in oxygen. The atomic structure of the tip apex and its ion emission characteristics are investigated with field ion microscopy. We have shown that the Ir single-atom tip can be a good field ion emitter, capable of emitting a variety of gas ion beams, such as He+, H2+, N2+, and O2+, with high brightness and stability. In addition, this tip can easily be maintained and regenerated in vacuum, ensuring it has sufficient lifetime for practical applications.

  1. Ionic force field optimization based on single-ion and ion-pair solvation properties: Going beyond standard mixing rules

    NASA Astrophysics Data System (ADS)

    Fyta, Maria; Netz, Roland R.

    2012-03-01

    Using molecular dynamics (MD) simulations in conjunction with the SPC/E water model, we optimize ionic force-field parameters for seven different halide and alkali ions, considering a total of eight ion-pairs. Our strategy is based on simultaneous optimizing single-ion and ion-pair properties, i.e., we first fix ion-water parameters based on single-ion solvation free energies, and in a second step determine the cation-anion interaction parameters (traditionally given by mixing or combination rules) based on the Kirkwood-Buff theory without modification of the ion-water interaction parameters. In doing so, we have introduced scaling factors for the cation-anion Lennard-Jones (LJ) interaction that quantify deviations from the standard mixing rules. For the rather size-symmetric salt solutions involving bromide and chloride ions, the standard mixing rules work fine. On the other hand, for the iodide and fluoride solutions, corresponding to the largest and smallest anion considered in this work, a rescaling of the mixing rules was necessary. For iodide, the experimental activities suggest more tightly bound ion pairing than given by the standard mixing rules, which is achieved in simulations by reducing the scaling factor of the cation-anion LJ energy. For fluoride, the situation is different and the simulations show too large attraction between fluoride and cations when compared with experimental data. For NaF, the situation can be rectified by increasing the cation-anion LJ energy. For KF, it proves necessary to increase the effective cation-anion Lennard-Jones diameter. The optimization strategy outlined in this work can be easily adapted to different kinds of ions.

  2. Large field-of-view asymmetric masks for high-energy x-ray phase imaging with standard x-ray tube

    NASA Astrophysics Data System (ADS)

    Endrizzi, M.; Astolfo, A.; Price, B.; Haig, I.; Olivo, A.

    2016-09-01

    We report on a new approach to large field-of-view laboratory-based X-ray phase-contrast imaging. The method is based upon the asymmetric mask design that enables the retrieval of the absorption, refraction and ultra-small- angle scattering properties of the sample without the need to move any component of the imaging system. The sample is scanned through the imaging system, which also removes possible aliasing problems that might arise from partial sample illumination when using the edge illumination technique. This concept can be extended to any desired number of apertures providing, at the same time, intensity projections at complementary illumination conditions. Experimental data simultaneously acquired at seven different illumination fractions are presented along with the results obtained from a numerical model that incorporates the actual detector performance. The ultimate shape of the illumination function is shown to be significantly dependent on these detector-specific characteristics. Based on this concept, a large field-of-view system was designed, which is also capable to cope with relatively high (100 kVp) X-ray energies. The imaging system obtained in this way, where the asymmetric mask design enables the data to be collected without moving any element of the instrumentation, adapts particularly well to those situations in medical, industrial and security imaging where the sample has to be scanned through the system.

  3. Transport of ions in presence of induced electric field and electrostatic turbulence - Source of ions injected into ring current

    NASA Technical Reports Server (NTRS)

    Cladis, J. B.; Francis, W. E.

    1985-01-01

    The transport of ions from the polar ionosphere to the inner magnetosphere during stormtime conditions has been computed using a Monte Carlo diffusion code. The effect of the electrostatic turbulence assumed to be present during the substorm expansion phase was simulated by a process that accelerated the ions stochastically perpendicular to the magnetic field with a diffusion coefficient proportional to the energization rate of the ions by the induced electric field. This diffusion process was continued as the ions were convected from the plasma sheet boundary layer to the double-spiral injection boundary. Inward of the injection boundary, the ions were convected adiabatically. By using as input an O(+) flux of 2.8 x 10 to the 8th per sq cm per s (w greater than 10 eV) and an H(+) flux of 5.5 x 10 to the 8th per sq cm per s (w greater than 0.63 eV), the computed distribution functions of the ions in the ring current were found to be in good agreement, over a wide range in L (4 to 8), with measurements made with the ISEE-1 satellite during a storm. This O(+) flux and a large part of the H(+) flux are consistent with the DE satellite measurements of the polar ionospheric outflow during disturbed times.

  4. Transport of ions in presence of induced electric field and electrostatic turbulence - source of ions injected into ring current

    SciTech Connect

    Cladis, J.B.; Francis, W.E.

    1985-01-01

    The transport of ions from the polar ionosphere to the inner magnetosphere during stormtime conditions has been computed using a Monte Carlo diffusion code. The effect of the electrostatic turbulence assumed to be present during the substorm expansion phase was simulated by a process that accelerated the ions stochastically perpendicular to the magnetic field with a diffusion coefficient proportional to the energization rate of the ions by the induced electric field. This diffusion process was continued as the ions were convected from the plasma sheet boundary layer to the double-spiral injection boundary. Inward of the injection boundary, the ions were convected adiabatically. By using as input an O(+) flux of 2.8 x 10 to the 8th per sq cm per s (w greater than 10 eV) and an H(+) flux of 5.5 x 10 to the 8th per sq cm per s (w greater than 0.63 eV), the computed distribution functions of the ions in the ring current were found to be in good agreement, over a wide range in L (4 to 8), with measurements made with the ISEE-1 satellite during a storm. This O(+) flux and a large part of the H(+) flux are consistent with the DE satellite measurements of the polar ionospheric outflow during disturbed times. 19 references.

  5. Atmospheric Pressure Ion Source Development: Experimental Validation of Simulated Ion Trajectories within Complex Flow and Electrical Fields

    NASA Astrophysics Data System (ADS)

    Wissdorf, Walter; Lorenz, Matthias; Pöhler, Thorsten; Hönen, Herwart; Benter, Thorsten

    2013-10-01

    Three-dimensionally (3D) resolved ion trajectory calculations within the complex viscous flow field of an atmospheric pressure ion source are presented. The model calculations are validated with spatially resolved measurements of the relative sensitivity distribution within the source enclosure, referred to as the distribution of ion acceptance (DIA) of the mass analyzer. In previous work, we have shown that the DIA shapes as well as the maximum signal strengths strongly depend on ion source operational parameters such as gas flows and temperatures, as well as electrical field gradients established by various source electrode potentials (e.g., capillary inlet port potential and spray shield potential). In all cases studied, distinct, reproducible, and, to some extent, surprising DIA patterns were observed. We have thus attempted to model selected experimental operational source modes (called operational points) using a validated computational flow dynamics derived 3D-velocity field as an input parameter set for SIMION/SDS, along with a suite of custom software for data analysis and parameter set processing. Despite the complexity of the system, the modeling results reproduce the experimentally derived DIA unexpectedly well. It is concluded that SIMION/SDS in combination with accurate computational fluid dynamics (CFD) input data and adequate analysis software is capable of successfully modeling operational points of an atmospheric pressure ion (API) source. This approach should be very useful in the computer-aided design of future API sources.

  6. Observations of the Ion Signatures of Double Merging and the Formation of Newly Closed Field Lines

    NASA Technical Reports Server (NTRS)

    Chandler, Michael O.; Avanov, Levon A.; Craven, Paul D.

    2007-01-01

    Observations from the Polar spacecraft, taken during a period of northward interplanetary magnetic field (IMF) show magnetosheath ions within the magnetosphere with velocity distributions resulting from multiple merging sites along the same field line. The observations from the TIDE instrument show two separate ion energy-time dispersions that are attributed to two widely separated (-20Re) merging sites. Estimates of the initial merging times show that they occurred nearly simultaneously (within 5 minutes.) Along with these populations, cold, ionospheric ions were observed counterstreaming along the field lines. The presence of such ions is evidence that these field lines are connected to the ionosphere on both ends. These results are consistent with the hypothesis that double merging can produce closed field lines populated by solar wind plasma. While the merging sites cannot be unambiguously located, the observations and analyses favor one site poleward of the northern cusp and a second site at low latitudes.

  7. Ion Trap Electric Field Characterization Using Slab Coupled Optical Fiber Sensors

    NASA Astrophysics Data System (ADS)

    Chadderdon, Spencer; Shumway, LeGrand; Powell, Andrew; Li, Ailin; Austin, Daniel E.; Hawkins, Aaron R.; Selfridge, Richard H.; Schultz, Stephen M.

    2014-09-01

    This paper presents a method for characterizing electric field profiles of radio frequency (rf) quadrupole ion trap structures using sensors based on slab coupled optical-fiber sensor (SCOS) technology. The all-dielectric and virtually optical fiber-sized SCOS fits within the compact environment required for ion traps and is able to distinguish electric field orientation and amplitude with minimal perturbation. Measurement of the fields offers insight into the functionality of traps, which may not be obtainable solely by performing simulations. The SCOS accurately mapped the well-known field profiles within a commercially available three-dimensional quadrupole ion trap (Paul trap). The results of this test allowed the SCOS to map the more complicated fields within the coaxial ion trap with a high degree of confidence as to the accuracy of the measurement. [Figure not available: see fulltext.

  8. Ion flux from vacuum arc cathode spots in the absence and presence of a magnetic field

    SciTech Connect

    Anders, Andre; Yushkov, George Yu.

    2001-10-02

    Because plasma production at vacuum cathode spots is approximately proportional to the arc current, arc current modulation can be used to generate ion current modulation that can be detected far from the spot using a negatively biased ion collector. The drift time to the ion detector can used to determine kinetic ion energies. A very wide range of cathode materials have been used. It has been found that the kinetic ion energy is higher at the beginning of each discharge and approximately constant after 150 {micro}s. The kinetic energy is correlated with the arc voltage and the cohesive energy of the cathode material. The ion erosion rate has in inverse relation to the cohesive energy, enhancing the effect that the power input per plasma particle correlates with the cohesive energy of the cathode material. The influence of three magnetic field configurations on the kinetic energy has been investigated. Generally, a magnetic field increases the plasma impedance, arc burning voltage, and kinetic ion energy. However, if the plasma is produced in a region of low field strength and streaming into a region of higher field strength, the velocity may decrease due to the mirror effect. A magnetic field can increase the plasma temperature but may reduce the density gradients by preventing free expansion into vacuum. Therefore, depending on the configuration, a magnetic field may increase or decrease the kinetic energy of ions. Additionally, the angular distribution of the ion flux and ion kinetic energy has been investigated in the absence of an external magnetic field. The result can be fitted by a superposition of an isotropic and a cosine distribution.

  9. Ion exchange with the solar wind for planets with negligible intrinsic magnetic fields

    NASA Technical Reports Server (NTRS)

    Nisbet, J. S.

    1979-01-01

    The exchange of ions between the ionosphere of a planet with negligible intrinsic magnetic field, and the solar wind is examined. It is suggested that a balance exists between the outflow of ionospheric ions at the plasmapause and ions from the solar wind in a restricted region close to the subsolar point. This results in a current system towards the subsolar point on the surface of the ionopause and a toroidal magnetic field. Simple calculations are made of the current and field configuration that might result from the system for conditions similar to those encountered on the Viking 1 and 2 transits of the Mars ionosphere.

  10. A new polarizable force field for alkali and halide ions

    SciTech Connect

    Kiss, Péter T.; Baranyai, András

    2014-09-21

    We developed transferable potentials for alkali and halide ions which are consistent with our recent model of water [P. T. Kiss and A. Baranyai, J. Chem. Phys. 138, 204507 (2013)]. Following the approach used for the water potential, we applied Gaussian charge distributions, exponential repulsion, and r{sup −6} attraction. One of the two charges of the ions is fixed to the center of the particle, while the other is connected to this charge by a harmonic spring to express polarization. Polarizability is taken from quantum chemical calculations. The repulsion between different species is expressed by the combining rule of Kong [J. Chem. Phys. 59, 2464 (1972)]. Our primary target was the hydration free energy of ions which is correct within the error of calculations. We calculated water-ion clusters up to 6 water molecules, and, as a crosscheck, we determined the density and internal energy of alkali-halide crystals at ambient conditions with acceptable accuracy. The structure of hydrated ions was also discussed.

  11. Highly Charged Ions from Laser-Cluster Interactions: Local-Field-Enhanced Impact Ionization and Frustrated Electron-Ion Recombination

    SciTech Connect

    Fennel, Thomas; Ramunno, Lora; Brabec, Thomas

    2007-12-07

    Our molecular dynamics analysis of Xe{sub 147-5083} clusters identifies two mechanisms that contribute to the yet unexplained observation of extremely highly charged ions in intense laser cluster experiments. First, electron impact ionization is enhanced by the local cluster electric field, increasing the highest charge states by up to 40%; a corresponding theoretical method is developed. Second, electron-ion recombination after the laser pulse is frustrated by acceleration electric fields typically used in ion detectors. This increases the highest charge states by up to 90%, as compared to the usual assumption of total recombination of all cluster-bound electrons. Both effects together augment the highest charge states by up to 120%, in reasonable agreement with experiments.

  12. Highly charged ions from laser-cluster interactions: local-field-enhanced impact ionization and frustrated electron-ion recombination.

    PubMed

    Fennel, Thomas; Ramunno, Lora; Brabec, Thomas

    2007-12-07

    Our molecular dynamics analysis of Xe_{147-5083} clusters identifies two mechanisms that contribute to the yet unexplained observation of extremely highly charged ions in intense laser cluster experiments. First, electron impact ionization is enhanced by the local cluster electric field, increasing the highest charge states by up to 40%; a corresponding theoretical method is developed. Second, electron-ion recombination after the laser pulse is frustrated by acceleration electric fields typically used in ion detectors. This increases the highest charge states by up to 90%, as compared to the usual assumption of total recombination of all cluster-bound electrons. Both effects together augment the highest charge states by up to 120%, in reasonable agreement with experiments.

  13. Use of axially symmetric electrostatic fields for ion-beam focussing

    SciTech Connect

    Colton, E.; Kelly, J.C.

    1983-01-01

    The 1/r electric field obtained between charged coaxial cylindrical electrodes is useful for focusing hollow ion beams in ion-microprobe and ion- implantation applications. The focusing strengths are mass-independent at nonrelativistic energies. Focused-particle densities can be enhanced by using a diverging-converging pair to flatten the dependence of focal length on incoming-beam radius. Transport of 425-keV and 1-MeV protons has been simulated and results are presented.

  14. Modified ion-acoustic solitary waves in plasmas with field-aligned shear flows

    SciTech Connect

    Saleem, H.; Haque, Q.

    2015-08-15

    The nonlinear dynamics of ion-acoustic waves is investigated in a plasma having field-aligned shear flow. A Korteweg-deVries-type nonlinear equation for a modified ion-acoustic wave is obtained which admits a single pulse soliton solution. The theoretical result has been applied to solar wind plasma at 1 AU for illustration.

  15. Electrolyte-gated organic field-effect transistor for selective reversible ion detection.

    PubMed

    Schmoltner, Kerstin; Kofler, Johannes; Klug, Andreas; List-Kratochvil, Emil J W

    2013-12-17

    An ion-sensitive electrolyte-gated organic field-effect transistor for selective and reversible detection of sodium (Na(+) ) down to 10(-6) M is presented. The inherent low voltage - high current operation of these transistors in combination with a state-of-the-art ion-selective membrane proves to be a novel, versatile modular sensor platform.

  16. Dynamics of the ion flow in a discharge with crossed E and H fields

    SciTech Connect

    Movsesyants, Yu. B. Tyuryukanov, P. M.

    2011-12-15

    The experimental and theoretical results of the investigation of an ion flow in a low-pressure discharge in crossed E and H fields are presented. It is shown that two quasi-stationary current states can be realized in a transonic collisionless flow of ions in a cold plasma.

  17. Catalytic Asymmetric Bromocyclization of Polyenes.

    PubMed

    Samanta, Ramesh C; Yamamoto, Hisashi

    2017-02-01

    The first catalytic asymmetric bromonium ion-induced polyene cyclization has been achieved by using a chiral BINOL-derived thiophosphoramide catalyst and 1,3-dibromo-5,5-dimethylhydantoin as an electrophilic bromine source. Bromocyclization products are obtained in high yields, with good enantiomeric ratios and high diastereoselectivity, and are abundantly found as scaffolds in natural products.

  18. On the Electron Dynamics during Rapid Asymmetric Magnetic Island Coalescence: Insights on the Electrons Agyrotropy with the Presence of a Guide Field

    NASA Astrophysics Data System (ADS)

    Cazzola, Emanuele; Lapenta, Giovanni; Innocenti, Maria Elena; Goldman, Martin; Newman, David; Markidis, Stefano

    2016-04-01

    The work presents a fully kinetic analysis of the electrons dynamics during rapid island coalescence in asymmetric magnetic reconnection, especially focused on the comparison between the case with and with no initial guide field. Formation and growth of the islands are caused by an intentionally unstable initial configuration across the current sheet with the same asymmetric profiles as those traditionally proposed in the literature (e.g. Pritchett, 2008). Particular attentions is given to the different evolution of the presumed reconnection sites. Three main regions are eventually identified, named by X-, D- and M-regions, which describe, respectively, the regions featuring a traditional reconnection event, those showing an opposite behavior with respect to the former and the reconnection regions occurring between two magnetic islands (Cazzola et al., 2015). Further analysis is mainly addressed to evaluate both the electrons departure from the isotropic and gyrotropic behavior. Whether the first quantity has been clearly established and confirmed by observations, the latter has always appeared of difficult interpretation, and an ultimate accepted method on how to render it from PIC simulations still seems far to be achieved. In light of the upcoming data from the freshly launched MMS NASA mission, outcomes from some of the main techniques to spot agyrotropic regions are here compared to highligh the presence of possible relevant differences (Scudder and Daughton, 2008; Swisdak, 2015). References [1] P. Pritchett, "Collisionless magnetic reconnection in an asymmetric current sheet," Journal of Geophysical Research: Space Physics (1978-2012), vol. 113, no. A6, 2008. [2] E. Cazzola, M. E. Innocenti, S. Markidis, M. V. Goldman, D. L. Newman, and G. Lapenta, "On the electron dynamics during island coalescence in asymmetric magnetic reconnection," Physics of Plasmas (1994-present), vol. 22, no. 9, p. 092901, 2015. [3] J. Scudder and W. Daughton, "Illuminating electron

  19. A field reciprocal transplant experiment reveals asymmetric costs of migration between lake and river ecotypes of three-spined sticklebacks (Gasterosteus aculeatus).

    PubMed

    Kaufmann, Joshka; Lenz, Tobias L; Kalbe, Martin; Milinski, Manfred; Eizaguirre, Christophe

    2017-02-17

    Theory of local adaptation predicts that non-adapted migrants will suffer increased costs compared to local residents. Ultimately this process can result in the reduction of gene flow and culminate in speciation. Here, we experimentally investigated the relative fitness of migrants in foreign habitats, focusing on diverging lake and river ecotypes of three-spined sticklebacks. A reciprocal transplant experiment performed in the field revealed asymmetric costs of migration: while mortality of river fish was increased under lake conditions, lake migrants suffered from reduced growth relative to river residents. Selection against migrants thus involved different traits in each habitat but generally contributed to bidirectional reduction in gene flow. Focusing particularly on the parasitic environments, migrant fish differed from resident fish in the parasite community they harboured. This pattern correlated with both cellular phenotypes of innate immunity as well as with allelic variation at the genes of the major histocompatibility complex. In addition to showing the costs of migration in three-spined sticklebacks, this study highlights the role of asymmetric selection particularly from parasitism in genotype sorting and in the emergence of local adaptation. This article is protected by copyright. All rights reserved.

  20. Decomposition of cyclohexane ion induced by intense femtosecond laser fields by ion-trap time-of-flight mass spectrometry

    SciTech Connect

    Yamazaki, Takao; Watanabe, Yusuke; Kanya, Reika; Yamanouchi, Kaoru

    2016-01-14

    Decomposition of cyclohexane cations induced by intense femtosecond laser fields at the wavelength of 800 nm is investigated by ion-trap time-of-flight mass spectrometry in which cyclohexane cations C{sub 6}H{sub 12}{sup +} stored in an ion trap are irradiated with intense femtosecond laser pulses and the generated fragment ions are recorded by time-of-flight mass spectrometry. The various fragment ion species, C{sub 5}H{sub n}{sup +} (n = 7, 9), C{sub 4}H{sub n}{sup +} (n = 5–8), C{sub 3}H{sub n}{sup +} (n = 3–7), C{sub 2}H{sub n}{sup +} (n = 2–6), and CH{sub 3}{sup +}, identified in the mass spectra show that decomposition of C{sub 6}H{sub 12}{sup +} proceeds efficiently by the photo-irradiation. From the laser intensity dependences of the yields of the fragment ion species, the numbers of photons required for producing the respective fragment ions are estimated.

  1. Dynamic characteristics of double-barrier nanostructures with asymmetric barriers of finite height and widths in a strong ac electric field

    SciTech Connect

    Chuenkov, V. A.

    2013-12-15

    The theory of the interaction of a monoenergetic flow of injected electrons with a strong high-frequency ac electric field in resonant-tunneling diode (RTD) structures with asymmetric barriers of finite height and width is generalized. In the quasi-classical approximation, electron wavefunctions and tunneling functions in the quantum well and barriers are found. Analytical expressions for polarization currents in RTDs are derived in both the general case and in a number of limiting cases. It is shown that the polarization currents and radiation power in RTDs with asymmetric barriers strongly depend on the ratio of the probabilities of electron tunneling through the emitter and collector barriers. In the quantum mode, when δ = ε − ε{sub r} = ħω ≪ Γ (ε is the energy of electrons injected in the RTD, ħ is Planck’s constant, ω is the ac field frequency, ε{sub r} and Γ are the energy and width of the resonance level, respectively), the active polarization current in a field of E ≈ 2.8ħω/ea (e is the electron charge and a is the quantum-well width) reaches a maximum equal in magnitude to 84% of the direct resonant current, if the probability of electron tunneling through the emitter barrier is much higher than that through the collector barrier. The radiation-generation power at frequencies of ω = 10{sup 12}–10{sup 13} s{sup −1} can reach 10{sup 5}–10{sup 6} W/cm{sup 2} in this case.

  2. Asymmetrical Capacitors for Propulsion

    NASA Technical Reports Server (NTRS)

    Canning, Francis X.; Melcher, Cory; Winet, Edwin

    2004-01-01

    Asymmetrical Capacitor Thrusters have been proposed as a source of propulsion. For over eighty years, it has been known that a thrust results when a high voltage is placed across an asymmetrical capacitor, when that voltage causes a leakage current to flow. However, there is surprisingly little experimental or theoretical data explaining this effect. This paper reports on the results of tests of several Asymmetrical Capacitor Thrusters (ACTs). The thrust they produce has been measured for various voltages, polarities, and ground configurations and their radiation in the VHF range has been recorded. These tests were performed at atmospheric pressure and at various reduced pressures. A simple model for the thrust was developed. The model assumed the thrust was due to electrostatic forces on the leakage current flowing across the capacitor. It was further assumed that this current involves charged ions which undergo multiple collisions with air. These collisions transfer momentum. All of the measured data was consistent with this model. Many configurations were tested, and the results suggest general design principles for ACTs to be used for a variety of purposes.

  3. Series-field-coil ion beam diode experiment and numerical simulation

    SciTech Connect

    Mendel, C.W. Jr.; Quintenz, J.P.; Zagar, D.M.; Johnson, P.R.; Anderson, R.J.; Widner, M.M.

    1984-08-01

    An experiment with a series-field-coil intense ion beam diode operating at the 1.6-MV, 0.8-TW level is described. The diode operates in the extraction mode with a 20-cm focal length. The diode design procedure is described together with some of the essential ion diode theory used in this design process. The experiment produced a well-focused ion beam while verifying some of the theoretical assumptions about ion diodes of this type. The experimental results are compared with numerical computer simulations and excellent agreement is obtained.

  4. Effect of mobile ions on the electric field needed to orient charged diblock copolymer thin films

    SciTech Connect

    Dehghan, Ashkan; Shi, An-Chang; Schick, M.

    2015-10-07

    We examine the behavior of lamellar phases of charged/neutral diblock copolymer thin films containing mobile ions in the presence of an external electric field. We employ self-consistent field theory and focus on the aligning effect of the electric field on the lamellae. Of particular interest are the effects of the mobile ions on the critical field, the value required to reorient the lamellae from the parallel configuration favored by the surface interaction to the perpendicular orientation favored by the field. We find that the critical field depends strongly on whether the neutral or charged species is favored by the substrates. In the case in which the neutral species is favored, the addition of charges decreases the critical electric field significantly. The effect is greater when the mobile ions are confined to the charged lamellae. In contrast, when the charged species is favored by the substrate, the addition of mobile ions stabilizes the parallel configuration and thus results in an increase in the critical electric field. The presence of ions in the system introduces a new mixed phase in addition to those reported previously.

  5. Formation of field-reversed ion rings in a magnetized background plasma

    SciTech Connect

    Omelchenko, Y.A.; Sudan, R.N.

    1995-07-01

    In typical field-reversed ion ring experiments, an intense annular ion beam is injected across a magnetic cusp into neutral gas immersed in a solenoidal magnetic field. In anticipation of a new experimental thrust to create strong field-reversed ion rings the beam evolution is investigated in a preformed background plasma on a time scale greater than an ion cyclotron period, using a new two and a half-dimensional (21/2-D) hybrid, particle-in-cell (PIC) code FIRE, in which the beam and background ions are treated as macro-particles and the electrons as a massless fluid. It is shown that under appropriate conditions axial beam bunching occurs in the downstream applied field and a compact field-reversed ring is formed. It is observed that the ring is reflected in a ramped magnetic field. Upon reflection its axial velocity is very much less than that expected from a single particle model due to the transfer of the mean axial momentum to the background ions. This increases the time available to apply a pulsed mirror for trapping the ring experimentally. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  6. Water confined in the local field of ions.

    PubMed

    Kojić, Dušan; Tsenkova, Roumiana; Tomobe, Katsufumi; Yasuoka, Kenji; Yasui, Masato

    2014-12-15

    Interionic distances are shorter in concentrated ionic solutions, thus instigating the interaction and overlap of hydration shells, as ions become separated by only one or two layers of water molecules. The simultaneous interaction of water with two oppositely charged ions has, so far, only been investigated by computer simulation studies, because the isolated vibrational spectroscopic signature of these molecules remains undetected. Our combined near-infrared spectroscopic and molecular dynamics simulation studies of alkali halide solutions present a distinct spectral feature, which is highly responsive to depletion of bulk water and merging of hydration shells. The analysis of this spectral feature demonstrates that absorption trends are in good agreement with the law of matching affinities, thus providing the first successful vibrational spectroscopic treatment of this topic. Combined with commonly observed near-infrared bands, this feature provides a spectral pattern that describes some relevant aspects of ionic hydration.

  7. Fabrication 3D buried channel optical waveguide modulators on field-driven ion exchange process

    NASA Astrophysics Data System (ADS)

    Zhou, Zigang; Chen, Wenqiang; Zhu, Li; Li, Jing; Luo, Xiaoying

    2010-10-01

    A high electric field technique was developed to fabricate buried optical waveguide modulator on K9 optical glass. The 80V voltage was applied on the glass to accelerate the field-driven ion exchange process by expeditiously replacing host sodium ions in the glass with silver ions. As a result, the optical loss for optical waveguide modulator was measured using the edge coupling technique with a 0.6328μm He-Ne laser. Loss of 0.20 dB/cm was obtained for channel waveguides of 25μm in depth, relatively low for waveguides of such depth at red wavelength.

  8. Kinetic response of ionospheric ions to onset of auroral electric fields

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Kan, J. R.

    1981-01-01

    By examining the exact analytic solution of a kinetic model of collisional interaction of ionospheric ions with atmospheric neutrals in the Bhatnagar-Gross-Krook approximation, we show that the onset of intense auroral electric fields in the topside ionosphere can produce the following kinetic effects: (1) heat the bulk ionospheric ions to approximately 2 eV, thus driving them up to higher altitudes where they can be subjected to collisionless plasma processes; (2) produce a non-Maxwellian superthermal tail in the distribution function; and (3) cause the ion distribution function to be anisotropic with respect to the magnetic field with the perpendicular average thermal energy exceeding the parallel thermal energy.

  9. Kinetics of ion admixture in a native gas in an external harmonic electric field

    NASA Astrophysics Data System (ADS)

    Ender, A. Ya.; Ender, I. A.; Gerasimenko, A. B.

    2016-11-01

    We have considered the spatially homogeneous problem of the behavior of an ion admixture in a background gas after applying a harmonic electric field with arbitrary parameters for various laws of interaction of particles. The Boltzmann equation has been solved using the modified method of moments. The ion distribution function and its first moments have been analyzed. It has been shown that the universal analytic expressions for the current density and the ion energy that we derived earlier for a small field amplitude-tofrequency ratio have a considerably wider range of applications.

  10. Status of the pulsed magnetic field electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Mühle, C.; Ratzinger, U.; Bleuel, W.; Jöst, G.; Leible, K.; Schennach, S.; Wolf, B. H.

    1994-04-01

    Synchrotrons like the heavy-ion synchrotron SIS at GSI need an efficient low duty cycle injector (typical 1-pulse/s and 200-μs pulse length). To improve the peak current, an electron cyclotron resonance (ECR) ion source has been designed using a pulsed magnetic field (PuMa) to force ion extraction. We replaced the hexapole of a 10-GHz Minimafios ECR ion source by a vacuum chamber containing a water-cooled bilayered solenoid coil and a decapole permanent magnetic structure. A pulse line feeds the solenoid with a 250-μs pulse which increases the magnetic field in the minimum B region by 0.3 T. This process opens the magnetic bottle along the beam axis resulting in an extracted ion pulse. First tests of the PuMa ECR configuration in cw and pulsed operation are presented and analyzed.

  11. Ion Dynamics and Field Structure of Quasi-perpendicular Collisionless Shocks near the Critical Mach Number

    NASA Astrophysics Data System (ADS)

    Balikhin, M. A.; Malkov, M.; Sagdeev, R.; Dudnikova, G.

    2015-12-01

    The structure of subcritical (laminar) collisionless shocks has been understood long time ago. When the Mach number exceeds a critical value, some of the incident ions are reflected. This needs to be included into the description of the shock structure and entropy production at the shock front. We present an analytical model of ion reflection from a quasi-perpendicular collisionless shock and the formation of the foot region associated with this reflection. Reflected ions perturb the electrostatic and magnetic fields in the foot region which we self-consistently include in determining the fraction of reflected ions, depending on the Mach number of the shock. The subsequent motion of the shock reflected ions downstream and formation of the downstream field structure is analyzed. Models for thermalization of the downstream plasma and approaches to Rankine-Hugoniot relations will also be discussed. The obtained overall shock structure is compared with the Cluster observations.

  12. Computation of two-dimensional electric field from the ion laser induced fluorescence measurements

    SciTech Connect

    Spektor, Rostislav

    2010-09-15

    This paper presents a method of computing two-dimensional electric field from ion laser induced fluorescence (LIF) measurements in a plasma flow. The expression for the field is derived by taking velocity moments of the Boltzmann equation for ions. It was found that the pressure tensor, related to the width of the ion velocity distribution, plays a critical role in the computation of the electric field. Even with the assumption of cold ion flow, the pressure tensor contribution may be significant when velocity spread is caused by other forces. Such a situation occurs in the flow of a Hall thruster, where velocity spread is caused by the ions born at different potentials. LIF measurements of the cylindrical hall thruster plume were used to demonstrate practical application of the derived method. Whenever the pressure tensor components are small as compared to the mean ion drift velocity, the electric field calculations reduce to a simple expression given in terms of mean ion drift velocity and its divergence.

  13. Effects of external field on elastic electron-ion collision in a plasma

    NASA Astrophysics Data System (ADS)

    Na, Sang-Chul; Jung, Young-Dae

    2008-12-01

    The field effects on elastic electron-ion collision are investigated in a plasma with the presence of the external field. The eikonal method and effective interaction potential including the far-field term caused by the external field is employed to obtain the eikonal phase shift and eikonal cross section as functions of the field strength, external frequency, impact parameter, collision energy, thermal energy and Debye length. The result shows that the effect of the external field on the eikonal cross section is given by the second-order eikonal phase. In addition, the external field effects suppress the eikonal cross section as well as eikonal phase for the elastic electron-ion collision. The eikonal phase and cross section are found to be increased with an increase of the frequency of the external field. It is also shown that the eikonal cross section increases with an increase of the thermal energy and Debye length.

  14. A new analytical approach based on asymmetrical flow field-flow fractionation coupled to ultraviolet spectrometry and light scattering detection for SWCNT aqueous dispersion studies.

    PubMed

    Gigault, Julien; Grassl, Bruno; Lespes, Gaëtane

    2012-02-21

    This work demonstrates the potential of asymmetrical flow field-flow fractionation (A4F) coupled to Ultraviolet spectrometry (UV) and multi-angle light scattering (MALS) for the study of single-walled carbon nanotube (SWCNT) dispersion in aqueous solutions containing a surfactant. The results indicate that this technique is a powerful analytical tool that is able to evaluate SWCNT dispersion states in aqueous media and, more importantly, determine the presence or absence of aggregates, the numbers and sizes of different SWCNT populations and the SWCNT size distribution. Dynamic light scattering was employed to complete and demonstrate the relevance of the data that were obtained via A4F-UV-MALS. Two different anionic surfactants that are used to disperse SWCNTs were then studied. The dispersing powers of the surfactants were experimentally evaluated based on their structural organizations. This study demonstrates that surfactant concentration and sonication energy are key parameters that control the SWCNT dispersion state and SWCNT structural integrity therein.

  15. Characterization of colloidal arsenic at two abandoned gold mine sites in Nova Scotia, Canada, using asymmetric flow-field flow fractionation-inductively coupled plasma mass spectrometry.

    PubMed

    Tindale, Kathryn J; Patel, Pritesh J; Wallschläger, Dirk

    2016-11-01

    Asymmetric flow-field flow fractionation-inductively-coupled plasma-mass spectrometry was used to determine whether colloidal arsenic (As) exists in soil pore water and soil extract samples at two arsenic-contaminated abandoned gold mines (Montague and Goldenville, Nova Scotia). Colloidal arsenic was found in 12 out of the 80 collected samples (=15%), and was primarily associated with iron (Fe) in the encountered colloids. The molar Fe/As ratios indicate that the colloids in some samples appeared to be discrete iron-arsenic minerals, whereas in other samples, they were more consistent with As-rich iron (oxy)hydroxides. Up to three discrete size fractions of colloidal As were encountered in the samples, with mean colloid diameters between 6 and 14nm. The pore water samples only contained one size fraction of As-bearing colloids (around 6nm diameter), while larger As-bearing colloids were only encountered in soil extracts.

  16. Octupole degree of freedom for the critical-point candidate nucleus Sm152 in a reflection-asymmetric relativistic mean-field approach

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Li, Z. P.; Zhang, S. Q.; Meng, J.

    2010-03-01

    The potential energy surfaces of even-even Sm146-156 are investigated in the constrained reflection-asymmetric relativistic mean-field approach with parameter set PK1. It is shown that the critical-point candidate nucleus Sm152 marks the shape/phase transition not only from U(5) to SU(3) symmetry, but also from the octupole-deformed ground state in Sm150 to the quadrupole-deformed ground state in Sm154. By including the octupole degree of freedom, an energy gap near the Fermi surface for single-particle levels in Sm152 with β2=0.14~0.26 is found and the important role of the octupole deformation driving pair ν2f7/2 and ν1i13/2 is demonstrated.

  17. Electric Field-Controlled Ion Transport In TiO2 Nanochannel.

    PubMed

    Li, Dan; Jing, Wenheng; Li, Shuaiqiang; Shen, Hao; Xing, Weihong

    2015-06-03

    On the basis of biological ion channels, we constructed TiO2 membranes with rigid channels of 2.3 nm to mimic biomembranes with flexible channels; an external electric field was employed to regulate ion transport in the confined channels at a high ionic strength in the absence of electrical double layer overlap. Results show that transport rates for both Na+ and Mg2+ were decreased irrespective of the direction of the electric field. Furthermore, a voltage-gated selective ion channel was formed, the Mg2+ channel closed at -2 V, and a reversed relative electric field gradient was at the same order of the concentration gradient, whereas the Na+ with smaller Stokes radius and lower valence was less sensitive to the electric field and thus preferentially occupied and passed the channel. Thus, when an external electric field is applied, membranes with larger nanochannels have promising applications in selective separation of mixture salts at a high concentration.

  18. Ion-sensitive field effect transistors for pH and potassium ion concentration sensing: towards detection of myocardial ischemia

    NASA Astrophysics Data System (ADS)

    Rai, Pratyush; Jung, Soyoun; Ji, Taeksoo; Varadan, Vijay K.

    2008-03-01

    Ion Sensitive Field Effect Transistors (ISFETs) for sensing change in ionic concentration in biological systems can be used for detecting critical conditions like Myocardial Ischemia. Having the ability to yield steady signal characteristics can be used to observe the ionic concentration gradients which mark the onset of ischemia. Two ionic concentrations, pH and [K +], have been considered as the indicator for Myocardial Ischemia in this study. The ISFETs in this study have an organic semi-conductor film as the electronically active component. Poly-3 hexylthiophene was chosen for its compatibility to the solution processing, which is a simple and economical method of thin film fabrication. The gate electrode, which regulates the current in the active layer, has been employed as the sensor element. The devices under study here were fabricated on a flexible substrate PEN. The pH sensor was designed with the Tantalum Oxide gate dielectric as the ion selective component. The charge accumulated on the surface of the metal oxide acts as the source of the effecter electric field. The device was tested for pH values between 6.5 and 7.5, which comprises the variation observed during ischemic attack. The potassium ion sensor has got a floating gate electrode which is functionalized to be selective to potassium ion. The device was tested for potassium ion concentration between 5 and 25 mM, which constitutes the variation in extra cellular potassium ion concentration during ischemic attack. The device incorporated a monolayer of Valinomycin, a potassium specific ionophore, on top of the gate electrode.

  19. Asymmetric Ashes

    NASA Astrophysics Data System (ADS)

    2006-11-01

    that oscillate in certain directions. Reflection or scattering of light favours certain orientations of the electric and magnetic fields over others. This is why polarising sunglasses can filter out the glint of sunlight reflected off a pond. When light scatters through the expanding debris of a supernova, it retains information about the orientation of the scattering layers. If the supernova is spherically symmetric, all orientations will be present equally and will average out, so there will be no net polarisation. If, however, the gas shell is not round, a slight net polarisation will be imprinted on the light. This is what broad-band polarimetry can accomplish. If additional spectral information is available ('spectro-polarimetry'), one can determine whether the asymmetry is in the continuum light or in some spectral lines. In the case of the Type Ia supernovae, the astronomers found that the continuum polarisation is very small so that the overall shape of the explosion is crudely spherical. But the much larger polarization in strongly blue-shifted spectral lines evidences the presence, in the outer regions, of fast moving clumps with peculiar chemical composition. "Our study reveals that explosions of Type Ia supernovae are really three-dimensional phenomena," says Dietrich Baade. "The outer regions of the blast cloud is asymmetric, with different materials found in 'clumps', while the inner regions are smooth." "This study was possible because polarimetry could unfold its full strength thanks to the light-collecting power of the Very Large Telescope and the very precise calibration of the FORS instrument," he adds. The research team first spotted this asymmetry in 2003, as part of the same observational campaign (ESO PR 23/03 and ESO PR Photo 26/05). The new, more extensive results show that the degree of polarisation and, hence, the asphericity, correlates with the intrinsic brightness of the explosion. The brighter the supernova, the smoother, or less clumpy

  20. Acceleration of ions by electric field pulses in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Artemyev, A.; Liu, J.; Angelopoulos, V.; Runov, A.

    2015-12-01

    Using THEMIS observations and test particle modeling, we investigate particle acceleration around L-shell ~7-9 in the nightside magnetosphere and demonstrate that intense (~5-15 mV/m), short-lived (<1 min) electric field pulses can effectively accelerate ions with tens of keV initial energy to hundreds of keV. This acceleration occurs because the ion gyroradius is comparable to the spatial scale of the localized electric field pulse at the leading edge of the earthward-propagating, dipolarizing flux bundles before it stops. The proposed acceleration mechanism can reproduce observed spectra of high-energy ions. We conclude that the electric field associated with dipolarizing flux bundles prior to their stoppage in the inner magnetosphere provides a natural site for intense local ion acceleration.

  1. Nonthermal ions and associated magnetic field behavior at a quasi-parallel earth's bow shock

    NASA Technical Reports Server (NTRS)

    Wilkinson, W. P.; Pardaens, A. K.; Schwartz, S. J.; Burgess, D.; Luehr, H.; Kessel, R. L.; Dunlop, M.; Farrugia, C. J.

    1993-01-01

    Attention is given to ion and magnetic field measurements at the earth's bow shock from the AMPTE-UKS and -IRM spacecraft, which were examined in high time resolution during a 45-min interval when the field remained closely aligned with the model bow shock normal. Dense ion beams were detected almost exclusively in the midst of short-duration periods of turbulent magnetic field wave activity. Many examples of propagation at large elevation angles relative to the ecliptic plane, which is inconsistent with reflection in the standard model shock configuration, were discovered. The associated waves are elliptically polarized and are preferentially left-handed in the observer's frame of reference, but are less confined to the maximum variance plane than other previously studied foreshock waves. The association of the wave activity with the ion beams suggests that the former may be triggered by an ion-driven instability, and possible candidates are discussed.

  2. Measurements of the Ion Species of Cathodic Arc Plasma in an Axial Magnetic Field

    SciTech Connect

    Oks, Efim; Anders, Andre

    2010-10-19

    Metal and gas ion species and their charge state distributions were measured for pulsed copper cathodic arcs in argon background gas in the presence of an axial magnetic field. It was found that changing the cathode position relative to anode and ion extraction system as well as increasing the gas pressure did not much affect the arc burning voltage and the related power dissipation. However, the burning voltage and power dissipation greatly increased as the magnetic field strength was increased. The fraction of metal ions and the mean ion charge state were reduced as the discharge length was increased. The observations can be explained by the combination of charge exchange collisions and electron impact ionization. They confirm that previously published data on characteristic material-dependent charge state distributions (e.g., Anders and Yushkov, J. Appl. Phys., Vol. 91, pp. 4824-4832, 2002) are not universal but valid for high vacuum conditions and the specifics of the applied magnetic fields.

  3. Steady-state hot-ion plasma produced by crossed electric and magnetic fields

    NASA Technical Reports Server (NTRS)

    Sigman, D. R.; Reinmann, J. J.

    1973-01-01

    Results of initial diagnostics on the Lewis Research Center hot-ion-plasma source (HIP-1) are reported. The mirror-contained plasma was heated by applying a radial electric field similar to that used in the ORNL burnout experiments. An electrostatic neutral particle analyzer was used to make a parametric study of ion energy distributions in both hydrogen and euterium plasmas. Ion temperatures as high as 2 keV were measured in plasmas with electron densities greater than 10 to 12th power/cu cm. The performance of the device was found to be extremely sensitive to a magnetic field. There are indications that ion heating was reduced when the size of the Larmor orbit was larger than the region of a strong radial electric field.

  4. Human perception of electric fields and ion currents associated with high-voltage DC transmission lines.

    PubMed

    Blondin, J P; Nguyen, D H; Sbeghen, J; Goulet, D; Cardinal, C; Maruvada, P S; Plante, M; Bailey, W H

    1996-01-01

    The objective of this study was to assess the ability of humans to detect the presence of DC electric field and ion currents. An exposure chamber simulating conditions present in the vicinity of high-voltage DC (HVDC) lines was designed and built for this purpose. In these experiments, the facility was used to expose observers to DC electric fields up to 50 kV/m and ion current densities up to 120 nA/m2. Forty-eight volunteers (25 women and 23 men) between the ages of 18 and 57 years served as observers. Perception of DC fields was examined by using two psychophysical methods: an adaptive staircase procedure and a rating method derived from signal-detection theory. Subjects completed three different series of observations by using each of these methods; one was conducted without ion currents, and the other two involved various combinations of electric fields and ion currents. Overall, subjects were significantly more likely to detect DC fields as the intensity increased. Observers were able to detect the presence of DC fields alone, but only at high intensities; the average threshold was 45 kV/m. Except in the most sensitive individuals, ion current densities up to 60 nA/m2 did not significantly facilitate the detection of DC fields. However, higher ion current densities were associated with a substantial lowering of sensory thresholds in a large majority of observers. Data analysis also revealed large variations in perceptual thresholds among observers. Normative data indicating DC field and ion current intensities that can be detected by 50% of all observers are provided. In addition, for the most sensitive observers, several other detection proportions were derived from the distribution of individual detection capabilities. These data can form the basis for environmental guidelines relating to the design of HVDC lines.

  5. Synthesis of nanowires via helium and neon focused ion beam induced deposition with the gas field ion microscope.

    PubMed

    Wu, H M; Stern, L A; Chen, J H; Huth, M; Schwalb, C H; Winhold, M; Porrati, F; Gonzalez, C M; Timilsina, R; Rack, P D

    2013-05-03

    The ion beam induced nanoscale synthesis of platinum nanowires using the trimethyl (methylcyclopentadienyl)platinum(IV) (MeCpPt(IV)Me3) precursor is investigated using helium and neon ion beams in the gas field ion microscope. The He(+) beam induced deposition resembles material deposited by electron beam induced deposition with very small platinum nanocrystallites suspended in a carbonaceous matrix. The He(+) deposited material composition was estimated to be 16% Pt in a matrix of amorphous carbon with a large room-temperature resistivity (∼3.5 × 10(4)-2.2 × 10(5) μΩ cm) and temperature-dependent transport behavior consistent with a granular material in the weak intergrain tunnel coupling regime. The Ne(+) deposited material has comparable composition (17%), however a much lower room-temperature resistivity (∼600-3.0 × 10(3) μΩ cm) and temperature-dependent electrical behavior representative of strong intergrain coupling. The Ne(+) deposited nanostructure has larger platinum nanoparticles and is rationalized via Monte Carlo ion-solid simulations which show that the neon energy density deposited during growth is much larger due to the smaller ion range and is dominated by nuclear stopping relative to helium which has a larger range and is dominated by electronic stopping.

  6. Kinetic simulation of capacitively coupled plasmas driven by trapezoidal asymmetric voltage pulses

    NASA Astrophysics Data System (ADS)

    Diomede, Paola; Economou, Demetre J.

    2014-06-01

    A kinetic Particle-In-Cell simulation with Monte Carlo Collisions was performed of a geometrically symmetric capacitively coupled, parallel-plate discharge in argon, driven by trapezoidal asymmetric voltage pulses with a period of 200 ns. The discharge was electrically asymmetric, making the ion energy distributions at the two electrodes different from one another. The fraction of the period (α), during which the voltage was kept at a constant (top-flat) positive value, was a critical control parameter. For the parameter range investigated, as α increased, the mean ion energy on the grounded electrode increased and the ions became more directional, whereas the opposite was found for the ions striking the powered electrode. The absolute value of the DC self-bias voltage decreased as α increased. Plasma instabilities, promoted by local double layers and electric field reversals during the time of the positive voltage excursion, were characterized by electron plasma waves launched from the sheath edge.

  7. Theoretical analysis of 1D resonant tunneling behavior in ion-enhanced cold field and thermo-field emission

    NASA Astrophysics Data System (ADS)

    Tan, Xi; Rumbach, Paul; Griggs, Nathaniel; Jensen, Kevin L.; Go, David B.

    2016-12-01

    In cold field and thermo-field emission, positive ions or adsorbates very close to the cathode surface can enhance emission current by both resonant and non-resonant processes. In this paper, resonant tunneling behavior is investigated by solving the one-dimensional Schrödinger equation in the presence of an ion, and the enhancement due to resonant processes is evaluated. Results shows that as the applied electric field increases, the resonant states move from higher to lower energies as the ion energy levels are shifted down. Conversely, as the ion position moves closer to the cathode, the resonant states shift up in energy. Further, through a simplified perturbation analysis, the general scaling of these trends can be predicted. These shifts of resonant states directly impact the emission current density, and they are especially relevant when the applied field is on the order of a few volts per nanometer (˜0.5-3 V/nm) and the ion is a few nanometers (˜0.5-3 nm) away from the cathode. Further, when the energy level for resonant emission coincides with the Fermi level of a metallic cathode, the current density is particularly enhanced. The results of this study suggest that it may be possible to control (augment/inhibit) the resonant emission current by manipulating the supply function of a cathode relative to the operating conditions of the emitter in either ion-enhanced or adsorbate-enhanced field emission, which can be applied to various plasma and electron emission technologies.

  8. Perspective on the Role of Negative Ions and Ion-Ion Plasmas in Heavy Ion Fusion Science, Magnetic Fusion Energy,and Related Fields

    SciTech Connect

    Grisham, L. R.; Kwan, J. W.

    2008-08-01

    Some years ago it was suggested that halogen negative ions could offer a feasible alternative path to positive ions as a heavy ion fusion driver beam which would not suffer degradation due to electron accumulation in the accelerator and beam transport system, and which could be converted to a neutral beam by photodetachment near the chamber entrance if desired. Since then, experiments have demonstrated that negative halogen beams can be extracted and accelerated away from the gas plume near the source with a surviving current density close to what could be achieved with a positive ion of similar mass, and with comparable optical quality. In demonstrating the feasibility of halogen negative ions as heavy ion driver beams, ion - ion plasmas, an interesting and somewhat novel state of matter, were produced. These plasmas, produced near the extractor plane of the sources, appear, based upon many lines of experimental evidence, to consist of almost equal densities of positive and negative chlorine ions, with only a small component of free electrons. Serendipitously, the need to extract beams from this plasma for driver development provides a unique diagnostic tool to investigate the plasma, since each component - positive ions, negative ions, and electrons - can be extracted and measured separately. We discuss the relevance of these observations to understanding negative ion beam extraction from electronegative plasmas such as halogens, or the more familiar hydrogen of magnetic fusion ion sources. We suggest a concept which might improve negative hydrogen extraction by the addition of a halogen. The possibility and challenges of producing ion - ion plasmas with thin targets of halogens or, perhaps, salt, is briefly addressed.

  9. Perspective on the Role of Negative Ions and Ion-Ion Plasmas in Heavy Ion Fusion Science, Magnetic Fusion Energy, and Related Fields

    SciTech Connect

    Grisham, L.R.; Kwan, J.W.

    2008-08-01

    Some years ago it was suggested that halogen negative ions [1]could offer a feasible alternative path to positive ions as a heavy ion fusion driver beam which would not suffer degradation due to electron accumulation in the accelerator and beam transport system, and which could be converted to a neutral beam by photodetachment near the chamber entrance if desired. Since then, experiments have demonstrated that negative halogen beams can be extracted and accelerated away from the gas plume near the source with a surviving current density close to what could be achieved with a positive ion of similar mass, and with comparable optical quality. In demonstrating the feasibility of halogen negative ions as heavy ion driver beams, ion - ion plasmas, an interesting and somewhat novel state of matter, were produced. These plasmas, produced near the extractor plane of the sources, appear, based upon many lines of experimental evidence, to consist of almost equal densities of positive and negative chlorine ions, with only a small component of free electrons. Serendipitously, the need to extract beams from this plasma for driver development provides a unique diagnostic tool to investigate the plasma, since each component - positive ions, negative ions, and electrons -- can be extracted and measured separately. We discuss the relevance of these observations to understanding negative ion beam extraction from electronegative plasmas such as halogens, or the more familiar hydrogen of magnetic fusion ion sources. We suggest a concept which might improve negative hydrogen extraction by the addition of a halogen. The possibility and challenges of producing ion-ion plasmas with thin targets of halogens or, perhaps, salt, is briefly addressed.

  10. Perspective on the Role of Negative Ions and Ion-Ion Plasmas in Heavy Ion Fusion Science, Magnetic Fusion Energy, and Related Fields

    SciTech Connect

    L. Grisham and J.W. Kwan

    2008-08-12

    Some years ago it was suggested that halogen negative ions [1] could offer a feasible alternative path to positive ions as a heavy ion fusion driver beam which would not suffer degradation due to electron accumulation in the accelerator and beam transport system, and which could be converted to a neutral beam by photodetachment near the chamber entrance if desired. Since then, experiments have demonstrated that negative halogen beams can be extracted and accelerated away from the gas plume near the source with a surviving current density close to what could be achieved with a positive ion of similar mass, and with comparable optical quality. In demonstrating the feasibility of halogen negative ions as heavy ion driver beams, ion - ion plasmas, an interesting and somewhat novel state of matter, were produced. These plasmas, produced near the extractor plane of the sources, appear, based upon many lines of experimental evidence, to consist of almost equal densities of positive and negative chlorine ions, with only a small component of free electrons. Serendipitously, the need to extract beams from this plasma for driver development provides a unique diagnostic tool to investigate the plasma, since each component - positive ions, negative ions, and electrons -- can be extracted and measured separately. We discuss the relevance of these observations to understanding negative ion beam extraction from electronegative plasmas such as halogens, or the more familiar hydrogen of magnetic fusion ion sources. We suggest a concept which might improve negative hydrogen extraction by the addition of a halogen. The possibility and challenges of producing ion-ion plasmas with thin targets of halogens or, perhaps, salt, is briefly addressed.

  11. Evidence for creation of strong electromagnetic fields in relativistic heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Toneev, V.; Rogachevsky, O.; Voronyuk, V.

    2016-08-01

    It is proposed to identify the strong electric field created during relativistic collisions of asymmetric nuclei via observation of pseudorapidity and transverse-momentum distributions of hadrons with the same mass but opposite charges. The detailed calculation results for the directed flow within the Parton-Hadron String Dynamics model are given for Cu-Au interactions at the NICA collision energies of √{s_{NN}} = 9 and 5 GeV. The separation effect is observable at 9GeV as clearly as at 200 GeV.

  12. Controlling trapping potentials and stray electric fields in a microfabricated ion trap through design and compensation

    NASA Astrophysics Data System (ADS)

    Doret, S. Charles; Amini, Jason M.; Wright, Kenneth; Volin, Curtis; Killian, Tyler; Ozakin, Arkadas; Denison, Douglas; Hayden, Harley; Pai, C.-S.; Slusher, Richart E.; Harter, Alexa W.

    2012-07-01

    Recent advances in quantum information processing with trapped ions have demonstrated the need for new ion trap architectures capable of holding and manipulating chains of many (>10) ions. Here we present the design and detailed characterization of a new linear trap, microfabricated with scalable complementary metal-oxide-semiconductor (CMOS) techniques, that is well-suited to this challenge. Forty-four individually controlled dc electrodes provide the many degrees of freedom required to construct anharmonic potential wells, shuttle ions, merge and split ion chains, precisely tune secular mode frequencies, and adjust the orientation of trap axes. Microfabricated capacitors on dc electrodes suppress radio-frequency pickup and excess micromotion, while a top-level ground layer simplifies modeling of electric fields and protects trap structures underneath. A localized aperture in the substrate provides access to the trapping region from an oven below, permitting deterministic loading of particular isotopic/elemental sequences via species-selective photoionization. The shapes of the aperture and radio-frequency electrodes are optimized to minimize perturbation of the trapping pseudopotential. Laboratory experiments verify simulated potentials and characterize trapping lifetimes, stray electric fields, and ion heating rates, while measurement and cancellation of spatially-varying stray electric fields permits the formation of nearly-equally spaced ion chains.

  13. Atom probe field ion microscopy and related topics: A bibliography 1993

    SciTech Connect

    Godfrey, R.D.; Miller, M.K.; Russell, K.F.

    1994-10-01

    This bibliography, covering the period 1993, includes references related to the following topics: atom probe field ion microscopy (APFIM), field emission (FE), and field ion microscopy (FIM). Technique-oriented studies and applications are included. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications. To reduce the length of this document, the references have been reduced to the minimum necessary to locate the articles. The references are listed alphabetically by authors, an Addendum of references missed in previous bibliographies is included.

  14. Ion Viscosity Mediated by Tangled Magnetic Fields: An Application to Black Hole Accretion Disks

    NASA Technical Reports Server (NTRS)

    Subramanian, Prasad; Becker, Peter A.; Kafatos, Menas

    1996-01-01

    We examine the viscosity associated with the shear stress exerted by ions in the presence of a tangled magnetic field. As an application, we consider the effect of this mechanism on the structure of black hole accretion disks. We do not attempt to include a self-consistent description of the magnetic field. Instead, we assume the existence of a tangled field with coherence length lambda(sub coh), which is the average distance between the magnetic 'kinks' that scatter the particles. For simplicity, we assume that the field is self-similar, and take lambda(sub coh) to be a fixed fraction zeta of the local disk height H. Ion viscosity in the presence of magnetic fields is generally taken to be the cross-field viscosity, wherein the effective mean free path is the ion Larmor radius lambda(sub L), which is much less than the ion-ion Coulomb mean free path A(sub ii) in hot accretion disks. However, we arrive at a formulation for a 'hybrid' viscosity in which the tangled magnetic field acts as an intermediary in the transfer of momentum between different layers in the shear flow. The hybrid viscosity greatly exceeds the standard cross-field viscosity when (lambda/lambda(sub L)) much greater than (lambda(sub L)/lambda(sub ii)), where lambda = ((lambda(sub ii)(sup -1) + lambda(sub (coh)(sup -1))(sup -1) is the effective mean free path for the ions. This inequality is well satisfied in hot accretion disks, which suggests that the ions may play a much larger role in the momentum transfer process in the presence of magnetic fields than was previously thought. The effect of the hybrid viscosity on the structure of a steady-state, two-temperature, quasi-Keplerian accretion disk is analyzed. The hybrid viscosity is influenced by the degree to which the magnetic field is tangled (represented by zeta = lambda(sub coh)), and also by the relative accretion rate M/M(sub E), where M(sub E) = L(sub E)/c(sup 2) and L(sub E) is the Eddington luminosity. We find that ion viscosity in the

  15. [Negative air ions generated by plants upon pulsed electric field stimulation applied to soil].

    PubMed

    Wu, Ren-ye; Deng, Chuan-yuan; Yang, Zhi-jian; Weng, Hai-yong; Zhu, Tie-jun-rong; Zheng, Jin-gui

    2015-02-01

    This paper investigated the capacity of plants (Schlumbergera truncata, Aloe vera var. chinensis, Chlorophytum comosum, Schlumbergera bridgesii, Gymnocalycium mihanovichii var. friedrichii, Aspidistra elatior, Cymbidium kanran, Echinocactus grusonii, Agave americana var. marginata, Asparagus setaceus) to generate negative air ions (NAI) under pulsed electric field stimulation. The results showed that single plant generated low amounts of NAI in natural condition. The capacity of C. comosum and G. mihanovichii var. friedrichii generated most NAI among the above ten species, with a daily average of 43 ion · cm(-3). The least one was A. americana var. marginata with the value of 19 ion · cm(-3). When proper pulsed electric field stimulation was applied to soil, the NAI of ten plant species were greatly improved. The effect of pulsed electric field u3 (average voltage over the pulse period was 2.0 x 10(4) V, pulse frequency was 1 Hz, and pulse duration was 50 ms) was the greatest. The mean NAI concentration of C. kanran was the highest 1454967 ion · cm(-3), which was 48498.9 times as much as that in natural condition. The lowest one was S. truncata with the value of 34567 ion · cm(-3), which was 843.1 times as much as that in natural condition. The capacity of the same plants to generate negative air ion varied extremely under different intensity pulsed electric fields.

  16. Magnetic field effects on the solute luminescence of alkane solutions irradiated with heavy ions

    SciTech Connect

    LaVerne, J.A.; Brocklehurst, B.

    1996-02-01

    The effects of track structure on the luminescence decays in cyclohexane and in 2,2,4-trimethylpentane (isoocatane) solutions of 2,5-diphenyloxazole (PPO) have been determined in the presence and in the absence of an external magnetic field. Irradiations were performed with protons of 1-15 MeV and with helium ions of 2-20 MeV energy. Companion studies were performed with {sup 90}Sr-{sup 90}Y {Beta}-radiolysis. The magnetic field effect is due to the hyperfine interaction of nuclear spins in the geminate pair of solvent radical ions produced. In both solvents, the effect of the magnetic field on luminescence decreases with increasing linear energy transfer (LET) from about 40% for {Beta}-particles to only a few percent with helium ions. Magnetic field effects with protons decrease in time whereas they are constant with {Beta}-particles. This result is attributed to the overlap of initially isolated spurs during the evolution of the proton track; the probability of nongeminate recombination increases with the number of neighboring ion pairs. The total luminescence intensity per incident particle remains constant with proton energy but increases slightly with increasing helium ion energy. At a given particle energy, the intensity is greater in cyclohexane than in isoocatane. The pulse shapes of the luminescence decays reflect the distributions in ion recombination times, and very little variation in luminescence decay rates is observed with increasing LET. 37 refs., 7 figs., 1 tab.

  17. Behavior of moving plasma in solenoidal magnetic field in a laser ion source.

    PubMed

    Ikeda, S; Takahashi, K; Okamura, M; Horioka, K

    2016-02-01

    In a laser ion source, a solenoidal magnetic field is useful to guide the plasma and to control the extracted beam current. However, the behavior of the plasma drifting in the magnetic field has not been well understood. Therefore, to investigate the behavior, we measured the plasma ion current and the total charge within a single pulse in the solenoid by changing the distance from the entrance of the solenoid to a detector. We observed that the decrease of the total charge along the distance became smaller as the magnetic field became larger and then the charge became almost constant with a certain magnetic flux density. The results indicate that the transverse spreading speed of the plasma decreased with increasing the field and the plasma was confined transversely with the magnetic flux density. We found that the reason of the confinement was not magnetization of ions but an influence induced by electrons.

  18. Behavior of moving plasma in solenoidal magnetic field in a laser ion source

    NASA Astrophysics Data System (ADS)

    Ikeda, S.; Takahashi, K.; Okamura, M.; Horioka, K.

    2016-02-01

    In a laser ion source, a solenoidal magnetic field is useful to guide the plasma and to control the extracted beam current. However, the behavior of the plasma drifting in the magnetic field has not been well understood. Therefore, to investigate the behavior, we measured the plasma ion current and the total charge within a single pulse in the solenoid by changing the distance from the entrance of the solenoid to a detector. We observed that the decrease of the total charge along the distance became smaller as the magnetic field became larger and then the charge became almost constant with a certain magnetic flux density. The results indicate that the transverse spreading speed of the plasma decreased with increasing the field and the plasma was confined transversely with the magnetic flux density. We found that the reason of the confinement was not magnetization of ions but an influence induced by electrons.

  19. Adhesion and transfer of polytetrafluoroethylene to tungsten studied by field ion microscopy

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.; Buckley, D. H.

    1972-01-01

    Mechanical contacts between polytetrafluoroethylene (PTFE) and tungsten field ion tips were made in situ in the field ion microscope. Both load and force of adhesion were measured for varying contact times and for clean and contaminated tungsten tips. Strong adhesion between the PTFE and clean tungsten was observed at contact times greater than 2.5 min (forces of adhesion were greater than three times the load). For times less than 2.5 min, the force of adhesion was immeasurably small. The increase in adhesion with contact time after 2.5 min can be attributed to the increase in true contact area by creep of PTFE. No adhesion was measurable at long contact times with contaminated tungsten tips. Neon field ion micrographs taken after the contacts show many linear and branched arrays which appear to represent PTFE that remains adhered to the surface even at the high electric fields required for imaging.

  20. Behavior of moving plasma in solenoidal magnetic field in a laser ion source

    SciTech Connect

    Ikeda, S.; Takahashi, K.; Okamura, M.; Horioka, K.

    2016-02-15

    In a laser ion source, a solenoidal magnetic field is useful to guide the plasma and to control the extracted beam current. However, the behavior of the plasma drifting in the magnetic field has not been well understood. Therefore, to investigate the behavior, we measured the plasma ion current and the total charge within a single pulse in the solenoid by changing the distance from the entrance of the solenoid to a detector. We observed that the decrease of the total charge along the distance became smaller as the magnetic field became larger and then the charge became almost constant with a certain magnetic flux density. The results indicate that the transverse spreading speed of the plasma decreased with increasing the field and the plasma was confined transversely with the magnetic flux density. We found that the reason of the confinement was not magnetization of ions but an influence induced by electrons.

  1. Effect of ionic temperature on the modulational instability of ion acoustic waves in the presence of a magnetic field

    NASA Astrophysics Data System (ADS)

    Murtaza, G.; Salahuddin, M.

    1981-12-01

    The modulational instability of ion acoustic waves is studied in the presence of a dc magnetic field, taking the ion temperature into account. It is well known that the instability sets in for wave numbers exceeding 1.47 kD when there is no magnetic field and the ion temperature is negligible. The instability behaviour, however, changes drastically when either the magnetic field is switched on or the ion temperature becomes important or both. In general three different regions emerge wherein the waves becomes modulationally unstable. The relative sizes of these regions change as the magnetic field, the angle of propagation and the ion temperature are varied.

  2. Dual metal and Lewis base catalysis approach for asymmetric synthesis of dihydroquinolines and the α-arylation of aldehydes via N-acyliminium ions.

    PubMed

    Volla, Chandra M R; Fava, Eleonora; Atodiresei, Iuliana; Rueping, Magnus

    2015-11-11

    A dual catalytic system consisting of indium triflate and a chiral imidazolidinone catalyzes the asymmetric addition of aldehydes to N-acyl quinoliniums furnishing optically active dihydroquinolines in good yields and excellent selectivities. The products were further functionalized into optically active tetrahydroquinolines, quinolines and 6-oxa-2-aza-bicyclo[3.3.1]nonanes.

  3. Individual-Ion Addressing with Microwave Field Gradients

    DTIC Science & Technology

    2013-04-22

    minimize the field on the trap axis as in method I, to avoid large ac Zeeman shifts. We measure Rabi rates mm;q1 ¼ 2 0:05ð1Þ kHz and mm;q2 ¼ 2 3...positioning precision and/or unequal phases of the radio-frequency electrodes [25]. This method leads to a differential ac Zeeman shift !acz ’ 2 430 Hz, due...to oscillating field amplitudes jBMW;q1j ’ 7 T and jBMW;q2j ’ 19 T, which must be compensated. Method III is based on differential ac Zeeman shifts

  4. Heterogeneous and asymmetric crustal accretion: New constraints from multibeam bathymetry and potential field data from the Rainbow area of the Mid-Atlantic Ridge (36°15'N)

    NASA Astrophysics Data System (ADS)

    Paulatto, Michele; Canales, Juan Pablo; Dunn, Robert A.; Sohn, Robert A.

    2015-09-01

    At slow-spreading mid-ocean ridges, crustal accretion style can vary significantly along and across ridge segments. In magma-poor regions, seafloor spreading can be accommodated largely by tectonic processes, however, the internal structure and formation mechanism of such highly tectonized crust are not fully understood. We analyze multibeam bathymetry and potential field data from the Rainbow area of the Mid-Atlantic Ridge (35°40'N-36°40'N), a section of the ridge that shows diverse accretion styles. We identify volcanic, tectonized and sedimented terrain and measure exposed fault area to estimate the tectonic strain, T, and the fraction of magmatic accretion, M. Estimated T values range from 0.2-0.4 on ridge segments to 0.6-0.8 at the Rainbow nontransform discontinuity (NTD). At segment ends T is asymmetric, reflecting asymmetries in accretion rate, topography and faulting between inside and outside offset corners. Detachment faults have formed preferentially at inside corners, where tectonic strain is higher. We identify at least two oceanic core complexes on the fossil trace of the NTD, in addition to the Rainbow massif, which occupies the offset today. A gravity high and low magnetization suggest that the Rainbow massif, which hosts a high-temperature hydrothermal system, was uplifted by a west dipping detachment fault. Asymmetric plate ages indicate localization of tectonic strain at the inside corners and migration of the detachment toward and across the ridge axis, which may have caused emplacement of magma into the footwall. Hydrothermal circulation and heat extraction is possibly favored by increased permeability generated by fracturing of the footwall and deep-penetrating second-generation faults.

  5. Pairwise-additive force fields for selected aqueous monovalent ions from adaptive force matching

    PubMed Central

    Li, Jicun; Wang, Feng

    2015-01-01

    Simple non-polarizable potentials were developed for Na+, K+, Cl−, and Br− using the adaptive force matching (AFM) method with ab initio MP2 method as reference. Our MP2-AFM force field predicts the solvation free energies of the four salts formed by the ions with an error of no more than 5%. Other properties such as the ion-water radial distribution functions, first solvation shell water tilt angle distributions, ion diffusion constants, concentration dependent diffusion constant of water, and concentration dependent surface tension of the solutions were calculated with this potential. Very good agreement was achieved for these properties. In particular, the diffusion constants of the ions are within 6% of experimental measurements. The model predicts bromide to be enriched at the interface in the 1.6M KBr solution but predicts the ion to be repelled for the surface at lower concentration. PMID:26590540

  6. Velocity dependence of the dynamic magnetic field acting on swift O and Sm ions

    NASA Astrophysics Data System (ADS)

    Shu, N. K. B.; Melnik, D.; Brennan, J. M.; Semmler, W.; Benczer-Koller, #.

    1980-05-01

    The hyperfine dynamic field acting on fast ions traversing polarized iron foils has been measured as a function of the ion velocity in the region 0.03ions. The dynamic field increases with velocity but not linearly. The same conclusions were obtained from measurements on oxygen ions traversing thin iron foils or stopping in thick iron foils. All available data on dynamic-field measurements at ions with 8field. The region of validity of this parametrization of the dynamic field, as well as possible explanations of its origin, are discussed. NUCLEAR REACTIONS 150,152Sm(16O, 16O')150,152Sm(2+1), 150,152Sm(32S, 32S')150,152Sm(2+1), and 16O(α,α')16O(3-1): E0~40 MeV, Es~70-80 MeV, Eα=17.55 MeV; measured W(θ,B,∞) through polarized iron; deduced BDYNAMIC(v); compiled existing data to obtain general parametrization for BDYNAMIC(v,Z).

  7. Improved Differential Ion Mobility Separations Using Linked Scans of Carrier Gas Composition and Compensation Field

    NASA Astrophysics Data System (ADS)

    Santiago, Brandon G.; Harris, Rachel A.; Isenberg, Samantha L.; Ridgeway, Mark E.; Pilo, Alice L.; Kaplan, Desmond A.; Glish, Gary L.

    2015-07-01

    Differential ion mobility spectrometry (DIMS) separates ions based on differences in their mobilities in low and high electric fields. When coupled to mass spectrometric analyses, DIMS has the ability to improve signal-to-background by eliminating isobaric and isomeric compounds for analytes in complex mixtures. DIMS separation power, often measured by resolution and peak capacity, can be improved through increasing the fraction of helium in the nitrogen carrier gas. However, because the mobility of ions is higher in helium, a greater number of ions collide with the DIMS electrodes or housing, yielding losses in signal intensity. To take advantage of the benefits of helium addition on DIMS separations and reduce ion losses, linked scans were developed. In a linked scan the helium content of the carrier gas is reduced as the compensation field is increased. Linked scans were compared with conventional compensation field scans with constant helium content for the protein ubiquitin and a tryptic digest of bovine serum albumin (BSA). Linked scans yield better separation of ubiquitin charge states and enhanced peak capacities for the analysis of BSA compared with compensation field scans with constant helium carrier gas percentages. Linked scans also offer improved signal intensity retention in comparison to compensation field scans with constant helium percentages in the carrier gas.

  8. Energetic-Particle-Driven Instabilities and Their Effect on Fast Ions in a Reversed Field Pinch

    NASA Astrophysics Data System (ADS)

    Lin, L.; Ding, W. X.; Brower, D. L.; Koliner, J. J.; Eilerman, S.; Reusch, J.; Anderson, J. K.; Almagri, A. F.; Chapman, B. E.; Nornberg, M. D.; Sarff, J. S.; Waksman, J.; Liu, D.

    2012-10-01

    During 1 MW tangential neutral-beam injection (NBI) into the MST reversed field pinch, multiple, bursty instabilities (n=5, 4 and -1) are detected by various fluctuation diagnostics. The spatial structure of associated density fluctuations peaks near the core where fast ions reside. Significant bicoherence among them is measured, indicating nonlinear three-wave coupling. These instabilities are also observed by a laser-based Faraday-rotation diagnostic, containing critical information on the internal magnetic field fluctuations. A tangential-view high-energy neutral particle analyzer (NPA) is used to study the fast-ion population. The measured NPA signal decreases by 15% following NBI-driven instabilities, indicating fluctuation-induced fast-ion transport. The NBI also reduces the amplitude of the innermost-resonant tearing mode by up to 65%. This mode-suppression is lessened following the NBI-driven bursts, consistent with fast ion loss/redistribution weakening the suppression effect.

  9. Ion Species and Charge States of Vacuum Arc Plasma with Gas Feed and Longitudinal Magnetic Field

    SciTech Connect

    Oks, Efim; Anders, Andre

    2010-06-23

    The evolution of copper ion species and charge state distributions is measured for a long vacuum arc discharge plasma operated in the presence of a longitudinal magnetic field of several 10 mT and working gas (Ar). It was found that changing the cathode-anode distance within 20 cm as well as increasing the gas pressure did not affect the arc burning voltage and power dissipation by much. In contrast, burning voltage and power dissipation were greatly increased as the magnetic field was increased. The longer the discharge gap the greater was the fraction of gaseous ions and the lower the fraction of metal ions, while the mean ion charge state was reduced. It is argued that the results are affected by charge exchange collisions and electron impact ionization.

  10. Asymmetric Flow Field Flow Fractionation of Aqueous C60 Nanoparticles with Size Determination by Dynamic Light Scattering and Quantification by Liquid Chromatography Atmospheric Pressure Photo-Ionization Mass Spectrometry

    EPA Science Inventory

    A size separation method was developed for aqueous C60 fullerene aggregates (aqu/C60) using asymmetric flow field flow fractionation (AF4) coupled to a dynamic light scattering detector in flow through mode. Surfactants, which are commonly used in AF4, were avoided as they may al...

  11. Fast ion confinement and stability in a neutral beam injected reversed field pincha)

    NASA Astrophysics Data System (ADS)

    Anderson, J. K.; Almagri, A. F.; Den Hartog, D. J.; Eilerman, S.; Forest, C. B.; Koliner, J. J.; Mirnov, V. V.; Morton, L. A.; Nornberg, M. D.; Parke, E.; Reusch, J. A.; Sarff, J. S.; Waksman, J.; Belykh, V.; Davydenko, V. I.; Ivanov, A. A.; Polosatkin, S. V.; Tsidulko, Y. A.; Lin, L.; Liu, D.; Fiksel, G.; Sakakita, H.; Spong, D. A.; Titus, J.

    2013-05-01

    The behavior of energetic ions is fundamentally important in the study of fusion plasmas. While well-studied in tokamak, spherical torus, and stellarator plasmas, relatively little is known in reversed field pinch plasmas about the dynamics of fast ions and the effects they cause as a large population. These studies are now underway in the Madison Symmetric Torus with an intense 25 keV, 1 MW hydrogen neutral beam injector (NBI). Measurements of the time-resolved fast ion distribution via a high energy neutral particle analyzer, as well as beam-target neutron flux (when NBI fuel is doped with 3-5% D2) both demonstrate that at low concentration the fast ion population is consistent with classical slowing of the fast ions, negligible cross-field transport, and charge exchange as the dominant ion loss mechanism. A significant population of fast ions develops; simulations predict a super-Alfvénic ion density of up to 25% of the electron density with both a significant velocity space gradient and a sharp radial density gradient. There are several effects on the background plasma including enhanced toroidal rotation, electron heating, and an altered current density profile. The abundant fast particles affect the plasma stability. Fast ions at the island of the core-most resonant tearing mode have a stabilizing effect, and up to 60% reduction in the magnetic fluctuation amplitude is observed during NBI. The sharp reduction in amplitude, however, has little effect on the underlying magnetic island structure. Simultaneously, beam driven instabilities are observed as repetitive ˜50 μs bursts which coincide with fast particle redistribution; data indicate a saturated core fast ion density well below purely classical predictions.

  12. Fast ion confinement and stability in a neutral beam injected reversed field pinch

    SciTech Connect

    Anderson, J. K.; Almagri, A. F.; Den Hartog, D. J.; Eilerman, S.; Forest, C. B.; Koliner, J. J.; Mirnov, V. V.; Morton, L. A.; Nornberg, M. D.; Parke, E.; Reusch, J. A.; Sarff, J. S.; Waksman, J.; Belykh, V.; Davydenko, V. I.; Ivanov, A. A.; Polosatkin, S. V.; Tsidulko, Y. A.; Lin, L.; Liu, D.; and others

    2013-05-15

    The behavior of energetic ions is fundamentally important in the study of fusion plasmas. While well-studied in tokamak, spherical torus, and stellarator plasmas, relatively little is known in reversed field pinch plasmas about the dynamics of fast ions and the effects they cause as a large population. These studies are now underway in the Madison Symmetric Torus with an intense 25 keV, 1 MW hydrogen neutral beam injector (NBI). Measurements of the time-resolved fast ion distribution via a high energy neutral particle analyzer, as well as beam-target neutron flux (when NBI fuel is doped with 3–5% D{sub 2}) both demonstrate that at low concentration the fast ion population is consistent with classical slowing of the fast ions, negligible cross-field transport, and charge exchange as the dominant ion loss mechanism. A significant population of fast ions develops; simulations predict a super-Alfvénic ion density of up to 25% of the electron density with both a significant velocity space gradient and a sharp radial density gradient. There are several effects on the background plasma including enhanced toroidal rotation, electron heating, and an altered current density profile. The abundant fast particles affect the plasma stability. Fast ions at the island of the core-most resonant tearing mode have a stabilizing effect, and up to 60% reduction in the magnetic fluctuation amplitude is observed during NBI. The sharp reduction in amplitude, however, has little effect on the underlying magnetic island structure. Simultaneously, beam driven instabilities are observed as repetitive ∼50 μs bursts which coincide with fast particle redistribution; data indicate a saturated core fast ion density well below purely classical predictions.

  13. Ion-sensitive field effect transistors using carbon nanotubes as the transducing layer.

    PubMed

    Cid, Cristina C; Riu, Jordi; Maroto, Alicia; Rius, F Xavier

    2008-08-01

    We report a new type of ion-sensitive field effect transistor (ISFET). This type of ISFET incorporates a new architecture, containing a network of single-walled carbon nanotubes (SWCNTs) as the transduction layer, making an external reference electrode unnecessary. To show an example of its application, the SWCNT-based ISFET is able to detect at least 10(-8) M of potassium in water using an ion-selective membrane containing valinomycin.

  14. Compact Full-Field Ion Detector System for SmallSats Beyond LEO

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Wrbanek, Susan Y.; Fralick, Gustave C.; Clark, Pamela E.; McNeil, Roger R.

    2014-01-01

    NASA Glenn Research Center (GRC) is applying its expertise and facilities in harsh environment instrumentation to develop a Compact Full-Field Ion Detector System (CFIDS). The CFIDS is designed to be an extremely compact, low cost instrument, capable of being flown on a wide variety of deep space platforms, to provide multi-directional, comprehensive (composition, velocity, and direction) in-situ measurements of heavy ions in space plasma environments.

  15. Compact Full-Field Ion Detector System for CubeSat Science Beyond LEO

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Wrbanek, Susan Y.; Fralick, Gustave C.; Clark, Pamela E.

    2013-01-01

    NASA Glenn Research Center (GRC) is applying its expertise and facilities in harsh environment instrumentation to develop a Compact Full-Field Ion Detector System (CFIDS). The CFIDS is designed to be an extremely compact, low cost instrument, capable of being flown on a wide variety of deep space platforms, to provide comprehensive (composition, velocity, and direction) in situ measurements of heavy ions in space plasma environments with higher fidelity, than previously available.

  16. Thermal ion orbit loss and radial electric field in DIII-D

    DOE PAGES

    deGrassie, John S.; Boedo, Jose A.; Grierson, Brian A.

    2015-08-14

    A relatively simple model for the generation of the radial electric field, Er, near the outboard boundary in a tokamak is presented. The model posits that Er is established to supply the return current necessary to balance the thermal ion orbit loss current. Comparison with DIII-D data is promising. Features of the model that promote a more negative edge Er are higher ion temperature, lower density, lower impurity ion content, and a shorter pathlength for orbit loss. Lastly, these scalings are consistent with experimentally established access to the high-confinement mode edge transport barrier.

  17. Magnetic-field-induced quantum criticality in a planar ferromagnet with single-ion anisotropy

    NASA Astrophysics Data System (ADS)

    Mercaldo, M. T.; Rabuffo, I.; De Cesare, L.; Caramico D'Auria, A.

    2014-08-01

    We analyze the effects induced by single-ion anisotropy on quantum criticality in a d-dimensional spin-3/2 planar ferromagnet. To tackle this problem we employ the two-time Green's function method, using the Tyablikov decoupling for exchange interactions and the Anderson-Callen decoupling for single-ion anisotropy. In our analysis the role of non-thermal control parameter which drives the quantum phase transition is played by a longitudinal external magnetic field. We find that the single-ion anisotropy has substantial effects on the structure of the phase diagram close to the quantum critical point.

  18. Acceleration and stability of a high-current ion beam in induction fields

    NASA Astrophysics Data System (ADS)

    Karas', V. I.; Manuilenko, O. V.; Tarakanov, V. P.; Federovskaya, O. V.

    2013-03-01

    A one-dimensional nonlinear analytic theory of the filamentation instability of a high-current ion beam is formulated. The results of 2.5-dimensional numerical particle-in-cell simulations of acceleration and stability of an annular compensated ion beam (CIB) in a linear induction particle accelerator are presented. It is shown that additional transverse injection of electron beams in magnetically insulated gaps (cusps) improves the quality of the ion-beam distribution function and provides uniform beam acceleration along the accelerator. The CIB filamentation instability in both the presence and the absence of an external magnetic field is considered.

  19. Acceleration and stability of a high-current ion beam in induction fields

    SciTech Connect

    Karas', V. I.; Manuilenko, O. V.; Tarakanov, V. P.; Federovskaya, O. V.

    2013-03-15

    A one-dimensional nonlinear analytic theory of the filamentation instability of a high-current ion beam is formulated. The results of 2.5-dimensional numerical particle-in-cell simulations of acceleration and stability of an annular compensated ion beam (CIB) in a linear induction particle accelerator are presented. It is shown that additional transverse injection of electron beams in magnetically insulated gaps (cusps) improves the quality of the ion-beam distribution function and provides uniform beam acceleration along the accelerator. The CIB filamentation instability in both the presence and the absence of an external magnetic field is considered.

  20. Oscillating asymmetric dark matter

    SciTech Connect

    Tulin, Sean; Yu, Hai-Bo; Zurek, Kathryn M. E-mail: haiboyu@umich.edu

    2012-05-01

    We study the dynamics of dark matter (DM) particle-antiparticle oscillations within the context of asymmetric DM. Oscillations arise due to small DM number-violating Majorana-type mass terms, and can lead to recoupling of annihilation after freeze-out and washout of the DM density. Asymmetric DM oscillations 'interpolate' between symmetric and asymmetric DM freeze-out scenarios, and allow for a larger DM model-building parameter space. We derive the density matrix equations for DM oscillations and freeze-out from first principles using nonequilibrium field theory, and our results are qualitatively different than in previous studies. DM dynamics exhibits particle-vs-antiparticle 'flavor' effects, depending on the interaction type, analogous to neutrino oscillations in a medium. 'Flavor-sensitive' DM interactions include scattering or annihilation through a new vector boson, while 'flavor-blind' interactions include scattering or s-channel annihilation through a new scalar boson. In particular, we find that flavor-sensitive annihilation does not recouple when coherent oscillations begin, and that flavor-blind scattering does not lead to decoherence.

  1. Oscillating asymmetric dark matter

    NASA Astrophysics Data System (ADS)

    Tulin, Sean; Yu, Hai-Bo; Zurek, Kathryn M.

    2012-05-01

    We study the dynamics of dark matter (DM) particle-antiparticle oscillations within the context of asymmetric DM. Oscillations arise due to small DM number-violating Majorana-type mass terms, and can lead to recoupling of annihilation after freeze-out and washout of the DM density. Asymmetric DM oscillations "interpolate" between symmetric and asymmetric DM freeze-out scenarios, and allow for a larger DM model-building parameter space. We derive the density matrix equations for DM oscillations and freeze-out from first principles using nonequilibrium field theory, and our results are qualitatively different than in previous studies. DM dynamics exhibits particle-vs-antiparticle "flavor" effects, depending on the interaction type, analogous to neutrino oscillations in a medium. "Flavor-sensitive" DM interactions include scattering or annihilation through a new vector boson, while "flavor-blind" interactions include scattering or s-channel annihilation through a new scalar boson. In particular, we find that flavor-sensitive annihilation does not recouple when coherent oscillations begin, and that flavor-blind scattering does not lead to decoherence.

  2. Transient effect of weak electromagnetic fields on calcium ion concentration in Arabidopsis thaliana

    PubMed Central

    Pazur, Alexander; Rassadina, Valentina

    2009-01-01

    Background Weak magnetic and electromagnetic fields can influence physiological processes in animals, plants and microorganisms, but the underlying way of perception is poorly understood. The ion cyclotron resonance is one of the discussed mechanisms, predicting biological effects for definite frequencies and intensities of electromagnetic fields possibly by affecting the physiological availability of small ions. Above all an influence on Calcium, which is crucial for many life processes, is in the focus of interest. We show that in Arabidopsis thaliana, changes in Ca2+-concentrations can be induced by combinations of magnetic and electromagnetic fields that match Ca2+-ion cyclotron resonance conditions. Results An aequorin expressing Arabidopsis thaliana mutant (Col0-1 Aeq Cy+) was subjected to a magnetic field around 65 microtesla (0.65 Gauss) and an electromagnetic field with the corresponding Ca2+ cyclotron frequency of 50 Hz. The resulting changes in free Ca2+ were monitored by aequorin bioluminescence, using a high sensitive photomultiplier unit. The experiments were referenced by the additional use of wild type plants. Transient increases of cytosolic Ca2+ were observed both after switching the electromagnetic field on and off, with the latter effect decreasing with increasing duration of the electromagnetic impact. Compared with this the uninfluenced long-term loss of bioluminescence activity without any exogenic impact was negligible. The magnetic field effect rapidly decreased if ion cyclotron resonance conditions were mismatched by varying the magnetic fieldstrength, also a dependence on the amplitude of the electromagnetic component was seen. Conclusion Considering the various functions of Ca2+ as a second messenger in plants, this mechanism may be relevant for perception of these combined fields. The applicability of recently hypothesized mechanisms for the ion cyclotron resonance effect in biological systems is discussed considering it's operating at

  3. Collective electric field effects on the confinement of fast ions in tokamaks

    SciTech Connect

    McClements, K.G.; Thyagaraja, A.

    2006-04-15

    The injection of neutral particle beams counter to the plasma current direction in the Mega-Ampere Spherical Tokamak (MAST) [A. Sykes, R. J. Akers, L. C. Appel et al., Nucl. Fusion, 41, 1423 (2001)] leads to substantial losses of energetic beam ions and also rapid toroidal rotation. The electrodynamic consequences of energetic ion loss on tokamak plasmas are explored in light of results from the MAST counterinjection experiments and test particle calculations of the current density due to escaping ions. Previous authors have noted that there are two possible consequences of such a current: either a compensating bulk plasma return current is set up, or the plasma behaves as an insulator, with the energetic ion current balanced by a displacement current rather than a conduction current. Radial electric fields and hence toroidal flows occur in both cases, but higher fields are predicted in the insulating case. Such fields are important because they can confine both fast ions and bulk plasma (via the suppression of turbulent transport). The return current scenario, which appears to be operative during counterinjection in MAST, is shown to be applicable if there is a sufficiently high level of momentum transport in the bulk ions; electrons cannot carry the return current, although they contribute to an ambipolar particle flux on the plasma confinement time scale. The insulating scenario may be applicable to high confinement regimes in burning tokamak plasmas.

  4. Collective electric field effects on the confinement of fast ions in tokamaks

    NASA Astrophysics Data System (ADS)

    McClements, K. G.; Thyagaraja, A.

    2006-04-01

    The injection of neutral particle beams counter to the plasma current direction in the Mega-Ampère Spherical Tokamak (MAST) [A. Sykes, R. J. Akers, L. C. Appel et al., Nucl. Fusion, 41, 1423 (2001)] leads to substantial losses of energetic beam ions and also rapid toroidal rotation. The electrodynamic consequences of energetic ion loss on tokamak plasmas are explored in light of results from the MAST counterinjection experiments and test particle calculations of the current density due to escaping ions. Previous authors have noted that there are two possible consequences of such a current: either a compensating bulk plasma return current is set up, or the plasma behaves as an insulator, with the energetic ion current balanced by a displacement current rather than a conduction current. Radial electric fields and hence toroidal flows occur in both cases, but higher fields are predicted in the insulating case. Such fields are important because they can confine both fast ions and bulk plasma (via the suppression of turbulent transport). The return current scenario, which appears to be operative during counterinjection in MAST, is shown to be applicable if there is a sufficiently high level of momentum transport in the bulk ions; electrons cannot carry the return current, although they contribute to an ambipolar particle flux on the plasma confinement time scale. The insulating scenario may be applicable to high confinement regimes in burning tokamak plasmas.

  5. Tail-ion transport and Knudsen layer formation in the presence of magnetic fields

    NASA Astrophysics Data System (ADS)

    Schmit, Paul; Molvig, Kim

    2013-10-01

    The impact of magnetic fields on Knudsen layer formation in ICF-relevant plasma is investigated for the first time. Magnetic fields change the energy scaling of the ion diffusivity in a way that eliminates the preferential losses of fast ions compared to thermal ions. Simple threshold criteria give conditions such that the restoration of the ion tail distribution is sufficient to recover much of the lost fusion reactivity. The tail-ion kinetic equations are solved for hot fuel bounded by a cold, nonreacting wall using a numerical stochastic differential equation solver, and the modified fusion reactivities are calculated. We find that modest magnetic fields too weak to magnetize thermal ions are still sufficient to restore much of the lost reactivity, consistent with the threshold conditions. We also find that the Maxwell-averaged fusion reactivities are recovered more fully in cylindrical targets compared to spherical targets. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  6. Ion acceleration by Alfvén waves on auroral field lines

    NASA Astrophysics Data System (ADS)

    Bingham, Robert; Eliasson, Bengt; Tito Mendonça, José; Stenflo, Lennart

    2013-05-01

    Observations of ion acceleration along auroral field lines at the boundary of the plasma sheet and tail lobe of the Earth show that the energy of the ions increases with decreasing density. The observations can be explained by ion acceleration through Landau resonance with kinetic Alfvén waves (KAWs) such that kA·vi = ωA, where kA is the wave vector, vi is the ion resonance velocity and ωA is the Alfvén wave frequency. The ion resonance velocities are proportional to the Alfvén velocity which increases with decreasing density. This is in agreement with the data if the process is occurring at the plasma sheet tail lobe boundary. A quasi-linear theory of ion acceleration by KAWs is presented. These ions propagate both down towards and away from the Earth. The paths of the Freja and Polar satellites indicate that the acceleration takes place between the two satellites, between 1Re and 5Re. The downward propagating ions develop a horseshoe-type of distribution which has a positive slope in the perpendicular direction. This type of distribution can produce intense lower hybrid wave activity, which is also observed. Finally, the filamentation of shear Alfvén waves is considered. It may be responsible for large-scale density striations. In memory of Padma Kant Shukla, a great scientist and a good friend.

  7. Study on reduction in electric field, charged voltage, ion current and ion density under HVDC transmission lines by parallel shield wires

    SciTech Connect

    Amano, Y.; Sunaga, Y.

    1989-04-01

    An important problem in the design and operation of HVDC transmission lines is to reduce electrical field effects such as ion flow electrification of objects, electric field, ion current and ion density at ground level in the vicinity of HVDC lines. Several models of shield wire were tested with the Shiobara HVDC test line. The models contain typical stranded wires that are generally used to reduce field effects at ground level, neutral conductors placed at lower parts of the DC line, and an ''earth corona model'' to cancel positive or negative ions intentionally by generating ions having opposite polarity to ions flowing into the wire. This report describes the experimental results of the effects of these shield wires and a method to predict shielding effects.

  8. Transport of ions through a (6,6) carbon nanotube under electric fields

    NASA Astrophysics Data System (ADS)

    Shen, Li; Xu, Zhen; Zhou, Zhe-Wei; Hu, Guo-Hui

    2014-11-01

    The transport of water and ions through carbon nanotubes (CNTs) is crucial in nanotechnology and biotechnology. Previous investigation indicated that the ions can hardly pass through (6,6) CNTs due to their hydrated shells. In the present study, utilizing molecular dynamics simulation, it is shown that the energy barrier mainly originating from the hydrated water molecules could be overcome by applying an electric field large enough in the CNT axis direction. Potential of mean force is calculated to show the reduction of energy barrier when the electric field is present for (Na+, K+, Cl-) ions. Consequently, ionic flux through (6,6) CNTs can be found once the electric field becomes larger than a threshold value. The variation of the coordination numbers of ions at different locations from the bulk to the center of the CNT is also explored to elaborate this dynamic process. The thresholds of the electric field are different for Na+, K+, and Cl- due to their characteristics. This consequence might be potentially applied in ion selectivity in the future.

  9. The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupole

    SciTech Connect

    Rodrigues, G. Kanjilal, D.; Roy, A.; Becker, R.; Baskaran, R.

    2014-02-15

    The ion current achievable from high intensity ECR sources for highly charged ions is limited by the high space charge. This makes classical extraction systems for the transport and subsequent matching to a radio frequency quadrupole (RFQ) accelerator less efficient. The direct plasma injection (DPI) method developed originally for the laser ion source avoids these problems and uses the combined focusing of the gap between the ion source and the RFQ vanes (or rods) and the focusing of the rf fields from the RFQ penetrating into this gap. For high performance ECR sources that use superconducting solenoids, the stray magnetic field of the source in addition to the DPI scheme provides focusing against the space charge blow-up of the beam. A combined extraction/matching system has been designed for a high performance ECR ion source injecting into an RFQ, allowing a total beam current of 10 mA from the ion source for the production of highly charged {sup 238}U{sup 40+} (1.33 mA) to be injected at an ion source voltage of 60 kV. In this design, the features of IGUN have been used to take into account the rf-focusing of an RFQ channel (without modulation), the electrostatic field between ion source extraction and the RFQ vanes, the magnetic stray field of the ECR superconducting solenoid, and the defocusing space charge of an ion beam. The stray magnetic field is shown to be critical in the case of a matched beam.

  10. The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupole

    NASA Astrophysics Data System (ADS)

    Rodrigues, G.; Becker, R.; Hamm, R. W.; Baskaran, R.; Kanjilal, D.; Roy, A.

    2014-02-01

    The ion current achievable from high intensity ECR sources for highly charged ions is limited by the high space charge. This makes classical extraction systems for the transport and subsequent matching to a radio frequency quadrupole (RFQ) accelerator less efficient. The direct plasma injection (DPI) method developed originally for the laser ion source avoids these problems and uses the combined focusing of the gap between the ion source and the RFQ vanes (or rods) and the focusing of the rf fields from the RFQ penetrating into this gap. For high performance ECR sources that use superconducting solenoids, the stray magnetic field of the source in addition to the DPI scheme provides focusing against the space charge blow-up of the beam. A combined extraction/matching system has been designed for a high performance ECR ion source injecting into an RFQ, allowing a total beam current of 10 mA from the ion source for the production of highly charged 238U40+ (1.33 mA) to be injected at an ion source voltage of 60 kV. In this design, the features of IGUN have been used to take into account the rf-focusing of an RFQ channel (without modulation), the electrostatic field between ion source extraction and the RFQ vanes, the magnetic stray field of the ECR superconducting solenoid, and the defocusing space charge of an ion beam. The stray magnetic field is shown to be critical in the case of a matched beam.

  11. The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupole.

    PubMed

    Rodrigues, G; Becker, R; Hamm, R W; Baskaran, R; Kanjilal, D; Roy, A

    2014-02-01

    The ion current achievable from high intensity ECR sources for highly charged ions is limited by the high space charge. This makes classical extraction systems for the transport and subsequent matching to a radio frequency quadrupole (RFQ) accelerator less efficient. The direct plasma injection (DPI) method developed originally for the laser ion source avoids these problems and uses the combined focusing of the gap between the ion source and the RFQ vanes (or rods) and the focusing of the rf fields from the RFQ penetrating into this gap. For high performance ECR sources that use superconducting solenoids, the stray magnetic field of the source in addition to the DPI scheme provides focusing against the space charge blow-up of the beam. A combined extraction/matching system has been designed for a high performance ECR ion source injecting into an RFQ, allowing a total beam current of 10 mA from the ion source for the production of highly charged (238)U(40+) (1.33 mA) to be injected at an ion source voltage of 60 kV. In this design, the features of IGUN have been used to take into account the rf-focusing of an RFQ channel (without modulation), the electrostatic field between ion source extraction and the RFQ vanes, the magnetic stray field of the ECR superconducting solenoid, and the defocusing space charge of an ion beam. The stray magnetic field is shown to be critical in the case of a matched beam.

  12. Spatial distribution and energy deposition of precipitating Oxygen ions and their relation with the Martian crustal fields

    NASA Astrophysics Data System (ADS)

    Li, Lei; Zhang, Yiteng

    In the electromagnetic environment set by the MHD model (Ma et al.,2004), considering the dynamic feature of O+ ions, the spatial distributions and energy spectra of O+ ions impacting the atmosphere of Mars are calculated by tracing the trajectories of cold O+ ions launched from the sunlit hemisphere. The effects of the crustal fields on the spatial distribution of precipitating O+ ions are investigated by turning on or off the crustal fields. Global maps of precipitating O+ ion flux show that the crustal fields have no significant effect on the spatial distribution of lower energy precipitating ions(<100eV), while the distribution of higher energyprecipitating O+ ions (>100eV) is closely related with the distribution of the crustal fields. Most O+ ions originated in lower exosphere impact day side atmosphere before getting much energy since the electric field is weak there. O+ ions from higher source may impact the atmosphere with higher energy deposition, forming patchy precipitation regions both at dayside and nightside when the crustal fields are present. A precipitation belt formed by high energy O+ ions (around 1keV) is found near the midnight region, revealing that the crustal fields may change the electromagnetic environment near Mars significantly and result in the acceleration of precipitating O+ ions at the nightside. Together with the rotation of the planet, the consequences of the impacting of O+, including heating and sputtering of the atmosphere and ionosphere, should be much more complicated than expected.

  13. Analysis of a sequence of energetic ion and magnetic field events upstream from the Saturnian magnetosphere

    NASA Astrophysics Data System (ADS)

    Krimigis, S. M.; Sergis, N.; Dialynas, K.; Mitchell, D. G.; Hamilton, D. C.; Krupp, N.; Dougherty, M.; Sarris, E. T.

    2009-12-01

    The existence of energetic particle events to ˜200 RS upstream and ˜1300 RS downstream of Saturn was established during the Voyager 1, 2 flybys in 1980 and 1981, respectively. The origin of the events could not be determined with certainty because of lack of particle charge state and species measurements at lower (<300 keV) energies, which dominate the spectra. High sensitivity observations of energetic ion directional intensities, energy spectra, and ion composition were obtained by the Ion and Neutral Camera (INCA) of the Magnetospheric IMaging Instrument (MIMI) complement, with a geometry factor of ˜2.5 cm 2 sr and some capability of separating light (H, He) and heavier (C, N, O) ion groups (henceforth referred to as 'hydrogen' and 'oxygen', respectively). Charge state information was provided where possible by the Charge-Energy-Mass Spectrometer (CHEMS) over the range ˜3-235 keV per charge, and magnetic field (IMF) data by the MAG instrument on Cassini. The observations revealed the presence of distinct upstream bursts of energetic hydrogen and oxygen ions whenever the IMF connected the spacecraft to the planetary bow shock to distances >80 RS. The events exhibited the following characteristics: (1) hydrogen ion bursts are observed in the energy range 3-220 keV (and occasionally to E>220 keV) and oxygen ion bursts in the energy range 32 to ˜700 keV. (2) Pitch angle distributions are initially anisotropic with ions moving away from the bow shock along the IMF, but tend to isotropize as the event progresses in time. (3) The duration of the ion bursts is several minutes up to 4 h. (4) The event examined in this study contains significant fluxes of singly charged oxygen. (5) Ion bursts are accompanied by distinct diamagnetic field depressions with β>10, and exhibit wave structures consistent with ion cyclotron waves for O + and O ++. Given the magnetic field configuration during the detection of the events and that energetic ions trapped within the

  14. Controlling electron-ion rescattering in two-color circularly polarized femtosecond laser fields

    NASA Astrophysics Data System (ADS)

    Mancuso, Christopher A.; Hickstein, Daniel D.; Dorney, Kevin M.; Ellis, Jennifer L.; Hasović, Elvedin; Knut, Ronny; Grychtol, Patrik; Gentry, Christian; Gopalakrishnan, Maithreyi; Zusin, Dmitriy; Dollar, Franklin J.; Tong, Xiao-Min; Milošević, Dejan B.; Becker, Wilhelm; Kapteyn, Henry C.; Murnane, Margaret M.

    2016-05-01

    High-harmonic generation driven by two-color counter-rotating circularly polarized laser fields was recently demonstrated experimentally as a breakthrough source of bright, coherent, circularly polarized beams in the extreme ultraviolet and soft-x-ray regions. However, the conditions for optimizing the single-atom yield are significantly more complex than for linearly polarized driving lasers and are not fully understood. Here we present a comprehensive study of strong-field ionization—the complementary process to high-harmonic generation—driven by two-color circularly polarized fields. We uncover the conditions that lead to enhanced electron-ion rescattering, which should correspond to the highest single-atom harmonic flux. Using a velocity map imaging photoelectron spectrometer and tomographic reconstruction techniques, we record three-dimensional photoelectron distributions resulting from the strong-field ionization of argon atoms across a broad range of driving laser intensity ratios. In combination with analytical predictions and advanced numerical simulations, we show that "hard" electron-ion rescattering is optimized when the second-harmonic field has an intensity approximately four times higher than that of the fundamental driving field. We also investigate electron-ion rescattering with co-rotating fields, and find that rescattering is significantly suppressed when compared with counter-rotating fields.

  15. Asymmetric Earth

    NASA Astrophysics Data System (ADS)

    Doglioni, Carlo; Carminati, Eugenio; Crespi, Mattia; Cuffaro, Marco; Ismail-Zadeh, Alik; Levshin, Anatoli; Panza, Giuliano F.; Riguzzi, Federica

    2010-05-01

    The net rotation, or so-called W-ward drift of the lithosphere, implies a decoupling of the plates relative to the underlying asthenosphere, and a relative "E-ward" mantle flow. This polarized flow can account for a number of asymmetries. When comparing the W-directed versus the E- to NE-directed subduction zones, as a general observation, they have the subduction hinge diverging versus converging relative to the upper plate; low versus high topography and structural elevation respectively; deep versus shallow trenches and foreland basins; shallow versus deep decollement; low versus high basement involvement; high versus low heat flow and gravity anomaly; shallow versus deep asthenosphere; etc. The western limbs of rift zones show S-waves faster in the lithosphere and slower in the asthenosphere with respect to the eastern limb. The asymmetry can be recognized when moving along the "tectonic equator", which describes the fastest flow of plates relative to the mantle, and it undulates relative to the geographic equator. In our reconstructions, the best fit for the tectonic equator has a pole of rotation at latitude -56.4° and longitude 136.7°, with an angular velocity of 1.2036°/Ma. Shear-wave splitting alignments tend to parallel the tectonic flow, apart along the subduction zones where they become orthogonal, as a flow encountering an obstacle. The tectonic equator lies close to the revolution plane of the Moon about the Earth. All these data and interpretations point for an asymmetric Earth, whose nature appears to be related to the rotation and its tidal despinning, combined with the thermal cooling of the planet. However, this model has been questioned on the basis of the high viscosity so far inferred in the asthenosphere. Preliminary modelling shows that the tidal oscillation can generate gravitational wave propagation in the lithosphere, and the wave velocity can increase with the decrease of the asthenospheric viscosity.

  16. QED and electron collisions in the super strong fields of K-shell actinide ions

    SciTech Connect

    Beiersdorfer, P

    2006-01-25

    Atomic physics of high-Z, heavy ions is very different from that encountered in low-Z or medium-Z ions. The reason is the ultra strong nuclear field found only in the heaviest ions. The highest-Z atomic systems available to physical investigation, the actinides, therefore, offer rich new physics that cannot be studied any other way. This ranges from new dominating forces in electron-ion collisions to tests of fundamental theories. A measurement of the two-loop Lamb shift in uranium is by many considered to be the ''holy grail'' of high-field QED tests of atomic systems. Such measurements have been attempted at heavy-ion accelerator facilities but have yet to succeed because of the difficulty to make measurements with the required accuracy. Also, electron collisions behave very differently in such tightly bound systems. The magnetic interaction between the ion and the incoming free electron (the so-called generalized Breit interaction) is essentially non-existent in collisions involving low and medium-Z ions. This interaction is therefore missing in essentially all electron collision codes. But in heavy, highly charged ions like uranium, the generalized Breit interaction readily is the dominant force, changing electron collision cross sections by a factor of two. This has never been experimentally observed. In fact, no K-shell emission spectrum of any heavy high-Z ion higher than krypton (Z=36) has ever been recorded from a collisional source. By studying the heaviest actinides such fundamental science can be extended to regimes where the highest precision tests can be made.

  17. Kinetic response of ionospheric ions to onset of auroral electric fields

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Kan, J. R.

    1981-01-01

    Examination of the exact analytic solution of a kinetic model of collisional interaction of ionospheric fions with atmospheric neutrals in the Bhatnagar-Gross-Krook approximation, shows that the onset of intense auroral electric fields in the topside ionosphere can produce the following kinetic effects: (1) heat the bulk ionospheric ions to approximately 2 eV, thus driving them up to higher altitudes where they can be subjected to collisionless plasma processes; (2) produce a nonMaxwellian superthermal tail in the distribution function; and (3) cause the ion distribution function to be anisotropic with respect to the magnetic field with the perpendicular average thermal energy exceeding the parallel thermal energy.

  18. Multielement characterization of metal-humic substances complexation by size exclusion chromatography, asymmetrical flow field-flow fractionation, ultrafiltration and inductively coupled plasma-mass spectrometry detection: a comparative approach.

    PubMed

    Bolea, E; Gorriz, M P; Bouby, M; Laborda, F; Castillo, J R; Geckeis, H

    2006-10-06

    The use of three different separation techniques, ultrafiltration (UF), high performance size exclusion chromatography (HPSEC) and asymmetrical flow field-flow fractionation (AsFlFFF), for the characterization of a compost leachate is described. The possible interaction of about 30 elements with different size fractions of humic substances (HS) has been investigated coupling these separation techniques with UV-vis absorption spectrophotometry and inductively coupled plasma-mass spectrometry (ICP-MS) as detection techniques. The organic matter is constituted by a polydisperse mixture of humic substances ranging from low molecular weights (around 1kDa) to significantly larger entities. Elements can be classified into three main groups with regard to their interaction with HS. The first group is constituted by primarily the monovalent alkaline metal ions and anionic species like B, W, Mo, As existing as oxyanions all being not significantly associated to HS. The second group consists of elements that are at least partly associated to a smaller HS size fraction (such as Ni, Cu, Cr and Co). A third group of mainly tri- and tetravalent metal ions like Al, Fe, the lanthanides, Sn and Th are rather associated to larger-sized HS fractions. The three separation techniques provide a fairly consistent size classification for most of the metal ions, even though slight disagreements were observed. The number-average molecular weight (Mn), the weight-average molecular weight (Mw) and the polydispersity (rho) parameters have been calculated both from AsFlFFF and HPSEC experiments and compared for HS and some metal-HS species. Differences in values can be partly explained by an overloading effect observed in the AsFlFFF experiments induced by electrostatic repulsion effects in the low ionic strength, high pH carrier solution. Size information obtained from ultrafiltration is not as resolved as for the other methods. Molecular weight cut-offs (MWCO) of the individual filter

  19. Atoms and Ions Interacting with Particles and Fields: Final Report

    SciTech Connect

    Robicheaux, Francis

    2014-09-18

    This grant supported research in basic atomic, molecular and optical physics related to the interactions of atoms with particles and fields. The duration of the grant was the 10 year period from 8/2003 to 8/2013. All of the support from the grant was used to pay salaries of the PI, postdocs, graduate students, and undergraduates and travel to conferences and meetings. The results were in the form of publications in peer reviewed journals. There were 65 peer reviewed publications over these 10 years with 8 of the publications in Physical Review Letters; all of the other articles were in respected peer reviewed journals (Physical Review A, New Journal of Physics, Journal of Physics B, ...). I will disuss the results for the periods of time relevant for each grant period.

  20. The influence of magnetic fields on the wake field and stopping power of an ion-beam pulse in plasmas

    SciTech Connect

    Zhao, Xiao-ying; Zhang, Ya-ling; Duan, Wen-shan; Qi, Xin E-mail: lyang@impcas.ac.cn; Shi, Jian; Zhang, Ling-yu; Yang, Lei E-mail: lyang@impcas.ac.cn

    2015-09-15

    We performed two-dimensional particle-in-cell simulations to investigate how a magnetic field affects the wake field and stopping power of an ion-beam pulse moving in plasmas. The corresponding density of plasma electrons is investigated. At a weak magnetic field, the wakes exhibit typical V-shaped cone structures. As the magnetic field strengthens, the wakes spread and lose their typical V-shaped structures. At a sufficiently strong magnetic field, the wakes exhibit conversed V-shaped structures. Additionally, strengthening the magnetic field reduces the stopping power in regions of low and high beam density. However, the influence of the magnetic field becomes complicated in regions of moderate beam density. The stopping power increases in a weak magnetic field, but it decreases in a strong magnetic field. At high beam density and moderate magnetic field, two low-density channels of plasma electrons appear on both sides of the incident beam pulse trajectory. This is because electrons near the beam pulses will be attracted and move along with the beam pulses, while other electrons nearby are restricted by the magnetic field and cannot fill the gap.

  1. Ion confinement and transport in a toroidal plasma with externally imposed radial electric fields

    NASA Technical Reports Server (NTRS)

    Roth, J. R.; Krawczonek, W. M.; Powers, E. J.; Kim, Y. C.; Hong, H. Y.

    1979-01-01

    Strong electric fields were imposed along the minor radius of the toroidal plasma by biasing it with electrodes maintained at kilovolt potentials. Coherent, low-frequency disturbances characteristic of various magnetohydrodynamic instabilities were absent in the high-density, well-confined regime. High, direct-current radial electric fields with magnitudes up to 135 volts per centimeter penetrated inward to at least one-half the plasma radius. When the electric field pointed radially toward, the ion transport was inward against a strong local density gradient; and the plasma density and confinement time were significantly enhanced. The radial transport along the electric field appeared to be consistent with fluctuation-induced transport. With negative electrode polarity the particle confinement was consistent with a balance of two processes: a radial infusion of ions, in those sectors of the plasma not containing electrodes, that resulted from the radially inward fields; and ion losses to the electrodes, each of the which acted as a sink and drew ions out of the plasma. A simple model of particle confinement was proposed in which the particle confinement time is proportional to the plasma volume. The scaling predicted by this model was consistent with experimental measurements.

  2. Improvements of the magnetic field design for SPIDER and MITICA negative ion beam sources

    SciTech Connect

    Chitarin, G.; Agostinetti, P.; Aprile, D.; Marconato, N.; Veltri, P.

    2015-04-08

    The design of the magnetic field configuration in the SPIDER and MITICA negative ion beam sources has evolved considerably during the past four years. This evolution was driven by three factors: 1) the experimental results of the large RF-driven ion sources at IPP, which have provided valuable indications on the optimal magnetic configurations for reliable RF plasma source operation and for large negative ion current extraction, 2) the comprehensive beam optics and heat load simulations, which showed that the magnetic field configuration in the accelerator is crucial for keeping the heat load due to electrons on the accelerator grids within tolerable limits, without compromising the optics of the negative ion beam in the foreseen operating scenarios, 3) the progress of the detailed mechanical design of the accelerator, which stimulated the evaluation of different solutions for the correction of beamlet deflections of various origin and for beamlet aiming. On this basis, new requirements and solution concepts for the magnetic field configuration in the SPIDER and MITICA beam sources have been progressively introduced and updated until the design converged. The paper presents how these concepts have been integrated into a final design solution based on a horizontal “long-range” field (few mT) in combination with a “local” vertical field of some tens of mT on the acceleration grids.

  3. Electrostatic ion-cyclotron instability caused by a nonuniform electric field perpendicular to the external magnetic field

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    A new mechanism that can destablize kinetic ion-cyclotron waves in the presence of a nonuniform electric field perpendicular to the uniform ambient magnetic field is given. In the absence of the electric field, the mode energy is positive, while in the presence of a uniform electric field the mode energy could be negative. However, when the electric field is nonuniform, it is possible for a finite region to be of negative wave energy surrounded by regions of positive wave energy. A nonlocal wave packet couples the two regions so that a flow of energy from the region of negative wave energy to the region of positive wave energy will cause the mode to grow. This gives rise to the instability.

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

    SciTech Connect

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

    2014-08-15

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

  5. Systematically Asymmetric Heliospheric Magnetic Field: Evidence for a Quadrupole Mode and Non-Axisymmetry with Polarity Flip-Flops

    NASA Astrophysics Data System (ADS)

    Mursula, K.; Hiltula, T.

    2004-10-01

    Recent studies of the heliospheric magnetic field (HMF) have detected interesting, systematic hemispherical and longitudinal asymmetries which have a profound significance for the understanding of solar magnetic fields. The in situ HMF measurements since the 1960s show that the heliospheric current sheet (HCS) is systematically shifted (coned) southward during solar minimum times, leading to the concept of a bashful ballerina. While temporary shifts can be considerably larger, the average HCS shift (coning) angle is a few degrees, less than the 7.2∘ tilt of the solar rotation axis. Recent solar observations during the last two solar cycles verify these results and show that the magnetic areas in the northern solar hemisphere are larger and their intensity weaker than in the south during long intervals in the late declining to minimum phase. The multipole expansion reveals a strong quadrupole term which is oppositely directed to the dipole term. These results imply that the Sun has a symmetric quadrupole S0 dynamo mode that oscillates in phase with the dominant dipole A0 mode. Moreover, the heliospheric magnetic field has a strong tendency to produce solar tilts that are roughly opposite in longitudinal phase. This implies is a systematic longitudinal asymmetry and leads to a “flip-flop” type behaviour in the dominant HMF sector whose period is about 3.2 years. This agrees very well with the similar flip-flop period found recently in sunspots, as well as with the observed ratio of three between the activity cycle period and the flip-flop period of sun-like stars. Accordingly, these results require that the solar dynamo includes three modes, A0, S0 and a non-axisymmetric mode. Obviously, these results have a great impact on solar modelling.

  6. Tail-ion transport and Knudsen layer formation in the presence of magnetic fields

    SciTech Connect

    Schmit, P. F.; Molvig, Kim; Nakhleh, C. W.

    2013-11-15

    Knudsen layer losses of tail fuel ions could reduce significantly the fusion reactivity of highly compressed cylindrical and spherical targets in inertial confinement fusion (ICF). With the class of magnetized ICF targets in mind, the effect of embedded magnetic fields on Knudsen layer formation is investigated for the first time. The modified energy scaling of ion diffusivity in magnetized hot spots is found to suppress the preferential losses of tail-ions perpendicular to the magnetic field lines to a degree that the tail distribution can be at least partially, if not fully, restored. Two simple threshold conditions are identified leading to the restoration of fusion reactivity in magnetized hot spots. A kinetic equation for tail-ion transport in the presence of a magnetic field is derived, and solutions to the equation are obtained numerically in simulations. Numerical results confirm the validity of the threshold conditions for restored reactivity and identify two different asymptotic regimes of the fusion fuel. While Knudsen layer formation is shown to be suppressed entirely in strongly magnetized cylindrical hot spot cavities, uniformly magnetized spherical cavities demonstrate remnant, albeit reduced, levels of tail-ion depletion.

  7. The statistical relationship between magnetosheath ion temperatures and magnetic field perturbations throughout the dayside magnetosheath.

    NASA Astrophysics Data System (ADS)

    Dimmock, Andrew; Osmane, Adnane; Pulkkinen, Tuija; Nykyri, Katariina

    2016-04-01

    The magnetosheath layer functions as an interface between interplanetary and near Earth space. As a result, the magnetosheath plasma properties dictate the efficiency and occurrence of processes which regulate the energy and momentum transport to the inner magnetosphere. Two (and possibly correlated) magnetosheath plasma properties which may play a significant role are ion temperatures and magnetic field perturbations; both of which comfortably exceed their solar wind counterparts. It has been proposed that magnetic field fluctuations, particularly those close to ion gyro-scales, can heat ions. In some cases, especially close to the magnetopause, these may facilitate diffusive plasma transport via kinetic Alfvén waves. The results presented here describe a statistical study using THEMIS and OMNI data between 2008 through 2015 in which we study the statistical relationship between magnetosheath ion temperatures and magnetic field variations over Pc 1-5 scale lengths. We show that higher amplitude fluctuations behind the quasi-parallel shock can produce higher ion temperatures subsequently driving a dawn-dusk asymmetry. We will also determine which scale/s are more effective at driving higher temperatures. We ascertain whether this relationship varies with spatial location, and if there are any global implications.

  8. Broadscale resolving power performance of a high precision uniform field ion mobility-mass spectrometer.

    PubMed

    May, Jody C; Dodds, James N; Kurulugama, Ruwan T; Stafford, George C; Fjeldsted, John C; McLean, John A

    2015-10-21

    An extensive study of two current ion mobility resolving power theories ("conditional" and "semi-empirical") was undertaken using a recently developed drift tube ion mobility-mass spectrometer. The current study investigates the quantitative agreement between experiment and theory at reduced pressure (4 Torr) for a wide range of initial ion gate widths (100 to 500 μs), and ion mobility values (K0 from 0.50 to 3.0 cm(2) V(-1) s(-1)) representing measurements obtained in helium, nitrogen, and carbon dioxide drift gas. Results suggest that the conditional resolving power theory deviates from experimental results for low mobility ions (e.g., high mass analytes) and for initial ion gate widths beyond 200 μs. A semi-empirical resolving power theory provided close-correlation of predicted resolving powers to experimental results across the full range of mobilities and gate widths investigated. Interpreting the results from the semi-empirical theory, the performance of the current instrumentation was found to be highly linear for a wide range of analytes, with optimal resolving powers being accessible for a narrow range of drift fields between 14 and 17 V cm(-1). While developed using singly-charged ion mobility data, preliminary results suggest that the semi-empirical theory has broader applicability to higher-charge state systems.

  9. Selective detection of heavy metal ions by self assembled chemical field effect transistors

    NASA Astrophysics Data System (ADS)

    Ruan, Hang; Kang, Yuhong; Gladwin, Elizabeth; Claus, Richard O.

    2015-04-01

    Multiple layer-by-layer sensor material modifications were designed and implemented to achieve selectivity of semiconductor based chemical field effect transistors (ChemFETs) to particular heavy metal ions. The ChemFET sensors were fabricated and modified in three ways, with the intent to initially target first mercury and lead ions and then chromium ions, respectively. Sensor characterization was performed with the gate regions of the sensor elements exposed to different concentrations of target heavy metal ion solutions. A minimum detection level in the range of 0.1 ppm and a 10%-90% response time of less than 10 s were demonstrated. By combining layer-by-layer gold nanoparticles and lead ionophores, a sensor is produced that is sensitive and selective not only to chromium but also to Cr3+ and Cr6+. This result supports the claim that high selectivity can be achieved by designing self-assembled bonding for lead, arsenic, chromium, cesium, mercury, and cadmium.

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

    SciTech Connect

    MacDonald, N. A.; Young, C. V.; Cappelli, M. A.; Hargus, W. A. Jr.

    2012-05-01

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

  11. Electric field simulation and measurement of a pulse line ion accelerator

    NASA Astrophysics Data System (ADS)

    Shen, Xiao-Kang; Zhang, Zi-Min; Cao, Shu-Chun; Zhao, Hong-Wei; Wang, Bo; Shen, Xiao-Li; Zhao, Quan-Tang; Liu, Ming; Jing, Yi

    2012-07-01

    An oil dielectric helical pulse line to demonstrate the principles of a Pulse Line Ion Accelerator (PLIA) has been designed and fabricated. The simulation of the axial electric field of an accelerator with CST code has been completed and the simulation results show complete agreement with the theoretical calculations. To fully understand the real value of the electric field excited from the helical line in PLIA, an optical electric integrated electric field measurement system was adopted. The measurement result shows that the real magnitude of axial electric field is smaller than that calculated, probably due to the actual pitch of the resister column which is much less than that of helix.

  12. An exposure chamber for studies on human perception of DC electric fields and ions

    SciTech Connect

    Nguyen, D.H.; Maruvada, P.S. )

    1994-10-01

    Direct current (DC) transmission lines are often used, for technical and economic reasons, as interconnections in modern high voltage power systems, which are essentially of the alternating current (AC) type. Significant differences exist, however, between the field effects produced in the vicinity of AC and DC transmission lines. DC electric fields induce charges, on the surface of a conducting body such as a human being and may therefore be ''perceived'' by humans due to hair stimulation and other sensations experienced by the skin. A human being exposed to the ionized field of a DC transmission line experiences not only surface charges but also the conducted ion currents. A systematic laboratory study has been undertaken by Hydro Quebec to investigate human perception, using well established psycho physical techniques, of DC electric fields and ions. The design, construction and operation of an exposure chamber for this purpose, in the high voltage laboratory of IREQ, are described in this paper.

  13. Influence of Magnet Multipole Field Components on Beam Dynamics in the JLEIC Ion Collider Ring

    SciTech Connect

    Wei, Guohui; Morozov, Vasiliy; Lin, Fanglei; Zhang, Yuhong; Pilat, Fulvia C.; Wang, Min-Huey

    2016-05-01

    To get a luminosity level of a few 1033 cm-2ses₋1 at all design points of the Jefferson Lab Electron Ion Collider (JLEIC) project, small β* values in both horizontal and vertical planes are necessary at the Interaction Point (IP) in the ion collider ring. This also means large β in the final focus area, chromaticity correction sections, etc. which sets a constraint on the field quality of magnets in large beta areas, in order to ensure a large enough dynamic aperture (DA). In this context, limiting multipole field components of magnets are surveyed to find a possible compromise between the requirements and what can be realistically achieved by a magnet manufacturer. This paper describes that work. Moreover, non-linear field dedicated correctors are also studied to provide semi-local corrections of specific multipole field components.

  14. Development of an applied-magnetic-field diode for ion-beam-transport experiments

    SciTech Connect

    Young, F.C.; Neri, J.M.; Boller, J.R.

    1996-12-31

    An applied-magnetic-field ion diode (ABD) is being developed to study the transport of intense ion beams for light-ion inertial confinement fusion. Initially, the beam from this diode will be used to test the concept of self-pinched transport (SPT). The design goal is diode operation at 1.5 MV and 250-kA total current on the Gamble 2 generator at NRL. For SPT experiments, the beam is extracted from the diode and focused into a transport channel. The ATHETA code is used to calculate B-field configurations in the diode and ion-beam trajectories. Shaping of the anode surface to aim the beam and to counteract focusing due to self B-field and solenoidal-lens effects results in a convex anode surface. Most of the beam can be focused within a spot size of 1.4-cm diameter at 65 cm from the anode. The B-field is generated with inner and outer cathode coils connected in series and driven by a 100-{micro}s risetime, 50-kA pulse. A shunt inductor in parallel with the outer coil is used to control the ratio of the currents in the two coils. To cancel flux penetration of the aluminum anode by the main B-field, a current pulse of opposite polarity with a 1-ms risetime is applied prior to the main pulse. This current is adjusted to place the B-field separatrix on the ion emission surface in the diode gap, accounting for anode plasma expansion. A grooved-anode flashover source is planned for initial experiments. Preliminary results are presented.

  15. Thermal ion imagers and Langmuir probes in the Swarm electric field instruments

    NASA Astrophysics Data System (ADS)

    Knudsen, D. J.; Burchill, J. K.; Buchert, S. C.; Eriksson, A. I.; Gill, R.; Wahlund, J.-E.; Åhlen, L.; Smith, M.; Moffat, B.

    2017-02-01

    The European Space Agency's three Swarm satellites were launched on 22 November 2013 into nearly polar, circular orbits, eventually reaching altitudes of 460 km (Swarm A and C) and 510 km (Swarm B). Swarm's multiyear mission is to make precision, multipoint measurements of low-frequency magnetic and electric fields in Earth's ionosphere for the purpose of characterizing magnetic fields generated both inside and external to the Earth, along with the electric fields and other plasma parameters associated with electric current systems in the ionosphere and magnetosphere. Electric fields perpendicular to the magnetic field B→ are determined through ion drift velocity v→i and magnetic field measurements via the relation E→⊥=-v→i×B→. Ion drift is derived from two-dimensional images of low-energy ion distribution functions provided by two Thermal Ion Imager (TII) sensors viewing in the horizontal and vertical planes; v→i is corrected for spacecraft potential as determined by two Langmuir probes (LPs) which also measure plasma density ne and electron temperature Te. The TII sensors use a microchannel-plate-intensified phosphor screen imaged by a charge-coupled device to generate high-resolution distribution images (66 × 40 pixels) at a rate of 16 s-1. Images are partially processed on board and further on the ground to generate calibrated data products at a rate of 2 s-1; these include v→i, E→⊥, and ion temperature Ti in addition to electron temperature Te and plasma density ne from the LPs.

  16. Field-enhanced ion transport in solids: Reexamination with molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Genreith-Schriever, A. R.; De Souza, R. A.

    2016-12-01

    Classical molecular-dynamics simulations were used to examine the effect of an electric field on the mobility of oxygen ions in the model crystalline oxide CeO2. Simulation cells containing oxygen vacancies were subjected at temperatures 1000 ≤T /K ≤1600 to electric field strengths 0.1 ≤E /MV cm-1≤40 to obtain the oxygen-ion mobility ui(E ,T ) . In addition, static nudged-elastic-band calculations were performed to obtain directly the forward/reverse barriers for oxygen-ion migration, Δ Hmigf /r . Qualitatively, ui behaves as expected: independent of E at low values of E and exponentially dependent on E at high values. The quantitative (standard) Mott-Gurney treatment, however, underestimates Δ Hmigf at high E and thus overestimates ui. A new, superior analytical expression for ui(E ,T ) is consequently derived.

  17. Concepts of magnetic filter fields in powerful negative ion sources for fusion

    SciTech Connect

    Kraus, W. Fantz, U.; Heinemann, B.; Wünderlich, D.

    2016-02-15

    The performance of large negative ion sources used in neutral beam injection systems is in long pulses mainly determined by the increase of the currents of co-extracted electrons. This is in particular a problem in deuterium and limits the ion currents which are for long pulses below the requirements for the ITER source. In the source of the ELISE test facility, the magnetic field in front of the first grid, which is essential to reduce the electron current, is generated by a current of several kA flowing through the plasma facing grid. Weakening of this field by the addition of permanent magnets placed close to the lateral walls has led to a reduction of the electron current by a factor three without loss of ion current when source was operated in volume production. If this effect can be validated for the cesiated source, it would be a large step towards achieving the ITER parameter in long pulses.

  18. Crystal-field calculations for transition-metal ions by application of an opposing potential

    DOE PAGES

    Zhou, Fei; Aberg, Daniel

    2016-02-16

    We propose a fully ab initio method, the opposing crystal potential (OCP), to calculate the crystal-field parameters of transition-metal impurities in insulator hosts. Through constrained density functional calculations, OCP obtains the constraining Lagrange multipliers, which act as a cancellation potential against the crystal field and lead to spherical d-electron distribution. Furthermore, the method is applied to several insulators doped with Mn4+ and Mn2+ ions and shown to be in good agreement with experiment.

  19. Analysis of β-glucan molar mass from barley malt and brewer's spent grain with asymmetric flow field-flow fractionation (AF4) and their association to proteins.

    PubMed

    Zielke, Claudia; Teixeira, Cristina; Ding, Huihuang; Cui, Steve; Nyman, Margareta; Nilsson, Lars

    2017-02-10

    β-Glucan benefits are related with its molar mass and it would be of interest to better understand how this parameter can be changed by processing and variety for design of food with specific health effects. For this purpose, extracts from barley malts and brewers' spent grain, processed at different conditions, were analysed regarding β-glucan content, molar mass, and protein content. Molar mass distribution was assessed using asymmetric flow field-flow fractionation (AF4) with multiangle light scattering (MALS), differential refractive index (dRI) and fluorescence (FL) detection. β-Glucan was detected in a wide molar mass range, <2000 to approximately 6.7×10(6)g/mol. Differences in molar masses were more noticeable between barley varieties and steeping malting conditions than by mashing of malt. Barley products processed to preserve β-glucan contained more β-glucan of high molar mass with potential to shift the fermentation site to the distal colon. Enzymatic degradation of proteins indicated presence of aggregates containing β-glucan and protein.

  20. Size separations of starch of different botanical origin studied by asymmetrical-flow field-flow fractionation and multiangle light scattering.

    PubMed

    Wahlund, Karl-Gustav; Leeman, Mats; Santacruz, Stalin

    2011-02-01

    Asymmetrical-flow field-flow fractionation combined with multiangle light scattering and refractive index detection has been revealed to be a powerful tool for starch characterization. It is based on size separation according to the hydrodynamic diameter of the starch components. Starch from a wide range of different botanical sources were studied, including normal starch and high-amylose and high-amylopectin starch. The starch was dissolved by heat treatment at elevated pressure in a laboratory autoclave. This gave clear solutions with no granular residues. Amylose retrogradation was prevented by using freshly dissolved samples. Programmed cross flow starting at 1.0 mL min(-1) and decreasing exponentially with a half-life of 4 min was utilised. The starches showed two size populations representing mainly amylose and mainly amylopectin with an overlapping region where amylose and amylopectin were possibly co-eluted. Most of the first population had molar masses below 10(6) g mol(-1), and most of the second size population had molar masses above 10(7) g mol(-1). Large differences were found in the relative amounts of the two populations, the molar mass, and hydrodynamic diameters, depending on the plant source and its varieties.

  1. Coupling asymmetric flow-field flow fractionation and fluorescence parallel factor analysis reveals stratification of dissolved organic matter in a drinking water reservoir.

    PubMed

    Pifer, Ashley D; Miskin, Daniel R; Cousins, Sarah L; Fairey, Julian L

    2011-07-08

    Using asymmetrical flow field-flow fractionation (AF4) and fluorescence parallel factor analysis (PARAFAC), we showed physicochemical properties of chromophoric dissolved organic matter (CDOM) in the Beaver Lake Reservoir (Lowell, AR) were stratified by depth. Sampling was performed at a drinking water intake structure from May to July 2010 at three depths (3-, 10-, and 18-m) below the water surface. AF4-fractograms showed that the CDOM had diffusion coefficient peak maximums between 3.5 and 2.8 x 10⁻⁶ cm² s⁻¹, which corresponded to a molecular weight range of 680-1950 Da and a size of 1.6-2.5 nm. Fluorescence excitation-emission matrices of whole water samples and AF4-generated fractions were decomposed with a PARAFAC model into five principal components. For the whole water samples, the average total maximum fluorescence was highest for the 10-m depth samples and lowest (about 40% less) for 18-m depth samples. While humic-like fluorophores comprised the majority of the total fluorescence at each depth, a protein-like fluorophore was in the least abundance at the 10-m depth, indicating stratification of both total fluorescence and the type of fluorophores. The results present a powerful approach to investigate CDOM properties and can be extended to investigate CDOM reactivity, with particular applications in areas such as disinfection byproduct formation and control and evaluating changes in drinking water source quality driven by climate change.

  2. Characterization of oxidized tannins: comparison of depolymerization methods, asymmetric flow field-flow fractionation and small-angle X-ray scattering.

    PubMed

    Vernhet, Aude; Dubascoux, Stéphane; Cabane, Bernard; Fulcrand, Hélène; Dubreucq, Eric; Poncet-Legrand, Céline

    2011-09-01

    Condensed tannins are a major class of plant polyphenols. They play an important part in the colour and taste of foods and beverages. Due to their chemical reactivity, tannins are not stable once extracted from plants. A number of chemical reactions can take place, leading to structural changes of the native structures to give so-called derived tannins and pigments. This paper compares results obtained on native and oxidized tannins with different techniques: depolymerization followed by high-performance liquid chromatography analysis, small-angle X-ray scattering (SAXS) and asymmetric flow field-flow fractionation (AF4). Upon oxidation, new macromolecules were formed. Thioglycolysis experiments showed no evidence of molecular weight increase, but thioglycolysis yields drastically decreased. When oxidation was performed at high concentration (e.g., 10 g L(-1)), the weight average degree of polymerization determined from SAXS increased, whereas it remained stable when oxidation was done at low concentration (0.1 g L(-1)), indicating that the reaction was intramolecular, yet the conformations were different. Differences in terms of solubility were observed; ethanol being a better solvent than water. We also separated soluble and non-water-soluble species of a much oxidized fraction. Thioglycolysis showed no big differences between the two fractions, whereas SAXS and AF4 showed that insoluble macromolecules have a weight average molecular weight ten times higher than the soluble ones.

  3. Importance of material matching in the calibration of asymmetric flow field-flow fractionation: material specificity and nanoparticle surface coating effects on retention time

    NASA Astrophysics Data System (ADS)

    Qu, Haiou; Quevedo, Ivan R.; Linder, Sean W.; Fong, Andrew; Mudalige, Thilak K.

    2016-10-01

    Asymmetric flow field-flow fractionation (AF4) coupled with dynamic light scattering or multiangle light scattering detectors is a promising technique for the size-based separation of colloidal particles (nano- and submicron scale) and the online determination of the particle size of the separated fractions in aqueous suspensions. In most cases, the applications of these detectors are problematic due to the material-specific properties of the analyte that results in erroneous calculations, and as an alternative, different nanoparticle size standards are required to properly calibrate the size-based retention in AF4. The availability of nanoparticle size standards in different materials is limited, and this deviation from ideal conditions of retention is mainly due to material-specific and particle coating-specific membrane-particle interactions. Here, we present an experimental method on the applicability of polystyrene nanoparticles (PS NP) as standard for AF4 calibration and compare with gold nanoparticle (Au NP) standards having different nominal sizes and surface functionalities.

  4. Asymmetric flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry for the quantification of quantum dots bioconjugation efficiency.

    PubMed

    Menéndez-Miranda, Mario; Encinar, Jorge Ruiz; Costa-Fernández, José M; Sanz-Medel, Alfredo

    2015-11-27

    Hyphenation of asymmetric flow field-flow fractionation (AF4) to an on-line elemental detection (inductively coupled plasma-mass spectrometry, ICP-MS) is proposed as a powerful diagnostic tool for quantum dots bioconjugation studies. In particular, conjugation effectiveness between a "model" monoclonal IgG antibody (Ab) and CdSe/ZnS core-shell Quantum Dots (QDs), surface-coated with an amphiphilic polymer, has been monitored here by such hybrid AF4-ICP-MS technique. Experimental conditions have been optimized searching for a proper separation between the sought bioconjugates from the eventual free reagents excesses employed during the bioconjugation (QDs and antibodies). Composition and pH of the carrier have been found to be critical parameters to ensure an efficient separation while ensuring high species recovery from the AF4 channel. An ICP-MS equipped with a triple quadropole was selected as elemental detector to enable sensitive and reliable simultaneous quantification of the elemental constituents, including sulfur, of the nanoparticulated species and the antibody. The hyphenated technique used provided nanoparticle size-based separation, elemental detection, and composition analysis capabilities that turned out to be instrumental in order to investigate in depth the Ab-QDs bioconjugation process. Moreover, the analytical strategy here proposed allowed us not only to clearly identify the bioconjugation reaction products but also to quantify nanoparticle:antibodies bioconjugation efficiency. This is a key issue in future development of analytical and bioanalytical photoluminescent QDs applications.

  5. Simulations of ion acceleration at non-relativistic shocks. II. Magnetic field amplification

    SciTech Connect

    Caprioli, D.; Spitkovsky, A.

    2014-10-10

    We use large hybrid simulations to study ion acceleration and generation of magnetic turbulence due to the streaming of particles that are self-consistently accelerated at non-relativistic shocks. When acceleration is efficient, we find that the upstream magnetic field is significantly amplified. The total amplification factor is larger than 10 for shocks with Alfvénic Mach number M = 100, and scales with the square root of M. The spectral energy density of excited magnetic turbulence is determined by the energy distribution of accelerated particles, and for moderately strong shocks (M ≲ 30) agrees well with the prediction of resonant streaming instability, in the framework of quasilinear theory of diffusive shock acceleration. For M ≳ 30, instead, Bell's non-resonant hybrid (NRH) instability is predicted and found to grow faster than resonant instability. NRH modes are excited far upstream by escaping particles, and initially grow without disrupting the current, their typical wavelengths being much shorter than the current ions' gyroradii. Then, in the nonlinear stage, most unstable modes migrate to larger and larger wavelengths, eventually becoming resonant in wavelength with the driving ions, which start diffuse. Ahead of strong shocks we distinguish two regions, separated by the free-escape boundary: the far upstream, where field amplification is provided by the current of escaping ions via NRH instability, and the shock precursor, where energetic particles are effectively magnetized, and field amplification is provided by the current in diffusing ions. The presented scalings of magnetic field amplification enable the inclusion of self-consistent microphysics into phenomenological models of ion acceleration at non-relativistic shocks.

  6. Probing High-Velocity Transient-Field Strength Using Heavy-ions Traversing Fe and Gd

    SciTech Connect

    Fiori, E.; Georgiev, G.; Cabaret, S.; Lozeva, R.; Jungclaus, A.; Modamio, V.; Walker, J.; Balabanski, D. L.; Blazhev, A.; Clement, E.; Grevy, S.; Stodel, C.; Thomas, J. C.; Danchev, M.; Daugas, J. M.; Hass, M.; Kumar, V.; Leske, J.; Pietralla, N.

    2009-08-26

    The transient field strength for {sup 76}Ge ions, passing through iron and gadolinium layers at velocities approxZv{sub 0}, has been measured. Although a sizeable value has been obtained for Gd, a vanishing strength has been observed in Fe.

  7. Field Ion Microscopy and Atom Probe Tomography of Metamorphic Magnetite Crystals

    NASA Technical Reports Server (NTRS)

    Kuhlman, K.; Martens, R. L.; Kelly, T. F.; Evans, N. D.; Miller, M. K.

    2001-01-01

    Magnetite has been analysed using Field Ion Microscopy (FIM) and Atom Probe Tomography (APT), highly attractive techniques for the nanoanalysis of geological materials despite the difficulties inherent in analyzing semiconducting and insulating materials. Additional information is contained in the original extended abstract.

  8. Observation of increased ion cyclotron resonance signal duration through electric field perturbations.

    PubMed

    Kaiser, Nathan K; Bruce, James E

    2005-09-15

    Ion motion in Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is complex and the subject of ongoing theoretical and experimental studies. Two predominant pathways for the loss of ICR signals are thought to include damping of cyclotron motion, in which ions lose kinetic energy and radially damp toward the center of the ICR cell, and dephasing of ion coherence, in which ions of like cyclotron frequency become distributed out of phase at similar cyclotron radii. Both mechanisms result in the loss of induced ion image current in FTICR-MS measurements and are normally inseparable during time-domain signal analysis. For conventional ICR measurements which take advantage of ion ensembles, maximization of the ion population size and density can produce the desired effect of increasing phase coherence of ions during cyclotron motion. However, this approach also presents the risk of coalescence of ion packets of similar frequencies. In general, ICR researchers in the past have lacked the tools necessary to distinguish or independently control dephasing and damping mechanisms for ICR signal loss. Nonetheless, the ability to impart greater phase coherence of ions in ICR measurements will allow significant advances in FTICR-MS research by improving the current understanding of ICR signal loss contributions of dephasing and damping of ion ensembles, increasing overall time-domain signal length, and possibly, resulting in more routine ultrahigh resolution measurements. The results presented here demonstrate the ability to employ a high density electron beam to perturb electric fields within the ICR cell during detection of cyclotron motion, in an approach we call electron-promoted ion coherence (EPIC). As such, EPIC reduces ICR signal degradation through loss of phase coherence, and much longer time-domain signals can be obtained. Our results demonstrate that time-domain signals can be extended by more than a factor of 4 with the implementation of EPIC, as

  9. Nanofriction in cold ion traps.

    PubMed

    Benassi, A; Vanossi, A; Tosatti, E

    2011-01-01

    Sliding friction between crystal lattices and the physics of cold ion traps are so far non-overlapping fields. Two sliding lattices may either stick and show static friction or slip with dynamic friction; cold ions are known to form static chains, helices or clusters, depending on the trapping conditions. Here we show, based on simulations, that much could be learnt about friction by sliding, through, for example, an electric field, the trapped ion chains over a corrugated potential. Unlike infinite chains, in which the theoretically predicted Aubry transition to free sliding may take place, trapped chains are always pinned. Yet, a properly defined static friction still vanishes Aubry-like at a symmetric-asymmetric structural transition, found for decreasing corrugation in both straight and zig-zag trapped chains. Dynamic friction is also accessible in ringdown oscillations of the ion trap. Long theorized static and dynamic one-dimensional friction phenomena could thus become accessible in future cold ion tribology.

  10. Transverse eV ion heating by random electric field fluctuations in the plasmasphere

    NASA Astrophysics Data System (ADS)

    Artemyev, A. V.; Mourenas, D.; Agapitov, O. V.; Blum, L.

    2017-02-01

    Charged particle acceleration in the Earth inner magnetosphere is believed to be mainly due to the local resonant wave-particle interaction or particle transport processes. However, the Van Allen Probes have recently provided interesting evidence of a relatively slow transverse heating of eV ions at distances about 2-3 Earth radii during quiet times. Waves that are able to resonantly interact with such very cold ions are generally rare in this region of space, called the plasmasphere. Thus, non-resonant wave-particle interactions are expected to play an important role in the observed ion heating. We demonstrate that stochastic heating by random transverse electric field fluctuations of whistler (and possibly electromagnetic ion cyclotron) waves could explain this weak and slow transverse heating of H+ and O+ ions in the inner magnetosphere. The essential element of the proposed model of ion heating is the presence of trains of random whistler (hiss) wave packets, with significant amplitude modulations produced by strong wave damping, rapid wave growth, or a superposition of wave packets of different frequencies, phases, and amplitudes. Such characteristics correspond to measured characteristics of hiss waves in this region. Using test particle simulations with typical wave and plasma parameters, we demonstrate that the corresponding stochastic transverse ion heating reaches 0.07-0.2 eV/h for protons and 0.007-0.015 eV/h for O+ ions. This global temperature increase of the Maxwellian ion population from an initial Ti˜0.3 eV could potentially explain the observations.

  11. Electron cyclotron resonance heating by magnetic filter field in a negative hydrogen ion source

    SciTech Connect

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

    2016-02-15

    The influence of magnetic filter field on plasma properties in the heating region has been investigated in a planar-type inductively coupled radio-frequency (RF) H{sup −} ion source. Besides filtering high energy electrons near the extraction region, the magnetic filter field is clearly observed to increase the electron temperature in the heating region at low pressure discharge. With increasing the operating pressure, enhancement of electron temperature in the heating region is reduced. The possibility of electron cyclotron resonance (ECR) heating in the heating region due to stray magnetic field generated by a filter magnet located at the extraction region is examined. It is found that ECR heating by RF wave field in the discharge region, where the strength of an axial magnetic field is approximately ∼4.8 G, can effectively heat low energy electrons. Depletion of low energy electrons in the electron energy distribution function measured at the heating region supports the occurrence of ECR heating. The present study suggests that addition of axial magnetic field as small as several G by an external electromagnet or permanent magnets can greatly increase the generation of highly ro-vibrationally excited hydrogen molecules in the heating region, thus improving the performance of H{sup −} ion generation in volume-produced negative hydrogen ion sources.

  12. Electrokinetic ion transport through unsaturated soil: 2. Application to a heterogeneous field site.

    PubMed

    Mattson, Earl D; Bowman, Robert S; Lindgren, Eric R

    2002-01-01

    Results of a field demonstration of electrokinetic transport of acetate through an unsaturated heterogeneous soil are compared to numerical modeling predictions. The numerical model was based on the groundwater flow and transport codes MODFLOW and MT3D modified to account for electrically induced ion transport. The 6-month field demonstration was conducted in an unsaturated layered soil profile where the soil moisture content ranged from 4% to 28% (m3 m(-3)). Specially designed ceramic-cased electrodes maintained a steady-state moisture content and electric potential field between the electrodes during the field demonstration. Acetate, a byproduct of acetic acid neutralization of the cathode electrolysis reaction, was transported from the cathode to the anode by electromigration. Field demonstration results indicated preferential transport of acetate through soil layers exhibiting higher moisture content/electrical conductivity. These field transport results agree with theoretical predictions that electromigration velocity is proportional to a power function of the effective moisture content. A numerical model using a homogeneous moisture content/electrical conductivity domain did not adequately predict the acetate field results. Numerical model predictions using a three-layer electrical conductivity/moisture content profile agreed qualitatively with the observed acetate distribution. These results suggest that field heterogeneities must be incorporated into electrokinetic models to predict ion transport at the field-scale.

  13. Hydrodynamic radius determination with asymmetrical flow field-flow fractionation using decaying cross-flows. Part I. A theoretical approach.

    PubMed

    Håkansson, Andreas; Magnusson, Emma; Bergenståhl, Björn; Nilsson, Lars

    2012-08-31

    Direct determination of hydrodynamic radius from retention time is an advantage of the field-flow fractionation techniques. However, this is not always completely straight forward since non-idealities exist and assumptions have been made in deriving the retention equations. In this study we investigate the effect on accuracy from two factors: (1) level of sophistication of the equations used to determine channel height from a calibration experiment and (2) the influence of secondary relaxation on the accuracy of hydrodynamic radius determination. A new improved technique for estimating the channel height from calibration experiments is suggested. It is concluded that severe systematic error can arise if the most common channel height equations are used and an alternative more rigorous approach is described. For secondary relaxation it is concluded that this effect increases with the cross-flow decay rate. The secondary relaxation effect is quantified for different conditions. This is part one of two. In the second part the determination of hydrodynamic radius are evaluated experimentally under similar conditions.

  14. Simulations of the equatorial thermosphere anomaly: Field-aligned ion drag effect

    NASA Astrophysics Data System (ADS)

    Lei, Jiuhou; Thayer, Jeffrey P.; Wang, Wenbin; Richmond, Arthur D.; Roble, Raymond; Luan, Xiaoli; Dou, Xiankang; Xue, Xianghui; Li, Tao

    2012-01-01

    In this paper the impact of the field-aligned ion drag on equatorial thermosphere temperature and density is quantitatively investigated on the basis of the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (NCAR TIEGCM) simulations under high solar activity (F107 = 180). The increase of upward vertical winds over the magnetic equator associated with the additional divergence of meridional winds, caused by the inclusion of field-aligned ion drag, leads to a reduction in thermosphere temperature and density at the magnetic equator through enhanced adiabatic cooling. We found that the field-aligned ion drag has an obvious impact on the thermosphere only over the magnetic equatorial region in the daytime and evening sectors, whereas it has less effect on the equatorial thermosphere anomaly (ETA) crests. The daytime neutral temperature over the magnetic equator is reduced by about 30 K, for altitudes above 250 km without significant altitudinal variations, when field-aligned ion drag is included in the simulation. The thermosphere density in the magnetic equatorial region starts to change slightly at 300 km and depletes by about 5% at 400 km, while experiencing a greater decrease with altitude. Furthermore, the trough produced in the neutral temperature and density corresponds well with the magnetic dip equator. The ETA features during 12:00-18:00 LT become obvious as a result of the inclusion of the field-aligned ion drag. Specifically, our results show that at 400 km the crest-trough differences in neutral temperature are about 30-60 K, and the crest-trough ratios in thermosphere density are 1.03-1.06, comparable with observations.

  15. Laser micro-machinability of borosilicate glass surface-modified by electric field-assisted ion-exchange method

    NASA Astrophysics Data System (ADS)

    Matsusaka, S.; Kobayakawa, T.; Hidai, H.; Morita, N.

    2012-08-01

    In order to improve the laser micro-machinability of borosilicate glass, the glass surface was doped with metal (silver or copper) ions by an electric field-assisted ion-exchange method. Doped ions drifted and diffused into the glass substrate under a DC electric field. The concentration of metal ions within the doped area was approximately constant because the ion penetration was caused by substitution between dopant metal and inherent sodium ions. Nanosecond ultraviolet laser irradiation of metal-containing regions produced flat, smooth and defect-free holes. However, the shapes of holes were degraded when the processed hole bottoms reached ion penetration depths. A numerical analysis of ionic drift-diffusion behaviour in glass material under an electric field was also carried out. The calculated results for penetration depth and ionic flux showed good agreement with the measured values.

  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. 'Junction-Level' Heterogeneous Integration of III-V Materials with Si CMOS for Novel Asymmetric Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Chang, Yoon Jung

    Driven by Moore's law, semiconductor chips have become faster, denser and cheaper through aggressive dimension scaling. The continued scaling not only led to dramatic performance improvements in digital logic applications but also in mixed-mode and/or communication applications. Moreover, size/weight/power (SWAP) restrictions on all high-performance system components have resulted in multi-functional integration of multiple integrated circuits (ICs)/dies in 3D packages/ICs by various system-level approaches. However, these approaches still possess shortcomings and in order to truly benefit from the most advanced digital technologies, the future high-speed/high power devices for communication applications need to be fully integrated into a single CMOS chip. Due to limitations in Si device performance in high-frequency/power applications as well as expensive III-V compound semiconductor devices with low integration density, heterogeneous integration of compound semiconductor materials/devices with Si CMOS platform has emerged as a viable solution to low-cost high-performance ICs. In this study, we first discuss on channel and drain engineering approaches in the state-of-the-art multiple-gate field-effect transistor to integrate III-V compound semiconductor materials with Si CMOS for improved device performance in mixed-mode and/or communication applications. Then, growth, characterization and electrical analysis on small-area (diameter < 100nm) complete selective-area epitaxy of GaAs/GaN will be demonstrated for achieving 'dislocation-free' III-V compound semiconductor film on a Si(001) substrate. Based on a success in dislocation-free heterogeneous III-V film growth, we propose a novel ultra-scaled 'junction-level' heterogeneous integration onto mainstream Si CMOS platform. Device architecture and its key features to overcome aforementioned challenges will be given to demonstrate the potential to improve the overall system performance with diverse functionality.

  18. Plasma and Energetic Particle Behaviors During Asymmetric Magnetic Reconnection at the Magnetopause

    NASA Technical Reports Server (NTRS)

    Lee, S. H.; Zhang, H.; Zong, Q.-G.; Otto, A.; Sibeck, D. G.; Wang, Y.; Glassmeier, K.-H.; Daly, P.W.; Reme, H.

    2014-01-01

    The factors controlling asymmetric reconnection and the role of the cold plasma population in the reconnection process are two outstanding questions. We present a case study of multipoint Cluster observations demonstrating that the separatrix and flow boundary angles are greater on the magnetosheath than on the magnetospheric side of the magnetopause, probably due to the stronger density than magnetic field asymmetry at this boundary. The motion of cold plasmaspheric ions entering the reconnection region differs from that of warmer magnetosheath and magnetospheric ions. In contrast to the warmer ions, which are probably accelerated by reconnection in the diffusion region near the subsolar magnetopause, the colder ions are simply entrained by ??×?? drifts at high latitudes on the recently reconnected magnetic field lines. This indicates that plasmaspheric ions can sometimes play only a very limited role in asymmetric reconnection, in contrast to previous simulation studies. Three cold ion populations (probably H+, He+, and O+) appear in the energy spectrum, consistent with ion acceleration to a common velocity.

  19. Characterization of cationic polymers by asymmetric flow field-flow fractionation and multi-angle light scattering-A comparison with traditional techniques.

    PubMed

    Wagner, Michael; Pietsch, Christian; Tauhardt, Lutz; Schallon, Anja; Schubert, Ulrich S

    2014-01-17

    In the field of nanomedicine, cationic polymers are the subject of intensive research and represent promising carriers for genetic material. The detailed characterization of these carriers is essential since the efficiency of gene delivery strongly depends on the properties of the used polymer. Common characterization methods such as size exclusion chromatography (SEC) or mass spectrometry (MS) suffer from problems, e.g. missing standards, or even failed for cationic polymers. As an alternative, asymmetrical flow field-flow fractionation (AF4) was investigated. Additionally, analytical ultracentrifugation (AUC) and (1)H NMR spectroscopy, as well-established techniques, were applied to evaluate the results obtained by AF4. In this study, different polymers of molar masses between 10 and 120kgmol(-1) with varying amine functionalities in the side chain or in the polymer backbone were investigated. To this end, some of the most successful gene delivery agents, namely linear poly(ethylene imine) (LPEI) (only secondary amines in the backbone), branched poly(ethylene imine) (B-PEI) (secondary and tertiary amino groups in the backbone, primary amine end groups), and poly(l-lysine) (amide backbone and primary amine side chains), were characterized. Moreover, poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), poly(2-(amino)ethyl methacrylate) (PAEMA), and poly(2-(tert-butylamino)ethyl methacrylate) (PtBAEMA) as polymers with primary, secondary, and tertiary amines in the side chain, have been investigated. Reliable results were obtained for all investigated polymers by AF4. In addition, important factors for all methods were evaluated, e.g. the influence of different elution buffers and AF4 membranes. Besides this, the correct determination of the partial specific volume and the suppression of the polyelectrolyte effect are the most critical issues for AUC investigations.

  20. Suppression of drift wave instability due to sheared field-aligned flow and negative ions

    NASA Astrophysics Data System (ADS)

    Ichiki, Ryuta; Hayashi, Kenichiro; Kaneko, Toshiro; Hatakeyama, Rikizo

    2006-10-01

    Sheared field-aligned plasma flow is a significant topic in space/circumterrestrial plasmas. Taking into account negative ions or dust grains will make the space plasma physics more general and accurate. Using the QT-Upgrade Machine, we have conducted laboratory experiments to examine negative ion effects on shear-modified drift waves. Field-aligned K^+ ion flow and its shear strength are controlled with a concentrically segmented W hot plate. Negative ions SF6^- are produced by introducing SF6 gas in the plasma. The drift wave shows a gradual monotonic decrease in amplitude as the shear strength is increased from zero. However, as the shear strength is decreased from zero to negative values, the amplitude increases up to a certain shear strength and rapidly decreases after the peaking. The negative ion introduction, in general, suppresses this instability while retaining the dependence of the amplitude on the shear. These wave characteristics are interpreted using the theories of current-driven (kinetic) and of D’Angelo (fluid) instabilities.

  1. Rational design of ion force fields based on thermodynamic solvation properties

    NASA Astrophysics Data System (ADS)

    Horinek, Dominik; Mamatkulov, Shavkat I.; Netz, Roland R.

    2009-03-01

    Most aqueous biological and technological systems contain solvated ions. Atomistic explicit-water simulations of ionic solutions rely crucially on accurate ionic force fields, which contain most commonly two adjustable parameters: the Lennard-Jones diameter and the interaction strength. Assuming these parameters to be properly optimized, the plethora of parameters one finds in the literature for one and the same ion is surprising. In principle, the two parameters should be uniquely determined by matching two ionic properties obtained for a particular water model and within a given simulation protocol with the corresponding experimental observables. Traditionally, ion parameters were chosen in a somewhat unsystematic way to reproduce the solvation free energy and to give the correct ion size when compared with scattering results. Which experimental observable one chooses to reproduce should in principle depend on the context within which the ionic force field is going to be used. In the present work we suggest to use the solvation free energy in conjunction with the solvation entropy to construct thermodynamically sound force fields for the alkali and halide ions for the simulation of ion-specific effects in aqueous environment. To that end we determine the solvation free energy and entropy of both cations and anions in the entire relevant parameter space. As an independent check on the quality of the resulting force fields we also determine the effective ionic radius from the first peak of the radial ion-water distribution function. Several difficulties during parameter optimization are discussed in detail. (i) Single-ion solvation depends decisively on water-air surface properties, which experimentally becomes relevant when introducing extrathermodynamic assumptions on the hydronium (H3O+) solvation energy. Fitting ion pairs circumvents this problem but leaves the parameters of one reference ion (here we choose chloride) undetermined. (ii) For the halides the

  2. Ion gyroradius effects on Alfvenic field aligned currents and electron energization in planetary magnetospheres.

    NASA Astrophysics Data System (ADS)

    Damiano, P. A.; Johnson, J.; Chaston, C. C.; Fox, W. R., II; Delamere, P. A.; Stauffer, B. H.

    2015-12-01

    Alfvenic current systems are a ubiquitous feature of planetary magnetospheres that can be generated by several mechanisms including the braking of flows (e.g. associated with reconnection at substorm onset) and via moon-planet interactions. The energetic electrons needed to carry the field-aligned currents are generally thought to be accelerated on either electron inertial or ion acoustic gyroradius scale lengths in the limit of inertial and kinetic Alfven waves respectively. Recent 2D dipolar hybrid gyrofluid-kinetic electron simulations of kinetic Alfven waves (Damiano et al., JGR, 2015), associated with the braking of fast flows in the terrestrial magnetotail, have illustrated that hot ion effects can act to limit the extent of the parallel current (all along the field line) from what would be expected in the cold ion limit. This correspondingly affects the characteristics of the electron energization, reducing both the parallel elongation in the electron distribution function associated with electron trapping in the kinetic Alfven wave regime and the extent of high energy tails evident in the inertial Alfven wave region above the ionosphere. In this presentation, we build on these initial simulation results analyzing the characteristics of the parallel current system and electron acceleration (associated with both inertial and kinetic Alfven waves) for a range of wave amplitudes and ratios of the electron to ion temperature. One finding is that for a given ion temperature, increasing wave amplitude recovers some of the features of the electron energization evident in the cold ion limit, but this is modulated by the effect of wave energy dispersion perpendicular to the ambient magnetic field. These results will be summarized and the relevance and extension of this work to consider Alfvenic aurora in the Jupiter magnetosphere (e.g. via either interchange motion or the Io-Jupiter interaction) will also be discussed.

  3. Balancing the interactions of ions, water, and DNA in the Drude polarizable force field.

    PubMed

    Savelyev, Alexey; MacKerell, Alexander D

    2014-06-19

    Recently we presented a first-generation all-atom Drude polarizable force field for DNA based on the classical Drude oscillator model, focusing on optimization of key dihedral angles followed by extensive validation of the force field parameters. Presently, we describe the procedure for balancing the electrostatic interactions between ions, water, and DNA as required for development of the Drude force field for DNA. The proper balance of these interactions is shown to impact DNA stability and subtler conformational properties, including the conformational equilibrium between the BI and BII states, and the A and B forms of DNA. The parametrization efforts were simultaneously guided by gas-phase quantum mechanics (QM) data on small model compounds and condensed-phase experimental data on the hydration and osmotic properties of biologically relevant ions and their solutions, as well as theoretical predictions for ionic distribution around DNA oligomer. In addition, fine-tuning of the internal base parameters was performed to obtain the final DNA model. Notably, the Drude model is shown to more accurately reproduce counterion condensation theory predictions of DNA charge neutralization by the condensed ions as compared to the CHARMM36 additive DNA force field, indicating an improved physical description of the forces dictating the ionic solvation of DNA due to the explicit treatment of electronic polarizability. In combination with the polarizable DNA force field, the availability of Drude polarizable parameters for proteins, lipids, and carbohydrates will allow for simulation studies of heterogeneous biological systems.

  4. Balancing the Interactions of Ions, Water, and DNA in the Drude Polarizable Force Field

    PubMed Central

    2015-01-01

    Recently we presented a first-generation all-atom Drude polarizable force field for DNA based on the classical Drude oscillator model, focusing on optimization of key dihedral angles followed by extensive validation of the force field parameters. Presently, we describe the procedure for balancing the electrostatic interactions between ions, water, and DNA as required for development of the Drude force field for DNA. The proper balance of these interactions is shown to impact DNA stability and subtler conformational properties, including the conformational equilibrium between the BI and BII states, and the A and B forms of DNA. The parametrization efforts were simultaneously guided by gas-phase quantum mechanics (QM) data on small model compounds and condensed-phase experimental data on the hydration and osmotic properties of biologically relevant ions and their solutions, as well as theoretical predictions for ionic distribution around DNA oligomer. In addition, fine-tuning of the internal base parameters was performed to obtain the final DNA model. Notably, the Drude model is shown to more accurately reproduce counterion condensation theory predictions of DNA charge neutralization by the condensed ions as compared to the CHARMM36 additive DNA force field, indicating an improved physical description of the forces dictating the ionic solvation of DNA due to the explicit treatment of electronic polarizability. In combination with the polarizable DNA force field, the availability of Drude polarizable parameters for proteins, lipids, and carbohydrates will allow for simulation studies of heterogeneous biological systems. PMID:24874104

  5. Magnetic field configurations on thruster performance in accordance with ion beam characteristics in cylindrical Hall thruster plasmas

    NASA Astrophysics Data System (ADS)

    Kim, Holak; Choe, Wonho; Lim, Youbong; Lee, Seunghun; Park, Sanghoo

    2017-03-01

    Magnetic field configuration is critical in Hall thrusters for achieving high performance, particularly in thrust, specific impulse, efficiency, etc. Ion beam features are also significantly influenced by magnetic field configurations. In two typical magnetic field configurations (i.e., co-current and counter-current configurations) of a cylindrical Hall thruster, ion beam characteristics are compared in relation to multiply charged ions. Our study shows that the co-current configuration brings about high ion current (or low electron current), high ionization rate, and small plume angle that lead to high thruster performance.

  6. Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic field.

    PubMed

    Oikawa, Kohei; Saito, Yuta; Komizunai, Shota; Takahashi, Kazunori; Ando, Akira

    2014-02-01

    Uniform axial magnetic field of about 70 G is applied to a radiofrequency (rf) hydrogen ion source by arrays of permanent magnets. The plasma density and electron temperature downstream of the source and near the magnetic filter are compared with those in the previously described ion source, where the axial field has been applied by two solenoids. The source is operated at ∼350 kHz and above 10 kW rf power with a field-effect-transistor-based invertor power supply in 1.5 Pa hydrogen. The results show that the plasma density of ∼10(19) m(-3) near the source exit and ∼10(18) m(-3) near the magnetic filter can be obtained, which are higher than those with the solenoids.

  7. Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic field

    SciTech Connect

    Oikawa, Kohei Saito, Yuta; Komizunai, Shota; Takahashi, Kazunori; Ando, Akira

    2014-02-15

    Uniform axial magnetic field of about 70 G is applied to a radiofrequency (rf) hydrogen ion source by arrays of permanent magnets. The plasma density and electron temperature downstream of the source and near the magnetic filter are compared with those in the previously described ion source, where the axial field has been applied by two solenoids. The source is operated at ∼350 kHz and above 10 kW rf power with a field-effect-transistor-based invertor power supply in 1.5 Pa hydrogen. The results show that the plasma density of ∼10{sup 19} m{sup −3} near the source exit and ∼10{sup 18} m{sup −3} near the magnetic filter can be obtained, which are higher than those with the solenoids.

  8. Influence of IMF draping direction and crustal magnetic field location on Martian ion beams

    NASA Astrophysics Data System (ADS)

    Carlsson, E.; Brain, D.; Luhmann, J.; Barabash, S.; Grigoriev, A.; Nilsson, H.; Lundin, R.

    2008-05-01

    Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite onboard Mars Express and data from the Magnetometer/Electron Reflectometer (MAG/ER) on Mars Global Surveyor have been analyzed to determine whether ion beam events (IBEs) are correlated with the direction of the draped interplanetary magnetic field (IMF) or the proximity of strong crustal magnetic fields to the subsolar point. We examined 150 IBEs and found that they are organized by IMF draping direction. However, no clear dependence on the subsolar longitude of the strongest magnetic anomaly is evident, making it uncertain whether crustal magnetic fields have an effect on the formation of the beams. We also examined data from the IMA sensor of the ASPERA-4 instrument suite on Venus Express and found that IBEs are observed at Venus as well, which indicates the morphology of the Martian and Venusian magnetotails are similar.

  9. Designing asymmetric multiferroics with strong magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Lu, Xuezeng; Xiang, Hongjun; Rondinelli, James; Materials Theory; Design Group Team

    2015-03-01

    Multiferroics offer exciting opportunities for electric-field control of magnetism. Single-phase multiferroics suitable for such applications at room temperature need much more study. Here, we propose the concept of an alternative type of multiferroics, namely, the ``asymmetric multiferroic.'' In asymmetric multiferroics, two locally stable ferroelectric states are not symmetrically equivalent, leading to different magnetic properties between these two states. Furthermore, we predict from first principles that a Fe-Cr-Mo superlattice with the LiNbO3-type structure is such an asymmetric multiferroic. The strong ferrimagnetism, high ferroelectric polarization, and significant dependence of the magnetic transition temperature on polarization make this asymmetric multiferroic an ideal candidate for realizing electric-field control of magnetism at room temperature. Our study suggests that the asymmetric multiferroic may provide an alternative playground for voltage control of magnetism and find its applications in spintronics and quantum computing.

  10. Designing asymmetric multiferroics with strong magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Lu, X. Z.; Xiang, H. J.

    2014-09-01

    Multiferroics offer exciting opportunities for electric-field control of magnetism. Single-phase multiferroics suitable for such applications at room temperature need much more study. Here, we propose the concept of an alternative type of multiferroics, namely, the "asymmetric multiferroic." In asymmetric multiferroics, two locally stable ferroelectric states are not symmetrically equivalent, leading to different magnetic properties between these two states. Furthermore, we predict from first principles that a Fe-Cr-Mo superlattice with the LiNbO3-type structure is such an asymmetric multiferroic. The strong ferrimagnetism, high ferroelectric polarization, and significant dependence of the magnetic transition temperature on polarization make this asymmetric multiferroic an ideal candidate for realizing electric-field control of magnetism at room temperature. Our study suggests that the asymmetric multiferroic may provide an alternative playground for voltage control of magnetism and find its applications in spintronics and quantum computing.

  11. Computer simulation of field ion images of nanoporous structure in the irradiated materials

    NASA Astrophysics Data System (ADS)

    Medvedeva, E. V.; Alexandrova, S. S.; Belykh, T. A.

    2012-02-01

    Computer simulation and interpretation of field ion microscopy images of ion irradiated platinum are discussed. Field ion microscopy technique provides direct precise atomic scale investigation of crystal lattice defects of atomically pure surface of material; at the same time it allows to analyze the structural defects in volume by controlled and sequential removal of surface atoms by electric field. Defects identification includes the following steps: at the first stage the type of crystalline structure and spatial orientation of crystallographic directions were determined. Thus, we obtain the data about exact position of all atoms of the given volume, i.e. the model image of an ideal crystal. At the second stage, the ion image was processed used the program to obtain the data about real arrangement of atoms of the investigated sample. At the third stage the program compares these two data sets, with a split-hair accuracy revealing a site of all defects in a material. Results of the quantitative analysis show that shape of nanopores are spherical or cylindrical, diameter on nanopores was varied from 1 to 5 run, their depth was fond to be from 1 to 9 nm. It was observed that nearly 40% of nanopores are concentrated in the subsurface layer 10 nm thick, the concentration of nanopores decreased linearly with the distance from the irradiated surface.

  12. Linear ion trap with added octopole field component: the property and method.

    PubMed

    Dang, Qiankun; Xu, Fuxing; Huang, Xiaohua; Fang, Xiang; Wang, Rizhi; Ding, Chuan-Fan

    2015-12-01

    It is well known that superimposition of some positive octopole field will benefit the performance of ion trap mass analyzer. In the radial-ejection linear ion trap (LIT), adding some octopole field component to the main quadrupole field is usually accomplished by stretching the ejection rod pair. In this study, the effect of octopole potential and some other higher order potential on the performance of LIT mass analyzer is investigated. A simple and effective method, which is to add some octopole component by building a LIT with a pair of rectangular electrodes and a pair of semi-circular electrodes, is reported. Its properties were studied by numerical simulations and experiments. The results showed that a certain amount of positive octopole component could be produced by simply adjusting the position and width of the rectangular electrodes. A resolution of over 1200 at m/z 609 (~1600 Da/s) was observed in this type of LIT. They also performed tandem mass spectrometry well. The device with optimum geometry for ion ejection from rectangular electrodes provided comparable performance to that for ion ejection from semi-circular electrodes. This type of LIT design is easy for fabrication and assembly.

  13. Effects of the crustal magnetic fields on the Martian atmospheric ion escape rate

    NASA Astrophysics Data System (ADS)

    Ramstad, Robin; Barabash, Stas; Futaana, Yoshifumi; Nilsson, Hans; Holmström, Mats

    2016-10-01

    Eight years (2007-2015) of ion flux measurements from Mars Express are used to statistically investigate the influence of the Martian magnetic crustal fields on the atmospheric ion escape rate. We combine all Analyzer of Space Plasmas and Energetic Atoms/Ion Mass Analyzer (ASPERA-3/IMA) measurements taken during nominal upstream solar wind and solar extreme ultraviolet conditions to compute global average ion distribution functions, individually for the north/south hemispheres and for varying solar zenith angles (SZAs) of the strongest crustal magnetic field. Escape rates are subsequently calculated from each of the average distribution functions. The maximum escape rate (4.2 ± 1.2) × 1024s-1 is found for SZA = 60°-80°, while the minimum escape rate (1.7 ± 0.6) × 1024s-1 is found for SZA = 28°-60°, showing that the dayside orientation of the crustal fields significantly affects the global escape rate (p = 97%). However, averaged over time, independent of SZA, we find no statistically significant difference in the escape rates from the two hemispheres (escape from southern hemisphere 46% ± 18% of global rate).

  14. Simulation of electrostatic ion instabilities in the presence of parallel currents and transverse electric fields

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Ganguli, G.; Lee, Y. C.; Palmadesso, P. J.

    1989-01-01

    A spatially two-dimensional electrostatic PIC simulation code was used to study the stability of a plasma equilibrium characterized by a localized transverse dc electric field and a field-aligned drift for L is much less than Lx, where Lx is the simulation length in the x direction and L is the scale length associated with the dc electric field. It is found that the dc electric field and the field-aligned current can together play a synergistic role to enable the excitation of electrostatic waves even when the threshold values of the field aligned drift and the E x B drift are individually subcritical. The simulation results show that the growing ion waves are associated with small vortices in the linear stage, which evolve to the nonlinear stage dominated by larger vortices with lower frequencies.

  15. Ion and electron emission from silver nanoparticles in intense laser fields

    SciTech Connect

    Doeppner, T.; Fennel, Th.; Radcliffe, P.; Tiggesbaeumker, J.; Meiwes-Broer, K.-H.

    2006-03-15

    By a comparative analysis of the emission of highly charged ions and energetic electrons the interaction dynamics of intense femtosecond laser fields (10{sup 13}-10{sup 14} W/cm{sup 2}) with nanometer-sized silver clusters is investigated. Using dual laser pulses with variable optical delay the time-dependent cluster response is resolved. A dramatic increase both in the atomic charge state of the ions and the maximum electron kinetic energy is observed for a certain delay of the pulses. Corresponding Vlasov calculations on a metal cluster model system indicate that enhanced cluster ionization as well as the generation of fast electrons coincide with resonant plasmon excitation.

  16. Creation and recovery of a W(111) single atom gas field ion source.

    PubMed

    Pitters, Jason L; Urban, Radovan; Wolkow, Robert A

    2012-04-21

    Tungsten single atom tips have been prepared from a single crystal W(111) oriented wire using the chemical assisted field evaporation and etching method. Etching to a single atom tip occurs through a symmetric structure and leads to a predictable last atom unlike etching with polycrystalline tips. The single atom tip formation procedure is shown in an atom by atom removal process. Rebuilds of single atom tips occur on the same crystalline axis as the original tip such that ion emission emanates along a fixed direction for all tip rebuilds. This preparation method could be utilized and developed to prepare single atom tips for ion source development.

  17. High-Fidelity Trapped-Ion Quantum Logic Using Near-Field Microwaves

    NASA Astrophysics Data System (ADS)

    Harty, T. P.; Sepiol, M. A.; Allcock, D. T. C.; Ballance, C. J.; Tarlton, J. E.; Lucas, D. M.

    2016-09-01

    We demonstrate a two-qubit logic gate driven by near-field microwaves in a room-temperature microfabricated surface ion trap. We introduce a dynamically decoupled gate method, which stabilizes the qubits against fluctuating energy shifts and avoids the need to null the microwave field. We use the gate to produce a Bell state with fidelity 99.7(1)%, after accounting for state preparation and measurement errors. The gate is applied directly to 43Ca+ hyperfine "atomic clock" qubits (coherence time T2*≈50 s ) using the oscillating magnetic field gradient produced by an integrated microwave electrode.

  18. Channel waveguides in glass via silver-sodium field-assisted ion exchange

    NASA Technical Reports Server (NTRS)

    Forrest, K.; Pagano, S. J.; Viehmann, W.

    1986-01-01

    Multimode channel waveguides have been formed in sodium aluminosilicate glass by field-assisted diffusion of Ag(+) ions from vacuum-evaporated Ag films. The two-dimensional refractive index profiles of the waveguides were controlled by varying the diffusion time, the diffusion temperature, and the electric field strength. Estimates of the diffusion rate through a strip aperture were obtained, assuming the electric field was strong 120-240 V/mm. The maximum change in refractive index in the sodium aluminosilicate glasses was estimated near 65 percent of the change in soda-lime silicate glass. The physical properties of the glasses are given in a table.

  19. Asymmetric dark matter

    SciTech Connect

    Kumar, Jason

    2014-06-24

    We review the theoretical framework underlying models of asymmetric dark matter, describe astrophysical constraints which arise from observations of neutron stars, and discuss the prospects for detecting asymmetric dark matter.

  20. Energy loss of ions by electric-field fluctuations in a magnetized plasma

    SciTech Connect

    Nersisyan, Hrachya B.; Deutsch, Claude

    2011-06-15

    The results of a theoretical investigation of the energy loss of charged particles in a magnetized classical plasma due to the electric-field fluctuations are reported. The energy loss for a test particle is calculated through the linear-response theory. At vanishing magnetic field, the electric-field fluctuations lead to an energy gain of the charged particle for all velocities. It has been shown that in the presence of strong magnetic field, this effect occurs only at low velocities. In the case of high velocities, the test particle systematically loses its energy due to the interaction with a stochastic electric field. The net effect of the fluctuations is the systematic reduction of the total energy loss (i.e., the sum of the polarization and stochastic energy losses) at vanishing magnetic field and reduction or enhancement at strong field, depending on the velocity of the particle. It is found that the energy loss of the slow heavy ion contains an anomalous term that depends logarithmically on the projectile mass. The physical origin of this anomalous term is the coupling between the cyclotron motion of the plasma electrons and the long-wavelength, low-frequency fluctuations produced by the projectile ion. This effect may strongly enhance the stochastic energy gain of the particle.

  1. Energy loss of ions by electric-field fluctuations in a magnetized plasma.

    PubMed

    Nersisyan, Hrachya B; Deutsch, Claude

    2011-06-01

    The results of a theoretical investigation of the energy loss of charged particles in a magnetized classical plasma due to the electric-field fluctuations are reported. The energy loss for a test particle is calculated through the linear-response theory. At vanishing magnetic field, the electric-field fluctuations lead to an energy gain of the charged particle for all velocities. It has been shown that in the presence of strong magnetic field, this effect occurs only at low velocities. In the case of high velocities, the test particle systematically loses its energy due to the interaction with a stochastic electric field. The net effect of the fluctuations is the systematic reduction of the total energy loss (i.e., the sum of the polarization and stochastic energy losses) at vanishing magnetic field and reduction or enhancement at strong field, depending on the velocity of the particle. It is found that the energy loss of the slow heavy ion contains an anomalous term that depends logarithmically on the projectile mass. The physical origin of this anomalous term is the coupling between the cyclotron motion of the plasma electrons and the long-wavelength, low-frequency fluctuations produced by the projectile ion. This effect may strongly enhance the stochastic energy gain of the particle.

  2. Acidity field of soils as ion-exchange systems and the diagnostics of genetic soil horizons

    NASA Astrophysics Data System (ADS)

    Kokotov, Yu. A.; Sukhacheva, E. Yu.; Aparin, B. F.

    2014-12-01

    For the comprehensive description of the acidity of a two-phase ion-exchange system, we should analyze two curves of the ionite titration by a strong base in water and salt solutions and find the quantitative relationships between the corresponding pH characteristics. An idea of the three-dimensional field of acidity of ion-exchange systems (the phase space of the soil acidity characteristics) and its three two-dimensional projections is suggested. For soils, three interrelated characteristics—the pH values of the salt and water extracts and the degree of base saturation—can serve as spatial coordinates for the acidity field. Representation of factual data in this field makes it possible to compare and analyze the acidity characteristics of different soils and soil horizons and to determine their specific features. Differentiation of the field into separate volumes allows one to present the data in a discrete form. We have studied the distribution patterns of the groups of soil horizons from Leningrad oblast and other regions of northwestern Russia in the acidity field. The studied samples are grouped in different partially overlapping areas of the projections of the acidity field. The results of this grouping attest to the correctness of the modern classification of Russian soils. A notion of the characteristic soil area in the acidity field is suggested; it can be applied to all the soils with a leaching soil water regime.

  3. Above-threshold ionization with highly charged ions in superstrong laser fields. I. Coulomb-corrected strong-field approximation

    NASA Astrophysics Data System (ADS)

    Klaiber, Michael; Yakaboylu, Enderalp; Hatsagortsyan, Karen Z.

    2013-02-01

    Aiming at the investigation of above-threshold ionization in superstrong laser fields with highly charged ions, we develop a Coulomb-corrected strong-field approximation (SFA). The influence of the Coulomb potential of the atomic core on the ionized electron dynamics in the continuum is taken into account via the eikonal approximation, treating the Coulomb potential perturbatively in the phase of the quasiclassical wave function of the continuum electron. In this paper the formalism of the Coulomb-corrected SFA for the nonrelativistic regime is discussed, employing velocity and length gauge. Direct ionization of a hydrogenlike system in a strong linearly polarized laser field is considered. The relation of the results in the different gauges to the Perelomov-Popov-Terent'ev imaginary-time method is discussed.

  4. Ion field-evaporation from ionic liquids infusing carbon xerogel microtips

    SciTech Connect

    Perez-Martinez, C. S. Lozano, P. C.

    2015-07-27

    Ionic liquid ion sources capable of producing positive and negative molecular ion beams from room-temperature molten salts have applications in diverse fields, from materials science to space propulsion. The electrostatic stressing of these ionic liquids places the liquid surfaces in a delicate balance that could yield unwanted droplet emission when not properly controlled. Micro-tip emitter configurations are required to guarantee that these sources will operate in a pure ionic regime with no additional droplets. Porous carbon based on resorcinol-formaldehyde xerogels is introduced as an emitter substrate. It is demonstrated that this material can be shaped to the required micron-sized geometry and has appropriate transport properties to favor pure ionic emission. Time-of-flight mass spectrometry is used to verify that charged particle beams contain solvated ions exclusively.

  5. Surface field analysis of splitting of orbitals of atoms and ions approaching a metal surface.

    NASA Technical Reports Server (NTRS)

    Rao, P. V. S.; Waber, J. T.

    1971-01-01

    The splitting of p- and d-orbitals of an atom or an ion which is caused by the locally varying potential near the surface of a realistic metal has been studied for bcc and fcc substrates. A quasi-ionic model is reasonable at close distance, inasmuch as the electron gas does not completely screen the ionic cores. The arrangement of ion cores near the surface causes the potential to vary in three dimensions. Expressions for energy levels were derived for an unsymmetric group using the quasi-ionic model and techniques used in the treatment of crystal field of nearest neighbors. A number of cases involving ions, as well as atoms in the vicinity of a metal substrate were numerically evaluated.

  6. A compact broadband ion beam focusing device based on laser-driven megagauss thermoelectric magnetic fields

    SciTech Connect

    Albertazzi, B.; D'Humières, E.; Lancia, L.; Antici, P.; Dervieux, V.; Nakatsutsumi, M.; Romagnani, L.; Fuchs, J.; Böcker, J.; Swantusch, M.; Willi, O.; Bonlie, J.; Cauble, B.; Shepherd, R.; Breil, J.; Feugeas, J. L.; Nicolaï, P.; Tikhonchuk, V. T.; Chen, S. N.; Sentoku, Y.; and others

    2015-04-15

    Ultra-intense lasers can nowadays routinely accelerate kiloampere ion beams. These unique sources of particle beams could impact many societal (e.g., proton-therapy or fuel recycling) and fundamental (e.g., neutron probing) domains. However, this requires overcoming the beam angular divergence at the source. This has been attempted, either with large-scale conventional setups or with compact plasma techniques that however have the restriction of short (<1 mm) focusing distances or a chromatic behavior. Here, we show that exploiting laser-triggered, long-lasting (>50 ps), thermoelectric multi-megagauss surface magnetic (B)-fields, compact capturing, and focusing of a diverging laser-driven multi-MeV ion beam can be achieved over a wide range of ion energies in the limit of a 5° acceptance angle.

  7. A compact broadband ion beam focusing device based on laser-driven megagauss thermoelectric magnetic fields.

    PubMed

    Albertazzi, B; d'Humières, E; Lancia, L; Dervieux, V; Antici, P; Böcker, J; Bonlie, J; Breil, J; Cauble, B; Chen, S N; Feugeas, J L; Nakatsutsumi, M; Nicolaï, P; Romagnani, L; Shepherd, R; Sentoku, Y; Swantusch, M; Tikhonchuk, V T; Borghesi, M; Willi, O; Pépin, H; Fuchs, J

    2015-04-01

    Ultra-intense lasers can nowadays routinely accelerate kiloampere ion beams. These unique sources of particle beams could impact many societal (e.g., proton-therapy or fuel recycling) and fundamental (e.g., neutron probing) domains. However, this requires overcoming the beam angular divergence at the source. This has been attempted, either with large-scale conventional setups or with compact plasma techniques that however have the restriction of short (<1 mm) focusing distances or a chromatic behavior. Here, we show that exploiting laser-triggered, long-lasting (>50 ps), thermoelectric multi-megagauss surface magnetic (B)-fields, compact capturing, and focusing of a diverging laser-driven multi-MeV ion beam can be achieved over a wide range of ion energies in the limit of a 5° acceptance angle.

  8. Manipulation of transport hysteresis on graphene field effect transistors with Ga ion irradiation

    SciTech Connect

    Wang, Quan; Liu, Shuai; Ren, Naifei

    2014-09-29

    We have studied the effect of Ga ion irradiation on the controllable hysteretic behavior of graphene field effect transistors fabricated on Si/SO{sub 2} substrates. The various densities of defects in graphene were monitored by Raman spectrum. It was found that the Dirac point shifted to the positive gate voltage constantly, while the hysteretic behavior was enhanced first and then weakened, with the dose of ion irradiation increasing. By contrasting the trap charges density induced by dopant and the total density of effective trap charges, it demonstrated that adsorbate doping was not the decisive factor that induced the hysteretic behavior. The tunneling between the defect sites induced by ion irradiation was also an important cause for the hysteresis.

  9. Ion heating, burnout of the high-frequency field, and ion sound generation under the development of a modulation instability of an intense Langmuir wave in a plasma

    SciTech Connect

    Kirichok, A. V. Kuklin, V. M.; Pryimak, A. V.; Zagorodny, A. G.

    2015-09-15

    The development of one-dimensional parametric instabilities of intense long plasma waves is considered in terms of the so-called hybrid models, with electrons being treated as a fluid and ions being regarded as particles. The analysis is performed for both cases when the average plasma field energy is lower (Zakharov's hybrid model—ZHM) or greater (Silin's hybrid model—SHM) than the plasma thermal energy. The efficiency of energy transfer to ions and to ion perturbations under the development of the instability is considered for various values of electron-to-ion mass ratios. The energy of low-frequency oscillations (ion-sound waves) is found to be much lower than the final ion kinetic energy. We also discuss the influence of the changes in the damping rate of the high-frequency (HF) field on the instability development. The decrease of the absorption of the HF field inhibits the HF field burnout within plasma density cavities and gives rise to the broadening of the HF spectrum. At the same time, the ion velocity distribution tends to the normal distribution in both ZHM and SHM.

  10. Ion heating, burnout of the high-frequency field, and ion sound generation under the development of a modulation instability of an intense Langmuir wave in a plasma

    NASA Astrophysics Data System (ADS)

    Kirichok, A. V.; Kuklin, V. M.; Pryimak, A. V.; Zagorodny, A. G.

    2015-09-01

    The development of one-dimensional parametric instabilities of intense long plasma waves is considered in terms of the so-called hybrid models, with electrons being treated as a fluid and ions being regarded as particles. The analysis is performed for both cases when the average plasma field energy is lower (Zakharov's hybrid model—ZHM) or greater (Silin's hybrid model—SHM) than the plasma thermal energy. The efficiency of energy transfer to ions and to ion perturbations under the development of the instability is considered for various values of electron-to-ion mass ratios. The energy of low-frequency oscillations (ion-sound waves) is found to be much lower than the final ion kinetic energy. We also discuss the influence of the changes in the damping rate of the high-frequency (HF) field on the instability development. The decrease of the absorption of the HF field inhibits the HF field burnout within plasma density cavities and gives rise to the broadening of the HF spectrum. At the same time, the ion velocity distribution tends to the normal distribution in both ZHM and SHM.

  11. Three-body fragmentation of triatomic molecular ions in a strong laser field

    NASA Astrophysics Data System (ADS)

    Ablikim, U.; Zohrabi, M.; Jochim, Bethany; Berry, Ben; Carnes, K. D.; Ben-Itzhak, I.

    2014-05-01

    Coincidence three-dimensional momentum imaging measurements of three-body fragmentation of transient triply-charged CO2 molecules reveal competing fragmentation paths involving bending, symmetric and asymmetric stretching, as well as the more complex sequential breakup (i.e. one bond at a time). We have extended these studies using a CO2+molecular-ion-beam target, providing similar results for the breakup of the transient CO23+ --> O+ + C+ + O+. The detection of neutral fragments also enables kinematically complete measurements of the three-body breakup of the transient CO22+ . Our results, for CO2+in ultrashort (~26 fs) intense (1015 to 1016 W/cm2) laser pulses at 790 nm, suggest significant bending in the C+ + O+ + O+ channel as well as sequential breakup. In contrast, sequential breakup is suppressed in the O+ + C+ + O and O+ + C +O+ channels. Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S.

  12. Combining asymmetrical flow field-flow fractionation with on- and off-line fluorescence detection to examine biodegradation of riverine dissolved and particulate organic matter.

    PubMed

    Lee, Sang Tak; Yang, Boram; Kim, Jin-Yong; Park, Ji-Hyung; Moon, Myeong Hee

    2015-08-28

    This study demonstrated that asymmetrical flow field-flow fractionation (AF4) coupled with on-line UV and fluorescence detection (FLD) and off-line excitation-emission matrix (EEM) fluorescence spectroscopy can be employed to analyze the influence of microbial metabolic activity on the consumption and production of freshwater organic matter. With the AF4 system, organic matter is on-line enriched during a focusing/relaxation period, which is an essential process prior to separation. Size-fractionated chromophoric and fluorophoric organic materials were simultaneously monitored during the 30-min AF4 separation process. Two fractions of different sizes (dissolved organic matter (DOM) and particulate organic matter (POM)) of freshwater samples from three locations (up-, mid-, and downstream) along the Han River basin of Korea were incubated with the same inoculum for 14 days to analyze fraction-specific alterations in optical properties using AF4-UV-FLD. A comparison of AF4 fractograms obtained from pre- and post-incubation samples revealed that POM-derived DOM were more susceptible to microbial metabolic activity than was DOM. Preferential microbial consumption of protein-like DOM components concurred with enhanced peaks of chromophoric and humic-like fluorescent components, presumably formed as by-products of microbial processing. AF4-UV-FLD combined with off-line identification of microbially processed components using EEM fluorescence spectroscopy provides a powerful tool to study the relationship between microbial activity and composition as well as biodegradability of DOM and POM-derived DOM from different origins, especially for the analysis of chromophoric and fluorophoric organic matter that are consumed and produced by microbial metabolic activity. The proposed AF4 system can be applied to organic matter in freshwater samples having low concentration range (0.3-2.5ppm of total organic carbon) without a pre-concentration procedure.

  13. Physicochemical characterization of titanium dioxide pigments using various techniques for size determination and asymmetric flow field flow fractionation hyphenated with inductively coupled plasma mass spectrometry.

    PubMed

    Helsper, Johannes P F G; Peters, Ruud J B; van Bemmel, Margaretha E M; Rivera, Zahira E Herrera; Wagner, Stephan; von der Kammer, Frank; Tromp, Peter C; Hofmann, Thilo; Weigel, Stefan

    2016-09-01

    Seven commercial titanium dioxide pigments and two other well-defined TiO2 materials (TiMs) were physicochemically characterised using asymmetric flow field flow fractionation (aF4) for separation, various techniques to determine size distribution and inductively coupled plasma mass spectrometry (ICPMS) for chemical characterization. The aF4-ICPMS conditions were optimised and validated for linearity, limit of detection, recovery, repeatability and reproducibility, all indicating good performance. Multi-element detection with aF4-ICPMS showed that some commercial pigments contained zirconium co-eluting with titanium in aF4. The other two TiMs, NM103 and NM104, contained aluminium as integral part of the titanium peak eluting in aF4. The materials were characterised using various size determination techniques: retention time in aF4, aF4 hyphenated with multi-angle laser light spectrometry (MALS), single particle ICPMS (spICPMS), scanning electron microscopy (SEM) and particle tracking analysis (PTA). PTA appeared inappropriate. For the other techniques, size distribution patterns were quite similar, i.e. high polydispersity with diameters from 20 to >700 nm, a modal peak between 200 and 500 nm and a shoulder at 600 nm. Number-based size distribution techniques as spICPMS and SEM showed smaller modal diameters than aF4-UV, from which mass-based diameters are calculated. With aF4-MALS calculated, light-scattering-based "diameters of gyration" (Øg) are similar to hydrodynamic diameters (Øh) from aF4-UV analyses and diameters observed with SEM, but much larger than with spICPMS. A Øg/Øh ratio of about 1 indicates that the TiMs are oblate spheres or fractal aggregates. SEM observations confirm the latter structure. The rationale for differences in modal peak diameter is discussed.

  14. High speed two-dimensional protein separation without gel by isoelectric focusing-asymmetrical flow field flow fractionation: application to urinary proteome.

    PubMed

    Kim, Ki Hun; Moon, Myeong Hee

    2009-09-01

    An online multilane channel system for isoelectric focusing and asymmetrical flow field-flow fractionation (IEF-AF4) is utilized for the two-dimensional separation (2D: isoelectric point, pI, and hydrodynamic diameter, d(s)) of a human proteome sample followed by the shotgun proteomic analysis using nanoflow liquid chromatography-electrospray ionization-tandem mass spectrometry (nLC-ESI-MS-MS). IEF-AF4 was recently developed to carry out nongel-based high speed two-dimensional protein separation [ Kim , K. , et al. Anal. Chem. 2009, 81 , 1715 ]. In IEF-AF4, proteins are separated according to pI along an IEF channel located at the head of six AF4 channels, and then the fractionated protein bands are directed to multilane AF4 channels for size-based separation. In this report, the original IEF-AF4 system has been modified to avoid the possible adsorption of proteins onto the membrane wall of IEF segments during isoelectric focusing by isolating the IEF channel segments from the multilane AF4 channels. The performance of the modified IEF-AF4 system was tested with protein standards and was further applied for the 2D fractionation of the human urinary proteome sample under two ampholyte solutions with different pH ranges (pH 3-10 and 3-6). The entire 2D separation was achieved in less than 30 min. The collected protein fractions were digested for peptide analysis using nLC-ESI-MS-MS, resulting in the identification of 245 total urinary proteins, including 110 unique proteins that are not yet reported in literature. Our experiments also showed a higher efficiency in the identification of urine proteins using ampholyte solution in the narrower pH range.

  15. Optimisation of asymmetric flow field-flow fractionation for the characterisation of nanoparticles in coated polydisperse TiO2 with applications in food and feed.

    PubMed

    Omar, J; Boix, A; Kerckhove, G; von Holst, C

    2016-12-01

    Titanium dioxide (TiO2) has various applications in consumer products and is also used as an additive in food and feeding stuffs. For the characterisation of this product, including the determination of nanoparticles, there is a strong need for the availability of corresponding methods of analysis. This paper presents an optimisation process for the characterisation of polydisperse-coated TiO2 nanoparticles. As a first step, probe ultrasonication was optimised using a central composite design in which the amplitude and time were the selected variables to disperse, i.e., to break up agglomerates and/or aggregates of the material. The results showed that high amplitudes (60%) favoured a better dispersion and time was fixed in mid-values (5 min). In a next step, key factors of asymmetric flow field-flow fraction (AF4), namely cross-flow (CF), detector flow (DF), exponential decay of the cross-flow (CFexp) and focus time (Ft), were studied through experimental design. Firstly, a full-factorial design was employed to establish the statistically significant factors (p < 0.05). Then, the information obtained from the full-factorial design was utilised by applying a central composite design to obtain the following optimum conditions of the system: CF, 1.6 ml min(-1); DF, 0.4 ml min(-1); Ft, 5 min; and CFexp, 0.6. Once the optimum conditions were obtained, the stability of the dispersed sample was measured for 24 h by analysing 10 replicates with AF4 in order to assess the performance of the optimised dispersion protocol. Finally, the recovery of the optimised method, particle shape and particle size distribution were estimated.

  16. Optimisation of asymmetric flow field-flow fractionation for the characterisation of nanoparticles in coated polydisperse TiO2 with applications in food and feed

    PubMed Central

    Omar, J.; Boix, A.; Kerckhove, G.; von Holst, C.

    2016-01-01

    ABSTRACT Titanium dioxide (TiO2) has various applications in consumer products and is also used as an additive in food and feeding stuffs. For the characterisation of this product, including the determination of nanoparticles, there is a strong need for the availability of corresponding methods of analysis. This paper presents an optimisation process for the characterisation of polydisperse-coated TiO2 nanoparticles. As a first step, probe ultrasonication was optimised using a central composite design in which the amplitude and time were the selected variables to disperse, i.e., to break up agglomerates and/or aggregates of the material. The results showed that high amplitudes (60%) favoured a better dispersion and time was fixed in mid-values (5 min). In a next step, key factors of asymmetric flow field-flow fraction (AF4), namely cross-flow (CF), detector flow (DF), exponential decay of the cross-flow (CFexp) and focus time (Ft), were studied through experimental design. Firstly, a full-factorial design was employed to establish the statistically significant factors (p < 0.05). Then, the information obtained from the full-factorial design was utilised by applying a central composite design to obtain the following optimum conditions of the system: CF, 1.6 ml min–1; DF, 0.4 ml min–1; Ft, 5 min; and CFexp, 0.6. Once the optimum conditions were obtained, the stability of the dispersed sample was measured for 24 h by analysing 10 replicates with AF4 in order to assess the performance of the optimised dispersion protocol. Finally, the recovery of the optimised method, particle shape and particle size distribution were estimated. PMID:27650879

  17. Prospects and difficulties in TiO₂ nanoparticles analysis in cosmetic and food products using asymmetrical flow field-flow fractionation hyphenated to inductively coupled plasma mass spectrometry.

    PubMed

    López-Heras, Isabel; Madrid, Yolanda; Cámara, Carmen

    2014-06-01

    In this work, we proposed an analytical approach based on asymmetrical flow field-flow fractionation combined to an inductively coupled plasma mass spectrometry (AsFlFFF-ICP-MS) for rutile titanium dioxide nanoparticles (TiO2NPs) characterization and quantification in cosmetic and food products. AsFlFFF-ICP-MS separation of TiO2NPs was performed using 0.2% (w/v) SDS, 6% (v/v) methanol at pH 8.7 as the carrier solution. Two problems were addressed during TiO2NPs analysis by AsFlFFF-ICP-MS: size distribution determination and element quantification of the NPs. Two approaches were used for size determination: size calibration using polystyrene latex standards of known sizes and transmission electron microscopy (TEM). A method based on focused sonication for preparing NPs dispersions followed by an on-line external calibration strategy based on AsFlFFF-ICP-MS, using rutile TiO2NPs as standards is presented here for the first time. The developed method suppressed non-specific interactions between NPs and membrane, and overcame possible erroneous results obtained when quantification is performed by using ionic Ti solutions. The applicability of the quantification method was tested on cosmetic products (moisturizing cream). Regarding validation, at the 95% confidence level, no significant differences were detected between titanium concentrations in the moisturizing cream prior sample mineralization (3865±139 mg Ti/kg sample), by FIA-ICP-MS analysis prior NPs extraction (3770±24 mg Ti/kg sample), and after using the optimized on-line calibration approach (3699±145 mg Ti/kg sample). Besides the high Ti content found in the studied food products (sugar glass and coffee cream), TiO2NPs were not detected.

  18. A Critical Fast Ion Beta in the Madison Symmetric Torus Reversed Field Pinch

    NASA Astrophysics Data System (ADS)

    Capecchi, William J.

    The first fast-ion profile measurements have been made in a reversed-field pinch (RFP) plasma. A large population of fast-ions are deposited in the core of the Madison Symmetric Torus (MST) through use of a 1 MW neutral beam injector (NBI) giving rise to a variety of beam-driven instabilities. One such mode, the energetic-particle mode (EPM) has been shown to reduce fast-ion content in MST, evident through drops in signal levels of the advanced neutral particle analyzer (ANPA). EPMs in MST appear as bursts of magnetic fluctuations at a lab frequency of ˜100 kHz reaching peak amplitude and decaying away within 100 microseconds. A burst ensemble of the neutron data does not reveal a drop in neutron emission across a burst, implying the population of fast-ions transported by a burst constitute a small fraction of the total. The burst may also pitch-angle scatter out of the ANPA phase space or be transported to mid-radius where charge-exchange with the background neutrals or fast-ion orbit stochasticity may reduce fast-ion confinement. Data gathered from the expanded neutron diagnostic suite including a new collimated neutron detector (CiNDe) was used to reconstruct the fast-ion profile in MST and measure critical fast-ion beta quantities. Measurements were made in plasma conditions with varying magnetic field strength in order to investigate the interplay between the energetic particle (EP) drive and Alfven continuum damping. The measured values of the core fast-ion beta (7.5% (1.2%) in 300 (500) kA plasmas) are reduced from classical predictions (TRANSP predicts up to 10% core value) due to EPM activity. The frequency, magnitude, and rate of occurrence of the bursts depends on the tearing mode amplitude, Alfven continuum damping rate, fast-ion profile shape, and resonant orbit dynamics. Marginal stability was reached in both moderate- (300 kA) and high- (500 kA) current discharges, marked by sustained EPM activity and a saturated global neutron signal during NBI

  19. Effect of tapered magnetic field on expanding laser-produced plasma for heavy-ion inertial fusion

    SciTech Connect

    Kanesue, Takeshi; Ikeda, Shunsuke

    2016-12-20

    A laser ion source is a promising candidate as an ion source for heavy ion inertial fusion (HIF), where a pulsed ultra-intense and low-charged heavy ion beam is required. It is a key development for a laser ion source to transport laser-produced plasma with a magnetic field to achieve a high current beam. The effect of a tapered magnetic field on laser produced plasma is demonstrated by comparing the results with a straight solenoid magnet. The magnetic field of interest is a wider aperture on a target side and narrower aperture on an extraction side. Furthermore, based on the experimentally obtained results, the performance of a scaled laser ion source for HIF was estimated.

  20. Effect of tapered magnetic field on expanding laser-produced plasma for heavy-ion inertial fusion

    DOE PAGES

    Kanesue, Takeshi; Ikeda, Shunsuke

    2016-12-20

    A laser ion source is a promising candidate as an ion source for heavy ion inertial fusion (HIF), where a pulsed ultra-intense and low-charged heavy ion beam is required. It is a key development for a laser ion source to transport laser-produced plasma with a magnetic field to achieve a high current beam. The effect of a tapered magnetic field on laser produced plasma is demonstrated by comparing the results with a straight solenoid magnet. The magnetic field of interest is a wider aperture on a target side and narrower aperture on an extraction side. Furthermore, based on the experimentallymore » obtained results, the performance of a scaled laser ion source for HIF was estimated.« less

  1. Ion temperature measurements of L-mode filaments in MAST by retarding field energy analyser

    NASA Astrophysics Data System (ADS)

    Allan, S. Y.; Elmore, S.; Fishpool, G.; Dudson, B.; the MAST Team; the EUROFusion MST1 Team

    2016-04-01

    Retarding field energy analysers (RFEAs) have been used to compare the ion temperature (T i ) of large plasma filaments with the background plasma (composed of small scale filaments) at the midplane and divertor target in L mode discharges in the Mega Amp spherical tokamak (MAST). At low densities, at the midplane and divertor, at distances from 2 to 4 cm from the separatrix the temperature of ions in large filaments was found to be 2 to 3 times larger than the background plasma. At the midplane, the electron temperature for both large filaments and background plasma was around 3 to 7 times smaller than the ion temperature and had a flat profile across the scrape off layer (SOL). At higher densities, at the midplane and divertor, both the filament and background ion temperatures were smaller than at low density. At the midplane, the filament and background ion and electron temperature profiles across the SOL were relatively flat and of comparable magnitude, ranging in temperature from 5 to 25 eV.

  2. Shocklets, SLAMS, and Field-Aligned Ion Beams in the Terrestrial Foreshock

    NASA Technical Reports Server (NTRS)

    Wilson, L. B.; Koval, A.; Sibeck, D. G.; Szabo, A.; Cattell, C. A.; Kasper, J. C.; Maruca, B. A.; Pulupa, M.; Salem, C. S.; Wilber, M.

    2012-01-01

    We present Wind spacecraft observations of ion distributions showing field- aligned beams (FABs) and large-amplitude magnetic fluctuations composed of a series of shocklets and short large-amplitude magnetic structures (SLAMS). The FABs are found to have T(sub k) approx 80-850 eV, V(sub b)/V(sub sw) approx 1.3-2.4, T(sub perpendicular,b)/T(sub paralell,b) approx 1-8, and n(sub b)/n(sub o) approx 0.2-11%. Saturation amplitudes for ion/ion resonant and non-resonant instabilities are too small to explain the observed SLAMS amplitudes. We show two examples where groups of SLAMS can act like a local quasi-perpendicular shock reflecting ions to produce the FABs, a scenario distinct from the more-common production at the quasi-perpendicular bow shock. The SLAMS exhibit a foot-like magnetic enhancement with a leading magnetosonic whistler train, consistent with previous observations. Strong ion and electron heating are observed within the series of shocklets and SLAMS with temperatures increasing by factors approx > 5 and approx >3, respectively. Both the core and halo electron components show strong perpendicular heating inside the feature.

  3. Global simulation of field-reversed configuration using fully kinetic ion and drift kinetic electron

    NASA Astrophysics Data System (ADS)

    Lau, Calvin; Fulton, Daniel; Kuley, Animesh; Bao, Jian; Lin, Zhihong; Binderbauer, Michael; Tajima, Toshiki; Schmitz, Lothar; the TAE Team Team

    2016-10-01

    In the last several years, the C-2/C-2U advanced beam-driven field-reversed configuration (FRC) experiments at Tri Alpha Energy have progressed to consistent, reproducible plasma lifetimes of 10+ ms, i.e. FRCs have reached transport limited regimes. In FRC geometry, the thermal ion gyroradius is on the order of the size of the plasma near the magnetic null-point. Fast ion orbits intersect both the FRC core and the scrape-off layer (SOL) regions. Previous local simulations of electrostatic drift-wave instabilities using the Gyrokinetic Toroidal Code (GTC) find the core to be robustly stable with driftwave instability only in the SOL at frequencies approaching the ion cyclotron frequency. Therefore, FRC transport studies require fully kinetic ion simulations with cross-separatrix coupling between the core and SOL. Here we report progress of such global simulations using fully kinetic ions and drift kinetic electrons, including the implementation of the Boris push scheme for cyclotron motion and cylindrical coordinates for the separatrix. Supported by the Norman Rostoker Fellowship.

  4. Spectroscopic Measurement of Ion Flow During Merging Start-up of Field-Reversed Configuration

    NASA Astrophysics Data System (ADS)

    Oka, Hirotaka; Inomoto, Michiaki; Tanabe, Hiroshi; Annoura, Masanobu; Ono, Yasushi; Nemoto, Koshichi

    2012-10-01

    The counter-helicity merging method [1] of field-reversed configuration (FRC) formation involves generation of bidirectional toroidal flow, known as a ``sling-shot.'' In two fluids regime, reconnection process is strongly affected by the Hall effect [2]. In this study, we have investigated the behavior of toroidal bidirectional flow generated by the counter-helicity merging in two-fluids regime. We use 2D Ion Doppler Spectroscopy to mesure toroidal ion flow during merging start-up of FRC from Ar gas. We defined two cases: one case with a radially pushed-in X line (case I) and the other case with a radially pushed-out X line(case O). The flow during the plasma merging shows radial asymmetry, as expected from the magnetic measurement, but finally relaxes to a unidirectional flow in plasma current direction in both cases. We observed larger toroidal flow in the plasma current direction in case I after FRC is formed, though the FRC in case O has larger magnetic flux. These results suggest that more ions are lost during merging start-up in case I. This selective ion loss might account for stability and confinement of FRCs probably maintained by high energy ions.[4pt] [1] Y. Ono, et al., Nucl. Fusion 39, pp. 2001-2008 (1999).[0pt] [2] M. Inomoto, et al., Phys. Rev. Lett., 97, 135002, (2006)

  5. Aharonov-Bohm Effect in the Photodetachment Microscopy of Hydrogen Negative Ions in an Electric Field

    NASA Astrophysics Data System (ADS)

    Wang, Dehua

    2014-09-01

    The Aharonov-Bohm (AB) effect in the photodetachment microscopy of the H- ions in an electric field has been studied on the basis of the semiclassical theory. After the H- ion is irradiated by a laser light, they provide a coherent electron source. When the detached electron is accelerated by a uniform electric field, two trajectories of a detached electron which run from the source to the same point on the detector, will interfere with each other and lead to an interference pattern in the photodetachment microscopy. After the solenoid is electrified beside the H- ion, even though no Lorentz force acts on the electron outside the solenoid, the photodetachment microscopy interference pattern on the detector is changed with the variation in the magnetic flux enclosed by the solenoid. This is caused by the AB effect. Under certain conditions, the interference pattern reaches the macroscopic dimensions and could be observed in a direct AB effect experiment. Our study can provide some predictions for the future experimental study of the AB effect in the photodetachment microscopy of negative ions.

  6. Enhanced electron field emission properties of conducting ultrananocrystalline diamond films after Cu and Au ion implantation.

    PubMed

    Sankaran, Kamatchi Jothiramalingam; Chen, Huang-Chin; Panda, Kalpataru; Sundaravel, Balakrishnan; Lee, Chi-Young; Tai, Nyan-Hwa; Lin, I-Nan

    2014-04-09

    The effects of Cu and Au ion implantation on the structural and electron field emission (EFE) properties of ultrananocrystalline diamond (UNCD) films were investigated. High electrical conductivity of 186 (Ω•cm)(-1) and enhanced EFE properties with low turn-on field of 4.5 V/μm and high EFE current density of 6.70 mA/cm(2) have been detected for Au-ion implanted UNCD (Au-UNCD) films that are superior to those of Cu-ion implanted UNCD (Cu-UNCD) ones. Transmission electron microscopic investigations revealed that Au-ion implantation induced a larger proportion of nanographitic phases at the grain boundaries for the Au-UNCD films in addition to the formation of uniformly distributed spherically shaped Au nanoparticles. In contrast, for Cu-UNCD films, plate-like Cu nanoparticles arranged in the row-like pattern were formed, and only a smaller proportion of nanographite phases along the grain boundaries was induced. From current imaging tunneling spectroscopy and local current-voltage curves of scanning tunneling spectroscopic measurements, it is observed that the electrons are dominantly emitted from the grain boundaries. Consequently, the presence of nanosized Au particles and the induction of abundant nanographitic phases in the grain boundaries of Au-UNCD films are believed to be the authentic factors, ensuing in high electrical conductivity and outstanding EFE properties of the films.

  7. Implementing Silicon Nanoribbon Field-Effect Transistors as Arrays for Multiple Ion Detection.

    PubMed

    Stoop, Ralph L; Wipf, Mathias; Müller, Steffen; Bedner, Kristine; Wright, Iain A; Martin, Colin J; Constable, Edwin C; Fanget, Axel; Schönenberger, Christian; Calame, Michel

    2016-05-06

    Ionic gradients play a crucial role in the physiology of the human body, ranging from metabolism in cells to muscle contractions or brain activities. To monitor these ions, inexpensive, label-free chemical sensing devices are needed. Field-effect transistors (FETs) based on silicon (Si) nanowires or nanoribbons (NRs) have a great potential as future biochemical sensors as they allow for the integration in microscopic devices at low production costs. Integrating NRs in dense arrays on a single chip expands the field of applications to implantable electrodes or multifunctional chemical sensing platforms. Ideally, such a platform is capable of detecting numerous species in a complex analyte. Here, we demonstrate the basis for simultaneous sodium and fluoride ion detection with a single sensor chip consisting of arrays of gold-coated SiNR FETs. A microfluidic system with individual channels allows modifying the NR surfaces with self-assembled monolayers of two types of ion receptors sensitive to sodium and fluoride ions. The functionalization procedure results in a differential setup having active fluoride- and sodium-sensitive NRs together with bare gold control NRs on the same chip. Comparing functionalized NRs with control NRs allows the compensation of non-specific contributions from changes in the background electrolyte concentration and reveals the response to the targeted species.

  8. Conversion of ion exchange resin to various functional resins and the application in the field of pharmaceutical sciences

    NASA Astrophysics Data System (ADS)

    Nakayama, Morio

    Ion exchange resins are widely used for separating ions in the solution, desalination, removal of impurities, and etc. Giving a new function to these ion exchange resins enables the application in more various fields. Until now, we carried out the research work about the following 5 project.: (1) Conversion of ion exchange resins into selective adsorbents by using low molecular reagents, which possess capabilities of a selective reaction with target ions, ion exchange reaction with the ion exchange resin and strong physical adsorption to the ion exchange resin. (2) Synthesis of resins for ion exchange high performance liquid chromatography (IEHPLC) and the analysis of biomaterials. (3) Development of insoluble macromolecular Sn(II) complex based on the aminophosphonic acid type ion exchange resin and its application to the 99mTc labeling of proteins. (4) Development of a new 68Ge-68Ga generator using N-methylglucamine type organic polymer as the adsorbent for 68Ge and production of 68Ga for PET. (5) Preparation of an ion-exchangeable polymer bead wrapped with bilayer membrane structures. In this paper, the application of various functional resins prepared based on ion exchange resin in the field of pharmaceutical sciences has been summarized.

  9. Hybrid Simulations of Ion Cyclotron Waves in Non-uniform Magnetic Field: Application to the Corona and Solar Wind

    NASA Astrophysics Data System (ADS)

    Omidi, N.; Russell, C. T.; Jian, L.; Isenberg, P. A.; Wei, H.

    2013-12-01

    The presence of ions with perpendicular temperature larger than parallel in the corona is expected to result in the generation of ion cyclotron waves. Spacecraft observations in the interplanetary medium provide evidence for the presence of ion cyclotron waves generated near the Sun. In this presentation we examine the possibility that the observed ion cyclotron waves are generated in the corona and propagate into the interplanetary medium. To this end, we perform 2.5-D electromagnetic hybrid (kinetic ions, fluid electrons) simulations with non-uniform magnetic field. By initializing ions with perpendicular temperature larger than parallel in a finite region of space, we investigate the generation of ion cyclotron waves in the high magnetic field region and their propagation to larger radial distances with weaker magnetic field strength. Specifically, we examine the propagation properties of the waves and the extent to which they are impacted by the presence of non-uninform magnetic field and nonlinear processes. Results show that at least in some cases, wave propagation is coupled to the outward motion (along the magnetic field) of the ions responsible for the generation of the waves. In such cases, wave generation may be ongoing for regions much larger than the initial source region where ions with temperature anisotropy are initialized. In this study we examine how the properties of ion cyclotron waves (e.g. spectral power, polarization) and their radial dependence vary with changes in the magnetic field model, level of temperature anisotropy, the nature of source ions (e.g. O5+; He++) and relative speed between the various ion species.

  10. On the reliability of scrape-off layer ion temperature measurements by retarding field analyzers

    SciTech Connect

    Kocan, M.; Gunn, J. P.; Pascal, J.-Y.; Gauthier, E.; Komm, M.; Bonhomme, G.

    2008-07-15

    The retarding field analyzer (RFA) is one of the only widely accepted diagnostics for measurements of ion temperature T{sub i} in the tokamak scrape-off layer. In this paper we analyze some instrumental effects of the RFA and their influence on T{sub i} measurements. It is shown that selective ion transmission through the RFA slit is responsible for an overestimation of T{sub i} by less than 14%, even for a relatively thick slit plate. Therefore, thicker slit plates are preferable, since they reduce, e.g., the risk of melting during off-normal events, and the effect of positive space charge inside the cavity. The influence of the electron repelling grid, as well as misalignment of the slit with respect to the magnetic field on T{sub i} measurements are negligible.

  11. Nonlinear density excitations in electron-positron-ion plasmas with trapping in a quantizing magnetic field

    NASA Astrophysics Data System (ADS)

    Iqbal, M. J.; Masood, W.; Shah, H. A.; Tsintsadze, N. L.

    2017-01-01

    In the present work, we have investigated the effect of trapping as a microscopic phenomenon on the formation of solitary structures in the presence of a quantizing magnetic field in an electron-positron-ion (e-p-i) plasma having degenerate electrons and positrons, whereas ions are taken to be classical and cold. We have found that positron concentration, quantizing magnetic field, and finite electron temperature effects not only affect the linear dispersion characteristics of the electrostatic waves under consideration but also have a significant bearing on the propagation of solitary structures in the nonlinear regime. Importantly, the system under consideration has been found to allow the formation of compressive solitary structures only. The work presented here may be beneficial to understand the propagation of nonlinear electrostatic structures in dense astrophysical environments and in intense-laser plasma interactions.

  12. Molecular dynamics simulations of ion conductance in field-stabilized nanoscale lipid electropores.

    PubMed

    Ho, Ming-Chak; Casciola, Maura; Levine, Zachary A; Vernier, P Thomas

    2013-10-03

    Molecular dynamics (MD) simulations of electrophoretic transport of monovalent ions through field-stabilized electropores in POPC lipid bilayers permit systematic characterization of the conductive properties of lipid nanopores. The radius of the electropore can be controlled by the magnitude of the applied sustaining external electric field, which also drives the transport of ions through the pore. We examined pore conductances for two monovalent salts, NaCl and KCl, at physiological concentrations. Na(+) conductance is significantly less than K(+) and Cl(-) conductance and is a nonlinear function of pore radius over the range of pore radii investigated. The single pore electrical conductance of KCl obtained from MD simulation is comparable to experimental values measured by chronopotentiometry.

  13. Ion gyroradius effects on particle trapping in kinetic Alfven waves along auroral field lines

    DOE PAGES

    Damiano, P. A.; Johnson, J. R.; Chaston, C. C.

    2016-11-10

    In this study, a 2-D self-consistent hybrid gyrofluid-kinetic electron model is used to investigate Alfven wave propagation along dipolar magnetic field lines for a range of ion to electron temperature ratios. The focus of the investigation is on understanding the role of these effects on electron trapping in kinetic Alfven waves sourced in the plasma sheet and the role of this trapping in contributing to the overall electron energization at the ionosphere. This work also builds on our previous effort by considering a similar system in the limit of fixed initial parallel current, rather than fixed initial perpendicular electric field.more » It is found that the effects of particle trapping are strongest in the cold ion limit and the kinetic Alfven wave is able to carry trapped electrons a large distance along the field line yielding a relatively large net energization of the trapped electron population as the phase speed of the wave is increased. However, as the ion temperature is increased, the ability of the kinetic Alfven wave to carry and energize trapped electrons is reduced by more significant wave energy dispersion perpendicular to the ambient magnetic field which reduces the amplitude of the wave. This reduction of wave amplitude in turn reduces both the parallel current and the extent of the high-energy tails evident in the energized electron populations at the ionospheric boundary (which may serve to explain the limited extent of the broadband electron energization seen in observations). Here, even in the cold ion limit, trapping effects in kinetic Alfven waves lead to only modest electron energization for the parameters considered (on the order of tens of eV) and the primary energization of electrons to keV levels coincides with the arrival of the wave at the ionospheric boundary.« less

  14. Ion gyroradius effects on particle trapping in kinetic Alfven waves along auroral field lines

    SciTech Connect

    Damiano, P. A.; Johnson, J. R.; Chaston, C. C.

    2016-11-10

    In this study, a 2-D self-consistent hybrid gyrofluid-kinetic electron model is used to investigate Alfven wave propagation along dipolar magnetic field lines for a range of ion to electron temperature ratios. The focus of the investigation is on understanding the role of these effects on electron trapping in kinetic Alfven waves sourced in the plasma sheet and the role of this trapping in contributing to the overall electron energization at the ionosphere. This work also builds on our previous effort by considering a similar system in the limit of fixed initial parallel current, rather than fixed initial perpendicular electric field. It is found that the effects of particle trapping are strongest in the cold ion limit and the kinetic Alfven wave is able to carry trapped electrons a large distance along the field line yielding a relatively large net energization of the trapped electron population as the phase speed of the wave is increased. However, as the ion temperature is increased, the ability of the kinetic Alfven wave to carry and energize trapped electrons is reduced by more significant wave energy dispersion perpendicular to the ambient magnetic field which reduces the amplitude of the wave. This reduction of wave amplitude in turn reduces both the parallel current and the extent of the high-energy tails evident in the energized electron populations at the ionospheric boundary (which may serve to explain the limited extent of the broadband electron energization seen in observations). Here, even in the cold ion limit, trapping effects in kinetic Alfven waves lead to only modest electron energization for the parameters considered (on the order of tens of eV) and the primary energization of electrons to keV levels coincides with the arrival of the wave at the ionospheric boundary.

  15. Techniques for Microwave Near-Field Quantum Control of Trapped Ions

    DTIC Science & Technology

    2013-01-31

    the inputs to the feedthroughs, we measured the frequency noise of the signals at 1.6865 GHz and estimated a negligible effect on the observed fidelity...position will cause off-resonant carrier transitions and ac Zeeman shifts [21], both of which will inhibit precise control. Thus, the